CO2‐to‐Cyclic Carbonate Transformation at Ambient Pressure Using a Mechanochemically Prepared Ti(III) Catalyst
Year: 2025
Type: article
Abstract: A readily accessible Ti(III) complex, [Li(thf)4][Ti(MesPDA)2] (4) (MesPDA = N, N′‐bis(2,4,6‐trimethylphenyl)‐o‐phenylenediamide), has been synthesized mechanochemically, offering a sustainable route to Ti(III) species. Complex 4, combined with [NBu4I] (TBAI), efficiently catalyzes the cycloaddition of CO2 (1 bar) with terminal and internal epoxides, bio‐resourced diepoxides, and the tri‐substituted limonene oxide. This work represents the first example of a Ti(III)‐based catalyst capable of efficiently synthesizing cyclic carbonates from CO2 and epoxides under atmospheric pressure, and demonstrates the superior catalytic activity of Ti(III) compared to its Ti(IV) analog [Ti(MesPDA)2] (3). A detailed mechanistic study is conducted through density functional theory analysis to explore the catalytic pathways mediated by Ti(III) and Ti(IV). Key steps include epoxide coordination to Ti, iodide‐mediated ring‐opening to form a Ti‐alkoxide species, and CO2 insertion into the Ti–O bond. The superior performance of Ti(III) arises from its lower oxophilicity, which weakens Ti–O interactions, enhancing CO2 insertion. Electron Paramagnetic Resonance (EPR) spectroscopy confirms epoxide coordination and supports the formation of a Ti(III)‐alkoxide intermediate. Further evidence for the latter species comes from X‐ray crystallography of the Ti(IV)‐alkoxide analog [Li(4‐crown‐12)2][Ti(MesPDA)2(OiPr)] (17), providing indirect structural evidence. These findings advance the development of Ti(III) systems in CO2 valorization and highlight the key role of oxidation state in catalytic efficiency.
Source: Advanced Synthesis & Catalysis
DOI: 10.1002/adsc.70057
Authors: Elena Álvarez‐Ruiz, Marta Navarro, Ignacio Sancho, Israel Fernández, Cristina Santamaría, Alberto Hernán‐Gómez
Language: English
Subfield: Process Chemistry and Technology
Field: Chemical Engineering
Domain: Physical Sciences
SDG: Climate action
Open Access status: hybrid
Estimated APC paid: $4,650
Awards: G1105844351, G1175115578, G1283467396, G2191822040, G2262748287, G294895050, G300979063, G3229492378, G3300199665, G3480869486, G410571670, G425668148, G451917667, G491712853, G5080475149, G523076202, G5539308778, G593054264, G5967599077, G6033112984, G6616449137, G7084143925, G7509229908, G7805626310, G7863371703, G8497050386
OpenAlex ID: W4413443745