π-Excess aromatic σ2P ligands: Unprecedented reductive C–C coupling of neopentylbenzazaphosphole at the PCH–N group by Fe3(CO)12 to an heterocyclic 1,2-bis(phosphido)-Fe2(CO)6 complex

•First reaction of a π-excess -PCH–N-heterocycle with a Mn(CO)m cluster.•First example for reductive C–C coupling of PCH–N by an M(0)–M(0) species.•The reaction presents a novel strategy to 1,2-diphosphido-MI2(CO)m complexes.

The aromatic PCH–N heterocycle 1 with dicoordinated phosphorus (σ2P) reacts with Fe3(CO)12 in toluene or benzene under reductive C–C coupling and coordination of the [Fe2(CO)6]2+ fragment to the μ2-bridging 1,2-bis(phosphido)Fe2(CO)6 chelate complex 2 (rac/meso 4:1 to 2:1). This reaction illustrates the potential of Fe3(CO)12 for C–C coupling reactions of easily reducible unsaturated heterocycles which may act as both, substrate and ligands for coordination of the resulting Fe2(CO)6 fragment. The products were identified by characteristic NMR data of the bis(dihydrobenzazaphospholide) ligands and rac-2·1.5 CDCl3 by crystal structure analysis.

Graphical abstractThe reaction of neopentyl-1,3-benzazaphosphole with Fe3(CO)12 exemplifies a novel Fe(0) mediated C–C coupling of unsaturated heterocycles combined with Fe2(CO)6 coordination.Figure optionsDownload full-size imageDownload as PowerPoint slide