Bobby L. Barnett

The molecular and crystal, structure of (tricyclohexylphosphine)methylnickel(II) 2,4-pentanedionate; A squareplanar complex containing a σ-nickel—carbon bond

Abstract The molecular and crystal structure of (tricyclohexylphosphine)methylnickel(II) 2,4-pentanedionate has been determined by conventional Patterson and Fourier synthesis and refined anisotropically to a final R value of 0.08, including hydrogen atoms. Coordination about the nickel atom is square-planar with the angles subtended at the nickel being: O(1)NiO(2) = 93°; O(1)NiC(19) = 84°; C(19)NiP = 93°; PNiO(2) = 90°. The NiC(19) σ-bond length is 1.94(1) A. The cyclohexyl rings are all in the chair conformation having an average CC distance of 1.53 A and are bonded equatorially to the phosphorus in a tetrahedral arrangement with the average PC distance being 1.861 A. The pentanedione ligand is planar within experimental error. Molecules of the title compound pack as discrete units in the crystal with no non-hydrogen intermolecular distance being less than 3.6 A.

The molecular configuration of two complexes with σ and π-nickel carbon bonds. : (π-pentenyl)(diisopropylphenylphosphine)methylnickel(II) and (π-pentenyl)(dimethylmethylphosphine)methyl ncikel(II)

The molecular conformation of two square planar π-pentenylnickel(II) complexes with σ and π nickelcarbon bonds, (π-pentenyl)(diisopropylphenylphosphine) methylnickel(II) and (π-pentenyl)(dimenthylmethylphosphine) methylnickel(II), have been determined from single crystal X-ray data collected at room temperature with counter methods. Molecule I crystallizes in the monoclinic space group P 2 1 / c with four molecules in a unit cell of the dimensions a 8.927(3), b 26,031(9), c 8.718(2)A, β 110.88(2)°;II crystallizes in the orthorhombic system, space group P 2 1 2 1 2 1 , with four molecules in a cell a 14.446(1) b 13.727(1), c 11.895(1)A. Both structures have been refined anisotropically to R values of 6.26 and 3.65%, respectively. The absolute configuration of II has been determined to be R on a 99.5% confidence level. Comments are made on the bonding situation of the π-allylic fragments as well as on the steric conformation of the phosphine ligands. The NiC(σ) bond distances were found to be 1.99(1) in compound I and 1.975(4)A in compound II.

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

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.