Abstract
The reaction of laser‐ablated iridium atoms with dinitrogen molecules and nitrogen atoms yield several neutral and ionic iridium dinitrogen complexes such as Ir(N2), Ir(N2)+, Ir(N2)2, Ir(N2)2 −, IrNNIr, as well as the nitrido complexes IrN, Ir(N)2 and IrIrN. These reaction products were deposited in solid neon, argon and nitrogen matrices and characterized by their infrared spectra. Assignments of vibrational bands are supported by ab initio and first principle calculations as well as 14/15N isotope substitution experiments. The structural and electronic properties of the new dinitrogen and nitrido iridium complexes are discussed. While the formation of the elusive dinitrido complex Ir(N)2 was observed in a subsequent reaction of IrN with N atoms within the cryogenic solid matrices, the threefold coordinated iridium trinitride Ir(N)3 could not be observed so far.
Highlights
Molecular complexes combining nitrogen and platinum group metals (PGM), such as dinitrogen complexes LmM(N2)n and polynitrido metal complexes LmM(N)n have recently attracted much attention.[1]
Molecular dinitrogen complexes are of vivid interest in nitrogen fixation and reduction since 1966, when the first iridium dinitrogen complex was published, shortly after the first transition metal dinitrogen complexes [Ru(NH3)5N2]X2 with X = BrÀ, IÀ and BF4À were reported in 1965.[2]. The activation and weakening of the strong triple bond in the N2 molecule is facilitated by p-back-bonding from orthogonal dxz and dyz or even p orbitals into the antibonding p*-orbitals of the N2 ligand.[1a,2c,3] This effect is readily observable spectroscopically by a red-shift of the NÀN stretching mode compared to free dinitrogen in the IR spectra
Laser-ablated iridium atoms were reacted with diluted dinitrogen in a vacuum chamber and the reaction products were subsequently deposited on a matrix support under cryogenic conditions and studied using IR spectroscopy
Summary
Molecular complexes combining nitrogen and platinum group metals (PGM), such as dinitrogen complexes LmM(N2)n and polynitrido metal complexes LmM(N)n have recently attracted much attention.[1]. Comparing our assignments to the frequencies calculated at the DFT level of theory there is a very good agreement for the antisymmetric NÀN stretching mode at 2149 cmÀ1 and an isotopic ratio of 1.0349.
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