We present the first synthesis of an Nheterocyclic carbene (NHC) rhodium catalyst immobilized to an amphiphilic, water-soluble block copolymer support. The resulting macroligand was applied in the hydroformylation of 1-octene under aqueous two-phase conditions in four consecutive cycles and showed high activity up to 2360 h -1 (TOF).
Amphiphilic copolymers (random P1 and block P2) based on 2-oxazolines were synthesised with triphenylphosphane ligands covalently linked to the polymers by means of a metal-free synthesis route. The resulting macroligands were used in the aqueous two-phase hydroformylation of 1-octene. The influence of the polymer architecture (random and block copolymers) on activity and selectivity of the hydroformylation reaction was investigated and compared with that of nonfunctionalised copolymers (random P3 and block P4) and Rh(I)/triphenylphosphane trisulfonate as a water-soluble catalyst. The highest activities were observed for the random copolymer P1 (p=50 bar, T=100 degrees C, c=8 x 10(-4) mol L(-1)) with a turnover frequency (TOF) of 3700 h(-1), whereas the corresponding block copolymer P2 reached TOF numbers of 1630 h(-1). Additionally, both macroligands indicated efficient suppression of isomerisation and led to almost constant n/iso selectivities of about 3 after complete substrate conversion. Copolymers P3 and P4 showed, under identical reaction conditions, strong isomerisation after 40-60 % conversion (n/iso approximately 0.7) and maximum activities of 1560 h(-1) (P3) and 1330 h(-1) (P4) at a concentration of 5 x 10(-3) mol L(-1).
The concept of micellar catalysis was transferred to the hydroaminomethylation of 1‐octene with N,N‐dimethylamine. In the first series of experiments a rhodium(I) complex with amphiphilic triphenylphosphane functionalized poly(2‐oxazoline)s as macroligand was applied as catalyst. Results obtained under standard hydroformylation conditions (T = 100 °C, p = 50 bar) were not satisfying with regard to activities and selectivities of the hydroaminomethylation reaction. Rising the temperature to 150 °C increased the yield of amine to 22% with a corresponding n/iso selectivity of 7.5 and a TOF number of 461 h−1. Best results were obtained by applying a dual Rh/Ir catalyst within the polymeric micelles leading at lower temperature of 130 °C to an amine yield of 24% with a corresponding n/iso selectivity of 11 and TOF numbers of about 600 h−1.magnified image
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