n-C4H9Li in petroleum ether addn. of n-C4H9Li (0.9 M in hexane) to soln. of hydrido complex at -20°C under atmosphere of C2H4, stirring, warming slowly to room temp. (red -> orange-yellow, white ppt. formed), 30-40 min; centrifugation, washing solid with Et2O, drying in vac. (lithium propionate), ethene complex isolated from soln.;