Donor tetrahydrothiophene

The X-ray structure of the bis(l,4,7-trithiacyclononane) zinc shows an unusual S6 thioether-coordinated zinc center.540 A rare monodentate thioether donor is observed in a phenyl-bridged zinc dimer that has been structurally characterized with a tetrahydrothiophene coordinated to each zinc center.541... 

In contrast, dipolar aprotic solvents possess large relative permittivities (sr > 15), sizeable dipole moments p > 8.3 10 ° Cm = 2.5 D), and average C.f values of 0.3 to 0.5. These solvents do not act as hydrogen-bond donors since their C—H bonds are not sufficiently polarized. However, they are usually good EPD solvents and hence cation sol-vators due to the presence of lone electron pairs. Among the most important dipolar aprotic solvents are acetone, acetonitrile [75], benzonitrile, A,A-dimethylacetamide [76, 77], A,A-dimethylformamide [76-78], dimethylsulfone [79], dimethyl sulfoxide [80-84], hex-amethylphosphoric triamide [85], 1-methylpyrrolidin-2-one [86], nitrobenzene, nitro-methane [87], cyclic carbonates such as propylene carbonate (4-methyl-l,3-dioxol-2-one) [88], sulfolane (tetrahydrothiophene-1,1-dioxide) [89, 90, 90a], 1,1,3,3-tetramethylurea [91, 91a] and tetrasubstituted cyclic ureas such as 3,4,5,6-tetrahydro-l,3-dimethyl-pyr-imidin-2-(l//)-one (dimethyl propylene urea, DMPU) [133]. The latter is a suitable substitute for the carcinogenic hexamethylphosphoric triamide cf. Table A-14) [134]. 

Addition of SO2 to the allenes 15 has been demonstrated to give the thiophene derivatives 16. The regio- and stereoselectivity of these reactions was corroborated by a computational study <05OL1565>. The formation of tetrahydrothiophene 1,1-dioxides has also been observed during radical annulations using SO2 as a radical acceptor/donor <05JOC10854>. 

As can be seen in Scheme 11, various procedures have been established for the further derivatization of dinuclear gold(II) ylide complexes by ligand substitution. Halide ligands can be substituted by neutral donor ligands such as tetrahydrothiophene or pyridine (giving the corresponding cationic complexes)249, or with other anionic ligands (such as... 

Some of the results that have been obtained in this field have already been reviewed and before presenting the more recent results some of the most noteworthy features relating to these Pt-Ag complexes will be discussed. To illustrate this part we have chosen the complexes obtained by reacting the tetrakis-pentafluorophenylplatinate or the cw-7 /5-pentafluorophenylbispentachlorophenyl-platinate anions with tetrahydrothiophene silver perchlorate in 1 1 molar ratio (Eq. U)). The resulting complexes which are presented in Figs. 2 and 3, contain a donor-... 

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