Organometallics in Superacidic Media: Characterization of Remarkably Stable Platinum–Methyl Bonds in HF/SbF5 Solution

Abstract

The protolytic stability of (dfepe)PtMe2 (dfepe = (C2F2)2PCH2CH2P(C2F5)2) and cis-(dfmp)2PtMe2 (dfmp = (C2F5)2PMe) and NMR characterization of their corresponding products in SbF5–HF superacid solvent mixtures are reported. Dissolution of (dfepe)Pt(Me)2 in 10 mol % of SbF5–HF at −60 °C resulted in the clean protonolysis of a single Pt–Me bond to form the cationic methyl complex (dfepe)Pt(Me)+; further conversion of (dfepe)Pt(Me)+ to (dfepe)Pt2+ occurred upon warming to −20 °C and followed pseudo-first-order kinetics (k = [1.4(2)] × 10–2 min–1). In contrast, dissolution of the nonchelating analogue cis-(dfmp)2PtMe2 in 10 mol % of SbF5–HF at 20 °C evolved methane and cleanly produced the stable monomethyl complex trans-(dfmp)2Pt(Me)+. trans-(dfmp)2Pt(Me)+ is the most protolytically stable organometallic known: 33% conversion to the cis dicationic product cis-(dfmp)2Pt2+ requires 2 weeks in 10 mol % of SbF5–HF at 20 °C, whereas >90% conversion was observed in 30 h in 50 mol % of SbF5–HF. Dissolution of cis-(...