Theoretical Study of Silyl-Bridged Dinuclear Palladium(I) and Platinum(I) Complexes, M2(-<img src="http://pubs.acs.org/imag
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- 作者：Shingo Nakajima ; Michinori Sumimoto ; Yoshihide Nakao ; Hirofumi Sato ; Shigeyoshi Sakaki ; and Kohtaro Osakada
- 刊名：Organometallics
- 出版年：2005
- 出版时间：August 1, 2005
- 年：2005
- 卷：24
- 期：16
- 页码：4029 - 4038
- 全文大小：544K
- 年卷期：v.24,no.16(August 1, 2005)
- ISSN：1520-6041
文摘
Silyl-bridged dinuclear palladium(I) and platinum(I) complexes with the composition M2(SiH3)2(PH3)2 (M = Pd or Pt) were theoretically investigated with DFT, MP2 to MP4(SDQ),and CCSD(T) methods. These complexes are more stable than two M(PH3)(SiH3) complexesby 80.6 kcal/mol for M = Pd and 105.6 kcal/mol for M = Pt, where the values calculatedwith the CCSD(T) method are given hereafter. Although this complex is understood to takethe silyl-bridged form in a formal sense, the NMR chemical shifts of Si and H atoms andthe Laplacian of electron density indicate that the electronic structure of the SiH3 groupsomewhat shifts toward that of the silylene + hydride groups and the agostic interaction isresponsible for this interesting electronic structure. These complexes are represented asM2(<IMG SRC="/images/entities/mgr.gif">-
2-H···SiH2)2(PH3)2, in which the formula of H···SiH2 indicates that this group is nota pure silyl group but possesses the characteristics of the hydride and 
-silylene groups toa considerable extent. The planar geometry of this compound comes from the presence ofthe three-center two-electron (3c-2e) interaction between the silyl sp3 orbital and the M-Mmoiety, while these complexes become nonplanar in the absence of the 3c-2e interaction.The agostic interaction between the Si-H bond and the M center contributes to thestabilization energies of 8.0 and 17.3 kcal/mol for M = Pd and Pt, respectively. The strongeragostic interaction and the larger stabilization energy of Pt2(-2-H···SiH2)2(PH3)2 than thoseof the Pd analogue result from the fact that the d orbital of Pt expands more than that ofPd.
2-H···SiH2)2(PH3)2, in which the formula of H···SiH2 indicates that this group is nota pure silyl group but possesses the characteristics of the hydride and -silylene groups toa considerable extent. The planar geometry of this compound comes from the presence ofthe three-center two-electron (3c-2e) interaction between the silyl sp3 orbital and the M-Mmoiety, while these complexes become nonplanar in the absence of the 3c-2e interaction.The agostic interaction between the Si-H bond and the M center contributes to thestabilization energies of 8.0 and 17.3 kcal/mol for M = Pd and Pt, respectively. The strongeragostic interaction and the larger stabilization energy of Pt2(-2-H···SiH2)2(PH3)2 than thoseof the Pd analogue result from the fact that the d orbital of Pt expands more than that ofPd.