Bonding, metal atom motion, and evidence for a phase transition in Fe metallocenes with a cyclo-P-5 ligand

Temperature-dependent Fe-57 Mossbauer spectroscopy has been employed to elu cidate the relationship between the bonding, symmetry of the electrostatic field, and details of the metal atom motion between ferrocene (3) and two c yclo-pentaphospha homologues. Evidence is presented for the presence of a p hase transition in solid [eta (5)-Cp*Fe-eta (5)-P-5] (1) which is also obse rved in DSC scans over the appropriate temperature range. The dynamics of t he ring motion in 1 is thought to account for the absence of long range ord er in this solid at room temperature. Differences in the electron distribut ion around the metal atom in several related ferrocene-type complexes are e xamined in detail. (C) 2000 Elsevier Science S.A. All rights reserved.