Cluster complexes tellurium

Examples of other interesting additions (225) across the Rh=Rh bond include complexes of S02 (96 ) (225,230,231), selenium (97 ) (225,232), tellurium (225), sulfur (225,233), and AuCl [from AuCl(CO)] (225,230). The latter reaction results in a Rh2Au triangle and is just one of a large number of heteropolymetallic cluster complexes built up from 4 and 5 (see below). 

Table 26.4 (continued) BDEs in Tellurium Clusters/Complexes... 

Within this context, the present article concentrates on transition metal cluster complexes of cobalt, iron and manganese with mixed chalcogen/carbonyl ligand spheres obtained by reaction of simple binary metal carbonyls with alkali-metal sulfides, alkali-metal thiolates or transition-metal thiolate complexes and their selenium or tellurium counterparts. 

In common with transition and other metals (Chapter 8), tellurium will form cluster complexes such as... 

Iron-sulfur-nitrosyl complexes (continued) from tetranuclear precursors, 32 343 tellurium analogs, 32 350 tetrairon complexes, N NMR spectroscopy, 32 365 x-ray crystallography [Fe(NO)(S2CNR2)2 and related clusters, 32 359-361... 

Dahl (175). The basic structure is defined by an octahedral core with trans-tellurium atoms and is isoelectronic with the ruthenium complex 183. Both clusters may also be compared with the ruthenium and osmium bismuth complexes, 125 and 129, which, although octahedral, contain two less electrons. A complex containing an additional carbonyl group, viz. [Te2Co4(CO)u], 185, has been described by Rauchfuss (172) as resulting from the reaction... 

It is evident from the above table that a considerable spread of chemical shift values is observed in tellurium-transition metal complexes, but the factors that determine the chemical shift are still poorly understood and data are not available for all known structural types. The most extensive compilations of data have been provided by Rauchfuss (187) and Herrmann (191), with the point being made in the former reference that chemical shifts are extremely sensitive to changes in cluster geometry. In principle, 12sTe NMR spectroscopy is a valuable method for studying tellurium-transition metal clusters in solution, but it is clear that more data are required before unambiguous structural assignments can be inferred. 

The situation close to that described above for sulfur is characteristic for the chal-cogenide elements. Atomic selenium [1,26,82-86] and tellurium [86] are part of di-, tri-, and polynuclear clusters, while diatomic molecules of these elements, when acting as ligands, have mostly a bridge function 52. Examples of di- and trinuclear monochalcogenide compounds are the complexes 53 and 54 [82-85] ... 

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