Synthesis, Characterization, and Crystal Structures of Silylium Compounds of the Weakly Coordinating Dianion [B₁₂Cl₁₂]²⁻

Abstract

The reaction of [Ph(3)C](2)[B(12)Cl(12)] with R(3)SiH (R = Me, Et, iPr) in 1,2-difluorobenzene yielded the corresponding silylium compounds (R(3)Si)(2)B(12)Cl(12) containing the weakly coordinating dianion [B(12)Cl(12)](2-). The products were fully characterized by IR and Raman spectroscopy and by multinuclear ((1)H, (11)B, (13)C, (29)Si) NMR spectroscopy in solution and the solid state (magic angle spinning). (Et(3)Si)(2)B(12)Cl(12) and (iPr(3)Si)(2)B(12)Cl(12) were characterized by X-ray diffraction. In the solid state, the silylium cations are coordinated to the [B(12)Cl(12)](2-) anion via silicon-chlorine contacts, which are significantly shorter than the sum of the van der Waals radii. Two different coordination patterns were found. The [Et(3)Si](+) cations are coordinated to chlorine atoms of [B(12)Cl(12)](2-) in the 1 and 12 positions, while the [iPr(3)Si](+) cations coordinate to chlorine atoms in the 1 and 7 positions. The 1,12 regioisomer is calculated [for (Me(3)Si)(2)B(12)Cl(12)] to be favored over the 1,7 isomer by only 8 kJ mol(-1), indicating that packing effects may cause the difference. The silylium cations are very reactive and bind to every Lewis base, being stronger than the aromatic solvent (e.g., benzene, 1,2-difluorobenzene, etc.) used. Consequently, three different crystal structures containing cationic Lewis acid-base complexes [iPr(3)Si-donor](+) were obtained from preparations of (iPr(3)Si)(2)[B(12)Cl(12)]. The presence of traces of water leads to crystals of [iPr(3)Si(OH(2))](2)[B(12)Cl(12)] containing the protonated silanol [iPr(3)Si(OH(2))](+), which is only the second example of its kind. Structures containing the [iPr(3)SiOS(H)OSiiPr(3)](+) cation were obtained from the reaction of [Ph(3)C](2)[B(12)Cl(12)].2SO(2) with an excess of iPr(3)SiH in 1,2-difluorobenzene. [iPr(3)SiOS(H)OSiiPr(3)](2)[B(12)Cl(12)] and [iPr(3)SiOS(H)OSiiPr(3)][(iPr(3)Si)B(12)Cl(12)] were structurally characterized by X-ray diffraction. On the basis of the structural data and quantum chemical calculations, the crystallographically invisible hydrogen atom bound to the sulfur atom was identified. A comparison of the weakly coordinating dianion [B(12)Cl(12)](2-) with the widely applied corresponding chlorinated carboranes based on several criteria including the nu(N-H) scale established the dianion [B(12)Cl(12)](2-) to be as weakly coordinating as the single negatively charged carboranes.

On Silylated Oxonium and Sulfonium Ions and Their Interaction with Weakly Coordinating Borate Anions

“…Similar structural features are found for the sulfur species, however,t he bending out of the Si 2 O 2 ring plane of the terminal Tg roups is much strongerp ronounced ( 59.68). [49,66,[72][73][74][87][88][89][90][91][92] Ion-pairs:A sd iscussed before, ion-pair formation stabilizes all silyliumi ons mentioned here. The difference in the SiÀEb ond lengths within the ring compared to the terminal distances is beste x-plained by as trong hyperconjugative effecto ft he lone pairs localized at both tricoordinated chalcogen atoms in a p-type atomic orbital as indicated by NBO investigations.…”

“…Withint he ring, both SiÀOb ond lengths are slightly shorterc ompared to both terminal distances (1.770 vs. 1.859 ). [49] It should be noted that there are av ariety of computational studies on oxonium and sulfonium species in literature. Hence, again the oxygen is an almostt rigonal environment( S](Si-O-Si) = 359.98), whiles ulfur prefers ap yramidal arrangement (S](Si-S-Si) = 325.08).…”

“…(1)]. [49] Results and Discussion Olah and Prakashe tal., [26] we have isolated this salt prior to the reaction with T-E-T,b ut not the T + -salt, since [T-H-T][B(C 6 F 5 ) 4 ]a lways forms, when [B(C 6 F 5 ) 4 ] À is the counterion. The group of Knapp-Jenne reported the synthesis, spectroscopica nd structural characterization of silylium cations[ R 3 Si] + (R = Me, Et, iPr) stabilized by the perchlorinated weakly coordinating dianion [B 12 Cl 12 ] 2À .…”

Thecloso‐Dodecaborate Dianion Fused with Oxazoles Provides 3D Diboraheterocycles with Selective Antimicrobial Activity

“…Such conditions were exploredb ya ssuming that rhodiumi se ssential for BÀHa ctivation. Surprisingly,s tepwise lowering of the amount of Rh III from 10 to 1% afforded increasing yields, and the use of only AgOAc without Rh III provided 2a in 92 %N MR yield (entries [4][5][6][7]. Surprisingly,s tepwise lowering of the amount of Rh III from 10 to 1% afforded increasing yields, and the use of only AgOAc without Rh III provided 2a in 92 %N MR yield (entries [4][5][6][7].…”

“…[1][2][3] Their delocalized electron system and strong exo BÀHb onds lead to remarkable thermal, chemical, and biological inertness. [4] The unique properties of this borohy-dride has led to an umber of applicationsi nd iversea reas such as weakly coordinating anions, [5] ligand design, [6] supramolecular chemistry, [7] host-guest interactions, [8] catalysis, [9] material science, [10] fluorescence/phosphorescence, [11] and medicinal chemistry. [4] The unique properties of this borohy-dride has led to an umber of applicationsi nd iversea reas such as weakly coordinating anions, [5] ligand design, [6] supramolecular chemistry, [7] host-guest interactions, [8] catalysis, [9] material science, [10] fluorescence/phosphorescence, [11] and medicinal chemistry.…”