Synthesis of novel bipyridyl ligands and application in preparation of polyketone

Abstract

In this article, novel 2,2 0 -bipyridyl derivatives were synthesized and the excellent bipyridyl ligands were chosen as catalyst to apply in the copolymerization of carbon monoxide (CO) and styrene (ST) to prepare polyketone. 4,4 0 -Dicarboxyl-2,2 0 -bipyridine(4,4 0 -dcpy) was synthesized by use of synthesized 4,4 0 -dimethyl-2,2 0 -bipyridine(4,4 0 -dmpy). The products (4,4 0 -dmpy and 4,4 0 -dcpy) were characterized by melting point, NMR, IR, GC-MS, and elemental analysis. The effects of different ligands and various reaction conditions incuding the usage of ligand, p-toluenesulfonic acid, solvent, p-benzoquinone, the CO pressure, and reaction temperature on catalytic activity of the copolymerization were investigated. The catalytic activity of 4,4 0 -dmpy, 4,4 0 -dcpy and 2,2 0 -bipyridine were compared. The results showed that the addition of the electron-donating substituent can enhance catalytic activity, with the sequence as follows: 4,4 0 -dimethyl-2,2 0 -bipyridine > 2,2 0 -bipyridine > 4, 4 0 -carboxy 2,2 0 -bipyridine.

Alternating copolymerization of carbon monoxide and vinyl arenes using [N,N] bidentate palladium catalysts

“…Figure 1 shows the general molecular structure of mono‐chelated and bis ‐chelated 2,2′‐bipyridine palladium compounds. Besides, in‐situ copolymerizations are also realized by mixing Pd salt and 2,2′‐bipyridine ligands 83 . For 2,2′‐bipyridine palladium catalysts, ligand modifications focus on the substituents installed at the pyridine ring.…”

“…For 2,2′‐bipyridine palladium catalysts, ligand modifications focus on the substituents installed at the pyridine ring. Figure 2 shows the reported 2,2′‐bipyridine ligands and Table 1 summarizes vinyl arene monomers, catalytic activity, and polyketone molecular weight although polymerization conditions are different 83–90 . The substituent effects on the 2,2′‐bipyridine ligand are summarized on basis of the substituent position.…”

“…Guo synthesized 4,4′‐dimethyl‐2,2′‐bipyridine and 4,4′‐dicarboxyl‐2,2′‐bipyridine ligands 83 . In‐situ copolymerization of CO and styrene by mixing Pd(OAc) 2 salt and ligands showed that methyl‐substituted ligand ( BP‐4a ) was more active than carboxyl substituted ligand ( BP‐4b ), indicating that introduction of electron‐donating substituents on position 4 of 2,2′‐bipyridine ( BP‐4a ) enhanced catalytic activity.…”

“…It can help Pd (II) and CO to form π complexes or coordinate with styrene, which further making Pd(II) complex stable. Therefore, 4,4′‐dimethyl‐2,2′‐bipyridine with electron‐donor methyl groups makes Pd‐ligand coordination structure more stable, which enables the catalytic system to have much higher activity and to gain higher molecular weight 83 …”

“…Because the palladium center itself does not possess elements of chirality, the chirality of the polymer should obey the chain end‐controlled enantioface selection mechanism. For palladiun catalysts bearing 2,2′‐bipyridine and 1,10‐phenanthroline ligands, the produced polyketones are largely syndiotactic, with a racemic diad ( uu ) contents of about 90% 83–93,95–97 …”