Chalcogenido-Dimethylgallates and -Indates DMPyr₂ [Me₂ M(μ₂ -E)]₂ (M=Ga, In; E=S, Se): Building Blocks for Higher and Lower Order Chalcogenidoindates

Metalation of the anions in the ionic liquids DMPyr[SH] and DMPyr[SeH] (DMPyr=1,1-dimethylpyrrolidinium) by trimethylgallium and trimethylindium is investigated. The reaction proceeds via pre-coordination of [EH]^- , methane elimination and formation of an unprecedented series of chalcogenido metalates DMPyr₂ [Me₂ M(μ₂ -E)]₂ (M=Ga, In; E=S, Se). These show the presences of dinuclear dianions with four-membered ring structures displaying highly nucleophilic bridging chalcogenide ligands in their crystallographically determined molecular structures. Some representative reactions of these building blocks with amphoteric electrophiles were studied: Addition of two equivalents of E(SiMe₃ )₂ (E=S, Se) to the indates DMPyr₂ [Me₂ In(μ₂ -S)]₂ and DMPyr₂ [Me₂ In(μ₂ -Se)]₂ leads to a cleavage of the ring, E silylation and formation of mononuclear, monoanionic indates DMPyr[Me₂ In(SSiMe₃ )₂ ], DMPyr[Me₂ In(SeSiMe₃ )₂ ], and even a mixed sulfido-selenido dimethylindate DMPyr[Me₂ In(SSiMe₃ )(SeSiMe₃ )]. Reaction of DMPyr₂ [Me₂ In(μ₂ -S)]₂ with two equivalents of Lewis acid Me₃ In leads to charge delocalization, ring expansion and formation of six-membered ring DMPyr₃ [Me₂ In(μ₂ -S-InMe₃ )]₃ . The latter is a key intermediate in the formation of dianionic sulfidoindate DMPyr₂ [(Me₂ In)₆ (μ₃ -S)₄ ] displaying an unusual inverse heteroadamantane cage structure with four capping sulfido ligands.