Light group 13 chloride diazadiene complexes: consequences of varying substituent bulk
作者:Alan Hinchliffe、Francis S. Mair、Eric J. L. McInnes、Robin G. Pritchard、John E. Warren
DOI:10.1039/b712911d
日期:——
BCl3 cyclizes diazadiene (2,6-Pri2C6H3NCH)21 through a dichloroborated intermediate [(2,6-Pri2C6H3NCHCl)2BCl] 3 to give, in polar aprotic solvents, a spontaneously dehyrochlorinated C-chloro diazaborole 4. In contrast, reaction of AlCl3 with 1 forms only acyclic mono- or di-adducts 5a/b and 6. Alkali metal reductions of 3 gave mixtures of 4 and diazaborole [(2,6-Pri2C6H3NCH)2BCl] 7. Pd(0) reduction cleanly gave diazaborole 7. Reduction of 6 gave a low yield of the closed shell C–C coupled dimer 8 of the putative diazadiene radical anion 1·AlCl2 complex monomer. An alternative synthesis for diazadiene (2,6-Pri2C6H4NCPh)2, 2, is reported. Reduction of 2/BCl3, in which additional phenyl groups on the diazadiene C-2 and C-3 atoms hinder the radical coupling observed in 8, gave predominantly diazaborole 2·BCl, (9a) contaminated with 2·BCl2, (9b) the first such stable radical diazadiene complex of boron. All compounds 2–9 were characterized by X-ray diffraction and NMR spectroscopy. Stable radical 9b was additionally characterized by EPR spectroscopy and density functional computation.
BCl3 通过二氯硼酸化中间体 [(2,6-Pri2C6H3NCHCl)2BCl] 3 环化二氮杂二烯 (2,6-Pri2C6H3NCH)21,在极性非质子溶剂中生成自发脱氢氯化的 C-氯二氮硼杂环 4。 相反,AlCl3 与1 仅形成无环单加合物或二加合物 5a/b 和 6。 3 的碱金属还原得到 4 和二氮杂硼杂环己烷的混合物 [(2,6-Pri2C6H3NCH)2BCl] 7. Pd(0) 还原干净地得到二氮杂硼杂环己烷 7. 还原6 给出了假定的二氮杂二烯自由基阴离子 1·AlCl2 复合单体的闭壳 C-C 偶联二聚体 8 的低产率。报道了二氮杂二烯 (2,6-Pri2C6H4NCPh)2, 2 的替代合成。 2/BCl3 的还原,其中二氮杂二烯 C-2 和 C-3 原子上的额外苯基阻碍了 8 中观察到的自由基偶联,主要得到二氮杂硼杂环戊二烯 2·BCl,(9a) 被 2·BCl2 污染,(9b)第一个这样的稳定的硼自由基二氮杂二烯络合物。所有化合物 2-9 均通过 X 射线衍射和核磁共振波谱进行表征。稳定自由基 9b 还通过 EPR 光谱和密度泛函计算进行了表征。