Diverse coordination geometry of cobalt (II), zinc (II), and cadmium (II) complexes comprising N,N-bis(1H-pyrazol-1-yl)methyl)amines derivatives: Synthesis, structures, and ring opening polymerization of rac-lactide

초록

A series of six new complexes of Co (II), Zn (II), and Cd (II) supported by bis(1H-pyrazol-1-yl)methyl)amine derivatives (N,N-bis((1H-pyrazol-1-yl)methyl)-1-phenylethanamine (L-A), N,N-bis((1H-pyrazol-1-yl)methyl)-1-(furan-2-yl)methanamine (L-B), and N,N-bis((1H-pyrazol-1-yl)methyl)-4-isopropylaniline (L-C) synthesized. The direct chelation of the ligands (L-n = L-A - L-C) with ZnCl2, CoCl2.6H(2)O, and CdBr2 center dot 4H(2)O produced [LnMX2] (L-n = L-A - L-C; M = Zn, Co; X = Cl; M = Cd, X = Br) and [LCCd(mu-Br)Br](2) in high yields. Structural studies revealed that [LnZnCl2] (L-n = L-A - L-C), [LACdBr2], and [LCCoCl2] adopted the distorted tetrahedral geometry, whereas [LACoCl2] and [LCCd(mu-Br)Br](2) adopted a distorted square pyramidal geometry by coordinating with corresponding ligands in a bidentate fashion. Additionally, [LBCdBr2] possessed a distorted trigonal bipyramidal geometry that was obtained by the chelation with corresponding ancillary ligands in the tridentate coordination mode. The dimethyl derivatives of [LnMMe2] (L-n = L-A - L-C; M = Zn, Co; X = Cl; M = Cd, X = Br), which were generated in situ, were employed to catalyze the ring-opening polymerization (ROP) of rac-lactide (rac-LA). Hetero-enriched polylactides (PLAs) were furnished with all these complexes (Complex [LBZnCl2] produced PLA with superior heterotactic bias (P-r of up to 0.93) at -25 degrees C). PLAs with wide-ranged polydispersity indices (PDI = 1.43-1.54) were produced in all the cases irrespective of the M (II) center and variations in ancillary ligands.

키워드