N‐(Hydroxy)thiazole‐2(3H)‐thiones 6–10 have been prepared in a short and efficient synthesis from p‐substituted acetophenones. Alkylation of heterocycles 6–10 in the form of their potassium or tetraalkylammonium salts 11–15 affords N‐alkoxy‐4‐arylthiazole‐2(3H)‐thiones 16–20 in good to satisfactory yields. The hitherto unknown thiones 16–20 have been subjected to a detailed structural investigation (NMR spectroscopy and X‐ray crystallography) and furthermore to a mechanistic study in order to explore their utility as sources of oxygen‐centered radicals in solution. From the results of these studies, the following conclusions can be drawn: (i) X‐ray analyses of the p‐chlorophenyl‐substituted acid 9, of the O‐alkyl derivatives 19c, 19f, and of the O‐mixed anhydride 19k indicate short C–S bonds [C2–S2 = 1.637(5)–1.684(2) Å] and long N–O connectivities [N3–O1 = 1.369(3)–1.379(2) Å] in the thiohydroxamate functionalities. Furthermore, O‐alkyl‐ or O‐acyl substituents at O1 are twisted out of the thiazolethione plane by ca. 90°, which points to lone‐pair repulsion between nitrogen and oxygen atom as the underlying structural motif of the cyclic thiohydroxamate derivatives. (ii) Alkylation of ambidentate thiohydroxamate anions (salts 11–15; oxygen and sulfur nucleophiles) affords almost exclusively O‐esters 16–20 (alkylation at the oxygen atom). (iii) Based on the results of X‐ray diffraction studies and on the 1H‐ and 13C‐NMR spectra, guidelines for the characterization of N‐(alkoxy)thiazolethiones 16–20 and 2‐(alkylsulfanyl)thiazole N‐oxides 21–25, i.e. the products of S‐alkylation of thiohydroxamate salts 11–15, could be derived. (iv) Photolyses of substituted N‐(4‐pentenoxy)‐4‐arylthiazolethiones 16–20 in general and in particular of p‐chloro derivatives 19 were carried out in the presence of the hydrogen donor Bu3SnH, and afforded substituted tetrahydrofurans 31 or tetrahydropyrans 32 as major products in good yields. The observed stereo‐ and regioselectivities of ethers 31 and 32 point to alkoxyl radicals 30 as reactive intermediates, which add intramolecularly by selective 5‐exo‐trig or 6‐endo‐trig pathways to the olefinic double bonds. In terms of synthetic access and ease of handling of the radical precursors, the p‐chlorophenyl‐substituted thiazolethiones 9 and 19 exhibit significant advantages over all the other thiones used in this study and are considered as excellent substitutes for the pyridinethiones as efficient sources of free alkoxyl radicals. Consequently, the present compounds may be of use in both mechanistic and synthetic studies.
The gold complexes n-Bu4N[Au(alpha-tpdt)2] (5), n-Bu4N[Au(dtpdt)2] (4) and n-Bu4N[Au(tpdt)2] (6) based on new dithiothiophene ligands (alpha-tpdt= 2,3-thiophenedithiolate, dtpdt=2,3-dihydro-5,6-thiophenedithiolate and tpdt = 3,4-thiophenedithiolate) have been prepared and characterised. These gold(III) complexes are diamagnetic, but they can be oxidised with iodine to the paramagnetic compounds [Au(alpha-tpdt)2] (8), [Au(dtpdt)2] (7) and n-Bu4N[[Au(tpdt)2]n-2] (9), which were isolated as fine powders and which exhibit paramagnetic susceptibilities that are almost temperature independent with room temperature values of 2.5 x 10(-4), 2.0 x 10(-4) and 5 x 10(-4) emu x mol(-1), respectively. Interestingly, the neutral complex [Au(alpha-tpdt)2] (8) as a polycrystalline sample displays the properties of a metallic system with a room temperature electrical conductivity of 6 S x cm(-1) and a thermoelectric power of 5.5 microVK(-1); this is the first time that this metallic property has been observed in a molecular system based on a neutral species.
The nickel complex nBu 4 N[Ni(α-tpdt) 2 ] (2) (α-tpdt = 2,3-thiophenedithiolate) has been prepared and characterized. A salt of this monoanionic paramagnetic complex, [Fe(Cp* ) 2 ][Ni(α-tpdt) 2 ] (3), was obtained with decamethylferrocene, crystallizing in the monoclinic space group P2 1 /a with a = 15.443(3), b = 10.237(1), c = 20.360(2) Å , β = 107.54(1)°, V = 3069.1(7) Å 3 , Z = 4. Its structure consists of alternating cationic and anionic layers, with short interlayer contacts defining alternating cation−anion chains. Magnetic characterization of 3 at low applied magnetic fields revealed an antiferro-
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