powdered single-crystal samples in a gelatin capsule with an
applied field of 0.1 T. The magnetization was measured from 2 up
to 20 K in the 0–5 T range. Data were corrected for magnetization
of the sample holder and for diamagnetic contributions, which
were estimated from Pascal constants.23
Experimental
General remarks
Starting materials were purchased from Aldrich. All ma-
nipulations were performed using materials as received.
Mn(O2CPh)2·2H2O,21 (nBu4N)MnO4 and the ligands22 3(5)-(2-
5
hydroxyphenyl)-5(3)-methylpyrazole (H2phpzMe) and 3(5)-(2-
hydroxyphenyl)-5(3)-phenylpyrazole (H2phpzPh) have been syn-
thesized according to reported procedures.
X-Ray crystallography†
Intensity data for single crystals of 1, 2 and 3 were collected using
˚
Mo Ka radiation (l = 0.71073 A) on a Nonius KappaCCD
General synthesis
diffractometer. Crystal and refinement data for 1, 2 and 3 are
collected in Table 1. The intensity data were corrected for Lorentz
and polarization effects, and for absorption (multiscan absorption
correction24). The structures were solved by Patterson methods.25
The programs EvalCCD,26,27 DIRDIF96,28 SHELXS-9729 and
SHELXL-9730 were used for data reduction, structure solution
and refinement, respectively. All non-hydrogen atoms were refined
with anisotropic displacement parameters. All hydrogen atoms
were placed at calculated positions and were refined riding on the
parent atoms. CCDC-713048 (1), CCDC-713050 (2) and CCDC-
713049 (3) contain the supplementary crystallographic data for
this paper.† Geometric calculations and molecular graphics were
performed with the PLATON package.31
Solid (nBu4N)MnO4 (0.07 mmol) was added to a solution of
Mn(O2CR¢)2·nH2O (R¢ = Me, Ph) (0.28 mmol) in ethanol. The
resulting solution was stirred for a few minutes, followed by the
addition of H2phpzR (R = Me, Ph) (0.21 mmol) in ethanol. The
solution mixture resulted in the formation of a brown precipitate,
which was filtered off and discarded. The filtrate was allowed to
evaporate slowly, affording brown crystals within a few days in all
cases. The crystals were collected by filtration, washed with Et2O
and dried in vacuum.
[Mn3(l3-O)(phpzMe)3(O2CMe)(EtOH)]·EtOH
(1). Yield:
17% (30 mg). Anal. Calcd for 1 (C36H39Mn3N6O8): C, 50.96; H,
4.63; N, 9.90. Found: C, 50.53; H, 5.05; N, 9.90. IR (nmax/cm-1):
3070 (w), 1597 (m), 1560 (m), 1550 (m), 1530 (s), 1496 (m), 1458
(s), 1322 (m), 1296 (vs), 1268 (vs), 1249 (vs), 1144 (w), 1127 (s),
1090 (m), 1062 (m), 1036 (s), 982 (w), 864 (s), 792 (s), 784 (m),
752 (s), 742 (s), 725 (s), 668 (vs), 647 (vs), 601 (vs), 484 (m),
418 (s), 381 (s), 312 (s).
Results and discussion
Synthesis
m3-Oxide bridged trinuclear manganese(III) compounds were
previously obtained by reacting mononuclear manganese(III)
building blocks containing phenol–pyrazole based ligands with
manganese(II) acetate or with sodium azide.15 These compounds
contain the same core with the general formula [Mn3(m3-
O)(phpzR)3]+; methanol molecules, and acetate or azide bridging
ligands have been found at the terminal positions. In the present
paper the influence of a different carboxylate ligand, namely
benzoate and a different starting solvent, namely ethanol, in
these type of trinuclear manganese(III) compounds is presented.
In addition, we have explored new synthetic routes by start-
ing from manganese(II) carboxylate salts, (nBu4N)MnO4 and
phenol–pyrazole ligands in the same reaction. Manganese(II)
salts together with (nBu4N)MnO4 are an excellent and well
known starting source to generate manganese(III) and/or man-
ganese(IV) ions; depending on the used ratio, complexes of
different nuclearities can be obtained.5,21 In our case, the man-
ganese(II) : manganese(VII) ratio employed can be either 4 : 1 or
3 : 1. The use of other (nBu4N)+ salts, i.e. (nBu4N)Br instead of
(nBu4N)MnO4, resulted in a decrease of the reaction yields. The
presence of nBu4N+ in the final product is necessary to balance the
charges in compounds (nBu4N)[Mn3(m3-O)(phpzMe)3(O2CPh)2]
(2) and (nBu4N)[Mn3(m3-O)(phpzPh)3(O2CPh)2] (3), because
there are two benzoate groups present. Compound [Mn3(m3-
O)(phpzMe)3(O2CMe)(EtOH)]·EtOH (1) contains one acetate
(nBu4N)[Mn3(l3-O)(phpzMe)3(O2CPh)2] (2). Yield: 11%
(28 mg). Anal. Calcd for 2 (C60H70Mn3N7O8): C, 60.97; H, 5.97;
N, 8.29. Found: C, 60.47; H, 6.78; N, 8.36. IR (nmax/cm-1): 2964
(m), 2875 (w), 1594 (s), 1563 (s), 1558 (vs), 1540 (m), 1531 (m),
1494 (s), 1456 (vs), 1374 (vs), 1330 (m), 1296 (vs), 1268 (vs), 1254
(vs), 1152 (m), 1127 (s), 1088 (m), 1064 (s), 1056 (s), 1034 (s), 988
(m), 938 (m), 866 (s), 834 (m), 782 (m), 766 (s), 760 (s), 752 (vs),
720 (vs), 680 (vs), 668 (vs), 642 (vs), 612 (s), 580 (s), 542 (m), 442
(s), 422 (s), 417 (s), 379 (vs), 350 (s), 334 (s).
(nBu4N)[Mn3(l3-O)(phpzPh)3(O2CPh)2]
(3). Yield:
13%
(37 mg). Anal. Calcd for 3 (C75H76Mn3N7O8): C, 65.84; H, 5.60;
N, 7.17. Found: C, 65.21; H, 6.37; N, 7.21. IR (nmax/cm-1): 2962
(m), 2880 (w), 1595 (s), 1564 (m), 1558 (vs), 1539 (m), 1532 (m),
1506 (m), 1476 (vs), 1456 (s), 1448 (s), 1428 (m), 1378 (vs), 1297
(s), 1266 (s), 1249 (s), 1175 (w), 1122 (s), 1098 (s), 1026 (m), 995
(m), 935 (w), 864 (s), 836 (w), 797 (m), 752 (s), 719 (vs), 710 (s),
696 (vs), 686 (s), 668 (vs), 662 (s), 646 (s), 610 (m), 588 (m), 534
(m), 492 (w), 456 (m), 448 (m), 435 (m), 421 (s), 378 (m), 374 (m),
333 (s).
Physical Measurements
Elemental analyses for C, H and N were performed on a
Perkin-Elmer 2400 series II analyzer. Infrared spectra (4000–
300 cm-1) were recorded on a Perkin-Elmer Paragon 1000 FTIR
spectrometer equipped with a Golden Gate ATR device, using
reflectance technique. DC and AC magnetic data were recorded
using a Quantum Design MPMS-5 SQUID susceptometer. The
magnetic susceptibilities were measured from 1.8 to 300 K on
n
group only, therefore the Bu4N+ is absent. The infrared spectra
of complexes 1–3 are very similar. The main difference is that
compounds 2 and 3 exhibit the bands expected for the nBu4N+ at
2964, 2875 and 1374 cm-1 that are absent in compound 1, which is
in agreement with the X-ray crystallographic studies.
7446 | Dalton Trans., 2009, 7445–7453
This journal is
The Royal Society of Chemistry 2009
©