Carborane analogs of cyclopentadienyl-metal complexes

This extensive adjunct to organometallic chemistry will be briefly illustrated to show that the metal-ligand description is particularly appropriate. That is, although the compounds can certainly be considered as clusters, important aspects of their behavior are readily accommodated in the context of coordination chemistry. The discussion will be limited to [C2B4Fl6]2 and [C2B9H11]2- analogs of the [Cp] ligand. 

Exercise 4.6. Test the compounds [(C2B9Hn)2Co] and [(C2B9Hn)2Ni]2 for electronic saturation both as metallocenes and as vertex-fused clusters. 

Answer. It is perhaps easier to let all the ligands remain neutral rather than trying to calculate metal oxidation states 8 CO + MeC + C2Me2B9H9 + 2 B-Fe bonds + W + 2 Fe + charge =16 + 3 + 4 + 2 + 6 +16 + 1= 48. 

How many different neutral square-pyramidal cluster compounds can you synthesize on paper using the isolobal principle, the cluster electron-counting rules, and SiH and CpRh fragments only. 

Analyze the bonding of the following two molecules. On the basis of your analysis, account for the fact that the compound containing a single Cr atom absorbs at 27 930 cur1 whereas the one with two Cr atoms absorbs at 16 070 cur1. 

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