Fluorination of deltahedral closo-borane and -carborane anions with N-fluoro reagents

The treatment of cesium salts of CB11H12-, CB9H10-, B12H2-, and B10H102- with the commercially available N-fluoro reagent 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)(F-TEDA) resulted in the formation of fluorinated derivatives of these 10- and 12-vertex borane and carborane anions. This is the first reported use of an N-fluoro reagent to fluorinate B-H bonds of any type. The effects of changing the solvent, temperature, and reagent stoichiometry were studied. The derivatives 1-B10H9F2-, 2-B10H9F2-, and 1,10-B10H8F22- are the first fluorinated derivatives of the parent B10H102- cluster. For the other three parent anions, reactions with F-TEDA resulted in a higher degree of fluorination than reactions with liquid anhydrous hydrogen fluoride (LAHF) at the same temperature. However, F-TEDA was found to be less regioselective than LAHF for B-H --> B-F transformations. (C) 1998 Elsevier Science S.A. All rights reserved.