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Exchange of the Apical Tin Atom in the nido-Cluster (CH3)5C5Sn+.

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The stable thioketones 3a, b can be isolated. The less
stable thioacetophenone 3c is trapped by mesitonitrile oxide as the addition product 4 . The labile thioketenes 3d, e
are converted in situ by azomethines into the Diels-Alder
adduct 5 and the 8-thiolactam 6 as [2+2]-cycloadduct, respectively. In the absence of scavenger the thioketene
dimer 7 is obtained from If.
Received- September 16, 1982;
revised: November 2, 1982 [ Z 148 IE]
German version: Angew. Chem. 95 (1983) S2
The complete version of this manuscript appears in:
Angew. Chem. Suppl. 1983. 63-69
[ I ] F. Duus in D. H. R. Barton, W. D. OKs: Comprehensive Organic Chemi.7try. Vol. 3. Pergamon Press, Oxford 1979, p. 373.
141 H. B. Henbest, S. A. Khan, Chem. Commun. 1968, 1036; D. Arndt in
Houben-Weyl-Muller: Methoden der Organischen Chemre. 4th edit., Vol.
I V / I h , Thieme, Stuttgart 1975, p. 647.
151 In a similar manner formaldehyde can be liberated from 1,3-oxathiolane
S.S-dioxide: K. Schank, R. Wilmes, G. Ferdinand, In!. J. Sulfur Chem. 8
(1973) 397.
[ I ] P. Jutzi, F. Kohl, C. Kruger, Angew. Chem. 9J (1979) 81: Angem,. Chem.
Int. Ed Engl. 18 (1979) 59: P. Jutzi, F. Kohl, P. Hofmann, C. Kruger, YiHung Tsay, Chem. Ber. 113 (1980) 757.
121 a) P. Jutzi, F. Kohl, C. Kriiger, G. Wolmershauser, P. Hofmann, P. Stauffert, Angew. Chem. 94 (1982) 66; Angew. Chem. Int. Ed. Engl. 21 (1982)
70; Angew. Chem. Suppl. 1982. 2 5 ; b) F. Kohl, P. Jutzi, E. Schluter, unpublished.
I31 Experimental: A solution of I (2.50 g, 6.20 mmol) in CHzCIz (25 mL) is
added dropwise to a solution of freshly sublimed BI, (2.49 g, 6.36 mmol)
in CH2Clr (125 mL). A yellow precipitate separates out, while the solution turns bright red in color. Repeated filtration and evaporation of the
solution affords a slurry of red crystals from which the readily volatile
components are removed by evaporation and condensation using a cold
finger (0.15 torr, S O T ) . Recrystallization of the residue from 2 m L
CH2CIr furnishes 0.40 g (15%) of 2.
[41 P. Jutzi, A. Seufert, Angew. Chem. 89 (1977) 339: Angew. Chem. Int. Ed.
Engl. 16 (1977) 330; Chem. Ber. 112 (1979) 2481.
[S] F. Kohl, P. Jutzi, unpublished results.
Some Cautions in the Interpretation of
Oxidoylide Reactions based on "P-NMR Data
By Edwin Vedejs and G. P. Meier
Exchange of the Apical Tin Atom in the
nido-Cluster (CH3)5C5Sn
+
By Franz Kohl and Peter Jutzi*
Nucleophiles attack the pentagonal-pyramidal cluster
(CH3)sC5SnC1'1at the apical Sn atom, resulting in a weakening of the q5-cyclopentadienyl-tin bond and formation
of the adducts [(CH,),C,SntNu]+ (e. g. with N u = pyridine[*"], 2,2'-bipyridyi[2b1).From preliminary investigations
with electrophiles it follows that these d o not attack at the
lone pair of electrons of the Sn atom but at the pentagonal
base of the cluster. We report here on a reaction which
leads via cyclopentadienyl-transfer to exchange of the apical atom in the nido-cluster.
On reaction of (q5-pentamethylcyclopentadienyl)tintrifluoromethanesulfonate 1 with boron triiodideC3lin dichloromethane, precipitation of yellow tin(I1) iodide was observed; the product remaining in solution was spectroscopically (NMR, MS) identified as ($-pentamethylcyclopentadieny1)iodoboron trifluoromethanesulfonate 2141.
Synthetically useful species described as 0-oxidotylodes
("betaine ylides", type 4) are formed when alkyllithiums
are added to the low temperature Wittig intermediates
formed from aldehydes and LiX-containing alkylidenetriphenylphosphoranes1'I. Under these conditions, oxaphosphetanes such as 1 ( + LiX) exist to some extent in equilibrium with ionic betaine-LiX adducts 2L2"1,and the deprotonation process can be understood as a typical base-phosphonium salt reaction.
Recently deprotonation of 1 by alkyllithium reagents in
the absence of lithium halides has been d e s ~ r i b e d [ ~ " ,In
~I.
salt-free Wittig reactions, betaines o r other ionic species
have not been observed by direct methods[*I, and hence the
mechanism of oxidoyiide formation in these examples is
unclear. Our own experiments with salt-free 1 contradict
some of the published result^[^".^^.
R
0-PPh,
a, It
Mechanistically, this reaction can be explained in terms
of an electrophilic attack at the cyclopentadienyl ring, as
also was observed for the formation of (CH3)&H or
(CH3& on protonation (with CF3S03H) or alkylation
(with CF3S03CH3)of lLsl.
However, the halide transfer is
accompanied by a complex reaction sequence, which f i nally results in exchange of the apical component in the
nido-complex. This novel type of reaction provides general
access to a variety of other cyclopentadienyl-element compounds with nido-cluster structure.
Received: August 20, 1982 (2 136 IEI
German version: Angew. Chem. 95 (1983) 55
[*I Prof. Dr. P. Jutzi, Dr. F. Kohl
Fakultat fur Chemie der Universitat
Postfach 8640, D-4800 Bielefeld I (Germany)
56
0 Verlag Chemre GmbH, 6940 Wernheim, 1983
=
CsH5; b,
R
= H
Homogeneous solutions of l a prepared from salt-free
ethylidenetriphenylphosphorane in tetrahydrofuran (THF)
d o not undergo significant deprotonation with n-C4H9Li or
"].
sec-C4H9Li at -78 "C in contrast to the l i t e r a t ~ r e ~ ~AIthough a red color appears immediately, the 31P-NMR
spectrum shows only traces of new complex signals in the
P'" region. A strong, sharp signal of unreacted la12a1
is observed and remains unchanged over 1.5 h at - 80 5 2 "C in
T H F in presence of sec-C4H9Li. Neither the signal at
6 = - 54 previously assigned to a metalated oxaphosphe[*] Prof. Dr. E. Vedejs, G. P. Meier
McElvain Laboratory of Organic Chemistry
Department of Chemistry, University of Wisconsin
Madison, Wisconsin 53 706 (USA)
[**I
This work was supported in part by the National Science Foundation
( G D 43 89 I X).
0570-0833/83/0101-0056 $ 0 2 . 5 0 / 0
Angew. Chem. Int. Ed Engl. 22 (1983) No I
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