Synthesis of platinum(II) cyclometallated compounds derived from imines containing pyridyl or pyrimidyl groups

Article abstract of DOI:10.1139/V08-084

The reaction of compounds [Pt₂Me₄(μ-SMe ₂)₂] and cis-[PtPh₂(SMe₂) ₂] with ligands 4-(2′-C₅H₄N)C ₆H₄CHN-CH₂CH₂NMe

Full text of DOI:10.1139/V08-084

Pagination not final/Pagination non finale
1
Synthesis of platinum(II) cyclometallated
compounds derived from imines containing pyridyl
or pyrimidyl groups1
Margarita Crespo, Craig M. Anderson, and Joseph M. Tanski
Abstract: The reaction of compounds [Pt2Me4(µ-SMe2)2] and cis-[PtPh2(SMe2)2] with ligands 4-(2′-C5H4N)C6H4CHN-
CH2CH2NMe2 (1a) and 4-(3′,5′-C4H3N2)C6H4CHNCH2CH2NMe2 (1b) carried out in acetone at room temperature pro-
duced compounds in which the imines act as bidentate [N,N′] ligands. Analogous compounds could be obtained in
refluxing methanol when cis-[PtCl2(DMSO)2] was used as starting material. The corresponding cyclometallation pro-
cesses leading to platinum(II) compounds with a tridentate [C,N,N′] ligand took place under different reaction condi-
tions, except for metallation of 1a with cis-[PtPh2(SMe2)2], which could not be achieved. All compounds were
characterized by usual techniques and [PtMe{4-(3′,5′-C4H3N2)C6H3CHNCH2CH2NMe2}] (3bMe) was also character-
ized crystallographically.
Key words: platinum, imines, pyridyl, pyrimidyl, cyclometallation, crystal structure.
Résumé : Opérant en solution dans l’acétone et à la température ambiante on a effectué la réaction des produits
[Pt2Me4(µ-SMe2)2] et cis-[PtPh2(SMe2)2] avec les ligands 4-(2′-C5H4N)C6H4CHNCH2CH2NMe2 (1a) et 4-(3′,5′-
C4H3N2)C6H4CHNCH2CH2NMe2 (1b) et on en a isolé des produits dans lesquels les imines agissent comme des li-
gands [N,N′]-bidentates. On a aussi pu obtenir des composés analogues en opérant dans le méthanol au reflux en pré-
sence de cis-[PtCl2(dmso)2] utilisé comme substrat. Les processus de cyclométallation correspondants qui conduisent à
la formation de composés du platine(II) avec un ligand tridentate [C,N,N′] se produit aussi dans des conditions réac-
tionnelles différentes, mais la métallation du composé 1a par le cis-[PtPh2(SMe2)2 ne peut pas être réalisée. On a ca-
ractérisé tous les produits par les techniques usuelles et on a fait appel à la diffraction des rayons X pour caractériser
le [PtMe{4-(3′,5′-C4H3N2)C6H3CHNCH2CH2NMe2}] (3bMe).
Mots-clés : platine, imines; pyridyle, pyrimidyle, cyclométallatation, structure cristalline.
[Traduit par la Rédaction] Crespo et al.
8
Introduction
factors that control the cyclometallation process are not fully
understood. Besides gross electronic and steric factors, sub-
tle differences in the substituents of the ligands to be
metallated can be decisive in the course of the reaction (9,
10). Following our studies of cycloplatination of imines con-
taining aromatic groups such as benzene (11, 12), thiophene
(13), furane (14), naphthalene (15), phenanthrene and
anthracene (16), and biphenyls (17, 18), we now report the
reactions of imines derived from 4-(2-pyridyl)benzaldehyde
(1a) and 5-(4-formylphenyl)pyrimidine (1b) with
metallating agents [Pt2Me4(µ-SMe2)2], cis-[PtPh2(SMe2)2] and
cis-[PtCl2(DMSO)2]. The aim of this study is to evaluate the
influence of pyridyl or pyrimidyl substituents in the aryl
group as well as of the metallating substrate used in the syn-
thesis of novel platinacycles. For all these systems, the labile
sulfide or sulfoxide ligands should be easily replaced by the
two nitrogen atoms of the ligands leading to isolation of
[N,N′] coordination compounds. The intramolecular C–H
bond activation may occur through either oxidative addition
or electrophilic substitution pathways (19). Moreover, the
presence of one or two nitrogen atoms in the aromatic moi-
ety introduces reactive sites on the ligands and allows fur-
ther chemical reactions of the corresponding cyclometallated
compounds (20).
Cycloplatinated compounds have been a topic of interest
in the last years as a consequence of the wide range of their
potential applications in many areas (1–8). In spite of the
large number of this type of compound described so far, the
Received 1 April 2008. Accepted 23 April 2008. Published
on NRC Research Press Web site at canjchem.nrc.ca on
17 July 2008.
We are pleased to contribute this paper to the Special Issue
recognizing the outstanding scientific career of Richard J.
Puddephatt, who we hold in the highest esteem and continues
to influence and inspire our own work.
M. Crespo.2 Departament de Química Inorgànica, Universitat
de Barcelona, Barcelona, Spain.
C.M. Anderson.2 Department of Chemistry, Bard College,
Annandale-on-Hudson, NY 12504, USA.
J.M. Tanski. Department of Chemistry, Vassar College,
Poughkeepsie, NY 12604, USA.
1This article is part of a Special Issue dedicated to Professor
R.J. Puddephatt.
2Corresponding authors (e-mail: margarita.crespo@qi.ub.es,
canderso@bard.edu).
Can. J. Chem. 87: 1–8 (2009)
doi:10.1139/V08-084
© 2008 NRC Canada

2
Can. J. Chem. Vol. 87, 2009
Chart 1.
Compound 2aMe was characterized by elemental analy-
ses, mass spectrometry, and H NMR spectra. Compound
Results and discussion
1
Ligands 4-(2′-C5H4N)C6H4CHNCH2CH2NMe2 (1a) and
4-(3′,5′-C4H3N2)C6H4CHNCH2CH2NMe2 (1b) were pre-
pared from the condensation reactions of N,N-dimethylethyl-
enediamine and the corresponding aldehyde carried out in
toluene at room temperature. The resulting imines were
2bMe was characterized in solution by NMR spectroscopy
but it could not be isolated in a pure form, since further re-
action at room temperature produces the corresponding
cyclometallated compound 3bMe within 1 h (see below). In
1
the H NMR spectra, two distinct resonances appear in the
1
methyl region, both coupled with 195Pt. The one at higher
field with a larger coupling to 195Pt is assigned to the methyl
trans to the NMe2 moiety (see Table 1). The coordination of
the ligand through both nitrogen atoms is confirmed by the
coupling of both amine and imine protons to platinum. The
J(H–Pt) values for the imine proton indicate an E conforma-
tion of the imine as previously observed for analogous com-
pounds (11–18).
characterized by H NMR spectroscopy.
Reactions of ligands 1a and 1b with [Pt2Me4(µ-SMe2)2]
The reactions of [Pt2Me4(µ-SMe2)2] with potentially tri-
dentate ligands 1a and 1b carried out in acetone at room
temperature produced the compounds [PtMe2{4-(2′-C5H4N)-
C6H4CHNCH2CH2NMe2}] (2aMe) and [PtMe2{4-(3′,5′-
C4H3N2)C6H4CHNCH2CH2NMe2}] (2bMe), respectively, in
which the imines act as bidentate [N,N′] ligands (see Chart 1).
Intramolecular activation of C–H bonds followed by
© 2008 NRC Canada

Crespo et al.
Table 1. Selected H NMR data.
3
1
Chart 2.
δ(NMe2)
CH=N
Me–Pt
Me–Pt
[3J(H–Pt)]
[3J(H–Pt)]
[2J(H–Pt)]a
[2J(H–Pt)]b
2aMe
2bMe
2aPh
2a!Ph
2bPh
2aCl
2bCl
3aMe
3bMe
3bPh
3aCl
2.84 (19)
2.85 (20)
2.67 (17)
2.62 (21)
2.67 (18)
3.14c
9.03 (45)
9.07 (42)
8.84 (44)
8.43 (28)
8.87 (43)
9.58 (52)
9.57c
8.64 (58)
8.68 (59)
8.56 (57)
8.13 (141)
8.43 (140)
0.25 (90)
0.21 (90)
—
—
—
—
—
—
—
0.63 (84)
0.64 (84)
—
—
—
—
—
1.06 (79)
3.15c
CHNCH2CH2NMe2}] (2bPh) in good yields. The obtained
2.86 (20)
2.87 (21)
2.80 (21)
2.91 (12)
2.93 (14)
compounds were characterized by elemental analyses, mass
1
1.04 (78)
spectrometry, and H NMR spectroscopy. As for the com-
—
—
—
—
—
—
pounds above, the coordination of the ligand through both
nitrogen atoms is confirmed by the coupling of both amine
and imine protons to platinum, and the J(H–Pt) values for
the imine proton indicate an E conformation.
Formation of the corresponding cyclometallated com-
pounds was attempted by refluxing toluene solutions of
2aPh or 2bPh for 6 h, a method previously reported for the
synthesis of analogous compounds with biphenyl ligands
(18), which consists in intramolecular activation of a
3bCl
Note: δ in ppm, J in Hz.
aMe trans to NMe2.
bMe trans to CH=N.
cCoupling to 195Pt was not observed.
methane elimination to yield [C,N,N′] cycloplatinated com-
pounds took place at room temperature for 2bMe and when
a toluene solution of compound 2aMe was refluxed for 2 h.
Compounds 3aMe and 3bMe were characterized by mass
spectrometry, NMR spectroscopy, and elemental analyses.
In addition, 3bMe was also characterized crystallographi-
cally. In the 1H NMR spectra, the methyl ligand, the
dimethylamino, and the imine groups are coupled to plati-
num, and the values of the coupling constants are in the
usual range for analogous compounds (11–18). In agreement
with previous data, the J(H–Pt) values of the imine group in-
crease from the coordination compounds to the cyclometal-
lated compounds (see Table 1). In addition, the aromatic
proton adjacent to the metallation site is also coupled to
platinum and provides evidence of the cyclometallation pro-
cess.
Imine 1a derived from 4-(2-pyridyl)benzaldehyde could in
principle produce binuclear compounds either mono- or dou-
bly-cyclometallated such as 4a and 5a shown in Chart 2.
Doubly cyclometallated compounds have been described for
both platinum and palladium (21, 22). With this aim, the re-
action of [Pt2Me4(µ-SMe2)2] with an equimolar amount of
imine 1a was carried out in acetone.
Unfortunately, the obtained orange solid was too insoluble
for NMR or mass spectra and could only be characterized by
elemental analyses, which were consistent with formation of
4a. This result indicates the ability of imine 1a to participate
in further reactions through the pyridyl nitrogen atom. At-
tempts to produce a doubly cyclometallated compound using
longer reaction times in acetone at room temperature or refluxing
a toluene suspension of compound 4a for several hours gave
insoluble materials that could not be identified. Because of
the difficulties arising from the low solubility of these
binuclear compounds, no further studies were carried out.
C
aromatic–H bond along with elimination of benzene. Using
this procedure for 2bPh, the corresponding [C,N,N′] cyclo-
metallated compound [PtPh{4-(3′,5′-C4H3N2)C6H3-
CHNCH2CH2NMe2}] (3bPh) was obtained as an orange red
solid. Compound 3bPh was characterized by elemental anal-
yses, mass spectrometry, and NMR spectra. As shown in Ta-
ble 1, the coupling constant of the imine proton to platinum
increases slightly compared with compound 2bPh as a result
of the formation of a metallacycle. Under the same experi-
mental conditions, the analogous compound 3aPh was not
obtained, since red solutions were formed, and the NMR
spectra taken for the final residue show only intense alde-
hyde signals, which indicate hydrolysis of the imine bond,
along with peaks for unidentified products. Hydrolysis of
imines with adventitious water in the solvent has been re-
ported under metallation conditions with palladium or plati-
num substrates (23, 24). Using shorter refluxing times did
not improve the results. Therefore, the synthesis of cyclo-
metallated compound 3aPh was attempted under milder con-
ditions such as stirring at room temperature a solution of
2aPh in acetone. After several hours, a new compound was
formed and its spectral data, in particular a small value of
J(H–Pt) for the imine proton (J(H–Pt) = 27.9 Hz), suggest
isomerization of the imine from the initial E conformation
observed in 2aPh to the less congested Z form leading to
compound 2a′Ph. After 24 h, the ratio 2a′Ph/2aPh is
0.54:1.00, and the amount of 2a′Ph increases slowly up to a
ratio of ~ 1.00:1.00 after 5 days in solution. No evidence of
formation of the expected cyclometallated compound is ob-
1
served in the H NMR spectra, while small amounts of the
aldehyde are formed. Isomerization from the most favoured
E conformation of the free ligand to the Z conformation
upon coordination to a platinum centre has been previously
observed for analogous systems (18) and can be explained
by the steric crowding in the coordination sphere of the plat-
inum(II) centre, which is minimized through this conforma-
tional change. It has to be noted, however, that the adequate
arrangement for producing cyclometallation at the aromatic
group is the E conformation, since isomerization to the less
Reactions of ligands 1a and 1b with cis-[PtPh2(SMe2)2]
The reactions carried out in acetone at room tempera-
ture produced compounds [PtPh2{4-(2′-C5H4N)C6H4CHNCH2-
CH2NMe2}] (2aPh) and [PtPh2{4-(3′,5′-C4H3N2)C6H4-
© 2008 NRC Canada

Pagination not final/Pagination non finale
4
Can. J. Chem. Vol. 87, 2009
Table 2. Selected bond lengths (Å) and
angles (°) with estimated standard devi-
ations for compound 3bMe.
congested Z form places the aromatic group away from the
platinum centre. Therefore, the reaction at room temperature
was not a good strategy for cyclometallation of 2aPh.
Bond lengths (Å)
Pt—C(8)
Pt—N(1)
N(1)—C(4)
N(2)—C(5)
C(6)—C(7)
Pt—C(1)
Reactions of ligands 1a and 1b with cis-[PtCl2(DMSO)2]
When equimolar amounts of cis-[PtCl2(DMSO)2] and
ligand 1a were refluxed in methanol for 5 h, the correspond-
ing compound [PtCl2{{4-(2′-C5H4N)C6H4CHNCH2CH2NMe2}]
(2aCl) was obtained in good yield. As previously noticed for
analogous systems (25), a Z conformation around the C=N
bond is adopted with the imine proton close to the platinum
1.990(5)
2.169(4)
1.499(7)
1.457(6)
1.447(7)
2.074(5)
2.017(4)
1.497(8)
1.279(6)
1.436(6)
Pt—N(2)
1
nucleus, which is evidenced in the H NMR spectrum by the
C(4)—C(5)
N(2)—C(6)
C(7)—C(8)
Bond angles (°)
C(8)–Pt–N(2)
N(1)–Pt–N(2)
C(1)–Pt–C(8)
C(1)–Pt–N(1)
downfield shift of the imine signal (δ = 9.58 ppm). This fact
suggests that coordination of a bidentate ligand to a PtCl2
moiety produces a conformational change from the most
stable E conformation of the free ligand to the Z, and conse-
quently Z–E isomerization should precede the cyclometalla-
tion step as previously reported for analogous systems. The
corresponding reaction for ligand 1b produced compound
[PtCl2{4-(3′,5′-C4H3N2)C6H4CHNCH2CH2NMe2}] (2bCl)
as a rather insoluble impure solid; attempts to obtain 2bCl in
a pure form were unsuccessful because of its low solubility.
The most widely used conditions for converting com-
pounds analogous to 2aCl and 2bCl into cycloplatinated de-
rivatives are refluxing for several hours in either toluene or
in a donor solvent such as methanol or ethanol, in some
cases in the presence of an external base, which favours the
formal elimination of HCl (25–30). When 2aCl was treated
with an equimolar amount of sodium acetate in refluxing
methanol for 48 h, cyclometallated compound 3aCl was pro-
duced. The process requires an initial step in which Z to E
imine isomerization brings the aryl ring closer to platinum
followed by the actual intramolecular C–H bond activation,
which leads to a five-membered metallacycle.
81.1(2)
81.9(2)
97.7(2)
99.3(2)
Fig. 1. Molecular structure of compound 3bMe.
2bPh, 2aPh, 2aMe (42–45 Hz) < 2aCl (52 Hz) < 3bPh,
3aMe, 3bMe (57–58 Hz) << 3aCl, 3bCl (140–141 Hz).
This sequence is consistent with the larger J(H–Pt) values
expected for: (i) cyclometallated vs. non-cyclometallated
compounds, (ii) imine moieties trans to a chloro ligand vs.
trans to a methyl or a phenyl ligand, and (iii) E vs. Z confor-
mation of the imine.
Alternatively, 3aCl could be obtained when equimolar
amounts of cis-[PtCl2(DMSO)2], ligand 1a and sodium ace-
tate were refluxed in methanol for 48 h. This method was
also used to obtain 3bCl. The obtained yields were lower
than those obtained for analogous compounds derived from
biphenyl such as [PtCl{4-C6H5C6H3CHNCH2CH2NMe2}]
and [PtCl{2-C6H5C6H3CHNCH2CH2NMe2}] (18). Further-
more, using prolonged reaction times, toluene–methanol
mixtures, and higher reaction temperatures (26–30) did not
improve the yields, since metallic platinum and high
amounts of aldehyde were formed under these conditions.
Compounds 3aCl and 3bCl were characterized by elemental
Crystal structure of 3bMe
Suitable crystals of 3bMe were grown by slow diffusion
of a CH2Cl2 solution into MeOH. The crystal structure is
composed of discrete molecules separated by van der Waals
interactions. Selected bond lengths and angles are given in
Table 2, and a molecular view is shown in Fig. 1.3
1
analyses, mass spectrometry, and NMR spectra. In the H
The ligand behaves as [C,N,N′]-tridentate and a three
fused [6,5,5] ring system containing a five-membered endo
metallacycle is formed. A methyl ligand completes the
square-planar coordination of the platinum atom. The
metallacycle is approximately planar as suggested by the
sum of internal angles, which is close to 540° (31) and
nearly co-planar with both the metallated phenyl and the
mean coordination plane. The dihedral angle between phenyl
and pyrimidyl groups is 31.8(2)°, which suggests, aside from
NMR spectra, a significant increase in the coupling constant
of the imine proton to platinum is observed upon
cyclometallation. The obtained values shown in Table 1 are
in the range reported for analogous cyclometallated com-
pounds in which a chloro ligand is in a trans position to the
1
imine (18). As a whole, analysis of the H NMR data re-
ported in Table 1 indicate that the J(H–Pt) values for the
imine proton increase in the order: 2a′Ph (28 Hz) < 2bMe,
3 Supplementary data for this article are available on the journal Web site (canjchem.nrc.ca) or may be purchased from the Depository of Un-
published Data, Document Delivery, CISTI, National Research Council Canada, Ottawa, ON K1A 0R6, Canada. DUD 3774. For more in-
formation on obtaining material, refer to cisti-icist.nrc-cnrc.gc.ca/irm/unpub_e.shtml. CCDC 6792371 contains the crystallographic data for
this manuscript. These data can be obtained, free of charge, via www.ccdc.cam.ac.uk/conts/retrieving.html (Or from the Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax +44 1223 336033; or deposit@ccdc.cam.ac.uk).
© 2008 NRC Canada

Crespo et al.
5
packing effects, a compromise between van der Waals repul-
sion of the ortho hydrogen atoms and the co-planarity re-
quired for resonance extended to both aryl rings. Tilt angles
ranging from 10.4° to 49.9° have been obtained for biphenyl
systems in analogous platinum(II) and platinum(IV)
cyclometallated compounds (17, 18). Bond lengths and an-
gles are in the expected range for analogous compounds
(11–13, 15–18). The Pt–NMe2 distance is longer
(2.169(4) Å) than the Pt–NCH (2.017(4) Å), which is con-
sistent with the relatively weak coordinating ability of ter-
tiary amines for platinum. Bond angles at platinum are close
to the ideal value of 90°, and the smallest angles correspond
to those involving the tridentate ligand with “bite” angles
C(8)–Pt–N(2) and N(1)–Pt–N(2) being 81.1(2)° and 81.9
(2)°, respectively.
more to electronic than to steric effects, since the substitu-
ents are away from the metallation position. In addition to
determining the success and ease of the cyclometallation,
these substituents emphasize the differences observed when
different metallating agents such as [Pt2Me4(µ-SMe2)2], cis-
[PtPh2(SMe2)2], and cis-[PtCl2(DMSO)2] are used, which is
further evidence of the different mechanisms operating for
such substrates (19). Further work aimed at evaluating the
ability of free pyridyl or pyrimidyl groups in the new com-
pounds to coordinate a second metallic fragment is in prog-
ress.
Experimental
General
Conclusions
NMR spectra were performed at the Unitat de RMN d’Alt
Camp de la Universitat de Barcelona using Mercury 400 and
Varian 300 spectrometers and referenced to SiMe4. δ values
are given in ppm and J values in Hz. J(H–Pt) values were
measured at 300 MHz to avoid errors arising from broaden-
ing of the 195Pt satellites observed at 400 MHz. Labelling of
the compounds is as shown in Chart 1. ES-mass spectra
were performed at the Servei d’Espectrometria de Masses de
la Universitat de Barcelona using a VG-Quattro spectrome-
ter. Microanalyses were performed by the Servei de
Recursos Científics i Tècnics de la Universitat Rovira i
Virgili (Tarragona).
All starting materials were purchased from commercial
sources and used as received. Toluene was distilled from so-
dium–benzophenone. Compounds [Pt2Me4(µ-SMe2)2] (34),
cis-[PtPh2(SMe2)2] (35, 36), and cis-[PtCl2(DMSO)2] (37)
were prepared according to literature methods.
The results here presented indicate that [C,N,N′]
cyclometallated compounds derived from 1a and 1b can be
easily obtained when [Pt2Me4(µ-SMe2)2] is used as a
metallation agent. The presence of two nitrogen atoms in the
pyrimidyl substituent in 1b facilitates the reaction, which
takes place under milder conditions than for 1a. When cis-
[PtPh2(SMe2)2] is used as starting material, the correspond-
ing [C,N,N′] cyclometallated compound could only be ob-
tained for the more activated 1b ligand. For both substrates
[Pt2Me4(µ-SMe2)2] and cis-[PtPh2(SMe2)2], the mechanism
consists of oxidative addition followed by elimination of
methane (32) or benzene (33), and therefore, the presence of
an additional nitrogen atom, more electronegative than a car-
bon atom, should have a similar activating effect in both
cases.
The failure to produce cyclometallation of ligand 1a with
cis-[PtPh2(SMe2)2] is however unexpected taking into ac-
count that this metallation agent was effective for 4-
biphenylimine and even for the more sterically demanding
2- biphenylimine (17, 18), and that, in this case, the presence
of one nitrogen atom in 1a should facilitate the process.
Based on the observed presence of aldehyde in the attempted
cyclometallation reaction, we might assume that ligand 1a is
more prone to experience hydrolysis than the corresponding
biphenyl ligands. This fact along with the lower reactivity of
cis-[PtPh2(SMe2)2] vs. [Pt2Me4(µ-SMe2)2] (18) may account
for the observed results.
When cis-[PtCl2(DMSO)2] was used as starting material,
the corresponding [C,N,N′] cyclometallated compounds
could also be obtained, although with poor yields. As previ-
ously indicated for analogous systems (18, 25), the greater
steric requirements of chloro vs. methyl or phenyl ligands in
the platinum substrate leads to a Z conformation of the
imine group in the [N,N′] compounds, and therefore, Z to E
isomerization should precede the cyclometallation. More-
over, the lower yields compared with those obtained for
biphenyl ligands (18) could be related to the higher procliv-
ity of ligands 1a and 1b to hydrolysis as well as to the re-
duced reactivity towards an electrophilic reagent expected
for ligands containing electron-withdrawing substituents.
As a whole, the above results indicate that pyridyl or
pyrimidyl substituents on the aryl group may have a decisive
influence in the cyclometallation process, which is attributed
Preparation of the compounds
Compounds 1 were prepared by the reaction of equimolar
amounts of N,N-dimethylethylenediamine and the corre-
sponding aldehyde in toluene (20 mL). The mixture was
stirred for 1 h and dried over Na2SO4. The solvent was re-
moved in a rotary evaporator to yield yellow oils.
4-(2′-C5H4N)C6H4CHNCH2CH2NMe2 (1a)
Obtained from 0.5 g (2.90 × 10–3 mol) of 4-(2-
pyridyl)benzaldehyde and 0.26 g of N,N-dimethylethyl-
enediamine. Yield: 0.5 g (67%). 1H NMR (400 MHz,
CDCl3) δ: 2.32 [s, 6H, Ha], 2.67 [t, J(H–H) = 7.2, 2H, Hb],
3.78 [td, J(H–H) = 7.2, 0.8, 2H, Hc], 7.26 [m, 1H, Hh], 7.77
[m, 2H, Hi,j], 7.84 [d, J(H–H) = 8.4, 2H, Hf], 8.05 [d, J(H–
H) = 8.4, 2H, He], 8.37 [s, 1H, Hd], 8.71 [dt, J(H–H) = 4.4,
1.4, 1H, Hg].
4-(3′,5′-C4H3N2)C6H4CHNCH2CH2NMe2 (1b)
Obtained from 0.4 g of 5-(4-formylphenyl)pyrimidine
(2.17 × 10–3 mol) and 0.19 g of N,N-dimethylethyl-
enediamine. Yield: 0.4 g (72%). 1H NMR (400 MHz,
CDCl3) δ: 2.34 [s, 6H, Ha], 2.69 [t, J(H–H) = 7.2, 2H, Hb],
3.80 [t, J(H–H) = 7.2, 2H, Hc], {7.64 [d, J(H–H) = 8.4, 2H],
7.89 [d, J(H–H) = 8.4, 2H], He,f}, 8.38 [s, 1H, Hd], 8.98 [s,
2H, Hg], 9.23 [s, 1H, Hh].
© 2008 NRC Canada

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6
Can. J. Chem. Vol. 87, 2009
4.20 [t, J(H–H) = 5.0, 2H, Hc], {6.34–6.36 [m, 2H], 6.80 [t,
J(H–H) = 8.0, 2H], 6.89–6.92 [m, 3H], 7.12 [d, J(H–H) =
8.4, 2H], 7.44–7.46 [m, 3H], 8.12 [d, J(H–H) = 8.0, 2H],
[PtMe2{4-(2′-C5H4N)C6H4CHNCH2CH2NMe2}] (2aMe)
Compound 2aMe was obtained from 88 mg (3.49 ×
10–4 mol) of ligand 1a and 100 mg (1.74 × 10–4 mol) of
compound [Pt2Me4(µ-SMe2)2] in acetone (20 mL). The mix-
ture was stirred for 30 min at room temperature. 2aMe was
obtained as an orange solid upon removal of the acetone in a
rotary evaporator and washing of the residue with ether (3 ×
2 mL).
3
8.81 [s, 2H], 9.20 [s, 1H], aromatics}, 8.87 [s, J(Pt–H) =
43, 1H, Hd]. ES (+)-MS (MeCN – H2O): 604 [M + H], 526
[M – Ph], 449 [M – 2Ph]. Anal. found: C, 53.2; H, 4.8; N,
9.0. Calcd. for C27H28N4Pt: C, 53.72; H, 4.67; N, 9.28 (%).
1
[PtCl2{4-(2′-C5H4N)C6H4CHNCH2CH2NMe2}] (2aCl)
Compound 2aCl was obtained from 150 mg (3.50 ×
10–4 mol) of cis-[PtCl2(DMSO)2] and the equimolar amount
(90.0 mg) of 1a after refluxing the mixture in methanol for
5 h. On cooling, a light yellow solid is formed.
Yield: 150 mg (90%). H NMR (400 MHz, CDCl3) δ:
2
2
0.25 [s, J(Pt–H) = 90, 3H, Hk], 0.63 [s, J(Pt–H) = 84, 3H,
Hl], 2.71 [t, J(H–H) = 5.2, 2H, Hb], 2.84 [s, J(H–Pt) = 19,
3
6H, Ha], 4.07 [t, J(H–H) = 5.2, 2H, Hc], 7.76–7.79 [m, 3H,
Hh,i,j], {8.01 [d, J(H–H) = 8.2, 2H], 8.37 [d, J(H–H) = 8.2,
1
2H],He,f}, 8.70 [d, J(H–H) = 5.2, 1H, Hg], 9.03 [s, J(Pt–
3
Yield: 120 mg (65%). H NMR (400 MHz, CDCl3) δ:
2
2.70 [t, J(H–H) = 6.0, 2H, Hb], 3.14 [s, 6H, Mea], 4.09 [td,
H) = 45, 1H, Hd]. ES (+)-MS (MeCN – H2O): 504 [M – Me +
MeCN], 489 [M – 2Me + MeCN], 463 [M – Me], 448 [M –
2Me]. Anal. found: C, 44.5; H, 5.9; N, 8.5. Calcd. for
C18H25N3Pt: C, 45.18; H, 5.26; N, 8.78 (%).
2J(H–H) = 6.0, 2.0, 2H, Hc], 7.33 [ddd, J(H–H) = 6.8, 4.8, 2,
3
1H, Hh], 7.64 [d, J(H–H) = 8.4, 2H, He or Hf], 7.80–7.82
3
[m, 2H, Hi, Hj], 8.13 [d, J(H–H) = 8.4, 2H, He or Hf], 8.73
3
[dt, J(H–H) = 4.8, 2, 1H, Hg], 9.58 [s, J(Pt–H) = 52, 1H,
Hd]. ESI-MS: 520 [M + H], 484 [M – Cl]. Anal. found: C,
36.2; H, 3.7; N, 8.0. Calcd. for C16H19Cl2N3Pt·H2O: C,
35.76; H, 3.94; N, 7.82 (%).
[PtMe2{4-(3′,5′-C4H3N2)C6H4CHNCH2CH2NMe2}] (2bMe)
Compound 2bMe was obtained following the same proce-
dure from 18 mg of ligand 1b and 20 mg (0.35 × 10–4 mol)
of compound [Pt2Me4(µ-SMe2)2] in acetone (10 mL). Com-
pound 2bMe could be characterized in solution, and within
an hour, produces 3bMe (see below).
[PtCl2{4-(3′,5′-C4H3N)C6H4CHNCH2CH2NMe2}] (2bCl)
Compound 2bCl was obtained as an insoluble impure
solid following the procedure reported above for 2aCl.
1H NMR (400 MHz, CDCl3) δ: 2.72 [m, 2H, Hb], 3.15 [s,
2
1H NMR (400 MHz, CDCl3) δ: 0.21 [s, J(Pt–H) = 90,
2
3H, Hi], 0.64 [s, J(Pt–H) = 84, 3H, Hj], 2.72 [m, 2H, Hb],
2
6H, Mea], 4.08 [t J(H–H) = 6.0, 2H, Hc], 7.73–7.76 [m,
3
2.85 [s, J(H–Pt) = 20, 6H, Ha], 4.11 [m, 2H, Hc], {7.60 [d,
4H], 8.99 [s, 2H,], 9.29 [s, 1H], 9.57 [s, 1H, Hd].
J(H–H) = 8.4, 2H], 8.45 [d, J(H–H) = 8.4, 2H], He,f}, 9.00
3
[s, 2H, Hg], 9.07 [s, J(Pt–H) = 42, 1H, Hd], 9.24 [s, 1H,
Hh].
[PtMe{4-(2′-C5H4N)C6H3CHNCH2CH2NMe2}] (3aMe)
Compound 3aMe was obtained after refluxing a toluene
solution (20 mL) containing 50 mg of compound 2aMe for
2 h. Toluene was totally removed, and the residue was
recrystallized from CH2Cl2–MeOH to yield 3aMe as a red
solid.
[PtPh2{4-(2′-C5H4N)C6H4CHNCH2CH2NMe2}] (2aPh)
Compound 2aPh was obtained as a yellow solid following
the same procedure as for 2aMe from 48 mg (0.19 mmol) of
ligand 1a and the equimolar amount of compound cis-
[PtPh2(SMe2)2] (90 mg) in acetone (10 mL).
1
Yield: 40 mg (83%). H NMR (400 MHz, CDCl3) δ: 1.06
[s, J(Pt–H) = 79, 3H, Hl], 2.86 [s, J(H–Pt) = 20, 6H, Ha],
3.19 [t, J(H–H) = 5.2, 2H, Hb], 4.09 [t, J(H–H) = 5.2, 2H,
Hc], 7.19 [m, 2H, Hi,j], {7.37 [d, J(H–H) = 8.0, 2H], 7.82 [d,
J(H–H) = 8.0, 2H],He,f}, 7.73 [d, J(H–H) = 6.8, 1H, Hk],
1
2
3
Yield: 80 mg (70%). H NMR (400 MHz, CDCl3) δ: 2.67
3
[s, J(Pt–H) = 17, 6H, Mea], 2.79 [t, J(H–H) = 5.0, 2H, Hb],
4.21 [t, J(H–H) = 5.0, 2H, Hc], {6.28 [t, J(H–H) = 7.0, 1H],
6.38 [t, J(H–H) = 7.4, 2H], 6.81 [t, J(H–H) = 7.2, 1H], 6.93
[m, 4H], 7.23 [ddd, J(H–H) = 7.6, 4.8, 1.2, 1H], 7.48 [d,
J(H–H) = 8.0, 2H], 7.55–7.58 [m, 3H], 7.73 [td, J(H–H) =
7.6, 2, 1H], 8.14 [d, J(H–H) = 8.4, 2H], 8.65 [ddd, J(H–H) =
8.07 [d, J(H–H) = 2, J(Pt–H) = 67, 1H, Hg], 8.64 [s, J(H–
Pt) = 58, 1H, Hd], 8.67 [d, J(H–H) = 4.8, 1H, Hh]. ES (+)-
MS (MeCN – H2O): 488 [M – Me + MeCN], 462 [M]. Anal.
found: C, 44.0; H, 4.7; N, 8.5. Calcd. for C17H21N3Pt: C,
44.15; H, 4.58; N, 9.09 (%).
3
3
3
4.4, 1.6, 1.0, 1H]}, 8.84 [s, J(Pt–H) = 44, 1H, Hd]. ES (+)-
MS (MeCN – H2O): 603 [M + H], 525 [M – Ph], 448 [M –
2Ph]. Anal. found: C, 54.5; H, 4.9; N, 6.5. Calcd. for
C28H29N3Pt·H2O: C, 54.18; H, 5.03; N, 6.77 (%).
Isomerization to 2a′Ph (Z isomer) took place in acetone at
[PtMe{4-(3′,5′-C4H3N2)C6H3CHNCH2CH2NMe2}] (3bMe)
Compound 3bMe was obtained from 89 mg (3.49 ×
10–4 mol) of ligand 1b and 100 mg (1.74 × 10–4 mol) of
compound [Pt2Me4(µ-SMe2)2] in acetone (20 mL). The mix-
ture was stirred for 1 h at room temperature, metallic plati-
num was filtered off, and acetone was removed in a rotary
evaporator. Red crystals of 3bMe were obtained upon
recrystallization of the residue from CH2Cl2–MeOH.
1
room temperature. H NMR (400 MHz, CDCl3) δ: 2.62 [s,
2J(Pt–H) = 21, 6H, Mea], 2.76 [t, J(H–H) = 6.0, 2H, Hb],
3
4.02 [td, J(H–H) = 6.0, 2,0, 2H, Hc], 8.43 [s, J(Pt–H) = 28,
1H, Hd].
[PtPh2{4-(3′,5′-C4H3N2)C6H4CHNCH2CH2NMe2}}] (2bPh)
Compound 2bPh was obtained as a yellow solid following
the same procedure as for 2aMe from 48.3 mg (0.19 mmol)
of ligand 1b and the equimolar amount of compound cis-
[PtPh2(SMe2)2] (90 mg) in acetone (10 mL).
1
Yield: 100 mg (62%). H NMR (400 MHz, CDCl3) δ:
2
3
1.04 [s, J(Pt–H) = 78, 3H, Hj], 2.87 [s, J(H–Pt) = 21, 6H,
Ha], 3.21 [t, J(H–H) = 6.0, 2H, Hb], 4.12 [td, J(H–H) = 6.0,
1.2, 2H, Hc], 7.16 [dd, J(H–H) = 7.6, 1.6, 1H, Hf], 7.38 [d,
1
4
Yield: 90 mg (78%). H NMR (400 MHz, CDCl3) δ: 2.67
J(H–H) = 7.6, J(H–Pt) = 10, 1H, He], 7.82 [d, J(H–H) =
[s, J(Pt–H) = 18, 6H, Mea], 2.80 [t, J(H–H) = 5.0, 2H, Hb],
2.0, 3J(H–Pt) = 65, 1H, Hg], 8.68 [s, 3J(H–Pt) = 59, 1H, Hd],
3
© 2008 NRC Canada

Crespo et al.
7
8.97 [s, 2H, Hh], 9.17 [s, 1H, Hi]. ES (+)-MS (MeCN –
H2O): 489 [M – Me + MeCN], 463 [M], 448 [M – Me].
Anal. found: C, 41.0; H, 4.3 N, 11.7. Calcd. for C16H20N4Pt:
C, 41.47; H, 4.35; N, 12.09 (%).
Table 3. Crystallographic and refinement data for compound 3bMe.
Formula
C16H20N4Pt
FW
463.45
T (K)
125(2)
Wavelength (Å)
Crystal system
Space group
0.71073
Monoclinic
P21/c
[PtPh{4-(3′,5′-C4H3N2)C6H3CHNCH2CH2NMe2}] (3bPh)
Compound 3bPh was obtained from 50 mg (8.3 ×
10–5 mol) of 2bPh in 20 mL of toluene. The mixture was
refluxed for 6 h, and toluene was removed in a rotary evapo-
rator. The residue was washed with ether to yield an orange–
red solid.
a (Å)
b (Å)
c (Å)
11.0787(8)
16.981(1)
8.1766(6)
94.310(1)
1533.9(2)
4
β (°)
1
V (Å3)
Z
Yield: 33 mg (76%). H NMR (400 MHz, CDCl3) δ: 2.80
3
[s, J(H–Pt) = 21, 6H, Ha], 3.24 [t, J(H–H) = 6.0, 2H, Hb],
4.11 [td, J(H–H) = 6.0, 1.2, 2H, Hc], 6.95 [tt, J(H–H) = 7.4,
1.6, 1H, p-Ph], 7.10 [t, J(H–H) = 7.4, 2H, m-Ph], 7.15 [dd,
J(H–H) = 7.4, 1.6, 1H, Hg], 7.32 [d, J(H–H) = 1.6, 1H, He],
7.37 [d, J(H–H) = 8, 1H, Hf], 7.55 [dd, J(H–H) = 8, 1.6,
Dcalcd. (g/cm3)
2.007
Abs. coeff. (mm–1)
θ range (°)
9.146
1.84–28.28
99.4
% Completeness to θ max
Data collected, unique
3
3J(H–Pt) = 59, 2H, o-Ph], 8.56 [s, J(H–Pt) = 57, 1H, Hd],
19507, 3781 (Rint = 0.0561)
8.79 [s, 2H, Hh], 9.10 [s, 1H, Hi]. ES (+)-MS (MeCN –
H2O): 973 [2M – Ph], 526 [M]. Anal. found: C, 48.7; H, 4.2;
N, 10.2. Calcd. for C21H22N4Pt: C, 48.00; H, 4.22; N, 10.66
(%).
Data, restraints, parameters
GOF on F2
3781, 0, 193
1.023
0.0295, 0.0574
R1, wR2 (F2, I > 2σ(I))
R1, wR2 (F2, all data)
0.0465, 0.0624
Peak and hole, e/Å–3
1.522 and –0.792
[PtCl{4-(2′-C5H4N)C6H3CHNCH2CH2NMe2}] (3aCl)
Compound 3aCl was prepared from 50 mg (9.6 ×
10–5 mol) of 2aCl and the equimolar amount of
Na(CH3COO) (8 mg) after refluxing the mixture in metha-
nol for 48 h. The reaction mixture was cooled, filtered to re-
move unreacted materials, and concentrated to dryness. The
obtained residue was recrystallized in dichloromethane–
methanol to yield an orange solid.
4a
Compound 4a was prepared from 22 mg (8.7 × 10–5 mol)
of ligand 1a and 50 mg (8.7 × 10–5 mol) of compound
[Pt2Me4(µ-SMe2)2] in acetone (20 mL). The mixture was
stirred for 5 h at room temperature, and the resulting orange
solid was filtered.
1
Yield: 15 mg (32%). H NMR (400 MHz, CDCl3) δ: 2.91
3
2
[s, J(H–Pt) = 12, 6H, Ha], 3.11 [t, J(H–H) = 6.0, 2H, Hb],
Yield: 60 mg (92%). 4a was too insoluble for NMR or
mass spectra. Anal. found: C, 33.3; H, 4.9 N, 5.2. Calcd. for
C21H34N3Pt2S: C, 33.60; H, 4.56; N, 5.60 (%).
3.97 [t, J(H–H) = 6.0, 2H, Hc], 7.22 [ddd, J(H–H) = 7.6,
2
5.0, 1.2, 1H, Hi], 7.32 [d, J(H–H) = 8.0, 1H, Hk], 7.74 [td,
3
J(H–H) = 7.6, 1.6, 1H, Hj], 7.79 [dd, J(H–H) = 8, 1.6, 1H,
He], 7.87 [d, J(H–H) = 8.0, 1H, Hf], 8.13 [s, J(Pt–H) =
3
3
5a
141, 1H, Hd], 8.18 [d, J(H–H) = 1.6, 1H, Hg], 8.67 [dd,
4
The preparation of compound 5a was attempted using a
procedure consisting of refluxing a toluene suspension of
compound 4a for 2 h. The obtained solid was too insoluble
for NMR or mass spectra, and the elemental analysis was
not consistent with the expected formula. An alternative pro-
cedure detailed below gave analogous results: 25 mg (5.2 ×
10–5 mol) of compound 3a and 15 mg (2.6 × 10–5 mol) of
compound [Pt2Me4(µ-SMe2)2] were allowed to react in ace-
tone at room temperature for 16 h. The resulting insoluble
solid was filtered. Yield: 30 mg (79%, based on the expected
formula C20H30N3Pt2S).
J(H–H) = 5.0, 1.6, 1H, Hh]. ES (+)-MS (MeCN – H2O): 447
[M – Cl]. Anal. found: C, 37.6; H, 4.1; N, 8.5. Calcd. for
C16H18ClN3Pt·H2O: C, 38.36; H, 4.02; N, 8.39 (%).
[PtCl{4-(3′,5′-C4H3N2)C6H3CHNCH2CH2NMe2}] (3bCl)
Compound 3bCl was prepared from 100 mg (2.37 ×
10–4 mol) of cis-[PtCl2(DMSO)2], 60.2 mg of 1b, and 20 mg
of sodium acetate after refluxing the mixture in methanol for
48 h. The reaction mixture was cooled, filtered to remove
unreacted materials, and concentrated to dryness. The ob-
tained residue was recrystallized in dichloromethane–
pentane to yield an orange solid.
X-ray structure determination
X-ray diffraction data were collected on a Bruker APEX 2
CCD platform diffractometer (Mo Kα, λ = 0.71073 Å) at
125 K (0 °C = 273.15 K). A suitable crystal was mounted in
a nylon loop with Paratone–N cryoprotectant oil. During
data examination and space-group determination with
XPREP, the σ(I) values were normalized and multiplied by a
factor of 0.5. The structure was solved using direct methods
and standard difference map techniques, and was refined by
full-matrix least-squares procedures on F2 with SHELXTL
(Version 6.14) (38). All non-hydrogen atoms were refined
1
Yield: 20 mg (17.4%). H NMR (400 MHz, CDCl3) δ:
3
2
2.93 [s, J(H–Pt) = 14, 6H, Ha], 3.15 [t, J(H–H) = 6.0, 2H,
Hb], 4.15 [td, J(H–H) = 6.0, 1.2, J(H–Pt) = 34, 2H, Hc],
2
3
7.21 [dd, J(H–H) = 8.0, 2.0, 1H, He], 7.39 [d, J(H–H) =
3
8.0, 1H, Hf], 7.98 [d, J(H–H) = 2.0, 1H, Hg], 8.43 [t, J(H–H)
= 1.2, J(Pt–H) = 140, 1H, Hd], 9.02 [s, 2H, Hh], 9.19 [s,
3
1H, Hi]. ES (+)-MS (MeCN – H2O): 503 [M + H2O]. Anal.
found: C, 33.3; H, 3.5; N, 9.5. Calcd. for
C15H17ClN4Pt·CH2Cl2: C, 33.78; H, 3.37; N, 9.85 (%).
© 2008 NRC Canada

Pagination not final/Pagination non finale
8
Can. J. Chem. Vol. 87, 2009
16. M. Crespo and E. Evangelio. J. Organomet. Chem. 689, 1956
(2004).
17. M. Crespo, M. Font-Bardia, and X. Solans. J. Organomet.
anisotropically. Hydrogen atoms were included in calculated
positions and were refined using a riding model. Crystal data
and refinement details are presented in Table 3.
Chem. 691, 444 (2006).
18. M. Crespo, M. Font-Bardia, and X. Solans. J. Organomet.
Chem. 691, 1897 (2006).
Acknowledgements
19. A.D. Ryabov. Chem. Rev. 90, 403 (1990).
20. C.K. Koo, Y.M. Ho, C.F. Chow, M.H.W. Lam, T.C. Lau, and
W.Y. Wong. Inorg. Chem. 46, 3603 (2007).
21. J.W. Slater and J.P. Rourke. J. Organomet. Chem. 688, 112
(2003).
We thank the Ministerio de Ciencia y Tecnología (project:
CTQ2006-02007/BQU (MC)), Bard College, Vassar College,
and The National Science Foundation (Grant NSF 0521237
to JMT (PI) and CMA) for financial support.
22. A. Zucca, A. Doppiu, M.A. Cinellu, S. Stoccoro, G. Minghetti,
and M. Manassero. Organometallics, 21, 783 (2002).
23. J. Bravo, C. Cativiela, R. Navarro, and E.P. Urriolabeitia. J.
Organomet. Chem. 650, 157 (2002).
24. C. López, A. Caubet, S. Pérez, X. Solans, M. Font-Bardia, and
E. Molins. Eur. J. Inorg. Chem. 3974 (2006).
25. M. Crespo, M. Font-Bardia, J. Granell, M. Martinez, and X.
Solans. Dalton Trans. 3763 (2003).
26. A. Capapé, M. Crespo, J. Granell, M. Font-Bardia, and X. So-
lans. J. Organomet. Chem. 690, 4309 (2005).
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© 2008 NRC Canada