Assembly of cyclopalladated units: Synthesis, characterisation, X-ray crystal structure and study of the reactivity of the tetrametallic cyclopalladated complex [Pd{C6H4-CH=N- (C6H4-2-O)}]4·2CHCl

Article abstract of DOI:10.1016/S0022-328X(03)00581-3

The reaction of the equimolar amounts of the Schiff base C₆ H₄-CH=N-(C₆H₄-2-OH) (1) and palladium (II) acetate in refluxing methanol for 2 h produces [Pd{C₆ H₄-CH=N-(C₆H₄

Full text of DOI:10.1016/S0022-328X(03)00581-3

Journal of Organometallic Chemistry 681 (2003) 82ꢁ90
/
www.elsevier.com/locate/jorganchem
Assembly of cyclopalladated units: synthesis, characterisation, X-ray
crystal structure and study of the reactivity of the tetrametallic
cyclopalladated complex [Pd{C6H4Ã
/
CHÄ
/
NÃ
/
(C6H4Ã
/
2-O)}]4×
/
2CHCl3
Concepcio´n Lo´pez a,*, Amparo Caubet a, Sonia Pe´rez a, Xavier Solans b,
Merce` Font-Bard´ıa b
a Facultat de Qu´ımica, Departament de Qu´ımica Inorga`nica, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain
b Facultat de Geolog´ıa, Departament de Cristal.lografia, Mineralogia i Dipo`sits Minerals, Mart´ı i Franque`s s/n, 08028 Barcelona, Spain
Received 5 March 2003; received in revised form 2 June 2003; accepted 2 June 2003
Abstract
The reaction of the equimolar amounts of the Schiff base C6H4Ã
/
CHÄ
/
NÃ
/
(C6H4Ã
/
2-OH) (1) and palladium(II) acetate in refluxing
2CHCl3 reveals that it
methanol for 2 h produces [Pd{C6H4ÃCHÄNÃ(C6H4Ã2-O)}]4 (2)×
/
/
/
/
/
2CHCl3. The X-ray crystal structure of 2×
/
contains a central non-planar eight-membered ring ‘‘Pd4O4’’ formed by the self-assembly of four cyclopalladated fragments in which
the ligand behaves as a [C, N, O]2ꢀ terdentate ligand and the oxygen atoms act as bridges between the monomeric units. The
reaction of 2 with triphenylphosphine or 1,1?-bis(diphenylphosphino)ferrocene (dppf) produces the opening of the central ‘‘Pd4O4’’
core and the formation of the monomeric derivative [Pd{C6H4Ã
complex [{Pd[C6H4ÃCHÄNÃ(C6H4Ã2-O)]}2(m-dppf)] (4), respectively. In 3 and 4, the ligand also behaves as a dianionic and
terdentate [C, N, O]2ꢀ group, thus indicating that the PdÃ
O bond exhibits remarkable stability. The X-ray crystal structure of 3×
CH2Cl2 confirmed the mode of binding of the Schiff base and a trans arrangement between the imine nitrogen and the PPh3 ligand.
/
CHÄ
/
NÃ
/
(C6H4Ã
/
2-O)}(PPh3)] (3)×/CH2Cl2 and the trimetallic
/
/
/
/
/
/
A comparative study of the spectrochemical properties of compounds 2ꢁ
/
4 is also reported.
# 2003 Elsevier B.V. All rights reserved.
Keywords: X-ray crystal structures; Cyclopalladated complexes; Self-assembly
1. Introduction
attention due to their potential applications in different
areas, including their ability as molecular receptors [3].
However, examples involving palladium(II) blocks con-
The crystal engineering of coordination networks and
taining a s(PdÃ
/
C) bond are not so common. A few
of metal-based supramolecular architectures has at-
tracted great interest in the late years [1]. In these cases,
the formation of the final macromolecular array is
usually achieved either using spacers (i.e. bridging
ligands or metal-containing fragments) to connect
several building blocks or by the self-assembly of a
given number of monomeric coordination complexes [2].
Among all the examples reported so far those containing
square-planar palladium(II) units have attracted special
articles focused on the use of bridging bidentate ligands
have been described [4,5], but examples of self-assembly
of cyclometallated units are scarce [5]. A few molecular
polygons and boxes having PdII and bidentate {(C, N)ꢀ
or (C, O)ꢀ} or terdentate {(C, N, N?)ꢀ, (N, C, N)ꢀ, (C,
N, S)ꢀ} ligands are known [5], but as far as we know,
self-assembly of palladacyclic arrays with (C, N, O)2ꢀ
ligands are not so common [6,7]. Vila and coworkers [6]
have recently postulated the formation of the poly-
nuclear compound [Pd{2,3,4-(MeO)3C6HÃ
/
CHÄ
/
NÃ
/
C6H3Ã2-(O)-4-R}]n (with RꢂH or Me) arising from
/
/
* Corresponding author. Tel.:
934907725.
ꢃ
/
34-934021274; fax:
ꢃ/34-
the self-assembly of cyclopalladated units, but to the
best of our knowledge, only one tetrametallic complex
E-mail address: conchi.lopez@qi.ub.es (C. Lo´pez).
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00581-3

C. Lo´pez et al. / Journal of Organometallic Chemistry 681 (2003) 82ꢁ
/90
83
containing four ‘‘Pd(C, N, O)’’ fragments has been
structurally characterised by X-ray diffraction [7].
Here we provide conclusive evidence of the formation
ment is the result.1 As a consequence of this distribution
of groups, two of the monomers, with a head-to-tail
orientation, are parallel and nearly orthogonal to the
of the tetranuclear palladium(II) complex [Pd{C6H4Ã
CHÄNÃ(C6H4Ã2-O)}]4 (2)×2CHCl3 formed by self-
assembly of four palladacycles arising from the activa-
tion of the s(CÃH) and s(OÃH) bonds of C6H5ÃCHÄ
NÃ(C6H4Ã2-OH) (1). The reactivity of 2 with the
/
other pair of ‘‘[Pd{C6H4Ã
/
CHÄ
/
NÃ
/
(C6H4Ã
/
2-O)}]’’ moi-
eties which have a similar arrangement. The distances
/
/
/
/
between the aryl rings belonging to each one of the
˚
‘‘quasi-parallel’’ units vary from 3.79 to 3.88 A. These
/
/
/
/
/
/
values fall in the range expected for van der Waals
interactions, and the shortest Oꢀ ꢀ ꢀO separation in the
phosphines: triphenylphosphine (PPh3) or 1,1?-bis(di-
phenylphosphino)ferrocene (dppf) is also studied and
˚
tetramer is 3.156 A. These findings indicate that the free
reveals the low lability of the terminal PdÃ
/
O bond in 2.
A comparative study of the spectrochemical properties
space available for a host molecule to enter into the
inner part of the tetramer is small and consequently, the
CHCl3 solvation molecules are not included in the
central part of the tetramer.
of 2 and 3 is also reported.
Despite the complexity of the tetrameric array of 2×
/
2. Results and discussion
1
2CHCl3 in the solid state, its H-NMR spectrum at 298
K showed only nine signals, which could be easily
identified with the use of two-dimensional heteronuclear
1H- and 13C-NMR experiments. These findings could be
indicative that the tetramer is fluxional or dissociates in
solution. In a first attempt to clarify this point, proton-
Ligand 1 was prepared by condensation between
2-OH using the general
method described for the preparation of organic keti-
mines [8]. Its characterisation data (see Section 3) agreed
with the proposed formulae.
Treatment of equimolar amounts of 1 and Pd(AcO)2
in refluxing methanol for 2 h, followed by the removal
of small amounts of the Pd(0) formed, produced
benzaldehyde and H2NÃ
/
C6H4Ã
/
NMR spectra of 2×
223ꢁ298 K using a Bruker Avance 600 MHz instrument
(Fig. 2AꢁD). In general terms, the spectra obtained at
278, 243 and 223 K (Fig. 2BꢁD) showed also nine
/2CHCl3 were registered in the range
/
/
/
[Pd{C6H4Ã
/
CHÄ
/
NÃ
/
(C6H4Ã
/
2-O)}]4
(2)×
/
2CHCl3
signals and only tiny differences in their chemical shifts
and their resolution were detected. Similar findings were
also shown when the spectra were recorded with a
Varian 300 MHz instrument in the same range of
(Scheme 1). Its elemental analyses (see Section 3) were
consistent with the proposed formulae. The FABꢃ mass
spectrum of 2 showed a peak at m/zꢂ
corresponds to [{MÃ
2(CHCl3)}]ꢃ cation. In the
MALDI-TOF spectrum, the presence of two additional
peaks at m/zꢂ905 {[{MÃ
2(CHCl3)}3/4]ꢃ} and 604
{[{MÃ
2(CHCl3)}/2]ꢃ} suggested the fragmentation of
/1206, which
/
temperatures. The ES-mass spectrum of 2×
/
2CHCl3
showed a peak at m/zꢂ603 which could be indicative
/
/
/
of the presence of a dimeric unit in solution.
/
Besides that, as can be easily seen in Fig. 2C and D,
for the lowest temperatures (248 and 223 K) the
presence of weak and poorly resolved additional signals
the tetrametallic array and the formation of trimeric and
dimeric units, respectively.
This compound has also been characterised by X-ray
diffraction. Its molecular structure is shown in Fig. 1
and a selection of bond lengths and angles is presented
in Table 1.
1
was also detected in the H-NMR spectra. This may be
indicative of the presence of small amounts of another
specie in solution. However, the low intensity of the
signals and their poor resolution did not allow us to
The crystal structure of 2×
presence of the tetranuclear complex [Pd{C6H4Ã
NÃ(C6H4Ã2-O)}]4 and CHCl3 (in a 1:2 molar ratio).
The tetramer (Fig. 1A) can be visualised as formed by
four nearly planar ‘‘[Pd{C6H4ÃCHÄNÃ(C6H4Ã2-O)}]’’
/2CHCl3 confirmed the
/
CHÄ
/
/
/
1
The least-squares equation of the plane defined by the atoms
O(11), O(41), N(12) and C(113) is (0.5881)XOꢃ
(ꢀ0.0278)ZOꢂ1.7048 (deviations from the plane are as follows:
O(11), ꢀ
/
(0.8023)YOꢃ
/
/
/
/
/
/
/
fragments, which share the oxygen atom with the
neighbouring unit, leading to a central non-planar
‘‘Pd4O4’’ eight-membered ring (Fig. 1B), in which all
the Pdꢀ ꢀ ꢀPd distances are greater than the sum of the
˚ ˚ ˚
0.083 A; O(41), 0.0720 A; N(12), 0.1040 A; and C(113),
/
˚
ꢀ/
0.0929 A). The least-squares equation of the plane defined by the
atoms O(11), O(21), N(21) and C(213) is (ꢀ0.2282)XOꢃ
(0.2740)YOꢃ(0.9174)ZOꢂ3.2970 (deviations from the plane are as
follows: O(11), ꢀ
/
/
/
/
˚
˚
˚
/
0.017 A; O(21), ꢀ
/
0.020 A; N(21), 0.024 A; and
0.022 A). The least-squares equation of the plane defined by
the atoms O(21), O(31), N(31) and C(313) is (0.4836)XOꢃ
(0.8738)YOꢃ(ꢀ0.0508)ZOꢂ4.9090 (deviations from the plane are
as follows: O(21), ꢀ
˚
van der Waals radii (3.22 A) [9], thus suggesting that
˚
C(213), ꢀ
/
there is no direct interaction between the PdII atoms.
In the tetramer, each palladium is bound to the two
heteroatoms (O and N) of the ligand and to the carbon
adjacent to the imine group, the remaining coordination
site being occupied by the oxygen atom of a neighbour-
/
/
/
/
˚
˚
˚
0.058 A; and
/
0.042 A; O(31), 0.047 A; N(31), ꢀ
C(113), 0.053 A). The least-squares equation of the plane defined by
the atoms O(311), O(41), N(41) and C(413) is (ꢀ0.1875)XOꢃ
(0.2200)YOꢃ(0.9573)ZOꢂ6.4110 (deviations from the plane are as
follows: O(31), ꢀ
/
˚
/
/
/
/
ing and nearly orthogonal ‘‘[Pd{C6H4Ã
/
CHÄ
/
NÃ
/
(C6H4Ã
/
˚
˚
˚
/
0.006 A; O(41), 0.007 A; N(41), ꢀ0.009 A; and
/
˚
2-O)}]’’ unit. A slightly distorted square-planar environ-
C(413), 0.0079 A).

84
C. Lo´pez et al. / Journal of Organometallic Chemistry 681 (2003) 82ꢁ90
/
Scheme 1. i) 4 Pd(AcO)2, in refluxing methanol, 2h. ii) 4 PPh3 in CDCL3. iii) dppf in CH2Cl2
clarify the nature of the minor component present in
solution.
cis arrangement of the PPh3 and the metallated carbon.
This is the typical arrangement of groups found in
related palladacycles derived from imines [10] due to the
transphobia effect [11]. When larger excesses of PPh3
The addition of PPh3 to a CHCl3 solution of 2×
2CHCl3 gave [Pd{C6H4ÃCHÄNÃ(C6H4Ã2-O)}(PPh3)]
(3)×
CH2Cl2 (Scheme 1). Its 31P{1H}-NMR spectrum
showed a singlet at 34.39 ppm, which is consistent with a
/
/
/
/
/
/
were used (PPh3: Pd molar ratio in the range 4ꢁ
/
12) no
evidence of the cleavage of the PdÃO bond was detected
/

C. Lo´pez et al. / Journal of Organometallic Chemistry 681 (2003) 82ꢁ
/90
85
Table 1
˚
Selected bond lengths (A) and angles (8) for 2×
/2CHCl3 (standard
deviation parameters are given in parenthesis)
Selected bond lengths
Pd(1)Ã
Pd(1)Ã
Pd(2)Ã
Pd(2)Ã
Pd(3)Ã
Pd(3)Ã
Pd(4)Ã
Pd(4)Ã
O(11)Ã
O(31)Ã
N(12)Ã
N(32)Ã
Pd(1)Ã
PdÃ
Pd(2)Ã
Pd(2)Ã
Pd(3)Ã
Pd(3)Ã
Pd(4)Ã
Pd(4)Ã
O(21)Ã
O(41)Ã
N(22)Ã
N(41)Ã
/
N(12)
O(41)
C(213)
O(11)
C(313)
O(31)
N(41)
O(31)
1.924(9)
2.058(6)
1.976(9)
2.023(8)
1.910(11)
2.029(7)
1.943(7)
2.132(11)
1.348(14)
1.396(14)
1.331(14)
1.294(13)
1.939(14)
2.149(9)
2.004(7)
2.191(11)
1.973(10)
2.131(7)
1.977(10)
1.943(7)
1.311(11)
1.336(12)
1.305(11)
1.261(11)
/
/
/
/
/
/
/
/
C(11)
C(31)
/
/
C(17)
C(37)
C(113)
/
/
/
O(11)
/
N(21)
O(21)
N(31)
O(31)
C(413)
O(41)
/
/
/
/
/
/
C(21)
C(41)
/
/C(27)
/C(47)
Selected bond angles
O(41)Ã
O(21)Ã
O(11)Ã
O(31)Ã
N(12)Ã
N(31)Ã
O(11)Ã
O(31)Ã
O(21)Ã
O(41)Ã
N(21)Ã
N(41)Ã
/
Pd(1)Ã
Pd(3)Ã
Pd(1)Ã
Pd(3)Ã
Pd(1)Ã
Pd(3)Ã
Pd(2)Ã
Pd(4)Ã
Pd(2)Ã
Pd(4)Ã
Pd(2)Ã
Pd(4)Ã
/
O(11)
O(31)
N(12)
N(31)
97.2(3)
82.1(4)
83.1(5)
82.1(14)
80.5(5)
80.7(5)
99.5(3)
98.4(3)
79.3(3)
81.9(3)
83.6(3)
82.5(4)
/
/
/
/
/
/
/
/
C(113)
C(313)
O(21)
O(41)
N(21)
N(41)
/
/
/
/
/
/
/
/
Fig. 1. (A) Molecular structure of the tetrametallic array (2) and atom
labelling scheme. (B) A schematic view of the central ‘‘Pd4O4’’ core.
Hydrogen atoms have been omitted for clarity.
/
/
/
/
C(213)
/
/
C(413)
1
by H- and 31P{1H}-NMR, thus suggesting a remark-
able stability of the PdÃ/O bond.
a cis arrangement in good agreement with the results
The molecular structure of 3 is shown in Fig. 3 and a
selection of bond lengths and angles is presented in
Table 2.
obtained from the NMR studies.
˚
C(13) bond length (1.938(8) A) does not
differ significantly from the average value found for 2
˚
(1.95(3) A) and agrees with the values reported for most
The PdÃ
/
The structure contains molecules of [Pd{C6H4Ã
/
CHÄ
/
NÃ(C6H4Ã2-O)}(PPh3)] and CH2Cl2 in a 1:1 molar
/
/
of cyclopalladated compounds containing bidentate [C,
N]ꢀ or terdentate [C, N, X]ꢀ (Xꢂ
N, S or P) ligands
ratio. In each one of the palladium(II)-containing
molecules the metal is in a slightly distorted square-
planar environment,2 bound to the imine nitrogen, N,
the oxygen, O, and the C(13) atom of the ligand, thus
confirming the [C, N, O]2ꢀ mode of binding of the
imine. The remaining coordination site is occupied by
/
˚
N bond in 3 is (1.995(6) A) slightly
larger, if significant, than in the tetranuclear derivative
[12], while the PdÃ
/
˚
(average value: 1.961(3) A). This difference could be
related to the different influence of the ligand in the
trans-position (an oxygen in 2 and a phosphorous in 3)
[13].
the phosphorus of PPh3. The PÃ
/
PdÃC(13) angle (81.48)
/
indicates that the metallated carbon and the PPh3 are in
In the crystal structures of 2×
/
2CHCl3 and 3×
/
CH2Cl2,
the aryl rings of the Schiff base are planar and their
main planes deviate by ca. 1.68, 1.18, 4.48 and 4.28 (in 2)
and by 3.18 (in 3) from co-planarity.
2
The least-squares equation of the plane defined by the atoms
C(13), N, O and P is (ꢀ
˚
5.6591 (deviations from the plane are as follows: C(13), 0.026 A; N,
/
0.4707)XOꢃ
/
(0.8614)YOꢃ
/
(ꢀ
/
0.1909)ZOꢂ
/
In the unit cell of 3×
/
CH2Cl2, the [Pd{C6H4Ã
/
CHÄ
/
NÃ
/
ꢀ
ꢀ/
/
˚
˚
˚
0.020 A).
0.030 A; O, 0.024 A and P, ꢀ
/
(C6H4Ã2ÃO)}(PPh3)] molecules are packed in such a
/
/

86
C. Lo´pez et al. / Journal of Organometallic Chemistry 681 (2003) 82ꢁ90
/
Fig. 3. Molecular structure of 3 and atom numbering scheme. CH2Cl2
molecule as well as the hydrogen atoms have been omitted for clarity.
way that the distance between the C(30)Ã
/
H(30A) bond
of one molecule and the phenyl ring defined by the set of
˚
C(13) (2.744 A) of a neighbouring unit
atoms C(8)Ã
suggests, according to the literature [14], the existence of
a CÃHꢀ ꢀ ꢀp interaction; a similar type of interaction is
also found between the C(32)ÃH(32A) bond of the
CH2Cl2 molecule and the C(14)ÃC(18) ring of the PPh3
/
/
/
/
ligand. Despite this arrangement of molecular units, the
˚
shortest intermolecular Pdꢀ ꢀ ꢀPd separation in 2 (7.10 A)
clearly exceeds the sum of their van der Waals radii [9],
thus suggesting that there is no direct interaction
between the two metals.
Recently, macromolecules arising from the assembly
of potentially bridging ligands and monomeric pallada-
cycles with [C(sp2, phenyl), N]ꢀ or [S, C(sp2, phenyl),
S]ꢀ groups have been described [4]. In the view of these
facts and the great ability of 2 to react with phosphine
ligands (i.e. PPh3), we decided to elucidate the potential
use of 2 as a supplier of building blocks for supramo-
lecular architectures; with this aim we studied the
reactivity of 2 with the diphosphine dppf.
Treatment of CHCl3 solution of 2×
(in a 2: dppf molar ratioꢂ0.5) at room temperature
/
2CHCl3 with dppf
/
(20 8C) produced after evaporation a deep-purple solid
(4). Its elemental analyses were consistent with those
expected
[{Pd[C6H4Ã
for
CHÄ
the
heterotrimetallic
compound
/
/
NÃ(C6H4Ã
/
/
2-O)]}2(m-dppf)] (4), in
Fig. 2. Partial view of the 1H-NMR spectra (600 MHz) of 2×
the range 6.25ꢁ7.52 ppm at different temperatures (Tꢂ298, 278, 248
/CHCl3 in
/
/
and 223 K). Labelling of the signals corresponds to those shown in
Scheme 1. The asterisks denote the additional weak signals detected at
low temperatures (see text).
Fig. 2

C. Lo´pez et al. / Journal of Organometallic Chemistry 681 (2003) 82ꢁ
/90
87
Table 2
Table 3
UVꢁvis spectroscopic data for compounds under study: wavelengths
(li , in nm) and extinction coefficients (oi )
˚
Selected bond lengths (A) and angles (8) for 3×
deviation parameters are given in parenthesis)
/
CH2Cl2 (standard
/
Selected bond lengths
Compound
l1 (o1)
l2 (o2)
l3 (o3)
PdÃ
PdÃ
OÃ
NÃ
C(1)Ã
C(3)Ã
C(7)Ã
C(9)Ã
C(11)Ã
C(13)Ã
/
C(13)
1.938(8)
1
276 (9184)
280 (8406)
291 (6638)
278 (9838)
352 (8309)
350 (4256)
340 (2765)
334 (6584)
ꢁ
/
/
O
2.070(5)
1.360(10)
1.402(9)
1.471(10)
1.334(10)
1.463(9)
1.395(10)
1.382(10)
1.460(10)
1.995(6)
2.070(5)
1.360(10)
1.189(8)
1.416(11)
1.408(10)
1.367(10)
1.384(10)
1.366(10)
2 a
3
532 (2187)
526 (2172)
496 (1669)
/
C(1)
C(6)
/
4
/
C(2)
C(4)
C(8)
C(10)
/
a
Additional bands at lꢂ
/
336 nm (sh) (oꢂ
/4256) and 464 nm (oꢂ
/
/
2488).
/
/C(12)
/C(8)
transitions, while the band at lower energies (in the
530 nm) with extinction coefficients (o)
PdÃ
PdÃ
/
N
range 490ꢁ
/
/
P
greater than 103 are assigned, according to the literature
[15], to metal to ligand charge transfer transitions
(MLCT) from the 4d(p) orbitals of the palladium(II)
C(1)Ã
NÃC(7)
C(2)Ã
C(4)Ã
C(8)Ã
/C(6)
/
/
C(3)
C(5)
C(9)
/
to a p* orbital of the ligand. The spectrum of 2×
was more complex than those of 3 and 4, since two
additional shoulders at lꢂ336 and 464 nm were also
detected in the spectrum. This finding may be related to
the presence of smaller units in solution (i.e. dimers or
trimers).
To sum up, the results presented here provide
conclusive evidence of the formation of a tetranuclear
cyclopalladated compound arising from the assembly of
four palladacyclic blocks with a [C, N, O]2ꢀ ligand. This
type of coordination, also present in 3 and 4, is not
common in the literature. On the other hand, it is well-
known that some palladacycles containing planar ter-
dentate [C, N, X]ꢀ ligands may be potentially useful
from the point of view of their optical properties (i.e.
their luminescence) [15]. Besides that, the presence of a
/
2CHCl3
/
C(10)Ã
/
C(11)
/
C(12)Ã
/
C(13)
Selected bond angles
C(13)ÃPdÃ
OÃPdÃ
PdÃOÃ
C(1)ÃC(6)Ã
NÃC(7)ÃC(8)
C(8)ÃC(13)ÃPd
NÃPdÃ
C(13)ÃPdÃ
OÃC(1)ÃC(6)
C(6)ÃNÃC(7)
C(7)ÃC(8)ÃC(13)
OÃPdÃC(13)
/
/
N
81.4(3)
101.33(16)
108.7(5)
111.8(8)
118.5(8)
138.1(7)
80.5(2)
/
/P
/
/C(1)
/
/N
/
/
/
/
/
/
O
/
/
P
96.8(3)
/
/
124.7(8)
128.8(7)
110.4(7)
161.9(3)
/
/
/
/
/
/
s(PdÃ
/
C) and a s(PdÃ
/
O) bonds in 2, 3 and 4 has an
N or O) ligands}
which two monomeric units ‘‘[Pd{C6H4Ã
(C6H4Ã2-O)}]’’ are connected by a bridging dppf ligand.
The 31P{1H}-NMR of 4 showed a singlet (at dꢂ
29.2
ppm) downfield-shifted from the free ligand, thus
suggesting that the two phosphorous atoms are equiva-
lent. The position of this signal was consistent with the
values reported for related palladium(II) compounds
containing a bridging dppf ligand [4a,6].
/
CHÄ
/
NÃ
/
additional interest {with [C, X]ꢀ (Xꢂ
/
/
due to their potential use as precursors or intermediates
in organic synthesis [16] as well as in homogeneous
catalysis [17].
/
3. Experimental
In a first attempt to elucidate the effect produced by
the coordination of the Schiff base to the palladium(II)
and the influence of the remaining ligands bound to the
palladium upon the spectroscopic properties of the
3.1. Materials and methods
Benzaldehyde and H2NÃ
/
C6H4Ã
/
2-OH were obtained
from Aldrich and used as received. All the solvents used
in this work were dried and distilled before use.
Elemental analyses (C, H and N) were carried out at
the Servei de Recursos Cientifics i Te`cnics (Universitat
Rovira i Virgili, Tarragona). Infrared spectra were
obtained with a Niccolet Impact-400 instrument using
KBr disks. Proton and the two-dimensional NMR
complexes, we decided to register the UVꢁ
/vis spectra
of the free ligand and compounds 2ꢁ4 in CH2Cl2. A
/
summary of the results obtained from these studies is
presented in Table 3.
The UVꢁvis spectrum of free ligand showed two
/
intense bands centred at 276 and 352 nm which are
assigned to charge transfer transitions. For compounds
3 and 4 three absorption bands were observed in the
experiments ({1Hꢁ1
/
H} COSY and NOESY) and the
C} heteronuclear correlations (HMBC and
{1Hꢁ13
/
spectra. Two of them, which appeared in the range 270ꢁ
/
HSQC) were recorded with a Bruker Avance 600 MHz
instrument at 20 8C using CDCl3 (99.9%) as solvent and
350 nm, are assigned to metal-perturbed intraligand

88
C. Lo´pez et al. / Journal of Organometallic Chemistry 681 (2003) 82ꢁ90
/
1
SiMe4 {for H and 13C} as reference, and the variable
temperature experiments were performed in the range
6.51 [td, 1H, H5?, Jꢂ
H6?, Jꢂ7.8 and 1.2 Hz] ppm. 13C{1H}-NMR data [18]:
dꢂ162.2 [Ã
], 155.4 [C1], 138.6 [C2], 127.0 [C3],
/
7.5 and 1.1 Hz] and 6.37 [d, 1H,
/
223ꢁ
/
298 K using a Bruker Avance 600 MHz and a
/
/
CHÄ
/
NÃ
/
Varian 300 MHz instruments using the same solvent as
for the 1H-NMR spectra at 298 K. 31P{1H}-NMR
spectra of 3 and 4 were obtained with a Bruker
250DRX instrument using CDCl3 as solvent and
132.5 [C3], 124.1 [C4], 131.0 [C5], 124.3 [C6], 151.0 [C1?],
136.2 [C2?], 127.0 [C3?], 117.2 [C4?], 127.0 [C5?] and 124.2
[C6?] ppm.
trimethylphosphite as reference (d 31P{P(OMe)3}ꢂ
/
3.1.3. Preparation of [Pd{C6H4Ã
O)}(PPh3)] (3)×CH2Cl2
Triphenylphosphine (22 mg, 8.4ꢄ
added to a CHCl3 solution (10 ml) of 2×
mg, 2.10ꢄ
10ꢀ5 mol). The mixture was stirred at
/
CHÄ
/
NÃ
/
(C6H4Ã
/
2-
140.17 ppm). Mass spectra [(FABꢃ) for 1ꢁ
/
4, ES (in
/
CHCl3) and MALDI-TOF for 2] were obtained with a
VG-Quatro-Fissions (for FABꢃ) or with a Voyager DE
RP Applied Biosystems (for MALDI-TOF) instru-
ments. The matrix used in each case was 3-nitrobenzy-
lalcohol (NBA) (for FABꢃ mass spectra) and 2,5-
dihydroxibenzoic acid (DBA) (for MALDI-TOF).
/
10ꢀ5 mol) was
/2CHCl3 (30
/
(20 8C) for 30 min and filtered out. The filtrate was
concentrated to dryness on a rotary evaporator. The
residue was then treated with CH2Cl2 (4 ml) and the
addition of n-hexane (:2 ml) followed by the slow
/
3.1.1. Preparation of C6H5Ã
Benzaldehyde (0.305 g, 4.35ꢄ
(C6H4Ã2-OH) (0.475 g, 4.35ꢄ
10ꢀ3 mol) were dissolved
in ethanol (30 ml). The mixture was refluxed for 1 h and
filtered out. The filtrate was concentrated to ca. 10 ml
on a rotary evaporator and then allowed to evaporate at
20 8C. The solid formed was collected and air-dried
(yield: 0.725 g, 84.5%). Anal. (%): C, 79.3; H, 5.7; N, 7.3;
C13H11NO requires: C, 79.2; H, 5.6; N, 7.1%. MS
/
CHÄ
/
NÃ
/
(C6H4Ã
/
2-OH) (1)
evaporation of the solvents produced microcrystals of 3,
which were collected and dried in vacuum (yield: 36 mg,
/
10ꢀ3 mol) and H2NÃ
/
/
/
74%). Anal. (%): C, 66.1; H, 4.4; N, 2.6; C31H24NOPPd×
/
CH2Cl2 requires: C, 66.0; H, 4.3; N, 2.5%. MS (FABꢃ):
m/zꢂ
/
[{MÃ
/
CH2Cl2}]ꢃ. IR (in cmꢀ1): 1601 [n(ꢀ
)]. H-NMR data [18]: dꢂ7.95 [d, 1H, ÃCHÄNÃ
4J(HÃ 8 Hz], 6.02 [dd, 1H, H3, Jꢂ
P)ꢂ
6.78 [td, 1H, H4, Jꢂ
Jꢂ
8.0 and 1.0 Hz], 7.12 [dd, 1H, H6, Jꢂ
Hz], 6.49 [dd, 1H, H3?, Jꢂ
7.6 and 1.1 Hz], 6.31 [td, 1H,
H4, Jꢂ7.6 and 1.1 Hz], 6.81 [td, 1H, H5?, Jꢂ
7.6 and 1.1
Hz] and 7.64 [dd, 1H, H6?, Jꢂ
7.6 and 1.1 Hz], 5.12 [s,
1H, CH2Cl2] and 7.28ꢁ7.53 [m, 15H, aromatic protons
of the PPh3] ppm. 13C{1H}-NMR data [18]: dꢂ
170.2
], 157.2 [C1], 137.6 [C2], 127.8 [C3], 124.1 [C4],
/
CÄ
/
1
NÃ
/
/
/
/
/
,
/
/
/
8.0 and 1.0 Hz],
8.0 and 1.0 Hz], 6.91 [td, 1H, H5,
8.0 and 1.0
/
/
/
(FABꢃ): m/zꢂ
H)] and 1625 [n(ꢀ
8.68 [s, 1H, ÃCHÄNÃ
/
197 [Mꢃ]. IR (in cmꢀ1): 3376 [n(OÃ
/
/
1
/
CÄ
/
NÃ
/
)]. H-NMR data [18]: dꢂ
/
/
/
3
/
/
/
], 7.91 [d, 2H, H2 and H6, Jꢂ
/
/
7.5 Hz], 7.50 [m, 2H, H3 and H5, Jꢂ
/
7.5 Hz], 7.21 [m,
8.0 Hz], 6.90 [t, 1H, H4?,
/
3
1H, H4], 7.02 [d, 1H, H3?, Jꢂ
/
/
3
3Jꢂ
/
8.0 Hz], 7.20 [t, 1H, H5?, Jꢂ
/8.0 Hz], 7.30 [d, 1H,
[Ã
/
CHÄ
/
NÃ
/
3
3
H6?, Jꢂ
/
8.0 Hz] and 7.47 [OH, partially overlapped by
the signal at dꢂ
7.50] ppm. 13C{1H}-NMR data [18]:
129.6 [C5], 126.7 [C6], 130.4 [C1?], 152.6 [C2?], 115.5 [C3?],
116.7 [C4?], 130.4 [C5?], 129.5 [C6?], 123.08, 128.4, 132.0
and 134.9 [Ca, Cb, Cc and Cd of the PPh3] ppm. 31P{1H}-
/
dꢂ
/
157.1 [Ã
/
CHÄ
/
NÃ
/
], 152.2 [C1], 128.7 [C2 and C6],
131.4 [C3 and C5], 128.8 [C4], 135.7 [C1?], 135.4 [C2?],
118.5 [C3?], 114.9 [C4?], 129.4 [C5?] and 115.6 [C6?] ppm.
NMR data: dꢂ34.4 ppm, s.
/
3.1.4. Preparation of [{Pd[C6H4Ã
O)]}2(m-dppf)] (4)
dppf (23 mg, 5.2ꢄ
solution (10 ml) containing 2×
/
CHÄ
/
NÃ
/
(C6H4Ã
/
2-
3.1.2. Preparation of [Pd{C6H4Ã
O)}]4 (2)×2CHCl3
Pd(AcO)2 (171 mg, 7.6ꢄ
7.6ꢄ
10ꢀ4 mol) were suspended in methanol (HPLC
grade, 20 ml) and refluxed for 2 h. The solid formed was
collected by filtration and air-dried. Then, it was
dissolved in CHCl3 (20 ml) and filtered through Celite.
Evaporation of the filtrate at 20 8C gave red prisms of 2
(yield: 158 mg, 60.2%). Anal. (%): C, 45.0; H, 2.7; N, 4.0;
C54H38Cl6N4O4Pd4 requires: C, 44.9; H, 2.6; N, 3.9%.
/
CHÄ
/
NÃ
/
(C6H4Ã
/
2-
/
/
10ꢀ5 mol) was added to a CHCl3
/
10ꢀ4 mol) and 1 (150 mg,
/
2CHCl3 (30 mg, 2.1ꢄ
/
/
10ꢀ5 mol). The reaction mixture was stirred at room
temperature for 6 h. After this period the non-dissolved
materials were removed by filtration and discarded and
the purple filtrate was concentrated on a rotary eva-
porator to ca. 2 ml. Slow evaporation of the solvent
produced the precipitation of violet thin needles of 4
(yield: 42 mg, 71.6%). Anal. (%): C, 62.3; H, 4.1; N, 2.5;
C60H46N2O2FeP2Pd2 requires: C, 62.2; H, 4.01; N, 2.4%.
MS (FABꢃ): m/zꢂ
(MALDI-TOF): m/zꢂ
[{MÃ
2(CHCl3)}3/4]ꢃ and 604 [{MÃ
IR (in cmꢀ1): 1595 and 1582 [n(ꢀ
CÄ
data [18] at 298 K: dꢂ7.11 [s, 1H, ÃCHÄ
1H, H3, Jꢂ7.8 and 1.2 Hz], 6.82 [td, 1H, H4, Jꢂ
and 1.2 Hz], 6.93 [td, 1H, H5, Jꢂ
7.8 and 1.2 Hz], 7.48
[dd, 1H, H6, Jꢂ7.8 and 1.2 Hz], 6.90 [dd, 1H, H3?, Jꢂ
7.5 and 1.1 Hz], 6.34 [td, 1H, H4?, Jꢂ
7.5 and 1.1 Hz],
/
1206 [{MÃ
/
2(CHCl3)}]ꢃ; MS
/
1206 [{MÃ
/
2(CHCl3)}]ꢃ, 905
MS (FABꢃ): m/zꢂ
/
1158 [M]ꢃ. IR (in cmꢀ1): 1608
)]. H-NMR data [18]: dꢂ7.90 [d, 2H, Ã
10.4 Hz], 5.95 [dd, 2H, H3, Jꢂ
7.8 and 1.1 Hz], 6.78 [td, 2H, H4, Jꢂ
7.8 and 1.1 Hz],
6.91 [td, 2H, H5, Jꢂ7.8 and 1.1 Hz], 7.10 [dd, 2H, H6,
Jꢂ 8.0 and 1.0
7.8 and 1.1 Hz], 6.55 [dd, 2H, H3?, Jꢂ
Hz], 6.39 [td, 2H, H4?, Jꢂ
8.0 and 1.0 Hz], 6.71 [td, 2H,
H5?, Jꢂ8.0 and 1.0 Hz], 7.64 [dd, 2H, H6?, Jꢂ
8.0 and
1
/
/
2(CHCl3)}/2]ꢃ.
[n(ꢀ
/
CÄ
/
NÃ
/
/
/
1
4
/
/
NÃ
/)]. H-NMR
CHÄNÃ
/
/
, J(HÃ
/
P)ꢂ
/
/
/
/
/
NÃ
/
], 6.40 [dt,
7.8
/
/
/
/
/
/
/
/
/
/
/
/
/

C. Lo´pez et al. / Journal of Organometallic Chemistry 681 (2003) 82ꢁ
/90
89
1.0 Hz], 5.16 [d, 4H, H2 and H5 (dppf), Jꢂ
[d, 4H, H3 and H4 (dppf), Jꢂ
1.3 Hz] and 7.28ꢁ
20H, aromatic protons of the PPh3] ppm. 13C{1H}-
],
/
1.3 Hz], 4.23
were assumed as observed applying the condition I ꢀ
/
/
/7.53 [m,
2s(I). Three reflections were measured every 2 h as
orientation and intensity control, and no significant
intensity decay was observed. Lorentz polarisation
corrections were performed but absorption corrections
were not.
The structures were solved by direct methods using
SHELXS computer program [19] and refined by full-
matrix least-squares method with the SHELX97 computer
program [20] using 8382 reflections (very negative
intensities were not assumed). The function minimised
NMR data [18] (selected data): dꢂ
/
174.0 [Ã
/
CHÄ
/
NÃ
/
157.8 [C1], 137.8 [d, C2], 138.9 [C3], 124.6 [C4], 128.1
[C5], 126.9 [C6], 130.8 [C1?], 150.8 [C2?], 115.9 [C3?], 113.6
[C4?], 131.4 [C5?], 129.5 [C6?], 73.1, 75.6 and 75.9 (three
doublets due to the three types of 13C nuclei of the dppf)
ppm. 31P{1H}-NMR data: dꢂ
29.2 ppm, s.
/
3.2. Crystallography
2
2 2
was awjjFoj ꢀ
(for 2×2CHCl3) and wꢂ
CH2Cl2) and Pꢂ
/
jFcj j , with wꢂ
/
[s2(I)ꢃ(0.0942P)2]ꢀ1
/
/
/
[s2(I)ꢃ(0.0001P)2]ꢀ1 (for 3×
/
/
A prismatic crystal of 2×
Table 4) was selected and mounted on a Enraf-Nonius-
CAD 4 four-circle diffractometer (for 3×CH2Cl2). In-
tensities were collected with graphite monochromatised
MoꢁKa radiation using v/2U scan technique. For 2×
2CHCl3, the number of reflections measured in the
range 2.0085U 529.958 was 8953 of which 8149 were
assumed as observed applying the condition I ꢀ2s(I),
while for 3×CH2Cl2 the number of reflections measured
in the range 2.0885U 530.158 was 8383 of which 1673
/
2CHCl3 or 3×/CH2Cl2 (sizes in
2
2
/
(jFoj ꢃ2jFcj )/3, and f, f ? and f ??
/
were taken from the literature [21].
/
For 3 all the hydrogen atoms were computed and
refined using a riding model, with an isotropic tempera-
ture factor equal to 1.2 times the equivalent temperature
factor of the atom linked to it. The final R values as well
as further details concerning the resolution and refine-
ment of the crystal structures are presented in Table 4.
/
/
/
/
/
/
/
/
4. Supplementary materials
Table 4
Crystal data and details of the refinement of the crystal structures of 2×
2CHCl3 and 3×CH2Cl2
/
Crystallographic data for the structural analyses have
been deposited at the Cambridge Crystallographic Data
Centre, CCDC Nos. 196567 and 205347. Copies of
this information can be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge CB2
/
2×
/
2CHCl3
3×CH2Cl2
/
Empirical formula
C54H38Cl6N4O4Pd4
1445.22
293(2)
C32H26Cl2NOPPd
648.81
293(2)
Mw
T
1EZ, UK (Fax: ꢃ44-1233-336033; e-mail: deposit@
/
˚
Wavelength (A)
0.71069
Monoclinic
P21/n
0.71069
Monoclinic
P21/c
ccdc.ac.uk or www: http://www.ccdc.cam.ac.uk).
Crystal system
Space group
Unit cell dimensions
˚
a (A)
20.690(4)
11.530(14)
21.782(7)
90
15.361(3)
8.30(2)
22.911(6)
90
Acknowledgements
˚
b (A)
˚
c (A)
We are grateful to the Ministerio de Ciencia y
Tecnolog´ıa of Spain (Grant BQU2000-0654) and to
the Generalitat de Catalunya (project 2001-SGR-0054)
for financial support.
aꢂ/g (8)
b (8)
Volume (A )
93.80
98.61(2)
2887(7)
4
3
˚
5185(7)
4
1.851
Z
Dcalc (Mg mꢀ3
F(0 0 0)
Crystal size (mm3)
)
1.439
1312
2832
0.1ꢄ/0.1ꢄ
/
0.1
0.1ꢄ/0.1ꢄ
/0.2
References
Theta range for data 2.00ꢁ
/29.95
2.08ꢁ/30.15
collection (8)
Number of reflections 8953
collected
8382
[1] (a) J.M. Lehn, Supramolecular Chemistry, VCH, Weinheim,
1995See for example: ;
Number of unique re- 8149 [Rint
flections
ꢂ
/
0.0641]
8382 [Rint
ꢂ0.0589]
/
(b) L. Fabbrizzi, A. Poggi, Transition Metals in Supramolecular
Chemistry, vol. 448, Kluwer Academic Publishers, Dordrecht,
1994;
Number of data
Number of para-
meters
8149
609
8382
343
(c) M. Eddaouli, D.B. Moler, H. Li, B. Chen, T.M. Reineke, M.
O’Keefe, O.M. Yaghi, Acc. Chem. Res. 34 (2001) 319;
(d) A.J. Blake, N.R. Champness, P. Hubberstey, W.S. Li, M.A.
Goodness of fit on F2 0.927
Final R indices [I ꢀ R1ꢂ0.0497, wR2ꢂ
0.1352
R1ꢂ0.1375, wR2ꢂ
0.1685
0.979 and ꢀ
0.784
/
/
/
R1ꢂ
0.0422
R1ꢂ0.3601, wR2ꢂ
0.0715
0.729 and ꢀ
/
0.0584, wR2ꢂ
/
Withersby, M. Schroder, Coord. Chem. Rev. 183 (1999) 117;
¨
(e) P.J. Hagrman, D. Hagrman, J. Zubieta, Angew. Chem. Int.
Ed. 38 (1999) 2638.
2s(I)]
R indices (all data)
/
/
/
/
[2] (a) L. Carlucci, G. Ciani, F. Porta, D.M. Proserpio, L. Santa-
gostini, Angew. Chem. Int. Ed. 41 (2002) 1907;
(b) M. Fujita, K. Ogura, Coord. Chem. Rev. 148 (1996) 249.
Largest difference
peak and hole
/
1.093
/
0.645

90
C. Lo´pez et al. / Journal of Organometallic Chemistry 681 (2003) 82ꢁ90
/
[3] J.W. Canary, B.C. Gibb, in: K.D. Karlin (Ed.), Progress in
(d) X. Riera, A. Caubet, C. Lo´pez, V. Moreno, E. Freisinger, M.
Willemann, B. Lippert, J. Organomet. Chem. 629 (2001) 97.
[11] (a) J. Vicente, J.A. Abad, A. Frankland, M.C. Ram´ırez de
Arellano, Chem. Eur. J. 5 (1999) 3066;
Inorganic Chemistry, vol. 45, Wiley, New York, 1997, p. 1.
[4] (a) M. Lo´pez-Torres, A. Ferna´ndez, J.J. Ferna´ndez, A. Sua´rez, S.
Castro-Juiz, J.M. Vila, M.T. Pereira, Organometallics 20 (2001)
1350;
(b) J. Vicente, A. Arcas, D. Bautista, M.C. Ram´ırez de Arellano,
J. Organomet. Chem. 663 (2002) 164.
(b) J.R. Hall, S.J. Loeb, G.K.H. Shimizu, G.P.A. Yap, Angew.
Chem. Int. Ed. 37 (1998) 121.
[12] T.H. Allen, O. Kennard, Chem. Des. Automat. News 8 (1993)
146.
[5] (a) R.F. Carina, A.F. Williams, G. Bernardinelli, Inorg. Chem. 40
(2001) 1826;
[13] G. Wilkinson, F.A. Stone, W.W. Abel (Eds.), Comprehensive
Organometallic Chemistry: The Synthesis, Reactions and Struc-
tures of Organometallic Compounds, Vol. 6, Pergamon Press,
New York, 1982, p. 236.
(b) C. Ferna´ndez-Rivas, D.J. Ca´rdenas, B. Mart´ın-Matute, A.
Monge, E. Gutie´rrez-Puebla, M.A. Echevarren, Organometallics
20 (2001) 2998;
(c) H.A. Ankersmit, P.T. Witte, H. Kooijman, M.T. Lakin, A.L.
Spek, K. Goubitz, K. Vrieze, G. Van Koten, Inorg. Chem. 35
(1996) 6035;
[14] S.J. Calson, T. Lu, R.L. Luck, Inorg. Chem. Commun. 6 (2003)
455.
[15] (a) M. Maestri, C. Deutsche-Cornioley, A. Von Zelewski, Coord.
Chem. Rev. 11 (1991) 117;
(d) C. Lo´pez, A. Caubet, R. Bosque, X. Solans, M. Font-Bard´ıa,
J. Organomet. Chem. 645 (2002) 146;
(b) F. Neve, A. Crispini, C. Di Pietro, S. Campagna, Organome-
tallics 21 (2002) 3511;
(e) T. Kawamoto, I. Nagasawa, H. Kuma, Y. Kushi, Inorg.
Chem. 35 (1996) 2427;
(c) D. Song, Q. Wu, A. Hook, I. Kosin, S. Wang, Organometallics
20 (2001) 4683.
(f) T. Kawamoto, I. Nagasawa, H. Kuma, Y. Kushi, Inorg. Chim.
Acta 265 (1997) 163;
[16] (a) I. Omae, Applications of Organometallic Compounds, Wiley,
Chichester, UK, 1998;
(g) F. Hueso-Urena, N.A. Illan-Cabeza, M.N. Moreno-Carretero,
A.L. Penas-Chamorro, R. Faure, Inorg. Chem. Commun. 2
(1999) 323;
(b) A.D. Ryabov, Synthesis (1985) 233 and references therein;
(c) J. Spencer, M. Pfeffer, Adv. Met. Org. Chem. 6 (1998) 103;
(d) K.E. Torraca, S.I. Kuwabe, S.L. Buchwald, J. Am. Chem.
Soc. 122 (2000) 12907;
(h) J. Vicente, M.C. Lagunas, E. Bleuel, M.C. Ram´ırez de
Arellano, J. Organomet. Chem. 648 (2001) 62.
[6] A. Ferna´ndez, D. Va´zquez-Garc´ıa, J.J. Ferna´ndez, M. Lo´pez-
Torres, A. Sua´rez, S. Castro-Ju´ız, J.M. Vila, New J. Chem. 26
(2002) 398.
(e) Q. Shelby, N. Kataoka, G. Mann, J. Hartwig, J. Am. Chem.
Soc. 122 (2000) 10718;
(f) J.L. Serrano (Ed.), Metallomesogens: Synthesis, Properties and
Applications, VCH, Weinheim, Germany, 1996;
(g) B.B. Eran, D. Singer, K. Praefcker, Eur. J. Inorg. Chem.
(2001) 111.
[7] H. Yang, M.A. Khan, K.M. Nicholas, Chem. Commun. (1992)
210.
[8] S. Pawlenko, Houben-Weyl. Methoden der organische Chemie:
organische Stickstoff Verbindunge mit einer C,N Doppelbindung,
Georg Thieme, Stuttgart (Germany), 1990, p. 222 (Band E 14/b,
Teil 1; Chapter 1).
[17] P.W. Jolly, G. Wilke, W.A. Kermann, B. Cornils (Eds.), Applied
Homogeneous Catalysis with Organometallic Compounds, VCH,
Weinheim, Germany, 1996.
[9] (a) A. Bondi, J. Phys. Chem. (1964) 441;
(b) A.I. Kitaigorodskii, Molecular Crystals and Molecules,
Academic Press, London, UK, 1973.
[18] Labelling of the atoms correspond to that shown in the scheme.
[19] G.M. Sheldrick, SHELXS: A Computer Program for Determina-
tion of Crystal Structures, University of Gottingen, Germany,
¨
[10] (a) J. Albert, J. Granell, J. Sales, M. Font-Bard´ıa, X. Solans,
Organometallics 14 (1995) 1393;
1997.
[20] G.M. Sheldrick, SHELX-97: A Computer Program for Determina-
(b) P.S. Pregosin, R.W. Kuntz, in: P. Diehl, E. Fluck, R. Kosfeld
(Eds.), 31P- and 13C-NMR of Transition Metal Phosphine
Complexes, Springer, Berlin, Germany, 1979;
(c) A. Ferna´ndez, E. Pereira, J.J. Ferna´ndez, M. Lo´pez-Torres, A.
Sua´rez, R. Mosteiro, J.M. Vila, Polyhedron 21 (2002) 39;
tion of Crystal Structures, University of Gottingen, Germany,
¨
1997.
[21] International Tables of X-ray Crystallography, Vol. IV, Kynoch,
Birmingham, UK, 1974, pp. 99ꢁ100.
/