Structure of Diferrocenyl Thioketone: From Molecule to Crystal.

Ferrocenyl-functionalized thioketones have recently been recognized as useful building blocks for sulfur-containing compounds with potential applications in materials chemistry. This work is devoted to a single representative of such thioketones, namely diferrocenyl thioketone (Fc2CS), whose structure has been determined here for the first time. Both X-ray crystallography and a wide variety of quantum-chemical methods were used to explore the structure of Fc2CS. In addition to the X-ray structure determination, intermolecular interactions occurring in the crystal structure of Fc2CS were examined in detail by quantum-chemical methods. These methods were also an invaluable tool in studying the molecular structure of Fc2CS, from the gas phase to solutions and to its crystal. Intramolecular interactions governing the conformational behavior of an isolated Fc2CS molecule were deduced from quantum-chemical analyses carried out in orbital space and real space. Our experimental and theoretical results indicate that the main structural features of an isolated Fc2CS molecule in its lowest-energy geometry are retained both upon solvation and in the crystal. The tilt of ferrocenyl groups is only slightly affected by crystal packing forces that are dominated by dispersion. Nonetheless, a network of intermolecular interactions, such as H···H, C···H and S···H, was detected in the Fc2CS crystal but each of them is fairly weak.

Efficient synthesis of ferrocifens and other ferrocenyl-substituted ethylenes via a 'sulfur approach'.

Stable and non-odorous alkyl ferrocenyl thioketones react with bis(4-methoxyphenyl)diazomethane according to the 'two-fold extrusion' reaction principles, and tetrasubstituted ethylenes obtained thereby can be demethylated to give (Fc,2OH)-ferrocifens in good yields. The method offers an alternative approach to this class of medically relevant compounds. A similar protocol with alkyl ferrocenyl thioketones and selected diaryldiazomethanes leads to ferrocenyl-substituted ethylenes including dibenzofulvenes. These products are of potential interest for electrochemical and photophysical studies.

Crystal structure of (E)-1,2-diferrocenyl-1,2-bis(furan-2-yl)ethene.

The title compound, [Fe2(C5H5)2(C20H14O2)], is the product of a new synthetic route towards tetra-aryl/hetaryl-substituted ethenes that reduces the occurrence of side-products. In the crystal, the mol-ecule is centrosymmetric and the cyclo-penta-dienyl (Cp) rings are nearly coplanar and aligned slightly closer to a staggered conformation than to an eclipsed one. The ethene plane is tilted by 32.40 (18)° with respect to that of the substituted Cp ring and by 63.19 (19)° with respect to that of the furan ring. C-H⋯π inter-actions link the mol-ecules into a three-dimensional supramolecular framework.

A novel application of 2-silylated 1,3-dithiolanes for the synthesis of aryl/hetaryl-substituted ethenes and dibenzofulvenes.

Trimethylsilyldiazomethane (TMS-CHN2) reacts readily with hetaryl thioketones to give sterically crowded 2-trimethylsilyl-4,4,5,5-tetrahetaryl-1,3-dithiolanes with complete regioselectivity at -75 °C as well as at rt. Thiofluorenone, a relatively stable and highly reactive aryl thioketone, yields upon treatment with TMS-CHN2 at -60 °C the corresponding 1,3,4-thiadiazoline. This unstable cycloadduct undergoes decomposition at ca. -45 °C and the silylated thiocarbonyl S-methanide generated thereby is trapped with complete regioselectivity by aryl or hetaryl thioketones forming also sterically crowded 2-trimethylsilyl-1,3-dithiolanes. The obtained 1,3-dithiolanes, by treatment with an equimolar amount of TBAF in a one-pot procedure, are converted in high yields into hetaryl/aryl-substituted ethenes or dibenzofulvenes, respectively, via a cycloreversion reaction of the intermediate 1,3-dithiolane carbanion. The presented protocol offers a new, highly efficient approach to tetrasubstituted ethenes and dibenzofulvenes bearing aryl and/or hetaryl substituents.

Synthesis of ferrocenyl-substituted 1,3-dithiolanes via [3 + 2]-cycloadditions of ferrocenyl hetaryl thioketones with thiocarbonyl S-methanides.

Ferrocenyl hetaryl thioketones react smoothly with in situ generated thiocarbonyl S-methanides to give 1,3-dithiolanes. In the case of aromatic S-methanides, the sterically more crowded 4,4,5,5-tetrasubstituted 1,3-dithiolanes (2-CH2 isomers) were formed as sole products. The reactions with cycloaliphatic S-methanides led to mixtures of 2-CH2 and 5-CH2 isomers with the major component being the sterically more crowded 2-CH2 isomers. The preferred formation of the latter products is explained by the assumption that the formal [3 + 2]-cycloadducts were formed via a stepwise reaction mechanism with a stabilized 1,5-diradical as a key intermediate. The complete change of the reaction mechanism toward the concerted [3 + 2]-cycloaddition was observed in the reaction of a sterically crowded cycloaliphatic thiocarbonyl ylide with ferrocenyl methyl thioketone.