The crystalstructures of two hypervalent silicon compounds (N → Si) (2-benzothiazolylthiomethyl)trifluorosilane and (N → Si) (2-benzoxazolylthiomethyl)trifluorosilane have been determined. Both molecules have similar geometrical parameters. The Si atom acquires a distorted trigonal bipyramidal penta-coordination due to five-membered ring closure by a donor-acceptor N → Si bond of lengths of 1.988(3)