Neutral and Cationic Aluminum Complexes Supported by Acetamidate and Thioacetamidate Heteroscorpionate Ligands as Initiators for Ring-Opening Polymerization of Cyclic Esters

• DOI: 10.1021/om1010676
• Publication Date: 2011-03-01T19:39:12Z
• Authors: Antonio Otero; Agustín Lara-Sánchez; Juan Fernández-Baeza; Carlos Alonso-Moreno; Jose A. Castro-Osma; I. Márquez-Segovia; Luis F. Sánchez-B...; Ana M. Rodríguez; Joaquin C. Garcia...
• Keywords: 01 natural sciences; 0104 chemical sciences

The synthesis, structures, and ring-opening polymerization (ROP) activity of heteroscorpionate aluminum alkyl and aryloxide complexes are reported. The reactions of the acetamide and thioacetamide heteroscorpionate protio ligands pbptamH (pbptamH = N-phenyl-2,2-bis(3,5-dimethylpyrazol-1-yl)thioacetamide), pbpamH (pbpamH = N-phenyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamide), sbpamH (sbpamH = N-sec-butyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamide), and (S)-mbpamH ((S)-mbpamH = (S)-(−)-N-α-methylbenzyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamide) with 1 equiv of AlR3 (R = Me, Et, iBu) proceed in very high yields to give the neutral heteroscorpionate dialkyl aluminum complexes [AlR2{κ2-pbptam}] (R = Me (1), Et (2)), [AlR2{κ2-pbptam}] (R = Me (3), Et (4), iBu (5)), [AlR2{κ2-pbptam}] (R = Me (6), Et (7), iBu (8)), and [AlR2{κ2-(S)-mbpam}] (R = Me (9), Et (10)). In the solid state, complexes 1−10 adopt a tetrahedral structure with the heteroscorpionate ligands arranged in a κ2 coordination mode; in the case of t...