Stepwise degradation of trifluoromethyl platinum(II) compounds

Abstract

The action of moisture on the homoleptic organoplatinum(II) compound [NBu4]2[Pt(CF3)4] (1) gives rise to the carbonyl derivative [NBu4][Pt(CF3)3(CO)] (2), which is itself moisture stable. However, treatment of compound 2 with HCl(aq) results in the formation of [NBu4][cis-Pt(CF 3)2Cl(CO)] (3), which undergoes degradation of an additional CF3 group by further treatment with HCl(aq) in large excess, affording [NBu4][cis-Pt(CF3)Cl2(CO)] (4). The carbonyl derivatives 2-4 are fairly stable species, in which the CO ligand, however, can be readily extruded by reaction with trimethylamine N-oxide (ONMe3). Thus, compound 2 reacts with ONMe3 in the presence of a number of neutral or anionic ligands affording a series of singly or doubly charged derivatives with the general formulae [NBu4] [Pt(CF3)3(L)] [L=CNtBu (5), PPh3 (6), P(o-tolyl)3 (7), tht (8; tht=tetrahydrothiophene)] and [NBu 4]2[Pt(CF3)3X] [X=Cl (9), Br (10), I (11)], respectively. Compound 2 also reacts with ONMe3 and pyridin-2-thiol (C5H5NS) giving rise to the five-membered metallacyclic derivative [NBu4][Pt(CF3) 2(CF2NC5H4S-κC,κS)] (12), which can be viewed as a difluorocarbene species stabilized by intramolecular base coordination. On the other hand, treatment of compound 3 with ONMe3 in the presence of C5H5NS yields the four-membered metallacyclic compound [NBu4][Pt(CF3) 2(NC5H4S-κN,κS)] (13). The geometries of the metallacycles in compounds 12 and 13 are compared. In the absence of any additional ligand, compound 3 undergoes dimerization producing the dinuclear species [NBu4]2[{Pt(CF3) 2}2(ο-Cl)2] (14). Halide abstraction in the latter compound with AgClO4 in THF yields the solvento compound cis-[Pt(CF3)2(thf)2] (15). The highly labile character of the THF ligands in compound 15 makes this species a convenient synthon of the >cis-Pt(CF3)2> unit. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.