Borate derivative

The final chapter in this volume by Alexander Sadimenko (University of Fort Hare, South Afiica) continues a series by this author on the organometaUic chemistry of heterocycles, of which 0,S monoheterocycles and N,P,Si,B monoheterocycles were published in volumes 78 and 79, respectively. The organometaUic chemistry of pyrazole is so broad that the present overview does not include the polyfunctional, chelating frameworks containing pyrazolyl units, which are typified by the pyrazolyl borate derivatives. These will be the subject of a future chapter. 

Borkett, N.F., Bruce, M.I. and Walsh, J.D. (1980) Chemistry of the group IB Metals. XIV Some poly(pyrazolyl)borate derivatives containing gold. Australian Journal of Chemistry, 33, 949. 

The organic solvent should feature a low solubility in water and a high dielectric constant. Numerous studies have been reported for liquid-liquid junctions involving DCE [43,62,70,71,73], nitrobenzene [67,68,74,75], and nitrophenyloctylether (NPOE) [56]. Various hydrophobic electrolytes have been employed in these solvents. Tetraphenylarsonium (TPAs+) [[71,75,76], bis-triphenylphosphoranylidene (BTPPA+) [43,50], and hydrophobic tetra-arylammonium [77,78] are among the cations used in the organic phase. The choice for anions has been mostly restricted to borate derivatives, tetraphenylborate (TPB ) [70,79,80], tetrakis(4-chlorophenyl)borate (TPBCH) [43,81,82], and tetrakis(penta-fluoro)phenylborate (TPFB ) [49,83], as well as dicarbollyl-cobaltate [75]. 

The fractions containing the diol auxiliary and those containing borate derivatives were concentrated, and treated with a solution of THF (2 mL), 1 N NaOH (1 mL), and H2O2 (1 mL of a 30% aqueous solution) for 16 hours. The resulting mixture was diluted with water (5 mL) and extracted with LtOAc (3 x 10 mL). The combined organic layers were dried over anhydrous MgS04, filtered, and concentrated. Flash chromatography (5% EtOAc/hexanes) afforded 891 mg of recovered (lR,25, 3R,45 )-2-phenyl-l,7,7-trimethylbomanediol (75% yield). 

The pyrrolylphosphines and the tris-(pyrazolyl)borate derivative were investigated [48, 73] at square-planar tetra-coordinate Rh complexes for which the Lever model was then extended (see in the following). 

Used for the precolumn preparation of fluorescent derivatives of primary and secondary amines in acetone solvent in the presence of sodium borate, derivation proceeds rapidly under alkaline conditions Reference 24... 

This section does not review comprehensively all the tetrahydro-borate derivatives, since these have been adequately covered elsewhere (50). The aluminohydride compound Cp2Zr(H)AlH4 has been mentioned, but several similar hydrides have been identified. Such compounds are relevant in particular to known reactions where titanium(IV) or zirconium(IV) compounds catalyze the addition of Al-H bonds to alkenes and alkynes (114, 115). 

All of these species (XIV, XV) have been for the most part applied towards function in the olefin polymerization arena use of these novel anions for the stabilization of other electrophilic species remains to be explored. Recently, the imidazolide anion XVI, as well as the perfluorinated tetraaryl borate derived from the diborane IX of Chart 2, have been used to stabilize iodonium cations.222 These cations are used as photoinitiators for cationic polymerization of epoxy resins in photolithography applications. While use of the [B(C6F5)4] led to a breakthrough in this area of research,223 higher activities are observed for more WCAs. 

Alkyl radicals can be generated from tetramethylammonium phenyltrialkylborate salts (used as electron donors) in the PET reaction with excited benzophenone in the presence of a 10-fold excess of an electron-poor olefin in an acetonitrile/benzene (1 5) solution [8]. The advantages of this method are that more than one equivalent of alkyl radicals is obtained per molecule of the borate derivative, and that part of the benzophenone is usually recovered after the reaction [8]. 

Brominated sulfimide was reacted with trithionane to afford sulfimidium salt 31 <2004NJC959>, which was further crystallized as tetraphenyl borate derivative and studied by H and 13C NMR and X-ray crystallography (Section 14.10.3.1). Contrary to MSH derivatives 73, and 74, excess of diphenyl sulfimide did not lead to disub-stituted product, which was attributed to bulkiness of phenyl groups. 

It is understandable, therefore, that since its introduction in 1966 this ligand system has been explored to a considerable extent, and by 1984 poly(l-pyrazolyl)borate derivatives of most transition metals (except for Sc, Hf and Os) up to Np have been described and a few brief reviews of this subject matter have appeared Since... 

Besides bidentate ligands, tripyrazolylborates (Tp) (see Tris(pyrazolyl)borates) derivatives, which are of anionic tridentate in facial configuration, also afford octahedral... 

Another novel diborane(4) compound has previously been obtained by adventitious hydrolysis of 1, namely the cyclic reduced boric acid species B402(0H)4 (8).8 Compound 8 is produced in much higher yield from a more controlled hydrolysis of either 1 or 2 but can be prepared almost quantitatively from the reaction between 3 and aqueous ethanol as a material with co-crystallised [NH2Me2]Cl.8 Electrospray mass spectrometry revealed that the more highly condensed species 9 can also be formed indicating that a large family of condensed, reduced boric acids/borates derived from B2(OH)4 may be synthetically accessible. 

Tp = tris(pyrazolyl)borate derivative, L = bispyridine (X = NO) or bisphenolate (X = O) bridging ligands [68]. Because of the presence of only 25.5 % as hyperfine coupling-active nuclei Mo ( Mo with 15.9 % and Mo with 9.6 %, both with I = 5/2), the delocalization is evident from the approximately halved hyperfine coupling constants (as compared with mononuclear Mo species) and from the relative ESR intensities of lines corresponding to molecules with Mo- Mo, Mo-Mo and Mo-Mo isotope combinations [67, 68]. 

Past attempts to prepare terminal phosphinidenes indicate that these species are inherently electrophilic. To compensate, phosphinidenes were prepared that possessed intramolecular base stabilization, e.g., by means of a pyrazolyl borate derivative. The precursor, [HB(pz )3]PCl2, is combined with a metal anion to form the complex in 70% yield ... 

The reaction of 2-lithiopyridines (9) with 10a,b affords borates 11, whereas reaction of 9b with 10b gives 13, suggesting some steric effect of the 6-methyl group on the pyridine ring in the reaction. Upon heating, 11a is converted to dimeric borane 12, which is obtainable alternatively by iodinolysis of the corresponding borate derived from 9 and triethylbo-rane (84H2471) (Scheme 5). 

Tridentate nitrogen ligand is one of the useful ligands capping coordination sites of metal ions. Hydrotris(pyrazolyl)borate derivatives have been used for this purpose. The starting material, [LW02(0H)] (L = hydrotris(3,5-dimethylpyrazol-l-yl)borate) was prepared from [LWI(CO)3] via transfer of two oxygen atoms from dimethyl sulfoxide. This reaction required water as the source... 

The synthesis of [ZrCl(ri-C8Hg)(K2-Bp)] has been reported by Hill and Smith, who described that the reaction of [ZrC Cn-CsHsllTHF)] with Bp gave only the organometallic oxide cluster [Zr4( x-0)4-( x-Cl)2(Cl)2(t -C8H8)4].35 Some deprotonated diindolylmethanes have been employed to coordinate Ti and Zr and the compounds obtained have been compared with analogous bis(pyrazolyl)borates derivatives.36... 

Nickel nitrosyl complexes in a sulfur-rich environment The first poly(mercaptoimidazolyl)-borate derivatives —N C S R, rV / 17... 

Two related mononuclear copper(I) nitrosyl complexes containing pyrazolyl methane and borate derivatives have been studied by X-ray, IR, EPR, and DFT calculations.52 They pertain to the CuNO 11 class, which are relevant as intermediates in the reactions of copper proteins with NO.4 9 The interpretation of the data allowed assigning the complexes as limiting Cu XO", with end-on coordination of the bent nitrosyl. 

Among the various chiral reagents used for the asymmetric reduction of 7,8-difluoro-3-methyl-2//-1, 4-benzoxazine (4), a borate derivative of the cyclic amino acid (S)-proline proves to be the most effective one affording the reduction product 6 with excellent enantioselectivity (95% cc) and in 92% yield32. 

Cordinhib. [Croda Chem. Ltd.] Borate derivs. corrosion inhibitor for metalworking fluids. 

Emulbon. (Toho Chem. Industry] Borate derivs. lubricant, plasticizm, emulsifier, di rsant, detergent, solvent. 

The hydrotris[(3,5-diisopropyl)pyrazolyl]borate derivative [Mn " (HB(3,5-iPr2pz)2(3-iPr0-5-iPrpz))]2(/t-0) (263) (Fig. 43), has a similar Mn-Mn distance, 3.53 A, and a more linear Mn-O-Mn geometry explained by steric demands of the hindered HB(3,5-iPr2pz)2(3-iPrO-5-iPrpz) ligand. The Mn complex with tetraphenyl porphyrin forms an oxo-bridged complex, [Mn (TPP)N3]2(jU.-0), with a nearly linear Mn-... 

Epoxidation. For epoxidation of electron-deficient alkenes KF supported on alumina is a useful base. Moderate ee values are observed when unfunctionalized alkenes are epoxidized in the presence of a chiral borate derived from dimethyl tartrate. 

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