Structure and reactivity of transition-metal complexes with polyatomic ligands. Part VI. Electron spin resonance and electronic absorption spectra of some chromium(I) nitrosyl complexes

Abstract

E.s.r. spectra have been recorded for the ions [Cr(NO)(H₂O)₅]²⁺ and [Cr(NO)(NH₃)₅]²⁺ in dilute fluid and rigid solution. The g and A(⁵³Cr) tensors have been calculation for both ions and the A(¹⁴N) tensor for the former. Superhyperfine structure was observed in fluid solutions of [Cr(NO)(NH₃)₅]²⁺ from A_iso(¹⁴N) for the NO, NH_3(axial) and NH_3(equat.) ligands were estimated. Isotropic coupling constants to ¹⁴N of the ammonia ligands are attributed to spin polarisation of σ-electrons. The electronic absorption spectra of these complexes, together with those of intermediates in the acid hydrolysis of [Cr(CN)₅NO]^3–, were measured and the results fitted to a generalised energy-level scheme.