Ligand Influence on Indium–Sulfide Cluster Formation and Reactivity

An indium-sulfide tetramer ([InMe₂(SSiMe₃)]₄), which contains reactive silyl and methyl groups, is shown to be an isolable intermediate in cluster synthesis. The reactive groups allow it to act as a synthon in the formation of multinuclear indium-sulfide architectures, evidenced by the crystallization of a coordination polymer ([In₂₀S₁₄Me₃₂(4,4'-bpy)₅·5CH₂Cl₂]_<i>n</i>) utilizing In₁₀S₇ clusters as nodes. The reaction between trimethylindium (InMe₃) and bis(trimethylsilyl)sulfide (S(SiMe₃)₂) is explored with and without the presence of a ligating bipyridine. In both cases, a sulfide-indium adduct is formed, which slowly converts into a multimetallic complex. The ligand 2,2'-bipyridine (2,2'-bpy) is coordinated to InMe₃ to form the adduct InMe₃(bpy), which upon addition of sulfide, eliminates tetramethylsilane (TMS) and binds two additional InMe₃ moieties (InMe₂(bpy)(μ₃-SSiMe₃)(InMe₃)₂). When reacted neatly without bipyridine, InMe₃ and S(SiMe₃)₂ form the adduct InMe₃(S(SiMe₃)₂), which subsequently eliminates TMS and intermolecularly associates to yield [InMe₂(SSiMe₃)]₄. Although stable in an inert atmosphere, [InMe₂(SSiMe₃)]₄ undergoes facile hydrolysis to yield [InMeS]_<i>n</i> when exposed to air. The effect of ligand addition (4,4'-bipyridine (4,4'-bpy)) to [InMe₂(SSiMe₃)]₄ is then examined. In every case, it is shown that the presence of the bpy ligand has a profound influence on the resulting structure, as shown by the unexpected formation of a trimer and In₁₀S₇ cluster network.