ansa-Chromocenes: An alternative route to Me2Si(C5Me4)2Cr

Article abstract of DOI:10.1016/j.ica.2010.02.034

The mechanism for the preparation of Me₂Si(C₅Me₄)₂Cr, 1, from CrCl₂(THF)_x and Me₂Si(C₅Me₄)₂Li₂ was investigated and - in contrast to earlier claims - no evidence was found for the participation of an auxiliary ligand. The formation and stability of 1 is attributed to the combination of correct reaction conditions and a highly substituted ligand framework. Reactions with other ligands under identical conditions did not lead to the formation of ansa-chromocenes. Reaction with H₄C₂Ind₂Li₂ afforded the η³-Ind bridged dimer {H₄C₂(η⁵-Ind)(μ-,η³-Ind)Cr}₂, 9. Complex 1 does not coordinate PPh₃ or carbenes, but from reaction with two equivalents of xylyl isocyanide the CH-activated complex Me₂Si(C₅Me₄)(η³-C₅Me₃(H)({double bond, long}CH₂)Cr(CNC₆MeH₃)₂, 7, was obtained. Complexes 7 and 9 were characterised by X-ray crystallography.

Full text of DOI:10.1016/j.ica.2010.02.034

Inorganica Chimica Acta 363 (2010) 1779–1784
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Inorganica Chimica Acta
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ansa-Chromocenes: An alternative route to Me2Si(C5Me4)2Cr
*
Fabien Charbonneau, Paul O. Oguadinma, Frank Schaper
Département de chimie, Université de Montréal, Montréal, Québec, Canada H3C 3J7
a r t i c l e i n f o
a b s t r a c t
Article history:
The mechanism for the preparation of Me2Si(C5Me4)2Cr, 1, from CrCl2(THF)x and Me2Si(C5Me4)2Li2 was
investigated and – in contrast to earlier claims – no evidence was found for the participation of an aux-
iliary ligand. The formation and stability of 1 is attributed to the combination of correct reaction condi-
tions and a highly substituted ligand framework. Reactions with other ligands under identical conditions
Received 23 January 2010
Received in revised form 25 February 2010
Accepted 26 February 2010
Available online 4 March 2010
did not lead to the formation of ansa-chromocenes. Reaction with H4C2Ind2Li2 afforded the
bridged dimer {H4C2( -,
5-Ind)( 3-Ind)Cr}2, 9. Complex 1 does not coordinate PPh3 or carbenes, but
from reaction with two equivalents of xylyl isocyanide the CH-activated complex Me2Si(C5Me4)(g3
g
3-Ind
g
l g
Keywords:
-
X-ray crystal structures
Chromium complexes
ansa-Chromocenes
C5Me3(H)(@CH2)Cr(CNC6MeH3)2, 7, was obtained. Complexes 7 and 9 were characterised by X-ray
crystallography.
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
peculiar and depended strongly on the point when xylyl isocyanide
was introduced in the reaction [13]: (i) Without xylyl isocyanide,
Metallocenes with bridged cyclopentadienyl rings (ansa-metal-
locenes) and their derivatives have found widespread application,
since the introduction of the ansa-bridge prevents the rotation
around the metal–cyclopentadienyl bond, ensures a rigid ligand
framework and activates the metal centre by bending of the cyclo-
pentadienyl rings out of a linear coordination [1]. In ansa-chromoc-
enes this pre-formed bending allowed coordination of carbon
monoxide at ambient conditions [2–4], whilst unbridged Cp2Cr
loses CO to revert to the coplanar orientation of the cyclopentadi-
enyl rings [5]. Despite a large number of reported first-row metal-
locenes of the general formula (C5R5)2M and an equally large
number of ansa-metallocenes X(C5R4)MLn (L = neutral or anionic li-
gand, X = ansa-bridge), first-row ansa-metallocenes of the general
formula X(C5R4)2M have been reported only for iron and cobalt
[6,7]. The reasons for the absence of these species might be found
in the formation of the empty or half-occupied 2a1 orbital in the
mean ligand plane, which is obtained upon bending of the cyclo-
pentadienyl rings out of the linear coordination geometry of typical
sandwich compounds [8]. Stable X(C5R4)2M complexes were ob-
tained, when the 2a1 orbital is filled, i.e. for Fe and Co [6]. In the
case of chromium complexes, attempted synthesis of X(C5R4)2Cr
led to insoluble, coloured and probably polymeric material
[2,4,9,10]. Isolable, monomeric complexes could only obtained if
an ancillary ligand, such as CO, isocyanide, pyridine, or B(C6F5)3,
was coordinated to the metal [2,3,9–15]. Two exceptions from this
rule have been published: Me2Si(C5Me4)2Cr, 1, [13] and
[Me4C2(C5H4)2Cr][HB(C6F5)3] [15]. Formation of 1 was somewhat
reaction of Me2Si(C5Me4)2Li2 with CrCl2 (THF)x had been reported
to yield only polymeric material [9]. (ii) Combining xylyl isocya-
nide with CrCl2 (THF)x before the addition of Me2Si(C5Me4)2Li2
led to the formation of Me2Si(C5Me4)2Cr(CNC6Me2H3), 2. (iii) Com-
bining xylyl isocyanide with Me2Si(C5Me4)2Li2 before the addition
of CrCl2 (THF)x, on the other hand, led to the isolation of 1. (iv)
Addition of xylyl isocyanide to 1 formed 2 in less than 5 min. The
mechanism in Scheme 1 was proposed to explain these apparently
contradicting observations [13]. The reported alkyllithium-initi-
ated trimerisation of xylyl isocyanide to a bidentate anionic ligand
3 [16] removes the isocyanide from the reaction mixture and thus
prevents formation of 2. Intermediate coordination of 3 to chro-
mium was proposed to protect the chromium centre from poly-
merisation during reaction with Me2Si(C5Me4)2Li2. In the
following, we will clarify the role of ancillary bidentate ligands in
the formation of 1 in an attempt to prove or disprove the mecha-
nism proposed earlier.
2. Results and discussion
2.1. Investigation of the proposed reaction mechanism
Preliminary attempts to confirm the proposed mechanism tar-
geted the isolation of intermediate 4, formed upon reaction of 3
with CrCl2 (THF)x. However, reactions of CrCl2 (THF)x with 3 (either
obtained as blue THF solutions upon reaction of 0.3 equiv of BuLi
with xylyl isocyanide or by isolation and subsequent deprotona-
tion of the protonated form of 3) did not afford any identified prod-
uct. In the only occasion, in which single crystals suitable for
* Corresponding author. Tel.: +1 5143436683; fax: +1 5143437586.
E-mail address: Frank.Schaper@umontreal.ca (F. Schaper).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.02.034

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F. Charbonneau et al. / Inorganica Chimica Acta 363 (2010) 1779–1784
Scheme 1.
analysis could be obtained, the product turned out to be the
simple coordination complex CrCl2(CNC6Me2H3)4 (see Supporting
Information). We thus decided to investigate reactions of Me2Si
(C5Me4)2Li2 with simpler model compounds of 4, in which 3 was
replaced by structurally very similar b-diketiminate (‘‘nacnac”)
ligands. Reaction of nacnaciPrLi with CrCl2 was reported to yield
the THF-coordinated dimer, 5a, [17] which was obtained using a
slight variation of the literature method. Following the same proce-
equivalent to the formation of 1 (THF, 0 °C). As observed for the
preparation of 1, red to brown THF solutions were obtained. Evap-
oration and extraction yielded red (in some cases, brown) hexane
extracts and – after evaporation – a reddish-brown powder, again
in accordance with observations made during the preparation of 1.
However, reaction of the unidentified crude product obtained, 6,
with xylyl isocyanide did not yield diamagnetic 2 or any other dia-
magnetic species after reaction. Paramagnetic 1H NMR spectra of 6
showed a clear difference to the paramagnetic spectra of 5a or 5b,
1 or decomposition products after exposure to air. Variation of the
solvent (THF, toluene, hexane), reaction temperature (À20 °C to re-
flux), reaction time (2-24 h), or the order of reagent addition did
not yield 1 in any noticeable amounts (<2% formation of 2 upon
reaction with isocyanide). Despite numerous attempts, no single
crystals of 6 have been obtained, nor could we isolate crystals after
derivatisation attempts with xylyl isocyanide or Me3SiCl.
Given the fact that the reported, crystallized yield of 1 (46%) ex-
ceeded the possible concentration of the trimer 3, the reaction
mechanism in Scheme 1 was proposed to be catalytic [13]. Indeed,
when 0.9 equiv of CrCl2 (THF)x and 0.05 equiv of dimer 5b were
added to Me2Si(C5Me4)2Li2 in THF, the targeted compound 1 was
now obtained from the hexane extracts. Coordination of the nacnac
ligand thus seems to be preferred over coordination of the second
cyclopentadienyl ring (Scheme 3) and nacnacLi is released from
chromium only if additional CrCl2 is present to reform the dimer
5. The products obtained above in the presence of equimolar
amounts of nacnac ligand are thus most likely the mono-coordi-
nated intermediates 6a and 6b, which did not seem to crystallize
easily (Scheme 3). In accordance with this, Smith and coworkers
observed that reaction of Cp2Cr with nacnacLi salts yields the
mixed compounds Cp(nacnac)Cr under probable elimination of
CpLi [18,19].
dure, {nacnacMeCr(
l-Cl)(THF)}2, 5b, was prepared (Scheme 2).
The crystal structure of 5b (Fig. 1) is very similar to the one of
5a, with the chromium centre in a square-pyramidal coordination.
Average Cr–Cl and Cr–N distances in 5b (2.405 0.01 Å and
2.061 0.02 Å) are slightly shorter than those observed in 5a
(2.4182(6) Å and 2.071(2) Å) [17] and the bite angle of the nacnac
ligand is slightly smaller (N1–Cr–N2, 5b: 89.78(6)°, 5a [17]:
91.3(1)°), but the differences are barely significant. Whilst replace-
ment of methyl by isopropyl is normally considered to increase the
steric bulk of diketiminate ligands, the effects here are rather small
and barely noticeable in the structure of the dimer.
Given the comparable solid state structures of 5a and 5b, both
complexes were reacted with Me2Si(C5Me4)2Li2 under conditions
The highest yields of the above mentioned reaction were ob-
tained under conditions identical to the reported formation of 1,
i. e. 0 °C in THF solution with slow addition of CrCl2 (THF)x to the
reaction mixture. These conditions were thus chosen to investigate
Scheme 2.

F. Charbonneau et al. / Inorganica Chimica Acta 363 (2010) 1779–1784
1781
Fig. 1. Crystal structure of 5b. Hydrogen atoms were omitted for clarity. Thermal ellipsoids are drawn at the 50% probability level. Selected geometrical data Cr1–N1:
2.0588(15) Å, Cr1–N2: 2.0629(14) Å, Cr1–Cl1: 2.3944(5) Å, Cr1–Cl1A: 2.4151(5) Å, Cr1–O1: 2.3944(14) Å, N1–Cr–N2: 89.78(6)°, Cl1–Cr1–Cl1A: 82.83(2)°.
Scheme 3.
influence of crystallisation.) Obtained yields of 1 were in the range
of 60–70% and seem to be rather independent from the amount,
source or type of nacnac ligand used. Most surprisingly, identical
yields were obtained even in the absence of any auxiliary ligand,
which is in contrast to literature reports that direct reaction of lith-
ium salts with CrCl2 yields insoluble products [2,4,9,10] and that
the reported yields for the reaction of Me2Si(C5Me4)2Li2 with CrCl2
(THF)x ligand in the presence of carbon monoxide never exceeded
39% [9]. Since neither the presence of nacnac ligands, nor the ori-
ginal protocol of pre-reacting xylyl isocyanide with the ligand lith-
ium salt significantly improves the reaction yield, we conclude that
the formation of 1 in the original synthesis was not due to the pres-
ence of an additional coordinating ligand, but to the serendipitous
choice of reaction conditions.
Table 1
Yields of the hexane-soluble fractiona in the presence of different sources of auxiliary
ligand.
Mol-%b
Yield (%)
5b
5b
5b
1
5
10
1
5
10
10
5
60
70
70
60
70
50
60
60
65c
nacnacMeLi
nacnacMeLi
nacnacMeLi
nacnacMeH
nacnaciPrLi
None
a
b
c
corrected for the formation of hexane-soluble 6a/6b.
Mol-% of nacnac ligand added, i.e. 2 Â mol-% of dimer 5b.
Isolated yield after recrystallisation: 44%.
2.2. Further reactions of 1
the influence of different sources of the nacnac ligand and its con-
centration on the formation of 1 (Table 1, yields are reported for
the amount of unpurified hexane-soluble product to exclude the
Complex 1, despite being a 16 eÀ-metallocene with pre-bent
cyclopentadienyl rings, does not readily coordinate ligands other

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F. Charbonneau et al. / Inorganica Chimica Acta 363 (2010) 1779–1784
than isocyanide or carbonyl, most likely due to steric interactions
of the incoming ligand with the cyclopentadienyl methyl substitu-
ents [13]. Addition of up to 5 equiv of PPh3 to C6D6 solutions of 1
did not yield any diamagnetic, NMR-observable species. Reactions
of 1 with ethyl diazoacetate, at 0 °C or reflux, likewise did not yield
any isolable, diamagnetic species.
If C6D6 solutions of 1 are reacted with excess xylyl isocyanide
for prolonged reaction times, signals of 2 begin to diminish and a
new asymmetric species 7 is formed. Synthesis and isolation of 7
identified it as a CH-activated bis(isocyanide) complex (Scheme 1,
Fig. 2). CH-activation of an
a
-methyl group and exocyclic allyl
coordination, instead of a simple g5
–g
3 haptotropic shift, has also
been observed for the coordination of a second carbonyl ligand to
Me2Si(C5Me4)2Cr(CO) and was ascribed to the release of the steric
strain introduced by the single-atom bridge in 1 [9]. Not surpris-
ingly, the geometrical data of 7 (Fig. 2) resembles very closely that
of its dicarbonyl analogue, 8 [9]. The only remarkable difference
are a slightly increased Cr-centroid distance in 7 (1.86 Å, 1.84 Å
in 8), increased Cr–C15 (2.209(4) Å, 2.19 Å in 8) and Cr–Cisocyanide
distances (1.87(1) Å, Cr–CCO = 1.81 Å) and an increased C1–Si1–
Fig. 2. Crystal structure of 7. Hydrogen atoms (with exception of H12a) were omitted for clarity. Thermal ellipsoids are drawn at the 50% probability level. Selected
geometrical data (Z1 = centroid C1–C5): Cr1–Z1: 1.86 Å, Cr1–C10: 2.404(4) Å, Cr1–C11: 2.227(4) Å, Cr1–C15: 2.209(4) Å, Cr1–C27: 1.885(4) Å, Cr1–C36: 1.864(5) Å, C27–N1:
1.195(5) Å, C36–N2: 1.197(5) Å, Cr1–C27–N1: 177.7(4)°, Cr1–C36–N2: 178.6(4)°, Z1–C1–Si1: 152°, C1–Si1–C10: 99.2(2)°.
Fig. 3. Crystal structure of 9. Hydrogen atoms were omitted for clarity. Thermal ellipsoids are drawn at the 50% probability level. Selected geometrical data (Z1 = centroid C1–
C4, C9; Z2 = centroid C21–C24, C29): Cr1–Cr2: 2.2601(4) Å, Cr1–Z1: 1.95 Å, Cr2–Z2: 1.98 Å, Cr1–C11: 2.195(2) Å, Cr1–C33: 2.153(2) Å, Cr2–C13: 2.180(2) Å, Cr2–C31:
2.193(2) Å, Cr1–C12: 2.269(2), Cr2–C32: 2.308(2) Å, Cr1–C32: 2.240(2), Cr2–C12: 2.281(2).

F. Charbonneau et al. / Inorganica Chimica Acta 363 (2010) 1779–1784
1783
C10 angle (99.2(2)° versus 98°), which all indicate a stronger steric
repulsion between the isocyanide ligand and the permethylated
five-membered rings in 7 than in the dicarbonyl complex. The
average C–N bond length of the coordinated isocyanide ligands
(1.196(5) Å) and the Cr–Cisocyanide distance (1.875(15) Å) are within
the margin of error identical to the values found for 2 (1.191(4) and
1.876(4) Å). The C–N bond is 0.02–0.04 Å longer, the Cr–C bond
0.04–0.14 Å shorter than in Cr(CNC6Me2H3)4Cl2 (1.156(3) and
2.017(2) Å, see Supporting Information) or Cr(CNC6Me2H3)6
(1.174(7) and 1.919(7) Å),[13] indicating an increased back-dona-
tion from the chromium centre in 7 in the presence of cyclopenta-
dienyl ligand(s).
nitrogen. C6D6 was distilled from Na and de-oxygenated by three
freeze-pump-thaw cycles. CrCl2 (THF)x [22], Me2Si(C5Me4)2Li2 [9],
nacnacMeH [23], nacnaciPrH [24], H4C2(C9H8)2 [25], and Me2Si-
(C5H5)2 [26] were prepared as described in the literature. All other
chemicals were obtained from commercial suppliers and used as
received. NMR spectra were recorded on a Bruker AV 400 MHz
spectrometer and referenced to residual solvent (C6D5H: d 7.15).
Elemental analyses were performed by the Laboratoire d’Analyse
Élémentaire (Université de Montréal).
4.1. {(NacnacMe)Cr(THF)(
l-Cl)}2, 5b
NacnacMeH (7.00 g, 22.8 mmol) in THF (50 mL) is deprotonated
by addition of nBuLi in hexane (2.7 M, 8.4 mL, 22.8 mmol) at À78 °C
and warmed to room temperature under stirring. CrCl2 (THF)x
(1 < x < 2, 6.09 g, 22.8–31.2 mmol), suspended in a minimum of
THF, is added and the reaction is stirred for 24 h at room temper-
ature to yield a green solution. The solvent is evaporated and the
residue extracted with dichloromethane (100 mL). The solvent is
again evaporated, the residue dissolved in a minimum of THF
and kept at À30 °C to yield 6.20 g (6.67 mmol, 59%) of green crys-
tals. 1H RMN (400 MHz, 298 K, C6D6) d 118 (bs). Anal. Calc. for
C50H66Cl2Cr2N4O2: C, 64.57; H, 7.15; N, 6.04. Found: C, 63.86; N,
6.85; H, 6.09%.
2.3. Extension to other ligands
Given the lack of reactivity of 1, it was of interest to explore to
which extent the reaction conditions employed for the synthesis of
1 could be applied to other ligand frameworks. Our initial attempts
focussed on the Me2Si(C5H4)2-ligand framework to explore the ef-
fects of unsubstituted cyclopentadienyl rings. Reaction of Me2Si-
(C5H4)2Li2 with CrCl2 (THF)x, initially under conditions identical
to those employed in the formation of 1, but later at different
temperatures (À78 °C to 50 °C), reaction times (4–72 h), or in the
presence of 0.1 equiv nacnacMeLi, did not yield any characterised
product. Varying amounts of hexane-soluble powders were iso-
lated, which could neither be crystallized, nor did they show the
formation of diamagnetic complexes by reactions with xylyl
isocyanide.
4.2. {(NacnaciPr)Cr(THF)(
l-Cl)}2, 5a [17]
Prepared using the same protocol as for 5b in 72% yield. 1H RMN
(400 MHz, 298 K, C6D6) d 127 (bs). Anal. Calc. for C66H98Cl2Cr2N4O2:
C, 68.67; H, 8.56; N, 4.85. Found: C, 67.65; H, 8.27; N, 5.47%.
Reaction of CrCl2 (THF)x with H4C2(Ind)2Li2 as well did not yield
an ansa-chromocene. From isolated crystals, obtained in insuffi-
cient amounts for further analysis, the reaction product was
instead identified as the dimeric complex {H4C2(g l -
5-Ind)( -,g3
4.3. Me2Si(C5Me4)2Cr, 1 [13]
Ind)Cr}2, 9. The structure of 9 resembles that of the unbridged
compound {Ind2Cr}2, which also crystallizes as a dimer with two
g
To a solution of Me2Si(C5Me4Li)2 (0.20 g, 0.64 mmol) in THF
(20 mL) at 0 °C, a suspension of CrCl2 (THF)x (1 < x < 2, 0.17 g,
0.64–0.87 mmol) in THF (70 mL) is added dropwise over 30 min
and afterwards stirred for 24 h at room temperature. The resulting
red solution is evaporated to dryness and extracted with hexane
(50 mL, 10 mL & 10 mL). The solution is concentrated and stored
at À30 °C to yield 1 in the form of red crystals (0.10 g, 0.28 mmol,
44 %). 1H RMN (400 MHz, 298 K, C6D6) d À4 (bs). (X-ray diffraction
yielded a unit cell identical to the one obtained for 1 [13].
3-coordinated, bridging indenyl ligands [20]. The main difference
upon introduction of the ansa-bridge is the orientation of the
bridging indenyl ligand which is syn (both annulated rings ori-
ented in the same direction) in 9 and anti in {Ind2Cr}2. The geomet-
ric data varies slightly between 9 and {Ind2Cr}2, with a longer
Cr–Cr distance (0.08 Å), shorter Cr–C12/C32 distances (0.03–
0.05 Å) and shorter Cr-centroid distances (0.02–0.05 Å) in 9, but
does not indicate noticeable steric strain introduced by the C2
bridge. The chromium–chromium distance of 2.2601(4) Å is above
the 2.0 Å threshold for Cr–Cr quadruple bonds [21], but close
enough that a quadruple bond might still be considered reasonable
(Fig. 3).
4.4. Formation of 1 in the presence of different nacnac ligands
To a solution of Me2Si(C5Me4)2Li2 (300 mg, 0.96 mmol) in THF
(320 mL) at 0 °C, the required amount of nacnac ligand is added
(see Table 1). A suspension of CrCl2 (THF)x (1 < x < 2, 260 mg,
0.97–1.3 mmol) in THF (80 mL) is added dropwise over 30–
60 min. After stirring at room temperature for 24 h, the resulting
solution is evaporated to dryness and extracted with hexane until
the extract remains colourless. The hexane extracts were evapo-
rated and yields were determined under the assumption that only
1 and 6a/6b were obtained. (Reaction of the obtained powders with
xylyl isocyanide resulted in complete disappearance of paramag-
netic peaks in 1H NMR spectra and in no other diamagnetic prod-
ucts than 2 and 7.)
3. Conclusions
Formation of 1 does not rely, as was postulated before, on the
presence of an ancillary ligand to prevent the formation of poly-
meric product. Instead, the correct choice of reaction conditions al-
lowed the isolation from a simple reaction between the ligand
lithium salt and chromium dichloride. Problems encountered by
us and others in isolating ligand-free ansa-chromocenes with other
ligand frameworks indicate that the stability of 1 is closely related
to the permethylation of its ligand framework, which also prevents
the coordination of nucleophiles other than CO and isocyanide.
4.5. Me2Si(g g
5-C5Me4)( 3-C5Me3(H)(@CH2))Cr(CNC6Me2H3)2, 7
4. Experimental section
To a solution of 1 (0.10 g, 0.28 mmol) in THF (25 mL), 2,6-xylyl
isocyanide (75 mg, 0.57 mmol) in THF (15 mL) were added. The
solution was stirred for 48 h, concentrated and kept at À30 °C to
yield deep-orange crystals (74 mg, 71%). 1H NMR (400 MHz,
298 K, C6D6): d 6.72–6.85 (m, 6H), 2.75 (s, 3H), 2.32 (s, 6H), 2.08
All reactions, except ligand synthesis, were carried out under
nitrogen atmosphere using Schlenk or glove box techniques. Sol-
vents were dried by passage through activated aluminum oxide
(MBraun SPS) and de-oxygenated by repeated extraction with

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F. Charbonneau et al. / Inorganica Chimica Acta 363 (2010) 1779–1784
Table 2
using a riding model. Further experimental details are listed in Ta-
ble 2 and given in the supporting information.
Details of X-ray Diffraction Studies.
5b
7
9
Acknowledgements
Formula
C50H66Cl2Cr2N4O2 C38H4CrN2Si
C40H32Cr2
616.66; 2560
150; 1.54178
monoclinic
P21/c
Mw (g/mol); F(0 0 0)
T (K); wavelength
Crystal system
Space group
929.97; 984
220; 1.54178
monoclinic
P21/c
612.87; 656
150; 1.54178
triclinic
We thank Francine Bélanger-Gariépy for the crystal structure
determination of complex 5b. Funding was provided by the Fonds
québécois de la recherche sur la nature et les technologies, and the
University of Montreal.
ꢀ
P1
Unit cell dimensions
a (Å)
b (Å)
c (Å)
12.9618(3)
12.7209(3)
15.1066(4)
8.8863(7)
12.4106(9)
15.4473(12)
89.555(4)
89.255(4)
79.292(4)
1673.8(2); 2
1.216
39.9472(8)
9.9804(2)
15.0248(3)
Appendix A. Supplementary material
a
(°)
b (°)
97.6750(10)
110.4370(10)
CCDC 723529, 723531 and 723532 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version, at
doi:10.1016/j.ica.2010.02.034.
c
(°)
V (Å3); Z
2468.5(1); 2
1.251
5613.2(2); 8
1.459
Dcalc (g/cm3)
h Range (°);
4.2–72.0; 1.00
2.9–71.4; 0.95 2.4–67.8; 0.99
completeness
Collected reflections;
14877; 0.022
4848; 0.022
20260; 0.095
6184; 0.041
44756; 0.015
5011; 0.036
R
r
unique reflections;
Rint
References
l
(mmÀ1); Abs. Corr.
4.936; multiscan
0.038; 0.112
3.353;
multiscan
0.065; 0.160
6.587;
multiscan
0.032; 0.091
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R1(F); wR(F2)
(I > 2 (I))
r
R1(F); wR(F2) (all data) 0.042; 0.115
0.111; 0.185
1.04
0.67, –0.87
0.033; 0.092
1.04
0.42, À0.43
GoF (F2)
1.09
0.52, –0.30
Residual electron
density
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1823.
(s, 6H), 2.02 (s, 6H), 1.87 (s, 3H), 1.58 (s, 3H), 1.33 (d, 3H), 1.32 (s,
3H), 0.72 (s, 3H), 0.02 (s, 3H).
4.6. H4C2(C9H7)2Cr, 9
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Organometallics 13 (1994) 1746.
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(2004) 3552.
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R.A. Zehnder, J.J. Nairn, Chem. Eur. J. 13 (2007) 6212.
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J. Inorg. Chem. (2001) 1895.
To a solution of C2H4(C9H6Li)2 (0.40 g, 1.48 mmol) in THF
(70 mL) at 0 °C, a suspension of CrCl2 (THF)x (1 < x < 2, 0.39 g,
1.5–2.0 mmol) in THF (125 mL) is added dropwise over 2 h and
afterwards stirred for 24 h at room temperature. The orange solu-
tion obtained is evaporated to dryness and extracted with toluene
(2 Â 50 mL). The brown-orange extract is reduced to 10 mL and
kept at À30 °C to yield 9 as orange crystals in amounts insufficient
for further characterisation.
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(1996) 5462.
5. X-ray diffraction studies
Diffraction data were collected on a Bruker SMART 6000 with
Montel 200 monochromator (5b) and a Bruker Microstar-Proteum
with Helios optics (7, 9), both equipped with a rotating anode
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W. Gal, Eur. J. Inorg. Chem. (2000) 753.
source for Cu Ka radiation. Cell refinement and data reduction
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[26] H. Yasuda, K. Nagasuna, M. Akita, K. Lee, A. Nakamura, Organometallics 3
were done using APEX2 [27]. Absorption corrections were applied
using SADABS [27]. Structures were solved by direct methods using
SHELXS97 and refined on F2 by full-matrix least squares using SHEL-
XL97 [28]. All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were refined isotropic on calculated positions
(1984) 1470.
[27]
APEX2, Release 2.1-0, Bruker AXS Inc., Madison, USA, 2006.
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