Multiple Si–H Bond Activations by tBu2PCH2CH2PtBu2 and tBu2PCH2PtBu2 Di(phosphine) Complexes of Rhodium and Iridium

Reactions of the di­(tert-butylphosphino)­ethane complex (dtbpe)­Rh­(CH2Ph) with Ph2SiH2 and Et2SiH2 resulted in isolation of (dtbpe)­Rh­(H)2(SiBnPh2) (1; Bn = CH2Ph) and (dtbpe)­Rh­(H)2(SiBnEt2) (2), respectively. Both 1 and 2 feature strong interactions between the rhodium hydride and silyl ligands, as indicated by large 2JSiH values (44.4 and 52.1 Hz). The reaction of (dtbpm)­Rh­(CH2Ph) (dtbpm = di­(tert-butylphosphino)­methane) with Mes2SiH2 gave the pseudo-three-coordinate Rh complex (dtbpm)­Rh­(SiHMes2) (3), which is stabilized in the solid state by agostic interactions between the rhodium center and two C–H bonds of a methyl substituent on the mesityl group. The analogous germanium compound (dtbpm)­Rh­(GeHMes2) (4) is also accessible. Complex 3 readily undergoes reactions with diphenylacetylene, phenylacetylene, and 2-butyne to give the silaallyl complexes (dtbpm)­Rh­[Si­(CPhCHPh)­Mes2] (5), (dtbpm)­Rh­[Si­(CHCHPh)­Mes2] (7), and (dtbpm)­Rh­(Si­(CMeCHMe)­Mes2) (8) via net insertions into the Si–H bond. The germaallyl complexes (dtbpm)­Rh­[Ge­(CPhCHPh)­Mes2] (6) and (dtbpm)­Rh­[Ge­(CMeCHMe)­Mes2] (9) were synthesized under identical conditions starting from 4. The reaction of (dtbpm)­Rh­(CH2Ph) with 1 equiv of TripPhSiH2 yielded (dtbpm)­Rh­(H)2[5,7-diisopropyl-3-methyl-1-phenyl-2,3-dihydro-1H-silaindenyl-κSi] (11), and catalytic investigations indicate that both (dtbpm)­Rh­(CH2Ph) and 11 are competent catalysts for the conversion of TripPhSiH2 to 5,7-diisopropyl-3-methyl-1-phenyl-2,3-dihydro-1H-silaindole. A dtbpm-supported Ir complex, [(dtbpm)­IrCl]2, was used to access the dinuclear bridging silylene complexes [(dtbpm)­IrH]­(μ-SiPh2)­(μ-Cl)2[(dtbpm)­IrH] (12) and [(dtbpm)­IrH]­(μ-SiMesCl)­(μ-Cl)­(μ-H)­[(dtbpm)­IrH] (13). The reaction of [(dtbpm)­IrCl]2 with a sterically bulky primary silane, (dmp)­SiH3 (dmp = 2,6-dimesitylphenyl), allowed isolation of the mononuclear complex (dtbpm)­Ir­(H)4(10-chloro-1-mesityl-5,7-dimethyl-9,10-dihydrosilaphenanthrene-κSi), in which the dmp substituent has undergone C–H activation.

双(叔丁基膦基)乙烷（di(tert-butylphosphino)ethane，缩写dtbpe）合铑(Ⅰ)苄基配合物[(dtbpe)Rh(CH₂Ph)]分别与二苯基硅烷(Ph₂SiH₂)和二乙基硅烷(Et₂SiH₂)反应，成功分离得到配合物[(dtbpe)Rh(H)₂(SiBnPh₂)]（1；Bn=CH₂Ph）与[(dtbpe)Rh(H)₂(SiBnEt₂)]（2）。配合物1与2均存在铑氢配体与硅基配体间的强相互作用，该作用可通过较大的²JSiH耦合常数（分别为44.4 Hz与52.1 Hz）得到证实。
双(叔丁基膦基)甲烷（di(tert-butylphosphino)methane，缩写dtbpm）合铑(Ⅰ)苄基配合物[(dtbpm)Rh(CH₂Ph)]与二均三甲苯基硅烷(Mes₂SiH₂，均三甲苯基的英文缩写为Mes)反应，生成假三配位铑配合物[(dtbpm)Rh(SiHMes₂)]（3），该配合物在固态下通过铑中心与均三甲苯基上两个甲基取代基的C-H键形成的agostic相互作用（agostic interaction）得以稳定。类似结构的锗基配合物[(dtbpm)Rh(GeHMes₂)]（4）同样可通过该路线合成。
配合物3可与二苯基乙炔、苯乙炔及2-丁炔顺利发生反应，经由Si-H键的净插入过程，分别得到硅杂烯丙基配合物[(dtbpm)Rh[Si(CPh=CHPh)Mes₂]]（5）、[(dtbpm)Rh[Si(CH=CHPh)Mes₂]]（7）与[(dtbpm)Rh(Si(CMe=CHMe)Mes₂)]（8）。以配合物4为起始原料，在完全相同的反应条件下，可合成对应的锗杂烯丙基配合物[(dtbpm)Rh[Ge(CPh=CHPh)Mes₂]]（6）与[(dtbpm)Rh[Ge(CMe=CHMe)Mes₂]]（9）。
[(dtbpm)Rh(CH₂Ph)]与1当量的二(2,4,6-三异丙基苯基)硅烷(TripPhSiH₂，其中2,4,6-三异丙基苯基的英文缩写为Trip)反应，得到配合物[(dtbpm)Rh(H)₂[5,7-二异丙基-3-甲基-1-苯基-2,3-二氢-1H-硅茚基-κSi]]（11）。催化研究结果表明，[(dtbpm)Rh(CH₂Ph)]与11均可作为活性催化剂，将TripPhSiH₂转化为5,7-二异丙基-3-甲基-1-苯基-2,3-二氢-1H-硅吲哚。
采用dtbpm支撑的铱配合物[(dtbpm)IrCl]₂，可制备得到双核桥连硅烯配合物[(dtbpm)IrH](μ-SiPh₂)(μ-Cl)₂[(dtbpm)IrH]（12）与[(dtbpm)IrH](μ-SiMesCl)(μ-Cl)(μ-H)[(dtbpm)IrH]（13）。[(dtbpm)IrCl]₂与空间位阻较大的一级硅烷(dmp)SiH₃（dmp=2,6-二(均三甲苯基)苯基，2,6-dimesitylphenyl）反应，成功分离得到单核配合物[(dtbpm)Ir(H)₄(10-氯-1-均三甲苯基-5,7-二甲基-9,10-二氢硅杂菲-κSi)]，该产物中dmp取代基发生了C-H键活化。