Triple C–H Bond Activation of a Nickel-Bound Methyl Group: Synthesis and X‑Ray Structure of a Carbide Cluster (NiCp)6(μ6‑C)

A new hexanuclear cyclopentadienylnickel carbide cluster (NiCp)6(μ6-C) (1) was obtained through the thermolysis of the alkene complex [NiCp­(CH3)­(η2-CH2CHC4H9)] (4). The X-ray molecular structure of 1 (monoclinic; P21/c; Ni–Ccarbide = 1.767(4)–2.109(4) Å) reveals a highly deformed octahedral arrangement of nickel atoms with two octahedron edges opened (Ni–Ni bonding distances = 2.410(1)–2.623(1) Å, Ni···Ni nonbonding distances = 3.107(2) and 3.108(2) Å). Cluster 1 is the first example of a homoleptic, cyclopentadienylnickel carbide cluster. Moreover, 13C-labeling studies proved that the carbido ligand in cluster 1 originated from the Ni-bound methyl group. This transformation requires a triple C–H bond activation in the methyl group, which has not been observed so far for late transition metal compounds.