Fluorine exchange between four-, five-, and six-coordinate silicon compounds

Intermolecular fluorine exchange in the systems SiF 4 –SiF 5 − , MeSiF 3 –MeSiF 4 − , PhSiF 3 –PhSiF 4 − , SiF 5 − –SiF 6 2− , SiF 4 –SiF 6 2− , and MeSiF 3 –SiF 6 2− has been studied by fluorine and proton nmr spectroscopy. Exchange is postulated to involve fluorine-bridged intermediates; alternative pathways of exchange, such as fluoride dissociation or impurity (HF and H 2 O) catalyzed exchange, have been eliminated. Addition of NH 3 to SiF 5 − –SiF 6 2− slows down exchange whereas addition of Et 2 NH to MeSiF 3 promotes exchange.