The fluxionality of (Z)-6,6,6-triphenyl-6-stannahexa-1,3-diene: evidence for symmetry-allowed suprafacial [1,5]-shifts in an organometallic compound

Abstract

The ¹H and ¹³C n.m.r. spectra of (E)- and (Z)-6,6,6-triphenyl-6-stannahexa-1,3-diene have been measured. The ¹H n.m.r. spectra have been fully assigned for the first time, but the ¹³C n.m.r. spectrum was only partially assigned. By use of spin-saturation transfer and line-broadening in the ¹H n.m.r. spectra, it is shown that the Z isomer is fluxional with ΔG^‡= 19.4 kcal mol^–1 and that there is no evidence for fluxionality in the E isomer or E–Z isomerism. The only reasonable interpretation of these data is a symmetry-allowed suprafacial [1,5]-shift.