Now uses an extension of the MMFF94 force field for tricoordinate boron compounds.
Most compounds containing B-X bonds where X=C,N,O,S,
and H are covered with the following exceptions: X=N(imine),N(sulfonamide),
N(pyridinium) and N(quaternary). Also not supported are compounds in which
boron is bonded to X=F,Cl,Br,I,B and Si, or makes a bond angle BYX.
Compounds in which boron is a part of four-membered rings of B1CCC1 type are also
not available in the current parameterization because their existence is questionable:
Ab initio calculations at the MP2/6-31G** level failed to identify stable structures
for them (highly polar structures in which boron is four-coordinated are formed).