Pd(II) complexes with 3,3′-substituted bipyridine ligands: Synthesis, crystal structure, DFT calculations and catalytic studies in compressed carbon dioxide

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

“…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.…”

“…Bis ‐chelated Pd(II) complexes bearing 3,3′‐diester‐2,2‐bipyridine ligands were prepared and tested as catalysts for the CO/ tert ‐butyl styrene copolymerization using compressed carbon dioxide (CO 2 ) as a solvent. These Pd(II) catalysts showed poor productivities, probably due to less stability of the species 89 . Palladium catalysts with fluorinated ester groups ( BP‐3a , BP‐3b ) were inactive for copolymerization because of the decomposition of the catalysts to Pd(0) species 89 …”

“…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 …”

“…Figure 2 shows the reported 2,2 0 -bipyridine ligands and Table 1 summarizes vinyl arene monomers, catalytic activity, and polyketone molecular weight although polymerization conditions are different. [83][84][85][86][87][88][89][90] The substituent effects on the 2,2 0 - 2,2 0 -Bipyridine palladium catalysts (BP-1) are efficient for CO/vinyl arene copolymerization and often produce highly syndiotactic polykenones. An important breakthrough is the first realization of living alternating copolymerization of 4-tert-butyl styrene (p-tBu-St) and CO using the 2,2 0 -bipyridine palladium catalyst (BP-1), which can precisely control molecular weight and polydispersity index (PDI) of the polyketones.…”

“…These Pd(II) catalysts showed poor productivities, probably due to less stability of the species. 89 Palladium catalysts with fluorinated ester groups (BP-3a, BP-3b) were inactive for copolymerization because of the decomposition of the catalysts to Pd(0) species. 89 Guo synthesized 4,4 0 -dimethyl-2,2 0 -bipyridine and 4,4 0 -dicarboxyl-2,2 0 -bipyridine ligands.…”