CRYSTAL-STRUCTURES OF NEUTRAL TRIGONAL BIPYRAMIDAL [NICL2(PMEPH2)(PNME2)]CENTER-DOT-1 2CH(2)CL(2) AND CATIONIC SQUARE-PLANAR [NICL(PMEPH2)(PNME2)][PF6] COMPLEXES/

The crystal structures of [NiCl2(PMePh2) . (PNMe2)] . 1/2 CH2Cl2 (1), C33H33Cl2NNiP2 . 1/2 CH2Cl2, and [NiCl(PMePh2) (PNMe2)][PF6] (2), C33H 34ClF6NNiP3, have been determined by X-ray diffraction. Complex 1 crys tallises in the monoclinic space group P2(1)/n, a = 11.305(6) Angstrom , b = 17.620(9) Angstrom, c = 18.061(9) Angstrom, beta = 90.48(4)degre es, V = 3597(3) Angstrom(3) and Z = 4. Refinement of 2508 observed ref lections and 275 parameters converges to a conventional R of 0.051. Th e coordination around the Ni(II) centre is distorted trigonal bipyrami dal with the two axial positions occupied by the phosphorus atom of th e monodentate phosphine and the tertiary amine nitrogen of the bidenta te PNMe2 chelate. The equatorial sites accommodate the remaining phosp horus of the amino-phosphine and two chlorine donors. Complex 2 crysta llites in the orthorhombic space group Pbca, a = 18.61(1) Angstrom, b = 15.42(1) Angstrom, c = 23.25(2) Angstrom, V = 6673(7) Angstrom(3) an d = 8. Refinement of 2351 observed reflections and 347 parameters yiel ds R = 0.051. A square planar geometry de scribes the coordination aro und the metal with the two phosphorus donors located in a mutual cis-a rrangement. As expected on the basis of the different coordination num ber, all of the metal-donor distances decrease on going from 1 to 2, a s evidenced, in particular, by the Ni-N bond which contracts from 2.32 5(8) Angstrom to 2.056(8) Angstrom.