Synthesis and Characterization of Fe 0 (2,2′‐bipyridine) (2‐aminoethyl‐pyridine) and its Reaction with Dihydrogen

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.