A Novel Cyclopentadienone and its Ruthenium and Iron Tricarbonyl Complexes

A simple and efficient protocol allows the oxidation of the cyclopentadiene derivative 5H-dibenzo[e,h]-dibenzo[3,4 : 6,7]cyclohept[1,2-a]azulene (Cp(C)H) provide according ketone Cp(C)O. Comparable to the situation found for Cp(C)H, the bending of the four annulated six-membered rings defines the C-2 symmetric molecular structure of Cp(C)O. The cyclopentadienone Cp(C)O readily reacts with [Ru-3(CO)(12)] and [Fe-3(CO)(12)] to generate tricarbonyl complexes of the type [(eta(4)-Cp(C)O)M(CO)(3)]. In contrast to [(eta(4)-Cp(C)O)Ru(CO)(3)], the tricarbonyliron(0) complex is sensitive to oxygen and moisture. Refluxing [(eta(4)-Cp(C)O)Ru(CO)(3)] in isopropanol makes the hydrido-bridged complex [((eta(4)-Cp(C)O)(2)H)Ru-2(CO)(4)H] accessible, an analogue to Shvo's catalyst. Both ruthenium complexes and their ligand Cp(C)O were characterized spectroscopically and by single crystal x-ray diffraction. The activity of [(eta(4)-Cp(C)O)Ru(CO)(3)] was investigated for a series of transfer hydrogenation reactions.