Palladium complexes hydrodehalogenation

Hydrodehalogenation of organic halides catalysed by Ru/tppms555 or palladium complexes generated from the ligands 20 (n=l, R=H) and 21 (R=Ph, n=3,4) (depicted in Table 2).124-125... 

This type of hydrodehalogenation has been performed generally in the presence of organic or inorganic bases to neutralize the hydrogen halides formed. Among published results, the use of rhodium complexes as catalysts dominates, but palladium and ruthenium complexes have also been applied on a frequent basis. 

Rhodium(III) complexes [e.g. (i-Pr,P)2Rh(H)Cl2] in the presence of quaternary ammonium salts are excellent catalysts for the hydrogenolysis of chloroarenes under mild conditions [5] other labile substituents are unaffected. Hydrodehalogenation of haloaryl ketones over a palladium catalyst to give acylbenzenes is also aided by the addition of Aliquat [6]. In the absence of the phase-transfer catalyst, or when the hydrogenation is conducted in ethanol, the major product is the corresponding alkyl-benzene, which is also produced by hydrodehalogenation of the halobenzyl alcohols. 

Surface reactions (1) and (2] have been widely used to prepare silica supported metal complex catalysts [6]. The stabilization of ionic forms of palladium was strurigly increased by the presence of -OLi moiety. Simultaneous presence of -OLi and (-D) Pd surface species resulted in a very active hydrodehalogenation and reduction catalyst. 

Hydrodehalogenation of aliphatic or benzylic halides were catalyzed by water soluble ruthenium phosphine complexes in the presence of sodium formate as hydrogen donor [194], Hydroxycarbonylations could also be performed with high palladium catalyst activities in biphasic systems [195-197]. 

Patzold, E. Ohme, G. (1993) Water-soluble palladium(ll) phosphine complexes as catalysts in the hydrodehalogenation of allyl and benzyl halogenides under biphasic and phase-transfer conditions, J. Prakt. Chem. - Chem. Ztg., 335,181-4. 

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