Reduction of (imine)Pt(IV) to (imine)Pt(II) complexes with carbonyl-stabilized phosphorus ylides

Article abstract of DOI:10.1021/ic000769c

A novel method is reported for generation of the difficult-to-obtain (imine)Pt(II) compounds that involves reduction of the corresponding readily available Pt(IV)-based imines by carbonyl-stabilized phosphorus ylides, Ph₃P= CHCO₂R, in nonaqueous media. The reaction between neutral (imino)Pt(IV) compounds [PtCl₄{NH=C(Me)-ON=CR¹R²}₂] [R¹R² = Me₂, (CH₂)₄, (CH₂)₅, (Me)C(Me)=NOH], [PtCl₄{NH=C(Me)ONR₂}₂] (R = Me, Et, CH₂Ph), [PtCl₄{N=C(Me)O-N(R³)-C(R¹) (R²)}₂] (R₁ = H; R² = Ph or C₆H₄Me; R³ = Me) as well as anionic-type platinum(IV) complexes (Ph₃PCH₂Ph)[PtCl₅{NH=C(Me) ON=CR₂}] [R₂ = Me₂, (CH₂)₄, (CH₂)₅] and 1 equiv of Ph₃P=CHCO₂R (R = Me, Et) proceeds under mild conditions (ca. 4 h, room temperature) to give selectively the platinum(II) products (in good to excellent isolated yields) without further reduction of the platinum center. All thus prepared compounds (excluding previously described Δ⁴-1,2,4-oxadiazoline complexes) were characterized by elemental analyses, FAB mass spectrometry, IR and ¹H, ¹³C{¹H}, ³¹P(¹H} and ¹⁹⁵Pt NMR spectroscopies, and X-ray single-crystal diffractometry, the latter for [PtCl₂{NH=C(Me)ON=CMe₂}₂] [crystal system tetragonal, space group P4₂/n (No. 86), a = b = 10.5050(10) A, c = 15.916(3) A] and (Ph₃PCH₂CO₂-Me)[PtCl₃(NCMe)] [crystal system orthorhombic, space group Pna2₁ (No. 33), a = 19.661(7) A, b = 12.486(4) A, c = 10.149(3) A]. The reaction is also extended to a variety of other Pt(II)/Pt(IV) couples, and the ylides Ph₃P=CHCO₂R are introduced as mild and selective reducing agents of wide applicability for the conversion of Pt(IV) to Pt(II) species in nonaqueous media, a route that is especially useful in the case of compounds that cannot be prepared directly from Pt(II) precursors, and for the generation of systematic series of Pt(II)/Pt(IV) complexes for biological studies.

Full text of DOI:10.1021/ic000769c

Inorg. Chem. 2001, 40, 1683-1689
1683
Reduction of (imine)Pt(IV) to (imine)Pt(II) Complexes with Carbonyl-Stabilized Phosphorus
Ylides
Gabriele Wagner,† Tatyana B. Pakhomova,‡ Nadezhda A. Bokach,‡
Joa˜o J. R. Frau´sto da Silva,† Jose Vicente,*,§ Armando J. L. Pombeiro,*,† and
Vadim Yu. Kukushkin*,‡
Centro de Qu´ımica Estrutural, Complexo I, Instituto Superior Te´cnico, Av. Rovisco Pais,
1049-001 Lisbon, Portugal, Department of Chemistry, St. Petersburg State University,
198904 Stary Petergof, Russian Federation, and Grupo de Qu´ımica Organometa´lica, Departamento de
Qu´ımica Inorga´nica, Facultad de Qu´ımica, Universidad de Murcia, Apartado 4021, 30071-Murcia, Spain
ReceiVed July 12, 2000
A novel method is reported for generation of the difficult-to-obtain (imine)Pt(II) compounds that involves reduction
of the corresponding readily available Pt(IV)-based imines by carbonyl-stabilized phosphorus ylides, Ph3Pd
CHCO2R, in nonaqueous media. The reaction between neutral (imino)Pt(IV) compounds [PtCl4{NHdC(Me)-
ONdCR1R2}2] [R1R2 ) Me2, (CH2)4, (CH2)5, (Me)C(Me)dNOH], [PtCl4{NHdC(Me)ONR2}2] (R ) Me, Et,
CH2Ph), [PtCl4{NdC(Me)O-N(R3)-C(R1)(R2)}2] (R1 ) H; R2 ) Ph or C6H4Me; R3 ) Me) as well as anionic-
type platinum(IV) complexes (Ph3PCH2Ph)[PtCl5{NHdC(Me)ONdCR2}] [R2 ) Me2, (CH2)4, (CH2)5] and 1
equiv of Ph3PdCHCO2R (R ) Me, Et) proceeds under mild conditions (ca. 4 h, room temperature) to give
selectively the platinum(II) products (in good to excellent isolated yields) without further reduction of the platinum
center. All thus prepared compounds (excluding previously described ∆4-1,2,4-oxadiazoline complexes) were
1
characterized by elemental analyses, FAB mass spectrometry, IR and H, 13C{1H}, 31P{1H} and 195Pt NMR
spectroscopies, and X-ray single-crystal diffractometry, the latter for [PtCl2{NHdC(Me)ONdCMe2}2] [crystal
system tetragonal, space group P42/n (No. 86), a ) b ) 10.5050(10) Å, c ) 15.916(3) Å] and (Ph3PCH2CO2-
Me)[PtCl3(NCMe)] [crystal system orthorhombic, space group Pna21 (No. 33), a ) 19.661(7) Å, b ) 12.486(4)
Å, c ) 10.149(3) Å]. The reaction is also extended to a variety of other Pt(II)/Pt(IV) couples, and the ylides
Ph3PdCHCO2R are introduced as mild and selective reducing agents of wide applicability for the conversion of
Pt(IV) to Pt(II) species in nonaqueous media, a route that is especially useful in the case of compounds that
cannot be prepared directly from Pt(II) precursors, and for the generation of systematic series of Pt(II)/Pt(IV)
complexes for biological studies.
Introduction
CH2Ph, Ph) and oximes, R1R2CdNOH, or dioximes, HONd
C{spacer}CdNOH, which led to the isolation of the imino
compounds [PtCl4{NHdC(R)ONdCR1R2}2]5 and [PtCl4{NHd
C(R)ONdC{spacer}CdNOH}2],6 respectively. It was also
found that the iminoacylation of oximes5,6 occurs only at the
Pt(IV) center (or at other metal centers in a relatively high
oxidation state7-9) and the reaction does not proceed at alls
even under harsh conditionssat either (organonitrile)Pt(II)
complexes or at free RCN. These observations were rationalized
by a mechanistic theoretical study10 that suggested both lower
activation energy and higher stability of products in the case of
platinum(IV) systems compared with the platinum(II) ones.
Alteration of reactivity of organic species upon their coor-
dination to a metal center opens up a possibility for metal-
mediated reactions that are not feasible for the substrates in the
noncoordinated state, and this area, i.e., ligand reactions, has
been a subject of rapt attention in the last two decades.1-4 It is
not unusual when the reactivity of substrates is different for a
different oxidation state of a particular metal ion. Our recent
comparative reactivity studies of (organonitrile)platinum(IV)
compounds vs the corresponding platinum(II) complexes are
illustrative in that respect. First, we have observed the reaction
between the platinum(IV) complexes [PtCl4(RCN)2] (R ) Me,
* Authors to whom correspondence should be addressed. E-mail:
jvs@um.es, pombeiro@ist.utl.pt, and kukushkin@VK2100.spb.edu.
† Instituto Superior Te´cnico.
(5) Kukushkin, V. Yu.; Pakhomova, T. B.; Kukushkin, Yu. N.; Herrmann,
R.; Wagner, G.; Pombeiro, A. J. L. Inorg. Chem. 1998, 37, 6511.
(6) Kukushkin, V. Yu.; Pakhomova, T. B.; Bokach, N. A.; Wagner, G.;
Kuznetsov, M. L.; Galanski M.; Pombeiro, A. J. L. Inorg. Chem. 2000,
39, 216.
‡ St. Petersburg State University.
§ Universidad de Murcia.
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10.1021/ic000769c CCC: $20.00 © 2001 American Chemical Society
Published on Web 03/02/2001

1684 Inorganic Chemistry, Vol. 40, No. 7, 2001
Wagner et al.
Second, we discovered an unusual coupling between nitriles
bound to the platinum(IV) center in [PtCl4(RCN)2] and nitrones
-ON+(R3)dCR1R2 11,12 (the latter can be viewed as the “frozen”,
by alkylation, form of the other oxime tautomer) to give, in the
course of [2 + 3] cycloaddition, ∆4-1,2,4-oxadiazoline com-
Scheme 1
pounds [PtCl4{NdC(Me)O-N(R3)-C(R1)(R2)}2].11,12 The role
of the metal oxidation state on the control of the reactivity was
verified when it was found that the highly reactive platinum-
(IV) complexes [PtCl4(RCN)2] exhibit such a leveling effect on
the cycloaddition that it might be performed under mild reaction
conditions starting even from a very unreactive organonitrile
bearing an electron-donor substituent, while for the much less
reactive organonitriles in platinum(II) complexes [PtCl2(RCN)2]
a differentiating effect is recognized in such a way that the
cycloaddition occurs only in the case of organonitriles with an
electron-acceptor substituent.12
These two reactions, which proceed at a quadruply charged
platinum center and are limited or even totally unreachable by
use of (organonitrile)Pt(II) precursors, allow the isolation of Pt-
(IV)-bound imino species that cannot be prepared in so-called
pure organic chemistry. Furthermore, imines NHdC(Me)ONd
CR1R2 with two donor substituents at the carbon, prepared in
the course of the reactions with oximes,5-9 represent a distinctive
subclass of unusually stable imines, and their preparation could
be useful both for coordination chemistry in modeling elusive
monodentate imine ligands13-15 and for organic chemistry as
models of unstable intermediates in a nitrilium ion catalyzed
Beckmann rearrangement.16,17
ammonia addition27 to nitrile platinum(II) complexes, or by
direct reaction of some stable organic imines and Pt(II)
precursors.28-30 We report herein on a novel method for
generation of (imine)Pt(II) compounds that involves reduction
of the corresponding readily available Pt(IV)-based imines by
carbonyl-stabilized phosphorus ylides, Ph3PdCHCO2R, in non-
aqueous media (Scheme 1). The easy-to-obtain34 ylides Ph3Pd
CHCO2R (R ) Me, Et) and in particular the former one that is
commercially available are now introduced as mild and selective
reducing agents for conversion of Pt(IV) to Pt(II) species, a route
that is especially useful in the case of compounds that cannot
be prepared directly from Pt(II) precursors. In this way we take
advantage of the stronger activation power of a Pt(IV) center
toward nucleophilic addition to organonitrile ligands to form,
upon addition followed by reduction, final (imine)Pt(II) com-
plexes which otherwise would not be accessible.
Results and Discussion
As a continuation of our project on the reactivity of
organonitrile platinum compounds5-12 and preparation and
biological investigation18 of metal-stabilized imino species, we
focused our attention on (imine)Pt(II) compounds. Complexes
of this type are rather scarce,19-30 and their chemistry is very
little explored despite intrinsic antitumor activity of some of
them.31-33 Previously (imine)Pt(II) species were prepared either
by base-catalyzed alcohol addition,19-25 by hydrolysis26 or
Reduction of (imine)Pt(IV) Compounds with Ph3Pd
CHCO2R and Characterization of Products. A systematic
approach to investigations of chemical reactivity1-4 and biologi-
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platinum(IV)-based compounds. The most common route for
preparation of these couples is oxidation of platinum(II)
complexes with Cl2 (or its so-called “solid chlorine equivalents”,
41-43
e.g., PCl5
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Reduction of (imine)Pt(IV) to (imine)Pt(II) Complexes
Inorganic Chemistry, Vol. 40, No. 7, 2001 1685
nonaqueous media to give [PtX4LL′] complexes or reaction with
hydrogen peroxide47-50 in water to generate [PtX2(OH)2LL′]
species. The opposite way, i.e., reduction of platinum(IV)
complexes, although known, is much less common, being
applied mostly for syntheses performed in aqueous media due
to better solubilities of the typical reducing agents,4 e.g.,
N2H4‚H2SO4, NH2OH‚HCl, oxalate, or ascorbate, in water. To
the best of our knowledge a reagent that effectively reduces in
nonaqueous media a variety of platinum(IV) centers to platinum-
(II) ones has not yet been devised although applications of SO2,
ethanol, olefins, or formaldehyde4 for the reduction of some
narrow classes of platinum(IV) compounds were reported in
the literature.
Scheme 2
During attempts to extend to [PtCl4(MeCN)2] the previous
studies on the nucleophilic attack of carbonyl-stabilized phos-
phorus ylides to organonitriles coordinated to Pt(II),51-53 we
observed a facile reduction of the platinum center that proceeded
under mild conditions (see below). This result prompted us to
explore further the potential of the phosphorus ylides for the
reduction of platinum(IV) complexes other than the nitrile-based
compounds. For this study we addressed (imine)Pt(IV) com-
plexes5,6 including (∆4-1,2,4-oxadiazoline)Pt(IV) compounds11
due to (i) the general interest in this class of complexes justified
in the Introduction and (ii) the necessity to develop a route to
(imine)Pt(II) species especially those that cannot be prepared
directly from Pt(II) precursors.
The reaction between [PtCl4{NHdC(Me)ONdCR1R2}2]
(R1R2 ) Me2, (CH2)4, (CH2)5, and (Me)C(Me)dNOH) and 1
equiv of Ph3PdCHCO2Me (Ph3PdCHCO2Et can be used
instead) proceeds under mild conditions (ca. 4 h, room tem-
perature) to give a mixture of one platinum-containing product
along with phosphorus-containing species (A f B in Scheme
2). The latter can be easily separated from the platinum material
by washing the mixture with ethanol and diethyl ether.
Alternatively, column chromatography is useful for the separa-
tion (see Experimental Section). Independently of the method
applied for the purification, the isolated yields of the platinum
compounds range from good to excellent (80-95%). The same
method of reduction was used for the conversion of other neutral
(imine)Pt(IV) compounds, i.e., [PtCl4{NHdC(Me)ONR2}2]
(R ) Me, Et, CH2Ph)54 (C f D in Scheme 2) and [PtCl4-
also detected in the reaction mixtures but only as minor
components and were not isolated and identified.
All thus prepared compounds (excluding previously described
∆4-1,2,4-oxadiazoline complexes12) were characterized by el-
emental analyses, FAB mass spectrometry and IR and 1H,
13C{1H}, and 195Pt NMR spectroscopies. The X-ray structure
determination of [PtCl2{NHdC(Me)ONdCMe2}2] (1) (Figure
1) revealed its trans configuration, and, similarly to the
corresponding platinum(IV) complex,5 the imine ligands exhibit
the one-end rather than the N,N-bidentate coordination mode.
The iminoacyl species are in the E conformation which is held
by a N-H‚‚‚N hydrogen bond [N(1)‚‚‚N(2), N(1)-H, N(1)H‚
‚‚N(2) are 2.66, 0.9641, and 2.2640 Å; N(1)-H‚‚‚N(2) 103.788°]
between the imine dNH atom and the oxime nitrogen. No
evidence for the Z conformation in solution was obtained by
NMR spectroscopy.
General features of the IR and 1H and 13C{1H} NMR spectra
of [PtCl2{NHdC(Me)ONdCR1R2}2], [PtCl2{NHdC(Me)-
ONR2}2], and [PtCl2{NdC(Me)O-N(R3)-C(R1)(R2)}2] are
similar to those observed for the appropriate platinum(IV)
complexes.5,6,11,54 The most significant difference between the
two types of complexes is their 195Pt NMR spectra which show
the disappearance of the Pt(IV) signal in the range from -156
to -194 ppm [from 0.8 to 2.6 for anionic Pt(IV) complexes],
while a new resonance emerges in the range from -2033 to
-2210 ppm [from -1807 to -1811 for the anionic-type Pt(II)
complexes].
Plausible Mechanism of Reducing Action of the Ylides.
In coordination chemistry, the carbonyl-stabilized phosphorus
ylides display two principal reactivity modes, i.e., they act as
C-donor ligands displacing poorer ligands55-64 and as nucleo-
philes in the addition to metal-activated organonitriles51-53 and
{NdC(Me)O-N(R3)-C(R1)(R2)}2] (R1 ) H; R2 ) Ph or C6H4-
Me; R3 ) Me11,12) (E f F in Scheme 2). In addition, the ylides
reduce readily the anionic-type compounds (Ph3PCH2Ph)[PtCl5-
{NHdC(Me)ONdCR2}] [R2 ) Me2, (CH2)4, (CH2)5] to give
the appropriate platinum(II) complexes (Ph3PCH2Ph)[PtCl3-
{NHdC(Me)ONdCR2}], which were isolated in individual
form in 60-70% yields after chromatography on silica gel. In
the latter case, some other platinum-containing species were
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1686 Inorganic Chemistry, Vol. 40, No. 7, 2001
Wagner et al.
Figure 1. PLATON drawing of trans-[PtCl2{NHdC(Me)ONdCMe2}2] with atomic numbering scheme. Selected bond distances (Å): Pt-Cl
2.296(8), Pt-N(1) 1.98(2), N(1)-C(1) 1.27(4), O-C(1) 1.34(3), O-N(2) 1.43(3), N(2)-C(3) 1.25(3).
alkenes.65 Reducing properties of the ylides are totally unex-
plored in coordination chemistry although they are known from
organic chemistry.66-69 It was shown that chlorination of
Ph3PdCHCO2Me gives (Ph3PCHClCO2Me)Cl, which imme-
diately reacts, by transylidation, with yet unreacted Ph3PdCHCO2-
Me to give (Ph3PCH2CO2Me)Cl and Ph3PdCClCO2Me.66
Further chlorination of Ph3PdCClCO2Me gives (Ph3PCCl2CO2-
Me)Cl and Ph3PdO. The latter presumably forms via hydrolytic
cleavage of (Ph3PCCl2CO2Me)Cl and/or Ph3PdCClCO2Me.67,68
In our systems, in accord with these findings, we observed the
formation of (Ph3PCH2CO2Me)Cl which was isolated from the
synthesis of [PtCl2{NHdC(Me)ONdCMe2}2] and characterized.
Triphenylphosphine oxide was also isolated after chromatog-
raphy on silica gel, and its appearance agrees with the previous
report indicating that Ph3PdCClCO2Et decomposes during
chromatography on Al2O3 to give Ph3PdO.68
The reaction between [PtCl4(MeCN)2] and Ph3PdCHCO2-
Me in acetonitrile is remarkable from the viewpoint of under-
standing the reducing action of the ylides. Treatment of the
Figure 2. PLATON drawing of (Ph3PCH2CO2Me)[PtCl3(NCMe)] with
complex with 1 equiv of Ph3PdCHCO2Me results in precipita-
atomic numbering scheme. Bond distances in the anion (Å): Pt-Cl(1)
tion of the platinum(II) complex [PtCl2(MeCN)2]. The filtrate,
2.329(5), Pt-Cl(2) 2.296(5), Pt-Cl(3) 2.260(6), Pt-N 1.951(18),
after removal of the insoluble material, was shown by TLC and
31P{1H} NMR monitoring to contain Ph3PdO. Subsequent
removal of the solvent and recrystallization of the residue from
EtOH allowed the isolation of pure (Ph3PCH2CO2Me)[PtCl3-
(MeCN)], where the phosphonium cation, formed in the course
of the process, was unambiguously identified by X-ray crystal-
lography (Figure 2, Table 1).
C(1)-N1.14(3), C(1)-C(2) 1.46(3).
Table 1. Crystal Data and Structure Refinement for
trans-[PtCl2{NHdC(Me)ONdCMe2}2] and
(Ph3PCH2CO2Me)[PtCl3(NCMe)]
empirical formula
fw
T, °C
C10H20N4Cl2O2Pt
494.29
20(2)
C23H23NCl3O2PPt
677.82
20(2)
Although the addition of ylides to coordinated nitrile species
should be easier in the case of [PtCl4(MeCN)2], as compared
to [PtCl2(MeCN)2],51-53 the reduction is conceivably faster and
becomes the dominant reaction path. It is reasonable to assume
that the reduction of [PtCl4(MeCN)2] leads to [PtCl2(MeCN)2]
and (Ph3PCH2CO2Me)Cl followed by replacement of the weakly
bonded acetonitrile ligand in nonaqueous media by the halide
to generate the anionic complex, a process that is known from
the chemistry of platinum(II)-based nitrile compounds.70
space group
a/Å
b/Å
c/Å
P42/n (No. 86)
10.5050(10)
10.5050(10)
15.916(3)
90
90
90
1756.4(4)
4
1.869
8.296
0.0394
Pna21 (No. 33)
19.661(7)
12.486(4)
10.149(3)
90
90
90
2491.4(14)
4
1.807
6.33
0.0379
0.0410
R/deg
â/deg
γ/deg
V/Å3
Z
Dc, Mg/m3
µ(Mo KR), mm-1
Ra
(61) Albanese, J. A.; Staley, D. L.; Rheingold, A. L.; Burmeister, J. L.
Inorg. Chem. 1990, 29, 2209.
b
Rw
0.0982
(62) Uson, R.; Fornies, J.; Navarro, R.; Ortega, A. M. J. Organomet. Chem.
1987, 334, 389.
(63) Facchin, G.; Bertani, R.; Calligaris, M.; Nardin, G.; Mari, M. J. Chem.
Soc., Dalton Trans. 1987, 1381.
(64) Soulivong, D.; Wieser, C.; Marcellin, M.; Matt, D.; Harriman, A.;
Toupet, L. J. Chem. Soc., Dalton Trans. 1997, 2257.
(65) Vicente, J.; Chicote, M. T.; MacBeath, C.; Ferna´ndez-Baeza, J.;
Bautista, D. Organometallics 1999, 18, 2677.
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2]]1/2.
Reduction of Other Platinum(IV) Complexes. Facile
reduction of (imine)Pt(IV) compounds with the ylides Ph3Pd
CHCO2R in nonaqueous media opens up a route to such (imine)-
Pt(II) complexes which are unaccessible by direct synthesis from
platinum(II) precursors. Moreover, despite the fact that this study
(66) Ma¨rkl, G. Chem. Ber. 1961, 94, 2996.
(67) Denney, D. B.; Ross, S. T. J. Org. Chem. 1962, 27, 998.
(68) Speziale, A. J.; Ratts, K. W. J. Org. Chem. 1963, 28, 465.
(69) Yamagata, K.; Takaki, M.; Yamazaki, M. Liebigs Ann. Chem. 1992,
1109.
(70) Kukushkin, V. Yu.; Krol, I. A.; Starikova, Z. A.; Tkachuk, V. M.
Koord. Khim. 1990, 16, 1406; SoV. Coord. Chem. (Engl. Transl.) 1990,
16, 746.

Reduction of (imine)Pt(IV) to (imine)Pt(II) Complexes
Inorganic Chemistry, Vol. 40, No. 7, 2001 1687
with the published method.79 Imino compounds5,6,11,54 (except [PtCl4-
{NHdC(Me)ONdCMeEt}2], whose synthesis is given below) and other
complexes trans-[PtCl4L2] (L ) Me2SO,80,81 Me2S,80 py,82 2-propanone
oxime,83 MeCN81), [PtCl4(py)(Me2S)],84,85 [PtCl4(Me2SO)(NHEt2)],80,81
and (Ph3PCH2Ph)[PtCl5(Me2SO)]80,81 were prepared in accord with the
published methods. C, H, and N elemental analyses were carried out
by the Microanalytical Service of the Instituto Superior Te´cnico. Melting
points were determined on a Kofler table. For TLC, Merck UV 254
SiO2 plates have been used. Positive-ion FAB mass spectra were
obtained on a Trio 2000 instrument by bombarding 3-nitrobenzyl
alcohol (NBA) matrixes of the samples with 8 keV (ca. 1.28 × 1015 J)
Xe atoms. Mass calibration for data system acquisition was achieved
using CsI. Infrared spectra (4000-400 cm-1) were recorded on a BIO-
was mostly focused around the reduction of (imine)Pt(IV)
species, the method is more general and it was also successfully
applied in this work to some other systems (see Experimental
Section) involving [PtCl4L2] (L ) Me2S, Me2SO, pyridine,
2-propanone oxime), [PtCl4(py)(Me2S)], [PtCl4(Me2SO)(NHEt2)],
and the anionic complex (Ph3PCH2Ph)[PtCl5(Me2SO)]. It is
worthwhile to mention that (i) dimethyl sulfoxide ligands remain
intact upon the reduction in spite of the fact that deoxygention
of the sulfinyl group with other phosphorus ylides,71 although
more reactive than Ph3PdCHCO2Me, is known; (ii) despite the
fact that coordinated 2-propanone oxime exhibits a significant
OH acidity,72 the reaction between [PtCl4(Me2CdNOH)2] and
Ph3PdCHCO2Me, which is a base, led to the reduction products
rather than to those derived from neutralization; and (iii)
chlorides which liberated upon the reduction in nonaqueous
media can displace the weakly bound ligands73-78 (such as, for
example, MeCN or Me2SO) in [PtCl2L2] to form the anionic
complexes [PtCl3L]-. The substitution of either acetonitrile or
dimethyl sulfoxide in [PtCl2L2] by Cl- in organic solvents has
previously been described.70,80
Concluding Remarks. It is anticipated that reduction with
ylides represents a very convenient method for generation of
imine and other platinum(II) compounds in a nonaqueous phase.
Indeed, the readily available ylides are highly soluble in the
most common organic solvents, and this allows the performance
of the syntheses in a homogeneous liquid phase. The reduction
proceeds rapidly and under mild conditions with 1 equiv of the
ylide to form selectively the platinum(II) products without
further reduction of the platinum center whichsin the case of
reduction to the platinum blackswould result in decomposition.
Moreover, the products of oxidation of the ylides can be easily
separated from the platinum products, and after workup the
platinum(II) compounds were isolated in good yields. The only
disadvantage we see so far is the case of anionic complexes,
since the generated phosphonium cation can compete with other
cations giving mixtures where the anionic platinum complex is
linked to two different counterions.
1
RAD FTS 3000MX instrument in KBr pellets. H, 13C{1H}, 31P{1H},
and 195Pt NMR spectra were measured on a Varian UNITY 300
spectrometer at ambient temperature. 195Pt chemical shifts are given
relative to Na2[PtCl6] (by using aqueous K2[PtCl4] ) -1630 ppm as a
standard), and half-height line widths are shown in parentheses.
[PtCl4{NHdC(Me)ONdCMeEt}2]. This platinum(IV) compound
for the reduction experiments was prepared accordingly to the published
method5 and used as the starting material for the reduction experiments
(see below). Anal. Calcd for C12H24N4Cl4O2Pt: C, 24.30; H, 4.08; N,
9.44. Found: C, 23.95; H, 4.28; N, 9.56. FAB+-MS, m/z: 615 [M +
Na]+, 593 [M + H]+, 557 [M - HCl]+, 522 [M - 2Cl]+. IR spectrum
(selected bands), cm-1: 3273 m ν(N-H), 1655 sh and 1634 s ν(Cd
1
N), 1183 m ν(C-O). H NMR in CDCl3, δ: 1.12 (t, 7.8 Hz, major
signal), 1.10 (t, 7.8 Hz, minor signal), 2.37 (quart., 7.8 Hz, major signal)
and 2.49 (quart., 7.8 Hz, minor signal) (Et), 2.06 (s, major signal) and
2.03 (s, minor signal) (Me), 2.62 (s, major signal) and 2.61 (minor
signal) (HNdC(Me)), 8.45 (br, NH). 13C{1H} NMR in CDCl3, δ: 18.0
(major signal) and 18.2 (minor signal) (HNdCMe), 10.2 (major signal),
10.1 (minor signal), 29.2 (major signal) and 24.3 (minor signal) (Et),
16.0 (major signal) and 19.3 (minor signal) (Me), 170.4 (major signal)
and 170.2 (minor signal) (NdC), 174.4 (major signal) and 174.2 (minor
signal) (HNdC). 195Pt NMR in CDCl3, δ: -160 (825 Hz). EtMeCd
NOH exists as an equilibrium mixture of ca. 75% E and 25% Z isomer;
therefore two sets of signals for the ligand in an approximate ratio of
4:1 were expected and observed.
Reduction of Pt(IV) Complexes to the Corresponding Pt(II)
Complexes with Ph3PdCHCO2Me. The solid phosphorus ylide
Ph3PdCHCO2Me (17 mg, 0.050 mmol) was added to a solution of the
corresponding Pt(IV) complex (0.050 mmol) in CH2Cl2 (3 mL)
whereupon the color of the solution changed from deep yellow to pale
yellow within ca. 1 h. The reaction mixture was kept at room
temperature for 3 h, then the solvent was evaporated and the residue
subjected to chromatography on silica gel. Elution with CH2Cl2/Et2O
(9:1, v/v) afforded the pure Pt(II) complex with yields ranges from
85% to 90% for neutral compounds and from 60% to 70% for anionic
complexes; subsequent elution with CH2Cl2/MeOH gave an approximate
1:1 mixture of two phosphorus-containing compounds, from which the
(Ph3PCH2CO2Me)Cl was crystallized as a colorless solid using CH2-
Cl2/Et2O as solvent of crystallization and Ph3PO was obtained from
the mother liquor. Identification of (Ph3PCH2CO2Me)Cl and Ph3PO was
The recommended procedure was proved to be efficient for
the reduction of different platinum(IV) complexes containing
N-donor ligands with sp3, sp2, and sp configurations of the N
atoms, and this implies that the method can be useful for the
generation of systematic series of Pt(II)/Pt(IV) complexes for
biological studies which most often involve complexes with
ligated N donors. Thus, the reduction gives the platinum(II)
members in Pt(II)/Pt(IV) couples, and reoxidation of the Pt(II)
complexes with, for instance, H2O2 should give the correspond-
ing dihydroxo species, thus forming the homologous sets of
complexes.
1
done by comparison of their H, 13C{1H}, and 31P{1H} NMR and IR
Experimental Section
spectra with those of commercial samples. Reduction of the anionic
complexes followed the same procedure and occurred without color
change. Completeness of the reaction was checked by TLC, and the
product was isolated by chromatography on silica gel, eluent CH2Cl2/
acetone (3:1, v/v).
Materials and Instrumentation. Solvents were obtained from
commercial sources and used as received. Ph3PdCHCO2Me was
purchased from Lancaster while other ylides were prepared in accord
(71) Amos, R. A. J. Org. Chem. 1985, 50, 1311.
(72) Kukushkin, V. Yu.; Tudela, D.; Pombeiro, A. J. L. Coord. Chem. ReV.
[PtCl2{NHdC(Me)ONdCMe2}2]. Anal. Calcd for C10H20N4Cl2O2-
Pt: C, 24.30; H, 4.08; N, 11.34. Found: C, 24.35; H, 4.00; N, 11.19.
1996, 156, 333.
(73) Davies, J. A.; Hartley, F. R. Chem. ReV. 1981, 81, 79.
(74) Hartley, F. R.; Davies, J. A. ReV. Inorg. Chem. 1982, 4, 27.
(75) Davies, J. A. AdV. Inorg. Chem. Radiochem. 1981, 24, 115.
(76) Dunbar, K. R. Comments Inorg. Chem. 1992, 13, 313.
(77) Berezin, B. D. SoV. J. Coord. Chem. (Engl. Transl.) 1991, 17, 597.
(78) Berezin, B. D. Russ. Chem. ReV. (Engl. Transl.) 1990, 60, 996.
(79) Vicente, J.; Chicote, M. T.; Saura-Llamas, I. J. Chem. Educ. 1993,
70, 163.
(80) Kukushkin, V. Yu.; Pankova, E. Yu., Simanova, S. A.; Sotman, S.
S.; Fundamensky, V. S.; Zenkevich, I. G.; Poliakova, I. A. Zh. Obshch.
Khim. 1990, 60, 587; J. Gen. Chem. (Engl. Transl.) 1990, 60, 513
and references therein.
(81) Kukushkin, V. Yu.; Kiseleva, N. P. Koord. Khim. 1988, 14, 693.
(82) Jørgensen, S. M. J. Prakt. Chem. 1886, 33, 489.
(83) Kukushkin, V. Yu.; Belsky, V. K.; Aleksandrova, E. A.; Konovalov,
V. E.; Kirakosyan, G. A. Inorg. Chem. 1992, 31, 3836.
(84) Kukushkin, V. Yu.; Belsky, V. K.; Aleksandrova, E. A.; Pankova, E.
Yu.; Konovalov, V. E.; Yakovlev, V. N.; Moiseev, A. I. Zh. Obshch.
Khim. 1991, 61, 318; J. Gen. Chem. (Engl. Transl.) 1991, 61, 284.
(85) Kukushkin, V. Yu.; Pankova, E. Yu.; Aleksandrova, E. A.; Poliakova,
I. A. Zh. Neorg. Khim. 1990, 35, 1778; Russ. J. Inorg. Chem. (Engl.
Transl.) 1990, 35, 1013.

1688 Inorganic Chemistry, Vol. 40, No. 7, 2001
Wagner et al.
1
FAB+-MS, m/z: 517 [M + Na]+, 494 [M]+, 458 [M - HCl]+, 421
[M - HONdCMe2]+, 385 [M - HONdCMe2 - HCl]+, 348 [M -
2HONdCMe2 - HCl]+. IR spectrum (selected bands), cm-1: 3222 m
ν(N-H), 1666 and 1646 s ν(CdN), 1173 m ν(C-O). 1H NMR in
CDCl3, δ: 2.02 and 2.03 (two s, 3H each, (dCMe2), 2.64 (s, 3H, Nd
CMe), 7.92 (br, 1H, NH). 13C{1H} NMR in CDCl3, δ: 17.1 and 21.8
(dCMe2), 19.4 (NdCMe), 164.1 (NdCMe2), 170.5 (HNdC). 195Pt
NMR in CDCl3, δ: -2040 (770 Hz).
1157 m ν(C-O). H NMR in CDCl3, δ: 2.30 (s, 3H, NdCMe), 3.98
and 4.05 (two d, 13.2 Hz, 2H each, (CH2Ph), 7.29 (m, 4H) and 7.36
(m, 6H) (CH2Ph), 8.14 (br, 1H, NH). 13C{1H} NMR in CDCl3, δ: 18.4
(NdCMe), 61.5 (CH2Ph), 128.3, 128.8, 129.6 and 133.9 (CH2Ph), 171.1
(HNdC). 195Pt NMR in CDCl3, δ: -2033 (580 Hz).
[Ph3PCH2Ph][PtCl3{NHdC(Et)ONdCMe2}]. Anal. Calcd for
C31H34N2Cl3OPPt: C, 47.55; H, 4.38; N, 3.58. Found: C, 46.38; H,
4.12; N, 3.41. FAB--MS, m/z: 429 [Manion]+. IR spectrum in KBr,
selected bands, cm-1: 3308 m-w ν(N-H), 3056 m-w and 2927 m
[PtCl2{NHdC(Me)ONdCMeEt}2]. Anal. Calcd for C12H24N4Cl2O2-
Pt: C, 27.59; H, 4.63; N, 10.73. Found: C, 28.01; H, 4.69; N, 10.70.
FAB+-MS, m/z: 522 [M]+, 486 [M - HCl]+, 450 [M - HCl - Cl]+.
IR spectrum (selected bands), cm-1: 3210 m ν(N-H), 1659 and 1643
1
ν(C-H), 1643 s ν(CdN), 1110 s-m ν(P-C). H NMR in CDCl3, δ:
7.7 (m, 15H, Ph), 7.1 (m, 5H, CH2Ph), 5.17 (d, JPH 14.0 Hz, 2H, CH2-
Ph), 3.11 (quart, JHH 7.6 Hz, 2H, Et), 1.24 (t, JHH 7.6 Hz, 3H, Et), 1.94
(s, 6H, dCMe2). 13C{1H} NMR in CDCl3, δ: 30.7 (1JPC 51.1 Hz, CH2-
Ph), 117.5 (1JPC 84.6 Hz, Cipso from Ph), 127.1 (2JPC 8.4 Hz, Cipso from
CH2Ph),128.3 (JPC 3.7 Hz, CHp from Ph), 128.7 (JPC 2.9 Hz, CHm from
Ph), 130.2 (JPC 12.7 Hz, CH from Ph), 131.5 (JPC 5.3 Hz, CHo from
CH2Ph), 134.3 (JPC 10.1 Hz, CH from Ph), 134.9 (JPC 2.7 Hz, CHp
from Ph), 163.4 (CdN from ONdCMe2), 172.6 (CdN from HNd
C(Et)), 26.7 (CH2 from Et), 10.1 (CH3 from Et), 16.9 and 21.8 (dCMe2).
31P{1H} in CDCl3, δ: 23.6. 195Pt NMR in CDCl3, δ: -1811 (660 Hz).
[Ph3PCH2Ph][PtCl3{NHdC(Et)ONdC(C4H8)}]. Anal. Calcd for
C33H36N2Cl3OPPt: C, 48.99; H, 4.48; N, 3.46. Found: C, 48,43; H,
4.51; N, 3.36. FAB--MS, m/z: 454 [Manion - H]+. IR spectrum in KBr,
selected bands, cm-1: 3311 m-w ν(N-H), 3057 m-w and 2927 m
1
s ν(CdN), 1177 m ν(C-O). H NMR in CDCl3, δ: 1.13 (t, 7.5 Hz,
major signal), 1.09 (t, 7.5 Hz, minor signal), 2.34 (quart., 7.8 Hz, major
signal) and 2.42 (quart., 7.8 Hz, minor signal) (Et), 1.99 (s, major signal)
and 2.00 (s, minor signal) (Me), 2.57 (s, major signal) and 2.56 (minor
signal) (HNdC(Me)), 7.91 (br, NH). 13C{1H} NMR in CDCl3, δ: 19.3
(major signal) and 19.5 (minor signal) (HNdCMe), 10.3 (major signal),
9.9 (minor signal), 29.2 (major signal) and 24.0 (minor signal) (Et),
15.6 (major signal) and 19.4 (minor signal) (Me), 168.7 (major signal)
and 169.5 (minor signal) (NdC), 170.9 (HNdC). 195Pt NMR in CDCl3,
δ: -2088 (800 Hz). EtMeCdNOH exists as an equilibrium mixture of
ca. 75% E and 25% Z isomer; therefore two sets of signals for the
ligand in an approximate ratio of 4:1 were expected and observed.
[PtCl2{NHdC(Me)ONdC(CH2)4}2]. Anal. Calcd for C14H24N4-
Cl2O2Pt: C, 30.78; H, 4.43; N, 10.25. Found: C, 30.96; H, 4.82; N,
10.05. FAB+-MS, m/z: 546 [M]+, 510 [M - Cl]+. IR spectrum
(selected bands), cm-1: 3220 m ν(N-H), 1651 s ν(CdN), 1170 m
ν(C-O). 1H NMR in CDCl3, δ: 1.82 (m, 4H) and 2.47 (m, 4H)
(dC(CH2)4), 2.54 (s, 3H, NdCMe), 7.83 (br, 1H, NH). 13C{1H} NMR
in CDCl3, δ: 19.4 (NdCMe), 24.4, 24.9, 29.6 and 31.4 ((CH2)4), 176.6
(NdC(CH2)4), 171.0 (HNdC). 195Pt NMR in CDCl3, δ: -2088 (840
Hz).
1
ν(C-H), 1646 s ν(CdN), 1110 s-m ν(P-C). H NMR in CDCl3, δ:
7.7 (m, 15H, Ph), 7.1 (m, 5H, CH2Ph), 5.21 (d, JPH 14.0 Hz, 2H, CH2-
Ph), 3.11 (quart, JHH 7.6 Hz, 2H, Et), 1.25 (t, JHH 7.6 Hz, 3H, Et), 2.42
(m, 4H, R-CH2 from dC(C4H8)), 1.78 (m, 4H, â-CH2 from dC(C4H8)).
13C{1H} NMR in CDCl3, δ: 30.7 (1JPC 45.0 Hz, CH2Ph), 117.5 (1JPC
84.6 Hz, Cipso from Ph), 127.1 (2JPC 8.4 Hz, Cipso from CH2Ph), 128.3
(JPC 3.7 Hz, CHp from Ph), 128.7 (JPC 2.9 Hz, CHm from Ph), 130.2
(JPC 12.7 Hz, CH from Ph), 131.5 (JPC 5.3 Hz, CHo from CH2Ph), 134.3
(JPC 10.1 Hz, CH from Ph), 134.9 (JPC 2.7 Hz, CHp from Ph), 174.9
(CdN from ONdC(C4H8)2), 172.8 (CdN from HNdC(Et)), 26.6 (CH2
from Et), 10.2 (CH3 from Et), 31.2 and 29.2 (R-CH2 from dC(C4H8)),
24.9 and 24.4 (â-CH2 from dC(C4H8)). 31P{1H} in CDCl3, δ: 23.6.
195Pt NMR in CDCl3, δ: -1808 (625 Hz).
[PtCl2{NHdC(Me)ONdC(CH2)5}2]. Anal. Calcd for C16H28N4-
Cl2O2Pt: C, 33.46; H, 4.91; N, 9.75. Found: C, 33.42; H, 5.05; N,
9.79. FAB+-MS, m/z: 597 [M + Na]+, 575 [M + H]+, 539 [M -
Cl]+, 539 [M - Cl - HCl]+. IR spectrum (selected bands), cm-1: 3209
1
m ν(N-H), 1663 and 1643 s ν(CdN), 1180 m ν(C-O). H NMR in
[Ph3PCH2Ph][PtCl3{NHdC(Et)ONdC(C5H10)}]. Anal. Calcd for
C34H38N2Cl3OPPt: C, 49.61; H, 4.65; N, 3.40. Found: C, 49.06; H,
4.64; N, 3.30. FAB+-MS, m/z: 468 [Manion - H]+. IR spectrum in KBr,
selected bands, cm-1: 3307 m-w ν(N-H), 3057 m-w, 2932 and 2859
m-w ν(C-H), 1639 s ν(CdN), 1109 s-m ν(P-C). 1H NMR in CDCl3,
δ: 7.7 (m, 15H, Ph), 7.1 (m, 5H, CH2Ph), 5.15 (d, JPH 14.3 Hz, 2H,
CH2Ph), 3.10 (quart, JHH 8.3 Hz, 2H, Et), 1.24 (t, JHH 8.3 Hz, 3H, Et),
2.46 (t, JHH 5 Hz, 2H, CH2 from dC(C5H10)), 2.23 (t, JHH 5.6 Hz, 2H,
CH2 from dC(C5H10)) 1.64 (m, 6H, CH2 from dC(C5H10)). 13C{1H}
NMR in CDCl3, δ: 30.7 (1JPC 53 Hz, CH2Ph), 117.5 (1JPC 86.7 Hz,
Cipso from Ph), 127.0 (2JPC 8.4 Hz, Cipso from CH2Ph), 128.3 (JPC 3.7
Hz, CHp from Ph), 128.7 (JPC 2.8 Hz, CHm from Ph), 130.2 (JPC 12.8
Hz, CH from Ph), 131.5 (JPC 5.4 Hz, CHo from CH2Ph), 134.3 (JPC 9.2
Hz, CH from Ph), 134.9 (JPC 2.8 Hz, CHp from Ph), 168.0 (CdN from
ONdCMe2), 172.8 (CdN from HNdCEt), 10.1 (CH3 from Et), 26.8
(CH2 from Et), 31.9 and 26.7 (R-CH2 from dC(C5H10)), 26.6, 25.6
and 25.2 (â- and γ-CH2 from dC(C5H10)). 31P{1H} NMR in CDCl3,
δ: 23.6. 195Pt NMR in CDCl3, δ: -1807 (700 Hz).
CDCl3, δ: 1.67 (m, 4H), 1.77 (m, 2H), 2.34 (t, 6.6 Hz, 2H) and 2.54
(t, 6.6 Hz, 2H) (dC(CH2)5), 2.59 (s, 3H, NdCMe), 7.92 (br, 1H, NH).
13C{1H} NMR in CDCl3, δ: 19.6 (NdCMe), 25.1, 25.7, 26.7, 27.1
and 31.9 ((CH2)5), 169.8 (NdC(CH2)5 and HNdC). 195Pt NMR in
CDCl3, δ: -2091 (680 Hz).
[PtCl2{NHdC(Me)ONdC(Me)C(Me)dNOH}2]. Anal. Calcd for
C12H22N6Cl2O4Pt: C, 24.84; H, 3.82; N, 12.22. Found: C, 25.12; H,
4.10; N, 12.13. FAB+-MS, m/z: 603 [M + Na]+, 580 [M]+, 545 [M -
Cl]+. IR spectrum (selected bands), cm-1: 3241 m ν(N-H), 1670 s
1
ν(CdN), 1189 m ν(C-O). H NMR in acetone-d6, δ: 2.09 and 2.18
(two s, 3H each, (dC(Me)C(Me)), 2.67 (s, 3H, NdCMe), 8.50 (br,
1H, NH). 13C{1H} NMR in acetone-d6, δ: 9.7 and 11.6 (dC(Me)C-
(Me)), 19.6 (NdCMe), 153.0 and 163.7 (two ONdC), 170.7 (HNd
C). 195Pt NMR in acetone-d6, δ: -2055 (400 Hz).
[PtCl2{NHdC(Me)ONMe2}2]. Anal. Calcd for C8H20N4Cl2O2Pt: C,
20.43; H, 4.29; N, 11.91. Found: C, 20.58; H, 4.18; N, 11.77. FAB+-
MS, m/z: 469 [M]+, 433 [M - Cl]+, 398 [M - 2Cl]+. IR spectrum in
1
KBr, selected bands, cm -1: 3247 m ν(N-H), 1665 s ν(CdN). H
NMR in CDCl3, δ: 2.48 (s, 3H, dCMe), 2.73 (s, 6H, NMe2) 8.05 (s,
br, 1H, NH). 13C{1H} NMR in CDCl3, δ: 18.8 (Me), 47.5 (NMe2),
170.7 (CdN). 195Pt NMR in CDCl3, δ: -2047 (800 Hz).
[PtCl2{NHdC(Me)ON(Me)CHR}2] (R ) Ph, C6H4Me). Isolated
1
yield is 99% (R ) Ph) and 87% (R ) C6H4Me). H, 13C{1H}, and
195Pt NMR are identical to those already described.12
[PtCl2{NHdC(Me)ONEt2}2]. Anal. Calcd for C12H28N4Cl2O2Pt: C,
27.38; H, 5.35; N, 10.64. Found: C, 27.57; H, 5.28; N, 10.55. FAB+-
MS, m/z: 526 [M]+, 454 [M - 2HCl]+. IR spectrum in KBr, selected
bands, cm -1: 3256 m-w ν(N-H), 1665 s ν(CdN). 1H NMR in
CDCl3, δ: 2.51 (s, 3H, dCMe), 1.09 (t, 7.2 Hz, 6H), 2.90 (quart., 6.6
Hz, 2H) and 2.91 (quart., 7.2 Hz, 2H) (NEt2) 8.15 (s, br, 1H, NH).
13C{1H} NMR in CDCl3, δ: 18.4 (Me), 11.6 and 52.7 (NEt2), 172.3
(CdN). 195Pt NMR in CDCl3, δ: -2028 (700 Hz).
[PtCl2{NHdC(Me)ON(CH2Ph)2}2]. Anal. Calcd for C32H36N4Cl2O2-
Pt: C, 49.62; H, 4.68; N, 7.23. Found: C, 49.80; H, 4.57; N, 7.14.
FAB+-MS, m/z: 797 [M + Na]+, 774 [M]+, 738 [M - HCl]+. IR
spectrum (selected bands), cm-1: 3271 m ν(N-H), 1655 s ν(CdN),
Reduction of Other Platinum(IV) Complexes. The reduction
proceeds similarly to the reduction of imine complexes, and NMR yields
are almost quantitative. All platinum(II) products from the reaction are
known, and their formation was confirmed by NMR spectroscopy (data
obtained are given below) and when possible by comparison of other
characteristics with those of known compounds.
trans-[PtCl2(HONdCMe2)2]:83 from the reduction of trans-[PtCl4-
(HONdCMe2)2]. 1H NMR in CDCl3, δ: 2.15 and 2.61 (two s, 3H each,
J
PtH not observed, NdCMe2), 9.80 (1H, OH). 13C{1H} NMR in CDCl3,
δ: 19.2 and 26.8 (NdCMe2), 164.0 (NdC). 195Pt NMR in CDCl3, δ:
-1998 (480 Hz).

Reduction of (imine)Pt(IV) to (imine)Pt(II) Complexes
Inorganic Chemistry, Vol. 40, No. 7, 2001 1689
trans-[PtCl2py2]:86 from the reduction of trans-[PtCl4py2]. 1H NMR
in CDCl3, δ: 7.13 (t, 7.5 Hz, 2H), 7.61 (“t”, 7.8 Hz, 1H), 8.62 (m, JPtH
31 Hz, 2H). 195Pt in CDCl3, δ: -1944 (600 Hz). The solubility of the
complex in CDCl3 is insufficient to measure the 13C{1H} NMR
spectrum even at high acquisition time.
coordinates obtained from the Patterson synthesis using the SHELXTL
package.90 After that, all reflections with I < 2σ(I) were excluded from
calculations. Refinement was done by full-matrix least squares based
on F2 using the SHELX-97 package.91 All non-H atoms were treated
anisotropically. H atoms were located in a difference Fourier map and
refined isotropically. An extinction correction has been applied. Lorentz,
polarization, and absorption corrections were made.92 Scattering factors
are from International Tables for X-ray Crystallography.93 Crystal data
are given in Table 1.
X-ray Structure Determination of (Ph3PCH2CO2Me)[PtCl3-
(MeCN)]. Yellow plates were obtained on slow evaporation of ethanol
solution. The cell dimensions and symmetry of crystals were defined
in the Weissenberg camera. Diffraction data were collected on a Syntex
P21 diffractometer using graphite-monochromated Mo KR radiation
(λ ) 0.71069 Å), ω-scan method with variable scan rate (2-29.3°/
min). Weak reflections were neglected. The intensity of one standard
reflection was measured every 50 reflections and showed practically
no change with time ((1%). After Lorentz and polarization correction,
the structure was solved by means of the Patterson technique (heavy
atom method) and following Fourier synthesis and was refined by a
full-matrix (anisotropic for all non-hydrogen atoms and isotropic for
hydrogen atoms) least-squares method based on F. No extinction
correction was made. Before anisotropic refinement an absorption
correction was made using the DIFABS94 program. The contribution
of hydrogen atoms was included at fixed calculated positions, based
on geometrical reqiurement. All experimental data processing, solving
and refinement were performed using CSD92 program.
trans-[PtCl2(py)(Me2S)]:87 from the reduction of trans-[PtCl4(py)-
1
(Me2S)]. H NMR in CDCl3, δ: 2.44 (JPtH 40.5 Hz, Me2S), 7.38 (m,
2H), 7.87 (m, 1H), 8.83 (m, 2H) (Py). 13C{1H} NMR in CDCl3, δ:
22.9 (JPtC 11.5 Hz), 125.4 (JPtC 34.7 Hz), 138.8, 152.2 (Py). 195Pt NMR
in CDCl3, δ: -2821 (500 Hz).
trans-[PtCl2(Me2S)2]:88 from the reduction of trans-[PtCl4(Me2S)2].
1H NMR in CDCl3, δ: 2.48 (JPtH 41.4 Hz). 13C{1H} NMR in CDCl3,
δ: 22.3 (JPtC 11.9 Hz). 195Pt NMR in CDCl3, δ: -3409.
trans-[PtCl2(Me2SO)(NHEt2)]:80,81 from the reduction of trans-
1
[PtCl4(Me2SO)(NHEt2)]. H NMR in CDCl3, δ: 1.48 (t, 7.2 Hz, 6H),
2.68 (m, 2H) and 3.18 (m, 2H) (Et), 3.37 (s + d, JPtH 19 Hz, 6H,
DMSO), 3.88 (br, 1H, NH). 13C{1H} NMR in CDCl3, δ: 14.7 and
48.8 (Et), 44.0 (JPtC 55 Hz, DMSO). 195Pt NMR in CDCl3, δ: -3139
(480 Hz).
[PtCl3(Me2SO)]-.80 The complex is formed upon reduction of either
(Ph3PCH2Ph)[PtCl5(Me2SO)] or [PtCl4(Me2SO)2]. In the latter case
liberation of a dimethyl sulfoxide molecule is observed along with the
formation of (Ph3PCH2CO2Me)[PtCl3(Me2SdO)]. For anion: 1H NMR
in CDCl3, δ: 3.39 (s + d, JPtH 20.7 Hz); 13C{1H} NMR in CDCl3, δ:
44.1 (JPtC 62.6 Hz); 195Pt NMR in CDCl3, δ: -3000. For free DMSO:
1H NMR in CDCl3, δ: 2.64 (s); 13C{1H} NMR in CDCl3, δ: 40.9.
The reduction of [PtCl4(MeCN)2] with 1 equiv of Ph3PdCHCO2-
Me in MeCN results in release of the solid [PtCl2(MeCN)2] (8%).
Subsequent removal of the solvent from the filtrate and recrystallization
of a precipitate formed from hot EtOH gives analytically pure [Ph3-
PCH2CO2Me][PtCl3(MeCN)] (37%). [Ph3PCH2CO2Me][PtCl3(MeCN)].
Anal. Calcd for C23H23NCl3O2PPt: C, 40.75; H, 3.42; N, 2.07. Found:
C, 40.98; H, 3.52; N, 1.81. FAB--MS, m/z: 342 [Manion]-, 299
[Manion - MeCN]-, 266 [Manion - MeCN - Cl]-; FAB+-MS, m/z: 335
[Mcation]+. IR spectrum (selected bands), cm-1: 2909 and 2874 m ν(C-
H), 1728 vs ν(CdO), 1437 vs ν(CdC), 1107 s ν(P-C); the band due
to ν(CtN) was not observed. 1H NMR in CDCl3, δ: 2.18 (s, 3H,
MeCN), 3.42 (s, 3H, OMe), 4.92 (d, JPH 13.8 Hz, 2H, PCH2), 7.50-
7.64 (m, 15H, Ph). 13C{1H} NMR in CDCl3, δ: 4.0 (MeCN), 31.6 (JPC
58 Hz, PCH2), 53.4 (OMe), 112.4 (MeCN), 117.4 (JPC 89 Hz, Cipso),
130.1 (JPC 12.8 Hz, CH), 133.6 (JPC 10.9 Hz, CH), 135.1 (JPC 3.6 Hz,
CHpara) (Ph), 164.7 (CdO). 31P{1H} NMR in CDCl3, δ: 20.8. 195Pt
NMR in CDCl3, δ: -2022 (355 Hz).
Acknowledgment. G.W. is grateful to the PRAXIS XXI
program for a fellowship (BPD11779/97). V.Yu.K. is very much
obliged to the PRAXIS XXI program (Grant BCC16428/98)
for financial support of this study. J.V. and V.Yu.K. are indebted
to INTAS for Grant 97-0166. N.A.B. thanks the Soros Founda-
tion for a fellowship. A.J.L.P. thanks the FCT (Foundation for
Science and Tecnology) and the PRAXIS XXI program for
financial support. We thank Dr. M. Galanski for valuable
comments on the manuscript, Profs. V. K. Belsky and V. S.
Fundamensky for the X-ray analyses, and Dr. Z. A. Khromen-
kova for providing us some platinum(IV) complexes for the
reduction studies.
Supporting Information Available: X-ray crystallographic files
in CIF format for the complexes trans-[PtCl2{NHdC(Me)ONdCMe2}2]
and (Ph3PCH2CO2Me)[PtCl3(NCMe)]. This material is available free
of charge via the Internet at http://pubs.acs.org.
X-ray Structure Determination of [PtCl2{NHdC(Me)ONd
CMe2}2]. Colorless plates of the complex were grown from dichlo-
romethane solution upon addition of diethyl ether. Diffraction data were
collected on an Enraf-Nonius CAD-4 diffractometer. Cell parameters
were obtained from 24 centered reflections with Θ between 11° and
13°. Range of hkl: h ) 0-12, k ) 0-11, l ) 0-19. Standard
reflections were measured every 100 min and showed practically no
change with time ((1%). Diffractometer data were processed by the
program PROFIT89 with profile analysis of reflections. The structures
were solved by means of Fourier synthesis based upon the Pt-atom
IC000769C
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