Novel stable silyl, germyl, and stannyl germanium(II) compounds containing an amidinato ligand

Article abstract of DOI:10.1021/om200024d

Reactions of the N,N′-chelated chlorogermanium(II) compound [Me ₃SiNC(Ph)NSiMe₃]GeCl with the magnesium reagents Mg[E(SiMe₃)₃]₂ (E = Si, Ge, Sn) gave the new metallyl germylenes [Me₃SiNC(Ph)NSiMe₃]GeE(SiMe ₃)₃, representing the first isolated silyl- and stannylgermylenes. These compounds have been fully characterized by multinuclear NMR spectroscopy and their structures determined by X-ray diffraction analysis.

Full text of DOI:10.1021/om200024d

ARTICLE
pubs.acs.org/Organometallics
Novel Stable Silyl, Germyl, and Stannyl Germanium(II) Compounds
Containing an Amidinato Ligand
Dimitri Matioszek,† Nadia Katir,† Sonia Ladeira,‡ and Annie Castel*,†
†Laboratoire Hꢀetꢀerochimie Fondamentale et Appliquꢀee, UMR/CNRS 5069, and ‡Structure Fꢀedꢀerative Toulousaine en Chimie
Molꢀeculaire (FR2599), Universitꢀe Paul Sabatier, 118, Route de Narbonne, 31062 Toulouse Cedex 09, France
S Supporting Information
b
ABSTRACT: Reactions of the N,N0-chelated chlorogermanium-
(II) compound [Me3SiNC(Ph)NSiMe3]GeCl with the magne-
sium reagents Mg[E(SiMe3)3]2 (E = Si, Ge, Sn) gave the new
metallyl germylenes [Me3SiNC(Ph)NSiMe3]GeE(SiMe3)3, repre-
senting the first isolated silyl- and stannylgermylenes. These
compounds have been fully characterized by multinuclear NMR
spectroscopy and their structures determined by X-ray diffraction
analysis.
’ INTRODUCTION
and tris(trimethylstannyl) germanium(II) compounds by taking
advantage of such a ligand.
The chemistry of germanium(II) compounds has received
considerable attention, due to their carbene-like properties.1 Such
compounds are very reactive and tend to polymerize. They can be
stabilized kinetically by incorporating bulky ligands and/or thermo-
dynamically by using electron-donating substituents at the group 14
metal center. Among the large number of stable monomeric
germanium(II) compounds reported to date,1 there are few exam-
ples of germylenes having electropositive silyl or germyl substitu-
ents. For a long time, silyl-,2 germyl-,3 and stannylgermylenes4 have
been postulated as transient species or intermediates in mechanistic
studies. Only two aminosilylgermylenes (I; Chart 1) have been
prepared; the first (R = 2,6-Me2-C6H2) is monomeric in the solid
state, whereas the second (R = i-Pr) dimerizes to give
disilyldigermene.5 The germylgermylenes6 are more accessible,
and some of them have been isolated and structurally characterized
(II,6a III,6b IV,6c V;6d Chart 1). In contrast, no stable germylene with
a stannyl substituent has been synthesized until now.
Recently, we stabilized the chlorogermylene [Me3SiNC(Ph)-
NSiMe3]GeCl7 (1) by using a bulky amidinate ligꢀand. These
bidentate ligands of general formula R0NC(R)NR0 offer the
possibility of modifying their steric and electronic properties by
changing the organic substituents at the nitrogen atom as well at
the bridging carbon atom. They have already been used in
transition-metal8 and group 14 chemistry (Si,9 Ge,10 Sn,11 Pb12).
The steric hindrance necessary to stabilize low-valent species is
generally governed by the substituents on the nitrogen atom, while
the substituent on the bridging carbon could influence the degree
of substitution. We have found that the presence of both
trimethylsilyl groups on nitrogen and a phenyl group on the
carbon atom induces a perfect selectivity of the metalationreaction
This paper starts with the synthesis of an unknown bis-
(germyl)magnesium species. Then, we report a convenient route
to the metallyl low-coordinate derivatives and their full char-
acterization, including single-crystal X-ray diffraction structure
determinations.
’ RESULTS AND DISCUSSION
The chlorogermanium(II) compound 1 was prepared as
previously described7 by a metathesis reaction between Cl2Ge
3
(dioxane) and lithium amidinate salts. All attempts at nucleo-
philic displacement of chloride with silyllithium or -potassium
reagents ((Me3Si)3SiM, M = Li, K) failed and led to complex
mixtures. Herein, we envisage an alternate route using magne-
sium reagents. The unknown digermylmagnesium derivative 2b
was prepared according to a literature procedure described for
2a13 and 2c.14 The reaction of 2 equiv of potassium germanide
(Me3Si)3GeK15 with magnesium bromide in THF led cleanly to
bis[tris(trimethylsilyl)germyl]magnesium in high yield (70%)
and purity (Scheme 1).
The 1H NMR spectrum reveals that compound 2b was obtained
as an adduct with two THF molecules. Crystals suitable for a single-
crystal X-ray diffraction analysis were grown from a saturated
pentane solution at 4 °C. The molecule crystallizes in the mono-
clinic space group C2/c (Figure 1). This structure very much
resembles that of the silicon analogue.13a The magnesium and the
two germanium atoms have distorted-tetrahedral configurations
with wide Ge(1)ꢀMg(1)ꢀGe(1)0 and Mg(1)ꢀGe(1)ꢀSi(1)
bond angles (130.82(3) and 115.65(2)°, respectively). There are
surprisingly only two compounds reported (VI16 and VII;17
Chart 2) that contain the GeꢀMgꢀGe moiety in the Cambridge
on Cl2Ge (dioxane), giving either mono- or diamidinato com-
3
pounds according to the stoichiometry used. The purpose of this
study is to prepare stable tris(trimethylsilyl), tris(trimethylgermyl),
Received: January 13, 2011
Published: March 23, 2011
r
2011 American Chemical Society
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ARTICLE
Chart 1
Scheme 1
Chart 2
During the preparation of 2c, colorless crystals suitable for
X-ray analysis were obtained from a saturated pentane solution at
4 °C. Compound 2c crystallizes in the monoclinic space group
C2/c (Figure 2). The geometries of the magnesium and tin
atoms are similar to those in the germanium analogue 2b, with
Sn(1)ꢀMg(1)ꢀSn(1)0 and Mg(1)ꢀSn(1)ꢀSi(1) bond angles
of 130.83(8) and 116.1(3)°, respectively. The SnꢀMg bond length
(2.817(1) Å) agrees with the sum of covalent radii (2.80 Å).20 To
the best of our knowledge, this is the first structurally characterized
stannylmagnesium compound.
The reaction of 1 equiv of the magnesium reagent Mg[E-
(SiMe3)3]2 (2; E = Si, Ge, Sn) with 2 equiv of the chlorogermy-
lene 1 in THF at ꢀ78 °C afforded compounds 3aꢀc (Scheme 2).
They were obtained as an air-sensitive solid for 3a (63%
yield) or waxy products for 3b,c (96% and 99% yield,
respectively). It is noteworthy that compounds 3a,c are the
first silylgermylene and stannylgermylene to be synthesized,
isolated, and characterized.
In the solid state, these germanium(II) species are stable under an
inert atmosphere at room temperature for a few days; however, it is
better to store them at low temperature (ꢀ24 °C) for a longer
period. They show a high solubility in organic solvents such as
pentane, hexane, diethyl ether, THF, and toluene. However, they are
less stable in solution at room temperature and their stability
decreases rapidly from 3a to 3c. This probably results from a
decrease in the bulkiness of the E(SiMe3)3 substituent. Indeed, the
steric demand of ꢀM(EMe3)3 (M and E are group 14 elements)
substituents has been gauged by using cone angles, and it was shown
that the cone angles decrease when the MꢀE distance is increased.21
The stannyl substituent, due to the longer SnꢀSi distance, should
Figure 1. ORTEP view of 2b (30% probability level for the thermal
ellipsoids). Hydrogen atoms and solvent (pentane) have been omitted for
clarity. Selected bond distances (Å) and bond angles (deg): Mg(1)ꢀGe-
(1), 2.679(1); Ge(1)ꢀSi(1), 2.390(1); Ge(1)ꢀSi(2), 2.394(1); Ge-
(1)ꢀSi(3), 2.388(1); Mg(1)ꢀO(1), 2.065(2); Ge(1)ꢀMg(1)ꢀGe(1)0,
130.82(3); O(1)ꢀMg(1)ꢀGe(1), 108.13(4); O(1)ꢀMg(1)ꢀGe(1)0,
105.46(4); O(1)0ꢀMg(1)ꢀGe(1), 105.46(4); O(1)0ꢀMg(1)ꢀGe(1)0,
108.13(4); O(1)ꢀMg(1)ꢀO(1)0, 92.07(9).
Structural Database.18 However, owing to the different coordina-
tion numbers (6 and 5, respectively) of the magnesium atom
in these two examples, it is not possible to compare the
GeꢀMgꢀGe bond angles. We can only note that the MgꢀGe
bond length (2.679(1) Å) in 2b lies in the range of those
previously observed (2.727, 2.717 Å for VI16,19 and 2.626(2),
2.766(2) Å for VII17).
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ARTICLE
present a smaller steric hindrance. Another factor, the strength of the
GeꢀE bond, can be also taken into account. The GeꢀE bond
dissociation energies decrease from Si to Sn (297.0 (E = Si), 264.4
(E = Ge) and 230.1 (E = Sn) kJ/mol);22 this explains the easier
dissociation of the GeꢀSn bond.
generally attributed to the nꢀp transition for two-coordinate
germanium(II) species (393ꢀ430 nm)24 and for an iron germy-
lene (428 nm).25 Due to the low stability in solution of
compounds 3, especially during successive dilutions, it was not
possible to conduct an UVꢀvis study.
The molecular structures of germylenes 3aꢀc were unam-
biguously established by X-ray diffraction analysis, as shown in
Figure 3. These molecules are isostructural and crystallize in the
monoclinic P21/c space group. They show the same general
features in the solid state, consisting of a perfect N-chelation of
the amidinato ligand to the germanium center.7 The three-
coordinate germanium atoms exhibit a distorted-pyramidal geo-
metry (sums of the bond angles 274.37° (3a), 273.86° (3b),
269.32° (3c)) with a GeꢀE bond nearly orthogonal to the
GeN2C cycle. The presence of metallyl substituents results in a
slight widening of the GeꢀE(vector)ꢀGeN2C(plane) angle
(111.46° (3a), 111.14° (3b), 108.25° (3c)) in comparison to
that observed in 1 (104.40°). Moreover, the NSiMe3 groups
present an “eclipsed” conformation, probably due to a steric
repulsion between the metallyl ligand and the NSiMe3 unit. The
smallest angle (108.25°) and the most unsymmetrical structure
were observed for 3c, in agreement with a decrease in the steric
strain.
Compounds 3aꢀc have been characterized by spectroscopic
1
methods and X-ray diffraction analysis. The H and 13C NMR
spectra reveal very close resonances for the trimethysilyl moieties
E(SiMe3)3 accompanied by 29Si satellites and similar coupling
1
constants (2JHꢀSi = 6.4ꢀ6.8 Hz and JCꢀSi = 41.4ꢀ43.4 Hz).
Additional 117/119Sn satellites with coupling constants (3JHꢀSn
=
17.7 Hz and 2JCꢀSn = 28.9 Hz, respectively) were observed for 3c.
The same weak variation (from ꢀ2.6 to ꢀ7.7 ppm) was observed
in the 29Si NMR spectra. In compound 3a, the chemical shift of
the Siatom bonded to the Geatomisathigh field (ꢀ111.74ppm).
The 119Sn NMR spectrum of 3c exhibits a signal at ꢀ574 ppm
which is shifted downfield compared to that of the magnesium
precursor Mg[Sn(SiMe3)3]2 (ꢀ828 ppm) and is comparable
with that observed in the stannylstannylene VIII (Chart 3) at
ꢀ502 ppm.23
The UVꢀvis spectrum of 1 only displayed intense absorptions
below 300 nm. We have not observed the higher energy band
With regard to the GeꢀE bond distance, the GeꢀSi distance
(2.525(1) Å) in 3a is similar to that of the silyldigermane
[(Me3Si)3SiGeCl2]2 (2.514(44) Å)21b but longer than that in
normal covalent bonds (∼2.40 Å).26 The GeꢀGe bond length in
3b (2.557(1) Å) is very close to those of the known germylgermy-
lenes (2.544(1) Å for II,6a 2.536(2) Å for III6c). The GeꢀSn
(2.746(1) Å) bond length in 3c is consistent with the GeꢀSn
distances in the germylenestannylene IX (2.721(1) Å)27 or in the
germylstannylene X (2.722(1) Å).6a (Chart 3).
’ CONCLUSION
The first stable silyl, germyl, and stannyl germanium(II)
compounds containing an amidinato ligand have been prepared
by a convenient route using dimetallylmagnesium reagents and
fully characterized, including single-crystal X-ray diffraction
analysis. We are currently investigating the reactivity of these
complexes and their ability to produce nanomaterials by con-
trolled thermolysis.
Figure 2. ORTEP view of 2c (30% probability level for the thermal
ellipsoids). Hydrogen atoms and disorder have been omitted for clarity.
THF and SiMe3 groups are disordered over two positions. THF is shown
with 53% occupancy, and Si1Me3, Si2Me3, and Si3Me3 are shown with
56%, 52%, and 46% occupancy, respectively. Selectedbonddistances (Å)]
and bond angles (deg): Mg(1)ꢀSn(1), 2.817(1); Sn(1)ꢀSi(1),
2.584(14); Sn(1)ꢀSi(2), 2.552(10); Sn(1)ꢀSi(3), 2.521(9); Mg-
(1)ꢀO(1), 2.062(9); Sn(1)ꢀMg(1)ꢀSn(1)0, 130.83(8); O(1)ꢀMg-
(1)ꢀSn(1), 108.8(4); O0(1)ꢀMg(1)ꢀSn(1)0, 108.8(4); O(1)0ꢀMg(1)ꢀ
Sn(1), 105.4(5); O(1)0ꢀMg(1)ꢀSn(1)0, 107.6(6); O(1)ꢀMg(1)ꢀ
O(1)0, 95.8(3).
’ EXPERIMENTAL SECTION
General Procedures. All manipulations with air-sensitive materi-
als were performed under a dry and oxygen-free atmosphere of argon by
using standard Schlenk-line and glovebox techniques. Solvents were
Scheme 2
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Chart 3
purified with the MBRAUN SBS-800 purification system, except for
THF, which was distilled upon Na/benzophenone. NMR spectra were
1
recorded with a Bruker Avance II 300: H (300.13 MHz), 13C (74.48
MHz), 29Si (59.63 MHz), and 119Sn (111.92 MHz) at 298 K. Chemical
shifts are expressed in parts per million with residual solvent signals as
internal reference (1H and 13C{1H}) or with an external reference
(SiMe4 for 29Si and SnMe4 for 119Sn). Mass spectra were measured with
a Hewlett-Packard 5989A in the electron impact mode (70 eV). Melting
points were measured with an Electrothermal capillary apparatus.
UVꢀvis data were recorded on a Hewlett-Packard 8453 instrument.
Figure 3. ORTEP view of compound 3a (30% probability level for the
thermal ellipsoids). Hydrogen atoms have been omitted for clarity. Selected
bond distances (Å) and bond angles (deg): Ge(1)ꢀSi(3), 2.525(1);
Ge(1)ꢀN(1), 2.043(2); Ge(1)ꢀN(2), 2.053(2); Si(3)ꢀSi(4),
2.347(1); Si(3)ꢀSi(5), 2.362(1); Si(3)ꢀSi(6), 2.353(1); N(1)ꢀGe-
(1)ꢀN(2), 65.63(7); N(1)ꢀGe(1)ꢀSi(3), 103.81(5); N(2)ꢀGe-
(1)ꢀSi(3), 104.93(5). Compounds 3b,c are isostructural with 3a and are
not shown. Structural metrics are given as follows. 3b (E = Ge): Ge(1)ꢀE,
2.557(1); Ge(1)ꢀN(1), 2.055(2); Ge(1)ꢀN(2), 2.042(2); EꢀSi(4),
2.382(1); EꢀSi(5), 2.391(1); EꢀSi(6), 2.398(1); N(1)ꢀGe(1)ꢀN(2),
65.66(6); N(1)ꢀGe(1)ꢀE, 104.66(5); N(2)ꢀGe(1)ꢀE, 103.54(5). 3c
(E = Sn): Ge(1)ꢀE, 2.746(1); Ge(1)ꢀN(1), 2.050(2); Ge(1)ꢀN(2),
2.056(2); EꢀSi(4), 2.572(1); EꢀSi(5), 2.583(1); EꢀSi(6), 2.579(1);
N(1)ꢀGe(1)ꢀN(2), 65.36(9); N(1)ꢀGe(1)ꢀE, 101.55(7); N(2)ꢀGe-
(1)ꢀE, 102.41(7).
The compounds [Me3SiNC(Ph)NSiMe3]GeCl,7 Mg[Si(SiMe3)3]2
3
2THF,28 (Me3Si)4Ge,29 and Mg[Sn(SiMe3)3]2 2THF14 were prepared
3
according to literature procedures. Reproducible microanalyses on all
compounds could not be obtained, due to the extreme air sensitivity of
the compounds.
Preparation of 2b. A solution of tetrakis(trimethylsilyl)germane
(5.00 g, 13.66 mmol) in THF (20 mL) was added to a solution of
potassium tert-butoxide (1.53 g, 13.66 mmol) in THF (30 mL). After 1 h
at room temperature, 1.25 g (6.83 mmol) of MgBr2 was added to the
resulting mixture, which was stirred for another 1 h, after which the
solvent was removed under reduced pressure. The residue was extracted
with pentane and filtered through a Celite-layered filter frit. The yellow
solution was reduced to incipient crystallization and stored at 4 °C.
2.01 (NSi). MS m/z (%): 629 [M þ 1]þ (1%); 337 [M ꢀ Ge-
(SiMe3)3]þ (32%); 73 [SiMe3]þ (100%).
Preparation of 3c. By using the same procedure as described for
3a, 0.5 mmol of bis[tris(trimethylsilyl)stannyl]magnesium in THF
(6 mL) and 1.0 mmol of amidinatogermylene in THF (4 mL) gave 3c
as a dark brown waxy product (0.67 g, 99%). Orange crystals were
1
Colorless crystals were obtained (3.59 g, 70%). Mp: 170 °C dec. H
NMR (C6D6): δ (ppm) 0.48 (s, 54 H, SiMe3), 1.33ꢀ1.37 (m, 8 H,
CH2), 3.72ꢀ3.77 (m, 8 H, OCH2). 13C NMR (C6D6): δ (ppm) 5.65
(SiMe3); 24.18 (CH2), 69.02 (OCH2). 29Si NMR (C6D6): δ (ppm)
ꢀ4.73 (SiMe3).
1
obtained from a saturated solution of pentane at ꢀ24 °C. H NMR
(C6D6): δ (ppm) 0.05 (s, 2JHꢀSi = 6.8 Hz, 18H, NSiMe3); 0.58 (s, 2JHꢀSi
= 6.6 Hz, 3JHꢀSn = 17.7 Hz, 27H, Si(SiMe3); 6.92ꢀ7.04 (m, 3H, C6H5);
7.23ꢀ7.26 (m, 2H, C6H5). 13C NMR (C6D6): δ (ppm) 0.95 (NSiMe3);
Preparation of 3a. A solution of bis[tris(trimethylsilyl)silyl]-
magnesium (0.18 g, 0.27 mmol) in THF (3 mL) was added to a solution
of amidinatogermylene (0.20 g, 0.54 mmol) in THF (4 mL) at ꢀ78 °C.
After 45 min, the reaction mixture was warmed to room temperature and
stirred for 20 h. The solvent was removed under vacuum, and the residue
was extracted with pentane (15 mL). After filtration, the filtrate was
concentrated to 1 mL and stored at ꢀ24 °C. Orange crystals of 3a (0.99
g, 63%) were obtained after 8 h. Mp: 89 °C. 1H NMR (C6D6): δ (ppm)
1
5.49 (2JCꢀSn = 28.9 Hz, JCꢀSi = 41.4 Hz, Si(SiMe3)3); 127.30 (Co);
127.94 (Cm); 129.71 (Cp); 138.79 (Ci); 166.57 (C6H5-C). 29Si NMR
(C6D6): δ (ppm) ꢀ6.52 (1J
117/119Sn = 219.4/228.7 Hz, SnSi); 1.89
29Siꢀ
(NSi). 119Sn NMR (C6D6): δ (ppm) ꢀ574.18. MS m/z (%): 601 [M ꢀ
SiMe3]þ (1%); 339 [M ꢀ C6H5C[NSiMe3]2Ge]þ (4%); 73 [SiMe3]þ
(100%).
2
0.05 (s, JHꢀSi = 6.7 Hz, 18H, NSiMe3); 0.51 (s, 2JHꢀSi = 6.4 Hz, 27H,
X-ray Structure Determinations. All data were collected at low
temperature (193(2) K) using an oil-coated shock-cooled crystal on a
Bruker-AXS APEX II diffractometer or a Bruker APEX II Quazar with
IμS, using Mo KR radiation (λ = 0.710 73 Å). The structures were solved
by direct methods (SHELXS-97),30 and all non-hydrogen atoms were
refined anisotropically using the least-squares method31 on F2. Structur-
al data are summarized in Table 1.
Si(SiMe3)3); 6.91ꢀ6.99 (m, 3H, C6H5); 7.28ꢀ7.31 (m, 2H, C6H5). 13
C
NMR (C6D6): δ (ppm) 1.57 (NSiMe3); 4.26 (1JCꢀSi = 43.4 Hz,
Si(SiMe3)3); 127.71 (Co); 127.76 (Cm); 129.23 (Cp); 138.78 (Ci);
169.26 (C6H5-C). 29Si NMR (C6D6): δ (ppm) ꢀ111.74 (GeSi); ꢀ7.72
(Si(SiMe3)3); 2.17 (NSi). MS m/z (%): 584 [M]þ (4%); 569 [M ꢀ Me]þ
(1%); 337 [M ꢀ Si(SiMe3)3]þ (43%); 73 [SiMe3]þ (100%).
Preparation of 3b. By using the same procedure as described for
3a, 0.28 mmol of bis[tris(trimethylsilyl)germyl]magnesium in THF
(4 mL) and 0.54 mmol of amidinatogermylene in THF (4 mL) gave
3b as an orange waxy product (0.33 g, 96%). Yellow crystals were
’ ASSOCIATED CONTENT
Supporting Information. Figures giving 1Hand13C NMR
1
S
obtained from a saturated solution of pentane at ꢀ24 °C. H NMR
b
(C6D6): δ (ppm) 0.05 (s, 18H, NSiMe3); 0.55 (s, 2JHꢀSi = 6.5 Hz, 27H,
spectra of 2b and 3aꢀc and CIF files giving X-ray crystal structure
data for 2b,c and 3aꢀc. This material is available free of charge via
the Internet at http://pubs.acs.org. In addition, CCDC-800058
(2b), -812308 (2c), -800059 (3a), -800060 (3b), and ꢀ800061
(3c) also contain the supplementary crystallographic data for this
Si(SiMe3)3); 6.94ꢀ6.97 (m, 3H, C6H5); 7.27ꢀ7.30 (m, 2H, C6H5). 13
C
NMR (C6D6): δ (ppm) 1.45 (NSiMe3); 4.86 (1JCꢀSi = 43.1 Hz,
Ge(SiMe3)3); 127.56 (Co); 127.79 (Cm); 129.21 (Cp); 138.78 (Ci);
169.26 (C6H5-C). 29Si NMR (C6D6): δ (ppm) ꢀ2.63 (GeSi);
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Table 1. Crystal Data for Compounds 2b,c and 3aꢀc
2b
2c
3a
3b
3c
empirical formula
formula wt
temp (K)
cryst syst
space group
a (Å)
C
26H70Ge2MgO2Si6,C5H12
C26H70MgO2Si6Sn2
845.09
C22H50GeN2Si6
583.77
C22H50Ge2N2Si5
628.31
C22H50GeN2Si5Sn
674.41
825.04
193(2)
193(2)
193(2)
193(2)
193(2)
monoclinic
C2/c
monoclinic
C2/c
monoclinic
P21/c
monoclinic
P21/c
monoclinic
P21/c
18.7428(3)
15.5144(3)
18.7568(3)
90
27.4165(15)
9.8904(5)
19.4619(10)
90
12.0229(2)
15.1530(3)
20.1949(4)
90
12.0398(2)
15.1685(3)
20.2419(4)
90
12.2717(3)
15.2516(4)
20.4014(6)
90
b (Å)
c (Å)
R (deg)
β (deg)
115.691(1)
90
119.091(2)
90
112.2390(10)
90
112.2830(10)
90
112.933(2)
90
γ (deg)
V (Å3)
4914.99(15)
4
4611.6(4)
4
3405.49(11)
4
3420.63(11)
4
3516.59(16)
4
Z
calcd density (g/cm3)
1.115
1.217
1.139
1.22
1.274
abs coeff (mmꢀ1
)
1.404
1.271
1.123
1.945
1.748
F(000)
1776
1752
1248
1320
1392
cryst size (mm)
0.5 ꢁ 0.4 ꢁ 0.22
1.78ꢀ30.50
40 766/7451
0.0308
0.2 ꢁ 0.16 ꢁ 0.04
3.04ꢀ25.35
16 354/4193
0.0317
0.60 ꢁ 0.40 ꢁ 0.05
2.18ꢀ25.35
31 585/6226
0.0388
0.40 ꢁ 0.30 ꢁ 0.10
1.73ꢀ30.68
49 515/10 411
0.052
0.28 ꢁ 0.2 ꢁ 0.16
2.55ꢀ30.38
50 426/10 425
0.0663
θ range for data collecn (deg)
no. of collected/unique rflns
Rint
no. of data/restraints/params
7451/2/201
1.036
4193/232/231
1.040
6226/0/295
1.057
10 411/0/295
0.991
10 425/0/295
0.996
goodness of fit
R indices [I > 2(σ)I]
R1
0.0331
0.0846
0.0501
0.1224
0.0287
0.0677
0.0351
0.0727
0.0397
0.0721
wR2
R indices (all data)
R1
0.0530
0.0620
0.0453
0.0698
0.0852
wR2
0.0971
0.1304
0.0760
0.0832
0.0845
largest diff peak and hole (e Åꢀ3
)
0.872, ꢀ0.461
0.617, ꢀ0.918
0.364, ꢀ0.204
0.483, ꢀ0.286
0.656, ꢀ0.499
paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre at www.ccdc.cam.ac.uk/
data_request/cif.
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’ ACKNOWLEDGMENT
We thank the Centre National de la Recherche Scientifique
(CNRS, ANR-08-BLAN-0105-01) for financial support. D.M. is
grateful to the Ministꢁere de l’Enseignement Supꢀerieur et de la
Recherche for his Ph.D. grant.
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