CO; C2H5OH; (Cp2Fe)(BF4) in methanol; ethanol; dichloromethane Dissolving of complex in CH2Cl2 spiked with EtOH under CO, dissolving of (Cp2Fe)(BF4) in MeOH under CO, cooling (-78°C) of both solns., stirring (10 min), addn. of CH2Cl2 soln. to MeOH soln., stirring (2 h, -78°C), warming to room temp.; Evapn., dissolving in CH2Cl2, filtering through Al2O3, vol. redn., chromy. (Al2O3, pentane/Et2O) of 9:1 mixt. of Et2OCC(CH2OMe)CMe2 and Et2OCC(CMe2OEt)CH2 gives pale yellow oil, IR, (1)H NMR, (13)C NMR, MS.;