First example of the solid-state thermal cyclometalation of ligated benzophenone imine giving novel luminescent platinum(II) species

Article abstract of DOI:10.1021/ic062414k

The (benzophenone imine)platinum(II) compounds trans-[PtCl ₂(Ph₂C=NH)(RR′SO)] [R, R′ = Me, Me (2); n-Pr, n-Pr (3); (CH₂)₄ (4); Me, Ph (5); Me, p-MeC ₆H₄ (6)] were prepared by the reaction of Ph ₂C=NH with K[PtCl₃(RR′SO)], obtained in situ from K₂[PtCl₄] and the corresponding sulfoxide, giving 2-6 as well as cis-[PtCl₂(Ph₂C=NH)₂] (1) as a minor product. The complexes were characterized by ¹H, ¹³C, and ¹⁹⁵Pt NMR and IR spectroscopy, electrospray ionization mass spectrometry, and C, H, and N elemental analysis. The X-ray crystallography of 1 enables confirmation of the cis configuration of the complex, while in 2 and 4·1/2CHCl₃, the imine and sulfoxide ligands are mutually trans. The solid-state structure of 4·1/2CHCl₃ consists of two dimeric Pt moieties representing a rather weak Pt...Pt interaction. The dimeric architecture of 4·1/2CHCl₃ is enhanced by the hydrogen bonding between imine H atoms and O atoms. The orthometalation of 1 and 2-6 proceeds both in the solid phase and in a toluene suspension, leading to the formation of [PtCl{Ph(C₆H₄)C=NH}(Ph₂C=NH)] (7) and [PtCl{Ph(C₆H₄)C=NH}(RR′SO)] (8-12), respectively, isolated in nearly quantitative yields. Complexes 8-12 are emissive at room temperature both in solution (λ_em ^max ～535 nm) and in the solid state (λ_em ^max 560-610 nm), with excited-state lifetimes of ca. 300-600 ns, representing a new family of Pt^II-based luminescent complexes. Compounds 8 and 10 have been characterized by X-ray analysis, confirming the square-planar coordination geometry of the metal center with the almost planar platinacycles. In 8, the asymmetric unit contains two independent Pt molecules, while in 10, it includes four Pt molecules linked by the intermolecular hydrogen-bonding network between the NH group and Cl atoms.

Full text of DOI:10.1021/ic062414k

Inorg. Chem. 2007, 46, 4469−4482
First Example of the Solid-State Thermal Cyclometalation of Ligated
Benzophenone Imine Giving Novel Luminescent Platinum(II) Species
Yulia Yu. Scaffidi-Domianello,†,‡ Alexey A. Nazarov,† Matti Haukka,§ Markus Galanski,*,†
Bernhard K. Keppler,† Jacob Schneider,| Pingwu Du,| Richard Eisenberg,*,| and
Vadim Yu. Kukushkin*,‡
Institute of Inorganic Chemistry, UniVersity of Vienna, Wa¨hringerstrasse 42, A-1090 Vienna,
Austria, Department of Chemistry, St. Petersburg State UniVersity, 198504 Stary Petergof, Russian
Federation, Department of Chemistry, UniVersity of Joensuu, P.O. Box 111, FI-80101 Joensuu,
Finland, and Department of Chemistry, UniVersity of Rochester, Rochester, New York 14627
Received December 16, 2006
The (benzophenone imine)platinum(II) compounds trans-[PtCl2(Ph2C
Pr (3); (CH2)4 (4); Me, Ph (5); Me, p-MeC6H4 (6)] were prepared by the reaction of Ph2C
d
NH)(RR
′
SO)] [R, R′ ) Me, Me (2); n-Pr, n-
NH with K[PtCl3(RR SO)],
6 as well as cis-[PtCl2(Ph2C NH)2] (1)
d
′
obtained in situ from K2[PtCl4] and the corresponding sulfoxide, giving 2
−
d
1
as a minor product. The complexes were characterized by H, 13C, and 195Pt NMR and IR spectroscopy, electrospray
ionization mass spectrometry, and C, H, and N elemental analysis. The X-ray crystallography of 1 enables confirmation
of the cis configuration of the complex, while in 2 and 4
trans. The solid-state structure of 4
1/2CHCl3 consists of two dimeric Pt moieties representing a rather weak Pt‚‚‚Pt
interaction. The dimeric architecture of 4
1/2CHCl3 is enhanced by the hydrogen bonding between imine H atoms
and O atoms. The orthometalation of 1 and 2 6 proceeds both in the solid phase and in a toluene suspension,
leading to the formation of [PtCl Ph(C6H4)C NH (Ph2C NH)] (7) and [PtCl Ph(C6H4)C NH (RR SO)] (8 12),
12 are emissive at room temperature both in
610 nm), with excited-state lifetimes of ca. 300 600 ns,
‚
1/2CHCl3, the imine and sulfoxide ligands are mutually
‚
‚
−
{
d
}
d
{
d
}
′
−
respectively, isolated in nearly quantitative yields. Complexes 8
−
max
em
max
em
solution (
λ
∼
535 nm) and in the solid state (
λ
560−
−
representing a new family of PtII-based luminescent complexes. Compounds 8 and 10 have been characterized by
X-ray analysis, confirming the square-planar coordination geometry of the metal center with the almost planar
platinacycles. In 8, the asymmetric unit contains two independent Pt molecules, while in 10, it includes four Pt
molecules linked by the intermolecular hydrogen-bonding network between the NH group and Cl atoms.
Introduction
type conversions.3 However, they can be stabilized via
coordination to a metal center; in particular, Pt group metals
provide enormous stabilization of the potentially unstable
imines.4-9
In the recent years, there has been an increasing interest
in metal-mediated synthesis, properties, and reactivity pat-
terns of ligated imines.1 Unlike N-substituted imines R′Nd
CR2 (R′ ) Alk, Ar; R ) H, Alk, Ar), which are mostly stable
and serve as ligands for many metal complexes,2 the
unsubstituted aldimines or ketimines HNdCR2 are, with the
exception of diarylketimines, very susceptible to hydrolysis
and subject to oligo- and polymerization and various redox-
Metal imine species are the subject of rapt attention
because of the importance of their potential properties, i.e.,
(i) PtII complexes containing coordinated acetimine display
a tumor cell growth inhibitory potency, similar to that of
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P. G. Angew. Chem., Int. Ed. Engl. 1997, 36, 1203. (b) Vicente, J.;
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* To whom correspondence should be addressed. E-mail:
markus.galanski@univie.ac.at (M.G.), eisenberg@chem.rochester.edu (R.E.),
kukushkin@VK2100.spb.edu (V.Yu.K.).
† University of Vienna.
‡ St. Petersburg State University.
§ University of Joensuu.
| University of Rochester.
10.1021/ic062414k CCC: $37.00
Published on Web 04/24/2007
© 2007 American Chemical Society
Inorganic Chemistry, Vol. 46, No. 11, 2007 4469

Scaffidi-Domianello et al.
the corresponding PtII complexes with iminoethers,10 and in
addition the ability to circumvent (either partially or com-
pletely) cisplatin resistance;11 (ii) ytterbium(II) imine com-
plexes exhibit a high catalytic activity in the dehydrogenative
silylation of terminal alkynes12a and hydrosilylation of
imines;12b (iii) metal complexes of simple imines are
observed/proposed to be intermediates in the metal-mediated
imine aziridination,13 imine/imide/alkylidene metathesis,14
and amine T nitrile interconversion;15 (iv) R,R-diimines in
their main-group metal complexes may possess different
oxidation states, thus acting as an electron sponge or
sink toward organic substrates;16 (v) PdII- and NiII-based
catalysts containing bulky diimine ligands exhibit extremely
high activities in the conversion of ethylene,17a-c R-olefins,17a,b,d
cyclopentene,17e and trans-1,2-disubstituted olefins17f to
high-molecular-weight polymers with unique microstructures
as well as in copolymerization of polar monomers with
ethylene and R-olefins.17g,h Therefore, synthetic approaches
to new arylimine metal complexes as well as examination
of their reactivity are crucial for the development of that
type of compound and to a considerable degree determinative
for the progress of metal-mediated arylimine functionaliza-
tion.
In view of our general interest in imines as ligands4-9
and ligand reactivity in general,18 we continued our work
in these directions and focused our attention on a rather stable
and commercially available imine, i.e., benzophenone imine,
HNdCPh2, which can be considered as a model for unstable
imines in examinations of their reactivity. Although coor-
dination properties of HNdCPh2 were extensively studied,
e.g., exhaustively in the case of group VIII metals (Fe,19 Ru,20
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4470 Inorganic Chemistry, Vol. 46, No. 11, 2007

Cyclometalation of Ligated Benzophenone Imine
Os;21 Co,22 Rh,23 Ir;23a Ni,24 Pd,25 Pt9b,26) and partially for
some representatives of group III (Sm27), IV (Ti,28 Zr28,29),
VI (Cr30), and VII (Mn,31 Re31,32) metals, reports on the
reactiVity of the metal-bound HNdCPh2 are rather scarce.
Thus, several papers devoted to its deprotonation, resulting
in the formation of azavinylidene complexes,21a,b the addition
of tolylacetilyde to the coordinated HNdCPh2,19 and the
formation of ligated σ-η1-C6H4C(Ph)dNH species, were
published.20d In this context, also a few reports on the
orthometalation of the coordinated HNdCPh2 species leading
to N,C-chelates, performed in most cases in toluene or
tetrahydrofuran solutions at elevated temperatures, are
available.20c,21c,h,j,22,23d,26
Results and Discussion
In general, the orthometalation reactionsactivation of a
C-H bond in the ortho position of an aromatic ring by a
transition-metal centerscontinues to be an important class
of reactions33 owing to the broad application spectrum of
the orthometalated species, e.g., in catalysis,33b,34 organic
synthesis,35 and material science.36 The activation of C-H
bonds by transition-metal compounds is of general interest
because of the possibility of functionalizing nonactivated
organic molecules.33a,37 For instance, the Murai reaction,38
which represents one of the most important processes in
organic synthesis, allows the alkylation of aromatic ketones,39
esters,40 and imines,41 as well as the copolymerization of
aromatic ketones and R,ω-divinylsilanes.42 Consequently,
stable and structurally characterized compounds
containing N,C-metallacycles are of high interest and can
be considered as models for the organometallic intermediates
in C-C coupling reactions between aromatic imines and
olefins.43
Orthometalation of PtII compounds with N-donor ligands
giving N,C-platinacycles is rather well documented.44 How-
ever, there are only a few examples of orthoplatinated imino
species.26,45 In addition to mononuclear platinacycles with
η2-coordinated imines,26,45e,i some PtII complexes with C,N,S-
45a and C,N,N-45d,g,j pincer ligands, orthoplatinated heterocycle-
derived imino species,45b and bridged45c,h and tetrameric
orthometalated PtII compounds45f obtained as a result of
metalation of a PtII-bound imine were reported.
Herein, we report on the preparation of (benzophenone
imine)(sulfoxide)platinum(II) complexes. The reactivity of
the HNdCPh2 ligand both in the solid state and in a toluene
suspension, leading to the formation of the corresponding
orthometalated species exhibiting luminescent properties, was
studied. It is worth emphasizing that within the framework
of this project we observed for the first time the solid-state
reactiVity of the coordinated benzophenone imine, namely,
the formation of a platinacycle via elimination of HCl upon
heating of the solid platinum(II) imine complexes.
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Thus, we have focused on the study of cyclometalation
of (Ph2CdNH)PtII species and intended (i) to prepare PtII
complexes with both benzophenone imine and various
sulfoxides, (ii) to investigate the solid-state and solution
reactivities of (Ph2CdNH)PtII species, (iii) to verify possible
routes for cyclometalation of (Ph2CdNH)PtII complexes, and
(iv) to study properties of the cyclomelatated species. The
report on our experiments given below follows these lines.
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Inorganic Chemistry, Vol. 46, No. 11, 2007 4471

Scaffidi-Domianello et al.
Scheme 1
Synthesis, Characterization, and X-ray Structure De-
The reaction between the platinum(II) sulfoxide complexes
K[PtCl3(RR′SO)] [R, R′ ) Me, Me; n-Pr, n-Pr; (CH2)4;
Me, Ph; Me, p-MeC6H4], obtained in situ from K2[PtCl4]
and the corresponding sulfoxide,46 and benzophenone
imine Ph2CdNH proceeds in aqueous solution at room
temperature and leads to the formation of trans-[PtCl2(Ph2Cd
NH)(RR′SO)] (2-6; Scheme 1) obtained as pale-
yellow precipitates and isolated in 40-60% yields. The
diiminoplatinum(II) complex cis-[PtCl2(Ph2CdNH)2]
(1), prepared earlier by Grøndahl et al. via the reaction
of trans-[PtCl2(CH3CN)2] with Ph2CdNH,26 is formed
in all syntheses as a minor product and isolated in 6-8%
yields.
terminations of (Benzophenone imine)platinum(II) Com-
plexes. As starting materials for the preparation of (ben-
zophenone imine)platinum(II) compounds, we addressed the
easily accessible complexes K[PtCl3(sulfoxide)]46 [sulfoxide
) Me2SO, n-Pr2SO, (CH2)4SO, racemic mixture of Me(Ph)-
SO, S-(-)-p-MeC6H4(Me)SO] for the following reasons: on
the one hand, a significant trans effect of S-coordinated
sulfoxides47 facilitates the substitution and directs the reaction
to the formation of the isomerically pure product; on the
other hand, as far as Me2SO is concerned, the coordinated
dimethyl sulfoxide ligand with its characteristic spectral
pattern48 serves as an “internal” reference for the integration
1
of H NMR spectra.
Complexes 1-6 were characterized by C, H, and N
1
microanalysis, H, 13C{1H}, and 195Pt NMR and IR spec-
(44) For recent works, see: (a) Janzen, D. E.; Mehne, L. F.; Van Derveer,
D. G.; Grant, G. J. Inorg. Chem. 2005, 44, 8182. (b) Otto, S.;
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Organometallics 1998, 17, 5411. (g) Krooglyak, E. V.; Kazankov, G.
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troscopy, electrospray ionization mass spectrometry (ESI-
MS), and also X-ray crystallography (for 1, 2, and 4). All
compounds gave satisfactory C, H, and N elemental analyses.
ESI-MS spectra displayed the fragments [M + Na]+ and [M
+ K]+ having isotopic patterns that were in accordance with
calculated ones. The IR spectra of 1-6 showed strong-to-
medium ν(CdN) [1597-1607 cm-1] and medium ν(NH)
[3195-3294 cm-1] stretching vibrations. In addition, 2-6
displayed very strong ν(SdO) [1113-1134 cm-1] bands
shifted vs ν(SdO) of the free sulfoxides due to S coordina-
tion.49
(45) (a) Jacquot-Rousseau, S.; Khatyr, A.; Schmitt, G.; Knorr, M.; Kubicki,
M. M.; Blacque, O. Inorg. Chem. Commun. 2005, 8, 610.
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The structures of 1, trans-[PtCl2(Ph2CdNH)(Me2SO)]
(2), and trans-[PtCl2(Ph2CdNH){(CH2)4SO}] (4) were de-
termined by X-ray single-crystal diffraction (Table 1 and
Figures 1-3). The coordination geometries of the three
complexes are slightly distorted square-planar.
In all three structures, the Pt atoms are located at a
crystallographic inversion center. The Pt-Cl bond distances
are in the range from 2.297 to 2.308 Å, and these distances
agree well with those in the previously characterized plati-
(47) (a) Elding, L. I.; Gro¨ning, O. Inorg. Chem. 1978, 17, 1872. (b)
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Ferreira, C. M. P.; Elding, L. I. Inorg. Synth. 2002, 33, 189. (c) Almeida,
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4472 Inorganic Chemistry, Vol. 46, No. 11, 2007

Cyclometalation of Ligated Benzophenone Imine
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 1, 2, 4‚1/2CHCl3, 8, and 10
1
2
4
4B
8
8B
10A
10B
10C
10D
Pt1-Cl1
Pt1-Cl2
Pt1-N1
Pt1-N2
Pt1-S1
Pt1-C13
Pt2-Cl3
Pt2-Cl4
Pt2-N2
Pt2-S2
S1-O1
2.298(2)
2.291(2)
2.001(7)
2.034(6)
2.2969(9)
2.3034(9)
2.021(3)
2.306(4)
2.307(4)
2.017(13)
2.302(4)
2.308(4)
2.024(13)
2.392(2)
2.395(2)
2.3925(11)
2.3864(11)
2.3808(11)
2.3971(12)
2.019(6)
2.022(6)
2.019(4)
2.016(4)
2.013(4)
2.021(4)
2.2131(9)
2.210(4)
2.215(4)
2.215(2)
2.006(9)
2.216(2)
1.978(9)
2.2063(13)
2.016(4)
2.2054(12)
2.010(4)
2.2215(12)
2.005(4)
2.2132(13)
2.001(5)
2.302(4)
2.298(4)
2.037(13)
2.222(4)
1.469(11)
1.464(11)
1.26(2)
2.305(4)
2.299(4)
2.029(12)
2.208(4)
1.457(11)
1.447(11)
1.27(2)
1.467(3)
1.289(4)
1.476(5)
1.480(5)
1.479(4)
1.474(3)
1.473(3)
1.472(4)
S2-O2
N1-C1
N2-C18
N2-C14
1.274(10)
1.259(10)
1.280(10)
1.282(10)
1.30(2)
1.26(2)
Cl1-Pt1-Cl2 92.83(8)
175.81(3)
176.94(15) 175.75(14)
N1-Pt1-N2
N1-Pt1-S1
C13-Pt1-N1
94.1(3)
175.66(9)
131.8(2)
175.2(4)
176.0(4)
179.7(2)
79.7(3)
178.9(2)
79.7(3)
175.40(11)
79.7(2)
175.73(12)
79.4(2)
178.30(12)
80.5(18)
174.38(12)
79.2(2)
Pt1-N1-C1 130.5(6)
Pt2-N2-C18
129.0(10)
129.0(11)
131.8(11)
131.0(11)
Pt1-N2-C14 137.2(6)
Cl3-Pt2-Cl4
N2-Pt2-S2
175.81(15) 176.18(15)
178.3(4) 177.2(4)
num(II) chloride compounds.50 In 1, the two imino ligands
are mutually cis, which is the thermodynamically stable form
for the complexes having two strong π-acceptor ligands
insofar as (d-d) π bonding is known to be more effective
in the cis configuration.51 In 2 and 4, the imine and sulfoxide
ligands are mutually trans, which is the result of a significant
trans effect of sulfoxides compared to chloride ligands
facilitating the formation of kinetically controlled trans
isomers. In the coordinated imine, the values of the CdN
bond length [1.261-1.300 Å] are similar within 3σ and
correspond to the previously reported distances of the CdN
double bond in the metal-bound Ph2CdNH [1.285-1.310
Å].20d,f,32 In complexes 2 and 4, the Pt-S bond distances
are in the range from 2.210 to 2.222 Å, which is in good
agreement with the mean values of the Pt-S bond [2.216
Å] for S-coordinated sulfoxides.52 The solid-state structure
of 4 consists of two dimeric Pt moieties with the Pt‚‚‚Pt
distances at 3.271 and 3.314 Å, which are less than a double
van der Waals radius for Pt [1.72 × 2 ) 3.44 Å]. This case
represents a rather weak interaction taking into account that
the Pt‚‚‚Pt contacts in numerous examples of dimeric PtII
complexes are in the range 2.7-3.4 Å; no Pt‚‚‚Pt contacts
of less than 5 Å were observed for the other complexes
studied in this work by X-ray crystallography.53 The dimeric
architecture of 4 is enhanced by the hydrogen bonding
between imine H atoms and O atoms. The N1‚‚‚O2 and N1B‚
‚‚O2B distances are 2.995(17) and 2.952(16) Å for the first
and second Pt2 moieties, respectively. These bond lengths
fall into the range of typical N‚‚‚O distances when NH‚‚‚O
hydrogen bonding takes place.54 The angles N1‚‚‚H1‚‚‚O2
and N1B‚‚‚H1B‚‚‚O2B are 158.0 and 160.4°, respectively.
Cyclometalation of the Ligated Benzophenone Imine.
For both 1 and 2-6, a thermally induced solid-state
cyclometalation was observed. A thermal analysis was
performed for all synthesized compounds, and the mass loss
on the first step of thermal conversion, corresponding to the
loss of 1 equiv of HCl, was observed when they were heated
to 150-200 °C, with the heating rate being 5 °C min-1 (see
Figures S1-S6 in the Supporting Information). In a prepara-
tive experiment, the yellow powders of 1-6 were heated in
an open test tube at a specific temperature (see the
Experimental Section) overnight, giving a bright-orange
product. The evolution of HCl was detected by a pH
indicator, and weight monitoring proved the loss of 1 equiv
of HCl. The measurement of the NMR spectra enabled the
establishment that a solid-state conversion of 1-6 into
orthometalated products [PtCl{Ph(C6H4)CdNH}(Ph2Cd
NH)] (7) and [PtCl{Ph(C6H4)CdNH}(RR′SO)] (8-12)
(Scheme 1) took place. The yield of 8 was almost quantita-
tive, while compounds 1 and 3-6 partially decomposed on
heating and were recrystallized to obtain analytically pure
samples.
Along with the solid-state cyclometalation of 1-6, an
analogous process was observed on heating of the compounds
in a toluene suspension. The complexes 1 and 2-6 were
refluxed in toluene for 12-16 h, resulting in the elimination
of 1 equiv of HCl and the formation of a five-membered
platinacycle. The cyclometalated products 7-12 (Scheme 1)
were isolated in nearly quantitative yields. For 1, a change
of the relative position of the N atoms proved to take place
as a result of the cyclometalation process. It is worth noticing
that 7 was obtained earlier but in rather low yield.26
(50) (a) Crespo, M.; Font-Bardia, M.; Granell, J.; Mart´ınez, M.; Solans,
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Inorganic Chemistry, Vol. 46, No. 11, 2007 4473

Scaffidi-Domianello et al.
Figure 3. View of complex 4‚1/2CHCl3 with the atomic numbering scheme.
Thermal ellipsoids are drawn with 50% probability. The second Pt2 moiety
has been omitted for clarity. Intermolecular contacts and hydrogen bond-
ing: Pt1‚‚‚Pt2 3.2871(9) Å, Pt1B‚‚‚Pt2B 3.3140(9) Å, N1-H1 0.88 Å, H1‚
‚‚O2 2.16 Å, N1‚‚‚O2 2.995(17) Å, N1-H1‚‚‚O2 158.0°, N2-H2 0.88 Å,
H2‚‚‚O1 2.15 Å, N2‚‚‚O1 2.991(16) Å, N2-H2‚‚‚O1 159.0°, N1B-H1B
0.88 Å, H1B‚‚‚O2B 2.11 Å, N1B‚‚‚O2B 2.952(16) Å, N1B-H1B‚‚‚O2B
160.4°, N2B-H2B 0.88 Å, H2B‚‚‚O1B 2.14 Å, N2B‚‚‚O1B 2.994(16) Å,
N2B-H2B‚‚‚O1B 164.6°.
Figure 1. View of complex 1 with the atomic numbering scheme. Thermal
ellipsoids are drawn with 50% probability.
by IrIII,58 O- and C-metalation of (dimethoxyphenyl)phos-
phines by PtII and PdII,59 cycloplatination of o-diphenyl-
phosphinebenzaldehyde,60a cyclopalladation of benzylamines,60b
cyclometalation of tris(1-pyrazolyl)methane by a PtII center,61
and 1-methyl-2,4′-bipyridinium by PtII and PdII centers.62
Hence, the solid-state conversion of the ligated Ph2CdNH
species at the PtII center represents the first example in the
chemistry of imines.
A significant research effort has been focused on cyclo-
metalated compounds because of the ability of some of them
to display interesting photophysical properties.63 In this
regard, the cyclometalated PtII complexes64 are among the
Figure 2. View of complex 2 with the atomic numbering scheme. Thermal
ellipsoids are drawn with 50% probability.
One should mention that, although numerous examples
of cyclometalation in solution were comprehensively covered
in the literature,55 reactions in the solid phase were studied
in much less detail. To our knowledge, only a few examples
of solid-state cyclometalation were reported, i.e., the cyclo-
platination of dimethyl(1-naphthyl)phosphine and dimethyl-
(1-naphthyl)arsine,56 O-metalation of (2-alkoxyphenyl)-
phosphines by PtII,57 cyclometalation of triphenylphosphine
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4474 Inorganic Chemistry, Vol. 46, No. 11, 2007

Cyclometalation of Ligated Benzophenone Imine
Figure 5. View of complex 8 with the atomic numbering scheme. Thermal
ellipsoids are drawn with 50% probability. The second Pt molecule in the
asymmetric unit has been omitted for clarity.
Figure 4. 1H-13C COSY NMR spectrum of 8 in CD3OD, showing the
C2-H2 correlation signal in the aromatic region. Pt satellites in the directly
measured one-dimensional 1H and 13C NMR spectra are marked with arrows.
Characterization and X-ray Structure Determinations
of the Cyclometalated PtII Complexes. The cyclometalated
complexes 8-12 gave satisfactory elemental analyses and
the expected molecular ion/fragmentation patterns in ESI-
MS spectra (the presence of the [M - Cl]+ and [M + Na]+
peaks was recognized). Complexes 8-12 were characterized
by IR spectroscopy: the characteristic ν(SdO) [1116-1126
cm-1], ν(CdN) [1569-1587 cm-1], and ν(NH) [3200-3340
cm-1] bands were observed. The most significant difference
of the stretching vibrations between the starting (imine)-
(sulfoxide)platinum(II) complexes (2-6) and the correspond-
ing cyclometalated products (8-12) was observed for the
CdN double bond: the respective absorption band showed
a red shift of up to 30 cm-1 in the IR spectrum. In 1H NMR
spectra of 8-12, protons H2 displayed satellites deriving
from the coupling of the protons with the 195Pt nuclei; typical
3JPt,H coupling constants between 47.0 and 49.2 Hz could
be detected. Coupling of the C2 atoms in complexes 8-12
most advantageous owing to such useful features as high
efficiency and long lifetimes of the emissive states and
potential applications in many fields, e.g., chemosensors65
and light-emitting diodes (LEDs).64g,66 In most cases, the
luminescence property is associated with cyclometalated PtII
compounds containing various heterocyclic ligands, e.g.,
pyridine64b,66b,67 and dipyridine,65b,c,67h,68 generally with dif-
ferent aromatic substituents, as well as 7,8-benzo-
quinoline,64c,67d,69 and aryldiamine64e,f ligands. Surprisingly,
nearly no attention was drawn so far to the luminescent
cycloplatinated imino species.64a,i In the present work, we
observed that the cyclometalated compounds (7-12) ob-
tained exhibit bright-yellow-to-orange luminescence at room
temperature in solution, in the solid state, and on being spread
onto thin-layer chromatography (TLC) SiO2 plates. There-
fore, we conducted a study of their solution and solid-state
photophysical properties, and the results are given below in
this paper.
to 195Pt were also determined in both directly measured 13
C
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1
NMR and two-dimensional H-13C COSY NMR spectra
(2JPt,C ) 52.5-61.2 Hz; Figure 4). The presence of the
satellites undoubtedly proves the elimination of HCl as a
consequence of the cyclometalation process. As expected, a
significant difference in δPt was observed between the starting
(imine)(sulfoxide)platinum(II) complexes 2-6 (between
-1292.3 and -1339.0 ppm) and the corresponding cyclo-
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Inorganic Chemistry, Vol. 46, No. 11, 2007 4475

Scaffidi-Domianello et al.
Figure 6. View of complex 10 with the atomic numbering scheme.
Thermal ellipsoids are drawn with 50% probability. The other three Pt
molecules in the asymmetric unit have been omitted for clarity (see
Figure 7).
Figure 7. Hydrogen-bonding network in structure 10: N1-H1 0.88 Å,
H1‚‚‚Cl1B 2.49 Å, N1‚‚‚Cl1B 3.366(4) Å, N1-H1‚‚‚Cl1B 176.0°, N1B-
H1B 0.88 Å, H1B‚‚‚Cl1 2.55 Å, N1B‚‚‚Cl1 3.426(4) Å, N1B-H1B‚‚‚Cl1
172.9°, N1C-H1C 0.88 Å, H1C‚‚‚Cl1D 2.54 Å, N1C‚‚‚Cl1D 3.416(4) Å,
N1C-H1C‚‚‚Cl1D 175.7°, N1D-H1D 0.88 Å, H1D‚‚‚Cl1C 2.38 Å, N1D‚
‚‚Cl1C 3.262(4) Å, N1D-H1D‚‚‚Cl1C 175.4°.
metalated products 8-12 (between -2240.3 and -2281.7
ppm) because of the change in the ligand sphere (Cl vs C).
The crystal structures of two cyclometalated products, i.e.,
8 and 10, were determined by X-ray diffraction (Table 1
and Figures 5 and 6). In both structures, the Pt atoms are
located at a crystallographic inversion center and display a
slightly distorted square-planar coordination. The Pt-Cl bond
distances are in the range from 2.381 to 2.397 Å, which is
significantly longer compared to those of the corresponding
noncyclometalated complexes [2.297-2.308 Å]. The differ-
ence in the Pt-Cl bond lengths trans to Cl and trans to C is
due to the well-known strong ground-state trans influence
of C-bonded ligands.70 However, these distances agree well
with those in the previously characterized PtII compounds
containing a Cl ligand in the trans position to the platinated
C atom.71 In 8 and 10, the coordinated sulfoxide and the
platinated C13 center are mutually cis, which is preferable
because both centers possess a significant trans influence.
The five-membered platinacycles deviate slightly from the
plane, with a maximum deviation of 0.149 Å. In 8, the
asymmetric unit contains two independent Pt molecules,
while in 10, it includes four Pt molecules linked by the
intermolecular hydrogen-bonding network between the NH
group and Cl atoms (Figure 7). The distances H1‚‚‚Cl1B,
H1B‚‚‚Cl1, H1C‚‚‚Cl1D, and H1D‚‚‚Cl1C are 2.49, 2.55,
2.54, and 2.38 Å, respectively, which fall into the range of
the typical NH‚‚‚Cl distances when this type of hydrogen
bonding takes place.72
Luminescence Studies. Luminescent square-planar PtII
complexes have attracted a great deal of interest because of
their useful photochemical properties, i.e., high efficiency
and long lifetimes of the emissive states and potential
applications in many fields, such as chemosensors,73 pho-
tocatalysts,74 LEDs,75 and photocatalytic devices.76 The
most advantageous d8 PtII luminescent systems are based on
[PtX2(diimine)] (X ) halide, cyanide, thiolate, alkyl, aryl,
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4476 Inorganic Chemistry, Vol. 46, No. 11, 2007

Cyclometalation of Ligated Benzophenone Imine
Table 2. Photophysical Properties of the Pt Complexes at Room
Temperature
Solution Data
ꢀ (dm3 mol-1 cm-1
(λab ) 400 nm)
)
sample
λ
em (nm)a
φem (%)b
8
9
10
11
12
3400
1600
3100
3900
1400
535, 565
535, 565
535, 565
500-750
535, 565
0.0071
0.019
0.0056
0.0042
0.0045
Figure 8. Absorption spectra of a 1.0 × 10-5 M solution in acetone at
Solid-State Data
λ
em (nm)a
τ (ns)c
room temperature.
sample
8
9
10
11
12
542, 571, 624
575, 655
525, 559, 610
600, 655
455
575
615
323
507
quantum yields of the complexes are rather low, with values
smaller than 0.0071, the exception being 9, the quantum yield
of which (0.019) is nearly 3 times that of the other
compounds.
608, 655
a λex ) 400 nm. b Determined using [Ru(bpy)3]2+ as the standard, φ )
0.062 (ref 83). c Excited state (λex ) 400 nm) lifetimes ((50 ns) reported
with λem ) 575 nm.
Figure 10 shows normalized solid-state emission spectra
for the complexes that exhibit differences with respect to
the structure and intensity of the emission bands but have
similar emission energies. The solid-state emission data listed
or acetylide),77 terpyridine78 complexes, or phosphorescent
platinum(II) porphryins.79 A separate group of PtII-based
luminescent compounds is comprised of complexes with
N,C,N-67a,75a,80 or S,C,S-80a,81 pincer ligands and some other
cyclometalated PtII compounds.64a,82
max
in Table 2 show compounds 8 and 10 having λ
at 571
em
and 559 nm, respectively. These two complexes also exhibit
some structure on the emission bands with high- and low-
energy shoulders at 542 and 624 nm and at 525 and 610
max
em
nm, respectively. Complex 9 shows a λ at 575 nm with a
The UV-vis absorption and emission data of complexes
8-12 are summarized in Table 2 (Attention! For ref 83, see
footnote b in Table 2). All of the complexes show an
absorption band at 400 nm (Figure 8) with extinction
coefficients (ꢀ) on the order of 103 dm3 mol-1 cm-1. These
characteristic metal complex absorptions are only reported
for λ > 350 nm. Below 350 nm, high-intensity intraligand
absorptions predominate in the spectra. The broad but well-
defined absorption band at 400 nm may be attributed to a
triplet metal-to-ligand charge-transfer (3MLCT) transition
corresponding to dπ(Pt) f π*(C∩N), based on similarities
in the energy and intensity of MLCT transitions of related
platinum(II) terpyridyl and cyclometalated diimine com-
shoulder at 655 nm. Complexes 11 and 12 exhibit a red shift
max
em
in the value of λ in going from solution to the solid state.
It is possible that, in the more rigid solid state, the phenyl
rings of the sulfoxide substituent in 11 and 12 have an effect
on their solid-state packing arrangement. For compounds
8-12, the excited-state emission lifetimes at 575 nm are in
the range of 320-615 ns (Table 2), consistent with the spin-
forbiddenness associated with metal complex phosphores-
cence.64c,74b There is no observed correlation of λem and τ.
Figure 11 shows the solution emission spectra of 12 at
three different concentrations. It is found that the emission
intensity increases with increasing concentration but the
max
em
plexes.76a,78,84 In Figure 9, all of the PtII complexes except
λ
energies do not change, consistent with the absence of
intermolecular Pt‚‚‚Pt aggregation.82c,85 Though the solid-
state quantum yields for the compounds were not obtained,
they are indeed very brightly emissive when irradiated with
400 nm light, raising the possibility that these systems may
be useful for sensor or display applications, upon proper
derivatization.
max
em
11 show an emission with λ
of 535 nm, along with
another less intense emission at 565 nm. Complex 11 has a
broad emission ranging from 500 to 650 nm. The solution
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Inorg. Chem. 2002, 41, 5653. (b) Bailey, J. A.; Hill, M. G.; Marsh,
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S. S.-Y.; Che, C.-M.; Zhu, N. J. Am. Chem. Soc. 2006, 128, 8297. (c)
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Final Remarks
In the current work, we succeeded in synthesizing a new
family of orthometalated PtII complexes of the general
formula [PtCl{Ph(C6H4)CdNH}(RR′SO)] [R, R′ ) Me, Me;
n-Pr, n-Pr; (CH2)4; Me, Ph; Me, p-MeC6H4] (8-12). It was
shown that the cyclometalation of trans-[PtCl2(Ph2CdNH)-
(RR′SO)] (2-6) proceeds both in the solid phase and in a
toluene suspension, leading to the formation of N,C-chelates
in high isolated yields. Thermogravimetric analysis (TGA)
proved to be a perfectly suitable method for the observation
of the processes taking place on heating of the solid sample
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Organometallics 2002, 21, 226.
Inorganic Chemistry, Vol. 46, No. 11, 2007 4477

Scaffidi-Domianello et al.
Figure 9. Emission spectra of a 1.0 × 10-5 M solution in acetone at room temperature.
Figure 10. Normalized solid-state emission spectra at room temperature.
CHN elemental analyzer. Melting points were determined with a
Bu¨chi B-540 melting point apparatus and are uncorrected. TGA/
DTA studies were performed with a Mettler Toledo TGA850
instrument (temperature range from 20 to 1000 °C with a heating
rate of 5 °C min-1, an air flow of 3 L h-1, and a sample mass of
5-10 mg in an aluminum crucible; the buoyancy correction for
TGA was done by measuring a blank). ESI-MS spectra were
obtained with a Bruker Esquire 3000 instrument. IR spectra (4000-
400 cm-1) were recorded with a Perkin-Elmer Fourier transform
1
(FTIR) instrument in KBr pellets. H, 13C{1H}, and 195Pt NMR
Figure 11. Emission spectra of 12 in acetone at different concentrations
at room temperature (λex ) 400 nm).
spectra were measured with a Bruker Avance DPX 400 spectrom-
eter at 400.13 MHz (1H), 100.63 MHz (13C), and 85.99 MHz
(
195Pt), correspondingly, at ambient temperature. 195Pt chemical
at elevated temperatures. It is important that the orthometa-
lated complexes obtained exhibit luminescent properties at
room temperature both in solution and in the solid state and
also on being spread onto TLC SiO2 plates. The broad
application spectrum of luminescent PtII complexes stimulates
our interest in the further elaboration of the current topic, and
studies on the cyclometalated benzophenone imine com-
plexes and on their emission properties are underway in our
group.
shifts are given relative to K2[PtCl4], and the half-height line width
is given in parentheses.
Reaction of Ph2CdNH with K[PtCl3(RR′SO)] Obtained in
Situ. In a typical experiment, a solution of RR′SO (0.25 mmol) in
water (1 mL) was added dropwise to a solution of K2[PtCl4] (100
mg, 0.24 mmol) in water (3 mL) at 20-25 °C. The mixture was
stirred for 4-5 h at room temperature until the color of the solution
turned from reddish-orange to yellow. When Me(Ph)SO and
p-MeC6H4(Me)SO were employed, small amounts of the known
pale-yellow cis-[PtCl2{Me(Ph)SO}2]46c,86 and cis-[PtCl2{p-MeC6H4-
(Me)SO}2]87 complexes were obtained and removed by filtration
(yields are 10 and 4%, respectively).
Experimental Section
A solution of Ph2CdNH (44 mg, 0.24 mmol) in CHCl3 (1 mL)
was added to the yellow filtrate obtained as described above. A
pale-yellow amorphous precipitate appeared immediately, where-
upon the reaction mixture was stirred overnight at room temperature
and the precipitate was separated by filtration. The yellow solid
was dried at 20-25 °C and washed with two 2-mL portions of
General Procedures. Solvents were obtained from commercial
sources and used as received. n-Propyl sulfoxide was purchased
from Acros, while the remaining sulfoxides and benzophenone
imine were obtained from Aldrich. The complexes K[PtCl3(RR′SO)]
(R, R′ ) Me, Me; n-Pr, n-Pr; (CH2)4; Me, Ph; Me, p-MeC6H4)
were prepared in situ according to published methods.46 For TLC,
Merck UV 254 SiO2 plates were used. Fluka silica gel 60 (220-
440 mesh) was used for column chromatography. C, H, and N
elemental analyses were carried out by the elemental analyses
laboratory of the University of Vienna using a Perkin-Elmer 2400
(86) Antolini, L.; Folli, U.; Iarossi, D.; Schenetti, L.; Taddei, F. J. Chem.
Soc., Perkin Trans. 2 1991, 7, 955.
(87) Spevak, V. N.; Skvortsov, N. K.; Belskii, V. K.; Konovalov, V. E.;
Lobadyuk, V. I. Zh. Obsh. Khim. 1992, 62, 2646.
4478 Inorganic Chemistry, Vol. 46, No. 11, 2007

Cyclometalation of Ligated Benzophenone Imine
Table 3. Crystallographic Data for 1, 2, 4‚1/2CHCl3, 8, and 10
1
2
4
8
10
empirical formula
fw
temp (K)
λ (Å)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
C26H22Cl2N2Pt
628.45
120(2)
0.710 73
triclinic
P1h
9.510(2)
9.680(2)
14.006(3)
70.557(18)
83.699(18)
67.909(12)
1126.3(4)
2
1.853
6.483
6792
3194
0.0351
0.0806
C15H17Cl2NOPtS
525.35
100(2)
0.710 73
monoclinic
P21/c
5.5695(5)
16.5381(13)
17.9682(15)
90
98.032(7)
90
1638.8(2)
4
2.129
9.012
C35H39Cl7N2O2Pt2S2
1222.13
120(2)
0.710 73
monoclinic
P21/c
19.869(2)
18.081(3)
23.197(2)
90
99.181(11)
90
8226.8(19)
8
1.973
7.385
57627
C15H16ClNOPtS
488.89
120(2)
0.710 73
triclinic
P1h
10.0666(3)
10.5808(3)
14.7570(3)
107.833(2)
95.223(2)
92.2130(10)
1486.40(7)
4
2.185
9.754
23370
5236
0.0320
0.0719
C17H18ClNOPtS
514.92
120(2)
0.710 73
monoclinic
P21
10.38390(10)
24.3071(4)
13.4799(2)
90
99.749(9)
90
3353.23(8)
8
2.040
8.653
Z
F
calc (Mg/m3)
µ(Mo KR) (mm-1
reflns collected
unique reflns
)
22642
3601
0.0201
0.0411
54166
15058
0.0231
0.0474
14385
0.0631
0.1462
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
2
diethyl ether. The analytically pure products 126 and 2-6 were
separated by column chromatography, correspondingly, in the first
and second fractions [eluent: 1:8 (v/v) Me2CO/CHCl3]. The
products were dried at room temperature. Yield of 1: 6-8%, based
on Pt. Yield of 2-6: 40-60%, based on Pt.
MeOH): m/z 604 [M + Na]+, 620 [M + K]+, 727 [M + Ph2Cd
NH - Cl]+. Mp: 134-135 °C. TGA curve, mass loss: 6.2%
(-HCl, 150 °C, calcd 6.3%), 26% (220 °C), 35% (370 °C). TLC
(8:1 (v/v) CHCl3/Me2CO): Rf ) 0.61. IR (KBr, cm-1): ν 3195
(m, NH), 1601 (m, CdN), 1113 (s, SdO), 702 (m, C-S). 1H NMR
(CDCl3): δ 8.90 (s, br, 1H, NH), 8.12 (d, 2H, 3JH,H ) 7.0 Hz) and
1. Anal. Calcd for C26H22N2Cl2Pt: C, 49.69; H, 3.53; N, 4.46.
Found: C, 49.52; H, 3.76; N, 4.36. ESI-MS+ (1:10 (v/v)
CHCl3/MeOH): m/z 433 [M - HCl - Ph2CdNH + Na]+, 556
[M - HCl - Cl]+, 651 [M + Na]+, 667 [M + K]+. ESI-MS-
(1:10 (v/v) CHCl3/MeOH): m/z 409 [M - HCl - Ph2CdNH -
H]-, 446 [M - HCl - Ph2CdNH + Cl]-, 627 [M - H]-, 663 [M
+ Cl]-. Mp: 212-213 °C. TGA curve, mass loss: 6.4% (-HCl,
200 °C, calcd 5.8%), 18% (310 °C), 37% (410 °C). TLC (20:1
(v/v) CHCl3/Me2CO): Rf ) 0.56. IR (KBr, cm-1): ν 3199 (m,
2
7.58 (m, 8H) (two Ph), 3.53 (td, 2H, 2SCHH, JH,H ) 12.6 Hz,
2
3
3JH,H ) 5.0 Hz), 3.08 (td, 2H, 2SCHH, JH,H ) 11.0 Hz, JH,H
)
5.0 Hz), 2.24 (m, 2H, CH2), 2.13 (m, 2H, CH2), 1.18 (t, 6H, 2CH3,
3JH,H ) 7.5 Hz). 13C{1H} NMR (CDCl3): δ 184.27 (CdNH),
133.60 (Car), 132.68 (Car), 131.47 (Car), 129.54 (Car), 129.46 (Car),
128.29 (Car), 56.34 (SCH2), 16.95 (CH2), 13.29 (CH3). 195Pt NMR
(CDCl3): δ -1329.1 (J ) 550 Hz).
4. Anal. Calcd for C17H19NCl2OPtS: C, 37.03; H, 3.47; N, 2.54.
Found: C, 37.05; H, 3.47; N, 2.54. ESI-MS+ (1:10 (v/v) CHCl3/
MeOH): m/z 516 [M - Cl]+, 574 [M + Na]+, 590 [M + K]+, 697
[M + Ph2CdNH - Cl]+. Mp: 168-169 °C. TGA curve, mass
loss: 6.2% (-HCl, 200 °C, calcd 6.6%), 16% (260 °C), 37%
(350 °C). TLC (8:1 (v/v) CHCl3/Me2CO): Rf ) 0.49. IR (KBr,
cm-1): ν 3227 (m, NH), 1607 (m, CdN), 1129 (s, SdO), 701 (s,
1
NH), 1591 and 1565 (s, CdN). H NMR (acetone-d6): δ 8.89 (s,
3
br, 2H, NH), 8.27 (d, 4H, Har(o), JH,H ) 7.0 Hz), 7.80 (t, 2H,
Har(p), 3JH,H ) 7.5 Hz), 7.63 (t, 4H, Har(m), 3JH,H ) 7.8 Hz), 7.47
3
3
(t, 2H, Har(p), JH,H ) 7.3 Hz), 7.25 (t, 4H, Har(m), JH,H ) 7.8
Hz), 6.59 (d, 4H, Har(o), 3JH,H ) 7.5 Hz). 13C{1H} NMR (CDCl3):
δ 179.08 (CdNH), 137.73 (Car), 136.74 (Car), 132.94 (Car), 132.69
(Car), 130.83 (Car), 129.06 (Car), 128.99 (Car), 128.59 (Car). 195Pt
NMR (acetone-d6): δ -240.5 (J ) 660 Hz). Crystals for X-ray
study were obtained by slow evaporation of a chloroform/acetone
solution.
1
C-S). H NMR (CDCl3): δ 9.48 (s, br, 1H, NH), 8.16 (d, 2H,
3JH,H ) 7.0 Hz) and 7.56 (m, 8H) (two Ph), 3.96 (m, 2H, SCH2),
3.50 (m, 2H, SCH2), 2.33 (m, 2H, CH2), 2.14 (m, 2H, CH2). 13C-
{1H} NMR (CDCl3): δ 183.65 (CdNH), 137.84 (Car), 137.16 (Car),
133.40 (Car), 132.78 (Car), 131.49 (Car), 129.86 (Car), 129.31 (Car),
128.26 (Car), 56.82 (SCH2), 25.19 (CH2). 195Pt NMR (CDCl3): δ
-1292.3 (J ) 470 Hz). Crystals for X-ray study were obtained by
slow evaporation of a chloroform/acetone solution.
2. Anal. Calcd for C15H17NCl2OPtS: C, 34.29; H, 3.26; N, 2.66.
Found: C, 34.31; H, 3.41; N, 2.40. ESI-MS+ (1:10 (v/v) CHCl3/
MeOH): m/z 490 [M - Cl]+, 548 [M + Na]+, 564 [M + K]+, 671
[M + Ph2CdNH - Cl]+, 706 [M + Ph2CdNH + H]+. ESI-MS-
(1:10 (v/v) CHCl3/MeOH): m/z 411 [M - Me2SO - Cl]-. Mp:
172 °C. TGA curve, mass loss: 7.5% (-HCl, 160 °C, calcd 7.0%),
21% (310 °C), 42% (450 °C). TLC (8:1 (v/v) CHCl3/Me2CO): Rf
) 0.56. IR (KBr, cm-1): ν 3294 (m, NH), 1599 (m, CdN), 1134
5. Anal. Calcd for C20H19NCl2OPtS: C, 40.89; H, 3.26; N, 2.38.
Found: C, 40.91; H, 3.41; N, 2.25. ESI-MS+ (1:10 (v/v) CHCl3/
MeOH): m/z 610 [M + Na]+, 626 [M + K]+, 734 [M + Ph2Cd
NH - Cl]+. ESI-MS- (1:10 (v/v) CHCl3/MeOH): m/z 441 [M -
Ph2CdNH + Cl]-. Mp: 162-163 °C. TGA curve, mass loss: 6.9%
(-HCl, 180 °C, calcd 6.4%), 14% (260 °C), 43% (370 °C). TLC
(20:1 (v/v) CHCl3/Me2CO): Rf ) 0.43. IR (KBr, cm-1): ν 3225
1
(s, SdO), 702 (s, C-S). H NMR (acetone-d6): δ 10.46 (s, br,
1H, NH), 8.15 (d, 2H, 3JH,H ) 7.0 Hz), 7.69 (m, 2H) and 7.59 (m,
3
6H) (two Ph), 3.29 (s + d, 6H, CH3, JPt,H ) 16.6 Hz). 13C{1H}
NMR (CDCl3): δ 183.79 (CdNH), 137.83 (Car), 137.13 (Car),
133.48 (Car), 132.83 (Car), 131.48 (Car), 129.85 (Car), 129.34 (Car),
128.28 (Car), 44.04 (CH3). 195Pt NMR (acetone-d6): δ -1339.0 (J
) 550 Hz). Crystals for X-ray study were obtained by slow
evaporation of a toluene/dichloromethane solution.
1
(m, NH), 1599 (s, CdN), 1133 (s, SdO). H NMR (acetone-d6):
3
δ 10.62 (s, br, 1H, NH), 8.10 (d, 2H, JH,H ) 7.0 Hz), 7.92 (m,
3
2H) and 7.60 (m, 11H) (three Ph), 3.32 (s + d, 3H, CH3, JPt,H
)
12.2 Hz). 13C{1H} NMR (CDCl3): δ 182.79 (CdNH), 143.18 (Car),
137.65 (Car), 137.59 (Car), 133.27 (Car), 132.85 (Car), 132.09 (Car),
3. Anal. Calcd for C19H25NCl2OPtS: C, 39.25; H, 4.33; N, 2.41.
Found: C, 39.20; H, 4.33; N, 2.42. ESI-MS+ (1:10 (v/v) CHCl3/
Inorganic Chemistry, Vol. 46, No. 11, 2007 4479

Scaffidi-Domianello et al.
131.29 (Car), 130.13 (Car), 129.52 (Car), 129.16 (Car), 128.25 (Car),
125.92 (Car), 45.23 (CH3). 195Pt NMR (CDCl3): δ -1334.1 (J )
520 Hz).
Me2CO/CHCl3): Rf ) 0.54. IR (KBr, cm-1): ν 3340 (m, NH),
1
1569 (m, CdN), 1126 (s, SdO). H NMR (CD3OD): δ 10.50 (s,
3
3
br, 1H, NH), 8.20 (d + q, 1H, H2, JH,H ) 7.5 Hz, JPt,H ) 48.7
Hz), 7.63 (m, 5H, Ph), 7.24 (m, 1H, H3), 7.13 (m, 2H, H4 and
H5), 3.55 (s + d, 6H, CH3, 3JPt,H ) 22.1 Hz). 13C{1H} NMR (CD3-
6. Anal. Calcd for C21H21NCl2OPtS: C, 41.94; H, 3.52; N,2.33.
Found: C, 41.90; H, 3.45; N, 2.38. ESI-MS+ (1:10 (v/v) CHCl3/
MeOH): m/z 602 [M + H]+, 624 [M + Na]+, 640 [M + K]+. Mp:
164-165 °C. TGA curve, mass loss: 6.3% (-HCl, 190 °C, calcd
6.1%), 6.2% (270 °C), 6.6% (340 °C), 45% (410 °C). TLC (8:1
(v/v) CHCl3/Me2CO): Rf ) 0.70. IR (KBr, cm-1): ν 3198 (m,
2
OD): δ 188.41 (CdN), 145.17 (C1), 134.13 (C2, JPt,C ) 54.4
3
Hz), 133.13 (C3, JPt,C ) 50.5 Hz), 131.55 (Car), 131.49 (C5),
2
128.99 (Car), 128.30 (Car), 124.28 (C4), 45.05 (CH3, JPt,C ) 55.4
Hz). 195Pt NMR (CD3OD): δ -2261.7 (J ) 710 Hz). Crystals for
X-ray study were obtained by slow evaporation of an acetone
solution.
1
NH), 1597 (s, CdN), 1131 (s, SdO), 699 (s, C-S). H NMR
(CDCl3): δ 9.83 (s, br, 1H, NH), 8.10 (d, 2H, H1 and H4, 3JH,H
)
3
7.0 Hz), 7.90 (d, 2H, H2 and H3, JH,H ) 8.1 Hz), 7.66 (m, 1H,
Har), 7.62 (m, 2H, 2Har), 7.53 (m, 3H, 3Har), 7.44 (m, 2H, 2Har),
7.38 (m, 2H, 2Har), 3.46 (s, 3H, SCH3), 2.50 (s, 3H, CH3). 13C-
{1H} NMR (CDCl3): δ 182.84 (CdNH), 143.65 (Car(q)), 140.06
(Car(q)), 137.67 (Car(q)), 137.61 (Car(q)), 133.26 (Car), 132.15 (Car),
3
131.34 (Car), 130.13 (Car), 130.09 (Car, JPt,C ) 87.5 Hz), 129.16
(Car), 128.25 (Car), 125.89 (Car), 45.42 (SCH3), 21.94 (CH3). 195Pt
NMR (CDCl3): δ -1318.0 (J ) 450 Hz).
Cyclometalation of the Complexed Benzophenone Imine in
the Solid State and on Heating in Toluene. The yellow powders
of 1 or 2-6 (0.04 mmol) were heated in an open test tube at
180 °C (1), 140 °C (2), 140 °C (3), 180 °C (4), 160 °C (5), or
170 °C (6) overnight, giving a bright-orange product; elimination
of HCl was detected by a pH indicator, and weight monitoring
proved the loss of 1 equiv of HCl. The yield of 8 was almost
quantitative. When 1 and 3-6 were heated, along with cyclom-
etalated complexes 7 and 9-12, the resulting orange solids
contained some impurities deriving from decomposition products,
9. Anal. Calcd for C19H24NClOPtS: C, 41.87; H, 4.44; N, 2.57.
Found: C, 41.93; H, 4.40; N, 2.55. ESI-MS+ (MeOH): m/z
509 [M - Cl]+, 568 [M + Na]+. Mp: 190-192 °C. TLC
(CHCl3): Rf ) 0.44. IR (KBr, cm-1): ν 3206 (w, NH), 1580
1
(m, CdN), 1116 (s, SdO). H NMR (CD3OD): δ 10.43 (s, br,
1H, NH), 8.23 (d + q, 1H, H2, 3JH,H ) 7.5 Hz, 3JPt,H ) 47.2 Hz),
7.63 (m, 5H, Ph), 7.22 (m, 1H, H3), 7.12 (m, 2H, H4 and
H5), 3.78 (m, 2H, SCH2), 3.40 (m, 2H, SCH2), 2.17 (m, 2H,
CH3CH2), 2.09 (m, 2H, CH3CH2), 1.19 (m, 6H, CH3). 13C{1H}
NMR (CD3OD): δ 177.06 (CdN), 144.69 (C1), 135.89 (C6),
134.35 (C2, 2JPt,C ) 52.5 Hz), 132.95 (C3, 3JPt,C ) 51.5 Hz), 132.57
(Car(q)), 131.49 (Car), 131.39 (C5), 128.99 (Car), 128.30 (Car), 124.18
1
as could be detected by H NMR spectroscopy.
In a typical experiment, suspensions of 1 or 2-6 (0.1 mmol) in
toluene (10 mL) were refluxed for 12-16 h, whereupon the solvent
was removed at 40 °C under reduced pressure. The bright-orange-
yellow powders of 7 or 8-12 were dried in vacuo at room
temperature. Yields were almost quantitative.
2
3
(C4), 57.81 (SCH2, JPt,C ) 38.9 Hz), 17.32 (CH2, JPt,C ) 22.4
Hz), 12.23 (CH3). 195Pt NMR (CD3OD): δ -2281.7 (J ) 570 Hz).
7. IR (KBr (selected bands), cm-1): ν(CdN) 1594 m [lit.26 IR
1597 m cm-1], ν(CdN) 1578 m [lit.26 IR 1577 m cm-1]. 1H NMR
(CDCl3): δ 9.99 (s, br, 1H, NH) [lit.26 δ 10.13], 8.91 (s, br, 1H,
3
NH) [lit.26 δ 8.87], 8.31 (d, 2H, Har, JH,H ) 7.3 Hz) [lit.26 δ 8.28
3
(d)], 7.66 (m, 1H, Har), 7.55 (m, 10H, Har), 7.42 (t, 2H, Har, JH,H
3
) 7.7 Hz) [lit.26 δ 7.35-7.7 (m)], 7.12 (dd, 1H, Har, JH,H ) 7.5
4
3
Hz, JH,H ) 1.6 Hz), 6.97 (m, 2H, Har), 6.85 (d, 1H, Har, JH,H
)
7.6 Hz) [lit.26 δ 6.8-7.1 (m)]. In addition, ESI-MS+ analysis was
carried out. ESI-MS+ (MeOH): m/z 556 [M - Cl]+, 732 [M +
Ph2CdNH - Cl]+.
10. Anal. Calcd for C17H18NClOPtS: C, 39.65; H, 3.52; N, 2.72.
Found: C, 39.82; H, 3.65; N, 2.85. ESI-MS+ (MeOH): m/z 538
[M + Na]+, 554 [M + K]+, 590 [M + HCl + K]+. Mp: 173-174
°C. TLC (1:10 (v/v) Me2CO/CHCl3): Rf ) 0.60. IR (KBr, cm-1):
ν 3212 (m, NH), 1587 (m, CdN), 1125 (s, SdO). 1H NMR (CD3-
3
OD): δ 10.57 (s, br, NH), 8.17 (d + q, 1H, H2, JH,H ) 7.5 Hz,
(90) Beurskens, P. T.; Beurskens, G.; Gelder, R.; Garcia-Granda, S.; Gould,
R. O.; Israel, R.; Smits, J. M. M. The DIRDIF-99 program system;
Crystallography Laboratory, University of Nijmegen: Nijmegen, The
Netherlands, 1999.
(91) Burla, M. C.; Camalli, M.; Carrozzini, B.; Cascarano, G. L.; Giaco-
vazzo, C.; Polidori, G.; Spagna, R. J. Appl. Crystallogr. 2003, 36,
1103.
8. Anal. Calcd for C15H16NClOPtS: C, 36.85; H, 3.29; N, 2.86.
Found: C, 37.08; H, 3.28; N, 2.86. ESI-MS+ (MeOH): m/z 453
[M - Cl]+, 511 [M + Na]+. Mp: 185-186 °C. TLC (1:10 (v/v)
(88) Duisenberg, A. J. M.; Kroon-Batenburg, L. M. J.; Schreurs, A. M.
M. J. Appl. Crystallogr. 2003, 36, 220.
(92) Sheldrick, G. M. SHELXS-97, Program for Crystal Structure
Determination; University of Go¨ttingen: Go¨ttingen, Germany,
1997.
(93) Sheldrick, G. M. SHELXTL, Version 6.14-1, Bruker Analytical X-ray
Systems; Bruker AXS, Inc.: Madison, WI, 2005.
(94) Sheldrick, G. M. SADABSsBruker Nonius scaling and ab-
sorption correction, Version 2.10; Bruker AXS, Inc.: Madison, WI,
2003.
(89) Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data
Collected in Oscillation Mode; Academic Press: New York,
1997; pp 307-326. Otwinowski, Z.; Minor, W. Macromolecular
Crystallography. In Methods Enzymology; Carter, C. W., Sweet, J.,
Eds.; Academic Press: New York, 1997; Vol. 276, Part A, pp 307-
326.
4480 Inorganic Chemistry, Vol. 46, No. 11, 2007

Cyclometalation of Ligated Benzophenone Imine
3JPt,H ) 49.2 Hz), 7.62 (m, 5H, Ph), 7.23 (m, 1H, H3), 7.14 (m,
2H, H4 and H5), 4.15 (m, 2H, CH2), 3.46 (m, 2H, CH2), 2.47 (m,
2H, CH2), 2.31 (m, 2H, CH2). 13C{1H} NMR (CD3OD): δ 185.66
2
(CdN), 145.26 (C1), 135.74 (C6), 134.51 (C2, JPt,C ) 61.2 Hz),
133.89 (Car(q)), 133.17 (C3, 3JPt,C ) 55.4 Hz), 131.58 (Car), 131.54
(C5), 128.99 (Car), 128.34 (Car), 124.28 (C4), 59.54 (2SCH2, 2JPt,C
) 59.3 Hz), 25.95 (2CH2, 3JPt,C ) 28.2 Hz). 195Pt NMR (CD3OD):
δ -2240.3 (J ) 730 Hz). Crystals for X-ray study were obtained
by slow evaporation of an acetone solution.
X-ray Crystallography. The crystals were immersed in
perfluoropolyether, mounted in cryoloops, and measured at
100 or 120 K temperature. The X-ray diffraction data were collected
with a Nonius Kappa CCD diffractometer using Mo KR
radiation (λ ) 0.71073 Å). The Denzo-Scalepack program or
EvalCCD packages88,89 were used for cell refinements and data
reductions. The structures were solved by direct methods or by the
heavy-atom method using the SHELXS-97 or SIR2002 or the
DIFDIF-99 programs, respectively, with the WinGX graphical user
interface.90-92 An empirical absorption correction based on equiva-
lent reflections was applied to all data (with XPREP
in SHELXTL or with SADABS).93,94 The maximum/minimum
transmission factors were 0.3458/0.6932, 0.1842/0.6367, 0.0972/
0.2271, 0.3095/0.4600, and 0.2530/0.5747 respectively for 1, 2, 4‚
1/2CHCl3, 8, and 10. Structural refinements were carried out with
SHELXL-97.95 The imine H atoms in 2 were located from the
difference Fourier map but constrained to ride on its parent atom
[Uiso ) 1.5Ueq (parent atom)]. Other H atoms were positioned
geometrically and allowed to ride on their parent atoms, with N-H
) 0.88 Å and Uiso ) 1.2Ueq (parent atom) and C-H ) 0.95-0.99
Å and Uiso ) 1.2-1.5Ueq (parent atom). The asymmetric unit of
4‚1/2CHCl3 contained two dimeric Pt units (four Pt) and one CHCl3
solvent molecule. Structure 8 contained two and structure 10
four Pt moieties in the asymmetric unit. In structure 10, two C
atoms (C15D and C16D) were disordered over two positions
with occupancies of 0.51 and 0.49. The selected bond lengths and
angles are summarized in Table 1 and crystallographic data in
Table 3.
11. Anal. Calcd for C20H18NClOPtS: C, 43.59; H, 3.29; N, 2.54.
Found: C, 43.44; H, 3.25; N, 2.50. ESI-MS+ (acetone): m/z
515 [M - Cl]+, 574 [M + Na]+, 590 [M + K]+. Mp: 178-180 °C.
TLC (1:20 (v/v) Me2CO/CHCl3): Rf ) 0.43. IR (KBr, cm-1): ν
3202 (m, NH), 1581 (s, CdN), 1122 (s, SdO). 1H NMR
3
(acetone-d6): δ 10.17 (s, br, 1H, NH), 8.24 (d, 2H, 2Har, JH,H
)
3
3
7.8 Hz), 8.05 (d + q, 1H, H2, JH,H ) 7.6 Hz, JPt,H ) 47.8
Hz), 7.67 (m, 8H, 8Har), 7.16 (m, 1H, H3), 7.09 (m, 2H, H4 and
H5), 3.68 (s + d, 3H, CH3, JPt,H ) 18.4 Hz). 13C{1H} NMR
3
(acetone-d6): δ 188.41 (CdN), 167.70 (C1), 146.86 (Car(q)), 145.08
2
3
(Car(q)), 134.92 (C2, JPt,C ) 53.5 Hz), 133.58 (C3, JPt,C
)
52.5 Hz), 132.80 (Car), 131.81 (Car), 131.67 (C5, 3JPt,C ) 48.6 Hz),
129.69 (Car), 129.16 (Car), 128.76 (Car), 125.97 (Car), 124.23 (C4),
47.17 (CH3, 2JPt,C ) 42.8 Hz). 195Pt NMR (acetone-d6): δ -2266.1
(J ) 600 Hz).
Luminescence Studies. Absorption spectra were recorded
using a Hitachi U2000 scanning spectrophotometer (200-1100
nm). Luminescence spectra were obtained using a Spex Fluoro-
max-P fluorimeter corrected for the spectral sensitivity of the
photomultiplier tube and the spectral output of the lamp with
monochromators positioned for a 2 nm bandpass. Excited-
state lifetimes were measured using a Lambda Physik nano-
second laser photolysis system. A Lextra 50 XeCl excimer
laser was used to pump 3002 dye laser containing diphenyl-
stilbene, which provided 7 ns, 1 mJ pulses at 400 nm. A
monochromator and a fast photomultiplier tube were used to
monitor sample emission at 575 nm. For kinetic analysis, the signal
from the photomultiplier tube was directed into a Tektronix
TDS 620 digitizing oscilloscope and then to a computer for
averaging, fitting, and storage. The metal complex concentration
of solution samples was 1.0 × 10-5 M, and each sample was
degassed by at least three freeze-pump-thaw cycles. Solid-state
emission and lifetime samples were prepared as a mixture of the
Pt complexes (4.10 × 10-5 mol) in a matrix of finely ground
KBr (3.24 × 10-3 mol). All data were recorded at room tem-
perature.
12. Anal. Calcd for C21H20NClOPtS: C, 44.64; H, 3.57; N, 2.48.
Found: C, 44.75; H, 3.65; N, 2.35. ESI-MS+ (MeOH): m/z 529
[M - Cl]+, 588 [M + Na]+. Mp: 169-170 °C. TLC (1:20
(v/v) Me2CO/CHCl3): Rf ) 0.66. IR (KBr, cm-1): ν 3200 (w, NH),
1
1583 (m, CdN), 1123 (s, SdO). H NMR (acetone-d6): δ 10.14
3
(s, br, 1H, NH), 8.11 (d, 2H, H7 and H10, JH,H ) 8.3 Hz),
3
3
8.05 (d + q, 1H, H2, JH,H ) 7.6 Hz, JPt,H ) 47.0 Hz), 7.66
3
(m, 5H, Ph), 7.49 (d, 2H, H8 and H9, JH,H ) 8.1 Hz), 7.16 (m,
3
1H, H3), 7.09 (m, 2H, H4 and H5), 3.65 (s + d, 3H, SCH3, JPt,H
) 18.4 Hz), 2.45 (s, 3H, CH3). 13C{1H} NMR (acetone-d6): δ
191.61 (CdN), 146.91 (Car(q)), 145.68 (Car(q)), 143.57 (Car(q)),
2
142.09 (Car(q)), 134.93 (C2, JPt,C ) 53.5 Hz), 133.93 (Car(q)),
3
133.56 (C3, JPt,C ) 51.5 Hz), 131.80 (Car), 131.64 (C5,
Acknowledgment. Y.Yu.S.-D., M.G., and B.K.K. are
indebted to the FWF (Austrian Science Funds) for finan-
3JPt,C ) 48.6 Hz), 130.19 (C7 and C10), 129.17 (Car), 128.76
(Car), 125.98 (C8 and C9), 124.18 (C4), 47.33 (SCH3, 2JPt,C ) 43.7
Hz), 20.82 (CH3). 195Pt NMR (acetone-d6): δ -2264.9 (J ) 620
Hz).
(95) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
Inorganic Chemistry, Vol. 46, No. 11, 2007 4481

Scaffidi-Domianello et al.
cial support. V.Yu.K. and Y.Yu.S.-D. are very much obliged
to the Russian Fund for Basic Research (Grants 06-03-90901
and 06-03-32065). V.Yu.K. is grateful to the Scientific
Council of the President of the Russian Federation (Grant
MK-1040.2005.3) and the Government of St. Petersburg.
M.H. and V.Yu.K. are indebted to the Academy of Finland
for support of their joint studies (Grant 110465). The authors
also acknowledge Paul Merkel for assistance with the
excited-state lifetime measurements. The authors gratefully
thank Dr. P. Unfried for support with the TGA.
Note Added after ASAP Publication. This article was
released ASAP on April 24, 2007. Additional changes were
made to Table 1, and the correct version was posted on
May 1, 2007.
Supporting Information Available: TGA curves of complexes
1-6 as well as crystallographic information files (CIF) of com-
pounds 1, 2, 4, 8, and 10. This material is available free of charge
via the Internet at http://pubs.acs.org.
IC062414K
4482 Inorganic Chemistry, Vol. 46, No. 11, 2007