Chelating and Pincer Oxime Complexes of Palladium: Rearrangement of a 1,3-Diacylbenzene Dioxime upon Palladium Coordination

The synthesis and structural characterization of a series of oxime-derived palladium complexes are reported. Coordination of 2-pyridyl-1-ketoxime to palladium as a neutral ligand has been achieved. Palladation of 1,1′-(1,3-phenylene)bis(pentan-1-one) dioxime (^BuPhdOxH₂) resulted in the formation of an unexpected N,C,O-pincer complex through a Beckman rearrangement of one oxime group to an amide. This complex is the first metalation of C2 of a 1,1′-(1,3-phenylene)bis(1-alkanone) dioximine. In contrast, the analogous 1,1′-(pyridine-2,6-diyl)bis(1-pentanone) dioxime (^BuPydOxH₂) gives the expected N,N,N-pincer complex without ligand rearrangement. Initial mechanistic studies suggest that the Beckman rearrangement of ^BuPhdOxH₂ occurs by a process involving palladium.