Cationic bronsted acids for the preparation of SnIV salts: Synthesis and characterisation of [Ph3Sn(OEt 2)][H2N{B(C6F5)3} 2], [Sn(NMe2)3(HNMe<sub

Article abstract of DOI:10.1002/ejic.200600397

Full English Title: Cationic bronsted acids for the preparation of Sn^IV salts: Synthesis and characterisation of [Ph₃Sn(OEt ₂)][H₂N{B(C₆F₅)₃} ₂], [Sn(NMe₂)<

Full text of DOI:10.1002/ejic.200600397

FULL PAPER
DOI: 10.1002/ejic.200600397
Cationic Brønsted Acids for the Preparation of SnIV Salts: Synthesis and
Characterisation of [Ph3Sn(OEt2)][H2N{B(C6F5)3}2],
[Sn(NMe2)3(HNMe2)2][B(C6F5)4] and [Me3Sn(HNMe2)2][B(C6F5)4]
Yann Sarazin,[a] Simon J. Coles,[b] David L. Hughes,[a] Michael B. Hursthouse,[b] and
Manfred Bochmann*[a]
Keywords: Tin / Cations / N ligands / Anions
Ph3SnN(SiMe3)2 (1) was prepared in good yields by reaction
of [{NaN(SiMe3)2}2·THF] (2) with Ph3SnF. Treatment of 1 with
[H(OEt2)2][H2N{B(C6F5)3}2] (4) in dichloromethane afforded
the stannylium cation [Ph3Sn(OEt2)][H2N{B(C6F5)3}2] (5),
which was characterised by 1H, 13C{1H}, 11B, 19F and 119Sn
NMR spectroscopy. The reaction of Sn(NMe2)4 with
[Ph2MeNH][B(C6F5)4] (3) gave the amidotin(IV) compound
[Sn(NMe2)3(HNMe2)2][B(C6F5)4] (6) which proved very
stable towards ligand substitution and resisted treatment
with Et2O, THF, TMEDA and pyrazine. Two new Brønsted
acid salts [H(NMe2H)2][B(C6F5)4] (7) and [(C4H4N2)H·OEt2]-
[H2N{B(C6F5)3}2] (8) were synthesised. The reaction of 7 with
Sn(NMe2)4 in Et2O allowed the preparation of 6 in a much
improved yield (83%). The treatment of
7 with Me3-
SnN(SiMe3)2 in Et2O yielded [Me3Sn(HNMe2)2][B(C6F5)4] (9)
nearly quantitatively. Compounds 1, 2, 6, 8 and 9 were char-
acterised by single-crystal X-ray diffraction analyses; 6 is the
first example of a structurally characterised amidotin(IV)
cation.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
Introduction
characterised in the solid state,[20–25] stannylium cations sta-
Organotin(IV) compounds have long attracted interest bilised by donor heteroatoms appear to be more readily ac-
due to their reactivity, their industrial applications and their cessible.[2] For instance, cationic tin species stabilised by a
intriguing biological activity.[1,2] In particular, organo- Y,C,Y-chelating pincer-type ligand (where Y is an hetero-
tin(IV) cations are thought to play an essential part in the atom such as oxygen or nitrogen) have been prepared very
cytotoxicity of organotin compounds[3] or in their catalytic successfully in the past 15 years.[26–32] The utilisation of
activity for esterification reactions,[4] and the search for N,C,N-coordinating ligands has even enabled the prepara-
stable examples of SnIV cations was initiated over half a tion of air-stable organotin cations.[33,34] Our interest in the
century ago.[5–19] However, to this date only few cationic chemistry of cationic tin species is based on our recent iso-
complexes of tin have been isolated. Even though in the lation of a thermally remarkably stable sec-alkyl carbo-
past decade or so fundamental breakthroughs have been cation that was generated by the attack of a Me3Sn+ inter-
achieved where tin cations free of donor atoms have been mediate on a suitably substituted propene (Scheme 1).[35,36]
Scheme 1. Involvement of Me3Sn+ in the formation of a tin-stabilised carbocation.
This prompted us to investigate the chemistry of cationic
tin species in more detail. We report here the reactions of a
number of tin amides with cation-generating agents. To the
best of our knowledge, simple SnIV-amide precursors have
never been employed efficiently for this purpose.
A convenient way of generating cationic metal species
is the reaction of protolysis-sensitive metal complexes with
[a] Wolfson Materials and Catalysis Centre, School of Chemical
Sciences and Pharmacy, University of East Anglia, University
Plain,
Norwich NR4 7TJ, UK
Fax: +44-01603-592044
E-mail: m.bochmann@uea.ac.uk
[b] School of Chemistry, University of Southampton,
Highfield, Southampton SO17 1BJ, UK
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Brønsted acidic salts of very weakly coordinating anions. sation from a concentrated toluene solution stored at
For example, the oxonium ions [H(L)x]+ [L = Et2O, THF, –26 °C. The tin atom in 1 has a tetrahedral coordination
x = 2; L = (MeC=NC6H3-iPr2-2,6)2, x = 1] as salts of per- geometry, while the nitrogen atom is trigonal planar coordi-
fluorinated anions have been synthesised and used with nated. A view of a molecule of 1 is depicted in Figure 1.
great success in recent years;[37–43] we have shown that they Viewed down the N(4)–Sn bond, the N(4)–Si(5) bond
can be applied as a very clean way to abstract alkyl, alkoxy eclipses the Sn–C(11) bond. The Si(5)–N(4)–Sn–C(11) tor-
and amido groups from various metals such as Mg, Zr, Zn sion angle is 0.8(4)°. The Sn–C(11), Sn–C(21) and Sn–C(31)
or Cd.[43–47] For instance, the reactions of ZnR2 [R = C6F5, bond lengths in 1 of 2.149(6), 2.154(6) and 2.114(6) Å,
Me, Et, N(SiMe3)2], MgR2 [R = Bu, N(SiMe3)2], or respectively, are typical of SnIV–aryl bonds.[31–32,51] The Sn–
Cp2Zr(O-iPr)2 with [H(OEt2)2]+[X]– [X = H2N{B(C6F5)3}2 N(4) bond is 2.060(5) Å, i.e. greater than the two Sn–N
or B(C6F5)4] allowed the characterisation of, respectively, bond lengths reported for (Me2N)2Sn(O-2,6-tBu2-C6H3)2
[(Et2O)3ZnR][X],[44–45] [(Et2O)3MgR][X][45] and [Cp2Zr(O- [1.980(4) and 1.997(4) Å][52] and the Sn–NMe2 bond length
iPr)(HO-iPr)][X].[46] In addition, the anilinium salts [2.013(3) Å] found in {(2,2,6,6-Me4C5H6N)–P=C(SiMe3)}-
[PhNMe2H][B(C6F5)4] and [Ph2NMeH][B(C6F5)4] have Sn{NMe2}{N(SiMe3)2}2,[53] but comparable to the two Sn–
long been known and used as activating agents in olefin- N(SiMe3)2 bond lengths [2.070(2) and 2.080(2) Å] also iden-
polymerisation catalysis.[48–49]
tified in the latter compound. In the crystal packing, there
As part of our ongoing studies on the preparation and is no stacking of parallel phenyl rings; instead, the principal
the reactivity of main-group element cations,[43–45,47,50] we packing features are those of hydrogen atoms (both of
describe here the preparation and reactions of the stan- phenyl and methyl groups) pointing into the centre of
nylium
compounds
[Ph3Sn(OEt2)][H2N{B(C6F5)3}2], phenyl rings, and of methyl–methyl interactions.
During the course of this work large crops of the crystal-
[Sn(NMe2)3(HNMe2)2][B(C6F5)4] and [Me3Sn(HNMe2)2]-
[B(C6F5)4]. The structures of [{NaN(SiMe3)2}2·THF], line sodium amide 2 were obtained fortuitously from a con-
Ph3SnN(SiMe3)2 and [(C4H4N2)H·OEt2][B(C6F5)4] are also centrated light petroleum solution stored at –26 °C. The
presented.
molecular structure of 2 was determined and, interestingly,
confirmed the presence of only 0.5 molecules of THF per
sodium atom.
The molecule of 2 contains a Na2N2 ring with a C2 axis
passing through the two sodium atoms (Figure 2). Na(1) is
bound only to the two bridging nitrogen atoms, whereas
Results and Discussion
Synthesis and Structure of Ph3SnN(SiMe3)2
First attempts to generate a sterically relatively unencum- Na(2) is coordinated to the same N atoms as well as to one
bered stannyl cation involved the reaction of THF ligand. Examination of the region on the “open” side
Ph3SnN(SiMe3)2 (1) with one equiv. of [Ph2Me- of Na(1) shows its closest neighbours to be two C(21)
NH][B(C6F5)4] (3). Compound 1 is conveniently accessible methyl groups of neighbouring molecules, with Na(1)···
from Ph3SnF and 0.5 equiv. of [{NaN(SiMe3)2}2·THF] (2) C(21ЈЈ) and Na(1)···C(21ЈЈЈ) distances of 3.104(6) Å; the
in hot toluene (Scheme 2). The 119Sn NMR spectrum of 1 closest H atoms are the H(21c) atoms of these methyl
exhibited a single peak at δ –106.4 ppm, i.e. there was a groups, at 2.61 Å. The shortest distances between the
noticeable highfield shift of ca. 145–185 ppm when com- methyl groups (about the twofold symmetry axis) are:
pared to other known R3Sn–NRЈ2 trialkyltin amides.[1] 1 is C(21ЈЈ)···C(21ЈЈЈ) 3.756(9), H(21bЈЈ)···H(21bЈЈЈ) 2.62, and
very soluble both in polar (CH2Cl2, Et2O, THF) and non- H(21bЈЈ)···H(21cЈЈЈ) 2.79 Å. Because the contact distance
polar (toluene, light petroleum) organic solvents.
between two hydrogen atoms is ca. 2.4 Å, there is negligible
Crystals of 1 suitable for X-ray diffraction crystallogra- space for any other atom or group in this region; the methyl
phy were isolated as large colourless blocks by recrystalli- groups cover this ‘open’ side of Na(1). There are other short
Scheme 2. Synthesis of Ph3SnN(SiMe3)2 (1) and its subsequent reactions with Brønsted acids [Ph2MeNH][B(C6F5)4] (3) and
[H(OEt2)2][H2N{B(C6F5)3}2] (4).
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Cationic Brønsted Acids for the Preparation of SnIV Salts
FULL PAPER
arrangement around Na(2) is trigonal planar, while each of
the two nitrogen atoms are in a slightly distorted tetrahe-
dral environment. The two N–Na(1)–N and N–Na(2)–N
angles are almost identical [99.7(2)° and 99.0(2)°, respec-
tively]. The presence of a THF molecule coordinated to
Na(2) has very little influence on the N–Na(2) distance, be-
cause the N–Na(1) bond length of 2.388(5) Å is only mar-
ginally shorter than the 2.400(5) Å found for N–Na(2). It is
remarkable that despite the presence of a unique molecule
of THF in the dimeric 2, all bond lengths and angles corre-
spond closely to those already reported for the bis-THF
adduct [{NaN(SiMe3)2}2·2THF].[54] For instance, the N–
Na(1), N–Na(2) and Na(2)–O(3) bond lengths of 2.388(5),
2.400(5) and 2.285(6) Å, respectively in 2 compare very well
with the Na(1)–N(1) and Na(1)–O(1) lengths of 2.399 and
2.267 Å given for [{NaN(SiMe3)2}2·2THF], and the N–
Na(2)–N in 2 [99.0(2)°] is very close to the 101.7° found for
N(1)–Na(1)–N(1) in the bis-THF adduct.
Figure 1. View of a molecule of 1, indicating the atom numbering
scheme; atoms labelled ‘n’ represent the carbon atoms C(n). Hydro-
gen atoms have been omitted for clarity. Thermal ellipsoids are
drawn at the 50% probability level. Selected bond lengths [Å] and
angles [°]: Sn–C(11) 2.149(6), Sn–C(21) 2.154(6), Sn–C(31)
2.114(6), Sn–N(4) 2.060(5), N(4)–Si(4) 1.738(5), N(4)–Si(5)
1.743(5); C(11)–Sn–C(21) 102.5(2), C(31)–Sn–C(11) 109.5(2),
C(31)–Sn–C(21) 114.0(2), N(4)–Sn–C(11) 112.9(2), N(4)–Sn–C(21)
112.8(2), N(4)–Sn–C(31) 105.3(2).
Synthesis of [Ph3Sn(OEt2)][H2N{B(C6F5)3}2] (5)
Treatment of 1 with an equimolar amount of [H(OEt2)2]-
[H2N{B(C6F5)3}2][38] (4) in dichloromethane yielded a vis-
cous oil, from which a fine white powder was obtained
upon repeated washing with light petroleum. NMR spectro-
scopic data of this solid were consistent with the formula-
tion [Ph3Sn(OEt2)][H2N{B(C6F5)3}2] (5), and the composi-
tion was confirmed by elemental analysis. Compound 5 is
very soluble in chlorinated solvents and diethyl ether, but
is only sparingly soluble in toluene and insoluble in light
petroleum. The 119Sn NMR resonance for 5 was found at
δ –76.0 ppm, i.e. at much higher field than reported for the
free ions (mesityl)3Sn+ (δ +806 ppm)[21] and (2,4,6-triiso-
propylphenyl)3Sn+ (δ +714 ppm).[23] All attempts to deter-
mine the molecular structure of 5 proved unsuccessful,
possibly due to its high air- and moisture-sensitivity. It was
not possible to remove the coordinated Et2O molecule, even
upon heating under vacuum.
Na···H contacts of similar distance in this structure, viz.
Na(1)···H(12a) 2.62, Na(1)···H(12c) 2.64 and Na(2)···
H(22a) 2.66 Å. There are also Me···Me contacts between
each of these C(21) groups and methyl groups of the Na(1)
complex, e.g. H(12a)···H(21bЈ) 2.76 Å, H(21a)···H(21aЈ)
2.80 Å and H(11c)···H(21aЈ) 2.73 Å. These contacts effec-
tively shield Na(1) from approach by any other ligand. The
Attempts to generate a stannyl cation free of coordinat-
ing ether by reacting 1 with [Ph2MeNH][B(C6F5)4] (3) in
dichloromethane at room temperature gave dark blue mix-
tures from which no tractable material could be isolated.
Synthesis, Characterisation and Reactivity of [Sn(NMe2)3-
(HNMe2)2][B(C6F5)4] (6), [H(HNMe2)2][B(C6F5)4] (7) and
[(C4H4N2)H·OEt2][H2N{B(C6F5)3}2] (8)
To the best of our knowledge simple amidotin(IV)–
amide complexes have never been used for the preparation
of organotin cations, and it prompted us to investigate the
potential of these simple precursors for such purposes.
The sterically very hindered amide MeSn[N(SiMe3)2]3
was treated with the cation-generating agents 3, 4,
[Ph3C][H2N{B(C6F5)3}2] or B(C6F5)3 in dichloromethane.
However, none of these reactions proceeded to give the ex-
pected organotin cations, but instead the starting material
MeSn[N(SiMe3)2]3 was recovered in all cases.[55]
Figure 2. View of a molecule of [{NaN(SiMe3)2}2·THF] (2), indi-
cating the atom numbering scheme. Hydrogen atoms have been
omitted for clarity. Thermal ellipsoids are drawn at the 50% prob-
ability level. Selected bond lengths [Å] and angles [°]: Na(1)–N
2.388(5), Na(2)–N 2.400(5), Na(2)–O(3) 2.285(6), N–Si(1) 1.696(5),
N–Si(2) 1.688(6); N–Na(1)–NЈ 99.7(2), N–Na(2)–NЈ 99.0(2), N–
Na(2)–O(3) 130.5(1).
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FULL PAPER
By contrast, the less encumbered Sn(NMe2)4 can be em-
ployed effectively for reactions with Brønsted acids. On ad-
dition of one equiv. of Sn(NMe2)4 to a colourless solution
of 3 in dichloromethane, a pale yellow, slightly cloudy solu-
tion was obtained (Scheme 3, Method A). The crude prod-
uct was isolated as a viscous yellow oil. Attempts to purify
the compound adequately with light petroleum failed. Nev-
ertheless, crystals were grown from a concentrated dichloro-
methane solution, and crystallographic studies carried out
on these colourless plates indicated the structure [Sn-
(NMe2)3(HNMe2)2][B(C6F5)4] (6), with two molecules of
dimethylamine coordinated to the metal centre. Elemental
analysis and NMR characterisation were in agreement with
1
the proposed structure. The H NMR spectrum displayed
a single sharp singlet for all methyl groups at δ 2.76 ppm,
while the N–H protons gave rise to a broad singlet centred
at δ 3.25 ppm. Whereas in the 119Sn NMR spectrum the
starting material Sn(NMe2)4 exhibited a resonance at δ
–122.4 ppm, the peak for 6 was high-field shifted by about Figure 3. View of the [Sn(NMe2)3(HNMe2)2]+ cation (6+), indicat-
ing the atom numbering scheme. Atoms labelled ‘n’ represent the
190 ppm, to δ –311.4 ppm. The borate anion showed an 11
B
carbon atoms C(n). Hydrogen atoms (except for the amino H
atoms) have been omitted for clarity. Thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths [Å] and angles
[°]: Sn–N(11) 2.382(7), Sn–N(12) 2.321(7), Sn–N(13) 2.013(7), Sn–
N(14) 2.005(6), Sn–N(15) 1.990(7); N(12)–Sn–N(11) 176.0(2),
N(13)–Sn–N(11) 91.4(3), N(14)–Sn–N(11) 90.4(3), N(15)–Sn–
N(11) 89.9(3), N(13)–Sn–N(12) 84.6(3), N(14)–Sn–N(12) 92.1(3),
N(15)–Sn–N(12) 91.5(3), N(14)–Sn–N(13) 120.8(3), N(15)–Sn–
N(13) 118.7(3), N(15)–Sn–N(14) 120.5(3).
NMR signal at δ –13.6 ppm, while the 19F NMR reso-
nances at δ –133.4, –160.6 and –166.1 ppm are typical of a
noncoordinated borate. Compound 6 is highly soluble in
diethyl ether, THF and dichloromethane, moderately solu-
ble in toluene and insoluble in light petroleum. It is very
air- and moisture-sensitive, but is thermally stable for
periods of weeks at room temperature, and does not show
any sign of deterioration upon prolonged exposure to
light.
The structure of the [Sn(NMe2)3(HNMe2)2]+ cation (6+)
The preparation described above gave 6 in low yield
is shown in Figure 3. The complex is trigonal-bipyramidal, (24% based on Sn). Consequently, a more economical route
with the two dimethylamine ligands trans to one another was developed, which consisted of protonating Sn(NMe2)4
[angle N(11)–Sn–N(12) 176.0(2)°; angle sum for Neq–Sn– while at the same time offering a second molecule of di-
Neq 360.0°]. The Sn–N distances to the axial HNMe2 li- methylamine (Scheme 3, Method B). For this purpose, the
gands [Sn–N(11) 2.382(7), Sn–N(12) 2.321(7) Å] are sub- new Brønsted acid [H(HNMe2)2][B(C6F5)4] (7) was pre-
stantially longer than those to the equatorial amido groups pared. The low basicity of NMePh2 compared to that of
[Sn–N(13) 2.013(7) Å, Sn–N(14) 2.005(6) and Sn–N(15) HNMe2 was exploited for the nearly-quantitative synthesis
1.990(7) Å]. The average Sn–Neq length in 6+ (2.003 Å) is of 7 (Scheme 4, top). Thus, the straightforward reaction of
somewhat shorter than the average Sn–Neq length of 3 with a large excess of HNMe2 in diethyl ether at room
2.038 Å found in the geometrically comparable neutral temperature yielded a white solid after removal of the vola-
complex Me2NSn(MeNCH2CH2N)3N,[56] which presum- tiles. Upon thorough washing with light petroleum, a fine
ably reflects the influence of the positive charge on the white powder was obtained, and the composition of 7 was
metal centre in 6+. To the best of our knowledge, 6 is the confirmed by elemental analysis and NMR spectroscopy. In
1
first example of a structurally characterised five-coordinate the H NMR spectrum (in CD2Cl2), all four methyl groups
amido SnIV-cation paired with a noncoordinating counter- appear as a sharp singlet at δ 2.61 ppm, while the three N–
anion.
H protons are equivalent and give rise to a sharp singlet at
Scheme 3. Preparation of [Sn(NMe2)3(HNMe2)2][B(C6F5)4] (6).
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Cationic Brønsted Acids for the Preparation of SnIV Salts
FULL PAPER
Scheme 4. Preparation of new Brønsted acids stabilised by weakly coordinating perfluorinated anions.
δ 7.04 ppm. It is worth noting that this reaction must not
The anion [H2N{B(C6F5)3}2]– was chosen in preference
–
be conducted in dichloromethane, as in this case crystalline to B(C6F5)4 because of its better crystallisation properties,
Me2NH·HCl is slowly formed in quantitative yield. For this and indeed crystals of 8 suitable for X-ray crystallography
reason, highly concentrated solutions of 7 and short acqui- were grown as colourless shards from a concentrated
sition times were used to record its NMR spectra. Com-
pound 7 dissolves in Et2O and THF but is hardly soluble
in toluene and insoluble in light petroleum. As anticipated,
the reaction of Sn(NMe2)4 with an equimolar amount of 7
in diethyl ether proceeded cleanly to yield ether-free 6 in a
substantially improved yield (83%; Scheme 3, Method B).
The stability of 6 was demonstrated by its remarkable
inertness towards ligand substitution. There is no reaction
with diethyl ether, THF or even a chelating ligand such as
tetramethylethylenediamine (TMEDA). Moreover, 6 was
also isolated as the only product of the reaction between 3
and Sn(NMe2)4 carried out in Et2O or THF instead of
CH2Cl2 (yield 10–20% with respect to Sn).
Because adding an excess of pyrazine to 6 proved ineffec-
tive in displacing one of the dimethylamine ligands, we en-
visaged adding [(C4H4N2)H·OEt2][H2N{B(C6F5)3}2] (8) to
Sn(NMe2)4, with the rationale that such reaction would
lead to the formation of a SnIV cation coordinated by at
least one bifunctional pyrazine ligand. Thus, the new
Brønsted acid 8 was conveniently prepared by addition of
pyrazine to a solution of 4 in dichloromethane (Scheme 4,
bottom, Method A). After removal of the volatile fraction
and several washings with light petroleum, analytically pure
8 was recovered in high yield (88%). Product 8 was also
readily obtained in 77% yield by reaction of solid pyrazin-
ium chloride with [Na(OEt2)4][H2N{B(C6F5)3}2] in dichlo-
romethane (Scheme 4, bottom, Method B). Compound 8
Figure 4. View of the salt [(C4H4N2)H·OEt2][H2N{B(C6F5)3}2] (8),
indicating the atom numbering scheme. Hydrogen atoms (except
for the amido and acidic atoms) have been omitted for clarity. Ther-
mal ellipsoids are drawn at the 50% probability level. Selected bond
can easily be dissolved in Et2O and chlorinated solvents,
but shows poor solubility in aromatic solvents and light pe-
troleum. Unexpectedly, no clean product could be recovered
from the reaction of Sn(NMe2)4 and 8 performed in
CH2Cl2; instead a complicated mixture of products was ob-
tained.
lengths [Å] and angles [°]: N(2)–H(2n) 1.27(5), O(1)–H(2n) 1.38(5),
N(2)–C(41) 1.335(6), N(2)–C(44) 1.337(6), N(3)–C(42) 1.321(6),
N(3)–C(43) 1.331(6), N(1)–B(1) 1.627(4), N(1)–B(2) 1.638(4),
N(1)–H(1a) 0.90, N(1)–H(1b) 0.90, H(1a)–F(5) 2.24, H(1a)–F(11)
2.13, H(1a)–F(26) 2.32, H(1b)–F(16) 1.98; N(2)–H(2n)–O(1)
156(5), C(41)–N(2)–C(44) 120.6(4), C(42)–N(3)–C(43) 114.9(4),
B(1)–N(1)–B(2) 133.2(2).
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dichloromethane solution cooled to –26 °C (Figure 4). The Synthesis and Characterisation of [Me3Sn(HNMe2)2]-
acidic proton in the cation was refined freely. It lies between [B(C6F5)4] (9)
the oxygen and nitrogen atoms and is located somewhat
closer to the latter [N(2)–H(2n) 1.27(5) Å, O(1)–H(2n)
As discussed above, no stannyl cation could be generated
1.38(5) Å]; the N(2)–H(2n)–O(1) angle is 156(5)°. The C–N from MeSn[N(SiMe3)2]3 upon treatment with various cat-
bonds of the protonated nitrogen [1.335(6) and 1.337(6) Å] ion-generating agents. On the other hand, the sterically less
are marginally longer than those to the nonprotonated ni- hindered mono-amide Me3SnN(SiMe3)2 reacted success-
trogen atom [1.321(6) and 1.331(6) Å]. The structure of the fully with one equiv. of 7 in Et2O to yield [Me3Sn-
anion resembles strongly that in [Na(OEt2)2][H2N{B- (HNMe2)2][B(C6F5)4] (9) in
a
near-quantitative yield
(C6F5)3}2] reported previously.[38]
(Scheme 5). Compound 9 was fully characterised by NMR
Scheme 5. Preparation of [Me3Sn(HNMe2)2][B(C6F5)4] (9).
Figure 5. View of the two independent ion pairs in the salt [Me3Sn(HNMe2)2][B(C6F5)4] (9), indicating the atom numbering scheme.
Hydrogen atoms have been omitted for clarity. Thermal ellipsoids are drawn at the 50% probability level. Selected bond lengths [Å] and
angles [°]: For the first cation, Sn(1)–N(1) 2.405(6), Sn(1)–N(2) 2.323(6), Sn(1)–C(1) 2.036(6), Sn(1)–C(2) 2.404(6), Sn(1)–C(3) 2.085(6);
N(1)–Sn(1)–N(2) 176.3(2), N(1)–Sn(1)–C(1) 78.4(2), N(1)–Sn(1)–C(2) 93.0(2), N(1)–Sn(1)–C(3) 94.0(2), N(2)–Sn(1)–C(1) 100.2(2), N(2)–
Sn(1)–C(2) 84.9(2), N(2)–Sn(1)–C(3) 89.7(2), C(1)–Sn(1)–C(2) 124.5(2), C(2)–Sn(1)–C(3) 127.9(2), C(1)–Sn(1)–C(3) 107.5(3). For the
second cation, Sn(2)–N(3) 2.263(5), Sn(2)–N(4) 2.272(4), Sn(2)–C(8) 2.417(7), Sn(2)–C(9) 2.049(6), Sn(2)–C(10) 2.154(6); N(3)–Sn(2)–
N(4) 177.0(2), N(3)–Sn(2)–C(8) 98.8(2), N(3)–Sn(2)–C(9) 80.2(2), N(3)–Sn(2)–C(10) 91.7(2), N(4)–Sn(2)–C(8) 84.0(2), N(4)–Sn(2)–C(9)
97.7(2), N(4)–Sn(2)–C(10) 87.3(2), C(8)–Sn(2)–C(9) 116.8(3), C(9)–Sn(2)–C(10) 116.1(3), C(8)–Sn(2)–C(10) 127.1(3).
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Eur. J. Inorg. Chem. 2006, 3211–3220

Cationic Brønsted Acids for the Preparation of SnIV Salts
FULL PAPER
spectroscopy in CD2Cl2, and its composition was con- the first example of a structurally characterised cationic
firmed by elemental analysis. It is readily soluble in ethers amidotin complex. The dimethylamine ligands exhibit a
and chlorinated solvents, but only poorly soluble in aro- surprising resistance to substitution by other Lewis bases.
matic hydrocarbons and totally insoluble in light petro- Future work will involve tailor-made cationic Brønsted ac-
leum. It is air- and moisture-sensitive, but is thermally ids and their use in combination with other main group
stable and does not deteriorate when exposed to light.
precursors for the development of new architectures built
The 119Sn NMR spectrum of 9 consists of a single peak around cationic metal centres and weakly coordinating
located at δ –25.3 ppm, i.e. it has undergone a high-field anions.
shift of about 77 ppm when compared to the starting mate-
rial (δ +52.1 ppm). By contrast, the 119Sn NMR resonance
for the free Bu3Sn+ appears at the much higher frequency
Experimental Section
1
(δ +454 ppm).[22] In the H NMR spectrum, the resonance
General: All manipulations were performed under argon using
for the nine Sn–CH3 protons is found at δ 0.60 ppm, exhib-
standard Schlenk techniques. Solvents were pre-dried, and distilled
2
iting a JH,Sn coupling of 30.7 Hz; the two N–H protons
under inert atmosphere over sodium (low-sulfur toluene), sodium–
display a resonance at δ 2.14 ppm, and are considerably
benzophenone (diethyl ether, THF), sodium–potassium alloy (light
more shielded than the two analogous protons in 6 (δ
petroleum, boiling point 40–60 °C) or calcium hydride (dichloro-
3.25 ppm). The 11B (δ –13.6 ppm) and 19F (δ –133.6, –164.0
methane). NMR solvents were dried with activated 4-Å molecular
and –168.0 ppm) NMR spectra are characteristic of the
noncoordinating nature of the counteranion.
sieves and degassed by several freeze–thaw cycles. NMR spectra
were recorded with a Bruker Avance DPX-300 spectrometer.
Chemical shifts are reported in ppm. 1H NMR spectra
(300.13 MHz) are referenced to the residual protons of the deuter-
ated solvent used. 13C NMR spectra (75.47 MHz) were referenced
internally to the D-coupled 13C resonances of the NMR solvent.
11B (96.29 MHz), 19F (282.38 MHz) and 119Sn (111.91 MHz) NMR
spectra were referenced externally to BF3·Et2O, CFCl3 and SnMe4,
respectively. HN(SiMe3)2, NMePh2, Ph3SnF, SnCl4, Me3SnCl,
MeSnCl3, C4H4N2, HNMe2 and N,N,NЈ,NЈ-tetramethylethylenedi-
amine were used as purchased without further purification.
B(C6F5)3,[58–59] [Ph2MeNH][B(C6F5)4] (3),[49] [Na(OEt2)4][H2N-
Single crystals of 9 were readily grown from a dichloro-
methane/light petroleum mixture at –28 °C as colourless
slabs, suitable for X-ray diffraction. The crystal structure
(Figure 5) indicates the presence of two independent ion
pairs per asymmetric unit. The arrangement around the tin
atoms of the two cations in 9 resembles that in 6. Each of
the cations has a distorted trigonal-bipyramidal environ-
ment, where the two dimethylamine ligands are situated in
apical positions [N(1)–Sn(1)–N(2) 176.3(2)°; N(3)–Sn(2)–
N(4) 177.0(2)°]. The average angle sums for Ceq–Sn(1)–Ceq {B(C6F5)3}2],[38] [H(OEt2)2][H2N{B(C6F5)3}2] (4),[38] [Ph3C][H2N-
{B(C6F5)3}2],[38] MeSn[N(SiMe3)2]3,[60] Me3SnN(SiMe3)2
and
[61]
[359.9(2)°] and Ceq–Sn(2)–Ceq [360.0(3)°] confirm the plan-
arity of the trigonal SnMe3 subunits. In both cations, one
of the three equatorial Sn–C bonds is significantly longer
than the other two [Sn(1)–C(2) 2.404(6) compared to Sn(1)–
C(1) 2.036(6) and Sn(1)–C(3) 2.085(6) Å; Sn(2)–C(8)
2.417(7) compared to Sn(2)–C(9) 2.049(6) and Sn(2)–C(10)
2.154(6) Å], and there are considerable variations in the
Ceq–Sn–Ceq angles [Ceq–Sn(1)–Ceq 107.5(3)–127.9(2)°; Ceq–
Sn(2)–Ceq 116.1(3)–127.1(3)°]. The axial Sn–N bond
lengths in 9 differ slightly between the two independent cat-
ions [Sn(1)–N(1) 2.405(6) and Sn(1)–N(2) 2.323(6) Å;
Sn(2)–N(3) 2.263(5) and Sn(2)–N(4) 2.272(4) Å], but overall
compare well with those found in 6 [2.382(7) and
2.321(7) Å] and in the related ammonia complex
[Me3Sn(NH3)2][N(SO2Me)2] (Sn–N 2.328 and 2.383 Å; N–
Sn–N 179.2°).[57] The equatorial Sn–C bond lengths in 9
are comparable to those reported for the latter compound
(Sn–C 2.117–2.124 Å).
[62]
Sn(NMe2)4 were prepared according to the literature methods.
Synthesis of Ph3SnN(SiMe3)2 (1): Ph3SnF (5.0 g, 13.5 mmol) was
added rapidly at –78 °C to a suspension of [{NaN(SiMe3)2}2·THF]
(6.0 g, 13.5 mmol) in light petroleum (80 mL). The mixture was
warmed slowly to room temperature and was stirred overnight. The
volatiles were removed under vacuum, giving a white solid which
was suspended in toluene (60 mL). The reaction mixture was stirred
at 60 °C for 5 hours. The precipitate of NaF was then removed by
filtration, and the supernatant was concentrated to 20 mL. X-ray
quality crystals were obtained by recrystallisation at –26 °C. Yield:
1
4.8 g (70%). H NMR (CD2Cl2, 25 °C, 300.13 MHz): δ = 7.66 (m,
6 H, Ar–H), 7.44 (m, 9 H, Ar–H), 0.10 (s, 18 H, SiMe3) ppm.
1
13C{1H} NMR (CD2Cl2, 25 °C, 75.48 MHz): δ = 142.5 (Ci, JC,Sn
= 298.9 Hz, SnPh3), 137.0 (Co, 2JC,Sn = 20.6 Hz, SnPh3), 129.6 (Cp,
3
4JC,Sn = 6.2 Hz, SnPh3), 129.1 (Cm, JC,Sn = 28.9 Hz, SnPh3), 5.6
(SiMe3) ppm. 119Sn NMR (CD2Cl2, 25 °C, 111.91 MHz): δ =
–106.4 ppm. C24H33NSi2Sn (510.4): calcd. C 56.48, H 6.52, N 2.74;
found C 56.71, H 6.52, N 2.87.
Preparation of [{NaN(SiMe3)2}2·THF](2): The solvent was removed
from a solution of NaN(SiMe3)2 (12.0 g, 65.4 mmol) in THF
(125 mL) under vacuum and the resulting solid extracted with light
petroleum (2×100 mL). The filtrate was concentrated to 50 mL
and stored overnight at –26 °C, affording a large crop of colourless
crystals suitable for X-ray diffraction crystallography. Yield 10.0 g,
22.8 mmol, 70%. 1H NMR (CD2Cl2, 25 °C, 300.13 MHz): δ = 3.41
(t, 4 H, J = 6.6 Hz, CH2–CH2–O), 1.22 (m, 4 H, CH2–CH2–O),
0.26 (s, 36 H, SiMe3) ppm. 13C NMR (CD2Cl2, 25 °C, 75.48 MHz):
δ = 68.4 (CH2–CH2–O), 25.4 (CH2–CH2–O), 7.0 (SiMe3) ppm.
C16H44N2Na2OSi4 (438.9): calcd. C 43.79, H 10.11, N 6.38; found
Conclusions
We have shown that Brønsted acids paired with weakly
coordinating perfluorinated counteranions can be em-
ployed as an effective way to generate cationic tin(IV) com-
plexes. With this aim in mind two new nitrogen-based
Brønsted acids have been developed. The SnIV cations
formed in such fashion are highly electrophilic. In particu-
lar, [Sn(NMe2)3(HNMe2)2]+ [B(C6F5)4]– was synthesized as C 43.01, H 10.10, N 6.40.
Eur. J. Inorg. Chem. 2006, 3211–3220
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3217

Y. Sarazin, S. J. Coles, D. L. Hughes, M. B. Hursthouse, M. Bochmann
FULL PAPER
[Ph3Sn(OEt2)][H2N{B(C6F5)3}2] (5): A colourless solution of 1
(0.5 g, 1.0 mmol) and 4 (1.2 g, 1.0 mmol) in CH2Cl2 (8 mL) was
stirred at room temperature for 12 hours. The solvent was then re-
moved under vacuum, leaving a sticky foam. Upon repeated wash-
ing with light petroleum a white powder was obtained which was
suspended in 3 mL of light petroleum, and dichloromethane (ca.
2 mL) was added until the solid was completely dissolved. Cooling
to –26 °C for several days gave a white microcrystalline solid, yield
0.5 g (30%). 1H NMR (CD2Cl2, 25 °C, 300.13 MHz): δ = 7.92–7.70
added to a solution of 4 (1.0 g, 0.8 mmol) in CH2Cl2 (25 mL). The
colourless mixture was stirred at room temperature overnight, and
the solvent was pumped off under vacuum to leave a white solid
which was washed with light petroleum (3×25 mL) and dried in
vacuo. Crystals suitable for X-ray diffraction were obtained by
recrystallisation from a concentrated CH2Cl2 solution at –26 °C.
Yield 0.8 g (88%). 1H NMR (CD2Cl2, 25 °C, 300.13 MHz): δ =
16.46 (br., 1 H, N–H), 10.36–8.10 (v br, 4 H, C–H), 5.70 (br. s, 2
H, H2N), 3.86 (q, 3JH,H = 7.0 Hz, 4 H, CH3–CH2–O), 1.34 (t, 3JH,H
= 7.0 Hz, 6 H,CH3–CH2–O) ppm. 13C{1H} NMR (CD2Cl2, 25 °C,
3
(m, 15 H, Ar–H), 5.70 (br. s, 2 H, H2N), 3.61 (q, JH,H = 7.0 Hz,
3
4 H, CH3–CH2–O), 0.99 (t, JH,H = 7.0 Hz, 6 H, CH3–CH2–O) 75.48 MHz): δ = 148.8, 146.6, 141.1, 138.6, 137.8, 135.4 (all ArF5–
ppm. 13C{1H} NMR (CD2Cl2, 25 °C, 75.48 MHz): δ = 149.8,
C), 142.7 (C4H4N2), 67.7 (CH3–CH2–O), 15.0 (CH3–CH2–O) ppm.
146.7, 141.2, 138.7, 137.8, 135.5 (all ArF5–C), 136.9 (Ci, SnPh3), 11B NMR (CD2Cl2, 96.29 MHz, 25 °C): δ = –5.3 ppm. 19F NMR
136.6 (2JC,Sn = 22.8 Hz, Co, SnPh3), 131.1 (Cp, SnPh3), 131.0 (3JC,Sn
(CD2Cl2, 282.38 MHz, 25 °C): δ = –133.4 (d, JF,F = 19.8 Hz, 12
3
= 33.8 Hz, Cm, SnPh3), 67.5 (CH3–CH2–O), 13.9 (CH3–CH2–O) F, Fo), –160.6 (t, 3JF,F = 19.8 Hz, 6 F, Fp), –166.1 (t, 3JF,F = 19.8 Hz,
ppm. 11B NMR (CD2Cl2, 96.29 MHz, 25 °C): δ = –5.3 ppm. 19F
12 F, Fm) ppm. C44H17B2F30N3O (1195.2): calcd. C 44.22, H 1.43,
N 3.52; found C 43.91, H 1.58, N 3.43.
3
NMR (CD2Cl2, 282.38 MHz, 25 °C): δ = –133.4 (d, JF,F
=
3
19.8 Hz, 12 F, Fo), –160.7 (t, JF,F = 19.8 Hz, 6 F, Fp), –166.0 (t,
3JF,F = 19.8 Hz, 12 F, Fm) ppm. 119Sn NMR (CD2Cl2, 25 °C,
111.91 MHz): δ = –76.0 ppm. C58H27B2F30NOSn (1464.1): calcd.
C 47.58, H 1.86, N 0.96; found C 47.45, H 2.02, N 1.04.
Method B: [Na(OEt2)4][H2N{B(C6F5)3}2] (1.9 g, 1.4 mmol) was
added at room temperature to a suspension of solid C4H4N2·HCl
(0.15 g, 1.3 mmol) in 25 mL of CH2Cl2. The pyrazinium chloride
reacted immediately, and the resulting solution turned pale yellow
while small amounts of NaCl precipitate persisted. The solution
was filtered off after 6 h, and the volatiles were removed under
vacuum. A white powder was isolated, the composition of which
was essentially identical to that of the solid obtained with Method
A above. Yield 1.2 g (77%).
[Sn(NMe2)3(HNMe2)2][B(C6F5)4] (6). Method A: To a colourless
solution of 3 (1.3 g, 1.5 mmol) in CH2Cl2 (15 mL) was added neat
Sn(NMe2)4 (0.5 g, 1.7 mmol). The solution was stirred at room
temperature for 5 h, when it gradually turned pale yellow and
cloudy. It was then concentrated to ca. 5 mL and crystals suitable
for X-ray crystallography were obtained after several days at
–26 °C. Yield 0.4 g (24% relative to Sn). 1H NMR (CD2Cl2, 25 °C,
300.13 MHz): δ = 3.25 (br., 2 H, N–H), 2.76 (s, 30 H, N–CH3)
ppm. 13C{1H} NMR (CD2Cl2, 25 °C, 75.48 MHz): δ = 150.0,
146.8, 140.2, 138.2, 136.9, 135.0 (all ArF5–C), 42.0 (br., N–CH3)
[Me3Sn(HNMe2)2][B(C6F5)4] (9): Compound 7 (0.8 g, 1.0 mmol)
was rapidly added to a solution of Me3SnN(SiMe3)2 (0.6 g,
1.8 mmol) in Et2O (30 mL). The resulting colourless solution was
stirred at room temperature for 1 h. Upon removal of the volatiles
in vacuo a white solid was obtained which was washed thoroughly
with light petroleum (2×50 mL) and dried in vacuo to constant
weight. Yield 0.9 g (96%). Recrystallisation from a dichlorometh-
ane/light petroleum mixture (4:1) kept at –26 °C afforded single
crystals of 9 as colourless slabs. 1H NMR (CD2Cl2, 25 °C,
300.13 MHz): δ = 2.42 (s, 12 H, N–CH3), 2.14 (br., 2 H, N–H),
0.60 (s, 9 H, Sn–CH3) ppm. 13C{1H} NMR (CD2Cl2, 25 °C,
75.48 MHz): δ = 150.1, 146.9, 140.2, 138.3, 137.0, 135.0 (all ArF5–
C), 37.8 (N–CH3), –5.4 (Sn–CH3) ppm. 11B NMR (CD2Cl2,
ppm. 11B NMR (CD2Cl2, 96.29 MHz, 25 °C): δ = –13.6 ppm. 19F
3
NMR (CD2Cl2, 282.38 MHz, 25 °C): δ = –133.6 (d, JF,F
=
3
19.8 Hz, 8 F, Fo), –164.1 (t, JF,F = 19.8 Hz, 4 F, Fp), –168.0 (t,
3JF,F = 19.8 Hz, 8 F, Fm) ppm. 119Sn NMR (CD2Cl2, 25 °C,
111.91 MHz): δ = –311.4 ppm. C34H32BF20N5Sn (1020.2): calcd. C
40.03, H 3.16, N 6.87; found C 39.52, H 2.95, N 6.48.
Method B: Neat Sn(NMe2)4 (0.4 g, 1.4 mmol) was added to a solu-
tion of 7 (0.9 g, 1.2 mmol) in Et2O (30 mL). A white precipitate
formed within 2 min. The reaction mixture was stirred overnight,
and light petroleum (10 mL) was added, yielding a white precipi-
tate. The supernatant was filtered off. The white solid residue was
washed with light petroleum (4×30 mL) and dried in vacuo. The
product proved to be identical to that prepared by Method A. Yield
1.0 g (83% relative to Sn).
96.29 MHz, 25 °C):
δ =
–13.6 ppm. 19F NMR (CD2Cl2,
282.38 MHz, 25 °C): δ = –133.6 (d, 3JF,F = 19.8 Hz, 8 F, Fo), –164.0
3
3
(t, JF,F = 19.8 Hz, 4 F, Fp), –168.0 (t, JF,F = 19.8 Hz, 8 F, Fm)
ppm. 119Sn NMR (CD2Cl2, 25 °C, 111.91 MHz): δ = –25.3 ppm.
C31H23BF20N2Sn (933.0): calcd. C 39.91, H 2.48, N 3.00; found C
40.07, H 2.40, N 3.06.
X-ray Crystallography: Crystal data and refinement results for com-
pounds 1, 2, 6, 8 and 9 are collated in Table 1. In each case, crystals
were mounted on glass fibres, either in oil and fixed in the cold
nitrogen stream on a Rigaku/MSC AFC7R diffractometer (sam-
ples 1, 2 and 6) or with epoxy resin on a Nonius KappaCCD dif-
fractometer (samples 8 and 9). Data were processed with the
TeXsan/PROCESS[63] or DENZO program,[64] and absorption cor-
rections applied. The structures were determined by heavy atom
methods (compounds 1 and 2) or direct methods (compounds 6, 8
and 9) in SHELXS.[65] Refinement was by full-matrix least-squares
methods in SHELXL.[65] In all, non-hydrogen atoms were refined
anisotropically; hydrogen atoms were included in idealised posi-
tions and their isotropic thermal parameters were set to ride on the
Ueq values of the parent carbon or nitrogen atoms. Scattering fac-
tors for neutral atoms were taken from ref.[66]. The relatively large
difference peaks and holes were located close to the tin atoms and
[H(HNMe2)2][B(C6F5)4] (7): Dimethylamine (6.6 g, 14.6 mmol) was
condensed into a Schlenk tube at –35 °C and transferred rapidly to
a solution of 3 (1.2 g, 1.4 mmol) in Et2O (25 mL). The resulting
colourless solution was stirred overnight at room temperature. The
volatiles were then removed in vacuo, yielding a white solid which
was washed thoroughly with light petroleum (5×20 mL) and dried
under vacuum. Yield 0.9 g (86%). 1H NMR (CD2Cl2, 25 °C,
300.13 MHz): δ = 7.04 (s, 3 H, N–H), 2.61 (s, 12 H, N–CH3) ppm.
13C{1H} NMR (CD2Cl2, 25 °C, 75.48 MHz): δ = 150.0, 147.1,
140.1, 138.0, 136.7, 135.0 (all ArF5–C), 36.7 (N–CH3) ppm. 11B
NMR (CD2Cl2, 96.29 MHz, 25 °C): δ = –11.7 ppm. 19F NMR
3
(CD2Cl2, 282.38 MHz, 25 °C): δ = –131.8 (d, JF,F = 19.8 Hz, 8 F,
3
3
Fo), –161.9 (t, JF,F = 19.8 Hz, 4 F, Fp), –165.9 (t, JF,F = 19.8 Hz,
8 F, Fm) ppm. C28H15BF20N2 (770.2): calcd. C 43.66, H 1.96, N
3.64; found C 43.92, H 1.82, N 3.65.
[(C4H4N2)H·OEt2][H2N{B(C6F5)3}2] (8). Method A: Pyrazine arise from inadequate absorption correction. No absorption correc-
(0.1 g, 1.2 mmol) was weighed under inert atmosphere and rapidly tion was applied in the case of compound 1.
3218
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 3211–3220

Cationic Brønsted Acids for the Preparation of SnIV Salts
FULL PAPER
Table 1. Crystal and structure refinement data for compounds 1, 2, 6, 8 and 9.
Compound
1
2
6
8
9
Elemental formula
Formula weight
C24H33NSi2Sn
510.4
C16H44N2Na2OSi4
438.9
C10H32N5Sn, C24BF20 C8H15N2O, C36H2B2F30
N
C62H46B2F40N4Sn2
1866.0
1020.2
1195.2
Crystal system
Space group
triclinic
monoclinic
C2/c (no. 15)
triclinic
orthorhombic
P212121 (no. 19)
triclinic
¯
¯
¯
P1 (no. 2)
P1 (no. 2)
P1 (no. 2)
Unit cell dimensions [Å, °]
a
b
c
α
11.799(14)
12.031(12)
9.405(11)
95.68(9)
107.33(9)
84.08(9)
1264(2)
2
11.195(13)
21.65(2)
11.877(13
90
109.73(9)
90
2710(5)
4
1.076
12.569(10)
14.304(12)
10.983(8))
91.59(7)
102.48(6)
85.87(7)
1923(3)
13.9820(2)
17.1460(2)
18.3470(3)
90
90
90
4398.43(11)
4
1.805
13.910(4)
14.102(3)
17.786(4)
88.92(2)
82.07(2)
89.94(2)
3454.9(15)
2
1.794
β
γ
Cell volume, V [Å3]
No. of formula units/cell, Z
Density (calculated) [mg/m3]
F(000)
2
1.340
524
1.762
1012
960
2360
1832
Absorption coefficient [mm–1
Temperature [K]
Crystal colour, shape
Crystal size [mm]
θ range [°] for data collection
Index ranges for h, k, l
Absorption correction
]
1.114
140(1)
colourless block
0.8×0.7×0.5
2.3–25.1
0.259
140(1)
colourless prism
0.5×0.25×0.2
1.9–20.0
0.796
140(1)
colourless plate
0.7×0.40×0.15
1.9–25.0
0.197
293(2)
0.875
120(2)
colourless shard
0.27×0.02×0.02
2.9–27.1
–17/16, –19/21, –23/23
Semi-empirical from
equivalents
0.996/0.949
63610
colourless slab
0.50×0.18×0.08
1.2–27.5
–17/17, –18/18, –22/22
Semi-empirical from
equivalents
0.933/0.669
70746
0/14, –14/14, –11/10 –1/10, –20/20, –11/10 0/13, –16/16, –12/12
Psi-scans
Psi-scans
Psi-scans
Max./min. transmission
Total no. of reflections measured
No. of unique reflections
Rint for equivalents
1.00/0.584
4681
4443
1.00/0.756
2028
1270
0.146
883
1.00/0.64
5537
5200
0.104
4053
9638
0.074
7707
14464
0.065
11285
0.088
No. of “observed” reflections (I Ͼ 2σI) 3851
Refinement
Data/restraints/parameters
Goodness-of-fit on F2, S
4443/0/254
1.048
1270/0/121
0.999
5200/0/563
0.996
9638/0/727
1.065
14464/0/1021
1.098
Final R indices (“observed” data)
R1 = 0.061,
wR2 = 0.156
R1 = 0.071,
wR2 = 0.164
3.23 and –1.92
R1 = 0.058,
wR2 = 0.114
R1 = 0.094,
wR2 = 0.126
0.22 and –0.30
R1 = 0.063,
wR2 = 0.158
R1 = 0.084,
wR2 = 0.170
1.52 and –2.22
R1 = 0.047,
wR2 = 0.104
R1 = 0.068,
wR2 = 0.113
0.60 and –0.29
R1 = 0.055,
wR2 = 0.150
R1 = 0.076,
wR2 = 0.160
2.07 and –1.79
Final R indices (all data)
Largest diff. peak and hole [e·Å–3
]
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Received: May 1, 2006
Published Online: June 28, 2006
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