(Ferrocenylpyrazolyl)palladium(II) complexes: Syntheses, characterization and rearrangement in solution

Article abstract of DOI:10.1016/j.jorganchem.2015.11.003

Reactions of L1-L6 (3-ferrocenylpyrazolyle (L1), 3-ferrocenyl-5-methylpyrazolyle (L2) 3-ferrocenylpyrazolyl-methylenepyridine (L3) and 3-ferrocenyl-5-methylpyrazolylmethylene-pyridine (L4), 3-ferrocenylpyrazolylethylamine (L5) and 3-ferrocenyl-5-methylpyrazolylethyl-amine (L6)) with [PdCl(Me) (cod)] formed the mononuclear complexes [PdCl(Me) (κ¹-L1)₂] (1), [PdCl(Me) (κ¹-L2)₂] (2), [PdCl(Me) (κ²-L3)] (3), [PdCl(Me) (κ²-L4)] (4), [PdCl(Me) (κ²-L5)] (5) and [PdCl(Me) (κ²-L6)] (6). Reactions of 1-6 with the halide abstractor, Na[BAr₄], (Ar = 3,5-(CF₃)₂C₆H₃), led to the formation of the salts, [PdMe(NCMe) (κ¹-L1)₂][BAr₄] (7), [PdMe(NCMe) (κ¹-L2)₂][BAr₄] (8), [PdMe(NCMe) (κ²-L3)][BAr₄] (9), [PdMe(NCMe) (κ²-L4)][BAr₄] (10), [PdMe(NCMe) (κ²-L5)][BAr₄] (11), [PdMe(NCMe) (κ²-L6)][BAr₄] (12) respectively. However, when 3 or 4 was reacted with of Na[BAr₄] and a slight excess of methyl acrylate, the products were surprisingly the bis(ligand)palladium complexes [Pd(κ²-L3)₂][BAr₄]₂ (13) and [Pd(κ²-L4)₂][BAr₄]₂ (14) instead of the expected acylpalladium chelate complexes ([(κ²-L)Pd{(CH₂)₂C(O)OMe}][BAr₄]). Complexes 1-6, activated with Na[BAr₄], and pre-activated complexes 7-12 at 10 bar of ethylene and 30 bar of carbon monoxide produced polyketones, albeit with low activity (ca. 1.00 g.mmol^-1Pd.h^-1); with the active catalysts rearranging to mainly bis(pyrazolyl)palladium complexes similar to 13 and 14.

Full text of DOI:10.1016/j.jorganchem.2015.11.003

Accepted Manuscript
(Ferrocenylpyrazolyl)palladium(II) complexes: Syntheses, characterization and
rearrangement in solution
Collins Obuah, James Darkwa
PII:
S0022-328X(15)30202-3
10.1016/j.jorganchem.2015.11.003
JOM 19290
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 8 April 2015
Revised Date: 22 October 2015
Accepted Date: 3 November 2015
Please cite this article as: C. Obuah, J. Darkwa, (Ferrocenylpyrazolyl)palladium(II) complexes:
Syntheses, characterization and rearrangement in solution, Journal of Organometallic Chemistry (2015),
doi: 10.1016/j.jorganchem.2015.11.003.
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ACCEPTED MANUSCRIPT
2
Pd
+
+
Na[BAr ]
2
4
CO
O
n
Polyketone

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(Ferrocenylpyrazolyl)palladium(II) complexes: Syntheses, characterization and
rearrangement in solution
Collins Obuah and James Darkwa*
Department of Chemistry, University of Johannesburg, Auckland Park Kingsway Campus,
Auckland Park 2006, Johannesburg, South Africa.e-mail: jdarkwa@uj.ac.za
Abstract
Reactions of L1-L6 (3-ferrocenylpyrazolyle (L1), 3-ferrocenyl-5-methylpyrazolyle (L2)
3-ferrocenylpyrazolyl-methylenepyridine (L3) and 3-ferrocenyl-5-methylpyrazolylmethylene-
pyridine (L4), 3-ferrocenylpyrazolylethylamine (L5) and 3-ferrocenyl-5-methylpyrazolylethyl-
amine (L6)) with [PdCl(Me)(cod)] formed the mononuclear complexes [PdCl(Me)(κ1-L1)2] (1),
[PdCl(Me)(κ1-L2)2] (2), [PdCl(Me)(κ2-L3)] (3), [PdCl(Me)(κ2-L4)] (4), [PdCl(Me)(κ2-L5)] (5)
and [PdCl(Me)(κ2-L6)] (6). Reactions of 1-6 with the halide abstractor, Na[BAr4], (Ar = 3,5-
(CF3)2C6H3), led to the formation of the salts, [PdMe(NCMe)(κ1-L1)2][BAr4] (7),
[PdMe(NCMe)(κ1-L2)2][BAr4] (8), [PdMe(NCMe)(κ2-L3)][BAr4] (9), [PdMe(NCMe)(κ2
-
L4)][BAr4] (10), [PdMe(NCMe)(κ2-L5)][BAr4] (11), [PdMe(NCMe)(κ2-L6)][BAr4] (12)
respectively. However, when 3 or 4 was reacted with of Na[BAr4] and a slight excess of methyl
acrylate, the products were surprisingly the bis(ligand)palladium complexes [Pd(
2-L4)2][BAr4]2 (14) instead of the expected acylpalladium chelate complexes
2-L)Pd{(CH2)2C(O)OMe}][BAr4]).
κ
2-L3)2][BAr4]2
(13) and [Pd(
κ
([(
κ
Complexes 1-6, activated with Na[BAr4], and pre-activated complexes 7-12 at 10 bar of
ethylene and 30 bar of carbon monoxide produced polyketones, albeit with low activity (ca. 1.00
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g.mmol-1Pd.h-1); with the active catalysts rearranging to mainly bis(pyrazolyl)palladium
complexes similar to 13 and 14.
Keywords: Ferrocenylprazolyl, palladium complexes, ethylene, carbon monoxide,
copolymerization
Introduction
Nitrogen-donor palladium complexes have been used extensively in catalysis partly due
to their electrophilic metal centres which enable them to form relatively strong Pd-H and Pd-C
bonds. Palladium also allows easy access to 0 and +2 oxidation states in which the palladium
centre initiate reactions, such as oxidative-addition, transmetallation and reductive-elimination
processes [1].
Since the seminal work by Brookhart and co-workers [2], nitrogen-donor palladium
complexes as catalysts have received considerable attention because these catalysts are very
active in the production of polyolefins and are tolerant to polar monomers. In particular the use
of α-diimine ligands to prepare nickel and palladium catalysts have dominated this area of
research [3]. One unique advantage of α-diimine ligands is their ability to form air and heat
stable cationic chelating acylpalladium complexes when (α-diimine)palladium chloromethyl
complexes are reacted with methylacrylate and NaBAr4 (Ar = 3,5-(CF3)2C6H3) [4]. This reaction
produces the cationic species, [(N^N)Pd{(CH2)2C(O)OMe}]+, which is essentially the active
catalysts when these chelating acylpalladium complexes are used in the polymerisation of
ethylene [5]. In this form the oxophilicity of the palladium centre is reduced; enabling such
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cationic species to catalyse the copolymerisation of ethylene with a variety of polar-functional
olefins.
Despite the attributes of (α-diimine)acylpalladium cationic species narrated above, there
are instances where these cationc species decompose even under mild conditions via pathways
that are not completely understood; leading to the formation of palladium black [6]. Brookhart
and co-workers have suggested that increasing the steric bulk of the α-diimine ligand in the (α-
diimine)acylpalladium cationic species could enhance their stability. This had led to several
modifications of the α-diimine ligand, especially the aniline part of the ligand and such
modifications have also improved the catalytic activity of (α-diimine)palladium complexes as
ethylene polymerization catalysts significantly [7].
Despite the attributes of (α-diimine)acylpalladium cationic species narrated above, there
are instances where these cationic species decompose even under mild conditions via pathways
that are not completely understood; leading to the formation of palladium black [6]. Brookhart
and co-workers have suggested that increasing the steric bulk of the α-diimine ligand in the (α-
diimine)acylpalladium cationic species could enhance their stability. This has led to several
modifications of the α-diimine ligand, especially the aniline part of the ligand and resulting also
in improved catalytic activity of (α-diimine)palladium complexes as ethylene polymerization
catalysts significantly [7].
Following the success of α-diimine ligands in producing good and relatively stable
palladium ethylene oligomerisation and polymerization catalysts, other bidentate nitrogen-donor
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palladium catalysts with ligands, such as 1,4-diazabutadiene, 2,2’-dipyridyl and 1,10-
phenanthroline, have been investigated as catalysts for ethylene reactions [8]. Similar to (α-
diimine)palladium catalysts, catalytic activity of these nitrogen-donor palladium complexes are
influenced by the electronic property and steric bulk of the nitrogen-donor ligands. So a good
balance between these two factors is crucial in producing an active and stable catalyst.
We have used ferrocenyl units to provide steric bulk in a mix of pyridine and pyrazole or
amine and pyrazole to prepare a series of (ferrocenylpyrazolylmethylenepyridine)palladium or
(ferrocenylpyrazolylethylamine)palladium chlorormethyl complexes and attempted to use these
palladium complexes to produce (pyrazolyl)acylpalladium cation species (complex A, Figure 1)
similar to the cationic species reported by Brookhart and co-workers (Figure 1). Although we
were able to prepare acylpalladium cations with our ligands, these acylpalladium complexes
were not very stable. In this report we provide some valuable insights into the decomposition that
these acylpalladium cations undergo.
Results and discussions
Syntheses and characterisation of palladium complexes 1-14
The syntheses of compounds L1-L6 were performed as reported in the literature [9-11].
The reaction of L1 and L2 with [PdClMe(cod)] were carried out in a 2:1 ratio; whilst the
reactions of L3-L6 were in a 1:1 ratio to produce complexes 1-6 (Scheme 1). All the palladium
complexes were isolated as air stable orange (1 and 2) or yellow (3-6) solids. On reacting 1-6
with Na[BAr4] in the presence of acetonitrile in a 1:1 mole ratio, complexes 7-12 could be
isolated as foamy or crispy orange solids (Scheme 2). However, on reacting 3 or 4 with
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Na[BAr4] and a slight excess of methylacrylate, intended to produce the acylpalladium cationic
compound
methylenepyridine)palladium][BAr4]
methylenepyridine)palladium][BAr4] (14) salts in Scheme 3.
A
in Figure 1, we instead isolated the [bis(3-ferrocenylpyrazolyl-
(13) and [bis(3-ferrocenyl-5-methyl-pyrazolyl-
All new palladium complexes (1-14) were characterized by NMR and IR spectroscopy,
mass spectrometry and elemental analyses; and in selected cases by single crystal X-ray
1
crystallography. The H NMR spectra of 1-6 showed characteristics of their corresponding
1
ligands but with downfield shifts. Whereas the H NMR spectra of complexes 3-6 showed the
presence of two structural isomers for each of these compounds, the 1H NMR spectra of 1 and 2
1
did not show features that would indicate the presence of isomers (Figure S1). For example H
NMR spectrum of complex 4 (Figure S2) shows peaks for the isomer as four set of peaks in the
7.00-9.30 ppm region for the four pyridinyl protons. In addition the at 6.21 ppm is assigned to
the pyrazolyl proton, the peaks at 4.40 ppm and 4.37 ppm are the protons on the substituted
cyclopentadienyl ring of the ferrocenyl group and the peak at 4.04 ppm is assigned to the
unsubstituted cyclopentadienyl of the ferrocenyl group. Lastly, methyl protons on the pyrazolyl
unit and the methyl group bonded to the palladium appear in the spectrum at 2.52 ppm and 0.61
ppm respectively. These peaks indicate the presence of a major product while lower intensity
peaks in the spectrum are indicative of the presence of a minor product.
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Me
Pd
H
Fc
N
R
N
N
Fc
N
H
Fc
Cl
N
N
H
H
N
N
1
N
H
H
Pd
N
Pd
Cl
Me
Fc
Cl
Me
R
L1
L5b
L6b
R = H (5a)
R = Me (6a)
L5a
R = H (5b)
R = Me (6b)
L6a
[PdClMe(cod)]
Fc
R
L3b
L3a
L4b
N
L4a
N
N
L2
N
N
N
Pd
Pd
Cl
Me
R
Cl
Me
Fc
R = H (3b)
R = Me (4b)
Me
H
R = H (3a)
R = Me (4a)
Fc
N
N
Pd
N
N
Fc
H
Cl
2
Scheme 1: Synthesis of (ferrocenylpyrazolyl)palladium chloromethyl complexes
6

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Scheme 2: Synthesis of cationic (ferrocenylpyrazolyl)palladium complexes
7

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2
O
R
2[BAr4]ꢀ
N
N
R
O
methyl acrylate
N
Pd
N
N
Fc
Pd
2
Na[BAr4]
Fc
N
N
N
Pd
Cl
Me
Fc
N
R = H (3)
R = Me (4)
R
R = H (13)
R = Me (14)
Fc = Ferrocenyl
Na[BAr4] = Sodium tetrakis(3,5 trifluoromethylphenyl)borate
Scheme 3: Synthesis of [bis(pyrazolyl)palladium][BAr4] complexes
8

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Figure 1: Acylpalladium chelate compounds
Further evidence of the presence of isomers of 4 could be found in the low temperature
o
1H NMR spectrum of 4 (Figure S2) at -50 C where the linker protons are observed. However,
these protons were not seen when the spectrum was run at room temperature. We have recently
observed linker protons in a low temperature spectrum for [{2,(3,5-ditert-butylpyrazol-1-
yl)ethyl}pyridine-2ylmethyleneiminemethylpalldium][BAr4] [12]. The spectrum of 4 has two
sets of doublets at 5.18 and 6.05 ppm and 5.42 and 5.90 ppm, for the two sets of CH2 linkers in
each isomer. We label these two isomers as 4a and 4b; and based on the electron-donor ability of
the ferrocenyl moiety in the ligand, assign the more abundant isomer as 4a. This is the isomer
that crystallised and whose solid state structure was determined by crystallography (Figure 2).
We recently reported the synthesis and characterisation of these ligands, including the crystal
structures of L3 and L4 [9,10] that support our assignment of 4 exhibiting structural isomers
with 4a as the major isomer. Indeed the structure of 4a in this report was found to be that
9

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proposed in Scheme 1. Furthermore, both isomers would have the chloro ligand bonded to the
palladium trans to the pyridyl nitrogen as observed in a report on the structure of
[(pyrazolylpyridyl)chloromethylpalladium], [13] where the chloro group is trans to the pyridyl
nitrogen. It is worth noting that two other isomers for complexes 3-12 are possible; namely the
geometrical isomer where the chloro ligand for 3-6 or the NCMe ligand for 7-12 bonded to
palladium is either trans to the pyridinyl nitrogen or trans to the pyrazolyl nitrogen. We do not
see evidence of such isomers from the NMR spectra of these complexes. We similarly used the
1H NMR spectra of the BAr4 salts 7-12 to establish that they also have structural isomers. The 1H
NMR spectrum of 9 (Figure S3) illustrates this; and based on the above assignments for 4
identify them as structural isomers 9a and 9b and conclude that the other BAr4 salts would exist
as two structural isomers. To further establish that there were no cis- and trans- geometrical
isomers present in these compounds, we performed NOE experiments on compounds 3, 4 and 6.
The NOE spectra of the compounds (Figure S4-S6) show that when the protons of the Pd-Me
units in the compounds were irradiated the spectra remain unchanged. This confirmed that the
isomers present in these compounds are not cis- and trans- geometrical isomers but are structural
isomers associated with the ligands.
The IR spectra of all the complexes showed higher amine stretching frequencies than the
amine in the free ligands. For example the IR spectrum of 5 has
(N-H) in L5 has a peak at 3340 cm-1. The mass spectral data for 1-6 showed the
υ
(N-H) peak at 3420 cm-1
whereas the
υ
respective molecular ions as expected (e.g. Figure S7). But where mass spectrometry was most
useful was in the characterisation of the BAr4 salts. Positive ion ESI mass spectrum was used to
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identify all the cations (e.g. Figure S8 for complex 10) and negative ion ESI mass spectrum (e.g.
Figure S9) was similarly used to identify the anion [BAr4]-.
Elemental analyses of all the complexes (1-12) the expected molecular formulae, thus
confirming their purity; and in the case of 4a its structure was confirmed by single crystal X-ray
diffraction.
Attempts to synthesise [acylpalladium][BAr4] salts
In attempts to synthesise [(ferrocenylpyrazolylmethylenepyridine)acylpalladium][BAr4]
salts (i.e complex A in Figure 1), similar to the very active Brookhart ethylene polymerisation
catalysts [(α-diimine)-acylpalladium][BAr4] in Figure 1, we reacted complexes 1-6 with
methylacrylate and Na[BAr4]. To our surprise we isolated [bis(pyrazolyl)palladium][BAr4] salts
associated with the neutral compounds 1-6. Two examples of these salts are 13 and 14 whose
structures were confirmed by single crystal X-ray crystallography (Figures 3 and 4). We also
identified two by-products of these reactions, namely methylbut-3-enoate and methylbutyrate.
1
Complexes 13 and 14 were initially characterised by a combination of H NMR spectroscopy,
and mass spectrometry; while the two by-products were characterised by GC and GC-MS
(Figures S10-S12). For example, a typical GC of a crude product from the metyl acrylate
reaction showed two peaks with retention times at 18 min and 20 min (Figure S10). The MS data
associated with these peaks showed molecular ions at m/z = 100 (Figure S11) and 102 (Figure
S12) respectively, and the compounds were identified as methyl but-3-enoate and methyl
butyrate respectively. We rationalise how the [bis(pyrazolyl)palladium][BAr4] salts and the two
esters were formed in Scheme 4. The reaction starts with the formation of the expected
[(pyrazolyl)acylpalladium][BAr4] salts, similar to the [(α-diimine)acylpalladium][BAr4] salts
11

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recently reported by Wu and co-workers [14]; thereafter the [(pyrazolyl)acylpalladium][BAr4]
salts decompose to a palladium hydride species and finally to either 13 or 14 depending on the
ligand used.
Molecular structures of 4a, 13 and 14
Single crystals of 4a suitable for X-ray analysis were obtained by slow evaporation of a
o
dichloromethane solution of 4a, while crystals of 13 and 14 were obtained at -4 C from
saturated dichloromethane solutions of these compounds. Crystallographic data for all three
compounds are in Table 1, whilst their molecular geometries are shown in Figures 2-4; with
selected bond lengths and angles listed in the captions of figures for each structure. The
molecular structure of 4a has a distorted square planar geometry with bond angles around the
palladium between 84.19(16)o and 95.84(14)o. Notably the chloro and methyl ligands on the
palladium show compositional disorder that have 50% occupancy at each position; it therefore
difficult to say with any certainty whether the methyl group is trans to a pyridinyl nitrogen or
not. The ferrocenylcyclopentadienyl rings are in an eclipsed conformation, similar to the
molecular structure of its ligand [9] and has a dihedral angle of 0.759o. The Pd-Cl bond length in
4a is 2.279 Å and is longer than the average Pd-Cl bond length of 2.516 Å calculated for 1 776
compounds containing Pd-Cl bonds, but the Pd-C bond length in 4a of 2.081 Å is similar to the
average bond length of 2.055 Å calculated for 351 similar complexes reported in the Cambridge
structural database [15]. The Pd-Npz (2.115 Å) and Pd-Npy (2.081 Å) bond lengths are similar to
other Pd-N bond lengths of 2.195 Å and 2.054 Å respectively, reported in the Cambridge
structural database [15].
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R
R
O
[BAr4]ꢀ
Na[BAr4]
N
N
N
N
2
NaCl
N
O
N
O
Pd
Pd
Cl
Fc
Me
Fc
methyl acrylate
H
Me
R = H (3)
R = Me (4)
O
H
2
R
2[BAr4]ꢀ
N
R
N
N
[BAr4]ꢀ
O
N
N
2
Fc
Pd
+
Pd(0)
2
Fc
N
O
Pd
N
N
N
Fc
H
R
O
+
+
O
O
O
R = H (13) and R = Me (14)
Scheme 4: Rationalisation for the formation of complexes 13 and 14 and ester by-products
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The molecular structures of 13 and 14 have cations that show distorted square planar
geometries about the palladium with angles between 86.48(18)o and 93.52(18)o. Both molecular
structures consist of cationic palladium species and two [BAr4]- counter ions. In these salts the
ferrocenylcyclopentadienyl rings show a staggered conformation, different from their
corresponding ligands which are eclipsed [9]. The pyridinyl unit and one cyclopentadienyl ring
in 13 or 14 have π-π stacking (Figures S13 and S14 respectively). The Pd-Npz and Pd-Npy bond
length for 13 is 1.992(5) Å and 2.037(4) Å while 14 is 2.001(5) Å and 2.035(4) Å respectively.
Interestingly only the a isomers of 13 and 14 crystallised although the ligands used in preparing
13 and 14 were a mixture of isomers a and b. This seems to suggest that in each case a is the
more stable isomer.
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Table 1: Crystal data and structure refinement for complexes 4a, 13 and 14
4a
13
C51H29BF24FeN3Pd0.5
1259.63
14
C56H32BF21FeN3Pd0.5
1212.40
Empirical formula
Formula weight
Temperature/ K
Wavelength/Å
Crystal system
Space group
C20.87H21.63Cl1.12FeN3Pd
516.58
100(2)
100(2)
100(2)
0.71073
1.54178
0.71073
Monoclinic
P21 /c
Triclinic
P-1
triclinic
P-1
a/ Å
b/ Å
15.286(2)
8.7381(12)
13.3530(11)
13.7363(12)
13.0582(16)
14.0879(17)
c/ Å
a/o
14.808(2)
14.4942(12)
86.401(4)
83.876(5)
70.096(4)
2484.5(4)
2
15.0938(19)
90
68.205(4)
β/o
101.786(4)
82.925(4)
γ/o
90
74.290(4)
3
)
1936.3(5)
2481.1(5)
Volume (Å
Z
4
2
3
)
1.772
1.684
1.623
Density (Mg/m
R indices (all data)
R1 = 0.1055, wR2 = 0.0953
R1 = 0.2404, wR2 = 0.2520
R1 = 0.0942, wR2 = 0.1858
R1 = 0.0639, wR2 = 0.1734
R1 = 0.0561, wR2 = 0.1660
Final R indices [I>2sigma(I)] R1 = 0.0495, wR2 = 0.0816
15

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Figure 2: Molecular structure of 4a, drawn with 50% probability ellipsoids. Selected
bond lengths [Å] and bond angles [o]: Pd1-N1, 2.115(4); Pd1-N3, 2.081; Pd1-Cl2, 2.279(4); Pd1-
Cl1, 2.255(3); Pd1-C1A, 2.02(3); Pd1-C2A, 1.964(19); N1-N2, 1.371(5); Cl1-Pd1-Cl2,
84.19(16); N1-Pd1-Cl1, 95.84(14); N1-Pd1-Cl2, 177.51(17); N3-Pd1-Cl1, 175.43(16); N3-Pd1-
N1, 84.73(15); N3-Pd1-Cl2, 95.05(17); C1A-Pd1- N1, 88.1(8); C1A-Pd1-N3, 170.2(8); C2A-
Pd1-N1, 173.7(7);C2A-Pd1-N3, 89.0(7); C2A-Pd1-C1A, 98.3(11).
16

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Figure 3: Molecular structure of 13, drawn with 50% probability ellipsoids. The two
counter ions [BAr4]- are omitted for clarity. Selected bond lengths [Å] and bond angles [o]: Pd1-
N2, 1.992(5); Pd1-N3, 2.037(4); N1-N2, 1.349(7); N1-C14, 1.459(7); N2(#1)-Pd1-N2, 180;
N2(#1)-Pd1-N3, 93.52(18); N2-Pd1-N3, 86.48(18); N3(#1)-Pd1-N3, 180.00(10); C19-C14-N1,
110.9(4).
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Figure 4: Molecular structure of 14, drawn with 50% probability ellipsoids. The two
counter ions [BAr4]- are removed for clarity. Selected bond lengths [Å] and bond angles [o]:
Pd1-N2, 2.001(5); Pd1-N3, 2.035(4); N1-N2, 1.385(7); N1-C14, 1.451(7); N2(#1)-Pd1-N2, 180;
N2(#1-Pd1-N3, 93.060(18); N2)-Pd1-N3, 86.940(18); N3(#1)-Pd1-N3, 180.00(10); C16-C14-
N1, 110.810(4).
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Attempts to copolymerise ethylene and carbon monoxide copolymerisation reactions
All the palladium complexes 1-6 and their [BAr4] salts, 7-12, were investigated for their
potential to catalyse carbon monoxide and ethylene copolymerisation reaction. First, we
attempted to generate catalysts in situ by reacting complexes 1-6 and Na[BAr4] in a mixture of
CH2Cl2 and NCMe in a reactor that was charged with both gases. The second attempts involved
using preformed cationic species, 7-12, under the same conditions used for complexes 1-6 to
catalyse the carbon monoxide and ethylene copolymerisation reaction. All the palladium
complexes produced small amounts of polyketones and palladium black, so the polyketones were
contaminated with palladium black and it took several purification steps to obtain clean off white
polymers. The best activities were observed with complexes 3, 4, 9 and 10 and even with these
complexes activities were typically about 1.00 g.mmol-1Pd.h-1 at 30 bar of carbon monoxide, 10
o
bar of ethylene for 1 h and at 30 C. However, reactions run for more than 1 h showed no
increase in polymer yield; indicating that after 1 h the catalysts had deactivated.
We the deactivation of the active species in the polymerisation reactions to the instability
of the [(pyrazolyl)palladium(OCMe)]+ species that should react with ethylene during the
polymerisation reaction. So we run an NMR tube reaction of 11 and carbon monoxide and
monitored the reaction by 1H NMR spectroscopy (Figure S15). Within 30 min we observed the
insertion of carbon monoxide into the Pd-Me bond leading to a palladium-acyl species.
However, after leaving the solution for 24 h much of the palladium-acyl signal was lost and with
a week found single crystals that were confirmed to be 13 (Table S1, Figure S13). We believe
the general instability of palladium-acyl species formed by these palladium complexes explains
the formation of all the [bis(pyrazolyl)palladium][BAr4] salts; thereby accounting for the poor
19

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activity of these palladium compounds as carbon monoxide and ethylene copolymerisation
catalysts.
The polyketones produced were characterised by 1H NMR and IR spectroscopy. The 1H
NMR spectrum (Figure S16) of these polymers which showed a single peak at 2.68 ppm,
assigned to the methylene protons in the polyketone backbone. The IR spectrum in Figure S17 is
a typical spectrum of the polyketone and showed the incorporation of the carbon monoxide in the
polymer as a sharp C=O stretching frequency at 1691 cm-1. These spectral data indicate that the
polyketone produced are perfectly alternating copolymer.
Conclusion
It is clear that all six neutral palladium complexes 1-6 can react with methyl
acrylate and Na[BAr4] to form [(pyrazolyl)palladium][BAr4] salts. However, the solution
stability of these salts are low and readily decompose to [bis(pyrazolyl)palladium][BAr4] salts.
The low activity of these neutral and palladium salts for carbon monoxide and ethylene
copolymerisation can be attributed to deactivation processes that lead to the formation of
[bis(pyrazolyl)palladium][BAr4]. This suggests that in order to use complexes 1-6 as catalysts for
this and other olefin reactions, sterically more bulky ligands are needed to stop the formation of
[bis(pyrazolyl)palladium][BAr4] species.
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Experimental section
Materials and instruments
Syntheses of all complexes were performed under nitrogen atmosphere using standard
Schlenk techniques. Diethyl ether was dried over Na, with benzophenone as indicator, while
acetonitrile was dried over CaH2. Sodium tetrakis(3,5-trifluoromethylphenyl)borate, Na[BAr4],
(Ar = 3,5-(CF3)2C6H3) was purchased from Alfa Aesar, while methyl acrylate (MA) was
purchased from Sigma Aldrich; both were used as received. Compounds [PdClMe(cod)] [16],
was synthesised according to literature procedures. Compounds L1-L6 were synthesised as
reported in literature [9-11].
Infrared (IR) spectra of complexes were recorded on a Bruker Tensor 27 equipped with a
diamond ATR. Elemental analyses were performed on a Vario elementar III microcube CHNS
analyzer at Rhodes University. The mass spectrometry unit at the University of Stellenbosch
performed the ESI-MS spectra on a Waters API Qualtro micro spectrophotometer. NMR spectra
were recorded on a Bruker 400 MHz instrument (1H at 400 MHz and 13C{1H} at 100 MHz). The
chemical shifts are reported in δ (ppm) and referenced to the residual proton and carbon signals
7.24 ppm and 77.0 ppm respectively of CDCl3 NMR solvent.
Synthesis of palladium complexes
Synthesis of {bis(3-ferrocenyl-1H-pyrazolyl}methylpalladium(II) chloride (1)
A diethyl ether solution (20 mL) of L1 (0.26 g, 1.02 mmol) was added to a suspension of
[PdClMe(cod)] (0.14 g, 0.51 mmol) in diethyl ether (10 mL) while stirring. The resulting
suspension was stirred for 12 h at room temperature. After the reaction time, a light orange
21

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precipitate formed and this product was isolated by filtration and the solid product washed three
1
times with 20 mL diethyl ether and dried in air. Yield = 82% (0.28 g). H NMR (CDCl3, 400
MHz,): δ 1.30 (s, 1H, Pd-CH3); 4.10 (s, 5H, η5-C5H5); 4.33 (s, 2H, η5-C5H4); 4.58 (s, 2H, η5-
C5H4); 6.27 (s, 1H, pz); 7.46 (s, 1H, pz); 12.22 (s, 1H, N-H). 13C{1H} NMR (CDCl3) δ:1.1; 66.8;
69.4; 69.9; 72.0; 103.1; 139.3; 143.7. IR (Diamond ATR, cm-1): 3320
υ(N-H) amine stretching
vibration. High resolution ESI-MS+ (m/z) (%) = 660.6734 (50%) [M+1]+. Anal. Calcd for
C27H27ClFe2N4Pd: C, 49.05; H, 4.12; N, 8.47%. Found: C, 49.23; H, 4.41; N, 8.51%.
Complexes 2-6 were prepared using the procedure described for 1 and with the appropriate
reagents.
Synthesis of {bis(3-ferrocenyl-5-methylpyrazolyl}methylpalladium(II) chloride (2)
Compound L2 (0.23 g, 0.90 mmol) was reacted with [PdClMe(cod)] (0.12 g, 0.45 mmol)
to give an orange solid. Yield = 90% (0.28 g). 1H NMR (CDCl3, 400 MHz,): δ: 1.36 (s, 1H, Pd-
CH3); 2.46 (s, 3H, CH3); 4.04 (s, 5H, η5-C5H5); 4.21 (s, 2H, η5-C5H4); 4.69 (s, 2H, η5-C5H4);
6.02 (s, 1H, pz); 13.39 (s, 1H, N-H). 13C{1H} NMR (CDCl3) δ: 1.1; 12.3; 66.8; 69.9; 70.0; 72.1;
103.8; 139.9; 145.1. IR (Diamond ATR, cm-1): 3341
υ(N-H) amine stretching vibration. High
resolution ESI-MS+ (m/z) (%) = 688.3451 (50%) [M+1]+. Anal. Calcd for C29H31ClFe2N4Pd: C,
50.54; H, 4.53; N, 8.13%. Found: C, 50.83; H, 4.94; N, 8.42%.
Synthesis of {3-ferrocenylpyrazolyl-methylenepyridine}methylpalladium(II) chloride (3a and
3b)
A mixture of L3a and L3b (0.12 g, 0.35 mmol) was reacted with [PdClMe(cod)] (0.09 g,
0.35 mmol) to afford a yellow solid. Yield = 75% (0.13 g). 1H NMR (CDCl3) δ: 0.61 (s, 3H, Pd-
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CH3); 1.06 (s, 3H, Pd-CH3)iso; 3.98 (s, 5H, η5-C5H5); 4.03 (s, 5H, η5-C5H5)iso; 4.19 (s, 2H, η5-
C5H4); 4.29 (s, 2H, η5-C5H4); 5.52 (s, 2H, CH2); 5.72 (s, 2H, CH2)iso; 6.22 (s, 1H, pz-H); 6.42 (s,
1H, pz-H)iso; 7.43 (t, 1H, JHH = 8.0 Hz, py); 7.54 (d, 1H, JHH = 10.0 Hz, py)iso; 7.60 (s,1H, py);
7.80 (t, 1H, JHH = 7.6 Hz, py); 8.62 (t, 1H, JHH = 5.2 Hz, py)iso; 9.01 (d, 1H, JHH = 4.4 Hz, py)iso;
9.17 (d, 1H, JHH = 4.8 Hz, py); 9.22 (d, 1H, JHH = 4.8 Hz, py)iso. 13C{1H} NMR (CDCl3) δ: -5.4;
9.6; 56.8; 58.1; 68.9; 69.5; 69.9; 105.5; 107.1; 123.5; 125.0; 132.0; 138.4; 191.0; 151.4; 151.5;
153.9; 154.7. IR (Diamond ATR, cm-1): 1615 υ(C=N). High resolution ESI-MS+ (m/z) (%) =
499.0390 (45%) [M+1]+. Anal. Calcd for C20H20ClFeN3Pd: C, 48.03; H, 4.03; N, 8.40%. Found:
C, 47.80; H, 4.10; N, 8.02%.
Synthesis of {3-ferrocenyl-5-methylpyrazolyl-methylenepyridine}methylpalladium(II) chloride
(4a and 4b)
A mixture of L4a and L4b (0.15 g, 0.42 mmol) was added to [PdClMe(cod)] (0.11 g,
1
0.42 mmol) to give a yellow solid. Yield = 72% (0.15 g). H NMR (CDCl3) δ: 0.81 (s, 3H, Pd-
CH3); 0.90 (s, 3H, Pd-CH3)iso; 2.34 (s, 3H, CH3); 2.42 (s, 3H, CH3)iso; 3.98 (s, 5H, η5-C5H5); 4.04
(s, 5H, η5-C5H5)iso; 4.19 (s, 2H, η5-C5H4); 4.23 (s, 2H, η5-C5H4)iso; 4.28 (s, 2H, η5-C5H4); 4.31 (s,
2H, η5-C5H4)iso; 6.01 (s, 2H, CH2); 6.21 (s, 2H, CH2)iso; 6.13 (s, 1H, pz-H); 6.17 (s, 1H, pz-H)iso;
7.37 (d, 1H, JHH = 7.6 Hz, py); 7.42 (t, 1H, JHH = 7.2 Hz, py); 7.80 (t, 1H, JHH = 6.0 Hz, py); 7.84
(t, 1H, JHH = 6.0 Hz, py)iso; 8.90 (d, 1H, JHH = 6.4 Hz, py)iso; 8.95 (d, 1H, JHH = 5.2 Hz, py)iso;
9.00 (d, 1H, JHH = 4.8 Hz, py). 13C{1H} NMR (CDCl3) δ: -4.5; 9.2; 12.3; 56.5; 58.6; 69.0; 69.8;
70.2; 106.0; 107.6; 124.0; 125.8; 132.5; 138.9; 152.2; 152.0; 154.9; 155.0; 192.0. IR (Diamond
ATR, cm-1): 1608 υ(C=N). High resolution ESI-MS+ (m/z) (%) = 512.1440 (65%) [M+1]+. Anal.
Calcd for C21H22ClFeN3Pd: C, 49.06; H, 4.31; N, 8.17%. Found: C, 48.92, H, 4.38; N, 7.99%.
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Synthesis of {3-ferrocenylpyrazolyl-ethylamine}methylpalladium(II) chloride (5a and 5b)
A mixture of L5a and L5b (0.10 g, 0.35 mmol) was added to [PdClMe(cod)] (0.09 g,
0.35 mmol) to give a yellow solid. Yield = 90% (0.14 g).1H NMR (CDCl3) δ: 0.71 (s, 3H, Pd-
CH3); : 0.75 (s, 3H, Pd-CH3)iso; 3.04 (m, 2H, JHH = 6.0 Hz, CH2); 4.01 (s, 5H, η5-C5H4); 4.11 (t,
2H, JHH = 6.0 Hz, CH2); 4.21 (s, 5H, η5-C5H5)iso; 4.27 (s, 2H, η5-C5H4); 4.25 (t, 2H, JHH = 6.0
Hz, CH2)iso; 4.34 (s, 2H, η5-C5H4)iso; 4.47 (s, 2H, η5-C5H4)iso; 4.68 (s, 2H, η5-C5H4); 6.28 (s, 1H,
pz-H); 6.38 (s, 1H, pz-H)iso; 7.38 (s, 1H, pz-H); 7.44 (s, pz-H)iso. 13C{1H} NMR (CDCl3) δ: 1.1;
1.3; 42.1; 42.5; 51.2; 52.5; 66.1; 68.5; 68.5; 70.1; 70.3; 103.6; 105.7; 140.7; 141.8; 146.0; 149.5.
IR (Diamond ATR, cm-1): 3420
υ(N-H) amine stretching vibration, 1650 υ(N-H) amine bending
vibration. High resolution ESI-MS+ (m/z) (%) = 453.1276 (50%) [M+1]+. Anal Calcd for
C16H20ClFeN3Pd: C, 42.51; H, 4.46; N, 9.30%. Found: C, 42.92; H, 4.53; N, 9.41%.
Synthesis of {3-ferrocenyl-5-methylpyrazolyl-ethylamine}methylpalladium(II) chloride (6a and
6b)
A mixture of L6a and L6b (0.12 g, 0.40 mmol) was added to [PdClMe(cod)] (0.11 g,
1
0.40 mmol) to give a yellow solid. Yield = 87% (0.16 g). H NMR (CDCl3) δ: 0.68 (s, 3H, Pd-
CH3); 0.72 (s, 3H, Pd-CH3)iso; 2.30 (s, 3H, CH3); 2.38 (s, 3H, CH3)iso; 3.13 (m, 4H, JHH = 6.0 Hz,
CH2); 4.05 (s, 5H, η5 C5H5); 4.10 (s, 5H, η5 C5H5)iso; 4.25 (s, 2H, η5 C5H4); 4.30 (s, 2H, η5
C5H4)iso; 4.51 (s, 2H, η5 C5H4)iso; 4.57 (s, 2H, η5 C5H4); 6.02 (s, 1H, pz-H); 6.12 (s, 1H, pz-H)iso.
13C{1H} NMR (CDCl3) δ: 1.2; 1.5; 11.9; 13.5; 42.0; 42.2; 51.4; 52.0; 66.4; 68.2; 68.7; 69.3;
69.6; 103.1; 105.1; 139.0; 141.5; 147.6; 150.0. IR (Diamond ATR, cm-1): 3447
(N-H) amine bending vibration. High resolution ESI-MS+ (m/z) (%)
υ(N-H) amine
stretching vibration, 1661
υ
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= 467.0947 (50%) [M+1]+. Anal. Calcd for C17H22ClFeN3Pd: C, 43.81; H, 4.76; N, 9.02%.
Found: C, 44.01; H, 4.56; N, 9.31%.
Synthesis of {bis(3-ferrocenyl-1H-pyrazolyl}methylpalladium(II) tetrakis(3,5-trifluoromethyl-
phenyl)borate (7)
A CH2Cl2 solution (20 mL) of complex 1 (0.20 g, 0.30 mmol) was added to an
acetonitrile solution (10 mL) of Na[BAr4] (0.27 g, 0.30 mmol). The resulting mixture was stirred
o
at 25 C for 2 h to afford a light orange mixture, which was filtered through a filter membrane
and the filtrate evaporated in vacuo to give an oily material. The oily material was dried under
high vacuum overnight, after which orange crispy solid formed. Yield = 87% (0.39 g). 1H NMR
(CDCl3, 400 MHz,) δ: 1.67 (s, 3H, Pd-CH3); 1.91 (s, 3H, NCCH3); 4.06 (s, 5H, η5-C5H5), 4.37 (s,
2H, η5-C5H4), 4.56 (s, 2H, η5-C5H4), 6.34 (s, 1H, pz); 7.47 (s, 4H, BAr4); 7.66 (s, 8H, BAr4);
13
7.79 (s, 1H, pz) 10.27 (s, 1H, N-H). C{1H} NMR (CDCl3) δ: 1.0; 1.9; 10.8; 11.2; 69.6; 69.9;
70.0; 70.2; 117.5; 123.3; 126.0; 128.9; 133.6; 134.7; 160.9; 161.4; 161.9; 162.4. IR (Diamond
ATR, cm-1): 3326
υ(N-H) amine stretching vibration. High resolution positive ion ESI MS m/z
(%) = 667.67128 (65%) [M+1]. High resolution negative ion ESI-MS (m/z) (%) = 863.0638
(100%) [M]-. Anal. Calcd for C61H42BF24Fe2N5Pd: C, 47.89; H, 2.77; N, 4.58%. Found: C,
48.01; H, 2.87; N, 4.42%.
Complexes 8-12 were prepared using the procedure described for 7 and the appropriate reagents.
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Synthesis of {bis(3-ferrocenyl-5-methylpyrazolyl}methylpalladium(II) tetrakis(3,5-trifluoro-
methylphenyl)borate (8)
Complex 2 (0.17 g, 0.24 mmol) was added to acetonitrile solution (10 mL) of Na[BAr4]
(0.21 g, 0.24 mmol) to give a crispy orange solid. Yield = 90% (0.34 g). 1H NMR (CDCl3, 400
MHz,) δ: 1.71 (s, 3H, Pd-CH3); 1.95 (s, 3H, NCCH3); 2.62 (s, 3H, CH3) 4.04 (s, 5H, η5-C5H5),
4.38 (s, 2H, η5-C5H4), 4.62 (s, 2H, η5-C5H4), 6.23 (s, 1H, pz); 7.48 (s, 4H, BAr4); 7.68 (s, 8H,
BAr4); 13.23 (s, 1H, N-H). 13C{1H} NMR (CDCl3) δ: 1.04; 1.97; 8.91; 10.34; 13.78; 15.56;
68.23; 69.56; 69.98; 71.45; 71.67; 116.56; 116.97; 124.56; 126.74; 129.12; 133.89; 135.01;
160.94; 161.43; 161.93; 162.42. IR (Diamond ATR, cm-1): 3351
υ(N-H) amine stretching
vibration. High resolution positive ion ESI MS m/z: (100%) = 695.8175 (65%) [M+1]. High
resolution negative ion ESI-MS (m/z) (%) = 863.0638 (100%) [M]-. Anal. Calcd for
C63H46BF24Fe2N5Pd: C, 48.57; H, 2.98; N, 4.50%. Found: C, 48.80; H, 3.21; N, 4.61%.
Synthesis of {3-ferrocenylpyrazolyl-methylenepyridine}methylpalladium(II) tetrakis(3,5-tri-
fluoromethylphenyl)borate (9a and 9b)
Complex 3 (0.12 g, 0.25 mmol) was added to acetonitrile solution of Na[BAr4] (0.22 g,
0.25 mmol) to afford a foamy light orange solid. Yield = 97% (0.33 g). 1H NMR (CDCl3) δ: 0.67
(s, 3H, Pd-CH3); 0.89 (s, 3H, Pd-CH3)iso; 1.79 (s, 3H, NCCH3); 1.81 (s, 3H, NCCH3)iso; 3.93 (s,
5H, η5-C5H5); 4.05 (s, 5H, η5-C5H5)iso; 4.21 (s, 2H, η5-C5H4); 4.26 (s, 2H, η5-C5H4)iso; 4.34 (s,
2H, η5-C5H4); 4.37 (s, 2H, η5-C5H4); 6.42 (s, 1H,pz-H); 6.51 (s, 1H, pz-H)iso; 7.32 (d, 1H, JHH
=
5.2 Hz, py)iso 7.44 (d, 1H, JHH = 5.2 Hz, py); 7.51 (s, 4H, BAr4); 7.68 (s, 8H, BAr4); 7.85 (t, 1H,
JHH = 10.0 Hz, py); 8.24 (d, 1H, JHH = 5.2 Hz, py)iso 8.43 (t, 1H, JHH = 5.2 Hz, py)iso 8.51 (d, 1H,
13
JHH = 5.2 Hz, py). C{1H} NMR (CDCl3) δ: 1.5; 1.8; 10.3; 10.6; 54.2; 56.2; 69.8; 69.9; 70.0;
26

ACCEPTED MANUSCRIPT
70.2; 107.0; 108.0; 117.5;120.4; 121.2; 123.2; 124.9; 125.9; 126.2; 128.6; 129.1; 134.5; 134.8;
140.6; 150.0; 150.4;152.6; 153.4; 161.0; 161.5; 162.2; 162.5. IR (Diamond ATR, cm-1): 1616
υ(C=N). High resolution positive ion ESI-MS (m/z) (%) = 506.0335 (50%) [M+1]+ High
.
resolution negative ion ESI-MS (m/z) (%) = 863.0638 (100%) [M]-. Anal. Calcd for
C54H35BF24FeN4Pd: C, 47.38; H, 2.58; N, 4.09%. Found: C, 47.52; H, 2.81; N, 4.23%.
Synthesis of {3-ferrocenyl-5-methylpyrazolyl-methylenepyridine}methylpalladium(II) tetrakis-
(3,5-trifluoromethylphenyl)borate (10a and 10b)
Complex 4 (0.10 g, 0.19 mmol) was added to acetonitrile solution (10 mL) of Na[BAr4]
1
(0.17 g, 0.19 mmol) to give a crispy orange solid. Yield = 95% (0.25 g). H NMR (CDCl3) δ:
0.65 (s, 3H, Pd-CH3); 0.87 (s, 3H, Pd-CH3)iso; 1.55 (s, 3H, NCCH3); 1.76 (s, 3H, NCCH3)iso; 2.27
(s, 3H, CH3); 2.31 (s, 3H, CH3)iso; 4.02 (s, 5H, η5-C5H4); 4.04 (s, 5H, η5-C5H4); 4.17 (s, 2H, η5-
C5H4); 4.19 (s, 2H, ɳ5-C5H4)iso; 4.28 (s, 2H, η5-C5H4); 6.18 (s, 1H, pz-H); 6.21 (s, 1H, pz-H)iso;
7.43 (d, 1H, JHH = 7.6 Hz, py); 7.49 (s, 4H, BAr4); 7.68 (s, 8H, BAr4); 7.83 (t, 1H, JHH = 7.2 Hz,
13
py); 8.58 (d, 1H, JHH = 4.8 Hz, py). C{1H} NMR (CDCl3) δ: 1.0; 1.8; 2.6; 10.9; 11.2; 52.5;
53.4; 68.6; 68.9; 69.3; 69.7; 69.8; 70.0; 70.0; 106.9; 108.3; 117.5; 120.4; 123.1; 124.8; 125.8;
125.6; 126.2;128.5;128.7; 129.1; 129.4; 134.8; 140.4; 140.6; 141.1; 150.1; 152.7; 152.9; 160.9;
161.4; 161.9; 162.4. IR (Diamond ATR, cm-1): 1609 υ(C=N). High resolution positive ion ESI-
MS (m/z) (%) = 519.0474 (50%) [M]+. High resolution negative ion ESI-MS (m/z) (%) =
863.0638 (100%) [M]-. Anal. Calcd for C55H37BF24FeN4Pd: C, 47.77; H, 2.70; N, 4.05%. Found:
C, 47.91; H, 2.82; N, 4.11%.
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Synthesis of {3-ferrocenylpyrazolyl-ethylamine}methylpalladium(II) tetrakis(3,5-trifluoro-
methylphenyl)borate (11a and 11b)
Complex 5 (0.09 g, 0.21 mmol) was added to acetonitrile solution (10 mL) of Na[BAr4]
1
(0.19 g, 0.21 mmol) to give an orange crispy solid. Yield = 90% (0.25 g). H NMR (CDCl3) δ:
0.75 (s, 3H, Pd-CH3); 0.87 (s, 3H, Pd-CH3)iso; 1.88 (s, 3H, NCCH3); 1.92 (s, 3H, NCCH3)iso; 3.34
(m, 2H, JHH = 5.6 Hz, CH2); 3.98 (s, 5H, η5-C5H4); 4.04 (s, 5H, η5-C5H4)iso; 4.55 (t, 2H, JHH = 5.6
Hz, CH2); 4.57 (s, 2H, η5-C5H4); 4.62 (t, 2H, JHH = 6.0 Hz, CH2); 4.67 (s, 2H, η5-C5H4)iso; 4.87
(s, 2H, η5-C5H4); 4.93 (s, 2H, η5-C5H4)iso; 6.32 (s, 1H, pz-H); 6.37 (s, 1H, pz-H)iso; 7.44 (s, 1H,
13
pz-H); 7.48 (s, 4H, BAr4); 7.52 (s, 1H, pz-H)iso; 7.65 (s, 8H, BAr4). C{1H} NMR (CDCl3) δ:
1.2; 1.3; 9.8; 10.2; 42.6; 42.8; 51.4; 52.7; 66.5; 68.9; 68.7; 70.7; 70.8; 104.0; 106.1; 140.9; 142.1;
146.5; 149.9; 160.9; 161.4; 161.9; 162.4. IR (Diamond ATR, cm-1): 3428
stretching vibration, 1655 (N-H) amine bending vibration. High resolution positive ion ESI-MS
υ(N-H) amine
υ
m/z (100%): 458.5231 (60%) [M+1]. High resolution negative ion ESI-MS (m/z) (%) = 863.0638
(100%) [M]-. Anal. Calcd for C50H35BF24FeN4Pd: C, 45.46; H, 2.67; N, 4.24%. Found: C, 45.61;
H, 2.71; N, 4.43%.
Synthesis of {3-ferrocenyl-5-methylpyrazolyl-ethylamine}methyl-palladium(II) tetrakis(3,5-
trifluoromethylphenyl)borate (12a and 12b)
Complex 6 (0.12 g, 0.26 mmol) was added to acetonitrile solution (10 mL) of Na[BAr4]
1
(0.23 g, 0.26 mmol) to give a crispy orange solid. Yield = 85% (0.29 g). H NMR (CDCl3) δ:
0.68 (s, 3H, Pd-CH3); 0.86 (s, 3H, Pd-CH3)iso; 1.87 (s, 3H, NCCH3); 1.91 (s, 3H, NCCH3)iso; 2.34
(s, 3H, CH3); 2.41 (s, 3H, CH3)iso; 3.17 (m, 4H, JHH = 6.0 Hz, CH2); 4.03 (s, 5H, η5-C5H5); 4.09
(s, 5H, η5-C5H5)iso; 4.25 (s, 2H, η5-C5H4); 4.32 (s, 2H, η5-C5H4)iso; 4.46 (s, 2H, η5-C5H4)iso; 4.61
28