Synthesis, Spectral, Valence-Bond Parameters, and Single Crystal X-ray Structural Studies on [Ni(dnpdtc)(PPh3)(NCS)] and [Ni(dnpdtc)(PPh3)(CN)]

Article abstract of DOI:10.1002/zaac.200300322

Two new nickel complexes withplanar surrounding of Ni [Ni(dnpdtc)(PPh ₃)(NCS)] (1) and [Ni(dnpdtc)(PPh₃)(CN)] (2) (dnpdtc=N,N-dipropyldithiocarbamate) were prepared from the parent dithiocarbamate and were characterized by elemental analysis, electronic, IR and NMR spectra. The structures of both the complexes were determined by single crystal X-ray crystallography. Thioureide stretching vibrations occur at 1528 cm^-1 and 1521 cm^-1 for 1 and 2 respectively. Large ³¹P chemical shifts were observed for the two compounds. A significant asymmetry in Ni-S bond distances was observed in compound 1 [2.1700(16) and 2.2251 (17)A] whereas in compound 2 the bond distances were almost similar [2.2100(14) and 2.2122(13)A]. A marginal difference was observed with respect to the thioureide bond distances [1.340(6)A for 1 and 1.312(5)A for 2]. The observation clearly supports the less effective trans influence of SCN^- over PPh₃. However, PPh₃ and CN^- show almost similar trans influence.

Full text of DOI:10.1002/zaac.200300322

Synthesis, Spectral, Valence-Bond Parameters, and Single Crystal X-ray
Structural Studies on [Ni(dnpdtc)(PPh3)(NCS)] and [Ni(dnpdtc)(PPh3)(CN)]
B. Arul Prakasama, K. Ramalingama, *, G. Bocellib, and R. Ollab
a
Annamalainagar/India, Department of Chemistry, Annamalai University
b
Parma/Italy, IMEM, CNR
Received September 23rd, 2003.
˚
Abstract. Two new nickel complexes withplanar surrounding of Ni
[Ni(dnpdtc)(PPh3)(NCS)] (1) and [Ni(dnpdtc)(PPh3)(CN)] (2)
(dnpdtcϭN,N-dipropyldithiocarbamate) were prepared from the
parent dithiocarbamate and were characterized by elemental analy-
sis, electronic, IR and NMR spectra. The structures of both the
complexes were determined by single crystal X-ray crystallography.
Thioureide stretching vibrations occur at 1528 cm-1 and 1521 cm-1
for 1 and 2 respectively. Large 31P chemical shifts were observed
for the two compounds. A significant asymmetry in NiϪS bond
2.2251(17)A] whereas in compound 2 the bond distances were al-
˚
most similar [2.2100(14) and 2.2122(13)A]. A marginal difference
was observed with respect to the thioureide bond distances
[1.340(6)A for 1 and 1.312(5)A for 2]. The observation clearly sup-
ports the less effective trans influence of SCNϪ over PPh3. How-
ever, PPh3 and CNϪ show almost similar trans influence.
˚
˚
Keywords: Nickel; Dithiocarbamate; Crystal structure; Tri-
distances was observed in compound
1
[2.1700(16) and
phenylphosphine; NMR spectroscopy
Synthese, Spektroskopie, Bindungs-Valenz-Parameter und
Einkristallstrukturuntersuchungen von [Ni(dnpdtc)(PPh3)(NCS)] und
[Ni(dnpdtc)(PPh3)(CN)]
Inhaltsübersicht. Zwei neue Nickelkomplexe mit planarer Umge-
bung an den Ni-Atomen, [Ni(dnpdtc)(PPh3)(NCS)] (1) und
[Ni(dnpdtc)(PPh3)(CN)] (2) (dnpdtc ϭ N,N-dipropyldithiocarba-
mat), wurden aus [Ni(dnpdtc)2] hergestellt und durch Elementar-
analysen, elektronischen, IR- und NMR-Spektren charakterisiert.
Die Strukturen beider Komplexe wurden durch Einkristallstruktur-
analysen röntgenographisch ermittelt. Die CN-Valenzschwingun-
gen der Dithiocarbamatgruppen liegen bei 1528 cmϪ1 (1) und 1521
cmϪ1 (2). In den 31P-NMR-Spektren werden große chemische Ver-
schiebungen beobachtet. Die NiϪS-Bindungen in 1 sind mit
˚
2,170(2) und 2,225(2) A signifikant verschieden, während sie in 2
˚
mit 2,210 und 2,212(1) A nahezu gleich sind. Die CN-Abstände
˚
der Dithiocarbamatliganden sind mit 1,340(6) A (1) und 1,312(5)
˚
A (2) nur marginal verschieden. Dies bestätigt den gegenüber PPh3
geringeren Transeinfluß von SCNϪ und den nahezu gleich großen
Transeinfluß von PPh3 und CNϪ.
Introduction
(C2H4OH), S2CN(C2H4OH)2, S2CN(C2H5)2, S2CN(C5H10)
have been reported from our laboratory [1Ϫ3]. In order to
understand the influence of SCN- and CN- donors on the
coordination environment around nickel atom and on the
thioureide bond, we report the synthesis, spectral and struc-
Dithiocarbamate ligands (dtc) display a strong prospenity
of binding to metal atoms such as nickel [1Ϫ4]. The nickel
complexes with phosphine ligands have been studied for
their anti-cancer activity [5]. Group VIII dithiolates con-
taining planar MS4 chromophores show variable behaviour
in their reactions with Lewis bases. Unlike it’s congeners
NiII is a borderline acceptor and it’s planar dithiocarbamate
ligand prefers to react with soft Lewis bases such as phos-
phines over hard nitrogenousbases. Nickel(II) dithiocarba-
mates in their reaction with PR3 form planar NiS2P2 chro-
mophores [6, 7]. Synthetic and structural studies on
[Ni(dtc)Cl(PPh3)], [Ni(dtc)(PPh3)2](ClO4) and [Ni(dtc)-
tural
characterization
of
two
new
complexes
[Ni(dnpdtc)(PPh3)(NCS)] (1) and [Ni(dnpdtc)(PPh3)(CN)]
(2) where dnpdtcϭN, N-dipropyldithiocarbamate in this
paper.
Results and Discussion
IR spectral studies
IR spectra show ν(N-C) bands at 1528 cm-1 for 1 and 1521
cm-1 for 2 The shift in ν(N-C) values to higher wave number
compared with parent [Ni(dnpdtc)2] complex observed at
1508 cm-1 is due to the mesomeric drift of electron density
from the dithiocarbamate ligand towards the metal atom
and this increases the contribution of polar thioureide for-
min both the cases. The bands at higher wave number 2093
(dppe)](BPh4)
where
dtcϭS2CN(C2H5)2,
S2CNH-
Dr. K. Ramalingam
Department of Chemistry
Annamalai University
Annamalainagar Ϫ 608 002 / India
E-mail: krauchem@yahoo.com
Z. Anorg. Allg. Chem. 2004, 630, 301Ϫ304
DOI: 10.1002/zaac.200300322
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
301

B. A. Prakasam, K. Ramalingam, G. Bocelli, R. Olla
Table 1 NMR Spectral data for 1 and 2. (Chemical shift values in ppm)
NMRa)
Compound
CH3
α-CH2
β-CH2
Aromatic
Thioureide
N-C
P
SϪ13CϪN
13CN
1H
1
2
1
2
1
2
0.81 (t) & 0.92 (t)
0.83 (t) & 0.93 (t)
11.11
11.11
Ϫ
1.60 (m)
1.65 (m)
20.59
20.64
Ϫ
3.30 (t) & 3.49 (t)
3.39 (t) & 3.56 (t)
50.69 & 50.87
50.01 & 50.87
Ϫ
7.26Ϫ7.73 (m)
7.26Ϫ7.73 (m)
128.16Ϫ134.24
128.57Ϫ134.32
Ϫ
Ϫ
Ϫ
203.63
205.21
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
22.03
30.28
Ϫ
Ϫ
143.69
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
ϳ130
Ϫ
13Cb)
31P
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
a)
CDCl3 was used as solvent
b)
13C NMR spectra were recorded in proton decoupled mode.
cm-1 for 1 and 2112 cm-1 for 2 indicate the presence of SCN-
in 1 and CN- in 2 respectively. The ν(C-S) band appears at
1095 cm-1 for 1 and at 1094cm-1 for 2 without any splitting,
supporting the bidentate coordination of the dithiocarba-
mate moiety [8].
NMR spectral studies
NMR spectra were recorded at room temperature using
TMS as internal reference. The NMR chemical shift values
are given in Table 1 with splitting pattern.
1HNMR. For compound 1 as expected two sets of signals
were obtained for the propyl group. The methyl group pro-
tons give two triplets at 0.81 and 0.92 ppm. The α-CH2
protons appear as a collapsed multipletin the region of 1.60
ppm. In the downfield region, two sets of triplets at 3.30
and 3.49 ppm were obtained for β-CH2 protons whereas in
the case of complexes with NiS2P2 chromophore, only one
set of signal was obtained for the propyl group. A multiplet
in the region of 7.26Ϫ7.73 ppm was due to aromatic pro-
tons. For compound 2 also the signals were obtained with
the same splitting pattern but with slight difference in
chemical shift values.
13C NMR. The most important chemical shift values of
thioureide carbon atom (S213C-N) were observed at 203.63
and 205.21 ppm for complexes 1 and 2, respectively. The
mesomeric shift of electron density from dithiocarbamate
moiety towards the metal atom contributes to the upfield
shift from the normal chemical shift value of [Ni(dtc)2]
complexes (206-210 ppm) [9]. The observation is supported
by the higher ν(N-C) values observed for complexes 1 and
2 in the present study. For compound 1, the low intensity
signal at 143.69 ppm was assigned to carbon atom present
in NCS moiety, whereas for compound 2, the signal for cy-
anide carbon merged with that of the aromatic carbons.
Fig. 1 ORTEP diagram of [Ni(dnpdtc)(PPh3)(NCS)]
B); 3.1117 (B/OK), 3.0715 (OK/B) for the two complexes 1
and 2, respectively. For both the complexes, the values are
higher than the expected formal oxidation state of ϩ2. The
higher value observed in the present set of compounds sup-
ports the fact that the Ni-S, Ni-P bonds are more covalent
and the back bonding effects are very highly pronounced
[12]. Between the SCN- and CN- donors, CN- appears to
alleviate the electron density on the metal atom to a greater
extent through back bonding leading to higher positive
charge as suggested by the larger BVS values.
Structural analysis
The ORTEP diagram of 1 is shown in Figure 1. The com-
plex is monomeric and discrete. Four units of
[Ni(dnpdtc)(PPh3)(NCS)] are present in the unit cell. Be-
cause of the small bite angle associated with the dithiocar-
bamate moiety [78.75(6)°], the NiS2PN chromophore is not
of perfect square planar arrangement. The planarity of the
surrounding of Ni atoms is inkeeping with the observed di-
amagnetism of the complex.The short thioureide N-C dis-
31P NMR. 31P NMR spectra for compound 1 and 2 show
signals at 22.03 and 30.28 ppm, respectively. In 31P NMR,
a large difference (ϳ8.25 ppm) was observed, suggesting
that the back bonding effects are felt more pronounced in 2.
Bond-valence parameter calculations
˚
tance, 1.340(6)A indicates that the π electron density is de-
For the two complexes values were calculated by two pro-
cedures [10, 11]. The values are 2.9931 (B/OK), 2.9456 (OK/
localized over S2CN moiety and that this bond has a strong
double bond character. This is also confirmed by the fact
302
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
zaac.wiley-vch.de
Z. Anorg. Allg. Chem. 2004, 630, 301Ϫ304

Studies on [Ni(dnpdtc)(PPh3)(NCS)] and [Ni(dnpdtc)(PPh3)(CN)]
Table 2 Crystal data, data collection and refinement parameters for [Ni(dnpdtc)(PPh3)(NCS)] (1) and [Ni(dnpdtc)(PPh3)(CN)] (2)
[Ni(dnpdtc)(PPh3)(NCS)]
[Ni(dnpdtc)(PPh3)(CN)]
Empirical formula
FW
C26H29N2NiPS3
555.4
0.21 x 0.23 x 0.34
monoclinic
P21/n
8.310(3)
20.433 (3)
16.963 (2)
C26H29N2NiPS2
523.3
Crystal dimensions (mm)
Crystal system
Space group
0.17 x 0.28 x 0.31
triclinic
¯
P1
˚
a/A
10.364 (2)
14.160 (3)
9.918 (3)
˚
b/A
˚
c/A
α/°
90
94.76 (2)
105.28 (3)
111.00 (3)
Enraf Nonius CAD 4
293K
1285.1 (5)
β/°
104.18 (2)
90
Phillips PW 100
293K
γ/°
Diffractometer
Temperature
3
˚
U/ A
2792.5 (11)
Z
4
2
Dc/g cm-3
µ/cm-1
F(000)
1.321
9.93
1160
1.352
3.312
548
˚
λ/A
Mo Ϫ Kα (0.71069)
Mo Ϫ Kα (0.71069)
θ range/°
Scan type
3.08Ϫ27.05
ωϪ2θ
3.41Ϫ69.98
ωϪ2θ
Index ranges
Ϫ0ՅhՅ10,0ՅkՅ26, Ϫ21ՅlՅ20
6094
Ϫ12ՅhՅ11, Ϫ17ՅkՅ17, 0ՅlՅ12
4858
Reflections collected
Observed reflections F0>4σ(F0)
Weighting scheme
1911
3235
W ϭ 1/[σ2(F02) ϩ (0.0215 P)2 ϩ 0.00 P]
W ϭ 1/[σ2(F02) ϩ (0.1198 P)2 ϩ 0.00 P]
2
2
where P ϭ (F0 ϩ 2 Fc2)/3
where P ϭ (F0 ϩ 2 Fc2)/3
Number of parameters refined
Final R, Rw (obs, data)
GOOF
414
443
0.0584, 0.0647
0.780
0.0541, 0.1421
0.872
Crystallographic data for the structures have been deposited with the Cambridge Crystallographic Data Centre (211256 & 211257 for 1 and 2, respectively).
Copies of the data can be obtained free of charge on application to The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: int.code ϩ(1223)336-
033; e-mail for inquiry: fileserv@ccdc.cam.ac.uk; e-mail for deposition: deposit@ccdc.cam.ac.uk).
˚
Table
3
Selected bond distances/A and angles/° for
In the isothiocyanate part, the N-C-S band angle is
˚
[Ni(dnpdtc)(PPh3)(NCS)] (1) and [Ni(dnpdtc)(PPh3)(CN)] (2)
179.1(6)° is . The C-N bond distance in N-C-S [1.148(6)A]
is shorter than that of thioureide N-C bond distance of
[Ni(dnpdtc)(PPh3)(NCS)]
[Ni(dnpdtc)(PPh3)(CN)]
˚
˚
1.340(6)A. The C-S bond length is 1.631(6)A which is simi-
˚
larto CϭS distance of 1.69 A. Phenyl rings show normal
Ni1-S3
Ni1-S2
Ni1-N12
Ni1-P15
S2-C4
S3-C4
N5-C4
N5-C9
N5-C6
2.170(2)
Ni1-S3
Ni1-S2
Ni1-C12
Ni1-P15
S2-C4
S3-C4
N5-C4
N5-C6
N5-C9
2.210(1)
2.225(2)
1.854(5)
2.198(2)
1.699(5)
1.722(6)
1.340(6)
1.486(8)
1.474(8)
1.501(11)
1.479(12)
1.506(11)
1.518(12)
1.148(6)
1.631(6)
174.2(2)
90.40(2)
95.42(6)
95.50(2)
78.75(6)
173.85(7)
85.4(2)
2.212(1)
1.861(4)
2.184(1)
1.719(4)
1.735(4)
1.312(5)
1.468(6)
1.472(6)
1.41(217)
1.66(2)
bond
parameters.
The
P-Ni-P
angle
in
[Ni(dnpdtc)(PPh3)2]ClO4 is 98.41(4)° whereas in compound
1 P-Ni-N bond angle is 90.39(15)°. The decrease of about
8° indicates that there is less steric crowding in 1 by the
replacement of PPh3 by NCS.
[Ni(dnpdtc)(PPh3)(CN)] (2) is monomeric with two mol-
ecules per unit cell. The ORTEP diagram of the molecule
is shown in Figure 2. The nickel atom has approximately
planar surrounding, in keeping with the observed diamag-
netism. The small bite angle of 78.85(5)° is observed in this
case, which is in agreement with the values of complexes,
which are reported earlier. The Ni-S [2.2100(1) and
C6-C7
C7-C8
C9-C10
C6-C7B
C6-C7A
C7A-C7B
C7A-C8B
C7A-C8A
C12-N13
C12-Ni1-P15
C12-Ni1-S3
P15-Ni1-S3
C12-Ni1-S2
P15-Ni1-S2
S3-Ni1-S2
C4-S2-Ni1
C4-S3-Ni1
N5-C4-S2
N5-C4-S3
S2-C4-S3
0.676(14)
1.01(2)
1.48(2)
C10-C11
N12-C13
C13-S14
N12-Ni1-S3
N12-Ni1-P15
S3-Ni1-P15
N12-Ni1-S2
S3-Ni1-S2
P15-Ni1-S2
C4-S2-Ni1
C4-S3-Ni1
N5-C4-S2
N5-C4-S3
S2-C4-S3
1.141(5)
95.11(13)
171.12(13)
93.73(6)
92.30(13)
167.56(5)
78.85(5)
85.71(14)
85.40(14)
125.8(3)
125.3(3)
108.8(2)
˚
˚
2.2122(1)A] and C-S [1.719(4) and 1.735(4)A] bonds are al-
most symmetric, indicating that the negative charge on the
dithiocarbamate ligand is equally distributed all over the
donor atoms. The short thioureide N-C distance of
86.6(2)
˚
126.4(5)
124.4(4)
109.2(3)
1.312(5)A is due to delocalized electron density over the
S2CN moiety and this bond has a partial double bond
˚
character. The C-N bond length of 1.141(5)A exemplifies
the triple bond character.
Comparison of 1 and 2 shows that S-Ni-S bite angles
[79.75(6) vs 78.85(5)°] and the Ni-S-C angles [86.0 vs
85.55°] are very similar. The C-N bond length in N-C-S
that the two S-C-N angles [124.4(4) and 126.4(5)°] are much
greater than that of S-C-S angle, 109.2(3)°.
Z. Anorg. Allg. Chem. 2004, 630, 301Ϫ304
zaac.wiley-vch.de
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
303

B. A. Prakasam, K. Ramalingam, G. Bocelli, R. Olla
50 cm3) and was then concentrated to ca 25 cm3. The dark purple-
red solution obtained was filtered and was kept for evaporation.
After 3 days, fine single crystals suitable for X-ray structural analy-
sis were obtained. (Yield 70%, 400 mg, dec. 185°C).
C26H29N2NiPS3 (555.4); C 55.93 (calc. 56.23); H 5.09 (5.26); N 4.93
(5.04) %.
(Cyano)(N,N-dipropyldithiocarbamato)(triphenylphosphine)-
nickel(II). A mixture of Ni(dnpdtc)2 (210 mg, 0.5 mmol), PPh3 (260
mg, 1 mmol), NiCl2·6H2O (120 mg, 0.5 mmol) and KCN (65 mg,
1 mmol) was refluxed for 4h in methanol-dichloromethane solvent
mixture (50:50, 50 cm3) and was then concentrated to ca 25 cm3.
The pale orange-red solution obtained was filtered and was kept
for evaporation. After 2 days orange-red solid separated out. Single
crystals suitable for X-ray structural analysis were obtained by re-
peated recrystallization from methanol-dichloromethane solvent
mixture. (Yield 65%, 370 mg, dec. 173°C) C26H29N2NiPS2 (523.3);
C 58.91 (calc. 59.67); H 5.50 (5.58); N 5.18 (5.34) %.
Fig. 2 ORTEP diagram of [Ni(dnpdtc)(PPh3)(CN)]
moiety of 1 [1.148(6)°] is comparable with the C-N bond
length of 2. For compound 1, the asymmetry in Ni-S dis-
X-ray crystallography
Details of the crystal data, data collection and refinement param-
eters for 1 and 2 are summarized in Table 2. The structure was
solved by direct methods using SHELXS-97 [13] and was refined
by SHELX-97 [14]. All the non-hydrogen atoms were refined aniso-
tropically and all the hydrogen atoms were refined isotropically.
Selected bond lengths and bond angles are given in Table 3.
˚
tances [2.170(2) and 2.225(2)A] was observed. The C-S
˚
bond lengths are also asymmetric [1.699(5) and 1.722(6)A].
This asymmetry shows that the negative charge is not equ-
ally spread over all the donor atoms. Thioureide bond dis-
tances in 1 and 2 are characteristic of partial double bond
nature indicating the mesomeric drift of electron density
from N towards the metal ion. Compound 2 shows an ap-
parently lower ν(N-C) value than that observed for 1 how-
ever, crystallographically N-Cbond distance observed in 2
is significantly shorter than that in compound 1. In the light
of the observed bond distances around nickel, SCNϪ exerts
a less effective trans influence over PPh3 on the Ni-S bonds.
References
[1] K. Ramalingam, G. Aravamudan, V. Venkatachalam, Bull.
Chem. Soc. Jpn. 1993, 66, 1554.
[2] A. Manohar, V. Venkatachalam, K. Ramalingam, U. Casel-
lato, R. Graziani, Polyhedron 1997, 16, 1971.
[3] V. Venkatachalam, K. Ramalingam, K. Akilan, K. Sivakumar,
K. Chinnakali, Hoong-Kun Fun, Polyhedron 1996, 15, 1295.
[4] R. Pastoreka, Z. Travniceka, J. Marekb, D. Dastychb, Z. Sin-
delara, Polyhedron 2000, 19, 1713.
[5] P. S. Jarrett, O. M. N. Dhubhghaill, P. J. Sadler, J. Chem. Soc.
Dalton Trans. 1993, 1863.
[6] D. Lachenal, Inorg. Nucl. Chem. Lett. 1975, 11, 101.
[7] R. P. Burns, F. P. McCullough, C. A. McAuliffe, Adv. Inorg.
Chem. Radiochem. 1980, 23, 211.
[8] F. Bonati, R. Ugo, J. Organomet. Chem. 1967, 110, 257.
[9] H. L. M. Van, Gaal, J. W. Diesveld, F. W. Pijpers, Van der
Linden, Inorg. Chem. 1979, 18, 3251.
Experimental
All the reagents and solvents employed were commercially available
analytical grade materials used as supplied, without further purifi-
cation. IR spectra were recorded on ABB Bomem MB 104 spectro-
photometer (range 4000Ϫ400 cmϪ1) as KBr pellets. The electronic
spectra were recorded in CH2Cl2 on a HITACHI U-2001 spectro-
photometer. NMR spectra were recorded on Brucker AMX-400
spectrometer at room temperature, using CDCl3 as solvent.
[10] N. E. Brese, M. O’Keeffe, Acta Crystallogr. 1991, B47, 192.
[11] M. O’Keeffe, N. E. Brese, J. Am. Chem. Soc. 1991, 113, 3226.
[12] S. P. Summers, K. A. Abboud, S. R. Farrah, G. J. Palenik,
Inorg. Chem. 1994, 33, 88.
[13] G. M. Sheldrick, Acta Crystallogr. 1990, A46, 467.
[14] G. M. Sheldrick, SHELX-97, Programs for crystal structure
analysis (Release 97-2) Univ. Göttingen, Germany, 1997.
Preparation of complexes
(N,N-Dipropyldithiocarbamato)(isothiocyanato)(triphenylphos-
phine) nickel(II). [Ni(dnpdtc)(PPh3)(NCS)] (1). A mixture of
Ni(dnpdtc)2 (210 mg, 0.5 mmol), PPh3 (260 mg, 1 mmol),
NiCl2·6H2O (120 mg, 0.5 mmol) and NH4SCN (75 mg, 1 mmol)
was refluxed for 3h in methanol-acetonitrile solvent mixture (50:50,
304
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
zaac.wiley-vch.de
Z. Anorg. Allg. Chem. 2004, 630, 301Ϫ304