Re: CCL:TM force fields - questions
Hi, just to add my 2 cents to the discussion.
I substantially agree with P-O Norrby and with R K Szilagy.
I have been working many years with pure MM methods on the stereo- and
regioselectivity in the polymerization of 1-alkenes with heterogeneous
and homogeneous Ziegler-Natta catalysts.
A few years ago, to make such calculations you had to "guess" several
force field parameters, or just fix some internal coordinates to
"reasonable" values. Although quite rude, the approach has worked.
In the last few years, however, several research groups developed MM
force fields for metallocenes, and now the MM calculations on these
systems can be done without any "guess" or fixing of internal
coordinates.
Force fields for metallocenes can be found in:
Doman et al JACS 1992, 114, 7264
Hollis et al Organometallics 1993, 12, 3385
Doman et al JACS 1995, 117, 1352
Howler et al Organometallics 1994, 13, 2380
Good resumes on the applications can be found in:
Resconi et al Chem Rev 2000, 100, 1253
Angermund et al Chem Rev 2000, 100, 1457
The improvements of MM force fields for TM complexes has been rather good
in the last years. And the results obtained with such developments are
there to witness the validity of such approaches. Clearly, people have to
know what CAN be done and what CANNOT be done with MM.
In the post of Szilagy, the applicability of such methods is briefly but
correctly reviewed.
Regards,
Luigi
--------------------------------------------------------------------------
| Dr. Luigi Cavallo Dept. of Chemistry |
| Ph: ++39-81-2536635 Univ. of Naples |
| Fax: ++39-81-5527771 Via Mezzocannone 4 |
| Email cavallo-: at :-chemistry.unina.it I-80134 Napoli, ITALY
|
--------------------------------------------------------------------------