Dithiolates 1,2-dithiolate-type, structure

The structure of [Mo3S4(dmit)3] (dmit=l,3-dithiole-2-thione-4,5-dithiolate) represents one of the rare examples of M3S4 clusters where each metal atom appears as pentacoordinate instead of its more common type-I structure octahedral environment [39]. Complexes [M3Q4(dmit)3] (M = Mo, W Q = S, Se) degrade in air with an almost quantitative yield and afford a series of M(V) dimers of formula [M202(//-Q)2(dmit)2] where the oxygen atoms are in a syn configuration. 

Interestingly, the introduction of two bromomethyl functions in 4- and 5-positions of ethylen-l,3-dithiole-2-thione leads to a packing determined by weak interactions involving also the bromine atoms. One I2 molecule behaves as an acceptor towards S and as donor towards the second I2 molecule, which in turn behaves as donor towards the a c Br orbital (Figure 13). Intermolecu-lar S- -Br, CFF Br and L -I contacts make up a three-dimensional network.480 Reaction of 5,5-dimethyl-2-selenoxoimidazoline-4-one with iodine provided the first structurally characterised compound of the type [RR C Se — I-I].32 The Se-I bond is shorter (269.9 pm) and the I-I contacts are longer (296.2 pm) than in 1 1 adducts of dialkylselenides with iodine (see Chapter 8.2). 

E) oxidation of NADH and NADPH in electron transport chains, and (F) oxidation of dithiols to disulfides or the reverse reaction. Three-dimensional structures are known for enzymes of each of these types. 

Related to this group of complexes are the transition metal half-sandwich dithiolates, almost exclusively with the mnt or tfd ligands, of the type CpMLm(mnt) , where m = 0-2 and n = 1 or 2. Examples7 are the linear CpCo(mnt) and CpCo(tfd) complexes (39) and CpMo(tfd)2 (40). The structure of the tetramethylcyclobutadieneNi(mnt) complex has been reported.54 The synthesis and structure of Rh(cod)(Me-mnt) has also been published.55... 

Aurated dications of a different type, bissulfonium salts 100 formed from dithiols, have been reported265,266 including the systematic study by Sladek and Schmidbaur.267 Single-crystal X-ray diffraction study indicated that they form complicated aggregated structures. 

Synthesis of 1,3,2-dithiazoles has been the most extensively studied. Various structural types of these compounds have been synthesized in 1990s from raV-dithiols, bis(sulfenylchlorides), and alkynes <1996CHEC-II(4)433>. Much attention has been paid to the preparation of stable 1,3,2-dithiazolyl radicals and, especially, cations. The synthetic potential of 1,3,2-oxathiazoles and 1,3,2-dioxazoles is restricted by several uncommon procedures including nitrosation of thiolcarboxylic acids and photochemical addition of nitrobenzene to alkenes <1996CHEC-II(4)433>. 

Among possible structural types 307 309, dithiolates are mostly represented by the structures 308 [1, vol.2 132,133,585,587] ... 

This situation has been widely discussed [592a-c] and has not been finally resolved [592d]. At the same time, there is experimental data (reactions with halogens) in favor of the existence of dithiol structures of type 318b containing M — S bonds (M = Ni, Pd, Pt) with metal oxidation number +4 [592e,f]. 

Compounds of interest are the l,2-dithiolylium-4-olates (7), 3-acylmethylene-l,2-dithioles (11) and various oxocyclohexadienylidene-l,2-dithioles (13) and (31). The compounds (7) appear by most physical data and chemical properties to be best represented by the structure shown (78AJC297,80PS(8)79>, and for the compounds of type (11) data indicate some measure of contributions from structures (lib) or (11c). However, the exact amount of polar or tetravalent sulfur contributors to each of the structures (11), (13) and (31) is a matter of some discussion (71AHC(13)161,80MI43100). 

As mentioned above (Section 4.31.2.1), 3-alkylidene-l,2-dithioles (3d) may possess considerable ionic character consistent with contributions from structures (62), and condense with suitable carbonyl or other compounds. Condensation reactions of 3-aIkyI-l,2-dithiol-ylium salts (105) (66ZC321, 64CI(L)461, 80AHC(27)15l> are readily explained in terms of initial proton transfer from the salt to the substrate, as in the formation of salts of type... 

Dioiganotin derivatives of substituted aryl dithiolates have been widely studied [Eqs. (60) and (61)]. The products form three distinct structural groupings. Compounds of type 71 are tetrahedral at tin in both solid state... 

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