Synthesis and solid-state characterization of platinum complexes with hexadentate amino- and iminophosphine ligands

Article abstract of DOI:10.1039/b907737e

Hexadentate ligands cis,cis-C₆H₉(NCHC ₆H₄(PPh₂))₃ (1) and cis,cis-C ₆H₉(NHCH₂C₆H₄(PPh ₂))₃ (2) were synthesized

Full text of DOI:10.1039/b907737e

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PAPER
www.rsc.org/dalton | Dalton Transactions
Synthesis and solid-state characterization of platinum complexes with
hexadentate amino- and iminophosphine ligands†
Marie-He´le`ne Thibault,a Bryan E.G. Lucier,b Robert W. Schurko*b and Fre´de´ric-Georges Fontaine*a
Received 17th April 2009, Accepted 29th June 2009
First published as an Advance Article on the web 29th July 2009
DOI: 10.1039/b907737e
=
Hexadentate ligands cis,cis-C6H9(N CHC6H4(PPh2))3 (1) and cis,cis-C6H9(NHCH2C6H4(PPh2))3 (2)
were synthesized starting from cis,cis-1,3,5-triaminocyclohexane, and characterized using NMR
spectroscopy and single-crystal X-ray diffraction. These ligands can bind both Pt(0) and Pt(II) metal
centers using either or both of the soft phosphine moieties and the hard amine/imine moieties. In many
cases the resulting complexes are negligibly soluble; hence, 31P and 195Pt solid-state NMR (SSNMR)
spectroscopy was applied to analyse the bonding modes of the hexadentate ligands. The 195Pt SSNMR
spectroscopy of these complexes is particularly challenging, since 1H–195Pt cross polarization is
extremely inefficient, the 195Pt longitudinal relaxation times are extremely long and the 195Pt powder
patterns are expected to be quite broad due to platinum chemical shift anisotropy. It is demonstrated
that the ultra-wideline 195Pt SSNMR spectra can be efficiently acquired with a combination of
frequency-stepped piecewise acquisitions and cross-polarization/Carr–Purcell Meiboom–Gill
(CP/CPMG) NMR experiments. The 195Pt and 31P SSNMR data are correlated to important structural
features in both Pt(0) and Pt(II) species.
and the affinity of hard ligands, such as amines and imines, to
Introduction
bind high-oxidation state metals.7 The cis,cis-triaminocyclohexane
The design and synthesis of multidentate ligands, which complex
framework is known to bind selectively and strongly with early
to a variety of metals via two or more atoms, continue to
be an important research area in coordination chemistry. The
metals when all of the amino functionalities are in the axial
position.8 Hence, it is logical to postulate that the addition of
success of multidentate ligands such as EDTA, corroles and
soft donors (such as phosphines) to the three amino moieties will
porphyrins in stabilizing metal centers in various oxidation states
also favor late metal coordination.
have spurred this continued interest. More recently, a number of
Some heterobimetallic species form as precipitates during syn-
studies have demonstrated the use of transition metal complexes
thesis. Though crystalline in nature, their insolubility prohibits the
containing phosphorus- or nitrogen-based multidentate ligands
growth of single crystals of the size and quality necessary for single-
as catalysts for various transformations such as olefin and
crystal X-ray diffraction experiments. Since the species discussed
ketone hydrogenation,1 allylic alkylation,2 Suzuki cross-coupling
herein feature both phosphorus-containing ligands and platinum
reactions and hydroboration,3 and olefin oligomerization.4 In
atoms, 31P and 195Pt solid-state NMR (SSNMR) experiments
homogeneous catalysis, where controlled variability of the metal
should prove useful for their structural characterization. While
oxidation state at the different steps of a catalytic cycle is crucial,
31P SSNMR experiments conducted under conditions of magic-
the adaptability observed in hemilabile ligands proves to be a
angle spinning (MAS) and cross polarization (CP) are routine, the
major asset in preventing the degradation of the catalyst and
195Pt SSNMR experiments on such systems are more challenging,
enhancing reactivity.5
since the platinum chemical shift anisotropies (CSA) are expected
One of our groups has initiated a research program aimed at
to be very large,9 resulting in extremely broad patterns with
synthesizing heterobimetallic species having both Lewis acids and
correspondingly low signal to noise (S/N) ratios. However, there
late transition metals in the same framework.6 In order to include
are a number of techniques that can be applied which are suitable
two transition metals having distinct reactivity on the same ligand,
for the enhancement of S/N and the acquisition of high quality
it is necessary to have at least two sites with distinct chemical
195Pt NMR spectra. In particular, the combination of frequency-
affinities. One of the best strategies relies on the affinity of soft
stepped piecewise acquisition of extremely broad spectra,10 and
ligands, such as phosphines, to bind low-oxidation state metals,
S/N enhancement via CP and repeated echo acquisition via
quadrupolar Carr–Purcell Meiboom–Gill (QCPMG) type pulse
aDe´partement de Chimie, Universite´ Laval, 1045 Avenue de la Me´decine,
sequences,11 have proven very successful for the acquisition of
Que´bec, Que´bec, Canada G1V 0A6. E-mail: frederic.fontaine@chm.
ultra-wideline (UW) SSNMR spectra of both spin-1/2 and
quadrupolar nuclei.12
Herein, in the first of a series of articles that will be de-
voted to the stabilization of heterobimetallic species with the
cis,cis-triaminocyclohexane framework, we report the synthesis
of two new hexadentate trisaminotrisphosphino ligands and their
ulaval.ca
bDepartment of Chemistry & Biochemistry, University of Windsor, 401
Sunset Ave., Windsor, Ontario, Canada N9B 3P4. E-mail: rschurko@
uwindsor.ca
† CCDC reference numbers 718421 for 1, 718422 for 2, and 718423 for
6. For crystallographic data in CIF or other electronic format see DOI:
10.1039/b907737e
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Scheme 1
coordination behavior in the presence of Pt(0) and Pt(II) precursor
complexes. The structures of these complexes are characterized
with a combination of solution and solid-state NMR experiments,
FTIR spectroscopy and X-ray diffraction techniques.
contrary to what is observed in solution. In both compounds, one
of the lone pair of electrons of the phosphine moieties is rotated
in the opposite direction relative to the other two. The ORTEP
diagrams illustrate the sheer bulk of the iminophosphanes and the
possible difficulties of designing a synthesis that would result in
the orientation of all three functional groups in axial positions. As
Results and discussion
˚
expected, the average C–N distances (1.259(6) A) in 1 are narrower
˚
than the average distances in 2 (1.462(9) A), and are characteristic
Ligand synthesis
of this family of compounds.15
The condensation of three equivalents of 2-diphenyl-phosphanyl-
benzaldehyde with cis,cis-1,3,5-triaminocyclohexane affords the
Coordination chemistry with platinum(0)
=
Schiff base cis,cis-C6H9(N CHC6H4(PPh2))3 (1, 67% yield), which
is then reduced using a slight excess of LiAlH4 to afford the
hexadentate ligand cis,cis-C6H9(NHCH2C6H4(PPh2))3 (2, 74%,
yield) as a colorless powder, as depicted in Scheme 1.
The addition of a colourless solution of tris(bicyclo[2.2.1]hept-
ene)platinum(0) (Pt(nbr)3) to a solution containing an equimolar
amount of compound 1 in toluene gave an orange solid after
removal of the volatile materials. A series of new signals and the
1
The 31P{ H} NMR spectrum of 1 in benzene-d6 exhibits a
1
single resonance for the three equivalent phosphines at -12.6 ppm,
absence of the characteristic peak of 1 at -12.6 ppm in the 31P{ H}
close to -13.0 ppm observed for a similar tripodal ligand
NMR spectrum indicate that all the phosphorus moieties of 1 are
involved in a coordination to platinum. Three pairs of doublets
of equal integrated intensities are observed at 50.7 and 28.6 ppm
(2JP–P = 7.5 Hz; 1JP–Pt = 2080 Hz and 1JP–Pt = 1820 Hz, respectively,
13
=
N(CH2CH2N CH(o-C6H4)PPh2)3. The single resonance indi-
cates that the phosphorus sites are chemically equivalent, and
implies that the cyclohexane moiety likely has C3 symmetry
which makes all moieties equivalent. The 1H NMR spectrum
of 1 is consistent with this hypothesis: the hydrogen atoms on
the cyclohexane ring are observed at three different resonances at
2.98, 1.97 and 1.41 ppm. The 3JH–H coupling constants of 11.7 Hz
and 3.6 Hz for the hydrogens geminal to the imine moiety at
2.98 ppm are typical of axial protons,14 confirming that bulky
iminophosphane groups are in equatorial positions. Furthermore,
the doublet at 9.04 ppm (4JH–P = 4.9 Hz) is typical of an imine
moiety close to a phosphorus atom.13
3a), 47.5 and 27.1 ppm (2JP-P = 7.5 Hz; 1JP–Pt = 1990 Hz and 1JP–Pt
=
1940 Hz, respectively, 3b), and 46.1 and 26.5 ppm (2JP–P = 4.1 Hz;
1JP–Pt = 1940 Hz and 1JP–Pt = 1940 Hz, respectively, 3c), as well as
a singlet at 29.0 ppm corresponding to the major product (4).
The 1H NMR spectrum gives further information on the nature
of 3. Three doublets of doublets of equal integrated intensity are
present in the hydride region at -1.2, -1.5, and -2.2 ppm (2JH–Pcis
=
2
26.4 Hz and JH–Ptrans = 172 Hz for 3a,2JH–Pcis = 25.0 Hz and
2
2
2JH–Ptrans = 178 Hz for 3b, and JH–Pcis = 23.0 Hz and JH–Ptrans
=
1
Upon reduction with LiAlH4, the imine resonance in the H
178 Hz for 3c). It is possible to assign each coupling constant
31
NMR spectrum disappears and a new resonance is observed at
by selective 1H{ P} NMR spectroscopy of individual resonances:
4
4.11 ppm (3JH–H = 7.1 Hz, JH–P = 1.5 Hz). The chemical shifts
31P signals at higher field correspond to the phosphine cis to the
hydride, while the resonances at the lower field correspond to the
trans phosphine. Also, three different imine signals are observed at
10.0, 9.6, and 9.5 ppm. Although it was not possible to purify the
reaction mixture or obtain a single crystal for structural analysis,
comparison with the work of Kurosawa et al. on the addition of
related iminophosphines to Pt(nbr)3 allows a clear assignment of
all species.16 3a–3c are assigned as the compounds resulting from
C–H oxidative addition of the C–H imine bond. The assignment
of the resonances for the cyclohexane ring could not be made due
of the protons on the cyclohexyl ring are similar to those of 1,
except for the axial proton on the carbon bound to the amine
(d = 2.11 ppm). The amine resonance, which is the only signal not
1
correlated to a carbon in the H–13C HMQC NMR spectrum, is
found at an unusually low chemical shift (0.78 ppm). The small
1
difference in the 31P{ H} NMR chemical shift between 1 and 2
(-12.6 versus -15.0 ppm) indicates minor chemical modifications
at the phosphorus atoms.
Crystals of 1 and 2 suitable for X-ray analyses were grown by
slow diffusion of pentane in a THF solution, and their ORTEP
representations are illustrated in Fig. 1 and 2, respectively. Both
compounds crystallize in the triclinic space group P-1 with Z =
2. In both solid state structures, the functional groups are in
equatorial positions. A notable feature in the solid state packing
of 1 and 2 is the different conformations of the N-substituents,
1
to the great complexity of the H NMR spectrum; however, it is
speculated that three different isomers are present in solution,
2
=
which may be due to C6H9(k -C,P-N C(C6H4)(PPh2)Pt(H)(P-
=
N))3-x(N CHC6H4(PPh2))x (x = 0 to 2) where one to three metals
are coordinated to the hexadentate ligand for various conformers
present in solution (Scheme 2). Kurosawa et al. assigned the signal
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Fig. 1 ORTEP diagram (50% probability) of 1. Hydrogen atoms have been omitted for clarity.
Table 1 195Pt static CP/CPMG NMR experimental parameters
at 29.8 ppm to a species identified as (N-P)2Pt(nbd) (1JP–Pt
=
3537 Hz). While 4 has a chemical shift very close to this, no 1JP–Pt
coupling constant is observed.
c
Compound
Site
diso (ppm)a
X (ppm)b
k
One equivalent of Pt(nbr)3 was stirred with one equivalent of
2 in toluene. A yellow precipitate insoluble in the usual solvents
appeared after a few minutes (5), differing from the analogous
reaction with 1 (Scheme 3). When the same reaction was performed
on a smaller scale in an NMR tube, free norbornene was observed
by 1H NMR spectroscopy as the only soluble species. In order to
collect more information on this precipitate, SSNMR and FTIR
spectroscopy were applied (vide infra).
5d
6
-4755 (120)
-4400 (75)
-4550 (100)
-4300 (60)
-4400 (50)
N/A
N/A
3600 (125)
3400 (175)
4550 (150)
3950 (75)
-0.82 (4)
-0.88 (7)
-0.75 (5)
-0.80 (7)
7
1
2
8
a Isotropic chemical shift: diso = (d11 + d22 + d33)/3. b Span: X = d11 - d33
.
c Skew: k = 3(d22 - diso)/X. d Due to disorder at the Pt sites, only the centre
of gravity is reported for the spectrum of this compound, as opposed to
the isotropic shift. No CS tensor parameters could be extracted.
Solid-state NMR and IR spectroscopy of the Pt(0) complexes
Absence of a signal in the 195Pt MAS NMR experiments using
long recycle delays (i.e., inter-scan delays of greater than 6 min)
indicate that the 195Pt T1 constants must be extremely long, whereas
1
The solid-state 31P{ H} MAS NMR spectrum of 5 (Fig. 3(a)
and see Table 1 for all parameters obtained from 31P SSNMR
experiments) shows only one signal at diso = 37.0(2.1) ppm
(diso = -16.7 ppm for the uncoordinated ligand, 2). 31P–
1
the failure of the H–195Pt CP/MAS NMR experiments, even at
very low spinning speeds, suggest that 1H and 195Pt nuclei are not
proximate, and that the small 1H–195Pt dipole–dipole couplings are
averaged, resulting in poor CP efficiency.
Therefore, a different strategy was applied to acquire these spec-
tra. Static (i.e., stationary sample) 1H–195Pt CP NMR experiments
were conducted, in order to exploit signal enhancement from CP
and short proton T1’s. However, since these 195Pt static NMR pow-
der patterns are expected to be broad and have very low signal to
noise (S/N), the spectra were acquired using (i) frequency-stepped
195Pt J-coupling is observed via the 195Pt satellites (1JP-Pt
=
4460(350) Hz), and is similar to that of a comparable compound,
1
tris(triphenylphosphine)platinum(0) (d(31P) = 49.9 ppm, JP–Pt
=
1
4550 Hz, C6D6).17 Initial 195Pt{ H} solution NMR experiments
were unsuccessful in detecting any resonances for 5; hence,
solid-state 195Pt NMR experiments were conducted. Both 195Pt
1
MAS Bloch decay (single pulse) and H–195Pt CP/MAS NMR
experiments were attempted on these samples without any success.
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Fig. 2 ORTEP diagram (50% probability) of 2. Hydrogen atoms have been omitted for clarity.
Scheme 2
Scheme 3
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Table 2 31P CP/MAS NMR experimental parameters
signals between 0.8–2.2 ppm, 3.4–4.5 ppm, and 6.5–8.0 ppm.
1
13C{ H} NMR experiments failed to yield any observable signals.
Compound
diso (ppm)
1JP–Pt (Hz)
The broad 1H resonances are suggestive of some sort of dynamic
process; therefore, 1H NMR spectra were acquired at -60 oC. The
1H peaks sharpen, but are still broad, preventing the observation
of any fine structure. Smaller scale syntheses in NMR tubes yielded
free codas the only product detectable insolution, andno insoluble
species were observed.
5
6
7
8
37 (2.1)
10 (1.3)
6 (4.6)
32.3 (3.4), 3.1 (4.2),
-17.1 (3.9)
4460 (350)
3425 (700)
N/A
3310 (700)
1
Interestingly, despite the lack of success with H NMR and
piecewise acquisition and (ii) Carr–Purcell Meiboom–Gill
(CPMG) echo trains.11,12 Piecewise acquisition is necessary since
the entire 195Pt NMR powder pattern cannot be uniformly excited
with standard coils and amplifier powers; hence, the transmitter
frequency is stepped in uniform increments across the entire
pattern, and individual sub-spectra are collected and then co-
added to produce the final pattern. Acquisition of CPMG echo
trains, the lengths of which are limited by the 195Pt transverse
relaxation time constants, T2, further enhance the S/N.
1
1
13C{ H} NMR experiments, relatively clean 31P{ H} spectra were
observed, revealing several broad resonances. For example, when
2 was added to (cod)PtI2, signals were observed at -14.47,
-15.40 ppm, and 4.22 ppm. The former two resonances are
assigned as free pendant phosphines since their chemical shifts are
closely related to the free ligand 2. The latter is attributed to the
presence of a square-planar intermediate, [PtI2(NHR2)(PAr3)].19
It is therefore assumed that several fluxional processes are taking
place when only one equivalent of (cod)PtI2 is added to the
hexadentate ligand, such as a change of conformation in the
cyclohexane ring, the presence of slow rotation around the
C–N bond of the aminocyclohexane, and/or ligand exchange
within the same hexadentate framework or with another hexaden-
tate ligand.20
1
The piecewise H–195Pt CP/CPMG NMR spectrum of 5 does
not reveal a clearly resolved, classical platinum CSA pattern
(Fig. 3(b) and see Table 2 for all parameters obtained from
195Pt SSNMR experiments); rather, the pattern is suggestive of
a distribution of Pt sites, making it difficult to accurately simulate
the spectrum and extract the chemical shift (CS) tensor parameters
(see Table 2 for parameter definitions). The spikelets comprising
this spectrum are the result of the direct Fourier transformation
of the CPMG echo train. The pattern covers a breadth of ca.
1350 ppm, and is clearly not representative of an axially symmetric
CS tensor (i.e., the skew, k, does not equal +1 or -1, since
there is no localization of intensity at either the low or high
frequency ends of the powder pattern). The centre of gravity
of the pattern is ca. -4755(120) ppm, and is comparable to
In order to limit the number of fluxional processes, the addition
of three equivalents of the platinum precursor was attempted.
Compound 1 was treated with three equivalents of (cod)PtI2 to
afford 6 (Scheme 4) as an orange powder; however, solubility issues
once again limited the application of solution NMR experiments,
and solid-state NMR spectroscopy was applied to characterize
this complex (vide infra). It was possible, however, to isolate a few
crystals for single-crystal X-ray diffraction experiments from a
diffusion of ethanol into both very dilute and saturated solutions
of 6 in DMSO. The platinum is in a square-planar environment
that of the tris(triphenylphosp◦hine)platinum(0) compound (diso
=
-4600 ppm, in C7D8 at -80 C).17 The relatively small pattern
breadth and clearly non-axial CS tensor are consistent with a
distorted, non-planar Pt environment.
2
(Fig. 5) and it is bound to 1 using a k -N,P interaction in a cis
fashion, with the iodides located at the two remaining sites. As
observed for 1, all three functional groups are in axial positions
of the cyclohexyl ring, with all the iodides pointing upwards.
However, the quasi-square-planar geometry of two of the three
platinum environments is distorted with the angles of trans-
substituents being significantly less than 180o (P(1)–Pt(1)–I(1)
and N(1)–Pt(1)–I(2) of 166.60(4)◦ and 165.43(11)◦, respectively,
and P(3)–Pt(3)–I(5) and N(3)–Pt(3)–I(6a) of 174.97(5)◦ and
162.23(12)◦, respectively). The average Pt–N and Pt–P bond
Comparison of the IR spectrum of 5 with free ligand 2 shows
that the N–H amine bands are similar (3298 cm-1 for 2 and
3302 cm-1 for 5). This, and the lack of Pt–N vibrations18 usually
observed between 275 cm-1 and 535 cm-1 (Fig. 4) imply the absence
of interactions between the amine and the platinum, as expected
for platinum(0) compounds which prefer binding to soft ligands
such as phosphines.
The insolubility of the yellow precipitate (opposite to that
observed for 4) and the spectroscopic evidence above make us
postulate that 5 possesses a polymeric structure (Scheme 3).
Changing the rate or sequence of addition, or the number of
equivalents of Pt(nbr)3, does not change the nature of the resulting
product. The use of a starting material with stronger ligands, such
as Pt(PPh3)4, did not yield any new product, and the starting
materials were recovered. This suggests that the lack of solubility
of 5 and the fast ligand substitution reaction inhibits eventual
reactions with the amine moieties and subsequent oxidation of
the amine into the imine (vide infra).
˚
lengths of 2.058(4) and 2.2182(16) A, respectively, are in the range
expected for iminophosphine platinum(II) complexes. A similar
reaction of 2 with three equivalents of (cod)PtI2 yielded a similarly
insoluble product, 7 (Scheme 5), that is also discussed below.
Solid state NMR and IR spectroscopy of the Pt(II) complexes
For a solid sample of 6, a single resonance was observed
using both 1H–31P CP/MAS and 1H–195Pt CP/CPMG NMR
spectroscopy (Fig. 6), indicating that all coordination sites have
similar bonding modes, and that the 31P nuclei are chemically
equivalent. The single 31P resonance appears at 10.0(1.3) ppm
(1JP–Pt = 3425(700) Hz), and compares very well to a previ-
ously reported complex, [PtI2(2-(diphenylphosphinobenzylidene-
a-methylbenzyl-amine)], which has a chemical shift of 9.4 ppm
Coordination chemistry of platinum(II) salts
One equivalent of the platinum precursor, (cod)PtI2, was added to
either 1 or 2; yellow precipitates were isolated. Quite surprisingly,
the resulting compounds have 1H NMR spectra with very broad
and 1JP–Pt = 3425 Hz from solution 31P{ H} NMR spectra.21
1
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Fig. 3 (a) 31P MAS NMR spectrum of 5, with 1JP–Pt shown; spinning sidebands are denoted with asterisks. (b) Static 1H–195Pt CP/CPMG NMR spectrum
of 5 (bottom trace). The slightly rolling baseline in (b) is an artifact of the co-addition of the sub-spectra.
The 195Pt CP/CPMG NMR spectrum reveals a sharp, well-
defined pattern with diso = -4400 (75) ppm, X = 3600 (125) ppm
and k = -0.82 (4). These parameters were obtained by first
comparing a simple CSA pattern to the outer manifold of the
CPMG spikelet pattern, and then refining them via simulations
of the spikelet pattern using the SIMPSON simulation package.22
These parameters describe a platinum CS tensor with the following
principal components: d11 = -2006(3) ppm, d22 = -5738(3) ppm
and d33 = -5756(3) ppm. The least shielded (highest frequency)
component of the CS tensor, d11, is the distinct component,
and due to the molecular symmetry, is likely oriented in a
direction perpendicular to a square planar Pt environment. The
intermediate and most shielded components, d22 and d33, are
similar in magnitude, and accordingly, are likely oriented in
the square plane in similar electronic environments. This result
is consistent with those for square planar Pt(II) complexes of
analogous systems, including Pt(II)[N(iPr2PSe)2]2 and one of the
23
starting reagents for this reaction, (cod)PtI2. For comparison, a
1
simple 195Pt{ H} MAS NMR spectrum was acquired for (cod)PtI2
(Fig. 7(a) and Table 3), from which Herzfeld–Berger analysis24
was used to extract the following CS tensor parameters: diso
=
-4281 (5.4) ppm, X = 3472 (4.4) ppm and k = -0.85 (4).
Coordination of platinum by the imine moieties was confirmed
by FTIR spectroscopy, which reveals Pt–N stretching bands at
525 cm-1 and 539 cm-1, thereby confirming that the three platinum
atoms coordinate to each one N–P moieties of the hexadentate
ligand (Fig. 4).
The 1H–31P CP/MAS NMR spectrum of 7 (Fig. 8(a)) reveals a
single, broad resonance centered at 6.0 (4.6) ppm; however, no 195Pt
satellites are clearly discernable underneath the broad lineshape.
There are several chemically distinct 31P sites which give rise to
a distribution of resonances and serve to obscure the satellite
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Fig. 4 FTIR spectrum of the region characteristic of Pt–N vibrations of 1 (black line), 2 (red line), 5 (green line), 6 (dark blue line), and 7 (light blue
line).
Scheme 4
Scheme 5
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Fig. 5 ORTEP diagram (50% probability) of 6. Hydrogen atoms have been omitted for clarity.
Table 3 195Pt MAS NMR experimental parameters
the net contribution from each type of 195Pt site (the simulated
powder patterns are presented in a 1:1 integrated intensity ratio
in Fig. 8(b) for comparison). The first set of parameters indicate
a Pt site similar to that observed for 6; however, the second set
of parameters, though possessing similar values of diso and k,
has a significantly larger span, similar to those of the (cod)PtCl2
species (also acquired with MAS, Fig. 7(b) and Table 3), with
diso = -3361(10) ppm, X = 6200(150) ppm and k = -0.86 (5),
and the completely planar Pt(II)[S2C2(CF3)2]2 species25 (though it
should be noted that the latter species has a positive skew). Again,
the distinct span and negative skew for each pattern indicate that
there are clearly two chemically distinct Pt environments which are
both square planar in nature. FTIR spectroscopy again confirms
the coordination of platinum by the amine moieties, with Pt–N
stretching bands observed at 516 cm-1 and 527 cm-1, along with
typical N–H vibration modes.
c
Compound
diso (ppm)a
X (ppm)b
k
(cod)PtI2
(cod)PtCl2
-4281 (5.4)
-3361 (10)
3472 (4.4)
6200 (150)
-0.85 (4)
-0.86 (5)
a Isotropic chemical shift: diso = (d11 + d22 + d33)/3. b Span: X = d11 - d33
.
c Skew: k = 3(d22-diso)/X. Note that the uncertainties for the analytical
HBA simulation for (cod)PtI2 are significantly lower than that of the
approximate SIMPSON simulation.
peaks arising from 31P–195Pt J-coupling. However, the 31P chemical
shift is in the typical range for (NHR2)(PPh3)PtCl complexes,
which normally occur at ca. 4 ppm.19 The H–195Pt CP/CPMG
NMR spectrum of 7 (Fig. 8(b)) is somewhat more complex than
that of 6. There are overlapping signals corresponding to two
different Pt environments, one having diso = -4550(100) ppm,
X = 3400(175) ppm and k = -0.88(7), and the other having
diso = -4300(60) ppm, X = 4550 (150) ppm and k = -0.75(5).
Due to the poor S/N and low spectral resolution, the errors
associated with these values are high, and it is difficult to quantify
1
Reactivity and structural characterization of one equivalent of
(cod)PtCl2 with 2
When one equivalent of (cod)PtCl2 is in solution for an extended
period of time (more than one week) in the presence of 2,
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1
Fig. 6 (a) 31P CP/MAS NMR spectrum of 6, with JP–Pt shown; spinning sidebands are denoted with asterisks. (b) Static 195Pt CP/CPMG NMR
spectrum of 6 (bottom trace), numerical simulation of the CPMG pattern using SIMPSON (middle trace), and analytical simulation of the corresponding
static pattern using WSOLIDS (top trace).
an insoluble material is isolated. The 1H NMR spectrum of
the solution shows only free cod and 1 as the soluble species,
thereby demonstrating that the ligand is being oxidized by the
platinum complex. The 1H–31P CP/MAS NMR spectrum of
8 reveals a resonance at 3.1(4.2) ppm (Fig. 9(a)). There is
a small peak to high frequency, which if treated as a 195Pt
7. However, the low frequency satellite, if it does exist, is obscured
by the presence of a broad resonance at ca. -17.1(3.9) ppm,
which may correspond to uncoordinated phosphine moieties.
Another resonance at 32.3(3.4) ppm is similar to the phosphorus
chemical shift of 5. The 1H–195Pt CP/CPMG spectrum (Fig. 9(b))
has similar parameters to those observed for 6 and 7 (diso
=
1
satellite, reveals a JP–Pt of 3310(700) Hz, similar to compound
-4400(50) ppm, X = 3950(75) ppm; k = -0.80(7)), again
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Fig. 7 (a) 195Pt MAS (nrot = 15.5 kHz) NMR spectrum of (cod)PtI2 (bottom trace) and simulation (top trace, using experimental parameters extracted
via Herzfeld–Berger analysis). (b) 195Pt MAS (nrot = 15.5 kHz) NMR spectrum of (cod)PtCl2 (bottom trace) and numerical simulation (top trace, using
SIMPSON). In each case, the isotropic peak is denoted with an asterisk.
indicating the presence of a square-planar species. However, the
agreement between the simulation and the experimental data
Conclusions
is not perfect, especially in the region of the low-frequency
(rightmost) discontinuity. It is possible that there is an underlying
pattern of low integrated intensity, perhaps corresponding to
the presence of a Pt(0) species; however, we cannot confirm
this with MAS NMR experiments for the reasons discussed
above.
Two new hexadentate iminophosphine and aminophosphine
ligands have been synthesized. A preliminary investigation of
their coordination chemistry with platinum(0) and platinum(II)
shows interesting reactivity and suggests great promise for future
directions in synthesis. Both reactions of 1 and 2 with Pt(nbr)3
yield compounds where the ligand interacts with the phosphine
7710 | Dalton Trans., 2009, 7701–7716
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Fig. 8 (a) 31P CP/MAS NMR spectrum of 7; spinning sidebands are denoted with asterisks. (b) Static 1H–195Pt CP/CPMG NMR spectrum of 7 (bottom
trace), numerical SIMPSON simulation (middle trace), and analytical WSOLIDS simulation (top trace).
of the hexadentate ligands. In the case of the iminophosphine, the
C–H activation of the imino proton was also observed. For the
Pt(II) salts, the affinity of the higher oxidation state metal for N,P-
coordinated ligands was observed by both 31P and 195Pt solid-state
NMR.
while challenging to acquire, revealed useful information about
the nature of the Pt sites. The 195Pt SSNMR spectra of the Pt(0)
species, 5, reveal some degree of disorder at the Pt centres, as well
as a moderate span and non-axial skew which are consistent with
non-square planar Pt sites. On the other hand, the Pt(II) species are
crystalline, and have extremely broad, well-defined CSA patterns
which indicate platinum CS tensors similar to those of other square
SSNMR experiments have proven very useful in the character-
ization of these insoluble compounds. The 195Pt SSNMR spectra,
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Fig. 9 (a) 31P CP/MAS NMR spectrum of 8; spinning sidebands are denoted with asterisks. (b) Static 1H–195Pt CP/CPMG NMR spectrum of 8 (bottom
trace), numerical SIMPSON simulation (middle trace), and analytical WSOLIDS simulation (top trace).
planar Pt(II) complexes which have been thoroughly characterized
by single-crystal XRD and 195Pt SSNMR spectroscopy. Finally,
the 31P SSNMR spectra are extremely useful for both establishing
connectivity/coordination between Pt and P-containing ligands,
and identifying P-containing starting reagents and by-products of
these reactions.
opening the way for interesting applications in stabilizing reactive
intermediates in catalysis, and that investigations of the solid-
state structures using both XRD and SSNMR are important for
future rational design of these systems. The hemilabile hexadentate
framework of 1 and 2 offers several sites that can stabilize various
oxidation states of platinum, and should demonstrate adaptability
during catalytic processes. Indeed, whereas in most systems the
reduction of platinum would lead to the loss of the metal as
The results presented herein clearly show that both Pt(0) and
Pt(II) complexes can be stabilized by the hexadentate ligand,
7712 | Dalton Trans., 2009, 7701–7716
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platinum black, here, the presence of multiple bonding sites allows
for the platinum to be stabilized. It is possible that an analogous
palladium system could prove very useful in catalysis by stabilizing
the reduced Pd oxidation states and increasing the life span of the
catalyst. Further studies on the reactivity and structure of such
platinum and palladium complexes are currently underway.
1H–31P CP/MAS NMR experiments were performed uti-
lizing the variable-amplitude cross polarization (VACP) pulse
sequence,30 along with two-pulse phase modulation (TPPM)
1
decoupling.31 A H p/2 pulse width of 3.38 ms was employed
along with contact times of 2 and 3 ms, recycle delays of 3 s, and a
spectral width of 100 kHz. A 1H cross-polarizing power of 56 kHz
and decoupling powers ranging from 56 to 115 kHz were used.
Spinning speeds of 10 and 12 kHz were employed. The solid state
31P MAS NMR experiments for sample 5 were performed on a
Bruker Advance spectrometer with SGU, 161.9 MHz (31P), with a
MAS 4 mm diameter probe and a zirconia rotor. The experiments
were performed utilizing a single sequence, along with two-pulse
phase modulation (TPPM) decoupling. A 31P p/2 pulse width of
3.75 ms was employed along with recycle delays of 4 s, and a spectral
width of 64 kHz. A spinning speed of 6.7 kHz was employed.
Simulations of solid-state NMR spectra were performed using the
WSOLIDS32 and SIMPSON22 software packages.
Experimental
Cis,cis-1,3,5-triaminocyclohexane·3HBr,26 2-diphenylphosphanyl-
benzaldehyde,27 tris(bicyclo[2.2.1]heptene)platinum(0),28 and
dichloro(1,5-cyclooctadiene)platinum(II)29
were
prepared
according to literature procedures. Diiodo(1,5-cyclooctadiene)-
platinum(II) was purchased from Strem chemicals and used as
received. Dry and deoxygenated solvents were used. HPLC grade
toluene was passed through a resin column and collected under
1
nitrogen. 1H (400.0 MHz), 31P{H} (161.9 MHz) and 13C{ H}
(100.568 MHz) solution NMR spectra were recorded on a Varian
Inova NMR AS400 spectrometer or on a Bruker NMR AC-300
spectrometer (1H (300.0 MHz), 31P{H} (121, 42 MHz) and
Vibrational spectroscopy
1
13C{ H} (75, 42 MHz).
Spectra were recorded on a Magna IR 850 Nicolet FTIR
spectrometer with a DTGS detector and a Golden Gate sampler.
VT-NMR experiments
Crystallographic structural determinations
1H (400 MHz) and 31P{ H}(161.904 MHz) NMR spectra were
1
acquired in CDCl3 at +22 ◦C, 0 ◦C, -20 ◦C, -40 ◦C and -55 ◦C.
The probes were tuned at each temperature. The temperatures
were measured using a thermocouple inside the probe which was
calibrated with methanol prior to use.
Crystallographic data are reported in Table 4. Single crystals were
coated with Paratone-N oil, mounted using a glass fibre and frozen
in the cold nitrogen stream of the goniometer. The data were
collected on a Bruker SMART APEX II diffractometer, except
for 1 which was collected on a Bruker AXS P4/SMART 1000
diffractometer. The data were reduced (SAINT)33 and corrected
for absorption (SADABS).34 The structure was solved and refined
using SHELXS-97 and SHELXL-97.35 In the case of 6, two
highly disordered ethanol molecules are present in the cell, which
was confirmed by both the volume and the electron density of
the disordered molecules using the PLATON software.36 Since
it was not possible to solve these molecules, they were squeezed
using PLATON.36 All non-H atoms were refined anisotropically.
The hydrogen atoms were placed at idealized positions. Neutral
atom scattering factors were taken from the International Tables
for X-Ray Crystallography.37 All calculations and drawings were
performed using the SHELXTL package.38 The final models for
1 and 2 were checked either for missed symmetry or voids in the
crystal structure using the PLATON software.
Solid-state NMR
Solid-state NMR spectra were collected using a Varian Infinity
Plus NMR spectrometer with an Oxford 9.4 T (1H = 400 MHz)
wide-bore magnet with n0(195Pt) = 87.34 MHz and n0(31P) =
161.81 MHz. The experiments were performed using 4.0 mm HXY,
4.0 mm HX, and 2.5 mm HX MAS probes along with zirconia
rotors. Air sensitive samples were packed under a dry nitrogen
atmosphere and sealed with air-tight TeflonTM caps in 4.0 mm
o.d. rotors. 195Pt chemical shifts were referenced with respect to
a 1.0 M solution of Na2PtCl6 (diso = 0.0 ppm) and 31P chemical
shifts were referenced with respect to an 85% solution of H3PO4
(diso = 0.0 ppm).
Static 195Pt NMR experiments were conducted using the cross-
polarization Carr–Purcell–Meiboom–Gill (CP/CPMG) pulse
sequence.11 Individual sub-spectra were collected by stepping the
frequency of the transmitter across the full breadth of the powder
pattern in increments ranging from 15 to 30 kHz.10 The number of
Meiboom–Gill (MG) loops was set to either 40 or 81, depending
on the T2 of the sample. A 1H p/2 pulse width of 1.98 or 2.04 ms
was utilized, along with a contact time of 3 or 4 ms, recycle delay
of 3 s, spectral width of 500 kHz, and spikelet separation of 5 or
10 kHz. Each powder pattern required the acquisition of 8 to 16
sub-spectra which were subsequently co-added to form the overall
=
cis,cis-C6H9(N CHC6H4(PPh2))3 (1)
cis,cis-1,3,5-triaminocyclohexane·3HBr (500 mg, 1.34 mmol) and
sodium methoxide (2.18 g, 40.3 mmol) were dissolved in 40 mL
of THF and heated under reflux for 18 h. The resulting slurry
was filtered and THF was removed under reduce pressure
to yield 1,3,5-triaminocyclohexane as a white powder. 1,3,5-
triaminocyclohexane and 2-diphenylphosphanylbenzaldehyde
(1.17 g, 4.0 mmol) were dissolved in 30 mL of absolute deoxy-
1
˚
spectrum. A H cross-polarizing power of 161 or 75 kHz and
genated ethanol in the presence of molecular sieves (4 A) and
decoupling power of 75 kHz were used. 195Pt MAS experiments
were conducted using a standard Bloch decay pulse sequence with
decoupling applied. A p/2 pulse width of 0.83 ms, spectral width of
1100 kHz, and pulse delay of 30 s were used to acquire the powder
pattern.
heated under reflux for 24 h, during which a yellow precipitate
appeared. The reaction mixture was cooled at -20 C and 1 was
isolated as a yellow powder by decanting the supernatant (855 mg,
67% yield). Crystals were grown from slow diffusion of pentane in
a THF solution of 1. 1H NMR (C6D6), d = 9.04 [d (4JH-H = 4.9 Hz),
◦
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Table 4 Crystallographic data
1
2
6
Formula
FW
C63H54N3P3
946.00
0.40 ¥ 0.40 ¥ 0.20
Triclinic
P-1
14.094(4)
14.538(4)
14.725(4)
94.118(4), 109.789(4), 111.535(4)
2573.6(11)
2
0.71073
1.221
0.159
996
C63H60N3P3
952.05
0.42 ¥ 0.35 ¥ 0.15
Triclinic
P-1
13.895(1)
14.198(1)
14.874(1)
94.163(1), 106.963(1), 109.808(1)
2592.1(3)
2
0.71073
1.220
0.158
1008
C63H54I6 N3P3Pt3
2292.67
0.14 ¥ 0.03 ¥ 0.01
Monoclinic
P2(1)/n
17.9294(17)
15.1395(15)
28.744(3)
90.0, 93.231(1), 90.0
7789.8(13)
4
Size (mm)
Cryst. syst.
Space group
˚
a (A)
˚
b (A)
˚
c (A)
a, b, g (◦)
3
˚
V (A )
Z
˚
Wavelength (A)
0.71073
1.955
7.848
4200
Dcalc (g cm-3)
Absorption coefficient (mm-1)
F000
Temp (K)
198(1)
200(2)
200(2)
No. of unique/total reflns
Rint
11 038/17 424
0.0217
12 227/31 797
0.0231
18 753/94 515
0.0418
Final R indices [I > 2s(I)]
R1 = 0.0533 wR2 = 0.1302
R1 = 0.0445 wR2 = 0.1308
R1 = 0.0388 wR2 = 0.0933
R indices (all data)
R1 = 0.0886, wR2 = 0.1556
R1 = 0.0584, wR2 = 0.1308
R1 = 0.0592, wR2 = 0.0987
=
3H, CH=N], 8.25 [m, 3H, o-PAr], 7.37 [m, 12H, o-PPh2], 7.02 [m,
27H, Ar], 2.98 [tt, 3JH–H = 3.6 Hz; 11.7 Hz, 3H, NCH], 1.97 [dd,
3JH-H = 12.2 Hz; 12.2 Hz, 3H, CHHax], 1.41 [dt, 3JH–H = 3.5 Hz;
cis,cis-C6H9(N CHC6H4(PPh2))3 + Pt(nbr)3 (3a–c and 4)
In a Schlenk tube under nitrogen, tris(bicyclo[2.2.1]heptene)-
platinum(0) (86 mg, 0.18 mmol) was dissolved in 5 mL toluene
immediately followed by 1 (170 mg, 0.18 mmol). The yellow
solution was stirred for 12 h and the volatiles removed under
vacuum. The product was dissolved in a minimum of toluene
and pentane was added. A precipitate appeared at -35 ◦C and
was filtered. The product was washed with 5 portions of hexane
(3 mL) to afford an orange powder (100 mg, 50% yield). 1H NMR
(C6D6, 22 ◦C), d = 10.02 [s], 9.63 [s], 9.48 [s], 9.46 [s, 1H], 8.46 [m,
1
1
12.2 Hz, 3H, CHHeq]; 31P{ H} (C6D6) d = -12.56; 13C{ H} (C6D6)
d = 157.35 [d, 3JC–P = 20.6 Hz], 140.52 [d, 2JC–P = 17.2 Hz], 137.79
[d, 1JC–P = 20.3 Hz], 137.60 [d, 1JC–P = 10.6 Hz], 134.39 [d, 1JC–P
=
20.0 Hz], 133.75 [s], 130.24 [s], 129.02 [s], 129.97 [s], 128.88 [s],
128.43 [d, 4.5 Hz], 66.53 [s], 41.36 [s]. IR-ATR (diamond cell),
n/cm-1 1632 [C N, str, m], 742 [P-o-Ar C–H def., s], 694 [P–Ar
=
C–H def., s]. HRMS (APPI) calc. for C63H54N3P3 (M+) = 945.3531;
found 945.3529. Elemental analysis: calc. for C63H54N3P3 C 79.98
H 5.75 N 4.44; found C 79.45 H 5.72 N 4.45
2
3H], 7.77 [m, 15H], 6.84 [m, 26H], -1.19 [dd, JH–Pcis = 26.4 Hz,
2JH–Ptrans = 172 Hz], -1.46 [2JH–Pcis = 25.0 Hz, 2JH–Ptrans = 178 Hz],
-2.15 [2JH–Pcis = 23.0 Hz; JH–Ptrans = 178 Hz]; 31P{ H} d = 50.7
2
1
2
1
[dd, JP–P = 7.5 Hz; JP–Pt = 2080 Hz], 28.6 [dd, JP–P = 7.5 Hz;
1JP–Pt = 1820 Hz], 47.5 [dd, 2JP–P = 4.1 Hz; 1JP–Pt = 1990 Hz], 27.1
cis,cis-C6H9(NHCH2C6H4(PPh2))3 (2)
2
1
2
To a solution of 1 in 50 mL of THF (1.29 g, 1.36 mmol), a
suspension of LiAlH4 (0.155 g, 4.09 mmol) in 10 mL of THF
was added. The suspension was stirred at room temperature for
48 h. The reaction was then filtered to remove excess LiAlH4 and
quenched with ethanol and water. The volatiles were removed
under vacuum and the remaining solid washed with 3 portions
of 20 mL of diethyl ether, and dried under vacuum to yield 2 as
[dd, JP–P = 4.1 Hz, JP–Pt = 1940 Hz]; 26.5 [dd, JP–P = 4.1 Hz,
1JP–Pt = 1940 Hz ], 46.1 [d, JP–Pt = 1940 Hz], 29.0 [s] ppm. 31P
1
CP/MAS diso = 46.313, 25.522, 2.460 ppm. 195Pt CP/CPMG diso
=
-4755(50) ppm, X = 1350(60), k = -0.33(6). IR-ATR (diamond
cell), n/cm-1 1632 [C N, str, m], 743 [P-o-Ar C–H def., s], 692
=
[P–Ar C–H def., s].
1
a yellow powder (0.95 g, 74% yield). H NMR (C6D6), d = 7.62
[m, o-PAr, 3H], 7.38 [m, o-PPh2, 12H], 7.08 [m, Ar, 27H], 4.11 [d,
cis,cis-C6H9(NHCH2C6H4(PPh2))3 + Pt(nbr)3 (5)
3JH–H = 7.1 Hz, CH2, 6H], 2.11 [m, 3JH–H = 11.6 Hz; 3JH–H = 4.2 Hz,
2
3
NCH, 3H], 1.77 [dt, JH-H = 11.6 Hz; JH–H = 3.3 Hz, CHHeq,
In a Schlenk tube under nitrogen, 2 (150 mg, 0.16 mmol)
was dissolved in 3 mL of toluene. Tris(bicyclo[2.2.1]heptene)-
platinum(0) (76.4 mg, 0.16 mmol) in 0.5 mL toluene was then
added to a stirred solution of 2. The color of the reaction changed
from clear to yellow instantly and after a few minutes the product
started to precipitate. The reaction was stirred for 12 h after which
the suspension was filtered and dried under vacuum. The yellow
powder was washed with 3 portions of pentane (1 mL). (162 mg,
3H], 0.78 [dd, 3JH–H = 6.9 Hz; 3JH-H = 11.6 Hz, NH, 3H] 0.62 [q,
3
1
2JH-H = 11.6 Hz; JH–H = 11.6 Hz, CHHax, 3H]; 31P{ H} (C6D6)
d = -15.01 ppm; 13C{ H}(C6D6) d = 146.25 [d, 1JC–P= 23.8 Hz],
1
137.88 [d, 3JC–P= 11.3 Hz], 136.09 [d, 2JC–P = 14.4 Hz], 134.32 [d,
2JC–P = 19.8 Hz], 134.01 [s], 128.72 [d, 2JC-P = 6.8 Hz], 128.72 [s],
128.56 [s], 128.18 [s], 127.36 [s], 53.66 [s], 50.02 [d, 3JC–P = 21.8 Hz],
40.71 [s] ppm. IR-ATR (diamond cell), n/cm-1 3298 [N–H str., w],
740 [N–H wag., C–P str., s], 694 [P–Ar C–H def., s]. HRMS (APPI)
calc. for C63H54N3P3 (M+) = 951.4000; found 951.3988. Elemental
analysis: calc. for C63H60N3P3 C 79.47 H 6.35 N 4.41; found C
78.76 H 6.36 N 4.39.
78%) NMR 31P{ H} (MAS 121.42 MHz) d = 37.0 (2.1) ppm
1
[t, 1JP-Pt = 4460 (350) Hz]. 195Pt CP/CPMG diso = -4755(120) ppm.
IR-ATR (diamond cell), n/cm-1 3302 [N–H str., w], 741–729
[N–H wag., C–P str., m] 691 [P–Ar C–H def., s]. Anal. Calcd:
7714 | Dalton Trans., 2009, 7701–7716
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for C63H60N3P3Pt; C 65.96 H 5.27 N 3.66 found: C 65.39 H 5.39
N 3.35.
for support in the form of an Early Researcher Award. R. W.
Schurko also thanks the Canadian Foundation for Innovation
(CFI), the Ontario Innovation Trust (OIT), the University of
Windsor and NSERC for funding of the solid-state NMR centre
at the University of Windsor, and the Centre for Catalysis and
Materials Research (CCMR) at Windsor for additional support.
B. E. G. Lucier thanks the University of Windsor for a tuition
scholarship. We acknowledge A. Decken for his help solving
the solid state structure of 1, and J.-F. Rioux and M. Pe´zolet
(Universite´ Laval) for their help with FTIR spectroscopy. We also
wish to thank Dr Joel Tang (NYU) for his help with the 195Pt NMR
experiments.
=
cis,cis-C6H9(N CHC6H4(PPh2))3 + 3 (cod)PtI2 (6)
82 mg (0.09 mmol) of 1 was dissolved in 4 mL toluene and 3 equiv.
of diiodo(1,5-cyclooctadiene)platinum(II) (145 mg, 0.26 mmol)
were added. The reaction was refluxed for 48 h during which
a precipitate was formed. The precipitate was filtered, washed
with 3 portions of pentane (3 mL) and dried under vacuum to
afford 137 mg (69% yield). Crystals were grown by a slow diffusion
of ethanol in a DMSO solution of 6. 31P CP/MAS diso = 10.0
(1.3) [1JP–Pt = 3425 (700) Hz] ppm. 195Pt CP/CPMG diso = -4400
(75) ppm, X = 3600 (125), k = -0.82(4). IR-ATR (diamond cell),
n/cm-1 1621[C N, str, m], 746 [P-o-Ar C–H def., s], 690 [P–Ar
References
=
C–H def., s], 525, 527 [Pt–N, str, s]. Elemental analysis: calc. for
C63H54N3P3Pt3I6 C 33.00 H 2.37 N 1.83; found C 28.55 H 2.16 N
1.58.
1 (a) A. Del Zotto, W. Baratta, M. Ballico, E. Herdtweck and P. Rigo,
Organometallics, 2007, 26, 5636; (b) B.-Z. Li, J.-S. Chen, Z. R. Dong,
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cis,cis-C6H9(NHCH2C6H4(PPh2))3 + 3 (cod)PtI2 (7)
2 (150 mg 0.158 mmol) was dissolved in 4 mL toluene. Diiodo(1,5-
cyclooctadiene)platinum(II) (264 mg, 0.474 mmol) was added and
the solution refluxed for 18 h. A precipitate was formed and filtered
to afford an orange powder which was washed with 3 ¥ 5 mL of
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1
hexane and dried under vacuum (174 mg, 60% yield). H NMR
(CDCl3, 400 MHz, 22 ◦C), d = 7.47 [m, br] ppm 31P CP/MAS
diso = 6.0 (4.6) ppm. 195Pt CP/CPMG diso = -4550(100) ppm, X =
3400(175), k = -0.88(7); diso = -4300(60) ppm, X = 4550(150),
k = -0.75(5). IR-ATR (Golden gate), n/cm-1 3145 [N–H str., w],
746 [N–H wag., C–P str., s], 690 [P–Ar C–H def., s], 516, 527 [Pt–
N, str., s]. Elemental analysis: calc. for C63H60N3P3Pt C 32.92 H
2.63 N 1.83; found C 36.50 H 3.00 N 2.01.
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9 T. M. Duncan, A Compilation of Chemical Shift Anisotropies, Farragut
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cis,cis-C6H9(NHCH2C6H4(PPh2))3 + (cod)PtCl2 (8)
2 (156 mg, 0.16 mmol) was dissolved in 4 mL toluene.
Dichloro(1,5-cyclooctadiene)platinum(II) (55 mg, 0.15 mmol) was
added and the solution stirred at room temperature for 12 h. A
precipitate was formed which was filtered, then washed with 3 ¥
3 mL of pentane and dried under vacuum (100 mg, 51% yield).
1H NMR (CDCl3, 400 MHz, 22 ◦C), d = 7.79–6.67 [m, aromatic];
◦
1
31P{ H} (CDCl3, 161.904 MHz, 22 C) d = 35.67 [s], 7.40 [s], 7.31
[s], -13.03 [s] ppm. RMN-VT 1H (CDCl3, 400 MHz, -55 ◦C), d =
8.05–6.32 [m, aromatic], 5.93 [m, CH2], 5.76 [m, CH2], 5.61 [s,
CH2] ppm. 31P{ H} (CDCl3, 161.904 MHz, -55 ◦C) d = 39.70
1
11 F. H. Larsen, H. J. Jakobsen, P. D. Ellis and N. C. Nielsen, J. Phys.
Chem. A, 1997, 101, 8597.
[br], 36.29 [s], 33.68 [s], 18.13 [br], 8.39–7.54 [m], -5.50 [s], -13.08
[s] ppm. 31P CP/MAS diso = 32.3 (3.4), 3.1 (4.2) [1JP–Pt/2 = 1655
(350) Hz], -17.1 (3.9) ppm. 195Pt CP/CPMG diso = -4400 (50) ppm,
X = 3950(75), k = -0.80(7). IR-ATR (Golden gate), n/cm-1 3380
[N–H str., w], 747–723 [N–H wag., C–P str. m], 692 [P–Ar C–H
def., m], 543, 519 [Pt–N, str., s].
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Acknowledgements
F.-G. Fontaine is grateful to NSERC (Canada), CFI (Canada),
FQRNT (Que´bec), and Universite´ Laval for financial support.
M.-H. Thibault acknowledges FQRNT for a scholarship. R. W.
Schurko thanks NSERC for supporting this research, and also
acknowledges the Ontario Ministry of Research and Innovation
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Dalton Trans., 2009, 7701–7716 | 7715
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