Chlorination of 1-Carba-closo-dodecaborate and 1-Ammonio-closo-dodecaborate Anions

Abstract

Fully chlorinated carborate and dodecaborate cages such as [CHBCl] and [MeNBCl] are prominent examples of valuable and chemically rather inert weakly coordinating anions. While both anions can be obtained by chlorination of the precursors [CHB] and [HNBH] with SOCl followed by methylation for the synthesis of [MeNBCl], best results were found using photochemical chlorination with SOCl for [CHB] and thermal chlorination with SOCl for [HNBH]. The hexachlorinated anion [n-PrNBHCl] was formed readily within 30 min by chlorination of [n-PrNBH], but attempts to synthesize isopropyl-substituted ammonio-dodecaborates with a higher chlorination number resulted in the formation of mixtures and partial decomposition. The silver and trityl salts of the anions [CHBCl], [MeNBCl], and [n-PrNBHCl] as well as the contact ion-pair [EtAl][MeNBCl] were also prepared, and the compounds [Ag(NCMe)][MeNBCl], [EtAl][MeNBCl], and [EtN][i-PrNBHCl] were also characterized by X-ray crystallography.

Taming the Cationic Beast: Novel Developments in the Synthesis and Application of Weakly Coordinating Anions

“…Li [113] R = HX= Cl: K [114] R = Me X = Cl: Na [114] R = Me X = Cl: Ag [115] R = Me X = Cl: NO [114] R = Me X = F:…”

“…[Ph 3 C] [114,115] R = Me X = F: Me [113] ; R = HX= F: Bu [113] R = Me X = Cl: Bu [114] R = HX= Cl: Et [115] R = nPr X = Cl: Et [115] [E(SO 2 R F ) n ] À (with E = N or C)…”

“…[103,105,106] Although being dianionic makes them unusual as WCAs, the [B 12 X 12 ] 2À closoborates (X = ForCl) have been shown to form highly potent Brønsted acids, [107] in addition to being stable against highly electrophilic silylium ions [105,108] and Group 13 dialkyl cations. [113][114][115] Thei ncorporation of the ammonium group reduces the overall charge to À1, thereby reducing lattice enthalpies and improving solubility compared to the parent dianionic [B 12 X 12 ] 2À closo-borates.T heir performance as WCAsh as seen [R 3 N-B 12 X 11 ] À ions employed in the formation of [Ph 3 C] + and [AlEt 2 ] + ions as well as in gold(I) catalysis. [110][111][112] Replacement of ah alogen atom in [B 12 X 12 ] 2À ions for an ammonium group and subsequent alkylation gives rise to the related monoanions of the type [R 3 N-B 12 X 11 ] À (R = alkyl;X= Fo rC l).…”

“…[110][111][112] Replacement of ah alogen atom in [B 12 X 12 ] 2À ions for an ammonium group and subsequent alkylation gives rise to the related monoanions of the type [R 3 N-B 12 X 11 ] À (R = alkyl;X= Fo rC l). [113][114][115] Thei ncorporation of the ammonium group reduces the overall charge to À1, thereby reducing lattice enthalpies and improving solubility compared to the parent dianionic [B 12 X 12 ] 2À closo-borates.T heir performance as WCAsh as seen [R 3 N-B 12 X 11 ] À ions employed in the formation of [Ph 3 C] + and [AlEt 2 ] + ions as well as in gold(I) catalysis. [116,117] Furthermore,t he use of the radical species Me 3 N-B 12 Cl 11 C as ap otent oxidant of species with high oxidation potentials has also recently been reported.…”

Silver Salts of the Weakly Coordinating Anion [Me3NB12Cl11]–

“…Recently, the chlorinated closo ‐dodecaborate anion [Me 3 NB 12 Cl 11 ] – was established as a new weakly coordinating anion, which is easily accessible and mimics the properties of the chlorinated 1‐carba‐ closo ‐dodecaborate(–) , , . Wehmschulte et al described the preparation of its silver(I) salt and its crystal structure with acetonitrile as coordinated ligand . In this work, we present the synthesis of Ag[Me 3 NB 12 Cl 11 ] on a 5 g scale.…”