Synthesis and electrochemical properties of cyclopentadienyliron(II) complexes with bis(diphenylphosphino)amine as ligand

The synthesis and properties of new cationic iron(II) complexes of general formula [(eta (5)-C5H5)FeL(eta (2) -dppa)]A [A=I-, L=CO(1); A=BF4, L=CO(2) CH3CN(4), eta (1)-dppa(5); dppa=NH(PPh2)(2)] are described. The carbonyl complex [(eta (5)-C5H5)Fe(CO)(eta (2)-dppa)]BF4 is deprotonated to give the neutral complex [(eta (5)-C5H5)Fe(CO){eta (2)-(PPh2)(2)N}](3). All complexes have been characterized by elemental analysis and IR and NMR spectroscopies. Cyclic voltammetry of complexes 1-5 shows a diverse redox chemistry in acetonitrile solution. While the reduction of 1 and 2 leads to the formation of a dinuclear Fe(I) complex, 4 and 5 form mononuclear species of Fe(I); oxidation of metal centers of 1 and 2 is not observed and in complexes 3 and 4 the metal centers are oxidized at potentials < 1. Complex 5 in acetonitrile solution is transformed into complex 4.