Subject: Re: metal complexes

From: <[email-masked]>
Date: Wed, 05 Jan 94 13:37:39 +0100

Dear Liu Jianling,

	molecular mechanics studies have been carried out on penta-coordinated
tungsten carbene complexes using the PCMODEL-PI V4.0 software with a new 
METMOD1 force field, developed for this application. This programme previously
provided a semi-quantitative guide to structures of transition metal
complexes using only the streching, van der Waals, and 1,3-interaction.

	METMOD1 uses all of the six original energy terms of MMX: 
streching, van der Waals, strech-bend, bending, torsion, and electronic
interactions. Only experimentally determined data for relevant compounds 
were used for parametrization. Slightly distorted trigonal-bipyramidal
structures with equatorial paralell carbene conformations are found to be
favoured.

	Structures calculated by PCMODEL, METMOD1 and ab initio methods are
compared with the relevant experimental data. All of the RMS fitting errors
between the METMOD1 and ab initio or experimental structures are less then
0.07 angstrom.

Further references:

Bencze L., Szilagyi R.: J. Mol. Catal., 1992, 76(1-3), 145-156
Bencze L., Szilagyi R.: J. Organomet Chem., 1994, in press JOM 23894
Bencze L., Szilagyi R.: J. Mol. Catal., 1994, May, in press

	We organize a microsymposium on Molecular Modelling in the first
week of this September. If you are interested in to attend to this school
do not hesitate to contact us. 

		Sincerelly Yours

						Rob