| Abstract
| - Trimethylplatinum(IV) systems with labile ligands and weakly coordinating anions were investigatedwith respect to their Lewis-acidity and their ability to act as Lewis-acidic catalysts. The Lewis-acidity oftetrameric trimethylplatinum(IV) triflate (triflate = trifluoromethanesulfonate, OTf), [{Me3PtOTf}4], towardcarbonyl compounds was quantified by NMR titration with crotonaldehyde (Childs' method) in CD2Cl2.The data show moderate but significant Lewis-acidity of the trimethyl platinum(IV) center (27% of theacidity of BBr3) and commensurate (moderate) intrinsic catalytic activity of the trimethylplatinum(IV)unit. Crystals of an aldehyde adduct were obtained. X-ray crystallography shows a binuclear metal complex,[{Me3Pt(crotonaldehyde)(μ-OTf)}2]. Despite the relatively low Lewis-acidity, in the absence of oxygen-donor ligands, the trimethylplatinum(IV) is capable of decomposing the [B(ArF)4]- anion (ArF = 3,5-(CF3)2C6H3) to yield B(ArF)3, apparently via aryl abstraction. Salt metathesis reactions of [{Me3PtOTf}4]with Na[B(ArF)4] in the presence of oxygen-donor ligands lead to mixtures that are highly catalyticallyactive in the diastereoselective Mukaiyama-aldol reaction, likely via generation of very electrophilic siliconspecies.
- Tetrameric trimethylplatinum(IV) triflate is investigated regarding its Lewis-acidity, both using NMR techniques (Childs' method) and by testing for catalytic performance as a Lewis acid. The crystal structure of an aldehyde adduct of platinum(IV), dimeric in nature, is discussed.
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