Synthesis, redox behaviour and molecular structures of new metal cluster species containing orthometallated [M₃(μ-H)(CO)₁₀(μ-NC₅H₄)] (M = Ru or Os) and ferrocene chromophores bridged by an aromatic unit

The ferrocenyl-functionalized pyridyl [Fe(η5-C5H5)(η5-C5H4C6H4C5H4N)] 1, which contains an aromatic entity in the backbone, has been prepared and structurally characterized by X-ray diffraction. Ligation of this redox-active compound with trinuclear carbonyl clusters [M3(CO)10L2] (M = Ru, L = CO; M = Os, L = MeCN) by oxidative addition provided [M3(μ-H)(CO)10{μ-NC5H3C6H4(η5-C5C4)Fe(η5-C5H5)}] (M = Ru 2 or Os 3) in high yields. Characterization of 2 and 3 by IR and1H NMR spectroscopy revealed that these complexes have analogous orthometallated molecular geometries. To confirm this, crystal structure determinations were carried out for both 2 and 3. Spectroscopic and structural evidence for both 2 and 3 suggests a new class of metal clusters consisting of an orthometallated trinuclear carbonyl cluster unit rigidly linked to a ferrocenyl moiety through an aromatic pathway. Electrochemical investigations revealed that both 2 and 3 undergo a reversible one-electron oxidation at iron followed by an irreverible oxidation of the metal cluster core.