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Lithium tetrakis(pentafluorophenyl)borate
Names
	Preferred IUPAC name Lithium tetrakis(pentafluorophenyl)boranuide
Identifiers
CAS Number	371162-53-7 (etherate) ;
3D model (JSmol)	Interactive image;
ChemSpider	8071952 ; 9160766 (etherate) ;
ECHA InfoCard	100.155.284
PubChem CID	9896287;
	InChI InChI=1S/C24BF20.Li/c26-5-1(6(27)14(35)21(42)13(5)34)25(2-7(28)15(36)22(43)16(37)8(2)29,3-9(30)17(38)23(44)18(39)10(3)31)4-11(32)19(40)24(45)20(41)12(4)33;/q-1;+1 Key: WTTFKRRTEAPVBI-UHFFFAOYSA-N ; InChI=1/C24BF20.Li/c26-5-1(6(27)14(35)21(42)13(5)34)25(2-7(28)15(36)22(43)16(37)8(2)29,3-9(30)17(38)23(44)18(39)10(3)31)4-11(32)19(40)24(45)20(41)12(4)33;/q-1;+1 Key: WTTFKRRTEAPVBI-UHFFFAOYAW;
	SMILES [Li+].Fc1c(c(F)c(F)c(F)c1F)[B-](c2c(F)c(F)c(F)c(F)c2F)(c3c(F)c(F)c(F)c(F)c3F)c4c(F)c(F)c(F)c(F)c4F;
Properties
Chemical formula	C24BF20Li
Molar mass	685.98 g·mol−1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Lithium tetrakis(pentafluorophenyl)borate is the lithium salt of the weakly coordinating anion (B(C₆F₅)₄)⁻. Because of its weakly coordinating abilities, lithium tetrakis(pentafluorophenyl)borate makes it commercially valuable in the salt form in the catalyst composition for olefin polymerization reactions and in electrochemistry. It is a water-soluble compound. Its anion is closely related to the non-coordinating anion known as BARF. The tetrakis(pentafluorophenyl)borates have the advantage of operating on a one-to-one stoichiometric basis with Group IV transition metal polyolefin catalysts, unlike methylaluminoxane (MAO) which may be used in large excess.

Structure and properties

The anion is tetrahedral with B-C bond lengths of approximately 1.65 Angstroms. The salt has only been obtained as the etherate, and the crystallography confirms that four ether (OEt₂) molecules are bound to the lithium cation, with Li-O bond lengths of approximately 1.95 Å. The [Li(OEt₂)₄]⁺ complex is tetrahedral.

Preparation

The salt was first produced in studies on tris(pentafluorophenyl)boron, a well known Lewis acidic compound. Combining equimolar ether solutions of pentafluorophenyllithium and tris(pentafluorophenyl)boron gives the lithium salt of tetrakis(pentafluorophenyl)borate, which precipitates the etherate as a white solid:^[1]

(C₆F₅)₃B + Li(C₆F₅) → [Li(OEt₂)₃][B(C₆F₅)₄]

Since its discovery, many revised syntheses have been described.^[2]

Reactions

Lithium tetrakis(pentafluorophenyl)borate is primarily used to prepare cationic transition metal complexes:

LiB(C₆F₅)₄) + ML_nCl → LiCl + [ML_n]B(C₆F₅)₄

LiB(C₆F₅)₄ is converted to the trityl reagent [Ph₃C][B(C₆F₅)₄], which is useful activator of Lewis-acid catalysts.^[3]^[4]

Safety

Lithium tetrakis(pentafluorophenyl)borate will deflagrate on melting (ca. 265 °C) giving thick black smoke, even under nitrogen.^[5] The mechanism is unknown. Metal tetrakis(pentafluorophenyl)borates of K and Na decompose vigorously as well.^[6]^[7]

References

^ A.G. Massey, A.J. Park. "Perfluorophenyl derivatives of the elements : I. Tris(pentafluorophenyl)boron." Journal of Organometallic Chemistry, 1964, 2, 245-250. doi:10.1016/S0022-328X(00)80518-5
^ Martin, Eddy, Hughes, David, and Lancaster, Simon. "The composition and structure of lithium tetrakis(pentafluorophenyl)borate diethyletherate." Inorganica Chimica Acta, 2010, 363, 275-278 doi:10.1016/j.ica.2009.09.013
^ Cordoneanu, Adina, Drewitt, Mark, Bavarian, Neda, Baird, Michael. "Synthesis and Characterization of Weakly Coordinating Anion Salts of a New, Stable Carbocationic Reagent, the Dibenzosuberenyl (Dibenzotropylium) Ion." New Journal of Chemistry, 2008, 32, 1890-1898. doi:10.1039/b804868a
^ Lancaster, Simon J.; Bochmann, Manfred (2002). "The Reaction of Cp*₂ZrMe₂ with [CPh₃][B(C₆F₅)₄]: Triphenylethane Does Not form ηⁿ-Arene Complexes with [Cp*₂ZrMe]⁺". Journal of Organometallic Chemistry. 654 (1–2): 221–223. doi:10.1016/S0022-328X(02)01319-0.
^ Martin, Eddy; Hughes, David L.; Lancaster, Simon J. (2010-01-04). "The composition and structure of lithium tetrakis(pentafluorophenyl)borate diethyletherate". Inorganica Chimica Acta. 363 (1): 275–278. doi:10.1016/j.ica.2009.09.013. ISSN 0020-1693.
^ Stockmann, Tom J.; Ding, Zhifeng (2012-10-25). "Tetraoctylphosphonium tetrakis(pentafluorophenyl)borate room temperature ionic liquid toward enhanced physicochemical properties for electrochemistry". The Journal of Physical Chemistry B. 116 (42): 12826–12834. doi:10.1021/jp3081832. ISSN 1520-5207. PMID 23009026.
^ Lee, Hyun-Ju; Baek, Jun-Won; Seo, Yeong-Hyun; Lee, Hong-Cheol; Jeong, Sun-Mi; Lee, Junseong; Lee, Chong-Gu; Lee, Bun-Yeoul (2021-05-10). "Preparation of High-Purity Ammonium Tetrakis(pentafluorophenyl)borate for the Activation of Olefin Polymerization Catalysts". Molecules. 26 (9): 2827. doi:10.3390/molecules26092827. ISSN 1420-3049. PMC 8126221. PMID 34068755.