Coordination chemistry of dinucleating P2N2S ligands: Preparation and characterization of cationic palladium complexes

Article abstract of DOI:10.1039/b613789j

The thioethers (4-tert-butyl-2,6-bis((2-(diphenylphosphino)ethylimino) methyl)phenyl)(tert-butyl)sulfane (tBuL³) and (4-tert-butyl-2,6- bis((2-(diphenylphosphino)ethylamino)methyl)phenyl)(tert-butyl)sulfane (tBuL⁴) react readily with [Pd(NCMe)₂Cl₂] to give the dinuclear palladium thiophenolate complexes [(L³)Pd ₂(Cl)₂]⁺ (4) and [(L⁴)Pd ₂(-Cl)]²⁺ (5) (HL³ = 2,6-bis((2- (diphenylphosphino)ethylimino)methyl)-4-tert-butylbenzenethiol, HL⁴ = 2,6-bis((2-(diphenylphosphino)ethylamino)methyl)-4-tert-butylbenzenethiol). The chlorides in 4 could be replaced by neutral (MeCN) and anionic ligands (NCS^-, N₃^-, I^-, CN^-) to give the dinuclear Pd^II complexes [(L³)Pd ₂(NCMe)₂]³⁺ (6), [(L³)Pd ₂(SCN)₂]⁺ (7), [(L³)Pd ₂(N₃)₂]⁺ (8), [(L ³)Pd₂(I)₂]⁺ (9), and [(L ³)Pd₂(CN)₂]⁺ (10). The acetonitrile ligands in 6 are readily hydrated to give the corresponding amidato complex [(L³)Pd₂(NHCOMe)]²⁺ (11). All complexes were isolated as perchlorate salts and studied by infrared, ¹H, and ³¹P NMR spectroscopy. In addition, complexes 4[ClO ₄]·EtOH, 5[ClO₄]₂, 9[ClO₄], 10[ClO₄]·EtOH, and 11[ClO₄]₂· MeCN·MeOH have been characterized by X-ray crystallography. The dipalladium complex 4 was found to catalyse the vinyl-addition polymerization of norbornene in the presence of MAO (methylalumoxane) and B(C₆F ₅)₃/AlEt₃. This journal is The Royal Society of Chemistry.

Full text of DOI:10.1039/b613789j

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www.rsc.org/dalton | Dalton Transactions
Coordination chemistry of dinucleating P2N2S ligands: preparation and
characterization of cationic palladium complexes
Gabriel Siedle,a Paul-Gerhard Lassahn,b Vasile Lozan,a Christoph Janiakb and Berthold Kersting*a
Received 21st September 2006, Accepted 23rd October 2006
First published as an Advance Article on the web 6th November 2006
DOI: 10.1039/b613789j
The thioethers (4-tert-butyl-2,6-bis((2-(diphenylphosphino)ethylimino)methyl)phenyl)(tert-butyl)-
sulfane (tBuL3) and (4-tert-butyl-2,6-bis((2-(diphenylphosphino)ethylamino)methyl)phenyl)-
(tert-butyl)sulfane (tBuL4) react readily with [Pd(NCMe)2Cl2] to give the dinuclear palladium
thiophenolate complexes [(L3)Pd2(Cl)2]+ (4) and [(L4)Pd2(l-Cl)]2+ (5) (HL3 = 2,6-bis((2-(diphenyl-
phosphino)ethylimino)methyl)-4-tert-butylbenzenethiol, HL4 = 2,6-bis((2-(diphenylphosphino)-
ethylamino)methyl)-4-tert-butylbenzenethiol). The chlorides in 4 could be replaced by neutral (MeCN)
and anionic ligands (NCS−, N3−, I−, CN−) to give the dinuclear PdII complexes [(L3)Pd2(NCMe)2]3+ (6),
[(L3)Pd2(SCN)2]+ (7), [(L3)Pd2(N3)2]+ (8), [(L3)Pd2(I)2]+ (9), and [(L3)Pd2(CN)2]+ (10). The acetonitrile
ligands in 6 are readily hydrated to give the corresponding amidato complex [(L3)Pd2(NHCOMe)]2+
(11). All complexes were isolated as perchlorate salts and studied by infrared, 1H, and 31P NMR
spectroscopy. In addition, complexes 4[ClO4]·EtOH, 5[ClO4]2, 9[ClO4], 10[ClO4]·EtOH, and 11[ClO4]2·
MeCN·MeOH have been characterized by X-ray crystallography. The dipalladium complex 4 was
found to catalyse the vinyl-addition polymerization of norbornene in the presence of MAO
(methylalumoxane) and B(C6F5)3/AlEt3.
Introduction
A large number of dinucleating ligands1 containing thiophenolate
subunits have been reported in the past several years.2–6 These
ligands represent “soft” analogues of the more familiar phenolate
systems,7 and offer the potential of forming dinuclear complexes
of catalytically active soft late transition metal ions such as Rh,
Ir, Pd and Pt.8,9 In order to enhance their affinity for these
metal ions further soft donor centres may be introduced into
the ligand backbone. Among these, phosphane functions, R2P–,
are immediately evident, because these bind very strongly to the
late 4d and 5d elements. Unfortunately, multidentate ligands with
mixed N/P/S donor sets are not readily available and often require
multistep reactions.10–13 This is true in particular for dinucleating
thiophenolate ligands. To the best of our knowledge, there are no
Scheme 1 Structures of the thioethers tBuL1–tBuL4 and the palladium
complexes [(L1)Pd2(Cl)2]+ (1) and [(L2)Pd2(l-Cl)]2+ (2).
previous examples of dinucleating thiophenolate-based systems
containing mixed N/P/S donor sets.9
In a previous paper we described that the open-chain aromatic
thioethers tBuL1 and tBuL2 can be readily deprotected with
[Pd(NCMe)2Cl2] to afford the corresponding dinuclear palladium
thiophenolate complexes [(L1)Pd2(Cl)2]+ and [(L2)Pd2(l-Cl)]2+
(Scheme 1).14 As part of this program, we sought to explore
the scope of this Pd-mediated S-deprotection reaction for the
synthesis of the phosphanyl-substituted ligands HL3 and HL4.
Herein we report the successful synthesis of these two novel
N2P2S ligands and the X-ray structures of a series of their
dinuclear palladium complexes. The structures of the present
N2P2S complexes are compared with those of the related N4S
complexes that we have reported previously. Results concerning
the catalytic activity of [(L3)Pd2(Cl)2]+ (4) in the vinyl-addition
polymerisation of norbornene are described.
Results and discussion
Synthesis and characterization of proligands and complexes
Scheme 2 shows the preparation of the aromatic thioethers
tBuL3 and tBuL4 and the palladium thiophenolate complexes
4–11. Following the method of preparing tBuL1,14 dialde-
hyde 315 was condensed with two equivalents of 2-(diphenyl-
phosphino)ethyleneamine to yield the Schiff base tBuL3 as a
colourless oil in nearly quantitative yield. Reduction of the imine
aInstitut fu¨r Anorganische Chemie, Universita¨t Leipzig, Johannisallee 29,
D-04103, Leipzig, Germany. E-mail: b.kersting@uni-leipzig.de; Fax: +49
(0)341-97-36199
bInstitut fu¨r Anorganische und Analytische Chemie, Universita¨t Freiburg,
Albertstr. 21, D-07139, Freiburg, Germany
52 | Dalton Trans., 2007, 52–61
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Scheme 2 Synthesis of proligands tBuL3 and tBuL4 and complexes 4–11.
functions of tBuL3 was accomplished with sodium borohydride
and produced the phosphanyl-substituted amine-thioether tBuL4.
Although the tert-butyl protected N2P2S proligands could not
be obtained in analytically pure form, they were of sufficient
purity for metal complex syntheses. Thus, the reaction of tBuL3
with two equivalents of [Pd(NCMe)2Cl2] in acetonitrile solution
at ambient temperature for 2 days gave a yellow solution, from
which, upon addition of an excess of LiClO4, yellow crystals
of [(L3)Pd2(Cl)2][ClO4] (4[ClO4]) precipitated in ca. 55% yield.
Likewise, the reaction of tert-butyl protected proligand tBuL4
with two equivalents of [Pd(NCMe)2Cl2] in acetonitrile at ambient
temperature for 12 h gave a yellow solution, from which, upon
addition of an excess of LiClO4, a compound of composition
[(L4)Pd2(Cl)][ClO4]2 (5[ClO4]2) was reproducibly obtained in ∼40%
yield. Thus the thiolate functions of tBuL3 and tBuL4 can be
selectively deprotected with [Pd(NCMe)2Cl2] without affecting
the phosphane groups. The selective cleavage of phosphanyl-
substituted aromatic thioethers is without precedence in the
literature. This reaction can now be further exploited for the design
and synthesis of other thiophenolate ligands with mixed P/N/S
donor sets.
N3−, I− and CN− to give the complexes [(L3)Pd2(SCN)2]+ (7),
[(L3)Pd2(N3)2]+ (8), [(L3)Pd2(I)2]+ (9) and [(L3)Pd2(CN)2]+ (10),
respectively, in good yields (Scheme 2). As was observed previously
for [(L1)Pd2(NCMe)2]3+,14 the Pd-bound acetonitrile ligands in
6 are readily transformed into acetamide. Thus, the reaction of
6 with NBu4OH proceeded smoothly to give the acetamidato
complex [(L3)Pd2(NHCOMe)]2+ (11). The perchlorate salts of
complexes 7, 9, 10 and 11 were obtained as analytically pure, yellow
to red, microcrystalline solids by crystallization from saturated
ethanol or acetonitrile–ethanol solutions. The perchlorate salts
of bis(acetonitrile) complex 6 and azido complex 8 could not be
obtained in analytically pure form. However, the spectroscopic
similarities with [(L1)Pd2(NCMe)2]3+ and [(L1)Pd2(N3)2]+ reported
previously14 are in good agreement with their formulation
(vide infra).
Infrared spectra of the perchlorate salts of the complexes 4–
11 were recorded as KBr pellets. The spectra display the bands
expected for the P2N2S ligands, counter ions and coligands. Each
compound reveals a strong band around 1100 cm−1, attributable
to the m3(F2) stretching vibration of the ClO4 ion.16 The sharp
−
band at ∼1436 cm−1 is seen in all complexes and is typical for
PPh2 groups.17 The most significant feature in the IR spectrum of
4[ClO4] is the band at 1627 cm−1, which can be readily assigned
In the course of this work it was found that the dinuclear
palladium complex [(L3)Pd2(Cl)2]+ (4) exhibits a rich coordination
chemistry. Thus, reaction of 4 with Pb(ClO4)2 in dry acetonitrile
gave the labile acetonitrile complex [(L3)Pd2(NCMe)2]3+ (6). This
compound reacted readily with various anions such as SCN−,
=
to the C N stretching frequency of the coordinated imines. As
expected, this band is absent in the IR spectrum of the dipalladium
complex 5 of the reduced phosphan-amine-thiophenolate ligand
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(L4)−. The IR spectrum of 6[ClO4]3 shows two bands at 2326
and 2298 cm−1 attributable to the C≡N stretching frequencies
of the Pd-bound acetonitrile ligands. Similar values (m = 2330
and 2303 cm−1) were observed for [(L1)Pd2(NCMe)2]3+.14 Complex
7[ClO4] exhibits a strong IR band at 2110 cm−1, indicative of
S-bound thiocyanates.14 In agreement with the formulation of
8[ClO4] the IR spectrum displays strong bands for the azide
groups at 2034 and 2017 cm−1 (m(N3−)). The terminal CN−
groups in 10[ClO4] give rise to a band at 2139 cm−1 typical of
monodentate cyanides.18 In the tetranuclear complex [{(L1)Pd2(l-
CN)}2][ClO4]4,14 the band for the bridging cyanides is centred
at 2184 cm−1. The IR spectrum of 11 exhibits a band at
3363 cm−1 attributable to the N–H stretching vibration of the
carboxamide unit. The bands expected for the asymmetric and
symmetric RCONH stretching vibrations are observed at 1571
and 1364 cm−1, respectively. Similar values were observed for
[(L1)Pd2(NHCOMe)]+,14 and other acetamidato compounds.19
Overall, the infrared data for the present P2N2S complexes are
very similar to those of the corresponding N4S compounds that
we have described in our earlier paper.14 The IR data show that the
electronic structures of the coligands are not significantly altered
when changing the donor set of the supporting ligand from N4S
to P2N2S. The similarities between the IR data sets imply that the
coligands are in a trans-orientation to the imine donors as found
in the [(L1)Pd2(Lꢀ)]+ species. These findings are confirmed by the
crystal structures described below.
The complexes were further characterized by 1H and 31P NMR
spectroscopy. 13C NMR spectroscopic data were recorded only for
tBuL3 and 4[ClO4]. Selected data for the compounds are presented
in Table 1.
The most diagnostic signals in the 1H NMR spectrum of tBuL3
in CDCl3 solution are the singlets for the tert-butyl groups (C1H3,
d = 1.27 and C4H3, d = 1.08, respectively), the aromatic protons
(C8H, d = 8.07), and the imine protons (C11H, d = 9.05, for atom
labels see inset Table 1). These 1H chemical shifts are very similar to
those of the amine-imine-thioether tBuL1, reported previously.14
Table 1 Selected 1H, 13C, and 31P NMR data for the thioethers tBuL3, tBuL4 and the palladium complexes 4–11
d(1H)
C1H3
C4H3
C5H2
C6H2
C8H
C11H(C11H2)
P(C6H5)2
31P
tBuL3,a
tBuL4,a
4[ClO4]b
1.27 s
1.21 s
1.35 s
1.08 s
1.15 s
—
3.70 m
2.66 m
4.05 m
4.21 m
3.98 m
4.32 m
4.10 m
4.24 m
2.40 m
2.21 m
2.59 m
2.64 m
2.67 m
3.07 m
2.64 m
2.73 m
8.07 s
obsc.e
obsc.e
9.05 s
4.00 br. s
8.68 s
7.25–7.43 m
7.29–7.44 m
7.51–7.68 m
7.91–7.97 m
7.35–7.89 m
−18.30a
−20.50a
48.95c
b
b
5[ClO4]2
6[ClO4]3
1.34 s
1.40 s
—
—
obsc.e
8.05 s
3.30 m
3.60 m
8.68 s
49.90a
59.40c
7.52–7.71 m
7.72–7.89 m
Coligand: 1.97 (CH3CN)
7[ClO4]b
8[ClO4]d
9[ClO4]b
1.40 s
1.39 s
1.39 s
1.37 s
1.42 s
—
—
—
—
—
4.06 m
4.20 m
4.05 m
4.20 m
3.88 m
4.13 m
4.06 m
4.21 m
4.43 m
4.52 m
2.69 m
2.75 m
2.81 m
2.85 m
2.62 m
2.62 m
2.73 m
2.79 m
2.72 m
2.83 m
8.02 s
8.18 s
7.85 s
obsc.e
8.16 s
8.77 s
9.04 s
8.54 s
8.77 s
7.54–7.70 m
7.82–7.95 m
7.57–7.70 m
7.94–8.04 m
7.50–7.70 m
8.00–8.20 m
7.52–7.67 m
7.92–8.03 m
7.62–7.73 m
7.85–7.96 m
51.80b
48.70d
49.30d
51.70b
10[ClO4]b
11[ClO4]c
8.65 s
8.87 s
49.42c
48.14
Coligand: 2.08 (CH3CONH), 6.02 (CH3CONH)
d(13C)
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
a
tBuL3
31.6
35.5
49.7
31.7
—
59.0 (25 Hz)f
64.5 (27 Hz)f
30.4 (15 Hz)g
27.7 (49 Hz)g
153.0
150.0
141.5
140.8
131.7
129.0
127.2
127.9
162.7
167.8
PPh2: 128.8, 129.0, 133.2, 138.9
30.8 35.2
PPh2: 130.2, 133.6, 134.3, 134.6
4[ClO4]c
—
a Recorded in CDCl3 solution. b Recorded in CD3CN solution. c Recorded in CD3NO2 solution. d Recorded in DMSO-d6 solution. e Signal obscured by
2
g
resonances due to the PPh2 groups. f JCP
. .
1JCP
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The same is true for the 13C NMR data. As expected, however,
the signals for the methylene carbon atoms denoted C5 and C6
appear as doublets. The doublets are caused by one and two bond
phosphorus–carbon couplings (2J(31P–13C) = 15 Hz, 1J(31P–13C) =
25 Hz)). The 31P NMR spectrum of tBuL3 reveals only one signal
at d = −18.3.
be a consequence of dynamic behaviour. It is assumed that the
two ligand side arms twist about the Ar–CH(imine) bonds. This
would result in the coalescence of the 31P NMR signals and the
complex’s time-averaged C2v symmetry. Thus, the conformations
found in the solid state are not locked in the solution state. The
1H NMR data for 5[ClO4]2 were also indicative of the presence
of a dinuclear palladium thiophenolate complex, showing only
one tert-butyl resonance at d = 1.34. The 31P NMR resonance is
shifted down field from d = −20.5 in tBuL4 to d = 49.90 in 5. The
1H NMR data of the complexes 7–11 closely resemble those of 4.
In all cases, singlets are observed for the tert-butyl groups labelled
C1H3, the aromatic C8H protons (d = 8.02–8.18), and the imine
C11H protons (d = 8.68–9.14), indicative of C2v or Cs symmetric
structures. Likewise, the 31P NMR spectra reveal only one 31P
NMR signal for the two equivalent phosphanyl groups, with the
31P NMR resonances in the 48–60 range. The attachment of a
bridging N,O-bound acetamidato unit to the [(L3)Pd2]3+ fragment
in 11 is expected to cause an NMR inequivalence of the two
The conversion of tBuL3 to tBuL4 was confirmed by 1H NMR
spectroscopy by the absence of the signal for the imine protons
=
(CH N) and the presence of a new signal at d = 4.00 for the
benzylic methylene protons. The formulation of tBuL4 was further
confirmed by 31P NMR spectroscopy (singlet at d = −20.5) and by
a crystal structure determination of one of its metal complexes (see
structure of compound 5 described below). Like its parent tBuL3,
the diphosphane-diamine-thioether tBuL4 could not be obtained
in analytically pure form. Nonetheless it was of sufficient purity
for metal complex syntheses.
The 1H NMR and 13C NMR spectral data for the dipalladium
complex 4 lack the signals of one tBu group, which confirms
the presence of the thiophenolate unit. The coordination of the
phosphane functions is supported by the 31P NMR spectrum by
the down field shift of the 31P NMR resonance from d = −18.3 in
1
ligand side arms. Indeed, the H NMR spectrum of 11[ClO4]2
in CD3NO2 solution reveals two equally intense 1H signals at d =
8.65 and 8.87 for the imine CH protons. In addition, two 31P
NMR resonances are clearly discernible in the 31P NMR spectrum.
In summary, the spectroscopic data have clearly established that
(L3)− and (L4)− are effective dinucleating N2P2S ligands that
support the formation of dinuclear palladium complexes with one
exchangeable coordination site on each metal ion.
1
tBuL3 to d = 48.95 in 4. From the H and 31P NMR data it can
also be seen that the two halves of (L3)− in 4 are equivalent. For
example, single resonances are observed for the imine protons
(C11H) and the pairs of carbon atoms labelled C8,8ꢀ and C9,9ꢀ
,
respectively. It indicates that 4 exhibits C2v symmetry on the NMR
time scale. A similar NMR equivalence of the ligand side arms
has been noted for 1 and the dinuclear [(L5)Pd2(Cl)2]+ complex,
where (L5)3− is the trianion derived from the condensation product
of cyclohexanecarbohydrazide and 2-mercapto-5-methylbenzene-
1,3-dialdehyde.20 It should be noted that complex 4 gives rise
to only one 31P NMR resonance. This is not in agreement with
the complex’s C1 point group symmetry found in the solid state.
Such a structure would give rise to two 31P NMR signals. The
observed higher symmetry in the solution state is believed to
Description of crystal structures
The formulation of the complexes 4[ClO4]·EtOH, 5[ClO4]2,
9[ClO4], 10[ClO4]·EtOH and 11[ClO4]2·MeCN·MeOH was fur-
ther confirmed by X-ray crystallography. Experimental crystal-
lographic data are summarized in Table 2.
Crystals of 4[ClO4]·EtOH were grown by recrystallization from
a mixed acetonitrile–ethanol solvent system. A perspective view
Table 2 Crystallographic data for 4[ClO4]·EtOH, 5[ClO4]2, 9[ClO4], 10[ClO4]·EtOH, and 11[ClO4]2·MeCN·MeOH
Compound
4[ClO4]·EtOH
5[ClO4]2
9[ClO4]
10[ClO4]·EtOH
11[ClO4]2·MeCN·MeOH
Formula
Mr/g mol−1
Space group
a/
C42H47Cl3N2O5P2Pd2S C40H45Cl3N2O8P2Pd2S C40H41ClI2N2O4P2Pd2S C44H47ClN4O5P2Pd2S C45H52Cl2N4O10P2Pd2S
1072.97
P21/c
18.566(4)
15.313(3)
16.854(3)
90.00
116.03(3)
90.00
4305(2)
1094.93
P1
1209.80
P21/c
15.572(3)
13.029(3)
26.549(5)
90.00
94.43(3)
90.00
5370(2)
1054.11
P21/c
19.193(4)
14.913(3)
17.329(4)
90.00
115.18(3)
90.00
4489(2)
1186.61
P1
¯
¯
12.666(3)
14.142(3)
14.318(3)
60.85(3)
72.15(3)
81.52(3)
2132.0(7)
2
12.694(3)
14.676(3)
15.751(3)
65.73(3)
69.65(3)
89.49(3)
2477.0(9)
2
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
3
˚
V/A
Z
d
4
4
4
calcd/g cm−3
1.655
1.706
1.496
1.560
1.591
Cryst. size/mm
l(Mo-Ka)/mm−1
h limits/◦
Measured refl.
Independent refl.
Observed refl.a
No. parameters
R1b (R1 all data)
wR2c (wR2 all data)
0.30 × 0.30 × 0.20
0.45 × 0.30 × 0.30
0.18 × 0.15 × 0.10
0.25 × 0.25 × 0.25
0.35 × 0.20 × 0.20
1.191
1.209
2.001
1.027
1.000
1.22–28.32
27042
10380
4945
514
1.65–28.29
19048
9825
7836
523
1.31–29.08
33663
13045
5705
440
1.17–29.01
40331
11031
5931
532
0.0478 (0.1080)
0.1076 (0.1370)
0.901, −0.660
1.53–28.34
22308
11487
7651
595
0.0396 (0.0706)
0.0852 (0.0962)
0.994, −0.747
0.0403 (0.1173)
0.0859 (0.1248)
0.790, −0.773
0.0288 (0.0410)
0.0667 (0.0718)
0.665, −0.573
0.0817 (0.1864)
0.2340 (0.2935)
1.420, −1.499
−3
˚
Max., min. peaks/e A
ꢀ
ꢀ
ꢀ
ꢀ
a Observation criterion: I > 2r(I). b R1 = ꢁFo| − |Fcꢁ/ |Fo|. c wR2 = { [w(Fo − Fc2)2]/ [w(Fo2)2]}
.
2
1/2
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of the structure of the cation 4 is shown in Fig. 1. Selected bond
lengths and angles are listed in the caption.
Fig. 2 Structure of the dication 5 in crystals of [(L4)Pd2(l-Cl)][ClO4]2
(5[ClO4]2) with thermal ellipsoids drawn at the 50% probability level.
Hydrogen atoms are omitted for reasons of clarity. Selected bond
◦
˚
lengths [A] and angles [ ]: Pd(1)–N(1) 2.062(2), Pd(1)–P(1) 2.266(1),
Pd(1)–S 2.362(1), Pd(1)–Cl(1) 2.3462(8), Pd(2)–N(2) 2.061(2), Pd(2)–P(2)
2.258(1), Pd(2)–S 2.367(1), Pd(2)–Cl(1) 2.358(1); Pd(1) · · · Pd(2) 3.0975(7);
Pd(1)–S–Pd(2) 81.84(3), Pd(1)–Cl(1)–Pd(2) 82.36(4).
Fig. 1 Structure of the cation 4 in crystals of (4[ClO4]·EtOH) with thermal
ellipsoids drawn at the 50% probability level. Hydrogen atoms are omitted
◦
˚
for reasons of clarity. Selected bond lengths [A] and angles [ ]: Pd(1)–N(1)
2.017(5), Pd(1)–P(1) 2.268(2), Pd(1)–S 2.341(2), Pd(1)–Cl(1) 2.294(2),
Pd(2)–N(2) 2.018(4), Pd(2)–P(2) 2.246(2), Pd(2)–S 2.378(2), Pd(2)–Cl(2)
2.284(2); Pd(1) · · · Pd(2) 4.389(1), Cl(1) · · · Cl(2) 3.817(2); Pd(1)–S–Pd(2)
136.87(7).
˚
O(4) · · · H(1)N(1) distances being 2.126 and 2.349 A, respectively.
This arrangement places the ClO4− in the vicinity of Pd(1), but the
−
˚
rather long Pd(1) · · · O(4)ClO3 distance of 3.135 A seems to rule
against any substantial bonding interactions.
Each palladium atom is surrounded by a N, S and P atom of
(L3)−, and a terminal chloro ligand in a distorted square planar
manner. The maximum deviations from the least-squares planes
defined by the atoms Pd(1), N(1), P(1), S, Cl(1) and Pd(2), N(2),
The conformation adopted by (L4)− is very similar to that of
(L2)− in [(L2)Pd2(l-Cl)]2+ (2).14 Thus the side arms associated
with Pd(1) and Pd(2) are equally twisted out of the plane of the
central aromatic unit; with the coordination planes of Pd(1) and
Pd(2) at similar dihedral angles of 49.1 and 45.1◦ to the central
aromatic ring. Similar angles are observed in 2 (34.1, 43.1◦). As
was observed for the pair of complexes above, the average Pd–
˚
P(2), S, Cl(1) are 0.0961 and 0.0527 A, respectively. The overall
conformation of the dinucleating P2N2S ligand in 4 is very similar
to that of the N4S ligand (L1)− in [(L1)Pd2(Cl)2]+ (1).14 Thus, in both
structures the side arm associated with Pd(2) is much more twisted
out of the plane of the central aromatic unit than the other. This
side arm twisting is presumably enforced by repulsive interactions
˚
S bonds in 5 at 2.365 A are significantly longer than in 2 (by
˚
≈0.10 A), again indicative of a trans influence of the phosphane
˚
groups. The average Pd–N (2.062 A) and Pd–Cl bond lengths
˚
˚
between the two chloro ligands (Cl(1) · · · Cl(2) = 3.817(2) A). The
(2.352 A) compare well with those in 2 and other four-coordinate
coordination plane at Pd(1) is at a dihedral angle of 22.2◦ to
the central aromatic ring, whereas the corresponding angle for
the coordination plane of ◦Pd(2) is at 41.5◦. Similar values were
observed for 1 (18.6, 48.3 ).14 In contrast to 1, there seems to
be no strain around the bridging thiophenolate sulfur atom in
4. Thus, the displacement of the S atom from the average plane
of the benzene ring to which it is attached has decreased from
Pd complexes.21,22 Thus, as was observed for (L3)−, the ligating
properties of (L4)− are not markedly affected by conversion of the
NMe2 into PPh2 groups.
The crystal structure determination of 9[ClO4] confirmed the
formulation of the diiodo complex [(L3)Pd2(I)2][ClO4]. Fig. 3
presents a perspective view of the structure of the cation 9
along with the atom labelling scheme. The palladium atoms are
four-coordinate; being surrounded by the N, P, and S atoms
of (L3)− and the iodide ligands. The coordination geometry for
Pd(1) is almost perfectly planar; as manifested by a maximum
˚
˚
0.304 A in 1 to 0.047 A in 4. Another difference concerns the Pd–
S bond distances. These are significantly longer in 4 (2.360(2) A
vs 2.266(2) A in 1), presumably due to a trans influence of the
˚
˚
˚
Ph2P groups. The Pd · · · Pd distance and the Pd–S–Pd angle in 4
deviation of only 0.014 A from the least-squares plane defined
◦
˚
(4.389 A and 136.9 , respective◦ly) are also markedly different from
by the atoms Pd(1), N(1), P(1), S, and I(1). The coordination
geometry for Pd(2), on the other hand, is significantly distorted
from square planar towards tetrahedral, as indicated by a P(2)–
Pd(2)–I(2)/N(2)–Pd(2)–S dihedral angle of 17.1◦ (mean deviation
˚
those in 1 (3.922 A and 119.9 , respectively). Thus, replacement
of the NMe2 functions in (L1)− by PPh2 groups in (L3)− does not
change the overall ligating properties of the supporting ligand but
releases some strain in the ligand backbone due do a lengthening
of the Pd–S bonds.
˚
from plane = 0.189 A). This value is a rather large distortion from
planarity. The other palladium complexes described in this study
are more rigorously square planar, the tetrahedral twists from the
PPdLꢀ/NPdS planes (Lꢀ = coligand) not exceeding 5◦. As in 4, the
two coordination planes are markedly twisted around the hinging
sulfur atom so that they are at an angle of 60.8◦ to each other
The crystal structure of 5[ClO4]2 consists of dinuclear
[(L4)Pd2(l-Cl)]2+ complexes and perchlorate anions (Fig. 2). One
of the two perchlorate ions is hydrogen bonded to the hydrogen
atoms of the secondary amine functions; the O(1) · · · H(2)N(2) and
56 | Dalton Trans., 2007, 52–61
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for both palladium atoms. The N(4) atom of the cyanide bonded
to Pd(2) seems to be hydrogen bonded to the CH(imine) group
of an adjacent complex, as indicated by the relatively short
ꢀ
ꢀ
˚
N(4) · · · H(10 )C(10 ) distance (2.437 A) and the slight deviation
of the Pd–C(18)–N(4) angle from 180◦. No such interactions are
observed for the other CN− function. In this case, the Pd–C–N
arrangement is almost perfectly linear. The average Pd–N, Pd–
P and Pd–S bond lengths of 10 show no unusual features and
compare well with those in the dihalogeno complexes 4 and 9
˚
described above. The average Pd–C bond length at 1.958(6) A
is normal for four-coordinate Pd(II) cyanide complexes.18 The
conformation of (L3)− adopted in 10 is slightly different from that
seen in 4 and 9. In 10, the side arms associated with Pd(1) and Pd(2)
are located above and below the plane of the central aromatic unit.
The coordination planes of Pd(1) and Pd(2) are at similar dihedral
angles of 32.3◦ and −32.9◦ to the central aromatic ring, generating
an idealized C2-axis of symmetry that contains the sulfur atom and
the quaternary carbon atom of the tert-butyl group.
Fig. 3 Structure of the cation 9 in crystals of 9[ClO4] with thermal
ellipsoids drawn at the 30% probability level. Hydrogen atoms are omitted
Crystals of 11[ClO4]2·MeCN·MeOH grown by slow evaporation
◦
˚
for reasons of clarity. Selected bond lengths [A] and angles [ ]: Pd(1)–N(1)
2.069(11), Pd(1)–P(1) 2.245(4), Pd(1)–S 2.313(4), Pd(1)–I(1) 2.5891(15),
Pd(2)–N(2) 2.056(11), Pd(2)–P(2) 2.237(4), Pd(2)–S 2.336(4), Pd(2)–I(2)
2.5650(14); Pd(1) · · · Pd(2) 4.154(1), I(1) · · · I(2) 4.112(2); Pd(1)–S–Pd(2)
126.6(2).
from a mixed acetonitrile–methanol solvent system are triclinic
¯
space group P1. Fig. 5 displays the structure of the dication
11. Selected bond lengths and angles are given in the figure
caption. The acetamidato unit bridges the two palladium atoms
˚
in a l1,3-bridging mode at a Pd · · · Pd distance of 3.711 A. The
(52.6◦ in 4). Likewise, the side arm associated with Pd(2) is much
more twisted out of the plane of the central aromatic unit than
the other. The coordination plane of Pd(2) is at a dihedral angle
of 44.6◦ to the central aromatic ring whereas the corresponding
angle for the coordination plane of Pd(1) is at 16.7◦. These values
are nearly identical with those in 4.
The single-crystal X-ray diffraction study of 10[ClO4] unam-
biguously confirmed the formulation of the dicyano complex
[(L3)Pd2(CN)2]+ (Fig. 4). Both cyanides act as monodentate
ligands, generating distorted square-planar NSPC environments
NH hydrogen atom H(3a) could be located unambiguously from
difference Fourier maps providing strong support that the present
orientation of the acetamidato ligand with the N atom bonded
to Pd(2) and the O atom attached to Pd(1), respectively, has been
assigned correctly. This assignment is further supported by the R1
values which converged at R1 = 0.0397 for the present structure
and at a slightly higher value (R1 = 0.0410) for the alternate
orientation. The Pd–O and Pd–N bond lengths at 2.023(2) and
˚
2.014(3) A show no unusual features and compare well with those
in [(L1)Pd2(NHCOCH2Cl)]2+.14
Fig.
5 Structure of the acetamido complex 11 in crystals of
11[ClO4]2·MeCN·MeOH with thermal ellipsoids drawn at the 50%
Fig. 4 Structure of the cyanide complex 10 in crystals of 10[ClO4]·EtOH
probability level. Hydrogen atoms, except those of the MeCONH−
˚
with thermal ellipsoids drawn at the 50% probability level. Hydrogen
coligand, are omitted for reasons of clarity. Selected bond lengths [A] and
atoms are omitted for reasons of clarity. Selected bond lengths [A] and
angles [◦]: Pd(1)–N(1) 2.013(3), Pd(1)–P(1) 2.271(1), Pd(1)–S 2.364(1),
Pd(1)–O(1) 2.032(3), Pd(2)–N(2) 2.021(3), Pd(2)–P(2) 2.257(1), Pd(2)–S
2.313(1), Pd(2)–N(3) 2.014(3), N(3)–C(17) 1.294(5), O(1)–C(17) 1.301(5),
Pd(1) · · · Pd(2); C(17)–N(3)–Pd(2) 133.0(3), C(17)–O(1)–Pd(1) 127.4(3),
N(3)–C(17)–O(1) 123.6(4), N(3)–C(17)–C(18) 119.5(4), O(1)–C(17)–C(18)
116.8(4), Pd(1)–S–Pd(2) 104.98(5).
˚
angles [◦]: Pd(1)–N(1) 2.043(4), Pd(1)–P(1) 2.263(1), Pd(1)–S 2.320(1),
Pd(1)–C(17) 1.956(6), Pd(2)–N(2) 2.024(4), Pd(2)–P(2) 2.255(1), Pd(2)–S
2.342(2), Pd(2)–C(18) 1.957(6), C(17)–N(3) 1.150(6), C(18)–N(4) 1.128(6);
Pd(1) · · · Pd(2) 4.357(1); Pd(1)–S–Pd(2) 138.30(7), Pd(1)–C(17)–N(3)
179.2(6), Pd(2)–C(18)–N(4) 176.0(5).
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Table 3 Norbornene polymerization activity of dinuclear complex 4
Runa
Complex 4/mmol
MAO/mmol
Time/min
Polymer yield/g
Activity/gpolymer molPd−1 h−1
1
2
3
4
5
6
0.0053
0.0053
0.0053
0.0053
0.0053
0.0053
1.056
1.056
—
1.056
1.056
1.056
1
1
60
1
1
0.1433
0.1533
—
0.1046
0.1521
0.1307
8.1 × 105
8.7 × 105
0
5.9 × 105
8.6 × 105
7.4 × 105
1
Runb
Complex 4/mmol
B(C6F5)3/mmol
AlEt3/mmol
Time/min
Polymer yield/g
Activity/gpolymer molPd−1 h−1
7
8
9
0.015
0.015
0.015
0.27
0.27
0.27
0.3
0.3
—
1
1
60
0.3812
0.4180
0.0398
7.6 × 105
8.4 × 105
1.3 × 103
a General conditions: 1.00 g (10.6 mmol) norbornene; molar ratios: Al(MAO) : Pd = 100 : 1, norbornene : Pd = 1000 : 1; total reaction volume 10 ml
(6 ml toluene + 4 ml CH2Cl2).
b General conditions: 2.834 g (30.1 mmol) norbornene; molar ratios: Al(AlEt3) : B : Pd = 10 : 9 : 1, norbornene : Pd = 1000 : 1; total reaction volume
40 ml (30 ml toluene + 10 ml CH2Cl2).
Activity of 4 in the vinyl-addition polymerization of norbornene
(L4)−, respectively. The phosphane groups are not affected under
these conditions. The P2N2S ligands support the formation of
dinuclear complexes of the type [(L3)Pd(Lꢀ)2]n+ and [(L4)Pd2(l-
Lꢀ)]n+, demonstrating that the conversion of the two imine-
functions in the lateral side arms of (L3)− to amine functions
in (L4)− can be used to adjust the type and number of their
active coordination sites. The dichloro-complex [(L3)Pd2(Cl)2]+
exhibits a rich coordination chemistry as illustrated by the
synthesis and structural characterization of the corresponding
acetonitrile, isothiocyanato, azido, iodo, cyanide, and acetamidato
complexes. Finally, it has been demonstrated that the dinuclear
palladium complex 4 catalyzes the vinyl-addition polymerisation
of norbornene when activated with methylalumoxane (MAO) or
B(C6F5)3/AlEt3. Work in progress is now directed towards the
elucidation of this polymerization mechanism. We think that such
studies can aid in an understanding of cooperative effects in
binuclear catalysis.
The catalytic behaviour of complex 4 in the vinyl-addition
polymerization of norbornene23–26 was tested in view of literature
reports that di- and polynuclear nickel and palladium complexes
exhibit high activities.24,27,28 The polymerization results are summa-
rized in Table 3. The dinuclear complex 4 shows norbornene vinyl-
−1
polymerization activities between 105 and 106 gpolymer molPd h−1
when activated with methylalumoxane (MAO) or B(C6F5)3/AlEt3.
The polymerization activities are easily reproducible (run 1–
2 and 4–6 with MAO, run 7 and 8 with borane/AlEt3).
Without a cocatalyst no activity is observed (run 3) and with
B(C6F5)3 alone only a very low activity can be obtained (run
9). The polynorbornenes were found to be insoluble in 1,2,4-
trichlorobenzene even at elevated temperature as is often the case
for palladium-derived vinyl-polynorbornenes, whereby preclud-
ing a polymer analysis by gel permeation chromatography.25,27
In comparison, the activity of
4 is lower than that
of the related (2,6-bis-(thio)semicarbazide-4-methylphenolato-
N,O,Oꢀ(S))-dichloro-dipalladium(II) compounds 12. Complexes
12 can also be activated with MAO and B(C6F5)3/AlEt3 to give
activities between 1.3 × 106 and 1.0 × 107 gpolymer molPd−1 h−1.27 We
trace this observation to the presence of the Ph2P-ligating group in
4 which can shield the active centre with its bulkiness and because
the Pd–P bond is less likely to open even in the presence of the
cocatalysts to create a necessary open coordination site.26
Experimental
All manipulations were carried out using standard Schlenk
techniques under a protective atmosphere of argon. Compound 3
was prepared as described in the literature.29 All other reagents
were purchased from commercial vendors and used without
further purification. Melting points were determined in open glass
capillaries and are uncorrected. NMR spectra were recorded on
a Bruker AVANCE DPX-200 spectrometer at 300 K. 1H and 13
C
chemical shifts refer to solvent signals. 31P NMR chemical shifts
were referenced to 85% H3PO4 at d = 0. Infrared spectra were
recorded on a Bruker VECTOR 22 FT-IR-spectrometer. Elemen-
tal analyses were carried out with a VARIO EL-elemental analyzer.
CAUTION! Perchlorate salts are potentially explosive and
should therefore be prepared only in small quantities and handled
with appropriate care.
Preparation of tBuL3
Conclusions
The proligands tBuL3 and tBuL4 can be selectively S-
deprotected with [Pd(NCMe)2Cl2] to afford the phosphan-imine
and phosphan-amine substituted thiophenolate ligands (L3)− and
To a solution of 2-(diphenylphosphino)ethanamine (1.38 g,
6.02 mmol) in EtOH (20 mL) was added a solution of 5-tert-butyl-
2-(tert-butylthio)benzene-1,3-dialdehyde (835 mg, 3.00 mmol) in
58 | Dalton Trans., 2007, 52–61
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CH2Cl2 (50 mL). The reaction mixture was stirred for 24 h and
evaporated to dryness to give a colorless oil. Yield: 2.10 g (>98%).
This compound was used without further purification for the
preparation of the metal complexes. 1H NMR (200 MHz, CDCl3):
d = 1.08 (s, 9 H, C4H3), 1.27 (s, 9 H, C1H3), 2.40 (m, 4 H, C6H2),
3.70 (m, 4 H, C5H2), 7.25–7.43 (m, 20 H, PhH), 8.07 (s, 2 H, C8H),
9.05 (s, 2 H, C11H). 13C NMR (50 MHz, CDCl3): d = 30.4 (d,
1JCP = 15 Hz, C6), 31.6 (C1), 31.7(C4), 35.5 (C2), 49.7 (C3), 59.0
Preparation of [(L4)Pd2(l-Cl)][ClO4]2 (5[ClO4]2)
To a solution of tBuL4 (200 mg, 0.284 mmol) in MeCN (30 mL)
was added a solution of [Pd(NCMe)2Cl2] (147 mg, 0.568 mmol) in
MeCN (10 mL). After stirring for 12 h at ambient temperature the
solution was concentrated in vacuo and combined with a solution
of LiClO4·3H2O (1.00 g, 6.23 mmol) in MeOH (50 mL). The
resulting solid was filtered off, washed with MeOH and dried in
◦
air. Yield: 128 mg (41%); mp 210 C (decomp). IR (KBr pellet):
2
(d, JCP = 25 Hz, C5), 127.2 (C10), 131.7 (C9), 141.5 (C8), 153.0
m/cm−1 3425(br s), 3156(m) m(N-H), 3056(m), 2960(s), 2931(m),
(C7), 162.7 (C11), 129.0 (PPh), 128.8 (d, JCP = 5 Hz, PPh), 133.2
(d, JCP = 20 Hz, PPh), 138.9 (d, JCP = 10 Hz, PPh). 31P NMR
(81 MHz, CDCl3): d = −18.3.
=
2903(w), 2867(w), 1658(m), 1470(m) m(C C), 1457(m), 1436(s)
m(P–C), 1407(m), 1152(w), 1137(m), 1088(vs) m(ClO4−), 998(w),
976(w), 928(w), 748(m), 723(m), 715(m), 692(s), 622(s). 1H NMR
(200 MHz, CD3CN): d = 1.34 (s, 9 H, C1H3), 2.67 (m, 2 H,
C6HH), 3.07 (m, 2 H, C6HH), 3.30 (m, 2 H, C11HH), 3.60 (m,
2 H, C11HH), 3.98 (m, 2 H, C5HH), 4.32 (m, 2 H, C5HH),
Preparation of tBuL4
To a solution of 2-(diphenylphosphino)ethanamine (211 mg,
0.92 mmol) in EtOH (30 mL) was added a solution of 5-tert-butyl-
2-(tert-butylthio)benzene-1,3-dialdehyde (128 mg, 0.46 mmol) in
CH2Cl2 (50 mL). After stirring for 12 h, sodium borohydride
(34 mg, 0.90 mmol) was added and the mixture was stirred for
a further 2 h. The solution was acidified with 12 M HCl and
evaporated to dryness. Water (50 mL) was added and the pH of
the solution adjusted to 8 by addition of 3 m KOH. The product
was extracted with CH2Cl2 (3 × 50 mL). The organic fractions
were combined, dried with K2CO3 and evaporated to dryness to
give a colourless oil. Yield: 200 mg (65%). This compound was
used without further purification for the preparation of the metal
complexes. 1H NMR (200 MHz, CDCl3): d = 1.15 (s, 9 H, C4H3),
5.43 (bs, 2 H, NH), 7.34–7.89 (m, 22 H, PhH + C8H). 31P{ H}
1
NMR (81.014 MHz, CDCl3): d = 49.90. Elemental analysis:
calc. (%) for C40H45Cl3N2O8P2Pd2S (1095.01): C 43.87, H 4.14,
N 2.56, S 2.93; found C 43.52, H 4.20, N 2.44, S 2.47. This
compound was additionally characterized by an X-ray crystal
structure determination.
Preparation of [(L3)Pd2(MeCN)2][ClO4]3 (6[ClO4]3)
To a solution of 4[ClO4] (513 mg, 0.500 mmol) in acetonitrile
(100 mL) was added a solution of Pb(ClO4)2 (203 mg, 0.500 mmol)
in acetonitrile (10 mL). The reaction mixture was stirred for 4 h and
the resulting precipitate of PbCl2 was removed by filtration. The
yellow solution was evaporated to dryness and dried in vacuum
to give an orange-red powder. The crude material could not
be obtained in analytically pure form. IR (KBr pellet): m/cm−1
3444(br s), 3058(m), 2964(s), 2929(s), 2869(w), 2326(m) (m(C≡N)),
3
1.21 (s, 9 H, C1H3), 2.21 (t, J = 7.7 Hz, 4 H, C6H2), 2.66 (dt,
3JH,H = 7.9 Hz, 2JH,P = 7.7 Hz, 4 H, C5H2), 4.00 (bs, 4 H, C11H2),
7.29–7.44 (m, 22 H, PhH + C8H). 31P NMR (81 MHz, CDCl3):
d = −20.5.
=
2298 (m(C≡N)), 1685(w), 1624(s) m(C N), 1586(w), 1574(m),
Preparation of [(L3)Pd2(Cl)2][ClO4] (4[ClO4])
=
1543(m), 1507(w), 1483(m) m(C C), 1436(s) m(P–C), 1397(w),
1366(w), 1338(w), 1312(w), 1278(w), 1233(m), 1191(w), 1091(vs)
m(ClO4−), 997(w), 948(w), 929(w), 910(w), 835(w), 814(w), 747(m),
To a solution of tBuL3 (2.10 g, 3.00 mmol) in MeCN (200 mL) was
added a solution of [Pd(NCMe)2Cl2] (1.56 g, 6.00 mmol) in MeCN
(50 mL). The reaction mixture was stirred for 2 days, evaporated
to dryness, and the residue redissolved in DMF (5 mL). To this
solution was added a solution of LiClO4·3H2O (7.00 g, 43.6 mmol)
in MeOH (100 mL). The resulting yellow solid was filtered off,
air-dried and recrystallized from MeCN. Yellow crystals. Yield:
1.70 g (1.66 mmol, 55%); mp 294 ◦C (decomp.). IR (KBr pellet):
1
728(m), 691(s), 625(s). H NMR (200 MHz, CD3CN): d = 1.40
(s, 9 H, C1H3), 1.97 (s, 6 H, CH3CN), 2.64 (m, 2 H, C6HH), 2.73
(m, 2 H, C6HH), 4.10 (m, 2 H, C5HH), 4.24 (m, 2 H, C5HH),
7.52–7.71 (m, 12 H, PhH), 7.72–7.89 (m, 8 H, PhH), 8.05 (s, 2 H,
C8H), 8.68 (s, 2 H, C11H). 31P{ H} NMR (81.014 MHz, CD3NO2):
1
d = 59.4.
m/cm−1 3436(br s), 3053(m), 2959(s), 2866(m), 1627(s) m(C N),
=
Preparation of [(L3)Pd2(SCN)2][ClO4] (7[ClO4])
=
1540(m), 1478(m) m(C C), 1436(s) m(P–C), 1400(m), 1365(w),
1337(w), 1312(w), 1275(w), 1232(m), 1193(w), 1100(vs) m(ClO4−),
997(w), 974(w), 946(w), 835(w), 749(m), 721(m), 689(m), 623(m),
548(m), 514(m), 476(m). 1H NMR (200 MHz, CD3CN): d = 1.35
(s, 9 H, C1H3), 2.59 (m, 2 H, C6HH), 2.64 (m, 2 H, C6HH), 4.05
(m, 2 H, C5HH), 4.21 (m, 2 H, C5HH), 7.51–7.68 (m, 12 H, PhH),
7.91–7.97 (m, 8 + 2 H, PhH + C8H), 8.68 (s, 2 H, C11H). 13C NMR
(50 MHz, CD3NO2): d = 27.7 (d, 1JCP = 49 Hz, C6), 30.8 (C1), 35.2
(C2), 64.5 (d, 2JCP = 28 Hz, C5), 127.9 (C10), 129.0 (C9), 140.8 (C8),
150.0 (C7), 167.8 (C11); 130.2 (m, PPh), 133.6 (PPh), 134.3 (m,
To a solution of 4[ClO4] (103 mg, 0.100 mmol) in MeCN (20 mL)
was added a solution of Pb(ClO4)2 (20.3 mg, 50.0 lmol) in MeCN
(2 mL). The reaction mixture was stirred for 4 h before PbCl2
was removed by filtration. To the yellow filtrate was added a
solution of NaSCN (16.2 mg, 0.200 mmol) in 1% aqueous MeOH
(20 mL). The solution was concentrated in vacuo to ca 10 mL,
diluted with EtOH (10 mL), and concentrated again to a final
volume of ≈5 mL. The resulting yellow solid was filtered off,
washed with EtOH and dried in air. Yield: 66 mg (55%). IR
1
PPh), 134.6 (m, PPh). 31P{ H} NMR (81.014 MHz, CD3NO2):
(KBr pellet): m/cm−1 = 3443(br s), 3052(w), 2960(s), 2865(m),
−
=
d = 48.95. Elemental analysis: calc. (%) for C40H41Cl3N2O4P2Pd2S
(1026.98): C 46.78, H 4.02, N 2.73, S 3.12; found C 47.00, H 4.12,
N 2.84, S 2.59. This compound was additionally characterized by
an X-ray crystal structure determination.
2110(vs) m(SCN ), 1628(s) m(C N), 1572(w), 1542(m), 1483(m)
=
m(C C), 1435(s) m(P–C), 1395(m), 1363(m), 1336(m), 1311(m),
1234(m), 1188(w), 1166(m), 1101(vs) m(ClO4−), 997(w), 978(w),
947(m), 833(m), 743(m), 726(m), 712(w), 689(s), 623(s). 1H NMR
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(200 MHz, CD3CN): d = 1.40 (s, 9 H, C1H3), 2.69 (m, 2 H,
C6HH), 2.75 (m, 2 H, C6HH), 4.06 (m, 2 H, C5HH), 4.20 (m,
2 H, C5HH), 7.54–7.70 (m, 12 H, PhH), 7.82–7.95 (m, 8 H,
reaction mixture was allowed to stir for 1 h at 60 ◦C and was then
evaporated to dryness. The resulting yellow solid was recrystallized
from a mixed MeCN–EtOH solvent system. Yield: 63 mg (62%);
◦
1
PhH), 8.02 (s, 2 H, C8H), 8.77 (s, 2 H, C11H). 31P{ H} NMR
mp 280 C (decomp.). IR (KBr pellet): m/cm−1 = 3421(bs),
(81.014 MHz, CD3CN): d = 51.8. Elemental analysis calcd (%) for
C42H41ClN4O4P2Pd2S3·2MeCN·3H2O (M = 1072.24 + 136.15): C
45.72, H 4.42, N 6.95; found C 45.16, H 4.35, N 7.57.
3055(m), 2961(s), 2924(w), 2864(m), 2139(m) m(C≡N−), 1629(s)
=
=
m(C N), 1540(m), 1474(w) m(C C), 1436(s) m(P–C), 1396(w),
1365(w), 1339(w), 1312(w), 1231(w), 1194(w), 1103(vs) m(ClO4−),
998(w), 947(w), 831(w), 749(m), 725(m), 691(s), 624(s). 1H NMR
(200 MHz, CD3CN): d = 1.37 (s, 9 H, C1H3), 2.73 (m, 2 H, C6HH),
2.79 (m, 2 H, C6HH), 4.06 (m, 2 H, C5HH), 4.21 (m, 2 H, C5HH),
7.52–7.67 (m, 12 H, PhH), 7.92–8.03 (m, 10 H, PhH + C8H), 8.77
Preparation of [(L3)Pd2(N3)2][ClO4] (8[ClO4])
To a solution of 4[ClO4] (103 mg, 0.100 mmol) in MeCN (20 mL)
was added a solution of Pb(ClO4)2 (20.3 mg, 50.0 lmol) in
MeCN (2 mL). The reaction mixture was stirred for 4 h before
PbCl2 was removed by filtration. To the yellow filtrate was added
a solution of NaN3 (13.0 mg, 0.200 mmol) in 1% aqueous
MeOH (20 mL). The solution was concentrated in vacuo to ca
10 mL, diluted with EtOH (10 mL), and concentrated again
to ca 5 mL. The resulting yellow solid was filtered off, washed
with EtOH and dried in air. This material could not be obtained
in analytically pure form. Yield: 78 mg (75%). IR (KBr pellet):
(s, 2 H, C11H). 31P{ H} NMR (81.014 MHz, CD3CN): d = 51.70.
1
Elemental analysis: calcd (%) for C42H41ClN4O4P2Pd2S (1008.11):
C 50.04, H 4.10, N 5.56, S 3.18; found C 50.03, H 4.42, N 5.28, S
2.76. This compound was additionally characterized by an X-ray
crystal structure determination.
Preparation of [(L3)Pd2(l1,3-NHCOMe)][ClO4]2 (11[ClO4]2)
To a solution of 4[ClO4] (103 mg, 0.100 mmol) in MeCN (50 mL)
was added a solution of Pb(ClO4)2 (20.3 mg, 0.050 mmol) in MeCN
(2 mL). The reaction mixture was stirred for 4 h before PbCl2 was
removed by filtration. To the yellow filtrate was added NnBu4OH
(260 mg of a 40% methanolic solution, 0.400 mmol). The resulting
red solution was concentrated in vacuo to ca 2 mL, diluted with
MeOH (10 mL), and kept for 5 days at room temperature. The
resulting red crystals were filtered off, washed with MeOH and
m/cm−1 = 3429(br s), 3051(w), 2957(s), 2864(m), 2034(vs) m(N3−),
−
=
=
2017(sh) m(N3 ), 1620(s) m(C N), 1541(w), 1483(w) m(C C),
1435(s) m(P–C), 1396(m), 1364(m), 1337(m), 1277(m), 1229(m),
1189(m), 1165(m), 1096(vs) m(ClO4−), 997(w), 974(w), 833(m),
745(m), 726(m), 690(s), 623(s). 1H NMR (200 MHz, DMSO-d6):
d = 1.39 (s, 9 H, C1H3), 2.81 (m, 2 H, C6HH), 2.85 (m, 2 H, C6HH),
4.05 (m, 2 H, C5HH), 4.20 (m, 2 H, C5HH), 7.57–7.70 (m, 12 H,
PhH), 7.94–8.04 (m, 8 H, PhH), 8.18 (s, 2 H, C8H), 9.04 (s, 2 H,
dried in air. Yield: 34.5 mg (30%). IR (KBr pellet): m/cm−1
3435(bs), 3363(s) m(N–H), 3056(m), 2961(s), 2932(m), 2863(w),
=
C11H). 31P{ H} NMR (81.014 MHz, DMSO-d6): d = 48.70.
1
1632(s) m(C N), 1571(s) masym(MeCONH−), 1512(w), 1481(s)
=
Preparation of [(L3)Pd2(I)2][ClO4] (9[ClO4])
m(C C), 1436(s) m(P–C), 1397(w), 1364(m) msymm(MeCONH−),
=
1311(w), 1278(w), 1233(m), 1189(w), 1169(w), 1093(vs) m(ClO4−),
997(w), 952(w), 832(w), 746(m), 729(m), 692(s), 622(s). 1H NMR
(200 MHz, CD3NO2): d = 1.42 (s, 9 H, C1H3), 2.08 (s, 3 H,
CH3CONH), 2.72 (m, 2 H, C6HH), 2.83 (m, 2 H, C6HH), 4.43 (m,
2 H, C5HH), 4.52 (m, 2 H, C5HH), 6.02 (m, 1 H, CH3CONH),
7.62–7.73 (m, 12 H, ArH), 7.85–7.96 (m, 8 H, Ph), 8.16 (s, 2 H,
To a solution of 4[ClO4] (103 mg, 0.100 mmol) in MeCN (20 mL)
was added a solution of Pb(ClO4)2 (20.3 mg, 50.0 lmol) in MeCN
(2 mL). The reaction mixture was stirred for 4 h before PbCl2 was
removed by filtration. To the yellow filtrate was added a solution
of NBu4I (73.9 mg, 0.200 mmol) in 1% aqueous MeOH (20 mL).
The solution was concentrated in vacuo to ca 10 mL, diluted with
EtOH (10 mL), and concentrated again to ca 5 mL. The resulting
yellow solid was filtered off, washed with EtOH and dried in air.
Yield: 66 mg (63%). IR (KBr pellet): m/cm−1 = 3421(br s), 3049(w),
1
C8H), 8.65 (s, 1 H, C11H), 8.87 (s, 1 H, C11H). 31P{ H} NMR
(81.014 MHz, CD3NO2): d = 49.42, 48.14. Elemental analysis:
calcd (%) for C42H45Cl2N3O9P2Pd2S·2H2O (1113.58 + 36.03): C
43.88, H 4.30, N 3.66; found C 43.51, H 4.37, N 3.97.
=
2961(m), 2920(m), 2864(m), 1614(s) m(C N), 1536(m), 1481(w)
=
m(C C), 1434(s) m(P–C), 1393(m), 1363(w), 1333(m), 1310(w),
1272(m), 1189(m), 1152(m), 1095(vs) m(ClO4−), 997(w), 972(w),
829(m), 745(m), 714(m), 689(s), 622(s). 1H NMR (200 MHz,
CD3CN): d = 1.39 (s, 9 H, C1H3), 2.62 (m, 2 H, C6HH), 2.62
(m, 2 H, C6HH), 3.88 (m, 2 H, C5HH), 4.13 (m, 2 H, C5HH),
7.50–7.70 (m, 12 H, PhH), 7.85 (s, 2 H, C8H), 8.00–8.20 (m, 8 H,
Polymerization experiments
Norbornene (Aldrich) was purified by distillation and used as
a solution in toluene. Toluene was dried over sodium metal,
distilled and stored under nitrogen. The pre-catalyst 4 was applied
as a solution in methylene chloride (dried over CaH2, distilled
under argon). A Schlenk-flask was charged with the norbornene
solution in toluene. For MAO (10% solution in toluene, Witco)
the cocatalyst solution and after 1 min the solution of the pre-
catalyst was added via syringe. For B(C6F5)3/AlEt3 the solution of
the pre-catalyst followed by the separate co-catalyst components
[B(C6F5)3 (Aldrich) and AlEt3 (1 mol l−1 solution in hexane,
Merck–Schuchardt)] were quickly added via syringe. The reaction
mixture was stirred with a magnetic stirrer. The polymerization
was stopped through the addition of 30–40 mL of a 10 :
1 methanol–conc. HCl mixture. The precipitated polymer was
filtered off, washed with methanol and dried in vacuo for 5 h.
PhH), 7.85 (s, 2 H, C8H), 8.54 (s, 2 H, C11H). 31P{ H} NMR
1
(81.014 MHz, DMSO-d6): d = 49.30. Elemental analysis: calcd
(%) for C40H41ClI2N2O4P2Pd2S (1209.88): C 39.71, H 3.42, N 2.32,
S 2.65; found C 40.29, H 3.41, N 2.52, S 1.82.
Preparation of [(L3)Pd2(CN)2][ClO4] (10[ClO4])
To a solution of 4[ClO4] (103 mg, 0.100 mmol) in MeCN (30 mL)
was added a solution of Pb(ClO4)2 (20.6 mg, 50.0 lmol) in MeCN
(2 mL). The reaction mixture was stirred for 4 h before PbCl2 was
removed by filtration. To the yellow filtrate was added a solution of
NaCN (12.3 mg, 0.250 mmol) in 1% aqueous MeOH (20 mL). The
60 | Dalton Trans., 2007, 52–61
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Polymerizations were conducted at room temperature in a water
bath to ensure a constant temperature during the reaction. The IR
spectra of the poly(norbornene)s obtained showed the absence of
a double bond at 1620 cm−1 to 1680 cm−1. This absence assured
that a vinyl/addition polymerization instead of a ring-opening
metathesis polymerization (ROMP) had occurred. The conversion
was calculated by gravimetric analysis of the polymer.
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X-Ray crystallography
Crystals of 4[ClO4]·EtOH, 9[ClO4] and 10[ClO4]·EtOH suitable
for X-ray crystallography were grown by slow evaporation of a
mixed acetonitrile–ethanol solvent system. Crystals of 5[ClO4]2
were obtained by slow evaporation of a methanolic solution.
Crystals of 11[ClO4]2·MeCN·MeOH were obtained from a mixed
acetonitrile–methanol solvent system. The diffraction experiments
were carried out at 180(2) K on a BRUKER CCD X-ray
diffractometer using Mo-Ka radiation. The data were processed
with SAINT30 and corrected for absorption using SADABS.31
Structures were solved by direct methods and refined by full-
matrix least-squares on the basis of all data against F2 using
SHELXL-97.32 H atoms were placed in calculated positions and
treated isotropically using the 1.2-fold Uiso value of the parent
atom except for the methyl protons, which were assigned the 1.5-
fold Uiso value of the parent C atoms. All non-hydrogen atoms
were refined anisotropically.
In the crystal structure of 9[ClO4] the ClO4− anion was found to
be severely disordered over two positions. It has not been possible
to refine the two orientations. Therefore, the O atoms were placed
in calculated positions (equal Cl–O and O · · · O distances, respec-
tively) and treated isotropically (AFIX 3 instruction implemented
in SHELXL) using the 1.2-fold Uiso value of the parent chlorine
atom. The site occupancies were calculated to be 0.35(1) (for
Cl(a)O(1a)–O(4a)) and 0.65(1) (for Cl(b)O(1b)–O(4b)).
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CCDC reference numbers 621802–621806.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b613789j
Acknowledgements
This work was supported by the Deutsche Forschungsgemein-
schaft (Project KE 585/3-3). We sincerely thank Professor Dr
H. Vahrenkamp for providing facilities for X-ray crystallographic
measurements.
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