Diverse Reactivity of the cyclo-Diphosphinophosphonium Cation [(PtBu)3Me]+: Parallels with Epoxides and New catena-Phosphorus Frameworks

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• 作者：Alasdair P. M. Robertson ; C. Adam Dyker ; Paul A. Gray ; Brian O. Patrick ; Andreas Decken ; Neil Burford
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：October 22, 2014
• 年：2014
• 卷：136
• 期：42
• 页码：14941-14950
• 全文大小：593K
• ISSN：1520-5126

文摘

The cyclo-diphosphinophosphonium salt [(PtBu)₃Me][OTf] (2) has been shown to be highly reactive toward Lewis bases, exhibiting diverse reactivity with phosphines, 4-(dimethylamino)pyridine (dmap) and chlorophosphines, providing approaches to new open-chain and cyclic catena-phosphorus frameworks. Reaction of 2 with R₃P (R = Me or nPr) or dmap led to the ring-opened adducts [R₃P鈥揚tBu鈥揚tBu鈥揚(Me)tBu][OTf] (R = Me (4a), nPr (4b)) and [(dmap)-PtBu鈥揚tBu鈥揚(Me)tBu][OTf] (6), respectively. The complicated ³¹P{¹H} NMR spectra of the three compounds were simulated, evidencing the presence of two diastereomeric forms of 4a, and single diastereomers of 4b and 6. This ring-opening reactivity of the cation in 2 parallels the reactivity of isolobal epoxides with nucleophiles under acidic conditions. Compound 2 was also shown to react with a 2:1 mixture of Me₂PCl and TMSOTf to form the unexpected cyclo-diphosphino-1,2-diphosphonium salt [(Me₂P)₂(PtBu)₂][OTf]₂ (8), which is postulated to result from two consecutive ring-opening and ring-closing steps. In contrast, reaction with MePCl₂ furnished [(MeP)(PtBu)₂(P(Me)tBu)][OTf] (9), consistent with insertion of a 鈥淢eP鈥?moiety into the cationic phosphorus framework of 2. The importance of ring strain on the reactivity of the cation in 2 was illustrated by comparative studies of the corresponding cyclo-tetraphosphorus cation in [(PtBu)₄Me][OTf] (10), which exhibits no reactivity under analogous conditions.