Activation of coordinated carbon dioxide in Fe(CO2)(depe)(2) by group 14 electrophiles

A CO2 complex of iron(0), Fe(CO2)(depe)(2) (I; depe = 1,2-bis(diethylphosphino)ethane) has been Prepared by replacement of N-2 in Fe(N-2)(depe)(2) by CO2. The X-ray structure analysis of 1 shows that it has a eta(2)(C,O)-CO2 ligand in a trigonal-bipyramidal Fe geometry with some contribution of an eta(1)(C) made. Reaction a I with R3SnCl in Et2O at -78 degrees C gives the iron carboxylate complexes FeCl(CO2SnR3)(depe)(2) (R = Me, (2a), Ph (2b)). The X-ray structure analysis of 2b shows that the CO2 fragment bridges between the Fe and Sn atoms in a mu-eta(1)(C):eta(2)(O,O')-CO2 fashion. Treatment of I with Me3SiCl results in the removal of an O atom from the CO2 ligand to give a cationic carbonyliron(II) complex, [FeCl(CO)(depe)(2)]Cl-+(-) (3a), and (Me3Si)(2)O. Similarly, 1 reacts with carbon electrophiles such as MeI and MeOTf to give the corresponding cationic iron(II) carbonyl complexes [FeX(CO)(depe)(2)]X-+(-) (X = I (3b), OTf (3c)) and Me2O.