Disulfido-ligands

Disiloxane, tetramesityl-, 3,206 Disproportionation iridium catalysts, 4,1159 Dissolution nuclear fuels, 6, 927 Distannene, 3,217 Distannoxane, 1,3-dichloro-, 3,207 Distibine, tetraphenyl-, 2,1008 Distibines, 2,1008 Disulfido ligands metal complexes, 2,531-540, 553 bonding, 2, 539 electron transfer, 2, 537 intramolecular redox reactions, 2,537 reactions, 2, 537... 

Disulfido ligands of structure type lb also exist in the interesting compound (NH4 )4 [Mo4 (N0)4 (S2 )5 S3 ] 2H2 O (11), which contains sulfur atoms in five different bonding situations. Four of the five S2 ligands unsymmetrically bridge pairs of Mo atoms (structure type lb). One S ligand is side-on coordinated to a single Mo atom (structure type la). 

In [Cp2Cr2S(S2)2] (40) two Cr atoms are bridged by a type III disulfido ligand, by a sulfido group and by a type IV ligand. This compound is the first example of type IV ligand. Both the type III and type IV S—S distances are unusually long (2.15 and 2.10 A, respectively). 

High coordination numbers of the metal atom are favored for type I and type III structures by the small coordination angle of bidentate disulfido ligand. High coordination numbers also protect the metal center from nucleophilic attack, an important factor in stabilizing metal-metal bonds. 

M—S distances are similar to those for metal complexes of other simple sulfur-containing ligands. Ligands of types la and III exhibit slightly asymmetric M—S distances. This inequality is usually 0.03-0.04 A however, it can be as large as 0.06-0.08 A in complexes which contain structual units such as (42) in which the sulfur atoms from two different disulfido ligands are approximately trans to one another. 

The frequencies of the type III bridging disulfido ligands are generally higher than those for type I structures. 

Guerchais and co-workers (43) recently found that irradiation of NbCp2( 17 -82)0113 does not result in the expulsion of the disulfido ligand but rather in the low-yield formation of the monosulfido methyl complex 39 [Eq. (54)]. No further details were provided. 

The number of well-defined metal complexes containing terminal sulfido or disulfido ligands is rather limited [1, 2], their syntheses are seldom simple and the compounds may be highly unstable in solution. Although these features may have precluded reactivity studies, and thus further attempts to model HDS-related reactions, it is very likely that other examples will become available in the near future particularly welcome would be some advances in the reactions of hydrogen with e.g. Mo or Co complexes containing such sulfur ligands, as well as studies of the reactions of M(H)(SH) and M(SH)2 complexes with thiophenes and other related molecules. 

Mixed-metal sulfido cluster complexes have attracted attention because of their application in catalysis." Although disulfido ligands exhibit great versatility as bridging ligands, dinuclear metal disulfides are still relatively rare. We have synthesized the new dimanganese disulfide complex, Mn2(CO)7(p-S2). ... 

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