The binary group 4 azides [Ti(N3)4], [P(C 6H5)4][Ti(N3)5], and [P(C6H5)4]2[Ti(N3) 6] and on linear Ti-N-NN coordination

Article abstract of DOI:10.1002/anie.200454156

Out of line? Theory predicts that [Ti(N₃)₄] should exhibit unprecedented linear Ti-N-NN bond angles as a consequence of the α-N atoms of the azide groups acting as tridentate donors into the empty tetrahedral d⁰ orbitals of a (+IV) Group 4 metal atom. The title compounds were prepared and characterized (see structure). They do not possess linear Ti-N-NN angles because their coordination numbers exceed four.

Full text of DOI:10.1002/anie.200454156

Communications
CH3CN
ƒƒƒƒ!
TiF4 þ 4 ðCH3Þ3SiN3
½TiðN Þ ꢁ þ 4 ðCH Þ SiF
ð1Þ
Azide Complexes
3
4
3 3
Removal of the volatile products (CH3CN, (CH3)3SiF, and
excess (CH3)3SiN3) at ambient temperature results in the
isolation of [Ti(N3)4] as an amorphous orange solid. All
attempts to obtain single crystals by recrystallization or
sublimation were unsuccessful.
The Binary Group 4 Azides [Ti(N3)4],
[P(C6H5)4][Ti(N3)5], and [P(C6H5)4]2[Ti(N3)6] and
ꢀ ꢀ
on Linear Ti N NN Coordination**
Ralf Haiges,* Jerry A. Boatz, Stefan Schneider,
Thorsten Schroer, Muhammed Yousufuddin, and
Karl O. Christe*
As expected for a highly endothermic, covalent polyazide
species, [Ti(N3)4] is very shock sensitive and can explode
violently when touched with a metal spatula or when exposed
to a rapid change in temperature (e.g. freezing with liquid
nitrogen). Its identity was established by the observed
material balance, and vibrational and NMR spectroscopy.
The presence of covalent azido ligands[10–15] is confirmed by
Whereas numerous partially azide-substituted titanium com-
pounds had been reported,[1–7] no binary Group 4 azides were
known. In a recent theoretical study, the Group 4 metal
tetrazides [M(N3)4] (M = Ti, Zr, Hf, Th) were predicted[8] to
be vibrationally stable, exhibiting tetrahedral structures with
14
1
the observed N NMR shifts of d = ꢀ134 ppm (Nb, Dn˜ =
=
2
1
26 Hz), ꢀ195 ppm (Ng, Dn˜ = = 39 Hz) and ꢀ255 ppm (Na,
2
ꢀ ꢀ
unique linear M N NN bond angles (see Figure 1). All the
extremely broad) in DMSO solution at 258C.
The observed Raman and IR spectra of solid [Ti(N3)4] are
shown in Figure 2, and the frequencies and intensities are
listed in the Experimental Section. The experimental vibra-
Figure 1. Predicted tetrahedral structure of free gaseous [Ti(N3)4] with
ꢀ ꢀ
linear Ti N NN bonds.
ꢀ
characterized covalent binary azide species possess bent M
ꢀ
N NN angles.[9] Herein, we report the synthesis, isolation, and
characterization of the first binary Group 4 azide species
[Ti(N3)4], [Ti(N3)5]ꢀ, and [Ti(N3)6]2ꢀ, and provide explana-
ꢀ ꢀ
tions for the observed and predicted Ti N NN bond angles.
The reaction of TiF4 with (CH3)3SiN3 in acetonitrile
solution at room temperature results within minutes in
complete fluoride-azide exchange and yields a clear orange
solution of [Ti(N3)4] according to Equation (1).
Figure 2. IR (top) and Raman (bottom) spectra of solid [Ti(N3)4].
[*] Dr. R. Haiges, Dr. S. Schneider, Dr. T. Schroer, M. Yousufuddin,
Prof. Dr. K. O. Christe
tional spectra deviate significantly from those calculated for
free [Ti(N3)4] at the B3LYP level of theory,[8,16] and resemble
Loker Research Institute
ꢀ ꢀ
those of higher-coordinated compounds with bent M N NN
University of Southern California
Los Angeles, CA 90089-1661 (USA)
Fax: (+1)213-740-6679
bonds. Therefore, the predicted[8] tetrahedral structure with
ꢀ ꢀ
linear Ti N NN bonds could not be confirmed. The discrep-
ancy between the calculated and observed spectra arises from
solid-state effects. The Ti atoms in [Ti(N3)4] are coordinatively
unsaturated seeking higher coordination numbers by the
formation of nitrogen bridges, and crystal-structure data will
be required for a reliable determination of the precise
arrangement of the azido ligands in solid [Ti(N3)4]. The
growing of single crystals for such a study will be difficult
because the compound is hard to recrystallize and does not
sublime without decomposition. The structure determination
of free monomeric [Ti(N3)4] and proof for its predicted
E-mail: haiges@usc.edu
kchriste@usc.edu
Dr. J. A. Boatz, Prof. Dr. K. O. Christe
ERC, Inc. and Space and Missile Propulsion Division
Air Force Research Laboratory (AFRL/PRSP)
10 East Saturn Boulevard, Bldg 8451, Edwards Air Force Base, CA
93524 (USA)
[**] This work was funded by the Defense Advanced Research Projects
Agency, with additional support from the Air Force Office of
Scientific Research and the National Science Foundation. We thank
Prof. G. A. Olah, and Drs. A. Morrish, D. Woodbury, and M. Berman,
for their steady support, and Prof. R. Bau and Dr. R. Wagner for their
help and stimulating discussions.
ꢀ ꢀ
tetrahedral structure with linear Ti N NN bonds will be even
more difficult.
3148
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/anie.200454156
Angew. Chem. Int. Ed. 2004, 43, 3148 –3152

Angewandte
Chemie
¯
The reaction of [Ti(N3)4] with one equivalent of ionic
azides leads to the formation of the [Ti(N3)5]ꢀ ion according to
Equation (2).
[PPh4]2[Ti(N3)6] crystallizes in the triclinic space group P1
and is the first structurally characterized binary titanium
azide. Figure 4 depicts the structure of the [Ti(N3)6]2ꢀ ion that
is only slightly distorted from perfect S6 symmetry. The
CH3CN
½TiðN3Þ4ꢁ þ ½PPh4ꢁN3
½PPh ꢁ½TiðN Þ ꢁ
ð2Þ
ƒƒƒƒ!
4
3 5
The [PPh4][Ti(N3)5] salt was isolated as an orange solid. It
is less sensitive than [Ti(N3)4] and does not explode upon
freezing with liquid nitrogen. It was characterized by its
14N NMR spectrum, and by infrared and Raman spectroscopy.
The observed Raman and IR spectra of [PPh4][Ti(N3)5] are
shown in Figure 3. The frequencies and intensities are listed in
Figure 4. ORTEP drawing of the dianion of the crystal structure of
[PPh4]2[Ti(N3)6]. Thermal ellipsoids are set at 50% probability. Selected
bond lengths [Š] and angles [8]: Ti-N1 2.002(2), Ti-N4 2.019(2), Ti-N7
2.048(2), N1-N2 1.173(2), N2-N3 1.138(2), N4-N5 1.200(2), N5-N6
1.146(3), N7-N8 1.197(2), N8-N9 1.140(3); N1-N2-N3 177.5(2), N4-
N5-N6 177.6(2), N7-N8-N9 176.9(2), N1-Ti-N4 91.68(9), N1-Ti-N7
90.18(7), N4-Ti-N7 89.73(9), Ti-N1-N2 140.64(14), Ti-N4-N5
126.01(13), Ti-N7-N8 129.67(14).
structure consists of an asymmetric TiN9 unit with three azido
groups covalently bonded to give a trigonal pyramidal
coordination environment around the titanium center. The
remaining three azide groups are generated by symmetry
Figure 3. IR (top) and Raman (bottom) spectra of [PPh4][Ti(N3)5]. The
ꢀ
(symmetry operation ꢀx + 2,ꢀy + 1,ꢀz). The average Ti N
bands belonging to the [Ti(N3)5]ꢀ ion are marked with asterisks.
distance of 2.02 Š is in good agreement with the one reported
for [(C5H5)2Ti(N3)2] (2.03(1) Š).[6] In the [PPh4 ]2[Ti(N3)6]2ꢀ
+
the Experimental Section. Three well-resolved 14N NMR
resonances were found the spectrum run in DMSO at 258C.
salt, the anions are well separated by twice as many large
counterions, and the closest Ti···N contacts between neigh-
boring anions are 7.1 Š.
1
It shows a sharp signal at d = ꢀ133 ppm (Dn˜ = = 28 Hz) for the
2
Nb atoms, a medium-sharp resonance at d = ꢀ194 ppm
Further support for the presence of the [Ti(N3)6]2ꢀ ion is
provided by the NMR spectrum. In analogy with [Te(N3)4]
and [Ti(N3)5]ꢀ, the 14N NMR spectra in DMSO show at d =
1
(Dn˜ = = 40 Hz) for the Ng atoms, and a very broad signal at
2
1
d = ꢀ263 ppm (Dn˜ = = 160 Hz) for the Na atoms, in accord
2
1
1
with our expectations for covalently bound azido groups and
ꢀ134 ppm (Nb, Dn˜ = = 30 Hz), ꢀ199 ppm (Ng, Dn˜ = = 35 Hz)
2
2
1
quadrupole relaxation effects. The calculated structure for the
free gaseous anion is that of a trigonal bipyramid, and its
calculated frequencies are listed in the Theoretical Methods
section.
and ꢀ264 ppm (Na, Dn˜ = = 165 Hz) resonances characteristic
2
for covalent azides.
The observed Raman and IR spectra of [PPh4]2[Ti(N3)6]
are shown in Figure 5, and the observed frequencies and
intensities are listed in the experimental section. Assignments
of the observed spectra were made by comparison with those
calculated at the B3LYP/SBKJC + (d) level of theory[16] and
are given in the Experimental Section.
By reaction of [Ti(N3)4] with two equivalents of ionic
azide, the [Ti(N3)6]2ꢀ ion is formed [Eq. (3)].
CH3 CN
ƒƒƒƒ!
½TiðN3Þ4ꢁ þ 2 ½PPh4ꢁN3
½PPh ꢁ ½TiðN Þ ꢁ
ð3Þ
4
2
3 6
ꢀ ꢀ
Although the occurrence of linear Ti N NN bond angles
[PPh4]2[Ti(N3)6] was isolated as an orange solid and is
stable at room temperature. Because of the presence of two
large counterions, it is much less sensitive and explosive than
[Ti(N3)4]. It can even be heated to its melting point at 1918C
without any signs of decomposition. The compound was
characterized by its crystal structure,[17] and vibrational and
14N NMR spectroscopy. Single crystals were obtained from a
solution in CH3CN.
could not be confirmed experimentally, we have confirmed by
independent computations the correctness of the previous
predictions[8] for free gaseous [Ti(N3)4]. Furthermore, it was
shown, both computationally and experimentally by our
crystal structure determination, that in higher coordinated
binary titanium azide species, such as [Ti(N3)6]2ꢀ, and in the
ꢀ ꢀ
main-group tetra-azides M(N3)4 (M = Si, Ge, Sn) the M N
NN bond angles are normal and strongly bent. It was also
Angew. Chem. Int. Ed. 2004, 43, 3148 –3152
www.angewandte.org
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3149

Communications
Figure 6. Crystal structure of [Zr(BH4)4] demonstrating the perfect
geometrical overlap of a tridentate donor into the empty d0 orbitals of
a (+iv) Group 4 transition-metal atom.[19]
Figure 5. IR (top) and Raman (bottom) spectra of [PPh4]2[Ti(N3)6]. The
bands belonging to the [Ti(N3)6]2ꢀ ion are marked with asterisks.
Experimental Section
Caution! Covalent azides are potentially hazardous and can decom-
pose explosively under various conditions! They should be handled
ꢀ ꢀ
shown that the occurrence of linear M N NN bond angles
should not be limited to Group 4 tetra-azides, but might also
occur in compounds, such as [Fe(N3)2].[18] Normal coordinate
analyses were carried out for the binary Ti-azides of this study
and showed that the modes owing to the azido ligands were
highly characteristic, while those of the [TiNn] skeletal modes
were strongly mixed and, therefore, are not reported herein.
However, the [TiNn] stretching-mode clusters clearly exhibit
the frequency decreases expected for increasing polarities of
only on
a scale of less than 2 mmol with appropriate safety
precautions (safety shields, safety glasses, face shields, leather
gloves, protective clothing, such as leather suits, and ear plugs).
Teflon containers should be used, whenever possible, to avoid
hazardous fragmentation. Pure [Ti(N3)4] has to be cooled or heated
carefully and slowly. A sample at ambient temperature must not be
cooled directly with liquid nitrogen. Doing so can result in violent
explosions. Handle the materials, whenever possible, in solution to
avoid detonation propagation. The use of large inert counterions as
spacers and the formation of anions which increases the partial
negative charges on the terminal Ng atoms and thereby reduce the
ꢀ
the Ti N bonds with increasing negative formal charges.
Thus, the range of the [TiNn] stretching modes decreases from
472–371 cmꢀ1 in [Ti(N3)4] to 448–355 cmꢀ1 in [Ti(N3)5]ꢀ and
398–307 cmꢀ1 in [Ti(N3)6]2ꢀ.
In the previous theoretical paper on the linearity of the
M N NN bond angles for M = Ti, Zr, and Hf, the linearity of
ꢀ
Nb Ng triple bond character, facilitate the manipulation of these
materials. Ignoring safety precautions can lead to serious injuries.
All reactions were carried out in Teflon-FEP (FEP = fluoroethy-
lene–propylene copolymer) ampules that were closed by stainless
steel valves. Volatile materials were handled in a Pyrex glass vacuum
line. All Teflon reaction vessels were passivated with ClF3 prior to use.
Nonvolatile materials were handled in the dry argon atmosphere of a
glove box.
ꢀ ꢀ
ꢀ ꢀ ꢀ
the M-N-NN angles was explained by M N N N conjuga-
tion.[8] In our opinion, the linearity of the M-N-NN angles is
due to a nearly ideal overlap between the three valence
electron pairs on the a-nitrogen atoms of the azide ligands
and the lobes of the d orbitals on the central metal atom.
Because the d orbitals of the (+ iv) central metal atoms are
unoccupied, the three valence electron pairs of the a-nitrogen
atoms can donate electron density equally into three lobes of
the empty d orbitals resulting in the a-nitrogen acting as a
tridentate donor ligand. The symmetry of the central axes of
these d orbitals is tetrahedral. Therefore, this tridentate type
of overlap is possible only for the tetracoordinate azide
complexes of Group 4 transition metals with d0 configura-
tions. For other coordination numbers or electron configu-
rations, the a-nitrogen atoms act usually as monodentate
donors with only one pair donating and two sterically active
Raman spectra were recorded at ꢀ808C in the range 4000–
80 cmꢀ1 on a Bruker Equinox 55 FT-RA spectrophotometer using a
Nd-YAG laser at 1064 nm with power levels of less than 200 mW.
Pyrex melting point tubes that were baked out at 3008C for 48 h at
10 mTorr vacuum or Teflon-FEP tubes with stainless steel valves that
were passivated with ClF3 were used as sample containers. Infrared
spectra were recorded in the range 4000–400 cmꢀ1 on a Midac,
M Series, FT-IR spectrometer using KBr or AgCl pellets. The pellets
were prepared inside the glove-box using an Econo press (Barnes
Engineering Co.).
14N NMR spectra were recorded unlocked at 36.13 MHz on a
Bruker AMX500 spectrometer using solutions of the compounds in
DMSO in sealed standard glass tubes. Neat CH3NO2 (0.00 ppm) was
used as the external reference.
The starting materials TiF4 and [P(C6H5)4]I(both from Aldrich)
were used without further purification. (CH3)3SiN3 (Aldrich) was
purified by fractional condensation prior to use. Solvents were dried
by standard methods and freshly distilled prior to use. [P(C6H5)4]N3
was prepared from [P(C6H5)4]Iand AgN 3.
[Ti(N3)4]: A sample of TiF4 (0.96 mmol) was loaded into a Teflon-
FEP ampule, followed by the addition of CH3CN (3 mL) and
(CH3)3SiN3 (4.32 mmol) in vacuo at ꢀ1968C. The mixture was
allowed to warm to room temperature. Within minutes, the mixture
turned yellow, and the color intensified while the reaction proceeded.
ꢀ
free valence electron pairs, thus resulting in strongly bent M
N NN bond angles. An excellent example for the validity of
ꢀ
our explanation is the known crystal structure of [Zr(BH4)4]
(see Figure 6) involving a (+ iv) Group 4 d0 transition-metal
central atom and for h3-BH4 ligands.[19] Another example for a
special geometry, dictated by the empty d0 orbitals of a (+ iv)
Group 4 transition metal is [Ti(O2ClO2)4] in which the
perchlorato groups act as bidentate ligands.[20]
3150
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
Angew. Chem. Int. Ed. 2004, 43, 3148 –3152

Angewandte
Chemie
After 1 hour, all volatile material was pumped off, leaving behind an
orange solid (0.20 g, weight calculated for 0.96 mmol [Ti(N3)4] =
0.21 g). The obtained orange solid was characterized by vibrational
and NMR spectroscopy. IR (AgCl): n˜ = 2141(vs), 2093(vs), 2051(vs)
(nasN3), 1376(s, br), 1253(s) (nsN3), 684(s) ,668(s), 665(s), 575(m),
561(m) (dN3), 458(w) cmꢀ1 (nTiNn). Raman (50 mW, ꢀ808C): n˜ =
2160(10.0), 2141(4.0), 2108(2.9), 2100(1.8), 2079(2.8) (nasN3),
1407(1.0), 1385(0.2), 1366(0.2), 1283(0.3), 1269(0.3) (nsN3), 671(0.3),
574(0.4) (dN3), 472(9.6), 454(4.9), 391(2.2), 371(1.8) (all nTiNn),
310(1.7), 270 (1.7), 227 (0.8), 168 (2.1), 135(2.0) cmꢀ1. For NMR
spectroscopy data see text.
(8.8) [0.0], 604 (3.9) [0.1], 599 (9.4) [0.1], 599 (9.9) [0.0], 598 (0.6)
[0.4], 409 (675) [0.4], 404 (540) [0.9], 404 (601) [1.2], 364 (1.2) [78],
284 (0.2) [11], 280 (0.1) [8.4], 264 (3.0) [7.0], 261 (5.4) [0.2], 250 (3.5)
[6.1], 235 (3.6) [8.7], 209 (0.1) [19], 205 (0.2) [7.4], 151 (1.2) [25], 150
(0.2) [15], 142 (0.4) [25], 78 (1.9) [2.2], 63 (0.1) [11], 62 (2.7) [0.4], 44
(2.2) [20], 40 (0.5) [28], 39 (0.0) [14], 33 (1.0) [28], 28 (2.0) [2.7], 23
(0.1) [13], 21 (1.2) [4.1], 16 (0. 1) [4.5], 15 (1.2) [6.8].
Received: March 2, 2004 [Z54156]
Published Online: May 19, 2004
[PPh4][Ti(N3)5]. A solution of [Ti(N3)4] (0.5 mmol) in CH3CN
(3 mL) was added to a mixture of [PPh4]N3 (0.5 mmL) in CH3CN
(2 mL) at ꢀ648C. The reaction mixture was warmed to ambient
temperature where it formed a clear orange solution. After 2 h, all
volatiles were slowly removed in a dynamic vacuum at 208C, leaving
behind an orange solid (0.450 g, weight calculated for 0.5 mmol [PPh4]
[Ti(N3)5] = 0.443 g). IR of [Ti(N3)5]ꢀ (KBr): n˜ = 2100(vs), 2070(vs),
2058(vs) (nasN3), 1373(m), 1356(s), 1320(s) (nsN3), 621(m), 595(w),
591(w), 580(vw) (dN3), 448(w), 440(vw) cmꢀ1 (both nTiNn). Raman of
[Ti(N3)5]ꢀ (50 mW, ꢀ808C): n˜ = 2133(10.0), 2110(4.4), 2083(2.9),
2070(2.2) (nasN3), 1367(0.3), 1342(0.3), 1325(0.2), 1314(0.1) (nsN3),
623(0.2), 608(0.1), 597(0.1) (dN3), 445(3.4), 438(1.0), 412(0.6),
398(2.2), 363(0.9), 355(0.7) (all nTiNn), 306(0.9), 245(1.3), 210(0.9),
174(1.6) cmꢀ1. For NMR spectroscopy data see text.
Keywords: azides · density functional calculations · structure
elucidation · titanium · vibrational spectroscopy
.
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[PPh4]2[Ti(N3)6]. A solution of [Ti(N3)4] (0.5 mmol) in CH3CN
(3 mL) was added to a mixture of [PPh4]N3 (1.0 mmL) in CH3CN
(2 mL) at ꢀ648C. The reaction mixture was warmed to ambient
temperature and an orange precipitate was formed. After 8 h, all
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[PPh4]2[Ti(N3)6] = 0.778 g). Single crystals were grown from a solution
in CH3CN by slow evaporation in a dynamic vacuum. IR of [Ti(N3)6]2ꢀ
(KBr): n˜ = 2109(m), 2061(vs), 2041(vs) (nasN3), 1356(s), 1322(s)
(nsN3), 622(m), 615(m), 595(w) cmꢀ1 (dN3). Raman of [Ti(N3)6]2ꢀ
(50 mW, ꢀ908C) n˜ = 2110(10.0), 2063(1.2), 2038(0.3) (nasN3),
1366(0.7), 1341(0.7), 1325(0.4) (nsN3), 631(0.2), 622(0.3), 608(0.3)
(dN3), 398(5.4), 316(1.1), 307(1.1) (nTiNn), 246(1.3), 210 (1.8),
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:
Theoretical Methods: The molecular structures and harmonic
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frequencies [cmꢀ1] and (infrared, kmmolꢀ1) and [Raman, Š4 amuꢀ1
]
intensities for [Ti(N3)4]: 2293 (0.0) [794], 2251 (5737) [1022], 1497
(0.0) [4.5], 1475 (2005) [48], 573 (110) [0.3], 571 (0.0) [0.3], 569 (0.0)
[0.0], 516 (933) [67], 373 (0.0) [103], 192 (17) [7.3], 167 (0.0) [14.0],
14.8 (0.0) [50], 14.0 (0.0) [71]. [Ti(N3)5]ꢀ (pseudo-trigonal bipyramid
of C1 symmetry): 2248 (72) [751], 2212 (3406) [42], 2206 (1441) [160],
2202 (1836) [77], 2200 (142) [278], 1445 (48) [28], 1433 (390) [4.3],
1415 (180) [16], 1404 (174) [17], 1402 (384) [6.9], 620 (50) [0.3], 618
(18) [0.8], 615 (57) [0.7], 602 (13) [1.2], 601 (12) [0.1], 599 (10) [0.7],
595 (12) [0.8], 594 (1.0) [0.4], 584 (19) [0.9], 577 (43) [0.4], 487 (325)
[1.2], 475 (347) [0.7], 456 (534) [1.8], 401 (1.2) [77], 322 (0.3) [4.2], 263
(2.6) [8.6], 252 (5.3) [7.3], 231 (3.9) [7.2], 228 (0.8) [19], 200 (0.7) [8.1],
131 (2.8) [4.8], 103 (1.1) [11], 94 (0.2) [12], 91 (0.5) [7.1], 66 (0.1) [1.9],
54 (1.1) [4.6], 40 (0.1) [18], 36 (0.1) [22], 33 (0.6) [18], 30 (0.2) [19], 24
(1.1) [2.4], 19 (0.7) [8.1]. [Ti(N3)6]2ꢀ: 2234 (1.4) [798], 2186 (3723)
[9.5], 2185 (2778) [90], 2180 (2776) [74], 2168 (25) [180], 2167 (468)
[134], 1438 (3.6) [70], 1429 (161) [18], 1428 (19) [46], 1425 (182) [23],
1424 (186) [24], 1424 (165) [17], 626 (4.1) [5.9], 622 (34) [1.2], 621 (39)
[2.8], 620 (59) [3.9], 620 (0.0) [2.9], 616 (3.1) [3.9], 608 (5.2) [0.2], 605
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Communications
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[17] Crystal data for C48H40N18P2Ti: Mr = 978.82, triclinic, space
¯
group P1, a = 10.106(11), b = 10.272(16), c = 12.348(13) Š, a =
88.029(18), b = 75.077(15), g = 70.298(18)8, V= 1164(2) Š3,
F(000) = 506, 1calcd (Z = 1) = 1.396 gcmꢀ3
,
m = 0.310 mmꢀ1
,
approximate crystal dimensions 0.65 ” 0.52 ” 0.19 mm3,
q
range = 1.71–27.678, MoKa (l = 0.71073 Š), T= 153 K, 7267
measured data (Bruker 3-circle, SMART APEX CCD with c-
axis fixed at 54.748, using the SMART V 5.625 program, Bruker
AXS: Madison, WI, 2001), of which 5057 (Rint = 0.0164) unique.
Lorentz and polarization correction (SAINT V 6.22 program,
Bruker AXS: Madison, WI, 2001), absorption correction
(SADABS program, Bruker AXS: Madison, WI, 2001). Struc-
ture solution by direct methods (SHELXTL 5.10, Bruker AXS:
Madison, WI, 2000), full-matrix least-squares refinement on F2,
data to parameters ratio: 16.2:1, final R indices [I > 2s(I)] : R1 =
0.0404, wR2 = 0.1050, R1 = 0.0476, wR2 = 0.1099 (all data), GOF
on F2 = 1.030. CCDC 232521 contains the supplementary crys-
tallographic data for this paper. These data can be obtained free
of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or
from the Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB21EZ, UK; fax: (+ 44)1223-336-033; or
deposit@ccdc.cam.ac.uk).
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3152
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
Angew. Chem. Int. Ed. 2004, 43, 3148 –3152