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。