Crystal and molecular structure of tricyclohexylphosphineethylidenenickel tricarbonyl: a reaction product of Ni(CO)₄ and (C₆H₁₁)₃P=(CH)CH₃

Abstract

The structure of tricyclohexylphosphineethylidenenickel tricarbonyl, (C₆H₁₁)₃P(CH)CH₃.Ni(CO)₃, has been determined by direct methods from 5858 automatic diffractometer data, and refined anisotropically to a finalR value of 0·094 (including hydrogen atoms). The crystals are monoclinic, space group P2₁/n, with a=10·670(1), b=13·879(2), c=16·222(2) Å, β=91·80(1)° and z=4. The main feature of the structure determination is the confirmation of the predicted arrangement of the ligand with its bonding to nickel via the secondary carbon of ylid-ligand. This carbon and the nickel atoms show approximate tetrahedral geometry. There seems to be no direct interaction between phosphorus and nickel (closest approach distance is 3·30 Å). The nickel-carbon distance (2·10 Å) is longer than any other Ni-C(sp³) distance previously reported.