PGSE diffusion NMR studies on mononuclear and dinuclear cationic platinum salts of (S)-MeO-Biphep and (R)-p-tolyl-BINAP

Article abstract of DOI:10.1016/j.ica.2007.03.029

PGSE diffusion NMR studies on a series of mononuclear and dinuclear cationic platinum salts derived from (S)-MeO-Biphep and (R)-p-tolyl-BINAP are reported. The data show that (a) one can readily distinguish between mononuclear and dinuclear cations (b) the amount of ion pairing can be estimated qualitatively and (c) the charge delocalization rather than the amount of formal charge per metal cation is important for the position of the anion. The solid-state structure of the chloro-bridged salt, [Pt(μ-Cl){(S)-MeO-Biphep}]₂(CF₃SO₃)₂, is reported.

Full text of DOI:10.1016/j.ica.2007.03.029

Inorganica Chimica Acta 360 (2007) 3203–3212
www.elsevier.com/locate/ica
PGSE diffusion NMR studies on mononuclear and dinuclear
cationic platinum salts of (S)-MeO-Biphep and (R)-p-tolyl-BINAP
a
a,
b
b
*
Dani e` le Schott , Paul S. Pregosin , Alberto Albinati , Silvia Rizzato
a
Laboratory of Inorganic Chemistry, ETHZ, H o¨ nggerberg CH-8093, Z u¨ rich, Switzerland
Department of Structural Chemistry (DCSSI), University of Milan, 20133 Milan, Italy
b
Received 29 January 2007; accepted 18 March 2007
Available online 27 March 2007
Abstract
PGSE diffusion NMR studies on a series of mononuclear and dinuclear cationic platinum salts derived from (S)-MeO-Biphep and
R)-p-tolyl-BINAP are reported. The data show that (a) one can readily distinguish between mononuclear and dinuclear cations (b)
(
the amount of ion pairing can be estimated qualitatively and (c) the charge delocalization rather than the amount of formal charge
per metal cation is important for the position of the anion. The solid-state structure of the chloro-bridged salt, [Pt(l-Cl){(S)-MeO-Bip-
hep}] (CF SO ) , is reported.
2
3
3 2
ꢀ
2007 Elsevier B.V. All rights reserved.
Keywords: Platinum complexes; Ion pairing; PGSE NMR diffusion; X-ray
1
. Introduction
and the echo forms. Spins, which diffuse out of their slice
into neighboring areas, via Brownian motion, will not be
refocused by the second gradient and this leads to an atten-
uation of the echo amplitude. As smaller molecules move
faster, they translate during the time interval D into slices
further apart from their origin, thus giving rise to smaller
spin echo intensities.
There is a growing interest in measuring diffusion con-
stants and several methodologies are currently in use.
These include attenuated total reflection infrared spectros-
copy [1], capacity intermittent titration techniques [2], long
capillary methods [3], and pulsed field gradient spin echo
(
PGSE) NMR spectroscopy.
In the PGSE Stejskal–Tanner experiment, Fig. 1, trans-
The amplitude of the echo can be expressed by:
ꢀ I
ꢁ
ꢀ
ꢁ
d
2
2
verse magnetization is generated by the initial p/2 pulse.
This magnetization dephases due to chemical shift, hetero-
ln
¼ ꢀðcdÞ G D ꢀ 3
D
ð1Þ
I
0
and homo-nuclear coupling evolution, and T relaxation.
where G is the gradient strength, D is the delay between the
midpoints of the gradients, D is the diffusion coefficient,
and d is the gradient length. The diffusion coefficient, D,
2
After application of the second p pulse, the magnetization
refocuses, generating an echo. The first of two pulsed gra-
dients results in strong dephasing of the magnetization (sig-
nal loss). Because the strength of the gradient varies
linearly along, e.g., the z-axis, only spins contained within
a narrow slice of the sample acquire the same phase angle.
The second gradient pulse reverses the respective phases
is obtained by plotting ln(I/I ) (I/I = observed spin echo
0 0
2
intensity/intensity without gradients) versus either D, d ,
2
(D ꢀ d/3) or G .
NMR diffusion methods are now routinely in use and
the basic experiment has been reviewed [4–11]. In more
recent reviews Cohen and co-workers [10], apply diffusion
NMR spectroscopy in supra-molecular and combinatorial
chemistry, whereas Berger and co-workers [11], center on
*
Corresponding author. Tel.: +41 44 632 29 15; fax: +41 44 633 10 71.
E-mail address: pregosin@inorg.chem.ethz.ch (P.S. Pregosin).
0
020-1693/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2007.03.029

3204
D. Schott et al. / Inorganica Chimica Acta 360 (2007) 3203–3212
2. Results and discussion
The dicationic platinum complexes [Pt(l-Cl){(S)-MeO-
Biphep}] (X) and [Pt(CH CN) {(S)-MeO-Biphep}](X) ,
2
2
ꢀ
3
2
2
ꢀ
X ¼ CF
3
SO3 and BF4 , plus several BINAP analogs,
were prepared as indicated in Scheme 1. The neutral PtCl
2
(diphosphine), which served as a starting material for the
syntheses of the dications, was also measured and served
as a model species. During the course of the preparation
of the salt, [Pt(CH CN) {(S)-MeO-Biphep}](BF ) , a low
3
2
4 2
1
frequency H resonance, d = ꢀ1.38, associated with a
minor component, was observed. As this chemical shift
was known to be typical for hydroxo-bridged complexes
[
27], the presumed salt, [Pt(l-OH){(S)-MeO-Bip-
Fig. 1. Pulse sequences for the PGSE measurements.
hep}] (BF ) , was prepared independently (see Section 4),
2
4 2
as indicated in Scheme 1, and shown, indeed, to be the
minor species.
intermolecular interactions as investigated by both NOE
and diffusion studies. An extensive compilation of diffusion
constants from PGSE measurements has just appeared
Given the increasing use of MeO-Biphep complexes [28–
1
13
3
1], the H and C characteristics of the salts were
[
12].
The experimental values for diffusion constants are usu-
ꢀ
10
2
ꢀ1
ally given in units of 10
m s and often these values
are not familiar to chemists. Consequently, the hydrody-
P
P
Cl
Cl
S
Cl
Cl
P
P
namic radius, r , of the species is also normally calculated,
Pt
H
Pt
CH Cl
-
using the Stokes–Einstein relation:
S
2
2
THT
kT
pgrH
7
2 % Yield
D ¼ 6
ð2Þ
P
P
= S-MeO-Biphep or (R)-p-tol-BINAP
where k is the Boltzmann constant, T is the absolute tem-
perature, g the viscosity and rH the hydrodynamic radius.
There is a continuing discussion in the literature con-
cerned with ‘‘anion effects’’ [13–24] in coordination chemis-
try and catalysis. The observed effects of the anion may
involve complexation, steric blocking or ion pairing, to
name just a few possibilities. Occasionally anion hydrolysis
will further complicate matters [25,26]. Unfortunately, it is
not always simple to ‘‘separate out’’ the ion pairing contri-
bution. Relative to other physical methods, an analysis of
the D values via PGSE NMR studies is both rapid and
instructive. If the diffusion characteristics of the anion
and cation can be measured separately, then inspection of
the regression lines for the cation and anion provides a
direct estimate of the ion pairing.
P
P
Cl
1 AgX
P
P
Cl
Cl
P
P
Pt
Pt
Pt
Pt
(X )
2
Cl
CH Cl
2
2
-AgCl
8
2 % Yield
1
AgX
P
Cl
Pt
P
P
Cl
Cl
(X)
CH CN dry
dilute conditions
P
NCCH3
3
-
AgCl
9
3 % yield
Given the general interest in group 10 cationic com-
plexes, we have prepared
P
P
Cl
2 AgX
P
NCCH3
Pt
Pt
(X )
2
Cl
CH CN dry
3
P
NCCH3
4
dilute conditions
5
6
3
2
-
2 AgCl
ca. 100% yield
MeO
PPh2
1
P(p-tol)2
P(p-tol)2
PPh2
MeO
H
P
P
Cl
Cl
P
O
P
P
2
AgBF4
Pt
Pt
Pt
(BF )
4 2
MeOH 90% / H O 10%
2
P
O
H
-
2 AgCl
several dicationic platinum salts of (S)-MeO-Biphep and
R)-p-tolyl-BINAP, and report here details of our diffusion
measurements on these species.
7
5 % Yield, for (S)-MeO-Biphep
(
Scheme 1.

D. Schott et al. / Inorganica Chimica Acta 360 (2007) 3203–3212
3205
1
Fig. 2. H NMR spectrum of [Pt(CH
3 2 3 3 2
CN) {(S)-MeO-Biphep}](CF SO ) in the aromatic region.
1
obtained by 2D NMR methods, Fig. 2 shows the H spec-
1. There is a very broad resonance, d ca. 7.75, due to the
dynamics associated with restricted rotation in such
atropisomeric complexes [32].
trum for [Pt(CH CN) {(S)-MeO-Biphep}](CF SO ) , and
3
2
3
3 2
a number of points are worthy of note:
1
1
Fig. 3. H, H COSY spectrum of [Pt(CH
3
2 3 3 2
CN) {(S)-MeO-Biphep}](CF SO ) in the aromatic region, identifying H3–H5.

3206
D. Schott et al. / Inorganica Chimica Acta 360 (2007) 3203–3212
˚
2
. The three low frequency proton signals, between d ca.
.6 and d ca. 7.2, are associated with the biaryl backbone
and [Pt(l-Cl){(S)-MeO-Biphep}] (CF SO ) , 8.1 A, are
2 3 3 2
6
clearly quite different. Similarly, the cation rH values
1
1
˚
moiety and not with the P-phenyl rings (see the H, H
for [Pt(CH CN) {(R)-p-tol-BINAP}](CF SO ) , 7.1 A,
3
2
3
3 2
1
3
1
˚
correlation in Fig. 3 and the C, H long-range correla-
tion in Fig. 4) and
and [Pt(l-Cl){(R)-p-tol-BINAP}] (CF SO ) 8.6 A, also
2 3 3 2
support this idea while showing that the (R)-p-tol-
BINAP salts are, as expected, larger than {(S)-MeO-
Biphep analogs. The rH values for the two neutral
dichloro-complexes, PtCl {(S)-MeO-Biphep}, 5.9 A
and PtCl {(R)-p-tol-BINAP}], 6.5 A, are in agreement
with the difference in size between these two chelating
diphosphine compounds. Further, we note (a) that the
rH value for the cation of [Pt(l-OH){(S)-MeO-Bip-
3
. The remaining well resolved proton resonance, at d ca.
7
.48, arises from the meta protons of the P-phenyl rings
˚
(
see Fig. 5).
2
˚
2
1
3
A selection of C assignments is given in the experimen-
tal section.
˚
2
.1. Diffusion results
hep}] (BF ) , 7.8 A, is consistent with a dinuclear spe-
2
4 2
cies and (b) that the rX-ray from the solid-state
structure of [Pt(l-Cl){(S)-MeO-Biphep}] (CF SO ) ,
Table 1 shows the D values and the hydrodynamic radii,
rH (A), for the Pt-salts, measured as 2 mM solutions in
2
3
3 2
˚
˚
7.8 A, is in good agreement with the hydrodynamic
radius calculated for the same cation in CD Cl . Corre-
CD Cl . Two points are clear:
2
2
2
2
lations between rH(NMR) and rX-ray are known [12] and
1
. The difference in size between the mono-and dinuclear
species is reflected in their rH values, thus suppor-
ting the view that PGSE measurements are useful struc-
ture probes. As an example, the cation rH values
usually reasonable.
2. Using the r values for the anion as an indication of the
H
ion pairing, one notes that there seems to be more ion
ꢀ
pairing of the CF
3
SO3 anion in the dinuclear species
˚
for [Pt(CH CN) {(S)-MeO-Biphep}](CF SO ) , 6.6 A,
[Pt(l-Cl){(S)-MeO-Biphep}] (CF SO ) , r (anion) =
2 3 3 2 H
3
2
3
3 2
1
3
1
Fig. 4. C, H multiple bond correlation spectrum for [Pt(CH
3
CN)
2 3 3 2
{(S)-MeO-Biphep}](CF SO ) which assigns the MeO-Biphep backbone proton, H4,
3
13
1
at 7.17 ppm, via a J( C, H) interaction with the ipso-C-OMe resonance at 157.8 ppm.

D. Schott et al. / Inorganica Chimica Acta 360 (2007) 3203–3212
19
3207
1
.2. H, F Overhauser results
2
As it was not obious why the dinuclear salts, e.g., [Pt(l-
Cl){(S)-MeO-Biphep}] (CF SO ) , with the two positive
2
3
3 2
charges spread across two metals, should show more ion
pairing than for the mononuclear dicationic bis-nitrile,
1
[
Pt(CH CN) {(S)-MeO-Biphep}](CF SO ) , several H,
3
2
3
3 2
1
9
F Overhauser (HOESY) spectra were measured. The
HOESY spectrum (see Fig. 5) for the dinuclear MeO-Bip-
hep salt shows strong cross peaks which arise from the
protons of the P-phenyls (which are expected [6–9,12])
but also
H
H
H
MeO
MeO
P
PPh2
fragment of the MeO-Biphep in
[
Pt(μ-Cl){(S)-MeO-Biphep}] (CF SO ) ,
2
3
3 2
with the arrows showing the HOESY contacts
two fairly strong cross-peaks from two of the three MeO-
Biphep biaryl protons, H-3 and H-4, but nothing to H-5
and only a very weak signal from the methoxy-group. This
suggests that the anion is localized close to the P-phenyl
groups, i.e., close to the platinum atom and the partially
positively charged P-atoms. In the analogous HOESY
spectrum for the bis-nitrile (not shown), there are no
cross-peaks to either of the backbone protons H-3 or H-4.
Fig. 5. HOESY spectrum for [Pt(l-Cl){(S)-MeO-Biphep}]
0 mM in CD Cl . Note the absence of a contact to H5 and the barely
detectable cross-peak from the methoxy-group.
2 3 3 2
(CF SO ) ; ca.
1
2
2
˚
ꢀ
3
SO3 in the bis-nitrile, [Pt-
5
(
4
.5 A, than for the CF
MeO
MeO
P
NCCH3
2+
CH CN) {(S)-MeO-Biphep}](CF SO ) , r (anion) =
3
˚
2
3
3 2
H
Pt
P
Ph
.8 A. In the absence of significant ion pairing, e.g., a
NCCH3
2
salt containing the CF SO anion dissolved in methanol
3
3
˚
solution, an r value for the anion of ca. 3 A is expected
H
[
7–9,12]. Consequently, in both the Pt dications, there
However, there are now new, strong, cross-peaks to the
methyl groups of the complexed acetonitrile ligands, plus
strong cross peaks to the P-phenyl protons, as noted previ-
ously. Obviously the positive charge on the cation is spread
over the two N-atoms as well as on the two P-atoms (and,
of course, the Pt). This dispersion of the positive charge
is a substantial amount of ion pairing. For the (S)-
MeO-Biphep salts, the BF4 anions show the same
trend, although the amount of ion pairing seems to be
somewhat smaller for this anion, relative to the triflate
salts.
ꢀ
1
over a larger number of atoms rationalizes the observation
ꢀ
that the ion pairing to the CF
3
SO3 is not quite so pro-
1
ꢀ
nounced in this mononuclear dicationic complex. Macchi-
oni and co-workers, [33–39] in an extensive series of papers
involving H, F HOESY measurements, have shown that
In methanol solution a typical r
H
value for the BF4 anion would be
˚
ca. 2.5 A. For the triflate, one cannot readily distinguish between ion
pairing, alone, and partial complexation together with partial ion pairing.
1
19

3208
D. Schott et al. / Inorganica Chimica Acta 360 (2007) 3203–3212
Table 1
ꢀ10
2
ꢀ1
˚
a
Values for the diffusion coefficient, D (·10
m s ) and the hydrodynamic radii, r
H
(A), in 2 mM CD
2
Cl
2
solutions for the Pt-salts
Dication
(S)-MeO-Biphep
(R)-p-tol-BINAP
a
a
D
r
H
D
r
H
Pt(Cl)
2
(P–P)
8.92
5.9
8.21
6.5
2
þ
½
Ptðl-ClÞðP–PÞꢁ2
cation
CF3SO3
6.53
9.54
8.1
5.5
6.17
9.40
8.6
5.6
ꢀ
ꢀ
2
+
Pt(CH
3
CN)
2
(P–P)
cation
CF3SO3
8.07
11.13
6.6
4.8
7.5
9.84
7.1
5.4
2þ
½
Ptðl-ClÞðP–PÞꢁ2
cation
BF4
6.64
10.51
8.0
5.0
ꢀ
2
+
Pt(CH
3
2
CN) (P–P)
cation
8.05
6.6
7.8
3.9
3.9
b
6
.82
ꢀ
BF4
13.67
13.53
ꢀ
d
BF4
½
Ptðl-OHÞðP–PÞꢁ22þ
cation
BF4
6.82
7.8
ꢀ
not measurable, too broad at RT
a
ꢀ1 ꢀ1
19
1
1
CH
2
Cl
2
g (299 K, kg s
m
): 0.414. The values for F were corrected to the gyromagnetic ratio relative to H. The cations were measured via H,the
1
9
anions via F NMR.
b
Impurity.
˚
Fig. 6. A view of the dinuclear Pt chloro-bridged MeO-Biphep dication. Selected bond distances (A) and angles (ꢁ): Pt(1)–Pt(1) 3.5805(7), Pt(1)–P(2)
0 0 0
.236(1), Pt(1)–P(1) 2.244(1), Pt(1)–Cl(1) 2.373(1), Pt(1)–Cl(1) 2.389(1); P(2)–Pt(1)–P(1) 93.26(5), P(2)–Pt(1)–Cl(1) 92.39(5), P(1)–Pt(1)–Cl(1) 172.20(5),
2
0
0
P(2)–Pt(1)–Cl(1) 172.26(5), P(1)–Pt(1)–Cl(1) 92.45(4), Cl(1) –Pt(1)–Cl(1) 82.46(5), Pt(1) –Cl(1)–Pt(1) 97.47(4). Primed atoms are obtained from those of
the asymmetric unit by the symmetry operation: (1 ꢀ x) + 1; ꢀy; z. Ellipsoids drawn at 50% probability.
unsaturated nitrogen donor ligands in cationic complexes
are often associated with a substantial amount of positive
charge and, therefore, that the anions are attracted to these
ligands.
located across a binary axis that generates the two ‘‘Pt(l-
Cl) Pt’’ dimers in the crystallographic unit cell. The geom-
2
etries of the two cations do not differ significantly and,
therefore, only a view of one of the two dications, together
with selected bond parameters, is given in Fig. 6. The
immediate coordination sphere around each Pt atom con-
sists of the two P-atoms from a coordinated MeO-Biphep
chelate and the two bridging chloride ligands. The Pt-
ligand–atom bond lengths and the coordination bond
angles are rather standard and a selection of these is given
in the caption to Fig. 6. There is no bending of the
2
Biphep}] (CF SO )
.3. Solid-state structure of [Pt(l-Cl){(S)-MeO-
2
3
3 2
The structure of this dicationic dinuclear Pt-complex
was determined via X-ray diffraction methods. There are
two independent half molecules in the asymmetric unit

D. Schott et al. / Inorganica Chimica Acta 360 (2007) 3203–3212
3209
Pt(Cl) Pt four-membered ring (i.e., no butterfly type struc-
experiments were carried out at a set temperature of
299 K within the NMR probe.
2
ture), due to the crystallographic symmetry, and the two
0
Pt-atoms are sufficiently far apart, Pt(1)-Pt(1) =
As indicated in Table 1, diffusion values were measured
on 2 mM dichloromethane solutions. Cation diffusion rates
˚
3
.5805(7) A, such that a metal–metal bonding interaction
1
is extremely unlikely. The two P-phenyl groups on any
one P-atom occupy pseudo-equatorial and pseudo-axial
positions with respect to the plane defined by the two
P-atoms, the metal and the two bridging halogens.
were measured using the H signal from either the aro-
1
matic, MeO, or CH CN protons depending on the H spec-
3
trum considered. Anion diffusion data was obtained from
1
9
the F NMR spectrum of the anion. The error in the D
values is thought to be ± 0.06.
3
. Conclusions
4.4. HOESY
Once again the PGSE diffusion methodology shows
1
9
1
itself to be useful in connection with recognizing mono-ver-
sus dinuclear complexes in solution. The amount of ion
pairing can be estimated qualitatively, and, when taken
F– H HOESY spectra were measured at concentra-
tions of 10 mM, in dichloromethane solutions, at 299 K
with a 0.8 s mixing time.
1
19
together with H, F Overhauser data, one obtains a view
as to where the anion resides and, thus, why one type of
salt might reveal more ion pairing than a related species.
4.5. PtCl ((S)-MeO-Biphep)
2
ꢀ
1
ꢀ3
PtCl (SC H ) (500 mg, 442.3 g mol , 1.13 · 10 mol)
and (S)-Meo-Biphep (659 mg, 582.6 g mol , 1.13 · 10
mol) were placed in a Schlenk vessel. CH Cl (15 mL) was
2
4
8
ꢀ1
ꢀ3
4
. Experimental
2
2
added under nitrogen and the resulting yellow solution
was stirred during approximately 14 h. The CH Cl was
4
.1. General Comments
2
2
removed i.v. and the resulting pale yellow solid was washed
several times with hexane in order to remove excess (S)-
Meo-Biphep and free SC H . After drying one obtains
All air sensitive manipulations were carried out under a
nitrogen atmosphere. All solvents were dried over appro-
priate drying agents, distilled under nitrogen. Deuterated
solvents were dried by distillation over molecular sieves,
and stored under nitrogen. The ligands (R)-p-tolyl-BINAP
4
8
1
680 mg, 72%, of product. NMR: H (CH Cl , 299 K,
2
2
300 MHz) 7.84 (b, ortho-phenyl ring a), 7.68 (m, ortho-phe-
nyl ring b), 7.48 (m, meta-phenyl b), 7.45 (m, para-phenyl
rings a and b), 7.30 (meta-phenyl ring a), 6.96 (dd, H4),
(
Strem) and the silver salts (Aldrich) were purchased from
3
1
commercial sources and used as received. The (S)-MeO-
Biphep was a gift from F. Hoffmann La-Roche, Basel,
Switzerland. The bis-tetrahydrothiophene (THT) complex
PtCl (THT) was synthesized in our laboratory according
6.72 (H3), 6.46 (d, H5), 3.52 (s, OMe); P (CH Cl ,
2 2
1
3
299 K, 121 MHz) 8.13 (JPPt 3647 Hz);
C (CH Cl ,
2 2
299 K, 75 MHz) 55.0 (s, OMe), 112.7 (s, C5), 124.7 (C3)
127.2 (meta-phenyl ring), 127.8 (tb, meta-phenyl ring),
129.2 (C4), 130.7 (s, para-phenyl ring), 131.4 (s, para-phenyl
ring), 135.2 (tb, ortho-phenyl ring), 157.5 (tb, quaternary
MeO-C); EA: Anal. Calc for C H O Cl P - Pt(H O): C,
2
2
to literature methods [40].
NMR spectra were recorded with Bruker DPX-300, 400
and 500 and 700 MHz spectrometers at room temperature
unless otherwise noted. Elemental analysis and mass spec-
tra were performed at ETH Z u¨ rich.
3
8
32
2
2
2
2
52.68; H, 3.92. Found: C, 52.69; H, 3.89%.
4
.2. General procedure (NMR)
4.6. [Pt(l-Cl)((S)-MeO-Biphep)] [CF SO ]
2 3 3 2
1
31
13
19
H, P, C and F NMR spectra were recorded on
Under an N atmosphere; PtCl ((S)-MeO-Biphep)
2 2
ꢀ
5
Bruker Avance 300, 400, 500 NMR spectrometers. Deuter-
ated solvents were dried by distillation over molecular
sieves, and stored under N2.
(60 mg, 7.07 · 10 mol) was dissolved in 5 mL of CH Cl
2
2
ꢀ
5
in a Schlenk tube. AgCF SO (18.16 mg, 7.07 · 10 mol)
3
3
was suspended in yet another 5 mL of CH Cl . and after
2
2
stirring for 15 min, the AgCF SO suspension was trans-
3
3
4
.3. Diffusion
ferred into the PtCl ((S)-MeO-Biphep) solution. After stir-
2
ring for 1 h, the white-grey solid, suspended in the pale
yellow solution is filtered over Celite via canula. The sol-
vent is reduced i.v. and the resulting solid is dried: Yield:
All the PGSE NMR measurements were performed on a
Bruker Avance spectrometer, 400 MHz, equipped with a
microprocessor-controlled gradient unit and a multinuclear
inverse probe with an actively shielded Z-gradient coil. The
gradient shape is rectangular and its length was 1.75 ms.
The gradient strength was increased by steps of 4% during
the course of the experiment. The time between midpoints
of the gradients was 167.75 ms for all experiments. The
1
56 mg, 82%. NMR: H (CH Cl , 299 K, 300 MHz) 7.69
2
2
(ortho-phenyl ring a) 7.63 (meta-phenyl ring a), 7.52
(para-phenyl ring a), 7.43 (ortho-phenyl ring b), 7.29 (meta-
andpara-phenyl ring b), 7.13 (H4). 7.05 (H3), 6.55 (d, H5),
3
1
3.45 (s, OMe); P (CH Cl , 299 K, 121 MHz) 7.82 (J
PPt
2
2
1
3
3776 Hz); C (CH Cl , 299 K, 75 MHz) 55.2 (s, OMe),
2
2

3210
D. Schott et al. / Inorganica Chimica Acta 360 (2007) 3203–3212
1
31
1
14.4 (s, C5), 124.7 (C4), 129.0 (meta-phenyl ring a), 130.3
gested by H and P NMR. To verify this, an independent
(
1
(
C3), 132.1 (para-phenyl ring b), 132.9 (para-phenyl ring a),
sample of [Pt(l-OH)((S)-MeO-Biphep)] [BF ] was synthe-
sized according to literature [41]. NMR for
2
4 2
1
9
35.0 (ortho-phenyl ring), 157.8 (quaternary MeO-C);
F
1
CH Cl , 299 K, 282.3 MHz) ꢀ79.2 (s). MS: 812.9
[Pt(CH CN) ((S)-MeO-Biphep)][BF ] :
H
(CH Cl ,
2 2
2
2
3
2
4 2
1
Pt(Cl)((S)-MeO-Biphep) 775.9 Pt((S)-MeO-Biphep). EA:
Calc.: C, 47.48; H, 3.35. Found: C, 47.54; H, 3.36%.
299 K, 400 MHz) 8.0–6.3 (50 H, aromatic region), 3.53
1
31
(12 H, OMe); P (CH Cl , 299 K, 161 MHz) ꢀ1.69 (J
2
2
PPt
1
9
3
630 Hz); F (CH Cl , 299 K, 376 MHz) ꢀ152.9 (s).
2
2
4
.7. [Pt(CH CN) ((S)-MeO-Biphep)][CF SO ]
3 2 3 3 2
4
.10. [Pt(l-OH)((S)-MeO-Biphep)] [BF ]
2 4 2
ꢀ
5
PtCl ((S)-MeO-Biphep) (60 mg, 7.07 · 10 mol) and
2
3
8 mg (2.1 equiv.) of AgCF SO were mixed in 20 ml
CH CN solution. The yellow solution remained turbid dur-
ing the reaction time and a precipitate is formed at a very
early stage. The reaction mixture was left to stir overnight
under N . The resulting suspension was filtered through a
Celite patch via canula, and the CH CN removed under
vacuum. The yield is quantitative. NMR: H (CD CN,
99 K, 700 MHz) 7.77 (ortho-phenyl ring a) 7.65 (m,
para-phenyl ring a), 7.47 (meta-phenyl ring a), 7.70
Under an N atmosphere; a solution of AgBF (27.6 mg,
2 4
3
3
ꢀ5
14.15 · 10 mol) in 6 mL of MeOH/H O (90/10) was
added to a suspension of PtCl ((S)-MeO-Biphep) (60 mg,
7.07 · 10
Schlenk tube. The reaction mixture was stirred for 1 h.
The resulting suspension was then filtered over Celite and
the volume reduced in vacuo to ca. 1 mL. At this point a
white crystalline precipitate formed which was recovered
by decantation and then washed with several aliquots of
cold methanol. The resulting white solid is dried in vacuo.
3
2
2
ꢀ5
mol) in 6 mL of MeOH/H O (90/10) in a
2
2
3
1
3
2
(
(
(
2
2
ortho-phenyl ring b), 7.72 (para-phenyl ring b), 7.66
meta-phenyl ring b), 6.71 (d, H5). 6.95 (H3), 7.17
ꢀ
5
1
Yield: 47 mg, 2.75 · 10 mol, 75%. NMR: H (CH Cl ,
2
2
3
1
dd,H4), 3.49 (s, OMe), 2.00 (s, CH CN); P (CH Cl ,
299 K, 300 MHz) 7.38 (ortho-phenyl ring a) 7.18 (meta-
phenyl ring a), 7.77 (ortho-phenyl ring b), 7.50, 7.62 (meta-
and para-phenyl ring b), 7.07 (m, H4), 6.72 (m, H3), 6.53
3
2
2
1
3
99 K, 283 MHz) ꢀ1.94 (J
3939 Hz); C (CH Cl ,
PPt 2 2
99 K, 176 MHz) 0.5 (CH CN) 55.2 (s, OMe), 115.2 (s,
C5), 124.8 (m, C3), 129.1 (m, meta-phenyl ring b), 129.2
m, meta-phenyl ring a), 130.7 (m, C4), 133.1 (s, para-phe-
3
3
1
(d, H5), 3.53 (s, OMe), ꢀ1.38 (s, (l-OH)); P (CH Cl ,
2
2
19
(
299 K, 121 MHz) 1.64 (J
3663 Hz);
F (CH Cl ,
2 2
PPt
nyl ring b), 133.4 (s, para-phenyl ring a), 134.8 (ortho-phe-
299 K, 282.3 MHz) ꢀ152.9 (s).
9
nyl ring b), 157.8 (quaternary MeO-C); F (CH Cl , 299 K,
PtCl ((R)-p-tol-BINAP), [Pt(l-Cl)((R)-p-tol-BINAP)] -
2
2
2
2
2
82.3 MHz) ꢀ79.2 (s). MS: 816.7 Pt(CH CN)((S)-MeO-
[CF SO ] , and [Pt(CH CN) ((R)-p-tol-BINAP)][CF SO ]
3 3 2 3 2 3 3 2
were prepared analogously to the corresponding MeO-Bip-
hep complexes.
3
Biphep), 775.9 Pt((S)-MeO-Biphep). EA: Calc.: C, 47.48;
H, 3.35. Found: C, 47.54; H, 3.36%.
4.11. PtCl ((R)-p-tol-BINAP)
2
4
.8. [Pt(l-Cl)((S)-MeO-Biphep)] [BF ]
2 4 2
ꢀ
1
ꢀ4
ꢀ1
From PtCl (SC H ) (100 mg, 442.3 g mol , 2.26 · 10
2
4
8
ꢀ
4
PtCl ((S)-MeO-Biphep) (100 mg, 1.18 · 10 mol) was
mol) and (R)-p-tol-BINAP (153 mg, 678.8 g mol ,
2.26 · 10 mol) one obtains 99 mg, Yield: 94%. NMR:
H (CH Cl , 299 K, 300 MHz) 8.00–6.4 (28 H, aromatic
2 2
2
ꢀ4
dissolved in 10 mL of CH Cl in a Schlenk tube under an
N atmosphere. To this was added solid AgBF (23 mg,
1
solid, observed in the pale yellow solution, was removed
via filtration. The solvent is reduced i.v. and the resulting
crude product is dried. Yield: 97.5 mg, 92%. NMR: H
2
2
1
1
2
4
ꢀ
4
1
1
31
.18 · 10 mol). After stirring for 3 h, the white-grey
region), 2.47 (6 H, Me), 2.04 (6 H, Me); P (CH Cl ,
2 2
1
9
299 K, 121 MHz) 8.33 (JPPt 3672 Hz);
299 K, 282.3 MHz) ꢀ78.2 (s).
F (CH Cl ,
2
2
1
1
(
CH Cl , 299 K, 400 MHz) 8.0–6.3 (50 H, aromatic
4.12. [Pt(l-Cl)((R)-p-tol-BINAP)] [CF SO ]
2 3 3 2
2
2
1
31
region), 3.45 (12 H, OMe); P (CH Cl , 299 K, 161 MHz)
2
2
1
9
ꢀ5
8
ꢀ
.74 (JPPt 3780 Hz),
152.9 (s).
F (CH Cl , 299 K, 376 MHz)
From PtCl ((R)-p-tol-BINAP) (100 mg, 10.6 · 10
5
2
2
2
ꢀ
mol), and AgCF SO (27.2 mg, 5.29 · 10 mol) one
3
3
1
obtains 93 mg, Yield: 83%. NMR: H (CH Cl , 299 K,
2
2
1
1
3
00 MHz) 8.0–6.4 (56 H, aromatic region), 2.13 (12 H,
Me); P (CH Cl , 299 K, 121 MHz) 9.76 (J
3
1
4
.9. [Pt(CH CN) ((S)-MeO-Biphep)][BF ]
3
3663 Hz);
PPt
2
4 2
2
2
1
9
F (CH Cl , 299 K, 282.3 MHz) ꢀ78.8 (s).
2
2
ꢀ
5
PtCl ((S)-MeO-Biphep) (50 mg, 5.90 · 10 mol) and
2
2
4 mg (2.03 equiv.) of AgBF4 were mixed in 20 mL
4.13. [Pt(CH CN) ((R)-p-tol-BINAP)][CF SO ]
3 2 3 3 2
CH CN. The reaction mixture was then stirred for 2 h
3
ꢀ
5
under N . The resulting suspension was filtered over Celite,
From PtCl (R)-p-tol-BINAP) (50 mg, 5.29 · 10 mol)
2
2
and the CH CN is removed i.v. The crude solid obtained is
and 28.4 mg (2.1 equiv.) of AgCF SO one obtains a quan-
3
3
3
a mixture of the desired [Pt(CH CN) ((S)-MeO-Bip-
titative amount of the product as a crude brownish solid.
NMR: H (CH Cl , 299 K, 300 MHz) 8.0–6.5 (56 H, aro-
2 2
3
2
1
1
hep)][BF ] and [Pt(l-OH)((S)-MeO-Biphep)][BF ] as sug-
4
2
4 2

D. Schott et al. / Inorganica Chimica Acta 360 (2007) 3203–3212
3211
1
1
31
matic region), 2.52 (6 H, Me), 2.10 (6 H, Me);
P
from the Fourier difference maps, and satisfactorily refined
anisotropically, even though with the expected large values
of the ADP’s. However, for each of the two half [Pt(l-
1
9
(
CH Cl , 299 K, 121 MHz) ꢀ0.8 (J
3675 Hz),
PPt
F
2
2
(
CH Cl , 299 K, 282.3 MHz) ꢀ78.1 (s).
2
2
Cl){(S)-MeO-Biphep}] dimers that form, the asymmetric
2
4
.14. X-ray crystal structure
unit (the dimeric units are generated by a crystallographic
ꢀ
binary axis), there is a half CF
3
SO3 disordered across a
Air stable, light yellow crystals of [Pt(l-Cl){(S)-MeO-
Biphep}] (CF SO ) , suitable for X-ray diffraction were
crystallographic, but not molecular, binary axis. The
resulting disorder is extremely difficult to model. The stron-
gest peaks in the Fourier difference maps were assumed to
represents the F, S and O atoms. A model, in which both
the CF and SO groups occupy the same positions, with
0.5 occupancy, was constructed and refined with isotropic
displacement parameters. Although the resulting geometry
could only be very approximate, most of the scattering den-
sity is taken into account and the refinement converged sat-
isfactorily. This disorder of the triflates does not affect the
geometry of the cations, as this is independent of the model
assumed for the refinement.
2
3
3 2
obtained by crystallization from CH Cl /hexane. A crystal
2
2
of the compound was mounted on a Bruker APEX diffrac-
tometer, equipped with a CCD detector, for the space
group and cell determination and for the data collection.
The space group was determined from the systematic
absences, while the cell constants were refined, at the end
of the data collection with the data reduction software
SAINT [42]. The experimental conditions for the data collec-
tion, crystallographic and other relevant data are listed in
Table 2 and in Supplementary material.
3
3
The collected intensities were corrected for Lorentz and
polarization factors [42]. and empirically for absorption
using the SADABS program [43]. The structure was solved
by direct and Fourier methods and refined by full matrix
Upon convergence, the final Fourier difference map
showed no significant features. The contribution of the
hydrogen atoms, in their calculated position was included
in the refinement using a riding model (B(H) = axB
(A ), where a = 1.5 for the hydrogen atoms of the methyl
groups and a = 1.4 for the other hydrogen atoms). No
extinction correction was deemed necessary. The scattering
factors used, corrected for the real and imaginary parts of
the anomalous dispersion, were taken from the literature
[45]. The handedness of the structure was confirmed by
refining the Flack’s parameter [46]. All calculations were
carried out by using the PC version of the programs:
WINGX [47], SHELX-97 [44] and ORTEP [48].
(Cbonded)
P
2
2
˚
least squares, [44] minimizing the function [ w(Fo ꢀ (1/
2
c
2
k)F ) ] and using anisotrospic displacement parameters
for all atoms of the cations, except for the hydrogens (see
below).
Of the two triflate anions, expected for each dimeric cat-
ionic Pt moiety, one was readily found, in general position,
Table 2
Experimental data for the X-ray diffraction study of compound: [Pt(l-
Cl){(S)-MeO-Biphep}] (CF SO )
2 3 3 2
Formula
78 2 6 8 4 2 2
C H64Cl F O P Pt S
Acknowledgements
Formula weight
Data collection T (K)
Diffractometer
Crystal system
Space group (No.)
1892.37
293 (2)
Brucker APEX CCD
orthorhombic
P.S.P. thanks the Swiss National Science Foundation,
and the ETH Zurich for support, as well as the Johnson
Matthey organization for the loan of platinum salts. A.A.
thanks MURST for a grant (PRIN 2004).
1 1
P2 2 2 (18)
˚
a (A)
26.7954(7)
30.2583(8)
9.9179(3)
8041.3(4)
4
˚
b (A)
˚
c (A)
˚
3
V (A )
Appendix A. Supplementary material
Z
ꢀ3
D
calc (g cm
)
1.563
37.39
ꢀ
1
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/
j.ica.2007.03.029.
l (cm
)
Radiation
Mo Ka (graphite monochromated,
k = 0.71073 A)
˚
h Range (ꢁ)
Data collected
1.52 < h < 26.07
75471
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