Self-Addition of Metallacyclic Nickel Enolate Complexes Stabilized by Monodentate Phosphine Ligands^†

In contrast with their stable counterparts bearing the chelating diphosphines, the nickelacyclic O-enolate complexes stabilized by monodentate ligands (R = H, Me, L = PMe3; R = H, L = PMe2Ph ) undergo an unusual self-addition process leading to dinuclear alkoxo-hydroxo derivatives. The α-substituted enolate complexes (R = Me) are less prone to undergo this transformation, and the corresponding nickelacycles with L = PMe3 or PMe2Ph can be isolated in pure form.