Tetrahedral cobalt(II) complexes stabilized by the aminodiphosphine PNP ligand [PNP = CH3CH2CH2N-(CH2CH2PPh2)(2)]

The reaction of CoCl2.6H(2)O and PNP [PNP = 1,1-bis(diphenylphosphinoethyl)-n-propylamine (CH3CH3CH3)-N(CH2CH2PPh2)(2)] in ethanol affords the blue Co(II) complex [CoCl3{eta(1)-PPPh2CH2CH2N(CH2CH2CH3)(H)-(CH2CH2P(O)Ph-2)}] (1), which has been characterized by spectroscopic methods and X-ray diffraction analysis. The structure of 1 consists of a tetrahedral cobalt atom coordinated by three chlorides and by an eta(1)-P-PNP ligand bearing a dangling P=O end and quaternised at the nitrogen atom. EPR measurements and a detailed analysis of the magnetic behaviour of I are consistent with a tetrahedral Co(II) ion and accordingly support the protonation of the PNP nitrogen atom. A mechanistic picture accounting for the formation of 1 has been proposed from the isolation and characterization of three reaction intermediates along the pathway leading to 1 which involve either eta(2)-P,P- and eta(2)-P,N-PNP cobalt complexes.