Bi- and tricyclic penta- and hexacoordinated phosphoranes with varying ring sizes: Synthesis, structures, and reactivity

Abstract

New tricyclic hexacoordinated phosphoranes 1-6 with internal N→P coordination containing ring sizes varying from five to eight membered have been synthesized by oxidative addition of a quinone or a diol to a cyclic phosphite. The bicyclic phosphorane (NC9H6O)P(O2(3,5-t-Bu)2C6H2)((O-2,4-(t-Bu)2C6H2)2CH2)· 1/4 H2O (7· 1/4 H2O) has been synthesized by adding the 3,5-di-tert-butyl-o-benzoquinone to the cyclic phosphite. The compound (NC9H6O)P(2,2'-OC6H4C6H4O)2 (6) results from a novel ring exchange reaction of a phosphorinane by a phosphepin in two ways: (a) by treating (OCH2CMe2CH2O)P((OC9H6N) with 2,2'-biphenol/N-chlorodiisopropylamine and (b) by treating (Et2N)P(OCH2CMe2CH2O)(2,2-OC6H4C6H4O) with 8-hydroxyquinoline. Treatment of the aminophosphorane (Et2N)P(OCH2CMe2CH2O)(O2C14H8) with 2,4,6-trimethylbenzoic acid led to the unique ester (OCH2CMe2CH2O)P(O){OC14H8O(C(O)-2,4,6-Me3C6H2)} (10). 31P NMR data for the new compounds are discussed with respect to the differing ring sizes and coordination number on phosphorus. X-ray analysis shows hexacoordination in 2, 4, and 6 with an N→P bond and pentacoordination in 7 without an N→P bond. The coordinating nitrogen is trans to an oxygen of the six-membered ring in 2 and of the seven-membered ring in 4. The eight-membered ring in 7 spans a diequatorial position in a trigonal bipyramidal arrangement.