Polynuclear copper(ii) pyrazolate complexes: Temperature-dependent protonolysis reactions, crystal structures and high catalytic activity toward the condensation of nitriles with 2-aminoalcohol

Article abstract of DOI:10.1039/c3dt51970h

Reaction of Cu(OAc)₂·H₂O and 1H-pyrazole-3,5-dicarboxylic acid dimethyl ester (Hdcmpz) in MeOH at room temperature afforded one tetranuclear Cu(ii)/pyrazolate complex [{Cu ₂(μ-OAc)₂}₂(μ-dcmpz)₂

Full text of DOI:10.1039/c3dt51970h

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An international journal of inorganic chemistry
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Volume 42 | Number 44 | 28 November 2013 | Pages 15523–15806
ISSN 1477-9226
COVER ARTICLE
Hong-Xi Li, Jian-Ping Lang et al.
Polynuclear copper(II) pyrazolate complexes: temperature-dependent protonolysis
reactions, crystal structures and high catalytic activity toward the condensation of
nitriles with 2-aminoalcohol

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PAPER
Polynuclear copper(II) pyrazolate complexes:
temperature-dependent protonolysis reactions, crystal
structures and high catalytic activity toward the
condensation of nitriles with 2-aminoalcohol†
Cite this: Dalton Trans., 2013, 42, 15570
Ling Wang,a Bin Guo,a Hong-Xi Li,*a Qi Li,a Hai-Yan Lia and Jian-Ping Lang*a,b
Reaction of Cu(OAc)2·H2O and 1H-pyrazole-3,5-dicarboxylic acid dimethyl ester (Hdcmpz) in MeOH at
room temperature afforded one tetranuclear Cu(II)/pyrazolate complex [{Cu2(μ-OAc)2}2(μ-dcmpz)2-
(μ-OAc)2] (1) in 89% yield. The similar reaction in refluxing MeOH produced a hexanuclear metallamacro-
cyclic Cu(II)/pyrazolate complex [{Cu(μ-dcmpz)}2(μ-OMe)2]3 (2) in 85% yield. Treatment of the same com-
ponents under solvothermal conditions resulted in the formation of another tetranuclear Cu(II)/pyrazolate/
carboxylate complex [{Cu(MeOH)}4(µ-mcccpz)4] (3, Hmcccpz = 5(3)-(methoxycarbonyl)-1H-pyrazole-3(5)-
carboxylic acid) in 30% yield. The mcccpz2− ion in 3 was in situ generated via the hydrolysis of one of two
esters on dcmpz ligand. Complexes 1–3 were characterized by elemental analysis, IR and single-crystal
X-ray diffraction. An X-ray analysis revealed that 1 contains two {Cu(μ-OAc)}2 fragments that are inter-
connected by two μ-η2,η2-dcmpz− ligands and two μ-η1,η1-OAc− ions, forming a unique tetrameric struc-
ture. Complex 2 is composed of three {Cu(µ-dcmpz)}2 fragments linked by three pairs of µ-OMe− anions,
forming a metallamacrocyclic crown structure. 3 consists of four {Cu(MeOH)} fragments linked by two
pairs of μ-η1,η2-mcccpz2− ligands, forming a tetrameric [2 × 2] grid-like structure. Complexes 1–3
displayed high catalytic activity toward the condensation of nitriles with 2-aminoalcohol under solvent-
free conditions to produce various 2-oxazolines.
Received 19th July 2013,
Accepted 9th September 2013
DOI: 10.1039/c3dt51970h
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pyrazole ligands in the presence of bases,2a,5a,c or oxidation
reactions of Cu(I) pyrazolates,5e,6c,d,8f or self-assembly reactions
Introduction
In the past few decades, copper pyrazolate complexes have from preformed copper pyrazolates,2a–c,5e or solvothermal reac-
been extensively studied due to their structural chemistry and tions of copper salts with pyrazole.6b,7a,b,8a–c However, another
their potential applications in magnetism, luminescence, and approach, protonolysis reactions of Cu(II) carboxylates with the
catalysis.1 The anion of pyrazole is well suited for its coordi- derivatives of pyrazole, has been less explored to synthesize
nation to copper ions via the N,N′-bridging mode. The struc- copper pyrazolates. This may be due to the fact that such
tures of the copper pyrazolate complexes ranged from di-,2 tri-,3 ligands could not serve as suitable precursors for protonolysis
tetra-, penta-,2a,c,4 hexa-,5 polynuclear6 structures to chains, as carboxylic acids may have a stronger acidity.4f,9 For example,
layers,7 or three-dimensional networks.8 These complexes were reaction of Cu(OAc)2 with pyrazole (Hpz) afforded one trinuc-
mostly prepared by direct reactions of Cu(I)/(II) ions with lear Cu(II)/pyrazolate complex [Cu3(µ3-OH)(µ-pz)3(OAc)2(Hpz)],
in which part of the OAc− anions in Cu(OAc)2 was protono-
lysed by Hpz ligand.9a However, the analogous reactions of
Cu(OAc)2 with some substituted pyrazoles such as 4-methyl-
1H-pyrazole (4-MepzH), 3,5-dimethyl-1H-pyrazole (3,5-Me2pzH),
3,4,5-trimethyl-1H-pyrazole (3,4,5-Me3pzH) and 3-methyl-4-
phenyl-1H-pyrazole (3-Me-4-PhpzH) only yielded the corres-
ponding undeprotonated products [Cu(OAc)2(L)2] (L = 4-MepzH,
3,5-Me2pzH, 3,4,5-Me3pzH, 3-Me-4-PhpzH).9a When the pyra-
zole ligand was designed to have some chelating groups on
the pyrazolyl ring, their protonolysis reactions with acetates
could proceed. For instance, mixing Cu(OAc)2 and 3,5-bis-
aCollege of Chemistry, Chemical Engineering and Materials Science,
Soochow University, Suzhou 215123, People’s Republic of China.
E-mail: jplang@suda.edu.cn, lihx@suda.edu.cn; Fax: +86 512 65882865;
Tel: +86 512 65882865
bState Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences, Shanghai 200032, People’s Republic of
China
†Electronic supplementary information (ESI) available: 1H and 13C NMR Spectrum
of 2-(4-(1H-pyrazol-3-yl)phenyl)-4,5-dihydrooxazole. CCDC reference numbers
951174–951176. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c3dt51970h
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(2,6-diisopropylphenyliminoacetyl)-1H-4-methylpyrazole (Hbsip- of nitriles with 2-aminoalcohol under solvent-free conditions
piampz) with chelating side arms on the pyrazolyl ring to generate various 2-oxazolines. Their syntheses, crystal struc-
resulted in the formation of a deprotonated product [(bsip- tures and catalytic properties are described below.
piampz)2Cu6(µ-OAc)6(µ4-O)2].9c Could other pyrazole ligands
with substituent groups attached on the pyrazolyl ring
promote such protonolysis reactions? We deliberately chose
another pyrazole derivative, 1H-pyrazole-3,5-dicarboxylic acid
Results and discussion
Synthetic and spectral aspects
dimethyl ester (Hdcmpz) that possesses two –COOMe groups
on the 3 and 5 positions on its pyrazolyl group based on the
following considerations. Firstly, the electron-withdrawing
ester groups on the pyrazolyl ring, which enhances the acidity
of the pyrazole ligand, may initiate the protonolysis reaction.
Secondly, the ester group COOMe is not a good O-donor
species but could weakly coordinate at Cu(II) centers,1f,10a
which may work as potential catalytic sites for some organic
substrates. Thirdly, copper(II) ion could catalyze the in situ
hydrolysis of the ester group into carboxylate anion, which in
turn binds Cu(II) centers to generate new Cu(II)/carboxylate
complexes.1f,10b In addition, it was found that solvothermal
reaction of Cu(OAc)2 with 3,5-Me2pzH gave rise to the trimeric
complex [Cu(3,5-Me2pz)]3, in which all OAc− anions could be
protonolysed by 3,5-Me2pzH ligands.10c Thus another question
was raised: could the reaction temperatures affect the protono-
lysis of the pyrazole ligand with acetate anion and the struc-
tures of the resulting Cu(II)/pyrazolate complexes? Bearing
these questions in mind, we carried out the reactions of
Cu(OAc)2·H2O with Hdcmpz in MeOH at three different reac-
tion temperatures, and isolated one tetranuclear and one hexa-
nuclear Cu(II)/pyrazolate complexes [{Cu2(μ-OAc)2}2(μ-dcmpz)2-
(μ-OAc)2] (1) and [{Cu(µ-dcmpz)}2(µ-OMe)2]3 (2) and one tetra-
nuclear Cu(II)/pyrazolate/carboxylate complex [{Cu(MeOH)}4-
(µ-mcccpz)4] (3, Hmcccpz = 5(3)-(methoxycarbonyl)-1H-pyra-
zole-3(5)-carboxylic acid). In all cases, the protonolysis of
Hdcmpz with OAc− anion did occur and in 3, one of two esters
on the dcmpz− ligand was in situ hydrolyzed into the mcccpz2−
anion.
As shown Scheme 1, reactions of Cu(OAc)2·H2O with two
equiv. of Hdcmpz in MeOH at room temperature, did not
afford the expected 1 : 2 product ‘Cu(dcmpz)2’, but a tetra-
copper pyrazolate complex [{Cu2(μ-OAc)2}2(μ-dcmpz)2(μ-OAc)2] (1)
in 89% yield. Compound 1 was the only product isolated
regardless of the Cu(OAc)2·H2O/Hdcmpz molar ratios. It is
noted that the acetates in Cu(OAc)2·H2O were partially protono-
lysed by Hdcmpz ligand, which may be due to the facts that
the electron-withdrawing ester groups on the pyrazolyl ring
may enhance the acidity of Hdcmpz ligand. If the reaction
temperature was raised, could all the acetates in Cu(OAc)2·
H2O be replaced by dcmpz− anions to form 1 : 2 product
‘Cu(dcmpz)2’? When the methanol solution containing
Cu(OAc)2·H2O and two equiv. of Hdcmpz was refluxed for
6 h, one hexanuclear copper(II) pyrazolate complex [{Cu-
(µ-dcmpz)}2(µ-OMe)2]3 (2) was isolated in 85% yield. In this
reaction, half of the OAc− anions in Cu(OAc)2·H2O were protono-
lysed by Hdcmpz ligands while the others were protonolysed
by MeOH molecules. To explore the temperature effect further,
we ran the reaction of Cu(OAc)2·H2O and Hdcmpz in MeOH
at 120 °C under solvothermal conditions to produce blue
On the other hand, 2-oxazolines are ubiquitous in bio-
chemical, biological, and medicinal structures and func-
tions.11 These 2-oxazolines could be prepared through the
cyclodehydration of hydroxyl amides,11b,c or the condensation
of carboxylic acids,12 esters,13 nitriles,14 N-acylbenzotriazoles,15
or aldehydes16 with amino alcohols. Recently, transition metal
catalysts such as molybdenum oxide,17 RuCl2(PPh3)2,18 and
tungstophosphoric acid14 were also employed to catalyze these
reactions. However, their catalytic reactions have some poten-
tial limitations because the transformations generally suffered
from poor functional group tolerance, elevated reaction temp-
eratures, low product yields, or using expensive catalysts and
environmentally unfriendly solvents. To this end, the develop-
ment of cheaper copper catalysts under solvent-free conditions
for such tandem reactions would be necessary. Several
groups6c,19–22 have found that copper pyrazolates exhibit high
reactivity in many organic transformations, including C–N
bond formation,19 oxidation of alkane,20 cyclopropanation of
olefins,9a,21 and polymerization of MMA.22 In this paper, com-
plexes 1–3 were employed to efficiently catalyze the condensation Scheme 1 Syntheses of complexes 1–3 at three different temperatures.
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Table 1 Selected bond lengths (Å) for 1–3a
Compound 1
octahedral crystals of [{Cu(MeOH)}4(µ-mcccpz)4]·4MeOH·0.5H2O
(3·4MeOH·0.5H2O) in 30% yield. In this reaction, one of two
COOMe groups of Hdcmpz was in situ hydrolyzed into a carb-
oxylate group, forming a new mcccpz2− ligand. All the OAc−
anions in Cu(OAc)2 were removed from the Cu(II) centers and
replaced by two N atoms of the deprotonated pyrazolyl groups
and one O atom of the carboxylate group of the mcccpz2−
ligand. Attempts to run the same reactions at 150 °C or higher
temperatures always led to the formation of an unidentified
precipitate that is insoluble in common solvents. To our
knowledge, it is uncommon that three different Cu(II)/pyrazo-
late complexes were generated from the same components via
controlling the reaction temperatures. Complexes 1–3 are
stable toward oxygen and moisture. They are insoluble in
toluene, hexane, Et2O, but soluble in DMSO and DMF. Their
elemental analyses were consistent with their chemical
formula. In the FT-IR spectra of 1–3, the strong peaks at 1710/
1687 cm−1 (1), 1711/1687 cm−1 (2) and 1694/1628 cm−1 (3)
were assigned to be the carboxylate stretching vibrations. The
bands at 1508/1487 cm−1 (1), 1512/1469 cm−1 (2), 1516/
1489 cm−1 (3) were assigned as the CvN stretching vibrations
of dcmpz− (1 and 2) or mcccpz2− (3) ligand. Their identities
were finally confirmed by X-ray crystallography. Powder X-ray
diffraction was employed to confirm the bulk phase homo-
geneity of the three complexes. For 1–3, the measured PXRD
patterns are closely matched with the simulated patterns
generated from the results of single crystal X-ray diffraction
data (ESI, Fig. S3–S5†). As shown in the TGA curve of 3 (ESI,
Fig. S6†), the weight loss of 12.50% in the range of 35–120 °C
was ascribed to the removal of all coordinated MeOH mole-
cules. TGA curves revealed that 1–3 were similar and began to
decompose upon 200 °C.
Cu(1)–O(14)
Cu(1)–O(17)
Cu(2)–O(11)
Cu(2)–O(20)
Cu(3)–O(10)
Cu(3)–O(12)
Cu(4)–O(15)
Cu(4)–O(13)
Cu(1)–O(1)
1.940(3)
1.973(3)
1.943(3)
1.969(3)
1.919(3)
1.958(3)
1.921(3)
1.953(3)
2.368(3)
2.525(3)
4.115(2)
3.736(2)
Cu(1)–O(16)
1.950(3)
2.001(3)
1.958(3)
1.997(3)
1.943(3)
1.958(3)
1.950(3)
1.955(3)
2.448(3)
2.670(3)
3.220(2)
3.180(2)
Cu(1)–N(1)
Cu(2)–O(9)
Cu(2)–N(2)
Cu(3)–O(18)
Cu(3)–N(3)
Cu(4)–O(19)
Cu(4)–N(4)
Cu(2)–O(3)
Cu(4)–O(5)
Cu(2)⋯Cu(3)
Cu(4)⋯Cu(1)
Cu(3)–O(5)
Cu(1)⋯Cu(2)
Cu(3)⋯Cu(4)
Compound 2
Cu(1)–O(29)
Cu(1)–N(3)
Cu(2)–O(10)
Cu(2)–N(4)
Cu(3)–O(9)
Cu(3)–N(5)
Cu(4)–O(20)
Cu(4)–N(6)
Cu(5)–O(19)
Cu(5)–N(9)
Cu(6)–O(30)
Cu(6)–N(12)
Cu(1)–O(5)
Cu(3)–O(15)
Cu(5)–O(21)
Cu(1)⋯Cu(6)
Cu(2)⋯Cu(3)
Cu(4)⋯Cu(5)
1.9026(11)
1.9911(19)
1.9011(14)
1.9720(16)
1.9094(14)
1.9644(17)
1.9098(14)
1.9678(14)
1.9098(14)
1.9677(16)
1.9162(11)
1.9651(13)
2.736(2)
Cu(1)–O(30)
Cu(1)–N(1)
Cu(2)–O(9)
Cu(2)–N(2)
Cu(3)–O(10)
Cu(3)–N(7)
Cu(4)–O(19)
Cu(4)–N(8)
Cu(5)–O(20)
Cu(5)–N(11)
Cu(6)–O(29)
Cu(6)–N(10)
Cu(2)–O(3)
Cu(4)–O(17)
Cu(6)–O(28)
Cu(1)⋯Cu(2)
Cu(3)⋯Cu(4)
Cu(5)⋯Cu(6)
1.9088(16)
1.9918(14)
1.9022(13)
1.9817(15)
1.9127(12)
1.9807(15)
1.9194(12)
1.9831(18)
1.9106(12)
1.9832(14)
1.9168(16)
1.9894(18)
2.641(2)
2.862(2)
2.802(2)
3.0087(9)
2.9907(7)
3.101(8)
2.812(2)
2.942(2)
3.1383(8)
3.172(1)
3.1818(8)
Compound 3
Cu(1)–O(3A)
Cu(1)–N(1)
Cu(1)–O(1)
1.947(3)
1.972(4)
2.436(3)
Cu(1)–N(2A)
Cu(1)–O(5)
Cu(1)⋯Cu(1A)
1.953(4)
1.983(3)
4.1160(6)
a Symmetry code: (A) 1.0 − x, 1.5 − y, 2.0 + z for 3.
Crystal structure of 1·3CH2Cl2. Compound 1·3CH2Cl2 crys-
ˉ
tallizes in the triclinic space group P1, and its asymmetric unit
contains the discrete molecule [{Cu2(µ-OAc)2}2(µ-dcmpz)2- by a pair of decussate µ-η1,η1-OAc− anions. Judged from the
(µ-OAc)2] and three CH2Cl2 solvent molecules. Compound 1 bond angles listed in Table 1, Cu(1) or Cu(2) in 1 can be
may be viewed as having a tetrahedral structure, in which two described as having a square pyramidal coordination geometry
{Cu(µ-η1,η1-OAc)}2 units are connected by two µ-η2,η2-dcmpz− in which O(14), O(16), O(17), and N(1) (or O(11), O(9), O(20),
ligands (Fig. 1). And the four Cu(II) centers are further bridged and N(2)) atoms sit on the basal plane while O(1) (or O(3))
atom from the COOMe group occupies the apical position.
While Cu(3) and Cu(4) atoms adopt a distorted trigonal bipyra-
midal coordination geometry, coordinated by one N and one
O atoms of dcmpz ligand and three O atoms from three brid-
ging OAc− anions. In 1, the Cu–O(AcO) bond lengths (1.919(3)
Å–1.973(3) Å) are longer than the Cu–O(CvO) bond lengths
(2.368(3) Å–2.670(3) Å). The mean Cu–O(AcO) bond length of
1.948(3) Å is comparable to that of the corresponding one in
[Cu3(µ3-OH)(µ-pz)3(AcO)2(Hpz)] (1.962(2) Å).9a The Cu(1)–N
(2.001(3) Å) and Cu(2)–N (1.997(3) Å) bond lengths are slightly
longer than Cu(3)–N (1.958(3) Å) and Cu(4)–N (1.955(3) Å)
bond lengths, which may be due to their different co-
ordination geometries. The Cu(1)⋯Cu(2) (4.115(2) Å) and
Cu(3)⋯Cu(4) (3.736(2) Å) separations bridged by the dcmpz
ligand are much longer than the Cu(2)⋯Cu(3) (3.220(2) Å) and
Cu(4)⋯Cu(1) (3.180(2) Å) contacts bridged by a pair of OAc−
Fig. 1 View of the molecular structure of 1 with a labelling scheme. All hydro-
gen atoms are omitted for clarity.
anions.
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Fig. 3 View of the molecular structure of 3 with a labelling scheme. All hydro-
gen atoms are omitted for clarity. Symmetry codes: A, −y + 3/4, x + 3/4, −z + 3/4;
B, −x, −y + 3/2, z; C, y − 3/4, −x + 3/4, −z + 3/4.
Fig. 2 View of the molecular structure of 2 with a labelling scheme. All hydro-
gen atoms are omitted for clarity.
Crystal structure of 2. Compound 2 crystallizes in the tri-
asymmetric unit contains one fourth of the discrete molecule
[{Cu(MeOH)}4(µ-mcccpz)4] and one MeOH and one water mole-
cules. In 3, four [Cu(MeOH)] fragments are connected by four
mcccpz2− ligands through two nitrogen and one oxygen atoms,
forming a tetranuclear [2 × 2] grid-type structure with a S4 sym-
metry (Fig. 3). Such a framework resembles those of complexes
[{Cu(H2O)}4(µ-mcccpz)4],4h [M4(HL1)4] (M = Cu(II), Ni(II); H3L1 =
N,N′-bis(2-pyridylmethyl)pyrazole-3,5-dicarboxamide),4h [Cu4L26-
(DMF)2][PF6]2 (HL2 = 3-(2-pyridyl)pyrazole) and [Cu4L34(DMF)4][PF6]4
(HL3 = 6-(3-pyrazolyl)-2,2A-bipyridine).4f The Cu⋯Cu contacts
in 3 are 4.1160(6) Å, and 4.3811(6) Å, which are too long
to include any metal–metal interaction. The four Cu(II)
atoms are located on the vertices of a distorted tetrahedron
with the Cu–Cu–Cu angles of 64.309(11)° and 57.846(11)°,
where the four short edges are spanned by four mcccpz2−
ligands. In the structure of 3, each Cu center is coordinated
by two N atoms and two O atoms of two mcccpz2− ligand, and
one MeOH molecule to form a square pyramidal coordination
geometry. The O(5), O(3C), N(2C) and N(1) atoms surrounding
Cu(1) atom sit on the basal plane while the O(1) atom from the
COOMe group of mcccpz2− ligands is located on the axial
position. The mean Cu–N bond distance of 1.962(4) Å is
shorter than those in 1 and 2 (Table 1). The Cu–O(COOMe)
(2.436(3) Å) bond length is much longer than the Cu–O(COO)
bond distance (1.947(3) Å) and the Cu–O(MeOH) bond dis-
tance (1.983(3) Å), suggesting weak coordination of COOMe
group at Cu(II) centers in 3.
ˉ
clinic space group P1, and the asymmetric unit consists of the
independent molecule [{Cu(µ-dcmpz)}2(µ-OMe)2]3. Complex 2
consists of three {Cu(µ-OMe)}2 units linked by three pairs of
µ-η1,η1-dcmpz anions, forming a metallamacrocyclic crown
structure with an approximate D3h symmetry (Fig. 2). Such a
crown structure was observed in some known hexanuclear
complexes [cis-Cu6(μ-OH)6(μ-pz)6],6b [Au(PPh3)2][trans-Cu6(μ-OH)6-
{µ-(3,5-CF3)2pz}6X] (X = Cl, Br, I).5e However, the connection
modes between Cu(II) atoms in these complexes are somewhat
different. In 2, the three [Cu2(µ-OMe)2] fragments approxi-
mately locate in a plane while three pairs of dcmpz ligands
stand above or below the Cu6 plane. While each Cu center in
[cis-Cu6(μ-OH)6(μ-pz)6] and the anion of [Au(PPh3)2][trans-
Cu6(μ-OH)6{µ-(3,5-CF3)2pz}6X] (X = Cl, Br, I) is interlinked by
one pyrazolate and one hydroxyl ligands with its neighboring
Cu(II) ions. In 2, each Cu(II) atom has a distorted square planar
geometry, coordinated by two OMe− and two dcmpz− ligands
to form a four-membered Cu2O2 ring and one six-membered
Cu2N4 ring. The Cu⋯Cu contacts of 3.1383(8)–3.1818(8) Å in
Cu2N4 rings are longer than the corresponding ones in Cu2O2
rings (2.9907(7)–3.101(8) Å) (Table 1). The Cu(1)–O(5), Cu(2)–O(3),
Cu(3)–O(15), Cu(4)–O(17), Cu(5)–O(21), and Cu(6)–O(28)
bond distances are relatively long (2.641(2) Å–2.942(2) Å), indi-
cating that the O atoms of CvO groups on dcmpz− ligand
interact only weakly with the Cu(II) centers. The mean Cu–N
bond length (1.978(2) Å) is consistent with that in 1. The
mean Cu–µ-O(OMe) bond length (1.910(2) Å) in
2 is
Synthesis of 2-oxazolines catalyzed by 1–3. As discussed
above, copper(II) ions in 1–3 weakly interact with the COOMe
groups, COO− anions, MeOH molecules or OMe− anions,
which may be easily replaced by organic substrates. Thus com-
plexes 1–3 may exhibit catalytic activity toward some organic
transformations. To explore the catalytic activities of 1–3
shorter than that observed in [Cu7(μ3-OH)4(μ-OCH3)2(μ-L)6]-
Cl2·xCH2Cl2 (1.935(4) Å and 2.176(4) Å; HL = 3-pyridyl-5-tert-
butylpyrazole).6f
Crystal structure of 3·4MeOH·0.5H2O. Compound 3·4MeOH·
0.5H2O crystallizes in the tetragonal space group I41/a, and its
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Table 2 Optimizing the reaction conditions for the synthesis of 2-phenyloxazoline
Catalyst loading
([Cu] (mol %))
Benzonitrile :
aminoalcohol
Entry
Cat.
Temp (°C)
Time (h)
Yielda (%)
1
2
3
4
5
6
7
8
1
2
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
—
8
8
8
8
8
8
8
8
8
8
8
8
4
80
80
80
20
40
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
2
4
8
6
1 : 3
1 : 3
1 : 3
1 : 3
1 : 3
1 : 3
1 : 3
1 : 3
1 : 1
1 : 2
1 : 4
1 : 5
1 : 4
1 : 4
1 : 4
1 : 4
1 : 4
1 : 4
1 : 4
1 : 4
63
65
67
—
—
2
85
50
18
33
90
89
47
59
88
90
36
85
59
38
60
100
120
100
100
100
100
100
100
100
100
100
100
100
100
9
10
11
12
13
14
15
16
17
18
19
20
6
10
12
8
8
8
—
a Isolated yield.
toward the condensation reaction of nitriles with aminoalcohol, the catalytic activity. To optimize the time interval, several
each catalyst (2.0 mol% (1), 1.33 mol% (2), 2.0 mol% (3)) was different time intervals (2, 4, 6, and 8 h) were employed while
mixed with benzonitrile (1.0 mmol), and 2-aminoalcohol keeping the other reaction conditions unchanged. As shown in
(3.0 mmol) at 80 °C for 6 h. A standard workup produced Table 2, while the time interval was raised, the yield of 2-phenyl-
2-phenyloxazoline in 63%, 65%, and 67% yield, respectively oxazoline increased in the forepart, and then that decreased
(Table 2, entries 1–3). These preliminary results showed that after 6 h. It is noteworthy that the reaction was not able to
the tandem reaction between nitrile and 2-aminoalcohol could proceed smoothly without using a catalyst, giving only a low
be efficiently catalyzed by 1–3.
yield (38%).
Upon the above optimization, the optimal reaction con-
As shown in Table 2, benzonitrile and 2-aminoalcohol were
chosen as the model substrates to optimize the reaction con- ditions were identified as follows: 1 or 2, 3, solvent-free,
ditions including reaction temperature, catalyst loading, and 1 : 4 molar ratio of nitriles to 2-aminoalcohol and with a reac-
the ratio of benzonitrile to 2-aminoalcohol. The reaction temp- tion temperature of 100 °C. With the optimized reaction con-
erature usually exerts great impact on such a reaction. At lower ditions in hand, a variety of substituted nitrile derivatives were
temperature (20 °C to 60 °C), the reaction did not work chosen as the substrates in this tandem reaction. As shown in
(entries 4 and 5) or gave the product in a very low yield Table 3, the condensation reactions were performed well for
(entry 6). When the reaction temperature was raised to 80 °C all the substrates examined, and the desired products were iso-
or 100 °C, the product yields could be raised to 63% and 85%, lated in moderate to excellent yields. To our delight, aromatic
respectively (entries 1 and 7). While the yield of the resulting nitriles substituted with functional groups such as NH2, NO2,
2-phenyloxazoline became only 50% as the temperature was pyrazole were tolerated without eroding the product yields
raised up to 120 °C (entry 8). To optimize the molar ratio of (Table 3, entries 5, 8 and 10). The reaction of nitriles bearing
benzonitrile to 2-aminoalcohol, several ratios (1 : 1, 1 : 2, 1 : 3, heterocycles (such as isonicotinonitrile, nicotinonitrile) or
1 : 4, 1 : 5) were employed. As shown in Table 2, the ratio of 2-naphthonitrile performed significantly well to give good yields
benzonitrile to 2-aminoalcohol imposed important effects on (entries 6, 7 and 9). It seemed that 4-substituents of the
the yield of 2-phenyloxazoline. The yield of 2-phenyloxazoline benzene ring did not hamper the condensation reaction
was gradually increased from 18% to 90% as the ratio of (entry 2). However, this reaction was sensitive to the 3- and
benzonitrile to 2-aminoalcohol was raised from 1 : 1 to 1 : 4 2-substituent of the benzene ring and good or moderate yields
(entries 1 and 9–11) at 100 °C. Furthermore, the catalyst were obtained for 3-methylbenzonitrile (70–74% yield; entry 3)
loading may also affect the catalytic activity to some extent. and 2-methylbenzonitrile (38–45% yield; entry 4), which may
The product yield was gradually increased from 47% to 90% as be ascribed to the steric hindrance during the course of the
the ratio of benzonitrile to 1 was raised from 100 : 1 to 200 : 1 condensation reaction. As shown in entries 5 and 8, electron-
(entries 11, 13 and 14). The reaction time can influence deficient p-substituted aromatic nitriles were found to proceed
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Table 3 Synthesis of 2-oxazolines catalyzed by 1–3a
Yieldb (%)
Entry
1
Nitrile
Product
1
2
3
90
93
95
2
3
85
74
90
70
92
77
4
38
41
45
5
6
7
91
88
81
94
86
79
96
89
84
8
9
47
77
46
76
48
80
10
53
56
58
a Reaction conditions: nitrile (1.0 mmol), 2-aminoalcohol (4.0 mmol), and catalyst loading = 8 mol% [Cu] at 100 °C for 6 h. b Isolated yield.
Table 4 Comparison of efficiency of various catalysts in the synthesis of 2-phenyloxazoline
Entry
Catalysta
Solvent
Temperature
Time
Addition
Yield (%)
1
2
3
4
5
6
7
8
9
1
2
3
—
—
—
—
—
—
PhCl
PhCl
—
100 °C
100 °C
100 °C
100 °C
100 °C
130 °C
130 °C
100–130 °C
100 °C
100 °C
6 h
6 h
6 h
6 h
6 h
20 h
26 h
25 h
5 h
—
—
—
—
NaOAc
—
—
—
—
90
93
95
82
Cu(OAc)2·H2O
CuL12·H2O
Cd(OAc)2·2H2O
Cd(OAc)2·2H2O
ZnCl2
ZrOCl2·8H2O
SiO2–TPA
8311a
9223a
8923b
7223c
9024a
9024b
10
—
3 h
—
a L1 = methacrylate; TPA = 12-tungstophosphoric acid.
in higher yields than those with electron-donating substituent
As shown in Table 3, complex 3 exhibited more efficient
groups. For example, higher yield (entry 5) was obtained catalytic performance on the condensation of nitriles with
for 4-nitrobenzonitrile bearing electron-withdrawing sub- 2-aminoalcohol than 1 and 2, which may be due to the steric
stituent group relative to those of electron-donating ones hindrance caused by two bulky COOMe groups on the dcmpz
(entries 8–10).
ligands in 1 and 2. Table 4 lists a comparison of the results for
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reaction temperatures generated one tetranuclear Cu(II)/pyrazo-
late complex 1, one hexanuclear Cu(II)/pyrazolate complex 2,
and one tetranuclear Cu(II)/pyrazolate/carboxylate complex 3.
In these three cases, the protonolysis of Hdcmpz with OAc−
anion took place, and especially one of two esters on the
dcmpz− ligand in 3 was in situ hydrolyzed into the mcccpz2−
anion. It is rare that three Cu(II)/pyrazolate complexes with
different structures could be isolated from the same com-
ponents via controlling the reaction temperature. Because the
COOMe groups, COO− anions, MeOH molecules or OMe−
anions in 1–3 interact weakly with the Cu(II) centers, and are
readily replaced by organic substrates, complexes 1–3 displayed
high catalytic activity toward the condensation of nitriles with
2-aminoalcohol under solvent-free conditions to produce the
corresponding 2-oxazolines with high yields. It is anticipated
that this synthetic methodology reported here could be
applied in the rational design and assembly of other Cu(II)/
pyrazolate complexes with new structures and higher catalytic
activities. Studies in this respect are underway in our
laboratory.
Scheme 2 The possible Cu(II)-catalyzed mechanism for the synthesis of
2-oxazolines.
the condensation reaction of benzonitrile with 2-aminoalcohol
using different catalysts. Comparative run with Cu(OAc)2·H2O
under the same reaction conditions indicated that 1–3 exhibi-
ted better catalytic performance as the yields (90–95%) of the
resulting 2-phenyloxazoline obtained by 1–3 are higher than
that (82%) obtained by Cu(OAc)2·H2O (Table 4, entries 1–4).
The catalytic activities of 1–3 were also higher than that of
cupric methacrylate complex in the presence of NaOAc.11a
Comparing with ZnCl2,23c Cd(OAc)2·2H2O23a,b catalysts
(Table 4, entries 6–8), complexes 1–3 showed a higher conver-
sion in a shorter time at lower reaction temperatures. In the
cases of entries 9 and 10 (Table 4), two catalysts (ZrOCl2·
8H2O24a and 12-tungstophosphoric acid (TPA) supposed by
SiO224b) showed comparable catalytic activities on the conden-
sation reaction of benzonitrile with 2-aminoalcohol than those
of 1–3. As described earlier in this article, 1 and 2 were
obtained by reactions of Cu(OAc)2·H2O with Hdcmpz in MeOH
at room temperature or in refluxing MeOH while reactions of
Cu(OAc)2·H2O with Hdcmpz in MeOH at 120 °C produced 3,
which may indicate that 3 is more stable than 1 and 2 in solu-
tion. Thus the frameworks of 1 and 2 may not be retained
under our catalytic conditions (100 °C) because they could not
be recycled for further use.
Experimental section
General procedures
All reagents were used as purchased from commercial sources
without further purification. Hdcmpz25 and 4-(1H-pyrazol-3-yl)-
benzonitrile26 were prepared according to the published
procedures. 1H NMR and 13C NMR spectra were recorded at
ambient temperature on a Varian UNITYplus-300 spectro-
meter. Elemental analyses for C, H, and N were performed on
a Carlo-Erbo CHNO-S microanalyzer. The IR spectra (KBr disc)
were recorded on a Nicolet MagNa-IR550 FT-IR spectrometer
(4000–400 cm−1). High-resolution mass spectra were obtained
by using a Microma GCT-TOF instrument. The uncorrected
melting points were measured on a Mel-Temo II apparatus.
The powder X-ray diffraction (PXRD) measurements were
carried out on a PANalytical X’Pert PRO MPD system (PW3040/
60). Thermal analysis was performed with a Perkin Elmer
TGA-7 thermogravimetric analyzer at a heating rate of 10 °C
min−1 and a flow rate of 100 cm3 min−1 (N2).
The possible catalytic reaction mechanism11a for the above
reactions is proposed as follows (Scheme 2). Firstly, the nitrile
molecule replaces the COOMe group or MeOH molecule and
binds at the Cu(II) center of 1–3, producing the intermediate
I. Secondly, the intermediate I may combine 2-aminoalcohol
to give the intermediate II through the nucleophilic addition.
Thirdly, the intermediate II may undergo intramolecular cyclo-
addition to generate III. Thirdly, the intermediate III may elim-
inate the tandem reaction product that loses one equivalent of
NH3, producing the 2-oxazoline and thus furnishing the cata-
lytic cycle.
[{Cu2(μ-OAc)2}2(μ-dcmpz)2(μ-OAc)2]·3CH2Cl2 (1·3CH2Cl2)
To a MeOH (10 mL) solution of Cu(OAc)2·H2O (203 mg,
1.0 mmol) was added a MeOH solution of Hdcmpz (372 mg,
2.0 mmol). The mixture was stirred overnight at ambient temp-
erature to form a blue precipitate. After filtration, the solid was
extracted with 10 mL of CH2Cl2 and MeOH (v : v = 1 : 1) and fil-
tered again. 20 mL of Et2O was layered on the filtrate to afford
blue plates of 1·3CH2Cl2, which were isolated by filtration,
washed with MeOH and dried in air. Yield: 221 mg (89%
based on Cu). Anal. Calc. for C26H32Cu4N4O20: C, 30.04;
H, 3.31; N, 5.75%. Found: C, 30.46; H, 3.49; N, 5.36%. IR
(KBr disk): 1710 (s), 1687 (m), 1622 (s), 1580 (s), 1508 (w), 1487
Conclusions
In this paper, we have demonstrated that the reactions of (m), 1441 (s), 1347 (m), 1265 (s), 1224 (m), 1181 (w), 1069 (m),
Cu(OAc)2·H2O with Hdcmpz in MeOH at three different 826 (w), 772 (m), 682 (w), 623 (w), 490 (w) cm−1
.
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[{Cu2(µ-dcmpz)2}(µ-OMe)2]3 (2)
entry 1). Benzonitrile (104 mg, 1 mmol), amino alcohol
(245 mg, 4 mmol), and 1 (19 mg, 2 mol%) were mixed and
stirred for 6 h at 100 °C. After completion of the reaction, the
mixture was cooled to room temperature, diluted with ethyl
acetate (10 mL), and filtered. The filtrate was concentrated
in vacuo, and the resulting residue was purified by silica gel
chromatography to provide the desired product.
To a MeOH (10 mL) solution of Cu(OAc)2·H2O (198 mg,
1.0 mmol) was added a MeOH solution of Hdcmpz (366 mg,
2.0 mmol). The resulting solution was refluxed for 6 h to form
a larger amount of blue precipitate. A similar work-up to that
used in the isolation of 1 generated blue crystals of 2. Yield:
235 mg (85% based on Cu). Anal. Calc. for C48H60Cu6N12O30:
C, 34.60; H, 3.63; N, 10.09%. Found C, 34.86; H, 3.46;
N, 9.79%. IR (KBr disk): 1711 (s), 1687 (m), 1630 (w), 1583 (w),
1512 (w), 1469 (w), 1435 (m), 1407 (w), 1352 (w), 1261 (s),
1123 (w), 1171 (w), 1071 (s), 959 (w), 820 (m), 768 (s), 632 (w),
1
2-Phenyl-4,5-dihydrooxazole. Colorless oil; H NMR (CDCl3,
ppm, 300 Hz): δ 7.869–7.845 (d, 2H, J = 7.2 Hz, aromatic CH),
7.394–7.194 (m, 3H, aromatic CH), 4.342–4.279 (t, 2H, CH2),
3.978–3.915 (t, 2H, CH2). MS (ESI): m/z = 148.1 [M + 1]+.
2-(p-Tolyl)-4,5-dihydrooxazole. White solid; mp: 67–68 °C
(lit.11a mp 71–73 °C). 1H NMR (CDCl3, ppm, 300 Hz):
δ 7.847–7.820 (d, 2H, J = 8.1 Hz, aromatic CH), 7.222–7.196
(d, 2H, J = 7.8 Hz, aromatic CH), 4.442–4.379 (t, 2H, CH2),
4.072–4.009 (t, 2H, CH2), 2.384 (s, 3H, CH3). MS (EI): m/z =
162.1 [M + 1]+.
482 (w), 432 (w) cm−1
.
[{Cu(MeOH)}4(µ-mcccpz)4]·4MeOH (3·4MeOH·0.5H2O)
To a Pyrex glass tube (15 cm in length, 7 mm in inner dia-
meter) was added Cu(OAc)2·H2O (101 mg, 0.5 mmol), dcmpz
(188 mg, 1.0 mmol) and MeOH (2 mL). The tube was sealed
and heated in an oven at 120 °C for one day to form blue solu-
tion. The filtrate was kept at −18 °C for several days to form
crystalline solids of 3·4MeOH·0.5H2O, which were isolated by
filtration, washed with MeOH and dried in air. Yield: 40 mg
(30% based on Cu). Anal. Calc. for C28H28Cu4N8O20: C, 32.01;
H, 2.69; N, 10.66. Found C, 32.47; H, 2.46; N, 10.35%. IR (KBr
disk): 1694 (s), 1628 (s), 1516 (m), 1489 (w), 1435 (w), 1392 (w),
1339 (m), 1318 (w), 1286 (m), 1286 (m), 1228 (m), 1070 (s),
2-(m-Tolyl)-4,5-dihydrooxazole. Colorless oil; 1H NMR (CDCl3,
ppm, 300 Hz): δ 7.719 (s, 1H, aromatic CH), 7.696–7.663
(m, 1H, aromatic CH), 7.234–7.217 (m, 2H, aromatic CH),
4.380–4.317 (t, 2H, CH2), 4.008–3.945 (t, 2H, CH2), 2.315
(s, 3H, CH3). MS (EI): m/z = 162.1 [M + 1]+.
2-(o-Tolyl)-4,5-dihydrooxazole. Colorless oil; 1H NMR (CDCl3,
ppm, 300 Hz):
δ 7.884–7.829 (m, 1H, aromatic CH),
7.610–7.585 (d, 1H, aromatic CH), 7.493–7.452 (m, 1H,
aromatic CH), 7.389–7.242 (m, 1H, aromatic CH), 4.502–4.439
(t, 2H, CH2), 4.162–4.099 (t, 2H, CH2), 2.552 (s, 3H, CH3).
MS (EI): m/z = 162.1 [M + 1]+.
1022 (w), 950 (w), 842 (w), 773 (m), 625 (w), 513 (w) cm−1
.
Typical procedure for the synthesis of 2-oxazolines
2-(4-Nitrophenyl)-4,5-dihydrooxazole. Slightly yellow solid;
The procedures for the catalytic reactions are the same mp: 175–177 °C (lit.11a mp 180–181 °C). 1H NMR (CDCl3, ppm,
(Table 5). And a typical reaction is given below (Table 5, 300 Hz): δ 8.279–8.251 (d, 2H, J = 8.4 Hz, aromatic CH),
Table 5 Crystal data and the structure refinement parameters for 1·3CH2Cl2, 2, and 3·4MeOH·0.5H2O
Compounds
1·3CH2Cl2
2
3·4MeOH·0.5H2O
Formula
Formula weight
C29H38Cl6Cu4N4O20
1229.49
C48H60Cu6N12O30
1666.32
C64H90Cu8N16O49
2375.84
Crystal system
Space group
a/Å
b/Å
c/Å
α (°)
β (°)
Triclinic
P1
Triclinic
P1
Tetragonal
I41/a
15.5074(10)
15.5074(10)
19.8920(12)
ˉ
ˉ
12.3277(5)
13.9177(5)
14.9095(5)
69.705(3)
72.104(3)
87.298(3)
2278.11(15)
1.792
15.722(3)
16.304(3)
16.721(3)
95.39(3)
115.01(3)
114.83(3)
3327.6(11)
1.663
γ (°)
V/Å3
4783.6(5)
1.626
2
1.845
2352
Dc/(g cm−3
)
Z
2
2
μ (Mo Kα)/mm−1
F(000)
2.271
1236
1.976
1692
Total reflections
Unique reflections
No observations
No parameters
Rint
20 777
8452
6800
184 702
22 193
18 161
883
0.0325
0.0312
0.0772
1.040
35 860
3106
2337
576
157
0.0355
0.0439
0.1065
1.052
0.0516
0.0590
0.1780
1.068
Ra
wRb
GOFc
a R = ∑||Fo| − |Fc||/∑|Fo|. b wR = {∑w(Fo2 − Fc2)2/∑w(Fo2)2}1/2
number of parameters refined.
.
c GOF = {∑w((Fo2 − Fc2)2)/(n − p)}1/2, where n = number of reflections and p = total
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8.129–8.101 (d, 2H, J = 8.4 Hz, aromatic CH), 4.536–4.472 MeOH molecule was split into two sites with an occupancy
(t, 2H, CH2), 4.156–4.093 (t, 2H, CH2). MS (EI): m/z = 193.1 ratio of 0.5/0.5 for O(6)/O(6A) and C(8)/C(8A). The H2O mole-
[M + 1]+.
cule was refined to one-eighth-occupancy to give acceptable
2-(Pyridin-4-yl)-4,5-dihydrooxazole. White solid; mp: 106– thermal parameters. Except for O(6), C(8) atoms of MeOH
107 °C (lit.11a mp 111–112 °C). 1H NMR (CDCl3, ppm, 300 Hz): molecule and O(7) atom of H2O molecule in 3·4MeOH·0.5H2O,
δ 8.685–8.669 (d, 2H, J = 4.8 Hz, aromatic CH), 7.752–7.733 all non-hydrogen atoms were refined on F2 anisotropically by
(d, 2H, J = 5.7 Hz, aromatic CH), 4.469–4.405 (t, 2H, CH2), full-matrix least squares method. Hydrogen atoms of the dis-
4.095–4.031 (t, 2H, CH2). MS (EI): m/z = 149.1 [M + 1]+.
ordered MeOH molecule (O(6), C(8) and O(6A), C(8A)) and the
2-(Pyridin-3-yl)-4,5-dihydrooxazole. White solid; mp: 65– uncoordinated water molecule (O(7)) in 3·4MeOH·0.5H2O were
66 °C (lit.11a mp 68–69 °C). 1H NMR (CDCl3, ppm, 300 Hz): not located. The hydrogen atom of O(5) from the coordinated
δ 9.125 (s, 1H, aromatic CH), 8.682–8.669 (d, 1H, J = 3.9 Hz, MeOH molecule was firstly located from Fourier maps and
aromatic CH), 8.199–8.173 (d, 1H, J = 7.8 Hz, aromatic CH), subsequently the O–H bond was fixed to be 0.86 Å. All other
7.346–7.304 (m, 1H, aromatic CH), 4.468–4.404 (t, 2H, CH2), hydrogen atoms introduced at the calculated positions and
4.088–4.025 (t, 2H, CH2). MS (EI): m/z = 149.1 [M + 1]+.
included in the structure-factor calculations. A summary of the
4-(4,5-Dihydrooxazol-2-yl)aniline. Slightly yellow solid. mp: important crystallographic information for 1·3CH2Cl2, 2, and
1
156–158 °C (lit.27 mp 160–161 °C. H NMR (CDCl3, ppm, 300 3·4MeOH·0.5H2O are summarized in Table 5.
Hz): δ 7.752–7.724 (d, 2H, J = 8.4 Hz, aromatic CH), 6.657–
6.629 (d, 1H, J = 8.4 Hz, aromatic CH), 4.405–4.342 (t, 2H,
CH2), 4.028–3.966 (t, 2H, CH2). MS (EI): m/z = 163.1 [M + 1]+.
Acknowledgements
2-(Naphthalen-2-yl)-4,5-dihydrooxazole. White solid; mp:
1
83–85 °C (lit.28 mp 84–85 °C). H NMR (CDCl3, ppm, 300 Hz): The authors thanked the National Natural Science Foundation
δ 8.443 (s, 1H, aromatic CH), 8.058–8.029 (d, 1H, J = 8.7 Hz, of China (21171124 and 21171125), State Key Laboratory of
aromatic CH), 7.918–7.874 (m, 3H, aromatic CH), 7.543–7.483 Organometallic Chemistry, Shanghai Institute of Organic
(m, 2H, aromatic CH), 4.511–4.448 (t, 2H, CH2), 4.142–4.080 Chemistry, Chinese Academy of Sciences (201201006) for
(t, 2H, CH2). MS (EI): m/z = 198.1 [M + 1]+.
financial support. J. P. Lang also highly appreciated the
2-(4-(1H-Pyrazol-3-yl)phenyl)-4,5-dihydrooxazole. White solid; support for the Qin-Lan Project and the “333” Project of
mp: 167–169 °C. 1H NMR (CDCl3, ppm, 300 Hz): δ 7.988–7.961 Jiangsu Province, the Priority Academic Program Development
(d, J = 8.1 Hz, 2H), 7.826–7.799 (t, J = 8.1 Hz, 2H), 7.614 (s, 1H), of Jiangsu Higher Education Institutions, and the “SooChow
6.661 (s, 1H), 4.482–4.420 (t, 2H), 4.115–4.052 (t, 2H). 13C NMR Scholar” Program of Suzhou University. Bin Guo thanks the
(CDCl3, ppm, 75 MHz): δ 164.9, 149.4, 135.6, 132.7, 129.0, support of the College Students’ Innovative Undertaking Train-
127.3, 125.9, 103.5, 68.0, 55.2. HRMS calcd for C12H11N3O ing Program. The authors also greatly thanked the helpful
214.0975, Found 214.0966. Anal. Calcd for
C12H11N3O: comments from the editor and the reviewers.
C, 67.59, H, 5.20, N, 19.71. Found: C, 67.33, H, 4.95, N, 19.54.
X-ray structure determinations
References
X-ray quality crystals of 1·3CH2Cl2, 2, and 3·4MeOH·0.5H2O
were obtained directly from the above preparations. Single
crystals of 1·3CH2Cl2, 2, and 3·4MeOH·0.5H2O were mounted
on glass fibers with grease and cooled in a liquid nitrogen
stream at 200 K (1·3CH2Cl2 and 2) or 173 K (3·4MeOH·0.5H2O).
Crystallographic measurements were made on a Xcalibur
Atlas Gemini (1·3CH2Cl2), or Bruker APEX-II CCD (2 and
3·4MeOH·0.5H2O) diffractometer by using graphite-monochro-
mated Mo-Kα (λ = 0.71070 Å). Diffraction data were collected at
ω mode with a detector distance of 35 mm to the crystals. The
collected data were reduced by using the program CrysAlisPro,
Agilent Technologies (CrysAlis171. NET, Version 1.171.36.28) or
Bruker APEX2 and an absorption correction (multi-scan) was
applied. The reflection data were also corrected for Lorentz
and polarization effects.
1 (a) H. V. R. Dias, H. V. K. Diyabalanage, M. A. Rawashdeh-
Omary, M. A. Franzman and M. A. Omary, J. Am. Chem.
Soc., 2003, 125, 12072; (b) L. Lamarque, P. Navarro,
C. Miranda, V. J. Arán, C. Ochoa, F. Escartí, E. García-
España, J. Latorre, S. V. Luis and J. F. Miravet, J. Am. Chem.
Soc., 2001, 123, 10560; (c) J. Forniés, S. Fuertes, A. Martín,
V. Sicilia, E. Lalinde and M. T. Moreno, Chem.–Eur. J., 2006,
12, 8253; (d) L. Mathivathanan, J. Torres-King,
J. N. Primera-Pedrozo, O. J. García-Ricard, A. J. Hernández-
Maldonado, J. A. Santana and R. G. Raptis, Cryst. Growth
Des., 2013, 13, 2628; (e) J. Pons, F. J. Sanchez, J. Casabó,
A. Alvarez-Larena, J. F. Piniella and J. Ros, Inorg. Chem.
Commun., 2003, 6, 833; (f) J. Mukherjee and R. Mukherjee,
Dalton Trans., 2006, 1611.
The crystal structures of 1·3CH2Cl2, 2, and 3·4MeOH·
0.5H2O were solved by direct methods and refined on F2 by
full-matrix least-squares techniques with the SHELXTL-97
program.29 In 1·3CH2Cl2, one CH2Cl2 molecule was split into
two sites with an occupancy ratio of 0.5/0.5 for Cl(2)/Cl(2A)
and C(27)/C(27A). In 3·4MeOH·0.5H2O, the uncoordinated
2 (a) G. A. Ardizzoia, S. Cenini, G. L. Monica, N. Masciocchi
and M. Moret, Inorg. Chem., 1994, 33, 1458; (b) M. A. Omary,
M. A. Rawashdeh-Omary, H. V. K. Diyabalanage and
H. V. R. Dias, Inorg. Chem., 2003, 42, 8612; (c) G. A. Ardizzoia,
E. M. Beccalli, G. L. Monica, N. Masciocchi and M. Moret,
Inorg. Chem., 1992, 31, 2706; (d) K. Singh, J. R. Long and
15578 | Dalton Trans., 2013, 42, 15570–15580
This journal is © The Royal Society of Chemistry 2013

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Dalton Transactions
Paper
P. Stavropoulos, Inorg. Chem., 1998, 37, 1073; (e) S. F. Huang,
Y. C. Chou, P. Misra, C. J. Lee, S. Mohanta and H. H. Wei,
Inorg. Chim. Acta, 2004, 357, 1627; (f) M. Du, S. T. Chen,
Y. M. Guo, X. H. Bu and J. Ribas, J. Mol. Struct., 2005, 737,
17; (g) O. Das, T. Malakar, A. Mandal, A. Paul and
T. K. Paine, Chem.–Asian J., 2013, 8, 623; (h) G. A. Ardizzoia,
M. A. Angaroni, G. L. Monica, N. Masciocchi and M. Moret,
J. Chem. Soc., Dalton Trans., 1990, 2277.
3 (a) R. G. Raptis and J. P. Fackler Jr., Inorg. Chem., 1988, 27,
4179; (b) V. N. Tsupreva, A. A. Titov, O. A. Filippov,
A. N. Bilyachenko, A. F. Smol’yakov, F. M. Dolgushin,
D. V. Agapkin, I. A. Godovikov, L. M. Epstein and
E. S. Shubina, Inorg. Chem., 2011, 50, 3325; (c) F. B. Gong,
Q. Wang, J. Chen, Z. P. Yang, M. Liu, S. Y. Li and
G. Q. Yang, Inorg. Chem., 2010, 49, 1658; (d) K. Singh,
J. R. Long and P. Stavropoulos, J. Am. Chem. Soc., 1997, 119,
2942; (e) M. K. Ehlert, S. J. Rettig, A. Storr, R. C. Thompson
and J. Trotter, Can. J. Chem., 1990, 68, 1444.
4 (a) S. O. Malinkin, Y. S. Moroz, L. V. Penkova, V. V. Bon,
E. Gumienna-Kontecka, V. A. Pavlenko, V. I. Pekhnyo,
F. Meyer and I. O. Fritsky, Polyhedron, 2012, 37, 77;
(b) M. Stollenz, M. John, H. Gehring, S. Dechert, C. Grosse
and F. Meyer, Inorg. Chem., 2009, 48, 10049; (c) W. Z. Shen,
L. Yi, P. Cheng, S. P. Yan, D. Z. Liao and Z. H. Jiang, Inorg.
Chem. Commun., 2004, 7, 819; (d) S. G. Naik, A. Mukherjee,
R. Raghunathan, M. Nethaji, S. Ramasesha and
A. R. Chakravarty, Polyhedron, 2006, 25, 2135; (e) J. C. Jeffery,
P. L. Jones, K. L. V. Mann, E. Psillakis, J. A. McCleverty,
M. D. Ward and C. M. White, Chem. Commun., 1997, 175;
(f) P. E. Kruger, F. Launay and V. McKee, Chem. Commun.,
1999, 639; (g) H. Zhang, D. G. Fu, F. Ji, G. X. Wang, K. B. Yu
and T. Y. Yao, J. Chem. Soc., Dalton Trans., 1996, 3799;
(h) J. Klingele, A. I. Prikhod’ko, G. Leibeling, S. Demeshko,
S. Dechert and F. Meyer, Dalton Trans., 2007, 2003.
7 (a) S. Z. Zhan, M. Li, X. P. Zhou, J. H. Wang, J. R. Yang and
D. Li, Chem.Commun., 2011, 47, 12441; (b) L. Hou,
W. J. Shi, Y. Y. Wang, H. H. Wang, L. Cui, P. X. Chen and
Q. Z. Shi, Inorg. Chem., 2011, 50, 261; (c) L. L. Zheng,
J. D. Leng, S. L. Zheng, Y. C. Zhaxi, W. X. Zhang and
M. L. Tong, CrystEngComm, 2008, 10, 1467; (d) A. Cingolani,
S. Galli, N. Masciocchi, L. Pandolfo, C. Pettinari and
A. Siron, J. Am. Chem. Soc., 2005, 127, 6144; (e) X. H. Zhou,
Y. H. Peng, Z. G. Gu, J. L. Zuo and X. Z. You, Inorg. Chim.
Acta, 2009, 362, 3447; (f) F. B. Hulsbergen,
R. W. M. t. Hoedt, G. C. Verschoor, J. Reedijk and
A. L. Spek, J. Chem. Soc., Dalton Trans., 1983, 539.
8 (a) J. H. Wang, M. Li and D. Li, Chem. Sci., 2013, 4, 1793;
(b) J. P. Zhang and S. Kitagawa, J. Am. Chem. Soc., 2008,
130, 907; (c) V. Colombo, S. Galli, H. J. Choi, G. D. Han,
A. Maspero, G. Palmisano, N. Masciocchic and J. R. Long,
Chem. Sci., 2011, 2, 1311; (d) P. King, R. Clérac,
C. E. Anson, C. Coulon and A. K. Powell, Inorg. Chem.,
2003, 42, 3492; (e) A. Tăbăcaru, C. Pettinari, N. Masciocchi,
S. Galli, F. Marchetti and M. Angjellari, Inorg. Chem., 2011,
50, 11506; (f) E. Q. Procopio, T. Fukushima, E. Barea,
J. A. R. Navarro, S. Horike and S. Kitagawa, Chem.–Eur. J.,
2012, 18, 13117.
9 (a) M. Casarin, C. Corvaja, C. d. Nicola, D. Falcomer,
L. Franco, M. Monari, L. Pandolfo, C. Pettinari, F. Piccinelli
and P. Tagliatesta, Inorg. Chem., 2004, 43, 5865;
(b) S. Contaldi, C. D. Nicola, F. Garau, Y. Y. Karabach,
L. M. D. R. S. Martins, M. Monari, L. Pandolfo, C. Pettinari
and A. J. L. Pombeiro, Dalton Trans., 2009, 4928;
(c) M. Casarin, A. Cingolani, C. D. Nicola, D. Falcomer,
M. Monari, L. Pandolfo and C. Pettinari, Cryst. Growth Des.,
2007, 7, 676; (d) A. Sachse, G. Noël, S. Dechert,
S. Demeshko, A. Honecker, A. Alfonsov, V. Kataev and
F. Meyer, Eur. J. Inorg. Chem., 2008, 5390.
5 (a) T. Jozak, Y. Sun, Y. Schmitt, S. Lebedkin, M. Kappes, 10 (a) M. Wanner, T. Sixt, K. W. Klinkhammer and W. Kaim,
M. Gerhards and W. R. Thiel, Chem.–Eur. J., 2011, 17, 3384;
(b) G. F. Gao, M. Li, S. Z. Zhan, Z. Lv, G. H. Chen and D. Li,
Chem.–Eur. J., 2011, 17, 4113; (c) E. M. Zueva, M. M. Petrova,
R. Herchel, Z. Trávníček, R. G. Raptis, L. Mathivathanan
Inorg. Chem., 1999, 38, 2753; (b) J. Chin and V. Jubian,
J. Chem. Soc., Chem. Commun., 1989, 839; (c) Z. L. Xu,
H. X. Li, Z. G. Ren, W. Y. Du, W. C. Xu and J. P. Lang, Tetra-
hedron, 2011, 67, 5282.
and J. E. McGrady, Dalton Trans., 2009, 5924; (d) L. F. Jones, 11 (a) X. N. Li, B. Y. Zhou, J. Zhang, M. Y. She, S. J. An,
C. A. Kilner, M. P. d. Miranda, J. Wolowska and
M. A. Halcrow, Angew. Chem., Int. Ed., 2007, 46, 4073;
(e) A. A. Mohamed, S. Ricci, A. Burini, R. Galassi,
C. Santini, G. M. Chiarella, D. Y. Melgarejo and J. P. Fackler
Jr., Inorg. Chem., 2011, 50, 1014.
H. X. Ge, C. Li, B. Yin, J. L. Li and Z. Shi, Eur. J. Org. Chem.,
2012, 1626; (b) A. J. Phillips, Y. Uto, P. Wipf, M. J. Reno and
D. R. Williams, Org. Lett., 2000, 2, 1165; (c) J. M. Benito,
C. A. Christensen and M. Meldal, Org. Lett., 2005, 7, 581.
12 (a) P. Wipf and X. D. Wang, J. Comb. Chem., 2002, 4, 656;
(b) J. A. Seijas, M. P. Vazquez-Tato and J. Crecente-Campo,
Tetrahedron, 2008, 64, 9280.
6 (a) M. Stollenz, C. Groβe and F. Meyer, Chem. Commun.,
2008, 1744; (b) G. Mezei, P. Baran and R. G. Raptis, Angew.
Chem., Int. Ed., 2004, 43, 574; (c) G. A. Ardizzoia, 13 (a) C. A. Busacca, Y. Dong and E. M. Spinelli, Tetrahedron
M. A. Angaroni, G. L. Monica, F. Cariati, S. Cenini,
M. Moret and N. Masciocchi, Inorg. Chem., 1991, 30, 4347;
Lett., 1996, 37, 2935; (b) B. Ilkgl, D. Gunes, O. Sirkecioglu
and N. Bicak, Tetrahedron Lett., 2010, 51, 5313.
(d) J. P. Tong, X. J. Sun, J. Tao, R. B. Huang and L. S. Zheng, 14 I. Mohammadpoor-Baltork, M. Moghadam, S. Tangestaninejad,
Inorg. Chem., 2010, 49, 1289; (e) K. Sakai, Y. Yamada,
T. Tsubomura, M. Yabuki and M. Yamaguchi, Inorg. Chem.,
V. Mirkhani and S. Fatemeh Hojati, Catal. Commun., 2008,
9, 1153.
1996, 35, 542; (f) J. J. Henkelis, L. F. Jones, M. P. d. Miranda, 15 A. R. Katritzky, C. M. Cai, K. Suzuki and S. K. Singh, J. Org.
C. A. Kilner and M. A. Halcrow, Inorg. Chem., 2010, 49,
Chem., 2004, 69, 811.
11127.
16 M. Ishihara and H. Togo, Tetrahedron, 2007, 63, 1474.
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 15570–15580 | 15579

View Article Online
Paper
Dalton Transactions
17 A. Sakakura, R. Kondo and K. Ishihara, Org. Lett., 2005, 7, 23 (a) T. Bodner, L. Ellmaier, V. Schenk, J. Albering and
1971.
F. Wiesbrock, Polym. Int., 2011, 60, 1173; (b) S. Kumar,
K. Kandasamy, H. B. Singh and R. J. Butcher, New J. Chem.,
2004, 28, 640; (c) H. Witte and W. Seeliger, Angew. Chem.,
Int. Ed. Engl., 1972, 11, 287.
18 X. Fernandez, R. Fellous and E. Duñach, Tetrahedron Lett.,
2000, 41, 3381.
19 Z. L. Xu, H. X. Li, Z. G. Ren, W. Y. Du, W. C. Xu and
J. P. Lang, Tetrahedron, 2011, 67, 5282.
20 (a) C. D. Nicola, Y. Y. Karabach, A. M. Kirillov, M. Monari,
L. Pandolfo, C. Pettinari and A. J. L. Pombeiro, Inorg.
Chem., 2007, 46, 221; (b) C. D. Nicola, F. Garau,
24 (a) I. Mohammadpoor-Baltork, A. R. Khosropour and
S. F. Hojati, Catal. Commun., 2007, 8, 200; (b) I. Mohammadpoor-
Baltork, M. Moghadam, S. Tangestaninejad, V. Mirkhani
and S. F. Hojati, Polyhedron, 2008, 27, 750.
Y. Y. Karabach, L. M. D. R. S. Martins, M. Monari, 25 J. L. Chou, J. P. Chyn, F. L. Urbach and D. F. Gervasio,
L. Pandolfo, C. Pettinari and A. J. L. Pombeiro, Eur. J. Inorg.
Chem., 2009, 666.
21 A. Maspero, S. Brenna, S. Galli and A. Penoni, J. Organomet.
Chem., 2003, 672, 123.
Polyhedron, 2000, 19, 2215.
26 S. R. Batten, M. B. Duriska, P. Jensen and J. Z. Lu,
Aust. J. Chem., 2007, 60, 72.
27 M. T. Leffler and R. Adams, J. Am. Chem. Soc., 1937, 59, 2252.
22 (a) H. X. Li, Z. G. Ren, D. Liu, Y. Chen, J. P. Lang, 28 P. J. Boissarie, Z. E. Hamilton, S. Lang, J. A. Murphy and
Z. P. Cheng, X. L. Zhu and B. F. Abrahams, Chem. C. J. Suckling, Org. Lett., 2011, 13, 6256.
Commun., 2010, 46, 8430; (b) L. L. Miao, H. X. Li, M. Yu, 29 (a) G. M. Sheldrick, SHELXS-97, University of Göttingen:
W. Zhao, W. J. Gong, J. Gao, Z. G. Ren, H. F. Wang and
Göttingen, Germany, 1997; (b) G. M. Sheldrick, SHELXL-97,
J. P. Lang, Dalton Trans., 2012, 41, 3424.
University of Göttingen: Göttingen, Germany, 1997.
15580 | Dalton Trans., 2013, 42, 15570–15580
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