Silapropargyl/Silaallenyl and Silylene Acetylide Complexes of [Cp(CO)2W]+. Theoretical Study of Their Interesting Bonding Nature and Formation Reaction
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- 作者：Mausumi Ray ; Yoshihide Nakao ; Hirofumi Sato ; Hiroyuki Sakaba ; Shigeyoshi Sakaki
- 刊名：Journal of the American Chemical Society
- 出版年：2006
- 出版时间：September 13, 2006
- 年：2006
- 卷：128
- 期：36
- 页码：11927 - 11939
- 全文大小：778K
- 年卷期：v.128,no.36(September 13, 2006)
- ISSN：1520-5126
文摘
The geometry and bonding nature of Cp(CO)2W(C
CH)(SiH2) (1) and the reaction leading tothe formation of 1 from Cp(CO)2W(Si(H)2C CH) (9) were theoretically investigated with DFT, MP2 to MP4(SDTQ), and CCSD(T) methods, where 9 and 1 were adopted as models of the interesting new complexesreported recently, Cp*(CO)2W(Si(Ph)2C CtBu) and Cp*(CO)2W(CCtBu)(SiPh2), respectively. Our computational results clearly indicate that 1 involves neither a pure silacyclopropenyl group nor pure silyleneand acetylide groups and that the silylene group strongly interacts with both the W center and the acetylidegroup. Frontier orbitals of 1 resemble those observed in the formation of silacyclopropene from silyleneand acetylene. The frontier orbitals, as well as the geometry, indicate that the (CCH)(SiH2) moiety of 1 canbe understood in terms of an interesting intermediate species trapped by the W center in that formationreaction. Complex 1 is easily formed from 9 through Si-C 
-bond activation with moderate activation barriersof 15.3, 18.8, and 15.8 kcal/mol, which are the DFT-, MP4(SDTQ)-, and CCSD(T)-calculated values,respectively. This reaction takes place without a change of the oxidation state of the W center. Intermediate9 is easily formed from Cp(CO)2W(Me)(H3SiCCH) via Si-H oxidative addition, followed by C-H reductiveelimination. The bonding nature of 9 is also very interesting; the nonbonding 
-orbital of the H2SiCCHmoiety is essentially the same as that of the propargyl group, but the -conjugation between Si and Catoms is very weak in the -orbital, unlike that in the propargyl group.
CH)(SiH2) (1) and the reaction leading tothe formation of 1 from CH)CtBu)CtBu)(SiPh2), respectively. Our computational results clearly indicate that 1 involves neither a pure silacyclopropenyl group nor pure silyleneand acetylide groups and that the silylene group strongly interacts with both the W center and the acetylidegroup. Frontier orbitals of 1 resemble those observed in the formation of silacyclopropene from silyleneand acetylene. The frontier orbitals, as well as the geometry, indicate that the (CCH)(SiH2) moiety of 1 canbe understood in terms of an interesting intermediate species trapped by the W center in that formationreaction. Complex 1 is easily formed from 9 through Si-C -bond activation with moderate activation barriersof 15.3, 18.8, and 15.8 kcal/mol, which are the DFT-, MP4(SDTQ)-, and CCSD(T)-calculated values,respectively. This reaction takes place without a change of the oxidation state of the W center. Intermediate9 is easily formed from Cp(CO)2W(Me)(H3SiCCH) via Si-H oxidative addition, followed by C-H reductiveelimination. The bonding nature of 9 is also very interesting; the nonbonding -orbital of the H2SiCCHmoiety is essentially the same as that of the propargyl group, but the -conjugation between Si and Catoms is very weak in the -orbital, unlike that in the propargyl group.