Octahedral and Tetrahedral Coinage Metal Clusters: Is Three-Dimensional d-Orbital Aromaticity Viable?

The first quant. evidence for the viability of three-dimensional arom. clusters involving d-orbitals in pseudo-octahedral coinage metal cages M6Lie2 (M = Cu, Tag, Au) as well as in tetrahedral coinage metal cages M'4Li4 (M' = Cu, Ag) was obtained computationally. These cages exhibit many features similar to those of their square planar M4Li2 analogs. The large neg. nucleus-independent chem. shifts (NICS) at the cage centers indicate three-dimensional delocalization. This diatropic character arises mostly from d-orbital delocalization combined with substantial contributions from the lowest-valence orbitals. The bonding MOs of the pseudo-octahedral clusters M6Li2 (M = Cu, Ag, Au) are analogous to those in similar octahedral clusters involving p-orbital delocalization (e.g., B6H62-). The M'4Li4 clusters exhibit two isomeric forms: metal tetrahedral cages tetracapped by lithium cations on the outside [(M'4).4Li] and lithium tetrahedra on the inside capped by coinage metal atoms on each of the four faces [(Li4).4M]. Whereas the (M'4).4Li type structure is preferred for copper, gold and silver favor the (Li4).4M arrangement. NBO-NICS anal. shows that the large diatropic character in (M'4).4Li structures is due to the favorable contribution from both s- and d-orbitals, whereas the small NICS values in the center of (Li4).4M are due only to the diatropic contributions from the s-orbitals. [on SciFinder (R)]

Published in:
Inorganic Chemistry, 45, 1, 214-219
CAN 144:135908
General Physical Chemistry
Center for Computational Chemistry and Department of Chemistry,University of Georgia,Athens,Georgia.
written in English.
873334-90-8; 873334-91-9; 873334-92-0; 873334-93-1; 873334-94-2; 873334-95-3 Role: PRP (Properties) (three-dimensional d-orbital aromaticity in octahedral and tetrahedral coinage metal clusters)

 Record created 2007-10-22, last modified 2018-03-17

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