Palladium Schiff Base Complexes: Potential catalysts for C-C bond reactions

Sabina Laulloo,Shabneez Bhewa,Salma Moosun,Minu Bhowon

doi:10.3390/ecsoc-20-a022

Abstract

The catalytic activities of two palladium complexes [Pd4(dbbs)4] (1) and [Pd(dpbs)Cl] (2) (where (dbbs)2 = N,N'-(1,1'-dithio-bis(phenylene))-bis(salicylideneimine) and (dpbs)2 = o,o’-(N,N’-dipicolinyldene)diazadiphenyl disulfide) were evaluated in the formation of C-C bond in Michael Addition, Heck and Suzuki reactions.  The formation of the coupling products were monitored using GC-MS.  The two palladium complexes were found to be ineffective catalyst towards Michael Addition reactions. However, both catalytic systems exhibited comparable activities in the Heck reaction with good to excellent yields of the desired products (> 99 %) even though complex 1 is tetranuclear and complex 2 is mononuclear.  The yields of the products were found to depend upon other parameters such as reaction time, catalyst loading, base, solvent and substrates. Preliminary investigations were also carried out in Suzuki reaction, where the cross-croupling product was obtained in the range of 60-99 %.  These two complexes are promising supramolecular skeleton for the construction of highly active catalysts.

Highlights

Cross-coupling reactions are important synthetic tools in Organic Chemistry and are used widely in C-C bond forming reactions [1,2,3]
In order to continue our studies directed towards the development of new efficient catalytic systems, we hereby report the use of Palladium Schiff base complexes [Pd4(dbbs)4] (1) and [Pd(dpds)Cl] (2) in Heck, Suzuki and Michael addition reactions
Heck reactions are known to play significant roles in modern synthetic chemistry for C-C bond formation and involve the coupling of an aryl, vinyl halide or sulfonate with an alkene [7,8,9]. This depends on parameters, such as the substrate, catalyst, solvent, base, and time. [Pd4(dbbs)4] (1) and [Pd(dpds)Cl] (2) (Fig 1) were chosen as models to investigate their catalytic behavior in this C-C coupling [11]

Summary

Introduction

Cross-coupling reactions are important synthetic tools in Organic Chemistry and are used widely in C-C bond forming reactions [1,2,3]. Researchers have achieved tremendous advances in organic reactions, where metal catalysts provide convenient synthetic routes for regio- and stereodefined systems [5, 6]. The formation of C-C bonds is known to be generally catalyzed by transition metal complexes. Different palladium catalysts have been used for C-C bond formation leading to high conversion [7,8,9]. In order to continue our studies directed towards the development of new efficient catalytic systems, we hereby report the use of Palladium Schiff base complexes [Pd4(dbbs)4] (1) and [Pd(dpds)Cl] (2) in Heck, Suzuki and Michael addition reactions

Results and discussion

Conclusion

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