High-pressure NMR studies on the alternating copolymerization of propene with carbon monoxide catalyzed by a palladium(II) complex of an unsymmetrical phosphine-phosphite ligand
K. Nozaki et al., High-pressure NMR studies on the alternating copolymerization of propene with carbon monoxide catalyzed by a palladium(II) complex of an unsymmetrical phosphine-phosphite ligand, ORGANOMETAL, 19(10), 2000, pp. 2031-2035
When high-pressure NMR techniques are employed, the following two facts are
revealed. (1) The cis/trans isomerization from (SP-4-4)-[Pt(CH3)(CO)(L-1)]
[BAr4] (8a; L-1 = (R,S)-BINAPHOS; Ar = 3,5-(CF3)(2)C6H3) to the more stable
SP-4-3 isomer (8b) is faster than CO insertion into either 8a or 8b, the C
O insertion being reversible. (2) For the Pd-II-L-1-catalyzed copolymerizat
ion of propene and CO, there exist at least two major resting states,most p
robably acylpalladium, (SP-4-3)-[Pd(COR)(L-2)(L-1)][BAr4] (3; L-2= CH3CN, C
O), and alkylpalladium, [Pd{CH2CH(CH3)C(=O)R}(L-1)][BAr4] (5a).