Abstract Novel chromium catalysts based on bidentate phenoxy-phosphinoyl (HO-2R 1-4R 2- 6 (Ph 2 P [DOUBLE BOND] O) C 6 H 2: R 1= R 2= H, 3a; R 1= tBu, R 2= H, 3b; R 1= R 2= tBu, 3c; R 1= R 2= cumyl, 3d; R 1= anthracenyl, R 2= H, 3e) and thiophenol-phosphine (HS- 2R 1-4R 2-6 (Ph 2 P) C 6 H 2: R 1= R 2= H, 4a; R 1= SiMe 3, R 2= H, 4b) were prepared and characterized. Treatment with modified methyaluminoxane, these catalysts displayed ...