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Synlett 2006(9): 1449-1450  
DOI: 10.1055/s-2006-941594
SPOTLIGHT
© Georg Thieme Verlag Stuttgart · New York

trans-Dichloro-bis(benzonitrile)palladium(II): A Versatile Reagent in Organic Synthesis

Sulagna Brahma*
Department of Chemistry, Indian Institute of Technology, ­Kharagpur 721302, India
e-Mail: sulogna1977@yahoo.co.in;
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Publikationsdatum:
22. Mai 2006 (online)

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Introduction

The use of Pd(II) complexes as catalysts in organic reactions has been well-established since the beginnings of ­organic synthesis. Due to its versatility, trans-dichloro-bis(benzonitrile)palladium(II) receives special attention as activating agent and also as stabilizing agent. Recently, Khinast and his coworkers reacted ligands like (N-[3-(trimethoxysilyl)propyl]ethylenediamine, 2-(2¢-pyridyl)ethyltrimethoxysilane, etc. with Pd(PhCN)2Cl2 to prepare immobilized catalysts with improved activity in Suzuki coupling reactions. [1] The presence of polar groups in the ligand can increase the interaction of the metal complexes with a substrate which is able to improve enantioselectivity in asymmetric catalysis. [2] With this aim Condom et al. used Pd(PhCN)2Cl2 for the synthesis of the new asymmetric, water-soluble phosphine (S)-(-)-(3-diphenylphosphino-2-hydroxy-propyl)trimethylammonium chloride from the accessible (S)-(-)-(3-chloro-2-hydroxypropyl)tri­methylammonium chloride. [3]

Various fluorinated arene ligands based on diimine and diacetylpyridine backbones, synthesized using Pd(PhCN)2Cl2, serve as precursor compounds for the investigations of π -stacking interaction. Pd(PhCN)2Cl2 is suitable for single-crystal X-ray diffraction studies, obtained by the growth from solution in benzonitrile, as it readily loses benzonitrile to form the cubic cluster Pd6Cl12, which co-crystallizes with a variety of planar aromatic hydro­carbons. [4]

Pd(PhCN)2Cl2 appears to be a versatile activating agent for the alcoholic and epoxide functionality under un­usually mild conditions. [5] Another important aspect of this reagent is that it can be used as stabilizing agent for unstable azirine compounds via formation of 1:2 and 1:1 complexes. [6]

This reagent is generally prepared by condensation of PdCl2 in benzonitrile and it is also commercially ­available.