Abstract:
Molecular mechanics calculations were done on tetrahedral phosphine oxide zinc
complexes in simulated water, benzene and hexane phases using the DREIDING II force
field in the BIOGRAF molecular modeling program. The SUN workstation computer
(SUN_ 4c, with SPARK station 1 processor) was used for the calculations. Experimental
structural information used in the parameterization was obtained from the September 1989
version of the Cambridge Structural Database.
2
Steric and solvation energies were calculated for complexes of the type ZnCl2 (RlO)2'
The calculations were done with and without inclusion of electrostatic interactions. More
reliable simulation results were obtained without inclusion of charges.
In the simulated gas phase, the steric energies increase regularly with number of
carbons in the alkyl group, whereas they go through a maximum when solvent shells are
included in the calculation. Simulated distribution ratios vary with chain length and type of
chain branching and the complexes are found to be more favourable for extraction by
benzene than by hexane, in accord with experimental data. Also, in line with what would be
expected for a favorable extraction, calculations without electrostatics predict that the
complexes are better solvated by the organic solvents than by water.
