Scandium and yttrium complexes of a heteroscorpionate [N,N,O]-donor-set ligand: Synthesis, characterization and catalytic activity in ethylene polymerization

New scandium and yttrium complexes ScL2(bpzmp)(THF) {L = Cl (1); L = CH2Si(CH3)3 (3)}, YL2(bpzmp) {L = Cl (2); L = OTf (5)} and Y(CH2SiMe3)2(bpzmp)(THF) (4) bearing the heteroscorpionate bpzmp ligand {bpzmp = (3,5-tBu2-2-phenoxo)bis(3,5-Me2-pyrazol-1-yl)methane} have been synthesized and characterized by means of NMR and Mass spectroscopy. The tridentate monoanionic ligand resulted κ3-coordinated to the metal via the oxygen and both the sp2 nitrogen atoms of the heterocycles, producing complexes in CS symmetry.The behavior of 1–4 in ethylene polymerization was investigated after proper activation with different activating agents. Complex 4, in combination with the Brönsted or Lewis acids [PhNMe2H][B(C6F5)4] or [Ph3C][B(C6F5)4], produced linear high molecular weight polyethylene in good yield.

Graphical abstractA series of scandium and yttrium complexes ScL2(bpzmp)(THF) {L = Cl (1); L = CH2Si(CH3)3 (3)}, YL2(bpzmp) {L = Cl (2); L = OTf (5)} and Y(CH2SiMe3)2(bpzmp)(THF) (4) bearing the heteroscorpionate bpzmp ligand {bpzmp = (3,5-tBu2-2-phenoxo)bis(3,5-Me2-pyrazol-1yl)methane} have been synthesized and characterized. Reaction of 1 with Me3SiI led to the formation of ScICl(bpzmp)(THF) (6). The behavior of 1–4 in ethylene polymerization was investigated after proper activation with different activating agents. Complex 4, in combination with the Brönsted or Lewis acids [PhNMe2H][B(C6F5)4] or [Ph3C][B(C6F5)4], produced linear high molecular weight polyethylene in good yield.Figure optionsDownload full-size imageDownload as PowerPoint slide