Thermally-Induced Transformations of Gallium and Indium Alkyl Phosphido Complexes: Dealkylsilylation Routes to MP (M = Ga, In)

Abstract

The dehalosilylation reaction of nBu2GaCl with 1 equiv of P(SiMe3)3 provided [nBu2GaP(SiMe3)2]2 (1) in good yield. A similar reaction between nBuGaCl2 and P(SiMe3)3 gave [nBu(Cl)GaP(SiMe3)2]2 (2). Compound 1 was characterized by X-ray crystallography and possesses an approximately square planar Ga2P2 molecular core. Both the P and the Ga centers are in distorted tetrahedral environments. Thermolysis of 1, at 400 °C, produced GaP and BuSiMe3 and no other crystalline products, as confirmed by thermogravimetric and spectroscopic analysis. The indium analogue of 1, [(nBu)2InP(SiMe3)2]2 (3), was prepared from the reaction of (nBu)2InCl with P(SiMe3)3. The thermolysis of 3 at 400 °C under nitrogen produced butene, butane, and butyltrimethylsilane as organic products and a dark grey solid. Powder X-ray diffraction of this solid revealed it to consist of InP and metallic indium. Combination of In(nBu)3 with P(SiMe3)3 produced the monomeric adduct (nBu)3In·P(SiMe3)3 (4). The thermal reactivity of complex 4 was investigated at various temperatures. At 130 °C in a sealed tube, the products of thermolysis are [(nBu)2InP(SiMe3)2]2 (3) and In0. While complex 1 is a potential precursor to GaP via a dealkylsilylation mechanism, the indium analogue 3 and the adduct 4 appear to have a more facile β-hydrogen elimination pathway which makes them less suitable for the production of pure InP.