Unexpected Macrocyclic Multinuclear Zinc and Nickel Complexes that Function as Multitasking Catalysts for CO₂ Fixations

Abstract

Unique self-assembled macrocyclic multinuclear Zn II and Ni II complexes with binaphthyl-bipyridyl ligands (L) were synthesized.X-ray analysis revealed that these complexes consisted of an outer ring (Zn 3 L 3 or Ni 3 L 3 )and an inner core (Zn 2 or Ni). In the Zn II complex, the inner Zn 2 part rotated rapidly inside the outer ring in solution on an NMR timescale. These complexes exhibited dual catalytic activities for CO 2 fixations:s ynthesis of cyclic carbonates from epoxides and CO 2 and temperature-switched N-formylation/N-methylation of amines with CO 2 and hydrosilane.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Non-covalent interactions in molecular architectures and solvent-free catalytic activity towards CO2 fixation of mononuclear Co(iii) complexes installed on modified Schiff base ligands

“…Among them, the most eminent and economically reliable method, especially in terms of maximum atom economy, is CO 2 fixation to epoxides. [24][25][26][27] A number of metal-complex catalysts such as zinc, [28][29][30][31][32] cobalt, 33-65b chromium, [66][67][68][69] magnesium, [70][71][72] iron, 73-75c nickel, [76][77][78] and rare-earth metal [79][80][81] based catalysts have been developed for CO 2 fixation. Among these, cobalt salen complexes are well known for their enhanced activity and selectivity towards CO 2 fixation.…”

Strategies for tuning the catalytic activity of zinc complexes in the solvent-free coupling reaction of CO2 and cyclohexene oxide

“…In particular, the ring-expansive carboxylation of epoxides with CO2, which affords cyclic carbonates, has gained significant recent attention not only due to the great current interest in carbon dioxide utilization but also because cyclic carbonates have various applications such as polar aprotic solvents, electrolytes for lithium batteries, synthetic intermediates of polymeric materials (e.g. polycarbonates and polyurethanes), fuel additives, alkylating factors for aromatic amines, phenols and thiols, precursors for pharmaceutical and fine chemicals [12][13][14][15][16][17][18][19][20]. The production of cyclic carbonates by coupling epoxide and CO2 is of particular relevance since it represents a greener and safer alternative to the traditional preparation from diols and toxic phosgene with HCl as a side product.…”

“…Both cyclic carbonates [23] and polycarbonates [22] are valuable chemicals but they should be selectively produced, in order to minimize the separation and purification steps, by choosing a suitable catalyst and appropriate reaction conditions. Although it is a challenging task due to the high thermodynamic and kinetic stability of CO2, a variety of catalysts allows the cycloaddition and/or copolymerization of epoxides and carbon dioxide [11,[20][21][22][23][24][25][26][27][28][29]. Among them, zinc complexes are of particular interest since their metal center is cheap and non-toxic.…”

Hexamethylenetetramine Complexes as Easy-to-Handle and Efficient Lewis Acid–Base Heterogeneous Catalysts for Coupling of CO2 under Mild Conditions

“…For the generation of cyclic carbonates, the key is to design catalysts of efficacy. For such an end, a great number of catalysts for CO 2 cycloaddition have been exploited, for example, organic bases, metal complexes, metal salts, ionic liquids (ILs), metal–organic framework, poly­(ionic liquid)­s, covalent organic framework, and supported catalysts . Furthermore, metal complexes (such as salen and porphyrin complexes) were demonstrated to be efficient for CO 2 cycloaddition reactions. , In general, a combined use of metal complexes and ILs as well as organic bases is recommended to enhance catalytic activity.…”