Mössbauer effect study of the electric field gradient tensor at the tin atom in [{Fe(π-C5H5)(CO)2}2SnCl2]

Abstract

The asymmetry parameter, η, of the electric field gradient tensor at a tin atom has been determined for the first time: application of a 50 KG magnetic field at 4·2 K to the diamagnetic complex [{Fe(π-C₅H₅)(CO)₂}₂SnCl₂] led to a value of η= 0·65 ± 0·05. Use of an oriented matrix of single crystals in a zero-field experiment at 78 K then established that the direction of V_zz was at 48° to the bc plane of the crystal. The results imply that 〈ψ|(3 cos²θ– 1)r^–3|ψ〉 is greater for the Sn–Fe bonds than for the Sn–Cl bonds and that there is therefore less withdrawal of tin 5p-electron density into the Sn–Fe bonds than into the Sn–Cl bonds.