Sulfur ligands binary structures

Our knowledge concerning soluble metal complexes with sulfide ions as ligands has increased considerably during the last two decades and this kind of Compound is still of topical interest. Some of the reasons for this are the development of a very flexible and fascinating structural chemistry of multinuclear metal-sulfur complexes, the fact that the active sites of some electron transfer proteins contain metal ions and labile sulfur,41,42 and also the relation of metal-sulfur cluster compounds to some heterogeneous catalysts. In addition, apart from the numerous binary and ternary sulfides which occur in nature, we have at our disposal a rich solid state chemistry of metal sulfides, which has been reviewed elsewhere and will be excluded here.43"17... 

The important point to appreciate is that the formal valency of zinc is satisfied by two bonds to sulfur so that the additional interactions are indeed hypervalent interactions. Thus, the nature of the adopted structures arises from the ability of the central element to form hypervalent, or secondary, interactions and it is proposed that this ability is moderated by steric considerations associated with the alkyl substituents. As noted from the structural studies for the uncoordinated xanthate anions summarized earlier in Section II, there are no electronic differences among the xanthate ligands that can be correlated with the nature of the oxygen-bound substituent. This conclusion is vindicated by the homogeneity of the molecular structures of the binary nickel xanthates as... 

There are single examples of sulfur and selenium xanthates with the remaining structures to be described in this section featuring tellurium as the central element. There are a significant number of binary xanthates and, in common with these, their organotellurium xanthates feature extensive supra-molecular association, usually, but not exclusively, via Te- S secondary bond interactions. A rare example of mixed-ligand 1,1-dithiolate structure is available where the odd dithiolate ligand is a dithiocarbamate. 

A great variety of binary Mo-S complex anions is formed and can be isolated in reactions of the tetrathiomolybdate anion [MoS ] " with various suinde and polysulfide anions. The nature of the anionic products that can be isolated from these reactions depends on (a) the amount of excess sulfur used (and the types of ligands present in the reaction mixtures), (b) the type of counterion used in the isolation of the complex anions, and (c) the type of solvent employed in the synthetic procedure. In a recent article, we described a scheme that interrelates the various [Mo2(S),(S2)6-,] anions. In this scheme (Fig. 1), any of the six homologs can hypothetically be obtained from any other by either the addition of sulfur, or the abstraction of sulfur by triphenylphosphine. Experimentally, the correctness of this scheme has been verified by the successful synthesis of most of the [Mo2(S) (S2)6 ] complexes, or of their internal redox isomers. In the [Mo2(S), (82)6 series, the homologs with n = 4, 5, and 6 have been characterized structurally. Those with n = 2 and 3 have been characterized structurally as the internal-redox isomers, [(S4)Mo(S)(//-S)2(S)Mo S2)] (ref. 3) and... 

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