Silylene complexes with group 10 transition metals

The silylene migration may be involved in some stoichiometric reactions of hydrodisilanes with transition-metal complexes, forming disilanyl complexes through activation of Si-H bonds. Binuclear Ru and Os complexes 39 having terminal silyl groups and silylene bridges are isolated in the reactions of pentame-thyldisilane with Ru3(CO)12 and Os3(CO)12, respectively, albeit in low yields (Eq. 16) [33]. Similar silylene migration may be involved in the reactions of hydrodisilane with other transition-metal carbonyls such as Fe2(CO)9 and Co2(CO)8 [34]. 

Displacement of a good leaving group from silicon in a noncoordinating solvent (equation 5) allows solvent-free complexes (1) to be prepared when the substituents on silicon are bound via sulfur. As would be expected by analogy with carbene complexes, the Si NMR chemical shift for these complexes is at very low held (264.4 and 268.7 ppm, respectively, for R = S-/ -tolyl and SEt, respectively) and they also react readily with donor molecules such as MeCN to give four-coordinate, donor stabilized silylene species. (See Section 6 below for further details of transition metal silyl complexes.)... 

A typical method of formation of a transition metal-silicon bond is the oxidative addition of silane derivatives, involving either Si-H or Si-Si bond cleavage, to a low valent, coordinatively unsaturated transition metal complex. Various kinds of transition metal silyl or silylene complexes have so far been synthesised via this method. However, in contrast to the rich chemistry of the late transition metal complexes with an M-Si bond, a limited number of syntheses of Group 6 metal complexes with an M-Si bond have been reported. ... 

In reactions that are formally analogous to hydrosilylation, transition-metal complexes catalyze the insertion of unsaturated hydrocarbons into other Si-X (X = C, Si, Sn, etc.) bonds. Palladium catalysts seem to work best in many of these reactions. The work of Kumada and coworkers has already been referred to in connection with metal-catalyzed silylene transfer to alkynes (see equation 47)95"97. Sakurai s group has shown that the cyclic disilane 55 will add to alkynes in the presence of a palladium catalyst (equation 110, see also equation 80). The unstrained disilane Me3SiSiMe3 undergoes a similar reaction... 

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