Fluorine borates

Further evidence for the existence of cationic centers is given by the activation of metallocene catalysts for olefin polymerization by the use of anionic counterions such as tetraphenylborate (CeFIs B-, carborane (C2B9H12), or fluorinated borate. The use of (CgF5)4B counterions by Hlatky et al. (83), Sishta et al. (84), and Zambelli et al. (85) leads to highly active metallocene catalysts, which are formed by the reaction of a dealkylated zirconocene with dimethylaniliniumtetra(/us,-perfluorophenyl)borate ... 

The originally used TPB- counteranion proved to be unstable in the presence of the cation in methylene chloride solutions at temperatures above —78 °C. 65,66 Therefore, salts with different fluorinated borate counteranions were prepared and crystal structures are reported for the TPB-9 (see Fig. 6), TFPB-64 66 and TSFPB-66 salts. 

The most deshielded material within this category (8) was reported in 2002 by Piers and coworkers. They used a novel, highly fluorinated borate anion, the solvent benzene, and hydride abstraction with trityl to produce the species Bu3Sn(benzene)+ with a Sn chemical shift of 5 434. By this time, authors were referring to such species as solvated stannyl cations. 

Even though they are largely overshadowed by the more widely used MAO and fluorinated borate anion activators, single-site catalysts activated by simple alkylaluminums continue to be studied because of the low cost, stability, and wide availability of the cocatalyst. Much of this research focuses on modifying the activator or support to improve catalyst activity, especially with respect to zirconocene catalysts. 

The use of the trifluoroacetate (CFs CXJajaB foi the removal of protecting groups in peptide chemistry and further investigations (boron halides with fluoro-ketones to yield fluorinated borates are dealt with in Chapter 3 (pp. 149,158). 

The synthesized zwitterionic iridium complexes containing various chiral P, N ligands with imidazoline or oxazoline were used as precatalysts for the asymmetric hydrogenation of unfunctionalized olefins. The cationic complexes with fluorinated borates as anions were superior catalysts in dichloromethane, whereas the iridium betaines were good catalysts in pure hydrocarbons. ... 

Figure 8 Metallocene activation via (a, b) fluorinated borate and (c) fluorinated boron activators.

The products resulting from such reactions should, therefore, have analogous names. If KBO2 is a borate, KBS2 is a thioborate and KBF is a fluoroborate. Similarly, the replacement of an oxygen atom by a sulfur atom or two fluorine atoms is understandable. However, the relationship of K2BN2 is less obvious, until one considers the dehydration and deammoniation schemes ... 

BF3 is used extensively as a catalyst in various industrial processes (p. 199) and can be prepared on a large scale by the fluorination of boric oxide or borates with fluorspar and concentrated H2SO4 ... 

The classical method for replacing a diazonio group by fluorine is the Balz-Schie-mann reaction (Balz and Schiemann, 1927) in which the arenediazonium tetrafluoro-borate is heated without a solvent. Although it gives fairly good yields in the majority of cases, it can lead to difficulties. These have been discussed by Wulfman (1978,... 

Experience in PTC with cationic catalysts showed that, in general, the most suitable compounds have symmetrical structures, are lipophilic, and have the active cationic charge centrally located or sterically shielded by substituents. For anionic catalysis sodium tetraphenylborate fulfills these conditions, but it is not stable under acidic conditions. However, certain derivatives of this compound, namely sodium tetra-kis[3,5-bis(trifluoromethyl)phenyl]borate (TFPB, 12.162) and sodium tetrakis[3,5-bis-(l,l,l,3,3,3-hexafluoro-2-methoxy-2-propyl)phenyl]borate (HFPB) are sufficiently stable to be used as PTC catalysts for azo coupling reactions (Iwamoto et al., 1983b 1984 Nishida et al., 1984). These fluorinated tetraphenylborates were found to catalyze strongly azo coupling reactions, some of which were carried out with the corresponding diazotization in situ. 

Using a fluorinated tris(pyrazolyl)borate ligand, Gorun and co-workers126 synthesized a complex (117) (t = 0.06). This group very successfully isolated and structurally characterized a dinuclear oxygenated complex, revealing that the crystal contains about 80% peroxo... 

A highly fluorinated bis(pyrazolyl)borate ligand, dihydridobis(3,5-bis(trifluoromethyl)pyrazo-lyl)borate has been synthesized. The zinc triflate complex was prepared from the potassium salt of the ligand and exhibits distorted tetrahedral coordination which allows comparison of the amount of distortion, in relation to the electronic properties of substituents, with the methylated analog.165... 

Methanol, ethanol and 3-methylbutanol [1], acetaldehyde, trichloroacetaldehyde [2] and acetone [3] all ignite in contact with gaseous fluorine. Lactic acid, benzoic acid and salicylic acid ignite, while gallic acid becomes incandescent. Ethyl acetate and methyl borate ignite in fluorine [2],... 

The Lewis acidity and reactivity of these alkyl aluminum cocatalysts and activators with Lewis basic polar monomers such as acrylates make them impractical components in the copolymerization of ethylene with acrylates. To address this shortcoming, Brookhart et al. developed well-defined cationic species such as that shown in Fig. 2, in which the counterion (not illustrated) was the now-ubiquitous fluorinated arylborate family [34] such as tetrakis(pentaflurophenyl)borate. At very low methyl acrylate levels the nickel catalysts gave linear copolymers but with near-zero levels of acrylate incorporation. 

The anion plays a crucial role. BArF and other bulky fluorinated tetra-arylbo-rates or tetraalkoxyaluminates are the most suitable anions. Hexafluorophos-phate-containing catalysts display high reactivity in the initial phase of the reaction, but suffer deactivation before the reaction reaches completion. Tetrafluoro-borate, triflate or other more strongly coordinating anions inhibit the catalyst. 

A dimethylaluminum complex [HB(3,5-(CF3)2Pz)3]AlMe2 (Figure 22) of the highly fluorinated tris(pyrazolyl)borate ligand [HB(3,5-(CF3)2Pz3] was obtained from the reaction between the silver adduct [HB(3,5-(GF3)2Pz)3]Ag(THF)... 

S.3.2.3. Lithium Borates with Nonaromatic Ligands. The presence of aromatic ligands in Barthel s salts was believed to be responsible for the high melting points and basicity of the borate anions, which in turn translate into moderate or poor solubilities and ion conductivities as well as low anodic stabilities. To avoid use of these bulky aromatic substituents, Xu and Angell synthesized a series of borate anions that are chelated by various alkyl-based bidentate ligands, which serve as electron-withdrawing moieties by the presence of fluorine or carbonyl functionalities. Table 13 lists the... 

On the basis of their previous experiences with lithium borates coordinated by substituted ligands. Barthel and co-workers modified the chelatophos-phate anion by placing various numbers of fluorines on the aromatic ligands. Table 13 lists these modified salts and their major physical properties. As expected, the introduction of the electron-with-drawing fluorines did promote the salt dissociation and reduce the basicity of phosphate anion, resulting in increased ion conductivity and anodic stability. The phosphate with the perfluorinated aromatic ligands showed an anodic decomposition limit of 4.3 V on Pt in EC/DEC solution. So far. these modified lithium phosphates have attracted only academic interest, and their future in lithium ion cell applications remains to be determined by more detailed studies. 

Their principal parent compound is Hydrofluoric (or Phthoric) Acid Gas. (Hydrogen Fluoride), HF, mw 20.01 colorless, very poisonous gas, density 0.713(Air l,0), sp gr of liquid 0.988 at +13.6°, fr p -83°, bp +19-4° sol in w or ale. Can be prepd by distilling from a mixture of Ca fluoride (fluorspar) and sulfuric acid. Used as an additive in liquid rocket proplnts and in refining of uranium. Also as fluorinating agent in org and inorg reaction prepn of A1 fluoride, other fluorides, fluoro-borates, fluomcarbonaces, fluorocarbons and fluorosili cates... 

The fluorination of pyridine with cesium fluoroxysulfate in the presence of sodium tetrafluoro-borate in acetonitrile at 0-5 C gives 1-fluoropyridinium tetrafluoroborate (3).42... 

The reaction of potassium dienoxy borates with A-fluorobis(phenylsulfonyl)amine (la) gives y-fluoro enones in good yield. The potassium dienoxy borates are prepared by treating potassium enolates derived from unsaturated ketones with 2-phenyl-1,3,2-benzodioxaborole. This methodology offers a convenient alternative to the traditional fluorination of dienol acetates, ethers, or enamines.145 An example is given by the formation of 13.145... 

The bulky methylaluminoxane anion stabilizes the coordinatively unsaturated metal cation. Stabilization by noncoordinating anions such as carbosilane dendrimers is also viable.571 Aluminoxanes, however, are required to be used in large excess to be effective. Alternatively, the active catalyst can also be prepared by reacting a metal dialkyl with fluorinated boranes, borate salts or aluminate salts. 

Enamels - [BARIUMCOMPOUNDS] (Vol3) - [ALUMINUMCOMPOUNDS - ALUMINIUMOXIDE(ALUMINA) - CALCINED,TABULAR, AND ALUMINATE CEMENTS] (Vol2) - [TIN COMPOUNDS] (Vol 24) -aluminum fluoride in [FLUORINE COMPOUNDS,INORGANIC - ALUMINUM](Vol 11) -antimony compds in [ANTIMONY COMPOUNDS] (Vol 3) -borate in [BORON COMPOUNDS - BORON OXIDES, BORIC ACID AND BORATES] (Vol 4) -boric oxide in prepn of [BORON COMPOUNDS - BORON OXIDES, BORIC ACID AND BORATES] (Vo 14) -lithium for [LITHIUM AND LITHIUM COMPOUNDS] (Vol 15)... 

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