Synthesis and free radical addition reactions of tris[(phenyldimethylsilyl)methyl]tin hydride

Article abstract of DOI:10.1021/om020936b

The synthesis of the new bulky tris[(phenyldimethylsilyl)methyl]tin hydride (9), tetrakis-[(phenyldimethylsilyl)methyl]tin (5), and hexakis[(phenyldimethylsilyl)methyl]ditin (10) as well as some physical properties are described. The addition of hydride 9

Full text of DOI:10.1021/om020936b

856
Organometallics 2003, 22, 856-860
Syn th esis a n d F r ee Ra d ica l Ad d ition Rea ction s of
Tr is[(p h en yld im eth ylsilyl)m eth yl]tin Hyd r id e
Vero´nica I. Dodero,† Terence N. Mitchell,*,‡ and J ulio C. Podesta´*,†
Departamento de Quı´mica, Universidad Nacional del Sur, Avenida Alem 1253,
8000 Bahı´a Blanca, and CONICET (Buenos Aires), Argentina, and Fachbereich Chemie,
Universita¨t Dortmund, D-44221 Dortmund, Germany
Received November 12, 2002
The synthesis of the new bulky tris[(phenyldimethylsilyl)methyl]tin hydride (9), tetrakis-
[(phenyldimethylsilyl)methyl]tin (5), and hexakis[(phenyldimethylsilyl)methyl]ditin (10) as
well as some physical properties are described. The addition of hydride 9 to seven mono-
and disubstituted alkynes under radical conditions indicates that these reactions take place
with complete stereoselectivity. Full 1H, 13C, 119Sn, and 29Si NMR characteristics are included.
In tr od u ction
the relationship between the steric volume of the
substituents attached to the tin atom and the reactivity
as well as the stereoselectivity of organotin compounds,
we considered it to be of interest to carry out the
synthesis of tris[(phenyldimethylsilyl)methyl]tin hy-
dride (9) and to study some reactions of this new bulky
tin hydride.
Organotin hydrides have found many applications in
organic synthesis not only as reducing reagents but also
as intermediates in the generation of carbon-carbon
bonds, and for the preparation of compounds such as
vinylstannanes, which are invaluable starting materials
for cross-coupling reactions.1 In previous studies we
have shown that the size of the organic ligands attached
to the tin atom affects not only the reactivity but also
the stereoselectivity of the reactions of these com-
pounds.2 Thus we reported the synthesis and reactions
of organotin compounds containing neophyl and (-)-
menthyl ligands.
In trineophyltin derivatives, the binding of the bulky
neophyl ligands to tin causes a serious distortion from
tetrahedral geometry. Thus, in trineophyltin chloride
the angles C-Sn-C are 117.2° (mean), whereas the
C-Sn-Cl angle is 99.7°.3 Replacement of the central
carbon atom of the neophyl ligands by silicon leads to
the tris(phenyldimethylsilylmethyl)tin chloride (3) and
to a decrease in steric strain because of a smaller
distortion from the tetrahedral geometry: C-Sn-C
angles 113.3° (mean) and C-Sn-Cl 105.3°.3 Taking into
account these facts, and following our investigations on
Resu lts a n d Discu ssion
Our initial synthetic goal was to prepare tris[(phen-
yldimethylsilyl)methyl]tin chloride (3), which, upon
reduction, should lead to the desired tin hydride. To
obtain 3, tin tetrachloride was alkylated with (phen-
yldimethylsilyl)methylmagnesium bromide (2) according
to Tacke et al.4 (Scheme 1). We repeated the reaction
using the ratio Grignard reagent/SnCl4 ) 3:1 six times,
always obtaining a mixture of chloride 3 and bis-
[(phenyldimethylsilyl)methyl]tin dichloride (4) in an
average ratio 3/4 ) 13.3:1 with an overall yield of 91%,
as shown by 119Sn NMR spectroscopy. These mixtures
were very soluble in methylene chloride, diethyl ether,
hexane, cyclohexane, and petroleum ether, even at low
temperatures (0 to -23 °C). Unlike Tacke, we were
unable to recrystallize 3 pure from these mixtures.
Taking into account these results, we decided to carry
out a study of the reaction under different conditions.
This study demonstrates (Table 1) that the tetraorga-
notin compound 5 is the only derivative with phen-
yldimethylsilylmethyl ligands that could be obtained
pure by alkylation of tin tetrachloride using an ap-
propriate Grignard reagent/SnCl4 ratio. It should be
noted that it is not possible to obtain the triorganotin
halide from 5 by halogenation because this reaction
leads to the cleavage of the Si-Ph bond. Table 1 shows
that, according to the ratio 2/SnCl4, in most cases we
obtained varying mixtures of chlorides 3 and 4, and the
tetraorganotin (5). These reactions were carried out by
using titrated solutions of 2 in diethyl ether. The results
obtained are summarized in Table 1. In all but one
† Universidad Nacional del Sur and CONICET.
‡ Universita¨t Dortmund.
(1) (a) Pereyre, M.; Quintard, J .-P.; Rahm, A. Tin in Organic
Synthesis; Butterworths: London, 1987. (b) Davies, A. Organotin
Chemistry; VCH: Weinheim, 1997. (c) Mitchell, T. N. Organotin
Reagents in Cross-Coupling. Chapter 4 in Metal-Catalyzed Cross-
Coupling Reactions; Diederich, F., Stang, P. J ., Eds.; Wiley-VCH:
Weinheim, Germany. (d) Giese, B. Radicals in Organic Synthesis:
Formation of Carbon-Carbon Bonds; Pergamon Press: Oxford, 1986.
(e) Marshall, J . A. Organotin Chemistry. In Organometallics in
Synthesis: A Manual; Schlosser, M., Ed.; J ohn Wiley & Sons Ltd: New
York, 2002.
(2) (a) Mata, E. G.; Mascaretti, O. A.; Zu´n˜iga, A. E.; Chopa; A. B.;
Podesta´, J . C. Tetrahedron Lett. 1989, 30, 3905. (b) Podesta´, J . C.;
Giagante, N. N.; Zu´n˜iga, A. E.; Danelo, G. O.; Mascaretti, O. A. J . Org.
Chem. 1994, 62, 6458. (c) Podesta´, J . C.; Chopa, A. B.; Giagante, N.
N.; Zu´n˜iga, A. E. J . Organomet. Chem. 1995, 494, 5. (d) Podesta´, J .
C.; Chopa, A. B.; Radivoy, G. E.; Vitale, C. A. J . Organomet. Chem.
1995, 494, 11. (e) Vitale, C. A.; Podesta´, J . C. J . Chem. Soc., Perkin
Trans. 1 1996, 2407. (f) Dodero, V. I.; Koll, L. C.; Mandolesi, S. D.;
Podesta´, J . C. J . Organomet. Chem. 2002, 650, 173.
(3) Schomburg, D.; Link, M.; Linoh, H.; Tacke, R. J . Organomet.
Chem. 1988, 339, 69.
(4) Tacke, R.; Link, M.; J oppien, H.; Ernst, L. Z. Naturforsch. 1986,
41b, 1123.
10.1021/om020936b CCC: $25.00 © 2003 American Chemical Society
Publication on Web 01/21/2003

Tris[(phenyldimethylsilyl)methyl]tin Hydride
Organometallics, Vol. 22, No. 4, 2003 857
Sch em e 1
Ta ble 1. Tin Tetr a ch lor id e Alk yla tion u n d er Differ en t Con d ition s
product relationships (%)b
entry
2/SnCl4 ratio
reaction conditionsa
yield (%)
R3SnCl (3)
R2SnCl2 (4)
R4Sn (5)
1
2
3
2.6
3.0
3.0
3.0
3.0
3.0
3.1
3.1
3.2
4.1
5.1
(1) rt; (2) rt 15 h; (3) refx. 3 h
(1) rt; (2) rt 15 h; (3) refx. 3 h
(1) 0 °C; (2) rt 1.5 h; (3) refx. 3 h
(1) 0 °C; (2) rt 1.5 h; (3) refx. 3 h
(1) 0 °C; (2) rt 1.5 h; (3) refx. 3 h
(1) 0 °C; (2) rt 1.5 h; (3) refx. 8 h
(1) rt; (2) rt 15 h; (3) refx. 3 h
(1) 0 °C; (2) rt 1.5 h; (3) refx. 3 h
(1) 0 °C; (2) rt 1.5 h; (3) refx. 3 h
(1) rt; (2) rt 15 h; (3) refx. 3 h
(1) 0 °C; (2) rt 12 h; (3) refx. 3 h
81
82
91
89
91
93
82
92
92
100
92
12.5
23.5
93.0
35.7
30.8
39.0
37.5
82.5
81.7
76.6
5.9
7.0
10.9
70.6
4c
5d
6
9.3
55.0
58.0
47.8
56.2
1.9
5.9
100
100
11.2
13.2
6.3
15.6
12.4
7
8
9
10
11
a
All the reactions were carried out by adding the Grignard reagent (GR) in diethyl ether onto a solution of SnCl4 in toluene, except
when otherwise stated; rt ) room temperature; refx. ) reflux. From 119Sn NMR spectra. c The solution of SnCl4 in toluene was added
to the GR in ether. SnCl4 was added in benzene.
b
d
experiment (entry 4) the Grignard reagent was added
dropwise to the solution of tin tetrachloride in toluene.
In view of these results, we decided that in order to
obtain the organotin hydride it might be convenient first
to convert the mixture of chlorides 3 and 4, obtained
under the conditions of entry 3 (Table 1), into the
mixture of the corresponding stannoxanes by treatment
with sodium hydroxide (Scheme 1) and then to attempt
the separation of the equilibrium mixture of hydroxide
7 and oxide 8 from oxide 6. Much to our surprise we
found that the 119Sn NMR spectrum of the crude product
showed only the peaks corresponding to a mixture of
compounds 7 and 8. This might be connected either with
the solubility of oxide 6 in water or to its insolubility in
both water and ether.
This result simplified the route to tris[(phenyldi-
methylsilyl)methyl]tin hydride (9) because by reduction
of the mixture of compounds 7 and 8 with borane in
THF,5 as shown in Scheme 1, the desired tris[(phen-
yldimethylsilyl)methyl]tin hydride (9) was obtained. In
summary, the direct conversion of the mixture of
chlorides 3 and 4, obtained from the alkylation of tin
tetrachloride with the Grignard reagent 2, into the
mixture of 7 and 8 by treatment with sodium hydroxide,
followed by the reduction of the mixture with borane in
THF led to tris[(phenyldimethylsilyl)methyl]tin hydride
(9) in 89% yield (based on tin tetrachloride used).
It can also be seen from Scheme 1 that while the
reaction of hydride 9 with CCl4 and CDCl3 leads to the
corresponding chloride 3, leaving this hydride in ben-
zene at 40 °C in argon atmosphere and in the presence
of catalytic amounts of bis(triphenylphosphine)palla-
dium dichloride gives hexakis[(phenyldimethylsilyl)-
methyl]ditin (10) in 74% yield.
The main spectroscopic characteristics of the new
compounds are summarized in Tables 2 and 3. In these
tables we have also included the characteristics of bis-
[(phenyldimethylsilyl)methyl]tin dichloride (4) because,
although this compound has already been reported,6
Chinese literature is often not readily available.
To test the possibility of carrying out stereoselective
hydrostannations using hydride 9 under radical condi-
tions, we carried out the addition of this hydride to some
terminal and internal alkynes. Taking into account
previous work,2f we considered it possible that under
radical conditions the main products of these reactions
should be those corresponding to an anti addition of the
tin hydride (A-1 and A-2), as shown in Table 4.
(5) Chopa, A. B.; Koll, L. C.; Podesta´, J . C.; Thorpe, F. G. Synthesis
1983, 722.
(6) Xie, Q.; Zhu, Y.; Yang, Zh. Hecheng Huaxue 1996, 4, 233.
Extracted from SciFinder.

858 Organometallics, Vol. 22, No. 4, 2003
Ta ble 2. 13C NMR Da ta of Com p ou n d s 4, 5, 9, a n d 10a
Dodero et al.
C(1)
C(2)
[1J (Sn,C)]
[1J (Si,C)]
[3J (Sn,C)]
[1J (Si,C)]
C(3)
compd no.
R
Z
[3J (Sn,C)]
C(4)
C(5)
C(6)
4
Cl
Cl
11.79 (278.0)
(nd)
-0.94
(54.4)
(23.3)
0.29
(52.5)
(12.9)
-0.56
(52.5)
(15.5)
0.68
138.27
(32.7)
133.25
129.51
128.62
128.79
128.79
128.03
5
PhMe2SiCH2
PhMe2SiCH2
PhMe2SiCH2
PhMe2SiCH2
H
-2.86
(239.1)
(33.9)
-5.41
(252.7)
(nd)
-3.77
(151.7)b
(26)
144.21
(21.1)
133.20
133.40
133.20
127.60
127.10
127.64
9
140.56
(18.5)
10
(PhMe2SiCH2)3Sn
141.26
(17.5)
(51.5)
(10.4)
a
In CDCl3; chemical shifts, δ, in ppm with respect to TMS; nJ (119Sn,13C) and 1J (29Si,13C) coupling constants in Hz (in parentheses); nd
) not determined. b 2J (119Sn,13C): 48.7 Hz.
Ta ble 3. 1H, 119Sn , a n d 29Si NMR Da ta of Com p ou n d s 4, 5, 9, a n d 10a
δ
29Si
δ
119Sn [2J (29Si,119Sn)]
compd no.
R
Z
1H NMR chemical shifts (δ, in ppm)a
2
4
Cl
PhMe2SiCH2 PhMe2SiCH2
PhMe2SiCH2
Cl
0.66 [s, 4H, J (Sn,H) 95.9]; 0.41 (s, 12H); 7.39-7.48 (m, 10H)
134.92
-3.18
(31.6)
-2.18
(21.7)
-2.25
(26.6)
-2.91
(24.2)
2
5
-0.11 [s, 8H, J (Sn,H) 69.8]; 0.26 (s, 24H); 7.40-7.60 (m, 20H)
25.93
2
9
H
0.034 [s, 6H, J (Sn,H) 73.3]; 0.34 (s, 18H); 7.20-7.50 (m, 15H) -86.41
2
b
10
PhMe2SiCH2 (PhMe2SiCH2)3Sn 0.093 [s, 12H, J (Sn,H) 62.3]; 0.21 (s, 36H); 7.28-7.40 (m, 30H) -71.03
a
In CDCl3; chemical shifts, δ, in ppm with respect to TMS (1H and 29Si spectra) and Me4Sn (119Sn spectra); coupling constants in Hz
(in parentheses). b 1J (119Sn,119Sn) ) 3775.3 Hz.
Ta ble 4. Tr is[(p h en yld im eth ylsilyl)m eth yl]tin
Hyd r id e Ra d ica l Ad d ition s to Su bstitu ted Alk yn es
propargyl alcohol, methyl propiolate, 1-butyn-3-ol, diphen-
ylethyne, 2-butyn-1-ol, and ethyl 3-phenylpropiolate
leads exclusively to the Z-vinylstannanes resulting from
an anti attack, typical of radical hydrostannations. In
this table it can also be seen that in the additions to
phenylethyne and diphenylethyne under radical condi-
tions E-adducts were the sole products. The formation
of the E-adducts from 11 and 15 could be explained by
taking into account that the known isomerization of the
initially formed kinetic Z-products by further addition/
elimination of the stannyl radical would favor, under
these reaction conditions (prolonged reaction times), the
formation of the thermodynamically more stable E-
vinylstannanes.7,8
compd time temp
A-2
S
yieldb 119Snc
no.
(h)
(°C)
R1
R2
(%) (%)
(%)
(ppm)
11
12
13
14
15
16
17
6
2
85
80
75
85
80
65
75
H
H
H
H
Ph
CH2OH
COOMe
MeCHOH 100
Ph
100
100
100
72
98
98
69
98
98
98
-17.2
-40.4
-37.3
-41.1
-27.3
-34.0
-23.7
0.7
2.3
7
1.5
1
Ph
100
CH2OH Me
COOEt Ph
100
100
The geometry assigned to compounds 12-14 and 16
and 17 follows from the large 3J (Sn,H) coupling con-
stants, mostly well over 120 Hz, that indicate the
existence of trans H-C-C-Sn linkages in these com-
a
The reactions were carried out under a nitrogen atmosphere;
ratio hydride/alkyne ) 1; AIBN 0.01 equiv; without solvent. b From
the 119Sn and 1H NMR. c In CDCl3.
3
pounds. The observed J (Sn,H) coupling constants for
A summary of the obtained results is shown in Table
4. This table also includes the best reaction conditions
for these additions. It can be seen that in most cases
only one of the two possible Z anti adducts (A-2) is
obtained, while in two cases E-adducts are obtained (S).
Table 4 shows that the addition of hydride 9 to
compounds 11 and 15, 81 and 84 Hz, respectively,
clearly indicate the existence of a cis H-C-C-Sn
(7) Betzer, J .-F.; Delaloge, F.; Muller, B.; Pancrazi, A. J . Org. Chem.
1997, 62, 7768.
(8) Leusink, A. J .; Budding, H. A.; Drenth, W. J . Organomet. Chem.
1968, 11, 541.

Tris[(phenyldimethylsilyl)methyl]tin Hydride
Organometallics, Vol. 22, No. 4, 2003 859
anhydrous MgSO4. The solvent was removed under reduced
pressure, and the 119Sn NMR spectrum of the liquid product
showed it to consist of an equilibrium mixture of hydroxide 7
and oxide 8 (45.5 g, 98-99%), which was used without further
purification for the synthesis of hydride 9.
linkage in these compounds. These structures were
1
confirmed by other H and 13C NMR data.
The results obtained show that the additions of the
new organotin hydride 9 to mono- and disubstituted
alkynes under radical reaction conditions lead to vinyl-
stannanes with both excellent stereoselectivity and even
better yields than the recently reported additions of the
bulky trineophyltin hydride to the same alkynes.2f
Further investigations on the properties of organotin
reagents with phenyldimethylsilylmethyl ligands are in
progress.
Syn th esis of Tr is[(p h en yld im eth ylsilyl)m eth yl]tin Hy-
d r id e (9). To a solution of the previous mixture of 7 and 8
(45.5 g) in dry tetrahydrofuran (200 mL) was added dropwise
a solution of borane in THF (0.088 mol, 88 mL of a 1 M
solution). The preparation was carried out under an atmo-
sphere of nitrogen and with magnetic stirring. The mixture
was refluxed during 1 h and the solvent distilled off under
reduced pressure. Diethyl ether (100 mL) and water (5 mL)
were then added. After 10 min stirring, the aqueous layer was
decanted and the ether layer was dried over MgSO4. The
solution was filtered, and removal of the solvent under reduced
Exp er im en ta l Section
NMR spectra were obtained using a Bruker ARX 300
instrument. Infrared spectra were recorded with a Nicolet
Nexus FT spectrometer. Mass spectra were obtained using a
Finnigan MAT Model 8230 at Dortmund University (Ger-
many). Microanalyses were performed at Dortmund Univer-
sity. The refractive indices were measured with a Universal
Abbe Zeiss J ena VEB instrument, and the melting points were
determined in a Kofler hot stage and are uncorrected. Methyl-
(bromomethyl)chlorosilane9 and (bromomethyl)phenyldimeth-
ylsilane (1)10 were obtained following known procedures. All
the solvents and reagents used were analytical reagent grade.
Syn th esis of Tr is[(ph en yldim eth ylsilyl)m eth yl]tin Ch lo-
r id e (3) a n d Bis[(p h en yld im eth ylsilyl)m eth yl]tin Dich lo-
r id e (4). To magnesium turnings (0.53 g, 0.0239 mol) in dry
diethyl ether (5 mL) under stirring was added slowly and
dropwise a solution of (bromomethyl)phenyldimethylsilane (1)
(4.97 g, 0.0217 mol) in diethyl ether (15 mL). The preparation
was carried out under an atmosphere of nitrogen. The reaction
was exothermic, and after the addition was completed the
mixture was refluxed during 1 h. Then the reaction mixture
was stirred for 15 h at room temperature. The solution of the
Grignard reagent 2 thus obtained had a 1.24 M concentration.
To a solution of SnCl4 (10.4 mL, 23 g, 0.088 mol) in dry
toluene (200 mL) at 0 °C under nitrogen was added slowly and
dropwise with stirring a solution of the Grignard reagent 2 in
diethyl ether (0.264 mol, 213 mL of 1.24 M solution). The
mixture was stirred for 1.5 h at room temperature, then
refluxed for 3 h, and finally left 15 h at room temperature with
stirring. After cooling at 0 °C, the reaction mixture was
decomposed with a saturated solution of NH4Cl (ca. 150 mL).
The organic layer was separated, and the aqueous layer was
extracted three times with diethyl ether (ca. 100 mL each).
The combined organic extracts were dried over anhydrous
MgSO4, and the solvent was removed under reduced pressure.
The 119Sn NMR of the resulting oil (47.53 g) showed it to
consist of a mixture of tris[(phenyldimethylsilyl)methyl]tin
chloride (3) and bis[(phenyldimethylsilyl)methyl]tin dichloride
(4) in a ratio 3/4 ) 13.28:1 (47.53 g, 91% yield of organotin
compounds based upon SnCl4 used). This mixture was very
soluble in solvents such as CH2Cl2, diethyl ether, cyclohexane,
hexane, and petroleum ether at 30-60 °C. In the latter solvent
even at low temperature (-23 °C) we were unable to obtain
pure crystals of these compounds.
25
pressure gave 9 as a liquid, µD 1.5674 (44.5 g, 0.0784 mol,
89% yield based upon SnCl4 used initially). MS (m/z, rel int):
419 (100%, [M - (CH2Si(CH3)2Ph)]+, Sn-pattern); 418 (57%,
[M - H)]+, Sn-pattern); 299 (3%, [HSnCH2Si(CH3)2Ph)]+, Sn-
pattern); 135 (76%, [Si(CH3)2Ph]+; 119 (8%, [Sn]+, Sn-pattern).
IR (KBr, cm-1): νSn-H 1816. Anal. Calcd for C27H40Si3Sn
(567.57): C, 57.13; H, 7.10. Found: C, 57.48; H, 7.24.
Syn th esis of Hexa k is[(p h en yld im eth ylsilyl)m eth yl]-
d ista n n a n e (10). To a solution of hydride 9 (0.38 g, 0.669
mmol) in dry benzene (1 mL) under an atmosphere of nitrogen
and with magnetic stirring was added Pd(PPh3)2Cl2 (0.116 g,
0.17 mmol), and the mixture was stirred 3 h at 40 °C. Then
the solvent was distilled off under reduced pressure, and the
crude product was purified by flash chromatography on silica
gel 60, distannane 10 (0,28 g, 0.247 mmol, 74%) being eluted
in the fraction cyclohexane/diethyl ether (99.3:0.7). Mp: 50-
52 °C. MS (m/z, rel int): 567 (100%, [M - Sn(CH2Si(CH3)2-
Ph)3]+, Sn-pattern); 417 (2%, [Sn(CH2Si(CH3)2Ph)2]+, Sn-
pattern); 357 (15%, [(CH2Si(CH3)2Ph)2]+ Sn-pattern); 268 (18%,
[(SnCH2Si(CH3)2Ph)]+ Sn-pattern); 135 (30%, [Si(CH3)2Ph]+);
119 (2%, [Sn]+, Sn-pattern). Anal. Calcd for C54H78Si6Sn2
(1133.10): C, 57.23; H, 6.94. Found: C, 57.36; H, 7.03.
Syn th esis of Tetr a k is[(p h en yld im eth ylsilyl)m eth yl]-
sta n n a n e (5). To a solution of SnCl4 (4 mL, 8.84 g, 0.0339
mol) in dry toluene (80 mL), under nitrogen, at room temper-
ature was added slowly and dropwise with stirring a solution
of the Grignard reagent 2 in diethyl ether (0.139 mol, 108 mL
of 1.24 M solution). The mixture was stirred for 15 h at room
temperature and then refluxed for 3 h. After cooling at 0 °C,
the reaction mixture was decomposed with a saturated solution
of NH4Cl (ca. 50 mL). The organic layer was separated, and
the aqueous layer was extracted three times with diethyl ether
(ca. 50 mL each). The combined organic extracts were dried
over anhydrous MgSO4, and the solvent was removed under
reduced pressure. One recrystallization of the resulting oil
from petroleum ether (30-60 °C) afforded 5 as a white
crystalline solid (24.25 g, 0.0338 mol, 99%). Mp: 48-50 °C.
MS (m/z, rel int): 567 (100%, [M - (CH2Si(CH3)2Ph)]+, Sn-
pattern); 475 (68%, [M - (CH2Si(CH3)2Ph)]+, Sn-pattern); 267
(9%, [(SnCH2Si(CH3)2Ph)]+ Sn-pattern); 135 (30%, [Si(CH3)2-
Ph]+); 119 (2%, [Sn]+, Sn-pattern). Anal. Calcd for C36H52Si4-
Sn (715.87): C, 60.40; H, 7.32. Found: C, 60.49; H, 7.39.
Syn th esis of Bis[(p h en yld im eth ylsilyl)m eth yl]tin Di-
ch lor id e (4). To a solution of SnCl4 (5.2 mL, 11.5 g, 0.044
mol) in dry toluene (100 mL) at room temperature was added
slowly and dropwise with stirring a solution of the Grignard
reagent 2 in diethyl ether (0.264 mol, 213 mL of 1.24 M
solution) under nitrogen. The mixture was left 15 h at room
temperature and then refluxed for 3 h. After cooling at 0 °C,
the reaction mixture was decomposed with a saturated solution
of NH4Cl (ca. 75 mL). The organic layer was separated, and
the aqueous layer was extracted three times with diethyl ether
(ca. 50 mL each). The combined organic extracts were dried
over anhydrous MgSO4, and the solvent was removed under
reduced pressure. The 119Sn NMR of the resulting oil showed
Syn th esis of Hexa k is[(p h en yld im eth ylsilyl)m eth yl]-
d ista n n oxa n e (6) a n d Tr is[(p h en yld im eth ylsilyl)m eth yl]-
tin Hyd r oxid e (7). To a solution of the mixture of tin
chlorides 3 and 4 in the ratio 3/4 ) 13.28:1 (47.53 g) in diethyl
ether (350 mL) was added a 10% aqueous solution of NaOH
(50 mL), and the mixture was vigorously stirred during 3 h.
The organic layer was decanted and treated again with the
aqueous solution of NaOH. Then the organic layer was
separated, washed three times with water, and dried with
(9) Carleer, R.; Anteunis, M. J . O. Org. Magn. Reson. 1980, 13, 253.
(10) Farbenfabriken Bayer, A.-G. Ger. Pat. 1,242,615 (Cl. C 07f);
Chem. Abstr. 1967, 67, 90931q.

860 Organometallics, Vol. 22, No. 4, 2003
Dodero et al.
it to consist of a mixture of tris[(phenyldimethylsilyl)methyl]-
tin chloride (3), bis[(phenyldimethylsilyl)methyl]tin dichloride
(4), and tetrakis[(phenyldimethylsilyl)methyl]tin (5) in a ratio
3/4/5 ) 1.14:6.98:1 (18.8 g, 81% yield of organotin compounds
based upon SnCl4 used). From this mixture and after repeated
recrystallizations in n-heptane we were able to obtain 4 pure
(4.56 g, 0.0093 mol, 21%).
Hyd r osta n n a tion of Su bstitu ted Alk yn es. All the reac-
tions were carried out following the same procedure. One
experiment is described in detail in order to illustrate the
methods used.
Ad d ition of Tr is[(p h en yld im eth ylsilyl)m eth yl]tin Hy-
d r id e (9): Syn t h esis of Met h yl (Z)-3-[(Tr is(p h en yld i-
m eth ylsilyl)m eth yl)sta n n yl]p r op en oa te (13). Methyl pro-
piolate (0.15 g, 1.78 mmol) was treated for 0.7 h with hydride
9 (1.01 g, 1.78 mmol) under nitrogen at 75 °C and with AIBN
as a catalyst (this optimal time of reaction was indicated by
earlier experiments in which the reaction was monitored by
taking samples at intervals and observing the disappearance
of the Sn-H absorption by IR). The 1H, 13C, and 119Sn NMR
spectrum of the crude product showed that it consisted of
isomer Z-13 only. We found that, unlike trineophyltin adducts,2f
most of these adducts tend to decompose in silica gel, bringing
the yields of isolated products down to 41-57%. Therefore, for
other studies we used adducts 11-17 without further purifica-
tion.
Ack n ow led gm en t. This work was supported by
CONICET (Capital Federal, Argentina) and Univer-
sidad Nacional del Sur (Bah´ıa Blanca, Argentina). We
acknowledge a research grant from Fundacio´n Antor-
chas (Argentina). Fellowships from the DAAD (Ger-
many) and CONICET to one of us (V.I.D.) are also
gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Mass spectra and
1
the H as well as 13C NMR characteristics of the new adducts
thus obtained are available as Supporting Information. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM020936B