The Re(NO)2+ moiety as [Re(NO)(NCS)3H2O]− or [Re(NO)(NCS)2(L-L)H2O]· [L-L = phen (1,10-phenanthroline) or bipy (2,2′-bipyridine)] undergoes proton-induced oxidation reaction with HX (X = Cl, Br) to produce a Re(NO)3+ moiety. The spectral and physico-chemical data suggest that the anionic complex is 5 coordinate and the neutral one is 6 coordinate with axial NO group and two NCS ligands intrans-equatorial positions. The complex, [Re(NO)(NCS)2(phen)Br]·H2O shows complicated magnetic behaviour which is discussed in the paper. The ESR spectrum of this compound shows typical rhenium hyperfines and <g>-tensor anisotropy compatible with the loss of axial symmetry. However, the spectrum of [Re(NO)(NCS)2Br2]− quite reasonably shows axial symmetry, other features being grossly comparable to the L-L compounds. The anionic species and the neutral L-L complex show irreversible one-electron oxidation waves at different voltages. This may correspond to a conversion of Re(NO)3+ to Re(NO)4+ in both the cases. Interestingly enough, only the neutral complexes exhibit an irreversible reduction wave due probably to a conversion of Re(NO)3+ to Re(NO)2+.
Volume 134, 2022
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