Nitrogen and oxygen bonded (2-pyrrolidinone)-pentaamminecobalt(III): The first monodentate linkage isomers of a secondary amide

The cyclic secondary amide 2-pyrrolidinone has been coordinated to the pentaamminecobalt(III) moiety to afford both O- and N-bonded linkage isomers. A deprotonated N-bonded form has also been isolated. In non-coordinating solvents the N-form rearranges to its O-bonded isomer, and in coordinating solvents some solvolysis competes with this, but much less so than for the primary amide ligand systems investigated previously. The O-bonded product ultimately loses the amide ligand completely in water, DMSO or aqueous base; there is no detectable C-N cleavage.