Platinum(iv)-mediated nucleophilic addition of 1,3-diphenylguanidine to propiononitrile

Article abstract of DOI:10.1007/s11172-008-0288-0

The reaction of the trans-[PtCl₄(EtCN)₂] complex with diphenylguanidine (DPG) in a molar ratio of 1: 2 proceeds via the nucleophilic addition of DPG to coordinated nitrile and the coordination of DPG to the metal center to form the [PtCl₄{NH=C(NHPh)₂}{NH=C(Et)-N=C(NHPh) ₂}] complex with the open-chain 1,3,5-triazapentadiene ligand. The latter undergoes chelation in solution (84 h, 50 °C, CDCl₃), and the ring closure is accompanied by the replacement of the coordinated chloride and the formation of the cationic complex [PtCl₃{NH=C(NHPh) ₂}{NH=C(Et)NHC(NHPh)=NPh}](Cl). The reaction of the trans-[PtCl ₄(EtCN)₂] complex with DPG in a molar ratio of 1: 4 affords the [PtCl₃{NH=C-(NHPh)₂}{NH=C(Et)NC(NHPh)=NPh}] complex with the chelating 1,3,5-triazapentadienate ligand.

Full text of DOI:10.1007/s11172-008-0288-0

Russian Chemical Bulletin, International Edition, Vol. 57, No. 10, pp. 2125—2131, October, 2008
2125
Platinum(IV)ꢀmediated nucleophilic addition of
1,3ꢀdiphenylguanidine to propiononitrile*
P. V. Gushchin,a M. Haukka,b N. A. Bokach,a and V. Yu. Kukushkina,c
aDepartment of Chemistry, St. Petersburg State University,
26 Universitetsky prosp., 198504 Stary Petergof, Russian Federation.
Fax: +7 (812) 428 6939. Eꢀmail: kukushkin@VK2100.spb.edu
bUniversity of Joensuu, Department of Chemistry, P. O. Box 111, Joensuu, FIꢀ80100 Finland
cInstitute of Macromolecular Compounds, Russian Academy of Sciences,
31 Bolshoii prosp., 199004 St. Petersburg, Russian Federation
The reaction of the transꢀ[PtCl4(EtCN)2] complex with diphenylguanidine (DPG) in a
molar ratio of 1 : 2 proceeds via the nucleophilic addition of DPG to coordinated nitrile and
the coordination of DPG to the metal center to form the [PtCl4{NH=C(NHPh)2}{NH=C(Et)ꢀ
N=C(NHPh)2}] complex with the openꢀchain 1,3,5ꢀtriazapentadiene ligand. The latter
undergoes chelation in solution (84 h, 50 °C, CDCl3), and the ring closure is accompanied by
the replacement of the coordinated chloride and the formation of the cationic complex
[PtCl3{NH=C(NHPh)2}{NH=C(Et)NHC(NHPh)=NPh}](Cl). The reaction of the
transꢀ[PtCl4(EtCN)2] complex with DPG in a molar ratio of 1 : 4 affords the [PtCl3{NH=Cꢀ
(NHPh)2}{NH=C(Et)NC(NHPh)=NPh}] complex with the chelating 1,3,5ꢀtriazapentadienate
ligand.
Key words: metalꢀmediated reactions, 1,3ꢀdiphenylguanidine, platinum(IV) nitrile comꢀ
plexes, nucleophilic addition, platinum(IV) 1,3,5ꢀtriazapentadiene complexes.
8
Metalꢀmediated reactions have found wide use both
in preparative chemistry and industry serving as key in
metalꢀcomplex catalysis. Studies of the reactions of coorꢀ
dinated nitriles giving rise to compounds with new C—C,
C—N, C—O, C—P, and C—S bonds, which are difficult
to prepare in metalꢀfree organic chemistry, are of imporꢀ
tance in this area of chemistry. Among these reactions
are nucleophilic and electrophilic additions or a dipolar
cycloaddition to the C≡N triple bond.1—4
The number of publications on the metalꢀmediated
reactions of nitriles appeared in recent years is rather
large, and these studies were devoted mainly to reactions
of RCN with such reagents as HOꢀ and HNꢀnucleophiles.1
The metalꢀmediated reactions of nitriles with HNꢀnuꢀ
cleophiles bearing an sp3ꢀhybridized nitrogen atom have
been studied in sufficient detail. Nucleophiles containing
an sp2ꢀhybridized nitrogen atom (for example, imines)
can also serve as reagents for the C—N bond formation.
The addition of imines and heteroimines to coordinated
nitriles has been investigated in recent years.5—12
C(Ar)(NHAr),10,11 SAr2,6 or PPh3 ), we investigated
the nucleophilic addition reactions of guanidines (ERn =
= C(NMe2)2,13 C(NHPh)214) to nitriles activated by coorꢀ
dination to a platinum(II) center. In the present study, we
continued research on the metalꢀmediated reactions of
DPG with nitriles. The study included two successive
steps. In the first step, we planned to investigate the
platinum(IV)ꢀmediated reactions of nitriles with DPG and
elucidate the influence of the oxidation state of the metal
center on this reaction. In the second step, we developed
a procedure for the synthesis of platinum(IV) 1,3,5ꢀtriazaꢀ
pentadienyl complexes.
Results and Discussion
The reactions of platinum(IV) nitrile complexes with
DPG were studied with the use of transꢀ[PtCl4(ЕtCN)2]15
as the dinitrile precursor. We chose this complex because
of its higher solubility in nonpolar solvents (in particular,
in CH2Cl2) compared to the commonly used nitrile comꢀ
pounds, such as PtCl4(RCN)2 (R = Me or Ph).
It is known that the platinum(IV) center is one of the best
activators of the C≡N bond and is superior in the degree
of activation to even such powerful classical activators as
the CF3 group.16,17 Unlike more labile platinum(II) comꢀ
In continuation of research on reactions of nitriles
RCN coordinated to platinum with imines (heteroꢀ
imines) HN=ERn (ERn = CPh2,5 C(Alkyl)(OAlkyl),7,12
* Dedicated to Academician B. A. Trofimov on the occasion of
his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2086—2092, October, 2008.
1066ꢀ5285/08/5710ꢀ2125 © 2008 Springer Science+Business Media, Inc.

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Gushchin et al.
plexes,14 kinetically inert platinum(IV) compounds are
much less prone to chelation. This is of interest for invesꢀ
tigating the reaction mechanism of the addition of
guanidines to coordinated nitriles.
Platinum(IV)ꢀmediated addition of 1,3ꢀdiphenylguaniꢀ
dine to propiononitrile. We found that the reaction of the
transꢀ[PtCl4(EtCN)2] complex with DPG in a molar ratio
of 1 : 2 afforded compound 1a (Scheme 1, path a) as a
result of two reactions: (i) the replacement of one nitrile
ligand EtCN with diphenylguanidine; (ii) the nucleophilic
addition of the HN=C group to the C≡N bond of the
second nitrile.
time (one day) afforded complex 2 with the bidentate
1,3,5ꢀtriazapentadienate ligand. Under the experimental
conditions, the intermediate steps of this reaction were
not detected. In this chemical transformation, DPG acts
as both the nucleophile and the dehydrochlorinating agent.
Apparently, the mechanism of formation of complex 2
involves three successive steps a—c (see Scheme 1).
In the present study, we found that in the case of
platinum(IV), the nucleophilic addition proceeds more
rapidly than in the case of platinum(II) (for platinum(IV),
the reaction is completed in a few minutes; for platinum(II),
in a few hours). The observed increase in the reactivity of
the platinum(IV) nitrile complex compared to the related
platinum(II) complexes can be explained not only in terms
of chargeꢀcontrolled reactions (the larger partial positive
charge on the carbon atom of the C≡N bond of coordiꢀ
nated organonitriles in PtIV complexes compared to PtII
complexes, which facilitates the nucleophilic attack) but
also by the nature of the metal center, which determines
the orbital control in the reaction (the smaller difference
between the levels of HOMO and LUMO of the reactants
in the case of PtIV complexes).18
Under analogous conditions, DPG does not react with
uncoordinated nitriles RCN (R = Et or Ph). This is eviꢀ
dence that the nucleophilic addition of DPG to nitrile is
mediated by the platinum(IV) center.
Then the ligand in compound 1a undergoes chelation
in a CDCl3 solution at 50 °C for 84 h, which is accompaꢀ
nied by the replacement of the coordinated chloride to form
cationic complex 1b with the N,Nꢀcoordinated 1,3,5ꢀtriꢀ
azapentadiene ligand (Scheme 1, path b). The transformaꢀ
1
tion of compound 1a into 1b was confirmed by H NMR
spectroscopy (a compound, which was obtained after
storage of complex 2 in the solid state in an HCl vapor,
was used as a blank sample; see the Experimental secꢀ
tion). It should be noted that the reverse reaction, viz.,
the ring opening giving rise to complex 1a, does not proceed at
room temperature, which is evidence for the intermoꢀ
lecular mechanism of the nucleophilic addition of DPG
to propiononitrile coordinated to the platinum(IV) center.
The subsequent spontaneous transformation of cationic
complex 1b into neutral complex 2 does not proceed.
The reaction of the transꢀ[PtCl4(EtCN)2] complex with
DPG in a molar ratio of 1 : 4 during the same period of
The study of the reaction with the platinum(IV) comꢀ
plex showed that the formation of the 1,3,5ꢀtriazapentaꢀ
diene metallacycle Pt—N(H)=C(Et)NC(N(H)Ph)=NPh
proceeds stepwise. As opposed to the previous study dealꢀ
ing with the platinum(II)ꢀmediated nucleophilic addition
of DPG to nitriles giving rise to 1,3,5ꢀtriazapentadiene
chelate complexes (Scheme 2),14 in the present study we
found that the reaction of DPG with EtCN coordinated
to platinum(IV) affords openꢀchain 1,3,5ꢀtriazapentadiene,
which may be indicative of the intermolecular reaction
mechanism a (see Scheme 1). The formation of chelate
1b instead of complex 1a in the reaction a (see Scheme 1)
Scheme 1
H

Addition of diphenylguanidine to ligated nitriles
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 10, October, 2008
2127
followed by the ring opening and the formation of comꢀ
pound 1a with the monodentate ligand seems unlikely
in the process with the involvement of the kinetically
inert metal center (PtIV). We suggest that the reaction of
1,3ꢀdiphenylguanidine with the propiononitrile ligand in
the platinum(IV) nitrile complex transꢀ[PtCl4(EtCN)2]
proceeds via nucleophilic attack on the nitrile carbon
atom by the guanidine N atom followed by the proton
transfer to the coordinated iminate group that is formed
in the course of the coupling. The formation of platinum(II)
complexes with the openꢀchain 1,3,5ꢀtriazapentadiene
ligands rather than with the chelate ligands (see Scheme 2)
was not observed,14 which is attributed to the higher
kinetic lability of platinum(II) compared to platinum(IV).
The latter fact, in turn, leads to the ease of the ring cloꢀ
sure in platinum(II) complexes compared to platinum(IV)
complexes.
Triaza analogs of 1,3ꢀdicarbonyl derivatives, such as
1,3,5ꢀtriazapentadienes, are less studied than related
1,3ꢀdicarbonyl compounds. Nevertheless, these comꢀ
pounds deserve special attention because they contain an
additional reaction center, viz., the central nitrogen atom,
which can be involved in the acidꢀbase equilibrium,11,19,20
thus imparting pHꢀdependent properties to these comꢀ
plexes (for example, the luminescence property, which
depends on the protolytic form of the reaction center11).
In spite of evident advantages and potential possible fields
of application of chelating systems based on 1,3,5ꢀtriazaꢀ
pentadienyls, general preparative methods for the syntheꢀ
sis of chelates based on those compounds are lacking, and
the specific methods described in the literature were not
systematically studied. Thus, 1,3,5ꢀtriazapentadienes
unstable in the free state (containing the unsubstituted
NH group and/or donor substituents at carbon atoms) are
generally produced by metalꢀmediated reactions, such as
(i) reactions of amidines with nitriles electrophilically
activated by coordination to MII (PtII,10,11,21 PdII,21,22
NiII,23 or PtIV (see Ref. 10)), the nucleophilic addition of
DPG to nitriles electrophilically activated by coordinaꢀ
tion to PtII (see Ref. 14 and Scheme 2), the coupling of
two adjacent nitriles in the platinum(II) cisꢀnitrile comꢀ
plexes cisꢀ[PtCl2(RCN)2] by the reaction with DPG;14
(ii) copperꢀ24,25 or nickelꢀmediated26 hydrolytic transforꢀ
mations of 1,3,5ꢀtriazine24,26 or 1,3,5ꢀtris(2ꢀpyridyl)ꢀ
2,4,6ꢀtriazine;25 (iii) the hydrolytic transformation of
nitriles mediated by the dinuclear nickel(II) complex
[Ni2(μꢀOH)2(tpa)2](ClO4)2 (tpa is tris(2ꢀpyridylmethyl)ꢀ
amine)27 or NiII acetate;28 (iv) the reaction of NiCl2•6H2O
with acetamidine in MeOH;29 and (v) the oximeꢀmediꢀ
ated transformation of nitriles with the involvement of
PtII (see Ref. 30) or NiII.19,20 In the present study, we
report the first example of the platinum(IV)ꢀmediated nuꢀ
cleophilic addition of guanidine to nitrile and the simple
procedure for the synthesis of 1,3,5ꢀtriazapentadiene
derivatives of PtIV.
Structures of (1,3,5ꢀtriazapentadienate)PtIV complexes.
A comparison of the IR spectra of compounds 1a, 1b, and
2 with the IR spectrum of the starting platinum(IV) dinitrile
complex transꢀ[PtCl4(EtCN)2] shows that stretching bands
of the C≡N triple bond are absent in the spectra of the
reaction products, but these spectra contain intense
stretching bands of C=N and C=C double bonds in the
1636—1442 cm–1 region, as well as N—H stretching bands
observed at higher frequencies (3396—3043 cm–1).
The positions of the N—H stretching bands in the IR
spectrum of complex 2 are similar to those in the specꢀ
trum of DPG. The IR spectrum of compound 2 shows
intense ν(C=N) and/or ν(C=C) bands at 1639—1462 cm–1
and ν(N—H) bands in the region from 3401 to 3244 cm–1
.
These frequencies agree well with those for ν(C=N) and/or
ν(C=C) (1636—1442 cm–1) and ν(N—H) (3422—3338 cm–1)
bands in the spectra of the (1,3,5ꢀtriazapentadiene)PtII
and/or (1,3,5ꢀtriazapentadienato)PtII complexes, viz.,
[PtCl(NCR){NH=C(R)NC(N(H)Ph)=N(Ph)}] and
[Pt{NH=C(R)NC(N(H)Ph)=N(Ph)}2] (Et, CH2Ph,
or Ph).14
In the 1H NMR spectrum of compound 2, the chemiꢀ
cal shifts and the multiplicities of the proton signals of the
phenyl groups at δ 7.90—6.90 differ from those observed
1
in the spectrum of free DPG. The H NMR spectra of
complexes 1a, 1b, and 2 at δ 5.00—3.90 are characterized
by the presence of a singlet + doublet with the spinꢀspin
coupling constant with 195Pt at 13—14 Hz assigned to the
proton of the N—H group.
The 1H NMR spectra of complexes 1a, 1b, and 2
display four singlets (1b) or one singlet (1a and 2) at
δ 13.30—7.50 and one (1b), two (1a), or three singlets (2)
belonging to H—N protons at δ 6.30—5.85. Therefore,
the protonation of the chelating 1,3,5ꢀtriazapentadiene
ligand in complex 2 giving rise to cationic complex 1b
leads to substantial downfield shifts of the signals for the
H—N protons. The transformation from the openꢀchain
Scheme 2

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Gushchin et al.
to the cyclic neutral form of the 1,3,5ꢀtriazapentadiene
ligand as a result of chelation is accompanied by upfield
shifts of the signals for the aromatic protons (signals for
twelve of twenty protons shift to frequencies lower than
7 ppm). The formation of the anionic form of the chelating
1,3,5ꢀtriazapentadiene ligand as a result of elimination of
HCl is accompanied by the opposite effect. In this case,
the signals for ten of twelve phenyl protons shift downfield
(to a region higher than 7 ppm). On the contrary, the
deprotonation of the cyclic neutral form of the 1,3,5ꢀtriꢀ
azapentadiene ligand leads to upfield shifts of the signals
of the ethyl substituent.
Compound 2 was characterized by Xꢀray diffraction
(Fig. 1). The coordination polyhedron of complex 2 is a
distorted octahedron formed by three N atoms and three
Cl atoms at the Pt atom. The atoms of the metallacycle
Pt(1)N(1)C(1)N(2)C(4)N(3) lie in a single plane (the
average deviation from the plane is 0.078(3) Å). In the
metallacycle, the CN double and single bonds are clearly
differentiated. The N(1)—C(1) bond length is 1.298(4) Å.
This value is more similar to the characteristics of the
C=N double bond and is comparable with the lengths
of the corresponding C=N double bonds in the monoꢀ
chelate and bischelate (1,3,5ꢀtriazapentadiene)PtII
and/or (1,3,5ꢀtriazapentadienato)PtII complexes, viz.,
[PtCl{NH=C(Et)NC(N(H)Ph)=NPh)}(EtCN)] (1.313(4) Å)
and [Pt{NH=C(Et)NC(N(H)Ph)=NPh)}2] (1.306(3) Å),
respectively.14 The N(2)—C(1) and N(2)—C(4) bond
lengths (1.337(5) and 1.338(4) Å, respectively) are similar
to the N—C bond lengths in PtII complexes containing
the same structural fragment Pt—NH=C(Et)NC(N(H)ꢀ
Ph)=NPh, viz., [PtCl{NH=C(Et)NC(N(H)Ph)=NPh)}ꢀ
(EtCN)] (1.333(4) and 1.346(4) Å, respectively) and
[Pt{NH=C(Et)NC(N(H)Ph)=NPh)}2] (1.344(3) and
1.332(3) Å, respectively).14 The N(3)—C(4) interatomic
distance (1.337(4) Å) is shorter than the corresponding
N=C double bonds in the complexes containing the
(1,3,5ꢀtriazapentadiene)M and/or (1,3,5ꢀtriazapentaꢀ
dienato)M structural unit (M = PtII or NiII),10,14,19 which
is apparently attributed to the influence of the N(H)Ph
group. However, this interatomic distance is typical
(within 3σ) of this type of 1,3,5ꢀtriazapentadieneꢀ and/or
1,3,5ꢀtriazapentadienatoꢀcontaining metallacycles and is
comparable with the lengths of the corresponding C=N
double bonds in the monochelate and bischelate (1,3,5ꢀtriꢀ
azapentadiene)PtII and/or (1,3,5ꢀtriazapentadienato)PtII
complexes [PtCl{NH=C(Et)NC(N(H)Ph)=NPh)}(EtCN)]
(1.330(4) Å) and [Pt{NH=C(Et)NC(N(H)Ph)=NPh)}2]
(1.339(3) Å), respectively.14 The N=C double bond lengths
and the N—C single bond lengths in the metallacycle, as
opposed to the complexes of the types (1,3,5ꢀtriazapentaꢀ
diene)M and/or (1,3,5ꢀtriazapentadienato)M (M = PtII
or NiII),10,14,19 are indicative of a higher degree of delocalꢀ
ization in the chelate metallacycle. The N(4)—C(4) bond
length (1.370(5) Å) is similar to the length of the correꢀ
sponding N—C single bond in PtII complexes containing
the analogous structural fragment Pt—NH=C(Et)NCꢀ
(N(H)Ph)=NPh, such as [PtCl{NH=C(Et)NC(N(H)ꢀ
Ph)=NPh)}(EtCN)] (1.370(4) Å) and [Pt{NH=C(Et)NCꢀ
(N(H)Ph)=NPh)}2] (1.381(3) Å).14
The N(5)—C(17) bond length (1.310(4) Å) in coordiꢀ
nated DPG in complex 2 is consistent (within 3σ) with
the lengths of the N=C double bonds in compounds conꢀ
taining the CAr—C=N—C fragment (aver., 1.279(8) Å)31
C(3)
Cl(3)
Cl(2)
C(20)
C(21)
C(19)
C(18)
C(2)
N(1)
N(6)
C(1)
N(2)
Pt(1)
C(22)
C(23)
C(17)
Cl(1)
N(5)
C(4)
N(7)
N(3)
C(11)
C(25)
C(26)
C(6)
C(24)
C(16)
C(5)
N(4)
C(29)
C(7)
C(8)
C(15)
C(14)
C(27)
C(12)
C(13)
C(10)
C(28)
C(9)
Fig. 1. Molecular structure of complex 2.

Addition of diphenylguanidine to ligated nitriles
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 10, October, 2008
2129
The reaction mixture turned orange for 1—2 min. After 1 day,
the solvent was evaporated to dryness, and the darkꢀorange oily
residue was dissolved in CHCl3 (0.75 mL). Complex 1a was
separated and purified by silica gel column chromatography
(Silicagel 60 F254, 0.063—0.200 mm, Merck; ethyl acetate:chloroꢀ
form = 1 : 20 as the eluent, Rf = 0.58, the first brightꢀyellow
fraction) and then dried in air at 20—25 °C.
and the lengths of the corresponding CN bond in coordiꢀ
nated 1,2,3ꢀtriphenylguanidine PhN=C(NHPh)2 in the
[CoCl2{PhN=C(NHPh)2}2] (1.312(8) and 1.295(8) Å) and
[Ag{PhN=C(NHPh)2}2][SO3CF3] (1.32(1) Å) complexes.32
Compound 2 is the first structurally characterized transiꢀ
tion metal complex with 1,3ꢀdiphenylguanidine serving
as the neutral monodentate ligand.
In the solid state, the hydrogen atom of the N(H)Ph
fragment of the coordinated diphenylguanidine and the
adjacent equatorial Cl atom are linked by a hydrogen
bond (N(6)—H(6A)...Cl(2), 2.30 Å). The plane of dipheꢀ
nylguanidine N(5)N(6)N(7)C(17) (the average deviation
from the plane is 0.007(3) Å) is perpendicular to the plane
of the metallacycle Pt(1)N(1)C(1)N(2)C(4)N(3) (the
angle between these planes is 89.37(17)°).
Hence, we performed the platinum(IV)ꢀmediated
nucleophilic addition of 1,3ꢀdiphenylguanidine to propionoꢀ
nitrile giving rise to 1,3,5ꢀtriazapentadiene complexes.
The results of the present study can be considered in three
aspects. First, DPG was demonstrated to be involved in
the metalꢀmediated nucleophilic addition to the nitrile
ligand in the transꢀ[PtCl4(EtCN)2] complex. Second, it
was found that the coordination mode of 1,3,5ꢀtriazaꢀ
pentadiene ligands substantially depends on the oxidation
state of the metal center. Thus, in the platinum(IV) comꢀ
plexes, the 1,3,5ꢀtriazapentadiene ligand exists in the
openꢀchain form, whereas the chelate forms of 1,3,5ꢀtriꢀ
azapentadiene are observed in the platinum(II) comꢀ
plexes (see Scheme 2).14 Third, the reaction provides a
simple method for synthesizing 1,3,5ꢀtriazapentadienyl
complexes.
The heating of a solution of complex 1a in CDCl3 at 50 °C
for 84 h afforded complex 1b.
Tetrachloro[{Nꢀ(dianilinomethylene)propanimidamide}ꢀ
(N,N´ꢀdiphenylguanidine)]platinum(IV), [PtCl4{NH=C(NHPh)2}ꢀ
{NH=C(Et)N=C(NHPh)2}] (1a). FAB+ MS, m/z: 816 [M + 2H]+,
779 [M – Cl]+, 744 [M – 2 Cl + H]+, 708 [M – 3 Cl]+, 671
[M – HCl – 3 Cl]+, 497 [M – 3 Cl – NH=C(NHPh)2]+, 459
[M – 2 HCl – 2 Cl – NH=C(NHPh)2]+. TLC data: Rf = 0.62
(Et2O : CHCl3, 1 : 10, as the eluent). IR, ν/cm–1: 3545, 3288
ν(N—H); 3057 ν(C—H (Ar)); 2979 ν(C—H (Et)); 1666, 1637
ν(C=N); 1593, 1545, 1496 ν(C=N and/or C=C (Ar)); 754,
694 δ(C—H (Ar)). 1H NMR (CDCl3), δ: 8.99 (s, 1 H, NH);
7.42—7.32 (m, 15 H, Ph), 7.17 (d, 5 H, Ph); 6.17 (br.s, 2 H),
5.00 (s + d, 1 H, JPt—H = 13.4 Hz) (NH); 3.14 (q, 2 H, CH2,
J = 7.5 Hz), 1.10 (t, 3 H, CH3, J = 7.5 Hz) (Et). We failed
to obtain a sufficient amount of the compound for C, H,
Nꢀelemental analyses and 13C{1H} NMR spectroscopy (see
Results and Discussion).
Reaction of complex 2 with HCl. Upon the treatment of comꢀ
pound 2 in the solid state (12 mg) with gaseous HCl for 10 min,
the color of the compound changed from orange to yellow. Then the
compound was dissolved in CDCl3 and analyzed by 1H NMR
spectroscopy, which detected the formation of complex 1b.
Trichloro[{Nꢀ(dianilinomethylene)propanimidamide}ꢀ
(N,N´ꢀdiphenylguanidine)]platinum(IV), [PtCl3{NH=C(NHPh)2}ꢀ
{NH=C(Et)NHC(NHPh)=NPh}](Cl) (1b). 1H NMR (CDCl3),
δ: 13.29, 10.25, 8.56, and 7.52 (all br.s, 1 H each, NH); 7.40 (d,
2 H), 7.22 (br.m, 6 H), 6.94 (d, 3 H), 6.81 (d, 4 H), 6.70 (t, 5 H)
(Ph); 6.11 (br.s, 1 H), 3.95 (s + d, 1 H, JPt—H = 14.2 Hz) (NH);
3.05 (q, 2 H, J = 7.1 Hz), 1.50 (t, 3 H, J = 7.1 Hz) (Et).
Reaction of the transꢀ[PtCl4(EtCN)2] complex with HN=Cꢀ
(NHPh)2 in a molar ratio of 1 : 3. Diphenylguanidine (88.5 mg,
0.42 mmol) was added to a suspension of the transꢀ[PtCl4(EtCN)2]
complex (0.10 mmol) in EtCN (2 mL) at room temperature.
The reaction mixture turned orangeꢀred during one day. Then
the solvent was evaporated to dryness, the red oily residue was
dissolved in CHCl3 (0.75 mL), and complex 2 was isolated by
silica gel column chromatography (Silicagel 60 F254, 0.063—
0.200 mm, Merck; Et2O : CHCl3 = 1 : 20, as the eluent, Rf = 0.51, the
first brightꢀyellow fraction). The reaction product was dried in
air at 20—25 °C. The yield of the analytically pure product was
51 mg (33%) (the reaction mixture contained a broad range of
products, including complex 1a).
Experimental
The elemental analysis was carried out on a 185В Carbon
Hydrogen Nitrogen Analyzer Hewlett Packard instrument by
burning samples in an air flow according to a known proceꢀ
dure.33 The IR spectra were recorded in KBr pellets on a
Shimadzu FTIRꢀ8400S spectrophotometer in the 4000—400 cm–1
region. The 1H and 13C{1H} NMR spectra were measured on a
Bruker DPX 300 spectrometer at room temperature. The chemiꢀ
cal shifts in the 1H (CDCl3, 7.27 ppm) and 13C{1H} (CDCl3,
77.4 ppm) NMR spectra were measured relative to the signals of
the corresponding solvents. The positiveꢀion fast atom bomꢀ
bardment (FAB+) mass spectra were obtained on a Trio 2000
instrument using 3ꢀnitrobenzyl alcohol as the matrix; samples
were bombarded with Xe atoms. Thinꢀlayer chromatography
was carried out on Al plates precoated with a layer of silica
gel Merck 60 F254. Thermogravimetric studies of compound 2
were carried out on a Mettler—Toledo TGA85 derivatograph in
aluminum crucibles at a heating rate of 8 K min–1 (the temperaꢀ
ture range was 20—1000 °C, the rate of air flow was 3 L h–1, the
weight of samples was 5—10 mg).
Trichloro[{anilino)phenylimino)methyl}(propanimidoyl)ꢀ
{azanide}(N,N´ꢀdiphenylguanidine)]platinum(IV), [PtCl3{NH=Cꢀ
(NHPh)2}{NH=C(Et)NC(NHPh)=NPh}] (2). Found (%): C,
44.75; H, 3.86; N, 12.60. C29H30N7Cl3Pt. Calculated (%): C, 44.90;
H, 3.84; N, 12.20. FAB+ MS, m/z: 778 [M]+, 708 [M – 2 Cl + H]+,
671 [M – 3 Cl]+, 497 [M – 2 Cl – NH=C(NHPh)2 + H]+, 460
[M – 3 Cl – (NH=C(NHPh)2)]+, 405 [M – HCl – 2 Cl – NH=C(Et)ꢀ
NC(NHPh)=NPh]+. TLC data: Rf = 0.51 (Et2O : CHCl3, 1 : 20,
as the eluent); DTA/TGA: 200 °C (gradual decomposition). IR,
ν/cm–1: 3404, 3357, 3215 ν(N—H); 3055 ν(C—H (Ar)); 2933
ν(C—H (Et)); 1693, 1595 ν(C=N); 1577, 1549, 1495, 1473
Reaction of the transꢀ[PtCl4(EtCN)2] complex with HN=Cꢀ
(NHPh)2 in a molar ratio of 1 : 2. Diphenylguanidine (46.7 mg,
0.22 mmol) was added to a suspension of the transꢀ[PtCl4(EtCN)2]
complex (0.10 mmol) in CH2Cl2 (1 mL) at room temperature.

2130
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 10, October, 2008
Gushchin et al.
ν(C=N and/or C=C (Ar)); 756, 694 δ(C—H (Ar)). 1H NMR
(CDCl3), δ: 8.77 (s, 1 H, NH); 7.46 (d, 2 H), 7.41 (d, 2 H), 7.34
(d, 2 H), 7.27 (d, 5 H), 7.21 (t, 6 H), 7.04 (quint, 1 H), 6.87 (d,
2 H) (Ph); 6.29 (br.s, 1 H), 5.93 (s, 1 H), 5.84 (br.s, 1 H), 4.23 (s
+ d, 1 H, JPt—H = 13 Hz) (NH); 2.56 (q, 2 H, CH2, J = 7.5 Hz),
1.24 (t, 3 H, CH3, J = 7.5 Hz) (Et). 13C{1H} NMR (CDCl3), δ:
165.66 (J = 5.6 Hz), 154.58 (J = 10 Hz), 146.11 (J = 5.6 Hz)
(C=N); 143.62, 138.92, 135.80, 134.54, 130.16, 130.11, 129.98,
129.77, 128.33, 128.26, 127.23, 126.83, 125.60, 124.59, 124.17,
123.26 (C=C (Ar)); 33.34 (J = 12.4 Hz, CH2), 11.57 (CH3)
(Et). Crystals suitable for Xꢀray diffraction were grown by slow
evaporation of a solution of complex 2 in a 3 : 1 hexane—chloꢀ
roform mixture.
Xꢀray diffraction study. A single crystal of complex 2 was
grown by slow evaporation of a solution of this compound in a
3 : 1 hexane : chloroform mixture at 20—25 °C. Before the
Xꢀray data collection, the crystal of complex 2 was mounted in a
Nylon loop and soaked in a cryo protectant. The Xꢀray diffracꢀ
tion data were collected on a Nonius Kappa CCD diffractometer
at 120(2) K, (monochromator, MoꢀKα radiation, λ = 0.71073 Å).
The unit cell parameters were refined and the Xꢀray data were
merged using the DenzoꢀScalepack34 or EvalCCD35 program
packages. The structure was solved by direct methods with the
use of the SIR97,36 SIR2002,37 and SHELXS9738 program packꢀ
ages and the WinGX graphics interface.39 The absorption
correction was applied based on the intensities of equivalent
reflections with the use of the XPREP program from the
SHELXTL v.6.14ꢀ1 program package40 and the SADABS v.2.10
program41 (Tmin/Tmax was 0.2187/0.3869). The structure was
refined using the SHELXL97 program package.42 The NH
hydrogen atoms were located in difference Fourier maps and
were not refined. All other hydrogen atoms were positioned
geometrically. The atomic coordinates and complete tables
of bond lengths and bond angles were deposited with the Camꢀ
bridge Structural Database. Principal crystallographic parameters
are given in Table 1. Selected bond lengths and bond angles are
listed in Table 2.
Table 2. Selected bond lengths (d) and bond angles (ω) in
complex 2
Bond
d/Å
Angle
ω/deg
Pt(1)—Cl(1)
Pt(1)—Cl(2)
Pt(1)—Cl(3)
Pt(1)—N(1)
N(1)—C(1)
N(2)—C(1)
N(2)—C(4)
N(3)—C(4)
N(4)—C(4)
Pt(1)—N(3)
Pt(1)—N(5)
N(5)—C(17)
N(6)—C(17)
N(7)—C(17)
2.3261(9)
2.3315(9)
2.3345(9)
1.986(3)
1.298(4)
1.337(5)
1.338(4)
1.337(4)
1.370(5)
2.023(3)
2.057(3)
1.310(4)
1.343(5)
1.366(4)
N(1)—Pt(1)—N(3)
N(3)—Pt(1)—N(5)
C(1)—N(1)—Pt(1)
N(1)—C(1)—N(2)
C(1)—N(2)—C(4)
N(3)—C(4)—N(2)
C(4)—N(3)—Pt(1)
C(4)—N(4)—C(5)
C(17)—N(5)—Pt(1)
C(17)—N(6)—C(18)
C(17)—N(7)—C(24)
N(5)—C(17)—N(6)
N(5)—C(17)—N(7)
N(6)—C(17)—N(7)
89.66(11)
93.22(11)
126.6(3)
126.9(3)
124.5(3)
128.2(3)
122.9(2)
130.8(3)
137.2(2)
124.7(3)
122.3(3)
122.6(3)
121.4(3)
116.0(3)
This study was financially supported by the Russian
Foundation for Basic Research (Project No. 08ꢀ03ꢀ12027ꢀofi)
and the Russian Academy of Sciences (Program of the
Presidium No. 8P).
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Table 1. Crystallographic data for complex 2
Parameter
Characteristics
Molecular formula
C
29H30Cl3N7Pt
778.04
Monoclinic
P21/n
9.9851(4)
18.1005(7)
16.4492(4)
90
90.720(2)
90
Molecular weight
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а/Å
b/Å
c/Å
α/deg
β/deg
γ/deg
V/А3
2972.72(18)
4
Z
dcalc/mg m–3
1.738
5.022
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37462
0.0442
μ/mm–1
Scanning range/deg
Number of measured reflections
Rint
R1 (I ≥ 2σ)
wR2 (I ≥ 2σ)
0.0275
0.0578

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Received August 18 2008;
in revised form September 29, 2008