Chiral triaryl phosphite-based palladacycles and platinacycles: synthesis and application to asymmetric Lewis acid catalysis

Robin B. Bedford, Helena Dumycz, Mairi F. Haddow, Lukasz T. Pilarski, A. Guy Orpen, Paul G. Pringle, Richard L. Wingad

Research output: Contribution to journalArticle (Academic Journal)peer-review

18 Citations (Scopus)

Abstract

The optically pure monophosphites P(OAr)(BINOLate) (7, where Ar = 2,4-di-tert-butylphenyl) have been prepared by treatment of PCl2(OAr) with R-or S-BINOL. Treatment of [PdCl2(NCMe)(2)] with 7 gave [PdCl2(7)(2)] (9) or the binuclear orthometallated complex [Pd2Cl2(7-H)(2)] (8) depending on the reaction conditions. Bridge cleavage reactions of 8 gave [PdCl(7-H)(L)] with L trans to carbon when L = PPh3 or 7 and cis to carbon when L = N-heterocyclic carbene. Treatment of [PtCl2(NCtBu)(2)] with 7 gave [PtCl2(7) 2] (18) which upon further reaction with PtCl2 furnished a mixture of binuclear [Pt2Cl2(7-H)(2)] (17) and cis-[PtCl(7-H)(7)] (19). The palladium complexes containing cyclometallated 7 were screened for catalysis of 1,4-conjugate addition of phenylboronic acid to cyclohexen-2-one and the allylation of benzaldehyde with allyltributyltin. Conversions were generally high in each case but enantioselectivities were low (15% e. e. at best). The X-ray crystal structures of 8, 17 and [PdCl(7-H)(NHC)] (10a, where NHC = 1,3-(dimesityl)imidazolidin-2-ylidene) have been determined.

Original languageEnglish
Pages (from-to)7796-7804
Number of pages9
JournalDalton Transactions
Issue number37
DOIs
Publication statusPublished - 2009

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