Subject: Ab initio on Ir(IV), Os(IV) and Ru(III, IV)

From: Achim Lienke <[email-masked]>
Date: Wed, 06 Jan 1999 13:18:49 -0800

I am calculating a series of chloro and aqua-chloro complexes of
Platin-Group-Metals (PGMs) (e.g. PtCl6-2, RhCl6-3, IrCl6-2) with ab
initio methods in order to obtain geometries, IR frequencies and point
charges. 

The results for all closed shell systems are good and reflect
experimental data and trends, but for the open-shell systems like
IrCl6-2 and OsCl6-2 this is probably not the case. There is a slight
Jahn-Teller distorsion (which is expected), but the avaraged bond
lengths are smaller than expected and - more important - the point
charges on the axial and equatorial chlorines differ substantially and
are larger than one would expect from experimental data (solvation).

My question: Can it be that those results are just artefacts because
some important effects and couplings are neglected? I am using Gaussian
94, Methods are SVWN (produces good results), B3LYP and MP2 (to check,
methods are in for this application inferior), basisset is LANL2DZ for
the metal and 6-31G for Cl, H and O

Achim Lienke
Department of Chemistry
University of Cape Town

[email-masked]