Mass spectrometry of coordination compounds of transition metals with tetradentate ligands. 11. isomeric quasi-macrocyclic Ni(II) complexes based on S-substituted isothiocarbohydrazides and the structure of “small” ions derived from them

Abstract

Two series of bonding isomers of Ni(II) coordination compounds with tetradentate quasimacrocyclic ligands based on S-substituted isothiocarbohydrazides were characterized by electron impact (EI) mass spectrometry and by tandem mass spectrometry methods. Conventional EI mass spectra were more isomer specific than metastable ion (MI) and collision induced dissociation (CID) mass spectra of the molecular ions. The MI (and CID) mass spectra of the isomers were very similar. This effect resulted from a facile randomization of Ni–N bonds in the ions possessing low internal energies, prior to their dissociation. The compounds were found to be convenient precursors for coordinatively unsaturated metal-containing ions, [NiL n ] + and [RNiL n ] + ( n = 1, 2; L = NCCH 3, NCSCH 3; R = OH, NO). Most of these species had a structure of mono- or disolvated nickel ion. The dissociation of [HONiNCCH 3] + ions was consistent with the formation of two isomers: one corresponding to the [HONi] + ion solvated by acetonitrile and the other is a complex of H 2O with [NiNCCH 2] +. A structure of [HO,Ni,(NCCH 3) 2] + ions was best represented by a five-membered cycle formed by two acetonitrile units and the metal atom with the OH group attached to one of the nitrogen atoms.