28090-32-6Relevant articles and documents
Investigations of mixed-ligand cobalt dithiocarbamate complexes by cobalt-59 nuclear magnetic resonance spectroscopy, mass spectrometry, and electrochemistry
Bond,Colton,Moir,Page
, p. 1298 - 1302 (2008/10/08)
Tris(dithiocarbamate) complexes of cobalt(III), CoL3 and CoL′3 (where L and L′ are different dithiocarbamato ligands), undergo ligand exchange at elevated temperatures both in an inert organic solvent and in the solid state to give CoL2L′ and CoLL′2. The mixed-ligand complexes may also be prepared by methods based on controlled-potential electrochemical oxidation or reduction of cobalt(III) dithiocarbamate complexes. In contrast to these preparative-scale electrolyses, short-time-scale voltammetric and polarographic data for oxidation and reduction exhibit independent responses for the mixed-ligand complexes, implying that the formally cobalt(IV) and cobalt(II) mixed-ligand species undergo slow rather than rapid ligand exchange. Cobalt-59 NMR spectroscopy and electrochemistry in CH2Cl2 solution and mass spectrometry are useful techniques to illustrate ligand exchange. Cobalt-59 chemical shifts of the dithiocarbamate complexes cover a wide range and allow identification of the mixed-ligand species in many reaction mixtures as the ligand exchange for the oxidation state III complexes is slow on the NMR (and synthetic) time scales at ambient temperatures. Generally, 59Co NMR chemical shifts do not correlate in a simple linear fashion with electrochemical E° data (or with 13C NMR data), implying that steric effects influence the two techniques in different ways. However, for the mixed-ligand series CoL3, CoL2L′, CoLL′2, and CoL′3, the E° and 59Co chemical shifts do correlate exceedingly well. Positive and negative ion mass spectra of CoL3 species, generally show the molecular ions [CoL3]+. and [CoL3]-., respectively, but the most abundant ions are [CoL2]+. and [CoL2]-.. Mass spectrometric examination of mixtures of CoL3 and CoL′3 show evidence of ligand exchange. Mass spectrometry in the gas phase and electrochemical data show interesting correlations.
