Nickel(II) N-benzyl-N-methyldithiocarbamato complexes as precursors for the preparation of graphite oxidation accelerators

Article abstract of DOI:10.1002/zaac.201000091

The nickel(II) N-benzyl-N-methyldithiocarbamato (BzMedto) complexes [Ni(BzMedtc)(PPh₃)Cl] (1), [Ni(BzMedto)(PPh3)Br] (2), [Ni(BzMedtc)(PPh₃)I] (3), and [Ni(BzMedtc)(PPh₃)(NCS)] (4) were synthesized using the reaction of [Ni(BzMedtc)₂] and [NiX ₂(PPh₃)₂] (X= Cl, Br, I and NCS). Subsequently, complex 1 was used for the preparation of [Ni(BzM.edtc)(PPh₃) ₂]C104 (5), [Ni(BzMedtc)(PPh₃)₂] BPh ₄ (6), and [Ni(BzMedtc)(PPh₃)₂]PF₆ (7). The obtained, complexes 1-7 were characterized by elemental analysis, thermal analysis and spectroscopic methods (IR, UV/Vis, ³¹P{ ¹H} NMR). The results of the magnetochemical and molar conductivity measurements proved the complexes as diamagnetic non-electrolytes (1-4) or 1:1 electrolytes (5-7). The molecular structures of 4 and 5-H₂O were determined by a single-crystal X-ray analysis. In all cases, the Ni^II atom is tetracoordinated in a distorted square-planar arrangement with the S₂PX, and S₂P₂ donor set, respectively. The catalytic influence of selected complexes 1, 3, 5, and 6 on graphite oxidation was studied. The results clearly indicated that the presence of the products of thermal degradation processes of the mentioned complexes has impact on the course of graphite oxidation. A decrease in the oxidation start temperatures by about 60-100 °C was observed in the cases of all the tested complexes in comparison, with pure graphite.

Full text of DOI:10.1002/zaac.201000091

ARTICLE
DOI: 10.1002/zaac.201000091
Nickel(II) N-Benzyl-N-methyldithiocarbamato Complexes as Precursors for
the Preparation of Graphite Oxidation Accelerators
Zdeněk Trávníček,*[a] Richard Pastorek,[a] Pavel Štarha,[a] Igor Popa,[a] and
Václav Slovák[b]
Keywords: Nickel; Homogeneous catalysis; Dithiocarbamato ligands; Thermochemistry; Graphite oxidation accelerator
Abstract. The nickel(II) N-benzyl-N-methyldithiocarbamato (BzMedtc) non-electrolytes (1–4) or 1:1 electrolytes (5–7). The molecular structures
complexes [Ni(BzMedtc)(PPh3)Cl] (1), [Ni(BzMedtc)(PPh3)Br] (2), of 4 and 5·H2O were determined by a single-crystal X-ray analysis. In
[Ni(BzMedtc)(PPh3)I] (3), and [Ni(BzMedtc)(PPh3)(NCS)] (4) were syn- all cases, the NiII atom is tetracoordinated in a distorted square-planar
thesized using the reaction of [Ni(BzMedtc)2] and [NiX2(PPh3)2] (X = Cl, arrangement with the S2PX, and S2P2 donor set, respectively. The catalytic
Br, I and NCS). Subsequently, complex 1 was used for the preparation of influence of selected complexes 1, 3, 5, and 6 on graphite oxidation was
[Ni(BzMedtc)(PPh3)2]ClO4 (5), [Ni(BzMedtc)(PPh3)2]BPh4 (6), and studied. The results clearly indicated that the presence of the products of
[Ni(BzMedtc)(PPh3)2]PF6 (7). The obtained complexes 1–7 were charac- thermal degradation processes of the mentioned complexes has impact on
terized by elemental analysis, thermal analysis and spectroscopic methods the course of graphite oxidation. A decrease in the oxidation start tempera-
(IR, UV/Vis, 31P{1H} NMR). The results of the magnetochemical and tures by about 60–100 °C was observed in the cases of all the tested
molar conductivity measurements proved the complexes as diamagnetic complexes in comparison with pure graphite.
Several thousand transition metal complexes with the dithio-
carbamate moiety have been prepared and reported to date and
Introduction
Many compounds with the dithiocarbamate (dtc) moiety
have been reported up to now in connection with their applica-
tions. These compounds were found to be useful as fungicides
[1] or accelerators of vulcanization [2]. However, the spectrum
of potential use of these compounds may be also broadened
on the field of in vitro anticancer activity as can be demon-
strated by the following examples. The 4(3H)-quinazolinone
derivatives with dithiocarbamate side chains, such as (3,4-di-
hydro-2-methyl-4-oxoquinazolin-6-yl)-methyl-[4-(4-fluoro-
phenyl)piperazine]-1-carbodithioate, showed promising in vi-
tro anticancer activity (IC50 = 0.5 μM) against human myelog-
enous leukaemia cell line (K562) [3]. Another dithiocarbamate
derivative, 4-methylsulfinyl-1-(S-methyldithiocarbamyl)-bu-
tane (sulforamate), serves as a bearer of cancer chemoprevent-
ive effect [4]. The efficient protection of N-benzyl-d-glucam-
ine-dithiocarbamate against cisplatin-induced nephrotoxicity
(it is able to chelate platinum and thus to decrease the possibil-
ity of its reactions with sulfur-containing renal proteins or en-
zymes) has also been reported recently [5].
some of them are very promising from the biological activity
point of view. The PtII complex of the [Pt(esdt)(py)Cl] compo-
sition (esdt = ethylsarcosinedithiocarbamate and py = pyridine)
is highly cytotoxic against several human cancer cell lines, and
moreover, this substance was not found as nephrotoxic, in con-
trast to cisplatin [6]. [Au(dmdt)X2] and [Au(esdt)X2] are the
representatives of non-platinum complex with the promising
anticancer activity, which is even higher than cisplatin (dmdt =
N,N'-dimethyldithiocarbamate, X = Cl or Br) [7]. The antifun-
gal activity, well-known for dithiocarbamate derivatives, was
proved for tin(IV) complexes with pyrrolidine-dithiocarbamate
[8].
Nickel is known as a suitable transition metal for the prepa-
ration of complexes and it is not surprising that over three
thousand compounds (SciFinder, 2010) and 163 X-ray struc-
tures (Crystallographic Structural Database, CSD, version
5.30, September 2009 update) [9] involving an NiS2CN motif
have been reported to date. Among these compounds, the
nickel(II) complexes involving the NiPN(S2CN) or
NiP2(S2CN) moiety, such as [Ni(4-MePzdtc)(PPh3)(NCS)]
[10], and [Ni(MeSdtc)(dppe)] [11], respectively, were de-
scribed in literature [4-MePzdtc = 4-methylpiperazine-dithicar-
bamate anion, PPh3 = triphenylphosphine, MeSdtc = N-methyl-
* Prof. Dr. Z. Trávníček
Fax: +420585 634 357
E-Mail: zdenek.travnicek@upol.cz
[a] Department of Inorganic Chemistry
Faculty of Science, Palacký University
Tř. 17. listopadu 12
N-sulfonyldithiocarbamate, dppe
=
1,2-bis(diphenylphos-
phine)ethane]. However, no nickel complexes containing the
N-benzyl-N-methyldithiocarbamate anion (BzMedtc) within
the mentioned moieties have been reported to date.
77146 Olomouc, Czech Republic
[b] Department of Chemistry
Faculty of Science, University of Ostrava
30. dubna 22
The presented series of compounds follows a great number
of nickel dithicarbamato complexes previously prepared at our
701 03 Ostrava, Czech Republic
Z. Anorg. Allg. Chem. 2010, 636, 1557–1564
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Z. Trávníček et al.
ARTICLE
department [see 12, 13 and the references cited therein]. In conductivity values (Table 1) indicate that complexes 1–4 dis-
this paper, we deal with seven nickel(II) complexes, whose solved in acetone behave as non-electrolytes [20], which indi-
structures, according to the literature research, for the first time rectly proved the coordination of the Cl– (1), Br– (2), I– (3),
involve a combination of the BzMedtc and PPh3 ligands. The and NCS– (4) anions to the NiII atom. On the other hand, the
complexes [Ni(BzMedtc)(PPh3)X] (1–4) were synthesized molar conductivity values of the remaining complexes proved
from [Ni(BzMedtc)2], using its reaction with [NiX2(PPh3)2], the ionic nature (1:1 electrolyte type) in acetone (5) or DMF
where X stands for Cl– (for the complex 1), Br– (2), I– (3) and (6, 7) solutions, which means that the ClO4 (5), BPh4 (6),
–
–
NCS– (4). The [Ni(BzMedtc)(PPh3)2]Y complexes (Y = ClO4
and PF6 (7) anions are situated outside of the inner coordina-
–
–
for 5, BPh4– for 6 and PF6– for 7) were prepared by the reaction tion sphere within the structure of the discussed complexes.
of complex 1 with the appropriate alkaline salt and triphenyl- The results of the room temperature magnetic measurements
phosphane (see Scheme 1). The products were characterized determined the prepared compounds to be diamagnetic, and
by various physical methods including 31P{1H} NMR spectro- thus, suggested on square-planar arrangements in the vicinity
scopy. The X-ray structures of the representatives of both types of the central atom.
of complexes, i.e. [Ni(BzMedtc)(PPh3)(NCS)] (4) and
Spectroscopic Characterization
[Ni(BzMedtc)(PPh3)2]ClO4·H2O (5·H2O), were determined by
single-crystal X-ray analysis. The arrangement of these com-
pounds is square-planar with the NiS2PN (4) and NiS2P2
(5·H2O) donor sets.
The PPh3 signals in the 31P{1H} NMR spectra of the CDCl3
solutions of 1–7 were found in the range of 21.1–32.1 ppm
(Table 1). These values differ significantly from that of
–4.52 ppm determined for the free PPh3 molecule, which is
caused by electron density redistribution from phosphorus to-
wards the NiII atom as a consequence of PPh3 coordination.
The spectrum of 7 contains a septuplet at –143.6 ppm assigna-
ble to the PF6– anion. It should be noted that the chemical shift
values of the complexes 1–4 increased in the order
[Ni(BzMedtc)(PPh3)Cl] (1) < [Ni(BzMedtc)(PPh3)(NCS)] (4)
< [Ni(BzMedtc)(PPh3)Br] (2) < [Ni(BzMedtc)(PPh3)I] (3),
which is in agreement with the results reported for the
nickel(II) complexes with N-benzyl-N-butyldithiocarbamate
[12].
The maxima observed in the IR spectra of the nickel(II) com-
plexes 1–7 at 990–998 cm–1, and 1510–1542 cm–1 (see Ta-
ble 1) are typical for the ν(C···S), and ν(C···N) vibrations of
the dithiocarbamate moiety, respectively [21, 22]. The peak of
the ν(C···S) stretching vibration is not split, which supports the
bidentate coordination of the BzMedtc anion. The peaks of the
ν(C≡N) and ν(C–S) vibrations of the NCS– anion were ob-
served in the IR spectrum of 4. The ionic nature of the perchlo-
rate anion in the complex 5, can be supported by two undi-
vided peaks at 622 and 1088 cm–1 [23]. The same conclusion
can be made for the complex 7, whose IR spectrum contains
Scheme 1. Schematic representation of the synthetic procedures ap-
plied for the preparation of the nickel(II) complexes 1–7; X = Cl– (1),
Br– (2), I– (3) and NCS– (4), MY = LiClO4·3H2O (5), Na[BPh4] (6)
and K[PF6] (7).
This work also describes the effect of the nickel(II) dithiocar-
bamates on the oxidation of graphite as a model study of the
coal combustion. As it is commonly known, the ignition tem-
perature of the coal combustion is one of the most important
properties influencing many industrial processes. This stage
can be affected by the presence of both natural and artificial
impurities [14, 15]. Formerly, several papers reported simple
nickel(II) compounds, such as NiO (mixed with KOH) or
Ni(NO3)2 (mixed with K2SO4), as the substances accelerating
graphite oxidation [16, 17]. Few years ago, we decided to
study the influence of the nickel(II, IV) dithiocarbamato com-
plexes [see 13, 18, 19, and references cited therein] on the
course of graphite oxidation. It was found that the presence
of these complexes causes the ignition temperature decrease.
Similar results were obtained also for the tested complexes 1,
3, 5, and 6, which were chosen as representatives of the pre-
sented compounds, as it is discussed in more detail within the
framework of this paper.
the non-split peak at 836 cm–1 assignable to ν(PF6 ), which
–
again indicates its ionic nature [24].
Diffuse-reflectance electronic spectra of the prepared com-
plexes 1–7 support the assumption of the square-planar ar-
rangement in the vicinity of the central NiII atom. Absorption
maxima at the 18400–20700 cm–1 region may be attributed to
1
the A1g→1B1g transition of the square-planar nickel(II) com-
plexes [25, 26]. The next maxima, also assignable to the dd
transitions, were found for the complexes 1 (25200 cm–1) and
2 (25000 cm–1). The maxima above 29000 cm–1 are probably
connected with the intraligand charge-transfer transitions in the
S2CN moiety [27].
X-ray Structure of [Ni(BzMedtc)(PPh3)(NCS)] (4) and
[Ni(BzMedtc)(PPh3)2]ClO4·H2O (5·H2O)
Results and Discussion
The nickel(II) complexes 1–7 were prepared according to the
The X-ray structure of the title complexes 4 (Figure 1) and
synthetic strategies depicted in Scheme 1. The obtained molar 5·H2O (Figure 2) was determined by a single-crystal X-ray
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Nickel(II) N-Benzyl-N-methyldithiocarbamato Complexes
Table 1. Results of molar conductivity measurements, IR, UV/Vis, and 31P{H} NMR spectroscopy of the complexes 1–7.
a)
d)
λM
2.2
2.1
IR /cm–1 b)
ν(C···S)
990m
UV/Vis /cm–1 c)
31P{H} NMR δ /ppm
ν(C···N)
1510m
other
1
2
19 200
25 200
29 000
18 900
25 000
29 000
18 400
31 400
20 400
29 000
19 900
31 000
20 700
30 900
19 800
29 300
21.1s
24.8s
996m
1520m
3
4
5
6
7
9.3
998m
996m
996w
990m
996m
1520m
1528m
1542m
1536s
31.6s
22.8s
32.0s
32.1s
1.7
840m ν(C–S)
2092s ν(C≡N)
–
99.0
77.3
66.9
622m ν4(ClO4 –)
1088s ν3(ClO4 )
–
1540m
836m ν4(PF6 )
32.0s,
–143.6sp
a) S·cm2·mol–1 (10–3 m acetone solutions for 1–5 and 5 × 10–4 m DMF solutions for 6 and 7).b) KBr pellets (w = weak, m = middle, s =
strong).c) Nujol technique.d) CDCl3 solutions (s = singlet, sp = septuplet).
analysis. The crystal data and structure refinements are given
in Table 2, whereas the selected bond lengths and angles are
summarized in Table 3.
Figure 1. Molecular structure of [Ni(BzMedtc)(PPh3)(NCS)] (4) with
non-hydrogen atoms drawn as thermal ellipsoids at the 50 % probabil-
ity level.
Figure 2. Molecular structure of [Ni(BzMedtc)(PPh3)2]ClO4·H2O
(5·H2O) with non-hydrogen atoms drawn as thermal ellipsoids at the
50 % probability level. The hydrogen atoms, perchlorate anion, and
water molecule of crystallization were omitted for clarity.
The central NiII atom of complex 4 (Figure 1) is tetracoordi-
nated by PPh3, the isothiocyanate anion, and the bidentate-co-
ordinated
N-benzyl-N-methyldithiocarbamate
anion
(BzMedtc). The atoms of a NiS2NP chromophore are arranged comparable with those of the transition metal (TM) complexes
in the distorted square-planar geometry around the metal center involving the (TM)S2CNR2 moiety and deposited within the
(Table 3). The Ni–S bond lengths of the title complex correlate CSD, which equal 1.717 Å, and 1.326 Å, respectively.
well with the mean value of 2.204 Å (2.155–2.258 Å interval)
The S1 atom is the most deviated one [0.0454(5) Å] from
determined for this band for the 116 square-planar nickel com- the plane created through the Ni1, S1, S2, P1, and N2 atoms
plexes involving bidentate-coordinated dithiocarbamato S-do- of the chromophore. Further, the described plane forms the
nor ligands, which have been up to now deposited in the Cam- dihedral angle of 83.10(5)° with the benzene ring of the
bridge Structural Database (CSD) [9].
BzMedtc anion and dihedral angles of 67.90(5)°, 69.63(5)°,
The well-known delocalization of π-electron density within and 47.85(4)° with the benzene rings of PPh3 containing the
the S2CN moiety of the dithiocarbamate anion was observed C30, C40, and C50 atoms, respectively. Mutual orientation of
for 4, since the C–N and C–S bond lengths of the studied com- the phenyl groups of PPh3 within the molecular structure of
pound (Table 2) were found to be significantly shorter than the 4 can be described by the 67.64(6)° (between benzene rings
single C–N (1.47 Å) and C–S (1.81 Å) σ-bond lengths [28]. containing C30 and C40), 66.06(6)° (between benzene rings
Further, the C–S and C–N bond length values of BzMedtc are containing C30 and C50) and 76.53(6)° (between benzene
Z. Anorg. Allg. Chem. 2010, 1557–1564
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Z. Trávníček et al.
ARTICLE
Table 2.
Crystal
data
and
structure
refinements
for Table 3. Selected bond lengths /Å and angles /° for the complexes
[Ni(BzMedtc)(PPh3)(NCS)] (4) and [Ni(BzMedtc)(PPh3)2]ClO4·H2O [Ni(BzMedtc)(PPh3)(NCS)] (4) and [Ni(BzMedtc) (PPh3)2]ClO4·H2O
(5·H2O).
(5·H2O).
Compound
4
5·H2O
Compound
4
5·H2O
Empirical formula
Formula weight
Temperature /K
Wavelength /Å
Crystal system
Space group
a /Å
C28H25N2NiPS3
575.36
C45H42ClNNiO5P2S2
897.02
Bond lengths
Ni1–S1
2.2245(5)
2.1758(5)
2.2162(5)
–
1.8564(17)
1.7125(19)
1.7214(19)
1.306(2)
1.163(2)
1.621(2)
2.2154(6)
2.2257(6)
2.2165(6)
2.2316(6)
–
113(2)
110(2)
Ni1–S2
0.71073
Monoclinic
P21/n
13.6177(3)
10.3556(2)
19.1287(4)
90
92.4015(18)
90
2695.6(9)
4, 1.418
1.032
0.71073
Ni1–P1
Triclinic
Ni1–P2
¯
P1
Ni1–N2
11.47995(13)
13.24049(16)
15.02884(19)
70.3319(11)
84.5683(10)
87.3995(9)
2141.23(4)
2, 1.391
C1–S1
1.731(2)
1.721(2)
1.307(3)
–
b /Å
C1–S2
c /Å
C1–N1
α /°
N2–C4
β /°
C4–S3
–
γ /°
Bond angles
S1–Ni1–S2
S1–Ni1–P1
S1–Ni1–N2
S1–Ni1–P2
S2–Ni1–P1
S2–Ni1–P2
S2–Ni1–N2
P1–Ni1–N2
P1–Ni1–P2
Ni1–S1–C1
Ni1–S2–C1
S1–C1–S2
S1–C1–N1
S2–C1–N1
Ni1–N2–C4
N2–C4–S3
V /Å3
78.643(19)
171.63(2)
92.06(5)
–
93.384(19)
–
170.70(5)
95.91(5)
–
85.71(7)
87.04(7)
108.60(11)
125.67(15)
125.73(15)
167.29(16)
178.52(19)
78.29(2)
91.28(2)
–
Z, Dcalc /g·cm–3
Absorption coefficient /
mm–1
0.734
167.08(2)
167.76(2)
88.91(2)
–
Crystal size /mm
F (000)
0.30 × 0.25 × 0.25 0.40 × 0.35 × 0.30
1192 932
2.90 ≤ θ ≤ 25.00 3.03 ≤ θ ≤ 25.00
θ range for data collec-
tion /°
–
Index ranges (h, k, l)
–16 ≤ h ≤ 16
–9 ≤ k ≤ 12
–22 ≤ l ≤ 22
22656/4743
(0.0246)
–13 ≤ h ≤ 13
101.24(2)
86.52(8)
86.42(8)
108.61(12)
126.50(17)
124.89(17)
–
–15 ≤ k ≤ 15
–17 ≤ l ≤ 15
Reflections collected/
unique (Rint)
18531/7526 (0.0108)
Max./min. transmission
0.7825/0.7471
0.8099/0.7578
7526/0/553
1.039
Data/restraints/parameters 4743/0/317
Goodness-of-fit on F2
1.065
–
Final R indices [I > 2σ(I)] R1 = 0.0282, wR2 = R1 = 0.0342, wR2 =
0.0673
0.1009
R indices (all data)
R1 = 0.0366, wR2 = R1 = 0.0388, wR2 =
0.0692
0.1031
1.343 and –0.611
Largest peak/hole /e·Å–3 0.344/–0.212
The S2 atom is the most deviated one [0.0903(6) Å] from
the plane created through the atoms of the chromophore. The
dihedral angles between this plane and benzene rings involving
C10, C20, C30, C40, C50, C60, and C70 are 86.39(5)°,
58.49(7)°, 87.97(5)°, 70.52(5)°, 71.64(5)°, 63.60(6)°, and
71.98(5)°, respectively. Non-bonding interactions of the
C–H···C and C···C types (C–H···O interactions with the dis-
torted perchlorate anion and water molecule of crystallization
are disregarded) were found in the crystal structure of the dis-
cussed nickel(II) complex (Table 4).
rings containing C40 and C50) dihedral angles. The C–H···C,
C–H···S and C···C types of the intermolecular non-bonding van
der Waals contacts were detected to stabilize the crystal struc-
ture of 4 (see Table 4). No typical hydrogen bond is present
within the structure of discussed complex.
In the case of 5·H2O, the NiII atom is tetracoordinated in the
distorted square-planar arrangement (Figure 2), similarly to the
above described structure of complex 4, by the bidentate-coor-
dinated S-donor BzMedtc ligand and by two P-donor PPh3
molecules. Selected bond lengths and angles are given in Ta-
TG/DTA Thermal Analysis
The thermal properties of the prepared nickel(II) complexes
ble 3. The positive charge of the [Ni(BzMedtc)(PPh3)2]+ cation were studied by TG and DTA methods. The TG and DTA
is compensated by the perchlorate anion; the shortest Ni1···Cl1 curves of 1 and 6 are depicted in Figure 3. Although the chem-
distance equals 7.131(2) Å.
ical composition of these complexes is different, their thermal
As it has been already mentioned in the case of complex 4, decomposition proceeded in a similar manner as indicated by
the bond lengths within the NiS2CN moiety of both structures analogical shapes of the TG curves. In cases of 2, 3 and 6, the
show on electron density redistribution in connection with π- sharp exo effects with maxima at 188 °C, 193 °C, and 188 °C,
electron density delocalization (see the C–S and C–N bond respectively, were accompanied by mass increase on the TG
lengths in Table 3). As for the Ni–P bonds of 5, their lengths curves, which can be attributed to the oxygen atom insertion
are in good agreement with the mean value of 2.208 Å (2.175– into the Ni–P bond [29]. This effect was not registered on the
2.252 Å interval) as determined from 36 X-ray structures of TG curves of the remaining complexes, where the oxygen
tetra-coordinated nickel dithiocarbamato complexes involving atom insertion is most likely combined with the decomposition
at least one PPh3 ligand and deposited within the CSD.
of the organic parts of the studied complexes.
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Z. Anorg. Allg. Chem. 2010, 1557–1564

Nickel(II) N-Benzyl-N-methyldithiocarbamato Complexes
Table 4. Selected intermolecular non-bonding contacts and their parameters /Å,° determined for the complexes 4 and 5·H2O.
D–H···A
d(D–H)
d(H···A)
d(D···A)
<(DHA)
4
C3–H3A···S3i
0.990
0.950
0.950
0.950
2.9234(6)
2.9389(5)
2.8695(6)
2.9701(6)
3.666(2)
3.717(2)
3.814(2)
3.883(2)
3.307(3)
132.43(12)
139.90(12)
172.48(12)
161.56(12)
C34–H34A···S2ii
C32–H32A···S3iii
C31–H31A···S1iii
C2···C32
5·H2O
C74–H74A···C32iv
C72–H72A···C54v
C2–H2B···C74iv
C14–H14A···C33vi
C13–H13A···C3v
C44–H44A···C64vii
C13···C71v
0.950
0.950
0.990
0.950
0.950
0.950
2.771(3)
2.781(2)
2.844(2)
2.746(3)
2.879(2)
2.872(3)
3.678(4)
3.554(3)
3.771(3)
3.666(4)
3.815(3)
3.653(4)
3.262(4)
3.391(3)
160.13(16)
139.11(16)
156.25(14)
163.31(16)
168.16(14)
140.17(16)
C70···C70iv
Symmetry codes: (i) x+0.5, 0.5–y, z–0.5; (ii) 1–x, 1–y, 1–z; (iii) 1.5–x, y+0.5, 1.5–z; (iv) –x, –y, –z; (v) –x, 1–y, –z; (vi) 1–x, 1–y, –z; (vii) –x,
1–y, 1– z.
showed a positive influence on graphite oxidation, because the
ignition temperature significantly decreased (by about 64–
99 °C) after the addition of the tested nickel(II) complexes to
pure graphite.
Figure 3. TG/DTA curves for complexes 1 and 6.
Figure 4. DTG curves obtained for pure graphite (black lines) and its
mixture with the complexes 1 (black dashed lines), 3 (dark gray line),
5 (gray line), and 6 (light gray line); the tangent method was employed
The final products of the TG studies (900 °C) were studied
by X-ray powder diffraction (XRD). NiO (PDF-4 No. 01-089-
7130) was determined as final product of the thermal decom-
position of 1–4. In the cases of the complexes 6 and 7, the
mixtures with significant predominance of NiO were detected.
The final product of the TG thermal study of 6 also contains
NiS (PDF-4 No. 4-004-5027) and Ni3B2O6 (PDF-4 No. 4-008-
3203), and some peaks could not be assigned. As for the com-
plex 7, Ni2P2O7 (PDF-4 No. 01-074-1604) and Ni3(PO4)2
(PDF-4 No. 01-072-3977) were detected by an XRD, whereas
some peaks were not assigned.
to determine the initial temperatures of the graphite oxidation.
Pure graphite oxidation proceeds in one step, whereas in the
cases of its mixtures with the tested complexes, two steps in a
larger temperature interval were detected on the appropriate
DTG curves (Table 5). The first step takes place at lower tem-
perature than pure graphite oxidation, whereas the oxidation
rate maxima (Tm) of the second step approximately correspond
to pure graphite. In addition, the oxidation mechanisms of both
steps are different, as it can be seen from the activation energy
(E) and frequency factor (A) values given in Table 5. More
graphite was oxidized during the second step with higher E
and A values.
Catalytic Influence of the Complexes on Graphite Oxida-
tion
At this point, we would like to discuss the described results
The influences of the presence of complexes 1, 3, 5, and 6 of the influence on the graphite oxidation in connection with
on graphite oxidation were studied. The results, summarized in the results of TG/DTA studies. Figure 3 clearly shows that the
Figure 4 (obtained DTG curves) and Table 5 (obtained data), thermal decomposition of the nickel(II) complexes is almost
Z. Anorg. Allg. Chem. 2010, 1557–1564
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Z. Trávníček et al.
ARTICLE
Table 5. Characteristic temperatures and kinetic parameters of catalytic influence on graphite given for pure graphite and its mixtures with
nickel(II) complexes 1, 3, 5 and 6a).
Sample
T /°C
Tm /°C
Step
n
A /s–1
E
w /%
Graphite
1
778–859
679–838
832
792
0.7
1.3
0.9
0.9
0.9
1.0
1.0
0.
1.97 × 109
3.62 × 107
1.09 × 109
4.08 × 106
9.10 × 107
1.47 × 107
4.08 × 109
5.88 × 106
1.17 × 109
247
190
235
174
220
183
250
176
238
I
43.58
56.42
34.48
65.52
36.06
63.94
23.48
76.52
II
I
3
5
6
696–879
693–860
714–861
838
815
812
II
I
II
I
II
1.1
a) T = temperature range of oxidation; Tm = oxidation rate maximum; n = reaction order; A = frequency factor; E = activation energy (kJ·mol–1);
w = mass of sample oxidized.
completely finished at the temperature of ca. 700 °C and the synthesized (X = Cl– for 1, Br– for 2, I– for 3 and NCS– for 4,
–
–
–
weight loss above this temperature is insignificant. Based on Y = ClO4 for 5, BPh4 for 6 and PF6 for 7). The obtained
this statement it may be concluded that not directly the dis- powder products were fully characterized by elemental analy-
cussed nickel(II) N-benzyl-N-methyldithiocarbamato com- sis, magnetic and molar conductivity measurements, thermal
plexes, but the products of their thermal decomposition proc- analysis and spectroscopic methods (IR, UV/Vis, 31P{1H}-
esses, affected graphite oxidation.
NMR). The molecular structures of the complexes
(4) and
In connection with the above-mentioned facts, the tested [Ni(BzMedtc)(PPh3)(NCS)]
complexes (except of 5) were heated in situ to the temperatures [Ni(BzMedtc)(PPh3)2]ClO4·H2O (5·H2O) were determined by
corresponding to the beginning and end of graphite oxidation a single-crystal X-ray analysis, which proved the distorted
(see Table 5). The products of thermal decomposition relating square-planar arrangement with the bidentate-coordinated S-
to the mentioned temperatures were analyzed by XRD. As for donor BzMedtc anion accompanied by PPh3 and NCS– (4) or
1–4, pure NiO was identified at both temperatures (Figure 5). by two PPh3 (5). This paper also describes the significant cata-
The slight differences in the 2θ values were caused by a dilata- lytic influence of the thermal degradation products of the se-
tion of the sample due to different measurement temperature. lected complexes 1, 3, 5, and 6 on graphite oxidation.
On the other hand, the mixtures of NiO, NiS, and Ni3B2O6 (for
6) and Ni2P2O7 and Ni3(PO4)2 (for 7) were detected by an
XRD (Figure 5). Their quantitative composition was similar at
both temperatures. Some peaks could not be assigned again.
Experimental Section
Materials and General Methods
Chemicals and solvents were purchased from Sigma–Aldrich Co.,
Acros Organics Co., Lachema Co. and Fluka Co. and they were used
as received. The starting compounds [Ni(BzMedtc)2], [Ni(PPh3)2Cl2],
[Ni(PPh3)2Br2], [Ni(PPh3)2I2], and [Ni(PPh3)2(NCS)2] were prepared
according to the formerly reported synthetic pathways [13, 30].
Elemental analyses (C, H, N) were performed with a Fisons EA-1108
CHNS-O Elemental Analyzer (Thermo Scientific). The content of
nickel was determined using the chelatometric titration with murexide
as an indicator. Chlorine, bromine, and iodine contents were deter-
mined with the Schöniger method. Diffuse-reflectance spectra were
recorded with a Perkin–Elmer Lamda35 UV/Vis spectrometer using
nujol techniques. IR spectra (KBr pellets) were recorded with a Per-
kin–Elmer Spectrum one FT-IR spectrometer in the 450–4000 cm–1
region. The molar conductivity values of 10–3 m acetone solutions of
1–5 and 5 × 10–4 m N,N'-dimethylformamide (DMF) solutions of 6
and 7 were determined with an LF 330/SET conductometer (WTW
GmbH) at 25 °C. The room temperature magnetic susceptibilities were
measured using the Faraday method with a laboratory designed instru-
ment with a Sartorius 4434 MP-8 microbalance; Co[Hg(NCS)4] was
used as calibrant and the correction for diamagnetism was performed
using Pascal constants.
Figure 5. XRD patterns of the thermal decomposition products of the
complexes 3 and 6. The detected diffraction lines belong to NiO for
3, and NiO, NiS, and Ni3B2O6 for 6; the start and end temperatures
are given in Table 5.
Conclusions
Seven nickel(II) complexes of the [Ni(BzMedtc)(PPh3)X]
Simultaneous thermogravimetric (TG) and differential thermal (DTA)
analyses were performed with an Exstar TG/DTA 6200 (Seiko Instru-
(1–4) and [Ni(BzMedtc)(PPh3)2]Y (5–7) compositions were ments Inc.) in a platinum crucible and dynamic air atmosphere
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© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2010, 1557–1564

Nickel(II) N-Benzyl-N-methyldithiocarbamato Complexes
(100 mL·min–1) from the laboratory temperature to 950 °C with a
2.5 °C·min–1 temperature gradient. The weights of the studied com-
plexes 1–4, 6, and 7 (5 was not studied for safety reasons, since it
contains the perchlorate anion) were ca. 10 mg. 31P{1H} NMR spectra
of the CDCl3 solutions were measured with a Bruker Avance 300 spec-
trometer at 300 K and the spectra were calibrated against 85 % H3PO4
used as an external reference. X-ray powder diffraction experiments
were performed with a PANalytical X'Pert PRO instrument (Co-Kα
radiation) equipped with an X'Celerator detector. Samples were placed
on a zero-background silicon slide and scanned in the 2θ range of 5–
90° in the steps of 0.017°. In situ measurements were realized in the
reaction cell XRK900 (Anton Paar). Evaluation was made using High-
Score Plus software and PDF-4 database.
Syntheses of the Nickel(II) Complexes 1–7
[Ni(BzMedtc)(PPh3)Cl]
(1),
[Ni(BzMedtc)(PPh3)Br]
(2),
[Ni(BzMedtc)(PPh3)I] (3) and [Ni(BzMedtc)(PPh3)(NCS)] (4):
Complex 1 was synthesized using the reaction of [Ni(BzMedtc)2]
(1 mmol) and [NiCl2(PPh3)2] (1 mmol). Both starting compounds were
suspended in chloroform (CHCl3) (each 25 mL). The mixture was
stirred at room temperature until the reaction components were com-
pletely dissolved. The resulting solution was filtered through activated
carbon. Diethyl ether was added to the filtrate, which was left to stand
at laboratory temperature. The precipitate of 1 formed after a few days.
The product was filtered off, washed with diethyl ether and dried at
40 °C under an infrared lamp. Complexes 2–4 were prepared as de-
scribed for 1, but [NiBr2(PPh3)2] (for 2), [NiI2(PPh3)2] (for 3) and
[Ni(NCS)2(PPh3)2] (for 4) were used instead of [NiCl2(PPh3)2]. In the
case of the complex 4, the crystals suitable for a single-crystal X-ray
analysis were obtained from the mother liquor after two days.
Single Crystal X-ray Analysis of the Complexes 4 and
5·H2O
[Ni(BzMedtc)(PPh3)Cl] (1): Yield: 78 %. Color: violet.
C27H25NS2PClNi (Mr = 552.8); C 58.7 (calcd. 58.4); H 4.6 (4.6); N
2.5 (2.4); S 11.6 (11.3); Cl 6.4 (6.5); Ni 10.6 (10.6) %. TG/DTA data:
the decomposition began at 177 °C and was finished at 704 °C with
the experimental weight loss of 84.5 % (calcd. to NiO residue:
86.5 %), exothermic peaks with the maxima at 231, 302, 420, and
463 °C.
Single-crystal X-ray measurements were performed with an
XcaliburTM2 diffractometer (Oxford Diffraction Ltd.) with Sapphire2
CCD detector, and with Mo-Kα (Monochromator Enhance, Oxford Dif-
fraction Ltd.) and at 113 K (4) and 110 K (5·H2O). Data collection and
reduction were performed by CrysAlis software [CrysAlis CCD and
CrysAlis RED, Version 1.171.33.52, Oxford Diffraction Ltd., Abing-
don, England, 2009]. The same software was used for data correction
for an absorption effect by the empirical absorption correction using
spherical harmonics, implemented in SCALE3 ABSPACK scaling al-
gorithm. Both structures were solved by direct methods using
SHELXS-97 software [31] and refined on F2 using the full-matrix
least-squares procedure (SHELXL-97). Non-hydrogen atoms were re-
fined anisotropically and all hydrogen atoms were located in difference
Fourier maps and refined by using the riding model with C–H = 0.95,
0.98, and 0.99 Å, and Uiso(H) = 1.2Ueq(CH, CH2) or 1.5Ueq(CH3),
except for those belonging to the crystal water molecule in 5. The
perchlorate anion as well as crystal water molecule was refined as
disordered over two positions with the occupancy factors 75 % and
25 %, and 57 % and 43 %, respectively. The crystal data and structure
refinements of 4 and 5 are given in Table 1. The molecular graphics
were drawn and the additional structural calculations were interpreted
using DIAMOND [32].
[Ni(BzMedtc)(PPh3)Br] (2): Yield: 90 %. Color: violet.
C27H25NS2PBrNi (Mr = 597.2); C 54.3 (calcd. 54.2); H 4.2 (4.1); N
2.3 (2.0); S 10.7 (10.3); Br 13.4 (13.1); Ni 9.8 (9.6) %. TG/DTA data:
the decomposition began at 156 °C and was finished at 1000 °C with
the weight loss of 86.0 % (calcd. to NiO residue: 87.5 %), exothermic
peaks with the maxima at 188, 282, 398, and 490 °C.
[Ni(BzMedtc)(PPh3)I] (3): Yield: 70 %. Color: dark violet.
C27H25NS2PINi (Mr = 644.2); C 50.3 (calcd. 49.9); H 3.9 (3.9); N 2.2
(2.2); S 10.0 (10.0); I 19.7 (19.3); Ni 9.1 (9.2) %. TG/DTA data: the
decomposition began at 180 °C and was finished at 829 °C with the
weight loss of 86.6 % (calcd. to NiO residue: 88.4 %), endothermic
peak with the maximum at 269 °C and exothermic peaks with the
maxima at 193, 246, 301, 457, and 544 °C.
[Ni(BzMedtc)(PPh3)(NCS)] (4): Yield: 82 %. Color: red.
C28H25N2S3PNi (Mr = 575.4); C 58.5 (calcd. 58.9); H 4.4 (4.1); N 4.9
(4.7); S 16.7 (16.6); Ni 10.2 (10.3) %. TG/DTA data: the decomposi-
tion began at 155 °C and was finished at 1047 °C with the weight loss
of 84.7 % (calcd. to NiO residue: 87.0 %), endothermic peak with the
maximum at 198 °C and exothermic peaks with the maxima at 227,
304, 336, 442, and 541 °C.
Crystallographic data have been deposited with the Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge CB21EZ, UK (Fax:
+44-1223-336033; E-Mail: deposit@ccdc.cam.ac.uk). Copies of the
data can be obtained free of charge on application to CCDC, as the
depository numbers CCDC-766048 (4) and CCDC-766049 (5·H2O).
[Ni(BzMedtc)(PPh3)2]ClO4 (5): LiClO4·3H2O (2 mmol) was poured
to a suspension of complex 1 (1 mmol) and PPh3 (2 mmol) in metha-
nol (25 mL). The reaction mixtures were heated under reflux for 3 h.
The resulting solution was filtered through activated carbon and left
to stand at room temperature. The crystals of 5·H2O suitable for a
single-crystal X-ray analysis formed from the mother liquor after a few
days. The complex was filtered off, washed with methanol and diethyl
ether and dried at 40 °C under an infrared lamp. Yield: 47 %. Color:
pink. C45H40NS2P2ClO4Ni (Mr = 879.0); C 61.5 (calcd. 61.8); H 4.6
(4.3); N 1.6 (1.5); S 7.3 (6.9); Cl 4.2 (4.6); Ni 6.7 (6.8) %.
Catalytic Studies
Graphite (0.6 g, diameter of particles less than 0.1 mm, ash residue
max. 0.2 %, mass drying loss max. 0.2 %) was mixed with an acetone
solution (2 mL) of the nickel(II) complex 1, 3, 5 or 6 (2, 4, and 7 were
not studied because of their insufficient solubility in acetone) to give
the final nickel concentration of 2.5 mmol·L–1. The mixtures were ho-
mogenized and dried at room temperature for 24 h. The study of the
catalytic influence of these samples on graphite was performed with a
Netzsch STA 449C device with an α-Al2O3 crucible without a standard
(10 °C·min–1 heating rate, sample weight of 5.0 mg, 100 mL·min–1 dy-
namic air atmosphere). The intersection point of the DTG curve tan- [Ni(BzMedtc)(PPh3)2]BPh4 (6): Na[BPh4] (2 mmol) was added to a
gents represents the initial temperatures of the graphite oxidation. The suspension of 1 (1 mmol) and PPh3 (2 mmol) in methanol (25 mL).
kinetic parameters were calculated by a direct non-linear regression The reaction mixture was heated under for reflux 3 h during which a
method [33].
pink solid appeared. The product was removed by filtration, washed
Z. Anorg. Allg. Chem. 2010, 1557–1564
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Z. Trávníček et al.
ARTICLE
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Yield: 69 %. Color: pink. C69H60NS2P2BNi (Mr = 1098.8); C 75.4
(calcd. 75.1); H 5.5 (5.2); N 1.3 (1.5); S 5.8 (5.6); Ni 5.3 (5.7) %. TG/
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Yield: 54 %. Color: red. C45H40NS2P3F6Ni (Mr = 924.5); C 58.5
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This work was financially supported by the Ministry of Education,
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Received: February 16, 2010
Published Online: May 7, 2010
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Z. Anorg. Allg. Chem. 2010, 1557–1564