DFT calcns. of the complex ions (μ4-TCNX)[Ru(NH3)5]48+, TCNX = tetracyanoethene (TCNE) and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), yield triplet state energy min. structures with nonplanar bridging ligands. The calcd. C-C bond distances and twist angles confirm considerable metal-to-ligand electron transfer from the metal centers to the TCNE and TCNQ bridges in the lowest triplet and singlet states. The resulting situation, involving a weak interaction between two strongly coupled malonodinitrilato-bridged Ru2.5Ru2.5 entities (Class III), agrees with exptl. results; the near-orthogonality found for the ground states of the mol. ions explains the obsd. magnetic exchange coupling between two S = 1/2 sites, the 1,258 cm-1 absorption in the IR spectrum of the TCNE complex, and the reversible two-electron oxidn. The nitrile stretching frequency shifts were reasonably reproduced by the calcns. A d.-of-states representation for the TCNQ complex shows a rather different electronic structure in comparison to that for the formally related (μ4-TCNQ)[Re(CO)3(bpy)]44+, in particular a different frontier orbital situation. In contrast to the (TCNQ0)(ReI)4 situation, the tetraruthenium species with an approx. (TCNX2-)(Ru2.5)4 formulation represent unconventional mixed-valent tetranuclear compds.; in other words, weakly coupled pairs of strongly coupled dinuclear moieties. EPR spectroscopy at the W band frequency (95 GHz) of the TCNE compd. confirms that the redn. of the complex leads to the oxidn. of TCNE2- to yield a (TCNE·-)(RuII)4 species. [on SciFinder(R)]
%0 Journal Article
%1 Zalis.2009
%A Zalis, Stanislav
%A Sarkar, Biprajit
%A Duboc, Carole
%A Kaim, Wolfgang.
%D 2009
%J Monatshefte fuer Chemie
%K complex configuration dimer mixed ruthenium tetracyanoethene tetranuclear valent
%N 7
%P 765--773
%R 10.1007/s00706-009-0129-3
%T Evidence for the dimer-of-(mixed-valent dimers) configuration in tetranuclear (μ4-TCNX)[Ru(NH3)5]48+, TCNX = TCNE and TCNQ, from DFT calculations
%V 140
%X DFT calcns. of the complex ions (μ4-TCNX)[Ru(NH3)5]48+, TCNX = tetracyanoethene (TCNE) and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), yield triplet state energy min. structures with nonplanar bridging ligands. The calcd. C-C bond distances and twist angles confirm considerable metal-to-ligand electron transfer from the metal centers to the TCNE and TCNQ bridges in the lowest triplet and singlet states. The resulting situation, involving a weak interaction between two strongly coupled malonodinitrilato-bridged Ru2.5Ru2.5 entities (Class III), agrees with exptl. results; the near-orthogonality found for the ground states of the mol. ions explains the obsd. magnetic exchange coupling between two S = 1/2 sites, the 1,258 cm-1 absorption in the IR spectrum of the TCNE complex, and the reversible two-electron oxidn. The nitrile stretching frequency shifts were reasonably reproduced by the calcns. A d.-of-states representation for the TCNQ complex shows a rather different electronic structure in comparison to that for the formally related (μ4-TCNQ)[Re(CO)3(bpy)]44+, in particular a different frontier orbital situation. In contrast to the (TCNQ0)(ReI)4 situation, the tetraruthenium species with an approx. (TCNX2-)(Ru2.5)4 formulation represent unconventional mixed-valent tetranuclear compds.; in other words, weakly coupled pairs of strongly coupled dinuclear moieties. EPR spectroscopy at the W band frequency (95 GHz) of the TCNE compd. confirms that the redn. of the complex leads to the oxidn. of TCNE2- to yield a (TCNE·-)(RuII)4 species. [on SciFinder(R)]
@article{Zalis.2009,
abstract = {DFT calcns. of the complex ions {(μ4-TCNX)[Ru(NH3)5]4}8+, TCNX = tetracyanoethene (TCNE) and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), yield triplet state energy min. structures with nonplanar bridging ligands. The calcd. C-C bond distances and twist angles confirm considerable metal-to-ligand electron transfer from the metal centers to the TCNE and TCNQ bridges in the lowest triplet and singlet states. The resulting situation, involving a weak interaction between two strongly coupled malonodinitrilato-bridged Ru2.5Ru2.5 entities (Class III), agrees with exptl. results; the near-orthogonality found for the ground states of the mol. ions explains the obsd. magnetic exchange coupling between two S = 1/2 sites, the 1,258 cm-1 absorption in the IR spectrum of the TCNE complex, and the reversible two-electron oxidn. The nitrile stretching frequency shifts were reasonably reproduced by the calcns. A d.-of-states representation for the TCNQ complex shows a rather different electronic structure in comparison to that for the formally related {(μ4-TCNQ)[Re(CO)3(bpy)]4}4+, in particular a different frontier orbital situation. In contrast to the (TCNQ0)(ReI)4 situation, the tetraruthenium species with an approx. (TCNX2-)(Ru2.5)4 formulation represent unconventional mixed-valent tetranuclear compds.; in other words, weakly coupled pairs of strongly coupled dinuclear moieties. EPR spectroscopy at the W band frequency (95 GHz) of the TCNE compd. confirms that the redn. of the complex leads to the oxidn. of TCNE2- to yield a (TCNE·-)(RuII)4 species. [on SciFinder(R)]},
added-at = {2022-06-15T11:26:56.000+0200},
author = {Zalis, Stanislav and Sarkar, Biprajit and Duboc, Carole and Kaim, Wolfgang.},
biburl = {https://puma.ub.uni-stuttgart.de/bibtex/26083511271abdb58f5d9ac606a09236c/huebleriac},
doi = {10.1007/s00706-009-0129-3},
interhash = {ff635f4179d968a25cbe6e1743ebcbf1},
intrahash = {6083511271abdb58f5d9ac606a09236c},
issn = {0026-9247},
journal = {Monatshefte fuer Chemie},
keywords = {complex configuration dimer mixed ruthenium tetracyanoethene tetranuclear valent},
number = 7,
pages = {765--773},
timestamp = {2022-06-15T09:26:56.000+0200},
title = {Evidence for the dimer-of-(mixed-valent dimers) configuration in tetranuclear {(μ4-TCNX)[Ru(NH3)5]4}8+, TCNX = TCNE and TCNQ, from DFT calculations},
volume = 140,
year = 2009
}
