N-Atom transfer via thermal or photolytic activation of a Co-azido complex with a PNP pincer ligandElectronic supplementary information (ESI) available: Experimental, crystallographic and computational data. CCDC 1518623 (3) and 1527630 (4). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7dt01712j

Thermal or photolytic activation of well-defined mononuclear [Co(N 3 )(PNP)] (PNP = 2,2′-bis(diisopropylphosphino)-4,4′-ditolylamido) results in the structurally characterized dinuclear species [Co(μ-N;κ 3 - P , N , N -PN P N)] 2 ( 3 ), with two N-bridging phosphiniminato bridgeheads. Density Functional Theory (DFT) calculations indicate the intermediacy of a mononuclear cobalt-nitrido complex, followed by N-migratory insertion into a Co-P bond. Reaction of 3 with two equiv. HCl leads to rupture of the dimer with formation of mononuclear [CoCl(PN P N H )] ( 4 ) by protonation of the N-bridges. Activation of a cobalt azido species yields a well-defined Co-dimer, which converts to a mononuclear Co-complex upon protonolysis.