End-On Cyanogen Complexes of Iridium, Palladium, and Platinum

Xiuting Chen; Zhixin Xiong; Lester Andrews; Yu Gong

doi:10.1021/acs.inorgchem.0c00582

End-On Cyanogen Complexes of Iridium, Palladium, and Platinum

Inorg Chem. 2020 May 4;59(9):6489-6495. doi: 10.1021/acs.inorgchem.0c00582. Epub 2020 Apr 22.

Authors

Xiuting Chen¹, Zhixin Xiong^{1

2}, Lester Andrews³, Yu Gong^{1

3}

Affiliations

¹ Department of Radiochemistry, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
² School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing 100049, China.
³ Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, United States.

PMID: 32320223
DOI: 10.1021/acs.inorgchem.0c00582

Abstract

The cyanogen complexes of iridium, palladium, and platinum were prepared via the reactions of noble metal atoms with cyanogen in argon matrixes, and the product structures were determined by infrared spectroscopy and density functional theory calculations. These complexes were predicted to possess linear geometries with the metal center coordinated by the nitrogen atom of cyanogen in end-on fashions. On the basis of the B3LYP calculations, doublet, singlet, and singlet spin states are most stable for [Ir(NCCN)], [Pd(NCCN)], and [Pt(NCCN)]. Bonding analysis revealed the presence of electron donation from the polarized σ orbital of cyanogen into the empty metal d_z² orbital and back-donation from the metal d_xz/yz orbitals to the 2π_u orbitals of cyanogen, the latter of which destabilizes the C-N bond and stabilizes the C-C bond. Such an effect causes an increase in C-N bond length by 0.01-0.015 Å and a decrease in C-C bond length by 0.013-0.02 Å for noble-metal-cyanogen complexes in comparison to the same bond in neutral cyanogen, and this is also consistent with the changes in vibrational frequencies. Although [Ir(NCCN)], [Pd(NCCN)], and [Pt(NCCN)] were formed spontaneously during sample annealing, neither cyanide nor isocyanide product was observed in the experiments, which is different from the cases of early transition, lanthanide, and actinide metals.