Pyrazolylamidino- and bis(pyrazole)manganese(I) complexes

Article abstract of DOI:10.1002/ejic.200500419

The pyrazolylamidino complexes fac-[MnBr(CO)₃{NH=C(R)-pz- κ²N,N}] or fac-[MnBr(CO)₃{NH=C(R)dmpz- κ²N,N}] (R = CH₃, C₆H₅) are obtained by reaction of fac-[MnBr(CO)₃-(NC

Full text of DOI:10.1002/ejic.200500419

FULL PAPER
Pyrazolylamidino- and Bis(pyrazole)manganese( ) Complexes
I
Marta Arroyo,[a] Álvaro López-Sanvicente,[a] Daniel Miguel,[a] and Fernando Villafañe*[a]
Keywords: Manganese / N ligands / Pyrazole / Pyrazolylamidino ligands
The pyrazolylamidino complexes fac-[MnBr(CO)3{NH=C(R)-
pz-κ2N,N}] or fac-[MnBr(CO)3{NH=C(R)dmpz-κ2N,N}] (R =
CH3, C6H5) are obtained by reaction of fac-[MnBr(CO)3-
(NCR)2] and equimolar amounts of pzH or dmpzH (dmpz =
3,5-Me2pz), although these reactions also afford the bis(pyr-
azole) complexes as by-products. The bispyrazole complexes
fac-[MnBr(CO)3(pzH)2] or fac-[MnBr(CO)3(dmpzH)2] are se-
lectively obtained from [MnBr(CO)5] and two equivalents of
pzH or dmpzH. Their solid-state structures, determined by
X-ray diffraction methods, show the N-bound hydrogens of
the pyrazoles pointing towards the bromine atom. The pyr-
azolylamidino complexes can also be prepared by reactions
of equimolar amounts of the bispyrazole and the bisnitrile
complexes. The solid-state structures of the pyrazolylamidino
complexes containing the dmpz fragment were determined
by X-ray diffraction methods.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
electrophiles including metal fragments, which would afford
heterometallic complexes.
Introduction
An increasing interest is being dedicated to pyrazole-con-
taining chelating ligands.[1] Among them, those containing
pyridyl and pyrazolyl fragments are receiving the highest
attention, probably because they are involved in different
and interdisciplinary aspects, such as the synthesis of supra-
molecular assemblies or the design of molecules displaying
physical properties of interest.[2,3] At the opposite side con-
cerning the attention received are pyrazolylamidines, since
only molybdenum, iridium, ruthenium, and platinum com-
plexes containing these ligands have been described so far.[4]
However, amidino has been found to be a promising li-
gand,[5] which may be attributed to several special features
of pyrazolylamidino complexes: (a) the different properties
of the two donor atoms and the electron delocalization
within the ligand makes them potentially interesting for
electron-transfer processes and related physical properties,
as occurs for the related pyridyl- and pyrazolyl-containing
polydentate ligands; (b) the pyrazolylamidino ligands are
synthesized in situ (Scheme 1), thus using different nitriles
and pyrazoles allows the opportunity of controlling both
the electronic and steric properties of the metal complexes,
in contrast with most of the ligands, which must be pre-
viously synthesized; (c) the NH group may be deproton-
ated, giving rise to further reactivity by attack of different
Scheme 1. General method for the synthesis of pyrazolylamidino
complexes.
As part of our studies on the chemistry of group 6 and
7 complexes with N-donor chelating ligands,[6] we decided
to study the coordination of the pyrazolylamidino ligand to
these metals, which has not been explored so far. The first
pyrazolylamidinomanganese complexes are reported here.[7]
During the course of this work we unexpectedly obtained
bis(pyrazole) manganese complexes, which had not been
previously reported, therefore their selective syntheses are
also described.
The chemistry of bis(pyrazole) complexes is also at-
tracting our attention,[8] since both their structures and re-
activity are promising aspects. Concerning their structures,
the N-bound hydrogen of pyrazole complexes is commonly
involved in hydrogen bonds that give rise to supramolecular
arrangements.[9,10] Concerning their reactivity, terminal
pyrazole ligands are very useful precursors for bridging pyr-
azolate homo- or heterobimetallic complexes, which may be
obtained by deprotonating the N-bound hydrogen of the
coordinated pyrazole when a second metallic substrate is
present. This strategy has been successively used by dif-
ferent groups, mainly with middle and late transition ele-
ments.[11]
[a] Química Inorgánica, Facultad de Ciencias, Universidad de Val-
ladolid,
47005 Valladolid, Spain
Fax: +34-983-423-013
E-mail: fervilla@qi.uva.es
4430
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200500419
Eur. J. Inorg. Chem. 2005, 4430–4437

Pyrazolylamidino- and Bis(pyrazole)manganese() Complexes
FULL PAPER
Results and Discussion
Synthesis and Characterization of Bis(pyrazole)manganese
Complexes
The
bis(pyrazole)manganese()
complexes
fac-
[MnBr(CO)3(pzH)2] (1a) and fac-[MnBr(CO)3(dmpzH)2]
(1b) were obtained when [MnBr(CO)5] was treated with a
twofold excess of pzH or dmpzH in warm CH2Cl2. A white
insoluble solid was detected in the reactions with pzH, al-
though the yield of 1a is still high.[12]
The fac geometry of both complexes is evident from their
IR spectra in the C–O stretching region, which show three
absorptions. The C–O frequencies are slightly higher for 1a
than for 1b, as is to be expected considering that Hdmpz is
a better donor than Hpz. This geometry is supported by
the NMR spectroscopic data, as both pyrazole ligands are
equivalent. The broadness of the HN signal must be due to
a protolysis process involving this proton, which is common
in pyrazole complexes. Homodecoupling experiments at low
temperature carried out on previously reported complexes
have allowed the unequivocal assignment of the signals of
the pyrazolic hydrogens.[8a] However, this assignment can-
not be unequivocally extended to the complexes described
herein, since the chemical shifts of the hydrogens or methyl
groups in positions 3 and 5 seem to be affected by different
factors that are difficult to evaluate: whether the hydrogen
(or methyl) group at position 3 resonates at higher field
than that at position 5, or vice versa, may vary in the same
family of complexes,[11g] or even depending on the solvent
used.[13] Therefore, the assignment proposed for the rest of
complexes in the Experimental Section shoud be considered
as tentative.
Structure reports of pyrazolemanganese() complexes
are quite common, but we have only been able to find one
report of a crystal structure of a pyrazolemanganese()
complex,[14] therefore the geometries of complexes 1 were
determined by X-ray diffractometric studies. The structures
are shown in Figure 1 and relevant distances and angles are
collected in Table 1.[15] The distances and angles are very
similar in both complexes, and the latter are also similar to
those found in previously reported structures of halotricar-
bonylmanganese() complexes containing two monodentate
Figure 1. Perspective views of fac-[MnBr(CO)3(pzH)2] (1a, top),
and fac-[MnBr(CO)3(dmpzH)2] (1b, bottom), showing the atom
numbering.
N-donor ligands, which show a slightly distorted octahedral reduces the steric hindrance, since the methyl groups bound
geometry.[16] These distortions are evidenced by the slight to the 5-carbon and the bulky bromine atom are at opposite
deviation from linearity shown by the ligands coordinated sides of the molecule. Steric hindrance is also responsible
trans [174.84(17)–176.7(2)°], as well as by the angles formed for the tilting of the Hdmpz ligands, which are bent in the
by the ligands coordinated cis [85.71(13)–96.3(2)°]. In both same sense around the Mo–N bonds, as has been found in
structures the smaller angles are those formed by the two other bis(Hdmpz) complexes.[8b] The average dihedral
pyrazoles, as occurs in the related manganese() complexes angles are 37(1)° and 34(1)°, so they are close to the planes
containing two monodentate N-donor ligands indicated that bisect the angles between the cis substituents. This tilt-
above.[16]
ing is not observed in 1a, where the deviation of the Hpz
The N-bound hydrogens of the pyrazoles point to the ligands from the plane perpendicular to that containing the
bromine atom, which may be attributed both to steric and metal and the nitrogen donor atoms is much lower [23(1)°
electronic reasons. Steric factors are obviously more impor- and –10(1)°]. The second difference between the pyrazole
tant in 1b, where this orientation brings the methyl groups ligands in 1a and 1b concerns their relative orientation: in
bound to the 5-carbon close to a carbonyl group, which is 1b they are tilted in the same direction in order to reduce
smaller than the bromine atom. Therefore, this orientation their steric hindrance, whereas in 1a the Hpz ligands are
Eur. J. Inorg. Chem. 2005, 4430–4437
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M. Arroyo, Á. López-Sanvicente, D. Miguel, F. Villafañe
FULL PAPER
Table 1. Selected distances [Å] and angles [°] for fac-[MnBr(CO)3- triles is a well-known reaction that has been extensively
used to obtain a wide variety of ligands.[19]
(pzH)2] (1a) and fac-[MnBr(CO)3(dmpzH)2] (1b).
The acetonitrile complex fac-[MnBr(CO)3(NCMe)2],
which was first described more than thirty years ago,[20] was
synthesized by heating [MnBr(CO)5] in acetonitrile under
controlled conditions in order to avoid bromide displace-
ment to yield the cationic product. It is well known that the
carbonyls are ejected before the substitution of the bromide
when a thermal process is carried out.[21] A similar method
was used to obtain fac-[MnBr(CO)3(NCPh)2] (see Exp.
Sect.), for which we have not been able to find any previous
report.[22]
1a
1b
Mn(1)–C(1)
Mn(1)–C(3)
Mn(1)–C(2)
Mn(1)–N(3)
Mn(1)–N(1)
Mn(1)–Br(1)
C(1)–O(1)
C(2)–O(2)
1.776(5)
1.790(5)
1.817(6)
2.070(3)
2.078(3)
2.5448(9)
1.135(6)
1.127(6)
1.144(6)
90.2(3)
90.0(3)
89.9(2)
91.93(19)
175.6(2)
93.9(2)
1.760(6)
1.799(6)
1.780(6)
2.080(4)
2.085(4)
2.5420(10)
1.159(6)
1.152(6)
1.147(5)
86.9(2)
90.7(3)
89.2(2)
96.3(2)
176.7(2)
91.5(2)
C(3)–O(3)
C(1)–Mn(1)–C(3)
C(1)–Mn(1)–C(2)
C(3)–Mn(1)–C(2)
C(1)–Mn(1)–N(3)
C(3)–Mn(1)–N(3)
C(2)–Mn(1)–N(3)
C(1)–Mn(1)–N(1)
C(3)–Mn(1)–N(1)
C(2)–Mn(1)–N(1)
N(3)–Mn(1)–N(1)
C(1)–Mn(1)–Br(1)
C(3)–Mn(1)–Br(1)
C(2)–Mn(1)–Br(1)
N(3)–Mn(1)–Br(1)
N(1)–Mn(1)–Br(1)
The reactions of the bis(nitrile) complexes and pyrazole
(Scheme 2, route i) afford the desired pyrazolylamidino
complexes fac-[MnBr(CO)3{NH=C(R)pz-κ2N,N}] (R
=
CH3, 2a; Ph, 3a) or fac-[MnBr(CO)3{NH=C(R)dmpz-
κ2N,N}] (R = CH3, 2b; Ph, 3b). However, variable amounts
of the bis(pyrazole) complexes 1 are also obtained as by-
products. The presence of the bispyrazole complexes could
be due to the instability of the bisnitrile complexes under
these reaction conditions, which would decrease the amount
of available manganese and therefore would increase the
manganese/pyrazole ratio. Thus, we decided to attempt the
syntheses of the pyrazolylamidino complexes by reacting
equimolar amounts of the bis(nitrile) and bis(pyrazole)
complexes (Scheme 2, route ii) as we believed this would
increase the amount of manganese present in the mixture
and would not increase the manganese/pyrazole ratio.
However, this method did not improve the selectivity of the
93.6(2)
90.3(2)
94.1(2)
92.7(2)
176.4(2)
85.71(13)
176.06(16)
88.98(18)
86.19(19)
89.17(10)
90.26(10)
174.9(2)
86.39(16)
174.84(17)
88.31(16)
87.37(19)
88.48(12)
88.01(11)
tilted slightly such that the C5-bound hydrogens are closer
than the N-bound hydrogens.
Electronic factors also explain why these hydrogens point
to the bromine atom, since they are involved in weak inter-
molecular hydrogen bonds. In 1a, only intramolecular hy-
drogen bonds are detected: 2.66 Å for H(2)···Br and 2.57 Å
for H(4)···Br. These and the corresponding N···Br distances
[3.206(1) and 3.212(1) Å] confirm the presence of a hydro-
gen bond, which may be considered as “weak”.[17] The bro-
mine atom in 1b is also involved in two weak intramolecular
hydrogen bonds with the N-bound hydrogens [2.62 Å for
H(2)···Br and 2.57 Å for H(4)···Br], the corresponding
N···Br distances being 3.218(1) and 3.191(1) Å, and by a
weak intermolecular hydrogen bond to one of the N-bound
hydrogen atoms of an adjacent molecule [2.68 Å for H(2)
···Br, with N···Br = 3.519(1)]. Similar hydrogen bond
lengths have been found for other bromo complexes con-
taining pyrazoles.[8a,18]
The structure of the related rhenium complex fac-
[ReBr(CO)3(pzH)2][18a] shows some analogies and differ-
ences with those reported here: the relative orientation of
the pzH ligands is similar to that of Hdmpz in 1b, but only
one of the N-bound hydrogens in the rhenium complex is
involved in a intermolecular hydrogen bond.
Synthesis and Characterization of
Pyrazolylamidinomanganese Complexes
The synthesis of pyrazolylamidinomanganese() com-
plexes was carried out by reacting equimolar amounts of
the corresponding bis(nitrile) complexes and pyrazole
(Scheme 1). Nucleophilic addition to metal-activated ni- Scheme 2. Synthesis of pyrazolylamidino complexes.
4432 © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjic.org
Eur. J. Inorg. Chem. 2005, 4430–4437

Pyrazolylamidino- and Bis(pyrazole)manganese() Complexes
FULL PAPER
Figure 2. Perspective views of fac-[MnBr(CO)3{NH=C(Me)dmpz-κ2N,N}] (2b, top) and fac-[MnBr(CO)3{NH=C(Ph)dmpz-κ2N,N}] (3b,
bottom) showing the atom numbering.
process since it afforded similar mixtures of 1 and 2 (see previously reported structures of halotricarbonylmangane-
Exp. Sect.).
se() complexes containing a bidentate N-donor ligand.[23]
The C–O stretching region of 2 in the IR spectra also The distances and angles found in the pyrazolylamidino li-
shows three absorptions, as expected for a fac geometry. gands are also similar to those found in other pyrazolylami-
The C–O frequencies follow the expected trends considering dino complexes.[4]
the better donor properties of (a) Hdmpz compared to Hpz,
The N-bound hydrogen atoms of both structures are in-
and (b) amidino ligands derived from acetonitrile compared volved in intermolecular hydrogen bonds, with the bromine
to those derived from benzonitrile. The C–N stretching ab- atom in 2b [H(3)···Br = 2.66 Å; N(3)···Br = 3.483(1) Å],
sorption of the amidine ligand is also evident in the IR which may be considered as “weak”,[17] whereas in 3b they
spectra. The C–N frequencies are slightly higher for com- are linked to a molecule of tetrahydrofuran present in the
plexes 2 than for complexes 3, which could point to a higher lattice [H(3)···O(90) = 1.90 Å; N(3)···O(90) = 2.873(7) Å] by
delocalization in the latter due to the presence of a phenyl a hydrogen bond which may be considered as “moder-
group instead of a methyl.
ate”.[17]
The NMR spectroscopic data do not provide structural
information, therefore one of each type of complex was
subjected to a crystallographic study. The structures are
shown in Figure 2 and relevant distances and angles are col-
lected in Table 2. The structural data are essentially the
Experimental Section
General Remarks: All manipulations were performed under N2 by
conventional Schlenk techniques. Filtrations were carried out with
same in both complexes, and very similar to those found in dry Celite under N2. Solvents were purified according to standard
Eur. J. Inorg. Chem. 2005, 4430–4437
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M. Arroyo, Á. López-Sanvicente, D. Miguel, F. Villafañe
FULL PAPER
1
w, 583 w, 512 w. H NMR (300 MHz): δ = 6.47 (s, 2 H, H4 Hpz),
Table 2. Selected distances [Å] and angles [°] for fac-[MnBr(CO)3-
{NH=C(Me)dmpz-κ2N,N}] (2b) and fac-[MnBr(CO)3{NH=C(Ph)-
dmpz-κ2N,N}] (3b).
7.81 (s, 2 H, H3 Hpz), 7.89 (s, 2 H, H5 Hpz), 12.16 (br., 2 H, HN)
ppm. 13C{1H} NMR (75.78 MHz): δ = 107.9 (s, C4 Hpz), 132.6 (s,
C3,5 Hpz), 144.2 (s, C5,3 Hpz), 222.8 (br., CO) ppm.
C9H8BrMnN4O3 (355.03): calcd. C 30.45, H 2.27, N 15.78; found
C 30.60, H 2.32, N 15.98.
2b
3b
Mn(1)–C(1)
Mn(1)–C(2)
Mn(1)–C(3)
Mn(1)–N(1)
Mn(1)–N(3)
Mn(1)–Br(1)
N(1)–N(2)
N(2)–C(4)
N(3)–C(4)
C(1)–O(1)
C(2)–O(2)
C(3)–O(3)
C(1)–Mn(1)–C(3)
C(1)–Mn(1)–C(2)
C(3)–Mn(1)–C(2)
C(1)–Mn(1)–N(3)
C(3)–Mn(1)–N(3)
C(2)–Mn(1)–N(3)
C(1)–Mn(1)–N(1)
C(3)–Mn(1)–N(1)
C(2)–Mn(1)–N(1)
N(3)–Mn(1)–N(1)
C(1)–Mn(1)–Br(1)
C(3)–Mn(1)–Br(1)
C(2)–Mn(1)–Br(1)
N(3)–Mn(1)–Br(1)
N(1)–Mn(1)–Br(1)
N(2)–N(1)–Mn(1)
N(1)–N(2)–C(4)
C(4)–N(3)–Mn(1)
N(3)–C(4)–N(2)
1.793(4)
1.807(4)
1.807(4)
2.041(2)
2.007(3)
2.5840(13)
1.391(3)
1.391(3)
1.275(3)
1.148(4)
1.147(4)
1.140(3)
91.31(13)
89.78(15)
89.58(16)
95.65(13)
94.07(13)
173.38(13)
89.78(11)
170.62(12)
99.74(13)
76.56(10)
177.55(10)
89.26(9)
87.84(12)
86.68(8)
90.04(7)
113.81(15)
115.0(2)
120.1(2)
114.4(2)
1.790(5)
1.802(5)
1.786(5)
2.039(3)
1.995(4)
2.5337(9)
1.379(4)
1.391(5)
1.267(5)
1.131(5)
1.145(5)
1.144(5)
90.37(19)
92.6(2)
88.81(19)
91.52(18)
94.88(18)
174.42(17)
93.97(17)
170.69(17)
93.97(17)
76.79(15)
178.73(15)
88.76(13)
88.26(14)
87.63(12)
86.75(9)
113.1(2)
115.7(3)
120.3(3)
114.0(4)
fac-[MnBr(CO)3(Hdmpz)2] (1b): Hdmpz (0.058 g, 0.6 mmol) was
added to a solution of [MnBr(CO)5] (0.082 g, 0.3 mmol) in CH2Cl2
(20 mL). The solution was stirred at 40 °C for 2 h. Hexane was
added (ca. 20 mL) and the solution was concentrated and cooled
to –20 °C to give a yellow-orange microcrystalline solid, which was
decanted, washed with hexane (3×3 mL approximately), and dried
in vacuo to yield 0.113 g (92%) of 1b. IR (THF): ν = 2026 cm–1 vs,
˜
1935 vs, 1904 vs. IR (KBr): ν = 3299 cm–1 m, 2930 w, 2022 vs, 1940
˜
vs, 1898 vs, 1574 s, 1470m, 1422 w, 1377 m, 1284 m, 1178 w, 1156
w, 1040 w, 1026 w, 817 w, 789m, 686 w, 658 w, 637 m, 560 w, 519
w, 469 w. 1H NMR (300 MHz): δ = 2.15 (s, 6 H, CH3 Hdmpz),
2.25 (s, 6 H, CH3 Hdmpz), 6.01 (s, 2 H, H4 Hdmpz), 11.02 (br., 2
H, HN) ppm. 13C{1H} NMR (75.78 MHz): δ = 10.8 (s, CH3
Hdmpz), 14.2 (s, CH3 Hdmpz), 107.8 (s, C4 Hdmpz), 143.1 (s, C3,5
Hdmpz), 154.2 (s, C5,3 Hdmpz), 222.8 (br., CO) ppm.
C13H16BrMnN4O3 (411.13): calcd. C 37.98, H 3.92, N 13.63; found
C 38.02, H 3.59, N 13.44.
fac-[MnBr(CO)3{NH=C(CH3)pz-κ2N,N}] (2a). Method A: A solu-
tion of [MnBr(CO)5] (0.137 g, 0.5 mmol) in CH3CN (20 mL) was
maintained at 60 °C for 30 min. Then, Hpz (0.034 g, 0.5 mmol) was
added and the solution was heated for 30 min. The solvent was
removed in vacuo and the yellow residue was extracted with THF
(ca. 20 mL) and filtered. Hexane was added (ca. 10 mL) and the
solution was concentrated and cooled to –20 °C to give a yellow-
orange microcrystalline solid, which was decanted, washed with
hexane (3×3 mL approximately), and dried in vacuo to yield
0.098 g (60%) of 2a. Concentration of the mother liquor and fur-
ther cooling to –20 °C, yielded 0.015 g (8% referred to manganese)
of 1a after decanting, washing with hexane (3×3 mL approxi-
mately), and drying in vacuo.
procedures.[24] fac-[MnBr(CO)3(NCMe)2] was obtained as de-
scribed below and its CO stretching bands were compared with
those described previously.[20] fac-[MnBr(CO)3(NCPh)2] was ob-
tained as described below and its CO stretching bands were com-
pared with those displayed by a sample of fac-[MnBr(CO)3-
(NCPh)2] obtained by the method previously described for the
MeCN complex.[20] All other reagents were obtained from the usual
commercial suppliers and used as received. IR spectra were re-
corded with a Perkin–Elmer RX I FT-IR apparatus as KBr pellets
from 4000 to 400 cm–1. NMR spectra were recorded with Bruker
AC-300 or ARX-300 instruments in (CD3)2CO, at room tempera-
ture unless otherwise stated. NMR spectra are referenced to the
Method B: A solution of [MnBr(CO)5] (0.082 g, 0.3 mmol) in
CH3CN (20 mL) was maintained at 60 °C for 30 min. Then, 1a
(0.106 g, 0.3 mmol) was added and the solution was heated for
30 min. The solvent was removed in vacuo and the yellow residue
was extracted with THF (ca. 20 mL) and filtered. Hexane was
added (ca. 10 mL) and the solution was concentrated and cooled
to –20 °C to give a yellow-orange microcrystalline solid, which was
decanted, washed with hexane (3×3 mL approximately), and dried
in vacuo to yield 0.123 g (62%) of 2a. Concentration of the mother
liquor and further cooling to –20 °C gave 0.018 g (8%) of 1a, after
decanting, washing with hexane (3×3 mL approximately), and dry-
internal residual solvent peak for H and 13C{1H} NMR. Assign-
1
ment of the 13C{1H} NMR spectroscopic data was supported by
DEPT experiments and relative intensities of the resonance signals.
Elemental analyses were performed on a Perkin–Elmer 2400B
microanalyzer.
ing in vacuo. IR (THF): ν = 2027 cm–1 vs, 1939 vs, 1912 vs. IR
˜
(KBr): ν = 3191 cm–1 m, 3143 w, 2034 vs, 1938 vs, 1918 vs, 1655m,
˜
1520 w, 1458 w, 1434 w, 1408m, 1397 w, 1373 w, 1330 w, 1241m,
1221 w, 1128 w, 1070 w, 1050 w, 1042 w, 1000 w, 962 w, 766 m, 686
fac-[MnBr(CO)3(Hpz)2] (1a): Hpz (0.041 g, 0.6 mmol) was added
to a solution of [MnBr(CO)5] (0.082 g, 0.3 mmol) in CH2Cl2
(20 mL). The solution was stirred at 40 °C for 2 h, during which
time a white solid precipitated. The solvent was removed in vacuo
and the yellow residue was extracted with THF (ca. 20 mL) and
filtered. Hexane was added (ca. 20 mL) and the solution was con-
centrated and cooled to –20 °C to give a yellow-orange microcrys-
talline solid, which was decanted, washed with hexane (3×3 mL
approximately), and dried in vacuo to yield 0.094 g (88%) of 1a.
IR (THF): ν = 2030 cm–1 vs, 1940 vs, 1910 vs. IR (KBr): ν =
1
w, 688 m, 632 m, 600 w, 517 m. H NMR (300 MHz): δ = 2.87 [s,
3 H, N=C(CH3)], 6.83 (s, 1 H, H4 pz), 8.38 (d, J = 1.5 Hz, 1 H,
H3 pz), 8.61 (d, J = 3.0 Hz, 1 H, H5 pz), 11.06 (br., 1 H, HN) ppm.
13C{1H} NMR (75.78 MHz): δ = 19.0 [s, HN=C(CH3)], 112.4 (s,
C4 pz), 133.4 (s, C3,5 pz), 147.7 (s, C5,3 pz), 161.8 [s, HN=C(CH3)]
ppm; CO not observed. C8H7BrMnN3O3 (328.00): calcd. C 29.29,
H 2.15, N 12.81; found C 28.97, H 2.31, N 13.07.
fac-[MnBr(CO)3{NH=C(CH3)dmpz-κ2N,N}] (2b). Method A: A
solution of [MnBr(CO)5] (0.137 g, 0.5 mmol) in CH3CN (20 mL)
was maintained at 60 °C for 30 min. Then, Hdmpz (0.048 g,
˜
˜
3341 cm–1 m, 3302 m, 3144 w, 2921 w, 2035 vs, 1940 vs, 1918 vs,
1468 w, 1352 w, 1139 w, 1127 m, 1056 m, 763 m, 676 w, 634 w, 602 0.5 mmol) was added and the solution was heated for 30 min.
4434 www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2005, 4430–4437

Pyrazolylamidino- and Bis(pyrazole)manganese() Complexes
FULL PAPER
Work-up as for 2a yielded 0.090 g (50%) of 2b and 0.005 g (2%
referred to manganese) of 1b.
Method B: C6H5CN (300 µL) was added to a solution of
[MnBr(CO)5] (0.082 g, 0.3 mmol) in THF (20 mL) and the mixture
was stirred at 70 °C for 1 h. Then, 1a (0.106 g, 0.3 mmol) was added
and the solution was heated at 70 °C for 45 min. Work-up as for
3a yielded 0.039 g (17%) of 3a and 0.013 g (5%) of 1a. IR (THF):
ν = 2027 cm–1 vs, 1941 s, 1914 s. IR (KBr): ν = 3401 cm–1 s, 2030
Method B: A solution of [MnBr(CO)5] (0.082 g, 0.3 mmol) in
CH3CN (20 mL) was maintained at 60 °C for 30 min. Then, 1b
(0.106 g, 0.3 mmol) was added and the solution was heated for
30 min. Work-up as for 2a yielded 0.135 g (57%) of 2b and 0.007 g
˜
˜
vs, 1936 vs, 1916 vs, 1628 m, 1560 w, 1452 w, 1429 w, 1406 w, 1383
w, 1262 w, 1218 w, 1088 w, 1054 w, 867 w, 776m, 699 w, 684 w, 639
w, 625 w, 521 w. 1H NMR (300 MHz): δ = 6.85 (s, 1 H, H4 pz),
7.68 (d, J = 7.1 Hz, 2 H, C6H5), 7.72 (d, J = 7.1 Hz, 1 H, C6H5),
7.80 (d, J = 7.1 Hz, 2 H, C6H5), 8.34 (s, 1 H, H3 pz), 8.51 (s, 1 H,
H5 pz), 11.53 (br., 1 H, HN) ppm. 13C{1H} NMR (75.78 MHz): δ
= 112.4 (s, C4 pz), 128.5 (s, C6H5), 128.7 (s, C6H5), 129.6 (s, C6H5),
132.9 (s, C6H5), 134.2 (s, C3,5 pz), 143.3 (s, Cipso C6H5), 147.9 (s,
C5,3 pz), 161.8 [s, HN=C(C6H5)] ppm; CO not observed.
C13H9BrMnN3O3 (390.07): calcd. C 40.03, H 2.32, N 10.77; found
C 40.31, H, 2.30, N 10.43.
(2%) of 1b. IR (THF): ν = 2023 cm–1 vs, 1934 vs, 1909 vs. IR (KBr):
˜
ν = 3444 cm–1 w, 3194 m, 2032 s, 1942 s, 1921 vs, 1909 vs, 1651 m,
˜
1574 w, 1453 w, 1410 m, 1357 w, 1246 w, 1097 w, 1044 w, 843 w,
802 w, 684 w, 634 w, 520 w. 1H NMR (300 MHz): δ = 2.58 (s, 3 H,
CH3 dmpz), 2.69 (s, 3 H, CH3 dmpz), 2.89 [s, 3 H, N=C(CH3)],
6.39 (s, 1 H, H4 dmpz), 10.67 (br., 1 H, HN) ppm. 13C{1H} NMR
(75.78 MHz): δ = 14.0 (s, CH3 dmpz), 15.3 (s, CH3 dmpz), 21.4 [s,
HN=C(CH3)], 114.3 (s, C4 dmpz), 145.5 (s, C5,3 dmpz), 157.0 (s,
C3,5 dmpz), 163.6 [s, HN=C(CH3)] ppm; CO not observed.
C10H11BrMnN3O3 (356.05): calcd. C 33.73, H 3.11, N 11.80; found
C 33.63, H 3.00, N 11.51.
fac-[MnBr(CO)3{NH=C(C6H5)dmpz-κ2N,N}] (3b): Method A:
C6H5CN (300 µL) was added to a solution of [MnBr(CO)5]
(0.082 g, 0.3 mmol) in THF (20 mL) and the mixture was stirred at
70 °C for 1 h. Then, Hdmpz (0.029 g, 0.3 mmol) was added and the
solution was heated at 70 °C for 30 min. Work-up as for 3a yielded
0.031 g (24%) of 3b and 0.038 g (32%) of 1b.
fac-[MnBr(CO)3{NH=C(C6H5)pz-κ2N,N}] (3a). Method A:
C6H5CN (500 µL) was added to a solution of [MnBr(CO)5]
(0.137 g, 0.5 mmol) in THF (20 mL) and the mixture was stirred at
70 °C for 1 h. Then, Hpz (0.034 g, 0.5 mmol) was added and the
solution was heated at 70 °C for an additional hour. The solvent
was removed in vacuo and the yellow residue was washed with
hexane (5×3 mL approximately), extracted with THF (ca. 20 mL),
and filtered. Hexane was added (ca. 10 mL) and the solution was
concentrated and cooled to –20 °C to give a yellow-orange micro-
crystalline solid, which was decanted, washed with hexane
(3×3 mL approximately), and dried in vacuo to yield 0.027 g (14%)
of 3a. Concentration of the mother liquor and further cooling to
–20 °C, yielded 0.014 g (8% referred to manganese) of 1a, after
decanting, washing with hexane (3×3 mL approximately), and dry-
ing in vacuo.
Method B: C6H5CN (300 µL) was added to
a solution of
[MnBr(CO)5] (0.082 g, 0.3 mmol) in THF (20 mL) and the mixture
was stirred at 70 °C for 1 h. Then, 1b (0.123 g, 0.3 mmol) was added
and the solution was heated at 70 °C for 45 min. Work-up as for
3a yielded 0.064 g (25%) of 3b and 0.013 g (22%) of 1b. IR (THF):
ν = 2024 cm–1 vs, 1936 vs, 1912 vs. IR (KBr): ν = 3164 cm–1 w,
˜
˜
2026 s, 1918 vs, 1637 w, 1508 w, 1420 m, 1356 m, 1259 w, 1122 w,
1055 w, 887 w, 822 w, 706 w, 683 w, 669 w, 646 w, 634 w, 520 w.
1H NMR (300 MHz): δ = 1.80 (s, 3 H, CH3 dmpz), 2.65 (s, 3 H,
Table 3. Crystal data and refinement details for 1a, 1b, 2b, and 3b.
1a
1b
2b
3b·THF
Formula
C9H8BrMnN4O3
355.04
C13H16BrMnN4O3
411.15
monoclinic
P21/c
13.562(3)
18.551(4)
13.973(3)
90
96.008(4)
90
C10H11BrMnN3O3
356.07
monoclinic
P21/c
8.721(6)
11.356(7)
14.363(9)
90
101.665(12)
90
C19H21BrMnN3O4
490.24
monoclinic
P21/n
8.150(2)
13.754(4)
19.635(6)
90
98.714(6)
90
Mol. mass
Crystal system
Space group
a [Å]
b [Å]
c [Å]
triclinic
¯
P1
8.194(2)
8.447(2)
10.857(3)
84.365(5)
83.156(5)
65.663(4)
678.8(3)
2
α [°]
β [°]
γ [°]
V [Å3]
3496.2(12)
8
1393.1(15)
4
2175.5(11)
4
Z
T [K]
296
1.737
348
296
1.562
1648
296
1.698
704
296
1.497
992
Dcalcd. [gcm–3]
F(000)
λ (Mo-Kα) [Å]
Crystal size [mm]
Color
0.71073
0.18×0.19×0.30
orange
0.71073
0.07×0.14×0.29
orange
0.71073
0.12×0.15×0.22
orange
0.71073
0.10×0.11×0.35
orange
µ [mm–1]
3.920
3.056
3.818
2.471
Scan range [°]
Absorption correction
Corr. factors (max., min.)
No. of refl. measured
1.89 Յ θ Յ 23.30
SADABS
1.000000, 0.249439
2979
1.51 Յ θ Յ 23.29
SADABS
1.000, 0.658220
15633
5029 [0.0616]
3141
2.30 Յ θ Յ 23.30
SADABS
1.00000, 0.694409
6110
2002 [0.0223]
1606
1.81 Յ θ Յ 23.30
SADABS
1.00000, 0.605570
9576
3118 [0.0391]
2155
No. of refl. independent [R(int.)] 1924 [0.0184]
No. of refl. observed [I Ն 2σ(I)] 1677
GOF on F2
1.051
1.006
1.014
1.005
No. of parameters
Residuals R, wR2
172
421
170
259
0.0429, 0.1274
0.0412, 0.0721
0.0240, 0.0564
0.0383, 0.0922
Eur. J. Inorg. Chem. 2005, 4430–4437
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4435

M. Arroyo, Á. López-Sanvicente, D. Miguel, F. Villafañe
FULL PAPER
CH3 dmpz), 6.40 (s, 1 H, H4 dmpz), 7.45 (m, 1 H, C6H5), 7.64 (m,
3 H, C6H5), 7.77 (m, 1 H, C6H5), 11.11 (br.,, 1 H HN) ppm.
13C{1H} NMR (75.78 MHz): δ = 14.0 (s, CH3 dmpz), 15.3 (s, CH3
dmpz), 114.6 (s, C4 dmpz), 128.9 (s, C6H5), 129.9 (s, C6H5), 131.3
(s, Cipso C6H5), 132.6 (s, C6H5), 146.0 (s, C3,5 dmpz), 157.9 (s, C3,5
dmpz), 164.3 [s, HN=C(C6H5)], 221.1 (s, CO), 223.9 (s, CO), 224.0
(s, CO) ppm. C15H13BrMnN3O3 (418.12): calcd. C 43.09, H 3.13,
N 10.05; found C 42.84, H, 3.03, N 9.99.
verty, A. S. Rothin, J. Chem. Soc., Dalton Trans. 1986, 109–
111.
[5]
[6]
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J. Pérez, L. Riera, V. Riera, R. Corzo-Suárez, S. García-
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Pérez, L. Riera, V. Riera, S. García-Granda, E. García-Rodríg-
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uez, D. Miguel, Chem. Commun. 2002, 384–385. For some re-
cent references concerning group 7 complexes, see: m) L. Cue-
sta, E. Hevia, D. Morales, J. Pérez, V. Riera, M. Seitz, D. Mig-
uel, Organometallics 2005, 24, 1772–1775; n) S. Nieto, J. Pérez,
V. Riera, D. Miguel, C. Alvarez, Chem. Commun. 2005, 546–
548; o) L. Cuesta, E. Hevia, D. Morales, J. Pérez, V. Riera, E.
Rodríguez, D. Miguel, Chem. Commun. 2005, 116–116; p) L.
Cuesta, D. C. Gerbino, E. Hevia, D. Morales, M. E. N. Cle-
mente, J. Pérez, L. Riera, V. Riera, D. Miguel, I. del Río, S.
García-Granda, Chem. Eur. J. 2004, 10, 1765–1777; q) E.
Hevia, J. Pérez, V. Riera, D. Miguel, P. Campomanes, M. I.
Menéndez, T. L. Sordo, S. García-Granda, J. Am. Chem. Soc.
2003, 125, 3706–3707; r) D. C. Gerbino, E. Hevia, D. Morales,
M. E. N. Clemente, J. Pérez, L. Riera, V. Riera, D. Miguel,
Chem. Commun. 2003, 328–329; s) E. Hevia, J. Pérez, V. Riera,
D. Miguel, Organometallics 2003, 22, 257–263; t) E. Hevia, J.
Pérez, V. Riera, D. Miguel, Angew. Chem. Int. Ed. 2002, 41,
3858–3860; u) E. Hevia, J. Pérez, V. Riera, D. Miguel, Chem.
Commun. 2002, 1814–1815.
X-ray Crystallographic Study of 1a, 1b, 2b, and 3b: Crystals were
grown by slow diffusion of hexane into concentrated solutions of
the complexes in CH2Cl2 (for 1a and 1b) or THF (for 2b and 3b)
at –20 °C. Relevant crystallographic details are given in Table 3. A
crystal was attached to a glass fiber and transferred to a Bruker
AXS SMART 1000 diffractometer with graphite-monochromated
Mo-Kα radiation and a CCD area detector. A hemisphere of the
reciprocal space was collected up to 2θ = 48.6°. Raw frame data
were integrated with the SAINT program.[25] The structure was
solved by direct methods with SHELXTL.[26] A semi-empirical ab-
sorption correction was applied with the program SADABS.[27] All
non-hydrogen atoms were refined anisotropically. Hydrogen atoms
were set in calculated positions and refined as riding atoms, with a
common thermal parameter. All calculations and graphics were
made with SHELXTL.
CCDC-266383 (for 1a), -266384 (for 1b), -266385 (for 2b), and
-266386 (for 3b) 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.
Acknowledgments
The authors thank the Spanish DGICYT (BQU2002-03414) and
the Junta de Castilla y León (VA052/03) for financial support, and
the MEC (Program FPI) for a grant to M. A.
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4436
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2005, 4430–4437

Pyrazolylamidino- and Bis(pyrazole)manganese() Complexes
FULL PAPER
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reported, they confirm the expected fac-tricarbonyl-cis-
bis(benzonitrile)geometry.
606, 197–202.
[12] All attempts to determine the nature of this white solid were
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1
to pzH but do not show CO stretching bands; no reliable H
NMR spectra could be obtained, which points to a paramag-
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Received: May 9, 2005
Published Online: September 15, 2005
Eur. J. Inorg. Chem. 2005, 4430–4437
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