Silyl-Komplexe des Molybdäns und Wolframs. Synthese, Reaktivität und Struktur

Abstract

The photochemical reaction of Cp 2MH 2 (M=Mo, 1; W, 2) with several hydridosilanes HSiR 3 produces the corresponding silyl hydride complexes Cp 2M(H)(SiR 3) (M=Mo: SiR 3SiEt 3, 3; SiCl 3, 4; Si(OEt) 3, 5; SiH 2(C 5Me 5), 6; SiH 2(C 5Me 4H) 2, 7; SiH(C 5Me 4H) 2, 8; SiH 2[2-(Me 2NCH 2)C 6H 4], 9; M=W: SiR 3SiCl 3, 10) by a reductive elimination/oxidative addition process. Analogous photolysis of 1 in the presence of (C 5Me 5) 2SiHCl or (C 5Me 5) 2SiH 2 does not yield the corresponding complexes Cp 2Mo(H)(SiR 3) (SiR 3SiCl(C 5Me 5) 2; SiH(C 5Me 5) 2). Treatment of 4 and 6, respectively, with LiAlH 4 leads to the hydridosilyl complex Cp 2Mo(H)(SiH 3) 11. Compounds 6–8 and 11 are expected to be single-source precursors for generation of molybdenum silicides. The hydride complexes 4, 5, and 6 are readily converted to the chloro compounds Cp 2Mo(Cl)(SiR 3) (SiR 3SiCl 3, 12; Si(OEt) 3, 13; SiH 2(C 5Me 5), 14). The reaction of 11 with CCl 4 yields complex 12 under exchange of each non-C-bound hydrogen atom. Spectroscopic data of the metallosilanes are discussed and compared with the ones of the parent silanes. An intramolecular N-donor coordination of the functionalized aryl substituent is indicated for 9 by means of 29Si NMR spectroscopy. 6 undergoes fast sigmatropic rearrangements within the Si–(C 5Me 5) fragment as proved by a variable temperature 1H NMR investigation. The structures of 6, 7, 8, and 12 have been determined by single-crystal X-ray diffractometry. Bonding parameters of these typical bent–sandwich complexes are discussed taking account of electronic and steric influences.