The influence of substituents (R) at N1 atom of thiophene-2-carbaldehyde thiosemicarbazones {(C4H3S)HC2{double bond, long}N3-N(H)-C1({double bond, long}S)N1HR} on bonding, nuclea

Article abstract of DOI:10.1016/j.ica.2009.03.043

The nuclearity, bonding and H-bonded networks of copper(I) halide complexes with thiophene-2-carbaldehyde thiosemicarbazones {(C₄H₃S)HC²{double bond, long}N³-N(H)-C¹({double bond, long}S)N¹

Full text of DOI:10.1016/j.ica.2009.03.043

Inorganica Chimica Acta 362 (2009) 3547–3554
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Inorganica Chimica Acta
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The influence of substituents (R) at N1 atom of thiophene-2-carbaldehyde
thiosemicarbazones {(C4H3S)HC2@N3–N(H)–C1(@S)N1HR} on bonding,
nuclearity and H-bonded networks of copper(I) complexes
a
b
a
c
Tarlok Singh Lobana a, , Rekha Sharma , Alfonso Castineiras , Geeta Hundal , Ray Jay Butcher
*
a Department of Chemistry, Guru Nanak Dev University, Amritsar 143 005, India
b Departamento De Quimica Inorganica, Facultad de Farmacia, Universidad de Santiago, 15782 Santiago, Spain
c Department of Chemistry, Howard University, Washington, DC 20059, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
The nuclearity, bonding and H-bonded networks of copper(I) halide complexes with thiophene-2-carbal-
dehyde thiosemicarbazones {(C4H3S)HC2@N3–N(H)–C1(@S)N1HR} are influenced by R substituents at N1
atom. Thiophene-2-carbaldehyde-N1-methyl thiosemicarbazone (HttscMe) or thiophene-2-carbalde-
hyde-N1-ethyl thiosemicarbazone (HttscEt) have yielded halogen-bridged dinuclear complexes,
Received 20 January 2009
Received in revised form 26 March 2009
Accepted 27 March 2009
Available online 5 April 2009
[Cu2(
phene-2-carbaldehyde-N1-phenyl thiosemicarbazone (HttscPh) has yielded mononuclear complexes,
[CuX( sulfur bridged dinuclear complex, [Cu2( -S-
1-S-HttscPh)2] (X, I, 7a; Br 8; Cl, 9) and
HttscPh)2(
to S-bridged dimers [Cu2(
l-X)2(g
1-S-Htsc)2(Ph3P)2] (Htsc, X: HttscMe, I, 1; Br, 2; Cl, 3; HttscEt, I, 4; Br, 5; Cl, 6), while thio-
Keywords:
Thiosemicarbazone
Copper(I) iodide
Thiophene-2-carbaldehyde
thiosemicarbazones
Dimer
g
a
l
g
1-S-HttscPh)2I2] 7b co-existing with 7a in the same unit cell. These results are in contrast
l
-S-Httsc)2(
g
1-Br)2(Ph3P)2] ꢀ 2H2O and [Cu2(
l
-S-Httsc)2(
g
1-Cl)2(Ph3P)2] ꢀ
2CH3CN obtained for R = H and X = Cl, Br (Httsc = thiophene-2-carbaldehyde thiosemicarbazone) as
reported earlier. The intermolecular CHPhꢀ ꢀ ꢀ
p interaction in 1–3 (2.797 Å, 1; 3.264 Å, 2; 3.257 Å, 3) have
formed linear polymers, whereas the CHPhꢀ ꢀ ꢀX and N3ꢀ ꢀ ꢀHCH interactions in 4–6 (2.791, 2.69 Å, 5; 2.776,
Three coordinated monomer
2.745 Å, 6, respectively) have led to the formation of H-bonded 2D polymer. The PhN1Hꢀ ꢀ ꢀ
p, interactions
(2.547 Å, 8, 2.599 Å, 9) have formed H-bonded dimers only. The Cuꢀ ꢀ ꢀCu separations are 3.221–3.404 Å
(1–6).
Ó 2009 Published by Elsevier B.V.
1. Introduction
Httsc)2(Ph3P)2] with copper(I) iodide and S-bridged dimers
[Cu2(
l
-S-Httsc)2(
g
1-Br)2(Ph3P)2] ꢀ 2H2O and [Cu2(
l -
-S-Httsc)2(g1
Thiosemicarbazones possessing several donor atoms are versa-
tile ligands, and have formed mononuclear, dinuclear and polynu-
clear complexes with transition metals [1–6]. These ligands have
also displayed ion-sensing ability [7–10], metal extraction proper-
ties [11,12] and pharmacological properties [13–17]. Thiosemicar-
bazones have displayed interesting H-bonded 1D and 2D networks
encapsulated organic molecules in the voids [6]. The coordination
compounds of several metals with thiophene-2-carbaldehyde thio-
semicarbazone (R = H, Httsc, I) exist as mononuclear and dinuclear
complexes [6,18–24,32,33]. Chart 1 shows various bonding modes
Cl)2(Ph3P)2] ꢀ 2CH3CN with copper(I) bromide or chloride, respec-
tively [22,23]. Dinuclear copper complexes are very important
due to their role in many copper proteins [25] electrolytic reduc-
tion of carbon dioxide [26] and other catalytic activities [27–29].
Further close Cuꢀ ꢀ ꢀCu contacts in dimers are anticipated to pro-
mote photoluminescent properties [30,31]. In this paper, a series
of substituted thiophene-2-carbaldehyde thiosemicarbazones as
shown in Chart 2 have been used for their interaction with cop-
per(I) halides and the results are presented herewith. The influence
of substituents (R) at N1 on bonding nuclearity and H-bonded net-
works is investigated.
of Httsc (neutral or anionic), namely: (i)
g l-S
1-S (mode A) [22], (ii)
(mode B) [23], (iii) N3, S-chelation (mode C) [20], (iv) N2, S-chela-
tion (mode D) [19] and (v) N3, S-chelation-cum-S-bridging (mode
E) [24] in these complexes.
2. Experimental
Heterocyclic thiosemicarbazones in literature have generally
formed dinuclear complexes, e.g. thiophene-2-carbaldehyde thio-
2.1. Chemical reagents
semicarbazone formed an iodo-bridged dimer [Cu2(l-I)2(g
1-S-
Copper(I) halides were prepared by the reduction of Cu-
SO4 ꢀ 5H2O using SO2 in the presence of NaX (X = Cl, Br, I) in dis-
tilled water [34]. N1-methyl thiosemicarbazide, N1-ethyl
* Corresponding author. Fax: +91 183 2258820.
E-mail address: tarlokslobana@yahoo.co.in (T.S. Lobana).
0020-1693/$ - see front matter Ó 2009 Published by Elsevier B.V.
doi:10.1016/j.ica.2009.03.043

3548
T.S. Lobana et al. / Inorganica Chimica Acta 362 (2009) 3547–3554
2.3.2. [Cu2(l-Br)2(g
1-S-HttscMe)2(Ph3P)2] 2
R
R
Yield, 0.0716 g, 68%, m.p. 220–222 °C. Anal. Calc. for
N2
S
S
N3
S
N3
C50H48Cu2Br2N6S4P2(%): C, 49.62; H, 3.97; N, 6.94. Found: C,
S
49.69; H, 4.18; N, 6.05%. IR data (KBr, cmꢁ1): 3371(w)
m
(NꢁH);
(CꢁH)Me
(P–CPh) 1099(s); (C–N)
M
M
M
M
M
M
M
S
3144(m)
(C@N) +
1029(s);
m
(–NH–); 2985(m)
m
(CꢁH)Ph
;
2785(w)
m
;
( A )
( B )
( C )
( E )
( D )
m
m
m
(C@C) 1674(m), 1591(m);
m
m
(C@S) 850(s). 1H NMR (CDCl3, d ppm): 12.16s (–N2H),
Chart 1.
8.52s (C2H), 7.31–7.52 m (C4,6H + PPh3 + N1H2), 7.05dd (C5H),
3.19d (–CH3). 13C NMR data (d (ppm); J (Hz), CDCl3): 173.9 (C1),
140.7 (C2), 137.9 (C3), 131.8 (C6), 127.9 (C5), 133.9 (o-C, JP–C
,
S
1
2
NH
15.01, PhP), 128.7 (m-C, JP–C, 9.85, PhP), 130.0 (p-C, PhP), 30.6
(CH3). 31P NMR (CDCl3, d ppm): ꢁ2.71 ppm,
D
d (d complex ꢁ d li-
C
2
C
3
N
1
S
NHR
gand) 1.99 ppm.
I
H
2.3.3. [Cu2(l-Cl)2(g
1-S-HttscMe)2(Ph3P)2] 3
R
Yield, 0.102 g, 72%, m.p. 222–225 °C. Anal. Calc. for
C50H48Cu2Cl2N6S4P2(%): C, 53.19; H, 4.25; N, 7.44. Found: C,
HttscMe = thiophene-2-carbaldehyde-N1-methyl thiosemicarbazone
HttscEt = thiophene-2-carbaldehyde-N1-ethyl thiosemicarbazone
HttscPh = thiophene-2-carbaldehyde-N1-phenyl thiosemicarbazone
Me
Et
53.51; H, 3.82; N, 6.56%. IR data (KBr, cmꢁ1): 3375(s)
m
(NꢁH);
(CꢁH)Me
(P–CPh) 1091(s); (C–N)
3109(m)
(C@N) +
1027(s);
m
(–NH–); 2947(m)
m
(CꢁH)Ph
;
2788(w)
m
;
Ph
m
m
m
(C@C) 1645(m), 1581(m);
m
m
(C@S) 850(s). 1H NMR (CDCl3, d ppm): 12.54s (–N2H),
Chart 2.
8.46s (C2H), 7.30–7.53 m (C4,6H + PPh3 + N1H2), 7.06dd (C5H),
3.20d (–CH3). 13C NMR data (d (ppm); J (Hz), CDCl3): 174.4 (C1),
141.1 (C2), 138.0 (C3), 131.7 (C6), 127.9 (C5), 133.9 (o-C, JP–C
,
thiosemicarbazide, N1-phenyl thiosemicarbazide, thiophene-2-
carbaldehyde and Ph3P were procured from Aldrich Sigma Ltd. Thi-
osemicarbazone ligands were prepared by condensation of thio-
phene-2-carbaldehyde with respective thiosemicarbazides.
15.09, PhP), 128.7 (m-C, JP–C, 9.81, PhP), 130.0 (p-C, PhP), 30.6
(CH3). 31P NMR (CDCl3, d ppm): ꢁ1.58 ppm, ꢁ30.3
plex ꢁ d ligand) 3.12, 34.96 ppm.
Dd (d com-
2.3.4. [Cu2(l-I)2(g
1-S-HttscEt)2(Ph3P)2] 4
2.2. Measurements
Yield, 0.0620 g, 71%, m.p. 230–235 °C. Anal. Calc. for
C52H52Cu2I2N6S4P2(%): C, 46.88; H, 3.91; N, 6.31. Found: C, 46.91;
Elemental analysis for C, H and N were carried out using a ther-
moelectron FLASHEA1112 analyser. The melting points were deter-
mined with a Gallenkamp electrically heated apparatus. The IR
spectra of the ligands and the complexes were recorded in the
range, 4000–200 cmꢁ1 (using KBr pellets) on the FTIR-SHIMADZU
8400 Fourier Transform Spectrophotometer and on Pye–Unicam
SP-3-300 spectrophotometer. 1H NMR spectra were recorded on
a JEOL AL300 FT spectrometer at 300 MHz in CDCl3 with TMS as
the internal reference. 13C NMR spectra of complexes were re-
corded at a frequency of 75.45 MHz using CDCl3 as solvent, and
TMS as internal reference. 31P NMR spectra were recorded at
121.5 MHz with o-phosphoric acid as the external reference taken
as zero position.
H, 4.10; N, 6.71%. IR data (KBr, cmꢁ1): 3371(s)
m
(NꢁH); 3149(m)
ðC—HÞ—CH 2856(w)
(P–CPh) 1099(s);
m
m
m
(–NH–); 3047(m)
(CꢁH)Me (C@N) +
(C–N) 1041(s);
m
(CꢁH)Ph
;
2933(m)
m
;
—
2
;
m
m
(C@C) 1594(m), 1556(s); m
m
(C@S) 850(s). 1H NMR (CDCl3, d ppm): 11.51s (–
N2H), 8.54s (C2H), 7.30–7.54 m (C4,6H + PPh3 + N1H2), 7.06dd
(C5H), 3.64 m (–CH3), 1.28t (–CH2–).13C NMR data (d (ppm); J
(Hz), CDCl3): 172.8 (C1), 139.5 (C2), 137.9 (C3), 131.6 (C6), 128.7
(C4), 127.8 (C5), 134.0 (o-C, JP–C, 15.08, PhP), 128.6 (m-C, JP–C
,
9.35, PhP), 129.8 (p-C, PhP), 38.8 (–CH2–), 14.5 (–CH3). 31P NMR
(CDCl3, d ppm): ꢁ5.07 ppm, d (d complex ꢁ d ligand) ꢁ0.37 ppm.
D
2.3.5. [Cu2( -Br)2(
1-S-HttscEt)2(Ph3P)2] 5
l
g
Yield, 0.0808 g, 75%, m.p. 210–212 °C. Anal. Calc. for
C52H52Cu2Br2N6S4P2(%): C, 50.44; H, 4.20; N, 6.79. Found: C,
2.3. Synthesis of compounds
50.37; H, 4.77; N, 6.83%. IR data (KBr, cmꢁ1): 3371(s)
m
(NꢁH);
3134(m)
2935(w)
m
m
(–NH–); 3045(m)
(CꢁH)Me (C@N) +
(P–CPh) 1099(s);
12.11s
(–N2H),
m
m
(CꢁH)Ph
(C@C) 1620(m), 1594(m), 1556(s);
(C@S) 850(s). 1H NMR (CDCl3,
8.54s 7.37–7.50 m
(C2H),
;
2983(m)
m
ðC—HÞ—CH
;
—
2
2.3.1. [Cu2(l-I)2(g
1-S-HttscMe)2(Ph3P)2] 1
;
m
To a solution of copper(I) iodide (0.025 g, 0.131 mmol) in 15 ml
acetonitrile, the ligand HttscMe (0.026 g, 0.131 mmol) was added,
and contents stirred for 3–4 h. It formed yellow precipitates and
addition of Ph3P (0.034 g, 0.131 mmol) followed by stirring for 5–
10 min formed a yellow colored solution, which on slow evapora-
tion at room temperature yielded yellow crystals. Yield, 0.0616 g,
72%, m.p. 200–202 °C. Anal. Calc. for C50H48Cu2I2N6S4P2(%): C,
46.05; H, 3.68; N, 6.45. Found: C, 46.58; H, 3.76; N, 6.47%. IR data
m(C–N) 1042(s);
m
m
d
ppm):
(C4,6H + PPh3 + N1H2), 7.05dd (C5H), 3.67 m (–CH3), 1.28t (–CH2–).
31P NMR (CDCl3, d ppm): ꢁ2.95 ppm,
D
d (d complex ꢁ d ligand)
1.75 ppm.
2.3.6. [Cu2(l-Cl)2(g
1-S-HttscEt)2(Ph3P)2] 6
Yield, 0.100 g, 69%, m.p. 210–212 °C. Anal. Calc. for
(KBr, cmꢁ1): 3369(s)
(CꢁH)Ph 2767(w)
1586(m), 1560(m);
m
m
(NꢁH); 3145(m)
(CꢁH)Me (C@N) +
(P–CPh) 1092(s); (C–N) 1027(s);
m
m
(–NH–); 2991(m)
(C@C) 1668(m),
(C@S)
C52H52Cu2Cl2N6S4P2(%): C, 54.35; H, 4.53; N, 7.32. Found: C, 54.20;
m
;
;
m
H, 5.12; N, 7.33%. IR data (KBr, cmꢁ1): 3362(s), 3292(s)
m
(NꢁH);
m
m
m
3141(m)
2931(w)
1094(s);
m
m
m
(–NH–); 3045(m)
(CꢁH)Me (C@N) +
(C–N) 1047(s);
m
(CꢁH)Ph
;
2975(m)
m
ðC—HÞ—CH
;
)
—
2
852(s). 1H NMR (CDCl3, d ppm): 11.55s (–N2H), 8.54s (C2H), 7.32–
7.56 m (C4,6H + PPh3 + N1H), 7.06dd (C5H), 3.15d (–CH3). 13C NMR
data (d (ppm); J (Hz), CDCl3): 176.8 (C1), 138.2 (C2), 137.2 (C3),
130.7 (C6), 128.3 (C4), 127.7 (C5), 134.0 (o-C, JP–C, 14.33, PhP),
128.6 (m-C, JP–C, 9.05, PhP), 129.9 (p-C, PhP), 30.8 (CH3). 31P NMR
;
m
m
(C@C) 1595(m), 1561(s); m(P–CPh
m
(C@S) 850(s). 1H NMR (CDCl3, d ppm):
12.48s (–N2H), 8.47s (C2H), 7.30–7.52 m (C4,6H + PPh3 + N1H2),
7.05dd (C5H), 3.67 m (–CH3), 1.30t (–CH2–). 31P NMR (CDCl3, d
ppm): ꢁ1.77 ppm,
D
d (d complex ꢁ d ligand) 2.93 ppm.
(CDCl3, d ppm): ꢁ30.5 ppm,
D
d (d complex ꢁ d ligand) 35.11 ppm.
Though complexes 7–9 were prepared by the method similar to
that for 1, direct reactions of copper(I) halides with two mole of
Complexes 2–9 are prepared by similar method

T.S. Lobana et al. / Inorganica Chimica Acta 362 (2009) 3547–3554
3549
thiosemicarbazome ligand (HttscPh) in 1:2 molar ratio in acetoni-
trile yielded identical products.
anisotropic atomic displacement parameters were refined for all
non-hydrogen atoms. Hydrogen atoms bonded to carbon were
placed geometrically and the N–H hydrogen atoms were initially
positioned at sites determined from difference maps, but the posi-
tional parameters of all H atoms were included as fixed contribu-
tions riding on attached atoms with isotropic thermal parameters
1.2 times those of their carrier atoms. Criteria of a satisfactory
complete analysis were the ratios of rms shift to standard deviation
less than 0.001 and no significant features in final difference maps.
A prismatic crystal of complex 6 was mounted on an automatic
Enraf-Nonius CAD-4 diffractometer equipped with a graphite
2.3.7. [CuI(g
1-S-HttscPh)2] 7
Two types of crystals (i) Brown crystals: Yield, 0.05 g, 54%, m.p.
190–195 °C. Anal. Calc. for C24H22CuIN6S4(%): C, 40.42; H, 3.09; N,
11.79. Found: C, 40.25; H, 3.28; N, 11.10%. IR data (KBr, cmꢁ1):
3304(s)
m
(NꢁH); 3118(m)
m
(–NH–); 3006(m)
m
(CꢁH)Ph; 2937(m);
m
m
(C@N) +
m
(C@C) 1620(m), 1596(m), 1560(s); m
(C–N) 1045(s);
(C@S) 826(s). 1H NMR (CDCl3, d ppm): 11.44s (–N2H), 8.87s
(C2H), 8.59s (C6H), 7.29d (C4H), 7.36–7.51 m (Ph), 7.1dd (C5H)
and (ii) Colorless crystals: 0.02 g, 36% yield, m.p. 210–215 °C. Anal.
Calc. for C18H15PCuI(%): C, 47.73; H, 3.31; Found: C, 48.02; H, 3.42%.
monochromator, and Mo Ka radiation (k = 0.71073 Å). The unit cell
dimensions and intensity data were measured at 296 K. The struc-
tures were solved by the direct methods and refined by full-matrix
least-square based on F2 with anisotropic thermal parameters for
non-hydrogen atoms using XCAD-49 (data reduction), and SHELXL
(absorption correction, structure solution refinement and molecu-
lar graphics) [42].
2.3.8. [CuBr(g
1-S-HttscPh)2] 8
Two types of crystals (i) Brown crystals: Yield, 0.0649 g, 56%,
m.p. 212–215 °C. Anal. Calc. for C24H22CuBrN6S4(%): C, 43.27; H,
3.31; N, 12.62. Found: C, 43.09; H, 3.60; N, 12.91%. IR data (KBr,
cmꢁ1): 3321(s)
2983(m); (C@N) +
1043(s);
m
(NꢁH); 3132(m)
m
(–NH–); 3028(m)
m
(CꢁH)Ph
;
m
m
(C@C) 1620(m), 1591(m), 1544(s); m
(C–N)
(C@S) 828(s). 1H NMR (CDCl3, d ppm): 11.80s (–N2H),
3. Results and discussion
m
8.87s (C2H), 8.55s (C6H), 7.29d (C4H), 7.36–7.51 m (Ph), 7.1dd
(C5H) and (ii) Colorless crystal: Yield 0.03 g, 40%, m.p. 190–195 °C.
3.1. Synthetic and general properties
2.3.9. [CuCl(g
1-S-HttscPh)2] 9
Thiophene-2-carbaldehyde thiosemicarbazones were reacted
with copper(I) halides in the presence of triphenylphosphine and
have yielded compounds of variable nuclearities. Scheme 1 depicts
compounds formed with thiophene-2-carbaldehyde thiosemicar-
bazones (HttscMe, HttscEt, HttscPh). Direct reactions of copper(I)
halides with thiosemicarbazones generally yield insoluble prod-
ucts, which could not be crystallized and triphenylphosphine was
necessary for obtaining crystalline products.
Two types of crystals (i) Brown crystals: Yield, 0.0753 g, 48%,
m.p. 212–215 °C. Anal. Calc. for C24H22CuClN6S4(%): C, 46.38; H,
3.45; N, 13.53. Found: C, 46.21; H, 3.87; N, 13.00%. IR data (KBr,
cmꢁ1): 3326(s)
2978(m); (C@N) +
1040(s);
m
(NꢁH); 3138(m)
m
(–NH–); 3041(m)
m
(CꢁH)Ph
;
m
m
(C@C) 1620(m), 1585(m), 1541(s); m
(C–N)
m
(C@S) 830(s). 1H NMR (CDCl3, d ppm): 11.99s (–N2H),
8.89s (C2H), 8.47s (C6H), 7.29d (C4H), 7.37–7.52 m (Ph), 7.1dd
(C5H) and (ii) Colorless crystals: Yield, 0.04 g, 48%, m.p. 185–189 °C.
For X = Cl, Br, I, thiophene-2-carbaldehyde thiosemicarbazones
(HttscMe, HttscEt) have formed halogen-bridged dimers, [Cu2(
l-
X)2(g
1-S-HL)2(Ph3P)2] (HL = HttscMe, X = I, 1; Br, 2; Cl, 3; HttscEt,
2.4. X-ray crystallography
X = I, 4; Br, 5; Cl, 6) (Scheme 1). A theoretical study on copper(I) ha-
lides interaction with model thiosemicarbazone, H2C@N–NH–
C(@S)–NH2 and PH3 has shown only halogen bridging as favoured
mode of bonding in dimeric copper(I) halide complexes [22]. The
theoretical; studies with two water molecules H-bonded to halo-
gens showed stabilization of sulfur-bridging for X = Cl, Br. This type
The data for 2–4, and 9 were collected at 293 K, on a Siemens P4
diffractometer using XSCANS [35]. The hꢁ2h technique was used to
measure the intensities, up to a maximum of 2h = 50°, with graph-
ite monochromatised Mo K
a radiator (k = 0.71073 Å). The data
were corrected for Lorentz and polarization factors. An empirical
psi absorption correction was applied. The structures were solved
by direct methods and refined by full-matrix least-squares meth-
ods based on F2. Hydrogen atoms were fixed geometrically and
were not refined. Scattering factors from the International Tables
for X-ray crystallography were used [36]. Data reduction, structure
solution, refinement and molecular graphics were performed using
of behavior has been established in [Cu2(
g
1-Br)2(
-S-Httsc)2(Ph3P)2] ꢀ 2CH3CN
l-S-Httsc)2
(Ph3P)2] ꢀ 2H2O and [Cu2(
g
1-Cl)2(
l
were obtained [22]. The chlorine–water and bromine–water H-
bonding being stronger than iodine–water, appear to have made
sulfur bridging possible in above complexes, while for X = I, halo-
gen bridging occurs ([Cu2(l-I)2(g
1-S-Httsc)2(Ph3P)2]) as predicted.
Interestingly For X = Cl, Br, the introduction of methyl and ethyl
substituents (R) at N1 has led to the change in bridge bonding from
sulfur-bridging (for Httsc) to halogen-bridging (for HttscMe and
HttscEt ligands) in 2, 3, 5 and 6.
SHELXTL-PC [37] and WINGX [38].
The data for 7 and 8 were measured on Bruker AXS SMART APEX
CCD diffractometer. Data were reduced and corrected for absorp-
tion using SMART and SAINT [39]. The structures were solved by direct
methods and refined by full-matrix least-squares based on F2 with
anisotropic thermal parameters for non-hydrogen atoms using
SHELXTL (structure solution, refinement and some molecular graph-
ics). All non-hydrogen atoms atoms were refined anisotropically.
All hydrogen atoms were placed in calculated positions and were
refined with an isotropic displacement parameter 1.5 (methyl) or
1.2 times (all others) that of the adjacent carbon or oxygen atom.
Crystals of 1 and 5 were mounted on a Bruker SMART CCD 1000
The introduction of phenyl substituent at N1(R), prevents coor-
dination by PPh3 causing copper(I) halides to bind to rather two
thio-ligands resulting in three coordinated complexes [CuX(g
1-S-
HttscPh)2] (X = I, 7; Br, 8; Cl, 9). It is possible that Ph3P and thio-li-
gand with phenyl at N1 nitrogen pose greater steric limiting coor-
dination of copper(I) halides to thio-ligands only. However, the
iodide complex exists as a three coordinated species (7a) along
with its sulfur-bridged dimeric form, [Cu2I2(l-S-HttscPh)2(g
1-S-
HttscPh)2] 7b, in the same unit cell.
diffractometer equipped with graphite monochromated Mo K
a
The presence of both,
m
(N–H) bands in the range 3304–
radiation (k = 0.71073 Å). The unit cell dimensions and intensity
data were measured at 100 K. The data were processed with SAINT
[40] and corrected for absorption using SADABS (transmissions fac-
tors: 0.724–0.515) [38]. The structure was solved by direct meth-
ods using the program SHELXS-97 and refined by full-matrix least-
squares techniques against F2 using SHELXL-97 [41]. Positional and
3375 cmꢁ1 (due to –N1HR) and
m
(N–H) bands in the range, 3109–
3161 cmꢁ1, in complexes 1–9 support the coordination of neutral
ligand. The (NꢁH) band of –N1HR group showed high-energy shift
in complexes vis-à-vis that in lies free ligands (see Supplementary
material). The most characteristic thioamide band due to m(C@S)

3550
T.S. Lobana et al. / Inorganica Chimica Acta 362 (2009) 3547–3554
R
S
S
PPh3
S
X
+
C
Ph3P
NH
R
+
Cu
CuX
Cu
NHR
C
N
S
S
X
Ph3P
R
H
R = Me, X = I, 1; Br, 2: Cl, 3
R = Et, X = I, 4; Br, 5: Cl, 6
X
Cu
S
R
S
X = Cl, Br
R
S
R
X = Br, 8; Cl, 9
S
C
R
+
PPh3
NHPh
NH
R
I
+
I
CuX
S
S
S
C
N
S
Cu
Cu
+
H
Cu
I
S
S
I
S
R
R
R
R
7b
7a
Scheme 1.
lies in the range 826–852 cmꢁ1 in complexes 1–9 undergoes low
energy shifts vis-à-vis the free ligands (856–860 cmꢁ1). This indi-
cates the coordination of sulfur to the copper center. The –N1HR
groups (R = methyl, ethyl, phenyl) in complexes appeared in the
3.2.2. Three coordinated monomers
The ligand, HttscPh (R = Ph) has not formed dinuclear com-
plexes similar to 1–6, rather three coordinated complexes, namely,
[CuX(g
1-S-HttscPh)2] (X = I, 7; Br, 8 (Fig. 4); Cl, 9) with no PPh3 li-
range, 2935–2767 cmꢁ1. The
m
(PꢁCPh) bands in complexes 1–6 ap-
gand bonded, were obtained. Each copper is bonded to two sulfur
atoms, and one halogen atom adopting distorted trigonal planar
geometry {angles, 112.63ꢁ122.45°}. However, the iodide complex
peared in the range, 1091ꢁ1099 cmꢁ1, and supported the presence
of coordinated triphenylphosphine in all these complexes.
has both three coordinated [CuI(
[Cu2( -S-HttscPh)2(g
1-S-HttscPh)2I2] 7b, moieties in the same unit
g
1-S-HttscPh)2] 7a, and its dimer
3.2. Crystal structure
l
cell (Fig. 5). As expected, the CuꢁS/CuꢁX bond distances are short-
er than those in dinuclear complexes discussed above (Table 3).
The three coordinated trigonal planar complexes in coinage metal
thiosemicarbazone chemistry are rare [44,45].
Complexes 1–6 crystallized in triclinic system with space group
P1, whereas complexes 7–9 crystallized in monoclinic system with
space group P2(1)/c. The unit cell of complex 7 contains both three
coordinated (7a), and its dimeric unit (7b) (Table 1).
ꢀ
3.3. Packing networks
3.2.1. Dinuclear complexes
X-ray crystallography has shown that the thio-ligands, namely,
In complexes 1–9, there is intra-molecular imino hydrogen-hal-
ogen hydrogen bonding (N2Hꢀ ꢀ ꢀX) (Chart 3). The substituted amino
group (HN1R, R = Me, Et) is engaged in strong H-bonding with azo-
methine (N3) nitrogen (N3ꢀ ꢀ ꢀHN1R) in 1–9. Dinuclear complexes 1–
HttscMe and HttscEt coordinate to copper(I) centers in
g
1-S mode
in halogen-bridged dimers [Cu2( -X)2(
l
g
1-S-HL)2(Ph3P)2] 1–6. In
these dimers, two bridging halogen, one P and one S atoms formed
tetra-coordination around each copper atom. The central cores
3 are interconnected via –C–Hꢀ ꢀ ꢀ
p interactions involving phenyl
Cu(l-X)2Cu form parallelograms and Ph3P/Htsc ligands occupy
rings of Ph3P leading to the formation of 1D networks (Fig. 6).
The inter-molecular H-bonding is different in complexes 4–6. Here
azomethine nitrogen is engaged in interaction with –CH2 group of
ethyl substituent at N1 (N3ꢀ ꢀ ꢀHCH, Et), resulting in a linear chain
along a-axis. Two such linear chains are interconnected via phe-
nyl–halogen interactions (–C–Hꢀ ꢀ ꢀX) yielding 2D networks (Fig. 7).
Three coordinated monomers 8 and 9 are interconnected via –
trans positions across these cores. The representative structures
of these halogen-bridged dimers are shown in Figs. 1–3. It is noted
that the substitution at N1 shortens the CuꢁS bond {Httsc,
2.3503(9) [21], HttscMe, 2.331ꢁ2.316, HttscEt, 2.306ꢁ2.298 Å}
(Table 2). The Ph3P ligands are terminally bonded and with a given
substituent, the Cu–P bond distances decreases with the increase
in electronegativity of the halogen atoms {HttscMe, 2.257(1),
2.238(2), 2.231(3); HttscEt, 2.260(4), 2.231(5), 2.227(6) Å}. The
substituents also influence copperꢁhalogen distance marginally
as shown in Table 2. The Cuꢀ ꢀ ꢀCu contacts lie in the range,
3.22ꢁ3.40 Å, which are greater than the sum of van der Waal’s ra-
N1HPh groups involving intermolecular N1Hꢀ ꢀ ꢀ
p(Ph) interactions
forming dimers (Fig. 8). There is no intermolecular interaction in
7a and 7b.
3.4. Solution phase studies
dius of copper atoms, 2.80 Å [43]. In the Cu(l-X)2Cu core, the an-
gles at copper and bridging halogen atoms vary in the
complementary fashion. For copper(I) iodide complexes with
Httsc, HttscMe and HttscEt, the angles at iodide increase with
the increase in bulk of the substituent at N1: Httsc, 72.65°,
HttscMe, 72.934°, HttscEt, 76.97°. The angles at bromine (2, 5) or
chlorine (3, 6) are nearly unaffected with the change of the substit-
uents at N1. The angles around each copper atom revealed a dis-
torted tetrahedral geometry (72.93ꢁ118.14°).
In 1H NMR spectra, the most characteristic N2H signal in the free
ligands (HttscMe, d 9.15 ppm; HttscEt, d 10.16 ppm; HttscPh,
11.33 ppm) showed downfield shifts in complexes 1–9, which indi-
cate the coordination of ligands to a metal center. Appearence of
N2H signal ensures that no deprotonation occurred during com-
plexation. Further the C2H signals of free ligands (HttscMe, d
7.93 ppm; HttscEt, d 8.15 ppm; HttscPh, d 9.16 ppm) undergo
downfield shifts in complexes 1–6 {d 8.46–8.89 ppm} and upfield

Table 1
Crystallographic data for complexes 1ꢁ9.
Compound 1
Compound 2
Compound 3
Compound 4
Compound 5
Compound 6
Compound 7
Compound 8
Compound 9
Formula
C50H48Cu2I2N6P2S4 C50H48Br2Cu2N6P2S4 C50H48Cl2Cu2N6P2S4 C52H52Cu2I2N6P2S4 C52H52Br2Cu2N6P2S4 C52H52Cl2Cu2N6P2S4 C96H88Cu4I4N24S16 C24H22BrCuN6S4 C24H22ClCuN6S4
Molecular weight (amu)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
1304.00
triclinic
P1 (no. 2)
1210.02
triclinic
P1
1121.10
triclinic
P1
1332.06
triclinic
P1
1238.08
triclinic
P1 (no. 2)
1149.16
triclinic
P1
2852.83
monoclinic
P2(1)/c
25.6035(10)
12.2375(5)
18.4646(7)
90.00
102.5190(10)
90.00
5647.8(4)
2
666.17
monoclinic
P2(1)/c
12.0011(6)
11.7383(5)
19.7185(9)
90.00
106.8350(10)
90.00
2658.7(2)
4
621.71
monoclinic
P2(1)/c
12.193(5)
11.722(5)
19.676(5)
90.000
105.051(5)
90.000
2715.7(17)
4
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
10.7328(2)
10.8736(2)
11.8583(2)
107.1810(10)
103.3190(10)
94.1030(10)
1272.01(4)
1
11.1860(10)
11.302(2)
12.0360(10)
91.580(10)
107.050(10)
113.460(10)
1316.3(3)
1
11.0530(10)
11.1610(10)
12.1320(10)
107.540(10)
91.470(10)
113.100(10)
1294.8(2)
1
11.242(5)
11.911(5)
11.932(5)
92.395(5)
106.676(5)
112.062(5)
1398.2(10)
2
10.5727(3)
11.2893(3)
13.0352(3)
114.7500(10)
93.0050(10)
106.5950(10)
1327.39(6)
1
10.8063(13)
11.3069(9)
12.7986(19)
111.902(10)
92.163(11)
109.364(9)
1345.4(3)
1
a
(°)
b (°)
c
(°)
V (Å3)
Z
T (K)
100(2)
1.702
2.318
295(2)
1.526
2.585
295(2)
1.438
1.188
293(2)
1.582
2.111
100(2)
1.549
2.566
296(2)
1.418
1.146
298(2)
1.677
2.188
100(2)
1.664
2.665
295(2)
1.521
1.236
Calculated density (g/cmꢁ3
)
l
(mmꢁ1
)
Number of observatory reflections 7822
4898
298
4.96
12.50
4715
298
4.12
10.56
5187
307
0.0321
0.0797
5455
307
0.0308
0.0567
8559
308
4.58
8.39
14 031
665
4.07
6462
341
4.04
9.39
5057
325
7.13
16.00
Number of parameters
298
1.72
4.00
R (%)
wR (%)
9.75

3552
T.S. Lobana et al. / Inorganica Chimica Acta 362 (2009) 3547–3554
Table 2
Important bond lengths (Å) and bond angles (°) of halogen-bridged dimers (1–6).
Complex (ligand), X
Cu–S
Cu–X
CuꢁP
2.2570(4)
Cu–X–CU
72.934(6)
XꢁCuꢁX
107.06(2)
Cuꢀ ꢀ ꢀCu
3.2213
1 (I)a
2.3306(4)
2.6917(2)
2.7278(2)
2 (Br)a
3 (Cl)a
4 (I)b
2.3129(14)
2.3163(13)
2.3214(14)
2.2977(7)
2.3062(8)
2.3505(9)
2.5506(7)
2.5675(8)
2.2381(12)
2.2312(11)
2.2605(12)
2.2308(7)
2.2273(9)
2.2613(9)
83.39(2)
96.61(2)
3.404
2.4185(11)
2.4492(11)
85.84(4)
94.16(2)
3.315
2.7268(10)
2.7002(12)
76.971(18)
83.635(12)
85.19(3)
103.029(18)
96.365(12)
94.81(3)
3.377
5 (Br)b
6 (Cl)b
(I)c
2.4981(3)
2.5544(4)
3.3690
3.279
2.3798(8)
2.4640(8)
2.6466(4)
2.8171(5)
75.586(14)
104.414(14)
3.351 [21]
a
HttscMe.
HttscEt.
Httsc.
b
c
Table 3
Important bond lengths (Å) and bond angles (°) of three coordinated monomers.
Ligand
complex
no. (X)
CuꢁX
CuꢁP CuꢁS
S–CuS
X–CuS
7ª,d
8d
2.5876(5) (I)
2.4207(4) (Br)
2.295(3) (Cl)
–
–
–
2.2526(9); 2.2613(9) 112.63(4)
2.2201(8); 2.2387(7) 116.13(3)
123.53(3)
122.45(2)
9d
2.214(3); 2.234(3)
116.21(10) 121.73(9)
d
HttscPh.
3
N
X
H
3
N
H
2
N
1
2
R2
N
N
Cu
S
C
H
Fig. 4. Structure of [CuBr(g
1-S-HttscPh)2] 8 with numbering scheme (complex 9
has similar structure).
C
H
1
S
S
X
X
N
R2
Cu
Cu
7− 9b
1− 6a
aR = Me or Et, X = I, Br,Cl 1-6
bR = Ph; X = I, Br, Cl 7-9
Chart 3.
of –N1HC2H5 group appear as two sets, one multiplet (d 3.64–
3.67 ppm, CH2); and one triplet (d 1.27–1.30 ppm, CH3) in com-
plexes 4–6. The coordination of ligand to copper results in a stable
complex with a defined orientation of the N1H proton. The N1 atom
becomes a stable chiral center resulting in the coupling of the N1H
proton with protons of alkyl groups (doublet of N–Me group) and a
diasterotopical splitting of CH2 of ethyl group (multiplet). The phe-
nyl protons of –N1HC6H5 appear in the range, d 7.36–7.52 ppm in
7–9. The C5H protons of thiophene ring appeared as a doublet of
doublet in the range, d 7.06–7.1 ppm in these complexes, while
other ring protons are obscured by protons of triphenyl phosphine.
13C NMR spectra of representative complexes, namely, 1–4
showed signals for 1C carbons at
d 176.8, 173.9, 174.3,
Fig. 5. Structure of complex 7 {[CuI(g l-S-HttscPh)2(g
1-S-HttscPh)2] [Cu2I2( 1-S-
HttscPh)2]} with numbering scheme.
172.8 ppm, respectively, which are upfield vis-à-vis free ligand
(HttscMe, d 177.8 ppm 1–3; HttscEt, 176.9 ppm 4). The 2C carbon

T.S. Lobana et al. / Inorganica Chimica Acta 362 (2009) 3547–3554
3553
Fig. 6. Packing diagram of [Cu2(l-Cl)2(g
1-S-HttscMe)2(Ph3P)2] 3 (complexes 1 and 2 have similar packing).
Fig. 7. Packing diagram of [Cu2(l-Cl)2(g
1-S-HttscEt)2(Ph3P)2] 6 (complexes 4 and 5 have similar packing).
signals at 139.8(1), 140.7(2), 141.1(3) and 139.9(4) ppm are low
field relative to the free ligand (138.16 ppm 1–3; 137.8 ppm 4).
The behavior of these complexes is similar to the literature trend
[22,23]. The methyl carbon at N1 gives signal in the range, 30.6–
30.8 ppm in complexes 1–3. Complex 4 showed –CH2– and CH3–
signals at 38.8 and 14.5 ppm, respectively. Further, the ring carbon
signals do not show any significant shifts on complexation, but i-C,
o-C, m-C and p-C signals of Ph3P are clearly resolved in complexes.
31P NMR of complexes 2, 4–6 showed a single signal in the
range, d ꢁ1.77 to d ꢁ5.07 ppm and are similar to those observed
in case of halogen-bridged dimers in literature [22]. 31P signal in
complex 1 appeared at d ꢁ30.5 ppm with a coordination shift of
D
d (d complex ꢁ d ligand), 35.1 ppm. Such high coordination shift
is a characteristic of S-bridged dimer in literature, which indicates
isomerisation of iodo-bridged dimer into S-bridged dimer in com-
plex 1 [22]. Complex 3 shows two bands at d ꢁ1.58 and d
ꢁ30.3 ppm, which supports equilibrium between S-bridged dimer
and halogen-bridged dimer in solution phase.
4. Conclusion
The presence of methyl/ethyl (HttscMe/HttscEt) substituents at
N1 nitrogen of thio-phene-2-carbaldehyde thiosemicarbazones
{(C4H3S)HC2@N3–N(H)–C1(@S)N1HR} has led to the formation of
halogen-bridged dinuclear complexes 2, 3, 5, 6 for X = Br, Cl, and
this behavior is different from that of Httsc for these halides
[22,23]. These observations strongly point to the role of sustituents
at N1 atoms in changing the nature of bridging. The effect could be
steric or involving H-bond interaction, or a combination of these
Fig. 8. Packing diagram of [CuCl(g
1-S-HttscPh)2] 9 (complex 8 has similar packing
diagram).

3554
T.S. Lobana et al. / Inorganica Chimica Acta 362 (2009) 3547–3554
factors. The presence of phenyl at N1 has yielded three coordinated
complexes 7–9, when copper(I) halides were reacted in 1:1:1
(Cu:HttscPh:PPh3) or 1:2 (Cu:2HttscPh) molar ratios. In each case,
the product was identical, i.e. no PPh3 was coordinating. The fact
that copper(I) is preferring to bind to two thio-ligands shows that
phenyl at N1 is probably decreasing Lewis basicity of sulfur and
copper is opting for two thio-ligands yielding three coordinated
complexes and these complexes have strong intramolecular –
N2Hꢀ ꢀ ꢀX interaction which probably is preventing coordination
by PPh3. Alternatively, in complexes 2, 3, 5, 6 and 7–9, it is the ste-
ric bulk at N1 which is favouring halogen bridging or preferring a
three coordinating geometry. Two monomeric units of 7a combine
via weak Cuꢀ ꢀ ꢀS bonds forming dimeric 7b moieties.
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Acknowledgments
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Polyhedron 26 (2007) 2621.
Financial assistance (RS) from CSIR (Scheme No.: 01(1993)/05/
EMR-II), New Delhi is gratefully acknowledged. The authors thank
Matthias Zeller of Youngstown State University, USA for X-ray
crystallography.
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Appendix A. Supplementary material
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Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2009.03.043.
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CCDC 691915, 691916, 691917, 691918, 691919, 691920,
691921, 691922, 691923, 691924 and 691925 contain the supple-
mentary crystallographic data for complexes 1, 2, 3, 4, 5, 6, 7, 8, 9,
10 and 11. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via <http://www.ccdc.
cam.ac.uk/data_request/cif>.
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