X-ray structure, magnetic and catalytic properties of a cyclic trinuclear CoII/CoIII/CoIII complex with a μ3-hydroxy anion

Article abstract of DOI:10.1002/1099-0682(200106)2001:6<1575::AID-EJIC1575>3.0.CO;2-H

The mixed-valent cyclic trinuclear cobalt(II)/cobalt(III)/cobalt(III) complex tris(dibenzoylmethanato-1κ²O,O′;2κ ²O,O′;3 κ² O, O′) (μ₃-hydroxo-1:2κ² O; 1:3κ² O;2:3κ²O) tetrakis (μ-pyrazolato-1:2κ⁴N¹N²; 1:3κ²N¹N²; 2:3κ²N¹N²) - 1,2-dicobalt(III)-3-cobalt(II) with four bridging pyrazolate anions and a μ³-hydroxy anion has been synthesized and its molecular structure has been elucidated on the basis of X-ray crystallographic, magnetic, NMR, and EPR studies. The remaining coordination sites of the pentacoordinate cobalt(II) and hexacoordinate cobalt(III) centers are occupied by oxygen donor atoms of dibenzoylmethanate anions, rendering the complex soluble in most organic solvents. The complex has been found to effectively catalyze the decomposition of tert-butyl hydroperoxide (TBHP) in chlorobenzene with a short induction period and a half-life of 80 min and to catalyze the oxidation of cyclohexene to 2-cyclohexen-1-one with oxygen and to 2-cyclohexen-1-ol with TBHP.

Full text of DOI:10.1002/1099-0682(200106)2001:6<1575::AID-EJIC1575>3.0.CO;2-H

FULL PAPER
X-ray Structure, Magnetic and Catalytic Properties of a Cyclic Trinuclear
CoII/CoIII/CoIII Complex with a µ3-Hydroxy Anion
Marta Łukasiewicz,[a] Zbigniew Ciunik,[a] Jarosław Mazurek,[a] Jarosław Sobczak,[a]
[b]
[b]
[a]
´
´
´
Aldona Staron, Stanisław Wołowiec,* and Jozef J. Ziołkowski*
Keywords: Cobalt / Mixed valent complexes / X-ray structure
The mixed-valent cyclic trinuclear cobalt(II)/cobalt(III)/co-
balt(III) complex tris(dibenzoylmethanato-1κ2O,OЈ;2κ2O,OЈ;3
κ2O,OЈ)(µ3-hydroxo-1:2κ2O;1:3κ2O;2:3κ2O)tetrakis(µ-pyr-
coordinate cobalt(III) centers are occupied by oxygen donor
atoms of dibenzoylmethanate anions, rendering the complex
soluble in most organic solvents. The complex has been
azolato-1:2κ4N1N2;1:3κ2N1N2;2:3κ2N1N2)-1,2-dicobalt- found to effectively catalyze the decomposition of tert-butyl
(III)-3-cobalt(II) with four bridging pyrazolate anions and a
µ3-hydroxy anion has been synthesized and its molecular tion period and a half-life of 80 min and to catalyze the oxida-
structure has been elucidated on the basis of X-ray crystallo- tion of cyclohexene to 2-cyclohexen-1-one with oxygen and
hydroperoxide (TBHP) in chlorobenzene with a short induc-
graphic, magnetic, NMR, and EPR studies. The remaining to 2-cyclohexen-1-ol with TBHP.
coordination sites of the pentacoordinate cobalt(II) and hexa-
Introduction
(1·2THF) required the use of dibenzoylmethane (DBMH)
and pyrazole (pzH) in a 4:3 stoichiometry and excess co-
balt(II) salt under basic aerobic conditions. The yield was
reasonable considering that a mixture of complexes was
formed. The trinuclear complex 1·2THF could be isolated
as a pure compound by extraction into an organic solvent.
Special care had to be taken due to the reactivity of 1 to-
wards chlorinated hydrocarbons (vide infra). Brick-red
crystals of 1·2THF, which proved to be stable and analytic-
ally pure, were grown by crystallization from THF/hexane.
Multinuclear complexes of transition metal ions attract a
lot of attention due to their potential catalytic activity. They
are constructed using many different polydentate ligands in-
cluding oxygen donor anionic ligands such as
carboxylates[1Ϫ8] and other oxy anions.[9,10] Nitrogen-donor
bridging ligands, especially pyrazoles, which are well-suited
for N,N-bridging, are frequently utilized in the construction
of such systems.[11Ϫ16] Amongst polynuclear systems, cyclic
trinuclear complexes constitute an important class of
compounds.[1Ϫ10,14Ϫ17] Cyclic trinuclear cobalt complexes
have been found to show some catalytic activity in the epox-
idation of olefins[1,18] and in the autoxidation of hydrocar-
bons.[19] Therefore, we have focused on the synthesis, isola-
tion, and structural characterization of another, mixed-val-
ent trinuclear cobalt complex soluble in organic solvents.
The ligands used in the synthesis were dibenzoylmethanate
(DBM) and pyrazolate (pz) anions. Starting from cobalt(II)
nitrate, the synthetic procedure led to the isolation of a trin-
uclear cyclic CoIII/CoIII/CoII complex, which has been char-
acterized in the solid state by X-ray diffraction analysis. The
product has been tested for its catalytic activity in the ox-
idation of hydrocarbons.
X-ray Crystallographic Results for the Cyclic Trinuclear
Complex Co3(DBM)3(pz)4(OH)·2THF
The molecular structure of 1·2THF together with bond
lengths and angles are presented in Figure 1. The core of
the cyclic trinuclear complex 1 consists of three cobalt cen-
ters, pentacoordinate Co(1) and hexacoordinate Co(2) and
Co(3) (for the numbering, see Figure 2). These are N,N-
bridged by four pyrazolate anionic ligands, two of which
bridge two cobalt ions, and are further bridged by a µ3-
hydroxide anion. The latter is displaced from the Co(1)-
˚
Co(2)Co(3) plane (P) by 0.441(1) A. Three of the four
bridging pyrazolate anions, i.e. pz1a, pz1b, and pz2a, lie at
the opposite side of the P plane in relation to µ3-OH (i.e.
in the exo position) and the angles between the pyrazolate
ring planes and P are 38.5(1)°, 41.4(1)°, and 30.4(1)°, re-
spectively. The fourth bridging pyrazolate, namely pz2a, is
endo with a pz2a vs. P angle of 67.8(1)°. The three DBM
ligands are each involved in O,O-chelation of the cobalt
centers. The chelate ring planes of the DBM ligands are
twisted in relation to the P plane by about 86.7(1)° (DBM1
vs. P), 61.5(1)° (DBM2 vs. P), and 68.4(1)° (DBM3 vs. P).
Consequently, the oxygen donors and phenyl groups of the
DBM ligands are non-equivalent, as reflected in the dis-
Results and Discussion
Synthetic Procedure and Analytical Data
The optimized synthetic route for obtaining a compound
of the analytical formula Co3(DBM)3(pz)4(OH)·2THF
[a]
Department of Chemistry, University of Wroclaw,
14 Joliot-Curie Str., 50-383 Wroclaw, Poland
[b]
´
Faculty of Chemistry, Rzeszow University of Technology,
´
´
6 Powstancow Warszawy Ave., 35-959 Rzeszow, Poland
Eur. J. Inorg. Chem. 2001, 1575Ϫ1579
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ1948/01/0606Ϫ1575 $ 17.50ϩ.50/0
1575

´
S. Wołiwiec, J. J. Ziołkowski et al.
FULL PAPER
tances of the oxygen atom donors from the P plane (see
Figure 2). Three of the oxygen donors, i.e. O(2), O(3), and
O(6), are endo, while O(1), O(4), and O(5) are exo. Thus,
two sides of the molecule of 1 are different; the endo one is
occupied by µ3-OH, pz2a, and mainly by DBM ligands,
while the three remaining pyrazolate anions (exo) lie at the
opposite side of the P plane. The cobalt centers are disting-
uished not only by their coordination numbers, but also in
terms of the cobaltϪdonor atom distances. The bond
lengths between the pentacoordinate Co(1) atom and both
the bridging pyrazolate nitrogens and the DBM oxygen
˚
atoms are about 2.00 A, whereas those between Co(2) and
Co(3) and the corresponding pyrazolate nitrogen atoms and
˚
DBM oxygen atoms are 1.91 A (CoϪN averaged) and
˚
1.89 A (CoϪO averaged), respectively. Furthermore, the
bond lengths between the bridging hydroxy oxygen atom
˚
and Co(2) and Co(3) (1.91 A) are shorter as compared to
Figure 1. Projection[27] of the trinuclear cobalt complex; thermal
ellipsoids are drawn at a 30% probability level; selected bond
˚
that between Co(1) and O(1B) (2.15 A), which results in a
lower value of Co(2)ϪO(1B)ϪCo(3) (108.6°) in comparison
with the mean Co(1)ϪO(1B)ϪCo(n) angle (118.5°). It is
also noteworthy that the pyrazolate anion pz2a that bridges
the Co(2) and Co(3) centers, i.e. the only endo pz, is the
most strongly bound to the cobalt ions (1.89 A) of all the
bridging pyrazolate anions; the bond lengths between the
pz2b (exo) nitrogen atoms and the cobalt ions are longer
(1.91 A), and those between the pz1 (exo) nitrogen atoms
and the cobalt centers are longer still (1.92 A). These struc-
˚
lengths [A] and angles [°]: Co(1)ϪN(7) 1.991(2), Co(1)ϪN(6)
2.002(2),
Co(1)ϪO(1)
2.014(2),
Co(1)ϪO(2)
1.981(2),
Co(1)ϪO(1B) 2.154(2), Co(2)ϪN(1) 1.886(2), Co(2)ϪN(3)
1.900(2), Co(2)ϪN(8) 1.920(2), Co(2)ϪO(5) 1.879(2), Co(2)ϪO(6)
1.881(2),
Co(2)ϪO(1B)
1.912(2),
Co(3)ϪN(2)
1.892(2),
˚
Co(3)ϪN(4) 1.917(2), Co(3)ϪN(5) 1.926(2), Co(3)ϪO(3) 1.898(2),
Co(3)ϪO(4) 1.886(2), Co(3)ϪO(1B) 1.914(2);
Co(2)ϪO(1B)ϪCo(3) 108.58(8), Co(2)ϪO(1B)ϪCo(1) 117.77(8),
Co(3)ϪO(1B)ϪCo(1) 119.32(8); the ellipsoids at carbon atom posi-
tions and most of the atom labels are omitted for clarity; the con-
tact between the meta-hydrogen atom of the endo-phenyl ring of
DBM2 and the face of the endo-phenyl ring of DBM1 are shown
with a dotted line (for acronyms used, see Figure 2)
˚
˚
tural features clearly demonstrate that the oxidation state
of Co(1) is close to CoII, whereas those of Co(2) and Co(3)
centers are formally CoIII [20]
Analysis of the periphery of 1
.
revealed different conformations for the three DBM li-
gands; the phenyl rings at DBM2 are almost coplanar with
its chelate ring, while the exo-phenyl rings of the other two
DBM ligands are twisted in relation to their chelate rings,
presumably due to weak interactions between their meta-
protons and the face of the exo-phenyl of DBM1 (the con-
˚
tact distance is 2.78 A, see Figure 1). However, the crystal
puckering, including the interaction of 1 with two THF
solvate molecules, may also affect the conformations of the
DBM ligands.
Electronic Structure of 1
A rather unusual feature of 1 is that both a well-resolved
1H NMR spectrum and an ESR spectrum (at liquid nitro-
gen temperature) could be obtained. Therefore, we have
measured the magnetic susceptibility of 1·2THF. The mag-
netic moment of 1·2THF is indicative of a total spin of 3/2
and is slightly temperature-dependent (Figure 3, A). At
77 K, 1 gives a rhombic EPR spectrum with g1 ϭ 5.35, g2 ϭ
3.34, and g3 ϭ 2.31 (Figure 3, B). The extent of the delocal-
Figure 2. Simplified representation of 1 showing selected donor
atoms and acronyms used throughout the discussion; the distances
between the oxygen donor atoms of the DBM ligands and the mean
˚
Co(1)Co(2)Co(3) plane [A] are indicated in the scheme; positive
values are attributed to the endo side; bridging pyrazolates pz1a,
pz1b, and pz2b are bound at the exo side
1
ization of the unpaired electron could be estimated by H
NMR spectral studies of the high-spin complex 1.
The spectrum consists of 22 resonances, which are par- 1 indicates that the asymmetry observed in the solid state
tially overlapped (Figure 3, C). Although a total assignment is retained in solution, leading to a separation of the o-, m-,
could not be made, the two most shifted resonances, ap- and p-H phenyl resonances of all three DBM ligands. On
pearing at δ ϭ 57 and Ϫ59 with relative intensities of 2:1, the other hand, the rotation of the phenyl groups within
could be attributed to 3,5-H and 4-H of one of the bridging each DBM remains fast on the NMR time scale. Con-
pyrazolates (pz2). The large number of resonances seen for sequently, twelve resonances due to the DBM phenyl
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Eur. J. Inorg. Chem. 2001, 1575Ϫ1579

A Cyclic Trinuclear CoII/CoIII/CoIII Complex with a µ3-Hydroxy Anion
FULL PAPER
anions; the product thus obtained was found to be a mix-
ture of complexes due to the additional asymmetry intro-
duced by this β-diketonate, resulting in a multiplication of
the 3(5)-H and 4-H (pz2) resonances, although the chemical
shift of the latter was very close to that in 1. This observa-
1
tion confirmed the assignment of the H NMR resonances
of 1 on the basis of its symmetry and that of its analogues
with other β-diketonate anions.
Catalytic Properties
Complex 1 has been found to catalyze the decomposition
of tert-butyl hydroperoxide (TBHP) in chlorobenzene with
a short induction period and a half-life of 80 min. We have
tested 1 for its catalytic ability in the oxidation of cyclohex-
ene by TBHP and dioxygen. These two oxidants showed
different chemoselectivities; in the former case active oxy-
gen was selectively transferred to the substrate with forma-
tion of 2-cyclohexen-1-ol, while in all other cases 2-cyclo-
hexen-1-one was the dominant product (Table 1).
Generation of the active form of the catalyst from 1 in
acetonitrile required a long induction period (Entry 3),
whereas a short induction period was observed in chlorob-
enzene. This induction period is consistent with the build-
ing-up of an appropriately high concentration of ROOH
from R (alkene, alkane) and O2. Addition of TBHP to the
reaction mixtures (Entry 4) obviated the need for such an
induction period. The main products clearly showed the in-
volvement of different catalytic forms of 1, although both
are the common products of oxygenated Fenton
chemistry.[22Ϫ24] Generally, oxidation of organic substrates
catalyzed by cobalt complexes can be divided into two cat-
egories based on the type of mechanism involved: free-rad-
ical autoxidation and catalytic oxygen transfer.[22] In the
first type of reaction, the cobalt catalyst induces decom-
position of an organic hydroperoxide (ROOH) to form rad-
icals according to a HaberϪWeiss mechanism. However,
the primary chemistry of ROOH towards metal coordina-
Figure 3. A: temperature dependence of the magnetic moment; B:
ESR spectrum measured in toluene glass at 77 K; C: 1H NMR
spectrum of 1 in CDCl3 at 293 K; the resonances due to the prod-
uct of conversion of 1 are labeled with asterisks
groups, two resonances due to the CϪH of DBM, the res- tion complexes is nucleophilic addition and ligand substitu-
onance of the central OH, three pz1 signals, and four pz2 tion with formation of the reactive intermediate for Fenton
signals give a total of 22 resonances for 1. The well-resolved chemistry and the precursor to the reactive intermediate for
1H NMR spectrum of 1 is consistent with a high-spin con- oxygenated Fenton chemistry (in the presence of O2).[23]
figuration of the CoII center and indicates rather extensive Catalytic oxygen transfer involves two major active species,
delocalization of the unpaired electron over the formally namely the peroxometal and oxometal complexes, as the
CoII/CoIII/CoIII core.
active oxidants.[24] The product derived from 1 in the pres-
Complex 1 was found to be unstable in chlorinated solv- ence of dioxygen led to the oxidation of cumene in a similar
ents (chloroform and dichloromethane). Presumably, chlor- reaction. The products obtained were found to be those de-
ide ions are abstracted from the solvent through formation rived from attack of the active form of 1 on the secondary
of a new complex 1Ј; the half-life for this conversion was carbon atoms (cumene and ethylbenzene, Entries 5 and 7)
estimated to be ca. 24 h. The spectrum of 1Ј is present even and not the primary carbon atoms (p-xylene, Entry 6) of
in a freshly prepared solution (Figure 3, C). Complex 1Ј aliphatic substrates.
becomes predominant in a synthetic mixture if removal of
Although the catalytic activity and chemoselectivity of 1
CH2Cl2 is delayed. In the case of the analogous complex are relatively low, we are currently modifying the trinuclear
with acetylacetonate (acac) instead of DBM, the instability cyclic complexes by replacing DBM with unsymmetrical β-
of the trinuclear OH-bridged complex is even greater and diketonates and by replacing the cobalt ions with other
the only product isolated was Co3(acac)3(pz)4Cl. We have metal ions with a view to improving the catalytic activity of
attempted to replace the DBM in 1 with benzoylacetonate these systems.
Eur. J. Inorg. Chem. 2001, 1575Ϫ1579
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´
S. Wołiwiec, J. J. Ziołkowski et al.
FULL PAPER
Table 1. The results of tests of the catalytic ability of tris(dibenzoylmethanato-1κ2O,OЈ;2κ2O,OЈ;3κ2O,OЈ)(µ3-hydroxo-
1:2κ2O;1:3κ2O;2:3κ2O)tetrakis(µ-pyrazolato-1:2κ4N1N2;1:3κ2N1N2;2:3κ2N1N2)-1,2-dicobalt(III)-3-cobalt(II) (1)
Test[a]
Substrate
(concentration)
Solvent
Oxidant
τ1/2
[min]
Products; yields [%][b]
1
cyclohexene
(2.1 )
chlorobenzene
TBHP
(0.276 )
120
120[c]
450[c]
150
2-cyclohexen-1-ol; 65.4
2-cyclohexen-1-one; 6.4
cyclohexane-1,2-epoxide; 3.2
total yield 75.0 (24 h)
2-cyclohexen-1-ol; 21.1
2-cyclohexen-1-one; 49.1
cyclohexane-1,2-epoxide; 7.3
total yield 77.4 (18.5 h)
2-cyclohexen-1-ol; 6.4
2-cyclohexen-1-one; 44.8
cyclohexane-1,2-epoxide; 9.9
Total yield 61.4 (20 h)
2-cyclohexen-1-ol; 13.1
2-cyclohexen-1-one; 48.8
cyclohexane-1,2-epoxide; 1.0
Total yield 68.1 (18.5 h)
2-phenylpropan-2-ol; 11.5
acetophenone; 10.8
2
3
4
5
cyclohexene
(0.97 )
chlorobenzene
acetonitrile
O2 (1 atm)
O2 (1 atm)
cyclohexene
(0.97 )
cyclohexene
(0.97 )
acetonitrile
O2 (1 atm)
ϩ TBHP[e]
cumene
(1.0 )
chlorobenzene
O2 (1 atm)
600
cumene hydroperoxide; 3.6
Total yield 25.8 (20 h)
no conversion products
were found (20 h)
[d]
6
7
p-xylene
(0.98 )
ethylbenzene
(0.98 )
chlorobenzene
chlorobenzene
O2 (1 atm)
O2 (1 atm)
600
acetophenone; 6.1 (18.5 h)
[a]
[b]
The concentration of 1 was 5·10Ϫ4 mol/dm3. Ϫ Calculated on the basis of substrate consumed, except for Entry 1, where the yield
[c]
was calculated on the basis of active oxygen transferred to the organic substrate. Ϫ With an induction period of 30 min (Entry 2) and
[d]
300 min (Entry 3); τ1/2 calculated starting from the point at which consumption of oxygen commenced. Ϫ No consumption of oxygen
was noticed. Ϫ The initial concentration of TBHP was 1.5·10Ϫ4 .
[e]
and polarization effects. No absorption correction was applied.
Data reduction and analysis were carried out with the Kuma Dif-
Experimental Section
fraction (Wroclaw) programs. The structure was solved by direct
Synthesis: In the optimized procedure, dibenzoylmethane (DBMH,
methods (program SHELXS-97[25]) and refined by the full-matrix
500 mg, 2.232 mmol) and pyrazole (pzH, 202 mg, 2.976 mmol)
least-squares methods on all F2 data using the program SHELXL-
were dissolved in tetrahydrofuran (THF, 20 mL) and the resulting
97.[26] Non-hydrogen atoms were refined with anisotropic thermal
solution was added dropwise to a 0.3 mol·dmϪ3 aq. cobalt(II) ni-
parameters; hydrogen atoms were included in geometrical positions
trate solution (75 mL) under vigorous stirring. Then, freshly dis-
and were not refined. The crystallographic data have been depos-
tilled dichloromethane (150 mL) was added to the mixture to ex-
ited with the CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K.
tract the desired, non-electrolyte product into the organic phase.
and are available on quoting the deposition number CCDC-
Additionally, 1  aq. NaOH was added dropwise to the mixture
under continuous stirring. After stirring for a further 10 min, the
150406.
reddish-brown organic phase was collected and the CH2Cl2 was
removed using a rotary evaporator. The solid residue was redis-
solved in THF and the crude product was crystallized from a THF/
hexane mixture. Recrystallization from this solvent mixture led to
the isolation of brick-red crystals of 1·2THF. The best yield of the
product was 14%. Ϫ C65H62Co3N8O9 (1276.2): calcd. C 61.17, H
4.90, N 9.41; found C 60.49, H 4.88, N 9.60. Ϫ IR (KBr and Nu-
jol): ν˜ ϭ 1591 (s), 1546 (s, br), 1521 (s, br), 1484 (s, br), 1450 (s),
1391 (s, br), 1377 (s), 1319 (m), 1308 (m, sh), 1225 (m), 1194 (w),
1180 (m, br), 1061 (s), 1025 (w), 999 (w), 951 (w), 751 (m, br), 740
(m), 721 (m), 687 (m), 626 (w), 581 (w, br), 543 cmϪ1 (w, br). Ϫ
UV/Vis: λ (ε) ϭ 537 nm (3.26·102 molϪ1·dm3·cmϪ1).
Magnetic and Spectral Measurements: The magnetic susceptibility
was measured as a function of temperature in the range 14Ϫ300 K
using a Quantum Design SQUID magnetometer (type MPMS-5).
Magnetic moments were calculated for the molecule of 1·2THF
after considering the appropriate diamagnetic corrections. Ϫ 1H
NMR spectra were recorded with a Bruker AMX 300 MHz instru-
ment, while X-band EPR spectra were measured with a Bruker
ESP 300E spectrometer, both for a solid sample and for a solution
of 1 in toluene, at 77 K and at ambient temperatures. Ϫ UV/Vis
spectra in appropriate solvents and IR spectra (Nujol mulls; KBr
discs) were recorded with HP 8453 diode-array and Bruker
IFS113V FT-IR spectrophotometers, respectively.
Crystallographic Studies: Crystal data, together with details of the
refinement, are given in Table 2. All measurements were made with
a Kuma KM4CCD κ-axis diffractometer using graphite-monoch-
Catalytic Tests: The catalytic activity of 1 was tested in oxidations
of various organic substrates using tert-butyl hydroperoxide
(TBHP) and dioxygen as oxidants in chlorobenzene and acetonitr-
romated Mo-Kα radiation. The crystal was positioned 65 mm from ile solution at 348 K. The progress of reactions was monitored by
the KM4CCD camera; 612 frames were measured at 0.75° intervals
with a counting time of 25 s. The data were corrected for Lorentz
iodometric titration of TBHP and by volumetric measurement of
dioxygen consumed. The products were separated and determined
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A Cyclic Trinuclear CoII/CoIII/CoIII Complex with a µ3-Hydroxy Anion
FULL PAPER
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[2]
Table 2. Crystal data and structure refinement
[3]
[4]
[5]
[6]
[7]
[8]
[9]
Empirical formula
Molecular mass
T [K]
C65H62N8O9Co3
1276.02
100(2)
˚
λ [A]
0.71073
Crystal system
Space group
triclinic
¯
P1
´
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˚
a [A]
13.618(3)
14.241(3)
16.069(3)
86.69(3)
72.47(3)
73.40(3)
2846.4(10)
2
1.489
˚
b [A]
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˚
c [A]
α [°]
β [°]
γ [°]
3
˚
V [A ]
Z
[10]
[11]
Dc [Mg·mϪ3
]
µ [mmϪ1
F(000)
]
0.932
1322
[12]
Crystal size [mm]
Crystal color and habit
Diffractometer
θ range for data collection [°]
Index ranges
0.20 ϫ 0.15 ϫ 0.15
brick-red prisms
Kuma KM4CCD
3.23Ϫ28.84
Ϫ18 Յ h Յ 17
Ϫ15 Յ k Յ 18
Ϫ21 Յ l Յ 21
20661
[13]
[14]
Reflections collected
[15]
[16]
[17]
[18]
[19]
[20]
K. Sakai, Y. Yamada, T. Tsubomura, M. Yabuki, M. Yamagu-
chi, Inorg. Chem. 1996, 35, 542Ϫ544.
A. V. Virovets, I. V. Podbereskaia, L. G. Lavrenova, Zh. Str.
Khim. 1997, 38, 532Ϫ538.
J. J. Ziolkowski, F. Pruchnik, T. Szymanska-Buzar, Inorg. Chim.
Independent reflections (Rint
)
12971 (0.0322)
7791
12971/766
0.0297, 0, 3
0.851
0.0380/0.0699
0.0802/0.0761
0.881/Ϫ0.397
Observed reflections (I Ն 2σI)
Data/parameters
Weighting scheme: a, b, c[a]
Goodness-of-fit (F2)
´
Acta 1973, 7, 473Ϫ476.
Final R1/wR2 indices (obs. refl.)[a]
Final R1/wR2 indices (indep. refl.)
´
T. Szymanska-Buzar, J. J. Ziolkowski, J. Mol. Catal. 1981, 11,
371Ϫ384.
Ϫ3
˚
Largest diff. peak/hole [e·A
]
D. E. Babushkin, E. P. Talsi, J. Mol. Catal. A 1998, 130,
131Ϫ137.
[a] w ϭ 1/[σ2(Fo ) ϩ (aP)2 ϩ bP], where P ϭ [Max(Fo ,0) ϩ 2Fc ]/c.
2
2
2
A literature search of crystallographic data, performed with the
VISTA program as included in the CSD package,[21] showed
that oxygen (of β-diketonate)Ϫcobalt bond lengths fall into
˚
two well-separated groups with 1.86Ϫ1.92 A and 1.99Ϫ2.12
by GC-MS using a HP 5890 series II chromatograph coupled to a
HP 5971 A mass spectrometer. The decomposition of 0.28  TBHP
in the presence of 5.2·10Ϫ4  1 in chlorobenzene at 348 K was mon-
itored by iodometric titration. The half-life for the conversion was
found to be 80 min. The products of TBHP decomposition (75%
conversion after 180 min) were identified and determined by GC-
MS as tert-butyl alcohol and a trace amount of bis(tert-butyl) per-
oxide. The results of the oxidation tests are summarized in Table 1.
A for Co and CoII, respectively. The CoIIϪN(pyrazole) and
III
˚
CoIIIϪN(pyrazole) bond lengths do not depend on the oxida-
tion state of the metal ion and fall within the range
˚
1.92Ϫ2.26 A.
[21]
F. H. Allen, J. E. Davies, J. J. Gelloy, O. Johnson, O. Kennard,
C. F. Macrae, E. M. Mitchell, G. F. Mitchell, J. M. Smith, D.
G. Watson, J. Chem. Int. Comp. Sci. 1991, 31, 187Ϫ204.
R. A. Sheldon, CHEMTECH 1991, 566Ϫ576.
D. T. Sawyer, A. Sobkowiak, T. Matsushita, Acc. Chem. Res.
1996, 29, 409Ϫ416.
G. A. Barf, R. A. Sheldon, J. Mol. Catal. A 1995, 102, 23Ϫ29.
G. M. Sheldrick, SHELXS-97, Program for Solution of Crystal
Structures, University of Göttingen, 1997.
[22]
[23]
[24]
[25]
Acknowledgments
J. S., S. W., and J. J. Z. kindly acknowledge financial support from
the State Committee for Scientific Research KBN (Grant PBZ-
KBN 15/T09/99/01D).
[26]
[27]
G. M. Sheldrick, SHELXL97, Program for Crystal Structure
Refinement, University of Göttingen, 1997.
G. M. Sheldrick, SHELXTL, V5.1, Bruker AXS, Inc., Madi-
son, Wisconsin, USA, 1999.
[1]
R. D. Cannon, R. P. White, Prog. Inorg. Chem. 1988, 36,
195Ϫ297.
Received October 11, 2000
[I00381]
Eur. J. Inorg. Chem. 2001, 1575Ϫ1579
1579