Infrared Spectroscopy of Gas-Phase M⁺(CO₂)_n (M = Co, Rh, Ir) Ion–Molecule Complexes

Abstract

The structures of gas-phase M(CO) (M = Co, Rh, Ir; n = 2-15) ion-molecule complexes have been investigated using a combination of infrared resonance-enhanced photodissociation (IR-REPD) spectroscopy and density functional theory. The results provide insight into fundamental metal ion-CO interactions, highlighting the trends with increasing ligand number and with different group 9 ions. Spectra have been recorded in the region of the CO asymmetric stretch around 2350 cm using the inert messenger technique and their interpretation has been aided by comparison with simulated infrared spectra of calculated low-energy isomeric structures. All vibrational bands in the smaller complexes are blue-shifted relative to the asymmetric stretch in free CO, consistent with direct binding to the metal center dominated by charge-quadrupole interactions. For all three metal ions, a core [M(CO)] structure is identified to which subsequent ligands are less strongly bound. No evidence is observed in this size regime for complete activation or insertion reactions.

Infrared Spectroscopy of Size‐Selected Hydrated Carbon Dioxide Radical Anions CO2.−(H2O)n (n=2–61) in the C−O Stretch Region

“…Mackenzie et al. studied the fundamental binding motifs and activation of CO 2 in cationic metal–CO 2 complexes M + (CO 2 ) n (M=Co, Rh, Ir), metal oxide clusters MO 2 + (CO 2 ) n (M=Nb, Ta), and in platinum clusters Pt n − ( n =4–7) by infrared spectroscopy . Bowen and co‐workers showed, by using photoelectron spectroscopy, that anionic complexes of coinage metals and CO 2 (MCO 2 ) − are present as chemisorbed (M=Ag, Au) or physisorbed isomers (M=Cu, Au).…”

Continuous Hydrogenation of Carbon Dioxide to Formic Acid and Methyl Formate by a Molecular Iridium Complex Stably Heterogenized on a Covalent Triazine Framework

“…For the IrÀ CTF, the two kinetically distinguishable spectra due to weakly interacting CO 2 with the material (Figure 4, orange and blue lines) show new spectral features in comparison to the case of the CTF. Hence, the Ir complex induces different interactions with CO 2 , [28] but not very strongly as suggested by the concentration profiles of these species. Furthermore, a direct interaction of CO 2 with the Ir sites is implied by the emergence of a band at 2008 cm À 1 under CO 2 over the IrÀ CTF (Supporting Information, Figure S10), which may be attributed to η 2 -C,O mode of CO 2 on the metal.…”

“…[27] In case of the IrÀ CTF, the band of CO 2 adsorbed on the CTF is also observed, but its removal is faster under Ar. Hence, the Ir complex induces different interactions with CO 2 , [28] but not very strongly as suggested by the concentration profiles of these species. For the IrÀ CTF, the two kinetically distinguishable spectra due to weakly interacting CO 2 with the .…”

Infrared Multiple Photon Dissociation Spectroscopy of Hydrated Cobalt Anions Doped with Carbon Dioxide CoCO2(H2O)n−, n=1–10, in the C−O Stretch Region

“…[28] Cobalt carbonylc ations Co(CO) n + (n = 1-9) were investigated in an Ar tagging experiment by the group of Duncan, finding one stronga bsorption for n = 1a t2 156 cm À1 . [29] Cationic metal-CO 2 complexes M + (CO 2 ) n (M = Mg, Al, Si, V, Fe, Co, Ni, Rh, Ir) have been exten-sively investigatedi nt he past decades, [30][31][32][33][34][35][36][37][38][39][40] and also anionic speciesM À (CO 2 ) n (M = Ti,M n, Fe, Co, Ni, Cu, Ag, Au, Sn, Bi) have received considerable attention,f oremost by the group of Weber. [41][42][43][44][45][46][47][48][49][50][51] Generally,t he anionic CO 2 À stretching vibrations shift to the red compared to neutral CO 2 vibrations.…”