ISOTOPIC LABELING INVESTIGATION OF THE OXYGENATION OF NICKEL-BOUND THIOLATES BY MOLECULAR-OXYGEN
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Discrete compounds resulting from the oxidation and oxygenation of nickel thiolate complexes have been isolated, separated, and characterized. Molecular oxygen or hydrogen peroxide reacted with [N,N-bis(mercaptoethyl)-1,5-diazacyclooctane] nickel(II), (BME-DACO)NiII (1), to produce two oxygenates, [(mercaptoethyl)(sulfinatoethyl)diazacyclooctane] nickel(II), (MESE-DACO)NiII (2), and [bis(sulfinatoethyl)diazacyclooctane]nickel(II), (BSE-DACO)NiII (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 (18O2/16O2 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; space group, Z, 2 range, unique observed reflections, R(Rw) (%). (MESE-DACON)NiII: 8.306 (3), 12.258 (3), 12.773 (4) ; 101.36 (3), P21/n, 4, 4.0/50.0, 2047 (I> 2.0(I)), 2.85 (3.61). {[BME-DACO)Ni]2Ni}(Br2: 7.144 (2), 10.931 (2), 17.296 (3) ; 91.72 (2), P21/c, 4, 4.0/50.0, 2053 (I > 2.0 (I)), 4.46 (4.84). The pseudo-square-planar NiN2S2 complex 2 has cis sulfur donor atoms and a tetrahedral twist of 18.4. The NiSsulfinato distance of 2.140 (1) is significantly shorter than the NiSthiolate distance, 2.163 (1) . 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). 1992, American Chemical Society. All rights reserved.
