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

摘要: Three 25,26-bridged para-tert-butyl-calix[4]arene phosphites, 1–3, have been synthesized by linking two proximal phenolic oxygen atoms of to a P(OR) [R = 2,6-But2–4-Me-C6H2 (1), 2,6-Pri2-C6H3 (2) or 2,4-But2-C6H3 (3)] moiety. NMR spectroscopic data and X-ray crystallographic studies (1 2 only) show that the calixarene framework in 1 adopts cone conformation, whereas 3 it assumes partial conformation. Unsymmetrical 25,26;27,28-dibridged bisphosphites 5–7 reaction phosphite with (R′O)PCl2 [R′ (5), (6) (1R,2S,5R)-(−)menthyl (7)]. investigations (homonuclear 31P COSY) revealed an unprecedented “through-space” phosphorus–phosphorus coupling 223–244 Hz for these unsymmetrical bisphosphites. The molecular structure 25,26;27,28-bridged bisphosphite 5 was determined crystallography; phosphorus are close proximity P⋯P distance (3.543(2) A) is less than sum their van der Walls radii.