coordination compounds in MM3

From: jz7 (a) duke.edu
Subject: coordination compounds in MM3
Date: Mon, 27 Jun 2005 16:50:15 -0400 (EDT)

Dear all,
 I want carry out some calculation on a metal-porphyrin coordination
 compound using MM3 force field. From MM3 manual, there should be two
 modification (1,3-electron pair repulsion and bending parameter
 adjustment). However, I didn't find what special commands I should use to
 indicate those coordinate bonds (eg. in conjugated systems we have to
 specify those pi atoms). Would anyone who is familiar with MM3 tell me
 what kind of special treatment I should apply to the coordination
 compound?
 Thanks a lot for the help!