(4′-chloro-2,2′:6′,2″-terpyridine-N,N′, N″)(diethylphosphinothioato-S)-platinum(II) tetraphenylborate

Article abstract of DOI:10.1107/S0108270100020023

The title compound, [Pt(C₄H₁₀O₃PS)(C₁₅H₁₀ CIN₃)](C₂₄H₂₀B), has distorted square-planar coordination geometry at the platinum (II) centre, due to the constraints of the tridentate terpyridine ligand. The Pt^II-bound diethylphosphinothioate ligand takes up a conformation to avoid non-bonding contacts with atoms H6 and H6″.

Full text of DOI:10.1107/S0108270100020023

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
mononuclear platinum(II)±phosphinothioate complex, (I).
The distorted square-planar geometry of the Pt centre in (I)
[N5ÐPt1ÐN16 = 161.61 (14)ꢀ; Fig. 1] is in agreement with
other reported (terpyridine)platinum(II) complexes (Cher-
nega et al., 1996; Jennette et al., 1976; Tzeng et al., 1999). The
Pt1ÐS21ÐP22 bond angle of 96.84 (5)ꢀ is quite acute and is
comparable with the equivalent PtÐSÐP angles of 107.0 (1)
and 104.6 (1)ꢀ in a related PtII±ZnII bridged dialkyl-
phosphinothioate complex reported by Poat et al. (1990).
The N5ÐPt1ÐS21ÐP22 torsion angle of 97.0 (3)ꢀ illus-
trates the necessity for the phosphinothioate ligand to adopt a
conformation which avoids non-bonding contacts with atoms
H6 and H600 (H61 and H171 in the present atom-labelling
scheme) of the terpyridine ligand. This torsion angle leads to
the P centre being displaced signi®cantly from the (ter-
pyridine)platinum(II) plane. Thus, intercalation of this
complex into double-stranded nucleic acids would almost
certainly lead to steric interactions between the phosphino-
thioate group and adjacent base pairs. Interestingly, O23 is
ISSN 0108-2701
(40-Chloro-2,20:60,200-terpyridine-
N,N0,N00)(diethylphosphinothioato-S)-
platinum(II) tetraphenylborate
Steven A. Ross,a Gordon Lowea* and David J. Watkinb
aDyson Perrins Laboratory, University of Oxford, South Parks Road, Oxford
OX1 3QY, England, and bChemical Crystallography Laboratory, 9 Parks Road,
Oxford OX1 3PD, England
Correspondence e-mail: gordon.lowe@chem.ox.ac.uk
Received 19 September 2000
Accepted 11 December 2000
Ê
displaced by 2.58 (2) A from the mean plane de®ned by Pt1,
The title compound, [Pt(C4H10O3PS)(C15H10ClN3)](C24H20B),
has a distorted square-planar coordination geometry at the
platinum(II) centre, due to the constraints of the tridentate
terpyridine ligand. The PtII-bound diethylphosphinothioate
ligand takes up a conformation to avoid non-bonding contacts
with atoms H6 and H600.
N5, N2, N16 and S21, which may facilitate hydrogen-bonding
interactions between O23 and the adjacent base pairs of DNA
upon intercalation.
Comment
Platinum(II) complexes of 2,20:60,200-terpyridine ligands are of
interest due to their photophysical properties (Tzeng et al.,
1999), fast ligand-substitution kinetics (Mureinik & Bidani,
1978; Carr et al., 2000), and antitumour (Lowe, Droz, Vilaivan,
Weaver, Park et al., 1999) and antiparasitic activity (Lowe,
Droz, Vilaivan, Weaver, Tweedale et al., 1999). Intercalation
into nucleic acids (McCoubrey et al., 1996) and irreversible
enzyme inhibition (Bonse et al., 2000) have been implicated as
possible modes of action of this class of compounds in vivo.
Oligo(deoxy)ribonucleotides containing phosphinothioate
linkages have been proposed as potential antisense or anti-
gene agents, due to their resistance to enzymatic hydrolysis in
vivo (Eckstein, 2000). Binding of platinum complexes to the
phosphinothioate linkage of oligonucleotides has been
reported by Elmroth & Lippard (1995), and crosslinking of
Figure 1
The molecular structure of the cation of (I) with the atom-labelling
scheme. Displacement ellipsoids are drawn at the 50% probability level.
oligonucleotides using binuclear platinum complexes has also
been reported (Gruff
& Orgel, 1991). In addition,
phosphinothioates have been used as chemoprotective agents
for platinum antitumour agents (Thompson et al., 1995). We
describe herein the ®rst single-crystal X-ray structure of a
Figure 2
The intermolecular stacking interactions of the cationic units of (I).
ꢁ
Acta Cryst. (2001). C57, 275±276
# 2001 International Union of Crystallography
Printed in Great Britain ± all rights reserved 275

metal-organic compounds
Table 1
Selected geometric parameters (A, ).
The crystal structure of (I) shows that the cations are
arranged in a stacked manner in the solid state (Fig. 2). This
has been observed previously with (terpyridine)platinum(II)
complexes (Chernega et al., 1996; Tzeng et al., 1999), and is a
good indication of the ability of these compounds to inter-
calate and also to stack in solution (Jennette et al., 1976). The
ꢀ
Ê
Pt1ÐS21
Pt1ÐN2
Pt1ÐN5
Pt1ÐN16
S21ÐP22
P22ÐO23
2.3230 (11)
1.946 (3)
2.020 (4)
2.027 (3)
2.0346 (16)
1.473 (3)
P22ÐO24
P22ÐO27
O24ÐC25
O27ÐC28
C25ÐC26
C28ÐC280
1.569 (3)
1.571 (3)
1.471 (6)
1.447 (6)
1.479 (8)
1.415 (9)
Ê
intermolecular stacking distance [3.59 (5) A between the
equivalent mean planes described above] and antiparallel
orientation are consistent with previously reported structures.
S21ÐPt1ÐN2
S21ÐPt1ÐN5
N2ÐPt1ÐN5
S21ÐPt1ÐN16
N2ÐPt1ÐN16
N5ÐPt1ÐN16
Pt1ÐS21ÐP22
S21ÐP22ÐO23
178.6 (1)
99.4 (1)
80.87 (14)
98.9 (1)
80.82 (14)
161.61 (14)
96.84 (5)
115.69 (15)
S21ÐP22ÐO24
O23ÐP22ÐO24
S21ÐP22ÐO27
O23ÐP22ÐO27
O24ÐP22ÐO27
P22ÐO24ÐC25
P22ÐO27ÐC28
106.56 (14)
112.52 (19)
103.76 (13)
113.92 (19)
103.22 (19)
121.2 (3)
0
Ê
The intermolecular Pt1Á Á ÁPt1 distance is 4.29 (5) A.
Finally, the structural parameters for the present plati-
num(II)±phosphinothioate complex will prove useful in
predicting how the (terpyridine)platinum(II) fragment will
bind to nucleic acids containing the phosphinothioate linkage.
118.2 (3)
Data collection: XPRESS (MacScience, 1989); cell re®nement:
DENZO (Otwinowski & Minor, 1997); data reduction: DENZO;
program(s) used to solve structure: SIR92 (Altomare et al., 1994);
program(s) used to re®ne structure: CRYSTALS (Watkin, Prout,
Carruthers & Betteridge, 1996); molecular graphics: CAMERON
(Watkin, Prout & Pearce, 1996); software used to prepare material for
publication: CRYSTALS.
Experimental
Complex (I) was prepared as its nitrate salt in 71% yield following the
general method of Lowe & Vilaivan (1996). Triethylammonium
diethylphosphinothioate was prepared as described previously by
Reynolds et al. (1983). Dissolution of the nitrate salt in water
followed by the addition of excess sodium tetraphenylborate afforded
a yellow precipitate which was redissolved by the addition of aceto-
nitrile. Evaporation of this water/acetonitrile solution afforded single
crystals of (I) (m.p. > 503 K). Spectroscopic analysis: 1H NMR
(200 MHz, d6-DMSO, ꢀ, p.p.m.): 1.12 (6H, t), 4.01 (4H, quin), 8.02
(2H, dd), 8.51 (2H, dd), 8.57 (2H, d), 9.00 (2H, s), 9.23 (2H, d);
We thank the EPSRC and BBSRC for support.
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: GD1116). Services for accessing these data are
described at the back of the journal.
31P NMR (101 MHz, d6-DMSO, ꢀ, p.p.m.) 31.93 (J
= 88 Hz);
195Pt 31P
elemental analysis calculated (for hexa¯uorophosphate salt): C 29.3,
H 2.6, N 5.4%; found: C 29.4, H 2.6, N 5.4%.
References
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Crystal data
3
[Pt(C4H10O3PS)(C15H10ClN3)]-
(C24H20B)
Mr = 951.20
Dx = 1.62 Mg m
Mo Kꢂ radiation
Cell parameters from 16 185
re¯ections
Monoclinic, P21/n
Ê
a = 10.7550 (5) A
ꢃ = 0±27ꢀ
ꢄ = 3.82 mm
T = 190 K
1
Ê
b = 13.5230 (3) A
Ê
c = 26.764 (1) A
ꢁ = 87.356 (2)ꢀ
Prism, yellow
0.8 Â 0.2 Â 0.2 mm
3
Ê
V = 3888.4 A
Z = 4
Data collection
Lowe, G., Droz, A. S., Vilaivan, T., Weaver, G. W., Park, J. J., Pratt, J. M.,
Tweedale, L. & Kelland, L. R. (1999). J. Med. Chem. 42, 3167±3174.
Lowe, G., Droz, A. S., Vilaivan, T., Weaver, G. W., Tweedale, L., Pratt, J. M.,
Rock, P., Yardley, V. & Croft, S. L. (1999). J. Med. Chem. 42, 999±1006.
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FEBS Lett. 380, 73±78.
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Soc. Chem. Commun. pp. 1036±1038.
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(1999). J. Chem. Soc. Dalton Trans. pp. 1017±1023.
Enraf±Nonius DIP2000 diffract-
ometer
! scans
Absorption correction: multi-scan
(DENZO; Otwinowski & Minor,
1997)
Tmin = 0.46, Tmax = 0.46
16 185 measured re¯ections
7838 independent re¯ections
5773 re¯ections with I > 3ꢅ(I)
Rint = 0.05
ꢃ
max = 26.57ꢀ
h = 13 ! 13
k = 0 ! 16
l = 0 ! 33
Re®nement
Re®nement on F
R = 0.030
wR = 0.037
Weighting scheme: Chebychev
polynomial with 3 parameters
(Carruthers & Watkin, 1979):
1.66, 0.505 and 1.28
S = 1.026
5773 re¯ections
487 parameters
H-atom parameters not re®ned
(Á/ꢅ)max < 0.001
3
Ê
Áꢆmax = 1.69 e A
3
Ê
0.84 e A
Áꢆmin
=
Watkin, D. J., Prout, C. K., Carruthers, J. R. & Betteridge, P. W. (1996).
CRYSTALS. Issue 10. Chemical Crystallography Laboratory, University of
Oxford, England.
Watkin, D. J., Prout, C. K. & Pearce, L. J. (1996). CAMERON. Chemical
Crystallography Laboratory, University of Oxford, England.
H atoms were placed geometrically after each cycle. The short
C28ÐC280 bond is probably a consequence of librational disorder,
but it could not be reliably modelled on this basis.
ꢁ
276 Ross, Lowe and Watkin
[Pt(C4H10O3PS)(C15H10ClN3)](C24H20B)
Acta Cryst. (2001). C57, 275±276