An Infrared Study of Gas-Phase Metal Nitrosyl Ion–Molecule Complexes

Abstract

We present a combined experimental and quantum chemical study of gas-phase group 9 metal nitrosyl complexes, M(NO) n + (M = Co, Rh, Ir). Experimental infrared photodissociation spectra of mass-selected ion-molecule complexes are presented in the region 1600 cm–1 to 2000 cm–1 which includes the NO stretch. These are interpreted by comparison with the simulated spectra of energetically low-lying structures calculated using density functional theory. A mix of linear and nonlinear ligand binding is observed, often within the same complex, and clear evidence of coordination shell closing is observed at n = 4 for Co(NO) n + and Ir(NO) n +. Calculations of Rh(NO) n + complexes suggest additional low-lying five-coordinate structures. In all cases, once a second coordination shell is occupied, new spectral features appear which are assigned to (NO)2 dimer moieties. Further evidence of such motifs comes from differences in the spectra recorded in the dissociation channels corresponding to single and double ligand loss.

Probing the binding and activation of small molecules by gas-phase transition metal clustersviaIR spectroscopy

“…271 More recently, cationic NO complexes of a number of late transition (Fe, Co, Rh, Ir) and coinage (Cu, Ag, Au) metal atoms have been studied in the gas phase by IR-PD. 268,272…”

“…271 More recently, cationic NO complexes of a number of late transition (Fe, Co, Rh, Ir) and coinage (Cu, Ag, Au) metal atoms have been studied in the gas phase by IR-PD. 268,272 Metal cluster reactivities. There have been some rather detailed studies of the reactions of metal clusters with NO as for the other nitrogen oxides like N 2 O, see below.…”

Virtual Issue on Photodissociation: From Fundamental Dynamics and Spectroscopy to Photochemistry in Planetary Atmospheres and in Space

“…Although most photodissociation studies focus on molecules that are stable in their ground states and are sufficiently volatile to be prepared in a molecular beam, photolytic or mass-spectrometric methods can also be used to prepare gaseous samples of free radicals, biradicals such as Criegee intermediates, or molecular cations. ,, The photodissociation dynamics of these reactive intermediates can then be explored using aforementioned techniques such as VMI, HRA PTS, and other time-of-flight mass spectrometry schemes. ,, Metal complexes can also be studied using these same methods, provided they have sufficient vapor pressure or can be transferred to the gas phase by laser ablation or desorption methods. Observation of fragmentation pathways, such as ligand detachment from metal complexes and measurement of kinetic energy release to the fragments, provides useful information about the nature of the bonding, the thermodynamics of ligand binding, and ligand dissociation pathways. ,, …”

“…Small molecular clusters held together by weak, noncovalent interactions can be prepared in the low temperature environment of a molecular beam, and their photodissociation dynamics can be studied using the same methods developed for isolated molecules. ,, Other strategies to produce clusters of various types include electrospray of anions or cations, ,,, plasma expansion, or laser ablation from a metal or graphite target. ,, Charged clusters can be accumulated, stored, and cooled in ion traps, entrained in supersonic expansions, or separated by ion mobility through a buffer gas. Microsolvation in these clusters offers a bridge between photodissociation in the gas phase and in solution, allowing in-depth study of the impacts of intermolecular interactions on photochemical outcomes.…”

“…Closer to home, chemists exploit photodissociation via the technique of flash photolysis to create reactive intermediates such as free radicals, carbenes, and carbonyl oxides (also known as Criegee intermediates). , These intermediates are important in atmospheric, plasma, and combustion chemistry; consequently, there is considerable interest in understanding their photochemical production, characterizing their spectra, and studying the mechanisms and kinetics of their reactions. Increasingly, photodissociation is being combined with mass spectrometry to study the spectra and structures of molecular clusters and coordination complexes. , …”