Pentacoordination at fluoro-substituted silanes by weak Lewis donor addition

Quantum chemical calculations at the ab initio level indicate that Lewis do nors such as amine or water form weak donor-acceptor complexes with fluoro- substituted silanes. The strength of the donor-acceptor formation increases with increasing degree of fluorine substitution. Amine and water form stro ng adducts only for tetrafluorosilane. The higher element homologues of Lew is donors, such as phosphane and sulfur dihydride, do not in essence coordi nate. A considerable role in donor-acceptor formation is exerted by chelati on effects which impose intramolecular interactions on functionalized ligan ds. The corresponding structures are explored.