Synthesis and characterization of bimetallic lanthanide-alkali metal complexes stabilized by aminophenoxy ligands and their catalytic activity for the polymerization of 2,2-dimethyltrimethylene carbonate

CO2-Based Polycarbonates through Ring-Opening Polymerization of Cyclic Carbonates Promoted by a NHC-Based Zinc Complex

A backbone-substituted N-heterocyclic carbene (NHC) zinc complex, in combination with alcohol initiators, has been shown to be an effective catalyst for the ring-opening polymerization (ROP) of trimethylene carbonate (TMC) to poly(trimethylene carbonate) (PTMC) devoid of oxetane linkages. The ROP of TMC proceeded in solution to give PTMC, possessing controlled molecular mass (2500 < Mn < 10000) and low dispersity (Đ ∼ 1.2). Changing the alcohol initiators, PTMCs with different end-groups were obtained, included a telechelic polymer. The results of MALDI-ToF and NMR analysis confirmed the controlled/living nature of the present ROP catalytic system, where side reactions, such as inter- and intramolecular transesterifications, were minimized during the polymerization. Solution studies in different solvents demonstrated the polymerization reaction to proceed via a mechanism first order in monomer and in catalyst. The zinc complex was also able to convert substituted cyclic carbonates, which were purposely synthesized from renewable feedstocks such as CO2 and 1,3-diols. For the asymmetric 2-Me TMC monomer, good regioselectivity was observed (Xreg up to 0.92). The excellent control of the polymerization process was finally brought to light through the preparation of polycarbonate/polyether triblock copolymers by using polyethylene glycol (PEG) as a macroinitiator and of well-defined di- and triblock polycarbonate/polylactide copolymers by sequential ROP of TMC and L-LA.

Variable coordination of carbazolyl-bis(tetrazole) ligands in lanthanide chemistry

Lanthanide complexes of 1,8-bis(2′-isopropyltetrazo-5′-yl)-3,6-di-tert-butylcarbazolide adopt geometries that include planar, buckled and tetrazolyl-bridged tridentate, as well as bidentate, bonding modes.

Crystal structure of bis[tetrakis(tetrahydrofuran-κO)lithium] bis[μ-2,2′,2′′-methanetriyltris(4,6-di-tert-butylphenolato)-κ4O,O′:O′,O′′]dimagnesiate

The heterobimetallic complex comprises discrete Li–THF complex cations and centrosymmetric bimetallic Mg dianions with the tridentate phenolic ligand tris­(3,5-di-tert-butyl-2-hy­droxy­phen­yl)methane in an ion-association mode, with each metal complex core four-coordinate with distorted tetra­hedral stereochemistry.

The title ion-association metal complex, [Li(C₄H₈O)₄]₂[Mg₂(C₄₃H₆₁O₃)₂], has been synthesized from the tridentate phenolic ligand tris­(3,5-di-tert-butyl-2-hy­droxy­phen­yl)methane in tetra­hydro­furan (THF). The aryl­oxo magnesiate complex anion is binuclear with each Mg₂O₄ complex unit inversion-related and bridged through the two tridentate chelating phenolate O-donors of the ligand. The complex centres have a distorted tetra­hedral stereochemistry [Mg—O range 1.8796 (17)–2.0005 (16) Å] and an Mg⋯Mg separation of 2.9430 (14) Å]. The LiO₄ coodination sphere of the cation comprises four THF O-donor atoms and has a slightly distorted tetra­hedral conformation [Li—O range 1.899 (5)– 1.953 (5) Å]. In the crystal, a number of stabilizing intra-anion C—H⋯O hydrogen-bonding inter­actions are present but no inter-species associations are found.

Ring-opening polymerization of rac-lactide catalyzed by crown ether complexes of sodium and potassium iminophenoxides

Crown ether complexes of sodium and potassium iminophenoxides were demonstrated to catalyze the stereoselective polymerization of rac-lactide.

Crown ether complexes of potassium quinolin-8-olates: synthesis, characterization and catalysis toward the ring-opening polymerization of rac-lactide

Crown ether complexes of potassium quinolin-8-olates were synthesized and demonstrated to catalyze the stereoselective polymerization of rac-lactide.

Aluminum chelates supported by β-quinolyl enolate ligands: synthesis and ROP of ε-CL

The ROP of ε-CL initiated by six aluminum β-quinolyl-enolates and their benzyloxides was reported.

Anionic phenoxy-amido rare-earth complexes as efficient catalysts for amidation of aldehydes with amines

A series of anionic organo-rare-earth amido complexes stabilized by dianionic phenoxy-amido ligands were synthesized, and their catalytic property for the amidation reactions of aldehydes with amines was explored.