Four-co-ordinate sulphur

Four-co-ordinate sulphur. The rate of decomposition of peroxodisulphate in aqueous dimethyl sulphoxide increases as the solvent becomes less aqueous. This trend is attributed to decreasing solvation of the initial state as the proportion of dimethyl sulphoxide increases. Kinetic parameters are reported for silver(i)-catalysed decomposition of peroxodisulphate and of peroxomonosulphate in aqueous solution. The 

Schulze-Rettmer, B. Buchheim, and W. Schlenter, Ber. Kernforschungsanlage Juelich 1969, Juel-59 -DE Chem. Abs., 1970, 72, 6549u). 

Reichardt, Angew. Chem. Internat. Edn., 1965, 4, 29 and refs, therein. 

Further kinetic information on hydrolysis of sulphonyl chlorides (R SOgCl) is contained in a paper which correlates kinetic data for hydrolysis of these and other halides, for example of phosphonic and phosphinic acids, with i.r. and n.q.r, spectroscopic data. Hydrolysis of the adduct McaEtN.SOa has been studied over a wide pH range. The rate-law determined in basic solution indicates 5 n2 attack by hydroxide at the sulphur atom, as earlier proposed for the parent adduct EtaN.SOg, 

Sulphur-fluorine bonds are generally inert to hydrolysis, not only in sulphur hexafluoride but also in sulphonyl fluorides. Exceptions to this general pattern occur when neighbouring-group participation is possible, as in the relatively fast hydrolysis, with concomitant acetyl loss, of the arylsulphonyl fluoride (35). All the foregoing examples have concerned 

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Two-co-ordinate sulphur. Opinions seem divided as to whether nucleophilic attack at two-co-ordinate sulphur,which is an associative process, has a synchronous or an addition-elimination mechanism. For reaction of diaryl sulphides with aromatic hydrocarbons, formation of a sulphonium cation and then of a four-co-ordinate sulphur intermediate has been proposed. The role of the "id orbitals on sulphur in nucleophilic substitutions has been discussed. ... 

Metal Complexes.—In an extensive study of the complexing power of thiazoles, numerous zinc(n), cobalt(n), copper(ii), nickel(ii), andplatinum(n) complexes of the parent compound, and of 4-alkyl- or 2,4-dialkyl-thiazoles, usually of the general type MX2L2, have been prepared. A consideration of their spectral and magnetic properties reveals that the zinc and cobalt complexes are tetrahedral, the 4-methyl copper and nickel complexes are octahedral, and the dialkyl complexes of copper and nickel and the platinum complexes are square planar. The four-co-ordinate dialkyl complexes follow the crystal field stabilization energy predictions as to the relative tendency to form tetrahedral or square-planar forms, i.e. Zn > Co > Cu > Ni. The complexes are invariably metal-nitrogen, and not metal-sulphur, co-ordinated. ... 

This type of co-ordination is also found in aikinite, PbCuBiSg, in which the lead atom has four bonds of lengths 2.95— 2.98 A to sulphur atoms on one side, and two contacts of 3.28 A to sulphur atoms on the opposite side of the molecule. Synthetic lead oxychloride, [PbsO QJ, contains lead atoms with four- and five-co-ordination. The geometries are very distorted but in each case all bonds lie on the same side of the molecule. Two lead atoms are four-co-ordinate, one forming a PbOaClj unit with Pb-O at 2.33 and 2.46 A, and Pb-Cl at 3.34 and 3.38 A, and the other a PbOQj unit with Pb-O at 2.19 A and Pb-Cl at 2.91, 3.09, and 3.52 A. The third Pb atom in the structure forms a PbOCl4 unit with Pb-O at 2.27 A and Pb-Cl at 2.97, 3.11, 3.25, and 3.53 A. 

The kinetics of the reaction between peroxomonosulphate and thiocyanate were earlier interpreted in terms of the intermediate of species such as HS(0)CN, (SCN)a, and HO(SO)CN. No definite proof of this is available, but the detection of similar intermediates, RSO2CN and R(SO)CN, in reactions between alkyl thiocyanates and peroxomonosulphate lends support to the intermediacy of HS(0)CN and HO(SO)CN in the peroxomonosulphate-thiocyanate reaction.The kinetics of decomposition of the iV-nitroso-hydroxylamine-A -sulphonate anion to sulphate and nitrous oxide have already been described under nitrogen. The mechanism of substitution at sulphur(iv) in sulphinyl compounds, RS(0)Y, is still a topic of unresolved discussion, despite much effort in this area. The question awaiting answer is whether the mechanism is simple Ssl or whether there is a four-co-ordinate intermediate of significant lifetime. > Though the determination of Bronsted coefficients did not provide definite mechanistic evidence relating to substitution at... 

Sulphur, Selenium, and Tellurium Compounds.—The crystal structure of the metal-rich zirconium sulphide Zr Sj has been determined and each sulphur atom shown to be at the centre of a square antiprism of zirconium atoms. The reaction of ZrS2 with potassium in liquid ammonia has been shown to give four K ZrS2 phases (.x = 1, 0.86, 0.71, or 0.71—0.22) which differ in the nature of the co-ordination sites occupied by the potassium atoms between the ZrS2 layers. ZrCl reacts with NaS2P(OEt)2 in toluene to form [Zr S2P-(OEt)2 4], which appears to involve a trigonal-dodecahedral arrangement of sulphur atoms about the metal. ... 

The manner in which the S2 unit is eliminated from thiosulphuric acid remains to be considered. Bassett and Durrant point out that when the known weakness of the second stage ionisation of sulphurous acid is considered in conjunction with the known tendency for sulphur to become co-ordinated with four atoms or groups, it would appear that the direct loss of sulphur by thiosulphuric acid is largely due to a hydrogen atom taking the place of the escaping sulphur atom, thus ... 

S-Donor ligands. As an extension of previous studies on related complexes of iron(n), cobalt(n), nickel(n), and zinc(n), the structure of Mn[SPPh2-N PPh2S]2 has been determined by X-ray methods. The metal atom is co-ordinated in an approximately tetrahedral manner by the four sulphur atoms. The two MnS2P2N rings adopt the twisted boat conformation with S and P atoms at the apices. The single-crystal electronic spectrum has been measured and interpreted.92... 

The addition of an aqueous solution of sodium diethyidithiocarbamate (Na-DDTC, cupral) (formula, 4.40) to a solution (at pH 4-11) containing small amounts of copper(II) ions produces a yellow-brown colour owing to a colloidal suspension of the sparingly-soluble copper 1 2 chelate with DDTC. The reagent co-ordinates with copper through the two sulphur atoms to form a chelate with four-membered rings, which is a rather rare configuration. Protective colloids (e.g., gum arabic) stabilize the pseudo-solution, and permit the spectrophotometric determination of copper. Cu (11) has been determined in aqueous solutions in the presence of surfactants [17],... 

Lead(ii)Pseudohalides. The crystal structure of the complex Pb(SCN)2,Cj2H2j-N2O4 shows that the lead ion lies in the plane of the four oxygen atoms, the two nitrogen atoms being on both sides. The co-ordination sphere of the lead is completed by the sulphur atoms of the NCS ions, one above and one below the ring. The lead thus has hexagonal-bipyramidal co-ordination. The... 

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