Reactivity of ruthenium complexes towards organogallium reagents: Gallium as a Z-type ligand or as a gallate counterion

The reaction of RuHCl(PPh3)3 with GaMe3 gives rise to the arene complex [(eta 6-C6H6)Ru(PPh3)(PPh2-o-C6H4- GaClMe], 1, with the Ga atom making part of an in situ generated ambiphilic phosphinogallyl ligand in a five-membered ruthenagallacycle ring with a tetracoordinate gallium. In the presence of excess GaMe3, 1 forms complex [(eta 6-C6H6)Ru(PPh3)(PPh2-o-C6H4-GaMe][GaMe3Cl], 2 also bearing a phosphinogallyl ligand. Crystals suitable for single-crystal X-ray diffraction were obtained of complex 2 ', [(eta 6-C6H6)Ru(PPh3)(PPh2-o-C6H4- GaMe][GaMe2Cl2], showing an ion pair with two Ga atoms in different coordination environments: the first with a coordination number of three makes part of a five-membered ruthenagallacyle ring, while the second Ga atom is a gallate anion. In both complexes 1 and 2, the Ga atom binds to Ru as a sigma-acceptor Z-type ligand. DFT cal-culations are in good agreement with the experimental single crystal X-ray diffraction data and provide Ru-Ga Wiberg bond indexes of 0.38 and 0.50, for 1 and 2 respectively. In contrast, treatment of RuHCl(PPh3)3 with GaMeCl2 and of RuCl2(PPh3)3 with GaMe3 gives rise to gallate species [(eta 6-C6H6)Ru(PPh3)2H][GaMeCl3], 3, and [(eta 6-C6H6)Ru(PPh3)2Me][GaMe2Cl2], 4, respectively.