2013/02/04 by Collins Obuah, Michael Kojo Ainooson, Michael K. Ainooson +4
Chemistry · #Catalytic Alkyne Reactions #Organometallic Complex Synthesis and Catalysis #Synthetic Organic Chemistry Methods
paper · doi:10.1021/om300798y
openalex publication_date 2013/02/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The pyrazolyl pyridylimine ligands [2-(3,5-dimethylpyrazol-1-yl)ethyl]pyridin-2-ylmethyleneimine ( L1 ) and [2-(3,5-di- tert -butylpyrazol-1-yl)ethyl]pyridin-2-ylmethyleneimine ( L2 ) and pyrazolyl thienylimine ligands [2-(3,5-dimethylpyrazol-1-yl)ethyl]thiophen-2-ylmethyleneimine ( L3 ), [2-(3,5-di- tert -butyl-pyrazol-1-yl)ethyl]thiophen-2-ylmethyleneimine ( L4 ), [2-(3,5-dimethylpyrazol-1-yl)ethyl]-2-bromothiophen-2-ylmethyleneimine ( L5 ), and [2-(3,5-di- tert -butyl-pyrazol-1-yl)ethyl]-2-bromothiophen-2-ylmethyleneimine ( L6 ) were synthesized by condensation of the appropriate pyrazolylamine and the corresponding aldehyde. Reactions of L1 – L6 with [PdCl(Me)(cod)] gave the corresponding palladium(II) complexes [PdCl(Me)(L)] (where L = L1 ( 1a ), L2 ( 2a ), L3 ( 3a ), L4 ( 4a ), L5 ( 5a ), L6 ( 6a )) in very good yields. The pyridylimine ligands L1 and L2 were found to coordinate via the imine and pyridine nitrogen atoms, while the thienylimine ligands L3 – L6 coordinate via imine and pyrazolyl nitrogen atoms to the palladium. The cationic complexes [Pd(Me)(A)] + (where A = L1 ( 1b ), L2 ( 2b ), L3 ( 3b ), L4 ( 4b ), L5 ( 5b ), L6 ( 6b )) were synthesized from 1a – 6a, respectively, using Na[BAr 4 ] (Ar = 3,5-(CF 3 ) 2 C 6 H 3 ) in a 1:1 ratio. The cationic palladium complexes 1b and 2b were stabilized by the pyrazolyl nitrogen atom of ligands L1 and L2, respectively, while complexes 3b – 6b were stabilized by NCMe. Attempts to activate 1a – 6a with Na[BAr 4 ] to produce active catalysts for ethylene/CO and styrene/CO led to the formation of palladium black. Using the cationic complexes 1b – 6b, only 2b and 3b were active in the copolymerization of ethylene/CO and styrene/CO.