Binuclear Magnesium, Calcium and Zinc Complexes Based on Bis(salicylaldimine) Ligands with Rigid Bridges

Abstract

Keywords: Alkaline earth metals / Magnesium / Calcium / Zinc / Polylactide Four dinucleating ligands based on sterically protected salicylaldimine units bridged by a variety of rigid groups have been prepared: 1,4-bis [(3,5-

Robust Zinc Complexes that Contain Pyrrolidine‐Based Ligands as Recyclable Catalysts for the Synthesis of Cyclic Carbonates from Carbon Dioxide and Epoxides

“…The metals, located at am ean distance of 6.75 , afford ar homboid arrangement with intermetallic angleso fa pproximately 70 and 1108.T he ligands are arranged in such aw ay that the benzylpyrrolidine moieties are located alternatively above and below the mean plane through the metal atoms,s o that the complex presents ap seudo-S 2 symmetry.E ach Zn II atom, chelated by two salicylaldimine N,O donors from different ligands, exhibits as lightly distorted tetrahedral geometry with comparableZ n ÀOa nd ZnÀNb ond lengths ( Table 1) that vary in the range 1.893(4)-1.921(3) and 2.000(3)-2.034 (3),r espectively.T he chelatingO ÀZnÀNb ond anglesa re an average of approximately 97.08.A ll these data are within the range de-tected in other salicylaldimine tetranuclearz inc complexes. [33,34] Nevertheless, af ew examples can be found in whicht wo Zn atoms are bound to one ligand, [34] which is indeed our scenario. This was attributed by Hardera nd co-workers to the rigidity of the backbone used.…”

“…[33,34] Nevertheless, af ew examples can be found in whicht wo Zn atoms are bound to one ligand, [34] which is indeed our scenario. [34] To test the stability of such at etrameric structure, as ample of Zn-1 was dissolved in [D 5 ]pyridine and a 1 HNMR spectrum was recorded. [34] To test the stability of such at etrameric structure, as ample of Zn-1 was dissolved in [D 5 ]pyridine and a 1 HNMR spectrum was recorded.…”

“…This was attributed by Hardera nd co-workers to the rigidity of the backbone used. [34] To test the stability of such at etrameric structure, as ample of Zn-1 was dissolved in [D 5 ]pyridine and a 1 HNMR spectrum was recorded. Twos ets of signals were detected in a1 :10 ratio, which indicates that two speciesw ere presentu nder these conditions.…”

Alkaline-Earth Metal Complexes in Homogeneous Polymerization Catalysis

“…In their first contribution, bis(salicyladimine) ligands containing rigid bridges were employed to obtain the corresponding Mg or Ca (or even Zn) heteroleptic bimetallic species (Fig. 35) [117]. The magnesium complexes 117-119 supported by the ligands with the PARA, META, or PYR bridge, respectively, were stable.…”

Synthesis of ChiralC2-Symmetric Bimetallic Zinc Complexes of Amido-Oxazolinates and Their Application in Copolymerization of CO2and Cyclohexene Oxide

“…Ligand redistribution of the resulting zinc silyloxide furnishes the homoleptic 3 b . While the bis‐chelating type zinc complexes such as 3 b were essentially inactive for copolymerization of CO 2 and CHO due to steric hindrance, 3 b can be active for the homopolymerization of CHO, as confirmed by experiments carried out with isolated 3 b under similar conditions (Table , entry 6). Experiment without CO 2 showed diminished homopolymerization reactivity for CHO, suggesting CO 2 might be needed.…”