Boronium ions

Displacement of a ligand from a boronium ion by a more basic ligand is also a useful synthetic procedure. 

Hydrolytic and oxidative stability of the cations increase with the base strength of the ligand. Bistrimethylamine-boronium cations are unusually stable. They have been recovered, apparently unchanged after prolonged periods of time at 100°in concentrated acids (HC1, H2SO4, andHNOs) and 10% NaOH. On the other hand bisdialkyl sulfide boronium ions are rapidly attacked by cold water. The ion [BH2(OH2)2]+ is perhaps the most unstable thermally and hydrolytically of the boronium ions reported. Evidence has been claimed for its existence in 8 MHC1 solution at 70° 95,96). 

Boronium ions containing mixed neutral ligands have been prepared also. A general preparative reaction is listed below 82,99-102)... 

Piers and co-workers have shown that pyridine-stabilized borabenzenes 76 (R = H, Me, Pr1) react with cationic Bronsted acids such as pyridinium hydrochloride to produce the boronium ions 77 and 78 in 1 1 ratio. Protonation occurs at C-2 and C-4, respectively, followed by addition of pyridine at electrophilic boron <2005CC2480>. 

As a result of the hydridic nature of the hydrogen attached to boron, amine-boranes are interesting and useful reducing agents and have been employed in the reduction of numerous organic carbonyl compounds. They have been utilized in studying the kinetics and mechanism of hydride reactions and are precursors for the synthesis of substituted boranes, borazines, boronium ions, higher boron hydrides, and carboranes. 

G. Rasul, G. K. S. Prakash and G. A. Olah, Calculated nB-13C NMR chemical shift relationship in hypercoordinate methonium and boronium ions. Proc. Natl. Acad. Sci. USA, 1998, 95, 7257-7259. 

Examples oftetra-coordinate boronium ions (41) have been known for many years. The quest for low-coordinate, neutral borane compounds also stimulated interest in the formation of three-coordinate borenium ions (42) and two-coordinate borinium ions (43). ... 

A reaction pathway involving heterolytic cleavage of the B—B bond might be expected to yield trans addition products if intermediates such as a coordinated boronium ion (VI) or a coordinatively stabilized carbonium ion (VII) were involved or nonspecific addition if a carbonium ion intermediate such as (VIII) were produced. The formally similar electrophilic addition of halogen to simple olefins is, of course, well known to lead to... 

Fox P A, Griffin S T, Reichert W M, et al. Exploiting isolobal relationships to create new ionic liquids Novel room-temperature ionic liquids based upon (N-alkylunidazole)(amine)BH2 "boronium" ions. Chem. Commun. 2005. 3679-3681. 

The BHy boronium ion, which is isoelectronic and isostructural with the computed carbon analog CHy trication, has Csv symmetrical form similar to... 

The data on boronium ions are very sparse, but two interesting examples, which are additionally optically active, have been recorded. The shift of the ion (18 X = H) is 17-8+ 0-5 p.p.m. (from trimethyl borate) with a coupling constant of 90 + 5c./sec., and that of (18 X = C1), the shift is 9 3 + 0-8 p.p.m. with coupling constant of... 

Synthesis, reactivity, and applications of cyclic and heteryl-substituted borinium, borenium, and boronium ions 05AG(E)5016. 

The reactive boronium ion (88) has been prepared from l,8-bis(dimethylamino) naphthalene and has been shown to be effective in the borylation of pyrrole and indole derivatives. Catechol-ligated borenium cations, such as (89), have also been used in the borylation of a range of anilines, thiophenes, and (V-heterocycles. ... 

Fox, P.A., Griffin, S.T., Reichert, W.M., Salter, E.A., Smith, A.B., Tlckell, M.D., Mcker, B.F., Cioffi, E.A., Davis, J.H., Rogers, R.D. and W erzbicki, A., Exploiting isolobal relationships to create new ionic liquids Novel room-tenperature ionic liquids based upon (iV-alkylimidazole)(amine) BH2 boronium ions, Chem. Commun. (29), 3679-3681 (2005). 

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