Identification of the Vibrational Modes in the Far-Infrared Spectra of Ruthenium Carbonyl Clusters and the Effect of Gold Substitution

Abstract

High-quality far-IR absorption spectra for a series of ligated atomically precise clusters containing Ru3, Ru4, and AuRu3 metal cores have been observed using synchrotron radiation, the latter two for the first time. The experimental spectra are compared with predicted IR spectra obtained following complete geometric optimization of the full cluster, including all ligands, using DFT. We find strong correlations between the experimental and predicted transitions for the low-frequency, low-intensity metal core vibrations as well as the higher frequency and intensity metal-ligand vibrations. The metal core vibrational bands appear at 150 cm(-1) for Ru3(CO)12, and 153 and 170 cm(-1) for H4Ru4(CO)12, while for the bimetallic Ru3(μ-AuPPh3)(μ-Cl)(CO)10 cluster these are shifted to 177 and 299 cm(-1) as a result of significant restructuring of the metal core and changes in chemical composition. The computationally predicted IR spectra also reveal the expected atomic motions giving rise to the intense peaks of metal-ligand vibrations at ca. 590 cm(-1) for Ru3, 580 cm(-1) for Ru4, and 560 cm(-1) for AuRu3. The obtained correlations allow an unambiguous identification of the key vibrational modes in the experimental far-IR spectra of these clusters for the first time.

The effect of counter ions on the far-infrared spectra of tris(triphenylphosphinegold)oxonium dimer salts

“…22 This level of theory has been utilized by us for similar ligated metal cluster systems previously, and has been shown to give good agreement to experimental results. 15,16 Except where calculating the energy of dimerization, all calculations reported are for the dimer of the Au 3 species, i.e. [{{Au(PPh 3 )} 3 (m 3 ÀO)} 2 ] 2+ (X À ) 2 , (X ¼ BF À 4 , MnO À 4 , or nothing), consistent with literature reports.…”

“…This region is of importance to ligated metal cluster species as vibrational modes involving metal-metal stretching appear within this region. 15,16 We have previously reported the far-infrared (50-650 cm À1 ) vibrational spectra of a range of gold, ruthenium, and gold-ruthenium species, which were accompanied by computational investigations to give an insight into the specic vibrational modes which give rise to each feature within the infrared spectra. 15,16 For all previous calculations involving species with counter-ions, the counter-ions were removed and the charge balanced for the primary cluster of interest, i.e.…”

Computational investigation of the ligand field effect to improve the photoacoustic properties of organometallic carbonyl clusters

“…It has been reported that, for large main group element clusters, the B3LYP/LanL2DZ method is sufficient. [46][47][48][49][50][51] This journal is © The Royal Society of Chemistry 2015…”

Au101–rGO nanocomposite: immobilization of phosphine-protected gold nanoclusters on reduced graphene oxide without aggregation

“…Also, the strongly size-dependent electronic properties of ultra-small metal clusters offer the opportunity to tune their reactivity by choice of appropriate size and composition. 3,4 Furthermore, such clusters are small enough to perform high level DFT calculations, 5,6,7 which are crucial for comprehensive understanding of the catalytic mechanisms needed for the development of superior catalysts. 8 Therefore, size-specific clusters are considered as a platform for investigation of catalysts at the atomic level.…”