Reactivity of a T-shaped cobalt() pincer-complex

The reactivity of a paramagnetic T-shaped cobalt( i ) complex, [( iPr boxmi)Co] , stabilised by a monoanionic bis(oxazolinylmethylidene)-isoindolate (boxmi) NNN pincer ligand is described. The exposure to carbon monoxide as an additional neutral ligand resulted in the square-planar species [( iPr boxmi)Co(CO)] , accompanied by a change in the electronic spin state from S = 1 to S = 0. In contrast, upon treatment with trimethylphosphine the formation of the distorted tetrahedral complex [( iPr boxmi)Co(PMe 3 )] was observed ( S = 1). Reacting [( iPr boxmi)Co] with iodine (I 2 ), organic peroxides ( t Bu 2 O 2 , (SiMe 3 ) 2 O 2 ) and diphenyldisulphide (Ph 2 S 2 ) yielded the tetracoordinated complexes [( iPr boxmi)CoI] , [( iPr boxmi)Co(O t Bu)] , [( iPr boxmi)Co(OSiMe 3 )] and [( iPr boxmi)Co(SPh)] , respectively, demonstrating the capability of the boxmi-supported cobalt( i ) complex to homolytically cleave bonds and thus its distinct one-electron reactivity. Furthermore, a square-planar cobalt( ii ) alkynyl complex [( iPr boxmi)Co(CCAr F )] was identified as the main product in the reaction between [( iPr boxmi)Co] and a terminal alkyne, 4-fluoro-1-ethynylbenzene. Putting such species in the context of the previously investigated hydroboration catalysis, its stoichiometric reaction with pinacolborane revealed its potential conversion into a cobalt( ii ) hydride complex, thus confirming its original attribution as off-cycle species. A paramagnetic T-shaped cobalt( i ) complex, stabilised by a monoanionic NNN pincer ligand, induces reductive bond cleavage and related transformations of small molecules.