Preparation and structural characterization of trimethyltin(iv) tropolonate. Investigation of a rare methyl-migrational dismutation in the solution, solid and liquid states

Article abstract of DOI:10.1039/b613692c

The synthesis and structural characterisation, by low temperature X-ray diffraction and solid-state NMR, of the highly reactive monomeric Me ₃Sn(trop) (1) complex has been studied; 1 rearranges into Me ₂Sn(trop)₂ (2) and Me₄Sn by methyl-transfer dismutation. Based on the NMR kinetic data it appears that complex 1 demethylates faster in the solid and liquid than in dilute CDCl₃ solution, but with a slower rate than in dilute CD₃OD solution. The Royal Society of Chemistry 2007.

Full text of DOI:10.1039/b613692c

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Preparation and structural characterization of trimethyltin(IV) tropolonate.
Investigation of a rare methyl-migrational dismutation in the solution, solid
and liquid states†
Andrea Dea´k,* Pe´ter Kira´ly and Ga´bor Ta´rka´nyi
Received 20th September 2006, Accepted 19th October 2006
First published as an Advance Article on the web 30th October 2006
DOI: 10.1039/b613692c
The synthesis and structural characterisation, by low temperature X-ray diffraction and solid-state
NMR, of the highly reactive monomeric Me3Sn(trop) (1) complex has been studied; 1 rearranges into
Me2Sn(trop)2 (2) and Me4Sn by methyl-transfer dismutation. Based on the NMR kinetic data it
appears that complex 1 demethylates faster in the solid and liquid than in dilute CDCl3 solution, but
with a slower rate than in dilute CD3OD solution.
much studied nature of organotin(IV) tropolonates and the absence
Introduction
of trimethyltin(IV) derivative suggests that this might be due
Toxic triorganotin complexes enter into the ambient environment
to its high dismutational reactivity which prevents its isolation.
in the form of insecticides, fungicides and antifouling paints.1 The
degradation products (via alkyl group removal from triorganotin
complexes) have been detected in the environment and the
degradation has been attributed to the action of UV light, chemical
cleavage and biological degradation by bacteria.2 In mammalian
organs, the toxic triorganotin complexes are gradually dealkylated
to inorganic Sn(IV), and it was shown that a linear peptide derived
Moreover, we have tentatively assumed that this triorganotin(IV)
complex also participates into methyl-transfer dismutation not
only in coordinating solvents but in the solid- and liquid-states.
Herein, we report the successful synthesis of Me3Sn(trop) (1), as
well as its X-ray structural determination and NMR analysis both
in the solution- and solid-states. In addition, the degradation of 1
into Me2Sn(trop)2 (2) and Me4Sn has also been investigated in the
from the membrane protein stannine is capable of dealkylating
solution-, solid- and liquid-states.
trimethyltin complexes.3 This sequential dealkylation of the tin
atom, generally results in a reduction in the toxicity. Recently it
Results and discussion
was reported that the Bu3SnCl undergoes redistribution to give
Bu2SnCl2 and Bu4Sn under the gas phase conditions that are used
in the CVD treatment of glass, but the tetrabutyltin does not
survive the conditions of the thermolysis and decomposes into
metallic tin, butene and butane.4 In contrast to thermally induced
solid-state methyl migrations in organic molecules which have
been the subject of extensive investigations,5 the solid-state methyl
transfer phenomenonin organometallic complexes has been barely
exploited. Recently, we have reported that single crystals of the
[Me3Sn(cupf)]4 (cupf = cupferronato anion, C6H5N2O2−) tetramer
demethylate into single crystals of the [Me2Sn(cupf)2]2 dimer and
volatile Me4Sn.6 The demethylation occurred upon heating and
it was accompanied by a significant change in the molecular and
crystal structure.6 We have shown that the dismutation proceeded
considerably faster in the melt than in the solid state,6 moreover
solvent induced conformational change was held responsible for its
demethylation in coordinating solvents, such as DMSO, pyridine
and methanol.7 Therefore, this methyl-migrational dismutation
process is a potential source of trimethyltin(IV) complex insta-
bility, which prevents the preparation of devised structures via
crystallization.7 Although, a series of organotin(IV) tropolonates
has been reported8 the trimethyltin(IV) tropolonato, Me3Sn(trop),
complex remained uncharacterised. This discrepancy between the
Synthesis and structural characterisation of Me3Sn(trop) (1)
Complex 1 was prepared by metathetical reaction between
trimethyltin(IV) chloride and ammonium tropolonate. As sus-
pected, compound 1 shows dismutational activity in methanol, but
appears to be stable in n-hexane and chloroform solution. Single
crystals of 1 were successfully obtained from n-hexane, but they
diffracted poorly at room temperature. The low-temperature X-ray
diffraction measurement reveals that in complex 1 the tin(IV) center
is five-coordinated (Fig. 1) in a geometry intermediate between
Institute of Structural Chemistry, Chemical Research Center of the
Hungarian Academy of Sciences, P. O. Box 17, 1525, Budapest, Hungary.
E-mail: deak@chemres.hu; Fax: +36-1-438-4141/201; Tel: +36-1-438-
4141/327
Fig. 1 A view of the molecular structure of complex 1 showing the atom
numbering scheme. Non-hydrogen atoms are shown as 50% probability
ellipsoids and hydrogen atoms are shown as circles.
† The HTML version of this article has been enhanced with colour images.
234 | Dalton Trans., 2007, 234–239
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˚
Table 2 119Sn chemical shielding data for 1 obtained from 7 kHz MASa
◦
Table 1 Selected interatomic bond distances (A) and bond angles ( ) for
complex 1
Complex 1
diso
d11
d22
d33
g
Sn(1)–C(1)
Sn(1)–C(3)
Sn(1)–O(2A)
2.159(3) Sn(1)–C(2)
2.140(3) Sn(1)–O(1A)
2.324(2)
2.137(3)
2.133(2)
Solid MAS NMR
Solution NMR (CDCl3)
Solution NMR (DMSO)
60.6
70.0
26.4
159.1
94.6
−71.9
0.48
C(1)–Sn(1)–C(2)
C(3)–Sn(1)–C(1)
C(1)–Sn(1)–O(2A) 152.1(1)
O(1A)–Sn(1)–C(2) 107.7(1)
109.8(2)
105.3(1)
C(2)–Sn(1)–C(3)
118.5(2)
a
119Sn chemical shielding tensor principal values are in ppm and are given
O(1A)–Sn(1)–O(2A)
O(1A)–Sn(1)–C(3)
C(2)–Sn(1)–O(2A)
C(3)–Sn(1)–O(2A)
69.8(1)
124.8(1)
88.5(2)
82.4(1)
according to the convention |d33 − diso| ≥ |d11 − diso| ≥ |d22 − diso| with
estimated errors of less than 1 ppm; the asymmetry parameter is defined
as g = (d22 − diso)/(d33 − diso).
O(1A)–Sn(1)–C(1)
84.3(1)
in line with the solid-state molecular geometry. The asymmetry
parameter g = 0.48 of the chemical shielding tensor rules out
axial symmetry in the solid state. The oxygen-attached carbons
of the tropolonato ligand were found to be non-equivalent from
the analysis of the isotropic chemical shifts in the 13C-MAS NMR
spectra as compared to the solution 13C-NMR (see Fig. 3). The
quaternary carbon which appears at 175.3 ppm (CDCl3) splits into
two distinguishable carbon sites diso = 171.6 and 176.6 ppm in the
solid-state spectra. This can be explained on the basis of the crystal
structure where the tropolonato ligand forms two different Sn–O
bond lengths. As a consequence, the two oxygen atoms attached to
quaternary carbon atoms experience different chemical shielding
in the solid-state.
square pyramidal (SP) and trigonal-bipyramidal (TBP); s = 0.46,
where values of 0 and 1 are indicative of perfect SP and TBP
geometries,9 respectively. Therefore, the coordination geometry
is heavily distorted from that of a regular TBP: the axial C(1)–
Sn(1)–O(2A) bond angle is closed from 180◦ to 152.1(1)◦, and
the corresponding equatorial bond angles range from 107.7(1) to
124.8(1)◦ (Table 1). The tropolonato anion is chelated to the metal
center forming a five-membered SnO2C2 ring and forcing a cis-TBP
geometry at tin. In this five-membered ring the O–Sn–O bite angle
◦
˚
is 69.8(1) , and the Sn–O bond distances differ by 0.191(2) A. The
structure of 1 is very similar to the triphenyltin(IV) tropolonate,
Ph3Sn(trop),8g in which the tropolonato anion is also chelated
to the tin(IV), and the metal center is five-coordinate showing
an intermediate SP/TBP geometry (s = 0.56). The structural
similarity between 1 and Ph3Sn(trop) is also reflected by the O–
Sn–O bite angles (69.8(1)◦ and 71.4(1)◦) and differential Sn–O
˚
˚
distances (0.191(2) A and 0.141(3) A).
Fig. 2 shows the 119Sn magic angle spinning (MAS) and the
solution (CDCl3) 119Sn NMR spectra of 1, which remained stable
over the course of these experiments. Table 2 lists the principal
values of the 119Sn chemical shielding tensor. The solution state
119Sn chemical shift is 70.0 ppm (CDCl3) and the isotropic chemical
shift of the MAS 119Sn experiment (diso) is 60.6 ppm. These
values are in general agreement with the literature data found
for trialkyltin(IV) compounds with bidentate ligands,7,10 and tin
coordination number of 4 or 5. The Me–Sn–Me angle calculated
Fig. 3 Above the solution 13C NMR of 1 recorded in CDCl3 at 25 ◦C (A)
are the 13C MAS spectra (150.8 MHz) of 1 at different spinning rates: (B)
mrot = 5 kHz and (C) mrot = 7 kHz. The identified isotropic chemical shifts
(diso) are marked with stars.
◦
1
from the J(119Sn–13C) coupling constant is 112 ,11 which is also
Methyl-migrational reactivity of complex 1 in the solution-, solid-
and liquid-states
To gain insight into the methyl migrational dismutation the
rearrangement of Me3Sn(trop) (1) into the Me2Sn(trop)2 (2) and
Me4Sn has been investigated in solution, as well as in the solid-
and liquid-states. In the non-polarizing solvent CDCl3 the methyl-
migrational dismutation of 1 is nearly infinitely slow (Fig. 4), while,
when dissolved in coordinating solvents compound 1 underwent
the dismutation process. Precise kinetic data have been collected
1
in methanol-d4 using H-NMR. The solvent has ’captured” the
byproduct Me4Sn and the 2A → B + C stoichiometry of the
reaction has been confirmed, suggesting second-order kinetics. To
verify this we constructed the 1/[A] vs. t curve in Fig. 4, which as
expected for second-order kinetics, provided a linear fit and the k
rate constant of 1.43× 10−5 l mol−1 s−1 was determined from the
slope. This latter was compared with the Me3Sn(cupf) dismutation
kꢀ rate constant6 using the same initial [A]0 = 0.11 mol l−1
concentration. We found that the two rates are of the same order
of magnitude in methanol-d4, however the tropolonato ligand
Fig. 2 Above the solution 119Sn NMR of 1 recorded in CDCl3 at 25 ◦C (A)
are the 119Sn MAS spectra (223.6 MHz) of 1 at different spinning rates: (B)
mrot = 5 kHz and (C) mrot = 7 kHz. The 7 kHz 119Sn MAS spectral simulation
is shown on top (D). The isotropic chemical shift (diso) is marked with an
arrow.
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defined,12 we set up the plot of the concentration change of
complex 1 versus time (Fig. 6) as the molar ratios of the methyl-
moieties were monitored by solution 1H-NMR spectroscopy.
Comparison of the slopes in Fig. 6, suggests that the solid
rearranges at a similar rate (k40 = 5.58 × 10−6 l mol−1 s−1)
◦
C
as the liquid (k60 = 6.04 × 10−6 l mol−1 s−1). Based on these
◦
C
data it appears that complex 1 rearranges faster in the solid and
liquid than in CDCl3 solution (see Fig. 4). Nevertheless, the rate
constants measured in the solid- and liquid-states are slower than
in dilute CD3OD solution.
Fig. 4 The 1/[A] versus t representation of the second-order dismutation
kinetics for complex 1 (᭺ line) and Me3Sn(cupf)6 (ꢀ line) in CD3OD, and
for complex 1 (D line) in CDCl3 (25 ◦C, [A]0 = 0.11 mol l−1). The estimated
rate constants (k and kꢀ) are in l mol−1 s−1. Data are from the integral
change of the corresponding Me3Sn(IV) species determined by 1H-NMR.
transforms Me3Sn(IV) into the Me2Sn(IV) and Me4Sn(IV) species
three times slower than the cupferronato ligand. When complex
1 was dissolved in a strongly coordinating solvent, DMSO, an
upfield shift was observed (26.4 ppm) for the tin, indicating that
coordination number five is also possible via solvent coordination,
as seen for trimethyltin(IV) cupferronate.6,10 This change in the
chemical shift relative to CDCl3 may be indicative of an underlying
conformational equilibrium, in which a distorted tetrahedron
as well as cis- and trans-TBP geometries are involved. Such
conformational changes are held responsible for inducing the
dismutation reaction via activation and stabilization of the charge
separated species.7
Fig. 6 The 1/[A] versus t plot used for the estimation of the k rate constant
of the second order dismutation process (2A → B + C) for 1 at 40 ◦C (᭺
line) and in the liquid at 60 ◦C (ꢀ line). [A] is the molar concentration of
1, and t is the time in seconds. An approximate density of 2.0 g cm−3 for
the liquid was used for the calculation of the initial concentration [A]0.
After 1 hour of heating of 1 at 150 ◦C the single crystals of
2 crystallized from the melt. The X-ray structure determination
confirmed the formation of 2 (Fig. 7), and thus, the demethylation
of 1. The crystal and structural parameters obtained for this
melt crystallized dismutation product 2 correspond closely to the
results reported previously for Me2Sn(trop)2 prepared by meta-
thetical reaction between sodium tropolonate and dimethyltin(IV)
dichloride.8e In the dismutation product 2, the tin centre is in a
distorted cis-octahedral geometry, where the methyl substituents
at the tin are substantially bent with the bond angle C(1)–Sn(1)–
C(2) of 109.3(3)◦. The axial C(1)–Sn(1)–O(2A) bond angle is
closed from 180◦ to 160.7(2)◦, and the corresponding equatorial
bond angles range from 72.6(2) to 107.5(3)◦. The tropolonato
anions are chelated to the tin centre forming two five-membered
SnO2C2 rings, with O–Sn–O bite angles of 73.3(1) and 72.6(2)◦,
respectively. Each tropolonato ligand forms two slightly different
After compound 1 was left for a month in open-end vials
exposed to direct sunlight 119Sn MAS and solution 1H-NMR
(CDCl3) experiments were carried out. The dismutation product
2 was readily identified by both methods (see Fig. 5).
˚
Sn–O bond lengths which differ by 0.055(4) and 0.038(4) A,
respectively.
Topochemical rationalisation of the dismutation reactivity in the
crystalline state
Fig. 5 119Sn MAS spectra (223.6 MHz) of complex 1 containing the
dismutation product 2 at mrot = 12.5 kHz after 1 was exposed to direct
sunlight for a month. The isotropic chemical shifts are marked with arrows.
The reactions occurring in the solid-state are generally induced
photochemically13 and/or thermally,14 and they proceed either by
topochemical or non-topochemical mechanisms.15 The topochem-
ical mechanism postulate states that the reactions in crystals
occur with minimum atomic and molecular motion,16 whereas
recently it was stated that the topochemical reactions without
molecular migrations are very rare and not all typical for solid-
state reactions.17 Chemical reactions in the solid state provide an
To get an overview of the kinetics of the solid-state and
liquid transformation of 1 into 2 and Me4Sn, samples of the
microcrystalline compound 1 were placed in open-end vials and
heated to 40 ◦C (solid) and 60 ◦C (liquid), respectively. Although
the concept of the rate constant in the crystalline state is ill
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Fig. 7 Thermally induced demethylation of crystals of 1 into crystals of 2 and volatile Me4Sn.
extreme case for evaluating the effect of intermolecular forces on
a reaction and their influence on a reaction mechanism.13g Since
most crystals are pure substances, the bimolecular reactions occur
between identical partners, and they require precise distances
and orientations between reaction partners.12a Unfortunately, the
topochemical “allowed” distances, i.e. suitable intermolecular
distances do not guarantee that a reaction will occur.13a The
knowledge of the crystal structure of a trimethyltin(IV) complex
provides a direct rationalisation of the dismutation reaction, but it
is difficult to predict the packing motifs for bimolecular reactions
in a reliable manner. Moreover, the thermal activation of the
dismutation reaction is likely related to the requirement for a
reorientation of the molecules relative to each other in order to
bring the reacting functions as close as possible in order to react.
This is in agreement with the fact that an arrangement of the
molecules in the crystal, which would be completely ideal for the
dismutation, would be identical with that of the transition state of
the reaction, and such a kind of crystal is not isolable.
Fig. 8 Section of the crystal structure of 1 showing the potentially reactive
pair of neighbouring molecules. Darker lines represent the corresponding
C(3) · · · Sn(1)i and Sn(1) · · · O(1A)i contacts; the lighter line represents the
short C–H · · · O contact [symmetry code: (i) x, 1/2 − y, 1/2 + z].
It must be pointed out that the mechanism of demethylation
of 1 cannot be deduced directly based on its crystal structure,
since the formation of ions during the reaction cannot be ruled
out.14n,o Thus, the solid state transformation of 1 into 2 and volatile
Me4Sn can also be triggered by the formation of Me3Sn+, trop−
and Me2Sn(trop)+, Me− ions. The destruction of the crystal lattice,
whichis aninevitable consequence of the dismutation reaction, will
create voids through which the diffusion of potentially formed ions
may be facilitated. Therefore, the trop− and Me2Sn(trop)+, and the
Me3Sn+ and Me− ions are then free to condense with one another
forming Me2Sn(trop)2 and Me4Sn, respectively. Nevertheless, at
the present time whether free ions exist in the crystal during the
reaction, or whether the removal of tropolonate and methyl groups
occurs in a concerted fashion, remains unanswered at the present
time. However, we must point out that both 1 and 2 crystallized in
space group P21/c, and as a consequence, the molecular packing
of 1 shows some obvious similarities to that of its dismutation
product 2. The molecules 1 are linked into dimers (Fig. 9) by C–
We have observed that the [Me3Sn(cupf)]4 tetramer dismutates
into the [Me2Sn(cupf)2]2 dimer and Me4Sn proceeds with signif-
icant change of the molecular and crystal structure, accordingly
6
¯
¯
the space group P421c becomes P1. In this tetramer the shortest
˚
intramolecular C · · · Sn distance is 4.69 A, whereas in the crystal
lattice, the molecules stack in columns and the shortest inter-
molecular C · · · Sn distance between neighbouring molecules is
6
˚
4.81 A. These values are somewhat higher than the sum of the
˚
van der Waals radii of carbon and tin (3.87 A) or methyl and
˚
tin (4.17 A). In complex 1, the shortest intermolecular C · · · Sn
˚
distance is only 4.38 A, which is shorter than the corresponding
distance in the [Me3Sn(cupf)]4 tetramer. On the basis of the
stacking pattern of 1, it is reasonable to expect that the observed
dismutation can occur through a cyclic bimolecular associate
(Fig. 8), where the C(3) · · · Sn(1)i and Sn(1) · · · O(1A)i contact
˚
distances are 4.38 and 4.73 A, respectively. This cyclic bimolecular
system requires only a small degree of reorientation to transfer
the methyl- and tropolonato-groups between themselves in a
concerted fashion to form 2 and Me4Sn. The C–H · · · O hydrogen
ii
ii
˚
H · · · O contacts [C(3A) · · · O(2A) 3.46(1) A; H(3A) · · · O(2A)
2.63 A, C(3A)–H(3A) · · · O(2A) 149.0◦; symmetry code (ii):
−x, −y, −z]. Accordingly, the molecules 2 are also linked into
dimers (Fig. 9), the single difference being that the latter is set
up by two sets of C–H · · · O hydrogen bonds [C(3A) · · · O(2A)ii
ii
˚
i
i
˚
˚
bond [C(3) · · · O(1A) 3.52(1) A; H(3D) · · · O(1A) 2.69 A, C(3)–
H(3D) · · · O(1A)i 145.0◦; symmetry code (i): x, 1/2 − y, 1/2 + z]
formed between the methyl hydrogen and tropolonato oxygen
atoms may facilitate the transfer of the methyl group via a jump
along the C–H · · · O contacts (Fig. 8).
ii
ii
˚
˚
˚
3.27(1) A; H(3A) · · · O(2A) 2.35 A, C(3A)–H(3A) · · · O(2A)
◦
ii
ii
˚
173.1 and C(4A) · · · O(2B) 3.49(1) A; H(4A) · · · O(2B) 2.66 A,
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Table 3 Crystal data and structure refinement parameters for complexes
1 and 2, respectively
Complex
1
2
Empirical formula
Formula mass
Crystal size/mm
Colour
C10H14O2Sn
284.90
C16H16O4Sn
390.98
0.17 × 0.20 × 0.35 0.23 × 0.41 × 0.41
Yellow
Monoclinic
P21/c
Yellow
Crystal system
Space group
T/◦C
Monoclinic
P21/c
22
3.14 ≤ h ≤ 27.67
10.732(4)
14.192(6)
10.561(4)
98.24(4)
1591.9(2)
4
−180
h Range for data collection/◦ 3.08 ≤ h ≤ 27.45
˚
a/A
10.572(6)
8.576(4)
12.235(7)
99.83(2)
1093.0(1)
4
˚
b/A
Fig. 9 View illustrating the C–H · · · O bonded dimers of 1 and 2.
˚
c/A
b /◦
V/A
C(4A)–H(4A) · · · O(2B)ii 149.5 Symmetry code (ii): −x, −y, −z].
Therefore, it is possible to see why at least in principle the solid-
state transformation between 1 and 2 is apparently facile since it
also allows the conservation of the hydrogen-bonding direction.
3
˚
Z
d
calc/Mg m−3
1.731
2.305
1.631
1.617
l/mm−1
F(000)
560
776
Index ranges
−13 ≤ h ≤ 13
−10 ≤ k ≤ 11
−15 ≤ l ≤ 15
9308
−12 ≤ h ≤ 11
−16 ≤ k ≤ 16
−12 ≤ l ≤ 12
10055
2750/0.031
2242
192
1.25
0.0329
0.1223
Experimental
No. of collected reflns.
No. of indep. reflns./Rint
No. of obsd. reflns. I > 2r(I) 2195
No. of parameters
GOOF
R1 (obsd. data)
wR2 (all data)
Largest diff. peak, hole/e A
Trimethyltin(IV) chloride and tropolone were purchased from
Aldrich as pure compounds and used as received. The preparation
and purification of the complexes were carried out in the open air
or in a dry atmosphere.
2493/0.036
121
1.26
0.0238
0.0712
0.57, −0.73
−3
˚
0.61, −0.60
Preparation of Me3Sn(trop) (1)
To a 10 ml aqueous solution of trimethyltin chloride (0.88 g,
4.41 mmol) and tropolone (0.538 g, 4.41 mmol) a few drops
of aqueous ammonia were added. A pale yellow precipitate
appeared gradually. After stirring for half an hour at room
temperature, the precipitate was filtered off and washed with
a small amount of water. This waxy precipitate was dissolved
in n-hexane and the resulting yellow solution was placed in a
refrigerator. After a few days, yellow blocky crystals were obtained,
mp = 55–56 ◦C. Yields, 0.92 g (3.23 mmol, 73.0%). Anal. Calc. for
C10H14O2Sn: C, 42.15; H, 4.95. Found: C, 42.4; H, 5.1%. 1H-NMR
(599.9 MHz, CDCl3): d 0.41 (s, 2J(117Sn/119Sn–1H) = 52.9/55.2 Hz,
9 H, CH3), 6.92–6.99 (m, J = 9.2, 1.0 Hz, 1 H, CH), 7.28–7.34
(m, J = 10.4, 1.0 Hz, 2H, CH), 7.35–7.42 (m, J = 10.4, 9.2,
1.0 Hz, 2H, CH). 13C-NMR (150.8 MHz, CDCl3): d −2.0 (s,
1J(117Sn/119Sn–13C) = 404/421 Hz, CH3), 125.3 (s, 3J(117Sn/119Sn–
13C) = 13.1/13.1 Hz, CH), 126.3 (s, CH), 138.4 (s, CH), 175.3
(s, 2J(117Sn/119Sn–13C) = 9.7/9.7 Hz, C). 119Sn-NMR (223.6 MHz,
CDCl3): d 70.0 ppm.
hydrogen atoms were refined anisotropically in F2 mode. Hydrogen
atomic positions were generated from assumed geometries. The
riding model was applied for the hydrogen atoms. In addition, the
riding methyl hydrogen atoms were allowed to rotate freely during
refinement.
CCDC reference numbers 621188 and 621189.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b613692c
NMR spectroscopy
NMR experiments were carried out on Varian Inova (400 MHz for
1H) and Varian NMR SYSTEM (600 MHz for 1H) spectrometers
1
using a switchable broadband X{ H}, and a direct detection
1
double tuneable pfg 5 mm X{ H–19F} probe (X = 13C, 119Sn)
respectively. Solid-state MAS spectra were recorded using a
3.2 mm HXY Varian Chemagnetics and a 6.0 mm HXY Varian
Chemagnetics tunable MAS probes in HX double resonance (DR)
mode. For 13C and 119Sn MAS experiments recycle delays of 30
X-Ray crystallography
1
Crystal data and refinement parameters are summarized in
Table 3. Crystals of 1 and 2 were mounted in Paratone-N oil within
a conventional cryo-loop, and intensity data were collected on a
Rigaku R-AXIS RAPID image plate diffractometer (k(Mo-Ka
and 45 s and H decoupling field strengths of 57 and 92 kHz
were used. Chemical shifts in the solid state were referenced
to adamantane (d13C = 29.5, 38.6 ppm) and tetracyclohexyltin
1
(d119Sn = −97.4 ppm). Solution H chemical shifts are referenced
radiation) = 0.71070 A), fitted with an X-stream low temperature
to the residual solvent signals. 119Sn shifts are given relative to the
internal reference Me4Sn. Deuterated (99.98 atom%) solvents were
˚
attachment. Several scans in the φ and x direction were made
to increase the number of redundant reflections, which were
averaged over the refinement cycles. The structures were solved
by direct methods (SIR92)18 and refined by full-matrix least-
squares (SHELXL-97).19 All calculations were carried out using
the WinGX package of crystallographic programs.20 All non-
R
purchased from Merckꢀ GmBH, Germany. 119Sn-NMR spectra
were recorded by using a 5 s recycle delay and WALTZ21 proton
R
decoupling during acquisition. Spectra were processed in VnmrJꢀ
2.1B. Solid-state simulations were performed by Varian software:
R
STARSꢀ.
238 | Dalton Trans., 2007, 234–239
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11 (a) T. P. Lockhart and W. F. Manders, Inorg. Chem., 1986, 25, 892;
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Acknowledgements
This work was supported by the Hungarian Scientific Research
Funds (OTKA) F 60496 and Hungarian GVOP-3.2.1.-2004-04-
0210/3.0 projects. A diffractometer purchase grant from the
National Office for Research and Technology (MU-00338/2003) is
gratefully acknowledged. We thank Dr Ma´tya´s Czugler for helpful
discussions.
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