Carboranes:  A New Class of Weakly Coordinating Anions for Strong Electrophiles, Oxidants, and Superacids

Abstract

After postdoctoral studies at Stanford University he joined the faculty at USC in 1973. His current research interests include the chemistry of iron porphyrins, magnetochemical phenomena, fullerenes, carborane anions, and the chemistry of reactive cations and acids across the periodic table.

Synthesis and structure of the coordinatively unsaturated boron subphthalocyanine cation, [B(SubPc)]+

“…We have therefore targeted the synthesis of this cation using a very weakly coordinating counterion. A carborane anion, CHB 11 Me 5 Br 6 − , was chosen because of its inertness toward reactive main group cations and its excellent crystallizing properties [8]. Tetraphenylborate is known to be unsuitable as a weakly coordinating anion since the phenyl derivative (C 6 H 5 )B(SubPc) is formed when 4 ] is reacted with phthalonitrile [9].…”

“…Thus, we were interested in whether a "bare" B(SubPc) + borenium ion could be prepared and how strongly it would interact with the "least coordinating" anion [8]. Out-of-plane displacements of the central iron atom in iron porphyrin complexes have been used as a measure of the coordinating ability of axial ligands [10,11] so it was of interest whether a boron atom, in the naturally domed subphthalocyanine ligand, would respond similarly.…”

From nonpeptide toward noncarbon protease inhibitors: Metallacarboranes as specific and potent inhibitors of HIV protease

“…These properties are reflected in unique solution properties and ion-pairing behavior of this ion, which in turn led to its known applications in extraction chemistry (24,25) and in the development of lowest coordinating anions (26) and compounds for radioimaging (14). However, the metal bis(dicarbollides) have never been considered as biologically active compounds or pharmacophores.…”

Exploration of the pentacyano-cyclo-pentadienide ion, C5(CN)5−, as a weakly coordinating anion and potential superacid conjugate base. Silylation and protonation

“…Silylation also provides a method of assessing the Lewis basicity of the C 5 (CN) 5 2 anion using a ranking for weakly coordinating anions based on downfield 29 Si NMR shifts in i-Pr 3 Si(Anion) compounds. 2 The C 5 (CN) 5 2 anion was prepared in multigram quantities as a trimethylammonium salt from tetracyano-1,4-dithiin 10 5 ] which was characterized by elemental analysis, IR, 1 H and 13 C NMR, and X-ray crystallography. ‡ Reaction of this trityl salt with trialkylsilanes in toluene solution is fast and stoichiometric, giving silyl species, R 3 Si(C 5 (CN) 5 ).…”