Triisopropylsilyl (TIPS) Alkynes as Building Blocks for Syntheses of

Article Cite This: Organometallics XXXX, XXX, XXX−XXX

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Triisopropylsilyl (TIPS) Alkynes as Building Blocks for Syntheses of Platinum Triisopropylsilylpolyynyl and Diplatinum Polyynediyl Complexes Nancy Weisbach,†,‡,§ Helene Kuhn,‡,§ Hashem Amini,† Andreas Ehnbom,† Frank Hampel,‡ Joseph H. Reibenspies,† Michael B. Hall,† and John A. Gladysz*,†,‡ †

Department of Chemistry, Texas A&M University, PO Box 30012, College Station, Texas 77842-3012, United States Institut für Organische Chemie and Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Henkestraße 42, 91054 Erlangen, Germany

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‡

S Supporting Information *

ABSTRACT: Hay oxidative cross coupling (O2/CuCl/ TMEDA) of trans-(p-tol)(p-tol3P)2Pt(CC)2H (PtTC4H) and excess H(CC)2Si-i-Pr3 (TIPSC4H) gives PtTC8TIPS (55%). Subsequent addition of n-Bu4N+F− and repetition of the Hay protocol yields PtTC12TIPS (56%) and the byproduct trans-i-Pr3Si(CC)2(p-tol3P)2Pt(CC)6Si-i-Pr3 (TIPSC4PtC12TIPS, 5%); another cycle gives PtTC16TIPS (13%). Analogous cross couplings of trans-(C6 F5 )(ptol3P)2Pt(CC)2H (PtFC4H) and excess TIPSCxH yield PtFC6TIPS (x = 2, 58%) and PtFC8TIPS (x = 4, 23%). Each is treated with n-Bu4N+F−, and repetition of the Hay protocol with TIPSC4H gives PtFC10TIPS (58%) and PtFC12TIPS (47%). When the Hay conditions are applied to PtFCxTIPS (x = 6, 8, 10, 12) without a cross-coupling partner, homocoupling to PtFC2xPtF occurs (68−99%). The reaction of trans-(p-tol3P)2PtCl2 and TIPSC4H (4.5 equiv; cat. CuI, CH2Cl2/HNEt2) yields TIPSC4PtC4TIPS (95%). Hay cross coupling of HC4PtC4H and excess TIPSC4H gives TIPSC4PtC4TIPS (6%), TIPSC4PtC8TIPS (12%), TIPSC8PtC8TIPS (10%), TIPSC4PtC12TIPS (7%), and TIPSC8PtC12TIPS (3%). Although TIPS can be a superior protecting group, it offers no advantage vs triethylsilyl in the preceding reactions. The crystal structures of PtTC8TIPS, PtTC12TIPS, PtFC6TIPS, PtFC8TIPS, TIPSC4PtC4TIPS, TIPSC8PtC8TIPS, TIPSC4PtC12TIPS. and PtFC20PtF are determined. The last is the longest dimetallapolyyne so characterized to date. The 13C NMR chemical shifts of the sp carbon atoms are accurately modeled by DFT calculations.

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INTRODUCTION The quest for polyynes with very long sp carbon chains can be viewed as both a sport and a scholarly endeavor that can help define the properties of macromolecular analogues that remain poorly characterized relative to the most familiar polymeric forms of carbon, graphite (sp2) and diamond (sp3).1 This synthetic challenge has attracted the attention of numerous research groups.2−15 Contemporary efforts have built upon an older literature based largely upon UV/visible characterization.2a,15 Some of these studies have featured alkyl or aryl chain capping endgroups,2,5−7 others trialkylsilyl endgroups,3,4 and still others transition-metal endgroups.8−13 Those for which eicosadecaynes, corresponding to C20 or (CC)10 bridges, have been prepared are depicted in Figure 1. The most successful efforts have featured sterically bulky endgroups, with the current “record” (CC)22 bridge held by a hexakis(tert-butyl)-substituted trityl group (III).7 However, there is a school of thought that electropositive endgroups are also helpful, given the more electronegative nature of sp-hybridized carbon.16 © XXXX American Chemical Society

We have been particularly invested in syntheses of the diplatinum polyynediyl complexes trans,trans-(Ar′)(Ar3P)2Pt(CC)nPt(PAr3)(Ar′) and have extensively explored two series, one with pentafluorophenyl-substituted endgroups (Ar′/Ar = C6F5/p-tol or PtF) and the other with p-tolylsubstituted endgroups (Ar′/Ar = p-tol/p-tol or PtT; VIII).17,18 To date, the isolation of complexes with n as high as 8 (C16, PtF)10 and 14 (C28, PtT)11 have been reported. However, adducts of much longer sp carbon chains have been isolated, as will be described in due course. Most of our published studies have involved triethylsilylsubstituted building blocks such as the readily available alkynes HCCSiEt3 (TESC2H) and H(CC)2SiEt3 (TESC4H).9−11 However, the triisopropylsilyl (Si-i-Pr3) or “TIPS” group sees extensive use in synthetic chemistry19 and appears to be superior to triethylsilyl as an endgroup for the stabilization of very long polyynes.3,4 Furthermore, triisopropylsilyl alkynes Received: June 2, 2019

A

DOI: 10.1021/acs.organomet.9b00368 Organometallics XXXX, XXX, XXX−XXX

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Organometallics

Figure 1. Endgroups previously employed in syntheses of eicosadecaynes Z(CC)10Z or higher polyynes.

PtTC8PtT was detected. The product, and all other new compounds accessed in sufficient quantity, were characterized by microanalysis, NMR (1H, 13C{1H}, 31P{1H}), IR, and UV/ visible spectroscopy, and mass spectrometry, as summarized in the Experimental Section and Tables 1−3. These data fully supported the assigned structures. For example, the 31P{1H} NMR spectra gave only one signal, with 1JPPt values (Table 1) diagnostic of trans phosphine ligands.22 A THF solution of PtTC8TIPS was cooled to 0 °C and treated with wet n-Bu4N+F−. Analogous protocols have been used to generate labile species with PtC8H linkages from related triethylsilyl complexes.10,11 Then an excess of Me3SiCla putative fluoride ion scavengerwas added, followed by a large excess of TIPSC4H. Hay cross-coupling conditions were again applied, and chromatography afforded the target dodecahexaynyl complex PtTC12TIPS as a redbrown solid in 56% yield, as well as a byproduct, TIPSC4PtC12TIPS, in 5% yield. The formulation of the latter was supported by a strong ion in the mass spectrum that would be appropriate for M+ and confirmed by a crystal structure described below. Next, a THF solution of PtTC12TIPS was cooled to −78 °C and an analogous sequence carried out. Earlier studies have established that desilylation becomes more facile as the sp carbon chain is lengthened.11 Indeed, TLC monitoring verified that deprotection was complete within 5 min at −78 °C. However, after oxidation, chromatography afforded PtTC16TIPS as a dark red solid in only 13% yield. Minor amounts of other chromatographically mobile products formed but were not analyzed. Similar sequences were carried out with the previously reported pentafluorophenyl platinum butadiynyl complex trans-(C6F5)(p-tol3P)2Pt(CC)2H (PtFC4H).10 As shown in Scheme 2, Hay cross couplings with 10−20-fold excesses of TIPSC2H or TIPSC4H at 65 °C afforded PtFC6TIPS or PtFC8TIPS in 58% or 23% yield after chromatography.21b In both cases, lesser amounts of the previously described homocoupling product PtFC8PtF were also isolated (10−32% of theory).10 As in Scheme 1, homologues with longer sp carbon chains were sought. Thus, acetone solutions of PtFC6TIPS and PtFC8TIPS were treated with wet n-Bu4N+F− at 0 °C, followed

have been directly employed in oxidative homocoupling sequences.19b Accordingly, we decided to carry out synthetic sequences parallel to those established earlier for triethylsilyl building blocks, as detailed in the narrative below. In the course of these efforts, DFT calculations were employed to help assign the 13C NMR signals associated with the sp carbon chains, and the crystal structure of a diplatinum eicosadecaynediyl complex (Pt(CC)10Pt) has been determined. Only one other polyyne with this sp carbon chain length has been structurally characterized to date.2c

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RESULTS

Syntheses of Triisopropylsilylpolyynyl Complexes. As shown in Scheme 1, the previously reported11b p-tolyl platinum butadiynyl complex trans-(p-tol)(p-tol 3 P) 2 Pt(CC) 2 H (PtTC4H) and a large excess of the diyne TIPSC4H (20 equiv)20 were combined under Hay oxidative cross-coupling conditions (CuCl/TMEDA and O2).21 Column chromatography gave the silylated octatetraynyl complex PtTC8TIPS as a yellow solid in 55% yield. No homocoupling byproduct Scheme 1. Cross Couplings of p-Tolyl Platinum Polyynyl Complexes with Excess H(CC)2Si-i-Pr3 (TIPSC4H)

B


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Organometallics Table 1. IR (Powder Film) and 31P{1H} NMR (121 or 162 MHz, CDCl3) Data complex

IR νCC (cm−1)

Pt C8TIPS PtTC12TIPS PtTC16TIPS PtFC6TIPS PtFC8TIPS PtFC10TIPS PtFC12TIPS PtFC12PtFb PtFC16PtFb PtFC20PtF PtFC24PtF TIPSC4PtC4TIPS TIPSC4PtC8TIPS TIPSC4PtC12TIPS

2124/2079/2058/2000 (m/s/s/m) 2141/2110/2018/1983 (m/w/s/s) 2095/2078/1947 (m/m/s) 2154/2019 (s/s) 2131/2092 (w/m) 2165/2142/2061/2003 (m/w/s/s) 2142/2116/2026/1999 (m/w/s/s) 2127/2088/1992 (m/s/m) 2154/2088/2054/1984 (w/w/s/m) 2158/2142/2053/2023/1988 (w/w/m/s/s) 2138/2115/2065/2003/1980/1918 (m/w/w/s/s/w) 2189/2133 (w/s) 2163/2086/2065/2013 (m/m/m/w) 2135/2024/1996 (m/s/s)

T

P{1H} NMR (δ (ppm)) [1JPPt (Hz)]a

31

19.8 19.7 19.8 17.9 17.8 17.8 17.8 17.7 18.0 17.8 17.8 16.5 16.8 17.0

[2909] [2898] [2894] [2637] [2625] [2616] [2611] [2622] [2609] [2609] [2602] [2544] [2506] [2497]

a

The coupling refers to a satellite (195Pt = 33.8%). bFrom ref 10b.

Table 2.

13

C{1H} NMR Data for sp-Hybridized Carbon Atoms (δ (ppm) [J (Hz)]; CDCl3)

complex T

PtC̲ C [2JCP]

PtCC̲ [3JCP]

C̲ CSi [4JCP]

CC̲ Si [5JCP]

Pt C8TIPS PtTC12TIPS PtTC16TIPS

120.1 [14.9] 123.7a 125.2 [14.4]

95.7 95.3 95.1

91.2 90.1 89.6

81.3 85.0 86.6

PtFC6TIPS PtFC8TIPS PtFC10TIPS PtFC12TIPS TIPSC4PtC4TIPS TIPSC4PtC8TIPS

103.3 106.1 107.8 a 104.2 [15.0] 110.6b [15.1] 103.5c [14.3] 113.6,a,b 103.1c [15.1] 106.5 109.1 a a

95.5 95.2 95.0 94.8 95.9 [2.3] 96.3b [2.0] 94.3c [2.3] 96.7,b [2.1] 93.93c,d [2.8] 95.5 95.0 94.7 94.7

91.9 90.9 90.3 90.0 94.4 [2.3] 90.9b 94.0c,d [2.1] 89.9,b 93.88c,d [2.7]

79.4 82.2 84.0 85.4 72.9 [1.1] 82.1b 73.8c 85.3,b 74.1c [1.3]

TIPSC4PtC12TIPS PtFC12PtFe PtFC16PtFe PtFC20PtF PtFC24PtF

PtCCC̲ through C̲ CCSi or C̲ CCPt 66.9, 58.7, 64.3, 55.1 61.1, 62.4, 65.9, 64.3, 67.4, 58.9, 60.2, 55.3 63.8, 65.0, 66.6, 67.8, 62.3, 61.6, 63.0, 60.1, 62.0, 55.4, 61.2, 58.8 66.5, 56.2 63.7, 59.6, 66.6, 56.3 62.7, 64.7, 66.5, 59.5, 60.4, 56.5 61.4, 62.1, 63.8, 63.2, 65.2, 59.6, 60.7, 56.5 63.8, 59.3, 66.2, 56.3 60.6, 59.5, 63.9, 62.1, 65.2, 61.4, 66.7, 56.4 57.1, 65.7, 61.0, 63.0f 56.8, 64.9, 60.1, 66.7, 61.5, 63.1f 56.5, 65.7, 59.7, 67.2, 60.8, 64.2, 62.0, 63.1f 56.5, 66.1, 59.5, 67.5, 60.6, 64.8, 61.6, 63.9, 62.4, 63.1f

a

This signal was very weak or not observed. bThese chemical shifts are for the C8TIPS or C12TIPS chain. cThese chemical shifts are for the C4TIPS chain. dThese two assignments are tentative and may be reversed. eFrom ref 10b. fThis sequence of chemical shifts should be repeated in reverse to reach that for the C̲ CCPt carbon atom.

Table 3. UV/Visible Data (CH2Cl2) complex PtTC8TIPS PtTC12TIPS PtFC12PtFa PtFC16PtFa PtFC20PtF PtFC24PtF TIPSC4PtC4TIPS TIPSC4PtC8TIPS TIPSC4PtC12TIPS

concn (mol/L)

absorption (nm) [ε (M−1cm−1)] 257 [82600], 271 [74500], 300 [109000], 324 [61200], 354 [8400], 412 [1300] 257 [69000], 270 [71200], 284 [68500], 300 [74200], 316 [95000], 335 [90000], 357 [11800], 368 [127000] 444 [1400], 484 [800] 315 [101000], 336 [267000], 359 [432000] 290 [46000], 306 [42000], 326 [54000], 346 [151000], 369 [397000], 397 [602000] 295 [44000], 310 [46000], 326 [49200], 347 [51000], 373 [94800], 399 [204000], 428 [264000] 308 [73000], 322 [75000], 337 [82000], 353 [83000], 372 [91000], 392 [142000], 422 [243000], 452 [283000] 326 [10800], 346 [29000] 257 [67000], 275 [77600], 292 [89500], 316 [28700], 335 [74100], 356 [18100], 382 [10600], 412 [4700] 269 [58100], 284 [59300], 298 [68200], 315 [83000], 333 [70600], 349 [78600], 371 [108000], 409 [5800], 445 [3200], 484 [1600]

1.01 × 10−5 1.26 × 10−5 1.25 1.25 2.25 1.52 1.52 2.44 1.42

× × × × × × ×

10−6 10−6 10−6 10−6 10−5 10−5 10−5

a

From ref 10b.

homocoupling product was also isolated (PtFC12PtF, 43% of theory). When only a 2-fold excess of TIPSC4H was used in the latter reaction, the yield of PtFC12TIPS dropped to 21%, and the homocoupling product PtFC16PtF was detected (14%). Finally, PtFC10TIPS was similarly treated with wet n-Bu4N+F−,

by Me3SiCl. Then 20-fold excesses of TIPSC4H were added and Hay cross-coupling conditions applied. Chromatographic workups gave the silylated decapentaynyl and dodecahexaynyl complexes PtFC10TIPS and PtFC12TIPS in 58% and 47% yields, respectively. In the former reaction, the diplatinum C


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Organometallics

Scheme 2. Cross Couplings of Pentafluorophenyl Platinum Polyynyl Complexes with Excess HCCSi-i-Pr3 (TIPSC2H) or H(CC)2Si-i-Pr3 (TIPSC4H)

Scheme 3. Oxidative Homocouplings of Platinum Triisopropylsilylpolyynyl Complexes

detected when the substrates were subjected to Hay conditions without the addition of fluoride ion. Accordingly, homocoupling was effected as summarized in Scheme 3, using conditions essentially equivalent to those for heterocoupling. The two shorter chain complexes PtFC12PtF and PtFC16PtF were isolated in >99% and 89% yields, respectively. The results were comparable when these complexes were similarly accessed from the corresponding triethylsilyl precursors PtFC6TES and PtFC8TES (92% and 92%).10 The two longer chain compounds PtFC20PtF and PtFC24PtF were obtained in 86% and 68% yields, respectively, following chromatography on a jacketed column (0 °C). As will be

Me3SiCl, and the two-carbon building block TIPSC2H (30fold excess). However, workup gave PtFC12TIPS in only 5% yield, together with some PtFC20PtF (36% of theory). Syntheses of Diplatinum Polyynediyl Complexes. Next, conversions of the pentafluorophenyl complexes PtFCxTIPS to the diplatinum polyynediyl complexes PtFC2xPtF were investigated. Previous work with the triethylsilyldodecahexaynyl complex trans-(p-tol)(p-tol3 P) 2 Pt(CC) 6 SiEt 3 (PtTC12TES) had demonstrated that protodesilylation and homocoupling to give PtTC24PtT could be effected without fluoride anion, presumably due to an increase in the leaving group ability of the Pt(CC)n moiety with an increase in the sp carbon chain length.11,23 However, no reactions could be D


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Organometallics

by routes similar to those in Scheme 2. When these are subjected to essentially the same homocoupling conditions as in Scheme 3, PtFC20PtF and PtFC24PtF, are isolated in 76% and 96% yields. Hence, there is no overall advantage to conducting homocouplings with triisopropylsilyl as opposed to triethylsilyl precursors. The new diplatinum polyynediyl complexes PtFC20PtF and F Pt C24PtF were isolated as analytically pure yellow-brown and red-brown powders. There was no significant decomposition over a period of several days in the solid state. However, they darkened in solution within a few weeks at room temperature. Poorer results were obtained when workups employed ambient temperature column chromatography. Thermal stability data for most of the new platinum complexes (e.g., TGA, DSC) are summarized in Table s1 in the the Supporting Information. Additional Reactions. In the course of developing the preceding chemistry, a number of exploratory reactions were conducted that yielded well-defined products but did not prove productive with respect to the ultimate target molecules. In the spirit of minimizing the fragmentation of related data, those that afforded complexes with PtCxTIPS linkages that could be crystallographically characterized are included in this report.

Scheme 4. Additional Triisopropylsilylpolyynyl Complexes

detailed in a future publication,24 the triethylsilyl precursors PtFC10TES10 and PtFC12TES can be prepared in good yields

Table 4. Crystallographic Distances (Å) and angles (deg) for Complexes with One sp Carbon Chain PtFC6TIPS Pt−C1 C1C2 C2−C3 C3C4 C4−C5 C5C6 C6−C7 C7C8 C8−C9 C9C10 C10−C11 C11C12 Csp−Si Pt−Cipsob Pt···Si or Pt···Pt sum, bond lengths from Pt1 to Si1 or Pt2 Cipsob−Pt1−C1 Pt1−C1−C2 C1−C2−C3 C2−C3−C4 C3−C4−C5 C4−C5−C6 C5−C6−C7 C6−C7−C8 C7−C8−C9 C8−C9−C10 C9−C10−C11 C10−C11−C12 Csp−Csp−Si av bond angle from Pt1 to Si or Pt2 av π stackingc stacking angled Cipso−Pt1−P−Cipsoe

PtFC8TIPS

PtTC8TIPS

PtTC12TIPS·0.5CH2Cl2

PtFC20PtF·0.8CH2Cl2a

1.973(5) 1.234(7) 1.355(8) 1.216(8) 1.343(8) 1.219(8) 1.348(9) 1.215(9) 1.352(9) 1.210(8) 1.365(8) 1.200(8) 1.843(6) 2.064(5) 17.636 17.873 174.5(2) 176.6(5) 175.5(6) 176.9(7) 176.8(7) 177.4(8) 178.1(9) 179.4(10) 177.5(8) 174.7(7) 175.9(7) 174.8(7) 169.7(6) 176.1

2.100(17)/2.047(19) 1.161(15)/1.154(15) 1.34(2)/1.41(3) 1.182(15)/1.186(15) 1.34(2)/1.34(2) 1.197(15)/1.182(15) 1.37(2)/1.43(3) 1.178(15)/1.197(15) 1.41(3)/1.34(3) 1.175(15)/1.187(15) 1.45(3)

2.006(3) 1.188(4) 1.377(4) 1.215(4) 1.364(4) 1.203(4)

1.994(3) 1.212(4) 1.360(4) 1.221(4) 1.348(4) 1.211(4) 1.372(4) 1.209(5)

2.000(3) 1.220(4) 1.362(4) 1.209(4) 1.355(4) 1.207(4) 1.378(4) 1.202(4)

1.843(3) 2.056(3) 10.167 10.196 179.4(1) 178.6(3) 177.1(3) 177.8(3) 176.9(4) 178.2(4)

1.841(3) 2.054(3) 12.552 12.768 179.01(11) 178.5(3) 178.2(3) 178.5(4) 175.9(4) 176.5(4) 174.7(4) 176.5(4)

1.849(3) 2.058(2) 12.705 12.782 178.6(1) 179.1(2) 179.2(3) 178.4(3)

177.2(3) 177.6 3.62 161.0 −5.07, −6.59

169.8(4) 176.1 4.06 153.8 −7.72, −20.43

177.4(3) 178.7(4)

176.7(3) 177.6

2.108(15)/2.109(15) 28.182 29.05 177.0(9)/178.8(9) 173(2)/175(2) 175(3)/171(3) 171(3)/174(3) 173(3)/174(3) 179(3)/167(3) 179(4)/176(3) 177(3)/178(3) 175(3)/177(3) 176(3)/174(3) 167(3)/173(3)

174.2 3.65/3.65 155.6/156.0 −1.9, 14.5/−5.2, 9.7

a

Values separated by a slash are derived from the second platinum endgroup; for the second value, the atom numbers differ from those in the CIF file. bCipso is the platinum-bound carbon of the aromatic ring. cAverage distance between the centroids of the C6F5 and C6H4R rings. dAngle of the centroids of the three rings in c. eWhen the torsion angle is 0°, the aryl groups are positioned directly above/below each other. E


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Organometallics Table 5. Crystallographic Distances (Å) and Angles (deg) for Complexes with Two sp Carbon Chains Pt−Csp Pt−P C1C2 C2−C3 C3C4 C4−C5 C5C6 C6−C7 C7C8 C8−C9 C9C10 C10−C11 C11C12 Csp−Si Pt···Si sum, bond lengths from Pt to Si Si···Si sum, bond lengths from Si to Si Csp−Pt−Csp Pt−C1−C2 C1−C2−C3 C2−C3−C4 C3−C4−C5 C4−C5−C6 C5−C6−C7 C6−C7−C8 C7−C8−C9 C8−C9−C10 C9−C10−C11 C10−C11−C12 Csp−Csp−Si av Csp−Csp−Csp angle

TIPSC4PtC4TIPS·4CH2Cl2

TIPSC8PtC8TIPS

TIPSC4PtC12TIPS·0.5CH2Cl2

1.985(2) 2.3113(6) 1.216(4) 1.373(4) 1.213(4)

1.992(4) 2.3297(10) 1.210(5) 1.375(6) 1.207(6) 1.353(6) 1.216(6) 1.369(6) 1.209(6)

1.834(3) 7.607 7.621 15.214 15.242 180.00(7) 178.0(2) 176.8(3) 179.3(3)

1.857(5) 12.613 12.788 25.226 25.576 180.0(3) 173.3(4) 174.3(5) 178.0(5) 176.8(5) 176.6(5) 176.1(5) 178.3(6)

175.2(3) 178.1

173.0(5) 176.7

1.974(3)a/1.991(3)b 2.3181(8)a/2.3248(8)b 1.224(4)a/1.213(5)b 1.352(4)a/1.373(5)b 1.213(5)a/1.213(5)b 1.352(5) 1.209(5) 1.344(5) 1.212(5) 1.355(6) 1.203(6) 1.377(6) 1.199(6) 1.843(4)a/1.829(4)b 17.606a/7.589b 17.857a/7.619b 24.812 25.476 179.44(13) 178.4(3)a/175.6(3)b 175.6(4)a/176.7(4)b 177.2(4)a/177.2(4)b 172.0(4) 173.7(4) 176.3(4) 177.6(5) 177.0(6) 178.9(8) 179.1(8) 179.7(9) 178.8(4)a/175.6(4)b 176.7a/177.0b

For the C12 sp carbon chain. bFor the C4 sp carbon chain; the atom numbers in the CIF file are C21−C24.

a

chloride complexes, the corresponding terminal alkynes, and a copper(I) halide catalyst in the presence of the base HNEt2. As shown in Scheme 4 (top), when this recipe was applied to the dichloride trans-(p-tol3P)2PtCl225 and excess TIPSC4H, the adduct TIPSC4PtC4TIPS could be isolated in 95% yield after workup. Several 2-fold sp carbon chain extension reactions were subsequently investigated, and these results are detailed elsewhere.26 A related type of 2-fold carbon chain extension is depicted in Scheme 4 (bottom). This oxidative cross coupling of the bis(butadiynyl) complex HC4PtC4H27 and excess TIPSC4H afforded a number of products in low yields, five of which could be at least partially characterized. These included the target complex TIPSC8PtC8TIPS (10%), derived from a single addition to each butadiynyl ligand, and two species that had been independently synthesized above (TIPSC4PtC4TIPS, 6%; TIPSC4PtC12TIPS, 7%). The last two, and the most abundant of the remaining products (TIPSC4PtC8TIPS, 12%; TIPSC8PtC12TIPS, 3%), seemingly require a σ-bond metathesis step (C4H/C4TIPS exchange). When solid samples of any of the complexes with two trans-disposed sp carbon chains were irradiated with 365 nm light, they luminesced. Structural Data. Efforts were made to crystallographically characterize as many of the preceding complexes as possible. Suitable single crystals of the triisopropylsilylpolyynyl complexes PtTC8TIPS, PtTC12TIPS, PtFC6TIPS, PtFC8TIPS,

Figure 2. Thermal ellipsoid plots (50% probability) of (top) PtTC8TIPS and (bottom) PtTC12TIPS.

The platinum alkynyl complexes used to initiate the preceding chemistry are generally prepared from platinum F


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Organometallics

shifts (NICS) for organic conjugated polyynes, which revealed several unanticipated trends.28 Importantly, excellent agreement between computed and experimental 13C NMR chemical shifts was realized. Given the projected need for 13C NMR assignments for higher homologues of various complexes in this study, we sought to benchmark our methodology versus the data for the adducts in Table 2particularly the signal rich species with unsymmetrically substituted sp carbon chains. Thus, 13C NMR chemical shifts were computed as described previously.28 Results for two representative complexes are depicted graphically in Figure 7. The agreement between the computed and observed signals is striking, although it must be kept in mind that there are error bars on both the experimental and computational sides.29 Thus, pairwise swaps involving closely spaced experimental peaks remain possible (e.g., signals assigned to C3 and C4 or C3 and C8 in TIPSC4PtC12TIPS in Figure 7 (right)). Similar representations for the remaining complexes in Table 2 are provided in the Supporting Information, together with the computed chemical shifts (Table s3). In principle, the signals of carbon atoms near the termini can exhibit couplings to 31P (100% natural abundance), 195Pt (33.8% natural abundance), or 29Si (4.67% natural abundance), all of which have nuclear spins (I) of 1/2. The phosphorus couplings would normally give triplets (two ptol3P ligands), and the platinum and silicon couplings doublets (as satellites). As is seen in Table 2, the phosphorus couplings of the PtC̲ C̲ signals were not always resolved, and some contributing factors are analyzed in the Discussion. Furthermore, no platinum or silicon satellites were observed, although these have sometimes been detected with triethylsilyl analogues.10b,26 With the more intense SiC̲ H(CH3)2 signals of Pt T C 8 TIPS, Pt T C 16 TIPS, TIPSC 4 PtC 8 TIPS, and TIPSC4PtC12TIPS, the silicon couplings could be observed (1JCSi = 56.4−56.9 Hz). In order to establish a baseline reference for all of these types of couplings, a 13C{1H} NMR spectrum of PtTC8TIPS was recorded for an extended period in a cryoprobe. As shown in Figure 8, phosphorus coupling was observed for the PtC̲ C signal (2JCP 14.8 Hz), but not the PtCC̲ signal, which had a width at half-height (2.4 Hz) similar to the 3JCP values exhibited by several of the complexes in Table 2 (2.0−2.8 Hz). Large platinum couplings were easily detected for the PtC̲ C̲ signals (1JCPt 865.0 Hz; 2JCPt 212.5 Hz). Silicon coupling was observed for the CC̲ Si signal (1JCSi 75.0 Hz), and the C̲  CSi signal appeared to exhibit a smaller less distinct coupling

TIPSC4PtC12TIPS, TIPSC4PtC4TIPS, and TIPSC8PtC8TIPS (or CH2Cl2 solvates thereof) could be obtained. The structures were solved as outlined in Table s2 and the Experimental Section. Key metrical parameters are provided in Tables 4 and 5. Thermal ellipsoid plots showing the molecular structures are depicted in Figures 2−5.

Figure 3. Thermal ellipsoid plots (50% probability) of (top) PtFC6TIPS and (bottom) PtFC8TIPS.

A solvate of the eicosadecaynediyl complex PtFC20PtF could also be crystallized, and the molecular structure is depicted in Figure 6. This represents the longest dimetallapolyynediyl complex crystallographically characterized to date. The structure of only one other polyyne with an equal sp carbon length, t-Bu(CC)10-t-Bu, has so far been determined.2c The platinum−platinum distance is 28.182 Å, and additional analyses of all of these crystal structures are provided in the Discussion. Computational and Cryoprobe 13C NMR Data. We recently computed the first nucleus-independent chemical

Figure 4. Thermal ellipsoid plot (50% probability) of TIPSC4PtC12TIPS. G


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Organometallics

Figure 5. Thermal ellipsoid plot (50% probability) of (top) TIPSC4PtC4TIPS and (bottom) TIPSC8PtC8TIPS, both of which feature an inversion center at the platinum atom.

Figure 6. Thermal ellipsoid plot (50% probability) of PtFC20PtF.

to involve the introduction of a C4TIPS moiety by σ-bond metathesis. The proportion of such nonredox products seems to increase when oxygen purging is not maintained throughout the reaction.24,26 The formation of complexes with PtC12TIPS linkages in Scheme 4 seemingly arise via partial protodesilylation of an initially formed PtC8TIPS species, followed by a second oxidative cross coupling with TIPSC4H. Such “spontaneous” protodesilylations of PtC10TES systems occur even more readily11 and can be useful in optimizing oxidative homocoupling conditions. As noted by a reviewer, some of these side reactions might be avoided with other types of coppercatalyzed alkyne/alkyne couplings, such as the Cadiot−

(2JCSi = 11 Hz; tentative assignment). Similar nJCSi values have been found with silylated butadiynes.30

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DISCUSSION The reactions in Schemes 1−3 establish that complexes with PtCxTIPS linkages generally duplicate the chemistry reported for PtCxTES analogues earlier.10,11 However, there are no apparent preparative advantages. While oxidative homocouplings proceed cleanly (Scheme 3), oxidative cross couplings areas seen in the triethylsilyl series24often accompanied by side reactions. Examples include the formation of TIPSC4PtC12TIPS in Scheme 1 or products of the formula TIPSC4PtCxTIPS in Scheme 4 (bottom), all of which appear H


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Organometallics

Figure 7. Correlation of 13C NMR chemical shifts computed for the dodecahexaynediyl (C12) segments of PtTC12TIPS and TIPSC4PtC12TIPS (blue diamonds) versus those observed experimentally (open circles).

Figure 8. 13C{1H} NMR spectrum of the PtCC and CCSi segments of PtTC8TIPS (125 MHz, CDCl3, cryoprobe).

The crystal structure of PtFC20PtF·0.8CH2Cl2 can be compared to those of three lower homologues, PtFC16PtF· 10C6H6, PtFC12PtF·4C6H6·EtOH, and PtFC8PtF·toluene.10,33 As is usually the case, the esd values associated with the Csp− Csp bond lengths are too large for meaningful comparisons to be made, either between or within molecules. However, a number of trends have been identified computationally.34 These include a 0.4% contraction of the Pt−Csp bond as x is increased from 4 to 26. Curiously, the experimental trend is in the opposite direction, with the Pt−Csp bonds lengthening from 1.951(5) Å (x = 8) to 1.972(6)−1.983(5) Å (x = 12, inequivalent termini), 1.981(2) Å (x = 16), and 2.047(19)− 2.100(17) Å (x = 20, inequivalent termini). However, the quality of the data for PtFC20PtF·0.8CH2Cl2 is not as good, as reflected by the higher R1 and wR2 values in Table s2 (0.0886, 0.1665) and the abnormally short PtC̲ C̲ bonds (1.161(15), 1.154(15) Å). Interestingly, PtFC20PtF crystallizes with only 0.8 solvent molecule per molecule of complex. The crystal lattices of the

Chodkiewicz reaction of terminal and halogenated alkynes. 5,9,12,15,31 Also, the conditions used to prepare TIPSC4PtC4TIPS in Scheme 4 (top) promote phosphine ligand scrambling,32 although that remains invisible for the complexes in this paper (all of which contain only p-tol3P). The diplatinum polyynediyl complexes PtFC20PtF and F Pt C24PtF feature the longest sp carbon chains prepared in this series to date. As found with all of the extended polyynes represented in Figure 1, increasing numbers of progressively more intense and red-shifted UV/visible bands are observed (Table 3). The numbers and maximum intensities of the IR νCC bands also increase with chain length (Table 1). These trends closely parallel those detailed for PtTC20PtT and PtTC24PtT in earlier papers,11 for which time-dependent DFT calculations34 have enabled assignments of electronic transitions. Hence, readers are referred to these earlier works for additional analyses. These themes will be revisited in future papers that feature still higher homologues.24 I


Article

Organometallics lower homologues PtFC16PtF and PtFC12PtF incorporate 10 and 5 solvent molecules, respectively. This suggests that, for some reason, PtFC20PtF is able to pack more efficiently with a smaller void volume. Accordingly, the density (ρcalc) of PtFC20PtF·0.8CH2Cl2 is greater than that of PtFC16PtF· 10C6H6 (1.508 vs 1.313 Mg/m3), although less than that of PtFC12PtF·4C6H6 EtOH (1.659 Mg/m3). Furthermore, the closest intermolecular C sp ···C sp contact in Pt F C 20 Pt F · 0.8CH2Cl2 (6.464 Å) is much shorter than those in PtFC12PtF·4C6H6·EtOH (7.536 Å) and PtFC16PtF·10C6H6 (8.786 Å). In all of these structures, the P−Pt−P vectors of the two endgroups are essentially parallel. This can be quantified by the angle defined by the two (P−Pt−P)Pt planes, which is 6.3° for PtFC20PtF and 0−18.4° for the lower homologues.10,34 There are no obvious trends associated with the PtCxPt angles in the diplatinum or monoplatinum complexes, but as analyzed elsewhere,33 the small individual deviations from 180° can be arranged in a number of patterns. This gives rise to various bow- and S-shaped motifs that are evident in Figures 2−6. A bow shape will generate the greatest contraction in the Pt···Si or Pt···Pt distance relative to the sum of the intervening bond lengths (Tables 4 and 5). Tykwinski has structurally characterized a series of bis(TIPS) polyynes TIPSCxTIPS (x = 8, 10, 12, 16).4a His Csp−Si bond lengths (1.845(4)− 1.8534(14) Å; average 1.850) are similar to those of the PtCxTIPS species in Table 4 (1.841(3)−1.849(3) Å; average 1.845 Å) and TIPSCxPtCx′TIPS species in Table 5 (1.829(4)− 1.857(5) Å; average 1.841 Å). As easily seen in Figures 3 and 6, the pentafluorophenyl ligands in PtFCxTIPS and PtFC20PtF·0.8CH2Cl2 engage in stacking interactions with two p-tolyl groups, one from each of the phosphine ligands. This has been found in virtually all complexes in this series,17,18,32b,35,36 and can be quantified in various ways as summarized in Table 4: (1) the average distances between the centroids of the C6F5 and p-tolyl groups (3.62 to 4.06 Å), (2) the angle defined by the three centroids (154−161°; 180° for an idealized stack), and (3) the two Cipso−P−Pt−Cipso torsion angles on each terminus (±1.9 to ±20.4°; 0° for maximum π overlap). These have been ascribed to attractive C6F5/C6H5 π interactions, which are well documented in a number of molecules.37 Prior to probing of the 13C NMR properties of the title complexes by DFT computations, as exemplified in Figure 7, some signal assignments were possible. On the basis of all of our previous studies of platinum polyynyl complexes, the PtC̲ C resonance is always the farthest downfield, although as illustrated in Table 2 the nature of the trans ligand significantly affects the chemical shift (103.1−125.2 ppm). These signals shift downfield when the sp carbon chain is lengthened, which is one of the criteria that allow the PtC4TIPS segments to be differentiated from the PtC8TIPS or PtC12TIPS segments in certain complexes (Table 2). The PtC̲ C signals are furthermore coupled to 31P (giving a triplet) and 195Pt (giving a doublet of satellites). As shown in Table 2, the 2JCP values range from 14.3 to 15.1 Hz but are not always detected or resolved. Similarly, platinum couplings can be difficult to observe in the absence of special measures, such as taken with Figure 8. Nonetheless, 1JCPt and 2JCPt values of 650−875 and 212−238 Hz have been observed for the related complexes PtTC4H, PtTC6H, PtTC6TES, and PtTC12PtT,11b,c in good agreement with Figure 8. The sp carbon atoms that are remote from the metal endgroups are at most very weakly

coupled to phosphorus and platinum; therefore, they give narrower and more intense signals. As shown in Table 2, the PtCC̲ signals fall into a narrower range (93.9−96.7 ppm) and shift very slightly upfield with increasing chain length. In optimal cases, small phosphorus couplings can be detected (3JCP = 2.0−2.8 Hz), but the signal/ noise ratio is compromised by the platinum couplings as noted above. As found with all extended polyynes in Figure 1, the signals for the sp carbon atoms that are more than two atoms removed from an endgroup fall into a relatively narrow upfield range (55.3−67.8 ppm in Table 2, or as seen graphically in Figure 7). For all complexes with PtCxSi linkages (x ≥ 6) that we have characterized, there are two additional resonances that are (1) upfield of the PtC̲ C̲ signals and (2) downfield of the signals of the carbon atoms that are more than two atoms removed from an endgroup. These are clearly associated with the C̲  C̲ Si moiety. With very well resolved spectra of the triethylsilylpolyynyl complexes PtFCxTES (x = 8, 10, 12), the upfield signals exhibit 1JCSi values of 73.0−75.9 Hz,26 in accord with the 75.0 Hz found for PtTC8TIPS in Figure 8. Hence, these are assigned to the CC̲ Si carbon atoms, in agreement with similar 1JCSi values of organic analogs.30 In some silylated polyynes, satellites can be detected for the more downfield C̲ CSi signals, but the 2JCSi values are much lower (10.8−16.1 Hz).26,30 The preceding 13C NMR features and DFT results have been emphasized, as it has become apparent that the assignments of C̲ C̲ Si signals have been reversed in two previous full papers.10b,11b Also, Tykwinski has synthesized bis(silylated) polyynes in which selected carbon atoms have been 13C-labeled.4a The coupling constant patterns in a mixture of TIPSCC13C̲ CCCTMS and TIPSC CC13C̲ CCTMS similarly confirm the downfield/upfield relationship of the C̲ C̲ Si signals. In summary, this study has detailed the use of triisopropylsilyl alkynes as building blocks for the syntheses of unusual and surprisingly stable platinum triisopropylsilylpolyynyl and diplatinum polyynediyl complexes. One consequence is that the endgroup PtF is now a member of the family represented in Figure 1. The spectroscopic properties of new complexesparticularly the 13C NMR signals associated with the sp carbon chains, which can be fully assigned with the help of DFT calculationsprovide valuable baseline data for future studies.24 The crystallographic results significantly add to the growing body of structural data for polyynes,33 especially with respect to compounds with TIPS endgroups and/or longer sp carbon chains.

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EXPERIMENTAL SECTION

General Considerations. All reactions were conducted under dry inert atmospheres using conventional Schlenk techniques, but workups were carried out in air. Chemicals were treated as follows: acetone, distilled from K2CO3; ethyl acetate, hexanes, THF, toluene, CH2Cl2 (5 × ACS grade), HNEt2, distilled from CaH2; methanol, ethanol, distilled (rotary evaporation) or used as received; Me3SiCl (≥98%, Alfa Aesar or Acros), HCCSi-i-Pr3 (TIPSC2H; 97%, Acros), n-Bu4N+F− (1.0 M in THF, 5 wt % water, Acros), CuI (99.999%, Alfa Aesar), CuCl (≥99.99%, Alfa Aesar or Aldrich), TMEDA (99%, Acros), silica gel (Acros, Fluoroflash or 60 M Macherey-Nagel), neutral alumina (Brockmann I, for chromatography, 50−200 μm, Acros), used as received. NMR spectra were obtained on standard 300−500 MHz spectrometers and referenced as follows (δ/ppm): 1H, residual CHCl3 (7.24); 13C{1H}, internal J


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Organometallics

NMR (δ/ppm, CDCl3): 1H (300 MHz)39 7.30−7.24 (m, 12H, o to P), 7.02 (d, 3JHH = 7.7 Hz, 12H, m to P), 6.26 (d, 3JHH = 7.8 Hz, 2H, o to Pt), 6.07 (d, 3JHH = 7.7 Hz, 2H, m to Pt), 2.32 (s, 18H, CH3 p to P), 1.94 (s, 3H, CH3 p to Pt), 1.06 (apparent s, 21H, CH(CH3)2); 13 C{1H} (101 MHz)40,41 149.4 (t, 2JCP = 9.9 Hz, i to Pt), 140.2 (s, p to P), 138.7 (s, o to Pt), 134.6 (virtual t, 2JCP = 6.1 Hz, o to P), 129.8 (s, m to Pt), 128.5 (virtual t, 3JCP = 5.3 Hz, m to P), 127.9 (s, p to Pt), 127.6 (virtual t, 1JCP = 29.7 Hz, i to P), 123.7 (s, PtC̲ C),44 95.3 (s, PtCC̲ ), 90.1 (s, C̲ CSi), 85.0 (s, CC̲ Si), 67.4, 65.9, 64.3, 62.4, 61.1, 60.2, 58.9, 55.3 (8 s, PtCC(C̲ C̲ )4; see Table s3), 21.3 (s, CH3 p to P), 20.5 (s, CH3 p to Pt), 18.4 (s, CH(C̲ H3)2), 11.2 (s, SiCH); 31P{1H}, Table 1. IR: Table 1. UV/vis: Table 3. MS:43 1195 ([M]+, 3%), 1104 ([M − tol]+, 3%), 894 ([M − C12TIPS − 1]+, 17%), 803 ([(tol3P)2Pt]+, 100%). TIPSC4PtC12TIPS. The sample slightly darkened at 105 °C, liquefied and turned black at 147 °C (capillary); DSC and TGA, Table s1. Anal. Calcd for C76H84P2PtSi2: C, 69.64; H, 6.46; found: C, 69.90; H, 7.23. NMR (δ/ppm, CDCl3): 1H (300 MHz)39 7.52−7.46 (m, 12H, o to P), 7.16 (d, 3JHH = 7.8 Hz, 12H, m to P), 2.35 (s, 18H, CH3 p to P), 1.05, 0.93 (2 m, 42H, Pt(CC)2SiCH(CH3)2 and (CC)6SiCH(CH3)2); 13C{1H} (101 MHz)40,41 141.0 (s, p to P), 134.8 (virtual t, 2JCP = 6.3 Hz, o to P), 128.8 (virtual t, 3JCP = 5.7 Hz, m to P), 127.0 (virtual t, 1JCP = 30.8 Hz, i to P), 113.6 (s, PtC̲  C(CC)5Si),44 103.1 (t, 2JCP = 15.1 Hz, PtC̲ CCCSi), 96.7 (t, 3 JCP = 2.1 Hz, PtCC̲ (CC)5Si), 93.93, 93.88 (2 t, nJCP = 2.8 and 2.7 Hz, PtCC̲ CCSi and PtCCC̲ CSi), 89.9 (s, Pt(C C)5C̲ CSi), 85.3 (s, Pt(CC)5CC̲ Si), 74.1 (t, 5JCP = 1.3 Hz, PtCCCC̲ Si), 66.7, 65.2, 63.9, 62.1, 61.4, 60.6, 59.5, 56.4 (8 s, PtCC(C̲ C̲ )4; see Table s3), 21.4 (s, CH3 p to P), 18.5, 18.4 (2 s, (CC)2SiCH(C̲ H3)2 and Pt(CC)6SiCH(C̲ H3)2), 11.3 (s, 1JCSi = 56.6 Hz, SiCH),30,42 11.2 (s, 1JCSi = 56.7 Hz, Si′CH);30,42 31P{1H}, Table 1. IR: Table 1. UV/vis: Table 3. MS43 1310 ([M]+, 11%), 1104 ([M − C4TIPS]+, 8%), 1008 ([M − C12TIPS]+, 11%), 802 ([(tol3P)2Pt − 1]+, 100%). trans-(p-tol)(p-tol3P)2Pt(CC)8Si-i-Pr3 (PtTC16TIPS). A threeneck round-bottom flask was fitted with a gas dispersion tube, charged with PtTC12TIPS (0.248 g, 0.207 mmol) and THF (40 mL), and cooled to −78 °C. Then wet n-Bu4N+F− (1.0 M in THF, 5 wt % water, 0.15 mL, 0.15 mmol) was added with stirring. After 5 min (TLC showed no remaining educt), Me3SiCl (0.10 mL, 0.78 mmol) and TIPSC4H (0.838 g, 4.060 mmol)20 were added and oxygen was bubbled through the mixture with stirring. Then a suspension generated by stirring CuCl (0.287 g, 2.90 mmol), acetone (8 mL), and TMEDA (0.80 mL, 0.64 g, 5.2 mmol) for 0.5 h was added. After 20 min, cold hexanes (80 mL) were added. The dark green suspension was filtered through silica gel (2.5 × 10 cm pad, packed in 1/1 v/v acetone/hexanes), which was rinsed (1/1 v/v acetone/ hexanes) until the filtrate was colorless. The solvent was removed from the filtrate by rotary evaporation (20 °C). The residue was chromatographed on silica gel (2.5 × 45 cm column, packed in hexanes, eluted first with hexanes and then a toluene → 2/5 v/v toluene/hexanes gradient). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum to give PtTC16TIPS as a dark red solid (0.032 g, 0.026 mmol, 13%). NMR (δ/ppm, CDCl3): 1H (300 MHz)39 7.30−7.25 (m, 12H, o to P), 7.02 (d, 3JHH = 7.8 Hz, 12H, m to P), 6.26 (d, 3JHH = 7.8 Hz, 2H, o to Pt), 6.08 (d, 3JHH = 7.6 Hz, 2H, m to Pt), 2.32 (s, 18H, CH3 p to P), 1.94 (s, 3H, CH3 p to Pt), 1.06 (apparent s, 21H, CH(CH3)2); 13C{1H} (100 MHz)40,41 149.1 (t, 2JCP = 6.2 Hz, i to Pt), 140.2 (s, p to P), 138.6 (br s, o to Pt), 134.5 (virtual t, 2JCP = 6.2 Hz, o to P), 129.8 (s, p to Pt), 128.5 (virtual t, 3JCP = 5.5 Hz, m to P), 127.7 (s, m to Pt), 127.4 (virtual t, 1JCP = 29.6 Hz, i to P), 125.2 (t, 2 JCP = 14.4 Hz, PtC̲ C), 95.1 (s, PtCC̲ ), 89.6 (s, C̲ CSi), 86.6 (s, CC̲ Si), 67.8, 66.6, 65.0, 63.8, 63.0, 62.3, 62.0, 61.6, 61.2, 60.1, 58.8, 55.4 (12 s, PtCC(C̲ C̲ )6; see Table s3), 21.4 (s, CH3 p to P), 20.6 (s, CH3 p to Pt), 18.5 (s, CH(C̲ H3)2), 11.2 (s, 1JCSi = 56.9 Hz, SiCH);30,42 31P{1H}, Table 1. IR: Table 1. trans-(C6F5)(p-tol3P)2Pt(CC)3Si-i-Pr3 (PtFC6TIPS). A threeneck flask was charged with PtFC4H (0.498 g, 0.488 mmol),10b TIPSC2H (2.19 mL, 9.76 mmol), and acetone (50 mL) and fitted

CDCl3 (77.0); 31P{1H}, external H3PO4 (0.00). The other instrumentation utilized has been itemized in previous full papers in this series.27b,38 trans-(p-tol)(p-tol3P)2Pt(CC)4Si-i-Pr3 (PtTC8TIPS). A threeneck round-bottom flask was fitted with a gas dispersion tube and a condenser and charged with PtTC4H (0.496 g, 0.525 mmol)11b and acetone (90 mL). Then oxygen was bubbled through the mixture with stirring and H(CC)2Si-i-Pr3 (TIPSC4H; 2.187 g, 10.60 mmol)20 was added, followed by a suspension generated by stirring CuCl (0.359 g, 3.63 mmol), acetone (10 mL), and TMEDA (1.0 mL, 0.80 g, 6.7 mmol) for 0.5 h. After 2 h (TLC showed no remaining educt),21b the solvent was removed from the dark green mixture by rotary evaporation. The residue was chromatographed on silica gel (3.5 × 30 cm column, packed in hexanes, eluted with hexanes, and then a CH2Cl2 → 3/2 v/v CH2Cl2/hexanes gradient). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum to give PtTC8TIPS as a yellow solid (0.329 g, 0.287 mmol, 55%). The sample slightly darkened at 96 °C, liquefied at 110 °C, (red-brown), and turned black at 147 °C (capillary); DSC and TGA, Table s1. Anal. Calcd for C66H70P2PtSi: C, 69.03; H, 6.14. Found: C, 68.83; H, 6.19. NMR (δ/ppm, CDCl3): 1 H (300 MHz)39 7.31−7.27 (m, 12H, o to P), 7.01 (d, 3JHH = 7.5 Hz, 12H, m to P), 6.26 (d, 3JHH = 7.7 Hz, 2H, o to Pt), 6.05 (d, 3JHH = 7.9 Hz, 2H, m to Pt), 2.31 (s, 18H, CH3 p to P), 1.93 (s, 3H, CH3 p to Pt), 1.03 (apparent s, 21H, CH(CH3)2); 13C{1H} (75 MHz)40,41 149.7 (t, 2JCP = 10.0 Hz, i to Pt), 140.0 (s, p to P), 138.7 (t, 3JCP = 2.4 Hz, o to Pt), 134.5 (virtual t, 2JCP = 6.2 Hz, o to P), 129.5 (t, 4JCP = 1.3 Hz, m to Pt), 128.4 (virtual t, 3JCP = 5.5 Hz, m to P), 127.7 (s, p to Pt), 127.6 (virtual t, 1JCP = 29.5 Hz, i to P), 120.1 (t, 2JCP = 14.9 Hz, PtC̲ C), 95.7 (s, PtCC̲ ), 91.2 (s, C̲ CSi), 81.3 (s, CC̲ Si), 66.9, 64.3, 58.7, 55.1 (4 s, PtCC(C̲ C̲ )2; see Table s3), 21.4 (s, CH3 p to P), 20.6 (s, CH3 p to Pt), 18.5 (s, CH(C̲ H3)2), 11.3 (s, 1JCSi = 56.8 Hz, SiCH);30,42 13C{1H} (125 MHz, cryoprobe)40,41 149.8 (t, 2JCP = 10.0 Hz, 1JCPt = 631.3 Hz,42 i to Pt), 140.1 (s, p to P), 138.9 (t, 3JCP = 2.3 Hz, o to Pt), 134.7 (virtual t, 2JCP = 6.3 Hz, o to P), 129.7 (s, m to Pt), 128.6 (virtual t, 3JCP = 5.5 Hz, m to P), 127.94 (s, p to Pt), 127.88 (virtual t, 1JCP = 29.8 Hz, i to P), 120.3 (t, 2JCP = 14.8 Hz, 1JCPt = 865 Hz,42 PtC̲ C), 95.9 (s, 2JCPt = 212 Hz,42 PtCC̲ ), 91.5 (s, 2JCSi = 11 Hz (tentative),42 C̲ CSi), 81.5 (s, 1JCSi = 75 Hz,42 CC̲ Si), 67.2, 64.6, 58.9, 55.3 (4 s, PtCC(C̲ C̲ )2), 21.5 (s, CH3 p to P), 20.7 (s, CH3 p to Pt), 18.7 (s, CH(C̲ H3)2), 11.5 (s, 1JCSi = 56.3 Hz,42 SiCH); 31 1 P{ H}, Table 1. IR: Table 1. UV/vis: Table 3. MS:43 1147 ([M − 1]+, 5%), 1056 ([M − tol]+, 5%), 894 ([M − C8TIPS − 1]+, 20%), 803 ([(tol3P)2Pt]+, 100%). trans-(p-tol)(p-tol3P)2Pt(CC)6Si-i-Pr3 (PtTC12TIPS). A threeneck round-bottom flask was fitted with a gas dispersion tube, charged with PtTC8TIPS (0.301 g, 0.263 mmol) and THF (40 mL), and cooled to 0 °C. Then wet n-Bu4N+F− (1.0 M in THF, 5 wt % water, 0.20 mL, 0.20 mmol) was added with stirring. After 30 min (TLC showed no remaining educt), Me3SiCl (0.15 mL, 1.2 mmol), acetone (40 mL), and TIPSC4H (1.115 g, 5.402 mmol)20 were sequentially added, and oxygen was bubbled through the mixture with stirring. Then a suspension generated by stirring CuCl (0.179 g, 1.81 mmol), acetone (5 mL), and TMEDA (0.50 mL, 0.40 g, 3.3 mmol) for 0.5 h was added. After 40 min, hexanes (100 mL) was added. The dark green suspension was filtered through silica gel (2.5 × 10 cm pad, packed in 1/1 v/v acetone/hexanes), which was rinsed (1/1 v/v acetone/hexanes) until the filtrate became colorless. The solvent was removed from the filtrate by rotary evaporation (25 °C). The residue was chromatographed on silica gel (3.5 × 45 cm column, packed in hexanes, eluted first with hexanes and then a toluene → 3/7 v/v toluene/hexanes gradient). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum to give PtTC12TIPS as a red-brown solid (0.176 g, 0.147 mmol, 56%) and trans-i-Pr3Si(CC)2(p-tol3P)2Pt(CC)6Si-i-Pr3 (TIPSC4PtC12TIPS) as an orange-brown solid (0.016 g, 0.012 mmol, 5%), which luminesced on irradiation at 365 nm. PtTC12TIPS. The sample slightly darkened at 85 °C, liquefied and turned black at 116 °C (capillary); DSC and TGA, Table s1. Anal. Calcd for C70H70P2PtSi: C, 70.27; H, 5.90. Found: C, 69.95; H, 6.19. K


Article

Organometallics with a gas dispersion tube and a condenser. A Schlenk flask was charged with CuCl (0.242 g, 2.44 mmol) and acetone (10 mL), and TMEDA (0.736 mL, 0.570 g, 4.88 mmol) was added with stirring. After 0.5 h, stirring was halted, and a green solid separated from a blue supernatant. Then oxygen was bubbled through the three-neck flask with stirring, and the solution was heated to 65 °C. The blue supernatant was added in portions. After 3.5 h, the solvent was removed by rotary evaporation. The residue was extracted with toluene (3 × 50 mL). The extracts were passed through alumina (10 × 2 cm column). The solvent was removed by rotary evaporation. The residue was chromatographed on silica gel (45 × 3 cm column, eluted with 5/95 v/v ethyl acetate/hexanes). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum to give PtFC6TIPS as a pale yellow powder (0.339 g, 0.283 mmol, 58%). A second band eluted with 20/80 v/v ethyl acetate/hexanes gave PtFC8PtF as a yellow powder (0.159 g, 0.078 mmol, 32% of theory).10 The PtFC6TIPS slightly darkened at 215 °C, slowly turned black with further heating, and liquefied at 240 °C (capillary); DSC and TGA, Table S1. Anal. Calcd for C63H63F5P2PtSi: C, 63.04; H, 5.29. Found: C 62.66; H 5.64. NMR (δ/ppm, CDCl3): 1H (400 MHz) 7.53−7.45 (m, 12H, o to P),39 7.12 (d, 3JHH = 7.8 Hz, 12H, m to P),39 2.36 (s, 18H, CH3 p to P), 1.01 (asym. apparent s, 21H, CH(CH3)3); 13C {1H} (101 MHz)40,41,45 140.8 (s, p to P), 134.2 (virtual t, 2JCP = 6.5 Hz, o to P), 128.6 (virtual t, 3JCP = 5.3 Hz, m to P), 127.0 (virtual t, 1JCP = 30.5 Hz, i to P), 103.3 (s, PtC̲ C), 95.5 (s, PtCC̲ ), 91.9 (s, C̲ CSi), 79.4 (s, CC̲ Si), 66.5 (s, PtCCC̲ ), 56.2 (s, PtCCCC̲ ), 21.3 (s, CH3 p to P), 18.5 (s, CH(C̲ H3)3), 11.3 (s, C̲ H(CH3)3; 31P{1H}, Table 1. IR: Table 1. MS:43 1200 ([M]+, 25%), 970 ([(C6F5)Pt(tol3P)2]+, 80%), 802 [(tol3P)2Pt − 1]+, 90%). trans-(C6F5)(p-tol3P)2Pt(CC)4Si-i-Pr3 (PtFC8TIPS). A threeneck flask was charged with PtFC4H (1.733 g, 1.699 mmol)10b and acetone (180 mL), and fitted with a gas dispersion tube and a condenser. A Schlenk flask was charged with CuCl (0.178 g, 1.798 mmol) and acetone (20 mL), and TMEDA (1.28 mL, 1.00 g, 8.49 mmol) was added with stirring. After 0.5 h, stirring was halted, and a green solid separated from a blue supernatant. Then oxygen was bubbled through the three-neck flask with stirring, and the solution was heated to 65 °C. After 10 min, TIPSC4H (3.504 g, 16.99 mmol)20 was added, followed by the blue supernatant in portions. After 2.5 h, the solvent was removed by rotary evaporation. The residue was extracted with toluene (3 × 50 mL). The extracts were passed through alumina (10 × 2 cm column). The solvent was removed by rotary evaporation. The residue was chromatographed on silica gel (45 × 4.5 cm column, eluted with 20/80 v/v ethyl acetate/ hexanes). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum to give PtFC8TIPS as a pale yellow powder (0.478 g, 0.391 mmol, 23%). A second band eluted with 20/80 v/v ethyl acetate/hexanes and gave PtFC8PtF as a yellow powder (0.173 g, 0.0849 mmol, 10% of theory).10 PtFC8TIPS melted at 176 °C (capillary); DSC and TGA, Table s1. Anal. Calcd for C65H63F5P2PtSi: C, 63.77; H, 5.19. Found: C, 62.91; H, 5.25. NMR (δ/ppm, CDCl3): 1H (400 MHz)39 7.47− 7.42 (m, 12H, o to P), 7.10 (d, 3JHH = 7.8 Hz, 12H, m to P), 2.35 (s, 18H, CH3 p to P), 1.03 (apparent asym. s, 21H, CH(CH3)3); 13 C{1H} (101 MHz)40,41,46 145.7 (dm, 1JCF = 201 Hz, o to Pt), 140.9 (s, p to P), 136.7−135.9 (m, m to Pt), 134.2 (virtual t, 2JCP = 6.5 Hz, o to P), 128.7 (virtual t, 3JCP = 5.3 Hz, m to P), 126.9 (virtual t, 1JCP = 30.5 Hz, i to P), 106.1 (s, PtC̲ C), 95.2 (s, PtCC̲ ), 90.9 (s, C̲  CSi), 82.2 (s, CC̲ Si), 66.6, 63.7, 59.6, 56.3 (4 s, PtCC(C̲ C̲ )2; see Table s3), 21.3 (s, CH3 p to P), 18.5 (s, CH(C̲ H3)3), 11.3 (s, C̲ H(CH3)3); 31P{1H}, Table 1. IR: Table 1. MS:43 1223 ([M]+, 7%), 970 ([(C6F5)Pt(Ptol3)2]+, 25%), 802 ([(tol3P)2Pt − 1]+, 65%). trans-(C6F5)(p-tol3P)2Pt(CC)5Si-i-Pr3 (PtFC10TIPS). A threeneck flask was charged with PtFC6TIPS (0.551 g, 0.459 mmol) and acetone (200 mL), fitted with a gas dispersion tube and a condenser, and cooled to 0 °C. Then wet n-Bu4N+F− (1.0 M in THF, 5 wt % water; 0.114 mL, 0.114 mmol) was added with stirring. After 0.5 h, Me3SiCl (0.058 mL, 0.459 mmol) was added. After 10 min, TIPSC4H (1.893 g, 9.171 mmol)20 was added. A Schlenk flask was charged with

CuCl (0.454 g, 4.591 mmol) and acetone (40 mL), and TMEDA (0.415 mL, 0.322 g, 2.754 mmol) was added with stirring. After 0.5 h, stirring was halted, and a green solid separated from a blue supernatant. Then oxygen was bubbled through the three-neck flask with stirring and the blue supernatant was added in portions. After 1 h, the cold bath was removed. After 1 h, the solvent was removed by rotary evaporation. The residue was extracted with toluene (3 × 50 mL). The extracts were passed through alumina (10 × 2 cm column). The solvent was removed by rotary evaporation. The residue was chromatographed on silica gel (45 × 3 cm column, eluted with 5/95 v/v ethyl acetate/hexanes). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum to give PtFC10TIPS as a yellow-orange solid (0.331 g, 0.265 mmol, 58%). A second band eluted with 20/80 v/v ethyl acetate/ hexanes and gave PtFC12PtF as a yellow solid (0.205 g, 0.098 mmol, 43% of theory).10 The PtFC10TIPS slightly darkened at 175 °C and turned black with melting at 215 °C (capillary); DSC and TGA, Table s1. Anal. Calcd for C67H63F5P2PtSi: C, 64.46; H, 5.09. Found: C, 64.03; H, 5.33. NMR (δ/ppm, CDCl3): 1H (400 MHz)39 7.48−7.42 (m, 12H, o to P), 7.10 (d, 3JHH = 7.7 Hz, 12H, m to P), 2.35 (s, 18H, CH3 p to P), 1.05 (asym. apparent s, 21H, CH(CH3)3); 13C{1H} (101 MHz)40,41,45 141.0 (s, p to P), 134.2 (virtual t, 2JCP = 6.6 Hz, o to P), 128.7 (virtual t, 3JCP = 5.5 Hz, m to P), 126.8 (virtual t, 1JCP = 30.7 Hz, i to P), 107.8 (s, PtC̲ C), 95.0 (s, PtCC̲ ), 90.3 (s, C̲  CSi), 84.0 (s, CC̲ Si), 66.5, 64.7, 62.7, 60.4, 59.5, 56.5 (6 s, PtC C(C̲ C̲ )3; see Table s3), 21.3 (s, CH3 p to P), 18.5 (m, CH(C̲ H3)3), 11.3 (s, C̲ H(CH3)3); 31P{1H}, Table 1. IR: Table 1. MS:43 1248 ([M]+, 15%), 1080 ([M − C6F5]+, 10%), 970 ([(C6F5)Pt(Ptol3)2]+, 45%), 802 [(tol3P)2Pt − 1]+, 55%). trans-(C6F5)(p-tol3P)2Pt(CC)6Si-i-Pr3 (PtFC12TIPS). (A) A three-neck round-bottom flask was fitted with a gas dispersion tube, charged with PtFC8TIPS (0.290 g, 0.237 mmol) and THF (20 mL), and cooled to 0 °C. Then wet n-Bu4N+F− (1.0 M in THF, 5 wt % water, 0.10 mL, 0.10 mmol) was added with stirring. After 30 min (TLC showed no remaining educt), Me3SiCl (0.10 mL, 0.8 mmol), cold acetone (50 mL), and TIPSC4H (1.022 g, 4.951 mmol)20 were sequentially added, and oxygen was bubbled through the mixture with stirring. Then a suspension generated by stirring CuCl (0.239 g, 2.41 mmol), acetone (7 mL), and TMEDA (0.70 mL, 0.50 g, 4.3 mmol) for 30 min was added. After 70 min, hexanes (100 mL) was added. The dark green suspension was filtered through silica gel (2.5 × 20 cm pad, packed in 1/1 v/v acetone/hexanes), which was rinsed (1/1 v/v acetone/hexanes) until the filtrate became colorless. The solvent was removed from the filtrate by rotary evaporation (20 °C). The residue was chromatographed on silica gel (2.5 × 30 cm column, packed in hexanes, eluted with 10/90 v/v CH2Cl2/hexanes). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum to give PtFC12TIPS as a yellow solid (0.142 g, 0.112 mmol, 47%). (B) A three-neck flask was charged with PtFC10TIPS (0.091 g, 0.073 mmol) and acetone (50 mL), fitted with a gas dispersion tube and a condenser, and cooled to 0 °C. Then wet n-Bu4N+F− (1.0 M in THF, 5 wt % water; 0.018 mL, 0.018 mmol) was added with stirring. After 0.5 h, Me3SiCl (0.009 mL, 0.073 mmol) was added. A Schlenk flask was charged with CuCl (0.072 g, 0.73 mmol) and acetone (10 mL), and TMEDA (0.066 mL, 0.051 g, 0.44 mmol) was added with stirring. After 0.5 h, stirring was halted, and a green solid separated from a blue supernatant. Then oxygen was bubbled through the threeneck flask with stirring. After 10 min, TIPSC2H (0.492 mL, 0.399 g, 2.19 mmol) was added to the solution of PtFC10TIPS, followed by the blue supernatant in portions. After 1 h, the cold bath was removed. After 1 h, the solvent was removed by rotary evaporation. The residue was extracted with toluene (3 × 15 mL). The extracts were passed through alumina (7 × 2 cm column). The solvent was removed by rotary evaporation. The residue was chromatographed on silica gel (45 × 2 cm column, eluted with 10/90 v/v ethyl acetate/hexanes). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum to give PtFC12TIPS as a yellow ocher solid (0.005 g, 0.004 mmol, 5%) and PtFC20PtF as a red solid (0.029 g, 0.013 mmol, 36% of theory).10 PtFC12TIPS turned L


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Organometallics

0.0687 g, 0.582 mmol), oxygen, wet n-Bu4N+F− (1.0 M in THF, 5 wt % water; 0.023 mL, 0.023 mmol), and Me3SiCl (0.011 mL, 0.087 mmol) were combined in a procedure analogous to that given for PtFC12PtF. The solvent was removed by rotary evaporation (ice bath) 2 h after the Me3SiCl addition. The residue was chromatographed on silica gel at 0 °C (20 × 2 cm jacketed column, 90/10 v/v hexanes/ CH2Cl2). The solvent was removed from the product-containing fractions by rotary evaporation (ice bath) and oil pump vacuum to give PtFC24PtF as a red-brown solid (0.044 g, 0.019 mmol, 68%). The sample slightly darkened at 120 °C and at 160 °C turned black without melting (capillary); DSC and TGA, Table s1. Anal. Calcd for C120H84F10P4Pt2: C, 64.63; H, 3.80. Found: C, 64.71; H, 3.86. NMR (δ/ppm, CDCl3): 1H (400 MHz)39 7.59−7.36 (m, 24H, o to P), 7.09 (d, 3JHH = 7.7 Hz, 24H, m to P), 2.34 (s, 36H, CH3); 13C{1H} (101 MHz)40,41,45 141.1 (s, p to P), 134.1 (virtual t, 2JCP = 6.6 Hz, o to P), 128.7 (virtual t, 3JCP = 5.4 Hz, m to P), 126.6 (virtual t, 1JCP = 30.2 Hz, i to P), 94.7 (s, PtCC̲ ), 67.5, 66.1, 64.8, 63.9, 63.1, 62.4, 61.6, 60.6, 59.5, 56.5 (10 s, PtCC(C̲ C̲ )5; see Table s3), 21.3 (s, CH3); 31 1 P{ H}, Table 1. IR: Table 1. UV/vis: Table 3. MS:43 2230 ([M]+, 7%), 970 ([(C6F5)Pt(tol3P)2]+, 35%), 802 ([(tol3P)2Pt − 1]+, 100%). trans-(p-tol 3 P) 2 Pt((CC) 2 Si-i-Pr 3 ) 2 (TIPSC 4 PtC 4 TIPS). A Schlenk flask was charged with trans-(p-tol3P)2PtCl2 (1.874 g, 2.143 mmol),25 CuI (0.144 g, 0.756 mmol), CH2Cl2 (30 mL), and HNEt2 (100 mL). Then TIPSC4H (1.983 g, 9.608 mmol)20 was added with stirring. After 4 h, the solvent was removed by rotary evaporation. The beige residue was chromatographed on silica gel (2.5 × 22 cm column; eluted with 1/2 v/v CH2Cl2/hexanes). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum to give TIPSC4PtC4TIPS as an off-white powder (2.480 g, 2.042 mmol, 95%), which luminesced on irradiation at 365 nm. The sample slightly darkened at 213 °C and turned black and liquefied at 235 °C (capillary); DSC and TGA, Table s1. Anal. Calcd for C68H84P2PtSi2: C, 67.24; H, 6.97. Found: C, 66.83; H, 6.94. NMR (δ/ppm, CDCl3): 1H (300 MHz)39 7.56−7.50 (m, 12H, o to P), 7.15 (d, 3JHH = 7.8 Hz, 12H, m to P) 2.33 (s, 18H, CH3 p to P), 0.94−0.83 (m, 42H, CH(CH3)2); 13C{1H} (101 MHz)40,41 140.4 (s, p to P), 135.0 (virtual t, 2JCP = 6.3 Hz, o to P), 128.6 (virtual t, 3JCP = 5.7 Hz, m to P), 127.5 (virtual t, 1JCP = 30.5 Hz, i to P), 104.2 (t, 2JCP = 15.0 Hz, PtC̲ C), 95.9 (t, 3JCP = 2.3 Hz, PtCC̲ ), 94.4 (t, 4JCP = 2.3 Hz, C̲ CSi), 72.9 (t, 5JCP = 1.1 Hz, CC̲ Si), 21.3 (s, CH3 p to P), 18.5 (s, CH(C̲ H3)2), 11.3 (s, SiCH); 31P{1H}, Table 1. IR: Table 1. UV/vis: Table 3. MS:43 1214 ([M]+, 23%), 1008 ([M − C4TIPS]+, 26%), 803 ([(tol3P)2Pt]+, 100%). Reaction of HC4PtC4H and Excess H(CC)2Si-i-Pr3. A threeneck round-bottom flask was fitted with a gas dispersion tube and a condenser and charged with HC4PtC4H (0.243 g, 0.269 mmol)27 and acetone (20 mL). Then oxygen was bubbled through the solution and TIPSC4H (3.062 g, 14.84 mmol)20 was added, followed by a suspension generated by stirring CuCl (0.287 g, 2.90 mmol), acetone (8 mL), and TMEDA (0.80 mL, 0.64 g, 5.2 mmol) for 0.5 h. After 90 min (TLC showed no remaining educt), the solvent was removed from the dark green mixture by rotary evaporation. The residue was extracted with hexanes (3 × 50 mL) and then toluene (4 × 15 mL). The extracts were filtered in sequence through alumina (2.5 × 7 cm column, packed in hexanes, rinsed with toluene). The solvent was removed from the filtrate by rotary evaporation. The brown residue was chromatographed on silica gel (2.5 × 30 cm column, packed in hexanes, eluted with 1/1 v/v toluene/hexanes). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum. The first fraction contained a mixture of compounds, and the second gave TIPSC4PtC4TIPS (0.020 g, 0.016 mmol, 6%) as an off-white powder. The first fraction was again chromatographed on silica gel (2.5 cm × 40 cm column, packed in hexanes, eluted with 3/7 v/v toluene/hexanes). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum to give (in order of elution) TIPSC8PtC12TIPS (0.012 g, 0.0088 mmol, 3%) as a brown solid, TIPSC8PtC8TIPS (0.035 g, 0.027 mmol, 10%) as an orange powder, TIPSC4PtC12TIPS (0.023 g, 0.018, 7%) as an orange-brown solid, and TIPSC4PtC8TIPS

black without melting at 205 °C (capillary). Anal. Calcd for C69H63F5P2PtSi: C, 65.13; H, 4.99. Found: C, 63.94; H, 5.00.47 NMR (δ/ppm, CDCl3): 1H (400 MHz)39 7.53−7.34 (m, 12H, o to P), 7.10 (d, 3JHH = 7.6 Hz, 12H, m to P), 2.35 (s, 18H, CH3 p to P), 1.05 (apparent asym. s, 21H, CH(CH 3 ) 3 ); 13 C{ 1 H} (101 MHz)40,41,45 141.0 (s, p to P), 134.7 (virtual t, 2JCP = 6.3 Hz, o to P), 128.8 (virtual t, 3JCP = 5.5 Hz, m to P), 126.8 (virtual t, 1JCP = 30.4 Hz, i to P), 94.8 (s, PtCC̲ ), 90.0 (s, C̲ CSi), 85.4 (s, CC̲ Si), 65.2, 63.8, 63.2, 62.1, 61.4, 60.7, 59.6, 56.5 (8 s, PtCC(C̲ C̲ )4; see Table s3), 21.3 (s, CH3 p to P), 18.5 (m, CH(C̲ H3)3), 11.3 (s, C̲ H(CH3)3); 31P{1H}, Table 1. IR: Table 1. MS:43 1272 ([M]+, 7%), 970 ([(C6F5)Pt(Ptol3)2]+, 30%), 802 [(tol3P)2Pt − 1]+, 80%), 497 ([(tol3P)Pt]+, 45%), 304 ([Ptol3]+, 70%). trans,trans-(C 6 F 5 )(p-tol 3 P) 2 Pt(CC) 6 Pt(P-p-tol 3 ) 2 (C 6 F 5 ) (PtFC12PtF). A three-neck flask was charged with PtFC6TIPS (0.085 g, 0.070 mmol) and acetone (40 mL), fitted with a gas dispersion tube and a condenser, and cooled to 0 °C. A Schlenk flask was charged with CuCl (0.068 g, 0.687 mmol) and acetone (10 mL), and TMEDA (0.064 mL, 0.050 g, 0.42 mmol) was added with stirring. After 0.5 h, stirring was halted, and a green solid separated from a blue supernatant. Then oxygen was bubbled through the three-neck flask with stirring, and the blue supernatant was added in portions. After 0.5 h (TLC showed no reaction), wet n-Bu4N+F− (1.0 M in THF, 5 wt % water; 0.020 mL, 0.020 mmol) was added with stirring. After 0.5 h, Me3SiCl (0.009 mL, 0.070 mmol) was added. After 1 h, the cold bath was removed. After 1 h, the solvent was removed by rotary evaporation. Ethanol was added, and the yellow powder was collected by filtration and dried by oil pump vacuum to give PtFC12PtF (0.075 g, 0.035 mmol, > 99%). The NMR spectra agreed with those reported earlier.10 trans,trans-(C 6 F 5 )(p-tol 3 P) 2 Pt(CC) 8 Pt(P-p-tol 3 ) 2 (C 6 F 5 ) (PtFC16PtF). Acetone (100 mL), PtFC8TIPS (0.276 g, 0.225 mmol), CuCl (0.223 g, 2.254 mmol), acetone (10 mL), TMEDA (0.510 mL, 0.395 g, 3.38 mmol), oxygen, wet n-Bu4N+F− (1.0 M in THF, 5 wt % water; 0.460 mL, 0.460 mmol) and Me3SiCl (0.357 mL, 2.795 mmol) were combined in a procedure analogous to that given for PtFC12PtF. The solvent was removed by rotary evaporation 1.5 h after the cold bath was removed. The residue was chromatographed on silica gel (45 × 2 cm column, eluted with 20/80 v/v ethyl acetate/hexanes). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum to give PtFC16PtF as a red solid (0.214 g, 0.100 mmol, 89%). The NMR spectra agreed with those reported earlier.10 trans,trans-(C 6 F 5 )(p-tol 3 P) 2 Pt(CC) 10 Pt(P-p-tol 3 ) 2 (C 6 F 5 ) (PtFC20PtF). Acetone (20 mL), PtFC10TIPS (0.071 g, 0.056 mmol), CuCl (0.028 g, 0.284 mmol), acetone (5 mL), TMEDA (0.085 mL, 0.066 g, 0.57 mmol), oxygen, wet n-Bu4N+F− (1.0 M in THF, 5 wt % water; 0.023 mL, 0.023 mmol), and Me3SiCl (0.087 mL, 0.682 mmol) were combined in a procedure analogous to that given for PtFC12PtF. The solvent was removed by rotary evaporation (ice bath) 2.5 h after the Me3SiCl addition. The residue was chromatographed on silica gel at 0 °C (20 × 2 cm jacketed column, eluted with 10/90 v/v ethyl acetate/hexanes). The solvent was removed from the productcontaining fractions by rotary evaporation (ice bath) and oil pump vacuum to give PtFC20PtF as a yellow-brown solid (0.053 g, 0.024 mmol, 86%). The sample slightly darkened at 140 °C and turned black without melting at 170 °C (capillary); DSC and TGA, Table s1. Anal. Calcd for C116H84F10P4Pt2: C, 63.57; H, 3.74. Found: C, 62.95; H, 4.53.47 NMR (δ/ppm, CDCl3): 1H (400 MHz)39 7.56−7.38 (m, 24H, o to P), 7.09 (d, 3JHH = 7.7 Hz, 24H, m to P), 2.33 (s, 36H, CH3); 13C{1H} (101 MHz)40,41,45 141.1 (s, p to P), 134.1 (virtual t, 2 JCP = 6.6 Hz, o to P), 128.7 (virtual t, 3JCP = 5.5 Hz, m to P), 126.7 (virtual t, 1JCP = 30.5 Hz, i to P), 94.7 (s, PtCC̲ ), 67.2, 65.7, 64.2, 63.1, 62.0, 60.8, 59.7, 56.5 (8 s, PtCC(C̲ C̲ )4; see Table s3), 21.3 (s, CH3); 31P{1H}, Table 1. IR: Table 1. UV/vis: Table 3. MS:43 2181 ([M]+, 5%), 970 ([(C6F5)Pt(Ptol3)2]+, 30%), 803 ([(tol3P)2Pt]+, 90%). trans,trans-(C 6 F 5 )(p-tol 3 P) 2 Pt(CC) 12 Pt(P-p-tol 3 ) 2 (C 6 F 5 ) (PtFC24PtF). Acetone (40 mL), PtFC12TIPS (0.074 g, 0.058 mmol), CuCl (0.028 g, 0.283 mmol), acetone (10 mL), TMEDA (0.0887 mL, M


Article

Organometallics

(G) A CH2Cl2 solution of TIPSC8PtC8TIPS was layered with methanol. After 9 days, bright red needles were collected. The structure was solved and refined (cell parameters from 10 frames using a 10° scan and refined with 6533 reflections) in a manner identical with that for PtFC6TIPS and exhibited an inversion center at the platinum atom. (H) A CH2Cl2 solution of PtFC20PtF was layered with hexanes. After 17 days, colorless needles of a CH2Cl2 solvate were collected. The structure was solved and refined in a manner similar to that for PtFC6TIPS (60 frames, 5° scans). The chlorine atoms were constrained to have identical anisotropic thermal parameters, and the CH2Cl2 occupancy was refined to 0.8 molecule per molecule of PtFC20PtF. The hydrogen atoms were placed in idealized positions and refined using a rigid model as generated in X-Seed (C−H = 0.96 Å, Uiso(H) = 1.2 × Uiso(C)).51

(0.041 g, 0.033 mmol, 12%) as a yellow powder. Data for the three complexes not characterized above follow. TIPSC8PtC12TIPS. NMR (δ/ppm, CDCl3): 1H (300 MHz)39 7.51− 7.45 (m, 12H, o to P), 7.18 (d, 3JHH = 6.8 Hz, 12H, m to P), 2.38 (s, 18H, CH3 p to P), 1.02 (m, 42H, 2 SiCH(CH3)2); 31P{1H} (121 MHz) 17.7 (s; satellites not observed). MS:43 1358 ([M]+, 9%), 1104 ([M − C8TIPS]+, 9%), 1056 ([M − C12TIPS]+, 21%), 802 ([(tol3P)2Pt − 1]+, 100%). TIPSC8PtC8TIPS. NMR (δ/ppm, CDCl3): 1H (300 MHz)39 7.52− 7.45 (m, 12H, o to P) 7.18 (d, 3JHH = 7.6 Hz, 12H, m to P), 2.38 (s, 18H, CH3 p to P), 1.03 (apparent s, 42H, CH(CH3)2); 31P{1H} (121 MHz) 17.5 (s, 1JPPt = 2479 Hz).42 MS:43 1310 ([M]+, 18%), 1056 ([M − C8TIPS]+, 26%), 802 ([(tol3P)2Pt − 1]+, 100%). TIPSC4PtC8TIPS. The sample slightly darkened at 116 °C and turned black and liquefied at 213 °C (capillary). NMR (δ/ppm, CDCl3): 1H (300 MHz)39 7.54−7.48 (m, 12H, o to P), 7.17 (d, 3JHH = 7.5 Hz, 12H, m to P), 2.36 (s, 18H, CH3 p to P), 1.03, 0.94 (2 m, 42H, Pt(CC)2SiCH(CH3)2 and (CC)4SiCH(CH3)2); 13C{1H} (126 MHz)40,41 140.8 (s, p to P), 134.8 (virtual t, 2JCP = 6.3 Hz, o to P), 128.7 (virtual t, 3JCP = 5.6 Hz, m to P), 127.1 (virtual t, 1JCP = 30.7 Hz, i to P), 110.6 (t, 2JCP = 15.1 Hz, PtC̲ C(CC)3Si), 103.5 (t, 2 JCP = 14.3 Hz, PtC̲ CCCSi), 96.3 (t, 3JCP = 2.0 Hz, PtCC̲ (C C)3Si), 94.3 (t, 3JCP = 2.3 Hz, PtCC̲ CCSi or PtCCC̲ CSi), 94.0 (t, 4JCP = 2.1 Hz, PtCCC̲ CSi or PtCC̲ CCSi), 90.9 (s, Pt(CC)3C̲ CSi), 82.1 (s, Pt(CC)3CC̲ Si), 73.8 (s, PtC CCC̲ Si), 66.2, 63.8, 59.3, 56.3 (4 s, PtCC(C̲ C̲ )2CCSi; see Table s3), 21.5 (s, CH3 p to P), 18.62, 18.52 (2 s, 2 SiCH(C̲ H3)2), 11.4, 11.3 (2 s, 1JCSi = 56.6 and 56.4 Hz, 2 SiCH);30,42 31P{1H}, Table 1. IR: Table 1. UV/vis: Table 3. MS:43 1262 ([M]+, 12%), 1056 ([M − C4TIPS]+, 9%), 1008 ([M − C8TIPS]+, 12%), 802 ([(tol3P)2Pt− 1]+, 100%). Crystallography. (A) A CH2Cl2 solution of PtFC6TIPS was layered with ethanol. After 5 days, yellow needles were collected and data were obtained as outlined in Table s2. Cell parameters were obtained from 10 frames using a 10° scan and refined with 12864 reflections. Lorentz, polarization, and absorption corrections48 were applied. The space group was determined from systematic absences and subsequent least-squares refinement. The structure was solved by direct methods. The parameters were refined with all data by fullmatrix least squares on F2 using SHELXL.49 Non-hydrogen atoms were refined with anisotropic thermal parameters. The hydrogen atoms were fixed in idealized positions using a riding model. Scattering factors were taken from the literature.50 (B) A CH2Cl2 solution of PtFC8TIPS was layered with ethanol. After 6 days, yellow needles were collected (cell parameters from 10 frames using a 10° scan and refined with 13256 reflections). The structure was solved and refined in a manner identical with that for PtFC6TIPS. (C) A CH2Cl2 solution of PtTC8TIPS was layered with methanol. After 5 days, bright yellow needles were collected. The structure was solved and refined (cell parameters from 10 frames using a 10° scan and refined with 12301 reflections) in a manner identical with that for PtFC6TIPS. (D) A CH2Cl2 solution of PtTC12TIPS was layered with methanol. After 6 days, red needles of a CH2Cl2 hemisolvate were collected. The structure was solved and refined (cell parameters from 10 frames using a 10° scan and refined with 11049 reflections) in a manner identical with that for PtFC6TIPS. One methyl group was disordered but could be refined to a 64:36 occupancy ratio (C14b, C14c). (E) A CH2Cl2 solution of TIPSC4PtC12TIPS was layered with methanol. After 3 days, bright red prisms of a CH2Cl2 hemisolvate were collected. The structure was solved and refined (cell parameters from 10 frames using a 10° scan and refined with 15648 reflections) in a manner identical with that for PtFC6TIPS. (F) A CH2Cl2 solution of TIPSC4PtC4TIPS was layered with methanol. After 2 days, colorless prisms of a CH2Cl2 tetrasolvate were collected. The structure was solved and refined (cell parameters from 10 frames using a 10° scan and refined with 8480 reflections) in a manner identical with that for PtFC6TIPS and exhibited an inversion center at the platinum atom.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.9b00368. Summaries of thermal stability and crystallographic data and computational methods and additional data (PDF) Optimized structures (XYZ) Accession Codes

CCDC 1920243−1920250 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Author

*E-mail for J.A.G.: [email protected]. ORCID

Hashem Amini: 0000-0002-9921-9816 Andreas Ehnbom: 0000-0002-7044-1712 Michael B. Hall: 0000-0003-3263-3219 John A. Gladysz: 0000-0002-7012-4872 Author Contributions §

N.W. and H.K. contributed equally to the experimental work.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank the Deutsche Forschungsgemeinschaft (DFG, SFB 583) and the U.S. National Science Foundation (CHE1566601 and CHE-1664866) for financial support and the Laboratory for Molecular Simulation and Texas A&M High Performance Research Computing Facility for computational resources.

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DEDICATION This paper is dedicated to a long-time friend, occasional collaborator, and leading expert on dimetallic polyynediyl complexes, Dr. Jean-François Halet, on the occasion of his 60th birthday.

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REFERENCES

(1) (a) Shi, L.; Rohringer, P.; Suenaga, K.; Niimi, Y.; Kotakoski, J.; Meyer, J. C.; Peterlik, H.; Wanko, M.; Cahangirov, S.; Rubio, A.;

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Organometallics

Span Two Platinum Atoms. Chem. - Eur. J. 2006, 12, 6486−6505. See also: (c) Peters, T. B.; Bohling, J. C.; Arif, A. M.; Gladysz, J. A. C8 and C12 sp Carbon Chains that Span Two Platinum Atoms; The First Structurally Characterized 1,3,5,7,9,11-hexayne. Organometallics 1999, 18, 3261−3263 and the Supporting Information. (12) Substituted ((2-anilino)pyridinate)4Ru2 endgroups (X, Figure 1): Cao, Z.; Xi, B.; Jodoin, D. S.; Zhang, L.; Cummings, S. P.; Gao, Y.; Tyler, S. F.; Fanwick, P. E.; Crutchley, R. J.; Ren, T. DirutheniumPolyyn-diyl-Diruthenium Wires: Electronic Coupling in the Long Distance Regime. J. Am. Chem. Soc. 2014, 136, 12174−12183. (13) (η5-C5Me5)Ru(PPh2CH2CH2PPh2) endgroups: Bruce, M. I.; Cole, M. L.; Ellis, B. G.; Gaudio, M.; Nicholson, B. K.; Parker, C. R.; Skelton, B. W.; White, A. H. The series of carbon-chain complexes {Ru(dppe)Cp*}2{μ(CC)x} (x = 4−8, 11): Synthesis, structures, properties and some reactions. Polyhedron 2015, 86, 43−56. (14) Additional organic endgroups: (a) Schermann, G.; Grösser, T.; Hampel, F.; Hirsch, A. Dicyanopolyynes: A Homologuous Series of End-Capped Linear sp Carbon. Chem. - Eur. J. 1997, 3, 1105−1112. (b) Luu, T.; Elliot, E.; Slepkov, A. D.; Eisler, S.; McDonald, R.; Hegmann, F. A.; Tykwinski, R. R. Synthesis, Structure, and Nonlinear Optical Properties of Diarylpolyynes. Org. Lett. 2005, 7, 51−54. (15) Review: Chalifoux, W. A.; Tykwinski, R. R. Synthesis of extended polyynes: Toward carbyne. C. R. Chim. 2009, 12, 341−358. (16) Alabugin, I. V.; Bresch, S.; Manoharan, M. Hybridization Trends for Main Group Elements and Expanding the Bent’s Rule Beyond Carbon: More than Electronegativity. J. Phys. Chem. A 2014, 118, 3663−3677. (17) A series with shorter polyynediyl segments features “insulating” α,ω-diphosphines Ar2P(CH2)yPAr2 that span the platinum termini: (a) Stahl, J.; Mohr, W.; de Quadras, L.; Peters, T. B.; Bohling, J. C.; Martín-Alvarez, J. M.; Owen, G. R.; Hampel, F.; Gladysz, J. A. sp Carbon Chains Surrounded by sp3 Carbon Double Helices: Coordination-Driven Self-Assembly of Wirelike Pt(CC)nPt Moieties That Are Spanned by Two P(CH2)mP Linkages. J. Am. Chem. Soc. 2007, 129, 8282−8295. (b) de Quadras, L.; Bauer, E. B.; Mohr, W.; Bohling, J. C.; Peters, T. B.; Martín-Alvarez, J. M.; Hampel, F.; Gladysz, J. A. sp Carbon Chains Surrounded by sp3 Carbon Double Helices: Directed Syntheses of Wirelike Pt(CC)nPt Moieties That Are Spanned by Two P(CH2)mP Linkages via Alkene Metathesis. J. Am. Chem. Soc. 2007, 129, 8296−8309. (c) de Quadras, L.; Bauer, E. B.; Stahl, J.; Zhuravlev, F.; Hampel, F.; Gladysz, J. A. sp Carbon chains surrounded by sp3 carbon double helices: wire-like Pt(C C)nPt moieties that are spanned by two α,ω-diphosphines that bear heteroatoms or alkyl substituents. New J. Chem. 2007, 31, 1594−1604. (d) Owen, G. R.; Stahl, J.; Hampel, F.; Gladysz, J. A. CoordinationDriven Self-Assembly, Structures, and Dynamic Properties of Diplatinum Hexatriynediyl and Butadiynediyl Complexes in which the sp Carbon Chains are Shielded by sp3 Carbon Chains: Towards Endgroup-Endgroup Interactions. Chem. - Eur. J. 2008, 14, 73−87. (18) Another series with shorter polyynediyl segments features rotaxanes in which the sp carbon chains thread through a macrocycle: (a) Weisbach, N.; Baranová, Z.; Gauthier, S.; Reibenspies, J. H.; Gladysz, J. A. A new type of insulated molecular wire: a rotaxane derived from a metal-capped conjugated tetrayne. Chem. Commun. 2012, 48, 7562−7564. (b) Baranová, Z.; Amini, H.; Bhuvanesh, N.; Gladysz, J. A. Rotaxanes Derived from Dimetallic Polyynediyl Complexes: Extended Axles and Expanded Macrocycles. Organometallics 2014, 33, 6746−6749. (19) (a) Rücker, C. The Triisopropylsilyl Group in Organic Chemistry: Just a Protective Group, or More? Chem. Rev. 1995, 95, 1009−1064. (b) Heuft, M. A.; Collins, S. K.; Yap, G. P. A.; Fallis, A. G. Synthesis of Diynes and Tetraynes from in Situ Desilylation/ Dimerization of Acetylenes. Org. Lett. 2001, 3, 2883−2886. (20) (a) Blanco, L.; Helson, H. E.; Hirthammer, M.; Mestdagh, H.; Spyroudis, S.; Vollhardt, K. P. C. 2,3,9,10-Tetrakis(trimethylsilyl)[5]phenylene. Synthesis via Regiospecific Cobalt-Catalyzed Cocyclization of 1,6-Bis(triisopropylsilyl)-1,3,5-hexatriyne. Angew. Chem., Int. Ed. Engl. 1987, 26, 1246−1247; 2,3,9,10 Tetrakis(trimethylsilyl) [5]phenylen durch regiospezifische cobaltkatalysierte Cocyclisierung

Lapin, Z. J.; Novotny, L.; Ayala, P.; Pichler, T. Confined linear carbon chains as a route to bulk carbyne. Nat. Mater. 2016, 15, 634−640 and earlier literature cited therein. (b) Casari, C. S.; Milani, A. Carbyne: from the elusive allotrope to stable carbon atom wires. MRS Commun. 2018, 8, 207−219. (2) t-Bu endgroups: (a) Jones, E. R. H.; Lee, H. H.; Whiting, M. C. Researches on Acetylenic Compounds. Part LXIV.* The Preparation of Conjugated Octa- and Deca-acetylenic Compounds. J. Chem. Soc. 1960, 3483−3489. (b) Johnson, T. R.; Walton, D. R. M. SILYLATION AS A PROTECTIVE METHOD IN ACETYLENE CHEMISTRY. POLYYNE CHAIN EXTENSIONS USING THE REAGENTS Et3Si(CC)mH(m = 1,2,4) IN MIXED OXIDATIVE COUPLINGS. Tetrahedron 1972, 28, 5221−5236. (c) Chalifoux, W. A.; McDonald, R.; Ferguson, M. J.; Tykwinski, R. R. tert-Butyl-EndCapped Polyynes: Crystallographic Evidence of Reduced BondLength Alternation. Angew. Chem., Int. Ed. 2009, 48, 7915−7919; Polyine mit tert-Butyl-Endgruppen: kristallographischer Nachweis einer reduzierten Bindungslängenalternanz. Angew. Chem. 2009, 121, 8056−8060. (3) SiEt3 (TES) endgroups: Eastmond, R.; Johnson, T. R.; Walton, D. R. M. SILYLATION AS A PROTECTIVE METHOD FOR TERMINAL ALKYNES IN OXIDATIVE COUPLINGS. A GENERAL SYNTHESIS OF THE PARENT POLYYNES H(CC)nH (n = 4−10,12). Tetrahedron 1972, 28, 4601−4616. Polyynes with n ≥ 8 were only generated and characterized in solution. (4) Si-i-Pr3 (TIPS) endgroups: (a) Eisler, S.; Slepkov, A. D.; Elliot, E.; Luu, T.; McDonald, R.; Hegmann, F. A.; Tykwinski, R. R. Polyynes as a Model for Carbyne: Synthesis, Physical Properties, and Nonlinear Optical Response. J. Am. Chem. Soc. 2005, 127, 2666− 2676. (b) Kohn, D. R.; Gawel, P.; Xiong, Y.; Christensen, K. E.; Anderson, H. L. Synthesis of Polyynes Using Dicobalt Masking Groups. J. Org. Chem. 2018, 83, 2077−2086. (5) Dendrimeric aryl endgroups (IV, Figure 1): Gibtner, T.; Hampel, F.; Gisselbrecht, J.-P.; Hirsch, A. End-Cap Stabilized Oligoynes: Model Compounds for the Linear sp Carbon AllotropeCarbyne. Chem. - Eur. J. 2002, 8, 408−432. (6) Adamantyl endgroups: Chalifoux, W. A.; Ferguson, M. J.; McDonald, R.; Melin, F.; Echegoyen, L.; Tykwinski, R. R. Adamantyl endcapped polyynes. J. Phys. Org. Chem. 2012, 25, 69−76. (7) Hexakis(t-Bu)-substituted trityl endgroups (III, Figure 1): Chalifoux, W. A.; Tykwinski, R. R. Synthesis of polyynes to model the sp-carbon allotrope carbyne. Nat. Chem. 2010, 2, 967−971. (8) Co3(CO)7L2C endgroups (XI, Figure 1): Bruce, M. I.; Zaitseva, N. N.; Nicholson, B. K.; Skelton, B. W.; White, A. H. Syntheses and molecular structures of some compounds containing many-atom chains end-capped by tricobalt carbonyl clusters. J. Organomet. Chem. 2008, 693, 2887−2897. (9) (η5-C5Me5)Re(NO)(PPh3) endgroups: Dembinski, R.; Bartik, T.; Bartik, B.; Jaeger, M.; Gladysz, J. A. Toward Metal-Capped OneDimensional Carbon Allotropes: Wirelike C6-C20 Polyynediyl Chains That Span Two Redox-Active (η5-C5Me5)Re(NO)(PPh3) Endgroups. J. Am. Chem. Soc. 2000, 122, 810−822. (10) trans-(C6F5)Pt(P-p-tol3)2 endgroups: (a) Mohr, W.; Stahl, J.; Hampel, F.; Gladysz, J. A. Bent and Stretched but Not Yet to the Breaking Point: C8-C16 sp Carbon Chains That Span Two Platinum Atoms and the First Structurally Characterized 1,3,5,7,9,11,13,15Octayne. Inorg. Chem. 2001, 40, 3263−3264. (b) Mohr, W.; Stahl, J.; Hampel, F.; Gladysz, J. A. Synthesis, Structure, and Reactivity of sp Carbon Chains with Bis(phosphine)Pentafluorophenylplatinum Endgroups: Butadiynediyl (C4) through Hexadecaoctaynediyl (C16) Bridges, and Beyond. Chem. - Eur. J. 2003, 9, 3324−3340. (11) trans-(p-tol)Pt(P-p-tol3)2 endgroups: (a) Zheng, Q.; Gladysz, J. A. A Synthetic Breakthrough into an Unanticipated Stability Regime: Readily Isolable Complexes in which C16-C28 Polyynediyl Chains Span Two Platinum Atoms. J. Am. Chem. Soc. 2005, 127, 10508− 10509. (b) Zheng, Q.; Bohling, J. C.; Peters, T. B.; Frisch, A. C.; Hampel, F.; Gladysz, J. A. A Synthetic Breakthrough into an Unanticipated Stability Regime: A Series of Isolable Complexes in which C6, C8, C10, C12, C16, C20, C24, and C28 Polyynediyl Chains O


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(31) Sindhu, K. S.; Thankachan, A. P.; Sajitha, P. S.; Anilkumar, G. Recent developments and applications of the Cadiot-Chodkiwicz reaction. Org. Biomol. Chem. 2015, 13, 6891−6905. (32) (a) Zhang, T.; Bhuvanesh, N.; Gladysz, J. A. A Quest for Atropisomerism in Cojoined Square-Planar Metal Complexes: Synthesis and Structures of Sterically Congested Diplatinum Ethynediyl Adducts. Eur. J. Inorg. Chem. 2017, 2017, 1017−1025. (b) Dey, S.; Zhang, T.; Bhuvanesh, N.; Gladysz, J. A. Syntheses and structures of square planar diplatinum butadiynediyl complexes with two different monophosphine ligands on each terminus; probing the feasibility of a new type of inorganic atropisomerism. J. Organomet. Chem. 2017, 849−850, 237−255. (33) Szafert, S.; Gladysz, J. A. Carbon in One Dimension: Structural Analysis of the Higher Conjugated Polyynes. Chem. Rev. 2003, 103, 4175−4205; Update 1 of: Carbon in One Dimension: Structural Analysis of the Higher Conjugated Polyynes. Chem. Rev. 2006, 106, PR1−PR33. (34) Zhuravlev, F.; Gladysz, J. A. Electronic Structure and ChainLength Effects in Diplatinum Polyynediyl Complexes trans,trans[(X)(R3P)2Pt(CC)nPt(PR3)2(X)]: A Computational Investigation. Chem. - Eur. J. 2004, 10, 6510−6522. (35) Mohr, W.; Peters, T. B.; Bohling, J. C.; Hampel, F.; Arif, A. M.; Gladysz, J. A. An unexpected insertion of acetone into the siliconcarbon terminus of an sp carbon chain: syntheses and structures of model monoplatinum hexatriynyl and octatetraynyl complexes. C. R. Chim. 2002, 5, 111−118. (36) (a) Gauthier, S.; Weisbach, N.; Bhuvanesh, N.; Gladysz, J. A. “Click” Chemistry in Metal Coordination Spheres: Copper(I)Catalyzed 3 + 2 Cycloadditions of Benzyl Azide and Platinum Polyynyl Complexes trans-(C6F5)(p-tol3P)2Pt(CC)nH (n = 2−6). Organometallics 2009, 28, 5597−5599. (b) Clough, M. C.; Zeits, P. D.; Bhuvanesh, N.; Gladysz, J. A. Toward Permetalated Alkyne/Azide 3 + 2 or “Click” Cycloadducts. Organometallics 2012, 31, 5231−5234. (37) (a) Adams, H.; Blanco, J.-L. J.; Chessari, G.; Hunter, C. A.; Low, C. M. R.; Sanderson, J. M.; Vinter, J. G. Quantitative Determination of Intermolecular Interactions with Fluorinated Aromatic Rings. Chem. - Eur. J. 2001, 7, 3494−3503. (b) Collings, J. C.; Roscoe, K. P.; Thomas, R. L.; Batsanov, A. S.; Stimson, L. M.; Howard, J. A. K.; Marder, T. B. Arene-perfluoroarene interactions in crystal engineering. Part 3. Single-crystal structures of 1:1 complexes of octafluoronaphthalene with fused-ring polyaromatic hydrocarbons. New J. Chem. 2001, 25, 1410−1417. (c) Mahanta, H.; Baishya, D.; Ahamed, Sk. S.; Paul, A. K. A Better Understanding of the Unimolecular Dissociation Dynamics of Weakly Bound Aromatic Compounds at High Temperature: A Study on C6H6-C6F6 and Comparison with C6H6 Dimer. J. Phys. Chem. A 2019, 123, 2517− 2526. (38) Owen, G. R.; Gauthier, S.; Weisbach, N.; Hampel, F.; Bhuvanesh, N.; Gladysz, J. A. Towards multistranded molecular wires: Syntheses, structures, and reactivities of tetraplatinum bis(polyynediyl) complexes with Pt-Cx-Pt-(P(CH2)3P)2-Pt-Cx-Pt-(P(CH2)3P)2 cores (x = 4, 6, 8). Dalton Trans 2010, 39, 5260−5271. (39) The aryl 1H NMR signal that appears as doublet is assigned to the meta CH group, and the signal that appears as a multiplet (presumably due to additional phosphorus coupling) is assigned to the ortho CH group. (40) For virtual triplets the xJCP values represent apparent couplings between adjacent peaks that take place through a minimum of x bonds: Hersh, W. H. False AA′X Spin-Spin Coupling Systems in 13C NMR: Examples Involving Phosphorus and a 20-Year-Old Mystery in Off-Resonance Decoupling. J. Chem. Educ. 1997, 74, 1485−1488. (41) Of the aryl 13C{1H} NMR signals, that with the chemical shift closest to benzene (128.4 ppm) is attributed to the meta carbon atom; the other signal of comparable intensity (and phosphorus coupling) is attributed to the ortho carbon atom. See: Mann, B. E. The Carbon-13 and Phosphorus-31 Nuclear Magnetic Resonance Spectra of Some Tertiary Phosphines. J. Chem. Soc., Perkin Trans. 2 1972, 2, 30−34. P


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Organometallics (42) This coupling represents a satellite (d, 29Si = 4.67% or 195Pt = 33.8%) and is not reflected in the peak multiplicity given. (43) FAB, 3-NBA, m/z (relative intensity, %); the most intense peak of the isotope envelope is given. (44) The signal/noise ratio for this signal is poor. (45) The signals of the C6F5 and/or PtC carbon atoms were not observed. (46) The signals of the ipso and para C6F5 carbon atoms were not observed. (47) This microanalysis poorly agrees with the empirical formula, but it is nonetheless reported as the best obtained to date. The NMR spectra indicate high purities (≥ 98%). (48) (a) “Collect” Data collection software; Nonius BV.: 1998. (b) Scalepack data processing software: Otwinowski, Z.; Minor, W. Processing of X-Ray Diffraction Data Collected in Oscillation Mode. Methods Enzymol. 1997, 276, 307−326 (Macromolecular Crystallography, Part A). (49) Sheldrick, G. M. Crystal structure refinement with SHELXL. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 3−8. (50) Cromer, D. T.; Waber, J. T. In International Tables for X-ray Crystallography; Ibers, J. A., Hamilton, W. C., Eds.; Kynoch: Birmingham, England, 1974. (51) Barbour, L. J. X-Seed  A Software Tool for Supramolecular Crystallography. J. Supramol. Chem. 2001, 1, 189−191.

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Triisopropylsilyl (TIPS) Alkynes as Building Blocks for Syntheses of

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