Arene C-H Amination at Nickel in Terphenyl Diphosphine Complexes with Labile Metal-Arene Interactions

摘要

The meta-terphenyl diphosphine, m-P2: >1, was utilized to support Ni centers in the oxidation states 0, I and II. A series of complexes bearing different substituents and/or ligands at Ni were prepared to investigate the dependence of metal-arene interactions on oxidation state and substitution at the metal. Compound (m-P2)Ni (>2), shows close Ni(0)-arene interactions between the metal centre and the central arene ring of the terphenyl ligand both in solution and the solid-state. These interactions are significantly less pronounced in Ni(0) complexes bearing L-type ligands (>2-L: L = CH3CN, CO, Ph2CN2), Ni(I)X complexes [>3-X: X = Cl, BF4, N3, N3B(C6F5)3] and (m-P2)Ni(II)Cl2 (>4). Complex >2 reacts with substrates such as diphenyldiazoalkane, sulfur ylides (Ph2S=CH2), organoazides (RN3: R = para-C₆H₅OMe, para-C₆H₅CF₃, 1-adamantyl) and N₂O with the locus of observed reactivity dependent on the nature of the substrate, leading to isolation of an η¹-diphenyldiazoalkane adduct (>2-Ph₂CN₂), methylidene insertion into a Ni-P bond, followed by rearrangement of a nickel-bound phosphorus ylide (>5) to a benzylphosphine (>6), Staudinger oxidation of the phosphine arms and metal-mediated nitrene insertion into an arene C-H bond of >1 to give the insertion product >8, all derived from the same compound (>2). Hydrogen atom abstraction from a nickel(I)-amide (>9) and resulting nitrene transfer chemistry supports the viability of nickel-imide intermediates in the reaction of >1 with 1-azido-arenes.