Pyramidal [Ga(PPh3)3]+ (see picture) is the first structurally characterized homoleptic gallium–phosphine complex. The synthesis of this ion was aided by the development of a facile route to gallium(I) salts with weakly coordinating anions (WCAs). These salts are an outstanding source of gallium in the oxidation state +1 for the generation of previously unknown low‐valent gallium compounds.

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In a new oxidative route, Ag(+)[Al(OR(F))(4)](-) (R(F)=C(CF(3))(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(OR(F))(4)](-) anion in quantitative yield. The In(+) salt and the known analogous Ga(+)[Al(OR(F))(4)](-) were used to synthesize a series of homoleptic PR(3) phosphane complexes [M(PR(3))(n)](+), that is, the weakly PPh(3)-bridged [(Ph(3)P)(3)In-(PPh(3))-In(PPh(3))(3)](2+) that essentially contains two independent [In(PPh(3))(3)](+) cations or, with increasing bulk of the phosphane, the carbene-analogous [M(PtBu(3))(2)](+) (M=Ga, In) cations. The M(I)-P 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.

Ga,In insights: A general explanation for the unusual tilted coordination mode of undisturbed gallium(I) and indium(I) carbene complexes of the weakly coordinating anion [Al(ORF)4]− (RF=C(CF3)3) is given, which is based on the experimental structures. The results are supported by extensive DFT studies.

Polybromide monoanions of the series [NAlk 4 ][Br 9 ] (Alk = methyl, ethyl, propyl, butyl) have been investigated. The corresponding salts were characterized by Raman spectroscopy, single-crystal Xray diffraction and state-of-the-art quantum-chemical calculations. Comparisons between their crystal structures and the gas-phase calculations have been made whereas the latter shows regular tetrahedral arrangement. Usually the nonabromides contain one central Branion at which all other four Br 2 molecules are coordinated. The only exception is [NBu 4 ][Br 9 ] where also a [Br 3 ]unit is found.Quantum-chemi-* Dr. S. Riedel