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]n) 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]n 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.