Pyrrole-2-carbaldehyde thiosemicarbazonates of Nickel(II) and palladium(II): Synthesis, structure, and spectroscopy

Article abstract of DOI:10.1002/zaac.201200012

Complexes of pyrrole-2-carbaldehyde thiosemicarbazones, [(C ₄H₄N⁴)(H)C²=N³-N ²(H)-C¹(=S)-N¹HR; R = Ph, H₂L ¹; Me, H₂L²; H, H₂L³] with nickel(II) and palladium(II) are described. The reaction of nickel(II) acetate with H₂L¹ in methanol in 1:1 molar ratio yielded a complex of composition, [Ni(I²-N³,S-HL ¹)₂] (1). Likewise reaction of NiCl₂ with H₂L² in 1:1 molar ratio in acetonitrile in the presence of triethylamine base followed by the addition of pyridine did not yield the anticipated [Ni(I³-N⁴,N³,S-L ²)(py)] complex, moreover a bis-square-planar complex, [Ni(I²-N³,S-HL²)₂] (2) was formed. However, in the presence of bipyridine (bipy), it yielded the addition product, [Ni(I²-N³,S-HL²) ₂(I²-N, N-bipy)] (3). Reaction of PdCl ₂(I²-P, P-PPh₂-CH₂-PPh ₂) with H₂L³ in toluene in the presence of triethylamine has yielded a complex of stoichiometry, [Pd(I³- N⁴,N³,S-L³)(I¹-P-PPh ₂-CH₂-P(O)Ph₂] (4). The ligands (HL ¹)^- and (HL²)^- are chelating to Ni^II metal atom as anions binding through N³,S-donor atoms with pendant pyrrole groups, and (L³)^2- is chelating to the Pd^II metal atom as dianion through N⁴,N ³,S-donor atoms (pyrrole is N⁴-bonded). Fourth site in 4 is bonded to one P-donor atom of PPh₂-CH₂-P(O)Ph ₂, whose pendant -PPh₂ group involves auto oxidation to -P(O)PPh₂ during reaction. These complexes were characterized using analytical data, IR, NMR (¹H, ³¹P) spectroscopy and X-ray crystallography. Complexes 1, 2, and 4 have square-planar arrangement, whereas complex 3 is octahedral. Copyright

Full text of DOI:10.1002/zaac.201200012

ARTICLE
DOI: 10.1002/zaac.201200012
Pyrrole-2-carbaldehyde Thiosemicarbazonates of Nickel(II) and
Palladium(II): Synthesis, Structure, and Spectroscopy
Tarlok S. Lobana,*[a] Poonam Kumari,[a] Gagandeep Bawa,[a] Geeta Hundal,[a]
Ray J. Butcher,[b] Francisco J. Fernandez,[c] Jerry P. Jasinski,[d] and James A. Golen[d]
Keywords: Thiosemicarbazone; Nickel; Palladium; Bis(diphenylphosphanyl)methane; Bipyridine
Abstract. Complexes of pyrrole-2-carbaldehyde thiosemicarbazones, PPh2–CH2–PPh2) with H2L3 in toluene in the presence of triethylamine
has yielded a complex of stoichiometry, [Pd(κ3-N4,N3,S–L3)(κ1-P–
PPh2–CH2–P(O)Ph2] (4). The ligands (HL1)– and (HL2)– are chelating
to NiII metal atom as anions binding through N3,S-donor atoms with
pendant pyrrole groups, and (L3)2– is chelating to the PdII metal atom
as dianion through N4,N3,S-donor atoms (pyrrole is N4-bonded).
Fourth site in 4 is bonded to one P-donor atom of PPh2–CH2–P(O)
Ph2, whose pendant –PPh2 group involves auto oxidation to –P(O)
PPh2 during reaction. These complexes were characterized using ana-
lytical data, IR, NMR (1H, 31P) spectroscopy and X-ray crystallogra-
phy. Complexes 1, 2, and 4 have square-planar arrangement, whereas
complex 3 is octahedral.
[(C4H4N4)(H)C2=N3–N2(H)–C1(=S)–N1HR; R = Ph, H2L1; Me, H2L2;
H, H2L3] with nickel(II) and palladium(II) are described. The reaction
of nickel(II) acetate with H2L1 in methanol in 1:1 molar ratio yielded
a complex of composition, [Ni(κ2-N3,S-HL1)2] (1). Likewise reaction
of NiCl2 with H2L2 in 1:1 molar ratio in acetonitrile in the presence
of triethylamine base followed by the addition of pyridine did not yield
the anticipated [Ni(κ3-N4,N3,S-L2)(py)] complex, moreover a bis-
square-planar complex, [Ni(κ2-N3,S-HL2)2] (2) was formed. However,
in the presence of bipyridine (bipy), it yielded the addition product,
[Ni(κ2-N3,S-HL2)2(κ2-N,N-bipy)] (3). Reaction of PdCl2(κ2-P,P–
ring remained pendant in modes I–IV, whereas it is coordinat-
ing in mode V.
Introduction
Thiosemicarbazones [R1R2C2=N3–N2(H)–C1(=S)–N1HR3]
are an important class of thio-ligands with biological rele-
vance,[1–3] they display variable bonding modes, which lead to
different metal-organic frameworks, metal-sensing properties,
and other analytical applications.[4–6] Pyrrole-2-carbaldehyde
thiosemicarbazones (H2L) have shown different bonding
modes. Modes I and II are observed in mononuclear ZnII, CdII,
and dinuclear CuI, AgI, and HgII complexes.[7] In these com-
plexes the thio ligands are neutral. The uninegative thio ligands
exhibit modes III and IV in mononuclear NiII, PdII, AuIII, or
HgII complexes.[8] Mode V is observed in square planar PdII
complexes, where thio ligands are dinegative.[9] The pyrrole
It has to be noted here that as mentioned above, NiII and
PdII metal atoms have formed bis square-planar complexes in
the absence of any co-ligand.[8] PdII has formed a square-
planar complex of type, [PdL(PPh3)], in the presence of PPh3
co-ligand.[9] However, there is no report of a NiII complex with
pyrrole-2-carabaldehyde thiosemicarbazones in the presence of
either P-donor or N-donor co-ligands.[5] In this paper, NiII and
PdII coordination chemistry with pyrrole-2-carbaldehyde thio-
semicarbazones in the presence of P-donor (Ph2PCH2PPh2,
dppm) and N-donor (pyridine, bipyridine) co-ligands was pur-
sued.
* Prof. Dr. T. S. Lobana
E-Mail: tarlokslobana@yahoo.co.in
[a] Department of Chemistry
Guru Nanak Dev University
Amritsar-143 005, India
[b] Department of Chemistry
Howard University
Washington DC 20059, USA
[c] Department of Structural and Quantitative Biology
Center for Biological Research (CIB–CSIC)
Ramiro de Maeztu 9
28040 Madrid, Spain
[d] Department of Chemistry
Keene State College
Experimental Section
229 Main Street
Keene, NH 03435–2001, USA
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201200012 or from the au-
thor.
Materials and Techniques: Metal salts Ni(OAc)2, PdCl2, NiCl2,
thiosemicarbazide, N-methyl thiosemicarbazide, N-phenyl thiosem-
icarbazide, pyrrole-2-carbaldehyde, bis(diphenyl-phosphanyl)methane,
804
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 638, (5), 804–810

Pyrrole-2-carbaldehyde Thiosemicarbazonates of Nickel(II) and Palladium(II)
pyridine, bipyridine, and Et3N were purchased from Sigma–Aldrich ene was added H2L3 (0.02, 0.09 mmol) followed by Et3N (2 mL) and
Ltd. The ligands H2L1, H2L2, and H2L3 were synthesized by conven-
solution stirred for 4 h. The Et3NH+Cl– salt separated at the bottom.
tional procedures.[10] C, H, and N analyses were carried out with a It was filtered to remove Et3NH+Cl– and allowed to evaporate at room
thermoelectron FLASHEA1112 analyzer. The melting points were de- temperature which led to the formation of bright red crystals. Yield
termined with a Gallenkamp electrically heated apparatus. The IR 70%; M.p. 160–162 °C. C31H28N4OP2PdS·C7H8: calcd. C 59.6; H
spectra were recorded using KBr pellets with a Varian 666-IR FT-IR
3.70; N 7.32%. found: C 59.76; H 4.70; N 7.47%. IR (KBr, selected
absorption bands): ν(N–H) 3360 s, 3307 s; ν(C=N) + δNH2 + ν(C=C)
spectrometer. The magnetic susceptibility of complex 3 was recorded
with Magnetic Susceptibility balance by Johnson Matthey, Catalytic 1643 s, 1556 s; ν(P–CPh) 1099 s, ν(C–S) 784 s cm–1. 1H NMR
Systems Division Equipment. The 1H NMR spectra were recorded
with a JEOL AL300 FT spectrometer at 300 MHz in CDCl3 with TMS
as the internal reference. The 31P NMR spectra were recorded at
(CDCl3): δ = 7.96–7.60 (m, 8 H, o-H), 7.46–7.24 (m, 13 H, m-and p-
H and C4H), 6.29 (q, 1 H, C5H), 6.49 (t, 1 H, C6H), 6.85 (t, 1 H,
C7H), 7.08 (d, 1 H, C8H), 5.79 (m, 1 H, C5H), 5.62 (s, 1 H, C2H),
121.5 MHz with P(OMe)3 as the external reference taken as zero posi- 4.60 (s, 2 H, -NH2), 3.50 (t, 2 H, CH2). 31P NMR (CDCl3): δ = –90.0,
tion.
–83.4 ppm; coordination shift, Δδ(δcomplex–δdppm) = 40.2.
Synthesis of Complexes
Ligands Used
[Ni(κ2-N3,S-HL1)2] (1): To a colorless solution of H2L1 (0.200 mmol)
in methanol (10 mL) was added solid Ni(OAc)2 (0.100 mmol). The
color of the solution changed to dark red and it was stirred for about
4 h. The clear solution after filtration was left for crystallization. Slow
evaporation of the solution at room temperature gave brown crystals.
Yield 71%; M.p. 226–230 °C. C24H22N8NiS2: calcd. C 52.81; H 4.03;
N 20.54%; found: C 52.97; H 4.27; N 20.62%. IR (KBr, selected
absorption bands): ν(N1–H) 3428 br; ν(N4–H) 3316 s; ν(C–H) 3061
m, 2995m; ν(C=N) + ν(C=C) 1598 s, 1542 s; ν(C–N) 1020 s; ν(C–S)
Pyrrole-2-carbaldehyde-N-phenyl Thiosemicarbazone (H2L1):
Color: brown (67%, M.p. 163–165 °C). IR (KBr, selected absorption
bands): ν(N1–H) 3354br; ν(N2–H) 3254 m; ν(N4–H) 3202 br; ν(C–H)
3007 m, 2975 m; ν(C=N) + ν(C=C) 1614 s, 1545 s; ν(C–N) 1089 s,
1
1035 s, 914 s; ν(C = S) 795 s cm–1. H NMR (CDCl3): δ = 9.38 (s, 1
H, N2H), 9.04 (s, 2 H, N4H + N1H), 7.71 (s, 1 H, C2H), 7.61 (d, 2 H,
o-H), 7.29 (m, 3 H, m- and p- H), 6.94 (t, 1 H, C6H), 6.56 (s, 1 H,
C4H), 6.29 (q, 1 H, C5H) ppm.
1
750s cm–1. H NMR (CDCl3): δ = 10.78 (s, 2 H, N4H), 7.41 (s, 2 H,
Pyrrole-2-carbaldehyde-N-methyl Thiosemicarbazone (H2L2):
Color: brown (83%, M.p. 175–177 °C). IR (KBr, selected absorption
bands): ν(N1–H) 3393br; ν(N2–H) 3242br; ν(N4–H) 3178br; ν(C–H)
2995 m, 2935 m, 2902 w; ν(C=N) + ν(C=C) 1543 s, 1514 s; ν(C–N)
1082 s, 1048 s, 927 s; ν(C=S) 800 s cm–1. 1H NMR (CDCl3): δ =
10.42 (1 H, sb, N2H), 10.24 (1 H, db, N4H), 8.06 (1 H, sb, N1H), 7.76
(s, 1 H, C2H), 6.87 (s, 1 H, C6H), 6.43 (s, 1 H, C4H), 6.19 (d, 1 H,
C5H), 3.12 (d, 3 H, CH3) ppm.
C2H), 7.36 (m, 4 H, o-H), 7.26 (m, 6 H, p- and m-H), 6.72 (2 H, sb,
C6H), 6.63 (2 H, sb, N1H), 6.53 (m, 2 H, C4H), 6.17 (m, 2 H, C5H)
ppm.
[Ni(κ2-N3,S-HL2)2] (2): To a light green solution of NiCl2·6H2O salt
(0.025 g, 0.105 mmol) in CH3CN was added solid H2L2 (0.018 g,
0.105 mmol) followed by the addition of Et3N base (1 mL) and stirred
for 6h. A brown colored compound got separated during stirring along
with the formation of Et3NH+Cl– salt. This compound was filtered and
dried. Analytical data supported the formation of complex of stoichi-
ometry, {NiL2} (Anal. for C7H8NiN4S: calcd. C 35.19; H 3.35; N
23.46%; found: C 34.93; H 4.31; N 23.84%). To a suspension of
{NiL2} (0.025 g, 0.111 mmol) in acetonitrile was added pyridine
(0.5 mL) and stirred until a clear solution was obtained. The slow
evaporation of this solution gave black crystals. Yield 75%; M.p. 240–
242 °C. C14H18N8NiS2: calcd. C 39.89; H 4.27; N 26.59%. found: C
40.12; H 4.22; N 26.78%. IR (KBr, selected absorption bands): ν(N1–
H) 3411 br; ν(N4–H) 3308 s; ν(C–H) 2995 m, 2876 m; ν(C=N) +
Pyrrole-2-carbaldehyde Thiosemicarbazone (H2L3): M. p. 194–
196 °C.
X-ray Crystallography
A single crystal was mounted on a glass fiber and used for data collec-
tion with a Bruker SMART APEXII CCD area detector (1), Xcalibur,
Eos, Gemini (2), Xcalibur, Ruby, Gemini (3) and Siemens P4 (4) dif-
fractometers equipped with graphite monochromated Cu-Kα radiations
in 1 (λ = 1.54178 Å) and with Mo-Kα radiations in 2–4 (λ =
0.71073 Å). Crystal data were collected at 100(2) (1) 170(2) (2) and
123(2) (3), and 295(2) (4) K. The data were processed with APEX2
and a multi-scan absorption correction was applied using SADABS[11]
for complex 1. For 2 and 3, data were processed with CrysAlisPro and
corrected for absorption using CrysAlisRED.[12] The data for 4 were
processed with Siemens software and a psi-scans absorption correction
was applied.[13] The structures were solved by direct methods using
the program SHELXS-97 in the SHELXTL-PC[14] or SIR-92[15] and
refined by full-matrix least-squares techniques against F2 using
SHELXL-97[16] in the SHELXTL-PC[14] or WinGX package.[17] All
non-hydrogen atoms in all structures were refined anisotropically. The
hydrogen atoms were placed at the calculated positions except for
amine hydrogen atoms in 2 and 3, which were located from the differ-
ence Fourier and were refined isotropically with a thermal parameter
of 1.2 times that of the carrier nitrogen atoms. Their bond lengths were
also needed to be restrained [0.86(2) Å] in 2. The complex 4 also
shows the presence of a disordered toluene molecule in the asymmetric
1
ν(C=C) 1578 s, 1502 s; ν(C–N) 1035 s; ν(C–S) 767 s cm–1. H NMR
(CDCl3): δ = 11.13 (2 H, sb, N4H), 7.22 (s, 2 H, C2H), 6.96 (s, 2 H,
C6H), 6.53 (t, 2 H, C4H), 6.22 (dd, 2 H, C5H), 4.90 (s, 2 H, N1HMe),
2.98 (d, 6 H, CH3) ppm.
[Ni(κ2-N3,S-HL2)2(κ2-N,N-bipy)] (3): To a suspension of {NiL2}
(0.025 g, 0.111 mmol) in acetonitrile was added solid bipyridine
(0.17 g, 0.111 mmol) and stirred until a clear solution was obtained.
Slow evaporation of this solution gave red-brown crystals. Yield 73%;
M.p. 160–162 °C. C24H26N10NiS2: calcd. C 49.88; H 4.50; N 24.25%.
found: C 50.02; H 4.42; N 24.43%. IR (KBr, selected absorption
bands): ν(N1–H) 3421 br; ν(N4–H) 3317 s; ν(C–H) 3098 w, 3054 w,
3022 w, 2928 m, 2850 w; ν(C=N) + ν(C=C) 1598 s, 1494 s; ν(C–
N) 1018 s, 963 s; ν(C–S) 762 s cm–1. Electronic absorption spectrum
(0.5ϫ10–4 m in DMSO, λmax /nm, ε /L·mol–1·cm–1): 413 (0.96ϫ104),
374 (1.89ϫ104), 353 (2.14ϫ104), 333 (2.01ϫ104), 307 (1.68ϫ104),
294 (2.00ϫ104), 275 (2.50ϫ104). Magnetic moment: μeff = 2.98 BM.
[Pd(κ3-N4,N3,S-L3)(κ1-P-PPh2–CH2–P(O)Ph2)]·C7H8
(4):
To
PdCl2(κ2-P,P–Ph2P–CH2–PPh2) (0.05, 0.09 mmol) suspended in tolu- unit. This disorder could be resolved for the phenyl ring with 52 and
Z. Anorg. Allg. Chem. 2012, 804–810
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
805

T. S. Lobana et al.
ARTICLE
Table 1. Crystallographic data for compounds 1–4.
1
2
3
4
Empirical formula
M
C24H22N8NiS2
545.33
C14H18N8NiS2
421.19
C24H26N10NiS2
577.38
C38H36N4OP2PdS
765.11
T /K
296(2)
170(2)
123(2)
295(2)
Crystal system
Space group
Unit cell dimensions
a /Å
monoclinic
P21/n
monoclinic
P21/n
monoclinic
C2/c
monoclinic
P21/c
9.401(4)
12.528(2)
15.736(2)
9.505(1)
b /Å
15.924(7)
5.414(6)
16.225(2)
18.215(2)
c /Å
16.360(7)
13.938(3)
10.768(2)
20.917(2)
α /°
90
90
90
90
β /°
104.78(1)
108.95(2)
103.95(2)
95.63(1)
γ /°
90
2368.1(2)
90
894.1(2)
90
2668.2(7)
90
3604.0(6)
V /Å3
Z
4
2
4
4
Dcalcd. /g·cm–3
1.530
3.084
1.565
1.334
1.437
0.918
1.410
0.697
μ /mm–1
F(000)
1128
436
1200
1568
Crystal size /mm
Reflections collected
Unique reflections
Data/ restraints /
parameters
Index ranges
0.10ϫ0.10ϫ0.10
31168
3904 [R(int) = 0.0196]
3904 / 0 / 316
0.44ϫ0.18ϫ0.10
7518
2308 [R(int) = 0.0647]
2308 / 2 / 123
0.51ϫ0.28ϫ0.25
23795
6861 [R(int) = 0.0200]
6861 / 0 / 177
0.20ϫ0.20ϫ0.10
7127
6702 [R(int) = 0.0479]
6702 / 1 / 379
–10 Յ h Յ 10
–18 Յ k Յ 18
–18 Յ l Յ 19
0.7479, 0.7689
–16 Յ h Յ 16
–7 Յ k Յ 7
–17 Յ l Յ 18
0.31865, 1.00000
–26 Յ h Յ 26
–27 Յ k Յ 27
–18 Յ l Յ 17
0.93887, 1.00000
0 Յ h Յ 11
0 Յ k Յ 22
–25 Յ l Յ 25
0.8731, 0.9335
Absorption correction
(Tmin, Tmax
)
Final R indices
[I Ͼ 2σ(I)]
R indices (all data)
R1 = 0.0231,
wR2 = 0.0642
R1 = 0.0237,
R1 = 0.0545,
wR2 = 0.1356
R1 = 0.0676,
R1 = 0.0264,
wR2 = 0.0694
R1 = 0.0330,
R1 = 0.0520,
wR2 = 0.1219
R1 = 0.1226,
wR2 = 0.0647
0.275 and –0.212
wR2 = 0.1559
1.522 and –0.966
wR2 = 0.0734
0.502 and –0.265
wR2 = 0.1657
0.781 and –0.552
Largest diff. peak and
hole /e·Å–3
complexes of type, [Ni(κ3-N4,N3,S-L1)(D)] (D = py, PPh3) on
the pattern of salicylaldehyde thiosemicarbazones, which
formed square-planar complexes, [Ni(O,N3,S-L)(D)] (D = py,
PPh3).[19] However, H2L1 preferred the bis-square-planar com-
plex, [Ni(κ2-N3, S-HL1)2] (1), involving deprotonation of
only –N2H– proton and no coordination by the co-ligand
py/PPh3 was observed. It is mentioned herein that the reactions
of Ni(OAc)2 with H2L2 or H2L3 in 1:2 molar ratio are known
to yield similar types of complexes, [Ni(κ2-N3,S-HL2)2] and
[Ni(κ2-N3,S-HL3)2.[8c] The reaction of NiCl2·6H2O with H2L2
in presence of triethylamine followed by addition of pyridine
in acetonitrile did not yield the anticipated [Ni(κ3-N4,N3,S-L2)
(py)] complex, moreover again a bis-square-planar complex,
[Ni(κ2-N3,S-HL2)2] (2), similar to 1 has formed. However, in
presence of bipyridine, the addition product, [Ni(κ2-N3,S-HL2)
2(κ2-N,N-bipy)] (3), was obtained. Thus, all the three ligands
have shown preference for N3,S chelation with pyrrole being
pendant in the each case.
48% occupancies (Figures S1–S5, Supporting Information). Both the
occupancies and Uiso parameters were refined as free variables. Molec-
ular graphics were used from PLATON[18a] and SCHAKAL.[18b] The
crystallographic data and important bond parameters and various hy-
drogen bonds of complexes 1–4 are given in Table 1, Table 2, and
Table 3, respectively.
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ,
UK. Copies of the data can be obtained free of charge on quoting the
depository numbers CCDC-861021, -861022, -861023, and -861024
(1–4) (Fax: +44-1223-336-033; E-Mail: deposit@ccdc.cam.ac.uk,
http://www.ccdc.cam.ac.uk).
Supporting Information (see footnote on the first page of this article):
Physical data of the ligands; Hydrogen bonding networks and packing
diagrams for complexes 1–4.
Results and Discussion
Furthermore, the reactions of PdCl2(κ2-P,P–PPh2–CH2–
PPh2) with H2L1 H2L2, and H2L3 in toluene in presence of
triethylamine base were carried out. Herein, both halogen
atoms were removed as Et3NH+Cl– salt and only the thio-li-
gand H2L3 gave a crystalline product of composition [Pd(κ3-
N4,N3,S-L3)(κ1-P–PPh2–CH2–P(O)Ph2)] (4). The tricoordin-
Syntheses and IR Spectroscopy
Scheme 1 depicts the formation of complexes with pyrrole
based
thiosemicarbazones,
[(C4H4N4)(H)C2=N3–N2(H)–
C1(=S)–N1HR; R = Ph, H2L1; Me, H2L2; H, H2L3]. The ligand
H2L1 on reaction with Ni(OAc)2 in methanol in 1:1 molar ratio
was anticipated to act as N4,N3,S chelating ligand and yielded ation by the thio ligand H2L3 is similar to that observed in
806
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© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 804–810

Pyrrole-2-carbaldehyde Thiosemicarbazonates of Nickel(II) and Palladium(II)
Table 2. Bond parameters of compounds 1–4.
1
Ni(1)–N(4)
Ni(1)–S(3)
N(4)–C(2)
C(1)–S(2)
N(4)–Ni(1)–S(3)
N(8)–Ni(1)–S(3)
N(4)–Ni(1)–N(8)
1.913(1)
2.179(7)
1.308(2)
1.742(2)
92.72(5)
86.06(5)
177.11(5)
Ni(1)–N(8)
Ni(1)–S(2)
N(8)–C(14)
C(13)–S(3)
N(8)–Ni(1)–S(2)
N(4)–Ni(1)–S(2)
S(3)–Ni(1)–S(2)
1.923(1)
2.196(7)
1.311(2)
1.740(2)
95.62(5)
85.85(5)
174.44(2)
2
Ni(1)–N(3)
Ni(1)–S(1)
N(3)–Ni(1)–S(1)
N(3)–Ni(1)–N(3)
1.923(2)
2.175(8)
85.76(7)
180.00(1)
S(1)–C(2)
1.730(3)
N(3)–Ni(1)–S(1)
S(1)–Ni(1)–S(1)
94.24(7)
180.00(3)
3
Ni–N(1B)
S–C(6A)
2.085(7)
1.739(7)
Ni–S#1
2.380(2)
Scheme 1.
N(1B)–Ni–N(1B) 78.45(4)
N(1B)–Ni–N(2A) 93.44(3)
#1
#1
forming bis square-planar complexes, [Pd(κ3-N3,S-HL)2].[8a,8c]
In 4 the pendant –PPh2 group involves auto oxidation to –P(O)
PPh2 during reaction. This behavior is unlike that observed
in salicylaldehyde thiosemicarbazone complex, [{Pd(O,N3,S-
L)}2(μ-P,P–PPh2–CH2–PPh2)] having bridging diphopshine
units.[20] The difference is attributed to the nature of the thio-
ligand. The salicylaldehyde thiosemicarbazone forms
Pd(O,N3,S-L) core with more electronegative oxygen as one
of the donor atoms, which links to both ends of PPh2–CH2–
PPh2 forming bridged complex. On the other hand pyrrole
thiosemicarbazone forms a Pd(κ3-N4,N3,S-L3) core, which has
less electronegative pyrrole nitrogen (N4) as one of the donor
atom instead of oxygen. The latter core appears to prefer to
bind to only one –PPh2 group of PPh2–CH2–PPh2 and leaving
the other pendant which undergoes oxidation to form –P(O)
Ph2.
N(2A)#1–Ni–
N(2A)
97.06(3)
N(1B)–Ni–S
87.20(2)
N(1B)#1–Ni–S
N(1B)#1–Ni–
N(2A)#1
94.24(2)
165.02(3)
N(2A)#1–Ni–S
S–Ni–S#1
97.96(2)
178.14(1)
4
Pd–N1
Pd–N2
O1–P2
C25–P2
N2–Pd–N1
N2–Pd–P1
N1–Pd–P1
2.064(6)
2.008(5)
1.451(5)
1.830(7)
80.4(2)
Pd–P1
Pd–S1
2.247(2)
2.266(2)
1.764(7)
1.844(7)
83.22(2)
163.59(2)
95.02(7)
C31–S1
C25–P1
N2–Pd–S1
N1–Pd–S1
P1–Pd–S1
174.12(2)
101.38(2)
Table 3. Hydrogen bonds /Å for complexes 1–4.
.
D–H···A
d(D–H) d(H···A) d(D···A) Ͻ(DHA)
The room temperature magnetic moment (μeff) of 2.98 BM
suggested the presence of paramagnetic nickel atom in com-
plex 3. IR spectroscopic measurements revealed deprotonation
of the –N2H– group in complexes 1–3.[12] Complex 4 also in-
volved deprotonation of –N4H– group during complex forma-
tion, which is further confirmed by single-crystal X-ray crys-
tallography (vide infra). The diagnostic ν(C–S) bands (750–
784 cm–1) show low energy shifts compared to the free ligands
(795–800 cm–1), which suggest that the thio ligands are coordi-
nating to the central metal atoms through the thiolato sulfur
atom. The presence of phosphine in 4 is supported by its char-
acteristic ν(P–CPh) band at 1099 cm–1.[21]
1
N(6)–H(6)···C(4)
N(10)–H(10A)···C(16) 0.859
N(10)–H(10A)···C(17) 0.859
0.860
2.835
2.878
2.588
2.831
2.835
2.218
3.467
3.722 167.66
3.419 162.85
3.656 148.35
3.467 131.75
131.75
C(18)–H(18)···C(22)
N(6)–H(6)···C(4)
N(5) –H(5)···N(3)
N(4)–H(4N)···N(2)
N(1)–H(1N)···S(1)
C(3)–H(3A)···S(1)
C(7)–H(7A)···N(4)
C(7)–H(7A)···C(7)
C(7)–H(7A)···C(4)
0.930
0.860
0.859
2.712
116.35
2
0.857(2) 2.120(3) 2.681(3) 122.00
0.853(2) 2.640(3) 3.411(3) 152.00
0.950
0.950
0.950
0.950
2.400
2.590
2.732
2.877
3.046(3) 125.20
3.456(4) 152.00
3.615 154.95
3.501
124.25
3
4
N(1A)–H(1A)···N(3A) 0.856(2) 2.164(2) 2.722(9) 122.60
N(4A)–H(4A)···S#2
C(1A)–H(1AA)
···C(5A)
0.855(2) 2.619(2) 3.405(8) 153.30
0.950
2.795
3.652 150.62
C(3B)–H(3BA)···S
C(21)–H(21)···C(3)
N(4)–H(4B)···O(1)
C(38)–H(38A)···C(11) 0.963
C(36)–H(36)···C(26)
C(35)–H(35)···C(5)
0.951
0.930
0.861
2.826
2.864
2.056
2.828
2.870
2.768
3.670
3.788
148.52
172.45
Crystal Structures
2.789 142.62
The crystal structure of complex, [Ni(κ2-N,S-HL1)2] (1),
shows that two uni-negative thio ligands (HL1)– are chelated
to nickel(II) metal atom through azomethine nitrogen (N) and
thiolato sulfur (S) atoms in trans-N2S2 manner forming five
membered chelate rings (Figure 1). The bond lengths, Ni–N
3.724
3.625
3.446
155.30
139.55
130.56
0.926
0.931
[Pd(κ3-N4,N3,S-L)(PPh3)] complexes of pyrrole thiosemicarb- [1.913(1), 1.923(1) Å] and Ni–S [2.179(7), 2.196(7) Å], are
azones reported earlier.[9] In absence of PPh3, the pyrrole thio- similar to those in a related complex [Ni(HL3)2]·2DMSO
semicarbazones are known to act as N3,S-chelating ligands [NiII–N 1.910(3); NiII–S 2.177(1) Å].[8c] The C–S bond length
Z. Anorg. Allg. Chem. 2012, 804–810
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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807

T. S. Lobana et al.
ARTICLE
[1.742(2), 1.740(2) Å] shows a double bond character [C–S,
1.62; C=S 1.81 Å] as observed earlier for such thiosemicarb-
azone complexes.[9] Other bond parameters are similar to those
reported in literature.[9] Trans angles, N–Ni–N [177.11(5)°]
and S–Ni–S [174.44(2)°], suggest a slight deviation from regu-
lar square-planar arrangement. Complex [Ni(κ2-N,S-HL2)2] (2)
has molecular structure and bond parameters similar to those
of complex 1 (Figure 2).
Figure 3. ORTEP diagram of complex [Ni(κ2-N,S-HL2)2(κ2-N,N-
bipy)] (3). Hydrogen atoms were omitted for clarity.
The crystal structure of complex [Pd(κ3-N,N,S-L3)(κ1-P–
PPh2–CH2–P(O)Ph2)] (4) has shown that the dinegative thio
ligand (L2)2– is coordinated to the palladium(II) atom by N,N-
and S-donor atoms. The fourth site around palladium is occu-
pied by phosphorus atom of one PPh2 group of dppm co-li-
gand, whereas the other end (PPh2) undergoes aerial oxidation
during reaction (Figure 4). The Pd–Npyrrole [2.064(6) Å], Pd–
Nazomethine [2.008(5) Å], Pd–S [2.266(2) Å] and Pd–P
[2.2470 Å] distances are close to those of similar complex
[PdL(PPh3)] reported earlier.[9a] The trans angle, N(1)–Pd–S(1)
[163.59(17)°] deviates significantly from linearity vis-à-vis the
Figure 1. ORTEP diagram of complex [Ni(κ2-N,S-HL1)2] (1). Hydro-
gen atoms were omitted for clarity.
Figure 2. ORTEP diagram of complex [Ni(κ2-N,S-HL2)2] (2). Hydro-
gen atoms were omitted for clarity.
Complex [Ni(κ2-N,S-HL2)2(κ2-N,N-bipy)] (3) has four sites
around the nickel atom occupied by N,S-donor atoms of two
uni-negative (HL2)– ligands and the remaining two sites are
occupied by N,N-donor atoms of the bipyridine co-ligand (Fig-
ure 3). The trans bond angles, N–Ni–N, N–Ni–N, S–Ni–S are
165.02(3), 165.02(3), and 178.14(1)° respectively, and suggest
distorted octahedral arrangement of the complex. The thiolato
sulfur atoms are in trans position, whereas the azomethine ni-
trogen atoms and bipyridyl nitrogen atoms occupy the cis posi-
tions of the octahedron. The bond lengths, Ni–N [2.086(6) Å]
and Ni–S [2.380(2) Å] are slightly longer than similar bond
lengths found in square-planar complex 1 [Ni–N, 1.913(1),
1.923(1); Ni–S, 2.179(7), 2.196(7) Å], as expected. The nickel
to bipyridine bond lengths, Ni–Nbipy, are 2.085(7), 2.085(7) Å,
which are slightly longer than those of the nitrogen atoms of
the thio ligand.
Figure 4. ORTEP diagram of complex [Pd(κ3-N,N,S-L3)(κ1-P–PPh2–
CH2–P(O)Ph2)] (4). The disordered toluene solvent molecule and hy-
drogen atoms were omitted for clarity.
808
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© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 804–810

Pyrrole-2-carbaldehyde Thiosemicarbazonates of Nickel(II) and Palladium(II)
second trans angle, N(2)–Pd–P(1) [174.12(17)°], probably due
Acknowledgement
to strain in the five membered chelate rings. These bond angles
suggest a distorted square-planar arrangement around the pal-
ladium(II) atom.
Financial assistance from Council of Scientific and Industrial Research
(CSIR) (letter no. 09/254(0188)/2009-EMR-I), New Delhi is gratefully
acknowledged.
Solution Phase Behavior
1
The H NMR spectrum of free thio ligand (H2L1) shows a
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Received: January 12, 2012
Published Online: March 25, 2012
810
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Z. Anorg. Allg. Chem. 2012, 804–810