Rhenium complexes trinuclear

Earlier, Herrmann et al. (1976 a, 1976 b) found that the mononuclear (pentacar-bonyl)(hydrido)manganese complex 10.74 forms a 10 1 mixture of the di- and trinuclear complexes 10.75 and 10.76 with diazomethane, if the reagents are mixed in THF at - 85 °C and the system is allowed to reach room temperature (10-34). In the same reaction with the analogous rhenium complex, only the binuclear complex... 

Penta- and hexanuclear clusters of the metals osmium and ruthenium coordinate with the same r ri ri - binding mode as the trinuclear clusters to CgQ. Such complexes are known for the clusters OsjC [75,76], RU5C [77-79], RugC [78], PtRu5C [77] and Rhg [80], In this collection of metal clusters rhenium plays a special role, because it forms a new fullerene-metal sandwich complex, where two C50 are bound to one cluster. 

Unlike most metal complexes containing the fa c-(diim i n c) Re1 (CO). unit, which are typically highly luminescent in solution, trinuclear rhenium carbonyl compounds 7 and 8 (see Fig. 11a) show only weak luminescence ( em = 0.0015) in CH3CN at room temperature [36], The quenching appears to occur via intramolecular... 

Fig. 11 (a) Trinuclear rhenium carbonyl complexes 7 and 8 and (b) UV-Vis difference spectra (Aabs = At - At = 0) of compound 7 in CH3CN at 293 K after irradiation at 366 nm for 0, 1,2, 3, 4, 6 h, and inset shows the emission spectral changes before and after photolysis (reproduced with permission from [39])... 

Rhenium occupies a very important place in the development of the chemistry of complexes containing metal metal double, triple and quadruple bonds. This chemistry involves coordination complexes that contain pairs or trinuclear clusters of rhenium atoms and has been surveyed in a recent monograph entitled Multiple Bonds Between Metal Atoms .5 This source, which covers the literature up to early 1981, has also been invaluable in preparing the present review and can be consulted for a more complete and detailed coverage of these classes of complexes. 

The trinuclear rhenium(III) halides Re3X9 (X = Cl, Br or I), and the mixed halides Re3X9 Y (e.g. Re3Cl3Br6), contain Re—Re double bonds174 and are the precursors to an extensive class of coordination complexes that are formed by the addition of up to three ligands to the available... 

It is in this oxidation state that the known chemistry of the two elements is most different. For rhenium di- and trinuclear cluster species predominate (Section 18-D-5), whereas for Tc there are only a few Tc and no Tc3+ complexes. Mononuclear Tc3+ species do occur. The only simple [MXJ3- complex known for either element is the [Tc(NCS)6]3 ion, but the mer-MCl3(PR3)3, MCl3py3, and [MX2(LL)2]+ complexes with X = halide, NCS , or MeS" and LL a diphosphine or diarsine are important.41 Some of these complexes can be reduced with retention of structure in the II and even I oxidation states.42... 

A number of complexes can be derived from the trinuclear and dinuclear rhenium(m) halides and halo complexes (page 979) with retention of the Re3 and Re2 units. 

Re(CO)3(/t-OCH3)3Re(CO)3] (64) whereas decreasing pressure favoured production of rhenium clusters of higher nuclearity with mixed (/t-oxo)- and (/r-methanolato) bridges. The presence of 1.33 equivalent of base per metal atom in the clusters 44 and 44b facilitates subsequent reactions, that demand base. The reaction of 44 with (HCsMes), for example, resulted in the quantitative formation of 45 [79], In the case of the trinuclear rhenium cluster 44b, reaction with the caibene precursor 1,1 -methylene-bis(3-methyl-1 //-imidazolium)-diiodide yielded the corresponding mononuclear Re(I) complex (65) with the bidentate caibene ligand (see Scheme 14) [80]. 

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