Ligand interactions silylated ligands

The synthesis, structures, and reactions of silicon-substituted alkyl derivatives of metals from groups 1, 2, and 3 have been recently reviewed. A diverse range of structures has been discovered with the alkali metals. More recently, some additional structures and an important discussion of structural trends observed among the silicon-substituted alkyl derivatives of the alkali metals have also been published. " Tris(trimethylsilyl)methyl lithium forms a solvent-free dimer, as well as several ate complexes in the presence of bases (THF or TMEDA). In the alkyl-bridged dimer of tris(trimethylsilyl)methyl lithium (2), there are interactions between the C-H bonds of the silyl ligand and the lithium atoms (3) (Li to C distances of 254.1(7) and 246.6(6) pm). ... 

Palladium(I) dimeric complexes are also known where the Pd-Pd bond is supported by electron-deficient hydrido or silyl ligands. In the case of SiR2H bridges, an agostic interaction (see Agostic Bonding) of one of the Pd atoms with the Si-H bond is observed (9). The same feature has been found for some phosphido-bridged Pd(I) dimers. 

The cis ligand alkene then inserts into the M—H bond (hydrometallation) of (6) to afford an alkyl metal complex (7), which interacts with another molecule of alkene to induce the coupling of the alkyl and silyl ligands and to regenerate the active catalyst (5). This last reaction is the rate-determining step of the catalytic cycle. 

The particular chemical behavior of hydridosilyl-manganese complex 166, which contrasts sharply with that of hydridosilyl-iron complexes (12,252), has been interpreted in terms of a bonding interaction between hydrido and silyl ligands this is detailed in Sect. IV-B-3 in connection with hydrosilylation processes. 

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