Novel cationic η3-methallyl palladium complexes bearing pyridinyl-imine ligands: Synthesis, characterization and X-ray study

Article abstract of DOI:10.1016/j.jorganchem.2014.09.015

Ligands (pyridin-2-ylmethylene)anilines (L1-L4) and (1-(pyridin-2-yl)ethylidene)anilines (L5-L6) were obtained by condensation reactions. These ligands react with Pd(dba)₂ in the presence of methallyloxytris(dimethylamino)phosphonium hexafluorophosphate [C₄H₇OP(NMe₂)₃]⁺PF₆^- to give the corresponding monometallic cationic η³-methallylpalladium complexes C1-C6 in high yields. All new complexes C1-C6 have been characterized by CHN analyses, ¹H, ¹³C, ³¹P NMR and IR spectroscopy. Solid state and electronic structures of complex C5 have been determined.

Full text of DOI:10.1016/j.jorganchem.2014.09.015

Accepted Manuscript
3
Novel cationic η -methallyl palladium complexes bearing pyridinyl-imine ligands:
synthesis, characterization and X-ray study
Sana Dridi, Ali Mechria, Moncef Msaddek
PII:
S0022-328X(14)00432-X
10.1016/j.jorganchem.2014.09.015
JOM 18719
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 25 July 2014
Revised Date: 7 September 2014
Accepted Date: 9 September 2014
3
Please cite this article as: S. Dridi, A. Mechria, M. Msaddek, Novel cationic η -methallyl palladium
complexes bearing pyridinyl-imine ligands: synthesis, characterization and X-ray study, Journal of
Organometallic Chemistry (2014), doi: 10.1016/j.jorganchem.2014.09.015.
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ACCEPTED MANUSCRIPT
Oxidative addition of the methallyloxytris(dimethylamino) phosphonium
+
-
hexafluorophosphate [C
H
4 7
OP(NMe
2
)
3
] PF
6
to the zerovalent Pd(dba)
2
3
in the presence of
pyridinylimine ligands gives the corresponding monometallic cationic η -methallylpalladium
complexes bearing pyridinylimine ligands in high yields.

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
3
Novel cationic η -methallyl palladium complexes bearing pyridinyl-imine
ligands: synthesis, characterization and X-ray study
a
a,
a
Sana Dridi , Ali Mechria ∗ and Moncef Msaddek
a
Laboratoire de chimie hétérocyclique, produits naturels et réactivité : L.C.H.P.N.R, Faculté des sciences de Monastir, Bd de
l’environnement, 5000 Monastir, Tunisie
Abstract
Ligands (pyridin-2-ylmethylene)anilines (L1-L4) and (1-(pyridin-2-yl)ethylidene)anilines
2
(L5-L6) were obtained by condensation reactions. These ligands react with Pd(dba) in the
presence
of
methallyloxytris(dimethylamino)phosphonium
hexafluorophosphate
+
-
3
[
C
4
H
7
OP(NMe
2
)
3
] PF
6
to give the corresponding monometallic cationic η -
methallylpalladium complexes C1-C6 in high yields. All new complexes C1-C6 have been
1
13
31
characterized by CHN analyses, H, C, P NMR and IR spectroscopy. Solid state and
electronic structures of complex C5 have been determined.
Key words: pyridinyl-imine; methallylpalladium; cationic; oxidative addition; X-ray
structure.
1. Introduction
Late transition metal-catalyzed olefin polymerization has received greater prominence over
the recent years as a result of Brookhart’s report on Pd(II) and Ni(II) diimine catalyst systems,
which were capable of polymerizing ethylene and other α-olefins to form high molecular
weight polymers [1–3]. The key feature of their catalysts is the symmetrical presence of bulky
ortho aryl substituents at the imino nitrogen atoms, which effectively block the axial
coordination sites thus retarding the rate of chain termination. Reduced steric bulk results in a
decrease in polymer molecular weight. For this class of catalysts, Pd(II)-based systems
produce highly branched polymers from ethylene. Subsequent to Brookhart’s initial work on
Ni and Pd, he as well as Gibson discovered that iron and cobalt-based complexes bearing
tridentate bis(imino)pyridine ligands with bulky aryl groups were also capable of converting
olefins to high molecular weight polymers as well as co-polymers [4–8]. Other groups have
also reported on Ni(II) and Pd(II) catalysts bearing asymmetrical bidentate aryl-substituted
pyridylimines [9–11], it was found that only oligomerization of ethylene was possible with
∗
Corresponding author. Tel.: +216-73-500-276; fax: +216-73-500-278; e-mail: ali.mechria@fsm.rnu.tn

ACCEPTED MANUSCRIPT
Ni(II) catalysts while Pd(II) analogues were found to be inactive. Structurally, in group 10
(Ni, Pd, Pt) pyridyl-imine complexes, Ni complexes exist as dimers or two ligand units
coordinated to Ni, achieving a 5-coordinated trigonal–bipyramidal structure [12–15]. In
contrast, Pd and Pt complexes with pyridinyl-imines appear as monomeric square-planar
structures [14–26]. In our knowledge, the reaction of N,N-chelate ligands with
allylpalladium(II) chloride dimer represents the standard synthetic approach to cationic allyl
palladium complexes bearing N,N-chelate ligands [27-29].
As part of our ongoing research in the field of late transition metal complexes containing α-
and β-diimines ligands [30-37], we describe herein the synthesis of a series of new cationic
3
η -methallyl palladium(II) complexes bearing pyridinyl-imine ligands containing a bulky
arylimino substituent on one side of the ligand and a relatively unhindered heterocyclic donor
on the other. The molecular structure of a Pd(II) complex was determined by X-ray
crystallography. A DFT optimized structure has been also discussed.
2. Results and discussion
2.1. Synthesis and characterization
Scheme 1 shows the synthetic route of the ligands and cationic Pd(II) complexes. The
addition of a primary amine to commercially available 2-pyridinecarboxaldehyde or 2-
acetylpyridine to afford the corresponding pyridinyl-imine ligand is a well-known route to a
versatile class of nitrogen bidentate ligands [17–26]. The reaction is an acid catalyzed
condensation which is conducted in alcohols or ethers. Variation of the amine therefore
allows for the facile design of ligands and subsequent metal complexes with different physical
and chemical properties. The new cationic methallyl palladium complexes C1–C6 were
prepared via an oxidative addition of methallyloxyphosphonium salt to the zerovalent
compound Pd(dba)
carried out in CH
methallyl Pd(II) complexes.
2
in the presence of pyridinyl-imine ligands (Scheme 1). The reaction is
2
Cl at room temperature and afford, in quantitative yields, the cationic
2

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Scheme 1. Synthesis of iminopyridine ligands and Pd(II) complexes
These new cationic methallyl complexes of palladium(II) (C1-C6) were isolated as a
yellow to orange solids soluble in dichloromethane but sparingly soluble in diethyl ether and
1
13
31
in n-hexane. H, C, P NMR, IR spectroscopy and elemental analyses were consistent with
the palladium(II) complex formulation. The NMR spectra of complexes C1-C6 show similar
trends especially in the aromatic region. There is a distinct shift of the signals of the aromatic
groups of the imine system including the pyridine ring on complexing of the ligand to the
metal centre. A rearrangement of the aromatic signals as compared to the ligand spectra. In all
cases, there is a shift of the doublet found around 8.50 ppm assigned to H-6 (see Fig. 1) and
the singlet found around 8.25 ppm assigned to H-7 in the ligand spectra. These two signals
shift to around 8.97 and 8.62 ppm, respectively, in the spectrum of the metal complex. Thus,
these two signals also exhibit a greater separation between each other when complexation
takes place.
Furthermore, the two triplets, which occur at 7.18 ppm (H-4) and 7.56 ppm (H-5) in the
ligand spectrum and move significantly downfield to 7.87 and 8.35 ppm during complexation.
1
The H NMR peaks of the Pd(II) complexes were shifted to low field by approximately d 0.1–
1
3
0
.5 ppm as compared with the ligands, while the C NMR peaks of the Pd(II) complexes

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were shifted to low field by approximately 5 ppm as compared with the ligands. The presence
-
31
of the non-coordinated PF
6
counter-ions in complexes C1-C6 was confirmed by the P NMR
spectra. In addition, IR spectra of the complexes showed typical lower absorption bands
-1
between 1620 and 1630 cm compared to the respective ligands [38]. All IR spectra present
-
-1
the characteristic band of the PF
6
counter-ion at around 832 cm .
2.2. Molecular structure of complex C5
Single crystals of complex C5 suitable for X-ray analyses were grown by slow diffusion of
diethyl ether into a dichloromethane solution at room temperature. Crystallographic data and
structural refinement parameters are given in Table 1 while selected bond lengths and angles
are contained in Table 2. Molecular structure of complex C5 is shown in Fig. 1. The single-
crystal X-ray diffraction study of complex C5 reveals a structure consisting of loosely
3
+
-
4 7 6
associated [(η -C H )Pd(L5)] cations and octahedral PF counteranions without direct
interactions as appears from the large distance between the metal and the nearest fluorine
atom (Pd-F5 = 4.171 Å). The geometry around the palladium atom in the complex C5 could
be described as distorted square planar consisting of two carbone atoms (C1 and C3) of the
allyl group and two nitrogen atoms (N1 and N2) of the ligand. For instance, the relatively
small N(1)-Pd(1)-N(2) bond angle in C5 of 78.0(2)° is a result of chelating ligand steric
constraints. The bond angles around the Pd atom which sum to 359.9(11)° are consistent with
a planar geometry. The metal-chelate ring (Pd-N1-C10-C9-N2) in complex C5 is almost flat
as indicated by the torsion angles of -3.4(9)°, 6.1(8)° and -0.9(7)° for N2-C9-C10-N1, Pd-N1-
C10-C9 and Pd-N2-C9-C10, respectively. The methyl on the allyl group is slightly tilted out
of the allyl plane by approximately 15° as indicated by the torsion angle of 165.1(8)° for C4-
C2-C3-C1. The allyl plane makes an angle of 112.2(4)° with the palldium coordinative plane
3
which is normal for η -2-methylallyl complexes of palladium [31-32]. The average Pd–N1
bond length of 2.082(5) Å in C5 compares well with bond lengths of 2.045(2) Å reported for
the unconjugated diimine palladium complexes [39]. The Pd(1)–N(2) bond length of 2.089(6)
Å in C5 is significantly similar to the Pd–N bond length of square planar imine Pd(II)
complexes [40]. The Pd–C bond lengths in C5 was reported as 2.0366(18) Å, and compares
well with the bond lengths of 2.005(12) Å observed in other related palladium complexes [31-
32].
Table 1
Crystal data and structure refinement for complex C5

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Chemical formula
19 23 2 6
C H N PdPF
3
Crystal size (mm )
0.2 x 0.1 x 0.1
530.76
Formula weight
Crystal system
Space group
a (Å)
Triclinic
P-1
7.511(5)
10.346(5)
14.773(5)
89.797(5)
94.519(5)
109.635(5)
1077.5(10)
2
b (Å)
c (Å)
α (°)
Β (°)
γ (°)
3
V (Å )
Z
T (K)
293(2)
-
3
1
3
2
0
5
0
.636
746
ρ
calc (g.cm )
Total reflections
Unique reflections
R(int)
314
.0743
9.92
.71073
2θmax (°)
λ (Å)
-1
0.99
µ (mm )
5
1
0
0
32
F(000)
.001
.0523
.1321
Goodness-of-fit
R
1
(I > 2σ(I))
wR
2
3
+
-
Experimental and theoretical bond distances of [(η -C
4
H
7
)Pd(L5)] PF
6
Bond lengths
Pd-N1
Experimental
2.082(5)
Theoretical
2.111
Pd-N2
2.089(6)
2.143
Pd-C1
2.110(7)
2.120
Pd-C2
2.136(7)
2.155

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Pd-C3
2.111(8)
1.283(8)
1.450(8)
1.354(8)
1.349(8)
2.106
1.279
1.431
1.331
1.350
N1-C10
N1-C12
N2-C5
N2-C9
3
+
-
Table 2: Experimental and theoretical bond angles of [(η -C
4
H
7
)Pd(L5)] PF
6
Bond lengths
N1-Pd-N2
N1-Pd-C1
N2-Pd-C1
N1-Pd-C3
N2-Pd-C3
C1-Pd-C3
N1-Pd-C2
N2-Pd-C2
C1-Pd-C2
C3-Pd-C2
Experimental
78.0(2)
Theoretical
76.88
174.4(3)
107.2(3)
106.0(3)
175.0(3)
68.7(3)
172.56
109.97
104.51
175.01
68.39
137.8(3)
139.0(3)
38.4(3)
136.31
142.22
38.59
38.7(3)
38.69

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Fig. 1. ORTEP representation of the molecular structure of C5 with atom labeling scheme and
anisotropic displacement ellipsoid depicted at 30% probability. Hydrogen atoms are omitted
for clarity.
2.3. Density functional theory (DFT) calculations
To obtain an insight in the electronic structures and bonding properties of the complex,
calculations using the density functional theory (DFT) method with the wB97XD functional
of GAUSSIAN-09 were carried out. Before the calculations, their geometry was optimized in
singlet states using the DFT method with the wB97XD functional.
3
+
4 7
The cation [(η -C H )Pd(L5)] attained a distorted square planar arrangement around
the Pd atom as shown in Fig. 2. Experimental and theoretical geometric parameters are
summarized in Tables 2 and 3. In general, the predicted bond lengths and angles are in very
good agreement with the values based on the X-ray crystal structure data, and the general
trends observed in the experimental data are well reproduced in the calculations as one can
see from the data given in Tables 2 and 3. It can be seen from the data collected in Tables 2

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and 3 the bond lengths are maximally elongated by 0.05 Å in the calculated gas phase
structure, while the bond angles changed maximally by 3°. The formal charge of palladium is
+2 in the complex C5. The calculated charge on the palladium atom, obtained from natural
population analysis, is 0.40. This is may be a result of charge donation from the ligand to the
metal center and also shows the strong σ-donor character of the ligand.
3
+
Fig. 2. DFT optimized structure of [(η -C
4 7
H )Pd(L5)] cation using the same atom labeling
scheme as ORTEP representation. Hydrogen atoms are omitted for clarity.
3. Conclusion
The oxidative
addition
of
methallyloxytris(dimethylamino)phosphonium
hexafluorophosphate to the zerovalent Pd(dba) in the presence of pyridinyl-imine compounds
2
produces new monometallic cationic methallylpalladium(II) complexes in which the ligands
coordinate via the pyridine and imine nitrogen atoms. Solid state structure and theoretical
optimized structure (DFT) both indicate a distorted square planar arrangement around the
palladium center.
4. Experimental
4.1. Materials and methods
All reactions were carried out under dry argon atmosphere using standard Schlenk
techniques. Dichloromethane and hexane were refluxed and distilled from phosphorus
pentoxyde (P ) while diethyl ether was dried over sodium wire and benzophenone. Aniline,
,6-dimethylaniline and 2,6-diisopropylaniline were distilled from potassium hydroxide prior
2
O
5
2

ACCEPTED MANUSCRIPT
to use. Pyridinylimine ligands [18,19], methallyloxyphosphonium hexafluorophosphate [41],
2
Pd(dba) [42] were prepared according to literature methods. NMR spectra were recorded on
a Bruker AMX 300 spectrometer. H and C chemical shifts were given in ppm and referenced
31
to the residual solvent resonance relative to TMS Starting materials. P chemical shifts are
given in ppm relative to an 85% H PO external reference. IR spectra were recorded on a
3
4
Perkin–Elmer Spectrum two FT-IR instrument with the Universal ATR Sampling Accessory.
Elemental analyses were performed on a Perkin-Elmer 2400 series II CHNS/O analyzer.
4.2. Synthesis of methallyloxytris(dimethylamino)phosphonium hexafluorophosphate 2
Tris(dimethylamino)phosphine (2.29 g, 14 mmol) was added drop-wise to a stirred solution of
-methylprop-2-en-1-ol (1 g, 14 mmol) and CCl (2.46 g, 16 mmol) in dry CH Cl (30 mL)
2
4
2
2
cooled at -30°C. Then, 15 mL of distilled water was added and the reaction mixture was
allowed to proceed at room temperature for 2 h. Organic phase was decanted and extracted
with water (2 x 40 mL). Aqueous phases were collected, washed with Et
2
O and decanted to
give an aqueous solution of methallyloxyphosphonium chloride. After the addition of KPF
6
(3.68 g, 20 mmol) in 10 mL of water, an immediate precipitate was formed. The mixture was
2
filtered and the crude product was washed with Et O and dried under vacuum.
Recrystallization from a mixture of chloroform: Et
2
O solution afforded salt 2 as a white solid.
). H-NMR (300 MHz, CDCl ): 1.78 (s, 3H, CH
N); 4.54 (d, 2H, CH -O); 5.01 (s, 1H, CH ); 5.08 (s, 1H, CH
): 18.7 (CH -allyl); 36.7 (CH -N); 71.9 (CH -O); 114.3 (CH
-1
-
1
Yield: 4.15 g (78%). IR [ν cm ]: 836 (PF
6
3
3
-
allyl); 2.76 (d, 18H, (CH
3
)
2
2
2
2
).
1
3
C-NMR (75.47 MHz, CDCl
37.7 (C).
3
3
3
2
2
);
1
4
.3. Synthesis of Pd(II) complexes
.3.1. Synthesis of complex C1
4
2 2 2
Pd(dba) (150 mg, 0.26 mmol), the ligand L1 (51 mg, 0.30 mmol) and CH Cl (20 ml) were
combined in a Schlenk tube and stirred at room temperature. After 15 min,
methallyloxytris(dimethylamino)phosphonium hexafluorophosphate (98.6 mg, 0.26 mmol)
was added and stirring continue overnight. The resulting solution was filtered through celite,
the solvent was removed under vacuum and the solid residue was washed with Et
2
O (3 x 20
ml) to give complex C1 as an orange solid. Recrystallization from a mixture of CH Cl : Et O
2
2
2
solution afforded single crystals suitable for X-ray analysis. Yield: 0.11 g (86%). Anal. Calc.
PPd (488.70): C, 39.32; H, 3.51; N, 5.73. Found: C, 39.32; H, 3.51; N, 5.73.
17 6 2
for C16H F N

ACCEPTED MANUSCRIPT
-1
-
1
IR [ν cm ]: 827 (PF
6
); 1485; 1582 (C=N). H-NMR (300 MHz, CD
2
Cl
2
): 2.13 (s, 3H, CH
3
-
allyl); 3.23 (s, 1H, Hanti); 3.37 (s, 1H, Hanti); 3.68 (s, 1H, Hsyn); 4.05 (s, 1H, Hsyn), 7.34-7.48
(m, 5H, Har); 7.69-7.74 (td, 1H, H4py); 8.06-8.09 (dd, 1H, H3py); 8.14-8.20 (td, 1H, H5py); 8.61
13
(
2 2
s, 1H, H-C=N); 8.72-8.74 (dd, 1H, H6py). C-NMR (75.47 MHz, CD Cl ): 23.69 (C4);
6
2.42, 64,02 (C1,3); 122.35, 129.80, 130.13, 130.19; 130.38; 136.82 (C
2
); 141.61, 149.68,
31
-
1
53.82, 154.48; 166.58 (C=N). P-NMR (121.48 MHz, CD Cl ): -144.39 (sept, PF ).
2
2
6
4.3.2. Complex C2
Complex C2 was prepared in a similar manner to complex C1. Pd(dba)
2
(150 mg, 0.26
mmol), the ligand L2 (60 mg, 0.30 mmol) and salt 2 (98 mg, 0.26 mmol). Yield: 0.12 g
91%). Anal. Calc. for C16 OPPd (504.70): C, 38.08; H, 3.40; N, 5.55. Found: C,
8.08; H, 3.40; N, 5.55. IR [ν cm ] : 826 (PF
CD Cl ): δ (ppm) 2.72 (s, 3H, CH -allyl); 3.40-3.43 (d, 2H, Hanti); 3.99 (s, 2H, Hsyn); 7.43-
.47 (d, 2H, H );8.01-8.03 (d, 2H, H ); 8.36-8.41 (td, 1H, H ); 8.76-8.79 (dd, 1H, H );
(
17 6 2
H F N
-1
-
1
3
6
); 1509, 1631 (C=N). H-NMR (300 MHz,
2
2
3
7
8
ar
ar
4py
5py
.85-8.91 (td, 1H, H3py); 9.45 (s, 1H, H-C=N); 9.50 (s, 1H, OH) ; 9.51-9.53 (dd, 1H, H6py).
1
3
C-NMR (75.47 MHz, CD
29.86, 130.34, 137.01 (C
Cl
2 2 3
Cl ): 23.45 (CH -allyl); 63.52-66.08 (C1,3); 116.90, 125.18,
3
1
1
2
);142.20, 142.80, 155.22, 155.32, 159.85; 165.74 (C=N). P-NMR
-
(121.48 MHz, CD
2
2
): -144.23 (sept, PF
6
).
4.3.3. Complex C3
Complex C3 was prepared in a similar manner to complex C1. Pd(dba)
mmol), the ligand L3 (63 mg, 0.30 mmol) and salt 2 (98 mg, 0.26 mmol). Yield: 125 mg
93%). Anal. Calc. for C18 PPd (516,76): C, 41.84; H, 4.10; N, 5.42. Found: C, 42.80;
2
(150 mg, 0.26
(
21 6 2
H F N
-
1
-
1
H, 4.35; N, 5.80. IR [ν cm ]: 829 (PF
6
); 1598, 1632 (C=N). H-NMR (300 MHz, CD
); 2.24 (s, 3H, CH -allyl); 2.94 (s, 1H, Hanti); 3.14 (s,
H, Hanti); 3.30 (s, 1H, Hsyn); 4.05 (s, 1H, Hsyn); 7.04-7.17 (m, 3H, Har); 7.76-7.80 (td, 1H,
4py); 8.04-8.07 (dd, 1H, H3py); 8.18-8.23 (td, 1H, H5py); 8.40 (s, 1H, H-C=N); 8.78-8.80 (dd,
2 2
Cl ):
2
1
.08 (s, 3H, o-CH
3
); 2.13 (s, 3H, o-CH
3
3
H
1
3
1
2 2 3 4
H, H6py). C-NMR (75.47 MHz, CD Cl ): 18.40, 18.74 (o-CH ); 23.74 (C ); 62.38-62.53
(
C ); 127.82, 128.04, 129.07, 129.18, 129.82, 130.95; 137.19 (C ); 141.77, 148.88, 153.04,
1
,3
2
31
-
1
54.84; 170.41 (C=N). P-NMR (121.48 MHz, CD
2
Cl
2
6
): -144.46 (sept, PF ).
4.3.4. Complex C4
Complex C4 was prepared in a similar manner to complex C1. Pd(dba) (150 mg, 0.26
2
mmol), the ligand L4 (80 mg, 0.30 mmol) and salt 2 (98 mg, 0.26 mmol). Yield: 141 mg

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29 6 2
(94%). Anal. Calc. for C22H F N PPd (572,86): C, 46.13; H, 5.10; N, 4.89. Found: C, 46.14;
-
1
-
1
H, 4.65; N, 5.24. IR [ν cm ]: 829 (PF
6
); 1597; 1623 (C=N). H-NMR (300 MHz, CD
-iPr); 1.13-1.21 (d, 6H, CH -iPr); 2.06 (s, 3H, CH -allyl); 2.92-
.98(sept, 2H, CH-iPr); 3.09-3.16 (quintuplet, 1H, Hanti); 3.20-3.22 (d, 1H, Hanti); 3.32 (s, 1H,
syn); 4.05-4.12 (d, 1H, Hsyn), 7.17-7.29 (m, 3H, Har); 7.79-7.83 (td, 1H, H4py); 8.06-8.08 (d,
2 2
Cl ):
1.06-1.09 (d, 6H, CH
3
3
3
2
H
13
1
H, H ); 8.19-8.25 (td, 1H, H ); 8.35 (s, 1H, H-C=N); 8.82-8.84 (dd, 1H, H ). C-NMR
3py 5py 6py
(
75.47 MHz, CD
2
Cl
2
): 22.77, 24.24 (CH
3
-iPr); 24.44 (C
4
); 28.68, 28.86 (CH-iPr); 62.26,
6
1
3,14 (C1,3); 124.36, 128.59, 129.87, 131.15; 137.55 (C
2
); 138.69, 138,97, 141.85, 146.36,
31
-
52.74, 155.14; 169.71 (C=N). P-NMR (121.48 MHz, CD Cl ): -144.41 (sept, PF ).
2
2
6
4.3.5. Complex C5
Complex C5 was prepared in a similar manner to complex C1. Pd(dba)
2
(115 mg, 0.20
mmol), the ligand L5 (52 mg, 0.23 mmol) and salt 2 (76 mg, 0.20 mmol). Yield: 98 mg
92%). Anal. Calc. for C19 PPd (530.78): C, 42.99; H, 4.37; N, 5.28. Found: C, 43.79;
(
23 6 2
H F N
-1
-
1
H, 4.71; N, 5.86. IR [ν cm ]: 831 (PF
6
); 1595; 1618 (C=N). H-NMR (300 MHz, CD
2 2
Cl ):
2
3
8
.03-2.04 (s, 6H, o-CH ); 2.14 (s, 3H, CH -C=N); 2.21 (s, 3H, CH -allyl); 2.82 (s, 2H, H );
3
3
3
anti
.23 (s, 1H, Hsyn); 3.95-3.96 (d, 1H, Hsyn), 7.09-7.19 (m, 3H, Har); 7.77-7.79 (td, 1H, H4py);
13
.07-8.15 (dd, 1H, H3py); 8.23-8.29 (td, 1H, H5py); 8.79-8.81 (dd, 1H, H6py). C-NMR (75.47
MHz, CD Cl ): 16.93 (CH -C=N); 18.08-18.16 (o-CH ); 23.84 (C ); 61.91-62.30 (C );
2
2
3
3
4
1,3
1
1
27.19, 127.36, 127.43, 127.78, 129.16, 129.27, 130.56; 137.04 (C
2
); 141.68, 146.98, 154.04,
31
-
54.78; 176.62 (C=N). P-NMR (121.48 MHz, CD
2
Cl
2
): -144.47 (sept, PF
6
).
4.3.6. Complex C6
Complex C6 was prepared in a similar manner to complex C1. Pd(dba)
mmol), the ligand L6 (65 mg, 0.23 mmol) and salt 2 (76 mg, 0.20 mmol). Yield: 106 mg
90%). Anal. Calc. for C23 PPd (586.89): C, 47.07; H, 5.32; N, 4.77. Found: C, 46.86;
2
(115 mg, 0.20
(
31 6 2
H F N
-1
-
1
H, 5.17; N, 5.54. IR [ν cm ]: 832 (PF
6
); 1597; 1618 (C=N). H-NMR (300 MHz, CD
2 2
Cl ):
1
.02-1.04 (d, 6H, CH -iPr); 1.07-1.20 (d, 6H, CH -iPr); 2.04 (s, 3H, CH -allyl); 2.25 (s,3H,
3
3
3
3
CH -C=N); 2.77-2.85 (sept, 2H, CH-iPr); 2.95-2.98 (d, 2H, Hanti); 3.28 (s, 1H, Hsyn); 3.96-
3
8
.97 (d, 1H, Hsyn), 7.21-7.26 (m, 3H, Har); 7.77-7.83 (td, 1H, H4py); 8.08-8.11 (dd, 1H, H3py);
13
.22-8.28 (td, 1H, H ); 8.81-8.83 (dd, 1H, H ). C-NMR (75.47 MHz, CD Cl ): 18.20
5py
6py
2
2
(
CH
3
-C=N); 23.44, 23.51, 23.81, 23.94 (CH
3
4
-iPr); 23.65 (C ); 28.84, 29.02 (CH-iPr); 62.03,
6
5
2,81 (C1,3); 124.55, 124.71, 127.91, 128.34, 130.64; 137.59, 137.98, 138.25, 141.75; 144.41
31
-
(C ), 153.94, 154.84; 176.77 (C=N). P-NMR (121.48 MHz, CD Cl ): -144.48 (sept, PF ).
2
2
2
6

ACCEPTED MANUSCRIPT
4.4. Crystal structure determination and refinement
X-ray quality crystals of C5 were grown from a mixture of CH
2
2
Cl /n-hexane solution upon
standing at ambient temperature. An orange prism, was chosen by size, habit, and polarized
light microscopy and mounted on a glass fiber. Intensity data were collected at ambient
temperature on an Enraf-Nonius CAD-4 diffractometer equipped with graphite
α
monochromated Mo K radiation. Reflection data were corrected for Lorentz-polarization
effects but not for absorption. The structure was solved by direct methods and subsequent
difference Fourier techniques (SIR-92) [43] and refined with SHELXL-2013 [44]. Non-
hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atoms were
placed in idealized positions on parent atoms in the final refinement. Details of the crystal
parameters, data collection, and structure refinement are given in Table 1.
4.5. Density functional theory (DFT) calculations
Geometry optimization reported in this article was done with the Gaussian09 [45]
program package supported by GaussView 5.0.8. The DFT [46-47] calculations have been
performed with the Long-range corrected hybrid density meta-GGA functional wB97XD [48-
50] with dispersion corrections. The initial geometry has been taken from crystal structure.
The geometry of C5 in the gas phase has been optimized using tight convergent SCF
procedure ignoring symmetry using S=0 spin state. In the calculation, the recently reported
basis LANL2TZ(f) was used for Pd atom [51]. It contains the LANL2 relativistic ECP of Hay
and Wadt [52] and a flexible triple-zeta basis set augmented with one set of 4f polarization
functions. For C, H and N, a valence triple zeta basis set with polarization functions on all
atoms 6-311G(d,p) [53] was employed for the calculation. The frequency calculation was
carried out, verifying if the optimized molecular structure corresponds to energy minimum,
thus only positive frequencies were expected.
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ACCEPTED MANUSCRIPT
•
•
•
•
This work represents a new way to access methallyl palladium complexes.
These new complexes were prepared via an oxidative addition reaction.
Distorted square planar arrangement around the palladium center.
Novel cationic palladium precursors can be useful as catalysts.