Distinctive Coordination of CO vs N₂ to Rhodium Cations: An Infrared and Computational Study

Abstract

Carbonyl and nitrogen complexes with Rh are produced in a molecular beam using laser ablation and a pulsed-nozzle source. Mass-selected ions of the form Rh(CO) and Rh(N) are investigated via infrared laser photodissociation spectroscopy. The fragmentation patterns and infrared spectra provide information on the coordination and geometries of these complexes. The shifts in vibrational frequencies relative to the uncoordinated ligands give insight into the nature of the bonding interactions involved. Experimental band positions and intensities are compared to those predicted by density functional theory (DFT). Rh coordinates only four nitrogen molecules, whereas it can accommodate five carbonyl ligands. The fifth CO ligand resides in an axial site with bonding intermediate between coordination and solvation. The carbonyl stretch in Rh(CO) (2160 cm) is blue-shifted with respect to the molecular CO vibration (2143 cm). Conversely, the N-N stretch in Rh(N) (2297 cm) is red-shifted with respect to the free N vibration (2330 cm). The opposite directions of these frequency shifts is explained by a combination of σ donation and electrostatic ligand polarization.

Twelve-Nitrogen-Atom Cyclic Structure Stabilized by 3d-Element Atoms: Quantum Chemical Modeling

“…Additionally, in the case of a positive answer to this question, to what degree do the molecular and electronic structure parameters of such compounds, as well as their thermodynamic characteristics, depend on the nature of the M atom? There is no information in the literature about such compounds, although a number of publications were devoted to two-element chemical substances containing atoms of s -, p - or d -elements and nitrogen atoms (in particular, [ 11 , 12 ] and articles by [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ] in the last 5 years). It should be noted that almost every one of these works mentioned the possible use of such compounds as potential high-energy materials.…”

Photodissociation and Infrared Spectroscopy of Uranium–Nitrogen Cation Complexes

“…Transition metal complexes with nitrogen are of course well-known in inorganic and organometallic chemistry because of the widespread importance of nitrogen activation in chemistry and biology. Transition metal neutral and ionic complexes with N 2 have been studied extensively with mass spectrometry and optical spectroscopy as well as computational chemistry. − Actinide–nitrogen complexes are much less common, and the presence of f electrons is expected to have a strong influence on their bonding. In this study we employ UV–vis and infrared photodissociation measurements to investigate U + (N 2 ) n complexes.…”

“…Infrared photodissociation (IR-PD) spectroscopy has been applied previously to transition metal cation–N 2 complexes of vanadium, niobium, and rhodium. ,, These were generally observed to have end-on bonding of nitrogen to metal, N–N stretches with strong IR activity, and N–N stretches that were shifted to the red from the frequency of isolated N 2 (2330 cm –1 ). IR-PD has also been successful in recent investigations of uranium oxides and carbonyl complexes. , In the case of U + (CO) 8 , the C–O stretch vibration was observed about 60 cm –1 to the red of the vibration in the isolated CO molecule (2143 cm –1 ) .…”

Structural evolution of LiNn+ (n = 2, 4, 6, 8, and 10) clusters: mass spectrometry and theoretical calculations

“…28,29 Rh(N 2 ) 4 + complexes were studied by infrared laser photodissociation spectroscopy and theoretical calculations. 30 TiN 12 + was generated by laser ablation, and the most stable structure was found to be Ti(N 2 ) 6 + with O h symmetry. 31 The VN n + (n ¼ 8, 9, and 10) clusters were generated and their most stable isomers were found to be in the form of V(N 2 ) 4 + , (h 2 -N 4 ) V + N(N 2 ) 2 and (h 4 -N 4 )V + (N 2 ) 3 , respectively.…”