Amine-promoted nucleophilic addition of tert-butyl hydroperoxide to 2,5-diphenylphosphacymantrene: oxygen-oxygen bond cleavage and novel rearrangement with RO group transfer from oxygen to phosphorus

Abstract

The reaction of 2,5 diphenyl 1 phosphacymantrene (1) with hydroperoxide Ме 3 СООН was carried out in MeCN-Et 2 NH. The attack of nucleophile Ме 3 СОО -to the phosphorus atom in compound 1 followed by the Arbuzov type rearrangement P III  P V afforded complex 2 with the  4 phosphoryl ligand characterized by X ray diffraction analysis, IR spectroscopy, and 1 Н, 13 С, and 31 Р spectroscopy.We have recently 1,2 described the addition of a strong nucleophile ОН -to the phosphorus atom in 2,5 diphenyl phosphacymantrene (1) promoted by amines NEt 2 H, NEt 3 , and NEtPr i 2 in the presence of a minor amount of water. The reaction affords ionic complexes, whose an ions are  4 manganese complexes with the tetracoordi nate phosphorus(V) atom bound by the double bond to the oxygen atom and by the ordinary bond to the hydrogen atom with the [NH 2 Et 2 ] + and [K Crown 6] + cations as counterions. The source of ОН -is a water molecule. The role of amine is the abstraction of the water proton and liberation of the strong nucleophile ОН -attacking the phosphorus atom. It is most likely that an unstable inter mediate with the Р-ОН bond is formed first and is almost instantly cleaved with H migration from oxygen to phos phorus. Solid KOH in a combination with crown ether was earlier applied 3 to obtain active ОН -, and the ionic complex [(СO) 3 Mn( 4 Ph 2 H 2 C 4 P(O)H)] -[K Crown 6] + was formed. To extend the number of nucleophiles react ing with phosphacymantrenes, we studied the reaction of compound 1 with tert butyl hydroperoxide (Scheme 1).The reaction of compound 1 with hydroperoxide Ме 3 СООН and diethylamine in benzene or MeCN af forded ionic complex [(CO) 3 Mn  4 -Ph 2 H 2 C 4 P(О)R] -[Et 2 NH 2 ] + (2, R = Me 3 COO) (see Scheme 1). It can be assumed that unstable intermediates with the Р-ОН or Р-ОR bond are formed first and immediately undergo rearrangement with the migration of the H atom or R substituent from the oxygen atom to the phosphorus atom. In the case of R = Bu t OР(О), anionic complex 2 with the Bu t O(P=O) moiety was isolated as a stable final product and protonated amine is a cation of the salt (see Scheme 1).The basic distinction between the reaction of com pound 1 with Ме 3 СООН and the previous examples 1-3 is that a fairly large organic group migrates rather than the hydrogen atom and the О-О bond is cleaved in this case. Evidently, the driving force of the second stage of the * To the 60th anniversary of the foundation of A. N. Nesmeya nov Institute of Organoelement Compounds of the Russian Acad emy of Sciences.