ORGANIC SYNTHESES VIA TRANSITION-METAL COMPLEXES .81. BIS(CARBENE) COMPLEX OF CHROMIUM CONNECTED BY A CONJUGATED AMMONIUM PENTADIENIDE BRIDGE

The reaction of pentacarbonyl(1-ethoxyethylidene)chromium and tetrachlorocyclopropene in the presence of triethylamine affords a bis(carbene) complex 3, in which the carbene chromium units are connected by a conjugated and planar ammonium pentadienide bridge. According to NMR measurements the compound adopts a fluctional (Z, E) configuration. The structure of 3 was established by X-ray structure analysis [C27H27Cr2NO12. 2CH(2)Cl(2), triclinic, space group P ($) over bar 1 (No. 2), a=12.703(1) Angstrom, b=12.847(1) Angstrom, c=13.667(2) Angstrom, alpha=95.77(1)degrees, beta=110.15(1)degrees, gamma=112.81(1)degrees Z=2, R=0.072, wR(2)=0.201].