A comparative study of the structures and reactivity of cyclometallated platinum compounds of N-benzylidenebenzylamines and cycloplatination of a primary amine

Article abstract of DOI:10.1039/b618128g

The reaction of cis-[PtCl₂(dmso)₂] with ligands 4-ClC₆H₄CHNCH₂C₆H₅ (1a) and 4-ClC₆H₄CHNCH₂(4-ClC₆H ₄) (1b) in the presence of sodium acetate and using either methanol or toluene as solvent produced the corresponding five-membered endo-metallacycles [PtCl{(4-ClC₆H₃)CHNCH₂C ₆H₅}{SOMe₂}] (2a) and [PtCl{(4-ClC ₆H₃)CHNCH₂(4′-ClC₆H ₄)}{SOMe₂}] (2b). An analogous reaction for ligands 2,6-Cl₂C₆H₃CHNCH₂C₆H ₅ (1c) and 2,6-Cl₂C₆H₃CHNCH ₂(4-ClC₆H₄) (1d) produced five-membered exo-metallacycles [PtCl{(2,6-Cl₂C₆H₃)CHNCH ₂C₆H₄}{SOMe₂}] (2c) and [PtCl{(2,6-Cl₂C₆H₃)CHNCH₂(4′- ClC₆H₃)}{SOMe₂}] (2d) when the reaction was carried out in methanol and seven-membered endo-platinacycles [PtCl{(MeC ₆H₃)ClC₆H₃CHNCH₂C ₆H₄}{SOMe₂}] (3c) and [PtCl{(MeC ₆H₃)ClC₆H₃CHNCH₂(4′ -ClC₆H₃)}{SOMe₂}] (3d) when toluene was used as a solvent. The reaction of 2,4,6-(CH₃)₃C ₆H₂CHNCH₂(4-ClC₆H₄) (1e) produced in both solvents an exo-platinacycle [PtCl{(2,4,6-(CH₃) ₃C₆H₂)CHNCH₂(4′-ClC ₆H₃)}{SO(CH₃)₂}] (2e). Cyclometallation of 4-chlorobenzylamine was also achieved to produce compound [PtCl{(4-ClC₆H₃)CH₂NH₂}{SOMe ₂}] (2g). The reactions of endo- and exo-metallacycles with phosphines evidenced the higher lability of the Pt-N bond in exo-metallacycles while a comparative analysis of the crystal structures points out a certain degree of aromaticity in the endo-metallacycle. The Royal Society of Chemistry.

Full text of DOI:10.1039/b618128g

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/dalton | Dalton Transactions
A comparative study of the structures and reactivity of cyclometallated
platinum compounds of N-benzylidenebenzylamines and cycloplatination
of a primary amine
Alejandro Capape´,a Margarita Crespo,*a Jaume Granell,a Merce` Font-Bard´ıab and Xavier Solansb
Received 12th December 2006, Accepted 13th February 2007
First published as an Advance Article on the web 23rd March 2007
DOI: 10.1039/b618128g
The reaction of cis-[PtCl2(dmso)2] with ligands 4-ClC6H4CHNCH2C6H5 (1a) and 4-ClC6H4-
CHNCH2(4-ClC6H4) (1b) in the presence of sodium acetate and using either methanol or toluene as
solvent produced the corresponding five-membered endo-metallacycles [PtCl{(4-ClC6H3)CHNCH2-
C6H5}{SOMe2}] (2a) and [PtCl{(4-ClC6H3)CHNCH2(4ꢀ-ClC6H4)}{SOMe2}] (2b). An analogous
reaction for ligands 2,6-Cl2C6H3CHNCH2C6H5 (1c) and 2,6-Cl2C6H3CHNCH2(4-ClC6H4) (1d)
produced five-membered exo-metallacycles [PtCl{(2,6-Cl2C6H3)CHNCH2C6H4}{SOMe2}] (2c) and
[PtCl{(2,6-Cl2C6H3)CHNCH2(4ꢀ-ClC6H3)}{SOMe2}] (2d) when the reaction was carried out in
methanol and seven-membered endo-platinacycles [PtCl{(MeC6H3)ClC6H3CHNCH2C6H4}{SOMe2}]
(3c) and [PtCl{(MeC6H3)ClC6H3CHNCH2(4ꢀ-ClC6H3)}{SOMe2}] (3d) when toluene was used as a
solvent. The reaction of 2,4,6-(CH3)3C6H2CHNCH2(4-ClC6H4) (1e) produced in both solvents an
exo-platinacycle [PtCl{(2,4,6-(CH3)3C6H2)CHNCH2(4ꢀ-ClC6H3)}{SO(CH3)2}] (2e). Cyclometallation
of 4-chlorobenzylamine was also achieved to produce compound [PtCl{(4-ClC6H3)CH2NH2}-
{SOMe2}] (2g). The reactions of endo- and exo-metallacycles with phosphines evidenced the higher
lability of the Pt–N bond in exo-metallacycles while a comparative analysis of the crystal structures
points out a certain degree of aromaticity in the endo-metallacycle.
tate [C,N] systems derived from imines,8 oximes,9 pyridines10 or
Introduction
even tertiary amines leading to either mono11 or dinuclear12 com-
Cyclometallation of N-donor ligands by platinum and palladium
has remained as one of the major topics in organometallic chem-
istry for nearly four decades.1 Although cyclometallated platinum
pounds. In all the reported examples leading to bidentate [C,N]
=
imines or oximes the obtained metallacycle contains the C N
functionality. In order to explore the synthetic ability of the plat-
group metal complexes containing nitrogen ligands have been
inum(II) sulfoxide complex in the preparation of exo-platinacycles,
extensively studied, the factors that control the regioselectivity
as well as to gain more insight into the factors responsible for the
of the process are not fully understood. Cyclometallation of N-
benzylidenebenzylamines could in principle produce two different
higher stability of endo- versus exo-metallacycles, the reactions of
cis-[PtCl2(dmso)2] with bifunctional N-benzylidenebenzylamines
five-membered metallacycles, one in which the cycle contains
of general formula RxC6H5−xCHNCH2(RyC6H5−y) was planned. In
the imine functionality (endo) and one in which it does not
particular, the crystallographic data should provide valuable infor-
(exo).2 The tendency to give endo-cycles is so strong that it
mation regarding the so-called endo effect, which is considered to
allows activation of an aliphatic C–H bond with formation of
play a major role in the regioselectivity of the cyclometallation
a six-membered palladacycle in preference to the activation of
reaction. A preliminary account of part of this work has been
already published.13 The present study is focused on two issues: (1)
an evaluation of the versatility of cis-[PtCl2(dmso)2] as metallating
agent in the synthesis of several types of platinacycles, (2) a
comparative analysis of the reactivity and structure of endo- versus
exo-platinacycles. Further work aimed at analyzing the extent
and mechanism of the formation of compounds 3 is currently
in progress.
an aromatic C–H bond with formation of a five-membered exo-
palladacycle.3 Aromaticity of the resulting metallacycle involving
=
=
the two conjugated bonds C C and C N and the filled palladium
d orbitals of appropriate symmetry has been proposed to explain
the greater stability of endo-cycles.4 Analogous results have been
obtained when the platinum compound [Pt2Me4(l-SMe2)2] was
used as metallation substrate,5 but activation of a C–H bond in
exo was not successful for this system.
Recently, cis-[PtCl2(dmso)2] has become an useful substrate for
direct cycloplatination, and numerous examples have been re-
ported including tridentate [C,N,X] (X = N6 or S7) as well as biden-
Results and discussion
Synthesis and characterization of cyclometallated compounds
aDepartament de Qu´ımica Inorga`nica, Universitat de Barcelona, Diag-
onal 647, 08028, Barcelona, Spain. E-mail: margarita.crespo@qi.ub.es;
Tel: +34934039132; Fax: +34934907725
The N-benzylidenebenzylamine ligands 1a–1e were prepared by
a condensation reaction of the corresponding amine with the
corresponding aldehyde.5 They were formed as single isomers
which are assumed to have the more stable E stereochemistry
bDepartament de Cristal·lografia, Mineralogia i Dipo`sits Minerals, Univer-
sitat de Barcelona, Mart´ı i Franque`s s/n, 08028, Barcelona, Spain
2030 | Dalton Trans., 2007, 2030–2039
This journal is
The Royal Society of Chemistry 2007
©

View Article Online
ClC6H4) (1d) and2,4,6-(CH3)3C6H2CHNCH2(4-ClC6H4) (1e) were
also tested. Ligands 1c and 1d contain chloro substituents in the
ortho positions of the benzal ring, although intramolecular C–
Cl bond activation for analogous ligands has been reported at
electron rich platinum(II) substrates,5 this process is not expected in
principle for an electrophilic substrate such as cis-[PtCl2(dmso)2],
and therefore formation of an exo-metallacycle would be forced.
Ligand 1e derives from mesitylaldehyde and activation of an
aliphatic C–H bond to yield a six-membered endo-metallacycle,
as reported for palladium systems3 could compete with formation
of a five-membered exo-metallacycle. Additionally, formation of
exo-metallacycles in which the imine bond is not included in the
metallacycle may lead to two different conformers with either E
Chart 1
=
about the C N bond. As shown in Chart 1, from the E form
both endo- and exo-cycles can be formed, while only exo-cycles
are possible for the Z form.
As reported in the literature,6b–d,8 the most widely used
conditions to prepare cyclometallated compounds using cis-
[PtCl2(dmso)2] as starting material are refluxing an equimolar
mixture of the platinum substrate and the required ligand in a
donor solvent such as methanol for long periods of time, in some
cases in the presence of an external base such as sodium acetate.
Initially, the reactions of imines 4-ClC6H4CHNCH2C6H5 (1a) and
4-ClC6H4CHNCH2(4-ClC6H4) (1b) were carried out using cis-
[PtCl2(dmso)2], the imine and Na(CH3CO2) in a 1 : 1 : 1 ratio and
heating the obtained mixture in refluxing methanol for 48 h. Under
these conditions, the formation of metallic platinum is observed.
In order to keep the reduction of platinum to a minimum the
temperature should be carefully controlled to avoid overheating
of the reaction mixture. Reaction times longer than 48 h should
also be avoided since decomposition increases with time. Work-
up of the reaction mixture includes filtration of metallic platinum
and insoluble residues, followed by crystallization of the desired
compounds 2a and 2b.
or Z arrangement around the C N bond.
=
The reactions of ligands 1c–e with cis-[PtCl2(dmso)2] in the
presence of Na(CH3CO2) in a 1 : 1 : 1 ratio were carried out
in refluxing methanol over 48 h and produced, in all cases, the
expected exo-metallacycles 2c–e although yields were extremely
low. Formation of large amounts of metallic platinum indicates
decomposition processes.
In order to improve the obtained yields, the reactions of 1c,
1d and 1e were also carried out using toluene–methanol mixtures
according to the method described above. For 1c and 1d, this
slight modification of the method gave striking differences in
the obtained compounds which were identified as compounds
3c and 3d, shown in Scheme 1. Compound 3d was crystallized
in dichloromethane–methanol from the crude product while 3c
was crystallized after purifying the crude product by column
chromatography (silica, ethyl acetate : hexane = 100 : 20). The new
compounds arise from a novel process leading to seven-membered
platinacycles via insertion of a solvent toluene molecule.13
Analogous seven-membered metallacycles have been ob-
tained in the reactions of cis-[PtPh2(SMe)2] with imines 2-
Following a method indicated in the literature8 a slight modifica-
tion was introduced in order to obtain higher yields. The reactions
were carried out under nitrogen using dry toluene as solvent, and
only a small amount of methanol was used to dissolve the sodium
acetate. The reaction mixture was heated at 90 ◦C for 48 h and
smaller amounts of metallic platinum were formed despite the
higher reaction temperature. Compounds 2a and 2b were obtained
in moderate yield and characterized by elemental analyses, FAB
mass spectra, IR and NMR spectroscopies and 2b was also
characterized crystallographically. As expected from the higher
stability of endo- versus exo-metallacycles, for both compounds
activation of the C–H bond took place at the benzal ring leading
to five-membered endo-metallacycles, as shown in Scheme 1. In
=
=
BrC6H4CH NCH2Ph or RCH NCH2CH2NMe2 (R = 2,6-
C6Cl2H3; 2-ClC6H4)15 as a result of formal insertion of a phenyl
ligand in the cyclometallated Pt–C bond, previously formed via C–
Br or C–Cl bond activation, and elimination of a C6H6 molecule.
The process here reported is more complex since it requires
both intramolecular C–Cl activation of the coordinated imine
to produce a [C,N]-metallacycle and intermolecular C–H bond
activation of the toluene molecule16 presumably to form a r-bond
Pt–Caryl with elimination of HCl, as previous steps to undergo the
formal insertion of toluene in the metallacycle with elimination
of another HCl molecule. Both the presence of sodium acetate
which facilitates HCl elimination and the lability of SOMe29 in the
plausible platinum(IV) intermediates, arising from intramolecular
activation of C–Cl bonds, enable this unprecedented process at
platinum. As discussed below, NMR data for compounds 3c
and 3d indicate the presence of two isomers both with an E
conformation of the imine.
1
the H NMR spectra, the imine and the methylene protons are
coupled to platinum (J(H–Pt) ca.114–117 Hz and J(H–Pt) ca.13–
20 Hz, respectively), as well as the aromatic hydrogen adjacent
to the metallation site (J(H–Pt) ca. 48 Hz) which confirms the
formation of a bidentate [C,N] chelate system. Both methyl groups
of the dimethylsulfoxide are equivalent and coupled to platinum.
2D-NOESY NMR spectra indicate that the dimethylsulfoxide is
close to the metallated ring, that is trans to the nitrogen atom.
195Pt NMR was also taken for 2b, and the chemical shift is in the
expected range for platinum(II) coordinated to a [C,N,S,Cl] donor
atoms set.14 FAB mass spectra are consistent with the proposed
formulae.
For 1e, a ligand containing two methyl groups in the ortho
positions of the benzal ring, no significant changes were observed
when the reaction was carried out in toluene–methanol mixtures.
This fact suggests that intramolecular C–Cl bond activation and
concomitant platinum(II) to platinum(IV) formal oxidation could
play a decisive role in the toluene insertion process described above
for 1c and 1d.
With the aim of obtaining cycloplatinated compounds contain-
ing an exo-metallacycle, the reactions of cis-[PtCl2(dmso)2] with
ligands 2,6-Cl2C6H3CHNCH2C6H5 (1c), 2,6-Cl2C6H3CHNCH2(4-
Compound 2e arising from C–H activation in the benzylamine
ring was obtained with a low yield which is possibly associated
This journal is
The Royal Society of Chemistry 2007
Dalton Trans., 2007, 2030–2039 | 2031
©

View Article Online
Scheme 1
with the low stability of exo-metallacycles. A Z conformation
around the imine bond is obtained from both synthetic strategies,
a result that can be related to the bulk of the mesityl group
which should favor a conformation in which the aryl group is
pointing away from the platinum centre. Despite the low yield
obtained for 2e, formation of a six-membered endo-metallacycle
arising from activation of an aliphatic C–H bond was not detected,
which indicates that for this system activation of an aromatic C–H
bond leading to a five-membered exo-metallacycle is preferred.
In order to attempt activation of an aliphatic C–H bond at
platinum, an analogous reaction was studied for the imine 2,4,6-
(CH3)3C6H2CHN(4-OMeC6H4) (1f) for which formation of a four-
membered exo-metallacycle is precluded. However, work-up of the
reaction mixture indicated only the presence of metallic platinum
and free ligand.
In the 1H NMR spectra of these compounds, the imine resonance
is downfield shifted and display a lower J(H–Pt) value (ca.
50 Hz) compared to the data for endo-cycles which suggests a Z
=
conformation around the C N bond. The methylene hydrogens
and the aromatic hydrogen adjacent to the metallation site in the
benzylamine ring are also coupled to platinum (J(H–Pt) ca. 32–
33 and 44–52 Hz, respectively) which confirms the formation
of a bidentate [C,N] chelate system. Consistently, 5 crossing
1
peaks are observed in the aromatic region of the { H-13C}-
heterocorrelation NMR spectrum taken for 2d. Both methyl
groups of the dimethylsulfoxide are equivalent and coupled to
platinum.
1
In the H NMR spectra of compounds 3c and 3d, the imine
hydrogen is coupled to platinum and both the methylene hydrogen
atoms and the methyl groups of the dimethylsulfoxide ligand
appear as non-equivalent, as a result of the lack of planarity
of the seven-membered metallacycle. The presence of the methyl
substituent in the tolyl group is confirmed by the corresponding
Compounds 2c, 2d, 3c, 3d and 2e were characterized by elemen-
tal analyses, FAB mass spectra, IR and NMR spectroscopies and
2e and 3c were also characterized crystallographically.
The proposed structures are shown in Scheme 1 and, as
expected, compounds 2c, 2d and 2e contain an exo-metallacycle.
1
signal in the H NMR spectra. In addition to the set of signals
described above, resonances due to a minor isomer (abundance
2032 | Dalton Trans., 2007, 2030–2039
This journal is
The Royal Society of Chemistry 2007
©

View Article Online
ca. 20% (3c) and 30% (3d)) with the same spectral pattern were
observed. Studies concerning activation of aromatic C–H bonds of
toluene16 indicate a selectivity order C–H (meta) > C–H (para) >
C–H (ortho); therefore, the major isomer could be assigned to that
with a meta arrangement between the Pt–C bond and the methyl
substituent (as in the crystal structure of 3c) and the minor isomer
could correspond to the para isomer. A singlet resonance coupled
to platinum at 6.63 (3c) or 6.56 ppm (3d) corresponding to the
major isomer is assigned to the aromatic proton adjacent to the
Pt–C bond.
The successful formation of exo-cyclometallated compounds
=
such as 2c–e indicates that the presence of a C N bond included
in the platinacycle is not essential for metallacycle formation.
Therefore, and in order to extend the reported synthetic strategy to
the cyclometallation of other nitrogen ligands, the reaction with
a primary amine was also tested. The reaction was carried out
using cis-[PtCl2(dmso)2], 4-chlorobenzylamine and Na(CH3CO2)
in a 1 : 1 : 1 ratio in toluene–methanol mixtures and heating the
obtained mixture at 80 ◦C for 5 days. Under these conditions,
cycloplatination of the primary amine was achieved leading to
compound 2g shown in Scheme 1. Compound 2g, obtained in
low yield, was characterized by 1H NMR spectroscopy, elemental
analyses and mass spectra. The amino group, which appears as a
broad signal, the methylene protons and the aromatic hydrogen
adjacent to the metallated position are coupled to platinum, thus
confirming the formation of a [C,N] platinacycle. Both methyl
groups of the dimethylsulfoxide are equivalent and coupled to
platinum as observed for analogous compounds 2a–e derived from
imines.
Fig. 2 Molecular structure of compound 2e with thermal ellipsoids at
50% probability.
It is interesting to point out that, in spite of initial difficulties17
well established methods18 have now been developed for the
cyclopalladation of primary amines, however, the preparation of
platinum analogues still remains uncommon.19
Crystal structures of 2b, 2e and 3c
Fig. 3 Molecular structure of compound 3 with thermal ellipsoids at 50%
probability.
Crystals of compounds 2b, 2e and 3c were grown from acetone (2b
and 2e) or methanol (3c). The crystals of 2e were of poor quality
but good enough to allow for structure resolution. The crystal
structures are composed of discrete molecules separated by van
der Waals distances. The structures are shown in Fig. 1–3 and
selected molecular dimensions are listed in Table 1. The molecular
structures confirm the geometries predicted from spectroscopic
data.
Compounds 2b and 2e consist of a fused [5, 6] bicyclical system
containing a five-membered metallacycle and the ortho-metallated
phenyl group. The molecular structures provide decisive evidence
of the fact that in 2b the imine bond is included in the metallacycle
leading to an endo system, while in 2e an exo structure is adopted
with a Z conformation around the imine bond. The molecular
structure of compound 3c was previously reported13 and contains
a seven-membered non-planar endo-metallacycle in which the
two phenyl rings of the metallated biphenyl are tilted 57.6(3)◦
from each other. In all cases, the square-planar coordination
environment of the metal is completed by a dimethylsulfoxide
ligand coordinated through the sulfur atom trans to the imine
nitrogen and a chloro ligand.
As shown in Table 1, bond lengths and angles are well within
the range of values obtained for analogous compounds.6,9,15,20 Most
bond angles at platinum are close to the ideal value of 90◦, and
the smallest angles correspond to the metallacycle (80.9(3)◦ (2b)
79.8(7)◦ (2e), 87.3(2)◦ (3c)).
The data obtained for 2b and 2e allow for a comparison between
these two types (endo or exo) of five-membered metallacycles. The
Fig. 1 Molecular structure of compound 2b with thermal ellipsoids at
50% probability.
This journal is
The Royal Society of Chemistry 2007
Dalton Trans., 2007, 2030–2039 | 2033
©

View Article Online
◦
˚
Table 1 Selected bond lengths (A) and angles ( ) with estimated standard deviations
2b
2e
3c
Pt–N
Pt–C(3)
Pt–S
Pt–Cl(1)
N–C(9)
C(3)–C(8)
C(8)–C(9)
2.066(6)
1.990(8)
2.200(2)
2.421(4)
1.315(15)
1.433(16)
1.464(19)
Pt–N
Pt–C(17)
Pt–S
1.98(2)
2.029(12)
2.209(6)
2.405(5)
1.23(2)
1.48(2)
1.67(2)
1.39(0)
Pt–N
Pt–C(16)
Pt–S
Pt–Cl(2)
N–C(8)
C(8)–C(9)
C(9)–C(14)
C(14)–C(15)
C(15)–C(16)
N–Pt–C(16)
C(16)–Pt–S
N–Pt–Cl(2)
S–Pt–Cl(2)
C(8)–N–Pt
N–C(8)–C(9)
C(8)–C(9)–C(14)
C(9)–C(14)–C(15)
C(16)–C(15)–C(14)
C(15)–C(16)–Pt
2.030(4)
2.082(7)
2.2092(14)
2.3978(19)
1.270(6)
1.478(7)
1.427(7)
1.447(7)
1.395(8)
87.3(2)
88.21(15)
90.78(14)
93.79(5)
123.3(4)
114.0(3)
125.7(5)
118.5(5)
128.2(6)
115.9(4)
Pt–Cl
N–C(1)
N–C(11)
C(11)–C(12)
C(12)–C(17)
C(3)–Pt–N
C(3)–Pt–S
N–Pt–Cl(1)
S–Pt–Cl(1)
C(9)–N–Pt
N–C(9)–C(8)
C(3)–C(8)–C(9)
C(8)–C(3)–Pt
80.9(3)
99.6(3)
91.2(2)
88.21(10)
114.9(7)
115.9(10)
114.2(11)
113.7(8)
N–Pt–C(17)
C(17)–Pt–S
N–Pt–Cl
79.8(7)
97.8(6)
91.5(5)
S–Pt–Cl
90.9(2)
C(12)–C(17)–Pt
C(17)–C(12)–C(11)
N–C(11)–C(12)
C(11)–N–Pt
113.2(12)
116.2(15)
98.3(15)
116.2(15)
sum of internal angles of the five-membered metallacycles are
539.6◦ (2b) and 523.7◦ (2e), which suggest a planar arrangement
for the endo-metallacycle in 2b (angle close to 540◦) and a deviation
from planarity for the exo-metallacycle in 2e.21 The dihedral
angles between the mean planes of the metallacycle and the
coordination plane are 11.09◦ (2b) and 25.81◦ (2e). A certain
degree of aromaticity in the endo-metallacycle involving the imine
phosphine in the coordination sphere of platinum should produce
the displacement of the more labile dimethylsulfoxide ligand,
while the reaction with an excess of a monodentate phosphine
or with bidentate phosphines may produce either cleavage of the
metallacycle leading to monodentate [C] systems or extrusion of
the chloride ligand giving an ionic derivative.
The reactions of triphenylphosphine with cyclometallated plat-
inum compounds 2a, 2b, 2d and 2e were studied and the resulting
compounds are depicted in Schemes 2 and 3. In compounds
4a, 4b, and 4d the imine behaves as a [C,N] bidentate ligand
and the square-planar coordination of platinum (II) is completed
with a phosphine and a chloro ligand. The trans arrangement of
the triphenylphosphine and the imine is expected according to
the transphobia effect,25 and experimental evidence is obtained
from the value of J(P–Pt) in the range 4050–4300 Hz and from
the observed coupling of the imine to the phosphorus in a
trans position. The coupling of the imine proton to platinum is
considerably reduced for the exo-derivative when compared to the
endo-analogues as a result of the mutual Z arrangement of the
=
bond, one C C bond of the phenyl ring and a filled d orbital of the
platinum as previously suggested for five-membered metallacycles4
=
is consistent with the greater C N bond length observed for
˚
˚
2b (1.315(15) A) than for 2e (1.23(2) A). Since no significant
=
differences in C N bond lengths have been observed for exo
and endo-cyclic five-membered cyclopalladated derivatives,2,22 we
might suggest that the more external 5d orbital of platinum is
more likely to be involved in aromaticity than the 4d orbital of
palladium. However, due to the poor resolution of 2e and the
different stereo-electronic features of imines 1b and 1e, the results
obtained are not conclusive.
In both compounds an intramolecular interaction C–H · · · O
=
between the oxygen atom of the dmso and one aryl carbon is
proton and the platinum around the C N bond. According to the
observed (d(C · · · O) = 2.993(14) A (2b) and 2.880(19) A (2e));
these interactions produce the equivalence of both methyl groups
as previously reported for analogous compounds.9 In 2e, the bulky
mesityl group is pointing away from the platinum centre, thus
minimising the steric crowding, and the imine proton is involved
in an interaction with the chloro ligand C–H · · · Cl (d(C · · · Cl) =
1H and 31P NMR spectra, the attempted synthesis of compound 4e
˚
˚
˚
˚
3.20 (2) A). In relation to intermolecular interactions, a ca. 3.7 A
distance was observed between the aromatic rings of 2b. That
might suggest p–p interactions within the aromatic moieties, as
reported previously for platinum cyclometallated compounds.23
Reactions with phosphines
The tendency of cyclometallated palladium and platinum com-
pounds to cleave the metal–nitrogen bond upon reaction with
phosphines has been taken as a metallacycle stability criterion.2,24
Therefore, a comparative analysis of the analogous endo- and
exo-platinacycles was planned. Coordination of a monodentate
Scheme 2
2034 | Dalton Trans., 2007, 2030–2039
This journal is
The Royal Society of Chemistry 2007
©

View Article Online
metallacycle or compound 2g with a metallated amine have been
prepared following analogous strategies. Compounds 3c and 3d
are obtained in a novel process involving intermolecular C–H
bond activation of a toluene molecule13 and cycloplatination of a
primary amine is still rather uncommon. Therefore the synthetic
procedure developed here might be considered a method with
wide scope for the preparation of several classes of interesting
cycloplatinated compounds.
Experimental
General
The solvents were purified and distilled by standard methods.
Methanol (dry, max. 0.005% H2O) was purchased from Panreac.
Mass spectra were performed by the Servei d’Espectrometria
de Masses de la Universitat de Barcelona. NMR spectra were
performed at the Unitat de NMR d’Alt Camp de la Universitat
de Barcelona. Microanalyses were performed by the Servei de
Recursos Cient´ıfics i Te`cnics de la Universitat Rovira i Virgili de
Tarragona.
Scheme 3
using the same procedure as above took place along with formation
of free ligand and [PtCl2(PPh3)2]. Attempts to obtain 4e in a pure
form were unsuccessful due to the low stability of this compound.
While 4a and 4b did not react further with triphenylphosphine,
the reaction of 4d with one equivalent of PPh3—or the reaction
of 2d with a 2 : 1 excess of PPh3—produced compound 5d. In
this compound the imine behaves as a monodentate [C] ligand,
and the coordination of platinum is completed with a chloro and
two mutually trans PPh3 ligands, as evidenced by the absence
of platinum satellites for the imine resonance and the observed
J(P–Pt) of 3035 Hz. The reaction of 2e with a twofold excess
of phosphine yielded [PtCl2(PPh3)2] and free ligand as the only
identified products. Such processes as cleavage of the metallacycle
(2d) or complete decoordination of the nitrogen ligand (2e) upon
reaction with an excess of triphenylphosphine point to a higher
lability of the Pt–N bond for exo- than for endo-platinacycles.
In order to study the stability of endo-platinacycles, the reactions
of 2a and 2b with bidentate 1,2-bis(diphenylphosphine)ethane
(dppe) were also carried out. In the resulting compounds 6a
and 6b both the imine and the diphosphine behave as bidentate
ligands leading to rather unstable ionic compounds which were
characterized spectroscopically. The 31P NMR spectra of com-
pounds 6 show two sets of resonances due to two non-equivalent
phosphorus atoms, both coupled to platinum. The mass spectra
are also consistent with the proposed ionic formulae, showing
in each case the peak assigned to the corresponding cation. The
formation of compounds 6a and 6b clearly shows the high stability
of the endo-metallacycles, which are resistant to cleavage even
when reacted with chelating diphosphine.
IR spectra were recorded using Nicolet 520, Thermo-Nicolet
5700 and Thermo-Nicolet Avatar 330 spectrophotometers, using
KBr pellets for solid samples and NaCl support for liquid samples.
FAB mass spectra were carried out with VG-Quattro (with a
3-nitrobenzyl alcohol matrix) and MALDI mass spectra using a
1
Voyager DE–RP (with a dithranol matrix) spectrometer. H, 31P
and 195Pt NMR spectra were recorded by using Varian Gemini-200
(1H, 200 MHz), Bruker DRX-250 (1H, 250 MHz, 31P, 101 MHz,
195Pt, 54 MHz), Mercury-400 (1H, 400 MHz, 1H-1H NOESY,
1
1H-13C gHSQC) and Bruker DMX-500 (1H, 500 MHz, H-1H
COSY) spectrometers, and referenced to SiMe4 (1H), P(OMe)3 in
(CD3)2CO (31P) and H2PtCl6 in D2O (195Pt). d values are given in
ppm and J values in Hz. Abbreviations used: s = singlet, d =
doublet, t = triplet, m = multiplet, b = broad, NMR labelling as
shown in Schemes 1–3.
Preparation of the compounds
[PtCl2(dmso)2]26 and ligands 1a-1f5 were prepared as reported
elsewhere.
Preparation of cyclometallated compounds
[PtCl{(4-ClC6H3)CHNCH2C6H5}{SOMe2}] (2a). 2a was ob-
tained from 0.187 g (0.44 mmol) of cis-[PtCl2(dmso)2], 0.102 g
(0.44 mmol) of imine 1a and 36 mg (0.44 mmol) of sodium acetate
(in 1 mL methanol) which were allowed to react in dry toluene
(30 mL) at 90 ◦C for 48 h. The reaction mixture was filtered,
the solvent was removed in a rotary evaporator and the residue
was recrystallized in dichloromethane–methanol, yielding a deep
yellow solid which was isolated by filtration in vacuo.. Yield 125 mg
Conclusions
The preparation of five-membered endo and exo cyclometallated
platinum compounds has been achieved using cis-[PtCl2(dmso)2]
as metallating agent and allows for a comparative study of their
structures and reactivity. The crystal structure of 2b indicates a
certain degree of aromaticity of the planar endo-platinacycles,
which are reluctant to cleave upon reaction with mono or
bidentate phosphines. In contrast, the Pt–N bond of the exo-
metallacycles is more labile and easily cleaved upon reaction with
triphenylphosphine. In addition, other types of cycloplatinated
compounds such as 3c and 3d containing a seven-membered
−1
1
=
(53%). IR: m(CH N) = 1608.5 cm . H NMR (250 MHz, CDCl3):
d = 8.25 [d, 4J(H–H) = 1.8, 3J(Pt–H) = 48.5, 1 H, H5], 7.79 [s, 1
H, 3J(Pt–H) = 116.8, 1 H, Hc], 7.50–7.30 [m, 5 H, H2ꢀ,3 ,4 ], 7.15 [d,
3J(H–H) = 8.0, 1 H, H2], 7.08 [dd, 3J(H–H) = 8.0, 4J(H–H) = 1.8,
H3], 5.18 [s, 3J(Pt–H) = 20.0, 2 H, Hb], 3.57 [s, 3J(Pt–H) = 23.78,
6 H, Ha]. FAB-MS, m/z: 502.3 [M–Cl]+, 461.2 [M–Cl–dmso]+,
423.28 [M–2Cl–dmso]+. Anal. Found (calc. for C16H17Cl2NOPtS):
C: 35.4 (35.76); H: 3.0 (3.19); N: 2.7 (2.60); S: 5.7 (5.97).
ꢀ
ꢀ
This journal is
The Royal Society of Chemistry 2007
Dalton Trans., 2007, 2030–2039 | 2035
©

View Article Online
[PtCl{(4-ClC6H3)CHNCH2(4ꢀ-ClC6H4)}{SOMe2}] (2b). 2b
was obtained from 0.160 g (0.38 mmol) of cis-[PtCl2(dmso)2],
0.100 g (0.38 mmol) of imine 1b and 31 mg (0.38 mmol) of sodium
acetate, using the procedure reported for 2a. Yield 119 mg (55%).
sodium acetate (dissolved in 1 mL methanol) which were allowed
to react in dry toluene (30 ml) at 90 ◦C for 48 h. The mixture was
filtered, the solvent was removed under vacuum and the residue
was eluted in a silica column chromatography using ethyl acetate
: hexane = 100 : 20 as eluent. The first fractions collected contain
aldehyde and 2c; 3c was obtained from a further fraction and
crystallized in dichloromethane–methanol. Yield 54 mg (15%). 1H
NMR (250 MHz, CDCl3): major isomer d = 8.53 [s, 3J(Pt–H) =
−1
1
=
IR: m(CH N) = 1624.6 cm . H NMR (250 MHz, CDCl3): d =
8.24 [d, 4J(H–H) = 2.0, 3J(Pt–H) = 48.3, 1 H, H5], 7.86 [s, 3J(Pt–
ꢀ
3
H) = 114.0, 1 H, Hc], 7.36 [d, J(H–H) = 8.6, 2 H, H2 ], 7.30 [d,
3J(H–H) = 8.6, 2 H, H3ꢀ ], 7.19 [s, 3J(H–H) = 8.0, 1 H, H2], 7.11 [dd,
3J(H–H) = 8.0, 4J(H–H) = 1.7, 1 H, H3], 5.15 [s, 3J(Pt–H) = 13.0,
2 H, Hb], 3.55 [s, 4J(Pt–H) = 24.0, 6 H, Ha]. 195Pt NMR (54 MHz,
CDCl3): d = −3833.96 [s]. FAB–MS, m/z: 536.3 [M–Cl]+, 459.3
[M–Cl–dmso]+. Anal. Found (calc. for C16H16Cl3NOPtS): C: 34.0
(33.61); H: 3.2 (2.82); N: 2.4 (2.45); S: 5.6 (5.61).
3
112.8, 1H, Hd], 7.47–7.31 [m, 4H], 7.27 [d, J(H–H) = 7.2, 2H],
3
3
7.18 [d, J(H–H) = 7.2, 2H], 6.85 [d, J(H–H) = 7.8, 1H], 6.76
[d, J(H–H) = 7.8, 1H], 6.63 [s, J(Pt–H) = 52.4, 1H, H5], 5.43
3
3
[d, J(H–H) = 13.2, 1H, Hc], 5.04 [d, J(H–H) = 13.2, 1H, Hc],
2
2
3
3
3.30 [s, J(Pt–H) = 20.4, 3H, Hb], 2.83 [s, J(Pt–H) = 31.2, 3H,
Hb], 2.14 [s, 3H, Mea], minor isomer d = 8.47 [s, 3J(Pt–H) = 109.6,
1H, Hd], 6.73 [dd, 3J(H–H) = 8.0, 4J(H–H) = 2.0, 1H], 5.35 [dd,
[PtCl{(2,6-Cl2C6H3)CHNCH2C6H4}{SOMe2}] (2c). 2c was
obtained from 0.215 g (0.51 mmol) of cis-[PtCl2(dmso)2], 0.134 g
(0.51 mmol) of imine 1c and 42 mg (0.51 mmol) of sodium acetate
which were allowed to react in refluxing methanol (30 ml) for
48 h. The reaction mixture was filtered, the solvent was removed
in a rotary evaporator and the residue was recrystallized in
dichloromethane–methanol, yielding a solid which was isolated
2J(H–H) = 14.2, J(H–H) = 2.0, 1H, Hc], 5.15 [d, J(H–H) =
14.2, 1H, Hc], 3.31 [s, 3H, Hb], 2.86 [s, 3H, Hb], 2.24 [s, 3H, Mea].
ES-MS, m/z: 592 [M–Cl]+, 514 [M–Cl–dmso]+. Anal. Found (calc.
for C23H23Cl2NOPtS): C: 43.7 (44.02); H: 4.0 (3.69); N: 2.3 (2.23);
S: 5.0 (5.11)
4
2
1
by filtration in vacuo.. Yield 44 mg (15%). H NMR (250 MHz,
[PtCl{(MeC6H3)ClC6H3CHNCH2(4ꢀ-ClC6H3)}{SOMe2}] (3d).
3d was obtained from 0.142 g (0.34 mmol) of cis-[PtCl2(dmso)2],
0.100 g (0.34 mmol) of imine 1d and 28 mg (0.34 mmol) of
sodium acetate (dissolved in 1 mL methanol) which were allowed
to react in dry toluene (30 ml) at 90 ◦C for 48 h. The mixture was
filtered, the solvent was removed under vacuum and the residue
was recrystallized in dichloromethane–methanol, yielding a light
yellow solid which was isolated by filtration in vacuo.. Yield 67.5 mg
4
3
CDCl3): d = 9.64 [t, J(H–H) = 2.4, J(Pt–H) = 51.5, 1H, Hc],
8.14 [m, 3J (Pt–H) = 44.0, 1H, H5], 7.44 [m, 3H], 7.09 [m, 2H], 6.97
[m, 1H], 4.70 [d, 4J(H–H) = 2.4, 2H, 3J(Pt–H) = 32.6, Hb], 3.63 [s,
3J(Pt–H) = 24.2, 6H, Ha]. FAB-MS, m/z:686.85[M+ Cl+ dmso]+,
650.90 [M + dmso]+. Anal. Found (calc. for C16H16Cl3NOPtS): C:
34.0 (33.61); H: 2.9 (2.82); N: 2.5 (2.45); S: 5.9 (5.61).
[PtCl{(2,6-Cl2C6H3)CHNCH2(4ꢀ-ClC6H3)}{SOMe2}]
(2d).
1
2d was obtained as a white solid from 0.218 g (0.52 mmol) of
cis-[PtCl2(dmso)2], 0.150 g (0.52 mmol) of imine 1d and 42 mg
(0.52 mmol) of sodium acetate using the procedure reported for
2c. Yield 57 mg (18%). 1H NMR (250 MHz, CDCl3): d = 9.59 [t,
(30%). H NMR (250 MHz, CDCl3): major isomer d = 8.59 [s,
3J(Pt–H) = 116.0, 1H, Hd], 7.46–7.34 [m, 3H], 7.24 [d, 3J(H–H) =
8.0, 2H], 7.12 [d, 3J(H–H) = 8.0, 2H], 6.84 [d, 3J(H–H) = 7.6, 1H],
6.77 [d, 3J(H–H) = 7.0, 1H], 6.56 [s, 3J(Pt–H) = 48.0, 1H, H5], 5.48
4J(H–H) = 2.2, J(Pt–H) = 50.0, 1H, Hc], 8.15 [d, J(H–H) =
[dd, J(H–H) = 13.0, J(H–H) = 1.6, 1H, Hc], 4.90 [d, J(H–H)
3
4
2
4
2
3
3
2.1, 3J(Pt–H) = 51.8, 1H, H5], 7.5–7.3 [m, 3H], 7.07 [dd, 3J(H–H)
= 13.0, J(Pt–H) = 50.0, 1H, Hc], 3.29 [s, J(Pt–H) = 21.6, 3H,
= 8.0, J(H–H) = 2.1, 1H], 6.88 [d, J(H–H) = 8.0, 1H], 4.66
Hb], 2.82 [s, J(Pt–H) = 30.0, 3H, Hb], 2.17 [s, 3H, Mea], minor
4
3
3
[d, J(H–H) = 2.2, J(Pt–H) = 32.8, 2H, Hb], 3.63 [s, J(Pt–H)
= 24.5, 6H, Ha]. 195Pt NMR (54 MHz, CDCl3): d = −3584.54.
FAB–MS, m/z: 607.05 [M+], 570.03 [M–Cl]+. Anal. Found (calc.
for C16H15Cl4NOPtS): C: 32.1 (31.70); H: 2.2 (2.49); N: 2.4 (2.31);
S: 4.8 (5.29).
isomer d = 8.52 [s, 3J(Pt–H) = 104.0, 1H, Hd], 7.24 [d, 3J(H–H) =
8.0, 2H], 7.13 [d, 3J(H–H) = 8.0, 2H], 5.40 [dd, 2J(H–H) = 13.6,
4J(H–H) = 1.7, 1H, Hc], 5.03 [d, 2J(H–H) = 14.2, 1H, Hc], 3.30 [s,
3H, Hb], 2.85 [s, 3J(Pt–H) = 30.0, 3H, Hb], 2.24 [s, 3H, Mea]. 195Pt
NMR (54 MHz, CDCl3): d = −3802.06 (major isomer). FAB-MS,
m/z: 626 [M–Cl]+, 548 [M–Cl–dmso]+, 510 [M–2Cl–dmso]+. Anal.
Found (calc. for C23H22Cl3NOPtS): C: 42.0 (41.73); H: 3.2 (3.35);
N: 2.1 (2.12); S: 5.0 (4.84).
4
3
3
[PtCl{(2,4,6-(CH3)3C6H2)CHNCH2(4ꢀ-ClC6H3)}{SO(CH3)2}]
(2e). 2e was obtained as a pale brown solid from 0.160 g
(0.38 mmol) of [PtCl2(dmso)2], 0.100 g (0. 38 mmol) of imine
1e and 0.031 g (0.38 mmol) of sodium acetate using either the
procedure reported for 2a or for 2c. Yield 33 mg (15%). IR:
[PtCl{(4-ClC6H3)CH2NH2}{SOMe2}] (2g). 2g was obtained
from 0.273
g (0.65 mmol) of cis-[PtCl2(dmso)2], 0.092 g
−1
1
=
m(CH N) = 1634.9 cm . H NMR (250 MHz, CDCl3): d = 9.61
(0.65 mmol) of 4-chlorobenzylamine and 53 mg (0.65 mmol)
of sodium acetate—dissolved in 1 mL of methanol—which were
allowed to react in toluene (30 ml) at 80 ◦C for 5 days. The reaction
mixture was filtered and the solvent was removed in a rotary
evaporator. The residue was recrystallized in dichloromethane–
methanol, yielding a solid which was isolated by filtration in
[s, J(Pt–H) = 52.7, 1H, Hc], 8.13 [d, J(H–H) = 1.7, J(Pt–H)
3
4
3
= 51.4, 1H, H5], 7.04 [dd, J(H–H) = 8.0, J(H–H) = 1.7, 1H,
3
4
ꢀ
ꢀ
H3], 6.93 [s, 2H, H3 ,5 ], 6.85 [d, J(H–H) = 8.0, 1H, H2], 4.50
3
[s, J(Pt–H) = 33.4, 2H, Hb], 3.61 [s, J(Pt–H) = 23.4, 6H, Ha],
3
3
2.33 [s, 3H, H4ꢀ ], 2.17 [s, 6H, H2ꢀ,6 ]. FAB–MS, m/z: 578.93 [M]+,
ꢀ
543.95 [M–Cl]+, 462.95 [M–Cl–dmso]+. Anal. Found (calc. for
C19H23Cl2NOPtS): C: 39.0 (39.38); H: 4.2 (4.00); N: 2.4 (2.42); S:
6.5 (5.53).
1
vacuo.. Yield 29 mg (10%). H NMR (250 MHz, CDCl3): d =
7.91[d, 4J(H–H) = 2.0, 3J(Pt–H) = 51.7, 1H, H5], 7.00 [dd, 3J(H–
4
3
H) = 7.5, J(H–H) = 2.0, 1H, H3], 6.90 [d, J(H–H) = 7.5, 1H,
3
3
[PtCl{(MeC6H3)ClC6H3CHNCH2C6H4}{SOMe2}] (3c). 3c
was obtained from 0.243 g (0.57 mmol) of cis-[PtCl2(dmso)2],
0.152 g (0.57 mmol) of imine 1c and 47 mg (0.57 mmol) of
H2], 4.66 [s, br, J(Pt–H) = 64.2, 2H, Hc], 4.14 [t, J(H–H) =
6.0, 3J(Pt–H) = 41.8, 2H, Hb], 3.49 [s, 3J(Pt–H) = 24.0, 6H, Ha].
MALDI-MS, m/z: 450.3 [M]+, 414.2 [M–Cl]+. Anal. Found (calc.
2036 | Dalton Trans., 2007, 2030–2039
This journal is
The Royal Society of Chemistry 2007
©

View Article Online
for C9H13Cl2NOPtS·2CH2Cl2): C: 20.9 (21.33); H: 2.4 (2.76); N:
compound 2d and 0.010 g (0.038 mmol) of triphenylphosphine
using the procedure reported for 4a. Yield 10 mg (47%). 1H NMR
(400 MHz, CDCl3): d = 7.87 [s, 1H, Ha], 7.69–7.64 [m, 2H], 7.58–
7.23 [m, 31 H], 6.64 [d, J(H–H) = 2.0, 1H], 6.48 [d, J(H–H) = 8.4,
1H], 6.39 [dd, J(H–H) = 8.4, 2.0, 1H], 4.73 [s, 2H, Hb]. 31P NMR
(101 MHz, CDCl3): d = 22.66 [s, 1J(P–Pt) = 3035.0].
2.4 (2.26); S: 5.9 (5.17).
Preparation of phosphine derivatives
[PtCl{(4-ClC6H3)CHNCH2C6H5}PPh3] (4a). 4a was ob-
tained from 0.030 g (0.056 mmol) of compound 2a and 0.014 g
(0.053 mmol) of triphenylphosphine which were allowed to
react in acetone at room temperature for 2 h. The solvent was
removed in a rotary evaporator and the residue was treated
with dichloromethane–methanol, yielding a bright yellow solid
[Pt{(4-ClC6H3)CHNCH2C6H5}Ph2P(CH2)2PPh2]Cl (6a). 6a
was obtained from 0.050 g (0.093 mmol) of compound 2a and
0.037 g (0.09 mmol) of bis(diphenylphosphino)ethane (dppe)
which were allowed to react in acetone at room temperature for
4 h. The solvent was removed in a rotary evaporator, yielding a
=
which was dried in vacuo.. Yield 30 mg (75%). IR: m(CH N) =
1620.2 cm−1. 1H NMR (400 MHz, CDCl3): d = 8.03 [d, 4J(H–P) =
8.8, 3J(Pt–H) = 92.0, 1H, Ha], 7.74 [d, 3J(H–H) = 7.2, 3J(P–H) =
−1
1
=
yellow oil. Yield 58 mg (75%). IR: m(CH N) = 1681.6 cm . H
4
3
NMR (400 MHz, CDCl3): d = 8.39 [d, J(H–P) = 9.0, J(Pt–H)
ꢀ
ꢀ ꢀ
12.0, 4J(H–H) = 1.2, 6H, Hc], 7.5–7.3 [m, 14H, Hd,e,2 ,3 ,4 ], 7.07 [d,
3J(H–H) = 8.0, 1H, H2], 6.84 [dd, 3J(H–H) = 8.0, 4J(H–H) = 1.8,
1H, H3], 6.39 [t, 4J(H–H) = 1.8, 3J(Pt–H) = 55.0, 1H, H5], 5.35 [s,
b, 2H, Hb]. 31P NMR (101 MHz, CDCl3): d = 20.09 [s, 1J(P–Pt) =
4050.2]. MALDI-MS, m/z: 686.4 [M–Cl]+. Anal. Found (calc. for
C32H26Cl2NPPt): C: 53.6 (53.27); H: 3.9 (3.63); N: 2.0 (1.94).
= 88.4, 1H, Ha], 7.86 [dd, J(P–H) = 12.3, J(H–H) = 7.3, 4H,
He], 7.74 [dd, 3J(P–H) = 11.3, 3J(H–H) = 7.3, 4H, He], 7.6–7.3 [m,
3
3
16H], 7.03 [dd, J(H–H) = 8.0, J(H–H) = 1.7, 1H, H2 or 3], 6.83
3
4
ꢀ
ꢀ
3
3
4
[d, J(H–H) = 6.4, 2H, H2 or 3 ], 6.75 [dt, J(P–H) = 6.8, J(H–
H) = 1.7, 3J(Pt–H) = 44.0, 1H, H5], 4.59 [s, b, 2H, Hb], 2.62 [m,
4H, Hc,d]. 31P NMR (101 MHz, CDCl3): d = 48.35 [s, 1J(Pt–PB)=
1
[PtCl{(4-ClC6H3)CHNCH2(4ꢀ-ClC6H4)}PPh3] (4b). 4b was
obtained as bright yellow crystals from 0.045 g (0.079 mmol) of
compound 2b and 0.020 g (0.076 mmol) of triphenylphosphine
using the procedure reported for 4a. Yield 35 mg (59%). IR:
1944.3, PB], 40.93 [s, J(Pt–PA)= 3584.5, PA]. MALDI-MS, m/z:
821.07 [M]+, 787.13 [M–Cl]+.
[Pt{(4-ClC6H4)CHNCH2(4ꢀ-ClC6H4)}(Ph2P(CH2)2PPh2)]Cl (6b).
6b was obtained as a dark oil from 0.050 g (0.087 mmol)
of compound 2b and 0.037 g (0.09 mmol) of bis(diphenyl-
−1
1
=
m(CH N) = 1622.2 cm . H NMR (250 MHz, CDCl3): d = 8.10
[d, 4J(H–P) = 9.2, 3J(Pt–H) = 90.0, 1H, Ha], 7.73 [d, 3J(H–H) =
phosphino)ethane (dppe) using the procedure reported for 4a.
8.0, J (P–H) = 12.0, J(H–H) = 1.5, 6H, Hc], 7.5–7.3 [m, 11H,
Hd,e,2,3], 7.11 [d, 3J(H–H) = 7.8, 2H, H3ꢀ ], 6.87 [d, 3J(H–H) = 7.8,
4J(H–H) = 1.8, 2H, H2ꢀ ], 6.39 [t, 3J(H–H) = 1.8, 3J(Pt–H) = 54.8,
1H, H5], 5.32–5.30 [2H, Hb]. 31P NMR (101 MHz, CDCl3): d =
3
4
−1
Yield 39 mg (50%). IR: m(CH N) = 1655.3 cm . 1H NMR
=
(400 MHz, CDCl3): d = 8.73 [d, 4J(P–H) = 7.6, 3J(Pt–H) = 85.0,
1H, Ha], 4.70 [s, b, 2H, Hb], 2.61 [s, 4H, Hc,d]. 31P NMR (101 MHz,
1
1
CDCl3): d 46.89 [s, J(PB–Pt)= 1940.0, PB], 40.00 [s, J(PA–Pt)=
20.00 [s, J(P–Pt) = 4143.1]. MALDI-MS, m/z: 719.95 [M–Cl]+;
1
3586.4, Pa]. FAB-MS, m/z: 856.18 [M]+, 732.12 [M–2Cl–C7H6]+.
Anal. Found (calc. for C32H25Cl3NPPt): C: 51.2 (50.84); H: 4.0
(3.33); N: 1.9 (1.85).
X-Ray structure analysis for 2b, 2e and 3c
[PtCl{(2,6-Cl2C6H3)CHNCH2(4ꢀ-ClC6H3)}PPh3] (4d). 4d was
obtained as a yellow solid from 0.012 g (0.020 mmol) of compound
2d and 0.005 g (0.019 mmol) of triphenylphosphine using the
procedure reported for 4a. Yield 10 mg (63%). 1H NMR (400 MHz,
CDCl3): d = 9.80 [dt, 4J(H–P) = 5.6, J(H–H) = 2.0, 3J(Pt–H) =
22.4, 1H, Ha], 7.82–7.77 [ꢀm, 5H, Hc], 7.51–7.39 [m, 10H, Hcꢀ ], 7.32
[t, J(H–H) = 7.4, 1H, H4 ], 7.17 [m, J(H–H) = 7.4, 2H, H3 ], 6.82
[m, 2H, H2,3], 6.44 [s, 3J (H–Pt) = 60.8, 1H, H5], 4.77 [s, br, 2H, Hb].
31P NMR (101 MHz, CDCl3): d = 21.55 [s, 1J(P–Pt) = 4315.8]. 195Pt
Prismatic crystals were selected and mounted on an Enraf-Nonius
CAD4 four circle (2b and 2e) or a MAR 345 (3c) diffractometers.
Unit cell parameters were determined from automatic centering of
25 reflections (12◦ < h < 21◦) (2b and 2e) or from 245 reflections
(3◦ < h < 31◦) for 3c and refined by least-squares methods.
Intensities were collected with graphite monochromatized Mo
Ka radiation. 2786 (2b), 6183 (2e) and 18 892 (3c) reflections
were measured in the range 2.22◦ < h < 29.99◦ (2b), 2.21◦
<
1
h < 29.96◦ (2e) or 3.42◦ < h < 31.34◦ (3c). 2625 (2b), 1019 (2e)
and 5735 (3c) reflections were observed applying the condition
I > 2r(I). Lorentz polarization and absorption corrections were
made.
NMR (54 MHz, CDCl3): d = −3956.00 [d, J(P–Pt) = 4315.8].
FAB-MS, m/z: 753.6 [M–Cl]+, 717.8 [M–2Cl]+. Anal. Found (calc.
for C32H24Cl4NPPt): C: 49.7 (48.62); H: 3.3 (3.06); N: 1.5 (1.77).
[PtCl{(2,4,6-(CH3)3C6H2)CHNCH2(4ꢀ-ClC6H3)}PPh3]
(4e).
The structures were solved by using the SHELXS program,27
and refined by full-matrix least-squares method with the
SHELXL97 computer program using 2786 (2b), 6183 (2e) and
5735 (3c) reflections. The function minimized was Rw||Fo|2–
|Fc|2 |2, where w = [r2(I) + (0.0640P)2]−1 (2b), w = [r2(I)]−1
4e was prepared from 0.040 g (0.069 mmol) of compound 2e and
0.018 g (0.069 mmol) of triphenylphosphine using the procedure
reported for 4a. The obtained product was contaminated with
[PtCl2(PPh3)2], but attempts to obtain 4e in a pure form lead to
1
further decomposition. H NMR (400 MHz, CDCl3): d = 9.82
(2e) or w = [r2(I) + (0.0355P)2]−1 (3c) and P = (|Fo|2
+
4
3
[d, J(H–P) = 6.0, J(Pt–H) = 38.8, 1H, Ha], 6.42 [t, J(H–H) =
2|Fc|2)/3. f , fꢀand fꢀꢀ were taken from the International Tables
of X-Ray Crystallography.28 All hydrogen atoms were computed
and refined using a riding model with an isotropic temperature
factor equal to 1.2 times the equivalent temperature factor of
the atom to which they are linked. Further details are given in
Table 2. CCDC reference numbers 630802, 630803 and 640014.
2.4, J(Pt–H) = 59.1, 1H, H5], 4.62 [t, J(H–H) = 2.4, J(Pt–H)
3
3
= 20.8, 2H, CH2], 2.32 [s, 3H, H4ꢀ ], 2.20 [s, 6H, H2,6 ;]. 31P NMR
ꢀ
(101 MHz, CDCl3): d = 24.44 [s, 1J(P–Pt) = 3169.4].
[PtCl{(2,6-Cl2C6H3)CHNCH2(4ꢀ-ClC6H3)}(PPh3)2] (5d). 5d
was obtained as a white solid from 0.012 g (0.020 mmol) of
This journal is
The Royal Society of Chemistry 2007
Dalton Trans., 2007, 2030–2039 | 2037
©

View Article Online
Table 2 Crystallographic and refinement data
Compound 2b
Compound 2e
Compound 3c
Empirical formula
Molecular weight
Temperature/K
Wavelength/A
Crystal system
Space group
C16H16Cl3NOPtS
571.8
293(2)
0.71073
Monoclinic
Cc
C19H23Cl2NOPtS
579.43
293(2)
0.71069
Monoclinic
P21/n
C23H23Cl2NOPtS
627.47
293(2)
0.71073
Monoclinic
P21/a
˚
Unit cell dimensions
˚
a/A
16.222(8)
13.120(6)
10.932(9)
127.88(6)
6.230(3)
27.614(9)
12.442(3)
96.60(3)
10.301(5)
22.018(9)
10.850(4)
109.34(3)
˚
b/A
˚
c/A
b/◦
Volume/A
3
˚
1836(2)
2126.3(13)
2322.0(17)
Z
4
4
4
Calculated density/Mg m−3
Absorption coefficient/mm−1
F(000)
2.068
8.192
1088
1.810
6.955
1120
1.795
6.377
1216
Crystal size/mm
0.1 × 0.1 × 0.2
0.1 × 0.1 × 0.2
0.1 × 0.1 × 0.2
Theta range for data collection
Reflections collected/unique
Completeness to theta (%)
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R1
2.22–29.99◦
2.21–29.96◦
3.42–31.34◦
2786/2786 [R(int) = 0.0430]
99.5 (h = 29.99)
Full-matrix least-squares on F2
2786/2/209
6183/6183 [R(int) = 0.0335]
100.0 (h = 29.96)
Full-matrix least-squares on F2
6183/0/202
18892/5735 [R(int) = 0.0605]
75.3 (h = 31.34)
Full-matrix least-squares on F2
5735/0/262
1.100
0.725
1.191
0.0342
0.0811
0.0424
0.0715
0.0281
0.0724
wR2
R indices (all data)
R1
0.0369
0.0822
0.732 and −0.865
0.0614
0.1339
0.958 and – 0.952
0.0410
0.0921
1.063 and −1.281
wR2
−3
˚
Largest diff. peak and hole/e A
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b618128g.
Organometallics, 1992, 11, 1288; (c) M. Crespo, C. Grande and A.
Klein, J. Chem. Soc., Dalton Trans., 1999, 1629.
6 (a) J. Bravo, C. Cativiela, R. Navarro and E. P. Urriolabeitia,
J. Organomet. Chem., 2002, 650, 157; (b) S. Pe´rez, C. Lo´pez, A. Caubet,
X. Solans and M. Font-Bard´ıa, New J. Chem., 2003, 27, 975; (c) M.
Crespo, M. Font-Bard´ıa, J. Granell, M. Mart´ınez and X. Solans, Dalton
Trans., 2003, 3763; (d) A. Capape´, M. Crespo, J. Granell, M. Font-
Bard´ıa and X. Solans, J. Organomet. Chem., 2005, 690, 4309.
7 (a) X. Riera, A. Caubet, C. Lo´pez, V. Moreno, X. Solans and M.
Font-Bard´ıa, Organometallics, 2000, 19, 1384; (b) X. Riera, C. Lo´pez,
A. Caubet, V. Moreno, X. Solans and M. Font-Bard´ıa, Eur. J. Inorg.
Chem., 2001, 2135.
8 (a) L. Ding, D. P. Zou and Y. J. Wu, Polyhedron, 1998, 17(15), 2511;
(b) C. Lo´pez, A. Caubet, S. Pe´rez, X. Solans and M. Font-Bard´ıa,
Chem. Commun., 2004, 540; (c) Y. J. Wu, L. Ding, H. X. Wang, Y. H.
Liu, H. Z. Yuan and X. A. Mao, J. Organomet. Chem., 1997, 535,
49.
9 (a) L. Alexandrova, O. G. D’yachenko, G. M. Kazankov, V. A. Polyakov,
P. V. Samuleev, E. Sansores and A. D. Ryabov, J. Am. Chem. Soc., 2000,
122, 5189; (b) A. D. Ryabov, G. M. Kazankov, I. M. Panyashkina, O. V.
Grozovsky, O. G. Dyachenko, V. A. Polyakov and L. M. Kuz´emina,
J. Chem. Soc., Dalton Trans., 1997, 4385; (c) A. D. Ryabov, S. Otto,
P. V. Samuleev, V. A. Polyakov, L. Alexandrova, G. M. Kazankov, S.
Shova, M. Revenco, J. Lipkowski and M. H. Johansson, Inorg. Chem.,
2002, 41(16), 4286.
10 (a) A. D. Ryabov, I. M. Panyashkina, V. A. Polyakov and A. Fischer,
Organometallics, 2002, 21, 1633; (b) S. Tollari, S. Cenini, A. Penoni, G.
Granata, G. Palmisano and F. J. Demartin, J. Organomet. Chem., 2000,
608, 34.
Acknowledgements
This work was supported by the Ministerio de Ciencia y Tec-
nolog´ıa (project: CTQ2006-02007/BQU).
References
1 (a) A. D. Ryabov, Synthesis, 1985, 233; (b) V. V. Dunina, O. A.
Zalevskaya and V. M. Potapov, Russ. Chem. Rev. (Engl. Transl.), 1988,
57, 434; (c) A. D. Ryabov, Chem. Rev., 1990, 90, 403; (d) P. Espinet,
M. A. Esteruelas, L. A. Oro, J. L. Serrano and E. Sola, Coord. Chem.
Rev., 1992, 117, 215; (e) C. Navarro-Ranninger, I. Lo´pez-Solera, J. M.
Pe´rez, J. R. Masaguer and C. Alonso, Appl. Organomet. Chem., 1993,
7, 57; (f) M. Albrecht, M. Lutz, A. L. Spek and G. van Koten, Nature,
2000, 406; (g) M. Albrecht and G. van Koten, Angew. Chem., Int. Ed.,
2001, 40, 3750; (h) J. Dupont, M. Pfeffer and J. Spencer, Eur. J. Inorg.
Chem., 2001, 1917; (i) I. Omae, Coord. Chem. Rev., 2004, 248, 995; (j) J.
Dupont, C. S. Consorti and J. Spencer, Chem. Rev., 2005, 105, 2527.
2 (a) J. Albert, M. Go´mez, J. Granell, J. Sales and X. Solans,
Organometallics, 1990, 9, 1405; (b) J. Albert, J. Granell, J. Sales, M.
Font-Bard´ıa and X. Solans, Organometallics, 1995, 14, 1393.
3 (a) J. Albert, J. Granell, J. Sales, X. Solans and M. Font-Altaba,
Organometallics, 1986, 5, 2567; (b) J. Albert, R. M. Ceder, M. Gomez,
J. Granell and J. Sales, Organometallics, 1992, 11, 1536.
4 (a) A. Crispini and M. Ghedini, J. Chem. Soc., Dalton Trans., 1997,
75; (b) C. Navarro-Ranninger, I. Lo´pez-Solera, A. Alvarez-Valde´s, J.
Rodriguez-Ramos, J. R. Masaguer, J. L. Garc´ıa-Ruano and X. Solans,
Organometallics, 1993, 12, 4104.
11 (a) R. Annunziata, S. Cenini, F. Demartin, G. Palmisano and S.
Tollari, J. Organomet. Chem., 1995, 496, C1; (b) M. D. Meijer, E. de
Wolf, M. Lutz, A. L. Spek, G. P. M. van Klink and G. van Koten,
Organometallics, 2001, 20, 4198; (c) P. R. R. Ranatunge-Bandarage,
B. H. Robinson and J. Simpson, Organometallics, 1994, 13, 500;
(d) A. D. Ryabov, I. M. Panyashkina, A. V. Polyakov, J. A. K. Howard,
L. G. Kuz’mina, M. S. Datt and C. Sacht, Organometallics, 1998, 17,
3615.
5 (a) C. M. Anderson, M. Crespo, M. C. Jenninngs, A. J. Lough,
G. Ferguson and R. J. Puddephatt, Organometallics, 1991, 10, 2672;
(b) M. Crespo, M. Martinez, J. Sales, X. Solans and M. Font-Bard´ıa,
2038 | Dalton Trans., 2007, 2030–2039
This journal is
The Royal Society of Chemistry 2007
©

View Article Online
12 (a) C. E. L. Headford, R. Mason, P. R. Ranatunge-Bandarage, B. H.
Robinson and J. Simpson, J. Chem. Soc., Chem. Commun., 1990, 601;
(b) M. D. Meijer, A. W. Kleij, M. Lutz, A. L. Spek and G. van Koten,
J. Organomet. Chem., 2001, 640, 166; (c) M. D. Meijer, A. W. Kleij,
B. S. Williams, D. Ellis, M. Lutz, A. L. Spek, G. P. M. van Klink and G.
van Koten, Organometallics, 2002, 21, 264; (d) P. R. R. Ranatunge-
Bandarage, N. W. Duffy, S. M. Johnston, B. H. Robinson and J.
Simpson, Organometallics, 1994, 13, 511.
13 A. Capape´, M. Crespo, J. Granell, A. Vizcarro, J. Zafrilla, M. Font-
Bard´ıa and X. Solans, Chem. Commun., 2006, 4128.
14 P. S. Pregosin, Coord. Chem. Rev., 1982, 44, 247.
15 (a) M. Font-Bard´ıa, C. Gallego, M. Mart´ınez and X. Solans,
Organometallics, 2002, 21, 3305; (b) M. Crespo, M. Font-Bard´ıa and
X. Solans, Organometallics, 2004, 23, 1708.
19 (a) N. W. Alcock, A. Avshu, R. D. O’Sullivan, A. W. Parkins and
R. M. Countryman, J. Chem. Soc., Dalton Trans., 1983, 1619; (b) P. J.
Bednarski, E. Ehrensperger, H. Sho¨nenberger and T. Burgemeister,
Inorg. Chem., 1990, 30, 3015; (c) R. Annunziata, S. Cenini, F. Demartin,
G. Palmisano and S. Tollari, J. Organomet. Chem., 1995, 496, C1.
20 (a) B. Teijido, A. Ferna´ndez, M. Lo´pez Torres, S. Castro-Ruiz, A.
Sua´rez, J. M. Ortigueira, J. M. Vila and J. J. Ferna´ndez, J. Organomet.
Chem., 2000, 598, 71; (b) D. Va´zquez-Garc´ıa, A. Ferna´ndez, J. J.
Ferna´ndez, M. Lo´pez-Torres, A. Sua´rez, J. M. Ortigueira, J. M. Vila and
H. Adams, J. Organomet. Chem., 2000, 595, 199; (c) J. M. Vila, M. T.
Pereira, J. M. Ortigueira, D. Lata, M. Lo´pez Torres, J. J. Ferna´ndez, A.
Ferna´ndez and H. Adams, J. Organomet. Chem., 1998, 566, 93.
21 H. F. Klein, S. Camadanli, R. Beck, D. Leukel and U. Flo¨rke, Angew.
Chem., Int. Ed., 2005, 44, 975.
16 (a) S. Reinartz, S. White, M. Brookhart and J. L. Templeton,
Organometallics, 2001, 20, 1709; (b) L. Johansson, O. B. Ryan, C.
Romming and M. Tilset, J. Am. Chem. Soc., 2001, 123, 6579; (c) A. F.
Heyduk, T. G. Driver, J. A. Labinger and J. E. Bercaw, J. Am. Chem.
Soc., 2004, 126, 15034; (d) F. Zhang, C. W. Kirby, D. W. Hairsine,
M. C. Jennings and R. J. Puddephatt, J. Am. Chem. Soc., 2005, 127,
14196; (e) T. G. Driver, M. W. Day, J. A. Labinger and J. E. Bercaw,
Organometallics, 2005, 24, 3644; (f) S. B. Zhao, D. Song, W. L. Jia and
S. Wang, Organometallics, 2005, 24, 3290.
17 A. C. Cope and E. C. Friedrich, J. Am. Chem. Soc., 1968, 90, 909.
18 (a) J. Vicente, I. Saura-Llamas, M. Palin, P. G. Jones and M. C. Ram´ırez
de Arellano, Organometallics, 1997, 16, 826; (b) J. Vicente, I. Saura-
Llamas, J. Cuadrado and M. C. Ram´ırez de Arellano, Organometallics,
2003, 22, 5513; (c) Y. Fuchita, K. Yoshinaga, T. Hanaki, H. Kawano
and J. Kinoshita-Nagaoka, J. Organomet. Chem., 1999, 580, 273; (d) Y.
Fuchita, K. Yoshinaga, Y. Ikeda and J. Kinoshita-Kawashima, J. Chem.
Soc., Dalton Trans., 1997, 2495; (e) J. Albert, J. Granell, J. Zafrilla, M.
Font-Bard´ıa and X. Solans, J. Organomet. Chem., 2005, 690, 422.
22 (a) J. Albert, J. Granell, R. Moragas, M. Font-Bard´ıa and X. Solans,
J. Organomet. Chem., 1996, 522, 59; (b) J. Albert, R. M. Ceder, J. Granell
and J. Sales, Organometallics, 1992, 11, 1536; (c) P. W. Clark, S. F. Dyke,
G. Smith and C. H. L. Kennard, J. Organomet. Chem., 1987, 330, 447.
23 W. Lu, C. W. Chan, K. K. Cheung and C. M. Che, Organometallics,
2001, 20, 2477.
24 (a) M. Crespo, X. Solans and M. Font-Bard´ıa, Organometallics, 1995,
14, 355; (b) M. Crespo, J. Granell, X. Solans and M. Font-Bard´ıa,
J. Organomet. Chem., 2003, 681, 143.
25 J. Vicente, J. A. Arcas, E. Mart´ınez-Viviente and P. G. Jones,
Organometallics, 2002, 21, 4454.
26 (a) J. H. Price, A. N. Williamson, R. F. Schramm and B. B. Wayland,
Inorg. Chem., 1972, 11(6), 1280; (b) V. Y. Kukushkin, A. J. L. Pombeiro,
C. M. P. Ferreira and L. I. Elding, Inorg. Synth., 2002, 33, 189.
27 G. M. Sheldrick, SHELXS97, A Computer Program for Crystal
Structure Determination, University of Go¨ttingen, Germany, 1997.
28 International Tables of X-Ray Crystallography, Kynoch Press, Birming-
ham, UK, 1974, vol. IV, pp. 99–100, 149.
This journal is
The Royal Society of Chemistry 2007
Dalton Trans., 2007, 2030–2039 | 2039
©