Anionic ruthenium(II) alkyls with ancillary diene and dienyl ligands: Synthesis and structures of [(η2,η2-C7H8)RuMe4]2− and [(η3,η2-C8H11)RuMe3]2−

Treatment of the ruthenium(II) diene complexes [(η2,η2-nbd)RuCl2]n or [(η2,η2-cod)RuCl2]n with 4 equiv. of methyllithium in the presence of N,N,N′,N′-tetramethylethylenediamine (tmed) yields the methyl complexes [Li(tmed)]2[(η2,η2-nbd)RuMe4] (1) and [Li(tmed)]2[(η3,η2-C8H11)RuMe3] (2), respectively, where nbd = norbornadiene and cod = 1,5-cyclooctadiene. In the latter compound, the cyclooctadiene ligand has been deprotonated to afford a η3,η2-1,2,3:5,6-cyclooctadienyl group. Both complexes were studied by 1H and 13C{1H} NMR spectroscopy, and the crystal structure of 2 was determined. One lithium atom in 2 is four-coordinate and bridges between one ruthenium-bound methyl group and one of the wingtip allylic carbon atoms in the η3,η2-C8H11 ligand. The other lithium atom is five-coordinate, and forms contacts with the other two Ru–Me groups and with the other wingtip carbon atom of the allyl unit.