New palladacyclopentadiene complexes containing an N,P-donor setting. Crystal structure of [Pd{C4(COOMe)4}(o-Ph2PC6H 4-CH=NiPr)]

Article abstract of DOI:10.1016/S0020-1693(01)00688-0

The synthesis of palladacyclopentadiene derivatives with the mixed-donor bidentate ligands o-Ph₂PC₆H₄-CH=NR (N^∧P) has been achieved. The new complexes of general formula [Pd{C₄(COOMe)₄}(o-Ph₂PC₆H ₄-CH=NR)] [R=Me (1), Et (2), ⁱPr (3), ^tBu (4), NH-Me (5)] have been prepared by reaction between the precursor [Pd{C₄(COOMe)₄}]_n and the corresponding iminophosphine. The polymer complex [Pd{C₄(COOMe)₄}]_n also reacts with pyridazine (C₄H₄N₂) to give the insoluble dinuclear complex [Pd{C₄(COOMe)₄}(μ-C₄H₄N ₂)]₂ (6), which has been successfully employed as precursor in the synthesis of pyridazine-based palladacyclopentadiene complexes. The reaction of 6 with tertiary phosphines yielded complexes containing an N,P-donor setting of formula [Pd{C₄(COOMe)₄}(C₄H₄N ₂)(L)] (L=PPh₃ (7), PPh₂Me (8), P(p-MeOC₆H₄)₃ (9), P(p-FC₆H₄)₃ (10)). The new complexes were characterized by partial elemental analyses and spectroscopic methods (IR, ¹H, ¹⁹F and ³¹P NMR). The molecular structure of complex 3 has been determined by a single-crystal diffraction study, showing that the iminophosphine acts as chelating ligand with coordination around the palladium atom slightly distorted from the square-planar geometry.

Full text of DOI:10.1016/S0020-1693(01)00688-0

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Inorganica Chimica Acta 328 (2002) 74–80
New palladacyclopentadiene complexes containing an N,P-donor
setting. Crystal structure of
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNiPr)]
Gregorio Sa´nchez a,*, Jorge Vives a, Jose´ L. Serrano b, Jose´ Pe´rez b, Gregorio Lo´pez a
a Departamento de Qu´ımica Inorga´nica, Uni6ersidad de Murcia, Campus Uni6ersitario de Espinardo, 30071 Murcia, Spain
b
´
Departamento de Ingenier´ıa Minera, Geolo´gica y Cartogra´fica, Area de Qu´ımica Inorga´nica, 30203 Cartagena, Spain
Received 25 May 2001; accepted 12 September 2001
Abstract
The synthesis of palladacyclopentadiene derivatives with the mixed-donor bidentate ligands o-Ph2PC6H4ꢀCHꢁNR (N P) has
‚
i
t
been achieved. The new complexes of general formula [Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNR)] [R=Me (1), Et (2), Pr (3), Bu
(4), NHꢀMe (5)] have been prepared by reaction between the precursor [Pd{C4(COOMe)4}]n and the corresponding iminophos-
phine. The polymer complex [Pd{C4(COOMe)4}]n also reacts with pyridazine (C4H4N2) to give the insoluble dinuclear complex
[Pd{C4(COOMe)4}(m-C4H4N2)]2 (6), which has been successfully employed as precursor in the synthesis of pyridazine-based
palladacyclopentadiene complexes. The reaction of 6 with tertiary phosphines yielded complexes containing an N,P-donor setting
of formula [Pd{C4(COOMe)4}(C4H4N2)(L)] (L=PPh3 (7), PPh2Me (8), P(p-MeOC6H4)3 (9), P(p-FC6H4)3 (10)). The new
complexes were characterized by partial elemental analyses and spectroscopic methods (IR, 1H, 19F and 31P NMR). The molecular
structure of complex 3 has been determined by a single-crystal diffraction study, showing that the iminophosphine acts as
chelating ligand with coordination around the palladium atom slightly distorted from the square-planar geometry. © 2002
Elsevier Science B.V. All rights reserved.
Keywords: Crystal structures; Palladium complexes; Metallocyclic complexes; Iminophosphine complexes
tion catalytic reactions [6], and also because of the
interesting behaviour as precursors in organometallic
chemistry of the compounds formed. Thus, the polymer
complex, palladacyclopentadiene, [Pd(C4R4)]n (R=
COOMe), formed in the reaction of dmad with
Pd(dba)2 (dba=dibenzylidenacetone) reacts with a
wide range of donor ligands to give soluble discrete
molecules [4,5,7,8]. To date, just a few crystal structures
of palladacyclopentadiene compounds are known [9].
Other features recently studied are their use as catalysts
in the metathesis of enynes [10,11], dimerization of
allenyl ketones [12], conversion of alkynes to conju-
gated dienes [9], and co-cyclotrimerizations of acetyle-
nes with other acetylenes, alkenes and allenes [13–15].
On the other hand, there has been a recent surge of
interest in the chemistry of polydentate ligands with
both hard and soft donor atoms [16–22]. The metal
complexes with N and P donor atoms display a variety
1. Introduction
The chemistry of metallacycles has received growing
interest during recent years, as a result of their involve-
ment in catalytic processes and their applications in
organic synthesis [1–3]. The cycloaddition of two un-
saturated fragments to a metal unit is one of the most
useful methods of metallacycle synthesis, since it gives
access to relatively complex structures starting from
small unsaturated molecules [1]. Particularly, the oxida-
tive cycloaddition of acetylenic esters such as dimethy-
lacetylenedicarboxylate (dmad) to a Ni, Pd and Pt has
received much attention [4,5], due in part to its involve-
ment in different oligomerization and co-oligomeriza-
* Corresponding author. Tel.: +34-968-307 100; fax: +34-968-
364 148.
E-mail address: gsg@um.es (G. Sa´nchez).
0020-1693/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00688-0

G. Sa´nchez et al. / Inorganica Chimica Acta 328 (2002) 74–80
75
2.2. Preparation of the complexes
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNR)] [R=Me
of coordination modes well beyond those of PꢀP or
NꢀN ligands [23]. Furthermore, these ligands show a
particular behaviour binding soft metal centres such as
Pd(II) and Pt(II) that make their complexes good pre-
cursors in catalytic processes [24–31]. Thus, it has been
found that some complexes with NꢀP ligands are suit-
able for palladium-catalyzed allylic alkylation [32],
oligomerization of olefins [33,34], homogeneous hydro-
genation of double and triple CꢀC bonds [35] and
co-polymerization of CO/olefins [36–38]. Among the
most widely studied ligands with these characteristics
are the pyridylphosphines and the iminophosphines
that we present in this work, from which palladium
complexes have been profusely reported [28–30,38–43].
In this sense, we have described in recent work the
syntheses of some organometallic derivatives containing
iminophosphine ligands, either with an ortho-metal-
lated palladium(II) backbone [44] or pentafluorophenyl
derivatives of nickel(II) [45] and palladium(II) [46].
Recently, new pyridazine complexes and their use as
convenient precursors in organometallic synthesis have
been reported [47].Other studies that make pyridazine
complexes interesting to us have focused on the ability
of this ligand to undergo metallotropic shifts between
the two equivalent contiguous N-donor atoms [48,49].
This paper deals with the synthesis of new palladacy-
clopentadiene complexes containing an N,P-donor set-
ting, made up either of iminophosphine ligands or by
means of a pyridazine–tertiary phosphine set.
i
t
(1), Et (2), Pr (3), Bu (4), NHꢀMe (5)]
The complexes were obtained by treating [Pd{C4-
(COOMe)4}]n with the corresponding iminophosphine
(molar ratio 1:1) in acetone according to the following
general method. To an acetone (5 ml) solution of the
precursor [Pd{C4(COOMe)4}]n (0.07 g, 0.18 mmol) was
added the calculated amount of iminophosphine in
acetone solution previously prepared. 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 yellow solids, which were filtered off, washed with
diethyl ether and air-dried. Yellow crystals of the com-
pounds (1–5) were obtained in high yield by recrystal-
lization from dichloromethane–diethyl ether.
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNMe)] (1) was
obtained in 84% yield. Anal. Calc. for C32H30NO8PPd:
C, 55.4; H, 4.4; N, 2.0. Found: C, 55.2; H, 4.4; N, 1.9%.
IR (cm−1): 1724, 1692 (CꢁO str), 1640 (CꢁN str). H
1
NMR (CDCl3): 2.63 (s, 3H, Me), 2.80 (s, 3H, COOMe),
3.45 (s, 3H, COOMe), 3.53 (s, 3H, COOMe), 3.55 (s,
3H, COOMe), 6.78 (m, 1H, arom), 7.42–7.74 (m, 13H,
arom), 8.32 (s, 1H, CHꢁN). 31P NMR (CDCl3): 28.1
(s). FAB MS (positive mode) m/z: 693 [Pd{C4-
(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNMe)]+.
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNEt)] (2) was
obtained in 79% yield. Anal. Calc. for C33H32NO8PPd:
C, 56.0; H, 4.6; N, 2.0. Found: C, 55.7; H, 4.4; N, 2.2%.
IR (cm−1): 1722, 1694 (CꢁO str), 1640 (CꢁN str). H
1
NMR (CDCl3): 1.00 (t, 3H, CH3), 2.67 (s, 3H,
COOMe), 3.48 (q-sh, 2H, CH2), 3.53 (s, 6H, COOMe),
3.54 (s, 3H, COOMe), 6.70 (m, 1H, arom), 7.50–7.77
(m, 13H, arom), 8.42 (d, 1H, CHꢁN; JPH=3.0). 31P
NMR (CDCl3): 27.3 (s). FAB MS (positive mode) m/z:
707 [Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNEt)]+.
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNiPr)] (3) was
obtained in 80% yield. Anal. Calc. for C34H34NO8PPd:
C, 56.6; H, 4.7; N, 1.9. Found: C, 56.3; H, 4.8; N, 1.7%.
2. Experimental
2.1. Materials and physical measurements
C, H and N analyses were carried out with a Perkin–
Elmer 240C microanalyzer. IR spectra were recorded
on a Perkin–Elmer spectrophotometer 16F PC FT–IR,
using Nujol mulls between polyethylene sheets. NMR
data were recorded on a Bruker AC 200E (1H) or a
Varian Unity 300 (1H, 19F, 31P) spectrometer. Mass
spectrometric analyses were performed on a Fisons VG
Autospec double-focusing spectrometer, operated in
positive mode. Ions were produced by fast atom bom-
bardment (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 palladacyclopentadiene precursor was prepared
by the published method [4]. The iminophosphine lig-
ands were prepared according to reported procedures
[25], and all the solvents were dried by standard meth-
ods before use.
1
IR (cm−1): 1718, 1694 (CꢁO str), 1642 (CꢁN str). H
NMR (CDCl3): 1.00 (s-br, 3H, CH3), 1.22 (s-br, 3H,
CH3), 2.70 (s, 3H, COOMe), 3.52 (s, 3H, COOMe),
3.53 (s, 3H, COOMe), 3.54 (s, 3H, COOMe), 4.28 (m,
1H, CH), 6.67 (m, 1H, arom), 7.47–7.86 (m, 13H,
arom), 8.44 (d, 1H, CHꢁN, JPH=3.0). 31P NMR
(CDCl3): 30.9 (s). FAB MS (positive mode) m/z: 721
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNiPr)]+.
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNtBu)] (4) was
obtained in 72% yield. Anal. Calc. for C35H36NO8PPd:
C, 57.1; H, 4.9; N, 1.9. Found: C, 56.9; H, 4.6; N, 2.1%.
1
IR (cm−1): 1714, 1704 (CꢁO str), 1622 (CꢁN str). H
NMR (CDCl3): 1.16 (s, 3H, CH3); 1.22 (s-br, 6H,
2CH3), 2.76 (s, 3H, COOMe), 3.49 (s, 3H, COOMe),
3,51 (s, 3H, COOMe), 3.54 (s, 3H, COOMe), 6.67 (m,
1H, arom), 7.40–7.80 (m, 13H, arom), 8.56 (d, 1H,

76
G. Sa´nchez et al. / Inorganica Chimica Acta 328 (2002) 74–80
CHꢁN, JPH=4.2). 31P NMR (CDCl3): 28.1 (s). FAB
MS (positive mode) m/z: 735 [Pd{C4(COOMe)4}(o-
Ph2PC6H4ꢀCHꢁNtBu)]+.
51.9; H, 4.4; N, 4.2. Found: C, 51.46; H, 4.6; N, 4.6%.
1
IR (cm−1): 1714, 1702 (CꢁO str), 1572 (pyz). H NMR
(CDCl3): 2.15 (d, 3H, PPh2Me, JPH=8.4), 2.77 (s, 3H,
COOMe), 2.94 (s, 3H, COOMe), 3.48 (s, 3H, COOMe),
3.50 (s, 3H, COOMe), 7.24–7.42 (m, 11H, PPh2Me+
pyz), 7.51 (m, 2H, pyz), 8.81 (m, 1H, pyz). 31P NMR
(CDCl3): 9.4 (s). FAB MS (positive mode) m/z: 670
[Pd{C4(COOMe)4}(C4H4N2)(PPh2Me)]+.
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNNHMe)] (5)
was obtained in 74% yield. Anal. Calc. for C32H31N2-
O8PPd: C, 54.2; H, 4.4; N, 3.9. Found: C, 54.3; H, 4.7;
N, 4.1%. IR (cm−1): 1720, 1696 (CꢁO str), 1630 (CꢁN
1
str). H NMR (CDCl3): 2.63 (s, 3H, COOMe), 2.76 (d,
3H, NMe), 3.52 (s, 3H, COOMe), 3.53 (s, 3H,
COOMe), 3.54 (s, 3H, COOMe), 6.70 (m, 1H, arom),
7.04 (q, 1H, NH), 7.29–7.59 (m, 13H, arom), 8.50 (s,
1H, CHꢁN). 31P NMR (CDCl3): 28.1 (s). FAB MS
(positive mode) m/z: 708 [Pd{C4(COOMe)4}(o-
Ph2PC6H4ꢀCHꢁNNHMe)]+.
[Pd{C4(COOMe)4}(C4H4N2){P(p-MeOC6H4)3}] (9)
was obtained in 76% yield. Anal. Calc. for
C37H37N2O11PPd: C, 54.0; H, 4.5; N, 3.4. Found: C,
53.9; H, 4.7; N, 3.7%. IR (cm−1): 1732, 1704 (CꢁO str),
1
1568 (pyz). H NMR (CDCl3): 2.58 (s, 3H, COOMe),
3.07 (s, 3H, COOMe), 3.60 (s, 6H, COOMe), 3.78 (s,
9H, P(p-MeOC6H4)3), 7.26–7.43 (m, 15H, P(p-
MeOC6H4)3+pyz), 8.67 (m, 1H, pyz). 31P NMR
(CDCl3): 27.9 (s). FAB MS (positive mode) m/z: 822
[Pd{C4(COOMe)4}(C4H4N2){P(p-MeOC6H4)3}]+.
[Pd{C4(COOMe)4}(C4H4N2){P(p-FC6H4)3}] (10) was
obtained in 77% yield. Anal. Calc. for C34H28F3N2-
O8PPd: C, 51.9; H, 3.6; N, 3.6. Found: C, 51.8; H, 3.9;
N, 3.4%. IR (cm−1): 1734, 1702 (CꢁO str), 1568 (pyz).
1H NMR (CDCl3): 2.57 (s, 3H, COOMe), 2.98 (s, 3H,
COOMe), 3.51 (s-br, 6H, COOMe), 7.14 (m, 6H, P(p-
FC6H4)3), 7.52–7.62 (m, 9H, P(p-FC6H4)3+pyz), 8.85
(m, 1H, pyz). 31P NMR (CDCl3): 27.9 (s). FAB MS
(positive mode) m/z: 786 [Pd{C4(COOMe)4}-
(C4H4N2){P(p-FC6H4)3}]+.
2.3. Preparation of the complex [Pd{C4(COOMe)4}-
(v-C4H4N2)]2(C4H4N2: pyridazine) (6)
Pyridazine (0.055 ml, 0.77 mmol) was added to an
acetone solution (10 ml) of the precursor
[Pd{C4(COOMe)4}]n (0.3 g, 0.77 mmol) and the reac-
tion was stirred at room temperature for 30 min. The
white solid precipitated after that time was filtered off,
washed with acetone (2 ml) and diethyl ether (5 ml) and
air-dried. Yield 85%. Anal. Calc. for C32H32N4O16Pd:
C, 40.8; H, 3.4; N, 5.9. Found: C, 40.6; H, 3.4; N, 5.9%.
IR (cm−1): 1720, 1702 (CꢁO str), 1560 (pyz). FAB MS
(positive mode) m/z: 911 [Pd{C4(COOMe)3(CO)}(m-
+
C4H4N2)]2+, 884 [Pd{C4(COOMe)3}(m-C4H4N2)]2
1, 884 [Pd2{C4(COOMe)4}2(C4H4N2)]++2.
+
2.5. Crystal structure determination of
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNiPr)] (3)
2.4. Preparation of the complexes
[Pd{C4(COOMe)4}(C4H4N2)(L)] [L=PPh3 (7),
PPh2Me (8), P(p-MeOC6H4)3 (9), P(p-FC6H4)3 (10)]
X-ray diffraction experiment was carried out on a
Siemens P4 diffractometer at −100 °C. The crystallo-
graphic data are shown in Table 1. Data were collected
using a single crystal of dimensions 0.4×0.3×0.2 mm.
Accurate cell parameters were determined by least-
squares fitting of 55 reflections. The scan method was ꢀ
with the range of hkl (−135h54, −165k516,
−245l524 corresponding to 2[max=50°. Two
molecules were found in the asymmetrical unit, the
structure was solved by the Patterson method and
refined anisotropically on F2 [50]. Hydrogen atoms
were introduced in calculated positions. The final R
Compounds 7–10 were obtained by reacting stoi-
chiometric amounts (molar ratio 1:2) of complex 6
(0.05 g, 0.053 mmol) and the corresponding phosphine
(0.106 mmol) in 5 ml of acetone. After 30 min stirring
at boiling temperature, the resulting solutions were
concentrated under reduced pressure to half volume.
The addition of diethyl ether caused precipitation of the
new complexes, which were filtered off and recrystal-
lized of CH2Cl2/diethyl ether.
factor was 0.0366 Rw=0.0754 where w=1[|2(Fo )+
2
[Pd{C4(COOMe)4}(C4H4N2)(PPh3)] (7) was obtained
in 70% yield. Anal. Calc. for C34H31N2O8PPd: C, 55.7;
H, 4.3; N, 3.8. Found: C, 55.4; H, 4.1; N, 3.9%. IR
(0.0380P)2] and P=(Fo +2Fc )/3 over 7958 observed
reflections [I\2|(I)].
2
2
(cm−1): 1720, 1696 (CꢁO str), 1570 (pyz). H NMR
1
(CDCl3): 2.43 (s, 3H, COOMe), 2.94 (s, 3H, COOMe),
3.48 (s, 3H, COOMe), 3.49 (s, 3H, COOMe), 7.27–7.55
(m, 18H, PPh3+pyz), 8.75 (m, 1H, pyz). 31P NMR
(CDCl3): 27.9 (s). FAB MS (positive mode) m/z: 732
[Pd{C4(COOMe)4}(C4H4N2)(PPh3)]+.
3. Results and discussion
3.1. Iminophosphine complexes
[Pd{C4(COOMe)4}(C4H4N2)(PPh2Me)] (8) was ob-
tained in 67% yield. Anal. Calc. for C29H29N2O8PPd: C,
In acetone, [Pd{C4(COOMe)4}]n, reacts with imino-
phosphines (molar ratio 1:1) under mild conditions to

G. Sa´nchez et al. / Inorganica Chimica Acta 328 (2002) 74–80
77
Table 1
Crystal data and structure refinement for [Pd{C4(COOMe)4}(o-
Ph2PC6H4ꢀCHꢁNiPr)]
Empirical formula
Formula weight
Temperature (K)
C34H34NO8PPd
721.99
173(2)
,
Wavelength (A)
0.71073
triclinic
Crystal system
Space group
(
P1
Unit cell dimensions
,
a (A)
11.8930(10)
13.8110(10)
20.235(2)
82.918(6)
,
b (A)
,
c (A)
h (°)
i (°)
88.618(8)
k (°)
79.864(8)
3246.8(5)
4
1.477
0.673
1480
3
,
V (A )
Z
Dcalc (Mg m−3
)
Absorption coefficient (mm−1
F(000)
)
Crystal size (mm)
q Range for data collection (°)
0.20×0.30×0.40
3.02–25.00
Fig. 1. Variable-temperature 1H NMR spectrum of 3 (methyl groups
of the isopropyl fragment).
Index ranges
−135h54, −165k516,
−245l524
Reflections collected
Independent reflections
Refinement method
16 613
give the corresponding neutral square-planar complexes
[Pd{C4(COOMe)4}(N P)] shown in Scheme 1.
11 401 [Rint=0.0402]
Full-matrix least-squares on
F2
11 401/0/811
0.888
‚
The new palladium complexes 1–5 are air-stable,
yellow solids that show negligible molar conductance.
The IR spectra of these complexes show two very strong
bands [w(CO)] at 1705920 cm−1 characteristic of the
carboxylate groups [4] and a band in the 1650–1600
cm−1 region attributed to the CꢁN stretching vibration
of the iminophosphine, shifted to lower frequencies than
in the free ligands [44].
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\2|(I)]
R indices (all data)
R1=0.0366, wR2=0.0754
R1=0.0632, wR2=0.0819
Largest difference peak and hole 0.563 and −0.716
−3
,
(e A
)
1
The H NMR spectra show the corresponding aro-
matic signals of the neutral ligands, with a typical iminic
singlet or doublet resonance in the 8–8.5 ppm region,
depending on the strength of the coupling to the phos-
phorus atom [25]. The most characteristic chemical
shifts of the compounds are the ones that correspond to
the methoxycarbonyl groups, which act as a probe for
the compounds’ geometry, i.e. symmetric complexes
show two signals and asymmetric show four resonances
[9]. The signals of one of the pairs of methoxycarbonyl
groups (b-positions relative to palladium) are relatively
insensitive to the nature of donor atoms in trans, and
occurred in the asymmetric iminophosphine complexes
as two resonance signals between 3.5 and 3.6 ppm. The
higher field resonances are then due to the methoxycar-
bonyl on the a-carbons, and the magnitude of the shift
is roughly related to the donor atom placed in trans
position [4]. Thus, the methoxycarbonyl group trans to
iminic nitrogen (between 3.45 and 3.52 ppm) occurred
to higher field that the methoxycarbonyl trans to phos-
phorus (between 2.70 and 2.80 ppm). An outstanding
1
feature was found in H NMR spectrum of complex 3.
It exhibited two broad signals for the methyl groups of
Scheme 1.
the isopropyl fragment at room temperature, suggesting

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G. Sa´nchez et al. / Inorganica Chimica Acta 328 (2002) 74–80
hindered rotation of the (CH3)2CH-substituent around
the NꢀC bond. Fig. 1 shows the spectra of complex 3 as
a function of temperature. At 0 °C and lower tempera-
tures the rotation is sufficiently sluggish to make the
methyl groups distinguishable by their chemical shifts,
and two 1:1 doublet resonances are observed. As the
temperature is raised the signals broaden and finally
coalescence in one resonance at 30 °C.
The 31P NMR spectra of the new iminophosphine
complexes consist of singlets with chemical shifts in the
range observed for related organometallic Pd(II) com-
pounds [44,46].
The proposed formulae of the new complexes are
also confirmed by FAB mass spectrometry. The posi-
tive FAB MS data of the complexes with the m/z values
Table 2
FAB mass spectrometric data for the palladium(II) complexes
Ions (m/z)
Fig. 2. ORTEP diagram of one of the two independent molecules
present in the asymmetric unit of 3.
1
2
3
4
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNMe)]+ (693)
[Pd{C4(COOMe)3(CO)}(o-Ph2PC6H4ꢀCHꢁNMe)]+ (662)
[Pd{C4(COOMe)3}(o-Ph2PC6H4ꢀCHꢁNMe)]+ (634)
[Pd(o-Ph2PC6H4ꢀCHꢁNMe)]+ (409)
Table 3
,
Selected bond lengths (A) and angles (°) for complex 3
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNEt)]+ (707)
[Pd{C4(COOMe)3(CO2)}(o-Ph2PC6H4ꢀCHꢁNEt)]+ (692)
[Pd{C4(COOMe)3}(o-Ph2PC6H4ꢀCHꢁNEt)]+ (648)
[Pd(o-Ph2PC6H4ꢀCHꢁNEt)]+ (423)
Pd(1)ꢀC(4)
Pd(1)ꢀC(1)
Pd(1)ꢀN(1)
Pd(1)ꢀP(1)
2.024(4)
2.084(4)
2.116(3)
2.2898(10)
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNiPr)]+ (721)
[Pd{C4(COOMe)3(CO)}(o-Ph2PC6H4ꢀCHꢁNiPr)]+ (690)
[Pd{C4(COOMe)3}(o-Ph2PC6H4ꢀCHꢁNiPr)]+ (662)
[Pd(o-Ph2PC6H4ꢀCHꢁNiPr)]+ (437)
C(4)ꢀPd(1)ꢀC(1)
C(4)ꢀPd(1)ꢀN(1)
C(1)ꢀPd(1)ꢀN(1)
C(4)ꢀPd(1)ꢀP(1)
C(1)ꢀPd(1)ꢀP(1)
N(1)ꢀPd(1)ꢀP(1)
79.53(15)
170.38(14)
96.27(13)
101.15(11)
167.80(11)
84.80(8)
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNtBu)]+ (735)
[Pd{C4(COOMe)3(CO)}(o-Ph2PC6H4ꢀCHꢁNtBu)]+ (704)
[Pd{C4(COOMe)3}(o-Ph2PC6H4ꢀCHꢁNtBu)]+ (676)
[Pd(o-Ph2PC6H4ꢀCHꢁNtBu)]+ (451)
Pd(2)ꢀC(38)
Pd(2)ꢀC(35)
Pd(2)ꢀN(2)
Pd(2)ꢀP(2)
2.029(4)
2.077(4)
2.113(3)
2.2914(10)
5
6
[Pd{C4(COOMe)4}(o-Ph2PC6H4ꢀCHꢁNNHMe)]+ (708)
[Pd{C4(COOMe)3(CO)}(o-Ph2PC6H4ꢀCHꢁNNHMe)]+ (677)
[Pd(o-Ph2PC6H4ꢀCHꢁNNHMe)]+ (423)
+
[Pd{C4(COOMe)3(CO)}(m-C4H4N2)]2 (911)
[Pd{C4(COOMe)3}(m-C4H4N2)]2++1 (884)
[Pd2{C4(COOMe)4}2(C4H4N2)]++2 (884)
[Pd2{C4(COOMe)3}2(C4H4N2)]+ (803)
C(38)ꢀPd(2)ꢀC(35)
C(38)ꢀPd(2)ꢀN(2)
C(35)ꢀPd(2)ꢀN(2)
C(38)ꢀPd(2)ꢀP(2)
C(35)ꢀPd(2)ꢀP(2)
N(2)ꢀPd(2)ꢀP(2)
79.43(15)
170.38(14)
95.44(13)
101.51(11)
169.37(11)
85.04(9)
7
8
[Pd{C4(COOMe)4}(C4H4N2)(PPh3)]+ (732)
[Pd{C4(COOMe)4}(PPh3)]+ (652),
[Pd{C4(COOMe)3(CO)}(PPh3)]+ (652),
[Pd{C4(COOMe)3}(PPh3)]+ (593), [Pd(PPh3)] (368)
[Pd{C4(COOMe)4}(C4H4N2)(PMePh2)]+ (670)
[Pd{C4(COOMe)3(CO)}(C4H4N2)(PMePh2)]+ (639)
[Pd{C4(COOMe)4}(PMePh2)]+ (590),
for the observed fragments are listed in Table 2. The
[Pd{C4(COOMe)3(CO)}(PMePh2)]+ (531),
[Pd{C4(COOMe)3}(PMePh2)]+ (531), [Pd(PMePh2)] (368)
[Pd{C4(COOMe)4}(C4H4N2){P(p-MeOꢀC6H4)3]+ (810)?
[Pd{C4(COOMe)4}{P(p-MeOꢀC6H4)3)}]+ (743),
[Pd{P(p-MeOꢀC6H4)3)}]+ (459)
spectra of 1–5 show the peaks of the molecular ion
‚
[Pd{C4(COOMe)4}(N P)]+ and additional peaks to
‚
[Pd{C4(COOMe)3(CO)}(N P)]+ (M+−MeO), [Pd-
9
‚
{C4(COOMe)3}(N P)]+ (M+−COOMe) and [Pd-
‚
(N P)]+ (M+−{C4(COOMe)4}).
10 [Pd{C4(COOMe)4}(C4H4N2){P(p-FC6H4)3]+ (786)
[Pd{C4(COOMe)3(CO)}(C4H4N2){P(p-FC6H4)3]+ (755)
[Pd{C4(COOMe)4}{P(p-FC6H4)3]+ (706)
[Pd{C4(COOMe)3(CO)}{P(p-FC6H4)3]+ (675)
[Pd{C4(COOMe)3}{P(p-FC6H4)3]+ (647), [Pd{P(p-FC6H4)3]+
(422)
The crystal structure of 3 is shown in Fig. 2, and
selected bond and angles are presented in Table 3. The
coordination around palladium is tetrahedrically dis-
torted from the ideal square-planar geometry, with a
mean angle (for the two molecules in the asymmetrical

G. Sa´nchez et al. / Inorganica Chimica Acta 328 (2002) 74–80
79
unit) between the C(1)ꢀPdꢀC(4) and N(1)ꢀPdꢀP(1)
planes of 15.0(1)°, with the N and P atoms of the
iminophosphine ligand lying in a different side in rela-
a Pd:ligand mol ratio of 1:2 was used, the same result
was obtained. The IR spectrum of 6 shows the charac-
teristic absorptions of methoxycarbonyl groups and a
band around 1560 cm−1 attributed to the pyridazine
ligand. The above-mentioned insolubility of the new
compound prevented the acquisition of good-quality
NMR spectra, although further evidence for its dinucle-
arity comes from the FAB MS spectrometry (Table 2).
This complex reacts with tertiary phosphines (molar
ratio 1:2) in acetone to give the soluble asymmetric
complexes of general formula [Pd{C4(COOMe)4}-
(C4H4N2)(L)] (7–10). The presence of pyridazine in the
mononuclear complexes is confirmed by 1H NMR spec-
troscopy. The spectra show the characteristic signals of
the methoxycarbonyl groups of the asymmetric com-
plexes, and the resonance signals corresponding to the
pyridazine ligand. The low field signal observed at
lꢀ8.7 is assigned to the H6 atom of monodentate
pyridazine [47]. The FAB MS data of the complexes are
listed in Table 2. Spectra of the new compounds show
a similar pattern of fragmentation which includes peaks
of the molecular ions, [Pd{C4(COOMe)4}(C4H4N2)-
(L)]+, as well as the same behaviour concerning the
{C4(COOMe)4} ligand that was observed for
iminophosphine complexes 1–5.
,
tion to the C(1)ꢀPdꢀC(4) plane (0.31 and 0.45 A,
respectively). Regarding the chelate rings, the pallada-
cycle is plane, and the six-membered one of the
iminophosphine adopts an envelope conformation simi-
lar to that described in other related complexes [44].
The COOMe groups are obviously planar and present
an alternate conformation regarding the chelate ring.
Thus, if one OMe lies in a side of the plane, then the
next group has the O in this side. The mean angle
between the COOMe and the chelate plane is 53.3(1)°.
The only significant difference between the two
molecules present in the asymmetric unit is the angle
between the COOMe group on the C(2) atom and the
chelate plane (38.3 and 46.5°, respectively).
3.2. Pyridazine complexes
The addition of pyridazine to a solution of the
[Pd{C4(COOMe)4}]n in acetone (molar ratio 1:1) leads
to the formation of the insoluble compound
[Pd{C4(COOMe)4}(m-C4H4N2)]2 (6) (Scheme 2). When
4. Supplementary data
Crystallographic data have been deposited with the
Cambridge Crystallographic Data Centre, CCDC No.
163514. Copies of this information may be obtained
free of charge from The Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (fax: +44-1223-336-
033; e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
Acknowledgements
Financial support of this work by the Direccio´n
General de Ensen˜anza Superior e Investigacio´n Cien-
t´ıfica (project PB-97-1036), Spain, is acknowledged.
J.V. thanks the Ministerio de Educacio´n y Ciencia,
Spain, for a research grant.
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