Synthesis, structural and multinuclear natural abundance (13C, 31P, 195Pt) CP/MAS NMR studies of crystalline O,O′-dialkyldithiophosphate platinum(II) complexes

Article abstract of DOI:10.1134/S1070328408080058

Platinum(II) O,O′-dicyclohexyl dithiophosphate [Pt{S ₂P(O-cyclo-C₆H₁₁)₂}₂] (I) and platinum(II) O,O′-diisopropyl dithiophosphate [Pt{S ₂P(O-iso-C₃H₇)₂}₂] (II) complexes were obtained and studied by solidstate ¹³C, ³¹P, and ¹⁹⁵Pt CP/MAS NMR spectroscopy. The dithiophosphate (Dtph) ligands in molecular structure I were found to be coordinated by platinum in S,S′-bidentate fashion to form the planar chromophore [PtS₄] (single-crystal X-ray diffraction data). For complex II, a new α-form (α-II) was obtained and identified by ³¹P MAS NMR spectroscopy. The ³¹P chemical shift anisotropy δ_aniso and the asymmetry parameter η of the ³¹P chemical shift tensor were calculated from the whole MAS spectra.

Full text of DOI:10.1134/S1070328408080058

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2008, Vol. 34, No. 8, pp. 584–593. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © A.V. Ivanov, I.A. Lutsenko, M.A. Ivanov, A.V. Gerasimenko, O.N. Antzutkin, 2008, published in Koordinatsionnaya Khimiya, 2008, Vol. 34, No. 8,
pp. 591–600.
Synthesis, Structural and Multinuclear Natural Abundance
(13C, 31P, 195Pt) CP/MAS NMR Studies of Crystalline
O,O'-Dialkyldithiophosphate Platinum(II) Complexes
A. V. Ivanova, I. A. Lutsenkoa, M. A. Ivanova, A. V. Gerasimenkob, and O. N. Antzutkinc
aInstitute of Geology and Nature Management, Amur Scientific Center, Far East Division, Russian Academy of Sciences,
Blagoveshchensk, 675000 Russia
bInstitute of Chemistry, Far East Division, Russian Academy of Sciences,
pr. Stoletiya Vladivostoka 159, Vladivostok, 690022 Russia
c Luleå University of Technology, S-97187, Luleå, Sweden
E-mail: alexander.v.ivanov@chemist.com
Received June 26, 2007
Abstract—Platinum(II) O,O'-dicyclohexyl dithiophosphate [Pt{S2P(O-cyclo-C6H11)2}2] (I) and platinum(II)
O,O'-diisopropyl dithiophosphate [Pt{S2P(O-iso-C3H7)2}2] (II) complexes were obtained and studied by solid-
state 13C, 31P, and 195Pt CP/MAS NMR spectroscopy. The dithiophosphate (Dtph) ligands in molecular struc-
ture I were found to be coordinated by platinum in S,S'-bidentate fashion to form the planar chromophore [PtS4]
(single-crystal X-ray diffraction data). For complex II, a new α-form (α-II) was obtained and identified by 31
MAS NMR spectroscopy. The 31P chemical shift anisotropy δaniso and the asymmetry parameter η of the 31
chemical shift tensor were calculated from the whole MAS spectra.
P
P
DOI: 10.1134/S1070328408080058
Most of the hitherto known platinum(II)
O,O'-dialkyldithiophosphates are liquids or oily com-
pounds [1]. Only two crystalline platinum complexes
EXPERIMENTAL
Synthesis. Crystalline complexes I and II were
[Pt{S2P(OR)2}2] have been structurally characterized: obtained by reactions of aqueous solutions of K2[PtCl4]
R = C2H5 [1] and iso-C3H7 [2]. In [3], we have demon-
strated with single-crystal cooperite (natural PtS) as an
example that 195Pt (both static and MAS) NMR spec-
troscopy can be employed for investigation of natural
minerals of platinum. In cooperite, platinum(II) is
included in square chromophores [PtS4]. However, a
structurally similar pattern has been found in dialkyl
dithiophosphates [1, 2]: the metal atom is surrounded
by four sulfur atoms making a slightly distorted square.
That is why we found it interesting to obtain crystalline
platinum(II) dialkyl dithiophosphates and compare
their 195Pt MAS NMR spectra and X-ray diffraction
patterns.
and appropriate salts K{S2P(OR)2}. The reaction mix-
tures were heated at 60°ë for a short period of time and
left overnight. The resulting yellow precipitates were
filtered off, washed with water, and dried on the filter.
Additional crops were obtained by extraction of the
complexes from the mother liquors by chloroform. Sin-
gle crystals of complex I for X-ray diffraction analysis
were obtained from chloroform.
For EPR study, complex III was synthesized in the
magnetically diluted state by mechanically grinding
complex I with a small amount of CuCl2 · 2H2O (Cu :
Pt = 1 : 1000). The use of this technique allows the mol-
ecules of complex III to be stabilized in the matrix of
In this study, we obtained the new complexes
bis(O,O'-dicyclohexyldithiophosphato-S,S')plati-
num(II) (I) and bis(O,O'-diisopropyldithiophosphato-
S,S')platinum(II) (II) of the general formula
[Pt{S2P(OR)2}2] (R = cyclo-C6H11 (I) and the α-form
for R = iso-C3H7 (II)) and the magnetically diluted
(with Pt(II)) isotope-substituted complex bis(O,O'-
dicyclohexyldithiophosphato-S,S')copper(II)
1
the platinum(II) complex. The content of the 63ëu iso-
tope in CuCl2 · 2H2O was 99.3(1) at %.
1
Copper(II) O,O'-dialkyl dithiophosphates do not exist in the indi-
vidual state because of prompt conversion into polynuclear cop-
per(I) complexes [4] and the corresponding bis(O,O'-dialkylthio-
phosphoryl) disulfides according to the intermolecular redox
reaction:
[63Cu{S2P(O-cyclo-C6H11)2}2] (III). The structures of
these complexes were studied by 13C, 31P, and 195Pt
CP/MAS NMR spectroscopy and EPR spectroscopy;
structure I was characterized by X-ray diffraction data.
2+
–
4Cu + 8(RO) P(S)S = 4[Cu{S P(OR) } ]
2
2
2 2
= [Cu {S P(OR) } ] + 2(RO) P(S)S–S(S)P(OR) .
4
2
2 4
2
2
584

SYNTHESIS, STRUCTURAL AND MULTINUCLEAR NATURAL ABUNDANCE
585
Crystalline complexes I and II and the starting proton resonance frequency (359.945 MHz). The total
potassium dithiophosphates were characterized by 13C width of experimental 195Pt MAS NMR spectra
MAS NMR spectroscopy:
(~290 kHz) made it impossible to simultaneously
excite the entire spectrum at a single carrier frequency.
For this reason, we varied the carrier frequency with a
step of 77 kHz to excite different regions of the spec-
trum. The whole pattern was obtained by summation of
the individual spectra recorded at 76.991, 77.068,
77.145, and 77.222 MHz. The summation was pre-
ceded by shifting the spectra so that the central signal
and all sidebands coincided exactly. The spinning fre-
quency was 5000(1) Hz. For each fragment, the number
of scans was 20 000 (for I) and 16 800 (for β-II); the
pulses were spaced at 3.0 s. Since the initial region of
the free induction decay (FID) diagrams of the MAS
NMR spectra was distorted by the decay of the exciting
pulse (due to the “ringdown” effect), the distorted range
was cut off. To avoid phase distortions of the MAS
NMR spectrum, the FID diagram was shifted before
Fourier transforms to the decay region by a required
number of points. Since the FID diagrams contained
over 15 (I) or 27 rotational echoes (β-II), removal of the
initial fragment did not result in critical spectral
changes. The magic angle was set by observing the 79Br
resonance frequency of crystalline KBr (90.189 MHz)
according to a standard procedure. Its adjustment was
performed by minimizing the line widths in the 195Pt
MAS NMR spectrum of natural single-crystal cooper-
ite (PtS), which is characterized by a considerable 195Pt
chemical shift anisotropy (δaniso = 5873 ppm, η = 0.37
[3]) and, consequently, by a high sensitivity of the line
width to small deviations of the magic angle.
Complex I, δ: (1 : 2 : 1 : 2) 76.2, 76.1 (1 : 1,
−OCH=), 32.9, 32.2 (1 : 1, o-CH2–), 26.2, 26.0 (p-CH2–),
21.4, 20.8 ppm (m-CH2–).
K{S2P(O-cyclo-C6H11)2}, δ: (1 : 2 : 3) 79.9, 78.8,
78.1, 77.1 (1 : 1 : 1 : 1, –OCH=), 35.7, 35.2, 34.7, 33.9
(o-CH2–), 26.2 ppm (m-, p-CH2–).
α-II, δ: (1 : 2) 74.1 (–OCH=), 26.5, 26.2, 25.7, 25.0
ppm (1 : 1 : 1 : 1, –CH3).
[Pt{S2P(O-iso-C3H7)2}2] (β-II), δ: (1 : 2) 73.1
(−OCH=), 25.2, 24.9, 24.6, 24.0 ppm (2 : 3 : 2 : 1,
−CH3).
K{S2P(O-iso-C3H7)2}, δ: (1 : 2) 73.0, 72.8, 70.5,
69.9 (1 : 1 : 1 : 1, –OCH=), 27.0, 26.7, 26.3, 25.4, 25.0,
24.1 ppm (1 : 1 : 2 : 6 : 2 : 4, –CH3).
EPR spectra were recorded on a 70-02 XD/1 radio
spectrometer (~9.5 GHz) at ~295 K. The operating fre-
quency was measured with a ChZ-46 microwave fre-
quency meter. g Factors were calculated with reference
to DPPH. The error in the determination of g factors
was 0.002; the constants of the hyperfine (HFS) and
extra hyperfine structures (EHFS) are quoted in oer-
steds (Oe) to within 2%. EPR spectra were modeled to
the second order of perturbation theory with the WIN-
EPR SimFonia program (Bruker software, version 1.2).
g Factors, HFS and EHFS constants, resonance line
widths, and percent contributions from the Lorentzian
and Gaussian functions to the line shapes were vari-
ables of the modeling.
13C, 31P, and 195Pt MAS NMR spectra were
recorded on a CMX-360 spectrometer operating at
90.52, 145.72, and 76.99–77.22 MHz, respectively
(superconducting magnet with Ç0 = 8.46 T; Fourier
transform). The 13C–1H and 31P–1H cross polarization
techniques were used; 13C–1H and 31P–1H dipolar inter-
actions were suppressed via proton decoupling in a
magnetic field with the corresponding proton resonance
frequency [5]. Samples (~300 mg) of the complexes
were packed into a zirconia rotor (7.5 mm in diameter).
The spinning frequencies in 13C/31P MAS NMR exper-
iments were 4000–5500/3200–5000(1) Hz. The num-
bers of scans were 1200–5200/256–400, respectively.
The proton π/2 pulse durations were 5.4/5.4 μs. The
1H−13C/1H–31P contact times were 1.5/2.0 ms; the
pulses were spaced at 3.0/3.0 s. Isotropic 13C, 31P, and
195Pt chemical shifts d (ppm) are referenced to a line of
crystalline adamantane [6] used as the external standard
(δ 38.48 ppm relative to tetramethylsilane [7]), 85%
H3PO4(0 ppm) [8], and aqueous 0.1 M H2[PtCl6]
(0 ppm; the corresponding 195Pt resonance frequency is
(77.3768 MHz) [9], respectively.
The width of the reference line for crystalline ada-
mantane (3.5 Hz) was used to check the homogeneity
of the magnetic field. The δiso values were corrected for
drift of the magnetic field strength during the measure-
ments (its frequency equivalents for the 13ë/31P/195Pt
nuclei were 0.051/0.11/0.044 Hz/h). The chemical
shifts, the integrated intensity ratios for the overlapping
signals, and the coupling constants were refined by
fragment-by-fragment mathematical modeling of
NMR spectra with regard to the line positions and
widths and the contributions from the Lorentzian and
Gaussian functions to the line shapes. The 31P chemical
shift anisotropy (δaniso = (δzz – δiso) and the asymmetry
parameter of the 31P chemical shift tensor (η = (δyy –
δxx)/(δzz – δiso)) were calculated from diagrams of the χ2
statistics [10]. Plotting of the diagrams was based on
quantitative analysis of the integrated intensity ratios
for sidebands (due to spinning) [11, 12] in the spectra
recorded at two different spinning frequencies. The cal-
culations were performed with the Mathematica pro-
gram (version 4.1.2) [13].
In 195Pt MAS NMR experiments, we used a 60°
direct excitation pulse with a 3.7-μs duration to excite
a spectral range of 45 kHz. 195Pt–1H interactions were
suppressed via proton decoupling in a magnetic field
Single-crystal X-ray diffraction analysis of com-
plex I was performed on a BRUKER SMART 1000
CCD diffractometer (MoKα radiation, λ = 0.71073 Å,
graphite monochromator) at 173(1) K. Reflections
(amplitude γB1/2π = 46.9 kHz) with the corresponding were collected in the hemisphere [14] (crystal–detector
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 8 2008

586
IVANOV et al.
Table 1. Crystallographic parameters and a summary of da- Table 2. Atomic coordinates and isotropic equivalent ther-
ta collection and refinement for structure I
Parameter
mal parameters Uequiv for structure I
Atom
Pt
Value
x
y
z
Uequiv, Å2
Empirical formula
C24H44O4P2S4Pt
781.86
0.5
0
1.0
0.02425(1)
M
Crystal system
Monoclinic
P21/n
S(1)
S(2)
P
0.54270(2) 0.20845(3) 0.91931(2) 0.04086(7)
0.69145(2) 0.00550(3) 1.05985(2) 0.03769(7)
0.70569(2) 0.17069(3) 0.96893(2) 0.03132(6)
0.78497(7) 0.14300(8) 0.88807(6) 0.0415(2)
0.77179(6) 0.30320(8) 1.01485(5) 0.0387(2)
0.7802(1) 0.0119(1) 0.82892(9) 0.0379(3)
0.7795(1) 0.0585(2) 0.7266(1) 0.0559(4)
0.8928(2) 0.1375(2) 0.7123(1) 0.0830(6)
0.9964(1) 0.0471(2) 0.7573(2) 0.0852(5)
0.9885(1) 0.0014(2) 0.8576(2) 0.0626(5)
0.8818(1) –0.0741(1) 0.8637(1) 0.0625(5)
0.73484(9) 0.3769(1) 1.09980(7) 0.0358(2)
0.7156(1) 0.5316(2) 1.0712(1) 0.0599(4)
0.8258(2) 0.6033(2) 1.0514(1) 0.0670(5)
Space group
a, Å
11.854(2)
9.354(1)
13.879(2)
96.49(1)
1529.0(4)
2
b, Å
c, Å
O(1)
O(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
β, deg
V, Å3
Z
ρ(calcd.), g/cm3
μ, mm–1
1.698
4.994
F(000)
784
Crystal shape (size, mm)
Prism
(0.38 × 0.29 × 0.15)
θ scan range, deg
2.14–35.50
Ranges of h, k, and l indice
–19 ≤ h ≤ 19
–10 ≤ k ≤ 15
–20 ≤ l ≤ 22
Number of measured reflections
18152
Number of independent reflections 6882 (Rint = 0.0317)
Number of reflections with I > 2σ(I)
Number of parameters refined
GOOF
5306
160
1.036
R factors for F2 > 2σ(F2)
R1 = 0.0291
C(10) 0.9182(2) 0.5863(2) 1.1347(1) 0.0773(5)
C(11) 0.9368(1) 0.4315(2) 1.1602(1) 0.0622(5)
C(12) 0.8277(1) 0.3600(2) 1.18200(8) 0.0461(3)
wR2 = 0.0697
R factors for all reflections
R1 = 0.0426
wR2 = 0.0760
Residualelectrondensity(min/max),
–1.031/1.651
e Å−3
and SAINT-Plus programs [14]. All calculations for
structure determination and refinement were performed
with the SHELXTL/PC programs [15].
distance 38 mm, ω scan mode, scan step 0.2°, frame
exposure time 20 s). Absorption correction was applied
from the face indices of the single crystal. Structure I
was solved by the direct method and refined by the
least-squares method (on F2) in the full-matrix aniso-
tropic approximation for non-hydrogen atoms. The
hydrogen atoms were located geometrically and refined
in the rider model. The collected data were edited and
Selected crystallographic parameters and a sum-
mary of data collection and refinement for structure I
are summarized in Table 1. Atomic coordinates and
thermal parameters are listed in Table 2. Bond lengths
the unit cell parameters were refined with the SMART and angles are given in Table 3.
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SYNTHESIS, STRUCTURAL AND MULTINUCLEAR NATURAL ABUNDANCE
587
Table 3. Selected bond lengths and angles in structure I
Bond d, Å Bond d, Å
Pt–S(1)
RESULTS AND DISCUSSION
The EPR spectrum of isotope-substituted complex
III magnetically diluted with platinum(II) is close to
the axially symmetric pattern (Fig. 1a). The EPR
parameters were refined by computer-assisted model-
ing of spectra (Fig. 1b), which revealed some anisot-
ropy of the g- and Ä tensors in the plane xy:
2.3324(4) C(2)–C(3)
2.3273(4) C(3)–C(4)
2.0077(5) C(4)–C(5)
2.0141(4) C(5)–C(6)
1.5645(9) C(7)–C(8)
1.5631(8) C(7)–C(12)
1.564(3)
1.562(3)
1.469(3)
1.459(2)
1.511(2)
1.501(2)
1.521(2)
1.508(2)
1.501(3)
1.517(2)
ω, deg
Pt–S(2)
g⊥
AP⊥, Oe
S(1)–P
AC|| u, Oe AP|| , Oe
154 9.6
AC⊥u, Oe
g||
2.088
2.025
2.023
36.0
35.8
9.7
9.7
S(2)–P
P–O(1)
Each orientation of the EPR spectrum shows a quar-
tet of the HFS components due to the 63ëu nucleus (I =
3/2) and an intense high-field extra absorption (EA)
peak [16, 17]. All the HFS components and the EA
peak are additionally split into triplets (1 : 2 : 1) of the
EHFS components due to the 31P nuclei (I = 1/2) in two
structurally equivalent Dtph ligands. The aforesaid g
factors and HFS constants suggest the presence of the
square chromophores [CuS4] in structure III. The
anisotropy of the EPR parameters in the plane xy we
P–O(2)
O(1)–C(1)
O(2)–C(7)
C(1)–C(6)
1.473(1)
1.474(1)
1.483(2)
1.485(2)
ω, deg
C(8)–C(9)
C(9)–C(10)
C(10)–C(11)
C(11)–C(12)
Angle
noted above can arise from a rhombic distortion of the C(1)–C(2)
chromophore because of some nonequivalence of cis-
oriented Cu–S bonds.
Angle
13
The C MAS NMR spectra of complexes I and II
(Fig. 2) contain signals for the –OCH=, o-CH2–,
m-CH2–, p-CH2–, and –CH3 groups of the alkyl substit-
S(1)PtS(2)
PS(1)Pt
84.10(1) C(2)C(1)C(6)
86.61(2) C(1)C(2)C(3)
86.60(2) C(4)C(3)C(2)
101.79(2) C(5)C(4)C(3)
114.57(3) C(6)C(5)C(4)
114.97(3) C(5)C(6)C(1)
114.77(3) O(2)C(7)C(12)
115.24(3) O(2)C(7)C(8)
96.30(4) C(12)C(7)C(8)
123.32(7) C(7)C(8)C(9)
121.08(7) C(10)C(9)C(8)
112.8(1)
110.4(1)
110.0(1)
113.9(1)
110.2(2)
113.4(1)
107.47(9)
106.7(1)
112.1(1)
111.3(1)
112.3(1)
110.9(1)
uents in the dithiophosphate ligands. Pairs of 13C NMR
signals for the o-, m-, and p-carbon atoms in the
(cyclo-C6H11O)2PS–2 ligands (Fig. 2a) suggest that the
PS(2)Pt
cyclic −C6H11 fragments are structurally nonequivalent.
Complex II exists in two spectrally different forms,
depending on the conditions of its synthesis: precipita-
tion from the aqueous phase mainly gives the α-form,
while crystallization from chloroform yields the β-form
(Figs. 2b, 2c).
S(1)PS(2)
O(1)PS(1)
O(1)PS(2)
O(2)PS(1)
O(2)PS(2)
O(2)PO(1)
C(1)O(1)P
C(7)O(2)P
Each signal in the 31P MAS NMR spectra of com-
plexes I and II (Fig. 3) has two symmetrically arranged
satellite signals (~1 : 4 : 1). Because naturally occurring
platinum contains the 195Pt nuclide (33.83 at %, μ =
0.60950 μN; I = 1/2), the observed multiplet structure
of the signals under discussion results from isotropic
31P–195Pt spin-spin couplings with the coupling con-
stant 2J(31ê−195Pt) (Table 4). The sole 31P NMR signal in
the center of gravity of the spectrum of complex I
(Fig. 3a) is indicative of the structural equivalence of
the Dtph ligands. The spectrum suggests the presence
of a small amount of a complex with the larger chemi-
cal shift: δ(31ê) = 101.9 ppm and 2J(31ê–195Pt) = 431 Hz.
A comparison of the 31P MAS NMR spectra of the sam-
ples of complex II obtained by precipitation from the
aqueous phase (Fig. 3b) and crystallization from chlo-
roform (Fig. 3c) showed that the former sample con-
tains both α- and β-forms (~30%). Additional inflec-
O(1)C(1)C(2) 106.52(9) C(11)C(10)C(9)
O(1)C(1)C(6) 107.0(1) C(10)C(11)C(12) 111.5(1)
C(7)C(12)C(11) 111.8(1)
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588
IVANOV et al.
DPPH
H 78 Oe
(a)
(b)
(a)
(c)
80
60
40
20 δ, ppm
(b)
13
Fig. 2.
C MAS NMR spectra of the complexes
[Pt{S P(OR) } ]: R = (a) cyclo-C H and (b, c) iso-C H .
2
2 2
6
11
3 7
The samples were obtained by (a, c) crystallization from
chloroform and (b) precipitation from the aqueous phase.
The number of scans/spinning frequency (Hz) are (a)
2800/4000, (b) 5200/5500, and (c) 1200/5500.
The shapes of the whole 31P MAS NMR spectra of
the complexes obtained suggest a nearly rhombic sym-
metry of the 31P chemical shift tensors. For quantitative
estimation of the 31P chemical shift anisotropy, we plot-
ted diagrams of the χ2 statistics (Fig. 4) as a function of
Fig. 1. (a) Experimental and (b) model EPR spectra of the
magnetically diluted isotope-substituted complex
Cu{S P(O-cyclo-C H ) } ].
63
[
2
6 11 } 2
tions on the triplet components in the 31P NMR spec-
trum of the α-form of complex II can be attributed to
the presence of two isomeric molecules in this form.
δ
aniso and η. At η = 0, the chemical shift tensor is axially
symmetric. An increase in η from 0 to 1 reflects an
Table 4. Parameters of the 31P and 195Pt MAS NMR spectra of complexes I and II*
31
195
P
Pt
Compound
2J
Pt, Hz
δiso, ppm
δaniso, ppm**
η**
δiso, ppm 2J
Pt, Hz
195P – 31
31P – 195
[Pt{S P(O-cyclo-C H ) } ] (I)
99.0
433.2 0.5
–30.8 0.2
0.98 0.02
–3963.6
435 15
2
6 11 2 2
K{S P(O-cyclo-C H ) } [30]
109.3
105.0
(1 : 1)
–110.6 1.5
–109.1 1.7
0.14 0.10
0.21 0.06
2
6 11 2
[Pt{S P(O-iso-C H ) } ] (α-II)
103.4
103.0
422 11
435 15
–35.9 0.4
–42.7 0.2
0.94 0.04
0.75 0.02
2
3 7 2 2
[Pt{S P(O-iso-C H ) } ] (β-II)
108.5
431.1 0.7
–4002.0
427
5
2
3 7 2 2
K{S P(O-iso-C H ) } [30]
111.7
103.8
(1 : 1)
–104.7 1.3
–116.7 1.1
0.32 0.03
0.07 0.07
2
3 7 2
Notes: * The isotropic chemical shifts δ (ppm) are referenced to 85% H PO and 0.1 M H [PtCl ].
3
4
2
6
** δ
= δ – δ ; η = (δ – δ )/(δ – δ ).
aniso
zz iso yy xx zz iso
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SYNTHESIS, STRUCTURAL AND MULTINUCLEAR NATURAL ABUNDANCE
589
*
100
95
(a)
* *
110
100
(b)
*
110
105
(c)
150
125
100
75
50 δ, ppm
31
Fig. 3. P MAS NMR spectra of the complexes [Pt{S P(OR) } ]: R = (a) cyclo-C H and (b, c) iso-C H . The samples were
2
2 2
6
11
3 7
obtained by (a, c) crystallization from chloroform and (b) precipitation from the aqueous phase. The spinning frequency is 3200 Hz;
the number of scans is (a) 256, (b) 400, and (c) 64. The signals in the center of gravity of the spectra are asterisked.
η
1.0
0.8
0.6
0.4
0.2
0
(‡)
(b)
(c)
–26 –28 –30 –32 –34 –36 –30 –32 –34 –36 –38 –40 –40 –42 –44 –46 –48 –50
δ, ppm
2
31
Fig. 4. Diagrams of the χ statistics (as a function of the parameters of the P chemical shift anisotropy) of (a) [Pt{S P(O-
2
cyclo-C H ) } ] and (b) the α- and β-form and (c) at spinning frequencies of 5000 and 3200 Hz (thin and thick lines, respectively).
The solid and dashed lines bound the 68.3% and 95.4% confidence limits, respectively, of δ
6
11 2 2
and η.
aniso
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590
IVANOV et al.
(a)
*
–3950
–4000
(b)
–4000 –4025
*
–1500
–2500
–3500
–4500
–5500
δ, ppm
195
Fig. 5.
êt MAS NMR spectra of (a) [Pt{S P(O-cyclo-C H ) } ] and (b) β-[Pt{S P(O-iso-C H ) } ]. The samples were
2 6 11 2 2 2 3 7 2 2
obtained by crystallization from chloroform. The spinning frequency is 5000 Hz; the number of scans is (a) 20000 and (b) 16 800.
The signals in the center of gravity of the spectra are asterisked.
increasing contribution from the rhombic component. β-II have the lowest δaniso values (30.8–42.7 ppm).
Since δaniso correlates with the SPS angle [30], we
expect that these angles are smallest in the platinum
complexes.
The values η = 0.98–0.75 obtained for the platinum(II)
complexes suggest a predominantly rhombic character
of the 31P chemical shift tensors. Compared to the
nickel(II) [18–20], zinc [19, 21], cadmium [20, 22–24],
lead(II) [25–27], silver(I) [28], and antimony(V)
The shapes of the whole 195Pt MAS NMR spectra of
complexes I and β-II (Fig. 5) corresponds to the axially
dialkyl dithiophosphates [29], complexes I, α-II, and symmetric 195Pt chemical shift tensor (for δzz > δxx,δyy,
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 8 2008

SYNTHESIS, STRUCTURAL AND MULTINUCLEAR NATURAL ABUNDANCE
591
x
0
z
y
Fig. 6. Projection of the crystal structure of [Pt{S P(O-cyclo-C H ) } ] onto the plane xz.
2
6 11 2 2
a
so δaniso > 0). On the whole, these spectra are similar to
the spectrum of single-crystal cooperite (natural PtS)
[3] and suggest the formation of square chromophores
[PtS4]. However, the 195Pt chemical shift anisotropy for
the platinum(II) complexes is much smaller for the δzz
component, which can be estimated from experimental
MAS spectra at –1800 ppm (for PtS, δzz = +4023 ppm
[3]). This also leads to a substantially difference
between the isotropic 195Pt chemical shifts. The signals
in the center of gravity of the NMR spectra that are
characterized by isotropic 195Pt chemical shifts are split
into triplets (1 : 2 : 1) due to 195Pt –31P spin-spin cou-
plings on two structurally equivalent Dtph ligands. The
coupling constants 2J(195Pt−31ê) are given in Table 4.
2
than that between the ligands S1···S2 (3.460 Å) . The
slight rhombic distortion of the chromophore is due to
the pair nonequivalence of the Pt–S bonds (2.3324 and
2.3273 Å) and the corresponding deviation of the
S…S…S angles from 90°. The bidentate coordination
of the Dtph ligands produces four-membered chelate
rings [PtS2P]. The torsion PtSSP and SPtPS angles
(169.5° and 170.2°, respectively) do not equal 180°
because of a tetrahedral distortion of the planar geome-
try of these rings. In addition, the trans-annular Pt…P
distances in the chelate rings are very short (2.986 Å).
As expected from 31P MAS NMR data, the S1PS2
angle is smallest (101.79°) among all the dithiophos-
phate complexes we studied earlier [18–30]. The P–S
bond lengths (2.0077 and 2.0141 Å) are intermediate
between the ideal single (2.14 Å) and double phospho-
rus–sulfur bonds (1.94 Å) [31]. This is direct evidence
for the delocalization of the π-electron density over the
structural fragments PS2. The phosphorus atoms are in
a nearly tetrahedral environment [O2S2]. The six-mem-
bered ë6ç11 rings are in the chair conformation.
To verify our conclusions drawn from MAS NMR
and EPR spectra, we examined structure I by X-ray dif-
fraction analysis.
The unit cell of complex I (Fig. 6) consists of two
structurally equivalent centrosymmetric molecules
[Pt{S2P(O-cyclo-C6H11)2}2] (Fig. 7; Table 3). The plat-
inum atom coordinates two Dtph ligands in S,S'-biden-
tate fashion to form the planar chromophore [PtS4]
(dsp2 hybridization state of platinum). The S1···S2 dis-
tance within the ligand (3.121 Å) is noticeably shorter
2
a
The symmetry operation code is –x + 1, –y, –z + 2.
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592
IVANOV et al.
(‡)
C(10)
C(11)
C(8)
C(12)
C(9)
C(7)
S(2)
O(2)
P
Pt
S(1)
O(1)
C(5)
C(6)
C(1)
C(4)
C(2)
C(3)
(b)
Pt
S(2)
C(11)
C(12)
C(6)
C(5)
C(7)
O(2)
C(4)
C(8)
C(10)
C(9)
P
O(1)
C(2)
C(3)
S(1)
Fig. 7. Two projections of the molecular structure of [Pt{S P(O-cyclo-C H ) } ].
2
6 11 2 2
To sum up, we obtained crystalline platinum(II) and we calculated the 31ê chemical shift anisotropy δaniso
and the asymmetry parameter η.
copper(II) complexes with O,O'-dicyclohexyl dithio-
phosphate and O,O'-diisopropyl dithiophosphate as
ligands and characterized them by 13C, 31P, and 195Pt
CP/MAS NMR and EPR spectroscopy. The molecular
structure of [Pt{S2P(O-cyclo-C6H11)2}2] (I) results
from S,S'-bidentate coordination of the Dtph ligands by
platinum(II) to form the planar chromophore [PtS4]
(X-ray diffraction data). For [Pt{S2P(O-iso-C3H7)2}2]
(II), a new α-form was obtained and identified from 31ê
ACKNOWLEDGMENTS
We are grateful to Cheminova Agro A/S (Denmark)
for providing potassium O,O'-dialkyldithiophosphates.
This work was supported by the Russian Foundation
for Basic Research and the Far East Division of the
Russian Academy of Sciences (Program “Dal’nii Vos-
MAS NMR spectra. For the platinum(II) complexes, tok”, grant no. 06-03-96009).
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SYNTHESIS, STRUCTURAL AND MULTINUCLEAR NATURAL ABUNDANCE
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