Supported gold catalysis derived from the interaction of a Au–phosphine complex with as-precipitated titanium hydroxide and titanium oxide

Supported gold catalysts derived from interaction of a Au–phosphine complex Au(PPh₃)(NO₃) (1) with conventional titanium oxide TiO₂ and as-precipitated titanium hydroxide (*, as-precipitated) have been characterized by means of XRD, XPS, EXAFS, and CP/MAS–NMR. The Au complex 1 was supported on TiO₂ and without loss of Au–P bonding at room temperature. The Au complex 1 on TiO₂ was readily and completely decomposed to form metallic gold particles by calcination at 473 K, whereas only a small part of the complex 1 on was transformed to metallic gold particles. By calcination of 1/ at 573 K the formation of both metallic gold particles and crystalline titanium oxides became notable as evidenced by XRD, XPS and CP/MAS–NMR. The mean diameter of Au particles in 1/ calcined at 673 K was less than 30 Å as estimated from Au(2 0 0) diffraction, which was about one-tenth of that for the corresponding 1/TiO₂. Thus the as-precipitated titanium hydroxide was able to stabilize the Au complex 1 to lead to the simultaneous decomposition of Au complex and . The catalyst 1/ calcined at 673 K afforded remarkably high catalytic activity for low-temperature CO oxidation at 273–373 K as compared to the catalyst 1/TiO₂.