Synthesis, Structure and Nickel Carbonyl Complexes of Dialkylterphenyl Phosphines

The experimental and computational characterization of a series of dialkylterphenyl phosphines, PR2Ar ' is described. The new P-donors comprise five compounds of general formula PR(2)ArDtbp2 (R=Me, Et, iPr, c-C5H9 and c-C6H11); ArDtbp2 = 2,6-C6H3-(3,5-C6H3-(CMe3)(2))(2)), and another five PR2Ar ' phosphines containing the bulky alkyl groups iPr, c-C5H9 or c-C6H11, in combination with Ar '=ArXyl2, ArXyl'2, or ArPh2 (L1-L10). Steric and electronic parameters have been determined computationally and from IR and X-ray data obtained for the phosphines and for some derivatives, including tricarbonyl and dicarbonyl nickel complexes, Ni(CO)(3)(PR2Ar ') and Ni(CO)(2)(PR2Ar '). In the solid state, the free phosphines PR2Ar ' adopt one of the three possible structures formally related by rotation around the C-ipso-P bond. Details on their relative energies and on the influence of the free phosphine structure on its coordination chemistry towards Ni(CO)(n) (n = 2, 3) fragments has been obtained by experimental and computational methods.