1054 HARMON, HESSE,KLEMANN, KOCIIER, ILICKINLEY, AND YOUNG AND
Inorgunic Chemistry
CONTRIBUTIOX FROM THE DEPARTMENT O F CHEMISTRY, HARVEY MUDD COLLEGE, CLAREXONT, CALIFoRhIA 91711, Dom CHEMICAL COMPANY RESEARCH LABORATORIES, WAYLAND, MASSACHUSETTS 01788, AXD MIDLAXD, MICHIGAN48640
Carbonium Ion Salts. XIII.
Stable Triarylcarbonium Pentahalostannate(1V) Salts1
BY KENNETH M. H X R M O S . ~ LE ~ E - L O U I S E HESSE, S . V. McKINLEY,2b ASD A. E. YOUXG2b
L.P. KLEIL.IANS,2b C.W.KOCHER,2C
Received ATooembev26, 1968 Certain triarylmethyl halides form stable 1: 1 adducts with stannic halide; facile hydride-transfer reactions, electronic spcctra, and a combiiiation of X-ray, infrared, and Mossbauer effect data deiiiotistrate that theje are salts of triarylcarboiiium ions and monomeric trigonal-bipyramidal pentalialostannate( IV) ions. The formation of these salts is not kinetically controlled, as the stoichiometry of the solid is not changed by use of excess halide, equilibration in strongly ionizing solvents, or preparation from preformed hexahalostannate(1V) ions. Variable-temperature nmr equilibrium measurements of the ionization of triphenylmethyl chloride by pentachlorostannate( IV) ion in methylene chloride yield the values A S o = 1.85 kcal/mol, A H o = -9.56 kcal!mol, and A S " = -38.6 eu a t 25" for this reaction and allow the prediction of the stability of other triarylcarboniurn ion pentaclilorostannate!IV) salts. The preparations and interconversions of a number of such salts and their bromide analogs are described.
Introduction Almost without exception, stable, isolable five-coordinate tin(1V) compounds can be classified as complexes between stannic halides and organic bases3 or anionbridged salts of the triphenyl- or trimethyltin(1V) cation.4 The unusual stoichiometry of these compounds may result from the bulk of the organic ligands and from intrinsic stabiLty of the planar trialkyltin cation, since with simple Lgands such as halide tin(1V) normally assumes the six-coordinate sp3d2c~nfiguration.~ Compounds of the type R4N+SnC15- have been prepared and the anion in these salts has tentatively been assigned the trigonal-bipyramidal sp3d con( 1 ) (a) Portions of this work were supported by gi-ants from the h-ational Science Foundation and the Petroleum Research Fund t o Harvey Mudd College. (b) Reported in part by K . M. Harmon, A. B. Harmon, S. D. Alderman, and L. Hesse, Abstracts, 155th Kational Meeting of t h e American Chemical Society. San Francisco, Calif., Api-il 1968, No. X181. (2) (a) Address inquiries t o K . M. H. a t Harvey hludd College. (h) Dow Chemical Co.. Eastern Keseai-ch Laboratory. (c) Dow Chemical Co., Radiochemical Research Laboratory. (3) (a) C. J. Wilkins and D . K. Grant, J . Chem. Soc., 927 (1953), (b) Woolf, J . I m r g . S u c l . Chem., 3 , 285 ( 1 8 5 6 ) ; (c) J. E. Fei-gusson, D. K. Grant, I
