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552810 
Journal Article 
Hydrosilylation vs. [2 + 2]-cycloaddition: A theoretical study with iron and ruthenium complexes 
Böhme, U 
2006 
Yes 
Journal of Organometallic Chemistry
ISSN: 0022-328X
EISSN: 1872-8561 
691 
21 
4400-4410 
Recently an exciting new mechanism of hydrosilylation had been found in experiments with the ruthenium-silylene complex [Cp*(i-Pr3P)Ru(H)2Si(H)Ph · OEt2][B(C6F5)4] by Glaser and Tilley. The mechanism of the hydrosilylation and possible alternative pathways are investigated with quantum chemical methods utilizing the B3LYP method, a double zeta pseudopotential basis set for iron and ruthenium and the 6-31G* basis set for all other elements. Starting from the model complex [Cp(H3P)Ru(H)2Si(H)Ph]+ the coordination of ethene at the silicon atom leads preferably to the hydrosilylation of a terminal Si-H-bond. The analysis of the electron density distribution of the catalytic active complex shows surprising bond features between Ru and Si. The Ru-Si bond is bridged by two hydrogen atoms. The [2 + 2]-cycloaddition of the alkene to the Ru-Si-bond, which would be a reasonable alternative reaction pathway, was not observed. It is necessary to make drastic changes in the ligand environment of the transition metal-silicone complex to observe cycloaddition reactions. With complexes of the type (OC)4MSi(H)Ph (M = Ru, Fe) the cycloaddition could be a serious alternative to the hydrosilylation. 
Homogeneous catalysis; Hydrosilylation; Ruthenium; Iron; Si ligands; DFT calculations