Bis(pyrazol-1-yl)acetates as tripodal "scorpionate" ligands in transition metal carbonyl chemistry: Syntheses, structures and reactivity of manganese and rhenium carbonyl complexes of the type [LM(CO)3] (L=bpza, bdmpza)

Article abstract of DOI:10.1016/S0022-328X(01)00648-9

The coordination of the ligands bis(3,5-dimethylpyrazol-1-yl)acetate (bdmpza) and bis(pyrazol-1-yl)acetate (bpza) to Group VII metal carbonyls has been investigated. The compounds [LM(CO)₃], where M=Mn, Re and L=bpza, bdmpza (2a-3b), have been

Full text of DOI:10.1016/S0022-328X(01)00648-9

Journal of Organometallic Chemistry 626 (2001) 16–23
www.elsevier.nl/locate/jorganchem
Bis(pyrazol-1-yl)acetates as tripodal ‘‘scorpionate’’ ligands in
transition metal carbonyl chemistry: syntheses, structures and
reactivity of manganese and rhenium carbonyl complexes of the
type [LM(CO) ] (L=bpza, bdmpza)
3
Nicolai Burzlaff *, Ina Hegelmann, Bernhard Weibert
Fachbereich Chemie, Uni6ersit a¨ t Konstanz, Fach M728, D-78457 Konstanz, Germany
Received 26 October 1999; received in revised form 29 November 2000; accepted 4 December 2000
Abstract
The coordination of the ligands bis(3,5-dimethylpyrazol-1-yl)acetate (bdmpza) and bis(pyrazol-1-yl)acetate (bpza) to Group VII
metal carbonyls has been investigated. The compounds [LM(CO) ], where M=Mn, Re and L=bpza, bdmpza (2a–3b), have been
3
synthesised. The new complexes [(bdmpza)Mn(CO) ] (2b), [(bpza)Re(CO) ] (3a) and [(bdmpza)Re(CO) ] (3b), and bis(pyrazol-1-
3
3
3
yl)acetic acid (1a) have been characterised by single-crystal X-ray analyses. Based on IR-spectroscopic and structural data the
Me
2
electronic properties of these ligands are compared with those of Tp, Tp , Cp and Cp*. The reaction of [(bdmpza)Re(CO) ] (3b)
3
with NOBF afforded [(bdmpza)Re(CO) (NO)]BF (4). © 2001 Elsevier Science B.V. All rights reserved.
4
2
4
Keywords: Manganese; Rhenium; Carbonyl; Bis(pyrazol-1-yl)acetate; Scorpionate ligands
metal carbonyl chemistry [1–4]. So Tp and its varia-
tions are often taken as an equivalent to C H (Cp) or
1. Introduction
5
5
−
C Me (Cp*). One of the most widely used Tp varia-
Tris(pyrazol-1-yl)borate, [(HB(pz)3)] (Tp), first in-
5 5
tions is the easily accessible tris(3,5-dimethylpyrazol-1-
troduced by S. Trofimenko more than 30 years ago,
now represents a ligand that is widely used in transition
Me
2
yl)borate (Tp ).
Recent investigations with Tp and Tp
Me
2
focused on
the electron donating properties of these two ligands. It
was found that their electron donating ability varies
with the coordinating metal and its oxidation state [5].
For all Group VII metal carbonyl complexes of the
Me
2
type [LM(CO) ] (L=Cp*,Cp,Tp,Tp ) structural and
3
infrared data are available from the literature [5–21].
Based on this data Bergman and co-workers recently
surmised the following trend in the donor capabilities
Me
2
of these ligands towards manganese: Cp*ꢀTp
CpꢀTp. For rhenium they suggested Cp*\Tp
Tp\Cp [5].
\
\
Me
2
Because of the enormous steric hindrance of Tp
ligands — for Tp complexes a Tolman angle close to
Me
2
Fig. 1. The ligands Cp, Cp*, Tp, Tp , bpza and bdmpza.
1
80° was observed [22] — it is rather difficult in tran-
sition metal carbonyl complexes with tripodal bound
Tp to exchange more than one carbonyl ligand by
bulky substituents [6]. The steric hindrance can be
*
Corresponding author. Tel.: +49-7531-882053; fax: +49-7531-
8
0
83136.
E-mail address: nicolai@chemie.uni-konstanz.de (N. Burzlaff).
022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00648-9

N. Burzlaff et al. / Journal of Organometallic Chemistry 626 (2001) 16–23
17
obtain bis(pyrazol-1-yl)acetic acid (1a) in even higher
yield (Eq. 1). Although a reaction of bis(pyrazol-1-
yl)acetic acid with biotin hydrazide was reported for
radiopharmaceutical studies recently [27], no synthetic
route or analytical data for 1a was available from the
literature until now.
Fig. 2. Molecular structure of the bis(pyrazol-1-yl)acetic acid (1a).
(1)
Table 1
Selected bond distances and bond angles of bis(pyrazol-1-yl)acetic
acid (1a)
This new, sterically less hindered N,N,O tripod ligand
a is not accessible via deprotonation of bis(pyrazol-1-
Bond distance (A
,
)
1a
Bond angle (°)
1a
1
C(4)ꢀC(5)
C(5)ꢀO(4)
C(5)ꢀO(5)
C(4)ꢀN(12)
C(4)ꢀN(22)
1.554(3)
1.318(3)
1.215(3)
1.468(3)
1.467(3)
O(4)ꢀC(5)ꢀO(5)
C(5)ꢀC(4)ꢀN(12)
C(5)ꢀC(4)ꢀN(22)
N(12)ꢀC(4)ꢀN(22)
125.4(2)
112.8(2)
109.2(2)
111.8(2)
yl)methane and subsequent addition of carbon dioxide,
similar to the literature method for bdmpza reported by
Otero et al. [24,25], due to deprotonation of the pyra-
zolyl group in positions 3 and 5. Suitable crystals for
X-ray structure determination were obtained from an
acetonitrile solution (Fig. 2). Selected distances and
angles are given in Table 1. The structure of 1a deviates
only slightly from that of bis(3,5-di-tert-butylpyrazol-1-
yl)acetic acid [26]. The differences are caused by the less
bulky pyrazolyl groups.
reduced by replacing one pyrazole by a less bulky
donor group. Furthermore, a pyrazolyl group is a good
and relatively hard s donor while a moderate acceptor.
These properties cause some Tp carbonyl complexes to
be more stable than their Cp or Cp* analogues [23]. So
one weaker donor group in the tripod ligand might also
modify the reactivity of these complexes.
In our aim to find suitable tripod N,N,O ligands as
mimics for the active sites of iron and zinc enzymes we
were interested in the new Tp-like ligand bis(3,5-
dimethylpyrazol-1-yl)acetate (bdmpza) (Fig. 1), recently
introduced by Otero et al. [24,25] on niob complexes
Usually the pentacarbonyl complexes [BrMn(CO)5]
and [BrRe(CO) ] are the starting materials to synthesise
5
tris(pyrazol-1-yl)borate complexes of manganese and
rhenium [9]. Using these substrates we were able to
obtain
bis(3,5-dimethylpyrazol-1-yl)acetate
and
bis(pyrazol-1-yl)acetate tricarbonyl complexes of these
metals in a reaction with potassium carboxylates of
bpza and bdmpza (Eq. 2). These carboxylates were
produced in situ from the acids and potassium tert-
butylate. The reactions were monitored by IR spec-
troscopy. During the reactions CO evolution was
observed. KBr and tert-butanol were removed from the
products by washing with degassed water.
such as [NbCl (bdmpza)(PhCCMe)] and their
2
structures.
As an alternative to the multi-step synthesis pub-
lished there, we recently developed a simple route to
bis(3,5-dimethylpyrazol-1-yl)acetic acid starting from
purchasable reagents [26]. Here we report on: (a) a
one-step synthesis of bis(pyrazol-1-yl)acetic acid; (b) the
application of its anion bpza as a new tripod ligand not
accessible by the synthetic route of Otero et al.; and (c)
the syntheses of new pseudotetrahedral tricarbonyl
complexes of manganese and rhenium with bpza or
bdmpza as tripod ligands.
(2)
2
. Results and discussion
The tricarbonyl complexes 2a–3b are rather stable
and can be stored as solids for days in air. The com-
plexes are soluble in THF, 2b and 3b in
dichloromethane and acetone as well due to the 3,5-
dimethylpyrazole groups. Crystals suitable for X-ray
As reported earlier bis(3,5-dimethylpyrazol-1-
yl)acetic acid (1b) and its acetate bdmpza can be syn-
thesised by a phase transfer catalysed reaction of
3,5-dimethylpyrazole with base and dibromoacetic acid
in 45% yield. This synthetic route can also be used to
determination
of
[(bdmpza)Mn(CO)3]
(2b),

1
8
N. Burzlaff et al. / Journal of Organometallic Chemistry 626 (2001) 16–23
Table 3
[
(bpza)Re(CO)3] (3a) and [(bdmpza)Re(CO)3] (3b)
Selected bond angles of the complexes 2b, 3a and 3b
could be obtained (Figs. 3–5). Selected distances and
angles are summarised in Tables 2 and 3.
Bond angle (°)
2b
85.98(10)
85.44(9)
84.83(9)
179.52(14)
175.82(15)
174.19(15)
90.8(2)
3a
81.8(2)
3b
80.9(4)
N(11)ꢀMꢀN(21)
O(4)ꢀMꢀN(11)
O(4)ꢀMꢀN(21)
O(4)ꢀMꢀC(2)
N(11)ꢀMꢀC(3)
N(21)ꢀMꢀC(1)
C(1)ꢀMꢀC(2)
C(1)ꢀMꢀC(3)
C(2)ꢀMꢀC(3)
81.4(2)
80.4(2)
176.3(3)
174.1(3)
174.4(3)
88.7(3)
87.8(3)
88.4(3)
82.1(3)
81.0(3)
177.2(4)
174.3(4)
171.7(5)
90.4(6)
87.8(5)
89.3(5)
87.7(2)
90.0(2)
The distances in the bpza and bdmpza ligands as well
as those of the carbonyl groups are in all structures
(
2b,3a,3b) similar to those reported in literature for the
Fig. 3. Molecular structure of [(bdmpza)Mn(CO) ] (2b).
Me
2
3
Tp or Tp
homologous [TpM(CO)3] and
Me
2
[Tp M(CO) ] [9]. Due to the clamp of the tripod
3
ligand the angles NꢀMꢀN and NꢀMꢀO differ 4–5°
from the 90° octahedral angle. The sterically demand-
ing pyrazolyl groups force two of the carbonyl groups
to close up 2°. The third carbonyl group forms a nearly
perfect 180° angle to the carboxylate donor. This em-
phasises the much smaller steric hindrance of bdmpza
Me
2
compared to Tp . Of the three metal–carbonyl dis-
tances MꢀC(2) is the shortest in all three structures.
This is due to the trans influence of the two pyrazolyl p
acceptor groups onto the other two metal–carbonyl
bonds. Most striking is the fact that in 2b, 3a and 3b all
three metal–carbonyl distances are significantly longer
Fig. 4. Molecular structure of [(bdmpza)Re(CO) ] (3b).
3
Me
2
than those of their Tp , Cp* and even Cp analogues
see Table 4). This implies that bdmpza and bpza are
(
less electron donating than even the Cp ligand.
The two pyrazolyl groups in 2a–3b are spectroscopi-
cally equivalent, showing only one set of signals in the
1
NMR spectra. The H-NMR signals of the manganese
complexes 2a and 2b are broad. The IR spectra of
2
a–3b are similar to those of ‘‘piano stool’’ type com-
plexes. Two strong signals A and E are observed, of
1
which E in THF is split into two absorptions. In a KBr
matrix these signals are in some cases split again. Due
to a smaller reduced mass of the metal the manganese
CO signals are found at slightly higher wavenumbers
compared with those of the rhenium compounds.
The bpza and bdmpza carboxylate groups are weaker
s donors compared with the pyrazolyl groups. There-
Fig. 5. Molecular structure of [(bpza)Re(CO) ] (3a).
3
Table 2
Selected bond distances of the complexes 2b, 3a and 3b
Bond distance (A
,
)
2b
3a
3b
fore, the IR spectra show CO vibrations that are at
MꢀN(11)
MꢀN(21)
MꢀO(4)
2.079(3)
2.093(3)
2.055(2)
1.819(4)
1.804(4)
1.816(4)
1.242(4)
1.273(4)
1.558(4)
2.216(6)
2.211(6)
2.184(5)
1.952(9)
1.930(10)
1.947(8)
1.230(9)
1.295(8)
1.570(10)
2.214(10)
2.200(10)
2.164(8)
1.956(14)
1.943(12)
1.973(13)
1.251(14)
1.293(14)
1.579(15)
−1
higher wavenumbers by 4–15 cm
corresponding complexes
than those of the
and
[TpM(CO)3]
Me
2
MꢀC(1)
MꢀC(2)
MꢀC(3)
[Tp M(CO) ] (Table 5). Also, the comparison with
3
the CO absorptions of the Cp and Cp* analogues
indicates that bpza and bdmpza are slightly less elec-
tron donating ligands, although the differences are only
minor and some of the data vary through different
publications.
O(5)ꢀC(5)
O(4)ꢀC(5)
C(4)ꢀC(5)

N. Burzlaff et al. / Journal of Organometallic Chemistry 626 (2001) 16–23
19
To verify these conclusions the reactivity of [(bdm-
a simple one-step synthesis from dibromoacetic acid.
The reaction of the Group VII metal carbonyls [BrMn-
(CO) ] and [BrMn(CO) ] with bis(pyrazol-1-yl)acetate
pza)Re(CO) ] (3b), which should be quite close to that
3
of [CpRe(CO) ], was checked in the first reaction. The
3
5
5
chemical behaviour of [(bdmpza)Re(CO) ] (3b) towards
nitrosyltetrafluoroborate is similar to that of
(bpza) and bis(3,5-dimethylpyrazol-1-yl)acetate (bdm-
pza) has been shown to yield the products
[(bpza)Mn(CO)3] (2a), [(bdmpza)Mn(CO)3] (2b),
[(bpza)Re(CO) ] (3a) and [(bdmpza)Re(CO) ] (3b).
3
[
CpRe(CO) ] [29]: 3b reacts with NOBF to form the
3
4
complex [(bdmpza)Re(CO) (NO)]BF (4) (Eq. 3).
2
4
3
3
From the IR-spectroscopic data of these complexes and
the single-crystal X-ray analyses of 2b–3b it follows
that for Group VII metal carbonyls bpza and bdmpza
Me
2
are less electron donating than Tp, Tp , Cp* and
even Cp. In the case of [(bdmpza)Re(CO) ] (3b) a
3
+
COꢀNO exchange yielded [(bdmpza)Re(CO) (NO)]-
BF (4), showing a reactivity similar to [CpRe(CO) ]. In
2
4
3
(
3)
future bpza and bdmpza might be as useful in coordi-
nation and organometallic chemistry as Tp and its
analogues.
In addition to the IR spectra and the structural data
this reactivity clearly shows the very similar electronic
properties of 3b compared with [CpRe(CO)3].
The IR spectra of 4 show a broad NO vibration at
−
1
1
712 cm . Two sets of signals are detected for the
4. Experimental
1
13
pyrazolyl groups in the H- and C-NMR spectra. This
clearly indicates a transposition of the NO group to one
of the good pyrazolyl s donors. 4 is a racemic mixture
of two enantiomers.
4.1. General
All experiments involving metal carbonyls were car-
ried out in Schlenk tubes under an atmosphere of argon
and using suitable purified solvents, although these
precautions might not be necessary. Micro-crystalline
precipitates were separated by centrifugation with a
Hettich Rotina 46 R Schlenk tube centrifuge. IR: Bio-
3
. Conclusions
Bis(pyrazol-1-yl)acetic acid (1a) and bis(3,5-
dimethylpyrazol-1-yl)acetic acid (1b) can be obtained in
rad FTS 60 and Perkin–Elmer FT 2000, CaF cuvets
2
Table 4
Me
2
−
Metal–carbonyl distances of the complexes [LM(CO) ] (M=Mn, Re; L=Cp*, Tp , Cp, B(Pz)4 , bpza, bdmpza)
3
Me
2
B(Pz) −4 a [21]
Ligand
Cp* [17,18]
1.738(9)
Tp
[9]
Cp [15,16]
bpza
bdmpza
d(MnꢀCO)
1.798(6)
1.782(7)
.794(6)
1.7947(25)
1.7876(25)
1.797(3)
1.802(5)
1.806(4)
1.820(5)
–
–
–
1.819(4)
1.804(4)
1.816(4)
b
1
.712(13)
1
d(ReꢀCO)
1.875(10)
1.904(9)
1.899(10)
1.904(10)
1.899(7)
1.888(7)
1.894(8)
–
–
–
1.952(9)
1.930(10)
1.947(8)
1.956(14)
1.943(12)
1.973(12)
b
b
1
1
.908(10)
.891(10)
a
Due to isotropic refinement of the carbon atoms, the structural data of [TpMn(CO) ] and [TpRe(CO) ] are less accurate [9] and were left out.
Distance d(MꢀCO) trans to the carboxylate donor.
3
3
b
Table 5
Selected IR signals (cm ) of [LMn(CO) ] and [LRe(CO) ]
−
1
3
3
Me
2
5
5
Ligand L
bpza
bdmpza
Tp
Tp
h -C H
h -C Me
5
5
5
5
w(CO) (THF)
2041, 1946, 1925
2036, 1942,
1915
2036, 1924
2033, 1930 [28] 2026, 1919 [28]
2026, 1938
–
2017, 1928
(hexane) [7]
–
[
LMn(CO)3]
w(CO) (KBr)
LMn(CO)3]
w(CO) (THF)
LRe(CO)3]
w(CO) (KBr)
LRe(CO)3]
2039, 1952, 1943,
1927, 1916
2029, 1924, 1904
2026, 1932,
1915 [9]
2024, 1914 [8]
2023, 1912 [9]
–
[
2025, 1918,
1896
2021, 1926 [5]
2019, 1897 [5]
2008, 1912 [5]
2000, 1908 [19]
[
2028, 1922, 1906, 1895 2023, 1915,
1903, 1883
2020, 1896 [9]
2017, 1893 [9]
[

2
0
N. Burzlaff et al. / Journal of Organometallic Chemistry 626 (2001) 16–23
1
13
(
0.5 ml) or KBr matrix. H-NMR and C-NMR:
4.3. General procedure for the syntheses of the
tricarbonyl complexes [LM(CO) ] (2a-3b)
Bruker WM 250, Bruker AC 250, JEOL GX 400, l
3
13
values relative to TMS; in some cases the C-NMR
signals of quaternary carbon atoms were too weak to
be detected. EIMS and FABMS: modified Finnigan
MAT 312. Elemental analyses: Analytical Laboratory
of the Fachbereich Chemie. A modified Siemens P4
diffractometer was used for X-ray structure
determinations.
Equivalent amounts of the bis(pyrazol-1-yl)acetic
acid (1a) or bis(3,5-dimethylpyrazol-1-yl)acetic acid (1b)
and potassium tert-butylate were dissolved in tetrahy-
drofurane and stirred at ambient temperature for 30
min. One equivalent of bromopentacarbonyl man-
ganese or rhenium complex was added to the white
suspension and the reaction mixture was heated under
reflux. CO evolution was observed. The reaction was
followed by IR spectroscopy. Finally the solvent was
removed in vacuo, the residue was washed with de-
gassed water to remove salts and tert-butanol, and
dried in vacuo.
Bis(3,5-dimethylpyrazol-1-yl)acetic acid (1b) was syn-
thesised from 3,5-dimethylpyrazole as reported recently
[
26]. 3,5-Dimethylpyrazole, pyrazole, dibromoacetic
acid, nitrosotetrafluoroborate and metal decacarbonyls
were used as purchased. [BrMn(CO) ] and [BrRe(CO) ]
5
5
were obtained according to the standard literature
method, from the decacarbonyls [30,31].
4
.3.1. Synthesis of [(bpza)Mn(CO) ] (2a)
3
The reaction of 192 mg (1.00 mmol) bis(pyrazol-1-
yl)acetic acid (1a) with 112 mg (1.00 mmol) tert-buty-
4
.2. Ligand synthesis: synthesis of
bis(pyrazol-1-yl)acetic acid (1a)
late and 275 mg (1.00 mmol) [BrMn(CO) ] in THF (50
5
ml) yielded [(bpza)Mn(CO) ] (2a) as a yellow powder.
3
Dibromoacetic acid (8.71 g, 40.00 mmol), pyrazole
5.45 g, 80.00 mmol), KOH (8.70 g, 155.5 mmol),
Yield 190 mg (0.58 mmol, 58%); m.p. 216–220°C
(
1
(
dec.). H-NMR (DMSO-d , 250 MHz): l=6.58 (s,
6
K CO (20.90 g, 151.22 mmol) and benzyltriethylam-
13
2
3
2H, H ), 7.29 (s, 1H, CH), 8.38 (s, 4H, H ) — C-
pz pz
monium chloride (1.00 g) serving as phase transfer
catalyst were dissolved in tetrahydrofurane (200 ml)
and heated under reflux for 5–6 h. The solvent was
removed in vacuo and the residue dissolved in water
NMR (DMSO-d , 62.5 MHz): l=70.4 (CH), 107.1
6
(C ), 133.1 (C ), 144.7 (C ), 219.1 (CO), 220.9
pz
pz
pz
+
(CO) — EIMS (70 eV, 270°C): m/z (%)=330 (1) [M
], 274 (10) [M −2 CO], 246 (15) [M −3 CO], 202
+
+
+
(
150 ml) and acidified to a pH value of 7 with half-con-
(60) [M −CO −3 CO] — IR (THF): wmax
2
−
1
centrated HCl. To remove excess pyrazole, the solution
was extracted with diethyl ether (2×150 ml). The water
phase was acidified further to a pH value of 1–2 and
extracted again with diethyl ether (6×150 ml). To
improve the extraction of the water-soluble bis(pyrazol-
(cm )=2041 s, 1946 s, 1925 s, 1679 m, 1636 m, 1516
−
1
w — IR (KBr): wmax (cm )=2039 s, 1952 s, 1943 s,
1927 s, 1916 s, 1672 m, 1646 w — Anal. Found: C,
3
9.69; H, 2.28; N, 16.60. Calc. for C H MnN O
11 7 4 5
(
330.14): C, 40.02; H, 2.14; N, 16.97%.
1
-yl)acetic acid (1a) tetrahydrofurane can be added.
4
.3.2. Synthesis of [(bdmpza)Mn(CO) ] (2b)
The reaction of 248 mg (1.00 mmol) bis(3,5-
The organic layer was dried (Na SO ) and the solvent
was removed in vacuo. The residue was re-crystallised
from acetone, yielding 1a as a colourless micro-crys-
talline powder and dried in vacuo over Sicapent . For
further purification bis(pyrazol-1-yl)acetic acid (1a) was
re-crystallised from acetonitrile to obtain 1a as colour-
less prisms.
3
2
4
dimethylpyrazol-1-yl)acetic acid (1b) with 112 mg (1.00
mmol) tert-butylate and 275 mg (1.00 mmol) [BrMn-
®
(CO) ] in THF (50 ml) yielded [(bdmpza)Mn(CO) ] (2b)
5
3
as a yellow powder. Crystals suitable for X-ray struc-
ture determination were obtained from a solution in
THF.
Yield 4.64 g (24.14 mmol, 60%); m.p. 166°C (dec.).
Yield 309 mg (0.80 mmol, 80%); m.p. 245–250°C
1
H-NMR (CH CN-d , 250 MHz): l=6.35 (dd, 2H,
1
3
3
(
dec.). H-NMR (CHCl -d, 250 MHz): l=2.42 (s, 6H,
3
3
3
JHꢀH=1.9 Hz, J
=1.6 Hz, H ), 7.27 (s, 1H, CH),
13
HꢀH
pz
CH ), 2.57 (s, 6H, CH ), 6.26 (s, 2H, H ) — C-
NMR (CHCl -d, 62.5 MHz): l=11.4 (CH ), 14.5
3
3
pz
3
7
.57 (d, 2H, JHꢀH=1.3 Hz, H ), 7.84 (d, 2H,
pz
3
3
3
13
JHꢀH=2.0 Hz, H ) — C-NMR (CH CN-d , 62.5
pz
3
3
(CH ), 67.2 (CH), 108.3 (C ), 141.5 (C ), 154.2 (C ),
3 pz pz pz
MHz): l=74.7 (CH), 107.8 (C ), 131.5 (C ),
1
1
CO H], 125 (9) [M −C H N ], 81 (100) [M −
CO −C H N ] — IR (THF): wmax (cm )=1761 s,
pz
pz
219.9 (CO), 223.4 (CO) — EIMS (70 eV, 265°C): m/z
(%)=386 (1) [M ], 330 (10) [M −2 CO], 302 (35)
41.4 (C ), 165.9 (CO H) — EIMS (70 eV,
+
+
pz
2
+
+
50°C): m/z (%)=192 (5) [M ], 147 (44) [M −
+
+
[M −3 CO], 258 (88) [M −CO −3 CO], 109 (43)
2
+
+
−
1
2
3
3
2
[C H N +CH ] — IR (THF): wmax (cm )=2036 s,
1942 s, 1915 s, 1683 m, 1560 w — IR (KBr): wmax
(cm )=3393 br, 2036 s, 1924 vs, 1664 m, 1560 w —
Anal. Found: C, 46.86; H, 4.29; N, 14.14. Calc. for
C H MnN O (386.25): C, 46.65; H, 3.91; N,
5 7 2 2
−
1
2
3
3
2
−
1
1
517 w — Anal. Found: C, 49.85; H, 4.19; N, 29.28.
Calc. for C H N O (192.18): Calc. C, 50.00; H, 4.20;
N, 29.15%.
8
8
4
2
15
15
4
5

N. Burzlaff et al. / Journal of Organometallic Chemistry 626 (2001) 16–23
21
1
4.51% — Crystals: Anal. Found: C, 45.14; H, 3.87;
for 24 h at ambient temperature. CO evolution was
1
N, 13.89. Calc. for C H MnN O × H O (395.25):
observed. NOBF addition was repeated until CO evo-
1
5
15
4
5
2
2
4
C, 45.58; H, 4.08; N, 14.17%.
lution stopped and a yellow precipitate formed. The
solvent was removed in vacuo and the residue was
dissolved in acetone (40 ml) to quench the excess
4.3.3. Synthesis of [(bpza)Re(CO) ] (3a)
3
The reaction of 473 mg (2.46 mmol) bis(pyrazol-1-
NOBF . The acetone solvent was evaporated, the
4
yl)acetic acid (1a) with 276 mg (2.46 mmol) tert-buty-
residue was washed with THF (5 ml) and the pale
yellow residue was dried in vacuo. Additional portions
of [(bdmpza)Re(CO) (NO)]BF (4) were obtained from
late and 1.00 g (2.46 mmol) [(BrReCO) ] in THF (50
5
ml) yielded [(bpza)Re(CO) ] (3a) as a white powder.
3
2
4
Crystals suitable for X-ray structure determination
the THF solution upon standing for three days at
were obtained from a solution in acetone.
ambient temperature.
Yield 930 mg (2.02 mmol, 82%); m.p. 279°C (dec.).
Yield 260 mg (0.43 mmol, 48%); m.p. 165–170°C
1
3
1
H-NMR (DMSO-d , 250 MHz): l=6.69 (t, 2H, J
(dec.). H-NMR (acetone-d , 250 MHz): l=2.63 (s,
6
H–
6
H=2.0 Hz, H ), 7.64 (s, 1H, CH), 8.45 (d, 4H,
3H, CH ), 2.66 (s, 3H, CH ), 2.72 (s, 3H, CH ), 2.75 (s,
pz
3
3
3
3
13
JH–H=2.0 Hz, H ) — C-NMR (DMSO-d , 62.5
3H, CH ), 6.58 (s, 1H, H ), 6.61 (s, 1H, CH), 7.10 (s
pz
6
3 pz
13
MHz): l=73.5 (CH), 109.8 (C ), 135.6 (C ), 147.5
1H, H ) — C-NMR (acetone-d , 62.5 MHz): l=
pz 6
pz
pz
(
(
C ), 164.2 (COO), 196.6 (CO), 197.0 (CO) — EIMS
11.2 (CH ), 11.5 (CH ), 15.1 (CH ), 16.0 (CH ), 68.5
(CH), 110.5 (C ), 110.7 (C ), 147.1 (C ), 148.2 (C ),
pz pz pz pz
pz
3 3 3 3
+
70 eV, 290°C): m/z (%)=462 (25) [M ], 418 (20)
+
+
+
[
M −CO ], 390 (60) [M −CO −CO], 362 (25) [M
157.1 (C ), 157.3 (C ), 161.7 (COO) — FABMS
2
2
pz pz
+
+
−
CO −2 CO], 334 (100) [M −CO −3 CO] — IR
(NBOH-matrix): m/z (%)=520 (35) [M ], 492 (14)
2
2
−
1
+
+
(THF): wmax (cm )=2029 s, 1924 s, 1904 s, 1695
[M −CO], 464 (4) [M −2 CO] — IR (CH Cl ):
2 2
−
1
−1
w — IR (KBr): wmax (cm )=2028 s, 1922 vs, 1906
s, 1895 s, 1677 s, 1655 w — Anal. Found: C, 28.75; H,
1
2
wmax (cm )=2113 s, 2045 s, 1824 s, 1712 m, 1558
−
1
w — IR (KBr): wmax (cm )=2117 s, 2044 vs, 1823
s, 1706 m, 1556 w — Anal. Found: C, 27.59; H, 2.77;
N 11.33. Calc. for C H BF N O Re (606.31): C,
.64; N, 12.11. Calc. for C H N O Re (461.41): C,
11 7 4 5
8.63; H, 1.53; N, 12.14%.
14
15
4
5
5
2
7.73; H, 2.49; N, 11.55%.
4
.3.4. Synthesis of [(bdmpza)Re(CO) ] (3b)
3
The reaction of 526 mg (2.12 mmol) bis(3,5-
4.5. X-ray structure determinations
dimethylpyrazol-1-yl)acetic acid (1b) with 242 mg (2.12
mmol) tert-butylate and 860 mg (2.12 mmol) [Br-
Re(CO) ] in THF (50 ml) yielded [(bdmpza)Re(CO) ]
Single crystals of 1a, 2b, 3a and 3b were sealed in
glass capillaries at room temperature. A modified
Siemens P4-Diffractometer was used for data collection
(Wyckhoff technique, graphite monochromator, Mo–
5
3
(
3b) as a white powder. Crystals suitable for X-ray
structure determination were obtained from a solution
in THF.
−
1
K radiation, u=0.71073, scan rate ꢀ 4–30° min ).
a
Yield 849 mg (1.64 mmol, 77%); m.p. 270–280°C
The structures were solved by using direct methods (in
case of 1a, 2b and 3a) and Patterson (in case of
1
(
dec.). H-NMR (CHCl -d, 250 MHz): l=2.45 (s, 6H,
3
CH ), 2.51 (s, 6H, CH ), 6.11 (s, 2H, H ), 6.47 (s, 1H,
3b){Siemens SHELXS-93 (VMS) [32]} and refined with
3
3
pz
1
3
2
CH) — C-NMR (CHCl -d, 62.5 MHz): l=11.0
full-matrix least-squares against F {Siemens SHELXL
-
3
(
1
CH ), 15.5 (CH ), 68.1 (CH), 108.2 (C ), 141.5 (C ),
96 (VMS) [33]}. A weighting scheme was applied in the
3
3
pz
pz
2
2
54.4 (C ), 163.8 (COO), 195.1 (CO), 196.2 (CO) —
last steps of the refinement with w=1/[| (F )+
pz
0
+
2
2
c
2
0
EIMS (70 eV, 240°C): m/z (%)=518 (15) [M ], 474
(aP) +bP] and P=[2F +Max(F ,0)]/3. 2b and 3b
+
+
(
20) [M −CO ], 446 (32) [M −CO −CO], 418 (15)
were first solved in P4 2 2. Due to a Flack parameter
2
2
1 1
+
+
[
M −CO −2 CO], 390 (100) [M −CO −3 CO] —
close to 1, the structure coordinates had to be inverted
and the symmetry operations were changed to those of
the enantiomorphic space group P4 2 2, causing a sig-
2
2
−
1
IR (THF): wmax (cm )=2025 s, 1918 s, 1896 s, 1694
−
1
m, 1559 w — IR (KBr): wmax (cm )=3399 s, 2023
s, 1915 vs, 1903 m, 1883 m, 1670 m, 1559 w —
Crystals: Anal. Found: C, 34.31; H, 3.21; N, 10.63.
Calc. for C H N O Re× H O (526.52): C, 34.22; H,
3
3
1
nificant decrease of the R factors. All the hydrogen
atoms in the structure of compound 2b were found and
refined isotropically. The hydrogen atoms of 1a, 3a and
3b were included in their calculated positions and
refined in a riding model.
2b and 3b crystallised as the solvate with half a water
molecule placed on a special position. These water
molecules interact via a hydrogen bond with the car-
boxylate group of the ligands. In the structure determi-
nation of 3b two restraints had to be applied to this
hydrogen. IR signals of 2b and 3b at 3393 and 3399
1
2
1
5
15
4
5
2
.06; N, 10.64%.
+
4
.4. COꢀNO exchange: synthesis of
[
(bdmpza)Re(CO) (NO)]BF (4)
2
4
To a solution of 460 mg (0.89 mmol) [(bdm-
pza)Re(CO) ] (3b) in dichloromethane (20 ml) 270 mg
3
(2.31 mmol) NOBF was added and the solution stirred
4

2
2
N. Burzlaff et al. / Journal of Organometallic Chemistry 626 (2001) 16–23
Table 6
Structure determination details of compounds 1a, 2b, 3a and 3b
1a
2b
3a
3b
Empirical formula
Formula weight
Crystal colour/habit
Crystal system
C H N O
192.18
White prism
Monoclinic
C2/c
C15H15MnN O ·0.5H O
395.26
C11H N O Re·C H O
519.48
White plate
Orthorhombic
Pbca
C15H15N O Re·0.5H O
526.52
8
8
4
2
4
5
2
7
4
5
3
6
4
5
2
Yellow prism
Tetragonal
P4 2 2
White cube
Tetragonal
P4 2 2
Space group
3
1
3 1
a (A
,
)
)
)
10.106(10)
11.001(11)
16.493(17)
90.00
105.12(2)
90.00
1770.1(31)
2.56–25.00
−12 to 6
−12 to 12
−18 to 19
8
10.056(5)
10.056(5)
35.183(19)
90.00
90.00
90.00
3557.9(30)
2.11–27.00
−12 to 12
−12 to 12
−44 to 44
8
9.130(12)
13.967(16)
27.776(30)
90.00
90.00
90.00
3541.9(71)
2.67–27.01
−11 to 10
−7 to 17
−12 to 35
8
10.176(6)
10.176(6)
35.474(32)
90.00
90.00
90.00
3673.1(46)
2.08–27.00
−12 to 12
−12 to 12
−40 to 45
8
b (A
,
c (A
,
h (°)
i (°)
k (°)
V (A
,
3)
q range (°)
H range
K range
L range
Z
v (Mo–K ) (mm−1)
0.109
0.778
6.899
6.652
a
Crystal size (mm)
Temperature (K)
Reflections collected
Independent reflections
Obs. reflections (\2|I)
Parameter
0.3×0.2×0.2
242(2)
2098
1552
1163
0.4×0.3×0.3
243(2)
8852
3896
3153
0.3×0.2×0.2
242(3)
6023
3861
2658
0.6×0.4×0.4
243(2)
8400
3989
3632
160
295
226
236
Restraints
0
0
0
2
WGHT parameter a
WGHT parameter b
R1 (obs.)
R2 (overall)
wR1 (obs.)
0.0493
2.0001
0.0427
0.0654
0.1010
0.1219
0.174/−0.266
0.0398
0.7485
0.0410
0.0579
0.0880
0.0957
0.254/−0.290
0.0479
6.5031
0.0423
0.0760
0.0916
0.1079
1.150/−1.577
0.0942
5.3358
0.0591
0.0644
0.1558
0.1806
2.162/−1.989
wR2 (overall)
Diff. peak/hole (eA
−3)
,
−
1
cm
confirm such hydrogen bridged OH groups.
Acknowledgements
Washing with water when working up the products (see
Section 4.3) as well as crystallisation using not perfectly
dry THF might be the sources of these water molecules.
In the structure of 3a one molecule of acetone co-crys-
tallised per asymmetric unit.
N.B. thanks the Fonds der Chemie for a Liebig-Fel-
lowship and Prof. Dr H. Fischer for support and
discussion. We are indebted to Mrs Quelle and Mr
H a¨ gele for recording mass spectra.
5. Supplementary material
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