PtII-mediated nitrile-tetramethylguanidine coupling as a key step for a novel synthesis of 1,6-dihydro-1,3,5-triazines

Article abstract of DOI:10.1021/ic061884b

The coupling between tetramethylguanidine, HN=C(NMe₂) ₂, and coordinated organonitriles in the platinum(II) complexes cis/trans-[PtCl₂(RCN)₂] (R = Me, Et, Ph) proceeds rapidly under mild conditions to afford the

Full text of DOI:10.1021/ic061884b

Inorg. Chem. 2007, 46, 1684−1693
PtII-Mediated Nitrile
Novel Synthesis of 1,6-Dihydro-1,3,5-triazines
−Tetramethylguanidine Coupling as a Key Step for a
O
Pavel V. Gushchin,† Nadezhda A. Bokach,† Konstantin V. Luzyanin,†,‡ Alexey A. Nazarov,§
Matti Haukka,| and Vadim Yu. Kukushkin*,†
Saint Petersburg State UniVersity, 198504 Stary Petergof, Russian Federation, Centro de Qu´ımica
Estrutural, Complexo I, Instituto Superior Te´cnico, AVenida RoVisco Pais, 1049-01 Lisbon,
Portugal, Institute of Inorganic Chemistry, UniVersity of Vienna, Wa¨hringer Strasse 42, A-1090,
Vienna, Austria, and Department of Chemistry, UniVersity of Joensuu, P.O. Box 111, FI-80101,
Joensuu, Finland
Received September 30, 2006
The coupling between tetramethylguanidine, HN
complexes cis/trans-[PtCl2(RCN)2] (R Me, Et, Ph) proceeds rapidly under mild conditions to afford the diimino
compounds containing two N-bound monodentate 1,3-diaza-1,3-diene ligands [PtCl2 NH C(R)N C(NMe2)2 2] (R
Et, trans-1; R Ph, trans-2; R Me, cis-3; R Et, cis-4), and this reaction is the first observation of metal-
mediated nucleophilic addition of a guanidine to ligated nitrile. Complexes 1 4 were characterized by elemental
analyses (C, H, N), X-ray diffraction, FAB mass spectrometry, IR, and 1H and 13C 1H
NMR spectroscopies;
assignment of signals from E/Z-forms of 1,3-diaza-1,3-diene ligands and verification of routes for their Z
dC(NMe2)2, and coordinated organonitriles in the platinum(II)
)
{
d
d
}
)
)
)
)
−
{
}
h
E
1
1
isomerization in solution were performed using 2D H,1H-COSY, H,13C-HETCOR, and 1D NOE NMR experiments.
The newly formed and previously unknown 1,3-diaza-1,3-dienes NH C(R)N C(NMe2)2 were liberated from the
platinum(II) complexes [PtCl2 NH C(R)N C(NMe2)2 2] (1 3) by substitution with 2 equiv of 1,2-bis-(diphenylphos-
phino)ethane (dppe) to give the uncomplexed HN C(R)N C(NMe2)2 species (5 7) in solution and the solid [Pt-
(dppe)2](Cl)2. The former were utilized in situ, after filtration of the latter, in the reaction with 1,3-di-p-tolylcarbodiimide,
(p-tol)N N(tol-p), in CDCl3 to generate (6E)-N,N-dimethyl-1-(4-methylphenyl)-6-[(4-methylphenyl)imino]-1,6-dihydro-
1,3,5-triazin-2-amines) (8
of 8
d
d
{
d
d
}
−
d
d
−
dCd
−
10) due to the [4
+
2]-cycloaddition accompanying elimination of HNMe2. The formulation
1
−
10 is based on ESI-MS, H, 13C
{
1H
}
NMR, and X-ray crystal structures determined for 9 and 10. The reaction
of 1,3-diaza-1,3-dienes with 1,3-di-p-tolylcarbodiimide, described in this article, constitutes a novel synthetic approach
to a useful class of heterocyclic species like 1,6-dihydro-1,3,5-triazines.
Introduction
results in a substantial activation of the imines toward di-,
tri-, and polymerizations and various redox-type conversions.
In particular, the imines R2CdNH with two donor substit-
uents are usually so reactive in hydrolysis and trimerizations
that some of these compounds are commonly treated as
elusiVe.2-4 The too high reactivity of such imines strongly
restricts their synthetic utilization.
The versatility of reactivity modes of imines RR′CdNR′′
and the overall chemical instability of these species are
mostly associated with the availability of the nitrogen lone
pair, whose activity can be modified by alteration of donor/
acceptor properties of substituents at the azomethine group.1
Donor substituents increase basicity of the N center, and this
Recently we5,6 and others7 found that platinum group metal
centers provide enormous stabilization of the potentially
unstable imines R2CdNH due to an efficient blocking of
the electron pair by coordination. Respectively, these ligands
can be “stored” without changes in the complexed form at
normal conditions for a prolonged time. We also reported8a
that the combination of the inertness of coordinated imines
R2CdNH with their high reactivity in the uncomplexed state
* To whom correspondence should be addressed. E-mail: kukushkin@
VK2100.spb.edu.
O Dedicated to Professor Mikhail G. Voronkov on the occasion of his
85th birthday.
† St. Petersburg State University.
‡ Instituto Superior Te´cnico.
§ University of Vienna.
| University of Joensuu.
(1) Constable, E. C. Metals and Ligand ReactiVity. An Introduction to
the Organic Chemistry of Metal Complexes; VCH: Weinheim, 1995.
1684 Inorganic Chemistry, Vol. 46, No. 5, 2007
10.1021/ic061884b CCC: $37.00
© 2007 American Chemical Society
Published on Web 02/01/2007

PtII-Mediated Nitrile-Tetramethylguanidine Coupling
could have some intrinsic practical implications. Indeed, if
the imine ligand is displaced under mild conditions from its
complex, the liberated reactive R2CdNH species can be
immediately used in situ for further reactions. We felt that
this “pop-the-cork” strategy8 warrants additional investigation
and can be applied to a metal-mediated synthesis and
stabilization of unusual 1,3-diaza-1,3-dienes followed by their
further exploitation (after liberation) in metal-free synthetic
transformations.
Thus, within our ongoing project on the metal-mediated
nitrile-imine coupling,8-14 we attempted to extend our
previous studies on reactions between platinum-bound RCN
species and HNdERn (ERn ) CPh2,9 C(Alkyl)(OAlkyl),8
C(Ar)(NHAr),10 SAr2,11,12 PPh313) to such specific imines as
guanidines (ERn ) C(NR2)2) to perform nitrile-guanidine
coupling and apply thus formed 1,3-diaza-1,3-dienes in
further reactions.
Me,15 Et,16 Ph17) compounds insofar as it has been demon-
strated that the PtII center provides sufficient activation of
RCN ligands to achieve the metal-mediated nitrile-imine
integration.8-14 Tetramethylguanidine (HNdC(NMe2)2; TMG),
commercially available and very soluble in organic solvents,
was used as a nucleophile for the addition. (ii) To perform
the liberation of the ligated 1,3-diaza-1,3-dienes HNd
C(R)NdC(NMe2)2, stabilized by coordination, and character-
ize them in the free form. Despite the general inertness of
the imino complexes toward ligand displacement, some
substitution methods have been previously developed,6,18,19
and it was anticipated to apply them for the liberation. (iii)
To utilize the released 1,3-diaza-1,3-dienes HNdC(R)Nd
C(NMe2)2 species in situ for further reactions by studying
their interplay with the carbodiimide (p-tol)NdCdN(tol-p),
which is a highly reactive reagent toward various N-donor
nucleophiles.20 All these resultssshowing the first example
of nitrile-guanidine coupling and application of the latter
reaction as the key step to achieve useful class of hetero-
cycles, i.e., 1,6-dihydro-1,3,5-triazine-2-aminessare reported
herein.
The scenario of this work was the following. (i) To use a
metal center as the promoter for formation of 1,3-diaza-1,3-
dienes derived from the previously unknown nucleophilic
addition of guanidines to (RCN)[M] species. For this part
of the study we addressed cis/trans-[PtCl2(RCN)2] (R )
Results and Discussion
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M. T.; Guerrero, R.; Vicente-Herna´ndez, I.; Alvarez-Falco´n, M. M.
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Nitrile-Guanidine Coupling at a Pt(II) Center. The
coupling between platinum(II)-bound nitriles in complexes
[PtCl2(RCN)2] and tetramethylguanidine (TMG) proceeds in
a molar ratio of 1:2 at 20-25 °C in MeCN (R ) Me), EtCN
(R ) Et), or CH2Cl2 (R ) Ph) and results in formation of
diimino complexes containing two N-bound monodentate
1,3-diaza-1,3-diene ligands [PtCl2{NHdC(R)NdC(NMe2)2}2].
It was proved that TMG does not react with RCN (R ) Et,
Ph) under the coupling conditions, and this implies that the
nitrile-TMG coupling is PtII mediated. We believe that the
(1,3-diaza-1,3-diene)PtII complexes are presumably formed
by nucleophilic attack of the imine N atom on the electro-
philically activated carbon atom of the nitrile.
(3) Prenzler, P. D.; Hockless, D. C. R.; Heath, G. A. Inorg. Chem. 1997,
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H. D.; Zheng, Z. P. Comm. Inorg. Chem. 2005, 26, 75.
Treatment of trans-[PtCl2(RCN)2] (R ) Et, Ph) with TMG
allows isolation of the trans-[PtCl2{NHdC(R)NdC(NMe2)2}2]
(1 and 2) complexes (route A in Scheme 1). Reaction
between cis-[PtCl2(RCN)2] (R ) Me, Et) and TMG leads to
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R.; Pombeiro, A. J. L.; Kukushkin, V. Yu.; Michelin, R. A. Inorg.
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Inorganic Chemistry, Vol. 46, No. 5, 2007 1685

Gushchin et al.
In the 1H NMR spectra recorded at room temperature, the
signal of the proton from the imino group CdNH (δ 6.90-
5.42 ppm) is shifted upfield compared to those observed in
NMR spectra of other platinum imine complexes (δ 8-9
ppm).22 In the latter, the hydrogen bonding involving the
imine CdNH proton was unambiguously recognized, while
in our case the position of the signal at such a high field
gives indirect evidence that the proton of the CdNH group
is not involved in the hydrogen bonding in solution.9,14 The
13C{1H} NMR spectra show two signals of the CdN bonds
in the range from 177.5 to 162.4 ppm, which corresponds
to the characteristic CdN resonances in platinum imine
complexes.14,18,22,23 In the 13C{1H} and 1H NMR spectra, the
resonances from the dimethylamino NMe2 carbons and
protons appear at δ 40.6-39.2 and 3.14-2.73 ppm, respec-
tively.
Scheme 1
In the 1H NMR spectra measured in CDCl3, 1-4 typically
display three or four sets of signals, which can be rationalized
by formation of complexes in EE-, EZ-, and ZZ-configura-
tions of the 1,3-diaza-1,3-diene ligands due to cis- (for the
E-form) and trans-addition (for the Z-form) of TMG to the
triple CtN bond and/or slow dynamic noncatalyzed Z-E
isomerization of the ligated diazadiene species similar to
those observed recently for other PtIV-bound diazadiene
systems.10,12 The difference in chemical shifts between E-
and Z-forms of the ligated imines (0.2-0.8 ppm for NH
protons and 0.2-0.4 ppm for NMe2 protons) in our case
agrees well with those previously reported for the PtIV-
complexed imino esters NHdC(R)OR′ (0.3-0.4 ppm; a
slightly smaller value (0.1 ppm) was reported for R ) Et6)
and the (imino ester)PtII complexes (0.6-0.7 ppm).24,25
Assignment of signals from E/Z-forms and verification of
routes for their Z h E isomerization have been performed
formation of cis-[PtCl2{NHdC(R)NdC(NMe2)2}2] (3 and
4) (route B in Scheme 1). Complexes cis-[PtCl2(RCN)2]
contain admixtures of trans isomers15,16 (see Experimental
Section); consequently, the isolated cis-[PtCl2{NHdC(R)Nd
C(NMe2)2}2] was contaminated with the appropriate trans
form; the latter can be removed by washing of solid residues
obtained upon complete evaporation of the reaction mixtures
(see Experimental Section).
The possibility of geometric cis/trans isomerization has
been verified for the isomeric pair 1/4. Thus, heating 1 either
in the solid state (100 °C, 6 h) or in solution (EtCN, 70 °C,
14 h) with TLC monitoring of the process shows no cis/
trans isomerization but gradual overall degradation of the
complex. In contrast, heating 4 under the same conditions
gives some quantities of 1 (route C, Scheme 1) along with
yet unidentified decomposition products. Heating 4 in the
solid state (110 °C, 17 h) with TLC monitoring of the process
shows no cis/trans isomerization but gradual overall degrada-
tion of 4. Hence, the geometric cis/trans isomers exhibit
significant stability and do not isomerize under normal
conditions.
using 2D H,1H-COSY, H,13C-HETCOR, and 1D NOE
NMR experiments. Thus, addition of TMG to the coordinated
nitriles in trans-[PtCl2(EtCN)2] leads to formation of trans-
[PtCl2{(Z)-HNdC(Et)NdC(NMe2)2}2] as the main product.
Upon dissolution in CDCl3, the latter complex is subject to
a slow dynamic Z h E isomerization giving trans-[PtCl2-
{(E)-HNdC(Et)NdC(NMe2)2}2] through the intermediate
formation of trans-[PtCl2{(Z)-HNdC(Et)NdC(NMe2)2}{(E)-
HNdC(Et)NdC(NMe2)2}]; all species were identified by 1D
NOE NMR. After 1 day, all forms exist in an equilibrium
1
1
Characterization of 1,3-Diaza-1,3-diene Complexes
1-4. Complexes 1-4 have been characterized by elemental
analysis, FAB+ mass spectrometry, infrared, and NMR (1H,
13C{1H}) spectroscopies. The compounds give satisfactory
C, H, and N elemental analyses for the proposed formulation.
In the FAB+ mass spectra, 1-4 give the expected molecular
ion [M]+ along with some fragmentation peaks.
1
and the ZZ:EZ:EE isomeric ratio, obtained by H NMR
integration, is ca. 1:2:1. Reaction between TMG and trans-
[PtCl2(PhCN)2] allows isolation of trans-[PtCl2{(Z)-HNd
C(Ph)NdC(NMe2)2}2] as the main solid product along with
EE- and EZ-forms of trans-[PtCl2{HNdC(Ph)NdC(NMe2)2}2]
as minor species that remain in solution. In the case of trans-
[PtCl2{HNdC(Ph)NdC(NMe2)2}2], the rate of the Z h E
The IR spectroscopic data additionally confirm the nu-
cleophilic addition of TMG to the RCN ligands and rule out
the possibility of displacement of nitriles by TMG. Thus,
comparison of the IR spectra of 1-4 with the spectra of the
starting complexes shows the absence of the ν(CtN)
absorption band in the typical range of 2350-2300 cm-1
and the presence of intense stretching bands ν(CdN) at lower
frequencies (1566-1525 cm-1). The latter stretches cor-
respond well to the ν(CdN) values (1540-1522 cm-1) for
PtII- or PtIV-bound heterodiazadiene11,12,14 or diazadiene
species (1561-1540 cm-1) for the previously reported PtII
complexes in which the imidoylamidinato ligand is che-
lated.10 In addition, weaker bands due to ν(N-H) are seen
for 1-4 in the region between 3510 and 3249 cm-1.
(21) Valenciano, J.; Sanchez-Pavon, E.; Cuadro, A. M.; Vaquero, J. J.;
Alvarez-Builla, J. J. Org. Chem. 2001, 66, 8528.
(22) Kukushkin, V. Yu.; Pakhomova, T. B.; Kukushkin, Yu. N.; Herrmann,
R.; Wagner, G.; Pombeiro, A. J. L. Inorg. Chem. 1998, 37, 6511.
(23) Luzyanin, K. V.; Haukka, M.; Bokach, N. A.; Kuznetsov, M. L.;
Kukushkin, V. Yu.; Pombeiro, A. J. L. Dalton Trans. 2002, 1882.
(24) Fanizzi, F. P.; Intini, F. P.; Natile, G. J. Chem. Soc., Dalton Trans.
1989, 947.
(25) Cini, R.; Caputo, P. A.; Intini, F. P.; Natile, G. Inorg. Chem. 1995,
34, 1130.
1686 Inorganic Chemistry, Vol. 46, No. 5, 2007

PtII-Mediated Nitrile-Tetramethylguanidine Coupling
Figure 1. Thermal ellipsoid view of 1 with atom-numbering scheme.
Thermal ellipsoids are drawn with 50% probability.
Figure 4. Thermal ellipsoid view of complex 4 with atom-numbering
scheme. Thermal ellipsoids are drawn with 50% probability.
The values of the Pt-Cl bond distances (2.30-2.32 Å)
agree well with previously characterized platinum(II) chloride
compounds.11,25,26 The N(1)-C(1) bond lengths in 1-4 and
N(2)-C(3) in 3 [1.296(3), 1.305(4), 1.300(5), 1.300(5),
1.308(7) Å, respectively] correspond, within 3σ, to the typical
CdN double bond [mean value 1.279(8) Å in compounds
with CAr-CdN-C moiety27]. The bond lengths N(2)-C(1)
in 1 and 2 [1.357(3) and 1.346(4) Å, respectively] have
values closer to a C-N single bond [Nsp2-Csp2 in amides
1.346(11) Å27]. N(2)-C(4) in 1 [1.326(3) Å], N(2)-C(8)
[1.324(4) Å] in 2, N(2)-C(1) [1.332(7) Å] in 3, and N(2)-
C(1) [1.334(5) Å] and N(2)-C(4) [1.317(5) Å] in 4 bond
lengths are intermediate between those values. These obser-
vations demonstrate the presence of electron delocalization
for N(2)-C(4) bonds in 1 and 4 and N(2)-C(8) in 2 of the
TMG moiety of the Pt(II)-bound 1,3-diaza-1,3-diene species,
which is relevant to that observed for the N(1)-C(1) bond
length [1.3292(17) Å] of NHdC(NMe2)2‚HCl (Figure S3)
and at any of the uncomplexed substituted guanidinium
species [C-(NH2)3]+ [av. Nsp2-Csp2 is 1.328(15) Å27].
However, in general, the data demonstrate the absence of
electron delocalization in the 1,3-diaza-1,3-diene ligand. A
similar phenomenon has been observed in the imidoylami-
dine NHdC(NEt2)NdC(Ph)NHPh10 and the diazadiene
Figure 2. Thermal ellipsoid view of complex 2 with atom-numbering
scheme. Thermal ellipsoids are drawn with 50% probability.
Figure 3. Thermal ellipsoid view of complex 3 with atom-numbering
scheme. Thermal ellipsoids are drawn with 30% probability.
isomerization is rather low and after 1 week at 20-25 °C
only 10% of the starting ZZ-isomer was isomerized to the
other forms.
9
The selectivity in formation of the E- or Z-form is less
noticeable for the cis-[PtCl2(1,3-diaza-1,3-diene)2] species
than for the appropriate trans complexes. Thus, the reaction
of cis-[PtCl2(NCR)2] (R ) Me, Et) with TMG in the
corresponding nitriles, used as solvents, gives cis-[PtCl2-
{HNdC(R)NdC(NMe2)2}2], whose 1H NMR spectrum,
measured right after completion of the coupling, shows the
simultaneous presence of the EE-, EZ-, and ZZ-isomers in
ca. 1:2:2 (R ) Me) and ca. 1:3:4 (R ) Et) ratios.
X-ray Structure Determinations of Pt Complexes. The
structures of 1-4 were determined by X-ray single-crystal
diffraction. In 1, 2, and 2b, two new 1,3-diaza-1,3-diene
ligands are in the mutually trans position, and they are both
in the E- (1; Figure 1) and Z-configuration (2 and 2b; Figure
2 for 2; for 2b see Figure S1 in Supporting Information). In
3 (Figure 3) and 4 (Figure 4), two new diazadiene ligands
are in the Z-configuration and cis to each other; the adjacent
molecules are linked by weak (NH‚‚‚Cl)2 interactions [2.71
Å for 3 and 2.67 Å for 4] (Figure S4, Table S2 and Figure
S5, Table S3, respectively).
NHdC(Et)NdCPh2 species monodentately coordinated to
a PtIV center, where the imine ligands have distinct single
and double CN bonds with no electron delocalization. The
N-C bond lengths N(3)-C(4) [1.361(3) Å] and N(4)-C(4)
[1.358(3) Å] in 1, N(3)-C(8) [1.346(4) Å] and N(4)-C(8)
[1.355(4) Å] in 2, N(3)-C(3) [1.361(7) Å] and N(4)-C(3)
[1.350(7) Å] in 3, and N(3)-C(4) [1.352(5) Å] and N(4)-
C(4) [1.347(5) Å] in 4 of dC-(NMe2)2 fragments cor-
respond, within 3σ, to N(2)-C(1) [1.3395(16) Å] or N(3)-
C(1) [1.3453(16) Å] bond lengths of NHdC(NMe2)2‚HCl
(Figure S3) and also to the typical Nsp2-Csp2 single bond
[av. 1.355(14) in C)C-N-(Csp3)2 (Nsp2 planar)27].
(26) Belluco, U.; Benetollo, F.; Bertani, R.; Bombieri, G.; Michelin, R.
A.; Mozzon, M.; Tonon, O.; Pombeiro, A. J. L.; Guedes da Silva, F.
C. Inorg. Chim. Acta. 2002, 334, 437. Michelin R. A.; Bertani, R.;
Mozzon, M.; Sassi, A.; Benetollo, F.; Bombieri, G.; Pombeiro, A. J.
L. Inorg. Chem. Commun. 2001, 4, 275. Cini, R.; Fanizzi, F. P.; Intini,
F. P.; Natile, G.; Pacifico, C. Inorg. Chim. Acta. 1996, 251, 111.
Gonzalez, A. M.; Cini, R.; Intini, F. P.; Pacifico, C.; Natile, G. Inorg.
Chem. 2002, 41, 470.
(27) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A.
G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1.
Inorganic Chemistry, Vol. 46, No. 5, 2007 1687

Gushchin et al.
Scheme 2
Liberation of the 1,3-Diaza-1,3-dienes. Insofar as 1,3-
In Situ Conversion of the Diazadienes to 1,6-Dihydro-
1,3,5-triazine-2-amines. In organic chemistry, 1,3-diaza-1,3-
dienes are useful for syntheses of six-membered nitrogen-
containing heterocycles, and their involvement in [4 + 2]
cycloadditions to give these systems was a subject of rapt
attention.28 We attempted to utilize the novel HNdC(R)N)C-
(NMe2)2 species for cycloaddition and used diazadienes 5-7
in situ in the reaction with 1,3-di-p-tolylcarbodiimide (reac-
tions of this reagent with various N-nucleophiles and dipoles
are well-known20,21) and observed that they readily react with
(p-tol)NdCdN(tol-p) in CDCl3 to generate 1,6-dihydro-
1,3,5-triazine derivatives (IUPAC name30 (6E)-N,N-dimethyl-
1-(4-methylphenyl)-6-[(4-methylphenyl)imino]-1,6-dihydro-
1,3,5-triazin-2-amines) (8-10) (route II, Scheme 2) due to
the [4 + 2]-cycloaddition accompanying elimination of
diaza-1,3-dienes are useful synthons for many organic
transformations28,29 and their formation easily occurs at the
PtII center, we suggest an efficient route for liberation of
the NHdC(R)NdC(NMe2)2 species from 1-3 by substitu-
tion with 1,2-bis-(diphenylphosphino)ethane (dppe) in accord
with previous reports.6,8,9 Displacement in CDCl3 resulted
in precipitation of the known6,8,9,14 highly insoluble complex
[Pt(dppe)2](Cl)2 (identified by 31P{1H} NMR), which was
separated by filtration from the solution containing the free
diazadiene NHdC(R)NdC(NMe2)2 (5-7) (route I, Scheme
2); the latter (IUPAC name30 N-[bis(dimethylamino)meth-
ylene]carboximidamide) were characterized by ESI-MS and
1H and 13C{1H} NMR spectroscopy (see Experimental
Section).
It was previously reported that although N-unsubstituted-
1,3-diaza-1,3-dienes are rather unstable, they have acceptable
stability under normal conditions depending on donor/
acceptor properties of substituents at the C2 atoms being more
stable with electron-withdrawing groups.1 We observed that,
accordingly, 5 and 7 containing donor groups (Me and Et,
respectively) are rather unstable in CDCl3 and decompose
after 6-12 h at room temperature, whereas phenyl-containing
6 is stable for at least 5 days under the same conditions.
The known synthetic pathways29 to achieve 1,3-diaza-1,3-
dienes do not include direct interaction between organoni-
triles and imines. In particular, the 1,3-diaza-1,3-dienes
[Me2NdC(R)NdC(NMe2)2](ClO4), which are the most rel-
evant to our systems, were obtained by treatment of
[(Me)2NdC(Cl)Ph](Cl) (R ) Ph)31 or [Me2NdC(OMe)Me]-
(MeSO4) (R ) Me)32 with TMG. Thus, the nitrile-TMG
coupling reported herein constitutes a potential alternatiVe
pathway to the synthesis of 1,3-diaza-1,3-dienes and a
consequence of the metal-mediated coupling, and the libera-
tion allows the facile synthesis of the previously unknown
N-unsubstituted 1,3-diaza-1,3-dienes HNdC(R)N)(NMe2)2.
1
HNMe2 (the latter was detected by H NMR, 2.42, and
13C{1H} NMR, 39.0 ppm); elimination of dimethylamine
from pyrimidine or pyrimido[4,5-d]pyrimidine derivatives
upon cycloaddition has several precedents in the past.33
1
The H NMR spectra of 8-10 display two p-CH3Ph
singlets in the range from 2.41 to 2.27 ppm and two NMe2
singlets at 3.18-3.08 and 2.87-2.74 ppm, respectively, in
a ratio of 1:5 obtained by integration. The 13C{1H} NMR
spectra of 8-10 and the X-ray structures of 9 and 10
confirmed the formulation. 13C{1H} NMR spectra of 8-10
display three characteristic signals at 175.1-150.6 ppm, four
(8 and 9) or five (10) characteristic signals at 146.6-131.4
ppm, two characteristic signals at 41.5-40.4 ppm, and two
characteristic signals at 21.6-21.3 ppm assigned to CdN,
Cipso, NMe2, and CH3Ph carbons, correspondingly.
In 9 (Figure 5) and 10 (Figure 6), characterized by X-ray
crystallography, the N(1)-C(18), N(1)-C(1), N(2)-C(1),
N(2)-C(8), and N(3)-C(8) bond lengths [1.370(2), 1.312-
(2), 1.349(2), 1.330(2), 1.378(2), and 1.3714(17), 1.3154-
(18), 1.3471(18), 1.3329(18), 1.3777(18) Å, respectively]
agree well with the mean value reported for CdN delocalized
double bonds in pyrimidine (overall) [1.336(14) Å27].
However, the N(1)-C(1) bond lengths [1.312(2) and 1.3154-
(18) Å, respectively] have values closer to the CdN double
bond [av. 1.313(11) Å in the -NdC-N fragment of
(28) Sain, B.; Singh, S. P.; Sandhu, J. S. Tetrahedron 1992, 48, 4567.
Muzumdar, S. N.; Mahajan, M. P. Synthesis 1990, 417. Muzumdar,
S. N.; Mukherjee, S.; Sharma, A. K.; Sengupta, D.; Mahajan, M. P.
Tetrahedron 1994, 50, 7579. Muzumdar, S. N.; Mahajan, M. P.
Tetrahedron 1991, 47, 1473.
(29) Guzma´n, A.; Romero, M.; Talama´s, F. X.; Villena, R.; Greenhouse,
R.; Muchowski, J. M. J. Org. Chem. 1996, 61, 2470.
(30) http://www.iupac.org/nomenclature/index.html.
(31) Gompper, R.; Schneider, C. S. Synthesis 1979, 3, 215.
(32) Gompper, R; Heinemann, U. Angew. Chem. 1980, 92 (3), 208.
(33) Guillon, J.; Le´ger, J.-M.; Massip, S.; The´, C.; Vidaillac, C.; Monti,
J.-P.; Jarry, C. Synlett 2002, 1. Prajapati, D.; Thakur, A. J. Tetrahedron
Lett. 2005, 46, 1433. Prajapati, D.; Gohain, M.; Thakur, A. J. Bioorg.
Med. Chem. Lett. 2006, 16, 3537.
1688 Inorganic Chemistry, Vol. 46, No. 5, 2007

PtII-Mediated Nitrile-Tetramethylguanidine Coupling
1.390(30) Å in compounds with fragment CAr-N-(Csp3)227].
In 9 and 10, six-membered rings N(1)C(1)N(2)C(8)N(3)C-
(18) are planar [rms of the deviations of atoms from the plane
N(1)C(1)N(2)C(8)N(3)C(18) are 0.048(1) (9) and 0.063(1)
Å (10)].
Thus, all data combined together indicate that 1,3-diaza-
1,3-dienes 5-7 undergo [4 + 2] cycloaddition with 1,3-di-
p-tolylcarbodiimide with concomitant loss of HNMe2, thus
converting into cycloadducts 8-10.
Dihydrotriazines are the known class of six-membered
heterocycles, and some of these compounds possess anti-
bacterial (e.g., against such bacteria as wild-type Plasmodium
falciparum dihydrofolate reductase, Escherichia coli and
Staphilococcus aureus, Plasmodium berghei in mice, Plas-
modium gallinaceum in hens),34-37 anti-diabetic,38 herbi-
cidal,39,40 and antitumor activities41 and also show hypogly-
cemic properties.42 Other successful applications of the
dihydrotriazines include controlling leukocytozoon disease
in chickens,43 use as insecticides,44,45 antithyroidal,46 anti-
malarial,47-51 or anti-inflammatory agents,52 as well as use
as corrosion inhibitors.53
Figure 5. Thermal ellipsoid view of 9 with atom-numbering scheme.
Thermal ellipsoids are drawn with 50% probability.
Dihydrotriazines are commonly prepared by (i) acid-
catalyzed cyclocondensation between biguanidines,35-38,54-56
cyanoguanidines, amines,40,45,48,50,56-58 N′-amidinothioureas,55
and carbonyl compounds, (ii) cyclocondensation of RCN
with carbonyl compound and NH3 in alcohols under harsh
conditions,59,60 (iii) cyclization of thiourea derivative52 or
polymer-bound guanidines (solid-phase synthesis)61 with
chlorcarbonylisocyanate and cyclization of two N′-(ami-
nocarbonyl)imidocarbamates,62 (iv) cyclization of imido-
thiocarbamate derivative63 or guanidine64 with isothiocyanate
derivative and cyclization of amidines with imidoylisothiocya-
nates,65and (v) trimerization of RCN induced by alkyllithium
Figure 6. Thermal ellipsoid view of 10 with atom-numbering scheme.
Thermal ellipsoids are drawn with 50% probability.
imidazole, av. 1.314(9) Å in the O-NdC-Csp2 moiety of
isoxazole27], whereas N(1)-C(18), N(2)-C(1) bond lengths
[1.370(2), 1.349(2), and 1.3714(17), 1.3471(18) Å, cor-
respondingly] have values closer to Csp2-Nsp2 single bond
[av. 1.376(11) Å in dN-CdC moiety of imidazole27].
The N-C bond lengths N(2)-C(8) in 9 and 10 [1.330(2)
and 1.3329(18) Å, respectively] correspond, within 3σ, to
the N(1)-C(1) bond length [1.3292(17) Å] of NHdC(NMe2)2‚
HCl (Figure S3) and also to the typical N-C single bond
in substituted guanidinium species [C-(NH2)3]+ [av.
Nsp2-Csp2 is 1.328(15) Å27]. This indicates the presence
of electron delocalization for the NdC double bond, appar-
ently induced by the neighboring NMe2 and N(p-(MeC6H4)
groups, i.e., analogous to substituted guanidinium species
[C-(NH2)3]+ [av. Nsp2-Csp2 is 1.328(15) Å27]. The N-C
bond lengths N(4)-C(8) in 9 and 10 [1.345(2) and 1.3403-
(18) Å, respectively] correspond, within 3σ, to the typical
Nsp2-Csp2 single bond [av. 1.355(14) in CdC-N-(Csp3)2
(Nsp2 planar)27]. The N(5)-C(18) bond lengths [1.290(2)
and 1.2811(18) Å, respectively] agree well, within 3σ, with
the typical CdN double bond [mean value 1.279(8) Å in
compounds with the CAr-CdN-C moiety27]. N(3)-C(18)
and N(3)-C(8) in 9 and 10 [1.429(2), 1.378(2) and 1.4332-
(17), 1.3777(18), respectively] correspond, within 3σ, to the
typical Nsp2-Csp2 single bond [av. 1.409(20) Å in imides
[Csp2-C()O)]2-N-Csp2 (Nsp2 planar)27]. N(3)-C(11) in
9 and 10 [1.450(2) and 1.4443(17) Å, respectively] corre-
sponds, within 3σ, to the typical CAr-N single bond [av.
(34) Hathaway, B. A.; Champine, J. E.; Casteneda, C.; VanWeelden, A.
Abstracts of Papers, 57th Southeast/61st Southwest Joint Regional
Meeting of the American Chemical Society, Memphis, TN, Nov
2005: American Chemical Society: Washington, DC, 2005; p 1.
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S.; Sirawaraporn, W.; Yuthavong, Y. Bioorg. Med. Chem. Lett. 2003,
11, 217.
(36) Mehrotra, S.; Pandey, V.; Lakhan, R.; Srivastava, P. K. J. Indian Chem.
Soc. 2002, 79, 176.
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100764.
(38) Moinet, G.; Cravo, D.; Doare, L.; Kergoat, M.; Mesangeau, D. PCT
Int. Appl. WO 01 55,122, 2001; Chem. Abstr. 2001, 135, 137527.
(39) Turnbull, M. D.; Crowley, P. J.; Chrystal, E. J. T.; Clough, J. M.;
Bryan, I. B.; Beautement, K.; Barnett, S. P.; Ponsford, R. J.; Outred,
D. J. PCT Int. Appl. WO 9615671, 1996; Chem. Abstr. 1996, 125,
107776.
(40) Smrz, R.; Cech, J.; Auerhan, J.; Simek, A. Czech. Patent 119,884,
1966; Chem. Abstr. 1967, 67, 11509.
(41) Hayashi, S.; Furukawa, M.; Yamamoto, J.; Nishizima, Y.; Sannomiya,
E.; Ueki, H. Kumamoto Pharm. Bull. 1966, 7, 7; Chem. Abstr. 1967,
66, 74623.
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Appl. 71/76,595, 1971; Chem. Abstr. 1981, 94, 77032.
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1996, 125, 268213.
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Chem. Abstr. 1994, 121, 230800.
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Arch. Pharmacal Res. 1995, 18, 356; Chem. Abstr. 1995, 124, 135323.
Prasad, R.; Srivastava, P. K. Arch. Pharm. 1993, 326, 963; Chem.
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Soc. 1992, 69, 664.
Inorganic Chemistry, Vol. 46, No. 5, 2007 1689

Gushchin et al.
derivatives66 or sodium.67 Hence, the [4 + 2]-cycloaddition
of 1,3-diaza-1,3-diene to carbodiimides, described in this
section, constitutes a novel synthetic approach to this useful
class of heterocyclic species.
Experimental Section
Materials and Instrumentation. Guanidine HNdC(NMe2)2,
1,3-di-p-tolylcarbodiimide (p-tol)NdCdN(tol-p) (Aldrich), and
solvents were obtained from commercial sources and used as
received. Complexes cis-[PtCl2(RCN)2] (R ) Me,15 Et16) were
prepared in accord with the published methods. These compounds
contain admixtures of the trans isomers (isomeric cis:trans ratio
obtained by NMR integration is ca. 5:1 for R ) Me,15 ca. 6:1 for
R ) Et16). The isomerically pure complexes trans-[PtCl2(RCN)2]
(R ) Et,16 Ph17) were obtained as previously described.
TLC was done on Merck 60 F254 SiO2 plates. Elemental analyses
were obtained on a Hewlett-Packard 185B Carbon Hydrogen
Nitrogen Analyzer at the Department of Organic Chemistry, St.
Petersburg State University. Positive-ion FAB mass spectra were
obtained on a Kratos MS-50C instrument by bombarding 3-ni-
trobenzyl alcohol (NBA) matrices of the samples with Xe atoms.
Electrospray ionization mass spectra of 5-10 were recorded on a
Bruker esquire3000 ion trap mass spectrometer in positive-ion mode
equipped with an orthogonal electrospray interface (Bruker Dal-
tonics, Bremen, Germany). The sample solution in methanol was
delivered at a flow rate of 3 µL/min using a syringe pump 74900
from Cole-Parmer Instrument Co. (Vernon Hills, IL), and N2 was
used as drying and nebulizing gas (flow rates 5 L/min). Expected
and experimental isotope distributions were compared. Infrared
spectra (4000-400 cm-1) were recorded on a BIO-RAD FTS
3000MX instrument in KBr pellets.
Final Remarks
The results from this work may be considered from three
perspectives. First, it was observed that addition of HNd
C(NMe2)2 to coordinated organonitriles is PtII mediated and
results in the previously unknown ligated HN-unsubstituted
1,3-diaza-1,3-dienes HNdC(R)NdC(NMe2)2, and the reac-
tion represents the first example of nitrile-guanidine cou-
pling. The PtII center plays a dual role in the synthesis of
the 1,3-diaza-1,3-dienes, i.e., it activates the organonitriles
toward the nucleophilic addition of TMG and stabilizes the
formed ligands (especially those with donor groups) by
complexation. We are continuing to explore the metal-
mediated nitrile-guanidine integration and apply for that
purpose various guanidines including more reactive species
HNdC(NHR)2 with partially substituted (R ) alkyl, aryl)
or unsubstituted (R ) H) amido groups. Second, the
consequence of the platinum(II)-mediated reactions followed
by ligand liberation provide a novel and facile route to the
previously unreported 1,3-diaza-1,3-dienes HNdC(R)Nd
C(NMe2)2. Third, we found that [4 + 2]-cycloaddition of
the 1,3-diaza-1,3-dienes to carbodiimidessperformed in situ
within the “pop-the-cork strategy”8sconstitutes a novel
synthetic approach to this useful class of heterocycles, 1,6-
dihydro-1,3,5-triazines.
1
1
1
1D H, 13C{1H}, 31P{1H}, NOE; 2D H,1H-COSY, and H,13C-
HETCOR NMR spectra were measured on a Bruker DPX 300
spectrometer at ambient temperature. Assignment of H chemical
1
shifts for the CH2 and CH3 protons from the Et group for all isomers
of both 1 and 4 was based on 2D 1H,1H-COSY NMR experiments.
The description of the NMR spectra given in the synthetic part
contains symbols {E} and {Z}, which designate the appropriate E-
and Z-forms, e.g., “{Z}-EZ” denote a ligand in the Z-form for the
EZ isomer.
(47) Mamalis, P.; Outred, D. J. Ger. Offen. 1,957,769, 1970; Chem. Abstr.
1971, 74, 76451.
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1970, 73, 131035.
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1957, 51, 73318. Bami, H. L. Excerpta Medica, Section 2: Physiology,
Biochemistry and Pharmacology 1954, 7 (Sect. II), 1230; Chem. Abstr.
1955, 49, 66317. Bami, H. L. Indian J. Malariology 1953, 7, 283;
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Synthetic Work. Reaction of trans-[PtCl2(RCN)2] and TMG.
HNdC(NMe2)2 (48 µL; 0.38 mmol) was added to a yellow solution
of trans-[PtCl2(RCN)2] (0.19 mmol) in EtCN (1.5 mL) (R ) Et)
or CH2Cl2 (1.5 mL) (R ) Ph) and left to stand for 1 h (R ) Et) or
5 min (R ) Ph) at 20-25 °C. In both cases, the greenish-yellow
solution formed was evaporated to dryness, and the yellow residue
was crystallized under a layer of Et2O (1 mL) to form yellow
powders which were washed with two 1-mL portions of acetone
and one 1-mL portion of Et2O (R ) Ph) or two 1-mL portions of
acetone:Et2O ) 1:1 mixture (R ) Et), and both were dried in air
at room temperature. Yields are 88 mg (77% (R ) Et)) and 110
mg (83% (R ) Ph)).
(54) Saesaengseerung, N.; Vilaivan, T.; Thebtaranonth, Y. Synth. Commun.
2002, 32, 2089.
trans-[PtCl2{NHdC(Et)NdC(NMe2)2}2] (1). Anal. Calcd for
C16H36N8Cl2Pt: C, 31.68; H, 5.94; N, 18.48. Found: C, 31.78; H,
6.05; N, 18.83. FAB+-MS, m/z: 606 [M]+, 171 [NHdC(Et)Nd
C(NMe2)2 + H]+. TLC: Rf ) 0.56 (eluent MeOH:CHCl3 ) 1:10).
IR (KBr, selected bands) cm-1: 3448 (br, w), 3327 (m-w), 3249
(w), ν(N-H); 2978 (m-w), 2925 (m-w), 2871 (m-w), ν(C-H from
Et and NMe2); 1566 (s), 1525 (s), ν(CdN); 1477 (s), 1448 (s),
(55) Li Loo, Ti. J. Am. Chem. Soc. 1954, 76, 5096.
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46455.
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Chem. Abstr. 1964, 60, 16906.
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1961, 55, 93613.
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Koho JP 82 26, 668 (1982); Chem. Abstr. 1982, 97, 23825.
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1
1392 (s), δ(C-H from Et and NMe2). H NMR (CDCl3), δ: 5.84
(s, br, {Z}-ZZ), 5.64 (s, br, {Z}-EZ), 5.42 (s, br, {E}-EZ), 5.40 (s,
br, {E}-EE) (2H, NH), 3.08, 2.84, and 2.82 (m, 24H, NMe2), 3.01
(q, 7.32 Hz, {Z}-ZZ), 2.93 (q, 7.32 Hz, {Z}-EZ), 2.39 (q, 7.32 Hz,
{E}-EZ), 2.33 (q, 7.32 Hz, {E}-EE) (4H, CH2 from Et), 1.34 (t,
7.32 Hz, {Z}-ZZ), 1.24 (t, 7.32 Hz, {Z}-EZ), 1.14 (t, 7.32 Hz, {E}-
EZ), 1.09 (t, 7.32 Hz, {E}-EE) (6H, CH3 from Et). 13C{1H} NMR
(CDCl3), δ: 178.2, 178.0, 176.0, 175.2, 163.2, 163.0, 162.9, 162.7
(65) Neuffer, J.; Goerdeler, J. Chem. Ber. 1971, 104, 3498.
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1690 Inorganic Chemistry, Vol. 46, No. 5, 2007

PtII-Mediated Nitrile-Tetramethylguanidine Coupling
(CdN), 40.6, 40.4, 40.3, 40.3 (NMe2), 35.0, 34.5, 31.7, 31.2 (CH2
from Et), 12.5, 12.4, 12.1, 11.9 (CH3 from Et). Crystals suitable
for X-ray diffraction study were obtained by slow evaporation of
a hexane:chloroform (1:1, v/v) solution of 1.
(m-s), 1397 (m-s), 1389 (s), δ(C-H from Et and NMe2). 1H NMR
(CDCl3), δ: 6.54 (s, br, {E}-EE), 6.32 (s, br, {Z}-EZ), 6.17 (s, br,
{E}-EZ), 5.90 (s, br, {Z}-ZZ) (2H, NH), 3.07 (s), 3.03 (s), 2.91 (s)
and 2.84 (s) (24H, NMe2), 2.97-2.91 (m, 7.26 Hz, {E}-EE), 2.74
(q, 7.26 Hz, {E}-EZ), 2.40 (q, 7.26 Hz, {Z}-EZ), 2.32 (q, 7.26 Hz,
{Z}-ZZ) (4H, CH2 from Et), 1.27 (t, 7.26 Hz, {E}-EE), 1.19-1.09
(m, {E}-EZ, {Z}-EZ, {Z}-ZZ) (6H, CH3 from Et). 13C{1H} NMR
(CDCl3), δ: 177.9, 175.5, 163.2, 163.0 (CdN), 40.6, 40.3 (NMe2),
34.6 (CH2 from Et), 12.2 (CH3 from Et). Crystals suitable for X-ray
diffraction study were obtained by slow evaporation of a hexane:
chloroform (1:1, v/v) solution of 4.
trans-[PtCl2{NHdC(Ph)NdC(NMe2)2}2] (2). Anal. Calcd for
C24H36N8Cl2Pt: C, 41.02; H, 5.13; N, 15.95. Found: C, 40.79; H,
5.28; N, 15.75. FAB+-MS, m/z: 703 [M + H]+, 666 [M - Cl]+,
630 [M - HCl - Cl]+, 219 [NHdC(Ph)NdC(NMe2)2 + H]+.
TLC: Rf ) 0.67 (eluent MeOH:CHCl3 ) 1:10). IR (KBr, selected
bands) cm-1: 3489 (m-w), 3323 (m-w), ν(N-H); 2937 (m-w), 2868
(w), ν(C-H from Ph and NMe2); 1533 (s), ν(CdN and/or CdC
from Ph); 1471 (m), 1421 (m-s), 1408 (m-s), 1390 (m-s), δ(C-H
Liberation of the Diazadiene from trans-[PtCl2{NHdC(R)-
NdC(NMe2)2}2]. 1,2-Bis-(diphenylphosphino)ethane (dppe; 0.2
mmol) was added to a solution of complex (1-3) (0.1 mmol) in
CDCl3 (1 mL) at 20-25 °C, and the mixture was left to stand for
1
from NMe2); 702 (m), δ(C-H from Ph). H NMR (CDCl3), δ:
7.65-7.61 (m, 4H), 7.40-7.28 (m, 6H) (Ph’s), 6.30 (s, br, 2H,
NH, {Z}-ZZ), 3.14 (s, {Z}-ZZ), 3.09 (s, {Z}-EZ), 2.91 (s, {E}-
EZ), 2.73 (s, {E}-EE) (24H, NMe2). 13C{1H} NMR (CDCl3), δ:
170.8, 163.7 (CdN), 130.6, 128.9, 127.4 (Ph’s), 40.8, 40.3 (NMe2).
Complex 2 crystallizes from a CH2Cl2:hexane (1:1, v/v) mixture
as trans-[PtCl2{NHdC(Ph)NdC(NMe2)2}2] (2) and from a CHCl3:
hexane (1:1, v/v) mixture as the monohydrate trans-[PtCl2{NHd
C(Ph)NdC(NMe2)2}2]‚H2O‚0.5CHCl3 (2b), and structures of both
2 and 2b were determined by X-ray crystallography.
Reaction of cis-[PtCl2(RCN)2] and TMG. HNdC(NMe2)2 (30
µL; 0.24 mmol) was added to a yellow suspension of cis-[PtCl2-
(MeCN)2] (0.12 mmol) in MeCN (1 mL) or a yellow solution of
cis-[PtCl2(EtCN)2] (0.12 mmol) in EtCN (1 mL). In the case of
cis-[PtCl2(MeCN)2], a pale-yellow precipitate starts to form im-
mediately. In both cases, bright yellow solutions were evaporated
to dryness. The solid residues formed were washed with two 2-mL
portions of acetone (R ) Me) or two 1.5-mL portions of a mixture
acetone:hexane ) 1:2 (R ) Et) and one 1.5-mL portion of Et2O
(R ) Me, Et) and dried in air at 20-25 °C. The washing waters
were kept in air for slow evaporation to two-thirds of the initial
volume. Released pale-yellow precipitates were separated by
decantation and washed with two 0.5-mL portions of Et2O (R )
Me) or one 0.5-mL portion of acetone:hexane ) 1:2 mixture and
one 0.5-mL portion of Et2O (R ) Et) and dried in air at 20-
25 °C. The separated compound dried in air at 20-25 °C and was
combined with the first fraction. Yields are 50 mg (72% (R ) Me))
and 43 mg (60% (R ) Et)).
20, 30, and 240 min (for 1, 2, and 3, respectively) until a colorless
6,8,9,14
precipitate of the known [Pt(dppe)2](Cl)2
(31P{1H} NMR in
CDCl3: 48.4 ppm, JPt-P 2348.5 Hz; lit.68 45.7 ppm, JPt-P 2360.5
Hz) was released. The latter complex was filtered off, and NHd
C(R)NdC(NMe2)2, liberated quantitatively, was characterized in
the filtrate by NMR and ESI-MS methods.
HNdC(Me)NdC(NMe2)2 (5). MS (ESI+) m/z: 157 [M + H]+.
1H NMR (CDCl3), δ: 2.81 (s, 12H, NMe2), 2.03 (s, 3H, Me). 13C-
{1H} NMR (CDCl3), δ: 172.1, 162.1 (CdN), 40.0 (NMe2),
25.9 (Me).
HNdC(Et)NdC(NMe2)2 (6). MS (ESI+) m/z: 171 [M + H]+.
1H NMR (CDCl3), δ: 2.80 (s, 12H, NMe2), 2.29 (q, 7.27 Hz, 2H,
CH2), 1.15 (t, 7.27 Hz, 3H, CH3) (Et). 13C{1H} NMR (CDCl3), δ:
176.0, 162.4 (CdN), 40.0 (NMe2), 32.0 (CH2), 11.8 (CH3) (Et).
HNdC(Ph)NdC(NMe2)2 (7). MS (ESI+) m/z: 219 [M + H]+.
1H NMR (CDCl3), δ: 7.35 (d, 3H), 7.29 (d, 2H) (Ph’s), 2.79 (s,
12H, NMe2). 13C{1H} NMR (CDCl3), δ: 170.4, 162.9 (CdN),
139.4 (Cipso), 130.0, 128.4, 127.9 (Ph’s), 40.0 (NMe2).
Reaction of Diazadienes 5-7 with 1,3-Di-p-tolylcarbodiimide.
Dppe (40 mg, 0.10 mmol) was added to a solution of 1-3 (0.05
mmol) in CDCl3 (1 mL), and the reaction mixture was left to stand
at 20-25 °C for 20, 30, and 240 min (for 1, 2, and 3, respectively),
whereupon the colorless precipitate of [Pt(dppe)2](Cl)2 was removed
by filtration and the filtrate was added to the suspension of 1,3-
di-p-tolylcarbodiimide (23 mg, 0.10 mmol) in CDCl3 (1 mL), and
the new reaction mixture was stirred for 20 h at 20-25 °C. The
pale-yellow (R ) Me, Et) or bright-yellow (R ) Ph) suspension
formed was evaporated to dryness. The solid residue thus obtained
was crystallized under a layer of EtOH (0.75 mL) to form pale-
yellow (R ) Me, Et) or bright-yellow (R ) Ph) precipitate, which
was filtered off after 2.5 h and washed with one 0.5-mL portion of
EtOH. Yields are 16 mg (47% (R ) Me; 8)), 17 mg (50% (R )
Et; 9)), and 21 mg (53% (R ) Ph; 10)).
cis-[PtCl2{NHdC(Me)NdC(NMe2)2}2] (3). Anal. Calcd for
C14H32N8Cl2Pt: C, 29.06; H, 5.53; N, 19.37. Found: C, 28.99; H,
5.57; N, 19.28. FAB+-MS, m/z: 601 [M + Na]+, 578 [M]+, 543
[M - Cl]+, 506 [M - 2Cl]+, 157 [NHdC(Me)NdC(NMe2)2 +
H]+. TLC: Rf ) 0.54 (eluent MeOH:CHCl3 ) 1:5). IR (KBr,
selected bands) cm-1: 3467 (br, m-w), 3257 (m-s), ν(N-H); 2925
(m), 2893 (m), 2797 (m-w), ν(C-H from Me and NMe2); 1544
(s), ν(CdN); 1484 (s), 1423 (s), 1390 (s), δ(C-H from Me and
1
NMe2). H NMR (CDCl3), δ: 6.88 (s, br, {E}-EE), 6.48 (s, br,
(6E)-N,N,4-Trimethyl-1-(4-methylphenyl)-6-[(4-methylphenyl)-
imino]-1,6-dihydro-1,3,5-triazin-2-amine (8). MS (ESI+) m/z: 334
{E}-EZ), 6.16 (s, br, {Z}-EZ and {Z}-ZZ) (2H, NH), 3.07 (s), 3.02
(s), 2.87 (s), 2.84 (s) (24H, NMe2), 2.56 (s, {E}-EE), 2.27 (s, {E}-
EZ), 2.13 (s, {Z}-EZ), 2.11 (s, {Z}-ZZ) (Me). 13C{1H} NMR
(CDCl3), δ: 173.1, 172.2, 171.5, 163.0, 162.9 (CdN), 40.6, 40.5,
40.2 (NMe2), 28.0, 27.2, 25.5, 24.0 (Me). Crystals suitable for X-ray
diffraction study were obtained by slow evaporation of a hexane:
chloroform (1:1, v/v) solution of 3.
cis-[PtCl2{NHdC(Et)NdC(NMe2)2}2] (4). Anal. Calcd for
C16H36N8Cl2Pt: C, 31.68; H, 5.94; N, 18.48. Found: C, 31.35; H,
5.93; N, 18.37. FAB+-MS, m/z: 629 [M + Na]+, 606 [M]+, 534
[M - HCl - Cl]+, 171 [NHdC(Et)NdC(NMe2)2 + H]+. TLC:
Rf ) 0.50 (eluent MeOH:CHCl3 ) 1:10). IR (KBr, selected bands)
cm-1: 3510 (br, m), 3267 (m-s), ν(N-H); 2934 (m), 2872 (m),
ν(C-H from Me and NMe2); 1544 (s), ν(CdN); 1472 (m-s), 1422
1
[M + H]+. H NMR (CDCl3), δ: 7.32 (d, 8 Hz, 2H), 7.22 (d, 8
Hz, 2H), 7.02 (d, 8 Hz, 2H), 6.88 (d, 8 Hz, 2H) (p-CH3Ph), 3.08
(s, 1H), 2.74 (s, 5H) (NMe2), 2.38 (s, 3H), 2.27 (s, 3H) (p-CH3Ph),
2.21 (s, 3H, Me). 13C{1H} NMR (CDCl3), δ: 171.4, 160.7, 150.6
(CdN), 146.6, 138.1, 137.8, 131.4 (Cipso), 129.7, 129.2, 123.3 (p-
CH3Ph), 41.2, 40.4 (NMe2), 26.4 (Me), 21.6, 21.3 (p-CH3Ph).
(6E)-4-Ethyl-N,N-dimethyl-1-(4-methylphenyl)-6-[(4-meth-
ylphenyl)imino]-1,6-dihydro-1,3,5-triazin-2-amine (9). MS (ESI+)
1
m/z: 348 [M + H]+. H NMR (CDCl3), δ: 7.33 (d, 8 Hz, 2H),
7.22 (d, 8 Hz, 2H), 7.01 (d, 8 Hz, 2H), 6.94 (d, 8 Hz, 2H) (p-
(68) Anderson, G. K.; Davies, J. A.; Schoeck, D. J. Inorg. Chim. Acta 1983,
76, L251.
Inorganic Chemistry, Vol. 46, No. 5, 2007 1691

Gushchin et al.
Table 1. Crystallographic Data for 1, 2, 2b, 3, 4, 9, 10, and 11
2b
C16H36Cl2N8Pt C24H36Cl2N8Pt C49H77Cl7N16O2Pt2 C15H33Cl5N8Pt C17H37Cl5N8Pt C21H25N5
1
2
3
4
9
10
11
empirical formula
fw
C25H25N5
395.50
120(2)
0.71073
monoclinic
P21/c
C5H14ClN3
151.64
120(2)
0.71073 Å
monoclinic
P21/n
606.52
120(2)
0.71073
monoclinic
P21/n
6.5007(2)
9.3467(4)
18.9815(6)
90
98.563(2)
90
1140.46(7)
2
1.766
6.404
9105
2618
0.0376
0.0201
0.0403
702.60
120(2)
0.71073
monoclinic
P21/c
10.4573(8)
11.2403(12)
12.2694(8)
90
112.070(7)
90
1336.5(2)
2
1560.60
120(2)
0.71073
triclinic
P1h
10.1658(8)
11.2026(8)
15.1162(10)
75.797(5)
85.330(7)
65.379(6)
1516.7(2)
1
697.83
105(2)
0.71073
monoclinic
C2/c
17.5830(8)
12.5070(7)
12.3850(4)
90
113.346(2)
90
2500.6(2)
4
725.89
120(2)
0.71073
monoclinic
C2/c
19.0947(11)
12.4624(8)
12.5981(6)
90
107.268(4)
90
2862.8(3)
4
347.46
120(2)
temp. (K)
λ (Å)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
0.71073
monoclinic
P21/n
10.2649(4)
15.1605(7)
12.3997(4)
90
104.013(3)
90
1872.23(13) 2106.56(8)
6.05060(10) 6.9690(2)
16.3902(4)
21.2859(5)
90
13.1080(4)
9.2807(3)
90
93.6880(10) 104.757(2)
90
90
819.82(4)
4
1.229
0.392
14 254
1867
0.0433
0.0286
0.0697
Z
F
4
4
calcd (mg/m3)
1.746
5.479
1.709
4.967
28 628
6936
1.854
6.165
1.684
5.389
1.233
0.076
17 497
4066
0.0452
0.0453
0.1036
1.247
0.076
50 887
4851
0.0651
0.0439
0.1007
µ(Mo KR) (mm-1
no. reflns
)
17 165
3050
0.0569
0.0253
0.0515
25 331
2868
0.0521
0.0292
0.0521
21 418
3299
0.0634
0.0303
0.0580
no. unique reflns
RInt
0.0558
R1a (I g 2σ)
wR2b (I g 2 σ)
0.0334
0.0688
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑[w(Fo - Fc )2]/∑[w(Fo )2]]1/2
.
2
2
2
Table 2. Bond Distances (Å) and Angles (deg) for 1, 2, 3 and 4
1
2
3
4
Pt(1)-N(1)
Pt(1)-Cl(1)
N(1)-C(1)
C(1)-C(2)
C(2)-C(3)
N(2)-C(1)
N(2)-C(4)
N(3)-C(4)
N(3)-C(5)
N(3)-C(6)
N(4)-C(4)
N(4)-C(7)
N(4)-C(8)
2.015(2)
2.3050(7) Pt(1)-Cl(1)
Pt(1)-N(1)
2.009(3)
2.2999(9) Pt(1)-Cl(1)
Pt(1)-N(1)
1.995(3)
2.3102(11) Pt(1)-Cl(1)
Pt(1)-N(1)
2.001(3)
2.3187(9)
1.300(5)
1.518(5)
1.503(6)
1.334(5)
1.317(5)
1.352(5)
1.443(5)
1.456(5)
1.347(5)
1.452(5)
1.458(5)
94.94(18)
177.27(10)
87.19(9)
90.73(5)
131.7(3)
118.5(3)
127.4(4)
113.8(3)
126.8(3)
124.0(4)
120.6(3)
122.1(4)
115.1(3)
117.8(4)
119.2(3)
123.5(4)
113.9(3)
117.6(3)
1.296(3)
1.503(3)
1.528(4)
1.357(3)
1.326(3)
1.361(3)
1.458(4)
1.467(3)
1.358(3)
1.457(3)
1.463(3)
180.00(12)
91.07(7)
N(1)-C(1)
N(2)-C(1)
N(2)-C(8)
N(3)-C(8)
N(3)-C(9)
N(3)-C(10)
N(4)-C(8)
N(4)-C(11)
N(4)-C(12)
1.305(4)
1.346(4)
1.324(4)
1.346(4)
1.453(5)
1.464(5)
1.355(4)
1.476(4)
1.441(4)
N(1)-C(1)
C(1)-C(2)
N(2)-C(1)
N(2)-C(3)
N(3)-C(3)
N(3)-C(4)
N(3)-C(5)
N(4)-C(3)
N(4)-C(6)
N(4)-C(7)
1.300(5)
1.500(7)
1.332(7)
1.308(7)
1.361(7)
1.451(7)
1.450(7)
1.350(7)
1.447(8)
1.453(8)
N(1)-C(1)
C(1)-C(2)
C(2)-C(3)
N(2)-C(1)
N(2)-C(4)
N(3)-C(4)
N(3)-C(5)
N(3)-C(6)
N(4)-C(4)
N(4)-C(7)
N(4)-C(8)
N(1)-Pt(1)-N(1A)
N(1)-Pt(1)-Cl(1)
N(1)-Pt(1)-Cl(1A)
Cl(1)-Pt(1)-Cl(1A)
C(1)-N(1)-Pt(1)
N(1)-C(1)-C(2)
N(1)-C(1)-N(2)
N(2)-C(1)-C(2)
C(4)-N(2)-C(1)
N(2)-C(4)-N(3)
C(4)-N(3)-C(5)
C(4)-N(3)-C(6)
C(5)-N(3)-C(6)
N(2)-C(4)-N(4)
C(4)-N(4)-C(7)
C(4)-N(4)-C(8)
C(7)-N(4)-C(8)
N(4)-C(4)-N(3)
N(1)-Pt(1)-N(1A)
N(1)-Pt(1)-Cl(1A)
N(1)-Pt(1)-N(1A)
N(1)-Pt(1)-Cl(1A)
Cl(1)-Pt(1)-Cl(1A) 179.999(1)
179.998(1)
92.92(9)
N(1)-Pt(1)-N(1)
N(1)-Pt(1)-Cl(1)
N(1)-Pt(1)-Cl(1)
Cl(1)-Pt(1)-Cl(1)
C(1)-N(1)-Pt(1)
N(1)-C(1)-C(2)
N(1)-C(1)-N(2)
N(2)-C(1)-C(2)
C(3)-N(2)-C(1)
N(2)-C(3)-N(3)
C(3)-N(3)-C(4)
C(3)-N(3)-C(5)
C(5)-N(3)-C(4)
N(2)-C(3)-N(4)
C(3)-N(4)-C(6)
C(3)-N(4)-C(7)
C(6)-N(4)-C(7)
N(4)-C(3)-N(3)
97.03(19)
176.53(10)
86.37(10)
90.24(6)
133.1(4)
119.0(5)
126.6(5)
114.2(4)
126.4(4)
124.5(5)
119.9(5)
122.3(4)
115.4(5)
119.0(6)
123.0(6)
118.0(6)
115.7(6)
116.1(6)
Cl(1)-Pt(1)-Cl(1A) 180.0
C(1)-N(1)-Pt(1)
N(1)-C(1)-C(2)
N(1)-C(1)-N(2)
N(2)-C(1)-C(2)
C(4)-N(2)-C(1)
N(2)-C(4)-N(3)
C(4)-N(3)-C(5)
C(4)-N(3)-C(6)
C(5)-N(3)-C(6)
N(2)-C(4)-N(4)
C(4)-N(4)-C(7)
C(4)-N(4)-C(8)
C(7)-N(4)-C(8)
N(4)-C(4)-N(3)
130.76(17)
C(1)-N(1)-Pt(1)
N(1)-C(1)-C(2)
N(1)-C(1)-N(2)
N(2)-C(1)-C(2)
C(8)-N(2)-C(1)
N(2)-C(8)-N(3)
C(8)-N(3)-C(9)
C(8)-N(3)-C(10)
C(9)-N(3)-C(10)
N(2)-C(8)-N(4)
C(8)-N(4)-C(11)
C(8)-N(4)-C(12)
C(12)-N(4)-C(11)
N(3)-C(8)-N(4)
135.3(2)
119.3(3)
125.7(3)
114.9(3)
125.9(3)
118.5(3)
119.2(3)
122.1(3)
114.5(3)
123.4(3)
122.3(3)
121.1(3)
114.1(3)
117.6(3)
119.7(2)
124.9(2)
115.2(2)
123.7(2)
118.2(2)
118.7(2)
122.4(2)
114.7(2)
124.8(2)
123.3(2)
121.5(2)
114.5(2)
116.9(2)
CH3Ph), 3.10 (s, 1H), 2.75 (s, 5H) (NMe2), 2.46 (q, 7.27 Hz, 2H,
CH2 from Et), 2.39 (s, 3H), 2.27 (s, 3H) (p-CH3Ph), 1.22 (t, 7.27
Hz, 3H, CH3 from Et). 13C{1H} NMR (CDCl3), δ: 175.1, 160.9,
150.9 (CdN), 146.4, 138.0, 137.8, 131.4 (Cipso), 129.7, 129.2, 129.1,
123.7 (p-CH3Ph), 41.3, 40.4 (NMe2), 32.5 (CH2 from Et), 21.6,
21.3 (p-CH3Ph), 11.6 (CH3 from Et). Crystals suitable for X-ray
single-crystal diffraction study were obtained by slow evaporation
of a toluene:chloroform (1:1, v/v) solution of 9.
7.39 (m, 5H), 7.26 (t, 2H), 7.08 (s, 4H) (p-CH3Ph), 3.18 (s, 1H),
2.87 (s, 5H) (NMe2), 2.41 (s, 3H), 2.33 (s, 3H) (p-CH3Ph). 13C-
{1H} NMR (CDCl3), δ: 165.3, 161.4, 151.2 (CdN), 146.6, 138.2,
137.8, 137.3, 131.4 (Cipso), 131.8, 129.8, 129.4, 129.3, 129.0, 128.4,
124.0 (p-CH3Ph), 41.5, 40.5 (NMe2), 21.6, 21.3 (p-CH3Ph). Crystals
suitable for X-ray diffraction study were obtained by slow evapora-
tion of a toluene:chloroform (1:1, v/v) solution of 10.
For comparison of X-ray data we prepared crystals of TMG‚
HCl (11) and determined its X-ray structure.
X-ray Structure Determinations. Crystals were immersed in
cryo-oil, mounted in a nylon loop, and measured at a temperature
(6E)-N,N-Dimethyl-1-(4-methylphenyl)-6-[(4-methylphenyl)-
imino]-4-phenyl-1,6-dihydro-1,3,5-triazin-2-amine (10). MS (ESI+)
1
m/z: 396 [M + H]+. H NMR (CDCl3), δ: 8.33 (d, 2H), 7.49-
1692 Inorganic Chemistry, Vol. 46, No. 5, 2007

PtII-Mediated Nitrile-Tetramethylguanidine Coupling
Table 3. Bond Distances (Å) and Angles (deg) for 9 and 10
0.9894, 0.9763/0.9921, and 0.9222/0.9414, respectively, for 1, 2,
2b, 3, 4, 9, 10, and 11). Structural refinements were carried out
using SHELXL-9777 with WinGX78 graphical user interface.
Complex 2 was crystallized without and with solvent of crystal-
lization in two different space groups P21/c (2) and P1h (2b). The
NH, NH2, and H2O hydrogens were located from the difference
Fourier map and either refined isotropically (2) or constrained to
ride on their parent atoms. Other hydrogens were positioned
geometrically and constrained to ride on their parent atoms. The
asymmetric unit of 2b contains two independent halves of the Pt
complexes. In all Pt structures, Pt atoms are coordinated by two
Cl atoms and two N atoms in a slightly distorted square planar
geometry. The CHCl3 solvent molecule in 2b is disordered over
two positions with two shared Cl atoms and equal occupation
parameters of 0.5. Also, in 3 the hydrogen and chlorine atoms of
the CHCl3 solvent are disordered over two positions with equal
occupation parameters of 0.5. In 4, the CHCl3 solvent molecule
was refined over two positions with equal occupancy of 0.5. The
crystallographic details are summarized in Table 1. The selected
bond lengths and angles are given in the figure captions and Tables
2 and 3.
bonds and angles
9
10
N(1)-C(1)
1.312(2)
1.349(2)
1.330(2)
1.345(2)
1.465(2)
1.465(2)
1.378(2)
1.450(2)
1.429(2)
1.3154(18)
1.3471(18)
1.3329(18)
1.3403(18)
1.4664(19)
1.4665(17)
1.3777(18)
1.4443(17)
1.4332(17)
1.2811(18)
1.4148(18)
1.3714(17)
127.44(12)
116.48(12)
117.43(12)
117.79(12)
114.22(11)
126.03(12)
121.44(12)
121.12(12)
123.22(11)
117.66(11)
118.49(11)
116.21(12)
120.41(12)
125.79(13)
118.00(12)
117.11(12).
N(2)-C(1)
N(2)-C(8)
N(4)-C(8)
N(4)-C(9)
N(4)-C(10)
N(3)-C(8)
N(3)-C(11)
N(3)-C(18)
N(5)-C(18)
1.290(2)
1.409(2)
1.370(2)
N(5)-C(19)
N(1)-C(18)
N(1)-C(1)-N(2)
C(8)-N(2)-C(1)
N(2)-C(8)-N(4)
C(8)-N(4)-C(9)
C(9)-N(4)-C(10)
C(8)-N(4)-C(10)
N(4)-C(8)-N(3)
N(2)-C(8)-N(3)
C(8)-N(3)-C(11)
C(18)-N(3)-C(11)
C(8)-N(3)-C(18)
N(5)-C(18)-N(3)
C(18)-N(5)-C(19)
N(5)-C(18)-N(1)
N(1)-C(18)-N(3)
C(1)-N(1)-C(18)
127.52(15)
116.09(14)
117.97(14)
118.20(15)
114.30(13)
125.31(14)
120.55(15)
121.46(14)
122.36(13)
117.14(12)
118.88(13)
115.40(14)
122.29(14)
126.60(14)
117.99(13)
117.29(13).
Acknowledgment. This work has been supported by the
Russian Fund for Basic Research (grants 05-03-32140, 06-
03-32065, and 06-03-90901), the Scientific Council of the
President of the Russian Federation (grant MK-1040.2005.3),
the Government of St. Petersburg (grant 46/06), and the
Academy of Finland (grant 110465). We thank Dr. S. I.
Selivanov for experimental assistance, Dr. A. V. Makary-
cheva-Mikhailova for valuable discussions, and Prof. A. J.
L. Pombeiro for putting IR facilities at the author’s disposal.
of 105-120 K. X-ray diffraction data was collected by means of
a Nonius KappaCCD diffractometer using Mo KR radiation (λ )
0.71073 Å). The DENZO/SCALEPACK69 or EvalCCD70 program
packages were used for cell refinements and data reductions. All
of the structures were solved by direct methods using
SHELXS-97,71 SIR-97,72 SIR2002,73 or SIR2004.74 An empirical
absorption correction was applied to all of the data (XPREP in
SHELXTL75 or SADABS;76 Tmax/Tmin were 0.2226/0.3371, 0.4048/
0.7199, 0.4048/0.7199, 0.2950/0.7818, 0.4672/0.7273, 0.9870/
Note Added after ASAP Publication: This article was
released ASAP on February 1, 2007 with minor errors in
the Title. The correct version was posted on February 12,
2007.
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Supporting Information Available: Figures S1 and S3 with
thermal ellipsoid views of 2b and 11, respectively, Figures S2, S4,
and S5 with hydrogen-bonding schemes for 2b, 3, and 4, Tables
S1-S3 with hydrogen bonds for 2b, 3, and 4, and X-ray
crystallographic files in CIF format. This material is available free
of charge via the Internet at http://pubs.acs.org.
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