Efficient and stereoselective syntheses of isomeric trifluoromethyl-platinum(IV) chlorides

Abstract

The homoleptic, square-planar trifluoromethylplatinate(ii) compound [NBu4]2[Pt(CF3)4] (1) reacts with SOCl2 undergoing oxidative addition of a S-Cl bond to give the octahedral species [NBu4]2[trans-Pt(CF3) 4Cl(SOCl)] (4), that contains the unusual chlorosulfinyl ligand. Compound 4 readily evolves into the dichloro-derivative [NBu4] 2[cis-Pt(CF3)4Cl2] (2), whereby the >Pt(CF3)4> unit undergoes a stereochemical rearrangement from an initial square-planar (equatorial) geometry to a final sawhorse disposition within the global Pt octahedral environment. Compound 2 is more reactive than the corresponding [NBu4]2[trans- Pt(CF3)4Cl2] (3) stereoisomer and thus affords the trichloro-derivative [NBu4]2[fac-Pt(CF 3)3Cl3] (5) by treatment with the stoichiometrically required amount of HCl(aq). Stereoisomer [NBu 4]2[mer-Pt(CF3)3Cl3] (6) has been obtained by oxidative addition of Cl2 to the organoplatinum(ii) precursor [NBu4]2[Pt(CF 3)3Cl]. All the synthetic procedures described here proceed in high yields and in a stereoselective manner. The optical properties of the cis-/trans-[Pt(CF3)4Cl2]2- and fac-/mer-[Pt(CF3)3Cl3]2- diastereomeric couples (diffuse reflectance) as well as the solid-state geometries of the latter couple (single-crystal X-ray diffraction methods) are conveniently compared. © 2011 The Royal Society of Chemistry.