Boron bromide complex

The phosphorus (V) chloride-boron chloride complex has been prepared by the chlorination of the phosphorus(III) bromide-boron bromide complex at room temperature, by chlorinating an equimolar mixture of phosphorus (III)... 

The X-ray structures of the boron bromide and boron chloride complexes confirm the tridentate coordination of the triacetylrhenato ligand to the boron atom. Both molecules have crystallographically imposed mirror symmetry. Although both compounds decompose appreciably during data... 

A comparison of catalytic activity of the triphenyl phosphate complexes of boron trifluoride,boron trichloride and boron tribromide showed that comparable rates of polymerization were obtained using the chloride or bromide complexes. The fluoride complex gave about half the rate of the bromide or chloride comparable molecular weights were obtained in all three cases. 

The boron trihalide complexes with a number of phosphine sulphides and selenides can be isolated for the chloride, bromide, or iodide but, consistent with its reduced Lewis acidity, the trifluoride does not react.600 Alkyldithio-phosphonic acids give tin, lead, and mercury derivatives such as Me3SnSP-(S)FEt, Pb[SP(S)FMe]2, and MeHgSP(S)FMe, which are monomeric in solution, and there is n.m.r. evidence for a bidentate phosphonate group in the tin compound.601 Vanadyl chelates of alkoxy-ethyl and alkoxy-phenyldi-thiophosphonates (87) have been synthesized and e.s.r. measurements... 

Addition of triethylaluminum or triethylborane to (61f) produces the ate complexes, which react with aldehydes at the a-position. In contrast to the ate complex of the oxygen-substituted anion, the ate complex of (61f) produces low diastereoselectivity. Reaction of the boron ate complex with y,y-dimethylal-lyl chloride and bromide occurs at the a-position with inversion of the allyl unit. 

The complexes of urea and thiourea with boron trifluoride have been studied and, as with other boron trifluoride complexes, the shifts are very similar namely 19 2+0-3 p.p.m. [with respect to (MeO)aB]. A similar shift was observed for the more complex adducts with cadmium chloride or nickel bromide. It was found that dimethyl ether-boron trifluoride (shift of 17-6) and di-t-butylthiourea-boron... 

Barium iodate 1-hydrate, synthesis 4 Indium(I) bromide, synthesis 6 Hexachlorodisiloxane, synthesis 7 Trichlorosilanethiol, synthesis 8 Tris(acetylacetonato)silicon chloride, synthesis 9 Titanium(III)chloride, synthesis 11 Bis[tris(acetylacetonato)titanium(IV)] hexachloro-titanate(IV), synthesis 12 Zirconium(IV) iodide, synthesis 13 (Triphenyl) aminophosphonium chloride, synthesis 19 (Dimethylamido)phosphoryl dichloride, synthesis 20 Bis(dimethylamido)phosphoryl chloride, synthesis 21 Trimeric and tetrameric phosphonitrilic bromides, synthesis 23 Phosphorus(V) chloride-boron trichloride complex, synthesis 24... 

The presence of a small amount of water enhances the efficiency of these Suzuki reactions of alkyl bromides. Thus, if anhydrous K3PO4 rather than K3P04-H20 is used, the cross-coupling proceeds much more slowly. B NMR studies revealed that, in the presence of water, a hydroxy-bound boron ate complex is formed, which was suggested might be the species that participates in the transmetalation step of the catalytic cycle. 

The palladium(II) template dimerization of the thiolato ligands in (%) with boron tribromide, which proceeds via internal nucleophilic displacements of bromide from an intermediate bis(benzyl bromide) complex, affords the 14-membered trans-AS2S2 macrocycle (R, R )- 97) (Figure 2) as air-... 

Boron trifluoride complexes easily with ethers. The complexes are stabilized by symbiosis of F and O ligands around the boron. Dialkyl ethers are ruptured by BBrj to furnish alkyl bromides (2, 3). This is a consequence of the mutual weakening of B-Br and O-R bonds (both are hard-soft pairs) on coordination. The splitting of the bromide ion from the complexes and its return attack on the alkyl group of the oxonium intermediates are favored on HSAB grounds. 

The reaction is irreversible and can be used to synthesize aUphatic and aromatic esters. In addition, there are no complications involving water removal or azeotrope formation. Boron tribromide can be used ia place of boron trichloride, but the bromide has a stronger tendency to halogenate the alkyl group of the alcohol (26). Boron tritiuoride does not give the ester, but gives either a complex or dehydrated product. 

In addition to the boron trifluoride-diethyl ether complex, chlorotrimcthylsilanc also shows a rate accelerating effect on cuprate addition reactions this effect emerges only if tetrahydrofuran is used as the reaction solvent. No significant difference in rate and diastereoselectivity is observed in diethyl ether as reaction solvent when addition of the cuprate, prepared from butyllithium and copper(I) bromide-dimethylsulfide complex, is performed in the presence or absence of chlorotrimethylsilane17. If, however, the reaction is performed in tetrahydrofuran, the reaction rate is accelerated in the presence of chlorotrimethylsilane and the diastereofacial selectivity increases to a ratio of 88 12 17. In contrast to the reaction in diethyl ether, the O-silylated product is predominantly formed in tetrahydrofuran. The alcohol product is only formed to a low extent and showed a diastereomeric ratio of 55 45, which is similar to the result obtained in the absence of chlorotrimethylsilane. This discrepancy indicates that the selective pathway leading to the O-silylated product is totally different and several times faster than the unselective pathway" which leads to the unsilylated alcohol adduct. A slight further increase in the Cram selectivity was achieved when 18-crown-6 was used in order to increase the steric bulk of the reagent. 

Excellent chelation control was observed using tributyl(2-propenyl)stannane and a-benzyloxy-cyclohexaneacetaldehyde with magnesium bromide or titanium(IV) chloride, whereas useful Cram selectivity was observed for boron trifluoride-diethyl ether complex induced reactions of the corresponding ferr-butyldimethylsilyl ether89. 

For a-benzyloxycyclohexaneacelaldehyde and 2-butenylstannanes, good chelation control was observed using zinc iodide and titanium(IV) chloride, but only weak synjanti selectivity. Better syn/anti selectivity was found using boron trifluoride-diethyl ether complex, but weak chelation control. Magnesium bromide gave excellent chelation control and acceptable syn/anli selectivity90. 

In a more recent study, Wang and coworkers have discussed microwave-assisted Suzuki couplings employing a reusable polymer-supported palladium complex [141]. The supported catalyst was prepared from commercial Merrifield polystyrene resin under ultrasound Bonification. In a typical procedure for biaryl synthesis, 1 mmol of the requisite aryl bromide together with 1.1 equivalents of the phenyl-boronic acid, 2.5 equivalents of potassium carbonate, and 10 mg of the polystyrene-... 

A similar approach was taken for the synthesis of 45 by Miyaura. " Shaughnessy and Booth synthesized the water-soluble alkylphosphine 46, and found it to provide very active palladium catalysts for the reaction of aryl bromides or chlorides with boronic acids. The more sterically demanding ligand 47 was shown to promote the reactions of aryl chlorides with better results than 46. Najera and co-workers recently reported on the synthesis of di(2-pyridyl)-methylamine-palladium dichloride complexes 48a and 48b, and their use in the coupling of a variety of electrophiles (aryl bromides or chlorides, allyl chlorides, acetates or carbonates) with alkyl- or arylboronic acids very low catalyst loadings at Palladium-oxime catalysts 8a and 8b) have also been developed. In conjunction with... 

---