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

Abstract

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 ZnCl 2 , CoCl 2 .6H 2 O, and CdBr 2 Á4H 2 O produced [L n MX 2 ] (L n = L A − L C ; M = Zn, Co; X = Cl; M = Cd, X = Br) and [L C Cd(μ-Br)Br] 2 in high yields. Structural studies revealed that [L n ZnCl 2 ] (L n = L A − L C ), [L A CdBr 2 ], and [L C CoCl 2 ] adopted the distorted tetrahedral geometry, whereas [L A CoCl 2 ] and [L C Cd(μ-Br)Br] 2 adopted a distorted square pyramidal geometry by coordinating with corresponding ligands in a bidentate fashion. Additionally, [L B CdBr 2 ] 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 [L n MMe 2 ] (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 [L B ZnCl 2 ] produced PLA with superior heterotactic bias (P r of up to 0.93) at −25 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. K E Y W O R D S (pyrazolyl)amine ligand, diverse coordination environment, hetero-enriched poly (lactide), ringopening polymerization

Synthesis and Characterization of Zinc(II), Cadmium(II), and Palladium(II) Complexes with the Thiophene-Derived Schiff Base Ligand

“…However, further increase in the [ rac -LA] 0 /[catalyst] ratio up to 700:1 resulted in only 31% conversion under identical experimental protocols, and a decrease in the molecular weight of resultant PLA was also observed with this decrease in conversion (Figure ). Depending on the metal center variation, [L TH ZnCl 2 ]/LiO i Pr resulted in a high heterotactic enchainment ( P r = 0.74 at 0 °C) compared to its Cd­(II) and Pd­(II) complexes, consistent with the findings of previous studies. , Decrease in polymerization temperature did not show any significant enhancement of the heterotactic bias, particularly for the Cd­(II)-based initiator. The geometry of the M­(II) complex might have steered the hetereotacticity of PLA in the studied complexes.…”

“…Depending on the metal center variation, [L TH ZnCl 2 ]/LiO i Pr resulted in a high heterotactic enchainment ( P r = 0.74 at 0 °C) 61 compared to its Cd(II) and Pd(II) complexes, consistent with the findings of previous studies. 62 , 63 Decrease in polymerization temperature did not show any significant enhancement of the heterotactic bias, particularly for the Cd(II)-based initiator. The geometry of the M(II) complex might have steered the hetereotacticity of PLA in the studied complexes.…”

Cationic N,S-chelate half-sandwich iridium complexes: synthesis, characterization, anticancer and antiplasmodial activity

“…Almost all the transition metals from group 8 to group 10 in the periodic table can be coordinated by the N-heterocyclic ligands. 1–4 Thus, transition metal complexes based on various types of N-heterocyclic ligands have been synthesized and employed in many areas, especially as efficient catalysts in diverse organic reactions, including hydrogenation, 5 oxidation, 6,7 polymerization, 8,9 cross-coupling, 10–16 amidation, 17,18 and reductive amination. 19–21 On the other hand, the prevalence of the N-heterocyclic motif in biologically active molecules has encouraged systematic explorations of such types of compounds.…”

Octahedral to Tetrahedral Conversion upon a Ligand-Substitution-Induced Single-Crystal to Single-Crystal Transformation in a Rectangular Zn(II) Metal–Organic Framework and Its Photocatalysis

“…Metal–organic frameworks (MOFs) and coordination polymers (CPs) are very attractive because of their designability and/or tunability in both crystalline structure and functionality, which offer an opportunity for developing advanced functional materials. , Structural transformations, especially single-crystal to single-crystal (SCSC) transformations, in these polymeric materials are attractive because they usually occur cooperatively with interesting phenomena that might promote and/or introduce exotic functionalities into the materials. − These particular properties could be triggered by various stimulators such as light, solvent, guest sorption–desorption, and even chemical reactions. − The SCSC transformation in coordination compounds, in some cases, causes a conversion of the metal coordination geometry that leads to a change in material properties such as optical properties, as well as catalytic activity. − Along with the exponential increase in the number of reported MOFs, various synthetic methods have been intensely explored in order to reduce the consumption of time and energy as well as minimize chemical waste. , Among the rapid and green synthetic routes to porous MOFs, the microwave-assisted technique has become one of the promising alternative ways that can facilitate the repeatable and controllable productions of these functional materials within a few minutes. − On the other hand, among the numbers of MOFs that exhibit semiconduction, the well-known Zn-MOF [Zn 4 O­(BDC) 6 ] or MOF-5, with a band gap energy of 3.4–4.0 eV, showed photocatalytic activity upon phenol degradation . Apart from ZnO semiconductors as photocatalysts, the potential application of Zn-MOFs in photocatalysis has become more attractive. , In addition, SCSC transformation studies involving both ligand substitution and time have rarely been reported and may reveal a greater understanding of the kinetics of the transformation .…”