1.2- Dithioketone

Few dithiolenes are prepared via reactions involving 1,2-dithioketones, a rare class of compounds prone to oligomerization. The first stable 1,2-dithione, l,2-bis(4-dimethylaminophenyl)ethane-l,2-dithione, was generated by photolysis... 

The in situ photochemical generation of 1,2-dithioketones and -aldehydes including dithioglyoxal, 3,3-dimethyl-2-thioxobutanethial, and camphor dithioquinone was confirmed by the subsequent trap of the 1,2-dithiocarbonyl compounds in [4 + 2] cycloadditions. The 1,2-dithioketones and 1,2-dithioaldehydes exhibited a preference for 4ir participation in inverse electron demand (LUMOdlene controlled) Diels-Alder reactions with electron-rich dienophiles (Scheme 8-X).37... 

Coordination compounds with delocalised ground states. The transition metal derivatives of dithioketones and ethylene(l,2)dithiolates (metal dithienes). G. N. Schrauzer, Acc. Chem. Res., 1969,2,72-80 (36). 

The Transition Metal Derivatives of Dithioketones and Ethylene(l,2)dithiolates 1668... 

Complexes of dithioacetylacetone (SacSac) have been reviewed.1830 As with acetylacetone complexes, th. chemical shift of the ring methine proton has been carefully studied for metal and substituent effects in order to probe for any aromatic or anisotropic behavior in these six-membered ring complexes.1830,1831 Much of the earlier work and theories on these complexes are summarized in an electrochemical study of the dithioketone complexes of Ni, Pd and Pt.1832 The complexes undergo two successive reversible one-electron reductions in the range -0.8 to —1.8 V yielding the MSJ and MS2- core.1832,1833 The monoanion MSJ is usually... 

Because the benzene resonance energy is much higher than that of an isolated double bond, the oxidation of an ethylenedithiolate to the butadiene-like dithione is easier to accomplish than the oxidation of a benzenedithiolate to the corresponding dithio-or /io-benzoquinone there is a difference in stability between the dianionic ligands (44) and (46) relative to the dithioketone forms (45) and (47) derived from them by a two-electron oxidation. 

Figure 3-20. The reaction of a 1,3-diketone with hydrogen sulfide only gives a monothio derivative, 3.11, rather than a 1,3-dithioketone.

Similar reactions may occur with 1,3-diketones and 1,3-diketonates, and these reactions have been exploited by co-ordination chemists to prepare novel sulfur containing chelating ligands. The metal-directed reactions are synthetically useful since it is not possible to prepare 1,3-dithioketones by direct reactions of free 1,3-diketones with hydrogen... 

Figure 3-21. The metal directed reaction of a monothio compound with hydrogen sulfide to yield a chelated 1,3-dithioketonate.

However, the dithioketones may be readily prepared by reaction of the metal complexes of the monothio derivatives, 3.11, with hydrogen sulfide (Fig. 3-21). In this case, the metal probably plays a dual role, both in polarising the ligand and stabilising the product. Clearly, the use of a soft metal ion such as lead(it) or platinum(u) is to be preferred in a reaction of this type. 

Sulfur participates as a donor center in sulfide complexes (Muller and Diemann, p. 515), dithiolenes (Miiller-Westerhoff and Vance, p. 595), and other S-containing ligands (thiosulfates, thiourea, mono-, and dithioketones) (Livingstone, p. 633). Some other complex compounds with Se and Te as donor centers have been described (Berry, p. 661). 

Among other complexes of S,S-chelating ligands, we note p-dithioketonates 328, (S-mercaplothioet h e rates 329, and imidodithiophosphinates 330, forming ICC with six-member metal-cycles. These coordination compounds are examined in pub-... 

For instance, in the synthesis of 2.19, the 1,4-diketone is converted into the corresponding 1,4-dithioketone followed by loss of hydrogen sulphide. 

Thioketones bearing an a carbonyl have been reported [87]. As these species are produced in situ and trapped by cycloaddition, this chemistry is reported in the corresponding section (Sect. 3.8). Sulfurisation of diketones by B2S3 led to dithioketones, which were later nicely found by the Steliou group [88, 89] to be capable of ejecting diatomic disulfur (S2) via an elusive... 

Much interest has been generated in various properties of metal derivatives of dithioketones, ethylene (1, 2) dithiolates, and related compounds in recent years (17,18,29, 43, 65, 66). There are many interesting facets of these fascinating compounds, and the previously mentioned references cover them in some detail. We limit ourselves here to the structures of the Pt group metals of these engrossing ligands. Unfortunately, some of the more interesting properties of the transition metals... 

The complex Mo(tfd)3 was reported by King and co-workers (86) to catalyze the conversion of quadricyclane to norbornadiene (Eq. 9), polymerization of quadricyclane or norbornadiene, as well as the addition of water to quadricyclane to give nortricyclanol (Eq. 15). The reactions appear to involve pseudo-[4 + 2] cycloaddition to the sulfur atoms in the dithioketone form of the metal... 

The present section and Section IV.A.4 complement each other. The GC of metal chelates derived from monothio-/3-diketones, /3-diketones, -dithioketones and /3-keto-enamines was reviewed. The discussion includes column phenomena, analytical improvements and limitations and various applications . A study of the GC behavior of Group 13 /9-diketonates 37 shows that when the chelate contains a Mef group its volatility is enhanced, while a Ph group tends to decrease it. When R and R are alkyl groups the retention time of the chelates increases with the molecular weight, but it does not depend on the volatility however, the retention time of the chelates containing a Mef group is almost inversely correlated with the volatility . ... 

Enedithiolate anions are redox-active ligands (see equation 1), capable of coordinating with a variety of metals as neutral dithioketones (1), thioketone radical thiolate monoanions (2) and ene-l,2-dithiolate dianions (3). The complexes are named dithiolenes irrespective of their oxidation state to remind one that they are noninnocent ligands . 

There is considerable ambiguity concerning the charge on this type of ligand. This K> because it may be formulated either as a neutral dithioketone or the dianion of an ufisaturated dithiol. The diRl ence of two electrons can be represented formally as ... 

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