Closo transition metal complexes

R 299 A. Sterzik, I. Maulana, S. Blaurock, P. Loennecke, E. Rys, V.N. Kalinin and E. Hey-Hawkins, Synthesis of Rac- and Meso-l,2-bis(tert-butyl-chlorophosphino)-1,2-dicarba-closo-dodecaborane( 12) and Transition-Metal Complexes Thereof, p. 85... 

Wade expanded the 1971 hypothesis to incorporate metal hydrocarbon 7T complexes, electron-rich aromatic ring systems, and aspects of transition metal cluster compounds [a parallel that had previously been noted by Corbett 19) for cationic bismuth clusters]. Rudolph and Pretzer chose to emphasize the redox nature of the closo, nido, and arachno interconversions within a given size framework, and based the attendant opening of the deltahedron after reduction (diagonally downward from left to right in Fig. 1) on first- and second-order Jahn-Teller distortions 115, 123). Rudolph and Pretzer have also successfully utilized the author s approach to predict the most stable configuration of SB9H9 (1-25) 115) and other thiaboranes. 

The formation of the bimetallic complexes 118-123 involves combination of di-cationic transition metal fragments with the dianion of compound 14. A further possibility exists, scarcely studied for 12-vertex closo-2,l-ReCBi0 species but more extensively exploited in the analogous 11-vertex closo- 1,2-MCBg system (M = Mn, Re) discussed in Section IV. Treatment of the dianion of 14 with two... 

As you become more familiar with transition metal clusters (no nonmetals in the framework) you will come to associate closo structures with numbers of electrons. A trimer will have 48 electrons, a tetrahedron will have 60 electrons, a trigonal bipyramid will have 72 electrons, and an octahedron will have 86. Some care is required, however, as can be illustrated with Os3H2(CO),o. An electron count gives us 46 electrons rather than 48. If, however, we allow for one Os—Os double bond, the electron count is as expected. In accord with this expectation, one osmium-osmium bond is found to be shorter than the other two and the complex shows the reactivity expected for an unsaturated complex. 

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