Bridging ligands cyclopentadienyl

Alike metallocomplex anion-radicals, cation-radicals of odd-electron structure exhibit enforced reactivity. Thus, the 17-electron cyclopentadienyl dicarbonyl cobalt cation-radical [CoCp(CO)2] undergoes an unusual organometallic chemical reaction with the neutral parent complex. The reaction leads to [Co2Cp2(CO)4]. This dimeric cation-radical contains a metal-metal bond unsupported by bridging ligands. The Co—Co bond happens to be robust and persists in all further transformations of the binuclear cation-radical (Nafady et al. 2006). 

Novel Types of Metal-Metal Bonded Complexes Containing Allyl and Cyclopentadienyl Bridging Ligands, 19, 155... 

Scheme 6.6 Preparation of the FeRu and Ru2 triple-decker sandwiches 13 and 14 containing a bridging unsubstituted cyclopentadienyl ligand...

The bridging chloride ligands in these [Ir(olefin)2Cl]2 compounds are susceptible to metathesis reactions, yielding new dimeric compounds of the form [Ir(olefin)2B]2 where B represents a new bridging ligand. AUcoxides, thiolates, and carboxylates have all been employed successfully in the replacement of chloride. The complexes with B = Br, I have also been prepared, both by metathesis reactions and by direct reaction of cyclooctene or cyclooctadiene with IrBrs or Iris The olefin complexes also provide excellent starting materials for the syntheses of arene and cyclopentadienyl iridium complexes, a subject that will be discussed in the next section. 

Treatment of 7 with DMD leads to the short-lived bis-silanol A. However, this intermediate undergoes intramolecular condensation, resulting immediately in the formation of the tungsten complex 8 bearing a disiloxane unit bridging the cyclopentadienyl ligand and the metal center. 8 is... 

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