P O LIGAND SYSTEMS - SYNTHESIS, REACTIVITY, AND STRUCTURE OF TERTIARYO-PHOSPHANYLPHENOL DERIVATIVES/

Reactions of C,O-dilithium reagents 1 (M = M' = Li) or C,O-lithium-sod ium reagents 1 (M = Li, M' = Na) with chlorophosphanes afford C,O-disu bstitution products 2 or phosphanylphenolates 3 which are treated subs equently with ClSiMe(3) to give 4-methyl- and bulky 4,6-di-tert-butyl substituted o-phosphanylphenol silyl ethers 4. These were applied for the preparation of the corresponding o-phosphanylphenols 5, mainly P-a symmetric derivatives. Limitations and side reactions by use of 1 in t he above synthesis are discussed. Acid-base properties, pH-dependent s olubility in water/hexane, and substitution reactions at oxygen and ph osphorus of selected representatives of 5 are reported. An example for the separation of enantiomers by esterification with (1S)-(-)-camphan ic acid chloride is given. IR studies revealed intramolecular P ... H- O bonds and (2)J(PC) the preferred trans arrangement of the phenoxy gr oup in solution. In the solid state, inter- and intramolecular P ... H -O bonds were detected by X-ray structure analysis. The trans arrangem ent of the phenoxy group is preserved. Because of steric hindrance, th e O substituents are tilted towards the phosphorus atom and thus induc e large through-space coupling constants. The P ... Sn distance of 336 .9 pm in the bulky substituted O-SnMe(3) moiety 8h is however too larg e for the formation of genuine intramolecular coordination. The versat ility of o-hydroxyarylphosphanes and objectives of further studies are shown by preliminary results on complex formation and applications of these phosphanes in catalysis.