Synthesis and characterisation of κ1-P and κ2-P,N palladium(II) complexes of the open cage water soluble aminophosphine PTN

Article abstract of DOI:10.1016/j.ica.2008.01.051

New palladium(II) complexes containing the water soluble aminophosphine PTN ligand (PTN = 7-phospha-3,7-dimethyl-1,3,5-triazabicyclo[3.3.1]nonane) in 1:1 and 1:2 ratio Pd/PTN ligand, respectively, were prepared and fully characterised by mono and bidimens

Full text of DOI:10.1016/j.ica.2008.01.051

Inorganica Chimica Acta 361 (2008) 3017–3023
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Inorganica Chimica Acta
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Synthesis and characterisation of j1-P and j2-P,N palladium(II) complexes
of the open cage water soluble aminophosphine PTN
Maria Caporali, Claudio Bianchini, Sandra Bolaño, Sylvain S. Bosquain, Luca Gonsalvi, Werner Oberhauser,
*
Andrea Rossin, Maurizio Peruzzini
Istituto di Chimica del Composti Organometallici, Consiglio Nazionale delle Ricerche (ICCOM-CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino (Firenze), Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
New palladium(II) complexes containing the water soluble aminophosphine PTN ligand (PTN = 7-phos-
pha-3,7-dimethyl-1,3,5-triazabicyclo[3.3.1]nonane) in 1:1 and 1:2 ratio Pd/PTN ligand, respectively, were
prepared and fully characterised by mono and bidimensional 31P, 1H and 13C NMR techniques showing
that PTN can adopt both j1-P and j2-P,N coordination modes. The complexes with Pd/PTN ratio 1:2 are
highly soluble in water at room temperature. Suitable crystals for X-ray structure determination were
obtained for the neutral complex j2-P,N-Pd(PTN)(OAc)2 (1) and for the monocationic complex [Pd(j2-
P,N-PTN)(j1-P-PTN)Cl][PF6] (5).
Received 23 October 2007
Accepted 11 January 2008
Available online 11 April 2008
Dedicated to Professor Robert J. Angelici in
recognition of his outstanding and creative
contributions to many important areas of
organometallic and coordination chemistry.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
Water soluble ligands
Palladium(II) complexes
Aminophosphines
PTN
X-ray crystallography
1. Introduction
Examples of coordination compounds bearing Ph– and Me–P
substituted PTNs include Au and Mo complexes either in mono-
Ligand design for homogeneous catalysts has progressed in the
last few years from bidentate diphosphines and diamines to mixed
donor atom moieties, such as phosphino ethers, phosphino thio-
ethers and, particularly, aminophosphines [1] and the correspond-
ing complexes were used in hydroformylation, hydrogenation,
hydrosilylation and allylic alkylation reactions [2–5]. Pd(II) com-
plexes have found extensive application as catalysts for olefin-CO
copolymerisation [6], C–C coupling reactions [7], etc., also bearing
P,N bidentate or hemilabile ligands.
or bidentate coordination mode, such as [AuCl{j1-P-PTN(R)}],
[AuCl{j1-P-PTN(Me)}2], [AuMe2{j2-P,N-PTN(Me)}][AuCl4] and
[Mo(CO)4{j2-P,N-PTN(R)}] (R = Me, Ph) reported by Schmidbaur
and co-workers [13].
More recently, we have reported the synthesis, spectroscopic
and X-ray crystal structural data for Rh(COD) complexes bearing
PTN, both as monodentate and chelate ligand [14], and their use
as catalysts for olefin hydroformylation in organic and biphasic or-
ganic/water solvent systems.
Among aminophosphine ligands, the neutral water-soluble
phosphine 1-phospha-3,5,7-triazaadamantane (PTA) [8] was suc-
cessfully used as monodentate ligand for transition metal com-
plexes able to bring about many catalysed processes such as
regioselective hydrogenations [9] and hydroformylation [10] of
olefins in aqueous media. The open cage aminophosphine 7-phos-
pha-3,7-dimethyl-1,3,5-triazabicyclo[3.3.1]nonane (PTN) [11] can
be considered as the P,N-bidentate analogue of PTA, and it was
demonstrated that both j1-P and j2-P,N coordination modes are
possible, both in solution and the solid state [12].
Hereby results on the synthesis, characterisation and solid state
structural determination of novel Pd(II)–PTN complexes are pre-
sented. The PTN ligand can adopt both coordination modes, mainly
depending on the choice of the metal precursor and reaction con-
ditions. X-ray crystal structures of [Pd(j2-P,N-PTN)(OAc)2] and
[Pd(j2-P,N-PTN)(j1-P-PTN)Cl](PF6) are reported and discussed.
2. Experimental
2.1. General procedures, methods and materials
All syntheses have been performed under a dry nitrogen atmo-
sphere applying standard Schlenk techniques. Solvents have been
* Corresponding author.
E-mail address: mperuzzini@iccom.cnr.it (M. Peruzzini).
0020-1693/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2008.01.051

3018
M. Caporali et al. / Inorganica Chimica Acta 361 (2008) 3017–3023
1
3
purified by distillation over suitable drying agents and degassed
prior to use. 7-Phospha-3,7-dimethyl-1,3,5-triazabicyclo[3.3.1]-
nonane PTN [11,13], NaBArF4 (ArF = 3,5-bis(trifluoromethyl)phenyl)
[15] and PdClMe(cod) (COD = 1,5-cyclooctadiene) [16] were pre-
pared according to the literature methods. All other reagents (tech-
nical grade) were used as purchased from Aldrich or Fluka, unless
otherwise stated. Deuterated solvents for routine NMR measure-
ments were dried over activated molecular sieves. 1H, 13C{1H},
31P{1H} NMR spectra were obtained on a Bruker Avance DRX-300
spectrometer (300.13, 75.47 and 121.49 MHz, respectively). Chem-
icals shifts (d) are reported in ppm relative to TMS, referenced to
the chemical shifts of residual solvent resonances (1H and
(d, JCP = 19.7 Hz, P-CHH0-N), 70.70 (d, JCP = 10.2 Hz, N-CHH0-
NCH3), 78.30 (d, JCP = 3.2 Hz, N-CHH0-N). 31P{1H} NMR (CD2Cl2,
25 °C): d ꢀ37.00 (s).
3
2.4. Synthesis of ½Pdðj2-P; N-PTNÞðMeÞðCH3CNÞꢁðBArF4Þð3Þ
To a degassed solution of 2 (50.0 mg, 0.152 mmol) in a CH2Cl2-
CH3CN solvent mixture (25:1, 8.0 ml) was added NaBAr4F
(141.0 mg, 0.159 mmol). The reaction mixture was allowed to stir
for 1.5 h, then the suspension was filtered through celite and the
resulting clear solution was concentrated to half of its original vol-
ume. On addition of diethyl ether (10 ml) an off-white product pre-
cipitated, which was filtered off, washed with cold diethyl ether
(2 ꢂ 5 ml) and dried in a stream of nitrogen. Yield 65%. Anal. Calc.
for C42H34N4BF24PPd: C, 42.07; H, 2.85; N, 4.67. Found: C, 42.12; H,
2.90; N, 4.57%. IR (KBr): m(CN) 2292, 2319 cmꢀ1 (w). 1H NMR
13C{1H}NMR) or 85% H3PO4 31P{1H} NMR). Elemental analyses
(
were performed using a Carlo Erba Model 1106 elemental analyzer
at the University of Florence. Infrared spectra were recorded on a
FT-IR Perkin–Elmer Spectrum BX instrument. Electrospray mass
spectrometry measurements have been carried out at the Univer-
sity of Pisa, Italy, on an Applied Biosystems Sciex API 4000 triple
quadrupole mass spectrometer (Sciex Co, Concord, Ontario, Can-
ada) equipped with a Turbo-V Ionspray interface, coupled to a Per-
kin–Elmer Series 200 Micro dual solvent delivery system and a
Perkin–Elmer Series 200 autosampler (Perkin–Elmer, Waltham,
MA, USA). The analyses were performed in flow injection mode
at 200 ll/min (mobile phase: water/acetonitrile 1:1 containing
0.1% formic acid).
3
(CD2Cl2, 25 °C): d 0.40 (d, JHP = 2.3 Hz, 3H, Pd–CH3), 1.30 (d,
2JHP = 11.6 Hz, 3H, P-CH3), 2.26 (s, 3H, CH3CN), 2.30 (s, 3H, N-
CH3), 3.70 (m, 2H, P-CHH0-N), 3.76 (m, 2H, N-CHH0-NCH3), 3.89
2
(m, 2H, P-CHH0-N), 3.90 (d, JHH= 13.0 Hz, 1H, N-CHH0-N), 4.00 (d,
2JHH = 13.0 Hz, 1H, N-CHH0-N), 4.29 (d, JHH = 11.2 Hz, 2H, N-
2
CHH0-NCH3), 7.54 (br s, 4H, Ar-Hp), 7.70 (br s, 8H, Ar-Ho). 13C{1H}
NMR (CD2Cl2, 25 °C): d ꢀ6.20 (s, Pd–CH3), 2.85 (s, CH3-CN), 5.20
1
1
(d, JCP = 25.5 HZ, P-CH3), 46.00 (s, N-CH3), 51.10 (d, JCP = 21.7 Hz,
3
3
P-CHH0-N), 70.30 (d, JCP = 10.7 Hz, N-CHH0-NCH3), 78.50 (d, JCP
=
3.6 Hz, N-CHH0-N), 117.50 (s, Ar-Cp), 119.20 (s, CN), 124.60 (q,
1JCF = 272.5 Hz, CF3), 128.90 (q, JCF = 30.7 Hz, C-CF3), 134.80 (s,
2
2.2. Synthesis of [Pd(j2-P,N-PTN)(OAc)2] (1)
Ar-Co), 161.80 (non-binomial q, JCB = 49.8 Hz, Ar-Ci). 31P{1H}
1
NMR (CD2Cl2, 25 °C): d ꢀ35.00 (s).
A solution of PTN (31.50 mg, 0.181 mmol) in dichloromethane
(10 ml) was added to a degassed solution of Pd(OAc)2 (40.0 mg,
0.178 mmol) in dichloromethane (12.0 ml) under stirring at room
temperature. After 20 min, diethyl ether (6.0 ml) was added to
the solution and a brown precipitate was obtained, which was then
filtered under nitrogen. The product was finally dried in a stream of
nitrogen. Yield 65%. Anal. Calc. for C11H22N3O4PPd: C, 33.24; H,
5.53; N, 10.56. Found: C, 33.00; H, 5.47; N, 10.47%. 1H NMR (CD2Cl2,
2.5. Synthesis of trans-[Pd(j1-P-PTN)2Cl2] (4)
To a degassed solution of Pd(cod)Cl2 (145.0 mg, 0.510 mmol) in
dichloromethane (40 ml) was added PTN (180.0 mg, 1.040 mmol)
and the resulting reaction mixture was allowed to stir for 1 h at
room temperature. The volume of the solution was then reduced
to 7 ml under nitrogen stream and diethyl ether (10 ml) was
added. The solid product obtained was filtered off, washed with
diethyl ether and dried in a stream of nitrogen, obtaining a yellow
microcrystalline compound. Yield 79%. Anal. Calc. for
2
25 °C): d 1.30 (d, JHP = 13.5 Hz, 3H, P-CH3), 1.80 (s, 3H, CH3-COO),
1.90 (s, 3H, CH3-COO), 2.34 (s, 3H, N-CH3), 3.50 (dd, 2JHH = 15.2 Hz,
2
2JHP = 8.6 Hz, 2H, P-CHH0-N), 3.70 (d, JHH = 12.5 Hz, 2H, N-CHH0-
2
2
NCH3), 3.88 (d, JHH = 13.8 Hz, 1H, N-CHH0-N), 3.98 (d, JHH
=
2
13.8 Hz, 1H, NCHH0-N), 4.14 (d, JHH = 15.2 Hz, 2H, P-CHH0-N),
C
14H32Cl2N6P2Pd: C, 32.12; H, 6.11; N, 16.05. Found: C, 32.10; H,
4.70 (d, JHH = 12.5 Hz, 2H, N-CHH0-NCH3). 13C{1H} NMR (CD2Cl2,
2
6.01; N, 15.98%. 1H NMR (CD2Cl2, 25 °C): d 1.20 (pseudo t,
2JHP+4JHP = 2.2 Hz, 6H, P-CH3), 2.30 (s, 6H, N-CH3), 3.20
1
25 °C): d 3.60 (d, JCP = 25.7 Hz, P-CH3), 22.0 (s, CH3-COO), 23.5 (s,
1
CH3-COO), 45.4 (s, N-CH3), 50.10 (d, JCP = 22.8 Hz, P-CHH0-N),
2
2
(d, JHH = 14.2 Hz, 4H, N-CHH0-NCH3), 3.54 (d, JHH = 10.8 Hz, 4H,
3
3
70.00 (d, JCP = 9.5 Hz, N-CHH0-NCH3), 79.90 (d, JCP = 5.6 Hz, N-
CHH0-N), 176.80 (s, COO), 177.20 (s, COO). 31P{1H} NMR (CD2Cl2,
25 °C): d ꢀ41.60 (s).
2
P-CHH0-N), 3.82 (d, JHH = 13.5 Hz, 2H, N-CHH0-N), 3.94 (d,
2JHH = 13.5 Hz, 2H, N-CHH0-N), 3.97 (d, JHH = 10.8 Hz, 4H, P-CHH0-
2
N), 4.50 (d, JHH = 14.2 Hz, 4H, N-CHH0-NCH3). 1H NMR (D2O,
2
2
4
25 °C): d 1.54 (dd, JHP = 11.0 Hz, JHP = 2.1 HZ, 6H, P-CH3), 2.37 (s,
2
6H, N-CH3), 3.72 (d, JHH = 11.3 Hz, 4H, P-CHH0-N), 3.80 (d,
2.3. Synthesis of [Pd(j2-P,N-PTN)(Me)Cl] (2)
2JHH = 15.0 Hz, 4H, N-CHH0-NCH3), 3.98 (AB, JHH = 14.9 Hz, 4H,
2
2
N-CHH0-N), 4.14 (AB, d, JHH= 15.0 Hz, 4H, N-CHH0-NCH3), 4.16 (d,
To a degassed solution of PdClMe(cod) (80.0 mg, 0.307 mmol) in
dichloromethane (7.0 ml) was added dropwise a solution of PTN
(54.0 mg, 0.316 mmol) in dichloromethane (7 ml) over 10 min.
The reaction mixture was allowed to stir for 40 min and then
evacuated to dryness. The off-white product was re-crystallised
from dichloromethane and n-pentane. Yield 80%. Anal. Calc. for
C8H19ClN3PPd: C, 29.12; H, 5.76; N, 12.73. Found: C, 29.00; H,
2JHH = 11.3 Hz, 4H, P-CHH0-N). 13C{1H} NMR (CD2Cl2, 25 °C): d
1
15.30 (t, JCP = 7.8 HZ, P-CH3), 38.70 (s, N-CH3), 49.90 (t,
1JCP+3JCP = 12.5 Hz, P-CHH0-N), 70.50 (t, JCP = 7.8 Hz, N-CHH0-
3
NCH3), 75.80 (s, N-CHH0-N). 13C{1H} NMR (D2O, 25 °C): d 12.05
1
1
(d, JCP = 20.2 Hz, P-CH3), 42.4 (s, N-CH3), 51.50 (d, JCP = 23.3 Hz,
3
P-CHH0-N), 68.10 (d, JCP = 11.1 Hz, N-CHH0-NCH3), 75.82 (s, N-
CHH0-N). 31P{1H} NMR (CD2Cl2, 25 °C): d ꢀ49.00 (s). 31P{1H}
NMR (D2O, 25 °C): d ꢀ31.20 (s). ESI-MS: m/z 489 (M+- Cl), 454
(M+ꢀ2Cl).
3
5.70; N, 12.69%. 1H NMR (CD2Cl2, 25 °C): d 0.50 (d, JHP = 3.4 Hz,
2
3H, Pd–CH3), 1.20 (d, JHP = 10.8 Hz, 3H, P-CH3), 2.40 (s, 3H, N-
2
4
CH3) 3.60 (dd, JHH = 12.5 Hz, JHP = 2.0 Hz, 2H, N-CHH0-NCH3),
2
2
3.67 (d, JHH = 9.2 Hz, 2H, P-CHH0-N) 3.88 (br d, JHH = 13.4 Hz,
2
1H, N-CHH0-N), 3.95 (d, JHH = 9.2 Hz, 2H, P-CHH0-N), 3.99 (d,
2.6. Synthesis of [Pd(j2-P,N-PTN)(j1-P-PTN)Cl](PF6) (5)
2JHH = 13.4 Hz, 1H, N-CHH0-N), 4.35 (dd, JHH = 12.5 Hz, JHP
=
2
4
2.0 Hz, 2H, N-CHH0-NCH3). 13C{1H} NMR (CD2Cl2, 25 °C): d ꢀ7.70
To a degassed solution of 4 (90.0 mg, 0.172 mmol) in dichloro-
methane (20 ml) was added AgPF6 (90.0 mg, 0.205 mmol). The
1
(s, Pd–CH3), 5.50 (d, JCP = 22.7 Hz, P-CH3), 46.30 (s, N-CH3), 52.10

M. Caporali et al. / Inorganica Chimica Acta 361 (2008) 3017–3023
3019
resulting suspension was allowed to stir in a aluminium foil-cov-
2.9. X-ray crystal structure determinations
ered Schlenk tube at room temperature for 1 h. Afterwards, the
suspension was filtered through celite and the clear solution was
concentrated to half of its original volume. Diethyl ether (15 ml)
was added, precipitating a pale yellow semi-crystalline compound,
which was filtered off, washed with additional diethyl ether
(10 ml) and dried under vacuum. Yield 63%. Anal. Calc. for
Single crystals of 1 and 5 were obtained upon slow evaporation
of the corresponding CH2Cl2 solutions at room temperature.
Diffraction data were collected at room temperature on an Enraf
Nonius CAD4 automatic diffractometer with Mo Ka radiation
(k = 0.71073 Å) and graphite monochromator. Unit cell parameters
were determined from least-squares refinement of the setting an-
gles of 25 carefully centred reflections. Crystal data and data col-
lection details are reported in Table 1. Atomic scattering factors
were taken from crystallographic tables [17]. The structures were
solved by direct methods and refined by full-matrix F2 refinement.
All non-hydrogen atoms were refined anisotropically, while hydro-
gen atoms were introduced in their calculated positions, with ther-
mal parameters 20% larger than those of the adjacent carbon
atoms. All the calculations were performed on a PC using the WINGX
package [18] with SIR-97 [19], SHELX-97 [20] and ORTEP-3 programs
[21] (see Scheme 1).
C
14H32ClF6N6P3Pd: C, 26.57; H, 5.06; N, 13.27. Found: C, 26.47; H,
4.99; N, 13.24%. 1H NMR (CD3COCD3, 25 °C): d 1.60 (br s, 3H, P-
CH3), 1.80 (br s, 3H, P-CH3), 2.40 (br s, 3H, N-CH3) 2.60 (br s, 3H,
N-CH3), 3.67–4.50 (m, 20H, P-CHH0-NCH3 + P-CHH0-NCH3 +
N-CHH0-NCH3 + N-CHH0-NCH3 + N-CHH0-N + N-CHH0-N).
13C{1H}
NMR (CD3COCD3, 25 °C): d 7.40 (br s, P-CH3), 16.90 (br s, P-CH3),
38.10 (br s, N-CH3), 46.40 (br s, N-CH3), 50.90 (br s, P-CHH0-N),
54.30 (br s, P-CHH0-N), 68.60 (br s, N-CHH0-NCH3), 69.30 (br s, N-
CHH0-NCH3), 78.40 (br s, N-CHH0-N). 31P{1H} NMR (CD3COCD3,
25 °C): d ꢀ25.00 (br s, P (trans N)), ꢀ45.60 (br s, P (trans Cl)),
1
ꢀ144.3 (sept, JPF = 708 Hz, PF6).
2.7. Synthesis of trans-[Pd(j1-P-PTN)2(Me)Cl] (6)
3. Results and discussion
3.1. Synthesis and characterisation of Pd–PTN complexes
To a degassed solution of PdClMe(cod) (161.4 mg, 0.610 mmol)
in dichloromethane (15 ml) was added
a solution of PTN
Novel palladium(II) complexes containing the water soluble
PTN ligand were prepared by reaction of the Pd(OAc)2, Pd(cod)Cl2
and PdMe(cod)Cl with either an equimolar amount of PTN (Scheme
2) or with 2 equiv. (Scheme 3), respectively.1 All complexes were
characterised in solution by standard NMR techniques and the rele-
vant data are summarised in Table 2. The complexes are generally
formed at room temperature immediately after the addition of the
ligand to the dichloromethane solution of the palladium precursor
and were isolated as moderately air-stable solids.
(210.8 mg, 1.220 mmol) in dichloromethane (7 ml). The resulting
clear mixture was allowed to stir at room temperature for
30 min, followed by concentration to a small volume (5 ml). Upon
addition of diethyl ether (10 ml) the product precipitated as an off-
white compound, which was filtered off, washed with fresh diethyl
ether (2 ꢂ 5 ml) and then dried in a stream of nitrogen. Yield 75%.
Anal. Calc. for C15H35ClN6P2Pd: C, 35.82; H, 6.96; N, 16.70. Found: C,
35.77; H, 6.89; N, 16.65%. 1H NMR (CDCl3, 25 °C): d 0.20 (t,
3JHP = 6.6 Hz, 3H, Pd–CH3) 1.20 (pseudo t, JHP+4JHP = 1.8 Hz, 6H,
2
2
P-CH3), 2.10 (s, 6H, N-CH3) 3.34 (d, JHH = 14.7 Hz, 4H, N-CHH0-
Starting from the palladium precursor Pd(OAc)2, the reaction
with 1 equiv. of PTN in dichloromethane afforded Pd(PTN)(OAc)2
(1). Upon slow evaporation of a dichloromethane solution of 1,
brown crystals suitable for X-ray crystallographic analysis were
isolated and the solid state structure confirmed the presence of
two monodentate acetate ligands and PTN behaving as bidentate
P,N-chelate (vide infra). In solution (CD2Cl2), 1 is characterised by
a singlet at ꢀ41.60 in the 31P{1H} spectrum. Of diagnostic relevance
were found to be the 1H signals corresponding to the CH3-P (1.30 d,
2JHP 13.5 Hz) and CH3-N groups (2.34 s) belonging to coordinated
NCH3) 3.50 (d, 2JHH = 10.8 Hz, 4H, P-CHH0-N), 3.84 (d,
2
2JHH = 13.4 Hz, 2H, N-CHH0-N), 3.92 (d, JHH = 10.8 Hz, 4H, P-CHH0-
2
2
N), 3.96 (d, JHH = 13.4 Hz, 2H, N-CHH0-N), 4.35 (d, JHH = 14.7 Hz,
4H, N-CHH0-NCH3). 13C{1H} NMR (CDCl3, 25 °C):
d
ꢀ8.40 (t,
1
2JCP = 5.3 Hz, Pd–CH3), 16.90 (t, JCP = 5.2 Hz, P-CH3), 38.30 (s, N-
1
3
CH3), 50.90 (t, JCP = 8.2 Hz, P-CHH0-N), 70.70 (t, JCP = 5.3 Hz, N-
CHH0-NCH3), 75.90 (s, N-CHH0-N). 31P{1H} NMR (CDCl3, 25 °C): d
ꢀ49.15 (s).
1
PTN, and the 13C{1H} values at 3.60 (d, JCP 25.7 Hz, CH3-P) and
2.8. Synthesis of trans-½Pdðj1-P-PTNÞ2ðMeÞꢁðBAr4F Þð7Þ
45.4 ppm (s, CH3-N). The acetate ligands gave resonances at 1.80
and 1.90 (s, 1H) and 176.8, 177.20 (s, 13C{1H}), suggesting that
the j2-P,N behaviour of PTN is maintained in solution. Complex 1
dissolved readily in water (377 mg/ml at 25 °C), however NMR
spectra in D2O indicated major decomposition to occur in this
solvent.
To a degassed solution of 6 (73.0 mg, 0.140 mmol) in dichloro-
methane (15 ml) was added NaBArF4 (135.0 mg, 0.150 mmol). The
reaction mixture was allowed to stir under nitrogen at room tem-
perature for 1 h, followed by filtration through celite. The solution
obtained was concentrated to dryness and diethyl ether (5 ml) was
added to the yellow residue. The suspension was stirred for 10
minutes and then the product was filtered off under nitrogen,
washed with diethyl ether (5 ml) and dried in a stream of nitrogen.
Yield 80%. Anal. Calc. for C47H47BF24N6P2Pd: C, 42.43; H, 3.53; N,
6.31. Found: C, 42.39; H, 3.49; N, 6.28%. 1H NMR (CDCl3, 25 °C): d
0.27 (t, 3JHP = 7.0 Hz, 3H, Pd–CH3), 1.18 (pseudo t,
2JHP + 4JHP = 2.7 Hz, 6H, P-CH3), 2.30 (s, 6H, N-CH3), 3.58 (d,
By reaction of [Pd(cod)(Me)Cl] with 1 equiv. of PTN, the corre-
sponding complex [PdMe(j2-P,N-PTN)Cl] (2) was isolated. The 1H
NMR signal due to Pd-Me shows as a doublet at 0.50 ppm with a
3
coupling constant JHP of 13.4 Hz, as expected for a cis Me–Pd–P
geometry. Chelate behaviour of PTN can be inferred from the sig-
2
nals belonging to CH3-P (1.20 d, JHP 10.8 Hz) and CH3-N groups
(2.40 s). Also the 13C{1H} NMR spectral data for 2 are quite compa-
1
rable with those of 1, with signals at 5.50 (d, JCP 22.7 Hz, CH3-P)
2
2JHH = 15.0 HZ, 4H, P-CHH0-N), 3.63 (d, JHH = 10.8 Hz, 4H, N-CHH0-
and 46.30 ppm (s, CH3-N). Subsequent treatment of 2 with NaBArF
4
NCH3), 3.75–3.97 (m, 8H, N-CHH0-N + N-CHH0-N + P-CHH0-N), 4.02
as halide scavenger in a mixture of dichloromethane and acetoni-
2
(d, JHH = 10.8 HZ, 4H, N-CHH0-NCH3), 7.55 (s, 4H, Ar-Hp) 7.72 (s,
trile, afforded the monocationic complex ½Pdðj2 ꢀ P; Nꢀ
8H, Ar-Ho). 13C{1H} NMR (CDCl3, 25 °C): d ꢀ5.20 (br s, Pd–CH3),
PTNÞðMeÞðCH3CNÞꢁ½BArF ꢁ (3). Coordination of acetonitrile to Pd
4
1
10.50 (br s, P-CH3), 45.30 (s, N-CH3), 52.00 (t, JCP = 7.9 Hz, P-
CHH0-N), 70.50 (br s, N-CHH0-NCH3), 77.90 (s, N-CHH0-N), 117.5
1
2
(s, Ar-Cp), 124.50 (q, JCF = 272.5 Hz, CF3), 128.90 (q, JCF = 31.0 Hz,
1
C-CF3), 134.80 (s, Ar-Co), 161.70 (non-binomial q, JCB = 49.8 Hz,
1
The reaction between Pd(cod)Cl2 and PTN (1:1 ratio) in CH2Cl2 gave an insoluble
Ar-Ci). 31P{1H} NMR (CDCl3, 25 °C): d ꢀ53.15 (s).
precipitate preventing characterisation by standard techniques.

3020
M. Caporali et al. / Inorganica Chimica Acta 361 (2008) 3017–3023
3
Table 1
value for Pd–Me (0.40 d, JHP 12.3 Hz) and the negligible position
2
Crystallographic data and structure refinement details for compounds 1 and 5
shift for the aminophosphine CH3-P (1.30 d, JHP 11.6 Hz) and
CH3-N groups (2.30 s). 13C{1H} data are in line with this attribution
(Table 2). The trend in 31P chemical shift variation upon passing
from acetate trans to P to chloride to acetonitrile is downfield as
expected (Table 2).
1
5
Empirical formula
Formula weight
Temperature (K)
Wavelength (Mo Ka) (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
C
11H22N3O4PPd
C14H32ClF6N6P3Pd
633.22
293(2)
397.69
293(2)
0.71073
monoclinic
P21/n
10.682(9)
12.329(2)
13.320(4)
90.00
113.370(4)
90.00
A second family of palladium(II) complexes was prepared by
reaction of the same Pd(II) precursors with 2 equiv. of PTN. Starting
from cis-[Pd(cod)Cl2] complex trans-[Pd(j1-P-PTN)2Cl2] (4) was ob-
tained. The correct attribution of the geometry came from the close
inspection of the 13C{1H} data, especially for the P-CH3 signal that
is now present as pseudo-triplet (15.30 ppm, 1JCP+3JCP = 7.8 Hz) and
N-CH3 (38.70 s), indicative of j1-P coordination of PTN [14]. By
contrast, little effect on the proton signals for these groups was ob-
served (Table 2). Further evidence for the presence of two coordi-
nated PTN molecules in 4 came from ESI-MS analysis showing a
peak at m/z 489 corresponding to the [MꢀCl] molecular peak.
Chloride lability can be due to the analysis conditions (MeCN/
H2O) and is reflected in the very high water solubility. The most
significant changes in NMR from CD2Cl2 to D2O were found for
triclinic
P1
ꢀ
9.716(5)
9.748(5)
14.448(5)
71.321(5)
72.814(5)
78.516(5)
1230.3(10)
2
a (°)
b (°)
c (°)
V (Å3)
Z
1610.3(15)
4
1.640
Dcalc (g cmꢀ3
)
1.709
1.118
Absorption coefficient
(mmꢀ1
F(000)
Crystal size (mm)
Theta range for data
collection (°)
1.267
)
808
640
0.75 ꢂ 0.50 ꢂ 0.42
0.35 ꢂ 0.35 ꢂ 0.30
2.08–26.99
2.73–24.98
the P-CH3 group, with the change in the 1H NMR from a pseudo-
Index range
ꢀ13 6 h 6 12,
0 6 k 6 15, 0 6 l 6 16
3496
ꢀ10 6 h 6 11,
2
triplet to
a
doublet of doublets at 1.54 (dd, JHP = 11.0 Hz,
ꢀ10 6 k 6 11, 0 6 l 6 17
4JHP = 2.1 Hz) and in the 13C spectrum from triplet to doublet
(12.05 d, 1JCP = 20.2 Hz). Moreover, the 31P{1H} singlet shifted from
ca. ꢀ49 to ꢀ31 ppm, likely due to trans ? cis rearrangement and
chloride displacement by water with formation of a cationic puta-
tive species cis-[Pd(j1-P-PTN)2Cl(H2O)]Cl (4a) whose isolation
however was not attempted.
Reflections collected
Independent reflections
Refinement method
Data/restraints/parameter
FinalR indices [I > 2r(I)]
4316
4316
3496
full-matrix least-square on F2
3496/0/185
R1 = 0.0284,
wR2 = 0.0747
R1 = 0.0359,
wR2 = 0.0769
1.045
4316/0/284
R1 = 0.0470, wR2 = 0.1218
R indices (all data)
R1 = 0.0628, wR2 = 0.1322
Complex 4 undergoes neat chloride abstraction when treated
with an equimolar amount of AgPF6 and the moderately water sol-
Goodness-of-fit on F2
1.039
0.925 and ꢀ0.588
Largest difference peak
0.081 and ꢀ0.848
uble ½SH Oð25 ꢃCÞ ¼ 6:47 mg=mlꢁ, monocationic pale yellow com-
and hole (e Åꢀ3
)
2
plex [Pd(PTN)2Cl][PF6] (5) was isolated. In acetone-d6, 5 shows
two broad bands in the 31P{1H} NMR spectrum, at ca. ꢀ25 (j1-P)
and ꢀ45 ppm (j2-P,N), denoting the presence of two inequivalent
cis-disposed phosphorus nuclei. By slow evaporation of a dichloro-
methane solution of 5, well-formed yellow crystals were isolated
and the solid state X-ray crystal structure of 5 determined as
[Pd(j2-P,N-PTN)(j1-P-PTN)Cl][PF6] featuring both coordination
modes possible for PTN. 31P{1H} NMR spectrum in D2O shows a
broad singlet at ca. ꢀ30 ppm while the 1H spectrum is character-
ised by signals superimposable to those of 4a, suggesting a hemil-
abile behaviour for the j2-P,N ligand under these conditions.
Double halide abstraction from 4 with a known excess (2.5 equiv.)
of AgPF6 in dichloromethane was also attempted. Initially an or-
ange precipitate is formed immediately upon mixing of the re-
agents, however it was observed to decompose quickly even if
stored at low temperature under a protecting nitrogen atmo-
sphere, hence preventing characterisation.
P
N
N
N
N
N
P
N
Me
Me
PTA
PTN
Scheme 1.
was ascertained from the presence of 1H singlet at 2.26 and IR
stretching bands at 2292 and 2319 cmꢀ1 [22].
The solvent is likely to replace the chloride anion in 2 without
disrupting the j2-P,N coordination, as deduced from the 1H NMR
Me
P
OAc
OAc
PTN
Pd(OAc)2
N
N
Pd
DCM, RT
N
Me
1
BArF
Me
Me
4
P
N
Me
Cl
P
NaBArF
Me
N
4
Me
Cl
PTN
Pd
Pd
Pd
N
N
NCMe
DCM, RT
- COD
DCM / MeCN, RT
N
N
Me
Me
2
3
Scheme 2. Synthesis of palladium complexes 1–3 with Pd:PTN ratio 1:1.

M. Caporali et al. / Inorganica Chimica Acta 361 (2008) 3017–3023
3021
PF6
Me
N
Me
Me
N
P
P
X=Cl, AgPF6
DCM, RT
N
N
N
Pd
Cl
N
H2O
Me
5
Me
Me
Y
N
N
N
N
Me
Me
Me
P
N
Me
Me
N
N
H2O
P
N
X
X
N
N
P
2 PTN
Pd
Pd
Pd
Cl
X = Cl
N
N
Cl
DCM, RT
Cl
OH2
P
Me
Y = Cl, PF6
4a
BArF
X = Cl, 4
X = Me, 6
Me
Me
Me
P
4
P
X=Me,NaBArF
DCM, RT
4
N
N
Pd
N
N
N
N
Me
Me
7
Scheme 3. Synthesis of palladium complexes 4–7 with Pd:PTN ratio 1:2.
Table 2
Selected 1H, 31P{1H} and 13C{1H} NMR data for 1–7, in CD2Cl2 unless stated
Complex
1H (d, ppm; JHP, HZ)
13C{1H} (d, ppm; JCP, HZ)
31P{1H}(d, ppm)
ꢀ41.60s
1.30 (d, 13.5, P-CH3); 2.34 (s, 3H, N-CH3);
1.80, 1.90 (s, 6H, CH3-COO).
3.60 (d, 25.7, P-CH3); 22.0, 23.5 (s, CH3-COO);
45.4 (s, N-CH3); 176.80, 177.20 (s, COO)
P
OAc
OAc
Pd
Pd
1
N
P
Me
2
0.50 (d, 3.4, Pd–CH3), 1.20 (d, 10.8 Hz, P-CH3),
2.40 (s, N-CH3)
ꢀ7.70 (s, Pd–CH3), 5.50 (d, 22.7, P-CH3),
ꢀ37.00s
ꢀ35.00s
46.30 (s, N-CH3)
Cl
N
P
N
BArF
4
Me
0.40 (d, 2.3, Pd–CH3), 1.30 (d, 11.6, P-CH3),
2.26 (s, CH3CN), 2.30 (s, N-CH3)
ꢀ6.20 (s, Pd–CH3), 2.85 (s, CH3-CN),
3
Pd
5.20 (d, 25.5, P-CH3), 46.00 (s, N-CH3)
NCMe
1.20 (pseudo t, 2.2, P-CH3), 2.30 (s, N-CH3).a
1.54 (dd, 11.0, 2.1 P-CH3), 2.37 (s, N-CH3).b
15.30 (pseudo t, 7.8, P-CH3), 38.70 (s, N-CH3).a
12.05(d, 20.2, P-CH3), 42.4 (s, N-CH3).b
ꢀ49.00sa
ꢀ31.20sb
Cl
P
N
Pd
4
Cl
N
N
P
PF6
Pb
Cl
N
Pa
1.60 (br s, P-CH3), 1.80 (br s, P-CH3),
2.40 (br s, N-CH3) 2.60 (br s, N-CH3).c
7.40 (br s, P-CH3), 16.90 (br s, P-CH3),
38.10 (br s, N-CH3), 46.40 (br s, N-CH3).c
ꢀ25.00s (Pa), ꢀ45.60s(Pb)
Pd
5
N
P
Me
P
N
0.20 (t, 6.6, Pd–CH3) 1.20 (pseudo t, 1.8, P-CH3),
2.10 (s, N-CH3).d
ꢀ8.40 (pseudo t, 5.3, Pd–CH3),
ꢀ49.15s
Pd
P
6
16.90 (t, 5.2, P-CH3), 38.30 (s, N-CH3).d
Cl
BArF
Me
Pd
4
P
0.27 (t, 7.0, Pd–CH3), 1.18 (pseudo t, 2.7, P-CH3),
2.30 (s, N-CH3).d
ꢀ5.20 (br s, Pd–CH3), 10.50 (br s, P-CH3),
ꢀ53.15s
7
45.30 (s, N-CH3).d
N
N
a
b
c
In CD2Cl2.
In D2O.
In acetone-d6.
In CDCl3.
d

3022
M. Caporali et al. / Inorganica Chimica Acta 361 (2008) 3017–3023
Table 3
By reaction of PdMe(cod)Cl with 2 equiv. of PTN, the off-white
complex trans-[PdMe(j1-P-PTN)2Cl] (6) was obtained. Similarly to
4, NMR data suggest that the two PTN ligands are trans to each
other, as from the 31P{1H} NMR singlet at d = ꢀ49 ppm and
13C{1H} triplet for the methyl group bound to palladium
Selected bond length (Å) and bond angles (°) for 1 and 5
1
5
Pd(1)–Cl(1)
Pd(1)–P(1)
Pd(1)–P(2)
Pd(1)–N(1)
Pd(1)–O(1)
Pd(1)–O(3)
P(1)–Pd(1)–N(1)
P(2)–Pd(1)–N(1)
P(1)–Pd(1)–Cl(1)
O(1)–Pd(1)–O(3)
2.380(2)
2.231(2)
2.256(2)
2.205(4)
2.187(1)
3
(0.20 ppm, JHP 6.6 Hz). Subsequent treatment of complex 6 with
1 equiv. of NaBArF4 as halide scavenger in dichloromethane,
2.109(2)
2.037(2)
2.103(2)
86.56(7)
afforded
the
monocationic
complex
trans-½PdMeðj1-P;
N-PTNÞ2ꢁ½BArF4ꢁ ð7Þ, yellow and highly insoluble in water as
expected from the presence of BArF4 counter ion. The NMR data
collected in CDCl3 (Table 2) suggest a highly fluxional situation
intermediate between j1-P and j2-P,N behaviour for PTN (Scheme
3). Addition of acetonitrile to a solution of 7 in CH2Cl2 in order to
stabilise the complex by solvent coordination failed as evidenced
by the absence of the 1H NMR signal corresponding to coordinated
MeCN.
83.57(13)
176.57(13)
167.40(6)
88.26(9)
Most significant intermolecular distances (Å) for 1 and 5
O(1)ꢄ ꢄ ꢄH(5B)
O(2)ꢄ ꢄ ꢄH(7B)
O(3)ꢄ ꢄ ꢄH(4)
O(4)ꢄ ꢄ ꢄH(11)
Pd(1)ꢄ ꢄ ꢄN(4)
P(1)ꢄ ꢄ ꢄN(1)
P(2)ꢄ ꢄ ꢄN(4)
Cl(1)ꢄ ꢄ ꢄH(5)
F(2)ꢄ ꢄ ꢄH(12)
F(3)ꢄ ꢄ ꢄH(6A)
F(3)ꢄ ꢄ ꢄH(8C)
F(4)ꢄ ꢄ ꢄH(7A)
F(5)ꢄ ꢄ ꢄH(1C)
2.385
2.634
2.455
2.712
3.142(5)
2.956(5)
2.867(5)
2.781
2.620
2.624
2.607
2.563
2.623
3.2. X-ray crystal structures of [Pd(j2-P,N-PTN)(OAc)2] (1) and [Pd(j2-
P,N-PTN)(j1-P-PTN)Cl](PF6) (5)
2.946(3)
The coordination geometry of palladium in compound 1 is best
described as square-planar, with one PTN-ligand coordinating to
the metal atom in the j2-P,N mode and occupying thus two cis-
coordination sites at the metal centre. An ORTEP drawing of the
molecular structure is shown in Fig. 1, while selected bond dis-
tances and angles are reported in Table 3.
The coordination sphere around palladium is completed by two
carboxylate oxygen atoms stemming from two acetate units. The
palladium atom deviates from the coordination plane, which is de-
fined by the atoms N(1), P(1), O(1) and O(3) of 0.0344(9) Å in the
direction of O(2). The P,N ligand coordinates in its most abundant
conformation, which corresponds to the exo/exo form [13]. Most
importantly, unlike related symmetrical Rh [14] and Au [13] com-
plexes, no disorder of the P(1), N(1)-donor sites was observed, due
to the fact that both carboxylic oxygen atoms O(2) and O(4) of the
coordinating acetate moieties point to the same spatial direction
and prevent thus a pseudo C2 symmetry of the molecule. The coor-
dinating PTN-ligand, which is almost symmetrically disposed with
respect to the mirror plane defined by the atoms N(1), C(6) and
P(1), shows a significant deviation of C(1) of 0.1298(39) Å from
the symmetry plane in direction of C(5). The P(1)–Pd(1)–N(1) bite
angle of 86.56(7)° is in the range of related metal complexes, which
exhibit a j2-P,N coordination mode of this ligand [13,14].
N(1), the acetate unit trans to the phosphorus donor atom is weak-
er bonded to the metal centre compared to that trans to the nitro-
gen atom N(1), which is supported by the different bond length of
the corresponding Pd–O(acetate) bonds of 2.037(2) Å (Pd(1)–O(1))
and of 2.103(2) Å (Pd(1)–O(3)). All four acetate oxygen atoms are
co-involved in the formation of a complex web of hydrogen bonds.
The shortest intermolecular distances found for all four acetate
oxygen atoms are reported in Table 2.
The crystal structure of the monocationic palladium complex 5
shows a square-planar coordinated palladium atom with a j2-P,N
and a j1-P coordinating PTN ligand. One PFꢀ6 counter-ion compen-
sates the positive charge of the palladium atom. An ORTEP drawing
of the molecular structure is shown in Fig. 2, while selected bond
distances and angles are reported in Table 3.
Since the coordinating phosphorus atom P(1) exerts a much
higher trans influence compared to the coordinating nitrogen atom
Fig. 1. ORTEP plot of 1. Hydrogen atoms are omitted for clarity and thermal ellip-
Fig. 2. ORTEP plot of 5. Hydrogen atoms and the counter-ion PF6 are omitted for
soids are shown at the 30% probability level.
clarity and thermal ellipsoids are shown at the 30% probability level.

M. Caporali et al. / Inorganica Chimica Acta 361 (2008) 3017–3023
3023
The fourth coordination site is occupied by a chloride atom,
Acknowledgements
which is located trans to the phosphorus atom (P1) of the j2-P,N
coordinating PTN unit. As a consequence the phosphorus donor
atom P(2) of the j1-P coordinating PTN unit coordinates trans to
the nitrogen atom N(1) of the j2-P,N PTN unit. The palladium atom
deviates from the coordination plane, which is defined by the
atoms N(1), P(1), P(2) and Cl(1) of 0.1004(14) Å in direction of
the non-coordinating nitrogen atom N(4). The intra-molecular
Pd(1)ꢄ ꢄ ꢄN(4) distance of 3.142(5) Å, is only slightly shorter than
the sum of the van der Waals radii of palladium and nitrogen
(3.170 Å) and thus only a very weak interaction may exist. The
j1-P coordinating ligand is orientated almost orthogonally with re-
spect to the coordination plane, showing the Cl(1)–Pd(1)–P(2)–
N(4) torsion angle of 77.67(10)°, which is comparable to the value
found for RhCl(COD)(j1-P-PTN) (82.38(8)°) [14]. The N(1)–Pd(1)–
P(1) bite angle of 83.57(13)° is slightly smaller than that found
for compound 1 (86.56(7)°), which is due to the shorter Pd(1)–
P(1) and Pd(1)–N(1) bond length found for the latter compound
and not to significantly different intra-molecular P(1)ꢄ ꢄ ꢄN(1) dis-
tances, which are 2.946(3) and 2.956(5) Å for 1 and 5, respectively.
The j1-P coordinating PTN unit in compound 5 exhibits an intra-
molecular P(2)ꢄ ꢄ ꢄN(4) distance of 2.867(5) Å, which is significantly
longer compared to the value found for the j2-P,N coordinated li-
gand, evidencing the occurrence of a ring strain of the ligand upon
its coordination to the metal atom [14]. As far as intermolecular
hydrogen bonds are concerned the chloride as well as fluorine
atoms build up a complex web of hydrogen bonding interactions
(Table 3).
Thanks are expressed to EC for promoting this scientific activ-
ity through the FP6 Research Training Network AQUACHEM
(Contract No. MCRTN-2003-503864). We also thank ‘‘FIRENZE
HYDROLAB”, a project sponsored by Ente Cassa di Risparmio di Fire-
nze, for access to high field NMR facilities. Dr. A. Raffaelli (IC-
COM CNR Pisa) is thanked for the ESI-MS measurements. Mr.
F. Zanobini (ICCOM CNR) is thanked for help in the synthesis
of PTN.
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4. Conclusions
New palladium(II) complexes bearing the water soluble amino-
phosphine PTN in 1:1 and 1:2 metal-to-ligand ratio were prepared
and fully characterised by conventional spectroscopic methods and
by X-ray diffraction analysis in the case of complexes 1 and 5. In
the case of j2,P,N coordination, hemilabile behaviour was observed
when dissolving complex 5 in water, in line with the long Pd–N
bond length in the corresponding X-ray crystal structure indicating
a highly tensioned cage in such bidentate coordination to the me-
tal. The Pd–PTN complexes described in this study show good sol-
ubility in water and are expected to be active species for bringing
about palladium-catalysed C–C coupling reactions in water or
water-biphasic conditions [23]. Attempts to explore these path-
ways are currently under scrutiny in our laboratory and will be re-
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[22] (a) C. Bianchini, A. Meli, G. Müller, W. Oberhauser, E. Passaglia,
Organometallics 21 (2002) 4965;
5. Supplementary material
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Organometallics 21 (2002) 16.
[23] Recently the Sonogashira reaction of aryl bromides and chlorides with
terminal alkynes catalyzed by [Pd(dmba)Cl(PTA)] and Pd(OAc)2/PTA has
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Organometallics 25 (2006) 5768.
CCDC 655262 and 662952 contain the supplementary
crystallographic data for 1 and 5. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.