Organometallic Chemistry of Ga+: Formation of an Unusual Gallium Dimer in the Coordination Sphere of Ruthenium

New insights into the distinct organometallic chemistry of the Ga+ ion are presented. Ga+ reacts its a strong electrophile with the electron rich ligand trismethylene-methane (C-(CH2)(3)(2-)) attached at Ru by insertion into a Ru-C bond. The resulting gallamethylallyl ligand behaves like strong nucleophile similar to known monovalent GaR species. This donor property leads to the dimeric structure of the product [{Ru(GaCp*)(3)-[eta(3)-(CH2)(2)C{CH2(mu-Ga)}]}(2)][BArF)(2)] (4) (Cp* = C5Me5. [BArF] = [B{C6H3-(CF3)(2)}(4)]). Very unexpectedly, the two gallium ligands in this dimer are found in close vicinity to each other with a distance in the range of Ga-Ga bonds. Indeed AIM calculations confirm it weak attractive closed shell Ga-Ga interaction. Finally, a novel example of it complex with substituent-free Ga+ as it ligand was found in the compound [Ru(PCy3)(2)(GaCp*)(2)(Ga)][BArF] (6) (Cy=C6H11, cyclohexyl), the very short Ru-Ga bond length confirming, the assumption that Ga+ represents a pure sigma/pi-accepting ligand in this case.