Synthesis, characterization and electrochemical studies of 1′,6′-bis(ethynyl)biferrocene and some metal complexes: Novel heterometallic compounds towards non-linear optics

The reaction of trimethylsilylacetylene and 1′,6′-diiodoferrocene (1) resulted in the formation of 1′,6′-bis(trimethylsilylethynyl)biferrocene (2) and, with subsequent desilylation, 1′,6′-bis(ethynyl)biferrocene (3), in excellent yields. The novel difunctional ligand 3 lends itself to metal coordination, and the multimetallic complexes 1′,6′-bis{manganese(I)tricarbonyl[1,2-bis(diphenylphosphino) methane]}biferrocene (4) and 1′,6′-bis{rutheniumbis[1,2-bis(diphenylphosphino)methane]chloride}biferrocene (5) were formed from {manganese(I)tricarbonyl[1,2-bis(diphenylphosphino)methane]bromide} and {rutheniumbis[1,2-bis(diphenylphosphino)methane]dichloride}, respectively. All the compounds have been fully characterized by analytical and spectroscopic methods. Cyclic voltammetry experiments indicate that there is a large electron delocalization between the iron atoms of the biferrocene moiety and the metal centres in the one-electron-oxidized complexes. Additionally, results show that the ruthenium and manganese centres donates electron density through the acetylene linkage to the (FeCp₂)₂ ligand.