Effects of ligand coverage on properties of palladium clusters. A
density functional theory study
Phys. Chem. Chem. Phys., 6 (23):
5338--5346 (2004)DOI: 10.1039/b413110j
Abstract
Ligand stabilized clusters of palladium are treated at density functional
theory level to investigate effects of ligand coverage on properties,
such as preferred coordination sites, metal - ligand binding energies,
and structure. Systems investigated include cores of Pd-n, for n
= 1,2,13,16,19,23,35,39, stabilized by CO, PH3, and P(CH3)(3),
which are either known experimentally or have been proposed as intermediates
in syntheses. Some of these systems, e.g. Pd-13(CO)(i), served
as models to study aspects of ligand metal binding. The main results
are the following. CO binds preferably as mu(3) such that coordination
sites share at most one vertex atom. The ligand coverage weakens
Pd-Pd bonding and quenches the high spin of pure metal clusters.
Ligands tend to stabilize Pd cores showing icosahedral Pd-13 structural
units such as biicosahedra in Pd-19 and Pd-23, whereas the corresponding
bare metal clusters are most stable as octahedron and decahedron,
respectively. The BP86 density functional yields reliable structure
parameters and ligand metal binding energies in cases where comparison
with experiment or accurate calculations is possible, only Pd(CO)(i),
i = 1 - 4, appears to be an exception.