Copper(II), cobalt(II), nickel(II) and zinc(II) complexes containing the enolate of N-acetyl-3-butanoyltetramic acid (Habta) and its phenylhydrazone derivative analogues. Crystal structure of [Cu(abta)2(py)2]·2H2O

Article abstract of DOI:10.1039/b007252o

Reaction of N-acetyl-3-butanoyltetramic acid (N-acetyl-3-butanoyl-4-hydroxypyrrolidin-2-one) (Habta) with M(CH₃CO₂)₂·xH₂O (x = 1, 2 or 4; M = Cu^II, Co^II or Ni^II) in a 1:1 ratio gave M(CH₃CO₂)(abta)·yH₂O 1, 3, 5 and in 1:2 ratio M(abta)₂·y′H₂O 2, 4, 6. A new ligand, the phenylhydrazone of Habta (HPhabta), has been prepared and reacts with M(CH₃CO₂)₂·xH₂O (x = 2 or 4; M = Cu^II or Co^II) in a 1:1 and 1:2 ratio to give the analogous complexes M(CH₃CO₂)(Phabta)·zH₂₂O 9, 11 and M(Phabta)₂·z′H₂O 10 respectively. The solid state structure of [Cu(abta)₂(py)₂]·2H₂O 2a has been determined by single crystal X-ray diffraction. It shows that copper adopts a slightly distorted octahedral co-ordination geometry with the abta enolate ligand adopting an O,O′ mode of co-ordination via the functionalities associated with C⁴ and the acyl group at C³ in the pyrrolidine ring. The reaction of Habta with Zn(CH₃CO₂)₂·2H₂O in 1:1 ratio gives a complex 7 with a deacetylated ligand whereas, with 1:2 ratio, Zn(abta)₂·2H₂O 8 is obtained. In contrast the reaction of HPhabta with Zn(CH₃CO₂)₂·2H₂O, irrespective of the metal to ligand ratio, gives Zn(CH₃CO₂)(Phbta)·2H₂O 12 containing the deacetylated ligand.

Full text of DOI:10.1039/b007252o

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Copper(II), cobalt(II), nickel(II) and zinc(II) complexes containing
the enolate of N-acetyl-3-butanoyltetramic acid (Habta) and its
phenylhydrazone derivative analogues. Crystal structure of
[Cu(abta)2(py)2]ؒ2H2O†
Efstathios Gavrielatos,a Christos Mitsos,a Giorgos Athanasellis,a Brian T. Heaton,c
Alexander Steiner,c Jamie F. Bickley,c Olga Igglessi-Markopoulou*a and John Markopoulosb
a Laboratory of Organic Chemistry, Department of Chemical Engineering,
National Technical University of Athens, Zografou Campus, GR-15773 Athens, Greece
b Laboratory of Inorganic Chemistry, Department of Chemistry, University of Athens,
Panepistimiopolis, GR-15771 Athens, Greece
c Department of Chemistry, Donnan Laboratories, University of Liverpool, PO Box 147,
Liverpool, UK L69 3BX
Received 7th September 2000, Accepted 9th January 2001
First published as an Advance Article on the web 12th February 2001
Reaction of N-acetyl-3-butanoyltetramic acid (N-acetyl-3-butanoyl-4-hydroxypyrrolidin-2-one) (Habta) with
M(CH3CO2)2ؒxH2O (x = 1, 2 or 4; M = CuII, CoII or NiII) in a 1:1 ratio gave M(CH3CO2)(abta)ؒyH2O 1, 3, 5 and in
1:2 ratio M(abta)2ؒyЈH2O 2, 4, 6. A new ligand, the phenylhydrazone of Habta (HPhabta), has been prepared and
reacts with M(CH3CO2)2ؒxH2O (x = 2 or 4; M = CuII or CoII) in a 1:1 and 1:2 ratio to give the analogous complexes
M(CH3CO2)(Phabta)ؒzH2O 9, 11 and M(Phabta)2ؒzЈH2O 10 respectively. The solid state structure of [Cu(abta)2(py)2]ؒ
2H2O 2a has been determined by single crystal X-ray diffraction. It shows that copper adopts a slightly distorted
octahedral co-ordination geometry with the abta enolate ligand adopting an O,OЈ mode of co-ordination via
the functionalities associated with C4 and the acyl group at C3 in the pyrrolidine ring. The reaction of Habta
with Zn(CH3CO2)2ؒ2H2O in 1:1 ratio gives a complex 7 with a deacetylated ligand whereas, with 1:2 ratio,
Zn(abta)2ؒ2H2O 8 is obtained. In contrast the reaction of HPhabta with Zn(CH3CO2)2ؒ2H2O, irrespective of
the metal to ligand ratio, gives Zn(CH3CO2)(Phbta)ؒ2H2O 12 containing the deacetylated ligand.
Introduction
The 3-acyltetramic acids (substituted pyrrolin-2-ones) (Fig. 1)
constitute a growing class of natural products displaying a
range of biological activities.1 The β,βЈ-tricarbonyl moiety
present in the 3-acyltetramic acids provides a suitable site for
bidentate complexation to a metal. “Magnesidin” (Fig. 2a), a
Fig. 1 3-Acyl-4-hydroxypyrrolin-2-ones.
natural antibiotic, was isolated as a 1:1 mixture of the covalent
magnesium chelates of 1-acetyl-3-hexanoyl- and -3-octanoyl-
tetramic acid derivatives.2 “Tenuazonic acid” (Fig. 2b), the
simplest compound of this class, was isolated as a mixture of
calcium() and magnesium() complexes, of 3-acetyl-5-sec-
butyltetramic acid.3 “Oleficin” (Fig. 2c) functions as an iono-
phore for Mg2ϩ and Ca2ϩ ions in isolated rat liver mitochondria.
This property can be attributed to the ability of the β,βЈ-
tricarbonyl moiety to form complexes with various metal ions.4
Thus the synthesis and spectroscopic studies of compounds
containing the pyrrolidine-2,4-dione ring system is of increas-
ing interest. The broad spectrum of biological activity of
3-acyltetramic acids prompted many research groups to syn-
thesize related complexes and evaluate their biological proper-
ties. The mechanisms responsible for the various biological
properties include complexation with various metal cations,
which increases their liposolubility and permeability through
cell walls.5 Such a feature has become evident on testing
copper() complexes containing 3-acetyl- and 3-decanoyl-
† Electronic supplementary information (ESI) available: colours and
elemental analysis data for complexes 1–12. See http://www.rsc.org/
suppdata/dt/b0/b007252o/
Fig. 2 Naturally occurring 3-acyltetramic acids.
J. Chem. Soc., Dalton Trans., 2001, 639–644
DOI: 10.1039/b007252o
639
This journal is © The Royal Society of Chemistry 2001

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tetramic acids for antimicrobial activity6,7 and it seems likely
that their biological activity is related to their complexing
ability.8 Recently new platinum() complexes containing
3-alkanoyltetramic acids have been shown to have a broad
spectrum of biological properties.9
The complexation of 3-butanoyl and 3-benzoyl N–H
tetramic acids with metal() halides has previously been exam-
ined by our team.10 However, the N-acetyl analogues are
expected to adopt a different co-ordination mode. In this paper
we describe the synthesis (Scheme 1) and characterization
Fig. 3 The ligands Habta and Hbta.
Fig. 4 The ligands HPhabta and HPhbta.
Scheme 1 Synthesis of the ligand Habta I and its phenylhydrazone
derivative II. (i) NaH, PhH, r.t.; (ii) H2NNHC6H5, abs. ethanol, reflux
2.5 h.
of metal() complexes of N-acetyl-3-butanoyltetramic acid
(Habta, I). The ability of Habta to substitute acetylacetonate as
a chelating monoanion has been well studied for rhodium()
complexes.11 We have extended our studies to the acetate salts
of the first row transition metals as well as zinc().
Moreover, our interest in the co-ordination chemistry of
hydrazones12–14 prompted us to synthesize the phenylhydrazone
derivative II (Scheme 1) of the above mentioned tetramic acid
and to test its complexing ability with copper(), cobalt()
and zinc() acetate salts. Ligands with N–N bonds have been
studied much in recent years because of their relationship
to the problem of conversion of dinitrogen into ammonia
or hydrazine. The interest in the study of hydrazones has
increased because of their use in biological systems,15 analytical
chemistry16 and in non-linear optics.17
Fig. 5 Crystal structure of the complex [Cu(abta)2(py)2]ؒ2H2O 2a.
water solution in a refrigerator overnight and the elemental
analysis of the resulting green crystals suggested the empirical
formula [Cu(abta)2(py)2]ؒ2H2O 2a which was confirmed by
X-ray analysis, see below. Efforts to prepare analogous com-
plexes with Zn(CH3CO2)2ؒH2O gave two products; with a 1:1
ligand to metal ion molar ratio deacetylation of the ligand
occurs, resulting in complexation of the N–H ligand (Hbta)
(Fig. 3) to give Zn(bta)2ؒ2H2O 7, whereas a 2:1 ligand to metal
ion molar ratio results in the formation of Zn(abta)2ؒ2H2O 8.
New complexes of general formulae M(CH3CO2)(Phabta)ؒ
2H2O (M = CuII 9 or CoII 11) and Cu(Phabta)2ؒ4H2O 10, where
HPhabta is the phenylhydrazone derivative of the ligand Habta,
have been prepared and characterized. The synthesis of the
phenylhydrazone of N-acetyl-3-butanoyltetramic acid (Scheme
1) is straightforward and the new ligand has been character-
Results and discussion
Synthesis
The synthesis of N-acetyl-3-butanoyltetramic acid (Habta),
1
together with its IR, H and 13C NMR spectra and X-ray
analysis, has previously been reported by our team.18 The com-
plexes M(CH3CO2)(abta)ؒyH2O (M = CuII 1, CoII 3 or NiII 5)
and M(abta)2ؒyЈH2O (M = CuII 2, CoII 4 or NiII 6) are readily
prepared (eqns. (1) and (2)) by reaction of the appropriate metal
1
ized by IR, H–13C NMR and elemental analysis (Fig. 4). As
found for the reaction of Habta with ZnII, loss of the acetyl
group from HPhabta occurs in the analogous reaction with ZnII
to give Zn(CH3CO2)(Phbta)ؒ2H2O 12 and the same complex is
formed irrespective of the metal to ligand ratio used (2:1, 1:1,
1:2).
M(CH3CO2)2ؒxH2O ϩ Habta →
M(CH3CO2)(abta)ؒyH2O ϩ CH3CO2H (1)
Crystal structure of [Cu(abta)2(py)2]ؒ2H2O 2a
M(CH3CO2)2ؒxH2O ϩ 2 Habta →
M(abta)2ؒyЈH2O ϩ 2 CH3CO2H (2)
A view of the molecular structure of complex 2a is shown in
Fig. 5. Selected bond lengths and angles are listed in Table 1.
Copper adopts a slightly distorted octahedral geometry. The
Cu(1)–O(1) [2.0257(18) Å] bond is shorter than that of Cu(1)–
O(2) [2.2463(18) Å], but both are much longer than Cu(1)–N(1)
[2.0076(19) Å] of the two axially co-ordinated pyridines. Each
abta ligand is co-ordinated to the copper ion through its
butanoyl oxygen atom O(1) and the oxygen O(2) (4-hydroxyl)
acetate salt M(CH3CO2)2ؒxH2O (x = 1, 2 or 4) and Habta in
MeOH under reflux by simply changing the metal to ligand
ratio. The complexes can be isolated as powders, which are
stable in the normal laboratory atmosphere and soluble in
MeOH and DMSO. Crystals suitable for a single crystal X-ray
study of Cu(abta)2ؒ2H2O 2 have been grown from a pyridine–
640
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Table 1 Selected bond distances (Å) and angles (Њ) for [Cu(abta)2-
(py)2]ؒ2H2O 2a with standard deviations in parentheses
Cu(1)–N(1)
Cu(1)–O(1)
Cu(1)–O(2)
C(10)–C(13)
N(2)–C(13)
O(3)–C(13)
C(10)–C(11)
C(9)–C(10)
C(11)–C(12)
2.0076(19)
2.0257(18)
2.2463(18)
1.458(3)
1.429(3)
1.211(3)
1.406(4)
1.435(4)
1.508(4)
O(2)–C(11)
N(2)–C(12)
C(8)–C(9)
O(1)–C(9)
C(7)–C(8)
C(6)–C(7)
C(14)–C(15)
N(2)–C(14)
O(4)–C(14)
1.247(3)
1.455(3)
1.505(4)
1.252(3)
1.491(4)
1.515(4)
1.490(4)
1.384(3)
1.219(3)
N(1)–Cu(1)–N(1)#1 180.0
C(9)–O(1)–Cu(1)
C(11)–O(2)–Cu(1)
N(1)–C(1)–C(2)
N(1)–C(5)–C(4)
O(1)–C(9)–C(10)
O(1)–C(9)–C(8)
O(2)–C(11)–C(10)
O(2)–C(11)–C(12)
O(3)–C(13)–N(2)
O(3)–C(13)–C(10)
N(2)–C(13)–C(10)
O(4)–C(14)–N(2)
O(4)–C(14)–C(15)
N(2)–C(14)–C(15)
129.6(16)
117.2(16)
122.8(3)
121.4(2)
122.0(2)
117.7(2)
130.7(2)
120.4(2)
123.1(2)
130.2(2)
106.6(2)
118.3(2)
122.1(2)
119.5(2)
N(1)–Cu(1)–O(1)#1
N(1)–Cu(1)–O(1)
O(1)#1–Cu(1)–O(1)
N(1)–Cu(1)–O(2)
N(1)#1–Cu(1)–O(2)
O(1)#1–Cu(1)–O(2)
O(1)–Cu(1)–O(2)
C(1)–N(1)–C(5)
89.0(7)
91.0(7)
180.0
89.6(7)
90.4(7)
93.0(7)
87.0(7)
118.5(2)
120.1(16)
121.3(17)
128.9(2)
119.9(2)
111.1(18)
Fig. 6 Tautomeric forms of Habta and its phenylhydrazone derivative
HPhabta.
plexation with zinc(), while C-4 is only shifted by 1.7 ppm. In 8
the carbonyl atoms C-4 and C-6 are shifted downfield while C-2
is only shifted by 1.4 ppm. The N-acetyl-3-hydrazonoalkyl
C(1)–N(1)–Cu(1)
C(5)–N(1)–Cu(1)
C(14)–N(2)–C(13)
C(14)–N(2)–C(12)
C(13)–N(2)–C(12)
tetramic acids can exist as enolic “internal” tautomers a
and c d, in addition to “external” tautomers ab
b
cd
(Fig. 6), demonstrating that a tautomeric equilibrium, due to
the various hydrogen-bonding strengths, exists between the
external tautomers a,b and c,d.20 In CDCl3 solution two sets of
of the pyrrolidine ring, as a β-diketonate anion. This arrange-
ment is probably preferred because of the higher electron
density on the hydroxyl oxygen compared to that of the
amide carbonyl O(3) in the 2 position. The two individual
ligand molecules are trans with respect to chelation to the
copper ion. The co-ordination environment around the copper
atom is completed with two axially co-ordinated pyridine
molecules. The equivalence of the O(1)–C(9) [1.252(3) Å] and
O(2)–C(11) [1.247(3) Å] and also of C(9)–C(10) [1.435(4) Å]
and C(10)–C(11) 1.406(4) Å] bonds indicates extensive delocal-
ization in the chelate rings and, within experimental error, the
two six-membered chelate rings are planar.
The crystal structure of complex 2a contains two water
molecules per Cu(abta)2(py)2 complex. Each forms hydrogen
bonds to two copper complexes via O(2) and O(4), respectively.
Hence, each complex is linked intermolecularly with two neigh-
bouring complexes by four water molecules, resulting in linear
chains featuring double H2O bridges between metal complexes.
The sites of co-ordination of Habta in this copper complex, as
well as the geometry around the copper center, differ markedly
from those found in the crystal structure of an analogous
copper() complex containing the naturally occurring tenu-
azonic acid.19 In this case tenuazonic acid chelates to copper via
the acetyl oxygen and the amide (2-carbonyl) oxygen of the
pyrrolidine ring. This difference could be due to the different
substituents on the nitrogen atom of the ring. In the case pre-
sented here the free electron pair on the nitrogen atom is shared
by the amide carbonyl group and the acetyl carbonyl, thus
reducing the electron density on the amide carbonyl. Con-
sequently the co-ordinating ability of the amide carbonyl is
reduced, inducing co-ordination from the 4-hydroxyl oxygen
which is deprotonated. On the other hand in tenuazonic acid,
according to Steyn’s20 tetramic acid model, the nitrogen atom
in the amide structure is better able to donate electrons to the
C-2 carbonyl group, thus enhancing its co-ordinating ability.
1
signals are thus observed for certain protons. The H and 13C
NMR spectra of 12 also exhibit two pairs of signals for all the
protons and the carbons, which must arise from the same
tautomerism as found in the “free” ligand. Deacetylation of the
latter on complexation to ZnII is clearly shown by the NMR
1
spectra of 12. Thus the H NMR verifies the existence of one
acetate unit per ligand, the single resonance at δ 2.08 is assigned
to the methyl protons of the acetate group. The resonance due
to the 5-methylene protons at δ 3.78 is shifted significantly
upfield consistent with the change in the ligand from N-acetyl
to N–H. Major shifts are observed in the 13C NMR for the
carbonyl atoms C-2, C-4, C-6 which is consistent with the com-
plexation via one oxygen atom and the imino nitrogen atom.
Complexation via the amine nitrogen of the hydrazono moiety
is excluded by the existence of a single resonance at δ 5.95 in the
1H NMR due to N–H.
Electronic spectra and magnetic moments
The high magnetic moments (4.9–5.3 µB) and electronic spectra
of the cobalt() complexes are characteristic of pseudo-
octahedral complexes, the two peaks in the electronic spectra
4
4
being assigned to transitions from the T1g to the T1g(P) and
4A2g states respectively. The nickel() complexes similarly show
magnetic and electronic spectroscopic properties which are
characteristic of an octahedral stereochemistry. They have
magnetic moments only a little above the spin-only value and
show two main peaks in the electronic spectra (the highest
energy band is obscured by an intense charge-transfer absorp-
tion), assignable to transitions from the 3A2g ground state to the
3T2g and 3T1g(F) states respectively. For the copper() complexes
the magnetic moments indicate that no reduction to copper()
has occurred and the electronic spectra show broad bands in the
15000–14000 cmϪ1 region with shoulders on the low frequency
side typical of Jahn–Teller distorted octahedral copper()
complexes.21
NMR spectroscopy studies
Vibrational spectra
1
From the H NMR spectra of complex 7 it is evident that
deacetylation of the ligand has occurred accounting for the
disappearance of the singlet at δ 2.39 assigned to the methyl
protons of the acetyl group. The deacetylation is further
demonstrated by the 13C NMR and the disappearance of the
two signals at δ 24.8 and 168.5. The carbonyl atoms C-2 and
C-6 are significantly shifted downfield for 7 as a result of com-
The IR spectra of complexes 1–8 show the ν(C᎐O) lactam and
᎐
ν(C᎐O) β-diketone, shifted to lower wavenumbers with respect
᎐
to that of the “free” ligand, confirming that two oxygens are
involved in the co-ordination of the metal. New bands at high
frequencies (>3200 cmϪ1) appear when Habta is complexed to
the metals. These can be attributed to the stretching vibration
J. Chem. Soc., Dalton Trans., 2001, 639–644
641

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of the O–H group from water molecules, which are either co-
ordinated or captured in the crystal lattice. The differences (∆ν)
N-Acetyl-3-butanoyltetramic acid (Habta) I. Ethyl butyryl-
acetate (6.64 g, 0.042 mol) was added dropwise to sodium
hydride (1.14 g, 0.028 mol, 60% sodium hydride in oil) in
anhydrous benzene (120 ml) and the thick white slurry thus
formed was stirred at room temperature for 1¹ h. The
Ϫ
Ϫ
of the asymmetric νasym(CO2 ) and symmetric νsym(CO2 )
carbonyl stretching frequencies of compounds 1, 3, 5 are much
larger than 200 cmϪ1 (240–255 cmϪ1), which indicates that the
acetate groups are co-ordinated in a monodentate fashion,
rather than as a chelate.22 We assign the band at 1570 cm Ϫ1 of
the phenylhydrazone of N-acetyl-3-butanoyltetramic acid to
¯
²
N-hydroxysuccinimide ester of N-acetylglycine (3 g, 0.014 mol)
was added and stirring continued for 2¹ h. Water was added
¯
²
and the aqueous layer separated and acidified with 10% hydro-
chloric acid in an ice–water bath. The product was formed
directly in the acidified solution as a white solid, which was
filtered off, washed with cold water, light petroleum (bp range
40–60 ЊC) (2 × 5 ml) and dried in vacuo over P2O5 (yield 1.6 g,
55%), mp 67–69 ЊC (Found: C, 56.3; H, 6.3; N, 6.9%. Calc. for
C10H13NO4: C, 56.9; H, 6.2; N, 6.6%). νmax/cmϪ1 (OH) 3330br,
ν(C᎐N) and that at 1080 cmϪ1 to ν(N–N) in accordance with
᎐
other assignments.23 A movement of the ν(C᎐N) band to
᎐
higher frequencies in the spectra of the complexes has been
observed similar to that for complexes of other ligands contain-
ing the C᎐N–N grouping24 in which the imino nitrogen
᎐
atom donates to the metal ion. The hydrazinic ν(N–N) band
shifts to higher wavenumbers in the spectra of the complexes
relative to the “free” ligand, as a result of co-ordination
through the imino nitrogen atom, similar to what has been
observed for hydrazine25 and other α-dihydrazone26 complexes.
Deacon and Phillips27 have established, in the case of acetate
compounds, some correlations between the ∆ν values of the
different modes of bonding of the carboxylate moiety found in
the molecular structure. The ∆ν value for compounds 9, 11, 12
is 150–220 cmϪ1 which is somewhere between the value for
monodentate and bis chelate co-ordination of the acetate
group. Therefore an unambiguous assignment of the mode of
co-ordination of the acetate group is not possible.
(N–COCH ) 1740s, (C᎐O lactam) 1720w and (C᎐O and C᎐C of
᎐
᎐
᎐
3
the enolic and β-diketone system) 1650br; δH(DMSO-d6) 0.86
(3H, t, H9), 1.52 (2H, mt, H8), 2.39 (3H, s, H11), 2.73 (2H, t, H7)
and 4.11 (2H, s, H5); δC(DMSO-d6) 194.2 C(6), 186.9 C(4),
169.2 C(2), 168.5 C(10), 105.1 C(3), 49.5 C(5), 39.7 C(7), 24.8
C(11), 17.8 C(8) and 13.7 C(9).
N-Acetyl-4-hydroxy-3-[1-(2-phenylhydrazono)butyl]pyrrolin-
2-one (HPhabta) II. A solution of phenylhydrazine (0.31 g,
2.84 mmol) in absolute ethanol was added dropwise to a solu-
tion of Habta (0.60 g, 2.84 mmol) in absolute ethanol and the
mixture stirred under reflux for 2.5 h. The resulting mixture was
concentrated in vacuo and the solid obtained was filtered off,
washed with cold ethanol and dried in vacuo over P2O5. Yield
Concluding remarks
0.50 g, 60%. mp 140–141 ЊC (Found: C, 62.5; H, 6.3; N, 13.6%.
1
–
The isolated copper(II), cobalt(II) and nickel(II) complexes of
Habta all have octahedral stereochemistry with bidentate
co-ordination through O(1) and O(2) (4-hydroxyl) atoms of
the pyrrolidine ring. The copper(II) and cobalt(II) complexes
of HPhabta have similar stereochemistry with bidentate
co-ordination through O(2) (4-hydroxyl) and N-methine atoms.
In contrast, complexation of Habta to ZnII is different and
depends on the ratio of ligand to metal ion. Using a 1:1 ratio
deacetylation of the ligand occurs whereas at a 2:1 ratio the
N-acetyl complex could be isolated. The reaction of the hydra-
zone analogue with ZnII results in deacetylation, which occurs
irrespective of the metal to ligand ratio used. The ligand co-
ordination mode in the zinc(II) complexes probably involves
O(1) and O(2) for Habta and O(2) and the N-methine atom
for the HPhabta ligand.
Calc. for C16H19N3O3ؒ 3H2O: C, 62.5; H, 6.4; N, 13.7%). νmax
/
cmϪ1 (NH and OH) 3260br, (C᎐N) 1570s and (N–N) 1080w;
᎐
δH(CDCl3) 1.04 (3H, t, H9), 1.65 (2H, mt, H8), 2.56 and 2.6 (3H,
2s, H11), 3.14 (2H, t, H7), 4.07 and 4.1 (2H, 2s, H5), 5.94
and 5.98 (1H, 2br, NH), 6.7–7.4 (5H, mt, C6H5), 11.5 and 12.28
(1H, 2br, OH); δC(CDCl3) 194.4/189.8 C(6), 178.0/177.5 C(4),
172.6/170.5 C(2), 169.8/168.1 C(10), 145.7/145.6 C(12), 129.8
C(13a, 13b), 122.9/122.8 C(14a, 14b), 113.7/113.6 C(15),
96.6/95.4 C(3), 53.2/51.3 C(5), 28.3/27.6 C(7), 25.2/25.1 C(11),
21.8/21.7 C(8) and 14.2/14.1 C(9).
M(CH3CO2)(abta)ؒyH2O. A solution of Habta (0.422 g,
2 mmol) in MeOH (10 ml) was added to a stirred solution of
M(CH3CO2)2ؒxH2O (2 mmol) in the same solvent (30 ml). The
homogeneous solution obtained was refluxed for 2 hours, then
the solvent was evaporated in vacuo to yield a coloured solid
which was collected by filtration, washed with cold MeOH
(5 ml) and Et2O (3 × 5 ml) and dried in vacuo over P2O5.
Experimental
Reagents and physical measurements
M(abta)2ؒyЈH2O. A solution of Habta (0.844 g, 4 mmol) in
MeOH (20 ml) was added to a stirred solution of M(CH3-
CO2)2ؒxH2O (2 mmol) in the same solvent (30 ml). The homo-
geneous solution obtained was refluxed for 2 hours, then the
solvent was evaporated in vacuo to yield a coloured solid which
was collected by filtration, washed with cold MeOH (5 ml) and
Et2O (3 × 5 ml) and dried in vacuo over P2O5.
All manipulations were performed under aerobic conditions
using reagents and solvents as received, except benzene, which
was distilled prior to use according to standard procedures.28
Melting points were determined on a Gallenkamp MFB-595
melting point apparatus and are uncorrected. C, H and N anal-
yses were conducted by the University of Liverpool, Chemistry
Department. IR spectra (4000–250 cmϪ1) were recorded on a
Perkin-Elmer 883 spectrometer with samples prepared as KBr
pellets, electronic spectra by diffuse reflectance on a Perkin-
Elmer 124 spectrophotometer over the range (25000–12500
cmϪ1) using MgO as standard. Magnetic susceptibilities of
powdered samples were recorded by the Gouy method at room
temperature against Hg[Co(SCN)4] as calibrant. Diamagnetic
corrections were estimated from Pascal constants. 1H, 13C, 2-D
HETCOR (heteronuclear correlation) NMR spectra were
recorded on a Varian Gemini-2000 300 MHz spectrometer.
M(CH3CO2)(Phabta)ؒzH2O. A solution of HPhabta (0.30 g,
1 mmol) in MeOH (10 ml) was added to a stirred solution of
M(CH3CO2)2ؒxH2O (1 mmol) in the same solvent (15 ml).
The homogeneous solution obtained was refluxed for 2 hours,
then the solvent was evaporated in vacuo to yield a coloured
solid which was collected by filtration, washed with cold
MeOH (5 ml) and Et2O (3 × 5 ml) and dried in vacuo over
P2O5.
M(Phabta)2ؒzЈH2O. A solution of HPhabta (0.60 g, 2 mmol)
in MeOH (20 ml) was added to a stirred solution of M(CH3-
CO2)2ؒxH2O (1 mmol) in the same solvent (15 ml). The homo-
geneous solution obtained was refluxed for 2 hours, then the
solvent was evaporated in vacuo to yield a coloured solid which
Syntheses
The N-hydroxysuccinimide ester of N-acetylglycine was syn-
thesized according to a previously reported method,29 as was
the compound Hbta from Habta.11
642
J. Chem. Soc., Dalton Trans., 2001, 639–644

View Article Online
Ϫ
Table 2 Crystal data and data-collection parameters for [Cu(abta)2-
(py)2]ؒ2H2O 2a
(νsymCO2 ) 1420s, (ring def.) 490w, (Cu–O and ring def.) 430w,
425w, (Cu–N) 360w; δH(CDCl3) 1.02 (3H, t, H9), 1.63 (2H, mt,
H8), 2.08 (3H, s, CH3CO2 ), 3.1 (2H, t, H7), 3.78 (2H, s, H5),
Ϫ
5.69 (1H, br, H1), 5.95 (1H, s, NH), 6.7–7.4 (5H, mt, C6H5);
δC(CDCl3) 197.8/193.5 C(6), 181.3 CH3CO2, 176.4/175.5 C(4),
175.9/173.1 C(2), 146.5/146.2 C(12), 129.7/129.3 C(13a, 13b),
122.5/122.3 C(14a, 14b), 114.6/113.5 C(15), 95.9/94.2 C(3),
51.5/49.5 C(5), 28.0/27.3 C(7), 22.9/22.1 C(8), 21.7 CH3CO2
and 14.1 C(9).
Empirical formula
Formula weight (M)
C30H38CuN4O10
678.26
T/K
Crystal system
Space group
213(2)
Triclinic
¯
P1
a/Å
b/Å
c/Å
α/Њ
8.9105(14)
10.2444(16)
10.4369(17)
63.643(17)
65.680(18)
75.792(18)
775.6(2)
X-Ray crystallography
β/Њ
γ/Њ
The crystal data and data-collection parameters are summar-
ized in Table 2. Crystal data were collected on a STOE-IPDS
diffractometer, using graphite-monochromated Mo-Kα radi-
ation (λ = 0.71073 Å). Structure solution and refinement were
carried out using the program SHELXS 97.30 Structure refine-
ment (SHELXL 97)31 by full-matrix least squares was based on
all data using F2. All non-hydrogen atoms were refined aniso-
tropically. Hydrogen atoms were included at calculated posi-
tions. The structure diagram was generated using ORTEP 3.32
CCDC reference number 186/2318.
V/Å3
Z
1
µ/mmϪ1
0.714
Reflections collected
Independent reflections
Data/restraints/parameters
Final R1 [I > 2σ(I)]
wR2 (all data)
4439
2044 [R(int) = 0.0568]
2044/0/211
0.0354
0.0898
was collected by filtration, washed with cold MeOH (5 ml) and
Et2O (3 × 5 ml) and dried in vacuo over P2O5.
See http://www.rsc.org/suppdata/dt/b0/b007252o/ for crystal-
lographic files in .cif format.
Cu(CH3CO2)(abta)ؒH2O 1. µeff 1.92 µB; UV (cmϪ1 × 103)
14.9; νmax/cmϪ1 (OH) 3460br, 3340br, 3250br, (C᎐O lactam)
᎐
Ϫ
Ϫ
1675s, (C᎐C and C᎐O) 1590s, (νasymCO2 ) 1690s, (νsymCO2 )
᎐
᎐
Acknowledgements
1450s, (Cu–O and ring def.) 530w, 475w.
We acknowledge support of this research by the National
Technical University of Athens (NTUA). J. M. would like to
thank the National and Kapodistrian University of Athens
for financial support (special account for research grant No.
70/4/3337).
Cu(abta)2ؒ2H2O 2. µeff 2.14 µB; UV (cmϪ1 × 103) 14.7; νmax
/
cmϪ1 (OH) 3520br, 3420br, 3240br, (C᎐O lactam) 1720s, 1680s,
᎐
(C᎐C and C᎐O) 1600s, (Cu–O and ring def.) 555w, 470w, 385w.
᎐
᎐
Co(CH3CO2)(abta)ؒ3H2O 3. µeff 4.93 µB; UV (cmϪ1 × 103)
18.9 and 21.5; νmax/cmϪ1 (OH) 3340br, (C᎐O lactam) 1710s,
᎐
Ϫ
Ϫ
(C᎐C and C᎐O) 1570s, (νasymCO2 ) 1650s, (νsymCO2 ) 1370s,
᎐
᎐
(Co–O and ring def.) 525w, 430w.
References
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16 W. Radecka-Paryzek and M. Gdaniec, Polyhedron, 1997, 20, 3681
and refs. therein.
Co(abta)2ؒ3H2O 4. µeff 5.02 µB; UV (cmϪ1 × 103) 18.9 and
20.8; νmax/cmϪ1 (OH) 3380br, 3310br, 3220br, (C᎐O lactam)
᎐
1720s, (C᎐C and C᎐O) 1620s, (Co–O and ring def.) 530w, 430w,
᎐
᎐
380w.
Ni(CH3CO2)(abta)ؒ2H2O 5. µeff 3.07 µB; UV (cmϪ1 × 103)
13.7, 14.9 and 25.6; νmax/cmϪ1 (OH) 3350br, (C᎐O lactam)
᎐
Ϫ
Ϫ
1715s, (C᎐C and C᎐O) 1610s, (νasymCO2 ) 1625s, (νsymCO2 )
᎐
᎐
1370s (Ni–O and ring def.) 535w, 450w.
Ni(abta)2ؒ2H2O 6. µeff 3.1 µB; UV (cmϪ1 × 103) 13.7, 15.9 and
21.3; νmax/cmϪ1 (OH) 3380br, 3240br, (C᎐O lactam) 1720s,
᎐
1630s, (C᎐C and C᎐O) 1580s, (Ni–O and ring def.) 540w, 450w.
᎐
᎐
Zn(bta)2ؒ2H2O 7. νmax/cmϪ1 (OH) 3350br, (C᎐O lactam)
᎐
1650s, 1640s, (Zn–O) 490w, 420w; δH(DMSO-d6) 0.84 (3H, t,
H9), 1.46 (2H, mt, H8), 2.64 (2H, t, H7), 3.44 (2H, s, H5) and
7.68 (1H, br, NH); δC(DMSO-d6) 193.5 C(6), 195.2 C(4), 178.7
C(2), 99.9 C(3), 50.0 C(5), 18.5 C(8) and 13.9 C(9).
Zn(abta)2ؒ2H2O 8. νmax/cmϪ1 (OH) 3400br, (C᎐O lactam)
᎐
1720s, 1660s, (Zn–O) 490w, 430w, 380w; δH(DMSO-d6) 0.84
(3H, t, H9), 1.47 (2H, mt, H8), 2.38 (3H, s, H11), 2.71 (2H, t, H7)
and 3.84 (2H, s, H5); δC(DMSO-d6) 198.8 C(6), 192.8 C(4),
170.6 C(2), 168.9 C(10), 102.6 C(3), 50.6 C(5), 24.8 C(11), 17.9
C(8) and 13.7 C(9).
Cu(CH3CO2)(Phabta)ؒ2H2O 9. µeff 2.11 µB; UV (cmϪ1
×
103) 14.3; νmax/cmϪ1 (NH, OH) 3420br, (C᎐N) 1590s, (N–N)
᎐
Ϫ
Ϫ
1095, (νasymCO2 ) 1590s, (νsymCO2 ) 1370s, (ring def.) 550w,
(Cu–O and ring def.) 470w, (Cu–N) 350w.
Cu(Phabta)2ؒ4H2O 10. µeff 2.3 µB; UV (cmϪ1 × 103) 14.3; νmax
/
cmϪ1 (NH, OH) 3410br, 3290br, (C᎐N) 1580s, (N–N) 1100s,
᎐
(ring def.) 500w, (Cu–O and ring def.) 420w, 380w, (Cu–N)
350w.
Co(CH3CO2)(Phabta)ؒ2H2O 11. µeff 5.28 µB; UV (cmϪ1
×
103) 19.8 and 21.3; νmax/cmϪ1 (NH, OH) 3310br, (C᎐N) 1575s,
17 T. Thami, P. Bassoul, M. A. Petit, J. Simon, A. Fort, M. Barzoukas
and A. Villaeys, J. Am. Chem. Soc., 1992, 114, 915.
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Perkin Trans. 2, 1994, 1271.
19 A. Dippenaar, C. W. Holzapfel and J. C. A. Boeyens, J. Cryst. Mol.
Struct., 1977, 7, 189.
᎐
Ϫ
Ϫ
(N–N) 1090s, (νasymCO2 ) 1570s, (νsymCO2 ) 1420s, (ring def.)
570w, (Cu–O and ring def.) 490w, 430w, (Cu–N) 355w.
Zn(CH3CO2)(Phbta)ؒ2H2O 12. νmax/cmϪ1 (OH, NH)
Ϫ
3500br, 3270br, (C᎐N) 1590s, (N–N) 1090s, (νasymCO2 ) 1580s,
᎐
J. Chem. Soc., Dalton Trans., 2001, 639–644
643

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J. Chem. Soc., Dalton Trans., 2001, 639–644