Density Functional Derived Structures and Molecular Properties of Nickel Dithiolenes and Related Complexes

Abstract

The molecular and electronic structure of the planar nickel dithiolene (1c, R = H) and of related complexes derived from nickel dithiolene by replacement of Ni by Pd (palladium dithiolene, 2c, R = H) or by Pt (platinum dithiolene, 3c, R = H), or by replacement of S by NH (nickel diiminolene, 1a, R = H), O (nickel dioxylene, 1b, R = H) or Se (nickel diselenolene, 1d, R = H), were studied by density functional theory using the B3LYP functional and the valence triple‐zeta basis set 6‐311+G* for all atoms except Pd and Pt. For the latter atoms the quasirelativistic effective core potentials of the Stuttgart group were employed. The molecular structure of nickel dithiolene (1c, R = H) is satisfactorily reproduced by DFT calculations. The geometry of the corresponding platinum complexes 3a–3d is more sensitive to relativistic effects, resulting in the contraction of the X–Pt bonds. As shown with the metal dithiolenes, the two ligands are structurally related to mononegative ions of open shell structure. The C–C bond lengths of the complexes are close to those of aromatic and chain‐type polymethine structures (about 1.4 Å). The nickel dithiolene (1c, R = H) and related complexes have D2h symmetry and are 14 π‐electron systems with 10 π‐electrons at the ligands and 4 π‐electrons at the metal center. The natural population analysis has confirmed that metal M++ does accept electrons from the ligands but to a lesser extent than expected. The empty d‐orbitals of M++ are only partly occupied in the molecular ground state. The positive charge of the metal decreases in the order Ni > Pd > Pt. The 1H chemical shifts and the nucleus‐independent chemical shifts (NICSs) of the ring moieties calculated by GIAO‐DFT display a pronounced electron delocalization. In agreement with the calculated C–C bond lengths the 1H chemical shifts and the NICS values show a marked bond delocalization. The NICS values show a change of the aromatic delocalization in the order Ni > Pd < Pt and NH > O < S < Se. The wave numbers of the IR spectra of the complexes calculated by DFT are grouped in separate frequency regions. The very intense absorption of 1c (R = H) in the visible region of the spectrum is surprisingly well reproduced by ab initio single‐only configuration interaction calculations. While the color band of the palladium complex is predicted to be red‐shifted relative to the nickel complex, a blue shift is calculated on passing from the palladium to the platinum complex. The blue shift is, in part, due to the relativistic contraction of bond lengths in the Pt complexes.

Coordination properties of 2-aminocyclopentene-1-dithiocarboxylic acid to transition metal ions as studied by ab initio calculations

“…As one would expect, the M-S bond length increases from Ni-S to Pd-S. The Pd-S and Pt-S bond lengths are nearly equal, as was previously found for the dithiolenes of these metal ions [40].…”

Analysis and Interpretation of Metal-Radical Coupling in a Series of Square Planar Nickel Complexes: Correlated Ab Initio and Density Functional Investigation of [Ni(LISQ)2] (LISQ=3,5-di-tert-butyl-o-diiminobenzosemiquinonate(1-))

“…The latter case also nicely illustrates the trend of increasing intensity with increasing transition energy of the LLCT transition which is predicted by the model. Previously Lauterbach and Fabian have predicted the higher energy of the LLCT transition to arise from the relativistic bond contraction present for the heavy central Pt(II) which leads to more efficient orbital overlap . This point of view is consistent with our interpretation and nicely explains why the [Pt(L ISQ ) 2 ] is more strongly antiferromagnetically coupled than [Ni(L ISQ ) 2 ]…”

Electronic Structure of Square Planar Bis(benzene-1,2-dithiolato)metal Complexes [M(L)2]z (z = 2−, 1−, 0; M = Ni, Pd, Pt, Cu, Au): An Experimental, Density Functional, and Correlated ab Initio Study

“…The ground-state electronic configuration of the [M(L • )(L)] z species is predicted to be The ground state 2 B 2g is in agreement with earlier results from extended Hückel calculations on the [Ni(L • )(L)] - complex. − The same ground state has been proposed for [M(L)(L • )] - (M = Ni, Pd, Pt) complexes from an analysis of their EPR spectra. − …”