Osmium sulfur ligands

Apparently, soft sulfur ligands alone cannot stabilize Ru or Os . The existing thioether, thiolato, and sulfide complexes of ruthenium(VI) and osmium(VI) are associated with either the 0x0 or the nitrido ligand and they have been discussed in the previous sections. 

Some four-electron capping units enter as such. This is the case for the many reactions forming/t3-sulfur ligands from elemental sulfur (103). It also holds for the triruthenium /i3-nitrene cluster 45, formed from Me3SiN3 and Ru3(CO)i2 (104). A versatile four-electron ligand is the acetylene moiety, which can add facially to M3 units as a two-center capping group, as found in the clusters 46, which can be obtained from trinuclear carbonyls of iron, ruthenium, and osmium (105, 106). 

Although there are areas of osmium-sulfur chemistry where recent and interesting work has been done (e.g. on dithio- and trithio-carbamates), there is also much poor work, often with complicated ligands where little more than the stoichiometry of the complex —and sometimes less—has been established. Much work remains to be done on the osmium chemistry of simple thio (and seleno) ligands. 

The reaction of an osmium carbene cluster containing the cyclic carbene ligand = C(CH=CH)2C(Ph)H which is side on bound to a nonacarbo-nyltriosmium unit with either elemental sulfur/NEt3 or cyclohexene sulfide also afforded a rf-thioketone complex.184... 

NMR all three osmium atoms are chemically equivalent (200). This may involve changing the bridging sulfur atom from a four-electron donor to a two-electron donor in order to gain a third Os-Os bond and an equilateral metal triangle. These ligand induced cluster rearrangements are a further demonstration of metal-metal bond weakness as the reason for cluster mobility. For application-oriented purposes they may be the most important ones. 

A related process has been reported for the synthesis of osmium nitrido complexes with 1,2-benzenedithiolate ligands. Thus, the synthesis of 173 was effected by treatment of (Bu4N)[OsNC14] with deprotonated 1,2-benzenedithiol (Eq. (70)). Interestingly, when 173 is treated with Me3OBF4 alkylation is observed to occur on the sulfur this contrasts the reaction of 173 with Ph3CPF6, for which reaction at the terminal nitride is observed [93]. 

Roper spearheaded the research on coordinated thioaldehydes. In 1977 he established the nucleophilicity of the ligand in an osmium complex (441) which can easily be alkylated at the sulfur atom to give 442. Acidification, however, yields first a methanethiolate complex (443) and eventually liberates methanethiol (263). 

The osmium carbyne complex 115 reacts with elemental sulfur, selenium, and tellurium to afford the complexes 135 in which the element atoms "bridge the metal-carbon triple bond [Eq. (123)] (56). Complex 115 also reacts with transition metal Lewis acids such as AgCl or Cul to give dinuclear compounds with bridging carbyne ligands. Reaction with elemental chlorine results in addition across the metal-carbon triple bond to generate the chlorocarbene osmium complex 136 [Eq. (124)]. 

Rhenium complex (46) is also known to add H2 and N2 <81CC451> to the metal center. Ruthenium complex (47) and osmium complex (48) add sulfur to give complexes with unusual S6 2 ligands <84AG(E)814>. 

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