The new Schiff‐base complex of copper(II) grafted on mesoporous KIT‐6 as an effective nanostructure catalyst for the homoselective synthesis of various tetrazoles

Abstract

In this work, KIT‐6 mesoporous silica material was used to create heterogeneous catalyst due to its excellent surface area, substantial pore volume, and highly functionalized surface. A copper(II) Schiff‐base complex was fabricated on the surface of KIT‐6. For this purpose, (3‐iodopropyl)trimethoxysilane (IPTMS) was synthesized as a linker from (3‐choloropropyl)trimethoxysilane through a simple SN2 reaction using NaI. On the other hand, ligand (a) was synthesized from condensation of diethylenetriamine (DETA) and salicylaldehyde (SA), which was identified by IR and 1H‐NMR techniques. In order to, prepare Sal(PMeOSi)DETA (b), ligand (a) was reacted with IPTMS. One of the challenges of this synthesis was to prove the linkage between the ligand (a) and the IPTMS, which was proved by 1H‐NMR technique. In the next step, the Schiff base complex of copper(Cu(II)[Sal(PMeOSi)DETA]) (c) was synthesized using a complexation reaction of Cu(NO3)2.3 H2O and b. Finally, the obtained copper complex was fixed on KIT‐6, {Cu(II)[Sal(PMeOSi)DETA]} as the new reusable and practical catalyst. This catalyst has been identified using IR, BET, EDS, XRD, SEM, and TGA methods and employed in the synthesis of different tetrazoles for the first time. All tetrazoles were prepared with high yields, and good TOF and TON values, indicating excellent catalytic performance. This catalyst shows excellent homoselectivity in the synthesis of five‐substituted 1H‐tetrazoles. Also, it can be recovered and reused several times without a significant decrease in its catalytic activity or copper leaching.