OH-exchange by hydroxo complexes of platinum(II)

The improved preparation and the new synthesis of the hydroxo complexes [Pt(Me)(OH)(P-P)] (P-P=Ph2PCH2CH2PPh2 (1), Ph2PCH=CHPPh2 (2)), abbreviated as [Pt]-OH, is reported. The chemical behavior of 1 towards bases, organic and organometallic halides has been tested. There was no NMR spectroscopic evidence for the formation of a reactive oxo intermediate [Pt]-O- upon reaction with a strong base. In the presence of an electrophilic organic reagent such as an alkyl halide R-X (R = Me, CH2Ph, Et, t-Bu; X = Cl, Br, I), the OH for X exchange process takes place with the formation of the organometallic derivative [Pt(Me)(X)(P-P)] and the corresponding alcohols ROH. Similar reactions carried out in the presence of an electrophilic organometallic species such as the neutral complexes [PtCl2(CdropNC(6)H(4)-p-OMe)(PPh3)] and [PtCl2(COD)] or the cationic derivative traps-[PtCl(Cdrop NMe)(PPh3)(2)][BF4] indicate primarily OH for Cl exchange with formation of the chloro species [Pt(Me)(Cl)(P-P)] and unstable hydroxo complexes, which decompose under the experimental conditions. In the case of the cationic complex also OH for PPh3 exchange is observed. A possible mechanism for the observed reactivity is described. (C) 2002 Elsevier Science B.V. All rights reserved.