title: Vibrational spectroscopy of the double complex salt Pd(NH3)4(ReO4)2, a bimetallic catalyst precursor.
abstract: Tetraamminepalladium(II) perrhenate, a double complex salt, has significant utility in PdRe catalyst preparation; however, the vibrational spectra of this readily prepared compound have not been described in the literature. Herein, we present the infrared (IR) and Raman spectra of tetraamminepalladium(II) perrhenate and several related compounds. The experimental spectra are complemented by an analysis of normal vibrational modes that compares the experimentally obtained spectra with spectra calculated using DFT (DMol3). The spectra are dominated by features due to the ammine groups and the ReO stretch in TdReO4-; lattice vibrations due to the D4hPd(NH3)42+are also observed in the Raman spectrum. Generally, we observe good agreement between ab initio calculations and experimental spectra. The calculated IR spectrum closely matches experimental results for peak positions and their relative intensities. The methods for calculating resonance Raman intensities are implemented using the time correlator formalism using two methods to obtain the excited state displacements and electron-vibration coupling constants, which are the needed inputs in addition to the normal mode wave numbers. Calculated excited state energy surfaces of Raman-active modes correctly predict relative intensities of the peaks and Franck-Condon activity; however, the position of Raman bands are predicted at lower frequencies than observed. Factor group splitting of Raman peaks observed in spectra of pure compounds is not predicted by DFT.
authors: Department of Chemical and Biomolecular Engineering, North Carolina State University, Campus Box 7905, Raleigh, NC 27695, United States.
authors: Simon T
authors: ST
authors: Thompson
authors: Department of Chemical and Biomolecular Engineering, North Carolina State University, Campus Box 7905, Raleigh, NC 27695, United States.
authors: H Henry
authors: HH
authors: Lamb
authors: Condensed Matter Theory Group, Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland.
authors: Bernard
authors: B
authors: Delley
authors: Department of Chemistry, North Carolina State University, Raleigh, NC 27695, United States. Electronic address: franzen@ncsu.edu.
authors: Stefan
authors: S
authors: Franzen
keywords: DMol(3); Double complex salt; FTIR; Perrhenate; Raman; Tetraamminepalladium (II) complex