Phosphorus-phosphorus coupling in a diphosphine with a ten bond P...P separation.
The large, unsymmetrical diphosphine 5,11,17,23-tetra-tert-butyl-25,26-bis(diphenylphosphinomethoxy)-27(or 28)-benzoyloxy-28(or 27)-hydroxycalix[4]arene, in which the phosphorus atoms are separated by ten bonds, was prepared by monobenzoylation of 5,11,17,23-tetra-tert-butyl-25,26-bis(diphenylphosphinoylmethoxy)-27,28-bis(hydroxy)calix[4]arene, followed by reduction with phenyl silane. Its molecular structure has been determined by X-ray crystallography. In the solid state, the phosphorus atoms are separated by 5.333(1) A. NMR investigations reveal an unexpected "through-space"J(PP') coupling constant of 8.0 Hz and also show that, in solution, the calixarene is conformationally mobile, the phenoxy ring flipping rapidly through the calixarene annulus. The spatial proximity of the two phosphorus atoms was further demonstrated by the ease of obtaining the cis-chelate complex [Pd(eta3-C3H4Me)(THF)2]BF4 (THF = tetrahydrofuran).
Kuhn
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Laboratoire de Chimie Inorganique Moléculaire, LC 3 CNRS-Université Louis Pasteur, 1 rue Blaise Pascal, F-67008 Strasbourg cedex, France.
Jeunesse
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Matt
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Harrowfield
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Ricard
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