Application of Molecular Modeling to C−H Activation in Organoiron Compounds

Molecular modeling has been applied to the products of the reaction between bidentate-phosphine-stabilized iron species and 1,5-hexadiene. On the basis of the TRIPOS force field, a complete set of parameters for an iron atom in a tetrahedral environment has been derived and the accessible molecular surface (AMS) model has been used to estimate the effect of the bidentate ligand upon the free coordination surface for a variety of (R 2 P(CH 2 ) n PR 2 )Fe fragments. The results suggest that the course of the reaction is largely controlled by steric factors associated with the bidentate ligands: sterically demanding ligands lead to a small AMS at the metal atom, and further reaction of the coordinated hexadiene is hindered; less demanding ligands lead to a larger AMS, which enables the metal atom to interact with a methylenic H atom with resulting H transfer and formation of a (η 5 -1-MeC 5 H 6 )Fe−H species.