From a simple pyrazole-derived 1,2-amino alcohol to mono- and multinuclear complexes by tailoring hydrogen bond patterns

Article abstract of DOI:10.1002/ejic.201001231

Starting from easily accessible ethyl-5(3)-methylpyrazole-3(5)-carboxylate, 2-[(1,5-dimethyl)pyrazol-3-yl]propan-2-ol (3) can be obtained in good yields in just two steps. The latter compound undergoes coordination to a series of transition metal ions; the resulting complexes were characterized by means of spectroscopy and magnetic measurements.

Full text of DOI:10.1002/ejic.201001231

FULL PAPER
DOI: 10.1002/ejic.201001231
From a Simple Pyrazole-Derived 1,2-Amino Alcohol to Mono- and
Multinuclear Complexes by Tailoring Hydrogen Bond Patterns
Christoph K. Seubert,[a] Yu Sun,[a] Yanhua Lan,[b] Annie K. Powell,[b] and
Werner R. Thiel*[a]
Keywords: Coordination chemistry / Hydrogen bonds / N ligands / Multinuclear complexes / Magnetic properties / Amino
alcohols
Starting from easily accessible ethyl-5(3)-methylpyrazole-
3(5)-carboxylate, 2-[(1,5-dimethyl)pyrazol-3-yl]propan-2-ol
(3) can be obtained in good yields in just two steps. The latter
compound undergoes coordination to a series of transition
metal ions; the resulting complexes were characterized by
means of spectroscopy and magnetic measurements.
Introduction
5(3)-methylpyrazole-3(5)-carboxylate (1).[7] The intermedi-
ate 2 had already been described in the literature, but the
published routes either gave a mixture of two regioiso-
mers[8] or used complex starting materials.[9]
Amino alcohols have found wide applications as ligands
in coordination chemistry for quite some time. They have
been used in enantioselective catalysis[1] as well as for
Metal-Organic Chemical Vapour Deposition[2] and other
purposes. In the past, we established an efficient method
to generate enantiomerically pure chiral 1,3-amino alcohols
bearing a pyrazole donor by the ring opening of epoxides,
followed by an enzymatic kinetic resolution. However, 1,2-
amino alcohols with a pyrazole fragment as the N-donor
site have rarely been reported in the literature, although the
pyrazole moiety allows the simple introduction of electron
donating or withdrawing substituents and thus enables a
fine-tuning of the electronic properties of the ligand.[3] They
can be accessed by [2+3] cycloaddition reactions of diazo-
methane to functionalised prop-1-en-2-ols[4] and used for
pharmaceutical applications.[5] Only a few metal complexes
carrying a hydroxymethylpyrazole as the chelating ligand
have been reported until now, most are coordinated with a
hydroxymethyl-functionalised pyrazolylborate ligand.[6]
Herein we present a rapid and non-toxic route to a novel
3-hydroxymethyl functionalised pyrazole and a series of
transition metal complexes derived from this ligand.
Scheme 1. I) NaH, CH3I, THF, room temp., 16 h; ii) MeMgCl,
THF, reflux., 16 h (this step was carried out twice).
Based on experiments on the regioselective N-alkylation
of pyrazolylpyridines[10] and 3-(2-hydroxyphenyl)pyr-
azole[11] it seemed likely that by deprotonation of the pyr-
azole NH unit of 1 with NaH and subsequent alkylation of
the resulting anion with CH3I, the desired regioisomer 2
should be accessible with high selectivity. Whenever there is
a chance for a pyrazolide anion to undergo chelation to a
metal cation (here Na+), alkylation occurs at the “free” ni-
trogen atom. As expected only traces of the undesired re-
gioisomer were formed, proving that even in the presence
of a rather poor donor, such as an ester group, this strategy
works.
Results and Discussion
Ligand Synthesis and Characterization
As outlined in Scheme 1, the synthesis of ligand 3 follows
a two-step procedure starting from easily available ethyl-
The proton at the 4-position at the pyrazole ring of 2
shows the typical shift to higher field (δ = 6.34 ppm) in the
1H NMR spectrum compared with that of 1, the two methyl
groups attached to the pyrazole ring can clearly be distin-
[a] Fachbereich Chemie, TU Kaiserslautern,
Erwin-Schrödinger-Str. Geb. 54, 67663 Kaiserslautern,
Germany
Fax: +49-631-2054647
E-mail: thiel@chemie.uni-kl.de
[b] Karlsruher Institut für Technologie (KIT), Institut für
Anorganische Chemie,
1
guished by their specific chemical shifts in the H NMR
spectrum [δ = 3.65 (NCH3) and 2.10 ppm (5-CH3)] and in
the 13C NMR spectrum [δ = 36.5 (NCH3) and 10.7 ppm (5-
CH3)].
Engesserstr. 15, 76131 Karlsruhe, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201001231.
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Tailoring of Hydrogen Bond Patterns
The desired 2-[(1,5-dimethyl)pyrazol-3-yl]propan-2-ol (3)
The treatment of two equivalents of 3 with the labile ben-
was prepared by treating 2 with an excess of MeMgCl in zonitrile complex Pd(PhCN)2Cl2 in CH2Cl2 solution gave
THF, a procedure that was required to be repeated since the desired palladium(II) complex 4 as a yellow solid. It
after the first conversion compound 3 was obtained in a was characterized by IR and NMR spectroscopies and ele-
mixture with a large amount of methyl (1,5-dimethylpyr- mental analysis. In the IR spectrum, the OH stretching fre-
azol-3-yl) ketone. The 1H NMR spectrum (CDCl3) of 3 ex- quency was observed at 3468 cm–1, indicating a stronger
hibits four singlets in a 6:3:3:1 ratio at δ = 1.43, 2.12, 3.60 OH bond due to a weaker hydrogen bond compared with
1
and 5.83 ppm corresponding to the C(OH)(CH3)2, CpzCH3, the free ligand 3. Whereas the H NMR resonance of the
NCH3 and Cpz–H protons, respectively. Highly pure 3 can proton in the 4-position of the pyrazole ring stays almost
be obtained by sublimation, leading directly to single crys- unaffected (δ = 5.94 ppm), all other resonances are shifted
tals suitable for X-ray diffraction analysis (Figure 1).
to lower field compared with 3, the signal of the NCH3
group (δ = 4.66 ppm) is shifted by more than 1 ppm.
Crystallization from CHCl3/Et2O resulted in the formation
of yellow prisms suitable for X-ray structure analysis (Fig-
ure 2).
Figure 2. Molecular structure of 4 in the solid state; characteristic
bond lengths [Å], angles [°] and dihedral angles [°]: Pd1–Cl1
2.3102(4), Pd1–N1 2.0138(13), O1–H1O 0.84, H1O···Cl1 2.45,
O1···Cl1 3.1844(12), Cl1–Pd1–N1 91.23(3), Cl1–Pd1–N1a 88.77(3),
O1–H1O···Cl1 146.00, Cl1–Pd1–N1–N2 –104.47(9), Cl1–Pd1–N1–
C1 83.61(12), Pd1–N1–C1–C6 –4.6(2), N1–C1–C6–O1–21.71(18).
Figure 1. Molecular structure of 3 in the solid state (top), forma-
tion of chains by hydrogen bonds (bottom). Characteristic lengths
[Å] and angles [°] of the hydrogen bond: O1–H1O 0.84, H1O···N2
2.10, O1···N2 2.930(2), O1–1O···N2 169.00.
As expected, the palladium(II) centre is coordinated in a
square-planar geometry with the two pyrazole ligands in a
trans orientation. There is no coordination of the hydroxy
groups, they undergo intramolecular hydrogen bond forma-
tion with the chloro ligands. This mode of coordination is
consistent with reports in the literature; compounds of the
type (pyrazole)2PdCl2 are generally found in trans geome-
try[13] except in systems in which pyrazole rings are part of
a macrocycle.[14] All bond parameters of 4 are in agreement
with data from the literature.[13] The metal site of 4 is lo-
cated in a centre of inversion, leading to a coplanar orienta-
tion of the two pyrazole rings. The rather long distance
H1O···Cl1 (2.45 Å) is consistent with a moderate to weak
hydrogen bond.[12]
The X-ray structure analysis proved that the desired re-
gioisomer was formed. As shown in Figure 1, compound 3
forms chains by intermolecular hydrogen bonds between
the OH group and the N2 atom of the pyrazole ring. The
OH proton is not located in the plane of the pyrazole ring,
it forms an angulated hydrogen bond of moderate
strength[12] corroborating the low melting and sublimation
temperatures of compound 3. Typically for alcohols under-
going hydrogen bonding, a strong absorption at 3353 cm–1
is observed in the IR spectrum of compound 3; the C=O
absorption of the starting material is no longer present.
Synthesis, Characterization and Molecular Structures of the
Metal Complexes
The reaction of two equivalents of 3 with CuCl2 in ace-
tone solution afforded a green solid. After recrystallization
To investigate the coordination chemistry of compound from CHCl3/Et2O the copper(II) complex 5 could be iso-
3, the ligand was treated with a series of different transition lated in 76% yield as green prisms suitable for X-ray struc-
metal dichlorides in a 2:1 ratio in appropriate solvents. ture analysis (Figure 3). Again, two ligands are coordinated
Since the ligand is able to coordinate in a mono- and a to the metal centre. Here, however, the ligands are found
bidentate fashion and also provides an OH proton for hy- in a bidentate N,O-coordination mode resulting in a five
drogen bond formation, a variety of different coordination coordinate cationic metal centre with the additional chlo-
geometries depending on the metal site could be expected.
ride ion as the counter anion. This is in contrast to the
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C. K. Seubert, Y. Sun, Y. Lan, A. K. Powell, W. R. Thiel
FULL PAPER
dichloro copper complex of the ligand trans-2-pyrazol-1-yl-
The reaction of two equivalents of 3 with CoCl2·(H2O)6
cyclohexan-1-ol,[15] in which a distorted octahedral coordi- or NiCl2·(H2O)6 in methanol afforded blue 6 and green 7 in
nation environment is observed. This may be due to an en- 87 and 83% yield, respectively, after recrystallization from
hanced steric hindrance caused by the substitution pattern MeOH/Et2O. Both compounds are isostructural and crys-
at the pyrazole ring of 3 and by the smaller ring size of the tallize in the monoclinic space group P21/n with nearly
resulting metallacycle. The coordination geometry of the identical cell parameters and interatomic distances and
copper(II) ion in 5 is neither square pyramidal nor trigonal angles. A similar behaviour was previously observed for the
bipyramidal (τ = 0.501) but almost exactly in the middle dichlorocobalt(II) and dichloronickel(II) complexes of 3(5)-
between these two geometries. Until now cationic cop- (4-methoxyphenyl)pyrazole.[18] In the following section, the
per(II) complexes of the type [CuO2N2Cl]+ have only been solid-state structure of the cobalt(II) complex 6 (Figure 4)
described with pyridine as the N-donor ligand.[16] In com- shall be discussed; the structural data of the nickel(II) com-
pound 5, the two nitrogen atoms as well as the two oxygen plex 7 can be found in the Supporting Information.
donor atoms are located in positions trans to each other.
The Cu–N1/Cu–N3/Cu–O/Cu–Cl distances are typical for
copper pyrazole/alcohol/chloro complexes.[15–17] By hydro-
gen bond formation between the OH groups and the chlo-
ride anions, a polymeric chain structure is established as
shown in Figure 3.
Figure 4. Solid state structure of 6, the inset shows the view along
the Co1···Co2 axis. Characteristic bond lengths [Å], angles [°]:
Co1–O1 2.105(3), Co1–O2 2.080(3), Co1–O3 2.100(3), Co1–N1
2.109(3), Co1–N3 2.109(3), Co1–N5 2.088(3), Co2–Cl1 2.2811(13),
Co2–Cl2 2.2982(12), Co2–Cl3 2.2875(10), Co2–Cl4 2.2525(11),
O1–H1O 0.843(19), H1O···Cl1 2.26(2), O1···Cl1 3.096(3), O2–H2O
0.84(3), H2O···Cl2 2.25(3), O2···Cl2 3.090(3), O3–H3O 0.83(3),
H3O···Cl3 2.28(3), O3···Cl3 3.105(3), O1–Co1–O2 90.68(11), O1–
Co1–O3 86.89(10), O1–Co1–N1 74.68(10), O1–Co1–N3
166.09(12), O1–Co1–N5 93.27(11), O2–Co1–O3 90.73(10), O2–
Co1–N1 95.46(11), O2–Co1–N3 75.43(11), O2–Co1–N5
165.50(10), O3–Co1–N1 160.58(12), O3–Co1–N3 93.69(12), O3–
Co1–N5 75.59(10), N1–Co1–N3 105.68(13), N1–Co1–N5
99.04(12), N3–Co1–N5 100.34(11), Cl3–Co2–Cl4 110.04(5), Cl1–
Co2–Cl4 111.70(4), Cl1–Co2–Cl2 110.39(5), Cl1–Co2–Cl3
107.33(4), Cl2–Co2–Cl3 109.17(5), Cl2–Co2–Cl4 108.19(4), O1–
H1O···Cl1 172(3), O2–H2O···Cl2 175(3), O3–H3O···Cl3 177(3).
The crystal structure revealed that the expected complex
Figure 3. Molecular structure of 5 in the solid state including chain with two bidentate coordinated ligand molecules and two
formation by hydrogen bonds. Characteristic bond lengths [Å],
chloride ligands was not formed. Here one octahedrally co-
angles [°] and dihedral angles [°]: Cu1–Cl1 2.2426(7), Cu1–O1
ordinated [CoL3]2+ cation is accompanied by a [CoCl4]2–
2.044(2), Cu1–O2 2.138(2), Cu1–N1 1.977(2), Cu1–N3 1.961(2),
anion. The nitrogen atoms of the three chelate ligands are
O1–H1O 0.83(3), H1O···Cl2 2.14(3), O1···Cl2 2.950(2), O2–H2O
found coordinating facially and the three oxygen atoms are
located on the opposite triangle of the octahedron. Thus,
the OH groups form a tridentate binding pattern for proton
acceptors allowing hydrogen bonds to three chloride li-
gands of the tetrachlorocobaltate(II) anion. The distances
H1O···Cl1 (2.26 Å), H2O···Cl2 (2.25 Å) and H3O···Cl3
0.804(19), H2O···Cl2 2.20(2), O2···Cl2 2.989(2), Cl1–Cu1–O1
134.20(7), Cl1–Cu1–O2 120.48(7), Cl1–Cu1–N1, 98.86(7), Cl1–
Cu1–N3 96.86(6), O1–Cu1–O2 105.23(9), O1–Cu1–N1 77.83(9),
O1–Cu1–N3 90.45(9), O2–Cu1–N1 96.18(9), O2–Cu1–N3 76.58(9),
N1–Cu1–N3 164.25(9), Cu1–O1–C6 118.83(15), Cu1–O2–C14
117.75(16), Cu1–O1–H1O 131(2), Cu1–O2–H2O 124(2), O1–
H1O···Cl2 168(3), O2–H2O···Cl2 168(3).
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Tailoring of Hydrogen Bond Patterns
(2.28 Å) and the corresponding angles O1–H1O···Cl1 spin-only cobalt(II) ions (S = 3/2) as a result of the strong
(172°), O2–H2O···Cl2 (175.2°) and O3–H3O···Cl3 (177°) orbital contribution. The behaviour of the χT curve is typi-
are consistent with weak to moderate hydrogen bonds.[12] cal of the spin-orbital coupling effect in which the χT prod-
The blue colour of crystalline 6 is typical for tetrahedrally uct continuously decreases on lowering the temperature.
coordinated cobalt(II) sites, such as Co2. The blue crystals, Furthermore, a small upturn observed in the χT value be-
however, formed directly from a pink coloured solution. low 2.7 K could be due to either the presence of a weak
This colour is typical for octahedrally coordinated co- ferromagnetic interaction between the cobalt(II) centres
balt(II) in a weak ligand field. From this observation one through the hydrogen bonding or the slight canting between
can conclude, that the tetrachlorocobaltate(II) ion is formed the two asymmetric cobalt(II) centres. The phenomenon of
during the crystallization process by a templating effect of spin canting, however, is not evidenced by either the M vs.
the cation.
H or the AC measurements, in which the critical tempera-
As expected, the Co2–Cl distances of the chloride ligands ture might be too low to be observable in these measure-
involved in hydrogen bonds are slightly longer (0.03– ments.
0.05 Å) than Co–Cl4, leading to a slightly distorted tetrahe-
dral coordination geometry of the [CoCl4]2– anion. The co-
ordination geometry of the Co1 site can be best explained
as a distorted, facially coordinated A3B3Co octahedron flat-
tened along the vector connecting the centroids of the nitro-
gen and the oxygen triangle. Whereas there is a whole series
of solid-state structures containing the tetrachlorocobalt-
ate(II) anion, in only a few is a threefold hydrogen-bonding
situation found.[19] For the tetrachloronickelate(II) anion in
complex 7, no similar hydrogen-bonding pattern has been
described until now.[20] There are some examples for fac-
N3O3M systems (M = Co, Ni) containing macrocyclic ni-
Figure 5. The plots of χT against T under a field of 1000 Oe for
trogen donor sites with three OH groups in side chains,[21]
compounds 6 and 7.
and some fac-N3O3Ni systems containing aromatic N-do-
nor sites in combination with alcohols.[22] Additionally,
The reaction of two equivalents of 3 with ZnCl2 in ace-
tone afforded a colourless solid. After recrystallization from
a mixture of CHCl3/CH2Cl2/Et2O, the zinc(II) complex 8
could be isolated in 92% yield as colourless prisms suitable
for X-ray diffraction. In this case, only one equivalent of
the N,O-chelate ligand coordinates to the metal centre, the
solid-state structure of 8 is shown in Figure 6.
there is one nickel complex with hydroxiquinoline as the
N,O-donor showing a hydrogen bond motif similar to 7.[22b]
Therein, a fac-tris(8-quinolinol)nickel(II) cation forms three
hydrogen bonds to a neighbouring fac-tris(8-quinolinolato)-
nickel(II) anion leading to a dimeric pelton wheel-like struc-
ture. The Ni–O and Ni–N distances are in complete agree-
ment with the data of 6 and 7. In contrast, 2-hydroxy-
methylpyridine coordinates in a meridional geometry to
nickel(II).[22d] It therefore seems likely that under certain
conditions, a templating effect leads to the fac-A3B3M
geometry found in the solid-state structures of 6 and 7. We
2–
will now investigate the exchange of the MCl4 anions
against other systems (e.g., SO42–, PO43–, etc.) that are able
to undergo hydrogen bonding with three proton-donating
sites.
From the structural point of view, no magnetic interac-
tion between the two paramagnetic centres should be pres-
ent as no obvious bridges suitable for superexchange are
present; the cation and the anion are linked together
through hydrogen bonds. To get an insight into the influ-
ence of the hydrogen bonding on the magnetic properties
of 6 and 7, magnetic measurements were carried out (Fig-
ure 5). The dc magnetic susceptibility data of the binuclear
NiII complex 7 shows that this compound is likely to be
paramagnetic over the whole temperature range. A slightly
temperature-dependent slope of the χT product is a conse-
quence of the significant contribution of the single-ion an-
isotropy of NiII ions. For the binuclear cobalt(II) complex
6, the room temperature χT of 5.73 cm3 Kmol–1 is much
Figure 6. Solid state structure of 8. Characteristic bond lengths [Å],
angles [°] and dihedral angles [°]: Zn1–Cl1 2.2219(7), Zn1–Cl2
2.1905(6), Zn1–O1 2.0579(16), Zn1–N1 1.9986(17), O1–H1O
0.78(2), H1O···Cl1 2.29(2), O1···Cl1 3.0590(17), Cl1–Zn1–Cl2
120.09(3), Cl1–Zn1–O1 109.37(5), Cl1–Zn1–N1 112.43(5), Cl2–
Zn1–O1 110.91(5), Cl2–Zn1–N1 117.97(6), O1–Zn1–N1 77.85(6),
higher than the expected value of 3.75 cm3 Kmol–1 for two O1–H1O···Cl1 170(2), N1–C1–C6–O1 –19.8(3).
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The hydrogen bonding between the OH group and one ligand. For the palladium complex 4, the resonance of the
of the chloro ligands of another zinc centre leads to the NCH3 group is observed at δ = 4.66 ppm, indicating an
formation of centrosymmetric dimers as shown in Figure 6. interaction of this methyl group with the empty d-orbital
The distance Zn–Cl1 is about 3 pm longer than Zn–Cl2 as of the 16VE palladium site. This interaction is probably en-
a result of the hydrogen bond. The H1O···Cl1 distance hanced by the intramolecular Cl···HO hydrogen bond fixing
(2.286 Å) and the angle O1–H1O···Cl1 (170.5°) are typical the pyrazole moiety in a position almost perpendicular to
for weak to moderate hydrogen bonds.[12] To the best of our the N2Cl2-plane. Following the order 3, 4, and 8, the OH
knowledge, compound 8 is the first example of a structur- group switches from an intermolecular proton donor (δ =
ally characterized tetrahedrally coordinated zinc complex of 3.44 ppm) to an intramolecular one (δ = 4.04 ppm) and
the type ZnCl2(N···OH) in which an amino alcohol ends up in a combination of an intermolecular proton do-
(N···OH) acts as a chelating ligand, although there is one nor site and an O–M donor (δ = 6.10 ppm), which corre-
example of a zinc compound with 2-(2-hydroxyethylamino)- lates well with the chemical shift of the OH proton.
6-benzylamino-9-methylpurine in a bridging coordination
The OH absorptions of the coordinated pyrazolyl
mode leading to a coordination polymer,[23] and some ex- alcohol ligands in different chemical environments, mea-
amples of five- and six-coordinate zinc dichloride com- sured in CH3CN solution do not differ distinctively in their
plexes with amino alcohols.[24] Steric reasons could account energies (see the Exp. Section). The free ligand shows an
for this behaviour; the two methyl groups at the 2-hydroxy- absorption (3526 cm–1) that is shifted slightly (by 14–
2-propyl moiety and the N–CH3 group of a second amino 18 cm–1) towards lower wavenumbers compared with the
alcohol will interfere with each other in a zinc complex of coordinated systems.
the type ZnCl2(N···OH)2.
Conclusion
Spectroscopy
The ligand 2-[(1,5-dimethyl)pyrazol-3-yl]propan-2-ol
Although NMR spectroscopic data could only be ob-
tained for ligand 3, the palladium complex 4 and the zinc
complex 8, since the copper, cobalt and nickel complexes
5–7 are paramagnetic, the comparison of their data allows
some correlations with the steric and electronic situation of
the N,O-donor under different environments. Table 1 sum-
turned out to be an easily accessible N,O-chelate for a series
of transition metal ions. Depending on the metal site and
its ligand environment, the OH group can undergo intra- or
intermolecular hydrogen bonding. For six-coordinate metal
sites, the facial arrangement of the three N-donors leads to
a facial arrangement of the OH groups, which are in an
ideal situation for cooperatively binding small tetrahedral
anions by O–H···X interactions.
1
marises the H and 13C NMR resonances of these species
according to the rules of nomenclature.
Table 1. NMR spectroscopic data (1H und 13C[a] NMR δ values,
ppm) of compounds 3, 4 and 8.
Experimental Section
General: All manipulations were carried out under an atmosphere
of purified nitrogen using standard Schlenk techniques. Elemental
analyses were carried out at the Department of Chemistry (TU
Kaiserslautern). Infrared spectra were recorded with a Jasco FT-
IR spectrometer. NMR spectra were recorded with a Bruker DPX
400 and a Bruker Avance 600 spectrometer.
H4
NCH3
5-CH3 COH
C(CH3)2
Ethyl 1,5-Dimethylpyrazole-3-carboxylate (2): A solution of 1
(2.80 g, 18.2 mmol) in dry THF (80 mL) was slowly treated with
NaH (440 mg, 18.2 mmol) at 0 °C. The mixture was warmed to
room temperature and stirred for 10 min until hydrogen evolution
ceased. CH3I (1.13 mL, 18.2 mmol) dissolved in dry THF (60 mL)
was added dropwise and the resulting mixture was stirred for 12 h
at room temperature. The solvent was removed in vacuo and an
aqueous solution of NaHCO3 (50 mL, 1 m) was added to the resi-
due. The solution was extracted three times with Et2O (50 mL), the
organic phases were combined, dried with Na2SO4, and the solvent
was evaporated; yield 2.70 g (89%), yellow liquid. All spectroscopic
data were in accordance with the data published in the litera-
ture.[8,9]
3
4
8
5.83
5.94
5.96
3.60
4.66
3.89
2.12
2.28
2.32
3.44
4.04
6.10
1.43
1.78
1.73
C3
C4
C5
NCH3
5-CH3 COH
C(CH3)2
3
4
8
158.2 101.1 139.0 35.6
158.9 105.4 143.4 38.5
156.5 101.7 144.3 36.4
30.4
31.4
30.6
69.1
69.4
75.4
11.0
12.3
11.5
[a] Measured in CDCl3 at room temperature.
As expected, the differences in the 13C NMR chemical
shifts are small and not of significance. The behaviour of
the 1H NMR chemical shifts between the compounds, how-
ever, varies greatly. Whereas the resonance of the proton at
C4 is almost unaffected by the chemical environment of the
pyrazole moiety, there is a general trend towards lower field
2-[(1,5-Dimethyl)pyrazol-3-yl]propan-2-ol (3):
A solution of 2
(2.70 g, 16.1 mmol) in dry THF (20 mL) was slowly treated with a
solution of MeMgCl (20 mL, 3 m) in THF. The resulting mixture
was refluxed for 16 h. After cooling to room temperature a satu-
for the resonances of the complexes compared with the free rated solution of NH4Cl (50 mL) was added to the yellow suspen-
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Tailoring of Hydrogen Bond Patterns
sion, which was then was extracted three times with Et2O (50 mL).
The combined organic layers were dried with Na2SO4 and the sol-
vent was removed. This procedure was repeated a second time. The
crude product was purified by sublimation under reduced pressure;
yield 1.69 g (68%), colourless prisms. C8H14N2O (154.21): calcd. C
62.31, H 9.15, N 18.17; found C 62.16, H 9.06, N 17.97. IR (KBr):
fac-Tris[2-(1,5-dimethylpyrazol-3-yl)propan-2-ol]nickel(II) Tetra-
chloronickelate (7): A solution of 3 (78 mg, 0.50 mmol) in methanol
(10 mL) was added to a solution of NiCl2·6H2O (59.4 mg,
0.25 mmol) in methanol (5 mL). The resulting green solution was
stirred for 4 h at room temperature. Then the solvent was reduced
to 10 mL. Slow diffusion of Et2O into this solution afforded 7 as
green crystals; yield 114 mg (63%). C24H42Cl4N6Ni2O3 (721.83):
ν = 3353 (vs, OH), 2968 (vs), 2930 (s), 1676 (s), 1551 (s), 1449 (s),
˜
1424 (s), 1374 (vs), 1360 (vs), 1217 (vs), 1175 (vs), 1145 (vs), 1009 calcd. C 39.93, H 5.86, N 11.64; found C 39.57, H 6.02, N 11.50.
(m), 954 (vs), 856 (s), 827 (vs), 649 (vs), 632 (s), 595 (s) cm–1. IR
IR (KBr): ν = 3392 (vs), 3229 (vs), 1626 (s), 1557 (s), 1444 (s), 1386
˜
1
(CH CN ): ν = 3526 (vs, OH) cm–1. H NMR (600 MHz, CDCl ): (s), 1293 (s), 1174 (s), 1119 (s), 1019 (s), 951 (m), 861 (s), 816 (m),
˜
3
3
δ = 5.83 (s, 1 H, H4), 3.60 (s, 3 H, NCH3), 2.95 (br., 1 H, OH),
764 (m), 655 (m) cm–1. IR (CH CN): ν = 3625 (vs, ν OH), 3540
˜
3 a
2.12 (s, 3 H, CH3), 1.43 [s, 6 H, C(OH)(CH3)2] ppm. 13C NMR (vs, νs OH) cm–1.
(150 MHz, CDCl3): δ = 158.1 (C-3), 139.0 (C-5), 101.1 (C-4), 69.1
Dichlorido[2-(1,5-dimethylpyrazol-3-yl)propan-2-ol]zinc(II) (8): A
solution of 3 (78 mg, 0.50 mmol) in acetone (10 mL) was added to
a solution of ZnCl2 (34.1 mg, 0.25 mmol) in acetone (5 mL). The
resulting colourless solution was stirred for 4 h at room tempera-
ture. The solvent was removed and the residue was redissolved in
CH2Cl2/CHCl3 (1:1; 10 mL). Slow diffusion of Et2O into this solu-
tion afforded 8 as colourless crystals; yield 67 mg (92 %).
C8H14Cl2N2OZn (290.53): calcd. C 33.07, H 4.86, N 9.64; found C
(COH), 35.6 (NCH3), 30.4 (5-CH3), 11.0 [C(CH3)2] ppm.
trans-Dichlorido{bis[2-(1,5-dimethylpyrazol-3-yl)propan-2-ol]}-
palladium(II) (4): A solution of 3 (78 mg, 0.50 mmol) in CH2Cl2
(10 mL) was added to a solution of (PhCN)2PdCl2 (95.8 mg,
0.25 mmol) in CH2Cl2 (5 mL). The resulting red-brown solution
was stirred for 2 h at room temperature, after which the colour
changed to yellow. The solvent was reduced to 5 mL, Et2O (20 mL)
was added and the resulting precipitate was collected by filtration.
After washing twice with Et2O (10 mL) the product was dried in
vacuo to obtain a yellow solid. Slow diffusion of Et2O into a solu-
tion of 4 in chloroform afforded yellow crystals; yield 76.3 mg
(33 %). C16H28Cl2N4O2Pd (485.75): calcd. C 39.56, H 5.81, N
33.22, H 4.89, N 9.69. IR (KBr ): ν = 3273 (vs, OH), 2978 (s), 1627
˜
(w), 1552 (vs), 1439 (s), 1386 (vs), 1303 (vs), 1295 (s), 1168 (vs),
1119 (vs), 1027 (s), 948 (m), 857 (vs), 817 (vs), 657 (m), 485 (w)
cm–1. IR (CH CN ): ν = 3628 (vs, ν OH), 3544 (vs, ν OH) cm–1.
˜
3
a
s
1H NMR (400 MHz, CDCl3): δ = 6.10 (br., 1 H, OH), 5.96 (s, 1
H, H4), 3.88 (s, 3 H, NCH3), 2.32 (s, 3 H, 5-CH3), 1.73 [s, 6 H,
C(OH)(CH3)2] ppm. 13C NMR (100 MHz, CDCl3): δ = 156.5 (s,
C3), 144.3 (s, C5), 101.7 (C4), 75.4 (s, COH), 36.4 (s, NCH3), 30.6
(s, 5-CH3), 11.5 [s, C(OH)(CH3)2] ppm.
11.53; found C 39.55, H 5.86, N 11.56. IR (KBr): ν = 3468 (vs,
˜
OH), 3134 (s), 2984 (vs), 2972 (vs), 2943 (s), 2927 (s), 1557 (vs),
1439 (vs), 1426 (vs), 1392 (vs), 1363 (vs), 1334 (s), 1211 (vs), 1193
(vs), 1141 (vs), 965 (vs), 865 (m), 810 (vs), 720 (m) cm–1. IR
1
(CH CN ): ν = 3628 (vs, ν OH), 3544 (vs, ν OH) cm–1. H NMR
˜
3
a
s
Magnetic Measurements: Magnetic susceptibility data (1.8–300 K)
were collected on powdered samples using SQUID magnetometer
on Quantum Design model MPMS-XL instrument under a 0.1 T
applied magnetic field. The magnetization isotherm was collected
between 0 and 7 T at 2, 3 and 5 K. All data were corrected for the
contribution of the sample holder.
(400 MHz, CDCl3): δ = 5.94 (s, 1 H, H4), 4.67 (s, 3 H, NCH3),
4.04 (br., 1 H, OH), 2.28 (s, 3 H, Mepz), 1.78 [s, 6 H, C(OH)-
(CH3)2] ppm. 13C NMR (150 MHz, CDCl3): δ = 158.9 (C-3), 143.4
(C-5), 105.4 (C-4), 69.4 (COH), 38.5 (NCH3), 31.4 (5-CH3), 12.3
[C(CH3)2] ppm.
Chlorido{bis[2-(1,5-dimethylpyrazol-3-yl)propan-2-ol]}copper(II)
Chloride (5): A solution of 3 (78 mg, 0.50 mmol) in acetone (10 mL)
was added to a solution of CuCl2 (33.6 mg, 0.25 mmol) in acetone
(5 mL). The resulting red-brown solution was stirred for 4 h at
room temperature, after which time the colour changed to green.
The solvent was removed and the residue redissolved in CHCl3
(10 mL). Slow diffusion of Et2O into this solution afforded com-
pound 5 as green crystals; yield 84 mg (76%). C16H28Cl2CuN4O2
(442.87): calcd. C 43.39, H 6.37, N 12.65; found C 43.42, H 6.33,
X-ray Structure Analyses: Crystal data and refinement parameters
(Oxford Diffraction Gemini) for compounds 3–8 are collected in
Table 2. The structures were solved by direct methods (SIR92[25]),
completed by subsequent difference Fourier syntheses, and refined
by full-matrix least-squares procedures.[26] Semi-empirical absorp-
tion corrections from equivalents (Multiscan) were carried out.[27]
All non-hydrogen atoms were refined with anisotropic displace-
ment parameters. All hydrogen atoms positions were calculated in
ideal positions (riding model) except for the hydrogen atoms H1O
and H2O bound to oxygen atoms O1 and O2, respectively, in 5,
the hydrogen atoms H1O, H2O and H3O bound to oxygen atoms
O1, O2 and O3, respectively, in 6, the hydrogen atoms H1O, H2O
and H3O bound to oxygen atoms O1, O2 and O3, respectively, in
7 and the hydrogen atom H1O bound to oxygen atom O1 in 8,
which were located in the difference Fourier synthesis. Each of
these hydrogen atoms were then refined semi-freely with the help
of a distance restraint, while constraining its U value to 1.5 times
the Ueq value of the bonded oxygen atom.
N 12.63. IR (KBr): ν = 3445 (m, OH), 3131 (s), 2974 (vs), 2851
˜
(s), 2706 (m), 1556 (s), 1436 (s), 1391 (vs), 1363 (vs), 1308 (s), 1207
(s), 1176 (vs), 1127 (vs), 1028 (s), 956 (s), 867 (s), 820 (s), 768 (m),
661 (m) cm–1. IR (CH CN ): ν = 3628 (vs, ν OH), 3540 (vs, νs
˜
3
a
OH) cm–1.
fac-Tris[2-(1,5-dimethylpyrazol-3-yl)propan-2-ol]cobalt(II) Tetra-
chlorocobaltate (6): A solution of 3 (78 mg, 0.50 mmol) in methanol
(10 mL) was added to a solution of CoCl2·6H2O (59.5 mg,
0.25 mmol) in methanol (5 mL). The resulting pink solution was
stirred for 4 h at room temperature. The solvent was reduced to
10 mL. Slow diffusion of Et2O into this solution afforded 6 as blue
crystals; yield 157 mg (87%). C24H42Cl4Co2N6O3 (722.31): calcd.
C 39.91, H 5.86, N 11.63; found C 39.35, H 5.65, N 11.44. IR
CCDC-812629 (for 3), -812630 (for 4), -812625 (for 5), -812628 (for
6), -812627 (for 7) and -812626 (for 8) 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.
(KBr): ν = 3221 (vs, OH), 2977 (vs), 2695 (m), 1631 (m), 1556 (vs),
˜
1497 (m), 1444 (s), 1385 (vs), 1352 (vs), 1289 (vs), 1205 (vs), 1177
(vs), 1119 (vs), 1018 (vs), 951 (s), 859 (s), 815 (s), 762 (m), 653 (m),
573 (m), 481 (m), 435 (m) cm–1. IR (CH CN ): ν = 3626 (vs, ν
Supporting Information (see footnote on the first page of this arti-
cle): IR and NMR spectra.
˜
3
a
OH), 3540 (vs, νs OH) cm–1.
Eur. J. Inorg. Chem. 2011, 1768–1775
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1773

C. K. Seubert, Y. Sun, Y. Lan, A. K. Powell, W. R. Thiel
Table 2. Summary of the crystallographic data and details of data collection and refinement for compounds 3–8.
FULL PAPER
3
4
5
6
7
8
Empirical formula C8H14N2O
C16H28Cl2N4O2Pd C16H28Cl2CuN4O2 C24H42Cl4Co2N6O3 C24H42Cl4N6Ni2O3 C8H14Cl2N2OZn
Formula weight
154.21
485.72
442.86
722.30
721.86
290.48
Crystal size [mm] 0.33ϫ0.11ϫ0.08
0.18ϫ0.17ϫ0.09
150(2)
0.24ϫ0.20ϫ0.20
150(2)
0.04ϫ0.04ϫ0.02
150(2)
0.08ϫ0.07ϫ0.06
150(2)
0.20ϫ0.12ϫ0.10
150(2)
T [K]
150(2)
λ [Å]
0.71073
orthorhombic
Pna21
9.6037(2)
11.6264(3)
7.7550(2)
90
0.71073
monoclinic
C2/c
15.6854(6)
9.3308(2)
16.1203(6)
90
1.54184
orthorhombic
Pna21
15.8306(2)
11.58740(10)
11.89110(10)
90
1.54184
monoclinic
P21/n
16.6076(5)
12.2490(3)
17.1278(5)
90
1.54184
monoclinic
P21/n
16.4985(6)
12.2317(3)
17.0830(5)
90
1.54184
monoclinic
P21/c
10.2664(2)
7.86270(10)
16.1469(2)
90
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
90
90
865.90(4)
4
1.183
0.080
2.75–32.35
11229
117.310(3)
90
2096.35(12)
4
1.539
1.156
2.92–32.42
14614
3527
90
90
110.980(4)
90
3253.26(18)
4
1.475
11.299
4.55–64.84
16134
5103
110.714(4)
90
3224.58(19)
4
1.487
4.790
4.55–62.92
16524
5054
106.062(2)
90
1252.52(4)
4
1.540
6.434
6.21–62.62
10994
1987
γ [°]
V [Å3]
2181.25(4)
4
1.349
3.797
4.73–62.65
15668
Z
ρcalcd. [gcm–3]
μ [mm–1]
θ range [o]
Reflections coll.
Indep. reflections
1579
3244
(Rint = 0.0451)
Data/restr./param. 1579/1/105
(Rint = 0.0306)
3527/0/120
0.0205,
0.0475
0.0302, 0.0490
0.973
(Rint = 0.0372)
3244/3/241
0.0263,
0.0650
0.0288, 0.0655
1.031
(Rint = 0.0665)
5103/3/373
0.0323,
0.0535
0.0767, 0.0638
0.833
(Rint = 0.0532)
5054/3/373
0.0320,
0.0599
0.0650, 0.0663
0.820
(Rint = 0.0338)
1987/1/134
0.0220,
0.0543
0.0270, 0.0551
0.970
Final R indices
0.0403,
0.0956
[IϾ2σ(I)][a]
R (all data)[b]
GooF[c]
0.0575, 0.1034
1.023
Flack parameter
10(10)[d]
–
0.475(15)
0.526/–0.252
–
–
–
Δρmax/min [eÅ–3]
0.259/–0.239
0.630/–0.445
0.376/–0.395
0.262/–0.264
0.273/–0.298
2
2 2
2
2
[a] R1 = Σ||Fo| – |Fc||/Σ|Fo|. [b] wR2 = [Σw(Fo – Fc ) /ΣwFo ]
2 1/2. [c] GooF = [Σw(Fo – Fc /n – p)]1/2. [d] During the refinement MERG 4
was used.
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Acknowledgments
The authors thank the Deutsche Forschungsgemeinschaft (DFG)
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Received: November 23, 2010
Published Online: February 23, 2011
Eur. J. Inorg. Chem. 2011, 1768–1775
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1775