Transition Metal Chemistry of Quinuclidinone-Containing Ligands. IV. Crystal Structure of Trans-2-(2'-Quinolyl)methylene-3-quinuclidinonedichloronickel(ii), a Five-coordinate Binuclear Complex


The crystal and molecular structure of the complex of nickel(II) chloride with trans-2-(2'-quinolyl)methylene-3-quinuclidinone, Qnqn, has been determined using three-dimensional X-ray diffraction techniques, from 2122 independent reflections (above 2.5σ) collected on a four-circle diffractometer. The yellow crystals are triclinic, space group P1, with (non-conventional) unit cell parameters a = 9.041 (3) Å, b = 15.345 (6) Å, c = 8.622 (7) Å, α = 42.93 (3)°, = 90.16 (3)°, γ = 79.96 (2)°, and V = 788.3 (9) Å3. The structure was solved by using Patterson and Fourier techniques and refined by fullmatrix least-squares procedures. All nonhydrogen atoms were refined with anisotropic thermal parameters and all hydrogen atoms were located by electron difference methods; the resulting conventional R factor is 2.6%. There is one dimeric molecule, [Ni(Qnqn)Cl2]2, per unit cell with ρexptl = 1.66 (2) g/cm3 and ρcalcd = 1.659 (3) g/cm3. The complex is binuclear, containing two nickel(II) ions, each with square-pyramidal coordination, with two slightly asymmetric bridging chloride ions (Ni-Cl distance 2.408 (2) and 2.422 (2) Å) in equatorial sites. The Ni-Ni nonbonded distance is 3.652 (1) Å. The two remaining equatorial coordination sites on each nickel ion are occupied by a terminal chloride ion (Ni-Cl distance, 2.296 (2) Å) and by the quinolyl nitrogen (Ni-N distance 2.047 (3) Å) atom. The apical coordination position is occupied by the quinuclidinone nitrogen (Ni-N distance 2.067 (2) Å) atom. The nickel ion is 0.40 Å above the basal plane of the square pyramid. The entire molecule is centrosymmetric. The bonding is discussed and compared with the bonding in other five-coordinate nickel complexes.



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