Platinum-mediated oxidative P-O coupling of white phosphorus and alcohols:an ab initio study

Ab initio quantum chemical investigations of the oxidative P-O coupling of white phosphorus and alcohol have been carried out by the model platinum co mplexes [PtCl3(CH3OH)(eta(2)-P-4)](+) (1), [PtCl3(CH3OH)(eta(2)-P-4)](-) (2 ), [PtBr3(CH3OH)(eta(2)-P-4)](+) (3), [PtBr3(CH3OH)(eta(2)-P-4)](-) (4) and [PtClBr2(CH3OH)(eta(2)-P-4)](+) (5) applying the B3PW91 model of density f unctional theory. According to the performed geometry optimizations, both t he tetrahedral P-4 and CH3OH molecules are deformed and activated in comple xes 1-5. The results of the calculated total atomic charge (TAC) and overla p population (OP) show that the better conditions accounting for the nucleo philic attack of the P-4 molecule by the alkoxide ion, that is originated f rom the coordinated CH3OH molecule, are found in the cationic Pt(IV) eta(2) -P-4 complexes 1, 3 and 5. In these molecules, the coordinated P-4 molecule acts as an electron-pair acceptor and easily reacts with the alkoxide liga nd. The results of the present calculations agree with the experimental obs ervation indicating that the P-O coupling reaction between P-4 and ROH, whi ch affords trialkylphosphates, proceeds only in the presence of a Pt(IV)(et a(2)-P-4) intermediate complexes. The halide ligands, which complete the co ordination sphere around Pt, do not directly participate in the reaction. H owever, they are active components of the catalytic cycle because they prom ote the reaction via nucleophilic assistance to the alcohol deprotonation s tep. (C) 2000 Elsevier Science S.A. All rights reserved.