Unexpected formation of highly stabilized tetrakis-(2-alkoxyphenyl)bismuthonium salts in the oxidation of tris-(2-alkoxyphenyl)bismuthanes with iodosylbenzene
作者:Hitomi Suzuki、Tohru Ikegami、Nagao Azuma
DOI:10.1039/a700379j
日期:——
Treatment of tris-(2-alkoxyphenyl)bismuthanes 1 with iodosylbenzene
in methylene dichloride at 40 °C led to none of the expected
bismuthane oxides 2 but, quite unexpectedly, gave
tetrakis-(2-alkoxyphenyl)bismuthonium chlorides 3 in moderate to good
yields. In some cases, bismuthonium formates 4 accompanied the main
reaction products. Similar treatment in benzene in the presence of
benzyl bromide, ethyl bromide, or 2,2,2-trifluoroethyl iodide led to the
corresponding bismuthonium bromides 7 and iodides 8. Through anion
exchange, a variety of bismuthonium salts including formate 4,
tetrafluoroborate 11, toluene-p-sulfonate 12, bromide 7, iodide
8 and perchlorate 13 were prepared from the salt 3 in good yields. In
contrast to the known tetraphenylbismuthonium salts, all of these new
bismuthonium salts exhibited high thermal stability. The molecular
structure of compound 7a was elucidated by X-ray analysis, where the
four neighbouring oxygen atoms are found to surround the bismuth atom
tetrahedrally via a weak through-space interaction with the
metal, making the bismuth centre less susceptible to nucleophilic attack
of the halide anion.
将三-(2-烷氧基苯基)铋烷1与碘苯在二氯甲烷中于40 °C反应,并没有得到预期的铋烷氧化物2,而是意外地得到了四-(2-烷氧基苯基)铋正离子氯化物3,产率中等至良好。在某些情况下,铋正离子甲酸盐4伴随主要反应产物出现。在苯中进行类似的反应,并存在苄溴、乙基溴或三氟乙基碘时,得到了相应的铋正离子溴化物7和碘化物8。通过阴离子交换,从盐3中制备了多种铋正离子盐,包括甲酸盐4、四氟硼酸盐11、对甲苯磺酸盐12、溴化物7、碘化物8和高氯酸盐13,产率均良好。与已知的四苯基铋正离子盐相比,这些新型铋正离子盐表现出高热稳定性。化合物7a的分子结构通过X射线分析阐明,其中四个相邻的氧原子通过与金属的弱间接相互作用以四面体方式围绕铋原子,使得铋中心对卤化阴离子的亲核攻击的敏感性降低。