Copolymerization of carbon monoxide with ethylene in the presence of palladium phosphine complexes

Abstract

We have already reported the possibility of the carbonylation of olefins, in particular, of ethylene, under mild conditions in the presence of a catalyst system consisting of a palladium phosphine complex and p-toluenesulfonic acid (PTSA) [I]. In expanding the pressure range, we unexpectedly found that copolymerization occurs in acetic acid solution beginning at 0.5-1.5 MPa. In this case, refractory polyketones (PK) are formed, which are insoluble in ordinary solvents. Elemental analysis, PMR, 13C NMR, and IR spectroscopy showed that these products are i:I alternating copolymers of carbon monoxide and ethylene. According to Enikolopyan et al. [2], PK are promising polymer materials with a set of interesting new properties. An induction period T 0 is observed during the copolymerization followed by a stationary segment and a reduction in rate, which is probably due to deactivation of the catalyst. The reaction rate, yield and mp of the PK, and the T 0 value and duration of the stationary segment depend on the concentration and nature of the phosphine ligand, concentration of PTSA, synthesis conditions, and other parameters. In a typical experiment, a mixture of 0.0125 mmole (PPh3)4Pd , 0.05 mmole PPh3, i mmole PTSA, and 25 ml acetic acid is added to a steel reactor and flushed with argon. Then, a I:I mixture of CO and ethylene was added to 4.4 MPa and strongly agitated at 90~ In this case, r 0 = 25 min. The stationary activity of the catalyst a 16.2 g PK/(g Pd.min). The yield = 700 g PK/g Pd, mp 217-221~ The following results were obtained for other phosphine ligands: P(C6H4CH3-p)3) T 0 ~ 15 min, a 15.7 g PK/(g Pd.min), ~ 864 g PK/g Pd, mp 222-226~ PPhzEt) T o = 5 min, a = 8.8 g PK/(g Pd.min), a 2450 g PK/g Pd, mp 226-237~ PPhEt2) T o 0 min, a = 5.9 g PK/(g pdomin), ~ = 1500 g PK/g Pd, mp 220-224~ In accord with Sen [3], the catalytically active intermediate in this case may be a cationic palladium phosphine complex.