A Novel Cyclopentadienone and its Ruthenium and Iron Tricarbonyl Complexes

Abstract

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 (CpCH) provide according ketone CpCO. Comparable to the situation found for CpCH, the bending of the four annulated six-membered rings defines the C2 symmetric molecular structure of CpCO. The cyclopentadienone CpCO readily reacts with [Ru3(CO)12] and [Fe3(CO)12] to generate tricarbonyl complexes of the type [(η4-CpCO)M(CO)3]. In contrast to [(η4-CpCO)Ru(CO)3], the tricarbonyliron(0) complex is sensitive to oxygen and moisture. Refluxing [(η4-CpCO)Ru(CO)3] in isopropanol makes the hydrido-bridged complex [((η4-CpCO)2H)Ru2(CO)4H] accessible, an analogue to Shvo's catalyst. Both ruthenium complexes and their ligand CpCO were characterized spectroscopically and by single crystal x-ray diffraction. The activity of [(η4-CpCO)Ru(CO)3] was investigated for a series of transfer hydrogenation reactions.