in dichloromethane Under anaerobic and anhyd. conditions, stirring of Mo-Co- and Fe-complexes in CH2Cl2 (5 min, -78°C), warming to room temp gives green soln.; Concg. in vac., gives a yellow ppt., addn. of Et2O gives further ppt. (Cp2Co)BF4. Evapn. of filtrate to dryness, column chromy. of residue (Al2O3 neutral, Et2O) gives Cp2Fe and then a green band, evapn. in vac., sublimation yields CpMo(NO)2Me.;