Dyker C Adam, Riegel Susanne D, Burford Neil, Lumsden Michael D, Decken Andreas
Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, B3H 4J3, Canada.
J Am Chem Soc. 2007 Jun 13;129(23):7464-74. doi: 10.1021/ja070764f. Epub 2007 May 22.
The first derivatives of catenated cyclotetraphosphinophosphonium cations, [(PhP)4PPhMe]+ (8a), [(MeP)4PMe2]+ (8b), [(CyP)4PPh2]+ (8d), [(CyP)4PMe2]+ (8e), [(PhP)4PPh2]+ (8f), [(PhP)4PMe2]+ (8g), are synthesized as trifluoromethanesulfonate (triflate, OSO2CF3-) salts through the reaction of cyclopentaphosphines (PhP)5 (4a) or (MeP)5 (4b) with methyl triflate (MeOTf) or by a net phosphenium ion [PR2+, R = Ph, Me; from R2PCl and trimethylsilyltriflate (Me3SiOTf)] insertion into the P-P bond of either cyclotetraphosphine (CyP)4 (3c) or cyclopentaphosphines (PhP)5 (4a) or (MeP)5 (4b). Although more conveniently prepared from 4a, compound 8a[OTf] can also be formed from (PhP)4 (3a) and MeOTf, and derivatives 8f[OTf] and 8g[OTf] are also accessible through reactions of 3a and R2PCl/Me3SiOTf with R = Ph or Me, respectively. A tetrachlorogallate salt of [(PhP)4PPhtBu]+ (8c) has been synthesized by alkylation of 4a with tBuCl/GaCl3. 31P[1H] NMR parameters for all derivatives of 8 have been determined by iterative simulation of experimental data. Derivatives 8a[OTf], 8b[OTf], 8c[GaCl4], 8e[OTf], 8f[OTf], and 8g[OTf] and have been characterized by X-ray crystallography, showing the most favorable all-trans configuration of substituents for the phosphine centers, thus minimizing steric interactions. Each derivative adopts a unique envelope or twist conformation of C1 symmetry. The effective C2 symmetry observed for 8b, d, e, f, and g in solution, signified by their 31P[1H] NMR AA'BB'X spin systems, implies a rapid conformational exchange for derivatives of 8. The core frameworks of the cations in the solid state are viewed as snapshots of different conformational isomers within the solution-phase pseudorotation process.
通过环戊基膦（PhP）5（4a）或（MeP）5（4b）与三氟甲磺酸甲酯（MeOTf）反应，或通过净磷鎓离子[PR2 +，R = Ph，Me；由R2PCl和三甲基甲硅烷基三氟甲磺酸盐（Me3SiOTf）]插入环四膦（CyP）4（3c）或环戊基膦（PhP）5（4a）或（MeP）5（4b）的P - P键中，合成了连环环四膦鎓阳离子[(PhP)4PPhMe]+ (8a)、[(MeP)4PMe2]+ (8b)、[(CyP)4PPh2]+ (8d)、[(CyP)4PMe2]+ (8e)、[(PhP)4PPh2]+ (8f)、[(PhP)4PMe2]+ (8g)的一价衍生物，以三氟甲磺酸盐（三氟甲磺酸盐，OSO2CF3-）盐的形式存在。尽管8a[OTf]更方便地由4a制备，但它也可以由（PhP）4（3a）和MeOTf形成，衍生物8f[OTf]和8g[OTf]也分别可以通过3a与R2PCl/Me3SiOTf（R = Ph或Me）的反应得到。[(PhP)4PPhtBu]+ (8c)的四氯镓酸盐已通过4a与tBuCl/GaCl3的烷基化反应合成。通过对实验数据的迭代模拟确定了8的所有衍生物的31P[1H] NMR参数。衍生物8a[OTf]、8b[OTf]、8c[GaCl4]、8e[OTf]、8f[OTf]和8g[OTf]已通过X射线晶体学表征，显示了膦中心取代基最有利的全反式构型，从而使空间相互作用最小化。每个衍生物都采用独特的C1对称信封式或扭曲构象。在溶液中观察到8b、d、e、f和g具有有效的C2对称性，由它们的31P[1H] NMR AA'BB'X自旋系统表示，这意味着8的衍生物存在快速的构象交换。固态阳离子的核心框架被视为溶液相假旋转过程中不同构象异构体的快照。
