Electron spin resonance spectra of [Cr(CN)5(NO)]3–, [Cr(NO)(NH3)5]2+, and [Cr(NO)(H2O)5]2+

Abstract

Electron spin resonance (e.s.r.) spectra of dilute fluid and rigid aqueous solutions of [Cr(CN)₅NO]^3–, [Cr(NO)(NH₃)₅]²⁺, and [Cr(NO)(H₂O)₅]²⁺ have been measured. [Cr(NO)(H₂O)₅]²⁺ appears axially symmetric with g⊥ considerably larger than g∥; ⁵³Cr and ¹⁴N hyperfine structure has been observed for this complex. In contrast, [Cr(NO)(NH₃)₅]²⁺ gives a broad unresolved e.s.r. signal from which only g_av and A_iso(⁵³Cr) can be determined. Data obtained for [Cr(CN)₅NO]^3– agree well with previous work. These results are discussed in terms of a molecular orbital energy level scheme similar to that proposed by H. B. Gray et al. Preliminary e.s.r. studies of the conversion of [Cr(NO)(NH₃)₅]²⁺ into [Cr(CN)₅NO]^3– in aqueous potassium cyanide solution are reported.