Phosphine and diphosphine complexes of silicon(IV) halides.
Phosphine and diphosphine complexes of silicon(IV) halides.
复制标题
卤化硅（IV）的膦和二膦络合物。
作者：
W. Levason;D. Pugh;G. Reid
SiX 4（X = Cl或Br）与PMe 3在无水CH 2Cl 2中的反应形成反式-[SiX 4（PMe 3）2]，而二膦Me 2 P（CH 2）2PMe 2、Et 2 P（CH 2）2 PEt 2和o-C6 H4（PMe 2）2形成顺式-[SiX 4（二膦）]，它们都含有六配位硅中心。用Me 2 PCH 2PMe 2，产物为反式-[SiCl 4（κ（1）-Me 2 PCH 2PMe 2）2]。通过X射线晶体学、微量元素分析、红外光谱和多核（1H，13 C{（1）H}，31 P{（1）H}）核磁共振谱对配合物进行了表征。配合物是稳定的固体，在非供体溶剂中不显著解离，尽管它们对水分和氧气非常敏感。这种稳定性与最近的密度泛函理论（DFT）计算（Wilson等人，Inorg.Chem.2012，51，7657-7668）的预测相冲突，该预测表明六配位硅膦将是不稳定的，并且还与未能分离与SiF 4的络合物（乔治等人，道尔顿trans.2011，40，1584-1593）形成对比。膦和SiI 4之间，或与SiX 4和砷化氢配体包括AsMe 3和o-C6 H4（AsMe 2）2之间没有发生反应。使用空间体积庞大的膦P（t）Bu 3、P（i）Pr 3或PCy 3制备五配位[SiX 4（PR 3）]的尝试失败，没有发生明显的反应，与预测一致（Wilson等人，Inorg.Chem.2012，51，7657-7668），这些化合物将是非常吸热的，而膦的大锥角可能阻止在小硅中心形成六配位。Si_2Cl_6与PMe_3或二膦在CH_2Cl_2中的反应导致SiCl_4加合物和聚氯硅烷的瞬间结晶，但从己烷溶液中产生非常不稳定的白色[Si_2Cl_6（PMe_3）_2]和[Si_2Cl_6（二膦）]（二膦= Me_2 P（CH_2）_2PMe_2或o-C_6 H_4（PMe_2）_2）沉淀。SiHCl 3与PMe 3和Me 2 P（CH 2）2PMe 2的反应也产生SiCl 4加合物，但使用Et 2 P（CH 2）2 PEt 2，分离出无色的[SiHCl 3 {Et 2 P（CH 2）2 PEt 2}]，其特征在于X射线结构，其显示出具有Si-H反式为P的假八面体络合物。将硅（IV）膦络合物还原为硅（II）的尝试不成功，与Si（II）的稳定的N-杂环卡宾加合物的分离形成对比。
The reaction of SiX4 (X = Cl or Br) with PMe3 in anhydrous CH2Cl2 forms trans-[SiX4(PMe3)2], while the diphosphines, Me2P(CH2)2PMe2, Et2P(CH2)2PEt2, and o-C6H4(PMe2)2 form cis-[SiX4(diphosphine)], all containing six-coordinate silicon centers. With Me2PCH2PMe2 the product was trans-[SiCl4(κ(1)-Me2PCH2PMe2)2]. The complexes have been characterized by X-ray crystallography, microanalysis, IR, and multinuclear ((1)H, (13)C{(1)H}, and (31)P{(1)H}) NMR spectroscopies. The complexes are stable solids and not significantly dissociated in nondonor solvents, although they are very moisture and oxygen sensitive. This stability conflicts with the predictions of recent density functional theory (DFT) calculations (Wilson et al. Inorg. Chem. 2012, 51, 7657-7668) which suggested six-coordinate silicon phosphines would be unstable, and also contrasts with the failure to isolate complexes with SiF4 (George et al. Dalton Trans. 2011, 40, 1584-1593). No reaction occurred between phosphines and SiI4, or with SiX4 and arsine ligands including AsMe3 and o-C6H4(AsMe2)2. Attempts to make five-coordinate [SiX4(PR3)] using the sterically bulky phosphines, P(t)Bu3, P(i)Pr3, or PCy3 failed, with no apparent reaction occurring, consistent with predictions (Wilson et al. Inorg. Chem. 2012, 51, 7657-7668) that such compounds would be very endothermic, while the large cone angles of the phosphines presumably preclude formation of six-coordination at the small silicon center. The reaction of Si2Cl6 with PMe3 or the diphosphines in CH2Cl2 results in instant disproportionation to the SiCl4 adducts and polychlorosilanes, but from hexane solution very unstable white [Si2Cl6(PMe3)2] and [Si2Cl6(diphosphine)] (diphosphine = Me2P(CH2)2PMe2 or o-C6H4(PMe2)2) precipitate. The reactions of SiHCl3 with PMe3 and Me2P(CH2)2PMe2 also produce the SiCl4 adducts, but using Et2P(CH2)2PEt2, colorless [SiHCl3{Et2P(CH2)2PEt2}] was isolated, which was characterized by an X-ray structure which showed a pseudo-octahedral complex with the Si-H trans to P. Attempts to reduce the silicon(IV) phosphine complexes to silicon(II) were unsuccessful, contrasting with the isolation of stable N-heterocyclic carbene adducts of Si(II).