Organometallic complexes that are reactive to CO2 are promising candidates for CO2 capture and utilization. Establishing safe synthetic procedures for these complexes that require minimal hazardous materials is essential to their implementation on an industrial scale. This study focuses on the development of a robust synthetic protocol for one of these organometallic complexes. The cobalt(I) complex supported by the macrocyclic ligand 3,10-C-meso-3,5,7,7,10,12,14, 14-octamethyl-1,4,8,11-tetra-azacyclotetradeca-4,11-diene (Me8[14]dieneN4) has been shown to react to CO2. The previously reported synthesis of the ligand requires the hazardous perchloric acid and the corresponding Co(I) complex contains a perchlorate anion making it potentially explosive. Additionally, perchlorates are known to interact with the metal centers of these complexes, competing with the binding of CO2. In this work, the synthesis of the CO2-reactive Co(I) complex was achieved in a perchlorate-free manner. The synthesis of the ligand was achieved by adding HBF4(aq) to a stirring acetone solution of 1,2 diaminopropane. The meso-isomer of the ligand was purified by crystallization. The structure of meso-Me8[14]dieneN4 was confirmed by NMR spectroscopy and X-ray crystallography, which showed the cocrystallization of two HBF4 molecules per ligand. The addition of the ligand to a methanol solution of cobalt acetate yielded the complex [Co(Me8[14]dieneN4)](BF4)2. The structure of [Co(Me8[14]dieneN4)](BF4)2 was confirmed by X-Ray Crystallography. Notably, no formal bonds were found between the metal center and the BF4- anions, indicating weaker interactions between the BF4- anion and the metal compared to the perchlorate derivative. Future work will be focused on increasing the synthetic yield of Me8[14]dieneN4(HBF4)2, synthesizing the Co(I) complex [Co(Me8[14]dieneN4)](BF4), and comparing the CO2 reactivity of the complex with the perchlorate derivative.

Synthesis of Me8[14]dieneN4(HBF4)2 and the corresponding Co(II) complex

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.