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

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• 作者：Thomas G. Parson ; Jeffrey L. Butikofer ; James F. Houlis ; Dean M. Roddick
• 刊名：Organometallics
• 出版年：2017
• 出版时间：January 9, 2017
• 年：2017
• 卷：36
• 期：1
• 页码：136-141
• 全文大小：313K
• ISSN：1520-6041

文摘

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-(dfmp)₂Pt(CD₃)₂ cleanly generated trans-(dfmp)₂Pt(CD₃)⁺, which subsequently underwent complete proton incorporation to produce trans-(dfmp)₂Pt(CH₃)⁺ within 1 h at 25 °C. This labeling study supports the reversible formation of the methane complex intermediate trans-(dfmp)₂Pt(CH₄)²⁺ under these conditions. Treatment of trans-(dfmp)₂Pt(Me)⁺ in 10 mol % of SbF₅–HF at −100 °C with 200 psi of H₂ resulted in the clean formation of the dihydrogen complex trans-(dfmp)₂Pt(Me)(η²-H₂)⁺, which upon warming to −20 °C underwent methane loss and generated the hydride product trans-(dfmp)₂Pt(H)⁺. The dihydrogen complex trans-(dfmp)₂Pt(H)(η²-H₂)⁺ has not been directly observed but has been implicated in exchange bradening behavior observed for trans-(dfmp)₂Pt(H)⁺ under H₂. Treatment of trans-(dfmp)₂Pt(CD₃)⁺ in 10 mol % of SbF₅–HF at −40 °C with 200 psi of H₂ cleanly produced trans-(dfmp)₂Pt(CD₃)(η²-H₂)⁺ No significant H/D exchange into the Pt–CD₃ group prior to trans-(dfmp)₂Pt(H)⁺ formation was observed.