Synthesis, Structure and Nickel Carbonyl Complexes of Dialkylterphenyl Phosphines.

The experimental and computational characterization of a series of dialkylterphenyl phosphines, PR ₂ Ar' is described. The new P-donors comprise five compounds of general formula PR ₂ Ar Dtbp 2 (R=Me, Et, iPr, c-C ₅ H ₉ and c-C ₆ H ₁₁ ); Ar Dtbp 2 = 2,6-C ₆ H ₃ -(3,5-C ₆ H ₃ -(CMe ₃ ) ₂ ) ₂ ), and another five PR ₂ Ar' phosphines containing the bulky alkyl groups iPr, c-C ₅ H ₉ or c-C ₆ H ₁₁ , in combination with Ar'=Ar Xyl 2 , Ar Xyl ' 2 , or Ar Ph 2 (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 (PR ₂ Ar') and Ni(CO) ₂ (PR ₂ Ar'). In the solid state, the free phosphines PR ₂ Ar' 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.
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