Dinuclear Palladium and Platinum Complexes with Bridging Silylene

ARTICLE pubs.acs.org/Organometallics

Dinuclear Palladium and Platinum Complexes with Bridging Silylene Ligands. Preparation Using (Aminosilyl)boronic Ester as the Ligand Precursor and Their Reactions with Alkynes Makoto Tanabe,† Jian Jiang,† Hideto Yamazawa,† Kohtaro Osakada,*,† Toshimichi Ohmura,‡ and Michinori Suginome‡ † ‡

Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1-3 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan

bS Supporting Information





ABSTRACT: Equimolar reactions of (aminosilyl)boronic ester







Et2NSiPh2 BOCMe2CMe2 O with zerovalent complexes of Pt and Pd, M(PMe3)4 (M = Pt, Pd), afforded the dinuclear complexes with bridging silylene ligands {M(PMe3)2}2(μ-SiPh2)2 (1: M = Pt, 2: M = Pd). X-ray crystallographic studies of 1 and 2 revealed a Si 3 3 3 Si interaction in the M2Si2 four-membered ring. Diplatinum complex 1 reacted with arylacetylenes HCtCAr (Ar =







C6H5, C6H4Me-4), yielding 3,5-disila-4-platinacyclopentene Pt(SiPh2CArdCH SiPh2)(PMe3)2 (3a: Ar = C6H5, 3b: Ar = C6H4Me-4), although the reaction mixture also contained complexes with the alkyne or the alkynyl ligands. The reaction of







PhCtCPh with dipalladium complex 2 gave Pd(SiPh2CPhdCPh SiPh2)(PMe3)2 as well as alkyne complex Pd(η2-PhCtCPh)(PMe3)2. The reactions of HCtCAr (Ar = C6H5, C6H4Me-4) with Pt(SiHPh2)2(PMe3)2 also formed 3a and 3b accompanied







by 6-sila-3-platina-1,4-cyclohexadienes Pt(CArdCHSiPh2CHd CAr)(PMe3)2 as the byproduct. A similar reaction of HCtCCOOMe with Pt(SiPh2H)2(PMe3)2 yielded the five-membered disilaplatinacycle Pt(SiPh2C(COOMe)dCH SiPh2)(PMe3)2 as the sole product. Both the dinuclear complexes of Pd and Pt with bridging silylene ligands and mononuclear Pt complexes with two silyl ligands were converted to the disilaplatinacyclopentene via independent pathways. Details of the mechanism are discussed.

’ INTRODUCTION Reactions of alkynes with Pd and Pt complexes having Si ligands have been extensively studied because they are related to the mechanism of hydrosilylation and bissilylation of alkynes catalyzed by complexes of the group 10 transition metals.1 Insertion of alkynes into M
Si bonds (M = Pd, Pt) and coupling of the silyl and alkenyl ligands from the alkenyl(silyl)metal complexes are believed to be the fundamental reactions that provide new C
Si bonds in the above catalysis. The Pt complexes with tertiary silyl ligands actually undergo insertion of alkynes into the Pt
Si bond.2 Eaborn et al. reported that terminal alkynes, such as acetylene and phenylacetylene, reacted with cis-Pt(SiHPh2)2(PMe2Ph)2 to afford five-membered 3,5-disila-4-platinacyclopentenes (Scheme 1).3 They proposed the multiple-step pathway shown in Scheme 1 to account for the reaction product. It involves initial formation of alkynylsilane formed via dehydrosilylation of the alkyne. Oxidative addition of the alkynylsilane to the Pt complex, forming an intermediate with diphenylsilyl and alkynylsilyl ligands, and r 2011 American Chemical Society

subsequent intramolecular hydrosilylation of the latter ligand leads to the formation of the metallacycle product. The authors did not prefer a pathway involving an intermediate having silylene (SiR2) ligands bonded to Pt, although they mentioned that the bis(silyl)platinum complexes were known to generate Pt-silylene species upon heating.4 Dinuclear Fe and Ru complexes with two bridging silylene ligands, {Fe(CO)4}2(μ-SiPh2)2 and (Cp*Ru)2(μ-H)2(μ-SiPh2)2, were reported to react with internal alkynes or acetylene to form disilametallacyclopentenes (Scheme 2(i) and (ii)).5 The Pd or Pt version of this reaction would provide the disilapallada- or disilaplatinacyclopentenes, but this reaction pathway has not been discussed in the reports of the reactions of alkynes with silyl complexes of these metals so far. We studied the reaction of dimethyl acetylenedicarboxylate with Pt(SiHPh2)2(PMe3)2 and Received: February 18, 2011 Published: July 06, 2011 3981

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Scheme 2

’ RESULTS AND DISCUSSION Dinuclear complexes of Pt,7 Pd,8 and Ni9 with bridging silylene (SiR2) ligands have been commonly prepared from the reactions of primary and secondary silanes with low-valent complexes of these metals. Oxidative addition of the silanes to these metals and dehydrogenative dimerization of the resulting mononuclear silyl complexes produces silylene-bridged dinuclear complexes. The preparation reactions, however, are often accompanied by formation of the byproduct, because once obtained, dinuclear complexes with bridging silylene ligands can be converted to mono- and dinuclear complexes with silyl (SiHR2) ligands in the reaction mixture. Organosilanes release the Si
H hydrogen easily to the bridging silylene ligand via Si
H bond activation reactions with Pd and Pt centers. Recently, we reported that H2SiPh2 enhanced the equilibrium between Pd(SiHPh2)2(dmpe) and {Pd(dmpe)}2(μ-SiPh2)2 (dmpe = 1, 2-bis(dimethylphosphino)ethane).8e On the other hand,


Scheme 1

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with an equimolar amount of Et2NSiPh2BOCMe2CMe2 O at 60 °C to produce the diplatinum or dipalladium complexes with bridging silylene ligands {M(PMe3)2}2(μ-SiPh2)2 (1: M = Pt; 80%, 2: M = Pd; 48%), as shown in eq 1. Accompanying


Scheme 3







(aminosilyl)boronic ester Et2NSiPh2BOCMe2CMe2 O10 has recently been found to act as a silylene precursor in palladiumcatalyzed reactions with unsaturated hydrocarbons.11,12 Thus, we used the (aminosilyl)boronic ester as a precursor of the silylene ligands of the dinuclear Pd and Pt complexes in this study. M(PMe3)4 (M = Pt, Pd), which were generated in situ by ligand substitution of M(PCy3)2 with PMe3 (1:4 ratio), reacted

formation of Et2NBOCMe2CMe2 O was observed in the 1H NMR spectra of the reaction mixture. The experiments using a smaller amount of PMe3 ([M]:[PMe3] = 1:2) gave the same products in lower yields (less than 30% in NMR yields).

4-sila-3-platinacyclobutene (B) after insertion of the unsaturated molecules into the Pt
Si bond followed by γ-hydrogen elimination (Scheme 3).6 The produced 4-sila-3-platinacyclobutene (B) reacts with H2SiPh2 to cause the reverse reaction, forming the 3-sila-1-propenylplatinum complex (A), whereas it reacts with further alkynes, giving 6-sila-3-platina-1,4-cyclohexadiene with πcoordinated alkyne (C). In this study, we conducted the reaction of alkynes with dinuclear Pd and Pt complexes having bridging silylene ligands expecting to form metallacyclic products. These reactions are compared with those of the alkyne with mononuclear bis(silyl)platinum complexes (Schemes 1 and 3). Structures and properties of the produced complexes are also described.

Figure 1 shows the molecular structures of 1 and 2 with a square-planar geometry, determined by X-ray crystallography. Table 1 compares their bond parameters and those of the analogues with a dmpe ligand. The Pd2Si2 rhombus of 2 forms a plane, whereas the Pt2Si2 ring of 1 has a slightly bent structure with the dihedral angle between two PtSi2 planes being 169.4°. The angle, however, is larger than the Pt2Si2 ring of {Pt(PEt3)2}2(μ-SiHCy)2 (dihedral angle = 132.3°).7b The Si 3 3 3 Si distances in the M2Si2 ring of 1, 2, and the dmpe complexes decrease in the order, {Pt(dmpe)}2(μ-SiPh2)2 (2.718(2) Å)7l > 1 (2.645(1) Å) > {Pd(dmpe)}2(μ-SiPh2)2 (2.5227(7) Å)8e > 2 (2.428(1) Å). The Pd
Si bond distances of 2 (2.4086(7), 2.4098(9) Å) are similar to the Pt
Si bonds of 1 (2.3902(7)
2.4065(7) Å). Accordingly, the Si
M
Si angles decrease in the same order, 3982

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{Pt(dmpe)}2(μ-SiPh2)2 (69.48(4)°)7l > 1 (67.12(2)°, 66.92(2)°) > {Pd(dmpe)}2(μ-SiPh2)2 (63.92(2)°)8e > 2 (60.51(2)°). The above results can be ascribed to more significant π-back-donation of the Pt center to the Si ligands than the Pd center. Sakaki reported that Si 3 3 3 Si interaction in the four-membered Pd2Si2 and Pt2Si2 rings was influenced by the degree of π-back-donation between the metal center and the coordinating Si atom based on their results of theoretical calculation.13 More significant π-backdonation of the Pt complexes weakens the Si 3 3 3 Si interaction, while lower energy levels of Pd weaken the π-back-donation and retain the Si 3 3 3 Si bonding interaction. Since the chelating diphosphines enhance π-back-donation to the Si ligand,13a the Si 3 3 3 Si distances of the dmpe complex are longer than the PMe3 complex in both Pt and Pd systems. The 29Si NMR resonances of the bridging SiPh2 ligands are observed in the order, {Pt(dmpe)}2(μ-SiPh2)2 (δ
95.5),7l 1 (δ
75.8), {Pd(dmpe)}2(μ-SiPh2)2 (δ
51.0),8e and 2 (δ
35.3).







Formal transfer of SiPh2 groups from the (aminosilyl)boronic ester to the zerovalent complexes of Pd and Pt yielded dinuclear complexes, similarly to the proposed mechanism of the Pdcatalyzed silylation of various unsaturated molecules using the (aminosilyl)boronic ester.11 Mononuclear silylene platinum complexes were isolated by introducing bulky mesityl groups to the Si ligand.14 Kira and Iwamoto reported the preparation of a dipalladium complex having one bridging dialkylsilylene ligand, {Pd(PCy3)}2(μ-SiRH2) (RH2 = 1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl), and proposed the formation pathway involving the reaction of the mononuclear silylene palladium intermediate (Cy3P)PddSiRH2 with a Pd(0)-phosphine complex.15 The reaction in eq 1 may involve mono- or dinuclear complexes as the intermediate, although the reaction details are not clear at present. Diplatinum complex 1 reacted with a 3-fold molar amount of HCtCAr (Ar = C 6 H 5 , C6 H4 Me-4) at room temperature to produce a mixture of 3,5-disila-4-platinacyclopentene Pt(SiPh2CArdCH SiPh2)(PMe3)2 (3a: Ar = C6H5; 62%, 3b: Ar = C6H4Me-4; 60%) and alkyne-coordinated complex Pt(PMe3)2(η2-HCtCAr) (4a: Ar = C6H5, 4b: Ar = C6H4Me-4) after 10 h (eq 2). The reaction of 4-ethynyltoluene yielded the dialkynyl platinum complex trans-Pt(CtCAr)2(PMe3)2 (5b) as the product. Roundhill proposed the conversion of the Pt complexes with π-coordinated alkyne ligands to the dialkynylplatinum complexes in the presence of excess alkynes.16

Five-membered disilaplatinacycles 3a and 3b were isolated and characterized by X-ray crystallography and NMR spectroscopy. Figure 2a shows the molecular structure of 3b, and selected bond distances and angles are listed in Table 2. The CdC bond distance of 3b (1.340(5) Å) is comparable with that of the unstrained disilylolefin (Z)-(PhSCH2)Me2SiC(Ph)d C(H)SiMe2(CH2SPh) (1.341(10) Å).17 The Pt
Si bond

Figure 1. Thermal ellipsoids (50% probability) of (a) 1 and (b) 2. Carbon-bound hydrogen atoms are omitted for simplicity. The molecule of 2 has a crystallographic symmetry at the midpoint of the two Pd atoms.

Table 1. Selected Bond Distances (Å) and Angles (deg) of 1, 2, and {M(dmpe)}2(μ-SiPh2)2 (M = Pt, Pd) 1 (M = Pt) M3 3 3M M
Si

{Pt(dmpe)}2(μ-SiPh2)2a

2 (M = Pd)

{Pd(dmpe)}2(μ-SiPh2)2b

3.9775(1)

3.9193(2)

4.162(2)

4.0438(2)

2.3930(6), 2.3916(7)

2.385(1), 2.3847(9)

2.4086(7), 2.4098(9)

2.3822(4), 2.3840(6)

2.3053(8), 2.299(1)

2.3792(7), 2.389(1)

2.3346(7), 2.3423(3)

2.3902(7), 2.4065(7) M
P

2.3248(6), 2.3327(7) 2.3340(6), 2.3312(7)

a

Si 3 3 3 Si Si
M
Si

2.645(1)

2.718(2)

2.428(1)

2.5227(7)

67.12(2), 66.92(2)

69.48(4)

60.51(2)

63.92(2)

M
Si
M P
M
P

112.51(3), 111.98(3) 96.63(2), 95.64(2)

110.52(4) 85.48(3)

119.49(3) 101.26(3)

116.08(2) 85.75(2)

Ref 7l. b Ref 8e. 3983

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CHSiMe3 (δ 6.36)19 and (o-C6H4)(SitBuMe)CPhdCH( SitBuMe) (δ 6.86)20 and are close to that of the disilanickelacyclopentene Ni(SiF2CtBudCHSiF2)(CO)2 (δ 7.27).21 The 29Si NMR signals of 3b are observed as two doublets at δ 23.9 and 34.6 flanked with the satellite signals of 195Pt nuclei (JPt
Si = 1176 and 1264 Hz, respectively). The 31P{1H} NMR spectrum of 3b exhibits a pair of










nacyclopentane Pt(SiPh2CH2C(dCHC6H4F) SiPh2)(PMe3)2 (Pt
Si: 2.365(2) and 2.374(2) Å, Si
Pt
Si: 79.74(7)°).18 Complexes 3a and 3b show 1H NMR peaks due to vinyl hydrogens in the five-membered rings at δ 7.42 and 7.44 flanked with 195Pt satellite signals (3JPt
H = 67 Hz). They are at lower magnetic field than the vinyl hydrogen signals of (Z)-Me3SiCPhd

doublets at δ
19.7 and
19.3 with 2JP
P = 29 Hz due to the unsymmetrical molecular structure. The 31P{1H} NMR spectra of the reaction mixture showed the signals due to the complex with a πcoordinated alkyne ligand, 4a and 4b. The coupling constants of 4a (JPt
P = 3227, 3350 Hz, JP
P = 36 Hz) and 4b (JPt
P = 3180, 3345 Hz, JP
P = 36 Hz) are comparable with those of Pt(η2-HCtCPh)(PPh3)2 (JPt
P = 3464, 3547 Hz, JP
P = 33 Hz).22 A similar reaction of dipalladium complex 2 with PhCtCPh in 1:2 ratio smoothly proceeded at room temperature to give the 3,5








distances (2.3705(9) and 2.357(1) Å) and Si
Pt
Si angle (80.56(4)°) are similar to those reported for 2,5-disila-1-plati-

disila-4-palladacyclopentene Pd(SiPh2CPhdCPhSiPh2)(PMe3)2 (6) after 10 h, along with Pd(η2-PhCtCPh)(PMe3)2 (7) in 50% and 30% yields, respectively (eq 3). The reactions of terminal alkynes formed a complicated mixture of products, which were not identified.

Complex 6 was characterized by X-ray crystallography (Figure 2b). The five-membered chelating ring has a symmetrical structure with similar Si
C
C bond angles within the ring (Si
C1
C2: 114.9(2)°; Si
C2
C1: 114.5(3)°). The 29Si and 31 P NMR signals of 6 are observed at δSi 34.5 and δP
33.5, respectively, with JSi
P = 64 Hz. Scheme 4 displays a plausible pathway for the formation of disilametallacyclopentene starting from dinuclear complexes and alkynes. Insertion of alkynes into a M
Si bond generates a sixmembered cyclic intermediate (D), and subsequent reductive elimination of the unsaturated complex M(PMe3)2 affords the five-membered metallacycle (E). Coordination of RCtCR0 in the mixture to M(PMe3)2 produces an alkyne complex (F). In Scheme 4

Figure 2. Thermal ellipsoid plots of (a) 3b (50% probability), (b) 6 (50% probability), and (c) 9 (30% probability). Carbon-bound hydrogen atoms are omitted for simplicity.

Table 2. Selected Bond Distances (Å) and Angles (deg) of 3b, 6, and 9 3b (M = Pt)

6 (M = Pd)

9 (M = Pt)

M
Si

2.3705(9), 2.357(1)

2.3637(9), 2.3523(9)

2.370(4), 2.359(3)

M
P

2.3420(8), 2.353(1)

2.3811(9), 2.3993(9)

2.344(5), 2.350(5)

CdC

1.340(5)

1.353(5)

1.30(2)

Si1
M
Si2 P1
M
P2

80.56(4) 95.49(4)

77.60(3) 95.36(3)

81.1(1) 97.0(2)

Si1
C1
C2

114.4(3)

114.9(2)

116(1)

Si2
C2
C1

119.6(3)

114.5(3)

120.5(9)

3984

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complex with PEt3 ligands, Pt(CPhdCHSiMe2CHd CPh)(PEt3)2, was obtained from the reaction of Pt(SiHMe2)2(PEt3)2 with excess HCtCPh.29

Figure 3 displays the molecular structures of 8a and 8b, which have a square-planar geometry around Pt. The six-membered silaplatinacyclohexadiene rings are equipped with two aryl groups at the R-carbons and have a boat conformation. The bond distances and angles are similar to the PEt3 analogue


Pt(CArdCHSiPh2CHdCAr)(PMe3)2 (8a: Ar = C6H5, 8b: Ar =

C6H4Me-4) (eq 4). The 31P{1H} NMR spectra of the reaction mixture indicated formation of these complexes with approximately 1:2 ratio. Use of a large excess of arylacetylenes caused exclusive formation of 8a and 8b. A similar six-membered cyclic










the case of terminal alkynes, the alkyne complex is converted slowly into the dialkynyl complex via C
H bond activation. Loss of H2 is presumably involved in the reaction to produce the dialkynyl complexes. The reaction pathway is similar to those proposed for the reaction of alkynes with dinuclear Fe and Ru complexes.5 Disilametallacycles containing group 10 metal complexes have been investigated as possible intermediates in the bissilylation of unsaturated compounds catalyzed by these metal complexes23,24 and have been prepared via Si
H or Si
Si bond activation of o-disilylbenzenes,25 o-disilylcarboranes,26 and disilacyclobutenes,27 and bis(disilane)s28 promoted by low-valent transition metals. The reactions of alkynes with mononuclear bis(silyl)platinum complexes were reported to yield several different products. They involve insertion of the alkyne into the Pt
Si bond of the mononuclear complexes in most cases. Reactions of bis(silyl)platinum complex Pt(SiHPh2)2(PMe3)2 with a 3-fold molar amount of arylacetylenes HCtCAr (Ar = C6H5, C6H4Me-4) gave a mixture of the 3,5-disila-4-platinacyclopentene 3a or 3b and 6-sila-3-platina-1,4-cyclohexadienes







Pt(CPhdCHSiMe2CHd CPh)(PEt3)229 (Table 3). Two phenyl groups attached to the Si atom are not equivalent in the crystal structure, and the 1H and 13C{1H} NMR signals of 8a and 8b suggest the presence of magnetically nonequivalent SiPh groups probably due to much slower inversion of the six-membered ring than the NMR time scale. Pt(SiHPh2)2(PMe3)2 reacted with HCtCCOOMe at 50 °C for 20 h to give disilaplatinacyclopentene Pt{SiPh2C(COOMe)dCHSiPh2}(PMe3)2 (9, 67%) as the sole product (eq 5).

Figure 3. Thermal ellipsoids of 8a (30% probability) and 8b (50% probability). Carbon-bound hydrogen atoms are omitted for simplicity. There are two crystallographically independent molecules of 8b in the unit cell.

The molecular structure of 9 determined by X-ray crystallography is shown in Figure 2c. The CdC bond of 9 (1.30(2) Å) is slightly shorter than those of disilaplatinacycle 3b (1.340(5) Å) and disilapalladacycle 6 (1.353(5) Å). The 1H NMR peak of the vinyl hydrogen (δ 8.60) is observed at lower magnetic field compared to the peaks of 3a (δ 7.42) and 3b (δ 7.44) probably due to electronwithdrawing COOMe groups. The observation of two 31P NMR signals (δP
19.7 and
19.1) and two 29Si NMR signals (δSi 24.4

Pt
C Pt
P CdC C
Pt
C P
Pt
P a







Table 3. Selected Bond Distances (Å) and Angles (deg) of 8a, 8b, and the PEt3 Analogue Pt(CPhdCHSiMe2CHd CPh)(PEt3)2a

8a

8b

2.067(5)

2.077(6), 2.082(6)

2.060(6)

2.077(6), 2.075(6)

2.05(1)

2.320(2)

2.323(2), 2.311(2)

2.355(4)

2.313(2)

2.327(2), 2.329(2)

2.354(4)

1.365(9)

1.353(9), 1.344(9)

1.35(2)

1.343(9)

1.349(9), 1.366(9)

1.34(2)

86.1(2) 96.42(7)

86.1(3), 88.1(3) 96.76(6), 94.70(6)

85.2(5) 97.2(1)

2.08(1)

Ref 29. 3985

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and 32.8) suggests an unsymmetrical ring structure similar to complex 3. The experiment performed at room temperature for a short period of time (3 h) gave a 3-sila-1-propenylplatinum complex Pt(SiPh2H){C(COOMe)dCHSiPh2H}(PMe3)2 (10) (or its regioisomer (100 )) in 50% yield, as shown in Scheme 5. The NMR data for 10 are comparable to those for the previously reported 3-sila-1-propenylplatinum complex A, which involves intramolecular interaction between the SiH group of the silapropenyl ligand and Pt via the Si
H
Pt bond.6 The 31P NMR signals at δ
29.3 (JPt
P = 1994 Hz) and
19.6 (JPt
P = 1457 Hz) are assigned to the P atom trans to the silapropenyl ligand and trans to the SiHPh2 ligand, respectively. The 1H NMR spectrum shows two Si
H signals at δ 5.48 (JPt
H = 40 Hz) and 5.70 (JPt
H = 17 Hz). The former signal with larger JPt
H value is attributed to the SiPh2H group bonded with the Pt atom directly, and the latter is matched to SiPh2H groups of the silapropenyl ligand. The extended reaction time of 24 h at room temperature afforded a mixture of 9 and 10 in 14% and 50% NMR yields, and further heating of the mixture at 50 °C for 20 h produced 9 as the sole product. Thus, formation of the disilaplatinacyclopentene 9 involves the sila(propenyl)platinum complex as the intermediate. Scheme 6 summarizes the pathways for the formation of disilaplatinacyclopentene from the bis(silyl)platinum complex and terminal alkynes. Insertion of a CtC bond into the Pt
Si bond gives a silyl(silapropenyl)platinum complex (G). Intramolecular γSi
H bond activation of G produces a silaplatinacyclobutene

’ CONCLUSION The amino-substituted silylboronic ester can be employed as the silylene precursor in the synthesis of the organotransition metal complexes as shown in this study, similarly to the catalytic reactions involving formal silylene transfer to the organic substrates.11 This method may also provide an effective access to the preparation of multinuclear complexes having Si ligands.30 The diplatinum and dipalladium complexes with bridging silylene ligands react with alkynes smoothly to produce the disilametallacyclopentenes. This reaction as well as already reported reactions of diiron and diruthenium complexes probably involves insertion of alkynes into a M
Si bond in the M2Si2 framework. A mononuclear bis(silyl)platinum complex also reacts with alkynes to produce the same product via the mononuclear intermediate. The insertion of an alkyne into the M
Si bond and coupling of the alkenyl and silyl ligands occur not only in the reaction of mononuclear complexes but also in that of the dinuclear complexes. We found the occurrence of these independent pathways, although mono- and dinuclear Pt complexes can be converted to each other. Details of the two pathways were revealed by previous and current studies. The dinuclear reaction mechanism is to be considered in discussions of the reaction of organosilanes and alkynes catalyzed by Pd and Pt complexes. ’ EXPERIMENTAL SECTION General Procedures. All manipulations of the complexes were carried out in a nitrogen-filled glovebox (Miwa MFG) or using standard Schlenk techniques under an argon or nitrogen atmosphere. Hexane and toluene were purified by using a solvent purification system (Glass Contour). 1H, 13C{1H}, 29Si{1H}, and 31P{1H} NMR spectra were recorded on Bruker Biospin Avance III 400 or Varian Mercury 300 spectrometers. Chemical shifts in 1H and 13C{1H} NMR spectra were referenced to the residual peaks of the solvents used. The aromatic signals of 3a, 3b, 6, 8a, and 8b in the 1H and 13C{1H} NMR spectra were assigned by 2D HMQC NMR experiments. The peak positions of the 29 Si{1H} or 31P{1H} NMR spectra were referenced to external SiMe4 (δ 0) or H3PO4 (δ 0) in C6D6. Elemental analysis was carried out using a LECO CHNS-932 or Yanaco MT-5 CHN autorecorder at the Center for Advanced Materials Analysis, Technical Department, Tokyo Institute of Technology. IR absorption spectra were recorded on a Shimadzu FT/IR


Scheme 6

intermediate (H), accompanied by elimination of H2SiPh2. Subsequent oxidative addition of H2SiPh2 to H followed by dehydrogenative cyclization of the γ-Si
H bond produces a five-membered disilaplatinacycle along with loss of H2. The fourmembered cyclic intermediate was not observed in the reaction in Scheme 5, although the corresponding complex was isolated and fully characterized from the reaction mixture using dimethyl acetylenedicarboxylate (Scheme 3). Two COOMe groups probably stabilize the ring-strained silaplatinacyclobutene. The reaction of arylacetylene with Pt(SiHPh2)2(PMe3)2 yields both disilaplatinacyclopentene and silaplatinacyclohexadiene, as shown in eq 4. The former product is formed via the reaction of H2SiPh2 with intermediate H, while the latter is obtained from the further reaction of alkyne with H. Formation of the two products can be explained by the pathway involving the common mononuclear intermediates (Schemes 5 and 6).




Scheme 5

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8100 spectrometer. Et2NSiPh2BOCMe2CMe2 O,10 Pd(PCy3)2,31 Pt(PCy3)2,32 and Pt(SiHPh2)2(PMe3)233 were prepared according to the reported procedure. HCtCPh, PhCtCPh, HCtCC6H4Me-4, and 3986

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Ph2BOCMe2CMe2 O (286 mg, 0.75 mmol) with Pd(PMe3)4,35 which was generated from phosphine exchange of Pd(PCy3)2 (500 mg, 0.75 mmol) and PMe3 (310 μL, 3.0 mmol) in 1:4 ratio. The procedure was similar to the preparation of 1. Anal. Calcd for C36H56P4Pd2Si2: C, 49.04; H, 6.40. Found: C, 48.60; H, 6.30. 1H NMR (400 MHz, C6D6, rt): δ 0.76 (d, 36H, PCH3, 2JP
H = 2.8 Hz), 7.12 (t, 4H, C6H5 para, 3JH
H = 7.5 Hz), 7.24 (t, 8H, C6H5 meta, 3JH
H = 7.5 Hz), 8.14 (d, 8H, C6H5 ortho, 3JH
H = 7.5 Hz). 13C{1H} NMR (101 MHz, C6D6, rt): δ 19.2 (d, PCH3, JP
C = 9.2 Hz), 125.9 (C6H5 para), 126.9 (C6H5 meta), 136.1 (C6H5 ortho), 149.4 (C6H5 ipso). 29Si{1H} NMR (79 MHz, C6D6, rt): δ
35.3 (br). 31 1 P{ H} NMR (162 MHz, C6D6, rt): δ
33.7 (br).

Preparation of Pt(SiPh2CPhdCH SiPh2)(PMe3)2 (3a). A mixture of 1 (200 mg, 0.19 mmol) and HCtCPh (58 mg, 0.57 mmol) in toluene (5 mL) was stirred at room temperature for 10 h. The initially yellow solution gradually turned red, and precipitation of a white solid was observed. The solid was washed three times with 2 mL of hexane and dried in vacuo to give 3a (95 mg, 62%) as a white solid. The 31P{1H} NMR spectrum of the reaction mixture after 10 h exhibited two doublets at δ
30.5 (JPt
P = 3227 Hz, JP
P = 36 Hz) and
28.3 (JPt
P = 3350 Hz, JP
P = 36 Hz), which were assigned as inequivalent phosphine ligands of Pt(η2-HCtCPh)(PMe3)2 (4a). The coupling constants are comparable to those of Pt(PPh3)2(η2-HCtCPh) (δ 27.1, JPt
P = 3547 and JP
P = 33.4 Hz; δ 31.0, JPt
P = 3464 and JP
P = 33.4 Hz).22 Data for 3a: Anal. Calcd for C38H44P2PtSi2 3 1/2toluene: C, 57.96; H, 5.63. Found: C, 58.23; H, 6.04. 1H NMR (400 MHz, C6D6, rt): δ 0.77 (br d, 9H, PCH3, 2JP
H = 7.0 Hz), 0.85 (br d, 9H, PCH3, 2JP
H = 7.0 Hz), 6.92 (s, 5H, dCC6H5), 7.24 (m, 6H, SiC6H5 para and meta, 3JH
H = 7.3 Hz), 7.34 (t, 4H, SiC6H5 meta, 3JH
H = 7.3 Hz), 7.42 (m, 1H, dCH, 4JP
H = 2.5 Hz, 3JPt
H = 67 Hz), 8.07 (d, 4H, SiC6H5 ortho, 3JH
H = 8.0 Hz), 8.15 (d, 4H, SiC6H5 ortho, 3JH
H = 8.0 Hz). One of the para hydrogen signals was overlapped with the solvent signals. 13C{1H} NMR (101 MHz, C6D6, rt): δ 18.7 (br, PCH3, JP
C = 13 Hz), 125.4 (dCC6H5 para), 136.9 (SiC6H5 ortho, 3JPt
C = 24 Hz), 146.7 (m, SiC6H5 ipso), 147.5 (dCC6H5 ipso, 3JPt
C = 21 Hz), 156.4 (apparent triplet, dCH, 3JP
C =

Preparation of Pt{SiPh2C(C6H4Me-4)dCH SiPh2}(PMe3)2 (3b). Complex 3b, a white solid (94 mg, 60%), was obtained by a similar procedure to the preparation of 3a from 1 (200 mg, 0.19 mmol) and HCtCC6H4Me-4 (72 μL, 0.57 mmol) in toluene (5 mL). The 31 1 P{ H} NMR spectrum of the reaction mixture after 10 h exhibited two doublets at δ
30.5 (JPt
P = 3180 Hz, JP
P = 36 Hz) and
28.2 (JPt
P = 3345 Hz, JP
P = 36 Hz), which were assigned as inequivalent phosphines of Pt(η2-HCtCC6H4Me-4)(PMe3)2 (4b). Cooling the filtrate for 5 days in a refrigerator resulted in the formation of trans-Pt(CtCC6H4Me-4)2(PMe3)2 (5b) (22 mg, 20%) as a white solid. Complex 5b was characterized on the basis of the NMR spectroscopic data in the literature.36 Data for 3b: Anal. Calcd for C39H46P2PtSi2 3 1/2hexane: C, 57.91; H, 6.13. Found: C, 57.59; H, 5.99. 1H NMR (400 MHz, C6D6, rt): δ 0.78 (br d, 9H, PCH3, 2JP
H = 8.0 Hz), 0.85 (br d, 9H, PCH3, 2JP
H = 8.0 Hz), 2.00 (s, 3H, C6H4CH3), 6.74 (d, 2H, CC6H4 ortho, 3JH
H = 8.0 Hz), 6.88 (d, 2H, CC6H4 meta, 3JH
H = 8.0 Hz), 7.25 (m, 6H, SiC6H5 para and meta, 3JH
H = 7.3 Hz), 7.34 (t, 4H, SiC6H5 meta, 3JH
H = 7.3 Hz), 7.44 (m, 1H, dCH, 4JP
H = 2.5 Hz, 3JPt
H = 67 Hz), 8.10 (d, 4H, SiC6H5 ortho, 3JH
H = 8.0 Hz), 8.15 (d, 4H, SiC6H5 ortho, 3JH
H = 8.0 Hz). One of the para hydrogen signals was overlapped with solvent signals. 13C{1H} NMR (101 MHz, C6D6, rt): δ 18.7 (br, PCH3, JP
C = 13 Hz), 21.1 (C6H4CH3), 134.4 (CC6H4 para), 136.9 (SiC6H5 ortho, 3 JPt
C = 24 Hz), 144.5 (CC6H4 ipso, 3JPt
C = 22 Hz), 146.6 (m, SiC6H5 ipso), 155.9 (apparent triplet, dCH, 3JP
C = 5.7 Hz, 2JPt
C = 127 Hz), 169.0 (apparent triplet, dCC6H5, 3JP
C = 5.9 Hz, 2JPt
C = 129 Hz). The para and meta carbon signals of the SiC6H5 group and meta and ortho carbon signals of the C6H4Me group were overlapped with the solvent signals. 29Si{1H} NMR (79 MHz, THF-d8, rt): δ 23.9 (d, JPt
Si = 1176 Hz, 2JP
Si = 137 Hz), 34.6 (d, JPt
Si = 1264 Hz, 2JP
Si = 144 Hz). 31 1 P{ H} NMR (162 MHz, C6D6, rt): δ
19.7 (JPt
P = 1539 Hz, 2JP
P = 29 Hz),
19.3 (JPt
P = 1572 Hz, 2JP
P = 29 Hz). Data for 5b: 1H NMR (400 MHz, CDCl3, rt): δ 1.73 (br, 18H, PCH3), 2.29 (s, 6H, C6H4CH3), 7.02 (d, 4H, C6H4 meta, 3JH
H = 8.0 Hz), 7.24 (d, 4H, C6H4 ortho, 3JH
H = 8.0 Hz). 31P{1H} NMR (162 MHz, CDCl3, rt): δ
20.3 (JPt
P = 2480 Hz).





crude products displayed formation of 1 and Et2NBOCMe2CMe2 O. The solvent and volatile materials were removed under reduced pressure. The residual material was washed three times with 3 mL of hexane and dried in vacuo to give complex 1 as a yellow solid (280 mg, 80%). Anal. Calcd for C36H56P4Pt2Si2: C, 40.83; H, 5.33. Found: C, 40.58; H, 4.95. 1H NMR (400 MHz, C6D6, rt): δ 0.86 (d, 36H, PCH3, 2JP
H = 6.4 Hz, 3JPt
H = 18 Hz), 7.18 (t, 4H, C6H5 para, 3JH
H = 7.5 Hz), 7.33 (t, 8H, C6H5 meta, 3 JH
H = 7.5 Hz), 8.23 (d, 8H, C6H5 ortho, 3JH
H = 7.5 Hz). 13C{1H} NMR (101 MHz, C6D6, rt): δ 20.2 (m, PCH3), 126.1 (C6H5 para, 5JPt
C = 7.4 Hz), 126.6 (C6H5 meta), 137.1 (C6H5 ortho, 3JPt
C = 23 Hz), 152.1 (C6H5 ipso, 3JP
C = 5.8 Hz). 29Si{1H} NMR (79 MHz, C6D6, rt): δ
75.8 (apparent quintet, JPt
Si = 715 Hz, 2JP
Si = 52 Hz). 31P{1H} NMR (162 MHz, C6D6, rt): δ
14.4 (JPt
P = 1665 Hz, 3JPt
P = 266 Hz, 2JSi
P = 52 Hz, 4JP
P =18 Hz). Preparation of {Pd(PMe3)2}2(μ-SiPh2)2 (2). Complex 2 (158 mg, 48%) as a yellow solid was obtained by the reaction of Et2NSi-













ratio, was added Et2NSiPh2BOCMe2CMe2O (252 mg, 0.66 mmol) at room temperature. The mixture was stirred at 60 °C for 40 h. The initially pale yellow solution gradually turned dark red. The 1H NMR spectra of the




5.9 Hz, 2JPt
C = 127 Hz), 169.2 (apparent triplet, dCC6H4, 3JP
C = 5.7 Hz, 2JPt
C = 128 Hz). The para and meta carbon signals of the SiC6H5 group and meta and ortho carbon signals of the CC6H4 group were overlapped with the solvent signals. 31P{1H} NMR (162 MHz, C6D6, rt): δ
19.8 (JPt
P = 1542 Hz, 2JP
P = 29 Hz),
19.3 (JPt
P = 1571 Hz, 2JP
P = 29 Hz).










HCtCCOOMe were purchased from Tokyo Chemical Industry and distilled prior to use. Commercially available PMe3 (Sigma-Aldrich) was used without any purification. Preparation of {Pt(PMe3)2}2(μ-SiPh2)2 (1). To a toluene solution (5 mL) of Pt(PMe3)4,34 prepared in situ from the ligand exchange of Pt(PCy3)2 (500 mg, 0.66 mmol) with PMe3 (273 μL, 2.6 mmol) in 1:4

Preparation of Pd(SiPh2CPhdCPh SiPh2)(PMe3)2 (6). To a toluene solution (3 mL) of 2 (200 mg, 0.23 mmol) was added a 2-fold molar amount of PhCtCPh (81 mg, 0.45 mmol), and then the resulting mixture was stirred at room temperature for 10 h. The initially dark red solution gradually turned gray. The solvent and volatile materials were removed under reduced pressure to produce an oily residue, which was washed three times with 2 mL of hexane and dried in vacuo to give complex 6 as a white solid (90 mg, 50%). The filtrate was stored in a refrigerator overnight to afford Pd(η2-PhCtCPh)(PMe3)2 (7) as a white solid (30 mg, 30%). The NMR data of 7 are comparable to those of an analogue, Pd(η2-PhCtCPh)(PMe2Ph)2.2d Data for 6: Anal. Calcd for C44H48P2PdSi2: C, 65.94; H, 6.04. Found: C, 65.66; H, 5.89. 1H NMR (400 MHz, C6D6, rt): δ 0.63 (m, 18H, PCH3, 2JP
H = 6.0 Hz), 6.57 (d, 4H, =CC6H5 ortho, 3JH
H = 6.7 Hz), 6.71 (t, 2H, =CC6H5 para, 3 JH
H = 7.0 Hz), 6.77 (t, 4H, dCC6H5 meta, 3JH
H = 7.2 Hz), 7.21 (t, 4H, SiC6H5 para, 3JH
H = 7.2 Hz), 7.29 (t, 8H, SiC6H5 meta, 3JH
H = 7.2 Hz), 8.06 (d, 8H, SiC6H5 ortho, 3JH
H = 7.8 Hz). 13C{1H} NMR (101 MHz, C6D6, rt): δ 17.5 (dd, PCH3, JP
C = 8.7, 11 Hz), 124.5 (dCC6H5 para), 127.0 (dCC6H5 meta), 127.5 (SiC6H5 meta), 129.1 (dCC6H5 ortho), 137.1 (SiC6H5 ortho), 144.9 (dCC6H5 ipso), 145.1 (apparent triplet, SiC6H5 ipso, 3JP
C = 13 Hz). 166.5 (apparent triplet, 3987

dx.doi.org/10.1021/om200156g |Organometallics 2011, 30, 3981–3991

Organometallics

ARTICLE

Table 4. Crystallographic Data and Details of Refinement of 1, 2, 3b, 6, 8a, 8b, and 9 1

2

3b 3 1/2toluene

6 3 1/2toluene C44H48P2PdSi2 3 (1/2 C7H8)

formula

C36H56P4Pt2Si2

C36H56P4Pd2Si2

C39H46P2PtSi2 3 (1/2 C7H8)

fw

1059.08

881.70

874.07

847.45

cryst size/mm

0.50  0.60  0.70

0.15  0.20  0.30

0.25  0.30  0.30

0.12  0.15  0.15

cryst syst

monoclinic

triclinic

monoclinic

monoclinic

cryst color

yellow

yellow

colorless

colorless

space group

P21/n (No. 14)

P1 (No. 2)

P21/c (No. 14)

P21/n (No. 14)

a/Å

11.574(2)

9.609(4)

12.678(3)

10.113(2)

b/Å c/Å

18.941(2) 19.224(2)

10.751(5) 11.421(5)

18.481(4) 18.113(4)

20.167(3) 21.381(3)

107.014(2)

111.692(4)

108.257(3)

96.812(2)

R/deg β/deg

98.784(1)

γ/deg

106.126(7)

V/Å3

4029.8(9)

1009.2(8)

4030(2)

4330(1)

Z

4

1

4

4

Dcalcd/g cm
3

1.746

1.451

1.440

1.300

F(000) μ/mm
1

2064 7.1496

452 1.1331

1764 3.6343

1764 0.5895

no. of reflns measd

32 570

8254

32 417

33 888

no. of unique reflns

9181

4427

9213

9841

Rint

0.030

0.030

0.0539

0.0737

no. of obsd reflns (I > 2σ(I))

8098

3408

7504

7738

no. of variables

410

200

442

479

R, Rw (I > 2σ(I))

0.0199, 0.0422

0.0316, 0.0828

0.0299, 0.0699

0.0470, 0.1080

R, Rw (all data) GOF on F2

0.0241, 0.0438 1.024

0.0404, 0.0861 0.989

0.0371, 0.0700 0.994

0.0666, 0.1175 1.093

8a

8b

9

formula

C34H40P2PtSi

C36H44P2PtSi

fw

733.81

761.87

795.91

cryst size/mm

0.26  0.32  0.64

0.10  0.10  0.15

0.22  0.28  0.55

cryst syst

monoclinic

monoclinic

monoclinic

cryst color

colorless

colorless

colorless

space group a/Å

P21/c (No. 14) 17.963(5)

P21/c (No. 14) 20.1864(6)

P21/n (No. 14) 13.006(7)

b/Å

10.544(4)

15.5085(3)

17.015(7)

c/Å

18.541(3)

21.8311(6)

16.417(6)

β/deg γ/deg V/Å3

111.40(2)

92.608(2)

101.849(7)

3270(2)

6827.4(3)

3556(3)

Z Dcalcd/g cm
3 F(000)

4 1.491 1464

8 1.482 3056

4 1.487 1592

μ/mm
1

4.4292

4.2454

4.1154

no. of reflns measd

7732

55 076

8511

no. of unique reflns

7499

15 605

8160

no. of obsd reflns (I > 2σ(I))

6373

12 578

5415

no. of variables R, Rw (I > 2σ(I)) R, Rw (all data) GOF on F2

349 0.0462, 0.1279 0.0553, 0.1348 1.027

737 0.0439, 0.1137 0.0597, 0.1536 1.099

377 0.0754, 0.2026 0.1195, 0.2286 1.048

C34H42O2P2PtSi2

R/deg

CdC, 3JP
C = 7.3 Hz). The para carbon signal of the SiC6H5 group was overlapped with the solvent signals. 29Si{1H} NMR (79 MHz, C6D6, rt):

δ 34.5 (apparent triplet, 2JP
Si = 64 Hz). 31P{1H} NMR (162 MHz, C6D6, rt): δ
33.5 (2JSi
P = 64 Hz). Data for 7: 1H NMR (400 MHz, 3988

dx.doi.org/10.1021/om200156g |Organometallics 2011, 30, 3981–3991

Organometallics

ARTICLE







C6D6, rt): δ 1.05 (br, 18H, PCH3), 7.03 (t, 2H, C6H5 para, 3JH
H = 7.2 Hz), 7.19 (t, 4H, C6H5 meta, 3JH
H = 7.2 Hz), 7.64 (d, 4H, C6H5 ortho, 3 JH
H = 7.2 Hz). 13C{1H} NMR (101 MHz, C6D6, rt): δ 20.0 (br, PCH3), 119.2 (br d, CtC, 2JP
C = 64 Hz), 125.1 (br, C6H5 para), 128.7 (br, C6H5 ortho), 137.5 (br, C6H5 ipso). The meta carbon signal of the C6H5 group was overlapped with the solvent signals. 31P{1H} NMR (162 MHz, C6D6, rt): δ
25.6. Reaction of Pt(SiHPh2)2(PMe3)2 with HCtCPh. To a toluene solution (10 mL) of Pt(SiHPh2)2(PMe3)2 (321 mg, 0.45 mmol) was added a 3-fold molar amount of HCtCPh (140 μL, 1.27 mmol), and then the resulting mixture was stirred at 60 °C for 7 h. The yellow solution gradually turned orange. The solvent and volatile materials were removed under reduced pressure. The obtained residue was washed three times with 5 mL of hexane to give a mixture of 3a and







Pt(CPhdCHSiPh2CHd CPh)(PMe3)2 (8a) in 1:1.9 ratio estimated by NMR spectroscopy. Repeated recrystallization with toluene/ hexane at room temperature gave 8a (84 mg, 25%) as a white solid. Anal. Calcd for C34H40P2PtSi: C, 55.65; H, 5.49. Found: C, 55.38; H, 5.39. 1H NMR (400 MHz, C6D6, rt): δ 0.64 (d, 18H, PCH3, 2JP
H = 8.0 Hz, 3JPt
H = 18 Hz), 7.06 (t, 2H, dCC6H5 para, 3JH
H = 7.6 Hz), 7.18
7.22 (m, 6H, SiC6H5 meta and para), 7.26 (t, 4H, dCC6H5 meta, 3JH
H = 7.6 Hz), 7.66 (d, 2H, dCH, 4JP
H = 15 Hz, 3JPt
H = 126 Hz), 7.77 (m, 2H, SiC6H5 ortho), 7.88 (m, 2H, SiC6H5 ortho), 8.05 (d, 4H, dCC6H5 ortho, JH
H = 8.0 Hz). 13C{1H} NMR (100 MHz, C6D6, rt): δ 16.7 (m, PCH3, JP
C = 30 Hz), 126.1 (dCC6H5 para), 127.5 (dCH, JPt
C was not observed), 127.8 (dCC6H5 meta), 128.6 (dCC6H5 ortho), 135.6 (SiC6H5 ortho), 136.3 (SiC6H5 ortho), 140.4 (SiC6H5 ipso), 143.8 (SiC6H5 ipso), 152.6 (apparent triplet, dCC6H5 ipso, 3JP
C = 5.5 Hz, 2JPt
C = 44 Hz), 192.8 (dd, dCC6H4, 2JPcis
C = 13 Hz, 2JPtrans
C = 109 Hz, JPt
C = 811 Hz). The para and meta carbon signals of the SiC6H5 group were overlapped with the solvent signals. 31P{1H} NMR (162 MHz, C6D6, rt): δ
29.5 (JPt
P = 1765 Hz). Reaction of Pt(SiHPh2)2(PMe3)2 with HCtCC6H4Me-4. A mixture of Pt(SiHPh 2)2(PMe 3)2 (300 mg, 0.42 mmol) and a 3-fold molar amount of HCtCC6 H4 Me-4 (244 mg, 2.1 mmol) in toluene (5 mL) was stirred at 60 °C for 10 h. The ratio of 3b and

Preparation of Pt(SiPh2H){C(COOMe)dCHSiPh2H}(PMe3)2 (10). To a toluene solution (6 mL) of Pt(SiHPh2)2(PMe3)2 (172 mg,

0.24 mmol) was added HCtCCOOMe (20 μL, 0.24 mmol), and then the resulting mixture was stirred at room temperature for 3 h. The initial yellow solution gradually turned pale yellow. The solvent and volatile materials were evaporated under reduced pressure to produce a residue, which was washed three times with 3 mL of hexane and dried in vacuo to give complex 10 or its regioisomer (100 ) as a white solid (96 mg, 50%). 1H NMR (300 MHz, C6D6, rt): δ 0.84 (d, 9H, PCH3, 2JP
H = 8.1 Hz, 3JPt
H = 17 Hz), 1.05 (d, 9H, PCH3, 2JP
H = 8.4 Hz, 3JPt
H = 23 Hz), 3.35 (s, 3H, OCH3), 5.48 (dd, 1H, PtSiH, 3JPcis
H = 10 Hz, 3JPtrans
H = 14 Hz, 2JPt
H = 40 Hz), 5.70 (d, 1H, CSiH, J = 5.6 Hz, JPt
H = 17 Hz), 7.08
7.30 (m, 12H, C6H5 meta and para), 7.49 (m, 2H, C6H5 ortho), 7.61 (m, 2H, C6H5 ortho), 7.90 (d, 2H, C6H5 ortho, JH
H = 8.1 Hz), 8.03 (d, 2H, C6H5 ortho, JH
H = 6.6 Hz), 8.16 (apparent double triplet, 1H, dCH, J = 5.6, 18 Hz). 31P{1H} NMR (122 MHz, C6D6, rt): δ
29.3 (d, JPt
P = 1994 Hz, 2JP
P = 21 Hz),
19.6 (d, JPt
P = 1457 Hz, 2JP
P = 21 Hz). IR (KBr): 2130 (νSi
H), 2039 (νSi
H), 1690 (νCdO) cm
1. The extended reaction of Pt(SiHPh2)2(PMe3)2 and HCtCCOOMe for 24 h at room temperature gave 9 and 10 as mixtures in 14% and 50% NMR yields, followed by heating of the mixture at 50 °C for 20 h to afford 9 as the sole product. X-ray Crystallography. Crystals of 1, 2, 3b, 6, 8a, 8b, and 9 suitable for X-ray crystallography were obtained by slow diffusion from toluene/ hexane at room temperature and were mounted on MicroMounts (MiTeGen). The crystallographic data for 1, 2, 3b, 6, and 8b were collected on a Rigaku Saturn CCD area detector equipped with monochromated Mo KR radiation (λ = 0.71073 Å) at
160 °C, and the data for 8a and 9 were collected on a Rigaku AFC-5R automated four-cycle diffractometer at room temperature. Calculations were carried out using the program package Crystal Structure, version 4.0, for Windows. The positional and thermal parameters of non-hydrogen atoms were refined anisotropically on F2 by the full-matrix least-squares method using SHELXL-97.37 Hydrogen atoms were placed at calculated positions and refined with a riding mode on their corresponding carbon atoms. Crystallographic data and details of refinement of 1, 2, 3b, 6, 8a, 8b, and 9 are summarized in Table 4.







Pt(CArdCHSiPh2CHd CAr)(PMe3)2 (8b: Ar = C6H4Me-4) was estimated as 1:2 by 31P NMR spectroscopy. Repeated recrystallization from toluene/hexane at room temperature gave 8b (65 mg, 20%) as a white solid. Anal. Calcd for C36H44P2PtSi: C, 56.75; H, 5.82. Found: C, 56.88 H, 5.33. 1H NMR (400 MHz, C6D6, rt): δ 0.67 (d, 18H, PCH3, 2JP
H = 8.0 Hz, 3JPt
H = 17 Hz), 2.18 (s, 6H, C6H4CH3), 7.09 (d, 4H, dCC6H4 meta, 3JH
H = 8.0 Hz), 7.18
7.21 (m, 6H, SiC6H5 meta and para), 7.64 (d, 2H, dCH, 4JP
H = 15 Hz, 3JPt
H = 127 Hz), 7.78 (m, 2H, SiC6H5 ortho), 7.91 (m, 2H, SiC6H5 ortho), 7.99 (d, 4H, =CC6H4 ortho, 3JH
H = 8.0 Hz). 13C{1H} NMR (101 MHz, C6D6, rt): δ 16.8 (m, PCH3, JP
C = 30 Hz), 21.2 (C6H4CH3), 126.3 (dCH, 2JPt
C = 27 Hz), 128.5 (dCC6H4 meta or ortho), 128.6 (dCC6H4 meta or ortho), 135.3 (dCC6H4 para), 135.7 (SiC6H5 ortho), 136.3 (SiC6H5 ortho), 140.7 (SiC6H5 ipso), 144.1 (SiC6H5 ipso), 149.9 (apparent triplet, dCC6H4 ipso, 3JP
C = 5.5 Hz, 2JPt
C = 41 Hz), 192.9 (dd, dCC6H4, 2JPcis
C = 13 Hz, 2 JPtrans
C = 108 Hz, JPt
C = 806 Hz). The para and meta carbon signals of the SiC6H5 group were overlapped with the solvent signals. 31P{1H} NMR (162 MHz, C6D6, rt): δ
29.4 (JPt
P = 1761 Hz).

evaporated under reduced pressure to produce a residue, which was washed three times with 5 mL of hexane and dried in vacuo to give complex 9 as a pale yellow solid (139 mg, 67%). Anal. Calcd for C34H42O2P2PtSi2: C, 51.31; H, 5.32. Found: C, 51.09; H, 5.30. 1H NMR (400 MHz, C6D6, rt): δ 0.74 (d, 9H, PCH3, 2JP
H = 8.0 Hz, 3JPt
H = 20 Hz), 0.83 (d, 9H, PCH3, 2 JP
H = 8.0 Hz, 3JPt
H = 19 Hz), 3.17 (s, 3H, OCH3), 7.17
7.22 (m, 4H, C6H5 para), 7.27 (t, 4H, C6H5 meta, 3JH
H = 8.0 Hz), 7.32 (t, 4H, C6H5 meta, 3JH
H = 8.0 Hz), 8.03 (d, 4H, C6H5 ortho, 3JH
H = 8.0 Hz), 8.43 (d, 4H, C6H5 ortho, 3JH
H = 8.0 Hz), 8.60 (d, 1H, dCH, 4JP
H = 6.0 Hz, 3 JPt
H = 66 Hz). 13C{1H} NMR (101 MHz, CD2Cl2, rt): δ 18.6 (m, PCH3, JP
C = 3.9 and 25 Hz), 19.1 (m, PCH3, J = 3.9 and 25 Hz), 50.9 (OCH3), 127.4 (C6H5 meta), 127.9 (C6H5 meta and para), 128.1 (C6H5 para), 136.7 (C6H5 ortho, 3JPt
C = 23 Hz), 137.0 (C6H5 ortho, 3JPt
C = 23 Hz), 144.8 (d, C6H5 ipso, 3JP
C = 3.9 Hz, 2JPt
C = 35 Hz), 145.5 (d, C6H5 ipso, 3JP
C = 9.7 Hz, 2JPt
C = 38 Hz), 157.6 (apparent triplet, dCH, 3JP
C = 9.7 Hz, 2JPt
C = 142 Hz), 168.3 (apparent triplet, =CCOO, 3 JP
C = 3.9 Hz, 2JPt
C = 137 Hz), 169.4 (CdO, 3JPt
C = 35 Hz). 29 Si{1H} NMR (79 MHz, CD2Cl2, rt): δ 24.4 (dd, JPt
Si = 1251 Hz, 2 JPtrans
Si = 145 Hz, 2JPcis
Si = 5.5 Hz), 32.8 (dd, JPt
Si = 1270 Hz, 2JPtrans
Si = 147 Hz, 2JPcis
Si = 3.7 Hz). 31P{1H} NMR (162 MHz, C6D6, rt): δ
19.7 (d, JPt
P = 1501 Hz, 2JP
P = 31 Hz),
19.1 (d, JPt
P = 1595 Hz, 2 JP
P = 31 Hz). IR (KBr): 1695 (νCdO) cm
1.

Preparation of Pt(SiPh2C(COOMe)dCH SiPh2)(PMe3)2 (9). To a toluene solution (7 mL) of Pt(SiHPh2)2(PMe3)2 (186 mg, 0.26 mmol) was added an equimolar amount of HCtCCOOMe (22 μL, 0.26 mmol), and then the resulting mixture was stirred at 50 °C for 20 h. The yellow solution gradually turned orange. The solvent and volatile materials were

’ ASSOCIATED CONTENT

bS

Supporting Information. Crystallographic data for 1, 2, 3b, 6, 8a, 8b, and 9 as a CIF file. This material is available free of charge via the Internet at http://pubs.acs.org.

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Organometallics

’ AUTHOR INFORMATION Corresponding Author

*E-mail: [email protected].

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