Rhenium complexes with a pyridinyl-naphthyridine ligand: Synthesis, characterization, and catalytic activity

Article abstract of DOI:10.1002/ejic.201201413

Treatment of [Re₂(CO)₈(CH₃CN)₂] with 2,7-dipyridinyl-1,8-naphthyridine (bpnp) thermally provided mononuclear [(N,N-bpnp)Re(CO)₃Cl] (1). Further reaction of 1 with rhenium carbonyls yielded ortho-metallation dinuclear rhenium complex 2. Both complexes were characterized by spectroscopic analyses and single-crystal X-ray determination. Complex 1 also reacted with [PdMeCl(COD)] and [Ir(COD)Cl] ₂ by means of ortho-metallation to yield the corresponding heterodinuclear species. Complex 2 appears to be an excellent precatalyst to promote the insertion of terminal alkynes into acetoacetates, which subsequently undergo cyclization to form 2-pyranones. Complexation of 2,7-dipyridinyl-1,8- naphthyridine with rhenium carbonyls provided a N,N-coordination complex, which subsequently reacted with rhenium carbonyls to form an o-metallated dinuclear species. This dirhenium complex is catalytically active for the insertion of terminal acetylenes into 2-methylacetoacetates. Copyright

Full text of DOI:10.1002/ejic.201201413

FULL PAPER
DOI:10.1002/ejic.201201413
Rhenium Complexes with a Pyridinyl-Naphthyridine
Ligand: Synthesis, Characterization, and Catalytic
Activity
Tzu-Chieh Su,[a] Yi-Hung Liu,[a] Shie-Ming Peng,[a] and
Shiuh-Tzung Liu*[a]
Keywords: Rhenium / N ligands / Homogenous catalysis / C–H activation
Treatment of [Re2(CO)8(CH3CN)2] with 2,7-dipyridinyl-1,8-
naphthyridine (bpnp) thermally provided mononuclear
[(N,NЈ-bpnp)Re(CO)3Cl] (1). Further reaction of 1 with rhe-
nium carbonyls yielded ortho-metallation dinuclear rhenium
complex 2. Both complexes were characterized by spectro-
scopic analyses and single-crystal X-ray determination.
Complex 1 also reacted with [PdMeCl(COD)] and [Ir(COD)-
Cl]2 by means of ortho-metallation to yield the corresponding
heterodinuclear species. Complex 2 appears to be an excel-
lent precatalyst to promote the insertion of terminal alkynes
into acetoacetates, which subsequently undergo cyclization
to form 2-pyranones.
Introduction
preparation of the dimetallic Re/Ir and Re/Pd complexes
was investigated. The new dirhenium complexes are good
catalysts for the insertion of alkynes into β-keto esters.
Ligands that can accommodate two metal ions in close
proximity have received considerable attention in recent
years. Such dinuclear complexes may display unusual prop-
erties between the metal ions, which are expected to lead to
synergic effects particularly in the catalytic reactions.[1] One
of the promising dinucleating ligands is 2,7-bis(2-pyridyl)-
1,8-naphthyridine (bpnp) (Scheme 1), which was first syn-
thesized by Caluwe in 1979.[2] The distance between two
pyridinyl nitrogen donors is about 8.6 Å, which is suitable
for constructing a stable dinuclear complex through the
chelation of the 1,8-naphthyridine unit. Indeed, this tetra-
dentate has been shown to form stable dinuclear complexes
of rhodium,[3] ruthenium,[4] copper,[5] and palladium.[6]
Results and Discussion
Synthesis and Characterization of Rhenium Complexes
Tetradentate bpnp was prepared according to the re-
ported method.[8] Thermal reaction of [Re2(CO)8(CH3-
CN)2] with bpnp in a 1:1 molar ratio in a sealed tube with
chlorobenzene as the solvent generated a mixture of air-
stable mono- and dirhenium complexes in 100% yield
(based on the ligand) (Scheme 2). Both 1 and 2 were iso-
lated in a ratio of 38:62 by a chromatographic separation.
By varying the reaction temperature and molar ratio of the
reactants, the yield of 2 did not improve significantly. It was
noted that the solvents used for the reaction affected the
product formation dramatically. If the reaction was carried
out in a non-chlorinated organic solvent, such as toluene
or xylene, no desired product was obtained. Presumably,
this is due to the chloride ligand coming from the solvent
Scheme 1. Structure of bpnp.
Kaska and coworkers reported that complexation of
bpnp with [Re(CO)3Br(THF)2] yielded a mononuclear rhe-
nium complex, [(bpnp)Re(CO)3Br].[7] However, no dinu-
clear rhenium complex that contains bpnp has been re-
ported. In the present work, we describe the complexes, in-
cluding mono- and dirhenium species, that were obtained
by treating bpnp with rhenium carbonyls. Furthermore, the
[a] Department of Chemistry, National Taiwan University,
1, Sec. 4, Roosevelt Road, Taipei, Taiwan 106
Fax: +88-62-33668671
E-mail: stliu@ntu.edu.tw
Homepage address: http://www.ch.ntu.edu.tw/
Scheme 2. Preparation of rhenium complexes.
Eur. J. Inorg. Chem. 2013, 2362–2367
2362
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
molecule. Complex 1 can be obtained exclusively by the
The bipyridine fragment of bpnp and the chloride ligand
substitution of [Re(CO)5Cl] with bpnp directly. Treatment around the metal center in complex 1 are arranged in a
of 1 with rhenium carbonyls, such as [Re2(CO)10] or facial configuration. This coordination mode is similar to
[Re2(CO)8(CH3CN)2], provided 2, but accompanied by that of [(bpnp)Re(CO)3Br].[7] Complex 1 adopts a slightly
various unidentified complexes. However, we did not ob- distorted octahedral geometry around the rhenium atom,
serve the formation of the expected dirhenium complex 3 where the two nitrogen donors constitute a five-member
in all of the cases, which was presumably due to steric hin- ring with the metal atom. The resulting bite angle is
drance.[7]
74.23(7)°. The bond lengths of Re–N in this complex are
Both 1 and 2 were isolated as crystalline solids and were 2.167(2) and 2.197(2) Å, respectively, whereas the distance
thoroughly characterized by spectroscopic and X-ray crys- of Re–Cl is 2.4957(7) Å. These values compare well to those
tallographic analyses. The presence of three CO bands observed in the related complex, [(bipyridine)Re(CO)3Cl].[9]
(2015, 1908, and 1884 cm–1) in the IR spectrum of 1 are The nonplanarity of the naphthyridine core of the uncoor-
consistent with the existence of a Re(CO)3 fragment, which dinated bipyridine is observed as evidenced by the dihedral
is similar to the bromo analog, [(bpnp)Re(CO)3Br].[7] Al- angle of N(3)–C(16)–C(17)–C(18) [12.7(4)°].
The FAB-mass spectrum of 2 shows a molecular ion
(C25H11ClN4O7Re2) at m/z = 887.9437, which indicates that
it is a dirhenium species. The structure of 2 was established
though NMR spectroscopic and mass spectroscopic data
provided the structural information of 1, the detailed coor-
dination configurations were confirmed by single-crystal X-
ray diffraction analysis of 1·(H2O). The ORTEP plot is
shown in Figure 1, while some relevant structural param-
eters are collected in Table 1.
1
by its distinct H NMR spectrum and X-ray crystallogra-
phy. Utilization of the spin-spin coupling of the adjacent
protons allowed for a convenient analysis of the C–H acti-
vation in the structure of 2 (Figure 2). Complex 1 displays
four sets of doublets for the naphthyridine protons. On the
other hand, three sets of signals [two sets of doublets (C5Ј–
H and C6Ј–H) and a singlet (C7Ј–H)] appear for the naph-
thyridine protons in complex 2, an indication that ortho-
metallation takes place at the C8Ј position. This formula-
tion was confirmed by X-ray crystallographic analysis.
Red crystals of 2 were grown by vaporization of a
CH2Cl2 solution at room temperature. The ORTEP plot of
2 is shown in Figure 3 and selected bond lengths and bond
angles are collected in Table 2. Both of the rhenium atoms
are in a distorted octahedral environment. The Re(2)–C(24)
[1.966(3) Å] bond length is slightly longer than the Re(2)–
C(25) distance [1.927(3) Å], which is an illustration of a
stronger back-bonding interaction between Re(2) and C(25)
(i.e. the pyridinyl nitrogen is a stronger donor than the ar-
ene carbon). The Re(2)–C(15) distance of 2.168(3) Å is
within the normal range of Re–C bonds. Unlike complex
1, the dihedral angles of N(1)–C(8)–C(9)–N(2) and C(15)–
C(16)–C(17)–N(4) are 0.4(3)° and 4.1(4)°, respectively,
which suggests that the naphthyridine core remains as a
planar geometry.
Figure 1. ORTEP plot of 1 (drawn with 30% probability ellipsoids).
Table 1. Selected bond lengths [Å] and angles [°] for 1.
Bond length
Bond angles
Re(1)–C(1)
Re(1)–C(2)
Re(1)–C(3)
Re(1)–N(1) 2.167(2)
Re(1)–N(2) 2.197(2)
Re(1)–Cl(1) 2.4956(7)
1.907(3)
1.925(3)
1.899(3)
N(1)–Re(1)–N(2)
N(1)–Re(1)–Cl(1)
N(1)–Re(1)–C(1)
N(1)–Re(1)–C(2)
N(1)–Re(1)–C(3)
N(2)–Re(1)–C(3)
74.24(7)
81.82(6)
99.2(1)
170.7(1)
96.6(1)
170.82(9)
1
Figure 2. H NMR spectra of (a) 1 and (b) 2 for the aromatic region.
Eur. J. Inorg. Chem. 2013, 2362–2367
2363
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
curred at that position. The downfield shifts (i.e. coordina-
tion chemical shifts) of H-9 protons for both 5 and 6 were
also observed in these complexes, which supports the coor-
dination of the pyridinyl nitrogen towards the metal centers.
The coordination of acetonitriles in the complexes was veri-
fied by the methyl shifts of CH3CN at δ = 2.05–2.30 ppm
1
in the H NMR spectra. The conductivities of 5 and 6 in
acetonitrile were 109 and 167 ohm–1 cm2 mol–1, indicative
of the presence of a 1:1 and 2:1 electrolyte, respectively. The
MALDI-mass spectrum of 5 shows m/z at 842.79, which
corresponds to the formula of C26H20N7O2IrRe [5-(CO)-
(BF4)]. Similarly, the peak at m/z = 787.73, which matches
with the formula of C23H14BF4N5O3PdRe [6–2(CH3CN) –
BF4], illustrates the dinuclear structure of 6.
Figure 3. ORTEP plot of 2 (drawn with 30% probability ellipsoids).
Table 2. Selected bond lengths [Å] and angles [°] for 2.
Bond length
Bond angles
Re(1)–C(1)
Re(1)–C(2)
Re(1)–C(3)
Re(1)–N(1)
Re(1)–N(2)
Re(1)–Cl(1)
Re(2)–C(22)
Re(2)–C(23)
Re(2)–C(24)
Re(2)–C(25)
Re(2)–C(15)
Re(2)–N(4)
1.908(3)
1.913(3)
1.914(3)
2.174(2)
2.181(2)
2.4777(7)
1.984(3)
2.005(4)
1.966(3)
1.927(3)
2.168(3)
2.199(2)
N(1)–Re(1)–N(2)
N(1)–Re(1)–Cl(1)
N(1)–Re(1)–C(1)
N(1)–Re(1)–C(2)
N(1)–Re(1)–C(3)
N(2)–Re(1)–C(3)
N(4)–Re(2)–C(15)
N(4)–Re(2)–C(22)
N(4)–Re(2)–C(23)
N(4)–Re(2)–C(24)
N(4)–Re(2)–C(25)
C(15)–Re(2)–C(24)
74.44(8)
79.84(6)
101.5(1)
166.3(1)
99.1(1)
173.5(1)
76.5(1)
91.0(1)
89.3(1)
95.7(1)
171.2(1)
171.4(1)
Scheme 3. Preparation of heterodinuclear complexes.
1
Table 3. H NMR shifts of naphthyridine protons for 1, 2, 5, and
6.
Treatment of 2 with equal molar amount of AgBF4 in
CH3CN readily provided the acetonitrile (ACN) coordi-
nated complex, [Re2(bpnp)(CO)7(ACN)]BF4 (4). Charac-
terization of 4 was achieved by both spectroscopic and ele-
mental analyses. The ESI-mass spectrum of 4 shows m/z =
894.15 and 853.15 for the ions of [Re2(bpnp)(CO)7(ACN)]+
and [Re2(bpnp)(CO)7]+, respectively. The 1H NMR spec-
trum of 4 is similar to that of 2 except for the shift due to
the methyl group of acetonitrile (δ = 2.15 ppm). Infrared
carbonyl stretching frequencies appear at 2093, 2032, 1991,
and 1920 cm–1, which are quite similar to those of 2.
H-5
H-6
H-7
H-8
H-9[a]
1
2
5
6
8.38 (d)
8.26 (d)
8.56 (d)
8.72 (d)
8.91 (d)
8.41 (d)
8.88 (d)
8.99 (d)
8.54 (d)
8.79 (s)
9.05 (s)
8.80 (s)
8.31 (d) 9.15 (d)
9.15 (d)
9.42 (d)
8.90 (d)
1
[a] The H NMR shift of H-9 of free ligand bpnp is δ = 8.81 ppm.
Heterodinuclear Rhenium Complexes
Catalysis
Learning from the formation of 2 by means of ortho-
metallation, we examined the possibility to prepare hetero-
dinuclear rhenium complexes. Scheme 3 outlines the prepa-
ration of Re/Pd and Re/Ir complexes. Treatment of 1 with
[Ir(COD)Cl]2 followed by the silver salt yielded Re/Ir dinu-
clear complex 5. Re/Pd complex 6 was obtained similarly
by using Pd(COD)MeCl as the palladium ion source. Char-
acterization of 5 and 6 was accomplished by NMR spectro-
scopic and mass spectroscopic analysis. The most informa-
tive proton nuclei, namely those that provide the most use-
ful structural information, are those from the naphthyridine
core (i.e. C5–C8 protons). These chemical shifts are summa-
rized in Table 3. The disappearance of the shift at C8-pro-
It has been demonstrated that rhenium carbonyl com-
plexes are active catalysts for the insertion of terminal
acetylenes into β-keto esters, which subsequently undergoes
cyclization to yield the pyranone derivatives (Scheme 4).[10]
With these rhenium complexes in hand, their catalytic ac-
tivities on the insertion of terminal acetylenes into β-keto
Scheme 4. Insertion of alkynes into β-keto esters followed by
ton in both 5 and 6 provides evidence that metallation oc- cyclization.
Eur. J. Inorg. Chem. 2013, 2362–2367
2364
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
esters were investigated. In order to create an environmen- Table 4. Formation of 7 catalyzed by various rhenium complexes.[a]
tally benign process, the catalytic reactions investigated in
this work do not use any organic solvents.
We first examined the insertion of phenylacetylene into
ethyl 2-methylacetoacetate catalyzed by 2 under photoirra-
diation at 350 nm. A series of screen tests suggested that
carrying out the reaction of phenylacetylene (0.55 mmol),
ethyl 2-methylacetoacetate (0.45 mmol), and 2 (0.5 mol-%)
at 90 °C under irradiation at 350 nm for 12 h provides ethyl
(2E)-2-methyl-5-oxo-3-phenyl-2-hexenoate (7) in 84% iso-
lated yield [Equation (1)]. It is noted that photoirradiation
is required in order to promote the reaction, presumably
due to the photodissociation of carbonyl ligands that assist
the coordination of substrates to the metal. Next, we ran a
series of trial reactions based on Equation (1) in the pres-
ence of various rhenium complexes to compare the selectiv-
ity of these catalysts (Table 4). Based on the yield, all of the
rhenium carbonyl complexes, except 10, have activity in the
insertion of phenylacetylene into acetoacetate to give 7 un-
der the catalytic conditions described above. Among these
catalysts, 2 and 4 prove to have the best activity in this
insertion reaction, whereas other complexes show moderate
activity.
(1)
The cyclization of 7 to yield pyranone 8a proceeded
smoothly at 90 °C with tetrabutylammonium fluoride
(TBAF) as the promoter. Thus, for the following study, we [a] Reaction conditions: phenylacetylene (0.55 mmol), ethyl 2-
methylacetoacetateate (0.45 mmol), and catalyst at 90 °C under ir-
radiation at 350 nm for 12 h. [b] Mol-% based on the limiting rea-
carried out the insertion reaction followed by the cycliza-
tion to provide the corresponding pyranone in a one-pot
gent.
procedure. Table 5 summarizes the scope of the pyranone
formation catalyzed by 2. For example, the treatment of β-
Table 5. Synthesis of 2-pyranones from β-keto esters and acetyl-
keto ester Ia with acetylene IIb in the presence of 2
(0.5 mol-%) at 90 °C under irradiation for 12 h, followed by
the addition of TBAF (10 mol-%) and stirring the mixture
at 90 °C for 12 h, gave 2-pyranone 8b in 92% yield (Table 5,
entry 2). Various terminal alkynes (IIa–IIe) react with 2-
methylacetoacetate followed by cyclization to generate the
corresponding pyranone (8a–8e) in excellent yields (Table 5,
entries 1–5). Under similar reaction conditions, the reaction
of 2-substituted acetoacetate with alkynes also provides
good yields of the resulting products (Table 5, entries 6–8).
These observations clearly demonstrate the excellent ac-
tivity of 2 in the insertion of terminal acetylenes into β-
keto esters. In terms of the catalytic activity, the turnover
frequency (TOF) of 2 in the production of 8a reaches 1.5
(mol·product)·(mol·catalyst)–1·h–1, which is superior to that
of the known catalyst [ReBr(CO)3(THF)]2 (TOF: 0.23).[10]
enes.[a]
Entry β-Keto ester
Acetylene
Yield[b] (%)
1
2
3
4
5
R1 = Me Ia
R1 = Me Ia
R1 = Me Ia
R1 = Me Ia
R1 = Me Ia
R2 = C6H5 IIa
R2 = p-MeC6H4 IIb
R2 = C6H5CH2 IIc
R2 = Cl(CH2)3 IId
R2 = 1-cyclohexenyl
IIe
8a (93)
8b (92)
8c (73)
8d (87)
8e (79)
6
R1 = H Ib
R1 = H Ib
R2 = 1-cyclohexenyl
IIe
8f (81)
7
8
R2 = p-FC6H4 IIf
8g (51)
8h (90)
R1 = C6H5CH2 Ic R2 = C6H5 Iia
Conclusions
[a] Reaction conditions: acetylene (0.55 mmol), keto ester
(0.45 mmol), and 2 (0.5 mol-%) at 90 °C under irradiation at
terization of a series of dinuclear complexes through o-me- 350 nm for 12 h. [b] Isolated yield.
In summary, we have reported the synthesis and charac-
Eur. J. Inorg. Chem. 2013, 2362–2367
2365
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
the filtrate was concentrated to give 4 as a red powder solid (15 mg,
97%). H NMR (400 MHz, CDCl3): δ = 2.15 (s, 3 H, CH3), 7.57
tallation with the use of 2,7-dipyridinyl-1,8-naphthyridine
(bpnp) as the ligand. The structures of these complexes
were unambiguously determined by spectroscopic methods
and through single-crystal X-ray analysis of 1 and 2. Com-
plex 2 appears to be catalytically active for the insertion of
terminal acetylenes into ethyl 2-methylacetoacetates to give
the substituted 5-oxo-2-hexenoates, which underwent
cyclization to provide pyranones. Studies on the catalytic
reactivity of these complexes are ongoing in our laboratory.
1
(t, J = 6.4 Hz, 1 H, 11-H), 7.74 (t, J = 6.4 Hz, 1 H, 2-H), 8.22 (t,
J = 8 Hz, 1 H, 3-H), 8.39 (t, J = 8 Hz, 1 H, 10-H), 8.51 (d, J =
8 Hz, 1 H, 5-H), 8.62 (d, J = 8.8 Hz, 1 H, 4-H), 8.83 (d, J = 8 Hz,
1 H, 6-H), 8.90 (s, 1 H, 7-H), 8.97 (d, J = 5.2 Hz, 1 H, 12-H), 9.02
(d, J = 8 Hz, 1 H, 9-H), 9.16 (d, J = 5.2 Hz, 1 H, 1-H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 3.3, 121.4, 121.8, 125.0, 125.9, 126.7,
127.4, 128.1, 128.5, 139.7, 140.1, 140.8, 150.5, 152.7, 153.3, 155.2,
156.8, 158.3, 161.4, 162.8, 170.8, 186.5, 186.6, 190.5, 191.0, 193.7
ppm. IR (KBr): ν
= 2093, 2032, 1991, 1920 cm–1. ESI-HRMS:
˜
C=O
calcd. for C27H14N5O7Re2 [M – BF4]+ 894.0008; found 894.0000.
C27H14BF4N5O7Re2 (979.64): calcd. C 33.10, H 1.44, N 7.15; found
C 32.87, H 1.38, N 6.82.
Experimental Section
General Information: All of the reactions and manipulation steps
were performed under a nitrogen atmosphere. Dichloromethane
and acetonitrile were dried with CaH2 and distilled under nitrogen.
The other chemicals and solvents were of analytical grade and were
used after a degassing process. Ligand bpnp was prepared accord-
ingly to the method reported previously.[8]
Complex 5: A mixture of 1 (10 mg, 0.017 mmol) and [Ir(COD)Cl]2
(6 mg, 0.009 mmol) in CH2Cl2 was stirred at 40 °C for 12 h. The
resulting red precipitate was collected and dissolved in CH3CN.
AgBF4 (9.9 mg, 0.05 mmol) was added and the mixture was stirred
at ambient temperature for 5 h. After removal of the solvent, the
residue was precipitated in hexane/CH3CN/CH2Cl2 to give 5 as a
red solid (12 mg, 74%). 1H NMR (400 MHz, CDCl3): δ = 2.05 (br.,
9 H, NC-CH3), 7.71 (m, 1 H, 10-H), 7.81 (m, 1 H, 2-H), 8.21 (t, J
= 7 Hz, 1 H, 11-H), 8.36 (t, J = 7.6 Hz, 1 H, 3-H), 8.56 (d, J =
8.8 Hz, 1 H, 5-H), 8.71 (d, J = 8.8 Hz, 1 H, 4-H), 8.88 (d, J = 8 Hz,
6-H), 8.93 (d, J = 8 Hz, 12-H), 9.05 (s, 1 H, 7-H), 9.21 (br., 1 H,
1-H), 9.42 (t, J = 7.6 Hz, 1 H, 9-H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 3.7, 3.8, 121.82, 126.63, 126.74, 128.73, 129.1, 139.8,
141.1, 141.6, 142.7, 143.0, 151.3, 152.2, 152.8, 155.1, 158.1, 158.5,
Nuclear magnetic resonance spectra were recorded in CDCl3 or
[D6]acetone with a Bruker AVANCE 400 spectrometer. The chemi-
cal shifts are given in parts per million relative to Me4Si for 1H and
13C NMR spectroscopy. The infrared spectra were measured with
a Nicolet Magna-IR 550 spectrometer (Series-II). The UV/Vis spec-
tra were recorded with a Hitachi U-2900 spectrometer.
Complex 1 and 2: A mixture of bpnp (20 mg, 0.07 mmol) and
Re2(CO)8(CH3CN)2 (48 mg, 0.07 mmol) in chlorobenzene (2.5 mL)
was sealed in a reaction tube. The mixture was heated at 200 °C
for 4 h. After removal of the solvents, the residue was chromato-
graphed on silica gel with 1% Et3N/EtOAc as the eluent. A dark
red band was collected to give 1 as a dark red solid (15.9 mg, 38%)
and then a red band was collected to give 2 as a red solid (38.7 mg,
62%).
160.2, 169.4, 192.1, 195.1, 196.2 ppm. IR (KBr): ν
= 2018,
˜
C=O
1903, 1892 cm–1. MALDI-MS: calcd. for C26H20N7O2IrRe [M –
(CO) – (BF4)]+ 894.0008; found 842.19. C27H20BF4IrN7O3Re
(955.72): calcd. C 33.93, H 2.11, N 10.26; found C 33.57, H 1.96,
N 9.89.
Complex 6: The procedure was similar to that for complex 5. (9 mg,
1
1
68%). H NMR (400 MHz, CDCl3): δ = 2.32 (br., 9 H, NC-CH3),
Complex 1: H NMR (400 MHz, CDCl3): δ = 7.45 (t, J = 5 Hz, 1
7.63 (t, J = 6 Hz, 1 H, 10-H), 7.86 (t, J = 6.4 Hz, 1 H, 2-H), 8.09
(t, J = 8 Hz, 1 H, 11-H), 8.42 (t, J = 8 Hz, 1 H, 3-H), 8.53 (d, J =
8 Hz, 1 H, 12-H), 8.72 (d, J = 8 Hz, 1 H, 5-H), 8.80 (s, 1 H, 7-H),
8.77 (d, J = 7 Hz, 1 H, 4-H), 8.90 (d, J = 7 Hz, 1 H, 9-H), 8.99 (d,
J = 5 Hz, 1 H, 6-H), 9.26 (d, J = 5 Hz, 1 H, 1-H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 2.7, 122.3, 123.7, 124.8, 125.6, 125.8, 126.7,
127.8, 130.1, 138.7, 140.7,141.9, 143.9, 151.1, 155.1, 155.2, 155.7,
H, 11-H), 7.60 (t, J = 8 Hz, 1 H, 2-H), 7.96 (t, J = 8 Hz, 1 H, 10-
H), 8.12 (t, J = 8 Hz, 1 H, 9-H), 8.31 (d, J = 8 Hz, 1 H, 8-H), 8.38
(d, J = 8 Hz, 1 H, 5-H), 8.40 (d, J = 8 Hz, 1 H, 4-H), 8.54 (d, J =
8 Hz, 1 H, 7-H), 8.72 (d, J = 5.2 Hz, 1 H, 12-H), 8.81 (d, J = 8 Hz,
1 H, 9-H), 8.91 (d, J = 8 Hz, 1 H, 6-H), 9.29 (d, J = 5.2 Hz, 1 H,
1-H) ppm. 13C NMR (100 MHz, CDCl3): δ = 119.7, 123.1, 123.2,
124.2, 1245.0, 127.0, 136.7, 137.7, 138.6, 140.3, 148.8, 153.1, 153.3,
157.9, 161.8, 163.3, 192.1, 195.5,195.7 ppm. IR (KBr): ν
=
˜
153.8, 156.4, 159.3, 161.5, 189.7, 196.9, 197.7 ppm. IR (KBr): ν
˜
C=O
C=O
2035, 1934 (br) cm–1. FAB-HRMS: calcd. for C23H14BF4N5O3-
= 2015, 1908, 1884 cm–1. FAB-HRMS: calcd. for C21H12ClN4O3Re
[M]+ 590.0156; found 590.0153. C21H12ClN4O3Re (590.00): calcd.
C 42.75, H 2.05, N 9.50; found C 42.56, H 2.13, N 9.30.
PdRe [M 2·(CH3CN) BF4] 787.9718; found 787.9723.
–
–
C27H20B2F8N7O3PdRe·CH3CN: calcd. C 34.91, H 2.32, N 11.23;
found C 34.48, H 2.03, N 10.87.
1
Complex 2: H NMR (400 MHz, CDCl3): δ = 7.48 (t, J = 6.4 Hz,
Crystallography: Crystals suitable for X-ray determination were ob-
tained for 1·(H2O) and 2 by recrystallization at room temperature.
Cell parameters were determined with a Siemens SMART CCD
diffractometer. The structure was solved by using the SHELXS-97
program[11] and refined by using the SHELXL-97 program[12] by
full-matrix least-squares on F2 values. CCDC-909557 (for complex
2), -909558 (for complex 1) contain the supplementary crystallo-
graphic 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.
1 H, 11-H), 7.56 (t, J = 6.4 Hz, 1 H, 2-H), 8.10 (t, J = 8 Hz, 1 H,
3-H), 8.17 (t, J = 8 Hz, 1 H, 10-H), 8.26 (d, J = 8.8 Hz, 1 H, 5-H),
8.36 (d, J = 8 Hz, 1 H, 4-H), 8.41 (d, J = 8 Hz, 1 H, 6-H), 8.79 (s,
1 H, 7-H), 8.89 (d, J = 5.2 Hz, 1 H, 12-H), 9.15 (d, J = 8 Hz, 1 H,
9-H), 9.26 (d, J = 5.2 Hz, 1 H, 1-H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 119.9, 124.6, 125.1, 126.8, 127.0, 127.3, 138.7, 138.8,
140.0, 150.3, 153.3, 153.7, 155.1, 157.5, 157.9, 161.3, 163.8, 171.2,
186.4, 187.2, 190.5, 191.1, 191.7, 197.9, 198.4 ppm. IR (KBr):
ν
= 2093, 2070, 1977, 1909 cm–1. FAB-HRMS: calcd. for
˜
C=O
C25H11ClN4O7Re2
[M]+
887.9432;
found
887.9439.
C25H11ClN4O7Re2 (887.24): calcd. C 33.84, H 1.25, N 6.31; found
C 33.67, H 1.35, N 6.01.
¯
Complex 1·(H2O): C21H14ClN4O4Re, triclinic, space group P1, a =
9.94520(10) Å, b = 10.41760(10) Å, c = 10.41760(10) Å; α =
Complex 4: A mixture of 2 (15 mg, 0.017 mmol) and AgBF4 (3 mg,
0.017 mmol) in anhydrous acetonitrile (2 mL) was heated at 90 °C
for 5 h. The mixture was passed through celite to remove salts and
77.7510(10)°,
β
=
73.5270(10)°,
γ
=
64.9680(10)°, V =
1007.454(17) Å3, Z = 2, ρcalcd. = 2.004 mgm–3, F(000) 584, crystal
size = 0.20ϫ0.15ϫ0.10 mm3, reflections collected 23387; indepen-
Eur. J. Inorg. Chem. 2013, 2362–2367
2366
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
dent reflections 4617 [R(int) = 0.0290]; θ range 3.03 to 27.50°;
goodness-of-fit on F2 1.032; final R indices [IϾ2σ(I)]: R1 = 0.0158,
wR2 = 0.0415; R indices (all data): R1 = 0.0175, wR2 = 0.0425.
2.23–2.32 (m, 7 H), 6.04 (s, 1 H), 6.15 (s, 1 H), 6.47 (t, J = 8 Hz,
1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 20.03, 21.56, 22.31,
25.47, 26.22, 101.14, 105.46, 132.80, 132.98, 155.39, 160.19, 164.29
ppm. IR (KBr): νCO = 1719 cm–1. ESI-HRMS: calcd. for C12H15O2
˜
Complex 2: C25H11ClN4O7Re2, monoclinic, space group C2/c, a =
29.8108(3) Å, b = 12.69290(10) Å, c = 13.6408(2) Å, α = 90°, β =
[M + H] 191.1072; found 191.1064.
96.5190(10)°, γ = 90°, V = 5128.11(10) Å3, Z = 8, ρcalcd.
=
4-(4-Fluorophenyl)-6-methyl-2H-pyran-2-one (8g): 1H NMR
(400 MHz, CDCl3): δ = 2.34 (s, 3 H), 6.28 (s, 1 H), 6.32 (s, 1 H),
7.16–7.20 (m, 2 H), 7.56–7.60 (m, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 20.19, 103.25, 107.96, 116.20, 116.42, 128.63, 128.71,
2.298 mgm–3, F(000) 3296, crystal size = 0.25ϫ0.20ϫ0.15 mm3,
reflections collected 30424, independent reflections 5878 [R(int) =
0.0252], θ range 3.01 to 27.50°, goodness-of-fit on F2 1.011, final
R indices [IϾ2σ(I)]: R1 = 0.0160, wR2 = 0.0401, R indices (all
data): R1 = 0.0183, wR2 = 0.0412.
131.92, 154.35, 162.33, 162.96, 163.24 ppm. IR (KBr): ν
=
˜
CO
1713 cm–1. ESI-HRMS: calcd. for C12H10O2F [M + H] 205.0665;
found 205.0664.
Catalysis: The typical procedure for the insertion of an alkyne into
ethyl 2-methylacetoacetate followed by cyclization is as follows: a
mixture of alkyne (0.55 mmol), keto ester (0.45 mmol), and rhe-
nium complex 2 (2.3ϫ10–3 mmol) was heated at 90 °C under irra-
diation at 350 nm for 12 h. Tetrabutylammonium fluoride
(0.045 mmol) was then added and heated at 90 °C for another 10 h.
After completion of the reaction, brine (3 mL) and CH2Cl2 (5 mL)
were added. The organic layer was separated and the aqueous layer
was extracted with CH2Cl2. The combined organic extracts were
dried with magnesium sulfate and concentrated. The products were
purified by chromatography with elution of CH2Cl2/EtOAc and
3-Benzyl-6-methyl-4-phenyl-2H-pyran-2-one (8h): 1H NMR
(400 MHz, CDCl3): δ = 2.28 (s, 3 H), 3.84 (s, 2 H), 6.02 (s, 1 H),
7.09 (d, J = 7.4 Hz, 2 H), 7.16–7.20 (m, 2 H), 7.20–7.28 (m, 5 H),
7.42–7.44 (m, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 19.70,
32.91, 106.88, 120.89, 126.07, 127.58, 128.26, 128.32, 128.68,
128.88, 137.70, 139.72, 153.70, 158.93, 164.19 ppm. IR (KBr): ν
˜
CO
= 1714 cm–1. ESI-HRMS: calcd. for C19H17O2 [M + H] 277.1229;
found 277.1223.
1
characterized by H and 13C NMR spectroscopy. Complexes 9 to
Acknowledgments
12 were prepared according to the reported method.[13]
3,6-Dimethyl-4-phenyl-2H-pyran-2-one
(8a):[10]
1H
NMR
We thank the National Science Council, Taiwan for financial sup-
port (grant number NSC-100-2113-M002-001-MY3).
(400 MHz, CDCl3): δ = 2.05 (s, 3 H), 2.28 (s, 3 H), 2.16 (s, 3 H),5.98
(s, 1 H), 7.26–7.30 (m, 2 H), 7.40–7.45 (m, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 13.77, 19.58, 106.59, 118.15, 127.87,
128.56, 128.74, 137.80, 152.04, 157.79, 164.84 ppm.
3,6-Dimethyl-4-p-tolyl-2H-pyran-2-one (8b): 1H NMR (400 MHz,
CDCl3): δ = 2.05 (s, 3 H), 2.25 (s, 3 H), 2.40 (s, 3 H), 5.97 (s, 1 H),
7.19 (d, J = 7.2 Hz, 2 H), 7.25 (d, J = 7.2 Hz, 2 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 13.82, 19.56, 21.27, 106.69, 117.84, 127.88,
[1] a) D. C. Powers, T. Ritter, Acc. Chem. Res. 2012, 45, 840–850;
b) R. D. Adams, B. Captain, Acc. Chem. Res. 2009, 42, 409–
418; c) M. H. Perez-Temprano, J. A. Casares, P. Espinet, Chem.
Eur. J. 2012, 18, 1864–1884; d) M. Shibasaki, S. Matsunaga,
N. Kumagai, Synlett 2008, 1583–1602; e) S. Maggini, Coord.
Chem. Rev. 2009, 253, 1793–1832.
[2] P. Caluwe, Macromolecules 1979, 12, 803–808.
[3] a) W. R. Tikkanen, E. Binamira-Soriaga, W. C. Kaska, P. C.
Ford, Inorg. Chem. 1984, 23, 141–146; b) W. R. Tikkanen, E.
Binamira-Soriaga, W. C. Kaska, P. C. Ford, Inorg. Chem. 1983,
22, 1147–1148.
[4] E. Binamira-Soriaga, N. L. Keder, W. C. Kaska, Inorg. Chem.
1990, 29, 3167–3171.
[5] a) W. R. Tikkanen, C. Krueger, K. D. Bomben, W. L. Jolly,
W. C. Kaska, P. C. Ford, Inorg. Chem. 1984, 23, 3633–3638; b)
B.-S. Liao, Y.-H. Liu, S.-M. Peng, S.-T. Liu, Dalton Trans.
2012, 41, 1158–1164.
[6] F.-M. Yang, P.-Y. Chen, C.-C. Lee, Y.-H. Liu, S.-M. Peng, S.-
T. Liu, Dalton Trans. 2012, 41, 5782–5784.
[7] W. Tikkanen, W. C. Kaska, S. Moya, T. Layman, R. Kane, C.
Krueger, Inorg. Chim. Acta 1983, 76, L29–L30.
[8] G. R. Newkome, S. J. Garbis, V. K. Majestic, F. R. Fronczek,
G. Chiari, J. Org. Chem. 1981, 46, 833–839.
[9] P. Kurz, B. Probst, B. Spingler, R. Alberto, Eur. J. Inorg. Chem.
2006, 2966–2974.
[10] Y. Kuninobu, A. Kawata, M. Nishi, H. Takata, K. Takai,
Chem. Commun. 2008, 6360–6362.
129.21, 134.84, 138.81, 152.10, 157.64, 164.91 ppm. IR (KBr): ν
˜
CO
= 1710 cm–1. ESI-HRMS: calcd. for C14H15O2 [M + H] 215.107;
found 215.1068.
4-Benzyl-3,6-dimethyl-2H-pyran-2-one (8c): 1H NMR (400 MHz,
CDCl3): δ = 2.11 (s, 3 H), 2.13 (s, 3 H), 3.74 (s, 2 H), 5.71 (s, 1 H),
7.11 (d, J = 8 Hz, 2 H), 7.22–7.32 (m, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 19.56, 38.53, 106.10, 106.13, 118.29,
126.71, 128.48, 128.65, 139.97, 151.58, 157.66, 164.32 ppm. IR
(KBr): ν
= 1720 cm–1. ESI-HRMS: calcd. for C14H15O2 [M +
˜
CO
H] 215.1072; found 215.1079.
4-(3-Chloropropyl)-3,6-dimethyl-2H-pyran-2-one (8d): 1H NMR
(400 MHz, CDCl3): δ = 1.97–2.04 (m, 2 H), 2.07 (s, 3 H), 2.21 (s,
3 H), 2.59 (t, J = 7.6 Hz, 2 H), 3.57 (t, J = 6.4 Hz, 2 H), 5.84 (s, 1
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 11.95, 19.52, 29.93,
31.09, 43.95, 105.92, 118.41, 152.04, 158.04, 164.41 ppm. IR (KBr):
ν
= 1719 cm–1. ESI-HRMS: calcd. for C10H14O2Cl [M + H]
˜
CO
201.0682; found 201.0679.
4-Cyclohexenyl-3,6-dimethyl-2H-pyran-2-one (8e):[10] 1H NMR
(400 MHz, CDCl3): δ = 1.63–1.70 (m, 2 H), 1.70–1.77 (m, 2 H), [11] SHELXS-90: G. M. Sheldrick, Acta Crystallogr., Sect. A 1990,
46, 467–473.
2.01 (s, 3 H), 2.03–2.13 (m, 2 H), 2.13–2.18 (m, 2 H), 2.19 (s, 3 H),
5.65 (t, J = 8 Hz, 1 H), 5.80 (s, 1 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 13.43, 19.47, 21.77, 22.49, 25.01, 27.68, 105.32, 116.79,
128.03, 135.31, 154.95, 157.58, 165.12 ppm.
4-Cyclohexenyl-6-methyl-2H-pyran-2-one (8f): 1H NMR(400 MHz,
CDCl3): δ = 1.62–1.68 (m, 2 H), 1.70 (s, 3 H), 1.73–1.80 (m, 2 H),
[12] G. M. Sheldrick, SHELXL-97, University of Göttingen, Ger-
many, 1997.
[13] C.-H. Chen, Y.-H. Liu, S.-M. Peng, J.-T. Chen, S.-T. Liu, Dal-
ton Trans. 2012, 41, 2747–2754.
Received: November 22, 2012
Published Online: March 1, 2013
Eur. J. Inorg. Chem. 2013, 2362–2367
2367
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim