Synthesis, Structures, and Properties of Mixed Dithiolene-Carbonyl and Dithiolene-Phosphine Complexes of Tungsten

摘要

A new, high yield synthesis of [Ni(S_2C_2Me_2)_2] (3) is described using 4,5-dimethyl-l,3-dithiol-2-one, Me_2C_2S_2C=0 (1), as dithiolene ligand precursor. Reaction of (Me_2C_2S_2)Sn~nBu_2, 2, with WC1_6 produces tris(dithiolene) [W(S_2C_2Me_2)_3] (6) and demonstrates the potential synthetic utility of this compound in metallodithiolene synthesis. The series of compounds [W(S_2C_2Me_2)_x(CO)_6_2x] (X = 1-3), obtàined as 'a mixture via the reaction of [Ni(S_2C_2Me_2)_2] with [W(MeCN)_3(CO)_3], has been characterized structurally. A trigonal prismatic geometry is observed for [W(S_2C_2M_e2)(CO)_4] (4) and confirmed by a DFT geometry optimization to be lower in energy than an octahedron by 5.1 kcal/mol. The tris(dithiolene) compound [W(S_2C_2Me_2)_3] crystallizes in disordered fashion upon a 2-fold axis in C2/c, a different space group than that observed for its molybdenum homologue (P1), which is attributed to a slightly smaller chelate fold angle, χ, in the former. The reactivity of 4 and [W(S_2C_2Me_2)_2(CO)_2] (5) toward PMe_3 has been examined. Compound 4 yields only [W(S_2C_2Me_2)(CO)_2(PMe_3)_2] (7), while 5 produces either [W(S_2C_2Me_2)_2(CO)(PMe_3)] (8) or [W(S_2C_2Me_2)_2(PMe_3)_2] (9) depending upon reaction conditions. Crystallographic characterization of 5, 8, and 9 reveals a trend toward greater reduction of the dithiolene ligand (i.e., more ene_1,2-dithiolate character) across the series, as manifested by C-C and C-S bond lengths. These structural data indicate a profound effect exerted by the π-acidic CO ligands upon the apparent state of reduction of the dithiolene ligand in compounds with ostensibly the same oxidation state.