Synthesis and (spectro)electrochemistry of mixed-valent diferrocenyl–dihydrothiopyran derivatives

Abstract

Three novel diferrocenyl complexes were prepared and characterised. 2,2-Diferrocenyl-4,5-dimethyl-3,6-dihydro-2H-thiopyran (1, sulphide) was accessible by the hetero-Diels-Alder reaction of diferrocenyl thioketone with 2,3-dimethyl-1,3-butadiene. Stepwise oxidation of 1 gave the respective oxides 2,2-diferrocenyl-4,5-dimethyl-3,6-dihydro-2H-thiopyran-1-oxide (2, sulfoxide) and 2,2-diferrocenyl-4,5-dimethyl-3,6-dihydro-2H-thiopyran-1,1-dioxide (3, sulfone), respectively. The molecular structures of 1 and 3 in the solid state were determined by single crystal X-ray crystallography. The oxidation of sulphide 1 to sulfone 3, plays only a minor role on the overall structure of the two compounds. Electrochemical (cyclic voltammetry (= CV), square wave voltammetry (= SWV)) and spectroelectrochemical (in situ UV-Vis/NIR spectroscopy) studies were carried out. The CV and SWV measurements showed that an increase of the sulphur atom oxidation from -2 in 1 to +2 in 3 causes an anodic shift of the ferrocenyl-based oxidation potentials of about 100 mV. The electrochemical oxidation of 1-3 generates mixed-valent cations 1(+)-3(+). These monooxidised species display low-energy electronic absorption bands between 1000 and 3000 nm assigned to IVCT (= Inter-Valence Charge Transfer) electronic transitions. Accordingly, the mixed-valent cations 1(+)-3(+) are classified as weakly coupled class II systems according to Robin and Day.

Synthesis of Ferrocenyl Thioketones and their Reactions with Diphenyldiazomethane

“…Despite the growing interest in ferrocenyl-containing S-heterocycles, 6 the ferrocenylsubstituted thioketones, which are attractive substrates for their synthesis, are only very little known. The synthesis of three representatives, i.e., ferrocenyl phenyl thioketone, ferrocenyl methyl thioketone, and tert-butyl ferrocenyl thioketones, was reported in 1978 without complete spectroscopic data.…”

Synthesis and anticancer activity studies of ferrocenyl-thymine-3,6-dihydro-2H-thiopyranes – A new class of metallocene-nucleobase derivatives

“…This reaction afforded thioketone 1 as a blue solid in 77% yield. The subsequent thermally-induced hetero-Diels-Alder cycloaddition reaction [19] of 1 with 2,3-dimethyl-1,3-butadiene gave the target complex 3 as a yellow solid in 77% yield. It is worth noting that the thionation reaction yielded a trace amount of thioketone 2, along with 1 as major product.…”

“…Selected bond lengths (Å) and angles ( ): C1eC2 1.416(4), C1eC5 1.442(3), C5eC6 1.451(3), S1eC6 1.651(3), O1eC12 1.229(3), N2eC12 1.366(3), N2eC11 1.374(3), S2eC11 1.665(3), C10eC13 1.504(3); C7eC6eS1 119.77(18), N2eC11eS2 119.23(18), N2eC12eN1 115.51(19).…”

A convenient access to 1,2-diferrocenyl-substituted ethylenes via [3 + 2]-cycloelimination of 2-silylated 4,4,5,5-tetrasubstituted 1,3-dithiolanes

“…sulfur heterocycles [6][7][8] and tetrasubstituted ethylenes [4,9]. The goal of present study was the reaction of ferrocenyl thioketones with (trimethylsilyl)diazomethane and subsequent desilylation of the expected 2-silylated 1,3-dithiolanes, and the observation of differences in the behavior of ferrocenyl hetaryl and alkyl ferrocenyl thioketones was of special interest.…”