Synthesis, characterization and catalytic activity in the carbonylation of ethene of compounds Ia and IIa (see abstract). X-ray structure of Ia and IIa·2CH2Cl2

Article abstract of DOI:10.1016/j.ica.2004.04.026

The complexes cis-[Pd(H₂O)₂(PPh₃) ₂]X₂·nH₂O (Ia: X=p-CH₃C ₆H₄SO₃, n=2; IIa: X=CH₃SO ₃, n=0) have been synthesized by reacting Pd(OAc)₂, PPh₃ and HX in acetone in the presence of H₂O. They have been characterized by IR, ¹H and ³¹P NMR spectroscopy and TA analysis. By re-crystallization of these complexes, crystals of Ia and IIa·2CH₂Cl₂ suitable for the X-ray analysis have been obtained. The solid-state investigation of Ia reveals that the two p-toluenesulfonato units act as counter anions of a dicationic complex, in which the metal atom is surrounded in a square planar environment realized by two water molecules and two PPh₃ moieties that are cis to each other. The X-ray investigation of IIa·2CH₂Cl₂ shows that also in this case the two PPh₃ are cis to each other and that in the acentric triclinic cell there are two independent [Pd(H₂O) ₂(PPh₃)₂]²⁺ units, together with two methanesulfonato counter anions and two crystallization molecules of CH ₂Cl₂. The cationic complexes Ia and IIa are easily inter-converted with the neutral species trans-[Pd(p-CH₃C ₆H₄SO₃)₂(PPh₃) ₂] (Ib) and trans-[Pd(CH₃SO₃) ₂(PPh₃)₂] (IIb), respectively, depending on temperature and solvent. In chloroform at r.t., complex Ia catalyzes the carbonylation of ethene to a polyketone; at higher temperature in methanol it catalyzes the hydroesterification of ethene. In both cases catalysis is accompanied by CO₂ evolution. These results suggest that catalysis occurs via initial formation of a Pd(II)-H species by interaction of H ₂O with CO on the metal center though a reaction closely related to that of the water gas-shift.

Full text of DOI:10.1016/j.ica.2004.04.026

Inorganica Chimica Acta 357 (2004) 2737–2747
www.elsevier.com/locate/ica
Synthesis, characterization and catalytic activity in the
carbonylation of ethene of cis-[Pd(H2O)2(PPh3)2]X2 Æ nH2O
(X ¼ p-CH3C6H4SO3, n ¼ 2; X ¼ CH3SO3, n ¼ 0). X-ray structure
of cis-[Pd(H2O)2(PPh3)2](p-CH3C6H4SO3)2 Æ 2H2O
and of cis-[Pd(H2O)2(PPh3)2](CH3SO3)2 Æ 2CH2Cl2
a
b
b,
c
Gianni Cavinato , Andrea Vavasori , Luigi Toniolo *, Alessandro Dolmella
a
Department of Chemistry Science, University of Padua, via Marzolo 1, 35100 Padua, Italy
b
Department of Chemistry, University of Venice, Dorsoduro 2137, 30123 Venice, Italy
c
Department of Pharmaceutical Science, University of Padua, via Marzolo 5, 35131 Padua, Italy
Received 28 February 2004; accepted 23 April 2004
Available online 15 June 2004
Abstract
The complexes cis-[Pd(H2O)2(PPh3)2]X2 Æ nH2O (Ia: X ¼ p-CH3C6H4SO3, n ¼ 2; IIa: X ¼ CH3SO3, n ¼ 0) have been synthesized
1
by reacting Pd(OAc)2, PPh3 and HX in acetone in the presence of H2O. They have been characterized by IR, H and 31P NMR
spectroscopy and TA analysis. By re-crystallization of these complexes, crystals of Ia and IIa Æ 2CH2Cl2 suitable for the X-ray
analysis have been obtained. The solid-state investigation of Ia reveals that the two p-toluenesulfonato units act as counter anions of
a dicationic complex, in which the metal atom is surrounded in a square planar environment realized by two water molecules and
two PPh3 moieties that are cis to each other. The X-ray investigation of IIa Æ 2CH2Cl2 shows that also in this case the two PPh3 are
cis to each other and that in the acentric triclinic cell there are two independent [Pd(H2O)2(PPh3)2]2þ units, together with two
methanesulfonato counter anions and two crystallization molecules of CH2Cl2. The cationic complexes Ia and IIa are easily inter-
converted with the neutral species trans-[Pd(p-CH3C6H4SO3)2(PPh3)2] (Ib) and trans-[Pd(CH3SO3)2(PPh3)2] (IIb), respectively,
depending on temperature and solvent. In chloroform at r.t., complex Ia catalyzes the carbonylation of ethene to a polyketone; at
higher temperature in methanol it catalyzes the hydroesterification of ethene. In both cases catalysis is accompanied by CO2
evolution. These results suggest that catalysis occurs via initial formation of a Pd(II)–H species by interaction of H2O with CO on
the metal center though a reaction closely related to that of the water gas-shift.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Palladium; Phosphine; Aqua; Complexes; Cis-geometry; Catalyst; Carbonylation; Olefin; Polyketone; Ester
1. Introduction
lysts for the carbonylation of olefins [1,2]. A wide
spectrum of products can be obtained. For example,
when ethene is carbonylated in MeOH, the products
range from methyl propanoate to oligomeric or high
molecular weight perfectly alternated polyketones [3].
The first highly efficient catalyst system that produced
a polyketone was prepared by Drent et al. [4,5], of
Shell Co., from equimolar amount of [Pd(AcO)2] and
1,3-bis(diphenylphosphine)propane together with two
equivalents of a Bronsted acid, such as p-CH3C6H4-
SO3H or HBF4, which displaces the acetate anion
Pd(II)–phosphine complexes in which the cationic
charge is balanced by weakly coordinating anions
readily displaceable by the reagents are efficient cata-
* Corresponding author. Tel.: +390-41-2348553; fax: +390-41-
2348517.
E-mail address: toniolo@unive.it (L. Toniolo).
0020-1693/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.04.026

2738
G. Cavinato et al. / Inorganica Chimica Acta 357 (2004) 2737–2747
with formation of a cationic complex having coordi-
nation sites readily available to the monomers. In
contrast, the catalyst prepared from [Pd(AcO)2], an
excess of PPh3 and of a Bronsted acid, produced se-
lectively propanoate [5]. It was proposed that the
striking difference in selectivity is related to the coor-
dination geometry of the ligands. The chelating dis-
phosphine ligand imposes a cis geometry also for the
growing polymeric chain and the site that coordinates
the monomer, thus favoring the multiple insertion
steps that bring to the polyketone [1]. In the other
case, the insertion of the monomer is also favored
when the two phosphine ligands are in cis position,
however, once an alkyl or acyl palladium intermediate
forms, the preferred geometry is that with the two
phosphine ligands in trans position in order to avoid
the unfavorable occurrence of a Pd–P bond trans a
Pd–C bond. Hence, chain growth becomes unfavor-
able and termination occurs just after only one mol-
ecule of each monomer inserts, thus resulting in the
production of propanoate [1]. However, at low tem-
perature the cis–trans isomerization is slow, or even
suppressed, and polymerization can occur also with
Pd–PPh3 based catalysts, as found using the series of
precursors [Pd(PPh3)n(CH3CN)4ꢀn](BF4) (n ¼ 1–3) at
r.t., in aprotic solvents such as chloroform [6–8]. The
active Pd–H species initiating the catalysis probably
forms from the interaction of Pd(II) with protic im-
purities or is related to the observed catalytic dimer-
ization of C2H4 in the absence of CO [7]. It was
proposed that internal coordination of Pd with a
carbonyl oxygen of the growing chain maintains the
cis geometry that favors the polymerization [1].
by Drent [9–14]. Pd(II)-hydrido and -acyl species were
detected by NMR spectroscopy [10]. Moreover, it has
been found that the catalytic activity is significantly
enhanced when catalysis is carried out in the presence
of a hydride source, such as H2O, p-CH3C6H4SO3H,
H2. It has been proposed that of the two widely ac-
cepted mechanims (Scheme 1), one via initial formation
of a Pd(II)–H species, followed by subsequential in-
sertion of the olefin and of CO, with formation of a
Pd(II)–acyl intermediate, which undergoes alkanol at-
tack with production of the ester and regeneration of
the Pd(II)–hydride [15,16], and the other one via initial
formation of a Pd(II)–COOR species, followed by in-
sertion of the olefin and by protonolysis of the resulting
Pd(II)–alkyl intermediate [17–19], the first one plays a
major role [9,11–13]. Further support to this suggestion
came very recently from the catalytic activity of the acyl
complex
trans-[Pd(COEt)(p-CH3C6H4SO3)(PPh3)2],
isolated in the course of the methoxycarbonylation of
ethene [14].
The precursor system was also investigated in solution.
In polar solvents, like methanol, the in situ generated
species from [Pd(AcO)2]/PPh3/p-CH3C6H4SO3H ¼ 1/4/
10, as evidenced by 31P NMR analysis, are [Pd(p-CH3-
C6H4SO3)2(PPh3)2],
[Pd(H2O)2(PPh3)2](p-CH3C6H4-
SO3)2, and [Pd(PPh3)3](p-CH3C6H4SO3)2 [10]. Up to
now scarce attention has been paid to the geometry of the
species generated from the precursor, although it may be
of paramount importance on influencing the catalytic
activity and selectivity.
In this paper, we report the synthesis, characteriza-
tion of the title complexes, the catalytic activity in the
carbonylation of ethene of Ia and of IIa and the X-ray
structures of cis-[Pd(H2O)2(PPh3)2](p-CH3C6H4-SO3)2 Æ
2H2O and of cis-[Pd(H2O)2(PPh3)2](CH3SO3)2 Æ 2CH2-
Cl2(IIa2CH2Cl2).
Recently, we extended the studies on the hydroeste-
rification of olefins using the catalytic system based on
Pd(AcO)2/p-CH3C6H4SO3H/PPh3 originally employed
O
Pd
OR
Pd-H
CO
Pd
Pd-OR
O
O
O
OR
Pd
CO
Pd
OR
ROH
Pd = [PdXL2]n+
X = TsO (n = 0); X = CO, C2H4, H2O, ROH (n = 1);
L = PPh3;
Scheme 1. Pd(II)–hydride and Pd(II)–carbomethoxy catalytic cycles.

G. Cavinato et al. / Inorganica Chimica Acta 357 (2004) 2737–2747
2739
2. Experimental
room temperature with stirring). After washing, a gas
sample was analyzed by GC: no CO2 was detected. Dur-
ing the reaction CO–ethene mixture (1/1) was supplied
from a gas reservoir connected to the autoclave through a
constant pressure regulator. The autoclave was provided
with a temperature control ( 0.5 K).
2.1. Materials
Methanol (purity >99.5%, 0.01% of water), n-hexane,
n-pentane, CH2Cl2, diethyl ether, toluene, acetone
(H2O ¼ 0.5%) and deuterated solvents CD3COCD3,
C6D6, and CDCl3 were purchased from Aldrich;
Pd(OAc)2, p-CH3C6H4SO3H Æ H2O, CH3SO3H and PPh3
were Fluka products. Carbon monoxide and ethene were
supplied by SIAD Company (‘research grade’, purity
>99.9%). The complexes [Pd(p-CH3C6H4SO3)2(PPh3)2],
trans-[Pd(COCH2CH3)(p-CH3C6H4SO3)(PPh3)2] and
trans-[Pd(COCH2CH3)Cl(PPh3)2] were prepared ac-
cording to the methods reported in the literature
[10,14,16].
2.3. Synthesis of cis-[Pd(H2O)2(PPh3)2](p-CH3C6H4-
SO3)2 ꢁ 2H2O (Ia) and of cis-[Pd(H2O)2 (PPh3)2]-
(CH3SO3)2 (IIa) complexes
Upon addition, dropwise and under vigorous stirring,
of a PPh3 acetone solution (2.1 mmol in 3 ml) to a
Pd(OAc)2 acetone solution (1 mmol in 10 ml), a pale
yellow solid precipitated, which dissolved by dropping
an acetone solution of p-CH3C6H4SO3H Æ H2O (2.1
mmol, 2 ml). Addition of n-hexane (20 ml) caused pre-
cipitation of a pale yellow solid. After filtration the solid
was washed with n-hexane and diethyl ether and dried
under vacuum. Yield 90% of Ia.
Yellow-orange crystals of Ia, suitable for X-ray dif-
fraction studies, have been obtained by recrystallization
from n-hexane–CH2Cl2 at )10 ꢁC.
Following the same procedure just reported, but
adding the acid CH3SO3H (2.1 mmol in 3 ml of acetone)
in place of p-CH3C6H4SO3H, complex IIa was obtained
in 90% yield.
2.2. General procedure
The IR spectra were recorded in nujol mull on a
Nicolet FT-IR instruments mod Nexus. 1H and 31P
NMR spectra of complexes were recorded on a Bruker
AMX 300 spectrometer equipped with a BB multinu-
clear probe operating in the FT mode at 300 and
121.442 MHz for H and 31P, respectively; samples ex-
1
amined were dissolved in CD3COCD3, C6D6 or CDCl3.
1
The H and 13C NMR spectra of the polyketone were
recorded on a Bruker Avance 300 spectrometer in
1,1,1,3,3,3-hexafluoroisopropanol/CDCl3 (10/1) using
the Inverse H-gated decoupling technique.
Recrystallization of IIa from n-pentane-CH2Cl2 at
)10 ꢁC gave yellow-orange crystals of IIa Æ 2CH2Cl2
suitable for X-ray diffraction studies.
1
Products of the hydroesterification reaction were
analyzed by GC on a HP 5890 series II instrument
equipped with a 30 m · 0.53 mm · 0.1 lm HP 5 column.
The gas-phase analysis for CO2 was performed using a
5.5 m · 3.8 mm SS Silica Gel, 60/80 packed column
(detector: TCD; carrier gas: helium, 30 ml/min; oven: 40
ꢁC (2 min) to 100 ꢁC at 15 ꢁC/min).
Complexes Ia and IIa have been obtained in high
yield (90%) also from preformed [Pd(OAc)2(PPh3)2]
following the procedure just described.
2.4. Interconversion of Ia and IIa to [Pd(p-
CH3C6H4SO3)2(PPh3)2] (Ib) and to [Pd(CH3SO3)2
(PPh3)2] (IIb)
Thermogravimetric analysis was performed using a
TA instrument model SDT 2960 simultaneous DSC-
TGA. The sample, Ia or IIa (5 mg), was placed on the
dish and heated from 25 to 130 ꢁC at 7 ꢁC/min with a
nitrogen flow of 30 ml/min.
By adding n-hexane to a toluene solution of Ia or IIa
warmed at 60 ꢁC, complexes Ib and IIb have been ob-
tained as pale yellow solids (yield 85%). Ia and IIa are
reobtained by adding n-hexane to an acetone solution of
Ib or IIb at r.t.
The catalytic carbonylation of ethene to polyketone
was carried out using a magnetically stirred autoclave of
ca. 50 ml capacity. The catalytic methoxycarbonylation of
ethene was carried out in a stainless steel autoclave of ca.
250 ml of capacity, provided with a self-aspirating tur-
bine. In both cases, in order to prevent contamination by
metallic species, due to corrosion of the internal surface of
the autoclave, the catalyst was added to the solvent in a
glass bottle or a teflon-beaker placed into the autoclave.
The solvent was degassed at r.t. with a mixture of CO/
C2H4 before adding the catalytic precursor. The auto-
clave was washed by pressurizing with a 1/1 mixture of
CO/C2H4 (ca. 0.5 MPa) and then depressurizing to at-
mospheric pressure (this cycle was repeated 5 times, at
2.5. Carbonylation of ethene to polyketone
The carbonylation was carried out at r.t. In a typical
experiment, complex Ia (0.1 mmol) was dissolved in 10
ml of CHCl3 containing four equivalents of CH3CN.
After purging the autoclave to eliminate traces of air
and of CO2, it was charged with 4.5 MPa of CO/ethene
1/1. After 20 h, reaction the gas phase was analyzed.
CO2 was unambiguously detected by GC. The autoclave
was then depressurized and opened. The white solid
polyketone was filtered, washed with CHCl3 and dieth-
ylether and dried under vacuum at 60 ꢁC.

2740
G. Cavinato et al. / Inorganica Chimica Acta 357 (2004) 2737–2747
2.6. Methoxycarbonylation of ethene
performed by full-matrix least-squares based on F 2. In
complex Ia, the non-hydrogen atoms were assigned an-
isotropic displacement parameters and the hydrogen
atoms were treated by means of a riding model. The
final Fourier difference maps did not show any feature;
the largest maximum, less than half an electron, being
close to O(1).
Unfortunately, the results obtained for complex
IIa Æ 2CH2Cl2 were far from optimal. The crystal proved
very sensitive towards X-rays, degraded very rapidly
and decomposed dramatically after only 4 h of irradia-
tion. Accordingly, it was impossible to perform any
absorption correction and, worst of all, it was also im-
possible to utilize diffraction data of high quality for the
refinement procedure and only Pd, Cl, S and P atoms
were assigned anisotropic displacement parameters. The
largest maxima of the final Fourier difference map, lo-
cated close to Pd(1) and Pd(2), were just more than one
electron. All calculations were made with the SHELXTL/
PC [20] and SHELXL-93 [21] suite of programs.
In a typical experiment, 1 mmol of Ia together with
PPh3 and p-CH3C6H4SO3H (1/6/8) was dissolved in 50
ml of CH3OH in a teflon beaker. After purging the
autoclave, it followed the procedure already described in
the literature [11]. After 2 h, reaction at 80 ꢁC under 4.5
MPa (CO/ethene ¼ 1/1), the gas phase was analyzed by
GC: CO2 was present. The autoclave was then cooled
and depressurized. The content of the beaker was ana-
lyzed by GC (TOF ¼ 420 mol of methyl propanoate/per
mol of Ia/h).
2.7. X-ray data collection, structure solution and refine-
ment
The X-ray crystal structure determinations of the
complexes Ia and IIa Æ 2CH2Cl2 were carried out at room
temperature with a STADI 4 CCD STOE area detector
diffractometer, using for both samples a single-crystal
mounted in a thin-walled glass capillary with graphite-
ꢀ
monochromated Mo Ka radiation (k ¼ 0:71073 A). A
summary of the crystal and refinement data is shown in
Table 1.
3. Results and discussion
The structure of both complexes was solved by the
heavy-atom methods and the refinement procedure was
3.1. Characterization of Ia, IIa, Ib and IIb
Complexes Ia and IIa were synthetized by reacting
Pd(OAc)2, PPh3 and HX (X ¼ p-CH3C6H4SO3,
CH3SO3) in acetone
Table 1
Crystal and refinement data for Ia and IIa Æ 2CH2Cl2
Complex
Ia
IIa Æ 2CH2Cl2
PdðOAcÞ þ 2PPh3 þ 2HX
2
Formula
Molecular weight
Color
C50H52O10P2S2Pd C40H44Cl4O8P2S2Pd
1045.4
ꢀAcOHþH O cis-½PdðH OÞ ðPPh ÞꢂðX Þ ꢁ nH O
2
1027.01
yellow
ꢀꢀꢀꢀꢀꢀ!
2
3
2
2
2
colorless
triclinic
ðIa;IIaÞ
Crystal system
Space group
triclinic
P1 (No. 1)
12.099(2)
12.622(3)
18.461(4)
93.45(3)
103.04(3)
99.77(3)
2247.4(8)
2
ꢀꢀH2O cis-½PdX2ðPPh3Þ ꢂ
ð1Þ
ꢁ
P1 (No. 2)
2
ꢀ
ðIb;IIbÞ
a (A)
12.432(3)
12.740(3)
15.966(3)
79.66(3)
89.69(3)
78.63(3)
2437(1)
2
ꢀ
b (A)
(Ia: X ¼ p-CH3C6H4SO3, n ¼ 2; IIa: X ¼ CH3SO3,
n ¼ 0; Ib, X ¼ p-CH3C6H4SO3; IIb, X ¼ CH3SO3).
As reported in Section 2, the aqua complexes easily
interconvert with the anhydrous ones depending on
solvent and temperature.
ꢀ
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
ꢀ
V (A )
Z
Elemental analysis, IR and NMR data are reported
in Table 2. The IR spectrum of both Ia and IIa shows
two broad absorptions at 3508, 3445 cmꢀ1 and 3534,
3489 cmꢀ1, respectively, assigned to mas(O–H) and ms(O–
H) of the water molecules [13,22–25]. The absorptions at
1227, 1033, 1008 cmꢀ1 and at 1233, 1036, 1009 cmꢀ1 are
Dcalc (g cmꢀ3
)
1.424
1080
1.518
1048
F ð000Þ
Crystal dimensions (mm) 0.25 · 0.25 · 0.25
0.20 · 0.10 · 0.10
3.6/26.1
7860
h limits (ꢁ)
Number of independent 9270
3.5/29.6
data
Number of data with
I > 2rðIÞ
4275
3229
ꢀ
characteristic of the –SO3 group of the anions p-CH3-
ꢀ
ꢀ
Number of variables
a
586
547
C6H4SO3 and CH3SO3 [13,26–28].
The 31P NMR spectrum shows a singlet at ca. 34
ppm, close to 39.05 ppm for cis-[Pd(H2O)2(PPh3)2]-
(CF3SO3)2 in acetone [29]. The 1H NMR spectrum of Ia
shows singlets at 2.30 and 3.83ꢀppm due to six CH3
protons of two p-CH3C6H4SO3 anions and to eight
OH protons of four H2O molecules, respectively. The
1H NMR spectrum of complex IIa shows singlets at 2.57
RðF Þ
0.044
0.055
0.355
0.0897
0.2030
1.081
b
wRðF 2Þ
Largest peak in DF
(e A
ꢀ3
ꢀ
)
Goodness-of-fit (GOF)c
0.747
0.838
.
P
P
a RðF Þ ¼ jjFoj ꢀ jFcjj= jFoj.
P
P
2
2
2
2 2 1=2
b wRðF 2Þ ¼ ½ wðjFoj ꢀ jFcj Þ = wðjFoj Þ ꢂ
P
2
2
2
1=2
c GOF ¼ ½ wðjFoj ꢀ jFcj Þ =ðn ꢀ pÞꢂ
.

G. Cavinato et al. / Inorganica Chimica Acta 357 (2004) 2737–2747
2741
Table 2
Elemental analysis, selected IR, 1H and 31P NMR data
IR (cmꢀ1
)
Analysis
1H NMR
31P NMR
(%)
C
H
S
d (ppm)
dꢃ (ppm)
Ia
Found
Calculated
57.33
57.44
4.85
5.01
6.11
6.13
3508, 3445 (OH, H2O)
1227, 1033, 1008
(SO3, p-CH3C6H4SO3)
2.30 s (CH3, 6H, TsO)
3.83 s (OH, 8H, H2O)
6.97–7.73 m (C6H5, 38H, PPh3 and
TsO)
34.43 s (PPh3)
IIa
Ib
Found
Calculated
53.62
53.25
4.70
4.70
7.57
7.48
3534, 3489 (OH, H2O)
1233, 1036, 1009
(SO3, CH3SO3)
2.57 s (CH3, 6H, CH3 SO3)
4.79 s (OH, 4H, H2O)
7.24–7.50 m (C6H5, 30H, PPh3)
34.48 s (PPh3)
33.91 s (PPh3)
33.70 s (PPh3)
Found
Calculated
59.71
61.60
4.73
4.55
6.61
6.58
1253, 1025, 1002
(SO3, p-CH3C6H4SO3)
2.06 s (CH3, 6H, TsO)
6.77–8.03 m (C6H5, 38H, PPh3 and
TsO)
IIb
Found
Calculated
55.67
55.58
4.27
4.42
8.10
7.81
1265, 1026, 1001
(SO3, CH3SO3)
2.46 s (CH3, 6H, CH3SO3)
7.23–7.53 m (C6H5, 30H, PPh3)
Abbreviations: s, singlet; m, multiplet; TsO, p-CH3C6H4SO3. 1H and 31P NMR spectra for Ia and Ib were taken in CD3COCD3 and for IIa and
IIb in CDCl3. ꢃd (31P) values in ppm from external 85% H3PO4, downfield shifts being taken as positive.
and 4.79 ppm assigned to six CH3 protons of two p-
ꢀ
two molecules of H2O coordinated to the metal and of
two molecules of H2O of crystallization.
CH3SO3 anions and to the four OH protons of two
H2O molecules, respectively.
Fig. 2 shows the DTA analysis of complex IIa: only
two endothermic signals are present at 66.51 and 75.11
ꢁC, which correspond to the loss of two molecules of
water with a mass loss of 2.10% and 2.00%, in agreement
with the calculated theoretical value of 2.10%. Thus, the
thermogram confirms the presence of two molecules of
water. The comparison with the attribution just reported
for Ia does not allow to establish unambiguously whe-
ther both molecules are coordinated, as in the case
shown by the X-ray structure of IIa Æ 2CH2Cl2. The
different TA behavior of the coordinated water mole-
cules in the two complexes might be ascribed at least
Fig. 1 shows the thermogram of Ia: the first ther-
mogravimetric step, accompanied by an endothermic
DTA signal at 66.51 ꢁC, is attributed to the loss of two
molecules of water of crystallization, for which a theo-
retical mass loss of 3.44% is calculated, in agreement
with the observed value of 3.30%. The endothermic
DTA signals at 77.38 and 98.97 ꢁC are attributed to the
loss of two molecules of coordinated water, for which a
theoretical mass loss of 1.72% is calculated, in agree-
ment with the observed value of 1.40% and 1.70%, re-
spectively. The thermogram confirms the presence of
Fig. 1. Thermogravimetric analysis of complex Ia.

2742
G. Cavinato et al. / Inorganica Chimica Acta 357 (2004) 2737–2747
Fig. 2. Thermogravimetric analysis of complex IIa.
partially to the influence of intermolecular interactions.
In fact, in IIa Æ 2CH2Cl2 the coordinated water molecules
are involved in a H-bond network; the latter is lacking in
Ia (see Section 3.2).
The solid-state investigation of Ia revealed that the
two p-toluenesulfonato units do not belong to the pal-
ladium coordination sphere, but they act as counter
anions of the dicationic complex, in which the metal
atom is surrounded in a square planar environment re-
alized by two water molecules and two triphenylphos-
phine moieties that are cis to each other. The atoms in
the basal plane P(1)–P(2)–O(1)–O(2) are roughly co-
3.2. X-ray structure analysis of the complexes Ia and
IIa ꢁ 2CH2Cl2
ꢀ
The ORTEP [30] molecular structures of the two
complexes, together with the numbering system em-
ployed, are depicted in Figs. 3 and 4; selected bond
lengths and angles for both Ia and IIa Æ 2CH2Cl2 are
reported in Table 3.
planar within 0.09 A, with the Pd center deviating by
ꢀ
0.03 A. The bond angles about Pd are around 90ꢁ; the
largest deviations are shown by P(1)–Pd–P(2), 97.6(1)ꢁ,
and O(1)–Pd–P(2), 84.1(1)ꢁ. The O(1)–Pd–P(1) angle
measures 176.9(1)ꢁ, whereas O(2)–Pd–P(2) is 169.4(1)ꢁ,
Fig. 3. A drawing of the complex Ia with the adopted numbering scheme. Ellipsoids have been drawn at the 40% probability level; the hydrogen
atoms and the phenyl rings of the PPh3 units have been omitted for clarity.

G. Cavinato et al. / Inorganica Chimica Acta 357 (2004) 2737–2747
2743
Fig. 4. The content of the unit cell of complex IIa Æ 2CH2Cl2. Ellipsoids have been drawn at the 40% probability level.
thus deviating appreciably from linearity. Despite these
deviations, the distortion of the square-planar arrange-
ment is little overall. In fact, the sum of the bond angles
about Pd is 360.3(1)ꢁ, while the tetrahedral distortion,
measured by the dihedral angle between the P(1)–Pd–
P(2) and the O(1)–Pd–O(2) planes, is limited to 6.5ꢁ.
A search for Pd(II) complexes of general formula
L2PdP2 (P ¼ monodentate neutral phosphorous ligand,
L ¼ monodentate ligand) in the Cambridge Structural
Database [31] revealed 22 structures where the two
phosphorous ligands adopt the cis arrangement. The
latter does not appear hence particularly unusual; ac-
tually, the studies of Nelson and co-workers [32–34]
indicate that if the steric effects of the phosphorous li-
gands are not too large, the cis isomer is thermody-
namically more stable than the trans one, especially in
the presence of favorable solute–solvent interactions. In
these cases, there is some degree of distortion of the
square planar environment towards the tetrahedral one,
defined as pseudotetrahedrality [32].
Table 3
ꢀ
Selected bond distances (A) and bond angles (ꢁ) for Ia and
IIa Æ 2CH2Cl2
I
Pd–P(1)
Pd–O(1)
2.258(1)
2.146(3)
1.812(4)
1.797(5)
1.817(5)
1.432(4)
1.467(4)
1.476(3)
1.483(3)
Pd–P(2)
Pd–O(2)
2.263(1)
2.129(3)
1.803(5)
1.805(4)
1.816(4)
1.452(3)
1.774(5)
1.452(3)
1.778(6)
P(1)–C(1)
P(1)–C(13)
P(2)–C(25)
S(1)–O(3)
S(1)–O(5)
S(2)–O(6)
S(2)–O(8)
P(1)–C(7)
P(2)–C(19)
P(2)–C(31)
S(1)–O(4)
S(1)–C(37)
S(2)–O(7)
S(2)–C(44)
O(1)–Pd–O(2)
P(2)–Pd–O(1)
P(1)–Pd–O(1)
87.4(1)
84.1(1)
P(2)–Pd–O(2)
P(1)–Pd–O(2)
P(1)–Pd–P(2)
169.4(1)
91.2(1)
97.6(1)
176.9(1)
105.7(2)
111.8(2)
112.1(3)
104.8(2)
113.5(2)
111.4(2)
O(5)–S(1)–C(37)
O(4)–S(1)–O(5)
O(3)–S(1)–O(5)
O(8)–S(2)–C(44)
O(7)–S(2)–O(8)
O(6)–S(2)–O(8)
O(4)–S(1)–C(37)
O(3)–S(1)–C(37)
O(3)–S(1)–O(4)
O(7)–S(2)–C(44)
O(6)–S(2)–C(44)
O(6)–S(2)–O(7)
105.2(2)
108.5(2)
112.9(2)
106.1(3)
106.4(2)
113.9(2)
In the present study, the tetrahedral distortion is
limited to 6.5ꢁ, a value similar to that of 6.1ꢁ found by
Mak and co-workers [35] in cis-[(Ph2Ppym)2PdCl2] Æ 1/
2CH2Cl2 and smaller than those found either by Jensen
and co-workers [36] in cis-PdCl2[P(CH3)3]2 and Rome-
rosa et al. [37] in [cis-Pd(8-BzTT)2(PPh3)2] (8.9ꢁ and
13.2ꢁ, respectively). The little steric demand of the two
coordinated water molecules in the present complex, if
compared to the bulk of other ligands [35–37], also
contributes to keep the tetrahedral distortion to a min-
imum and help in stabilizing the cis geometry.
IIa Æ 2CH2Cl2
(A)
(B)
Pd(1)–P(1A)
Pd(1)–P(2A)
Pd(1)–O(1A)
Pd(1)–O(2A)
2.25(1)
2.25(1)
2.11(2)
2.15(2)
Pd(2)–P(1B)
Pd(2)–P(2B)
Pd(2)–O(1B)
Pd(2)–O(2B)
2.28(1)
2.25(1)
2.12(2)
2.09(2)
P(1A)–Pd(1)–P(2A) 96.1(3)
P(1A)–Pd(1)–O(1A) 169.4(6)
P(1A)–Pd(1)–O(2A) 83.8(6)
P(2A)–Pd(1)–O(1A) 91.0(6)
P(2A)–Pd(1)–O(2A) 179.1(7)
O(1A)–Pd(1)–O(2A) 89.0(8)
P(1B)–Pd(2)–P(2B)
P(1B)–Pd(2)–O(1B)
P(1B)–Pd(2)–O(2B)
P(2B)–Pd(2)–O(1B)
P(2B)–Pd(2)–O(2B)
96.7(3)
170.1(7)
83.4(6)
91.5(7)
178.1(7)
It is also interesting to note that, despite the rather
large number of reports about Pd(II)–aqua complexes in
O(1B)–Pd(2)–O(2B) 88.6(8)

2744
G. Cavinato et al. / Inorganica Chimica Acta 357 (2004) 2737–2747
ꢀ
and 2.277(1) A) and in [Pd(H2O)2(dppf)](OTf)2 [41]
the Cambridge Structural Database, we could find only
six monoaqua and five diaqua-cis-diphosphine palla-
dium(II) derivatives [24,29,38–42]. In all these structures
but one [29] the phosphorous atom belongs to a chelate
diphosphine ligand. Furthermore, one of such structures
appears to be suffering from some disorder [38], whereas
compound [29] turned out to have the Pd center sur-
rounded by the same coordination environment as in
both Ia and IIa Æ 2CH2Cl2. Table 4 reports a detailed
comparison of the main geometric features of these
complexes.
0
ꢀ
(2.263(1) and 2.267(1) A), where the ligand is 1,1 -
bis(diphenylphosphino)ferrocene. In any case, these
values fit nicely in the range reported for 102 square
planar Pd(II) complexes deposited within the Cam-
bridge Structural Database. The Pd–O distances in Ta-
ꢀ
ble 4 range between 2.106(4) A in [Pd(OTf)(H2O)
ꢀ
(dppp)](OTf) [25] and 2.254(3) A in [Pd(H2O){1,3-bis-
ꢀ
DTBOEPP}](BF4)2 [40] (mean value ¼ 2.14 A). In Ia,
ꢀ
Pd–O distances are 2.146(3) and 2.129(3) A, just about
the reported average and in good agreement with the
values reported for [Pd(H2O)2(PPh3)2](OTf)2 [29]. P–
ꢀ
Cph distances, with an average value of 1.808 A, do not
The Pd–P distances in the reported complexes range
ꢀ
between 2.206(1) A in [Pd(H2O){1,3-bis-DTBOEPP}]-
(BF4)2 (DTBOEPP ¼ di(2-t-buthoxyethyl)phosphino-
show instead any special feature and remain within the
range of reported data.
ꢀ
propane) [41] and 2.279(2) A in [Pd(H2O)2(dppomf)2]-
ꢀ
(OTf)2 [40] (mean value ¼ 2.25 A). In Ia, the Pd–P
With respect to the bond angles listed in Table 4, the
P(1)–Pd–P(2) angle ranges between 88.61(4)ꢁ in [Pd(p-
CH3C6H4SO3)(H2O)(dppp)](p-CH3C6H4SO3) [24] and
101.32(5)ꢁ in [Pd(H2O)2(dppomf)2](OTf)2 [41] (mean
ꢀ
distances are 2.258(1) and 2.263(1) A, slightly above the
average and similar to those found in the nearly iden-
tical complex [Pd(H2O)2(PPh3)2](OTf)2 [29] (2.250(1)
Table 4
Geometrical parameters of reported monoaqua- and diaqua-cis-diphosphine Pd(II) derivatives
Pd–P
Pd–O
P(1)–Pd–P(2)
O(1)–Pd–(O2)
Monoaqua complexes
[Pd(H2O)(dppp)(OTs)](OTs) [24]
2.236(1)
2.236(1)
2.237(1)
2.228(1)
2.248(4)
2.256(4)
2.206(1)
2.233(1)
2.267
2.138(4)
2.152(3)a
2.106(4)
2.159(3)b
2.147(9)
2.13(1)c
2.154(3)
2.254(3)d
2.156
88.61(4)
90.98(4)
90.7(2)
89.71(5)
101.26
85.9(1)
86.1(2)
87.1(4)
96.4(1)
[Pd(H2O)(dppp)(OTf)](OTf) [25]
[Pd(H2O){(S)-MeO-BIPHEP}(THF)](OTf)2 [39]
[Pd(H2O){1,3-bis-DTBOEPP}](BF4)2 [40]
[Pd(H2O)(dippf)(NCMe)](OTf)2 Æ 2H2O [42]e
[Pd(H2O)((R)-BINAP)(NCMe)](OTf)2 Æ 1/2H2O [42]e
2.270
2.255
2.245
2.136
91.15
Diaqua complexed
[Pd(H2O)2((R)-Tol-BINAP)](BF4)2 Æ 2H2O [38]
2.257(3)
2.235(3)
2.226(1)
2.231(1)
2.250(1)
2.277(1)
2.258(1)
2.263(1)
2.25(1)
2.159(9)
2.160(9)
2.127(2)
2.135(2)
2.130(2)
2.119(2)
2.146(3)
2.129(3)
2.11(1)
91.4(1)
90.33(2)
94.94(2)
97.6(1)
87.0(4)
87.66(8)
87.06(7)
87.4(1)
89.0(8)
88.6(8)
87.6(1)
87.0(2)
[Pd(H2O)2(dppp)](OTf)2 [25]
[Pd(H2O)2(PPh3)2](OTf)2 [29]
[Pd(H2O)2(PPh3)2](OTs)2 Æ 2H2O [this work]
[Pd(H2O)2(PPh3)2](OSO2Me)2 Æ 2 CH2Cl2 [this work]f
96.1(3)
2.25(1)
2.25(2)
2.28(2)
2.15(1)
2.12(2)
2.09(2)
96.7(3)
[Pd(H2O)2(dppf)](OTf)2 [41]
2.263(1)
2.267(1)
2.279(2)
2.271(2)
2.117(3)
2.132(3)
2.117(4)
2.169(4)
96.38(4)
101.32(5)
[Pd(H2O)2(dppomf)2](OTf)2 [41]
Mean
2.25
2.14
94.1
88.1
a Refers to the p-toluensulfonate oxygen.
b Refers to the trifluoromethansulfonate oxygen.
c Refers to the tetrahydrofurane oxygen.
d Refers to the buthoxyethyl oxygen.
e Bond distances and angles extracted from the Cambridge Structural Database; standard deviations unavailable.
f Low quality of diffraction data.

G. Cavinato et al. / Inorganica Chimica Acta 357 (2004) 2737–2747
2745
value ¼ 94.1ꢁ). In the complex described in this work,
the P(1)–Pd–P(2) angle measures 97.6(1)ꢁ. This is the
third largest value recorded so far for aqua cis-diphos-
phine palladium(II) derivatives and is also slightly larger
than that found in the almost equal [Pd(H2O)2(PPh3)2]-
(OTf)2 [29] (94.94(2)ꢁ). On the other side, the O(1)–Pd–
O(2) angle does not change very much (mean value ¼
88.1ꢁ), but for complex [Pd(H2O){1,3-bis-DTBOEPP}]-
(BF4)2 [41] (96.4(1)ꢁ). In Ia, it measures 87.4(1)ꢁ and
agrees well with the values reported for the other diaqua
complexes.
Interestingly, despite the presence of two hydration
water molecules and of two p-toluenesulfonato anions, a
situation similar to that reported by Stang et al. [25], no
efficient intermolecular interactions are present in the
complex. In fact, the closest intermolecular contacts
between the complexed water molecules and the oxygen
leads to the irremediable disruption of the crystal
structure. In just few hours, an amorphous dark residue
replaces the starting needle-shaped yellow crystals and
the process obviously spoils the X-ray data collection.
The bad quality of the diffraction data reduced the
information obtained from the diffraction experiment
and in effect the most valuable result of the crystallo-
graphic determination is the stereochemistry of the
complex. The palladium coordination sphere of both
[Pd(H2O)2(PPh3)2]2þ units shows the same environment
found either in complex Ia or [Pd(H2O)2(PPh3)2](OTf)2
[29]; some caution is instead necessary when discussing
bond lengths and angles (Table 4). Bond angles around
the metal centers appear close to 90ꢁ; hence, also in
IIa Æ 2CH2Cl2 the overall distortion of the square-planar
arrangement appears to be little, with the sum of the
bond angles about the two palladium atoms being just
about 360ꢁ.
ꢀ
atoms of the sulfonato groups are greater than 2.6 A;
the distances between the OW1 and OW2 atoms of the
hydration water molecules and the oxygen atoms of the
sulfonato groups are even larger.
Opposite to what has been found for complex Ia, the
coordination water molecules of the two independent
[Pd(H2O)2(PPh3)2]2þ units are engaged in some rather
loose hydrogen bonds (Fig. 5). In particular, the O(1A)
and O(2A) oxygens are bonded, respectively, to the
O(10) and O(11) atoms of a methanesulfonato group
belonging to a different unit placed at x; 1 þ y; z, with
The X-ray investigation of IIa Æ 2CH2Cl2 showed that
in the acentric triclinic cell there are two independent (A
and B) [Pd(H2O)2(PPh3)2]2þ units, together with two
methanesulfonato counter anions and two crystalliza-
tion CH2Cl2 molecules. All the molecules suffer from
high thermal motions and this is especially true for the
atoms belonging to the dichloromethane molecules.
Actually, the solvent molecules are the main responsible
for the poor stability of the crystal and their presence
ꢀ
Oꢁ ꢁ ꢁO contact distances of 2.56 and 2.60 A, respectively.
In the same way, the O(1B) and O(2B) atoms are linked
to the O(1) and O(2) oxygens of a second metha-
nesulfonato moiety, again placed at x; 1 þ y; z, with
ꢀ
Oꢁ ꢁ ꢁO contact distances of 2.68 and 2.59 A, respectively.
Fig. 5. A cell packing diagram illustrating the hydrogen bond network in complex IIa Æ 2CH2Cl2.

2746
G. Cavinato et al. / Inorganica Chimica Acta 357 (2004) 2737–2747
The hydrogen bond network is completed by some in-
teractions taking place within the same crystallographic
unit and linking in turn O(1A) and O(4), O(2A) and
O(5), O(1B) and O(7), O(2B) and O(8). The Oꢁ ꢁ ꢁO
the polyketone (ca. 2 g of polymer/g of Pd). It is likely
that cis–trans isomerization occurs even at r.t. and that
catalysis is promoted by the cis isomer.
The catalytic activity of Ia to methyl propanoate has
been also tested in the presence of H2O and of p-
CH3C6H4SO3H, which have been proven to promote
the catalysis, and in the presence also of PPh3 to stabi-
lize the catalytic system [11]. In MeOH at 80 ꢁC and 4.5
MPa (CO/ethene ¼ 1/1), Ia or IIa affords methyl pro-
panoate with a TOF of ca. 420 hꢀ1 in the presence of 800
ppm of H2O and with a Pd/PPh3/p-CH3C6H4SO3H ra-
tio of 1/8/8, as found when [Pd(p-CH3C6H4SO3)2-
(PPh3)2] or trans-[Pd(COEt)(p-CH3C6H4SO3)(PPh3)2]
are used as precursors [11,14]. The formation of CO2
during the catalysis suggests that it starts via a Pd(II)–H
species. In this case, after the insertion of just one
molecule of C2H4 and of CO with formation of Pd(II)–
acyl intermediate, methanolysis to methyl propanoate
interrupts the chain growing.
ꢀ
contact distances are of 2.88, 2.75, 2.67 and 2.65 A,
respectively, just a little longer than those mentioned
above.
The hydrogen bond network of IIa Æ 2CH2Cl2 looks
similar to those described in [Pd(OTf)(H2O)(dppp)]-
(OTf) [25] and in the nearly identical complex
[Pd(H2O)2(PPh3)2](OTf)2 [29]. In particular, both coor-
dinate water molecules are doubly hydrogen-bonded to
the two methanesulfonato anions, and the two water
molecules are each hydrogen-bonded to different anions
rather than to the same one. This hydrogen bond pat-
tern is likely to afford some stability to the crystal
structure of IIa Æ 2CH2Cl2.
3.3. Catalytic activity of Ia in the carbonylation of ethene
The catalytic activity of complex Ia has been tested at
r.t., in chloroform as solvent and in the presence of four
equivalents of CH3CN, in order to get close to the
conditions reported by Sen and Lai [6,7], which used as
precursor the system [Pd(CH3CN)4](BF4)2 in combina-
tion with two equivalents of PPh3. After ca. 20 h, there
was production of 25 g of polymer/g of Pd. 13C NMR
analysis shows average n ¼ 27 and that only keto end-
groups CH3CH2CO– are present. Moreover, catalysis
occurs with formation of CO2. Thus, the polymerization
can be schematized as follows: (i) the Pd(II)–hydride
that starts the catalysis forms upon interaction of H2O
with CO on the metal center and decarboxylation of the
resulting Pd(II)–carboxy species; (ii) multiple subse-
quential insertion of C2H4 and CO; and (iii) protonol-
ysis of a Pd(II)–C bond of the growing chain giving the
polyketone and Pd(II) species back to the catalytic cycle.
It is interesting to underline that with the precursor used
by Lai and Sen [7], water is not introduced by the
complex and that the molecular weight of the polyke-
tone is so high not to allow the identification of the end
groups.
References
[1] E. Drent, P.H.M. Budzelaar, Chem. Rev. 96 (1996) 663.
[2] G. Kiss, Chem. Rev. 101 (2001) 3435.
[3] R.A.M. Robertson, D.J. Cole-Hamilton, Coord. Chem. Rev. 225
(2002) 67.
[4] E. Drent (Shell), EP 121 965, 1984.
[5] E. Drent, J.A.M. Van Broekhoven, M.J. Doyle, J. Organomet.
Chem. 417 (1991) 235.
[6] A. Sen, T.-W.T. Lai, J. Am. Chem. Soc. 104 (1982) 3520.
[7] T.-W. Lai, A. Sen, Organometallics 3 (1984) 866.
[8] A. Sen, Acc. Chem. Res. 26 (1993) 303.
[9] A. Seayad, A.A. Kelkar, L. Toniolo, R.V. Chaudhari, J. Mol.
Catal. 151 (2000) 47.
[10] A. Seayad, S. Jayasree, K. Damodaran, L. Toniolo, R.V.
Chaudhari, J. Organomet. Chem. 601 (2000) 100.
[11] A. Vavasori, G. Cavinato, L. Toniolo, J. Mol. Catal. 176 (2001)
11.
[12] A. Vavasori, G. Cavinato, L. Toniolo, J. Mol. Catal. 191 (2003) 9.
[13] G. Cavinato, A. Vavasori, L. Toniolo, F. Benetollo, Inorg. Chim.
Acta 343 (2003) 183.
[14] G. Cavinato, L. Toniolo, A. Vavasori, J. Mol. Catal., in press.
[15] J. Knifton, J. Org. Chem. 41 (1976) 2885.
[16] G. Cavinato, L. Toniolo, J. Organomet. Chem. 198 (1990) 187.
[17] S. Otsuka, A. Nakamura, T. Yoshida, M. Naruto, K. Ataka, J.
Am. Chem. Soc. 95 (1973) 3180.
[18] D.M. Fenton, J. Org. Chem. 38 (1973) 3192.
[19] D. Milstein, Acc. Chem. Res. 21 (1988) 428.
[20] G.M. Sheldrick, SHELXTL/PC: Version 5.03, Siemens Analytical
X-ray Instruments Inc., Madison, WI, 1994.
ꢀHþ
Pd2þ–ðH2OÞ þ CO ꢀ Pd2þ–ðCOOHÞꢀ!CO2 Pd2þ–H
þ;H2O
Pd2þ–HC2H4;CO Pd2þ–½C H –ðCOC H Þꢂ –H H
ꢀꢀꢀꢀ!
ꢀꢀꢀꢀ!
2
4
2
4
Pd2þ–ðH2OÞ þ CH3CH2–ðCOC2H4Þꢂ n–H
ð2Þ
[21] G.M. Sheldrick, SHELXL-93: Program for the Refinement of
€
Crystal Structures, University of Gottingen, Germany, 1993.
n
[22] B. Chiswell, L.M. Venanzi, J. Chem Soc. A (1966) 1246.
[23] P. Leoni, M. Sommovigo, M. Pasquali, S. Midollini, D. Braga, P.
Sabatino, Organometallics 11 (1991) 1038.
The capability of complex Ia to catalyze the copoly-
merization may be related to its cis geometry [1].
However, we have found that also the acyl complex
[24] F. Benetollo, R. Bertani, G. Bombieri, L. Toniolo, Inorg. Chim.
Acta 233 (1995) 5.
trans-[Pd(COEt)(p-CH3C6H4SO3)(PPh3)2],
a possible
[25] P.J. Stang, D.H. Cao, G.T. Poulter, A.M. Arif, Organometallics
14 (1995) 1110.
intermediate in the polymerization process that may
form after the insertion of just one molecule of ethene
and of CO into the Pd(II)–H species, in the presence of
four equivalents of CH3CN catalyzes the formation of
[26] U. Bohner, G. Zundel, J. Phys. Chem. 89 (1985) 1408.
[27] G.J. Kubas, C.J. Burns, G.R.K. Khalsa, L.S. Van Der Sluys, G.
Kiss, C.D. Hoff, Organometallics 11 (1992) 3390.

G. Cavinato et al. / Inorganica Chimica Acta 357 (2004) 2737–2747
2747
[28] R.K. Merwin, D.M. Roddick, J. Organomet. Chem. 487 (1995) 69.
[29] Z. Qin, M.C. Jennings, R.J. Puddephatt, Inorg. Chim. 40 (2001)
6220.
[36] G. Schultz, N.Yu. Subbotina, C.M. Jensen, J.A. Golen, I.
Hargittai, Inorg. Chim. Acta 191 (1992) 85.
[37] A. Romerosa, C. Lopez-Magana, M. Saoud, S. Manas,
E. Colacio, J. Suarez-Varela, Inorg. Chim. Acta 307 (2000)
125.
[30] C.K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National
Laboratory, Oak Ridge, TN, 1976.
[31] F.H. Allen, Acta Crystallogr., Sect. B 58 (2002) 380, Cambridge
Crystallographic Database (Version 5.25 of November 2003).
[32] J.J. MacDougall, J.H. Nelson, F. Mathey, J.J. Mayerle, Inorg.
Chem. 19 (1980) 709.
[38] M. Sodeoka, R. Tokunoh, F. Miyazaki, E. Hagiwara, M.
Shibasaki, Synlett 463 (1997).
[39] M. Sperrle, V. Gramlich, G. Consiglio, Organometallics 15 (1996)
5196.
[33] J.J. MacDougall, E.M. Holt, P. de Meester, N.W. Alcock, F.
Mathey, J.H. Nelson, Inorg. Chem. 19 (1980) 1439.
[34] K.D. Redwine, W.L. Wilson, D.G. Moses, V.J. Catalano, J.H.
Nelson, Inorg. Chem. 39 (2000) 3392.
[40] E. Lindner, M. Schmid, P. Wegner, C. Nachtigal, M. Steimann,
R. Fawzi, Inorg. Chim. Acta 296 (1999) 103.
[41] O.V. Gusev, A.M. Kalsin, M.G. Peterleitner, P.P. Petrovskii,
K.A. Lissenko, Organometallics 21 (2002) 3637.
[42] K. Li, P.N. Norton, M.B. Hursthouse, K.K. Hii, J. Organomet.
Chem. 665 (2003) 250.
[35] S.-L. Li, Z.-Z. Zhang, B.-M. Wu, T.C.W. Mak, Inorg. Chim. Acta
255 (1997) 239.