Structural Characterization, DFT Analysis and Catalysis by Highly Active Cationic Fe(II)-Cu(I) Complexes in the Green Synthesis of Triazoles in Water

Two bimetallic Fe(II)-Cu(I) complexes, with tetrahedral Cu(I) center stabilized in a S2P2 environment, were synthesized and fully characterized using single crystal X-ray diffraction, multinuclear NMR, IR and UV-Visible spectroscopy techniques. Density functional theory with PBE0-D3(BJ) functional was employed to elucidate the electronic features of these novel metal complexes. The computational analysis revealed that while all Cu(I) complexes adopted a tetrahedral geometry in the gas phase with shorter P-Cu(I) bonds than the S-Cu(I) bonds. These cationic complexes were highly active in the catalytic cycloaddition reaction of azides onto terminal alkynes. The CuAAC reaction were carried out at room temperature with as low as 1 mg (0.1 mol %) of catalyst loading to deliver high yields of the corresponding 1,4 adducts of 1,2,3-triazoles in water under aerobic conditions. Cationic Fe(II)-Cu(I) complexes in S2P2 ligand environment constitute highly active catalysts for the cycloaddition of azides onto alkynes. The catalyst loading could be as low as 1 mg for the conversion of 1 mmol of substrates to the products in high yields at low temperature under aerobic conditions.image