CATECHOLATE COMPLEXES OF SILICON - SYNTHESIS AND MOLECULAR AND CRYSTAL-STRUCTURES OF [SI(CAT)(2)]CENTER-DOT-2THF AND LI-2[SI(CAT)(3)].3.5DME (CAT=CATECHOLATE DIANION)

The neutral complex [Si(cat)(2)] (1) and the anionic complex Li-2[Si(cat)(3)] (2) (cat = catecholate dianion) have been prepared by addition of stoichiometric amounts of Li(2)cat to a solution of SiCl4 in THF, The THF-soluble Li(2)cat starting material was obtained by deprotonation of catechol with n-BuLi or LiH in THF. Both the neutral complex 1 and the lithium salt 2 show good solubility in THF. The molecular structures of both 1 and 2 have been determined by X-ray diffraction. Crystals of 1 . 2THF belong to the monoclinic space group P2(1)/c with unit cell parameters a = 6.3428(8) Angstrom, b = 17.7274(13) Angstrom, c = 9.1337(10) Angstrom, beta = 108.763(10)degrees, V = 973.5(4) Angstrom(3), and Z = 2; R (R(w)) = 3.89% (4.79%) for 125 refined parameters and 1142 reflections with F-o(2) greater than or equal to 3 sigma(F-o(2)). The silicon atom in 1 . 2THF lies on an inversion center in the unit cell and is coordinated in an octahedral fashion by four catecholate and two THF oxygen atoms. Compound 2 was crystallized from dme: (dme = 1,2-dimethoxyethane) in the triclinic space group P ($) over bar 1 as Li-2[Si(cat)(3)] . 3.5dme (2 . 3.5dme) with unit cell parameters a = 11.7680(13) Angstrom, b = 12.3986(13) Angstrom, c = 13.7981(15) Angstrom, alpha = 79.833(9)degrees, beta = 81.158(10)degrees, gamma = 63.676(10)degrees V = 1769.6(3) Angstrom(3), and Z = 2; R (R(w)) = 3.99% (5.32%) for 434 refined parameters and 4833 reflections with F-0(2) greater than or equal to 3 sigma(F-0(2)). The silicon atom in 2 . 3.5dme is at the center of an octahedron consisting the six catecholate oxygen atoms. Each of the two lithium cations is at the center of a distorted octahedron composed of three facial oxygen atoms of the SiO6 octahedron and three oxygen atoms from dme solvent molecules.