Synthesis and Characterization of Chloro- and Alkyliron Complexes with N-Donor Ligands and Their Reactivity towards CO2

New iron(II) compounds with N-donor ligands [2,2′-bipyridine (bpy) and 2-(2-pyridyl)ethylamine (pyea)] were synthesized, and their reactivity with carbon dioxide was investigated. The reactions of Fe(bpy)(pyea)Cl2 (1) with CO2 (0.9 MPa) afforded the carbamato derivative Fe(bpy)(pyea-CO2)Cl2 (2), which reacted with CH3Li to afford the monomethyl carbamato complex Fe(bpy)(pyea-CO2)ClCH3 (3), an example of a carbamato species that is stable over a carboxylato moiety. Fe[(bpy)(pyea)](CH3)2 (4), obtained by reaction of 1 with CH3Li, was treated with CO2 (0.3-0.5 MPa) to afford the dicarboxylato species Fe[(bpy)(pyea)](O2CCH3)2 (5), which provides evidence of normal double insertion of CO2 into the Fe-C bond. The reaction of 5 with HCl afforded 1 and CH3-CO2H, which confirmed the mode of bonding of the -O2CCH3 moiety to the Fe center. To verify the preference of insertion of CO2 into the Fe-C or the Fe-N bond, 1 was treated with MeLi (1 equiv.), and Fe(bpy)(pyea)Cl(CH3) (6) was isolated as a low-melting solid. The latter was treated with CO2 (0.5 MPa), and the product of insertion into the Fe-CH3 bond was observed as the only carboxylate (7). The faster insertion into the Fe-CH3 bond is explained by the fact that the N donor is quaternarized upon interaction with the metal center and has no free electrons available to interact with the C acceptor of the cumulene molecule; thus, more-forcing conditions (0.9 MPa) are required for the insertion to occur.