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

Abstract

AbstractDicobalt complexes supported by flexible macrocyclic ligands were used to target the generation of the bridging nitrido species [(nPDI2)Co2(μ‐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 [(2PDI2)Co2(μ‐NPMe3)(PMe3)2]3+, amido [(nPDI2)Co2(μ‐NH2)(PMe3)2]3+ (n=2, 3), and C−H amination [(3PDI2*‐μ‐NH)Co2(PMe3)2]3+ products. All results are consistent with the initial formation of [(nPDI2)Co2(μ‐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 nPDI2 ligand.