SILYL COMPLEXES OF MOLYBDENUM AND TUNGSTE N - SYNTHESIS, REACTIVITY AND STRUCTURE

The photochemical reaction of Cp2MH2 (M = Mo, 1; W, 2) with several hy dridosilanes HSiR3 produces the corresponding silyl hydride complexes Cp2M(H)(SiR3) (M=Mo: SiR3=SiEt3, 3; SiCl3, 4; Si(OEt)(3), 5; SiH2(C5Me 5), 6; SiH2(C5Me4H)(2), 7; SiH(C5Me4H)(2), 8; SiH2[2-(Me2NCH2)C6H4], 9 ; M = W: SiR3=SiCl3, 10) by a reductive elimination/oxidative addition process. Analogous photolysis of 1 in the presence of (C5Me5)(2)SiHCl or (C5Me5)(2)SiH2 does not yield the corresponding complexes Cp2Mo(H) (SiR3) (SiR3=SiCl(C5Me5)(2); SiH(C5Me5)(2)). Treatment of 4 and 6, res pectively, with LiAlH4 leads to the hydridosilyl complex Cp2Mo(H)(SiH3 ) 11. Compounds 6-8 and 11 are expected to be single-source precursors for generation of molybdenum silicides. The hydride complexes 4, 5, a nd 6 are readily converted to the chloro compounds Cp2Mo(Cl)(SiR3) (Si R3=SiCl3, 12; Si(OEt)(3), 13; SiH2(C5Me5), 14). The reaction of 11 wit h CCl4 yields complex 12 under exchange of each non-C-bound hydrogen a tom. Spectroscopic data of the metallosilanes are discussed and compar ed with the ones of the parent silanes. An intramolecular N-donor coor dination of the functionalized aryl substituent is indicated for 9 by means of Si-29 NMR spectroscopy. 6 undergoes fast sigmatropic rearrang ements within the Si-(C5Me5) fragment as proved by a variable temperat ure H-1 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.