Devendra Ransi, Edmonds Neil R, Söhnel Tilo
School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand.
Uroxsys Ltd., P.O. Box 58333, Botany, Auckland, New Zealand.
Heliyon. 2020 May 28;6(5):e04074. doi: 10.1016/j.heliyon.2020.e04074. eCollection 2020 May.
The reaction mechanism of the urethane formation for both aliphatic and aromatic isocyanates in the presence of organotin dicarboxylate as a catalyst is investigated theoretically and experimentally. Modelling on a dispersion corrected DFT level of theory (B3LYP-D3) shows that an alkoxide complex is formed between organotin dicarboxylate and alcohol. This complex is the dominant catalyst for the urethane formation reaction. In this study, the interaction between the alkoxide complex and isocyanate through N-coordination is considered. By using thermochemical data, it is possible to show that aliphatic isocyanates can be more sensitive to the carboxylic ligand content of the organotin compound as a catalyst in urethane formation in non-polar solvents compared to aromatic isocyanates. The interactions of carboxylic acid, which is formed as an intermediate in the catalysis process, with isocyanate and the effects on the catalytic process are also discussed.
理论和实验研究了在二羧酸有机锡作为催化剂存在下，脂肪族和芳香族异氰酸酯生成聚氨酯的反应机理。基于色散校正密度泛函理论（B3LYP-D3）水平的建模表明，二羧酸有机锡与醇之间形成了醇盐配合物。该配合物是聚氨酯生成反应的主要催化剂。在本研究中，考虑了醇盐配合物与异氰酸酯通过氮配位的相互作用。利用热化学数据可以表明，在非极性溶剂中生成聚氨酯时，与芳香族异氰酸酯相比，脂肪族异氰酸酯对作为催化剂的有机锡化合物的羧酸配体含量可能更敏感。还讨论了在催化过程中作为中间体形成的羧酸与异氰酸酯的相互作用及其对催化过程的影响。
