INFLUENCE OF THE AMINO SUBSTITUENTS OF POTENTIALLY BIS ORTHO CHELATING ARYL LIGANDS (2,6-(R1R2NCH2)2C6H3)- ON THE SYNTHESIS AND PROPERTIES OF THEIR ORGANONICKEL(II) COMPLEXES

Two series of square-planar organometallic Ni(II) complexes that contain various monoanionic, potentially terdentate ligands (2,6-{R1R2NCH2}2C6H3)- (= R1R2NCN') have been synthesized. In the first series [NiX(R1R2NCN')], i.c., [NiBr(Me2NCN')], [NiX(Et2NCN')] (X = Br, I), [NiBr(i-Pr2NCN')], [NiX((i-Pr)MeNCN')] (X = Br, I), and [NiBr((t-Bu)MeNCN')], this ligand is terdentate bonded to the Ni(II) center via C(ipso) and the two N donor atoms. In the second series [NiX(R1RNCN')(PR3)2], i.e., [NiBr((t-Bu)MeNCN')(PR3)2] (R = Me, Et) and [NiX((Ph)MeNCN')(PR3)2] (X = Br, R = Me, Et, Bu; X = Cl, I, R = Et), the Ni(II) center is bonded to a halide anion, to two phosphorus ligands, and to only C(ipso) of the R1R2NCN' ligand. From two Ni(II) complexes [NiBr(Et2NCN')] and [NiBr((i-Pr)MeNCN')] were synthesized the corresponding ionic complexes [Ni(R1R2NCN')(OH2)]Otf (Otf = CF3SO3), by reaction with 1 equiv of AgOtf, and the organonickel(III) species [NiBr2 (R1R2NCN')], by reaction with 0.5 equiv of Br2. The molecular structures of three complexes have been determined by X-ray crystallographic methods. [NiBr(C6H3{CH2N(i-Pr)Me}2-2,6)] (4b): C16H27N2NiBr, monoclinic, space group P2(1)/n, with unit cell dimensions a - 11.632 (6) angstrom, b = 14.259 (7) angstrom, c = 10.636 (2) angstrom, beta = 99.12 (4)degrees, and Z = 4. [NiBr(C6H3{CH2N(t-Bu)Me}2-2,6)] (5): C18H31N2NiBr, monoclinic, space group P2(1)/n, with unit cell dimensions a = 14.148 (6) angstrom, b = 13.044 (2) angstrom, c = 11.149 (3) angstrom, beta = 112.04 (2)degrees, and Z = 4. [NiBr(C6H3{CH2N(Ph)Me}2-2,6)(PEt3)2].0.5Et2O (8b): C34H53N2P2NiBr.0.5C4H10O, monoclinic, space group P2(1)/c, with unit cell dimensions a = 20.044 (2) angstrom, b = 9.8127 (7) angstrom, c = 20.857 (1) angstrom, beta = 110.519 (5)degrees, and Z = 4. The crystal structures were solved either by direct methods (4b, 5) or Patterson methods (8b). Anisotropic least-squares refinement converged at R = 0.059 (1371 observed reflections) for 4b, 0.069 (1318 observed reflections) for 5 and 0.055 (3164 observed reflections) for 8b. The ligand strength of the various amino groups toward the Ni(II) center decreases in the order Me2N > Et2N > (i-Pr)MeN > (t-Bu)MeN > (Ph)MeN. Resonance Raman spectroscopic data indicate that in solution the complexes [NiI(Et2NCN')] and [NiI((i-Pr)MeNCN')] interact with added 12.