New Pincer-Type Diphosphinito (POCOP) Complexes of Nickel

Abstract

This report describes the synthesis, characterization, and reactivities of a new series of pincer-type nickel complexes based on the diphosphinito (POCOP) ligands 1,3-(i-Pr2PO)2C6H4, 1, and (i-Pr2POCH2)2CH2, 2. Reacting these ligands with (THF)1.5NiCl2, (THF)2NiBr2, or (CH3CN)nNiX2 (X = Br, n = 2; I, n = 3) gives pincer-type complexes by metalation of the central carbon atom. The yields of these (POCOP)NiX complexes vary with the type of ligand and Ni precursor used, as well as the reaction conditions. In general, the aromatic ligand 1 was metalated more readily to give excellent yields of the pincer complexes {2,6-(i-Pr2PO)2C6H3}NiX (X = Cl, 1a, 85% yield; X = Br, 1b, 95% yield; X = I, 1c, 85% yield), especially when the reaction mixture was heated to 60 °C for 1 h in the presence of 1 equiv of 4-dimethylaminopyridine (DMAP). The analogous reactions of ligand 2 were more sluggish and required refluxing in toluene to give {(i-Pr2POCH2)2CH}NiX (X = Cl, 2a, 33% yield; X = Br, 2b, 93% yield; X = I, 2c, 70% y...