Control of reactivity of dinuclear nickel(II) amine-thiolate complexes

The coordination chemistry of a series of dinickel complexes of the new sep tadentate amine-thiolate ligand N,N'-bis[2-thio-3-aminomethyl-5-tert-butylb enzyl]di H(2)9, has been investigated in the context of ligand binding and oxidation state changes. The complexes [Ni-2(9)(L)][ClO4](2) (10), [Ni-2(9) (Cl)][Cl] (11), [Ni-2(9)(L)][BPh4](2) (12), and [Ni-2(9)(NCS)][OH . OH2] (1 3) have central N2Ni(mu-SR)(2)NiN'L-3 cores [L = labile solvent molecule (1 0, 12), Cl- (11), and NCS- (13)] composed of dithiolate bridged planar NiN2 S2 and six-coordinate NiN'3S2L units. This is demonstrated for 11 and 13 by crystal structure determinations and for 10 and 12 by UV/Vis spectroscopy and room temperature magnetic susceptibility measurements. Complexes 10, 11 , or 12 readily add other coligands at the NiN'3S2L fragment by substitutio n of the solvent molecule L (10, 12) or the chloride substituent (11). The overall structure of the parent complexes is not affected by the substituti on reactions. An electrochemical study has shown that complex 10 undergoes two successive one-electron oxidations at +0.88 and +0.41 V vs SCE. The oxi dized species are not thermally stable, but electronic absorption spectra a nd EPR spectra are indicative of the presence of Ni-III species.