NICKEL TEMPLATE SYNTHESES OF PENTADENTATE AND MACROCYCLIC NITROGEN SULFUR LIGANDS - SINGLE-CRYSTAL X-RAY STRUCTURE OF (1,10-DIAZA-4,7,13,16-TETRATHIA-5,6-14,15-DIBENZOCYCLOOACTADECANE)NICKEL(II) BIS(TETRAPHENYLBORATE)-ACETONITRILE(1/3)

Complexes of nickel with macrocyclic and pentadentate nitrogen-sulfur donor ligands have been prepared via the reaction of [Ni(bdt)2]- with bis(2-chloroethyl)amine and 2,6-bis(chloromethyl)pyridine, respectively. The coordination sphere of the pentacoordinate compound (2,6-bis(((2-mercaptophenyl)thio)methyl)pyridinato)nickel(II) (2) consists of an aromatic amine, two thioether, and two thiolate donors. It is thermochromic, being yellow-orange at low temperatures and red-violet upon heating, and there is no major change in the vis-near-IR spectrum, which simply show a shift of lambda-max from 480 to 520 nm. Magnetic measurements indicate that the compound contains high-spin Ni(II) (mu-eff 3.05-mu-B). A rather low quasi-reversible oxidation potential is observed at +0.144 V (all potentials are reported vs SCE), a second is observed at +0.546 V, and two irreversible reduction potentials are observed at -0.754 and -1.228 V. The hexadentate, macrocyclic complex (1,10-diaza-4,7,13,16-tetrathia-5,6:14,15-dibenzocyclooctadecane)nickel(II) bis(tetraphenylborate) (3) was characterized by X-ray crystallography, which showed the complex to be a distorted octahedron with the four thioether donors (Ni-S = 2.398 (2), 2.440 (2) angstrom) in the equatorial plane and the nitrogen atoms (Ni-N = 2.082 (4) angstrom) in the axial positions. Crystal data are a = 18.213 (4) angstrom, b = 18.213 (12) angstrom, c = 20.115 (8) angstrom, and beta = 103.51-degrees with space group C2/c, Z = 4, R = 0.0434, and R(w) = 0.0434. This complex has a high, irreversible oxidation potential at +0.964 V and a quasi-reversible reduction wave at -0.864 V. No hydrogen bonding is observed in the solid state but the N-H stretch of the amine is lowered to 3200 cm-1 upon coordination to the nickel ion.