Arene c?￡?h amination at nickel in terphenyl-diphosphine complexes with labile metal-arene interactions

摘要

The meta-terphenyl diphosphine, m-P_2, 1, was utilized to support Ni centers in the oxidation states 0, I, and II. A series of complexes bearing different substituents or ligands at Ni was prepared to investigate the dependence of metal-arene interactions on oxidation state and substitution at the metal center. Complex (m-P_2)Ni (2) shows strong Ni ~0-arene interactions involving 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=CH_3CN, CO, Ph_2CN_2), Ni~IX complexes (3-X: X=Cl, BF_4, N_3, N_3B(C _6F_5)_3), and [(m-P_2)Ni ~(II)Cl_2] (4). Complex 2 reacts with substrates, such as diphenyldiazoalkane, sulfur ylides (Ph_2S?￡CH_2), organoazides (RN_3: R=para-C_6H_4OMe, para-C _6H_4CF_3, 1-adamantyl), and N_2O with the locus of observed reactivity dependent on the nature of the substrate. These reactions led to isolation of an η~1-diphenyldiazoalkane adduct (2-Ph_2CN_2), 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, all derived from the same compound (2). Hydrogen-atom abstraction from a Ni~I-amide (9) and the resulting nitrene transfer supports the viability of Ni-imide intermediates in the reaction of 1 with 1-azido-arenes. Put a ring on it: The utilization of a meta-terphenyl diphosphine ligand leads to labile metal-arene interactions in Ni complexes in various oxidation states and coordination environments. When these complexes are treated with group-transfer reagents, such as diazoalkanes, sulfur ylides, or azides, various types of ligand-centered reactivity were observed, including methylidene insertion into a P?￡?C bond and amination of an arene C?￡?H bond.