Affiliations: [a] Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Avenida Universidad, Colonia Chamilpa, Cuernavaca, Morelos, Mexico | [b] Centro Universitario de Ciencias Exactas e Ingenierías, Departamento de Química, Universidad de Guadalajara, Boulevard Marcelino García Barragán, Guadalajara, Jalisco, Mexico | [c] Facultad de Química, Universidad Nacional Autónoma de México, Mexico City, Mexico
Correspondence:
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Correspondence to: Miguel-Ángel Muñoz-Hernández, Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Avenida Universidad, Colonia Chamilpa, Cuernavaca, Morelos 62209, Mexico. [email protected]
Abstract: Alkane elimination reactions of β-enaminoketonate ligands OCMeCHCMeN(2,6-Me2C6H3) (1), OCMeCHCMeN(2,6,-iPr2C6H3) (2), OCMeCHCMeN(4-tBu-C6H3) (3) with ZnEt2 afforded bis-chelate and bimetallic zinc com-plexes [(OCMeCHCMeNAr)2Zn]; Ar = 2,6-Me2C6H3 (4), 2,6-iPr2C6H3 (5) and 4-tBu-C6H3 (6) in 85–94% yield; and [{OCMeCHCMeN(2,6-iPr2C6H3)}ZnEt]2 (8), [{OCMeCHCMeN(2,6-Me2-C6H3)}ZnEt]2 (7) and [{OCMeCHCMeN(4-tBu-C6H3)}ZnEt]2 (9) in 50–90% yield. 7–9 are mixed with 4–6, respectively, DFT computations of 1H chemical shifts allowed the unambiguous assignment of the species in solution. X-ray single crystal analyses of 4, 6, 7–9 showed that 4 and 6 are bis-chelate complexes in which the coordination geometry about zinc is distorted tetrahedral and overall C2 symmetry. 7–9 are bimetallic complexes in which the coordination geometry about zinc is distorted tetrahedral but with overall S2 symmetry. The optimized geometry of DFT models 4a and 4b (CH2Cl2 as solvent) indicated that the distortion of the geometry in 4 is due in part to the CH2Cl2 present in the unit cell. ROP of rac-LA catalyzed by complexes 4–9 and 8-OiPr was carried out in toluene solutions. All complexes were active but the best results were obtained with 7–9 and 8-OiPr.
Keywords: Zinc complexes, β-enaminoketonate ligands, ROP of rac-LA, DFT computations
