Physical Properties of High-Nuclearity Metal Cluster Compounds

Abstract

Polynuclear metal cluster compounds provide an interesting class of model systems for small metal particles with chemisorbed molecules. They are composed of large macromolecules consisting of a metal core of a certain number (n) of metal atoms, to which core a “shell” of ligands is coordinated. In fig. 1 the carbonyl cluster [Ni38Pt6(CO)48H]5- is shown as an example. In going from compound to compound the type of metal atom can be varied, as well as the number n of atoms in the metal core. For Au, Pt, Ru and Rh, the maximum value of n reached at this moment is already n = 55, namely in A;u55(PPh3)12Cl6 (fig. 2) and related Pt, Ru and Rh cluster compounds. For Pd a metal core as large as n = 570 has recently been reported3. The advantages of these materials for fundamental research in small metal particle physics are clearly: (i) complete homogeneity of the metal cluster size in each sample; (ii) possibility to study the properties as a function of cluster size by comparing compounds with different n; (iii) availability of macroscopically large (0,01 – 10 g) samples for a variety of physical experiments.