Rhenium mixed-metal clusters

Mixed-metal clusters that contain rhenium, e.g. the phase Mol sRe4 5Se8, can also be prepared by direct reaction of the elements. They contain the octahedral (Mo,Re)6 cluster.203... 

F, 1 NMR studies on the dynamic behaviour in solution of rhenium-platinum mixed metal clusters containing P-donor ligands... 

The bimetalhc rhenium thiolato complex Re2(p-S2NC7H4)2(CO)e has been reacted with trimetallic group 8 carbonyl clusters M3(CO)i2 (M = Fe, Ru) and Os3(CO)io(NCMe) to give the mixed-metal clusters 49-51. Reaction of 50 (M = Os) with PPhs results in mono- and bis-substitution,... 

We discuss here two examples of vibronic effects in polynuclear highly symmetrical transition metal clusters. The existence of degenerate and quasi-degenerate molecular orbitals in their energy spectra results in the Jahn-Teller effect or in the vibronic mixing of different electronic states. We show that both quantum-chemical methods and model approaches can provide valuable information about these vibronic effects. In the case of the hexanuclear rhenium tri-anion, the Jahn-Teller effect is responsible for the experimentally observed tetragonal distortion of the cluster. The vibronic model of mixed-valence compounds allows to explain the nature of a transient in the photo-catalytic reaction of the decatungstate cluster. 

Metal carbonyl clusters are also numerous. In addition to dinuclear carbonyls such as M2(CO)io (M = Mn, Tc, Re), many hydrido clusters and ionic species exist which contain three or more metal atoms [M3H3(CO)i2] (M = Mn, Tc, Re), Mn3(CO)i (linear compound, 1)4 ), and Re3(/i-H)(CO)i4 (the Re —Re —Re angle is 90°). Rhenium forms a number of tetranuclear compounds. Some of them have a butterfly structure while others adopt a triangle of rhenium atoms with one Re attached to it Re4(/i3-H)4(CO)i2, [(Re4( -H)4(CO)i3] , [Re4( -H)6(CO)i4], and [Re4(CO)i6]. Rhenium also forms mixed metal carbonyls possessing several metal atoms (Table 3.14). There are numerous clusters of the group 7 metals containing cyclopentadienyl groups, ... 

A somewhat different situation is presented by the pressure effects seen in the emission spectra of the rhenium(I) complex ReBr(CO)3(phen) and the copper(I) cluster Cu4I4py4 (where py = pyridine) and related species. The former displays strong MLCT emission in ambient temperature fluid benzene [35] solutions while the latter displays a strong emission from an cluster centered (CC) excited state assigned as having mixed d-to-s metal-centered and iodide-to-copper charge-transfer character [36]. In each case, the emission is markedly dependent on the rigidity of the medium, and... 

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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