ISOTOPIC LABELING INVESTIGATION OF THE OXYGENATION OF NICKEL-BOUND THIOLATES BY MOLECULAR-OXYGEN

Discrete compounds resulting from thc oxidation and oxygenation of nickel thiolate complexes have been isolated, separated, and characterized. Molecular oxygen or hydrogen peroxide reacted with [NN'-bis(mercaptoethyl)-1,5-diazacyclooctane]nickel(II), (BME-DACO)Ni(II) (1), to produce two oxygenates, [(mercaptoethyl)(sulfinatoethyl)diazacyclooctane]nickel(II), (MESE-DACO)Ni(II) (2), and [bis(sulfinatoethyl)diazacyclooctane]nickel(II), (BSE-DACO)Ni(II) (3), as well as a trimetallic, [(BME-DACO)Ni]2Ni2+ (4). Matrix-assisted laser desorption (MALD) ionization was used to obtain Fourier transform ion cyclotron resonance (FT-ICR) mass spectra on isotopomers of 2 and 3. Isotopic labeling experiments (O-18(2)/O-16(2) mixtures) demonstrated that both oxygens in the sulfinate ligand of 1 were derived from the same dioxygen molecule. The molecular structures of 2 and 4 were determined by X-ray crystallography. Crystallographic data are given as a, b, c; beta; space group, Z, 2-theta range, unique observed reflections, R(R(w)) (%). (MESE-DACON)Ni(II): 8.306 (3), 12.258 (3), 12.773 (4) angstrom; 101.36 (3)-degrees, P2(1)/n, 4, 4.0-degrees/50.0-degrees, 2047 (I > 2.0-sigma(I)), 2.85 (3.61). {[(BME-DACO)Ni]2Ni}Br2: 7.144 (2), 10.931 (2), 17.296 (3) angstrom; 91.72 (2)-degrees, P2(1)/c, 4, 4.0-degrees/50.0-degrees, 2053 (I > 2.0-sigma(I), 4.46 (4.84). The pseudo-square-planar NiN2S2 complex 2 has cis sulfur donor atoms and a tetrahedral twist of 18.4-degrees. The Ni-S(sulfinato) distance of 2.140 (1) angstrom is significantly shorter than the Ni-S(thiolate) distance, 2.163 (1) angstrom. The trimetallic 4 contains a staircaselike structure where two molecules of 1 serve as metallothiolate ligands to the central Ni2+ creating an NiS4 square plane (dihedral angle between best square planes = 103.4-degrees).