[Fp(CH4)](+), [? (5)-CpRu(CO)(2)(CH4)](+), and [? (5)-CpOs(CO)(2)(CH4)](+): A Complete Set of Group 8 Metal-Methane Complexes

Here, we report the NMR spectroscopic analysis of the group 8 transition metal methane sigma-complexes [eta 5-CpM-(CO)(2)(CH4)][Al(OC(CF3)(3))(4)] (M = Fe, Ru) at -90 ? in the weakly coordinating solvent 1,1,1,3,3,3-hexafluoropropane. The iron(II)-methane complex has a 1H resonance at delta -4.27, a 13C resonance at delta -53.0, and1JC-H = 126 Hz for the bound methane fragment. The ruthenium(II)-methane complex has a 1H resonance at delta -2.10, a 13C resonance at delta -48.8, and a1JC-H = 126 Hz for the bound methane fragment. DFT and ab initio calculations support these experimental observations and provide further detail on the structures of the [eta 5-CpM(CO)2(CH4)]+ (M = Fe, Ru) complexes of the Group 8 metals. Both the iron centered methane complex, [eta(5)-CpFe(CO)(2)(CH4)][Al(OC(CF3)(3))(4)], and the ruthenium centered methane complex, [eta(5)-CpRu-(CO)(2)(CH4)][Al(OC(CF3)(3))(4)], are significantly less stable than the previously reported osmium-methane complex [eta 5- CpOs(CO)(2)(CH4)][Al(OC(CF3)(3))(4)].