NICKEL-COMPLEXES OF TRIDENTATE LIGANDS INCORPORATING THIOETHER AND TRIAZENE-1-OXIDE FUNCTIONS - SYNTHESIS, STRUCTURE AND METAL REDOX

The reaction of nickel(II) acetate with RN(O)NNHC6H4SMe (HL1: R = Me; HL2: R = Pr(n); general abbreviation HL) in aqueous ethanol affords [N iL2] as brown crystalline solids. The X-ray structure of [NiL22] is re ported. Each ligand acts in the tridentate meridional SNO fashion. The Ni(SNO)2 coordination sphere is severely distorted from octahedral ge ometry. The Ni-S distances, 2.519(2) and 2.549(2) angstrom, constitute the longest nickel(II)-thioether bonds reported so far. Due to low sy mmetry, the octahedral nu1 band of the complexes are split into compon ents lying at ca 1400 and 1000 nm. The complexes display quasireversib le cyclic voltammograms corresponding to the metal redox couple [Ni(II I)L2]+/[Ni(II)L2], E1/2 approximately 0.75 V (vs S.C.E.). Coulometrica lly generated [Ni(III)L2]+ displays rhombic EPR spectra, the g values of the perpendicular components being larger than that of the parallel component corresponding to the (d(z)2)1 ground state.