Diborane(4) compounds with bidentate diamino groups

Abstract

The reaction between B₂(NMe₂)₄ and 1,2-(NH₂)₂-4-Bu^tC₆H₃ affords the diborane(4) compound 1,2-B₂{1,2-(NH)₂-4-Bu^tC₆H₃}₂ as the exclusive product whilst the reaction between rac-1,2-(NH₂)₂C₆H₁₀ and B₂(NMe₂)₄ also affords only the 1,2-isomer, i.e.1,2-B₂{1,2-(NH)₂C₆H₁₀}₂, which is shown to be the more stable isomer by computational methods. The previously reported compounds 1,1-B₂{1,2-(NH)₂C₆H₄}₂ and 1,2-B₂{1,2-(NH)₂C₆H₄}₂ both react with four equivalents of BuⁿLi to give what are presumed to be tetra-anions which react further with MeI, SnClMe₃ or SnClPh₃ to give the tetrasubstituted products 1,1-B₂{1,2-(NMe)₂C₆H₄}₂, 1,1-B₂{1,2-(NSnMe₃)₂C₆H₄}₂ and 1,2-B₂{1,2-(NSnPh₃)₂C₆H₄}₂ respectively. The compound 1,1-B₂{1,8-(NH)₂C₁₀H₆}₂ has also been prepared from the reaction between B₂(NMe₂)₄ and 1,8-diaminonaphthalene. Lithiation and subsequent reaction with SnClMe₃, SnCl₂Me₂ or SnCl₂Ph₂ affords 1,1-B₂{1,8-(NSnMe₃)₂C₁₀H₆}₂, 1,1-B₂{1,8-(N₂-μ-SnMe₂)C₁₀H₆}₂ and 1,1-B₂{1,8-(N₂-μ-SnPh₂)C₁₀H₆}₂ respectively. All new compounds have been characterised by X-ray crystallography.