Nitrile-amidine coupling at Pt(IV) and Pt(II) centers. An easy entry to imidoylamidine complexes

Article abstract of DOI:10.1021/ic050037q

Treatment of trans-[PtCl₄(RCN)₂] (R = Me, Et, Ph, NEt₂) with 2 equiv of the amidine PhC(=NH)NHPh in a suspension of MeCN (R = Me), CHCl₃ (R = Et, Ph), or in CHCl₃ solution (R = NEt₂) results in the formation of the imidoylamidine complexes trans-[PtCl₄{NH=C(R)N=C(Ph)NHPh}₂] (1-4) isolated in good yields (66-84%). The reaction of soluble complexes 3 and 4 with 2 equiv of Ph₃P=CHCO₂Me in CH₂Cl₂ (40°C, 5 h) leads to dehydrochlorination resulting in a chelate ring closure to furnish the platinum(IV) chelates [PtCl₂{NH=C(R)NC(Ph)=NPh}₂] (R = Ph, 5; R = NEt₂, 6), accordingly, and the phosphonium salt [Ph ₃PCH₂CO₂Me]Cl. Treatment of 5 with 3 equiv of Ph₃P=CHCO₂-Me at 50°C for 5 d resulted in only a 30% conversion to the corresponding Pt(II) complex [Pt{NH=C(NEt₂)NC-(Ph)= NPh}₂] (15). The reduction can be achieved within several minutes, when Ph₂PCH₂CH₂PPh₂ in CDCl ₃ is used. When the platinum(II) complex trans-[PtCl ₂(RCN)₂] is reacted with 2 equiv of the amidine, the imidoylamidinato complexes [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) and [PhC(=NH)NHPh]·HCl (7) are formed. The reaction of trans-[PtCl ₂(RCN)₂] with 4 equiv of the amidine under a prolonged reaction time or treatment of [PtCl(RCN)-{NH=C(R)NC(Ph)=NHPh}] (8-11) with 2 more equiv of the amidine yields the complex bearing two chelate rings [Pt{NH=C(R)NC(Ph)=NHPh}₂] (12-15). The treatment of cis-[PtCl ₂(RCN)₂] (R = Me, Et) with the amidine gives ca. 50-60% yield of [PtCl₂{NH=C(R)NHC(Ph)=MHPh}] (16 and 17). All of the platinum compounds were characterized by elemental analyses; FAB mass spectrometry; IR spectroscopy; ¹H, ¹³C{¹H}, and ¹⁹⁵Pt NMR spectroscopies, and four of them (4, 6, 8, and 15) were also characterized by X-ray crystallography. The coupling of the Pt-bound nitriles and the amidine is metal-mediated insofar as RCN and PhC(=NH)NHPh do not react in the absence of the metal centers in conditions more drastic than those of the observed reactions. The nitrile-amidine coupling reported in this work constitutes a route to the synthesis of imidoylamidine complexes, some of them exhibiting luminescent properties.

Full text of DOI:10.1021/ic050037q

Inorg. Chem. 2005, 44, 5152−5160
Nitrile−Amidine Coupling at Pt(IV) and Pt(II) Centers. An Easy Entry to
Imidoylamidine Complexes
Nadezhda A. Bokach,†,‡ Tatyana V. Kuznetsova,§ Svetlana A. Simanova,§ Matti Haukka,|
Armando J. L. Pombeiro,*,‡ and Vadim Yu. Kukushkin*,†
St. Petersburg State UniVersity, 198504 Stary Petergof, Russian Federation, Centro de Qu´ımica
Estrutural, Complexo I, Instituto Superior Te´cnico, AV. RoVisco Pais, 1049-001 Lisbon, Portugal,
Department of Chemistry, Inorganic Chemistry, St. Petersburg State Technological Institute,
198013 St. Petersburg, Russian Federation, and Department of Chemistry, UniVersity of Joensuu,
P.O. Box 111, FIN-80101 Joensuu, Finland
Received January 11, 2005
Treatment of trans-[PtCl4(RCN)2] (R
of MeCN (R Me), CHCl3 (R Et, Ph), or in CHCl3 solution (R
complexes trans-[PtCl4 NH C(R)N C(Ph)NHPh 2] (1 4) isolated in good yields (66
complexes 3 and 4 with 2 equiv of Ph3P CHCO2Me in CH2Cl2 (40 C, 5 h) leads to dehydrochlorination resulting
in a chelate ring closure to furnish the platinum(IV) chelates [PtCl2
NEt2, 6), accordingly, and the phosphonium salt [Ph3PCH2CO2Me]Cl. Treatment of 5 with 3 equiv of Ph3P
Me at 50 C for 5 d resulted in only a 30% conversion to the corresponding Pt(II) complex [Pt NH
(Ph) NPh 2] (15). The reduction can be achieved within several minutes, when Ph2PCH2CH2PPh2 in CDCl3 is
used. When the platinum(II) complex trans-[PtCl2(RCN)2] is reacted with 2 equiv of the amidine, the imidoylamidinato
complexes [PtCl(RCN) NH C(R)NC(Ph) NHPh ] (8 11) and [PhC( NH)NHPh] HCl (7) are formed. The reaction
of trans-[PtCl2(RCN)2] with 4 equiv of the amidine under a prolonged reaction time or treatment of [PtCl(RCN)-
NH C(R)NC(Ph) NHPh ] (8 11) with 2 more equiv of the amidine yields the complex bearing two chelate rings
[Pt NH C(R)NC(Ph) NHPh 2] (12 15). The treatment of cis-[PtCl2(RCN)2] (R Me, Et) with the amidine gives
ca. 50 60% yield of [PtCl2 NH C(R)NHC(Ph) NHPh ] (16 and 17). All of the platinum compounds were
characterized by elemental analyses; FAB mass spectrometry; IR spectroscopy; 1H, 13C 1H , and 195Pt NMR
spectroscopies, and four of them (4, 6, 8, and 15) were also characterized by X-ray crystallography. The coupling
of the Pt-bound nitriles and the amidine is metal-mediated insofar as RCN and PhC( NH)NHPh do not react in
the absence of the metal centers in conditions more drastic than those of the observed reactions. The nitrile
)
Me, Et, Ph, NEt2) with 2 equiv of the amidine PhC(
NEt2) results in the formation of the imidoylamidine
84%). The reaction of soluble
dNH)NHPh in a suspension
)
)
)
{
d
d
}
−
−
d
°
{
NHdC(R)NC(Ph)
d
NPh}
2] (R
)
Ph, 5; R
)
dCHCO2-
°
{
dC(NEt2)NC-
d
}
{
d
d
}
−
d
‚
{
d
d
}
−
{
d
d
}
−
)
−
{
d
d
}
{
}
d
−
amidine coupling reported in this work constitutes a route to the synthesis of imidoylamidine complexes, some of
them exhibiting luminescent properties.
Introduction
focused, in particular, on nucleophilic additions to ligands
in (RCN)[M] complexes, and this topic has been the subject
of comprehensive reviews and books,1 including recent
surveys by some of us.2-5 The analysis of experimental
material collected to date1-5 shows that the largest fraction
of works in this area is devoted to the creation of the C-N
bond by the addition of ammonia and amines, hydrazines,
and hydroxylamines as well as by the coupling of some
nitrogen heterocycles with ligated RCN species;2 for recent
examples, see ref 6.
The wealth of ligand reactivity patterns exhibited by metal-
bound RCtN species and their useful applications (e.g., the
usage of nitriles as versatile synthons for the preparation of
new compounds via C-O, C-N, C-C, C-P, and C-S bond
making and the metal-catalyzed hydrolytic transformation
of RCN species to amides of industrial and pharmacological
significance) have triggered a large amount of studies
* To whom correspondence should be addressed. E-mail: pombeiro@
ist.utl.pt (A.J.L.P.); kukushkin@VK2100.spb.edu (V.Yu.K.).
† St. Petersburg State University.
Despite the great number of examples of the metal-
mediated RCN-amine integration, only a few reports deal
with nitrile-imine (or heteroimine) coupling. Thus, all
‡ Instituto Superior Tec´nico.
§ St. Petersburg State Technological Institute.
| University of Joensuu.
5152 Inorganic Chemistry, Vol. 44, No. 14, 2005
10.1021/ic050037q CCC: $30.25
© 2005 American Chemical Society
Published on Web 06/07/2005

Nitrile-Amidine Coupling at Pt(IV) and Pt(II) Centers
Scheme 1
studies known to date include platinum-mediated nitrile-
imine coupling with the imines HNdER′R′′ (E ) C, R′ )
R′′ ) Ph;7 E ) S, R′/R′′ ) aryls;8,9 E ) C, R′/R′′ ) Alkyl/
OAlkyl10) to give products of the type HNdC(R)-
NdER′R′′2, which are difficult to obtain by conventional
organic synthesis. Our current interest in the addition of
imines to complexed nitriles has recently been sparked by
the discovery of two unusual reactions mediated jointly by
a Ni(II) center and a ketoxime (e.g., Me2CdNOH; Scheme
1), that is, the formation of imidoylamidines11 (top) and
phthalocyanines12 (bottom). The triaza fragment of the two
molecules shown in bold could be, at least formally,
considered as derived from nitrile-amidine coupling, which,
however, was not observed.
Hence, we now have to extend our investigations of
reactions of metal-activated nitriles, in general,2-5 and of
nitrile-imine coupling, in particular,7,9,10 to studies of the
coupling between complexed nitriles and amidines. For this
work, we addressed, on one hand, the kinetically inert
(relative to other nitrile metal compounds) (nitrile)Pt(II and
IV) complexes [PtCln(RCN)2] (n ) 2, 4), which proved to
be superior models for investigations of the additions to
nitriles, and, on the other hand, the easily accessible13 and
soluble solid amidine HNdC(Ph)NHPh, which can be
handled as a stable free base. Our interest in studying the
addition of the latter to the former was three-fold: (i) to
observe nitrile coupling with a nucleophile of a novel type,
that is, amidine; (ii) to verify the effect of the oxidation state
of the Pt center on the addition of amidines to coordinated
nitriles; and (iii) to develop an understanding of the mech-
anism for the formation of imidoylamidines and phthalo-
cyanines at a Ni(II) center.
(1) Michelin, R. A.; Mozzon, M.; Bertani, R. Coord. Chem. ReV. 1996,
147, 299. Eglin, J. Comments Inorg. Chem. 2002, 23, 23. Murahashi,
S. I.; Takaya, H. Acc. Chem. Res. 2000, 33, 225. Kukushkin, Yu. N.
Russ. J. Coord. Chem. 1998, 24, 173. Parkins, A. W.; Platinum Met.
ReV. 1996, 40, 169. da Rocha, Z. N.; Chiericato, G., Jr.; Tfouni, E.
AdV. Chem. Ser. 1997, 297. Kuznetsov, M. L. Usp. Khim. (Russ. Chem.
ReV.) 2002, 71, 307. Constable, E. C. Metals and Ligand ReactiVity.
An Introduction to the Organic Chemistry of Metal Complexes;
VCH: Weinheim, Germany, 1995; p 65. Corain, B.; Basato, M.;
Veronese, A. C. J. Mol. Catal. 1993, 81, 133. Chin, J. Acc. Chem.
Res. 1991, 24, 145. Eloy, F.; Lenaers, R. Chem. ReV. 1962, 62, 155.
Zilberman, E. N. Reactions of Nitriles, in Russian; Khimia: Moscow,
1972; p 166. Dayagi, S.; Degani, Y. In The Chemistry of the Carbon-
Nitrogen Double Bond; Patai, S., Ed.; Interscience: London, 1970; p
111.
Results and Discussion
Nitrile-Amidine Coupling at a Pt(IV) Center. Treat-
ment of the platinum(IV) complexes trans-[PtCl4(RCN)2] (R
) Me, Et, Ph, NEt2) with 2 equiv of the amidine PhC(dNH)-
NHPh (Scheme 2) in a suspension of MeCN (R ) Me),
CHCl3 (R ) Et, Ph), or in a CHCl3 solution (R ) NEt2) in
the temperature range from 25 to 40 °C for 1-7 h (reaction
time depends mostly on solubility of the starting material)
results in the formation of the imidoylamidine complexes
trans-[PtCl4{NHdC(R)NdC(Ph)NHPh}2] (1-4) isolated in
good yields (66-84%). The reaction failed only in the case
of [PtCl4(PhCH2CN)2], where the formation of a broad
mixture of products, which were not separated, was observed.
Complexes 1-4 gave satisfactory C, H, and N elemental
analyses and the expected molecular ion/fragmentation
patterns (typically [M - nCl]+, n ) 1-4) in FAB+ mass
spectra. These four compounds were also characterized by
(2) Kukushkin, V. Yu.; Pombeiro, A. J. L. Chem. ReV. 2002, 102, 1771.
(3) Pombeiro, A. J. L.; Kukushkin, V. Yu. Reactions of Coordinated
Nitriles. In ComprehensiVe Coordination Chemistry, second edition;
Elsevier: New York, 2003, Chapter 1.34, Vol. 1, pp 639-660.
(4) Kukushkin, V. Yu.; Pombeiro, A. J. L. Inorg. Chim. Acta 2005, 358, 1.
(5) Bokach, N. A.; Kukushkin, V. Yu. Usp. Khim. (Russ. Chem. ReV.)
2005, 74, 164.
(6) Zhang, J. P.; Zheng, S. L.; Huang, X. C.; Chen, X. M. Angew. Chem.,
Int. Ed. 2004, 43, 206. Kumagai, N.; Matsunaga, S.; Shibasaki, M. J.
Am. Chem. Soc. 2004, 126, 13632. Fomina, I. G.; Sidorov, A. A.;
Aleksandrov, G. G.; Mikhailova, T. B.; Pakhmutova, E. V.; Novo-
tortsev, V. M.; Ikorskii, V. N.; Eremenko, I. L. Russ. Chem. Bull.
2004, 53, 1477. Makarycheva-Mikhailova, A. V.; Kukushkin, V. Yu.;
Nazarov, A. A.; Garnovskii, D. A.; Pombeiro, A. J. L.; Haukka, M.;
Keppler, B. K.; Galanski, M. Inorg. Chem. 2003, 42, 2805. Kollipara,
M. R.; Sarkhel, P.; Chakraborty, S.; Lalrempuia, R. J. Coord. Chem.
2003, 56, 1085. 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. Makarycheva-
Mikhailova, A. V.; Tronova, E. A.; Kukushkin, V. Yu. Russ. Chem.
Bull. 2005, in press.
(7) Garnovskii, D. A.; Kukushkin, V. Yu.; Haukka, M.; Wagner, G.;
Pombeiro, A. J. L. J. Chem. Soc., Dalton Trans. 2001, 560.
(8) Kelly, P. F.; Slawin, A. M. Z. Chem. Commun. 1999, 1081. Kelly, P.
F.; Slawin, A. M. Z. Eur. J. Inorg. Chem. 2001, 263.
1
IR and H, 13C{1H}, and 195Pt NMR spectroscopies and
(complex 4; see below) by X-ray crystallography.
(9) Makarycheva-Mikhailova, A. V.; Bokach, N. A.; Kukushkin, V. Yu.;
Kelly, P. F.; Gilby, L. M.; Kuznetsov, M. L.; Holmes, K. E.; Haukka,
M.; Parr, J.; Stonehouse, J. M.; Elsegood, M. R. J.; Pombeiro, A. J.
L. Inorg. Chem. 2003, 42, 301. Makarycheva-Mikhailova, A. V.;
Selivanov, S. I.; Bokach, N. A.; Kukushkin, V. Yu.; Kelly, P. F.;
Pombeiro, A. J. L. Russ. Chem. Bull. 2004, 1618.
(10) Bokach, N. A.; Kukushkin, V. Yu.; Haukka, M.; Frau´sto da Silva, J.
J. R.; Pombeiro, A. J. L. Inorg. Chem. 2003, 42, 3602.
(11) Kopylovich, M. N.; Pombeiro, A. J. L.; Fischer, A.; Kloo, L.;
Kukushkin, V. Yu. Inorg. Chem. 2003, 42, 7239.
In the IR spectra, 1-4 exhibit one strong band in the range
from 1645 to 1656 cm-1, which corresponds to ν(NdC)
stretching vibrations of the monodentately coordinated imi-
doylamidine species, and another band of ν(NdC) appears
on the interval between 1531 and 1537 cm-1 and overlaps
with ν(CdC) vibrations. Because of a very low solubility, 2
was characterized only by 1H NMR, whereas 1 is so poorly
(12) Kopylovich, M. N.; Kukushkin, V. Yu.; Haukka, M.; Luzyanin, K.
V.; Pombeiro, A. J. L. J. Am. Chem. Soc. 2004, 126, 15040.
(13) Cooper, F.; Partridg, M. Org. Synth. 1958, 36, 62.
Inorganic Chemistry, Vol. 44, No. 14, 2005 5153

Bokach et al.
Scheme 2
Figure 1. Thermal ellipsoid view of complex 4 with atomic numbering
scheme. Thermal ellipsoids are drawn at 50% probability. Selected bond
lengths (Å) and angles (deg): Pt(1)-N(1) 2.036(4), Pt(1)-Cl(2) 2.3095(11),
Pt(1)-Cl(1) 2.3249(11), N(1)-C(1) 1.301(6), N(1)-Pt(1)-N(1A) 180,
N(1)-Pt(1)-Cl(1) 89.15(11), N(1)-Pt(1)-Cl(2) 82.58(12), Pt(1)-N(1)-
C(1) 134.1(3).
soluble that it was not characterized even by the latter
method. Complexes 3 and 4, which are sufficiently soluble
in the common deuterated solvents, were characterized by
1H, 13C{1H}, and 195Pt NMR spectroscopies. In the 195Pt
spectra, both 3 and 4 exhibit two signals, which are probably
due to their existence in two configurations; these signals
are unlikely due to cis and trans isomers because (i) 3 and
4 were derived from the isomerically pure trans-[PtCl4-
(RCN)2] and subsequent trans-to-cis isomerization is unlikely
for octahedral Pt(IV) complexes14 and (ii) both 3 and 4
display only one spot each on thin layer chromatography
(TLC), whereas the geometric isomers of Pt complexes are
usually strongly different in Rf values. All signals from the
(NHPh)2}],17 and [Co(NH3)5{NHdC(NH2)NMe2}]2+,18 where
the guanidine ligands have distinct single and double CN
bonds with no electron delocalization.
Dehydrochlorination of 3 and 4. In coordination
chemistry, the carbonyl-stabilized phosphorus ylides
Ph3PdCHCO2R display two principal reactivity modes; that
is, they act as C-donor ligands toward metal centers19 and
as nucleophiles in the addition to metal-activated organoni-
triles20 and alkenes.21 Rather recently, we discovered an
efficient method for the generation of (imine)Pt(II) com-
pounds that involves reduction (i.e., a third reactivity pattern
of the ylides in coordination chemistry) of the corresponding
readily available Pt(IV)-based imines by Ph3PdCHCO2R in
nonaqueous media.22 We attempted to apply the latter
technique to the reduction of 3 and 4 (low solubility of 1
and 2 precluded our endeavors) and treated these complexes
with 2 equiv of Ph3PdCHCO2Me in CH2Cl2 (40 °C, 5 h).
In contrast to our expectations, instead of the reduction, we
observed the dehydrochlorination of 3 and 4, resulting in
chelate ring closure (Scheme 2) to furnish 5 and 6,
respectively, and the phosphonium salt [Ph3PCH2CO2Me]-
1
imidoylamidine ligand in the H NMR spectrum of 4 are
broad because of exchange processes in the coordinated
NHdC(NEt2)NdC(Ph)NHPh species such as, for example,
dynamic E-Z isomerization observed recently, by some of
us, in other Pt(IV)-bound diazadiene species.9
In the solid state, complex 4 has two imidoylamidine
ligands in the mutually trans position and both are in Z
configuration (Figure 1).
In the (Z)-NHdC(NEt2)-NdC(Ph)-NHPh fragment, the
NdC bond lengths [N(1)-C(1) and N(3)-C(6), 1.301(6)
and 1.298(6) Å, respectively] correspond, within 3σ, to the
typical double NdC bonds [1.279(8) Å in CAr-CdN-C15],
whereas the N(3)-C(1) [1.365(6) Å], N(4)-C(6) [1.331(6)
Å], and N(2)-C(1) [1.357(6) Å] distances belong to the
typical single N-C bonds [e.g., Nsp2-Csp2 in amides
1.346(11) Å15]. All of these observations demonstrate the
absence of electron delocalization in the imine ligand. A
similar phenomenon has been observed in the guanidine
complexes [PtI2{NHdC(NEt2)2}(NHEt2)],16 [PdCl2{NPhdC-
(16) Fehlhammer, W. P.; Metzner, R.; Sperber, W. Chem. Ber. 1994, 127,
829.
(17) Mincheva, N.; Todorov, T.; Angelova, O.; Bailey, P. J.; Miteva, M.
J. Coord. Chem. 2000, 60, 169.
(18) Fairlie, D. P.; Jackson, W. G.; Skelton, B. W.; Wen, H.; White, A.
H.; Wickramasinghe, W. A.; Woon, T. C.; Taube, H. Inorg. Chem.
1997, 36, 1020.
(19) Bokach, N. A.; Selivanov, S. I.; Kukushkin, V. Yu.; Vicente, J.;
Haukka, M.; Pombeiro, A. J. L. Organometallics 2002, 21, 3744.
(20) Vicente, J.; Chicote, M. T.; Beswick, M. A.; Ramirez de Arellano,
M. C. Inorg. Chem. 1996, 35, 6592. Vicente, J.; Chicote, M. T.;
Lagunas, M. C.; Jones, P. G. Inorg. Chem. 1995, 34, 5441. Vicente,
J.; Chicote, M. T.; Ferna´ndez-Baeza, J.; Lahoz, F. Inorg. Chem. 1991,
30, 3617.
(21) Vicente, J.; Chicote, M. T.; MacBeath, C.; Ferna´ndez-Baeza, J.;
Bautista, D. Organometallics, 1999, 18, 2677.
(22) Wagner, G.; Pakhomova, T. B.; Bokach, N. A.; Frau´sto da Silva, J. J.
R.; Vicente, J.; Pombeiro, A. J. L.; Kukushkin, V. Yu. Inorg. Chem.
2001, 40, 1683.
(14) Kukushkin, V. Yu. Zh. Neorg. Khim. 1988, 33, 1905; Russ. J. Inorg.
Chem. 1988, 33, 1085.
(15) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A.
G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1.
5154 Inorganic Chemistry, Vol. 44, No. 14, 2005

Nitrile-Amidine Coupling at Pt(IV) and Pt(II) Centers
C(1)-N(3)#1, 8.4(4); Pt(1)-N(4)-C(6)-N(3), 18.6(4); and
C(1)#1-N(3)-C(6)-N(4), 7.1(5); the maximum deviation
of the N(1) atom from the plane Pt(1)N(1)C(1)N(3)C(6)N(4)
is 0.196(3) Å [N(1), -0.145(3) Å; N(3), -0.159(3) Å], and
the root mean square of the deviations from the plane is
0.203(3) Å.
Hence, in the reaction with 3 and 4, the phosphorus ylide
Ph3PdCHCO2Me abstracts HCl, acting as a base, and this
reactivity mode is the fourth one observed in coordination
chemistry for the carbonyl-stabilized phosphorus ylides.
Nitrile-Amidine Coupling at a Pt(II) Center. The route
of the reaction between the platinum(II) complexes [PtCl2-
(RCN)2] and the amidine PhC(dNH)NHPh depends on the
cis/trans configuration of the starting metal complex (Scheme
3, A24), the molar ratio of the reactants, and the reaction time.
In this section, we will consider first the nitrile-amidine
coupling at trans-[PtCl2(RCN)2] (R ) Et, Ph, CH2Ph, NEt2;
the acetonitrile complex was not employed because of its
very poor solubility), whereupon the coupling with the
nitriles in cis-[PtCl2(RCN)2] (R ) Me, Et) will be described.
When trans-[PtCl2(RCN)2] was reacted with 2 equiv of the
amidine (Scheme 3, B), two products were isolated from the
reaction mixture. The first one corresponds to the addition
of one amidine to the nitrile C atom of trans-[PtCl2(RCN)2]
and the ring closure of the imidoylamidinato ligand formed
in the metal-mediated reaction, that is, [PtCl(RCN)-
{NHdC(R)NC(Ph)dNPh}] (8-11); another product released
from the reaction mixture is the hydrochloride [PhC(dNH)-
NHPh]‚HCl (7; characterized by FAB+ MS and X-ray
crystallography, see Experimental Section and the Supporting
Information). When trans-[PtCl2(RCN)2] reacts with 4 equiv
of the amidine under a prolonged reaction time (Scheme 3,
C) or [PtCl(RCN){NHdC(R)NC(Ph)dNPh}] (8-11) is treat-
ed with 2 more equiv of the amidine (Scheme 3, D), the
complex bearing two chelate rings [Pt{NHdC(R)NC-
(Ph)dNPh}2] (12-15) is formed. We discovered that the
latter group of complexes represents a new class of efficient
Pt-based luminophores showing pH-dependent phosphores-
cence previously not recognized by others.25 These results
include the photophysical properties of [Pt{NHdC(R)NC-
(Ph)dNPh}2].26
Figure 2. Thermal ellipsoid view of complex 6 with atomic numbering
scheme. Thermal ellipsoids are drawn at 50% probability. Selected bond
lengths (Å) and angles (deg): Pt(1)-N(1) 2.018(2), Pt(1)-N(4) 2.054(3),
Pt(1)-Cl(2) 2.3313(8), N(1)-Pt(1)-N(4) 92.95(10), N(1)-Pt(1)-Cl(2)
87.53(8), N(4)-Pt(1)-Cl(2) 87.44(7).
Cl. Treatment of 6 with 3 equiv of Ph3PdCHCO2Me at 50
°C for 5 d resulted in only 30% conversion to the corre-
sponding Pt(II) complex [Pt{NHdC(NEt2)NC(Ph)dNPh}2]
(15). The reduction can be achieved within several minutes,
when Ph2PCH2CH2PPh2 (dppe) in CDCl3 is used. However,
in the latter case, (imidolyamidinato)PtII complex 15 is
contaminated with the solid [Pt(dppe)2]Cl2.
In the IR spectra of 5 and 6, in contrast to those of 3 and
4 (where strong bands at 1656 and 1645 cm-1, correspond-
ingly, from ν(NdC) in the monodentately bound imidoyla-
midine were observed), there is a strong band at 1550 (5)
and 1556 cm-1 (6); its appearance is typical for the bidentate-
bound imidoylamidines in the platinum(II) complexes (see
below). Complex 5 was not analyzed by NMR spectroscopy
because of its poor solubility in the most common deuterated
solvents. In the 1H and 13C{1H} NMR spectra of 6, all signals
from the organic ligand are well-resolved, reflecting the
absence of the proton exchange or a rotation in the ligand,
which is observed for the coordinated imidoylamidine species
in complex 4. Compound 6 exhibits one signal in the 195Pt
NMR spectrum at 103 ppm, in the region characteristic for
some other trans-[PtCl4(imine)2] complexes.23
When cis-[PtCl2(RCN)2] (R ) Me, Et; ca. 80:20% cis/
trans mixtures) reacts with the amidine, the latter couples
with one RCN moiety with the substitution of the other RCN
for the other end of the bidentate imidoylamidine (Scheme
3, E). The reaction proceeds at 40 °C for 1 h to give ca.
50-60% yield of [PtCl2{NHdC(R)NHC(Ph)dNPh}] (16
and 17).
The X-ray structure was obtained for 6 (Figure 2). The
bond lengths, N(1)-C(1) [1.318(4) Å], N(2)-C(1) [1.358(4)
Å], N(3)-C(1) [1.357(4) Å], N(3)-C(6) [1.316(4) Å], and
N(3)-C(6) [1.335(4) Å], in the metallacycle are similar
within 3σ with those found in complex 4 for the monoden-
tately coordinated ligand. Similar to 4, bond delocalization
was not observed in the NCNCN fragment. The metallacycles
are distorted square planes: torsion angles are Pt(1)-N(1)-
In a related work, Baker and colleagues treated benzami-
dine hydrochloride, PhC(dNH)NH2‚HCl, with two equiv of
(24) Svensson, P.; Lo¨vqvist, K.; Kukushkin, V. Yu.; Oskarsson, Å. Acta
Chem. Scand. 1995, 49, 72. Kukushkin, V. Yu.; Oskarsson, Å.; Elding,
L. I. Zh. Obsch. Khim. 1994, 64, 881; Russ. J. Gen. Chem. 1994, 64,
793. Kukushkin, V. Yu.; Oskarsson, Å.; Elding, L. I. Inorg. Synth.
1997, 31, 279. Kukushkin, V. Yu.; Tkachuk, V. M. Z. Anorg. Allg.
Chem. 1992, 613, 123.
(25) Baker, J.; Kilner, M.; Mahmoud, M. M.; Wallwork, S. C. J. Chem.
Soc., Dalton Trans. 1989, 837.
(26) Sarova, G. H.; Bokach, N. A.; Berberan Santos, M. N.; Kukushkin,
V. Yu.; Pombeiro, A. J. L. 2005, manuscript in preparation.
(23) Kukushkin, V. Yu.; Pakhomova, T. B.; Kukushkin, Yu. N.; Herrmann,
R.; Wagner, G.; Pombeiro, A. J. L. Inorg. Chem. 1998, 37, 6511.
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. Luzyanin, K. V.; Kukushkin, V. Yu.; Kuznetsov, M.
L.; Garnovskii, D. A.; Haukka, M.; Pombeiro, A. J. L. Inorg. Chem.
2002, 41, 2981. Makarycheva-Mikhailova, A. V.; Haukka, M.; Bokach,
N. A.; Garnovskii, D. A.; Galanski, M.; Keppler, B. K.; Pombeiro,
A. J. L.; Kukushkin, V. Yu. New J. Chem. 2002, 26, 1085.
Inorganic Chemistry, Vol. 44, No. 14, 2005 5155

Bokach et al.
Scheme 3
Li(Bu-n) in diethyl ether, with a further reaction of Li-
[(NH)2CPh], obtained in situ, with the platinum(II) complex
[PtCl2(PhCN)2].25 Nucleophilic addition of (NH)2CPh- to the
ligated benzonitrile gave the azametallacycle, depicted in
Scheme 4.
cm-1, which could be attributed to ν(CdN); ν(CdC) (from
Ar) might contribute to the overall intensity. The ν(CtN)
vibrations were detected for complexes 10 and 11. In the
1H NMR spectra, complexes 8-15 exhibit one signal for
the NH group, at 5.56-7.34 ppm for 8-11 and 3.84-6.38
ppm for 12-15. In the 13C{1H} spectra of [PtCl(RCN)-
{NHdC(R)NC(Ph)dNPh}] (8-10), the signal from the RCN
(R ) Et, Ph, PhCH2) moiety appears at 109.65-118.08 ppm.
13C signals of the CdN group vary in the range 158.66-
187.03 ppm for the NHdC and 145.86-151.82 ppm for the
NPhdC fragments. Complexes 8-15 exhibit one signal in
the 195Pt NMR spectra in the range from -2145 to -2296
ppm; this range agrees well with 195Pt NMR parameters for
other (imino)Pt(II) complexes.22,23
Scheme 4
The X-ray crystal structure was determined, but the poor
quality of crystals and, consequently, high estimated standard
deviations precluded any solid conclusions on bond delo-
calization within the metallacycle. Hence, the structure of
the product in Scheme 4 is given in accord with our
observations. Our experiments, in contrast to those of the
previous work,25 show that additional activation of amidines
toward the coupling, by deprotonation, is not necessary and
amidines are sufficiently nucleophilic in these reactions.
Characterization of (Imidoylamidine)Pt(II) Complexes.
All complexes give satisfactory elemental analyses for the
proposed formulation. In FAB+ MS, the complexes [PtCl-
(RCN){NHdC(R)NC(Ph)dNPh}] give fragmentation pat-
terns characteristic for platinum chlorides with the following
ions: [M - Cl]+, [M - RCN]+, [M - RCN - Cl]+ (8-11),
and [M]+ or [M + H]+ for [Pt{NHdC(R)NC(Ph)dNPh}2]
(12-15). There are two types of imidoylamidine complexes
that were prepared from trans-[PtCl2(RCN)2] (R ) Et, Ph,
CH2Ph, NEt2), which are [PtCl(RCN){NHdC(R)NC-
(Ph)dNPh}] (8-11) and [Pt{NHdC(R)NC(Ph)dNPh}2]
(12-15). These compounds do not have intense bands at
ca. 1650 cm-1, but they exhibit a strong band at 1540-1561
In the IR spectra, complexes [PtCl2{NHdC(R)NHC-
(Ph)dNPh}] (R ) Me, 16 and R ) Et, 17) exhibit strong
bands at 1685 and 1688 cm-1, respectively, from ν(CdN)
and, in the H NMR spectra, two signals from the two
different NH hydrogens (10.07 and 7.39 for 16; 11.33 and
9.98 for 17).
The structures of 8 and 15 were determined by X-ray
single-crystal diffraction (Figures 3 and 4), and it was
observed that both have square planar geometry. Atoms of
the metallacycles lie in one plane with a maximum deviation
of 0.045(2) Å for N(2), 0.028(1) Å for Pt(1), and 0.028(2)
Å for C(7) in Pt(1)N(2)C(4)N(3)C(7)N(4), and the root mean
square of the deviations for this ring is 0.039(2) Å in 8. The
NdC bond lengths [N(2)C(4), 1.305(3) and N(4)C(7),
1.323(3) Å for 8] and the N-C bond lengths [N(3)C(4),
1.338(4) and N(3)C(7), 1.342(3) Å for 8] in the metallacycle
have values typical for bonds in Ni(II) imidoylamidine(ato)
complexes.11,27 Complex 15 has another, based on bond
1
(27) Kryatov, S. V.; Nazarenko, A. Y.; Smith, M. B.; Rybak-Akimova, E.
V. Chem. Commun. 2001, 1174. Norrestam, R. Acta Crystallogr., Sect.
C 1984, 40, 955.
5156 Inorganic Chemistry, Vol. 44, No. 14, 2005

Nitrile-Amidine Coupling at Pt(IV) and Pt(II) Centers
the Pt(II) center does, and Pt(II) shows a stepwise pattern
for the reaction. Thus, for the Pt(II) complexes, the reaction
between [PtCl2(RCN)2] and PhC(dNH)NHPh leads to the
addition of amidine to the coordinated nitrile followed by
the coordination of the newly formed imidoylamidine via
the NHPh end to the Pt(II) center with a ring closure
accompanied by the leaving behind of one of the ligands
(Cl- or RCN).
Hence, the nitrile-amidine coupling reported herein
constitutes a route to the synthesis of imidoylamidine
complexes,11,27 some of them, as we have also found,26
exhibiting useful luminescent properties. In addition, results
from this study support the hypothesis that nitrile-amidine
coupling could be one of the plausible steps in the recently
discovered Ni(II)/oxime-mediated conversion of nitriles to
imidoylamidines11 and phthalonitriles.12
Figure 3. Thermal ellipsoid view of complex 8 with atomic numbering
scheme. Thermal ellipsoids are drawn at 50% probability. Selected bond
lengths (Å) and angles (deg): Pt(1)-N(1) 1.987(2), Pt(1)-N(2) 1.945(2),
Pt(1)-N(4) 1.998(2), Pt(1)-Cl(2) 2.3015(6), N(1)-C(3) 1.126(3), N(1)-
Pt(1)-N(2) 177.35(8), N(2)-Pt(1)-N(4) 88.98(9), N(1)-Pt(1)-N(4)
93.40(9), N(1)-Pt(1)-Cl(2) 88.92(6), Pt(1)-N(1)-C(3) 177.0(2).
Experimental Section
Materials and Instrumentation. Solvents were obtained from
commercial sources and used as received. PhC(dNH)NHPh,13
[PtCl2(RCN)2], and [PtCl4(RCN)2] (R ) Me, Et, Ph, CH2Ph, NEt2)
were prepared in accord with the published method.28 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 (400-
4000 cm-1) were recorded on a Nicolet magna 750 FT/IR
instrument using KBr pellets. TLC were performed on Merck 60
F
254 SiO2 plates.1H, 13C{1H}, and 195Pt NMR spectra were measured
on Bruker-DPX 300 and Varian UNITY 300 spectrometers at
ambient temperature. 195Pt chemical shifts (measured on a Varian
UNITY 300 spectrometer) are given relative to Na2[PtCl6] (by using
K2[PtCl4], δ ) -1630, as a standard), and the half-height line width
is given in parentheses.
Nitrile-Amidine Coupling at a Pt(IV) Center. A solution of
the amidine HNdC(Ph)NHPh (97 mg, 0.49 mmol) in CH2Cl2 (2
mL) was added dropwise while stirring at room temperature to a
suspension of [PtCl4(RCN)2] (R ) Me, Et, Ph, NEt2) (0.24 mmol)
in CH2Cl2 (3 mL). For R ) Me, the reaction mixture was stirred at
room temperature overnight until completeness of the reaction, and
for the other cases (R ) Et, Ph, NEt2), the reaction mixture was
left to stand at 40 °C for 1, 7, and 3 h, respectively. For R ) Me,
Et, and Ph, poorly soluble product was filtered off, washed with
Et2O (three 5-mL portions), and dried in the air, whereas for R )
NEt2, the reaction mixture was evaporated and the yellow oily
residue released was crystallized under a layer of Et2O and dried
on air at 20-25 °C. Yields are 66-84%.
[PtCl4{NHdC(Me)NdC(Ph)NHPh}2] (1). Anal. Calcd for
C30H30N6Cl4Pt‚2H2O: C, 42.52; H, 4.04; N, 9.92. Found: C, 42.50;
H, 3.65; N, 10.21%. FAB+ MS, m/z: 812 [M - H]+, 788 [M -
Cl]+, 740 [M - 2HCl]+, 705 [M - 2HCl - Cl]+. mp ) 178 °C.
TLC: Rf ) 0.37 (eluent: CH2Cl2). IR (KBr, selected bands, cm-1):
3404 (w), ν(O-H); 3299 (m), 3265 (w), ν(N-H); 1655 (s),
ν(CdN); 1535 (s), ν(CdN and CdC from Ar); 773 (w), 693 (m),
δ(C-H). The compound is insoluble in all common deuterated
solvents, and this precluded NMR measurements.
Figure 4. Thermal ellipsoid view of complex 15 with atomic numbering
scheme. The asymmetric unit contains a complete molecule and two halves
(labeled B and C). Thermal ellipsoids are drawn at 50% probability. Selected
bond lengths (Å) and angles (deg): Pt(1)-N(1) 2.000(3), Pt(1)-N(4)
2.023(3), Pt(1)-N(5) 2.003(3), Pt(1)-N(7) 2.032(3), Pt(1B)-N(1B) 2.005(3),
Pt(1B)-N(4B) 2.040(3), Pt(1C)-N(1C) 2.000(3), Pt(1C)-N(4C) 2.028(3),
N(1)-Pt(1)-N(4) 87.33(12), N(5)-Pt(1)-N(7) 87.54(12), N(1B)-Pt(1B)-
N(4B) 87.42(13), N(1C)-Pt(1C)-N(4C) 87.68(13).
lengths, distribution of double and single CN bonds in the
metallacycle [N(1)C(1), 1.318(4) Å; C(1)N(3), 1.357(4) Å;
N(3)C(6), 1.316(4) Å; and C(6)N(4), 1.335(4) Å], which can
be related to the influence of the NEt2 group, but all values
still remain typical, within 3σ, for such types of imidoyla-
midine(ato) metallacycles. Atoms of the metallacycles lie
in one plane, with a maximum deviation of 0.016(4) Å for
N(1) and 0.013(4) Å for N(4) in Pt(1)N(1)C(1)N(3)C(6)N(4),
and the root mean square of the deviations for this ring is
0.019(3) Å in 15.
Final Remarks. Heating of the free nitriles (in particular,
PhCN as the most reactive toward the nucleophilic addition
among chosen for this study) and the amidine PhC(dNH)-
NHPh gave no reaction for at least 1 d, whereas the
coordinated nitriles react rapidly under milder conditions.
These observations provide explicit evidence for the metal-
mediated character of the coupling. Moreover, it is clear that
Pt(IV) provides a better activation toward the coupling than
[PtCl4{NHdC(Et)NdC(Ph)NHPh}2] (2). Anal. Calcd for
C32H34N6Cl4Pt‚H2O: C, 44.82; H, 4.23; N, 9.80. Found: C, 44.97;
(28) Luzyanin, K. V.; Haukka, M.; Bokach, N. A.; Kuznetsov, M. L.;
Kukushkin, V. Yu.; Pombeiro, A. J. L. Dalton Trans. 2002, 1882.
Bokach, N. A.; Pakhomova, T. B.; Kukushkin, V. Yu.; Haukka, M.;
Pombeiro, A. J. L. Inorg. Chem. 2003, 42, 7560.
Inorganic Chemistry, Vol. 44, No. 14, 2005 5157

Bokach et al.
H, 4.05; N, 9.70%. FAB+ MS, m/z: 732 [M - 3HCl]+, 696 [M -
3HCl - Cl]+. mp ) 184 °C (dec). TLC: Rf ) 0.35 (eluent CH2-
Cl2). IR (KBr, selected bands, cm-1): 3429 (w), ν(O-H); 3320
(m), 3273 (w), ν(N-H); 1656 (s), ν(CdN); 1531 (s), ν(CdN and
CdC from Ar); 773 (w), 693 (m), δ(C-H). 1H NMR (CD2Cl2, δ):
12.83 (s, br, 1H, NH), 7.56 (s, br, 1H, NH), 6.8-7.4 (m, 10H, 2
Ph), 3.22 (q, 7.4 Hz, 2H, CH2), 1.38 (t, 7.4 Hz, 3H, CH3).
127.17, 125.73 (CPh); 42.65 and 13.37 (Et2NCdN).195Pt NMR
(CDCl3, δ): 103 (305 Hz).
The Nitrile-Amidine Coupling at Pt(II) Center. Reaction of
trans-[PtCl2(RCN)2] and the Amidine (2 Equiv). trans-[PtCl2-
(RCN)2] (0.053 mmol) and PhC(dNH)NHPh (21 mg, 0.106 mmol)
were dissolved in CH2Cl2 (0.5 mL) and left overnight at 40 °C.
The released colorless crystals of the amidinium hydrochloride were
removed by filtration, and the filtrate was evaporated until dryness
under a vacuum at room temperature to form a pale-yellow powder
of the platinum complexes, which were recrystallized from CH2-
Cl2-Et2O to give analytically pure samples. Yields of 8-11 after
crystallization were 50-60%. The amidinium hydrochloride (7) was
also detected in the reaction mixture.
[PtCl4{NHdC(Ph)NdC(Ph)NHPh}2] (3). Anal. Calcd for
C40H34N6Cl4Pt: C, 52.14; H, 4.03; N, 8.57. Found: C, 51.95; H,
3.74; N, 8.84%. FAB+ MS, m/z: 935 [M]+, 900 [M - Cl]+, 862
[M - 2HCl]+, 830 [M - 3Cl]+, 793 [M - 3HCl - Cl]+. mp )
155 °C (dec). TLC: Rf ) 0.56 (eluent CH2Cl2). IR (KBr, selected
bands, cm-1): 3429 (w), ν(O-H); 3320 (m), 3273 (w), ν(N-H);
1656 (s), ν(CdN); 1531 (s), ν(CdN and CdC from Ar); 773 (w),
[PhC(dNH)NHPh]‚HCl (7). Colorless crystals, insoluble in
CH2Cl2. FAB+MS, m/z: 197 [M]+. For X-ray structure, see
Supporting Information.
1
693 (m), δ(C-H). H NMR (CDCl3, δ): 9.89 and 9.64 (2 s, br,
1H, NH), 7.91 (t, 2H, Ph), 7.4-7.0 (m, 11H, Ph), 6.92 (t, 2H, Ph),
6.44 (s, br, 1H, NH). 13C{1H} NMR (CDCl3, δ): 168.49 (br, CdN);
147.92 and 146.88 (2 s, N-CdN); 135.24, 132.60, 132.32, 132.10,
131.46, 131.22, 129.53, 129.00, 128.67, 128.58, 128.15, 128.07,
127.57, 127.24, 124.71, 121.44, 120.92 (carbons in Ph’s). 195Pt
NMR (CDCl3, δ): -139.74 (299.1 Hz) (60%), -192.46 (375.4 Hz)
(40%).
[PtCl(NCEt){NHdC(Et)NC(Ph)NPh}] (8). Anal. Calcd for
C19H21N4ClPt: C, 42.50; H, 3.95; N, 10.45. Found: C, 42.90; H,
3.87; N, 10.13%. FAB+ MS, m/z: 536 [M]+, 500 [M - Cl]+, 481
[M - EtCN]+, 444 [M - Cl - EtCN]+. mp ) 213 °C (dec). TLC:
Rf ) 0.38 (eluent Et2O/CH2Cl2 ) 2:3). IR (KBr, selected bands,
cm-1): 3341 (mw), 3282 (m), ν(N-H); 1552 (ms), ν(CdN and
CdC from Ar); 1444 (s), ν(CdC from Ar); 700 (m), δ(C-H). 1H
NMR (CDCl3, δ): 7.34 (s, br, 1H, NH), 7.10 (t, 2H, m-Ph), 7.07
(m, 5H, Ph), 6.96 (d, 2H, o-Ph), 6.88 (t, 1H, p-Ph-N), 2.41 (q, 7.5
Hz, 2H) and 1.25 (t, 7.5 Hz, 3H) (EtCdN), 2.14 (q, 7.5 Hz, 2H)
and 0.92 (t, 7.5 Hz, 3H) (EtCtN). 13C{1H} NMR (CDCl3, δ):
162.03 (CdN-H); 150.73 (CdN-Ph); 129.53 (Cipso); 127.71,
127.56, 127.41, 125.31 (carbons in Ph’s); 118.08 (CtN); 32.75
and 11.20 (EtCdN); 11.63 and 9.03 (EtCtN). 195Pt NMR (CDCl3,
δ): -2295 (811 Hz).
[PtCl(NCCH2Ph){NHdC(CH2Ph)NC(Ph)dNPh}] (9). Anal.
Calcd for C29H25N4ClPt: C, 52.69; H, 3.96; N, 8.48. Found: C,
52.25; H, 4.16; N, 8.87%. FAB+ MS, m/z: 660 [M]+, 624 [M -
Cl]+, 543 [M - PhCH2CN]+, 506 [M - HCl - PhCN]+. mp )
127 °C. TLC: Rf ) 0.53 (eluent Et2O/CH2Cl2 ) 1:3). IR (KBr,
selected bands, cm-1): 3320 (m), ν(N-H); 1559 (ms), ν(CdN and
CdC from Ar); 1449 (s), ν(CdC from Ar); 698 (m), δ(C-H). 1H
NMR (CDCl3, δ): 7.29 and 7.09-6.93 (m, 20H, Ph’s), 6.74 (s, br,
1H, NH), 3.69 (s, 2H, NdCCH2Ph), 3.48 (m, 4.5 Hz, 2H, NtCCH2-
Ph). 13C{1H} NMR (CDCl3, δ): 159.50 (CdN-H); 150.34 (CdN-
Ph); 134.95 (Cipso); 129.66, 129.16, 128.98, 128.76, 128.48, 127.95,
127.58, 127.46, 125.35 (carbons in Ph’s); 115.65 (NtC); 45.35
(PhCH2CdN); 23.90 (PhCH2CdN). 195Pt NMR (CDCl3, δ): -2296
(1151 Hz).
[PtCl(NCPh){NHdC(Ph)NHC(Ph)dNPh}] (10). Anal. Calcd
for C27H22N4ClPt: C, 51.31; H, 3.35; N, 8.86. Found: C, 51.38;
H, 3.48; N, 8.70%. FAB+ MS, m/z: 632 [M]+, 596 [M - Cl]+,
529 [M - PhCN]+, 492 [M - HCl - PhCN]+. mp ) 213 °C (dec).
TLC: Rf ) 0.50 (eluent CH2Cl2). IR (KBr, selected bands, cm-1):
3359 (m), 3340 (m), ν(N-H); 2281 (w), ν(CtN); 1540 (ms),
ν(CdN and CdC from Ar); 1456 (s), ν(CdC from Ar); 698 (m),
δ(C-H). 1H NMR (CDCl3, δ): 7.95 (d, 2H, o-PhCtN from nitrile),
7.81 (d, 2H, PhCdN from nitrile), 7.57-7.11 (m, 15H, Ph’s), 6.88
(t, 1H, p-Ph). 13C{1H} NMR (CDCl3, δ): 158.66 (CdN-H); 150.93
(CdN-Ph); 134.23, 132.92, 130.45, 128.95, 128.57, 127.95,
127.76, 127.44, 127.26, 126.93, 125.48 (carbons in Ph’s); 109.65
(CtN). 195Pt NMR (CDCl3, δ): -2256 (1029 Hz).
[PtCl4{NHdC(NEt2)NHC(Ph)dNPh}2] (4). Anal. Calcd for
C32H44N8Cl4Pt‚H2O: C, 45.82; H, 4.91; N, 11.87. Found: C, 45.90;
H, 5.12; N, 11.64%. FAB+ MS, m/z: 926 [M]+, 891 [M - Cl]+,
853 [M - 2HCl]+, 819 [M - 3Cl]+, 782 [M - 2Cl - 2HCl]+. mp
) 162 °C. TLC: Rf ) 0.54 (eluent CH2Cl2). IR (KBr, selected
bands, cm-1): 3358 (m), ν(N-H); 1645 (ms), ν(CdN); 1596 (m),
1537 (s), ν(CdN and CdC from Ar); 759 (m), 697 (m), δ(C-H).
1H NMR (CDCl3, δ): 7.7-7.2 (m, 10H, 2 Ph), 5.30 (s, br, 1H,
NH), 3.37 (s, br, 4H, CH2), 1.10 (s, br, 3H, CH3). 13C{1H} NMR
(CDCl3, δ): 130.39, 129.28, 128.62, 128.20, 123.88, 122.01 (Ph);
43.80 and 13.13 (Et). 195Pt NMR (CDCl3, δ): 193.05 (323.4 Hz)
(50%), 86.92 (50%) (290.1 Hz).
Dehydrohalogenation of 3 and 4 with the ylide Ph3PdCH-
CO2Me. Complex 3 or 4 (0.032 mmol) and Ph3PdCHCO2Me (11
mg, 0.033 mmol) were dissolved (4) or suspended (3) in CH2Cl2
(1 mL) and left to stand for 5 h at 40 °C. Completeness of the
reaction was monitored by TLC. After 5 h, product 6 was separated
by column chromatography on silicagel (Aldrich, 70-230 mesh,
70 Å) in the first fraction by using CH2Cl2 as an eluent. Product 5
was released and separated as a yellow powder after 12 h. Yields
are ca. 50%.
[PtCl2{NHdC(Ph)NC(Ph)dNPh}2] (5). Anal. Calcd for
C40H32N6Cl2Pt‚0.5CH2Cl2: C, 53.74; H, 3.67; N, 9.28. Found: C,
53.97; H, 3.50; N, 9.17%. FAB+ MS, m/z: 862 [M]+, 828 [M -
Cl + H]+, 792 [M - 2Cl]+. mp ) 280 °C (dec). TLC: Rf ) 0.67
(eluent CH2Cl2/acetone ) 1:1). IR (KBr, selected bands, cm-1):
3343 (m), ν(N-H); 1550 (s), ν(CdN and CdC from Ar); 1417
(ms), ν(CdC from Ar); 699 (m), δ(C-H). NMR spectra were not
measured because of the poor solubility of the complex.
[PtCl2{NHdC(NEt2)NC(Ph)dNPh}2] (6). Anal. Calcd for
C36H42N8Cl2Pt: C, 50.70; H, 4.96; N, 13.14. Found: C, 50.52; H,
5.12; N, 12.77%. FAB+ MS, m/z: 853 [M - H]+, 816 [M - 3H
- Cl]+, 781 [M - 4H - 2Cl]+. mp ) 217 °C (dec). TLC: Rf )
0.34 (eluent CH2Cl2). IR (KBr, selected bands, cm-1): 3412 (m),
ν(N-H); 1556 (s), ν(CdN and CdC from Ar); 1471 (ms), ν(CdC
1
from Ar); 694 (m), δ(C-H). H NMR (CDCl3, δ): 7.18 (m, 10H,
[PtCl(NCNEt2){NHdC(NEt2)NC(Ph)dNPh}] (11). Anal. Cal-
cd for C23H31N6ClPt: C, 44.34; H, 5.18; N, 13.49. Found: C, 44.46;
H, 5.32; N, 13.29%. FAB+ MS, m/z: 622 [M]+, 593 [M - Et]+,
587 [M - Cl]+. mp ) 199 °C. TLC: Rf ) 0.54 (eluent CH2Cl2).
IR (KBr, selected bands, cm-1): 3395 (m), ν(N-H); 2287 (sm),
2 Ph), 4.77 (sd, 26.37 Hz, 1H, NH), 3.18 and 3.05 (2 m, 4H, CH2),
0.94 (t, 7.2 Hz, 3H, CH3). 13C{1H}NMR (CDCl3, δ): 160.08
(CdN-Pt); 147.82 and 147.32 (CdN); 140.92, 131.26, 131.14,
128.94, 128.86, 128.07, 127.99 (all br, NHPh); 128.21, 127.27,
5158 Inorganic Chemistry, Vol. 44, No. 14, 2005

Nitrile-Amidine Coupling at Pt(IV) and Pt(II) Centers
Table 1. Crystal Data for Compounds 4, 6, 8, and 15
4
6
8
15
empirical formula
fw
temp (K)
λ (Å)
cryst syst
space group
a (Å)
b (Å)
c (Å)
a (deg)
â (deg)
γ (deg)
V (Å3)
C36H44Cl4N8Pt
925.68
110(2)
0.71073
monoclinic
P21/c
10.9802(16)
19.4181(18)
9.6964(11)
90
112.080(10)
90
1915.8(4)
2
1.605
3.979
C36H42Cl2N8Pt
852.77
100(2) K
0.71073
monoclinic
P21/n
9.3749(3)
9.6825(4)
19.2244(7)
90
103.766(3)
90
1694.92(11)
2
1.671
4.337
0.0239
C19H21ClN4Pt
535.94
100(2)
0.71073
monoclinic
P21/n
12.1385(8)
10.4006(8)
15.0235(10)
90
90.997(6)
90
1896.4(2)
4
1.877
7.549
C72H84N16Pt2
1563.73
100(2)
0.71073
triclinic
P1h
12.3627(3)
12.9400(4)
22.0075(6)
77.720(2)
83.761(2)
71.5490(10)
3259.97(16)
2
Z
F
calc (Mg/m3)
1.593
4.343
0.0323
0.0734
µ(Mo KR) (mm-1
R1a (I g 2σ)
)
0.0308
0.0558
0.0165
0.0355
wR2b (I g 2σ)
0.0576
a R1 ) Σ||Fo| - |Fc||/Σ|Fo|. b wR2 ) {Σ[w(Fo - Fc )2]/ Σ[w(Fo )2]}1/2
.
2
2
2
ν(CtN); 1559 (s), ν(CdN and CdC from Ar); 1469 (s), ν(CdC
from Ar); 701 (m), δ(C-H). H NMR (CDCl3, δ): 7.02 (m, 9H,
3.30 (m, 4.5 Hz, 2H, NdCCH2Ph). 13C{1H} NMR (CDCl3, δ):
129.26, 128.57, 127.60, 127.47, 127.31, 126.88, 126.20 (carbons
in Ph) (PhCH2CdN and CdN were not detected). 195Pt NMR
(CDCl3, δ): -2261 (540 Hz).
1
Ph), 6.83 (t, 1H, o-Ph), 7.10 (t, 2H, m-Ph), 7.07 (m, 5H, Ph), 5.56
(s, br, 1H, NH), 3.41 (q, 4H) and 1.17 (t, 6H) (Et2NCdN), 2.75
(q, 4H) and 1.01 (t, 6H) (Et2NCtN). 13C{1H} NMR (CDCl3, δ):
187.03 (CdN-H); 151.82 (CdN-Ph); 129.53 (Cipso); 128.63,
128.13, 127.17, 126.85, 126.60, 124.20 (carbons in Ph’s); 45.19
and 12.76 (Et2NCdN); 42.85 and 13.51 (Et2NCtN). 195Pt NMR
(CDCl3, δ): -2273 (788 Hz).
[Pt{NHdC(Ph)NC(Ph)dNPh}2] (14). Anal. Calcd for C40H32N6-
Pt: C, 60.68; H, 4.07; N, 10.61. Found: C, 60.54; H, 4.52; N,
10.60%. FAB+ MS, m/z: 792 [M]+. IR (KBr, selected bands, cm-1):
3350 (ms), ν(N-H); 1540 (s), ν(CdN and CdC from Ar); 1465
1
(ms), ν(CdC from Ar); 702 (m), δ(C-H). H NMR (CDCl3, δ):
7.30 (m, 4H), 7.16 (m, 8H) and 7.08 (m, 3H) (Ph), 6.38 (s, br, 1H,
NH). 13C{1H} NMR (CDCl3, δ): 156.15 and 156.05 (2 CdN);
129.11, 128.40, 128.06, 127.59, 127.22, 126.39, 125.85 (carbons
in Ph). 195Pt NMR (CDCl3, δ): -2270 (520 Hz).
Reaction of trans-[PtCl2(RCN)2] and the Amidine (4 Equiv).
General Method B. trans-[PtCl2(RCN)2] (0.053 mmol) (R ) Et,
NEt2) and PhC(dNH)NHPh (42 mg, 0.212 mmol) were dissolved
in CH2Cl2 (0.5 mL) and left at 40 °C. For R ) Et, the pale-yellow
needles appeared on the top of the vial after 3 d. They were filtered
off and mechanically separated from the colorless crystals of
byproduct PhC(dNH)NHPh‚HCl. For R ) Et, crystals can be
dissolved in warm CH2Cl2; the solvent was separated from the
colorless crystals and evaporated to give the product. For R ) NEt2,
after 5 d, a yellow solution with colorless crystals of PhC(dNH)-
NHPh‚HCl (7) was obtained, the crystals were filtered off, and the
filtrate was evaporated to half of its volume, whereupon Et2O (0.2
mL) was added dropwise. The released yellow precipitate was
filtered off, washed with Et2O (0.5 mL), and dried. Yields: 50 and
35% for R ) Et and NEt2, respectively. The complexes with R )
CH2Ph (13) and Ph (14) are prepared analogously.
[Pt{NHdC(NEt2)NC(Ph)dNPh}2] (15). Anal. Calcd for
C36H42N8Pt: C, 55.30; H, 5.41; N, 14.33. Found: C, 55.46; H,
5.61; N, 13.93%. FAB+ MS, m/z: 783 [M + H]+. mp ) 209 °C.
TLC: Rf ) 0.47 (eluent Et2O/CH2Cl2 ) 1:4). IR (KBr, selected
bands, cm-1): 3392 (ms), ν(N-H); 1541 (s), ν(CdN and CdC
from Ar); 1471 (s), ν(CdC from Ar); 695 (m), δ(C-H). 1H NMR
(CDCl3, δ): 7.11 and 7.08 (2 m, 10H, Ph), 3.84 (s, br, 1H, NH),
2.81 (q, 4H) and 0.79 (t, 6H) (Et2NCdN). 13C{1H} NMR (CDCl3,
δ): 160.82 (CdN-H); 150.57 and 147.79 (CdN-Ph); 129.52,
129.28, 128.70, 128.53, 127.77, 127.17, 126.75, 126.09, 124.87,
122.32 (carbons in Ph’s); 41.85 and 13.70 (Et2NCdN). 195Pt NMR
(CDCl3, δ): -2259 (441 Hz).
[Pt{NHdC(Et)NC(Ph)NPh}2] (12). Anal. Calcd for C32H32N6-
Pt‚Et2O: C, 55.73; H, 5.09; N, 11.47%. Found: C, 55.75; H, 4.87;
N, 11.41%. FAB+ MS, m/z: 696 [M + H]+. mp ) 207 °C (dec).
TLC: Rf ) 0.47 (eluent CH2Cl2/acetone ) 1:1). IR (KBr, selected
bands, cm-1): 3347 (m), ν(N-H); 1632 (m), ν(CdN); 1561 (ms),
ν(CdN and CdC from Ar); 1446 (s), 1430 (s), ν(CdC from Ar);
697 (ms), δ(C-H). 1H NMR (CDCl3, δ): 7.22 (t, 2H, m-Ph), 7.05
(m, 8H, Ph), 5.77 (s, br, 1H, NH), 2.04 (q, 7.5 Hz, 2H) and 0.56
(t, 7.5 Hz, 3H) (EtCdN). 13C{1H}NMR (CDCl3, δ): 163.03
(CdN-H); 145.86 (CdN-Ph); 128.85, 128.29, 127.47, 127.24,
125.99 (carbons in Ph’s); 32.92 and 9.48 (EtCdN). 195Pt NMR
(CDCl3, δ): -2145 (538 Hz).
[Pt{NHdC(CH2Ph)NC(Ph)dNPh}2] (13). Anal. Calcd for
C42H36N6Pt: C, 61.53; H, 4.43; N, 10.25. Found: C, 61.49; H,
4.80; N, 10.26%. FAB+ MS, m/z: 820 [M]+. IR (KBr, selected
bands, cm-1): 3339 (ms), ν(N-H); 1558 (s), ν(CdN and CdC
from Ar); 1448 (s), ν(CdC from Ar); 697 (ms), δ(C-H). 1H NMR
(CDCl3, δ): 7.22 and 7.01 (m, 15H, Ph), 5.61 (s, br, 1H, NH),
Reaction of cis-[PtCl2(RCN)2] and the Amidine (2 Equiv). A
solution of the amidine HNdC(Ph)NHPh (106.8 mg, 0.54 mmol)
in CHCl3 (2 mL) was added dropwise to a suspension of cis-[PtCl2-
(EtCN)2] (100 mg, 0.27 mmol) in CHCl3 (3 mL) {or cis-[PtCl2-
(MeCN)2] in MeCN}. The reaction mixture was left to stand for 1
h at 40 °C; during this time, a pale-yellow powder of the product
started to release. The product was filtered off, washed with Et2O
(three 4-mL portions), and dried in the air. Yield is 50-60%.
[PtCl2{NHdC(Me)NdC(Ph)NHPh}] (16). Anal. Calcd for
C15H15N3Cl2Pt: C, 35.80; H, 3.00; N, 8.35. Found: C, 36.14; H,
3.36; N, 8.50%. FAB+ MS, m/z: 503 [M]+, 468 [M - Cl + H]+.
The compound has no characteristic mp; upon heating, it decom-
poses above 255 °C. TLC: Rf ) 0.70 (eluent CH2Cl2/acetone )
1:1). IR (KBr, selected bands, cm-1): 3345 (m), 3230 (m), 3187
(m), ν(N-H); 1685 (s), 1629 (ms), ν(CdN); 1527 (s), ν(CdC from
Ar); 696 (m), δ(C-H). 1H NMR (DMSO-d6, δ): 10.07 (s, br, 1H,
NH), 7.39 (s, br, 1H, NH), 6.8-7.2 (m, 10H, two Ph), 1.99 (s, 3H,
Me).
Inorganic Chemistry, Vol. 44, No. 14, 2005 5159

Bokach et al.
[PtCl2{NHdC(Et)NdC(Ph)NHPh}] (17). Anal. Calcd for
C16H17N3Cl2Pt: C, 37.15; H, 3.31; N, 8.12. Found: C, 37.27; H,
3.33; N, 7.84%. FAB+ MS, m/z: 517 [M]+, 482 [M - Cl + H]+,
444 [M - 2HCl]+. The compound has no characteristic mp, and
upon heating, it decomposes above 285 °C. TLC: Rf ) 0.60 (eluent
CH2Cl2/acetone ) 3:1). IR (KBr, selected bands, cm-1): 3349 (m),
3230 (m), 3188 (m), ν(N-H); 1688 (s), 1628 (ms), ν(CdN); 1529
(s), ν(CdC from Ar); 807 (m), 695 (m), δ(C-H). 1H NMR
(DMSO-d6, δ): 11.33 (s, br, 1H, NH), 9.98 (s, br, 1H, NH), 6.3-
7.3 (m, 10H, 2 Ph), 3.32 (q, 7.4 Hz, 2H, CH2), 1.14 (t, 7.4 Hz, 3H,
CH3).
map and refined isotropically. In 8, NH hydrogens were also located
from the difference Fourier map but not refined. All other hydrogens
were placed in idealized positions and constrained to ride on their
parent atom. The asymmetric unit of 15 contains a complete
molecule and two halves, which have been labeled as molecules B
and C. The crystallographic details for 4, 6, 8, and 15 are
summarized in Table 1, and the selected bond lengths and angles
are found in the figure captions. The crystallographic details of 7
are given as Supporting Information.
Acknowledgment. This work has been supported by the
Russian Fund for Basic Research (Grants 03-03-32363 and
05-03-32140) and the Fundac¸a˜o para a Cieˆncia e a Tecno-
logia (FCT), Portugal, and its POCTI program (POCTI/QUI/
43415/2001 project) (FEDER funded). N.A.B., M.H., and
V.Yu.K. thank the Academy of Finland for financial support.
N.A.B. and V.Yu.K. express gratitude to the POCTI program,
Portugal, for Grant SFRH/BPD/11448/2002 (N.A.B.) and a
grant for Cientista Convidado/Professor at the Instituto
Superior Te´cnico (V.Yu.K.). V.Yu.K. is very much obliged
to ISSEP for a Soros Professorship (2001-2004). The
authors also thank NATO for the Collaborative Linkage
Grant PST.CLG.979289.
X-ray Structure Determinations. The X-ray diffraction data
were collected with a Nonius Kappa CCD diffractometer. The
Denzo-Scalepack29 or EvalCCD30 program packages were used for
cell refinements and data reduction. Structures were solved by direct
methods using the SHELXS-97 or SIR-2002 programs.31,32
A
multiscan absorption correction based on equivalent reflections
(XPREP in SHELXTL version 6.12 or SADABS version 2.05)33,34
was applied to all data (Tmin/Tmax values were 0.5345/0.8168,
0.14737/0.22322, 0.22453/0.26323, 0.3136/0.7040, and 0.12102/
0.20939 for 4, 6-8, and 15, respectively). All structures were
refined with SHELXL-9735 and the WinGX graphical user inter-
face.36 In 4, NH hydrogens were located from the difference Fourier
Supporting Information Available: Crystallographic data in
CIF format. Tables of crystallographic data, atomic coordinates,
bond lengths and angles, anisotropic displacement parameters,
hydrogen coordinates and isotropic displacement parameters, torsion
angles, and hydrogen bonds for 4, 6, 7, 8, and 15. Thermal ellipsoid
view of 7. This material is available free of charge via the Internet
at http://pubs.acs.org.
(29) Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data
Collected in Oscillation Mode. Methods in Enzymology, Macromo-
lecular Crystallography, Part A; Carter, C. W., Jr., Sweet, R. M., Eds.;
Academic Press: New York, 1997; Vol. 276, pp 307-326.
(30) Duisenberg, A. J. M.; Kroon-Batenburg, L. M. J.; Schreurs, A. M.
M. J. Appl. Crystallogr. 2003, 36, 220.
(31) Sheldrick, G. M. SHELXS-97; University of Go¨ttingen, Go¨ttingen,
Germany, 1997.
(32) Burla, M. C.; Camalli, M.; Carrozzini, B.; Cascarano, G. L.; Giaco-
vazzo, C.; Polidori, G.; Spagna, R. J. Appl. Crystallogr. 2003, 36,
1103.
IC050037Q
(33) Sheldrick, G. M. SHELXTL, version 6.14; Bruker AXS, Inc.: Madison,
WI, 2003.
(34) Sheldrick, G. M. SADABS, version 2.05; Bruker Axs, Inc.: Madison,
WI, 2002.
(35) Sheldrick, G. M. SHELXL97; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.
(36) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
5160 Inorganic Chemistry, Vol. 44, No. 14, 2005