Boron Halide-Amine Coordination Compounds

Submitted by Dallas T. Hurd and Robert C. Osthoff Checked by Albert W. LAUBENGAYERf and Daniel Jacobs  

The boron halides form a number of coordination compounds with various amines, the variety of such compounds decreasing from the trifluoride to the triiodide and from the tertiary amines to the primary.1,2 Preparation is usually effected by direct combination of boron halide and amine,3- often with provision for external cooling to remove heat released in the reaction. The following syntheses exemplify general methods that can be employed. 

A slow current of trimethylamine is admitted to the flask. Then the valve on the boron fluoride cylinder is opened slowly. The flask will fill immediately with dense white fumes of the product. The valve on the boron fluoride cylinder is adjusted so that the bubbler shows no appreciable net flow of gas out of the flask, and the reaction is allowed to continue until the desired quantity of product has accumulated in the flask. The flow of trimethylamine is discontinued, and then that of boron fluoride is stopped, t The white solid product can be recrystallized from benzene or ethanol. The yield for a reaction time of 40 minutes is ca. 12.5 g. 

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Borazole (borazine), derivatives of, from boron halide-amine coordination compounds, 5 28 Boric acid, H3BO3, esters of, 6 29 Boron bromide, 3 27, 29 Boron chloride, 3 27, 28, 29 Boron chloride-trimethylamine, 6 27... 

Boron halides, coordination compounds with amines, 5 26 Boron imide, condensed derivatives of, from boron halide-amine coordination compounds, 6 28 Boron oxide, porous, 2 22 Bromamide, di- (NHBr2), 1 62 analysis of, 1 64... 

Boron halide-amine coordination compounds, synthesis 8... 

Amines, coordination compounds with boron halides, 6 26 1-Aminobiuret (allophanyl hydrazide), 5 48, 50, 51 Aminoguanidonium hydrogen carbonate, 3 45 analysis of, 3 46... 

A review of the chemistry of Group III complexes shows that many of the concepts of Werner s coordination chemistry may be applied to these elements. Furthermore, the differences observed in the complexing behavior between ammonia and trimethylamine refiect fundamental differences in the amines. Ammonia tends to give ionic compounds, whereas trimethylamine tends to give non-ionic products. Trends observed with the metal halides can be extrapolated into hydrides of boron, aluminum, and gallium. An extension of Werner s concepts provides a significant... 

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