Facile synthesis and reactivity study of mixed phosphane-isocyanide Pd(II) and Pd(0) complexes

Article abstract of DOI:10.1016/j.ica.2011.09.006

The reaction between an equimolecular mixture of isocyanide CNR (CNR = di-methylphenyl isocyanide (DIC), tert-butyl isocyanide (TIC), triphenyl phosphane (PPh₃) and a dechlorinated solution of the palladium allyl dimers [Pd(η³-allyl)Cl]₂ (allyl = 2-Meallyl, 1,1-Me₂allyl) in stoichiometric ratio yields the mixed derivative [Pd(η³-allyl)(CNR)(PPh₃)] only. Apparently, the mixed derivative represents the most stable species among all the possible ones that might be formed under those experimental conditions. Theoretical calculations are in agreement with the experimental observation and the energy stabilization of the mixed species with respect to the homoleptic derivatives is traced back to an overall push-pull effect exerted by the isocyanide and the phosphane acting synergically. Similar behavior is observed in the case of the synthesis of the palladacyclopentadienyl complexes [Pd(C₄(COOMe) ₄)(CNR)(PPh₃)] and of the palladium(0) olefin complexes whose synthesis invariably yields the mixed [Pd(η²-olefin)(CNR) (PPh₃)] derivatives. The paper includes studies on the reactivity toward allylamination in the case of the palladium(II) allyl complexes. A diffractometric investigation on the solid state structures of four different palladium isocyanide-phosphane complexes is also included.

Full text of DOI:10.1016/j.ica.2011.09.006

Inorganica Chimica Acta 378 (2011) 239–249
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Facile synthesis and reactivity study of mixed phosphane–isocyanide Pd(II)
and Pd(0) complexes
a
a
a
b
Luciano Canovese a, , Fabiano Visentin , Carlo Levi , Claudio Santo , Valerio Bertolasi
⇑
a Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari, Venice, Italy
b Dipartimento di Chimica e Centro di Strutturistica Diffrattometrica, Università di Ferrara, Ferrara, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 July 2011
Received in revised form 1 September 2011
Accepted 2 September 2011
Available online 10 September 2011
The reaction between an equimolecular mixture of isocyanide CNR (CNR = di-methylphenyl isocyanide
(DIC), tert-butyl isocyanide (TIC), triphenyl phosphane (PPh3) and a dechlorinated solution of the palla-
dium allyl dimers [Pd(
g
3-allyl)Cl]2 (allyl = 2-Meallyl, 1,1-Me2allyl) in stoichiometric ratio yields the
mixed derivative [Pd(
g
3-allyl)(CNR)(PPh3)] only. Apparently, the mixed derivative represents the most
stable species among all the possible ones that might be formed under those experimental conditions.
Theoretical calculations are in agreement with the experimental observation and the energy stabilization
of the mixed species with respect to the homoleptic derivatives is traced back to an overall push–pull
effect exerted by the isocyanide and the phosphane acting synergically. Similar behavior is observed in
the case of the synthesis of the palladacyclopentadienyl complexes [Pd(C4(COOMe)4)(CNR)(PPh3)] and
Keywords:
Palladium mixed complexes
Isocyanide
Phosphane
of the palladium(0) olefin complexes whose synthesis invariably yields the mixed [Pd(g
2-ole-
fin)(CNR)(PPh3)] derivatives. The paper includes studies on the reactivity toward allylamination in the
case of the palladium(II) allyl complexes. A diffractometric investigation on the solid state structures
of four different palladium isocyanide–phosphane complexes is also included.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
(25%:50%:25%) of all the possible species [3] irrespectively of their
remarkable different steric hindrance and electron donating
With the aim of evaluating the electronic characteristics of the spec-
tator ligands fromkinetic data, we have been recentlyinvolvedin a study
dealing with the reactivity toward amination of palladium allyl com-
plexes bearing mixed monodentate carbene, phosphite, phosphane
and isocyanide ligands. The synthesis of the allyl derivatives bearing
phosphanes and isocyanides ([Pd(g3-allyl)(L0)(L00)]ClO4), was indeed
trivial since the complexes required were obtained by simple addition
of equimolecular amounts of phosphane and isocyanide to a CH2Cl2
characteristics.
Therefore, among the explored ligands, only the equimolecular
mixture of phosphanes (L0) and isocyanides (L00) yields the mixed
derivatives [Pd(g3-allyl)(L0)(L00)]ClO4 as the sole products of the
synthesis. In order to rationalize such a surprising behavior we
undertook an accurate literature investigation on complexes of
the type cis-[Pd(E-E)(CNR)(PR03)]n+ (n = 0, 1; E–E = generic coordi-
nating systems imposing cis geometry) [4]. Some derivatives
([Pd(CNR)(PR03)X2] [5], [Pd(CNR)(PR03)(R00)X] [8]) bearing the phos-
phanes trans to isocyanides can also be found in the literature to-
gether with complexes of the type trans-[Pd(CNR)2(PR03)2] [4h,6].
From such an investigation it was clear that the mixed com-
plexes were synthesized by means of different synthetic protocols
and with different stoichiometric ratios among phosphanes, isocy-
anides and the metal, suggesting that no generalized approaches
has in any case been exploited.
solution of the allyl dimer [Pd(g l-Cl)]2 dechlorinated with
3-allyl)(
NaClO4 [1,2]. We have also noticed that a non statistical mixture of
homoleptic and mixed complexes was obtained when equimolecular
solutions of different ligands (L0 = phosphites, L00 = isocyanides, and
phosphanes) were added to the dechlorinated allyl dimer obtained as
previously described.1 Moreover, simultaneous addition of different
isocyanides, namely di-methylphenyl isocyanide (DIC) and tert-butyl
isocyanide (TIC) again gave rise to the statistical mixture
Thus, we thought that an understanding of the energetic rea-
sons governing the formation of the mixed (or homoleptic) com-
plexes and consequently the simplest experimental conditions
for the achievement of the former was in order. In this respect,
we have undertaken a systematic experimental investigation on
the facile synthesis of some of the above mentioned mixed com-
plexes of palladium(0) and palladium(II) and a theoretical study
of their thermodynamic stability. Moreover, we have also carried
⇑
Corresponding author.
E-mail address: cano@unive.it (L. Canovese).
Remarkably, the obtainment of the allyl complexes bearing mixed L0 (L0 = NHCs)
1
and L00 (L00 = phosphane, phosphite, isocyanide) ligands was strictly governed by the
sequence of addition of the monodentate ligands. In this respect, the pure mixed L0–L00
species can only be obtained by the addition in situ of the phosphane, phosphite and
isocyanide moieties to a dechlorinated CH2Cl2 solution of the previously synthesized
[Pd(g3-allyl)(NHC)Cl] derivatives. Apparently, the added L00 ligands, although very
efficient, cannot displace the NHC fragment probably for kinetic reasons (see Section
2).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.09.006

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L. Canovese et al. / Inorganica Chimica Acta 378 (2011) 239–249
out a diffractometric study on some of these substrates and inves-
tigation on the reactivity of the palladium(II) mixed allyl deriva-
tives toward amination.
(MeN-SPh)]. Simultaneous addition of an equimolecular solution
of DIC or TIC and PR03 to the latter gave rise to the mixed
[Pd(CNR)(PR03)(C4(COOMe)4)] complexes (3a, 3b) as the only prod-
ucts. The 1H and 13C NMR spectra display four different groups of
signals ascribable to the four magnetically non equivalents –
OCH3 fragments. The structural distribution of the ligands can also
be determined from the 1H and 13C signals due to phosphane and
isocyanide groups which clearly indicate the concomitant presence
of only one phosphane and one isocyanide and from the 31P spectra
displaying only one singlet ascribable to the phosphorus atom in
both cases (ꢁ26 ppm) (see Section 4 and Supporting Information
for a selection of NMR spectra).
2. Result and discussion
The species and the complexes involved in the present study are
summarized in Scheme 1.
2.1. Synthesis of [Pd(g
3-allyl)(PPh3)(CNR)]ClO4 complexes (allyl = 2-
Meallyl; 1,1-Me2allyl; CNR = DIC, TIC)
g
2-olefin)(PPh3)(CNR)] complexes (CNR= DIC,
Addition of an equimolecular mixture of CNR (CNR = DIC, a; TIC,
b) and PR03 (c) (Pd: CNR: PPh3 = 1:1:1) to a solution of the allyl di-
2.3. Synthesis of [Pd(
TIC)
mer [Pd(
and NaClO4 in CH2Cl2:MeOH (3:1 v:v) yields the mixed allyl palla-
dium(II) complexes [Pd(
3-allyl)(DIC)(PPh3)]+ (1a, 2a) or [Pd(g3
g l-Cl)]2 (allyl = 2-Meallyl (1), 1,1-Me2-allyl (2))
3-allyl)(
The synthesis of the complexes of palladium(0) of the type
[Pd(g2-olefin)(CNR)(PR03)] was also achieved taking advantage of
the lability of the ligand MeN-SPh since the direct ‘‘classical’’ addi-
tion of equimolecular amounts of CNR and PR03 to the complex
g
-
allyl)(TIC)(PPh3)]+ (1b, 2b) only after the precipitation of NaCl.
The ensuing complexes are stable in the solid and in solution of
chloridated solvents and their characterization is easily obtained
by means of 1H, 31P and 13C NMR. In the cases of the complexes
bearing the symmetric allyl fragment 2-Meallyl, (1a, 1b) four
signals due to the anti and syn allyl protons are detectable. The
syn proton trans to phosphorus resonates as a pseudo triplet
.
[Pd2(DBA)3 CHCl3] in the presence of the olefin induces a massive
formation of metallic palladium along with the wanted complex.
We have therefore synthesized the complexes [Pd(g
2-olefin)
(MeN-SPh)] [9] (olefin = ma, 4; nq, 5; tmetc, 6; fn, 7; cis-SO2-tol,
8; trans-SO2-tol, 9) which were reacted with the usual equimolec-
ular mixture of CNR (CNR = DIC, a; TIC, b) and PR03. The expected
mixed complexes 4a, 5a, 6a, 7a, 8a, 9a and 4b, 5b, 6b were ob-
tained. All the ensuing derivatives were stable in the solid and in
solution and the presence of homoleptic complexes was never de-
tected, as confirmed by their 31P NMR spectra which always dis-
play only one singlet between 26.0 and 29.4 ppm.
4
(3JP–H ꢀ JH–H ꢀ 5 Hz) at the lowest field with respect to the other
allyl protons, while the anti proton trans to phosphorus resonates
as a doublet (3JP–H = 10 Hz). The signals of the methyl protons of
CNR and of the phenyl groups of PPh3 belonging to the pure mixed
complexes are also detectable at high and low field, respectively,
confirming that no homoleptic species are present in solution.
Notably, both the mixed derivatives of the asymmetric
1,1-Me2allyl (2a, 2b) are detectable only as the unique isomers
bearing the bis-substituted allyl carbon trans to phosphorus. As a
matter of fact, the protons of the anti methyl substituents at the
terminal allyl carbon (CH3anti) resonate as doublets at higher field
with respect to the syn (CH3syn) whereas, only the couplings with
the central proton (two doublets) are detectable in the case of
the terminal anti and syn allyl protons (trans to CNR). All the
NMR experiments (1H, 31P, 13C NMR, HMQC and HMBC) are in
accord with the proposed formulation. In particular the 13C NMR
spectra clearly display three different signals for the allyl carbons
in both cases. The allyl carbons trans to phosphorus in any case
resonate as a doublet at the lowest field (3JP–C ꢀ 24–27 Hz). More-
over, the 31P NMR spectra display a unique singlet (between 26 and
28 ppm) in all the allyl complexes synthesized, thereby confirming
the presence in solution of the sole isomer previously described in
the case of complexes 2a and 2b [1] (see Section 4 and Supporting
Information for a selection of NMR spectra).
The spectator ligands CNR and PR03 were also detected by
means of 1H, 13C and 31P NMR spectra displaying all the expected
signals. The coordinated olefins are also detectable by NMR tech-
niques and their coordination is characterized by a high field shift
of the olefin protons and carbons (63, 680 ppm, respectively) with
respect to those of the uncoordinated ones. Moreover, the complex
asymmetry and the presence of the NMR active phosphorus allow a
prompt identification of the olefin protons and carbons. As an
example, the proton of maleic anhydride cis to phosphorus in the
complex 4b resonates as a pseudo triplet (JP–H ꢀ JH–H ꢀ 4.1 Hz) at
3.94 ppm whereas the signal of the trans proton at 4.73 ppm reso-
nates as a doublet of doublets (JP–H = 9.8 Hz). Similar behavior can
be observed in the case of the olefin carbons (50.1 ppm cis to P and
50.9, trans to P, JP–C = 26.3 Hz) and generally speaking in all the pal-
ladium(0) olefin derivatives. In agreement with the general behav-
ior the complexes of the symmetric olefin tmetc 6a and 6b display
only two singlets related to the two different olefin methyl substit-
uents (3.27 ppm cis to P and 3.73 trans to P) (see Section 4 and
Supporting Information for a selection of NMR spectra).
2.2. Synthesis of [Pd(C4(COOMe)4)(PPh3)(CNR)] complexes (CNR = DIC,
TIC)
2.4. Crystal structure determinations
The palladacyclopentadienyl complexes of the type
[Pd(C4(COOMe)4)(CNR)(PPh3)], (3) cannot be synthesized from
the usual polymeric starting substrate [Pd(C4(COOMe)4)]n [7] upon
addition of CNR and PPh3, since the formation of a mixture of not
easily identifiable species was observed in those cases, probably
due to the low solubility of the polymeric precursor. Since the
alternative procedure based on the oxidative coupling of di-
methyl-2-butynedioate (dma) of a mixed CNR–PPh3 palladium(0)
substrate gave no appreciable result, we have adopted a tailored
At the best of our knowledge the crystal structures reported in
this paper represent the first diffractometric study on complexes of
palladium(0) olefin complexes, allyl palladium(II) and palladacy-
clopentadiene derivatives bearing mixed phosphane and isocya-
nide as spectator ligands.
ORTEP [10] views of the allyl cationic complexes 2a and 2b are
shown in Figs. 1 and 2. Selected bond distances and angles are gi-
ven in Table 1.
In these two complexes the palladium atom, bound to one tri-
approach derived from
a
synthetic protocol we proposed
phenylphosphane group, one isocyanide carbon and two g
3-allylic
elsewhere [8], consisting in the reaction of the labile 6-methyl-2-
phenylthiomethylpyridine (MeN-SPh) ligand with the polymer
[Pd(C4(COOMe)4)]n yielding the complex [Pd(C4(COOMe)4)
terminal carbon atoms, shows distorted square-planar coordina-
tion. In both 2a and 2b complexes the C3 terminal carbon bearing
the dimethyl substituents is trans to the thriphenylphosphane

L. Canovese et al. / Inorganica Chimica Acta 378 (2011) 239–249
241
Scheme 1. Ligands and complexes synthesized and studied.
group. The trans influence exerted by the phosphane is evidenced
by the lengthening of Pd–C3 (allyl) bond distances, ranging from
2.265(5) to 2.293(5) Å, if compared with the Pd–C1 ones, trans to
isocyanide carbon atoms, which are in the range 2.114(6)–
2.143(6) Å. Apparently the substituents are involved in Pd–C bond
complexes, 2a and 2b, respectively. The central C2 atoms of the
3-allyl groups are situated above the mean coordination plane
by 0.47(1) and 0.623(6) Å, respectively (Figs. 1s, 2s Supporting
g
Information).
An ORTEP view of the neutral palladacyclopentadiene complex 3a
is shown in Fig. 3 and selected bond distances and angles are re-
ported in Table 2. The geometry around the palladium center is dis-
torted square planar. The four positions around the central
palladium are occupied by the 1,4 carbon atoms of the 1,2,3,4-tet-
rakis(methoxycarbonyl)buta-1,3-diene-1,4-diyl anionic ligand, one
triphenylphosphane and one isocyanide carbon atom. The
lengthening as observed also in other [Pd(g
3-substituted-al-
lyl)(C,P)] complexes where Pd–C(trans to P) distances become
longer upon terminal substitution from 2.18(2) to 2.28(2) Å (on
average) [11]. The
g
3-allyl fragments are obliquely placed with re-
spect to the metal square coordination plane and form with the
same plane dihedral angles of 65.1(8)° and 58.6(6)°, for the two

242
L. Canovese et al. / Inorganica Chimica Acta 378 (2011) 239–249
Table 1
Selected bond distances and angles (Å and °) for compounds 2a and 2b.
2a
2b
Pd1–P1
Pd1–C1
Pd1–C2
Pd1–C3
Pd1–C6
C1–C2
C2–C3
P1–Pd1–C1
P1–Pd1–C2
P1–Pd1–C3
P1–Pd1–C6
C6–Pd1–C1
C6–Pd1–C2
C6–Pd1–C3
C1–C2–C3
P1,Pd1,C6^C1,C2,C3
2.324(1)
2.143(5)
2.156(7)
2.293(5)
2.002(5)
1.453(12)
1.330(10)
97.6(2)
132.9(3)
164.5(1)
97.6(1)
163.8(2)
127.7(3)
97.2(2)
2.322(1)
2.114(6)
2.144(5)
2.265(5)
2.001(5)
1.394(9)
1.387(8)
99.0(2)
133.4(2)
165.2(2)
102.4(2)
158.5(2)
121.2(2)
91.4(2)
123.9(9)
65.1(8)
121.9(5)
68.4(6)
^ = Dihedral angle.
Fig. 1. An ORTEP view of complex 2a showing the thermal elipsoides at 30%
probability level. (For the sake of clarity the perchlorate anion was omitted.)
Fig. 3. An ORTEP view of complex 3a showing the thermal ellipsoids at 30%
probability level.
maximum deviation from the basal plane is 0.078(3) Å for the iso-
cyanide carbon C1. The palladacyclopentadiene ring is approxi-
mately planar with maximum deviations from the mean plane
for C12 and C13 atoms of ꢂ0.022(3) and 0.023(3) Å, respectively,
and forms an angle of only 1.42(7)° with the coordination plane.
The Pd1–C10 and Pd1–C13 bonds display distances of 2.067(3)
and 2.073(3) Å longer than analogous distances in similar com-
pounds, with a Pd–C average bond length of 2.02(2) Å, where the
carbon atoms are in trans positions to nitrogen or sulphur atoms,
showing that the triphenylphosphane and isocyanide groups exert
a comparably slight trans influence on Pd–C(diene) distances. [12]
An ORTEP view of complex [Pd(g
2-ma)(TIC)(PPh3)] (4b) is shown
in Fig. 4. A selection of bond distances and angles is given in
Table 3. The palladium is bound to one isocyanide carbon atom,
one triphenylphosphane group and
double bond of the maleic anhydride. The structure shows that
g
2-coordinated to the C@C
Fig. 2. An ORTEP view of complex 2b showing the thermal elipsoides at 30%
probability level. (For the sake of clarity the perchlorate anion was omitted.)

L. Canovese et al. / Inorganica Chimica Acta 378 (2011) 239–249
243
Table 2
Selected bond distances and angles (Å and °) for compound 3a.
Table 3
Selected bond distances and angles (Å and degrees) for compound 4b.
Pd1–P1
Pd1–C1
Pd1–C10
Pd1–C13
P1–Pd1–C1
P1–Pd1–C10
P1–Pd1–C13
C1–Pd1–C10
2.3627(8)
1.991(4)
2.067(3)
2.073(3)
90.8(1)
98.0(1)
177.1(1)
170.4(1)
C10–C11
C11–C12
C12–C13
1.347(4)
1.480(4)
1.336(4)
Pd1–P1
Pd1–C1
Pd1–C2
Pd1–C5
2.3387(5)
2.126(2)
2.095(2)
2.012(5)
1.425(3)
149.35(6)
110.96(6)
94.68(5)
69.1(1)
C2–C3
C3–O3
C4–O3
C1–C4
1.467(3)
1.407(2)
1.394(3)
1.452(3)
C1–Pd1–C13
C10–Pd1–C13
Pd1–C10–C11
Pd1–C13–C12
91.7(1)
79.4(1)
114.2(2)
114.9(2)
C1–C2
P1–Pd1–C1
P1–Pd1–C2
P1–Pd1–C5
Pd1–C1–C2
Pd1,C1,C5 ^C1,C2,C3,C4,O3
Pd1–C2–C1
Pd1–C1–C4
Pd1–C2–C3
71.5(1)
110.1(1)
107.8(1)
68.42(6)
^ = Dihedral angle.
which obviously depends on the chemical characteristics of the
added ligands, other things being equal. Thus a similar stability
among complexes yields an almost statistical distribution of the
derivatives (25%:50%:25%) [3]. Intuitively, in the case of a different
stability between the two homoleptic complexes, the mixed species
will generally have a stability intermediate between those of the
formers. Such a situation is the most usual and experimentally ver-
ified and gives rise to a distribution of the species governed by the
mutual equilibrium constants. In order to rationalize these observa-
tions let us first suppose that the addition of equimolecular amounts
of the ligands A and B to a generic species ML2 ([A]0 = [B]0 = [ML2]0;
L = labile ligand; M = metal) yields the mixed species MAB only
according to the reaction:
ML2 þ A þ B ! MAB þ 2L
ð1Þ
Also, consider the reactions that the mixed species undergoes when
reacting with the ligands A or B to give the homoleptic derivatives.
½MAAꢃ½Bꢃ
MAB þ A ¼ MAA þ B K1
MAB þ B ¼ MBB þ A K2
¼
¼
;
D
G10
ð2Þ
ð3Þ
½MABꢃ½Aꢃ
½MBBꢃ½Aꢃ
;
D
G20
½MABꢃ½Bꢃ
The mixed complex MAB may also react to give the homoleptic
complexes according to reaction (4) where the condition
[M]0 = [A]0 = [B]0 is implicit:
Fig. 4. An ORTEP view of complex 4b showing the thermal ellipsoids at 30%
probability level.
½MAAꢃ½MBBꢃ
;
2MAB ¼ MAA þ MBB K3
¼
the palladium center is trigonal planar, as expected for zero-valent
complexes of the type [Pd(g2-olefin)(L0)(L00)]. Pd1–C1 and Pd1–C2
bond distances of 2.126(2) and 2.095(2) Å are in perfect agreement
with the Pd(0)–C distances in other similar complexes of Pd(0)
with maleic anhydride. [13] The C1@C2 alkene bond length of
1.425(4) Å is 0.093 Å longer than in the free alkene and is consis-
tent with p-back bonding from Pd(0). The maleic anhydride moiety
forms an angle of 68.42(6)° with the Pd1–P1–C5 coordination
plane (Fig. 3s, Supporting Information).
2
½MABꢃ
D
G03 ¼
D
G01 þ
D
G20
ð4Þ
Obviously, the stability of complex MAB is governed by the magni-
tude of K3 and in particular the degree of advancement of reaction
(5) is:
pffiffiffiffiffiffi
0
D
G
½MABꢃ0 ꢄ K3
pffiffiffiffiffiffi
3
n3 ¼
;
K3 ¼ eꢂ
ð5Þ
RT
2
K3 þ 1
where [MAB]0 represents the starting concentration of the mixed
complex (see Eq. (1)).2 A very small equilibrium constant K 3
2.5. Formation of the mixed complexes
(D
G03 ꢅ 0) renders the degree of advancement negligible and conse-
Substitutionamongligands in the case of palladium derivativesis
generally fast so that, the ratios among the ensuing products are
under thermodynamic control. It would hence be importantto stress
that when we talk of equimolecular conditions we mean that the
synthesis of the complexes is carried out by mixing equal
concentrations of all the involved species ([starting com-
plex]0 = [CNR]0 = [PPh3]0) since such a stoichiometric constraint
plays a fundamental role in the reaction economy. However, even
under such a condition the formation of mixed species only occurs
rarely, the formation of all the possible complexes (one mixed and
two homoleptic)being themost frequent event. This factis governed
by the mutual stability (stability constants) of the ensuing species
quently the mixed derivative the most prominent species. Appar-
ently, the stability of the mixed complex MAB with respect to the
combination of the stabilities of the homoleptic species
(D D D
G01 + G02 = G03) is the sole condition required in order to enrich
the reaction mixture in the mixed derivative. The formation of only
the mixed complexes [Pd(g
3-allyl)(L)(X)] (L = neutral ligand,
Xꢂ = halide) is often observed when the allyl-halide palladium
dimer is reacted with the stoichiometric amount of L in chloridated
solvents. On the contrary, mixed complexes bearing neutral mole-
cules as spectator ligands are less frequent and are observed when
2
Under non equimolecular conditions such a conclusion will no longer be valid.

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L. Canovese et al. / Inorganica Chimica Acta 378 (2011) 239–249
the two neutral ligands are weak (CH3CN, pyridine) and strong
(P(OR)3, PR3) [2] coordinating species, respectively.3 Apparently,
the condition expressed by Eq. (5) can also be achieved when only
one of the homoleptic derivatives is very unstable, the equilibrium
monitored the amine attack at the allyl fragment of homoleptic
and mixed complexes by NMR experiments at 273 K. At this tem-
perature the amine attack is still fast whereas the subsequent
isomerization is remarkably slower. The regioisomer distribution
is reported in the following Table 4.
constant being modulated only by the
D
G03 value. Obviously, in that
case the stoichiometric equivalence among concentrations and con-
sequently the degree of advancement is an essential prerequisite.
In any case, the bis-substituted allyl carbon is far more prone to
nucleophilic attack by piperidine than its un-substituted analog
probably due to the stabilization exerted by the two methyl groups
of the incipient cation formed upon the amine attack to the coor-
dinated allyl fragment (Scheme 4). [1,16] Moreover such an effect
is somewhat enhanced by the presence of a phosphorus atom trans
to the bis-substituted allyl carbon (entries 3, 4, 5 versus 1, 2 in
Table 4), probably thanks to the weakening of the Pd–Ctrans-P bond,
as pointed out by the crystallographic data (vide supra). Conse-
quently, the mixed PPh3/CNR 1,1-Me2allyl complexes display a
selectivity comparable to that of the bis-phosphane derivative 2P2.
We have carried out a detailed kinetic study whose results
based on reaction Scheme 4 [1,16] are reported in Table 5. It is evi-
dent that complexes bearing the 1,1-Me2allyl fragment (2a, 2b) re-
act faster than those bearing the less hindered 2-Me-allyl despite
their steric hindrance, in agreement with the stabilizing effect in-
However, in our case both the homoleptic species ([Pd(
g
3-al-
lyl)(CNR)2]ClO4, [Pd(
g
3-allyl)(PPh3)2]ClO4), are very stable com-
plexes since both phosphane and isocyanide are strong ligands.
Therefore, the formation of only the mixed derivative was some-
what unexpected. Remarkably, we have experimentally shown that
the use of equimolecular amount of triphenylphosphane and isocy-
anide induces the formation of the mixed derivatives only, also
when different substrates of Pd(II) or Pd(0) are used.
In order to rationalize the problem we have resorted to a theo-
retical investigation by means of the functional hybrid meta-GGA
M06 software [14]. The results for the allyl (C3H5) Pd(II) and the
maleic anhydride Pd(0) derivatives with DIC and PPh3 are reported
in Scheme 2
The equilibrium constants derived from the
D D
G03 and G06 values
are K3 = 9.5 ꢆ 10ꢂ9 and K6 = 4.2 ꢆ 10ꢂ6 and the corresponding
duced by the two methyl substituents on the
g
2-allylamonium
degrees of advancement n3=[[Pd(g3-C3H5)(DIC)(PR03)] ClO4]0 ꢆ 9.7
intermediate (Fig. 4s, Supporting Information).4
ꢆ 10ꢂ5 and n6 = [Pd(
g
2-ma)(DIC)(PPh3)]0 ꢆ 2.1 ꢆ 10ꢂ3
, respec-
For the sake of clarity in Scheme 4 we have reported only the
attack at the most substituted carbon. However, the attack at the
less substituted allyl termini is also possible (see Table 4; ratio = 5:
95). Since the ratio between products is equal to the ratio between
second order rate constants it is evident that the attack at the most
substituted carbon is more than one order of magnitude faster than
that occurring at the unsubstituted allyl termini (ꢁ20:1). The dif-
ference in reactivity between complexes bearing different isocya-
nides (Table 5) is easily interpreted on the basis of the different
inductive effect of the two isocyanides.
tively, indicating that in any case the mixed species hardly revert
into their homoleptic precursors (Eq. (5)). We crosschecked this
theoretical result by mixing equimolecular amounts of the
homoleptic complexes [Pd(g -
3-C3H5)(DIC)2]ClO4 and [Pd(g3
C3H5)(PR’3)2]ClO4 in CDCl3. As expected, the subsequent fast
reaction yielded only the mixed [Pd(g3-C3H5)(DIC)(PR03)]ClO4
derivative. At the best of our knowledge only the use of isocyanides
and posphanes induces the formation of mixed complexes. Appar-
ently, phosphanes and isocyanides act synergically probably
thanks to a push–pull global effect strongly stabilizing their deriv-
atives. Similar stabilization might also be achieved with ligand
mixtures that we have not investigated yet, such as carbenes/iso-
cyanides or carbenes/phosphanes, as at least one paper in the liter-
ature seems to indicate [15].
2.7. Reaction of complex 5b with dimethyl-2-butynedioate (dma)
As already stated, the mixed palladacyclopentadienyl deriva-
tives can be obtained neither by reacting the [Pd(C4(COOMe)4)]
polymer with CNR and PPh3 nor by oxidative coupling [8b,17] of
complexes of the type [Pd(g
2-olefin)(CNR)(PPh3)] with dimethyl-
2.6. Reactivity of the allyl complexes toward amination
2-butynedioate (dma) since both these approaches yielded several
not easily identifiable decomposition products. Thus, in order to
obtain some more information we have undertaken an NMR study
As a part of an ongoing study carried out in our laboratory [16] we
have also investigated the allylamination of the CNR/PPh3 mixed al-
lyl complexes with piperidine whose remarkable basicity
(pKa = 11.12) coupled with a reduced steric hindrance renders the
reaction rate easily accessible. Preliminary studies were carried
out in CDCl3 by 1H and 31P NMR experiments whereas the reaction
rates were measured by UV–Vis techniques. Amination of the
complexes bearing the symmetric allyl fragment 1a and 1b in the
presence of dimethylfumarate (dmfu) as stabilizing olefin yields
of the reaction of the complexes [Pd(
dma at reduced temperature (253 K). The formation in solution
of the complexes [Pd(
2-dma)(TIC)(PPh3)] was observed as indi-
g
2-nq)(TIC)(PPh3)] (5b) with
g
cated by the signals attributable to the protons of the ester groups
–COOCH3 at 3.33 and 3.85 ppm of the coordinated dma and by the
31P signal at 31.1 ppm with respect to 29.2 ppm of the starting
complexes. These derivatives are quite rare and stabilized by a lim-
ited number of bulky spectator ligands [9a,18] (Section 4).
1-(2-methylallyl)piperidine only and the complex [Pd(g2
-
dmfu)(CNR)(PPh3)] as can be deduced from the NMR spectra of the
reaction mixture (see Section 4). On the contrary, the derivatives
2a and 2b according to the asymmetric nature of the allyl fragment
give the two allylpiperidine regioisomers, namely 1-(1,1-
Me2allyl)piperidine (RA) and 1-(3,3-Me2allyl)piperidine (RB)
(Scheme 3):
Notably, the regioisomer RA is significantly less stable than RB.
Nevertheless it represents the species that is formed in excess. In
order to minimize the rearrangement of RA into RB we have
3. Conclusion
We have prepared some new mixed complexes of palladium in
different oxidation states bearing isocyanides and triphenylphos-
phane as mixed spectator ligands. The synthetic protocol was
based on the reaction with strictly stoichiometric ratios of all the
4
From Scheme 4 the observed rate constants are of the type kobs = k2ꢄ[PIP]0 and
were obtained by non linear regression analysis of the monoexponential function
3
A positive
G2) and a negative value of
homoleptic complex MAA (or MBB) is much more unstable than the other, as
probably is the case of the complexes [Pd(
3-allyl)(CH3CN)2]+ or [Pd( 3-allyl)(py)2]+
with respect to [Pd(
3-allyl)(P(OR)3)2]+ and [Pd( 3-allyl)(PR3)2]+. The stoichiometric
constraint ([A]0 = [B]0 = [ML2]0) causes the formation of the mixed derivative only.
D
G3 can also be obtained from the combination of a highly positive
D
G1
(Dt ꢂ D = (D0 ꢂ D ꢄ exp(ꢂkobsꢄt) recorded from the UV–Vis experiments obtained at
1
1
(or
D
D
Gꢇ2 (or Gꢇ1). This situation is verified when the
D
suitable wavelengths and at various [PIP]0 concentrations. Dt, D0 and D represent
1
the optical density at time t, at the beginning and at the end of reaction, respectively.
The second order k2 constants were calculated from linear regression analysis of the
kobs versus piperidine concentration data (see as an example Fig. 4s, Supporting
Information).
g
g
g
g

L. Canovese et al. / Inorganica Chimica Acta 378 (2011) 239–249
245
Scheme 2. Calculated DG0f for homoleptic and mixed palladium(II) and palladium(0) complexes.
Scheme 3. Amination reaction of palladium allyl derivatives bearing mixed ligands.
Table 4
reactants involved and was traced back to the considerable stabil-
ity imparted to the resulting mixed complexes by the synergic
push–pull effect exerted by the concomitant presence of one isocy-
anide and one phosphane group. Notably such a result can also be
achieved by mixing equimolecular amounts of the two homoleptic
complexes which rapidly and completely revert to the mixed sub-
strate. We have furthermore studied the reactivity of the mixed
species by means of some standard reactions (i.e. allyl amination
and olefin exchange in the case of Pd(II) allyl or Pd(0) olefin
Regioisomer distribution upon the piperidine attack at 273 K on the complexes in
column 2.
Entries
Complex
% RA
% RB
1
2
3
4
5
[Pd(
[Pd(
[Pd(
[Pd(
[Pd(
g
g
g
g
g
3-1,1-Me2allyl)(DIC)2]ClO4 (2a2)
3-1,1-Me2allyl)(TIC)2]ClO4 (2b2)
3-1,1-Me2allyl)(PPh3)2]ClO4 (2P2)
3-1,1-Me2allyl)(DIC)(PPh3)]ClO4 (2ac)
3-1,1-Me2allyl)(TIC)(PPh3)]ClO4 (2bc)
66
67
93
95
95
34
33
7
5
5

246
L. Canovese et al. / Inorganica Chimica Acta 378 (2011) 239–249
Scheme 4. Detailed mechanism for the allyl amination reaction of palladium allyl derivatives.
Table 5
4.4. Preliminary NMR studies and kinetic measurements
Second order rate constants at 298 K in CHCl3.
The kinetics of attack of piperidine on allyl palladium com-
plexes were carried out by means of 1H or 31P NMR techniques
at 298 K by dissolving the complex under study in 0.8 ml of CDCl3
in the presence of dimethylfumarate ([dmfu]0 = 2.7 ꢆ 10ꢂ2, [com-
plex]0 = 1.8 ꢆ 10ꢂ2 moldmꢂ3, [complex] = 1a, 2a, 1b, 2b, 2a2, 2b2,
2P2). An appropriate aliquot of piperidine was added
([pip]0 = 9 ꢆ 10ꢂ2 moldmꢂ3) and the reactions were followed to
completion by monitoring the disappearance of the starting com-
plexes and the concomitant appearance of the Pd(0) olefin
complex.
Complex
k2 (dm3 molꢂ1 sꢂ1
)
[Pd(
[Pd(
[Pd(
[Pd(
g
g
g
g
3-1,1-Me2allyl)(DIC)(PPh3)]ClO4 (2a)
3-1,1-Me2allyl)(TIC)(PPh3)]ClO4 (2b)
3-2-Me-allyl)(DIC)(PPh3)]ClO4 (1a)
3-2-Me-allyl)(TIC)(PPh3)]ClO4 (1b)
5.15 0.24
0.89 0.07
1.72 0.07
0.41 0.02
derivatives, respectively). For the sake of completeness we have
carried out the X-ray structural determination of four novel isocy-
anide–phosphane substrates.
4. Experimental
4.5. Spectrophotometric kinetic measurements
4.1. Materials
A 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 ꢀ 1 ꢆ 10ꢂ4 moldmꢂ3) in the presence of dimethylfu-
All solvents were purified by standard procedures and distilled
under argon immediately prior to use. Fumaronitrile was purified
by sublimation under vacuum and piperidine distilled over NaOH.
1D- and 2D-NMR spectra were recorded using a Bruker 300 Avance
spectrometer. Chemical shifts (ppm) are given relative to TMS (1H
marate ([dmfu]0 ꢀ 3 ꢆ 10ꢂ4 moldmꢂ3
)
was placed in the
thermostatted (298 K) cell compartment of the UV–Vis spectropho-
tometer. Adequate aliquots of a concentrated solution of piperidine
were then added ([pip]0 P 10 ꢆ [complex]0) by means of a micropi-
pette. The reaction was monitored by recording the UV–Vis spectra
as a function of time corresponding to the largest absorbance change
in the 260–400 nm wavelength intervals. The kinetics of nucleo-
philic attack at a fixed wavelength were recorded under pseudo-first
order conditions at 310 nm. The piperidine concentrations were
within the 1 ꢆ 10ꢂ3–1 ꢆ 10ꢂ2 moldmꢂ3 interval and were obtained
by adding known aliquots of the mother solution of piperidine (0.1–
0.3 moldmꢂ3) to a solution of the complex under study dissolved in
3 mL of freshly distilled CHCl3 ([complex]0 ꢀ 1 ꢆ 10ꢂ4 moldmꢂ3) in
the presence of dimethylfumarate ([dmfu]0 ꢀ 3 ꢆ 10ꢂ4 moldmꢂ3).
and 13C NMR) and 85% H3PO4 31P NMR). UV–Vis spectra were re-
(
corded 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.
4.2. Crystal structure determinations
The crystal data of compounds 2a, 2b, 3a, and 4b were collected
at room temperature using a Nonius Kappa CCD diffractometer
with graphite monochromated Mo Ka radiation. The data sets were
integrated with the Denzo-SMN package [19] and corrected for
Lorentz, polarization and absorption effects (SORTAV) [20]. The
structures were solved by direct methods using SIR97 [21] system
of programs and refined using full-matrix least-squares with all
non-hydrogen atoms anisotropically and hydrogens included on
calculated positions, riding on their carrier atoms. In complex 4b
the disordered C21H3 methyl of the methoxy carbonyl group
bonded to C13 was refined over two positions with occupancies
of 0.60 and 0.40, respectively.
4.6. NMR studies on the exchange reaction of naphthoquinone in
complex 5b with dimethyl-2-butynedioate (dma)
Complex
[Pd(
g
2-nq)(TIC)(PPh3)]
(5b)
(6.4mg,
1.05ꢆ
10ꢂ2 mmol) were dissolved in 0.8 ml of CDCl3 at 253 K.
Dimethyl-2-butynedioate (dma) (4.5 mg, 3.2 ꢆ 10ꢂ2 mmol) were
added. The reaction went to completion in few minutes.
All calculations were performed using SHELXL-97 [22] and PARST
[23] implemented in WINGX [24] system of programs. The crystal
data are given in Table 1s (Supporting Information).
4.7. Synthesis of the precursors, Intermediates and complexes 2 and 2b
The synthesis of the precursors bis-[Pd(
[Pd(g
g
3-1,1-Me2allyl)Cl]2, bis-
3-2-Meallyl)Cl]2 [27], [Pd2(DBA)3 CHCl3] [28], [Pd(C4(COO-
Me)4)]n [29] and of the intermediates [Pd(C4(COOMe)4)(MeN-SPh)]
[8b], [Pd(
2-ma)(MeN-SPh)], [Pd( 2-nq)(MeN-SPh)], [Pd(g2
tmetc)(MeN-SPh)], [Pd(
2-fn)(MeN-SPh)], [Pd( 2-cis-SO2-tol)
(MeN-SPh)] and [Pd(
2-trans-SO2-tol)(MeN-SPh)] [9b] (MeN-
.
4.3. Computational details
Theoretical calculations were performed with the GAUSSIAN 09
[25] package using the functional hybrid meta-GGA M06 [14]
and the Def2-TZVP basis set [26]. The geometry optimization was
performed without any symmetry constraint, followed by analyti-
cal frequency calculation to confirm that a minimum had been
reached.
g
g
-
g
g
g
SPh = 6-methyl-2-phenylthiomethylpyridine) [16e] was carried
out according to published procedures. Complexes 2a and 2b were
synthesized as reported in Ref. [1].

L. Canovese et al. / Inorganica Chimica Acta 378 (2011) 239–249
247
4.8. Synthesis of the complex [Pd(
g
3-2-Meallyl)(DIC)(PPh3)]ClO4 (1a)
31P {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 26.2.
IR (KBr pellets, cmꢂ1): mC@O 1700, mC„N 2183.
The following complex was obtained in an analogous way using
To 0.0821 g (0.21 mmol) of the allyl dimer [Pd(
g
3-2-Meallyl)Cl]2
dissolved in 7 ml of CH2Cl2 were added in sequence 0.0547 g
the appropriate intermediate.
(0.42 mmol) of DIC dissolved in 4 ml of CH2Cl2, 0.1169 g (0.83 mmol)
.
of NaClO4 H2O dissolved in 5 ml of MeOH and 0.1092 g (0.42 mmol)
of PPh3. The cloudy solution (NaCl) was stirred for 30 m and eventu-
ally dried under reduced pressure. The residue was dissolved in
CH2Cl2 (10 ml), treated with activated carbon and filtered by means
of a celite filter. The resulting clear solution concentrated under re-
duced pressure yields the title complex as white solid (0.254 g,
0.39 mmol, yield 94%) upon addition of diethyl ether.
4.11. [Pd (C4(COOMe)4)(TIC)(PPh3)] (3b)
(Pale yellow micro crystals, 84 % yield).
1H NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 1.12 (s, 9H, t-Bu),
2.56 (s, 3H, OCH3), 3.59 (s, 3H, OCH3), 3.69 (s, 3H, OCH3), 3.75 (s,
3H, OCH3), 7.42 (m, 9H, Ph), 7.59 (m, 6H, Ph).
13C {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 29.4 (CH3, t-
Bu), 50.0 (CH3, OCH3), 50.5 (CH3, OCH3) 51.1 (CH3, OCH3) 51.2 (CH3,
OCH3), 57.6 (C, C(CH3)3), 150.5 (C, Ccyclo), 162.6 (d, C, J = 9.5 Hz, Ccy-
clo), 164 (C, CO), 165.6 (C, CO), 168.8 (C, Ccyclo), 170.2 (C, Ccyclo),
172.6 (d, C, J = 6.4 Hz, CO), 174.8 (d, C, J = 6.4 Hz, CO).
31P {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 25.6.
IR (KBr pellets, cmꢂ1): mC@O 1700, mC„N 2203.
Notably, this complex can also be obtained by mixing equimo-
lecular amounts of [Pd(g g
3-2-Meallyl)(DIC)2]ClO4 and [Pd( 3-2-
Meallyl)(PPh3)2]ClO4 in CDCl3. The 1H and 13C NMR spectra of the
reaction product is virtually undistinguishable from those of an
authentic sample of the title complex.
1H NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 1.99 (s, 3H,
CH3allyl), 2.13 (s, 6H, CH3dic) 3.46 (bs, 1H, allyl Hanti trans-C), 3.73
(bs, 1H, allyl Hsyn trans-C), 3.91 (d, 1H, J = 9.9 Hz, allyl Hanti trans-P),
4.99 (q, 1H, J = 3.9 Hz allyl Hsyn trans-P), 7.07 (d, 2H, J = 7.5 Hz, Hc),
7.24 (t, 1H, J = 7.5 Hz, Hd), 7.51 (m, 15H, Ph).
4.12. [Pd(
g
2-ma)(DIC)(PPh3)] (4a)
13C {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 18.4 (CH3,
(CH3)2dic), 23.8 (CH3, CH3allyl), 72.4 (CH2, allyl CH2trans-C), 74.6 (d,
CH2, JCP = 26.9 Hz, allyl CH2trans-P), 128 (CH, Cc), 130.3 (CH, Cd),
135.7 (C, Cb), 138.4 (d, C, JCP = 5.5 Hz, allyl Ccentral).
To 0.0715 g (0.17 mmol) of the intermediate [Pd(
g
2-ma)(MeN-
SPh)] dissolved in 10 ml of anhydrous CH2Cl2 under inert atmo-
sphere (Ar), 0.0223 g (0.17 mmol) of DIC and 0.0448 g (0.17 mmol)
of PPh3 were added in sequence. The resulting stirred yellow solu-
tion in 45 m decolorates to pale yellow. Addition of activated car-
bon, filtration through celite filter, reduction to small volume
under reduced pressure and eventually addition of diethyl ether
yield the title compound as pale yellow solid. 0.0827 g (0.12 mmol,
yield = 81%) of the complex was obtained after washing the precip-
itate with diethyl ether and pentane.
31P {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 25.8.
IR (KBr pellets, cmꢂ1): mC„N 2169, mClO 1094, dClO 622.
The following complexes were obtained in an analogous way
using the appropriate isocyanide and allyl fragment.
4.9. [Pd(g
3-2-Meallyl)(TIC)(PPh3)]ClO4 (1b)
(White micro crystals, 94 % yield).
1H NMR (300 MHz, CDCl3, T = 278 K, d(ppm)): 2.14 (s, 6H, CH3),
4.05 (bs, 1H, Htrans-C), 4.54 (bs, 1H, Htrans-P), 7.05 (d, 2H, J = 7.8 Hz,
Hc), 7.19 (t, 1H, J = 7.8 Hz, Hd), 7.46 (m, 15H, Ph).
1H NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 1.33 (s, 9H, t-Bu),
1.95 (s, 3H, CH3allyl), 3.18 (bs, 1H, allyl Hanti trans-C), 3.65 (d, 1H,
JHP = 9.2 Hz allyl Hanti trans-P), 3.66 (s, 1H, allyl Hsyn trans-C), 4.94
(dd, 1H, JHP ꢁ JHH = 4.5 Hz allyl Hsyn trans-P), 7.48 (m, 15H, Ph).
13C {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 23.6 (CH3,
CH3allyl), 29.6 (CH3, t-Bu), 58.9 (C, C(CH3)3), 70.5 (CH2, allyl CH2
trans-C), 74.4 (d, CH2, JCP = 27.1 Hz, allyl CH2trans-P), 135.3 (C, CN),
138.2 (d, C, JCP = 5.4 Hz, allyl Ccentral).
13C {1H} NMR (300 MHz, CDCl3, T = 278 K, d(ppm)): 18.5 (CH3,
(CH3)dic), 51.1 (CH, Colefin trans-C), 51.6 (d, CH, JCP = 30.3 Hz,
Colefin trans-P), 126.5 (C, Ca), 127.8 (CH, Cc), 129.2 (CH, Cd), 135.2
(C, Cb), 156.3 (C, CN), 171.2 (C, COtrans-N), 171.4 (d, C, JCP = 6.3 Hz,
COtrans-P).
31P {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 28.1.
IR (KBr pellets, cmꢂ1): mC@O 1734, mC@O 1799, mC„N 2150.
The following complexes were obtained in an analogous way
using the appropriate intermediate and isocyanide. In the case of
partial or remarkable solubility of the complexes in diethyl ether,
the reaction mixture was evaporated to dryness under reduced
pressure, recovered by diethyl ether or pentane and washed by
pentane only.
31P {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 26.
IR (KBr pellets, cmꢂ1): mC„N 2216, mClO 1091, dClO 623.
4.10. [Pd(C4(COOMe)4)(DIC)(PPh3)] (3a)
To 0.07 g (0.12 mmol) of the intermediate [Pd(C4(COOMe)4)
(MeN-SPh))] dissolved in anhydrous CH2Cl2 were added in se-
quence and under inert atmosphere (Ar) 0.0152 g (0.12 mmol) of
DIC and 0.034 g (0.12 mmol) of PPh3. The resulting yellow solution
was stirred for 45 m and eventually treated with activated carbon.
The mixture was then filtered on a celite filter and the clear yellow
solution concentrated under reduced pressure. Addition of diethyl
ether induces the precipitation of 0.0757 g (0.10 mmol, yield 84%)
of the title compound as pale yellow solid.
4.13. [Pd(g
2-nq)(DIC)(PPh3)] (5a)
(Dark yellow micro crystals, 75 % yield).
1H NMR (300 MHz, CDCl3, T = 278 K, d(ppm)): 2.10 (s, 6H, CH3),
4.83 (d, 1H, J = 8.0 Hz, Htrans-C), 5.15 (dd, 1H, JHH = 8.0, JHP = 7.5 Hz,
1H NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 2.03 (s, 6H, CH3),
2.66 (s, 3H, OCH3), 3.40 (s, 3H, OCH3), 3.62 (s, 3H, OCH3), 3.67 (s,
3H, OCH3), 6.99 (d, 2H, J = 7.8 Hz, Hc), 7.16 (t, 1H, J = 7.8 Hz, Hd),
7.34 (m, 9H, Ph), 7.61 (m, 6H, Ph).
H
trans-P), 7.02 (d, 2H, J = 7.5 Hz, Hc), 7.16 (t, 1H, J = 7.5 Hz, Hd),
7.34 (m, 16H, Hnq, Ph), 7.55 (m, 2H, Hnq), 8.05 (d, 1H, J = 9.0, Hnq).
13C {1H} NMR (300 MHz, CDCl3, T = 278 K, d(ppm)): 18.5 (CH3,
(CH3)dic), 67.0 (CH, Colefin trans-C), 68.2 (d, CH, JCP = 16.8 Hz,
Colefin trans-P), 124.9 (CH, CHnq), 125.6 (CH, CHnq), 126.3 (C, Ca),
127.7 (CH, Cc), 128.9 (CH, Cd), 131.4 (CH, (CHnq)2), 135.1 (C, Cb),
184.9 (C, COtrans-C), 185 (d, C, JCP = 6.3 Hz, COtrans-P).
13C {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 18.1 (CH3,
(CH3)dic), 50.1 (CH3, OCH3), 50.8 (CH3, OCH3), 51.2 (CH3, OCH3),
51.4 (CH3, OCH3), 125.5 (C, Ca), 128.2 (CH, Cc), 131.2 (CH, Cd),
134.8 (C, Cb), 151.5 (C, Ccyclo), 161.7 (d, C, J = 9.6 Hz, Ccyclo), 163.6
(d, C, J = 8.4 Hz, CO), 165.8 (C, Ccyclo), 170.3 (C, CO), 171.7 (C, Ccyclo),
172.6 (d, C, J = 6.8 Hz, CO), 174.9 (d, C, J = 5.4 Hz, CO).
31P {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 28.7.
IR (KBr pellets, cmꢂ1): mC@O 1591, mC@O 1636, mC„N 2132.

248
L. Canovese et al. / Inorganica Chimica Acta 378 (2011) 239–249
4.14. [Pd(
g
2-tmetc)(DIC)(PPh3)] (6a)
1H NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 1.26 (s, 9H, t-Bu),
3.94 (t, 1H, JHH = JPH = 4.2 Hz, Htrans-C), 4.38 (dd, 1H, JPH = 9.7 Hz,
JHH = 4.2 Hz, Htrans-P), 7.44 (m,15H, Ph).
(Partially soluble in diethyl ether, white micro crystals, 77%
yield).
13C {1H} NMR: (300 MHz, CDCl3, T = 298 K, d(ppm)): 30 (CH3,
t-Bu), 50.1 (CH, CHolefin trans-C), 50.9 (d, CH, JCP = 26.3 Hz, CHolefin
trans-P), 56.9 (C, C(CH3)3), 171.3 (CO, Ctrans-C), 171.5 (CO, Ctrans-P).
31P {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 28.2.
IR (KBr pellets, cmꢂ1): mC@O 1731, mC@O 1800, mC„N 2171.
1H NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 2.07 (s, 6H,
CH3dic), 3.28 (s, 6H, CH3olefin trans-C), 3.72 (s, 6H, CH3olefin trans-P),
7.01 (d, 2H, J = 7.8 Hz, Hc), 7.15 (d, 1H, J = 7.8 Hz, Hd), 7.52 (m,
15H, Ph).
13C {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 18.4 (CH3,
(CH3)dic), 51.8 (CH3, OCH3 trans-C), 52.4 (CH3, OCH3 trans-P), 66.5 (C,
Colefin trans-C), 67.4 (d, C, JCP = 33.7 Hz, Colefin trans-P), 126.2 (C, Ca),
4.19. [Pd(g
2-nq)(TIC)(PPh3)] (5b)
127.8 (CH, Cc), 129.1 (CH, Cd), 135.5 (C, Cb), 169.0 (C, COtrans-C
169.3 (d, C, JCP = 4.6 Hz, COtrans-P).
)
(Soluble in diethyl ether, orange micro crystals, 81% yield).
1H NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 1.25 (s, 9H, t-Bu),
31P {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 26.4.
IR (KBr pellets, cmꢂ1): mC@O 1695, mC@O 1730, mC„N 2142.
4.74 (d, 1H, J = 7.6 Hz,
Htrans-C), 5.02 (dd,1H, JHP = 9.1 Hz,
JHH = 7.6 Hz, Htrans-P), 7.37 (m,15H, Ph, 1H, Hnq), 7.59 (m, 2H, Hnq),
8.07 (d, 1H, J = 7.7 Hz, Hnq).
13C {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 30.0 (CH3,
t-Bu), 56.5 (C, C(CH3)3), 66.2 (CH, CHolefin trans-C), 67.5 (d, CH,
JCP = 13.0 Hz, CHolefin trans-P), 124.8 (CH, CHnq), 125.5 (CH, CHnq),
4.15. [Pd(
g
2-fn)(DIC)(PPh3)] (7a)
(White micro crystals, 85% yield).
1H NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 2.20 (s, 6H, CH3),
3.02 (dd, 1H, J = 10.0, J = 3.9 Hz, Holefin trans-C), 3.41 (dd, 1H,
JHH = JHP = 10.0 Hz, Holefin trans-P), 7.07 (d, 2H, J = 7.5 Hz, Hc), 7.21
(t, 1H, J = 7.5 Hz, Hd), 7.48 (m, 15H, Ph).
131.0 (CH, CHnq), 134.0 (CH, CHnq), 136.1 (C, Cnq), 136.2 (C, Cnq
)
184.5 (C, COtrans-C), 184.6 (d, C, JCP = 6.3 Hz, COtrans-p).
31P {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 29.4.
IR (KBr pellets, cmꢂ1): mC@O 1630,
mC@O1640 mC„N 2166.
13C {1H} NMR (300 MHz, CDCl3, T = 278 K, d(ppm)): 18.6 (CH3,
(CH3)dic), 28.0 (d, CH, JCP = 34.8 Hz, CHolefin trans-P), 28.5 (CH,
CHolefin trans-C), 121.4 (C, CNtrans-C), 122.1 (d, C, JCP = 7.6 Hz,
CNtrans-P), 126.5 (C, Ca), 127.9 (CH, Cc), 129.3 (CH, Cd), 135.1 (C, Cb).
31P {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 26.0.
IR (KBr pellets, cmꢂ1): mC„N 2134, mC„N 2203.
4.20. [Pd(g
2-tmetc)(TIC)(PPh3)] (6b)
(Pale yellow micro crystals, 81% yield). 1H NMR (300 MHz,
CDCl3, T = 298 K, d(ppm)): 1.26 (s, 9H, t-Bu), 3.27 (s, 6H, OCH3
trans-C), 3.73 (s, 6H, OCH3 trans-P), 7.37 (m, 9H, Ph), 7.48 (m, 6H, Ph).
13C {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 30 (CH3,
t-Bu), 51.5 (CH3, OCH3 trans-C), 52.0 (CH3, OCH3trans-P), 56.5 (C, Colefin
trans-C), 66.2 (d, C, JCP = 36.3 Hz, Colefin trans-P), 56.3 (C, C(CH3)3), 168.9
(C, COtrans-C), 169.0 (d, C, JCP = 4.6 Hz, COtrans-P).
4.16. [Pd(g
2-cis-SO2-tol)(DIC)(PPh3)] (8a)
(White micro crystals, 84% yield).
31P {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 27.4.
1H NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 2.11 (s, 6H,
(CH3)dic), 2.30 (s, 3H, 3 CH3tol), 2.31 (s, 3H, 3 CH3tol), 4.27 (m(ABC
system), 2H, JHH = 9.7, JHP = 7.2, JHP = 3.5 Hz, Holefin), 7.01 (m, 6H,
Hc, Htol), 7.14 (t, 1H, J = 7.5 Hz, Hd), 7.36 (m, 9H, Ph), 7.49 (d, 2H,
J = 8.2 Hz, Htol), 7.57 (m, 6H, Ph), 7.75 (d, 2H, J = 8.2 Hz, Htol).
13C {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 18.4 (CH3,
(CH3)dic), 21.3 (CH3, (CH3)tol), 21.4 (CH3, (CH3)tol), 65.4 (CH,
CHolefin trans-C), 66.6 (d, CH, JCP = 39.8 Hz, CHolefin trans-P), 126.4 (s,
C, JCP = 5.4 Hz, Ca), 127.5 (CH, Cc), 128.7 (CH, Cd), 135.5 (C, Cb),
141.3 (C, CSO2olefin trans-C), 141.8 (d, C, JCP = 6.7 Hz, CSO2olefin trans-P).
31P {1H} NMR (300 MHz, CDCl3, T = 298 K, d(ppm)): 26.7.
IR (KBr pellets, cm-1): mS„O 1142, mS„O 1299, mC„N 2151.
IR (KBr pellets, cmꢂ1): mC@O 1695,
m
C@O1726 mC„N 2176.
Appendix A. Supplementary material
CCDC 825710 (2a), 825711 (2b), 25712 (3a), 825713 (4b) con-
tains the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2011.09.006.
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