Structural and spectroscopic studies of nickel(II) complexes with a library of Bis(oxime)amine-containing ligands.

A library of tripodal amine ligands with two oxime donor arms and a variable coordinating or noncoordinating third arm has been synthesized, including two chiral ligands based on l-phenylalanine. Their Ni(II) complexes have been synthesized and characterized by X-ray crystallography, UV-vis absorption, circular dichroism, and FTIR spectroscopy, mass spectrometry, and room-temperature magnetic susceptibility. At least one crystal structure is reported for all but one Ni/ligand combination. All show a six-coordinate pseudo-octahedral coordination geometry around the nickel center, with the bis(oxime)amine unit coordinating in a facial mode. Three distinct structure types are observed: (1) for tetradentate ligands, six-coordinate monomers are formed, with anions and/or solvent filling out the coordination sphere; (2) for tridentate ligands, six-coordinate monomers are formed with Ni(II)(NO(3))(2), with one monodentate and one bidentate nitrate filling the remaining coordination positions; (3) for tridentate ligands, six-coordinate, bis(mu-Cl) dimers are formed with Ni(II)Cl(2), with one terminal and two bridging chlorides filling the coordination sphere. The UV-vis absorption spectra of the complexes show that the value of 10 Dq varies according to the nature of the third arm of the ligand. The trend based on the third arm follows the order alkyl/aryl < amide < carboxylate < alcohol < pyridyl < oxime.

A New Class of Complexes Possessing Cofacially-Oriented, Planar, Metal-Containing Subunits. Synthesis, Characterization, and Reactivity of [(MoO(2))(2)(&mgr;-O)](2+)-Linked, Catechol-Functionalized, Tetraazamacrocyclic and Salicylideneamine Complexes.

A new synthetic route to molecules that contain cofacially oriented, [Mo(2)O(5)](2+)-bridged bis(catecholate) dianions is described. This synthesis has been useful in the preparation of supermolecular molecules containing catechol-functionalized, metalated macrocyclic [M(II)(TAD(OH)(2))] (M = Co, Ni) and SALPHEN [M(II)(R(2)R'(2)SALPHEN(OH)(2))] (M = H(2), Mn, Fe, Co, Ni, Cu) ligands. Of the former, the (Bu(4)N)(2)[Mo(2)O(5)[Ni(TAD(O)(2))](2)] (7) complex has been structurally characterized. The complex crystallizes in the triclinic space group P&onemacr; with unit cell dimensions a = 12.324(3) Å, b = 17.740(4) Å, c = 20.920(4) Å, alpha = 108.79(3) degrees, beta = 98.20(3) degrees, and gamma = 103.12(3) degrees. The nearly-planar macrocyclic ligands are essentially parallel, with a dihedral angle of 6.5(2) degrees. The Ni(1)--Ni(2) separation in the anion is 3.938 Å. The structure of (Bu(4)N)(2)[Mo(2)O(5)[Cu(EtO(2)H(2)SALPHEN(O)(2))](2)] (19) has also been determined. This complex crystallizes in the monoclinic space group P2(1)/c, with unit cell dimensions a = 20.821(4) Å, b = 23.133(5) Å, c = 20.056(4) Å, and beta = 117.71(3) degrees. The Cu(1)--Cu(2) separation is 4.110 Å, and the dihedral angle between SALPHEN "planes" is approximately 9.7(1) degrees. Analytical and spectroscopic properties are provided. Reactions of these molecules with oxidants and strongly coordinating ligands are presented. The ability of the Fe(II) and Co(II) analogues of 19 to bind ligands such as O(2)(-) or S(2)(-) and O(2), respectively, in the "pocket" of the complex is described, and the products have been characterized. The synthesis and characterization of the unique "mixed catecholate" complexes (Bu(4)N)(2)[Mo(2)O(5)(D(t)()BC)(M(II)((t)()Bu(4)SALPHEN(O)(2)))] (M = H(2), Fe, Co, Ni, Cu) is described, and comparisons between these latter systems and the bis(M(II)SALPHEN-catecholate) complexes are provided.