The novel chiral cyclopentadiene-type ligand CpCH is accessible from dibenzosuberenone in a five-step sequence with overall yields of 64%. NMR spectroscopy as well as DFT calculations prove that the racemization of this compound is slow at room temperature. By deprotonation of CpCH and subsequent reaction with appropriate iron­(II) precursors, the novel ferrocene derivatives (CpC)2Fe and (CpC)­Fe­(4Cp) are accessible in good yields. The latter could structurally be characterized by means of single-crystal X-ray crystallography. Mössbauer spectroscopy proves the ferrocene nature of (CpC)2Fe and (CpC)­Fe­(4Cp), and electrochemical investigations carried out with (CpC)­Fe­(4Cp) show that the compound is, as expected, more easily oxidized than ferrocene.

Cyclopentadienide derivatives possessing intrinsic helical chirality have only rarely been published in the past. The ligand Cp C H, which is well-accessible from inexpensive dibenzosuberenone, is paradigm for such a ligand. Here, the synthesis as well as the spectroscopic and structural characterization of a series of platinum group metal complexes containing this ligand are presented. While alkaline metal salts of Cp C H failed in transferring the (Cp C ) −1 unit to this type of metal sites, (Cp C )Tl turned out to be an excellent precursor for the synthesis of ruthenium ([(η 5 -Cp C )Ru(η 6 -arene)]PF 6 , [(η 5 -Cp C )Ru(NCCH 3 ) 3 )]PF 6 ), rhodium ((η 5 -Cp C )Rh(η 4 -COD)), and iridium ((η 5 -Cp C )Ir(η 4 -COD), [(η 5 -Cp*)Ir(η 5 -Cp C )]PF 6 ) complexes with Cp C ligands. EXSY NMR studies were carried out to obtain a deeper insight into the ligand dynamics of Cp C complexes.

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Dedicated to Prof. Wolfgang Beck on the occasion of his 90th birthday.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 [(η 4 -Cp C O)M(CO) 3 ]. In contrast to [(η 4 -Cp C O)Ru(CO) 3 ], the tricarbonyliron(0) complex is sensitive to oxygen and moisture. Refluxing [(η 4 -Cp C O)Ru(CO) 3 ] in isopropanol makes the hydrido-bridged complex [((η 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 [(η 4 -Cp C O)Ru(CO) 3 ] was investigated for a series of transfer hydrogenation reactions.