| Title
| - Electronic Structure of Square Planar Bis(benzene-1,2-dithiolato)metalComplexes [M(L)2]z (z = 2−, 1−, 0; M = Ni, Pd, Pt, Cu, Au): AnExperimental, Density Functional, and Correlated ab Initio Study
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| Abstract
| - The three diamagnetic square planar complexes of nickel(II), palladium(II), and platinum(II) containing two S,S-coordinated 3,5-di-tert-butylbenzene-1,2-dithiolate ligands, (LBu)2-, namely [MII(LBu)2]2-, have been synthesized. Thecorresponding paramagnetic monoanions [MII(LBu)(LBu•)]- (S = 1/2) and the neutral diamagnetic species [MII(LBu•)2](M = Ni, Pd, Pt) have also been generated in solution or in the solid state as [N(n-Bu)4][MII(LBu)(LBu•)] salts. Thecorresponding complex [CuIII(LBu)2]- has also been investigated. The complexes have been studied by UV−vis, IR,and EPR spectroscopy and by X-ray crystallography; their electro- and magnetochemistry is reported. The electron-transfer series [M(LBu)2]2-,-,0 is shown to be ligand based involving formally one (LBu•)- π radical in the monoanionor two in the neutral species [MII(LBu•)2] (M = Ni, Pd, Pt). Geometry optimizations using all-electron density functionaltheory with scalar relativistic corrections at the second-order Douglas−Kroll−Hess (DKH2) and zeroth-order regularapproximation (ZORA) levels result in excellent agreement with the experimentally determined structures and electronicspectra. For the three neutral species a detailed analysis of the orbital structures reveals that the species may bestbe described as containing two strongly antiferromagnetically interacting ligand radicals. Furthermore, multiconfigurational ab initio calculations using the spectroscopy oriented configuration interaction (SORCI) approach includingthe ZORA correction were carried out. The calculations predict the position of the intervalence charge-transferband well. Chemical trends in the diradical characters deduced from the multiconfigurational singlet ground-statewave function along a series of metals and ligands were discussed.
- A comprehensive set of experimental data together with state-of-the-art electronic structure calculations is presented to argue that the title compounds should best be viewed as singlet diradicals.
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