Reactions of a highly crowded triorganotin iodide with silver salts. Migration of a methyl group from silicon to tin within a cation

Article abstract of DOI:10.1021/om011079z

Reaction of the highly crowded organotin iodide CH₂Me₂Si(Me₃Si)₂CSnMeIC(SiMe₃ )₂SiMe₂CH₂ with AgBF₄ gives the fluoride CH₂Me₂Si(Me₃Si)₂CSnMeFC(SiMe₃ )₂SiMe₂CH₂. Reaction with AgOSO₂C₆H₄Me followed by workup in moist air gives the hydroxide CH₂-Me₂Si(Me₃Si)₂CSnMe(OH)C(SiMe ₃)₂SiMe₂CH₂2, 2f. With AgOSO₂CF₃ the product is the organosilicon trifluoromethanesulfonate CH₂Me₂Si(Me₃Si)₂CSnMe₂C(S iMe₃)(SiMe₂OSO₂CF₃)-SiMe₂ CH₂, 5, formed apparently by an unprecedented 1,3-migration of a methyl group from silicon to tin within a cation. Compound 5 and Ph₃SiOSC₂CF₃ are the first silicon trifluoromethanesulfonates to be characterized by X-ray structure determinations. In both the Si-O bonds are long, ca. 1.75 ?, consistent with the ready nucleophilic displacement of [OSC₂CF₃]^- from silicon centers. The crystal structures of the fluoride CH₂Me₂Si(Me₃Si)₂CSn-(CH₂P h)FC(SiMe₃)₂SiMe₂CH₂ and the hydroxide 2f have also been determined.

Full text of DOI:10.1021/om011079z

Organometallics 2002, 21, 2183-2188
2183
Rea ction s of a High ly Cr ow d ed Tr ior ga n otin Iod id e w ith
Silver Sa lts. Migr a tion of a Meth yl Gr ou p fr om Silicon to
Tin w ith in a Ca tion
Ashrafolmolouk Asadi, Anthony G. Avent, Colin Eaborn,* Michael S. Hill,
Peter B. Hitchcock, Margaret M. Meehan, and J . David Smith*
School of Chemistry, Physics and Environmental Science, University of Sussex,
Brighton, U.K. BN1 9QJ
Received December 19, 2001
Reaction of the highly crowded organotin iodide CH2Me2Si(Me3Si)2CSnMeIC(SiMe3)2-
SiMe2CH2 with AgBF4 gives the fluoride CH2Me2Si(Me3Si)2CSnMeFC(SiMe3)2SiMe2CH2.
Reaction with AgOSO2C6H4Me followed by workup in moist air gives the hydroxide CH2-
Me2Si(Me3Si)2CSnMe(OH)C(SiMe3)2SiMe2CH2, 2f. With AgOSO2CF3 the product is the
organosilicon trifluoromethanesulfonate CH2Me2Si(Me3Si)2CSnMe2C(SiMe3)(SiMe2OSO2CF3)-
SiMe2CH2, 5, formed apparently by an unprecedented 1,3-migration of a methyl group from
silicon to tin within a cation. Compound 5 and Ph3SiOSO2CF3 are the first silicon
trifluoromethanesulfonates to be characterized by X-ray structure determinations. In both
the Si-O bonds are long, ca. 1.75 Å, consistent with the ready nucleophilic displacement of
[OSO2CF3]- from silicon centers. The crystal structures of the fluoride CH2Me2Si(Me3Si)2CSn-
(CH2Ph)FC(SiMe3)2SiMe2CH2 and the hydroxide 2f have also been determined.
In tr od u ction
(SnMe3)(SiMe2I) was treated with silver salts AgX
(X ) OCOCH3, OCOCF3, or OSO2CF3) in CH2Cl2, the
products being wholly the rearranged (Me3Si)3CSnMe2X.4
The rearrangement is consistent with formation of the
bridged cation II by anchimeric assistance to the leaving
of the iodide ion. Subsequent attack of X- occurs at the
larger, and thus less hindered, metal center, i.e., at tin.
In the course of our studies on the triorganotin iodide
2a, containing the bidentate “trisiamyl” ligand C(SiMe3)2-
SiMe2CH2CH2Me2Si(Me3Si)2C, we have observed an
example of migration of a methyl group in the opposite
direction, from silicon to tin. Compound 2a is obtained
by oxidative addition of MeI to the cyclic stannylene 1.5
Reactions of organosilicon iodides (Me3Si)3CSiR2I with
silver salts AgX are known to give rearranged products
(Me3Si)2C(SiR2Me)(SiMe2X), sometimes virtually exclu-
sively, e.g., when R ) Ph, and sometimes along with
the unrearranged isomer (Me3Si)3CSiR2X, e.g., when R
) Et.1,2 The rearrangement is attributed to the forma-
tion of a methyl-bridged cation I, which can be attacked
by the anion X- either at the R-Si atom to give
unrearranged product or at the γ-Si atom to give the
rearranged product. The extent of rearrangement is
often, but not always, determined by the relative degree
of steric hindrance to attack at the R- and γ-silicon
atoms, but it can also be influenced by the nature of X
and the solvent.3
Analogous migration of a methyl group from tin to
silicon was observed when the silicon iodide (Me3Si)2C-
* E-mail: c.eaborn@susx.ac.uk; j.d.smith@susx.ac.uk.
(1) Eaborn, C.; Happer, D. A. R.; Hopper, S. P.; Safa, K. D. J .
Organomet. Chem. 1980, 188, 179.
(2) Black, J . R.; Eaborn, C.; Garrity, P. M.; Happer, D. A. R. J . Chem.
Soc., Perkin Trans. 2 1997, 1633.
(3) Eaborn, C. J . Chem. Soc., Dalton Trans. 2001, 3397.
10.1021/om011079z CCC: $22.00 © 2002 American Chemical Society
Publication on Web 05/02/2002

2184 Organometallics, Vol. 21, No. 11, 2002
Asadi et al.
F igu r e 2. Molecular structure of 2f.
F igu r e 1. Molecular structure of 3a .
this in a pure state, but its formation is confirmed by
the fact that on workup in moist air we obtained the
crystalline tin hydroxide 2f. This was characterized by
elemental analysis, a sharp ν(OH) absorption at 3667
cm-1, and NMR spectroscopy. Its structure was deter-
mined by an X-ray study. The solid was found to consist
of discrete molecules (Figure 2) with no intermolecular
O‚‚‚O distances less than 4 Å. Only one other compound
R3SnOH containing four-coordinate tin has previously
been structurally characterized, namely, trimesityltin
hydroxide 4,8 which adopts a structure consisting of
discrete molecules, like that of 2f. Other organotin
hydroxides form hydrogen-bonded dimers9,10 or poly-
mers containing five-coordinate tin.11 Bond lengths and
angles in 2f are given in Table 1. The Sn-O bond length
[2.000(3) Å] is the same as that in 4, confirming this as
the “normal” distance from four-coordinate tin to oxy-
gen. The distance is slightly shorter than that [2.102-
(3) Å] in 2d , perhaps a reflection of the weak nucleo-
philicity of trifluoracetate, but the other corresponding
bond lengths and angles are not significantly different
in the two compounds.
Resu lts a n d Discu ssion
Rea ction of th e Iod id e 2a w ith AgBF 4. We con-
sidered that it might be possible to obtain compounds
containing three-coordinate tin cations by replacement
of the iodide in 2a by less nucleophilic anions. We first
treated 2a with AgBF4. There was no reaction in
hexane. In THF the initial product was probably the
fluoride-bridged tetrafluoroborate 2b, but after workup
the only crystalline product was the fluoride 2c. The
compounds (Me3Si)3CSnR′2BF4 (R′ ) Me or Ph) were
previously6 found to lose BF3 readily, especially in the
presence of donor solvents such as methanol. We could
not obtain crystals of 2c suitable for an X-ray structure
determination, but the high solubility in organic sol-
vents and the spectroscopic data [in particular the value,
1
2396 Hz, of J SnF (lit. values 2256-2463 Hz6,7)] are
characteristic of triorganotin fluorides that contain
bulky organic groups and in consequence crystallize in
lattices consisting of discrete molecules with no signifi-
cant secondary Sn‚‚‚F contacts.6,8
The benzyl compound 3a was made similarly in good
yield by treatment of the stannylene 1 with benzyl
bromide and then AgBF4. The bromide intermediate 3b
was not isolated. Spectroscopic data were very similar
to those of 2c, and the structure, determined by an X-ray
study, is shown in Figure 1. The data in Table 1 indicate
that the Sn-F bond length [1.956(2) Å] is the same,
within experimental uncertainty, as those [1.957(4)-
1.965(8) Å] in the previously characterized four-coordi-
nate organotin fluorides.6,8
Rea ction of th e Iod id e 2a w ith AgOCOCF 3 a n d
AgOSO2C6H4Me. When the organotin iodide was treated
with silver trifluoroacetate, it gave, in 76% yield after
recrystallization, the product of direct replacement of
I- by CF3CO2-, i.e., compound 2d , the identity of which
was indicated by NMR spectroscopy and confirmed by
a crystal structure determination.5
The ready formation of the hydroxide 2f from the
tosylate 2e is puzzling, since we have shown that
reactions of the iodide 2a with nucleophiles are in
general slow.12 Indeed, the tin centers in four-coordinate
compounds bearing the trisiamyl ligand are probably
the most crowded ever studied. It is however possible
that there is less hindrance to displacement of the
smaller oxygen of tosylate than of the larger iodine.
Rea ction of th e Iod id e 2a w ith AgOSO2CF 3. In
an attempt to make the tin trifluoromethanesulfonate
(triflate) 2g, we treated the iodide 2a with AgOSO2CF3.
The product obtained in 68% yield after recrystallization
was the silicon triflate 5, as indicated by NMR spec-
troscopy (including a two-dimensional 1H-29Si shift
correlation) and confirmed by a crystal structure deter-
mination (Figure 3 and Table 1).
The reaction of 2a with silver p-toluenesulfonate
(tosylate) gave the tin tosylate 2e. We did not isolate
(4) Dhaher, S. M.; Eaborn, C.; Smith, J . D. J . Chem. Soc., Chem.
Commun. 1987, 1183.
(5) Eaborn, C.; Hill, M. S.; Hitchcock, P. B.; Patel, D.; Smith, J . D.;
Zhang, S. Organometallics 2000, 19, 49.
(6) Al-J uaid, S. S.; Dhaher, S. M.; Eaborn, C.; Hitchcock, P. B.;
Smith, J . D. J . Organomet. Chem. 1987, 325, 117.
(7) Bai, H.; Harris, R. K.; Reuter, H. J . Organomet. Chem. 1991,
408, 167.
(8) Reuter, H.; Puff, H. J . Organomet. Chem. 1989, 379, 223.

Triorganotin Iodide Reactions with Silver Salts
Organometallics, Vol. 21, No. 11, 2002 2185
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles (d eg)
For 2f
Sn-Me
Sn-C1
Sn-C2
Sn-O
C1-Si1
C1-Si2
C1-Si3
2.149(5)
2.221(4)
2.229(4)
2.000(3)
1.907(4)
1.946(4)
1.888(4)
C2-Si4
C2-Si5
C2-Si6
Si-Me
Si-CH2
CH2-CH2
1.915(4)
1.907(4)
1.931(4)
1.889(5)a
1.872(5)a
1.549(7)
C1-Sn-C2
133.38(14)
Me-Sn-O
C1-Sn-O
C2-Sn-O
Si-C-Si
Me-Si-CH2
Si-C-C
106.6(2)
95.77(14)
99.84(14)
104.80(18)-114.07(19)
101.7(2)-108.5(3)
117.7(4), 121.1(4)
Me-Sn-C
108.5(2)a
Me-Si-Me
102.7(3)-107.2(3)
109.9(2)-115.9(2)
111.7(2), 115.4(2)
104.80(18)-114.07(19)
107.78(18), 109.71(19)
C1,2-Si-Me
C1,2-Si-CH2
Sn-C-Si(exo)
Sn-C-Si(endo)
For 3a b
Sn-F
1.956(2)
2.178(5)
2.227(5)
2.216(5)
C1-Si
1.924(5)a
1.875(5)a
1.871(5)a
1.551(7)
Sn-C(21)
Sn-C1
Sn-C2
Si-Me
Si-CH2
CH2-CH2
C1-Sn-C2
133.17(18)
101.9(2)
117.9(2)
102.7(3)-107.5(3)
111.3(2)-115.7(2)
105.7(2)-111.8(2)
109.9(2), 112.2(2)
F-Sn-C(21)
F-Sn-C(ring)
Si-C-Si(exo)
Si-C-Si(endo)
C1,2-Si-CH2
Si-C-C
102.37(17)
C1-Sn-C(21)
C2-Sn-C(21)
Me-Si-Me
98.28(14), 96.20(14)
108.0(2), 109.1(3)
108.4(2)-111.1(2)
111.5(2), 115.8(2)
118.0(3), 119.7(4)
102.7(3)-107.8(2)
C1,2-Si-Me
Sn-C-Si(exo)
Sn-C-Si(endo)
Me-Si-CH2
For 5
Sn-C21
Sn-C22
Sn-C1
Sn-C2
Si-O
2.162(6)
2.149(5)
2.286(5)
2.251(5)
1.760(4)
1.521(4)
1.418(5)
1.424(5)
1.834(7)
C1-Si1
C1-Si2
C1-Si3
C2-Si4
C2-Si5
C2-Si6
Si-Me
1.861(5)
1.958(5)
1.915(6)
1.906(6)
1.917(6)
1.907(5)
1.878(6)a
1.893(6)a
1.536(8)
S-O1
S-O2
S-O3
Si-CH2
CH2-CH2
S-C
Me-Sn-Me
C1-Sn-C2
Me-Sn-C
106.3(2)
127.45(19)
Si-C-Si
106.3(3)-111.9(3)
111.7(2)
110.3(3)
120.9(3)
132.2(2)
O1-S-O2
O1-S-O3
O2-S-O3
Si-O-S
103.5(2)-108.6(2)
106.4(2)-114.4(2)
101.7(3)-107.7(3)
112.6(3)-119.5(3)
115.1(2), 112.0(3)
Sn-C-Si
Me-Si-Me
C1,2-Si-Me
C1,2-Si-CH2
Me-Si-CH2
Si-C-C
102.9(3)-107.3(3)
118.7(4), 121.4(4)
For 7
Si-O1
S-O1
S-O2
1.743(2)
1.531(2)
1.420(2)
S-O3
S-C19
Si-C
1.414(2)
1.819(3)
1.850(2)a
C-Si-C
113.72(11)a
106.14(9)
101.06(9)
107.14(9)
Si-O1-S
O1-S-O2
O1-S-O3
O2-S-O3
120.05(11)
111.55(10)
111.06(10)
120.73(12)
O-Si-C1
O-Si-C7
O-Si-C13
a
Mean value; esd’s are for individual measurements, none of which differs significantly from the mean. b Values for one of the independent
molecules. Bond lengths show no significant differences between the two molecules; there are small differences in bond angles.
Immediately after the addition of AgOSO2CF3 to the
solution of 2a in CD2Cl2 the only peak in the 19F NMR
spectrum, at δ -80.2, can be assigned to the silver salt
itself. After several hours at room temperature another
peak appears at δ -79.3; this then decays and is
replaced by the signal at δ -77.4 due to 5. We tenta-
(9) Sharma, H. K.; Cervantes-Lee, F.; Mahmoud, J . S.; Pannell, K.
H. Organometallics 1999, 18, 399.
(10) Schager, F.; Goddard, R.; Seevogel, K.; Po¨rschke, K.-R. Orga-
nometallics 1998, 17, 1546.
(11) Glidewell, C.; Liles, D. C. Acta Crystallogr. Sect. B 1978, 34,
129.
(12) Asadi, A.; Eaborn, C.; Hill, M. S.; Hitchcock, P. B.; Meehan, M.
M.; Smith, J . D. Organometallics 2002, 21, OM 020106Y.
F igu r e 3. Molecular structure of 5.

2186 Organometallics, Vol. 21, No. 11, 2002
Asadi et al.
tively assume that the initial product is the tin triflate
2g, which then ionizes, with anchimeric assistance by
a methyl group on silicon, to give the bridged cation III
and triflate anion. Comparison of II and III shows that
the tin atom in III is much the more crowded. Hence,
whereas any ionization of triflate from the previously
characterized (Me3Si)3CSnMe2OSO2CF3 to give II leads
to reattachment at tin so that no rearrangement is
observed, similar ionization of triflate from 2g leads,
sometimes at least, to irreversible attachment to the
silicon atom of the bridge, reattachment at the larger
tin atom being hindered by the crowding there. This
crowding is evident from the fact that the tin atom bears
two tris(triorganosilyl)methyl substituents, whereas the
silicon atom bears only one bulky bis(triorganosilyl)-
(trisorganostannyl)methyl group. No rearrangement has
so far been observed for the trifluoroacetate 2d , sug-
gesting that, if there is any ionization of this compound,
the equilibrium concentration of the ionic species is
much lower than that of the triflate. The formation of
5 may also be favored by the formation of the strong
Si-O bond, but within the limits of accuracy of the
available data,13,14 the sum of the energies for a Si-O
and a Sn-Me bond (ca. 500 + 270 kJ mol-1) is similar
to that for a Si-Me and a Sn-O bond (ca. 370 + 400
kJ mol-1).
F igu r e 4. Molecular structure of 7.
ranged compound 2d , but there is no significant differ-
ence in the average exocyclic Sn-Me bond lengths
[2.155(6) Å in 5 and 2.160(4) Å in 2d ].
In an attempt to obtain the unrearranged triflate 2g,
we treated the hydroxide 2f with 1 equiv of CF3SO2Cl
in CD2Cl2 in an NMR tube. No reaction was detected
during several days, presumably because the hydroxide
is well protected by the bulky ligand. When an excess
of CF3SO2Cl was added, the 2f was completely con-
sumed to produce a complex mixture of products, none
of which could be identified as 5. Further work is
therefore necessary before we can be sure that the
intermediate 2g is indeed involved in the formation of
5.
Silicon Tr ifla tes. The length of the Si-O bond in 5,
1.760(4) Å, is significantly greater than those, 1.64-
1.66 Å,20 normally observed for Si-O bonds. As no
structural data for silicon triflates were available in the
literature for comparison, we determined the crystal
structure of Ph3SiOSO2CF3, 7. This compound has been
made in sulfolane, and cryoscopic measurements have
shown that it is not dissociated.21 The molecular struc-
ture is shown in Figure 4, and bond lengths and angles
are given in Table 1. The Si-O bond is slightly shorter
[1.743(2) Å] than that in 5, but similar to those in the
cyanate (Me3Si)2(PhMe2Si)CSiMe2OCN [1.756(10) Å]22
and the perchlorate Ph3SiOClO3 [mean 1.744(4) Å].23
Distances of 1.74-1.76 Å correspond to Pauling covalent
bond orders of 0.68-0.62, implying that there is a
significant ionic component in the bonding.24 Silylium
cation character in compounds R3SiY is also reflected
in the mean value of the C-Si-C angles. For 5 the
average C-Si1-C angle (115.4°) is slightly higher than
The bond lengths and angles within the SnCSiCCSiC
ring in 5 are similar to those in 2f, 3a , and related
crowded SnIV compounds,5,12 but those involving the tin
and silicon centers require some comment. The only
bonds to tin are from carbon so that, in the absence of
marked steric or electronic effects, the C-Sn-C angles
are expected to be about 109°. The exocyclic Me-Sn-
Me angle [106.3(2)°] is slightly less than the tetrahedral
value, but significantly wider than the exocyclic O-Sn-O
angles (83-84°) in compounds containing the same ring
system.12 The wider exocyclic angle in 5 reflects the
larger size of methyl than of oxygen as well as the
greater s character in Sn-C than in Sn-O bonds. The
endocyclic C-Sn-C angle [127.45(19)°] is markedly
wider than 109°, indicating that crowding within the
seven-membered bidentate ligand holds the carbon
atoms apart. A similar effect is found in the stannylene
1, where there is a lone pair in place of the two exocyclic
methyl groups of 5; the C-Sn-C angle (118°)5 is wider
than those (96-104°) in acyclic stannylenes15-18 and the
less crowded cyclic stannylene 6 [C-Sn-C 86.7(2)°].19
The mean Sn-C(ring) bond length in 5 [2.269(5) Å] is
slightly longer than that [2.227(5) Å] in the unrear-
(15) Goldberg, D. E.; Hitchcock, P. B.; Lappert, M. F.; Thomas, K.
M.; Thorne, A. J .; Fjeldberg, T.; Haaland, A.; Schilling, B. E. R. J .
Chem. Soc., Dalton Trans. 1986, 2387.
(16) Fjeldberg, T.; Haaland, A.; Schilling, B. E. R.; Lappert, M. F.;
Thorne, A. J . J . Chem. Soc., Dalton Trans. 1986, 1551.
(17) Gru¨tzmacher, H.; Pritzkow, H.; Edelmann, F. T. Organometal-
lics 1991, 10, 23.
(18) Weidenbruch, M.; Schlaefke, J .; Scha¨fer, A.; Peters, K.; von
Schnering, H. G.; Marsmann, H. Angew. Chem., Int. Ed. Engl. 1994,
33, 1846.
(19) Kira, M.; Yauchibara, R.; Hirano, R.; Kabuto, C.; Sakurai, H.
J . Am. Chem. Soc. 1991, 113, 7785.
(20) Lukevics, E.; Pudova, O.; Sturkovich, R. Molecular Structure
of Organosilicon Compounds; Horwood: Chichester (UK), 1989; p 180.
(21) Lambert, J . B.; Schulz, W. J .; McConnell, J . A.; Schilf, W. J .
Am. Chem. Soc. 1988, 110, 2201.
(22) Al-J uaid, S. S.; Al-Nasr, A. A. K.; Ayoko, G. A.; Eaborn, C.;
Hitchcock, P. B. J . Organomet. Chem. 1995, 488, 155.
(23) Prakash, G. K. S.; Keyaniyan, S.; Aniszfeld, R.; Heiliger, L.;
Olah, G. A.; Stevens, R. C.; Choi, H.-K.; Bau, R. J . Am. Chem. Soc.
1987, 109, 5123.
(13) Harrison, P. G. In Chemistry of Tin, 2nd ed.; Smith, P. J ., Ed.;
Chapman and Hall: London, 1998; p 14.
(14) Brook, M. A. Silicon in Organic, Organometallic and Polymer
Chemistry; Wiley: New York, 2000; p 29.
(24) Lickiss, P. D. In The Chemistry of Organosilicon Compounds;
Rappoport, Z., Apeloig, Y., Eds.; Wiley: Chichester, 1998; Vol. 2, Part
1, Chapter 11.

Triorganotin Iodide Reactions with Silver Salts
Organometallics, Vol. 21, No. 11, 2002 2187
vacuum to leave a slightly sticky solid, which was extracted
with hexane (20 mL). The extract was filtered, the volume of
the filtrate was reduced to 5 mL, and colorless needles of 2c,
mp 241-244 °C (0.26 g, 74%), separated at -30 °C. Anal. Calcd
the C-Si-C angles in 7 (113.7°) and Ph3SiOClO3
(113.6°) and at the lower end of the range (115-117°)
found in a series of closo-CB11H6Br6 derivatives, which
have bond orders of about 0.4.25 The wide C-Si-C
angles in 5 are associated with short Si(1)-C bond
distances; the Si(1)-C(1) distance [1.861(5) Å] is sig-
nificantly smaller than the other Si-C(1,2) distances
[mean 1.920(6) Å], and the Si(1)-Me distances
[1.866(6) and 1.854(5) Å] are only just within three
standard deviations (determined from experimental
values for individual measurements) of the mean
Si-Me distance for the molecule as a whole. These
distances reflect the delocalization of the partial positive
charge on the atom Si(1).
1
for C21H55FSi6Sn: C, 41.1; H, 9.0. Found: C, 41.3; H, 9.2. H
NMR (C6D6): δ 0.26 and 0.43 (18H, s, SiMe3), 0.28 and 0.32
3
2
(6H, s, SiMe2), 0.85 (3H, d, J HF ) 3.0 Hz, J SnH ) 48.5 Hz,
SnMe), 0.91-1.15 (4H, m, CH2). 13C NMR: δ 4.7 (s, SiMe2),
5.1 (d, J FC ) 5.0 Hz, SiMe2), 6.69 and 6.70 (SiMe3), 12.0 (d,
4
2J CF ) 9.4 Hz, SnMe), 14.2 (CH2), 21.8 (d, 2J CF ) 11.7 Hz, CSi3-
Sn). 19F NMR: δ -161.1 (1J SnF ) 2396 Hz). 29Si NMR: δ -3.0
(d, 3J SiF ) 6.1 Hz, SiMe3), 0.4 (d, 3J SiF ) 4.5 Hz, SiMe3), 2.6 (d,
3J SiF ) 1.2 Hz, SiMe2). 119Sn NMR: δ 108.9 (1J SnF ) 2404, 2J SnH
) 46 Hz). MS: m/z 599 (30, M - Me), 379 (90, M -
(Me3Si)2CSiMe2F), 351 (60, M - (Me3Si)2CSiMe2F - C2H4), 263
(30, SnMeC(SiMe2)2), 201 (100, Me3SiC(SiMe2)2), 73 (97,
SiMe3).
This is also shown by the marked shifts to high
frequency of the resonance corresponding to 29Si atoms
adjacent to triflate; 29Si shifts are at δ -2.6 to +2.7 in
2d , -0.9 to 2.4 and 39.4 in 5, 80-100 in carborane
derivatives, and 225 for the unsolvated trimesitylsilyl
cation.26 The shift in 7 (δ 3.6) is similar to that (3.0) in
Ph3SiOClO3.23,25 A similar comparison may be made of
tin chemical shifts: namely, δ 16.9 in 5, 232 in the
C H 2 M e 2 S i (M e 3 S i )2 C S n F (C H 2 C 6 H 5 )C (S i M e 3 )2 S i -
Me2CH2, 3a . Benzyl bromide (0.089 g, 0.52 mmol) was added
to a solution of 1 (0.30 g, 0.52 mmol) in hexane (30 mL). After
5 min the solution became colorless and the solvent was
removed under reduced pressure to leave a sticky solid. This
was immediately dissolved in CH2Cl2 (30 mL), and AgBF4 (0.3
g, 1.5 mmol) was added to the mixture, which was stirred for
18 h at room temperature, then filtered. The solvent was
removed from the filtrate under vacuum to give a white
residue. This was dissolved in the minimum amount of hexane
(about 2 mL), and the solution was left at room temperature
to give 3a as colorless plates (0.21 g, 75%), mp 180-183 °C.
Anal. Calcd for C27H59FSi6Sn: C, 47.0; H, 8.6. Found: C, 46.8;
H, 8.8. 1H NMR: δ 0.28 and 0.40 (18H, s, SiMe3), 0.35 and
0.39 (6H, s, SiMe2), 0.90-0.98 (ddd) and 1.12-1.20 (2H, ddd,
27
triflate (Me3Si)3CSnMe2OSO2CF3 (cf. 148.5 in 2d ,
461.2 in crystalline [Bu3Sn]+[CB11Me12]-,28 and 806 in
the trimesitylstannyl cation).26
The compounds (Me3Si)3CSiMe2Y with Y ) OClO3,
OSO2CF3, or OCN are comparable in reactivity toward
MeOH and much more reactive than, for example,
(Me3Si)3CSiMe2I. It is reasonable to associate the high
reactivity with the lengths of the Si-O bonds and with
the relatively weak coordination (and high leaving
ability) of the three oxygen-centered ligands. In keeping
with this, the Si-O bond in the p-toluenesulfonate
(tosylate) (Me3Si)3CSiPhHOSO2C6H4Me-p, 8,2a which is
much less reactive than 7 toward MeOH, is somewhat
shorter [1.716(8) Å] than that in 7. The long Si-O bond
in 7 is associated with short S-O and SdO bonds
[1.531(2) and mean 1.417(2) Å, respectively]. The
corresponding bond distances in 5 are 1.521(4) and
1.421(5) Å, respectively, and in 8 1.587(7) Å [1.549(7) Å
in a second molecule] and 1.430(8) Å.29 It is noteworthy
that in both 5 and 7 there is no significant difference
between the O-S-O(2) and O-S-O(3) angles, in
contrast to the data for 8 and some organic tosylates.
3
2
CH2), 3.07 (2H, d, J HF ) 3.9 Hz, J SnH ) 56 Hz, CH2Ph), 6.99
(1H, tt, p-H), 7.13 (2H, dd, m-H), 7.44 (2H, d, o-H). 13C NMR:
δ 5.4 and 6.3 (4J CF ) 9.6 Hz, SiMe2), 6.9 (4J CF ) 4.6 Hz), 7.1
(SiMe3), 15.3 (CH2Si), 25.9 (2J CF ) 6.4 Hz, 1J SnC ) 51 Hz, CSi3-
Sn), 38.5 (2J CF ) 6.1 Hz, d, CH2Ph), 125.8 (p-C), 128.6 (m-C),
130.7 (o-C), 138.8 (i-C). 19F NMR: δ -165.7 (1J SnF ) 2559 Hz).
29Si NMR: δ -2.5 (3J SiF ) 5.2 Hz), 0.6 (d, 3J SiF ) 4.8 Hz, SiMe3),
1
1.8 (s, SiMe2). 119Sn NMR: δ 60.7 (d, J SnF ) 2561 Hz). MS:
m/z 675 (3, M - Me), 599 (44, M - Bz), 379 (25), 263 (20), 201
(90), 91 (50, Bz), 73 (100, SiMe3).
CH2Me2Si(Me3Si)2CSn (OH)MeC(SiMe3)2SiMe2CH2, 2e.
A solution of 2a (0.39 g, 0.54 mmol) in CH2Cl2 (25 mL) was
added to a stirred slurry of AgO3SC6H4Me (0.77 g, 2.76 mmol)
in CH2Cl2 (30 mL). The suspension was stirred in the absence
of light for 14 h, then filtered, and solvent was removed from
the filtrate. Attempts to crystallize the residue at low tem-
perature were unsuccessful, so a solution in hexane was
allowed to evaporate slowly in the open air to produce 2e as
colorless crystals suitable for an X-ray diffraction study (ca.
0.15 g, 45%). Anal. Calcd for C21H56OSi6Sn: C, 41.3; H, 9.17.
Found: C, 41.3; H, 9.25. 1H NMR: δ 0.10 and 0.30 (6H, s,
Exp er im en ta l Section
Air and moisture were excluded as far as possible by the
use of flame-dried glassware and Ar as blanket gas. The
stannylene 1 and the iodide 2a were made as described
previously.5
2
SiMe2), 0.29, 0.33 (18H, s, SiMe3), 0.74 (3H, s, J SnH ) 48 Hz,
SnMe), 0.90-1.53 (4H, m, CH2). 13C NMR: δ -0.8 (SiMe2),
2.7, 3.0 (SiMe3), 9.7 (CH2), 14.8 (CSi3). 29Si NMR: δ -2.6 and
-0.5 (SiMe3), 2.5 (SiMe2). 119Sn NMR: δ 68.4. IR (Nujol
mull): 3667 cm-1 (ν(OH)). MS: m/z 597 (50, M - Me), 453
(10, M - Me - Me3SiCHdSiMe2), 425 (30, M - Me - Me3-
SiCHSiMe2CH2CH2), 381 (30, M - Me - (Me3Si)2CdSiMe2),
309 (10), 275 (40), 217 (90, (Me3Si)2CHSiMe2), 147 (20), 129
(60), 73 (100).
CH2Me2Si(Me3Si)2CSn FMeC(SiMe3)2SiMe2CH2, 2c. Pow-
dered AgBF4 (0.25 g, 1.28 mmol) was added in a single portion
to a solution of 2a (0.41 g, 0.57 mmol) in hexane (25 mL), and
the suspension was stirred for 15 h at room temperature. The
1H NMR spectrum of a small sample showed that no reaction
had occurred. THF (5 mL) was added, and the suspension was
stirred for 4 h. The volatile material was removed under
(25) Lambert, J . B.; Kania, L.; Zhang, S. Chem. Rev. 1995, 95, 1191.
(26) Lambert, J . B.; Zhao, Y.; Wu, H.; Tse, W. C.; Kuhlmann, B. J .
Am. Chem. Soc. 1999, 121, 5001.
(27) Dhaher, S. M.; Eaborn, C.; Smith, J . D. J . Organomet. Chem.
1988, 355, 33.
(28) Zharov, I.; King, B. T.; Havlas, Z.; Pardi, A.; Michl, J . J . Am.
Chem. Soc. 2000, 122, 10253.
(29) Al-J uaid, S. S.; Al-Nasr, A. A. K.; Eaborn, C.; Hitchcock, P. B.
J . Organomet. Chem. 1993, 455, 57.
CH 2Me2Si(Me3Si)2CSn Me2C(SiMe2OSO2CF 3)(SiMe3)-
SiMe2CH2, 5. Silver triflate (0.50 g, 1.95 mmol) was added to
a solution of the iodide 2a (0.30 g, 0.41 mmol) in CH2Cl2 (20
mL). The mixture was stirred for 5 h at room temperature,
then filtered, and the solvent was removed under vacuum. The
residue was dissolved in hexane and the solution kept at -30

2188 Organometallics, Vol. 21, No. 11, 2002
Ta ble 2. Su m m a r y of Cr ysta llogr a p h ic Da ta for 2f, 3a , 5, a n d 7
Asadi et al.
2f
3a
5
7
chemical formula
fw
C
21H56OSi6Sn
C27H59FSi6Sn
689.97
C22H55F3O3SSi6Sn
743.95
C19H15F3O3SSi
408.46
611.89
T/K
173(2)
173(2)
173(2)
173(2)
cryst syst
space group
a/Å
b/Å
monoclinic
C2/c
36.930(2)
9.1769(3)
22.9057(13)
triclinic
monoclinic
P21/n
13.0809(10)
16.3780(7)
17.1546(13)
monoclinic
P21/c
10.3023(4)
9.0227(6)
20.3428(12)
P1h No. 2
9.3336(3)
19.3177(9)
20.2094(9)
91.816(2)
94.810(3)
94.102(2)
3619.1(3)
4
c/Å
R/deg
â/deg
124.694(2)
107.052(3)
91.934(4)
γ/deg
U/Å3
6382.7(6)
8
1.27
0.046, 0.102
0.060, 0.108
15114/5584/0.076
4666
3513.6(4)
4
1.03
0.053, 0.121
0.081, 0.133
20193/6151/0.090
4508
1889.9(2)
4
0.28
0.042, 0.093
0.062, 0.102
9355/3313/0.055
2508
Z
µ/mm-1
0.93
R1 wR2, I > 2σ(I)
0.050, 0.096
0.085, 0.109
25413/12716/0.066
9023
all data
no. of measured/indep rflns /R(int)
no. of rflns with I > 2σ(I)
°C to give colorless needles of 5 (0.21 g, 68%), mp 181-183
Cr ysta llogr a p h y. Data were collected on a Kappa CCD
diffractometer by use of Mo KR radiation, and structure
refinement was by the SHELXL-97 program.30 Further details
are given in Table 2. An absorption correction was applied for
5 but not for 7. The atoms Si4B, Si5B, and Si6B of one of the
independent molecules of 3a are disordered 0.87:0.13 over two
sets of sites sharing a common connected C atom site. This
corresponds to alternative conformations of the chelating ring.
Molecules of 2f are disordered 0.89:0.11 over an approximate
mirror plane through C1, C2, and O. There are common C1,
C2, O, and C(Si) sites and resolved low-occupancy sites for Sn,
Si, C11, C12, and C21.
°C. Anal. Calcd for C22H55F3O3Si6SSn: C, 35.5; H, 7.45.
1
Found: C, 35.6; H, 7.56. H NMR (CD2Cl2, for numbering see
Figure 1): δ 0.29 and 0.30 (3H, s, Si4Me2), 0.31, (18H, Si5,6
-
Me3), 0.34 and 0.35 (3H, s, Si3Me2), 0.35 (9H, s, Si2Me3), 0.66
2
2
(3H, s, J 119SnC ) 46.8 Hz, SnMe), 0.7 (3H, s, J 119SnH ) 48.2
Hz, SnMe), 0.77, 0.82 (3H, s, Si1Me2), 0.85-1.00 (4H, m, CH2).
13C NMR (CD2Cl2): δ 4.88, 4.96, 6.10, and 7.30 (Si3,4Me2), 7.40
(Si1Me2), 7.82 and 7.85 (Si5,6Me3), 8.19, 8.47, (SnMe), 11.9, 12.6
(CSi3Sn), 13.9, 14.1 (CH2), 118.6 (q, 1J CF ) 317.8 Hz, CF3). 19
F
NMR (CD2Cl2): δ -79.3. 29Si NMR (CD2Cl2): δ -0.89 and
-0.75 (Si5,6Me3), -0.2 (Si2Me3), 1.7 (Si4Me2), 2.4 (Si3Me3), 39.4
(Si1Me2). 119Sn NMR (CD2Cl2): δ 16.9 (qq). MS: m/z 744 (1%,
M), 729 (6, M - Me), 513 (10, M - C(SiMe3)3), 379 (M -
C(SiMe3)2(SiMe2OTf)), 335 (40, (Me2Si)2CSiMe2OTf), 201(100,
Me3SiC(SiMe2)2), 73 (80) (Tf ) SO2CF3).
Ack n ow led gm en t. We thank the EPSRC for sup-
port (Grant GR/L83585) and the Government of Iran
for award of a scholarship to A.A.
P h 3SiOSO2CF 3, 7. An excess of AgOSO2CF3 (1.57 g, 6.10
mmol) was added to a solution of Ph3SiCl (0.90 g, 3.05 mmol)
in CH2Cl2 (40 mL) with exclusion of light. The solution was
stirred for 2 days, then the solvent was removed under
vacuum, and the residue was extracted with hexane (20 mL).
The extract was filtered, and the filtrate reduced to 10 mL
and kept at -30 °C to give colorless crystals of 7 (0.92 g, 74%).
Anal. Calcd for C19H15F3O3SSi: C, 55.9; H, 3.7. Found: C, 55.8;
H, 3.6. 1H NMR (CDCl3): δ 7.54 (2H, dd, m-H), 7.61 (1H, d,
Su p p or tin g In for m a tion Ava ila ble: Tables showing
details of crystal structure determinations, atom coordinates,
equivalent isotropic displacement factors, bond lengths, bond
angles, and hydrogen coordinates for compounds 2f, 3a , 5, and
7. This material is available free of charge via the Internet at
http://pubs.acs.org.
1
p-H), 7.71 (2H, d, o-H). 13C NMR (CD2Cl2): δ 118.75 (q, J CF
OM011079Z
) 317.9 Hz CF3), 128.8 (m-C), 132.4 (p-C), 135.9 (o-C). 19F
NMR: δ -79.2. 29Si NMR: δ 3.6. MS: m/z 408 (10, M), 259
(5, SiPh3), 201 (30, SiPh2F) 78 (100).
(30) Sheldrick, G. M. SHELXL 97; University of Go¨ttingen, 1997.