Inorganic Chemistry, Vol.46, No.23, 9841-9852, 2007
Conformationally rigid chelate rings in metal complexes of pyridyloxy-substituted 2,2'-dioxybiphenyl-cyclotetra- and cyclotriphosphazene platforms
Divalent metal halides react with pyridyloxy-substituted 2,2'-dioxybiphenyl-cyclotri- and cyclotetraphosphazene ligands to form the complexes, [MLX2] [M = Co or Cu; L = (2,2'-dioxybiphenyl)tetrakis(2-pyridyloxy)cyclotriphosphazene (L-1) or (2,2'-dioxybiphenyl)tetrakis(4-methyl-2-pyridyloxy)cyclotriphosphazene (L-2); X = Cl or Br], [ZnLCl2] [L = bis(2,2'-dioxybiphenyl)bis(2-pyridyloxy)cyclotriphosphazene (L-3) or bis(2,2'-dioxybiphenyl)bis(4-methyl-2-pyridyloxy)cyclotriphosphazene (L-4)], [MLCl2] [M = Cu or Hg; L = tris(2,2'-dioxybiphenyl)bis(2-pyridyloxy)cyclotetraphosphazene (L-5)] and [Cu2LCl4] (L = trans-bis(2,2'-dioxybiphenyl)tetrakis(2-pyridyloxy)cyclotetraphosphazene (L-6)]. Single-crystal X-ray structures show the L-2 ligand complexes to have a N3Cl2 five-coordinate, trigonal-bipyramidal donor set with the phosphazene ring and pendant pyridyloxy nitrogens binding to the metal ions. The coordinated L-2 ligand in the complex, [(CoLCl2)-Cl-2], slowly hydrolyses in acetonitrile with the loss of a pyridine pendant arm to form a dimetallic species, which has been characterized by crystallography as [{(CoLCl)-Cl-2a}](2)center dot 4MeCN (L-2a = [N3P3(biph)(OPy)(3)(O)](-), biph = 2,2'-dioxybiphenyl, OPy = 2-oxopyridine). The ligands, L-3, L-4, L-5, and L-6, bind to the metal halides via gem-substituted pyridyloxy nitrogens only. The resulting rigid eight-membered chelate rings all have distorted boat conformations, which force distorted-tetrahedral N2Cl2 Coordination environments onto the metal ions. The spectroscopic (ESR and electronic) and magnetic properties of the complexes are reported.