Hydrogen-bonding network in new scorpionate-type ligand composed of pyridine/pyrrole hybrid and anion-binding behavior of the corresponding rhodium complexes in alkyne cyclotrimerization reaction

Article abstract of DOI:10.1016/j.jorganchem.2008.07.005

New heteroscorpionate ligands (1 and 2) having a di(pyridin-2-yl)(1H-pyrrol-2-yl)methane substructure are synthesized. X-ray crystallographic analysis on 1 and 2 reveals that they form unique hydrogen bonding networks depending on the size of neighboring

Full text of DOI:10.1016/j.jorganchem.2008.07.005

Journal of Organometallic Chemistry 693 (2008) 3141–3150
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Hydrogen-bonding network in new scorpionate-type ligand composed of
pyridine/pyrrole hybrid and anion-binding behavior of the corresponding
rhodium complexes in alkyne cyclotrimerization reaction
*
Motoki Toganoh, Naoyuki Harada, Hiroyuki Furuta
Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
New heteroscorpionate ligands (1 and 2) having a di(pyridin-2-yl)(1H-pyrrol-2-yl)methane substructure
are synthesized. X-ray crystallographic analysis on 1 and 2 reveals that they form unique hydrogen bond-
ing networks depending on the size of neighboring groups in solid states. 1 and 2 can form cationic rho-
dium(I) complexes, wherein the counter anions form hydrogen bondings with the pyrrolic NH moiety. In
alkyne cyclotrimerization reactions using those complexes as catalyst, the catalytic activity is signifi-
cantly enhanced when electron-donating counter anions is placed near the metal center.
Ó 2008 Elsevier B.V. All rights reserved.
Received 12 May 2008
Received in revised form 1 July 2008
Accepted 3 July 2008
Available online 10 July 2008
Keywords:
Rhodium
Scorpionate ligand
Cyclotrimerization
Anion-binding
1. Introduction
reactions [16] through the anion exchange of the catalysts. Never-
theless, detailed research, especially from the viewpoint of coordi-
Monoanionic tripodal nitrogen donor ligands such as tris(pyraz-
olyl)borate are isoelectronic with the cyclopentadienyl ligand and
widely employed in coordination chemistry and catalyst [1,2].
They have been commonly used as supporting ligands, which en-
able isolation of structurally as well as electronically interesting
transition metal complexes [3]. Unique asymmetrical monoanionic
tripodal ligands based on tetrapyrrolic units have been developed
recently and applied for catalyst and stabilization of high oxidation
state of the metal center [4]. Alternatively, heteroscorpionate li-
gands and related compounds including functionalized bis(pyra-
zol-1-yl)methane are also studied extensively because of their
high flexibility on metal coordination [5–8].
nation chemistry, has not enough pursued yet.
This time, a connection of different metal coordination sites like
pyridine and pyrrole [17] was studied to produce new heteroscor-
pionate ligands (1 and 2, Chart 1), which showed unique hydrogen-
bonding networks depending on the size of neighboring groups.
Beside, rhodium(I) complexes bearing a variety of counter anions
were prepared with those ligands and alkyne cyclotrimerization
reactions [18] were carried out with those complexes. The reactiv-
ity is significantly dependent on counter anions and the result af-
fords fundamental information about the anion effect on alkyne
cyclotrimerization reactions.
We are currently interested in hydrogen bonding networks as
well as anion-bindings by pyrrolic NH moieties [9]. Such anion rec-
ognition has been applied to the controlling redox or photophysical
properties [10], construction of supramolecules [11], and so on. In
particular, anion effects on the reactions catalyzed by cationic me-
tal complexes have gathered much attention, because such strat-
egy does not require tedious chemical transformations for
modification of catalysts and, consequently, has hopeful prospect
in the field of catalysis [12,13]. For instance, significant refinement
of reactivity is observed in the rhodium catalyzed hydroamination
reactions [14], aldol reactions [15], and intramolecular cyclization
2. Results and discussion
The new monoanionic tripodal nitrogen donor ligands (1 and 2)
composed of two pyridine units and one pyrrole unit can be pre-
pared easily as follows (Scheme 1). The ligand 1a was synthesized
from 2,2’-dipyridylketone (3) and pyrrole. Upon treatment of 3 in
pyrrole with trifluoroacetic acid (TFA) at ambient temperature,
addition reaction proceeded smoothly to give 1a in 67% yield. Since
N-substitution competes against O-substitution in alkylation reac-
tions of 1a with alkyl halides, chemical transformation from 1a to
1b,c is so far ineffective. Then, preparation of 1b,c was achieved
through protection of the pyrrole moiety. First, N-BOC-2-bromo-
pyrrole (4, BOC = t-butoxycarbonyl), prepared as reported, was
lithiated with n-BuLi at À78 °C [19]. Second, 3 was added to the
* Corresponding author.
E-mail address: hfuruta@cstf.kyushu-u.ac.jp (H. Furuta).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.07.005

3142
M. Toganoh et al. / Journal of Organometallic Chemistry 693 (2008) 3141–3150
N
HN
N
OR
N
NH
N
N
1a: R = H
1b: R = Me
1c: R = Et
2
Chart 1. Structures of new scorpionate-type ligands.
O
HN
N
TFA
(3.6 equiv)
OH
N
N
N
pyrrole
(10 equiv)
23 °C, 1 h
3
1a
67%
n-BuLi
3
N
BOC
N
BOC
(2 equiv) (1 equiv)
OH
Br
THF
THF
-78 °C
15 min
-78 °C
N
N
60 min
(2 equiv)
92%
4
5
NaOR/ROH
(5 equiv)
HN
OR
N
THF
23 °C
30 min
N
1b: R = Me (40%)
1c: R = Et (47%)
Scheme 1. Preparation of 1a–c.
resulting N-BOC-2-lithiopyrrole to give a carbinol (5) in 92% yield.
5 can be prepared by protection of 1a albeit in much lower yield.
Finally, treatment of 5 with NaOMe or NaOEt afforded 1b or 1c
in 40% or 47% yield, respectively [20]. The ligand 2 was prepared
via Pictet–Spengler reaction (Scheme 2) [21,22]. Heating of 3 and
tryptamine (6) in the presence of p-toluenesulfonic acid (TsOH)
gave the adduct 7 in 78% yield. Subsequent treatment of 7 with
MeI under basic conditions afforded 2 in 99% yield [23]. The expe-
ditious routes developed here allow us to obtain 1 and 2 in gram
scales within a few days.
Fig. 1. Crystal structures of: (a) 1a, (b) 1b, and (c) 1c. Thermal ellipsoids are shown
at the 30% probability level.
observed in 1a–c. Directions of the pyrrole rings as well as the pyr-
idine rings differ in each molecule, indicating flexible rotation of
these rings. Fig. 2 shows the X-ray structure of 2. Compared to 1,
2 has the rigid structure due to bridging between the indole moiety
and the bis(2-pyridyl)methane moiety and hence the direction of
NH moiety relative to the two pyridine rings is nearly fixed.
Because 1 and 2 have the hydrogen-donating pyrrole ring and
the hydrogen-accepting pyridine ring in addition to the hydroxy
or alkoxy groups, they form ordered architectures through hydro-
The structures of 1 and 2 are elucidated by X-ray crystallo-
graphic analysis. The ORTEP drawings of 1a–c are shown in
Fig. 1. The bis(2-pyridyl)pyrrolylmethane substructures are clearly
O
NH
N
TsOH
NH2
(0.1 equiv)
+
NH
N
N
toluene
reflux
8 h
N
H
6
N
3
7
78%
MeI
N
N
(90 equiv)
NH
NaHCO3
(14 equiv)
MeOH
N
2
23 °C, 2 d
99%
Fig. 2. Crystal structure of 2. Thermal ellipsoids are shown at the 30% probability
Scheme 2. Preparation of 2.
level.

M. Toganoh et al. / Journal of Organometallic Chemistry 693 (2008) 3141–3150
3143
Fig. 5. Hydrogen-bonding network of 1c in solid state.
Fig. 3. Hydrogen-bonding network of 1a in solid state.
gen bondings in solid states. In the case of 1a, formation of a di-
meric structure is found as shown in Fig. 3. Intermolecular hydro-
gen bonding is formed between the pyrrolic NH moiety of one
molecule and the oxygen atom of the adjacent molecule. The inter-
molecular N–O bond length is 3.0905(14) Å. The intramolecular
NH–O bond (N–O bond length: 2.6368(14) Å) and the intramolec-
ular OH–N bond (N–O bond length: 2.5572(14) Å) are also ob-
served in 1a. When the methyl group is introduced to the
hydroxy moiety of 1a, hydrogen bondings around this moiety are
disturbed and 1D chain hydrogen-bonding network is constructed
as illustrated with 1b (Fig. 4). In 1b, the methoxy group is not en-
gaged for hydrogen bondings. Alternatively, sequential NH–N
hydrogen bonds (N–N bond length: 3.1051(18) Å) are formed to
construct zigzag alignments. Interestingly, this 1D chain network
is easily torn into dimers by changing the methoxy group to the
ethoxy group. In the solid state structure of 1c, only a dimeric
architecture is observed (Fig. 5) and no 1D chain networks are
found at all. The oxygen atom does not contribute to hydrogen
bondings and only intra- and intermolecular NH–N bonds (N–N
bond lengths: 2.8895(14) and 2.9738(14) Å) are detected. Possibly
due to different configuration derived from hydrogen bonding net-
work, 1a–c have totally different crystal systems (1a: monoclinic,
1b: orthorhombic, 1c: triclinic), although they do not contain any
solvent molecules. In the case of 2, only intermolecular NH–N
bonds (N–N bond length: 3.0288(14) Å), which result in a forma-
tion of dimer, are observed (Fig. 6).
Fig. 6. Hydrogen-bonding network of 2 in solid state.
responding rhodium complex 9-Cl in 95% yield. In the 1H NMR
spectra, the signals ascribable to the pyrrolic NH moieties are ob-
served at
d 11.03 ppm for 8a-Cl, 11.65 ppm for 8b-Cl, and
13.43 ppm for 9-Cl. Such significant low-field shifts from those of
the intact ligands 1 and 2 (d 9.41 ppm (1a), 10.78 ppm (1b), and
8.94 ppm (2)) suggest the existence of hydrogen bondings between
the pyrrole NH moieties and the chloride anions [24].
Strong evidence for the structural assignment of the rhodium
complexes is derived from the X-ray crystallographic analysis on
8a-Cl. The ORTEP drawing of 8a-Cl is shown in Fig. 7 and the se-
lected structural parameters are listed in Table 1. The rhodium me-
tal is coordinated by the two pyridine nitrogen atoms as well as the
cod ligand. The distance between the chloride anion and the pyr-
role nitrogen atom or the hydroxyl oxygen atom is 3.322(3) or
3.031(2) Å, respectively. These values show that the chloride anion
is recognized by both the NH and OH moieties. While 8a-Cl for-
mally has the Cs symmetric structure, the bond lengths and the
bond angles around the metal center are asymmetrical in solid
The cationic rhodium complexes 8a-Cl, 8b-Cl, and 9-Cl are read-
ily prepared by treatment of 1 and 2 with [RhCl(cod)]2 (cod = 1,5-
cyclooctadiene) at ambient temperature (Scheme 3). When 1a was
treated with [RhCl(cod)]2 in CH2Cl2, coordination of 1a to a rho-
dium metal proceeded smoothly to give the rhodium(I) complex
8a-Cl in 95% yield. Similarly, treatment of 1b afforded 8b-Cl in
95% yield. The reaction of 2 with [RhCl(cod)]2 also afforded the cor-
Fig. 4. Hydrogen-bonding 1D chain network of 1b in solid state.

3144
M. Toganoh et al. / Journal of Organometallic Chemistry 693 (2008) 3141–3150
neutral complexes 10b or 11, respectively (Scheme 4) [25].
Cl
Furthermore, treatment of 10b or 11 with NH4Cl caused regenera-
tion of 8b-Cl or 9-Cl. These cycles are essentially reversible and
interchange between the pyrrole ring and the pyridine ring occurs
without decomposition of the complexes. In 10b and 11, a loss of
hydrogen atom attached to the pyrrole nitrogen atom is surely
confirmed by the 1H NMR spectra and the detailed structure
of 11 is elucidated by X-ray crystallographic analysis (Fig. 8 and
Table 2). The anionic pyrrole nitrogen atom (N3) and one of the
two pyridine nitrogen atoms (N1) coordinate to the metal center
and another pyridine nitrogen atom (N2) remains free.
Manipulation of anions in 8a-Cl and 9-Cl is achieved in a com-
mon manner (Scheme 5). Anion exchange is possible by treatment
with silver salts or sodium salts. For example, mixing of 8a-Cl with
AgPF6 and subsequent recrystallization affords 8a-PF6. In a similar
manner, the reactions of 9-Cl with the corresponding silver salts
give 9-PF6, 9-NO3, and 9-OCOCF3. In addition, treatment of 9-Cl
with NaBPh4 gives 9-BPh4. The 1H NMR signals of pyrrolic NH pro-
tons give definite information on the structures of the anion-ex-
changed rhodium complexes. The exchange of anions from
chloride to hexafluorophosphate causes the high-field shifts (d
9.28 ppm (8a-PF6) and 11.71 ppm (9-PF6)), which suggests weaker
interaction between the NH moieties and the anions. While
distinct anion bindings are implied for 9-NO3 (d 12.90 ppm) and
9-OCOCF3 (d 12.72 ppm), almost no interaction between the NH
moiety and the anion is recognized in 9-BPh4 (d7.95 ppm).
OH
N
[RhCl(cod)]2
(0.6 equiv)
H
N
HN
N
OH
N
N
Rh
CH2Cl2
23 °C, 15 min
95%
8a-Cl
Cl
1a
1b
OMe
N
[RhCl(cod)]2
(0.6 equiv)
H
HN
N
N
OMe
N
N
Rh
CH2Cl2
23 °C, 15 min
95%
8b-Cl
N
[RhCl(cod)]2
(0.6 equiv)
N
N
N
H
N
CH2Cl2
NH
N
23 °C, 15 min
Cl
Rh
N
2
95%
9-Cl
Scheme 3. Rhodium metalation of 1 and 2.
Cl
OMe
OMe
N
N
H
N
NaHCO3
NH4Cl
N
N
Rh
N
Rh
8b-Cl
10b
N
N
N
NaHCO3
NH4Cl
N
N
N
H
N
N
Rh
Cl
Rh
9-Cl
11
Scheme 4. Reversible interchange of the pyridine rings and the pyrrolic ring.
Fig. 7. Crystal structure of 8a-Cl. Thermal ellipsoids are shown at the 30%
probability level.
Table 1
Selected bond lengths (Å) and angles (°) for the X-ray structure of 8a-Cl
RhÀC1
RhÀC2
RhÀC3
RhÀC4
RhÀN1
RhÀN2
OÀCl
2.160(3)
2.143(2)
2.100(3)
2.092(4)
2.117(2)
2.177(2)
3.031(2)
3.320(3)
C1ÀC2
1.389(4)
1.406(5)
82.60(8)
37.7(1)
81.2(1)
39.2(1)
81.0(1)
C3ÀC4
\N1–Rh–N2
\C1–Rh–C2
\C2–Rh–C3
\C3–Rh–C4
\C4–Rh–C1
N3ÀCl
state. For example the RhÀN1 bond length (2.117(2) Å) is shorter
than the RhÀN2 bond length (2.177(2) Å) by 0.06 Å.
Treatment of 8b-Cl or 9-Cl with NaHCO3 resulted in the coordi-
nation of anionic pyrrole nitrogen atom through a loss of the HCl
molecule as well as decoordination of one pyridine ligand to give
Fig. 8. Crystal structure of 11. Thermal ellipsoids are shown at the 30% probability
level.

M. Toganoh et al. / Journal of Organometallic Chemistry 693 (2008) 3141–3150
3145
Table 2
Selected bond lengths (Å) and angles (°) for the X-ray structure of 11
Table 3
Selected bond lengths (Å) and angles (°) for the X-ray structure of 8a-PF6
RhÀC1
RhÀC2
RhÀC3
RhÀC4
RhÀN1
RhÀN3
C1ÀC2
2.109(5)
2.153(5)
2.141(5)
2.134(5)
2.116(4)
2.076(4)
1.353(8)
C3ÀC4
1.350(8)
81.29(14)
37.0(2)
80.6(2)
36.8(2)
82.0(3)
RhÀC1
RhÀC2
RhÀC3
RhÀC4
RhÀN1
RhÀN2
O–F1
2.172(9)
2.169(10)
2.133(9)
2.136(9)
2.137(7)
2.201(7)
3.012(11)
2.969(13)
C1ÀC2
1.408(15)
1.426(15)
82.5(3)
37.8(4)
80.6(4)
\N1–Rh–N3
\C1–Rh–C2
\C2–Rh–C3
\C3–Rh–C4
\C4–Rh–C1
C3ÀC4
\N1–Rh–N2
\C1–Rh–C2
\C2–Rh–C3
\C3–Rh–C4
\C4–Rh–C1
39.0(4)
81.1(4)
N3–F2
Cl
N
PF6
example, the Rh–N1 bond length (2.137(7) Å) and the Rh-N2 bond
length (2.201(7) Å) differ significantly although it is Cs symmetric
formally. The hexafluorophosphate ion is also recognized by both
the NH and OH moieties. The shortest N3–F and the O–F bond
lengths are 2.969(13) and 3.012(11) Å, respectively.
H
N
H
N
OH
OH
AgPF6
N
N
N
Rh
Rh
With a variety of rhodium complexes in hands, anion effect in
cyclotrimerization reactions of dimethyl acetylenedicarboxylate
(DMAD) was investigated. A solution of DMAD in toluene or chlo-
robenzene was heated at 80 °C for 1 d in the presence of 1 mol% of
the catalyst. The non-coordinative solvents would be important for
the efficient cyclotrimerization, because no reaction proceeded
when the reactions were carried out in THF at the refluxed temper-
ature. The lower reaction temperature and the less amount of cat-
alyst were adopted to establish anion effect, while the quantitative
yields were obtained under the harsh conditions. The reactions
proceeded cleanly and only the starting material and the product
except for the catalysts were detected by 1H NMR analysis after
heating. The results are summarized in Table 4. The reactions with
8a-Cl and 8b-Cl essentially give the same results (21% yields), indi-
cating both of the complexes take the similar structures in solution
(entries 1 and 3). The use of 8a-PF6 affords the similar result (16%
yield, entry 2). The solid phase structures of 8a-Cl and 8a-PF6 sug-
gest that the counter anions are placed on the opposite side of the
ligands with the metal ions. Hence, the difference of the anions
would not affect the reactions. Meanwhile, in the case of the reac-
tions with 9-X, where the anions would be placed on the same side
with the metal center, considerable anion effect is observed in the
alkyne cyclotrimerization reactions. Study on the anion effect with
9-X is performed in chlorobenzene because of poor solubility of the
catalysts in toluene. Note that the reactivity in chlorobenzene is
8a-PF6
8a-Cl
N
N
AgX
or
NaX
N
H
N
N
N
H
N
N
Cl
X
Rh
Rh
9-Cl
9-X
X = PF6, BPh4, NO3, OCOCF3
Scheme 5. Manipulation of anion in the anion-recognizing rhodium complexes.
Table 4
Rhodium catalyzed cyclotrimerization reactions of DMAD
COOMe
Catalyst
MeOOC
COOMe
(1 mol %)
MeOOC
COOMe
Solvent
MeOOC
COOMe
COOMe
80 °C, 1 d
Entry
Catalyst
Solvent
Yield (%)
d (ppm)a
1
2
3
4
5
6
7
8
8a-Cl
8a-PF6
8b-Cl
9-Cl
Toluene
Toluene
Toluene
Toluene
Chlorobenzene
Chlorobenzene
Chlorobenzene
Chlorobenzene
Chlorobenzene
Chlorobenzene
Toluene
21
16
21
54
64
31
22
17
9
11.03
9.28
11.65
13.43
13.43
11.71
7.95
12.90
12.72
–
9-Cl
Fig. 9. Crystal structure of 8a-PF6. Thermal ellipsoids are shown at the 30%
probability level.
9-PF6
9-BPh4
9-NO3
9-OCOCF3
10b
9
10
11
12
58
21
39
Evidence for the structure of 8a-PF6 is obtained from X-ray
crystallographic analyses. The ORTEP drawing of 8a-PF6 is shown
in Fig. 9 and the selected structural parameters are summarized
in Table 3. The structure of 8a-PF6 is similar to that of 8a-Cl. For
11
11
–
–
Chlorobenzene
a
The chemical shift values of NH moieties in CDCl3.

3146
M. Toganoh et al. / Journal of Organometallic Chemistry 693 (2008) 3141–3150
somewhat superior to those in toluene as illustrated in entries 4, 5
and 11, 12. The rhodium complexes 9-PF6, 9-BPh4, 9-NO3, and 9-
OCOCF3 are examined in addition to 9-Cl. Among the catalysts
examined, 9-Cl shows the best reactivity (64% yield, entry 5). In
the case of 9-BPh4, where no anion-recognition is expected, the
yield is significantly decreased (22%, entry 7). This means that
the presence of the chloride anion near the metal center enhances
activity of the catalysts in alkyne cyclotrimerization reactions. The
PF6 anion can also improve the reactivity (31% yield, entry 6),
though the effect is small. In contrast, less reactivity than 9-BPh4
is observed in the reactions with 9-NO3 (17% yield, entry 8) and
9-OCOCF3 (9% yield, entry 9). Since the anions would be placed
near the metal centers in 9-NO3 and 9-OCOCF3, the anions disturb
the catalytic reactions in these cases.
On the assumption that a rate-determining step in the rho-
dium-catalyzed cyclotrimerization reactions is a dimerization step
of two alkyne molecules, which is suggested by theoretical studies
[26], the experimental results can be rationalized as follows
(Scheme 6). In the dimerization step of electron-poor DMAD,
back-donation from metal to DMAD enhances the bond formation
between the two alkyne molecules through enlargement of orbital
overlapping. Electron donation from anion to the metal center
would support such back-donation. When the reactions are carried
out with 8a-Cl, 8a-PF6, and 8b-Cl, the counter anions place far from
the rhodium metal throughout the reactions and thus electron
donation from the counter anions to the metal center hardly ex-
pected in the midst of the reactions (Scheme 7a). In contrast, the
counter anion places near the metal center in an intermediate de-
rived from 9-Cl (Scheme 7b) and chloride anion could donate elec-
tron considerably to the metal center, which causes appreciable
enhancement of the reactivity. In the case of the reaction with 9-
PF6, electron donation in an intermediate would be modest due
to the weaker electron-donating ability of PFÀ6 , which results in
the moderate yield in the catalytic reaction. The interaction between
the pyrrolic NH moiety and BPh4À is negligible and the poor yield is
obtained when the reaction was carried out with 9-BPh4. Whereas
the interaction between NOÀ3 (OCOCFÀ3 ) and pyrrolic NH moiety
would be strong in 9-NO3 (9-OCOCF3) as suggested by the 1H NMR
analyses, the yields are very low probably due to the weaker elec-
tron-donating abilities of nitrate and trifluoroacetate. Additionally,
the steric repulsion between the counter anions and DMAD might
be another important factor in the anion effect. Large anions near
the metal center would inhibit coordination of DMAD to the rho-
dium metal. Nevertheless, the steric effect cannot explain all the
experimental result (e.g. entries 6–8) and hence electronic perturba-
(a)
(b)
X
N
N
H
N
OH
N
H
N
N
N
Rh
X
E
Rh
E
E
E
E
E
E
E
Scheme 7. Supposed structures of intermediates in rhodium catalyzed alkyne
cyclotrimerization reactions.
tion from the counter anion to the metal center would be worth not-
ing when one consider catalytic reactions with cationic complexes.
3. Conclusion
In conclusion, the new hetero-scorpionate ligands composed of
pyrrole and pyridine (1 and 2) and the corresponding rhodium
complexes (8–11) were synthesized and characterized. In the solid
state structures of 1 and 2, varied hydrogen-bonding networks are
observed depending on the steric hindrance imposed by the neigh-
boring groups. With the cationic rhodium complexes prepared,
where the counter anions are recognized by the pyrrolic NH moie-
ties, anion effect on the rhodium-catalyzed alkyne cyclotrimeriza-
tion reactions is observed. When the chloride anion places near the
metal center, definite enhancement of the catalytic activity is de-
tected. Detailed mechanistic study such as in situ observation of
catalysts and theoretical approach to reactive species would give
further important information on the alkyne cyclotrimerization
reactions in the near future.
4. Experimental
All the reactions were carried out in oven-dried vessels under Ar
or N2 atmosphere. Commercially available solvents and reagents
were used without further purification unless otherwise men-
tioned. THF was distilled over benzophenone ketyl. Thin-layer
chromatography (TLC) was carried out on aluminium sheets coated
with silica gel 60 (Merck5554). Preparative separations were per-
formed by silica gel column chromatography (KANTO Silica Gel
60 N, spherical, neutral, 40–50 lm and KANTO Silica Gel 60 N,
spherical, neutral, 63–210
l
m). 1H NMR spectra were recorded in
E
Rh
Rh
slow
E
E
E
E
8a-Cl, 8a-PF6
8b-Cl, 9-BPh4
E
X
E
X
E
Rh
X
20%
cf. Scheme 7a
electron-donation
+
E
X
E
E
E
E
E
fast
Rh
E
E
2
Anion is placed near Rh.
X
9-Cl, 9-PF6
E
E
E
E
30~60%
E
E
Rh
X
E
E
slow
Rh
E
E
cf. Scheme 7b
9-NO3
9-OCOCF3
E = CO2Me
E
E
10~20%
Scheme 6. Anion effect in rhodium catalyzed alkyne cyclotrimerization reactions.

M. Toganoh et al. / Journal of Organometallic Chemistry 693 (2008) 3141–3150
3147
CDCl3 solution on a JEOL JNM-AI SERIES FT-NMR (300 MHz) spec-
4.4. Preparation of 1c
trometer, and chemical shifts were reported relative to residual
proton of deuterated solvent, CHCl3 (d = 7.26) in ppm. 13C NMR
spectra were recorded in CDCl3 solution on the same instrument,
and chemical shifts were reported relative to CDCl3 (d = 77.00) in
ppm. Mass spectra were recorded on a Bruker Daltonics autoflex
MALDI-TOF MS spectrometer.
A solution of NaOEt (1.45 g, 21 mmol, 5 equiv.) in EtOH (10 mL)
was added to a solution of 5 (1.50 g, 4.2 mmol, 1 equiv.) in THF
(20 mL) and stirred for 1 h at room temperature. After quenching
with H2O, and the reaction mixture was diluted with brine and
CH2Cl2. The organic layer was separated, dried over Na2SO4, filtered
and evaporated under reduced pressure. The residue was purified
by silica gel column chromatography to give 1c (0.53 g, 1.9 mmol,
45% yield). 1H NMR (CDCl3, 300 MHz, ppm): d 10.78 (br s, 1H), 8.55
(dd, J = 1.8, 4.8 Hz, 2H), 7.66 (dt, J = 1.8, 8.1 Hz, 2H), 7.59 (dd, J = 0.9,
8.1 Hz, 2H), 7.14 (ddd, J = 0.9, 4.8, 8.1 Hz, 2H), 6.83 (m, 1H), 6.19
(m, 1H), 6.14 (m, 1H), 3.21 (s, 3H); 13C NMR (CDCl3, 75 MHz,
ppm): d 163.73, 148.24, 136.64, 132.57, 121.91, 121.70, 116.96,
108.30, 107.76, 83.03, 60.14, 15.54. Anal. Calc. for 1c: C, 73.10; H,
6.13; N, 15.04. Found: C, 73.06; H, 6.13; N, 15.16%.
4.1. Preparation of 1a
CF3CO2H (150 lL, 1.95 mmol, 3.6 equiv.) was added to a mix-
ture of pyrrole (0.36 mL, 5.4 mmol, 10 equiv.) and di-(2-pyri-
dyl)ketone (3, 100 mg, 0.54 mmol, 1 equiv.) and the reaction
mixture was stirred for 1 h at room temperature. After quenching
by addition of Et3N, the reaction mixture was diluted with CH2Cl2
and then purified by silica gel column chromatography to give 1a
in 67% yield (90 mg, 0.36 mmol, 67% yield). 1H NMR (CDCl3,
300 MHz, ppm): d 9.41 (br s, 1H), 8.52 (dd, J = 1.5, 4.8 Hz, 2H),
7.82 (d, J = 7.8 Hz, 2H), 7.67 (dt, J = 1.5, 7.8 Hz, 2H), 7.18 (dd,
J = 4.8, 7.8 Hz, 2H), 6.89 (br s, 1H), 6.77 (d, J = 1.8 Hz, 1H), 6.16
(m, 2H); 13C NMR (CDCl3, 75 MHz, ppm): d 162.48, 147.47,
136.88, 134.95, 122.34, 121.65, 117.22, 108.24, 106.85, 76.39. Anal.
Calc. for 1a: C, 71.70; H, 5.21; N, 16.72. Found: C, 71.58; H, 5.24; N,
16.74%.
4.5. Preparation of 7
To a solution of tryptamine (6) (0.87 g, 5.4 mmol, 1 equiv.) and
di-(2-pyridyl)ketone (3) (1.0 g, 5.4 mmol, 1 equiv.) in toluene
(18 mL), p-toluenesulfonic acid (93 mg, 0.54 mmol, 0.1 equiv.)
was added and the reaction mixture was refluxed for 8 h. After
cooling, the resulting mixture was quenched with aq NaHCO3
and diluted with CH2Cl2. The organic layer was separated, dried
over anhydrous Na2SO4, and filtered. The filtrate was concentrated
under reduced pressure and the residue was purified by silica gel
column chromatography to give 7 (1.35 g, 4.1 mmol, 77% yield).
1H NMR (CDCl3, 300 MHz, ppm): d 9.51 (br s, 1H), 8.53 (d,
J = 4.8 Hz, 2H), 7.65 (t, J = 4.8 Hz, 4H), 7.54 (d, J = 7.8 Hz, 1H), 7.36
(d, J = 7.8 Hz, 1H), 7.19À7.07 (m, 4H), 3.30 (br s, 1H), 3.06 (t,
J = 5.4 Hz, 2H), 2.90 (t, J = 5.4 Hz, 2H); 13C NMR (CDCl3, 75 MHz,
ppm): d 165.00, 149.07, 136.54, 135.85, 133.62, 127.06, 121.82,
121.76, 121.72, 119.12, 118.50, 111.15, 110.31, 66.01, 40.10,
22.15. Anal. Calc. for 7: C, 77.28; H, 5.56; N, 17.17. Found: C,
77.30; H, 5.55; N, 17.34%.
4.2. Preparation of 5
To a solution of 4 (11 g, 44.7 mmol, 2.0 equiv.) in THF (140 mL),
n-BuLi in hexane (1.6 M, 27.3 mL, 43.8 mmol, 2.0 equiv.) was
added at À78 °C under an argon atmosphere. After stirring for
15 min, di-(2-pyridyl)ketone 3 (4.0 g, 21.9 mmol, 1 equiv.) was
added to the reaction mixture at that temperature. The resulting
solution was stirred for 1 h and then quenched with 1% CH3CO2H
in THF. After removing the cooling bath, the reaction mixture
was diluted with water and CH2Cl2. The organic layer was sepa-
rated, washed with brine and dried over anhydrous Na2SO4. After
filtration, the solvent was removed under reduced pressure and
the residual oil was purified by silica gel column chromatography
to give 5 (7.3 g, 20.8 mmol, 92% yield). While small amount of
impurities were contaminated after silica gel column separation,
it was used in the next step without further purification. 1H NMR
(CDCl3, 300 MHz, ppm): d 8.50 (d, J = 4.8 Hz, 2H), 7.64–7.66 (m,
4H), 7.23 (dd, J = 1.8, 3.3 Hz, 1H), 7.14 (m, 2H), 6.53 (s, 1H), 6.02
(t, J = 3.3 Hz, 1H), 5.42 (dd, J = 1.8, 3.3 Hz, 1H), 1.36 (s, 9H); 13C
NMR (CDCl3, 75 MHz, ppm): d 163.46, 149.82, 147.69, 138.11,
136.04, 122.91, 122.02, 121.76, 116.42, 109.47, 84.00, 78.61,
27.48; MS (MALDI, positive): m/z = 352.2 ([MH]+).
4.6. Preparation of 2
A suspension of 7 (0.10 g, 0.31 mmol, 1 equiv.), NaHCO3 (0.36 g,
4.3 mmol, 14 equiv.) and MeI (1.8 mL, 29 mmol, 90 equiv.) in
MeOH (40 mL) was stirred for 2 d at room temperature. The reac-
tion mixture was quenched with aq NH4Cl and diluted with CH2Cl2.
The organic layer was separated, dried over anhydrous Na2SO4, and
filtered. The solvent was removed under reduced pressure and the
residue was purified by silica gel column chromatography to give 2
(104 mg, 0.30 mmol, 99% yield). 1H NMR (CDCl3, 300 MHz, ppm): d
8.94 (br s, 1H), 8.61 (dd, J = 1.2, 4.8 Hz, 2H), 7.63 (dt, J = 1.2, 7.8 Hz,
2H), 7.54 (d, J = 1.2, 7.2 Hz, 1H), 7.52 (dd, J = 1.2, 7.8 Hz, 2H), 7.23
(d, J = 1.2, 7.2 Hz, 1H), 7.15 (ddd, J = 1.2, 4.8, 7.8 Hz, 2H), 7.09 (dt,
J = 1.2, 7.2 Hz, 2H), 2.98 (s, 4H), 2.28 (s, 3H); 13C NMR (CDCl3,
75 MHz, ppm): d 161.85, 148.45, 136.26, 136.06, 134.72, 126.55,
123.44, 121.79, 121.63, 118.98, 118.41, 111.06, 109.42, 71.10,
48.12, 40.14, 21.14; MS (MALDI, positive): m/z = 340.9 ([MH]+).
Anal. Calc. for 2 Á 0.1CH2Cl2: C, 76.07; H, 5.84; N, 16.06. Found: C,
76.13; H, 5.92; N, 16.09%.
4.3. Preparation of 1b
A solution of NaOMe (3.35 g, 62 mmol, 3 equiv.) in MeOH
(10 mL) was added to a solution of 5 (7.26 g, 20.7 mmol, 1 equiv.)
in THF (100 mL) and stirred for 1 h at room temperature. After
quenching with H2O, and the reaction mixture was diluted with
brine and CH2Cl2. The organic layer was separated, dried over
Na2SO4, filtered and evaporated under reduced pressure. The resi-
due was purified by silica gel column chromatography to give 1b
(2.21 g, 8.3 mmol, 40% yield). 1H NMR (CDCl3, 300 MHz, ppm): d
10.78 (br s, 1H), 8.55 (dd, J = 1.8, 4.8 Hz, 2H), 7.66 (dt, J = 1.8,
8.1 Hz, 2H), 7.59 (dd, J = 0.9, 8.1 Hz, 2H), 7.14 (ddd, J = 0.9, 4.8,
8.1 Hz, 2H), 6.83 (m, 1H), 6.19 (m, 1H), 6.14 (m, 1H), 3.21 (s, 3H);
13C NMR (CDCl3, 75 MHz, ppm): d 163.09, 148.28, 136.64, 131.72,
122.00, 121.91, 117.18, 109.03, 107.82, 83.50, 52.53. Anal. Calc.
for 1b: C, 72.43; H, 5.70; N, 15.84. Found: C, 72.24; H, 5.71; N,
15.94%.
4.7. Preparation of 8a-Cl
A solution of 1a (50 mg, 0.20 mmol, 1 equiv.) and [RhCl(cod)]2
(59 mg, 0.12 mmol, 0.6 equiv.) in CH2Cl2 (10 mL) was stirred for
15 min at room temperature. The solvent was removed under re-
duced pressure and the residue was purified by silica gel column
chromatography to give 8a-Cl (94 mg, 0.19 mmol, 95% yield). 1H
NMR (CDCl3, 300 MHz, ppm): d 11.03 (br s, 1H), 8.44 (br s, 2H),

3148
M. Toganoh et al. / Journal of Organometallic Chemistry 693 (2008) 3141–3150
8.28 (d, J = 7.8 Hz, 2H), 7.90 (t, J = 7.8 Hz, 2H), 7.32 (m, 3H), 7.15 (br
s, 1H), 6.47 (s, 1H), 6.26 (s, 1H), 4.13 (s, 1H), 3.31 (br s, 3H), 2.37 (br
s, 4H), 1.76 (br s, 4H); 13C NMR (CDCl3, 75 MHz, ppm): d 161.79,
148.23, 139.14, 132.72, 125.23, 124.71, 123.83, 110.24, 107.56,
78.46, 30.92, 30.52; MS (MALDI, positive): m/z = 461.1 ([MÀHCl]+).
d 9.28 (br s, 1H), 8.49 (d, J = 4.8 Hz, 2H), 8.25 (d, J = 7.9 Hz, 2H), 7.97
(dt, J = 1.8, 7.9 Hz, 2H), 7.38 (ddd, J = 1.2, 5.5, 7.3 Hz, 2H), 7.20 (dd,
J = 2.8, 4.0 Hz, 2H), 6.38–6.34 (m, 2H), 4.15 (s, 1H), 3.70–3.47 (m,
4H), 2.41–2.30 (m, 4H), 1.82–1.74 (m, 4H).
4.12. Preparation of 9-PF6
4.8. Preparation of 8b-Cl and 10b
Starting from 10 mg (17
lmol) of 9-Cl, 10 mg of 9-PF6 was ob-
A solution of 1b (50 mg, 0.19 mmol, 1 equiv.) and [RhCl(cod)]2
(56 mg, 0.11 mmol, 0.6 equiv.) in CH2Cl2 (10 mL) was stirred for
15 min at room temperature. The solvent was removed under re-
duced pressure and the residue was purified by silica gel column
chromatography to give 8b-Cl (91 mg, 0.18 mmol, 95% yield).
Treatment of a CH2Cl2 solution of 8b-Cl with aq NaHCO3 afforded
10b in a quantitative yield. 8b-Cl: 1H NMR (CDCl3, 300 MHz,
ppm): d 11.65 (br s, 1H), 8.97 (br s, 1H), 7.89 (s, 5H), 7.35 (m,
3H), 6.41 (s, 1H), 6.31 (s, 1H), 4.04 (s, 1H), 3.66 (br s, 1H), 2.97 (s,
3H), 2.43À1.54 (m, 8H); 13C NMR (CDCl3, 75 MHz, ppm): d
149.49139.40, 126.25, 125.88, 123.66, 116.10, 107.32, 84.21,
52.94, 31.55, 30.95, 27.97, 22.62, 14.10. 10b: 1H NMR (CDCl3,
300 MHz, ppm): d 8.52 (d, J = 4.8 Hz, 2H), 7.73 (m, 4H), 7.15 (m,
2H), 6.53 (s, 1H), 6.27 (s, 1H), 6.10 (s, 1H), 4.13 (br s, 2H), 3.34
(br s, 2H), 3.24 (s, 3H), 2.12À1.61 (m, 8H); 13C NMR (CDCl3,
75 MHz, ppm): d 149.49, 136.74, 132.43, 125.66, 125.64, 125.08,
122.37, 106.28, 106.26, 105.98, 87.21, 81.80 (br), 79.91 (br),
53.60, 29.91. Anal. Calc. for 10b Á 0.7CH2Cl2: C, 55.47; H, 5.16; N,
7.86. Found: C, 55.80; H. 5.18; N, 7.85%.
tained (14
l
mol, 84% yield). 1H NMR (CDCl3, 300 MHz, ppm): d
11.71 (br s, 1H), 8.97 (d, J = 4.4 Hz, 1H), 8.80 (d, J = 8.0 Hz, 1H),
8.25 (d, J = 5.1 Hz, 1H), 8.12 (dt, J = 1.0, 8.0 Hz, 1H), 8.06 (d,
J = 8.0 Hz, 1H), 7.68 (t, J = 8.0 Hz, 1H), 7.55 (d, J = 7.8 Hz, 1H), 7.48
(d, J = 8.0 Hz, 1H), 7.46–7.42 (m, 1H), 7.38–7.15 (m, 3H, overlapped
with the CHCl3 signal), 3.82 (dd, J = 5.2, 13.2 Hz, 1H), 3.75–3.68 (m,
4H), 3.32–3.06 (m, 2H), 2.82–2.46 (m, 5H), 2.44 (s, 3H), 2.13–1.91
(m, 4H).
4.13. Preparation of 9-BPh4
Starting from 30 mg (51
lmol) of 9-Cl, 40 mg of 9-BPh4 was ob-
tained (46
l
mol, 90% yield). 1H NMR (CDCl3, 300 MHz, ppm): d
11.60 (br s, 1H), 8.27 (d, J = 5.1 Hz, 1H), 7.95 (s, 1H), 7.70–7.65
(m, 1H), 7.54 (d, J = 7.6 Hz, 1H), 7.45–7.13 (m, 16H, overlapped
with the CHCl3 signal), 6.91–6.75 (m, 12H), 3.73–3.61 (m, 5H),
3.24–3.10 (m, 1H), 3.00–2.88 (m, 1H), 2.76–2.50 (m, 5H), 2.29 (s,
3H), 2.12–1.90 (m, 4H).
4.9. Preparation of 9-Cl and 11
4.14. Preparation of 9-NO3
A solution of 2 (50 mg, 0.15 mmol, 1 equiv.) and [RhCl(cod)]2
(45 mg, 0.091 mmol, 0.6 equiv.) in CH2Cl2 (10 mL) was stirred for
15 min at room temperature under an argon atmosphere. The sol-
vent was removed under reduced pressure and the residue was
purified by silica gel column chromatography to give 9-Cl
(85 mg, 0.15 mmol, 95% yield). Treatment of a CH2Cl2 solution of
9-Cl with aq NaHCO3 afforded 11 in a quantitative yield. 9-Cl: 1H
Starting from 106 mg (181
lmol) of 9-Cl, 110 mg of 9-NO3 was
obtained (179
l
mol, 99% yield). 1H NMR (CDCl3, 300 MHz, ppm): d
12.90 (br s, 1H), 8.95 (d, J = 5.1 Hz, 1H), 8.90 (d, J = 8.1 Hz, 1H), 8.23
(d, J = 5.1 Hz, 1H), 8.12 (dt, J = 1.8, 7.8 Hz, 1H), 8.02 (d, J = 8.1 Hz,
1H), 7.70 (dt, J = 1.5, 7.8 Hz, 1H), 7.58 (d, J = 7.8 Hz, 1H), 7.55 (d,
J = 8.1 Hz, 1H), 7.45–7.39 (m, 1H), 7.36–7.14 (m, 3H, overlapped
with the CHCl3 signal), 3.82 (dd, J = 5.4, 13.0 Hz, 1H), 3.75–3.66
(m, 4H), 3.33–3.07 (m, 2H), 2.79 (dd, J = 4.8, 13.0 Hz, 1H), 2.77–
2.45 (m, 5H), 2.44 (s, 3H), 2.14–1.90 (m, 4H).
NMR (CDCl3, 300 MHz, ppm):
d 13.43 (br s, 1H), 9.11 (d,
J = 7.2 Hz, 1H), 8.94 (d, J = 5.4 Hz, 1H), 8.22À8.13 (m, 3H),
7.72À7.64 (m, 2H), 7.53 (d, J = 7.2 Hz, 1H), 7.42 (d, J = 6.9 Hz, 1H),
7.13–7.36 (m, 3H), 3.86À3.80 (m, 1H), 3.70 (s, 4H), 3.07À3.29 (m,
2H), 2.81À2.57 (m, 5H), 2.43 (s, 3H), 2.09À1.95 (m, 4H); 13C
NMR (CDCl3, 75 MHz, ppm): d 160.57, 155.11, 149.91, 146.49,
140.44, 140.08, 137.77, 127.49, 127.07, 125.95, 125.54, 124.85,
124.24, 123.11, 119.71, 117.76, 117.68, 114.34, 108.72, 75.47 (d,
JRh–C = 13.7 Hz), 75.03 (d, JRh–C = 14.3 Hz), 51.30, 38.95, 31.73,
30.61, 17.50; MS (MALDI, positive): m/z = 551 ([M–Cl]+). 11: 1H
NMR (CDCl3, 300 MHz, ppm): d 8.67 (d, J = 4.9 Hz, 2H), 7.82 (br s,
2H), 7.74 (dt, J = 1.4, 7.6 Hz, 2H) 7.46À7.36 (m, 2H), 7.20 (br t,
J = 6.0 Hz, 2H), 6.93À6.83 (m, 2H), 3.43 (br s, 2H), 2.98 (s, 5H);
13C NMR (CDCl3, 75 MHz, ppm): d 148.78, 145.26, 145.24, 138.98,
136.61, 128.93, 125.21, 121.89, 118.37, 117.38, 115.88, 114.24,
108.01, 79.24, 74.16, 53.42, 48.87, 40.98, 29.47, 22.20; Anal. Calc.
for 11 Á 0.8CH2Cl2: C, 59.72; H, 5.47; N, 9.04. Found: C, 59.95; H.
5.36; N, 9.00%.
4.15. Preparation of 9-OCOCF3
Starting from 106 mg (181
lmol) of 9-Cl, 85 mg of 9-OCOCF3
was obtained (125
l
mol, 69% yield). 1H NMR (CDCl3, 300 MHz,
ppm): d 12.72 (s, 1H), 8.97 (d, J = 4.8 Hz, 1H), 8.78 (d, J = 8.4 Hz,
1H), 8.25 (d, J = 5.1 Hz, 1H), 8.05 (dt, J = 1.8, 8.0 Hz, 1H), 7.85 (d,
J = 8.0 Hz, 1H), 7.66 (dt, J = 1.5, 8.4 Hz, 1H), 7.56 (d, J = 7.7 Hz,
1H), 7.50 (d, J = 7.7 Hz, 1H), 7.43 (dd, J = 5.6, 7.4 Hz, 1H), 7.35–
7.15 (m, 3H, overlapped with the CHCl3 signal), 3.83 (dd, J = 5.1,
12.6 Hz, 1H), 3.76–3.69 (m, 4H), 3.33–3.07 (m, 2H), 2.80 (dd,
J = 4.5, 16.2 Hz, 1H), 2.74–2.51 (m, 5H), 2.44 (s, 3H), 2.15–1.90
(m, 4H).
4.16. X-ray diffraction studies
X-ray analysis was performed on a SMART APEX equipped with
4.10. Typical procedure for anion exchange
CCD detector (Brucker) using Mo K
a (graphite, monochromated,
k = 0.71069 Å) radiation. Crystal data and data statistics of 1a, 1b,
1c, 2, 8a-Cl, 8a-PF6, and 11 are summarized in Tables 5 and 6.
The structures were solved by the direct method of SHELXS-97 and
refined using the SHELXL-97 program [27]. The non-hydrogen atoms
were refined anisotropically by the full-matrix least square
method. Hydrogen atoms were refined isotropically for 1a, 1b,
1c, and 2, and were placed at calculated positions for 8a-Cl, 8a-
PF6, and 11.
8-Cl or 9-Cl in CH2Cl2 was treated with slightly excess amounts
of AgX or NaX. After filtration and evaporation, the residue was
recrystallized from CH2Cl2/hexane to give 8-X or 9-X.
4.11. Preparation of 8a-PF6
Starting from 58 mg (0.12 mmol) of 8a-Cl, 64 mg of 8a-PF6 was
obtained (0.105 mmol, 88% yield). 1H NMR (CDCl3, 300 MHz, ppm):

M. Toganoh et al. / Journal of Organometallic Chemistry 693 (2008) 3141–3150
3149
Table 5
Crystal data and structure analysis results
La
lb
lc
2
Formula
Crystal system
Space group
C
15H13N30
C16H15N30
Orthorhombic
Pbca (No. 61)
0.0320, 0.0476
0.0765, 0.0810
0.919
10.918(5)
14.885(6)
16.612(7)
90
C17H17N30
Triclinic
P1 (No. 2)
0.0473, 0.0530
0.1337,0.1388
1.073
8.6358(6)
8.8382(6)
10.4813(7)
95.551(2)
100.537(1)
105.804(1)
747.63(9)
2
C22H20N4
Monoclinic
Monoclinic
P2l/c (No. 14)
0.0390, 0.0453
0.1009,0.1051
1.057
11.1699(19)
8.0159(13)
13.685(2)
90
91.249(4)
90
1225.0(3)
4
ꢀ
P2l/c (No. 14)
0.0400, 0.0685
0.0831,0.0896
0.850
8.5804(5)
12.2131(7)
17.1707(10)
90
100.226(2)
90
1770.79(18)
4
R, Rw(I > 2
r(I))
Rl, wR2 (all data)
Goodness-of-fit
a (Å)
b (Å)
c (Å)
a
(°)
b (°)
90
90
2700(2)
8
c
(°)
V (Å3)
Z
T (K)
223(2)
223(2)
173(2)
223(2)
Crystal size (mm)
0.36 Â 0.31 Â 0.22
0.22 Â 0.12 Â 0.08
0.60 Â 0.36 Â 0.14
0.15 Â 0.12 Â 0.08
Dcalc (g cmÀ3
)
1.363
1.306
1.241
1.277
2h lv,2h
la
(°)
3.6, 52.0
2399
4.9, 50.5
2437
4.0, 55.0
3402
4.1,55.0
4074
l
n
Number of reflections measured (unique)
Number of reflections measured (I > 2
r(I))
1987
1769
2863
2541
Number of parameters
225
0.241, À0.186
242
0.179, À0.143
259
0.418, À0.300
316
0.215, À0.215
D
(e ÅÀ3
)
Table 6
Crystal data and structure analysis results
8a-Cl
8a-PF6
11
Formula
Crystal system
Space group
C
23H24ClN3ORh
C30H31N4Rh Á 0.5CH2Cl2
Orthorhombic
Pna21 (No. 33)
0.0385, 0.0562
0.0755, 0.0794
0.880
20.2257(10)
18.3289(9)
14.1306(7)
90
2(C30H31N4Rh) Á CH2Cl2
Orthorhombic
Pna21 (No. 33)
0.0326, 0.0449
0.0692, 0.0719
0.927
20.2257(10)
18.3289(9)
14.1306(7)
90
Triclinic
P1 (No. 2)
0.0344, 0.0377
0.0889, 0.0904
1.008
9.4982(5)
10.5132(5)
12.1101(6)
95.953(1)
106.676(1)
113.828(1)
1025.84(9)
2
ꢀ
R, Rw(I > 2
r(I))
Rl,wR2 (all data)
Goodness-of-fit
a (Å)
b (Å)
c (Å)
a
(°)
b (°)
90
90
5238.4(4)
8
90
90
5238.4(4)
4
c
(°)
V (ÅÀ3
Z
)
T (K)
223(2)
243(2)
243(2)
Crystal size (mm)
Dcalc (g cmÀ3
2h lv,2h (°)
0.23 Â 0.15 Â 0.05
0.18 Â 0.06 Â 0.05
0.18 Â 0.06 Â 0.05
)
1.608
1.504
1.504
3.6, 52.0
4009
3.0, 52.0
10,268
3.0, 52.0
5379
l
lan
Number of reflections measured (unique)
Number of reflections measured (I > 2
r(I))
3604
7695
4344
Number of parameters
D
263
0.712, À0.765
660
0.954, À0.367
660
0.990, À0.360
(e Å3)
Acknowledgements
References
[1] S. Trofimenko, J. Am. Chem. Soc. 88 (1966) 1842.
[2] (a) S. Trofimenko, Chem. Rev. 93 (1993) 943;
(b) D.L. Roger, Coord. Chem. Rev. 147 (1996) 571;
(c) M. Etienne, Coord. Chem. Rev. 156 (1997) 201;
(d) C. Janiak, Coord. Chem. Rev. 163 (1997) 107.
[3] (a) M. Akita, J. Organomet. Chem. 689 (2004) 4540;
The present work was supported by the Grant-in-Aid for
Scientific Research (16350024 and 19750036) and the Global COE
Program ‘‘Science for Future Molecular Systems” from the Ministry
of Education, Culture, Sports, Science and Technology of Japan.
(b) M. Akita, S. Hikichi, Bull. Chem. Soc. Jpn. 75 (2002) 1657.
[4] (a) M. Toganoh, T. Ishizuka, H. Furuta, Chem. Commun. (2004) 2464;
(b) M. Toganoh, H. Furuta, Chem. Lett. (2005) 1034;
Appendix A. Supplementary material
(c) M. Toganoh, S. Ikeda, H. Furuta, Chem. Commun. (2005) 4589;
(d) M. Toganoh, S. Ikeda, H. Furuta, Inorg. Chem. 46 (2007) 10003;
(e) M. Toganoh, K. Fujino, S. Ikeda, H. Furuta, Tetrahedron Lett. 49 (2008) 1488.
[5] A. Otero, J. Fernández-Baeza, A. Antiñolo, J. Tejeda, A. Lara-Sánchez, Dalton
Trans. (2004) 1499.
[6] C. Pettinari, A. Cingolani, G. Gioia Lobbia, F. Marchetti, D. Martini, M. Pellei, R.
Pettinari, C. Santini, Polyhedron 23 (2004) 451.
[7] (a) C. Janiak, J. Chem. Soc., Chem. Commun. (1994) 545;
(b) J. Reglinski, M. Garner, I.D. Cassidy, P.A. Slavin, M.D. Spicer, D.R. Armstrong,
J. Chem. Soc., Dalton Trans. (1999) 2119;
CCDC 678429, 678430, 678431, 678432, 664292, 664293 and
664294 contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/j.jorganchem.
2008.07.005.

3150
M. Toganoh et al. / Journal of Organometallic Chemistry 693 (2008) 3141–3150
(c) W. Kläui, M. Berghahn, W. Frank, G.J. Reiß, T. Schönherr, G. Rheinwald, H.
Lang, Eur. J. Inorg. Chem. (2003) 2059;
(d) S.-J. Chiou, P. Ge, C.G. Riordan, L.M. Liable-Sands, A.L. Rheingold, Chem.
Commun. (1999) 159;
(e) P.J. Bailey, M. Lanfranchi, L. Marchiò, S. Parsons, Inorg. Chem. 40 (2001)
5030;
[16] (a) X. Tong, Z. Zhang, X. Zhang, J. Am. Chem. Soc. 125 (2003) 6370;
(b) K. Tanaka, G.C. Fu, J. Am. Chem. Soc. 123 (2001) 11492.
[17] (a) Y. Ono, H. Furuta, Chem. Lett. 35 (2006) 750;
(b) F. Ito, T. Nagai, Y. Ono, K. Yamaguchi, H. Furuta, T. Nagamura, Chem. Phys.
Lett. 435 (2007) 283.
[18] A. Borrini, P. Diversi, G. Ingrosso, A. Lucherini, G. Serra, J. Mol. Catal. 30 (1985)
181.
[19] (a) W. Chen, M.P. Cava, Tetrahedron Lett. 28 (1987) 6025;
(b) W. Chen, E.K. Stephenson, M.P. Cava, Y.A. Jackson, Org. Synth. 70 (1992)
151.
(f) M. Careri, L. Elviri, M. Lanfranchi, L. Marchiò, C. Mora, M.A. Pellinghelli,
Inrog. Chem. 42 (2003) 2109.
[8] (a) S. Trofimenko, J. Am. Chem. Soc. 92 (1970) 5118;
(b) V.S. Joshi, V.K. Kale, K.M. Sathe, A. Sarkar, S.S. Tavale, C.G. Soresh,
Organometallics 10 (1991) 2898;
[20] I. Hasan, E.R. Marinelli, L.C. Lin, F.W. Fowler, A.B. Levy, J. Org. Chem. 41 (1976)
3668.
(c) C. Kimblin, V.J. Murphy, G. Parkin, J. Chem. Soc., Chem. Commun. (1996)
235;
(d) L.M. Richburg, J.A. Farouq, C.D. Incarvito, A.L. Rheingold, D. Rabinovich,
Polyhedron 19 (2000) 1815.
[21] E.D. Cox, J.M. Cook, Chem. Rev. 95 (1995) 1797.
[22] (a) J.P. Mayer, D. Bankaitis-Davis, J. Zhang, G. Beaton, K. Bjergarde, C.M.
Andersen, B.A. Goodman, C.J. Herrera, Tetrahedron Lett. 37 (1996) 5633;
(b) W.-B. Yeh, M.-J. Lin, C.-M. Sun, Tetrahedron Lett. 44 (2003) 4923.
[23] G. Bringmann, D. Feineis, R. God, K. Maksimenka, J. Mühlbacher, K. Messer, M.
Münchbach, K.-P. Gulden, E.-M. Peters, K. Peters, Tetrahedron 60 (2004) 8143.
[24] Inter or intramolecular hydrogen bondings could be formed in 1 and 2 in
solution and cause the considerable low-field shifts from a free pyrrolic NH
moiety (d ꢀ 8.2 ppm).
[9] (a) J.L. Sessler, S. Camiolo, P.A. Gale, Coord. Chem. Rev. 240 (2003) 17;
(b) H. Maeda, Eur. J. Org. Chem. (2007) 5313.
[10] (a) H. Maeda, Y. Ishikawa, T. Matsuda, A. Osuka, H. Furuta, J. Am. Chem. Soc.
125 (2003) 11822;
(b) H. Maeda, T. Morimoto, A. Osuka, H. Furuta, Chem. Asian J. 1 (2006)
832;
(c) Y. Xie, T. Morimoto, H. Furuta, Angew. Chem., Int. Ed. 45 (2006) 6907.
[11] (a) H. Maeda, A. Osuka, H. Furuta, Supramol. Chem. 15 (2003) 447;
(b) T. Morimoto, H. Furuta, Supramol. Chem. 19 (2007) 493.
[12] A. Macchioni, Chem. Rev. 105 (2005) 2039.
[25] In the case of 8a-Cl, significant amount of a bis-Rh(I) complex of 1a was
obtained after treatment with base and hence the reaction was not completely
reversible.
[26] (a) L. Orian, J.N.P. van Stralen, F.M. Bickelhaupt, Organometallics 26 (2007)
3816;
[13] (a) P.A. Duckmanton, A.J. Blake, J.B. Love, Inorg. Chem. 44 (2005) 7708;
(b) J. van den Broeke, E. de Wolf, B.-J. Deelman, G. van Koten, Adv. Synth. Catal.
345 (2003) 625.
(b) K. Kirchner, M.J. Calhorda, R. Schmid, L.F. Veiros, J. Am. Chem. Soc. 125
(2003) 11721.
[14] S. Burling, L.D. Field, B.A. Messerle, P. Turner, Organometallics 23 (2004) 1714.
[15] H. Terai, H. Takaya, T. Naota, Tetrahedron Lett. 47 (2006) 1705.
[27] G.M. Sheldrick, Program for the Solution of Crystal Structures, University of
Göttingen, Göttingen, Germany, 1997.