Silyl ligands

Keywords Multiple bonding. Clusters, Group 13 elements. Radicals, Terphenyls, Silyl ligands. Bulky groups... 

The change in the group trans to the silyl ligand is thought to account for the reversal of substitution pattern in the case of the monodentate phosphine 63). Six-coordinate Pt(IV) intermediates have been postulated for these Pt(II) reactions (27, 71). Such an intermediate has recently been isolated [Eq. (62)] (27). 

In addition to routine spectroscopic characterization, transition metal silyls have been examined by a variety of physical methods, principally to determine (1) the definite presence of an Si—M bond, (2) the manner in which such a bond is influenced by other ligands, (3) whether such a bond possesses any w-component, and (4) the trans influence of the silyl ligand. 

The Ir1 silyl complex Ir(PMe3)2(CO)2(SiMe2Ph), (313), is formed by reaction Scheme 29 and is characterized by X-ray crystallography.507 This result shows that metalation of silyl ligands can be a facile, reversible process. 

Heterometallic Complexes with a Bridging Alkoxy-Silyl Ligand r 2- i,2-Si(OR)3... 

The preparative potential of silyl- or stannyl-substituted polynuclear complexes is currently far from being exploited. Due to the reactivity of silyl ligands, selective cleavage of metal-silicon bonds is possible. In some cases this was observed during the reaction of an anionic silyl complex with metal... 

The tris(trimethylsilyl)silyl ligands can be easily modified by reactions with silyl chlorides, as shown with a series of phenylated species Mes Ph SiCl (n = 0-3). Furthermore, triisopropyl, thexyldimethylsilyl, or tert-butyldimethylsilyl substitution are all easily possible.190 The crystallographic characterization of some of the alkali metal derivatives indicates a direct correlation between ligand size and resulting structural parameters. 

Recently, the crystal structure of a nickel(II) complex with a tridentate silyl ligand has been reported [20]. The structure in the solid state shows an //2-(Si-H) binding to nickel, with a Ni-H distance of 1.47 A NMR spectra of the complex in solution at -80 °C suggest the formation of a nickel(IV) hydride species through oxidative addition of the silyl-hydrogen to nickel [20]. 

The transfer of the silyl ligand onto the a-carbon of the substrate is followed by the formation of an intermediate in which the (1-phenylethyl)trichlorosilane product still weakly coordinated in a rj2-fashion. The corresponding endo and exo intermediates (11a and lib, respectively) are 3.5 and 4.2 kcal/mol, respectively, more stable than the endo 7i-complex, 8a Therefore the exo-stereoisomer is again thermodynamically more stable than the endo form. Finally, the oxidative addition of a molecule of trichlorosilane occurs with concomitant liberation of the products. The formation of both R and S products is exothermic by -20 kcal/mol. 

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