High-valent molybdenum imido complexes with tethered olefins

Article abstract of DOI:10.1002/zaac.200500508

Against the background of the (propene)Mo(=O)(=NH) and (allyl)Mo(=O)(=NH) surface species suggested as intermediates of the SOHIO process the potential of H₂N-C₆H₄-CH₂-CH=CH-CH₃, (I), for the introduction of chelating imido/olefin or imido/allyl ligands at highvalent Mo centres was tested. Reaction of I with Na₂[MoO ₄] and trimethylchlorosilane yielded [Cl₂Mo(=N-C ₆H₄-CH₂-CH=CH-CH₃)₂(dme)] (1), containing pendant olefinic arms. All attempts to introduce the olefin into the coordination sphere of the Mo centre failed. The same observation was made with [Cl₂Mo(=O)(=N-C₆H₄-CH₂-CH= CH-CH₃)(dme)] (2), synthesised via a commutation reaction from 1 and [(dme)Cl₂Mo(=O)₂]. Reaction of three equivalents of I with [CpMoCl_4′] yields [CpCl₂Mo(=N-C ₆H₄-CH₂-CH=CH-CH₃)], (3), again with a pendant olefin arm; the products of experiments aiming at coordinating it to the Mo atom eluded isolation. I thus does not seem suitable for the synthesis of complexes with imido/olefin or imido/allyl ligands. However, products 1-3, (two of which (1, 3) were also characterised by single crystal X-ray diffraction) are nevertheless interesting, e.g., with respect to the grafting of molybdenum complexes on the surfaces of solid supports to obtain heterogeneous oxidation catalysts.

Full text of DOI:10.1002/zaac.200500508

DOI: 10.1002/zaac.200500508
High-valent Molybdenum Imido Complexes with Tethered Olefins
Inke Siewert, Christian Limberg,* and Burkhard Ziemer
Berlin Humboldt-Universität zu Berlin, Institut für Chemie
Received December 21st, 2005.
Dedicated to Professor Hansgeorg Schnöckel on the Occasion of his 65th Birthday
Abstract. Against the background of the (propene)Mo(ϭO)(ϭNH)
and (allyl)Mo(ϭO)(ϭNH) surface species suggested as intermedi-
ates of the SOHIO process the potential of H2NϪC6H4ϪCH2Ϫ
CHϭCHϪCH3, (I), for the introduction of chelating imido/olefin
or imido/allyl ligands at highvalent Mo centres was tested. Reac-
tion of I with Na2[MoO4] and trimethylchlorosilane yielded
[Cl2Mo(ϭNϪC6H4ϪCH2ϪCHϭCHϪCH3)2(dme)] (1), containing
pendant olefinic arms. All attempts to introduce the olefin into the
coordination sphere of the Mo centre failed. The same observation
[CpMoCl4Ј] yields [CpCl2Mo(ϭNϪC6H4ϪCH2ϪCHϭCHϪCH3)],
(3), again with a pendant olefin arm; the products of experiments
aiming at coordinating it to the Mo atom eluded isolation. I thus
does not seem suitable for the synthesis of complexes with imido/
olefin or imido/allyl ligands. However, products 1Ϫ3, (two of which
(1, 3) were also characterised by single crystal X-ray diffraction)
are nevertheless interesting, e.g., with respect to the grafting of mo-
lybdenum complexes on the surfaces of solid supports to obtain
heterogeneous oxidation catalysts.
was
made
with
[Cl2Mo(ϭO)(ϭNϪC6H4ϪCH2ϪCHϭ
CHϪCH3)(dme)] (2), synthesised via a commutation reaction from
1 and[(dme)Cl2Mo(ϭO)2]. Reaction of three equivalents of I with
Keywords: Molybdenum; Imido complexes; Crystal structures;
Olefin tether; SOHIO process
Introduction
beside each other it would be interesting to investigate the
synthesis of complexes containing OϭMoϭNR units that
are capable of binding olefin or allyl ligands. As the oxo
ligand therein makes the metal centre “harder” in compari-
son to a situation where the first imido ligand is joined by
a Cp ligand or a second imido ligand (vide supra), it should
be more difficult to coordinate the “soft” organic ligands.
Recently, we succeeded in synthesizing an allylmolyb-
denum(IV) complex (a very rare example of a π-allyl-Mo
complex where the metal centre is in a comparatively high
oxidation state and additionally binds hard chloro ligands)
via tethering of the allyl ligand to a coordinating donor
function [5]. Hence, the question arose whether allyl and/or
olefin ligands could be stabilized in the coordination sphere
of oxo/imido molybdenum complex metal fragments, when
these organic functions are tethered to the imido ligand.
Here we described the results obtained in that context.
The acrylonitrile synthesis via propene oxidation in the
presence of ammonia on bismuthmolybdate catalysts
(SOHIO process) [1] is proposed to proceed via surface in-
termediates with π-olefin and π-allyl ligands bound to high-
valent MoV/VI oxo/imido moieties [2]. These intermediates
are considered to be very short-lived, as the combination of
a “soft” π-olefin or π-allyl ligand with a “hard” molyb-
denum oxo/imido unit is naturally unstable, and, moreover,
metal atoms in high oxidation states are not capable of stab-
ilizing metal-ligand π-bonds by efficient backbonding.
This conception stimulates research with the aim of pre-
paring molecular compounds that are modelled on this situ-
ation to see how these behave. Green et al. were able to
prepare a [CpMoIV(ϭNR)(π-allyl)] complex [3]. Sunder-
meyer et al. reported the synthesis of the compound [(t-
BuNϭ)2MoVI(allyl)2], which could not be characterized
structurally, but spectroscopic investigations hinted to a π-
coordination of one of the allyl ligands [4]. Since the bis-
muthmolybdate surface during the SOHIO process is sug-
gested to contain both oxo and imido ligands at MoVI sites
Results and Discussion
First of all it had to be decided concerning the length of the
tether between the potential imido ligand and the olefinic
function (being substituted by an additional methyl group
to grant the possibility of a later conversion to an allylic
unit). As in the previous work [5] it had proved reasonable
to integrate an arylic unit into the tether to establish at least
some rigidity, and as moreover MoϭNϪAr complexes are
a well studied class of compounds [6] we came down to a
decision between the ligands A and B (Chart 1).
* Prof. Dr. C. Limberg
Humboldt-Universität zu Berlin
Institut für Chemie
Brook-Taylor-Str. 2
D-12489 Berlin
Fax: 030-20936966
E-mail christian.limberg@chemie.hu-berlin.de
1078
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Molybdenum Imido Complexes with Tethered Olefins
Chart 1 Potentially chelating imido/olefin ligands.
The results of DFT modelling studies for several situ-
ations gave rise to a choice in favour of A. Usually imido
ligands are prepared starting form the corresponding
amines which are reacted with MoϭO precursors under for-
mal elimination of water. Accordingly, 2-(nbut-2-en-1-yl)an-
iline (I), was synthesized starting from aniline and 3-chloro-
1-butene which in the presence of Na2CO3 react at 100 °C
to give a mixture of two different amines (Eq. (1)); sub-
sequent treatment with sulfuric acid and work up yields
pure I in form of a trans/cis mixture (7.2 : 1) [7].
Figure 1 Molecular structure of complex 1. All hydrogen atoms
˚
were omitted for clarity. Selected bond distances /A and angles /°:
MoϪN ϭ 1.74 (2), MoϪCl1 ϭ 2.41 (1), MoϪCl2 ϭ 2.41 (1),
NϪC5 ϭ 1.36(2), MoϪNϪC5 ϭ 167 (2).
As cis/trans isomerizations can be expected to occur in
the presence of a metal centre anyway [5], the mixture was
employed as such for subsequent reactions.
We started our investigation with diimido complexes
whose synthesis is more facile than the one of oxo/imido
complexes and which were envisioned to provide pre-
liminary information concerning the potential of the
strategy and the properties of ligand A. In analogy to the
synthesis of molybdenumdiimido complexes reported
previously by Schrock et al. [8] Na2[MoO4] was reacted
The arrangement of the ligands around the metal atom
can be described as distorted octahedral. The MoϪNϪCar
units are almost linear (167°) which points to a singnificant
MoϵN triple bond character. Accordingly, the average
˚
MoϪN bond distance is with 1.74 A similar to comparable
imido complexes containing a MoϵN triple bond [9].
In order to introduce the olefinic units of the pendant
arms into the coordination sphere of the Mo atoms several
experiments were performed. First of all it seemed desirable
to replace the chloride by methyl ligands [10], as a sub-
sequent treatment with B(C6F5)3 would then lead to a cat-
ionic complex [11], where the olefinic function would find
sufficient room at the metal atoms to coordinate (Eq. (3)).
Surprisingly, 1 behaved inert in the presence of two equiv-
alents of MeMgI, while four equivalents led to a slow re-
duction. 1 was thus reacted directly with excessive B(C6F5)3
and after work up the product was investigated NMR spec-
troscopically. The signals belonging to the dimethoxyethane
ligand had vanished (probably due to acid/base reaction
with the borane and precipitation), and there was only one
set of signals for the ligand A. However, comparison of the
chemical shifts with those of other d0-transition metal π-
olefin complexes did not hint to a coordination of the olef-
inic units to the metal atom [12].
with
I and trimethylchlorosilane to give [Cl2Mo(ϭ
NϪC6H4ϪCH2ϪCHϭCHϪCH3)2(dme)] (1) in 83 % yield
after work up (Eq. (2)).
Starting from an isomeric mixture of I of course the for-
mation of three stereoisomers of 1 could be expected; ac-
1
cording to H NMR spectroscopic investigations the trans
: cis ratio for the ligands altogether amounted to 5.3 : 1, but
it was not possible to determine the ratio of the individual
stereoisomers of 1. Overlayering a solution of 1 in dichloro-
methane with pentane at Ϫ30 °C led to disordered crystals
that were suitable for a rough crystal X-ray analysis. The
result is shown in Figure 1, which illustrates one compound
of the superposition structure. The ligands A display an all
trans configuration.
Z. Anorg. Allg. Chem. 2006, 1078Ϫ1082
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1079

I. Siewert, C. Limberg, B. Ziemer
Several experiments were carried out in this respect. Simi-
lar systems eliminated HCl after photochemical activation
[5], but 2 behaved inert under these conditions. In the next
step it was tried to induce the elimination of HCl by adding
a suitable (low nucleophilicity, low oxophilicity and hardly
any reducing properties) base. However, neither LiNMe2
(decomposition of 2) nor NaN(SiMe3)2 led to the desired
product, and with K2CO3 no conversion was observed.
In order to see whether the d0 configuration or the
specific coordination of the starting materials chosen pose
the problems preventing the ligand A from adopting a chel-
ating binding mode, we finally prepared the cyclopen-
tadienyl MoV complex
[CpCl2MoϭNϪC6H4ϪCH2ϪCHϭCHϪCH3] (3), via re-
action of [CpMoCl4] with 3 eq. I (Eq. (6)) [15].
Despite this discouraging result we envisionened the
syntheses of a mixed oxo/imido molybdenum(VI) complex
with a pendant olefin arm. This goal seemed particularly
attractive for the following reason: the SOHIO process is
proposed to proceed via OϭMoVIϭNH units to which then
propene is coordinated before the first H atom abstraction
occurs.
A
complex containing the OϭMoVIϭ
NϪC6H4ϪCH2ϪCHϭCHϪCH3 moiety would thus con-
tain all “ingredients” to model such a situation. We
therefore attempted the synthesis of [Cl2Mo(ϭO)-
(ϭNϪC6H4ϪCH2ϪCHϭCHϪCH3)(dme)] (2), similarly to
the synthesis of 1 with only one equivalent of I [compare
13]. This experiment was successful, however, many
unidentified by-products formed, which made the work up
difficult, so that the yield of 2 was quite low via this
procedure. An alternative route reported to provide molyb-
denum oxo imido compounds [14] proved to be more suit-
able: the dioxo complex [(dme)Cl2Mo(ϭO)2] was reacted
with the diimido compound 1 to give 2 in a commutation
reaction (Eq. 4) with an isolated yield of 36 %.
After work up 3 was obtained in 90 % yield, and it was
characterised by IR spectroscopy, elemental analysis as well
as by single crystal X-ray diffraction. The result is shown
in Figure 2.
The molecular structure can be described as a three-
legged piano-stool. The MoϪNϪC6 angle of 163.2° and
˚
the MoϪN bond distance of 1.735 A again point to a
MoϵN triple bond, and thus to a 17 electron configuration.
Again attempts were made to replace the chloride by methyl
ligands via reaction with two equivalents of MeMgI. A
colour change from dark purple to dark green could be
noticed, and cooling of a pentane solution yielded a dark
green solid which, however, proved to decompose rapidly
during work up and thus eluded isolation and characteriz-
1
2 was fully characterized, and according to the H NMR
spectrum the trans/cis ratio within the ligand A amounts to
10.3 : 1. In principle 2 is ideally suited for experiments
along the lines described above, i.e. abstraction of an
anionic ligand to coordinate the olefinic function of A or
even additional proton abstraction (Ǟaltogether HCl elim-
ination) to convert it into an allyl ligand (Eq. 5).
Figure 2 Molecular structure of complex 3. All hydrogen atoms
˚
were omitted for clarity. Selected bond distances /A and angles /°:
MoϪN ϭ 1.735(3), MoϪCl2 ϭ 2.376(1), MoϪCl1 ϭ 2.351 (1),
NϪC6 ϭ 1.393(4), MoϪNϪC6 ϭ 163.2 (2).
1080
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Z. Anorg. Allg. Chem. 2006, 1078Ϫ1082

Molybdenum Imido Complexes with Tethered Olefins
ation. Hence, in an additional experiment the dark green
intermediate was reacted in situ with B(C6F5)3 leading to a
further colour change to red-brown, but yet again the
product was highly sensitive and could not be identified.
[Mo(NC6H4CH2CHCHCH3)2Cl2(dme)] (1)
To a stirred suspension of 510 mg (2.48 mmol) sodium molybdate
in 90 ml dme 730 mg (4.96 mmol) (nbut-2-en-1-yl)amine I and
1.39 ml (9.9 mmol) triethylamine each in 10 ml dme were added.
Finally, 2.53 ml (19.8 mmol) chlorotrimethylsilane was added over
a period of 5 min, and the resulting reaction mixture was heated
18h at 80 °C. The red solution was cooled to room temperature
and filtered to remove the precipitate. The volatile components
were removed from the filtrate in vacuo, and the solid residue was
recrystallized from toluene/pentane at Ϫ30 °C to yield 1.125 g
(2.05 mmol, 83 %) dark red crystals.
Conclusions
Three molybdenum complexes containing the ligand A have
been prepared and fully characterized: a diimido complex,
1, a cyclopentadienylimido complex 3, and an oxo/imido
compound, 2. 2 is of special interest since it has all pre-
requisites to model the first step of the SOHIO process, the
binding of an olefin to a OϭMoϭNH unit with subsequent
formation of an allylic ligand. However, the ligand A is ob-
viously not suited to bind to a MoVI atom in a chelating
allyl/Nϭ or olefin/Nϭ mode, especially with the back-
ground that the existence of a diimidomolybdenum(π-allyl)
complex has been reported [4] so that electronic problems
can be excluded. The reasons for that are not quite clear,
possibly the tether is chosen to short. Nevertheless, the
compounds 1-3 are also interesting in a different context:
the grafting of molybdenum complexes on the surfaces of
solid supports for the preparation of heterogeneous oxi-
dation catalysts [16]. Only recently many attempts were
made to fix CpMo complex metal fragments on surfaces
via the co-ligands, in order to obtain heterogeneous epoxid-
ation catalysts [16], and the olefinic function in A should
allow for a facile grafting (leaching should be minimal as
the imido end forms a very strong bond to molybdenum).
In the same context it has to be mentioned that (RNϭ)2M
compounds were shown to represent active polymerization
catalysts after activation [17], and again the olefinic func-
tions in 1 could represent a starting point for grafting.
Elemental analysis for C24H32Cl2MoN2O2 (547.4); C 51.58 (calc.
52.66); H 5.86 (5.89); N 5.12 (5.12) %. Concerning the deviation
of the C value compare [8].
1H-NMR (CD3CN) δ ϭ 1.58 [d, J(H,H)ϭ5.2 Hz, 3H, CHϪCH3], 3.41 [d,
J(H,H)ϭ6.0 Hz, 2H, ArylϪCH2], 3.56 [s, 3H, OϪCH3], 3.72 [s, 2H,
OϪCH2], 5.52 [m, 2H, CHϪCHϪCH3], 7.02 [td, J(H,H)ϭ5.7, 0.9 Hz, 1H,
CHar], 7.12 [m, 2H, CHar], 7.21 [d, J(H,H)ϭ6.1 Hz, 1H, CHar].
13C{1H}؊NMR (CD3CN) δ ϭ 18.0 [CHϪCH3], 35.1 [ArylϪCH2], 61.6 [br.,
OϪCH3], 72.3 [OϪCH2], 125.5 [CHϪCH3], 127.1 [CHar], 127.3 [CHar], 127.9
[CHar], 129.7 [CHar], 130.5 [CHϪCHϪCH3], 134.1 [CϪCH2], 156.3 [CϪN].
IR /cmϪ1: ν˜ ϭ 3035, 3019 (vw), 2936 (w), 2851 (vw), 1584 (w), 1557 (w),
1491 (vw), 1468 (m), 1441 (s), 1375 (vw), 1285 (s), 1188 (m), 1156 (vw), 1109
(m), 1088 (s), 1047 (vs), 1006 (m), 973 (vs), 858 (vs), 826 (m), 798 (w), 764
(vs), 670 (w), 602 (vw).
[MoO(NC6H4CH2CHCHCH3)Cl2(dme)] (2)
1. To a stirred suspension of 1.399 g (6.8 mmol) sodium molybdate
in 90 ml dme 1 g (6.8 mmol) (nbut-2-en-1-yl)amine I, 5.72 ml
(40.7 mmol) triethylamine and 1.73 ml (13.6 mmol) chlorotrime-
thylsilane each in 10 ml dme were added. The reaction mixture was
stirred 1h at room temperature and additional 6 h at 60 °C. The
red solution was cooled to room temperature and filtered to remove
the precipitate. The volatile components were evaporated from the
filtrate in vacuo yielding a red oil. The product was extracted with
4 x 30 ml diethylether and the solution was reduced in vacuum to
15 ml. The solution was kept at Ϫ80 °C overnight and then at
Ϫ30 °C for a few days. After filtration analytically pure red-orange
crystals were obtained in a yield of 368 mg (0.88 mmol, 13 %).
Experimental Section
2. To a stirred solution of 712 mg (1.3 mmol) 1 in 50 ml dme
376 mg (1.3 mmol) MoO2Cl2(dme) were added. The reaction mix-
ture was heated 6h at 85 °C. The volatile components were then
removed in vacuum and the product isolated as described above;
yield 394 mg (0.94 mmol, 36 %).
General Procedures
All manipulations were carried out in a glove-box, or else by means
of Schlenk-type techniques involving the use of a dry argon atmos-
phere. The 1H and 13C NMR spectra were recorded on a Bruker AV
400 NMR spectrometer (1H 400.13 MHz; 13C 100.63 MHz) with
CD2Cl2 or CD3CN as solvents at 20 °C. The 1H and 13C NMR
spectra were calibrated against the residual proton and natural
abundance 13C resonances of the deuterated solvent (CD2Cl2 δH
5.32 ppm or CD3CN δH 1.94). Microanalyses were performed on
a Leco CHNS-932 elemental analyser. Infrared (IR) spectra were
recorded using samples prepared as KBr pellets with a Digilab Ex-
calibur FTS 4000 FTIR-spectrometer. Melting Points were per-
formed with a Stuart SMP 10.
Melting Point: 83 °C (decomposition). Elemental analysis for
C14H21Cl2MoNO3 (418.2); C 40.08 (calc. 40.21); H 4.92 (5.06); N
3.21 (3.35); Cl 17.30 (16.96) %.
1H-NMR (CD2Cl2) δ ϭ 1.68 [dd, J(H,H)ϭ6.0, 0.8 Hz, 3H, CHϪCH3], 3.79
[d, J(H,H)ϭ6.8 Hz, 2H, ArylϪCH2], 3.96 [s, 6H, OϪCH3], 4.02 [s, 4H,
OϪCH2], 5.59 [m, 1H, CHϪCH3], 5.69 [m, 1H, CHϪCHϪCH3], 7.22 [t,
J(H,H)ϭ7.2, 1H, CHar], 7.31 [m, 2H, CHar], 7.56 [d, J(H,H)ϭ8.0, 1H, CHar].
13C{1H}-NMR (CD2Cl2) δ ϭ 18.1 [CHϪCH3], 35.0 [ArylϪCH2], 64.6
[OϪCH3], 72.0 [OϪCH2], 126.9 [CHar], 127.0 [CHCHCHϪ3], 127.7 [CHar],
129.6 [CHar], 129.7 [CHar], 130.7 [CHϪCHϪCH3], 139.6 [CϪCH2], 154.6
[CϪN]. IR /cmϪ1: ν˜ ϭ 3021 (vw), 2940, 2851 (w), 1584 (m), 1557 (w), 1455
(s), 1443, 1373 (w), 1279 (m), 1240 (s), 1189 (s), 1159 (m), 1119 (w), 1086,
1047 (vs), 970, 923, 862 (s), 826, 779 (m), 731, 710, 661, 586 (w), 503, 541,
517 (m).
Materials
Solvents were purified, dried and degassed prior to use. Triethyl-
amine was freshly distilled and degassed, I was degassed and
NaMoO4 was heated at 150 °C and dried in vacuum.
[MoO2Cl2(dme)] [13], N-(but-3-en-2-yl)aniline, 2-(nbut-2-en-1-yl)-
aniline [7] were prepared according to the literature procedure.
[(C5H5)Mo(NC6H4CH2CHCHCH3)Cl2] (3)
To a stirred suspension of 500 mg (1.65 mmol) (C5H5)MoCl4 in
30 ml toluene 729 mg (4.95 mmol) (nbut-2-en-1-yl)amine I in 20 ml
Z. Anorg. Allg. Chem. 2006, 1078Ϫ1082
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1081

I. Siewert, C. Limberg, B. Ziemer
Acknowledgements. We are grateful to the Deutsche Forschungs-
gemeinschaft, the Fonds der Chemischen Industrie, the BMBF and
the Dr. Otto Röhm Gedächtnisstiftung for financial support. We
also would like to thank P. Neubauer for crystal structure analyses.
Table 1 Crystal data and details for the crystal structure refine-
ment of 1 and 3.
1
3
formula
C24H32Cl2MoN2O2
547.36
C15H16Cl2MoN
g
weight, g·molϪ1
temp, K
377.13
/
mol
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toluene were added over a period of 5 min. The reaction mixture
was stirred for 2h at room temperature. The solvent was removed
in vacuo, and the product was extracted with 4 x 30 ml dietylether
from the ammonium salt of I formed as a byproduct. The solution
was evaporated in vacuum to 15 ml and 50 ml of pentane were
added. After a few days at Ϫ30 °C 764 mg (1.50 mmol, 90 %) dark
purple crystals were obtained.
Elemental analysis for C15H16Cl2MoN (377.14); C 47.89 (calc.
47.77); H 4.35 (4.28); N 3.70 (3.71); Cl 18.83 (18.80) %.
IR /cmϪ1: ν˜ ϭ 3100 (vw), 2919, 2848, 2359, 2334, 2331, 1584, 1493 (w), 1468
(s), 1442 (m), 1437, 1417 (vs), 1377 (w), 1294 (m), 1262, 1157, 1112, 1101,
1062 (w), 1034 (s), 1018, 991 (m), 969 (s), 855 (m), 836 (s), 821 (vs), 804, 767
(s), 668 (w).
[11] X. Yang, C. L. Stern, T. J. Marks, J. Am. Chem. Soc. 1994,
116, 10015.
[12] J.-F. Carpentier, Z. Wu, C. W. Lee, S. Strömberg, J. N. Chris-
topher, R. F. Jordan, J. Am. Chem Soc. 2000, 122, 7750; C. P.
Casey, D. W. Carpenetti II, Organometallics 2000, 19, 3970.
[13] K. A. Rufanov, D. N. Zarubin, N. A. Ustynyuk, D. N. Goure-
vitch, J. Sundermeyer, A. V. Churakov, J. A. K. Howard, Poly-
hedron 2001, 20, 379.
[14] A. Galindo, F. Montilla, A. Pastor, E. Carmona, Inorg. Chem.
1997, 36, 2379.
[15] M. L. H. Green, P. C. Konidaris, P. Mountford, J. Chem. Soc.,
Dalton Trans. 1994, 2851.
Crystal Structure Determinations
Single crystals of 1 (disordered) were obtained by overlayering a
solution of 1 in dichloromethane with pentane at Ϫ30 °C. Single
crystals of 3 were obtained by overlayering a solution of 3 in di-
ethylether with pentane at Ϫ30 °C. The crystals were mounted on
a glass fiber and then transferred into the cold nitrogen gas stream
of the diffractometer (Stoe STADI 4 (1) and Stoe IPDS (3)) using
˚
MoKα radiation, λ ϭ 0.71073 A, and both structures were solved
by direct methods (SHELXS-97) [18], refined versus F2 (SHELXL-
97) [19] with anisotropic temperature factors for all non-hydrogen
atoms (Table 1). All hydrogen atoms were added geometrically and
refined by using a riding model.
[16] A. Sakthivel, J. Zhao, M. Hanzlik, F. E. Kühn, Dalton Trans.
2004, 3338; A. Sakthivel, J. Zhao, G. Raudaschl-Sieber, M.
Hanzlik, A. S. T. Chiang, F. E. Kühn, Appl. Catal. A 2005,
281, 267.
[17] M. P. Coles, C. I. Dalby, V. C. Gibson, W. Clegg, M. R. J.
Elsegood, J. Chem. Soc., Chem. Commun. 1995, 1709; M. P.
Coles, V. C. Gibson, Polym. Bull. 1994, 33, 529.
[18] G. M. Sheldrick, SHELXS-97, Program for Crystal Structure
Solution, University of Göttingen, 1997.
The crystallographic data (apart from structure factors) of 1 and 3
were deposited at the Cambridge Crystallographic Data Centre as
supplementary publication no. CCDC 289393 (1) and 289392 (3).
Copies of the data can be ordered free of charge on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ (FAX: (ϩ44)1223-
336-033; E-mail: deposit@ccdc.cam.ac.uk).
[19] G. M. Sheldrick, SHELXL-97, Program for Crystal Structure
R efinement, University of Göttingen, 1997.
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