Catalytic Ethylene Polymerisation in Carbon Dioxide as a Reaction Medium with Soluble Nickel(II) Catalysts

A series of neutral Ni II –salicylaldiminato complexes substituted with perfluorooctyl‐ and trifluoromethyl groups, [Ni{ κ 2 ‐ N , O ‐6‐C(H)NAr‐2,4‐R′ 2 C 6 H 2 O}(Me)(pyridine)] ( 6 a : Ar=2,6‐{4‐(F 17 C 8 )C 6 H 4 } 2 C 6 H 3 , R′=I; 6 b : Ar=2,6‐{4‐(F 3 C)C 6 H 4 } 2 C 6 H 3 , R′=I; 6 c : Ar=2,6‐{3,5‐(F 3 C) 2 C 6 H 3 } 2 C 6 H 3 , R′=3,5‐(F 3 C) 2 C 6 H 3 ; 6 d : Ar=2,6‐{4‐(F 17 C 8 )C 6 H 4 } 2 C 6 H 3 , R′=3,5‐(F 3 C) 2 C 6 H 3 ; 6 e : Ar=2,6‐{3,5‐(F 3 C) 2 C 6 H 3 } 2 C 6 H 3 , R′=I) were studied as catalyst precursors for ethylene polymerisation in supercritical CO 2 . Catalyst precursors 6 a and 6 c , which are soluble in scCO 2 , afford the highest polymer yields, corresponding to 2×10 3 turnovers. Semicrystalline polyethylene ( M n typically 10 4 g mol −1 ) is obtained with variable degrees of branching (11 to 24 branches per 1000 carbon atoms, predominantly Me branches) and crystallinities (54 to 21 %), depending on the substitution pattern of the catalyst.