New palladacyclic complexes with pyridylphosphine ligands: Crystal structures of [Pd(Azb)(Ph2POCH2Py-P,N)][PF6] and [Pd(Phpy)(Ph2PNHPy-P,N)][PF6]

Article abstract of DOI:10.1016/j.ica.2004.06.040

The synthesis of palladacyclic derivatives with the hybrid pyridylphosphine ligands Py(CH₂)OPPh₂ and PyNHPPh₂ in a neutral P,N-chelating coordination mode is described. The crystal structures of compounds [Pd(Azb)(Ph₂POCH₂Py-P,N)][PF₆] and [Pd(Phpy)(Ph₂PNHPy-P,N)][PF₆] have been determined. The new palladacyclopentadiene precursor [Pd{C₄COOMe₄}(CH ₃CN)₂] has been prepared and its usefulness in the preparation of new derivatives has been tested. The reactions of appropriate hydroxo-bridged precursors with PyNHPPh₂ afforded mononuclear complexes in which a less common anionic P,N-binding mode is observed. The synthesis of palladacyclic derivatives with the hybrid pyridylphosphine ligands Py(CH₂)OPPh₂ (a) and PyNHPPh₂ (b) in a neutral P,N-chelating coordination mode has been achieved. Treatment of selected chloride-bridged cyclometallated precursors [Pd(C^{^}N)(μ-Cl)] ₂ [C^{^}N = 2-pyridinin-phenyl Phpy, I-compounds; 7,8-benzoquinolyl Bzq, II-compounds; phenylazophenyl Azb, III-compounds or 2-(2-oxazolinyl)phenyl Phox, IV-compounds] with a or b in the presence of stoichiometric KPF₆ gave the mononuclear derivatives Ia-IVa and Ib-IVb. The crystal structures of compounds [Pd(Azb)(Ph₂POCH ₂Py-P,N)][PF₆] (IIIa) and [Pd(Phpy)(Ph₂PNHPy-P, N)][PF₆] (Ib) have been determined. The new palladacyclopentadiene precursor [Pd{C₄COOMe₄}(CH₃CN)₂] (V) has been prepared starting from the polymeric complex [Pd{C ₄COOMe₄}]_n. Its usefulness in the preparation of new derivatives has been tested by means of the straightforward reaction with ligands (a) or (b) to give mononuclear compounds [Pd{C₄(COOMe) ₄}(Ph₂POCH₂Py-P,N)] (Va) and [Pd{C ₄(COOMe)₄}(Ph₂PNHPy-P,N)] (Vb). The reactions of hydroxo-bridged precursors [Pd(C^{^}N)(μ-OH)]₂ or [Pd₂{C₄(COOMe)₄}₂ (μ-OH) ₂][NBu₄]₂ with PyNHPPh₂ afforded mononuclear complexes Ic-Vc (PyNPPh2-=cligand) in which a less common anionic P,N-binding mode is forced as a result of ligand deprotonation. The new complexes were characterised by partial elemental analyses and spectroscopic methods (IR, FAB, ¹H and ³¹P{¹H} NMR).

Full text of DOI:10.1016/j.ica.2004.06.040

Inorganica Chimica Acta 357 (2004) 4568–4576
www.elsevier.com/locate/ica
New palladacyclic complexes with pyridylphosphine ligands:
crystal structures of [Pd(Azb)(Ph2POCH2Py-P,N)][PF6]
and [Pd(Phpy)(Ph2PNHPy-P,N)][PF6]
a,
Gregorio Sanchez , Joaquın Garcıa , David Meseguer , Jose L. Serrano ,
a
a
b
*
´
´
Luis Garcıa , Jose Perez , Gregorio Lopez
´
´
b
b
a
´
´ ´
´
a
´ ´
Departamento de Quımica Inorganica, Universidad de Murcia, 30071 Murcia, Spain
´
Departamento de Ingenierıa Minera, Geologica y Cartografica. Area de Quımica Inorganica, 30203 Cartagena, Spain
b
´
´
´
´
´
Received 2 April 2004; accepted 26 June 2004
Available online 30 July 2004
Abstract
The synthesis of palladacyclic derivatives with the hybrid pyridylphosphine ligands Py(CH2)OPPh2 (a) and PyNHPPh2 (b) in a
neutral P,N-chelating coordination mode has been achieved. Treatment of selected chloride-bridged cyclometallated precursors
[Pd(CꢀN)(l-Cl)]2 [CꢀN=2-pyridinin-phenyl Phpy, I-compounds; 7,8-benzoquinolyl Bzq, II-compounds; phenylazophenyl Azb,
III-compounds or 2-(2-oxazolinyl)phenyl Phox, IV-compounds] with a or b in the presence of stoichiometric KPF6 gave the mono-
nuclear derivatives Ia–IVa and Ib–IVb. The crystal structures of compounds [Pd(Azb)(Ph2POCH2Py-P,N)][PF6] (IIIa) and
[Pd(Phpy)(Ph2PNHPy-P,N)][PF6] (Ib) have been determined. The new palladacyclopentadiene precursor [Pd{C4CO-
OMe4}(CH3CN)2] (V) has been prepared starting from the polymeric complex [Pd{C4COOMe4}]n. Its usefulness in the preparation
of new derivatives has been tested by means of the straightforward reaction with ligands (a) or (b) to give mononuclear compounds
[Pd{C4(COOMe)4}(Ph2POCH2Py-P,N)] (Va) and [Pd{C4(COOMe)4}(Ph2PNHPy-P,N)] (Vb). The reactions of hydroxo-bridged
precursorsꢀ[Pd(CꢀN)(l-OH)]2 or [Pd2{C4(COOMe)4}2 (l-OH)2][NBu4]2 with PyNHPPh2 afforded mononuclear complexes Ic–Vc
ðPyNPPh2 ¼ c ligandÞ in which a less common anionic P,N-binding mode is forced as a result of ligand deprotonation. The
1
new complexes were characterised by partial elemental analyses and spectroscopic methods (IR, FAB, H and 31P{1H} NMR).
ꢁ 2004 Elsevier B.V. All rights reserved.
Keywords: Pyridylphosphine ligands; Palladacycles; Hydroxo-complexes; Crystal structures
1. Introduction
ligands with these characteristics are pyridylphosphines
[2,17,18], that have found widespread applications in
homogeneous catalysis [19]. Thus, 2-(diphenylphosphi-
no)pyridine (Ph2Ppy) has attracted continuous research
in this field due to its ability to coordinate trasition met-
als as P-monodentate, N-monodentate or P,N-bridging,
generating complexes with different properties and appli-
cations [17]. The P,N-chelating coordination mode is
quite less common as a consequence of ring strain, and
related ligands containing organic spacer groups have
been developed in order to increase the distance between
P and N donor sites [20 and references therein], allowing
The considerable attention received by hybrid ligands
containing both a soft phosphine donor atom and a hard
functionality [1–4] comes from their versatile coordina-
tion behaviour [5,6] and its potential hemilability [3,4],
that make their complexes useful as the foundation for
molecule-based sensors [7–9], as well as good precursors
in catalytic processes [4,10–16]. An important group of
*
Corresponding author. Tel.: +96-836-7454; fax: +96-836-4148.
´
E-mail address: gsg@um.es (G. Sanchez).
0020-1693/$ - see front matter ꢁ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.06.040

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G. Sanchez et al. / Inorganica Chimica Acta 357 (2004) 4568–4576
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in this way the preparation of new mononuclear com-
plexes. In this sense, ligands such as Py(CH2)nOPPh2(n=
1–3) [21], Py(CH2)nNHPPh2 (n=0,1) [20,22,23] and
others related that include a hydrazine backbone [24]
or N-substitution [23] have recently been described. In
addition to their intrinsic interest regarding coordination
properties [20], the modification in alkyl chain length and
the functionalisation of pyridylphosphines have permit-
ted the tuning of both bite angle and electronic properties
of the ligands, leading in some cases to enhancement in
catalytic reactivity [21,25–29].
We have recently been interested in the synthesis of
some Ni and Pd organometallic derivatives containing
N,P-ligands, either with a bis-pentafluorophenyl [30],
palladacyclopentadiene [31] or ortho-metallated back-
bone [32,33]. In the last example we have employed se-
lected di-l-hydroxo-complexes [34] as precursors in the
preparation of new compounds when ligand deproto-
nation was required. Thus, stronger basic treatments
were avoided, reaffirming the unique characteristics of
such hydroxo-complexes as starting materials by means
of simple acid–base reaction with protic electrophiles
[35–39]. In this sense, we have also described the syn-
thesis of the binuclear complex [Pd2{C4(CO-
OMe)4}2(l-OH)2][NBu4]2 [40] and its use in the
preparation on new palladacyclopentadiene derivatives
that have shown interesting catalytic properties. To
date just a few crystal structures of palladacyclopentad-
iene compounds are known, and the most common
starting materials employed to access them are
Pd(dba)2, [Pd(CH3CN)2-(dmbd)2] (dmbd=dimethyl-2-
butynedioate) [41], or the less soluble polymeric com-
plex [Pd{C4COOMe4}]n, sometimes inconvenient [42].
The new precursor [Pd{C4(COOMe)4}(CH3CN)2] (V)
that we present here, together with the above men-
tioned hydroxo-complex, allows the enlargement of
the field providing new synthetic routes to prepare pal-
ladacyclopentadiene derivatives.
Nujol mulls between polyethylene sheets. NMR data
(1H, 13C, 31P) were recorded on Bruker Avance 200,
300 and 400 spectrometers. Mass spectrometric analy-
ses were performed on a Fisons VG Autospec dou-
ble-focusing spectrometer, operated in positive mode.
Ions were produced by fast atom bombardment
(FAB) with a beam of 25-keV Cs atoms. The mass
spectrometer was operated with an accelerating voltage
of 8 kV and a resolution of at least 1000. Conductance
measurements were performed with a Crison 525 con-
ductimeter (in acetone solutions, 5·10ꢀ4 M). TG and
DTG curves were recorded on a TA Instruments
SDT 2960 thermobalance using an atmosphere of pure
nitrogen (50 cm3 minꢀ1) All the solvents were dried by
conventional methods.
The cyclometallated precursors [Pd(CꢀN)(l-Cl)]2 and
[Pd(CꢀN)(l-OH)]2[CꢀN=2-pyridinin-phenyl (Phpy or
I), 7,8-benzoquinolyl (Bzq or II), phenylazophenyl
(Azb or III), and 2-(2-oxazolinyl)phenyl (Phox or IV)]
were prepared as described in the literature [34,43,44].
The palladacyclopentadiene precursors [Pd{C4CO-
OMe4}]n [42] and [Pd2{C4(COOMe)4}2(l-OH)2][NBu4]2
[40] and the pyridylphosphine ligands Py(CH2)OPPh2
[21] and PyNHPPh2 [20] were synthesised according to
reported procedures.
2.2. Preparation of [Pd{C4(COOMe)4}(CH3CN)2]
(V)
An acetonitrile (5 ml) solution of the precursor
[Pd{C4(COOMe)4}]n (0.100 g, 0.256 mmol) was vigor-
ously stirred for 15 min, and then concentrated under re-
duced pressure to half of the initial volume. The
addition of diethyl ether caused the formation of a yel-
low solid that was filtered off, washed with ether and
air dried. Yield: 102.9 mg (85%). Anal. Calc. for
C16H18N2O8Pd: C, 40.6; H, 3.8; N, 5.9. Found: C,
40.3; H, 3.6; N, 6.0%. IR (nujol mull cmꢀ1): m(C„N)
2322s, 2292s; m(C‚O) 1710vs, 1548s. 1H NMR [CDCl3]:
d 2.09 (s, 6H, CH3CN), 3.66 (s, 6H, COOMe), 3.74 (s,
6H, COOMe). 13C{1H} NMR [CDCl3]: d 2.2 (CH3CN),
51.5 (COOCH3).
In this paper, we mainly report the synthesis and
characterisation of new palladacycles that contain
the ligands Py(CH2)OPPh2 and PyNHPPh2 acting as
neutral P,N-chelating. A series of new complexes with
the less usual anionic [PyNPPh2]ꢀ ligand has also been
prepared using the appropriated hydroxo-complexes
as precursors under clean and mild conditions of
reaction.
2.3. Synthesis of complexes [Pd(CꢀN)(Ph2POCH2Py-
P,N][PF6][CꢀN=2-pyridinin-phenyl (Ia), 7,8-benzo-
quinolyl (IIa), phenylazophenyl (IIIa) and 2-(2-oxazol-
inyl)phenyl (IVa)]
2. Experimental
The new complexes were obtained by treating
[Pd(CꢀN)(l-Cl)]2 with 2-(diphenylphosphinyl)oxymeth-
ylpyridine in molar ratio 1:2, using CH2Cl2 as solvent
and according to the following general method. To a di-
chloromethane solution (10 ml) of the corresponding
precursor [Pd(CꢀN)(l-Cl)]2 (60 mg) was added the stoi-
2.1. General remarks
C, H and N analyses were carried out with a Carlo
Erba instrument. IR spectra were recorded on a Per-
kin–Elmer spectrophotometer 16F PC FT-IR, using

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G. Sanchez et al. / Inorganica Chimica Acta 357 (2004) 4568–4576
4570
chiometric amount of a THF solution of 2-(diphenyl-
phosphinyl)oxymethylpyridine and solid KPF6. After
stirring for 30 min at room temperature, the KCl was fil-
tered and then the solution concentrated under reduced
pressure to half volume. Addition of diethyl ether
caused precipitation of the new complexes, which were
filtered off, air dried and recrystallised from dichloro-
methane–diethylether.
[Pd(Phpy)(Ph2POCH2Py-P,N)][PF6] (Ia). Yield:
109.0 mg (77%). Anal. Calc. for C29H24F6N2OP2Pd: C,
49.8; H, 3.5; N, 4.0. Found: C, 50.0; H, 3.6; N, 4.1%.
FT-IR (nujol mull cmꢀ1): m(C‚N) 1604vs, 1570s;
m(PF6) 840vs. 1H NMR [(CD3)2CO]: d 5.55 (d, 2H,
OCH2, JPH =18.4), 6.72 (m, 2H, aromatics), 7.13 (m,
1H, aromatics), 7.59 (m, 7H, aromatics), 7.93 (m, 7H,
aromatics), 8.23 (m, 4H, aromatics), 9.14 (d, br, 1H,
H6 pyridine). 31P{1H} NMR [(CD3)2CO]: d 129.5 (s,
Ph2POCH2Py), ꢀ143.7 (m, PF6). FAB-MS (positive
mode) m/z: 553 (M+ ꢀPF6).
2.4. Preparation of [Pd{C4(COOMe)4}(Ph2POCH2Py-
P,N)] (Va)
To an acetone (5 ml) solution of the precursor
[Pd{C4(COOMe)4}(CH3CN)2] (0.07 g, 0.15 mmol) was
added the stoichiometric amount of a THF solution of
2-(diphenylphosphinyl)oxymethylpyridine. The reaction
was stirred at room temperature for 30 min, and then
the solvent was partially evaporated under reduced pres-
sure. The addition of diethyl ether caused the formation
of a yellow crude, that was obtained as a solid after re-
crystallisation from dichloromethane–hexane. Yield:
72.2 mg (71%). Anal. Calc. for C30H28NO9PPd: C,
52.7; H, 4.1; N, 2.1. Found: C, 52.8; H, 4.3; N, 2.2%.
FT-IR (nujol mull cmꢀ1): m(C‚O) 1714vs; m(C‚N)
1
1606s. H NMR [(CD3)2CO]: d 3.37 (s, 3H, COOMe),
3.49 (s, 3H, COOMe), 3,53 (s, 3H, COOMe), 3.70 (s,
3H, COOMe), 5.50 (d, 2H, OCH2, JPH =20.0), 7.13–
7.90 (m, 13H, aromatics), 9.26 (s, br, 1H, H6 pyridine).
31P{1H} NMR [(CD3)2CO]: d 116.3 (s, Ph2POCH2Py).
FAB-MS (positive mode) m/z: 684 (M+).
[Pd(Bzq)(Ph2POCH2Py-P,N)][PF6] (IIa). Yield: 92.1
mg (68%). Anal. Calc. for C31H24F6N2OP2Pd: C, 51.5;
H, 3.3; N, 3.9. Found: C, 51.6; H, 3.5; N, 4.0%. FT-
IR (nujol mull cmꢀ1): m(C‚N) 1606vs, 1568s; m(PF6)
840vs. 1H NMR [(CD3)2CO]: d 5.65 (d, 2H, OCH2,
JPH =19.6), 6.85 (m, 1H, aromatics), 7.14 (m, 1H, aro-
matics), 7.65 (m, 7H, aromatics), 7.96 (m, 9H, aromat-
ics), 8.30 (m, 1H, aromatics), 8.53 (m, br, 1H,
aromatic), 8.77 (d, H2 Bzq, JHH =16.0 Hz), 9.27 (d,
1H, H6 pyridine, JHH =10.4 Hz). 31P{1H} NMR
[(CD3)2CO]: d 130.3 (s, Ph2POCH2Py), ꢀ143.7 (m,
PF6). FAB-MS (positive mode) m/z: 577 (M+ ꢀPF6).
[Pd(Azb)(Ph2POCH2Py-P,N)][PF6] (IIIa). Yield:
93.0 mg (69%). Anal. Calc. for C30H25F6N3OP2Pd: C,
49.6; H, 3.5; N, 5.8. Found: C, 49.6; H, 3.5; N,
5.9%. FT-IR (nujol mull cmꢀ1): m(C‚N) 1610vs,
2.5. Synthesis of complexes [Pd(CꢀN)(Ph2PNHPy-
P,N)][PF6] [CꢀN=2-pyridinin-phenyl (Ib), 7,8-benzo-
quinolyl (IIb), phenylazophenyl (IIIb) and 2-(2-oxazol-
inyl)phenyl (IVb)]
The new complexes were obtained by treating
[Pd(CꢀN)(l-Cl)]2 with 2-(diphenylphosphinoamino)py-
ridine in molar ratio 1:2, using CH2Cl2 as solvent and
according to the following general method. To a dichlo-
romethane solution (10 ml) of the corresponding precur-
sor [Pd(CꢀN)(l-Cl)]2 (60 mg) was added the
stoichiometric amount of solid 2-(diphenylphosphino-
amino)pyridine and KPF6. After stirring for 30 min at
room temperature, the KCl was filtered and then the so-
lution concentrated under reduced pressure to half vol-
ume. Addition of hexane caused precipitation of the
new complexes, which were filtered off, air dried and re-
crystallised from dichloromethane–hexane.
1
1578s; m(PF6) 844vs. H NMR [(CD3)2CO]: d 5.69 (d,
2H, OCH2, JPH =20.2), 6.68 (m, 1H, aromatics), 6.99
(m, 1H, aromatics), 7.25–7.73 (m, 12H, aromatics),
7.91 (m, 6H, aromatics), 8.14 (m, 2H, aromatics),
8.62 (d, 1H, H6 pyridine, JHH =10.4 Hz). 31P{1H}
NMR [(CD3)2CO]: d 129.0 (s, Ph2POCH2Py), ꢀ143.7
(m, PF6). FAB-MS (positive mode) m/z: 580
(M+ ꢀPF6).
[Pd(Phpy)(Ph2PNHPy-P,N)][PF6] (Ib). Yield:
102.5 mg (74%). Anal. Calc. for C28H23F6N3P2Pd: C,
49.2; H, 3.4; N, 6.1. Found: C, 49.3; H, 3.4; N, 6.2%.
FT-IR (nujol mull cmꢀ1): m(NH) 3336s; m(C‚N)
1616vs, 1574s; m(PN) 896s; m(PF6) 840vs. 1H NMR
[(CD3)2CO]: d 7.02 (m, 5H, aromatics), 7.59–8.06 (m,
14H, aromatics and NH), 8.24 (m, 2H, aromatics),
8.51 (d, 1H, H2 Phpy, JHH =5.6 Hz), 8.78 (d, 1H, H6 py-
ridine, JHH =6.0 Hz). 31P{1H} NMR [(CD3)2CO]: d 84.2
(s, Ph2PNHpy), ꢀ143.7 (m, PF6). FAB-MS (positive
mode) m/z: 538 (M+ ꢀPF6).
[Pd(Phox)(Ph2POCH2Py-P,N)][PF6] (IVa). Yield:
83.4 mg (58%). Anal. Calc. for C27H24F6N2O2P2Pd: C,
46.9; H, 3.5; N, 4.0. Found: C, 47.1; H, 3.6; N, 4.2%.
FT-IR (nujol mull cmꢀ1): m(C‚N) 1634vs, 1606s,
1
1588s; m(PF6) 840vs. H NMR [(CD3)2CO]: d 4.13 (t,
2H, Phox, JHH =9.4 Hz), 4.94 (t, 2H, Phox, JHH =9.4
Hz), 5.39 (d, 2H, OCH2, JPH =20.4), 6.61 (m, 1H, aro-
matics), 6.89 (m, 1H, aromatics), 7.14 (t, 1H, aromatic),
7.47 (m, 1H, aromatic), 7.78 (m, 12H, aromatics), 8.27
(m, 1H, aromatics), 9.20 (d, 1H, H6 pyridine,
JHH =10.1 Hz). 31P{1H} NMR [(CD3)2CO]: d 131.1 (s,
Ph2POCH2Py), ꢀ143.7 (m, PF6). FAB-MS (positive
mode) m/z: 545 (M+ ꢀPF6).
[Pd(Bzq)(Ph2PNHPy-P,N)][PF6] (IIb). Yield:
99.5 mg (75%). Anal. Calc. for C30H23F6N3P2Pd: C,
50.9; H, 3.3; N, 5.9. Found: C, 51.0; H, 3.4; N,
6.0%. FT-IR (nujol mull cmꢀ1): m(NH) 3340s;
1
m(C‚N) 1612vs; m(PN) 906s; m(PF6) 844vs. H NMR

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G. Sanchez et al. / Inorganica Chimica Acta 357 (2004) 4568–4576
4571
[(CD3)2CO]: d 7.28 (m, 4H, aromatics), 7.55–7.73 (m,
8H, aromatics and NH), 7.89–8.11 (m, 8H, aromatics),
8.75 (m, 2H, aromatics), 9.21 (d, 1H, H6 pyridine,
JHH =6.0 Hz). 31P{1H} NMR [(CD3)2CO]: d 84.9 (s,
Ph2PNHpy), ꢀ143.7 (m, PF6). FAB-MS (positive
mode) m/z: 562 (M+ ꢀPF6).
2.7. Crystal structure determination of [Pd(Azb)(Ph2-
POCH2Py-P,N)][PF6] (IIIa) and [Pd(Phpy)(Ph2PN-
HPy-P,N)][PF6] (Ib)
Crystals of (IIIa) (0.25·0.16·0.12 mm3) and (Ib)
(0.19·0.13·0.10 mm3) suitable for X-ray diffraction
studies were prepared by slow diffusion of hexane into
their dichloromethane solutions, mounted on glass fibre
and transferred to an Bruker Smart CCD diffractometer
at ꢀ173 ꢂC. The crystallographic data are summarised
[Pd(Azb)(Ph2PNHPy-P,N)][PF6] (IIIb). Yield:
77.9 mg (59%). Anal. Calc. for C29H24F6N4P2Pd: C,
49.0; H, 3.4; N, 7.9. Found: C, 49.2; H, 3.5; N,
8.0%. FT-IR (nujol mull cmꢀ1): m(NH) 3340s;
m(C‚N) 1614vs; m(PN) 906s; m(PF6) 842vs. 1H
NMR [(CD3)2CO]: d 6.45 (m, 1H, aromatics), 6.87
(m, 2H, aromatics), 7.24–7.71 (m, 20H, aromatics
and NH), 7.97 (d, 1H, H6 pyridine, JHH =7.6 Hz).
31P{1H} NMR [(CD3)2CO]: d 83.5 (s, Ph2PNHpy),
ꢀ143.7 (m, PF6). FAB-MS (positive mode) m/z: 565
(M+ ꢀPF6).
˚
in Table 1. Mo Ka radiation was used (k=0.71073 A).
The structures were solved by Patterson methods [45]
and refined anisotropically on F2 [45].
The ranges of hkl were ꢀ156h614, ꢀ126k611,
ꢀ376l637 for IIIa, and ꢀ116h611, ꢀ186k619,
ꢀ276l628 for Ib. Two molecules were found in the
asymmetrical unit of the latter. Hydrogen atoms were
introduced in calculated positions.
[Pd(Phox)(Ph2PNHPy-P,N)][PF6] (IVb). Yield:
105.6 mg (75%). Anal. Calc. for C26H23F6N3OP2Pd:
C, 46.2; H, 3.4; N, 6.2. Found: C, 46.4; H, 3.5; N,
6.2%. FT-IR (nujol mull cmꢀ1): m(NH) 3326s;
m(C‚N) 1614vs; m(PN) 904s; m(PF6) 848vs. 1H
NMR [(CD3)2CO]: d 4.52 (t, 2H, Phox, JHH =9.5
Hz), 5.03 (t, 2H, Phox, JHH =9.5 Hz), 6.98 (m, 2H,
aromatics), 7.15 (m, 2H, aromatics), 7.27 (d, 1H, ar-
omatic, JHH =8.4 Hz), 7.46 (d, 1H, aromatic,
JHH =7.4 Hz), 7.67 (m, 7H, aromatics and NH),
7.98 (m, 5H, aromatics), 8.49 (d, 1H, H6 pyridine,
JHH =6.0 Hz). 31P{1H} NMR [(CD3)2CO]: d 82.9 (s,
Ph2PNHpy), ꢀ143.7 (m, PF6). FAB-MS (positive
mode) m/z: 530 (M+ ꢀPF6).
2.8. Synthesis of complexes [Pd(CꢀN)(Ph2PNPy-
P,N)][CꢀN=2-pyridinin-phenyl (Ic), 7,8-benzoquinolyl
(IIc), phenylazophenyl (IIIc) and 2-(2-oxazolinyl)phe-
nyl (IVc)]
The new complexes were obtained by treating
[Pd(CꢀN)(l-OH)]2 with 2-(diphenylphosphinoami-
no)pyridine in molar ratio 1:2, using CH2Cl2 as solvent
and according to the following general method. To a di-
chloromethane solution (10 ml) of the corresponding
precursor [Pd(CꢀN)(l-OH)]2 (60 mg) was added the sto-
ichiometric amount of solid 2-(diphenylphosphinoami-
no)pyridine. After stirring for 30 min at room
temperature, the solution was concentrated under re-
duced pressure to half volume. Addition of hexane
caused precipitation of the new complexes, which were
filtered off, air dried and recrystallised from dichloro-
methane–hexane.
2.6. Preparation of [Pd{C4(COOMe)4}(Ph2PNHPy-
P,N)](Vb)
To an acetone (5 ml) solution of the precursor
[Pd{C4(COOMe)4}(CH3CN)2] (0.07 g, 0.15 mmol)
was added the stoichiometric amount of solid 2-(diph-
enylphosphinoamino)pyridine. The reaction was stir-
red at room temperature for 30 min, and then the
solvent was partially evaporated under reduced pres-
sure. The addition of diethyl ether caused the forma-
tion of a yellow solid, that was filtered off, air dried
and recrystallised from dichloromethane–hexane.
[Pd(Phpy)(Ph2PNPy-P,N)] (Ic). Yield: 92.9 mg
(80%). Anal. Calc. for C28H22N3PPd: C, 62.5; H, 4.1;
N, 7.8. Found: C, 62.6; H, 4.4; N, 8.0%. FT-IR (nujol
1
mull cmꢀ1): m(C‚N) 1598vs, 1578s; m(P–N) 934s. H
NMR [CDCl3]: d 6.26 (m, 1H, aromatics),6.82 (m, 1H,
aromatics),7.02 (m, 1H, aromatics), 7.06 (m, 1H, aro-
matics), 7.13 (m, 1H, aromatics), 7.24–7.46 (m, 8H, aro-
matics), 7.60 (m, 1H, aromatics), 7.77 (m, 1H,
aromatics), 7.90 (m, 6H, aromatics), 8.51 (d, 1H, H6 py-
ridine). 31P{1H} NMR [CDCl3]: d 89.1 (s, Ph2PNpy).
FAB-MS (positive mode) m/z: 537 (M+).
Yield:
58.8
mg
(69%).
Anal.
Calc.
for
C29H27N2O8PPd: C, 52.1; H, 4.1; N, 4.2. Found: C,
52.3; H, 4.4; N, 4.3%. FT-IR (nujol mull cmꢀ1):
m(NH) 3236s; m(C‚O) 1704vs; m(C‚N) 1656s; m(PN)
[Pd(Bzq)(Ph2PNPy-P,N)] (IIc). Yield: 98.3 mg
(88%). Anal. Calc. for C30H22N3PPd: C, 64.1; H, 3.9;
N, 7.5. Found: C, 64.0; H, 3.9; N, 7.4%. FT-IR (nujol
mull cmꢀ1): m(C‚N) 1602vs; m(P–N) 942s. 1H NMR
[CDCl3]: d 6.26 (m, 1H, aromatics), 6.90 (m, 1H, aromat-
ics), 7.12 (m, 1H, aromatics), 7.22–7.34 (m, 8H, aromat-
ics), 7.46 (m, 1H, aromatics), 7.54 (m, 2H, aromatics),
7.71 (m, 1H, aromatics), 7.90 (m, 5H, aromatics), 8.28
1
904s. H NMR [(CD ) CO]: d 2.77 (s, 3H, COOMe),
3 2
3.51 (s, 3H, COOMe), 3.56 (s, 3H, COOMe), 3.61 (s,
3H, COOMe), 6.91 (m, 1H, aromatics), 7.01 (m, 1H,
aromatics), 7.48–7.89 (m, 11H, aromatics and NH),
8.13 (m, 1H, aromatics), 8.42 (s, br, 1H, H6 pyridine).
31P{1H} NMR [(CD3)2CO]: d 77.9 (s, Ph2PNHpy).
FAB-MS (positive mode) m/z: 669 (M+).

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G. Sanchez et al. / Inorganica Chimica Acta 357 (2004) 4568–4576
4572
Table 1
Crystal data and structure refinement details for compounds IIIa and Ib
IIIa
Ib
Empirical formula
Formula weight
C30H25F6N3OP2Pd
725.87
C28H23F6N3P2Pd
683.83
100(2)
Temperature (K)
Absorption coefficient (mmꢀ1
Crystal system
100(2)
0.821
)
0.888
triclinic
monoclinic
P21/c
ꢀ
Space group
˚
P1
8.6055(4)
a (A)
˚
11.3185(7)
9.0996(6)
b (A)
14.8741(7)
21.6614(11)
˚
c (A)
28.3540(19)
90
a (ꢂ)
b (ꢂ)
c (ꢂ)
96.35(1)
91.61(1)
97.5450(10)
90
2895.0(3)
105.40(1)
2651.9(2)
3
˚
V (A )
Z
4
1.665
4
1.713
Dcalc (Mg mꢀ3
F(000)
)
1456
32565
1368
30989
Reflections collected
Independent reflections (Rint
Parameters
)
6691 (0.220)
388
full-matrix least-squares on F2
0.0374
11840 (0.0205)
721
full-matrix least-squares on F2
0.0347
Refinement method
a
R1
wRb
Sc
0.0805
1.241
0.0806
0.975
ꢀ3
˚
Maximum, minimum Dq (e A
)
0.795, ꢀ0.506
0.599, ꢀ0.611
P
P
a
R1 = jFojꢀjFcj/ jFoj for reflections with I>2rI.
n
o
1=2
P
P
2
2
b
wR2 ¼
½wðF 2o ꢀ F c2Þ ꢁ= ½wðF 2oÞ ꢁ
for all reflections; wꢀ1 =r2(F2)+(aP)2 +bP, where P ¼ ð2F c2 þ F o2Þ=3 and a and b are constants set by
the program.
n
o
1=2
P
2
c
S ¼
½wðF 2o ꢀ F 2c Þ ꢁ=ðn ꢀ pÞ
; n is the number of reflections and p, the total number of parameters refined.
(m, 1H, aromatics), 8.89 (m, 1H, H6 pyridine). 31P1H
NMR [CDCl3]: d 89.6 (s, Ph2PNpy). FAB-MS (positive
mode) m/z: 561 (M+).
2.9. Preparation of [Pd{C4(COOMe)4}(Ph2PNPy-
P,N)][NBu4] (Vc)
[Pd(Azb)(Ph2PNPy-P,N)] (IIIc). Yield: 84.6 mg
(76%). Anal. Calc. for C29H23N4PPd: C, 61.7; H, 4.1;
N, 9.9. Found: C, 61.7; H, 4.0; N, 9.7%. FT-IR (nujol
mull cmꢀ1): m(C‚N) 1604vs; m(P–N) 940s. 1H NMR
[CDCl3]: d 5.90 (m, 1H, aromatics), 6.93 (m, 3H, aro-
matics), 7.16 (m, 3H, aromatics), 7.32–7.46 (m, 9H, ar-
omatics), 7.61 (m, 2H, aromatics), 7.83 (m, 4H,
aromatics), 8.00 (d, 1H, H6 pyridine, JHH =7.5Hz).
31P1H NMR [CDCl3]: d 87.0 (s, Ph2PNpy). FAB-MS
(positive mode) m/z: 564 (M+).
[Pd(Phox)(Ph2PNPy-P,N)] (IVc). Yield: 90.8 mg
(77%). Anal. Calc. for C26H22F6N3OPPd: C, 58.9; H,
4.2; N, 7.9. Found: C, 59.0; H, 4.3; N, 8.1%. FT-IR (nujol
mull cmꢀ1): m(C‚N) 1604vs; m(P–N) 942s. 1H NMR
[CDCl3]: d 4.16 (t, 2H, Phox, JHH =9.4 Hz), 4.70 (t, 2H,
Phox, JHH =9.4 Hz), 6.24 (m, 1H, aromatics), 6.89 (m,
3H, aromatics), 7.03 (m, 4H, aromatics), 7.13–7.44 (m,
7H, aromatics), 7.97 (m, 3H, aromatics). 31P{1H}
NMR [CDCl3]: d 84.7 (s, Ph 2 PNpy). FAB-MS (positive
mode) m/z: 529 (M+).
To an acetone (15 ml) solution of the precursor
[Pd2{C4(COOMe)4}2(l-OH)2][NBu4]2 (0.06 g, 0.05
mmol) was added the stoichiometric amount of solid
2-(diphenylphosphinoamino)pyridine. The reaction
was stirred at room temperature for 60 min, and then
the solvent was partially evaporated under reduced
pressure. The addition of diethyl ether caused the
formation of a yellow solid, that was filtered off,
air dried and recrystallised from dichloromethane–
hexane. Yield: 57.1 mg (68%). Anal. Calc. for
C45H62N3O8PPd: C, 59.4; H, 6.9; N, 4.6. Found: C,
59.4; H, 6.9; N, 4.7%. FT-IR (nujol mull cmꢀ1):
m(C‚O) 1718s; m(C‚N) 1602vs. m(P–N) 933s 1H
NMR [CDCl3]: d 1.01 (t, 12H, NBu4), 1.41 (m, 8H,
NBu4), 1.65 (m, 8H, NBu4), 3.47 (m, 20H,
NBu4 +COOMe), 6.31 (m, 1H, aromatics), 6.91 (m,
1H, aromatics), 6.87–7.38 (m, 11H, aromatics), 7.76
(s, br, 1H, H6 pyridine). 31P{1H} NMR [CDCl3]: d
85.3 (s, Ph2PNpy). FAB-MS (negative mode) m/z:
667 (Mꢀ).

´
G. Sanchez et al. / Inorganica Chimica Acta 357 (2004) 4568–4576
4573
3. Results and discussion
from the rest aromatic resonances. In both series the
lowest field values for this proton is shown by the Phpy
derivative, whereas Bzq complexes present the highest
one. The 31P{1H} NMR spectra of the mononuclear
complexes confirm their cationic nature and the absence
of any fluxional process, and consist of a [PF6]ꢀ septup-
let centered at ꢀ143.7 ppm together with sharp singlets
with chemical shifts in the usual range of Pd(II)-bound
phosphorus atom. There are not marked differences in
chemical shift on varying the cyclometallated ligand (a
compounds 129.0–131.1 ppm; b compounds 82.9–84.9
ppm). The FAB mass spectrometry displays the expect-
ed fragments corresponding to [M+ ꢀPF6], in accord-
ance with reported data for related compounds [20,21].
On the other hand, recrystallisation of [Pd{C4(CO-
OMe)4}]n from acetonitrile affords in good yield a novel
complex with satisfactory microanalytical data for
[Pd{C4COOMe4}(CH3CN)2] (V). The incorporation of
acetonitrile was substantiated by the presence of IR ab-
sorption bands of strong intensity at 2322 and 2292
cmꢀ1, and further confirmed by NMR data, as shown
in Section 2. The results of a thermogravimetric analysis
of V in nitrogen display a weight loss at ca. 115 ꢂC of
about 17% of the total weight, that corresponds to liber-
ation of two CH3CN molecules. In acetone, the new pre-
cursor V reacts with ligands a or b (molar ratio 1:1)
under mild conditions to give the corresponding neutral
square-planar complexes Va and Vb shown in Scheme 2.
The new palladium complexes are air-stable yellow sol-
ids that show negligible molar conductance. The IR
spectra of these complexes show a very strong bands
[m(CO)] at ꢂ1705 cmꢀ1 characteristic of the carboxylate
groups [31,42] together with the above mentioned absor-
bances that confirm the presence of the pyridylphos-
phine ligands.
In dichloromethane, the chloro-bridged cyclometal-
lated dimers [{Pd(l-Cl)(CꢀN)}2][CꢀN=2-pyridinin-phe-
nyl I, 7,8-benzoquinolyl II, phenylazophenyl III and
2-(2-oxazolinyl)phenyl IV] react with ligands a or b in
the presence of stoichiometric KPF6 under the smooth
conditions described in Section 2, to afford the white
compounds [Pd(CꢀN)(Ph2POCH2Py-P,N][PF6] (Ia–
IVa) or [Pd(CꢀN)(Ph2PNHPy-P,N)][PF6] (Ib–IVb), in
which a rigid P,N-chelation of the ligands is induced
(Scheme 1). Measurements of their molar conductivity
in acetone solutions indicate that all the complexes be-
have as 1:1 electrolytes [46], in accordance with the
proposed formulae. The new palladium complexes are
air-stable and their IR spectra show the characteristic
absorptions of the PF6 ꢀ anion at ca. 840 and 558
cmꢀ1, together with two bands in the 1632–1568 cmꢀ1
region, attributed to the C‚N stretching vibrations of
the P,N-ligands and the corresponding cyclometallated
backbone. The m(C‚N) band that appears at higher
wavenumber can be assigned to the P,N-pyridine ring
involved in a chelating coordination mode. As expected
on the analogy of previously reported data [20 and ref-
erences therein], this band is shifted with regard to the
free ligands (1601 cmꢀ1). The IR spectra of compounds
Ib–IVb also display m(P–N) bands around 900 cmꢀ1
characteristic of –NH protonated ligand, and a sharp
strong m(N–H) absorption at ꢂ3330 cmꢀ1 that suggest
little hydrogen-bonding interaction between the amine
protons and the [PF6]ꢀ anion.
1
The H NMR spectra show the corresponding aro-
matic signals of the cyclometallated ligands, with a typ-
ical doublet resonance attributed to the pyridyl C [6]
proton in the 7.97–9.27 ppm region, shifted downfield
P
N
C
N
X
C
N
Cl
Cl
N
C
Pd
+ 2 N-P + 2 KPF6
- 2 KCl
Pd
Pd
2
[PF6]
C
N
X = -CH2-O-; Ia, IIa, IIIa, IVa.
X = -NH-; Ib, IIb, IIIb, IVb.
N
N
N
N
O
N
(I)
(II)
(IV)
(III)
Scheme 1.

´
G. Sanchez et al. / Inorganica Chimica Acta 357 (2004) 4568–4576
4574
[Pd{C4(COOMe)4}]n + CH3CN(solvent)
R
R
R
R
P
N
X
(CH3)2CO
- 2CH3CN
Pd
[Pd{C4(COOMe)4}(CH3CN)2] + N-P
Ph
Ph
Ph
Ph
P
P
O
NH
or
CH2
N-P =
N
N
X = -CH2-O-;Va.
X = -NH-; Vb.
b
a
Scheme 2.
1
The H NMR spectra also display the aromatic sig-
nals of the neutral ligands, with the typical low field res-
onance of H6 as outstanding feature, together with the
characteristic four resonances of asymmetric palladacy-
clopentadiene compounds that correspond to the differ-
ent methoxycarbonyl groups [41]. As expected,
complexes Va and Vb bearing a palladacyclopentadiene
backbone present the highest field 31P{1H} NMR sig-
nals in its respective series. This variation is in agree-
ment with our previous results found when comparing
the same cyclometallated systems with iminophosphine
ligands [31,32].
tra of new compounds with regards to those of the start-
ing materials, together with the expected 1H NMR data,
confirmed that the proposed reactions took place. An
increase in P–N bond order and consequent shifting of
the m(PN) absorption to higher frequencies has been ob-
served in P–N-py systems upon deprotonation. In our
compounds Ic–Vc, a significant shift of ca. 35 cmꢀ1 in
the m(PN) band is detected in comparison with related
Ib–Vb complexes. Deprotonation of the amino group al-
so involves displacement of singlet resonances in the
31P{1H} NMR spectra, that now appear in the range
84.7–89.1 ppm.
In order to prepare new complexes with the anionic
[PyNPPh2]ꢀ ligand c, the di-l-hydroxo-complexes
3.1. X-ray structures of IIIa and Ib
[{Pd(l-OH)(CꢀN)}2]
and
[Pd2{C4(COOMe)4}2(l-
OH)2][NBu4]2 were employed as precursors in reactions
with PyNHPPh2. A few examples of compounds con-
taining c have been described [20,47], involving in their
Selected bond distances and angles are presented in
Table 2. To the best of our knowledge (Cambridge
Structural Database V. 5.24 with February, April and
July 2003 updates), the X-ray data of IIIa (Fig. 1) repre-
sents the first description of a crystal structure in which
the 2-(diphenylphosphinyl)oxymethylpyridine ligand
appears coordinated to a metal centre. The bite angle
of this ligand coordinated to palladium in IIIa is
91.16(6)ꢂ. The coordination around the metal centre is
t
preparation treatment with BuOK/MeOH. The recog-
nised basicity of such precursors and its usefulness in
previous synthetic work prompt us to perform the reac-
tions shown in Scheme 3 to obtain Ic–Vc with satisfac-
tory microanalytical and FAB mass spectrometry data.
The loss of both m(NH) and m(OH) bands in the IR spec-
n-
P
2n-
Ph
C
H
Ph
N
C
X
O
X
C
P
Pd
NH
Pd
Pd
+ 2
2
X
N
N
-2 H2O
O
H
X = -N; n = 0; Ic, IIc, IIIc, IVc.
X = -C; n = 1; Vc
Scheme 3.

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G. Sanchez et al. / Inorganica Chimica Acta 357 (2004) 4568–4576
4575
Table 2
˚
Selected bond lengths (A), angles (ꢂ) and torsion angles (ꢂ)
˚
Bond length (A)/angle/torsion angle (ꢂ) IIIa
Ib
Pd(1)–C(1)
Pd(1)–N(1)
Pd(1)–N(2)
Pd(1)–P(1)
1.998(3)
2.002(3)
2.094(2)
2.129(2)
2.2137(7)
2.110(2)
2.138(2)
2.2329(7)
C(1)–Pd(1)–N(1)
C(1)–Pd(1)–N(2)
C(1)–Pd(1)–P(1
N(1)–Pd(1)–N(2)
N(1)–Pd(1)–P(1)
N(2)–Pd(1)–P(1)
78.91(10)
166.93(9)
94.64(8)
96.41(8)
171.13(6)
91.16(6)
81.20(10)
171.05(9)
98.03(8)
100.52(9)
170.02(6)
81.78(6)
tetrahedrally distorted with improper torsion angles of
ꢀ4.44ꢂ for P(1)–C(1)–N(1)–Pd(1) and ꢀ8.25ꢂ for
N(2)–N(1)–C(1)–Pd(1) [48]. In accordance with the clas-
sification from Allen and Taylor [49], the six-membered
ring defined by the palladium atom and the chelating
P,N-ligand show a distorted sofa conformation. The tor-
sion angles in the complex do not conform to the ideal
of around 20ꢂ.
Fig. 2. ORTEP diagram of one of the two independent molecules
present in the asymmetry unit of Ib. For clarity, all hydrogen atoms
have been omitted.
A slight tetrahedral distortion of the planar palladi-
um environment is observed in Ib (Fig. 2), with improp-
er torsion angles of ꢀ6.92ꢂ for P(1)–C(1)–N(1)–Pd(1)
and ꢀ5.72ꢂ for N(2)–N(1)–C(1)–Pd(1) (mean angles of
the two complexes in the the asymmetrical unit) [48].
The small bite angle of the ligand is similar to that found
in related compounds, and other trends reported for pal-
ladium complexes in comparison with the free ligand are
also followed [20]. Thus, a little reduction in the P–N
observed, together with a small elongation in N(3)–
˚
˚
C(16) length [1.385(3) A; free ligand 1.374(5) A]. In
our complex is also detected an elongation in N(2)–
˚
˚
C(16) length [1.345(3) A; free ligand 1.329(4) A]. The ab-
sence of solid state hydrogen bonding between the NH
proton and PF6 counter ion is confirmed by N–F dis-
˚
tances over 3.6 A, in agreement with the interpretation
of the IR spectra.
˚
˚
length [1.696(2) A; free ligand 1.705(3) A] and P(1)–
N(3)–C(16) angle [119.06(18)ꢂ; free ligand 124.4(2)ꢂ] is
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 235179 (IIIa), 235180 (Ib)
Copies of this information may be obtained from The
Director, CCDC, 12 Union Road, Cambridge, CB
1EZ, UK (fax: +44-1233-336033; e-mail: depos-
it@ccdc.cam.ac.uk or www:http://www.ccdc.cam.ac.uk).
Acknowledgement
´
Financial support of this work by Direccion General
de Investigacion (project-BQU2001-0979-C02-01/02) is
´
gratefully acknowledged.
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