Al and Zn complexes bearing N,N,N-tridentate quinolinyl anilido-imine ligands: synthesis, characterization and catalysis in l-lactide polymerization?

Dalton Transactions Pub Date: 2012-07-17 DOI: 10.1039/C2DT30594A

Abstract

Reactions of N,N,N-tridentate quinolinyl anilido-imine ligands with AlMe3 afford mononuclear aluminum complexes {κ3-[{2-[ArN[double bond, length as m-dash]C(H)]C6H4}N(8-C9H6N)]}AlMe2 (Ar = 2,6-Me2C6H3 (1a), 2,6-Et2C6H3 (1b), 2,6-iPr2C6H3 (1c)) or dinuclear complexes AlMe3{κ1-[{2-[ArN[double bond, length as m-dash]C(H)C6H4]N(8-C9H6N)}-κ2]AlMe2 (R = 2,6-Me2C6H3 (2a), 2,6-Et2C6H3 (2b), 2,6-iPr2C6H3 (2c)) depending on the ratios of reactants used. Similar reactions of ZnEt2 with these ligands give the monoligated ethyl zinc complexes {κ3-[{2-[ArN[double bond, length as m-dash]C(H)]C6H4}N(8-C9H6N)]}ZnEt (Ar = 2,6-Me2C6H3 (3a), 2,6-Et2C6H3 (3b), 2,6-iPr2C6H3 (3c)) or bisligated complexes {κ3-[{2-[ArN[double bond, length as m-dash]C(H)]C6H4}N(8-C9H6N)]}Zn{κ2-[{2-[ArN[double bond, length as m-dash]C(H)]C6H4}N(8-C9H6N)]} (Ar = 2,6-Me2C6H3 (4a), 2,6-Et2C6H3 (4b), 2,6-iPr2C6H3 (4c)). These complexes were well characterized by NMR and the structures of 1a, 2a, 2c, 3b and 4c were confirmed by X-ray diffraction analysis. The aluminum and zinc complexes were tested to initiate lactide polymerization in which the zinc complexes show moderate to high activities in the presence of benzyl alcohol.

Graphical abstract: Al and Zn complexes bearing N,N,N-tridentate quinolinyl anilido-imine ligands: synthesis, characterization and catalysis in l-lactide polymerization
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