NMR and X-ray crystallographic studies of unsymmetrical 25,26;27,28-dibridged para-tert-butyl calix[4]arene bisphosphites with a large “through-space” P–P coupling
作者:Pathik Maji、Setharampattu S. Krishnamurthy、Munirathinam Nethaji
DOI:10.1039/b903771c
日期:——
Three 25,26-bridged para-tert-butyl-calix[4]arene phosphites, 1â3, have been synthesized by linking two proximal phenolic oxygen atoms of para-tert-butyl-calix[4]arene to a P(OR) [R = 2,6-But2â4-Me-C6H2 (1), 2,6-Pri2-C6H3 (2) or 2,4-But2-C6H3 (3)] moiety. NMR spectroscopic data and X-ray crystallographic studies (1 and 2 only) show that the calixarene framework in 1 adopts a cone conformation, whereas in 2 and 3 it assumes a partial cone conformation. Unsymmetrical 25,26;27,28-dibridged para-tert-butyl-calix[4]arene bisphosphites 5â7 have been synthesized by the reaction of 25,26-bridged para-tert-butyl-calix[4]arene phosphite 1 with (Râ²O)PCl2 [Râ² = 2,4-But2-C6H3 (5), 2,6-Pri2-C6H3 (6) or (1R,2S,5R)-(â)menthyl (7)]. NMR investigations (homonuclear 31P COSY) revealed an unprecedented âthrough-spaceâ phosphorusâphosphorus coupling of 223â244 Hz for these unsymmetrical 25,26;27,28-dibridged para-tert-butyl-calix[4]arene bisphosphites. The molecular structure of unsymmetrical 25,26;27,28-bridged bisphosphite 5 was determined by X-ray crystallography; the two phosphorus atoms are in close proximity and the Pâ¯P distance (3.543(2) Ã
) is less than the sum of their van der Walls radii.
通过将对叔丁基杯[4]芳烃的两个近端酚羟基氧原子连接到P(OR) [R = 2,6-二丁基-4-甲基苯(1), 2,6-二异丙基苯(2)或2,4-二丁基苯(3)]基团上,合成了三种25,26-桥联的对叔丁基杯[4]芳烃膦酸酯1-3。核磁共振(NMR)光谱数据和X射线晶体学研究(仅1和2)显示,1中的杯芳烃骨架采用圆锥构型,而在2和3中则为部分圆锥构型。通过25,26-桥联的对叔丁基杯[4]芳烃膦酸酯1与(R'O)PCl2 [R' = 2,4-二丁基苯(5), 2,6-二异丙基苯(6)或(1R,2S,5R)-(+)-薄荷基(7)]反应,合成了三种不对称25,26;27,28-双桥联的对叔丁基杯[4]芳烃双膦酸酯5-7。NMR研究(同核31P COSY)揭示了这些不对称25,26;27,28-双桥联的对叔丁基杯[4]芳烃双膦酸酯中前所未有的“跨空间”磷-磷耦合,耦合常数为223-244 Hz。通过X射线晶体学确定了不对称25,26;27,28-双桥联双膦酸酯5的分子结构;两个磷原子距离很近,P···P距离(3.543(2) Å)小于它们范德华半径之和。