Fluoride-ion deboronation of p-fluorophenyl- ortho- and - meta-carboranes. NMR evidence for the new fluoroborate, HOBHF 2−

Abstract

The reactions of 1-(4-fluorophenyl)-1,2-dicarbadodecaborane(12) 1 and 1-(4-fluorophenyl)-1,7-dicarbadodecaborane(12) 2 with tetrabutylammonium fluoride hydrate in tetrahydrofuran or acetonitrile have been monitored by 19F and 11B NMR. No carborane intermediates were observed prior to formation of the nido- anions 7-(4-FC 6H 4)-7,8-C 2B 9H 11 − 3 and 7-(4-FC 6H 4)-7,9-C 2B 9H 11 − 4 which each required two molecular proportions of fluoride and, by inference, one of water for complete reaction. The spectra of the initial anionic monoboron product of both reactions showed it to be the new fluoroborate HOBHF 2 − 5. The B-attached hydrogen atom of the fluoroborate 5 is derived from the starting carborane, since it was retained when Bu 4NF·(D 2O) n was used, but the nido-anions 3 and 4 bonded deuterium at the open face in this experiment. The 1H, 11B, 19F and 13C NMR spectra of carboranes 1–4 have been recorded and assigned.