Metal-CatalyzedReactions in Water

Until recently, and in con-trast to organic chemistry,

reactions in water as solventwere important only for ionic

reactions in inorganic chemistry—mostlikely are hydrogenations or transfer

hydrogenations over heterogeneous catalystsas examples of large-scale and economicallyimportant transformations. This changed as aconsequence of the development of water-soluble ligands (or ligands soluble in othermedia) and their application in novelhomogeneously catalyzed biphasic processessuch as SHOP (Shell) or the Ruhrchemie/Rh�ne-Poulenc process. In parallel, a series ofreviews (e.g., that by Li and Chan) appeared,promoting water as a “green” solvent, thusclaiming the fashionable advantages of “greensynthesis” or “green catalysis”. The variousreports about special developments in the use ofwater deal with reactions “on water”, or withsupercritical water, or with water as catalyst, orother related topics.

With regard to the past background, this book isin certain ways an extended and updated version ofthe book Aqueous-Phase Organometallic Catalysis,issued in 2004 by the same publisher. While thatbook concentrated on the announcement andintroduction of the then novel methodology ofaqueous catalysis by transition metals according tothe applications known at that time—with the focuson the most important process, aqueous biphasichydroformylation—this book edited by Dixneufand Cadierno describes the many widely differentbasic metal-catalyzed reactions in water that areknown at present.

Accordingly, the book has chapters coveringthe following chemical transformations: Metal-Catalyzed Cross-Couplings of Aryl Halides toForm C�C Bonds (Shaughnessy); Metal-CatalyzedC�H Bond Activation and C�C Bond Formation(Li and Dixneuf); Catalytic Nucleophilic Additionsof Alkynes (Yao and Li); Water-Soluble Hydro-formylation Catalysis (Nguyen, Urrutigoity, andKalck); Green Catalytic Oxidations (Sheldon);Hydrogenation and Transfer Hydrogenation (Wuand Xiao); Catalytic Rearrangements and Allyla-tion Reactions (Cadierno, Garc�a-Alvarez, andGarc�a-Garrido); Alkene Metathesis (Grela,Gulajski, and Skowerski); and Nanocatalysis inWater (Baig and Varma. All chapters present anup-to-date description of the corresponding reac-

tions and of the exciting spectrum of the homoge-neous catalysis involved, and discuss the advan-tages of the method with regard to yield, selectivity,and the possibility of separating the reactionproducts from the catalyst immediately after thereaction.

This review will not describe the book�s contentin detail. Instead I draw attention to some partic-ular aspects. Firstly, large-scale applications areonly touched on, even where they are known (forexample, for the Suzuki coupling or for someoxidations). The exception is the interesting chap-ter on hydroformylation by Kalck and co-authors.It doesn�t matter that the relevant industrialprocess that has been known for 30 years isincorrectly described in another chapter as the“Rh�ne-Poulenc process” (p. 3): this is only half ofthe truth and just demonstrates the incompletenessof the writer�s knowledge. The inclusion of nano-catalysts in the book by Dixneuf and Cadierno isdebatable. The authors Nasir Baig and RajenderVarma justify this decision by their opinion thatnanocatalysts are a kind of heterogenized homoge-neous catalysts, which fits into the book�s structurein view of their size and the availability of the activecenters. Obviously this is not wrong, but forconsistency it would also fit for other variants ofthe heterogenization of homogeneous catalysts,e.g., for clusters. In general, this is a matter ofdefinition: other books draw the line differently.With the above definition, many heterogeneouslycatalyzed reactions in water ought to be subsumedunder the book�s title.

Another conspicuous feature of the book—theincessant reference to the adjective “green” foroperations in water—seems rather labored andartificial. To improve yield and selectivity wasalways the aim of each generation of chemists, eventhose who developed multistep syntheses that taketime and only achieve marginal improvements of afew percent. A certain arrogance and disregard forchemists of the past is thus the basis of today�soverestimation of “green” processes, which informer times were treated by the same principlesand methodologies, but under other honest names.Dixneuf and Cadierno prove with their book thatmetal-catalyzed reactions in water are one of themost successful principles of a sustainable chemis-try, which does not need the trivialities of the“green chemistry” of Anastas and his epigones.

Boy CornilsHofheim am Taunus (Germany)

DOI: 10.1002/anie.201305528

Metal-Catalyzed Reactions inWaterEdited by Pierre H. Dixneufand Victorio Cadierno.Wiley-VCH, Weinheim, 2013.408 pp., hardcover,E 139.00.—ISBN 978-3527331888

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