New cyclometalated palladium(II) complexes with iminophosphines: Crystal structures of [Pd(C^N)(o-Ph2PC6H4-CH=NR)][PF6] (C^N=azobenzene, R=Et; C^N=2-phenylpyridine, R=Me)

Article abstract of DOI:10.1016/S0277-5387(99)00229-6

The synthesis of new cyclometalated compounds of palladium(II) with the mixed-donor bidentate ligands o-Ph₂PC₆H₄-CH=NR is described. Two series of complexes [Pd(C^N)(o-Ph₂PC₆H₄-CH=NR)][PF₆] have been prepared using either azobenzene or 2-phenylpyridine as cyclometalated ligands [C^N=azobenzene (azb); R=Me (1a), Et (2a), ⁿPr (3a), ⁱPr (4a), ^tBu (5a), Ph (6a), NH-Me (7a); C^N=2-phenylpyridine (phpy); R=Me (1b), Et (2b), ⁿPr (3b), ⁱPr (4b), ^tBu (5b), Ph (6b), NH-Me (7b)]. The new complexes were characterized by partial elemental analyses and spectroscopic methods (IR, FAB, ¹H and ³¹P NMR). The molecular structures of compounds 2a (monoclinic, P 2₁/n) and 1b (monoclinic, C 2/c) have been determined by a single-crystal diffraction study. In both cases this technique revealed the relative trans configuration between the phosphorus atom and the nitrogen atom of the ortho-metalated ligand. Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(99)00229-6

Polyhedron 18 (1999) 3057–3064
www.elsevier.nl/locate/poly
New cyclometalated palladium(II) complexes with iminophosphines
Crystal structures of [Pd(C3N)(o-Ph2PC6H4 –CH5NR)][PF6]
(C3N5azobenzene, R5Et; C3N52-phenylpyridine, R5Me)
a ,
a
a
a
b
a
*
´
´
´
´
´
Gregorio Sanchez , Jose L. Serrano , M.A. Moral , Jose Perez , Elies Molins , Gregorio Lopez
a
´
´
Departamento de Quımica Inorganica, Universidad de Murcia, 30071 Murcia, Spain
b
`
Institut de Ciencia de Materials de Barcelona-CSIC. Campus Universitari de Bellaterra, E-08193 Cerdanyola, Barcelona, Spain
Received 17 May 1999; accepted 5 August 1999
Abstract
The synthesis of new cyclometalated compounds of palladium(II) with the mixed-donor bidentate ligands o-Ph2PC6H4 –CH5NR is
described. Two series of complexes [Pd(C3N)(o-Ph2PC6H4 –CH5NR)][PF6] have been prepared using either azobenzene or 2-
phenylpyridine as cyclometalated ligands [C3N5azobenzene (azb); R5Me (1a), Et (2a), nPr (3a), iPr (4a), tBu (5a), Ph (6a), NH–Me
(7a); C3N52-phenylpyridine (phpy); R5Me (1b), Et (2b), nPr (3b), iPr (4b), tBu (5b), Ph (6b), NH–Me (7b)]. The new complexes were
1
characterized by partial elemental analyses and spectroscopic methods (IR, FAB, H and 31P NMR). The molecular structures of
compounds 2a (monoclinic, P 21 /n) and 1b (monoclinic, C 2/c) have been determined by a single-crystal diffraction study. In both cases
this technique revealed the relative trans configuration between the phosphorus atom and the nitrogen atom of the ortho-metalated ligand.
1999 Elsevier Science Ltd. All rights reserved.
Keywords: Cyclometalated palladium(II) complexes; Iminophosphine ligands; Crystal structures
1. Introduction
been implicated as potential photosensitizers [8–14] there
has been a growing interest in this kind of compounds.
On the other hand, there has also recently been consider-
able interest in the chemistry of polydentate ligands with
both hard and soft donor atoms [15–21]. In this sense, the
metal complexes with N and P donor atoms display a
variety of coordination well beyond those of P–P or N–N
ligands [22]. Furthermore, this N,P-ligands show a par-
ticular behaviour binding soft metal centres such as Pd(II)
and Pt(II) that make their complexes good precursors in
catalytic processes [23–29]. Thus, the hard-ligand com-
ponents can readily dissociate generating a vacant site on
the metal ion for potential substrate binding. Among the
most widely studied ligands with this characteristics are
the pyridylphosphines and the iminophosphines that we
present in this work, which have been profusely reported
since 1992 in complexes with rhodium [25], iridium [23],
ruthenium [30] and palladium [27–34].
Azobenzenes and heteroaromatic ligands such as 2-
phenylpyridine can easily be orthometalated by Pd(II) salts
via C(sp2)–H bond cleavage [1,2] to usually give the
corresponding acetato or halide-bridged dimers. These
dinuclear complexes have been thoroughly studied [3] and
employed as precursors of mononuclear cyclometalates of
general formula M(C3N)LX (M5Pd, Pt; C3N5ortho-
metalated ligand; L5neutral monodentate ligand such as
pyridines and phosphines; X5halide) [4–6]. However,
there is an apparent lack of data for analogous reactions
with neutral bidentate ligands [7], which imply the loss of
both halide ligands and the presence of an appropiate
anion. It should be noted that since a number of ortho-
metalated complexes of the platinum group elements have
Here we report the preparation of some ortho-metalated
palladium(II) derivatives [C3N5azobenzene (azb) or 2-
phenylpyridine (phpy)] with the mixed-donor bidentate
*Corresponding author. Tel.: 134-968-8367454; fax: 134-968-364-
148.
´
E-mail address: gsg@fcu.um.es (G. Sanchez)
0277-5387/99/$ – see front matter
PII: S0277-5387(99)00229-6
1999 Elsevier Science Ltd. All rights reserved.

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G. Sanchez et al. / Polyhedron 18 (1999) 3057–3064
3058
iminophosphine ligands (N,P-donors). The iminophosphine
ligands were prepared via Schiff-base reaction between
o-(diphenylphosphino)benzaldehyde and the corresponding
amine [25].
[Pd(azb)hP(o-C6H4 –CH5N–R)Ph2j][PF6]
(R5Et)
(2a)was obtained in 82% yield. Anal. calc. for
C33F6H29N3P2Pd: C, 52.8; H, 3.9; N, 5.6. Found: C, 52.6;
H, 3.8; N, 5.5%. LM5145 V21 cm2 mol21. IR (cm21):
1644 (C5N str). FAB–MS (positive mode) m/z: 604
[Pd(azb)hP(o-C6H4 –CH5N–Et)Ph2j]1.
[Pd(azb)hP(o-C6H4 –CH5N–R)Ph2j][PF6]
(R5nPr)
2. Experimental
(3a)was obtained in 75% yield. Anal. calc. for
C34F6H31N3P2Pd: C, 53.4; H, 4.1; N, 5.5. Found: C, 53.3;
H, 4.0; N, 5.5%. LM5132 V21 cm2 mol21. IR (cm21):
1638 (C5N str). FAB–MS (positive mode) m/z: 618
[Pd(azb)hP(o-C6H4 –CH5N–nPr)Ph2j]1.
C, H and N analyses were carried out with a Perkin–
Elmer 240C microanalyser. IR spectra were recorded on a
Perkin–Elmer 1430 spectrophotometer using Nujol mulls
between polyethylene sheets. NMR data were recorded on
a Bruker AC 200E (1H) or a Varian Unity 300 (1H, 31P)
spectrometer. Conductance measurements were performed
with a Crison 525 conductimeter (in acetone; c51023 M).
Mass spectrometric analyses were performed on a FISONS
VG AUTOSPEC double-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.
The cyclometalated precursors [hPd(C3N)(m-Cl)j2]
(C3N5azobenzene or 2-phenylpyridine) were prepared as
described in the literature [35,5]. The iminophosphine [25]
ligands were prepared according to reported procedures
and all the solvents were dried by standard methods before
use.
[Pd(azb)hP(o-C6H4 –CH5N–R)Ph2j][PF6]
(R5iPr)
(4a)was obtained in 82% yield. Anal. calc. for
C34F6H31N3P2Pd: C, 53.4; H, 4.1; N, 5.5. Found: C, 53.5;
H, 4.3; N, 5.5%. LM5117 V21 cm2 mol21. IR (cm21):
1646 (C5N str). FAB–MS (positive mode) m/z: 618
[Pd(azb)hP(o-C6H4 –CH5N–iPr)Ph2j]1.
[Pd(azb)hP(o-C6H4 –CH5N–R)Ph2j][PF6]
(R5tBu)
(5a)was obtained in 76% yield. Anal. calc. for
C35F6H33N3P2Pd: C, 54.0; H, 4.2; N, 5.4. Found: C, 54.2;
H, 4.3; N, 5.5%. LM5134 V21 cm2 mol21. IR (cm21):
1626 (C5N str). FAB–MS (positive mode) m/z: 632
[Pd(azb)hP(o-C6H4-CH5N–tBu)Ph2j]1.
[Pd(azb)hP(o-C6H4 –CH5N–R)Ph2j][PF6]
(R5Ph)
(6a)was obtained in 90% yield. Anal. calc. for
C37F6H29N3P2Pd: C, 55.7; H, 3.6; N, 5.3. Found: C, 55.8;
H, 3.5; N, 5.5%. LM5125 V21 cm2 mol21. IR (cm21):
1618 (C5N str). FAB–MS (positive mode) m/z: 652
[Pd(azb)hP(o-C6H4 –CH5N–Ph)Ph2j]1.
2.1. Preparation of the complexes
[Pd(azb)hP(o-C6H4 –CH5N–R)Ph2j][PF6]
(R5NH–
Complexes
[Pd(C3N)(o-Ph2PC6H4 –CH5NR)][PF6]
n
Me) (7a) was obtained in 88% yield. Anal. calc. for
C32F6H28N4P2Pd: C, 51.2; H, 3.7; N, 7.5. Found: C, 51.2;
H, 3.5; N, 7.5%. LM5144 V21 cm2 mol21. IR (cm21):
3406 (N–H str.), 1630 (C5N str). FAB–MS (positive
[C3N5azobenzene (azb); R5Me (1a), Et (2a), Pr (3a),
t
iPr (4a), Bu (5a), Ph (6a), NH–Me (7a); C3N52-
phenylpyridine (phpy); R5Me (1b), Et (2b), nPr (3b), iPr
(4b), tBu (5b), Ph (6b), NH–Me (7b)]
mode)
NHMe)Ph2j]1.
[Pd(phpy)hP(o-C6H4 –CH5N–R)Ph2j][PF6]
m/z:
605
[Pd(azb)hP(o-C6H4 –CH5N–
The complexes were obtained by treating [hPd(C3
N)(F–Cl)j2] (C3N5azobenzene or 2-phenylpyridine)
with the corresponding iminophosphine (molar ratio 1:2) in
acetone according to the following general method. To an
acetone (5 ml) suspension of the precursor [hPd(C3N)(F–
Cl)j2] (0.07 mmol.) was added the stoichiometric amount
of the previously prepared iminophosphine dissolved in
acetone (5 ml) and KPF6 (0.140 mmol.). The reaction
changed colour immediately and the mixture was refluxed
for 15 min. The hot solution was filtered through celite and
then concentrated under reduced pressure to half volume.
Addition of hexane caused precipitation of the new com-
plexes, which were filtered off, air-dried and recrystallized
from acetone–hexane.
(R5Me)
(1b)was obtained in 69% yield. Anal. calc. for
C31F6H26N2P2Pd: C, 52.5; H, 3.7; N, 3.9. Found: C, 52.3;
H, 3.5; N, 3.8%. LM5140 V21 cm2 mol21. IR (cm21):
1642 (C5N str). FAB–MS (positive mode) m/z: 563
[Pd(phpy)hP(o-C6H4 –CH5N–Me)Ph2j]1.
[Pd(phpy)hP(o-C6H4 –CH5N–R)Ph2j][PF6]
(R5Et)
(2b)was obtained in 75% yield. Anal. calc. for
C32F6H28N2P2Pd: C, 53.2; H, 3.9; N, 3.9. Found: C, 53.5;
H, 3.8; N, 3.8%. LM5148 V21 cm2 mol21. IR (cm21):
1638 (C5N str). FAB–MS (positive mode) m/z: 577
[Pd(phpy)hP(o-C6H4 –CH5N–Et)Ph2j]1.
[Pd(phpy)hP(o-C6H4 –CH5N–R)Ph2j][PF6]
(R5nPr)
[Pd(azb)hP(o-C6H4 –CH5N–R)Ph2j][PF6]
(R5Me)
(3b)was obtained in 71% yield. Anal. calc. for
C33F6H30N2P2Pd: C, 53.8; H, 4.1; N, 3.8. Found: C, 53.9;
H, 4.2; N, 3.6%. LM5129 V21 cm2 mol21. IR (cm21):
1641 (C5N str). FAB–MS (positive mode) m/z: 591
[Pd(phpy)hP(o-C6H4 –CH5N–nPr)Ph2j]1.
(1a)was obtained in 72% yield. Anal. calc. for
C32F6H27N3P2Pd: C, 52.2; H, 3.7; N, 5.7. Found: C, 52.3;
H, 3.5; N, 5.5%. LM5134 V21 cm2 mol21. IR (cm21):
1646 (C5N str). FAB–MS (positive mode) m/z: 590
[Pd(azb)hP(o-C6H4 –CH5N–Me)Ph2j]1.
[Pd(phpy)hP(o-C6H4 –CH5N–R)Ph2j][PF6]
(R5iPr)

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G. Sanchez et al. / Polyhedron 18 (1999) 3057–3064
3059
Table 1
1640 (C5N str). FAB–MS (positive mode) m/z: 605
[Pd(phpy)hP(o-C6H4 –CH5N–tBu)Ph2j]1.
Crystal data and summary of data collection and refinement for
[Pd(azb)hP(o-C6H4 –CH5N–Et)Ph2j][PF6] (2a) and [Pd(phpy)hP(o-
C6H4 –CH5N–Me)Ph2j][PF6] (1b)
[Pd(phpy)hP(o-C6H4 –CH5N–R)Ph2j][PF6]
(R5Ph)
(6b)was obtained in 65% yield. Anal. calc. for
C36F6H28N2P2Pd: C, 53.5; H, 3.5; N, 3.5. Found: C, 53.7;
H, 3.7; N, 3.5%. LM5137 V21 cm2 mol21. IR (cm21):
1638 (C5N str). FAB–MS (positive mode) m/z: 661
[Pd(phpy)hP(o-C6H4 –CH5N–Ph)Ph2j]1.
[Pd(phpy)hP(o-C6H4 –CH5N–R)Ph2j][PF6] (R5NH–
Me) (7b) was obtained in 66% yield. Anal. calc. for
C31F6H27N3P2Pd: C, 49.0; H, 3.5; N, 3.7. Found: C, 49.2;
H, 3.5; N, 3.5%. LM5137 V21 cm2 mol21. IR (cm21):
3406 (N–H str.), 1680 (C5N str). FAB–MS (positive
2a
1b
Empirical formula
Form. weight
Crystal system
Space group
Unit cell
C33H29F6N3P2Pd
749.3
monoclinic
P21 /n
a59.293(2) A
b514.3842(10) A
c523.938(2) A
a5908
b5100.783(10)8
g5908
3143,1(7)
4
1.585
0.757
0.71073
6209
0.0454, 0.1115
1.044
C31H26F6N3P2Pd
708.8
monoclinic
C2/c
a521.253(4) A
b515.379(3) A
˚
˚
˚
˚
˚
dimensions
˚
c519.274(4) A
a5908
b5104.29(3)8
g5908
6105 (2)
8
1.543
0.773
0.71073
4887
0.0366, 0.0903
1.129
3
mode)
m/z:
614
[Pd(phpy)hP(o-C6H4 –CH5N–
˚
V (A )
Z
NHMe)Ph2j]1.
Dcalcd (Mg/m3)
Crystal Structure determination of [Pd(azb)(o-
Ph2PC6H4 –CH5NEt)][PF6] (2a) and [Pd(phpy)(o-
Ph2PC6H4 –CH5NMe)][PF6] (1b)
X-ray diffraction experiments were carried out on a
Siemens P4 diffractometer equipped with a graphite mono-
chromator for Mo Ka radiation. The crystallographic data
are shown in Table 1. Empirical C-scan mode absorption
correction was made.
F (mm21
l (A)
)
˚
Obs. refl.
R1, Rw2
GooF
(4b)was obtained in 80% yield. Anal. calc. for
C33F6H30N2P2Pd: C, 53.8; H, 4.1; N, 3.8. Found: C, 53.7;
H, 4.2; N, 3.6%. LM5131 V21 cm2 mol21. IR (cm21):
1640 (C5N str). FAB–MS (positive mode) m/z: 591
[Pd(phpy)hP(o-C6H4 –CH5N–iPr)Ph2j]1.
Data for 2a were collected using a single crystal of
approximate dimensions 0.2030.2530.22 mm. Accurate
cell parameters were determined by least-squares fitting of
25 high-angle reflections. The scan method was v with the
range of hkl (0< h<11,214<k<14,214<l<14) corre-
sponding to2Qmax5508. The structure was solved by the
Patterson methods and refined anisotropically on F2 [36].
Hydrogen atoms were introduced in calculated positions.
The final R factor was 0.0454 [Rw50.1115, where w51/
[Pd(phpy)hP(o-C6H4 –CH5N–R)Ph2j][PF6] (R5tBu)
(5b)was obtained in 85% yield. Anal. calc. for
C34F6H32N2P2Pd: C, 54.4; H, 4.3; N, 3.7. Found: C, 54.2;
H, 4.4; N, 3.5%. LM5142 V21 cm2 mol21. IR (cm21):
Scheme 1.

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G. Sanchez et al. / Polyhedron 18 (1999) 3057–3064
3060
Table 2
NMR data (ppm; J in Hz) for the palladium(II) complexes (solvent CDCl3)
Complex
1H (SiMe4)
31P (H3PO4)
1a
6.26 (m, 1H, 39-azb)
40.2 (s, NP)
6.82 (m, 1H, 49-azb)
102.4 (spt, PF6, J5710)
7.03 (dd, 1H, 30-NP, JHH510.8; JHP510.5)
7.23 (m, 1H, 59-azb)
7.55 (m, 16H; 2,3,4,5,6-azb; 40-NP; Ph)
7.80 (m, 1H, 50-NP)
8.05 (d, 1H, 69-azb)
8.17 (dd, 1H, 60-NP,JHH57,5; JHP57,2)
8.57 (s, 1H, CH5N)
2a
0.73 (t, 3H, CH3-, J57,3)
3.30 (cd, 2H, -CH2-, J57,0)
6.33 (m, 1H, 39-azb)
38.9 (s, NP)
102.4 (spt, PF6, J5710)
6.83 (m, 2H, 49-azb; 6-NP)
7.16 (m, 1H, 59-azb)
7.40 (m, 16H, 2,3,4,5,6-azb; 40-NP; Ph)
7.77 (m, 1H, 50-NP)
8.00 (d, 1H, 69-azb, J51.17)
8.16 (dd, 1H, 60-NP, JHH57,4; JHP57,1)
8.57 (s, 1H, CH5N)
3a
0.29 (t, 3H, CH3-)
38.3 (s, NP)
1.70 (m, 2H, -CH2-)
102.4 (spt, PF6, J5710)
3.28 (t, 2H, -CH2-, J56,9)
6.40 (m, 1H, 39-azb)
6.85 (m, 1H, 49-azb)
6.94 (dd, 1H, 30-NP, JHH58,1; JHP58,0)
7.25 (m, 1H, 59-azb)
7.51 (m, 16H, 2,3,4,5,6-Azb; 40-NP; Ph)
7.84 (m, 1H, 50-NP)
8.06 (d, 1H, 69-azb, J57,8)
8.22 (m, 1H, 60-NP)
8.56 (s, 1H, CH5N)
4a
0.78 (s-br, 6H, 2CH3-)
38.6 (s, NP)
3,64 (spt, 1H, CH)
102.4 (spt, PF6, J5710)
6.40 (m, 1H, 39-azb)
6.82 (m, 2H, 49-azb; 3-NP)
7.36 (m, 17H, 2,3,4,5,6,8-Azb; 40-NP; Ph)
7.81 (m, 1H, 50-NP)
8.00 (d, 1H, 69-azb, J57,5)
8.20 (dd, 1H, 60-NP, JHH511.4; JHP511.2)
8.51 (s, 1H, CH5N)
5a
0.82 (s, 9H, 3CH3-)
39.1 (s, NP)
6.46 (m, 1H, 39-azb)
102.5 (spt, PF6, J5710)
6.82 (m, 2H, 49-azb; 3-NP)
7.20 (m, 1H, 59-azb)
7.49 (m, 16H, 2,3,4,5,6-azb; 40-NP; Ph)
7.84 (m, 1H, 50-NP)
7.96 (d, 1H, 69-azb, J58,7)
8.22 (dd, 1H, 60-NP, JHH56,9; JHP56,7)
8.60 (d, 1H, CH5N, J53,3)
6.37 (m, 1H, 39-azb)
6a
7a
38.7 (s, NP)
102.5 (spt, PF6, J5710)
6.85 (m, 1H, 49-azb)
7.03 (m, 2H, 59-azb; 3’-NP)
7.41 (m, 21H, 2,3,4,5,6-azb; 40-NP; Ph)
7.90 (m, 1H, 50-NP)
8.00 (d, 1H, 69-azb, J57,5)
8.40 (m, 1H, 6’-NP)
8.58 (s, 1H, CH5N)
2.45 (d, 3H, Me)
39.0 (s, NP)
6.01 (m, 1H, NH)
102.5 (spt, PF6, J5710)
6.14 (m, 1H, 39-azb)
6.72 (m, 1H, 49-azb)
6.95 (dd, 1H, 30-NP, JHH510.9; JHP510.7)
7.15 (m, 1H, 59-azb)
7.50 (m, 18H, 2,3,4,5,6,69-Azb; 40,50-NP; Ph)
7.79 (m, 1H, 60-NP)
7.97 (d, 1H, CH5N, J57,8)

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G. Sanchez et al. / Polyhedron 18 (1999) 3057–3064
3061
Table 2. Continued
Complex
1H (SiMe4)
31P (H3PO4)
40.8 (s, NP)
1b
3.59 (s, 1H, Me)
6.32 (m, 1H, 39-phpy)
102.3 (spt, PF6, J5710)
6.64 (m, 1H, 49-phpy)
6.90 (dd, 1H, 30-NP, JHH510.5; JHP510.7)
7.00 (m, 1H,59-phpy)
7.46 (m, 14H; 5,69-phpy; 40,50-NP; Ph)
7.73 (d, 1H, 3-phpy, J56,4)
7.78 (m, 2H, 4-phpy, 60-NP)
8.41 (m, 1H, 6-phpy)
8.52 (s, 1H, CH5N)
2b
0.89 (t, 3H, CH3-)
38.9 (s, NP)
3.99 (s-br, 2H, -CH2-)
102.4 (spt, PF6, J5710)
6.47 (m, 1H, 39-phpy)
6.65 (m, 1H, 49-phpy)
6.79 (dd, 1H, 30-NP, JHH510.8; JHP510.5)
7.01 (m, 1H, 59-phpy)
7.56 (m, 15H; 3,5,69-phpy; 40,50-NP; Ph)
7.89 (m, 2H, 4-phpy, 60-NP)
8.37 (m, 1H, 6-phpy)
8.58 (s, 1H, CH5N)
3b
0.35 (t, 3H, CH3)
38.4 (s)
1.67 (m, 2H, -CH2-)
102.3 (spt, PF6, J5710)
3.27 (m, 2H, -CH2-)
6.47 (m, 1H, 39-phpy)
6.63 (m, 1H, 49-phpy)
6.79 (dd, 1H, 30-NP, JHH510.1; JHP510.7)
7.02 (m, 1H, 59-phpy)
7.47 (m, 14H; 5,69-phpy; 40,50-NP; Ph)
7.75 (d, 1H, 3-phpy, J58,0)
1.10 (d, 3H, CH3-, J56,0)
4b
38.4 (s, NP)
1.40 (d, 3H, CH3- J56,0)
102.4 (spt, PF6, J5710)
,
4.33 (spt, 1H, CH, J56,0)
6.56 (m, 1H, 39-phpy)
6.70 (m, 1H, 49-phpy)
6.78 (dd, 1H, 30-NP, JHH510.5; JHP510.8)
7.07 (m, 1H, 59-phpy)
7.40 (m, 13H; 5,69-phpy; 40-NP; Ph)
7.73 (m, 1H, 50-NP)
7.79 (d, 1H, 3-phpy, J57,8)
7.93 (m, 1H, 4-phpy)
8.05 (dd, 1H, 60-NP, JHH510.8; JHP53,0)
8.31 (m, 1H, 6-phpy)
8.61 (s, 1H, CH5N)
5b
1.26 (s-br, 6H, 2CH3-)
38.2 (s, NP)
1.61 (s, 3H, CH3-)
102.4 (spt, PF6, J5711)
6.55 (m, 1H, 39-phpy)
6.68 (m, 2H, 49-phpy; 39-NP)
7.01 (m, 1H, 59-phpy)
7.56 (m, 15H; 3,5,69-phpy; 40,50-NP; Ph)
7.85 (m, 1H, 4-phpy)
8.03 (m, 1H, 60-NP)
8.33 (s-br, 1H, 6-phpy)
8.64 (d, 1H, CH5N, J53,0)
6.35 (m, 1H, 39-phpy)
6b
38.7 (s, NP)
6.55 (m, 2H, 49-phpy; 30-NP)
7.10 (m, 1H, 59-phpy)
102.5 (spt, PF6, J5710)
7.60 (m, 20H; 3,5,69-phpy; 40,50-NP; Ph)
7.85 (m, 1H, 4-phpy)
8.03 (m, 1H, 60-NP)
8.33 (s-br, 1H, 6-phpy)
8.64 (d, 1H, CH5N, J53,0)

´
3062
G. Sanchez et al. / Polyhedron 18 (1999) 3057–3064
Table 2. Continued
Complex
1H (SiMe4)
31P (H3PO4)
7b
2.89 (d, 3H, Me)
39.2 (s, NP)
6.32 (m, 2H; 39-phpy; NH)
6.56 (m, 1H, 49-phpy)
102.4 (spt, PF6, J5710)
6.85 (dd, 1H, 30-NP, JHH510.9; JHP510.9)
6.98 (m, 1H, 59-phpy)
7.45 (m, 14H; 5,69-phpy; 40,50-NP; Ph)
7.73 (d, 1H, 3-phpy, J58,0)
7.87 (m, 3H, 4-phpy, 6’-NP, CH5N)
8.73 (m, 1H, 6-phpy)
s2(Fo2)1(0.0581P)2 and P5(Fo212F2c )/3] over 2607 ob-
served reflections [I.2s(I)].
cm21, together with the bands assigned to the corre-
sponding cyclometalated ligand. Two medium intensity
bands at 1578 and 1552 cm21 were observed in the IR
spectra of the the azobenzene compounds, while relevant
bands for 2-phenylpyridinate compounds appeared at 1604
and 1576 cm21. The presence of iminophosphine ligands
coordinated to palladium(II) is detected by a single strong
band in the 1650–1620 cm21 region attributed to the C5N
stretching vibrations, shifted to lower frequencies than in
the free ligands. The positive FAB-mass data of the
complexes, with the m/z values for the observed frag-
ments, are collected in the experimental section. All the
peaks exhibited the expected isotopomer distribution.
The 1H and 31P-NMR data of the iminophosphine
complexes are collected in Table 2. The 31P-NMR spectra
consist on singlets with chemical shifts in the usual range
of Pd(II) complexes, and the typical septuplet resonance
showed by the PF26 anion. Unlike the dichloro-bridged
precursors, whose low solubility prevented the acquisition
of good-quality spectra [5,35,38], the mononuclear com-
plexes are soluble in common organic solvents, and
extensive 1H-RMN study has been done. Thus, assign-
ments of resonances were made through comparison with
spectra of the free ligands and of similar compounds
[5,8,9,12] helped by the use of homonuclear shift correla-
tion spectroscopy (COSY).
Data for 1b were collected using a single crystal of
approximate dimensions 0.2030.2330.25 mm. Accurate
cell parameters were determined by least-squares fitting of
46 high-angle reflections. The scan method was v with the
range of hkl (225#h#1, 218#k#1,222#l#23) corre-
sponding to2Qmax5508. The structure was solved by the
Patterson methods and refined anisotropically on F2 [36].
Hydrogen atoms were introduced in calculated positions.
The final R factor was 0.0366 [Rw50.0903, where w51/
s2(Fo2)1(0.0394P)2 and P5(Fo212F2c )/3] over 3424 ob-
served reflections [I.2s(I)].
3. Results and discussion
In acetone, the chloro-bridged cyclometalated dimers
[hPd(C3N)(F–Cl)j2]
(C3N5azobenzene
or
2-
phenylpyridine) react under mild conditions with im-
inophosphines (molar ratio 1:2) in the presence of the
stoichiometric amount of KPF6 to give the corresponding
square-planar
cationic
complexes
[Pd(C3N)(o-
Ph2PC6H4 –CH5NR)][PF6] presented in Scheme 1.
The new azobenzene derivatives with iminophosphines
are air-stable orange solids, while the 2-phenylpyridinate
complexes present a pale yellow colour. Measurements of
their molar conductivity in acetone solutions indicate that
all the complexes behave as 1:1 electrolytes [37], in
accordance with the proposed formulae. There are two
possible conformations for the new complexes, depending
on the relative positions adopted by the four atoms directly
bonded to the palladium centre. As we represent in Scheme
1, the new complexes with ortho-metalated azobenzene or
2-phenylpyridine exhibit a P,N-trans geometry. This is
concluded from the X-ray crystal structure determination
of complexes 2a and 1b (discussed below), and in accord-
ance with previously reported data for related compounds
[3,4,8,9].
Fig. 1 shows the aromatic section of the 1H-COSY
spectrum of 4b, where nine resonances are observed
integrating for a total of 23 aromatic protons in the 6.0–9.0
ppm range. Several second order couplings were observed
in this experiment, making easier the proposed assignment.
Resonances attributed to H(5), H(69) and H(40) protons are
hidden by the broad signals of phenyl groups, while the
rest of signals are fairly distinguishable, even those of
H(3)–H(50) and H(30)–H(40) which appear partly over-
lapped and were listed as multiplets integrating two
protons. The two signals that integrate for one proton each
observed downfield between 8.20 and 8.60 ppm were
assigned to the H(6) and .CH5N– protons, adjacent to
the coordinated nitrogens of the phenylpyridine and im-
inophosphine ligands respectively. The appreciable cou-
pling to the phosphorus atom exhibited by the H(6), H(39),
Infrared spectra of all compounds show the characteris-
tic absorptions of the PF26 anion at ca. 840 vs. and 558 s

´
G. Sanchez et al. / Polyhedron 18 (1999) 3057–3064
3063
Fig. 2. Structure of the [Pd(azb)hP(o-C6H4 –CH5N–Et)Ph2j]1 cation in
the single crystal structure of 2a. For clarity, all hydrogen atoms have
been omitted.
Fig. 1. 1H-1H COSY spectrum of 4b in the aromatic region.
planes through Pd, C(1), N(1) and through Pd, P(1), N(2)
of 20.98. The Pd–P bond length in compound 2a [2.246(2)
˚
˚
A)] is clearly larger than in 1b [2.2087(13) A)] but this
variation is easily explained in terms of the different
electron-donor nature of the nitrogen in trans-arrangement.
The narrow NMC bite angle is characteristic of ortho-
metalated and cyclometalated transition metal complexes
[39]. In 2a that C(1)PdN(2) bite angle is 78.4(3)8, similar
to that found in others (phenylazophenyl) palladium
complexes [40] while in 1b is 80.8(2)8.
H(30) and H(60) protons (expected as doublets resonances
1
a priori), is the most remarkable aspect of the H-NMR
spectra.
3.1. X-ray structures of 2a and 1b
The planar coordination around palladium is tetrahedral-
ly distorted in both cases. Selected bond distances and
angles are presented in Table 3. In 2a (Fig. 2) the planar
arrangement around palladium is slightly distorted with a
twist angle between the planes through Pd,C(1),N(2) and
through Pd,N(3),P of 9.6(3) 8, and compound 1b (Fig. 3)
shows a larger distortion with a twist angle between the
In 2a the chelating ring (PdC(1)C(6)N(1)N(2)) is planar
within 0.01 A. Planar [40] and not planar [41] geometries
˚
Table 3
˚
Selected bond lenghts (A) and angles (8) for 2a and 1b
Lengths
Angles
2a
1b
Pd–C(1)
Pd–N(2)
Pd–N(3)
Pd–P
1.996(8)
C(1)–Pd–N(2)
C(1)–Pd–N(3)
N(2)–Pd–N(3)
C(1)–Pd–P
N(2)–Pd–P
N(3)–Pd–P
C(1)–Pd–N(1)
C(1)–Pd–N(2)
N(1)–Pd–N(2)
C(1)–Pd–P(1)
N(1)–Pd–P(1)
N(2)–Pd–P(1)
78.4(3)
172.6(3)
97.7(2)
101.3(3)
173.6(2)
83.2(2)
80.8(2)
168.5(2)
98.3(2)
2.108(6)
2.135(5)
2.246(2)
Pd–C(1)
Pd–N(1)
Pd–N(2)
Pd–P(1)
1.993(4)
2.088(3)
2.120(4)
2.2087(13)
99.03(14)
163.87(12)
85.04(12)
Fig. 3. Structure of the [Pd(phpy)hP(o-C6H4 –CH5N–Me)Ph2j]1 cation
in the single crystal structure of 1b.

´
G. Sanchez et al. / Polyhedron 18 (1999) 3057–3064
3064
[13] L. Chassot, E. Muller, A. von Zelewsky, Inorg. Chem. 23 (1984)
4249.
[14] A.D. Ryabov, L.G. Kuz’mina, N.V. Dvortsova, D.J. Stufkens, R. van
Eldik, Inorg. Chem. 32 (1993) 3166.
[15] J.R. Dilworth, S.D. Howe, A.J. Hutson, J.R. Miller, J. Silver, R.M.
Thomson, M. Harman, M.B. Hursthouse, J. Chem. Soc., Dalton
Trans. (1994) 3553.
[16] J.R. Dilworth, A.J. Hutson, J.S. Lewis, J. R. Miller, Y. Zheng, Q.
Chen, J. Zubieta, J. Chem. Soc., Dalton Trans. (1995) 1093.
[17] J.R. Dilworth, J. R. Miller, N. Wheatley, M.J. Baker, G. Sunley, J.
Chem. Soc., Chem. Commun. (1995) 1579.
have been reported for these rings. The dihedral angle
formed by the free phenyl group with the best weighted
least-squares plane of the palladium–azophenyl moiety is
49.2(2) 8. The N(1)–N(2) distance is 1.278(7)A, this value
is slightly longer than that observed for the N5N bond in
trans-azobenzene [42].
˚
In 1b The five-membered ring chelate is approximately
planar, the largest deviation from the mean plane defined
˚
by the five atoms is 0.05 A for C(7). The phenyl and the
[18] G.P.C.M. Dekker, A. Buijs, C.J. Elsevier, K. Vrieze, P.W.N.M. van
Leeuven, W.J.J. Smeets, A.L. Spek, Y.F. Wang, C.H. Stam, Or-
ganometallics 1992 (1937) 11.
[19] G.R. Newkome, Chem. Rev. 93 (1993) 2067.
[20] S. Stoccoro, G. Chelucci, A. Zucca, M.A. Cinellu, G. Minghetti, J.
Manassero, J. Chem. Soc., Dalton Trans. (1996) 1295.
[21] D.Ch. Mudalige, E.S. Ma, S.J. Retting, B.R. James, W.R. Cullen,
Inorg. Chem. 36 (1997) 5426.
pyridyl rings of the ortho-metalated phenylpyridine ligand
have an angle of 11.88 between their planes. There is a
potential crystallographic ambiguity in the assignment of
the C and N atoms of the cyclometalated ligand; however
the thermal parameters and the bond lengths are all
consistent with the assignment that we have made.
The torsion angles of 22.98 for C(18)–C(17)–C(12)–
P(1) and 48.48 for the Pd–P(1)–C(12)–C(17) units point
to a perturbed envelope conformation of the six-membered
ring chelate.
[22] G.M. Kapteijn, M.P.R. Spee, D.M. Grove, H. Kooijman, A.L. Spek,
G. van Koten, Organometallics 15 (1996) 1405.
[23] P. Barbaro, C. Bianchini, F. Laschi, S. Midollini, S. Moneti, G.
Scapacci, P. Zanello, Inorg. Chem. 33 (1994) 1622.
[24] S. Stoccoro, G. Chelucci, A. Zucca, M.A. Cinellu, G. Minghetti, J.J.
Manassero, J. Chem. Soc., Dalton Trans. (1996) 1295.
[25] C.A. Ghilardi, S. Midollini, S. Moneti, A. Orlandini, G. Scapacci, J.
Chem. Soc., Dalton Trans. (1992) 3371.
Acknowledgements
[26] E. Drent, P. Arnoldy, P.H.M. Budzelaar, J. Organomet. Chem. 475
(1994) 57.
Financial support of this work by the DGES (project
PB97-1036), Spain, is acknowledged. J. L. Serrano thanks
Cajamurcia for a research grant and Peter Ware for his
kind suggestions.
¨
[27] H. Brunner, J. Fusrt, Inorg. Chim. Acta 220 (1994) 63.
[28] P. Wehman, H.M.A. van Donge, A. Hagos, P.C.J. Kamer, P.W.N.M.
van c¸leuven, J. Organomet. Chem. 535 (1997) 183.
[29] A. Bacchi, M. Carcelli, M. Costa, A. Leporati, E. Leporati, P.
Pelagatti, C. Pelizzi, G. Pelizzi, J. Organomet. Chem. 535 (1997)
107.
[30] J-X. Gao, T. Ikariya, R. Noyoro, Organometallics 15 (1996) 1087.
[31] S. Antonaroli, B. Crociani, J. Organomet. Chem., 560 (1998) 137.
[32] L. Crociani, G. Bandoli, A. Dolmella, M. Basato, B. Corain, Eur. J.
Inorg. Chem. (1998) 1811.
[33] A.G.J. Ligtenbarg, E.K.van den Beuken, A. Meestma, N. Veldman,
W.J.J. Smeets, A.L. Speck, B.L. Feringa, J. Chem. Soc., Dalton
Trans. (1998) 263.
References
[1] A.C. Cope, R.W. Siekman, J. Am. Chem. Soc. 87 (1965) 3272.
[2] A. Kasahara, Bull. Chem. Soc. Jpn. 41 (1968) 1272.
[3] E.C. Constable, A.M.W. Cargill Thomson, T.A. Leese, D.G.F.
Reese, D.A. Tocher, Inorg. Chim. Acta 182 (1991) 93.
[4] D.L. Weaver, Inorg. Chem. 9 (1970) 2250.
[5] M.A. Gutierrez, G.R. Newkome, J. Selbin, J. Organomet. Chem. 202
(1980) 341.
[6] J.M. Vila, M. Gayoso, M. Pereira, A. Romar, J.J. Fernandez, M.
Thornton-Pett, J. Organomet. Chem. 401 (1991) 385.
[7] B. Crociani, T. Boschi, R. Pietropaolo, U. Belluco, J. Chem. Soc. A
(1970) 531.
[8] M.M. Mdleleni, J.S. Bridgewater, R.J. Watts, P.C. Ford, Inorg.
Chem. 34 (1995) 2334.
[9] C.A. Craig, R.J. Watts, Inorg. Chem. 28 (1989) 309.
[10] Y. Ohsawa, S. Sprouse, A.K. King, M.K. DeArmond, K.W. Hanck,
R.J. Watts, J. Phys. Chem. 91 (1987) 1047.
¨
[34] R.E. Rulke, V.E. Kaasjager, P. Wehman, C.J. Elsevier, P.W.N.M. van
Leeuwen, K. Vrieze, Organometallics 15 (1996) 3022.
[35] M.I. Bruce, M.J. Liddell, G.N. Pain, Inorg. Synth. 26 (1989) 175.
[36] SHELXTL-5.0, Siemens Analytical X-Ray Instruments, Madison,
WI.
[37] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81.
[38] J. Selbin, M.A. Gutierrez, J. Organomet. Chem. 214 (1981) 253.
[39] M.C. Etter, A.R. Siedle, J. Am. Chem. Soc. 105 (1983) 643.
[40] R.C. Elder, R.D.P. Cruea, R.F. Morrison, Inorg. Chem. 15 (1976)
1623.
[41] G.R. Newkome, W.E. Puckett, V.K. Gupta, G.E. Kiefer, Chem. Rev.
86 (1986) 451.
[42] C.J. Brown, Acta Crystallogr. 21 (1966) 146.
[11] K.A. King, P.J. Spellane, R.J. Watts, J. Am. Chem. Soc. 107 (1985)
1431.
[12] L. Chassot, A. von Zelewsky, Inorg. Chem. 26 (1987) 2814.