3802
A.A. Recio Despaigne et al. / Polyhedron 28 (2009) 3797–3803
ies appreciably with the metal ion. Similarly, the bond angles with-
in the hydrazone backbone do not change significantly but the
angles around the metal undergo appreciable variations upon
changing the metal center.
The crystallization DMSO solvent molecule in crystals 1 and 3
acts as acceptor of a N3–Hꢁ ꢁ ꢁO bond [N3ꢁ ꢁ ꢁO length and N3–
Hꢁ ꢁ ꢁO angle of 2.685 Å and 149.6° for 1 and 2.706 Å and 161.6°
for 3].
4. Conclusions
2-Formylpyridine-para-cholro-phenyl-hydrazone (H2FopClPh)
and
2-formylpyridine-para-nitro-phenyl-hydrazone
(H2Fop-
NO2Ph) react with copper chloride and with zinc chloride with for-
mation of [Cu(H2FopClPh)Cl2] (1), [Cu(2FopNO2Ph)Cl] (2),
[Zn(H2FopClPh)Cl2] (3) and [Zn(H2FopNO2Ph)Cl2] (4), in which
the hydrazones coordinate to the metal center as Npy–N–O chelat-
ing systems. Upon crystallization in DMSO:acetone conversion of 2
into [Cu(2FopNO2Ph)Cl(DMSO)] (2a) and of 4 into [Zn(2Fop-
NO2Ph)Cl(DMSO)] (4a) occurs. In the case of 2a the coordinating
ability of DMSO leads to its attachment to the metal center with
expansion of the metal coordination number. The electron-with-
drawing effect of the para-nitro group probably makes the metal
center more positive and more able to accept the fifth ligand. In
the case of 4a the electron-withdrawing effect of the para-nitro
group favors deprotonation at N3, with release of HCl, and attach-
ment of a DMSO molecule to the metal. Interestingly, as we
showed in a previous work, crystallization of [Zn(H2BzpNO2Ph)Cl2]
(H2BzpNO2Ph = 2-benzoylpyridine-para-nitro-phenyl-hydrazone)
in DMSO:acetone lead to the formation of [Zn(2BzpNO2Ph)Cl(DM-
SO)], also promoted by the presence of the para-nitro group [20].
Fig. 6. Molecular plot of [Zn(2FopNO2Ph)Cl(DMSO)] (4a).
The copper(II) and zinc(II) ions present coordination number
five, and are attached to a hydrazone molecule acting as a triden-
tate ligand through the pyridine and imine nitrogens, and the car-
bonyl oxygen. Two chloride ions occupy the remaining
coordination positions in the complexes with H2FopClPh. In the
complexes with H2FopNO2Ph one chloride and one O-bonded
DMSO are attached to the metal, along with an anionic hydrazone.
In all compounds, the hydrazone Pyr(C@N)N(C@O)N skeletal
fragment defines the coordination plane [rms deviation of atoms
from the least-squares plane less than 0.040 Å] with the metal
ion laying closer onto this plane in complexes 2a and 4a than in
complexes 1 and 3 [Cu(II) ions at 0.382(2) and 0.104(1) Å in 1
and 2a and Zn(II) ions at 0.358(2) and 0.105(2) Å in 3 and 4a,
respectively]. In 2a and 4a a competition between one chloride
ion and the anionic hydrazone for the positively charged metal
probably occurs. The interaction between the metal center and
the anionic hydrazone results in the metal laying closer to the
hydrazone skeleton plane in 2a and 4a than in 1 and 3, where
the attraction effect of two chloride ions for the positive metal cen-
ter predominates over the interaction between the metal and a
neutral hydrazone. The phenyl ring and the coordination plane in
complexes 1, 2a, 3 and 4a subtend dihedral angles of 22.0(1),
9.5(1), 9.5(2), and 2.5(1)°. In 2a and 4a the terminal NO2 group is
nearly coplanar with the phenyl ring [angled at 7.1(5) and
0.2(6)°, respectively].
Supplementary data
CCDC 714806, 714807, 714808, and 714809 contain the supple-
mentary crystallographic data for complexes 1, 2a, 3 and 4a. These
conts/retrieving.html, or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Acknowledgements
For complexes 1 and 3 the hydrazone C8–O1 bond distances are
1.243(3) and 1.231(4) Å, respectively, while in complexes 2a and
4a the C8–O1 bond distances are 1.285(3) and 1.268(3) Å respec-
tively, in accordance with a higher single bond character for the
latter which present an anionic hydrazone ligand. Similarly, the
N3–C8 bond distances are 1.359(3) and 1.366(4) Å for 1 and 3
respectively and 1.331(3) and 1.337(3) Å for 2a and 4a respec-
tively, in agreement with a higher double bond character in the lat-
ter. Interestingly, the O1–M bond distances are 2.137(2) and
2.250(2) Å for 1 and 3 and 1.988(2) and 2.098(2) Å for 2a and 4a,
in accordance with the presence of a negative charge at the oxygen
in the latter, which increases the strength of the M–O1 bond.
In going from complexes 1 and 3 to complexes 2a and 4a the
N1–M–N2 and N2–M–O1 angles undergo small changes (ca. 1–
3°, see Table 2); the N1–M–O1 changes from 150.28(8) and
143.18(9)° in 1 and 3, respectively, to 158.06(8) and 149.56(7)°
in 2a and 4a due to higher delocalization in the latter and to the
change of the N3 hybridization from sp3 to sp2. Similarly the N3–
C8–O1 angles goes from 120.4(2) and 120.5(3)° in 1 and 3 to
125.1(2) and 126.0(2)° in 2a and 4a due to the same effect.
Comparison between 1 and 3 and between 2a and 4a reveals
that the bond distances within the hydrazone ligand are not very
different but, as expected, the M–L [M = Cu(II), Zn(II)] distance var-
The authors are grateful to Capes and CNPq (Brasil) and to CON-
ICET (Argentina) for financial support. O.E.P. is a research fellow of
CONICET, Argentina.
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