Azacarbaborane chemistry. Butyl nitrite synthesis of the new eight-, nine- and ten-vertex azacarbaboranes exo- and endo-7-CH3-hypho-7,8-NCB6H11, nido-6,8,9-NC2B7H10, arachno-6,5,9-NC2B7H12 and arachno-6,5,10-C2NB7H12

Abstract

The reaction between excess n-C₄H₉ONO and arachno-4,5-C₂B₇H₁₃ (1) in diethyl ether at room temperature results in the formation of the first representatives of the arachno ten-vertex azadicarbaborane family, arachno-6,5,9-NC₂B₇H₁₂ (2) and arachno-6,5,10-NC₂B₇H₁₂ (3) in yields of 6 and 20%, respectively. The reaction also generates exo-8-CH₃-hypho-7,8-NCB₆H₁₁ (4) (yield 5%) as a result of the extrusion of the CH₂ group from the cluster of the starting dicarbaborane to generate a terminal methyl unit. The reaction between 8,9-μ-NH₂-arachno-5,6-C₂B₈H₁₁ (5) and NaH, followed by treatment with iodine and water, produced the unique endo isomer of 4, endo-8-CH₃-hypho-7,8-NCB₆H₁₁ (6) (yield 22%). The reaction between n-C₄H₉ONO and nido-5,6-C₂B₈H₁₂ (7) in hexane at reflux generates the first compound of the ten-vertex nido azadicarbaborane family, nido-6,8,9-C₂NB₇H₁₀ (8), in 13% yield. The structures of all the compounds isolated are proposed on the basis of NMR spectroscopy, the geometries optimized at the RMP2(fc)/6-31G* level and their correctness was supported on the basis of GIAO-SCF NMR calculations.