[Fp(CH 4 )] + , [η 5 -CpRu(CO) 2 (CH 4 )] + , and [η 5 -CpOs(CO) 2 (CH 4 )] + : A Complete Set of Group 8 Metal-Methane Complexes.

Here, we report the NMR spectroscopic analysis of the group 8 transition metal methane σ-complexes [η 5 -CpM(CO) 2 (CH 4 )][Al(OC(CF 3 ) 3 ) 4 ] (M = Fe, Ru) at -90 °C in the weakly coordinating solvent 1,1,1,3,3,3-hexafluoropropane. The iron(II)-methane complex has a 1 H resonance at δ -4.27, a 13 C resonance at δ -53.0, and 1 J C-H = 126 Hz for the bound methane fragment. The ruthenium(II)-methane complex has a 1 H resonance at δ -2.10, a 13 C resonance at δ -48.8, and a 1 J C-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 [η 5 -CpM(CO) 2 (CH 4 )] + (M = Fe, Ru) complexes of the Group 8 metals. Both the iron centered methane complex, [η 5 -CpFe(CO) 2 (CH 4 )][Al(OC(CF 3 ) 3 ) 4 ], and the ruthenium centered methane complex, [η 5 -CpRu(CO) 2 (CH 4 )][Al(OC(CF 3 ) 3 ) 4 ], are significantly less stable than the previously reported osmium-methane complex [η 5 -CpOs(CO) 2 (CH 4 )][Al(OC(CF 3 ) 3 ) 4 ].