Homopiperazine platinum(II) complexes containing substituted disulfide groups: Crystal structure of [PtII(homopiperazine)(diphenylsulfide)Cl]NO3

Article abstract of DOI:10.1016/S0277-5387(01)00967-6

A series of new cationic platinum(II) complexes of the type [Pt(L)(R′R″S)Cl]NO₃ (where L = homopiperazine or 1-methylhomopiperazine and R′R″S = dimethylsulfide, diethylsulfide, dipropylsulfide, diisopropylsulfide, dibutylsulfide, diphenylsulfide, dibenzylsulfide, methylphenylsulfide, or methyl p-tolylsulfide) were synthesized and characterized by elemental analysis and infrared, ¹H and ¹⁹⁵Pt nuclear magnetic resonance spectroscopy. Among the complexes synthesized, [Pt¹¹(homopiperazine)(diphenylsulfide)Cl]NO₃ was examined by single-crystal X-ray diffraction. The slightly distorted square plane of the platinum complex included the amino groups of the homopiperazine molecule in a cis orientation, the sulfur atom of diphenyl sulfide, and a chloride ion. The homopiperazine molecule adopts a boat conformation and forms five- and six-membered chelating rings with platinum. Hydrogen bonding plays an important part in holding the crystal together.

Full text of DOI:10.1016/S0277-5387(01)00967-6

Polyhedron 21 (2002) 125–131
www.elsevier.com/locate/poly
Homopiperazine platinum(II) complexes containing substituted
disulfide groups: crystal structure of
[PtII(homopiperazine)(diphenylsulfide)Cl]NO3
Mohammad S. Ali a, Uday Mukhopadhyay a, Shervin M. Shirvani a, John Thurston b,
Kenton H. Whitmire b, Abdul R. Khokhar a,*
a Department of Experimental Therapeutics, Box 353, The Uni6ersity of Texas, M.D. Anderson Cancer Center,
1515 Holcombe Boule6ard, Houston, TX 77030, USA
b Department of Chemistry, MS 60, Rice Uni6ersity, 6100 Main Street, Houston, TX 77005, USA
Received 9 April 2001; accepted 9 October 2001
Abstract
A series of new cationic platinum(II) complexes of the type [Pt(L)(R%R¦S)Cl]NO3 (where L=homopiperazine or 1-methylho-
mopiperazine and R%R¦S=dimethylsulfide, diethylsulfide, dipropylsulfide, diisopropylsulfide, dibutylsulfide, diphenylsulfide,
dibenzylsulfide, methylphenylsulfide, or methyl p-tolylsulfide) were synthesized and characterized by elemental analysis and
infrared, 1H and 195Pt nuclear magnetic resonance spectroscopy. Among the complexes synthesized, [PtII(homopiperazine)-
(diphenylsulfide)Cl]NO3 was examined by single-crystal X-ray diffraction. The slightly distorted square plane of the platinum
complex included the amino groups of the homopiperazine molecule in a cis orientation, the sulfur atom of diphenyl sulfide, and
a chloride ion. The homopiperazine molecule adopts a boat conformation and forms five- and six-membered chelating rings with
platinum. Hydrogen bonding plays an important part in holding the crystal together. © 2002 Elsevier Science Ltd. All rights
reserved.
Keywords: Platinum(II); Homopiperazines; Disubstituted sulfides; Synthesis; Crystal structure
alkylamines [8]. Carboplatin (diammine-1,1-cyclobu-
tanedicarboxylatoplatinum(II) [9,10], one of a number
of cisplatin analogs developed in this way, is now used
clinically. Many other compounds that have 1,2-di-
aminocyclohexane as a carrier ligand and chloride or
carboxylate ion as a leaving group, such as oxaliplatin
(trans - l - 1,2 - diaminocyclohexaneoxalatoplatinum(II)
1. Introduction
The wide success of cisplatin in the treatment of a
variety of human cancers [1], especially those of the
testes, ovaries, head, and neck [2–5], has encouraged
the search for new cisplatin derivatives in an effort to
improve the therapeutic index of its compounds, which
is reduced by dose-limiting toxic effects, namely,
nephrotoxicity, myelotoxicity, neurotoxicity, nausea,
and vomiting [6,7]. The clinical effectiveness of cisplatin
has been improved by replacing the labile chloro lig-
ands with other leaving groups of intermediate lability
so as to alter the pharmacokinetics as well as by
substituting stable amine ligands with cyclic or acyclic
and
L-NDDP [liposome-entrapped bis(neodecanoato)-
(trans-1R,2R-diaminocyclohexane)platinum(II)]
are
now in clinical trials [10–12].
Platinum antitumor complexes like cisplatin and its
analogs are neutral complexes that obey the general
formula [cis-Pt(Am)2(X)2] in which Am is an amine
ligand having at least one NH group and X is a
moderately strongly bound anionic leaving group, such
as chloride [13,14]. These complexes are bifunctional in
nature, which is probably necessary to form an in-
trastrand cross-link between two adjacent guanine
bases in DNA [15,16]. However, two cationic classes of
* Corresponding author. Tel.: +1-713-792-2387; fax: +1-713-745-
1176.
E-mail address: akhokhar@mdanderson.org (A.R. Khokhar).
0277-5387/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0277-5387(01)00967-6

126
M.S. Ali et al. / Polyhedron 21 (2002) 125–131
platinum complexes having antitumor properties have
been described, both of which are much more soluble in
water than the neutral complexes are. Such complexes
have the general formula [cis-Pt(NH3)2(N-het)Cl]Cl (N-
het=heterocyclic amine) or [Pt(diam)(R%R¦SO)Cl]NO3
(diam=bidentate diamine, R%R¦SO=substituted sulf-
oxide) [17,18]. On the other hand, related monofunc-
tional cationic complexes like [Pt(dien)Cl]Cl and
[Pt(NH3)3Cl]Cl are antitumor inactive [19,20]. Eventu-
ally, compounds having the formula [Pt(diam)-
(R%R¦SO)Cl]NO3 or [Pt(diam)Cl2] will form the same
adduct with 5%GMP and d(GpG) [21]. In principle, the
same adducts can be expected with DNA, therefore, the
mechanisms of action of both types of compounds
might well be related to each other but are unlikely to
be the same as that of cisplatin [21].
Hollis et al. [17] reported on a series of cationic
platinum(II) complexes whose antitumor activity vio-
lates some of the rules of classical structure-activity
relationships. However researchers have known of
cationic diammineplatinum(II) complexes with substi-
tuted sulfoxide for the past 2 decades [22,23]. It has
been reported that these complexes have antitumor
activity in certain tumor models [24,25]. We have been
developing platinum complexes with diamines such as
diaminocyclohexane as a carrier ligand and disulfides as
leaving groups [26]. Complexes containing thioether
groups can reduce cisplatin-induced nephrotoxicity
when administered simultaneously with cisplatin [27].
Hence we report here the synthesis and characterization
of cationic platinum(II) complexes of the type
[PtL(R%R¦S)Cl]NO3 along with the crystal structure of
[PtII(homopiperazine)(diphenylsulfide)Cl]NO3.
Perkin–Elmer 2000 spectrophotometer. 1H nuclear
magnetic resonance (NMR) spectra in MeOH-d4 and
195Pt NMR spectra in methanol were recorded using a
Bruker Advance 300 spectrometer. 1H spectra were
recorded with a 5-mm tunable probe at 300.13 MHz,
195Pt spectra were recorded at 43.055 MHz, and the
shifts were measured relative to an external standard of
2.2 M Na2PtCl6 in D2O at 0.00 ppm.
2.3. Preparation of {Pt(hpip)[(CH3)2S]Cl}NO3
(hpip=homopiperazine) (complex 1)
K2PtCl4 (20.76 g, 50 mmol) was dissolved in 250 ml
of deionized water and filtered. KI (83.0 g, 0.5 mol) in
100 ml of water was added to it, and the reaction
mixture was stirred for 10 min. Next, homopiperazine
(8.5 g, 100 mmol) was added dropwise to the mixture
while stirring to obtain a yellow precipitate of [Pt(h-
pip)I2]. The stirring was continued for a further 30 min,
and the precipitate was then collected by filtration. This
compound was stirred in 100 ml of dimethylformamide,
filtered, washed with water, ethanol, and acetone, and
dried under vacuum (yield, 95%). [Pt(hpip)I2] (12.38 g,
20 mmol) was suspended in an aqueous solution of
silver nitrate (6.72 g, 39.8 mmol) in 250 mL of water.
The reaction mixture was stirred for 24 h at room
temperature (r.t.) in the dark. The AgI precipitate was
filtered off, and a solution of NaCl was added dropwise
to the filtrate with constant stirring until a yellow
precipitate of [Pt(hpip)Cl2] formed. The precipitate was
filtered and recrystallized from dimethylformamide.
The yellow crystals obtained were washed with water
and acetone and dried under vacuum (yield, 75%). An
equivalent amount of AgNO3 (0.338 g, 2 mmol) dis-
solved in 100 ml of hot methanol was added to a slurry
of [Pt(hpip)Cl2] (0.872 g, 2 mmol) in 100 ml of
methanol. An equivalent amount of dimethylsulfide
(0.15 mg, 2 mmol) in 20 ml of methanol was added to
this mixture. The reaction mixture was then stirred
overnight in the dark. The AgCl precipitate was filtered
off and the filtrate was evaporated to dryness under
reduced pressure. A yellow solid was obtained, which
was recrystallized from methanol and ether. Finally, the
light yellow compound, [Pt(hpip)(CH3)2S)Cl]NO3, was
obtained, which was then dried under vacuum (yield,
70%).
2. Experimental
2.1. Chemicals
K2PtCl4 was purchased from Johnson Matthey,
Seabrook, MA. Homopiperazine, 1-methylhomopiper-
azine, dimethylsulfide, diethylsulfide, dipropylsulfide,
diisopropylsulfide,
dibutylsulfide,
diphenylsulfide,
dibenzylsulfide, methylphenylsulfide, and methyl p-
tolylsulfide were purchased from Aldrich Chemical Co.,
Milwaukee, WI. Silver nitrate was obtained from Fisher
Scientific Co., Houston, TX. All chemicals obtained
from commercial sources were used as supplied.
Complexes 2–18 (Table 2) were prepared in a similar
manner.
2.2. Physical measurements
Complex 11 [PtII(hpip)(diphenylsulfide)Cl]NO3 (100
mg) was dissolved in 100 ml of methanol, after which
the volume of the solution was reduced to 50 ml and
filtered. The filtrate was allowed to evaporate slowly at
r.t. Within 2 weeks, colorless needle-shaped crystals
were separated from the solution, which were used for
X-ray crystallography.
Elemental analyses of the complexes were performed
by Robertson Laboratory Inc., Madison, NJ. Infrared
(IR) spectra in the range of 600–4000 cm−1 and far-IR
spectra in the range of 150–600 cm−1 were recorded in
KBr and polyethylene pellets, respectively, on
a

M.S. Ali et al. / Polyhedron 21 (2002) 125–131
127
,
0.71073 A) and the data was corrected for Lorentz and
polarization effects. Absorption correction was applied
using the program SADABS [28]. No appreciable decay
of the crystal was detected during data collection.
The structure was solved using direct methods with
the SHELXTL software package [28]. Scattering factors
were taken from the literature [29]. Heavy atoms were
located initially to set the correct phases for the model.
All other atoms were located by successive Fourier
maps and were refined using the full-matrix least-
squares method on F2. All non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were placed in
2.4. Single crystal X-ray crystallographic study
The experimental details of the X-ray data collection,
the structure solution and refinement of the title com-
pound are compiled in Table 1. A single crystal of
[PtII(homopiperazine)(diphenylsulfide)Cl]NO3
was
coated with a thin layer of epoxy cement and glued to
the end of a glass fiber. The fiber was mounted on the
goniometer of a Bruker SMART 1K diffractometer
equipped with a CCD area detector at 298 K. The
orientation matrix and all data were collected at this
temperature. The diffractometer is equipped with
graphite monochromated Mo Ka radiation (u=
,
calculated positions (dC–H=0.96 A) and allowed to
ride on the adjacent carbon atom. Refinement of posi-
tional and anisotropic parameters led to convergence.
Table 1
Crystal data and structure refinement for [PtII(homopiperazine)-
(diphenylsulfide)Cl]NO3
3. Results and discussion
Empirical formula
Formula weight
Temperature (K)
C17H20ClN3O3PtS
576.96
293(2)
3.1. Synthesis of platinum complexes
,
Wavelength (A)
0.71073
monoclinic
P21/c
The procedure used in the synthesis of complexes is
shown in Scheme 1. [PtLCl2] was prepared according to
the method described by Dhara [30], which was
adopted because it is rapid and easy and provides a
much higher yield than when K2PtCl4 is treated directly
with homopiperazines. K2PtCl4 mixed with an excess of
KI produced K2PtI4 in solution. K2PtI4 was then re-
acted with one equivalent of hpip or mhpip (1-methyl-
homopiperazine) to precipitate [PtLI2]. The reaction of
[PtLI2] with AgNO3 led to the formation of
[PtL(H2O)2](NO3)2 in solution, which was further con-
verted to [PtIILCl2] by treating it with a NaCl solution.
Finally [PtII(L)Cl2] was reacted with one equivalent of
AgNO3 and subsequently with thioethers to form the
required compounds of the type [Pt(L)(R%R¦S)Cl]NO3
in solution, while the insoluble AgCl was separated by
filtration. The yellow solid [Pt(L)(R%R¦S)Cl]NO3 was
obtained [26] upon removal of the solvent.
Crystal system
Space group
Unit cell dimensions
,
a (A)
17.666(4)
8.8116(18)
12.619(3)
101.02(3)
1928.1(7)
4
1.988
7.546
,
b (A)
,
c (A)
i (°)
3
,
V (A )
Z
Dcalc (Mg m−3
)
Absorption coefficient (mm−1
F(000)
)
1112
Crystal size (mm)
q Range for data collection (°)
Limiting indices
0.318×0.242×0.163
1.17–23.33
−195h517, −95k59,
−125l513
Reflections collected
Independent reflections
Refinement method
8122
2740 (Rint=0.0785)
Full-matrix least-squares on
F2
2740/0/235
1.057
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\2|(I)] a
R indices (all data)
R1=0.0400, wR2=0.1035
R1=0.0416, wR2=0.1110
3.2. Characterization of platinum complexes
Largest difference peak and hole 1.865 and −1.319
−3
The complexes were characterized by elemental anal-
,
(e A
)
1
ysis and IR, H NMR, and 195Pt NMR spectroscopy.
a R1=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ. Rw=[S w(Fo2−Fc2)2]/S[w(Fo2)2]1/2
. w=
The composition of each complex as determined by
elemental analysis showed good agreement between the
theoretical and actual values. The analytical results are
summarized in Table 2. The results of characterization
by IR and 195Pt NMR are shown in Table 3.
[|2(Fo2)+(0.0833P)2]−1. P=(Fo2+2Fc2)/3. a=0.0833, b=0.
The IR spectra of the complexes in general showed a
broad absorption between 3204 and 3009 cm−1, which
was due to the wN–H stretching vibrations of coordi-
nated homopiperazine and 1-methylhomopiperazine.
The intense band observed in the region 1331–1385
cm−1 was due to the wS–C stretching vibrations in all
the complexes [31–33]. The wPt–S stretching vibrations
Scheme 1.

128
M.S. Ali et al. / Polyhedron 21 (2002) 125–131
Table 2
Elemental analysis of [PtII(L)(R%R¦S)Cl]NO3
Complex
Complex name
Observed (calculated)
C (%)
H (%)
N (%)
1
2
3
4
5
6
7
8
[PtII(hpip)(dimethylsulfide)Cl]NO3
[PtII(1-mhpip)(dimethylsulfide)Cl]NO3
[PtII(hpip)(diethylsulfide)Cl]NO3
18.50 (18.72)
20.33 (20.50)
22.35 (22.37)
24.29 (24.17)
25.91 (25.85)
27.38 (27.47)
25.56 (25.85)
27.31 (27.47)
29.01 (31.41)
30.09 (30.41)
35.02 (35.26)
36.76 (36.46)
37.74 (37.59)
38.58 (38.68)
27.86 (27.87)
29.69 (29.41)
30.02 (29.40)
30.69 (30.87)
3.94 (4.01)
4.20 (4.30)
4.51 (4.56)
4.78 (4.87)
5.02 (5.09)
5.23 (5.38)
5.05 (5.09)
5.03 (5.38)
5.55 (6.04)
5.84 (5.83)
3.92 (3.80)
4.14 (4.08)
4.28 (4.14)
4.57 (4.54)
3.87 (3.87)
4.20 (4.18)
4.24 (4.14)
4.41 (4.44)
9.20 (9.36)
8.80 (8.97)
8.69 (8.70)
8.36 (8.34)
8.21 (8.22)
7.91 (8.01)
8.29 (8.22)
8.20 (8.01)
7.77 (6.04)
7.55 (7.60)
7.37 (7.26)
7.08 (7.09)
6.92 (6.80)
6.68 (6.77)
8.13 (8.06)
7.77 (7.92)
7.82 (7.91)
7.62 (7.72)
[Pt(1-mhpip)(diethylsulfide)Cl]NO3
[PtII(hpip)(dipropylsulfide)Cl]NO3
[PtII(1-mhpip)(dipropylsulfide)Cl]NO3
[PtII(hpip)(diisopropylsulfide)Cl]NO3
[PtII(1-mhpip)(diisopropylsulfide)Cl]NO3
[PtII(hpip)(dibutylsulfide)Cl]NO3
9
10
11
12
13
14
15
16
17
18
[PtII(hpip)(dibutylsulfide)Cl]NO3
[PtII(hpip)(diphenylsulfide)Cl]NO3
[PtII(1-mhpip)(diphenylsulfide)Cl]NO3
[PtII(hpip)(dibenzylsulfide)Cl]NO3
[PtII(1-mhpip)(dibenzylsulfide)Cl]NO3
[PtII(hpip)(methylphenylsulfide)Cl]NO3
[PtII(1-mhpip)(methylphenylsulfide)Cl]NO3
[PtII(hpip)(methyl p-tolylsulfide)Cl]NO3
[PtII(1-mhpip)(methyl p-tolylsulfide)Cl]NO3
L=homopiperazine (hpip) or 1-methylhomopiperazine (1-mhpip).
were observed around 350–400 cm−1, which were close
to the values reported for such compounds
[26,27,34,35]. The absorption for wPt–Cl stretching vibra-
tions were seen around 300 cm−1 [26,27,36].
with the angles ranging from 77.1(2) to 96.69(6)°. The
distortion is caused by limitation in the bite distances of
the chelating ligand.
In the platinum square plane, two adjacent corners
are occupied by the two nitrogen atoms of the ho-
mopiperazine ligand, whereas the remaining two cis
positions are coordinated with one chloride ion and one
sulfur atom of the diphenylsulfide. All Pt–N, Pt–Cl,
and Pt–S bond lengths are in the range normally
1
The H NMR spectra, which are shown in Table 4,
were most informative with respect to the structures of
the complexes. Platinum coordination at S atom of
substituted disulfides in all complexes leads a downfield
shift of S–CH protons relative to the free ligands.
1
Hence, evidence of H NMR spectra suggests the coor-
dination of platinum(II) with sulfur atom.
Table 3
The 195Pt NMR data shown in Table 3 further confi-
rmed the structures of these platinum complexes. The
singlet observed in the range of −3178 to −3415 ppm
indicated the coordination of amino nitrogens of ho-
mopiperazine, and 1-methylhomopiperazine to the two
adjacent corners of square planar platinum(II), while
the other two positions were bound to the chloride and
sulfur atoms of the thioether group. Such chemical
shifts are characteristic for the square planar platinu-
m(II) complexes in which platinum(II) is bound by two
nitrogen atoms, one sulfur atom, and one chlorine
atom [26,27,37]. Fig. 1 shows the general structure of
the complexes.
IR and 195Pt NMR data for [PtII(L)(R%R¦S)Cl]NO3
Complex
IR (cm−1
)
195Pt NMR (ppm)
wN–H
wS–C
1
2
3
4
5
6
7
8
3139
3115
3049
3130
3009
3102
3039
3104
3058
3140
3204
3127
3124
3107
3091
3152
3151
3113
1384
1331
1383
1337
1384
1331
1384
1338
1384
1338
1384
1340
1385
1338
1384
1337
1384
1335
−3415
−3192
−3215
−3210
−3144
−3208
−3144
−3208
−3173
−3178
−3138
−3151
−3165
−3098
−3153
−3105
−3160
−3145
9
10
11
12
13
14
15
16
17
18
3.3. Crystal structure
Fig. 2 shows a view of the crystal structure of
[PtII(hpip)(diphenylsulfide)Cl]NO3.
Selected
bond
lengths and bond angles are given in Table 5. In this
molecule, the coordination environment around the
platinum atom is a slightly distorted square planar one,

M.S. Ali et al. / Polyhedron 21 (2002) 125–131
129
Table 4
1H NMR data for [PtII(L)(R%R¦S)Cl]NO3
Ligand/complex no.
Dimethylsulfide
S–CH3
S–CH2–
–CH2–
–CH2–
–CH3
S–C–H
C6H5
2.07 s
2.50 s
2.45 s
Diethylsulfide
3
4
Dipropylsulfide
5
6
Diisopropylsulfide
7
8
Dibutylsulfide
9
10
2.52 q
2.99 m
2.98 m
2.46 t
3.00 m
2.95 m
1.22 t
1.45 t
1.43 t
0.97 t
1.11 t
1.09 t
1.21 d
1.52 d
1.52 d
0.91 t
1.24 t
0.99 t
1.58 m
1.92 m
1.90 m
2.95 m
3.35 m
3.36 m
2.49 t
2.77 t
3.04 m
1.54 m
1.86 m
1.80 m
1.42 m
1.61 m
1.54 m
Diphenylsulfide
7.17 m
7.25 m
7.53 m
7.78 m
7.51 m
7.76 m
7.26 m
7.28 m
8.35 m
7.45 m
7.66 m
7.08 m
7.20 m
7.53 m
7.93 m
7.53 m
7.97 m
C6H4
11
12
Dibenzylsulfide
13
3.59 s
4.11 d
14
4.11 d
4.39 d
Methylphenylsulfide
2.42 s
2.88 s
2.86 s
15
16
Methyl-p-tolylsulfide
2.25 s
2.72 s
2.83 s
2.38 s
2.37 s
2.38 s
7.02 d
7.14 d
7.23 d
7.72 d
7.33 d
7.86 d
17
18
Chemical shift in ppm; 1H NMR spectra were recorded in deuterated methanol. s=singlet, d=doublet, t=triplet, q=quartet, m=multiplet.
The coordination structure of platinum with two ring
nitrogens of homopiperazine is considerably strained,
and the N(1)–Pt(1)–N(2) bond angle is contracted to
77.1(2)° due to geometric constraints imposed by the
ligand. This angle is close to that reported for
[PtII(hpip)Cl2] (76.9 (3)°) [39], PtII(1-methylhomopiper-
azine)(methylmalonato)]·2H2O (77.8(8)° [36], and
observed for platinum(II) complexes. The average Pt–
,
N bond length of 2.041(5) A is consistent with those
found in homopiperazine containing complexes. For
II
,
instance, this length is 2.02(10) A in [Pt (hpip)-
II
,
(pentadecanoate)2] [38], 1.99(2) A in Pt (1-methylho-
mopiperazine)(methylmalonato)]·2H2O [34], and
2.027(6) A in [Pt (hpip)Cl2] [39]. The Pt(1)–Cl(1) bond
length of 2.3021(17) A is normal as compared with the
values observed in other Pt(II) dichloride complexes,
II
,
,
II
,
,
e.g. 2.309 (2) A in [Pt (hpip)Cl2] [39] and 2.315(2) A in
[Pt(piperidine)Cl2]·H2O [40]. The Pt–S bond distance of
,
2.284(15) A is not significantly different from the
Fig. 1. Structure of [Pt(L)(R%R¦S)Cl]. X=X%=H=Homopiperazine
(L). X=H, X%=CH3=1-methyl homopiperazine (L). R%, R¦=
methyl, ethyl, propyl, isopropyl, butyl, phenyl or benzyl, in complexes
1–14, R%=methyl, R¦=phenyl in complexes 15 and 16, R%=methyl,
R¦=p-tolyl in complexes 17 and 18.
,
2.279(7) A observed in the sulfide complex [Pt(m-
SC5H9NM)Br [41].
Homopiperazine is in boat conformation and forms
five- and six-membered chelating rings with platinum.

130
M.S. Ali et al. / Polyhedron 21 (2002) 125–131
Fig. 2. ORTEP representation of [PtII(homopiperazine)(diphenyl-
sulfide)Cl]NO3. Counter ion omitted for clarity. Thermal ellipsoids
drawn at 50% probability.
Table 5
II
,
Selected bond lengths (A) and bond angles (°) for [Pt (homopipera-
zine)(diphenylsulphide)Cl]NO3
Bond lengths
Pt(1)–N(1)
Pt(1)–N(2)
2.042(5)
2.050(5)
Pt(1)–S(1)
Pt(1)–Cl(1)
2.2846(15)
2.3021(17)
Bond angles
N(1)–Pt(1)–N(2) 77.1(2)
N(1)–Pt(1)–S(1) 168.82(16)
C(11)–S(1)–Pt(1)
C(21)–S(1)–Pt(1)
C(1)–N(1)–Pt(1)
C(5)–N(1)–Pt(1)
C(2)–N(2)–Pt(1)
C(3)–N(2)–Pt(1)
114.6(2)
110.1(2)
107.3(4)
107.9(4)
106.7(4)
109.2(4)
N(2)–Pt(1)–S(1)
92.53(15)
N(1)–Pt(1)–Cl(1) 93.67(16)
N(2)–Pt(1)–Cl(1) 170.77(15)
S(1)–Pt(1)–Cl(1)
96.69(6)
Fig. 3. Packing diagram of [PtII(homopiperazine)(diphenylsulfide)-
Cl]NO3. Orientation is along the 0 1 0 axis. Thermal ellipsoids drawn
at 50% probability.
[PtII(hpip)(pentadecanoate)2] (76.3(4)°) [38]. In addi-
tion, the contraction of the N1–Pt–N2 bond angle is
compensated for with expansion of the N(2)–Pt(1)–
S(1), N(1)–Pt(1)–Cl(1) and S(1)–Pt(1)–Cl(1) bond an-
gles to 92.53(15)°, 93.67(16)° and 96.69(6)°,
respectively. The Pt(1)–N(1)–C(1) and Pt(1)–N(1)–
C(5) bond angles in the present study are 107.3(4)° and
107.9(4)°, respectively, these angles are 107.7(4)° and
109.0(4)°, respectively, in [PtII(hpip)Cl2] [39], 105.9(8)°
and 112.1(7)°, respectively, in [PtII(hpip)(penta-
decanoate)2] [38], and 104.3(14)° and 109.5(14)°, respec-
tively, in PtII(1-methylhomopiperazine)(methylmalo-
nato)]·2H2O [36]. The molecules in the crystal show a
system of N–H···O hydrogen bonds (Fig. 3).
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Centre, CCDC No. 160939. Copies of this information
may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(fax: +44-1233-336-033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements
This work was supported by grants CA-77332 and
CA-82361 from the National Cancer Institute and by
grant C0976 from the Robert A. Welch Foundation.
In summary, we have synthesized and characterized a
series of new platinum(II) complexes containing ho-
mopiperazine or 1-methylhomopiperazine as nonleav-
ing amine ligands and different sulfide groups as
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