Synthesis, NMR and single crystal X-ray structural studies on planar NiS4 and NiS2PN chromophores: Steric and electronic effects

Article abstract of DOI:10.1016/j.poly.2011.11.027

The planar nickel(II) complexes [Ni(echdtc)₂] (1) and [Ni(echdtc)(PPh₃)(NCS)] (2), (where echdtc = ethylcyclohexyl dithiocarbamate) have been prepared, characterized by elemental analysis, electronic, IR and NMR (¹H,

Full text of DOI:10.1016/j.poly.2011.11.027

Polyhedron 33 (2012) 60–66
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Polyhedron
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Synthesis, NMR and single crystal X-ray structural studies on planar NiS4 and
NiS2PN chromophores: Steric and electronic effects
b
S. Srinivasan a, K. Ramalingam a, , C. Rizzoli
⇑
a Department of Chemistry, Annamalai University, Annamalainagar 608002, Tamilnadu, India
b Department of General and Inorganic Chemistry, University of Parma, Parma 43100, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 16 May 2011
Accepted 7 November 2011
Available online 26 November 2011
The planar nickel(II) complexes [Ni(echdtc)2] (1) and [Ni(echdtc)(PPh3)(NCS)] (2), (where echdtc = ethyl-
cyclohexyl dithiocarbamate) have been prepared, characterized by elemental analysis, electronic, IR and
NMR (1H, 13C, and 31P) spectra, and their structures have been determined by single crystal X-ray crys-
tallography. Both the complexes are diamagnetic and planar. The characteristic thioureide bands occur
at 1485 and 1504 cmꢀ1 for (1) and (2), respectively. NMR spectra of the complexes show the (N)13CS2-
chemical shifts at 206.29 and 202.68 ppm for (1) and (2), respectively. The 31P chemical shift for (2)
was observed at 22.51 ppm, indicating a strong interaction. Electronic spectra of complexes (1) and (2)
show signature bands at 412 and 478 nm, corresponding to dz2 ? dxy/dx2—y2 transitions. Single crystal
X-ray structures of [Ni(echdtc)2] (1) and [Ni(echdtc)(PPh3)(NCS)] (2) indicate that the central atom is
in a planar environment in the complexes. In both complexes, the Ni–S distances are significantly differ-
ent due to steric and electronic effects of the donors. Complex (2) is asymmetric with respect to the Ni–S
distances, attributed to the trans influence exerted by PPh3 and NCSꢀ. The decrease in the S–Ni–S bite
angle [78.63(3)°] for (2) compared to that of (1) [79.19(2)°] is due to steric crowding around the metal
center. The P–Ni–S angle, 170.91(3)°, clearly shows the steric influence of the triphenylphosphine, which
contrasts well with the much cramped S–Ni–S angle of 78.63(3)°.
Keywords:
Nickel(II)
Dithiocarbamate
Thiocyanate-N
Thioureide
X-ray crystal structure
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
characterization of [Ni(echdtc)2] (1) and [Ni(echdtc)(PPh3)(NCS)]
(2) (where echdtc = ethylcyclohexyl dithiocarbamate).
Group X dithiocarbamate complexes with phosphines and
nitrogenous ligands show structural novelties [1] and interesting
biological profiles [2]. The symbiotically induced softness and the
electronic effects of the substituents on the dithiocarbamate
ligands are important factors in deciding the reactivity [3,4].
Divalent nickel complexes of dithiocarbamates with different sub-
stituents contain planar diamagnetic MS4 chromophores [5,6].
Ni(II) dithiocarbamates are borderline acceptors and they prefer
to react with soft Lewis bases such as phosphines and hard bases
such as nitrogenous ligands. Synthetic and structural studies on
2. Experimental
All the reagents and solvents employed were commercially avail-
able analytical grade materials and were used as supplied without
further purification. IR spectra were recorded on an Avatar Nicolet
FT-IR spectrometer [range 4000–400 cmꢀ1] as KBr pellets of the
compounds. Electronic spectra were recorded in CH2Cl2 on a Hitachi
U-2001 double beam spectrometer. 1H, 13C and 31P NMR spectra
were recorded on a Bruker AMX-400 spectrometer at room temper-
ature using CDCl3 as the solvent.
[Ni(dtc)(PPh3)X] complexes, where dtc = S2CN(C2H5)2ꢀ, S2CN(CH3)
(C2H4OH)ꢀ, S2CN(C2H4OH)2ꢀ, S2CN(C3H7)2ꢀ, S2CN(C5H10 2
)
and
ꢀ
X = Cl, SCN, CN, have been reported from our laboratory [7–10].
In continuation of our interest [11] in exploring the synthetic
and structural chemistry of transition metal dithiocarbamates, in
this paper we report the synthesis, spectral and structural
2.1. X-ray crystallography
Intensity data were collected at ambient temperature (295 K)
on a Bruker APEX-II CCD diffractometer with graphite monochro-
mated MoK
a radiation (k = 0.71073 Å) and were corrected for
absorptions with a multi-scan technique [12–14]. The structures
were solved by direct methods using SIR97 and were refined by
SHELX97 [15]. The non-hydrogen atoms were refined anisotropically
⇑
Corresponding author. Tel.: +91 413 2202834; fax: +91 414 42265.
E-mail address: krauchem@yahoo.com (K. Ramalingam).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.11.027

S. Srinivasan et al. / Polyhedron 33 (2012) 60–66
61
and all the hydrogen atoms were fixed geometrically. Molecular
plots were obtained using the ORTEP-3 program [16].
band at 2087 cmꢀ1 for complex (2) is attributed to the ‘N’ coordi-
nated thiocyanate anion.
3.3. NMR spectral studies
2.2. Preparation of the complexes
NMR spectra were recorded at room temperature using TMS as
an internal reference and CDCl3 as the solvent for the compounds.
The 13C NMR spectra were recorded in the proton decoupled mode.
NMR spectra of the complexes are shown in Figs. 1 and 2. The 1H,
13C and 31P NMR chemical shifts are given in Table 1.
2.2.1. Bis (N-ethylcyclohexylcarbodithioato)nickel(II); [Ni(echdtc)2]
A mixture of N-ethylcyclohexylamine (0.3 ml, 2 mmol) and CS2
(76 mg, 1 mmol) in ethanol (50 ml) was kept under ice cold condi-
tions (ꢀ5 °C) for 10 min, and to the resultant pale yellow solution,
NiCl2ꢁ6H2O (0.24 g, 1 mmol) in water (25 ml) was added slowly
with vigorous stirring. A dark green precipitate separated, which
was filtered, washed with water and subsequently with ether.
The solid was dried over anhydrous calcium chloride (yield 95%,
dec., 230 °C). Anal. Calc. for C18H32N2NiS4: C, 46.45; H, 6.96; N,
6.04. Found: C, 46.17; H, 6.69; N, 6.10%.
3.3.1. 1H NMR
In the complex, the alkyl groups are non-equivalent and a, b, c
methylene protons and terminal methyl protons give only broad
signals, indicating a substantial barrier to C–N< bond rotation.
The observed deshielding of the –CH2 protons in the compounds
[20] is attributed to the shift of electron density on the sulfur (or
2.2.2. (N-ethylcyclohexylcarbodithioato)(thiocyanato-N)(triphenyl-
phosphine) nickel(II); [Ni(echdtc)(PPh3)(NCS)]
the metal) through the thioureide
p system. The a-methylene pro-
tons adjacent to the nitrogen atom undergo strong deshielding and
are observed in the region, 4.36–4.42 ppm. The b-CH2 signals are
observed in the range: 1.32–1.84 ppm and assignments are made
on the basis of proton integral values obtained for the correspond-
ing signals. For complex (2), overlapping multiplets are observed in
the region 7.45–7.73 ppm due to aromatic protons involving P–H
and H–H coupling.
A mixture of [Ni(echdtc)2], (0.19 g, 0.4 mmol), PPh3 (0.21 g,
0.8 mmol), NiCl2ꢁ6H2O (0.09 g, 0.4 mmol) and NH4SCN (0.6 g,
0.8 mmol) was refluxed for 3 h in an acetonitrile–methanol solvent
mixture (1:1 v/v, 50 cm3) and the solution was then concentrated
to ca. 20 cm3. The resultant dark purple red solution was left for
evaporation. After 2 days a purple red solid separated from the
solution, which was filtered and dried over anhydrous calcium
chloride. Single crystals suitable for X-ray analysis were obtained
by repeated recrystallization from the same solvent mixture (yield
75%, dec., 189 °C). Anal. Calc. for C28H31N2NiPS3: C, 57.84; H, 5.37;
N, 4.82. Found: C, 57.57; H, 5.10; N, 4.57%.
3.3.2. 13C NMR
13C chemical shifts of thioureide carbon atoms are correlated to
the
p bonding in the NCS2-fragment [9]. Generally higher m(C–N) val-
ues correlate with lower N13CS2 NMR shifts for d-block elements.
The chemical shifts of the thioureide carbon atom (N–13CS2) were
observed at 206.29 and 202.68 ppm for complexes (1) and (2),
respectively [21]. This is due to the alleviation of excess electron
density on nickel by the phosphine ligand, which results in a drift
of electron density towards the metal through the thioureide bond
from the nitrogen atom, supporting the bidentate coordination of
the dithiocarbamate and strong back bonding. The thiocyanate car-
bon appears at 143.00 ppm as a weak signal. In the cyclohexyl ring,
3. Results and discussion
3.1. Electronic spectra
Electronic spectra of the compounds show bands below 350 nm,
which are due to intraligand
p–
p⁄ transitions, mainly associated
with the N–C@S and S–C@S groups. Intense bands in the 350–
425 nm region are due to charge transfers in compounds (1) and
(2) [17,18]. In addition to the charge transfer bands, bands ob-
served in the range 425–650 nm are due to d–d transitions. The
the a-methylene carbon appears to be deshielded to a greater extent
and signals are observed around 59 ppm for (1) and (2). The terminal
methyl carbon signals are observed in the upfield region
two bands at 624 nm (kmax 16025 cmꢀ1; 2 6540 l molꢀ1 cmꢀ1
)
(14.40 ppm) relative to the
c-CH2 carbon signals (25.23 ppm) in
and 471 nm (kmax 21231 cmꢀ1; 2 21660 l molꢀ1 cmꢀ1) corre-
complex (1). The b-CH2 carbon signals are observed at 30.27 and
30.16 ppm for complexes (1) and (2), respectively. In the aromatic
region, ortho carbon signals are observed at 134.19 and
134.11 ppm and the meta carbon signals are observed at 128.81
and 128.73 ppm. However, the para carbon signals (single carbon,
relatively low intensity) are observed at 130.96 and 130.97 ppm.
Quaternary ipso carbons are observed at 128.20 and 128.56 ppm
as very weak signals. The deshielding of the ipso carbons is due to
their increased electron density through a back bonding Ni–P
interaction.
spond to dxy ? dx2—y2 and dz2 ? dx2
transitions, respectively.
—y2
The position corresponding to the dxz ? dx2—y2 and dyz ? dx2—y2
transitions would be between the dxy ? dx2—y2 (624 nm) and
dz2 ? dx2
(471 nm) transitions. However, an earlier report [19]
—y2
suggested the same set of transitions with a different coordinate
system. Of the two bands shown by the parent, the band at
625 nm shifts to higher wavelength in the mixed ligand complex.
The band at 478 nm in the mixed ligand complex shows a red shift
due to the replacement of the chelating dithiocarbamate ligand by
PPh3 and NCSꢀ. The electronic spectra of the complexes reflect the
square planar geometry around nickel in both complexes.
3.3.3. 31P NMR
The 31P chemicals shift is observed at 22.51 ppm for (2) and it is
assigned to the coordinated phosphorus. Free PPh3 phosphorus res-
onates in the upfield region at ꢀ5.8 ppm [22]. Very high deshielding
is observed for the coordinated phosphorus in compound (2) com-
pared with the free phosphine, indicating strong synergic bonding.
3.2. IR spectral studies
For complexes (1) and (2), m(C–N) thioureide bands are observed
at 1485 and 1504 cmꢀ1, respectively. The increase in the wave
number for the mixed ligand complex (1504 cmꢀ1) compared to
that observed for its parent complex (1) (1485 cmꢀ1) is attributed
to the mesomeric drift of electron density towards the nickel atom
through the S2C–N< bond from the dithiocarbamate ligand. The
m(C–S) stretching bands are observed around 1000 cmꢀ1 for (1)
and (2) without any splitting, supporting the bidentate coordina-
tion of the dithiocarbamate moiety [20]. The observed stretching
3.4. Structural analysis
Crystal data, data collection and refinement parameters are gi-
ven in Table 2. Selected bond parameters are given in Table 3. The
single crystal X-ray structure of (1) contains four discrete molecules
per unit cell. The ORTEP diagram of the molecule is shown in Fig. 3.

62
S. Srinivasan et al. / Polyhedron 33 (2012) 60–66
Fig. 1. NMR spectra of [Ni(echdtc)2].
The observed distortion of the square planar coordination around
nickel is attributed to the small bite angle of the dithiocarbamate li-
gand [79.188(16)°]. The planarity of the molecule is in keeping with
the observed diamagnetism of the complex. The C–S bond lengths
are 1.7210(16) and 1.7274(18) Å, shorter than the typical single
bond length of 1.81 Å and longer than the C@S distance of 1.69 Å.
The observed intermediate value indicates the partial double bond
character of the thioureide bond.

S. Srinivasan et al. / Polyhedron 33 (2012) 60–66
63
Fig. 2. NMR spectra of [Ni(echdtc)(PPh3)(NCS)].

64
S. Srinivasan et al. / Polyhedron 33 (2012) 60–66
Table 1
NMR chemical shifts of the complexes (ppm).
Alkyl
[Ni(echdtc)2]
1H
[Ni(echdtc)(PPh3)(NCS)]
1H
Coupling constant (J)
13C
13C
31P
a0-CH3
1.24–1.27 (t)
3.52–3.57(q)
4.42–4.36(m)
1.32–1.84(m)
collapsed multiplet
9.0
9.0
–
40.57
14.38
58.90
30.27(m)
1.26–1.27(m)
3.55–3.57(m)
4.36 (m)
1.36–1.82(m)
collapsed multiplet
40.89
14.26–14.52
59.22
–
–
–
–
a-CH2
Cyclohexyl
b-CH2
a
-CH2
–
30.16
c
-CH2
25.49
25.23
206.29
–
25.47
25.22
202.68
d-CH2
>N13CS2
PPh3
–
–
–
–
–
–
7.45–7.73(t)
128.20–134.19b
(phenyl ring)
22.51
overlapping multipletsa
Meta-carbon signals are observed at 128.81 and 128.73 ppm.
Para-carbon signals (single carbon, relatively low intensity) are observed at 130.96 and 130.97 ppm.
Ipso carbons (quaternary, very low intensity) observed at 128.20 and 128.56 ppm are deshielded due to increased electron density on them through a back bonding Ni–P
interaction.
Thiocyanate carbon signal of very low intensity was observed at 143.00 ppm.
a
Overlapping multiplets due to P–H and H–H coupling.
Ortho-carbon signals are observed at 134.19 and 134.11 ppm.
b
Table 2
Crystal data, data collection and refinement parameters for [Ni(echdtc)2] and [Ni(echdtc)(PPh3)(NCS)].
Compound
[Ni(echdtc)2]
18H32N2NiS4
463.4
dark green
block
[Ni(echdtc)(PPh)3(NCS)]
Empirical formula
Formula weight
Colour
C
C28H31N2NiPS3
581.4
violet
Habit
prism
Crystal system
Space group
Crystal dimension (mm3)
a (Å)
b (Å)
c (Å)
orthorhombic
Pbca
triclinic
P1
ꢀ
0.18 ꢂ 0.15 ꢂ 0.12
10.1338(6)
12.5256(7)
17.5736(9)
90.00
90.00
90.00
2230.7(2)
4
1.380
0.38 ꢂ 0.19 ꢂ 0.18
10.3324(5)
17.1601(9)
17.6992(9)
82.3925(8)
83.9928(9)
74.8981(8)
2995.0(3)
4
a
(°)
b (°)
c
(°)
U (Å3)
Z
Dcalc (g cmꢀ3
l
)
1.289
0.929
(mmꢀ1)
1.249
F (000)
984
1216
k (Å)
MoK
a
(0.71073)
MoKa (0.71073)
h Range (°)
Scan type
Index range
Reflections collected
Reflections [Fo > 2 (Fo)]
Weighting scheme
2.32–26.03
multi
1.16–25.90
multi
ꢀ12 ꢃ h ꢃ 12, ꢀ15 ꢃ k ꢃ 15, ꢀ21 ꢃ l ꢃ 21
ꢀ12 ꢃ h ꢃ 12, ꢀ20 ꢃ k ꢃ 21, ꢀ21 ꢃ 1 ꢃ 21
2205
1826
11610
7787
r
2
2
W ¼ ðF2oÞ þ ð0:0305PÞ
W ¼ ðF2oÞ þ ð0:04769PÞ
1
1
r2
r2
where P ¼ ðF2o þ 2Fo2Þ=3
where P ¼ maxðF2o þ 2Fco2Þ=3
Number of parameters refined
Final R, Rw (obs, data)
Goodness-of-fit (GOF)
115
650
0.0244, 0.0603
1.032
0.0397, 0.0924
1.046
Table 3
Selected bond distances (Å) and bond angles (°) for (1) and (2).
Single crystal X-ray structure of (2) contains four discrete mol-
ecules per unit cell. The ORTEP diagram of the molecule is shown in
Fig. 4. Distortion of the square planar coordination around nickel is
due to the small bite angle of the dithiocarbamate ligand
[78.63(3)°], and the steric influence exerted by PPh3. The bite angle
of the dithiocarbamate ligand shows a significant decrease in (2),
[Ni(echdtc)2] (1)
[Ni(echdtc)(PPh3)(NCS)] (2)
Bond distances
Ni(1)–S(1)
Ni(1)–S(2)
S(1)–C(1)
2.2108(4)
2.2004(5)
1.7274(18)
1.7210(16)
1.319(2)
Ni(1)–S(1)
Ni(1)–S(2)
Ni(1)–P(1)
Ni(1)–N(2)
S(1)–C(1)
S(2)–C(1)
C(1)–N(1)
2.1779(7)
2.2127(7)
2.2072(7)
1.874(2)
1.724(3)
1.710(3)
1.316(3)
indicating the steric influence of PPh3. Delocalization of
p electron
S(2)–C(1)
density over the (S2–CN<) moiety leads to a decrease in the C–N
(S2–C–N<) distance [1.316(3) Å] and also an increase in the S–C–
N angles [126.0(2)° and 125.8(2)°] over the S–C–S angle
N(1)–C(1)
N(1)–C(8)
N(1)–C(2)
1.486(2)
1.1487(2)
[108.21(14)°]. The observed difference in the Ni–S distance
[2.1779(7) Å (trans to NCS) and 2.2127(7) Å (trans to PPh3)] is
attributed to the differences in the trans influencing properties of
Bond angles
S(2)–Ni(1)–S(1)
S(2)–C(1)–S(1)
N(1)–C(2)–C(3)
N(1)–C(2)–C(7)
79.188(16)
109.23(9)
110.16(14)
112.58(15)
P(1)–Ni(1)–N(2)
S(2)–Ni(1)–S(1)
S(2)–C(1)–S(1)
N(1)–C(1)–S(2)
94.49(6)
78.63(3)
108.21(14)
126.0(2)
NCS and PPh3. PPh3, being a good
p acceptor, has a greater trans
influence and hence the Ni–S bond trans to PPh3 is longer than

S. Srinivasan et al. / Polyhedron 33 (2012) 60–66
65
Fig. 3. ORTEP of [Ni(echdtc)2].
Complex (2) is asymmetric with respect to the Ni–S distances,
attributed to the trans influences exerted by PPh3 and NCSꢀ. The
thioureide C–N distances do not differ significantly. The decrease
in the S–Ni–S bite angle [78.63(3)°] for compound (2) compared
to that of parent compound (1) [79.19(2)°] is due to the steric
crowding around the metal center. The P–Ni–S angle, 170.91(3)°
clearly shows the steric influence of the triphenylphosphine ligand,
which contrasts well with the much cramped S–Ni–S angle of
78.63(3)°.
3.4.1. Statistical analysis of selected bond parameters
Divalent nickel bisdithiocarbamates are diamagnetic complexes
with planar geometries. A close examination of the crystal struc-
tures reported in the literature very clearly supports the planarity
with very little deviation. A strong reason for the observation is
the S–Ni–S bite angle of the ligand, in the range of 77.49–79.6°.
The bond parameters reported for [Ni(echdtc)2] (1) in the present
investigation are in good agreement with the mean values obtained
from the statistical data for the compounds in Table 5, similar to the
approach followed in the literature [23]. The mean deviations of the
atoms from the S2NiS2 plane in all the cases is less than 0.03 Å. The
reported thioureide C–N distance [1.319(2) Å] is well within the
wide range of magnitudes reported, clearly indicating the qualita-
tive nature of the predicted electronic effects due to the nature of
the substituents. Notable deviations from the mean values are with
reference to S–C–S and S–Ni–S angles due to predominant steric
effects. [Ni(echdtc)(PPh3)(NCS)] (2) shows a clear tetrahedral distor-
tion from the planar geometry of the parent bisdithiocarbamates.
However, the substituents on the dithiocarbamates reported so far
in CSD, all from our laboratory, vary to a large extent in their bulk
and nature. The interplanar angles defined between the acute
S–Ni–P and S–Ni–N planes, and obtuse S–Ni–P and S–Ni–N planes
is considered as a measure of the tetrahedral distortion. Fig. 5 shows
the variation of the interplanar angle for the compounds. The in-
crease in distortion follows the order: di-n-propyl < methylbenzyl <
dicyclohexyl < di-n-butyl < ethylbenzyl < methylpiperazine < ethyl
cyclohexyl. Both angles show similar variations. A minimum tetra-
hedral distortion is observed for di-n-propyl and a maximum for
methylpiperazine. The ethylcyclohexyl analogue reported in the
Fig. 4. ORTEP of [Ni(echdtc)(PPh3)(NCS)].
the other Ni–S bond. The Ni–N distance [1.874(2) Å] is quite short,
showing the effective bonding between the nickel atom and NCSꢀ.
The C–S bond length in the N–C–S moiety is 1.625(3) Å, which is
similar to the C@S distance of 1.69 Å. The N–C–S bond angle is
179.5(3)°, indicating that it is almost linear [10]. The phenyl groups
in the triphenylphosphine ligand show normal bond parameters.
The Ni–N–C angle [177.3(2)°] deviates marginally from linearity
due to the bulky triphenylphosphine ligand. A comparison of rele-
vant bond lengths and angles for (1) and (2) is given in Table 4.
Table 4
Comparison of bond distances (Å) and angles (°).
Ni–S(1)
Ni–S(2)
C–N
S–Ni–S
S–C–S
P–Ni–S
(1)
(2)
2.2108 (4)
2.1779(7) (t-NCS)
2.2004 (5)
2.2127(7) (t-PPh3)
1.319(2)
1.316(3)
79.188(16)
78.63(3)
109.23(9)
108.21(14)
–
170.91(3)

66
S. Srinivasan et al. / Polyhedron 33 (2012) 60–66
Table 5
Statistical analysis of selected bond parameters in (1) and (2).
a,c
[Ni(dtc)2]a,b
[Ni(dtc) PPh3(NCS)]
Mean value
Bond
Mean value
Range
Range
Ni–S (Å)
2.2145(3)
2.2049(3)
1.71(8)
2.204–2.237
2.198–2.219
1.70–1.74
1.66–1.73
1.30–1.37
2.1768(6) [trans to NCS]
2.2197(7) [trans to PPh3]
1.6835(4)
1.7236(4)
1.3412(4)
2.1650–2.1845
2.2040–2.2360
1.307–1.732
1.710–1.736
1.295–1.696
107.65–109.27
78.20–79.04
C–S (Å)
C–N (Å) (thioureide)
S–C–S (°)
S–Ni–S (°)
1.33(3)
110.16(5)
78.95(4)
107.3–111.6
77.49–79.60
108.39(9)
78.70(4)
a
b
c
dtc is general notation for dithiocarbamates.
Bond parameters of 20 [Ni(dtc)2] complexes with R < 0.05 have been considered.
Bond parameters of 7 [Ni(dtc) PPh3(NCS)] complexes with R < 0.05 have been considered.
Fig. 5. Plot of interplanar angles. 1, di-n-propyl; 2, methylbenzyl; 3, dicyclohexyl; 4, di-n-butyl; 5, ethylbenzyl; 6, methylpiperazine; 7, ethylcyclohexyl. Red plot: acute
interplanar angle; Blue: obtuse interplanar angle (acute interplanar angles are represented as: angle ꢂ 10 for the sake of brevity). (Colour online.)
[5] J.A. Mc Cleverty, N.J. Morrison, J. Chem. Soc., Dalton Trans. (1976) 541.
[6] R.P. Burns, F.P. McCullough, C.A. McAuliffe, Adv. Inorg. Chem. Radiochem. 23
present investigation shows a reasonably higher distortion due to
the steric demand of the substituent. In conclusion, the crystal data
(1980) 211.
clearly shows the influence of the steric demand of the substituents
on the geometry around the metal centre and the related distortion
in the solid state. However, in the NiS4 chromophore, distortions
from the planar geometry is minimal and the deviations from the
square disposition is forced by the characteristic low bite angle asso-
ciated with the ligand. The tetrahedral distortion in the NiS2PN chro-
mophore is primarily due to the steric influence of the PPh3 ligand.
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(2004) 301.
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Appendix A. Supplementary data
CCDC 746325 and 784437 contain the supplementary crystallo-
graphic data for compounds (1) and (2). These data can be obtained
free of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223 336 033; or
e-mail: deposit@ccdc.cam.ac.uk.
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