Bernhard Olk

Multinuclear (1H, 13C, 59Co, 77Se) NMR studies of thioseleno- and diselenocarbamato complexes of cobalt(III) and indium(III) in CDCl3 solution

Abstract The proton decoupled 13C NMR spectra of several Co(Se2CNR2)3, Co(SSeCNR2)3, In(Se2CNR2)3 and In(SSeCNR2)3 complexes(where R=organic substituent) have been measured in CDCl3 solution (23–64 mM). Each of the diselenocarbamate complexes exhibits a single peak for the NCSe2 carbon at 188–197 ppm for Co(III) and at 186–198 ppm for In(III) complexes. The alkyl carbons in the position alpha to the amine N also appear as a single peak. The In(SSeCNR2)3 complexes exhibit single peaks for the NCSSe carbons (192–202 ppm), but the alkyl carbons in the position alpha to the amine N appear as two distinct singlets, indicating hindered rotation about the SSeCNR2 bond. The Co(SSeCNR2)3 complexes exhibit four peaks of approximately equal intensity for the NCSSe carbon which is interpreted as evidence for the stereochemical rigidity of the facial and meridional isomers. The alkyl carbons in the position alpha to the amine N appear as six peaks (except for occasional accidental degeneracy) which is interpreted as evidence for hindered rotation about the SSeCNR2 bond in these two isomers. The 1H NMR spectra of these complexes have been measured in CDCl3 solution (30–63 mM). The 1H spectra of Co(Se2CNR2)3 are similar to those reported for Co(S2CNR2)3, but those for the Co(SSeCNR2)3 complexes are further split by hindered rotation about the SSeCNR2 bond rendering each R non-equivalent. The 1H spectra for the various derivatives of In(SSeCNR2)3 and In(Se2CNR2)3 are similar and indicate ra pid D⇄cL interconversion and evidence (in the case of In(SSeCNR2)3) for hindered rotation about the CN bond. The 59Co NMR spectra of the Co(Se2CNR2)3 complexes exhibit signals (6690–7260 ppm) in close agreement with results reported in the literature. The 59Co NMR signals of Co(SSeCNR2)3 are approximately identical to those of the corresponding Co(S2CNR2)3 complexes but are generally at lower field than for the corresponding Co(Se2CNR2)3 complexes. Similar to the dithiocarbamate complexes, there is evidence for a correlation between the 59Co chemical shifts and μeff2 for the corresponding Fe(SSeCNR2)3. The 77Se NMR spectra of these complexes have been measured in saturated CDCl3 solution. The 77Se spectra of the diselenocarbamates exhibits single peaks with In exhibiting a higher chemical shift (approx. 400 ppm) than the corresponding Co complex. This trend is seen in the corresponding thiosclenocarbamates, but the Co derivatives generally exhibit two peaks of approximately equal intensity, indicating the stereochemical rigidity of the fac and mer isomers.