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A series of monoiodoborane adducts LBH 2 I (L = N(CH 3 ) 3 pyridine, 3-methylpyridine, 4-methylpyridine or (C 6 H 5 ) 3 P) has been prepared. Ideally, the addition of suitable amines, phosphines or trimethylarsine to a benzene solution of these adducts would be expected to yield boronium salts containing two different donors coordinated to a central boron atom. These salts, of the general formula LL′BH 2 I, were formed in several instances (L′ = (CH 3 ) 3 P, (C 6 H 5 ) 3 P, (CH 3 ) 3 N). Six previously unreported boronium cations have been characterized. The iodide salts of these boronium cations may be easily converted to their hexafluorophosphate analogs except for the large ligands such as (C 6 H 5 ) 3 P or 3-methylpyridine. In contrast, trimethylarsine reacted with 4-MepyBH 2 I in benzene to give 4-MepyH + I − and [(CH 3 ) 3 AsI] + I − . The proton and boron NMR spectra of all species were investigated when experimentally feasible.

The adducts of BI3 and BBr3 with various tertiary phosphines and their chalcogenide derivatives are described. The proton and boron-11 NMR spectra of many of these compounds are reported for the first time. Although the methyl proton-phosphorus-31 coupling constants are nearly identical in the (CH3)3PBX3 (X = F, Cl, Br, I) series, the boron-phosphorus coupling constant, JBP, is anomalously low for (CH3)3PBI3 (116 Hz) relative to other members of the series. The phosphine adducts of BBr3 and BI3 are white, air and water insensitive solids, whereas the phosphine chalcogenide adducts are quite moisture sensitive. The BI3 adducts with phosphine chalcogenides lose iodine fairly readily to form intractable material.

The addition of an equivalent of Cl 2 , Br 2 or I 2 to a solution of Na[H 3 BCN] in glyme (1,2-dimethoxyethane) yields the cyanoborane cyclic oiligomers previously reported. The addition of an excess of a Lewis base (e.g. a pyridine, a tertiary amine or a tertiary phosphine) to the cyanoborane yields a cyanoborane adduct, LBH 2 CN. The addition of an excess of chlorine yields a solution believed to contain [glyme]-BH 2 CN. This solution reacts slowly with Lewis bases (L) to yield LBH 2 CN, and small amounts of chlorinated cyanoborane adducts. The proportion of chlorinated products relative to LBH 2 CN increases as the amount of moisture in the reaction mixture increases and as the base strength of L is reduced. The chlorination of LBH 2 CN in moist benzene yields LBCl 2 CN as the principal product when L is pyridine, while a complex misture is obtained when L = (C 2 H 5 ) 3 N.

A series of monohalo- and monopseudohalo-broane adducts LBH 2 X, (L = pyridine, (CH 3 ) 3 N, (CH 3 ) 3 P; X = F, Cl, Br, I, NCS, NCSe) has been prepared and characterized. A correlation was made between the boron-hydrogen coupling constant ( J BH ), the electronegativity of X ( E x ) and the estimated B-X bond distance ( D x ). For L = (CH 3 ) 3 N, J BH = 3·336 E x + 36·426 D x + 47·233, while for L = pyridine, J BH = 34·583 E x + 18·116 D x − 10·328. There was negligible change in J BH in the (CH 3 ) 3 PBH 2 X series.

The new compound tris(trifluoromethylthio)borane, (CF3S)3B, has been prepared by interaction of BBr3 and Hg(SCF3)2 in hydrocarbon solvent. The thioborane is a fairly volatile liquid which decomposes slowly at room temperature yielding BF3 and SCF2. Due to the enhanced Lewis acidity of B(SCF3)3 relative to its proton analog, reaction of the compound with excess trimethylamine gives a white 1:1 adduct whereas B(SCH3)3 does not. The new adduct decomposes in the solid state or in solution to yield (CH3)3NBF3 and a brown-yellow solid material.

New 1 : 1 adducts of BBr3 and BI3 with (CH3)3As and (CH3)3Sb are reported. The (CH3)3As adducts are stable indefinitely at room temperature under an inert atmosphere while the (CH3)3Sb compounds slowly decompose at that temperature to form (CH3)3SbX2 (X = Br, I). Boron-11 and proton NMR data suggest that these species may exist as ions in chloroform solution.