Nickel Phosphanido Hydride Complex: An Intermediate in the Hydrophosphination of Unactivated Alkenes by Primary Phosphine

Heating of a mixture of [Ni(CH2CH2)(dtbpe)] (dtbpe = 1,2-bis(di-tert-butylphosphino)ethane) and 2,6-dimesitylphenylphosphine (DmpPH2) in toluene gives the secondary phosphine (Dmp)P(Et)(H) (1) as the main product. However, thermolysis of [Ni(CH3)2(dtbpe)] in the presence of DmpPH2 in toluene leads to the mononuclear nickel phosphanido hydride complex [NiH{P(Dmp)(H)}(dtbpe)] (2), the product of an oxidative addition of a primary phosphine to nickel(0). The structure of complex 2 was confirmed by single-crystal X-ray diffraction and DNMR studies. The mutual exchange of tautomers in which the Ni–H and P–H hydrogen atoms interchange as well as the position of the hydrido and the phosphanido ligand occurs in solution. The stoichiometric reaction of 2 with 1-hexene proceeds regiospecifically to form the secondary phosphine (Dmp)P(Hex)(H) (3).