Toward Cationic Gallane- and Indanediyl Complexes:  Synthetic Approaches to Three-Coordinate Halogallyl and -indyl Precursors

Transition metal complexes containing ligands featuring three-coordinate, halide-functionalized gallium or indium donors represent key precursors to unsaturated cationic species of the type [L_nM(EX)]⁺ via halide abstraction chemistry. Two routes to these three-coordinate systems have been demonstrated:  (i) salt elimination, such as the reaction between Na[Cp*Fe(CO)₂] and Mes*GaCl₂ or Mes*InBr₂ (Mes* = C₆H₂^tBu₃-2,4,6, supermesityl) to generate Cp*Fe(CO)₂E(Mes*)X (3a, E = Ga, X = Cl; 5, E = In, X = Br), and (ii) insertion of a gallium(I) or indium(I) halide into a metal−halogen or metal−metal bond followed, where necessary, by substitution by a sterically bulky anionic nucleophile. Crystallographic studies have confirmed the presence of the target trigonal planar ligand systems both in gallyl/indyl complexes of the type L_nM-E(Aryl)X and in halide-functionalized gallane- and indane-diyl systems of the type (L_nM)₂EX.