A new family of low-spin CoIII bis(amidate) complexes with two cis or trans cyanides

Article abstract of DOI:10.1002/ejic.200300645

Four low-spin dicyanodicarboxamidocobalt(III) complexes have been prepared from N,N′-bis(8-quinolyl)malonamide derivatives, the malonyl fragment of which was either unsubstituted (Et₄N)[Co(BQM)(CN)₂] (3a), monosubstituted by a benzyl group (Et₄N)[Co(mono-BenzBQM)(CN) ₂] (3b), or disubstituted by two benzyl or two phenylethyl groups, (Et₄N)[Co(di-BenzBQM)(CN)₂] (3c) and (Et ₄N)[Co(di-PhEtBQM)(CN)₂] (3d), respectively. The X-ray crystal structures of 3a and 3c reveal that the tetradentate ligand adopts a helical or a planar configuration around the cobalt centre of 3a and 3c, respectively. Complexes 3a-3d were characterised in solution by ¹H NMR spectroscopy by 1D and 2D COSY H-H techniques. The solid-state structures of 3a and 3c are retained in solution, and complexes 3b and 3d adopt structures similar to 3a and 3c, respectively, showing that the level of the malonic substitution determines the configuration of the tetradentate ligand around the cobalt centre and forces the cyanide ligands to adopt either cis or trans orientations. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejic.200300645

FULL PAPER
A New Family of Low-Spin CoIII Bis(amidate) Complexes with Two cis or
trans Cyanides
Olaf Rotthaus,[a] Sophie LeRoy,[a] Alain Tomas,[b] Kathleen M. Barkigia,[c] and
Isabelle Artaud*[a]
Keywords: Cobalt / Cyanides / N ligands
Four low-spin dicyanodicarboxamidocobalt(III
have been prepared from N,NЈ-bis(8-quinolyl)malonamide
derivatives, the malonyl fragment of which was either unsub-
)
complexes
terised in solution by 1H NMR spectroscopy by 1D and 2D
COSY H-H techniques. The solid-state structures of 3a and
3c are retained in solution, and complexes 3b and 3d adopt
stituted (Et4N)[Co(BQM)(CN)2] (3a), monosubstituted by a structures similar to 3a and 3c, respectively, showing that the
benzyl group (Et4N)[Co(mono-BenzBQM)(CN)2] (3b), or dis- level of the malonic substitution determines the configura-
ubstituted by two benzyl or two phenylethyl groups, tion of the tetradentate ligand around the cobalt centre and
(Et4N)[Co(di-BenzBQM)(CN)2] (3c) and (Et4N)[Co(di- forces the cyanide ligands to adopt either cis or trans orienta-
PhEtBQM)(CN)2] (3d), respectively. The X-ray crystal struc-
tures of 3a and 3c reveal that the tetradentate ligand adopts
a helical or a planar configuration around the cobalt centre
tions.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
of 3a and 3c, respectively. Complexes 3a−3d were charac- Germany, 2004)
Introduction
or hydrocarbons with tBuOOH or H2O2.[7,8] Tetradentate
ligands containing two amides usually derive from picolinic
acid and afford six-coordinate complexes with four nitro-
gens that occupy the equatorial plane and two exogenous
ligands in the axial positions.[9] We report here the synthesis
and characterisation of a new family of dicyano CoIII com-
plexes of N,NЈ-bis(8-quinolyl)malonamide derivatives. We
show that different substitutions of the malonic fragment
control the coordination geometry of the four nitrogen do-
nors to the metal centre. The tetradentate chelate adopts a
planar or a helical configuration around the metal cation,
providing two types of complexes with two cis or trans cy-
anides.
Prompted by the work of Collins’ group showing the ca-
pacity of deprotonated amides to be strong metal donors
and to stabilize high oxidation states,[1] this area of chemis-
try has received increased attention with the recent findings
that amides from a peptide backbone could also be nitrogen
donors to the metal centre of metalloproteins, such as the
nitrogenase P-cluster[2] or the nitrile hydratase family.[3] Our
group[4] and others[5,6] have synthesised iron and cobalt
mimics of the nitrile hydratase active site. Our choice of
N2S2 tetradentate ligands has illustrated the new properties
of this series of complexes.[4] We are now aiming to develop
nitrogen-containing ligands to prepare new mononuclear
complexes that could be used as catalysts for oxidation re-
actions.
Results and Discussion
It is well-known that introducing one or more carbox-
amido nitrogens in the metal environment increases the sta-
bility of FeIII or CoIII complexes[1,7] and provides catalysts
with significant catalytic activity for the oxidation of olefins
Synthesis of CoIII Complexes
We have prepared a series of N,NЈ-bis(8-quinolyl)malon-
amide (BQM) derivatives, shown in Scheme 1, containing a
malonyl fragment that is either unsubstituted (1a), mono-
substituted by a benzyl group (1b), or disubstituted by two
benzyl (1c), or two 2-phenylethyl (1d) groups. These ligands
were easily synthesised by condensing 8-aminoquinoline
with malonyl dichloride derivatives, as previously reported
for the disubstituted malonamide compounds.[10] Cobalt()
was reacted with the ligands as CoCl2 in the presence of
triethylamine as a soft base. Depending on the ligand sub-
[a]
Laboratoire de Chimie et Biochimie Pharmacologiques et
´
´
Toxicologiques, UMR 8601, Universite Rene Descartes
`
45 rue des Sts Peres, 75270 Paris cedex 06, France
Fax: (internat.) ϩ33-1-42868387
E-mail: isabelle.artaud@biomedicale.univ-paris5.fr
Laboratoire de Cristallographie et de RMN biologiques, UMR
[b]
[c]
´
8015, Faculte de Pharmacie,
4 rue de l’Observatoire, 75270 Paris cedex 06, France
Materials Science Department, Brookhaven National
Laboratory,
Upton, New York, 11973, USA
Eur. J. Inorg. Chem. 2004, 1545Ϫ1551
DOI: 10.1002/ejic.200300645
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1545

O. Rotthaus, S. LeRoy, A. Tomas, K. M. Barkigia, I. Artaud
FULL PAPER
stitution, two different procedures were applied, as outlined CoII complex of N,NЈ-bis(pyridin-2-ylmethylene)benzene-
in Scheme 1. For the unsubstituted or monosubstituted 1,2-diamine, Co(bpb).[11] CoIII complexes with carbox-
compounds 1a and 1b, the CoII insertion was carried out amido nitrogen donors are typically six coordinate.[9] Thus,
in a mixture of CH2Cl2 and MeOH and led to the precipi- the oxidation was performed in the presence of cyanides to
tation of the CoII complex 2a and 2b, respectively. Complex introduce two strong exogenous ligands to complete the
2a precipitated readily from the solution, and 2b precipi- cobalt coordination sphere and to stabilize the CoIII state.
tated after concentration in vacuo. Once isolated, the CoII
X-ray Crystal Structure of (Et4N)[Co(BQM)(CN)2] (3a)
and (Et4N)[Co(di-BenzBQM)(CN)2] (3c)
complexes are sparingly soluble in any solvent and were oxi-
dized suspended in aerated CH2Cl2 after addition of two
equivalents of tetraethylammonium cyanide to stabilize the
CoIII complexes (Scheme 1, route A). Orange precipitates
of the CoIII complexes 3a and 3b were obtained after partial
removal of the solvent and addition of diethyl ether. The
CoII complexes of the disubstituted compounds 1c and 1d
are highly soluble in CH2Cl2/MeOH and, consequently,
more difficult to isolate. The one-pot synthesis of the dicy-
ano CoIII complexes in DMF was therefore preferred. After
preparing the CoII complexes in solution, the cyanide
ligands were added as Et4NCN at Ϫ30 °C and the oxi-
dation was performed with the one-electron oxidizing
agent 4-fluorobenzenediazonium hexafluorophosphate[10]
(Scheme 1, route B). After removing the solvent, the crude
products were redissolved in CH2Cl2 and complexes 3c and
3d were precipitated by addition of diethyl ether and iso-
lated as orange powders in good yields.
Crystals suitable for X-ray analysis were grown from
CH2Cl2/hexane for 3a and from acetonitrile/diethyl ether
for 3c. Views of the anions of 3a and 3c are presented in
Figure 1 and 2. Selected bond angles and distances are
listed in Table 1. In both structures the cobalt is six-coordi-
nate in an octahedral environment to two deprotonated am-
ide and two pyridyl nitrogens of the ligand and two exogen-
ous cyanides. However, while the four nitrogen donors
N1ϪN4 in 3c (Figure 2) lie in the equatorial plane, with
the two cyanides situated axially trans to each other, in 3a
(Figure 1) only three nitrogens (N1, N2 and N3) lie in the
equatorial plane, with the fourth (N4) in an apical position
and with the two cyanides occupying cis sites, one equa-
torial (C22ϪN5) and the other axial (C23ϪN6). Whereas
in the trans configuration C11 deviates from the mean plane
˚
defined by N1N2C10C12N3N4 by 0.3 A, the distortions
are more important in the cis configuration. The angle be-
tween the planes N1N2N3 and N2C10C12N3 is 22° and
the angle between C10C11C12 and N2C10C12N3 is 44°.
Consequently the CH2 fragment is in close proximity to the
axial cyanide (C23N6).The distance between C11 of the
˚
CH2 and C23 of the CN is 3.02 A. This explains why a
disubstituted derivative cannot adopt a cis configuration.
Scheme 1. Reaction pathways for the synthesis of the CoIII dicy-
ano complexes
Characterisation of [CoII(BQM)] (2a)
CoII complexes were formed as intermediates during the
synthesis of CoIII derivatives and, with the exception of 2a,
are not very stable under aerobic conditions, even as solids.
Consequently, we characterised only 2a to obtain some in-
sight into the cobalt coordination. Its elemental analysis is
in agreement with the formulation [CoII(BQM)]. The IR
spectrum of the ligand 1a shows ν(NϪH) and ν(CϭO) vi-
brations at 3279 and 1646 cmϪ1, respectively. The absence
of the ν(NϪH) band and the shift of the ν(CϭO) band to a
Figure 1. Thermal ellipsoid plot (50% probability level) of the
anion of 3a; H atoms are omitted for clarity
An unexpected aspect of the structure of 3a, which crys-
lower energy of 1605 cmϪ1 in the metal complex confirm tallises with two water molecules per metal complex, is that
that the amide nitrogens are coordinated to the Co in their the water molecules form an extended hydrogen-bonded
deprotonated form. The X-band powder EPR spectrum at network that links three chelates through the N5 nitrogens
4 K shows a single resonance at g ϭ 1.99 characteristic of of the cyano group to the oxygens O1 and O2 of two ad-
a low-spin CoII state. This complex is four-coordinate and ditional ligands, as shown in Figure 3. The distance be-
is probably square planar, as previously proposed for the tween the oxygen of a water and the cyano group (N5ϪO:
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Eur. J. Inorg. Chem. 2004, 1545Ϫ1551

A New Family of Low-Spin CoIII Bis(amidate) Complexes
FULL PAPER
Solution Structure of (Et4N)[Co(BQM)(CN)2] (3a) and
(Et4N)[Co(di-BenzBQM)(CN)2] (3c)
With the strong cyanide ligands, these complexes exist in
a low-spin CoIII state. Their structures can be readily ana-
1
lysed by H NMR spectroscopy. NMR assignments were
based on 1D and 2D COSY H-H experiments. The spec-
trum of 3c, shown in Figure 4, indicates a solution structure
with a C2 symmetry, as in the solid state (Figure 2). Both
quinolyl rings are equivalent and the pyridyl proton spin
system (H1, H2, H3) appears as a set of three well-resolved
resonances between δ ϭ 7.7 and 9.0 ppm. The proton label-
ling is indicated in Scheme 1. The same NMR spectrum was
obtained when compound 3c was prepared according to the
procedure following route A (Scheme 1), or when the NMR
sample was heated up to 360 K. In contrast, the spectrum
of 3a, shown in Figure 4, exhibits a more complicated pat-
tern indicative of the lack of any symmetry, as in the crystal
structure (Figure 1). The quinolyl resonances are split into
two spin systems H1, H2, H3, H4, H5, H6 and H1Ј, H2Ј,
H3Ј, H4Ј, H5Ј, H6Ј. Correlations were made by a 2D COSY
experiment. For the assignments, the protons of the quino-
lyl ring in the equatorial plane were assumed to appear at
chemical shifts very close to those found in the trans com-
plex 3c. The two pyridyl systems are very different. The
ortho and meta pyridyl protons in the axial position are
shifted upfield relative to those in the equatorial plane (H1Ј:
Figure 2. Thermal ellipsoid plot (50% probability level) of the
anion of 3c; H atoms are omitted for clarity
˚
Table 1. Selected bond angles (°) and distances (A) for complexes
[Co(BQM)(CN)2]Et4N (3a) and [Co(di-BenzBQM)(CN)2]Et4N (3c)
3a
3c
CoϪN1
CoϪN2
CoϪN3
CoϪN4
CoϪC22
CoϪC23
C22ϪN5
C23ϪN6
1.934(3)
1.945(3)
1.930(3)
1.995(3)
1.889(4)
1.875(4)
1.156(6)
1.148(5)
1.957(4)
1.933(4)
1.931(4)
1.959(4)
1.932(6)
1.922(6) δ ϭ 6.17 ppm; H1: δ ϭ 9.07 ppm; H2Ј: δ ϭ 7.28 ppm; H2:
1.132(7)
1.151(7)
δ ϭ 7.87 ppm). Finally, the two malonyl protons are in-
equivalent; their signals appeared at two chemical shifts
(δ ϭ 2.97 and 5.02 ppm) located apart from the value of
the unique CH2 resonance (δ ϭ 3.87 ppm) found for the
free ligand. These results show that the unexpected solid-
state structure of 3a is retained in solution.
N2ϪCoϪN4
N1ϪCoϪN4
C23ϪCoϪC22
C22ϪCoϪN2
C23ϪCoϪN4
98.06(12)
91.33(14)
83.7(2)
174.18(14)
170.6(2)
174.27(18)
99.22(16)
177.01(18)
92.4(2)
86.24(19)
Solution Structure of (Et4N)[Co(mono-BenzBQM)(CN)2]
(3b) and (Et4N)[Co(di-PhEtBQM)(CN)2] (3d)
˚
2.89 A) is clearly indicative of hydrogen bonding, as are the
O2ϪO4 water molecule and O1ϪO3 water molecule dis-
Since NMR spectroscopy proved suitable for the analysis
of the two structurally related complexes 3a and 3c, we also
used this technique to determine whether the cyanides in
complexes 3b and 3d were orientated in a cis or a trans
fashion. The aim was to determine the influence of the mal-
onyl substitution level on the coordination geometry and,
for the disubstituted derivatives, the effect of lengthening
the chain by one CϪC bond. The NMR spectra of 3d (Fig-
ure 4) and 3c are very similar, supporting a planar configu-
ration of the tetradentate chelate and a trans coordination
of the cyanides to the cobalt cation. In contrast, the NMR
spectrum of the monobenzylated derivative 3b (Figure 4)
displays, as for 3a, two quinolyl proton spin-systems. The
H1Ј and H1 resonances are located in the upfield and down-
field regions at δ ϭ 6.11 ppm and 9.06 ppm, respectively.
The Hα malonyl proton signal appears at δ ϭ 5.55 ppm, a
value similar to that of the low-field resonance found for
one of the two malonyl protons Hα and HαЈ in 3a. The
benzylic resonance appears at δ ϭ 3.18 ppm, showing that
the benzylic protons in 3b are slightly shielded relative to
˚
tances of 2.73 and 2.82 A, respectively. The water
˚
(O3)Ϫwater (O4) distance is 2.78 A.
Figure 3. Hydrogen-bond network between water and 3a molecules those in the trans complex 3c. Thus, the monobenzylated
Eur. J. Inorg. Chem. 2004, 1545Ϫ1551
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O. Rotthaus, S. LeRoy, A. Tomas, K. M. Barkigia, I. Artaud
FULL PAPER
two cyanides are oriented cis or trans to the cobalt centre.
The crystal structures of two representative complexes of
this series have been solved. When unsubstituted or mono-
substituted, the stable configuration is twisted with three
nitrogens and one cyanide in the equatorial plane, and the
fourth nitrogen and the second cyanide in apical positions.
When disubstituted by two benzyl or two phenylethyl
groups, the steric interaction of the malonyl substituent
with the axial cyanide ligand destabilizes the cis configura-
tion and forces the ligand to adopt a planar arrangement
with two trans cyanides. Consequently, without changing
the nature of the nitrogen donors, a disubstitution at the
periphery of the ligand framework modulates the cis or
trans coordination of the two exogenous ligands. Cyanides
were introduced to facilitate the characterisation of the di-
cyano CoIII complexes, and therefore we next intend to in-
troduce more labile exogenous ligands to compare the
chemical reactivity of these complexes with the same nitro-
gen donor set and two cis or trans labile sites.
Experimental Section
Chemicals: All solvents and chemicals were purchased in analytical
grade from SDS, Fluka or Aldrich. Sephadex LH-20 resin was pur-
chased from Amersham Biosciences. Solvents were dried by stand-
ard procedures.
Spectroscopic Measurements: UV/Visible spectra were recorded at
room temperature on a Safas UV mc2 spectrophotometer. X-band
EPR spectra were recorded on a Bruker ESP300 spectrometer op-
erating at a 9.5 GHz microwave frequency, with a 100 kHz modu-
1
lation frequency and a 1 G modulation amplitude. H NMR spec-
tra were recorded at 300 K on a Bruker ARX-250 spectrometer.
Chemical shifts are reported in ppm downfield from TMS. Infrared
spectra were obtained with a PerkinϪElmer Spectrum One FT-IR
spectrometer equipped either with a sample holder for KBr pellets
or with a MIRacleTM single reflection horizontal ATR unit which
allowed spectra of solid compounds to be recorded directly
(marked as ‘‘neat’’). Mass spectrometry (ESIϪ and ESIϩ) was per-
formed on a Thermo Finnigan LCD Advantage spectrometer. El-
emental analyses were carried out by the microanalysis service of
Paris VI University.
1
Figure 4. H NMR spectra of the cis-3a and -3b and the trans-3c
and -3d complexes at 250 MHz in [D6]DMSO
and the unsubstituted complex, 3b and 3a, adopt the same
helical arrangement of the N4 ligand and the same cis con-
figuration of the cyanides.
It is noteworthy that while the NMR spectra of the two
types of complexes are very different, their IR spectra do
not reveal significant differences. They show a unique νCN
N,NЈ-Bis(8-quinolyl)malonamide (BQMH2) (1a): Malonic acid
chloride (972 µL, 9.5 mmol) was added under argon to a CH2Cl2
solution (100 mL) of 8-aminoquinoline (3.17 g, 22 mmol) and tri-
ethylamine (Et3N, 3.0 mL, 20 mmoL). Then the mixture was stirred
stretching band at 2120 cmϪ1 suggesting that the two cyan- for 12 h at room temperature. After dissolution of all the precipi-
tated condensation product by further addition of CH2Cl2 the solu-
tion was washed three times with water, then with saturated aque-
ous NaHCO3 (30 mL each) and dried over MgSO4. Removal of the
solvent and recrystallisation of the product from CH2Cl2 afforded
ligand 1a as a white solid (1.32 g, 39%). C21H16N4O2 (356.13):
calcd. C 70.78, H 4.49, N 15.73; found C 70.60, H 4.66, N 15.68.
UV/Vis (CH2Cl2) λmax (ε) ϭ 243 (80000 Ϫ1·cmϪ1), 319 (13000)
nm. IR (neat): ν˜ ϭ 3279 w (νNH) and 1646 s (νCO) cmϪ1. 1H NMR
(250 MHz, CDCl3): δ ϭ 10.78 (s, 2 H, NH), 8.89 (dd, 3J ϭ 4.4,
ides have the same surroundings. A similar observation has
been reported for other cis-dicyano complexes such as cis-
dicyanobis(1,10-phenanthroline)iron()[12] or bis(2,2Ј-bi-
pyridine)-cis-dicyanoiron() perchlorate.[13]
Conclusion
In conclusion, we have prepared four new six-coordinate
low-spin CoIII dicyano complexes that contain an N,NЈ-
bis(8-quinolyl)malonamide ligand. Interestingly, the substi-
3
3
4J ϭ 1.6 Hz, 2 H, H1), 8.83 (dd, J ϭ 3.6, J ϭ 5.6 Hz, 2 H, H5),
3
4
3
8.16 (dd, J ϭ 8.4, J ϭ 1.6 Hz, 2 H, H3), 7.54 (d, J ϭ 3.6, 2 H,
H4 or H6), 7.55 (d, 3J ϭ 5.6 Hz, 2 H, H4 or H6), 7.46 (dd, 3J ϭ
3
tution level of the malonyl fragment determines whether the 4.4, J ϭ 8.4 Hz, 2 H, H2), 3.87 (s, 2 H, CH2) ppm.
1548
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Eur. J. Inorg. Chem. 2004, 1545Ϫ1551

A New Family of Low-Spin CoIII Bis(amidate) Complexes
FULL PAPER
2-Benzyl(ethyl malonate): NaH (0.96 g, 40 mmol) and then benzyl
0.48 mmol) resulted in the dissolution of the complex. Exposure
bromide (4.7 mL, 40 mmol) were slowly added to a dried THF of the solution to air caused oxidation of the cobalt. Stirring was
solution (80 mL) of diethyl malonate (6 mL, 40 mmol). The reac-
tion mixture was refluxed for 24 h. Then, diethyl ether was added
(120 mL) and the solution was washed three times with water (3 ϫ
80 mL) and dried over MgSO4. After evaporation of the solvent,
the slightly yellow residue was distilled off as a clear oil (bp,
continued for 2 h, then half of the solvent was evaporated and the
product was precipitated by addition of diethyl ether. Purification
over LH-20 (30 g) with CH2Cl2/MeOH (8:2) as eluent, and precipi-
tation from CH2Cl2/pentane afforded (Et4N)[Co(BQM)(CN)2] as
an orange powder (70 mg, 50%). C31H34CoN7O2·H2O·CH2Cl2
133Ϫ135 °C, P 0.6 Torr, 6.3 g, 63%). 1H NMR (250 MHz, CDCl3): (697.17): calcd. C 55.02, H 5.48, N 14.04; found C 54.89, H 5.46,
δ ϭ 7.30Ϫ7.15 (m, 5 H, H-Ph), 4.14 (q, 3J ϭ 7.1 Hz, 4 H,
N 13.99. UV/Vis (MeOH) λ (ε) ϭ 257 (29900 Ϫ1cmϪ1), 380 (6040)
3
3
1
CH2(OEt)), 3.63 (t, J ϭ 7.8 Hz, 1 H, CH), 3.20 (d, J ϭ 7.8 Hz, nm. IR (KBr): ν˜ ϭ 2126w (νCN) and 1601s (νCO) cmϪ1. H NMR
3
3
2 H, CH2), 1.19 [t, J ϭ 7.1 Hz, 6 H, CH3(OEt)] ppm.
(250 MHz, [D6]DMSO): δ ϭ 9.07 (d, J ϭ 5.0 Hz, 1 H, H1), 8.81
3
3
(d, J ϭ 7.1 Hz, 1 H, H4 or H6), 8.71 (d, J ϭ 8.2 Hz, 1 H, H3),
2-Benzylmalonic Acid: 2-Benzyl(ethyl malonate) (5.2 g, 21 mmol)
was poured onto pulverized KOH (4.7 g, 94 mmol) in an ice/water
bath. The mixture rapidly became highly viscous and ethanol
(2 mL) and water (1.3 mL) were added to allow stirring. After 6 h
of stirring at 90 °C, the suspension was dissolved in H2O (30 mL)
and twice washed with CH2Cl2 (3 ϫ 10 mL) before concentrated
HCl was added to reach pH 1. The reaction product was collected
by washing with CH2Cl2 (5 ϫ 20 mL). The solution was dried over
MgSO4, and evaporation of the solvent afforded 2-benzylmalonic
acid (1.7 g, 41%). 1H NMR (250 MHz, [D4]MeOH): δ ϭ 7.30Ϫ7.10
(m, 5 H, H-Ph), 3.62 (t, 3J ϭ 7.7 Hz, 1 H, CH), 3.15 (d, 3J ϭ
7.7 Hz, 2 H, CH2) ppm.
8.41 (d, J ϭ 8.1 Hz, 1 H, H3Ј), 8.15 (d, J ϭ 7.2 Hz, 1 H, H4Ј or
3
3
H6Ј), 7.87 (dd, J ϭ 8.2, 3J ϭ 5.0 Hz, 1 H, H2), 7.75Ϫ7.40 (m, 4
3
H, H5 ϩ H5Ј, H4 or H4Ј and H6 or H6Ј), 7.28 (dd, J ϭ 8.1, J ϭ
3
3
4.9 Hz, 1 H, H2Ј), 6.17 (d, 3J ϭ 4.9 Hz, 1 H, H1Ј), 5.02 (d, 2J ϭ
15.1 Hz, 1 H, Hα or HαЈ), 2.97 (d, J ϭ 15.1 Hz, 1 H, Hα or HαЈ)
2
ppm. MS: m/z (%) ϭ 465 (100) [Co(BQM)(CN)2]Ϫ.
(Et4N)[Co(mono-BenzBQM)(CN)2] (3b): Under argon, the mono-
substituted ligand mono-BenzBQMH2 (1b) (0.1 g, 0.22 mmol) was
dissolved in CH2Cl2 (30 mL) and Et3N (0.15 mL, 1.1 mmol) was
added, followed by a solution of CoCl2 (32 mg, 0.24 mmol) in
MeOH (5 mL). After removal of three quarters of the solvent [CoII-
(mono-BenzBQM)] (2b) precipitated as a yellow powder and was
collected by filtration, then washed with CH2Cl2, MeOH and di-
ethyl ether (50 mg, 45%). Like 2a, it is insoluble. The oxidation
procedure described for 2a was applied to 2b (20 mg, 0.04 mmol)
2-Benzyl-N,NЈ-bis(8-quinolyl)malonamide
(mono-BenzBQMH2)
(1b): Under argon, 2-benzylmalonic acid (0.25 g, 1.3 mmol) was
dissolved in 4 mL of SOCl2 and the mixture was stirred for 4 h at
60 °C. After removal of the excess thionyl chloride in vacuo, 2-
benzyldiethylmalonic acid chloride was obtained as a yellow oil,
which was directly converted into 1b. Two equiv. of 8-aminoquino-
line (0.37 g, 2.6 mmol) were added to the acid chloride dissolved in
dry toluene (5 mL). The orange suspension was stirred for 1 h at
room temperature, then Et3N (0.33 mL, 2.5 mmol) was added and
the mixture stirred overnight at 60 °C. Then, CH2Cl2 (20 mL) was
added, the solution was washed with H2O (4 ϫ 10 mL) and the
organic layer was dried over MgSO4. After recrystallization from
CH2Cl2 1b was obtained as a white solid (0.37 g, 63%). UV/Vis
(CH2Cl2) λmax (ε) ϭ 248 (18800 Ϫ1·cmϪ1), 307 (11700) nm. IR
with
Et4NCN
(12.5 mg,
0.08 mmol).
(Et4N)[Co(mono-
BenzBQM)(CN)2] (3b) was obtained as an orange powder (18 mg,
65%). C38H40CoN7O2 (685.26): calcd. C 66.56, H 5.88, N 14.30;
found C 66.06, H 5.85, N 14.20. UV/Vis (MeOH): λmax (ε) ϭ 259
(31300 Ϫ1cmϪ1) and 387 (6230) nm. IR (KBr): ν˜ ϭ 2125 w (νCN
)
and 1618 s (νCO) cmϪ1. 1H NMR (250 MHz, [D6]DMSO): δ ϭ 9.06
3
(d, 3J ϭ 5.2 Hz, H1, 1 H), 8.90 (dd, J ϭ 7.3, 4J ϭ 1.2 Hz, 1 H, H4
3
3
or H6), 8.69 (d, J ϭ 8.1 Hz, 1 H, H3), 8.40 (d, J ϭ 8.0 Hz, 1 H,
H3Ј), 8.00 (d, 3J ϭ 7.1 Hz, 1 H, H4Ј or H6Ј), 7.86 (dd, 3J ϭ 8.1,
3J ϭ 5.2 Hz, 1 H, H2), 7.75Ϫ7.45 (m, 4 H, H5 ϩH5Ј, H4 or H4Ј
and H6 or H6Ј), 7.45Ϫ7.00 (m, 6 H, H2Ј and H-Ph,), 6.11 (d, J ϭ
3
(neat): ν˜ ϭ 3271 w (νNH) and 1666 s (νCO) cmϪ1 1H NMR
.
4.6 Hz, 1 H, H1Ј), 5.55 (t, 3J ϭ 6.5 Hz, 1 H, CH), 3.18 (d, 3J ϭ
6.5 Hz, 2 H, CH2) ppm. MS: m/z (%) ϭ 555 (100) [Co(mono-
BenzBQM)(CN)2]Ϫ.
(250 MHz, CDCl3): δ ϭ 10.60 (s, 2 H, NH), 8.85Ϫ7.76 (m, 4 H,
3
H1 ϩ H5), 8.12 (d, J ϭ 8.2 Hz, 2 H, H3), 7.55Ϫ7.48 (m, 4 H, H4
3
3
ϩ H6), 7.43 (dd, J ϭ 8.2, J ϭ 4.2 Hz, 2 H, H2), 7.38Ϫ7.05 (m,
3
3
H-Ph, 5 H), 3.91 (t, J ϭ 7.6 Hz, 1 H, CH), 3.59 (d, J ϭ 7.6 Hz,
(Et4N)[Co(di-BenzBQM)(CN)2] (3c) and (Et4N)[Co(di-PhEtBQM)-
(CN)2] (3d): A mixture of CoCl2 (27 mg, 0.21 mmol) and the ligand
di-BenzBQMH2 (1c; 0.11 g, 0.21 mmol) or di-PhEtBQMH2 (1d;
0.12 g, 0.21 mmol), respectively, was dissolved in dry DMF (10 mL)
under argon. After addition of Et3N (0.11 mL, 0.84 mmol) the
solution turned orange. Stirring at room temperature was con-
tinued for 30 min before the solution was cooled to Ϫ30 °C.
Et4NCN (0.2 g, 1.3 mmol) in DMF (5 mL) was then added, and
the solution was stirred for a further 30 min at this temperature.
Oxidation to CoIII was performed by addition of the oxidizing
2 H, CH2) ppm. MS: m/z (%) ϭ 447 (100) [M ϩ H]ϩ).
2,2Ј-Dibenzyl-N,NЈ-bis(8-quinolyl)malonamide
(di-BenzBQMH2;
1c) and 2,2Ј-Bis(2-phenylethyl)-N,NЈ-bis(8-quinolyl)malonamide (di-
PhEtBQMH2; 1d): The disubstituted ligands 1c and 1d were syn-
thesised according to Hirose et al,[14] but the saponification of the
malonic esters was carried out as reported by Maslak et al.[15]
[Co(BQM)] (2a): Et3N (0.56 mL, 4.2 mmol) was added under argon
to a solution of the BQMH2 ligand (1a; 0.3 g, 0.84 mmol) in a
CH2Cl2/MeOH mixture (30 mL/20 mL). Upon addition of a meth-
anolic solution (10 mL) of CoCl2 (0.12 g, 0.92 mmol) the mixture
turned orange and within five minutes [CoII(BQM)] precipitated as
a completely insoluble orange solid that was washed with CH2Cl2,
MeOH and diethyl ether (20 mL each) (0.3 g, 73%).
C21H16CoN4O2·1.5H2O (440.06): calcd. C 55.89, H 3.65, N 12.40;
[10]
agent C6H4FN2PF6 (1.5 equiv.), dissolved in DMF (2 mL). The
reaction mixture was allowed to warm to room temperature and
DMF was removed in vacuo. The brown/orange solid was dissolved
in acetonitrile (20 mL), the remaining white residue — unconverted
ligand — was filtered off. An orange product was obtained after
evaporation of the solvent. The product was further purified over
LH-20 (30 g) with MeOH and finally precipitated with diethyl ether
as an orange powder (3c: 0.13 g, 79%; 3d: 59 mg, 35%).
found C 57.28, H 3.89, N 12.72. IR (KBr): ν˜ ϭ 1605 s (νCO) cmϪ1
EPR (powder, 4 K) g ϭ 1.99.
.
(Et4N)[Co(BQM)(CN)2] (3a): Complex 2a (0.1 g, 0.24 mmol) was 3c: C45H46CoN7O2·3H2O·3MeOH·1.5MeCN (945.93): calcd. C
suspended in CH2Cl2 (2 mL). Addition of a CH2Cl2 solution 62.18, H 6.98, N, 11.10; found C 61.94, H 6.96, N 11.07. UV/Vis
(5 mL) of tetraethylammonium cyanide (Et4NCN, 75 mg, (MeOH): λmax (ε) ϭ 268 (26500 Ϫ1·cmϪ1) and 400 (6090) nm. IR
Eur. J. Inorg. Chem. 2004, 1545Ϫ1551
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1549

O. Rotthaus, S. LeRoy, A. Tomas, K. M. Barkigia, I. Artaud
Table 2. Experimental crystallographic details for [Co(BQM)(CN)2]Et4N (3a) and [Co(di-BenzBQM)(CN)2]Et4N (3c)
FULL PAPER
Formula
Crystallized from
Mol. mass
Space group
Z
C31H34CoN7O2·2H2O
dichloromethane/hexane
631.61
C2/c
8
C37H26CoN6O2·C8H20N·C2H3N
acetonitrile/diethyl ether
816.87
Pbc21
4
T (K)
150
293
˚
a (A)
33.789 (4)
13.707 (2)
14.358 (2)
90
92.43(1)
6643 (9)
orange
irregular wedge
1.263
0.14 ϫ 0.12 ϫ 0.10
0.561
0.9037
11.170 (2)
19.199 (3)
19.375 (3)
90
˚
b (A)
˚
c (A)
α (°)
β (°)
90
3
˚
V (A )
4155.0 (1)
orange
parallelepiped
1.306
0.5 ϫ 0.3 ϫ 0.2
0.462
0.71069
Crystal colour
Crystal shape
Density calcd.
Dimensions (mm)
µ (mmϪ1
λ (A)
)
˚
2θ range (°)
2.04Ϫ30.48
none
43991/4614
4306
3.50Ϫ24.71
MULABS[21]
20155/5343
4406
Absorption correction
reflections total/independent
Reflections with I Ͼ 2σ(I)
No of parameters refined
R1; wR2 [I Ͼ 2σ(I)]
R1; wR2 (all data)
GOF
390
528
0.072; 0.196[19]
0.079; 0.209
1.129
0.0514; 0.1138
0.0631; 0.1214
1.057
(KBr): ν˜ ϭ 2120 w (νCN) and 1601 s (νCO) cmϪ1
.
1H NMR
2σ(I) and wR2 ϭ 0.216 for 4614 reflections. ORTEP[21] diagrams
3
4
(250 MHz, [D6]DMSO): δ ϭ 9.03 (dd, J ϭ 7.3, J ϭ 1.9 Hz, 2 H, of 3a and 3c are given in Figures 1 and 2.
3
3
H4 or H6), 8.95 (d, J ϭ 5.3 Hz, 2 H, H1), 8.60 (d, J ϭ 8.1 Hz, 2 CCDC-214648 (3a) and -211026 (3c) contain the supplementary
H, H3), 7.84 (dd, J ϭ 8.1, J ϭ 5.3 Hz, 2 H, H2), 7.60Ϫ7.45 (m,
crystallographic data for this paper. These data can be obtained
3
3
4 H, H5 and H4 or H6), 7.35Ϫ7.00 (m, 10 H, H-Ph), 3.6Ϫ3.5 (m, free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or
4
H, CH2) ppm. MS: m/z (%)
ϭ
645 (100) [Co(di-
from the Cambridge Crystallographic Data Centre, 12, Union
Road, Cambridge CB2 1EZ, UK; Fax: (internat.) ϩ44-1223/336-
033; E-mail: deposit@ccdc.cam.ac.uk].
BenzBQM)(CN)2]Ϫ.
3d: C47H50CoN7O2·2/3DMF·1/3H2O (858.04): calcd. C 68.54, H
6.50, N 12.51; found C 68.02, H 6.48, N 12.55. UV/Vis (MeOH):
λmax (ε) ϭ 266 (28900 Ϫ1·cmϪ1) and 394 (7180) nm. IR (KBr):
Acknowledgments
ν˜ ϭ 2117 w (νCN) and 1603 s (νCO) cmϪ1 1H NMR (250 MHz,
.
[D4]MeOH): δ ϭ 9.31 (d, 3J ϭ 7.8 Hz, 2 H, H4 or H6), 8.94 (d,
3J ϭ 5.3 Hz, 2 H, H1), 8.52 (d, 3J ϭ 8.1 Hz, 2 H, H3), 7.76 (dd,
3J ϭ 8.1, 3J ϭ 5.3 Hz, 2 H, H2), 7.69 (t, 3J ϭ 7.8 Hz, 2 H, H5),
7.57 (d, 3J ϭ 7.8 Hz, 2 H, H4 or H6), 7.3Ϫ7.0 (m, 10 H, H-Ph),
2.95Ϫ2.80 (m, 4 H, CH2), 2.6Ϫ2.4 (m, 4 H, CH2) ppm. MS: m/z
(%) ϭ 673 (100) [Co(di-PhEtBQM)(CN)2]Ϫ.
This work was supported by the European Commission, TMR-
NOHEMIP research network No. ERBFMRXCT98Ϫ0174 and by
the Division of Chemical Sciences, US Department of Energy, un-
der contract DE-AC02-98CH10886 (at BNL). We thank the the
EC for providing O. R. with a postdoctoral fellowship and Jack
Fajer for helpful discussions.
X-ray Crystallography: Crystal data for 3a and 3c are presented in
Table 2. Data for 3a were collected at beamline X7B (λ ϭ 0.9376
A) at the Brookhaven National Synchrotron Light Source with a
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