Trimerization of acetylferrocene and of (acetylcyclopentadienyl)tricarbonyl-manganese proceeds efficiently in the presence of ethanol and tetrachlorosilane. The resulting 1,3,5-trisubstituted benzenes have been characterized by X-ray crystallography and compared with the structure of (1,3,5-triphenylbenzene)tris(tricarbonylchromium). The efficacy of EtOH–SiCl4 as a combined reagent for the trimerization of polycyclic ketones is also discussed. Finally, the synthesis and structure of [CpMn(CO)2]2(µ-C=CHPr), derived from the reaction of cymantrene with butyllithium and phenylacetyl chloride at room temperature, is described.Key words: ketone, condensation, cyclization, organometallics, arenes.

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Diels-Alder addition of diphenylacetylene or of 1,2,3-triphenylcyclopropene to 3-ferrocenyl-2,4,5-triphenylcyclopentadienone yields, upon thermolysis, C 6 Ph 5 Fc (5) or C 7 Ph 6 FcH (8), respectively. Subsequent treatment of 8 with triethyloxonium hexachloroantimonate results in the formation of the ferricinium complex [C 7 Ph 6 FcH] + [SbCl 6 ] -(13), rather than the anticipated tropylium cation [C 7 Ph 6 Fc] + . The substituted ferrocene derivatives 5, 8, and 13 have been characterized by X-ray crystallography. From the solid-state structure of 5 it is evident that the peripheral aryl substituents do not adopt a regular propeller type conformation, but instead exhibit an incremental progression of twist angles relative to the central ring. The dynamics of peripheral ring rotations in 5 and 8 have been studied by variable-temperature NMR.

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Trindane (the condensation trimer of cyclopentanone) yields complexes of the type (η6-trindane)ML n , where ML n = Cr(CO)3 (6), Mo(CO)3 (8), Mn(CO)3 + (9), or (C5H5)Fe+ (10a,10b). X-ray crystallographic data are reported for (η6-trindane)Cr(CO)3 (6) and show that the three five-membered rings adopt envelope conformations in which the central methylene groups are bent toward the metal. When the chromium complex 6 is stirred with DMSO-d 6 in the presence of t-BuOK, up to 12 benzyl protons can be exchanged for deuterons, giving a mixture of partially deuterated products. In contrast, the iron complex 10b undergoes complete H/D exchange at all 12 benzylic sites. The possibility of preparing all-cis hexamethyltrindane as a precursor to sumanene is discussed.