Univalent Gallium and Indium Phosphane Complexes: From Pyramidal M(PPh3)3+ to Carbene-Analogous Bent M(PtBu3)2+ (M=Ga, In) Complexes

In a new oxidative route, Ag+[Al(ORF)4]− (RF=C(CF3)3) and metallic indium were sonicated in aromatic solvents, such as fluorobenzene (PhF), to give a precipitate of silver metal and highly soluble [In(PhF)n]+ salts (n=2, 3) with the weakly coordinating [Al(ORF)4]− anion in quantitative yield. The In+ salt and the known analogous Ga+[Al(ORF)4]− were used to synthesize a series of homoleptic PR3 phosphane complexes [M(PR3)n]+, that is, the weakly PPh3-bridged [(Ph3P)3In–(PPh3)–In(PPh3)3]2+ that essentially contains two independent [In(PPh3)3]+ cations or, with increasing bulk of the phosphane, the carbene-analogous [M(PtBu3)2]+ (M=Ga, In) cations. The MIP distances are 27 to 29 pm longer for indium, and thus considerably longer than the difference between their tabulated radii (18 pm). The structure, formation, and frontier orbitals of these complexes were investigated by calculations at the BP86/SV(P), B3LYP/def2-TZVPP, MP2/def2-TZVPP, and SCS-MP2/def2-TZVPP levels.