Synthesis, Characterization, and the N Atom Transfer Reactivity of a Nitridochromium(V) Complex Stabilized by a Corrolato Ligand

Abstract

Metal complexes bearing nitrido ligands (M≡N) are at the forefront of current scientific research due to their resemblances with the metal complexes involved in the nitrogen fixation reactions. An oxo(corrolato)chromium(V) complex was used as a precursor complex for the facile synthesis of a new nitrido(corrolato)chromium(V) complex. The nitrido(corrolato)chromium(V) complex was characterized by various spectroscopic techniques. Density functional theory (DFT) calculations were performed on the nitrido(corrolato)chromium(V) complex to assign the vibrational and electronic transitions of this complex. The chromium–nitrogen (nitrido) bond distance obtained in the DFT-optimized structure is 1.530 Å and matches well with the earlier reported authentic Cr≡N bond distances obtained from the single-crystal X-ray diffraction data. This nitrido(corrolato)chromium(V) compound exhibited a sharp Soret band at 438 nm and a Q band at 608 nm. DFT calculations deliver that the origin of the bands at 438 and 608 nm is due to the intraligand charge transfer transitions. The nitrido(corrolato)chromium(V) complex showed one reversible oxidation and one reversible reduction couple at +0.53 and −0.06 V, respectively, vs the Ag/AgCl reference electrode. The simulation of the electron paramagnetic resonance data of the nitrido(corrolato)chromium(V) compound provided the following parameters: g iso = 1.987, A 53 Cr = 26 G, and A 14 N = 2.71 G. From all these analyses, we can conclude that the electronic configuration in the native state of nitrido(corrolato)chromium(V) can be best described as [(cor 3– )Cr V (N 3– )] − . Reactions of nitrido(corrolato)chromium(V) with the chloro(porphyrinato)chromium(III) complex resulted in a complete intermetal N atom transfer reaction between chromium corrole and chromium porphyrin complexes. A second-order rate constant of 4.29 ± 0.10 M –1 s –1 was obtained for this reaction. It was also proposed that this reaction proceeds via a bimetallic μ-nitrido intermediate.

Magnetic Relaxations of Chromium Nitride Porphyrinato Complexes Driven by the Anisotropic g‐Factor

“…Frequency calculations using UB3LYP‐D3BJ/Def2‐SVP also support the similarity in the IR spectra for 1 and 2 (lower part of Figure 2), where the positions of the IR absorption of both complexes are almost identical except for the difference in the position of Cr≡N (1132 cm −1 ) and V=O (1097 cm −1 ) stretching modes. These calculated vibrational energies are similar with those of the experimental CrN 2+ , MnN 2+ and VO 2+ complexes (970–1080 cm −1 ) [30,35–39] . Despite the difference in the calculated vibrational energy of the Cr≡N and V=O stretching, it is difficult to distinguish them in the experimental spectra due to the intense absorptions of the TPP core in the same energy region [30] …”

“…These calculated vibrational energies are similar with those of the experimental CrN 2 + , MnN 2 + and VO 2 + complexes (970-1080 cm À 1 ). [30,[35][36][37][38][39] Despite the difference in the calculated vibrational energy of the Cr�N and V=O stretching, it is difficult to distinguish them in the experimental spectra due to the intense absorptions of the TPP core in the same energy region. [30]…”