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Shibasaki catalysts constitute a class of hetero-bimetallic complexes with the general formula n(binol)3(M)3">binol.html" ;"title="n(binol">n(binol)3(M)3(M = alkali metal, Ln = lanthanide). They are named after Masakatsu Shibasaki, whose group first developed them, and are used as asymmetric catalysis, asymmetric catalysts.
Shibasaki catalysts constitute a class of hetero-bimetallic complexes with the general formula n(binol)3(M)3">binol.html" ;"title="n(binol">n(binol)3(M)3(M = alkali metal, Ln = lanthanide). They are named after Masakatsu Shibasaki, whose group first developed them, and are used as asymmetric catalysis, asymmetric catalysts.
Development
The Shibasaki group produced the first chiral lanthanide-binaphtholate complex in 1992, which was used to catalyse nitroaldol reactions. The complex was not characterised but was the first to perform the reaction enantioselectively. This success led to further research which resulted in the development of heterometallic complexes with the formula n(binol)3(M)3 the structure of which was elucidated byX-ray crystallography
X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...
.
Scope
Shibasaki catalysts are effective for a wide range ofenantioselective
In chemistry, stereoselectivity is the property of a chemical reaction in which a single reactant forms an unequal mixture of stereoisomers during a non- stereospecific creation of a new stereocenter or during a non-stereospecific transformation o ...
reactions including nitroaldol, Michael
Michael may refer to:
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* Michael (given name), a given name
* he He ..., a given name
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* Michael (bishop elect)">Michael (surname)">he He ..., a given nam ...
, Diels-Alder and hydrophosphonylation reactions.
Their effectiveness arises in part from their ability to act as both a Brønsted base by virtue of the metal alkoxide and a Lewis acid via the lanthanide ion. Enantioselectivity has been found to be sensitive to both Ln and M; with the nitroaldol reaction being most effective when Ln = Eu and M = Li
whereas the Michael reaction requires Ln = La and M = Na. It was observed that alterations of Ln and M caused predictable changes in the bite angle
In coordination chemistry, the bite angle is the angle on a central atom between two bonds to a bidentate ligand. This ligand–metal–ligand geometric parameter is used to classify chelation, chelating ligands, including those in organometallic ...
of the binaphthol backbone.
References
{{Reflist Catalysts