Bridging ligands electron counting

Mathematical cluster chemistry/Metal-metal interactions in transition metal clusters with donor ligands/Electron count versus structural arrangement in clusters based on a cubic transition metal core with bridging Main Group elements/Metalloboranes/ Clusters with interstitial atoms from the p-block How do Wade s rules handle them /Diverse naked clusters of the heavy Main Group elements Electronic regularities and analogies... 

Halet )-F, Saillard )-Y (1997) Electron Count Versus Structural Arrangement in Clusters Based on a Cubic Transition Metal Core with Bridging Main Group Elements. 87 81-110 Hall DI, Ling JH, Nyholm RS (1973) Metal Complexes of Chelating Olefin-Group V Ligands. 15 3-51... 

Many organometallic complexes are clusters involving multiple metals that feature metal-metal bonds. The electrons in Me-Me bonds are counted by contributing one electron to each metal connected. Bridging ligands contribute one-half of their electrons to each metal center. Some simple examples in Figure 1.9 illustrate application of the rules. 

The molecular structure of the manganese dimer clearly reveals that there is an Mn—Mn bond (Fig. I5.la. b). In the cobalt structure, two of the CO ligands are bridging, i.e.. they are simultaneously bound to both Co atoms (Fig. IS.Ic, d). This does not affect the electron count, however, because CO and other neutral ligands donate two electrons to a complex whether they are terminal or bridging (Table IS. I) ... 

Whereas in ligand bridged dinuclear complexes, removal or addition of two electrons makes or breaks one metal-metal bond (15) this does not seem to be the case for clusters, presumably because of their delocalized bonding. At least for one case, however, two-electron reduction can induce a significant change in cluster shape (18,42) the 84-electron cluster Os6(CO),g with framework 1 is easily reduced to the 86-electron anion Os6(CO) g with framework 2, in accordance with skeletal electron counting rules. 

Electron-beam heating, in metal vapor synthesis, 1, 232 Electron-beam vaporization, in metal vapor synthesis, 1, 224 Electron correlation, and computational chemistry, 1, 642 Electron counting, in transition metal complexes bridging ligands, 1, 14 examples, 1, 9 ligand electrons, 1, 5/... 

Carbyne ligands may bridge two (p) or three (p3) metal centres, providing a total of 3VE to the overall electron count. Earlier synthetic routes to such complexes involved the reactions of carbonyl metallates with 1,1,1-trihaloalkanes, or the cleavage of alkyne ligands coordinated to clusters (Figure 5.46). 

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