Optical and EPR spectra of the thionitrosyl complex [Cr(OH2)5(NS)]2+

The green thionitrosyl complex [Cr(OH2)5(NS)]2+ was isolated in solution by the hydrolysis of [Cr(NCCH3)5(NS)]2+. The optical absorption spectra of both compounds are dominated by a band with vibrational progression around 600 nm assigned as a {dyz,zx, π∗(NS)} → {π∗(NS), dyz,zx}∗ transition. The optical data indicate that the NS ligand is a weaker π-acceptor than the NO ligand. The EPR parameters of [Cr(OH2)5(NS)]2+ were determined: giso, g∥ and g⊥: 1.96515, 1.92686(5) and 1.986860(8); Aiso(53Cr), A∥(53Cr) and A⊥(53Cr): 25.3 × 10−4, 38 × 10−4 and 18.5 × 10−4 cm−1; Aiso(14N), A∥(14N) and A⊥(14N): 6.5 × 10−4, 2.81 × 10−4 and 8.346(12) × 10−4 cm−1.