Synthesis and Characterization of the Neutral Three-Coordinate Thiolate Complexes Al[S(2,4,6-t-Bu₃C₆H₂)]₃ and Ga[S(2,4,6-t-Bu₃C₆H₂)]₃

The first monomeric, three-coordinate aluminum and gallium thiolate compounds have been synthesized and structurally characterized. The compounds were prepared by the reaction of the corresponding metal halide with 2 equiv of LiSMes* (Mes* = 2,4,6-t-Bu₃C₆H₂) to give the aluminum derivative Al(SMes*)₃ (1) or with 3 equiv of the lithium thiolate to give the gallium species Ga(SMes*)₃ (2). The compounds were characterized by ¹H NMR and infrared spectroscopy and X-ray crystallography. Crystal data with Mo Kα; (λ = 0.71069 Å) radiation at 130 K: 1, Al(SMes*)₃, C₅₄H₈₇AlS₃, a = 10.229 (5) Å, b = 26.137 (7) Å, C = 19.908 (5) Å, β = 91.260 (3)°, Z = 4, monoclinic, space group P2₁/n, R(F) = 0.049; 2, Ga(SMes*)₃, C₅₄H₈₇GaS₃, a = 10.243 (2) Å, b = 26.189 (8) Å, c = 20.031 (3) Å,β = 91.554 (1)°, Z = 4, monoclinic, space grup P2₁/n, R(F) = 0.049. The structural data show that 1 and 2 have a very similar three-coordinate, almost planar, geometry at the metal. Distortions from idealized trigonal-planar coordination, as well as other structural features can be explained on the basis of ionic M-S bonding character and of some M⋯H interactions involving the o-t-Bu groups of the ligand.