Structural characterization and preliminary decomposition study of four unsymmetrically substituted nickel dithiocarbamate complexes

Article abstract of DOI:10.1080/00958972.2015.1107904

Single-crystal X-ray structures of four nickel dithiocarbamate complexes, the homoleptic mixed-organic bis-dithiocarbamates Ni[S2CN(isopropyl)(benzyl)]2, Ni[S2CN(ethyl)(n-butyl)]2, and Ni[S2CN(phenyl)(benzyl)]2, as well as the heteroleptic mixed-ligand co

Full text of DOI:10.1080/00958972.2015.1107904

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Structural characterization and preliminary
decomposition study of four unsymmetrically
substituted nickel dithiocarbamate complexes
John Masnovi, Norman V. Duffy, Philip E. Fanwick & Aloysius F. Hepp
To cite this article: John Masnovi, Norman V. Duffy, Philip E. Fanwick & Aloysius F. Hepp (2016)
Structural characterization and preliminary decomposition study of four unsymmetrically
substituted nickel dithiocarbamate complexes, Journal of Coordination Chemistry, 69:1, 90-102,
DOI: 10.1080/00958972.2015.1107904
To link to this article: http://dx.doi.org/10.1080/00958972.2015.1107904
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Date: 13 January 2016, At: 18:44

Journal of Coordination Chemistry, 2016
Vol. 69, no. 1, 90–102
http://dx.doi.org/10.1080/00958972.2015.1107904
Structural characterization and preliminary decomposition study
of four unsymmetrically substituted nickel dithiocarbamate
complexes
John Masnovia, Norman V. Duffyb, Philip E. Fanwickc and Aloysius F. Heppd
adepartmentofChemistry, Clevelandstateuniversity, Cleveland, oh, usa; bdepartmentofChemistry,Wheeling Jesuit
university, Wheeling, WV, usa; cdepartment of Chemistry, Purdue university, West lafayette, in, usa; dPhotovoltaics
and electrochemical systems Branch, nasa Glenn research Center, Cleveland, oh, usa
ARTICLE HISTORY
ABSTRACT
received 4 august 2015
accepted 7 october 2015
Single-crystal X-ray structures of four nickel dithiocarbamate complexes, the
homoleptic mixed-organic bis-dithiocarbamates Ni[S2CN(isopropyl)(benzyl)]2,
Ni[S2CN(ethyl)(n-butyl)]2, and Ni[S2CN(phenyl)(benzyl)]2, as well as the
heteroleptic mixed-ligand complex NiCl[P(phenyl)3][(S2CN(phenyl)(benzyl)],
were determined. A slightly distorted square-planar nickel coordination
environment was observed for all four complexes. The organic residues
adopt conformations to minimize steric interactions. Steric effects also may
determine puckering, if any, about the nickel and nitrogen atoms, both of
which are planar or nearly so. A trans-influence affects the Ni-S bond distances.
Nitrogens interact with the CS2 carbons with a bond order near two; the other
substituents on nitrogen display transoid conformations. There are no strong
intermolecular interactions, consistent with prior observations of the volatility
of nickel dithiocarbamate complexes. A preliminary thermolysis study of
the homoleptic species results in production of 1:1 nickel sulfide phases,
indicating the potential utility of these species as“single-source”precursors.
KEYWORDS
nickel dithiocarbamate;
X-ray diffraction;
triphenylphosphine;
crystal structures;
thermogravimetric analysis
1. Introduction
The structure and properties of metal dithiocarbamates M(S2CNRR′)x and closely related compounds
[1–5] remain an important area of research [6–10]. This is due to fundamental insights into coordina-
tion chemistry to be gained from in-depth studies of dithiocarbamates [6] and wide-ranging, practical
applications in agriculture [11–13], biomedicine [13–16], surface science [16, 17], and materials science
[18–27].
CONTACT aloysius f. hepp
aloysius.f.hepp@nasa.gov
supplemental data for this article can be accessed http://dx.doi.org/10.1080/00958972.2015.1107904.
this work was authored as part of the Contributor's official duties as an employee of the united states Government and is therefore a work of the
united states Government. in accordance with 17 u.s.C. 105, no copyright protection is available for such works under u.s. law.

JouRNAl oF CooRDiNATioN CHEMiSTRy
91
The present and a closely related follow-on [28] study are the most recent reports from an ongoing
effort to prepare new metal coordination compounds with sulfur-containing ligands (thiolates or dith-
iocarbamates), determine their single-crystal structures, and probe their decomposition to assess their
value as (new)“single-source”precursors for solid-state, thin-film, and/or nanoparticles of sulfides [21,
29–36] for possible aerospace applications. ideally, such precursors should be readily prepared from
inexpensive starting materials, easily handled (preferably air-stable), and/or cleanly decomposed via
chemical (vapor) processing to be economically viable [19–36]. in fact, these useful properties overlap
quite well with the anticipated advantages to be realized by use of single-source precursors.
our interest in this particular class of compounds concerns their use as precursors for nickel sulfide
solid-state materials [18–20, 23, 25–27]. in this report, we detail the synthesis and characterization of
four new Ni(ii) dithiocarbamate complexes, the homoleptic unsymmetrically substituted bis-dithiocar-
bamates Ni[S2CN(isopropyl)(benzyl)]2 (1), Ni[S2CN(ethyl)(n-butyl)]2 (2), and Ni[S2CN(phenyl)(benzyl)]2 (3),
together with the heteroleptic mixed-ligand complex Ni[P(phenyl)3)Cl(S2CN(phenyl)(benzyl)] (4). The
three homoleptic dithiocarbamates are of particular interest, as their decomposition under anaerobic
conditions at 400 °C results in a mass loss consistent with the formation of a 1 :1 nickel sulfide phase
consistent with prior literature [19, 20, 23, 25, 26].
2. Experimental
unless otherwise indicated, chemicals and solvents were used as received. Galbraith laboratories, inc.,
Knoxville, TN, performed elemental analyses of final compounds. A Cahn TG-2131 thermogravimetric
analysis (TGA) instrument was utilized with a heating rate of 5 °C/min starting at room temperature to
800 °C under flowing nitrogen [21, 32]; the mass loss was determined at 400 °C, based on prior studies
[18–20, 23, 25].
Sodium N-R-N-R′-carbodithioate salts were prepared by the method of von Braun [37] and Delepine
[38], later modified by Akerstrom [39]. Sodium hydroxide (6 g) was added slowly to distilled water
(10 ml) cooled in an ice bath. With continued cooling, 0.10 mol of N-isopropyl-N-benzylamine, N-ethyl-
N-butylamine, or N-phenyl-N-benzylamine [HN(R)(R′), with R, R′ = i-C3H7 (iPr), CH2C6H5 (Bz); C2H5 (Et),
n-C4H9 (nBu); or C6H5 (Ph), Bz; Aldrich, iR grade] was added slowly with rapid stirring, followed by rea-
gent grade CS2 (6.0 ml, 0.10 mol, Fisher Scientific). After stirring and cooling for two hours, light brown
crystals were separated and dissolved in boiling distilled water (20 ml). The mixture was cooled and,
after addition of absolute ethanol (5 ml), the resulting crystals were separated by filtration, washed
repeatedly with petroleum ether, air-dried overnight, and used without purification.
Synthesis of unsymmetrical dithiocarbamates began with mixing aqueous solutions of nickel(ii)
chloride hexahydrate, NiCl2·6H2o (0.714 g, 3 mmol), and a sodium N-R-N-R′-carbodithioate salt (6 mmol).
Bright green micro-crystals formed immediately and were collected on a sintered glass filter. The solid
was transferred to a beaker and dissolved in CHCl3 (50 ml). Any remaining aqueous fraction was dis-
carded and the CHCl3 solution was transferred to a filter flask. After addition of hexanes (50 ml), the
solvent was evaporated under reduced pressure. When most of the CHCl3 was removed, fine green
crystals of product precipitated and were collected on a sintered glass filter. The wet crystals were
washed with hexanes until the filtrate was colorless. The compound was dried overnight; a typical yield
of dithiocarbamates was ~70%.
Results of elemental analyses and thermogravimetric analysis are reported as follows: abbreviated
compound structural formula, empirical formula, color, molecular weight, analysis (%) calculated (found),
and % mass remaining at 400 °C (calculated for NiS). Results for: 1 [Ni(S2CNiPrBz)2] (C22H28N2S4Ni), green;
507.43; C, 52.1 (50.4); H, 5.6 (5.2); N, 5.5 (5.3); 18.4 (17.9); 2a [Ni(S2CNEtnBu)2] (C14H28N2S4Ni), dark green;
411.34; C, 40.9 (40.8); H, 6.9 (6.6); N, 6.8 (6.8); 21.2 (19.5); and 3 [Ni(S2CNPhBz)2] (C28H24N2S4Ni), green;
575.47; C, 58.4 (57.9); H, 4.2 (4.2); N, 4.9 (4.9); 15.2 (15.8).
Chloro(N-phenyl-N-benzylcarbodithioato)(triphenylphosphine)nickel(ii), NiCl[P(C6H5)3][S2CN(C6H5)-
(CH2C6H5)] (4), was prepared by dissolving [Ni(S2CNPhBz)] (0.575 g, 1.00 mmol), triphenylphosphine,
PPh3 (0.525 g, 2.0 mmol), and NiCl2·6H2o (0.238 g, 1.00 mmol) in boiling absolute ethanol (~20 ml). The

92
J. MASNoVi ET Al.
solution was stirred at reflux for 30 min. As the solution began to cool, a fine green precipitate settled to
the bottom of the beaker. The solution was filtered through a medium sintered glass filter to remove the
precipitate. The red-violet solution was allowed to cool to room temperature and then cooled further
in an ice bath. After 30 min, red-violet crystals formed and n-heptane (10 ml) was added to further
precipitate the complex. The solid was recovered by filtration through a medium sintered glass filter,
washed with n-heptane, and air-dried overnight. Results of elemental analyses and thermogravimetric
analysis are reported as follows: abbreviated compound structural formula, empirical formula, color,
molecular weight, analysis (%) calculated (found), and % mass remaining at 400 °C (calculated for NiS).
Results for 4 [NiCl(S2CNPhBz)PPh3] (C32H27NS2PClNi), violet; anal. 614.82; C, 62.5 (61.0); H, 4.4 (4.5); N, 2.3
(2.4); 22.0 (16.5). The most likely cause of the low carbon analysis for 1 and 4 is precipitation of unreacted
NiCl2·6H2o along with the heteroleptic dithiocarbamate complexes.
Microcrystals of each compound were taken up in hot ethanol, and single crystals suitable for X-ray
diffraction grew by slow evaporation of the solvent upon standing for three weeks at room temperature.
Crystals of 1 were dark green equant, 2a dichroic orange prismatic, 3 dichroic green prismatic, and 4
violet prismatic. Single crystals were cemented to a quartz fiber with epoxy glue in a random orienta-
tion. X-ray intensity data were collected at 150 K on a Nonius KappaCCD X-ray diffractometer system
using graphite monochromated Mo Kα radiation (λ = 0.71073 Å). Cell constants for data collection were
obtained from least squares refinement, and the space groups were determined using the program
xprep. Frames were integrated with denzo-smn [40]. lorentz and polarization corrections were applied to
the data. Structures were solved using the program patty in dirdif-99 [41] for 1, 2a, and 4 and by direct
methods using sir-2004 for 3 [42]. Scattering factors were taken from the international tables for crystal-
lography [43]. Refinement was performed on an AlphaServer 2100 using shelx-97 [44]. Crystallographic
drawings were produced using ortep and pluto [45, 46]. The crystallographic information is summarized
in Table 1. oRTEPs showing the atom labeling schemes are given in Figures 1–4, and cell diagrams are
shown in Figure 5. Deposition numbers for crystallographic information files (CiFs) deposited with the
Cambridge Crystallographic Data Center are given in Table 1.
3. Results and discussion
Single-crystal X-ray determinations for the four complexes (Table 2) allow for a comparison to the
abundant literature for structures of dithiocarbamate complexes related to both homoleptic (1–3) [5,
23, 26, 47–53] and heteroleptic (4) [54–56] compounds of this study (Table 3). A structure determination
for [Ni(S2CNEtnBu)2] (2b) has been reported previously [51] with a different unit cell although in the
same space group, and our modification (2a) is included here for comparison. The asymmetric units
of 2a and 3 comprise one half of these molecules with the metal atoms lying on inversion centers. As
expected, the phenyl groups in 1, 3, and 4 are essentially planar. The butyl chain in 2a has an all-anti
conformation, and the butyl and ethyl chains also are directed to opposite sides of the core structure;
this should be the lowest energy conformation, minimizing steric interactions. The nickel ions neces-
sarily reside in the plane of the ligands in 2a and 3 due to the symmetry, but they pucker slightly to lie
above this plane by 0.0212(3) Å in 1 and 0.0446(5) Å in 4.
The average Ni–S bond lengths for the three homoleptic [2.2020(5)–2.2084(6) Å] and the mixed-li-
gand 4 [2.2110(8) Å] complexes are unexceptional. of the three homoleptic species, the bis(isopropylb-
enzyl) complex (1) is the most asymmetric with a difference in Ni−S bond lengths of 0.0118(5) Å, similar
to several other homoleptic unsymmetrical complexes involving mixed (aryl–alkyl or proton–alkyl)
substituents (R-R′ = nBu-Bz, H-Pr, H-Adamantyl, Methyl-Ph) [26, 48–50]. The unsymmetrically substituted
2a and 3 with either two aliphatic or aromatic substituents have nearly symmetrical Ni–S coordination,
typical of other nickel dithiocarbamates [5, 23, 47, 51–53].
The Ni−S bonding in 4 and analogous complexes [54–56] is quite asymmetric, however, with the
Ni−S(1) bond trans to the electron-withdrawing chloride being shorter than the Ni−S bond trans to
the phosphine by 0.0464(8) Å. This asymmetry has been observed previously for structurally related
neutral compounds, including symmetrically substituted heterocyclic complexes [Ni(X)(S2CNRR′)(PPh3),

JouRNAl oF CooRDiNATioN CHEMiSTRy
93
Figure 1. orteP diagram with 30% thermal ellipsoids and atomic labeling scheme of ni(s2CniPrBz)2 (1).
Figure 2. orteP diagram with 30% thermal ellipsoids and atomic labeling scheme of ni(s2CnnBuet)2 (2a).
X = Cl, Br, i, NCS; R,R′ = Et, nBu, (CH2)4] [57–59]. it can be ascribed to a structural trans-effect, phosphines
being stronger trans-influencing ligands than chloride as found commonly in square-planar complexes
of Pd and Pt [60].

94
J. MASNoVi ET Al.
Figure 3. orteP diagram with 30% thermal ellipsoids and atomic labeling scheme of ni(s2CnPhBz)2 (3).
Figure 4. orteP diagram with 30% thermal ellipsoids and atomic labeling scheme of niCl(s2CnBzPh)(PPh3) (4).
Bond lengths involving the sp2 hybridized carbons (C1 or C10) near the core of the dithiocarbamate
complexes are typically 1.71(1)–1.73(2) Å for S⋯C and 1.29(1)–1.33(1) Å for N⋯C, consistent with a
number of previously reported homoleptic and heteroleptic complexes [5, 23, 26, 47–59]. As expected,

JouRNAl oF CooRDiNATioN CHEMiSTRy
95
Figure 5. Cell diagram stereoviews of (a) 1, (b) 2a, (c) 3, and (d) 4. atom colors: C gray, Cl brown, h cyan, n blue, ni green, P magenta,
and s red (see http://dx.doi.org/10.1080/00958972.2015.1107904 for color version).
the N−C(sp3) single bonds attached to the organic substituents are longer by ~0.15 Å than the N−CS2
bond and are typical (1.47 0.02 Å) for all four complexes [5]. Bond lengths near 1.3 Å found for the
N−CS2 bonds are more characteristic of N=C double bonds [61] and indicate considerable double bond
character to be present between N and the CS2 carbon in these complexes [49].

96
J. MASNoVi ET Al.
Table 1. summary of crystallographic data for 1–4.
Compound
1
2a
3
4
empirical formula
molecular weight
Crystal system
space group
a (Å)
b (Å)
c (Å)
C22h28n2nis4
507.43
C14h28n2nis4
411.34
C28h24n2nis4
575.46
C32h27ClnniPs2
614.82
monoclinic
P21/n (no. 14)
10.5407(2)
11.1598(2)
19.9164(5)
90
92.3629(8)
90
2340.82(8)
4
monoclinic
P21/n (no. 14)
8.4442(5)
8.4633(6)
13.5293(9)
90
94.626(4)
90
963.73(11)
2
monoclinic
P21/c (no. 14)
10.0329(6)
11.7342(7)
11.4362(4)
90
92.709(8)
90
1344.86(12)
2
monoclinic
P21/n (no. 14)
13.9479(3)
9.7908(3)
22.4583(7)
90
107.7183(12)
90
2921.45(14)
4
α (°)
β (°)
γ (°)
V (Å3)
Z
Dcalc (g cm−3)
1.440
1.186
1.417
1.423
1.421
1.042
1.398
0.972
μ (mm−1)
F(0 0 0)
1064
0.30 × 0.30 × 0.30
150
2.05–27.48
17,437
5297 (0.027)
0.70, 0.61
4106
436
596
1272
0.44 × 0.35 × 0.31
150
2.04–27.48
20,715
6653 (0.048)
0.74, 0.65
4428
Crystal size (mm)
temperature (K)
θ range collected (°)
data collected
unique data (Rint)
Tmax, Tmin
0.30 × 0.30 × 0.18
150
2.41–27.47
7118
2161 (0.029)
0.77, 0.67
1682
0.44 × 0.35 × 0.28
150
2.49–27.50
18,305
3024 (0.037)
0.75, 0.67
2394
data with I > 2.0σ(I)
R(Fo)a
0.035
0.080
0.37/−0.65
0.993
761,180
0.037
0.100
0.58/−0.72
1.020
761,181
0.030
0.072
0.36/−0.32
1.071
601,390
0.045
0.106
0.66/−0.58
1.025
761,182
wR(Fo2)b
largest diff. peak/hole (eÅ−3)
Goodness of fit (Gof) on F2
CCdC deposit no.
aR = Σ||F | − |F ||/Σ|F | for Fo2 > 2휎(Fo2).
o
∑
c
o
∑
2
bwR = [ w(�Fo2� − �Fc2�)2)∕ w(�Fo2� )]1∕2
.
Table 2. selected average bond lengths (Å) and angles (°) in 1–4.
Distancesa
Bond
1
2a
2b
3
4
ni−s
2.2040
2.2082
2.2033
2.2020
2.1878(8)b
2.2342(8)c
1.718
s−C
1.7235
1.3185
1.4725
1.492
1.5205
1.5135
1.720(2)
1.321(3)
1.714
1.319(3)
1.7194
1.318
1.445
1.475
n−Cs2
n−Ph
n−Ch
alkyl C−C
C−Ph
ni−Cl
ni−P
1.313(4)
1.456(4)
1.478(3)
1.471
1.521
1.4735
1.5095
1.509(2)
1.510(4)
2.18000(8)
2.2010(8)
anglesa
2b
79.55
100.45
180.00
85.20
121.16
117.48
110.04
124.98
Bonds
s−ni−s
1
2a
3
79.281
100.71
178.75
85.555
120.28
118.54
109.34
125.33
79.28(2)
100.72(2)
180.00
78.31(3)
ni−s−C
C−n−Cs2
C−n−C
s−C−s
85.42
121.44
117.1(2)
109.87(15)
125.06
86.48
121.1
117.8(2)
108.71(16)
125.65
s−C−n
aValues reported with standard deviations are unique.
bs1 (trans to Cl).
cs2 (trans to P).
A hybridization of sp2 also is consistent with the observation of small pyramidalization of the
nitrogens, which are nearly planar in 2a and 3 (Table 4). The effect would be to shift electron den-
sity from nitrogen to sulfur, placing the nickel in a relatively electron-rich environment. The greatest

JouRNAl oF CooRDiNATioN CHEMiSTRy
Table 3. average bond distances and angles for unsymmetrical ni dithiocarbamate complexes.a,b
97
S–Ni–S
(°)
S⋯C
Ni–S–C
(°)
Text Ref./
Cmpd.
Compound
Ni–S (Å)
(Å)
S–C–S (°)
C⋯N (Å)
C–N (Å)
ni(s2Cnhme)2
ni(s2CnhPr)2
ni(s2Cnhadm)2
2.200
2.198
2.201
2.203
2.203
2.2033
2.2084
2.1967
2.2040
79.2
79.92
79.12
79.20
79.3
79.18
79.28
79.58
79.29
79.20
79.48
79.55
78.83(12) 1.718
79.02(3) 1.730
78.31(12) 1.718
1.71
1.715
1.725
1.716
1.72
1.714
1.722
1.724
1.724
1.715
1.731
1.720
109.8
110.7
108.69
109.8
109.3
110.04
109.9
109.3
109.4
109.9
109.0
–
1.30
1.295
1.314
1.315
1.30
1.319
1.321
1.314
1.319
1.322
1.292
1.318
1.326(14)
1.47
1.455
1.473
–
[47]
[48]
[49]
[23]
[50]
[51]/(2b)
(2a)
[52]
(1)
[26]
84.5
86.05
–
c
ni(s2CnmenBu)2
ni(s2CnmePh)2
ni(s2CnetnBu)2
85.6
85.40
85.42
85.57
85.69
85.4
85.8
85.20
86.3
1.48
1.481
1.471
1.484
1.482
1.482
1.487
1.460
1.485
d
Ni(S2CNEtnBu)2
e
ni(s2CnetCy)2
d
Ni(S2CNiPrBz)2 c
ni(s2CnnBuBz)2
2.2041
2.205
2.2020
ni(s2CnCh2C4h3nBz)2
[53]
(3)
[54]
d
Ni(S2CNPhBz)2
110.04
108.4(6)
ni(Cl)(PPh3)(s2CniPrBz)
ni(Cl)(PPh3)(s2CnnBuBz)f
Ni(Cl)(PPh3)(S2CNPhBz)d
ni(Br)(PPh3)(s2CniPrBz)
ni(Br)(PPh3)(s2Cn(h)Ph)f
ni(i)(PPh3)(s2CniPrBz)
2.215(3)g
2.176(3)
2.2224(11)g
2.1745(11)
2.2342(8)g
2.1878(8)
2.2205(8)g
2.1851(8)
2.2128(16)g
2.1814(16)
2.2087(12)g
2.1882(12)
107.93(11)
108.7(1)
107.9(2)
108.3(3)
107.7(2)
86.53
86.5
87.0
86.3
87.1
1.309(3)
1.313(4)
1.316(4)
1.329(8)
1.325(4)
1.471
1.467
1.487
1.436
1.477
[55]
(4)
78.05(3)
78.38(6)
79.13(5)
1.716
1.713
1.717
[54]
[56]
[54]
aValues with standard deviations are unique.
btemperature of data collection 293 2 K or:
c120 K.
d150 K.
e200 K.
f100 K.
gBond trans to phosphorus.
Table 4. distances (Å) of atoms from the specified planes.
Cmpd.
Ni from ligands
C(S2) from ligands
N from attached C
1
0.0212(3)
0.0221(19), 0.045(2)
0.020(3)
0.081(2), 0.0763(19)
0.016(2)
2a
2ba
3
0
0
0
0.007(3)
0.011(2)
0.004(3)
0.009(3)
0.0367(16)
0.004(3)
4
0.0446(5)
aCoordinates from reference [51].
Figure 6. transoid orientation of the alky groups (r and r′) in 1–4.
pyramidalization is found in 1, due possibly to the steric demands of the isopropyl group. However, since
the nitrogens in 3 and 4 are similarly substituted yet pyramidalize to different degrees, other effects
such as molecular packing likely contribute as well. Small pyramidalization about nitrogen is common
in sp2-hybridized aromatic amines such as carbazoles and occurs with little sacrifice of energy [62].

98
J. MASNoVi ET Al.
Since the nitrogens are nearly planar and lie close to the plane of the inorganic core atoms, cisoid and
transoid conformations are possible for the two alkyl or aryl substituents R and R′ on nitrogen in the
homoleptic derivatives 1–3. The transoid geometry, in which the same organic groups are located on
opposite sides of the structure, is found for all three (Figure 6). This orientation should minimize steric
interactions and is expected to be lowest in energy.
The chelated S−Ni−S bond angles for the three homoleptic compounds are similar [79.28(2)–
79.55(2)°], typical for homoleptic complexes reported with an average bond angle of 79.5 0.4° [5,
23, 26, 47–53]. The heteroleptic 4 has a smaller bite of 78.31(12)°, within the margin of error for related
mixed-ligand (pseudo)halide triphenylphosphine dithiocarbamate complexes, with an average bond
angle of 78.7 0.4° [54–59]. The S−C−S bond angle of 110.04° for 3 is similar to that of 1 and 2a and is
typical for asymmetrically substituted homoleptic compounds [5, 23, 26, 47–53]. This angle is more than
one degree smaller in 4, which like 3 also bears benzyl and phenyl organic residues, and corresponds
with an S−Ni−S angle which is smaller by about the same amount, consistent with observations for other
heteroleptic compounds [54–59]. The smaller bite angles about nickel and carbon in 4 are probably
once again attributable to steric effects, here involving the five phenyl groups.
The Ni−S−C bond angles for 1–3 of 85.20(6)–85.68(7)° are in the midrange of 85.5 0.5° observed
for other homoleptic compounds [5, 23, 26, 47–53], and the slightly wider angle found in 4 of 86.5(1)° is
typical of heteroleptic species [54–59]. Slight differences in the shape of the central ring of the two types
of compounds could be a result of the effect of electron-withdrawing (pseudo-)halides. Bond lengths
and angles outside of the core ring structure vary considerably as there are a large number of structural
types, and more overarching analyses of bonding-structure correlations in dithiocarbamates and related
complexes as well as potential correlations to spectroscopy have been addressed previously [1–5].
The structures reveal only weak intermolecular interactions. Putative weak intermolecular hydrogen
bonds to sulfur with S⋯H′ distances less than the sum of the van der Waals radii (3.0 Å) are found in 1,
2a, and 4, whereas the interactions in 3 occur just beyond this distance (Table 5). The closest contacts
are found in 1 (2.824 Å) and in 2a (2.631 Å), indicating that steric effects involving the phenyl groups
Table 5. nonbonded intramolecular (dashed) and intermolecular (dotted) distances (Å) and angles (°).
interactiona
Distances
Angles
1
ni⋯h214
3.008
3.022
2.824
s11⋯h113′
s12⋯h213′
C223⋯C223′
C10−s11⋯h113′
C10−s12⋯h213′
145.1
166.7
ni−s11⋯h113′
ni−s12⋯h213′
89.0
104.6
s11⋯h113′−C113′
s12⋯h213′−C213′
147.4
148.5
3.390(4)
2a
ni⋯h14C
s1⋯h16B′
s2⋯h15a′
3.454
2.847
2.631
C1−s1⋯h16B′
C1−s2⋯h15a′
173.8
159.4
ni−s1⋯h16B′
ni−s2⋯h15a′
98.0
151.6
s1⋯h16B′−C16′
s2⋯h15a′−C15′
101.0
107.5
3
ni⋯h24
3.157
3.019
3.018
3.014
s1⋯h12′
s1⋯h23′
s2⋯h20a′
C1−s1⋯h12′
C1−s1⋯h23′
C1−s2⋯h20a′
134.7
91.7
96.2
ni−s1⋯h12′
ni−s1⋯h23′
ni−s2⋯h20a′
92.0
111.8
114.5
s1⋯h12′−C12′
s1⋯h23′−C23′
s2⋯h20a′−C20′
132.9
155.7
127.3
4
ni⋯h215
3.327
2.958
2.901
2.956
2.891
2.972
2.975
Cl⋯h116′
Cl⋯h123′
s2⋯h116′
s2⋯h215′
C114⋯h212′
C214⋯h233′
ni−Cl⋯h116′
ni−Cl⋯h123′
C10−s2⋯h116′
C10−s2⋯h215′
94.0
Cl⋯h116′−C116′
147.2
165.9
92.9
164.0 Cl⋯h123′−C123′
60.0
88.5
ni−s2⋯h116′
ni−s2⋯h215′
s2⋯h116′−C116′
s2⋯h215′−C215′
145.0
141.2
79.8
adashed lines represent intramolecular interactions, dotted lines intermolecular interactions, and primed atoms repre-
sent positions in a different molecule. van der Waals contact distances: Ch 2.90, CC 3.40, sh 3.00, Clh 2.95, nih 2.83; see:
http://periodictable.com/Properties/a/VanderWaalsradius.al.html.

JouRNAl oF CooRDiNATioN CHEMiSTRy
99
likely prevent as close an approach to the core ring in 3 and 4. Two additional weak hydrogen bonds
involving Cl also are present in 4 with Cl⋯H′ distances near the sum of the van der Waals radii (2.95 Å).
The interaction diagrams in Figure 7 indicate that the nickel ions have no close intermolecular contacts
despite the coordination being essentially planar. instead, the organic moieties of adjacent molecules
fit hand-in-glove in the region about the open axial coordination sites. Steric effects arising from the
organic groups would be present here as well and in 1 and 4 intramolecular hydrogens approach nickel
(Table 5), further obstructing the coordination site about the plane of the inorganic core. However, nickel
exhibits low propensity for axial coordination relative to copper and zinc in related bis(diethyldithio-
carbamate) compounds [63], which likely plays a large role in these heteroleptic analogs as well. The
absence of stronger intermolecular interactions is responsible for the volatility of the nickel-containing
compounds as discussed below.
Comparison of the two modifications of 2 reveals that the unit cell volume [1002.23(18) Å3] reported
previously for 2b [51] is 4% larger than that [963.73(11) Å3] for the structure 2a determined here. A
smaller cell is preferable as a larger volume allows for greater thermal motion and other disorder,
and large temperature factors may afford bond distances smaller than the actual values [64]. indeed,
the isotropic temperature factors on the refined atoms of the published structure are about twice as
large as those on corresponding atoms of 2a with the smaller volume, and 10 of the 11 unique bond
distances between refined positions reported for modification 2b are smaller than those determined
for 2a. More efficient packing in the smaller cell also would allow greater intermolecular interactions,
decreasing volatility as discussed below. otherwise, the structures of the two modifications are similar,
with the most significant difference (over 4°) being the dihedral angle formed between the planes of
the core structure and the aminoisopropyl group (Table 6).
The volatility of some nickel(ii) dithiocarbamates has been reported for more than a century and
more recently reviewed [65, 66]. bis(diisopropyldithiocarbamato)nickel(ii), for example, sublimes in
vacuum almost without decomposition [38], whereas bis(diisobutyldithiocarbamato)nickel(ii) exhibits
a single mass loss of 93% at 390 °C [67] and bis(dibutyldithiocarbamato)nickel(ii) also exhibits signifi-
cant volatility [18]. likewise, o’Brien and coworkers observed mass loss greater than that predicted for
Figure 7. interaction diagram showing close contacts to the core structures of (a) 1, (b) 2a, (c) 3, and (d) 4.

100
J. MASNoVi ET Al.
Table 6. dihedral angles (°) between selected planes.
Cmpd.
Plane
Atoms in plane
Planes
Angle
Planes
Angle
1
1
2
3
4
5
1
2
3
1
2
3
1
2
3
4
5
6
ni,s11–s22,C10,C20
C111–C116
C211–C216
C121–C123
C221–C223
ni,s1–s2,C1
n1,C11–C14
n1,C15–C16
ni,s1–s2,C1
C11–C16
1,2
1,3
1,4
1,5
2,3
1,2
1,3
2,3
1,2
1,3
2,3
1,2
1,3
1,4
1,5
1,6
2,3
2,4
2,5
80.98(6)
109.05(5)
95.06(9)
2,4
2,5
3,4
3,5
4,5
135.90(16)
132.71(17)
17.92(9)
96.59(9)
19.11(11)
3.7(2)
146.70(8)
85.81(15)a
92.99(18)a
64.42(13)a
82.08(5)
73.97(6)
64.14(7)
63.91(10)
108.31(9)
42.36(8)
2
3
4
87.08(16)b
97.1(2)b
65.42(16)b
C21–C26
ni,s1–2,P2,C1,C10
C111–C116
C121–C126
C211–C216
C221–C226
C231–C236
2,6
3,4
3,5
3,6
4,5
4,6
5,6
43.05(12)
68.29(12)
102.34(12)
22.11(12)
106.35(10)
74.38(11)
80.23(11)
84.96(7)
106.16(8)
46.61(13)
34.43(12)
84.89(11)
aCompound 2a.
bCorresponding positions for 2b with coordinates from reference [51].
elemental nickel residue for symmetrically and unsymmetrically substituted Ni(S2CNRR′)2 complexes
(R, R′ = Me, Et, nBu, Cy) [20]. Nevertheless, in the same report, low-pressure chemical vapor deposition
of four homoleptic complexes resulted in the production of one or two NiS phases.
As outlined in Section 2, our preliminary TGA results also are consistent with formation of 1:1 NiS
phases for 1–3, as mass residues are within 5% of prediction for NiS. This can be contrasted with the
heteroleptic complex where a 33% differential is clearly inconsistent with production of a 1 :1 phase.
The relatively high conversions of these unsymmetrically substituted complexes, even 2a which is an
isomer of bis(diisopropyldithiocarbamato)nickel(ii), may result from their greater surface areas and
packing efficiencies (Figure 7). We currently are completing in-depth TGA, pyrolysis, and solid-state
materials studies of the thermolysis of five homoleptic nickel dithiocarbamates [28].
4. Conclusion
A slightly distorted square-planar nickel coordination environment is observed for all four unsymmet-
rically substituted nickel(ii) dithiocarbamate complexes. Compound 1 exhibits the greatest asymmetry
of the Ni–S bonds among the homoleptic compounds, and a trans-influence affects the Ni–S bond dis-
tances in 4. The organic residues adopt conformations (transoid and anti) to minimize steric interactions.
Steric effects also may determine the puckering of the nickel and nitrogens, both being planar or nearly
so. The nitrogens essentially form double bonds to the CS2 carbons. The other substituents on nitrogen
in 1–3 adopt transoid conformations. There are no strong intermolecular interactions, consistent with
previous reports of the volatility of these compounds. Preliminary TGA results are consistent with pro-
duction of 1:1 NiS phases, pointing to the utility of these complexes for the fabrication of solid-state
materials; a more detailed study is currently underway at NASA GRC.
Supplementary material
The Cambridge Crystallographic Data Center contains the full set of supplementary crystallographic data (CiFs) for this
paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Center via www.ccdc.cam.
ac.uk/data_request/cif (see Experimental and/or Table 1 for specific deposition numbers). More complete tables of bond
lengths and angles (Tables S1–S4) are included in the Supplementary information.

JouRNAl oF CooRDiNATioN CHEMiSTRy
101
Acknowledgments
The authors thank Mark Cundick (Kent State university) for synthesis of nickel dithiocarbamate complexes and Dr Douglas
ogrin (ohio Aerospace institute) for crystal growth. N.V. Duffy thanks the NASA West Virginia EPSCoR program for financial
support.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
Work at NASA Glenn Research Center was supported by several internal research and development programs (A.F. Hepp
and D. ogrin) and the NASA GRC Faculty Fellowship Program (for J. Masnovi).
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