Effect of SBA-15-based immobilization of a new phosphoric triamide Ag (I) complex on its catalytic activity: Synthesis, characterization, crystallography and catalytic investigation

Abstract

A new Ag (Ⅰ) complex (C) containing phosphoric triamide ligand (L) with a formula of [Ag ((C5H4NC (O) NHP (O) (NC6H12)2)2NO3] 2 was synthesized by the reaction of AgNO3 with N-nicotinyl –N′, N″-bis (hexamethylenyl) phosphoric triamide. The complex (C) was characterized by Fourier transform infrared spectroscopy (FT-IR), molar conductivity, thermal gravimetric analysis (TGA), and X-ray crystallography techniques. Results showed that complexation occurred via the nitrogen atom of the pyridine ring. The molecular structure of C, refined from single-crystal X-ray diffraction, is triclinic with a P-1 space group. The complex was immobilized on SBA-15 and the produced compound (C@SBA-15) was identified by BET, AAS, FT-IR, XRD, and TGA methods. Successful loading of the complex on SBA-15 was determined by the BET method. According to AAS findings, the amount of silver in the C@SBA-15 composition was 18%. FT-IR and XRD results showed that the complex was absorbed on the support physically and the hexagonal structure of the support was retained after immobilization. Thermal stability of C@SBA-15 was confirmed by TGA analysis. The homogeneous complex (C) and heterogeneous C@SBA-15 were used as catalysts in the oxidation reaction of aromatic aldehydes and sulfides and their catalytic properties compared. H2O2 was used as a green oxidant, some effective parameters (reaction temperature, substrate to oxidant molar ratio, catalyst amount, and solvent type) were optimized, and the conversion percentages of 70% (for C catalyst) and 50% (for C@SBA-15 catalyst) obtained. The reusability of C@SBA-15 and the generality of both catalysts were evaluated and confirmed. The results showed that when the complex was immobilized on SBA-15, its catalytic efficiency decreased, and its recoverability increased. A comparison with other published reports showed that the catalytic efficiency of the catalysts in the oxidation reaction of aldehydes and sulfides was within acceptable limits.