Experimental and Theoretical Study of a Tungsten Dihydride Silyl Complex: New Insight into Its Bonding Nature and Fluxional Behavior
Experimental and Theoretical Study of a Tungsten Dihydride Silyl Complex: New Insight into Its Bonding Nature and Fluxional Behavior
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DOI：
10.1021/om100653v
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发表时间：
2010-11
期刊：
影响因子：
2.8
通讯作者：
M. Ray;Y. Nakao;Hirofumi Sato;S. Sakaki;Takahito Watanabe;H. Hashimoto;H. Tobita
中科院分区：
文献类型：
--
作者：
M. Ray;Y. Nakao;Hirofumi Sato;S. Sakaki;Takahito Watanabe;H. Hashimoto;H. Tobita
通过硅烯配合物Cp*（CO）2（H）W <$Si（H）{C（SiMe 3）3}（R2）与甲醇反应，合成了二氢化钨硅烯配合物Cp*（CO）2 W（H）2[SiH（OMe）{C（SiMe 3）3}]（R1）。配合物R1的特征在于通过光谱数据以及元素分析，其几何结构由X射线晶体学支持。有趣的是，变温1H NMR光谱显示，R1显示出高度流动性的行为，其中两个非对映异构体的异构体在NMR时间尺度上迅速交换它们的位置。作为R1模型的Cp（CO）2 W（H）2[SiH（OMe）{C（SiH 3）3}]（1a）的DFT优化几何结构表明，除了两个弱的Si-H相互作用外，还存在一个W-甲硅烷基和两个W-氢化物键。通过对1a分子轨道和电子布居的分析，从理论上对1a分子有了如下认识：（i）1a既不是纯的具有d_2电子构型的W（Ⅳ）二氢化硅烷配合物，也不是纯的具有d_4电子构型的W（Ⅱ）硅酸盐配合物;（ii）1a分子既不是纯的具有d_4电子构型的W（Ⅳ）二氢化硅烷配合物，也不是纯的具有d_4电子构型的W（Ⅱ）硅酸盐配合物;（iii）1a分子既不是纯的具有d_4电子构型的W（Ⅳ）二氢化硅烷配合物，也不是纯的具有d_4电子构型的W（Ⅱ）硅酸盐配合物。
Tungsten dihydride silyl complex Cp*(CO)2W(H)2[SiH(OMe){C(SiMe3)3}] (R1) was synthesized by the reaction of silylene complex Cp*(CO)2(H)W═Si(H){C(SiMe3)3} (R2) with MeOH. Complex R1 was characterized by spectroscopic data as well as elemental analysis, and its geometry was supported by X-ray crystallography. Interestingly, the variable-temperature 1H NMR spectroscopy revealed that R1 shows highly fluxional behavior, in which two diastereotopic hydrides rapidly exchange their positions in the NMR time scale. The DFT-optimized geometry of Cp(CO)2W(H)2[SiH(OMe){C(SiH3)3}] (1a), which was employed as a model of R1, indicates the presence of a W−silyl and two W−hydride bonds in addition to two weak Si---H interactions. Based on the analyses of molecular orbitals and electron populations, a theoretical understanding of 1a is presented, as follows: (i) 1a is neither a pure dihydride silyl complex of W(IV) bearing d2 electron configuration nor a pure silicate complex of W(II) bearing d4 electron configuration, (i...