Bonding, metal atom motion, and evidence for a phase transition in Fe metallocenes with a cyclo-P5 ligand

Temperature-dependent Fe-57 Mossbauer spectroscopy has been employed to elucidate the relationship between the bonding, symmetry of the electrostatic field, and details of the metal atom motion between ferrocene (3) and two cyclo-pentaphospha homologues. Evidence is presented for the presence of a phase transition in solid [eta (5)-Cp*Fe-eta (5)-P-5] (1) which is also observed in DSC scans over the appropriate temperature range. The dynamics of the ring motion in 1 is thought to account for the absence of long range order in this solid at room temperature. Differences in the electron distribution around the metal atom in several related ferrocene-type complexes are examined in detail. (C) 2000 Elsevier Science S.A. All rights reserved.