The electron spin resonance spectra of CpCr(CO)3 and CpCr(CO)2P(C6H5)3 in single crystals of their Mn analogues

Abstract

The e.s.r. spectra of CpCr(CO)₃ and CpCr(CO)₂L, where L is P(C₆H₅)₃ and Cp is cyclopentadienyl, have been examined in single crystals of their respective Mn derivatives. In both cases an axis (z) passing through the chromium atom and the centre of the Cp ring is the direction of maximum g, indicating that the semi-occupied orbital is predominantly xy or x²–y², where x and y are perpendicular to z. The effective symmetry in both instances is C_s, with x lying perpendicular to the symmetry plane. In CpCr(CO)₃, x is the direction of intermediate g-factor, whereas in CpCr(CO)₂L, x is the direction of minimum g-factor. The reasons for this difference are discussed in terms of the energy levels of the t⁵_2ge⁰_g manifold under O_h, C_3v and C_s symmetries. The ⁵³Cr hyperfine interaction in CpCr(CO)₃ is also analysed.