Conversion of site-specific deuterated closo-1,2 and 1,7-C2B10H12 to deuterated nido-7,8-and 7,9-[C2B9H12](-) ions, respectively; mechanistic inferences. Comparisons of GIAO-NMR generated [C2B9H12](-) chemical shifts with experimental values, and consideration of two principal isomers of the 7,8-[C2B9H12](-) ion by comparison of geometry optimization data, NMR chemical shift data, and NMR coupling data to respective experimental data

Regioselective deuterated nido-[C2B9H12](-) ions were obtained from a fluor ide ion promoted debor reaction of deuterated closo-1,X-C2B10H12 (X = 2, 7) cage compounds. The position(s) of the deuterium atom(s) in the product, a s determined by NMR, were consistent with the prior suggestion that a boron neighboring both cage carbons in the starting material is the atom that is removed in this reaction. Ab-initio geometry optimized structures of the n ido systems were obtained and compared with available literature structures ; and ab-initio/NMR calculated data, as well as FPT-INDO calculational resu lts are compared with the experimental data for the two probable structures previously proposed for the 7,8- isomer of the nido-[C2B9H12](-) ion. Addi tionally, ab-initio/NMR calculations on geometry optimized structures were used to confirm B-11 NMR assignments. (C) 1999 Elsevier Science S.A. All ri ghts reserved.