Synthesis and Isolation of Cuboctahedral and Icosahedral Platinum Nanoparticles. Ligand-Dependent Structures

Abstract

The reaction of Pt(dba) 2 with CO (1 atm) in toluene affords a brown precipitate which can be isolated and redissolved in CH 2 Cl 2 to give a colloidal solution of fcc platinum particles with a large size dispersity (10-20 Å, I). Redissolution of I in THF leads to stable 12 Å fcc platinum particles (II) which can be isolated and characterized by high-resolution electron microscopy (HREM) and wide-angle X-ray scattering (WAXS). The original reaction in THF leads to the direct formation of II. Addition of 0.2 equiv of PPh 3 to II yields a new colloid, III, of the same size but of icosahedral structure. III was characterized by HREM and spectroscopic techniques. In particular, 13 C and 31 P NMR spectroscopy demonstrates the absence of a Knight shift for these particles. Addition of excess triphenylphosphine leads to another species, IV, displaying broader size distribution with a maximum at 17 Å and an fcc structure. The reaction of I with more than 0.2 equiv of PPh 3 affords mixtures containing colloids, clusters (predominantly Pt 5 (CO) 6 (PPh 3 ) 4 ), and mononuclear complexes. Both the formation of the colloids and their transformation into molecular species is rapid at room temperature. It is suggested that such processes may be more frequent in organometallic chemistry than previously thought.

A new specifically designed calix[8]arene for the synthesis of functionalized, nanometric and subnanometric Pd, Pt and Ru nanoparticles

“…In most cases, the solutionphase synthesis of metallic nanoparticles involves the controlled self-condensation of reduced metal centers in the presence of a suitable ligand. This ligand usually acts a stabilizer for the coordinatively unsaturated metal centers, prevents the agglomeration of the nanoparticles and controls the particle's size [8][9][10][11][12][13][14][15][16][17]. The stabilization of nanoparticles by ligands containing multiple anchoring groups is interesting, as it may improve the stability of the ligand shell due to the cooperative binding of all these groups.…”

Organometallic Nanoparticles of Metals or Metal Oxides

“…In this case, if the reaction is carried out in THF, no stabilizer is necessary and stable particles of ca 1.5 nm form in solution [27].…”

Palladium Supported on Mesoporous Alumina Catalyst for Selective Hydrogenation

“…Size and shapecontrolled metal particles offer incentives for their wider applications as catalyst in many chemical processes [2]. It is well understood that the properties of metal nanoparticles for these applications are size and shape dependent [3]. Further, in catalysis, control of the particle size and their growth kinetics show a direct relation between the catalytic activity and the particle morphology.…”

“…Therefore, there has been considerable interest in developing colloidal routes to synthesize well-defined nanoparticles that could be used to prepare heterogeneous catalysts [4][5][6]. Typically, solution routes require various reducing agents such as hydrazine [7], alkalineborohydrides [8], or amine groups [9] where the particles are protected by polymer groups, surfactants or ligands to prevent agglomeration and growth [3].…”