Synthesis and coordination properties of palladium(II) and platinum(II) complexes with phosphonated triphenylphosphine derivatives

Article abstract of DOI:10.1016/j.jorganchem.2006.01.024

Two triphenylphosphine derivatives, diethyl [4-(diphenylphosphanyl)benzyl]phosphonate (3a) and tetraethyl {[5-(diphenylphosphanyl)-1,3-phenylene]dimethylene}bis(phosphonate) (3b), and also the corresponding free acids 4a and 4b were prepared. These ligands were characterized by ¹H, ¹³C and ³¹P NMR spectroscopy and mass spectrometry. A full set of their Pd(II) and Pt(II) complexes of the general formula [MCl₂L₂] and one dinuclear complex trans-[Pd₂Cl₄(3a)₂] were synthesized and their isomerization behaviour in solution was studied. The complexes were characterized by ¹H, ¹³C, ³¹P and ¹⁹⁵Pt NMR spectroscopy, mass spectrometry and far-IR spectroscopy. The X-ray structures of all complexes with 3a or 3b have usual slightly distorted square-planar geometry on the metal ion. Salts of phosphonic acids 4a and 4b and their complexes are freely soluble in aqueous solution; therefore, they can be potentially useful in aqueous or biphasic catalysis.

Full text of DOI:10.1016/j.jorganchem.2006.01.024

Journal of Organometallic Chemistry 691 (2006) 2409–2423
www.elsevier.com/locate/jorganchem
Synthesis and coordination properties of palladium(II) and platinum(II)
complexes with phosphonated triphenylphosphine derivatives
a
a,b
a
a
a
ˇ
´
´
ˇ
Zbynek Rohlık , Petr Holzhauser , Jan Kotek , Jakub Rudovsky , Ivan Nemec ,
a,
a
Petr Hermann *, Ivan Lukesˇ
a
Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
b
Department of Inorganic Technology, Institute of Chemical Technology, Technicka´ 5, 166 28 Prague 6, Czech Republic
Received 9 November 2005; received in revised form 23 December 2005; accepted 11 January 2006
Available online 7 March 2006
Abstract
Two triphenylphosphine derivatives, diethyl [4-(diphenylphosphanyl)benzyl]phosphonate (3a) and tetraethyl {[5-(diphenylphospha-
nyl)-1,3-phenylene]dimethylene}bis(phosphonate) (3b), and also the corresponding free acids 4a and 4b were prepared. These ligands
1
were characterized by H, 13C and 31P NMR spectroscopy and mass spectrometry. A full set of their Pd(II) and Pt(II) complexes of
the general formula [MCl2L2] and one dinuclear complex trans-[Pd2Cl4(3a)2] were synthesized and their isomerization behaviour in solu-
1
tion was studied. The complexes were characterized by H, 13C, 31P and 195Pt NMR spectroscopy, mass spectrometry and far-IR spec-
troscopy. The X-ray structures of all complexes with 3a or 3b have usual slightly distorted square-planar geometry on the metal ion. Salts
of phosphonic acids 4a and 4b and their complexes are freely soluble in aqueous solution; therefore, they can be potentially useful in
aqueous or biphasic catalysis.
ꢀ 2006 Elseiver B.V. All rights reserved.
Keywords: Phosphonato phosphines; Water soluble phosphines; Phosphonate complexes; Palladium complexes; Platinum complexes; Crystal structure
determination; Isomerism
1. Introduction
carbon–carbon double bond hydrogenation or hydro-
formylation [4,5], Pd-catalysed benzyl halide carbonylation
[6] and Suzuki coupling [7]). A great advantage (compared
with other hydrophilic moieties) is the possibility to bind
the phosphonated ligand to an inert oxide surface (e.g.,
Al2O3) [8], onto activated carbon surface [9] or into a lay-
ered framework, e.g., zirconium phosphonate [10,12] or zir-
conium phosphite/phosphonate hybrid material [13]. Such
supported catalysts have been successfully tested in Rh-
catalysed alkene hydroformylation [12,14], Rh-catalysed
methanol carbonylation [9,15], Ru-catalysed asymmetric
b-keto ester hydrogenation [4,11] or Heck reaction [13]. Sev-
eral tests were also performed in organic solvents under
homogeneous conditions (e.g., Pt/Sn-catalysed alkene hyd-
roformylation [11], Rh-catalysed methanol carbonylation
[16] and Rh-catalysed styrene hydroformylation [17]).
Here we present the synthesis of triphenylphosphine-
based ligands bearing one or two diethyl phosphonomethyl
Transition metal-phosphine complexes are of great
importance for both industrial- and laboratory-scale cata-
lytic applications. Ambitions to use various ‘‘field-proven’’
homogeneous catalysts under aqueous and biphasic condi-
tions made for the synthesis of a vast amount of phosphines
modified by hydrophilic groups such as ammonium and
phosphonium (cationic), sulfonate, phosphonate and car-
boxylate (anionic) or alcohol and polyether chain (neutral)
[1]. Phosphines modified by phosphonate moiety [2] have
been attracting attention as alternatives to well-established
sulfonates [1]; several examples of their use in biphasic catal-
ysis have been mentioned in literature [3–17] (e.g., Pd-catal-
ysed electrochemical reduction of CO2 [3], Rh-catalysed
*
Corresponding author. Tel.: +420 22195 1263; fax: +420 22195 1253.
E-mail address: petrh@natur.cuni.cz (P. Hermann).
0022-328X/$ - see front matter ꢀ 2006 Elseiver B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.01.024

2410
Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
[CH3]n
groups (3a and 3b) and corresponding acids (4a and
4b) (Fig. 1) as well as a study of their Pd(II) and Pt(II)
complexes. The ligand design promises similar coordina-
tion behaviour and catalytic activity as is known for triphe-
nylphosphine, good solubility in water and flexible strong
attachment to a solid surface. The ortho and meta isomers
of 3a and 4a (and their disodium salts) were already
reported by Liek et al. [7] having been used as catalysts
in Pd-catalysed Suzuki coupling under biphasic conditions
with satisfactory results. Later, also the para isomer has
been mentioned [14] in a set of phosphanyl-phosphonates
(including 4a and its disodium salt) and experiments on
Rh-catalyzed hydroformylation were performed, but no
details on characterization of the complexes were men-
tioned and no attention to Pd(II) and Pt(II) chemistry
was paid. To our knowledge, ligands 3b and 4b have not
been reported yet.
[CH3]n
[CH2Br]n
i
iii
ii
I
NH2
I
[CH2P(O)(OEt)2]n [CH2P(O)(OEt)2]n
iv
[CH2P(O)(OH)2]n
v
I
PPh2
PPh2
2a, 2b
3a, 3b
4a, 4b
vii
vi
[CH2P(O)(OEt)2]n
i
ii
1) NaNO2, H2SO4 2) KI
NBS, AIBN, CCl4 or MeOAc
NaP(O)(OEt)2,THF
iii
iv
v
vi
vii
2. Results and discussion
Ph2PH, Pd(OAc)2, KOAc, toluene
HCl (azeotropic)
Ph2P·BH3
THF·BH3, THF
2.1. Ligands
1) HBF4·OMe2, 2) NaHCO3(aq)
3a·BH3
3b·BH3
2.1.1. Synthesis
n = 1
n = 2
p-monosubstituted
m-disubstituted
a
b
Ligands 3a, 3b and 4a, 4b were synthesized according to
Scheme 1. For the synthesis of iodoaryl phosphonates,
standard methods of organic and organophosphorus syn-
thesis were used (Sandmeyer reaction, radical bromination
and Michaelis–Becker reaction [18]). The last reaction
required at least two-fold molar excess of NaP(O)(OEt)2
for complete substitution; the residual reagent was then
removed by extraction with 2% (w/w) aqueous NaOH solu-
tion. Out of a variety of reactions introducing the phospha-
nyl group into the molecule [18] we chose a mild
Pd-catalyzed P–C cross-coupling reaction employing the
reaction conditions similar to those already used [7,19]. In
this reaction diphenylphosphine is used; we have summa-
rized the synthetic methods for its preparation [20] and pro-
posed a simplified procedure, in which we reduced the
volume of solvents, avoided unnecessary drying and deoxy-
Scheme 1. Synthesis of the ligands 3a, 3b, 4a and 4b.
genation procedures and minimized the number of extrac-
tion and washing steps [21]. For details, see Section 4.
After several unsuccessful experiments with bromoaryl
derivatives as starting materials we used more reactive aryl
iodides, which were treated with diphenylphosphine in the
presence of 0.2 mol% of Pd(OAc)2 as catalyst and anhy-
drous KOAc as base. Under the reaction conditions used
(toluene, 70–90 ꢁC, 12–36 h), the 31P NMR signal of
Ph2PH disappeared and a new signal assigned to the
desired product appeared. A small excess (2 mol%) of
Ph2PH was used to ensure total conversion.
After work-up of the reaction mixture, compounds 3a
and 3b were obtained as yellowish oils well soluble in
organic solvents and in strongly acidic aqueous solutions.
Purity of the samples varied between 93% and 97% (31P
NMR spectroscopy), which was acceptable for most pur-
poses. In order to prepare samples of higher purity and also
to enable the recovery of the ligands from partially oxi-
dized samples, the standard borane protection method
was employed [23]. The synthesis of borane adducts of 3a
and 3b was performed by the reaction with excess of com-
mercial THF Æ BH3 solution and standard work-up of the
reaction mixture [24]. The 3a Æ BH3 was purified by column
chromatography and then obtained as colourless crystal-
line powder upon recrystallization from THF/hexanes
(purity 98+% 31P NMR). We failed to crystallize 3b Æ BH3
before as well as after chromatographic purification; it was
obtained with purity 96% (31P NMR).
O
OR
P
RO
P
OR
P
RO
O
O
OR
OR
8
8
5
7
6
7
6
5
3
3
P
P
4
4
2
1
2
1
3a, 4a
3b, 4b
R
3a, 3b Et
4a, 4b
H
The adducts were deprotected after the purification. The
use of secondary amines as the deprotection agent was not
Fig. 1. Structure of 3a, 3b, 4a and 4b.

Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
2411
suitable for our purpose because of possible interaction
with the phosphonate group and, also, a rather inconve-
nient separation of the amine-borane adduct from the
deprotected ligand (filtration through alumina column
[24] or vacuum sublimation [7]). Both general methods
trans arrangement for Pd(II) complexes and cis for their
Pt(II) analogues (vide infra). A small amount of dinuclear
palladium(II) complex trans-[Pd2Cl4(3a)2] Æ 2CHCl3 was
isolated by work-up of the mother liquor after crystalliza-
tion of trans-[PdCl2(3a)2] Æ 2CHCl3; it originates probably
in an inaccuracy of the ligand-to-metal ratio in the starting
reaction mixture (Scheme 2).
˚
reported in literature (deprotection with a mixture of 4 A
molecular sieve, aliphatic alcohol and cyclic ether [25] and
deprotection using HBF4 Æ OMe2 in dichloromethane [26])
were successful and we chose the later one for its simplicity.
The ligands were obtained as colourless turbid oils of purity
corresponding to the purity of the borane adducts.
For the preparation of free acids 4a and 4b hydrolysis in
20% aqueous HCl was the method of choice. This concen-
tration of the acid was sufficient for dissolution of the ester
ligands. Compounds 4a and 4b were obtained as white
solid foams soluble in methanol, ethanol, strongly acidic
and alkaline aqueous solutions, but almost insoluble in
water in the pH range 2–6. The salts of 4a and 4b were
not isolated and their solubilities in water were not quanti-
fied, but salts of the 4b are apparently more soluble.
Various synthetic methods were reported for prepara-
tion of complexes with polar acid-modified phosphines.
Experimental conditions depend on the solubility of the
ligand and the metal-containing compound [1,6,27–31].
Reactions in water are further limited by the pH value
because of decomposition and deposition of the precious
metal in alkaline solutions. Synthesis of Pd(II) complexes
of 4a and 4b by a simple biphasic reaction between ligand
solution in 20% aqueous HCl and [PdCl2(cod)] solution in
CH2Cl2 (ligand-to-metal ratio = 2:1) failed. The required
complexes were formed upon treatment of solid PdCl2 with
ligand solution in ethanol, but their purity was not satisfac-
tory. Finally, the reaction of ligand solution in 20% aque-
ous HCl with freshly prepared slurry of PdCl2 in the
same solvent was successful (Scheme 2). The isolated yel-
low complexes are soluble in common organic solvents
but only slightly soluble in water (pH 6). The low complex
solubility is probably caused by polymerization through
hydrogen bond network in the solid state (such polymeric
structure is proposed for a Pd(II) complex of a similar
phosphanyl-phosphonate [13]). The complexes are well sol-
uble in aqueous alkaline solutions (pH > 7).
2.1.2. NMR spectroscopy
1H and 13C NMR spectra of all ligands and their borane
adducts are in agreement with expectations. In 31P NMR
the chemical shift of the diethoxyphosphoryl group in both
ligands is typically around 26 ppm, the chemical shift of the
phosphine functionality is around ꢀ6 ppm similarly to tri-
phenylphosphine. In the case of the borane adducts, the
phosphine signal is shifted to ca. 20 ppm and broadened
significantly, which makes impossible to determine the
1JPB coupling constant.
In the case of Pt(II) complexes, a biphasic reaction of
the ligand solution in 20% aqueous HCl with a dichloro-
methane solution of [PtCl2(cod)] (ligand-to-metal ratio
2:1) was successful. The products were isolated as white
powders, hardly soluble in water and common organic sol-
vents. The solubility in aqueous alkaline solutions is similar
to the Pd(II) complexes (vide supra).
The 31P NMR of 4a and 4b in water is highly pH-depen-
dent due to acid–base properties of both phosphorus-
containing moieties. The values of dP in methanol-d4, conc.
aqueous HCl and NaOH solutions are listed in Table 1.
2.2. Pt(II) and Pd(II) complexes
2.2.2. NMR spectroscopy
2.2.1. Synthesis
In the 31P NMR spectra of the Pd(II) complexes, the
phosphonate group chemical shift remains almost the same
(around 24 ppm), but the phosphine functionality is shifted
significantly. In 31P NMR spectra of [PdCl2(3a)2] in CDCl3
Synthesis of Pd(II) and Pt(II) complexes of ester ligands
3a and 3b was straightforward. It was performed by mixing
the dichloromethane solutions of the ligand and of the
metal precursor ([PdCl2(cod)] or [PtCl2(cod)]; cod = cyclo-
octa-1,5-diene) in the ligand-to-metal molar ratio 2:1. The
isolated complexes have the stoichiometry [MCl2L2] with
i
cis-[PtCl2(3a)2]
[PtCl2(cod)] + 3a
[PtCl2(cod)] + 3b
[PdCl2(cod)] + 3a
[PdCl2(cod)] + 3b
[PtCl2(cod)] + 4a
[PtCl2(cod)] + 4b
PdCl2 + 4a
i
i
i
cis-[PtCl2(3b)2]
trans-[PdCl2(3a)2] + trans-[Pd2Cl4(3a)2]
trans-[PdCl2(3b)2]
cis-[PtCl2(4a)2]
Table 1
31P{H} NMR chemical shifts of 4a and 4b (ppm) in various solvents
ii
ii
Solvent
4a
4b
cis-[PtCl2(4b)2]
dP(V)
dP(III)
dP(V)
dP(III)
iii
iii
trans-[PdCl2(4a)2]
cis-[PdCl2(4b)2]
MeOD
32% HCl
1 M NaOH
a
26.8
28.5
20.3
ꢀ3.4
+4.7a
ꢀ7.6
25.7
28.5
20.5
ꢀ4.0
+4.6b
ꢀ6.0
PdCl2 + 4b
i
ii
iii
40 ˚C, 8 h, CH2Cl2
RT, 8 h, CH2Cl2/HCl, H2O
RT, 8 h, HCl, H2O
In non-decoupled 31P NMR doublet, JPH = 523 Hz (phosphonium
1
salt).
b
1
In non-decoupled 31P NMR doublet, JPH = 505 Hz (phosphonium
salt).
Scheme 2. Synthesis of Pd(II) and Pt(II) complexes of 3a, 3b, 4a and 4b.

2412
Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
solution, besides the two major signals assigned to
phosphonate and phosphine functionalities, a couple of
minor signals with 1:1 intensity appeared. The signals did
not belong to the oxidized ligand, because after addition
of 3a-oxide (prepared by oxidation of 3a with 30% aqueous
H2O2 in ethanol) to the sample, new separate peaks
appeared. As Pd(II) phosphine complexes are known to
produce an equilibrium mixture of cis/trans isomers upon
dissolution [32], we expected the same behaviour in our
case. In order to support this hypothesis and to distinguish
and assign the signals of both isomers, we used the linear
correlation of the coordination chemical shift with the free
phosphine chemical shift (Eq. (1)) [33].
in slightly alkaline aqueous media) and no interaction of
phosphoryl group with the metal ion was observed (no
2JPtP was detected). The coordination of the phosphine to
the metal ion caused a large shift to ca. 14 ppm in all cases.
1
The values of JPtP ca. 3600 Hz were found, which corre-
sponds to the phosphine opposite to chlorine [34], i.e., with
cis arrangement of the phosphine ligands. The value corre-
sponding to the trans isomer should be much lower, ca.
2000–2700 Hz [34]. Only cis isomers of all the complexes
were present in solutions in various solvents (toluene,
CDCl3, and methanol for 3a and 3b complexes, alkaline
aqueous solution for complexes of 4a and 4b) (Tables 3
and 4). In the case of CDCl3 solution of cis-[PtCl2(3a)2],
one of the Pt–P satellites overlapped with the signal of
phosphonate group; its presence was revealed either by
using methanol as solvent or by the addition of the
tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyloctane-3,5-dionate)
europium(III) complex (EuFOD NMR shift agent).
DdP ¼ dPðcoord.Þ ꢀ dPðfreeÞ ¼ A ꢁ dPðfreeÞ þ B
ð1Þ
Constants A and B have been estimated for a wide range of
metal-phosphine complexes; their values are characteristic
of the metal ion and the complex stoichiometry. Moreover,
the constants differ significantly for various isomers, which
allows to use the correlation for assignment of the isomer
signals. The relevant coefficients taken from Ref. [33a]
are listed in Table 2 (For the calculations, the change in
the 31P chemical shift convention in the 1970s must be
taken into account, which makes necessary to change the
sign of B extracted from the original articles [33a]; this cor-
rection enables to use recent values of chemical shifts.).
On the basis of Eq. (1) we found out that the set of
minor signals belongs to cis isomer (see Table 3). In addi-
tion, we measured 31P NMR spectra of the same complex
in toluene, where only two signals were present with chem-
ical shift corresponding to the trans isomer, and in metha-
nol, where four signals were found corresponding to a
mixture of both isomers (Fig. 2), with higher abundance
of cis isomer compared with CDCl3 solution. This is in
accord with the dependence of the cis/trans isomer ratio
on the solvent polarity reported for various Pd(II) phos-
phine complexes [32]. Similar behaviour was observed for
the complex [PdCl2(3b)2] as well. 31P NMR of [PdCl2(4a)2]
and [PdCl2(4b)2] dissolved in slightly alkaline aqueous solu-
tion (pH 9) contained only the signals corresponding to cis
isomer (Table 4). This preference of cis isomer formation
also corresponds well with the above-mentioned overall
trend in the isomerization behaviour of the ester ligand
complexes.
In order to obtain spectral data of trans isomers also for
Pt(II) complexes, we carried out a simple photochemical
isomerization experiment as described by Mastin and
Haake [35]. The 3a and 3b complexes dissolved in CDCl3
or 4a and 4b complexes in NaOH/D2O were irradiated with
an 8 W UV lamp (k = 366 nm) at room temperature for
5 h. Before and after the irradiation, 31P {1H} and 195Pt
NMR spectra were measured. In the case of ester com-
plexes, the isomerization occurred indeed, although only
to a small extent (ca. 20%, 195Pt NMR spectra). In the
195Pt NMR spectra (Fig. 3b and d), the new isomers man-
1
ifested themselves by a triplet with JPtP characteristic of
trans arrangement (ꢂ2640 Hz, vide supra); in 31P {1H}
NMR spectra (Fig. 3a and c), another set of signals corre-
sponding to the trans isomer appeared (Table 3), the signals
of coordinated phosphine having 195Pt satellites with the
1
same JPtP value as that found in 195Pt NMR spectra. In
the spectra of acid ligand complexes, no signals assignable
to the isomerization product were found after irradiation.
This is in accord with the observation made in the original
paper that the photochemical transition state is stabilized
only in non-polar solvents [35]. The 31P {1H} chemical
shifts of the prepared platinum-containing complexes were
correlated using a relationship analogous to Eq. (1) with
appropriate coefficients A and B obtained from literature
data (Table 2) [33a]. The observed values are in good agree-
ment with the predicted values (Tables 3 and 4).
In the case of platinum(II) complexes, the chemical shift
of the phosphonate group was similar to the value observed
for uncoordinated ligand (about 25 ppm for 3a and 3b
complexes in CDCl3 and 18 ppm for 4a and 4b complexes
2.2.3. IR spectroscopy
Kinetic inertness of Pt(II) complexes usually allows to
isolate both cis and trans isomers in the solid state from
the complex solution. On the contrary, palladium(II) com-
plexes are less inert and undergo rapid isomerization upon
dissolution. Because of thermodynamic and kinetic effects,
the trans isomer is generally preferred when a Pd(II) com-
plex is being isolated in the solid state from its solution,
even when a pure cis isomer solution is used [36]. To deter-
mine the stereochemistry of our complexes in the solid
state, we employed far-IR spectroscopy. Due to a differ-
Table 2
Coefficients A and B in Eq. (1) for cis and trans isomers of Pd(II) and
Pt(II) complexes of the formula [MCl2L2] [33]
Complex
[PdCl2L2]
A
B
cis
trans
ꢀ0.315 0.033
ꢀ0.359 0.023
ꢀ38.11 0.86
ꢀ28.01 0.61
[PtCl2L2]
cis
trans
ꢀ0.326 0.070
ꢀ18.83 1.82
ꢀ0.481 0.023
ꢀ21.41 0.55

Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
2413
Table 3
Phosphine chemical shifts dP of the free ligands 3a and 3b and their Pd(II) and Pt(II) complexes
Parameter
Solvent
3a
3b
[PdCl2(3a)2]
[PdCl2(3b)2]
[PtCl2(3a)2]
[PtCl2(3b)2]
cis
trans
cis
trans
cis
trans
cis
trans
dP
CDCl3
Toluene
MeOH
ꢀ5.4
ꢀ6.1
ꢀ5.8
ꢀ5.4
ꢀ5.4
ꢀ5.0
32.9
–
33.9
21.2
23.5
27.2
33.3
–
34.2
24.2
24.3
27.2
13.8
14.7
14.2
18.1a
14.4
15.0
14.8
20.7a
b
b
b
b
–
b
–
b
–
–
DdP(exp)
DdP(calc)
CDCl3
Toluene
MeOH
–
–
–
–
–
–
38.3
–
39.7
26.6
29.6
33.0
38.7
–
39.2
29.6
29.7
32.2
19.2
20.8
20.0
23.5
19.8
20.4
19.8
26.1
b
b
b
b
–
–
–
–
b
b
CDCl3
Toluene
MeOH
–
–
–
–
–
–
39.8
40.0
39.9
29.9
30.2
30.1
39.8
39.8
39.7
29.9
29.9
29.8
20.6
20.8
20.7
24.0
24.3
24.2
20.6
20.6
20.5
24.0
24.0
23.8
Comparison of experimental (DdP(exp)) and calculated (DdP(calc)) coordination chemical shifts for their cis and trans isomers in CDCl3, toluene and
methanol.
a
After irradiation of the cis isomer, see text.
Not observed or calculated.
b
ison, we measured both ester ligands and acid ligands com-
plexes, configurations of the former being independently
determined by X-ray single crystal analysis (vide infra).
Data are summarized in Table 5. All four platinum(II)
complexes showed cis arrangement, as was expected from
the NMR spectroscopy of their solutions. Three palla-
dium(II) complexes were found to be trans and [PdCl2(4b)2]
was found to be cis in the solid state. The cis stereochemis-
try is probably a result of intramolecular interaction via
hydrogen bonds of phosphonic acid groups. Unfortu-
nately, the distinction between intra- and intermolecular
hydrogen bonding investigated by infrared spectroscopy
may not be straightforward; this hypothesis could be
therefore confirmed only by crystallography. However,
our attempts to grow a single crystal of this complex were
unsuccessful.
2.2.4. X-ray crystallography
The stereochemistry of 3a and 3b complex species was
confirmed by X-ray crystallography. Table 6 shows
selected interatomic distances and angles. Relevant experi-
mental parameters are listed in Table 7.
The two phosphine ligands in both mononuclear Pd(II)
complexes have a mutual trans arrangement (Figs. 4 and
5). Both complexes are centrosymmetric with palladium
atom in the centre of symmetry. The coordination sphere
is square-planar, with small distortion of bond angles P–
Pd–Cl (84.6ꢁ and 94.4ꢁ for trans-[PdCl2(3a)2] Æ 2CHCl3
and 87.5ꢁ and 92.5ꢁ for trans-[PdCl2(3b)2] Æ 2H2O). The
coordination bond lengths are in the expected range as
observed for similar complexes [39] (Pd–Cl 2.38 and Pd–
Fig. 2. 31P{1H} NMR spectra of [PdCl2(3a)2] in toluene (A) and methanol
(B) showing solvent-dependent cis/trans equilibrium.
˚
P
2.33 A for trans-[PdCl2(3a)2] Æ 2CHCl3 and Pd–Cl
˚
˚
2.30 A and Pd–P 2.33 A for trans-[PdCl2(3b)2] Æ 2H2O).
Contrary to the palladium(II) compounds, both plati-
num(II) complexes have a slightly distorted square-planar
coordination sphere with two phosphine ligands in mutu-
ally cis positions (Figs. 6 and 7). The bond angles P–Pt–P
are 96.3ꢁ for cis-[PtCl2(3a)2] Æ 0.5CHCl3 and 98.8ꢁ for cis-
[PtCl2(3b)2] Æ H2O Æ PhMe thus showing larger distortion
ence in coordination polyhedron symmetry, the Pd–Cl and
Pt–Cl stretching vibrations (at 250–350 cmꢀ1 in similar
complexes [37]) exhibit two bands in cis and only one band
in trans complexes. In the case of dinuclear complexes, the
spectrum is more complicated due to the difference between
Pd–Clterminal and Pd–Clbridging vibrations [38]. For compar-

2414
Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
Table 4
Phosphine chemical shifts dP of the free ligands 4a and 4b and their Pd(II) and Pt(II) complexes
Parameter
Solvent
4a
4b
[PdCl2(4a)2]
[PdCl2(4b)2]
[PtCl2(4a)2]
[PtCl2(4b)2]
cis
trans
cis
trans
cis
trans
cis
trans
a
a
a
a
a
a
a
a
dP
NaOH solution in D2O (pH 9)
ꢀ7.7
ꢀ6.7
34.0
41.7
40.5
–
–
35.2
41.9
40.2
–
–
11.2
18.9
21.3
–
–
11.7
18.4
21.0
–
–
DdP(exp)
DdP(calc)
–
–
–
–
30.8
30.4
25.1
24.6
Comparison of experimental (DdP(exp)) and calculated (DdP(calc)) coordination chemical shifts for their cis and trans isomers in alkaline D2O solution.
a
Not observed or calculated.
Fig. 3. Photochemical isomerization of cis-[PtCl2(3a)2]: 31P NMR before (A) and after (C) and 195Pt NMR before (B) and after (D) UV-irradiation.
of the regular square-planar geometry in the case of more
sterically demanding ligand 3b. The lengths of coordina-
tion bonds are in the expected range for this type of com-
The Pd–Cl distances to the terminal chloride anions are
shorter (2.28 A) than those to the bridging chloride anions;
˚
bond length to chloro ligand positioned trans to phospho-
˚
˚
˚
pounds [39] (Pt–Cl 2.33 and 2.36 A, Pt–P 2.25 and 2.27 A
rus atom is longer (2.41 A) than that trans to the terminal
˚
for cis-[PdCl2(3a)2] Æ 0.5CHCl3 and Pt–Cl 2.35 and
chloride anion (2.32 A).
˚
˚
2.34 A, Pt–P 2.26 and 2.27 A for cis-[PdCl2(3b)2] Æ H2O Æ
PhMe).
3. Conclusion
In mother liquor after crystallization of trans-
[PdCl2(3a)2] Æ 2CHCl3, several red crystals appeared after
standing in refrigerator for several months. The X-ray crys-
tallographic study revealed the dinuclear complex of the
formula trans-[Pd2Cl4(3a)2] Æ 2CHCl3 (Fig. 8). The mole-
cule has a centre of symmetry on half-way between palla-
dium atoms, with phosphine ligands in trans positions.
We have synthesized triphenylphosphine derivatives
containing phosphonomethyl groups and studied their
coordination behaviour towards Pd(II) and Pt(II). The
phosphonic acid derivatives and their complexes are
well soluble in water after neutralization of the acids; there-
fore, their use in aqueous or biphasic catalysis is possible,

Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
2415
Table 5
methyl acetate (Fluka, used as received), ethyl acetate,
hexane, chloroform and methanol (Lachema, used as
received), 35% aqueous HCl (Lachema, distilled under
Ar), D2O (99%), CDCl3 (Chemotrade, used as received)
and CD3OD (Deutero GmbH, used as received).
Stretching Pd–Cl or Pt–Cl vibration in Pd(II) and Pt(II) complexes of 3a,
3b, 4a and 4b
Complex
Wavenumber (cmꢀ1 a
)
Stereochemistry
IR
X-ray
Reagents and chemicals were obtained as follows:
4-methylaniline (Lachema, vacuum-distilled), 3,5-dimethy-
laniline (Aldrich), charcoal (Fluka), a,a0-azobis(isobutyro-
nitrile) (AIBN, Fluka), diethyl phosphite (Fluka), PtCl2
[PtCl2(3a)2]
[PtCl2(3b)2]
[PtCl2(4a)2]
[PtCl2(4b)2]
[PdCl2(3a)2]
[PdCl2(3b)2]
[PdCl2(4a)2]
[PdCl2(4b)2]
[Pd2Cl4(3a)2]
293s, 318s
294s, 317s
287s, 311s
291s, 312s
356s
cis
cis
cis
cis
cis
cis
–
–
trans
trans
trans
trans
cis
ꢀ
and PdCl2 (Strem), anhydrous MgSO4 (Acros), triphenyl-
357s
358s
trans
–
–
ꢀ
phosphine (Acros), anhydrous Na2SO4 (Lachema),
289s, 307s
259s, 299m, 313m, 359s
N-bromosuccinimide (Fluka), tris(6,6,7,7,8,8,8-heptaflu-
Dinuclear
Dinuclear
oro-2,2-dimethyloctane-3,5-dionate)europium(III)
com-
Comparison of stereochemistry deduced from far-IR spectroscopy with
results of X-ray diffraction analysis.
plex (EuFOD, Lachema), THF Æ BH3 (Fluka), HBF4 Æ
OMe2 (Aldrich), MS 4 A (Fluka), anhydrous KOAc
˚
a
m – medium, s – strong.
ꢀ
(Acros).
Chemicals prepared according to literature procedures:
1-iodo-3,5-dimethylbenzene and 3,5-bis(bromomethyl)-1-
iodobenzene [40], 4-iodotoluene and 4-bromomethyl-1-iodo-
benzene (prepared analogously to the m-xylene derivatives),
palladium(II) acetate [41], [PdCl2(cod)] and [PtCl2(cod)]
[42].
generally under the conditions and in the catalytic reac-
tions already described for triphenylphosphine and its
hydrophilic derivatives [1,2].
1H (399.95 MHz, TMS (internal) d = 0.00 ppm;
CHD2OD (internal) d = 3.31 ppm), 11B (128.32 MHz,
BF3 Æ OEt2 (external) d = 0.00 ppm), 13C (100.6 MHz,
TMS (internal) d = 0.0 ppm; CHCl3 (internal) d =
77.0 ppm), 31P (161.9 MHz, 85% H3PO4 (external) d =
0.0 ppm) and 195Pt (85.6 MHz, K2PtCl4, saturated solution
in D2O (external) d = 1620 ppm) NMR spectra were
recorded on Varian UNITYINOVA 400 spectrometer at
25 ꢁC. Multiplicity of the signals is indicated as follows: s
– singlet, d – doublet, t – triplet, q – quartet, m – multiplet,
br – broad. Values of chemical shifts are in ppm, the values
4. Experimental
4.1. General
All manipulations involving air-sensitive compounds
were performed under an atmosphere of argon (5.6, Linde)
using standard Schlenk techniques. Solvents were obtained
and purified as follows: diethyl ether (Lachema, distilled
from Na), dichloromethane (Lachema, distilled from
P2O5 under Ar), N,N-dimethylacetamide (Fluka, vacuum-
distilled from BaO under Ar), tetrahydrofurane (Lachema,
distilled from Na,K/benzophenone under Ar), toluene
(Lachema, distilled from Na,K/benzophenone under Ar),
of coupling constants in Hz. For assignment of 1H and 13
NMR signals of 3a, 3b, 4a and 4b, HSQC and HMBC pulse
C
Table 6
˚
Selected interatomic distances (A) and angles (ꢁ) in crystal structures of the complexes cis-[PtCl2(3a)2] Æ 0.5CH2Cl2, cis-[PtCl2(3b)2] Æ H2O Æ PhMe, trans-
[PdCl2(3a)2] Æ 2CHCl3, trans-[PdCl2(3b)2] Æ 2H2O and trans-[Pd2Cl4(3a)2] Æ 2CHCl3
b
Parameter
cis-[PtCl2(3a)2] Æ
0.5CH2Cl2
cis-[PtCl2(3b)2] Æ
H2O Æ PhMe
trans-[PdCl2(3a)2] Æ
2CHCl3
trans-[PdCl2(3b)2] Æ
trans-[Pd2Cl4(3a)2] Æ 2CHCl3
2H2Oa
a
˚
Distance (A)
M–P1
M–P2
M–Cl1
M–Cl2
2.2545(11)
2.2701(12)
2.3331(14)
2.3548(12)
2.2572(9)
2.2682(9)
2.3396(9)
2.3543(9)
2.3318(5)
2.3261(10)
M–P1
2.2340(8)
–
–
M–Cltc
2.2794(8)
2.3202(8)
2.4143(8)
3.4761(8)
d
2.3044(5)
–
2.3014(10)
–
M–Cll
M–Cl0l
Pd–Pd0
Angle (ꢁ)
P1–M–P2
P1–M–Cl1
P1–M–Cl2
P2–M–Cl1
P2–M–Cl2
Cl1–M–Cl2
a
96.32(4)
89.47(5)
175.96(5)
173.56(4)
86.95(5)
87.38(5)
98.83(3)
89.51(3)
176.35(3)
171.25(3)
84.59(3)
87.14(3)
180
94.39(2)
85.61(2)
–
–
180
180
92.46(4)
87.54(4)
–
–
180
P1–M–Clt
P1–M–Cll
P1–M–Cl0l
Clt–M–Cll
Clt–M–Cl0l
Cll–M–Cl0l
89.40(3)
95.58(3)
177.72(3)
173.35(3)
89.34(3)
85.54(3)
Centrosymmetric structures with an inversion centre on Pd atom.
b
Centrosymmetric structure with an inversion centre between Pd atoms in the dinuclear complex; inversion-associated atom is labelled by an
apostrophe.
c
Terminal chlorine atom.
Bridging chlorine atom.
d

2416
Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
Table 7
Crystal data for the complexes cis-[PtCl2(3a)2] Æ 0.5CH2Cl2, cis-[PtCl2(3b)2] Æ H2O Æ PhMe, trans-[PdCl2(3a)2] Æ 2CHCl3, trans-[PdCl2(3b)2] Æ 2H2O and
trans-[Pd2Cl4(3a)2] Æ 2CHCl3
Parameter
cis-[PtCl2(3a)2] Æ
0.5CH2Cl2
cis-[PtCl2(3b)2] Æ
H2O Æ PhMe
trans-[PdCl2(3a)2] Æ
2CHCl3
trans-[PdCl2(3b)2] Æ
2H2O
trans-[Pd2Cl4(3a)2] Æ
2CHCl3
Formula
M
C46.5H53Cl3O6P4Pt
1133.21
Colourless
Plate
C63H84Cl2O13P6Pt
1501.11
Colourless
Rod
C48H54Cl8O6P4Pd
1240.80
Yellow
C56H78Cl2O14P6Pd
1338.30
Yellow
Needle
Triclinic
8.8757(4)
11.3631(5)
16.1874(8)
93.889(2)
102.764(2)
98.082(3)
1568.14(13)
150
C48H54Cl10O6P4Pd2
1418.10
Red
Irregular
Triclinic
9.6361(2)
13.2749(3)
13.6129(3)
96.8988(14)
110.1794(13)
107.4107(12)
1510.30(6)
150
Crystal colour
Crystal shape
Crystal system
Prism
Triclinic
Triclinic
Monoclinic
10.5661(1)
25.1416(2)
10.6636(1)
90
107.0962(5)
90
2707.60(4)
150
˚
a (A)
10.2008(2)
16.6091(3)
16.6894(3)
65.5852(8)
79.8597(8)
79.0313(9)
2512.68(8)
294
14.1892(3)
15.2810(3)
16.6641(3)
67.1336(11)
87.8977(11)
86.6652(10)
3323.22(11)
150
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
U (A )
T (K)
ꢀ
ꢀ
ꢀ
ꢀ
Space group
P1 (no. 2)
2
P1 (no. 2)
2
P21/n (no. 14)
2
0.902
P1 (no. 2)
1
P1 (no. 2)
1
Z
l (mmꢀ1
)
3.123
2.396
0.595
1.187
Reflections (measured/unique)
11462/10420
0.0456
0.1286
15190/13020
0.0366
0.0918
6212/5456
0.0324
0.0858
7197/4517
0.0589
0.1409
6909/6345
0.0439
0.1281
a
R1
wR2
b
P
P
a
R = |Fo ꢀ Fc|/ |Fc|.
P
P
P
2
2
2
wR ¼ ½ wðF 2o ꢀ F 2c Þ = wðF o2Þ2ꢃ1=2, w ¼ 1=½ ðF o2Þ þ ðA ꢁ PÞ þ B ꢁ Pꢃ; where P ¼ ðF o2 þ 2F 2cÞ=3.
b
Fig. 4. Molecular structure of trans-[PdCl2(3a)2] in trans-[PdCl2(3a)2] Æ 2CHCl3. Phenyl rings are omitted for clarity, only pivot atoms C7 and C13 are
shown.
sequences were employed. The carbon aromatic frame of the
molecules is numbered (see Fig. 1). NMR spectra presented
in figures were obtained by deconvolution of experimental
data using program MESTRE-C 4.1.7.0 [43].
MS spectra were recorded on a Bruker Esquire 3000
spectrometer equipped with electro-spray ion source and
ion trap in positive and/or negative mode. For simplicity,
the oxidized form (phosphine oxide) of the ligand is
denoted as Mox. The positive or negative mode of measure-
ment is distinguished by a superscript attached to the
parentheses describing the fragmentation.
All air-stable organic compounds gave satisfactory ele-
mental analyses; however, the oily nature and tendency
to oxidize did not allow obtaining reliable elemental data
for phosphines. In the case of metal complexes, microanal-
yses are not reported because of variable and non-stoichi-
ometric solvation and general problems with combustion.
The yields of Pd(II) and Pt(II) complexes are not
optimized.
4.2. Syntheses
Far-IR spectra were measured on a FTIR spectrometer
Magna 760 (Nicolet) in polyethylene pellets in the range
100–600 cmꢀ1 with resolution 4 cmꢀ1 at 25 ꢁC in an atmo-
sphere of dry air. The relative intensity of the signals is
described as m – medium or s – strong.
4.2.1. Diphenylphosphine (1) [21]
Under a stream of argon, lithium metal sheets (3.0 g,
0.43 mol) were added into a stirred slurry of triphenylphos-
phine (50 g, 0.19 mol) in THF (400 mL) in a 2-L Schlenk
vessel on cooling (ice-bath). Lithium dissolved within 5 h

Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
2417
Fig. 5. Molecular structure of trans-[PdCl2(3b)2] in trans-[PdCl2(3b)2] Æ 2H2O. Phenyl rings are omitted for clarity, only pivot atoms C7 and C13 are
shown.
Fig. 6. Molecular structure of cis-[PtCl2(3a)2] in cis-[PtCl2(3a)2] Æ 0.5CH2Cl2. Phenyl rings are omitted for clarity, only pivot atoms C7 and C13 are shown.

2418
Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
Fig. 7. Molecular structure of cis-[PtCl2(3b)2] in cis-[PtCl2(3b)2] Æ H2O Æ PhMe. Phenyl rings are omitted for clarity, only pivot atoms C7 and C13 are
shown.
Fig. 8. Molecular structure of trans-[Pd2Cl4(3a)2] in trans-[Pd2Cl4(3a)2] Æ 2CHCl3. Phenyl rings are omitted for clarity, only pivot atoms C7 and C13 are
shown.
to a deep red solution. Water (150 mL) was added (50 mL
dropwise, 100 mL in one portion) on cooling (ice-bath).
Deoxygenated diethyl ether (200 mL) was added and the
mixture was stirred vigorously. The organic phase was sep-
arated and washed with diluted HCl (200 mL, 1:15) and
twice with water (200 mL). The organic phase was dried

Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
2419
over anhydrous Na2SO4. After filtration, all volatiles were
removed under reduced pressure. The residual oil was then
distilled in vacuo (85 ꢁC, 54 Pa). Purity according to 31P
NMR 98+%.
4.2.3. Diethyl [4-(diphenylphosphanyl)benzyl]phosphonate
(3a) and tetraethyl {[5-(diphenylphosphanyl)-1,3-
phenylene]dimethylene}bis(phosphonate) (3b)
A 50 mL Schlenk flask was charged with 2a (2.48 g,
7.00 mmol) or 2b (3.53 g, 7.00 mmol), dry deoxygenated
toluene (25 mL), anhydrous KOAc (0.8 g, 8.0 mmol) and
diphenylphosphine (1) (1.35 g, 7.18 mmol). The reaction
was started by injection of a solution of Pd(OAc)2
(3.5 mg, 0.2 mol%) in dry N,N-dimethylacetamide (2 mL).
The flask was stoppered and the reaction mixture was
heated to 90 ꢁC in an oil bath and periodically checked
by 31P NMR. After 12–24 h (3a) or 24–36 h (3b), the mix-
ture was cooled to RT and deoxygenated water (25 mL)
was added. After several minutes of vigorous stirring the
emulsion was left standing to separate. Organic layer was
transferred by means of a syringe into a 50 mL Schlenk
flask containing anhydrous Na2SO4. The mixture was fil-
tered and the drying agent was washed with a small volume
of dry toluene. Volatiles were removed in vacuo and the
oily residue was dried by prolonged heating in vacuo at
80 ꢁC. Resulting oils contained 93–97% of the target com-
pounds (31P NMR).
1
1 (26 g, 73% based on PPh3) NMR (CDCl3): H d 3.83
1
(P–H, 1H, d, JPH = 217); 5.87–5.90 (ArH, 6H, m); 6.04–
6.08 (ArH, 4H, m); 13C{1H} d 128.4 (p-CH, 2C, s); 128.5
3
(m-CH, 4C, d, JPC = 6.4); 133.9 (o-CH, 4C, d,
1
2JPC = 6.8); 134.6 (C–P, 2C, d, JPC = 9.9); 31P NMR d
1
ꢀ42.1 (d, JPH = 216); 31P{1H} d ꢀ42.1 (s).
4.2.2. Diethyl (4-iodobenzyl)phosphonate (2a) and
tetraethyl [(5-iodo-1,3-phenylene)dimethylene]-
bis(phosphonate) (2b)
A 100 mL Schlenk flask equipped with a reflux con-
denser was charged with sodium wire (1.90 g, 83.0 mmol)
and dry THF (17 mL). Diethyl phosphite (11.3 g,
82.0 mmol) was added by means of a syringe under argon
atmosphere. The mixture was stirred overnight in water/
ice-bath under a gentle argon stream. A solution of 4-bro-
momethyl-1-iodobenzene (11.9 g, 40.0 mmol) or 3,5-
bis(bromomethyl)-1-iodobenzene (8.00 g, 21.0 mmol) in
dry THF (15 mL) was added dropwise at RT within
30 min. The reaction was completed by a short reflux and
checked by TLC (silica gel, hexane, no reactant detectable
at Rf = 0.2 or 0.5). Following manipulations were done
under air. The white precipitate (NaBr) was removed by
centrifugation and washed with a small volume of THF.
Supernatants were collected and evaporated on a rotary
evaporator. The oily residue was dissolved in ethyl acetate
(50 mL) and washed with 2% aqueous NaOH (3 · 30 mL).
Organic phase was dried with anhydrous MgSO4 and fil-
tered. After treatment with charcoal and filtration, all vol-
atiles were evaporated. The product was dried by heating at
70 ꢁC in vacuo for 8 h. Ester 2b can be recrystallized from
hexanes.
1
3a (2.40 g, 83%) NMR (CDCl3): H d 1.23 (CH3, 6H, t,
2
3JHH = 6.8); 3.14 (CH2–P, 2H, d, JPH = 21.6); 4.01 (O–
CH2, 4H, m); 7.27–7.33 (ArH, 14H, m); 13C{1H} d 16.3
3
(CH3, 2C, d, JPC = 5.7); 33.6 (CH2–P, 1C, d,
2
1JPC = 138); 62.1 (O–CH2, 2C, d, JPC = 6.8); 128.4 (C2,
3
4C, d, JPC = 6.8); 128.7 (C1, 2C, s); 129.9 (C7, 2C, t,
2
3JPC = 6.8); 132.3 (C5, 1C, d, JPC = 9.2); 133.6 (C3, 4C,
2
2
d, JPC = 19.4); 133.8 (C6, 2C, dd, JPC = 19.8,
4JPC = 2.7); 135.6 (C8, 1C, dd, JPC = 9.2, JPC = 3.2);
2
4
137.0 (C4, 2C, d, JPC = 10.7); 31P{1H} d ꢀ5.4 (P, 1P, s);
1
26.9 (P@O, 1P, br); MS: m/z 451.2 (Mox + H)+; 435.2
(M + Na)+; m/z 427.1 (Mox ꢀ H)ꢀ.
3b (3.40 g, 86%) NMR (CDCl3): 1H d 1.11 (CH3, 12H, t,
3JHH = 7.2); 3.01 (CH2–P, 4H, d, JPH = 21.6); 4.89 (O–
2
2a (12.7 g, 89%) Elemental analysis: found C, 33.4; H,
4.25; I, 32.3; C11H16IO3P requires C, 37.3; H, 4.55; I,
CH2, 8H, m); 7.03 (ArH, 2H, m); 7.16 (ArH, 1H, m);
7.23 (ArH, 10H, m); 13C{1H} d 16.3 (CH3, 4C, d,
1
35.8% NMR (CDCl3): 1H
d
1.25 (CH3, 6H, t,
3JPC = 6.1); 33.5 (CH2–P, 2C, d, JPC = 138); 62.0 (O–
2
2
3
3JHH = 7.2); 3.14 (CH2–P, 2H, d, JPH = 22.0); 4.06 (O–
CH2, 4C, d, JPC = 6.8); 128.4 (C2, 4C, d, JPC = 6.9);
CH2, 4H, m); 7.32 (Ar–H, 4H, m); 13C{1H} d 16.3 (CH3,
2C, d, JPC = 6.1); 33.3 (CH2–P, 1C, d, JPC = 138); 62.2
128.8 (C1, 2C, s); 131.6 (C8, 1C, t, JPC = 6.5); 132.3
(C7, 2C, m); 133.4 (C6, 2C, dt, JPC = 19.8, JPC = 4.9);
3
3
1
2
3
2
5
2
(O–CH2, 2C, d, JPC = 6.5); 92.2 (C–I, 1C, d, JPC = 6.6);
133.7 (C3, 4C, d, JPC = 19.4); 136.7 (C4, 2C, d,
2
1
4
131.3 (C–CH2, 1C, d, JPC = 9.2); 131.6 (C–H, 2C, d,
1JPC = 10.7); 137.8 (C5, 1C, dt, JPC = 12.3, JPC = 2.9);
31P{1H} d ꢀ5.4 (P, 1P, s); 26.0 (P@O, 2P, br); MS: 585.3
(M + Na)+; 563.1 (M + H)+; 561.1 (M ꢀ H)ꢀ.
3JPC = 6.6); 137.5 (C–H, 2C, d, JPC = 3.1); 31P{1H} d
2
23.7 (s); MS: m/z 377.0 (M + Na)+; 355.1 (M + H)+.
2b (8.80 g, 85%) Elemental analysis: found C, 37.3; H,
5.40; I, 24.6; C16H27IO6P2 requires C, 38.1; H, 5.40; I,
4.2.4. Borane adducts of diethyl [4-(diphenylphosphanyl)
benzyl]phosphonate (3a Æ BH3) and tetraethyl {[5-(diphenyl-
phosphanyl)-1,3-phenylene]dimethylene}bis(phosphonate)
(3b Æ BH3)
The adducts were prepared from the impure ligand sam-
ples by treatment with ca. threefold molar excess of a 1 M
THF Æ BH3 solution upon cooling in an ice-bath. After 2 h
stirring solvents were evaporated in vacuo and the products
were purified by column chromatography (silica gel,
EtOAc) and crystallization from THF/hexanes (3a Æ BH3)
25.2% NMR (CDCl3): 1H
d 1.27 (CH3, 12H, t,
3JHH = 7.2); 3.06 (CH2–P, 4H, d, JPH = 21.6); 4.04
2
(O–CH2, 8H, m); 7.20 (Ar–H, 1H, m); 7.55 (Ar–H,
3
2H, m); 13C{1H} d 16.4 (CH3, 4C, d, JPC = 6.1); 33.1
1
(CH2–P, 2C, d, JPC = 138); 62.3 (O–CH2, 4C, d,
2JPC = 6.8); 94.1 (C–I, 1C, s); 130.6 (C–H, 1C, m,
2
3JPC = 6.4); 134.1 (C–CH2, 2C, m, JPC = 6.1); 137.1
(C–H, 2C, m); 31P{1H} d 25.9 (s); MS: m/z 527.1
(M + Na)+; 505.0 (M + H)+.

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Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
1
or by column chromatography (silica gel, THF/Et2O/H2O
10:3:1) (3b Æ BH3). The purified products had purity 98+%
(3a Æ BH3) and 96+% (3b Æ BH3) (31P NMR).
4b (0.38 g, 95%) NMR (d4-methanol): H d 3.10 (CH2–
2
P, 4H, d, JPH = 22.0); 7.21 (CH, 2H, m); 7.30 (C–CH–
C, 1H, m); 7.30–7.39 (ArH, 10H, m); 13C{1H} d 35.4
1
3a Æ BH3 NMR (CDCl3): 1H d 1.25 (CH3, 6H, t,
3JHH = 7.0); 1.3 (BH3, 3H, br); 3.18 (CH2–P, 2H, d,
2JPH = 22.0); 4.04 (O–CH2, 4H, m); 7.36–7.59 (ArH, 14H,
m); 11B d ꢀ38.03 (P–BH3, br s) 13C{1H} d 11.2 (CH3, 2C,
(CH2–P, 2C, d, JPC = 134.3); 129.7 (C2, 4C, d,
3JPC = 4.2); 130.3 (C1, 2C, s); 133.2 (C8, 1C, m); 134.3–
2
134.9 (C6 and C7, 4C, m); 134.8 (C3, 4C, d, JPC = 19.0);
137.2 (C4, 2C, d, JPC = 5.3); 138.0 (C5, 1C, m); 31P{1H}
1
3
1
d, JPC = 5.7); 28.6 (CH2–P, 1C, d, JPC = 138); 57.1 (O–
d ꢀ4.0 (P, 1P, s); 25.7 (P@O, 2P, s); MS: 489.1
(Mox + Na)+; 473.1 (M + Na)+; 451.1 (M + H)+; 449.2
(M ꢀ H)ꢀ.
2
2
CH2, 2C, d, JPC = 6.5); 122.4 (C5, 1C, dd, JPC = 9.2,
5JPC = 3.4); 123.6 (C2, 4C, d, JPC = 10.0); 123.9 (C4, 2C,
3
1
3
d, JPC = 55.0); 125.0 (C7, 2C, dd, JPC = 10.3 and 6.5);
4
126.0 (C1, 2C, d, JPC = 1.9); 127.9 (C3, 4C, d,
4.2.7. cis-[PtCl2(3a)2], trans-[PdCl2(3a)2] and trans-
[Pd2Cl4(3a)2]
2JPC = 9.56); 128.1 (C6, 2C, dd, JPC = 9.86, JPC = 2.7);
2
4
130.2 (C8, 1C, dd, JPC = 2.2, JPC = 9.2); 31P{1H} d 20.5
(P–BH3, 1P, br); 25.4 (P@O, 1P, s); MS: m/z 449.2
(M + Na)+; 435.1 (M ꢀ BH3 + Na)+; m/z 413.2
(M ꢀ BH3 + H)+.
A solution of 3a (480 mg, 1160 lmol) in dichloromethane
(5 mL) in a 25 mL Schlenk flask was treated with a solution
of [PtCl2(cod)] (217 mg, 570 lmol) or [PdCl2(cod)] (163 mg,
570 lmol) in 5 mL of the same solvent. The flask was stop-
pered and the reaction mixture was stirred overnight at
35 ꢁC in an oil bath. Following manipulations were done
under air. Volatiles were removed in vacuo, the residue
was dissolved in 1 mL of dichloromethane and precipitated
by slow addition of hexane. The products were collected by
centrifugation, washed with hexane (3 · 5 mL) and dried
in vacuo.
4
2
3b Æ BH3 NMR (CDCl3): 1H d 1.12 (CH3, 12H, t,
3JHH = 7.2); 1.3 (BH3, 3H, br); 3.05 (CH2–P, 4H, d,
2JPH = 22.0); 3.90 (O–CH2, 8H, m); 7.30–7.52 (ArH,
13H, m); 11B d ꢀ38.13 (P–BH3, br s) 13C{1H} d 16.3
3
(CH3, 4C, d, JPC = 6.1); 33.5 (CH2–P, 2C, d,
1JPC = 138); 62.0 (O–CH2, 4C, d, JPC = 6.8); 128.8 (C3,
2
2
1
4C, d, JPC = 10.2); 128.8 (C4, 2C, d, JPC = 57.9); 129.7
(C5, 1C, dt, JPC = 56.8, JPC = 3.0); 131.3 (C1, 2C, d,
4JPC = 2.3); 132.7–133.2 (C6 + C7, 4C, m); 133.1 (C2,
2
3
From the mother liquors after crystallization of trans-
[PdCl2(3a)2] Æ 2CHCl3 left in refrigerator at ꢀ20 ꢁC for sev-
eral months, red crystalline trans-[Pd2Cl4(3a)2] Æ 2CHCl3
was isolated by filtration and dried in vacuo.
3
3
4C, d, JPC = 9.9); 134.3 (C8, 1C, td, JPC = 6.5,
4JPC = 2.3); 31P{1H} d 20.5 (P–BH3, 1P, br); 25.2 (P@O,
2P, s); MS: 599.3 (M + Na)+; 585.2 (M ꢀ BH3 + Na)+;
563.1 (M ꢀ BH3 + H)+.
cis-[PtCl2(3a)2] (420 mg, 66%) NMR (CDCl3): 1H d 1.23
3
(CH3, 6H, t, JHH = 6.8); 3.13 (CH2–P, 2H, d,
2JPH = 22.0); 4.00 (O–CH2, 4H, m); 7.14–7.48 (Ar, 14H,
1
4.2.5. Deprotection of 3a Æ BH3 and 3b Æ BH3 [26]
After deprotection, the spectral characteristics of the
products corresponded to those mentioned above; the pur-
ity remained unchanged.
m); 31P{1H} d 13.8 (Pt–P, 1P, s + d, JPtP = 3672); 25.3
(P@O, 1P, s); 195Pt d ꢀ1192 (t, JPtP = 3666); MS: 1113.1
1
(M + Na)+; 1078.8 (M ꢀ Cl + Na)+; far-IR: mPtACl/cmꢀ1
293s, 318s.
trans-[PdCl2(3a)2] Æ 2CHCl3 (366 mg, 64%) NMR
1
3
4.2.6. [4-(Diphenylphosphanyl)benzyl]phosphonic acid
(4a) and {[5-(diphenylphosphanyl)-1,3-phenylene]-
dimethylene}bis(phosphonic) acid (4b)
(CDCl3): H d 1.22 (CH3, 6H, t, JHH = 7.2); 3.16 (CH2–
2
P, 2H, d, JPH = 22.0); 3.99 (O–CH2, 4H, m); 7.31–7.44
(Ar, 10H, m), 7.60–7.73 (Ar, 4H, m); 31P{1H} d 21.2
In a closed Schlenk flask, the phosphonic acid ester
(0.5 g) was heated with 30 mL of 20% aqueous HCl to
100 ꢁC for 24 h in the case of 4a or 48 h for 4b. After
cooling to RT, the mixture was filtered and all volatiles
were evaporated in vacuo. The residue was dissolved in
15 mL of deoxygenated ethanol, stirred for 15 min and
evaporated again. The glassy product was dried for 3 h
in vacuo. Purity of the products was 98+% (4a) and
97+% (4b).
(Pd–P, 1P, s); 23.7 (P@O, 1P, s); MS: 1025.1 (M + Na)+;
965.2 (M ꢀ Cl)+; 624.9 (M ꢀ L + Cl)ꢀ; far-IR mPdACl
/
cmꢀ1 356s.
trans-[Pd2Cl4(3a)2] Æ 2CHCl3 (40.0 mg) NMR (CDCl3):
1H d 1.24 (CH3, 12H, t, JHH = 7.2); 3.17 (P–CH2, 4H, d,
3
2JPH = 22.0); 4.01 (O–CH2, 8H, m); 7.35 (ArH, 4H, m);
7.42 (ArH, 8H, m); 7.52 (ArH, 4H, m); 7.63 (ArH, 4H,
m); 7.73 (ArH, 8H, m); 31P{1H} d 23.1 (P@O, 1P, s);
30.7 (Pd–P, 1P, s); MS: 1202.9 (M + Na)+; 625.0
([PdCl3(3a)])ꢀ; far-IR mPdACl/cmꢀ1 259s, 299m, 313m, 359s.
1
4a (0.41 g, 95%) NMR (d4-methanol): H d 3.14 (CH2–
2
P, 2H, d, JPH = 22.0); 7.22–7.34 (ArH, 14H, m);
1
13C{1H} d 35.6 (CH2–P, 1C, d, JPC = 134.4); 129.7 (C2,
4.2.8. cis-[PtCl2(3b)2] and trans-[PdCl2(3b)2]
3
4C, d, JPC = 6.8); 130.1 (C1, 2C, s); 133.8 (C7, 2C, t,
A solution of 3b (240 mg, 430 lmol) in dichloromethane
(5 mL) in a 25 mL Schlenk flask was treated with a solution
of [PtCl2(cod)] (77.0 mg, 205 lmol) or [PdCl2(cod)]
(58.5 mg, 205 lmol) in 5 mL of the same solvent. The flask
was stoppered and the reaction mixture was stirred over-
night at 35 ꢁC in an oil bath. Following manipulations were
2
3JPC = 6.8); 134.7 (C3, 4C, d, JPC = 19.1); 135.0 (C6,
2
4
2C, dd, JPC = 19.8, JPC = 2.3); 135.6 (C5, 1C, m); 137.7
(C4, 2C, m); 31P{1H} d ꢀ3.4 (P, 1P, s); 26.8 (P@O, 1P,
br); MS: 395.0 (Mox + Na)+; 379.3 (M + Na)+; 372.1
(Mox)+; 357.1 (M + H)+; 355.2 (M ꢀ H)ꢀ.

Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
2421
done under air atmosphere. Volatiles were evaporated
under reduced pressure and residual cycloocta-1,5-diene
was removed by evaporation of the residue with 5 mL of
dichloromethane. Remaining yellowish oils were dried in
vacuo.
1P, s); MS: 854.1 (M ꢀ Cl)+; 889.0 (M ꢀ H)ꢀ; far-IR
m
PdACl/cmꢀ1 358s.
cis-[PdCl2(4b)2] (88.0 mg, 62%) NMR (D2O + NaOD,
1
2
pH 9): H d 2.31 (CH2–P, 4H, d, JPH = 8.4); 6.78–7.73
(ArH, 13H, m); 31P{1H} d 18.4 (P@O, 1P, s); 35.1 (Pd–P,
1P, s); MS: 1076.9 (M ꢀ H)ꢀ; 1040.9 (M ꢀ 2H ꢀ Cl)ꢀ;
far-IR mPdACl/cmꢀ1 289s, 307s.
cis-[PtCl2(3b)2] (230 mg, 80%) NMR (CDCl3): 1H d 1.21
3
(CH3, 12H, t, JHH = 6.8); 3.01 (CH2–P, 4H, d,
2JPH = 22.0); 3.97 (O–CH2, 8H, m); 7.16–7.46 (ArH,
1
13H, m); 31P{1H} d 14.3 (Pt–P, 1P, s + d, JPtP = 3666);
4.2.11. Photochemical isomerization of Pt(II) complexes
cis-[PtCl2(3a)2] and cis-[PtCl2(3b)2]: 20 mg of the com-
plex was dissolved in 0.7 ml of CDCl3 in a quartz NMR
tube. The sample was irradiated for 5 h with an 8 W UV
lamp (k = 366 nm).
1
25.1 (P@O, 2P, s); 195Pt d ꢀ1198 (t, JPtP = 3662); MS:
1413.1 (M + Na ꢀ H)+; 1425.5 (M + Cl ꢀ H)ꢀ; far-IR
m
PtACl/cmꢀ1 294s, 317s.
1
trans-[PdCl2(3b)2] (219 mg, 82%) NMR (CDCl3): H d
3
1.15 (CH3, 12H, t, JHH = 7.2); 3.11 (CH2–P, 4H, d,
2JPH = 22.0); 3.93 (O–CH2, 8H, m); 7.35–7.53 (Ar, 10H,
m), 7.65–7.70 (Ar, 3H, m); 31P{1H} d 24.2 (Pd–P, 1P, s);
26.0 (P@O, 2P, s); MS: 1325.1 (M + Na)+; 773.5
(M ꢀ L + Cl)ꢀ; far-IR mPdACl/cmꢀ1 357s.
cis-[PtCl2(4a)2] and cis-[PtCl2(4b)2]: A 20 mg sample of
the complex was suspended in 0.2 ml of D2O and a 0.3 M
NaOD in D2O was added dropwise until the solid dis-
solved. The volume of the sample was adjusted to 0.7 ml
with D2O. After transfer into a quartz NMR tube, the sam-
ple was irradiated as described above.
4.2.9. cis-[PtCl2(4a)2] and cis-[PtCl2(4b)2]
cis- and trans-[PtCl2(3a)2] NMR (CDCl3, after irradia-
1
A solution of 4a (190 mg, 423 lmol) or 4b (151 mg,
423 lmol) in 20% aqueous HCl (5 mL) in a 25 mL Schlenk
flask was treated with a solution of [PtCl2(cod)] (81.0 mg,
216 lmol) in 5 mL of dichloromethane. The reaction mix-
ture was stirred vigorously overnight at RT. Aqueous
phase was removed by means of a syringe and the organic
layer containing a white precipitate was evaporated to dry-
ness. The residue was evaporated to dryness with methanol
(3 · 5 mL) and washed with hexane (3 · 5 mL). The residue
was stirred in dichloromethane (10 ml) overnight, sepa-
rated by centrifugation, washed with dichloromethane
(5 mL) and dried in vacuo.
tion): 31P{1H} d 12.0 (P–Pt cis, s + d, JPtP = 3669 Hz);
1
18.1 (P–Pt trans, s + d, JPtP = 2634 Hz); 23.5 (P@O cis,
1
s); 23.8 (P@O trans, s); 195Pt d ꢀ1196 (cis, t, JPtP
=
1
3665 Hz); ꢀ814 (trans, t, JPtP = 2643 Hz).
cis- and trans-[PtCl2(3b)2] NMR (CDCl3, after irradia-
tion): 31P{1H} d 14.4 (P–Pt cis, s + d, JPtP = 3667 Hz);
1
1
20.7 (P–Pt trans, s + d, JPtP = 2643 Hz); 25.4 (P@O cis,
1
s); 25.6 (P@O trans, s); 195Pt d ꢀ1199 (cis, t, JPtP
=
1
3663 Hz); ꢀ823 (trans, t, JPtP = 2645 Hz).
4.3. X-ray crystallography
cis-[PtCl2(4a)2] (176 mg, 84%) NMR (D2O + NaOD,
The single crystals of compound cis-[PtCl2(3a)2] Æ
0.5CH2Cl2 were prepared from its dichloromethane solu-
tion by slow diffusion of hexane. The crystals of cis-
[PtCl2(3b)2] Æ PhMe Æ H2O were prepared by slow diffusion
of hexane to a solution of the complex in chloroform/tolu-
ene. Trans-[PdCl2(3a)2] Æ 2CHCl3 crystallized from hexane/
ethanol/chloroform mixture on cooling to ꢀ18 ꢁC, trans-
[PdCl2(3b)2] Æ 2H2O crystallized from its oil upon standing.
Dinuclear complex trans-[Pd2Cl4(3a)2] Æ 2CHCl3 crystal-
lized on prolonged standing of mother liquor after crystal-
lization of trans-[PdCl2(3a)2] Æ 2CHCl3.
The selected crystals were mounted in random orienta-
tions onto a glass fibre using nujol or epoxy glue. The data
were collected on Nonius Kappa CCD diffractometer
(Enraf-Nonius) at 294 K (cis-[PtCl2(3a)2] Æ 0.5CH2Cl2) or
150 K (Cryostream Cooler Oxford Cryosystem) (all other
complexes). Data were analyzed using the HKL DENZO pro-
gram package [44].
1
2
pH 9): H d 2.88 (CH2–P, 2H, d, JPH = 22.4); 6.92–7.22
(ArH, 14H, m); 31P{1H} d 11.0 (Pt–P, 1P, s + d,
1JPtP = 3709); 17.4 (P@O, 1P, s); 195Pt d ꢀ1185 (Pt–P, t,
1JPtP = 3705); MS: 943.1 (M ꢀ Cl)+; 977.2 (M ꢀ H)ꢀ;
far-IR mPtACl/cmꢀ1 287s, 311s.
cis-[PtCl2(4b)2] (137 mg, 56%) NMR (D2O + NaOD,
1
2
pH 9): H d 2.55 (CH2–P, 4H, d, JPH = 20.0); 7.05 (CH,
2
2H, d, JPH = 10.4); 7.13 (CH, 4H, m); 7.23 (CH, 1H, s);
7.28 (CH, 2H, m); 7.42 (CH, 4H, m); 31P{1H} d 11.7 (Pt–
P, 1P, s + d, JPtP = 3560); 20.5 (P@O, 2P, s); 195Pt d
1
ꢀ875 (Pt–P, t, JPtP = 3580); MS: 1165.5 (M ꢀ H)ꢀ; far-
1
IR mPt–Cl/cmꢀ1 291s, 312s.
4.2.10. trans-[PdCl2(4a)2] and cis-[PdCl2(4b)2]
A freshly prepared slurry of PdCl2 (22.3 mg, 126 lmol)
in 20% aqueous HCl (2 mL) was added to a solution of
4a (95.0 mg, 265 lmol) or 4b (120 mg, 265 lmol) in 20%
aqueous HCl (3 mL) in a 25 mL Schlenk flask. The slurry
was stirred overnight at RT. The yellow product was sepa-
rated by centrifugation, washed with 20% aqueous HCl
(2 mL) and dried in a desiccator (over NaOH).
All crystal structures were solved by direct methods
(SIR92 [45]). Positions of heavy metal, phosphorus, oxygen
and some carbon atoms were determined from direct solu-
tion, other non-hydrogen atoms were found as maxima in
the difference map of the electron density. All structures
were refined by least-squares technique (SHELXL97 [46]).
Pictures were processed by PLATON98 [47]. In general, the
trans-[PdCl2(4a)2] (84.0 mg, 73%) NMR (D2O + NaOD,
1
2
pH 9): H d 2.56 (CH2–P, 2H, d, JPH = 8.2); 6.99–7.63
(ArH, 14H, m); 31P{1H} d 16.4 (P@O, 1P, s); 34.0 (Pd–P,

2422
Z. Rohlı´k et al. / Journal of Organometallic Chemistry 691 (2006) 2409–2423
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hydrogen atoms of the phosphine moieties were fixed in
theoretical positions using a riding model, with their isotro-
pic thermal factors restrained to 1.2 multiple of U-value of
corresponding carbon atoms. The hydrogen atoms of ester
groups were restrained in the same way, using isotropic
thermal factors of 1.2 for methylene and 1.5 for methyl
groups.
The structure of cis-[PtCl2(3a)2] contains a disordered
molecule of dichloromethane. This disorder was preferably
described by the presence of half-occupied solvent molecule
with one of the chlorine atoms equally distributed over two
positions, so the compound is therefore formulated as cis-
[PtCl2(3a)2] Æ 0.5CH2Cl2. In the crystal structure of cis-
[PtCl2(3b)2] Æ PhMe Æ H2O, rather unusual combination of
toluene and water solvate molecules was found. Both trans
palladium(II) complexes are centrosymmetric, having
chloroform (trans-[PdCl2(3a)2] Æ 2CHCl3) or water (trans-
[PdCl2(3b)2] Æ 2H2O) as solvates. The dinuclear complex
shows also a centre of symmetry, possessing one half of
the molecule as crystallographically independent unit,
and chloroform solvate, giving the formula trans-
[Pd2Cl4(3a)2] Æ 2CHCl3.
[14] S. Bischoff, A. Ko¨ckritz, M. Kant, Top. Catal. 13 (2000) 327.
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Organomet. Chem. 567 (1998) 13.
[18] G.M. Kosolapoff, L. Maier (Eds.), Organic Phosphorus Compounds,
second ed., Wiley-Interscience, 1972.
[19] O. Herd, A. Hessler, M. Hingst, M. Tepper, O. Seltzer, J. Organomet.
Chem. 522 (1996) 69.
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(b) W. Gee, R.A. Shaw, B.C. Smith, Inorg. Synth. 9 (1967) 19;
(c) G.W. Luther III, G. Beyerle, Inorg. Synth. 17 (1977) 186.
[21] There is no need to deoxygenate water and aqueous HCl, because the
loss of Ph2PH caused by dissolved oxygen is negligible on large scale.
A smaller volume of non-dried THF can be used with a positive effect
on the rate of Ph2PLi formation [22]; no vigorous or uncontrolled
reaction was observed. All this modifications did not affect the yield
and/or purity of the product significantly.
[22] P. Brooks, M.J. Gallagher, A. Sarroff, Aust. J. Chem. 40 (1987)
1341.
[23] (a) for a review see B. Carboni, L. Monnier, Tetrahedron 55 (1999)
1197;
The experimental and refinement data are listed in Table
7. All data for the structures reported here have been
deposited with the Cambridge Crystallographic Data Cen-
tre as CCDC reference numbers 281318–281322.
(b) J.M. Brunel, B. Faure, M. Maffei, Coordin. Chem. Rev. 178–180
(1998) 665.
Acknowledgements
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[26] L. McKinstry, T. Livinghouse, Tetrahedron 51 (1995) 7655.
[27] S. Ganguly, J.T. Mague, D.M. Roundhill, Inorg. Chem. 31 (1992)
3500.
This project was supported by the Grant Agency of the
Charles University (grant No. 321/2005/B-CH/PrF). We
´ˇ
also wish to thank V. Kubıcek for MS measurements and
´
ˇ
´
K. Teubner and Dr. I. Cısarova for X-ray data collection.
Appendix A. Supplementary data
[28] T. Hayashi, M. Konishi, M. Kumada, Tetrahedron Lett. 21 (1979)
1871.
´
´
[29] F. Joo, Z. Toth, J. Mol. Catal. 8 (1980) 369.
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Stein, Inorg. Chim. Acta 290 (1999) 189.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.
2006.01.024.
[31] P. Roffia, F. Conti, G. Gregori, Chem. Ind. (Milan) 53 (1971)
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