Synthesis, structure determination and immobilization of some dirhodium complexes with chiral binding thiolato ligands. Investigation of their catalytic activity for enantioselective hydrogenation

Moris Eisen, Pnina Weitz, Sarah Shtelzer, Jochanan Blum*, Herbert Schumann, Boris Gorella, Frank H. Görlitz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

(-)-cis[Dicarbonyl-μ-chloro-[μ-6,6-dimethylbicyclo[3.1.1]heptane-2-methanethiolato-S:S)]]bis[tris(1,1-dimethylethyl)phosphine]dirhodium (5a) and (+)-cis-[dicarbonyl-μ-chloro-[μ-5β-methyl-2α-(1-methyl-ethyl)cyclohexanethiolato-S:S]]bis[tris(1,1-dimethylethyl)phosphine]dirhodium (5b) were prepared from [Rh(CO)2]2(μ-Cl)2, P(t-Bu)3 and the corresponding sulfides (-)-cis-(myrtanethio)trimethylsilane (4a) and (+)-(neomenthanethio)trimethylsilane (4b). The molecular structures of 5a and 5b were determined by single-crystal X-ray diffraction (5a: C2221, a = 13.749(4), b = 23.509(9), c = 27.271(9) Å, Z = 8, R = 0.0443, Rw = 0.0491. 5b: P1, a = 16.209(6), b = 14.150(5), c=9.899(3) Å, Z = 2, R = 0.058, Rw = 0.094). Complex 5b was found to exist in the crystal as a pair of 1R,2R,5S- and 1S,2R,5S-epimers. Both chiral complexes have been immobilized by attachment to divinylbenzene-crosslinked polystyrene resins. Application of the chiral dirhodium complexes as catalysts for hydrogenation of methyl α-acetamidocinnamate revealed that while 5b leads to optically active N-acetylphenylalanine methyl ester (up to 50% ee) 5a gives only the racemic product. The immobilization of the complexes proved to improve the enantioselectivity of 5a but decreases the ability of 5b to induce asymmetric reduction.

Original languageEnglish
Pages (from-to)167-176
Number of pages10
JournalInorganica Chimica Acta
Volume188
Issue number2
DOIs
StatePublished - 15 Oct 1991
Externally publishedYes

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