Ring-Size-Modulated Reactivity of Putative Dicobalt-Bridging Nitrides: C-H Activation versus Phosphinimide Formation

摘要

Dicobalt complexes supported by flexible macrocyclic ligands were used to target the generation of the bridging nitrido species [((PDI2)-P-n)Co-2(-N)(PMe3)(2)](3+) (PDI=2,6-pyridyldiimine; n=2, 3, corresponding to the number of catenated methylene units between imino nitrogen atoms). Depending on the size of the macrocycle and the reaction conditions (solution versus solid-state), the thermolysis of azide precursors yielded bridging phosphinimido [((PDI2)-P-2)Co-2(-NPMe3)(PMe3)(2)](3+), amido [((PDI2)-P-n)Co-2(-NH2)(PMe3)(2)](3+) (n=2, 3), and C-H amination [((PDI2)-P-3*--NH)Co-2(PMe3)(2)](3+) products. All results are consistent with the initial formation of [((PDI2)-P-n)Co-2(-N)(PMe3)(2)](3+), followed by 1)PMe3 attack on the nitride, 2)net hydrogen-atom transfer to form N-H bonds, or 3)C-H amination of the alkyl linker of the (PDI2)-P-n ligand.