X-ray crystal structures of novel platinum(II) and palladium(II) complexes of dialkyl phosphonated phosphines

Article abstract of DOI:10.1016/S0022-328X(02)01144-0

Two diethyl phosphonated phosphine ligands of formula Ph₂P(CH₂)₃PO₃Et₂ (ligand L) and Ph₂P(4-C₆H₄PO₃Et₂) (ligand L′) were used to prepare different complexes of platinum(II) (1, cis-PtCl₂L₂; 2, trans-PtCl₂L₂·H₂O; 3A and 3B, cis- and trans-PtCl₂L₂′) and palladium(II) (4, [PdCl₂L]₂; 5, trans-PdCl₂L₂·H₂O; 6, trans-PdCl₂L₂′·Ch₂ Cl₂). The single-crystal X-ray structure analyses of complexes 1, 2, 4-6 indicate that complexation involved only the phosphine end, whereas the strong polarization of the P=O bond was highlighted by the formation of hydrogen bonds with a water molecule in 2 and 5, and with a dichloromethane molecule in 6, with an exceptionally short C-H(triple dot sign)O hydrogen bond length (C(triple dot sign)O separation 3.094(3) A?).

Full text of DOI:10.1016/S0022-328X(02)01144-0

Journal of Organometallic Chemistry 649 (2002) 113–120
www.elsevier.com/locate/jorganchem
X-ray crystal structures of novel platinum(II) and palladium(II)
complexes of dialkyl phosphonated phosphines
Gilles Guerrero a, P. Hubert Mutin a,*, Franc¸oise Dahan b, Andre´ Vioux a
a UMR CNRS 5637, Chimie Mole´culaire et Organisation du Solide, Uni6ersite´ de Montpellier II, cc 007, 34095 Montpellier Cedex 5, France
b UPR CNRS 8241, Laboratoire de Chimie de Coordination du CNRS, 205 Route de Narbonne 31077 Toulouse Cedex 4, France
Received 22 October 2001; accepted 7 January 2002
Abstract
Two diethyl phosphonated phosphine ligands of formula Ph2P(CH2)3PO3Et2 (ligand L) and Ph2P(4-C6H4PO3Et2) (ligand L%)
were used to prepare different complexes of platinum(II) (1, cis-PtCl2L2; 2, trans-PtCl2L2·H2O; 3A and 3B, cis- and trans-PtCl2L2%)
and palladium(II) (4, [PdCl2L]2; 5, trans-PdCl2L2·H2O; 6, trans-PdCl2L2%·CH2Cl2). The single-crystal X-ray structure analyses of
complexes 1, 2, 4–6 indicate that complexation involved only the phosphine end, whereas the strong polarization of the PꢀO bond
was highlighted by the formation of hydrogen bonds with a water molecule in 2 and 5, and with a dichloromethane molecule in
,
6, with an exceptionally short CꢁH···O hydrogen bond length (C···O separation 3.094(3) A). © 2002 Elsevier Science B.V. All
rights reserved.
Keywords: Platinum(II) complexes; Palladium(II) complexes; Dialkyl phosphonated phosphines; Hydrogen bonding
1. Introduction
ray structures have been reported for platinum(II) [4] or
palladium(II) [10] complexes with such ligands.
Platinum(II) and palladium(II) complexes are well
known not only for their great importance as catalysts
in organic synthesis [1], but also for their biological and
pharmacological interest [2]. Ligands containing both a
strongly electron-donating phosphine group and a co-
ordinatively labile phosphonate group are prone to
form hemilabile transition metal complexes, which are
of interest in catalytic applications [3,4]. Moreover
phosphonated phosphines provide a route to water-sol-
uble complexes [5–13] alternative to sulfonated phos-
phines. An important feature of phosphine-phos-
phonate complexes is the possibility to immobilize them
between the layers of zirconium phosphates [12,14] or
double hydroxides [15]. The phosphonate group may
also be used to anchor these complexes on supports
such as metal oxides or bone tissues, thus opening a
wide field of applications in supported catalysis and
chemotherapy [3,16,17]. However, despite the interest
raised by phosphine-phosphonate ligands very few X-
We recently reported that not only phosphonic acids
but also phosphonic esters (ethyl or trimethylsilyl)
could be used as coupling agents to modify titania or
alumina surfaces [18,19]; alternatively, the phosphonate
groups can be dispersed within a matrix of metal oxide
by sol–gel processing [19,20]. Our purpose in studying
complexes with phosphine-phosphonate ligands is to
prepare heterogeneous catalysts by these two routes.
Here we report the preparation and characterization of
platinum(II) and palladium(II) complexes derived from
the ligands Ph2P(CH2)3PO3Et2 (ligand L) and Ph2P(4-
C6H4PO3Et2) (ligand L%) (Table 1). The single-crystal
X-ray structure analysis of five of these compounds
indicates that the complexation of the metal involves
Table 1
Platinum(II) and palladium(II) complexes prepared
L=Ph2P(CH2)3PO3Et2 L%=Ph2P(4-C6H4PO3Et2)
Platinum
cis-PtCl2L2 a, 1
cis-PtCl2L2% , 3A
trans-PtCl2L2·H2O a, 2
trans-PtCl2L2% , 3B
Palladium [PdCl2L]2 a, 4
trans-PdCl2L2% ·CH2Cl2 a, 6
trans-PdCl2L2·H2O a, 5
* Corresponding author. Fax: +33-4-67-143852.
E-mail address: mutin@univ-montp2.fr (P.H. Mutin).
a Structure determined by single-crystal X-ray diffraction.
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(02)01144-0

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G. Guerrero et al. / Journal of Organometallic Chemistry 649 (2002) 113–120
only the phosphine end, whereas the strongly polarized
phosphoryl oxygen forms hydrogen bonds with a water
molecule in 2 and 5, and with a dichloromethane
molecule in 6.
2. Results and discussion
2.1. Synthesis of the ligands
Ligand L was synthesized in two steps according to
Eq. (1). Br(CH2)3PO3Et2 (I) was obtained by an Arbu-
zov reaction [21]. Then the nucleophilic phosphination
with Ph2PK [22] afforded L in high yield (86%) as a
colourless oil which presented 31P-NMR chemical shifts
at −17.5 ppm (Ph2P) and at 30.9 ppm (PO(OEt)2) in
CH2Cl2–acetone-d6 mixture.
Fig. 1. ORTEP representation of complex 1 (thermal ellipsoids are
shown at 30% probability; hydrogen atoms have been omitted for
clarity).
Table 2
,
Selected bond lengths (A) and bond angles (°) for compound 1
(1)
Bond lengths
PtꢁP(1)
PtꢁP(2)
P(1)ꢁC(1)
P(3)ꢁO(1)
P(3)ꢁC(3)
P(3)ꢁO(2)
P(3)ꢁO(3)
2.2567(9)
2.2507(9)
1.828(4)
1.452(3)
1.766(4)
1.583(3)
1.574(4)
PtꢁCl(1)
PtꢁCl(2)
P(2)ꢁC(4)
P(4)ꢁO(4)
P(4)ꢁC(6)
P(4)ꢁO(5)
P(4)ꢁO(6)
2.3452(9)
2.3563(9)
1.827(3)
1.472(3)
1.786(4)
1.574(3)
1.568(3)
Ligand L% was synthesized in two steps according to
Eq. (2). The intermediate Br(4-C6H4PPh2) (I%) was pre-
pared by the method reported by McEwen et al. [23],
then it was subjected to a Pd catalyzed coupling reac-
tion [24] to give L% as a yellow oil in 52% yield
(31P-NMR chemical shifts at −4.6 ppm (Ph2P) and
18.3 ppm (PO3Et2) in acetone-d6).
Bond angles
P(1)ꢁPtꢁP(2)
P(1)ꢁPtꢁCl(1)
P(1)ꢁPtꢁCl(2)
PtꢁP(1)ꢁC(1)
O(1)ꢁP(3)ꢁC(3)
O(1)ꢁP(3)ꢁO(2)
O(1)ꢁP(3)ꢁO(3)
99.64(3)
176.62(3)
89.92(3)
114.62(12)
116.02(19)
113.98(19)
114.6(2)
P(2)ꢁPtꢁCl(1)
P(2)ꢁPtꢁCl(2)
Cl(1)ꢁPtꢁCl(2)
PtꢁP(2)ꢁC(4)
O(4)ꢁP(4)ꢁC(6)
O(4)ꢁP(4)ꢁO(5)
O(4)ꢁP(4)ꢁO(6)
83.06(3)
169.60(3)
87.54(4)
112.99(13)
114.64(19)
115.56(19)
115.29(17)
atom, as shown by the values of bond angles
P(2)ꢁPtꢁCl(1) (83.06(3)°) and P(1)ꢁPtꢁP(2) (99.64(3)°),
P(1)ꢁPtꢁCl(1) (176.62°), and P(2)ꢁPtꢁCl(2) (169.60(3)°)
(Table 2). Moreover the bond lengths PtꢁP (2.2567(9)
(2)
,
and 2.2507(9) A), and PtꢁCl (2.3452(9) and 2.3563(9)
,
2.2. Complexes of platinum(II)
A) are close, but not equal. Solid-state 31P-MAS NMR
spectroscopy gave interesting informations owing to the
coupling with 195Pt (I=1/2; 33.8%). The signal assigned
to the phosphonate groups appeared as one singlet at
31.4 ppm, whereas the two signals assigned to the
phosphine ligands, at 10.2 and −6.3 ppm (1/1 ratio),
2.2.1. Ligand L
Usually, the reaction of PtCl2(PhCN)2 with phos-
phine ligands leads to mixtures of cis and trans isomers
[25–29]. Actually the reaction of (PtCl2(PhCN)2) with
two equivalents of ligand L in dichloromethane led to a
mixture of white (complex 1) and yellow crystals (com-
plex 2). Complexes 1 and 2 were separated by crystal-
lization from a CH2Cl2–pentane mixture and single
crystals suitable for X-ray diffraction study were
obtained.
Complex 1 presents a cis square-planar geometry
(Fig. 1) in which the phosphonate groups are not
coordinated to the platinum atom. The square-planar
geometry is slightly distorted around the platinum
1
presented satellites with constants J(PtP) of 3844 and
3556 Hz, respectively. The presence of two signals for
the phosphorus atoms of the two phosphine ligands
reflects their crystallographic non-equivalence and the
distorted structure of complex 1. Such a solid-state
distortion is common for cis complexes of platinum
[28]. Conversely the solution 31P-NMR spectrum of
complex 1 in a CH2Cl2–acetone-d6 mixture presented
only one singlet at 7.5 ppm with two 31P–195Pt satellites
(1J(PtP)=3643 Hz) ascribed to the phosphine ligands,

G. Guerrero et al. / Journal of Organometallic Chemistry 649 (2002) 113–120
115
besides a sharp singlet at 30.2 ppm assigned to
P(O)(OEt)2 groups. Note that the coupling constants
1J(PtP) observed in the solid state as well as in solution
are in the same range, higher than 3000 Hz as expected
for a cis geometry [30].
Complex 2, PtCl2L2·H2O, presents a trans geometry
(Fig. 2) with a slightly distorted square-planar geometry
around the platinum atom, as shown by the 175.27(3)°
value of the Cl(1)ꢁPtꢁCl(2) bond angle (Table 3). The
oxygen atoms of the phosphoryl groups are not coordi-
nated to the platinum atom, but they are bridged via
hydrogen bonds to a molecule of adventitious water.
Because of these hydrogen bonds the phosphonate
groups must face each other, forming tongs, instead of
being oriented away from the square plan. The lengths
,
of the two hydrogen bonds are 1.90(4) and 1.94(5) A.
The bond angles OꢁHꢁO of 170(4) and 151(4)° indicate
a distortion (Table 3). The literature [31] gives an
Fig. 3. ORTEP representation of complex 4 (thermal ellipsoids are
shown at 30% probability; hydrogen atoms have been omitted for
clarity).
example of a water molecule hydrogen bonded to two
molecules of triphenylphosphine oxide, with H···O dis-
,
tances of 1.85 and 1.77 A, and OꢁHꢁO angles of 161
and 168°.
2.2.2. Ligand L%
The treatment of (PtCl2(PhCN)2) with two equiva-
lents of ligand L% led to complexes 3A cis and 3B trans
as a mixture of white and yellow crystals. Attempts to
separate them by crystallization remained unsuccessful.
The 31P-NMR spectrum in acetone-d6 displayed two
singlets with two 31P–195Pt satellites at 14.6 ppm
(1J(PtP)=3833 Hz) and at 21.3 ppm (1J(PtP)=2469
Hz) in a 43:57 ratio, which were assigned to the cis (3A)
and trans (3B) coordinated phosphines, respectively,
and two singlets at 17.2 and 16.7 ppm ascribed to the
phosphonate groups.
Fig. 2. ORTEP representation of complex 2 (thermal ellipsoids are
shown at 30% probability; hydrogen atoms have been omitted for
clarity).
Table 3
,
Selected bond lengths (A) and bond angles (°) for compound 2
Bond lengths
PtꢁP(1)
PtꢁP(2)
2.3256(8)
2.3269(8)
1.830(3)
1.795(3)
1.465(3)
0.91(5)
PtꢁCl(1)
PtꢁCl(2)
2.3054(8)
2.3073(8)
1.832(3)
1.776(3)
1.454(3)
0.93(5)
2.3. Complexes of palladium(II)
P(1)ꢁC(1)
P(3)ꢁC(3)
P(3)ꢁO(1)
O(7)ꢁH(71)
O(1)ꢁH(71)
O(1)ꢁO(7)
P(2)ꢁC(4)
P(4)ꢁC(6)
P(4)ꢁO(4)
O(7)ꢁH(72)
O(4)ꢁH(72)
O(4)ꢁO(7)
2.3.1. Ligand L
The reaction of PdCl2 with two equivalents of L in
THF led to a mixture of complexes 4 and 5, which
could be separated by successive crystallizations from
CH2Cl2–pentane as orange and yellow crystals in 15
and 65% yields, respectively. The crystals obtained
turned out to be suitable for structure determination by
X-ray diffraction.
Compound 4 has a centrosymmetric dimeric struc-
ture in which the two metal centres are linked through
bridging chlorine atoms (Fig. 3 and Table 4). The two
palladium atoms adopt a quasi-square planar geometry
in trans arrangement so that a centre of symmetry lies
between them, as confirmed by 31P-MAS NMR with
1.90(4)
2.797(4)
1.94(5)
2.790(4)
Bond angles
P(1)ꢁPtꢁP(2)
P(1)ꢁPtꢁCl(1)
P(1)ꢁPtꢁCl(2)
PtꢁP(1)ꢁC(1)
O(1)ꢁP(3)ꢁC(3)
O(1)ꢁP(3)ꢁO(2)
O(1)ꢁP(3)ꢁO(3)
177.40(3)
88.57(3)
91.21(3)
116.42(10)
115.03(18)
114.02(16)
115.95(17)
P(2)ꢁPtꢁCl(1)
P(2)ꢁPtꢁCl(2)
Cl(1)ꢁPtꢁCl(2)
PtꢁP(2)ꢁC(4)
O(4)ꢁP(4)ꢁC(6)
O(4)ꢁP(4)ꢁO(5)
O(4)ꢁP(4)ꢁO(6)
89.78(3)
90.26(3)
175.27(3)
115.50(11)
114.66(17)
113.03(17)
115.98(17)
H(71)ꢁO(7)ꢁH(72) 104(4)
O(4)ꢁH(72)ꢁO(7) 151(4)
O(1)ꢁH(71)ꢁO(7) 170(4)

116
G. Guerrero et al. / Journal of Organometallic Chemistry 649 (2002) 113–120
only two peaks at 30.6 ppm (PO3Et2) and 28.7 ppm
(PPh2). The solution 31P-NMR chemical shifts (30.8
and 30.3 ppm) point at a similar solution structure.
These chemical shifts are in good agreement with litera-
ture values for dimeric complexes of palladium [32,33].
The ligands L are bonded to the palladium atoms
through the trivalent phosphorus atoms of the phos-
phine groups, whereas the free phosphonate groups
point out on each side of the plan formed by chlorine
and palladium atoms to reduce steric repulsions. Such
chlorine-bridged
dimeric
palladium
complexes
[PdCl2L]2 are known to form in the reaction of
monometallic complexes L2PdCl2 with an excess of
PdCl2. Conversely the chloro bridges are cleaved by
amines and phosphines and dimeric complexes are con-
sidered as intermediates in the synthesis of monometal-
lic complexes with L–Pd ratios higher than 2 [34,35]. In
complex 4, the bond lengths between a palladium atom
Fig. 4. ORTEP representation of complex 5 (thermal ellipsoids are
shown at 30% probability; hydrogen atoms have been omitted for
clarity).
Table 5
,
and either the terminal chlorine atom (2.2752(7) A) or
,
Selected bond lengths (A) and bond angles (°) for compound 5
,
the bridging chlorine atoms (2.3273(7) and 2.4244(7) A)
are similar to those reported in the literature for chlo-
rine-bridged dimeric palladium complexes [33,35–37],
as are the ClꢁPdꢁCl% bond angles (85.66(2) and
91.89(2)°) (Table 4).
Bond lengths
P(3)ꢁO(1)
P(4)ꢁO(4)
P(3)ꢁC(3)
P(4)ꢁC(6)
PdꢁCl(2)
O(7)ꢁH(71)
O(1)ꢁH(71)
O(1)ꢁO(7)
1.4554(17)
1.4578(19)
1.780(2)
1.768(2)
2.3027(6)
0.90(3)
P(1)ꢁC(1)
P(2)ꢁC(4)
PdꢁP(1)
1.824(2)
1.829(2)
2.3279(5)
2.3287(6)
2.3000(6)
0.96(3)
PdꢁP(2)
Complex 5 is monometallic. Its structure (Fig. 4)
presents a trans square-planar geometry around the
palladium atom. Actually complex 5 is isomorphous of
complex 2, with a slightly distorted square-planar ge-
ometry around the palladium atom: the P(1)ꢁPdꢁP(2)
and Cl(1)ꢁPdꢁCl(2) bond angles both depart from 180°,
and PꢁPdꢁCl bond angles are slightly different from 90°
(Table 5). 31P-NMR spectroscopy in CDCl3 confirm the
trans arrangement with two peaks at 31.0 ppm
(4J(PP)=2.5 Hz, PO3Et2) and at 16.4 ppm (4J(PP)=
2.4 Hz, PPh2) comparable with literature values for
trans coordinated alkyldiarylphosphines [30,38,39];
there is no indication of an equilibrium between cis-
and trans-complexes. As in complex 2, a water
molecule forms hydrogen bonds with the phosphoryl
groups, forcing the two phosphonate groups to face
PdꢁCl(1)
O(7)ꢁH(72)
O(4)ꢁH(72)
O(4)ꢁO(7)
1.89(3)
2.789(3)
1.97(3)
2.779(3)
Bond angles
P(1)ꢁPdꢁP(2)
P(1)ꢁPdꢁCl(1)
P(2)ꢁPdꢁCl(2)
PdꢁP(1)ꢁC(1)
O(1)ꢁP(3)ꢁC(3)
O(1)ꢁP(3)ꢁO(2)
O(1)ꢁP(3)ꢁO(3)
177.39(2)
88.58(2)
90.22(2)
116.48(7)
114.98(12)
113.91(10)
116.13(11)
Cl(1)ꢁPdꢁCl(2)
P(2)ꢁPdꢁCl(1)
P(1)ꢁPdꢁCl(2)
PdꢁP(2)ꢁC(4)
O(4)ꢁP(4)ꢁC(6)
O(4)ꢁP(4)ꢁO(5)
O(4)ꢁP(4)ꢁO(6)
175.10(2)
89.75(2)
91.26(2)
115.51(7)
115.01(11)
113.22(11)
115.63(11)
H(71)ꢁO(7)ꢁH(72) 95(3)
O(4)ꢁH(72)ꢁO(7) 140(3)
O(1)ꢁH(71)ꢁO(7) 173(3)
each other. Distortion of the hydrogen bonds is
reflected by the values of O(4)ꢁH(72)ꢁO(7) (140(3)°)
and O(1)ꢁH(71)ꢁO(7) (173(3)°) bond angles.
Table 4
,
Selected bond lengths (A) and bond angles (°) for compound 4
2.3.2. Ligand L%
The treatment of palladium chloride PdCl2 with two
equivalents of ligand L% led to orange crystals of com-
Bond lengths
P(2)ꢁO(1)
P(2)ꢁO(2)
P(2)ꢁO(3)
P(2)ꢁC(3)
P(1)ꢁC(8)
P(1)ꢁC(14)
1.4709(18)
1.558(2)
1.571(2)
1.784(2)
1.808(2)
1.807(2)
P(1)ꢁC(1)
P(1)ꢁPd
PdꢁCl(1)
PdꢁCl(2)
PdꢁCl(1%)
1.828(2)
2.2171(6)
2.3273(7)
2.2752(7)
2.4244(7)
plex 6 (PdCl2L%·CH2Cl2) after crystallization from a
2
mixture CH2Cl2–pentane. Complex 6 has crystallo-
graphic inversion symmetry with the Pd on an inversion
center (Fig. 5), which implies a precise planar coordina-
Bond angles
P(1)ꢁPdꢁCl(1)
P(1)ꢁPdꢁCl(2)
P(1)ꢁPdꢁCl(1%) 177.13(2)
PdꢁP(1)ꢁC(1)
PdꢁP(1)ꢁC(8)
,
tion symmetry with close PdꢁP (2.3400(7) A) and PdꢁCl
93.45(2)
88.82(2)
Cl(1)ꢁPdꢁCl(2)
Cl(1)ꢁPdꢁCl(1%)
Cl(2)ꢁPdꢁCl(1%)
O(2)ꢁP(2)ꢁO(1)
O(2)ꢁP(2)ꢁC(3)
PdꢁCl(1)ꢁPd%
175.68(2)
85.66(2)
91.89(2)
115.14(11)
106.01(11)
94.34(2)
,
(2.2919(6) A) bond lengths, and exact trans 180° angles
(Table 6). This is confirmed by the presence of only two
peaks in the 31P-MAS NMR (15.5 ppm (PO3Et2), 21.8
ppm (PPh2ꢁPd) values that are in agreement with those
of trans triarylphosphines palladium complexes de-
116.76(7)
112.70(7)
PdꢁP(1)ꢁC(14) 108.66(7)

G. Guerrero et al. / Journal of Organometallic Chemistry 649 (2002) 113–120
117
the hydrogen bond length depends on both the acidity
of the hydrogen bond donor and the basicity of the
hydrogen bond acceptor. Accordingly, the strong polar-
ization of the PꢀO bond is evidenced by the exception-
,
,
ally short CH···OꢀP (2.14 A) and C···OꢀP (3.03 A)
separations in complex 6, as compared to the CH···O
,
,
(2.27–2.6 A) and C···O (3.21–3.51 A) separations re-
ported for various H-bonded acceptors and
dichloromethane.
3. Experimental
3.1. General
All manipulations were carried out under an atmo-
sphere of dry Ar using standard Schlenk and glovebox
techniques. Solvents were purified by conventional pro-
cedures and distilled prior to use. Tetrahydrofuran was
distilled from CaH2 first, then from sodium pellets.
Diethylether was distilled over sodium pellets.
Dichloromethane was distilled over P2O5. Toluene, hex-
ane and pentane were distilled over CaH2. All the
Fig. 5. ORTEP representation of complex 6 (thermal ellipsoids are
shown at 30% probability; hydrogen atoms have been omitted for
clarity).
Table 6
,
Selected bond lengths (A) and bond angles (°) for compound 6
,
Bond lengths
solvents were stored over molecular sieves (4 A). Et3N
P(2)ꢁO(1)
P(2)ꢁO(3)
P(2)ꢁC(4)
P(1)ꢁC(1)
C(23)ꢁH(23B)
1.445(2)
1.565(2)
1.770(3)
1.815(2)
0.98
P(2)ꢁO(2)
PdꢁP(1)
PdꢁCl(1)
C(23)ꢁO(1)
O(1)ꢁH(23B)
1.555(2)
2.3400(7)
2.2919(6)
3.094(3)
2.14
was distilled before use and Ph2PK (0.5 M in THF) was
used without further purification. Elemental analyses
were performed at the laboratory of microanalysis of
the CNRS in Vernaison (France). Solution 1H- and
13C-NMR were performed in a Bruker Avance DPX
200. 31P-NMR analyses were performed using a Bruker
AC 200 spectrometer. When CH2Cl2 was used as sol-
vent for NMR experiments, samples were transferred
under an Ar atmosphere into a 5 mm NMR tube and
an acetone-d6 capillary was used as a lock standard.
1H-, 13C-NMR chemical shifts are referenced to Me4Si
and 31P-NMR chemical shifts to H3PO4 (85% in water).
31P solid state NMR spectra were obtained with a
Bruker Avance DPX300 spectrometer, using magic an-
gle spinning (MAS) (spinning rate 10 kHz) and high-
power proton decoupling; 31P-MAS NMR spectra were
recorded without cross-polarization (CP) using a 45°
flip angle and a 10 s recycling delay; chemical shifts are
referenced to H3PO4 (85% in water). FTIR spectrum
was obtained in a Perkin–Elmer Spectrum 2000 spec-
trophotometer between NaCl windows. Mass spectra
were recorded in a JEOL JMS D300 with the fast atom
bombardment method using m-nitrobenzylic alcohol
(NBA) or thioglycerol (GT) as matrices.
Bond angles
P(1)ꢁPdꢁP(1%)
P(1)ꢁPdꢁCl(1)
O(1)ꢁP(2)ꢁO(2)
180.0
92.95(2)
114.27(11)
Cl(1)ꢁPdꢁP(1%)
PdꢁP(1)ꢁC(1)
O(1)ꢁP(2)ꢁC(4) 113.44(15)
O(1)ꢁP(2)ꢁO(3) 101.66(11)
87.05(2)
117.67(7)
C(23)ꢁH(23B)ꢁO(1) 164
scribed in the literature [38,40]. The 31P-NMR spectrum
in CDCl3 displayed only two resonances (17.9 ppm
(PO3Et2), 24.2 ppm (PPh2ꢁPd)), which suggests a trans
solution structure and that no cis–trans isomerization
took place. The phosphonate groups lie on each part of
the square plan, pointing away from the palladium
center. The presence of a dichloromethane molecule
bonded through a CH···OꢀP hydrogen bond to one
phosphoryl group is noteworthy. In Table 7, the C···O
and H···O separations in complex 6 are compared with
some values reported in the literature for
dichloromethane molecules hydrogen-bonded to accep-
tors of growing strength. It is well known [41–43] that
Table 7
,
Mean C···O and H···O distances (A) for CꢁH···O hydrogen bonds from CH2Cl2 to PꢀO (in complex 6) and other H-bond acceptors from the
literature [42]
Acceptors
CꢁOH
CꢁOꢁC
SꢀO
NO2
CꢀO
PꢀO (in 6)
Mean C···O
Mean H···O
3.51
2.6
3.43
2.50
3.3
2.4
3.32
2.41
3.21
2.27
3.03
2.14

118
G. Guerrero et al. / Journal of Organometallic Chemistry 649 (2002) 113–120
X-ray data were collected [44] in a Stoe Imaging
J(PC)=12.7 Hz) aromatics). FABMS; m/z: 365 ([M+
H]+, 100%).
Plate Diffractometer System (IPDS), equipped with an
Oxford Cryosystems cooler device, at 203 K using
Mo–Ka radiation with a graphite monochromator
3.2.2. Ph2P(4-C6H4PO3Et2) (L%)
,
(u=0.71073 A). In both cases, data were collected with
A 100 ml three-necked flask under Ar was charged
with I% (12.79 g, 37.5 mmol), diethylphosphite (5.69 g,
41.2 mmol), Et3N (4.16 g, 41.2 mmol), toluene (20 ml),
a stirrer bar and heated at 90 °C. Then, Pd(PPh3)4
(2.16 g, 1.87 mmol) was added. After the addition was
complete, the reaction mixture was stirred at 90 °C for
72 h. After cooling, dry Et2O (100 ml) was added and
a precipitate immediately formed. After filtration, the
filtrate was concentrated under vacuum. The residue
was chromatographed on a silica column (toluene–
THF gradient) to give L% as a yellow oil (7.76 g, 19.5
mmol, yield 52%). 31P-NMR (CH2Cl2–CD3COCD3): l
a crystal-to-detector distance of 70 mm, in the 2q range
of 3.3–52.1° with a € rotation movement (€=0.0–
250.6°, D€=1.4° for 1; €=0.0–249.6°, D€=1.6° for
3) or with a € oscillation movement (€=0.0–200.4°,
D€=1.2° for 2; €=0.0–249.6°, D€=1.6° for 4; €=
0.0–200.2°, D€=1.1° for 5). The structures were
solved using the direct methods [45] and refined [46] by
full-matrix least-squares F2. All non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were
found on a difference Fourier and introduced in calcu-
lations with a riding model, with Uiso equal to 1.1 times
that of atom of attachment. The atomic scattering
factors and anomalous dispersion terms were taken
from the standard compilation [47].
1
−4.6 (PPh2), 18.3 (P(O)(OEt)2). H-NMR (CDCl3): l
1.38 (t, 6H, CH3), 4.15 (q, 4H, CH2), 7.32–7.72 (m,
14H, aromatics). 13C-NMR (CDCl3): l 16.83–16.78 (d,
J(PC)=8.0 Hz, CH3), 63.19–63.16 (d, J(PC)=6.0 Hz,
CH2), 128.49–128.51 (d, J(PC)=4 Hz), 128.82–128.78
(d, J(PC)=8 Hz), 130.60–130.51 (d, J(PC)=18 Hz),
131.12–132.05 (d, J(PC)=186 Hz), 133.05–133.14 (d,
J(PC)=18 Hz), 133.58–133.63 (d, J(PC)=10 Hz),
137.4–137.0 (d, J(PC)=82 Hz) 141.23–141.26 (d,
J(PC)=6 Hz) (aromatics). FABMS; m/z: 399 ([M+
H]+).
3.2. Synthesis
Br(CH2)3PO3Et2 (I) [21] and Br(4-C6H4PPh2) (I%) [23]
were prepared according to literature methods. Starting
materials were characterized by 1H-, 31P-, and 13C-
NMR spectroscopy and mass spectrometry.
3.2.1. Ph2P(CH2)3PO3Et2 (L)
A 250 ml three-necked round-bottom flask equipped
with a pressure-equalizing addition funnel was charged
under Ar with 12.95 g (0.05 mol) of bromopropyldi-
ethylphosphonate (I) in 30 ml of dry THF. The mixture
was cooled under stirring to 5 °C. A solution of potas-
sium diphenylphosphide (100 ml, 0.5 M in THF) was
added dropwise over 30 min. Then the reaction mixture
was allowed to warm to room temperature (r.t.) and
stirred for 15 h. Degassed water (3×50 ml) and EtOAc
(100 ml) were added. The organic phase was separated
and dried over Na2SO4. The solvent was removed un-
der vacuum and the crude product chromatographed
(SiO2 column; EtOAc–hexane 80/20). The solvent was
removed from the eluate under vacuum to give L as a
pure colorless oil (15.58 g, 42.8 mmol, yield 86%). Anal.
Found: C, 62.15; H, 7.19; O, 14.04; P, 16.35. Calc.: C,
62.64; H, 7.14; O, 13.19; P, 17.03%. 31P-NMR
(CH2Cl2–CD3COCD3): l −17.5 (d, PPh2, J(PP)=2.9
Hz) and 30.9 (d, PꢀO, J(PP)=3.0 Hz). 1H-NMR
(CDCl3): l 1.30 (t, 6H, CH3), 1.73–2.00 (m, 4H,
CH2P), 2.19 (t, 2H, CH2), 4.08 (q, 4H, CH2) and
7.29–7.48 (m, 10H, aromatics). 13C-NMR (CDCl3): l
16.9–16.8 (d, J(PC)=6.0 Hz, CH3), 19.9–19.46 (dd,
3.2.3. cis-[PtCl2{Ph2P(CH2)3P(O)(OEt)2}2] (1) and
trans-[PtCl2{Ph2P(CH2)3P(O)(OEt)2}2·H2O] (2)
PtCl2(PhCN)2 (0.325 g, 0.685 mmol) was added to a
solution of compound L (0.5 g, 1.37 mmol) in dry
CH2Cl2 (15 ml). The mixture was heated at 40 °C
under stirring for 24 h, then cooled down to r.t., filtered
and the solvent removed under vacuum. The crude
yellow oil was crystallized from CH2Cl2–pentane under
an Ar atmosphere to give, after filtration, compound 1
as white crystals (352 mg, 0.354 mmol, yield 58%).
Anal. Found: C, 45.35; H, 5.07; Cl, 7.48; P, 11.70; Pt,
15.27. Calc.: C, 45.84; H, 5.23; Cl, 7.14; P, 12.47; Pt,
19.60%. 31P-NMR (CH2Cl2–CD3COCD3): l 7.5 (t,
PPh2, 1J(PtP)=3643 Hz); 30.2 (PꢀO). 31P-NMR
(HPDEC MAS): l −6.3 (PPh2, 1J(PtP)=3556 Hz);
1
1
10.2 (PPh2, J(PtP)=3844 Hz), 31.4 (PꢀO). H-NMR
(CDCl3): l 1.26 (t, 12H, CH3), 1.58–1.90 (m, 8H,
CH2P), 2.47 (m, 4H, CH2), 4.01 (q, 8H, OCH2), 7.19–
7.49 (m, 20H, aromatics). 13C-NMR (CDCl3): l 16.92–
16.82 (d, J(PC)=5.8 Hz, CH3), 19.24–19.17 (d,
J(PC)=3.7 Hz, CH2), 27.40–25.85 (dd, J(PC)=139
Hz, P(O)CH2), 31.88–31.46 (dd, J(PC)=42 Hz,
PꢁCH2), 62.02–61.92 (d, J(PC)=5 Hz, OCH2),
128.65–128.86 (t, J(PC)=10 Hz), 129.87–129.93 (d,
J(PC)=3 Hz), 131.44 (s), and 133.67–133.87 (d,
J(PC)=5 Hz) (aromatics).
2J(PC)=12.0 Hz, CH2), 28.8–25.8 (dd, J(PC)=140
1
1
Hz, CH2), 29.6–29.12 (dd, J(PC)=18.0 Hz, PCH2),
61.9–61.7 (d, J(PC)=6.5 Hz, OCH2), 128.9–128.8 (d,
J(PC)=6.7 Hz), 129.0 (d, J(PC)=0.4 Hz), 133.27–
132.90 (d, J(PC)=18.6 Hz) and 138.8–138.5 (d,
The filtrate was concentrated and the yellow oil
crystallized from CH2Cl2–pentane under an Ar atmo-

G. Guerrero et al. / Journal of Organometallic Chemistry 649 (2002) 113–120
119
Table 8
Crystal data and structure refinement parameters for compounds cis-PtCl2L2, 1; trans-PtCl2L2·H2O, 2; [PdCl2L]2, 4; trans-PdCl2L2·H2O, 5; and
trans-PdCl2L2% ·CH2Cl2, 6
Compound
1
2
4
5
6
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C38H52Cl2O6P4Pt
994.67
203
C38H54Cl2O7P4Pt
1012.68
203
Monoclinic
P21/c (no. 14)
C38H52Cl4O6P4Pd2
1083.28
203
C38H54Cl2O7P4Pd
923.99
203
Monoclinic
P21/c (no. 14)
C46H52Cl6O6P4Pd
1143.86
203
Triclinic
Triclinic
Triclinic
(
(
(
P1 (no. 2)
P1 (no. 2)
P1 (no. 2)
Unit cell dimensions
,
a (A)
9.4292(13)
24.692(3)
9.3706(12)
94.480(15)
103.537(16)
80.323(15)
2089.2(5)
2
12.0208(12)
28.105(3)
13.9179(14)
11.7497(16)
11.9417(18)
8.2332(12)
96.432(17)
94.697(17)
77.998(17)
1120.8(3)
1
12.0144(14)
27.954(2)
13.8792(17)
11.4884(13)
14.0418(16)
9.1419(11)
98.329(14)
105.748(14)
66.043(12)
1296.1(3)
1
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
V (A )
111.616(11)
111.556(13)
3
,
4371.4(8)
4
3.522
29 967
7927
4335.3(8)
4
0.743
33 758
8181
Z
v (mm−1
Total reflections
Independent reflections 7014
)
3.682
17 487
1.226
10 937
4025
0.835
12 614
4673
Rint
R
0.0331
0.0307
0.0337
0.0352
0.0307
0.0298
0.0318
0.0356
0.0318
0.0287
3.2.5. [Pd2Cl4{Ph2P(CH2)3P(O)(OEt)2}2] (4) and
trans-[PdCl2{Ph2P(CH2)3P(O)(OEt)2}2·H2O] (5)
sphere to give after filtration, compound 2 as yellow
crystals (110 mg, 0.11 mmol, yield 18%). Anal. Found:
C, 44.98; H, 5.29; Cl, 6.94; P, 12.00; Pt, 17.90. Calc.: C,
45.03; H, 5.33; Cl, 7.01; P, 12.24; Pt, 19.26%. 31P-NMR
PdCl2 (0.121 g, 0.68 mmol) was added to a solution
of compound L (0.5 g, 1.37 mmol) in THF (20 ml). The
mixture was heated under stirring at 80 °C for 24 h,
then cooled to r.t., filtered and evaporated under vac-
uum. The crude orange oil was crystallized from
CH2Cl2–pentane under Ar to give after filtration com-
plex 4 as orange crystals (110 mg, 0,101 mmol). Yield
15%. Elemental analysis: Found: C, 41.86; H, 4.90; Cl,
13.64; P, 11.0; Pd, 18.2. Calc.: C, 42.13; H, 4.84; Cl,
13.09; P, 11.44; Pd, 19.64%. 31P-NMR (CDCl3): l 30.3
(PPh2); 30.8 (P(O)(OEt)2). 31P-MAS NMR: l 28.7
1
(CDCl3): l 12.4 (PPh2, J(PtP)=2550 Hz); 31.1 (PꢀO).
1H-NMR (CDCl3): l 1.25 (t, 12H, CH3), 1.72–1.86 (m,
8H, CH2P), 2.50–2.59 (m, 4H, CH2), 4.01 (q, 8H,
OCH2), 7.41–7.46 (m, 12H) and 7.74–7.81 (m, 8H)
aromatics. 13C-NMR (CDCl3):
l 16.86–16.80 (d,
J(PC)=5.9 Hz, CH3), 17.92–17.88 (d, J(PC)=4.1 Hz,
CH2), 25.29–25.13 (dd, J(PC)=16 Hz, PꢁCH2),
26.28–27.68 (dd, J(PC)=140 Hz, P(O)CH2), 61.89–
61.96 (d, J(PC)=6.3 Hz, OCH2), 128.65–128.75 (t,
J(PC)=10 Hz), 129.42–129.96 (t, J(PC)=54 Hz),
130.99 (s) and 134.07–134.18 (t, J(PC)=11.5 Hz)
(aromatics).
1
(PPh2); 30.6 ppm (P(O)(OEt)2). H-NMR (CDCl3): l
1.44 (t, 12H, CH3), 1.70–1.92 (m, 8H, CH2P), 2.47–
2.60 (m, 4H, CH2), 4.4 (q, 8H, CH2), 7.44–7.83 (m,
20H, aromatics). 13C-NMR (CDCl3): l 16.9–16.83 (d,
J(PC)=5.9 Hz, CH3), 18.02 (d, CH2), 27.49–25.92 (dd,
J(PC)=140 Hz, P(O)CH2), 28.39 (d, PꢁCH2), 62.1–
62.06 (d, J(PC)=6.2 Hz, CH2), 127.72, 127.15 (d,
J(PC)=60 Hz), 129.34, 129.23 (d, J(PC)=12 Hz),
132.38 (s), 133.74–133.64 (d, J(PC)=9.7 Hz)
(aromatics).
3.2.4. cis-[PtCl2{Ph2PC6H4P(O)(OEt)2}2] (3A) and
trans-[PtCl2{Ph2PC6H4P(O)(OEt)2}2] (3B)
PtCl2(PhCN)2 (0.347 g, 0.735 mmol) was added to a
solution of compound L% (0.587 g, 1. 47 mmol) in dry
CH2Cl2 (30 ml). The mixture was heated under stirring
at 40 °C for 24 h, then allowed to cool to r.t., filtered
and the solvent removed under vacuum. The crude
yellow oil was crystallized from CH2Cl2–pentane
under an Ar atmosphere to give after filtration, com-
pounds 3A and 3B as a mixture of white and yellow
crystals (0.570 g, 0.536 mmol, yield 73%, trans/cis:
57:43).
The above filtrate was concentrated and the yellow
oil crystallized from a CH2Cl2–pentane solution to give
complex 5 as yellow needles (405 mg, 0.44 mmol, yield
65%). Elemental analysis: Found: C, 49.15; H, 5.82; Cl,
7.27; P, 13.0; Pd, 11.35. Calc.: C, 49.39; H, 5.89; Cl,
7.67; P, 13.41; Pd, 11.51%. 31P-NMR (CDCl3): l 16.4
1
(PPh2); 31.0 (P(O)(OEt)2). H-NMR (CDCl3): l 1.25 (t,
31P-NMR (CH2Cl2–CD3COCD3): 3A: l 14.6 (t,
12H, CH3), 1.71–1.92 (m, 8H, CH2P), 2.54–2.63 (m,
4H, CH2), 4.02 (q, 8H, OCH2), 7.30–7.49 (m, 12H) and
7.69–7.79 (m, 8H) (aromatics). 13C-NMR (CDCl3): l
1
PPh2, J(PtP)=3833 Hz), and 16.7 (PꢀO). 3B: l 21.3
1
(t, PPh2, J(PtP)=2469 Hz) and 17.2 (PꢀO).

120
G. Guerrero et al. / Journal of Organometallic Chemistry 649 (2002) 113–120
[9] P. Machnitzki, M. Tepper, K. Wenz, O. Stelzer, E. Herdweck, J.
Organomet. Chem. 602 (2001) 158.
[10] S. Ganguly, J.T. Mague, D.M. Roundhill, Inorg. Chem. 31 (1992)
3500.
[11] V. Penicaud, C. Maillet, P. Janvier, M. Pipelier, B. Bujoli, Eur.
J. Org. Chem. (1999) 1745.
[12] S. Bischoff, A. Kockritz, M. Kant, Top. Catal. 13 (2000) 327.
[13] E. Lindner, M. Khanfar, J. Organomet. Chem. 630 (2001) 244.
[14] D. Villemin, P.-A. Jaffres, B. Nechab, F. Courivaud, Tetrahedron
Lett. 38 (1997) 6581.
[15] V. Pre´vot, C. Forrano, J.P. Besse, Appl. Clay Sci. 18 (2001) 3.
[16] L. Trynda-Lemiesz, H. Kozlowski, B.K. Keppler, J. Inorg.
Biochem. 77 (1999) 141.
[17] C. Maillet, P. Janvier, M. Pipelier, T. Praveen, Y. Andres, B.
Bujoli, Chem. Mater. 13 (2001) 2879.
[18] G. Guerrero, P.H. Mutin, A. Vioux, Chem. Mater. 13 (2001) 4367.
[19] G. Guerrero, P.H. Mutin, A. Vioux, J. Mater. Chem. 11 (2001)
3161.
[20] G. Guerrero, P.H. Mutin, A. Vioux, Chem. Mater. 12 (2000) 1268.
[21] D.G. Hewitt, M.W. Teese, Aust. J. Chem. 37 (1984) 205.
[22] P. Machnitzki, T. Nickel, O. Stelzer, C. Lanfgrafe, Eur. J. Inorg.
Chem. (1998) 1029.
[23] W.E. McEwen, A.B. Janes, J.W. Knapczyk, V.L. Kyllingstad,
W.I. Shiau, S. Shore, J.H. Smith, J. Am. Chem. Soc. 100 (1978)
7304.
[24] T. Hirao, T. Masunaga, Y. Ohshiro, T. Agawa, Synthesis (1981)
56.
[25] E. Bayer, V. Schurig, Angew. Chem. Int. Ed. Engl. 14 (1975) 493.
[26] H.C. Clark, J.A. Davies, C.A. Fyfe, P.J. Hayes, R.E. Wasylishen,
Organometallics 2 (1983) 177.
[27] L. Bemi, H.C. Clark, J.A. Davies, C.A. Fyfe, R.E. Wasylishen,
J. Am. Chem. Soc. 104 (1982) 438.
15.39–15.45 (d, J(PC)=6.0 Hz, CH3), 16.78 (d, CH2),
21.66 (dd, P(O)CH2), 24.90 (d, PꢁCH2), 60.46–60.53 (d,
J(PC)=6.2 Hz, OCH2), 127.36 (s), 128.63–128.86 (d,
J(PC)=23 Hz), 129.6 (s) and 132.64–132.75 (d,
J(PC)=12 Hz) (aromatics). FABMS; m/z: 924 ([M+
H]+).
3.2.6. trans-[PdCl2{Ph2PC6H4P(O)(OEt)2}2·CH2Cl2] (6)
PdCl2 (0.523 g, 2.94 mmol) was added to a solution
of compound L% (2.34 g, 5.87 mmol) in THF (40 ml).
The reaction mixture was heated under stirring at
80 °C for 24 h; then cooled to r.t., filtered and the
solvent was removed under vacuum. The crude orange
oil was crystallized from a CH2Cl2–pentane solution
under an Ar atmosphere, to give after filtration com-
pound 6 as orange crystals (2.55 g, 2.23 mmol, yield
76%). Elemental analysis: Found: C, 48.28; H, 4.40; P,
10.50; Pd, 10.90. Calc.: C, 48.26; H, 4.55; P, 10.84; Pd,
9.30%. 31P-NMR (CDCl3):
l 24.2 (PPh2); 17.9
1
(P(O)(OEt)2). H-NMR (CDCl3): l 1.36 (t, 12H, CH3),
4.17 (q, 8H, OCH2), 5.22 (s, 4H, CH2Cl2), 7.32–7.74
(m, 28H (aromatics). 13C-NMR (CDCl3): l 16.7–16.8
(d, J(PC)=6.3 Hz, CH3), 53.84 (s, CH2Cl2), 62.8–
60.86 (d, J(PC)=5.6 Hz, OCH2), 128.49–129.01 (m),
131.31–131.42 (t, J(PC)=10 Hz) and 134.92–135.57
(m) (aromatics).
[28] J.A. Rahn, D.J. O’Donnell, A.R. Palmer, J.H. Nelson, Inorg.
Chem. 28 (1989) 2631.
[29] S.B. Sembiring, S.B. Colbran, D.C. Craig, J. Chem. Soc. Dalton
Trans. (1999) 1543.
[30] J.A. Rahn, L. Baltusis, J.H. Nelson, Inorg. Chem. 29 (1990) 750.
[31] B.M. Kariuki, K.D.M. Harris, D. Philp, J.M.A. Robinson, J. Am.
Chem. Soc. 119 (1997) 12679.
3.3. X-ray crystallography
Details of the structures of compounds 1, 2, 4–6 are
given in Table 8.
[32] P.W. Dyer, P.J. Dyson, S.L. James, P. Suman, J.E. Davies, C.M.
Martin, J. Chem. Soc. Chem. Commun. (1998) 1375.
[33] G.R. Newkome, D.W. Evans, F.R. Fronczek, Inorg. Chem. 26
(1987) 3500.
[34] H.C. Clark, G. Ferguson, V.K. Jain, M. Parvez, Inorg. Chem. 24
(1985) 1477.
Acknowledgements
We wish to thank Dr. Sylvian Dutremez for his help
in the discussion of the results.
[35] W.J. Grigsby, B.K. Nicholson, Acta Crystallogr. Sect. C: Cryst.
Struct. Commun. 48 (1992) 362.
[36] P.A. Chaloner, S.Z. Dewa, P.B. Hitchcock, Acta Crystallogr. Sect.
C: Cryst. Struct. Commun. 51 (1995) 232.
References
[37] D. Fenske, H. Prokscha, P. Stock, H.J. Becher, Z. Naturforsch.
B: Anorg. Chem. Org. Chem. 35 (1980) 1075.
[38] R.A. Komoroski, A.J. Magistro, P.P. Nicholas, Inorg. Chem. 25
(1986) 3917.
[39] S.O. Grim, Inorg. Chim. Acta 4 (1970) 56.
[40] J.-P. Bezombes, C. Chuit, R.J.-P. Corriu, C. Reye´, J. Mater.
Chem. 8 (1998) 1749.
[41] T. Steiner, J. Chem. Soc. Chem. Commun. (1994) 2341.
[42] T. Steiner, Chem. Commun. (1997) 727.
[43] G.R. Desiraju, V.R. Pedireddi, J. Chem. Soc. Chem. Commun.
(1992) 988.
[1] J. Tsuji, Palladium Reagents and Catalysts, Innovation in Organic
Synthesis, Wiley, New York, 1995.
[2] L. Tusec-Bozic, I. Matijasic, G. Bocelli, G. Calestani, A. Furlani,
V. Scarcia, A. Papaioannou, J. Chem. Soc. Dalton Trans. (1991)
195.
[3] S. Bischoff, A. Weigt, H. Mießner, B. Lu¨cke, J. Mol. Catal. A.:
Chem. 107 (1996) 339.
[4] D.D. Ellis, G. Harrison, A.G. Orpen, H. Phetmung, P.G. Pringe,
J.G. DeVries, H. Oevering, J. Chem. Soc. Dalton Trans. (2000)
671.
[5] T.L. Schull, J.C. Fettinger, D.A. Knight, Inorg. Chem. 35 (1996)
6717.
[6] T.L. Schull, J.C. Fettinger, D.A. Knight, J. Chem. Soc. Chem.
Commun. (1995) 1487.
[7] W.J. Dressick, C. George, S.L. Brandow, T.L. Schull, D.A.
Knight, J. Org. Chem. 65 (2000) 5059.
[44] Stoe, Stoe&Cie, Darmstadt, Germany, 1997.
[45] G.M. Sheldrick, SHELXS-97, Program for Crystal Structure Solu-
tion, University of Go¨ttingen, Go¨ttingen, Germany, 1990.
[46] G.M. Sheldrick, SHELXL-97, Program for the Refinement of
Crystal Structures from Diffraction Data, University of Go¨ttin-
gen, Go¨ttingen, Germany, 1997.
[8] T.L. Schull, S.L. Brandow, W.J. Dressick, Tetrahedron Lett. 42
(2001) 5373.
[47] International Tables for Crystallography, vol. C, Kluwer Aca-
demic, Dordrecht, 1992.