Cu(II) Complex Heterogenized on SBA-15: A Highly Efficient and Additive-Free Solid Catalyst for the Homocoupling of Alkynes.

A Cu(II) complex has been heterogenized on SBA-15 by functionalization of SBA-15 with (N1-propylethane-1,2-diamine) triethoxysilane (NN-SBA-15) followed by anchoring of 2-pyridinecarboxaldehyde through Schiff's base formation between the terminal –NH2 and the aldehyde group of 2-pyridinecarboxaldehyde (Py-NN-SBA-15), and finally, copper(II) was immobilized through complexation. Copper(II) complex heterogenized on SBA-15 (Cu(II)-SBA-15) has been thoroughly characterized by different techniques such as N2 sorption, small-angle X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and solid-state 13C CP-MAS NMR spectroscopy. Cu(II)-SBA-15 is an efficient heterogenized solid catalyst for the oxidative homocoupling of phenyl acetylene into 1,4-diphenylbuta-1,3-diyne with a yield of 97%, even in the absence of palladium, co-catalyst and base additives. In the case of the homocoupling of other aromatic and aliphatic terminal alkynes, the yields were 85–98%.