[Pd(acac)(PR3)(PhCN)][BF4] and [Pd(acac)(S)2][BF4] (R = phenyl, 2-methoxyphenyl; S = benzonitrile, pyridine): Synthesis, characterization, reactivity and catalytic behavior. Crystal structure of Pd(κ2-O,O′-acac)(κ1-C-acac)(P(2-MeOC6H

Article abstract of DOI:10.1016/j.molstruc.2020.128425

The Pd(II)complexes [Pd(acac)(PR₃)(PhCN)][BF₄] and [Pd(acac)(S)₂][BF₄] (acac = acetylacetonate; R = phenyl, 2-methoxyphenyl; S = benzonitrile, pyridine, CD₃CN) were synthesized by the reaction of Pd(a

Full text of DOI:10.1016/j.molstruc.2020.128425

Journal of Molecular Structure 1217 (2020) 128425
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
[Pd(acac)(PR3)(PhCN)][BF4] and [Pd(acac)(S)2][BF4] (R ¼ phenyl, 2-
methoxyphenyl; S ¼ benzonitrile, pyridine): Synthesis,
characterization, reactivity and catalytic behavior. Crystal structure of
Pd(k2-O,O0-acac)( 1-C-acac)(P(2-MeOC6H4)3)
k
,
D.S. Suslov a *, M.V. Bykov a, M.V. Pakhomova a, Z.D. Abramov a, G.V. Ratovskii a,
,
I.A. Ushakov b c, T.N. Borodina b, V.I. Smirnov b, V.S. Tkach a
a Irkutsk State University, Ul. K.Marksa, 1, Irkutsk, 664003, Russia
b A.E. Favorsky Irkutsk Institute of Chemistry SB RAS, Favorsky st., 1, Irkutsk, 664033, Russia
c National Research Irkutsk State Technical University, Lermontov St, 83, Irkutsk, 664074, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
The Pd(II)complexes [Pd(acac)(PR3)(PhCN)][BF4] and [Pd(acac)(S)2][BF4] (acac
¼
acetylacetonate;
Received 18 December 2019
Received in revised form
8 May 2020
Accepted 8 May 2020
Available online 10 May 2020
R ¼ phenyl, 2-methoxyphenyl; S ¼ benzonitrile, pyridine, CD3CN) were synthesized by the reaction of
Pd(acac)2 or Pd(acac)2$PR3 with 2 equiv. of BF3$OEt2 in the presence of appropriate ligands (S). The
structural features of the complexes were analyzed by NMR and FTIR spectroscopies. Computed FTIR
spectra was in agreement with the corresponding experimental data, the correlation between n(CN) of
the
k
1-nitrile ligands and DFT-calculated geometrical features of the complexes was proposed. Complex
Pd (k2-O,O0-acac)(
k
1-C-acac)(TOMPP) (TOMPP ¼ tris(ortho-methoxyphenyl)phosphine) was characterized
Keywords:
Palladium
by X-ray diffractometry. XRD, 1H and 31P NMR analyses were consistent with formation of three un-
equally populated rotamers of Pd(k2-O,O0-acac)( 1-C-acac)(TOMPP) in CDCl3 which differ in the orien-
k
Acetylacetonate
Norbornene
Phenylacetylene
Polymerization
tris(2-methoxyphenyl)phosphine
tation of the endo-(2-methoxy)phenyl ring in exo2 conformation of coordinated TOMPP. Reaction of
[Pd(acac)(PR3)(PhCN)]BF4 with L (L ¼ pyridine, morpholine, TOMPP) in the majority of cases gave
mixtures of [Pd(acac)(PR3)(L)]BF4, [Pd(acac)(L)2]BF4, and [Pd(acac)(PR3)2]BF4 as result of sequence of
ligand substitution reactions. The cationic palladium catalyst precursors were found to be active catalysts
for phenylacetylene polymerization and oligomerization. Only cationic pre-catalysts with bulky TOMPP
ligand gave high-molecular weight polyphenylacetylene. Catalysts with less bulky substituents mostly
formed phenylacetylene oligomers. When activated with BF3,OEt2, these palladium complexes can also
be used as catalysts for the vinyl addition polymerization of norbornene with activities 104e107 gpolymer
molPd hꢀ1
.
© 2020 Elsevier B.V. All rights reserved.
1. Introduction
based catalysis typically involves either a sensitive organometallic
precursor or activators such as aluminum alkyls [23,24]. Exceptions
are cationic palladium (II) methyl (alkyl) or allyl complexes
[10,23,25e34], which require no cocatalyst for their activation to-
ward olefins oligomerization and polymerization, and dicationic
palladium complexes activated by MeOH or, presumably, by water
impurities [9,18,27,35e41]. In addition, aluminum alkyls free
cationic Pd-catalyzed systems with OhO-chelating ligands
Mono- and dicationic palladium (II) complexes play an impor-
tant role in a number of catalytic transformations, e.g., addition
polymerization of norbornene (NB) and its functionalized de-
rivatives [1e5], alkenes and vinylarenes dimerization [6e13],
phenylacetylene (PA) polymerization [14e18], selected hydro-
amination reactions [19e22]. Polymerization transition metal
(OhO ¼
b-diketonates or carboxylates) in combination with Lewis
acids have shown promising results for selective dimerization of
styrene [6,42e45], polymerization of norbornene and its derivates
[46e48].
* Corresponding author. Irkutsk State University, ul. K.Marksa, 1, Irkutsk, 664003,
Russia.
E-mail addresses: suslov@chem.isu.ru, suslov.dmitry@gmail.com (D.S. Suslov).
https://doi.org/10.1016/j.molstruc.2020.128425
0022-2860/© 2020 Elsevier B.V. All rights reserved.

2
D.S. Suslov et al. / Journal of Molecular Structure 1217 (2020) 128425
Recently we reported synthesis of novel acetylacetonate
reagents were obtained commercially and used as received. Mo-
lecular weights and polydispersity of the polymers were estimated
in THF by a Thermo-Dionex HPLC system. A set of monodisperse
polystyrene standards (Agilent) covering the molecular weight
range of 103 to 106 was used for molecular weight calibration. All
NMR spectra were recorded at room temperature on Bruker DPX-
250, or Bruker DPX-400 spectrometers. IR spectra were recorded
on a Simex Infralum FT 801 spectrometer. TGA/DSC measurements
were performed with a Netzsch STA 449-F3 instrument with cru-
cibles made of aluminum (sample masses were in the range of
3e4 mg) at a heating rate of 5 K/min in a nitrogen atmosphere.
cationic palladium complexes as well as the results of their usage as
efficient precursors for the selective styrene hydroamination [49],
polymerization of NB and its derivates [50e52], and polymerization
of PA [53]. Complexes of such type can be obtained in different
manner: a) by acetylacetonate ligand abstraction from Pd(acac)2
[54e58], b) by reaction of Pd (0) [59] or dicationic Pd(II) [59,60]
complexes with acetylacetone, c) by consecutive haloids displace-
ment [61], or d) by acetonitrile displacement [62,63].
Prompted by our interest in the use of these catalyst systems in
the field of late transition metals oligo-/polymerization catalysis,
we describe here the synthesis of cationic (acetylacetonate-k
2-O,O
′)palladium (II) mixed-ligands complexes with triarylphosphine
and weakly coordinating N-ligands. The six new compounds have
been fully characterized (Scheme 1, complexes: 2e4, 6e8), and
2.1.1. General procedure for phenylacetylene polymerization
All the polymerizations were carried out in a 10 mL glass reactor
equipped with a magnetic stirrer under Ar. Pd catalyst was stirred
in the solvent (1 mL or 2.3 mL), after which a PA (1 mL (9.1 mmol) or
2.7 mL (24.6 mmol)) was added. After being stirred for the indi-
cated time, the reaction mixture was poured into a large amount of
acidified methanol to precipitate the polymer as yellow powder.
The product was isolated by filtration and dried under vacuum to
constant weight. The polymer was purified, when necessary, by
dissolution in THF and precipitation with methanol to give a fine
yellow powder. Polymer samples were characterized by 1H, 13C
NMR, FT-IR and GPC analysis. The polyphenylacetylene (PPA) pro-
duced showed IR absorption bands and 1H NMR resonances char-
acteristic of mixture of head-to-tail cis-transoidal PPA or trans-
cisoidal PPA isomers [15,67,68].
crystal
structure
of
Pd(k2-O,O0-acac)( 1-C-acac)(TOMPP)
k
(TOMPP ¼ P(2-MeOC6H4)3) have been determined by means of X-
ray diffraction. IR and NMR spectroscopy features of the cationic
complexes are discussed. In order to examine the influence of the
ligand structure on the catalytic properties, the addition polymer-
ization of norbornene and phenylacetylene with these complexes
were also investigated.
2. Experimental section
2.1. General procedures and materials
All air- and/or moisture-sensitive compounds were manipu-
lated by using standard high-vacuum line, Schlenk, or cannula
techniques under an argon atmosphere. Argon (Arnika-Prom-Ser-
vice) was purified before feeding to the reactor by passing through
columns packed with oxygen scavenger (Fisher REDOX) and mo-
lecular sieve 4 A (Aldrich), respectively. Diethyl ether, benzene,
toluene and hexane (ZAO Vekton) were distilled from
sodiumꢀbenzophenone. CH2Cl2 (ZAO Vekton), CH3CN (ZAO Vek-
ton), diethylamine (ZAO Vekton), morpholine (Aldrich), phenyl-
acetylene (99%, Aldrich) were distilled from CaH2. Solvents were
stored over molecular sieves. All glassware was dried for at least 3 h
in a 150 ꢁC oven and cooled under an argon atmosphere. Styrene
(99%, Aldrich) was purified by distillation under reduced pressure
over CaH2. Norbornene (Acros, 99%) were distilled from sodium-
benzophenone and used as a solution (80 mol.%) in CH2Cl2. Pd(a-
cac)2 was synthesized according to a literature procedure [64] and
recrystallized from acetone. Complexes 1, 5, 9, 10 were prepared
according to literature procedures [49e52,58,65,66]. All other
2.1.2. General procedure for catalytic polymerization of norbornene
Polymerizations were carried out in a 10-mL glass reactor
equipped with a magnetic stirrer. The reactor was filled with nor-
bornene as a solution in CH2Cl2, the solution was kept at desired
temperature for 15 min and then the palladium complex was
added. Polymerizations were initiated by the injection of boron
compound. After stirring for a time needed, the polymers formed
were precipitated in ethanol. The precipitated polymers were
washed three times with ethanol, and dried in vacuum at 80 ꢁC for
6 h. The resulting polynorbornenes were insoluble in common
solvents such as benzene, chloroform, methylene chloride, THF,
toluene, and 1,2,4-trichlorobenzene. IR (KBr disk) analysis of the
polynorbornene showed no absorbance in the 1600e1670 cmꢀ1
range indicating that the polymerization occurred via a vinyl
addition pathway. Thermoanalytical measurements (TGA/DSC) of
the obtained polymers showed typical for vinyl addition PNB high
decomposition temperatures between 400 and 420 ꢁC.
Scheme 1. Numbering schemes for complexes prepared (top) and hydrogen/carbon atoms (R’ ¼ H or OMe) (bottom).

D.S. Suslov et al. / Journal of Molecular Structure 1217 (2020) 128425
3
2.2. Syntheses of complexes
2-O,O′-acac)( 1-C-acac)(PPh3) (1). The synthetic route to
precipitate was collected, washed with diethyl ether (3 ꢂ 10 mL),
and dried under vacuum (4 h, rt).
Pd(k
k
[Pd(k
2-O,O′-acac)(PhCN)(PPh3)]BF4 (3). The general procedure
Pd(acac)2$PPh3 complex was loosely adapted from that of Baba
et al. [69] and Childress et al. [70]. A suspension of Pd(acac)2
(544 mg, 1.79 mmol) and PPh3 (480 mg, 1.83 mmol) in 20 mL of n-
hexane was stirred at room temperature for 24 h. The resulting
lemon precipitate was filtered, washed with n-hexane (2 ꢂ 10 mL),
and dried under vacuum to give Pd(acac)2$PPh3 (725 mg, 71%).
was followed using 0.49 mL (4.00 mmol) of BF3$OEt2, 1.134 g
(2.00 mmol) of Pd(acac)2$PPh3, 0.62 mL (6.00 mmol) of benzoni-
trile, and benzene (40 mL). Yield: 1.235 g, 84%. Anal. Calcd for
C
30H27BF4NO2PPd: C, 54.78; H, 4.14; N, 2.13. Found: C, 54.90; H,
4.19; N, 2.04.1H NMR (400 MHz, CDCl3, 25 ꢁC):
d
7.8e7.3 (m, HAri
/
HPhi), 5.58 (s, 1H, H3), 2.19 (s, 3H, H1), 1.75 (s, 3H, H5)$13C{1H} NMR
Pd(k
2-O,O′-acac)(
k
1-C-acac)(TOMPP) (2). A solution of Pd(a-
(101 MHz, CDCl3, 25 ꢁC):
d
188.99 (d, 3J (P,C2) ¼ 3.3 Hz, C2), 184.17 (s,
cac)2 (390 mg, 1.28 mmol) and TOMPP (452 mg, 1.28 mmol) in
10 mL of CH2Cl2 was stirred at room temperature for 24 h. The
resulting yellow solution was filtered, and the solution was
concentrated to 5 mL under vacuum. Addition of diethyl ether
(20 mL) formed a yellow precipitate over 20 h (at ꢀ18 ꢁC), which
was collected, washed with diethyl ether (3 ꢂ 10 mL), and dried
under vacuum to give 2 which contained traces (<5%) of Et2O by 1H
NMR analysis (764 mg, 91%). Anal. Calcd for C28H29O4PPd: C, 59.32;
H, 5.16. Found: C, 59.75; H, 5.27.1H NMR (400 MHz, CDCl3, 25 ꢁC,
Spinsystem1 (S1), Spinsystem2 (S2), Spinsystem3 (S3)) (the rele-
C4), 136.11 (s, CPh4), 134.32 (d, 2J(P,CAr2/CAr6) ¼ 10.8 Hz, CAr2/CAr6),
133.34 (s, CPh3/CPh5), 133.03 (d, 4J(P,CAr4) ¼ 2.5 Hz, CAr4), 129.87 (s,
C
Ph2/CPh6), 129.56 (d, 3J(P,CAr3/CAr5) ¼ 11.8 Hz, CAr3/CAr5), 124.88 (d,
4J (P,CAr1) ¼ 57.6 Hz, CAr1), 123.18 (s, CCN), 107.54 (s, CPh1), 101.35 (s,
C3), 26.76 (d, 4J(P,C1) ¼ 8.8 Hz, C1), 25.68 (d, 4J (P,C5) ¼ 3.1 Hz, C5). 13
C
{1H} NMR (101 MHz, CD3CN, 25 ꢁC)
d
188.58 (d, 3J (P,C2) ¼ 3.5 Hz,
C2), 184.06 (d, 3J (P,C4) ¼ 1.5 Hz, C4), 133.93 (d, 2J (P,CAr2
/
CAr6
)
¼
10.8 Hz, CAr2/CAr6), 132.68 (s, CPh4), 132.28 (d,
4J(P,CAr4) ¼ 3.1 Hz, CAr4), 131.80 (s, CPh2/CPh6), 128.92 (s, overlapping,
C
Ph3/CPh5), 128.80 128.86 (d, 3J(P,CAr3/CAr5) ¼ 11.5 Hz, CAr3/CAr5),
vant numbering scheme is shown in Scheme 1):
d
7.64 (br., 3H,
124.79 (d, 4J (P,CAr1) ¼ 57.7 Hz, CAr1), 118.38 (s, CCN), 111.62 (s, CPh1),
100.27 (s, C3), 25.45 (d, 4J(P,C1) ¼ 8.9 Hz, C1), 24.37 (d, 4J
overlapping, HAr6(S1)/HAr6(S2)/HAr6(S3)), 7.45 (t, 3J(HAr3,HAr4) ¼ 7.8,
3J(HAr5,HAr4) ¼ 7.8 Hz), 3H, overlapping, HAr4(S1)/HAr4(S2)/HAr4(S3)),
6.99 (t, 3J(HAr4,HAr5) ¼ 7.2, 3J(HAr6,HAr5) ¼ 7.2 Hz), 3H, overlapping,
(P,C5) ¼ 3.6 Hz, C5). 31P{1H} NMR (162 MHz, CDCl3, 25 ꢁC):
d 28.88
(s). 19F NMR (376 MHz, CDCl3, 25 ꢁC):
d
ꢀ154.24, ꢀ154.29 (intensity
H
Ar5(S1)/HAr5(S2)/HAr5(S3)), 6.87 (dd, 3J(HAr4,HAr3
)
¼
8.0,
ratio of approximately 20:80 corresponding to the natural abun-
4J(P,HAr3) ¼ 4.6 Hz), 3H, overlapping, HAr3(S1)/HAr3(S2)/HAr3(S3)), 5.30
dances of 10B and 11B, respectively).). IR (nujol, NaCl plates, cmꢀ1):
(
k2-O,O0-acac)-group: 1564 (C$$$O and C$$$C); 1523 (C$$$C and
n n
(s, 0.1H, H3(S1), acac), 5.23 (s, 0.2H, H3(S2), acac), 5.17 (s, 0.7H, H3(S3)
,
, g J
-acac), 3.74 (d, 3
C$$$O); 1364 ds (CeH from CH3); 1278 ns (CeCH3) and chelate de-
formations; 1163 (CeH from CH) and chelate deformations; 1006
chelate deformations and (CeCH3); 938 nas (CeCH3) and chelate
deformations; 758 (CeH from CH, off-plane); 682 chelate de-
formations and ns (PdeO). (PhCN)-group: 3102 and 3066 (CeH
from Ph); 2270 (C^N); 1594, 1585, 1495 and 1449 (C]C from Ph)
and ring deformations; 1297, 1187 (CeH from Ph, plane); 1200
(CAreCN); 1087 ring deformations; 997, 980, 943, 851, 754, 695
acac), 3.87 (m, 0.3H, overlapping, H3’(S1)/H3’ (S2)
(P,H2) ¼ 5.6 Hz, 0.7H, H3’(S3) -acac), 3.57 (s, 0.7H, HOMe(S1)), 3.54 (s,
1.8H, HOMe(S2)), 3.50 (s, 6.5H, HOMe(S3)), 2.50 (s, 0.2H, H1’(S1)/H5’(S1)
,
g
d
/
/
d
H1’(S2)/H5’(S2)), 2.36 (s, 0.2H, overlapping, H1’(S1)/H5’(S1)/H1’(S2)
d
H5’(S2), 2.25 (s, 0.3H, overlapping, H1’(S1)/H5’(S1)/H1’(S2)/H5’(S2)), 2.21
n
(s, 4.5H, H1’(S3)/H5’(S3)), 2.08 (s, 0.1H, H1(S1)), 2.05 (s, 0.6H, H1’(S1)
/
n
n
H
5’(S1)/H1’(S2)/H5’(S2)), 2.03 (s, 0.7H, H1(S2)), 1.99 (s, 2.1H, H1(S3)), 1.61
d
(s, 0.2H, H5(S1)), 1.51 (s, 0.7H, H5(S2)), 1.34 (s, 2.1H, H5(S3)). 13C{1H}
NMR data from 1H,13C HMBC NMR spectrum (101 MHz, CDCl3,
n
d
(CeH from Ph, off-plane). (PPh3)-group: 3102 and 3066
(C]C from Ph) and ring deformations;
(CeH from Ph, plane); 1087, 1047, 1024 ring de-
formations, 928, 864, 805, 754, 744, 715, 704, 695 (CeH from Ph,
off-plane). (BF4)-group: 1094, 1056, 1033 (BeF).
[Pd(
2-O,O′-acac)(PhCN)(TOMPP)]BF4·0.5C7H8 (4). The general
n(CeH
25 ꢁC):
d 207.42, 202.45,191.41,187.17,185.87,184.42,161.75,160.90,
from Ph); 1564, 1482, 1440
1317, 1179, 1100
n
120.67, 117.02, 111.21, 100.74, 99.39, 55.63, 47.09, 31.52, 28.47, 27.27,
d
26.22, 25.26.31P{1H} NMR (162 MHz, CDCl3, 25 ꢁC, Spinsystem1
d
(S1), Spinsystem2 (S2), Spinsystem3 (S3)):
20.06 (s, 0.2P, S2), 13.78 (s, 0.7P, S3). IR (nujol, NaCl plates, cmꢀ1):
k2-O,O0-acac)-group: 1560 (C$$$O and C$$$C); 1514 (C$$$C and
C$$$O); 1344 ds (CeH from CH3); 1277 ns (CeCH3) and chelate de-
formations; 1195 (CeH from CH) and chelate deformations; 1014
chelate deformations and (CeCH3); 934 nas (CeCH3) and chelate
deformations; 776 (CeH from CH, off-plane); 689 chelate de-
formations and ns (PdeO). ( (C]
1-C-acac)-group: 1668 and 1656
O); 1344 ds (CeH from CH3); 1222 ns (CeCH3); 1186 (CeH from
CH); 1156 nas (CeC(O)); 844 nas (CeCH3); 786 (eC(O)eCH3).
(TOMPP)-group: 3061 (CeH from Ar); 1580, 1576 and 1430 (C]C
d 25.70 (s, 0.1P, S1),
n
k
(
n
n
procedure was followed using 0.20 mL (1.60 mmol) of BF3$OEt2,
527 mg (0.80 mmol) of Pd(acac)2$TOMPP, 0.25 mL (2.40 mmol) of
benzonitrile, and toluene (60 mL). Yield: 523 mg, 87%. The product
contained toluene as adduct (approx. 6%) and traces (<2%) of Et2O
by 1H NMR analysis. In the 1H NMR spectrum of 4 additional signals
also were detected due to exchange between CD3CN, water impu-
rities in CD3CN, and PhCN. Anal. Calcd for C36.5H37BF4NO5PPd: C,
55.22; H, 4.70; N, 1.76. Found: C, 54.91; H, 4.55; N, 1.64.1H NMR
d
d
d
k
n
d
d
n
n
(400 MHz, CD3CN, 25 ꢁC):
8H, HAri/HPhi), 5.52 (s, 1H, H3), 3.72 (s, 1.2H, HOMe), 3.63 (s, 7.8H,
OMe), 2.33 (s, 1.5H, CH3C6H5), 2.18 (s, 1.2H, H1/H5), 2.06 (s, 2.4H,
d 7.8e7.4 (m, 11.5H, HAri/HPhi), 7.3e7.0 (m,
from Ar) and ring deformations; 1473 (sh) das (CeH from OeCH3);
1387 ds (CeH from OeCH3); 1291 das (CeH from Ar, plane); 1247
H
n
(CAreOeC, quasi nas) and das (CeH from Ar, plane); 1178
from OeCH3); 1164 (CAreOeC, quasi ns); 1135 ds (CeH from Ar,
plane); 1072 and 1020 (OeCH3) and ring deformations; 1043 and
799 ring deformations; 950 and 863 (CeH from Ar, off-plane); 747
(CeH, characteristic for ortho-substituted Ar).
d
(CeH
H1), 1.58 (s, 2.4H, H5)$13C{1H} NMR (101 MHz, CD3CN, 25 ꢁC):
n
d
188.62 (d, 3J (P,C2) ¼ 3.5 Hz, C2), 184.42 (d, 3J (P,C4) ¼ 1.6 Hz, C4),
n
160.54 (d, 2J (P,CAr2
)
¼
2.6 Hz, CAr2,
major), 160.38 (d, 2J
d
(P,CAr2) ¼ 2.6 Hz, CAr2, minor), 160.05 (d, 2J (P,CAr2) ¼ 2.4 Hz, CAr2,
minor), 137.87 (s, CPhMe), 135.26 (d, 2J(P,CAr6) ¼ 8.7 Hz, CAr6), 134.16
(d, 4J (P,CAr4) ¼ 2.4 Hz, CAr4), 133.05 (s, CPh4), 132.15 (s, CPh2/CPh6),
129.26 (s, CPh3/CPh5), 128.89 (s, CPhMe), 128.19 (s, CPhMe), 125.23 (s,
d
C
PhMe), 121.60 (d, 3J(P,CAr5) ¼ 12.7 Hz, CAr5, minor), 120.93 (d, 3J
2.2.1. General procedure for the synthesis of cationic palladium
complexes 3, 4, 6,7
A glass reactor was used to add in small portions 2 equiv. of
BF3$OEt2 to a solution of Pd(acac)2$PR3 (or Pd (acac)2) and L (ꢃ2
equiv.) dissolved in solvent (benzene or toluene), and the reaction
mixture was stirred for 1 h at room temperature. The resulting
(P,CAr5) ¼ 12.0 Hz, CAr5, major), 120.63 (d, 3J (P,CAr5) ¼ 12.4 Hz, CAr5
,
minor), 118.75 (s, CCN), 113.05 (d, 1J(P,CAr1) ¼ 65.0 Hz, CAr1, major,
overlapping peaks), 111.98 (s, overlapping, CPh1), 111.94 (d, over-
lapping, 3J(P,CAr3) ¼ 5.6 Hz, CAr3), 100.14 (s, C3), 55.89 (s, COMe
,

4
D.S. Suslov et al. / Journal of Molecular Structure 1217 (2020) 128425
minor), 55.46 (s, COMe, major), 25.87 (d, 4J(P,C1) ¼ 9.0 Hz, C1), 24.83
(d, 4J (P,C5) ¼ 3.9 Hz, C5), 20.44 (s, CPhMe). 31P{1H} NMR (162 MHz,
Ph) and ring deformations; 1284 and 1185
1202 (CAreCN); 813 ring deformations; 997, 880, 760 and 679
(CeH from Ph, off-plane). (BF4)-group: 1098, 1056, 1038 (BeF).
(C7H8)-group: 3102 and 3065 (CeH from Ph); 1607, 1550 and 1496
(sh) (C]C from Ph) and ring deformations; 1256, 1230 and 1180
(CeH from Ph, plane); 813 ring deformations; 727 and 679 (CeH
from Ph, off-plane).
[Pd(
2-O,O′-acac)(Py)2]BF4 (8). [Pd(acac)(MeCN)2]BF4 (494 mg,
132 mmol) was added slowly to solution of pyridine (209 mg,
2.64 mmol) in CH2Cl2 (10 mL) and stirred at room temperature for
1 h. The resulting yellow solution was evaporated to ca. 2 mL, and
Et2O was added. The yellow solid obtained was filtered off, washed
twice with Et2O (2 ꢂ 10 mL) and dried under vacuum (419 mg, 70%).
Anal. Calcd for C15H17BF4N2O2Pd: C, 39.99; H, 3.80; N, 6.22. Found:
C, 40.28; H, 3.84; N, 5.92.1H NMR (400 MHz, (CD3)2CO, 25 ꢁC):
d(CeH from Ph, plane);
n
CD3CN, 25 ꢁC):
d
16.67 (s, 0.14P), 11.97 (s, 0.86P). IR (nujol, NaCl
d
n
plates, cmꢀ1): (k2-O,O0-acac)-group: 1566
n
n
(C$$$O and C$$$C); 1515
n
(C$$$C and C$$$O); 1282 ns (CeCH3) and chelate deformations; 1180
n
d
d
d
(CeH from CH) and chelate deformations; 1018 chelate de-
(CeCH3); 936 nas (CeCH3) and chelate de-
formations; 766 (sh) (CeH from CH, off-plane); 688 chelate
deformations and ns (PdeO). (PhCN)-group: 3067 (CeH from Ph);
2281 (C^N); 1592 (sh), 1586, 1495 and 1434 (C]C from Ph) and
ring deformations; 1282, 1137 (CeH from Ph, plane); 1203
(CAreCN); 1073 ring deformations; 936, 860, 738, 697 (CeH from
Ph, off-plane). (TOMPP)-group: 3067 (CeH from Ar); 1586, 1572
and 1434 (C]C from Ar) and ring deformations; 1474 (sh) das (CeH
from OeCH3); 1387 (sh) ds (CeH from OeCH3); 1282 das (CeH from
Ar, plane); 1247 (CAreOeC, quasi nas) and das (CeH from Ar, plane);
1180 (CeH from OeCH3); 1167 (CAreOeC, quasi ns); 1137 ds (CeH
from Ar, plane); 1073 (OeCH3) and ring deformations; 799 ring
deformations; 936 and 860 (CeH from Ar, off-plane); 761 (CeH,
characteristic for ortho-substituted Ar). (BF4)-group: 1098, 1061,
1039 (BeF). Toluene (C7H8) was detected as weak shoulder at
1604 cmꢀ1
[Pd (
2-O,O′-acac)(CD3CN)2]BF4 (6).
formations and
d
k
d
n
n
n
d
n
d
n
n
d
8.80e8.73 (m, 4H, HPy1,5), 8.25e8.16 (m, 2H, HPy3), 7.75e7.66 (m,
4H, HPy2,4), 5.80 (s, 1H, H3), 2.09 (s, 6H, H1,5). 13C{1H} NMR
(101 MHz, (CD3)2CO, 25 ꢁC)
187.05 (s, C2/C4), 151.54 (s, CPy1,5),
140.36 (s, CPy3), 126.28 (s, CPy2,3), 101.14 (s, C3), 24.25 (s, C1/C5). 19
NMR (376 MHz, (CD3)2CO, 25 ꢁC):
n
d
n
d
n
F
d
d
d
ꢀ151.89, ꢀ151.94 (intensity
ratio of approximately 20:80 corresponding to the natural abun-
n
dances of 10B and 11B, respectively). IR (nujol, NaCl plates, cmꢀ1):
.
k
( n n
k2-O,O0-acac)-group: 1551 (C$$$O and C$$$C); 1524 (C$$$C and
The general procedure was followed using 0.13 mL mL
(1.05 mmol) of BF3$OEt2, 160 mg (2.10 mmol) of Pd (acac)2, 0.12 mL
of CD3CN, and toluene (30 mL). Yield: 173 mg, 87%. Anal. Calcd for
C9H7D6BF4N2O2Pd: C, 28.41; N, 7.36. Found: C, 28.24; N, 7.08.1H
C$$$O); 1458 (sh) das (CeH from CH3); 1364 ds (CeH from CH3); 1277
ns (CeCH3) and chelate deformations; 1159 (CeH from CH) and
chelate deformations; 1014 chelate deformations and (CeCH3);
948 nas (CeCH3) and chelate deformations; 770 (CeH from CH, off-
d
d
d
NMR (400.1 MHz, CD3CN, 25 ꢁC):
13C{1H} NMR (100.7 MHz, CD3CN, 25 ꢁC):
100.87(s, C3), 22.77 (s, C1/C5). IR (nujol, NaCl plates, cmꢀ1): (k2-O,O0-
acac)-group: 1581
(C$$$O and C$$$C); 1558 combination band; 1524
(C$$$C and C$$$O); 1361 ds (CeH from CH3); 1284 ns (CeCH3) and
chelate deformations; 1205 (CeH from CH) and chelate de-
formations; 1016 chelate deformations and (CeCH3); 943 nas
(CeCH3) and chelate deformations; 663 chelate deformations and
ns (PdeO); 655 (CH3eC(O)/C). (CD3CN)-group: 3274, 3190, 3101
combination bands; 2327 ns (C^N); 2322 nas (C^N); 2262, 2252 nas
(CeD); 2111 ns (CeD); 1652 combination of (CeC) and (CD3,
rocking); 1205 combination of (CD3, rocking) and (CeC^N,
bending); 1113 and 1046 (CeD); 873 (CD3, rocking); 845 and 838
(sh) (CeC). (BF4)-group: 1094 (sh), 1067, 1035 (BeF).
[Pd (
2-O,O′-acac)(PhCN)2]BF4·0.5C7H8 (7).
d
5.77 (s, 1H, H3), 2.19 (s, 6H, H1,5).
186.13(s, C2/C4),
plane); 699 chelate deformations and ns (PdeO). (Py)-group: 3117,
3107, 3093, 2724 overtones (of 1558, 1554, 1547, 1364); 3071 and
d
3052
and C]C) and ring deformations; 1539 overtone of 767; 1370
combination band; 1355, 1284,1263, 1240 and 1215 (CeH, plane)
and ring deformations; 1043 and 1021 ring deformations; 987, 879,
825, 805, 767, 722 and 695 (CeH, off-plane). (BF4)-group: 1098,
1055, 1036 (BeF).
[Pd(
2-O,O′-acac)(TOMPP)2]BF4 (9). Synthesis of complex 9
n(CeH); 1607, 1575, 1558, 1554, 1547, 1487, 1451, 1437 n(C]N
n
d
n
d
d
d
n
k
p
have been reported previously [58]; however, NMR and FT-IR
spectroscopy data for 9 are lacking in the literature. According to
the procedure for 8 with the following modification: using [Pd(a-
cac)(MeCN)2]BF4 (250 mg, 0.67 mmol), TOMPP (465 mg,
1.34 mmol) and 10 mL of CH2Cl2. Yield: 625 mg, 94%. 1H NMR
n
d
d
d
d
d
n
n
(400 MHz, CDCl3, 25 ꢁC):
3.6e3.0 (br, 18H, HOMe), 1.30 (s, 6H, H1,5).31P{1H} NMR (162 MHz,
CD3CN, 25 ꢁC): 18e16 (br). 19F NMR (376 MHz, CDCl3, 25 ꢁC):
ꢀ154.89, ꢀ154.94 (intensity ratio of approximately 20:80 corre-
sponding to the natural abundances of 10B and 11B, respectively). IR
(nujol, NaCl plates, cmꢀ1): (k2-O,O0-acac)-group: 1570 (C$$$O and
C$$$C); 1514 (C$$$C and C$$$O); 1278 ns (CeCH3) and chelate de-
formations; 1178 (CeH from CH) and chelate deformations; 1016
chelate deformations and (CeCH3); 938 nas (CeCH3) and chelate
deformations; 688 chelate deformations and ns (PdeO). (TOMPP)-
group: 3061 (CeH from Ar); 1586, 1573, 1560 and 1432 (C]C
from Ar) and ring deformations; 1476 (sh) das (CeH from OeCH3);
1248 (CAreOeC, quasi nas) and das (CeH from Ar, plane); 1178
(CeH from OeCH3); 1165 (CAreOeC, quasi ns); 1134 ds (CeH from
Ar, plane); 1073 (OeCH3) and ring deformations; 1045 (sh) and
799 ring deformations; 850, 732, 728 and 723 (CeH from Ar, off-
plane); 747 (CeH, characteristic for ortho-substituted Ar). (BF4)-
group: 1095, 1055, 1036 (BeF).
d 7.5e6.7 (br, 24H, HAri), 5.16 (s, 1H, H3),
k
The general procedure was followed using 0.41 mL (3.26 mmol)
of BF3$OEt2, 500 mg (1.63 mmol) of Pd(acac)2, 0.34 mL (6.00 mmol)
of benzonitrile, and toluene (40 mL). Yield: 752 mg. The product
contained toluene as adduct (approx. 6%). Anal. Calcd for
d
d
C
22$5H21BF4N2O2Pd: C, 48.62; H, 3.89; N, 5.14. Found: C, 48.06; H,
n
3.71; N, 4.91. In the 1H NMR spectrum of 7 additional signals were
n
detected due to exchange between CD3CN, water impurities in
d
CD3CN, and PhCN. 1H NMR (400.1 MHz, CD3CN, 25 ꢁC):
d
7.80e7.73
d
(m, 2H, HPh2,6), 7.73e7.67 (m, 1H, HPh4), 7.61e7.52 (m, 2H, HPh3,5),
7.31e7.13 (m, 2.5H, CH3C6H5) 5.77 (s, 1H, H3), 2.35 (s, 1.5H,
CH3C6H5), 2.11 (s, 6H, H1,5). 13C{1H} NMR (101 MHz, CD3CN, 25 ꢁC):
n
n
d
187.60 (s, C2,4), 138.90 (s, CPhMe), 134.02 (s, CPh4), 133.16 (s, CPh2
/
n
C
Ph6), 130.27 (s, CPh3/CPh5), 129.90 (s, CPhMe), 129.20 (s, CPhMe),
d
n
126.24 (s, CPhMe), 119.73 (s, CCN), 113.04 (s, CPh1), 102.36 (s, C3), 24.26
n
(s, C1,5), 21.42 (s, CPhMe). IR (nujol, NaCl plates, cmꢀ1): (k2-O,O0-
d
n n
(C$$$O and C$$$C); 1527 (C$$$C and C$$$O); 1361
d
acac)-group: 1575
ds (CeH from CH3); 1276 ns (CeCH3) and chelate deformations; 1172
(CeH from CH) and chelate deformations; 1014 and 930 chelate
deformations and (CeCH3); 943 nas (CeCH3) and chelate de-
formations; 768 (CeH from CH, off-plane); 685 chelate de-
formations and ns (PdeO). (PhCN)-group: 3102 and 3065 (CeH
from Ph); 2298 (C^N); 1597, 1560, 1489 and 1450 (sh) (C]C from
n
d
d
2.3. Reactions of 3 and 4 with pyridine, morpholine and TOMPP
d
n
2.3.1. General procedure
n
n
A solution of [Pd(k2-O,O0-acac)(PhCN)(PR3)]BF4 and L in 15 mL of

D.S. Suslov et al. / Journal of Molecular Structure 1217 (2020) 128425
5
CH2Cl2 was stirred at room temperature for 1 h. The resulting
yellow solution was concentrated to 5 mL under vacuum. Addition
of diethyl ether (20 mL) formed a lemon precipitate over 5 min,
which was collected, washed with diethyl ether (3 ꢂ 15 mL), and
dried under vacuum.
acac)(PPh3)(HNC4H8O)]BF4 (3% in mixture, based on 1H NMR data
and 31P NMR data):
7.9e7.3 (br., overlapping, HAr(S3)/HAr(S2)), 5.53
(s, minor, H3(S3), acac), 5.49 (s, 0.6H, H3(S1), acac), 5.34 (s, 0.4H,
d
H
3(S2), acac), 4.69 (dd, br., overlapping, J ¼ 9.5 Hz, 1.2H, NH in
morpholine), 3.90 (t(d), br., overlapping, J ¼ 11.7 Hz, Ha,
b-CH2 in
Reaction of [Pd(
dine. The general procedure was followed using [Pd (k2-O,O0-
acac)(PhCN)(PPh3)]BF4 (329 mg, 0.50 mmol) and pyridine (40 L,
k
2-O,O′-acac)(PhCN)(PPh3)]BF4 with pyri-
morpholine), 3.74 (d(d), br., overlapping, J ¼ 9.7 Hz, 2.4H, He,
in morpholine), 3.23 (q(d), br., overlapping, J ¼ 11.0, 2.4H, Hа,
in morpholine), 3.02 (d., overlapping, br., J ¼ 12.7 Hz, 2.4H, He,
b
a
a
-CH2
-CH2
-CH2
m
in morpholine), 2.16 (s, H5(S3)), 2.06 (s, H1,5(S1)), 1.71 (s, H1(S3)), 1.52
0.50 mmol). Yield: 287 mg. Anal. Calcd for C28H27BF4NO2PPd: C,
53.07; H, 4.29; N, 2.21. Found: C, 54.42; H, 4.03; N, 2.14. Spinsys-
tem1: [Pd (k2-O,O0-acac)(PPh3)(Py)]BF4 (82% in mixture, based on
(s, H1,5(S2)). 13C{1H} NMR (101 MHz, CDCl3, 25 ꢁC):
2,4(S1)), 186.35 (t, 3J(P,C)
1.7 Hz, C2,4(S2)), 132.28 (t,
J(P,CAr2,6 5.6 Hz, CAr2,6(S2)), 133.20 (s, CAr4(S2)), 128.9 (t,
J(P,CAr3,5) ¼ 5.7 Hz, CAr3,5(S2)), 126.6e125.5 (m, CAr1(S2)), 101.70 (s,
3(S1)), 100.71 (s, C3(S2)), 66.50 (s, -CH2 in morpholine), 49.82(s,
CH2 in morpholine), 26.25 (t, J(P,C) ¼ 5.4 Hz, C1,5(S2)), 26.12 (s,
1,5(S1)). 31P{1H} NMR (162 MHz, CDCl3, 25 ꢁC):
38.15 (s, 0.08P,
d 186.80 (s,
C
¼
1H NMR). 1H NMR (400 MHz, CD3CN, 25 ꢁC):
d 8.42e8.32 (m, 2H,
)
¼
H
Py1,5), 7.81e7.75 (m, 1H, HPy3), 7.67e7.56 (m, 9H, HAr1,3,5),
7.48e7.43 (m, 6H, HAr2,4), 7.24e7.14 (m, 2H, HPy2,4), 5.67 (d, 5J(P,
H1) ¼ 0.5 Hz, 1H, H3), 2.01 (s, 3H, H1), 1.75 (s, 3H, H5). 13C{1H} NMR
C
b
a-
(101 MHz, CD3CN, 25 ꢁC)
d
189.78 (d, 3J (P,C2) ¼ 3.1 Hz, C2), 186.05
C
d
(d, 3J (P,C4) ¼ 0.9 Hz, C4), 153.11 (d, 3J (P,CPy1,5) ¼ 1.1 Hz, CPy1,5),
[Pd(PPh3)n][BF4]2), 35.44 (s, 0.88P, S2), 26.25 (s, 0.04P, S3). No
chemical analyses were completed.
140.89 (s, CPy3), 135.01 (d, 2J(P,CAr2,6) ¼ 10.9 Hz, CAr2,6), 133.18 (d 4
J
Reaction of [Pd(
pyridine.
The general procedure was followed using [Pd(k2-O,O0-
acac)(PhCN)(TOMPP)]BF4 (186 mg, 0.25 mmol), pyridine (20 L,
0.25 mmol), and 20 mL of CH2Cl2. Yield: 147 mg. Anal. Calcd for
k
2-O,O′-acac)(PhCN)(TOMPP)]BF4 with
(P,CAr4) ¼ 3.1 Hz, CAr4), 130.09 (d, 3J (P,CAr3,5) ¼ 11.5 Hz, CAr3,5),
127.39 (s, CPy2,4), 126.67 (d, 1J(P,CAr1) ¼ 55.7 Hz, CAr1), 101.64 (s, C3),
26.90 (d, 4J(P,C1) ¼ 8.1 Hz, C1), 26.20 (d, 4J (P,C5) ¼ 2.6 Hz, C5). 31P
{1H} NMR (162 MHz, CDCl3, 25 ꢁC):
d
26.21 (s). 19F NMR (376 MHz,
m
CDCl3, 25 ꢁC):
20:80 corresponding to the natural abundances of 10B and 11B,
respectively). Spinsystem2: [Pd
k2-O,O0-acac)(Py)2]BF4 (9% in
mixture, based on 1H NMR).1H NMR (400 MHz, CD3CN, 25 ꢁC):
8.50e8.44 (m, 2H), 8.10e8.00 (m, 1H), 7.73e7.69 (m, 2H), 5.72 (s,
1H), 2.06 (s, 6H). 13C{1H} NMR (101 MHz, CD3CN, 25 ꢁC)
188.52 (s,
d
ꢀ152.01, ꢀ152.07 (intensity ratio of approximately
C
31H33BF4NO5PPd: C, 51.44; H, 4.60; N, 1.94. Found: C, 50.36; H,
4.26; N, 1.52. [Pd(k2-O,O0-acac)(TOMPP)(Py)]BF4 (>95% in mixture,
(
based on H NMR). 1H NMR (400 MHz, CDCl3, 25 ꢁC):
d 8.45e8.35
1
(m, 2H, HPy1,5), 7.85e7.70 (m, 1H, HPy3), 7.65e7.30 (m, 6H, HAri),
7.25e7.16 (m, 2H, HPy2,4), 7.15e6.65 (m, 6H, HAri), 5.35 (s, 0.7H, H3),
5.23 (s, 0.3H, H3), 3.77 (s, 0.1H, HOMe) 3.57 (s, 1.3H, HOMe), 3.42 (s,
7.4H, HOMe), 2.23 (s, 0.2H, H1,5), 2.20 (s, 0.2H, H1,5), 2.12 (s, 0.3H,
d
d
C
2,4), 152.68 (s, CPy1,5), 141.61 (s, CPy3), 127.45 (s, CPy2,4), 101.64 (s,
C3), 26.49 (s, C1,5). Spinsystem3: [Pd (k2-O,O0-acac)(PPh3)2]BF4 (9%
H
1,5)), 2.00 (s, 0.6H, H1,5), 1.96 (s, 2.3H, H1), 1.45 (s, 2.3H, H5)$13C{1H}
in mixture, based on H NMR). 1H NMR (400 MHz, CD3CN, 25 ꢁC):
1
NMR (101 MHz, CDCl3, 25 ꢁC)
d
188.33 (d, 3J (P,C2) ¼ 3.2 Hz, C2),
d
7.43e7.39 (m, 15H), 7.35e7.27 (m, 15H), 5.53 (t, 1H), 1.52 (s, 6H).
184.86 (s), 160.36 (d, 2J (P,CAr2) ¼ 2.4 Hz, CAr2, major), 160.11 (d, 2J
13C{1H} NMR (101 MHz, CD3CN, 25 ꢁC):
d
187.44 (s, C2,4), 135.45 (s,
(P,CAr2) ¼ 2.4 Hz, CAr2, minor), 151.60 (d, 3J (P,CPy1,5) ¼ 1.3 Hz, CPy1,5),
C
Ar2,6), 132.99 (s, CAr4), 129.75 (CAr3,4), 101.64 (s, C3), 25.64 (s, C1,5).
139.52 (s, CPy3), 135.86 (br., CAr6), 134.67 (d, 4J(P,CAr4) ¼ 2.0 Hz, CAr4
minor), 133.93 (d, 4J (P,CAr4) ¼ 2.0 Hz, CAr4, major), 126.14 (s, CPy2,3
minor) 125.37 (s, CPy2,3, major), 121.51 (d, 3J(P,CAr5) ¼ 12.3 Hz, CAr5
,
,
,
31P{1H} NMR (162 MHz, CDCl3, 25 ꢁC):
d 34.87 (s).
Reaction of [Pd(k
2-O,O′-acac)(PhCN)(PPh3)]BF4 with TOMPP.
The general procedure was followed using [Pd(k2-O,O0-
acac)(PhCN)(PPh3)]BF4 (239 mg, 0.36 mmol) TOMPP (128 mg,
0.36 mmol), and 10 mL of CH2Cl2. Yield: 300 mg. Chemical analyses
results: C, 52.13; H, 4.13.1H NMR (400 MHz, CDCl3, 25 ꢁC, Spinsys-
tem1 (S1): [Pd(k2-O,O0-acac)(PPh3)(TOMPP)]BF4 (57% in mixture,
based on 1H NMR), Spinsystem2 (S2): [Pd(k2-O,O0-acac)(PPh3)2]BF4
(26% in mixture), Spinsystem3 (S3): [Pd(k2-O,O0-acac)(TOMPP)2]
minor), 121.14 (d, 3J (P,CAr5) ¼ 12.1 Hz, CAr5, major), 113.05 (d, 1J
(P,CAr1) ¼ 66.0 Hz, CAr1), 112.15 (d, 3J (P,CAr3) ¼ 5.1 Hz, CAr3, minor),
111.62 (d, 3J (P,CAr3) ¼ 5.1 Hz, CAr3, major), 100.73 (s, C3), 55.88 (s,
C
OMe, minor), 55.71 (s, COMe, major), 26.96 (d, 4J(P,C1) ¼ 8.5 Hz, C1),
25.79 (d, 4J (P,C5) ¼ 2.6 Hz, C5). 31P{1H} NMR (162 MHz, CDCl3,
25 ꢁC):
d 14.24 (s).
BF4 (17% in mixture)):
0.3H, H3(S2), acac), 5.26 (s, 0.6H, H3(S1), acac), 5.17 (s, 0.2H, H3(S3)
acac), 3.7e3.0 (br., 9H, overlapping, HOMe), 1.51 (s, 3.2H, HMe1 5(S2)
H5(S1)), 1.41 (s, 1.7H, H1(S1)), 1.31 (s, 1.1H, H1,5(S3)), 13C{1H} NMR
(101 MHz, CDCl3, 25 ꢁC):
186.45, 185.31, 160.51, 134.44, 134.38,
134.33, 134.26, 133.77, 132.29, 131.67, 131.65, 129.22, 129.06, 129.00,
128.95, 128.53, 128.53, 128.41, 128.41, 127.67, 127.67, 127.12, 127.12,
126.64, 126.48, 126.48, 126.20, 126.20, 126.19, 125.91, 125.91, 125.75,
120.81, 120.70, 111.68, 100.82, 100.03, 55.48, 26.38, 26.3.31P{1H}
d 7.7e6.5 (br., 27H, overlapping, HAr), 5.42 (s,
,
2.4. Calculations
,
/
All density functional theory calculations were performed with
the ORCA program [71]. All geometry optimizations were run with
tight convergence criteria, using the BP86 functional [72,73],
making use of the resolution of the identity technique [74]. The
applicability of gradient-corrected functionals as BP86 for the
structural prediction of transition metal compounds and reliable
determination of the kinetic balance are well documented [75e80].
The basis sets that were used were the WeigendꢀAhlrichs basis
d
NMR (162 MHz, CDCl3, 25 ꢁC):
d
35.43 (s, 0.27P, S2), 33.9 (br., 0.28P,
S1), 19.5 (br.), 17.4 (br., S3). 19F NMR (376 MHz, CDCl3, 25 ꢁC):
ꢀ154.84e154.89 (intensity ratio of approximately 20:80 corre-
sponding to the natural abundances of 10B and 11B, respectively).
Reaction of [Pd(
2-O,O′-acac)(PhCN)(PPh3)]BF4 with mor-
pholine. The general procedure was followed using [Pd(k2-O,O0-
acac)(PhCN)(PPh3)]BF4 (267 mg, 0.41 mmol), morpholine (35 L,
d
sets [81,82]. Triple-x-quality basis sets with one set of polarization
functions (def2-TZVP) were used for the palladium and phosphorus
in connection with effective core potentials for Pd. The remaining
atoms were described by slightly smaller def2-SVP basis sets.
k
m
0.41 mmol), and 20 mL of CH2Cl2. Yield: 171 mg. Chemical analyses
results: C, 40.22; H, 6.05; N, 4.25.1H NMR (400 MHz, CDCl3, 25 ꢁC,
Spinsystem1 (S1): [Pd(k2-O,O0-acac)(HNC4H8O)2]BF4 (57% in
mixture, based on 1H NMR data), Spinsystem2 (S2): [Pd(k2-O,O0-
acac)(PPh3)2]BF4 (34% in mixture), Spinsystem3 (S3): [Pd(k2-O,O0-
2.5. X-ray diffraction studies
Data were collected on a BRUKER D8 VENTURE PHOTON 100
CMOS diffractometer with MoK
a
radiation (l ¼ 0.71073 Å) using the
f
and scans technique. The structures were solved and refined by
u

6
D.S. Suslov et al. / Journal of Molecular Structure 1217 (2020) 128425
Table 1
X-ray crystallographic data for 2.
CCDC number
Empirical formula
Formula weight/g$molꢀ1
Crystal system
Space group
a/Å
1 971 485
33H35N7PPd
656.96
C
triclinic
P
-1
9.905 (5)
b/Å
11.172 (6)
c/Å
14.534 (8)
85.97(2), 81.51(3), 67.776(17)
1472.2 (13)
2
1.482
0.730
ꢁ
a,
b
,
g/
Volume/Å3
Z
Density (calculated)/g$cmꢀ3
Absorptions coefficient/mmꢀ1
Radiation (
Temperature/K
range/ꢁ
l
/Å)
MoKa (0.71073)
100 (2)
2.24e30.20
2
Q
Crystal size/mm
Crystal habit
0.151 ꢂ 0.136 ꢂ 0.030
colorless, rhombohedral
F (000)
676
Index ranges
ꢀ13 ꢄ h<¼13, ꢀ15 ꢄ k<¼15, ꢀ20 ꢄ l<¼20
Reflections collected
Independent reflections
Number of ref. parameters
56 910
8654 [R (int) ¼ 0.1440]
371
R1/wR2 [I > 2
s
(I)]
0.0334/0.0760
0.0743/0.0836
1.019
R1/wR2 (all data)
Goodness-of-fit on F2
Completeness [%]
99.1
Largest diff. peak and hole/e$Åꢀ3
Weight scheme
0.911/ꢀ0.929
w ¼ 1/[
s
2(F2o)þ(0.0362P)2þ0.0000P]
where P¼(F2oþ2Fc2)/3
direct methods using the SHELX [83]. Data were corrected for ab-
sorption effects using the multi-scan method (SADABS) [84]. All
non-hydrogen atoms were refined anisotropically using SHELX
[83]. The coordinates of the hydrogen atoms were calculated from
geometrical positions.
Crystal data and experimental details are given in Table 1. Se-
lective bond lengths, bond angles and torsion angles are given in
Table S1 (see Supporting Information (SI)).
Table 1 contains CCDC reference number of the supplementary
crystallographic data for this paper. These data can be obtained free
of charge from The Cambridge Crystallographic Data Center via
http://www.ccdc.cam.ac.uk.
the trans- and cis-position, respectively. The signals at 123.18 (CCN),
107.54 (Cipso,Ph), and 136.11 (Cpara,P) ppm is characteristic of the
coordinated benzonitrile ligand [86]. 31P{1H} NMR spectrum of 3
showed a sharp singlet at 28.9 ppm shifted upfield when compared
to the bis-phosphine complex 10 (36.0 ppm) [58] may be because of
less back-donation from palladium to the P-ligand in the case of 10.
For comparison, complex 7 with two benzonitrile ligands was also
obtained. The complex was fully characterized by 1H, 19F and 13C
NMR, and FTIR spectroscopy as well as elemental analysis. The
d
values obtained from 1H and 13C NMR spectra are consistent with
NMR data for 3.
It should be noted that synthetic procedures reported for
preparation of Pd(acac)2$PPh3 by Baba et al. [69] and Childress et al.
[70] were not suitable for synthesis of TOMPP-analogue 2. Longer
reaction times and more polar reaction media (CH2Cl2) were
necessary to obtain complex 2 in 90% yield. The 1H and 13C NMR
spectra, assigned according to reported analogues in the literature
[69,70], confirm the presence of both oxygen- and carbon-bonded
acetylacetonate ligands in 2. In particular, the presence of carbon-
ligated acac was evident from the doublet peaks of methine pro-
ton of acac ligand at 3.74 ppm with 3J (P,H) ¼ 5.6 Hz. The 1H NMR
spectrum of 2 in CDCl3 reveal a 7:2:1 ratio of signals in sets of e.g.
k2-O,O0-acac-methyl resonances at 1.34, 1.51, 1.61 ppm (shielded by
TOMPP aromatic ring current) and at 1.99, 2.03, 2.08 ppm, 2-
methoxy-group resonances at 3.50, 3.35, 3.57 ppm, and reso-
nances at 5.17, 5.23, 5.30 ppm from CH-proton of k2-O,O0-acac
ligand. The 31P NMR spectrum of the palladium complex showed
three phosphorus resonances with the same (7:2:1) ratio of signals.
These results are comparable to that observed for sterically hin-
dered P(o-tolyl)3 complexes as described by Buchwald et al. [87],
Howell et al. [88] and most consistent with hindered rotation of the
PdeP bond in an exo2 conformation of tris(2-methoxyphenyl)
phosphine ligand (“the term exo2 defines the number of proximal
o-methoxy group” [88]). Formally two conformations (exo2 and
exo3) of TOMPP are accessible (Fig. 1a) and have been observed in
3. Results and discussion
3.1. Synthesis and characterization of acetylacetonate palladium (II)
complexes
Following the synthetic routes reported previously by our group
[50,51,58,65,85] five new cationic (acetylacetonate-k
2-O,O′)palla-
dium (II) complexes with P-, N-mixed-ligands (3, 4) and weakly
coordinating N-ligands (6e8) were prepared (Scheme 1).
The reaction of two equivalents of BF3$OEt2 with Pd
(acac)2$PPh3 in the presence of three equivalents of benzonitrile in
benzene gave [Pd(acac)(PhCN)(PPh3)]BF4 with good yields. We
have attempted to carry out synthesis of [Pd(acac)(L)(PPh3)]BF4
(L ¼ MeCN, DMSO) by the same pathway, but the reaction resulted
in oily residues that could not be isolated pure.
The formation of the mixed-ligand complex 3 was evident from
the distinctive proton signal resonances at 2.19 and 1.75 ppm (the
last shielded by phenyl aromatic ring current) from CH3-group of
acac ligand in the 1H NMR spectrum. In addition, the 13C{1H} NMR
spectrum revealed the appearance of diagnostic carbon doublet
peaks of acac ligand (188.58 (d, 3J ¼ 3.5 Hz) and 184.06 (d,
3J ¼ 1.5 Hz) for carbonyl, 25.45 (d, 4J ¼ 8.9 Hz) and 24.35 (d,
4J ¼ 3.6 Hz) for methyl), which were split by the adjacent PPh3 of

D.S. Suslov et al. / Journal of Molecular Structure 1217 (2020) 128425
7
Fig. 1. Possible conformers and rotamers of 2: (a) exo3 and exo2 conformations of the TOMPP ligand, as viewed down the MeP; (b) PdeP bond rotamers of the exo2-TOMPP ligand in
2 relative to the k2-O,O0- and 1-C-acetylacetonate ligands, as viewed down the OePdeP axis. Ligands structures are not shown for clarity.
k
structurally characterized metal complexes [89e92]. However, to
the best of our knowledge exo3-conformation of TOMPP was re-
ported only for the free ligand [93] and for linear gold complex
(TOMPP)AuCl [90]. Thereby, the observed NMR data can be inter-
preted as formation of three unequally populated rotamers of 2 in
CDCl3 at 25 ꢁC (Fig. 1b) which differ in the orientation of the endo-
(2-methoxy)phenyl ring in exo2 conformation of TOMPP relative to
the acac ligands.
The crystal structure of 2 was determined by X-ray diffraction.
Crystals of 2 were grown from CH2Cl2 solution by overlaying with
Et2O. The molecule structure of 2 is reported in Fig. 2. The result
shows a Pd complex with a distorted-square-planar geometry
around Pd defined by C29, P1, O1 and O2; distance are Pd1eO1
2.071 [2] Å, Pd1eO2 2.071 [2] Å, Pd1eP1 2.260 [1] Å, Pd1eC29
2.078 [2] Å; angles are O2Pd1C29 88.42 (7)ꢁ, O1Pd1O2 91.12 (6)ꢁ,
O1Pd1P1 85.29 (5)ꢁ, P1Pd1C29 95.16 (6)ꢁ. The molecule structure
determination of 2 (Fig. 2, Table 1) confirms the exo2 conformation
of the coordinated TOMPP (Figs. 2 and 3).
Reacting 2 with 2 equiv of BF3$OEt2 in toluene in the presence of
three equivalents of benzonitrile at ambient temperature affords a
Fig. 3. The exo2 conformation of the TOMPP in 2. Hydrogen atoms are omitted for
clarity.
yellow solution, from which cationic complex 4 separate in 87%
yield. The 1H, 13C and 31P NMR spectra of 4 showed two sets of
signals of different intensity e.g. for carbons and protons of 2-
methoxy-group, aryl carbons, k2-O,O0-acac-methyl protons sug-
gesting the presence of the two possible isomers of the mixed
cationic complex. The ratio between the different isomers was
calculated from integration signals of 31P NMR spectrum and was
nearly 9:1. Cationic complex 4 furnish the characteristic resonances
in the 13C{1H} NMR spectrum for CO and CH3 groups of the acac
ligand (188.62 (d, 3J ¼ 3.5 Hz) and 184.42 (d, 3J ¼ 1.6 Hz); 25.87 (d,
4J ¼ 9.0 Hz) and 24.83 (d, 4J ¼ 3.9 Hz)), which were split, as in case of
3, by phosphorus atom of TOMPP of the trans- and cis-position,
respectively. Furthermore, by the analogy for 3, 31P{1H} NMR
spectrum of 4 showed a singlet from the major isomer at 11.9 ppm
shifted upfield when compared to the bis-TOMPP complex 9
(17.5 ppm).
Fig. 2. ORTEP plot of 2 with thermal ellipsoids drawn at the 50% probability level.
Hydrogen atoms are omitted for clarity.

8
D.S. Suslov et al. / Journal of Molecular Structure 1217 (2020) 128425
3.2. IR spectroscopy features and DFT studies
2299 cmꢀ1) and [(ShP)Pd(CH3CN)2](BF4)2 (2325 and 2299 cmꢀ1
)
[99] (ShAs e (1-(thiomethyl)-2-(diphenylarsino)ethane; ShP e 1-
(thiomethyl)-2-(diphenylphosphino)ethane). Therefore, it can be
assumed that the formal charge of Pd in the complexes (0; þ1; þ2)
makes minor contribution to the shifts of the bands.
To gain more insight into the structural and vibrational spec-
troscopy features of the cationic species, we performed IR spec-
troscopy studies and DFT calculations for the 3e7. It is well known
that on coordination of nitriles to a metal, the
higher, or to a lower frequencies, depending on the mode of coor-
dination (
1-N-end-on or 2-CN-side-on), the oxidation state and
n
(CN) shift to a
Calculations of structures and infrared spectra of gas-phase
cations for the 3e7 were performed using DFT methods. Within the
limits of the basis set employed, the optimized geometry of cation
of 5 in gas phase was good representation of the structure previ-
ously reported from the crystallographic studies [65] (Table S2, SI).
As expected, for a similar complex, [Pd(acac)(PhCN)2]BF4 (7), the
combination band is absent due to the presence of a heavy phenyl
substituent on nitrile. The IR spectrum exhibits the intense band at
k
h
the charge of a metal atom [94,95]. We earlier reported on the
synthesis and structure of [Pd(acac)(CH3CN)2]BF4 (5) in which two
acetonitrile molecules coordinated (end-on) to Pd(II) in cis-dispo-
sition [65]. It was noted [65] that in the IR spectrum of the complex,
two bands at 2331 and 2302 cme1 are shifted to a higher frequency
in comparison with acetonitrile (2293 and 2254 cme1). One of the
bands is related to the stretching vibration of the C^N bond, while
the second can be attributed to a combination band involving the ds
2298 cmꢀ1
(
DnC≡N ¼ þ69 cmꢀ1 relative to free PhCN: 2229 cmꢀ1
,
liquid film) and a shoulder band at 2280 cmꢀ1, which correspond to
symmetric and antisymmetric stretching vibrations of C^N bonds.
The latter was confirmed by DFT calculations of the IR spectrum for
(CH3) and
(Fig. 4a; А2
n
(С-С). The increased intensity of the combination band
А1 ¼ 0.375) are probably due to Fermi resonance [96]. A
/
[Pd(acac)(PhCN)2]þ (gas phase): ns ¼ 2294 cmꢀ1
,
nas ¼ 2288 cmꢀ1
.
similar phenomenon was observed for neutral Pd(CH3CN)2Cl2
(2334 and 2305 cmꢀ1) [97] and dicationic [Pd(CH3CN)4](BF4)2
(2347 and 2318 cmꢀ1) [98]. Nevertheless, ambiguity still remains in
the assignment of these two bands.
According to the DFT calculations, appearance of the two bands
from symmetric and antisymmetric vibrations of C^N bond is due
to the interaction of C^N and PdeN bonds (similar to the data for 5,
see above).
To resolve this ambiguity the complex [Pd(acac)(CD3CN)2]BF4
(6) was prepared. In the IR spectrum of the complex, the combi-
Again, n(CN) becomes higher on complex formation for 3
(2270 cmꢀ1) and 4 (2281 cmꢀ1), but DnC≡N is decreased as
compared to that of bis-benzonitrile analogue 7. In our opinion,
nation band is absent. In addition, the splitting of
n
(C^N) (2326
and 2322 cme1) was observed. By comparison,
n
(C^N) of free
these n(CN) large shifts for benzonitrile upon coordination to Pd
CD3CN is 2262 cmꢀ1. According to DFT calculations (gas-phase
cation) of the infrared spectrum for [Pd(acac)(CH3CN)2]þ two bands
should be observed in IR spectrum (ns (C^N) ¼ 2338 cmꢀ1 and nas
(C^N) ¼ 2333 cmꢀ1). One can suppose that the appearance of the
two bands from symmetric and antisymmetric vibrations of C^N
bond is due to the interaction of C^N and PdeN bonds. Therefore,
band splitting in 6 can be explained in terms of symmetric
might be caused not only by a change in the electronic structure of
complexes, but also by a more complex interaction, in which the
metal atom also takes part in these vibrations. To gain more
detailed information concerning shifts of n(CN) of benzonitrile to a
higher frequency, DFTcalculations of cis- and trans-Pd(PhCN)2Cl2 as
a model compound were performed and compared with experi-
mental data for trans-Pd(PhCN)2Cl2 (Table S3, SI). Preparation of cis-
Pd(PhCN)2Cl2 was not reported, thus only DFT data was used for
comparison. Trans-Pd(PhCN)2Cl2 was synthesized according to the
literature procedure [97,100]. When comparing the calculated IR
spectra for cis- and trans-isomers of Pd(PhCN)2Cl2, it can be noted
(
ns
¼
2326 cmꢀ1
)
n
and antisymmetric stretching vibrations
(C^N). Thus, 5 symmetric and antisymmetric
(
nas ¼ 2322 cmꢀ1) of
stretching vibrations of C^N bonds appear at 2331 cmꢀ1
(
DnC≡N ¼ þ77 cmꢀ1 with respect to free CH3CN, liquid film), and the
signal at 2302 cmꢀ1 is a combination band.
Surprisingly, the obtained frequencies for
that cis-configurations are characterized by lower n(CN). The same
n
(C^N) in 5 (2331 and
trend was observed for similar platinum complexes, where bands
at 2290 cmꢀ1 and 2285 cmꢀ1 were observed for a mixture of cis-
and trans-isomers [86,97].
2302 cme1) nicely matches to the experimental data reported
previously for neutral Pd(CH3CN)2Cl2 (2334 and 2305 cmꢀ1) [97]
and dicationic complexes [(ShAs)Pd(CH3CN)2](BF4)2 (2327 and
If we consider the atoms located along the axis passing through
Fig. 4. Intensity ratio for
n(C^N) and the combination band (ds(CH3)þ
n(С-С)) for 5(a) and 6(b).

D.S. Suslov et al. / Journal of Molecular Structure 1217 (2020) 128425
9
Fig. 5. Schematic representation of the “diagonal” axis and angles between bonds located along this axis: (a) based on DFT for cis-Pd(PhCN)2Cl2; (b) based on DFT for trans-
Pd(PhCN)2Cl2; (c) based on XRD for trans-Pd(PhCN)2Cl2.
the diagonal of a square with the metal atom in the center (the
“diagonal” axis), then it can be noted that in the calculated cis-
Pd(PhCN)2Cl2 geometry, the ClePdeNeC-CAr atoms deviate from
this axis almost for 15ꢁ after the nitrogen atom (Fig. 5a). In the case
of trans-Pd(PhCN)2Cl2, the CAr-C-N-Pd-N-C-CAr atoms slightly
deviate from the “diagonal” axis both according to the DFT calcu-
lations and the XRD data (Fig. 5b and c). Thus, it can be assumed
that the smaller the deviation (ideally, one-dimensional, all angles
[Pd(acac)(PhCN)(TOMPP)]þ, and [Pd(acac)(PhCN)(PPh3)]þ showed
significant difference in the frequencies of the antisymmetric vi-
brations n(PdeO) (Table 2) by comparing their symmetric vibra-
tions. Probably, the interaction of symmetric and antisymmetric
stretching vibrations of the PdeO bonds and the corresponding
vibrations of the CeN bonds occurs. According to calculations of the
vibration spectrum, symmetric and antisymmetric vibrations
n
(CeN) are accompanied by stretching of the PdeN bond and occur
are 180ꢁ), the stronger
the same axis) are shifted to a higher frequencies.
n(CN) (the vibration bands directed along
along the axes passing through the PdeO bonds.
For 3, 4, 7 a decrease of
[Pd(acac)(PhCN)2]BF4
n
(CN) was observed in the order:
[Pd(acac)(PhCN)(TOMPP)]
3.3. Substitution reactions behavior of 3 and 4 with pyridine,
amines and phosphines
>
BF4 > [Pd(acac)(PhCN)(PPh3)]BF4. When comparing the calculated
structural parameters of the complexes (Table 2), the deviation of
the positions of the OePdeNeC-CAr atoms from the “diagonal” axis
increases in the same sequence. Thus, the observed correlation
between the deviation of the atomic position from this axis (the
main contribution is made by the distortion of the PdeNeC angle)
We also attempted to synthesize the mixed-ligands complexes
[Pd(acac)(PR3)(L)]BF4, where L ¼ Py, NHR2, PR’3, by reacting
[Pd(acac)(PR3)(PhCN)]BF4 with 1 equiv of L in dichloromethane, but
pure enough [Pd(acac)(PR3)(L)]BF4 could not be obtained by this
synthetic route. In the majority of cases mixtures of [Pd(a-
cac)(PR3)(L)]BF4, [Pd(acac)(L)2]BF4, and [Pd(acac)(PR3)2]BF4 were
precipitated from the reaction mixtures. The formation of these
products can be conceived as sequence of ligand substitution re-
actions passing via a target product [Pd(acac)(PR3)(L)]BF4 as pre-
sented in Scheme 2.
and the shift of
dium complexes with coordinated acetonitrile, a similar correlation
should be observed. Information on the frequencies of (CN) and
n(CN) support our working hypothesis. For palla-
n
structural parameters of some dicationic palladium complexes are
presented in Table S4 (SI). As can be seen from Table S4, the shift of
(CN) of the acetonitrile ligand correlates with the deviation of the
n
The reaction of 3 with pyridine in CH2Cl2 affords yellow
atoms position from the “diagonal” axis. It is interesting to note that
the major displacement is observed for [Pd(NCCH3)4][BF4]2, in
which the angles between the CeCePdeCeC atoms are close to
180ꢁ.
It should be noted that DFT calculations for [Pd(acac)(PhCN)2]þ,
Table 2
Calculated structural parameters for complex cations and vibrational frequencies for
[(acac)Pd(PhCN)(L)]BF4.
Bond angle or frequency
L ¼
PhCN
TOMPP
PPh3
ꢁ
DFT, :OePdeN (on the axis),
178,8
176,1
179,9
ns ¼ 2294;
nas ¼ 2288
ns ¼ 684;
nas ¼ 647
2298
178,2
172,5
179,6
2284
178,8
171,1
179,4
2282
DFT, :PdeNeC, ꢁ
ꢁ
DFT, :NeC-СAr
,
DFT, nC≡N, cmꢀ1
DFT, nPdeO, cmꢀ1
ns ¼ 670;
nas ¼ 612
2281
ns ¼ 688
ns ¼ 671;
nas ¼ 615
2270
ns ¼ 682
Experimental, nC≡N, cmꢀ1
Experimental, nPdeO, cmꢀ1
ns ¼ 685
Scheme 2.

10
D.S. Suslov et al. / Journal of Molecular Structure 1217 (2020) 128425
precipitate consisting mainly of [Pd(acac)(PPh3)(Py)]BF4 (82% in
mixture, based on 1H and 31P NMR spectral data). The other two
complexes in precipitate were [Pd(acac)(Py)2]BF4 and [Pd(a-
cac)(PPh3)2]BF4. The ratio between the different complexes (8 and
10) was calculated from integration signals of 1H NMR spectrum
and was nearly 1:1. It should be noted that in order to assign NMR
spectral data more accurately, complex 8 with two pyridine ligands
was also obtained (Scheme 1). The complex was fully characterized
by 1H, 19F and 13C NMR, and FTIR spectroscopy as well as elemental
analysis. The substitution of PhCN and PPh3 in 3 with an aryl-
phosphine ligand, proceeded with a higher degree of conversion as
expected. According to 1H and 31P NMR results, reaction of 3 with
TOMPP gave mixture of [Pd(k2-O,O0-acac)(PPh3)(TOMPP)]BF4 (57%,
based on 1H NMR data), [Pd(k2-O,O0-acac)(PPh3)2]BF4 (26%), and
[Pd(k2-O,O0-acac)(TOMPP)2]BF4 (17%).
Treating 3 with 1 equiv of morpholine in CH2Cl2 affords after
addition of diethyl ether precipitate of [Pd (k2-O,O0-acac)(HN-
C4H8O)2]BF4 (57% in mixture, based on 1H NMR data), but not the
target complex [Pd(k2-O,O0-acac)(PPh3)(HNC4H8O)]BF4 (only 3%).
The other complexes detected in NMR spectra of the obtained
precipitate were [Pd(k2-O,O0-acac)(PPh3)2]BF4 (34%) and
[Pd(PPh3)n][BF4]2 (<3%). In the 1H NMR spectrum of the residue
there are four multiples characterized for eight coordinated mor-
pholine protons attached to carbon (Fig. 6). This is expected since
upon coordination to palladium, one chair conformation of mor-
pholine is fixed. All the chemical shifts and coupling constants for
morpholine and acac ligands are in good agreement with the re-
ported 1H NMR spectrum of [Pd(k2-O,O0-acac)(HNC4H8O)2]BF4 [85].
The formation of the mixture of complexes, mainly [Pd(k2-O,O0-
acac)(HNC4H8O)2]BF4 and 10 was also evident from the 13C{1H}
NMR spectrum revealed the appearance of carbon triplet (split by
the two adjacent PPh3 ligands) and singlet peaks of acac ligand
(186.35 (t, 3J ¼ 1.7 Hz) and 186.80 (s) for carbonyl; 26.25 (t,
4J ¼ 5.4 Hz) and 26.12 (s) for methyl). 31P{1H} NMR spectrum of the
precipitate showed three singlets at 26.3, 35.4, and 38.2 ppm from
[Pd(k2-O,O0-acac)(PPh3)(HNC4H8O)]BF4, 10 and [Pd(PPh3)n][BF4]2,
respectively. The NMR data were assigned to 10, and [Pd(PPh3)n]
[BF4]2 by comparison with literature values [38,58,101]. In our
opinion, formation of dicationic palladium species suggests acac
ligand substitution (although to a small degree) by morpholine
occurred in the systems under study. The obtained results were
surprising. Despite formation of ArPdX(PPh3)(amine) (X e halide)
complexes by substitution of one phosphine ligand by an amine in
trans-ArPdX(PPh3)2 complexes is well-known [102], substitution of
a formally “second” phosphine (in terms of PdeP bond energy) was
not expected. These findings can be rationalized by invoking somþe
sort of ion-pair formation between [Pd(k2-O,O0-acac)(HNC4H8O)2]
and [BF4]e which additionally stabilize formation of the bis-mor-
,
pholine complex instead of [Pd(k2-O,O0-acac)(PPh3)(HNC4H8O)]BF4.
Previously it was shown by DFT calculations [85] that the cation-
anion interactions in [Pd(k2-O,O0-acac)(HNC4H8O)2]BF4 can be
estimated as
hydrogen bonding on the
D
Ee ¼ ꢀ46 kcal/mol in CHCl3 as solvent. The effect of
D
Ee of ion-pairing is marginal and the
interaction with the anion must be electrostatic in nature. These
results establish that in catalytic reactions with cationic palladium
complexes postulated as active species (like diene telomerization
[21,103e105] or hydroamination [21,106e108], where amine is
used in large excess to Pd), the formation of bis-amine complexes
has to be taken into account. It is interesting that if one assumes
that the ligand substitution proceeds according to Scheme 3, the
ratio of substitution constants (K2) can be estimated as: K2
(L ¼ Py):K2 (L ¼ TOMPP):K2 (L ¼ morpholine) z 1:11:18 000.
The reaction of 4 with pyridine in CH2Cl2 affords yellow pre-
cipitate consisting mainly of [Pd(acac)(TOMPP)(Py)]BF4 (>95% in
mixture, based on 1H spectral data). The complex was fully char-
acterized by 1H, 31P and 13C NMR. The palladium complex 4 was
also treated with 1 equiv of morpholine in CH2Cl2. Upon addition of
diethyl ether precipitation of orange powder occurred. In the 1H
NMR spectrum of the orange residue resonances from acetylacet-
onate group were not observed, only multiplets in the range of
2.7e4.1 ppm and 6.4e7.7 were observable, which did not provide
useful information, due to severe line broadening. The same reac-
tion of 4 with 1 equiv of NHEt2 in CH2Cl2 also gave orange pre-
cipitate after treatment with Et2O (1H NMR
d 7.5e6.7 (m), 3.51 (s,
6H), 3.26 (s, 3H), 3.06 (q, J ¼ 7.1 Hz, 4H), 1.28 (t, J ¼ 7.2 Hz, 6H); 13
C
NMR: d 161.88, 160.52, 134.67, 134.54, 133.59, 121.34, 121.21, 112.46,
112.39, 56.17, 55.45, 44.09, 11.66; anal. calcd for C25H31BF4NO3PPd:
C, 48.61; H, 5.06; N, 2.27; found: C, 49.84; H, 5.32; N, 2.04). One can
speculate that the observed NMR data may be due to formation of
bridging amide-type complexes (Scheme 3). Attempted isolation of
these presumably amides as pure compounds were unsuccessful
and further research is needed.
Fig. 6. Fragment of 1H NMR spectrum of reaction products between 3 and 1 equiv of morpholine.

D.S. Suslov et al. / Journal of Molecular Structure 1217 (2020) 128425
11
Scheme 3. A plausible pathway for the reaction of 4 with NHR2 (NHR2 ¼ diethylamine, morpholine, Ar ¼ 2-OMeC6H4).
3.4. Catalysis
Pd(acac)(TOMPP)2]BF4
>
[Pd(acac)(PPh3)(TOMPP)]
> [Pd(acac)(TOMPP)(Py)]
BF4 [Pd(acac)(TOMPP)(PhCN)]BF4
>
Phenylacetylene oligo-/polymerization. Transition metal-
catalyzed polymerization of substituted acetylenes generates
polyenes with p-conjugated backbones, which brings about inter-
BF4 [ [Pd(acac)(Py)2]BF4. This result correlates with the trend
towards a decrease in steric bulkiness of the ligands [115,116] in the
series of catalyst precursors. Unfortunately, no such relation can be
found in the oligomerization of PA.
esting physical properties such as electrical conductivity, photo-
conductivity, nonlinear optical properties, liquid crystallinity, and
gas permeability [14]. Poly (phenylacetylene) (PPA) is produced
mainly from catalyzed reactions of phenylacetylene (PA) by early
and late transition metal complexes driven by metathesis or coor-
dination/insertion polymerization mechanisms [14]. Most of the
late transition metal catalysts for PPAs polymerization are
rhodium- [67,109,110] and palladium-based compounds [14,17].
The cationic palladium complexes 1e10 (Scheme 1) with phos-
phine and nitrogen ligands were screened for their ability to
polymerize PA. These studies were carried out in CH2Cl2 solutions.
As shown in Table 3, the yields and molecular weights of the
polymers largely depended on the nature of the catalyst. In most
cases, low-molecular weight powdery products with relatively
narrow polydispersity indices were obtained. A mixture of cis-
transoidal (up to 87%) and trans-cisoidal isomers was observed as
determined by FT-IR and 1H NMR spectroscopy. Compared with
known Pd(II) catalysts, the catalysts described here showed mod-
erate to high activity. In general complexes 2, 3 and 10 were the
most active, but only cationic pre-catalysts with bulky TOMPP
ligand gave high-molecular weight polyphenylacetylene. Catalysts
with less bulky substituents mostly formed phenylacetylene olig-
omers. Steric bulk of catalyst is a well established property that
promotes chain propagation in polymerization of substituted
acetylenes [18,53,111e114]. The order of catalytic activity of cationic
complexes in polymerization of PA may be arranged as follows:
Norbornene polymerization. Norbornene (NB) and its de-
rivatives are representative cyclic olefin monomers which can be
polymerized according to three different schemes: metathesis,
addition and isomerization mechanisms. Palladium based catalysts
usually polymerize norbornene via a vinyl addition mechanism.
Vinyl polynorbornene (PNB) has received considerable attention
owing to its optical, dielectric and mechanical properties for tech-
nical application [1,3,4]. In contrast to PA polymerization results,
excess amounts of co-catalyst, BF3$OEt2, are required to obtain high
catalyst activity of cationic palladium complexes 1e10 in the
polymerization of NB. The catalytic performance of 1e5, 7, and 8 in
the polymerization of norbornene in the presence of 20e50 eq
BF3,OEt2 displayed good yields and high activities in the order of
106e107 gPNB mol Pꢀd1 hꢀ1 (Table 4). Obtained PNBs were insoluble in
1,2,4-trichlorobenzene at room temperatures. The structures of the
Pd(II) complexes highly affected catalyst activity. The catalyst sys-
tem activity (gPNB$(molPd$h)ꢀ1
)
ranged between 8.3$104 and
2.0$107, with the highest activity observed for 8 (Table 4). The order
of catalytic activity may be arranged as follows: [Pd (acac)(Py)2]
BF4
>
[Pd(acac)(TOMPP)(Py)]BF4
>
Pd(acac)2,PPh3>
Pd(acac)2,TOMPP > [Pd(acac)(PPh3)(PhCN)]BF4 z [Pd (acac)(-
TOMPP)(PhCN)]BF4 > [Pd(acac)(PhCN)2]BF4> [Pd(acac)(PPh3)(Py)]
BF4 [ [Pd(acac)(PPh3)2]BF4 z [Pd(acac)(TOMPP)2]BF4. Concerning
the productivity, bis-phosphine complexes 9, 10, and [Pd(a-
cac)(TOMPP)(PPh3)]BF4 render the less productive catalysts,
Table 3
Oligo-/polymerization of PA with Pd catalysts.
Entry[a]
Complex
Yield (%)
TON[b]
Activity[c]
Cis[d] (%)
polymer
oligomer
Mw (/103)[e]
Mw/M[ne]
Mw (/103)[e]
Mw/M[ne]
1
2
3
4
5
6
7
8
[Pd(acac)(PhCN)2]BF4
[Pd(acac)(Py)2]BF4
Pd(acac)2,PPh3
30.7
2.6
77
7
46
142
48
328
30
77
87
15.9 (2%)[f]
1.1
1.1
e
2.0
5.0
0.9
0.9
0.8
0.8
0.7
1.2
0.9
1.4
0.8
1.8
1.81
1.4
1.3
1.3
1.4
1.4
1.2
1.5
1.1
1.5
28.4 (44%)[f]
18.1
56.5
18.9
16.9
73.5
73.6
23.4
15.9
97.0
196
604
204
183
782
782
251
170
1033
<40
<40
<40
<40
80
<40
82
70
e
[Pd(acac)(PPh3)(PhCN)]BF4
[Pd(acac)(PPh3)(Py)]BF4[g]
[Pd(acac)(PPh3)2]BF4
e
e
e
e
43
e
e
[Pd(acac)(PPh3)(TOMPP)]BF4[g]
Pd(acac)2,TOMPP
184
184
59
38
243
13.4 (32%)[f]
e
1.7
e
9
10
11
[Pd(acac)(TOMPP)(PhCN)]BF4
[Pd(acac)(TOMPP)(Py)]BF4[g]
[Pd(acac)(TOMPP)2]BF4
15.0 (32%)[f]
24.7 (36%)[f]
15.1 (81%)[f]
1.8
1.1
1.8
74
[a] Reaction conditions: 0.4 mol% of Pd, [PA]0/[Pd]0 ¼ 250, nPd ¼ 36.4
m
mol, VPA ¼ 1.0 mL, Vsolvent ¼ 1.0 mL, t ¼ 25 ꢁC, reaction time e 24 h, solvent e dichloromethane.[b] In units
of (mol of PA) (mol of Pd)ꢀ1 [c] In units of (g of polymer) (mol of Pd)ꢀ1 hꢀ1 [d] The percentages of cis sequences determined as prescribed in Ref. [68].[e] Estimated by GPC in THF
.
.
(polystyrene standard).[f] Polymer/oligomer peak-area ratio, as determined by GPC. The other part corresponded to low-molecular-weight oligomers.[g] The precipitate was
used as a catalyst with a predominant content of the complex.

12
D.S. Suslov et al. / Journal of Molecular Structure 1217 (2020) 128425
Table 4
Polymerization of NB with Pd catalysts, activated with boron trifluoride etherate.
Entry[a]
Complex
[NB]0/[Pd]0
[B]0/[Pd]0
t
(min)
Yield (%)
TON[b]
Activity[c]
1
2
3
4
5
6
7
8
[Pd(acac)(PhCN)2]BF4
”
15 000
30 000
75 000
15 000
30 000
75 000
75 000
15 000
30 000
75 000
15 000
30 000
75 000
15 000
30 000
75 000
15 000
15 000
75 000
30 000
75 000
30 000
75 000
75 000
15 000
20
20
50
20
20
50
50
20
20
50
20
20
50
20
20
50
20
20
50
20
50
20
50
50
20
30
30
30
30
30
5
99.9
99.9
13.0
99.9
99.9
24.1
24.7
99.9
99.9
30.2
99.9
95.3
19.4
53.7
52.1
6.7
15 000
30 000
9750
2.8$106
5.6$106
1.8$106
2.8$106
5.6$106
2.0$107
3.5$106
2.8$106
5.6$106
4.3$106
2.8$106
5.4$106
2.7$106
1.5$106
2.9$106
9.5$105
8.3$104
6.5$104
3.6$106
4.1$106
2.8$106
5.6$106
1.5$107
4.4$106
8.3$104
”
[Pd(acac)(Py)2]BF4
”
15 000
30 000
18 080
18 530
15 000
30 000
22 650
15 000
28 590
14 550
8060
”
”
30
30
30
30
30
30
30
30
30
30
60
60
30
30
30
30
5
Pd(acac)2,PPh3
”
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
”
[Pd(acac)(PPh3)(PhCN)]BF4
”
”
[Pd(acac)(PPh3)(Py)]BF4[d]
”
15 630
5030
890
”
[Pd(acac)(PPh3)2]BF4
8.5
4.6
[Pd(acac)(PPh3)(TOMPP)]BF4[d]
690
Pd(acac)2,TOMPP
[Pd(acac)(TOMPP)(PhCN)]BF4
25.4
73.1
20.1
99.9
17.2
31.2
5.9
19 050
21 930
15 080
30 000
12 860
23 400
890
”
[Pd(acac)(TOMPP)(Py)]BF4[d]
”
”
30
60
[Pd(acac)(TOMPP)2]BF4
[a]
Reaction conditions: {1.3,10ꢀ3, 3.3,10ꢀ3, or 6.6,10ꢀ3} mol% of Pd, nPd ¼ {0.3269, 0.8173, or 1.6346}
m
mol, nNB ¼ 24.5 mmol, V0 ¼ 3.7 mL, t ¼ 23 ꢁC, solvent e dichlor-
omethane.[b] In units of (mol of NB) (mol of Pd)ꢀ1 [c] In units of (g of polymer) (mol of Pd)ꢀ1 hꢀ1 [d]
. The precipitate was used as a catalyst with a predominant content of the
.
complex.
exhibiting a TON of only 890 and 690, respectively (Table 4, entries
17, 18, and 25). By contrast, mono-phosphine or solvent-stabilized
complexes 1e4, and 7, 8 are the most productive catalysts of the
series (TON up to 30 000). It seems difficult to find a trend con-
cerning the properties of ligands and the productivity/activity of
the catalyst as complexes with PPh3, TOMPP, PhCN, Py as ligands,
which are electronically and sterically different, give the most
promising results. It should be noted that such relationships can be
attributed not only to influence of electronic or steric properties of
phosphines but also to a differences in reactivity of these phos-
phines with BF3$OEt2 if they dissociate. Previous work has shown
that upon borane activation phosphine ligands can be lost to give a
“naked” Pd as the active species [117]. Hence, more weakly bound
ligands which can be removed faster will lead more quickly to the
active palladium “naked” species [118].
complexes as catalyst in the oligo-/polymerization of phenyl-
acetylene showed that only cationic pre-catalysts with bulky
TOMPP ligand gave high-molecular weight polyphenylacetylene
with high to moderate activities. When activated with BF3,OEt2,
these palladium complexes can also be used as catalysts for the
vinyl addition polymerization of norbornene with activities
104e107 gpolymer molPd hꢀ1
.
CRediT authorship contribution statement
D.S. Suslov: Conceptualization, Investigation, Writing - original
draft, Writing - review & editing. M.V. Bykov: Conceptualization,
Investigation, Writing - review & editing. M.V. Pakhomova:
Investigation. Z.D. Abramov: Investigation. G.V. Ratovskii: Inves-
tigation, Writing - review & editing. I.A. Ushakov: Investigation,
Writing - review & editing. T.N. Borodina: Investigation, Writing -
review & editing. V.I. Smirnov: Investigation, Writing - review &
editing. V.S. Tkach: Supervision.
4. Conclusions
Cationic palladium complexes Pd(acac)(PR3)(PhCN)][BF4] and
[Pd(acac)(S)2][BF4]
(R
¼
phenyl,
2-methoxyphenyl;
S ¼ benzonitrile, pyridine, CD3CN) were prepared in good yields by
the reaction of Pd (acac)2 or Pd(acac)2$PR3 with 2 equiv. of BF3$OEt2
in the presence of appropriate ligands (S). DFT study was performed
to obtain insights on structural and vibrational spectroscopy fea-
tures of the cationic species. Computed FTIR spectra agree with the
Acknowledgments
This work was supported by the Government Assignment for
Scientific Research from the Ministry of Science and Higher Edu-
cation of the Russian Federation (FZZE-2020-0022). Marina V.
Pakhomova acknowledges Ministry of Science and Higher Educa-
tion of the Russian Federation for scholarship (Ord. No. 231 of April
3, 2018). Igor A. Ushakov acknowledges financial support of INRTU
(grant 04-fpk-19) e registration and interpretation of NMR spectra.
The studies were carried out using the equipment of the Baikal
Analytical Center of Collective Use SB RAS (http://ckp-rf.ru/ckp/
3050/) as well as the equipment of the Center for Collective Use
of Analytical Equipment of the Irkutsk State University (http://ckp-
rf.ru/ckp/3264/).
corresponding experimental data, the correlation between
the
1-nitrile ligands and calculated geometrical features of the
complexes was proposed. An X-ray diffraction and NMR results for
Pd(k2-O,O0-acac)( 1-C-acac)(TOMPP) establish formation of three
unequally populated rotamers of Pd(k2-O,O0-acac)( 1-C-acac)(-
n(CN) of
k
k
k
TOMPP) in CDCl3 at 25 ꢁC which differ in the orientation of the
endo-(2-methoxy)phenyl ring in exo2 conformation of TOMPP
relative to the acac ligands. The reaction of [Pd(acac)(PR3)(PhCN)]
BF4 with L (L ¼ pyridine, morpholine, TOMPP) in the majority of
cases gave mixtures of [Pd(acac)(PR3)(L)]BF4, [Pd(acac)(L)2]BF4, and
[Pd(acac)(PR3)2]BF4. The tests of the synthesized palladium (II)

D.S. Suslov et al. / Journal of Molecular Structure 1217 (2020) 128425
13
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Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.molstruc.2020.128425.
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