Borate, tris phenyl

Photoisomerizations of tetracoordinate 1-alkynylboranes offer some synthetic prospects of unusual significance, namely, an entree into the boracycloprene system (45). Thus, irradiation of lithium tri-phenyl(phenylethynyl)borate in THF and acetolytic work-up gave, in high conversion, a 1 5.6 ratio of biphenyl and c/j-stilbene. The low yield of biphenyl (15%) and hydrogen gas (13%) shows that the cleavage of the path a type (Scheme 5) is minor here. When the photolyzate was treated with DOAc, the isolated cw-stilbene was 45% a,a -dideuterated, 44% a-deuterated, and 11% undeuterated. The principal course of this reaction... 

Although the ratio of biaryls formed in these halogenative oxidations is somewhat sensitive to the reaction medium, it is noteworthy that the amount of biaryl formation is quite dependent both on the nature of the solvent and the metal ion (L, Na" ", or K+). Although potassium phenyl(tri-/7-tolyl)borate (58) dissolved in chloroform reacted with iodine to yield a 1.4 1.0 ratio of biaryl to p-iodotoluene, the same reaction in dimethylformamide gave almost exclusively p-iodotoluene. Likewise, the sodium analog of 58 gave a biaryl p-iodotoluene ratio of 1 32 (48). 

FIG. 10 Faradaic admittance coefficient Yq for the interface between 0.1 M LiCl in water and 0.02 M tetrabutylammonium tetraphenylborate ( ) or tetrapentylammonium tetrakis[3,5-bis(tri-fluoromethyl)phenyl]borate ( ) in o-nitrophenyl octyl ether as a function of the interfacial potential difference A y. (From Ref 73.)... 

Silver(I) complexes are known with the tris(pyrazolyl)borate [HB(pz)3] and the methyl, phenyl, bromo, or trifluoromethyl-substituted derivatives. The structure of the silver tri(pyrazolyl)borato species has been a puzzle since it was first reported.385,386 It was suggested that the structure could be oligomeric, but recently the crystal structure of the compound [Ag HB(3,5-Me2pz)3 ]2 shows that it has a dimeric structure387 where the silver(I) centers are tricoordinated by a bidentate arm of one ligand and a monodentate arm of the other ligand (29). The related complexes [Ag HB(4-Brpz)3 ]2, [Ag HB(4-Mepz)3 ]2, [Ag HB(3,5-Me2pz)3 ]2, [Ag HB(3-Mepz)3 ] , [Ag B(pz)4 ], and... 

HPA = (4-pyridylthio)aceticacid 2-fur = 2-furoate a-fur = a-furoate = ([Pg.116]

Cyclooctadiene)- 2-(2-phenyl-5-methyl-4,5-dihydro-oxazol-4-yl)-l,3-diphenyl-2-diphenylphosphimte-propane mdium(l)]-tetrakis[3,5-bis(tri-fluoromethyl)phenyl]borate (1.72mg, l.Opmol). The catalyst is available from Strem Chemicals, Inc. (catalogue no. 77-5020). 

Cyclotrigermenes were obtained from the reaction of metal-14 anions with tris(tri-r-butylsilyl)cyclotrigermenium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, the TFPB behaving as the leaving group (equation 156)168. The cyclotrigermene structure was established by X-ray determination. 

The regioselective anti-Markovnikov addition of benzoic acid to phenyl-acetylene has also been carried out with success at 111 °C in the presence of ruthenium complexes containing a tris(pyrazolyl)borate (Tp) ligand [RuCl(Tp)(cod), RuCl(Tp)(pyridine), RuCl(Tp)(N,N,Ar,AT-tetramethylethyl-enediamine )] with a stereoselectivity in favour of the (E)-enol ester isomer [22]. The o-enynyl complex Ru(Tp)[PhC=C(Ph)C=CPh](PMe/-Pr2) (C) efficiently catalyses the regioselective cyclization of a,cu-alkynoic acids to give en-docyclic enol lactones [23] (Eq. 2). 

Borat Phenyl-trihydro-Lithium-Salz XIII/3b, 821 Tris-pi 5-cyclopenta dieny l -uran- Salz XIII/3b, 828 Borinat 1-Methyl- (Tl-Salz) XIII/3a, 313... 

Model studies for metallo- 3-lactamases have been performed using mononuclear zinc hydroxide complexes.99,129,130 The breadth of (3-lactam hydrolysis reactivity of hydro-tris(pyrazolyl)borate-ligated mononuclear zinc hydroxide complexes has been explored.129 Treatment of the mononuclear zinc hydroxide complex [(Tpph Mc)Zn OH] with simple 3-lactams ( 3-propiolactam, 4-phenyl-(3-propiolactam, Scheme 21) does not result in ring opening, but instead results in the formation of 3-lactamide complexes and water. Treatment of [(Tpph,Me)Zn-OH] with /V-alkyl or -aryl 3-lactam derivatives instead results in no reaction (Scheme 21). Use of natural derivatives of penicillin and cephalosporin (Scheme 22) did not yield 3-lactam hydrolysis, but instead coordination of the carboxylate moiety of the antibiotic derivatives to the mononuclear Zn(II) center and release of water. 

---