The Reaction of the B₂₀H₁₈^-2 Ion with Hydroxide Ion

The versatile chemistry of the [B20H18]2– ions: novel reactions and structural motifs

“…While the bonding in this closo dianion is delocalized and aromatic, [closo-B 10 H 10 ] 22 is more reactive than the icosahedral [closo-B 12 H 12 ] 22 in electrophilic substitution reactions 8 due to its reduced symmetry relative to that of the latter. This same difference in reactivities prevails when these two dianions are subjected to oxidation reactions with simple reagents such as Ce 4+ or Fe 3+ in aqueous acid solution; [closo-B 12 H 12 ] 22 is unreactive 9 while [closo-B 10 H 10 ] 22 undergoes [10][11][12] smooth oxidative conversion to [trans-B 20 H 18 ] 22 , trans-1. This oxidative dimerization reaction proceeds in virtually quantitative yield with Fe 3+ as the oxidant [Scheme 1 and eqn.…”

“…These species have been observed and the pK a of the labile proton estimated to be in the 6-7 range by potentiometric titrations. 11,23 The 11 B NMR spectra of these protonated species usually display complexity which has been attributed to facile proton exchange and isomer interconversion in polar or protic solvents, and the fluxionality of the bridging proton as it tautomerizes between the intercage B-B s bond and adjacent sites having high electron density. 25 Although protonation is a common occurrence for derivatives of 2, the potential formation and rapid equilibration of isomers, as well as the higher solubility of species of type 3 compared to those of type 2, has made the isomeric 3 ions difficult to isolate and characterize in stereochemically pure form.…”

“…Proton loss from the B-H-B bridge of the latter species to produce a two-center, two-electron bond provides the substituted 2 isomer commonly observed. These so-called reductive substitution reactions were immediately recognized 10,12 following the discovery of trans-1.…”

Investigation of the interactions of polyhedral borane anions with serum albumins

“…The structure of the anion is characterized by an electron-deficient, three-center, two-electron bonding region. Reactions with nucleophiles, such as [OH] À [33,34] [22][23][24][25][26][27][28].…”

“…, [OR] À[33,34] and[NH 2 ] À[23], have been reported. Nucleophilic attack by protein substituents would result in the covalent binding of the polyhedral borane anion in the interior of a tumor cell.…”