Experiment 3A. Molecular Modeling of Organometallic Molybdenum Compounds
The goal of this experiment is to model a series of organometallic complexes
that have one ligand that is varied and to see how this variation of the
ligand changes the properties of the complexes as predicted by molecular
modeling. You will use these molecular modeling results to make some predictions
about the properties of these complexes. You will then prepare the complexes
you modeled (Experiment 3B) and see how well your predictions of chemical
properties obtained from the modeling experiments fit the observed properties.
The CAChe program allows you to calculate a number of properties of your
complexes. These include optimized geometry with bond distances, electron
density, HOMO-5 to LUMO+4, electrostatic potential, electrophilic susceptibility,
nucleophilic susceptibility, etc.. You should pick a property that you think
you can correlate to an experimentally observable quantity that can be measured on the department's equipment.
[Mo(CO)4(NN)] with two different NN ligands.
In this experiment you will model two different molybdenum complexes that
vary in the particular nitrogen donor ligands which are utilized. The NN
ligands would commonly be a bidentate diimine ligand like 2,2-bipyridine,
1,10-phenanthroline or a variety of substituted analogs. Your laboratory
report needs to address how this modification of the ligands is predicted
to change the properties of your complexes. For some ideas, look over the
tutorials on electrochemistry, electronic and vibrational spectroscopy,
and NMR in the tutorials
section. You need to use these modeling results to make predictions
about the relative physical properties of the two systems you modeled.
You don't have to try to make absolute predictions of properties. Properties
that you might try to correlate to modeling results are IR spectroscopy,
UV-vis spectroscopy, electrochemistry, NMR spectroscopy, etc.. The ligands
you select for the modeling studies will be the ones used in the synthesis
part of this experiment (Experiment 3B) so make sure to consider their availability
in your ligand selection process. The ligands you plan to use need to be
approved by your TA prior to beginning Exp. 3A. To begin this experiment
you need to go to the inorganic laboratory in Davidson 128 and open Netscape.
This experiment has to be performed in our laboratory or computing lab
since they are the only available computers which have the necessary software
to utilize the CAChe molecular modeling software.
This molecular modeling experiment is composed of two parts. Part I will
take you through a series of WWW based tutorials to teach you to use the
CAChe molecular modeling package. After you have learned how to use this
program Part II will involve the modeling of the compounds of interest to
you in your experiment. After you have completed your molecular modeling,
you will prepare your laboratory report for the modeling part of this experiment.
It must include your modeling results as well as predictions concerning
the properties of the complexes you propose to prepare. The laboratory report
on your molecular modeling results must be submitted to Prof. Brewer prior
to performing the synthesis and characterization of your complexes.
Experiment 3A and 3B are part of an integrated molecular modeling, synthesis
and characterization laboratory designed to teach molecular modeling concepts
in an integrated laboratory setting. This approach uses the internet and
distributed learning to assist in the instruction of molecular modeling
concepts and software usage. The design of the experiment allows for student
input in the selection of the compounds to model and prepare and the nature
of the molecular modeling performed. Students also select the physical property
they want to make predictions concerning as a result of their molecular
modeling results. The experimental design for Experiments 3A and 3B is as
follows: