Complexes of stannous fluoride and other group IVB dihalides with mammalian hemoproteins

Stannous fluoride, the widely used anticaries toothpaste additive, and other tin and germanium dihalides form complexes with hemoproteins such as hepatic cytochrome P-450, hemoglobin, and peroxidase. These complexes are characterized by visible spectra closely similar in shape, molar absorptivity, and absorbance maxima to those obtained with analogous complexes of carbon monoxide. Evidence is presented that the observed complexes are formed with uncharged MX2 or LMX2, moieties (where L is a neutral Lewis base, M is a metal, and X is a halogen) acting as pi-acceptor ligands.