Modular synthesis of a new type of Chiral Bis(carbene) Ligand from L-Valinol and Iridium (I) and Rhodium(I) complexes thereof

Article abstract of DOI:10.1002/ejic.200800933

New, chiral bis(imidazol-2-y1idene) ligands, and their rhodium(I) and iridium(I) complexes, have been prepared by a simple six-step synthesis starting from commercially available enantiomerically pure L-valinol. The stepwise introduction of the imidazoles

Full text of DOI:10.1002/ejic.200800933

FULL PAPER
DOI: 10.1002/ejic.200800933
Modular Synthesis of a New Type of Chiral Bis(carbene) Ligand from
L
-Valinol and Iridium(I) and Rhodium(I) Complexes Thereof
Ulrich Nagel*[a] and Claus Diez[a]
Keywords: Nitrogen heterocycles / Carbene ligands / Iridium / Rhodium
New, chiral bis(imidazol-2-ylidene) ligands, and their rhodi-
um(I) and iridium(I) complexes, have been prepared by a
a one-pot transmetallation reaction gives the endo and exo
stereoisomers in different ratios, depending on the metal and
simple six-step synthesis starting from commercially avail- the reaction conditions. Diastereomerically pure material was
able enantiomerically pure
L-valinol. The stepwise introduc-
obtained by crystallisation.
tion of the imidazoles makes it possible to create chiral
bis(NHC) complexes with different substituents at the ter-
minal nitrogen atoms. Formation of IrI and RhI complexes by
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
precursor must either have two amino functions for the
condensation, or two leaving groups if the precursor acts
as an alkylating agent.[18] Another method, published by
Douthwaite et al., uses a base-induced 1,3-cycloaddition to
form imidazoles.[19]
In the early 1990s, Itoh, Pfaltz and others demonstrated
that valinol-based chiral ligands are useful for asymmetric
catalysis.[20–23] They used valinol and other β-amino
alcohols as building blocks for chiral oxazolines, which
were then combined with pyridines, phosphanes and, more
recently, by Herrmann and Gade with carbenes.[7,24–26] Be-
side oxazolines, valinol has also been used to prepare chiral
phosphanes and alkoxy-NHC ligands.[24,27,28]
In this article we report a synthetic strategy that offers a
basis for a great number of different chiral bis(NHC) li-
gands and their unsymmetrical rhodium and iridium com-
plexes, inspired by the well-established concept of C1-sym-
metrical enantioselective catalysts. Our aim was to find a
simple synthesis for chiral chelating N-heterocyclic carbene
ligand precursors derived from readily available, enantio-
merically pure amino acids or their corresponding chiral β-
amino alcohols.
Apart from the choice of starting material, this synthetic
pathway should offer further possibilities for ligand modifi-
cation. The stepwise introduction of the imidazole units by
combining two different methods allows unsymmetrical
substitution of the terminal nitrogen atoms at both imid-
azole rings. Starting with bromide 3, it should be possible
to introduce other nucleophilic coordinating units like
phosphanes or amines into the ligand precursor. With re-
gard to a catalytic application of the rhodium and iridium
complexes, the modular synthesis of the ligand offers sev-
eral possibilities for adjusting the catalytic activity and
selectivity.
Introduction
Since their discovery, stable N-heterocyclic carbenes
(NHCs) have been the subject of intense interest, primarily
as ligands for transition metals. NHC complexes display
significant advantages in comparison with phosphane com-
plexes, particularly their stability towards air, moisture and
heat.[1–3] Their use in transition-metal-mediated C–C coup-
ling and metathesis reactions has established N-heterocyclic
carbenes as a new class of ligands alongside traditional
phosphane and amine ligands.[3–6] The field of asymmetric
catalysis with NHC-containing ligands is dominated by
mixed ligands with a carbene unit and a second coordinat-
ing group, such as a phosphane or oxazoline.[7–12] These
unsymmetrical ligands illustrate the fact that C2 symmetry
is not a necessary criterion for efficient enantioselectivity in
asymmetric catalysis.
Applications of bis(N-heterocyclic carbene) complexes in
asymmetric catalysis, however, are rare, and we are only
aware of one example with good to excellent ee values that
has been reported in the literature by Shi et al. for the
hydrosilylation of prochiral ketones.[13] Further potential
applications of chiral bis(NHC) complexes are transfer hy-
drogenations of prochiral ketones. Recent reports by
Crabtree, Peris and co-workers have indicated the high ac-
tivity of [bis(NHC)]rhodium and -iridium complexes in hy-
drogen-transfer reactions.[14,15]
Most of the existing routes to chiral bidentate NHC li-
gands use condensation reactions or alkylation of N-substi-
tuted imidazoles with a suitable precursor.[13,16,17] This
[a] Institut für Anorganische Chemie, Universität Tübingen,
Auf der Morgenstelle 18, 72076 Tübingen, Germany
E-mail: Ulrich.Nagel@uni-tuebingen.de
1248
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 1248–1255

IrI and RhI Complexes of Chiral Bis(carbene) Ligands
Results and Discussion
Synthesis of Ligand Precursors
Starting from commercially available, enantiomerically
pure -valinol, the first imidazole was introduced according
to a method of Saigo et al. by a condensation reaction with
ammonium acetate, glyoxal and formaldehyde in moderate
yields.[29]
To make the alcohol a good leaving group, compound 2
was converted into the tosylate according to a conventional
method by treatment with p-tosyl chloride and pyridine at
–10 to 0 °C in a maximum isolated yield of 81%. Attempts
to tosylate the alcohol with tosyl chloride in thf/water/so-
dium hydroxide gave the product in lower yields along with Scheme 2. Preparation of the bis(imidazolium) salts 5a–c.
a higher amount of by-products.
With regard to complex synthesis by transmetallation
with silver(I) oxide, tosylate 2 was converted into the bro-
gave lower yields and more by-products. Compound 4 is a
hygroscopic, air-stable, white solid that shows characteristic
1H NMR signals at δ = 8.9 ppm (in CDCl3) and 13C NMR
signals at δ = 139.0 ppm for the NCHN proton and carbon
atom of the imidazolium salts, respectively. The bis(imid-
azolium) salts were prepared by SN2 displacement of bro-
mide from the electrophiles RBr (R = nPr, iPr and 2,6-di-
fluorobenzyl) by the remaining imidazole nitrogen atom of
4. However, only electrophiles with bromine in a primary,
benzylic or at least secondary position provided good
yields.[32] The reactions were carried out in acetonitrile at
reflux temperature and gave the bis(imidazolium) salts 5a–
c in Ͼ78% yield.[16,19] All compounds obtained are hygro-
scopic, white solids, which are soluble in water, methanol,
dichloromethane and acetonitrile but insoluble in diethyl
mide under Finkelstein conditions by treatment with lith-
ium bromide in acetone (Scheme 1).[30] Direct methods to
convert the alcohol into the bromide, such as an Appel reac-
tion or treatment with thionyl bromide, were not success-
ful.[31] The major side reactions observed for compounds 2
and 3 were elimination of TsOH or HBr and intermolecular
dimerisation or polymerisation. To avoid these reactions, all
conversions were carried out at low temperatures or in di-
lute solution.
1
ether and hexane. The H and 13C NMR spectra of com-
pounds 5a–c show the typical signals of bis(imidazolium)
salts in the range δ = 9.1–9.4 ppm for the NCHN protons
and δ = 136.4–138.9 ppm for the corresponding carbon
atoms, in CD3OD or D2O as solvent.[33] Further character-
istic NMR signals for compounds 1–5 are the separate sig-
nals for the diastereotopic methyl groups at δ ≈ 19 ppm in
the 13C NMR spectra and two doublets at δ ≈ 0.9 ppm in
1
1
the H NMR spectrum. The H NMR signals of the dia-
stereotopic methylene protons are separated as well.
Scheme 1. Synthesis of the chiral imidazole bromide 3.
Preparation and Stereochemistry of the Complexes
With imidazole bromide 3 as starting point, it was pos-
sible to obtain chiral ligand precursors with different sub-
All iridium(I) and rhodium(I) complexes of 5a–c were
stituents in two steps (Scheme 2). The first step was the al- prepared from the bis(imidazolium) bromides by treatment
kylation of 1-methylimidazole with 3 as alkylating agent. with silver(I) oxide and [MCl(cod)]2 in dichloromethane ac-
Generally, all N-monoalkylated imidazoles, even those with cording to the method of Mata et al. under slightly different
sterically demanding substituents, can be used in this reac- conditions (Scheme 3).[33] To avoid the previously observed
tion.[32]
formation of dimetallated species, especially at this linker
The correct choice of reaction conditions proved to be length, all complex syntheses were carried out as one-pot
of great importance to achieve acceptable yields of 4. The reactions with 2 equiv. of silver(I) oxide. Whereas the iri-
best result (82%) was obtained without solvent, with an dium complexes were prepared by stirring the reaction mix-
excess of 1-methylimidazole at 50 °C, and a reaction time of tures overnight at ambient temperature, the reactions with
3 d. The excess 1-methylimidazole was necessary to prevent rhodium were conducted at reflux temperature for 2 h and
intermolecular alkylation of imidazole bromides. Conver- then with stirring at ambient temperature for 3 h. All com-
sions in toluene as solvent at 95–105 °C and reaction times plexes were purified by gradient column chromatography
of approximately 12 h were also partially successful but on silica gel, with dichloromethane/acetone as eluent and
Eur. J. Inorg. Chem. 2009, 1248–1255
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1249

U. Nagel, C. Diez
FULL PAPER
KPF6 for anion exchange, to give the rhodium(I) (6a,b) and gave a yellow oily precipitate and crystals. Whereas the crys-
iridium(I) (7a,b) complexes in 58–68% yield.[33,34] An ad- tals were a 1:1 mixture of endo/exo stereoisomers, the oil
ditional aspect of complexation was the formation of two contained only the endo form.
diastereomers, which were not separable by column
The described complexes were tested in catalysis and
chromatography. The reaction between [IrCl(cod)]2, Ag2O showed no activity in the hydrogenation of ithaconic acid
and 5a or 5b gave the exo isomer as the major product, and low activity, with poor enantioselectivity, in the hydro-
where the backbone isopropyl group lies out of the coordi- silylation of prochiral ketones. Promising preliminary re-
nation plane, as depicted in Figure 2 (vide infra). After col- sults with ee values of up to 60% have been obtained in
umn chromatography, complex 7a was obtained with an transfer hydrogenations of phenyl ketones by using 2-pro-
exo/endo ratio of 96:4, whereas 7b was obtained as a 92:8 panol as hydrogen source. These results indicate that the
mixture under the conditions described above. To investi- activity and enantioselectivity of the tested complexes de-
gate the stability of the complexes and the stereoisomers, pend on the ligand architecture, the metal and the ketones,
complex 7a was dissolved in [D6]dmso and heated in an but presumably not on the exo/endo ratio.
NMR tube at 85 °C. No decomposition of the complex was
All complexes were characterised by NMR spectroscopy,
observed after 3 d at this temperature, but the exo/endo ra- high-resolution mass spectrometry, elemental analysis and
tio decreased from 96:4 to 85:15. The reaction between 5a some by single-crystal X-ray diffractometry. Due to the lack
and [IrCl(cod)]2 was also carried out in refluxing dichloro- of symmetry, 13C NMR spectra of the iridium and rhodium
methane and gave 7a as a 65:35 exo/endo mixture.
complexes show a signal for each carbon atom. Thus, the
spectra for the rhodium compounds display two character-
istic doublets at δ ≈ 179 ppm, with typical Rh–C coupling
constants of 52 Hz, for the metallated carbene carbon
atoms, and four doublets for the vinylic carbon atoms of
the cod ring with coupling constants ranging from 7.7 to
8.2 Hz.[33,35] The diastereotopic methyl groups appear as
two signals between δ = 18 and 20 ppm. The spectra of the
iridium complexes are very similar to the rhodium ones,
except for the absence of metal–carbon coupling and a
high-field shift by ca. 15 ppm for the vinylic cod signals.[34]
The existence of two stereoisomers is indicated by a double
set of signals with intensities that correspond to the
Scheme 3. Synthesis of complexes 6a,b and 7a,b. DCM = dichloro-
methane.
1
exo/endo ratios. The H NMR shifts of the backbone pro-
tons are characteristic for the exo and endo isomers. Thus,
The opposite diastereoselectivity was observed for the re- the signal for the single proton at the chiral carbon atom
action between [RhCl(cod)]2, Ag2O and bis(imidazolium) appears as a triplet of doublets at δ = 6.5 ppm for the exo
salts 5a and 5c, with the endo stereoisomers of 6a and 6b isomer, whereras the diastereotopic protons of the adjacent
being the major products (exo/endo ratios of 15:85 and methylene group give rise to a signal located in the range δ
20:80). As shown in Figure 1 (vide infra), the isopropyl = 4.1–4.5 ppm, beneath the signals of the vinylic cod pro-
group in the endo isomer is oriented in the coordination tons. The chemical shifts of the three relevant backbone
plane. Complex 6a was heated in an NMR tube at 85 °C in protons are inverted for the endo isomer. Thus, the signal
[D6]dmso for 2 d like the iridium compound 7a and showed for the methylene proton oriented towards the metal atom
complete decomposition. Only slow decomposition and no appears as a doublet of doublets at δ = 6.0 ppm, whereas
alteration of the exo/endo ratio was observed at 50 °C.
the signals for the second methylene proton and for the pro-
In summary, the small exo/endo preference is primarily ton at the chiral carbon atom are in the range δ = 4.1–
related to the metal, although the factors determining this 4.7 ppm.
ratio are not obvious. At higher temperatures, the iridium
complex 7a generally tends to give lower exo values, which
is indicative of a kinetically controlled formation of the exo
complex under the reaction conditions described. A rapid
Crystal Structures of 6a and 7a
isomerisation to the products of thermodynamic equilib-
Crystals of 6a and 7a suitable for X-ray diffraction were
rium is prevented by the kinetic stability of the resulting obtained by layering a concentrated thf (6a) or thf/CH2Cl2
complexes even in hot, coordinating solvents like dimethyl (7a) solution with cyclohexane. The molecular structures
sulfoxide. Another possible reason for the exo preference shows that the geometry about the rhodium and iridium
of iridium could be weak agostic interactions between the atom is distorted square-planar, with C–M–C bite angles of
backbone C–H and the metal centre, although the data we 80.6° for the rhodium complex and 79.8° for the iridium
have do not corroborate this hypothesis.
complex. The M–Ccarbene bond lengths are between 2.015
Diastereomerically pure material was obtained by crys- and 2.068 Å, as expected for (NHC)rhodium(I) and -iridi-
tallisation for both iridium complexes (exo) and the rho- um(I) compounds.[33,34,36,37] The seven-membered rings
dium complex 6a (endo). Attempts to crystallise 6b always formed by the ligands and the metal atoms adopt boat-like
1250
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 1248–1255

IrI and RhI Complexes of Chiral Bis(carbene) Ligands
conformations, as known for cycloheptane, with the back- between the bridging methylene carbon atom and the metal
bone isopropyl group in either the endo (Figure 1) or exo atom is 3.17 Å, and that between the asymmetric carbon
position (Figure 2).
atom and the metal atom is 3.56 Å; for the exo isomer 7a
the M–C distances are 3.11 Å for the asymmetric carbon
atom and 3.55 Å for the methylene carbon atom. The dis-
tances between the metal atom and the methyl/isopropyl
carbon atoms at the imidazole nitrogen atoms are also af-
fected by the stereoisomers of the chelate ring. Thus,
whereas the isopropyl carbon atom is ca. 0.2 Å closer to the
Rh centre than the methyl carbon atom in the structure of
6a, the positions in the structure of 7a are inverted.
Conclusions
We have demonstrated that chiral bis(NHC) ligand pre-
cursors are accessible from chiral amino alcohols by a five-
step synthesis. This synthetic pathway makes it possible to
use a large number of enantiomerically pure amino acids as
the starting point for further preparations of chiral, chelat-
ing NHC complexes. The modular build-up of the ligand
offers several opportunities for its modification, including
the introduction of different substituents at the terminal ni-
trogen atoms of the imidazole rings or, possibly, the intro-
duction of other coordinating groups instead of the second
imidazole. Furthermore, we have shown that a one-pot
transmetallation procedure is also applicable to this kind of
ligand, with formation of two stable diastereomers. Dia-
stereomerically pure complexes were obtained by crystalli-
sation. Preliminary results for the transfer hydrogenation of
prochiral ketones indicate a potential application for the
described complexes. Our future investigations will focus on
diastereoselective complex synthesis and the catalytic ac-
tivity and stereoselectivity of the prepared iridium and rho-
dium complexes and their dependence on variations in the
substitution pattern of the ligand.
Figure 1. ORTEP diagram of 6a (thermal ellipsoids at the 50%
probability level). Hydrogen atoms [except H at C(111)] and the
–
counterion (PF6 ) have been omitted for clarity. Selected bond
lengths [Å] and angles [°]: Rh(1)–C(11) 2.035(3), Rh(1)–C(12)
2.026(8), Rh(1)–C(403) 2.204(5), Rh(1)–C(404) 2.218(4), Rh(1)–
C(407) 2.173(3), Rh(1)–C(408) 2.202(6), Rh(1)–C(121) 3.174(14),
Rh(1)–C(111) 3.561(16), Rh(1)–C(122) 3.620(6), Rh(1)–C(115)
3.448(7); C(11)–Rh(1)–C(12) 80.62(12), C(407)–Rh(1)–C(404)
81.17(11), C(408)–Rh(1)–C(403) 81.20(11).
Experimental Section
General Remarks: NMR spectra were recorded with a Bruker
DRX-400 spectrometer, with CDCl3, CD3OD or D2O as solvent.
Elemental analyses were performed with a VARIO EL analyzer.
Electron impact (EI+) and fast atom bombardment (FAB+) mass
spectra were recorded with a Finnigan MAT, TSQ 70 instrument
by using 3-nitrobenzyl alcohol as matrix. Electrospray mass spectra
were recorded with a Bruker Daltonics APEX II FT-ICR instru-
ment by using CH3OH as solvent and nitrogen as drying and nebul-
izing gas. Imidazole 1 was prepared from -valinol (97% ee, Sigma-
Aldrich) according to a literature procedure.[29] All other reagents
were commercially available and were used as received.
Figure 2. ORTEP diagram of 7a (thermal ellipsoids at the 50%
probability level). Hydrogen atoms [except H at C(113)] and the
–
counterion (PF6 ) have been omitted for clarity. Selected bond
lengths [Å] and angles [°]: Ir(1)–C(11) 2.068(4), Ir(1)–C(21)
2.015(6), Ir(1)–C(1) 2.204(3), Ir(1)–C(2) 2.147(4), Ir(1)–C(5)
2.186(5), Ir(1)–C(6) 2.197(4), Ir(1)–C(112) 3.552(14), Ir(1)–C(113)
3.112(13), Ir(1)–C(151) 3.442(7), Ir(1)–C(225) 3.628(8); C(11)–
Ir(1)–C(21) 79.76(10), C(5)–Ir(1)–C(2) 80.95 (10), C(6)–Ir(1)–C(1)
81.19 (11).
(2S)-2-(1-Imidazolyl)-3-methylbutyl 4-Methylbenzenesulfonate (2):
A pyridine (20 mL) solution of 1 (3.6 g, 23.4 mmol) was cooled to
–10 °C in an ice/NaCl bath. p-Tosyl chloride (4.9 g, 25.7 mmol) was
added in one portion, then the solution was stirred at –10 °C for
1 h and at 0 °C for a further 4 h. Water (50 mL) was then added
dropwise, and the resulting mixture was extracted with CH2Cl2
(3ϫ100 mL). The combined organic extracts were dried with
Na2SO4, and all volatiles were removed under reduced pressure to
A comparison of the distances between the metal atom
and the backbone carbon atoms of both stereoisomers
shows that these carbon atoms change their positions rela-
tive to the metal atom. For the endo isomer 6a the distance give 2 as a pale-yellow oil. Yield: 5.8 g (81%). MS (EI): m/z (%) =
Eur. J. Inorg. Chem. 2009, 1248–1255
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1251

U. Nagel, C. Diez
FULL PAPER
308 (70). MS (HREI+): calcd. for C15H20N2O3S 308.1194; found in dichloromethane and extracted into water (2ϫ5 mL). The water
308.1183. 1H NMR (CDCl3, 400 MHz): δ = 7.65 (m, 2 H,
was removed under reduced pressure, and the resulting white solid
SCCHCH), 7.49 (s, 1 H, NCHN), 7.31 (m, 2 H, SCCHCHCCH3), was washed with diethyl ether (2ϫ10 mL) and dried in vacuo to
3
7.02 (s, 1 H, NCHCHN), 6.86 (s, 1 H, NCHCHN), 4.29 (d, JH,H
give 5a as a very hygroscopic, white solid. Yield: 190 mg (79%).
1
= 5.2 Hz, 2 H, OCH2CH), 3.92 [m, 1 H, CH2 CHCH(CH3)2], 2.43
(s, 3 H, C6H4CH3), 2.13 [m, 1 H, CHCH(CH3)2], 0.98 [d, JH,H
MS (FA): m/z (%) = 341 (30). H NMR (CD3OD, 400 MHz): δ =
3
=
9.41 (s, 1 H, NCHN), 9.09 (s, 1 H, NCHN), 7.90 (d, 3JH,H = 1.8 Hz,
3
3
6.6 Hz, 3 H, CH(CH3)2], 0.65 [d, JH,H = 6.7 Hz, 3 H, CH(CH3)2]
1 H, CHimid), 7.82 (br. s, 1 H, CHimid), 7.49 (d, JH,H = 1.8 Hz, 1
ppm. 13C{1H} NMR (CDCl3, 100 MHz): δ = 145.21 (CSO3),
H, CHimid), 7.44 (br. s, 1 H, CHimid), 4.95 (t, JH,H = 4.8 Hz, 2 H,
3
136.70 (NCHN), 132.06 (CHCCH3), 129.93 (CHCHCCH3), 129.24 NCH2CH), 4.87 (m, 1 H, CH2CHN), 4.65 [m, 1 H, NCH(CH3)2],
3
(SCCHCH), 127.72 (NCHCHN), 117.22 (NCHCHN), 69.37
3.85 (s, 1 H, NCH3), 2.36 [m, 1 H, CHCH(CH3)2], 1.48 [d, JH,H
3
(OCH2CH), 62.76 (CH2CHCH), 26.81 [CHCH(CH3)2], 21.51 = 6.7 Hz, 6 H, CHCH(CH3)2], 1.13 [d, JH,H = 6.6 Hz, 3 H,
3
(CCH3), 19.47, 18.92 [CH(CH3)2] ppm.
CHCH(CH3)2], 0.82 [d, JH,H = 6.7 Hz, 3 H, CHCH(CH3)2] ppm.
13C{1H} NMR (CD3OD, 100 MHz): δ = 138.85, 136.40 (NCN),
125.54, 123.75, 123.38, 122.78 (CHimid), 68.21 (CH2CHN), 55.23
[NCH(CH3 )2 ], 51.88 (NCH2 CH), 37.19 (NCH3 ), 32.31
[CHCH(CH3)2], 23.22, 23.13 [NCH(CH3)2], 19.69, 19.15 [CH-
(CH3)2] ppm.
1-[(1S)-1-(Bromomethyl)-2-methylpropyl]imidazole (3): A mixture of
2 (5.8 g, 18.8 mmol) and lithium bromide (4.9 g, 56.4 mmol) was
stirred in refluxing acetone (60 mL) for 5 h. After cooling to ambi-
ent temperature, the formed precipitate was removed by filtration,
and the volatiles were removed under reduced pressure. Water
(100 mL) was added to the residue to remove excess LiBr, and the
mixture was extracted with CHCl3 (3ϫ80 mL). The organic ex-
tracts were combined, washed with brine and dried with Na2SO4.
After filtration, all volatiles were removed under reduced pressure.
The crude product was then purified by gradient column
chromatography [SiO2; first CH2Cl2/acetone (1:1), then acetone] to
give 3 as a colourless oil. Yield: 3.5 g (85%). MS (EI): m/z (%)
= 216 (60). MS (HREI+): calcd. for C8H13BrN2 216.0262; found
1-{(1S)-2-Methyl-1-[(3-methyl-1-imidazolium)methyl]propyl}-3-
propylimidazolium Dibromide (5b): An acetonitrile solution (3 mL)
of 4 (165 mg, 0.55 mmol) and 1-bromopropane (1 mL) was stirred
at reflux temperature under argon for 20 h. The volatiles were then
removed under reduced pressure, and the resulting solid was dis-
solved in dichloromethane and added dropwise to diethyl ether,
with stirring, to give a white, fluffy precipitate. This precipitate was
washed with diethyl ether (2ϫ10 mL) and dried in vacuo to give
5b as a hygroscopic, white powder. Yield: 200 mg (86%). MS (FA):
m/z (%) = 341 (40). H NMR (CD3OD, 400 MHz): δ = 9.32 (s, 1
H, NCHN), 9.08 (s, 1 H, NCHN), 7.91 (d, JH,H = 1.8 Hz, 1 H,
CHimid), 7.75 (d, JH,H = 1.7 Hz 1 H, CHimid), 7.52 (d, JH,H
1.7 Hz, 1 H, CHimid), 7.50 (d, JH,H = 1.8 Hz, 1 H, CHimid), 5.00–
1
216.0254. H NMR (CDCl3, 400 MHz): δ = 7.46 (s, 1 H, NCHN),
1
7.03 (s, 1 H, NCHCHN), 6.91 (s, 1 H, NCHCHN), 3.86 (m, 1 H,
CH2CHN), 3.69 (m, 2 H, CHCH2Br), 2.11 [m, 1 H, CHCH-
(CH3)2], 0.96 [d, 3JH,H = 6.7 Hz, 3 H, CHCH(CH3)2], 0.72 [d, 3JH,H
= 6.8 Hz, 3 H, CHCH(CH3)2] ppm. 13C{1H} NMR (CDCl3,
100 MHz): δ = 136.75 (NCHN), 129.11 (CHimid), 116.82 (CHimid),
64.79 (CH2CHN), 34.15 (CHCH2Br), 32.04 [CHCH (CH3)2],
19.43, 18.62 [CH(CH3)2] ppm.
3
3
3
=
3
3
4.85 (m, 3 H, CH2CHN, NCH2CH), 4.18 (t, JH,H = 7.1 Hz, 2 H,
NCH2CH2), 3.88 (s, 3 H, NCH3), 2.38 [m, 1 H, CHCH(CH3)2],
1.87 (sext, JH,H = 3.6 Hz, 2 H, NCH2CH2), 1.17 [d, JH,H
3
3
=
6.7 Hz, 3 H, CHCH(CH3)2], 1.06 [m, 6 H, CH2CH3, CHCH-
(CH3)2] ppm. 13C{1H} NMR (CD3OD, 100 MHz): δ = 138.91,
137.82 (NCN), 125.76, 125.29, 123.91, 122.70 (CHimid), 68.27
(CH2CHN), 52.96 (NCH2CH), 51.96 (NCH2CH2), 37.19 (NCH3),
32.53 [CHCH(CH3)2], 24.45 (NCH2CH2), 19.75, 19.11 [CH-
(CH3)2], 11.00 (CH2CH3) ppm.
1-[(2S)-2-(1-Imidazolyl)-3-methylbutyl]-3-methylimidazolium Bro-
mide (4): A mixture of 3 (495 mg, 2.28 mmol) and 1-methylimid-
azole (936 mg, 11.4 mmol) was stirred at 50 °C for 72 h. After cool-
ing to ambient temperature, diethyl ether (20 mL) was added,
whilst stirring, to dissolve excess 1-methylimidazole. The diethyl
ether fraction was then removed with a syringe and the colourless,
oily precipitate was washed two more times with diethyl ether and
dried in vacuo. The oil was then dissolved in CHCl3 (10 mL) and
extracted into water (2ϫ8 mL). After removal of the water under
reduced pressure, the resulting solid was washed with diethyl ether
(2ϫ15 mL) and dried in vacuo to give 4 as a hygroscopic, white
solid. Yield: 556 mg (82%). MS (FA): m/z (%) = 219 (100). MS
(HRESI+): calcd. for C12H19N4 219.16042; found 219.16042. 1H
NMR (CD3OD, 400 MHz): δ = 8.93 (s, 1 H, NCHN), 7.77 (s, 1 H,
3-(2,6-Difluorobenzyl)-1-{(1S)-2-methyl-1-[(3-methylimidazolium)-
methyl]propyl}imidazolium Dibromide (5c): 2,6-Difluorobenzyl bro-
mide (207 mg, 1.0 mmol) was added to a solution of 4 (146 mg,
0.49 mmol) in acetonitrile in one portion, and the mixture was
heated at reflux temperature for 17 h. The same procedure used to
give 5b was applied to give 5c as a white, hygroscopic solid. Yield:
1
192 mg (78%). MS (FA+): m/z (%) = 425 (25). H NMR (CDCl3,
400 MHz): δ = 10.04, 9.66 (s, 2 H, NCHN), 8.37, 8.07 (s, 1 H,
CHimid), 7.43 (m, 1 H, CHphenyl), 7.27, 7.18 (s, 1 H, CHimid), 6.97
3
NCHN), 7.54 (t, JH,H = 1.6 Hz, 1 H, CHimid), 7.47 (br. s, 1 H,
4
(m, 2 H, CHphenyl), 5.51 [q, JH,F = 13.6 Hz, 2 H, NCH2C(CF)2],
3
CHimid), 7.42 (t, JH,H = 1.7 Hz, 1 H, CHimid), 7.08 (br. s, 1 H,
5.85 (m, 1 H, NCH2CHN), 4.85–4.56 (m, 2 H, NCHCH2N), 3.88
3
CHimid), 4.98–4.81 (m, 2 H, NCH2CH), 4.60 (qd, JH,H = 3.4 Hz,
3
(s, 3 H, NCH3), 2.41 [m, 1 H, CHCH(CH3)2], 1.11 [d, JH,H
=
1 H, CH2CHN), 3.90 (s, 3 H, NCH3), 2.35 [m, 1 H, CHCH-
(CH3)2], 1.20 [d, 3JH,H = 6.7 Hz, 3 H, CHCH(CH3)2], 0.86 [d, 3JH,H
= 6.7 Hz, 3 H, CHCH(CH3)2] ppm. 13C{1H} NMR (CD3OD,
100 MHz): δ = 139.06, 138.40 (NCN), 129.89, 124.99, 123.88,
119.21 (CHimid), 65.41 (CH2CHN), 52.93 (NCH2CH), 36.83
(NCH3), 32.79 [CHCH(CH3)2], 20.03, 19.43 [CH(CH3)2] ppm.
3
6.5 Hz, 3 H, CHCH(CH3)2], 0.84 [d, JH,H = 6.6 Hz, 3 H,
CHCH(CH3)2] ppm. 19F{1H} NMR (CDCl3, 376 MHz): δ =
–115.69, –115.52 ppm. 13C{1H} NMR (CDCl3, 100 MHz): δ =
162.33 (d, JC,F = 5.9 Hz, CF), 152.82 (d, JC,F = 6.3 Hz, CF),
137.35, 137.04 (NCHN), 132.67 (t, JC,F = 10.9 Hz, CHphenyl),
1
1
2
123.82, 122.32, 121.93, 120.55 (CHimid), 112.22 (m, 2 C, CHphenyl),
2
109.46 (t, JC,F = 18.8 Hz, Cq phenyl), 65.89 (CH2CHN), 50.13
3-Isopropyl-1-{(1S)-2-methyl-1-[(3-methylimidazolium)methyl]-
propyl}imidazolium Dibromide (5a): An acetonitrile solution (5 mL)
of 4 (170 mg, 0.57 mmol) and 2-bromopropane (1 mL), was stirred
under argon at reflux temperature for 48 h. After removal of all
volatiles under reduced pressure, the remaining solid was dissolved
(NCH2 CH), 41.59 [NCH2 C(CF)2 ] 36.74 (NCH3 ), 31.44
[CHCH(CH3)2], 19.09, 18.26 [CH(CH3)2] ppm.
(η4-1,5-Cyclooctadiene)(3-isopropyl-1-{(1S)-2-methyl-1-[(3-methyl-
imidazol-2-ylidene)methyl]propyl}imidazol-2-ylidene)rhodium(I)
1252
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 1248–1255

IrI and RhI Complexes of Chiral Bis(carbene) Ligands
Hexafluorophosphate (6a): Silver(I) oxide (130 mg, 0.56 mmol) was 19.67, 18.42 [CH(CH3)2] ppm. C27H34F8N4PRh (705.74): calcd. C
added to a dichloromethane (12 mL) solution of 5a (120 mg,
0.28 mmol), and the mixture was stirred under argon at ambient
temperature for 2 h. [Rh(cod)Cl]2 (69 mg, 0.14 mmol) was added
to the resulting grey suspension in one portion to give a white pre-
cipitate. To complete the reaction, the mixture was stirred in the
dark under argon at reflux temperature for 2 h and at room tem-
perature for a further 3 h. The suspension was filtered through Ce-
lite to remove insoluble silver salts and the resulting yellow solution
was concentrated under reduced pressure. The crude solid was then
purified by gradient column chromatography [SiO2; first CH2Cl2,
CH2Cl2/acetone (2:1), then CH2Cl2/acetone (1:1) and 2 equiv.
KPF6]. A second flash chromatography with CH2Cl2/acetone (4:1)
as eluent gave the title compound as an analytically pure, yellow
powder. Crystals were obtained by layering a thf solution of 6a
with cyclohexane. Yield: 118 mg (68 %). M.p. 115 °C (dec. at
46.30, H 4.89, N 8.00; found C 46.00, H 5.13, N 7.70.
(η4-1,5-Cyclooctadiene)(3-isopropyl-1-{(1S)-2-methyl-1-[(3-methyl-
imidazol-2-ylidene)methyl]propyl}imidazol-2-ylidene)iridium(I)
Hexafluorophosphate (7a): Silver(I) oxide (162 mg, 0.70 mmol) was
added to a dichloromethane (15 mL) solution of 5a (140 mg,
0.33 mmol), and the mixture was stirred in the dark at room tem-
perature under argon for 2.5 h. [Ir(cod)Cl]2 (101 mg, 0.15 mmol)
was then added to the grey suspension in one portion to give a
white precipitate. To complete the reaction, the mixture was stirred
in the dark at room temperature for 14 h. The suspension was fil-
tered through Celite to remove insoluble silver salts, and the re-
sulting orange-red solution was concentrated under reduced pres-
sure. The crude solid was then purified by gradient column
chromatography [SiO2; first CH2Cl2, CH2Cl2/acetone (2:1), then
CH2Cl2/acetone (1:1) and 2 equiv. KPF6]. Analytically pure mate-
rial was obtained by a second flash column chromatography with
CH2Cl2/acetone (7:1) as eluent to give the title compound as an
orange-red solid. Crystalline material was obtained by layering a
thf/CH2Cl2 (1:1) solution of 7a with cyclohexane. Yield: 143 mg
(62 %). M.p. 151 °C (dec. at 205 °C). MS (HRESI+): calcd. for
165 °C). MS (HRESI+): calcd. for C23H36N4Rh 471.19895; found
3
471.19907. 1H NMR (CDCl3, 400 MHz): δ = 7.10 (d, JH,H
=
3
1.8 Hz, 1 H, CHimid), 6.79 (d, JH,H = 1.9 Hz, 1 H, CHimid), 6.76
3
3
(d, JH,H = 1.8 Hz, 1 H, CHimid), 6.65 (d, JH,H = 1.8 Hz, 1 H,
CHimid), 5.94 (dd, JH,H = 11.4, 14.1 Hz, 1 H, NCH2CH), 5.27 [m,
1 H, NCH(CH3)2], 4.66–4.34 (m, 5 H, NCH2CH, CHcod), 4.11 [m,
1 H, NCHCH(CH3)2], 3.61 (s, 3 H, NCH3), 2.51–2.04 [m, 9 H,
CHCH(CH3)2, CH2 cod], 1.39 [d, JH,H = 6.7 Hz, 3 H, NCH-
(CH3)2], 1.25 [d, JH,H = 6.6 Hz, 3 H, NCH(CH3)2], 1.12 [d, JH,H
C
23H36IrN4 559.25404; found 559.25396. 1H NMR (CDCl3,
400 MHz): δ = 7.03 (d, 3JH,H = 2.1 Hz, 1 H, CHimid), 6.89 (d, 3JH,H
3
3
3
3
= 2.0 Hz, 1 H, CHimid), 6.81 (m, 2 H, CHimid), 6.41 (td, JH,H
=
3
3
4.6, 10.9 Hz, 1 H, CH2CHN), 4.54 [vsept, JH,H = 6.8 Hz, 1 H,
NCH(CH3)2], 4.26 (m, 3 H, CHcod, NCH2), 4.09–3.92 (m, 3 H,
= 6.8 Hz, 3 H, CHCH(CH3)2], 0.88 [d, JH,H = 6.7 Hz 3 H,
CHCH(CH3)2] ppm. 13C{1H} NMR (CDCl3, 100 MHz): δ =
1
1
CHcod, NCH2), 3.84 (s, 3 H, NCH3), 2.39–2.20 [m, 3 H, CH2 cod
,
180.54 (d, JC,Rh = 52.3 Hz, RhC), 176.86 (d, JC,Rh = 51.5 Hz,
1
CHCH(CH3)2], 2.09 (m, 3 H, CH2 cod), 1.87 (m, 3 H, CH2 cod), 1.35
RhC), 126.33, 122.37, 122.00, 115.72 (CHimid), 91.06 (d, JC,Rh
=
3
3
1
1
[d, JH,H = 6.8 Hz, 3 H, NCH(CH3)2], 1.17 [d, JH,H = 6.5 Hz, 3
H, NCH(CH3)2], 1.10 [d, 3JH,H = 6.8 Hz, 3 H, CHCH(CH3)2], 0.98
7.9 Hz, CHcod), 88.51 (d, JC,Rh = 7.7 Hz, CHcod), 88.0 (d, JC,Rh
= 8.2 Hz, CHcod), 86.54 (d, JC,Rh = 7.8 Hz, CHcod), 65.04
1
3
[d, JH,H = 6.4 Hz, 3 H, CHCH(CH3)2] ppm. 13C{1H} NMR
(CH2CHN), 54.16 [NCH(CH3)2], 50.21 (NCH2CHN), 36.74
(NCH3), 35.28 [CHCH(CH3)2], 31.37, 31.25, 29.66, 29.22
(CH2 cod), 24.14, 23.43 [NCH(CH3)2], 19.78, 18.57 [CHCH(CH3)2]
ppm. C25H40F6N4PRh (616.43): calcd. C 44.81, H 5.89, N 9.09;
found C 44.52, H 5.61, N 8.93.
(CDCl3, 100 MHz): δ = 175.47, 173.61 (IrC), 124.72, 121.67,
118.17, 117.49 (CHimid), 77.82, 74.63, 74.34, 73.34 (CHcod), 64.29
(CH2CHN), 52.59 [NCH(CH3)2], 52.08 (NCH2CH), 39.12 (NCH3),
32.12 [CHCH(CH3)2], 32.09, 30.67, 30.39, 29.34 (CH2 cod), 23.58,
23.32 [NCH(CH3)2], 20.87, 19.82 [CH(CH3)2] ppm. C23H36F6IrN4P
(705.74): calcd. C 39.14, H 5.14, N 7.94; found C 38.82, H 5.03, N
8.06.
(η4-1,5-Cyclooctadiene)[3-(2,6-difluorobenzyl)-1-{(1S)-2-methyl-1-
[(3-methylimidazol-2-ylidene)methyl]propyl}imidazol-2-ylidene)-
rhodium(I) Hexafluorophosphate (6b): The same procedure was
used as for 6a. The reaction between 5c (230 mg, 0.45 mmol), sil-
ver(I) oxide (209 mg, 0.90 mmol) and [Rh(cod)Cl]2 (118 mg,
0.24 mmol) in dichloromethane (15 mL) gave the title compound
6b as a yellow powder. Crystalline material was obtained by layer-
ing a thf/CH2Cl2 (7:1) solution of 6b with cyclohexane. Yield:
184 mg (58%). M.p. 127 °C (dec. at 195 °C). MS (HRESI+): calcd.
(η4-1,5-Cyclooctadiene)(1-{(1S)-2-methyl-1-[(3-methylimidazol-2-
ylidene)methyl]propyl}-3-propylimidazol-2-ylidene)iridium(I) Hexa-
fluorophosphate (7b): The same procedure was used as for 7a. Reac-
tion between 5b (145 mg, 0.34 mmol), silver(I) oxide (162 mg,
0.70 mmol) and [Ir(cod)Cl]2 (108 mg, 0.16 mmol) in dichlorometh-
ane (15 mL) gave 7b as an orange-red solid. Crystalline material
for C27H34F2N4Rh 555.18011; found 555.17968. 1H NMR (CDCl3, was obtained by layering a thf/CH2Cl2 (3:1) solution of 7b with
3
400 MHz): δ = 7.34 (m, 1 H, CFCHCH), 7.15 (d, JH,H = 1.8 Hz, cyclohexane. Yield: 152 mg (63%). M.p. 159 °C (dec. at 209 °C).
3
1 H, CHimid), 6.92 (m, 2 H, CFCH), 6.78 (d, JH,H = 1.9 Hz, 1 H,
MS (HRESI+): calcd. for C23H36IrN4 561.25638; found 561.25631.
3
3
3
CHimid), 6.65 (d, JH,H = 1.7 Hz, 1 H, CHimid), 6.50 (d, JH,H
=
1H NMR (CDCl3, 400 MHz): δ = 7.02 (d, JH,H = 2.0 Hz, 1 H,
3
3
1.7 Hz, 1 H, CHimid), 6.03 (dd, JH,H = 11.6, 14.1 Hz, 1 H, CHimid), 6.90 (d, JH,H = 1.9 Hz, 1 H, CHimid), 6.81 (d, JH,H
=
CH2CHN), 5.85, 5.35 [d, 4JH,F = 14.0 Hz, 2 H, CH2C(CF)2], 4.73– 2.0 Hz, 1 H, CHimid), 6.78 (d, JH,H = 2.0 Hz, 1 H, CHimid), 6.49
3
4.20 (m, 6 H, NCHCH2N, CHcod), 3.62 (s, 3 H, NCH3), 2.58–1.95 (td, JH,H = 4.3, 12.5 Hz, 1 H, CH2CHN), 4.38 (td, JH,H = 2.8,
3
[m, 9 H, CHCH(CH3)2, CH2 cod], 1.13 [d, JH,H = 6.8 Hz, 3 H, 7.2 Hz 1 H, CHCH2N), 4.31–4.25 (m, 2 H, CHcod), 4.08 (m, 1 H,
CH(CH3)2], 0.93 [d, 3JH,H = 6.8 Hz, 3 H, CH(CH3)2] ppm. 13C{1H} CHCH2N), 3.99–3.87 (m, 2 H, CHcod), 3.83 (s, 3 H, NCH3), 3.79
1
NMR (CDCl3, 100 MHz): δ = 179.77 (d, JC,Rh = 52.1 Hz, RhC), (td, JH,H = 3.4, 7.2 Hz, 2 H, NCH2CH2), 2.42–1.78 [m, 9 H,
1
1
3
179.12 (d, JC,Rh = 52.1 Hz, RhC), 162.65 (d, JC,F = 7.0 Hz,
CH2 cod, CHCH(CH3)2], 1.67 (sext, JH,H = 7.3 Hz, 2 H,
1
3
CHCF), 160.16 (d, JC,F = 7.1 Hz, CHCF),131.64 (t, JC,F
=
NCH2CH2), 1.16 [d, 3JH,H = 6.5 Hz, 1 H, CH(CH3)2], 0.97 [d, 3JH,H
3
10.5 Hz, CFCHCH), 125.08, 122.18, 122.09, 118.82 (CHimid), = 6.4 Hz, 3 H, CH(CH3)2], 0.69 (t, JH,H = 7.4 Hz, 1 H, 3 H,
2
2
112.08 (t, JC,F = 12.3 Hz, CFCH), 111.08 (t, JC,F = 18.4 Hz,
CH2CH3) ppm. 13C{1H} NMR (CDCl3, 100 MHz): δ = 176.06,
173.35 (IrC), 124.59, 121.87, 121.65, 117.53 (CHimid), 77.86, 74.30,
74.23, 72.56 (CHcod), 64.34 (CH2CHN), 52.54 (NCH2CH2), 51.42
(NCH2CH), 39.31 (NCH3), 32.67 [CHCH(CH3)2], 32.64, 30.18,
29.89, 29.32 (CH2 cod), 24.46 (NCH2CH2), 20.82, 19.88 [CH-
CFC), 91.51 (d, 1JC,Rh = 8.1 Hz, CHcod), 88.62 (d, 1JC,Rh = 8.2 Hz,
1
1
CHcod), 88.02 (d, JC,Rh = 7.7 Hz, CHcod), 87.33 (d, JC,Rh
7.9 Hz, CHcod), 65.33 (CH2CHN), 49.88 (NCH2CH), 44.09
(NCH2C), 35.17 (NCH3), 31.72, 31.61, 29.39, 29.09 (CH2 cod),
=
Eur. J. Inorg. Chem. 2009, 1248–1255
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1253

U. Nagel, C. Diez
FULL PAPER
Table 1. Crystallographic data.
6a
7a
Empirical formula
Formula mass
C23H36F6N4PRh·C4H8O
688.54
C23H36F6IrN4P
705.73
T [K]
λ [Å]
173
0.71073
173
0.71073
Crystal system
Space group
triclinic
P1
orthorhombic
P212121
a [Å]
b [Å]
c [Å]
α [°]
9.7115(8)
11.8538(10)
14.8137(12)
94.839(7)
92.479(7)
112.774(6)
1561.4(2)
2
10.2580(6)
13.2530(8)
19.2342(14)
90
90
90
2614.9(3)
β [°]
γ [°]
V [Å3]
Z
4
ρcalcd. [gcm–3]
1.465
0.661
1.793
5.229
µ [mm–1]
F(000)
712
1392
θ range for data collection
Index ranges
3.44–29.30
–13 Յ h Յ 13
–16 Յ k Յ 16
–20 Յ l Յ 20
27159
3.07–26.80
–12 Յ h Յ 12
–16 Յ k Յ 16
–24 Յ l Յ 24
36294
Reflections collected
Independent reflections
15322
[R(int) = 0.0509]
5549
[R(int) = 0.0947]
full matrix least-squares on F2
5549/0/311
1.071
Refinement method
Data/restraints/parameters
15322/3/721
1.101
Goodness of fit on F2
Absolute structure factor
Final R indices [IՆ2σ(I)]
R indices (all data)
–0.02(2)
–0.018(13)
R1 = 0.0402, wR2 = 0.0818
R1 = 0.0461, wR2 = 0.0840
+1.810/–1.618
R1 = 0.0466, wR2 = 0.1076
R1 = 0.0545, wR2 = 0.1127
+0.982/–0.830
Largest difference peak/hole [eÅ–3]
[6]
W. A. Herrmann, C. Kocher, Angew. Chem. Int. Ed. Engl. 1997,
36, 2162–2182.
V. C ésar, S. Bellemin-Laponnaz, L. H. Gade, Angew. Chem. Int.
Ed. 2004, 43, 1014.
H. Clavier, L. Coutable, J. C. Guillemin, M. Mauduit, Tetrahe-
dron: Asymmetry 2005, 16, 921–924.
T. Focken, G. Raabe, C. Bolm, Tetrahedron: Asymmetry 2004,
15, 1693–1706.
K. Källström, P. G. Andersson, Tetrahedron Lett. 2006, 47,
7477–7478.
M. C. Perry, X. Cui, M. T. Powell, D.-R. Hou, J. H. Reiben-
spiess, K. Burgess, J. Am. Chem. Soc. 2003, 125, 113–123.
M. T. Powell, D.-R. Hou, M. C. Perry, X. Cui, K. Burgess, J.
Am. Chem. Soc. 2001, 123, 8878–8879.
W. L. Duan, M. Shi, G. B. Rong, Chem. Commun. 2003, 2916–
2917.
M. Albrecht, J. R. Miecznikowski, A. Samuel, J. W. Faller,
R. H. Crabtree, Organometallics 2002, 21, 3596–3604.
E. Mas-Marza, M. Poyatos, M. Sanau, E. Peris, Organometal-
lics 2004, 23, 323–325.
D. S. Clyne, J. Jin, E. Genest, J. C. Gallucci, T. V. RajanBabu,
Org. Lett. 2000, 2, 1125–1128.
C. Marshall, M. F. Ward, W. T. Harrison, Tetrahedron Lett.
2004, 45, 5703–5706.
T. L. Gilchrist, Heterocyclic Chemistry, 2nd ed., Longman Sci-
(CH3)2], 10.58 (CH2CH3) ppm. C23H36F6IrN4P (705.74): calcd. C
39.14, H 5.14, N 7.94; found C 39.17, H 5.19, N 8.02.
[7]
X-ray Diffraction Studies: Data were collected with a Stoe IPDS
2T diffractometer (Mo-Kα radiation) and processed by using Stoe’s
X-AREA[38] and the WinGX[39] suite of programs. The structures
were solved by direct methods and expanded with Fourier tech-
niques using SHELXS and SHELXL.[40,41] Numerical absorption
correction based on crystal-shape optimisation was applied with X-
Red and X-Shape.[42,43] Graphical illustrations and calculations
were performed with the SHELXTL 5.1 package. Further details
can be found in Table 1. CCDC-696022 (6a) and -696021 (7a) con-
tain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
Acknowledgments
We would like to thank Dr. H. Schubert, Dr. C. Maichle-Mössmer,
E. Niquet, and M. Steimann for their help in solving and pro-
cessing the crystal structures.
[1] C. M. Crudden, D. P. Allen, Coord. Chem. Rev. 2004, 248,
2247–2273.
entific & Technical, Harlow, U.K., 1992.
L. G. Bonnet, R. E. Douthwaite, R. Hodgson, Organometallics
2003, 22, 4384–4386.
A. Pfaltz, P. v. Matt, Angew. Chem. Int. Ed. Engl. 1993, 32,
566–568.
H. Nishiyama, M. Kondo, T. Nakamura, K. Itoh, Organome-
tallics 1991, 10, 500–508.
C. Bolm, Angew. Chem. Int. Ed. Engl. 1991, 30, 542–543.
[2] E. Peris, R. H. Crabtree, Coord. Chem. Rev. 2004, 248, 2239–
2246.
[3] W. A. Herrmann, Angew. Chem. 2002, 114, 1342–1363.
[4] D. Bourissou, O. Guerret, F. P. Gabbai, G. Bertrand, Chem.
Rev. 2000, 100, 39–92.
[5] V. Cesar, S. Bellemin-Laponnaz, L. H. Gade, Chem. Soc. Rev.
2004, 33, 619–636.
1254
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 1248–1255

IrI and RhI Complexes of Chiral Bis(carbene) Ligands
[23] G. Desimoni, G. Faita, P. Quadrelli, Chem. Rev. 2003, 103,
3119–3154.
[24] H. Clavier, L. Coutable, L. Toupet, J. C. Guillemin, M. Maud-
uit, J. Organomet. Chem. 2005, 690, 5237–5254.
[25] F. Glorius, G. Altenhoff, R. Goddard, C. Lehmann, Chem.
Commun. 2002, 2704–2705.
[26] W. A. Herrmann, L. J. Goossen, M. Spiegler, Organometallics
1998, 17, 2162–2168.
[27] H. U. Blaser, Chem. Rev. 1992, 92, 935–952.
[28] A. Karim, A. Mortreux, F. Petit, G. Buono, G. Peiffer, C. Siv,
J. Organomet. Chem. 1986, 317, 93–104.
[34]
[35]
[36]
[37]
[38]
M. Viciano, M. Poyatos, M. Sanau, E. Peris, A. Rossin, G.
Ujaque, A. Lledos, Organometallics 2006, 25, 1120–1134.
M. Poyatos, E. Mas-Marzá, J. A. Mata, M. Sanaú, E. Peris,
Eur. J. Inorg. Chem. 2003, 1215–1221.
A. R. Chianese, X. Li, M. C. Janzen, J. W. Faller, R. H.
Crabtree, Organometallics 2003, 22, 1663–1667.
A. C. Hillier, H. M. Lee, E. D. Stevens, S. P. Nolan, Organome-
tallics 2001, 20, 4246–4252.
X-AREA 1.26, Stoe & Cie. GmbH, Darmstadt, Germany,
2004.
[29] Y. Matsuoka, Y. Ishida, D. Sasaki, K. Saigo, Tetrahedron 2006,
62, 8199–8206.
[30] H. M. J. Wang, I. J. B. Lin, Organometallics 1998, 17, 972–975.
[31] R. Appel, Angew. Chem. Int. Ed. Engl. 1975, 14, 801–811.
[32] O. V. Starikova, G. V. Dolgushin, L. I. Larina, P. E. Ushakov,
T. N. Komarova, V. A. Lopyrev, Russ. J. Org. Chem. 2003, 39,
1467–1470.
[33] J. A. Mata, A. R. Chianese, J. R. Miecznikowski, M. Poyatos,
E. Peris, J. W. Faller, R. H. Crabtree, Organometallics 2004, 23,
1253–1263.
[39] J. L. Farrugia, J. Appl. Crystallogr. 1999, 32, 837–838.
[40] G. M. Sheldrick, SHELXS-97, University of Göttingen, Ger-
many, 1997.
[41] G. M. Sheldrick, SHELXL-97, University of Göttingen, Ger-
many, 1997.
[42] X-RED 1.26, Stoe & Cie. GmbH, Darmstadt, Germany, 2004.
[43] X-SHAPE 2.05, Stoe & Cie. GmbH, Darmstadt, Germany,
2004.
Received: September 19, 2008
Published Online: February 17, 2009
Eur. J. Inorg. Chem. 2009, 1248–1255
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1255