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

Abstract

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-C₅H₄)Fe(η⁵-C₅H₅)}](M = Ru 2 or Os 3) in high yields. Characterization of 2 and 3 by IR and ¹H 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.