Salts of the Bis(catecholato)borate Anion with Organic Cations

Chiral anionic layers in tartramide spiroborate salts and variable solvation for [NR4][B(TarNH2)2] (R = Et, Pr or Bu)

The spiroborate anion, namely, 2,3,7,8-tetracarboxamido-1,4,6,9-tetraoxa-5λ⁴-boraspiro[4.4]nonane, [B(TarNH₂)₂]^-, derived from the diol L-tartramide TarNH₂, [CH(O)(CONH₂)]₂, shows a novel self-assembly into two-dimensional (2D) layer structures in its salts with alkylammonium cations, [NR₄]⁺ (R = Et, Pr and Bu), and sparteinium, [HSpa]⁺, in which the cations and anions are segregated. The structures of four such salts are reported, namely, the tetrapropylazanium salt, C₁₂H₂₈N⁺·C₈H₁₂BN₄O₈^-, the tetraethylazanium salt hydrate, C₈H₂₀N⁺·C₈H₁₂BN₄O₈^-·6.375H₂O, the tetrabutylazanium salt as the ethanol monosolvate hemihydrate, C₁₆H₃₆N⁺·C₈H₁₂BN₄O₈^-·C₂H₅OH·0.5H₂O, and the sparteinium (7-aza-15-azoniatetracyclo[7.7.1.0^2,7.0^10,15]heptadecane) salt as the ethanol monosolvate, C₁₅H₂₇N₂⁺·C₈H₁₂BN₄O₈^-·C₂H₅OH. The 2D anion layers have preserved intermolecular hydrogen bonding between the amide groups and a typical metric repeat of around 10 × 15 Å. The constraint of matching the interfacial area organizes the cations into quite different solvated arrangements, i.e. the [NEt₄] salt is highly hydrated with around 6.5H₂O per cation, the [NPr₄] salt apparently has a good metric match to the anion layer and is unsolvated, whilst the [NBu₄] salt is intermediate and has EtOH and H₂O in its cation layer, which is similar to the arrangement for the chiral [HSpa]⁺ cation. This family of salts shows highly organized chiral space and offers potential for the resolution of both chiral cations and neutral chiral solvent molecules.

A chiral spiroborate anion from diphenyl-l-tartramide [B{l-Tar(NHPh)2}2]−applied to some challenging resolutions

A chiral spiroborate anion [B{l-Tar(NHPh)₂}₂]⁻is effective in challenging high yield, 1-pot resolutions, as for the S-2-phenylpropylammonium salt shown.

Isolation and enantiostability of the B-chiral bis(salicylato)borate anions [BR(Sal)2] and [BS(Sal)2]

Both chiral hands of bis(salicylato)borate anion [B_S(Sal)₂] and [B_R(Sal)₂] are isolated and CD spectroscopy indicates they can be configurationally stable.

Chiral bis(mandelato)borate salts for resolution via metathesis crystallization

Spiroborate anions have potential for crystallization or resolution and chiral bis(mandelato)borate anions can be used for the efficient resolution of a diverse range of racemic cations via diastereomeric salt formation. The syntheses, X-ray crystal structures and solubilities of three chiral bis(mandelato)borate salts, namely poly[[aqua-μ3-bis[(R)-mandelato]borato-lithium(I)] monohydrate], [Li(C16H12BO6)(H2O)] n or Li[B(R-Man)2]·H2O, (1), ammonium bis[(R)-mandelato]borate, NH4 +·C16H12BO6 − or NH4[B(R-Man)2], (2), and tetra-n-butylammonium bis[(R)-mandelato]borate, C16H36N+·C16H12BO6 − or NBu4[B(R-Man)2], (3), are reported. They all have a B S configuration and show a reasonably well-conserved anion geometry. The main conformational variation is the orientation of the two phenyl groups, supporting the idea that [B(Man)2]− is a semi-rigid anion. The salts are differentially soluble in a range of solvents, meaning they could be useful as reagents for resolution via a metathesis crystallization approach.

New lithium borates with bistetrazolato2- and pyrazinediolato2- ligands - potentially interesting lithium electrolyte additives

We present a convenient synthesis of the first silylated bistetrazole via a catalyzed twin [2 + 3] cycloaddition of TMS-azide at cyanogen and its application to access bistetrazolatoborates, structurally characterized by a unique unsaturated ten-membered B₂N₄C₄ heterocyclic system. Furthermore, new borate anions with two pyrazine-2,3-diolato ligands were synthesized from tetrafluoroborate salts and structurally characterized. Their organic cation can be exchanged for Li⁺via cation exchange. The conceptual relation of these new salts to lithium ion battery bisoxalalatoborate additive LiBOB, a prominent solid electrolyte interface (SEI) generator, is discussed.

Bis(mandelato)borate: an effective, inexpensive spiroborate anion for chiral resolution

Bis(mandelato)borate [B(Man)2](-) (R- or S-) anions are simply prepared and appear widely effective for resolution of racemic cations. Three examples demonstrate their scope; the alkaloid tetrahydropalmatine (THP), 1,2-diaminopropane (1,2-dap) and the metal-organic complex [Co(phen)3](3+) are readily resolved, either by a facile one-pot procedure, or via counter-ion metathesis.

Synthesis and characterization of fluorinated phosphonium ionic liquids

A wide variety of phosphonium ionic liquids containing fluorous ponytails Rfn (Rfn = –(CF2)n–1CF3; n = 4, 6, 10) are synthesized by the reaction of Rfn-(CH2)2-I with trialkylphosphines (R3P; R = Me, nBu, nOct). The efficacy of multiple metathetical routes to anion exchange have been investigated, thus the corresponding BF4–, PF6–, tosylate (OTs–) and triflate (OTf–) derivatives have also been prepared. All compounds have been comprehensively characterized by multinuclear NMR spectroscopy, ESI-MS, DSC, and TGA/SDTA, and in the case of [Me3PCH2CH2Rf4][I] by single crystal X-ray diffraction. These materials range from high melting solids (e.g., [Me3P(CH2)2Rf4][I] Tm = 195 °C) to very low melting liquids (e.g., [nOct3P(CH2)2Rf4][OTf] Tg = –64 °C), and they all have high thermal decomposition points (295 to 394 °C). Incorporation of the more weakly coordinating BF4– and PF6– yielded a significant increase in the melting point of the materials, in contrast to OTf– and OTs– derivatives, which all exhibited significantly depressed melting points.Key words: phosphonium ionic liquids, alternative solvents, fluorine, phosphorus, fluorous ponytails.

Syntheses and reactions of the bis-boryloxide O(Bpin)2(pin = O2C2Me4)

The reaction of the phosphine oxides, OPEt31 and OPn-Bu32 with pinacolborane (HBpin) results in phosphine oxide reduction and the formation of O(Bpin)23. In contrast, the phosphine oxide OPn-Bu3 reacts with HB(C6F5)2 or B(C6F5)3 to give only the donor-acceptor adducts. Compound 3 reacts with HNPt-Bu3 to give the phosphinimonium borate salt, [t-Bu3PNH2][(Bpin(OBpin)2]6, while reaction with Cp2ZrMe2 affords the species Cp2Zr(OBpin)27.