Description of the Ground State Wave Functions of Ni Dithiolenes Using Sulfur K-edge X-ray Absorption Spectroscopy

• Published in: Journal of the American Chemical Society 2003-07, Vol.125 (30), p.9158-9169
• Main Authors: Szilagyi, Robert K, Lim, Booyong S, Glaser, Thorsten, Holm, Richard H, Hedman, Britt, Hodgson, Keith O, Solomon, Edward I
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Calculations and mathematical techniques in atomic and molecular physics (excluding electron correlation calculations); Density-functional theory; Electronic structure of atoms, molecules and their ions: theory; Exact sciences and technology; Models, Molecular; Nickel - chemistry; Physics; Spectrometry, X-Ray Emission - methods; Sulfur - chemistry; Toluene - analogs & derivatives; Toluene - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja029806k

The pterin-dithiolene cofactor is an essential component of the catalytic sites of all molybdoenzymes except nitrogenase. Understanding its bonding to transition metals allows for development of electronic structure/function correlations in catalysis. The electronic structure description for a series of bis(dithiolene) complexes ([NiL2] Z , L = 1,2-Me2C2S2; Z = 2−, 1−, 0) using sulfur XAS provides the basis for extension to the biologically relevant metal-containing dithiolenes. The transition dipole integral has been developed for the dithiolene sulfur through correlation of XAS pre-edge energy positions of sulfide-, thiolate-, and enedithiolate-S. The ground state wave functions of all three NiL2 complexes have more than 50% S character experimentally demonstrating the noninnocent behavior of the dithiolene ligand. The S K-edge experimental results are correlated with spin-unrestricted, broken-symmetry density functional calculations. These show only limited spin polarization in the neutral complex and delocalized, ligand based ground states for the mono- and dianionic complexes. These XAS and DFT results are correlated with other spectroscopic features and provide insight into reactivity.