CYCLOHEPTATRIENYL BRIDGED HETEROBIMETALLIC COMPLEXES - FLUXIONAL BEHAVIOR AND X-RAY CRYSTAL-STRUCTURE OF SYN-(MU(3)ETA(2)-C7H7)FE(CO)(3)PD(ETA(3)-C3H5)

The structure and fluxionality of (mu-C7H7)Fe(CO)(3)Pd(eta(3)-C3H5) ar e described. In solution the molecule is fluxional. Although ring whiz zing of the C7H7 ring is still rapid, allyl group fluxionality is stop ped at low temperature. H-1 and C-13 NMR spectra indicate an asymmetri c ground state structure. This is confirmed by X-ray crystallography w hich shows that this is the second example of a mu-eta(3):eta(2) bondi ng for a bridging cycloheptatrienyl moiety, i.e. one double bond of th e ring remains uncoordinated. Crystal data for n-(mu-eta(3):eta(2)-C7H 7)Fe(CO)(3)Pd(eta(3)-C3H5): monoclinic, space group P2(1)/n, a = 8.486 (1), b = 22.105(4), c = 14.018(4)Angstrom, beta = 104.84(2)degrees, V = 2542(2) Angstrom(3), Z = 8, R = 0.037 and R(w) = 0.051 based on 2482 reflections with I greater than or equal to 3 sigma(I).