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

Abstract

Among the polyhedral [closo-BnHn]2- ion series (n = 5-12 inclusive) the aromatic [closo-B10H10]2- ion is both readily available and quite reactive. Among its many reactions which retain its cage structure one finds the oxidative dimerization reaction in which two [closo-B10H12]2- ions each formally lose a hydride ion and undergo dimerization of the resulting [closo-B10H9]- ions to produce the [trans-B20H18]2- ion. The two-component [closo-B10H9]- ions of the latter are linked together by a pair of unique B-B-B bonds which provide unprecedented reactivity to the structure. Among these reactions are the two-electron reduction to a set of three interconvertible [B20H18]4- ions having intercage B-B bonds and the related reductive substitution reaction in which [trans-B20H18]2- undergoes attack by nucleophile, L, to produce [B20H18L]2-. The latter species is formally a substituted [B20H19]3- (L = H) ion formed by B-B bond protonation of one of the isomeric [B20H18]4- ions. These and a variety of novel reactions are described here along with interrelated reaction mechanisms considered for the first time.

Boron neutron capture therapy demonstrated in mice bearing EMT6 tumors following selective delivery of boron by rationally designed liposomes

“…Evidence suggests that the persistence of TAC in the tumor is a result of covalent bond formation with nucleophiles present on endogenous intracellular proteins (21)(22)(23)(24)(25)(26)(27) (Fig. 1 − (25)(26)(27), which is readily produced in oxidizing environments like those often possessed by tumor cell interiors (28,29). Experiments have provided spectroscopic and crystallographic confirmation that binding occurs on the unsubstitued boron cage (26), although other isomers are possible, and all would serve to prolong confinement of TAC to the intracellular medium.…”

Geometric, Spectroscopic, and Magnetic Characteristics of [Tris(1,10-phenanthroline)manganese](2+) 1,2;1′,2′-trans-Bis[nonahydro-closo-decaborate](2−) Bis(dimethylformamide)

“…Here we report on a compound containing the 1,2;1`,2`-trans-bis-[nonahydro-closo-decaborate] (23) anion, [B 20 H 18 ] 2! , belonging to the scope of chemistry of macropolyhedral clusters [3,4]. Active studies of the synthetic potential of this anion and its derivatives were initiated in the 1990s within the framework of a search for boron-containing materials suitable for neutron chemotherapy of cancer.…”

closo‐[B21H18]− – ein flächenverknüpftes diikosaedrisches Borat‐Ion

“…[9] Unseres Wissens sind bislang keinerlei ecken-, kanten-oder flächenverknüpfte closo-Borat-Ionen bekannt. Es gibt jedoch ein closo-Boran mit der Formel B 20 H 16 , bei dem sich zwei B 12 -Ikosaeder vier Boratome teilen.…”

“…Das bislang nur theoretisch untersuchte closo-[B 21 H 18 ] À -Ion [24] -Ion verknüpft. [9] Über das trans-Isomer hinaus wurden zwei weitere, weniger stabile Isomere beschrieben, deren Strukturen in Abbildung 1 wiedergegeben sind. [9] 2À handelt (Abbildung 1).…”

“…[9] Über das trans-Isomer hinaus wurden zwei weitere, weniger stabile Isomere beschrieben, deren Strukturen in Abbildung 1 wiedergegeben sind. [9] 2À handelt (Abbildung 1). [32] Borane und Borate mit dem flächenverknüpften {B 20 }-Gerüst wurden auch durch Reaktionen von B 20 H 16 mit LewisBasen erhalten, [10,11,33] und der neuen fac-Spezies (B3LYP/6-311 + + G(d,p)).…”