Copper(I) complexes of phenanthro-annulated n-heterocyclic carbenes: Synthesis and transmetalation reactions

Article abstract of DOI:10.1002/ejic.201301499

Copper(I) complexes with phenanthro-annulated N-heterocyclic carbene ligands were prepared by reaction of imidazolium salts with copper(I) oxide. Transmetalation of the copper complexes with [RhCl(cod)]₂ in usual solvents like CH₂Cl₂ led to an equilibrium between the reactants and the products. For rhodium complexes 4 and 5 this equilibrium could be shifted to the product side by carrying out the reaction in acetonitrile. The ester functionalized rhodium complex 6 was prepared in a two phase mixture of chloroform and aqueous CaCl₂ starting from copper complex 3c. The rhodium complexes were characterized by NMR and X-ray measurements. Copper complexes with phenanthro-annulated N-heterocyclic carbene ligands were prepared from imidazolium salts and Cu₂O. Initial transmetalation experiments with [RhCl(cod)] showed an equilibrium in most solvents. Two rhodium complexes could be prepared using acetonitrile as the solvent. One was prepared in a two phase mixture of chloroform and aqueous CaCl₂.

Full text of DOI:10.1002/ejic.201301499

FULL PAPER
DOI:10.1002/ejic.201301499
Copper(I) Complexes of Phenanthro-Annulated
N-Heterocyclic Carbenes: Synthesis and Transmetalation
Reactions
Jaroslaw Mormul,[a] Manfred Steimann,[a] and Ulrich Nagel*[a]
Keywords: N-Heterocyclic carbene / Carbenes / Copper / Rhodium / Transmetalation
Copper(I) complexes with phenanthro-annulated N-hetero-
cyclic carbene ligands were prepared by reaction of imid-
azolium salts with copper(I) oxide. Transmetalation of the
copper complexes with [RhCl(cod)]2 in usual solvents like
CH2Cl2 led to an equilibrium between the reactants and the
products. For rhodium complexes 4 and 5 this equilibrium
could be shifted to the product side by carrying out the reac-
tion in acetonitrile. The ester functionalized rhodium com-
plex 6 was prepared in a two phase mixture of chloroform
and aqueous CaCl2 starting from copper complex 3c. The
rhodium complexes were characterized by NMR and X-ray
measurements.
we describe the preparation of similar copper(I) complexes
and their transmetalation with [RhCl(cod)]2.
Introduction
Since the synthesis of the first stable N-heterocyclic carb-
ene (NHC) in 1991 by Arduengo and co-workers significant
progress has been made in this field.[1] In the last 20 years
many groups have explored new procedures for the synthe-
sis of NHC metal complexes. Thus, a variety of methods
are now established. For instance, the use of free carbenes
or reaction of imidazolium salts with basic metal precursors
are well known.[2–11] Consequently, NHC complexes of al-
most every transition metal are known and widely used in
homogeneous catalysis.[12–14] A mild and therefore very im-
portant route to NHC metal complexes involves the use of
silver complexes as transmetalation agents; this approach
was developed by Wang and Lin in 1998.[15] The silver com-
plexes are most often obtained by reacting imidazolium
salts with silver(I) oxide.[16–22] The first NHC copper com-
plex was prepared by Arduengo et al. in 1993 by reacting a
free carbene with copper(I) triflate.[23] In 2001 Danopoulos
and co-workers showed that NHC copper complexes can
be prepared by reacting an imidazolium salt with copper(I)
oxide.[24] The first application of copper complexes as trans-
metalation agents was published in 2009 by Albrecht and
co-workers.[25] Accordingly, there are now several reports
about the transmetalation with copper NHC com-
plexes.[26–29] Recently, we reported a simple synthesis of chi-
ral phenanthro-annulated imidazolium salts and their con-
version to silver(I) and ruthenium(II) complexes.[30,31] Here
Results and Discussion
Imidazolium chlorides 2a and 2b were prepared accord-
ing to our published procedure.[30,31] Imidazolium salt 2c
was analogously obtained by alkylation of imidazole deriv-
ative 1 with ethyl 2-bromoacetate (Scheme 1). To avoid
problems with different types of anions in transmetalation
reactions the anion was exchanged to chloride by the use
[a] Institut für Anorganische Chemie, Eberhard Karls Universität
Tübingen,
Auf der Morgenstelle 18, 72076 Tübingen, Germany
E-mail: ulrich.nagel@uni-tuebingen.de
http://anorganik.uni-tuebingen.de/aknagel/index.html
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201301499.
Scheme 1. Synthesis of compounds 2a–c, 3a–c, 4Cl, 5Cl and 6Cl.
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of a commercially available ion exchange resin (Amberlyst (5Cl/Br, Figure 3). These crystals were obtained during our
A21).[32,33]
first experiments in which we used imidazolium bromides
Copper complexes 3a–c were prepared in high yield by and iodides and did not exchange any anions to chloride.
reaction of the imidazolium salts 2a–c with copper(I) oxide
in 1,4-dioxane. As reported for our silver(I) complexes, the
NMR spectra of copper(I) complexes 3a–c also showed
strongly broadened signals, probably because of hindered
rotation of the chiral 1-phenylethyl substituent about the
exocyclic C–N bond. The signals for the carbene carbon
atoms could be detected by HMBC NMR spectroscopy (3a:
182.9 ppm, 3b: 184.4 ppm, 3c: 184.8 ppm). Notably, these
chemical shifts are higher than those for copper complexes
with imidazolin-2-ylidene ligands but lower than those with
saturated imidazolidin-2-ylidene ligands.[34]
Initial transmetalation experiments of the copper com-
plexes with [RhCl(cod)]2 in CD2Cl2 were characterized by
a fast reaction towards the desired rhodium complexes. Un-
fortunately, the conversion did not proceed to completion.
Rather, the transmetalation was found to cease at an equi-
librium of about 1:3 (reactants:products). We envisioned
that the noted equilibrium might be a result of the better
solubility of copper chloride, versus silver chloride, in or-
ganic solvents. Consequently, we tried different common
solvents for the transmetalation reaction (CH2Cl2, THF,
1,4-dioxane, CHCl3). We have yet to find a solvent in which
copper(I) chloride is insoluble but the desired rhodium
complex is soluble. Fortunately, rhodium NHC complexes
4Cl and 5Cl were found to be poorly soluble in aceto-
nitrile. Hence, these complexes could be prepared in aceto-
nitrile and separated from the soluble copper chloride by
simple filtration.
Figure 2. Molecular structure of complex 4I (R-enantiomer) show-
ing 50% probability ellipsoids. Most hydrogen atoms have been
omitted for clarity.
Rhodium complex 4 could be crystallized with bromide
or iodide anions (4Br and 4I, Figures 1 and 2) and rhodium
complex 5 was crystallized with a chloride/ bromide mixture
Figure 3. Molecular structure of complex 5Cl/Br (S-enantiomer)
showing 50% probability ellipsoids. Most hydrogen atoms have
been omitted for clarity.
In all structures the coordination sphere around the rho-
dium atom is square planar. The distances between rho-
dium and the carbene carbon atom are in the typical range
for similar rhodium NHC complexes (see Supporting Infor-
mation for selected bond lengths and angles).[24,35–42] The
proton at the chiral center (H16) always points towards the
metal atom leading to short Rh–H16 distances of about
2.5 Å. In the 1H NMR spectra, this proton is shifted down-
Figure 1. Molecular structure of complex 4Br (S-enantiomer) show-
ing 50% probability ellipsoids. Most hydrogen atoms have been
omitted for clarity.
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field by more than 1.5 ppm compared with the respective plexes 4Br, 4I and 5Cl/Br. Again, the proton at the chiral cen-
copper complexes. This shift probably is the result of an ter (H16) points towards the rhodium atom and again, this
electrostatic (“anagostic”)[43] interaction of the proton with proton is shifted downfield by over 1.5 ppm relative to that
the metal center and indicates that the position of the 1- of copper complex 3c. The carbene carbon atom resonates
phenylethyl substituent is retained in solution and that no as a doublet at δ = 194.8 ppm (1JRhC = 51.3 Hz).
rotation of the chiral substituent about the C–N bond oc-
curs on the NMR timescale.[44] Since we detected four ole-
Conclusions
1
finic signals for the cod ligand in the H and 13C NMR
In summary, we have shown the synthesis of three dif-
ferent copper(I) complexes with N-heterocyclic carbene li-
gands. Initial transmetalation reactions with a rhodium(I)
precursor led to an equilibrium between the copper and the
rhodium complexes. To avoid this problem we developed
two different procedures. First, the equilibrium can be
shifted to the product side by precipitation of the desired
rhodium complex from acetonitrile, the reaction solvent.
When the product does not precipitate from acetonitrile,
the rhodium complex can be prepared in a two-phase mix-
ture of chloroform and aqueous CaCl2. Here, the equilib-
rium is shifted by extraction of copper chloride into the
aqueous phase. To the best of our knowledge, these are the
first examples of rhodium(I) NHC complexes prepared by
transmetalation from copper(I) NHC complexes.
spectra it appears that rotation about the Rh–C1 bond is
also hindered.
The chemical shifts for the carbene carbon atom in the
13C NMR spectra are 193.0 ppm (4Cl) and 194.6 ppm (5Cl)
with characteristic coupling constants (1JRhC) of about
52 Hz, and are therefore similar to data from rhodium com-
plexes with benzimidazoline-2-ylidene ligands.[34]
In the developed procedure the equilibrium is shifted by
precipitation of the rhodium complex from acetonitrile. An-
alogue experiments with ester functionalized copper com-
plex 3c failed because the rhodium complex did not precipi-
tate during the reaction. Thus, a more general route needed
to be established. Copper(I) chloride is almost completely
insoluble in water but shows good solubility in aqueous al-
kali and alkaline earth metal salt solutions. Therefore, we
carried out the transmetalation reaction in a two-phase
mixture of chloroform and aqueous CaCl2 (Scheme 1).
Vigorous stirring allowed the copper chloride to be trans-
ferred into the aqueous phase, whereas rhodium complex
6Cl remained in the organic phase and could ultimately be
obtained in an acceptable yield of about 60%.
Experimental Section
General Comments: Reactions involving metal complexes were car-
ried out under an argon atmosphere in dried solvents using Schlenk
techniques. All products could be handled in air as solids. Solvents
were dried using standard procedures. All other reagents were used
as received from commercial sources. Most compounds were pre-
pared in both enantiomeric forms.
Crystallographically suitable single crystals of 6Cl were
obtained by slow evaporation of a saturated diethyl ether
solution (Figure 4). The bond lengths and angles for com-
plex 6Cl were found to be similar to those of rhodium com-
1-Ethoxycarbonylmethyl-3-(1-phenylethyl)phenanthro[9,10-d]imid-
azolium Chloride (2c): 1-(1-Phenylethyl)-phenanthro[9,10-d]imid-
azole (1.92 g, 5.96 mmol) was mixed with ethyl 2-bromoacetate
(10 mL, 90 mmol) and N-methyl-2-pyrrolidone (5 mL) and stirred
for 3 d at 70 °C. After cooling, diethyl ether (20 mL) was added to
the suspension, the white precipitate was filtered off and washed
with another aliquot diethyl ether (5 mL). The raw product was
dissolved in dichloromethane (10 mL) and precipitated with diethyl
ether (10 mL). For further purification, this procedure was repeated
twice. After filtration and drying under reduced pressure 2.4 g
(82 %) of imidazolium bromide were obtained as a hygroscopic
white powder. 500 mg of the imidazolium bromide were dissolved
in methanol and passed through a column charged with the anion
exchange resin (Amberlyst A21 charged with HCl). The solvent was
removed under reduced pressure to give 450 mg of 2c as a hygro-
1
scopic white powder. H NMR (400 MHz, [D6]DMSO): δ = 10.25
3
(s, 1 H, NCHN), 9.02–9.07 (m, 1 H, ArH), 9.01 (d, J = 8.0 Hz, 1
H, ArH), 8.49 (d, 3J = 8.3 Hz, 1 H, ArH), 8.29–8.34 (m, 1 H, ArH),
3
7.85–7.90 (m, 2 H, ArH), 7.78 (t, J = 7.2 Hz, 1 H, ArH), 7.69 (t,
3J = 8.1 Hz, 1 H, ArH), 7.27–7.40 (m, 5 H, ArH), 6.94 (q, 3J =
2
2
6.6 Hz, 1 H, NCH), 6.22 (d, J = 18.5 Hz, 1 H, NCH2), 6.17 (d, J
3
= 18.5 Hz, 1 H, NCH2), 4.23–4.35 (m, 2 H, OCH2), 2.14 (d, J =
6.6 Hz, 3 H, NCCH3), 1.23 (t, J = 7.1 Hz, 3 H, OCH2CH3) ppm.
3
13C{1H} NMR (101 MHz, [D6]DMSO): δ = 166.5 [C(O)O], 141.8
(NCHN), 139.5, 129.4, 129.3, 129.2, 128.5, 128.5, 128.4, 128.2,
128.1, 126.8, 125.8, 125.7, 124.7, 124.6, 123.1, 121.9, 120.2, 119.9
(ArC), 62.3 (OCH2), 60.0 (NCH), 51.5 (NCH2), 23.8 (NCCH3),
14.0 (OCH2CH3) ppm. HRMS (ESI+ in MeCN) of C27H25N2O2Cl:
calcd. for cation (C27H25N2O2+) 409.191054, found 409.190734.
Figure 4. Molecular structure of complex 6Cl (S-enantiomer) show-
ing 50% probability ellipsoids. Most hydrogen atoms have been
omitted for clarity.
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Chloro-[1-butyl-3-(1-phenylethyl)phenanthro[9,10-d]imidazolin-2- troscopy. 13C{1H} NMR (101 MHz, CDCl3): δ = 184.8 (NCN),
ylidene]copper(I) (3a): 1-Butyl-3-(1-phenylethyl)phenanthro[9,10-
d]imidazolium chloride (2a) (920 mg, 2.22 mmol) were mixed with
Cu2O (320 mg, 2.24 mmol), suspended in dry 1,4-dioxane (20 mL)
and stirred for 16 h at reflux. After cooling, the solvent was evapo-
rated, the residue suspended in dichloromethane (20 mL) and fil-
tered via cannula. The solution was concentrated to a quarter of
its volume by evaporation and the product precipitated as a white
powder by addition of diethyl ether (10 mL). After filtration the
product was dried under reduced pressure to obtain a white pow-
167.1 (C=O), 129.6, 127.9, 126.8, 126.6, 124.4, 120.7 (ArC), 62.5
(OCH2), 14.0 (CH2CH3) ppm. C27H24ClCuN2O2 (507.49): calcd. C
63.90, H 4.77, N 5.52; found C 64.34, H 5.01, N 5.36.
Chloro(η4-1,5-cod)[1-butyl-3-(1-phenylethyl)phenanthro[9,10-d]-
imidazolin-2-ylidene]rhodium(I) (4Cl): [RhCl(cod)]2 (43 mg,
87 μmol) and copper complex 3a (83 mg, 174 μmol) were dissolved
in acetonitrile (2 mL) and stirred for approximately 1 h till the
product precipitated as a yellow solid. The mixture was filtered via
cannula and the product washed twice with 1 mL of acetonitrile
each. After drying under reduced pressure 74 mg (68%) of 4Cl were
1
der, yield 900 mg (85%). H NMR (400 MHz, CDCl3): δ = 8.77–
3
8.86 (m, 2 H, ArH), 8.38 (d, J = 7.8 Hz, 1 H, ArH), 8.20 (br. s, 1
1
3
obtained. H NMR (400 MHz, CDCl3): δ = 8.78 (d, J = 8.0 Hz,
H, ArH), 7.71–7.81 (m, 2 H, ArH), 7.65 (br. t, 1 H, ArH), 7.55 (br.
s, 1 H, ArH), 7.30–7.44 (m, 5 H, ArH), 6.71 (br. s, 1 H, NCH),
5.07 (t, 3J = 7.4 Hz, 2 H, NCH2), 2.35 (br. s, 3 H, NCHCH3), 2.01–
2.11 (m, 2 H, NCH2CH2), 1.52–1.64 (m, 2 H, CH2CH3), 1.02 (t,
3J = 7.3 Hz, 3 H, CH2CH3) ppm. 13C NMR spectra showed only
a few broadened signals. Some could be assigned with HSQC and
HMBC spectroscopy. 13C{1H} NMR (101 MHz, CDCl3): δ = 182.9
(NCN), 139.7, 129.3, 127.9, 126.8, 124.3, 121.6 (ArC), 53.2
(NCH2), 32.7 (NCH2CH2), 19.8 (CH2CH3), 13.6 (CH2CH3) ppm.
C27H26ClCuN2 (477.51): calcd. C 67.91, H 5.49, N 5.87; found C
67.72, H 5.28, N 5.82.
3
3
1 H, ArH), 8.70 (d, J = 8.4 Hz, 1 H, ArH), 8.51 (q, J = 7.1 Hz,
1 H, NCH), 8.42 (d, J = 7.8 Hz, 1 H, ArH), 7.72–7.77 (m, 1 H,
3
ArH), 7.64–7.70 (m, 2 H, ArH), 7.44–7.49 (m, 1 H, ArH), 7.26–
7.36 (m, 5 H, ArH), 7.19–7.25 (m, 1 H, ArH), 5.91 (ddd, 2J = 13.8,
3J = 12.6, 5.1 Hz, 1 H, NCH2CH2), 5.38 (ddd, 2J = 13.9, 3J = 12.4,
4.3 Hz, 1 H, NCH2CH2), 5.17–5.25 (m, 1 H, CHcod), 5.03–5.10 (m,
1 H, CHcod), 3.47–3.56 (m, 2 H, CHcod), 2.35–2.59 (m, 3 H), 2.25
(d, 3J = 7.2 Hz, 3 H, NCHCH3), 2.15–2.26 (m, 1 H), 1.69–2.12 (m,
8 H), 1.21 (t, 3J = 7.4 Hz, 3 H, CH2CH3) ppm. 13C{1H} NMR
1
(101 MHz, CDCl3): δ = 193.0 (d, JRhC = 51.6 Hz, NCN), 141.7,
129.0, 128.7, 128.7, 128.4, 128.2, 127.3, 127.0, 126.2, 125.8, 125.5,
1
Chloro[1-benzyl-3-(1-phenylethyl)phenanthro[9,10-d]imidazolin-2-
ylidene]copper(I) (3b): 1-Benzyl-3-(1-phenylethyl)phenanthro[9,10-
d]imidazolium chloride (2b) (740 mg, 1.65 mmol) was mixed with
Cu2O (236 mg, 1.65 mmol), suspended in dry 1,4-dioxane (20 mL)
and stirred for 16 h at reflux. After cooling, the solvent was evapo-
rated, the residue suspended in dichloromethane (20 mL) and fil-
tered via cannula. The solution was concentrated to a quarter of
its volume by evaporation and the product precipitated as a white
powder by addition of diethyl ether (10 mL). After filtration the
product was dried under reduced pressure to obtain 3b with
0.4 equiv. CH2Cl2, yield 670 mg (75%). The product was used with-
out further purification and a small amount was washed with
dichloromethane for elemental analysis and NMR measurements.
125.3, 125.2, 124.0, 123.4, 121.7, 121.5, 120.7 (ArC), 99.1 (d, J =
6.8 Hz, CHcod), 98.5 (d, 1J = 6.9 Hz, CHcod), 69.5 (d, 1J = 14.2 Hz,
CHcod), 68.5 (d, J = 14.5 Hz, CHcod), 62.3 (NCH), 52.0 (NCH2),
33.2, 32.3, 31.6, 29.6, 28.1, 20.4, 18.9 (CHCH3 ), 13.8
(CH2CH3) ppm. C35H38ClN2Rh (625.05): calcd. C 67.25, H 6.13,
N 4.48; found C 67.25, H 6.00, N 4.66.
Chloro(η4-1,5-cod)[1-benzyl-3-(1-phenylethyl)phenanthro[9,10-d]-
imidazolin-2-ylidene]rhodium(I) (5Cl): [RhCl(cod)]2 (23 mg,
47 μmol) and copper complex 3b (52 mg, 95 μmol) were dissolved
in acetonitrile (1 mL) and stirred until the product precipitated as a
yellow solid. The mixture was filtered via cannula and the product
washed with acetonitrile (0.5 mL). After drying under reduced
1
3
1H NMR (400 MHz, CDCl3): δ = 8.78 (d, J = 8.3 Hz, 1 H, ArH),
pressure 51 mg (80%) of 5Cl were obtained. H NMR (400 MHz,
3
3
CDCl3): δ = 8.67–8.75 (m, 2 H, ArH), 8.61 (q, J = 7.2 Hz, 1 H,
8.75 (d, J = 8.3 Hz, 1 H, ArH), 8.24 (br. s, 1 H, ArH), 7.47–7.70
3
3
3
NCH), 8.13 (d, J = 8.4 Hz, 1 H, ArH), 7.74 (d, J = 8.2 Hz, 1 H,
ArH), 7.70 (d, 2J = 17.1 Hz, 1 H, NCH2), 7.22–7.59 (m, 14 H,
ArH), 6.40 (d, 2J = 17.7 Hz, 1 H, NCH2), 5.11–5.21 (m, 1 H,
CHcod), 5.00–5.08 (m, 1 H, CHcod), 3.47–3.55 (m, 1 H, CHcod),
3.24–3.33 (m, 1 H, CHcod), 2.27–2.40 [m, 1 H, (CH2)cod], 2.30 (d,
3J = 7.2 Hz, 3 H, CH3), 2.12–2.24 [m, 1 H, (CH2)cod], 1.52–1.95
[m, 6 H, (CH2)cod] ppm. 13C{1H} NMR (101 MHz, CDCl3): δ =
194.6 (d, 1JRhC = 51.9 Hz, NCN), 141.6, 137.4, 129.9, 129.1, 129.1,
128.7, 128.6, 128.1, 127.5, 127.2, 127.1, 126.3, 125.9, 125.7, 125.4,
(m, 4 H, ArH), 7.23–7.46 (m, 8 H, ArH), 7.13 (d, J = 7.1 Hz, 2
H, ArH), 6.81 (br. s, 1 H, NCH), 6.32 (s, 2 H, NCH2), 2.42 (br. s,
3 H, NCHCH3) ppm. 13C NMR spectra showed only a few broad-
ened signals. Some could be assigned with HSQC and HMBC spec-
troscopy at 50 °C. 13C{1H} NMR (101 MHz, CDCl3): δ = 184.4
(NCN), 139.8, 135.3, 129.5, 128.4, 127.8, 126.8, 125.8, 123.7, 122.1,
1 2 1 . 3 ( A r C ) , 5 9 . 7 ( N C H ) , 5 6 . 8 ( N C H 2 ) p p m .
C30H24ClCuN2·0.4CH2Cl2 (545.50): calcd. C 66.93, H 4.58, N 5.14;
found C 66.73, H 4.31, N 5.18.
3
125.1, 123.6, 123.4, 122.1, 121.2, 120.7 (ArC), 99.4 (d, J = 6.8 Hz,
Chloro[1-ethoxycarbonylmethyl-3-(1-phenylethyl)phenanthro[9,10-
d]imidazolin-2-ylidene]copper(I) (3c): Compound 2c (450 mg,
1.01 mmol) was mixed with Cu2O (145 mg, 1.01 mmol), suspended
in dry 1,4-dioxane (15 mL) and stirred for 18 h at reflux. After
cooling, the solvent was evaporated, the residue suspended in
dichloromethane (20 mL) and filtered via cannula. The solvent was
evaporated and the residue washed with petroleum ether (10 mL).
After filtration the product was dried under reduced pressure to
obtain 3c as an off-white powder, yield 380 mg (74%). The product
was used without further purification. 1H NMR (400 MHz,
CDCl3): δ = 8.78–8.85 (m, 2 H, ArH), 8.27 (br. s, 1 H, ArH), 8.08–
CHcod), 98.5 (d, 3J = 6.9 Hz, CHcod), 69.5 (d, 3J = 14.1 Hz, CHcod),
69.4 (d, 3J = 14.3 Hz, CHcod), 62.4 (NCH), 55.5 (NCH2), 32.9
[(CH2)cod], 32.0 [(CH2)cod], 29.1 [(CH2)cod], 28.2 [(CH2)cod], 18.7
(CH3) ppm. C38H36ClN2Rh·0.33MeCN (672.61): calcd. C 69.03, H
5.54, N 4.85; found C 69.01, H 5.81, N 4.79.
Chloro(η4-1,5-cod)[1-ethoxycarbonylmethyl-3-(1-phenylethyl)-
phenanthro[9,10-d]imidazolin-2-ylidene]rhodium(I) (6Cl):
[RhCl(cod)]2 (23 mg, 47 μmol) and copper complex 3c (50 mg,
99 μmol) were dissolved in chloroform (2 mL), whereby a precipi-
tation of copper(I)chloride occurred. A saturated aqueous CaCl2
solution (2 mL) were added and the mixture stirred vigorously for
8.14 (m, 1 H, ArH), 7.52–7.76 (m, 4 H, ArH), 7.32–7.46 (m, 5 H,
3
ArH), 6.72 (br. s, 1 H, NCH), 5.84 (s, 2 H, NCH2), 4.29 (q, J = a few minutes. The organic layer was separated and the aqueous
7.1 Hz, 2 H, OCH2), 2.38 (br., 3 H, NCHCH3), 1.28 (t, 3J = 7.1 Hz,
3 H, OCH2CH3) ppm. 13C NMR spectra showed only a few broad-
ened signals. Some could be assigned with HSQC and HMBC spec-
phase extracted with CHCl3 (1 mL). The organic phases were com-
bined and again washed with the saturated CaCl2 solution (2 mL).
The organic phase was dried with MgSO4 and passed through a
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[12] X. Bantreil, J. Broggi, S. P. Nolan, Annu. Rep. Prog. Chem.
Sect. B: Org. Chem. 2009, 105, 232–263.
[13] S. Díez-González, N. Marion, S. P. Nolan, Chem. Rev. 2009,
109, 3612–3676.
small column containing silica gel and kieselguhr. The column was
washed with approximately chloroform (3 mL). The solvent was
evaporated and the residue washed with acetonitrile (1 mL). After
filtration the product was dried under reduced pressure to give
37 mg (61 %) of 6Cl as a yellow powder. 1H NMR (400 MHz,
[14] D. R. Snead, H. Seo, S. Hong, Curr. Org. Chem. 2008, 12,
1370–1387.
3
CDCl3): δ = 8.75–8.80 (m, 1 H, ArH), 8.70 (d, J = 8.4 Hz, 1 H,
[15] H. M. J. Wang, I. J. B. Lin, Organometallics 1998, 17, 972–975.
[16] I. J. B. Lin, C. S. Vasam, Coord. Chem. Rev. 2007, 251, 642–
670.
3
ArH), 8.45 (q, J = 7.2 Hz, 1 H, NCH), 8.06–8.11 (m, 1 H, ArH),
7.63–7.70 (m, 3 H, ArH), 7.50–7.70 (br. m, 1 H, NCH2), 7.45–7.51
(m, 1 H, ArH), 7.28–7.41 (m, 5 H, ArH), 7.20–7.26 (m, 1 H, ArH), [17] K. M. Lee, H. M. J. Wang, I. J. B. Lin, J. Chem. Soc., Dalton
Trans. 2002, 2852–2856.
5.48–5.96 (br. m, 1 H, NCH2), 5.17–5.26 (m, 1 H, CHcod), 5.03–
5.12 (m, 1 H, CHcod), 4.42 (q, J = 7.0 Hz, 2 H, OCH2), 3.63–3.72
3
[18] C. K. Lee, C. S. Vasam, T. W. Huang, H. M. J. Wang, R. Y.
Yang, C. S. Lee, I. J. B. Lin, Organometallics 2006, 25, 3768–
3775.
(m, 1 H, CHcod), 3.48–3.56 (m, 1 H, CHcod), 2.21–2.50 [m, 3 H,
(CH2)cod], 2.24 (d, 3J = 7.2 Hz, 3 H, NCHCH3), 1.83–2.04 [m, 4
[19] C. P. Newman, G. J. Clarkson, J. P. Rourke, J. Organomet.
Chem. 2007, 692, 4962–4968.
[20] J. Berding, H. Kooijman, A. L. Spek, E. Bouwman, J. Or-
ganomet. Chem. 2009, 694, 2217–2221.
3
H, (CH2)cod], 1.65–1.77 [m, 1 H, (CH2)cod], 1.38 (t, J = 7.0 Hz, 3
H, CH2CH3) ppm. 13C{1H} NMR (101 MHz, CDCl3): δ = 194.8
1
(d, JRhC = 51.3 Hz, NCN), 169.3 (C=O), 141.3, 129.7, 129.1,
128.9, 128.6, 128.0, 127.4, 127.2, 126.3, 126.0, 125.5, 125.4, 125.3,
124.1, 123.5, 121.5, 120.7, 120.6 (ArC), 100.1 (d, 1J = 6.2 Hz,
CHcod), 99.4 (d, 1J = 6.2 Hz, CHcod), 69.9 (d, 1J = 14.0 Hz, CHcod),
69.0 (d, 1J = 14.0 Hz, CHcod), 62.4 (NCH), 62.2 (OCH2), 54.2
(NCH2), 32.9, 32.5, 28.9, 28.6 [(CH2)cod], 18.8 (NCHCH3), 14.3
(CH2CH3) ppm. C35H36ClN2O2Rh (655.03): calcd. C 64.18, H
5.54, N 4.28; found C 64.06, H 5.33, N 4.46.
[21] H.-L. Su, L. M. Pérez, S.-J. Lee, J. H. Reibenspies, H. S. Bazzi,
D. E. Bergbreiter, Organometallics 2012, 31, 4063–4071.
[22] F. E. Hahn, C. Radloff, T. Pape, A. Hepp, Chem. Eur. J. 2008,
14, 10900–10904.
[23] A. J. Arduengo, H. V. R. Dias, J. C. Calabrese, F. Davidson,
Organometallics 1993, 12, 3405–3409.
[24] A. A. D. Tulloch, A. A. Danopoulos, S. Kleinhenz, M. E.
Light, M. B. Hursthouse, G. Eastham, Organometallics 2001,
20, 2027–2031.
[25] G. Venkatachalam, M. Heckenroth, A. Neels, M. Albrecht,
Helv. Chim. Acta 2009, 92, 1034–1045.
[26] X. Liu, R. Pattacini, P. Deglmann, P. Braunstein, Organometal-
lics 2011, 30, 3302–3310.
[27] M. R. L. Furst, C. S. J. Cazin, Chem. Commun. 2010, 46, 6924.
[28] C. Chen, H. Qiu, W. Chen, J. Organomet. Chem. 2012, 696,
4166–4172.
[29] E. K. Bullough, M. A. Little, C. E. Willans, Organometallics
2013, 32, 570–577.
[30] J. Mormul, M. Steimann, C. Maichle-Mössmer, U. Nagel, Eur.
J. Inorg. Chem. 2013, 3421–3428.
CCDC-974757 (for 5Cl/Br), CCDC-974758 (for 4Br), CCDC-974759
(for 4I) and CCDC-974760 (for 6Cl) 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.
Supporting Information (see footnote on the first page of this arti-
cle): A complete description of the X-ray crystallographic determi-
nations on 4Br, 4I, 5Cl/Br and 6Cl. 1H NMR spectra of all com-
pounds, 13C NMR spectra of the rhodium complexes.
[31] J. Mormul, Dissertation, University of Tübingen, Germany,
2013.
[32] I. Dinarès, C. Garcia de Miguel, A. Ibáñez, N. Mesquida, E.
Alcalde, Green Chem. 2009, 11, 1507.
[33] K. A. Kun, R. Kunin, J. Polym. Sci., Part C Polym. Symp.
1967, 16, 1457–1469.
Acknowledgments
The authors thank Dr. Cäcilia Maichle-Mössmer for the X ray-
measurements.
[34] D. Tapu, D. A. Dixon, C. Roe, Chem. Rev. 2009, 109, 3385–
3407.
[35] K. H. Park, S. Y. Kim, S. U. Son, Y. K. Chung, Eur. J. Org.
Chem. 2003, 4341–4345.
[1] A. J. Arduengo, R. L. Harlow, M. Kline, J. Am. Chem. Soc.
1991, 113, 361–363.
[2] W. A. Herrmann, C. Köcher, Angew. Chem. 1997, 109, 2256;
Angew. Chem. Int. Ed. Engl. 1997, 36, 2162–2187.
[3] D. Bourissou, O. Guerret, F. P. Gabbaï, G. Bertrand, Chem.
Rev. 2000, 100, 39–92.
[4] W. A. Herrmann, Angew. Chem. 2002, 114, 1342; Angew.
Chem. Int. Ed. 2002, 41, 1290–1309.
[5] J. C. Garrison, W. J. Youngs, Chem. Rev. 2005, 105, 3978–4008.
[6] F. E. Hahn, M. C. Jahnke, Angew. Chem. 2008, 120, 3166; An-
gew. Chem. Int. Ed. 2008, 47, 3122–3172.
[7] B. Liu, Y. Zhang, D. Xu, W. Chen, Chem. Commun. 2011, 47,
2883.
[8] B. R. M. Lake, E. K. Bullough, T. J. Williams, A. C. Whit-
wood, M. A. Little, C. E. Willans, Chem. Commun. 2012, 48,
4887–4889.
[9] S. M. Opalka, J. K. Park, A. R. Longstreet, D. T. McQuade,
Org. Lett. 2013, 15, 996–999.
[36] H. Seo, B. Y. Kim, J. H. Lee, H.-J. Park, S. U. Son, Y. K.
Chung, Organometallics 2003, 22, 4783–4791.
[37] H. Türkmen, T. Pape, F. E. Hahn, B. Çetinkaya, Eur. J. Inorg.
Chem. 2008, 34, 5418–5423.
[38] M. T. Zarka, M. Bortenschlager, K. Wurst, O. Nuyken, R.
Weberskirch, Organometallics 2004, 23, 4817–4820.
[39] S. Burling, M. F. Mahon, S. P. Reade, M. K. Whittlesey, Orga-
nometallics 2006, 25, 3761–3767.
[40] D. Baskakov, W. A. Herrmann, E. Herdtweck, S. D.
Hoffmann, Organometallics 2007, 26, 626–632.
[41] A. Bittermann, P. Haerter, E. Herdtweck, S. D. Hoffmann,
W. A. Herrmann, J. Organomet. Chem. 2008, 693, 2079–2090.
[42] F. E. Hahn, T. v. Fehren, L. Wittenbecher, R. Fröhlich, Z. Nat-
urforsch. B 2004, 59, 544–546.
[43] H. V. Huynh, L. R. Wong, P. S. Ng, Organometallics 2008, 27,
2231–2237.
[10] D. Tapu, C. Owens, D. VanDerveer, K. Gwaltney, Organo-
metallics 2009, 28, 270–276.
[11] F. Ullah, M. K. Kindermann, P. G. Jones, J. Heinicke, Organo-
metallics 2009, 28, 2441–2449.
[44] M. Brookhart, M. L. H. Green, G. Parkin, Proc. Natl. Acad.
Sci. USA 2007, 104, 6908–6914.
Received: November 28, 2013
Published Online: January 30, 2014
Eur. J. Inorg. Chem. 2014, 1389–1393
1393
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