Synthesis, Reactivity, and Catalytic Application of a Nickel Pincer Hydride Complex

The nickel(II) hydride complex [( Me N 2 N)Ni-H] ( 2 ) was synthesized by the reaction of [( Me N 2 N)Ni-OMe] ( 6 ) with Ph 2 SiH 2 and was characterized by NMR and IR spectroscopy as well as X-ray crystallography. 2 was unstable in solution, and it decomposed via two reaction pathways. The first pathway was intramolecular N–H reductive elimination to give Me N 2 NH and nickel particles. The second pathway was intermolecular, with H 2, nickel particles, and a five-coordinate Ni(II) complex [( Me N 2 N) 2 Ni] ( 8 ) as the products. 2 reacted with acetone and ethylene, forming [( Me N 2 N)Ni-O i Pr] ( 9 ) and [( Me N 2 N)Ni-Et] ( 10 ), respectively. 2 also reacted with alkyl halides, yielding nickel halide complexes and alkanes. The reduction of alkyl halides was rendered catalytically, using [( Me N 2 N)Ni-Cl] ( 1 ) as catalyst, NaO i Pr or NaOMe as base, and Ph 2 SiH 2 or Me(EtO) 2 SiH as the hydride source. The catalysis appears to operate via a radical mechanism.