Planar compounds sulfides

A number of relevant review articles have appeared. Their subjects include the chemistry of antitumor platinum complexes, complexes of platinum metals with weak donor ligands, and transition metal complexes of sulfide, selenide, and telluride ligands (which includes much material on square-planar compounds). A review by Chanon and Tobe " on electron transfer catalysis relates to many reaction types, including ligand replacements at square planes. 

The copper(I) ion, electronic stmcture [Ar]3t/ , is diamagnetic and colorless. Certain compounds such as cuprous oxide [1317-39-1] or cuprous sulfide [22205-45 ] are iatensely colored, however, because of metal-to-ligand charge-transfer bands. Copper(I) is isoelectronic with ziac(II) and has similar stereochemistry. The preferred configuration is tetrahedral. Liaear and trigonal planar stmctures are not uncommon, ia part because the stereochemistry about the metal is determined by steric as well as electronic requirements of the ligands (see Coordination compounds). 

Beck et al. discovered that there were two polymorphs of the carbon-sulfide compound C(yS8 20 a previously discovered planar polymorph, a, and a V-shaped polymorph, / , with the central dithiin ring angled at 133° about the C-S-C bonds <2005NJC465>. 

Biological oxidation of sulfides involves cytochromes P-450 or flavin-dependent oxygenases. A chiral flavin model was prepared by Shinkai etal. and used as the catalyst in the oxidation of aryl methyl sulfides [87]. Flavinophane 30 (Scheme 6C.10) is a compound with planar chirality. It catalyzes the oxidation of sulfides with 35% H202 in aqueous methanol at -20°C in the dark. 

In many cyclic aromatic compounds an element other than carbon (commonly N, O, or S) is also present in the ring. These compounds are called heterocycles. Figure 14.2.3 shows some nitrogen heterocycles commonly used as ligands, as well as planar, sunflower-like octathio[8]circulene, C Ss, which can be regarded as a novel form of carbon sulfide. 

The almost-planar o ,/3-isomer 105, with lowest symmetry and whose crystal structure was determined, is one of the four possible isomers (compounds 107-109 being the rest) of carbon sulfides of the formula C4S6. 

In the noncyclic compounds for which structural data are available, a dihedral angle of about 90° occurs between the planes of the valencies of adjacent sulfur atoms. Reported values lie between 74° in cesium hexa-sulfide (3) and 108° in barium pentathionates (119). In six- and particularly in five-membered cyclic disulfides, the angle is smaller, and may for steric reasons also become larger, but planar, tram groups with 180° dihedral angle have not been observed. 

From the reaction of divalent, first-row hexaaqua transition metal ions and MS4 (M = Mo, W), [Co(MS4)2] and [Ni(MS4)2] can be isolated, typically as quaternary phosphonium salts. The [MS4] ions act as bidentate ligands to the divalent metal ion, but the coordination geometries are different - tetrahedral for Co and square planar for Ni. These compounds model, in a structurally well-defined way, sulfide-bridged Co-Mo and Ni-Mo interactions and may serve as references for such interactions in CoMoS and NiMoS phases. 

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