16-electron (arene)ruthenium complexes with superbasic bis(imidazolin- 2imine) ligands and their use in catalytic transfer hydrogenation

Article abstract of DOI:10.1002/ejic.200900570

The ligands N,N'-bis(l,3,4,5-tetramethylimidazolin-2-ylidene)-l,2- ethanediamine (BL^Me) and N,N-bis(l,3-diisopropyl-4,5- dimethylimidazolin-2-ylidene)-l,2-ethanediamine (BL^IPr) react with [(η⁵-C₅Me₅)R

Full text of DOI:10.1002/ejic.200900570

FULL PAPER
DOI: 10.1002/ejic.200900570
16-Electron (Arene)ruthenium Complexes with Superbasic Bis(imidazolin-2-
imine) Ligands and Their Use in Catalytic Transfer Hydrogenation
Thomas Glöge,[a] Dejan Petrovic,[a] Cristian Hrib,[a] Peter G. Jones,[a] and
Matthias Tamm*[a]
Keywords: Ruthenium / Arene ligands / N ligands / Coordinative unsaturation / Hydrogenation
The ligands N,NЈ-bis(1,3,4,5-tetramethylimidazolin-2-ylid-
ene)-1,2-ethanediamine (BLMe) and N,NЈ-bis(1,3-diisopro- [5]Cl2 reveals the absence of any direct Ru–Cl interaction,
(BLR)]2+ (R = Me, 7; R = iPr, 8). The X-ray crystal structure of
pyl-4,5-dimethylimidazolin-2-ylidene)-1,2-ethanediamine
(BLiPr) react with [(η5-C5Me5)RuCl]4 to afford cationic 16-
electron half-sandwich complexes [(η5-C5Me5)Ru(BLR)]+ (R =
Me, 3; R = iPr, 4), which resist coordination of the chloride
counterion because of the strong electron-donating ability of
the diimine ligands. Upon reaction with [(η6-C6H6)RuCl2]2 or
[(η6-C10H14)RuCl2]2, these ligands stabilize dicationic 16-
whereas a long Ru–Cl bond, supported by two CH···Cl hydro-
gen bonds, is observed for [(6)Cl]Cl in the solid state. Treat-
ment of the dichlorides of 6 and 8 with NaBF4 affords [6]-
(BF4)2 and [8](BF4)2, which are composed of individual dicat-
ions and tetrafluoroborate ions with no direct Ru–F interac-
tion. All complexes catalyze the transfer hydrogenation of
acetophenone in boiling 2-propanol.
electron benzene and cymene complexes of the type [(η6- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
C6H6)Ru(BLR)]2+ (R = Me, 5; R = iPr, 6) and [(η6-C10H14)Ru-
Germany, 2009)
Introduction
Poly(guanidine) ligands[1] have found remarkable appli-
cations as superbasic proton sponges[2] and as ligands for
transition metal complexation,[3] with particular emphasis
on copper coordination and dioxygen activation chemis-
try.[4,5] Moreover, mono- and bis(guanidine) chelate ligands
have been used for the preparation of homogeneous cata-
lysts, e.g. for the ring-opening polymerization of lactides
and for the atom transfer radical polymerization of styr-
ene.[6,7] In general, guanidine ligands attain their unique
properties from the ability to delocalize a positive charge
over the guanidine CN3 moiety, producing compounds with
considerably enhanced basicity and nucleophilicity. These
characteristics become even more pronounced in poly(imid-
azolin-2-imine) ligands, since the imidazole ring is particu-
larly effective in stabilizing a positive charge. This induces
a strong polarization of the exocyclic C=N bond,[8,9] which
can be described by the two resonance structures A and B
for the BLiPr and BLMe ligands (Scheme 1). Upon metal
coordination, the contribution of the ylidic form B can be
expected to increase considerably, and thus these ligands
exhibit a particularly strong electron-donating capacity to-
ward transition metal atoms.[10–14]
Scheme 1.
The bidentate ligands BLiPr and BLMe can be conve-
niently synthesized by introducing a CH2CH2 bridge be-
tween two imidazolin-2-imines, which have proved to be
valuable ligands in their own right[11] and can be obtained
from the reaction of trimethylsilyl azide (Me3SiN3) with N-
heterocyclic carbenes of the imidazolin-2-ylidene type.[9]
The pronounced electron-donor properties of these bis-
(imidazolin-2-imines) were documented by the preparation
of highly reactive copper(I) complexes, allowing effective
[a] Institut für Anorganische und Analytische Chemie, Technische
Universität Carolo-Wilhelmina,
Hagenring 30, 38106 Braunschweig, Germany
Fax: +49-251-391-5309
E-mail: m.tamm@tu-bs.de
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(Arene)ruthenium Complexes with Bis(imidazolin-2-imine) Ligands
O=O and C–Cl bond activation, CO2 fixation and CuI dis-
proportionation.[7,12] Furthermore, it was shown that the
unusual stability of coordinatively unsaturated 16-electron
molybdenum and ruthenium half-sandwich complexes of
the type [(η7-C7H7)Mo(BLR)]+ (R = Me, 1; R = iPr, 2) and
[(η5-C5Me5)Ru(BLR)]+ (R = Me, 3; R = iPr, 4) can be as-
cribed to the strongly π-basic nature of these ligand systems
(Schemes 1 and 2).[13,14]
Scheme 3.
Scheme 2.
Substitution of the Cp* ring in [(η5-C5Me5)Ru(BLR)]+ by
benzene or cymene (1-isopropyl-4-methylbenzene, C10H14)
affords the half-sandwich complex fragments [(η6-C6H6)-
Ru(BLR)]2+ (R = Me, 5; R = iPr, 6) and [(η6-C10H14)-
Ru(BLR)]2+ (R = Me, 7; R = iPr, 8), respectively, and, be-
cause dicationic 16-electron half-sandwich ruthenium com-
plexes are to the best of our knowledge unknown, we aimed
at the stabilization of such complexes by the BLR ligands.
The resulting complexes are also potential catalysts for vari-
ous organic transformations, in view of the fact that 16-
electron (arene)ruthenium complexes are frequently en-
countered as intermediates in ruthenium-catalyzed reac-
tions.[15] In addition, numerous catalytic applications are
Scheme 4. Synthesis of [7] and [8].
Results and Discussion
As previously reported in a short communication,[13a] the
known for monocationic complexes of the type [(η6-C6H6)- complexes [(η5-C5Me5)Ru(BLMe)]Cl ([3]Cl) and [(η5-
Ru(NʝN)X]Y and [(η6-C10H14)Ru(NʝN)X]Y, where NʝN C5Me5)Ru(BLiPr)]Cl ([4]Cl) are isolated as violet, crystalline
represents a bidentate nitrogen-donor ligand, X a halogen complexes from the reaction of tetrameric [(η5-C5Me5)-
atom and Y a non-coordinating anion.[16] For instance, RuCl]4 (Scheme 2)[23,24] with the ligands BLMe and BLiPr
.
these systems have been used as catalysts for the hydrogena- The chloride counteranions in these complexes can be easily
tion of alkenes,[17] olefin metathesis,[18] Diels–Alder reac- exchanged for the triflate (OTf) or tetrakis[3,5-bis(trifluoro-
tions,[19] and, most prominently, for hydrogen-transfer re- methyl)phenyl]borate (BArF) anions by reaction with the
duction of ketones[20] and imines;[21] the latter reaction has corresponding sodium salts. The solid-state structures of
been brought to near perfection with high yields and high [3]OTf, [4]Cl and [4]OTf revealed the presence of cationic
enantiopurity by application of ruthenium complexes such 16-electron complexes and the absence of metal–anion con-
as [(η6-arene)Ru(NH2CHRCHRNTos)X].[22] In a similar tacts.[13a] We have now obtained single crystals of [3]Cl from
fashion, we envisaged that coordinative unsaturation to- acetone/diethyl ether solution. The shortest Ru–Cl distance
gether with the presence of amido-type nitrogen groups is 6.01 Å, indicating a lack of significant contacts between
(Schemes 1, 2, 3, and 4) renders the Mo and Ru complexes the Ru centers and the chloride anions. As expected, the
1–8 active in hydrogen transfer catalysis. Accordingly, this cationic half-sandwich complex exhibits a two-legged pi-
contribution provides a comparative study of the catalytic ano-stool geometry with the η5-C5Me5 and the η2-diimine
activity of 1–8 in transfer hydrogenation of acetophenone ligands adopting a pseudotrigonal-planar coordination
with 2-propanol as the hydrogen source.
sphere around the ruthenium atom (Figure 1).
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FULL PAPER
best of our knowledge, 5 is the first example of a stable 16-
electron dicationic half-sandwich ruthenium complex, un-
derlining once again the strong electron-donating ability of
the BLMe ligand. This affords an exceptionally short Ru–
N1 bond of 1.977(2) Å together with an elongated N1–C2
bond of 1.364(3) Å, which even exceeds the values for the
intra-ring C2–N2 and C2–N3 distances of 1.340(3) and
1.345(3) Å. Consequently, the ρ value of 1.016 indicates an
inversion of the usual bond length distribution in the guani-
dine system. The dihedral angle between the imidazole and
N1–Ru–N1A planes is 88.3°, in agreement with the ex-
pected orthogonality.
Figure 1. ORTEP diagram of the complex [3]Cl with thermal dis-
placement parameters drawn at 50% probability.
The N1–Ru–N2 angle is 77.33(4)°, and the sum of this
ligand bite angle and the two Ct–Ru–N angles is 360.0° (Ct
= centroid of the Cp* ring). Accordingly, the cation 3 can
be regarded as being almost perfectly C2v-symmetric. The
Ru–N distances of 2.0626(10) and 2.0741(10) Å are almost
identical with those determined for [3]OTf [2.0604(17) Å
and 2.0729(16) Å];[13a] they are significantly shorter than
those in the related complex [(η5-C5Me5)Ru(tmeda)]BArF
[2.183(7) Å, 2.180(6) Å][25] and fall in the same range as ob-
served for the neutral amidinate complex [(η5-C5Me5)-
Ru{iPrNC(Me)NiPr}] [2.073(3) Å].[26] The short Ru–N
bonds in [3]Cl are consistent with the expected strong elec-
tron-releasing capability of the BLMe ligand, as indicated by
the ylidic resonance structure shown in Scheme 2. Charge
separation and delocalization in the coordinated BLMe li-
Figure 2. ORTEP diagram of [(η6-C6H6)Ru(BLMe)]Cl2 ([5]Cl2) with
thermal displacement parameters drawn at 50% probability. The
letter “A” indicates atoms generated via the twofold axis.
In contrast to the blue color of [5]Cl2, treatment of [(η6-
gand can also be clearly deduced from the observation of C6H6)RuCl2]2 with BLiPr afforded a dark red solid of the
perpendicularly oriented imidazole moieties with respect to composition [6]Cl2, suggesting the presence of a different
the N–Ru–N plane (dihedral angles 81.8 and 86.4°); this coordination sphere. Indeed, X-ray diffraction analysis of
orientation rules out the possibility of any substantial π- [6]Cl2·thf revealed an asymmetric unit that is composed of
interaction between the coordinated nitrogen atoms and the an [(η6-C6H6)Ru(BLiPr)Cl]+ cation together with an unco-
imidazole rings. Consequently, the exocyclic C–N bonds ordinated chloride counterion and a thf solvate molecule
[C3–N1 1.3411(14) Å, C10–N2 1.3532(15) Å] are elongated (Figure 3, thf omitted for clarity). The cation exhibits a
and become almost equal to the intra-ring C3–N3/N4 and three-legged piano-stool geometry with ruthenium–nitrogen
C10-N5/N6 bond lengths, respectively. This structural fea- distances of Ru–N1 2.0732(12) Å and Ru–N2 2.0849(11) Å
ture can be illustrated by the parameter ρ = 2a/(b + c), with that are significantly longer than those observed in 5. Pre-
a, b and c representing the exo- (a) and endocyclic (b, c) sumably, this elongation is largely a consequence of ad-
distances within the CN3 guanidine moiety.[3b,6b] In agree- ditional chloride coordination, despite the fact that the Ru–
ment with efficient charge delocalization, ρ values of 0.990 Cl1 distance of 2.4853(4) Å indicates a comparatively weak
and 0.998 are determined for the two different CN3 sites.
interaction. In fact, this Ru–Cl bond seems to be the longest
A suitable starting material for providing the [(η6-C6H6)- ever observed for cationic complexes of the type [(η6-C6H6)-
Ru]2+ moiety is dimeric [(η6-C6H6)RuCl2]2,[27] and its reac- Ru(NʝN)Cl]+,[28] and a longer Ru-Cl distance of 2.521(1) Å
tion with BLMe afforded [(η6-C6H6)Ru(BLMe)]Cl2 ([5]Cl2) has only been observed for a neutral (benzene)rutheni-
as a deep-blue solid after precipitation from thf solution um(II) complex containing the anionic β-diketiminate li-
with n-hexane. The resulting complex is soluble in polar gand XyN–C(Me)–CH–C(Me)–NXy (Xy = 2,6-dimeth-
1
solvents such as acetonitrile and dichloromethane. Its H ylphenyl).[29]
NMR spectrum in CD3CN exhibits a benzene resonance at
In view of the larger steric requirements of the BLiPr li-
δ = 5.15 ppm and three additional singlets at δ = 3.64, 2.88 gand in comparison with BLMe, the presence of Ru–Cl
and 2.21 ppm for the NCH3, NCH2 and CCH3 groups, bonding in [6]Cl2 and its absence in [5]Cl2 seems to be coun-
respectively, indicating fast chlorine exchange or the pres- terintuitive; however, close inspection of the [(η6-C6H6)Ru-
ence of the C2v-symmetric dication 5 in solution. Single (BLiPr)Cl]+ structure reveals two additional intracationic
crystals suitable for an X-ray diffraction analysis were CH···Cl1 contacts of 2.64 and 2.82 Å that fall below the
grown from dichloromethane solution, and the molecular sum of the van der Waals radii of 2.95 Å [rvdW(Cl) =
structure of [5]Cl2, which displays crystallographic C2 sym- 1.75 Å, rvdW(H) = 1.20 Å][30] and might therefore support
metry, is shown in Figure 2. The shortest Ru–Cl distance is the weak Ru–Cl interaction in the solid state (Figure 3). In
5.15 Å, excluding any metal–chlorine interaction. To the contrast, solution NMR studies indicate C2v symmetry,
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(Arene)ruthenium Complexes with Bis(imidazolin-2-imine) Ligands
Figure 4. ORTEP diagram of the cation in [6](BF4)2·CH2Cl2 with
thermal displacement parameters drawn at 50% probability; the
ethylene bridge is disordered.
In a similar fashion as described for the preparation of
the (benzene)ruthenium complexes (vide supra), the corre-
sponding cymene complexes [7]Cl2 and [8]Cl2 were isolated
as blue or red solids from the reaction of [(η6-C10H14)-
RuCl2]2[27] with BLMe or BLiPr, respectively (Scheme 4). The
1H and 13C NMR spectra exhibit the typical resonances for
the cymene ligand.[17a,18,19b] The signals arising from the
coordinated BLMe and BLiPr ligands match those reported
for the benzene complexes 5 and 6, apart from the observa-
tion of just one broad singlet for the isopropyl methyl
groups in 8, which indicates a different or more complex
dynamic behavior. Addition of 2 equiv. of NaBF4 to a
dichloromethane solution of [8]Cl2 yielded the dark blue
complex [8](BF4)2. The molecular structure of [8](BF4)2·
CH2Cl2 was established by X-ray diffraction analysis (Fig-
ure 5), revealing the absence of any short Ru–F contacts
Figure 3. Two ORTEP diagrams of [(η6-C6H6)Ru(BLiPr)Cl]Cl in
[6]Cl2·thf with thermal displacement parameters drawn at 50%
probability; the ethylene bridge is disordered.
which implies rapid dynamic behavior and fast exchange of
1
the chloride anions. Accordingly, the H NMR spectrum in
[D6]acetone shows three singlets at δ = 5.20, 2.89 and
2.39 ppm for the C6H6, NCH2 and CCH3 hydrogen atoms,
respectively. The isopropyl groups give rise to a septet, or
more specifically a quartet-of-quartets CH resonance at δ
= 5.62 ppm and to two broad doublets at δ = 1.73 and
1.46 ppm for the diastereotopic methyl groups, indicating a
hindered rotation around the N1–C3 and N2–C14 axes at
room temperature on the NMR timescale. At lower tem-
perature, only a sharpening of these doublets is observed,
whereas the chloride ion is still rapidly exchanged even at
–50 °C.
–
between the [(η6-C10H14)Ru(BLiPr)]2+ and the BF4 ions.
The structural parameters of the dication 8 are very similar
to those established for the tetrafluoroborate salt of 6, and
the same pseudotrigonal-planar coordination sphere is ob-
served, with only slightly longer Ru–N bonds of 1.994(2)
and 2.003(2) Å. In contrast to the ecliptic orientation of the
benzene ring in 6 with respect to the imine C–N and arene
C–H bonds, the cymene ligand in 8 is oriented in a stag-
The chloride ions can be easily exchanged by weakly co-
ordinating anions such as tetrafluoroborate. This can be ac-
complished by addition of 2 equiv. of NaBF4 to a CH2Cl2
solution of [6]Cl2 followed by removal of NaCl (Scheme 3);
a deep blue solid is obtained. Single crystals of [6](BF4)2·
CH2Cl2 were obtained by diffusion of diethyl ether into a
saturated dichloromethane solution. In contrast to [6]Cl2,
no metal–anion interaction is observed, affording again a
pseudotrigonal-planar coordination sphere at the ruthe-
nium atom (Figure 4). As expected, the Ru–N bonds
[1.9818(16) and 1.9883(17) Å] are shorter than those found
in [6]Cl2 and are almost identical to the Ru–N distances in
[5]Cl2. Consequently, similar ρ values of 1.011 and 1.012
are determined. In contrast to the molecular structure of
the Cp* complex [4]OTf, there is no indication of intramo-
lecular CH···Ru contacts.[13a]
Figure 5. ORTEP diagram of the cation in [8](BF4)2·CH2Cl2 with
thermal displacement parameters drawn at 50% probability; the
ethylene bridge is disordered.
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T. Glöge, D. Petrovic, C. Hrib, P. G. Jones, M. Tamm
FULL PAPER
gered fashion, allowing the iPr and Me substituents to geners. The impact of the anion on the catalytic activity
adopt the sterically least hindered positions between the seems to be negligible, as exemplified for the most active
two imidazole sites. It should be noted that complex 8 rep- Cp*Ru system by comparison of the conversion/time dia-
resents the first example of a stable 16-electron dicationic grams for [3]Cl and [3]BArF (Figure 6). In contrast, changes
(cymene)ruthenium complex to the best of our knowledge; of the reaction conditions strongly influence the progress of
structurally related complexes have only been obtained with the ketone reduction. In the absence of KOH, the reaction
mono- and dianionic κ2-NʝN ligands.[31] For instance, Ru– slows down significantly; however, [3]OTf is still catalyti-
N bond lengths of 2.065(6) and 1.897(6) Å have been re- cally active, indicating that the diimine ligand BLMe is basic
ported for [(η6-C10H14)Ru(NH–CHPh–CHPh–NTos)][31b] enough to promote activation and deprotonation of 2-pro-
and 1.966(3)/1.946(3) Å for [(η6-C10H14)Ru(sMes-N–N=N– panol. Furthermore, attempts to carry out transfer hydro-
N–Mes)] (sMes = 2,4,6-tBu3C6H2, Mes = 2,4,6-Me3C6H2), genation at room temperature met with only limited success
which contains a dianionic tetrazene ligand.[31c]
(Table 1).
Transfer Hydrogenation of Acetophenone
Transfer hydrogenation,[32] in particular its asymmetric
version,[33] has become a standard method for the reduction
of ketones to secondary alcohols, with 2-propanol serving
as the most common organic hydrogen source. Because this
reaction can be catalyzed efficiently by numerous (benzene)-
and (cymene)ruthenium complexes, we have studied the
catalytic performance of the molybdenum and ruthenium
complexes 1–7 in the transfer hydrogenation of acetophe-
none (Scheme 5). The reactions were performed in boiling
2-propanol (b.p. = 82 °C) with 1 mol-% of catalyst loadings
and potassium hydroxide (10 mol-%) as the base. The reac-
tion progress was monitored by gas chromatography (GC),
and the results are summarized in Table 1. The Mo com-
plexes [1]PF6 and [2]BF4 proved to be insufficiently active,
and only 9% and 18% conversion was determined after
24 h, respectively. In contrast, all Ru complexes are capable
of completing this reaction within 1.5–6 h, with the BLMe
complexes being generally more active than their BLiPr con-
Figure 6. Conversion/time diagrams for [3]Cl (squares) and [3]BArF
(triangles).
Conclusions
We have shown that the bis(imidazolin-2-imine) ligands
BLMe and BLiPr can stabilize cationic and dicationic 16-
electron half-sandwich ruthenium complexes containing
pentamethylcyclopentadienyl, benzene or cymene ligands.
The unusual stability of these complexes can be ascribed to
the strong π-electron-releasing ability of BLMe and BLiPr
,
leading to a weak propensity of the Ru atom to coordinate
other π-basic ligands such as chloride. In accord with the
presence of 16-electron species in solution, reasonable ac-
tivity in transfer hydrogenation of ketones can be observed.
Scheme 5. Transfer hydrogenation of acetophenone.
Table 1. Catalytic transfer hydrogenation of acetophenone.[a]
Substrate
Catalyst
Time [h]
Conversion [%]
Experimental Section
Acetophenone [1]PF6
Acetophenone [2]BF4
Acetophenone [3]Cl
24
24
1.5
1.5
6
144
24
6
9
18
96
98
77
40
7
90
33
96
97
99
General: All operations were performed under dry argon by using
Schlenk and vacuum techniques. All solvents were purified by stan-
Acetophenone [3]BArF
Acetophenone [3]OTf[b]
Acetophenone [3]OTf[c]
Acetophenone [3]OTf[d]
Acetophenone [4]BArF
Acetophenone [4]BArF[e]
Acetophenone [5]Cl2
Acetophenone [6]Cl2
Acetophenone [7]Cl2
dard methods and distilled prior to use. H and 13C NMR spectra
1
were recorded with Bruker DPX 200 and DPX 400 devices. The
chemical shifts are given in ppm relative to TMS. The spin coupling
patterns are indicated as s (singlet), d (doublet), m (multiplet), sept
(septet) and br. (broad, for unresolved signals). Elemental analyses
(C, H, N) were performed with an Elementar Vario EL III CHNS
elemental analyzer. Mass spectrometry was performed with a Fin-
nigan MAT 90 device. UV/Vis spectra were recorded with a Varian
Cary 50 device. Sodium triflate, sodium tetrafluoroborate and so-
dium BArF were obtained from Aldrich and used as received.
24
2
6
2
[a] Conditions: 0.02 mmol of cat., 0.2 mmol of KOH, 10 mL of
iPrOH, 2 mmol of acetophenone, temperature: 82 °C. [b] Without
KOH. [c] Room temperature. [d] Room temperature and 5 bar H2
pressure. [e] 0.1 mol-% catalyst loading.
BLMe [13a]
,
BLiPr [13a] [1]PF6,[14] [2]BF4,[14] the ruthenium heterocub-
,
ane [Cp*RuCl]4,[23] the ruthenium dimers [(η6-C6H6)RuCl2]2 and
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(Arene)ruthenium Complexes with Bis(imidazolin-2-imine) Ligands
[(η6-C10H14)RuCl2]2,[27] and phellandrene[34] were prepared accord-
ing to literature procedures.
(CH2), 49.1 (NCH), 23.4 (CHCH3), 22.4 (CHCH3), 11.5 (C5Me5),
10.5 (CCH3) ppm. UV/Vis(CH2Cl2): λmax (ε) = 514 (1801) nm.
C35H59F3N6O3RuS (802.01): calcd. C 52.42, H 7.41, N 10.48; found
C 50.45, H 6.94, N 9.61.
[(η5-C5Me5)Ru(BLMe)]Cl ([3]Cl): A solution of BLMe (127.9 mg,
0.42 mmol) in thf (5 mL) was added dropwise to an orange suspen-
sion of [(η5-C5Me5)RuCl]4 (108.7 mg, 0.10 mmol) in thf (10 mL) at
room temperature. During the addition of the ligand the reaction
mixture turned purple, and the solution was stirred for 3 h. The
volume of thf was reduced to 5 mL, and the product was precipi-
tated with n-hexane (20 mL). Filtration, washing with n-hexane
(2ϫ10 mL) and drying in vacuo afforded the product as a purple
solid (189 mg, 82%). 1H NMR (400 MHz, [D6]acetone, 25 °C): δ =
3.69 (s, 12 H, NCH3), 2.62 (s, 4 H, CH2), 2.32 (s, 12 H, CCH3),
[(η5-C5Me5)Ru(BLMe)]BArF ([3]BArF):
A
solution of NaBArF
(292.4 mg, 0.33 mmol) in thf (15 mL) was added dropwise to a pur-
ple solution of [(η5-C5Me5)Ru(BLMe)]Cl (188.1 mg, 0.33 mmol) in
thf (25 mL) at room temperature. The solution was stirred for 2 h
and then filtered. The volume of thf was reduced to 5 mL and the
product precipitated with n-hexane (30 mL). Filtration, washing
with n-hexane (2ϫ15 mL) and drying in vacuo afforded the prod-
1
uct as a purple solid (418.4 mg, 90%). H NMR (400 MHz, [D6]-
1.33 (s, 15 H, CpCH3) ppm. 13C NMR (100.52 MHz, [D6]acetone, acetone, 25 °C): δ = 7.66 (m, 8 H, ortho-BArF), 7.54 (m, 4 H, para-
25 °C): δ = 157.2 (NCN), 120.0 (NCCH3), 71.1 (C5Me5), 55.1 BArF), 3.54 (s, 12 H, NCH3), 2.49 (s, 4 H, CH2), 2.16 (s, 12 H,
(CH2), 31.1 (NCH3), 11.2 (C5Me5), 8.7 (CCH3) ppm. UV/ CCH3), 1.19 (s, 15 H, CpCH3) ppm. 13C NMR (100.6 MHz, [D6]-
Vis(CH2Cl2): λmax (ε) = 526 (2507) nm. IR (KBr/Nujol): ν = 1462 acetone, 25 °C): δ = 162.5 (B-ipsoC), 157.3 (NCN), 135.6 (B-or-
˜
(C=N) cm–1. C26H43ClN6Ru (576.2): calcd. C 54.20, H 7.52, N thoC), 129.9 (CF3), 126.8 (B-metaC), 120.3 (NCCH3), 118.5 (B-
14.59; found C 53.59, H 7.23, N 14.32.
paraC), 71.1 (C5Me5), 55.0 (CH2), 31.0 (NCH3), 11.1 (CCH3), 8.6
(C5Me5) ppm. C58H55BClF24N6Ru (1404.0): calcd. C 49.62, H 3.95,
N 5.99; found C 49.52, H 4.41, N 5.41.
[(η5-C5Me5)Ru(BLiPr)]Cl ([4]Cl): A solution of BLiPr (175.0 mg,
0.42 mmol) in thf (10 mL) was added dropwise to an orange sus-
pension of [(η5-C5Me5)RuCl]4 (108.7 mg, 0.10 mmol) in thf (5 mL)
at room temperature. During the addition of the ligand the reaction
mixture turned purple, and the solution was stirred overnight. The
volume of thf was reduced to 5 mL, and the product was precipi-
tated with n-hexane (20 mL). Filtration, washing with n-hexane
(2ϫ10 mL) and drying in vacuo afforded the product as a purple
solid (238 mg, 88%). 1H NMR (400 MHz, [D6]acetone, 25 °C): δ =
5.27 (sept, 4 H, NCH), 2.60 (s, 4 H, CH2), 2.40 (s, 12 H, CCH3), uct as a purple solid (406.3 mg, 92%). H NMR (400 MHz, [D6]-
1.80 (d, 12 H, CHCH3), 1.48 (s, 15 H, CpCH3) 1.42 (d, 12 H, acetone, 25 °C): δ = 7.82 (m, 8 H, ortho), 7.70 (s, 4 H, para), 5.29
CHCH3) ppm. 13C NMR (100.52 MHz, [D6]acetone, 25 °C): δ = (sept, 4 H, NCH), 2.63 (s, 4 H, CH2), 2.42 (s, 12 H, NCCH3), 1.82
157.3 (NCN), 118.5 (NCCH3), 70.7 (C5Me5), 58.0 (CH2), 49.1 (d, 12 H, CHCH3), 1.50 (s, 15 H, Cp*-CH3), 1.45 (d, 12 H,
(NCH), 23.4 (CHCH3), 22.4 (CHCH3), 11.5 (C5Me5), 10.5 (CCH3) CHCH3) ppm. 13C NMR (100.52 MHz, [D6]acetone, 25 °C): δ =
[(η5-C5Me5)Ru(BLiPr)]BArF ([4]BArF):
A
solution of NaBArF
(257.5 mg, 0.29 mmol) in thf (15 mL) was added dropwise to a pur-
ple solution of [(η5-C5Me5)Ru(BLiPr)]Cl (200.0 mg, 0.29 mmol) in
thf (20 mL) at room temperature. The solution was stirred for 2 h
and then filtered. The volume of thf was reduced to 5 mL and the
product precipitated with n-hexane (30 mL). Filtration, washing
with n-hexane (2ϫ15 mL) and drying in vacuo afforded the prod-
1
ppm. UV/Vis(CH2Cl2): λmax (ε) = 494 (1636) nm. IR (KBr/Nujol):
163.4 (B-Carom.), 162.9 (B-Carom.), 162.4 (B-Carom.), 161.9 (B-
Carom.), 157.3 (NCN), 135.6 (CF3), 130.5 (Carom.), 130.2 (Carom.),
129.9 (Carom.), 129.5 (CF3), 126.8 (Carom.), 124.0 (CF3), 121.0 (p-
CH), 118.5 (NCCH3), 118.4 (CF3), 70.7 (C5Me5), 58.0 (NC2H4N),
49.1 [NCH(CH3)2], 23.4 (NCHCH3), 22.4 (NCHCH3), 11.5
(C5Me5), 10.5 (CCH3) ppm. C66H71BF24N6Ru (1516.2): calcd. C
52.28, H 4.72, N 5.54; found C 52.35, H 4.64, N 4.81.
ν = 1462 (C=N) cm–1. C H ClN Ru (688.40): calcd. C 59.32, H
˜
34 59
6
8.64, N 12.21; found C 58.67, H 8.71, N 11.27.
[(η5-C5Me5)Ru(BLMe)]OTf ([3]OTf):
A
solution of NaOTf
(178.9 mg, 1.04 mmol) in thf (15 mL) was added dropwise to a pur-
ple solution of [3]Cl (600 mg, 1.04 mmol) in thf (25 mL) at room
temperature. The solution was stirred for 2 h and then filtered. The
volume of thf was reduced to 5 mL and the product precipitated
[(η6-C6H6)Ru(BLMe)]Cl2 ([5]Cl2): A solution of BLMe (63.9 mg,
with n-hexane (30 mL). Filtration, washing with n-hexane 0.21 mmol) in thf (5 mL) was added dropwise to a brown suspen-
(2ϫ15 mL) and drying in vacuo afforded the product as a purple
solid (681 mg, 95%). 1H NMR (400 MHz, [D6]acetone, 25 °C): δ =
3.68 (s, 12 H, NCH3), 2.62 (s, 4 H, CH2), 2.31 (s, 12 H, CCH3),
sion of [(η6-C6H6)RuCl2]2 (50.0 mg, 0.10 mmol) in thf (10 mL) at
room temperature. During the addition of the ligand the reaction
mixture turned blue, and the solution was stirred overnight. The
1.33 (s, 15 H, CpCH3) ppm. 13C NMR (100.52 MHz, [D6]acetone, volume of thf was reduced to 5 mL and the product precipitated
25 °C): δ = 157.3 (NCN), 122.5 (CF3), 120.0 (NCCH3), 71.1 with n-hexane (20 mL). Filtration, washing with n-hexane
(C5Me5), 55.1 (CH2), 31.0 (NCH3), 11.1 (C5Me5), 8.7 (CCH3) ppm. (2ϫ10 mL) and drying in vacuo afforded the product as a blue
UV/Vis(CH2Cl2): λmax (ε) = 526 (2252) nm. C27H43F3N6O3RuS solid (105.8 mg, 95%). 1H NMR (400 MHz, [D3]acetonitrile,
(689.80): calcd. C 47.01, H 6.28, N 12.18; found C 47.05, H 6.43,
N 11.86.
25 °C): δ = 5.15 (s, 6 H, C6H6), 3.64 (s, 12 H, NCH3), 2.88 (s, 4 H,
CH2), 2.21 (s, 12 H, CCH3) ppm. 13C NMR (100.6 MHz, [D3]-
acetonitrile, 25 °C): δ = 157.2 (NCN), 121.1 (NCCH3), 82.0 (C6H6),
56.3 (CH2), 32.6 (NCH3), 9.1 (CCH3) ppm. C22H34Cl2N6Ru
(554.5): calcd. C 47.65, H 6.18, N 15.16; found C 47.30, H 6.27, N
15.30.
[(η5-C5Me5)Ru(BLiPr)]OTf ([4]OTf):
A
solution of NaOTf
(55.1 mg, 0.32 mmol) in thf (10 mL) was added dropwise to a pur-
ple solution of [4]Cl (222 mg, 0.32 mmol) in thf (15 mL) at room
temperature. The solution was stirred for 2 h and then filtered. The
volume of thf was reduced to 5 mL, and the product was precipi-
tated with n-hexane (20 mL). Filtration, washing with n-hexane
(2ϫ10 mL) and drying in vacuo afforded the product as a purple
[(η6-C6H6)Ru(BLiPr)]Cl2 ([6]Cl2): A solution of BLiPr (250.0 mg,
0.60 mmol) in thf (5 mL) was added dropwise to a brown suspen-
sion of [(η6-C6H6)RuCl2]2 (150.0 mg, 0.3 mmol) in thf (10 mL) at
solid (230 mg, 91%). 1H NMR (400 MHz, [D6]acetone, 25 °C): δ = room temperature. During the addition of the ligand the reaction
5.27 (sept, 4 H, NCH), 2.60 (s, 4 H, CH2), 2.40 (s, 12 H, CCH3), mixture turned red, and the suspension was stirred overnight. The
1.80 (d, 12 H, CHCH3), 1.48 (s, 15 H, CpCH3) 1.42 (d, 12 H, volume of thf was reduced to 5 mL and the product precipitated
CHCH3) ppm. 13C NMR (100.52 MHz, [D6]acetone, 25 °C): δ = with n-hexane (20 mL). Filtration, washing with n-hexane
157.3 (NCN), 122.5 (CF3), 118.5 (NCCH3), 70.7 (C5Me5), 58.0
(2ϫ10 mL) and drying in vacuo afforded the product as a red solid
Eur. J. Inorg. Chem. 2009, 4538–4546
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4543

T. Glöge, D. Petrovic, C. Hrib, P. G. Jones, M. Tamm
FULL PAPER
(338.5 mg, 85%). 1H NMR (400 MHz, [D6]acetone, 25 °C): δ = δ = 5.15 (dd, 4 H, C6H4), 3.63 (s, 12 H, NCH3), 2.83 (s, 4 H, CH2),
3
3
5.62 (sept, J = 7 Hz, 4 H, NCH), 5.20 (s, 6 H, C6H6), 2.89 (s, 4
2.44 (sept, J = 7 Hz, 1 H, C6H4CH), 2.25 (s, 12 H, CCH3), 2.10
H, CH2), 2.39 (s, 12 H, CCH3), 1.83 (d, 3J = 7 Hz, 12 H, CHCH3), (s, 3 H, C6H4CH3), 1.23 [d, J = 7 Hz, 6 H, C6H4CH(CH3)2] ppm.
3
1.53 (d, 3J = 7 Hz, 12 H, CHCH3) ppm. 13C NMR (100.6 MHz, 1H NMR (400 MHz, [D2]dichloromethane, 25 °C): δ = 4.92 (m, 4
3
[D6]acetone, 25 °C): δ = 156.4 (NCN), 122.1 (NCCH3), 81.4
H, C6H4), 3.65 (s, 12 H, NCH3), 2.90 (s, 4 H, CH2), 2.41 (sept, J
(C6H6), 56.8 (CH2), 49.2 (NCH), 22.5 (CHCH3), 22.0 (CHCH3), = 7 Hz, 1 H, C6H4CH), 2.17 (s, 12 H, CCH3), 2.09 (s, 3 H,
10.5 (CCH3) ppm. C30H50Cl2N6Ru (666.7): calcd. C 54.04, H 7.56,
N 12.60; found C 53.19, H 7.55, N 12.17.
C6H4CH3), 1.20 [d, 3J = 7 Hz, 6 H, C6H4CH(CH3)2] ppm. 13C
NMR (100.6 MHz, [D2]dichloromethane, 25 °C): δ = 156.8 (NCN),
120.0 (NCCH3), 101.4 (aryl-CCHCH3), 94.4 (aryl-CCH3), 81.7
(aryl-CH), 79.9 (aryl-CH), 55.9 (CH2), 32.8 (NCH3), 31.1 (aryl-
CHCH3), 22.7 (CCHCH3), 18.7 (aryl-CCH3), 9.4 (CCH3) ppm.
C26H42Cl2N6Ru (610.6): calcd. C 51.14, H 6.93, N 13.76; found C
51.09, H 7.02, N 12.83.
[(η6-C10H14)Ru(BLiPr)]Cl2 ([8]Cl2): A solution of BLiPr (135.8 mg,
0.326 mmol) in thf (5 mL) was added dropwise to a brown suspen-
sion of [(η6-C10H14)RuCl2]2 (100.0 mg, 0.163 mmol) in thf (10 mL)
at room temperature. During the addition of the ligand the reaction
mixture turned red, and the suspension was stirred overnight. The
[(η6-C6H6)Ru(BLiPr)](BF4)2 ([6](BF4)2): Solid NaBF4 (32.9 mg,
0.30 mmol) was added to a solution of [(η6-C6H6)Ru(BLiPr)]Cl2
(100.0 mg, 0.15 mmol) in dichloromethane (20 mL) at room tem-
perature and the mixture stirred overnight. During the reaction the
mixture turned dark blue. The solution was filtered, and the volume
of dichloromethane was reduced to 5 mL, after which the product
was precipitated with diethyl ether (40 mL). Filtration, washing
with diethyl ether (2ϫ10 mL) and drying in vacuo afforded the
1
product as a dark blue solid (92.3 mg, 80%). H NMR (400 MHz,
3
[D6]acetone, 25 °C): δ = 5.74 (s, 6 H, C6H6), 5.29 (sept, J = 7 Hz,
3
4 H, NCH), 2.93 (s, 4 H, CH2), 2.49 (s, 12 H, CCH3), 1.83 (d, J volume of thf was reduced to 5 mL and the product precipitated
3
= 7 Hz, 12 H, CHCH3), 1.53 (d, J = 7 Hz, 12 H, CHCH3) ppm.
with n-hexane (20 mL). Filtration, washing with n-hexane
13C NMR (100.6 MHz, [D6]acetone, 25 °C): δ = 153.2 (NCN), (2ϫ10 mL) and drying in vacuo afforded the product as a red solid
1
124.0 (NCCH3), 79.1 (C6H6), 60.0 (CH2), 50.5 (NCH), 22.3
(163.5 mg, 70.6%). H NMR (400 MHz, [D6]acetone, 25 °C): δ =
(CHCH3), 21.8 (CHCH3), 10.4 (CCH3) ppm. 19F NMR 5.68 (sept, J = 7 Hz, 4 H, NCH), 5.25 (dd, 4 H, C6H4), 2.93 (s, 4
3
(188.3 MHz,
[D6]acetone,
25 °C):
δ
=
–150.9 ppm.
H, CH2), 2.74 (sept, 3J = 7 Hz, 1 H, C6H4CH), 2.35 (s, 12 H,
CCH3), 2.11 (s, 3 H, C6H4CH3), 1.55 (br. s, 24 H, CHCH3), 1.23
C30H50B2F8N6Ru (769.4): calcd. C 46.83, H 6.55, N 10.92; found
C 46.88, H 6.61, N 10.55.
3
[d, J = 7 Hz, 6 H, C6H4CH(CH3)2] ppm. 13C NMR (100.6 MHz,
[D6]acetone, 25 °C): δ = 157.3 (NCN), 121.9 (NCCH3), 103.8 (aryl-
CCHCH3), 92.7 (aryl-CCH3), 81.4 (aryl-CH), 78.8 (aryl-CH), 58.2
(CH2), 49.3 (NCH), 31.2 (aryl-CHCH3), 22.7 (NCHCH3), 22.5
(NCHCH3), 18.7 (aryl-CCH3), 10.8 (CCH3), 10.8 (CCHCH3) ppm.
C34H58N6RuCl2 (722.9): calcd. C 56.49, H 8.09, N 11.63; found C
55.68, H 7.94, N 10.71.
[(η6-C10H14)Ru(BLMe)]Cl2 ([7]Cl2): A solution of BLMe (49.9 mg,
0.164 mmol) in thf (5 mL) was added dropwise to a brown suspen-
sion of [(η6-C10H14)RuCl2]2 (50.0 mg, 0.082 mmol) in thf (10 mL)
at room temperature. During the addition of the ligand the reaction
mixture turned blue, and the solution was stirred overnight. The
volume of thf was reduced to 5 mL and the product precipitated
with n-hexane (20 mL). Filtration, washing with n-hexane [(η6-C10H14)Ru(BLiPr)](BF4)2 ([8](BF4)2): Solid AgBF4 (53.8 mg,
(2ϫ10 mL) and drying in vacuo afforded the product as a blue
0.28 mmol) was added to a solution of [(η6-C10H14)Ru(BLiPr)]Cl2
1
solid (41 mg, 40%). H NMR (400 MHz, [D3]acetonitrile, 25 °C):
(100.0 mg, 0.14 mmol) in dichloromethane (80 mL) at room tem-
Table 2. Selected bond lengths [Å] and angles [°] for [3]Cl, [5]Cl2, [6]Cl2·thf, [6](BF4)2·CH2Cl2 and [8](BF4)2·CH2Cl2 with estimated
standard deviations in parentheses.
[a]
[3]Cl
[5]Cl2
[6]Cl2·thf
[6](BF4)2·CH2Cl2
[8](BF4)2·CH2Cl2
Ru–N1
Ru–N2
2.0626(10)
2.0741(10)
1.977(2)
2.0732(12)
2.0849(11)
1.9883(17)
1.9818(16)
2.003(2)
1.994(2)
Ru–C(ring)
N1–C3
N1–C2
2.1163(11)–2.1643(11) 2.150(3)–2.212(3)
1.3411(14)
1.364(3)
2.1571(18)–2.1965(17) 2.149(2)–2.212(2)
2.166(2)–2.192(3)
1.364(3)
1.3407(17)
1.364(2)
N2–C10
N2–C14
Ru–Cl1
Ru–Cl2
Ru–F
1.3532(15)
1.3488(18)
2.4853(4)
5.45
1.368(2)
1.367(3)
6.01
5.15
5.33–7.93
79.96(7)
84.8, 89.6
4.04–7.93
80.31(8)
83.4, 86.8
N1–Ru–N2
77.33(4)
78.58(13)
88.3
75.88(5)
(N–Ru–N)/(C3N2)[b] 81.8, 86.4
H1···Cl; H2···Cl
58.1, 76.6
2.82; 2.64
1.3528(17)
1.3629(18)
C3–N3
C3–N4
C10–N5
C10–N6
C2–N2
C2–N3
C14–N5
C14–N6
ρ[c]
1.3538(15)
1.3554(15)
1.3531(16)
1.3575(14)
1.350(3)
1.349(2)
1.346(3)
1.350(3)
1.340(3)
1.345(3)
1.3562(18)
1.3542(18)
0.988; 0.995
1.352(2)
1.351(3)
1.011; 1.012
1.356(3)
1.333(3)
1.012; 1.016
0.990; 0.998
1.016
[a] The cation has twofold symmetry. [b] Angle between the RuN2 and imidazole ring planes. [c] ρ = 2a/(b + c), with a, b and c representing
the exo- (a) and endocyclic (b, c) distances within the CN3 guanidine moiety.
4544
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 4538–4546

(Arene)ruthenium Complexes with Bis(imidazolin-2-imine) Ligands
Table 3. Crystallographic data for [3]Cl, [5]Cl2, [6]Cl2·thf, [6](BF4)2·CH2Cl2 and [8](BF4)2·CH2Cl2.
[3]Cl
[5]Cl2
[6]Cl2·thf
[6](BF4)2·CH2Cl2
[8](BF4)2·CH2Cl2
Empirical formula
Formula weight
Space group
a [Å]
b [Å]
c [Å]
C26H43ClN6Ru
576.18
P21/c
12.3542(3)
15.5561(3)
15.1258(3)
90
C22H34Cl2N6Ru
554.52
C2/c
16.1088(6)
10.7763(3)
15.4499(5)
90
C34H58Cl2N6ORu
738.83
P21/n
17.6825(2)
10.2456(3)
21.5597(4)
90
C31H52B2Cl2F8N6Ru C35H58B2Cl2F8N6Ru
854.38
P21/c
908.46
P21
10.6820(2)
15.0442(2)
13.9604(2)
90
19.8375(8)
13.4419(6)
15.2597(12)
90
α [°]
β [°]
107.976(3)
90
2765.02(10)
4
116.738(4)
90
2395.21(14)
4
112.491(2)
90
3608.83(13)
4
110.396(10)
90
3814.0(4)
4
112.274(2)
90
2076.06(6)
2
γ [°]
V [Å3]
Z
T [°C]
–173
0.71073
1.384
–173
0.71073
1.538
–173
0.71073
1.360
–173
0.71073
1.488
–173
0.71073
1.453
λ [Å]
Dcalcd. [gcm–3]
µ [mm–1]
0.689
0.900
0.618
0.622
0.576
R(Fo)
Rw(Fo
0.0210
0.0564
0.0314
0.0694
0.0280
0.0622
0.0310
0.0724
0.0310
0.0637
2
)
perature and the mixture stirred overnight. During the reaction the
mixture turned dark blue. The solution was filtered, washed with
20 mL dichloromethane, and the volume of the solution was re-
duced to 10 mL, followed by the precipitation of the product with
diethyl ether (40 mL). Filtration, washing with diethyl ether
(2ϫ10 mL) and drying in vacuo afforded the product as a dark
blue solid (62.5 mg, 54%). 1H NMR (400 MHz, [D3]acetonitrile,
paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. See Table 2 for selected molecular dimensions and
Table 3 for crystallographic data.
Acknowledgments
3
25 °C): δ = 5.39 (s, 4 H, C6H4), 4.94 (sept, J = 7 Hz, 4 H, NCH),
3
This work was supported by the Deutsche Forschungsgemeinschaft
(DFG) through grant number Ta 189/6-2.
2.60 (s, 4 H, CH2), 2.54 (sept, J = 7 Hz, 1 H, C6H4CH), 2.43 (s,
3
12 H, CCH3), 2.12 (s, 3 H, C6H4CH3), 1.81 (d, J = 7 Hz, 12 H,
3
3
CHCH3), 1.45 (d, J = 7 Hz, 12 H, CHCH3), 1.32 [d, J = 7 Hz, 6
H, C6H4CH(CH3)2] ppm. 13C NMR (100.6 MHz, [D1]chloroform,
25 °C): δ = 152.3 (NCN), 123.1 (NCCH3), 103.8 (aryl-CCHCH3),
88.2 (aryl-CCH3), 80.4 (aryl-CH), 78.0 (aryl-CH), 59.4 (CH2), 50.0
[1] a) S. Herres-Pawlis, Nachr. Chem. 2009, 57, 20–23; b) S. Herres-
Pawlis, A. Neuba, O. Seewald, T. Seshadri, H. Egold, U.
Flörke, G. Henkel, Eur. J. Org. Chem. 2005, 4879–4890.
(NCH), 31.5 (aryl-CHCH3), 22.9 (NCHCH3), 21.4 (NCHCH3), [2] a) A. L. Llamas-Saiz, C. Faces-Focesa, J. Elguero, J. Mol.
Struct. 1994, 328, 297–323; b) V. Raab, J. Kipke, R. M.
Gschwind, J. Sundermeyer, Chem. Eur. J. 2002, 8, 1682–1693;
c) U. Wild, O. Hübner, A. Maronna, M. Enders, E. Kaifer,
H. Wadepohl, H.-J. Himmel, Eur. J. Inorg. Chem. 2008, 4440–
4447.
19.0 (aryl-CCH3), 10.3 (CCH3), 9.9 (CCHCH3) ppm.
C34H58B2F8N6Ru (825.6): calcd. C 49.47, H 7.08, N 10.18; found
C 49.41, H 6.56, N 9.89.
General Procedure for the Transfer Hydrogenation of Acetophenone:
Potassium hydroxide (11.2 mg, 0.2 mmol) was added to the catalyst
solution (0.02 mmol, 1 mol-%) in 2-propanol (10 mL) at room tem-
perature. The solution was heated to 81 °C, and acetophenone
(240 mg, 2 mmol, 0.2 ) was added. Approximately 0.1 mL samples
were regularly taken and filtered through the short silica gel column
by using diethyl ether as a solvent. The reaction progress was moni-
tored by gas chromatography (GC).
[3] a) A. Hoffmann, J. Börner, U. Flörke, S. Herres-Pawlis, Inorg.
Chim. Acta 2009, 362, 1185–1193; b) A. Neuba, R. Haase, M.
Bernard, U. Flörke, S. Herres-Pawlis, Z. Anorg. Allg. Chem.
2008, 634, 2511–2517; c) A. Neuba, S. Herres-Pawlis, U.
Flörke, G. Henkel, Z. Anorg. Allg. Chem. 2008, 634, 771–777;
d) U. Wild, P. Roquette, E. Kaifer, J. Mautz, O. Hübner, H.
Wadepohl, H.-J. Himmel, Chem. Eur. J. 2008, 14, 7813–7821;
e) H. Wittmann, V. Raab, A. Schorm, J. Plackmeyer, J. Sun-
dermeyer, Eur. J. Inorg. Chem. 2001, 1937–1948; f) N. Kuhn,
M. Grathwohl, M. Steinmann, G. Henkel, Z. Naturforsch. Teil
B 1998, 53, 997–1003.
Single-Crystal X-ray Structure Determinations: Data were recorded
at low temperature with an Oxford Diffraction Xcalibur S dif-
fractometer by using Mo-Kα radiation. Structures were refined an-
isotropically on F2 by using the program system SHELXL-97.[35]
Hydrogen atoms were included in the models at geometrically cal-
culated positions and refined by using a riding model or with rigid
methyl groups. Special features: The ethylene bridge was disordered
over two positions for [6]Cl2·thf, [6](BF4)2·CH2Cl2 and [8](BF4)2·
CH2Cl2. Close inspection of diffraction patterns for [5]Cl2 revealed
a small extent of twinning by 180° rotation about the x axis; the
data reduction was modified appropriately for a twinned crystal,
and the structure quality improved significantly. Reflection num-
bers cannot be counted reliably for twinned crystals. For [8](BF4)2·
CH2Cl2 the Flack parameter refined to 0.000(16). CCDC-733779
{[6]Cl2·thf}, CCDC-733780 {[3]Cl2}, CCDC-733781 {[5]Cl2},
CCDC-733782 {[6](BF4)2·CH2Cl2} and CCDC-733783 {[8](BF4)2·
CH2Cl2} contain the supplementary crystallographic data for this
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Received: June 22, 2009
Published Online: September 10, 2009
4546
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 4538–4546