closo‐[B₂₁H₁₈]⁻: A Face‐Fused Diicosahedral Borate Ion

Abstract

Siamese borates: Syntheses are described for salts of the closo‐[B21H18]− and fac‐[B20H18]2− ions. The [B21H18]− ion is the first example of a singly charged closo‐borate ion in which two icosahedral fragments are fused together such that they have a common face. The synthesis of novel weakly coordinating anions based on these frameworks is thus within reach.

Solid‐State Reactions of Eicosaborate [B20H18]2− Salts and Complexes

“…X-ray crystallography confirmed that crystal parameters of obtained single crystals of 2c coincide with those of complex {Ag 2 (Ph 3 P) 6 [iso-B 20 H 18 ]} reported in Ref. [26][27][28];a nd their relative energies estimated with B3LYP/6-311 ++G(d,p). [26][27][28];a nd their relative energies estimated with B3LYP/6-311 ++G(d,p).…”

“…[28] that was obtained in the course of single-crystal-to-single-crystal photocontrolled isomerism under UV radiation of crystal 1c,o rs yn-Scheme1.Isomerization reactionso fknown [B 20 H 18 ] 2À isomers as described at refs. [27] Scheme2.Synthesis of complexes 1c-1e, 2c.C onditions: i)[HNEt 3 ] 2 [trans-B 20 H 18 ]( 1equiv), AgNO 3 (2 equiv), PPh 3 (4 or 6equiv),D MF or [Ag(Ph 3 P) 3 11 BNMR spectra,n os ignals corresponding to the iso-form of the boron clusterw ere detected after 3m onths of their standing in air.I ti sc lear that presence of silver(I) and Ph 3 Pi sn eeded for preparation and isolation of the iso-form of the macropolyhedron. [27] Scheme2.Synthesis of complexes 1c-1e, 2c.C onditions: i)[HNEt 3 ] 2 [trans-B 20 H 18 ]( 1equiv), AgNO 3 (2 equiv), PPh 3 (4 or 6equiv),D MF or [Ag(Ph 3 P) 3 11 BNMR spectra,n os ignals corresponding to the iso-form of the boron clusterw ere detected after 3m onths of their standing in air.I ti sc lear that presence of silver(I) and Ph 3 Pi sn eeded for preparation and isolation of the iso-form of the macropolyhedron.…”

“…[28] that was obtained in the course of single-crystal-to-single-crystal photocontrolled isomerism under UV radiation of crystal 1c,o rs yn-Scheme1.Isomerization reactionso fknown [B 20 H 18 ] 2À isomers as described at refs. [26][27][28];a nd their relative energies estimated with B3LYP/6-311 ++G(d,p). [27] Scheme2.Synthesis of complexes 1c-1e, 2c.…”

“…Among all boron cages we used [B 20 H 18 ] 2À as an investigation object to analyze crystal packinge ffects on ar eaction with small atomic shifts of tens of atoms.I nc ontrast with carboranes and metallacarboranes, it has only four structurally characterized isomers( Scheme 1), [26,27] and reactionc onditions in solutions are well understood.R ecently,i tw as confirmed that trans-to-iso isomerization of the octadecahydro-eicosaborate can proceed in solids withoutd egradation, [28] so that the reactionc an be studied in situ. Here, we presents ynthesis of a series of salts andc omplexes containing two forms of the anion, their sensitivity to UV radiation and heating, as well as discussc rystal packing effects and possible mechanisms of the trans-to-iso isomerizationr eaction.…”

Binary twinned-icosahedral [B21H18]− interacts with cyclodextrins as a precedent for its complexation with other organic motifs

“…It is important to mention that (also due to its complicated synthesis 3 ) no parent macropolyhedral borate has been found to interact with any organic molecule. We have therefore undertaken investigations aimed at testing the possibilities of the mutual interaction of purely organic and purely inorganic systems in the gas phase, the inorganic species being a unique joint-icosahedral boron hydride.…”