Dimethylplatinum (II) complexes with isocyanocoumarin ligands: The crystal structure of cis-dimethylbis-(7-diethylamino-3-isocyanocoumarin)platinum(II)

Article abstract of DOI:10.1016/j.jorganchem.2004.09.007

Platinum complexes that contain isocyanocourmarin ligands have been prepared. [Pt₂Me₄(μ-SMe₂)₂] and [PtPh₂(SMe₂)₂] react with ligands L, (L = 7-diethylamino-3-isocyanocoumarin, I

Full text of DOI:10.1016/j.jorganchem.2004.09.007

Journal of Organometallic Chemistry 690 (2005) 168–176
www.elsevier.com/locate/jorganchem
Dimethylplatinum (II) complexes with isocyanocoumarin
ligands: the crystal structure of cis-
dimethylbis-(7-diethylamino-3-isocyanocoumarin)platinum(II)
a,
b
c
a
Craig Anderson *, Daniel A. Freedman , Michael Jennings , Brenda Gray
a
Department of Chemistry, Bard College, 30 Campus Road, Annandale-on-Hudson, NY 12504, USA
Department of Chemistry, State University of New York at New Paltz, New Paltz, NY 12561, USA
b
c
Department of Chemistry, University of Western Ontario, London, Ont., Canada N6A 5B7
Received 29 June 2004; accepted 2 September 2004
Available online 7 October 2004
Abstract
Platinum complexes that contain isocyanocourmarin ligands have been prepared. [Pt2Me4(l-SMe2)2] and [PtPh2(SMe2)2] react
with ligands L, (L = 7-diethylamino-3-isocyanocoumarin, Idc; 7-isocyano-4-methylcoumarin, Mic; 7-isocyano-4-trifluoromethyl-
coumarin, Tic; 3-chloro-4-methyl-7-isocyanocoumarin, Cmic), to give PtR2L2, monomers in high yield. The NMR and IR spectra
of these complexes are consistent with cis stereochemistry. The UV–Vis absorption spectra of the complexes show bands assigned to
ligand-centered transitions. Excitation into the absorption bands of the Idc complexes gives emission at room temperature in meth-
ylene chloride solution. The oxidative addition reaction of two of these complexes with methyl iodide has been studied. Platinum
(IV) species with fac geometry have been isolated and characterized. Cis-dimethylbis-(7-diethylamino-3-isocyanocoumarin)plati-
num(II) was characterized by X-ray diffraction.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Platinum; Oxidative addition; Photochemistry; Isocyanide; Coumarin
1. Introduction
where CNR is an isocyanocoumarin ligand (7-diethyl-
amino-3-isocyanocoumarin, Idc; 7-isocyano-4-methyl-
coumarin, Mic; 7-isocyano-4-trifluoromethylcoumarin,
Tic; 3-chloro-4-methyl-7-isocyanocoumarin, Cmic).
The preparation of three of the isocyanocoumarin lig-
ands and the Mo(CO)4L2 complexes of the ligands was
recently reported [2]. The molybdenum complexes dis-
played intense visible absorption and emission bands
that were assigned to MLCT transitions. The assign-
ment was, in part, based on the similarities between
the isocyanocoumarin complexes and analogous
Mo(pp)(CO)4 complexes (pp = polypyridyl) which have
very well characterized emissive MLCT excited states
[3]. It seems reasonable that MLCT excited states should
also be observed for Pt–isocyanocoumarin complexes.
We also report the preparation of a new isocyanocou-
marin ligand, Idc, which differs from the other isocyano-
Square-planar platinum (II) complexes with metal-to-
ligand charge transfer (MLCT) excited states have been
the subject of considerable interest due to their interest-
ing photophysical properties, their potential applica-
tions as light emitting diodes, and as devices for solar
energy conversion and hydrogen production [1]. The
vast majority of these studies have focused on Pt(II)
complexes of polypyridyl-type ligands. We thought it
would be interesting to examine other Pt(II) complexes
also likely to exhibit MLCT excited states. Therefore,
in this work we describe the synthesis and characteriza-
tion of a series of R2Pt(CNR)2 (R = Me, Ph) complexes
*
Corresponding author. Tel.: +845 758 7293; fax: +845 758 7628.
E-mail address: canderso@bard.edu (C. Anderson).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.09.007

C. Anderson et al. / Journal of Organometallic Chemistry 690 (2005) 168–176
169
O
NO2
O
H
i
O2N
+
OEt
OH
Et2N
Et2N
O
O
O
C
NO2
H
N
N
ii
H
iii
Et2N
O
Et2N
Et2N
O
O
O
O
O
Scheme 1. (i) Reflux in toluene with piperidine. (ii) Reflux with Sn in toluene/formic acid. (iii) Stir with POCL3/Net3 in CH2Cl2.
coumarin ligands in that it contains an intramolecular
charge transfer (ICT) chromophore which generates in-
tense visible absorption and emission bands. There is
considerable evidence in the literature that platinum
complexes with isocyanide ligands should be stable
and display interesting properties. Recent reports on
Pt(II)–isocyanide complexes have explored their liquid
crystal properties [4], their use as probes for important
intermediates in platinum catalyzed reactions [5], and
their use as vapochromic sensors [6]. Coumarins and
their derivatives [7] are of interest in natural products
chemistry [8], have been shown to bond with DNA [9],
and have exciting photochemical and photophysical
properties of their own [10].
solution is dominated by an intense band at 420 nm.
Also shown in Fig. 1 is the intense emission centered
at 490 nm generated by excitation into the absorption
band. Both the absorption and emission bands are con-
sistent with what has been observed for other 7-amino-
coumarin compounds [2]. The emissive excited state
can be represented by the resonance structure on the
right shown below (Fig. 2) where charge has been trans-
ferred from the amine to the unsaturated lactone ring.
3. Synthesis and characterization of the PtR2(CNR)2
complexes, R = Me or Ph
Pt(CH3)2(CNR)2 complexes were readily prepared
from [Pt(CH3)2(l-SMe2)]2 and PtPh2(CNR)2 complexes
were prepared from PtPh2 (SMe2)2 by displacement of
the sulfide ligand with an isocyanocoumarin ligand
(Chart 1) by mixing the appropriate ligand with the me-
tal complex. Complexes were isolated in high yield as
light yellow (Mic, Tic, Cmic complexes) or yellow-or-
ange (Idc complexes) powders (Chart 1 and Reactions
(1) and (2)).
2. Preparation and characterization of 7-diethylamino-3-
isocyanocoumarin (Idc)
Idc is easily prepared in the three steps shown in
Scheme 1. Idc was fully characterized by elemental anal-
ysis, and by NMR, IR, UV–Vis, and emission spectros-
copies. The absorbance spectrum (Fig. 1) in CH2Cl2
5.0
4.0
3.0
2.0
1.0
0
2000
1500
1000
500
250
350
450
550
650
Wavelength (nm)
Fig. 1. Absorption and emission spectra of Idc in methylene chloride solution.

170
C. Anderson et al. / Journal of Organometallic Chemistry 690 (2005) 168–176
C
C
methyl [18]. The platinum carbon bond for the isocy-
N
N
anocoumarin ligand is slightly shorter than in a related
complex, Mo(CO)4(Tic)2 [2], partially attributable to
the CNR ligand being trans to methyl groups which
are known to be stronger r donors and weaker p acids
than CO. Examination of the bond angles between adja-
cent atoms around the platinum (87ꢁ, 88ꢁ, 88ꢁ and 98ꢁ)
shows the platinum center to be roughly square planar.
The largest angle (98ꢁ) is between the coumarin rings as
anticipated from a strictly steric consideration. A plane
defined by the platinum atom and its four coordinated
O
O
Et2N
Et2N
O
O
Fig. 2. Resonance structures for Idc.
½PtðCH3Þ ðl-SMe2Þꢀ þ 4CNR
! cis ꢁ ½PtðCH3Þ ðCNRÞ ꢀ
2
2
ð1Þ
2
2
˚
atoms has a mean deviation of 0.0305 A. Both coumarin
Ph2Pt(SMe2)2
+
2 CNR, CNR = Idc, Mic
rings are twisted with respect to the platinum square
plane. The C1–O13 coumarin is twisted 8.9ꢁ from the
platinum square plane and the C21–O31 coumarin is
twisted 32.4ꢁ from the platinum plane. Each coumarin
ring forms loose stacks with the rings of adjacent mole-
cules in a head-to-tail fashion. The C1–O13 coumarin
ring completely eclipses itself, as does the C21–O31 cou-
marin ring. This full-eclipse puts the two coumarin rings
CNR
Pt
ð2Þ
CNR
o
p
m
˚
at a perpendicular distance of 3.51(1) A for C1–O13 and
˚
The complexes were characterized by elemental analysis
and IR, NMR, UV–Vis and emission spectroscopies.
The infrared spectra of the complexes display two iso-
cyanide stretches, consistent with cis geometry. The pro-
ton NMR spectra of the complexes with R = Me shows
one peak for the methyl ligands with platinum satellites
with coupling constants of 74 Hz, consistent with the
JMe–Pt values for two other cis-dimethylplatinum(II)–
isocyanide complexes already reported [11,12]. This
indicates that the trans influence of the isocyanocouma-
rins ligands is similar to other isocyanide ligands and
intermediate between bipy and phosphine ligands [13–
17]. The geometry was confirmed by the crystal structure
of the [Pt(CH3)2(Idc)2] (see below). The 1H NMR peaks
assigned to the isocyanocoumarin ligands are shifted
slightly, but are otherwise nearly identical to the analo-
gous peaks observed for the free ligands.
3.52(1) A for C21–O31. It is assumed that pp interaction
governs this contact distance. Thus the coumarin rings
appear to pack in an orderly manner up the diagonal
with the left ‘‘wing’’ eclipsing the ‘‘wing’’ below it and
the right ‘‘wing’’ being eclipsed by the ‘‘wing’’ above
it. There is some partial overlap of the coumarin rings
as these extended, full-eclipse chains pack together.
The C1–O13 manages to get within a perpendicular dis-
˚
tance of 3.19(1) A of itself. The C21–O31 stays further
˚
apart, 3.99(1) A. Fig. 4 shows the two molecules in the
unit cell that are in full-eclipse.
5. Oxidative addition study and platinum (IV) species
Dimethylplatinum(II) complexes are highly reactive
towards oxidative addition [19,20]. In order to deter-
mine any effect that a change in oxidation state might
have on the ligand-centered emission, the PtMe2(Idc)2
complex was reacted with methyl iodide to obtain a
six-coordinate platinum (IV) complex. Reaction of
Pt(CH3)2(Idc)2 (reaction (3)) with an excess of methyl
iodide
4. X-ray crystallography
X-ray quality crystals of PtMe2(Idc)2 were grown
from a concentrated methylene chloride solution by
slow diffusion of methanol. The crystal structure is com-
posed of discrete molecules separated by van der Waals
forces. A view of the molecule showing the labeling
scheme is seen in Fig. 3. The molecule adopts a cis con-
figuration as expected from the Pt precursor used and
consistent with the IR and NMR data. Selected bond
lengths and angles are given in Table 1.
Bond lengths in the coordination sphere of platinum
are in the usual range and not significantly different than
those reported for the similar complex, dimethylbis–
(dimethylisocyanide)platinum (II) and are approxi-
mately the sum of the covalent radii for Pt (II) and sp3
cis ꢁ ½PtðCH3Þ ðCNRÞ ꢀ þ MeI
2
2
! fac-½PtðCH3Þ ðCNRÞ Iꢀ
ð3Þ
3
2
gave a yellow-orange solid. The reaction was complete
within 24 h under the above conditions and can be
approximated to be on the slower end of the range for
similar dimethylplatinum complexes containing nitrogen
ligands and comparable to cis-dimethylbis-(o-tolylisocy-
anide) [11,20]. It is generally accepted that oxidative
addition of alkyl halides to platinum (II) compounds
give trans stereochemistry, although cis isomers can be

C. Anderson et al. / Journal of Organometallic Chemistry 690 (2005) 168–176
171
Ligand (RNC)
Platinum (II) Complex
Platinum (IV) Complexes
Me
a
5
4
Mic
Mic
Me
H
3
10
6
Pt
a
Me
2
7
9
CN
O
O
8
5
Mic
Me
4
a
Cl
3
10
Cmic
Cmic
Me
6
Pt
2
a
Me
7
9
CN
O
O
8
Cmic
CF3
5
b
4
a
a
Me
H
Me
3
10
6
Tic
Tic
Me
Tic
Pt
Pt
2
a
Me
a
Tic
Me
7
9
CN
O
I
O
8
Tic
H
5
13
b
4
a
NC
Me
Pt
I
a
Me
3
10
6
Idc
Idc
Me
IDC
IDC
Pt
Et
2
a
a
Me
Me
7
9
N
11
12
O
O
8
CH2
Idc
CH3
Chart 1.
produced by subsequent isomerization reactions [19].
1
the formation of any carbene products that may have re-
sulted by attack at the isocyanide or any polymeric or
cationic species that have been reported for related com-
plexes [21,22]. It appears that the complex, due to the
two methyls groups, is electron-rich enough to give a
single product, that of oxidative addition [11]. The fac
geometry is the preferred geometry as it has no mutually
trans carbon ligands which have a high trans influence
and the values for platinum coupling constants for
mutually trans methyls are much lower than those ob-
served here (see below) [23]. The methylplatinum region
of the proton NMR spectrum is very helpful in this
assignment. Upon oxidative addition the peak for the
two equivalent methyl groups of the platinum (II) spe-
cies disappears and two new peaks in a 2:1 ratio appear
shifted slightly upfield in comparison. The 2J(Pt–H) cou-
pling constant for the methyls trans to the isocyanocou-
marin ligands (the greater ratio of the methyl peaks)
The H and 13C NMR spectra are consistent with trans
addition and no isomerization process to give a single
product, fac-[Pt(CH3)3(Idc)2I]. We also did not witness
Fig. 3. Molecular structure of compound 3.

172
C. Anderson et al. / Journal of Organometallic Chemistry 690 (2005) 168–176
Table 1
Selected bond lengths and bond angles in compound 3
6.0
Bond lengths
Pt–C(21)
Pt–C(1)
1.955(8)
1.971(7)
2.084(6)
2.087(7)
1.146(9)
1.385(9)
4.0
2.0
0
Pt–C(41)
Pt–C(42)
C(10)–N(2)
N(2)–C(3)
Bond angles
C(21)–Pt–C(1)
C(21)–Pt–C(41)
C(1)–Pt–C(41)
C(21)–Pt–C(42)
C(1)–Pt–C(42)
C(41)–Pt–C(42)
C(1)–N(2)–C(3)
N(2)–C(1)–Pt
98.6(3)
88.3(3)
172.8(3)
173.1(3)
86.3(3)
86.3(3)
170.9(7)
174.6(6)
250
300
350
400
450
500
550
Wavelength (nm)
Fig. 5. Absorption spectra of PtL2Me2 complexes in methylene
chloride solution (----- L = Mic; ꢂ ꢂ ꢂꢂ ꢂ ꢂL = Cmic; solid line L = Tic).
to both the spectra of the free ligands and to bands ob-
served in the spectra of the Mo(CO)4(7-isocyanocouma-
rin)2 complexes [2]. This suggests that these bands can
be assigned to ligand-centered transitions as they were
in the Mo complexes. Surprisingly, there is no evidence
for any Pt ! coumarin charge transfer transitions. No
room temperature emission was observed from these
complexes. The absorption spectra of all three of the
Idc complexes also display a striking resemblance to
the absorbance spectrum of the free ligand, being dom-
inated by an intense visible band with a high energy
shoulder. One notable difference is that the band under-
goes a ca. 20 nm red-shift in the complexes vs. the free
ligand. We still assign these peaks to ligand-centered
transition. The red-shift can be rationalized by consider-
ing the Pt as an electron-withdrawing substituent on the
coumarin ring which stabilizes the ICT excited state by
withdrawing a portion of the negative charge placed
on the lactone carbonyl oxygen. The electron-withdraw-
ing nature of the Pt is supported by the shift of the iso-
cyanide CN stretching frequency to higher energy upon
complexation.
Emission from both of the PtR2(Idc)2 complexes was
observed at room temperature in dichloromethane solu-
tion upon excitation into the ligand-centered absorb-
ance bands. The resulting emission spectrum for
Pt(Idc)2Me2 is shown in Fig. 6. Emission data below
550 nm is omitted because of emission due to contami-
nation by a small amount of the free Idc ligand. As with
the absorbance bands, the emission profiles are similar
in appearance to the emission from the free ligand, how-
ever the Stokes shift for the complexes is approximately
double (135 vs. 70 nm) that observed for the free ligand.
A similar effect was observed recently in platinum and
iridium complexes of cyclometallated coumarin ligands
[1a,24]. These complexes emit from ligand-centered
Fig. 4. Stacking of two molecules showing eclipsed coumarin rings.
decreases from 74 Hz in the platinum (II) complex to 63
Hz for the platinum (IV) complex as is expected and typ-
ical of oxidative addition products [20,23]. The methyl
trans to iodide is assigned to the peak at higher field
as it integrates to half the size of the other methyl peak
and has a coupling constant of 71 Hz. The coupling con-
stant, which is greater than that of the other methyl
peak, is expected due to iodine having a weaker trans
influence than isocyanide. The carbon-13 NMR shows
the same pattern for chemical shifts and coupling con-
stants as the proton thus confirming the stereochemistry
of the product.
6. Electronic spectroscopy
The UV–Vis spectra of the 7-isocyanocoumarin com-
plexes are shown in Fig. 5 and the UV–Vis and emission
spectra of PtMe2(Idc)2 are shown in Fig. 6, respectively.
The 7-isocyanocoumarin complexes have two prominent
absorbance bands between 250 and 350 nm that are
nearly identical in wavelength and general appearance

C. Anderson et al. / Journal of Organometallic Chemistry 690 (2005) 168–176
173
3000
2000
1000
0
12
8.0
4.0
0
300
400
500
600
700
Wavelength (nm)
Fig. 6. Absorption and emission spectra of Pt(Idc)2Me2 in methylene chloride solution.
Table 2
UV–Vis absorption (kmax in nm (e in cmꢁ1 Mꢁ1 · 104)) and emission
spectral data for Idc and Pt isocyanocoumarin compounds
triplet states as opposed to the singlet emission observed
from the free ligands. The rapid intersystem crossing in
the ligand-centered excited state is attributed to the in-
creased spin–orbit coupling induced by the presence of
the heavy transition metals. The same explanation
should be applicable to the PtR2(Idc)2 complexes, there-
fore, we assign the emission from these as arising from
ligand-centered triplet states. The fact that we see no
emission from the 7-isocyanocoumarin complexes
strongly indicates that the emission cannot arise from
charge transfer states. Surprisingly, no emission was
observed from PtMe3(Idc)2I. The reason for this is not
entirely clear, but it is possible that the ligand-centered
excited state inter-system crosses to non-emissive metal-
centered states. The lack of emission from many Pt(IV)–
bipyridine complexes has been attributed to this cause
[25] (see Table 2).
Absorption
Emission
p–p*
p–p*
ICT
kmax
Idc
262 (1.8)
266 (2.9)
265 (3.0)
265 (3.8)
334 (5.0)
337 (3.3)
334 (4.4)
420 (8.7)
442 (10)
490
577
578
a
Pt(Idc)2Me2
Pt(Idc)2Ph2
Pt(Idc)2Me3I
Pt(Mic)2Me2
Pt(Tic)2Me2
Pt(Cmic)2Me2
a
442 (9.6)
439 (8.7)
293 (3.7)
295 (2.4)
294 (3.2)
a
a
a
a
a
a
Not observed.
little effect on the energy of the ligand-centered excited
state since all of the Idc complexes have nearly identical
absorption and emission maxima. It is intriguing that
the ligand-centered emission was ‘‘switched off’’ by the
oxidation of Pt(II) to Pt(IV). Future studies will focus
on preparing Idc complexes in which the oxidation state
of the metal can be easily and reversibly changed.
7. Concluding remarks
A series of platinum (II) complexes, PtR2(CNR)2
R = methyl or phenyl, with isocyanocoumarin ligands
have been synthesized and characterized. The absorp-
tion spectra of the 7-isocyanocoumarin complexes ap-
pear to display only ligand centered bands and unlike
other square-planar Pt complexes, no evidence for
MLCT or metal-centered bands arising from Pt–Pt
interactions were observed. It is possible that the MLCT
transitions are present, but are sufficiently high in energy
to be masked by the intense ligand-centered bands. In-
tense visible absorption and emission bands were ob-
served for the square planar Idc complexes assigned to
ligand-centered excited states. It appears that changes
in the Pt coordination sphere and oxidation state have
8. Experimental
8.1. General considerations
All reagents were purchased from Aldrich. Dichloro-
methane was distilled from P2O5 under nitrogen. All
other reagents were used as received. Proton and carbon
NMR spectra were recorded on a Varian or Joel 300
MHz spectrometer (proton 300 MHz, carbon 75.4
MHz) and referenced to SiMe4. d values are given in
ppm and J values in Hz. Microanalyses were performed
by MHW Laboratories, Phoenix, AZ. Infrared spectra

174
C. Anderson et al. / Journal of Organometallic Chemistry 690 (2005) 168–176
were recorded in methylene chloride solution using a
Perkin–Elmer 1600 FT-IR spectrometer. Absorption
spectra were recorded an Ocean Optics Chem 2000 fiber
optic spectrometer. Emission spectra were recorded on
an Ocean Optics S2000 CCD Array fiber optic spec-
trometer. Excitation at 405 nm was provided by a 200
W mercury vapor lamp using the appropriate interfer-
ence filter. Emission from the sample was focused on
to the fiber optic cable with a fiber-optic focusing assem-
bly (Oriel). A 450 nm cut-off filter was placed over the
focusing assembly to prevent interference from the exci-
tation line. No corrections were made for grating effi-
ciency and detector response.
mL, 0.0259 mol), and toluene (75 mL) were added to
a 100 mL flask equipped with a stir bar, reflux conden-
sor, and Dean-Stark trap. Piperidine (0.25 mL) was then
added. The solution was then refluxed for 24 h, cooled,
and the resulting orange product was isolated by filtra-
tion. Recrystalization from 95% ethanol gave 5.46 g
(80% yield) of orange needles. 1H NMR (300 MHz,
CDCl3): d = 1.26 [t, 3J(H12–H11) = 7.1, H12]; 3.49 [q,
4
3J(H11–H12) = 7.1, H11]; 6.48 [d, J(H8–H6) = 2.5, H8];
6.70 [dd, 4J(H6–H8) = 2.5, 3J(H6–H5) = 9.1, H6]; 7.44
3
[d, J(H6–H5) = 9.0, H5]; 8.72 [s, H4].
7-diethylamino-3-formylcoumarin. 7-diethylamino-3-
nitrocoumarin (2.0 g, 0.00763 mol), granular tin (4.0 g,
0.0343 mol), formic acid (20 mL), and toluene (40 mL)
were added to a round bottom flask equipped with a stir
bar, reflux condensor, and Dean-Stark trap. The mix-
ture was refluxed for 14 h after which the heat was in-
creased to distill off the formic acid. The solution was
cooled and the supernatant was decanted off leaving a
sticky orange solid. The solid was washed with ca.
150 mL of dichloromethane which was filtered through
diatomaceous earth and concentrated by rotary
evaporation. Addition of ether and cooling yielded
1.0 g of yellow crystals (51% yield). Anal. Calc. for
C14H16N2O3: C, 64.60; H, 6.20; N, 10.76. Found: C,
64.65; H, 6.25; N, 10.83%.
9. X-ray diffraction analysis
A yellow rectangular plate (0.04 · 0.15 · 0.35 mm)
was mounted on a glass fibre. Data were collected at
ꢁ73 ꢁC on a Nonius Kappa-CCD diffractometer using
Nonius software [26]. Crystallographic measurements
were done with graphite-monochromatized Mo Ka
(k = 0.071073) radiation using the //x scan technique.
12,792 reflections were measured in the range
2.67 < h < 27.51ꢁ, 6364 (Rint = 0.057) of which were
independent reflections. Crystal cell refinement and data
reduction (Lorentz and polarization effects as well as
absorption) were carried out using DENZO-SMN [27].
The unit cell parameters [a = 8.1790(2), b = 8.4502(2),
7-diethylamino-3-isocyanocoumarin (Idc). A 50 mL
flask was charges with 0.800 g (3.1 mmol) of 3-formyl-
7-diethylaminecoumarin. Methylene chloride (15 mL)
was added via syringe follwed by 3 mL of triethylamine
added through a short column of activated alumina.
Phosphorous oxychloride (0.29 mL, 3.1 mmol) was the
added dropwise by syringe. The reaction was stirred
for 30 min, during which time the formamide completely
dissolved leaving a clear yellow solution. The reaction
mixture was extracted with 2 · 10 mL portions of water
and once with 10 mL of saturated NaCl solution. The
methylene chloride layer was dried with anhydrous
MgSO4 and suction filtered through 5 cm of silica gel
in a fritted funnel. The solvent was removed via rotary
evaporation giving the product a yellow powder which
was dried in vacuo (0.62 g, 83% yield). The crude prod-
uct was suitable for synthesis. Chromatography on silica
gel, eluting with methylene chloride, gave analytically
pure material. Anal. Calc. for C14H14N2O2: C, 69.41;
H, 5.82; N, 11.56. Found: C, 69.43; H, 5.79; N,
11.57%. 1H NMR (300 MHz, CDCl3): d = 1.29
c = 23.2226(9),
a = 0.6780(10)ꢁ,
b = 86.0480(10)ꢁ,
c = 62.6840(10)ꢁ] were calculated and refined from the
full data set.
The reflection data were consistent with a triclinic
ꢀ
space group: P1. The structure was solved by direct
methods, using the SHELXS 97 computer program and
refined using the SHELXL 97 computer program [28].
Two molecules [C30H34N4O4Pt] were found in the unit
cell. The refinement of the structure was done on F2
by the full-matrix least-squares method. All of the
non-hydrogen atoms were refined with anisotropic ther-
mal parameters. The hydrogen atom positions were cal-
culated geometrically and were included as riding on
their respective carbon atoms. The largest residue elec-
3
˚
tron density peak (2.247 e/A ) was associated with the
platinum atom. Full-matrix least-squares refinement
on F2 of 352 parameters converged to R1 = 5.07 for 2r
data and wR2 = 12.04 for all data.
3
[t,3J(H12–H11) = 7, H12]; 3.35 [q, J(H11–H12) = 7, H11];
6.40 [d, 4J(H8–H6) = 2, H8]; 6.55 [dd, 4J(H6–H8) = 2,
3J(H6–H5) = 9, H6]; 7.19 [d, 3J(H5–H6) = 9, H5]; 7.61
10. Preparation of the compounds
[s, H4]. Selected IR: m(CN) 2125(vs) cmꢁ1
.
[PtMe2(Idc)2], 3, was prepared by the reaction of 4
equivalents of isocyanocoumarin ligand with compound
1 (150 mg) in methylene chloride solution and allowed
to stir for 2 h. The solvent was removed by evaporation
and resulting solid washed twice diethyl ether (5 mL)
Compounds [Pt2Me4(l-SMe2)2], 1, and [PtPh2(S-
Me2)2], 2, were prepared as previously reported [29,30].
7-diethylamino-3-nitrocoumarin. Diethylaminosalicyl-
aldehyde (5.0 g, 0.0259 mol), ethylnitroacetate (5.75

C. Anderson et al. / Journal of Organometallic Chemistry 690 (2005) 168–176
175
and under vacuum. Yield 80%. Crystals suitable for
X-ray diffraction analysis were recrystallized from meth-
Yield 48 mg (59%). 1H NMR (300 MHz, CDCl3): = 1.36
[s, 2J(Pt–H) = 63, Mea]; 1.46 [s, 2J(Pt–H) = 73, Meb];
1.24 [t, 3J(H12–H11) = 7.5, H12]; 3.46 [q, 3J(H11–
H12) = 7.5, H11]; 6.44 [d, 4J(H8–H6) = 2.2, H8]; 6.65
[dd, 3J(H6–H5) = 9.3, 4J(H6–H8) = 2.2, H6]; 7.30 [d,
3J(H5–H6) = 9.3, H5]; 7.90 [s, H4]. 13C NMR (75.4
MHz, CDCl3): d = ꢁ2.86 [J(Pt–C) = 513, Mea]; 2.05
[J(Pt–C) = 577, Meb]; 134.7 [J(Pt–C) = 701, C13]; 45.5
[C11]; 12.9 [C12]; {97.4, 110.6, 130.5, 141.8 [H4,5,6,8]};
106.4,106.8,152.6,156.7 [H2,3,7,9,10]. Selected IR m(CN)
2194(s), 2181(vs) cmꢁ1. Anal. Calc. for C31 H37IN4-
O4Pt(0.5CH2Cl2): C, 42.3; H, 4.25; N, 6.26. Found: C,
42.1; H, 4.60; N, 5.83%.
1
ylene chloride/methanol. H NMR (300 MHz, CDCl3):
d = 0.77 [s, 2J(Pt–H) = 74, Mea]; 1.26 [t, 3J(H12–
3
H11) = 7, H12]; 3.44 [q, J(H11–H12) = 7, H11]; 6.48 [d,
4J(H8–H6) = 2, H8]; 6.62 [dd, 4J(H6–H8) = 2, 3J(H6–
3
H5) = 9, H6]; 7.30 [d, J(H5–H6) = 9, H5]; 7.81 [s, H4].
Selected IR m(CN) 2166(s), 2120(vs) cmꢁ1
.
[PtMe2(Mic)2], 4, was prepared similarly. Yield
80%. 1H NMR (300 MHz, CD2Cl2): d = 0.697 [s,
2J(Pt–H) = 74, Mea]; 2.43 [s, Me4]; 6.34 [s, H3]; 7.39 [d,
3J(H5–H6) = 9, H5]; 7.66 [d, 3J(H6–H5) = 9, H6]; 7.30
[apparent s, H8]. Selected IR m(CN) 2168(s), 2124(vs)
cmꢁ1. Anal. Calc. for C24H20N2O4Pt: C, 48.4; H, 3.39;
N, 4.71. Found: C, 48.3; H, 3.52; N, 4.73%.
[PtMe3I(Tic)2], 10, was prepared similar to complex
1
9. Yield 55%. H NMR (300 MHz, CDCl3): = 1.44 [s,
2
[PtMe2(Tic)2], 5, was prepared similarly. Yield 80%.
2
2J(Pt–H) = 63, Mea]; 1.45 [s, J(Pt–H) = 71, Meb]; 6.92
1H NMR (300 MHz, CDCl3): = 0.82 [s, J(Pt–H) = 74,
[q, 4J(H3–CF3 = 1), H3]; 7.85 [dq, 3J(H5–H6) = 9,
5J(H5–CF3 = 1), H5]; 7.55 [m, H6,8]. Anal. Calc. for
C25H17F6IN2O4Pt(0.5CH2Cl2): C, 34.5; H, 1.94; N,
3.16. Found: C, 34.5; H, 2.30; N, 2.90%.
Mea]; 6.90 [s, H3]; 7.44 [dd, 3J(H5–H6 = 8.5), 4J(H6–
H8) = 1.9, H6]; 7.78 [dq, 3J(H5–H6) = 8.5, 5J(H5–
4
CF3) = 1.6, H5]; 7.49 [d, J(H8–H6) = 1.9, H8]. Selected
IR m(CN) 2168(s), 2115(vs) cmꢁ1. Anal. Calc. for
C24H14F6N2O4Pt: C, 41.0; H, 2.01; N, 3.98. Found: C,
41.2; H, 1.86; N, 3.98%.
11. Supplementary material
[PtMe2(Cmic)2], 6, was prepared similarly. Yield
1
2
80%. H NMR (300 MHz, CDCl3): d = 0.79 [s, J(Pt–
H) = 74, Mea]; 2.61 [s, Me4]; 7.68 [m, H5]; 7.41 [m,
H6]; 7.43 [m, H8]. Selected IR m(CN) 2169(s), 2123(vs)
cmꢁ1. Anal. Calc. For C24H18Cl2N2O4Pt: C, 43.8; H,
1.84; N, 4.26. Found: C, 44.0; H, 2.00; N, 4.19%.
Crystallographic data for the structure analysis have
been deposited with the Cambridge Crystallographic
Data Center, CCDC No. 243903 for compound 3. Copies
of this information may be obtained free of charge from
the Director, CCDC, 12 Union Road, Cambridge CB2
1EZ (fax: +44 1223 336033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk.).
[PtPh2(Idc)2], 7, was prepared similarly except com-
plex 2 was used as the platinum complex. Yield 70%. %.
1H NMR (300 MHz, CDCl3): d = 6.92 [m, Hp, 1H]; 7.05
[m, Hm, 2H]; 7.44 [d, 3J(Ho–Hm) = 7, 3J(Pt–H) = 64, Ho,
2H]; 1.22 [t, 3J(H12–H11) = 6, H12]; 3.43 [q, 3J(H11–
H12) = 6, H11]; 6.45 [d, 4J(H8–H6) = 2, H8, 1H]; 6.60
[dd, 4J(H6–H8) = 2, 3J(H6–H5) = 7, H6, 1H]; 7.24 [d,
3J(H5–H6) = 7, H5, 1H]; 7.70 [s, H4, 1H]. Selected IR
m(CN) 2180(s), 2148(vs) cmꢁ1
C40H38N4O4Pt(0.25CH2Cl2): C, 56.6; H, 4.50; N, 6.56.
Found: C, 56.6; H, 4.83; N, 6.20%.
Acknowledgements
C.A. acknowledges the support of Orgometa. D.A.F.
acknowledges the support of The Research Corporation
who funded a portion of this work.
.
Anal. Calc. for
[PtPh2(Mic)2], 8, was prepared similarly. Yield
75%. d = 6.45 [m, Hp, 1H]; 7.75 [m, Hm, 2H]; 7.41 [dd,
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