METALLOTRIHYDRIDOSILANES OF MOLYBDENUM AND TUNGSTEN - SYNTHESIS, CHARACTERIZATION, AND VIBRATIONAL STUDIES OF (C(5)R(5))(OC)(2)(ME(3)P)M-SIH3 (M=MO,W, R=H,ME)

The lithium metalates Li[M(CO)(2)(PMe(3))C(5)R(5)] (2a-c), prepared fr om the corresponding metal hydrides C(5)R(5)(OC)(2)(Me(3)P)M-H [R = H, M = Mo (1a), W (1b); R = Me, M = Mo (1c)] with n-butyllithium, react with HSiCl3 (5) to give C(5)R(5)(OC)(2)(Me(3)P)M-Si(H)Cl-2 (6a-c). Com pound 6b is additionally obtained, starting with the tetramethylphosph onium metalate [Me(4)P][W(Co)(2)(PMe(3))C5H5] (4), generated from Ib w ith the ylide Me(3)P=CH2 (3). On treatment with LiAlH4, 6a-c undergo s mooth Cl/H exchange at the silicon to afford the metallotrihydridosila nes C(5)R(5)(OC)(2)(Me(3)P)M-SiH3 (7a-c). The spectroscopic properties of all the compounds have been extensively studied by NMR and IR spec troscopy. In the case of 7a-c, detailed studies of the Raman spectra h ave been performed as well as force field calculations for the M-SiH3 units, yielding valuable information with respect to Si-H and M-Si for ce constants.