[Et4N][V(CO)4L2] salts (L2 = dppe, arphos) give upon treatment with triphenyl-cyclopropenylium bromide under hydrogenation acyl complexes of the type (η2-COC3Ph3H2)V(CO)3L2. The acyl group is linked to the metal atom via its C and O atom, acting formally as a three-electron donor. A single-crystal X-ray structure investigation of [η2-(C, O)-triphenylcyclopropylcarbonyl]tricarbonyl(1-diphenylphosphino-2-diphenylarsinoethane)vanadium has been carried out (R = 0.062, 1720 reflexions). The monoclinic unit cell (space group P21/c) contains 4 molecules. Considering the acyl group as a monodentate ligand, the central V atom is coordinated pseudo-octahedrally with the CO groups in facial positions. Attempts to prepare analogous complexes with L2 = dppm, diars were not successful. © 1979.