Nickel Hydride Complexes Supported by a Pyrrole-Derived Phosphine Ligand

The synthesis of two nickel hydride complexes bearing the pyrrole-derived phosphine ligand ^CyPN^H (2-(dicyclohexylphosphino)­methyl-1H-pyrrole) was developed, namely, (κ^P-^CyPN^H)­(κ^P,κ^N-^CyPN)­NiH and the acid-stable trans-(κ^P-^CyPN^H)₂Ni­(OAc)­H·HOAc. (κ^P-^CyPN^H)­(κ^P,κ^N-^CyPN)­NiH stoichiometrically reduces benzaldehyde and acetophenone in a metal–ligand cooperative manner and catalytically dimerizes ethylene and cycloisomerizes 1,5-cyclooctadiene and 1,5-hexadiene. trans-(κ^P-^CyPN^H)₂Ni­(OAc)­H·HOAc, available from the protonation of (κ^P-^CyPN^H)­(κ^P,κ^N-^CyPN)­NiH with acetic acid, catalyzes the cycloisomerization of 1,5-cyclooctadiene more effectively and produces the less thermodynamically favored cycloisomers of 1,5-cyclooctadiene.