Strained, ring tilted dicarbon-bridged [2]ferrocenophanes and ferrocene revisited: Fe-57 Mossbauer spectroscopic study of bonding, hyperfine interactions, and lattice dynamics

The temperature dependencies of the nuclear hyperfine interactions (isomer shift, quadrupole splitting and resonance effect magnitude) for two [2]ferr ocenophanes have been studied by Fe-57 Mossbauer effect spectroscopy over t he temperature range from 90 K to above room temperature, and compared to a nalogous data for both staggered and eclipsed forms of unbridged ferrocene. The effect of the two-atom bridge, as well as the possibility of a direct metal atom-olefin moiety interaction have been examined in detail. The temp erature dependence of the quadrupole splitting is not uniquely related to t he tilt angle of the two Cp rings, and is distinct from that observed for r elated [1]ferrocenophanes. (C) 1999 Elsevier Science S.A. All rights reserv ed.