Infrared Spectra of RhCO⁺, RhCO, and RhCO^- in Solid Neon:  A Scale for Charge in Supported Rh(CO) Catalyst Systems

Abstract

Laser-ablated Rh + , Rh, and electrons react with CO on condensation in excess neon at 4 K to form RhCO + , RhCO, RhCO -, and Rh(CO) 2 + , Rh(CO) 2 , Rh(CO) 2 -, and higher carbonyls. These rhodium carbonyls are identified by isotopic substitution ( 13 CO, C 18 O, and mixtures), electron trapping with added CCl 4 , and comparison with DFT calculations of isotopic frequencies. This is the first spectroscopy of isolated rhodium carbonyl cations and anions. The isolated monocarbonyl species provide a scale to estimate local charge on Rh(CO) sites in catalyst systems.

Infrared spectroscopy of mass-selected metal carbonyl cations

“…Again, the 18-electron rule is useful to describe stable stoichiometries. Unsaturated metal carbonyls have also been produced and isolated in rare gas matrices [6,22] or in the gas phase via photoelectron spectroscopy of mass-selected anions [23][24][25][26]. The frequency of the CO stretch in all of these systems shifts systematically depending on the electronic structure and bonding, and these effects have been studied extensively with theory [6,22,[27][28][29][30][31].…”

“…In this environment, there are many studies of reactions and energy-controlled collisions that provide bonding thermochemistry. Vibrational spectroscopy of anion and cation metal carbonyls have been obtained by matrix isolation-IR spectroscopy, where the ion data could be compared with corresponding neutrals [6,22]. Gas phase spectroscopy studies of ionized carbonyls are quite limited.…”

CO Interaction with Small Rhodium Clusters from Density Functional Theory: Spectroscopic Properties and Bonding Analysis

“…Theoretical data on CO/Rh species, coming from different levels of computation, have also been reported, [6][7][8][9][10][11][12][13][14] mainly concerning the geometrical and electronic structures as well as vibrational frequencies of RhCO and Rh(CO) 2 . The geometrical and vibrational features of Rh(CO) 3 and Rh(CO) 4 computed by using hybrid and nonlocal functionals within density functional theory (DFT) are also available.…”

“…The geometrical and vibrational features of Rh(CO) 3 and Rh(CO) 4 computed by using hybrid and nonlocal functionals within density functional theory (DFT) are also available. 10,11 To our knowledge, there is a limited number of theoretical studies dealing with the interaction of CO with rhodium clusters containing more than two metal atoms. 13,14 In these papers the computations were performed without relaxing the geometry of the metal cluster.…”

Theoretical study on the gas‐phase reaction mechanism between rhodium monoxide and methane for methanol production

“…These calculated characteristic vibration frequencies scaled by a factor of 0.963 are summarized in Table 1 [62][63][64] It is inferred that the calculated vibration frequencies for all species in the reaction between RhO and CH 4 will provide some useful information for the assignment of spectroscopic results in the corresponding experimental study. Furthermore, the ion energeticses (IEs) are calculated for some experimentally available species (Rh, ORh, O 2 Rh, CRh, and C 2 Rh) at CCSD(T)/ 6-3111G(2d, 2p), SDD//B3IYP/6-3111G(2d, 2p), SDD level, and compared with the experimental data.…”