Metal Complexes of π-Ligands Containing Organosilicon Groups

Abstract

Publisher Summary This chapter discusses the metal complexes of π -ligands containing organosilicon groups. Organometallic compounds containing both organosilicon groups and transition metal atoms have received much attention in several research laboratories. The organic ligands are classified, as is usual in transition-metal organic chemistry, according to the number of electrons contributed by the organic ligands to the vacant metal orbitals. Some examples in the chapter illustrate the use of organosilicon groups to protect reactive sites in the synthesis of transition-metal organic compounds that cannot be obtained by a direct reaction. Thus, chromium or cobalt carbonyl complexes of monosubstituted acetylenes cannot be obtained directly, either because of the lack of reaction or because of the polymerization and/or secondary reactions of the ligand. The migration of organosilicon groups from metal to ligand is believed to be a key step in the mechanism of olefin hydrosilylation catalyzed by nickel–phosphine complexes. The structures of the silylated cyclobutadiene complexes were established by mass spectrometry and X-ray diffraction studies. Various substituted silacyclopentadienes react with iron or cobalt carbonyl compounds to give stable η 4 -silacyclopentadiene complexes. Silacyclohexadienes may, in principle, act as 4-electron donors. Cyclopentadienyl tricarbonyl manganese can also be metalated with η -butyllithium and then converted into organosilicon derivatives. Aromatic organosilicon compounds react with chromium hexacarbonyl on prolonged heating to give the corresponding silylated η 6 -arene chromium tricarbonyl complexes.