Organometallics 1999, 18, 4889-4890
4889
Ea sy Gen er a l Meth od for In ter h a lid e Con ver sion s in
Or ga n otin Com p ou n d s
Bernhard Zobel, Allan E. K. Lim, Kerri Dunn, and Dainis Dakternieks*
Centre for Chiral and Molecular Technologies, Deakin University,
Geelong, Victoria 3217, Australia
Received J uly 8, 1999
Summary: The halides in organotin halides are easily
interconverted in excellent yields using aqueous am-
monium halide solutions and various organic solvents.
A few methods of converting some alkyltin fluorides
into the corresponding chlorides and bromides have
been published. Armitage and Tarassoli have reported
the synthesis of tri-n-butyltin bromide in 88% yield via
the direct reaction of triethylbromosilane and tri-n-
butyltin fluoride.10 Mitchell and co-workers11 reported
the use of sodium chloride or sodium bromide in
anhydrous THF for the preparation of trialkyltin chlo-
rides or bromides from the corresponding fluorides in
yields ranging from 48 to 86% using reaction times
between 3 and 5 days. It is noteworthy that their
attempts to convert triphenyltin fluoride into the cor-
responding chloride or bromide were unsuccessful.
With the exception of the organotin fluoride synthe-
ses, all of the previously described methods require the
halide interconversions to be performed under anhy-
drous conditions, presumably to avoid hydrolysis of
the organotin halides. Furthermore, some methods have
the added disadvantages of involving either costly
reagents9,10 or lengthy reaction times.9,11
Surprisingly, there appear to be no reports concerning
the use of ammonium halides nor any involving the use
of aqueous conditions (other than for organotin fluoride
syntheses8) for halogen exchange reactions at tin. We
now describe a general method that enables (1) halogen
interconversion within both aryl and alkyltin halides,
(2) the exchange of any halide within an organotin
halide with all other possible halides, and (3) performing
these conversions both up and down group 17 by the
use of saturated aqueous ammonium halide solutions
as halide conversion agents. Of particular significance
is the rapid conversion of triorganotin fluorides into the
corresponding chlorides. Owing to their extremely low
solubility in common organic solvents, organotin fluo-
rides are usually formed as a means of removing
organotin byproducts in both organic and organometallic
syntheses. With the method reported here, it is now
possible to recycle triorganotin fluorides easily and
quickly via conversion into the corresponding chloride,
bromide, or iodide.
In tr od u ction
Organotin halides are well-known compounds that
have found extensive use within both academe and
industry.1-4 Most other functional organotin compounds
such as organotin hydrides, alkoxides, amides, and
carboxylates are prepared using the corresponding
organotin halide as a starting material.1
A particular potential application of diorganotin di-
halides is as antitumor agents.2 The biological activity
of diorganotin dihalides is found to vary with different
halides.2 It would therefore be extremely useful to be
able to easily interconvert the halogens in an organotin
compound.
Several investigations regarding the exchange of
halides in organotin halides have been published.
Tributyltin chloride and dibutyltin dichloride were
converted into their respective bromides or iodides via
a halogen exchange reaction with certain alkyl bromides
or iodides (e.g., allyl bromide, dibromomethane, or
iodoethane) in the presence of 5 mol % of the corre-
sponding tetrabutylammonium halide as a catalyst.5
Organotin bromides and iodides can also be prepared
from the corresponding chlorides via metathesis with
the appropriate sodium halide in acetone,6,7 whereas the
corresponding fluorides can be prepared by reaction
with sodium or potassium fluoride in aqueous alcohol
solution.8
While it is generally straightforward to exchange a
lighter halogen with a heavier halogen on tin (the
fluoride syntheses being a major exception), there are
far fewer methods for replacing a heavy halogen with a
lighter analogue. For example, organotin iodides can be
converted to the corresponding chlorides via stirring
with silver chloride in dry acetonitrile with the exclusion
of light for 14 days.9
(1) Davies, A. G. Organotin Chemistry; VCH: Weinheim, 1997.
(2) Crowe, A. J .; Smith, P. J .; Atassi, G. Chem.-Biol. Interact. 1980,
32, 171.
(3) Neumann, W. P. Die Organische Chemie des Zinns; Ferdinand
Enke Verlag: Stuttgart, 1967.
(4) Ingham, R. K.; Rosenberg, S. D.; Gilman, H. Chem. Rev. 1960,
60, 459.
Resu lts a n d Discu ssion
While this study was performed using butyl and
phenyl tin compounds as representative examples, these
reactions can be utilized for most if not all other
(5) Friedrich, E. C.; Abma C. B.; Delucca, G. J . Organomet. Chem.
1982, 228, 217.
(6) Kocheskov, K. A.; Nesmeyanov, A. N. Chem. Ber. 1931, 64, 628.
(7) Pikina, E. I.; Talalaeva T. N.; Kocheskov, K. A. J . Gen. Chem.
USSR 1938, 8, 1844.
(8) Davies, A. G.; Smith, P. J . In Comprehensive Organometallic
Chemistry; Wilkinson, G., Ed.; Pergamon Press: Oxford, 1982; Vol. 2,
pp 519-627. (b) Krause, E.; Weinberg, K. Chem. Ber. 1930, 63, 381.
(9) Altmann, R.; J urkschat, K.; Schu¨rmann, M.; Dakternieks, D.;
Duthie, A. Organometallics 1997, 16, 5716.
(10) Armitage, D. A.; Tarassoli, A. Inorg. Chem., 1975, 14, 1210.
(11) Mitchell, T. N.; Kwetkat K.; Godry, B. Organometallics 1991,
10, 1633.
(12) Dakternieks, D.; Dunn, K.; Schiesser C. H. Organometallics,
submitted.
10.1021/om990528g CCC: $18.00 © 1999 American Chemical Society
Publication on Web 10/13/1999