Synthesis of an unprecedented Cui polymer with alternate Cu(μ-S)2Cu and Cu(μ-Cl)2Cu cores bridged by pyridine-2-carbaldehyde thiosemicarbazone

Article abstract of DOI:10.1002/zaac.200900363

Pyridine-2-carbaldehyde thiosemicarbazone {(C₅H ₅N)(H)C²= N-NH-C¹=S)NH₂; Hpytsc} formes an unprecedented 1D copper(I) coordination polymer, {Cu ₄Cl₄(μ₃-S,N⁴

Full text of DOI:10.1002/zaac.200900363

SHORT COMMUNICATION
DOI: 10.1002/zaac.200900363
Synthesis of an Unprecedented CuI Polymer with Alternate Cu(μ-S)2Cu and
Cu(μ-Cl)2Cu Cores Bridged by Pyridine-2-carbaldehyde Thiosemicarbazone
Tarlok S Lobana,*[a] Sonia Khanna,[a] Alfonso Castineiras,[b] and Geeta Hundal[a]
Keywords: Copper; Pyridine-2-carbaldehyde thiosemicarbazone; Polynuclear complexes; Solvent mixture; Bridging ligands
Abstract. Pyridine-2-carbaldehyde thiosemicarbazone {(C5H5N)(H)C2= units, to form alternate Cu(μ-S)2Cu and Cu(μ-Cl)2Cu cores in the poly-
N–NH–C1(=S)NH2; Hpytsc} formes an unprecedented 1D copper(I) co- mer. The Cu···Cu contact in Cu(μ-Cl)2Cu core [3.0877(6) Å] is shorter
ordination polymer, {Cu4Cl4(μ3-S,N4-Hpytsc)2 (PPh3)4}n (1) in which than in Cu(μ-S)2Cu core [3.1826(6) Å].
pyridyl nitrogen binds to Cu(μ-Cl)2Cu core and sulfur bridges two CuCl
Introduction
The interaction of copper with thiosemicarbazones is of cur-
rent interest from the points of view of the bonding, structure
and biological aspects [1–3]. Pyridine-2-carbaldehyde thio-
semicarbazone [(C5H4N)(H)C2=N3N2H–C1(=S)–N1H2] is a
well known N,N,S donor ligand, and has exhibited variable
bonding modes in its complexes with several transition metals
[1–3]. In case of copper, as a neutral ligand, modes A and B
[4, 5], and as an anionic ligand, modes B and C [6, 7] were
observed. With other metals, it has shown modes A, B, D
(rare), E and F [8–13]. In this communication, we report the
first example of a coordination polymer with a thiosemicarba-
zone ligand [1]. Here, the Hpytsc ligand shows bridging be-
haviour through pyridyl and thione donor atoms in copper(I)
coordination polymer, [Cu4Cl4(μ3-S,N4-Hpytsc)2(PPh3)4]n (1).
not be obtained because of the poor solubility of complex 1 in
Result and Discussion
common organic solvent. The molecular structure of polynu-
clear complex [Cu4Cl4(μ3-S,N4-Hpytsc)2(PPh3)4]n (1) reveals
the presence of two types of units, Cu2(μ-Cl)2 (unit A) and
Cu2(μ-S)2 (unit B), and the Hpytsc ligand is acting as a bridge
between two dimeric units through its pyridyl N4 and S donor
atoms (Scheme 1).
Reaction of copper(I) chloride with PPh3 in 1:1 molar ratio
in CH3CN (10 cm3) followed by addition of the ligand Hpytsc
(1 mol) in CHCl3 (5 cm3), yielded dark orange-coloured crys-
tals of unusual composition, [Cu2Cl2(PPh3)2(Hpytsc)]. The IR
spectroscopic data of 1 confirmed the presence of ν(N–H),
ν(C–N), ν(C=C), ν(C=N) and ν(P–C) vibrational modes. The
thioamide bands ν(C=S) at 837 and 877 cm–1 show marginal
shifts relative to the free ligand [14]. An NMR spectrum could
In unit A, the copper(I) atom is bonded to two chlorine [Cu–
Cl, 2.3817(7), 2.6752(11) Å] and one phosphorus atoms of
PPh3 [Cu–P, 2.012(7) Å] and the other coordination site is oc-
cupied by pyridine nitrogen atom of Hpytsc [Cu(1)–N(11),
2.0564(19) Å]. The sulfur atom of the same Hpytsc ligand
bridges two [CuCl(PPh3)]2 units at Cu–S distance of
2.3663(6) Å to form a second unit (B). Copper atom in unit
B is further coordinated to a terminal chlorine atom [Cu–Cl,
2.3085(7) Å], and one terminal phosphorus atom of PPh3 [Cu–
P, 2.2341(6) Å], and thereby yielding a polymeric chain (Fig-
ure 1). The Cu···Cu contacts in unit A [3.0877(6) Å], and unit
B [3.1826(6) Å] are similar to the literature reports [4]. The
bond angles of unit A, P–Cu–Cl [110.88(2), 114.66(2)°] and
Cl–Cu–Cl [99.93(2)°] are similar to the analogous halogen
* Prof. Dr. T. S Lobana
Fax: +91-183-2-258820
E-Mail: tarlokslobana@yahoo.co.in
[a] Department of Chemistry
Guru Nanak Dev University
Amritsar – 143 005, India
[b] Departmento De Quimica Inorganica
Facultad de Farmacia
Universidad de Santiago de Compostela
15782 Santiago de Compostela, Spain
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.200900363 or from the
author.
454
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2010, 636, 454–456

CuI Polymer with Alternate Cu(μ-S)2Cu and Cu(μ-Cl)2Cu Cores
Scheme 1.
bridged dimers in literature [4]. In contrast, core bond angles
of unit B, P–Cu–S [114.35(2), 106.85(2)°] and S–Cu–S
[97.67(2)°] are shorter than in analogous complex [Cu2(μ-S-
Hbtsc)2Cl2(PPh3)2] [P–Cu–S, 118.76(2), 107.15(2)°, S–Cu–S,
107.833(17)°] [4].
Figure 2. Packing diagram of complex [Cu4Cl4(μ3-S, N11-
Hpytsc)2(PPh3)4]n (1) (a) 1D chain, (b) 2D network.
Figure 3. Molecular structure of [CuBr2(η1-S-Hpytsc-N1H+)
(PPh3)]·H2O (3).
Figure 1. Repeat unit of polymer [Cu4Cl4(μ3-S,N11-Hpytsc)2(PPh3)4]n
(1) (hydrogen atoms removed for clarity).
The packing diagram of complex 1 shows the presence of
intramolecular hydrogen bonding between terminal chlorine
with amino hydrogen (Cl···HNH, 2.829 Å) in unit B yielding
a linear chain. Two linear chains are interlinked by CH···π in-
teractions involving phenyl rings of PPh3 (2.792 Å) and chlo-
rine atom (2.806 Å), resulting in formation of 2D network in
ab plane (Figure 2).
For X = Br as an anion, a polymer [Cu4Br4(μ3-S, N1-
Hpytsc)2(PPh3)4·CH3CN·H2O]n (2) similar to 1 is formed. In
addition,
a
protonated product [CuBr2(η1-S-Hpytsc-
N1H+)(PPh3)]·H2O (3) was also isolated (Figure 3). For X = I,
an iodo-bridged dimer, [Cu2(μ-I)2(η1-S-Hpytsc)2(PPh3)2] (4)
was obtained. Complex 2 showed similar bonding behaviour
as in 1 (Figure 4) and the bond parameters are similar (see
Supporting Information). The complexes are stable to air and
Figure 4. Repeat unit of polymer {Cu4Br4(μ3-S,N1-Hpytsc)2(PPh3)4}n
(2) (solvent molecules have been removed for clarity, see Supporting
moisture for several weeks. It may be pointed out here that Information).
Z. Anorg. Allg. Chem. 2010, 454–456
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
455

T. S. Lobana, S. Khanna, A. Castineiras, G. Hundal
SHORT COMMUNICATION
Bruker AXS SMART APEX CCD diffractometer with graphite-mono-
chromated Mo-Kα radiation, unique 10649 (Rint = 0.0406). The final
R1 is 0.0559 and wR2 is 0.1288.
reactions of Cu4X4 clusters (X = Cl, Br) with bidentate 1, 3-
bis(diphenylphosphanyl)propane (dppp) in presence of pyrimi-
dine-2-thione ligand (pymSH) yielded mononuclear com-
plexes, [CuX(η1-S-pymSH)(η2-P,P-dppp)] [15]. Reactions of
[Cu4X4(L4)] cubanes (L = PPh3, o-tolyl3P) with N,S-donor li-
gands such as pymSH and 1,3-thiazolidine-2-thione have also
formed mononuclear complexes [16, 17].
For the crystallographic data of complexes 3 and 4, see Supporting
Information
CCDC-728182 (1), 728183 (2), 728184 (3) and -666766 (4) 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.
Conclusions
The ligand Hpytsc in CH3CN/CHCl3 mixture has formed
novel polynuclear complexes 1 and 2 with copper(I) chloride/
bromide exhibiting unprecedented bridging by Hpytsc ligand.
The complexes are stable to air and moisture for several weeks.
It may be noted that the reactions of Hpytsc with copper(I)
halides in CH3CN has formed only mononuclear complexes of
type, [CuX(η1-S-Hpytsc)(PPh3)2] (X = Cl, Br, I) [4], and addi-
tion of chloroform to the reaction mixture did not give any
significant change in bonding and nuclearity of the complexes.
Supporting Information (see footnote on the first page of this article):
Selected bond lengths and angles for complexes 1–4. Syntheses and
crystallographic data of complexes 3 and 4.
Acknowledgement
Financial support (SK) from Council of Scientific and Industrial Re-
search, New Delhi, is gratefully acknowledged. The authors thank
Matthias Zeller of Youngstown State University, USA for partial help
in X-ray crystallography.
Experimental Section
Synthesis of 1: PPh3 (0.066 g, 0.25 mmol) was added to a solution of
copper(I) chloride (0.025 g, 0.25 mmol) in CH3CN, followed by stir-
ring for 1 h. A colourless precipitate formed to which the ligand
Hpytsc (0.045 g, 0.25 mmol) and CHCl3 (5 mL) were added. The mix-
ture was heated under reflux and a dark orange solution formed, which
on slow evaporation resulted in the formation of orange-coloured crys-
tals of 1 (Yield 52 %, M.p. 205–207 °C). C43H38Cl2Cu2N8P2S2·
0.25CHCl3: calcd. C 55.69, H 4.10, N 6.00; found C 55.46, H 3.97, N
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Received: July 30, 2009
Published Online: December 10, 2009
456
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© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2010, 454–456