Novel tailoring reaction for two adjacent coordinated nitriles giving platinum 1,3,5-triazapentadiene complexes

Article abstract of DOI:10.1021/ic702483w

The tailoring reaction of the two adjacent nitrile ligands in cis-[PtCl₂(RCN)₂] (R = Me, Et, CH₂Ph, Ph) and [Pt(tmeda)(EtCN)₂][SO₃CF₃]₂ (8·(OTf)₂; tmeda = N,N,N′,N′- tetramethylethylenediamine) upon their interplay with N,N′- diphenylguanidine (DPG; NH=C(NHPh)₂), in a 1:2 molar ratio gives the 1,3,5-triazapentadiene complexes [PtCl₂{NHC(R)NHC(R)=NH}] (1-4) and [Pt(tmeda){NHC(Et)NHC(Et)NH}][SO₃CF₃]₂ (10·(OTf)₂), respectively. In contrast to the reaction of 8·(OTf)₂ with NH=C(NHPh)₂, interaction of 8·(OTf)₂ with excess gaseous NH₃ leads to formation of the platinum(II) bis(amidine) complex cis-[Pt(tmeda){NH=C(NH ₂)Et}₂][SO₃CF₃]₂ (9·(OTf)₂). Treatment of trans-[PtCl₂(RCN) ₂] (R = Et, CH₂Ph, Ph) with 2 equiv of NH=C(NHPh) ₂ in EtCN (R = Et) and CH₂Cl₂ (R = CH ₂Ph, Ph) solutions at 20-25°C leads to [PtCl{NH=C(R)NC(NHPh)=NPh} (RCN)] (11-13). When any of the trans-[PtCl₂(RCN)₂] (R = Et, CH₂Ph, Ph) complexes reacts in the corresponding nitrile RCN with 4 equiv of DPG at prolonged reaction time (75°C, 1-2 days), complexes containing two bidentate 1,3,5-triazapentadiene ligands, i.e. [Pt{NH=C(R)NC(NHPh)=NPh}₂] (14-16), are formed. Complexes 14-16 exhibit strong phosphorescence in the solid state, with quantum yields (peak wavelengths) of 0.39 (530 nm), 0.61 (460 nm), and 0.74 (530 nm), respectively. The formulation of the obtained complexes was supported by satisfactory C, H, and N elemental analyses, in agreement with FAB-MS, ESI-MS, IR, and ¹H and ¹³C{¹H} NMR spectra. The structures of 1, 2, 4, 11, 13, 14, 9· (picrate)₂, and 10·(picrate) ₂ were determined by single-crystal X-ray diffraction.

Full text of DOI:10.1021/ic702483w

Inorg. Chem. 2008, 47, 11487-11500
Novel Tailoring Reaction for Two Adjacent Coordinated Nitriles Giving
Platinum 1,3,5-Triazapentadiene Complexes
Pavel V. Gushchin,† Marina R. Tyan,† Nadezhda A. Bokach,† Mikhail D. Revenco,‡ Matti Haukka,§
Meng-Jiy Wang,⊥ Cheng-Hsuan Lai,¶ Pi-Tai Chou,*,¶ and Vadim Yu. Kukushkin*,†,||
St. Petersburg State UniVersity, 198504 Stary Petergof, Russian Federation, Department of
Chemistry, State UniVersity of MoldoVa, MD 2009 Chisinau, Republic of MoldoVa, Institute of
Macromolecular Compounds of the Russian Academy of Sciences, Bolshoii Pr. 31,
199004 St. Petersburg, Russian Federation, Department of Chemistry, UniVersity of Joensuu,
P.O. Box 111, FI-80101 Joensuu, Finland, Department of Chemical Engineering, National Taiwan
UniVersity of Science and Technology, 43, Keelung Road, Section 4, Taipei, 106 Taiwan, and
Department of Chemistry, National Taiwan UniVersity, No. 1, RooseVelt Road, Section 4, Taipei, Taiwan
Received December 22, 2007
The tailoring reaction of the two adjacent nitrile ligands in cis-[PtCl2(RCN)2] (R ) Me, Et, CH2Ph, Ph) and
[Pt(tmeda)(EtCN)2][SO3CF3]2 (8· (OTf)2; tmeda ) N,N,N′,N′-tetramethylethylenediamine) upon their interplay with
N,N′-diphenylguanidine (DPG; NHdC(NHPh)2), in a 1:2 molar ratio gives the 1,3,5-triazapentadiene complexes
[PtCl2{NHC(R)NHC(R)dNH}] (1–4) and [Pt(tmeda){NHC(Et)NHC(Et)NH}][SO3CF3]2 (10 · (OTf)2), respectively. In
contrast to the reaction of 8· (OTf)2 with NHdC(NHPh)2, interaction of 8· (OTf)2 with excess gaseous NH3 leads
to formation of the platinum(II) bis(amidine) complex cis-[Pt(tmeda){NHdC(NH2)Et}2][SO3CF3]2 (9· (OTf)2). Treatment
of trans-[PtCl2(RCN)2] (R ) Et, CH2Ph, Ph) with 2 equiv of NHdC(NHPh)2 in EtCN (R ) Et) and CH2Cl2 (R )
CH2Ph, Ph) solutions at 20–25 °C leads to [PtCl{NHdC(R)NC(NHPh)dNPh}(RCN)] (11–13). When any of the
trans-[PtCl2(RCN)2] (R ) Et, CH2Ph, Ph) complexes reacts in the corresponding nitrile RCN with 4 equiv of DPG
at prolonged reaction time (75 °C, 1–2 days), complexes containing two bidentate 1,3,5-triazapentadiene ligands,
i.e. [Pt{NHdC(R)NC(NHPh)dNPh}2] (14–16), are formed. Complexes 14–16 exhibit strong phosphorescence in
the solid state, with quantum yields (peak wavelengths) of 0.39 (530 nm), 0.61 (460 nm), and 0.74 (530 nm),
respectively. The formulation of the obtained complexes was supported by satisfactory C, H, and N elemental
analyses, in agreement with FAB-MS, ESI-MS, IR, and 1H and 13C{1H} NMR spectra. The structures of 1, 2, 4, 11,
13, 14, 9· (picrate)2, and 10· (picrate)2 were determined by single-crystal X-ray diffraction.
Introduction
tions are known.1 The dinitrogen analogues of 1,3-dicarbonyl
compounds, i.e. 1,5-diazapentadienyl (or ꢀ-diketiminate)
species (B), have been much less studied but over the past
decade they have fast become one of the most useful groups
of monoanionic nitrogen-based ligands in chemistry. Their
complexes serve as useful models for synthetic, reactivity,
and structural investigations2–5 and also for modeling active
sites of metalloenzymes.6 In addition, ꢀ-diketiminates of
1,3-Dicarbonyl derivatives (Chart 1, A) in general and
acetylacetone in particular represent one of the oldest and,
concurrently, one of the most valuable classes of ligands for
metal ion chelation with a substantial fraction of the elements
in the periodic table. The rich chemistry of these species is
well-documented, and a good number of industrial applica-
* Author to whom correspondence should be addressed. E-mail:
kukushkin@vk2100.spb.edu.
(1) Pettinari, C.; Marchetti, F.; Drozdov, A. ꢀ-Diketones and Related
Ligands. In ComprehensiVe Coordination Chemistry, 2nd ed.; Elsevier:
Amsterdam, 2004; Vol. 1, Chapter 1.6, pp 97–115.
(2) (a) Piers, W.; Emslie, D. J. H. Coord. Chem. ReV. 2002, 131, 233. (b)
Bailey, P. J.; Pace, S. Coord. Chem. ReV. 2001, 214, 91. (c) Coles,
M. P. Dalton Trans. 2006, 985.
†
St. Petersburg State University.
Institute of Macromolecular Compounds of the Russian Academy of
||
Sciences.
‡
State University of Moldova.
University of Joensuu.
National Taiwan University of Science and Technology.
National Taiwan University.
§
⊥
(3) Bourget-Merle, L.; Lappert, M. F.; Severn, J. R. Chem. ReV. 2002,
¶
102, 3031.
10.1021/ic702483w CCC: $40.75  2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 24, 2008 11487
Published on Web 04/01/2008

Gushchin et al.
per-23,24 or nickel-mediated25 hydrolytic conversion of 1,3,5-
triazine23,25 or 1,3,5-tris(2-pyridyl)-2,4,6-triazine,24 (iii) hy-
drolytic conversion of RCN mediated by the dinuclear
nickel(II) complex [Ni2(µ-OH)2(tpa)2](ClO4)2 (tpa ) tris-(2-
pyridylmethyl)amine)26 or Ni(II) acetate,27 (iv) evaporating
a MeOH solution of NiCl2 ·6H2O and acetamidine,28 and (v)
Chart 1. Skeletons of 1,3-Dicarbonyl (A), 1,5-Diazapentadienyl (B),
and 1,3,5-Triazapentadienyl (C) Species
labile metal centers have intrinsic practical applications: e.g.,
as polymerization catalysts.7–9
29
10,11
by oxime-assisted conversion of nitriles at PtII and NiII
The trinitrogen analogues of the 1,3-dicarbonyls, i.e. 1,3,5-
triazapentadienyl (or imidoylamidine) species (C), have been
substantially less explored than the relevant A and B systems,
but they deserve special attention from coordination chemists,
as C ligands offer an additional coordination site at the
central nitrogen atom, especially in their anionic form.
Moreover, this N atom takes part in facile acid–base
equilibria,10–12 thus providing pH sensing properties to their
complexes: e.g., those exhibiting luminescent properties.12
Despite the obvious advantages and potential of the 1,3,5-
triazapentadienyl chelating systems, these species are small
in number, since as facile and general synthetic methods for
their generation have thus far been rather poorly developed.
Thus, reactions between the preprepared 1,3,5-triazapen-
tadiene and metal sources are rather rare because the ligands,
especially those with donor substituents, are highly reactive
and therefore many of them are elusiVe in the free state.
Direct metal–ligand reactions have been realized only with
stable 1,3,5-triazapentadienes, which bear strong electron
acceptor groups at the C atoms, e.g. fluoroalkyls, and they
are N substituted, e.g. NAr.13–18
centers.
In the course of our ongoing studies on reactions of metal-
activated nitriles,30 giving in particular 1,3,5-triazapentadiene
complexes,10–12,20 we have discovered a novel tailoring
reaction between the guanidine NHdC(NHPh)2 (DPG) and
two cis nitriles at the PtII center, leading to platinum(II) 1,3,5-
triazapentadiene complexes. The developed method, which
is based on this reaction, represents a facile route to (1,3,5-
triazapentadiene)PtII species with luminescent properties.
Details of these results are elaborated in this article.
Results and Discussion
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11488 Inorganic Chemistry, Vol. 47, No. 24, 2008

Platinum 1,3,5-Triazapentadiene Complexes
Scheme 1. Tailoring Reaction in the Temperature Range (A) from 20
to 40 °C (R ) Me (1), Et (2), CH2Ph (3), Ph (4)) and (B) from -20 to
4 °C (R ) Et (5), CH2Ph (6))
Scheme 2
properties of the bis(guanidine) explain the insufficient
selectivity of the tailoring: ESI+-MS monitoring of the
reaction mixture allows the detection of the bisguanidine
chelation products (see the Experimental Section).
The reaction in CH2Cl2 proceeds differently at lower
temperatures. When the reaction between cis-[PtCl2(RCN)2]
(R ) Et, CH2Ph) and DPG in a 1:2 molar ratio starts at -20
°C followed by heating to 4 °C and keeping the mixture
under this temperature for 1 day, the NH tailoring (com-
pounds 2 and 3; isolated yields are 35% and 26%, respec-
tively) (Scheme 1, route A) is accompanied by the NPh
tailoring, giving 5 and 6 in ca. 4% and 25% yields,
respectively (Scheme 1, route B). Precipitates were weighed,
fully dissolved in DMSO-d6, and analyzed by 1H NMR. The
molar ratios 2:5 and 3:6 obtained by NMR integration are
ca. 8:1 and ca. 1:1, respectively. Yields of 2 and 5 and of 3
under mild conditions and afforded diimino compounds
containing two N-bound monodentate 1,3-diaza-1,3-diene
ligands, [PtCl2{NHdC(R)NdC(NMe2)2}2]; this reaction was
the first observation of metal-mediated nucleophilic addition
of a guanidine to ligated nitrile.
As a continuation of the project focused on the study of
metal-mediated nitrile-guanidine interplay, we attempted the
reaction between another guanidine, e.g. N,N′-diphenylguani-
dine (NHdC(NHPh)2) and the PtII precursors and found that
the process with NHdC(NHPh)2 was strongly different from
that with HNdC(NMe2)2. Indeed, at the cis-PtII centers a
novel tailoring process is realized instead of the coupling,
although at the trans-PtII centers the interaction follows the
expected route; all of these processes will be considered
below in separate sections.
Nitrile-Guanidine Coupling at the cis-(RCN)2PtII
Center. The tailoring reaction of the two adjacent nitrile
ligands in cis-[PtCl2(RCN)2] (R ) Me, Et, CH2Ph, Ph) upon
interaction with NHdC(NHPh)2 in a 1:2 molar ratio proceeds
in the corresponding RCN (for R ) Me, Et) and in CH2Cl2
(for R ) Ph, CH2Ph) at 20–25 °C for 24 h or at 40 °C for
2 h and gives a 50–60% yield of Pt 1,3,5-triazapentadiene
complexes 1–4 (Scheme 1, route A).
In all cases, the complexes were separated by filtration
and the filtrates contain, as was verified by TLC, more than
10 as yet unidentified products. In addition to 1–4, another
major product formed in the reaction is, most likely,
diphenylcarbodiimide PhNdCdNPh, but this heterocumu-
lene is highly reactive and couples with HNdC(NHPh)2 to
give the biguanidine PhNdC(NHPh)NdC(NHPh)2, which
was detected by ESI+-MS (m/z 406 [M + H]+) (Scheme 1,
route A); similar reactions between carbodiimides and
various N-donor nucleophiles are well-known from the
literature.31,32 It is worth noticing that (i) we did not observe
the higher molecular weight products, which may originate
from further bis(guanidine) and (nitrile)PtII coupling, in
accord with our previous findings33 and (ii) N,N-chelating
1
and 6 were calculated on the basis of these H NMR data.
Another product of the route B (Scheme 1) is the known34
phenylcyanamide (ESI--MS, m/z 117 [M - H]-). In two
other cases (i.e., R ) Ph, Me), we were unable to isolate
the NPh-tailoring products: first, the reaction of cis-
[PtCl2(PhCN)2] with DPG at –20 °C in CH2Cl2 is not
selective, and in addition, all products which were formed
exhibit solubility too high to allow separation by fractional
recrystallization; second, the very poor solubility of cis-
[PtCl2(MeCN)2] prevented us from pursuing further studies.
It is worth noting that complex 6 could also be obtained
at 20–25 °C in CH2Cl2 by the reaction of cis-[PtCl2-
(PhCH2CN)2] with DPG in a 1:4 molar ratio; however, the
yield of solid product 6 (9%) is small and the filtrate contains
a broad spectrum of as yet unidentified products. It was also
found that 6 is not formed at all in the reaction between
cis-[PtCl2(PhCH2CN)2] and the guanidine in a 1:4 molar ratio
at 20–25 °C in MeNO2; in the latter case the only poorly
soluble product is complex 3 (yield 33%). Consequently, one
might assume that the selectivity of the tailoring reaction,
i.e. NH vs. NPh tailoring, of the two adjacent RCN nitrile
ligands in cis-[PtCl2(RCN)2] depends on the solvent polarity.
This viewpoint can be rationalized by the solvent-dependent
tautomeric equilibrium of DPG35 (Scheme 2; the left form
predominates in polar solvents) and, consequently, by
involvement of two different nucleophilic centers (NH vs
NPh) in the initial step of the reaction.
A plausible mechanism (Scheme 3) of the tailoring
involves nucleophilic attack of the PtII-activated nitrile by
either the NH (route C) or NPh (route G) center and
formation of the eight-membered chelates formed via routes
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Inorganic Chemistry, Vol. 47, No. 24, 2008 11489

Gushchin et al.
Scheme 3
C/D and G/H. Although these chelates should be unstable,
they could be isolated by us for the complexes cis-[PtCl2-
(RCN)2] bearing highly conjugated RCN species, and these
data will be published separately.36 Extruding the carbodi-
imide and narrowing the chelate ring (routes E and I) gives
the products of NH and NPh tailoring, respectively. The fate
of the carbodiimide is different and depends on its nature.
Thus, PhNdCdNPh couples with excess DPG (route F),
yielding the bis(guanidine), while HNdCdNPh rapidly
tautomerizes37 to the nitrile NCN(H)Ph (route J), which is
unreactive toward DPG.
Thus, we can see that the guanidine NHdC(NHPh)2 reacts
with cis-(RCN)2PtII centers and serves as the NH2R1-tailoring
reagent (R1 ) H, Ph) for the two adjacent nitrile ligands in
cis-[PtCl2(RCN)2] (R ) Me, Et, CH2Ph, Ph) at 20–25 °C
(R1 ) H) or at –20 °C (R1 ) Ph).
tetramethylethylenediamine (tmeda) complex cis-[Pt(tmeda)-
(EtCN)2][SO3CF3]2 (8 · (OTf)2; prepared from 738 via route
K, Scheme 4). It is important that the tmeda chelation
provides exclusive cis arrangement of the nitrile species, thus
making the complex 8 · (OTf)2 a convenient model for
studying the tailoring reaction with DPG as well as for
comparison of reactivity modes between the cis-(EtCN)2PtII
moiety and DPG vs NH3.
When a dichloromethane solution of 8·(OTf)2 was treated
with an excess of gaseous ammonia at 20-25 °C for 6 h
(Scheme 4, route L), the formation of the platinum(II)
bis(amidine) complex cis-[Pt(tmeda){NHdC(NH2)Et}2]-
[SO3CF3]2 (9 · (OTf)2) was observed and it was isolated in
85% yield; the ammination proceeds in accord with previous
observations.39–45 1H NMR monitoring proved the ab-
sence of the tailoring product [Pt(tmeda){NHdC(Et)}2NH]-
[SO3CF3]2 (10 · (OTf)2) in the reaction mixture. In contrast,
Different Reactivity Modes of the cis-(EtCN)2PtII
Moiety and DPG or NH3. Being interested in the amplifica-
tion of the tailoring reaction to other (RCN)2PtII complexes,
we decided to apply the reaction with DPG for the N,N,N′,N′-
(38) Monti, E.; Gariboldi, M.; Maiocchi, A.; Marengo, E.; Cassino, C.;
Gabano, E.; Osella, D. J. Med. Chem. 2005, 48, 857.
(39) Kukushkin, V. Yu.; Aleksandrova, E. A.; Kukushkin, Yu. N. Zh.
Obshch. Khim. 1995, 65, 1937; Chem. Abstr. 1996, 125, 24936.
(40) Kukushkin, Yu. N.; Aleksandrova, E. A.; Pakhomova, T. B. Zh.
Obshch. Khim. 1994, 64, 151; Chem. Abstr. 1994, 122, 121719.
(41) Kukushkin, Yu. N.; Aleksandrova, E. A.; Pakhomova, T. B.; Vlasova,
R. A. Zh. Obshch. Khim. 1994, 64, 705; Chem. Abstr. 1995, 121,
147636.
(36) Gushchin, P. V.; Bokach, N. A.; Haukka, M.; Kukushkin, V. Yu.
Unpublished work.
(37) Boyer, J. H.; Frints, P. J. A. J. Heterocycl. Chem. 1970, 7, 71; Chem.
Abstr. 1970, 72, 90378. Lempert, K.; Puskas, J.; Bekassy, S. Period.
Polytech., Chem. Eng. 1968, 12, 123; Chem. Abstr. 1969, 70, 11239.
(42) Longato, B.; Bandoli, G.; Mucci, A.; Schenetti, L. Eur. J. Inorg. Chem.
2001, 3021.
11490 Inorganic Chemistry, Vol. 47, No. 24, 2008

Platinum 1,3,5-Triazapentadiene Complexes
Scheme 4
Scheme 5
the reaction of 8 · (OTf)2 and DPG performed under similar
conditions (Scheme 4, route M) led to the (1,3,5-triazapen-
tadiene)PtII complex 10 · (OTf)2, derived from the tailoring
reaction, and no 9· (OTf)2 was detected in the reaction
mixture.
Moreover, in separate experiments it was established that
(i) the chelate 10 · (OTf)2 did not react with ammonia in a
methanolic solution (6 h, 20–25 °C) to give 9 · (OTf)2 and
(ii) the bis(amidine) complex 9 · (OTf)2 did not convert to
10 · (OTf)2 upon heating either in solution (24 h, 100 °C,
MeNO2) or in the solid state (gradual decomposition from
ca. 115 °C on TG; see Figure S1 in the Supporting Infor-
mation). These observations (Scheme 4, routes L and M)
indicate the unique character of the reaction and point out
that the role of DPG is more complicated and does not come
from the donation of ammonia in the novel tailoring reaction,
thus additionally supporting the plausible mechanism de-
picted in Scheme 3.
Nitrile-Guanidine Coupling at the trans-(RCN)2PtII
Center. The complex trans-[PtCl2(MeCN)2] exhibits poor
solubility in most noncoordinating solvents, and the reaction
between DPG and the more soluble trans-[PtCl2(RCN)2] (R
) Et, CH2Ph, Ph) was studied. Treatment of trans-
[PtCl2(RCN)2] (R ) Et, CH2Ph, Ph) with 2 equiv of DPG in
EtCN (R ) Et) or CH2Cl2 (R ) CH2Ph, Ph) solutions at
20–25 °C for 15–24 h resulted in formation of [PtCl{NHd
C(R)NC(NHPh)dNPh}(RCN)] (11–13), which were isolated
in 45, 26, and 20% yields, respectively, by taking the reaction
mixture to dryness, followed by washing of the solid residue
with MeOH (R ) Et) or after column chromatography on
SiO2 (R ) CH2Ph, Ph); in all three cases solutions also
contain a broad mixture of as yet unidentified compounds.
Complexes 11–13 formed as products of the nucleophilic
addition of DPG to the nitrile carbon atom, followed by ring
closure of the formed 1,3,5-triazapentadiene ligand (Scheme
5, route N). It is noteworthy that when trans-[PtCl2(RCN)2]
(R ) Et, CH2Ph, Ph) reacts with 2 equiv of DPG at room
temperature, complexes 14–16 (see below) are not formed.
A further increase in the amount of DPG from 2 to 3 equiv
decreases the yield of 11–13 to ca. 10%. The yield of 11 is
higher if the solvent is the corresponding nitrile rather than
CH2Cl2 or CHCl3 (45% when the reaction is carried out in
EtCN vs 20% in CH2Cl2). Unfortunately, the preparation of
12 and 13 in PhCH2CN or PhCN, respectively, is not
practical due to the low volatility of these solvents and
difficulties in crystallizing the final products.
When trans-[PtCl2(RCN)2] (R ) Et, CH2Ph, Ph) react in
the corresponding nitrile RCN with 4 equiv of DPG for a
prolonged reaction time (1–2 days) at 75 °C (Scheme 5, route
O) or 11–13 are treated with 2 equiv more of DPG at the
same temperature (Scheme 5, route P), complexes containing
two bidentate 1,3,5-triazapentadiene ligands, i.e. [Pt{NHd
C(R)NC(NHPh)dNPh}2] (14–16), are formed and they are
isolated in 63–73% yields. Thus, the reaction of DPG and
the trans-(RCN)2Pt complexes follows the expected path
(43) 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.
(44) Belluco, U.; Benetollo, F.; Bertani, R.; Bombieri, G.; Michelin, R. A.;
Mozzon, M.; Pombeiro, A. J. L.; Guedes da Silva, F. C. Inorg. Chim.
Acta 2002, 330, 225.
(45) Natile, G.; Intini, F. P.; Bertani, R.; Michelin, R. A.; Mozzon, M.;
Sbovata, S. M.; Venzo, A.; Seraglia, R. J. Organomet. Chem. 2005,
690, 2121.
Inorganic Chemistry, Vol. 47, No. 24, 2008 11491

Gushchin et al.
all have square-planar geometry. In 1, 2, and 4, atoms
forming the metallacycles lie in one plane with the rms
deviations 0.009(3) (1), 0.059(3) (2), and 0.064(5) Å (4).
The CN bonds in the metallacycles of 1, 2, and 4 have a
low degree of delocalization. The bond lengths N(1)-C(1),
N(2)-C(2) in 1, 2, and 4 are 1.287(4), 1.285(4) Å, 1.287(5),
1.281(5) Å, and 1.289(7), 1.286(7), 1.297(7), 1.298(7),
1.281(7), 1.291(7) Å, respectively (Table 1). These values
are closer to the CdN double-bond value and comparable
with the corresponding CdN double bonds of the bis-cationic
(1,3,5-triazapentadiene/ato)NiII complex [Ni{NHdC(R)NHC-
(R)dNH}2]2+ (1.282(3)–1.294(3) Å).10 The bond lengths
N(3)-C(1), N(3)-C(2) in 1, 2, and 4 are 1.363(4), 1.374(4)
Å, 1.368(4), 1.379(4) Å, and 1.391(7), 1.366(7), 1.378(7),
1.374(7), 1.386(7), 1.376(8) Å, respectively. These values
are closer to the C-N single-bond value and comparable
with the corresponding C-N single-bond values of the bis-
cationic (1,3,5-triazapentadiene/ato)NiII complex [Ni{NHd
C(R)NHC(R))NH}2]2+ (1.357(4)–1.374(4) Å).10 In 4, the
adjacent molecules are linked by weak (NH · · · Cl) interac-
tions (Figure S5 and Table S1 in the Supporting Information).
Figure 1. Thermal ellipsoid view of complex 4 with the atomic numbering
scheme. Thermal ellipsoids are drawn at the 50% probability level.
previously established by us for the metal-mediated nitrile-
amidine coupling.20
(B) Complexes 9 ·(OTf)2 and 10 ·(OTf)2. In the IR spectra
of 9·(OTf)2 and 10 ·(OTf)2, the PtII-bound amidine and 1,3,5-
triazapentadiene ligands exhibit medium-to-strong bands at
3439–3242 cm-1, which can be attributed to the N-H
stretching vibrations, and display no bands in the region
specific to ν(CtN) stretches. The IR spectrum of 9 · (OTf)2
shows CdN absorption bands in the range between 1659
and 1616 cm-1 characteristic of amidine ligands, while for
10 · (OTf)2, the ν(CdN) peaks of the 1,3,5-triazapentadiene
ligand appear as two strong bands at 1610 and 1547 cm-1.
The latter values are lower than those for the (amidine)2PtII
complex 9 · (OTf)2, and this fact can be rationalized by a
conjugation (although of low degree; see later discussion on
the X-ray structures) within the 1,3,5-triazapentadienyl
chelating system.
Characterization of (1,3,5-triazapentadiene)PtII Com-
plexes. The formulation of complexes 1–4, 9 · (OTf)2,
10 · (OTf)2, and 11–16 was supported by satisfactory C, H,
and N elemental analyses, in agreement with FAB+ (1–3,
9·(OTf)2, 11–16), ESI+-MS (5, 6, 8·(OTf)2, 10 ·(OTf)2), and
ESI--MS (1–6) data. In the IR spectra, (1,3,5-triazapenta-
diene/ato)PtII (1–4), 10 · (OTf)2, 11–16, and also the
(amidine)2PtII complex 9 · (OTf)2 display strong ν(CdN) or
ν(CdN and/or CdC) bands in the range 1672–1442 cm-1.
The structures of 1, 2, 4, 11, 13, and 14 and picrates of
complexes 92+ and 102+ were determined by single-crystal
X-ray diffraction.
(A) Complexes 1–4. Comparison of the IR spectra of 1–4
with those of the starting materials indicates the absence of
the CtN stretching vibrations and the presence of strong
ν(CdN) bands in the range 1672–1539 cm-1 and N-H
stretching vibrations, which emerge at higher frequencies
(3396–3043 cm-1). A characteristic feature of the 1H NMR
spectra of 1–4 is the availability of two singlets with 1:2
intensities from the NH protons at 11.28–10.65 and 10.22–9.45
ppm, respectively. The position of the signals at such a low
field gives indirect evidence that the NH proton is involved
in hydrogen bonding in solution.46 The most downfield signal
in the region of 11.28–10.65 ppm corresponds to the proton
at the central N atom.
The amidine resonances of 9 · (OTf)2 are observed in the
1H NMR spectrum as broad singlets in a 1:1:1 ratio at 6.68
ppm for the imino (HNdC) protons and at 7.07 and 7.43
ppm for the amido (H2NC) protons; we believe these sets of
signals are related to the existence of a few conformational
1
forms in solution. In the H NMR spectrum of 10 · (OTf)2,
NH resonances moved to low field and emerged at 10.94
ppm for the proton at the central N atom and at 9.22 ppm
for the imino protons (HNdC) in a 1:2 ratio. In the 13C{1H}
NMR spectra, the carbons from the NdC-N moiety were
detected at ca. 174 ppm for 9 · (OTf)2 and at ca. 164 ppm
for 10 · (OTf)2.
The structures of 1, 2, and 4 were determined by X-ray
single-crystal diffraction (Figure 1 and Figures S2 and S3
in the Supporting Information), and it was observed that they
Complexes 92+ and 102+ were isolated as the picrates, and
these two salts give crystals suitable for X-ray diffraction
studies (Figure 2, Table 2). The Pt-Ntmeda bonds in 92+
(2.059(6), 2.074(5) Å) and 102+ (2.071(3), 2.078(3) Å) and
the Pt-Nimine bonds in 92+ (1.997(5), 1.999(5) Å) and 102+
(1.987(3), 1.991(3) Å) agree well with each other and with
those found in [Pt{NHdC(NH2)NMe2}(dien)][SO3CF3]2
(dien ) diethylenetriamine) (2.036(6)-2.049(6) Å for
(46) Makarycheva-Mikhailova, A. V.; Haukka, M.; Bokach, N. A.; Gar-
novskii, D. A.; Galanski, M.; Keppler, B. K.; Pombeiro, A. J. L.;
Kukushkin, V. Yu. New J. Chem. 2002, 26, 1085. 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.
Kukushkin, V. Yu.; Pakhomova, T. B.; Kukushkin, Yu. N.; Herrmann,
R.; Wagner, G.; Pombeiro, A. J. L. Inorg. Chem. 1998, 37, 6511.
11492 Inorganic Chemistry, Vol. 47, No. 24, 2008

Platinum 1,3,5-Triazapentadiene Complexes
Figure 2. Thermal ellipsoid views of complexes 92+ (left) and 102+ (right) with the atomic numbering scheme. Thermal ellipsoids are drawn at the 50%
probability level. The picrate anions are omitted for simplicity.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 1, 2, and 4
1
2
4Aa
4Ba
4Ca
Pt(1)-N(1)
Pt(2)-N(2)
Pt(1)-Cl(1)
Pt(1)-Cl(2)
N(1)-C(1)
N(2)-C(2)
N(3)-C(1)
N(3)-C(2)
1.965(2)
1.964(3)
2.3250(8)
2.3190(8)
1.287(4)
1.285(4)
1.363(4)
1.374(4)
1.969(3)
1.971(3)
2.3139(8)
2.3226(8)
1.287(5)
1.281(5)
1.368(4)
1.379(4)
1.965(5)
1.960(5)
2.3167(14)
2.3121(14)
1.289(7)
1.286(7)
1.391(7)
1.366(7)
1.975(4)
1.970(5)
2.3174(13)
2.3146(14)
1.297(7)
1.298(7)
1.378(7)
1.374(7)
1.959(5)
1.968(5)
2.3144(15)
2.3071(14)
1.281(7)
1.291(7)
1.386(7)
1.376(8)
N(1)-Pt(1)-N(2)
Cl(1)-Pt(1)-Cl(2)
C(1)-N(3)-C(2)
89.66(10)
93.93(3)
129.1(3)
89.63(12)
92.65(3)
128.7(3)
89.4(2)
95.72(5)
127.8(5)
89.4(2)
92.56(5)
127.9(5)
89.5(2)
94.51(5)
128.0(5)
a The asymmetric unit of 4 contains three independent molecules.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 92+ and 102+
(C) Complexes 11–16. The IR spectra of these compounds
display strong ν(CdN and/or CdC) bands at 1636–1442
cm-1 and N-H stretching vibrations in the range of
3422-3338 cm-1. These ranges agree well with values of
ν(CdN and/or CdC) (1632-1430 cm-1) and ν(N-H)
(3395–3282 cm-1) bands for the (1,3,5-triazapentadiene/
ato)PtII complexes [PtCl(NCR){NHdC(R)NC(Ph)N(Ph)}]
and [Pt{NHdC(R)NC(Ph)N(Ph)}2] (Et, CH2Ph, Ph).20 The
weak CtN stretching vibrations are present in the IR spectra
for compounds 11-13 but not in those for complexes 14-16.
This can be rationalized by the fact that 14-16 are products
of the nucleophilic addition of DPG to both nitriles RCN of
trans-[PtCl2(RCN)2] (R ) Et, CH2Ph, Ph), while 11-13 are
formed in the reaction incorporating one ligand RCN of
trans-[PtCl2(RCN)2] (R ) Et, CH2Ph, Ph) with DPG. The
92+
102+
Pt(1)-N(1)
Pt(1)-N(2)
Pt(1)-N(3)
Pt(1)-N(4)
N(1)-C(3)
N(2)-C(4)
N(3)-C(7)
N(5)-C(7)
C(3)-C(4)
2.059(6)
2.074(5)
1.999(5)
1.997(5)
1.494(9)
1.494(8)
1.299(8)
1.326(8)
1.491(10)
2.071(3)
2.078(3)
1.991(3)
1.987(3)
1.505(5)
1.495(5)
1.282(5)
1.364(5)
1.493(6)
N(1)-Pt(1)-N(2)
N(3)-Pt(1)-N(4)
N(3)-C(7)-N(5)
85.6(2)
88.3(2)
120.9(6)
85.31(12)
88.08(12)
122.0(3)
Pt-Ndien and 1.997(6), 2.018(7) Å for Pt-Nimine).47 The CdN
bond lengths in (amidine)2PtII(tmeda) (1.288(8) and 1.299(8)
Å) and (1,3,5-triazapentadiene)PtII(tmeda) (1.279(5) and
1.282(5) Å) and the C-N bond lengths (1.326(8) and
1.340(8) Å and 1.364(5) and 1.371(5) Å, respectively) have
values typical for the (amidine)2PtII complexes43,44 and for
the (1,3,5-triazapentadiene)PtII complexes, listed above, and
correspond, within 3σ, with each other. Therefore, the bond
lengths are statistically equivalent within the two classes of
ligands, and differences between complexes 92+ and 102+
are observed only in their spectra.
1
characteristic feature of H NMR spectra of the (1,3,5-
triazapentadiene/ato)PtII complexes 11-16 is the presence
of two singlets due to the NH protons in the range of
6.50–4.84 ppm.
The structures of 11, 13, and 14 were determined by
single-crystal X-ray diffraction (Figures 3 and 4, Table 3,
and Figure S4 in the Supporting Information). They all have
square-planar geometry. In 11, the disordered coordinated
nitrile is bent (N(4)-C(3)-C(4A) ) 168.4(6)° and N(4)-
C(4)-C(C4B) ) 154.9(6)°), probably because of the steric
repulsion from the aromatic ring of the chelated ligand, while
in 13 the nitrile fragment is linear (N(4)-C(3)-C(4) )
179.0(7)°). The bond lengths of N(3)-C(2) in 11 and
(47) 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.
Inorganic Chemistry, Vol. 47, No. 24, 2008 11493

Gushchin et al.
Figure 5. Absorption spectra in CH2Cl2 and the normalized solid-state
emission spectra of 14 (O), 15 (0), and 16 (4). Inset: emission spectrum
of 16 in CH2Cl2. The excitation wavelength is set at 350 nm. All
measurements were performed at 25 °C.
Figure 3. Thermal ellipsoid view of complex 13 with the atomic numbering
scheme. Thermal ellipsoids are drawn at the 50% probability level.
CAr-CdN-C moiety48 (mean value 1.279(8) Å). The bond
lengths N(2)-C(2) and N(2)-C(1) in 11 (1.333(4) and
1.346(4) Å, respectively) and in 14 (1.344(3) and 1.332(3)
Å, respectively) have values closer to the corresponding N-C
bonds in both (1,3,5-triazapentadiene/ato)M (M ) PtII, NiII)
complexes.10,20 The bond lengths N(1)-C(1) in 11 (1.330(4)
Å) and in 14 (1.339(3) Å) are longer than the corresponding
NdC bond lengths in both (1,3,5-triazapentadiene/ato)M (M
) PtII, NiII) complexes,10,20 which can be related to the
influence of the NHPh group. However, all values still remain
typical, within 3σ, for such types of 1,3,5-triazapentadiene/
ato metallacycles. The NdC and N-C bond lengths in the
metallacycles 11 and 14, in contrast to the case for (1,3,5-
triazapentadiene/ato)M (M ) PtII, NiII),10,20 exhibit a greater
degree of delocalization in the ring. The distinct distribution
of double and single CN bonds in the metallacycle 13 is
vague (the bond lengths N(3)-C(2), N(2)-C(2), N(2)-C(1),
and N(1)-C(1) are 1.330(8), 1.352(8), 1.345(8), and 1.354(8)
Å, respectively); it has a greater degree of the delocalization
in comparison to 11 and 14 and a significantly higher degree
of delocalization as compared with PtII and NiII 1,3,5-
triazapentadiene/ato complexes.10,20 In 11, 13, and 14 the
atoms of the metallacycles lie in one plane with rms
deviations 0.094(3) (11), 0.061(5) (13), and 0.143(2) Å (14).
Photophysical Data for 14–16 and Theoretical Ap-
proaches for Their Interpretation. Focus of this section
is mainly on complexes 14–16, due to their unique structures
and great luminescence intensity in the solid state (vide infra).
The absorption and luminescence spectra have been recorded
for 14–16 in CH2Cl2 and in the solid state. The associated
spectra are depicted in Figure 5, and pertinent data are
summarized in Table 4. In general, the high-energy absorp-
tion bands at <300 nm for 14–16 can be reasonably assigned
to the 1,3,5-triazapentadiene ππ* transition. The next lower
energy band with a shoulder at ∼350 nm (390 nm for 16) is
assigned to the spin-allowed metal-to-ligand charge transfer
(1MLCT) transition, due to its relatively lower absorptivity.
Supplementary support of these assignments is also provided
Figure 4. Thermal ellipsoid view of complex 14 with the atomic numbering
scheme. Thermal ellipsoids are drawn at the 50% probability level.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for 11, 13,
and 14
11
13
14
Pt(1)-N(1)
Pt(1)-N(3)
Pt(1)-N(4)
Pt(1)-Cl(1)
N(1)-C(1)
N(2)-C(1)
N(2)-C(2)
N(3)-C(2)
N(5)-C(1)
N(5)-C(16)
N(4)-C(3)
C(3)-C(4)
C(3)-C(4A)a
C(3)-C(4B)a
2.017(2)
1.952(3)
2.001(3)
2.3112(8)
1.330(4)
1.346(4)
1.333(4)
1.313(4)
1.370(4)
1.414(4)
1.115(5)
2.001(5)
1.941(5)
1.979(5)
2.3169(15)
1.354(8)
1.345(8)
1.352(8)
1.330(8)
1.372(8)
1.422(8)
1.154(8)
1.434(8)
2.039(2)
1.990(2)
1.339(3)
1.332(3)
1.344(3)
1.306(3)
1.381(3)
1.414(3)
1.489(7)
1.605(12)
N(1)-Pt(1)-N(3)
Cl(1)-Pt(1)-N(4)
C(1)-Pt(1)-C(2)
C(1)-N(5)-C(16)
Pt(1)-N(4)-C(3)
88.76(10)
89.14(8)
123.3(3)
128.9(2)
174.8(3)
89.6(2)
90.26(15)
121.9(5)
127.9(5)
172.9(5)
87.23(8)
122.8(2)
130.5(2)
a In 11, C(4) is disordered over two sites.
N(3)-C(2) in 14 (1.313(4) and 1.306(3) Å, respectively)
have values typical for the corresponding NdC bonds in both
PtII and NiII 1,3,5-triazapentadiene/ato complexes10,20 and,
within 3σ, the NdC bond in compounds with the
(48) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A. G.;
Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1.
11494 Inorganic Chemistry, Vol. 47, No. 24, 2008

Platinum 1,3,5-Triazapentadiene Complexes
Table 4. Photophysical Properties of 14–16
To gain more insight into the above photophysical
behavior, the electronic transition properties calculations of
14–16 were performed using density functional theory
method (DFT). With the use of the TD-B3LYP method
incorporating the obtained geometries from the structural
optimization calculations, the vertical (i.e., Franck–Condon)
excitation energy from the ground state to the lowest lying
electronic excited state in both singlet and triplet manifolds
was calculated. The TDDFT results are summarized in Figure
6. Clearly, the calculated S1 and T1 energy levels for the
title complexes are qualitatively consistent with the 0–0 onset
of the absorption (S1) and phosphorescence (T1) spectra.
Thus, the theoretical level adopted here should be suitable
for studying the photophysical properties of these complexes
in a qualitative manner. As shown in Figure 6, the transitions
to S1 and T1 are mainly attributed to the HOMO f LUMO
transition for complexes 14 and 16, while the excitation, in
part, also involves the HOMO f LUMO+1 transition for
complex 15. The frontier orbitals, HOMO, and LUMO
for 14–16 are also depicted in Figure 6. Evidently, the
HOMO f LUMO transition for all the complexes involves
metal to ligand charge transfer (MLCT) and part of the ligand
ππ* character. For complexes 14 and 15, the transitions also
incorporate certain degrees of the dd* transition. Knowing
that a dd* transition normally causes weakness of the
metal–ligand bonding strength, the results may partially
account for the nonemissive properties of complexes 14 and
15 in CH2Cl2. Further support is given by complex 16. In
sharp contrast to complexes 14 and 15, the lowest lying state
of complex 16 involves negligible dd* transition and hence
16 exhibits a relatively higher quantum yield of 0.007 in
CH2Cl2. It is also noteworthy that a similar dd* transition
may not cause drastic radiationless quenching in the solid
state due to the confinement of the lattice energy.
λabs (nm)a
λ
emission, nmb
Φfb
τobs (µs)b
τr (µs)b
14
15
16
295, 353
290, 351
315, 380
530
460
530
535
0.39
0.61
2.62
3.69
0.82
0.01c
6.72b
6.04b
1.10b
1.71c
0.74
0.007c
a The absorption spectrum was acquired in CH2Cl2. b Measurements were
perfomed in the solid state. τobs and τr denote the observed and radiative
decay times, respectively. c Data were recorded in degassed CH2Cl2 solution
using three freeze–pump–thaw cycles.
by the computational approaches (vide infra). We unfortu-
nately could not resolve any emission for complexes 14 and
15 in degassed CH2Cl2 solutions at room temperature, while
a weak emission (quantum yield Φf ≈ 7 × 10-3) was
resolved with a peak wavelength at ∼535 nm (see inset of
Figure 5). Taking into account the sensitivity of the current
detection system, the emission yield for 14 and 15, if there
is any, is concluded to be less than 10-5. Such an observation
is similar to the case for many PtII complexes, which are
emissive in the solid state, whereas they are nonemissive in
fluid solutions at room temperature.49 The title Pt complexes
are in a square-planar configuration and possess an empty d
orbital perpendicular to the plane. The empty orbital is
subject to coordination by electron donors in the solvent,
resulting in a dominant radiationless transition. The quench-
ing processes associated with e.g. solvent collision and/or
large amplitude motions can be drastically reduced in the
form of a solid film. Supporting evidence is provided by the
strong emission acquired in the solid state for the studied
complexes, with Φf being measured to be 0.39, 0.61, and
0.74 for 14-16, respectively (see Figure 5 and Table 4).
Knowing that Φf × τr ) τobs, where τobs and τr denote the
measured and radiative lifetimes, respectively, τr for 14–16
can thus be calculated and are given in Table 4. Clearly, the
deduced radiative lifetime of microseconds for all 14–16
confirms the origin of emission from the triplet manifold:
i.e., phosphorescence.50,51 Furthermore, the short radiative
lifetime, in combination with the lack of vibronic progression
in emission spectra, manifests the T1-S0 transition to be
MLCT mixed, in part, with ππ* character. For complex 16,
the emission spectrum in view of peak wavelength and
spectral features in CH2Cl2 is similar to that in the solid film.
Since 16 should exist in a well-dispersed, monomeric form
in CH2Cl2, it is thus reasonable to conclude negligible
intermolecular Pt-Pt nonbonding interactions for 16 in the
solid film. Knowing such interactions frequently take place
in PtII complexes,52 the negligible PtII packing interaction
in solid films can possibly be rationalized by the overall
nonplanar structure, avoiding significant intermolecular
interaction.
Final Remarks
The results from this work can be summarized into three
perspectives. First, the tailoring reaction between two cis-
ligated RCN species represents a novel reactivity mode,
which has never been reported at any metal center. Although
this synthetic transformation was demonstrated only for
nitriles at PtII centers, we anticipate amplifying this type of
reaction to RCN ligands at other metal centers and extending
the application to, for example various homoleptic nitrile hard
or soft metal complexes.53 Second, the tailoring reaction
constitutes a facile route to the trinitrogen analogues of the
1,3-dicarbonyls, i.e., Pt 1,3,5-triazapentadienyl complexes.
Despite increasing interest in the latter systems, relevant
reports are rare, mainly because the synthetic methods so
far are rather poorly developed. Third, bis(1,3,5-triazapen-
tadiene)PtII complexes such as 14–16 are found to exhibit
strong luminescence in the solid state, raising the future
possibility that these systems may be useful for sensing or
(49) Kui, S. C. F.; Chui, S. S. Y.; Che, C. M.; Zhu, N. J. Am. Chem. Soc.
2006, 128, 8297.
(50) Chang, S.-Y.; Kavitha, J.; Hung, J.-Y.; Chi, Y.; Cheng, Y.-M.; Li,
E. Y.; Chou, P.-T.; Lee, G.-H.; Carty, A. J. Inorg. Chem. 2007, 46,
7064.
(51) Scaffidi-Domianello, Y. Yu.; Nazarov, A. A.; Haukka, M.; Galanski,
M.; Keppler, B. K.; Schneider, J.; Du, P.; Eisenberg, R.; Kukushkin,
V. Yu. Inorg. Chem. 2007, 46, 4469.
(52) Chang, S.-Y.; Kavitha, J.; Li, S.-W.; Hsu, C.-S.; Chi, Y.; Yeh, Y.-S.;
Chou, P.-T.; Lee, G.-H.; Carty, A. J.; Tao, Y.-T.; Chien, C.-H. Inorg.
Chem. 2006, 45, 137.
(53) Davies, J. A.; Hockensmith, C. M.; Kukushkin, V. Yu.; Kukushkin,
Yu. N. Synthetic Coordination Chemistry: Principles and Practice;
World Scientific: Singapore, 1996; pp 95–156.
Inorganic Chemistry, Vol. 47, No. 24, 2008 11495

Gushchin et al.
Figure 6. Descriptions, energy gaps, oscillation strengths of S1 and T1, and HOMO and LUMO of 14–16.
isomeric cis:trans ratio obtained by NMR integration is ca. 5:1
for R ) Me54 and ca. 6:1 for R ) Et55). The isomerically pure
complexes trans-[PtCl2(RCN)2] (R ) Et,55 CH2Ph56) and cis-
[PtCl2(PhCH2CN)2]56 were obtained as previously described. The
complex trans-[PtCl2(PhCN)2] was obtained upon heating
display applications, upon proper derivatization. Work focus-
ing on these projects is underway in our group.
Experimental Section
Materials and Instrumentation. The guanidine HNdC(NHPh)2
(Aldrich) and solvents were obtained from commercial sources
and used as received. The complexes cis-[PtCl2(RCN)2] (R )
Me,54 Et55) were prepared in accord with the published methods.
These compounds contain admixtures of the trans isomers (an
(54) Fanizzi, F. P.; Intini, F. P.; Maresca, L.; Natile, G. J. Chem. Soc.,
Dalton Trans. 1990, 199.
(55) Svensson, P.; Lövqvist, K.; Kukushkin, V. Yu.; Oskarsson, Å. Acta
Chem. Scand. 1995, 49, 72. Kukushkin, V. Yu.; Oskarsson, Å.; Elding,
L. I. Inorg. Synth. 1997, 31, 279.
11496 Inorganic Chemistry, Vol. 47, No. 24, 2008

Platinum 1,3,5-Triazapentadiene Complexes
Table 5. Crystal Data
1
2
4
92+
102+
11
13
14
empirical formula C4H9Cl2N3Pt C6H13Cl2N3Pt C90H92Cl12N18O3Pt6 C24H36N12O14Pt C24H33N11O14Pt C19H22ClN5Pt C27H22ClN5Pt C32H34N8Pt
fw
temp (K)
λ (Å)
cryst syst
space group
a (Å)
365.13
120(2)
0.710 73
monoclinic
P21/c
393.18
120(2)
0.710 73
monoclinic
P21/n
3069.76
120(2)
0.710 73
monoclinic
P21/c
18.8625(11)
16.8259(3)
16.1677(4)
90
103.071(1)
90
4998.3(3)
2
911.74
120(2)
894.70
120(2)
0.710 73
monoclinic
P2/c
23.7788(6)
8.25930(10)
16.7947(5)
90
104.5010(10)
90
3193.34(13)
4
1.861
4.480
36 698
7314
550.96
150(2)
647.04
120(2)
725.76
120(2)
0.710 73
triclinic
0.710 73
triclinic
0.710 73
triclinic
0.710 73
Ttriclinic
j
j
j
j
P1
P1
P1
P1
16.0700(12) 7.0744(2)
8.8755(4)
12.8837(4)
15.8393(9)
79.692(3)
84.415(2)
71.220(3)
1685.58(13)
2
1.796
4.246
25 566
6362
10.2632(3)
10.4416(3)
10.9637(3)
64.084(2)
85.286(2)
67.6680(10)
972.52(5)
2
1.881
7.364
17 081
4428
9.1616(5)
10.1225(4)
13.6355(8)
99.329(3)
105.703(2)
93.557(3)
1193.75(11)
2
1.800
6.015
18 018
5210
5.9465(2)
11.2920(3)
12.0993(4)
109.305(1)
101.928(2)
103.712(2)
707.99(4)
1
1.702
4.992
9087
3225
b (Å)
c (Å)
9.8856(8)
12.9953(8)
90
123.432(3)
90
1722.9(2)
8
2.815
10.9430(2)
13.4809(3)
90
101.901(1)
90
1021.19(4)
4
2.557
14.215
19 450
2338
0.0488
0.0185
0.0432
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
Z
Fcalcd (Mg/m3)
2.040
8.742
µ (Mo KR) (mm3) 16.840
no. of rflns
10 483
90 669
11 421
0.0557
0.0335
0.0644
2
no. of unique rflns 1972
Rint
0.0293
0.0156
0.0281
0.0568
0.0384
0.0946
0.0562
0.0319
0.0586
0.0324
0.0195
0.0486
0.0656
0.0419
0.0932
0.0362
0.0178
0.0426
R1a (I g 2σ)
wR2b (I g 2σ)
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑[w(Fo - Fc )2]/∑[w(Fo )2]]1/2
.
2
2
[PtCl2(MeCN)2] with PhCN,57 followed by separation of the
admixture of the cis isomer by column chromatography on SiO2
(silica gel 60 F254, 0.063–0.200 mm, Merck; eluent is 1/20
(v/v) ethyl acetate-CHCl3, Rf for the trans isomer is 0.68). The
cis-[PtCl2(PhCN)2] complex was separated from the cis/trans
isomeric mixture, which was obtained in the reaction58 between
K2[PtCl4] and PhCN in water, by column chromatography on
SiO2 (silica gel 60 F254, 0.063–0.200 mm, Merck; eluent 1/20
ethyl acetate-CHCl3, Rf for the cis isomer is 0.31). TLC was
done on Merck 60 F254 SiO2 plates.
solved by direct methods using SHELXS-97,61 SIR2002, or SIR2004
with the WinGX62 graphical user interface. An empirical absorption
correction was applied to all of the data (SADABS63 or XPREP in
SHELXTL64). Structural refinements were carried out using SHELXL-
97.65 The asymmetric unit of 4 contains three independent Pt
molecules, an acetone molecule, and half of a water molecule. In
11 the carbon atoms C(4) and C(5) were disordered over two sites
with occupancies 0.43/0.57. In 1, 2, 4, 92+, 102+, 11, and 14 the
NH and H2O hydrogen atoms were located from the difference
Fourier map but constrained to ride on their parent atom with Uiso
being 1.5 times the Ueq value for the parent atom. Other hydrogens
were positioned geometrically and constrained to ride on their parent
atoms, with C-H ) 0.95–0.99 Å, N-H ) 0.88 Å, and Uiso being
1.2–1.5 times the Ueq value for the parent atom. The crystallographic
details are summarized in Table 5, and selected bond lengths and
angles in Tables 1-3.
Luminescence Study of 14–16. Steady-state absorption and
emission spectra were recorded by a Hitachi (U-3310) spectropho-
tometer and an Edinburgh (FS920) fluorimeter, respectively. Both
the wavelength-dependent excitation and emission responses of the
fluorimeter were calibrated. A configuration of the front-face
excitation was used to measure the emission of the solid sample,
for which the cell was made by assembling two edge-polished
quartz plates with various Teflon spacers. A combination of
appropriate filters was used to avoid interference from the scattering
light. An integrating sphere (Labsphere) was applied to measure
the quantum yield in the solid state, with excitation by a 365 nm
Ar+ laser line. The resulting luminescence was acquired with a
charge-coupled detector (Princeton Instruments, Model CCD-1100)
for subsequent quantum yield analyses. Lifetime studies were
performed with an Edinburgh FL 900 photon-counting system with
a hydrogen-filled or nitrogen lamp as the excitation source.
Theoretical Methodology. All calculations were done with the
Gaussian 03 program.66 The geometries of complexes 14–16 were
Elemental analyses were obtained on a Hewlett-Packard 185B
carbon hydrogen nitrogen analyzer. DTA/TG measurements were
performed using a Perkin-Elmer (Diamond TG/DTA) derivatograph
in air at a heating rate of 10 °C/min (carrier gas air, 200 mL/min).
ESI-TOF mass spectra were obtained on a MX-5310 mass
spectrometer. Positive-ion FAB mass spectra of the platinum(II)
complexes were obtained on a MS-50C (Kratos) instrument by
bombarding 3-nitrobenzyl alcohol matrices of the samples with 8
keV (ca. 1.28 × 1015 J) Xe atoms. Mass calibration for data system
acquisition was achieved using CsI. Infrared spectra (4000–400
cm-1) were recorded on a Shimadzu FTIR 8400S instrument in
1
KBr pellets. H and 13C{1H} NMR spectra were measured on a
Bruker-DPX 300 spectrometer at ambient temperature.
X-ray Crystal Structure Determinations. The crystals were
immersed in cryo oil and mounted in a nylon loop, and the data
were measured at a temperature of 120 or 150 K. The X-ray
diffraction data were collected by means of a Nonius KappaCCD
diffractometer using Mo KR radiation (λ ) 0.710 73 Å). The
Denzo-Scalepack59 and EvalCCD60 program packages were used
for cell refinements and data reductions. All of the structures were
(56) Kukushkin, V. Yu.; Tkachuk, V. M.; Vorobiov-Desiatovsky, N. V.
Inorg. Synth. 1998, 32, 144.
(57) 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.
(61) Sheldrick, G. M. SHELXS-97, Program for Crystal Structure Deter-
mination, University of Göttingen, Göttingen, Germany, 1997.
(62) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
(63) Sheldrick, G. M. SADABS - Bruker Nonius Scaling and Absorption
Correction, V 2.10; Bruker AXS, Inc., Madison, WI, 2003.
(64) Sheldrick, G. M. SHELXTL V. 6.14-1; Bruker AXS, Inc., Madison,
WI, 2005.
(58) Fanizzi, F. P.; Intini, F. P.; Natile, G. J. Chem. Soc., Dalton Trans.
1989, 947.
(59) Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data
Collected in Oscillation Mode. In Methods in Enzymology; Carter,
C. W., Sweet, J., Eds.; Academic Press: New York, 1997; Vol. 276,
Macromolecular Crystallography, Part A, pp 307–326.
(60) Duisenberg, A. J. M.; Kroon-Batenburg, L. M. J.; Schreurs, A. M. M.
J. Appl. Crystallogr. 2003, 36, 220–229.
(65) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Refine-
ment; University of Göttingen, Göttingen, Germany, 1997.
Inorganic Chemistry, Vol. 47, No. 24, 2008 11497

Gushchin et al.
calculated by the hybrid DFT B3LYP functional.67 Except for the
platinum element, the split-valence basis set 6-31G* was chosen
to describe the other elements. The pseudopotential LANL2
combines a valence double-ꢁ basis set; i.e., LANL2DZ was chosen
for platinum in order to describe its relativistic effect.68 All minima
were identified positively, as the number of imaginary frequencies
is zero. On the basis of the converged geometries, the vertical
excitation energies were calculated by TDB3LYP with the same
basis set mentioned above.69
(s), ν(N-H); 3028 (m), ν(N-H and/or C-H from Et); 2993 (m),
2978 (m), 2941 (m), 2879 (m-w), 2758 (m-w), ν(C-H from Et);
1664 (s), 1543 (s), ν(CdN). H NMR (DMSO-d6, δ): 10.87 (s,
1H, NH), 9.87 (s, br, 2H, NHdCEt), 2.39 (q, 7.3 Hz, 4H, CH2),
1.09 (t, 7.3 Hz, 6H, CH3) (Et). 13C{1H} NMR (DMSO-d6, δ): 157.26
(CdN), 28.73 (CH2), 11.73 (CH3) (Et). Crystals suitable for an
X-ray diffraction study were obtained directly from the reaction
mixture.
1
3. Anal. Calcd for C16H17N3Cl2Pt: C, 37.15; H, 3.31; N, 8.12.
Found: C, 37.02; H, 3.39; N, 7.91. ESI--MS (m/z): 516 [M - H]-.
FAB+-MS (m/z): 556 [M + K]+, 540 [M + Na]+, 517 [M]+, 482
[M - Cl]+. TLC: Rf ) 0.33 (eluent 1/10 MeOH-CHCl3). IR (KBr,
selected bands, cm-1): 3309 (m-s), 3256 (m-s), 3166 (m-s),
ν(N-H); 3043 (m), ν(N-H and/or C-H from Ar); 2908 (m-w),
2732 (w), ν(C-H from CH2Ph); 1672 (s), ν(CdN); 1592 (w), 1543
(m-s), ν(CdN and/or CdC from Ar); 745 (m-s), 701 (s), δ(C-H
Synthetic Work. Reaction of cis-[PtCl2(RCN)2] and DPG
(2 equiv). HNdC(NHPh)2 (53 mg, 0.25 mmol) was added to a
solution of cis-[PtCl2(RCN)2] (0.12 mmol) in MeCN (1.2 mL; R
) Me), EtCN (1 mL; R ) Et), or CH2Cl2 (1 mL; R ) CH2Ph, Ph),
and the mixture was left to stand for 2 h at 40 °C and then (for
digestion of the initially formed precipitate) for 22 h at 20–25 °C
(R ) Me, Et) (crystals started to release already after 5-10 min)
or 24 h at 20–25 °C (R ) CH2Ph, Ph) (pale yellow precipitate
immediately began to release for R ) CH2Ph). Pale yellow crystals
(R ) Me, Et) or a pale yellow precipitate (R ) CH2Ph) was filtered
off, washed with two 0.5 mL portions of Me2CO and one 0.5 mL
portion of Et2O, and dried in air at 20–25 °C. The greenish yellow
solution formed for R ) Ph was evaporated to dryness, and the
green oily residue was crystallized under a layer of hexane (1 mL)
to form the solid yellow powder, which was washed with two 1
mL portions of Et2O, dissolved in CHCl3, purified by column
chromatography on SiO2 (silica gel 60 F254, 0.063–0.200 mm,
Merck; eluent 1/10 Me2CO-CHCl3, Rf ) 0.40), and dried in air at
20–25 °C. Yields are 19 mg, 44% (R ) Me), 25 mg, 54% (R )
Et), 36 mg, 58% (R ) CH2Ph), and 17 mg, 30% (R ) Ph).
1. Anal. Calcd for C4H9N3Cl2Pt: C, 13.16; H, 2.48; N, 11.51.
Found: C, 13.19; H, 2.48; N, 11.59. ESI--MS (m/z): 364 [M -
H]-. FAB+-MS (m/z): 388 [M + Na]+, 365 [M]+, 329 [M - Cl]+.
TLC: Rf ) 0.69 (eluent 1/5 MeOH-CHCl3). IR (KBr, selected
bands, cm-1): 3338 (m), 3282 (s), 3248 (s), 3149 (s), 3043 (m-s),
ν(N-H); 2989 (m), ν(N-H and/or C-H from Me); 2773 (m-w),
ν(C-H from Me); 1672 (s), 1545 (s), ν(CdN). 1H NMR (DMSO-
d6, δ): 10.86 (s, 1H, NH), 9.94 (s, br, 2H, NHdCMe), 1.90 (s, 6H,
CH3). 13C{1H} NMR (DMSO-d6, δ): 152.37 (CdN), 21.59 (CH3).
Crystals suitable for an X-ray diffraction study were obtained
directly from the reaction mixture.
1
from Ar). H NMR (DMSO-d6, δ): 11.28 (s, 1H, NH), 10.22 (s,
2H, NHdCCH2Ph), 7.31 (s, 10H, Ph), 3.78 (s, 4H, CH2Ph). 13C{1H}
NMR (DMSO-d6, δ): 154.13 (CdN), 134.28 (Cipso), 129.53, 129.36,
126.13 (carbons in Ph).
4·2½H2O. The hydrate was obtained using undried solvents, and
the isolated solid was dried in air at 20–25 °C. Anal. Calcd for
C14H13N3Cl2Pt·2½H2O: C, 31.52; H, 3.40; N, 7.88. Found: C,
31.78; H, 3.65; N, 8.07. ESI--MS (m/z): 488 [M - H]-. TLC: Rf
) 0.40 (eluent 1/5 Me2CO-CHCl3). IR (KBr, selected bands,
cm-1): 3396 (w), 3347 (w), 3233 (m-w), ν(N-H); 3057 (m-w),
ν(N-H and/or C-H from Ph); 1624 (s), ν(CdN); 1594 (s), 1539
(s), ν(CdN and/or CdC from Ar); 755 (m-s), 695 (s), δ(C-H from
1
Ar). H NMR (Me2CO-d6, δ): 10.65 (s, br, 1H, NH), 9.45 (s, br,
2H, NHdCPh), 7.94 (d, 4H, o-Ph), 7.72 (t, 2H, p-Ph), 7.57 (t, 4H,
m-Ph). 13C{1H} NMR (CDCl3, δ): 157.67 (CdN), 136.68 (Cipso),
129.61, 129.04, 126.77 (carbons in Ph). Crystals of [PtCl2-
{NHC(Ph)NHC(Ph))NH}]3 ·Me2CO·½H2O suitable for an X-ray
diffraction study were obtained by slow evaporation at 20–25 °C
of a CH2Cl2-Me2CO (1/1, v/v) solution.
Reaction of cis-[PtCl2(RCN)2] (R ) Et, CH2Ph, Ph) and
DPG (2 equiv) at -20 °C. cis-[PtCl2(RCN)2] (R ) Et, CH2Ph,
Ph) (0.12 mmol) and HNdC(NHPh)2 (52.7 mg, 0.25 mmol) were
dissolved in CH2Cl2 at -20 °C and left to stand for 2 h with slow
heating to 4 °C, and then the reaction mixture was kept for 24 h at
4 °C. The pale yellow precipitate that formed was filtered off,
washed with two 0.5 mL portions of CH2Cl2, and one 0.5 mL
portion of Et2O, and dried in air at 20–25 °C. It was weighed, fully
dissolved in DMSO-d6, and analyzed by 1H NMR. Molar ratios of
complexes 2 and 5 and of 3 and 6 obtained by the NMR integration
are ca. 8:1 and ca. 1:1, respectively. Yields of 2, 5, 3, and 6 were
2. Anal. Calcd for C6H13N3Cl2Pt: C, 18.32; H, 3.31; N, 10.68.
Found: C, 18.76; H, 3.38; N, 10.65. ESI--MS (m/z): 392 [M -
H]-. FAB+-MS (m/z): 416 [M + Na]+, 393 [M]+, 357 [M - Cl]+,
321 [M - HCl - Cl]+. TLC: Rf ) 0.43 (eluent 1/10 MeOH-CHCl3).
IR (KBr, selected bands, cm-1): 3325 (m), 3284 (s), 3234 (s), 3140
1
(66) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
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K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone,
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Ehara, M.; Toyota, K.; Hada, M.; Fukuda, R.; Hasegawa, J.; Ishida,
M.; Nakajima, T.; Kitao, O.; Nakai, H.; Honda, Y.; Nakatsuji, H.; Li,
X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Adamo, C.; Jaramillo,
J.; Cammi, R.; Pomelli, C.; Gomperts, R.; Stratmann, R. E.; Ochterski,
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Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas,
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A.1; Gaussian, Inc., Pittsburgh, PA, 2002.
calculated on the basis of H NMR data. The yields are 35% (2)
and 4% (5), 26% (3), and 26% (6). In the case of cis-[PtCl2-
(PhCN)2], the conductance of the reaction with DPG at -20 °C in
CH2Cl2 led to formation of the tailoring product formulas. The latter
exhibit very high solubility, and they were not isolated as solids
but were characterized in the solution by ESI-MS.
5. We did not obtain sufficient amount of this material (see
Results and Discussion) to conduct C, H, N analyses. ESI+-MS
(m/z): 492 [M + Na]+, 508 [M + K]+. ESI--MS (m/z): 392 [M -
1
Ph]-. H NMR (DMSO-d6, δ): 10.28 (s, br, 2H, NH), 7.58 (m,
2H), 7.67 (m, 3H) (Ph), 2.03 (q, 7.5 Hz, 4H, CH2), 0.83 (t, 7.5 Hz,
6H, CH3) (Et).
6. We did not obtain sufficient amount of this material (see
Results and Discussion) to conduct C, H, N analyses. ESI+-MS
(m/z): 616 [M + Na]+. ESI--MS (m/z): 516 [M - Ph]-. 1H NMR
(DMSO-d6, δ): 10.55 (s, br, 2H, NH), 7.36 (t, 1H), 7.15 (t, 2H),
6.93 (d, 2H) (Ph), 7.22 (t, 6H), 6.73 (d, 4H) (CH2Ph), 3.46 (s, 4H,
(67) (a) Becke, A. D. Phys. ReV. A 1988, 38, 3098. (b) Lee, C.; Yang, W.;
Parr, R. G. Phys. ReV. B 1988, 37, 785.
(68) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299.
(69) Stratmann, R. E.; Scuseria, G. E.; Frisch, M. J. J. Chem. Phys. 1998,
109, 8218.
11498 Inorganic Chemistry, Vol. 47, No. 24, 2008

Platinum 1,3,5-Triazapentadiene Complexes
CH2Ph). 13C{1H} NMR (DMSO-d6, δ): 156.01 (CdN), 137.80,
130.77 (Cipso), 133.18, 131.14, 129.62, 129.40, 128.90, 128.12
(carbons in Ar), 42.97 (CH2Ph).
1229 (s), 1166 (s), 1026 (s), ν(C-N from the amidine or tmeda).
1H NMR (Me2CO-d6, δ): 7.43 (s, br, 2H, -NH2), 7.07 (s, br, 2H,
-NH2), 6.68 (s, br, 2H, -NHdC-), 3.08 (s, 4H, N-CH2), 2.97
(s, 12H, N-CH3), 2.51 (q, JHH ) 7.3 Hz, 4H, -CH2CH3), 1.21 (t,
JHH ) 7.3 Hz, 6H, -CH2CH3). 13C{1H} NMR (Me2CO-d6, δ):
173.80 (CdN), 64.28 (N-CH2), 51.42 (N-CH3), 11.89
(-CH2CH3). TG curve (Figure S1, Supporting Information): >115
°C gradual dec. When the colorless cis-[Pt(tmeda){NHdC-
(NH2)Et}2][SO3CF3]2 was heated in the solid phase at 200 °C for
12 h, the complex turned into a dark brown yet unidentified
compound, which was characterized by 1H NMR spectroscopy
(Me2CO-d6, δ): 8.48 (s, br, 6H, NH), 3.06 (s, 4H, N-CH2), 2.99
(s, 12H, NCH3), 2.71 (q, JHH ) 7.3 Hz, 4H, -CH2CH3), 1.36 (t,
JHH ) 7.3 Hz, 6H, -CH2CH3).
cis-[Pt(tmeda){NHdC(NH2)Et}2][C6H2N3O7]2 was obtained by
mixing cis-[Pt(tmeda){NHdC(NH2)Et}2][SO3CF3]2 with a 2-fold
excess of picric acid at room temperature in methanol solution,
giving a yellow solution followed by slow evaporation at room
temperature to furnish crystals suitable for X-ray crystallography.
Caution! Picrate salts of metal complexes are potentially explosive!
10 ·(OTf)2 ·H2O. HNdC(NHPh)2 (0.06 g, 0.28 mmol) was added
to a solution of cis-[Pt(tmeda)(EtCN)2][SO3CF3]2 [prepared from
cis-[PtI2(tmeda)] (0.14 mmol) as described above] in CH2Cl2 (2
mL) and the reaction mixture was stirred for 6 h at room
temperature. A lilac residue formed was thoroughly washed (with
decantation) with small portions of Et2O and CHCl3 to avoid
dissolution of the target product. Yield is 0.05 g, 46%.
Reaction of cis-[PtCl2(RCN)2] (R ) Et, CH2Ph, Ph) and
DPG (4 equiv) at 20–25 °C. cis-[PtCl2(PhCH2CN)2] (0.12 mmol)
and HNdC(NHPh)2 (52.7 mg, 0.25 mmol) were dissolved in
CH2Cl2 and left to stand for 24 h at 20–25 °C. The pale yellow
precipitate that formed was filtered off, washed with two 0.5 mL
portions of Me2CO and one 0.5 mL portion of Et2O, and dried in
air at 20–25 °C. The yield of 6 is 6 mg, 9%. The filtrate, as verified
1
by means of both H NMR and TLC methods, contains a broad
mixture of as yet unidentified products but does not contain 6. It
was determined by ESI-MS that the filtrates contain products of
the NH tailoring with substitution of two chloride Cl- ligands by
the bis(guanidine) PhNdC(NHPh)NdC(NHPh)2 (m/z 743 [M +
H2O]+, 727 [M + 2H]+, 708 [M - NH3]+, 672 [M + 2H - EtCN]+
(R ) Et); 868 [M + H2O]+, 850 [M]+ (R ) CH2Ph); 839 [M +
H2O]+, 822 [M + H]+ (R ) Ph)) and substitution of one Cl- ligand
by HNdC(NHPh)2 (m/z 569 [M + H]+ (R ) Et); 693 [M + H]+,
691 [M - H]- (R ) CH2Ph); 665 [M + H]+, 663 [M - H]- (R )
Ph)).
Synthesis of [Pt(tmeda)(EtCN)2]2+ and Its Reaction with
NH3 and DPG. 7. This compound was obtained by the reaction of
K2[PtCl4] with KI followed by the addition of tmeda (yield 86%;
see the Supporting Information).38 TLC on Merck 60 F254 SiO2
plates: Rf ) 0.39 (eluent CHCl3-Me2CO, 5/2 v/v), one spot. IR
(KBr, selected bands, cm-1): 3016 (m-w), 2974 (m-w), 2914 (s)
1
ν(N-H and/or C-H). H NMR (DMSO-d6, δ): 2.97 (s, 12 H,
Anal. Calcd for PtC14H29N5F6S2O6 ·H2O: C, 22.28; H, 4.14; N,
9.28. Found C, 22.57; H, 4.25; N, 9.33. ESI+-MS (m/z): 437 [M -
H]+. IR (KBr, selected bands, cm-1): 3439 (m), 3269 (m), ν(N-H);
2831 (m-w), ν(C-H from Et); 1610 (s), 1547 (s), ν(CdN); 1224
(s), 1163 (s), 1030 (s), ν(C-N from the 1,3,5-triazapentadiene and/
N-CH3), 2.77 (s, 4 H, N-CH2). 13C{1H} NMR (DMSO-d6, δ):
64.29 (N-CH2), 53.57 (N-CH3).
8·(OTf)2. AgSO3CF3 (0.58 g, 2.23 mmol) was added to a
suspension of 7 (0.62 g, 1.10 mmol) in EtCN (4 mL), and the
mixture was stirred in the dark at room temperature for 12 h,
whereupon it was filtered to remove the solid AgI and the solvent
was evaporated to dryness under vacuum to give a pale yellow
oily residue. The latter was dissolved in a CH2Cl2-Me2CO solvent
mixture (2/1 v/v), and the released solid AgI was centrifugated and
separated by decantation. The solution was evaporated under
vacuum at 20–25 °C to give a colorless oily residue, which was
dried under vacuum at 20–25 °C. The residue was used for further
synthetic transformations. ESI+-MS (m/z): 439 [M + H2O]+, 384
[M - EtCN + H2O]+. IR (KBr, selected bands, cm-1): 2997 (m-
w), 2961 (m-w), ν(C-H from Et); 2187 (w), ν(CtN); 1266 (vs),
1165 (s), 1032 (s), ν(C-N from the tmeda). 1H NMR (Me2CO-d6,
1
or tmeda). H NMR (Me2CO-d6, δ): 10.94 (s, br, 1H, -NH-),
9.22 (s, br, 2H, -NHdC-), 3.23 (s, 4H, N-CH2), 3.17 (s, 12H,
N-CH3), 2.83 (q, JHH ) 7.3 Hz, 4H, -CH2CH3), 1.32 (t, JHH
)
7.3 Hz, 6H, -CH2CH3). 13C{1H} NMR (Me2CO-d6, δ): 163.81
(CdN), 64.94 (N-CH2), 52.26 (N-CH3), 11.56 (-CH2CH3).
[Pt(tmeda){NHC(Et)NHC(Et)NH}][C6H2N3O7]2 was obtained by
mixing the cis-[Pt(tmeda){NHC(Et)NHC(Et)NH}][SO3CF3]2 com-
plex with a 2-fold excess of picric acid at room temperature in
methanol solution, giving a yellow solution followed by its slow
evaporation at room temperature to furnish crystals suitable for
X-ray crystallography. Caution! Picrate salts of metal complexes
are potentially explosive!
δ): 3.28 (s, 4 H, N-CH2), 3.23 (s, 12 H, N-CH3), 2.96 (q, JHH
)
Attempted Reaction between 10 ·(OTf)2 ·H2O and Ammo-
nia. The complex (20 mg) was dissolved in MeOH (2 mL). The
obtained solution was stirred under an atmosphere of gaseous
ammonia at 20–25 °C for 6 h, whereupon the solvent was
evaporated to dryness at room temperature under vacuum, redis-
solved in Me2CO-d6, and characterized by 1H NMR spectroscopy.
The obtained spectrum corresponds to the intact 10 ·(OTf)2, and
no traces of 9·(OTf)2 were detected.
Reaction of trans-[PtCl2(RCN)2] and DPG (2 equiv). trans-
[PtCl2(RCN)2] (R ) Et, CH2Ph, Ph) (0.12 mmol) and HNd
C(NHPh)2 (50.7 mg, 0.24 mmol) were dissolved in EtCN (1 mL)
(R ) Et) or CH2Cl2 (1 mL) (R ) CH2Ph, Ph) and left to stand for
24 h (R ) Et) or 15 h (R ) CH2Ph, Ph) at 20–25 °C. The yellow
solutions (R ) Et, CH2Ph, Ph) were evaporated to dryness. The
pale yellow solid residue for R ) Et was washed with one 0.5 mL
portion of MeOH, filtered off, washed with one 0.5 mL portion of
Et2O, and dried in air at 20–25 °C. Products for R ) CH2Ph, Ph
were separated from yellow oily residues by column chromatog-
raphy on SiO2 (silica gel 60 F254, 0.063–0.200 mm, Merck; eluent
7.3 Hz, 4 H, -CH2CH3), 1.45 (t, JHH ) 7.3 Hz, 6 H, -CH2CH3).
13C{1H} NMR (Me2CO-d6, δ): 65.64 (N-CH2), 53.72 (N-CH3),
13.41 (-CH2CH3), 9.48 (-CH2CH3).
9 · (OTf)2. A solution of the bis(nitrile) complex cis-[Pt-
(tmeda)(EtCN)2][SO3CF3]2 (prepared from cis-[PtI2(tmeda)] (1.10
mmol) as described above) in a CH2Cl2-Me2CO solution (2/1 v/v,
2 mL) was treated with an excess of gaseous ammonia for 6 h and
stirred at room temperature. The colorless solution was evaporated
to dryness under vacuum at 20–25 °C to give a pale yellow oily
residue, which was crystallized under a layer of Et2O to furnish
the colorless solid. The latter was washed with two 2 mL portions
of Et2O (with decantation) and dried under vacuum at 20–25 °C.
The yield is 0.70 g, 85%.
Anal. Calcd for PtC14H32N6F6S2O6: C, 22.31; H, 4.28; N, 11.15.
Found C, 22.68; H, 4.31; N, 10.46. FAB+-MS (m/z): 381 [M - L
- 2H]+, 115 [tmeda - H]+, 72 [L]+. IR (KBr, selected bands,
cm-1): 3403 (m), 3338 (m), 3295 (m), 3242 (m), ν(N-H); 2991
(m-w), 2942 (m), ν(C-H from Et); 1659 (s), 1616 (s), ν(CdN);
Inorganic Chemistry, Vol. 47, No. 24, 2008 11499

Gushchin et al.
1/10 Et2O-CHCl3 (R ) CH2Ph) or 1/20 ethyl acetate-CHCl3 (R
) Ph), first fractions) and washed with one 0.5 mL portion of Et2O.
Yields are 30 mg, 45% (R ) Et), 21 mg, 26% (R ) CH2Ph), and
15 mg, 20% (R ) Ph).
on the amount of DPG (4, 6, or 8 equiv). Yields are 46 mg, 63%
(R ) Et), 62 mg, 73% (R ) CH2Ph), and 55 mg, 67% (R ) Ph)
(data for reactions performed with trans-[PtCl2(RCN)2] and 4 equiv
of DPG).
11. Anal. Calcd for C19H22N5ClPt: C, 41.42; H, 4.02; N, 12.71.
Found: C, 41.89; H, 4.19; N, 12.78. FAB+-MS (m/z): 550 [M]+,
515 [M - Cl]+, 495 [M - EtCN]+, 459 [M - HCl - EtCN]+.
TLC: Rf ) 0.39 (eluent 1/20 Me2CO-CHCl3). IR (KBr, selected
bands, cm-1): 3456 (m-w), 3355 (m-w), ν(N-H); 1636 (s),
14. Anal. Calcd for C32H34N8Pt: C, 53.00; H, 4.70; N, 15.41.
Found: C, 53.61; H, 4.87; N, 15.65. FAB+-MS (m/z): 726 [M]+.
TLC: Rf ) 0.53 (eluent 1/4 Me2CO-CHCl3). DTA/TG: 277 °C
(gradual dec). IR (KBr, selected bands, cm-1): 3420 (m-s), 3355
(m-s), ν(N-H); 3093 (w), 3057 (m-w), 3023 (m-w), ν(C-H from
Ar); 2962 (m), 2935 (m-w), 2908 (m-w), 2875 (m-w), 2825 (w),
2779 (w), ν(C-H from Et); 1596 (s), 1571 (s), 1538 (m-s), ν(CdN
1
ν(CdN); 1582 (s), 1543 (s), ν(CdN and/or CdC from Ar). H
NMR (CDCl3, δ): 7.47 (t, 2H), 7.30 (d, 2H), 7.27–7.16 (m, 5H),
6.98 (t, 1H) (Ph), 6.64 (s, br, 1H), 5.87 (s, 1H) (NH), 2.33 (q, 7.6
Hz, 2H, CH2 in NtCEt), 2.16 (q, 7.6 Hz, 2H, CH2 in HNdCEt),
1.19 (t, 7.6 Hz, 3H, CH3 in NtCEt), 0.94 (t, 7.6 Hz, 3H, CH3 in
HNdCEt). 13C{1H} NMR (CDCl3, δ): 164.91 (CdN-H), 148.68,
147.00, 139.87 (CdN-Ph and/or Cipso), 129.90, 128.66, 128.24,
127.05, 123.47, 122.37 (carbons in Ph), 118.05 (CtN), 33.34 (CH2
in HNdCEt), 12.09 (CH2 in NtCEt), 11.75 (CH3 in HNdCEt),
9.54 (CH3 in NtCEt).
1
and/or CdC from Ar); 749 (m-s), 702 (s), δ(C-H from Ar). H
NMR (CDCl3, δ): 7.56 (t, 4H), 7.38–7.28 (m, 6H), 7.21–7.12 (m,
8H), 6.93 (t, 2H) (Ph), 5.81 (s, br, 2H), 4.88 (s, br, 2H) (NH), 1.92
(q, 7.5 Hz, 4H), and 0.71 (t, 7.5 Hz, 6H) (Et). 13C{1H} NMR
(CDCl3, δ): 165.04 (CdN-H), 147.64, 144.91, 140.55 (CdN-Ph
and/or Cipso), 130.83, 128.83, 128.58, 127.26, 122.80, 121.89
(carbons in Ph), 33.68 (CH2), and 10.50 (CH3) (Et).
15. Anal. Calcd for C42H38N8Pt: C, 59.36; H, 4.51; N, 13.18.
Found: C, 59.59; H, 4.55; N, 13.55. FAB+-MS (m/z): 849 [M]+.
TLC: Rf ) 0.45 (eluent 1/10 Et2O-CHCl3). DTA/TG: 282 °C
(gradual dec). IR (KBr, selected bands, cm-1): 3413 (m-s), 3338
(m-s), ν(N-H); 3057 (m-w), 3029 (m-w), ν(C-H from Ar); 2954
(w), 2928 (w), ν(C-H from CH2Ph); 1602 (s), 1572 (s), 1538 (m-
s), ν(CdN and/or CdC from Ar); 749 (m-s), 702 (s), δ(C-H from
Ar). 1H NMR (CDCl3, δ): 7.43 (t, 4H), 7.27–7.20 (m, 11H),
7.11–6.99 (m, 13H), 6.91 (t, 2H) (Ph), 5.75 (s, br, 2H), 4.81 (s, br,
2H) (NH), 3.12 (s, 4H, CH2Ph). The compound is poorly soluble
in all common deuterated solvents, and this precluded 13C{1H}
NMR measurements.
12. Anal. Calcd for C29H26N5ClPt: C, 51.60; H, 3.88; N, 10.37.
Found: C, 51.64; H, 3.91; N, 10.38. FAB+-MS (m/z): 676 [M +
H]+, 640 [M + H - Cl]+, 558 [M - PhCH2CN]+, 522 [M - Cl
- PhCH2CN]+. TLC: Rf ) 0.64 (eluent 1/10 Et2O-CHCl3). IR
(KBr, selected bands, cm-1): 3408 (m-w), 3362 (m-w), 3332 (m-
w), ν(N-H); 3055 (w), 3026 (w), ν(C-H from Ar); 2949 (w), 2916
(w), ν(C-H from CH2Ph), 1598 (m-s), 1570 (s), ν(CdN and/or
1
CdC from Ar); 746 (m), 698 (m-s), δ(C-H from Ar). H NMR
(CDCl3, δ): 7.36–7.23 (m, 12H), 7.09 (q, 3H), 7.04–7.01 (m, 4H),
6.96 (t, 1H) (Ph’s), 6.76 (s, br, 1H), 5.85 (s, 1H) (NH), 3.63 (s,
2H), 3.51 (s, 2H) (CH2Ph). 13C{1H} NMR (CDCl3, δ): 162.62
(CdN-H), 148.28, 147.12, 139.67, 136.52 (CdN-Ph and/or Cipso),
130.09, 129.90, 129.65, 129.00, 128.67, 128.46, 128.01, 127.56,
127.33, 127.05, 123.40, 122.21 (carbons in Ph), 115.56 (CtN),
46.45, 24.39 (CH2Ph).
16. Anal. Calcd for C40H34N8Pt: C, 58.46; H, 4.17; N, 13.63.
Found: C, 58.12; H, 4.17; N, 13.12%. FAB+-MS (m/z): 822 [M +
H]+. TLC: Rf ) 0.41 (eluent 1/20 Et2O-CHCl3). DTA/TG: 302
°C (gradual dec). IR (KBr, selected bands, cm-1): 3422 (m), 3366
(m), ν(N-H); 3057 (m-w), ν(C-H from Ar); 1590 (m-s), 1558
(s), 1522 (m-s), ν(CdN and/or CdC from Ar); 749 (m), 694 (m-
13. Anal. Calcd for C27H22N5ClPt: C, 50.12; H, 3.43; N, 10.82.
Found: C, 50.44; H, 3.35; N, 10.76. FAB+-MS (m/z): 647 [M]+,
611 [M - Cl]+, 543 [M - PhCN]+, 507 [M - HCl - PhCN]+.
TLC: Rf ) 0.69 (eluent 1/20 Me2CO-CHCl3). IR (KBr, selected
bands, cm-1): 3396 (m-w), 3366 (m-w), ν(N-H); 3060 (m-w),
ν(C-H from Ar); 2274 (w), ν(CtN); 1594 (s), 1560 (s), 1519 (s),
ν(CdN and/or CdC from Ar); 752 (m), 697 (m-s), δ(C-H from
1
s), δ(C-H from Ar). H NMR (CDCl3, δ): 7.65 (t, 4H), 7.45 (d,
6H), 7.35 (t, 2H), 7.24–7.13 (m, 16H), 7.01 (t, 2H) (Ph), 5.91 (s,
2H), 5.68 (s, br, 2H) (NH). The compound is poorly soluble in all
common deuterated solvents, and this precluded 13C{1H} NMR
measurements.
1
Ar). H NMR (CDCl3, δ): 7.88 (d, 2H), 7.64 (t, 1H), 7.49–7.36
Acknowledgment. This work has been supported by the
Russian Fund for Basic Research (Grant 08-03-90100) and
also by the bilateral RFBR-NSF (Taiwan) Grant 07-03-
92002. M.-J.W. and V.Yu.K. express their gratitude to the
National Taiwan University of Science and Technology for
the Cooperation Grant NTUST-2007-R-01 and for the
Visiting Chair Professorship provided for V.Yu.K. M.H. and
V.Yu.K. thank the Academy of Finland for financial support
(Grant 121266). We are very much obliged to Dr. A. A.
Nazarov for running ESI mass spectra and Prof. D. Osella
for the synthetic procedure for [PtI2(tmeda)].
(m, 12H), 7.30–7.19 (m, 4H), 7.06 (t, 1H) (Ph), 6.50 (s, 1H), 6.00
(s, 1H) (NH). 13C{1H} NMR (CDCl3, δ): 158.37 (CdN-H),
148.69, 147.95, 139.84 (CdN-Ph and/or Cipso), 134.58, 133.29,
130.72, 130.13, 129.40, 128.86, 128.74, 128.17, 127.48, 127.21,
123.96, 123.29 (carbons in Ph), 110.26 (CtN).
Reaction of trans-[PtCl2(RCN)2] and DPG (4, 6, or 8
equiv). trans-[PtCl2(RCN)2] (R ) Et, CH2Ph, Ph) (0.10 mmol) and
HNdC(NHPh)2 (85 mg, 0.40 mmol for 4 equiv, 127 mg, 0.60 mmol
for 6 equiv, and 169 mg, 0.80 mmol for 8 equiv) were dissolved
in the corresponding RCN (1 mL) (R ) Et, CH2Ph, Ph) and left to
react with stirring for 48 h (R ) Et) or without stirring for 24 h (R
) CH2Ph, Ph) at 75 °C. The obtained colorless precipitate for R )
Et was separated by decantation, washed with two 1.5 mL portions
of Me2CO and one 1.5 mL portion of Et2O, and dried in air at
20–25 °C. The solution for R ) CH2Ph, Ph was evaporated to
dryness, and the colorless (R ) CH2Ph) or yellow (R ) Ph)
needlelike precipitate was washed with one 1 mL portion of Me2CO,
filtered off, washed with one 1 mL portion of Me2CO and one 1
mL portion of Et2O, and dried in air at 20-25 °C. TG curves: 277
and 282 °C (for complexes 14 and 15, respectively) and 301 °C
(for complex 16). Yields of complexes do not depend significantly
Supporting Information Available: Figure S1, giving the TG
curve for 9·(OTf)2, Figures S2–S4, giving molecular structures of
1, 2, and 11, Figure S5, giving the hydrogen-bonding scheme for
4, Table S1, giving the hydrogen bonds for 4, CIF files giving
crystallographic data, and text giving a detailed description of the
synthetic procedure for cis-[PtI2(tmeda)] (7). This material is
available free of charge via the Internet at http://pubs.acs.org.
IC702483W
11500 Inorganic Chemistry, Vol. 47, No. 24, 2008