Efficient palladium catalysts for the copolymerization of carbon monoxide with olefins to produce perfectly alternating polyketones

Chemistry of Bis(aryloxo)palladium(II) Complexes with N-Donor Ligands: Structural Features of the Palladium-to-Oxygen Bond and Formation of O−H···O Bonds

“…The solvents acetone (p.a) and methanol (p.a) and the materials 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2′-bipyridyl, phenol, pentafluorophenol, and Celite (filter aid) were purchased from Janssen Chimica. 1 H (300.13 MHz) and 13 C NMR (75.03 MHz) spectra were recorded on a Bruker AC 300 spectrometer at ambient temperature in NMR solvents (CDCl 3, CD2Cl2, and C6D6) obtained from ISOTEC Inc. 1 H and 13 C NMR data of the new complexes 1-13 are summarized in Tables 3 and 4, respectively. Infrared spectra (KBr disks) were recorded on a Perkin-Elmer 283 spectrometer.…”

“…11 Recent examples include the methoxycarbonylation of alkynes 12 and the perfectly alternating copolymerization of CO and olefins. 13 Results so far obtained with late transition metal alkoxides suggest a rich and varied catalytic chemistry for such complexes, and there is a great demand for structural and mechanistic information to supplement the limited data available. In a continuation of our study of N-donor-ligated alkoxopalladium-(II) complexes, 14 we now report the synthesis, properties, and reactivity of a new class of palladium(II) complexes which contain bidentate N-donor ligands with either two aryloxide groups or one alkoxide in combination with one aryloxide.…”

Highly active [Pd(AcO)2(dppp)] catalyst for the CO-C2H4 copolymerization in H2O-CH3COOH solvent [dppp = 1,3-bis(diphenylphosphino)propane]

“…The metal centre has to be coordinated by a bidentate phosphorus-, nitrogen-ligand, of the type bipy, phen and their alkyl-substituted derivatives, or by ligands containing both phosphorus and nitrogen coordinating atoms. Diphosphines with a hydrocarbon backbone of three methylene groups give the most active catalysts, provided that the cationic charge of the metal centre is balanced by a weakly coordinating anion, conjugated base of a strong acid, for example TsOH (p-toluenesulfonic acid), HBF 4 , HPF 6 , CF 3 COOH, CF 3 SO 3 H [7,8]. cis-Coordination of the bidentate ligand assures the chain growth of the polymer, which occurs via alternated insertion of the monomers for thermodynamic and kinetic reasons [3,4,9].…”

“…The catalyst can be prepared in situ from Pd(OAc) 2 , the ligand and the strong protic acid which, by displacing the coordinating anion AcO creates a facile access of the monomers to Pd(II). Thus the three catalysts Pd(dppp)X 2 (X = TsO, CF 3 COO or CH 3 COO) prepared in situ by adding dppp and HX to Pd(OAc) 2 in MeOH, at 90 • C and 4.56 MPa of total pressure of CO and ethylene (1/1), show a drastically different productivity (6200 g polymer/g of Pd per hour when X = TsO or CF 3 COO, while no polymer forms when X = CH 3 COO: Table 1, entries 1 and 5) [7]. The catalyst activity depends also on the Pd/acid ratio and also on the presence of water, which acts as a Pd-H source, one of the species that start the catalytic cycle [10].…”

“…The catalyst activity depends also on the Pd/acid ratio and also on the presence of water, which acts as a Pd-H source, one of the species that start the catalytic cycle [10]. In addition, the catalyst requires the co-presence of an oxidant, such as 1,4-benzoquinone [7], which regenerates the low-valent Pd(I) or Pd(0) species which form because of the reducing conditions of the copolymerization reaction [11]. The CO-C 2 H 4 copolymerization has been accomplished also by using [Pd(OAc) 2 (dppp)] or [PdCl(COtBu)(dppp)] as catalyst precursors in combination with alumoxanes, which have the function to abstract the acetate or the chloride ligands, thus activating the metal centre for easy coordination of the co-monomers [12].…”