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

The aromatic P=CH-N heterocycle 1 with dicoordinated phosphorus (sigma P-2) reacts with Fe-3(CO)(12) in toluene or benzene under reductive C-C coupling and coordination of the [Fe-2(CO)(6)](2+) fragment to the mu(2)-bridging 1,2-bis(phosphido)Fe-2(CO)(6) chelate complex 2 (rac/meso 4:1 to 2:1). This reaction illustrates the potential of Fe-3(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 Fe-2(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. (C) 2014 Elsevier B.V. All rights reserved.