Synthesis of coordinatively unsaturated diphosphine nickel( II ) and palladium( II )β-agostic ethyl cations: X-ray crystal structure of [Ni{Bu t 2 P(CH 2 ) 2 PBu t 2 }(C 2 H 5 )][BF 4 ]

Protonation of [M(L2)(η2-C2H4)](L2= chelating diphosphine; M = Ni, Pd) with HBF4 affords a series of cations [M(L2)(C2H5)]+ characterized as β-agostic ethyl complexes by NMR spectroscopy and X-ray structure analysis.