Tin and Lead Phosphanido Complexes: Reactivity ... - ACS Publications

Article Cite This: Inorg. Chem. 2017, 56, 14831−14841

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Tin and Lead Phosphanido Complexes: Reactivity with Chalcogens Eric C. Y. Tam,† David C. Apperley,‡ J. David Smith,† Martyn P. Coles,†,§ and J. Robin Fulton*,†,§ †

Department of Chemistry, University of Sussex, Falmer, Brighton BN1 9QJ, U.K. Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, U.K. § School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6012, New Zealand ‡

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ABSTRACT: The reactivity of tin and lead phosphanido complexes with chalogens is reported. The addition of sulfur to [(BDI)MPCy2] (M = Sn, Pb; BDI = CH{(CH3)CN-2,6-iPr2C6H3}2) results in the formation of phosphinodithioates [(BDI)MSP(S)Cy2] regardless of the conditions; however, when selenium is added to [(BDI)MPCy2], a selenium insertion product, phosphinoselenoite [(BDI)MSePCy2], can be isolated. This compound readily reacts with additional selenium to form the phosphinodiselenoate complex [(BDI)MSeP(Se)Cy2]. In contrast, the addition of selenium to [(BDI)SnP(SiMe3)2] results in the formation of the heavy ether [(BDI)SnSeSiMe3]. Differences in the solution and solid-state molecular species of tin phosphinoselenoite and phosphinodiselenoate complexes were probed using multinuclear solution and solid-state NMR spectroscopy.

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INTRODUCTION Group 14/16 nanomaterials have received an increasing amount of attention in the past decade because of their potential use in optoelectronic devices.1 Traditionally, these materials are synthesized by the treatment of a metal halide with trioctylphosphane chalcogenide (i.e., TOPE, where E = S, Se, or Te). The phosphane chalcogenide creates a soluble source of the heavier chalcogen, minimizing any kinetic barrier for the growth of the group 14/16 particles. The mechanism for nucleation of these particles is poorly understood. Although tertiary phosphines are responsible for chalogen transfer in nanoparticle growth, there is evidence that secondary phosphine (R2HPSe and R2HPTe) impurities are key in the nucleation step, resulting in the formation of both phosphinochalcogenoite and phosphinodichalcogenoate complexes [LMEPR2 and LMEP(E)R2, respectively; M = Ge, Sn, Pb; E = S, Se, Te; L = anionic ligand such as oleate] as intermediates.2,3 Several examples of group 14 phosphinodichalcogenoate complexes [LMEP(E)PR2] have been reported;4−8 however, outside our studies,9,10 group 14 phosphinochalcogenoite complexes (LMEPR2) have been implicated only through either computational studies or pure speculation; indeed, this type of ligand class has been characterized only on titanium and tungsten centers.11,12 Thus, little is known about the stability and reactivity of such group 14 complexes. We have recently reported the reactivity of β-diketiminatogermanium phosphanide complexes [(BDI)GePR2] (1-Ge-R; BDI = CH{(CH3)CN-2,6-iPr2C6H3}2; R = Cy, Ph, SiMe3) with chalcogens (E = S, Se, Te) and noted a range of products depending upon both the phosphanido ligand and the chalcogen (Figure 1).9,10,13 The lightest chalcogen oxidized both redox-active germanium(II) and phosphorus(III) centers © 2017 American Chemical Society

Figure 1. Variety of products from the reaction of 1-Ge-PR2 with S, Se, or Te.

of 1-Ge-Cy to form complexes of the types 3-Ge-Cy-S, 4-GeCy-S2, and 5-Ge-Cy-S3, whereas the heaviest chalcogen only inserted into the Ge−P bond to form a complex of the type 2Ge-Cy-Te. Selenium gave products from both insertion and oxidation, e.g., complexes of the type 2-Ge-R-Se (R = Cy, Ph), 3-Ge-R-Se (R = Cy, SiMe3), and 4-Ge-R-Se2 (R = Cy, Ph). Only minor differences were observed between the aliphatic and aromatic phosphanido ligands (R = Cy, Ph); however, the different hybridization of the phosphorus atom in the bis(trimethylsilyl)phosphanido ligand of 1-Ge-SiMe3 from that in 1-Ge-Cy and 1-Ge-Ph results in both an increase in the Ge−P bond length and a decreased nucleophilicity at the Received: August 8, 2017 Published: November 30, 2017 14831

DOI: 10.1021/acs.inorgchem.7b02040 Inorg. Chem. 2017, 56, 14831−14841

Article

Inorganic Chemistry

In the solid state, 2-Sn-Cy-Se is isostructural with the germanium analogue, with a rare κ-Se binding mode for the phosphinoselenoite ligand (Figure 2 and Table 1 for selected

phosphorus center. Thus, the only reactivity observed toward selenium is at germanium. Because the heavier group 14 congeners do not typically undergo oxidative addition of chalcogens,14−17 we thought it worthwhile to make a comparative study of the germanium compounds of those of the heavier cogeners. The related [(BDIPh/TMS)Sn(N{SiMe3}2)] (BDIPh/TMS = CH{(Ph)CN(SiMe3)}2) undergoes oxidative addition with both sulfur and selenium to form tin(IV) complexes, similar to structures of the type 3 (Figure 1),14 but as was conceivable in the analogous tin phosphanide complexes, it would be possible to observe a competition between the two redox-active centers at tin and phosphorus. Because both tin(II) and lead(II) diphenylphospanide complexes proved to be unstable, decomposing in solution to form an insoluble black precipitate and tetraphenyldiphosphine, we focused on tin(II) and lead(II) dicyclohexylphospanides (1-Sn-Cy and 1-Pb-Cy, respectively) and tin(II) bis(trimethylsilyl)phosphanide (1-Sn-SiMe3). The NMR-active nuclei in some of the resulting products allowed us to examine the relationships between the solution- and solidphase structures. We did not examine the reactivity between the phosphanide complexes with the lightest chalcogen, oxygen, and no reactivity was observed between either the tin or lead phosphanide complexes and tellurium. Indeed, the only group 14 phosphanide complex observed to react with tellurium is germanium(II) dicyclohexylphospanide.

Figure 2. ORTEP diagram of tin(II) dicyclohexylphosphinoselenoite (2-Sn-Cy-Se). Hydrogen atoms are omitted and BDI carbon atoms minimized for clarity. The ellipsoid probability is shown at 30%.

Table 1. Selected Bond Lengths (Å) and Angles (deg) for Compounds 2-Ge-Cy-Se, 2-Sn-Cy-Se, and 2-Pb-Cy-Se

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RESULTS AND DISCUSSION Reactivity of 1-Sn-Cy with Selenium. The addition of selenium to 1-Sn-Cy results in the formation of both tin(II) dicyclohexylphosphinoselenoite, 2-Sn-Cy-Se, and tin(II) dicyclohexylphosphinodiselenoate, 4-Sn-Cy-Se2 (Scheme 1). The Scheme 1

ratio of the products is highly dependent on the stoichiometry and reaction conditions. When the reaction is performed on a small scale in an NMR tube, both products are observed, even when only 1 equiv of selenium is added. Yields of 2-Sn-Cy-Se are maximized by the slow stirring of a 1:1 mixture of 1-Sn-Cy and elemental selenium, although 4-Sn-Cy-Se2 and 1-Sn-Cy are both observed in the NMR analysis of the crude reaction mixture. The phosphinodiselenoate complex 4-Sn-Cy-Se2 can be synthesized either directly by treatment of the phosphinoselenoite complex 2-Sn-Cy-Se with selenium or from the phosphanide complex 1-Sn-Cy with an excess of selenium. The formation of 4-Sn-Cy-Se2 from 2-Sn-Cy-Se is reversible; that is, the addition of the phosphanide complex 1-Sn-Cy to 4-Sn-CySe2 results in formation of the phosphinoselenoite complex 2Sn-Cy-Se, indicating an equilibrium between 2-Sn-Cy-Se and 4-Sn-Cy-Se2. Yields for both products are maximized by allowing the reactions to proceed overnight; however, good conversion is observed after 2 h at room temperature. These complexes decompose in solution to a black metallic precipitate; however, they can be stored as solids at −30 °C for several weeks.

(BDI)Ge(SePCy2) (2-Ge-Cy-Se)9,10

(BDI) Sn(SePCy2) (2Sn-Cy-Se)

(BDI) Pb(SePCy2) (2Pb-Cy-Se)

M−N1 M−N2 M−Se Se−P P−C30 P−C36

2.027(2) 2.027(2) 2.4498(5) 2.2609(9) 1.875(3) 1.877(3)

2.2097(18) 2.2192(19) 2.6059(3) 2.2584(6) 1.873(2) 1.867(2)

2.326(3) 2.321(3) 2.6811(4) 2.2543(9) 1.873(4) 1.868(4)

N1−M−Se N2−M−Se N1−M−N2 M−Se−P Se−P−C30 Se−P−C36 C30−P−C36 MNCCCN planea sum of the angles around M DP (%)b

100.66(7) 96.98(7) 88.07(10) 94.07(3) 102.09(10) 100.32(10) 100.96(14) 0.927

99.31(5) 95.36(5) 82.68(7) 91.388(17) 102.29(8) 100.61(8) 101.61(11) 1.025

99.34(7) 95.76(7) 79.97(9) 88.59(3) 102.50(12) 100.77(11) 102.07(16) 1.052

285.71

277.35

275.07

82.5

91.8

94.4

a

Distance between M and the plane defined by the BDI backbone (N−C−C−C−N plane). bDP = (360 − sum of the angles)/0.9.44

bond lengths and angles).10,13 The Sn−Se bond length of 2.6059(3) Å is within the range reported for Sn−Se single bonds (2.55−2.68 Å)18−20 and longer than that reported for SnSe double bonds (2.25−2.39 Å).21−26 The Se−P bond length of 2.2584(6) Å is similar to that of the germanium analogue [2.2602(9) Å], with the Sn−Se−P bond angle [91.388(17)°] more acute than the Ge−Se−P angle system [94.07(3)°]. The 31P{1H} NMR spectrum of 2-Sn-Cy-Se in benzene-d6 shows a single resonance at δP 35.6 ppm with both selenium and tin satellites (1JPSe = 178 Hz, 2JP119Sn = 960 Hz, and 2JP117Sn = 916 Hz). This phosphorus resonance is downfield from the parent phosphanido complex 1-Sn-Cy (δP −15.4 ppm). The phosphorus−tin and phosphorus−selenium couplings are confirmed by the 119Sn (δSn 60 ppm; 2JP119Sn = 959 Hz) and 14832


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Figure 3. Magnified view of the solution-phase 31P{1H} NMR spectrum (toluene-d8) of 2-Sn-Cy-Se. Impurities (approximately 0.5%) are designated by §.

Se (δSe −70 ppm; 1JPSe = 179 Hz) NMR spectra, with the phosphorus−selenium coupling in the range for compounds with a P−Se single bond.27 A 31P{1H} NMR spectrum recorded from a concentrated sample of 2-Sn-Cy-Se in toluene-d8 with an extended acquisition time revealed additional satellites (Figure 3) showing coupling with the 115Sn nuclei (2JPSn(115) = 844 Hz) and selenium satellites (1JPSe = 178 Hz) alongside both the 117Sn and 119Sn satellites. The solid-state 31P{1H} NMR spectrum of 2-Sn-Cy-Se shows a single resonance at δP(solid) 31.9 ppm, with selenium and tin satellites (1JPSe(solid) = 190 Hz and 2JPSn(solid) = 897 Hz), similar to that observed in solution (Figure S4). The solid-state 77 Se NMR spectrum of 2-Sn-Cy-Se shows a doublet centered at δSe(solid) −71.3 ppm, with the selenium−phosphorus coupling 1 JPSe(solid) = 184 Hz (Figure S5). Although 1JSeSn coupling was not observed in either the 119Sn or 77Se NMR solution spectra, it was observed in the solid-state 77Se NMR spectra of 2-Sn-CySe (1JSeSn = 1160 Hz). Taken together, these data suggest that the conformation of 2-Sn-Cy-Se in the solid state is preserved in solution. The crystal structure of 4-Sn-Cy-Se2 (Figure 4 and Table 2 for selected bond lengths and angles) is similar to that of the germanium analogue, with η1 binding of the phosphinodiselenoate ligand to tin, an exo conformation of the phosphinodiselenoate ligand to the β-diketiminato tin metallocycle,28 and an acute Sn−Se−P bond angle (95.14°). The Sn−Se1 bond length of 2.6549(5) Å is similar those in other Sn−Se single bonds.18−20 The P−Se1 single bond [2.2194(11) Å] is shorter than the P−Se bond of 2-Sn-Cy-Se but longer than the PSe2 double bond [2.1197(11) Å]. Although the Sn···Se2 distance of 77

Figure 4. ORTEP diagram of tin(II) dicyclohexylphosphinodiselenoate (4-Sn-Cy-Se2). Hydrogen atoms are omitted and BDI carbon atoms minimized for clarity. The ellipsoid probability is shown at 30%.

3.508 Å is smaller than the sum of the van der Waals radii for tin and selenium (4.07 Å),29 the distance is much longer than that of a typical Sn−Se bond (2.55−2.60 Å),18−20 indicating that there is, at most, only a weak interaction. The 31P{1H} NMR spectrum in C6D6 of 4-Sn-Cy-Se2 shows a single resonance at δP 58.7 ppm, with tin and selenium satellites (2JP119Sn = 246 Hz, 2JP117Sn = 236 Hz, and 1JPSe = 539 Hz). The phosphorus−tin coupling constants 2JPSn are significantly smaller than those observed in 2-Sn-Cy-Se. The phosphorus−selenium coupling constant 1JPSe is similar to those observed for the germanium analogue and other compounds containing a delocalized phosphinodiselenoate anion.11,27,30−32 A 31P{1H} NMR spectrum of 4-Sn-Cy-Se2 with an extended acquisition time revealed additional satellites 14833


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Inorganic Chemistry

(Figure 5). Tin satellites are found around the selenium satellites, and phosphorus−carbon couplings (1JCP = 36 Hz and 2 JCP = 14 Hz) are also found in the spectrum. The 13C NMR spectrum revealed similar couplings; the resonance at 42.5 ppm, confirmed to be the ipso-carbon atom on the cyclohexane ring, showed carbon−phosphorus coupling (1JCP = 36 Hz). In addition, the resonance at 26.6 ppm also showed carbon− phosphorus coupling (2JCP = 14 Hz). The 77Se NMR spectrum of 4-Sn-Cy-Se2 shows a doublet centered at δSe −78 ppm with selenium−phosphorus coupling 1JPSe = 540 Hz, and a pair of tin satellites is observed alongside each signal (1JSeSn = 307 Hz). The presence of only one set of selenium satellites is in contrast to what would be expected based on the solid-state structure of 4-Sn-Cy-Se2 and indicates that the inequivalent selenium sites in the solid may be rapidly interconverting on the NMR time scale in solution. The solid-state 31P{1H} NMR spectrum of 4-Sn-Cy-Se2 shows two resonances in a roughly 1:1 ratio at δP(solid) 58.7 and 60.5 ppm (Figure S6). Each signal contains a set of tin satellites (2JPSn(solid) = 232 and 275 Hz, respectively) and two sets of selenium satellites, one consistent with a P−Se single bond (1JPSe(solid) = 385 and 385 Hz, respectively) and the second consistent with a PSe double bond (1JPSe(solid) = 693 and 684 Hz, respectively).27 These data indicate an η1 binding mode for the phosphinodiselenoate ligand. Note the average coupling constants (1JPSe(solid) = 539 and 535 Hz, respectively) are similar to that measured in solution (1JPSe = 540 Hz), providing further evidence for a rapid exchange of the selenium in solution. The solid-state 77Se{1H} NMR spectrum of 4-SnCy-Se2 shows two groups of signals in an approximate 1:1 ratio,

Table 2. Selected Bond Lengths (Å) and Angles (deg) for Compounds 4-Ge-Cy-Se2, 4-Sn-Cy-Se2, and 4-Pb-Cy-Se2 (BDI)GeSeP(Se) Cy2 (4-Ge-CySe2)9,10

(BDI)SnSeP(Se) Cy2 (4-Sn-CySe2)

(BDI)PbSeP(Se) Cy2 (4-Pb-CySe2)

M−N1 M−N2 M−Se1 Se1−P P−Se2 P−C30 P−C36

2.020(2) 2.0320(19) 2.4613(4) 2.2208(7) 2.1114(7) 1.849(3) 1.837(3)

2.239(3) 2.225(3) 2.6549(5) 2.2194(11) 2.1197(11) 1.843(4) 1.846(4)

2.356(3) 2.346(3) 2.7417(4) 2.2094(10 2.1287(11) 1.845(4) 1.841(4)

N1−M−Se1 N2−M−Se1 N1−M−N2 M−Se1−P Se1−P−Se2 Se1−P−C30 Se1−P−C36 Se2−P−C30 Se2−P−C36 MNCCCN planea sum of the angles around M DP (%)b

94.84(6) 94.20(6) 88.72(8) 100.77(2) 117.92(3) 103.01(9) 102.00(9) 112.52(9) 113.29(10) 0.987

96.83(8) 91.53(8) 82.89(11) 95.14(3) 116.62(5) 104.39(13) 105.48(14) 111.17(4) 111.29(15) 1.089

90.05(7) 97.93(7) 80.13(10) 92.79(3) 115.97(5) 105.91(14) 105.18(13) 110.95(14) 110.82(13) 1.146

277.8

271.3

268.11

91.4

98.6

102.1

a


Figure 5. Magnified view of the solution-phase 31P{1H} NMR spectrum of 4-Sn-Cy-Se2. Impurities (approximately 1%) are designated by §. 14834


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Inorganic Chemistry

Figure 6. Solid-state 77Se{1H} NMR spectrum of 4-Sn-Cy-Se2. Impurities are designated by §.

The phosphinoselenoite complex 2-Pb-Cy-Se is isostructural with the tin and germanium analogues, with a Pb−Se bond length of 2.6811(4) Å and a Se−P bond length of 2.2543(9) Å (Figure S1 and Table 1 for selected bond lengths and angles). The Pb−Se−P bond angle of 88.59(3)° is more acute than either the tin or germanium analogues. The 31P{1H} NMR spectrum shows a single resonance at δP 23.9 ppm with selenium and lead satellites (1JPSe = 192 Hz and 2 JPPb = 1469 Hz). The phosphorus resonance is similar to that in the parent lead(II) phosphanide complex 1-Pb-Cy (δP = 26.9 ppm). The 77Se NMR spectrum shows a doublet centered at δSe −24 ppm with selenium−phosphorus coupling 1JPSe = 192 Hz. A doublet centered at δPb 2596 ppm with lead−phosphorus coupling 2JPPb = 1453 Hz is shown in the 207Pb NMR spectrum of 2-Pb-Cy-Se. The solid-state structure of 4-Pb-Cy-Se2 is isomorphous with the tin analogue (4-Sn-Cy-Se2), with the Pb−Se(1) bond [2.7417(4) Å] slightly longer than the Pb−Se bond in 2-PbCy-Se, although the Se−P1 and Se−P2 bond lengths [2.2094(10) and 2.1287(11) Å, respectively] are similar to those of the tin analogue (Figure S2 and Table 2 for selected bond lengths and angles). The Pb···Se2 distance (3.396 Å) is shorter than the sum of the van der Waals radii for lead and selenium (3.92 Å)29 but significantly longer than any formal Pb−Se bond, indicating the presence of only a weak interaction between Pb and Se2. The Pb−Se1−P bond angle [92.97(3)°] is more acute than those in the germanium and tin analogues. The solution-phase 77Se{1H} NMR spectrum shows a doublet centered at δSe −47 ppm with selenium phosphorus coupling at 1JPSe = 544 Hz. Consistent with this, the 31P NMR spectrum of 4-Pb-Cy-Se2 shows a single resonance at δP 57.0 ppm, with selenium and lead satellites (1JPSe = 521 Hz and 2 JPPb= 218 Hz). The 207Pb NMR spectrum shows a doublet centered at δPb 1909 ppm, with lead−phosphorus coupling 2JPPb = 217 Hz. These data are consistent with a rapid κ-Se-to-κ-Se interconversion, as observed with both the germanium and tin analogues.

each with individual phosphorus couplings and tin satellites (Figure 6). There are two doublets centered at δSe(solid) 28 and 39 ppm in the high-frequency region, with selenium− phosphorus couplings, 1 J PSe(solid) = 382 and 394 Hz, respectively, and tin satellites (1JSeSn(solid) = 1182 and 1132 Hz, respectively). We assign these signals to the selenium in the singly bonded P−Se fragment. In the low-frequency regions, there are two doublets centered at δSe(solid) −204 and −224 ppm, with selenium−phosphorus couplings, 1JPSe(solid) = 686 and 699 Hz, respectively, and tin satellites (3JSeSn(solid) = 601 and 512 Hz, respectively). These signals are assigned to the selenium in the doubly bonded PSe fragment. The reason for the doubling of the phosphorus and selenium signals in the solid-state spectra of 4-Sn-Cy-Se2 is not clear. It is possible that there were two polymorphs in the crystalline sample used for the NMR experiment, but only one was selected for X-ray crystallographic analysis. The difference between the solution-phase and solid-state structures can be attributed to either an η2 binding mode of the phosphinodiselenoate ligand in solution or, more likely, a rapid equilibrium (relative to the NMR time scale) in which the two selenium atoms are exchange sites. Variable-temperature 1H and 31P{1H} NMR studies did not reveal any further insight into the solution-phase structure. Reactivity of 1-Pb-Cy with Selenium. Both the phosphinoselenoite (2-Pb-Cy-Se) and phosphinodiselenoate (4-Pb-Cy-Se2) complexes were formed upon treatment of the lead phosphanide 1-Pb-Cy with selenium. Complex 2-Pb-CySe is isolable without the presence of 4-Pb-Cy-Se2 only when a deficiency (0.8 equiv) of selenium was used. As with the tin system, the treatment of 4-Pb-Cy-Se2 with the phosphanide 1Pb-Cy gives the phosphinoselenoite complex 2-Pb-Cy-Se, and the addition of selenium to 2-Pb-Cy-Se results in formation of the phosphinodiselenoate complex 4-Pb-Cy-Se2. Both of these compounds decompose in solution and appear to be sensitive to light. However, they can be stored as solids with only minimal decomposition. 14835


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Inorganic Chemistry Reactivity of 1-Sn-Cy and 1-Pb-Cy with Sulfur. Reactions of the β-diketeminatotin(II) or -lead(II) dicyclohexylphosphanide 1-Sn-Cy or 1-Pb-Cy with elemental sulfur in a 1:1 ratio did not give the expected phosphinothioito complexes 2-M-Cy-S (M = Sn, Pb). Instead, a mixture of the phosphanide 1-M-Cy and phosphinodithioates (4-M-Cy-S2) was observed. Both 4-Sn-Cy-S2 and 4-Pb-Cy-S2 could be isolated in good yields when excess sulfur was added to the parent phoshanide complexes. These data imply that initially formed 2-M-Cy-S reacts much more rapidly with sulfur than does 1-M-Cy. The reactivity contrasts with that of the germanium system in which oxidation at the group 14 metal center is observed. In the solid state, 4-Sn-Cy-S2 (Figure S3 and Table 3 for selected bond lengths and angles) is isostructural with the

Figure 7. ORTEP diagram of lead(II) dicyclohexylphosphinodiselenoate (4-Pb-Cy-S2). Hydrogen atoms are omitted and BDI carbon atoms minimized for clarity. The ellipsoid probability is shown at 30%.

the selenium analogue, 4-Pb-Cy-Se2. The Pb−S1, P−S1, and PS2 bond distances are 2.6370(13), 2.0528(17), and 1.9755(18) Å, respectively. The latter bond length is similar to those in other compounds with PS double bonds.36 The Pb···S2 distance (3.276 Å) is smaller than the sum of the van der Waals radii (3.82 Å),29 suggesting that there may be weak interaction. The 31P{1H} NMR spectrum of 4-Pb-Cy-S2 shows a single resonance at δP 84.6 ppm, with lead satellites (2JPPb = 189 Hz). The 207 Pb NMR spectrum shows a doublet at δPb 1554 ppm (2JPPb = 159 Hz), upfield from those in the phosphanide complex 1-Pb-Cy (δPb 3981 ppm) and the phosphinodiselenoate complex 4-Pb-Cy-Se2. To examine the preference of chalcogen bonding to the metal center, the phosphinoselenoito complex 2-Sn-Cy-Se was treated with 1 equiv of elemental sulfur (Scheme 2). The

Table 3. Selected Bond Lengths (Å) and Angles (deg) for Compounds 4-Sn-Cy-S2 and 4-Pb-Cy-S2 (BDI)SnSP(S)Cy2 (4Sn-Cy-S2)

(BDI)PbSP(S)Cy2 (4Pb-Cy-S2)

M−N1 M−N2 M−Se1 S1−P P−S2 P−C30 P−C36

2.2215(16) 2.2107(17) 2.5107(6) 2.0641(7) 1.9655(8) 1.833(2) 1.841(2)

2.355(4) 2.340(4) 2.6470(13) 2.0528(17) 1.9755(18) 1.848(5) 1.832(6)

N1−M−S1 N2−M−S1 N1−M−N2 M−S1−P S1−P−S2 S1−P−C30 S1−P−C36 S2−P−C30 S2−P−C36 MNCCCN planea sum of the angles around M DP (%)b

91.90(5) 90.08(5) 83.23(6) 100.91(3) 116.72(3) 102.98(7) 103.84(7) 112.83(8) 112.30(8) 1.160 265.2

96.92(10) 90.36(10) 80.07(14) 95.28(6) 115.43(8) 105.56(16) 106.70(18) 110.89(17) 110.70(18) 1.144 267.4

105.32

102.9

Scheme 2

product formed was indeed the mixed chalcogen complex 4-SnCy-SeS. However, the diffraction study of crystals of this compound could only confirm the connectivity because we were unable to resolve the chalcogen atoms, indicating that there is an exchange between the coordination of selenium and sulfur in solution and thus disorder in the crystal. The 31P{1H} NMR spectrum of 4-Sn-Cy-SeS shows a major resonance at δP 72.3 ppm, with tin and selenium satellites (1JPSe = 490 Hz, 2 119 JP Sn = 209 Hz, and 2JP117Sn = 200 Hz). There are two minor resonances at δP 82.2 and 58.8 ppm, which can be assigned respectively to the dithio compound 4-Sn-Cy-S2 and diseleno compound 4-Sn-Cy-Se2. The 119Sn NMR spectrum shows a major doublet centered at δ119Sn −119 ppm, with tin− phosphorus coupling 2JP119Sn = 209 Hz observed. A major doublet at δSe −42 ppm (1JPSe = 490 Hz) is observed in the 77Se NMR spectrum, together with a weaker signal corresponding to the diseleno complex 4-Sn-Cy-Se2. Together, the NMR data of 4-Sn-Cy-SeS indicate that there is no significant thermodynamic preference between the Sn−S and Sn−Se bonds in this complex and that there is a rapid interchange between the κ-S and κ-Se binding modes. The formation of both 4-Sn-Cy-S2 and 4-Sn-Cy-Se2 must be due to reversible chalcogen transfer from the phosphorus(V) to phosphorus(III) centers. Reactivity of 1-Sn-SiMe3 with Selenium. As previously mentioned, both the tin(II) and lead(II) diphenylphosphanide

a


germanium phosphinodiselenoate complex 4-Ge-Cy-Se2. The Sn−S1 bond length of 2.5107(6) Å is slightly longer than that in [Ph3SnSP(S)Ph2] [2.4252(1) Å]33 but similar to that of the Sn−S bond in [N(CH2CMe2O)3SnSP(S)Ph2] [2.428(1) Å].5 The P−S1 bond distance [2.0641(7) Å] is longer than the P S2 bond length [1.9655(8) Å]. The Sn···S2 distance is less than the sum of the van der Waals radii of tin and sulfur (3.97 Å), suggesting that there may be weak interaction between the two atoms. Similar weak interactions are observed in [Me2Sn(S 2 PPh 2 ) 2 ] (Sn···S2 = 3.325 Å) and [Me 2 Sn{S 2 P(pC6H4OMe)(OMe)}2] (Sn···S2 = 3.1090 Å).34,35 The 31P{1H} NMR spectrum of 4-Sn-Cy-S2 shows a single resonance at δP 82.2 ppm, with tin satellites (2JP119Sn = 180 Hz and 2JP117Sn = 173 Hz). The 119Sn NMR spectrum shows a doublet centered at δSn −175 ppm (2JP119Sn = 160 Hz), upfield from that in the tin(II) phosphinodiselenoate 4-Sn-Cy-Se2. We attribute these small differences in the coupling constant to the low resolution of the 119Sn NMR spectrum. In the solid state, 4-Pb-Cy-S2 (Figure 7 and Table 3 for selected bond lengths and angles) is isostructural with that of 14836


Article

Inorganic Chemistry

100.60(3)°, comparable to those of [(tmeda)Zn(SeSiMe3)2] [101.5(4)−105.024°] and [(3,5-Me2C6H3)2Co(SeSiMe3)2] [101.3(3)−106.17(3)°].37,38 The NMR data show that this structure is preserved in solution, with a single resonance found at δSn 87 ppm in the 119Sn NMR spectrum, a singlet at δSe −176 ppm in the 77Se{1H} NMR spectrum, and a single resonance at δSi 7.4 ppm in the 29Si{1H} NMR spectrum. This is the first time that the Sn−Se−Si sequence of atoms has been crystallographically characterized in a noncyclic structure39,40 and the overall first time involving a low-valent tin atom. The homoleptic compound Sn[SeSi{SiMe3}3]2 has been characterized by 1H and 13C NMR spectrscopy and elemental analysis data.41 Because of the heterogeneous nature of this reaction, we have been unable to determine any mechanistic details and the fate of the phosphorus has not been determined. Summary of the NMR Data. These experiments have allowed us to compile NMR spectroscopic data from a series of related germanium, tin, and lead dicyclohexylphosphanide (1M-Cy), dicyclohexylphosphinochalcogenoite (2-M-Cy-E) and dicyclohexylphosphinodichalcogenoate (4-M-Cy-E2) complexes (M = Ge, Sn, Pb; E = S, Se, Te; Table 5). With the presence of several NMR-active nuclei, we were able to observe a wide range of multinuclear couplings, as exemplified in the long acquisition spectra of both 2-Sn-Cy-Se and 4-Sn-Cy-Se2 (Figures 3 and 5). Of note are the two-bond coupling (2JPSn) observed for 2-Sn-Cy-Se between the 31P nuclei and all three NMR-active isotopes of tin (119Sn, 117Sn, and 115Sn in 8.58%, 7.61%, and 0.35% natural abundance, respectively) and the coupling detected for 4-Sn-Cy-Se2 between the 31P nuclei and three separate nuclei, 13C, 77Se, and 119/117Sn. The 31P NMR chemical shift of the reported compounds depends on both the oxidation state of the phosphorus nuclei (compare complexes of the type 4 to the types 1 and 2) as well as the electronegativity of the groups on the phosphorus centers, as exemplified in the type 2 complexes and the diselenoate and dithioate complexes (4-M-Cy-Se2 and 4-M-Cy-S2, respectively). Although the 77Se chemical shifts were more variable, the solid-state data revealed that the terminal selenium nuclei (PSe; δSe = −204 and −224 ppm) to be significantly upfield

complexes are sensitive to decomposition, with Ph2PPPh2 a major decomposition byproduct. However, the tin(II) bis(trimethylsilyl)phosphanide complex 1-Sn-SiMe3 was stable enough for a study of its reactivity. Unexpectedly, the addition of selenium to 1-Sn-SiMe3 gave the (trimethylsilyl)selenide complex [(BDI)SnSeSiMe3] (6; Figure 8 and Table 4 for

Figure 8. ORTEP diagram of the tin(II) selenide 6. Hydrogen atoms are omitted and BDI carbon atoms minimized for clarity. The ellipsoid probability is shown at 30%.

Table 4. Selected Bond Lengths (Å) and Angles (deg) for Compound 6 Sn−N1 Sn−N2 Sn−Se Se−Si MNCCCN planea

2.207(3) 2.202(3) 2.6333(5) 2.2815(12) 0.506

N1−Sn−Se N2−Sn−Se N1−Sn−N2 Sn−Se−Se sum of the angles around M DP (%)b

94.38(8) 94.65(8) 85.15(11) 100.60(3) 274.2 95.4

a


selected bond lengths and angles). This complex adopts the endo conformation in the solid state, with the (trimethylsilyl)selenide ligand below the plane of the β-diketiminatate ligand. The Sn−Se bond distance [2.6333(5) Å] is similar to that in 2Sn-Cy-Se, and the Sn−Se−Si bond angle for this heavy ether is

Table 5. Selected Spectroscopic Data for 1-M-Cy, 2-M-Cy-Se, 2-Ge-Cy-Te, 4-M-Cy-Se2, and 4-M-Cy-S2 (M = Ge, Sn, Pb)a 31

P

1-Ge-Cy 1-Sn-Cy13 1-Pb-Cy13 2-Ge-Cy-Se10 2-Ge-Cy-Te10 2-Sn-Cy-Sesoln 2-Sn-Cy-Sesolid 2-Pb-Cy-Se 4-Ge-Cy-Se210 4-Sn-Cy-Se2soln 4-Sn-Cy-Se2solidA

−14.1 −15.4 26.9 41.9 26.1 35.6 31.9 23.9 63.7 58.7 58.7

4-Sn-Cy-Se2solidB

60.5

4-Pb-Cy-Se2 4-Sn-Cy-S2 4-Pb-Cy-S2

57.0 82.2 84.6

13

a

77

Se

−19 (−296.8)b −70 −71.3 −24 −18 −73 28 −224 39 −204 −47

|1JPSe|

198 (407)c 178 190 192 551 539 385 693 385 684 521

119

358 3981

964 1084 198

60 not measured 2596

960 897 1453

−88

246 232

1909 −175 1554

|1JSeSn|

1160

1182 |3JSeSn| = 601 1132 |3JSeSn| = 512

275

Italicized values are reported elsewhere. Chemical shifts are in ppm; coupling constants are in Hz. bδ 14837

|JP119Sn|/|JPPb|

Sn/207Pb

218 180 189 125

Te ppm. c|JPTe|. DOI: 10.1021/acs.inorgchem.7b02040 Inorg. Chem. 2017, 56, 14831−14841

Article

Inorganic Chemistry of the internal selenium nuclei (Sn−Se−P; δSe = 28 and 39 ppm). The only notable difference between the solution-phase and solid-state data was in the 1JPSe coupling for 4-Sn-Cy-Se2. The solid-state NMR spectra allowed us to measure the 1JPSe coupling for both the P−Se single and double bonds (385 and 689ave, respectively). The average of these values (537ave Hz) is similar to that observed in solution, indicating that the inequivalent selenium sites in the solid are rapidly interconverting on the NMR time scale in solution.

included in the Supporting Information. The data for the X-ray structures were collected at 173 K on a Nonius Kappa CCD diffractometer [λ(Mo Kα) = 0.71073 Å] and refined using the SHELXL-97 software package.48 [(BDI)Sn(PCy 2)] (1-Sn-Cy), [(BDI)Pb(PCy2)] (1-Pb-Cy), and [(BDI)-SnP(SiMe3)2] (1-SnSiMe3) were made according to published procedures.13 [(CH{(CH3)CN-2,6-iPr2C6H3}2)SnSeP(C6H11)2] (2-Sn-Cy-Se). A 10 mL toluene solution of [(BDI)SnPCy2] (1-Sn-Cy; 0.22 g, 0.30 mmol) was added to elemental selenium (0.02 g, 0.30 mmol). The mixture was stirred very slowly at room temperature for 20 h, after which it was filtered through a pad of Celite and the volatiles were removed in vacuo. The residue was washed with cold pentane (3 Å, ∼5 mL), and the solid was dissolved in a minimum amount of toluene. Yellow crystals of 2-Sn-Cy-Se were obtained at −30 °C. Yield: 0.12 g, 48%. Mp: 182−184 °C. 1H NMR (399.50 MHz, 303 K): δ 7.19 (d, J = 7.3 Hz, 2H, m-H), 7.12 (t, J = 7.6 Hz, 2H, p-H), 7.05 (d, J = 7.6 Hz, 2H, m-H), 4.70 (s, 1H, γ-CH), 3.71 (septet, J = 6.8 Hz, 2H, CHMe2), 3.24 (septet, J = 6.8 Hz, 2H, CHMe2), 1.66 (d, J = 6.8 Hz, 6H, CHMe2), 1.59 (s, 6H, NCMe), 1.46 (br, 2H, Cy-CH2), 1.36 (d, J = 6.8 Hz, 6H, CHMe2), 1.21 (d, J = 6.8 Hz, 6H, CHMe2), 1.18 (d, J = 6.8 Hz, 6H, CHMe2), 1.10 (br, 6H, Cy-CH2), 0.84 (br, 2H, Cy-CH2). 13 C{1H} NMR (100.46 MHz, 303 K): δ 166.8 (NCMe), 144.4 (ipsoC), 144.2 (o-C), 144.2 (o-C), 126.9 (p-C), 124.8 (m-C), 124.7 (m-C), 97.0 (γ-CH), 35.4 (d, JCP = 27 Hz, CyCH), 33.4, 31.9, 30.7, 30.5, 29.9 (Cy-CH2), 29.7, 29.0 (CHMe2), 28.3, 28.1, 28.0, 27.9, 27.8, 27.7 (CyCH2), 27.3, 25.5, 25.2, 25.1 (CHMe2), 23.9 (NCMe). 31P{1H} NMR (161.72 MHz, 303 K): δ 35.6 (JPSe = 178 Hz, JP119Sn = 960 Hz, and JP117Sn = 916 Hz). 77Se NMR (76.19 MHz, 303 K): δ −70 (d, JSeP = 179 Hz). 119Sn NMR (148.96 MHz, C6D6, 303 K): δ 60 (d, J119SnP = 959 Hz). IR (Nujol, ν/cm−1): 1551 (s), 1515 (s), 1316 (s), 1262 (s), 1173 (s), 1014 (s), 792 (s). UV−vis [pentane; λmax, nm (ε, M−1 cm−1)]: 366.1 (4180), 439.1 (3180). EI-MS (m/z): 812, 538, 417, 374, 202, 157, 115, 87, 59, 41. Anal. Calcd for C41H63N2PSeSn (812.60): C, 60.60; H, 7.81; N, 3.44. Found: C, 60.65; H, 7.93; N, 3.42. [(CH{(CH3)CN-2,6-iPr2C6H3}2)PbSeP(C6H11)2] (2-Pb-Cy-Se). A procedure similar to that of the synthesis of 2-Sn-Cy-Se was followed using 0.15 g (0.19 mmol) of 1-Pb-Cy and 0.010 g (0.15 mmol) of elemental selenium. Orange crystals of 2-Pb-Cy-Se were obtained by crystallization from toluene at −30 °C. Yield: 0.08 g, 47%. 1H NMR (399.50 MHz, 303 K): δ 7.22 (br, 2H, ArH), 7.05 (br, 4H, ArH), 4.60 (s, 1H, γ-CH), 3.75 (septet, J = 6.4 Hz, 2H, CHMe2), 3.13 (septet, J = 6.4 Hz, 2H, CHMe2), 1.66 (s, 6H, NCMe), 1.61 (br, 8H, Cy-CH2), 1.44 (br, 2H, Cy-CH2), 1.26 (d, J = 8.0 Hz, 12H, CHMe2), 1.18 (d, J = 6.8 Hz, 12H, CHMe2), 1.10 (br, 6H, Cy-CH2), 0.85 (br, 2H, Cy-CH2). 13 C{1H} NMR (100.46 MHz, 303 K): δ 165.1 (NCMe), 144.1 (ipsoC), 143.1 (o-C), 142.9 (o-C), 124.7 (p-C), 124.1 (m-C), 123.9 (m-C), 98.9 (γ-CH), 35.3 (d, J = 27 Hz, Cy-CH), 30.6, 30.1 (CHMe2), 29.0, 28.0, 27.9, 27.8, 27.2, 25.4 (Cy-CH2), 25.2, 24.9, 24.0, 23.8 (CHMe2), 21.1 (NCMe). 31P{1H} NMR (161.72 MHz, 303 K): δ 23.9 (JPSe = 192 Hz and JPPb = 1469 Hz). 77Se NMR (76.19 MHz, 303 K): δ −24 (d, JSeP = 192 Hz). 207Pb NMR (76.19 MHz, 303 K): δ 2596 (d, JPbP = 1453 Hz). [(CH{(CH3)CN-2,6-iPr2C6H3}2)SnSeP(Se)(C6H11)2] (4-Sn-Cy-Se2). Method A. A 10 mL toluene solution of 1-Sn-Cy (0.20 g, 0.28 mmol) was added to a stirred suspension of an excess of elemental selenium (0.11 g, 1.39 mmol) in toluene (5 mL). The mixture was stirred vigorously at room temperature for 30 h. The dark-orange mixture was filtered through a pad of Celite, and the solvent was removed from the filtrate under vacuum. The solid residue was washed with cold pentane and crystallized from a minimum amount of toluene at −30 °C to give orange crystals of 4−Sn-Se. Yield: 0.13 g, 52%. Method B. A 5 mL toluene solution of [(BDI)SnSePCy2] (2-Sn-Cy-Se; 0.10 g, 0.12 mmol) was added to a stirred suspension of elemental selenium (0.05 g, 0.62 mmol) in toluene (5 mL). The mixture was stirred vigorously at room temperature for 30 h. The workup procedure is identical with those stated above. Yield: 0.06 g, 58%. Mp: 203−205 °C. 1H NMR (399.50 MHz, toluene-d8, 303 K): δ 7.09 (s, 6H, ArH), 4.66 (γ-CH), 3.49 (br, 2H, CHMe2), 3.18 (br, 2H, CHMe2), 1.58 (s, 6H, NCMe), 1.53 (d, J = 6.8 Hz, 12H, CHMe2), 1.17 (d, J = 6.8 Hz, 12H, CHMe2), 1.27−0.96 (m, Cy-CH2), 0.87 (t, JHP =

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CONCLUSIONS Lead and tin dialkylphosphanido complexes react readily with the lighter chalcogens sulfur and selenium to give phosphinodithioate and phosphinodiselenoate complexes via phosphinoselenoite complexes. These reactions are similar to those of the germanium analogues, but oxidation of the metal center is not observed with the heaver group 14 elements. Although phosphinoselenoites have been implied as intermediates in the nucleation of metal selenide nanoparticles,2,3 our work shows that they react readily with selenium sources, with increasingly facile reactivity with chalcogens upon descending the group 14 elements. The solid-state structures of phosphinodichalcogenoate complexes, as observed by both NMR spectroscopy and Xray analysis, clearly show the monodendate binding mode of the [E2PR2] ligand. The bidentate binding mode of this ligand class has previously been observed only at tetravalent group 14 metal centers.4,42 Homoleptic four-coordinate β-diketiminato complexes have been reported;43 however, conversion of the trigonal-pyramidal geometry of the three-coordinate complexes described here into the seesaw geometry of the four-coordinate complexes must involve considerable reorganizational energy. This observation is consistent with all of our previous studies showing a preference for three-coordinate group 14 centers in heteroleptic β-diketiminate complexes44−46 and in contrast to the group 12 analogues.47

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EXPERIMENTAL SECTION

General Procedures. All manipulations were carried out under an inert atmosphere of dry nitrogen by use of standard Schlenk techniques or in an inert-atmosphere glovebox. Solvents were dried from the appropriate drying agent, distilled, degassed, and stored over 4 Å molecular sieves. 1H and 13C NMR spectra were recorded on Varian 400 and 500 MHz spectrometers. The solution-phase 29Si, 31P, 119 Sn, and 207Pb NMR spectra were recorded on a Varian 400 MHz spectrometer that was equipped with a X{1H} broad-band-observed probe. All spectra were recorded in C6D6 at 300 K, unless stated otherwise. The 1H and 13C NMR chemical shifts are given relative to residual solvent peaks, the 29Si signals were externally referenced to SiMe4, the 31P signals were externally referenced to H3PO4(aq), the 119 Sn signals were externally referenced to SnMe4, and the 207Pb signals were externally referenced to PbMe4. All assignments were confirmed by two-dimensional spectroscopy. Coupling constants J are quoted in hertz (Hz); coupling involving tin is quoted for the 119Sn isotope. Solid-state NMR data were recorded on a Varian VNMRS spectrometer operating at 79.45 MHz (29Si), 149.17 MHz (119Sn), and 161.87 MHz (31P). Spectral referencing is with respect to neat SiMe4, 85% H3PO4 (by setting the signal from Brushite to 1 ppm), and Sn(CH3)4 [by setting the signal from (Sn(C6H12)4 to −97.4 ppm]. The samples were packed under nitrogen or helium; the spinning gas was nitrogen. UV−vis spectroscopic studies were performed on a Cary 50 spectrophotometer, and combustion analysis was performed by Stephen Boyer at the London Metropolitan University. Repeated attempts at combustion analysis for 2-Pb-Cy-Se, 4-Sn-Cy-S2, and 4Pb-Cy-S2 were unsuccessful. NMR spectra of these compounds are 14838


Article

Inorganic Chemistry

P{1H} NMR (161.72 MHz, 303 K): δ 84.6 (JPPb = 189 Hz). 207Pb NMR (83.83 MHz, 303 K): δ 1554 (d, JPbP = 159 Hz). [(CH{(CH3)CN-2,6-iPr2C6H3}2)Sn(S/Se)P(S/Se)(C6H11)2] (4-Sn-CyS/Se). A 10 mL 1:1 pentane/toluene solution of 2-Sn-Cy-Se (0.11 g, 0.13 mmol) was added to elemental sulfur (4.0 mg, 0.13 mmol) in toluene (2 mL). After vigorous stirring for 30 min at room temperature, the mixture was filtered through a pad of Celite. The filtrate was concentrated and stored at −30 °C. Bright yellow crystals of 4-Sn-Cy-S/Se were obtained. Yield: 0.06 g, 52%. 1H NMR (399.50 MHz, 303 K): δ 7.03−7.16 (m, 6H, Ar-H), 4.66 (s, 1H, γ-CH), 3.58 (br, 2H, CHMe2), 3.18 (br, 2H, CHMe2), 2.12 (s, 3H, NCMe), 1.58 (br, 10H, CHMe2, Cy-CH, Cy-CH2), 1.18 (d, J = 6.4 Hz, 10H, CHMe2, Cy-CH2), 1.02 (d, J = 8.0 Hz, 9H, CHMe2, Cy-CH2). 13 C{1H} NMR (100.46 MHz, 303 K): δ 166.8 (NCMe), 142.3 (ipsoC), 129.7 (o-C), 128.9 (o-C), 126.8 (p-C), 126.0 (m-C), 125.1 (m-C), 96.7 (γ-CH), 43.2 (d, JCP = 43 Hz, Cy-CH), 29.6, 29.5 (CHMe2), 27.2, 27.1, 27.0, 26.9, 26.9 (Cy-CH2), 25.6, 24.9, 23.9, 23.8 (CHMe2), 21.8 (NCMe). 31P{1H} NMR (161.72 MHz, 303 K): δ 72.3 (JPSe = 490 Hz, JP119Sn = 209 Hz, and JP117Sn = 200 Hz). 77Se NMR (76.19 MHz, 303 K): δ −42 (d, JSeP = 490 Hz). 119Sn NMR (148.95 MHz, 303 K): δ −119 (d, J119SnP = 209 Hz). 117Sn NMR (142.28 MHz, 303 K): δ −119 (d, J117SnP = 205 Hz). [(CH{(CH3)CN-2,6-iPr2C6H3}2)SnSeSi(CH3)3] (6). A 15 mL toluene solution of 1-Sn-SiMe3 (0.19 g, 0.26 mmol) in toluene (15 mL) was added to an excess of elemental selenium (0.10 g, 1.32 mmol) suspended in toluene (5 mL). The mixture was stirred vigorously at room temperature for 20 h, and the yellow suspension was filtered through a pad of Celite. Volatiles were removed from the filtrate, and the residue was washed with n-hexane (3 Å, ∼5 mL). Yellow crystals of 6 were obtained by crystallization from toluene at −30 °C. Yield: 0.11 g, 61%. 1H NMR (399.50 MHz, 303 K): δ 7.21 (dd, J = 7.6, 1.2 Hz, 2H, m-H), 7.13 (t, J = 7.6 Hz, 2H, p-H), 7.07 (dd, J = 7.6, 1.2 Hz, 2H, m-H), 4.79 (s, 1H, γ-CH), 3.90 (septet, J = 6.8 Hz, 2H, CHMe2), 3.29 (septet, J = 6.8 Hz, 2H, CHMe2), 1.61 (s, 6H, NCMe), 1.60 (d, J = 6.4 Hz, 6H, CHMe2), 1.34 (d, J = 7.2 Hz, 6H, CHMe2), 1.23 (d, J = 6.8 Hz, 6H, CHMe2), 1.14 (d, J = 6.8 Hz, 6H, CHMe2), 0.26 (s, 9H, SiMe3). 13C{1H} NMR (100.46 MHz, 303 K): δ 167.2 (NCMe), 145.7 (ipso-C), 143.7 (o-C), 142.2 (o-C), 127.4 (p-C), 125.3 (m-C), 124.7 (m-C), 98.5 (γ-CH), 29.3, 29.0 (CHMe2), 27.0, 26.2, 25.2, 25.1 (CHMe2), 24.4 (NCMe), 6.2 (SiMe3). 119Sn NMR (148.96 MHz, 303 K): δ 87. 77Se NMR (76.19 MHz, 303 K): δ −176. 29Si{1H} NMR (79.37 MHz, 303 K): δ 7.4. IR (Nujol, ν/cm−1): 1524 (s), 1314 (s), 1170 (s), 1021 (s), 936 (s). Anal. Calcd for C32H50N2SeSiSn (688.51): C, 55.82; H, 7.32; N, 4.07. Found: C, 55.91; H, 7.32; N, 3.94.

6.8 Hz, 2H, Cy-CH). 13C{1H} NMR (100.46 MHz, toluene-d8, 303 K): δ 166.5 (NCMe), 143.7 (ipso-C), 142.1 (o-C), 137.4 (o-C), 129.3 (p-C), 126.4 (m-C), 124.4 (m-C), 96.3 (γ-CH), 42.5 (d, JCP = 36 Hz, Cy-CH), 34.5 (Cy-CH2), 29.2 (CHMe2), 26.6 (d, JCP = 36 Hz, CyCH2), 26.3, 26.2 (Cy-CH2), 25.2 (CHMe2), 23.6, 22.8 (CHMe2), 14.2 (NCMe). 31P{1H} NMR (161.72 MHz, toluene-d8, 303 K): δ 58.7 (JPSe = 539 Hz, JP119Sn = 246 Hz, and JP117Sn = 236 Hz). 77Se NMR (76.19 MHz, 303 K): δ −73 (JSeP = 540 Hz and JSeSn = 307 Hz). 119Sn NMR (148.96 MHz, 303 K): δ −88 (d, J119SnP = 247 Hz). IR (Nujol, ν/ cm−1): 1539 (s), 1316 (s), 1174 (s), 790 (s). UV−vis [pentane; λmax, nm (ε, M−1 cm−1)]: 438.0 (2660). EI-MS (m/z): 892, 538, 391, 278, 201, 160, 83, 41. Anal. Calcd for C41H63PN2Se2Sn (891.56): C, 55.23; H, 7.12; N, 3.14. Found: C, 55.28; H, 7.16; N, 3.16. [(CH{(CH3)CN-2,6-iPr2C6H3}2)PbSeP(Se)(C6H11)2] (4-Pb-Cy-Se2). A procedure similar to that of the synthesis of 4-Sn-Cy-Se2 (Method A) was followed using 0.26 g (0.31 mmol) of 1-Pb-Cy and 0.12 g (1.57 mmol) of elemental selenium. Orange crystals of 4-Pb-Cy-Se2 were obtained by crystallization from toluene at −30 °C. Yield: 0.25 g, 83%. Alternative synthesis of 4-Pb-Cy-Se2. A 5 mL toluene solution of [(BDI)PbSePCy2] (2-Pb-Cy-Se; 0.10 g, 0.11 mmol) was added to a stirred suspension of elemental selenium (0.04 g, 0.55 mmol) in toluene (5 mL). The mixture was stirred vigorously at room temperature for 20 h. The workup procedure is identical with those stated above. Yield: 0.08 g, 69%. 1H NMR (399.50 MHz, 303 K): δ 7.18 (s, 2H, p-H), 7.01−7.14 (m, 4H, ArH), 4.58 (s, 1H, γ-CH), 3.36 (septet, J = 6.8 Hz, 4H, CHMe2), 1.72 (br, 6H, Cy-CH2), 1.65 (s, 6H, NCMe), 1.57 (d, J = 6.8 Hz, 12H, CHMe2), 1.47 (br, 2H, Cy-CH2), 1.34 (br, 4H, Cy-CH2), 1.22 (d, J = 6.8 Hz, CHMe2), 1.02 (br, 6H, Cy-CH2, Cy-CH). 13C{1H} NMR (100.46 MHz, 303 K): δ 165.0 (NCMe), 144.9 (ipso-C), 143.5 (o-C), 129.7 (o-C), 128.9 (p-C), 126.3 (m-C), 124.4 (m-C), 98.3 (γ-CH), 43.7 (d, JCP = 34 Hz, Cy-CH), 29.1, 26.9 (CHMe2), 26.7, (Cy-CH2), 26.6, 26.1, 25.6, 24.3 (CHMe2), 21.8 (NCMe). 31P{1H} NMR (161.72 MHz, 303 K): δ 57.0 (JPSe = 521 Hz and JPPb = 218 Hz). 77Se NMR (76.19 MHz, 303 K): δ −47 (d, JSeP = 544 Hz). 207Pb NMR (83.83 MHz, 303 K): δ 1909 (d, JPbP = 217 Hz). IR (Nujol, ν/cm−1): 1548 (s), 1315 (s), 1170 (s), 1097 (s), 1014 (s), 934 (s). Anal. Calcd for C41H63N2PPbSe2 (980.05): C, 50.25; H, 6.48; N, 2.86. Found: C, 50.29; H, 6.62; N, 2.72. [(CH{(CH3)CN-2,6-iPr2C6H3}2)SnSP(S)(C6H11)2] (4-Sn-Cy-S2). A procedure similar to that of the synthesis of 4-Sn-Cy-Se2 (Method A) was followed using 0.26 g (0.35 mmol) of 1-Sn-Cy and 0.06 g (1.76 mmol) of elemental sulfur. Yellow crystals of 4-Sn-Cy-S2 were obtained by crystallization from a minimum amount of toluene at −30 °C. Yield: 0.21 g, 76%. 1H NMR (399.50 MHz, 303 K): δ 7.20 (d, J = 7.6 Hz, 2H, m-H), 7.12−7.14 (m, 2H, p-H), 7.04 (d, J = 8.8 Hz, 2H, m-H), 4.66 (s, 1H, γ-CH), 3.61 (septet, J = 6.8 Hz, 2H, CHMe2), 3.21 (septet, J = 6.8 Hz, 2H, CHMe2), 1.60 (br, 16H, NCMe, Cy-CH, CHMe2), 1.54 (d, J = 6.4 Hz, 6H, CHMe2), 1.21 (d, J = 7.6 Hz, 13H, CHMe2, Cy-CH2). 13C{1H} NMR (100.46 MHz, 303 K): δ 166.6 (NCMe), 144.4 (ipso-C), 144.3 (o-C), 141.9 (o-C), 129.7 (m-C), 128.9 (m-C), 126.8 (m-C), 126.0 (p-C), 125.1 (p-C), 124.5 (m-C), 96.5 (γ-CH), 43.1 (d, JCP = 50 Hz, Cy-CH), 29.6, 29.5 (CHMe2), 27.2, 27.0, 26.7 (Cy-CH2), 25.7 (CHMe2), 25.6 (Cy-CH2), 24.9 (CHMe2), 23.9 (NCMe). 31P{1H} NMR (161.72 MHz, 303 K): δ 82.2 (JP119Sn = 180 Hz and JP117Sn = 173 Hz). 119Sn NMR (148.95 MHz, 303 K): δ −175 (d, J119SnP = 160 Hz). [(CH{(CH3)CN-2,6-iPr2C6H3}2)PbSP(S)(C6H11)2] (4-Pb-Cy-S2). A procedure similar to that of the synthesis of 4-Sn-Cy-Se2 (Method A) was followed using 0.20 g (0.24 mmol) of 1-Pb-Cy and 0.04 g (1.22 mmol) of elemental sulfur. Yellow crystals of 4-Pb-Cy-S2 were obtained by crystallization from a minimum amount of toluene at −30 °C. Yield: 0.16 g, 73%. 1H NMR (399.50 MHz, 303 K): δ 7.17 (d, J = 7.2 Hz, 2H, m-H), 7.12 (t, J = 7.6 Hz, 2H, p-H), 7.01−7.08 (m, 2H, mH), 4.55 (s, 1H, γ-CH), 3.35 (septet, J = 6.8 Hz, 4H, CHMe2), 1.66 (s, 6H, NCMe), 1.60 (br, 8H, Cy-CH, Cy-CH2), 1.54 (d, J = 6.8 Hz, CHMe2), 1.22 (d, J = 6.8 Hz, 12H, CHMe2), 1.03 (br, 6H, Cy-CH2). 13 C{1H} NMR (100.46 MHz, 303 K): δ 164.7 (NCMe), 144.1 (ipsoC), 143.6 (o-C), 129.7 (o-C), 126.3 (p-C), 126.0 (m-C), 124.5 (m-C), 98.2 (γ-CH), 43.8 (d, JCP = 49 Hz, Cy-CH), 29.1 (CHMe2), 27.1, 26.9, 26.7, 26.7 (Cy-CH2), 26.1 (CHMe2), 25.6 (Cy-CH2), 24.2 (NCMe).

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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.inorgchem.7b02040. ORTEP diagrams, selected NMR data for compounds 2Sn-Cy-Se, 4-Sn-Cy-Se2, 2-Pb-Cy-Se, 4-Sn-Cy-S2, 4-PbC-S2, and 4-Sn-Cy-S/Se, and data collection parameter tables and thermal ellipsoid plots of 2-Sn-Cy-Se, 2-PbCy-Se, 4-Sn-Cy-Se2, 4-Pb-Cy-Se2, 4-Sn-Cy-S2, 4-Pb-CyS2, and 6 (PDF) Accession Codes

CCDC 1560373−1560376 and 873978−873980 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]. uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033. 14839


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Inorganic Chemistry

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Martyn P. Coles: 0000-0003-3558-271X J. Robin Fulton: 0000-0002-6370-6452 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We gratefully acknowledge the University of Sussex for funding. REFERENCES

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