Synthesis, characterization, dynamics and reactivity toward amination of η3-allyl palladium complexes bearing mixed ancillary ligands. evaluation of the electronic characteristics of the ligands from kinetic data

Article abstract of DOI:10.1039/c0dt00811g

On the basis of an original protocol, we have synthesized several complexes of the type [Pd(η³-C₃H₃R ₂)(LL′)]ClO₄ (R = H, Me; L, L′ = PPh ₃, P(OEt)₃, 2,6-dimethylphenylisocyanide

Full text of DOI:10.1039/c0dt00811g

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PAPER
Synthesis, characterization, dynamics and reactivity toward amination of
g3-allyl palladium complexes bearing mixed ancillary ligands. evaluation of
the electronic characteristics of the ligands from kinetic data†
Luciano Canovese,*a Fabiano Visentin,a Carlo Levia and Alessandro Dolmellab
Received 8th July 2010, Accepted 10th November 2010
DOI: 10.1039/c0dt00811g
On the basis of an original protocol, we have synthesized several complexes of the type
3
[Pd(h -C3H3R2)(LL¢)]ClO4 (R = H, Me; L, L¢ = PPh3, P(OEt)3, 2,6-dimethylphenylisocyanide,
t-butylisocyanide, 1,3-dimesitylimidazolidine, 1,3-dimesitylimidazol-2-ylidene). The complexes, some
of which are completely new species, were fully characterized and their behaviour in solution was
studied by means of 1H NMR. The reactions of the complexes bearing the symmetric allyl moiety
3
[Pd(h -C3H5)(LL¢)]ClO4 with piperidine in the presence of the olefin dimethylfumarate were followed
under kinetically controlled conditions. Formation of allyl-amine and of the palladium(0) derivatives
2
[Pd(h -dmfu)(LL¢] was observed. The reaction rates k2 proved to be strongly dependent on the ancillary
ligand nature and allowed a direct comparison among the electronic characteristics of the ligands. The
reactivity trend determined appears to be mainly influenced by the capability of the ancillary ligands in
transferring electron density to the metal centre and consequently on the allyl fragment.
plexes was studied in detail in order to determine how the trans-
effect/influence of different atoms may affect the reactivity of
Introduction
the complexes.5a It was apparent that the phosphino-carbene
derivative is far less reactive than its P–N analogue. The electronic
withdrawal from palladium to the allyl fragment induced by the
almost pure s-donor carbene6,7 disfavors nucleophilic attack by the
amine on the terminal carbons of the allyl fragment. Thus, it was
proved that carbene carbon represents a better donating atom than
the pyrazole nitrogen. Such an experimental outcome indicates
the valuable opportunity of extending this kinetic approach to
comparing the donor/acceptor properties of the ancillary ligands.
With this goal in mind, we have chosen to synthesize several allyl
Phosphines and phosphites are efficient spectator ligands which
historically have represented a suitable choice when the stabiliza-
tion of complexes of the platinum group metals was the synthetic
aim. Within this class of ligands it is now appropriate to take into
consideration the carbene derivatives NHC. Since Arduengo and
co-workers synthesized the first stable NHC derivatives,1 carbene
complexes of transition metals have acquired an increasing
importance in the field of metal catalyzed reactions2 and the
carbene derivatives of palladium were often employed as useful
substitutes of phosphine or phosphite complexes.2l,3 This is mainly
due to their low toxicity, their stability toward heat, moisture and
air4 and the easy modulation of the substituents at the imidazolic
nitrogen 5 which renders these compounds interesting alternatives
among ligands that can stabilize the catalysts. It is well known that
the chemical character of metal complexes is markedly influenced
by the ability of the ligands in transferring or removing electronic
density to or from the metal centre.
3
complexes of the type [Pd(h -C3H3R2)(LL¢) (R = H, Me; L, L¢ =
NHC, phosphine, phosphite and isocyanide, Scheme 1) and to
determine the reactivity toward amination of the allyl group by
piperidine (Scheme 2). Incidentally, the appropriate rate and easy
monitoring of the reaction progress render such methodology
suitable for our purpose.8
It is well known that attack of the amine on the allyl fragment
in a palladium(II) complex takes place on the allyl face opposite to
the metal, therefore reducing the steric involvement of the ancillary
ligands.9 Furthermore, when a symmetric allyl moiety is employed,
no complication due to the regiochemical nature of the attack
will arise.10 Thus, we surmise that in the allyl amination by the
scarcely hindered piperidine (Scheme 2), the overall reactivity will
be mainly modulated by the electronic status of the allyl fragment
which will be influenced only by the electron density on the
palladium centre, thereby providing a valuable direct comparison
among the electronic characteristics of all the ligands taken into
consideration.
Quite recently, the allyl amination of isostructural phosphino-
pyrazole (P–N) and phosphino-carbene (P–C) allyl Pd(II) com-
aDipartimento di Chimica, Universita` Ca’ Foscari di Venezia, 30129, Venice,
Italy
bDipartimento di Scienze Farmaceutiche, Universita` di Padova, 35100,
Padua, Italy
† Electronic supplementary information (ESI) available: Crystallographic
data. CCDC reference numbers 800526 and 800527. For ESI and
crystallographic data in CIF or other electronic format see DOI:
10.1039/c0dt00811g
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Scheme 1
Scheme 2
This study is based on the comparison of the reactivity of
allyl complexes bearing four different classes of neutral ligands
with marked s-donating and different p-electron withdrawing
allyl)(NHC)(PR3)]+ have been recently synthesized by Cavell and
co-workers.12 The isocyanide derivatives have been inserted in
this study owing to the well recognized s-donating ability of the
isocyanides themselves and the scarcity of data available in the
literature when the latter are used as ancillary ligands toward allyl
derivatives.13
3
character.11 The complexes of the type [Pd(h -allyl)(NHC)L]+
(L = CNR, P(OEt)3) represent a completely new class of
3
derivatives while similar carbene-phosphine derivatives [Pd(h -
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3
Table 1 Selected 1H and 13C NMR data for complexes [Pd(h -C3H5)(NHC)(L)]+ at 298 K (NHC = SIMes, IMes; L = DIC, TIC, PPh3, P(OEt)3)
s(1H) allyl
trans L
Hsyn
s(13C) allyl
trans NHC
Hanti
Hsyn
Hanti
Hcentral
CtransL
CtransNHC
Ccentral
s(13C) carbenic
3
[Pd(h -C3H5)(SIMes)(DIC)]+
3.97
3.85
3.80
3.78
4.35
4.18b
4.47
4.33
2.08
2.13
2.05
2.08
2.39
2.15a,b
2.41
2.36
4.28a
4.39
4.16a
4.27
3.04
3.15b
3.78
3.88
2.68
2.83
2.53
2.68
2.02
2.40a,b
2.22
2.15
5.04
5.01
4.91
5.01
4.94
5.08b
5.08
5.20
63.5
63.9
62.1
62.5
69.9
70.2
71.3
71.5
68.0
68.1
67.9
67.9
72.4
71.9
61.2
61.2
120.9
121.0
120.2
120.3
119.8
120.2
121.5
121.8
204.0
175.7
205.3
176.5
209.0
179.2
207.0
177.9
3
[Pd(h -C3H5)(IMes)(DIC)]+
3
[Pd(h -C3H5)(SIMes)(TIC)]+
3
[Pd(h -C3H5)(IMes)(TIC)]+
3
[Pd(h -C3H5)(SIMes)(PPh3)]+
3
[Pd(h -C3H5)(IMes)(PPh3)]+
3
[Pd(h -C3H5)(SIMes)(P(OEt)3)]+
3
[Pd(h -C3H5)(IMes)(P(OEt)3)]+
a From 1H-2D COSY spectrum. b From low temperature (253 K) spectrum.
on the metal centre induced by the strong s-donor NHC ligands
although some electronic shielding exerted by the carbenic mesityl
substituents on the allyl termini has to be invoked.16 Eventually, a
significant and not unprecedented difference between the chemical
Results and discussion
Synthesis of palladium allyl and 1,1- dimethyl allyl complexes
bearing NHC-L¢ ligands (NHC = SIMes, IMes; L¢ = DIC, TIC,
PPh3, P(OEt)3)
shifts of the carbenic carbons in SIMes and IMes derivatives is
14a,17
~
noticed also in these complexes (Dd 30 ppm).
In the case of
=
The transmetalation reaction between the palladium allyl dimers
complexes [Pd(h -C3H5)(NHC)(POEt3)]+ (NHC = SIMes, IMes)
the terminal allyl protons and carbons again display different
chemical shifts. The structural investigation in solution is favoured
by the easily observable coupling of the terminal allyl protons
3
3
[Pd(m-Cl)(h -C3H3R2)]2 (R = H, Me) and the silver carbenic
complexes NHC-Ag-Cl (NHC = SIMes, IMes)14 carried out at
3
RT in CH2Cl2 yields the complexes [Pd(h -C3H3R2)(NHC)Cl],
which have been obtained by Nolan and co-workers by an
alternative procedure.15 Probably, owing to the considerable steric
hindrance of the carbenic ligand used in our case, at variance
with Cavell’s findings12 no formation of di-carbenic species has
been observed with our synthetic procedure. Dechlorination by
NaClO4 in mixed solvent (CH2Cl2/CH3OH; 3/1) of the complexes
1
and carbons with the phosphorus trans to them in the H and
13C{ H}NMR spectra, respectively5a,12 and by the previously cited
1
HMBC cross-peak between the carbenic carbon and the anti allyl
proton trans to it.5a These complexes, at variance with the case
discussed previously, display the allyl protons and carbons trans
to carbenes resonating at higher field than those trans to phosphite.
The reduced electron back-donation of the phosphite when
compared with that of isocyanide ligands probably offsets the
shielding brought about by the NHC substituents. The complexes
3
[Pd(h -C3H3R2)(NHC)Cl] and addition of the appropriate ligand
L¢ (L¢ = DIC, TIC, P(OEt)3 and PPh3) yields the allyl derivatives
3
3
[Pd(h -C3H3R2)(NHC)(L¢)]+. Apart from the complexes [Pd(h -
allyl)(NHC)(PR3)]+ (where NHC represents the little hindered
tmiy and dipdmiy) obtained by Cavell16 the species described in
this paper represent to the best of our knowledge a new class of
mixed ligand palladium allyl compounds.
[Pd(h -C3H5)(NHC)(PPh3)]+ (NHC = SIMes, IMes) display a
3
spectrometric behaviour very similar to that of the phosphite
derivatives. The signals of the allyl protons and carbons trans
to the carbenes still resonate at higher field than those ascribable
to the allyl protons trans to phosphite although the difference of
chemical shifts Dd in this latter case is smaller than that previously
described. Remarkably, the difference between chemical shifts
of the carbenic carbons of the complexes bearing SIMes and
IMes is also confirmed in the case of the co-ligands PPh3 and
P(OEt)3.14a,18
Generally speaking, the chemical shifts of the carbenic carbons
of the ligands SIMes and IMes are scarcely influenced by the nature
of the co-ligand and in any case these carbons resonate within a
narrow interval (4-5 ppm). Notably, the allyl complexes bearing
the NHC ligands tmiy and dipdmiy and a variety of phosphines
display a similar behaviour.12 (See Table 1).
Characterization of palladium allyl complexes bearing NHC-L¢
ligands (NHC = SIMes, IMes; L¢ = DIC, TIC, PPh3, P(OEt)3)
The 1H and 13C NMR spectra, recorded at RT, of the complexes
bearing carbenic and isocyanide ligands display the signals of the
terminal allyl protons and carbons resonating at different frequen-
cies owing to the asymmetry arising from two different ancillary
ligands. According to previous findings,5a an easy assignment of
the allyl signals can be obtained on the basis of the intense cross-
peak related to the carbenic carbon and the anti allyl proton trans
to it in the 2D HMBC spectra. These complexes display the allyl
protons and carbons trans to carbenes resonating at lower field
than those trans to isocyanides (See Table 1). Notably, the signals
ascribable to the central allyl proton and carbon and the terminal
allyl protons trans to isocyanides resonate at significantly higher
Solution dynamics of the palladium allyl complexes bearing
NHC-CNR ligands (NHC = SIMes, IMes; CNR = DIC, TIC)
3
field than those of the homoleptic symmetric derivative [Pd(h -
As observed elsewhere,12 the coordinated allyl fragment does not
3
1
3
C3H5)(CNR)2]+ (CNR = DIC, TIC) (See Experimental). These
undergo h -h -h isomerization since no negative-phase cross-
high-field shifts can be traced back to the high electron density
peaks among terminal allyl protons are observed in the NOESY
968 | Dalton Trans., 2011, 40, 966–981
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experiments. The signals ascribable to the terminal and central
protons are sharp and distinct and no related cross-peaks are
detectable by NOESY experiments. This fact probably depends
on the strong s-donor capability of the ligands coupled with the
poor coordinative nature of the solvent used which are not able to
trigger a fluxional mechanism analogous to that recently proposed
by Pregosin and co-workers.7
Solution dynamics of the palladium allyl complexes bearing
NHC-L¢ ligands (NHC = SIMes, IMes; L¢ = PPh3, P(OEt)3)
3
In the case of complexes [Pd(h -C3H5)(NHC)(L¢)]+ (NHC =
SIMes, IMes; L¢ = PPh3, P(OEt)3) a complete or partially hindered
rotation of one phenyl substituent of carbene is observed. Thus,
3
the complex [Pd(h -C3H5)(SIMes)(PPh3)]+ displays six distinct
groups of signals at RT integrating 3 H each ascribable to the
methyl protons of the phenyl substituent since the shielding
effect exerted by the phosphine PPh3 probably renders the para
methyl protons different enough to be independently detected.
Accordingly, the signals of the aromatic protons (b, b¢ and e, e¢) are
At variance with the allyl fragment, an unequivocal rota-
tional rearrangement of the imidazolic aromatic substituents
3
is detectable at RT in the case of the complexes [Pd(h -
C3H5)(NHC)(CNR)]+ (NHC = SIMes, IMes; CNR = DIC, TIC).
The signals ascribable to the ortho methyl groups in ortho position
of the phenyl substituents of carbenic ligands generate two
independent singlets integrating 6 H each owing to their mutual
position with respect to the main coordination plane. Similarly, the
aromatic protons (b, b¢ and e,e¢; Fig. 1) resonate as two singlets
at different chemical shifts. Conversely, the methyl groups in para
position are isochronous and this fact is probably due to their long
distance from the asymmetric centre of the complex.
3
detectable as four distinct singlets. Conversely, the complex [Pd(h -
C3H5)(IMes)(PPh3)]+ displays a more extensive fluxionality which
1
however can be easily “frozen” at 253 K. The ensuing H NMR
spectrum at reduced temperature becomes perfectly comparable
3
with that of complex [Pd(h -C3H5)(SIMes)(PPh3)]+ recorded at
RT.
3
The RT solution behaviour of the complexes [Pd(h -
C3H5)(NHC)(P(OEt)3)]+ (NHC = SIMes, IMes) can be traced
back to that of the corresponding phosphine complexes. Thus,
3
complex [Pd(h -C3H5)(SIMes)(P(OEt)3)]+ displays three singlets
integrating 3 H each related to three distinct ortho methyl protons
and one singlet (integrating 9 H) which is comprehensive of the
para and ortho methyl groups (c, f) resonating at almost the same
chemical shift. The aromatic protons (b, b¢ and e, e¢) resonate as
two singlets of 1 : 3 relative intensity.
3
The RT spectrum of complex [Pd(h -C3H5)(IMes)(P(OEt)3)]+
still displays a generalized fluxionality and the three distinct signals
3
of the ortho methyl groups detected in the case of complex [Pd(h -
C3H5)(SIMes)(P(OEt)3)]+ resonate in this case as a broad singlet.
Synthesis, characterization and dynamics of palladium allyl
complexes bearing PPh3-CNR ligands (CNR = DIC, TIC)
3
The complexes of the type [Pd(h -C3H5)(CNR)(PPh3)]+ (CNR =
DIC, TIC) are synthesized by adding to a solution of the palladium
3
allyl dimer [Pd(m-Cl)(h -C3H5)]2 the stoichiometric amount of
PPh3 followed by addition of the appropriate isocyanide in the
presence of NaClO4 or alternatively by adding the isocyanide
followed by PPh3 again in the presence of NaClO4 (Scheme 3).
3
Fig. 1 Spatial representation of the complexes [Pd(h -C3H5)(NHC)(L¢)]+
3
(A) and [Pd(h -1,1-Me2C3H3)(NHC)(L¢)]+ (B).
Scheme 3
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3
Remarkably, both the intermediates (namely [Pd(h -C3H5)-
(IMes)(P(OEt)3)]+) in solution behave similarly to their analogues
bearing the symmetric allyl group. No rotation of the mesityl
substituents at the imidazole nitrogens is detected at RT and
therefore six distinct groups of signals integrating 3 H each
related to the ortho and para methyl protons are detectable
in the 1H NMR spectra. Sometimes, in the most favourable
cases the four signals integrating 1 H related to the b, b¢,e,
e¢ aromatic protons are also detectable (Fig. 1(B)). On the
contrary, the phenyl substituents of the ligands NHC in the
3
(PPh3)Cl] and [Pd(h -C3H5)(CNR)Cl]) can be separated from the
reaction mixture and reacted with the adequate ligand in the
presence of NaClO4 to give the final reaction product and NaCl.
The 1H and 13C NMR spectra of the complexes [Pd(h -
3
C3H5)(DIC)(PPh3)]+ and [Pd(h -C3H5)(TIC)(PPh3)]+ show no hint
3
3
1
3
of h -h -h allyl isomerization and are promptly interpreted on
the basis of the coupling between the phosphorus atom with
the protons (J3PH) and carbon (J2PC) of the allyl termini trans
to it. In the case of the complex [Pd(h -C3H5)(DIC)(PPh3)]+ the
carbene-DIC derivatives ([Pd(h -1,1-Me2C3H3)(SIMes)(DIC)]+,
3
3
3
coupling between the phosphorus and the allyl carbon cis to it
[Pd(h -1,1-Me2C3H3)(IMes)(DIC)]+) rotate freely and therefore
is also detectable. However, the coupling constant in this case is
two distinct signals integrating 6 H each ascribable to the methyl
groups ortho to the phenyl substituents of imidazole nitrogens
and one signal integrating 6 H related to the isochronous methyl
groups in para position are detectable. Accordingly, two different
signals for the aromatic protons b, b¢-e, e¢ integrating 2 H each are
also observable.
considerably smaller (J2
= 2.6 Hz, J2
= 25.7 Hz). Irre-
PCcis
PCtrans
spective of the complexes [Pd(h -C3H5)(DIC)(PPh3)]+ or [Pd(h -
C3H5)(TIC)(PPh3)]+, the carbon of the allyl termini trans to
phosphine displays the same chemical shift whereas the chemical
shift of the carbon trans to isocyanide is influenced by the
nature of the isocyanide itself. In this respect, the allyl carbon
3
3
trans to TIC (complex [Pd(h -C3H5)(TIC)(PPh3)]+) resonates at
3
Kinetic studies
3
higher field (~2 ppm) than that trans to DIC (complex [Pd(h -
The reaction in Scheme 2 was preliminarily studied in CDCl3
C3H5)(DIC)(PPh3)]+). Apparently, the alkyl substituent renders
the t-butyl-isocyanide (TIC) a stronger electron donating species
than di-methylphenylisocyanide (DIC) thereby inducing an in-
creasing electron density on palladium and consequently on the
allyl termini trans to it (this effect might be invoked in order to
at 25 ◦C by 1H NMR techniques. The allyl amine and the
8
palladium(0) complexes were easily identified among the reaction
products. The signals ascribable to the olefinic methoxy group and
those of the protons of the coordinated dmfu of the latter resonate
up-field and down-field respectively with respect to the signals
of the uncoordinated olefin.19 Moreover, the spectral features
strongly depend on the ancillary ligands. Thus, the presence of
ligands with a phophorus atom strongly influence the coupling
constant of the olefin proton trans to it (JPHtrans > JPHcis). In these
cases, the reaction progress can be easily followed by 31P NMR
technique by monitoring the disappearance of the phosphorus
signal of the allyl complex and the concomitant appearance
of that of the olefin complex which resonates down-field (3–
5 ppm in the case of phosphine and ~20 ppm in the case
of phosphite complexes). A table summarizing some selected
3
explain the difference in reactivity between the complexes [Pd(h -
C3H5)(DIC)(PPh3)]+ and [Pd(h -C3H5)(TIC)(PPh3)]+, Vide post).
3
Characterization of palladium 1,1-dimethyl allyl complexes
bearing NHC-L¢ ligands (NHC = SIMes, IMes; L¢ = DIC, TIC,
PPh3, P(OEt)3)
3
1
3
Also in the case of the title complexes no h -h -h isomerisation of
the allyl fragment is observable. Furthermore, the allyl asymmetry
allows an unequivocal structural investigation.
Remarkably, only the geometric isomer bearing the dimethyl
substituted allyl termini trans to NHC ligands is detectable in
solution (Fig. 1(B)). This fact is clearly confirmed by the ensuing
cross-peak (J4) between the carbenic carbon and the allyl protons
of the syn and anti methyl groups trans to it. Moreover, in the cases
of the complexes bearing PPh3 and P(OEt)3 the coupling between
the phosphorus and the syn and anti protons of the allyl termini
trans to it is clearly detectable.
1
2
characteristic H and 31P NMR signals of the complexes [Pd(h -
dmfu)(LL¢)] is reported in the Experimental section. Then the
kinetics were carried out under pseudo-first order conditions by
adding appropriate concentrations of piperidine to a chloroform
solution of the complex under study in a thermostatted cell
of a UV-Vis spectrophotometer in the presence of an adequate
concentration of dimethylfumarate (dmfu) which stabilizes the
2
ensuing derivatives [Pd(h -dmfu)(L)(L¢)]. It is noteworthy that
the dmfu concentration does not influence the overall reaction
rate since such olefin quickly displaces the allylamine from its
palladium(0) derivative8,9 (Scheme 4).
Solution dynamics of palladium 1,1-dimethyl allyl complexes
bearing NHC-L¢ ligands (NHC = SIMes, IMes; L¢ = DIC, PPh3,
P(OEt)3)
3
In the cases of the carbenic complexes ([Pd(h -
3
3
The phosphino and phosphito carbenic derivatives ([Pd(h -1,1-
C3H5)(SIMes)(TIC)]+ and [Pd(h -C3H5)(IMes)(TIC)]+ the
3
1
Me2C3H3)(SIMes)(PPh3)]+, [Pd(h -1,1-Me2C3H3)(IMes)(PPh3)]+,
slow reactions were followed by means of H NMR technique
3
3
[Pd(h -1,1-Me2C3H3)(SIMes)(P(OEt)3)]+, [Pd(h -1,1-Me2C3H3)-
since the high concentrations ensure a shortened reaction time.
Scheme 4
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Table 2 Rate constants k2 for the allyl amination reaction (Scheme 2) determined in CHCl3 at 25 ◦C measured by UV/Vis or 1H NMR techniques
Complex
k2 (mol-1dm3s-1)
Complex
k2 (mol-1dm3s-1)
3
3
[Pd(h -C3H5)(PPh3)2]+
50
9.8 0.4
61
9.7 0.3
3
[Pd(h -C3H5)(SIMes)(P(OEt)3)]+
(7.8 0.1) ¥ 10-2
(7.4 0.2) ¥ 10-2
(7.3 0.3) ¥ 10-2
(5.7 0.1) ¥ 10-2
(8.3 0.4) ¥ 10-3a
(5.5 0.2) ¥ 10-3a
5.0 0.3
3
3
[Pd(h -C3H5)(P(OEt)3)2]+
[Pd(h -C3H5)(IMes)(P(OEt)3)]+
3
3
[Pd(h -C3H5)(DIC)2)]+
4
[Pd(h -C3H5)(SIMes)(DIC)]+
3
3
[Pd(h -C3H5)(TIC)2]+
[Pd(h -C3H5)(IMes)(DIC)]+
3
3
[Pd(h -C3H5)(DIC)(PPh3)]+
56
20
3
1
[Pd(h -C3H5)(SIMes)(TIC)]+
3
3
[Pd(h -C3H5)(TIC)(PPh3)]+
[Pd(h -C3H5)(IMes)(TIC)]+
3
3
[Pd(h -C3H5)(SIMes)(PPh3)]+
(1.58 0.05) ¥ 10-1
(1.84 0.09) ¥ 10-1
[Pd(h -C3H5)(DIC)(P(n-Bu)3)]+
3
[Pd(h -C3H5)(IMes)(PPh3)]+
a Reactions carried out by 1H NMR experiments in CDCl3 at 298 K.
3
3
[Pd(h -C3H5)(PPh3)2]+ ꢀ [Pd(h -C3H5)(SIMes)(PPh3)]+
~
All the studied reactions went smoothly to completion and follow
the rate law:
=
[Pd(h -C3H5)(IMes)(PPh3)]+
3
d[Complex]
3
3
[Pd(h -C3H5)(P(OEt)3)2]+ ꢀ [Pd(h -C3H5)(SIMes)(P(OEt)3)]+
~
−
= k2[Pip]0[Complex]
=
dt
[Pd(h -C3H5)(IMes)(P(OEt)3)]+
3
Each kobs was evaluated by means of a non-linear regression
analysis of the observed mono-exponential dependence of the
absorbance (or concentration) of the reaction mixture (or of the
starting allyl complex) as a function of time. The k2 values were
determined by unweighted linear regression of the calculated kobs
vs. piperidine concentration [Pip]0 and are reported in Table 2.
No statistically significant intercept was detectable in any linear
regression analysis.20
We surmise that the allyl amination represents a valuable test
in determining the electronic influence of the ligands on the
metal centre and hence on the coordinated organic substrates.
Steric hindrance of the ancillary ligand could hardly influence the
reaction rate as can be deduced from the following observations
and subsequent related experimental evidence:
3
3
+
[Pd(h -C3H5)(DIC)(PPh3)]+ [Pd(h -C H )(DIC) ] ꢀ
~
=
3
5
2
[Pd(h -C3H5)(SIMes)(DIC)]+ [Pd(h -C H )(IMes)(DIC)]
3
3
+
~
=
3
5
This confirms that the bulkiness of the ligands does not affect
the reactivity of the related derivatives, the latter being modulated
by the electronic properties of the ligands only.
As a matter of fact:
a) The NHC ligands (SIMes, IMes) impart an almost
indistinguishable reactivity to their derivatives bearing the
3
same co-ligand (cfr. the reactivity of the couples [Pd(h -
C3H5)(SIMes)(PPh3)]+ -[Pd(h -C3H5)(IMes)(PPh3)]+, [Pd(h -
3
3
C3H5)(SIMes)(P(OEt)3)]+
-[Pd(h -C3H5)(IMes)(P(OEt)3)]+,
3
[Pd(h -C3H5)(SIMes)(DIC)]+- [Pd(h -C3H5)(IMes)(DIC)]+ and
3
3
[Pd(h -C3H5)(SIMes)(TIC)]+- [Pd(h -C3H5)(IMes)(TIC)]+). This
3
3
fact can be traced back to their very similar TEP.22
i) It is well known that the piperidine attacks the allyl fragment
at the face opposite to the metal.9
b) The Tolman Electronic Parameters would explain also the
reactivity of the complexes bearing DIC isocyanides and the co-
ligands PPh3, P(n-Bu)3, SIMes and IMes. The ensuing reactivity
ii) The steric hindrance of the ligands IMes, SIMes and PPh3
is very similar as can be deduced from the buried volume of the
ligands themselves (26, 27, 27% respectively).21and refs. therein
iii) The buried volumes of the triethylphosphites and of n-
butylphosphine are not available. It is however known that P(OEt)3
and P(n-Bu)3 display a reduced cone angle with respect to PPh3
(H/qP(OEt)3 = 109◦; H/qP(n-Bu)3 = 132; H/qPPh3 = 145◦) 22and therefore
they are less bulky ligands than the phosphine itself.
[Pd(h -C3H5)(DIC)(PPh3)]+ > [Pd(h -C3H5)(DIC)(P(n-Bu)3)]+ ꢀ
3
3
[Pd(h -C3H5)(SIMes)(DIC)]+ [Pd(h -C H )(IMes)(DIC)] par-
3
3
+
~
=
3
5
allels the tabulated TEP values of PPh3 (2068.9 cm-1), P(n-Bu)3
(2060.3 cm-1), SIMes (2051.5 cm-1) and IMes (2050.7 cm-1). A
similar reactivity trend is noticed also in the case of isocyanide
TIC.
iv) The isocyanide ligands exert a reduced hindrance if compared
with the other ligands described in the present paper. As a matter of
fact isocyanides have a unique substituent R which is in addition
separated by the coordinating carbon by one spacing nitrogen
atom. This conclusion might also be supported by the structure of
c) The smallest rate constant values are observed in the case
of the complexes of the type [Pd(h -C3H5)(NHC)(TIC)] (NHC =
3
SIMes, IMes). In these cases the strong donating ability of the
carbene NHC is coupled with that of the isocyanide TIC bearing
the electron donating butyl substituents.
3
the complex [Pd(h -C3H5)(IMes)(DIC)]+ reported in this paper.
3
d) The complexes [Pd(h -C3H5)(TIC)(L¢)]+ (L¢ = NHC, TIC,
v) The DIC isocyanide displays a global unfavourable fan angle
which is remarkably wider but only slightly narrower than TIC.
(Fan angle 1DIC = 106, Fan angle 1TIC = 70; Fan angle 2DIC = 53,
Fan angle 2TIC = 68).23
From these considerations it is apparent that the steric bulk of
the ligands obey the following order:
PPh3) are always less reactive than the corresponding species
3
[Pd(h -C3H5)(DIC)(L¢)]+ (L¢ = NHC, DIC, PPh3). This observa-
tion is in agreement with the electronic donor properties of the
isocyanides themselves.
3
3
e) When the complexes [Pd(h -C3H5)(P(OEt)3)2]+, [Pd(h -
C3H5)(SIMes)(P(OEt)3)]+ and [Pd(h -C3H5)(IMes)(P(OEt)3)]+ are
3
considered, it is apparent that their reactivity again fits
~
~
PPh3 SIMes IMes > P(n-Bu) > P(OEt) > DIC ≥ TIC
=
=
3
3
their specific TEP values (TEPP(OEt)3 = 2076.3 cm-1). As a
3
3
whereas, from the experimental kinetic data reported in Table 2 it
is apparent that the complexes display the following reactivity:
matter of fact [Pd(h -C3H5)(SIMes)(P(OEt)3)]+ and [Pd(h -
C3H5)(IMes)(P(OEt)3)]+ react slower than bis-phosphite species.
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Table 3 Selected 1H and 31P NMR signals of the palladium(0) olefin complexes in CDCl3 at 298 K
Complex
Olefinic protons
O-CH3
31P resonance
2
[Pd(h -dmfu)(SIMes)(DIC)]
3.42 d (9.7a); 2.93 (9.7)a
3.52 d (9.7a); 2.93 (9.7)a
3.25 d (9.7a); 2.82 (9.7)a
3.31 d (9.6a); 2.80 (9.6)a
3.35 dd (9.5a; 9.5b); 2.64 dd (9.5a; 4.6c);
3.35 dd (9.5a; 9.5b); 2.79 dd (9.5a; 4.6c);
3.17d (9.6a; 3.6c); 3.10d (9.6a; 13b);
3.26d (9.4a; 5.0c); 3.13d (9.4a; 14b);
4.43 dd (9.8a; 9.8b); 4.15 dd (9.8a; 3.2c);
4.27 dd (9.9a; 9.9b); 4.03 dd (9.9a; 3.1c);
4.12 dd (9.9a; 9.9b); 4.03 dd (9.9a; 3.3c);
4.27 s
3.40 s; 3.24 s
3.35 s; 3.30 s
3.39 s; 3.24 s
3.34 s; 3.31 s
3.23 s; 2.75 s
3.23 s; 2.78 s
3.30 s; 3.24 s
3.29 s; 3.28 s
3.65 s; 2.96 s
3.66 s; 2.97 s
3.61 s; 3.58 s
3.64 s
2
[Pd(h -dmfu)(IMes)(DIC)]
2
[Pd(h -dmfu)(SIMes)(TIC)]
2
[Pd(h -dmfu)(IMes)(TIC)]
2
[Pd(h -dmfu)(SIMes)(PPh3)]
27.0
27.4
151.3
151.0
27.5
28.0
9.07
2
[Pd(h -dmfu)(IMes)(PPh3)]
2
[Pd(h -dmfu)(SIMes)(P(OEt)3)]
2
[Pd(h -dmfu)(IMes)(P(OEt)3)]
2
[Pd(h -dmfu)(DIC)(PPh3)]
2
[Pd(h -dmfu)(TIC)(PPh3)]
2
[Pd(h -dmfu)(DIC)(P(n-Bu)3)]
2
[Pd(h -dmfu)(DIC)2)]
2
[Pd(h -dmfu)(TIC)2)]
3.97 s
3.63 s
2.99
3.59
2
[Pd(h -dmfu (PPh3)2]
4.14 me
27.4
148.6
2
[Pd(h -dmfu)(P(OEt)3)2]
4.07 me
a JHH, Hz. b PH, Hz (trans position). c PH, Hz (cis position). d AB part of an ABX system. e A2 part of an A2X2 system.
J J
˚
Table 4 Selected bond lengths (A) and angles (deg) for the complex cation
f) At variance with the preceding observation, it is ap-
parent that phosphite derivatives display a reduced reactivity
with respect to the phosphine analogues despite their TEP
values and bulkiness, which would suggest an opposite re-
sult. In this respect it is noteworthy that the reactivity of
the complexes bearing phosphine ligands is always higher
3
[Pd(h -C3H5)(IMes)(DIC)](ClO4)
Bond lengths
Pd–C(1)
Pd–C(22)
Pd–C(23)
Pd–C(24)
2.046
2.190
2.166
2.133
1.999
C(1)–N(1)
C(1)–N(2)
C(25)–N(3)
C(22)–C(23)
C(23)–C(24)
1.359
1.353
1.148
1.389
1.397
3
than that of their phosphite analogues ([Pd(h -C3H5)(PPh3)2]+>
3
3
3
[Pd(h -C3H5)(P(OEt)3)2]+, [Pd(h -C3H5)(SIMes)(PPh3)]+ >[Pd(h -
Pd–C(25)
C3H5)(SIMes)(P(OEt)3)]+, [Pd(h -C3H5)(IMes)(PPh3)]+ >[Pd(h -
C3H5)(IMes)(P(OEt)3)]+). Notably, the correlation between the
electronic parameters determined by the spectral features and
the reactivity of the complexes is not always feasible, especially
when comparison among different metals is considered and
the differences between parameters are not particularly high
(TEPPPh3 = 2068.9, TEPP(OEt)3 = 2076.3 cm-1).24
3
3
Bond angles
C(1)–Pd–C(22)
C(1)–Pd–C(24)
C(1)–Pd–C(25)
C(1)–Pd–C(23)
C(22)–Pd–C(23)
C(22)–Pd–C(24)
C(22)–Pd–C(25)
C(23)–Pd–C(24)
C(23)–Pd–C(25)
163.2
96.1
94.4
129.9
37.2
67.7
101.5
37.9
133.7
C(24)–Pd–C(25)
Pd–C(1)–N(1)
Pd–C(1)–N(2)
N(1)–C(1)–N(2)
Pd–C(25)–N(3)
Pd–C(22)–C(23)
Pd–C(23)–C(24)
Pd–C(23)–C(22)
Pd–C(24)–C(23)
168.7
128.7
126.7
104.6
174.4
70.4
69.8
72.4
72.3
3
g) The complexes of the type [Pd(h -C3H5)(NHC)(L)] (NHC =
SIMes, IMes;
L = PPh3, DIC) react similarly although
3
3
the phosphino-species [Pd(h -C3H5)(SIMes)(PPh3)]+ and [Pd(h -
[Pd(h -C3H5)(IMes)(DIC)]+ appears to be, to the best of our
knowledge, among the so far rare examples27k,29 of a mononuclear
Pd complex surrounded only by C donor atoms and showing
both a carbene and an isocyanide ligand.
3
C3H5)(IMes)(PPh3)]+ display a slightly enhanced reactivity with re-
spect to that of DIC derivatives [Pd(h -C3H5)(SIMes)(DIC)]+ and
3
3
[Pd(h -C3H5)(IMes)(DIC)]+, while the homoleptic compounds
3
3
[Pd(h -C3H5)(PPh3)2]+ and [Pd(h -C3H5)(DIC)2]+ display similar
In [Pd(h -C3H5)(IMes)(DIC)]+ the allyl anion binds the metal
centre in the h mode and the environment about the metal can
be viewed as distorted square planar. In this description, the main
coordination plane, beside Pd, is defined by the atoms C(1), C(22),
3
rate constants.
3
Thus, the following order that can be traced back to the net
capabilities of the ligands in transferring electron density to the
metal and then to the allyl fragment can be proposed:
˚
C(24) and C(25), which are coplanar within 0.03 A, while Pd is off
˚
by 0.06 A.
~
~
IMes ~ SIMes ꢀ P(n-Bu) > TIC P(OEt) > DIC PPh
=
=
3
3
3
We performed a search in the CCDC database looking for
mononuclear Pd complexes showing a metal environment closely
resembling that of the present complex (at least four donor C
Remarkably, when similar ligands are taken into consideration,
this order turns out to be coincident with that proposed by Cavell
and co-workers.25
3
atoms and at least an h -bound allyl/allyl-like ligand).15,27b,d,e,g,k,30
By limiting the comparison to carbene complexes and con-
sidering Pd–C distances involving the peripheral carbon atoms
of the ligand, it can be noted that in complexes reported there
X-ray crystal structures
3
˚
The
crystal
structures
of
the
complexes
[Pd(h -
is a trend, on the average, towards bonds ca. 0.02 A longer
C3H5)(IMes)(DIC)]+ and [Pd(h -1,1-Me2C3H3)(IMes)(PPh3)]+are
shown in Fig. 2 and the main crystallographic data and bond
lengths and angles are listed in Table 3, Table 4 and Table
5, respectively. In the CCDC26 database only 15 entries show
a Pd with an environment of 5 carbon atoms.27–29 Complex
than those found in the present study (2.210 vs. 2.190(2) A,
3
˚
˚
2.132 vs. 2.133(2) A, respectively). The opposite is true for
the central Pd–C bond, which in this study has been found
˚
to be about 0.03 A longer than the reported mean (2.133 vs.
˚
2.166(2) A). The Pd–C(23) distance found here is the longest
972 | Dalton Trans., 2011, 40, 966–981
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3
3
Fig. 2 ORTEP33 view of the two complex cations [Pd(h -C3H5)(IMes)(DIC)]+ (top) and [Pd(h -1,1-Me2C3H3)(IMes)(PPh3)]+ (bottom), showing also
the numbering scheme used. Thermal ellipsoids are at the 40% probability level. The hydrogen atoms and the perchlorate anions have been omitted. In
3
the view of complex [Pd(h -1,1-Me2C3H3)(IMes)(PPh3)]+, the position of the 1,1,-dimethylallyl moiety with refined site occupancy = 0.23 has been drawn
with white bonds.
3
one reported so far for Pd carbene complexes, and it ranks
The
overall
arrangement
of
complex
[Pd(h -1,1-
˚
second longest after the one (2.170 A) found in the cation
Me2C3H3)(IMes)(PPh3)]+ does not appear too different from
that of [Pd(h -C3H5)(IMes)(DIC)]+, except for the replacement
of the isocyanide ligand with the triphenylphosphine group.
Remarkably, the dimethyl bis-substituted allyl terminus is trans
3
3
t - butylisocyanido - (acetyl(triphenylphosphonio)methyl) - (h - 2 -
methylallyl)-palladium(II),27k where Pd is also cooordinated by a
neutral isocyanide ligand.
1
As for the other Pd–C distances, the one involving the carbene
to NHC ligand as observed in solution by H NMR technique.
˚
ligand, 2.046(2) A, falls very close to the mean value found in
The metal environment is almost regular square planar, as the
dihedral angle between the planes defined by the atoms C(22),
Pd, C(24) and P, Pd, C(1) is 9.4◦, and that between the planes
defined by the atoms P, Pd, C(1) and C(22A), Pd, C(24) is 4.8◦.
In both cases, the sum of the bond angles about Pd equals almost
exactly 360◦. The 1,1-dimethylallyl residue again binds Pd in
˚
the seventeen structures mentioned above (2.049 A); the one
involving the isocyanide ligand, 1.999(2) A, fits in the restricted
range of known data (1.979–2.038 A) and ranks as second longest.
On trying an overall comparison of the structural parameters
in the coordination sphere, compounds most resembling our
˚
˚
3
3
complex are (h -allyl)-chloro-(N,N¢-dimesitylimidazol-2-ylidene)-
the h mode and the atoms in the coordination sphere, that is,
P, C(1), C(22) and C(24), deviate from the best mean plane by
3
palladium(0), (h -allyl)-chloro-(N,N¢-bis(2,6-diisopropylphenyl)-
imidazol-2-ylidene)-palladium(0)15 and chloro-(N,N¢-bis(2,6-
0.06, 0,10, 0.12 and 0.11 A, respectively (Pd off by 0.05 A). In
the alternate arrangement with C(22A) in place of C(22) all the
˚
˚
3
di-isopropylphenyl)imidazol-2-ylidene)-(h -1-phenylallyl)-palla-
dium(II).30c
atoms, including Pd, are coplanar within 0.06 A.
˚
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Pd complexes8c,30c,31a,b as well as in the compounds described in
ref. 32.
˚
Table 5 Selected bond lengths (A) and angles (deg) for the complex cation
3
[Pd(h -1,1-Me2C3H3)(IMes)(PPh3)] (ClO4)a
˚
The Pd–C distance of the carbene ligand, 2.070(3) A, is
Bond lengths
3
˚
about 0.02 A longer than the corresponding distance in [Pd(h -
C3H5)(IMes)(DIC)]+ and also longer than the mean value found
Pd–C(1)
Pd–C(22)
Pd–C(22A)
Pd–C(23)
Pd–C(23A)
Pd–C(24)
Pd–P
Bond angles
C(1)–Pd–C(22)
C(1)–Pd–C(22A)
C(1)–Pd–C(24)
C(1)–Pd–P
C(1)–Pd–C(23)
C(1)–Pd–C(23A)
C(22)–Pd–C(23)
C(22A)–Pd–C(23A)
C(22)–Pd–C(24)
C(22A)–Pd–C(24)
C(22)–Pd–P
2.070(3)
2.353(4)
2.28(1)
2.173(4)
2.09(1)
2.133(3)
2.358(1)
C(1)–N(1)
C(1)–N(2)
P–CPh*
C(22)–C(23)
C(22)–C(23A)
C(23)–C(24)
C(23A)–C(24)
1.361(3)
1.370(3)
1.828(3)
1.401(6)
1.37(2)
1.437(5)
1.40(1)
3
in the seventeen structures mentioned when discussing [Pd(h -
C3H5)(IMes)(DIC)] (2.049 A), which is also the mean value for
the complexes reported in ref. 32 (2.049 A); however, excluding the
coordination position held by the isocyanide or triphenylphos-
phine ligand in the two molecules, the distance setting around
Pd looks similar, with a short Pd–C bond involving the carbene
doublet and allyl ligand in which the Pd–C(22) bond is always
longer than the Pd–C(23), Pd–C(24) ones. As for the Pd–P length,
+
˚
˚
156.2(1)
155.6(4)
91.6(1)
108.1(1)
127.6(1)
124.7(4)
35.8(2)
36.1(5)
66.4(1)
64.4(4)
94.1(1)
96.0(4)
39.0(1)
38.7(4)
122.2(1)
123.4(4)
C(24)–Pd–P
160.3(1)
130.4(2)
125.5(2)
103.8(2)
115.2(9)
65.1(2)
64.5.(7)
69.0(2)
72.2(6)
79.1(2)
79.4(8)
72.0(2)
69.1(5)
120.5(4)
116.8(1)
Pd–C(1)–N(1)
Pd–C(1)–N(2)
N(1)–C(1)–N(2)
Pd–P–CPh*
Pd–C(22)–C(23)
Pd–C(22A)–C(23)
Pd–C(23)–C(24)
Pd–C(23A)–C(24)
Pd–C(23)–C(22)
Pd–C(23A)–C(22A)
Pd–C(24)–C(23)
Pd–C(24)–C(23A)
C(22)–C(23)–C(24)
C(22A)–C(23A)–C(24)
˚
2.358(1) A, it is not too different from the average found for 933
˚
Pd-PPh3 fragments in the CCDC database (2.300 A).
Conclusion
We have prepared, by means of original synthetic paths, several
novel allyl complexes bearing mixed, strong coordinating ligands.
The complexes were completely characterized in solution and in
two cases we have determined the crystal structures of the related
allyl complexes. On the basis of kinetic studies of the reaction
of allyl amination we were able to compare the donor/acceptor
properties of different spectator ligands. It was apparent that the
NHC species induce the highest electron density on the metal
among all the ligands considered.
C(22A)–Pd–P
C(23)–Pd–C(24)
C(23A)–Pd–C(24)
C(23)–Pd–P
C(23A)–Pd–P
a Atom labels with a final ‘A’ refer to the alternate arrangement of the
disordered 1,1-dimethylallyl residue. *Average of the three P–C(phenyl)
distances/angles.
3
To the best of our knowledge, compound [Pd(h -1,1-
Experimental
Me2C3H3)(IMes)(PPh3)]+ would be the second instance of a
Pd complex showing this coordination environment. In known
structures,8c,31,32 the Pd–C bond distances of the allyl moiety
Solvents and reagents
CH2Cl2 was distilled over CaH2 under inert atmosphere
(Ar), CHCl3 was distilled and stored on silver foil. All other
chemicals were commercial grade and were used without further
˚
˚
span a rather wide range of 0.36 A (2.075–2.430 A); the values
3
found for the two arrangements of the allyl moiety in [Pd(h -1,1-
Me2C3H3)(IMes)(PPh3)]+ remain within this range and span an
3
3
purification. [Pd(m-Cl)(h -C3H5)]2,34 [Pd(m-Cl)(h -C3H3Me2)]2,35
˚
interval of about 0.26 A.
3
3
[Pd(h -C3H5)(PPh3)2](ClO4),36
[Pd(h -C3H5)(DIC)2](ClO4)37
As a general trend, in known h dimethylallyl complexes8c,31 the
longest Pd–C distance is the one involving the peripheral carbon
atom bearing the two methyl residues (mean value of 2.276 A),
3
3
[Pd(h -C3H5)(TIC)2](ClO4),37 [IMesAgCl]14a and [SIMesAgCl]14b
were prepared following literature procedures.
˚
˚
whereas the other terminal C (mean value of 2.131 A) makes the
NMR, UV-Vis and IR measurements
shortest one in about one half of the reported complexes. The same
setting has been found in [Pd(h -1,1-Me2C3H3)(IMes)(PPh3)]+ for
the allyl residue in the arrangement with larger site occupancy
(2.353(4) and 2.133(3) A). In the other arrangement, the shorter
Pd–C distance (2.09(1) A) is the one involving the central atom of
the allyl, a situation found in the other half of reported compounds
(the mean bond length for the central Pd–C distance in all reported
complexes is 2.149 A). In the structures of ref. 32 the situation
is different, with average values indicating a reduced difference
between central and terminal Pd–C distances and, in general, a
3
1D- and 2D-NMR spectra were recorded using a Bruker 300
Avance spectrometer. Chemical shifts (ppm) are given relative to
TMS (1H and 13C NMR) and 85% H3PO4 (31P NMR).
˚
˚
Peaks are labelled as singlet (s), doublet (d), triplet (t), quartet
(q), multiplet (m) and broad (br). The proton and carbon
1
1
assignment was carried out by H-2D COSY, H-2D NOESY,
1H-13C HMQC and HMBC experiments.
˚
UV-Vis spectra were recorded on a Perkin-Elmer lambda 40
spectrophotometer equipped with a Perkin-Elmer PTP 6 (Peltier
temperature programmer) apparatus.
IR spectra were recorded on a Perkin-Elmer Spectrum One
spectrophotometer.
˚
˚
central bond (2.154 A) being ca. 0.01–0.02 A shorter than the
˚
terminal ones (2.161, 2.176 A).
With respect to C–C distances in the allyl, the bond length
between the central C atom and the methyl-bearing carbon in
˚
both arrangements is 0.03–0.04 A longer than the bond between
Preliminary studies and kinetic measurements
the central and the other terminal C atom, opposite to what
has been observed in [Pd(h -C3H5)(IMes)(DIC)]+, where the two
distances are much closer (1.389(3) and 1.397(3) A), a situation
that has already been observed in the other known dimethylallyl
3
1
All the reactions were firstly analyzed by H NMR technique
˚
by dissolving the complex under study in 0.8 mL of CD2Cl2
([complex]0 ª 0.02 mol dm-3) in the presence of dimethyl-fumarate
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([dmfu]0 ª 0.025 mol dm-3) as stabilizing olefin of the final Pd(0)
complex. An appropriate aliquot of piperidine was added ([pip]0
ª 0.12 mol dm-3), and the reaction was followed to completion by
monitoring the disappearance of the starting complex (1) and the
concomitant appearance of the Pd(0) olefin complex (2).
C1), 128.1 (DIC C3, C5), 130.6 (DIC C4), 135.7 (DIC C2, C6), 142.7
(DIC CNR).
31P NMR (CDCl3, T = 298 K, ppm): d 24.9.
IR (KBr pellet, cm-1) n 2170.8 (CN), 1094.7 (ClO4). Anal. Calcd.
for C30H29ClNO4PPd: C, 56.26; H, 4.56; N, 2.19. Found C, 55.98;
H, 4.41; N, 2.09.
An UV-Vis preliminary investigation was carried out in order
to determine the wavelength of the highest absorbance change.
Thus, 3 mL of freshly distilled CHCl3 solution of the complex
under study ([complex]0 ª 1 ¥ 10-4 mol dm-3) in the presence
of dimethylfumarate ([dmfu]0 ª 3 ¥ 10-4 mol dm-3) was placed
in a thermostatted (298 K) cell compartment of the UV-Vis
spectrophotometer. Adequate aliquots of a concentrated solution
of piperidine were then added ([pip]0 ≥ 10 ¥ [complex]0) by means
of a micropipette. The reactions were monitored by recording
the UV-Vis spectra as a function of time corresponding to the
largest absorbance change in the 260–400 nm wavelength interval.
The kinetics of nucleophilic attack at a fixed wavelength were
recorded under pseudo-first order conditions at 310 nm. The
piperidine concentrations spanned within the 1 ¥ 10-3–1 ¥ 10-2
mol dm-3 interval and were obtained by adding known aliquots
of the mother solution of piperidine (0.1–0.3 mol dm-3) to a
solution of the complex under study dissolved in 3 mL of freshly
distilled CHCl3 ([complex]0 ª 1 ¥ 10-4 mol dm-3) in the presence
of dimethylfumarate ([dmfu]0 ª 3 ¥ 10-4 mol dm-3). In the case of
The following complexes were synthesized following a similar
procedure using the same starting complex and the appropriate
ancillary ligands.
[Pd(g3-C3H5)(TIC)(PPh3)](ClO4). Yield: 88%, pale yellow mi-
crocrystals.
1H NMR (CDCl3, T = 298 K, ppm): d 1.60 (s, 9H, TIC CH3),
3.24 (d, 1H, allyl Hanti trans TIC, J = 13.5 Hz), 3.80 (dd, 1H, allyl
Hanti trans PPh3, JHH = 13.5 Hz, JPH = 9.5 Hz), 3.93 (d, 1H, Hsyn
trans TIC, J = 7 Hz), 5.21 (td, 1H, allyl Hsyn trans PPh3, J = 7 Hz,
J = 2 Hz), 5.79 (m, 1H, allyl Hcentral), 7.44-7.54 (m, 15H, P(C6H5)3).
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 29.6 (TIC CH3),
58.9 (C(CH3)3), 70.6 (allyl CH2 trans TIC), 76.2 (allyl CH2 trans
PPh3), 122.3 (allyl CH, JCP = 5.4 Hz), 131.3 (TIC CNR).
31P NMR (CDCl3, T = 298 K, ppm): d 25.0.
IR (KBr pellet, cm-1) n 2220.4 (CN), 1091.0 (ClO4). Anal. Calcd.
for C26H29ClNO4PPd: C, 52.72; H, 4.93; N, 2.36. Found C, 52.54;
H, 4.88; N, 2.30.
3
the complexes [Pd(h -C3H5)(TIC)(NHC)]ClO4 (NHC = SIMes,
[Pd(g3-C3H5)(DIC)(P(n-Bu)3)](ClO4). After treatment with
activated charcoal, the solvent removal under reduced pressure
induces the precipitation of the crude product as a black oil which
was washed with n-hexane. Yield: 88%.
IMes) the reactions under UV-Vis conditions were slow and
with inadequate spectral change. The reactions were therefore
followed by means of NMR technique by integration of the
decreasing signal ascribable to the central allylic proton of the
starting complex in CDCl3 at 298 K ([complex]0 : [dmfu] : [pip]0 =
0.02 : 0.025 : 0.1 (and 0.2) mol dm-3).
1H NMR (CDCl3, T = 298 K, ppm): d 0.93 (t, 9H,
PCH2CH2CH3), 1.41–1.53 (m, 6H, PCH2CH2CH3), 1.93-2.02 (m,
6H, PCH2CH2CH3), 2.48 (s, 6H, DIC CH3), 3.19 (d, 1H, allyl Hanti
trans DIC, J = 16 Hz), 3.66 (dd, 1H, allyl Hanti trans PPh3, JHH
=
14 Hz, JPH = 9 Hz), 4.31 (d, 1H, Hsyn trans DIC, J = 7 Hz), 5.07
(td, 1H, allyl Hsyn trans PPh3, J = 7 Hz, J = 2 Hz), 5.70 (m, 1H,
allyl Hcentral), 7.20 (d, 2H, DIC H3 and H5, J = 8 Hz), 7.33 (t, 1H,
Synthesis of the complexes
[Pd(g3-C3H5)(DIC)(PPh3)](ClO4). To 0.082 g (0.224 mmol)
DIC H4).
3
1
of [Pd(m-Cl)(h -C3H5)]2 dissolved in CH2Cl2 (8 mL), 0.059 g
13C{ H} NMR (CDCl3,
T = 298 K, ppm): d 13.6
(0.448 mmol) of DIC, 0.118 g (0.448 mmol) of PPh3 individually
dissolved in CH2Cl2 (4 + 4 mL) and 0.126 g (0.896 mmol) of
NaClO4·H2O in CH3OH (5 mL) were added. The decoloration
of the solution and the concomitant precipitation of NaCl was
soon noticed. The reaction mixture was filtered over a Millipore
filter, stirred for 30 min, and the solvent was removed under
reduced pressure. The resulting sticky solid was dissolved in
20 mL of CH2Cl2, treated with activated charcoal, and filtered off
through Celite. The clear solution was concentrated under reduced
pressure. Upon addition of diethyl ether the crude product was
obtained as pale yellow residue. The resulting solid was filtered
off, washed with diethyl ether (3 ¥ 3 mL) and with n-pentane (2 ¥
3 mL) and eventually dried under vacuum. Yield: 0.240 g (97%).
1H NMR (CDCl3, T = 298 K, ppm): d 2.12 (s, 6H, DIC CH3),
3.45 (d, 1H, allyl Hanti trans DIC, J = 13.5 Hz), 3.95 (dd, 1H, allyl
Hanti trans PPh3, JHH = 13.5 Hz, JPH = 10 Hz), 4.01 (d, 1H, Hsyn
trans DIC, J = 7 Hz), 5.28 (td, 1H, allyl Hsyn trans PPh3, J = 6 Hz,
J = 2 Hz), 5.95 (m, 1H, allyl Hcentral), 7.06 (d, 2H, DIC H3 and H5,
J = 8 Hz), 7.23 (t, 1H, DIC H4), 7.47–7.57 (m, 15H, P(C6H5)3).
(PCH2CH2CH3), 18.9 (DIC CH3), 24.1 (PCH2CH2CH3, JCP =
25.1 Hz), 26.3 (PCH2CH2CH3, JCP = 13.8 Hz), 64.5 (allyl CH2
trans DIC), 76.1 (allyl CH2 trans P(n-Bu)3), 122.7 (allyl CH, JCP
=
5.6 Hz), 125.6 (DIC C1), 128.4 (DIC C3, C5), 130.6 (DIC C4), 135.4
(DIC C2, C6), (DIC CNR not found).
31P NMR (CDCl3, T = 298 K, ppm): d 15.3.
IR (KBr pellet, cm-1) n 2174.6 (CN), 1088.4 (ClO4).
Anal. Calcd. for C19H31ClNO4PPd: C, 44.72; H, 6.12; N, 2.74.
Found C, 44.69; H, 6.16; N, 2.68.
[Pd(g3-C3H5)(P(OEt)3)2](ClO4). Precipitated with 1 : 1 mix-
ture of diethyl ether/n-hexane. Yield: 69%, grey microcrystals.
1H NMR (CDCl3, T = 298 K, ppm): d 1.36 (t, 18H, OCH2CH3),
3.55 (m, 2H, allyl Hanti), 4.04–4.14 (m, 12H, OCH2CH3), 4.72 (dd,
2H, allyl Hsyn, J = 12 Hz, J = 6.6 Hz), 5.77 (m, 1H, allyl Hcentral).
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 15.9 (d, OCH2CH3,
J = 20.8 Hz), 62.0 (OCH2CH3), 71.6 (allyl CH2), 124.4 (allyl CH).
31P NMR (CDCl3, 298 K): d 126.6.
Anal. Calcd. for C15H35ClO10P2Pd: C, 3.10; H, 6.09. Found C,
3.14; H, 6.03.
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 18.3 (DIC CH3),
72.4 (allyl CH2 trans DIC, JCP = 2.6 Hz), 76.2 (allyl CH2 trans
PPh3, JCP = 25.7 Hz), 123.7 (allyl CH, JCP = 5.6 Hz), 125.3 (DIC
[Pd(g3-C3H5)(IMes)Cl]. 0.08 g (0.219 mmol) of solid [Pd(m-
3
Cl)(h -C3H5)]2 was added to a 0.212 g (0.437 mmol) of IMesAgCl
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The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 966–981 | 975
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dissolved in CH2Cl2 (20 mL). The cloudy solution was filtered over
Millipore and the solvent removed under reduced pressure. The
colorless product was treated with a 1 : 1 mixture of diethylether/n-
hexane and filtered over a Gooch filter, washed with diethyl ether
(3 ¥ 3 mL) and with n-pentane (2 ¥ 3 mL). The resulting white
[Pd(g3-C3H5)(IMes)(PPh3)](ClO4). Yield: 97%, white micro-
crystals.
1H NMR (CDCl3, T = K, ppm): d 1.68 (bs, 3H, Mesityl CH3),
1.87 (bs, 3H, Mesityl CH3), 2.13–2.22 (m, 7H, allyl Hanti trans IMes
and Mesityl CH3), 2.33-2.48 (m, 7H, allyl Hanti trans P and Mesityl
CH3), 3.18 (d, 1H, allyl Hsyn trans IMes, J = 7.2 Hz), 4.22 (bt, 1H,
allyl Hsyn trans P), 5.11 (m, 1H, allyl Hcentral), 6.63 (bs, 1H, Mesityl
H), 6.87–6.93 (m, 6H, P(C6H5)3), 6.96–7.10 (m, 3H, Mesityl H),
7.38 (bs, 2H, -HC CH-), 7.28–7.48 (m, 9H, P(C6H5)3).
1
compound was dried under vacuum. Yield: 0.211 g (99%). H
NMR (CDCl3, T = K, ppm): d 2.21 (s, 6H, Mesityl CH3), 2.23
(s, 6H, Mesityl CH3), 2.34 (s, 6H, Mesityl CH3), 1.81 (d, 1H, allyl
Hanti, J = 11.7 Hz), 2.82 (d, 1H, allyl Hanti, J = 13.5 Hz), 3.21 (d,
1H, allyl Hsyn, J = 5.4 Hz), 3.89 (dd, 1H, allyl Hsyn, J = 9.0 Hz, J =
2.4 Hz), 4.87 (m, 1H, allyl Hcentral), 6.98 (s, 4H, Mesityl H), 7.10 (s,
2H, -HC CH-).
The following complex was synthesized following a similar
procedure using the same starting complex and appropriate
ancillary ligands.
1
13C{ H} NMR (CDCl3, T = K, ppm): d 18.5, 18.7, 21.0, (Mesityl
CH3), 70.2 (d, allyl CH2 trans P, JCP = 29.6 Hz), 71.9 (allyl CH2
trans IMes), 120.2 (d, allyl CH, JCP = 4.6 Hz), 125.2 (-HC = CH-),
129.5, 129.6 (Mesityl CH), 134.8 (Mesityl CCH3), 139.5 (Mesityl
quaternary CN), 179.2 (d, carbenic carbon, JCP = 15.1 Hz).
31P NMR (CDCl3, T = K, ppm): d 22.6.
IR(KBrpellet, cm-1)n2918.7(CH), 1608.7(CN), 1483.6, 1436.5
(CC), 1093.1 (ClO4).
[Pd(g3-C3H5)(SIMes)Cl]. Yield: 97%, white microcrystals.
1H NMR (CDCl3, T = K, ppm): d 2.29 (s, 6H, Mesityl CH3),
2.43 (s, 12H, Mesityl CH3), 1.78 (d, 1H, allyl Hanti, J = 12.0 Hz),
2.75 (d, 1H, allyl Hanti, J = 13.2 Hz), 3.27 (bd, 1H, allyl Hsyn, J =
6.3 Hz), 3.83 (dd, 1H, allyl Hsyn, J = 7.5 Hz, J = 1.5 Hz), 3.99 (s,
4H, CH2-CH2), 4.79 (m, 1H, allyl Hcentral), 6.93 (s, 4H, Mesityl H).
Anal. Calcd. for C42H44ClN2O4PPd: C, 62.00; H, 5,45; N, 3.44.
Found C, 62.11; H, 5,40; N, 3.49.
[Pd(g3-C3H5)(SIMes)(P(OEt)3)](ClO4). Precipitated by addi-
tion of a 1 : 1 mixture of diethyl ether/n-hexane. Yield: 73%, grey
microcrystals.
[Pd(g3-C3H5)(SIMes)(PPh3)](ClO4). To a solution of 0.082 g
1H NMR (CDCl3, T = 298 K, ppm): d 1.17 (t, 9H, OCH2CH3,
J = 7 Hz), 2.22 (1H, allyl Hanti trans SIMes), 2.24 (s, 3H, Mesityl
CH3), 2.26 (s, 3H, Mesityl CH3), 2.29 (s, 3H, Mesityl CH3), 2.41
(bs, 10H, Mesityl CH3, allyl Hanti trans P), 3.40-3.67 (m, 6H,
OCH2CH3), 3.78 (d, 1H, allyl Hsyn trans SIMes, J = 7.5 Hz), 4.05-
4.29 (m, 4H, CH2-CH2), 4.47 (td, 1H, allyl Hsyn trans P, J = 9 Hz,
J = 2.4 Hz), 5.01-5.15 (m, 1H, allyl Hcentral), 6.91 (s, 2H, Mesityl
H), 6.96 (s, 2H, Mesityl H).
3
(0.168 mmol) of [Pd(h -C3H5)(SIMes)Cl] in CH2Cl2 (8 mL), 0.044
g (0.168 mmol) of PPh3 dissolved in 4 mL of CH2Cl2 was added.
Addition of 0.047 g (0.336 mmol) of NaClO4·H2O dissolved in
CH3OH (4 mL) to the stirred mixture yielded the precipitation of
NaCl which was filtered off over a Millipore filter. The reaction
mixture was stirred for 30 min and the solvent removed under
reduced pressure. The resulting sticky solid was dissolved in 20 mL
of CH2Cl2, treated with activated charcoal, and filtered through
Celite. The clear solution, concentrated under reduced pressure
yielded the crude product upon addition of diethyl ether. The
white residue was filtered off, washed with diethyl ether (3 ¥ 3 mL)
and n-pentane (2 ¥ 3 mL) and dried under vacuum. Yield: 0.125 g
(91%).
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 15.9 (d, OCH2CH3,
JCP = 6.3 Hz), 18.0, 18.1 20.8, 20.9 (Mesityl CH3), 51.8, 52.1 (SIMes
CH2), 61.2 (allyl CH2 trans SIMes), 61.2 (OCH2CH3), 71.3 (d, allyl
CH2 trans P, JCP = 45.3 Hz), 121.5 (d, allyl CH, JCP = 8.5 Hz), 129.4
(Mesityl CH), 134.7, 135.0, 135.4, 135.7, 136.0, 136.2 (Mesityl
CCH3), 138.5, 138.9 (Mesityl CN), 207.0 (d, carbenic carbon,
JCP = 23.5 Hz).
1H NMR (CDCl3, T = 298 K, ppm): d 1.77 (s, 3H, Mesityl CH3),
2.01 (s, 3H, Mesityl CH3), 2.27 (s, 3H, Mesityl CH3), 2.34 (s, 3H,
Mesityl CH3), 2.36 (s, 3H, Mesityl CH3), 2.47 (Mesityl CH3), 2.02
(d, allyl Hanti trans SIMes), 2.39 (d, 1H, allyl Hanti trans P), 3.04 (d,
1H, allyl Hsyn trans SIMes, J = 6.9 Hz), 4.07-4.29 (m, 4H, CH2-
CH2), 4.35 (t, 1H, allyl Hsyn trans P, J = 6.0 Hz), 4.94 (m, 1H, allyl
Hcentral), 6.53 (s, 1H, Mesityl H), 6.84 (s, 1H, Mesityl H), 6.89-6.96
(m, 6H, P(C6H5)3), 6.97 (s, 1H, Mesityl H), 7.04 (s, 1H, Mesityl
H), 7.27–7.49 (m, 9H, P(C6H5)3).
31P NMR (CDCl3, T = 298 K, ppm): d 129.0.
IR (KBr pellet, cm-1)
n 2982.4, 2918.4 (CH), 1608.5
(CN), 1490.2, 1442.3 (CC), 1093.7 (ClO4). Anal. Calcd. for
C30H46ClN2O7PPd: C, 50.08; H, 6.44; N, 3.89. Found C, 50.01;
H, 6.38; N, 3.81.
[Pd(g3-C3H5)(IMes)(P(OEt)3)](ClO4). Precipitated by addi-
tion of a 1 : 1 mixture of diethyl ether/n-hexane. Yield: 91%, grey
microcrystals.
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 18.3, 18.4, 18.5,
18.85, 20.9, 21.0 (Mesityl CH3), 52.3, 52.6 (SIMes CH2), 69.9 (d,
allyl CH2 trans P, JCP = 28.5 Hz), 72.4 (allyl CH2 trans SIMes),
119.8 (d, allyl CH, JCP = 4.8 Hz), 129.5, 129.6 (Mesityl CH), 135.0,
135.2, 135.7, 135.9, 136.1 (Mesityl CCH3), 138.4, 138.7 (Mesityl
CN), 209.0 (d, carbenic carbon, JCP = 62.1 Hz).
31P NMR (CDCl3, T = 298 K, ppm): d 22.1.
1H NMR (CDCl3, T = 298 K, ppm): d 1.14 (t, 9H, OCH2CH3,
J = 7.8 Hz), 2.15 (bs, 13H, Mesityl CH3, allyl Hanti trans IMes),
2.33 (s, 6H, Mesityl CH3), 2.36 (dd, 1H, allyl Hanti trans P, partially
obscured), 3.42-3.69 (m, 6H, OCH2CH3), 3.88 (d, 1H, allyl Hsyn
trans IMes, J = 7.2 Hz), 4.33 (td, 1H, allyl Hsyn trans P, J = 8 Hz,
J = 2 Hz), 5.13–5.27 (m, 1H, allyl Hcentral), 7.00 (s, 4H, Mesityl H),
7.33 (s, 2H, -HC CH-).
IR(KBrpellet, cm-1)n2919.7(CH), 1608.7(CN), 1482.5, 1436.4
(CC), 1093.2 (ClO4).
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 16.0 (d, OCH2CH3,
Anal. Calcd. for C42H46ClN2O4PPd: C, 61.84; H, 5.68; N, 3.43.
Found C, 61.77; H, 5.61; N, 3.38.
The following complexes were synthesized following a similar
procedure using the appropriate starting complexes and ancillary
ligands.
JCP = 6.8 Hz), 17.9, 18.1, 20.9 (Mesityl CH3), 61.2 (allyl CH2 trans
IMes), 61.2 (OCH2CH3), 71.5 (d, allyl CH2 trans P, JCP = 47 Hz),
121.8 (d, allyl CH, JCP = 8.8 Hz), 125.1 (-HC = CH-), 129.3, 129.4
(Mesityl CH), 134.7, 134.8 (Mesityl CCH3), 139.7 (Mesityl CN),
177.9 (d, carbenic carbon, JCP = 26.3 Hz).
976 | Dalton Trans., 2011, 40, 966–981
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31P NMR (CDCl3, T = 298 K, ppm): d 128.8.
IR(KBrpellet, cm-1)n2980.5, 2921.5(CH), 1609.6(CN), 1488.4
(CC), 1090.3 (ClO4).
Anal. Calcd. for C30H44ClN2O7PPd: C, 50.22; H, 6.18; N, 3.90.
Found C, 50.15; H, 6.11; N, 3.87.
62.1 (allyl CH2 trans TIC), 67.9 (allyl CH2 trans SIMes), 120.2
(allyl CH), 129.5, 129.7 (Mesityl CH), 134.9, 135.2, 135.3 (Mesityl
CCH3), 138.7 (Mesityl CN), 150.2 (TIC CNR), 205.3 (carbenic
carbon).
IR (KBr pellet, cm-1): n 2985.5, 2921.5 (CH), 2199.3 (CN),
1609.6 (CN), 1493.2, 1455.3 (CC), 1090.4 (ClO4).
Anal. Calcd. for C29H40ClN3O4Pd: C, 54.72; H, 6.33; N, 6.60.
Found C, 54.65; H, 6.27; N, 6.56.
[Pd(g3-C3H5)(SIMes)(DIC)](ClO4). Yield: 90%, white micro-
crystals.
1H NMR (CDCl3, T = 298 K, ppm): d 2.23 (s, 6H, DIC CH3),
2.28 (s, 6H, Mesityl CH3), 2.32 (s, 6H, Mesityl CH3), 2.33 (s, 6H,
Mesityl CH3), 2.08 (d, 1H, allyl Hanti trans DIC, J = 13.2 Hz), 2.68
(d, 1H, allyl Hanti trans SIMes, J = 13.5 Hz), 3.97 (d, 1H, allyl Hsyn
trans DIC, J = 7.2 Hz), 4.23-4.28 (m, 5H, CH2-CH2 and allyl Hsyn
trans SIMes), 5.04 (m, 1H, allyl Hcentral), 6.84 (s, 2H, Mesityl H),
6.90 (s, 2H, Mesityl H), 7.20 (d, 2H, DIC H3 and H5, J = 7.8 Hz),
7.34 (t, 1H, DIC H4).
[Pd(g3-C3H5)(IMes)(TIC)](ClO4). Yield: 94%, white micro-
crystals.
1H NMR (CDCl3, T = 298 K, ppm): d 1.63 (s, 9H, TIC CH3),
2.11 (s, 6H, Mesityl CH3), 2.12 (s, 6H, Mesityl CH3), 2.36 (s, 6H,
Mesityl CH3), 2.08 (d, 1H, allyl Hanti trans TIC), 2.68 (d, 1H, allyl
Hanti trans IMes, J = 13.8 Hz), 3.78 (d, 1H, allyl Hsyn trans TIC,
J = 7 Hz), 4.27 (dd, 1H, allyl Hsyn trans IMes, J = 7.5 Hz, J =
2.4 Hz), 5.01 (m, 1H, allyl Hcentral), 7.03 (s, 4H, Mesityl H), 7.34 (s,
2H, -HC CH-).
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 17.8, 18.0, 20.9
(Mesityl CH3), 18.5 (DIC CH3), 52.0 (SIMes CH2), 63.5 (allyl
CH2 trans DIC), 68.0 (allyl CH2 trans SIMes), 120.9 (allyl CH),
120.9 (DIC C1), 128.4 (DIC C3, C5), 130.5 (DIC C4), 135.2 (DIC
C2, C6), 129.5, 129.7 (Mesityl CH), 134.3, 134.6, 134.7 (Mesityl
CCH3), 138.7 (Mesityl CN), 146.6 (DIC CNR), 204.0 (carbenic
carbon).
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 17.8, 18.0, 21.0
(Mesityl CH3), 29.9 (TIC CH3), 58.9 (C(CH3)3), 62.5 (allyl CH2
trans TIC), 67.9 (allyl CH2 trans IMes), 120.3 (allyl CH), 124.4
(-HC = CH-), 129.4, 129.6 (Mesityl CH), 134.2, 134.4, 135.0
(Mesityl CCH3), 139.7 (Mesityl CN), TIC CNR not observed,
176.5 (carbenic carbon).
IR (KBr pellet, cm-1) n 2921.5 (CH), 2162.6 (CN), 1608.6 (CN),
1492.2, 1454.3 (CC), 1093.3 (ClO4).
Anal. Calcd. for C33H40ClN3O4Pd: C, 57.90; H, 5.89; N, 6.14.
Found C, 57.85; H, 5.80; N, 6.07.
IR (KBr pellet, cm-1): n 2980.6, 2922.6 (CH), 2199.2 (CN),
1608.6 (CN), 1488.4, 1460.5 (CC), 1093.4 (ClO4).
Anal. Calcd. for C29H38ClN3O4Pd: C, 54.90; H, 6.04; N, 6.62.
Found C, 54.91; H, 6.09; N, 6.58.
[Pd(g3-C3H5)(IMes)(DIC)](ClO4). Yield: 92%, white micro-
crystals.
[Pd(g3-1,1-Me2C3H3)(SIMes)Cl]. 0.174 g (0.412 mmol) of
3
1H NMR (CDCl3, T = 298 K, ppm): d 2.08 (s, 6H, DIC CH3),
2.13 (s, 6H, Mesityl CH3), 2.19 (s, 6H, Mesityl CH3), 2.31 (s, 6H,
Mesityl CH3), 2.13 (d, 1H, allyl Hanti trans DIC, J = 13.1 Hz), 2.83
(d, 1H, allyl Hanti trans IMes, J = 13.8 Hz), 3.85 (d, 1H, allyl Hsyn
trans DIC, J = 7.2 Hz), 4.39 (dd, 1H, allyl Hsyn trans IMes, J = 7 Hz,
J = 2 Hz), 5.01 (m, 1H, allyl Hcentral), 6.91 (s, 2H, Mesityl H), 6.98
(s, 2H, Mesityl H), 7.19 (d, 2H, DIC H3 and H5, J = 7.5 Hz), 7.30
solid [Pd(m-Cl)(h -C3H3Me2)]2 was added to 0.400 g (0.823 mmol)
SIMesAgCl dissolved in CH2Cl2 (40 mL). The cloudy solution
was filtered over a Millipore filter and the solvent removed under
reduced pressure. The colorless product was treated with a 1 : 1
mixture of diethylether/n-hexane and filtered over a Gooch filter,
washed with diethyl ether (3 ¥ 3 mL), n-pentane (2 ¥ 3 mL) and
dried under vacuum. Yield: 0.405 g (95%).
(t, 1H, DIC H4), 7.39 (s, 2H, -HC CH-). 13C{ H} NMR (CDCl3,
1H NMR (CDCl3, T = 298 K, ppm): d 0.63 (s, 3H, allyl CH3 anti),
1.43 (s, 3H, allyl CH3 syn), 1.71 (dd, 1H, allyl Hanti, J = 12 Hz, J =
1.8 Hz), 2.28 (s, 6H, Mesityl CH3), 2.43 (s, 6H, Mesityl CH3), 2.44
(s, 6H, Mesityl CH3), 2.84 (dd, 1H, allyl Hsyn, J = 7.2 Hz, J =
1.9 Hz), 3.99 (s, 4H, CH2-CH2), 4.37 (dd, 1H, allyl Hcentral, J =
12 Hz, J = 7.2 Hz), 6.93 (s, 4H, Mesityl H).
1
T = 298 K, ppm): d 17.8 (Mesityl CH3), 17.9 (Mesityl CH3), 18.4
(DIC CH3), 21.0 (Mesityl CH3), 63.9 (allyl CH2 trans DIC), 68.1
(allyl CH2 trans IMes), 121.0 (allyl CH), 124.5 (-HC = CH-),
125.3 (DIC C1), 128.3 (DIC C3, C5), 130.4 (DIC C4), 135.2 (DIC
C2, C6), 129.3, 129.6 (Mesityl CH), 134.3, 134.6, 134.7 (Mesityl
CCH3), 140.0 (Mesityl CN), DIC CNR obscured, 175.7 (carbenic
carbon).
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 18.3, 18.4, 20.9
(Mesityl CH3), 19.1 (allyl CH3 anti), 25.4 (allyl CH3 syn), 40.1 (allyl
CH2), 50.9 (SIMes CH2), 106.1 (allyl CH), 107.5 (allyl C(CH3)2),
129.1 (Mesityl CH carbons), 136.2, 136.4, 137.7 (Mesityl CCH3),
Mesityl CN not observed, 212.7 (carbenic carbon).
IR(KBrpellet, cm-1)n2915.6(CH), 1608.7(CN), 1488.3, 1452.5
(CC).
IR (KBr pellet, cm-1) n 2918.7 (CH), 2175.4 (CN), 1608.7 (CN),
1487.6 (CC), 1093.2 (ClO4).
Anal. Calcd. for C33H38ClN3O4Pd: C, 58.07; H, 5.61; N, 6.16.
Found C, 58.14; H, 5.54; N, 6.09.
[Pd(g3-C3H5)(SIMes)(TIC)](ClO4). Yield: 93%, white micro-
crystals.
Anal. Calcd. for C26H35ClN2Pd: C, 60.35; H, 6.82; N, 5.41.
Found C, 60.27; H, 6.77; N, 5.38.
The following complex was synthesized following a similar
procedure using the same starting complex and IMesAgCl.
1H NMR (CDCl3, T = 298 K, ppm): d 1.53 (s, 9H, TIC CH3),
2.30 (s, 6H, Mesityl CH3), 2.31 (s, 6H, Mesityl CH3), 2.36 (s, 6H,
Mesityl CH3), 2.05 (d, 1H, allyl Hanti trans TIC, J = 13.2 Hz), 2.53
(d, 1H, allyl Hanti trans SIMes, J = 13.5 Hz), 3.90 (d, 1H, allyl Hsyn
trans TIC, J = 7 Hz), 4.14-4.20 (m, 5H, CH2-CH2 and allyl Hsyn
trans SIMes), 4.91 (m, 1H, allyl Hcentral), 6.94 (s, 4H, Mesityl H).
[Pd(g3-1,1-Me2C3H3)(IMes)Cl]. Yield: 87%, white microcrys-
tals.
1H NMR (CDCl3, T = 298 K, ppm): d 0.72 (s, 3H, allyl CH3 anti),
1.48 (s, 3H, allyl CH3 syn), 1.73 (dd, 1H, allyl Hanti, J = 12 Hz, J =
1.4 Hz), 2.21 (s, 6H, Mesityl CH3), 2.24 (s, 6H, Mesityl CH3), 2.33
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 17.9, 18.0, 20.9
(Mesityl CH3), 30.0 (TIC CH3), 51.9 (SIMes CH2), 58.9 (C(CH3)3),
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(s, 6H, Mesityl CH3), 2.81 (dd, 1H, allyl Hsyn, J = 7.2 Hz, J =
2.1 Hz), 4.44 (dd, 1H, allyl Hcentral, J = 12 Hz, J = 7.2 Hz), 6.97 (s,
4H, Mesityl H), 7.10 (s, 2H, -HC CH-).
5H, P(C6H5)3), 7.01 (bs, 1H, Mesityl H), 7.14 (bs, 1H, Mesityl H),
HC CH- obscured, 7.29–7.48 (m, 10H, P(C6H5)3).
1
13C{ H} NMR (CDCl3, T = K, ppm): d 17.1, 17.3, (Mesityl
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 18.1, 18.3, 21.0
CH3), 21.0 (allyl CH3anti), 25.5 (allyl CH3syn), 54.7 (allyl CH2), allyl
C (CH3)2 and allyl CH not observed, 125.1 (-HC = CH-) 129.8
(Mesityl CH), 134.3 (Mesityl CCH3), 139.2 (Mesityl CN), 177.0
(d, carbenic carbon, JCP = 10.9 Hz).
(Mesityl CH3), 19.3 (allyl CH3 anti), 25.5 (allyl CH3 syn), 39.9 (allyl
CH2), 105.9 (allyl CH), 106.3 (allyl C(CH3)2), 122.6 (IMes -
HC CH-), 128.8 (Mesityl CH), 135.5, 135.6, 136.1 (Mesityl
CCH3), 137.4 (Mesityl CN), 185.2 (carbenic carbon).
IR(KBrpellet, cm-1)n2916.5(CH), 1608.6(CN), 1485.4, 1444.5
(CC). Anal. Calcd. for C26H33ClN2Pd: C, 60.59; H, 6.45; N, 5.43.
Found C, 60.51; H, 6.38; N, 5.40.
31P NMR (CDCl3, T = K, ppm): d 22.4.
IR(KBrpellet, cm-1)n2918.8(CH), 1608.8(CN), 1485.6, 1436.6
(CC), 1093.2 (ClO4). Anal. Calcd. for C44H48ClN2O4PPd: C, 62.79;
H, 5.75; N, 3.33. Found C, 62.83; H, 5.70; N, 3.29.
[Pd(g3-1,1-Me2C3H3)(SIMes)(PPh3)](ClO4). To a solution of
[Pd(h -C3H3Me2)(SIMes)Cl] (0.080 g, 0.144 mmol) in CH2Cl2
[Pd(g3-1,1-Me2C3H3)(SIMes)(P(OEt)3)](ClO4). Precipitated
by addition of a 1 : 1 mixture of diethyl ether/n-hexane. Yield:
65%, grey microcrystals
3
(8 mL), 0.041 g (0.156 mmol) of PPh3 dissolved in CH2Cl2 (4 mL)
was added. Addition under stirring of 0.043 g (0.308 mmol)
NaClO4·H2O dissolved in CH3OH (4 mL) to the resulting solution
induced the precipitation of NaCl which was filtered off on a
Millipore filter. The reaction mixture was stirred for 30 min and the
solvent removed under reduced pressure. The resulting sticky solid
was dissolved in 20 mL of CH2Cl2, treated with activated charcoal,
and filtered through celite. The clear solution concentrated under
reduced pressure yielded the crude product upon addition of
diethyl ether. The white residue was filtered off, washed with
diethyl ether (3 ¥ 3 mL), n-pentane (2 ¥ 3 mL) and dried under
vacuum. Yield: 0.110 g (87%).
1H NMR (CDCl3, T = 298 K, ppm): d 0.65 (d, 3H, allyl CH3 anti
,
JPH = 8.4 Hz), 1.22 (t, 9H, OCH2CH3, J = 7 Hz), 1.66 (d, 3H,
allyl CH3 syn, JPH = 10.8 Hz), 2.13 (dd, 1H, allyl Hanti trans P, J =
14.9 Hz, J = 1.5 Hz), 2.24 (s, 3H, Mesityl CH3), 2.27 (s, 3H, Mesityl
CH3), 2.29 (s, 3H, Mesityl CH3), 2.40 (s, 3H, Mesityl CH3), 2.43
(s, 3H, Mesityl CH3), 2.45 (s, 3H, Mesityl CH3), 3.44–3.75 (m,
6H, OCH2CH3), 3.77 (dd, 1H, allyl Hsyn trans P, J = 7.8 Hz, J =
2 Hz), 4.22–4.32 (m, 4H, CH2-CH2), 4.74 (dd, 1H, allyl Hcentral, J =
13.5 Hz, J = 7.8 Hz), 6.91 (s, 1H, Mesityl H), 6.93 (s, 1H, Mesityl
H), 6.95 (s, 1H, Mesityl H), 6.98 (s, 1H, Mesityl H).
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 16.0 (d, OCH2CH3,
1H NMR (CDCl3, T = 298 K, ppm): d 0.23 (d, 3H, allyl CH3 anti
,
JCP = 6.9 Hz), 18.1, 18.3, 18.4, 20.7, 20.8 (Mesityl CH3), 19.2 (allyl
CH3 anti), 26.3 (allyl CH3 syn), 51.5, 52.3 (SIMes CH2), 57.7 (d, allyl
CH2 trans P, JCP = 48.7 Hz), 61.5 (d, OCH2CH3, JCP = 3.7 Hz),
JPH = 3.6 Hz), 0.71 (d, 3H, allyl CH3 syn, JPH = 5.4 Hz), (allyl Hanti
trans P obscured by methyl signals), 1.79 (s, 3H, Mesityl CH3),
1.96 (s, 3H, Mesityl CH3), 2.26 (s, 3H, Mesityl CH3), 2.39 (s, 3H,
Mesityl CH3), 2.43 (s, 3H, Mesityl CH3), 2.46 (s, 3H, Mesityl
CH3), 3.62 (t, 1H, allyl Hsyn trans P, J = 2.4 Hz), 4.15–4.24 (m, 4H,
CH2-CH2), 4.63 (dd, 1H, allyl Hcentral, J = 12.5 Hz, J = 8.3 Hz),
6.55 (s, 1H, Mesityl H), 6.84 (s, 1H, Mesityl H), 6.90-6.96 (m, 7H,
Mesityl H and P(C6H5)3), 7.06 (s, 1H, Mesityl H), 7.31–7.49 (m,
9H, P(C6H5)3).
102.6 (d, allyl C(CH3)2, JCP = 6.7 Hz), 113.1 (d, allyl CH, JCP
=
9.8 Hz), 129.2, 129.3, 129.5 (Mesityl CH), 135.0, 135.4, 135.6,
135.8, 136.0, 136.5 (Mesityl CCH3), 138.3, 138.8 (Mesityl CN),
208.3 (d, carbenic carbon, JCP = 26.9 Hz).
31P NMR (CDCl3, T = 298 K, ppm): d 122.9.
IR (KBr pellet, cm-1) n 2983.3, 2918.4 (CH), 1630.5, 1608.5
(CN), 1489.8, 1441.2 (CC), 1093.1 (ClO4).
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 17.3, 18.3, 18.7,
Anal. Calcd. for C32H50ClN2O7PPd: C, 51.41; H, 6.74; N, 3.75.
Found C, 51.26; H, 6.68; N, 3.79.
18.5, 19.5, 20.9 (Mesityl CH3), 19.8 (allyl CH3 anti), 25.5 (allyl
CH3 syn), 52.3 (SIMes CH2), 54.5 (d, allyl CH2, JCP = 30.7 Hz), 110.7
(allyl C(CH3)2), 111.9 (allyl CH), 129.3, 129.5, 129.7 (Mesityl CH),
134.7, 134.9, 135.5, 135.9, 136.2, 136.6 (Mesityl CCH3), 138.47,
138.7 (Mesityl CN), 209.6 (carbenic carbon).
[Pd(g3-1,1-Me2C3H3)(IMes)(P(OEt)3)](ClO4). Precipitated
by addition of a 1 : 1 mixture of diethyl ether/n-hexane. Yield:
81%, grey microcrystals.
1H NMR (CDCl3, T = 298 K, ppm): d 0.75 (d, 3H, allyl CH3 anti
,
31P NMR (CDCl3, T = 298 K, ppm): d 22.0.
IR(KBrpellet, cm-1)n2918.7(CH), 1608.7(CN), 1482.5, 1435.5
(CC), 1090.3 (ClO4).
JPH = 8.4 Hz), 1.19 (t, 9H, OCH2CH3, J = 7 Hz), 1.74 (m, 4H,
allyl CH3 syn,, allyl Hanti trans P), 2.08 (s, 3H, Mesityl CH3), 2.14 (s,
3H, Mesityl CH3), 2.21 (s, 3H, Mesityl CH3), 2.24 (s, 3H, Mesityl
CH3), 2.33 (s, 3H, Mesityl CH3), 2.34 (s, 3H, Mesityl CH3), 3.46–
3.73 (m, 7H, allyl Hsyn trans P, OCH2CH3), 4.86 (ddd, 1H, allyl
Hcentral, J = 13.5 Hz, J = 7.8 Hz, J = 1.2 Hz), 7.02 (s, 4H, Mesityl
H), 7.34 (s, 2H, -HC CH-).
Anal. Calcd. for C44H50ClN2O4PPd: C, 62.64; H, 5.97; N, 3.32.
Found C, 62.58; H, 5.89; N, 3.27.
The following complexes were prepared under similar condi-
tions using the appropriate ligands and precursors.
[Pd(g3-1,1-Me2C3H3)(IMes)(PPh3)](ClO4). Yield: 85%, white
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 16.0 (d, OCH2CH3,
1
microcrystals.
JCP = 6.7 Hz), 18.0, 18.1, 18.3, 18.5, 20.8, 20.9 (Mesityl CH3), 19.4
1H NMR (CDCl3, T = K, ppm): d 0.31 (bd, 3H, allyl CH3 anti
,
(allyl CH3 anti), 26.4 (allyl CH3 syn), 57.8 (d, allyl CH2 trans P, JCP =
JPH = 3.3 Hz), 0.80 (bd, 3H, allyl CH3 syn, JPH = 3.0 Hz), (allyl
Hanti trans P obscured by methyl signals), 1.62 (bs, 3H, Mesityl
CH3), 1.93 (bs, 3H, Mesityl CH3), 2.17 (bs, 3H, Mesityl CH3),
2.20 (bs, 3H, Mesityl CH3), 2.31 (bs, 3H, Mesityl CH3), 2.45 (bs,
3H, Mesityl CH3), 3.52 (bt, 1H, allyl Hsyn trans P), 4.79 (bt, 1H,
allyl Hcentral, J = 10.8 Hz), 6.68 (s, 1H, Mesityl H), 6.90–6.96 (m,
50.1 Hz), 61.5 (d, OCH2CH3, JCP = 3.0 Hz), 102.0 (d, allyl C(CH3)2
JCP = 6.9 Hz), 113.4 (d, allyl CH, JCP = 9.7 Hz), 124.0, 125.3
(-HC = CH-), 129.1, 129.3, 129.5, 129.7 (Mesityl CH), 134.6,
134.9, 135.4, 135.5 (Mesityl CCH3), 139.4, 139.7 (Mesityl CN),
179.1 (d, carbenic carbon, JCP = 30.6 Hz).
31P NMR (CDCl3, T = 298 K, ppm): d 122.3.
978 | Dalton Trans., 2011, 40, 966–981
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IR (KBr pellet, cm-1)
(CN), 1488.5, 1446.6 (CC), 1093.1 (ClO4). Anal. Calcd. for
C32H48ClN2O7PPd: C, 51.55; H, 6.49; N, 3.76. Found C, 51.61;
H, 6.43; N, 3.69.
n
2983.6, 2918.6 (CH), 1608.5
on the top of a Lindemann glass capillary and centered on the four-
circle kappa goniometer head of an Oxford Diffraction Gemini
E diffractometer, equipped with a 2 K ¥ 2 K EOS CCD area
detector and sealed-tube Enhance (Mo) and (Cu) X-ray sources,
under a cold nitrogen stream provided by an Oxford Instruments
CryojetXL sample chiller. The diffraction data collection (w scan
technique) was carried out at T = 150.0(1) K, by using graphite–
[Pd(g3-1,1-Me2C3H3)(SIMes)(DIC)](ClO4). Yield:
white microcrystals
95%,
1H NMR (CDCl3, T = 298 K, ppm): d 0.91 (s, 3H, allyl CH3 anti),
1.81 (s, 3H, allyl CH3 syn), 1.93 (dd, 1H, allyl Hanti, J = 13.8 Hz, J =
2.4 Hz), 2.19 (6H, DIC CH3), 2.27 (s, 6H, Mesityl CH3), 2.30 (s,
6H, Mesityl CH3), 2.32 (s, 6H, Mesityl CH3), 3.35 (dd, 1H, allyl
Hsyn, J = 7.8 Hz, J = 2 Hz), 4.17–4.25 (m, 4H, CH2-CH2), 4.75 (dd,
1H, allyl Hcentral, J = 12.9 Hz, J = 7.8 Hz), 6.82 (s, 2H, Mesityl H),
6.92 (s, 2H, Mesityl H), 7.20 (d, 2H, DIC H3 and H5, J = 7.5 Hz),
7.35 (t, 1H, DIC H4).
˚
monochromated Mo Ka radiation (l = 0.71073 A), in a 1024 ¥
1024 pixel mode, using 2 ¥ 2 pixel binning.
A total of 825 frames in eleven runs and 794 frames in
3
3
thirteen runs for [Pd(h -C3H5)(IMes)(DIC)](ClO4) and [Pd(h -1,1-
Me2C3H3)(IMes)(PPh3)](ClO4)respectively, were measured with a
step of 1◦. The diffraction intensities were corrected for Lorentz
and polarization effects and were also optimized with respect
to absorption. Empirical multi-scan absorption corrections using
equivalent reflections were performed with the scaling algorithm
SCALE3 ABSPACK. Data collection, data reduction and final-
ization were carried out through the CrysAlis Pro software.38 Ac-
curate unit-cell parameters were determined during the whole data
collection by least–squares refinement of all reflection positions.
Crystal stability was checked by measuring in both cases two
reference frames every 50 frames; no sign of systematic changes
was noticed either in peak positions or in intensities.
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 17.8, 18.1, 20.5
(Mesityl CH3), 18.3 (DIC CH3), 20.9 (allyl CH3 anti), 27.3 (allyl
CH3 syn), 51.8 (SIMes CH2), 52.0 (allyl CH2), 106.6 (allyl C(CH3)2),
112.0 (allyl CH), 125.2 (DIC C1), 128.4 (DIC C3, C5), 130.4 (DIC
C4), 135.4 (DIC C2, C6), 129.3, 129.6 (Mesityl CH), 134.7, 135.5,
135.7 (Mesityl CCH3), 138.6 (Mesityl CN), 150.7 (DIC CNR),
205.3 (carbenic carbon).
IR (KBr pellet, cm-1) n 2946.5, 2919.5 (CH), 2168.2 (CN),
1630.6, 1608.6 (CN), 1490.1, 1454.3 (CC), 1090.2 (ClO4).
Anal. Calcd. for C35H44ClN3O4Pd: C, 58.99; H, 6.22; N, 5.90.
Found C, 58.89; H, 6.26; N, 5.98.
The structures were solved by means of the heavy-atom methods
using SHELXTL-NT39 and refined by full-matrix least-squares
methods based on Fo with SHELXL-97.40 In the late stage
2
[Pd(g3-1,1-Me2C3H3)(IMes)(DIC)](ClO4). Yield: 95%, white
microcrystals.
1H NMR (CDCl3, T = 298 K, ppm): d 1.06 (s, 3H, allyl CH3 anti),
1.87 (s, 3H, allyl CH3 syn), 1.91 (dd, 1H, allyl Hanti, J = 13.4 Hz, J =
2.7 Hz), 2.07 (s, 6H, Mesityl CH3), 2.14 (s, 6H, Mesityl CH3), 2.17
3
of refinement for [Pd(h -1,1-Me2C3H3)(IMes)(PPh3)](ClO4), some
peaks appeared in positions compatible with a second chemically
reasonable arrangement of the allyl group. At the end of the
refinement, the C(22), C(23), C(25) and C(26) atoms of the allyl
ligand were found to be disordered over two sites. The two alternate
arrangements were refined isotropically, with partial occupancies
of 0.77 and 0.23, respectively. With the exception of disordered
atoms, all non-H atoms were allowed to vibrate anisotropically in
the last cycles of refinement. H atoms were placed in calculated
positions and refined as “riding model”. The Uiso values of
hydrogen atoms were set at 1.2 (1.5 for methyl group) times Ueq of
the pertinent carrier carbon atom.
The main crystallographic data are listed in Table 1SI† (Sup-
plementary Information); selected bond lengths and angles are
listed in Table 4. Full listings of atomic coordinates, bond lengths
and angles, and anisotropic thermal parameters are available as
supporting information (see below).
(6H, DIC CH3), 2.32 (s, 6H, Mesityl CH3), 3.27 (dd, 1H, allyl Hsyn
,
J = 7.8 Hz, J = 2.6 Hz), 4.87 (dd, 1H, allyl Hcentral, J = 13.2 Hz, J =
7.8 Hz), 6.88 (s, 2H, Mesityl H), 7.00 (s, 2H, Mesityl H), 7.20 (d,
2H, DIC H3 and H5, J = 7.5 Hz), 7.35 (t, 1H, DIC H4), 7.37 (s,
2H, -HC CH-).
1
13C{ H} NMR (CDCl3, T = 298 K, ppm): d 17.8, 17.9, 21.0
(Mesityl CH3), 18.3 (DIC CH3), 21.0 (allyl CH3 anti), 27.4 (allyl
CH3 syn), 52.2 (allyl CH2), 106.7 (allyl Cquaternary), 112.1 (allyl CH),
124.3 (IMes -HC CH-), (DIC C1 not found), 128.4 (DIC C3, C5),
130.4 (DIC C4), 135.4 (DIC C2, C6), 129.2 129.5 (Mesityl CH),
134.4, 134.5, 134.8 (Mesityl quaternary CCH3), 136.9(Mesityl
quaternary CN), 150.6 (DIC CNR), 177.1 (carbenic carbon).
IR (KBr pellet, cm-1) n 2952.6, 2920.5 (CH), 2168.1 (CN),
1630.2, 1608.6 (CN), 1486.4, 1448.5 (CC), 1090.5 (ClO4).
Anal. Calcd. for C35H42ClN3O4Pd: C, 59.16; H, 5.96; N, 5.91.
Found C, 59.25; H, 5.88; N, 5.87.
Acknowledgements
Financial support for the acquisition of the Oxford Diffraction
Gemini E diffractometer was provided by the University of Padova
through the 2008 Scientific Equipment for Research initiative.
Characterization of the complexes [Pd(g2-dmfu)(L)(L¢)]
2
In Table 3 the characterization of the complexes [Pd(h -
1
dmfu)(L)(L¢)] based on some selected H and 31P NMR signals
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This journal is
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Dalton Trans., 2011, 40, 966–981 | 979
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