Sulphur compounds containing anions

Mixtures of nitric and sulphuric acids contain nitronium sulphates which have been described by Ingold and associates, Woolf and Emeleus(Vo). I,p. 19). Reval-licr and co-workers [10] have found by Raman spectroscopy and vapour pressure measurements, that compounds made by acting with SOj on nitric acid are salts of nitronium ion (NO ) and sulphate anions. Vitse [11] established the structure of the compound N2 0s,4S03 as nitronium ion salt by X-ray crystallography. The salts of pyrosulphuric acid (Vol. 1, p. 12) can be present only in a mixture of nitric acid with oleum or SO3. They are described in the paragraph on nitronium salts (p. 27). The presence of NO in various solutions was discussed in Vol. I, pp. 14- 49. 

Section 15.4 contains anion radicals from nitro compounds. No subdivision has been made into compounds containg one, two or more nitro groups. In the case of a dianion that follows die monoanion directly. Section 15.5 contains tables of magnetic data obtained from anion radicals wifli carbonyl functionality and their sulphur analogs. The data have been divided into subsections consisting of esters and thioesters aldehydes, ketones and their thio analogs semidiones and acid anhydrides. These subsections have been furdier subdivided, for example the subsection Esters and thioesters has been subdivided into arylesters, fliioe-sters and oxocarbothioate and dithioate esters. 

The formation of compounds containing complex anions is expected to occur easily in an acceptor solvent such as sulphur dioxide. The formation of K3SbCl6 and KSbCle has been reported . Reactions between nitrosyl chloride, acetyl chloride or benzoyl chloride and antimony(V) chloride lead in liquid sulphur dioxide to the respective chloro-complexes, namely N0[SbCl6], [CH3CO]SbCl6 and [C6H5CO][SbCl6] , but the latter has recently been shown to be Cl... 

The Af-HjO diagrams present the equilibria at various pHs and potentials between the metal, metal ions and solid oxides and hydroxides for systems in which the only reactants are metal, water, and hydrogen and hydroxyl ions a situation that is extremely unlikely to prevail in real solutions that usually contain a variety of electrolytes and non-electrolytes. Thus a solution of pH 1 may be prepared from either hydrochloric, sulphuric, nitric or perchloric acids, and in each case a different anion will be introduced into the solution with the consequent possibility of the formation of species other than those predicted in the Af-HjO system. In general, anions that form soluble complexes will tend to extend the zones of corrosion, whereas anions that form insoluble compounds will tend to extend the zone of passivity. However, provided the relevant thermodynamic data are aveiil-able, the effect of these anions can be incorporated into the diagram, and diagrams of the type Af-HjO-A" are available in Cebelcor reports and in the published literature. 

Substrate analogues containing the mercaptan functionaUty have been extensively investigated as collagenase inhibitors, and some other sulphur-based functionalities have also been explored [1,161,172-185]. The mercap-tans tend to be very potent inhibitors of all of the MMP, presumably due to the strong interaction between the active site Zn(II) and the mercaptide anion. Unfortunately, these compounds tend to undergo inactivation by oxidative disulphide formation. However, the rate at which this occurs varies widely and depends on the structure of the inhibitor. The most common synthetic route to these derivatives again leads to a diastereomeric mixture. 

Thiourea forms MX (thiourea) 4 compounds if the lattice energy of MX is iess than 160 Kcal/mole, so that M = K, Rb, or Cs. Other large cations form similar compounds, for example, thallium and lead. The structures consist of columns of cations surrounded by eight sulphur atoms at the comers of an approximately regular cube. Each sulphur atom is shared by two cations. The S—C bonds lie in planes normal to the column, and the NHg groups project into channels which contain the anion, and sometimes water molecules (34). 

Arsenious oxide is insoluble in dilute sulphuric acid but reacts with fuming sulphuric acid to give a series of very unstable crystalline compounds of general formula As203.nS03. These are resolved into arsenious oxide and sulphuric acid on contact with water. The formation of a crystalline arsenyl tartrate, Na(As0)C4H406, analogous to potassium antimonyl tartrate, has been cited as evidence of the basic nature of arsenious oxide, but the product may contain the arsenic in a complex anion. 

As a last example of a 1 1 structure derived from a cubic close-packed anion sublattice we mention that of the mineral sulvanite CU3VS4. Here, the copper atoms occupy three of the four positions of one set of tetrahedral holes, while the vanadium atom is located at one position of the other set. Thus, the anion is no longer tetrahedrally coordinated but has all four cation neighbours on the same side. In C113VS4 vanadium may be replaced by Nb and Ta and the sulphur by Se and Te (178). These compounds all are diamagnetic semiconductors containing monovalent copper and a pentavalent transition element, as does CuTaS3 (179) where Ta, however, is octahedrally coordinated. 

Other Sulphur-containing Compounds.—The crystal structure of rubidium hydroxylamine-NN-disulphonate, Rb5 [0N(S03)2]2H, 3H20, has been determined by direct methods and refined.264 The structure contains two formula units in the space group Pi, and the two [0N(S03)2]2H 5 anions... 

The mono-thio, -seleno and -telluro analogues of phosphonic and phosphinic acids are tautomeric (equations 1, 2 and 4). In the case of the sulphur-containing compounds, an attempt has been made to estimate the equilibrium compositions of a variety of acids by means of physicochemical measurements. The alkali metal salts of phosphonothioate and phosphinothioate acids possess anions which are mesomeric and, theoretically, it is possible for such ions to act as sources of both O-and S-substituted products. The same products can be obtained through reactions between the free acids and diazoalkanes, and because these reactions are relatively fast, it might be expected that the composition of the product mixtures might be a reflection of the tautomer composition of the acids. 

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