Synthesis, structure and electronic properties of N-dialkylamino- and N-alkoxy-1,2,4-triazol-3-ylidene ligands

Article abstract of DOI:10.1016/j.jorganchem.2005.07.120

4-Amino- and 4-alkoxy-1,2,4-triazoles 4a-d and 6 were readily obtained from the reaction of N,N-dimethylformamidazin dihydrochloride 3 with hydrazines 2 and hydroxylamine 5. Alkylation of compounds 4a-d and 6 by MeOTf or MeI afforded azolium salts 9-11, w

Full text of DOI:10.1016/j.jorganchem.2005.07.120

Journal of Organometallic Chemistry 690 (2005) 5979–5988
www.elsevier.com/locate/jorganchem
Synthesis, structure and electronic properties of N-dialkylamino-
and N-alkoxy-1,2,4-triazol-3-ylidene ligands
a
b,
a
a,
*
´
*
´
´
Manuel Alcarazo , Rosario Fernandez , Eleuterio Alvarez , Jose M. Lassaletta
a
Instituto de Investigaciones Quı´micas (CSIC-Use), C/Ame´rico Vespucio s/n, Isla de la Cartuja, E-41092 Seville, Spain
b
Departamento de Quı´mica Orga´nica, Universidad de Sevilla, E-41012 Seville, Spain
Received 31 May 2005; received in revised form 25 July 2005; accepted 26 July 2005
Available online 25 October 2005
Abstract
4-Amino- and 4-alkoxy-1,2,4-triazoles 4a–d and 6 were readily obtained from the reaction of N,N-dimethylformamidazin dihydro-
chloride 3 with hydrazines 2 and hydroxylamine 5. Alkylation of compounds 4a–d and 6 by MeOTf or MeI afforded azolium salts
9–11, which in turn were transformed into Rh(I) carbene complexes 13–15, Ag carbenes 16, and cationic Rh(I) bis-carbenes 17. Addi-
tionally, complexes 13 and 15 were transformed into dicarbonyl derivatives 18 and 19, and the carbonyl stretching frequencies of these
compounds were used to evaluate the effect of the amino and alkoxy groups in the r-donor ability of these 1,2,4-triazol-3-ylidenes.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Heterocycles; Carbenes; Rhodium
1. Introduction
Since the pioneering work of Enders and co-workers [5],
relatively little attention has been devoted to the chemistry
of 1,2,4-triazol-5-ylidene metal complexes [6], a phenome-
non that is surprising considering that there are relatively
simple routes to access these compounds, and that the cat-
alytic activity has been demonstrated [7], even though
1,2,4-triazol-3-ylidenes are weaker r donors than other
NHCs as imidazol-2-ylidenes or imidazolin-2-ylidene [2].
Additionally, chiral triazol-5-ylidenes have been success-
fully used as organocatalysts in the benzoin condensation
[8] and the intramolecular Stetter reaction [9].
Very recently we have reported the synthesis of 1,3-
bis(N,N-dialkylamino)imidazolin-2-ylidenes [10] and we
found out that substitution by N-dialkylamino groups
slightly increases the donor ability of these ligands with
respect to alkyl or aryl analogues in a way that these
compounds appear as the best known donors in the imidaz-
olin-2-ylidene series [11]. In this paper we wish to report on
the first efficient synthesis of 4-dialkylamino- and 4-alkoxy-
1,2,4-triazoles (A), their transformation into the corres-
ponding triazolium salts (B) and triazol-5-ylidene metal
complexes (C) (Fig. 1), and the comparative analysis of
the carbene ligand donor ability in the latter.
Since the isolation of the first stable N-heterocyclic car-
bene (NHC) by Arduengo and co-workers,[1] the chemistry
of these compounds has developed rapidly [2], fueled
mainly by their application as C-ligands [3]. Late transition
metal complexes containing NHC ligands are usually air
stable and kinetically robust compounds, which are partic-
ularly promising in the field of catalysis in general and in
asymmetric catalysis in particular. Nevertheless, there are
still some limitations that reduce the scope of application
of these ligands. Thus, although steric demand is easily
tuned using different substitution patterns, the electron do-
nor ability of NHCs can only be modified slightly, mainly
by the choice of the formal parent heterocyclic precursor
between imidazol, dihydroimidazol and triazole, while the
effect of the substituents at the heterocyclic nitrogen atoms
seems to be negligible [4].
*
Corresponding authors. Fax: +34 954460565.
´
E-mail addresses: ffernan@us.es (R. Fernandez), jmlassa@cica.es (J.M.
Lassaletta).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.07.120

5980
M. Alcarazo et al. / Journal of Organometallic Chemistry 690 (2005) 5979–5988
NR1R2
X
N
X
N
X
N
N
R1R2NNH2
N
2a-c
+
N
MLn
H
N
H
N
N
R3
N
R3
N
Py
4a (43%)
4b (64%)
4c (58%)
N
N
N
N
N
A
B
C
2HCl
X = NR1R2 or OBn
BnONH2
3
5
OBn
N
Fig. 1. Target compounds in this study.
Py
N
N
6 (42%)
2. Results and discussion
For the synthesis of the target 1-alkyl-4-dialkylamino-
1,2,4-triazol-5-ylidene complexes C, we decided to use the
corresponding triazolium salts B as the most common type
of precursors. In turn, these compounds can be obtained
by a direct cyclisation from a suitable precursor or by a sim-
ple alkylation of 4-dialkylamino triazoles A. Surprisingly, a
search of the pertinent literature sources revealed that, in
spite of the simplicity of their structures, there are no efficient
methods reported for the synthesis of such heterocycles.
Initially, we tried to apply the method used by Boyd [12]
for the direct synthesis of triazolium salts. Unfortunately,
reaction of 1,3,4-oxadiazolium salts 1 with N,N-dial-
kylhydrazines 2 did not take place, even under forcing con-
ditions (Scheme 1).
Comparing with BoydÕs [12a] and EndersÕ [12b] results
using primary aryl amines, the lack of reactivity in our case
suggests that the strong acidic medium required results in
eliminate the nucleophilicity of the more basic hydrazines
2 by protonation. Therefore, we concluded that less acidic
conditions are required, and, consequently, N,N-dimethyl-
formamidazin dihydrochloride 3 was made to react with
hydrazines 2 in pyridine as the solvent to afford, as for ani-
lines [13], the corresponding 4-amino-1,2,4-triazoles 4a–c in
moderate yields. Moreover, this method proved to be also
suitable for the synthesis of the 4-benzyloxy-1,2,4-triazole
6, readily obtained by reaction of O-benzyl hydroxylamine
5 with the same reagent in 42% yield (Scheme 2).
NR1R2
Bn
Bn
Ph
Me
Ph
N
Ph
N
N
4
a
b
c
Scheme 2.
With the heterocycles 4a–d and 6 in hand, the synthesis
of the required azolium salts B was easily accomplished.
Thus, alkylation of the new N-dialkylamino and N-alkoxy
heterocycles 4a–d, 6 with MeOTf or MeI proceeds cleanly
to afford the 1,2,4-triazolium salts 9a–d, 10c,d, and 11 in
good-to-excellent yields (Scheme 4 and Table 1).
The reactivity of the salts 9–11 was then explored in dif-
ferent contexts. The synthesis of the corresponding free
carbenes was attempted by deprotonation with NaH in
Me
O
Toluene
NH2
Me
N
+
N
Me
N
N
PTSA
86%
N
Me
O
N
N
7
8
4d
Scheme 3.
X
X
N
X
N
MeOTf
N
MeI
+
N
+
N
N
87-97%
N
Me
87-97%
N
Finally, 4-[2,5-dimethylpyrrol-1-yl]-1,2,4-triazole 4d was
also considered as an interesting substrate in order to fur-
ther increase the structural diversity of the study. This com-
pound had been previously synthesized by reaction of a
methanolic solution of commercially available 4-amino-
1,2,4-triazole 7 with 2,5-hexanedione 8, but a very poor
7% yield was reported [14]. Fortunately, a modification
of the reaction conditions allowed the synthesis of the tar-
get heterocycle 4d in 86% yield from the same starting
materials (Scheme 3).
TfO
N
I
Me
9a-d, 11
10c,d
4a-d, 6
Scheme 4.
Table 1
Synthesis of 4-(amino- or alkoxy)-1,2,4-triazolium salts 9–11
Starting
material
X
Anion Product
T
t (h) Yield (%)
4a
4b
4c
4c
NBn2
N(Me)Ph
NPh2
OTf
OTf
OTf
I
9a
9b
rt
rt
rt
1
1
1
87
97
94
81
9c
10c
NPh2
60 ꢁC 48
NR1R2
ClO4
N
N
R
O
H2NNR1R2
N
N
R
N
+
4d
OTf
9d
rt
1
96
Me
Me
Me
N
ClO4
4d
6
I
10d
11
60 ꢁC 48
rt
79
89
1
2
Me
N
OBn
OTf
1
Scheme 1.

M. Alcarazo et al. / Journal of Organometallic Chemistry 690 (2005) 5979–5988
5981
atom with the carbene ligand perpendicular to this plane.
The carbene carbon-rhodium bond lengths of 201.6 and
201.1 pm, respectively, are similar to those observed in
other NHC-rhodium(I) complexes [17]. In 14d, the 2,5-
dimethylpyrrol-1-yl substituent on the 1,2,4-triazol-3-yli-
dene ring also adopts a relative perpendicular orientation
that minimizes steric interactions.
Me
Me
H
Me
Me
N
N
N
LiHBEt3
N
+
N
H
H
N
N
N
OTf
Me
Me
9d
12
Scheme 5.
Starting from iodides 10c,d, a simple reaction with Ag2O
led to the silver carbenes 16c,d in good yields (Table 2, en-
tries 8 and 9). These compounds are particularly useful as a
potential source for other transition metal complexes via
the efficient transmetalation procedures recently reported
[18].
Finally, a reaction of the carbene complexes 13b and 13d
with their parent salts 9b and 9d in the presence of AgOTf as
a halide scavenger was performed to obtain the cationic bis-
carbene complexes 17b and 17d in 69% and 57% yield,
respectively (Scheme 6). Considering that the starting mate-
rial possesses a stable chiral axis and that the reaction gen-
erates a second one, the product of this reaction could in
THF at low temperature (ꢀ78 to ꢀ30 ꢁC), followed by re-
moval of the solvent and extraction with toluene, but,
unfortunately, this procedure led to a complex mixture,
presumably resulting from the decomposition of the free
carbenes. Alternatively, the reaction of 9d with LiHBEt3
was investigated. This reagent has been recently used to
prepare the BEt3 adducts of imidazol-2-ylidenes from the
corresponding imidazolium salts [15]. In our case, however,
the conditions described afforded the reduction 1H-triazo-
line product 12 instead, which was isolated in 71% yield
(Scheme 5).
Much better results were observed for the direct synthe-
sis of some transition metal complexes. First, both triflates
9a–d, 11 and iodides 10c,d were reacted with [RhCl(COD)]2
in the presence of Et3N to afford Rh(NHC)Z(COD) com-
plexes 13a–d (Z = Cl) (Scheme 6, Table 2), 14c,d (Z = I)
and 15, which proved to be air and moisture-tolerant prod-
ucts that even resisted chromatographic purification on sil-
ica-gel to isolate high yields of pure products.
The existence of diastereotopic signals for benzylic pro-
tons in 13a and 15 and for methyl groups in the pyrrol moi-
ety in 13d and14d indicates a high rotation barrier of the
carbene carbon–rhodium bond and, therefore, the exis-
tence of a configurationally stable chiral axis can be postu-
lated in these complexes as a result of steric interactions
[16].
Table 2
Synthesis of Rh and Ag triazolylidene complexes 13–16
Entry Starting
material
X
Y
Z
Product Yield (%)
1
2
3
4
9a
9b
NBn2
N(Me)Ph
NPh2
OTf Cl 13a
OTf Cl 13b
OTf Cl
64
86
91
81
9c
10c
13c
14c
NPh2
I
I
5
6
9d
OTf Cl 13d
14d
OTf Cl 15
93
68
Me
Me
Me
N
10d
I
I
Me
N
OBn
NPh2
7
8
11
10c
89
91
I
–
16c
The X-ray structures of 14c and 14d (Fig. 2) show the
expected square-planar geometry around the rhodium
9
10d
I
–
16d
88
Me
Me
N
X
Z
X
[RhCl(COD)]2
Et3N
N
N
+
Rh
H
Y
N
N
N
N
Me
Me
13a-d: X = NR1R2, Z = Cl
14c,d: X = NR1R2, Z = I
15: X = OBn; Z = Cl
9a-d: X = NR1R2, Y = OTf
10c,d: X = NR1R2, Y = I
11: X = OBn; Y = OTf
Ag2O
9b,d, AgTfO, Et3N
Me
OTf
N
N
NR1R2
N
X
N
I
Rh
Ag
N
X
N
N
N
N
Me
Me
16c,d
17b,d
Scheme 6.

5982
M. Alcarazo et al. / Journal of Organometallic Chemistry 690 (2005) 5979–5988
Fig. 2. X-ray structures of 14c and 14d. H atoms are omitted for clarity. A single enantiomer is shown for each complex, though both compounds
crystallized as racemate.
Fig. 3. X-ray structures of the cations of 17b and 17d. H atoms and and counteranions are omitted for clarity. A single enantiomer of each structure is
represented, although both salts crystallized as racemate.
theory be a mixture of meso and racemic compounds [19],
associated to a ÔparallelÕ or ÔantiparallelÕ arrangement of
the triazol-5-ylidene ligands, respectively. As was already
observed in the recently reported bis-imidazo[1,5-a]pyri-
dine-3-ylidene Rh(I) cationic complexes [20], these reactions
exclusively afforded the chiral racemic compounds, a fact
attributed to the higher steric interactions expected for the
ÔparallelÕ arrangement of the carbene ligands. The structures
of compounds 17b and 17d were unambiguously deter-
mined by single-crystal X-ray diffractometry (Fig. 3), show-
ing again the characteristic square-planar geometry with
CRhC angles of 91.6ꢁ and 91.3ꢁ, respectively.
In order to gain some information about the electronic
properties of these carbene complexes, compounds 13a,b,d
and 15 were reacted with carbon monoxide to afford dicar-
bonyl complexes 18a,b,d and 19 in excellent yields (Scheme
7), and their carbonyl stretching frequencies were used to
evaluate the r donor ability of the ligands. For comparative
purposes and in order to acquire a better overview of the
effect of the substituent at N(4), triazolium 20 [21] and
oxadiazolium 21 [22] salts were also transformed into the
corresponding Rh(NHC)Cl(COD) complexes 22 and 23
and the dicarbonyl derivatives Rh(NHC)Cl(CO)2 24 and
25 following standard procedures.

M. Alcarazo et al. / Journal of Organometallic Chemistry 690 (2005) 5979–5988
5983
X
N
X
N
Cl
Cl
CO
CO
Rh
Rh
CO
89-96%
N
N
N
N
Me
Me
18a,b,d: X = NR1R2
19: X = OBn
13a,b,d: X = NR1R2
15: X = OBn
[RhCl(COD)]2
Cl
Rh
CO
N
N
Cl
Rh
N
+
N
Et3N
87%
N
N
96%
N
N
CO
TfO
H
N
CO
Me
Me
Me
24
20
22
Cl
Cl
O
[RhCl(COD)]2
CO
O
O
CO
+
N
Rh
Rh
ClO4
78%
N
Et3N
42%
H
CO
N
N
N
N
Ph
Ph
Ph
21
23
25
Scheme 7.
Probably the expected inductive effect that should re-
Table 3
duce the donor ability is waged by a conjugative n ! p
interaction in solution, also observed in imidazolin-2-ylid-
enes,[10] between the dialkylamino group and the triazoly-
lidene system. Supporting this hypothesis, the data
collected for 18d indicate a clear loss of r donor ability;
a negligible n ! p interaction is expected, as the N lone
pair is involved in the pyrrole aromaticity, and, therefore,
only the inductive effect is observed. Thus, the average
Carbonyl stretching frequencies for Rh(NHC)Cl(CO)2 complexes 18, 19,
24 and 25
IR frequency
Compound
18a
18b
18d
19
24
25
m
m
m
CO(trans)
CO(cis)
CO(average)
2010
2092
2051
2011
2088
2050
2013
2095
2054
2012
2090
2051
2010
2090
2050
2020
2098
2059
The analysis of the mCO stretching frequencies collected
mCO frequency for 18d falls between that of the triazol-3-yli-
in Table 3 suggests that the introduction of amino (data
for 18a,b) or alkoxy (data for 19) groups at N(4) does
not significantly modify the r-donor ability exhibited by
4-alkyl(aryl) analogues.
dene derivatives 18a–b, 19, and 24 and the 1,3,4-oxadiazol-
2-ylidene complex 25, which, due to the poorer p-donor
and higher electronegativity of the oxygen atom, exhibits
the poorer r-donor ability in this series (Fig. 4).
Me
Me
Me
N(Me)Ph
Ph
Me
Me
O
N
N
N
N
N
Ph
N
N
Me
N
Me
2050
N N
2050
2059
2042
Me
_
ν
CO(cm-1)
stronger donor
weaker donor
2040
2050
2060
NBn2
N
Me
N
OBn
N
Mes
N
Me
N
N
N
N
Me
N
Me
N
Mes
2038
N
N
Me
2051
2051
2054
Fig. 4. Scale of r-donor ability of various carbene ligands, as correlated with the average mCO frequencies in their corresponding Rh(I)(carbene)(CO)2
complexes.

5984
M. Alcarazo et al. / Journal of Organometallic Chemistry 690 (2005) 5979–5988
In conclusion we have developed a new procedure for
3.2. Synthesis of 4d
the synthesis of N,N-dialkylamino- and alkoxy-1,2,4-triaz-
oles and for some transition metal complexes containing
the triazolylidenes derived from them. A study of the effect
of the amino or alkoxy groups on the r-donor ability of
these ligands points to the existence of opposite mesomeric
and inductive effects.
The synthesis of analogues of the products described in
this paper containing chiral dialkylamino moieties and
their application in asymmetric catalysis is the current ob-
ject of study in our laboratory.
To a solution of 2,5-hexanedione 8 (3.42 g, 30 mmol)
and 4-amino-1,2,4-triazole 7 (2.52 g, 30 mmol) in toluene
was added a catalytic amount of p-toluenesulfonic acid
(few crystals), and the mixture was heated to reflux for
3 h with azeotropic removal of water. The solvent was then
removed in vacuo and resulting residue was washed with n-
hexane to yield crude 4d (4.1 g, 86%), which had character-
ization data identical to those previously reported [23].
Colorless crystals were obtained by crystallization from
toluene.
3. Experimental
3.3. Synthesis of 4-(dialkylamino or alkoxy)-1-methyl-1,2,4-
triazolium triflates 9a–d, 11, and iodides 10c, and 10d
3.1. Synthesis of 4-(dialkylamino or alkoxy)-1,2,4-triazoles
1a–c
To a solution of triazole 4a–d or 6 (1 mmol) in dry
CH2Cl2 (1 mL) was added MeOTf (164 mg, 1 mmol) and
the mixture was stirred for 1 h at room temperature. The
supernatant was decanted and the remaining solid was
washed with Et2O (2 · 10 mL) to afford pure products
9a–d and 11. Alternatively, MeI (6 mmol) was added to a
solution of triazole 4c or 4d (1 mmol) in THF (1 mL) and
the mixture was stirred for 48 h at 60 ꢁC. The supernatant
was decanted and the solid was treated as described above
to afford 10c and 10d. Starting materials, yields, and char-
acterization data for these compounds are as follows:
9a: From 4a and MeOTf, the above general procedure
To a solution of hydrazine 2a–c or O-benzylhydroxyl-
amine 5 (1 mmol) in pyridine (2 mL) was added N,N-dim-
ethylformamidazin dihydrochloride 3 (325 mg, 1.5 mmol)
and the reaction mixture was stirred for 4 h at 100 ꢁC.
The solvent was then removed in vacuo, and the residue
was dissolved in a 1:1 H2O: satd. NaHCO3 mixture and ex-
tracted with CH2Cl2(3 · 5 mL). The organic layer was
dried (MgSO4), concentrated, and the residue was purified
by flash chromatography (AcOEt). Starting materials,
yields, and characterization data for compounds 4a–c
and 6 are as follows:
4a: From 2a, the above general procedure yielded
114 mg (43%) of 4a as a colorless oil. 1H NMR
(300 MHz, CDCl3): d 8.30 (s, 2H), 7.28–7.04 (m, 10H),
3.81 (s, 4H). 13C NMR (75 MHz, CDCl3): d 143.6, 136.4,
128.6, 128.1, 127.4, 57.8. Anal. Calc. for C16H16N4: C,
72.70; H, 6.10; N, 21.20. Found: C, 72.53; H, 5.97; N,
21.01%.
1
yielded 9a (372 mg, 87%) as a colorless syrup. H NMR
(500 MHz, CDCl3): d 10.70 (s, 1H), 7.85 (s, 1H), 7.22–
7.40 (m, 10H), 4.44 (s, 4H), 4.01 (s, 3H). 13C NMR
(125 MHz, CDCl3): d 143.9, 143.5, 133.8, 129.8, 129.5,
128.5, 62.7, 40.3. Anal. Calc. for C18H19N4F3O3S: C,
50.46; H, 4.47; N, 13.08. Found: C, 50.81; H, 4.87; N,
12.86%.
4b: From 2b, the above general procedure yielded
111 mg (64%) of 4b as
9b: From 4b and MeOTf, the above general procedure
yielded 9b (328 mg, 97%) as a white solid. 1H NMR
(300 MHz, acetone-d6): d 10.48 (s, 1H), 9.49 (s, 1H), 7.37
(dd, J = 8.7, 7.5 Hz, 2H), 7.13 (t, J = 7.5 Hz, 1H), 7.02
(d, J = 8.7 Hz, 2H), 4.31 (s, 3H), 3.63 (s, 3H). 13C NMR
(75 MHz, CDCl3): d 147.9, 145.0, 144.5, 129.9, 124.2,
116.2, 43.2, 39.9. Anal. Calc. for C11H13N4F3O3S: C,
39.05; H, 3.87; N, 16.56. Found: C, 39.14; H, 3.93; N,
16.60%.
9c: From 4c and MeOTf, the above general procedure
yielded 9c (376 mg, 94%) as a light-yellow solid. M.p.
128–130 ꢁC (dec.); 1H NMR (300 MHz, acetone-d6): d
10.70 (s, 1H), 9.70 (s, 1H), 7.46 (t, J = 7.8 Hz, 4H), 7.30
(t, J = 7.5 Hz, 2H), 7.21 (d, J = 7.8 Hz, 4H), 4.32 (s, 3H).
13C NMR (75 MHz, acetone-d6): d 146.3, 145.9, 145.3,
130.9, 127.2, 122.2, 40.8. Anal. Calc. for C16H15N4F3O3S:
C, 48.00; H, 3.78; N, 13.99. Found: C, 47.87; H, 3.68; N,
13.78%.
a
white solid. 1H NMR
(300 MHz, CDCl3): d 8.31 (s, 2H), 7.24 (dd, J = 8.7,
7.5 Hz, 2H), 6.97 (t, J = 7.5 Hz, 1H), 6.54 (d, J = 8.7 Hz,
2H), 3.37 (s, 3H). 13C NMR (75 MHz, CDCl3): d 148.7,
142.7, 129.9, 122.8, 114.3, 43.6. Anal. Calc. for C9H10N4:
C, 62.05; H, 5.79; N, 32.16. Found: C, 62.11; H, 5.69; N,
32.04%.
4c: From 4c, the above general procedure yielded
137 mg (58%) of 4c as a light pink solid. 1H NMR
(500 MHz, CDCl3): d 8.40 (s, 2H), 7.31 (dd, J = 8.0,
7.5 Hz, 4H), 7.14 (t, J = 8.0 Hz, 2H), 6.91 (d, J = 7.5 Hz,
4H). 13C NMR (150 MHz, CDCl3): d 145.1, 143.2, 129.9,
125.2, 120.0. Anal. Calc. for C14H12N4: C, 71.17; H, 5.12;
N, 23.21. Found: C, 71.24; H, 5.13; N, 23.20%.
6: From 5, the above general procedure yielded 74 mg
1
(42%) of 6 as a colorless oil. H NMR (400 MHz, CDCl3):
d 8.00 (s, 2H), 7.43–7.35 (m, 3H), 7.24 (d, J = 6.4 Hz, 2H),
5.11 (s, 2H). 13C NMR (100 MHz, CDCl3): d 138.9, 132.5,
130.3, 129.9, 129.2, 83.5. Anal. Calc. for C9H9N3O: C,
61.70; H, 5.18; N, 23.99. Found: C, 61.52; H, 5.01; N,
23.78%.
10c: From 4c and MeI, the above general procedure
yielded crystalline 10c (303 mg, 81%). M.p. 120–121 ꢁC
1
(dec.); H NMR (300 MHz, acetone-d6): d 11.31 (s, 1H),
9.72 (s, 1H), 7.43 (t, J = 7.8 Hz, 4H), 7.28 (t, J = 7.5 Hz,

M. Alcarazo et al. / Journal of Organometallic Chemistry 690 (2005) 5979–5988
5985
2H), 7.23 (d, J = 7.8 Hz, 4H), 4.29 (s, 3H). 13C NMR
(75 MHz, acetone-d6): d 146.7, 145.8, 145.1, 140.0, 127.1,
122.2, 40.7. Anal. Calc. for C15H15N4I: C, 47.64; H, 4.00;
N, 14.81. Found: C, 47.39; H, 3.91; N, 14.72%.
9d: From 4d and MeOTf, the above general procedure
yielded 9d (3.1 g, 96%) as a white solid. 1H NMR
(300 MHz, acetone-d6): d 10.68 (s, 1H), 9.61 (s, 1H), 5.94
(s, 2H), 4.41 (s, 3H), 2.10 (s, 6H). 13C NMR (75 MHz, ace-
tone-d6): d 145.7, 145.6, 129.6, 107.3, 41.1, 10.6. Anal. Calc.
for C10H13N4F3O3S: C, 36.81; H, 4.02; N, 17.17. Found: C,
36.70; H, 3.90; N, 16.89%.
1.90–1.70 (m, 2H). 13C NMR (75 MHz, CDCl3): d 184.9
(d, JC–Rh = 50.3 Hz), 142.4, 135.9, 129.8, 128.9, 128.5,
98.9 (d,JC–Rh = 7.2 Hz), 98.6 (d, JC–Rh = 7.0 Hz), 71.2
(d,JC–Rh = 14.5 Hz), 68.2 (d, JC–Rh = 14.1 Hz), 60.7, 41.6,
34.3, 31.9, 30.5, 28.2. HRMS m/z Calc. for C25H30N4
ClRh524.1214, found 524.1206. Anal. Calc. for
C25H30N4ClRh: C, 57.21; H, 5.76; N, 10.67. Found: C,
57.09; H, 5.84; N, 10.88%.
13b: From 9b, the above general procedure yielded
188 mg (86%) of 13b as a yellow solid. M.p. 182–184 ꢁC
1
(dec.); H NMR (300 MHz, CDCl3): d 8.02 (s, 1H), 7.28
10d: From 4d and MeI, the above general procedure
yielded crystalline 10d (241 mg, 79%). M.p. 230–130 ꢁC
(t, J = 7.8 Hz, 2H), 6.97 (t, J = 7.2 Hz, 1H), 6.64 (d,
J = 8.4 Hz, 2H), 5.01 (br s, 2H), 4.34 (s, 3H), 3.78 (s,
3H), 3.41 (br s, 1H), 2.76 (br s, 1H), 2.41 (br s, 1H),
2.32–2–20 (m, 2H), 1.93 (br s, 2H), 1.62 (br s, 2H), 1.51
(br s, 1H).13C NMR (75 MHz, CDCl3): d 187.6 (d,
JC–Rh = 50.9 Hz), 149.1, 143.9, 129.8, 126.5, 122.0, 114.1,
99.2 (d, JC–Rh = 7.1 Hz), 70.2 (br s), 68.2 (br s), 44.0,
41.5, 34.2 (br s), 31.9 (br s), 30.0 (br s), 28.2 (br s). HRMS
m/z Calc. for C18H28N4ClRh 434.0745, found 434.0736.
Anal. Calc. for C18H24N4ClRh: C, 49.73; H, 5.56; N,
12.89. Found: C, 49.81; H, 5.50; N, 13.00%.
1
(dec.); H NMR (500 MHz, acetone-d6): d 11.25 (s, 1H),
9.61 (s, 1H), 5.91 (s, 2H), 4.39 (s, 3H), 2.13 (s, 6H). 13C
NMR (75 MHz, acetone-d6): d 146.3, 145.6, 129.4, 107.3,
40.2, 10.7. Anal. Calc. for C9H13N4I: C, 35.54; H, 4.31;
N, 18.42. Found: C, 35.42; H, 4.58; N, 18.22%.
11: From 6 and MeOTf, the above general procedure
1
yielded 11 (302 mg, 89%) as a colorless syrup. H NMR
(500 MHz, acetone-d6): d 10.45 (s, 1H), 9.29 (s, 1H), 7.57
(d, J = 6.5 Hz, 2H), 7.47 (m, 3H), 5.68 (s, 2H), 4.23 (s,
3H). 13C NMR (125 MHz, acetone-d6): d 142.0, 141.9,
132.7, 131.4, 131.2, 129.9, 86.1, 40.6. Anal. Calc. for
C11H12N3OF3S: C, 38.94; H, 3.56; N, 12.38. Found: C,
38.64; H, 3.22; N, 12.47%.
13c: From 9c, the above general procedure yielded
226 mg (91%) of 13c as a yellow solid. M.p. 188–190 ꢁC
1
(dec.); H NMR (400 MHz, CDCl3): d 8.03 (s, 1H), 7.31
(t, J = 7.6 Hz, 4H), 7.20–7.05 (m, 6H), 4.97 (br s, 2H),
4.35 (br s, 3H), 3.43 (br s, 1H), 2.85 (br s, 1H), 2.50–2.40
(m, 1H), 2.34–2.22 (m, 1H), 2.20–2.10 (br s, 1H) 1.94 (br
s, 2H), 1.71 (br s, 2H), 1.48 (br s, 1H).13C NMR
(100 MHz, CDCl3): d 188.3 (d,JC–Rh = 50.1 Hz), 145.3,
143.4, 129.6, 124.7, 120.6, 99.0 (d, JC–Rh = 12.1 Hz), 69.9
(d,JC–Rh = 13.7 Hz), 67.4 (d, JC–Rh = 13.1 Hz), 41.1, 34.4,
31.4, 29.7, 27.7. HRMS Calc. for C23H26N4ClRh
496.0901, found 496.0904. Anal. Calc. for C23H26N4ClRh:
C, 55.60; H, 5.27; N, 11.28. Found: C, 55.82; H, 5.43; N,
11.09%.
3.4. Synthesis of 12
Triazolium salt 4d (1 mmol) was treated with LiBEt3H
as described in the literature [15] to afford triazoline 12
1
(127 mg, 71%) as a colorless syrup. H-RMN (300 MHz,
CDCl3): d 6.84 (s, 1H), 5.72 (s, 2H), 4.43 (s, 2H), 2.83 (s,
3H), 2.21 (s, 6H). 13C-RMN (75 MHz, CDCl3): d 143.1,
128.6, 105.1, 77.6, 43.6, 12.7. HRMS m/z Calc. for
C9H14N4: 178.1219, found: 178.1224.
14c: From 10c, the above general procedure yielded
238 mg (81%) of 14c as a yellow solid. M.p. 216–218 ꢁC
(dec.); 1H NMR (400 MHz, CDCl3): d 8.08 (s, 1H),
7.31 (t, J = 8.0 Hz, 4H), 7.20–7.05 (m, 6H), 5.20 (br s,
2H), 4.25 (s, 3H), 3.62–3.54 (m, 1H), 2.95–2.85 (m,
1H), 2.50–2.20 (m, 2H), 2.15–2.03 (m, 1H), 2.00–1.90
(m, 1H), 1.85–1.53 (m, 2H), 1.62–1.50 (m, 4H), 1.42–
1.30 (m, 1H).13C NMR (100 MHz, CDCl3): d 188.4
(d,JC–Rh = 49.3 Hz), 145.2, 143.5, 129.6, 124.9, 121.0,
96.9 (d, JC–Rh = 9.4 Hz), 96.8 (d, JC–Rh = 10.0 Hz), 73.1
(d, JC–Rh = 14.0 Hz), 71.0 (d, JC–Rh = 13.5 Hz), 41.7,
34.3, 30.8, 30.4, 28.0. Anal. Calc. for C23H26N4IRh: C,
46.96; H, 4.45; N, 9.52. Found: C, 47.12; H, 4.49; N,
9.31%.
3.5. Synthesis of RhCl(COD)[4-(dialkylamino or alkoxy)-
1-methyl-1,2,4-triazol-5-ylidenes] 13a–d, 14c,d and 15:
General procedure
To a suspension of 4-(dialkylamino or alkoxy)-1-
methyl-1,2,4-triazolium salt 9a–d, 10c,d or 11 (0.5 mmol)
and [RhCl(COD)]2 (123 mg, 0.25 mmol) in THF (5 mL)
was added Et3N (76 lL, 0.55 mmol) and the mixture was
stirred for 1 h at room temperature. The solvent was re-
moved in vacuo and the residue was purified by flash chro-
matography (AcOEt-Hex 1:4) to afford products 13a–d,
14c, d and 15. Starting materials, yields, and characteriza-
tion data for these compounds are as follows:
13a: From 9a, the above general procedure yielded
179 mg (64%) of 13a as a yellow solid. 1H NMR
(300 MHz, CDCl3): d 7.48–7.21 (m, 11H), 5.32–5.16 (m,
1H), 5.12–5.00 (m, 1H), 4.72 (d, J = 13.2 Hz, 2H), 4.52
(d, J = 13.2 Hz, 2H), 4.27 (s, 3H), 3.50–3.36 (m, 1H),
3.35–3.20 (m, 1H), 2.70–2.60 (m, 1H), 2.60–2.40 (m, 1H),
2.40–2.20 (m, 2H), 2.20–2.10 (m, 1H), 2.10–2.00 (m, 1H),
13d: From 9d, the above general procedure yielded
197 mg (93%) of 13d as a yellow solid. 1H NMR
(300 MHz, CDCl3): d 7.99 (s, 1H), 5.91 (br s, 2H), 4.98
(br s, 2H), 4.37 (s, 3H), 3.47 (br s, 1H), 3.00 (br s, 1H),
2.40 (br s, 4H), 2.28–2.10 (m, 2H), 1.67 (br s, 8H). 13C
NMR (75 MHz, CDCl3): d 187.3 (d, JC–Rh = 51.8 Hz),
142.7, 130.9, 127.2, 106.3, 105.7, 99.9 (br s), 69.6 (d,

5986
M. Alcarazo et al. / Journal of Organometallic Chemistry 690 (2005) 5979–5988
JC–Rh = 14.4 Hz), 68.3 (d, JC–Rh = 13.5 Hz), 47.0, 34.4,
32.1, 29.5, 28.4, 12.9, 11.3. Anal. Calc. for C17H24N4ClRh:
C, 48.30; H, 5.72; N, 13.25. Found: C, 48.06; H, 5.65; N,
13.08%.
(2-methyl-4-phenyl-1-oxa-3,4-diazol-5-ylidene) 23: 1H
NMR (400 MHz, CDCl3): d 7.60–7.40 (m, 5H), 5.27 (br
s, 2H), 3.30 (br s, 2H), 2.57 (s, 3H), 2.30–2.45 (m, 2H),
2.30–2.15 (m, 2H), 2.05–1.90 (m, 2H), 1.90–1.80 (m, 2H).
13C NMR (100 MHz, CDCl3): d 204.8 (d, JC–Rh = 56.5
Hz), 166.6, 136.6, 129.4, 129.0, 123.3, 102.4 (t,JC–Rh = 6.6
Hz), 70.3 (t, JC–Rh = 13.9 Hz), 32.6, 28.7, 11.1. Anal. Calc.
for C17H20N2ClRhO: C, 50.20; H, 4.96; N, 6.89. Found: C,
50.02; H, 5.14; N, 6.72%.
14d: From 10d, the above general procedure yielded
175 mg (68%) of 14d as a yellow solid. M.p. 178–180 ꢁC
1
(dec.); H-RMN (400 MHz, CDCl3): d 7.99 (s, 1H), 5.91
(s, 2H), 5.32–5.27 (m, 1H), 5.31–5.14 (m, 1H), 4.31 (s,
3H), 3.72–3.62 (m, 1H), 3.33–3.25 (m, 1H), 2.46 (s, 3H),
2.40–2.25 (m, 1H), 2.25–2.05 (m, 2H), 1.95–1.85 (m, 1H),
1.85–1.65 (m, 6H), 1.55–1.45 (m, 1H).13C-RMN
(100 MHz, CDCl3): d 187.48 (d,JC–Rh = 50.1 Hz), 143.1,
130.5, 127.0, 106.2, 105.6, 97.5 (d, JC–Rh = 6.4 Hz), 97.4
(d, JC–Rh = 6.0 Hz), 72.6 (d, JC–Rh = 13.2 Hz), 71.3 (d,
JC–Rh = 13.3 Hz), 43.0, 33.9, 31.0, 30.2, 28.6, 14.4, 11.1.
Anal. Calc. for C17H24N4IRh: C, 39.71; H, 4.70; N, 10.90.
Found: C, 39.52; H, 4.51; N, 10.81.
15: From 11, the above general procedure yielded
167 mg (77%) of 15 as a yellow solid. 1H NMR
(500 MHz, CDCl3): d 7.60–7.50 (m, 2H), 7.45–7.30 (m,
4H), 5.85 (br s, 1H), 5.77 (br s, 1H), 5.15 (br s, 2H), 4.22
(s, 3H), 3.87 (br s, 1H), 3.43 (br s, 1H), 2.41 (br s, 4H),
2.00 (br s, 4H). 13C NMR (75 MHz, CDCl3): d 181.1 (d,
JC–Rh = 50.3 Hz), 139.2, 133.4, 130.8, 130.0, 129.2, 99.7
(br s), 99.4 (br s), 83.0, 69.9 (br s), 41.5, 33.2 (br s), 29.4
(br s). Anal. Calc. for C18H23N3ClORh: C, 49.61; H,
5.32; N, 9.64. Found: C, 49.82; H, 5.21; N, 9.87%.
3.8. Synthesis of silver carbenes 16c,d: General procedure
To a solution of 10c or 10d (1 mmol) in CH2Cl2 (20 mL)
was added Ag2O (128 mg, 0.55 mmol) and the mixture was
stirred in the darkness at room temperature for 3 h. The
mixture was then filtered through a celite pad and concen-
trated to yield the products 16c and 16d as white foams.
Starting materials, yields, and characterization data for
these compounds are as follows:
16c: From 10c, the above general procedure yielded
440 mg (91%) of 16c as a white foam. 1H NMR
(300 MHz, CDCl3): d 8.15 (s, 1H), 7.23 (t, J = 7.8 Hz,
4H), 7.06 (t, J = 7.2 Hz, 2H), 6.94 (d, J = 7.2 Hz, 4H),
3.98 (s, 3H).13C NMR (75 MHz, CDCl3): d 145.1, 143.2,
130.0, 125.2, 121.0, 42.3. Anal. Calc. for C15H14N4IAg:
C, 37.14; H, 2.91; N, 11.55. Found: C, 37.25; H, 2.99; N,
11.78%.
16d: From 10d, the above general procedure yielded
361 mg (88%) of 16d as a white foam. 1H NMR
(300 MHz, CDCl3): d 8.21 (s, 1H), 5.88 (s, 2H), 3.96 (s,
3H), 2.08 (s, 6H). 13C NMR (75 MHz, acetone-d6): d
145.3, 129.1, 107.2, 42.1, 10.6. Anal. Calc. for
C9H12N4IAg: C, 26.30; H, 2.94; N, 13.63. Found: C,
25.98; H, 3.13; N, 13.79%.
3.6. Synthesis of 22
To a solution of 1-methyl-4-(3,5-dimethylphenyl)-1,2,4-
triazolium triflate 20 [21] (101 mg, 0.3 mmol) in THF
(10 mL) was added [RhCl(COD)]2 (74 mg, 0.15 mmol)
and Et3N (38 lL, 0.3 mmol) and the mixture was stirred
at room temperature for 30 min. The solvent was removed
in vacuo an the residue was purified by flash chromatogra-
phy (AcOEt-hexane 1:3) to yield 22 (114 mg, 87%) as a yel-
3.9. Synthesis of cationic rhodium complexes 17b,d: General
procedure
1
low powder. H NMR (300 MHz, CDCl3): d 8.09 (s, 1H),
7.76 (s, 2H), 7.11 (s, 1H), 5.17–5.10 (m, 1H), 5.05–4.97
(m, 1H), 4.32 (s, 3H), 3.32 (s, 1H), 2.68–2.48 (m, 1H),
2.43 (s, 6H), 2.38–2.25 (m, 2H), 2.15–2.05 (m, 1H), 1.93–
1.78 (m, 3H), 1.64–1.50 (m, 2H).13C NMR (75 MHz,
CDCl3): d 185.6 (d, JC–Rh = 51.1 Hz), 141.3, 139.5,
136.5, 130.7, 122.4, 99.2 (t, JC–Rh = 6.0 Hz), 69.0 (t,
JC–Rh = 15.8 Hz), 40.6, 33.7, 32.0, 29.5, 28.7, 21.6. Anal.
Calc. for C19H25N3ClRh: C, 52.49; H, 6.03; N, 9.66.
Found: C, 52.31; H, 5.89; N, 9.73%.
To a solution of RhCl(1,2,4-triazol-5-ylidene)(COD)
13b or 13d (0.2 mmol) in dry THF (4 mL) was added the
corresponding azolium triflate 9b or 9d, AgOTf (51 mg,
0.2 mmol) and Et3N (22 lL, 0.2 mmol). The mixture was
stirred in the darkness for 2 h, the solvent was removed
in vacuo and the residue was purified by flash chromatog-
raphy (AcOEt/CH2Cl2 1:1) to yield 17b or 17d. Crystals
suitable for X-ray diffraction analysis were grown by slow
diffusion of diethyl ether in a solution of the complex in
dichloromethane. Starting materials, yields, and character-
ization data for these compounds are as follows:
3.7. Synthesis of 23
17b: From 13b and 9b, the above general procedure
1
To a solution of 2-methyl-4-phenyl-1-oxa-3,4-diazolium
perchlorate 21 [22] (78 mg, 0.3 mmol) in THF (10 ml) was
added [RhCl(COD)]2 (74 mg, 0.15 mmol) and Et3N
(38 lL, 0.3 mmol) and the mixture was stirred for 30 min
at room temperature. The solvent was then removed in va-
cuo and the residue was purified by flash chromatography
(AcOEt/hexane 1:3) to afford 51 mg (42%) of RhCl(COD)-
yielded 102 mg (69%) of 17b as a yellow solid. H NMR
(400 MHz, CDCl3): d 8.20 (s, 2H), 7.23 (t, J = 8.0 Hz,
4H), 7.01 (t, J = 7.2 Hz, 2H), 6.32 (d, J = 8.0 Hz, 4H),
4.56 (br s, 2H), 4.18 (br s, 2H), 3.74 (br s, 6H), 3.52 (s,
6H), 2.45–2.20 (m, 6H), 2.10–2.00 (m, 2H).13C NMR
(100 MHz, CDCl3): d 185.1 (d, JC–Rh = 52.2 Hz), 148.1,
142.9, 129.9, 122.8, 113.5, 92.7 (d, JC–Rh = 7.4 Hz), 90.0

M. Alcarazo et al. / Journal of Organometallic Chemistry 690 (2005) 5979–5988
5987
(d,JC–Rh = 6.5 Hz), 43.7, 40.3, 31.9, 29.0. Anal. Calc. for
C29H36N8F3O3SRh: C, 47.16; H, 5.06; N, 15.17. Found:
C, 47.21; H, 5.21; N, 15.01%.
FTIR:
m
CO = 2090, 2012 cmꢀ1
.
Anal. Calc. for
C12H11N3ClO3Rh: C, 37.47; H, 3.14; N, 10.93. Found: C,
37.23; H, 3.02; N, 11.21%.
17d: From 13d and 9d, the above general procedure
yielded 82 mg (57%) of crystalline 17d. M.p. 252–253 ꢁC
24: From 22, the above general procedure yielded 36 mg
(96%) of 24 as a yellow powder. 1H NMR (300 MHz,
CDCl3): d 8.18 (s, 1H), 7.27 (s, 2H), 7.14 (s, 1H), 4.22 (s,
3H), 2.40 (s, 6H). 13C NMR (100 MHz, CDCl3): d 184.8
(d,JC–Rh = 55.2 Hz), 181.8 (d, JC–Rh = 68.4 Hz), 177.6
(d,JC–Rh = 44.1 Hz), 142.0, 139.8, 135.4, 131.6, 123.0,
40.9, 21.3. FTIR: mCO = 2090, 2010 cmꢀ1. Anal. Calc. for
C13H13N3ClO2Rh: C, 40.91; H, 3.43; N, 11.01. Found: C,
41.12; H, 3.23; N, 11.15%.
1
(dec.); H NMR (300 MHz, CDCl3): d 8.22 (s, 2H), 6.00
(d, J = 6.9 Hz, 4H), 4.81 (br s, 2H), 4.25–4.15 (m, 2H),
3.98 (s, 6H), 2.40–2.10 (m, 8H), 2.02 (s, 6H), 1.37 (s, 6H).
13C NMR (75 MHz, CDCl3): d 185.4 (d, JC–Rh = 52.9 Hz),
145.2, 128.9, 127.9, 108.0, 107.8, 94.1 (d, J
= 8.0 Hz),
C–Rh
90.0 (d, JC–Rh = 7.2 Hz), 41.8, 31.6, 29.7, 11.9, 11.1. Anal.
Calc. for C27H36N8F3O3SRh: C, 45.38; H, 5.30; N, 15.68.
Found: C, 45.28; H, 5.42; N, 15.47%.
25: From 23, the above general procedure yielded 28 mg
(78%) of 25 as a yellow solid. 1H NMR (300 MHz, CDCl3):
d 8.10–8.00 (m, 2H), 7.65–7.45 (m, 3H), 2.59 (s, 3H).13C
NMR (100 MHz, CDCl3): d 196.3 (d, JC–Rh = 65.2 Hz),
184.4 (d, JC–Rh = 74.2 Hz), 181.5 (br s), 168.0, 135.8,
3.10. Synthesis of rhodium dicarbonyl complexes 18a,b,d, 19,
24, and 25: General procedure
CO was bubbled through a solution of Rhodium cyclo-
octadiene complexes 13a,b,d, 15, 22 or 23 (0.1 mmol) in
THF (3 mL) for 10 min. The solvent was then removed
in vacuo and the residue was washed several times with
n-pentane and dried in high vacuum. Starting materials,
yields, and characterization data for these compounds are
as follows:
18a: From 13a, the above general procedure yielded
42 mg (89%) of 18a as a yellow syrup. 1H NMR
(300 MHz, CDCl3): d 7.44 (s, 1H), 7.40–7.20 (m, 10H),
4.59 (s, 4H), 4.08 (s, 3H). 13C NMR (75 MHz, CDCl3): d
185.0 (d,JC–Rh = 55.1 Hz), 182.4 (d, JC–Rh = 74.8 Hz),
176.8 (d,JC–Rh = 43.5 Hz), 144.3, 135.6, 129.9, 129.0,
128.9, 61.9, 42.6. FTIR: mCO = 2092, 2010 cmꢀ1. Anal.
Calc. for C19H18N4ClO2Rh: C, 48.27; H, 3.84; N, 11.85.
Found: C, 48.60; H, 3.51; N, 11.89.
130.9, 129.7, 124.7, 11.4. FTIR: mCO = 2098, 2020 cmꢀ1
.
Anal. Calc. for C11H8N2ClO3Rh: C, 37.26; H, 2.27; N,
7.90. Found: C, 37.31; H, 2.44; N, 7.98%.
3.11. X-ray crystallography
A single crystal of suitable size was mounted on glass
fiber with perfluoropolyether oil (FOMBLINꢂ 140/13, Al-
drich) and attached to the goniometer head on a Bruker-
Nonius X8Apex-II CCD diffractometer using graphite
˚
monochromator k (Mo Ka1) = 0.71073 A, and equipped
with a Bruker-Nonius Kryo-Flex low temperature device
cooled at 100 K. Data collection was performed using x
and / scans with a width of 0.30ꢁ and exposure times of
10 s (in the range 5.70 < 2h < 61.12ꢁ, 14c), 15 s (in the range
5.90 < 2h < 61.16ꢁ, 14d), 10 s (in the range 2.66 < 2h <
61.14ꢁ, 17b) or 30 s (in the range 4.68 < 2h < 55.60ꢁ, 17d)
with a detector distance of 37.5 mm. The data were reduced
(SAINT) [24] and corrected for Lorentz polarization effects
and absorption (SADABS [25]. The structure was solved by
direct methods (SIR-2002) [26] and refined against all F2
data by full-matrix least-squares techniques (SHELXTL-
6.12) [27]. All the non-hydrogen atoms were refined with
anisotropic displacement parameters. The hydrogen atoms
were included from calculated positions and refined riding
on their respective carbon atoms with isotropic displace-
ment parameters.
18b: From 13b, the above general procedure yielded
37 mg (96%) of 18b as a yellow powder. 1H NMR
(300 MHz, CDCl3): d 8.20 (s, 1H), 7.31 (t, J = 7.8 Hz,
2H), 7.03 (t, J = 7.5 Hz, 1H), 6.70 (d, J = 8.1 Hz, 2H),
4.17 (s, 3H), 3.55 (s, 3H). 13C NMR (75 MHz, CDCl3): d
184.9 (d, JC–Rh = 55.4 Hz), 181.4 (d, JC–Rh = 71.3 Hz),
148.0, 143.7, 129.4, 123.2, 115.4, 43.8, 42.1. FTIR:
m
CO = 2088, 2010 cmꢀ1. Anal. Calc. for C12H12N4ClO2Rh:
C, 37.57; H, 3.42; N, 14.60. Found: C, 37.45; H, 3.22; N,
14.94%.
18d: From 13d, the above general procedure yielded
33 mg (93%) of 18b as a yellow powder. 1H NMR
(400 MHz, CDCl3): d 8.20 (s, 1H), 5.92 (s, 2H), 4.23 (s,
3H), 2.06 (s, 6H). 13C NMR (100 MHz, CDCl3): d 184.1
(d, JC–Rh = 55.7 Hz), 181.2 (br s), 181.1 (d,JC–Rh = 47.6
Hz), 142.8, 128.5, 106.2, 41.8, 11.6. FTIR: mCO = 2095,
2013 cmꢀ1. Anal. Calc. for C11H12N4ClO2Rh: C, 35.65;
H, 3.26; N, 15.12. Found: C, 35.39; H, 3.03; N, 15.01%.
19: From 15, the above general procedure yielded 35 mg
(91%) of 19 as a yellow syrup. 1H NMR (300 MHz,
CDCl3): d 7.51–7.30 (m, 6H), 5.56 (s, 2H), 4.09 (s,
3.12. Crystallographic data for 14c
C23H26IN4Rh, Mr = 588.29, yellow prism crystal (0.34 ·
0.33 · 0.31 mm3) from hexane– CH2Cl2; monoclinic, space
˚
˚
3
group P21/n (no.14), a = 9.8051(2) A, b = 13.1029(3) A,
˚
˚
c = 17.4440(4) A, b = 101.8510(10)ꢁ, V = 2193.35(8) A ,
Z = 4,
q , F(000) = 1160, l = 2.203
calc = 1.782 g cmꢀ3
mmꢀ1, 30,946 measured reflections, of which 6692 were un-
ique (Rint = 0.0225); 264 refined parameters,R1 = 0.0176 for
reflections with I > 2r(I) and wR2 = 0.0456 for all data
(GOF = 1.079).
3H).13C NMR (75 MHz, CDCl3): d 184.6 (d,JC–Rh
55.7 Hz), 181.6 (d, JC–Rh = 72.2 Hz), 173.8 (d,JC–Rh
=
=
43.5 Hz), 139.3, 132.3, 130.5, 130.2, 129.2, 83.3, 42.7.

5988
M. Alcarazo et al. / Journal of Organometallic Chemistry 690 (2005) 5979–5988
3.13. Crystallographic data for 14d
References
[1] A.J. Arduengo, R.L. Harlow, M. Kline, J. Am. Chem. Soc. 113
(1991) 361.
[2] (a) D. Bourissou, O. Guerret, F.P. Gabla¨ı, G. Bertrand, Chem. Rev.
100 (2000) 39–91;
C17H24IN4Rh, Mr = 514.21, orange prism crystal (0.28 ·
0.26 · 0.25 mm3) from hexane– CH2Cl2; monoclinic, space
˚
˚
group C2/c (no. 15), a = 24.2857(8) A, b = 12.1154(4) A,
3
˚
˚
c = 16.1964(5) A, b = 128.5620(10)ꢁ, V = 3726.3(2) A ,
(b) R.W. Alder, in: G. Bertrand (Ed.), Carbene Chemistry: From
Fleeting Intermediates to Powerful Reagents, Marcel Dekker Inc,
New York, 2002, pp. 153–176 (Chapter 5).
Z = 8,
q , F(000) = 2016, l = 2.578
calc = 1.833 g cmꢀ3
mmꢀ1, 21,308 measured reflections, of which 5643 were un-
ique (Rint = 0.0240); 212 refined parameters, R1 = 0.0282 for
reflections with I > 2r(I) and wR2 = 0.0768 for all data
(GOF = 1.049).
[3] W.A. Herrmann, Angew. Chem. Int. Ed. 41 (2002) 1290.
[4] A.J. Arduengo, H.V.R. Dias, R.L. Harlow, M. Kline, J. Am. Chem.
Soc. 114 (1992) 5530.
[5] D. Enders, K. Breuer, G. Raabe, J. Runsink, J.H. Teles, J. Melder,
K. Ebel, S. Brode, Angew. Chem. Int. Ed. Engl. 34 (1995) 1021.
[6] A. Furstner, L. Ackermann, B. Gabor, R. Goddard, C.W. Lehmann,
¨
3.14. Crystallographic data for 17b
R. Mynott, F. Stelzer, O.R. Thiel, Chem. Eur. J. 7 (2001) 3236.
[7] Review: D. Enders, H. Gielen, J. Organomet. Chem. 617–618 (2001)
70.
[8] D. Enders, U. Kallfass, Angew. Chem., Int. Ed. Engl. 41 (2002) 1743.
[9] J. Read de Alaniz, T. Rovis, J. Am. Chem. Soc. 127 (2005) 6284, and
references therein.
C29H36F N8O3RhS, Mr = 736.63, yellow prism crystal
(0.48 · 0.45 · 0.43 mm3) from ethyl ether–CH2Cl2; mono-
˚
clinic, space group P21/n (no. 14), a = 17.6377(5) A,
˚
˚
b = 9.5102(2) A, c = 20.3236(6) A, b = 108.7710(10)ꢁ,
´
´
[10] M. Alcarazo, S. Roseblade, E. Alonso, R. Fernandez, E. Alvarez,
F.L. Lahoz, J.M. Lassaletta, J. Am. Chem. Soc. 126 (2004) 13242.
[11] K. Denk, P. Sirsh, W.A. Herrmann, J. Organomet. Chem. 649 (2002)
219.
3
V = 3227.72(15) A , Z = 4, qcalc = 1.516 g cmꢀ3, F(000) =
˚
1512, l = 0.655 mmꢀ1, 36,959 measured reflections, of
which 9471 were unique (Rint = 0.0248); 410 refined param-
eters, R1 = 0.0571 for reflections with I > 2r(I) and
wR2 = 0.1532 for all data (GOF = 1.032).
[12] (a) G.V. Boyd, A.J.H. Summers, J. Chem. Soc. 36 (1971) 409;
(b) J.H. Teles, J.P. Melder, K. Ebel, R. Schneider, E. Gehrer, W.
Harder, S. Brode, D. Enders, K. Breuer, G. Raabe, Helv. Chim.
Acta 79 (1996) 61–83.
[13] R.K. Bartlett, I.R. Humphrey, J. Chem. Soc. (C) (1967) 1664.
[14] A.R. Katritzky, J.W. Suwinski, Tetrahedron 31 (1975) 1549.
[15] Y. Yamaguchi, T. Kashiwabara, K. Ogata, Y. Miura, Y. Nakamura,
K. Kobayashi, I. Takashi, Chem. Commun. (2004) 2160.
[16] The stability of such a chiral axis in related compounds has previously
been reported. See Ref. [2].
[17] D. Enders, H. Gielen, J. Runsink, K. Breuer, S. Brode, K. Boehn,
Eur. J. Inorg. Chem. (1998) 913.
[18] (a) H.M.J. Wang, I.J.B. Lin, Organometallics 17 (1998) 972;
(b) D.S. McGuinness, K.J. Cavell, Organometallics 19 (2000) 741.
[19] Related Pd bis-carbenes with two chiral axes have been prepared,
though in a less selective way. See Ref. [12].
3.15. Crystallographic data for 17d
C27H36F3N8O3RhS, Mr = 712.61, yellow block crystal
(0.20 · 0.17 · 0.07 mm3) from ethyl ether–CH2Cl2; mono-
˚
clinic, space group P21/c (no. 14), a = 16.8666(5) A,
˚
˚
b = 21.0129(6) A, c = 17.4842(4) A, b = 96.1430(10)ꢁ,
3
V = 6161.1(3) A , Z = 8, qcalc = 1.536 g cmꢀ3, F(000) =
˚
2928, l = 0.683 mmꢀ1, 57,059 measured reflections, of
which 14,522 were unique (Rint = 0.0835); 775 refined
parameters, R1 = 0.0585 for reflections with I > 2r(I) and
wR2 = 0.1670 for all data (GOF = 1.018).
´
[20] M. Alcarazo, S.J. Roseblade, A.R. Cowley, R. Fernandez, J.M.
Brown, J.M. Lassaletta, J. Am. Chem. Soc. 127 (2005) 3290.
[21] Obtained from 3,5-dimethylaniline by condensation with 3 and
alkylation with MeOTf.
4. Supplementary material
[22] G.V. Boyd, R.S. Dando, J. Chem. Soc. (C) (1970) 1397.
[23] A.R. Katritzky, J.W. Suwinski, Tetrahedron 31 (1975) 1549.
[24] SAINT 6.02, BRUKER-AXS, Inc., Madison, WI 53711-5373 USA,
1997–1999.
[25] SADABS George Sheldrick, Bruker AXS, Inc., Madison,Wisconsin,
USA, 1999.
[26] M.C. Burla, M. Camalli, B. Carrozzini, G.L. Cascarano, C. Giaco-
vazzo, G. Polidori, R. Spagna, SIR2002: the program, J. Appl. Cryst.
36 (2003) 1103.
[27] SHELXTL 6.14, Bruker AXS, Inc., Madison, Wisconsin, USA, 2000–
2003.
Full crystallographic data (CIF files) for 14c, 14d, 17b
and 17d have been deposited with the Cambridge Crystal-
lographic Data Centre, CCDC Nos. 273322–273325. Cop-
ies of this information may be obtained free of charge from
The Director, Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223
336033; e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).