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Fe0(bpy)(pyea) ( 2; bpy=2,2′-bipyridine, pyea=2-aminoethyl-pyridine), a 16-electron species, was synthesized by reduction of FeCl2(bpy)(pyea) ( 1) using Na-strips. It is a diamagnetic low-melting solid (m.p. 295 K) stable under N2 and easily decomposed by radiations even at low temperature. It was fully characterized by elemental analyses and multinuclear NMR. Complex 2 acts as an active hydrogenation catalyst, but has a very short lifetime. In fact, it reacts with H2 (0.1-1 MPa) at room temperature in toluene and affords in a few minutes a new Fe0 complex characterized as Fe0(bpy)(η6-picoline) ( 3), inactive to hydrogenation. Picoline is derived from the sp3-sp3 C−C bond cleavage of the aminoethyl arm of the pyea ligand. The rapid evolution of the putative intermediate FeH2(bpy)(pyea) ( 4) has not allowed the isolation such Fe-hydrido species. The interaction of H2 with 2 has been studied by DFT, which has allowed to demonstrate that 3 is lower in energy than 2+H2, justifying the fact that the intermediate dihydride was not isolated. Interestingly, 3 was also obtained by reaction of 1 with NaBH4 or with glycerol-KOH. Complex 2 is one of the rare examples of Fe0 complex stabilized by a set of only N-donor atoms. The reaction with glycerol confirms the potential role of Fe in catalytic hydrogenation reactions using bio-glycerol as a H-source. [ABSTRACT FROM AUTHOR]

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]

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]

Fe 0 (bpy)(pyea) (2; bpy=2,2'-bipyridine, pyea=2-aminoethyl-pyridine), a 16-electron species, was synthesized by reduction of FeCl 2 (bpy)(pyea) (1) using Na-strips. It is a diamagnetic low-melting solid (m.p. 295 K) stable under N 2 and easily decomposed by radiations even at low temperature. It was fully characterized by elemental analyses and multinuclear NMR. Complex 2 acts as an active hydrogenation catalyst, but has a very short lifetime. In fact, it reacts with H 2 (0.1-1 MPa) at room temperature in toluene and affords in a few minutes a new Fe 0 complex characterized as Fe 0 (bpy)(η 6 -picoline) (3), inactive to hydrogenation. Picoline is derived from the sp 3 -sp 3 C-C bond cleavage of the aminoethyl arm of the pyea ligand. The rapid evolution of the putative intermediate FeH 2 (bpy)(pyea) (4) has not allowed the isolation such Fe-hydrido species. The interaction of H 2 with 2 has been studied by DFT, which has allowed to demonstrate that 3 is lower in energy than 2+H 2 , justifying the fact that the intermediate dihydride was not isolated. Interestingly, 3 was also obtained by reaction of 1 with NaBH 4 or with glycerol-KOH. Complex 2 is one of the rare examples of Fe 0 complex stabilized by a set of only N-donor atoms. The reaction with glycerol confirms the potential role of Fe in catalytic hydrogenation reactions using bio-glycerol as a H-source., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)