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. [ABSTRACT FROM AUTHOR]