ELECTROSPRAY MASS-SPECTROMETRIC STUDY OF THE NATURE AND LABILITY OF CATIONIC COMPLEXES GENERATED BY THE REACTION OF SOLUTIONS OF NEUTRAL IRON(III), COBALT(III), NICKEL(II) AND COPPER(II) DITHIOCARBAMATES WITH NITROSONIUM TETRAFLUOROBORATE

Cationic products formed by reaction of Fe(R2dtc)3, Co(R2dtc)3, Ni(R2dtc)2, and Cu(R2dtc)2 (R2dtc = S2CNR2, dithiocarbamate) with NOBF4 in dichloromethane are readily identified directly from the solutions by electrospray mass spectrometry (ESMS). Previously characterized species such as [Fe(R2dtc)3]+, [Co2(R2dtC)5]+, [Ni(R2dtc3]+, and [Cu(R2dtc)2]+ are major products resulting from NO+ acting as a one-electron oxidant, and intact ions corresponding to these formulations are observed in the electrospray mass spectra at low ion source energies. At higher ion source energies, fragment ions such as [Fe(R2dtC)2]+, [Ni(R2dtC)2]+ etc are observed. The paramagnetic Fe(IV), Ni(IV), and Cu(III) complexes are all shown to be kinetically labile, since complete ligand exchange occurs on mixing different cations. In contrast, mixing different dicobalt(III) cations shows exchange of the [Co(R2dtC)2]+ units rather than global ligand exchange. The previously unreported sulfur-rich cations [Co2(R2dtc)5S]+ are identified as products of the reaction between Co(R2dtC)3 and NOBF4, and [Co2(R2dtC)5S2]+ is observed to be a product of the reaction of [Co2(R2dtC)5S]+ with elemental sulfur. Other products identified by reaction of neutral dithiocarbamates with NOBF4 include [Fe(R2dtC)2NO]+, [{Fe(R2dtC)3}2(R4bitt)]2+ ([R4bitt]2+ = 3,5-bis(N,N-dialkyliminium 1,2,4-trithiolane) and [Cu(R2dtc)2S]+. The studies undertaken in this work confirm the relative ease of identifying cationic species in solution by ESMS irrespective of whether they are diamagnetic or paramagnetic and whether they are kinetically labile or inert in the ligand exchange sense.