Intramolecular nitrogen ligand stabilization of phenyl-imidazolidine derived silicon species

The synthesis of some new functional aminoarylsilanes with the aromatic ring substituted in the ortho-position by a 2-(1,3-dimethyl)imidazolidine ligand is presented. The donating properties of the imidazolidine fragment, in which the two coordinating nitrogen atoms are located on the same side of the silicon center induce a specific chemical behavior of the organosilicon species. Thus, only one Si-H bond of ArSiH3 was found to react with an excess of organic acids and heterocumulenes. NMR studies showed that, if in imidazolidinylphenyldihydrosilanes containing a strong electronegative substituent, the silicon center is pentacoordinated by forming one additional N-->Si bond, only a small activation energy is sufficient to exchange the two donating nitrogen atoms. The reason for this easy exchange is probably the small distance between the two donor centers and the rigidity caused by the bridging ethylene unit. (C) 1998 Elsevier Science S.A. All rights reserved.