Does anyone know of good chemical drawing software for inorganic chemistry.  In the past I have used ISIS/Draw, however with a change to Windows 7 I tried to download Symyx Draw 3.3.  I cannot figure out how to input NH3 for an ammine ligand.  I have also tried ChemSketch.  Unfortunately I cannot figure how to turn off the charge function.  The program insists on changing NH3 to NH2 and if I force it to NH3 it includes a positive charge on nitrogen (and puts a negative charge on my metal center with NH2).  Any help either with these programs or another free/shareware package is greatl