Cyclopalladation of azobenzenes and their reactivity towards N-substituted imidazolidine-2-thiones and allied ligands: Synthesis, structures, spectroscopy and ESI-mass studies

Article abstract of DOI:10.1016/j.jorganchem.2018.02.037

Reactions of palladium(II) chloride with azobenzene (azbH), p-methoxyazobenzene (mazbH) and 4, 4′-diethoxyazobenzene (deazbH) in methanol yielded halogen bridged dinuclear precursors [Pd₂(κ²:C,N-L)₂(μ-Cl)₂] (here L = azb^?, mazb^? and deazb^?). These precursors were further reacted with a series of N, S- donor thio-ligands, namely, 1,3-imidazolidine-2-thiones (imdzSH-NR; R = H, Me, Et, Prⁿ, Buⁿ, Ph), N-methyl-imidazoline-2-thione (imzSH-NMe), 1,3-benzimidazoline-2-thione (bzimSH-NH) and 1, 3- thiazolidine-2-thione (tzdSH). Nineteen dinuclear organometallic compounds synthesized are listed as follows: (a) [Pd₂(κ²:C, N-azb)₂(μ-N, S-imdzS-NR)₂] (R = H, 1; Me, 2; Et 3; Prⁿ 4; Buⁿ 5; Ph 6), (b) [Pd₂(κ²:C, N-mazb)₂(N, S-imdzS-NR)₂] (R = Me, 7; Et, 8; Prⁿ 9; Buⁿ 10), (c) [Pd₂(κ²:C, N-deazb)₂(N, S-imdzS-NR)₂] (R = Et, 11; Prⁿ 12; Buⁿ 13; Ph 14), (d) [Pd₂(κ²:C, N-azb)₂(μ-N, S-L)₂] (L = bzimS-NH 15; imzS-NMe 16; tzdS 17), and (e) [Pd₂(κ²:C, N-deazb)₂(N, S-L)₂] (L = bzimS-NH 18; imzS-NMe 19). All these compounds have been characterized with the help of analytical data, electron absorption, NMR and fluoresecence spectroscopy, ESI-mass spectrometry and single crystal X-ray crystallography. The loss of one C-H proton of an azobenzene and one N-H proton of a thio-ligand occurred per palladium metal center in dinuclear complexes synthesized, which have C, N-chelating azobenzenes and N, S-bridging heterocyclic thiolates.

Full text of DOI:10.1016/j.jorganchem.2018.02.037

Journal of Organometallic Chemistry 861 (2018) 112e124
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Cyclopalladation of azobenzenes and their reactivity towards N-
substituted imidazolidine-2-thiones and allied ligands: Synthesis,
structures, spectroscopy and ESI-mass studies
,
Amanpreet K. Sandhu a, Tarlok S. Lobana a *, Balkaran S. Sran a, Geeta Hundal a,
Jerry P. Jasinski b
a Department of Chemistry, Guru Nanak Dev University, Amritsar, 143 005, India
b Department of Chemistry, Keene State College, Keene, NH 03435-2001, USA
a r t i c l e i n f o
a b s t r a c t
Reactions of palladium(II) chloride with azobenzene (azbH), p-methoxyazobenzene (mazbH) and 4, 40-
Article history:
diethoxyazobenzene (deazbH) in methanol yielded halogen bridged dinuclear precursors [Pd2(k
2:C,N-
Received 30 December 2017
Received in revised form
15 February 2018
Accepted 21 February 2018
Available online 26 February 2018
L)2(
m
-Cl)2] (here L ¼ azbꢀ, mazbꢀ and deazbꢀ). These precursors were further reacted with a series of
N, S- donor thio-ligands, namely, 1,3-imidazolidine-2-thiones (imdzSH-NR; R ¼ H, Me, Et, Prn, Bun, Ph),
N-methyl-imidazoline-2-thione (imzSH-NMe), 1,3-benzimidazoline-2-thione (bzimSH-NH) and 1, 3-
thiazolidine-2-thione (tzdSH). Nineteen dinuclear organometallic compounds synthesized are listed as
follows: (a) [Pd2(
[Pd2(
k
2:C, N-azb)2(
m
-N, S-imdzS-NR)2] (R ¼ H, 1; Me, 2; Et 3; Prn 4; Bun 5; Ph 6), (b)
Keywords:
Cyclopalladation
k
2:C, N-mazb)2(N, S-imdzS-NR)2] (R ¼ Me, 7; Et, 8; Prn 9; Bun 10), (c) [Pd2(
k
2:C, N-deazb)2(N, S-
imdzS-NR)2] (R ¼ Et, 11; Prn 12; Bun 13; Ph 14), (d) [Pd2(
k
2:C, N-azb)2(
m
-N, S-L)2] (L ¼ bzimS-NH 15;
N-methyl-imidazolidine-2-thione
N-ethyl-imidazolidine-2-thione
N-(n-propyl)imidazolidine-2-thione
N-(n-butyl)imidazolidine-2-thione
N-phenyl-imidazolidine-2-thione
Thiazolidine-2-thione
imzS-NMe 16; tzdS 17), and (e) [Pd2(
k
2:C, N-deazb)2(N, S-L)2] (L ¼ bzimS-NH 18; imzS-NMe 19). All
these compounds have been characterized with the help of analytical data, electron absorption, NMR
and fluoresecence spectroscopy, ESI-mass spectrometry and single crystal X-ray crystallography. The
loss of one C-H proton of an azobenzene and one N-H proton of a thio-ligand occurred per palladium
metal center in dinuclear complexes synthesized, which have C, N-chelating azobenzenes and N, S-
bridging heterocyclic thiolates.
© 2018 Elsevier B.V. All rights reserved.
1. Introduction
thio-ligands, namely, pyridine-2-thione and pyrimidine-2-thione
with azobenzenes [34]. Keeping in view the importance of cyclo-
The chemistry of cyclopalladated compounds [1,2] of azo-
benzenes has invited interest of several researchers owing to their
importance in organic synthesis [3e6], catalysis [7e17], photo-
chemistry [18e22] and metallomesogen chemistry [23,24]. The
cyclopalladated complexes containing N-donor ligands are impor-
tant because of their potential applications as model compounds
for photoactive units in different optical devices [1,25e27], as dif-
ferential chromogenic and fluorescent chemosensors [17,28e32],
and in catalysts [7e17]. Recently, it was observed that coordination
chemistry of cyclopalladated azobenzenes bonded to N, S-donor
atoms was poorly investigated [33,34], and in this context we re-
ported a few complexes of cyclopalladated azobenzenes with the
palladated compounds of azobenzenes, and our experience in
palladium-heterocyclic-2-thione chemistry [35], in this paper we
are reporting cyclopalladated azobenzenes (see Chart 1) and their
coordination to imidazolidine-2-thiones and allied thio-ligands
(see Chart 2).
Heterocyclic -2- thiones as shown in Chart 2 above possess
chemically active groups such as, eN(H)eC(¼S)e 4 eN¼C(eSH)e,
and are expected to coordinate to the metal center as anions
through N, S- donor atoms, after deprotonation of one eN-H group.
This is expected on the pattern of pyridine-2-thione/pyrimidine-2-
thione as reported earlier [35]. A major interest lies in the antici-
pation of formation of N,S-bridged dinuclear complexes which
could be useful molecules in terms of higher flexibility of dinuclear
moieties from catalysis point of view and enhanced fluorescent
property due to binding of hard-soft (N,S) donors to metal centere
which could of importance for optical materials [7e22]. Chart 1
* Corresponding author.
E-mail address: tarlokslobana@yahoo.co.in (T.S. Lobana).
https://doi.org/10.1016/j.jorganchem.2018.02.037
0022-328X/© 2018 Elsevier B.V. All rights reserved.

A.K. Sandhu et al. / Journal of Organometallic Chemistry 861 (2018) 112e124
113
2.2. Synthesis of complexes
2.2.1. [Pd2(
k
2:C, N-azb)2(
m
-N, S-imdzS-NH)2] ∙2H2O 1
To an orange suspension of [Pd2(
k
2:C, N-azb)2(
m- Cl)2] (0.025 g,
0.040 mmol) in dichloro-methane (5 mL), imidazolidine-2-thione
(0.009 g, 0.080 mmol) was added in presence of Et3N base
(0.5 mL). The color of the reaction mixture became dark red brown
and it was stirred for 5e6 h. The solution was filtered, toluene
(1 mL) was added and left to evaporate slowly. The dark red brown
crystals of compound 1 were obtained along with the formation of
Et3NHþClꢀ after a period of 4e5 d. Yield 0.021 g, 68%, m.p.
190e192 ꢁC. Anal. found: C, 44.33; H, 3.90; N, 13.75%;
Chart 1. Azobenzene, p-methoxyazobenzene and 4, 40-diethoxyazobenzene;
*indicates metallation site.
shows various azobenzenes which will be first reacted with palla-
dium(II) followed by their reactions with thio-ligands as listed in
Chart 2. The substitution in rings of azobenzenes is arbitrarily
incorporated.
C
30H32N8O2Pd2S2 requires: C, 44.29; H, 3.96; N, 13.77%. IR bands
(KBr pellets, cmꢀ1):
(N-H) þ (O-H), 3418s, 3400s; (C-H), 3043 m,
2935 m, 2871 m; (N-H),1671s; (N¼N) þ (C-N) þ (C-
(O-H)þ
C) þ (C-H), 1574w, 1534s, 1481w, 1426s, 1391s; other bands, 1302s,
1275 m, 1257w, 1237w, 1216 m; (C-S), 1188s; other bands, 1095w,
1072w, 1036 m, 1017 m, 916w, 770s, 714 m, 694s, 619w, 591w,
n
n
n
d
d
n
n
n
d
n
2. Experimental
547w, 527w, 497w, 445w. 1H NMR (
d, ppm, J, Hz, CDCl3): 8.04 (bs,
2H, NH), 7.65 (m, 6H, H9, 10, 14), 7.50 (d, 2H, J, 5 Hz, H6), 7.45 (m, 6H,
2.1. Materials and techniques
H11, 13, 12), 7.10 (m, 4H, H7, 8), 3.86 (m, 2H, C4H2), 3.70 (m, 2H, C4H2),
3.44 (m, 2H, C5H2), 3.32 (m, 2H, C5H2). UVevis. data, CH2Cl2, lmax
/
Palladium(II) chloride, 1, 3-imidazolidine-2-thione (imdzSH-
NH), N-methyl-imidazoline-2-thione (imzSH-NMe), thiazolidine-
2-thione (tzdSH), benzimidazoline-2-thione (bzimSH-NH), azo-
benzene (azbH), p-methoxy- azobenzene (mazbH) and 4, 40-
nm, ε/L molꢀ1cmꢀ1: [10ꢀ4 M] 459 (0.47 ꢂ 104), 341 (1.28 ꢂ 104), 242
em
ex
(3.84 ꢂ 104). Fluorescence data (
l
¼ 652 nm,
l
¼ 270 nm).
max
max
Compounds 2e6, 16 and 19 were prepared by the method used for
compound 1.
diethoxyazobenzene
(deazbH)
were
procured
from
SigmaeAldrich Ltd. The N-substituted imidazolidine-2-thiones
were prepared as follows. For example, N-methyl-imidazoli-
dine-2-thione prepared by the addition of carbon disulfide
dropwise to a cooled solution of 1-methyl-ethylenediamine in
ethanol and water. The reaction mixture was heated under reflux
(110 ꢁC) for 1 h and conc. HCl was added. The mixture was heated
under reflux for a further period 10 h. The reaction mixture was
cooled and stored in a freezer. The resulting precipitate were
filtered and washed with cold acetone to give the desired ligand.
N-ethyl-imidazolidine-2-thione, N-(n-propyl)-imidazolidine-2-
thione, N-(n-butyl)-imidazolidine-2-thione (imzdSH-Bun) and
N-phenylimidazolidine-2-thione (imzdSH-Ph) were prepared
[36] (see Supporting Information). The precursor, namely,
2.2.2. [Pd2(k m-N, S-imdzS-NMe)2] 2
2:C, N-azb)2(
Compound 2 was prepared by following a method used for
compound 1. Yield 0.025 g, 81%, m.p. 190e192 ꢁC. Anal. found: C,
47.65; H, 4.11; N,13.85; C32H32N8Pd2S2 requires: C, 47.71; H, 4.00; N,
13.91%. IR bands (KBr pellets, cmꢀ1):
n
(C-H), 3041w, 2997w,
(C-C) þ (C-H),1597 m, 1579s,
1552 m, 1524s, 1501 m, 1483w, 1457 m, 1424 m, 1375s; other bands,
1326 m, 1300 m, 1254s, 1218 m, 1201 m, 1173w, 1157 m; (C-S),
2933 m, 2832 m;
n
(N¼N) þ
n(C-N) þ
n
d
n
1124 m; other bands, 1105s, 1082w, 1034s, 1024s, 956w, 876w,
831 m, 798w, 787w, 763s, 723w, 711w, 694 m, 672w, 649w, 633w,
530 m, 497w, 444w. 1H NMR ( , ppm, J, Hz, CDCl3): 7.65 (m, 6H, H9,
d
10, 14), 7.49 (d, 2H, J, 10 Hz, H6), 7.42 (m, 6H, H11, 12, 13), 7.09 (m, 4H,
H7,8), 3.56 (m, 4H, J, 9.34 Hz, C4H2), 3.32 (m, 2H, C5H2), 3.11 (m, 2H,
C5H2), 1.58 (s, 6H, CH3). UVevis. data, CH2Cl2, lmax/nm, ε/L
[Pd2(
azobenzene (azbH) to a suspension of PdCl2 in methanol fol-
lowed by overnight stirring [37]. Similarly, precursors [Pd2(
2: C,
N-mazb)2( -Cl)2] and [Pd2( -Cl)2] were pre-
2: C, N-deazb)2(
k m-Cl)2] was prepared by the addition of an
2: C, N-azb)2(
k
molꢀ1cmꢀ1
:
[10ꢀ4 M] 450 (1.09 ꢂ 104), 361 (1.80 ꢂ 104), 245
m
k
m
em
ex
(3.96 ꢂ 104). Fluorescence data (
l
¼ 651 nm,
l
¼ 270 nm).
max
max
pared. The melting point was determined with a Gallenkamp
electrically heated apparatus. Elemental analysis for C, H and N
were carried out using a thermoelectron FLASHEA1112 analyzer.
The IR spectra were recorded using KBr pellets on a Varian 660
FT IR Spectrometer in the 4000-200 cmꢀ1 range. The 1H NMR
spectra were recorded in CDCl3 using a Bruker Avance 500 NMR
spectrometer at 500 MHz using TMS as an internal reference. ESI-
MS mass spectrometer was micro TOF-QII 10356 in positive
mode. UVevisible spectra of complexes were recorded using UV-
1800 Shimadzu spectrophotometer and fluorescence spectra of
complexes were recorded with a Varian Cary Eclipse and Perkin
Elmer Fluorescence spectrophotometers.
2.2.3. [Pd2(k m-N, S-imdzS-NEt)2] 3
2:C, N-azb)2(
Compound 3 was prepared by following a method used for
compound 1. Yield 0.026 g, 81%, m.p. 210e212 ꢁC. Anal. found: C,
48.78; H, 4.60; N, 13.32; C34H38N8Pd2S2 requires: C, 48.87; H, 4.58;
N, 13.41%. IR bands (KBr pellets, cmꢀ1):
n
(C-H), 3051w, 2965 m,
(C-C) þ (C-H),1578w,1552w,
1523s, 1483 m, 1457 m, 1440 m, 1396s, 1376 m; other bands, 1355w,
1316 m, 1290 m, 1259s, 1234s, 1207 m, 1178w, 1153w; (C-S),
2927 m, 2854 m;
n
(N¼N) þ
n
(C-N) þ
n
d
n
1124 m; other bands, 1108w, 1084 m, 1074 m, 1042w, 1022 m, 971w,
957w, 945w, 916w, 832w, 771s, 759 m, 706 m, 697s, 649 m, 622w,
Chart 2. The thio-ligands used for synthesis.

114
A.K. Sandhu et al. / Journal of Organometallic Chemistry 861 (2018) 112e124
592w, 548w, 525w, 499w, 439w. 1H NMR (
d
, ppm, J, Hz, CDCl3): 7.66
(5 mL) was added and was left to evaporate slowly. The red brown
crystals of compound 7 were obtained after a period of 4e5 d. Yield
0.023 g, 76%, m.p. 158e160 ꢁC. Anal. found: C, 47.30; H, 4.22; N,
12.90%; C34H36N8O2Pd2S2 requires: C, 47.17; H, 4.19; N, 12.90%. IR
(m, 6H, H9, 10, 14), 7.47 (d, 2H, J, 5 Hz, H6), 7.42 (m, 6H, H11, 12, 13), 7.14
(t, 2H, J, 7.5 Hz, H8), 7.07 (t, 2H, J, 7.5 Hz, H7), 3.60 (m, 4H, C4H2), 3.27
(m, 8H, C5H2, N-CH2), 0.95 (s, 6H, CH3). UVevis. data, CH2Cl2, lmax
/
nm, ε/L molꢀ1cmꢀ1: [10ꢀ4 M] 452 (0.558 ꢂ 104), 353 (1.24 ꢂ 104),
bands (KBr pellets, cmꢀ1):
N) þ (C-C) þ
other bands, 1376 m, 1298 m, 1257s, 1157 m;
bands, 1032s, 955w, 830 m, 799w, 761 m, 722w, 693w, 647w, 586w,
n
(C-H), 2930 m, 2832 m;
(C-H), 1598s, 1580s, 1552w, 1528s, 1482w, 1458w;
(C-S), 1106s; other
n
(N¼N) þ
n(C-
em
242
(3.99 ꢂ 104).
Fluorescence
data
(l
¼ 652 nm,
n
d
max
ex
l
max
¼ 270 nm).
n
2.2.4. [Pd2(
k
2:C, N-azb)2(
m
-N, S-imdzS-NPrn)2] 4
529 m, 496w. 1H NMR ( , ppm, J, Hz, CDCl3): 7.63 (m, 6H, H9, 10, 14),
d
Compound 4 was prepared by following a method used for
compound 1. Yield 0.025 g, 76%, m.p. 180e182 ꢁC. Anal. found: C,
50.24; H, 4.70; N, 13.20; C36H40N8Pd2S2 requires: C, 50.18; H, 4.68;
7.44 (m, 6H, H11, 12, 13), 7.07 (m, 2H, H7), 6.90 (d, 2H, J, 5 Hz, H6), 3.88
(d, 6H, -OCH3), 2.88 (m, 8H, C4H2, C5H2), 1.58 (s, 6H, CH3). UVevis.
data, CH2Cl2, lmax/nm, ε/L molꢀ1cmꢀ1: [10ꢀ4 M] 444 (1.51 ꢂ 104),
N, 13.00%. IR bands (KBr pellets, cmꢀ1):
n
(C-H), 3050 m, 2956 m,
(C-C) þ (C-H),1577 m,1523s,
1480 m, 1455 m, 1396s; other bands, 1298s, 1254 m, 1221s; (C-S),
1130 m; other bands, 1088w, 1072w, 1028w, 965w, 911w, 768s,
367
(2.10 ꢂ 104),
244
(3.99 ꢂ 104).
Fluorescence
data
em
ex
2922 m, 2854 m;
n
(N¼N) þ
n
(C-N) þ
n
d
(l
max
¼ 652 nm,
l
¼ 275 nm). Compounds 8e15, and 18 were
max
n
prepared by the method used for compound 7.
695w, 670w, 638w, 592w, 544w, 526w, 499w, 454w. 1H NMR (
d
,
2.2.8. [Pd2(
k
2:C, N-mazb)2(
m-N, S-imdzS-NEt)2] 8
ppm, J, Hz, CDCl3): 7.66 (m, 6H, H9, 10, 14), 7.47 (d, 2H, J, 5 Hz, H6),
7.42 (m, 6H, H11, 12, 13), 7.13 (t, 2H, J, 5 Hz, H8), 7.07 (t, 2H, J, 5 Hz, H7),
3.59 (m, 4H, C4H2), 3.24 (m, 8H, C5H2, N-CH2), 1.40 (m, 4H, -CH2-),
0.85 (t, 6H, J, 7.5 Hz, CH3). UVevis. data, CH2Cl2, lmax/nm, ε/L
Compound 8 was prepared by following a method used for
compound 7. Yield 0.025 g, 78%, m.p. 160e162 ꢁC. Anal. found: C,
48.35; H, 4.50; N, 12.51%; C36H40N8O2Pd2S2 requires: C, 48.38; H,
4.51; N, 12.54%. IR bands (KBr pellets, cmꢀ1):
n
(C-H), 3054w,
(C-C) þ (C-
molꢀ1cmꢀ1
:
[10ꢀ4 M] 451 (0.66 ꢂ 104), 348 (1.50 ꢂ 104), 252
2965 m, 2928 m, 2859 m, 2834 m;
n
(N¼N) þ
n
(C-N) þ
n
d
(3.96 ꢂ 104). Fluorescence data (
l
¼ 652 nm,
l
¼ 270 nm).
H), 1579s, 1553s, 1523s, 1483w, 1458 m, 1426w, 1398w, 1375 m;
other bands, 1326w, 1310 m, 1253s, 1235s, 1218s, 1202 m, 1173 m;
em
ex
max
max
2.2.5. [Pd2(
k
2:C, N-azb)2(
m
-N, S-imdzS-NBun)2] 5
n(C-S), 1124s; other bands, 1073w, 1034s, 958w, 915w, 876w, 833w,
Compound 5 was prepared by following a method used for
compound 1. Yield 0.027 g, 79%, m.p. 190e192 ꢁC. Anal. found: C,
51.32; H, 4.90; N, 12.50; C38H44N8Pd2S2 requires: C, 51.29; H, 4.98;
789w, 763 m, 724w, 694 m, 673w, 649w, 623w, 593w, 527 m, 500w,
443w. 1H NMR ( , ppm, J, Hz, CDCl3): 7.62 (m, 6H, H9, 10, 14), 7.48 (t,
d
2H, J, 5 Hz, H12), 7.40 (m, 4H, H11, 13), 7.07 (m, 2H, H8), 6.83 (d, 2H, J,
N, 12.59%. IR bands (KBr pellets, cmꢀ1):
n
(C-H), 3046 m, 2956s,
(C-H), 1575 m, 1526s,
1478 m, 1453 m, 1392s, 1376s; other bands, 1294s, 1254s, 1234 m,
1205s, 1179 m; (C-S), 1130s; other bands, 1113 m, 1088w, 1071w,
1025 m, 964w, 938w, 911w, 864w, 838w, 767s, 732w, 709w, 693 m,
10 Hz, H6), 3.88 (d, 6H, -OCH3), 3.42 (m, 12H, C4H2, C5H2, N-CH2),
2926s, 2854s;
n
(N¼N) þ
n
(C-N) þ
n
(C-C) þ
d
0.99 (m, 6H, CH3).$UVevis. data, CH2Cl2, lmax/nm, ε/L molꢀ1cmꢀ1
:
[10ꢀ4 M] 455 (0.94 ꢂ 104), 369 (1.48 ꢂ 104), 249 (3.85 ꢂ 104). Fluo-
em
ex
n
rescence data (
l
¼ 652 nm,
l
¼ 275 nm).
max
max
654w, 590w, 546w, 525w, 497w, 443w. 1H NMR (
d
, ppm, J, Hz,
2.2.9. [Pd2(k m
2:C, N-mazb)2( -N, S-imdzS-N Prn)2] 9
CDCl3): 7.66 (m, 6H, H9, 10, 14), 7.47 (dd, 2H, J, 5 Hz, H6), 7.41 (m, 6H,
H11, 12, 13), 7.13 (t, 2H, J, 7.5 Hz, H8), 7.07 (t, 2H, J, 5 Hz, H7), 3.58 (m,
4H, C4H2), 3.20 (m, 8H, C5H2, N-CH2), 1.32 (m, 8H, -CH2CH2-), 0.94
Compound 9 was prepared by a method used for compound 7.
Yield 0.025 g, 79%, m.p. 210e212 ꢁC. Anal. found: C, 49.54; H, 4.80;
N,12.20%; C38H44N8O2Pd2S2 requires: C, 49.51; H, 4.81; N,12.16%. IR
(t, 6H, J, 7.5 Hz, CH3). UVevis. data, CH2Cl2, lmax/nm, ε/L molꢀ1cmꢀ1
:
bands (KBr pellets, cmꢀ1):
2834 m; (N¼N) þ
(C¼C) þ
1574s, 1552 m, 1520s, 1500 m, 1479 m, 1456 m, 1428 m, 1398 m,
1371 m; other bands, 1300 m, 1250s, 1231s, 1220s, 1154 m; (C-S),
n(C-H), 3000w, 2957 m, 2927 m, 2859 m,
[10ꢀ4 M] 448 (0.37 ꢂ 104), 344 (1.03 ꢂ 104), 244 (3.89 ꢂ 104). Fluo-
n
n
n
(C-N) þ (C-C) þ (C-H), 1597 m,
n
d
em
ex
rescence data (
l
¼ 652 nm,
l
¼ 270 nm).
max
max
n
2.2.6. [Pd2(
k
2:C, N-azb)2(
m-N, S-imdzS-NPh)2] 6
1108s; other bands, 1122s, 1024s, 967w, 910w, 859w, 829w, 814w,
798w, 762 m, 722w, 688w, 643w, 587w, 526 m, 496w, 466w, 440w.
Compound 6 was prepared by following a method used for
compound 1. Yield 0.028 g, 78%, m.p. 230e232 ꢁC. Anal. found: C,
54.32; H, 3.82; N, 12.20; C42H36N8Pd2S2 requires: C, 54.26; H, 3.90;
1H NMR ( , ppm, J, Hz, CDCl3): 7.63 (m, 6H, H9, 10, 14), 7.43 (m, 6H,
d
H11, 12,13), 7.07 (m, 2H, H8), 6.89 (d, 2H, J, 10 Hz, H6), 3.89 (d, 6H,
-OCH3), 3.60 (m, 4H, C4H2), 3.22 (m, 8H, C5H2, N-CH2), 1.43 (m, 4H,
-CH2-), 0.87 (m, 6H, CH3). UVevis. data, DCM, lmax/nm, ε/L
N, 12.05%. IR bands (KBr pellets, cmꢀ1):
n
(C-H), 3030 m, 2960w,
(C-C) þ (C-H), 1597s, 1577 m,
1550w, 1521s, 1496s, 1450 m, 1389 m, 1370s; other bands, 1337w,
1317 m, 1297s, 1255w, 1297s, 1255w, 1218s; (C-S), 1108w; other
2925w, 2858 m;
n
(N¼N) þ
n
(C-N) þ
n
d
molꢀ1cmꢀ1
:
[10ꢀ4 M] 451 (1.27 ꢂ 104), 368 (1.87 ꢂ 104), 249
em
ex
n
(4.00 ꢂ 104). Fluorescence data (
l
¼ 652 nm,
l
¼ 275 nm).
max
max
bands, 1075w, 1043 m, 1022 m, 956w, 916w, 832w, 764s, 715w,
707w, 692s, 665w, 635w, 589w, 550 m, 529w, 507w, 465w, 438w.
2.2.10. [Pd2(k m
2:C, N-mazb)2( -N, S-imdzS-NBun)2] 10
1H NMR (
d
, ppm, J, Hz, CDCl3): 7.71 (m, 4H, H9, 10), 7.66 (d, 2H, J, 5 Hz,
Compound 10 was prepared by a method used for compound 7.
Yield 0.025 g, 75%, m.p.110e112 ꢁC. Anal. found: C, 50.52; H, 5.10; N,
11.78%; C40H48N8O2Pd2S2 requires: C, 50.58; H, 5.09; N, 11.80%. IR
H14), 7.48 (m, 8H, H6, 12, m-H(Ph)), 7.33 (t, 4H, J, 7.5 Hz, H11, 13), 7.20
(d, 4H, J, 10 Hz, o-H (Ph)), 7.14 (t, 4H, J, 7.5 Hz, H8, p-H (Ph)), 6.99 (t,
2H, J, 7.5 Hz, H7), 3.82 (m, 8H, C4H2, C5H2). UVevis. data, CH2Cl2,
bands (KBr pellets, cmꢀ1):
2925 m, 2857 m, 2832 m;
1598 m, 1578s, 1552 m, 1523s, 1500 m, 1482w, 1456 m, 1426 m,
1377 m; other bands, 1325w, 1297 m, 1251s, 1235s, 1214s, 1175 m;
n
(C-H), 3105w, 3040w, 2999w, 2952 m,
(C-H),
lmax/nm, ε/L molꢀ1cmꢀ1
:
[10ꢀ4 M] 453 (0.34 ꢂ 104), 351
n
(N¼N) þ
n
(C-N) þ
n
(C-C) þ
d
em
(0.85 ꢂ 104), 245 (3.03 ꢂ 104). Fluorescence data (
l
¼ 652 nm,
max
ex
l
¼ 270 nm).
max
other bands, 1158 m, 1121 m; n(C-S), 1109 m; other bands, 1087w,
2.2.7. [Pd2(
k
2:C, N-mazb)2(
m
-N, S-imdzS-NMe)2] 7
1031s, 939w, 910w, 886w, 865w, 830 m, 797w, 761s, 722w, 711w,
To an orange suspension of [Pd2(
k
2:C, N-mazb)2(
m-Cl)2] (0.025 g,
692 m, 671w, 646w, 634w, 588w, 526 m, 503w, 467w, 443w. 1H
0.040 mmol) in dichloromethane (5 mL), N-methylimidazolidine-
2-thione (0.012 g, 0.080 mmol) was added in presence of Et3N base
(0.5 mL). The color of the reaction mixture became red brown and
was stirred for 5e6 h. The solution was filtered and methanol
NMR (d
, ppm, J, Hz, CDCl3): 7.63 (m, 6H, H9, 10, 14), 7.48 (m, 2H, H12),
7.39 (m, 4H, H11, 13), 7.07 (m, 2H, H8), 6.96 (d, 2H, J, 5 Hz, H6), 3.89 (d,
6H, -OCH3), 3.60 (m, 4H, C4H2), 3.22 (m, 8H, C5H2, N-CH2), 1.43 (m,
8H, -CH2CH2-), 0.87 (m, 6H, CH3). UVevis. data, CH2Cl2, lmax/nm, ε/L

A.K. Sandhu et al. / Journal of Organometallic Chemistry 861 (2018) 112e124
115
molꢀ1cmꢀ1
:
[10ꢀ4 M] 453 (0.68 ꢂ 104), 351 (1.45 ꢂ 104), 246
1314 m, 1298 m, 1243s, 1230s, 1214s, 1200s, 1156 m; other bands,
1128 m; (C-S), 1111 m; other bands, 1088w, 1045s, 924 m, 890w,
860w, 834 m, 824 m, 797 m, 771w, 729w, 671w, 639w, 588w, 556w,
548 m, 534 m, 497w, 440w. 1H NMR (
, ppm, J, Hz, CDCl3): 7.56 (d,
em
ex
(3.98 ꢂ 104). Fluorescence data (
l
¼ 652 nm,
l
¼ 275 nm).
n
max
max
2.2.11. [Pd2(k m-N, S-imdzS-NEt)2] 11
2:C, N-deazb)2(
d
4H, J, 10 Hz, H10,14), 7.40 (d, 2H, J, 5 Hz, H9), 7.14 (d, 2H, J, 5 Hz, H6),
6.84 (d, 4H, J, 5 Hz, H11,13), 6.55 (d, 2H, J, 5 Hz, H8), 4.09 (m, 8H, C4H2,
C5H2), 3.59 (m, 4H, N-CH2), 3.30 (m, 8H, -CH2CH2-), 1.30 (s, 8H,
-OCH2-), 1.47 (t, 12H, J, 6.25 Hz, CH3), 0.95 (t, 6H, J, 7.5 Hz, CH3).
UVevis. data, CH2Cl2, lmax/nm, ε/L molꢀ1cmꢀ1: [10ꢀ4 M] 449
(1.62 ꢂ 104), 375 (1.72 ꢂ 104), 248 (3.96 ꢂ 104). Fluorescence data
Compound 11 was prepared by a method used for compound 7.
Yield 0.024 g, 78%, m.p. 160e162 ꢁC. Anal. found: C, 49.80; H, 5.21;
N, 11.15%; C42H52N8O4Pd2S2 requires: C, 49.95; H, 5.19; N, 11.10%. IR
bands (KBr pellets, cmꢀ1):
(N¼N) þ (C-N) þ (C-C) þ
1500s, 1477 m, 1441 m, 1392s; other bands, 1373s, 1316s, 1246s,
1201s, 1158 m; (C-S), 1115s; other bands, 1085 m, 1069 m, 1043s,
960w, 925 m, 887w, 861w, 830 m, 798 m, 772w, 674w, 644 m,
n(C-H), 3057w, 2975s, 2926s, 2862s;
n
n
n
d(C-H), 1600s, 1578s, 1551s, 1522s,
em
ex
(l
¼ 652 nm,
l
¼ 275 nm).
n
max
max
624w, 590w, 553 m, 535 m, 497w, 440w. 1H NMR (
d, ppm, J, Hz,
2.2.14. [Pd2(k m-N, S-imdzS-NPh)2] 14
2:C, N-deazb)2(
Compound 14 was prepared by a method used for compound 7.
Yield 0.026 g, 80%, m.p. 210e212 ꢁC. Anal. found: C, 54.29; H, 4.70;
N, 10.15%; C50H52N8O4Pd2S2 requires: C, 54.30; H, 4.74; N, 10.13%. IR
CDCl3): 7.55 (d, 4H, H10,14), 7.40 (d, 2H, J, 7.5 Hz, H9), 7.13 (d, 2H, J,
15 Hz, H6), 6.83 (m, 4H, H11,13), 6.55 (dd, 2H, J, 5 Hz, H8), 4.09 (m, 8H,
C4H2, C5H2), 3.49 (m, 12H, N-CH2, -OCH2-), 1.46 (t, 12H, J, 7.5 Hz,
CH3), 1.02 (t, 6H, J, 7.5 Hz, CH3). UVevis. data, CH2Cl2, lmax/nm, ε/L
bands (KBr pellets, cmꢀ1):
(N¼N) þ (C-N) þ (C-C) þ
1444 m; other bands, 1365 m, 1317 m, 1297 m, 1248s, 1231s, 1202s,
1157 m; (C-S), 1109 m; other bands, 1045s, 958w, 923w, 858w,
824 m, 756w, 690w, 592w, 544 m. 1H NMR ( , ppm, J, Hz, CDCl3): 1H
NMR (
, ppm, J, Hz, CDCl3): 7.60 (d, 4H, J, 10 Hz, H10,14), 7.41 (d, 2H, J,
n
(C-H), 3047w, 2975w, 2928w, 2853w;
(C-H), 1597 m, 1577s, 1553 m, 1476 m,
molꢀ1cmꢀ1
:
[10ꢀ4 M] 449 (1.90 ꢂ 104), 375 (2.03 ꢂ 104), 250
n
n
n
d
em
ex
(3.92 ꢂ 104). Fluorescence data (
l
¼ 561 nm,
l
¼ 275 nm).
max
max
n
2.2.12. [Pd2(k m
2:C, N-deazb)2( -N, S-imdzS-NPrn)2] 12
d
Compound 12 was prepared by a method used for compound 7.
Yield 0.024 g, 76%, m.p. 190e192 ꢁC. Anal. found: C, 50.95; H, 5.40;
N, 10.82%; C44H56N8O4Pd2S2 requires: C, 50.92; H, 5.44; N, 10.80%.
d
10 Hz, H9), 7.31 (m, 8H, o-H, m-H(Ph)), 7.14 (m, 4H, H6, p-H(Ph)),
6.88 (d, 4H, J, 10 Hz, H11,13), 6.56 (d, 2H, J, 5 Hz, H8), 4.09 (m, 8H,
C4H2, C5H2), 3.85 (m, 8H, -OCH2-), 1.48 (m, 12H, J, 6.25 Hz, CH3).
UVevis. data, DMSO, lmax/nm, ε/L molꢀ1cmꢀ1: [10ꢀ4 M] 444
(1.79 ꢂ 104), 375 (1.93 ꢂ 104), 257 (4.00 ꢂ 104). Fluorescence data
IR bands (KBr pellets, cmꢀ1):
2857 m, 2822 m;
n
(C-H), 3044w, 2959 m, 2926 m,
(C-H), 1598s, 1576s,
n(N¼N) þ
n
(C-N) þ
n
(C-C) þ
d
1551s, 1524s, 1500s, 1475 m, 1454 m, 1439 m, 1390s; other bands,
1368s, 1321s, 1296 m, 1244s, 1217s, 1202s, 1159 m; other bands,
em
ex
(l
¼ 652 nm,
l
¼ 275 nm).
max
max
1126s;
879w, 872w, 835 m, 825 m, 796 m, 772w, 759w, 672w, 641w,
588 m, 557 m, 534 m, 490w, 436w. 1H NMR (
, ppm, J, Hz, CDCl3):
n(C-S), 1114s; other bands, 1086 m, 1045s, 967w, 921 m,
2.2.15. [Pd2(k m-N, S- bzimS-NH)2] 15
2:C, N-azb)2(
d
7.57 (d, 4H, J, 10 Hz, H10,14), 7.40 (d, 2H, J, 10 Hz, H9), 7.14 (d, 2H, J,
5 Hz, H6), 6.84 (d, 4H, J, 10 Hz, H11,13), 6.55 (dd, 2H, J, 5 Hz, H8), 4.08
(m, 8H, C4H2, C5H2), 3.64 (m, 4H, N-CH2), 3.29 (m, 4H, -CH2-), 1.58
(s, 8H, -OCH2-), 1.46 (m, 12H, CH3), 0.89 (t, 6H, J, 7.5 Hz, CH3).
UVevis. data, CH2Cl2, lmax/nm, ε/L molꢀ1cmꢀ1: [10ꢀ4 M] 448
(2.34 ꢂ 104), 375 (2.46 ꢂ 104), 257 (3.91 ꢂ 104). Fluorescence data
Compound 15 was prepared by a method used for compound 7.
Yield 0.027 g, 81%, m.p. 230e232 ꢁC. Anal. found: C, 52.35; H, 3.42;
N, 12.60%; C38H28N8Pd2S2 requires: C, 52.24; H, 3.23; N, 12.83%. IR
bands (KBr pellets, cmꢀ1):
(C¼C) þ (N¼N) þ (C-N) þ
1483 m, 1429s, 1417s, 1387s; other bands, 1357 m, 1316w, 1295s,
1277s, 1199 m, 1160w; (C-S), 1107w; other bands, 1021 m, 919w,
n
(N-H), 3417s;
(C-C) þ
n
(C-H), 3047 m, 2966 m;
n
n
n
n
d(C-H), 1575 m, 1552w,
em
ex
(l
¼ 652 nm,
l
¼ 275 nm).
n
max
max
805w, 742s, 767s, 711s, 690s, 607w, 591w, 550w, 525w. 1H NMR (
d,
2.2.13. [Pd2(
k
2:C, N-deazb)2(
m
-N, S-imdzS-N Bun)2] 13
ppm, J, Hz, CDCl3): 8.27 (s, 2H, NH), 7.91 (d, 2H, J, 10 Hz, H11), 7.77 (d,
2H, J, 5 Hz, H12), 7.55 (d, 2H, J,10 Hz, H16), 7.29 (m, 4H, H4, 7), 7.20 (m,
10 H, H5, 6. 13, 14, 15), 7.03 (t, 2H, J, 7.5 Hz, H10), 6.98 (t, 2H, J,10 Hz, H9),
6.90 (d, 2H, J, 10 Hz, H8). UVevis. data, CH2Cl2, lmax/nm, ε/L
Compound 13 was prepared by a method used for compound 7.
Yield 0.025 g, 78%, m.p. 158e160 ꢁC. Anal. found: C, 51.75; H, 5.60;
N, 10.48%; C46H60N8O4Pd2S2 requires: C, 51.83; H, 5.67; N, 10.51%. IR
bands (KBr pellets, cmꢀ1):
2865 m;
n
(C-H), 3050w, 2974 m, 2956 m, 2925 m,
(C-H), 1600s, 1578s, 1552s,
molꢀ1cmꢀ1
:
[10ꢀ4 M] 454 (0.05 ꢂ 104), 364 (1.26 ꢂ 104), 308
em
n
(N¼N) þ
n
(C-N) þ
n
(C-C) þ
d
(2.87 ꢂ 104), 243 (3.98 ꢂ 104). Fluorescence data (
l
¼ 645 nm,
max
ex
1524s,1500s,1476 m,1455 m,1439 m,1392 m; other bands,1369 m,
l
¼ 270 nm).
max
X
X
N
RN
N
X = Y = H; 1-6;
-
N
S
R =H, Me, Et, Pr, Bu, Ph
S
N
NMe
S
N
N
H
Pd
Pd
X = OMe, Y =H; 7-10;
-
S
N
S
R = Me, Et, Pr, Bu
-
X = H; Y = H 15
X = Y= OEt 18
N
Y
S
N
Y
N
X = H; Y = H 16
X = Y= OEt 19
X = Y= H
X = Y = OEt; 11-14;
17
R =Et, Pr, Bu, Ph
NR
1-14
Chart 3. A chem draw view of structures of complexes.

116
A.K. Sandhu et al. / Journal of Organometallic Chemistry 861 (2018) 112e124
Table 1
Crystallographic data for complexes 1e5, 7e9, 11e13 and 15e19.
1
2
3
4
CCDC
1586210
1586208
1586199
1586205
Empirical formula
M
C30H32N8O2Pd2S2
813.56
C32H32N8Pd2S2
805.60
C34H38N8Pd2S2
835.66
C36H40N8Pd2S2
861.70
T/K
296(2)
296(2)
296(2)
296(2)
Crystal system
Space group
a(Å)
b(Å)
c(Å)
Monoclinic
P 21/n
11.7896(5)
17.8469(8)
15.2663(6)
90.00
90.715(2)
90.00
3211.9(2)
4
Monoclinic
C 2/c
23.9164(5)
10.8069(2)
14.0908(3)
90.00
117.8840(10)
90.00
3219.10(12)
4
Monoclinic
C 2/c
24.340(4)
10.9758(18)
14.054(2)
90.00
115.893(7)
90.00
3377.6(9)
4
Monoclinic
C 2/c
17.893(3)
16.029(3)
14.666(2)
90.00
119.570(4)
90.00
3658.5(11)
4
a
b
g
(º)
(º)
(º)
V(Å3)
Z
Dcalcd (g.cmꢀ3
)
1.682
1.292
1.662
1.283
1.643
1.226
1.564
1.135
m
(mmꢀ1
)
F(000)
1632
1616
1688
1744
Reflections collected
Unique reflections
76730
9768
15835
4147
14527
4507
17873
4490
(Rint, 0.0458)
9768/0/407
7429
(Rint, 0.0201)
4147/0/200
3645
(Rint, 0.0689)
4507/0/208
3008
(Rint, 0.0281)
4490/0/217
3939
Data/restraints/parameters
Reflens with [I > 2s(I)]
R indices [I > 2s(I)]
R1
wR2
0.0429
0.0871
0.0215
0.0551
0.0832
0.1928
0.0282
0.0746
R indices (all data)
R1
0.0679
0.0263
0.1250
0.0333
wR2
0.1060
0.0582
0.2319
0.0804
Largest diff. Peak and hole
CCDC
0.902 and
0.228 and
2.042 and
0.883 and
0.709 e.Åꢀ3
ꢀ0.640 e.Åꢀ3
ꢀ1.934 e.Åꢀ3
ꢀ0.868 e.Åꢀ3
5
7
8
9
1586206
1586204
1586207
1586203
Empirical formula
M
C38H4N8Pd2S2
889.75
C34H36N8O2Pd2S2
865.65
C36H40N8O2Pd2S2
893.70
C38H44N8O2Pd2S2
921.75
T/K
296(2)
296(2)
296(2)
296(2)
Crystal system
Space group
a(Å)
b(Å)
c(Å)
Monoclinic
C 2/c
17.8636(8)
16.4959(8)
14.5533(6)
90.00
119.4870(10)
90.00
3733.0(3)
4
Monoclinic
P 21/c
21.6585(12)
12.3518(7)
13.9936(7)
90.00
97.671(2)
90.00
3710.1(3)
4
Monoclinic
C 2/c
18.2527(11)
16.3634(10)
14.2858(7)
90.00
116.449(2)
90.00
3820.2(4)
4
Monoclinic
C 2/c
19.1230(13)
16.1995(11)
14.4318(7)
90.00
116.148(3)
90.00
4013.2(4)
4
a
b
g
(º)
(º)
(º)
V(Å3)
Z
Dcalcd (g.cmꢀ3
)
1.583
1.115
1.550
1.123
1.554
1.094
1.526
1.044
m
(mmꢀ1
)
F(000)
1808
1744
1808
1872
Reflections collected
Unique reflections
13101
3554
27613
7446
17014
4648
13073
3658
(Rint, 0.0289)
3554/0/227
3072
(Rint, 0.0408)
7446/0/437
5092
(Rint, 0.0233)
4648/1/228
3522
(Rint, 0.0376)
3658/1/237
2231
Data/restraints/parameters
Reflens with [I > 2s(I)]
R indices [I > 2s(I)]
R1
wR2
0.0354
0.0857
0.0622
0.1651
0.0414
0.1052
0.0953
0.2232
R indices (all data)
R1
0.0431
0.0947
0.0625
0.1482
wR2
0.0941
0.1889
0.1212
0.2630
Largest diff. Peak and hole
0.982 and
1.963 and
1.632 and
3.508 and
ꢀ0.859 e.Åꢀ3
ꢀ0.710 e.Åꢀ3
ꢀ0.872 e.Åꢀ3
ꢀ1.831 e.Åꢀ3
11
12
13
15
CCDC
1559369
1559372
1559370
1586196
Empirical formula
M
C42H52N8 O4Pd2 S2
1009.83
C87H109 N16O8Pd4 S4
2060.74
C46H60N8O4Pd2S2
1065.94
C38H28N8Pd2S2
873.62
T/K
173(2)
173(2)
173(2)
296(2)
Crystal system
Space group
a(Å)
Monoclinic
P21/n
15.3507(2)
14.88128(17)
Triclinic
Monoclinic
P 21/n
15.0869(7)
17.4305(6)
Monoclinic
P 2/c
26.2740(18)
14.3731(9)
P ꢀ1
14.9498(5)
15.3528(5)
b(Å)

A.K. Sandhu et al. / Journal of Organometallic Chemistry 861 (2018) 112e124
117
Table 1 (continued )
1
2
3
4
CCDC
c(Å)
1586210
1586208
1586199
1586205
37.8108(5)
90
96.0707(11)
90
8589.00(19)
8
1.562
20.6048(7)
80.278(3)
79.442(3)
89.394(3)
4581.4(3)
2
18.9673(8)
90
106.299(5)
90
4787.4(4)
4
1.479
15.1744(11)
90.00
92.762(3)
90.00
5723.8(7)
6
1.521
a
b
g
(º)
(º)
(º)
V(Å3)
Z
Dcalcd (g.cmꢀ3
)
1.494
7.586
m
(mmꢀ1
)
0.986
0.889
1.090
F(000)
4128
2110
2192
2616
Reflections collected
Unique reflections
120420
29526
36159
17305
64491
16482
55502
13936
(Rint, 0.0395)
29526/0/1057
23880
(Rint, 0.0436)
17305/0/1084
14565
(Rint, 0.0447)
16482/90/588
12569
(Rint, 0.0393)
13936/3/685
9116
Data/restraints/parameters
Reflens.with [I > 2s(I)]
R indices [I > 2s(I)]
R1
wR2
0.0408
0.0760
0.0414
0.1057
0.0409
0.0885
0.0546
0.1395
R indices (all data)
R1
0.0554
0.0514
0.0679
0.0998
wR2
0.0816
0.1136
0.1074
0.1688
Largest diff. Peak and hole
CCDC
0.969 and
1.990 and
1.026 and
1.919 and
ꢀ1.493 e.Åꢀ3
ꢀ1.325 e.Åꢀ3
ꢀ0.633 e.Åꢀ3
ꢀ0.775 e.Åꢀ3
16
17
18
19
1586197
1586200
1559371
1586209
Empirical formula
M
T/K
C32H28N8Pd2S2
801.56
296(2)
C30H26N6Pd2S4
811.65
296(2)
C46H42N8O4Pd2S2
1047.80
173(2)
C40H44N8O4Pd2S2
977.77
100(2)
Crystal system
Space group
a(Å)
b(Å)
c(Å)
Monoclinic
C 2/c
22.8542(15)
10.8604(7)
14.0090(10)
90.00
116.401(3)
90.00
3114.5(4)
6
Orthorhombic
P b c a
18.2830(5)
15.3470(4)
22.6650(6)
90.00
90.00
90.00
6359.6(3)
8
1.695
Triclinic
P ꢀ1
Triclinic
P ꢀ1
11.8002(5)
13.4399(6)
16.1828(4)
110.070(3)
94.720(3)
97.643(4)
2366.56(16)
2
14.699(4)
15.097(5)
21.085(6)
96.374(3)
103.979(5)
113.931(2)
4033(2)
4
a
b
g
(º)
(º)
(º)
V(Å3)
Z
Dcalcd (g.cmꢀ3
)
1.521
1.090
1.470
0.898
1.610
1.047
m
(mmꢀ1
)
1.425
F(000)
2616
3232
1060
1984
Reflections collected
Unique reflections
55502
13936
52581
12472
29746
15528
24788
13357
(Rint, 0.0393)
13936/3/685
9116
(Rint, 0.0372)
12472/0/379
7816
(Rint, 0.0394)
15528/0/563
11590
(Rint, 0.0753)
13357/6/1002
8877
Data/restraints/parameters
Reflens.with [I > 2s(I)]
R indices [I > 2s(I)]
R1
wR2
0.0546
0.1395
0.0381
0.0888
0.0439
0.1038
0.0559
0.1116
R indices (all data)
R1
0.0998
0.0837
0.0636
0.0940
wR2
0.1688
0.1211
0.1174
0.1261
Largest diff. Peak and hole
1.919 and
1.020 and
1.372 and
0.628 and
ꢀ0.775 e.Åꢀ3
- 0.540 e.Åꢀ3
ꢀ1.602 e.Åꢀ3
ꢀ0.759 e.Åꢀ3
2.2.16. [Pd2(
k
2:C, N-azb)2(
m
-N, S- imzS-NMe)2] 16
6H, CH3). UVevis. data, CH2Cl2, lmax/nm, ε/L molꢀ1cmꢀ1: [10ꢀ4 M]
452 (0.68 ꢂ 104), 333 (1.79 ꢂ 104), 245 (3.98 ꢂ 104). Fluorescence
Compound 16 was prepared by following a method used for
compound 1. Yield 0.024 g, 77%, m.p. 200e202 ꢁC. Anal. found: C,
48.20; H, 3.60; N, 13.85%; C32H28N8Pd2S2 requires: C, 47.95; H, 3.52;
em
ex
data (
l
¼ 652 nm,
l
¼ 270 nm).
max
max
N, 13.98%. IR bands (KBr pellets, cmꢀ1):
n
(C-H), 3154, 3048 m,
(C-H, CH3), 2854 m, 2808 m; (C-
(N¼N) þ
(C-H), 1591w, 1576 m, 1552w, 1523s, 1480s, 1445s,
1413 m, 1396s, 1375s; other bands, 1313 m, 1296s, 1282 m, 1260 m,
1233 m, 1201 m, 1178w, 1165w, 1145s; (C-S), 1104s; other bands,
2.2.17. [Pd2(
k
2:C, N-azb)2(
m
-N, S- tzdS)2] 17
To an orange suspension of [Pd2(
k
2:C, N-azb)2(
m- Cl)2] (0.025 g,
2968 m, 2940 m;
N) þ (C-C) þ
n
n
n
n
d
0.040 mmol) in dichloromethane (5 mL), thiazolidine-2-thione
(0.010 g, 0.080 mmol) was added in presence of Et3N base
(0.5 mL). The color of the reaction mixture became dark red brown
and contents were stirred for 5e6 h. The solution was filtered and
toluene (1 mL) was added and left to evaporate slowly. The dark red
brown crystalline compound was obtained along with the forma-
tion of Et3NHþClꢀ after a period of 4e5 d. Crystalline compound
formed was recrystallized from dichloromethane and methanol.
n
1076s, 1040w, 1017 m, 1002w, 968w, 953w, 938w, 919w, 862w,
826w, 773s, 758s, 721s, 697s, 686s, 651 m, 591 m, 546 m, 525w,
521w, 509w, 496w, 440w, 424w, 412w. 1H NMR (
d, ppm, J, Hz,
CDCl3): 7.62 (m, 6H, H9, 10, 14), 7.43 (m, 6H, H11, 12, 13), 7.13 (m, 4H, H7,
8), 6.69 (d, 2H, J, 5 Hz, H6), 3.36 (s, 2H, C4H), 2.83 (s, 2H, C5H), 1.58 (s,

118
A.K. Sandhu et al. / Journal of Organometallic Chemistry 861 (2018) 112e124
The dark red brown crystals of compound 17 were obtained after a
period of 4e5 days. Yield 0.022 g, 71%, m.p. 192e194 ꢁC. Anal.
found: C, 44.20; H, 3.15; N, 10.42%; C30H26N6Pd2S4 requires: C,
2.2.18. [Pd2(k m-N, S- bzimS-NH)2] 18
2:C, N-deazb)2(
Compound 18 was prepared by following a method used for
compound 7. Yield 0.024 g, 76%, m.p. 222e224 ꢁC. Anal. found: C,
52.60; H, 4.25; N, 10.62%; C46H44N8O4Pd2S2 requires: C, 52.63 H,
44.39; H, 3.23; N, 10.35%. IR bands (KBr pellets, cmꢀ1):
n
(C-H),
3048 m, 2977 m, 2940 m, 2849 m;
H), 1589w, 1574 m, 1551w, 1524s, 1481w, 1456w, 1445w, 1432w,
1392 m; other bands, 1315w, 1300 m, 1253w, 1236 m, 1194 m,
n
(N¼N) þ
n
(C-N) þ
n
(C-C) þ (C-
d
4.22; N, 10.67%. IR bands (KBr pellets, cmꢀ1):
n
(C-H), 2974 m,
(C-H), 1579s, 1553s, 1500 m,
1454 m, 1391 m; other bands, 1361 m, 1322 m, 1257s, 1222 m,
1200 m, 1160 m; other bands, 1131 m; (C-S), 1112 m; other bands,
1044 m, 923w, 876w, 839 m, 802 m, 731w, 699w, 591w, 560 m, 536,
2927 m;
n
(N¼N) þ
n
(C-N) þ
n
(C-C) þ
d
1154w;
n
(C-S), 1104s; other bands, 1109w, 1073w, 1036s, 973s,
n
940 m, 913 m, 860w, 836w, 765s, 711 m, 691s, 589w, 547w, 520w,
437w, 417w. 1H NMR (
d
, ppm, J, Hz, CDCl3): 7.61 (d, 2H, J, 10 Hz, H9),
432s. 1H NMR (
d, ppm, J, Hz, CDCl3): 8.32 (s, 2H, NH), 7.95 (d, 2H, J,
7. 56 (d, 4H, J, 5 Hz, H10, 14), 7.48 (m, 8H, H6, 11, 12, 13), 7.13 (m, 4H, H7,
8), 4.27 (m, 2H, C4H2), 4.07 (m, 2H, C4H2), 3.28 (m, 4H, C5H2).
UVevis. data, CH2Cl2, lmax/nm, ε/L molꢀ1cmꢀ1: [10ꢀ4 M] 451
(0.26 ꢂ 104), 387 (0.41 ꢂ 104), 329 (1.29 ꢂ 104), 248 (2.45 ꢂ 104).
10 Hz, H11), 7.47 (d, 4H, J,10 Hz, H12,16), 7.28 (s, 4H, H4,7), 7.17 (t, 4H, J,
7.5 Hz, H5,6), 7.05 (m, 4H, H13,15), 6.67 (dd, 2H, J, 10 Hz, H10), 6.42 (d,
2H, J, 10 Hz, H8), 4.20 (m, 4H, -OCH2-), 3.91 (m, 4H, -OCH2-), 1.54 (t,
6H, J, 7.5 Hz, CH3), 1.36 (t, 6H, J, 7.5 Hz, CH3). UVevis. data, CH2Cl2,
em
ex
Fluorescence data (
l
¼ 652 nm,
l
¼ 270 nm).
lmax/nm, ε/L molꢀ1cmꢀ1
:
[10ꢀ4 M] 454 (1.05 ꢂ 104), 375
max
max
Table 2
Important bond lengths (Å) and angles (ꢁ) of complexes 1e5, 7e9, 11e13 and 15e19.
Complex No.
Pd-Ca
Pd-Na
Pd-Nb
Pd-Sb
Pd-Pd
C-S
1
1.986(4),
1.978(4)
1.9838(19)
1.985(8)
1.979(2)
1.986(4)
1.958(9),
1.975(7)
1.989(4)
2.070(3),
2.065(3)
2.0676(15)
2.062(6)
2.0601(18)
2.067(3)
2.083(6),
2.055(7)
2.064(3)
2.106(3),
2.111(3)
2.1140(14)
2.085(7)
2.0909(19)
2.110(3)
2.103(7),
2.112(6)
2.096(3)
2.3055(10),
2.3063(11)
2.3082(5)
2.312(2)
2.3097(7)
2.2997(9)
2.306(2),
2.9851(4)
1.734(4),
1.733(4)
1.7287(19)
1.737(9)
1.742(3)
1.735(4)
1.720(9),
1.734(8)
1.735(5)
2
3
4
5
7
2.9408(3)
2.9355(13)
2.9659(5)
2.9428(5)
2.9524(7)
2.276(2)
8
2.3109(11),
2.3110(11)
2.299(4)
2.3108(5),
2.3043(5)
2.3105(8),
2.3029(8)
2.3061(7),
2.3021(7)
2.3088(19)
2.9563(6)
9
11
2.019(15)
1.975(2),
1.979(2)
1.982(3),
1.977(3)
1.978(3),
1.978(3)
1.979(6),
1.985(6)
1.9815(17)
1.972(3),
1.979(3)
1.971(2),
1.984(3)
1.977(6),
1.996(7)
2.064(12)
2.0745(17),
2.0988(18)
2.074(3),
2.094(3)
2.097(2),
2.079(2)
2.061(5)
2.074(13)
2.1086(18),
2.1061(18)
2.118(3),
2.105(3)
2.105(2),
2.102(2)
2.108(5)
2.9596(16)
2.9229(2)
1.759(15)
1.733(2),
1.728(2)
1.729(3),
1.731(3)
1.736(3),
1.739(3)
1.721(6)
12
13
15
2.9128(3)
2.9444(3)
3.0019(9)
16
17
2.0662(14)
2.068(3),
2.070(3)
2.068(2),
2.082(2)
2.085(5),
2.059(6)
2.1197(14)
2.112(3),
2.118(3)
2.139(2),
2.150(2)
2.113(5),
2.119(5)
2.3075(5)
2.3052(8),
2.3130(9)
2.3019(7),
2.2956(8)
2.298(2),
2.294(2)
2.9672(3)
2.9656(3)
1.7270(18)
1.719(3),
1.757(3)
1.729(2),
1.731(2)
1.737(7),
1.739(7)
18
19
3.0633(3)
4.702
Na-Pd-C
Na-Pd-S
Nb-Pd-C
Nb-Pd-S
1
78.73(14),
78.61(15)
78.45(7)
79.5(3)
78.88(8)
78.77(13)
78.5(3),
171.65(9),
171.17(9)
170.85(5)
172.2(2)
172.55(6)
170.66(9)
170.1(2),
173.52(14),
174.10(15)
174.02(7)
174.3(3)
172.29(9)
171.37(13)
176.8(3),
90.61(9),
90.83(9)
92.21(4)
91.72(18)
91.54(6)
93.48(8)
90.76(19),
90.4(2)
2
3
4
5
7
79.1(3)
171.1(2)
175.9(3)
8
9
79.39(16)
79.6(6)
172.10(10)
171.9(4)
173.73(16)
174.6(5)
91.21(10)
91.6(3)
11
78.95(8),
78.81(8)
78.97(12),
78.95(12)
79.35(10),
78.56(10)
78.6(3)
78.57(7)
78.86(13),
78.47(13)
79.05(10),
78.82(11)
79.6(2),
172.34(5),
168.09(5)
171.26(8),
169.15(7)
170.05(7),
171.23(6)
171.67(16)
171.69(4)
170.83(8),
171.76(8)
169.49(6),
167.79(7)
168.00(15),
167.87(17)
172.89(8),
177.20(8)
174.37(12),
176.93(12)
179.40(10),
177.44(10)
175.4(2)
172.34(6)
176.34(12),
175.53(13)
176.80(9),
178.05(11)
171.2(2),
90.78(5),
91.44(5)
90.49(7),
91.67(8)
88.96(7),
89.52(6)
89.64(14)
92.76(4)
90.65(8),
90.45(8)
88.84(6),
89.03(7)
93.44(15),
94.93(16)
12
13
15
16
17
18
19
79.2(3)
170.0(2)
a
Azobenzenes.
Thio-ligands.
b

A.K. Sandhu et al. / Journal of Organometallic Chemistry 861 (2018) 112e124
119
Fig. 3. Molecular structure of [Pd2(
(Molecular structure of 8e9, see Supporting Information).
k m-N, S-imdzS-NMe)2] 7
2:C, N-mazb)2(
2H, H6), 6.66 (d, 4H, J, 10 Hz, H11,13), 6.43 (d, 2H, J, 5 Hz, H8), 4.09
(m, 12H, C4H2, C5H2, -OCH2-), 1.58 (s, 12H, CH3), 1.49 (t, 3H, J,
Fig. 1. Molecular structure of [Pd2(k m-N, S-imdzS-NH)2] 1∙2H2O (1)
2:C, N-azb)2(
(Disordered oxygens O1W and O2W of lattice water are omitted for clarity).
7.5 Hz, CH3), 1.42 (t, 3H, J, 7.5 Hz, CH3). UVevis. data, CH2Cl2, lmax
/
nm, ε/L molꢀ1cmꢀ1: [10ꢀ4 M] 451 (1.39 ꢂ 104), 374 (1.51 ꢂ 104),
(2.52 ꢂ 104).
Fluorescence
data
(
l
¼ 652 nm,
em
(1.09 ꢂ 104), 302 (1.76 ꢂ 104), 251 (2.36 ꢂ 104). Fluorescence data
258
max
ex
em
ex
l
¼ 275 nm).
max
(l
¼ 653 nm,
l
¼ 275 nm.
max
max
2.3. X-ray crystallography
2.2.19. [Pd2(k m-N, S- imzS-NMe)2] 19
2:C, N-deazb)2(
Compound 19 was prepared by a method used for compound 1.
Yield 0.022 g, 75%, m.p. 218e220 ꢁC. Anal. found: C, 49.10; H, 4.51;
N, 11.38%; C40H44N8O4Pd2S2 requires: C,49.13; H, 4.54; N, 11.46%.
The X-ray data of the complexes (1e5, 7e9, 15e17, 19) were
collected on a Bruker's Apex-II CCD diffractometer using Mo K
¼ 0.71069 Å) at room temperature except for the complex 19,
a
(l
IR bands (KBr pellets, cmꢀ1):
2925 m; (C-N) þ
(N¼N) þ
n
(C-H), 3177 m, 3060 m, 2976 m,
(C-C) þ (C-H), 1576s, 1552 m,
which is done at 100 K. The data were processed by SAINT and
Lorentz and polarization effects and empirical absorption correc-
tions were applied using SADABS from Bruker. The structures were
solved by direct methods, using SIR-92 [38] and refined by full-
matrix least squares refinement methods based on F2, using
SHELX-2015 [39]. The hydrogen atoms of water molecules were
located from the difference Fourier synthesis and were refined
isotropically with distance of 0.82(0.02) Å with Uiso values 1.2 times
that of their carrier oxygen atoms. All non-hydrogen atoms were
refined anisotropically. All hydrogen atoms were fixed geometri-
cally with their Uiso values 1.2 times of methane, methylene and
phenylene carbon atoms and 1.5 times that of methyl carbon atoms
The hydrogens of the disordered water molecules in1, could not be
located. Complex 7and 15 showed disorder in some aromatic car-
bons and the C of the terminal methyl group, which could not be
resolved. These atoms were refined with constraints.Some struc-
tures showed residual peaks (~1e2 eÅ3) very close to the Pd(II) ion
which may be due to the series termination error because of the
heavy metal. All calculations were performed using Wingx package
[40].
n
n
n
d
1500 m, 1432 m, 1390 m; other bands, 1363 m, 1320 m, 1246s,
1201s, 1159 m; (C-S), 1112 m; other bands, 1044s, 926w, 835 m,
799w, 793 m, 706w, 590w, 535 m, 434w. 1H NMR (
, ppm, J, Hz,
CDCl3): 7.45 (d, 2H, J, 10 Hz, H9), 7.33 (d, 4H, J, 10 Hz, H10,14), 7.14 (d,
n
d
The data for complexes 11e13 and 18 were collected using
Agilent, Eos, Gemini and Rigaku Oxford diffraction diffractometer
equipped with a graphite monochromator and Mo-K
a radiation
(
l
¼ 0.71073 Å, for 11, 13 and 18, or Cu- K radiation; ¼ 1.54184 Å,
a
l
for 12). The unit cell dimensions and intensity data were
measured at 173(2) (11e13 and 18). The data were processed with
CrysAlisPro (data collection, cell refinement), CrysAlisRED (data
reduction). The structure was solved by direct methods using the
program SHELXS-97, SIR-92 or SHELXL-2015 (13, 19) and SUPER-
FLIP and refined by full-matrix least-squares techniques against F2
using SHELXL-97 or SHELXL-2012, SHELXL-2014 and SHELXL-2015
[39,41e46].
Fig. 2. Molecular structure of [Pd2(
(Molecular structures of 3e5, see Supporting Information).
k m-N, S-imdzS-NMe)2] 2
2:C, N-azb)2(

120
A.K. Sandhu et al. / Journal of Organometallic Chemistry 861 (2018) 112e124
Fig. 4. Molecular structure of [Pd2(k m-N, S-imdzS-NEt)2] 11
2:C, N-deazb)2(
{Molecular structures, 12 and 13 see SI}.
Fig. 5. Molecular structure of complex [Pd2(k m-N, S-bzimS-NH)2] 15.
2:C, N-azb)2(
3. Result and discussion
preferential C-H bond activation of methoxy phenyl ring occurred
instead of phenyl ring. Complexes 1e14 have N, S-bridged imida-
zolidine-2-thiolate ligands while complexes 15e19 have similarly
bonded other anionic thio-lgands shown in Chart 3. Complexes are
soluble in the organic solvents such as chloroform, dichloro-
methane and dimethylsulfoxide.
3.1. Synthetic comments and IR spectroscopy
Cyclopalladated precursors, [Pd2(
k
2:C, N-azb)2(
m
-
Cl)2],
[Pd2( -Cl)2] and [Pd2(
k
2:C, N-mazb)2(
m
k
2:C, N-deazb)2(
-Cl)2] were
m
prepared initially, which were then reacted with the thio-ligands
(Chart 2) in the presence of Et3N base and the color change
occurred from a light yellow solution to red-brown. The Et3N base
deprotonated the thio-ligands (N-H protons) with the formation of
Et3NHþClꢀ salt. The addition of toluene or methanol assisted in the
formation of crystals. The palladium activated C-H bond of one
phenyl ring of azobenzene, or p-ethoxy phenyl ring of 4, 40-dieth-
oxyazobenzene, but in case of p-methoxy azobenzene, the
A brief commentary on the IR spectral data of complexes is
provided here. The thio-lgands, 1,3-imidazolidine-2-thiones
(imdzSH-NR; R ¼ Me, Et, Prn, Bun, Ph) showed the
n(NeH)
stretching bands in the region, 3188 to 3204 cmꢀ1, which dis-
appeared in their complexes 2e14, supporting that the thio-ligands
are coordinating as anionic ligands. The
and imzSH-NMe ligands at 3138 and 3106 cmꢀ1 respectively dis-
appeared in their complexes, [Pd2( -N, S- tzdS)2] 17,
2:C, N-azb)2(
n(NeH) bands of free tzdSH
k
m

A.K. Sandhu et al. / Journal of Organometallic Chemistry 861 (2018) 112e124
121
in Table 1 and important bond lengths and angles given in Table 2.
Among the nineteen complexes, crystal structures of 16 complexes
(except 6, 10 and 14) have been obtained and only representative
structures are discussed below, while others are placed in
Supporting Information.
The molecular structure of azobenzene (azbH) complex,
[Pd2(
azobenzene binds in C, N-chelation mode to one Pd(II) ion forming
Pd(
2:C, N-azb) moiety (Fig. 1). Two such moieties are then con-
k m-N, S-imdzS-NH)2] 1 is shown in Fig. 1. Each
2:C, N-azb)2(
k
nected with two N, S-bridging imidazolidine-2-thiolates (imdzS-
NH-). The trans bond angles, {C-Pd-N,173.52(14),174.10(15)ꢁ; N-Pd-
S, 171.65(9), 171.17(9)ꢁ} suggest that the geometry of each Pd metal
is distorted square planar (Table 2). The C-Pd-N bite angle of angle
of ca. 79ꢁ was the shortest bond angle of Pd metal center.The metal-
ligand bond distances in complex 1 {Pd-C, 1.986(4), 1.978(4) Å; Pd-
S, 2.3055(10), 2.3063(11) Å and Pd-N, 2.070(3), 2.065(3), 2.106(3),
2.111(3) Å} are less than the sum of covalent radii of Pd and donor
atoms {Pd-C, 2.10e2.22 Å; Pd-S, 2.35e2.47 Å and Pd-N,
2.08e2.20 Å} which suggest shortening of the bonds on complex-
ation [47].
Fig. 6. Molecular structure of complex [Pd2(k m-N, S-imzS-NMe)2] 16.
2:C, N-azb)2(
It was noted that Pd-N(azobenzene) bond distance was marginally
shorter than Pd-N(thio-ligand) bond distance. The Pd∙∙∙Pd bond
distance of 2.9851(4) Å is less than the sum of van der Waals radii of
Pd atoms (3.20 Å), which is indicative of close metal-metal contact
[47]. The Pd-donor atom bond distances are comparable to the
literature bond distances {Pd-C, 1.990(2); Pd-S, 2.3052(6),
2.3781(7), 2.7113(8), Pd-N, 2.0353(19) Å}, as for example, noted in
complex,
[Pd(
k
2-C,N-azb)(
k
3-S,S,S-L)][PF6]
{L ¼ 1,
4,
7-
trithiocyclononane} [48]. Complex 1 has disordered oxygens O1W
and O2W of water in the crystal lattice (Fig. 1). The molecular
structures of complexes 2e5 with N-R substituents of imdzS-NR
moiety (R ¼ Me to Bun) made marginal effect on the bond dis-
tances/bond angles (Table 2) and structures are similar to that of
complex 1. Thus the molecular structure of representative complex
2 (R ¼ Me) is shown in Fig. 2 and those of others are placed in SI.
Complexes 7e9 have one methoxy substitution in phenyl group
of azobenzene (mazbH). The crystal structures of these three
complexes have shown that it is methoxy substituted ring which is
metallated and not the phenyl ring. The thio-ligands are N, S-
bridging as was the case for dinuclear complexes, 1e5. Molecular
Fig. 7. Molecular structure of complex [Pd2(
(See SI for molecular structures of 18 and 19).
k m-N, S-tzdS)2] 17
2:C, N-azb)2(
structure of a representative complex, namely, [Pd2(
mazb)2( -N, S-imdzS-NMe)2] 7 is shown in Fig. 3. Complexes 11e13
k
2:C, N-
m
have ethoxy substitution in both the azobenzene rings, but one ring
per metal is metallated as found in complex 1. Molecular structure
of representative complex 11 is shown in Fig. 4. The unit cell has
two crystallographically independent dimeric molecules in the
asymmetric unit with marginal differences in the bond parameters.
The bond distances/angles are similar to those found for complexes
1e5 or 7e9.
[Pd2(
deazb)2(
nation by the thio-ligands as anions. The free ligand (imdzSH-NR,
R ¼ H) with two N-H hydrogens showed the (NeH) band at
3247 cmꢀ1 which appeared at 3230 cmꢀ1 in its complex 1. The
presence of water in complex 1 is shown by an intense (OeH) band
at 3418 cmꢀ1. Finally, the
(NeH) stretching band of free bzimSH-
NH (at 3153 cmꢀ1) shifted to 3118 cmꢀ1 and 3200 cmꢀ1 in its
complexes, [Pd2( -N, S- bzimS-NH)2] 15 and
2:C, N-azb)2(
[Pd2( -N, S- bzimS-NH)2] 18, respectively. The free
2:C, N-deazb)2(
(C-S)
k
2:C, N-azb)2(
m-N, S- imzS-NMe)2] 16 and [Pd2(k
2:C, N-
m-N, S- imzS-NMe)2] 19, which again supported coordi-
n
n
The thio-ligands, bzimSH-NH, imzSH-NMe and tzdSH have
n
formed complexes, [Pd2(
15; imzS-NMe 16; tzdS 17), and [Pd2(
k
2:C, N-azb)2(
m
k
-N, S-L)2] (L ¼ bzimS-NH
2:C, N-deazb)2(N, S-L)2]
k
m
(L ¼ bzimS-NH 18; imzS-NMe 19), whose crystal structures have
shown N, S-bridged anioinic ligands with chelating azobenzenes as
was the case for imidazolidine-2-thiones. The unit cell of complex
15 has two crystallographically independent molecules in the
asymmetric unit (Fig. 5). Similarly, molecular structures of com-
plexes 16 and 17 are shown in Figs. 6 and 7 respectively.
k
m
thio-ligands showed another diagnostic band due to
n
stretching frequency in the region,1150 to 1205 cmꢀ1 which shifted
to low energy region, 1104 to 1178 cmꢀ1, supporting coordination
through S-donor atom of the thio-ligands in their complexes (see
experimental and Supporting Information).
3.3. Molecular spectroscopy (NMR, UVevisible, fluorescence)
3.2. Molecular structures
Proton NMR spectra of complexes 1e19 were recorded in CHCl3-
D and the NMR data are listed in the experimental section (see
Charts 4 and 5 for numbering; Tables S2eSI). The free imdzSH-NH
Complexes crystallized in triclinic (P-1, 12, 18 and 19), mono-
clinic (P21/n, 1, 11, 13; C 2/c, 2e5, 8, 9 and 16; P21/c, 7; P 2/c, 15) and
orthorhombic (Pbca, 17) crystal systems. The crystal data are given
ligand showed a broad signal at
d 10.0 ppm due to NH protons,

122
A.K. Sandhu et al. / Journal of Organometallic Chemistry 861 (2018) 112e124
5
4
5
4
N
N
S
5
4
S
3
1
imdzSH-NH (1)
3
1
3
N
1
N
NMe
imdzS-NMe (2, 7)
N
_
S
=
N
S
2
2
NR
Pd
N
Pd
2
imdzS-NEt (3, 8, 11)
imdzSH-NPrn (4, 9, 12)
imdzSH-NBun (5, 10, 13
_
_
C
C
C
S
S
N
S
-
-
imzS-Me
16, 19
tzdS
17
mdzSH-NPh (6, 14)
1- 14
7
6
OC2H5
11
12
14
11 12
8
10
13
13
10
=
9
N
14
14
9
N
N
N
N
9
N
N
13
12
8
8
10
7
H3CO
11
6
7
C2H5O
6
-
-
p-mazb
7-10
-
1, 2-6, 16, 17
azb
deazb
11-14, 19
Chart 4. Numbering of various atoms for NMR.
azbꢀ protons in complex are assigned at
d
¼ 7.50 (H6) (doublet),
4
H
7.65 (m, H9, H10, H14), 7.45 (m, H11, H12, H13) and 7.10 (m, H7, H8). The
N-substituted imidazolidine-2-thiolate complexes, namely, 2, 3, 4,
5 and 6, did not show eNH proton signals and thus confirmed that
the thio-ligands coordinate as monoanions after deprotonation of
eNH moiety. Further, the C4,5H2 proton signals of these complexes
N
N
N3
S
S
5
2
S
N
=
6
S
Pd
Pd
1 N
H
7
C
C
N
-
N
bzimS-NH
15, 18
appeared as a set of multiplets in the range
relatively upfield as compared to the free ligands (see SI). The -N-
CH2-, -CH2-, CH3 protons also appeared as multiplets at 3.20, 3.24,
d 3.20e3.82 ppm at
15, 18
OC2H5
9
8
14
13
d
10
12
15
1.32, 1.40 and 0.85e1.58 ppm; the azobenzene anion proton signals
have pattern similar to that of complex 1. Dinuclear complexes
7e14 have similar NMR pattern (see Chart 4).
16
11
11
16
N
N
N
N
10
-
15
14
deazb
=
N
C
9
-
azb
The free imzSH-Me ligand shows a broad proton signal at
12
C2H5O
8
13
d
11.3 ppm due to NH protons, and its absence in complexes 16 and
19 confirmed the deprotonation of the thio-ligands. The C4H and
18
15
Chart 5. Numbering scheme of bzimS-NH- complexes.
C5H protons of free imzSH-Me ligand (see SI) moved to high-field at
d
2.83e4.09 ppm in its complexes. The N-methyl protons also
shifted upfield at
1.42e1.58 ppm in complexes. Finally, the 1H
NMR spectrum of free thiazolidine-2-thione (tzdSH) ligand showed
a broad signal at 7.61 ppm due to the NH protons and its absence
d
d
in complex 17 showed deprotonation of eNH moiety. The signals
due to C4/5H protons of free tzdSH ligand appear as a triplet
centered at
d
d
3.57 ppm which shifted to the region,
3.28e4.27 ppm in its complex. Various signals due to azbꢀ and
deazbꢀ anions are also listed in experimental section
(Tables S2eSI). The 1H NMR patterns of complexes 15 and 18 are
similar to the trends of thio-ligands as discussed above (Chart 5).
The electronic absorption spectra of complexes 2, 3, and 7e14
have shown the absorption bands in the region 242e280 nm which
are assigned to the
bands in the region 308e387 nm incorporate absorption due to
azobenzenes/thio-ligands involving n/ * transitions from N/S
p/p* transitions. The electronic absorption
Fig. 8. Fluorescence spectra of complexes 2e6.
p
donor atoms. Finally, the bands in the region 443e459 nm are
attributed to LMCT/DMSO‑d6 (1A1g/1A2g) transitions [49]. Molar
absorptivity (ε) appears to vary with the nature of a thio-ligand and
the type of azobenzene used (see SI; Table S1). In general the imi-
dazolidine/imidazoline based thio-ligands and the presence of
double ethoxy substitution of phenyl rings of azobenzenes lowered
ε values. A rigorous correlation is not possible. Complexes 18 and 19
have less molar absorptivity as compared to that of other
which shifted to the low energy region at
d
8.04 ppm in complex 1
(Chart 4). The C4,5H2 protons of free imdzSH-NH ligand appeared as
a singlet at
signal shifted to low field at
signal shifted to high field at
different chemical environments. The signals due to the anionic
d
3.59 ppm, however, in its complex the C4H proton
3.70e3.86 ppm while C5H proton
3.32e3.44 ppm, as these protons face
d
d

A.K. Sandhu et al. / Journal of Organometallic Chemistry 861 (2018) 112e124
123
+
N
S
(1)
imdzS-NH
N
S
N
NMe
N
_
NR
=
S
N
n (9)
_
imdzS -NPr
imdzS-NPh
Pd
Pd
N
S
S
(6, 14)
C
C
16
N
OC2H5
[M]+
1, 6, 9, 14, 16
N
N
N
N
N
N
C
N =
H3CO
C2H5O
Azobenzene
p-methoxyazobenzene
4, 4'-diethoxyazobenzene
1, 6, 16
9
14
Chart 6. Molecular ion formation by complexes 1, 6, 9, 14, 16.
homologous complexes, namely, 11, 12, 13 and 14, containing
substituted imidazolidines ((See SI; Fig. S5.1 to S5.7).
diethoxyazobenzene complexes (see SI; Fig. S6.1-6.5).
The fluorescence spectra of complexes 2e6 (Fig. 8) showed
intense emission in the visible region covering a wide spectral
range, 600e780 nm corresponding to the excitation in the range
270e277 nm. In literature, similar type of fluorescence behavior
has been observed [18,28e32]. Complexes 3 and 15 have displayed
high fluoresecence intensity among other complexes containing
azobenzene as a co-ligand. Among complexes containing p-
methoxyazobenzene, complex 10 has shown high fluorescence
intensity. Similarly, complex 14 has shown high fluorescence in-
tensity as compared to that of other complexes of 4, 40-
3.4. ESI-mass spectral studies
ESI-mass spectral data of complexes (1e5, 8, 10e13, 15, 17 and
18) have been obtained. Complexes 1, 6, 9, 14 and 16 have shown
the formation of the molecular ion species (Chart 6), [M]þ {1: m/z
obsd. 775.98, calcd. 775.98; 6: m/z obsd. 928.04, calcd. 928.06; 9: m/
z obsd. 920.62, calcd. 920.11; 14: m/z obsd. 1104.13, calcd. 1104.16
and 16: m/z obsd. 799.99, calcd. 799.99} in conformity with the
molecular structures solved by X-ray crystallography [50]. These
complexes as well as other complexes also formed rearranged
H
N
+
C
N
N
NMe
N
_
S
=
S
N
NR
N
Pd
N
H
_
S
S
S
18
19
1, 3-6, 9, 12-14, 18, 19
1, 3-6, 9, 12-14
imdzS-NBun (5, 13)
imdzS-NH
(1)
imdzS-NEt (3)
imdzS-NPh
(6, 14)
imdzS-NPrn
(4, 9, 12)
OC2H5
N
N
N
N
N
N
C
N
=
H3CO
C2H5O
Azobenzene
p-methoxyazobenzene
4, 4'-diethoxyazobenzene
12-14, 18, 19
1, 3 - 6
9
Chart 7. Formation of rearranged species of various complexes.

124
A.K. Sandhu et al. / Journal of Organometallic Chemistry 861 (2018) 112e124
2427e2440.
species as shown in Chart 7 (see SI; Fig. S7.1-S7.16).
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In our previous investigation pyridine-2-thione (pySH) and py-
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azobenzenes [Pd2(
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m
-Cl)2] formed N, S-bridged
dinuclear complexes, [Pd(
k
2:C, N- azb/mazb)2(
m-N, S-pyS/mpyS)2]
[34]. Here functional groups, -N(H)-C(¼S)- and eN(H)-C(¼S)-
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m-N, S-L)2]
(L0 ¼ azb, mazb, deazb; L ¼ anionic N, S- thio-ligand), is similar and
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Financial assistance from University Grants Commission (UGC)
Major Project F. No. 34-307/2008 (SR), under UGC(BSR) scheme and
the Council of Scientific and Industrial Research (CSIR), New Delhi,
for Emeritus Grant [21(0904)/12-EMR-II] to Tarlok Singh Lobana,
New Delhi are gratefully acknowledged.
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