Structural and dynamic studies in solution of anionic dinuclear azolato-bridged palladium(II) complexes

Article abstract of DOI:10.1016/S0022-328X(02)01772-2

Detailed analysis of the 19F-NMR spectra of the boat-shaped complexes dimethylpyrazolate (dmpz), 2), HH- (head-to-head) and HT- (head-to-tail) (NBu₄)₂[Pd₂(μ-LL)₂ R₄] (LL = 3-methylpyrazolate (mpz), 3; indazolate (indz), 4), (NBu₄)₂[Pd₂(μ-dmpz)(μ-LL) R₄] (LL = mpz, 6; indz, 7), and (NBu₄)₂ [R₂Pd(μ-LL)₂Pd (C₆F₅)₂] (LL = pz, 8; dmpz, 9) affords valuable structural information in solution. The substituents of the azolate ligands, which reduce the dihedral angle between the coordination planes of the two metals, place the endo F_ortho of different PdR₂ fragments at short distances. A single-crystal X-ray structure has been obtained for compound HT-4 and the distances between F_ortho compared with that calculated from the NMR spectra. The study of the dynamic processes for these complexes reveals the involvement of different mechanisms such as: (a) rotation of the R groups, (b) boat-boat inversion of the six-membered Pd(μ-LL)₂Pd ring, (c)σ-1,2-metallotropic shift, and (d) associative exchange of PdR2 fragments between 1 and mononuclear complexes.

Full text of DOI:10.1016/S0022-328X(02)01772-2

Journal of Organometallic Chemistry 663 (2002) 108ꢂ117
/
www.elsevier.com/locate/jorganchem
Structural and dynamic studies in solution of anionic dinuclear
azolato-bridged palladium(II) complexes
Raquel de la Cruz, Pablo Espinet ꢀ, Ana M. Gallego, Jose M. Mart´ın-Alvarez,
Jesu´s M. Mart´ınez-Ilarduya
´ ´
Departamento de Quımica Inorganica, Facultad de Ciencias, Universidad de Valladolid, E-47005 Valladolid, Spain
Received 23 May 2002; accepted 23 July 2002
Dedicated to our former mentor and always friend Pascual Royo, who pentafluorophenylated our lives
Abstract
Detailed analysis of the 19F-NMR spectra of the boat-shaped complexes (NBu4)2[Pd2(m-LL)2R4] (Rꢁ
pyrazolate (pz), 1; dimethylpyrazolate (dmpz), 2), HH- (head-to-head) and HT- (head-to-tail) (NBu4)2[Pd2(m-LL)2R4] (LLꢁ
methylpyrazolate (mpz), 3; indazolate (indz), 4), (NBu4)2[Pd2(m-dmpz)(m-LL)R4] (LLꢁmpz, 6; indz, 7), and (NBu4)2[R2Pd(m-
LL)2Pd(C6F5)2] (LLꢁpz, 8; dmpz, 9) affords valuable structural information in solution. The substituents of the azolate ligands,
/
3,5-C6Cl2F3) (LLꢁ
/
/3-
/
/
which reduce the dihedral angle between the coordination planes of the two metals, place the endo Fortho of different PdR2
fragments at short distances. A single-crystal X-ray structure has been obtained for compound HT-4 and the distances between
Fortho compared with that calculated from the NMR spectra. The study of the dynamic processes for these complexes reveals the
involvement of different mechanisms such as: (a) rotation of the R groups, (b) boatꢂboat inversion of the six-membered Pd(m-
/
LL)2Pd ring, (c) s-1,2-metallotropic shift, and (d) associative exchange of PdR2 fragments between 1 and mononuclear complexes.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Palladium; Pyrazol; Indazol; Fluxionality; Through-space coupling
1. Introduction
dynamic behaviors in solution for such complexes are
very scarce [3].
We have reported recently a reinvestigation of the
Dinuclear complexes in which the metal centers are
disposed near to each other by bridging ligands have
attracted considerable attention. This is mainly asso-
ciated to the expectation that the cooperative effects
between the two metal units may have a profound
influence on the reactivity and other properties of these
complexes. Among the ligands capable of forming these
complexes, azolates have been used extensively [1], and
consequently a large amount of structural information is
available. The main structural feature for dinuclear
bis(azolato)complexes is the boat-like conformation of
solution behavior of (NBu4)2[M2(m-LL)2R4] (Mꢁ
Pd, Pt; LLꢁpyrazolate (pz), dimethylpyrazolate
(dmpz), 3-methylpyrazolate (mpz), indazolate (indz);
RꢁC6F5, 2,4,6-C6F3H2) [4], but the complete study of
/
Ni,
/
/
these systems was not carried out due to the complexity
of their 19F-NMR spectra. In order to get a deeper
insight into the solution behavior and structures we
decided to investigate the related 3,5-dichlorotrifluor-
ophenyl (R from now) palladium complexes [5]. These
give rise to more simple 19F-NMR spectra due to the
simpler spin system of 19F nuclei within the R group and
to the fact that the couplings between these nuclei (in
meta positions) are usually less than the half-height
the ‘M(Nꢀ/N)2M’ six-membered metallacycle [2], which
has a remarkable flexibility allowing a wide range of
intermetallic distances. Surprisingly, reports describing
band-width. Thus, through-space inter-ring Fꢀ
/
F cou-
plings can be easily observed [6], and computer simula-
tions to obtain activation parameters for different
processes can be carried out. We have reported recently
ꢀ Corresponding author. Tel.: ꢃ
3013
E-mail address: espinet@qi.uva.es (P. Espinet).
/
34-983-42-3231; fax: ꢃ34-983-42-
/
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 7 7 2 - 2

R. de la Cruz et al. / Journal of Organometallic Chemistry 663 (2002) 108ꢂ
/117
109
the typical patterns for static 19F-NMR spectra in the
Fortho region for cis-PdR2 fragments in square-planar
complexes with different symmetry elements giving rise
to different chemical or magnetic equivalence situations,
and the influence of several dynamic processes in these
Fortho signals [7].
relative head-to-head (HH) and head-to-tail (HT) dis-
position of the bridging ligands were present for the
complexes with two unsymmetrical substituted azolates
(3, 4). The molar ratio between the major and the minor
isomer is close to 10:1 reflecting the similar behavior of
mpz and indz ligands.
The compounds described in this paper allow us to
carry out a structural study of anionic dinuclear azolato-
Single crystals of the HT complex (NBu4)2[Pd2(m-
indz)2R4] (HT-4) were obtained by layering a dichlor-
omethane solution with hexane. An X-ray diffraction
analysis of one of them showed the boat conformation
of the central Pd2N4 ring (vide infra). The solutions
prepared at 203 K from crystalline samples obtained as
described above exhibit only the major isomer (HT-4)
while the minor isomer (HH-4) is formed by isomeriza-
tion, slowly on standing at low temperature, or rapidly
on raising the temperature, until the equilibrium is
reached. These results are in accord with our previous
assignation of isomers made for the analogous com-
plexes with C6F5 and C6F3H2 [4].
bridged palladium(II) complexes in solution using Fꢀ
/F
inter-ring couplings. These are sensitive to the distor-
tions produced by the presence of substituents in the
azolate ligands. In addition, the dynamic behavior of
these complexes has been investigated, revealing the
occurrence of the following processes: (a) exchange of
endo and exo Fortho, (b) exchange of HT and HH
isomers, and (c) exchange of PdR2 fragments, for which
different mechanisms have been proposed.
2. Results and discussion
The room temperature 19F-NMR spectra of 1ꢂ
7 in
/
(CD3)2CO exhibit almost in all cases one or several
broad bands in the Fortho region, suggesting the
occurrence of fluxional processes. Their variable tem-
perature 19F-NMR spectra have been recorded in the
2.1. Synthesis of the complexes
The complexes (NBu4)2[Pd2(m-LL)2R4] (LLꢁ
/
pz, 1;
dmpz, 2; mpz, 3; indz, 4) were obtained by reaction of
[PdR2(COD)] with a methanol solution of H(LL) and
NBu4OH in 1:1:1 ratio (1, 3, 4), or by treatment of a
solution of cis-[PdR2(Hdmpz)2] in acetone with
NBu4OH in 1:1 ratio (2) [8]. Mixtures of 2 and
(NBu4)2[Pd2(m-dmpz)(m-OH)R4] (5) were obtained
when the first method was used for Hdmpz. However,
the reaction of [PdR2(COD)] with a methanol solution
of Hdmpz and NBu4OH in 2:1:2 ratio afforded only 5.
range 180ꢂ328 K and provide a better understanding of
/
the dynamic behavior of dinuclear pyrazolato com-
pounds, as we discuss below.
2.2.1. Crystal structure of the HT complex
(NBu4)2[Pd2(m-indz)2R4] (HT-4)
The structure of the [Pd2(m-indz)2R4]2ꢄ anion is
depicted in Fig. 1. Selected atom distances and bond
angles are collected in Table 1. The anion has two fold
symmetry and is comprised of two Pd atoms bridged by
Treatment of 5 with H(LL) (LLꢁmpz, indz) in acetone
produced the mixed complexes (NBu4)2[Pd2(m-dmpz)(m-
LL)R4] (6, 7).
/
two indazolate ligands, with a Pd(1)Á Á ÁPd(1)# separa-
˚
tion of 3.538(10) A indicative of no metalꢂ
/metal bond
In addition, (NBu4)2[R2Pd(m-LL)2Pd(C6F5)2] (LLꢁ
/
pz, 8; dmpz, 9) were detected by 19F-NMR in the
mixture of products resulting from the reaction of cis-
interaction. The two remaining coordination sites
around each Pd atom are occupied by two R ligands.
[Pd(C6F5)2(THF)2]
or
[Pd(C6F5)2(COD)]
and
(NBu4)2[Pd2(m-LL)2R4] in (CD3)2CO at room tempera-
ture, showing that these reorganization reactions pro-
ceed very fast. However, the same products 8ꢂ9 were
/
detected from mixtures of (NBu4)2[Pd2(m-LL)2R4] and
(NBu4)2[Pd2(m-LL)2(C6F5)4] only after heating in
(CD3)2CO at 323 K for several days.
2.2. Characterization of the complexes
Complexes 1ꢂ7 are white, air-stable, and were char-
/
acterized by elemental analysis, spectroscopic methods,
and measurements of the molar conductivity in acetone
1
solution. Their room temperature H-NMR spectra in
(CD3)2CO showed the characteristic resonances due to
the hydrogens of the bridging azolate groups and
indicated that the two diastereoisomers arising from
Fig. 1. ORTEP view of the anion of HT-4 (30% probability ellipsoids).

110
R. de la Cruz et al. / Journal of Organometallic Chemistry 663 (2002) 108ꢂ
/117
Table 1
a
˚
Selected interatomic distances (A) and bond angles (8) for HT-4
Bond lengths
Pd(1)ꢀC(11)
Pd(1)ꢀC(21)
Pd(1)ꢀN(1)
Pd(1)ꢀN(2)
N(1)ꢀN(2)#1
1.998(9)
2.005(10)
2.073(7)
2.080(7)
1.374(9)
Non-bonded distances
F2aꢂ
F2aꢂ
F2aꢂ
F2bꢂ
F6aꢂ
/
F2b
F2c
F2d
3.260(12)
2.770(13)
4.308(14)
4.070(14)
2.959(12)
3.538(10)
/
/
/
F2c
/
F6b
Pd(1)ꢂPd(1)#1
/
Bond angles
C(11)ꢀPd(1)ꢀC(21)
C(11)ꢀPd(1)ꢀN(1)
C(21)ꢀPd(1)ꢀN(2)
N(1)ꢀPd(1)ꢀN(2)
N(2)#1ꢀN(1)ꢀPd(1)
N(1)#1ꢀN(2)ꢀPd(1)
88.1(4)
90.3(3)
91.6(3)
90.0(3)
120.6(6)
122.1(6)
Fig. 2. Downfield Fortho (R group) signals of (NBu4)2[R2Pd(m-
a
Symmetry transformations used to generate equivalent atoms: #1
ꢄxꢃ3/2, yꢃ0, ꢄzꢃ0.
LL)2Pd(C6F5)2] (LLꢁpz (8), dmpz (9)) ((CD3)2CO, 282.35 MHz,
/
180 K) and estimated J values in Hz.
Deviation from the least-squares plane defined by the
Pd atom and the donor atoms, are 0.0071, 0.0184,
˚
complexes 8 and 9, in which the endo Fortho nuclei are
not equivalent.
The Fortho region (R group) at 180 K of 8 and 9 in
(CD3)2CO shows two signals, one singlet (upfield, F6)
and one multiplet (downfield, F2). The appearance of
the F2 signals of R (Fig. 2) is due to the presence of
ꢄ
/
0.0146, ꢄ0.0140, and 0.0173 A for Pd(1), C(11),
/
C(21), N(1) and N(2) atoms, respectively. The R rings
present Cꢀ
/
Cꢀ
/
C angles at the Cipso lower than 1208
(114.9(9) and 113.8(10)), as usually observed for perha-
logenated aryl rings [9].
inter-aryl Fꢀ
/
F couplings with the endo Fortho nuclei
The ‘Pd2N4’ ring adopts the typical boat conforma-
tion placing the endo Fortho of the PdR2 moieties at very
short distances. Consequently large through-space cou-
pling constants between these nuclei are expected [10]. In
addition, a tilt of two R aryl rings occurs to minimize
repulsions between R and the aryl ring of the indazolate.
This causes an approach of the exo Fortho (F6) in each
PdR2 moiety.
belonging to the Pd(C6F5)2 fragments. Compared with
8, the spectrum of 9 reflects the steric effect of the
methyl substituents of the dmpz ligands. These force a
reduction of the dihedral angle between the coordina-
tion planes of the two metals, bringing closer the endo
Fortho atoms on rings at different sides of the azolato
bridge (2aꢂ
/
2c, 2bꢂ
/
2d, 2bꢂ
/
2c, 2aꢂ2d). Consequently the
/
coupling constants between them increase noticeably
[11].
2.2.2. Static 19F-NMR spectra of the complexes
Complex 5 displays in its 19F-NMR spectra (in the
The complexes with symmetric azolates, 1 and 2,
display in their 19F-NMR spectra at 180 K two signals
in the Fortho region and only one signal in the Fpara
region. This is consistent with the static 19F-NMR
spectrum expected for a di-m-azolate complex with a
boat conformation and C2v symmetry (Fig. 2), which
contains four equivalent R groups and two different
types of Fortho (endo or F2 and exo or F6). These Fortho
signals are singlets with ca. 4 Hz band-width at half-
range 180ꢂ328 K) two signals in the Fortho region and
/
two signals in the Fpara region. This agrees with the
presence of a symmetry plane in the anion that relates
the two PdR2 fragments, and the existence of a low
activation process. This could be a fast envelope-shift
movement of the Pd2N2O ring (which is not planar; see
the structure of (NBu4)2[Pt2(m-OH)(m-dmpz)(C6F5)4])
[12], or a fast fluoroaryl rotation of all the R groups
around the Pdꢀ/C bond. The latter possibility is less
height [7], and are clearly more deshielded (ꢀ5 ppm)
/
likely considering the steric hindrance in the coordina-
tion environment of the Pd center [13].
The complexes with two asymmetric azolates, 3 and 4,
have a lower symmetry (C2 for the HT isomer; Cs for the
HH isomer). Four Fortho and two Fpara signals are
expected and observed for each isomer in the slow
for 2 than for 1. Unfortunately, the analysis of the
influence of the methyl substituents of the azolate
ligands cannot be made in these complexes because the
Fꢀ
/
F through-space coupling constants have no reflect
in the observed spectrum of these highly symmetric
complexes. To this end, we considered the mixed

R. de la Cruz et al. / Journal of Organometallic Chemistry 663 (2002) 108ꢂ
/117
111
Fig. 3. Fortho region of the 19F-NMR spectrum of 4 ((CD3)2CO, 282.35 MHz, 248 K) and assignment of the different signals.
exchange limit (Fig. 3). The assignment of the Fortho
signals of each R group (A and K or X and M) is made
Table 2
19Fꢀ19F couplings (in Hz) in selected dinuclear azolato-bridged
palladium complexes
easily using 19Fꢀ
/
19F EXSY (EXchange SpectroscopY)
a
experiments at higher temperatures, as we discuss later.
However, only the two upfield signals for both
isomers (exo Fortho) show the expected doublet of
doublets for the HT complex or the expected singlet
for the HH complex [7]. The downfield signals for both
isomers (endo Fortho) appear as somewhat distorted
Complex/T (K)
b
c
c
FꢀF
HT-4/248
HT-6/195
HT-7/195
2aꢂ
2aꢂ
2aꢂ
2bꢂ
2bꢂ
2cꢂ
6aꢂ
6cꢂ
/
2b
2c
2d
5.4
48.0
0.0
0.0
105.0
0.0
0.0
112.6
0.0
/
/
‘doublets’ with a large coupling constant (JAX
ꢃ
/
J
AX?ꢀ
/
/
2c
2d
2d
2.5
16.3
59.5
5.0
13.0
62.6
5.8
/
48.0
5.4
50 Hz). This is due to the non-zero through-space
coupling constant JAX (the scalar contribution for a
9JAX can be neglected). This coupling makes separate
treatment of the individual PdR2 fragments impossible,
and a spin system with eight nuclei must be considered
to simulate the downfield Fortho signals of each isomer.
The different J values estimated by simulation of the
static spectra for the HT-4 isomer (for HT-3 the results
are very similar) are collected in Table 2. These JFꢀF
/
/
6b
8.8
8.8
9.7
35.5
10.6
37.6
/
6d
a
b
c
In (CD3)2CO.
Pyrazolate substituents are located near positions a and d.
Pyrazolate substituents are located near positions a, c and d.
Table 3
Application of the Ernst’s formula to X-ray and solution data for HT-
values are roughly consistent with the Fꢀ
/
F distances
4
obtained by X-ray diffraction and confirm that, average,
the tilt of the aryl groups is maintained in solution.
However, the measured JFF values differ noticeably
from the results predicted using the Ernst’s formula and
the solid-state distances (Table 3). Probably the solid
state packing forces distort the solution structure and a
better correlation should not be expected.
X-ray data
Solution data
J (Hz) Distances (A)
a
a
˚
Distances (A)
˚
J (Hz)
F2aꢂ
F2aꢂ
F6aꢂ
/
F2b 3.260(12)
F2c 2.770(13)
F6b 2.959(12)
7.8
37.7
20.6
5.4
48.0
8.8
3.375
2.695
3.223
/
/
The simulation of the static spectra for the HH
isomers is more difficult and less informative, as these
are minor isomers with some overlapped signals, and the
magnitude of some coupling constants does not affect
significantly the appearance of the spectrum. Only the
a
Calculated by the Ernst’s formula.
large values of J(2aꢂ
bigger than in the HT isomers, need to be discussed. In
/
2c)ꢁ
/
J(2bꢂ
/
2d)ꢁ75 Hz, which are
/

112
R. de la Cruz et al. / Journal of Organometallic Chemistry 663 (2002) 108ꢂ117
/
the HH isomers both azolate substituents are situated
close to one of the Pd atoms altering the usual shape of
the boat Pd(m-NN)2Pd ring by reduction of the dihedral
angle a (Fig. 4) between the coordination plane of the
mentioned Pd atom and the least-square plane formed
by the four N atoms of the azolate rings. This distortion
produces an approach of the endo Fortho giving a more
crowded situation in the HH than in the HT isomer.
This suggests that the HH isomer should be less stable,
which is in accord with the isomer ratio found by NMR
clear in HH-3, HH-4 (the R groups with their Fortho
signals clearly more deshielded show the faster ex-
change) and also in 6 and 7 (Fig. 6). Additional
experiments in CDCl3 show similar o slightly higher
activation energies for the exchange of endo and exo
Fortho except in the case of 1 which shows a clearly
smaller value (Table 4).
We can rule out the breaking of the Pd2N4 cycle, that
would be energetically more demanding, should produce
exchange of endo and exo Fortho with the same barrier
for the inequivalent R groups, and should be easier in
more donor solvents such as (CD3)2CO. Among the rest
of the mechanisms, we consider the following as more
likely: (a) the inversion of the boat conformation of the
six-membered Pd(m-LL)2Pd ring; and (b) the fluoroaryl
(HT:HHꢁ10:1).
/
The static spectra of the complexes 6 and 7, which
have the lowest symmetry with all the fluorine atoms
chemically inequivalent, can be easily interpreted con-
sidering the spatial distribution of the azolate substitu-
ents (near positions a, c, and d), the information
rotation around the Pdꢀ/C bond. Theoretical calcula-
provided by 19Fꢀ
/
19F EXSY experiments, and the
tions show that the planar non-polar conformation of
the six-membered M(m-LL)2M ring seems to be acces-
distortions produced by the substituents of the azolate
ligands by their interaction with R groups close to them.
For instance, the Fortho region of (NBu4)2[Pd2(m-
dmpz)(m-indz)R4] (7) in (CD3)2CO at 195 K (Fig. 6)
sible energetically only for LLꢁpz [3b]. This leaves
/
rotation as the mechanism giving rise to Fortho exchange
for 2ꢂ
/
4 and 6ꢂ7. The change in the appearance of the
/
can be fully assigned taking into account that J(2aꢂ
should be the largest coupling constant between endo
ortho, and that J(6cꢂ6d) the largest between exo Fortho.
/
2c)
F6d in 7 from doublet (coupled to F6c, 195 K, Fig. 6) to
triplet (coupled to F2c and F6c, 250 K) is a proof of the
rotation of Rc.
F
/
For 1, the exchange of Fortho is slower in (CD3)2CO
than in CDCl3. This can be understood for a boatꢂboat
/
2.3. Dynamic behavior of the complexes
inversion mechanism, because in that case the planar
transition state is non-polar, whereas the boat-shaped
ground stated is polar. Moreover, the activation para-
meters change dramatically with the solvent, and DS%
inverts its sign. Assuming that DS% is importantly
influenced by solvent effects, the similar behavior of 1
and 2 in (CD3)2CO suggests that the fast process
producing equivalence of the Fortho for 1 in (CD3)2CO
is aryl rotation. The inversion in DS% sign (to positive)
suggests that the mechanism detected in CDCl3 is
different and consistent with a boat inversion. In effect,
a polar non planar ground state should induce higher
solvent ordering than a non polar planar transition
state, giving rise to a positive DS% value. In the more
We will analyze three different processes: (a) exchange
of endo and exo Fortho, (b) exchange of HT and HH
isomers, and (c) exchange of PdR2 fragments. The
exchange rates were measured by magnetization transfer
experiments (MT) [14], and/or line-shape analysis (LSA)
[15], and the activation-energy parameters were calcu-
lated (Table 4).
The Fortho signals observed at low temperature for all
the di-m-azolato complexes in (CD3)2CO broadened
soon (Figs. 5 and 6) on heating, due to the exchange
of the Fortho atoms of the same R rings. Other exchanges
(between different R groups of the same isomer or
between R groups of different isomers), which can be
detected in the Fpara region, are much slower.
The broadening of the Fortho signals in complexes
with inequivalent R groups indicates the existence of
different activation energies for the exchange of endo
and exo Fortho in each R group. Surprisingly the lower
energies correspond to the R groups close to the
substituents of the azolate rings. This is particularly
polar (CD3)2CO, the barrier for boatꢂ
higher than that for R rotations, and R rotation is
preferred. In the less polar CDCl3, the barrier for boatꢂ
boat inversion is lower, and this mechanism is faster
than R rotation. The boatꢂboat inversion, has been
previously suggested [3aꢂd].
Looking at the Fpara region, 19Fꢀ
ments above room temperature revealed exchanges
between different R groups (RalRc and RblRd) of
/
boat inversion is
/
/
/
/
19F EXSY experi-
/
/
the same complex (HT-3, HT-4, 6 and 7) and between R
groups of different isomers (3, 4). MT experiments in the
Fpara region carried out a 298 K for 6 and 7 in CDCl3
showed that the free activation energy values found for
this exchange are smaller for 6 (m-dmpz-m-mpz) than for
7 (m-dmpz-m-indz). The mechanism proposed to explain
this kind of exchange is the so-called sliding mechanism
Fig. 4. Distortion of the M(m-NN)2M? ring when the two pyrazolate
substituents R? are close to M?.

R. de la Cruz et al. / Journal of Organometallic Chemistry 663 (2002) 108ꢂ
/117
113
Table 4
Activation parameters for the different processes observed for complexes 1, 2, 6 and 7 (S.D. in parentheses)
Complex/solvent
Process
Method
DG%298 (kJ molꢄ1
)
DH% (kJ molꢄ1
)
DS% (J Kꢄ1 molꢄ1
)
1/(CD3)2CO
1/CDCl3
Exchange of Fortho
Exchange of Fortho
Exchange of Fortho
Exchange of Fortho
Exchange RblRd
Exchange RblRd
Exchange of PdR2 fragment
TMꢃLSA 48.2(0.3)
TMꢃLSA 38.7(1.1)
TMꢃLSA 43.4(0.8)
45.09(0.18)
48.8(0.7)
38.5(0.4)
ꢄ10.6(0.8)
33(3)
2/(CD3)2CO
2/CDCl3
6/CDCl3
ꢄ16(2)
a
Tcoalescence
TM
45.1(0.3)
71.41(0.05)
74.95(0.04)
77.62(0.08)
7/CDCl3
1ꢃ[PdR2(THF)2]/(CD3)2CO
TM
TM
b
a
Calculated at 254 K due to the unstability of 2 in CDCl3.
[1]ꢁ0.008 M.
b
MT experiments in the Fpara region and its value
suggests that probably monobridged dinuclear species,
arising from dissociation of one Pdꢀ/N bond, are
involved. The uncoordinated N end can then produce
a nucleophilic associative substitution of ligand on the
cis-[PdR2(THF)2] complex. The use of less labile ligands
coordinated to the PdR2 fragment, (COD instead of
THF) [17], slowed down the process to the point that it
cannot be detected by MT or EXSY experiments.
However, using 2:1 mixtures of [Pd(C6F5)2(COD)] and
1 we can detect three new species: [PdR2(COD)],
(NBu4)2[R2Pd(m-pz)2Pd(C6F5)2]
(8),
and
Fig. 5. Variable temperature 19F-NMR spectra ((CD3)2CO, 282.35
(NBu4)2[Pd2(m-LL)2(C6F5)4], which reach their equili-
brium concentrations after a few minutes. The associa-
tive attack to a less electrophilic anionic system should
be much more difficult. In fact, mixtures of 1 and
MHz, Fortho region) of (NBu4)2[Pd2(m-pz)2R4] (1).
(NBu4)2[Pd2(m-pz)2(C6F5)4] gave 8 (molar fractionꢁ
/
0.5) only after heating in (CD3)2CO at 323 K for several
days. This supports the mechanism proposed.
3. Experimental
3.1. General
Reagents and solvents used were of commercially
available reagent quality. [PdR2(COD)] was prepared as
previously reported [5a]. Elemental analysis for carbon,
hydrogen and nitrogen was performed on a Perkinꢂ
/
Fig. 6. Variable temperature 19F-NMR spectra ((CD3)2CO, 282.35
Elmer 2400 CHN elemental analyzer. Conductivity
measurements were done with a Mettler Toledo
MC226 conductivimeter. Infrared spectra were recorded
MHz, Fortho region) of (NBu4)2[Pd2(m-dmpz)(m-indz)R4] (7).
[3b], which requires the breaking of at least one Pdꢀ
/
N
bond and the exchange of the nitrogen of the mono-
with a PerkinꢂElmer FTIR 1720 X spectrophotometer
/
with samples prepared as Nujol mulls. The 1H- and 19F-
NMR measurements were performed with a Bruker
ARX-300 and a Bruker AC-300 equipped with a control
temperature unit VT-100. Chemical shifts (ppm) were
dentate azolate directly bonded to the palladium (s-1,2-
metallotropic shift) [16] before the Pdꢀ
/
N bond is
reformed.
In addition, 19Fꢀ
/
19F EXSY experiments above room
1
referred to SiMe4 (1H) and CCl3F (19F). All the H-
temperature of 2:1 mixtures of cis-[PdR2(THF)2] and
(NBu4)2[Pd2(m-pz)2R4] (1) in (CD3)2CO also revealed
exchanges between R groups of different PdR2 frag-
ments. For this process, DG%298 has been obtained using
NMR spectra (300.13 MHz, (CD3)2CO, 293 K) of the
complexes 1ꢂ
to the hydrogens of the NBu4ꢃ group at dꢁ
CH3), 1.40 (m, 16H, CH2CH3), 1.80 (m, 16H,
/
7 contain the characteristic resonances due
/
0.95 (t, 24H,

114
R. de la Cruz et al. / Journal of Organometallic Chemistry 663 (2002) 108ꢂ117
/
NCH2CH2) and 3.40 (m, 16H, NCH2). The EXSY
experiments were carried out with a standard NOSEY
program operating in phase sensitive mode, with a 5% of
random variation of the evolution time to avoid COSY
cross-peaks, with a mixing time of 0.6 s. X-ray crystal-
lographic structure of HT-4 was resolved in a Bruker
SMART CCD diffractometer.
(coupling constants in the indz ring: JH6,H7
JH4,H5 8.0 Hz, JH5,H6 6.6 Hz, JH3,H7
JH4,H7 JH5,H7 1.0 Hz); HH 6.60 (ddd, JH,H
6.6, 1.0 Hz, 2H, H5 indz), 6.86 (ddd, JH,H
8.6, 6.6, 1.0
Hz, 2H, H6 indz), 7.30 (dt, JH,H 8.0, 1.0 Hz, 2H, H4
indz), 7.75 (d, JH,H
1.0 Hz, 2H, H3 indz), 7.93 (dc,
JH,H
8.6, 1.0 Hz, 2H, H7 indz), (coupling constants in
the indz ring: JH6,H7 8.6 Hz, JH4,H5 8.0 Hz, JH5,H6
6.6 Hz, JH3,H7 JH4,H6 JH4,H7 JH5,H7 1.0 Hz).
Ratio HT/HHꢁ
10:1. 19F-NMR (282.35 MHz,
(CD3)2CO, 220 K) dꢁ
2F, F2), ꢄ
81.79 (m, Nꢁ
JF,F
7.1 Hz, 2F, F6), ꢄ
F6), ꢄ123.19 (s, 2F, F4), ꢄ
78.94 (m, Nꢁ
75.8 Hz, 2F, F2), ꢄ
Hz, 2F, F2), ꢄ83.95 (s, 2F, F6), ꢄ
122.68 (s, 2F, F4), ꢄ123.37 (s, 2F, F4). LM (acetone,
5.0ꢅ
10ꢄ4 M, 298.15 K)ꢁ174.0 S cm2 molꢄ1
ꢁ
/
8.6 Hz,
JH4,H6
8.0,
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
3.2. Synthesis
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
/
3.2.1. (NBu4)2[Pd2(m-LL)2R4] (LLꢁ
/
pz, 1; mpz, 3;
/
HT ꢄ
51.6 Hz, 2F, F2), ꢄ
88.81 (d, JF,F
123.25 (s, 2F, F4); HH
80.64 (m, Nꢁ75.8
87.56 (s, 2F, F6),
/
80.25 (m, Nꢁ/51.6 Hz,
indz, 4)
/
/
/86.43 (d,
A 40% aqueous solution of NBu4OH (262 ml, 0.400
mmol) was added to a methanol (15 ml) solution of
H(LL) (0.400 mmol). After 5 min of constant stirring the
complex [PdR2(COD)] (246 mg, 0.400 mmol) was added
and the resulted solution was stirred for 8 h. For 1 and
4, a suspension was obtained and the white solid was
filtered off, washed with methanol (5 ml) and dried off.
For 3, a solution was obtained and was concentrated
until 2 ml. The addition of isopropanol (5 ml) afforded 3
as a white solid that was filtered off, washed with
isopropanol (5 ml) and vacuum-dried. Compound 1:
yield: 85%. C62H78F12Cl8N6Pd2 (1631.758): Calc.: C,
45.64; H, 4.82; N, 5.15. Found: C, 45.59; H, 4.86; N,
5.13%. IR (Nujol mulls, cmꢄ1): 1047, 771, 695, 684. 1H-
ꢁ
/
/
ꢁ7.1 Hz, 2F,
/
/
/
ꢄ
/
/
/
/
/
/
ꢄ
/
/
/
/
.
3.2.2. cis-[PdR2(Hdmpz)2]
Hdmpz (54.8 mg, 0.570 mmol) was added to a
solution of [PdR2(COD)] (350 mg, 0.570 mmol) in
chloroform (60 ml). After 30 min of stirring, the solution
was evaporated to dryness and the residue was triturated
with hexane (20 ml), filtered off, washed with hexane (5
ml) and vacuum-dried. Yield: 90%. C22H16Cl4F6N4Pd
(698.602): Calc.: C, 37.82; H, 2.31; N, 8.02. Found: C,
NMR (300.13 MHz, (CD3)2CO, 293 K) dꢁ
1.9 Hz, 2H, H4), 7.03 (d, JH3,H4
JH4,H5 1.9 Hz, 4H,
H3ꢃH5). 19F-NMR (282.35 MHz, (CD3)2CO, 220 K)
dꢁ 123.25 (s,
82.13 (s, 4F, F2), ꢄ87.85 (s, 4F, F6), ꢄ
4F, F4). LM ((CH3)2CO, 5.0ꢅ10ꢄ4 M, 298.15 K)ꢁ
203.0 Compound 3: yield: 75%.
cm2 molꢄ1
/
5.68 (t, Jꢁ
/
ꢁ
/
ꢁ
/
37.79; H, 2.33; N, 7.96%. IR (Nujol mulls, cmꢄ1): 3436
1
/
(m, st Nꢀ
dꢁ
JH1,H4
(282.35 MHz, CDCl3, 293 K) d ꢄ
119.79 (s, 2F, F4).
/H). H-NMR (300.13 MHz, CDCl3, 293 K)
/
ꢄ
/
/
/
/
2.14 (s, 6H, Me3), 2.16 (s, 6H, Me5), 5.79 (d,
2.3 Hz, 2H, H4), 9.83 (a, 2H, H1). 19F-NMR
91.37 (s, 4F, F2,6),
/
/
ꢁ
/
S
.
/
C64H82F12Cl8N6Pd2 (1659.812): Calc.: C, 46.31; H,
4.98; N, 5.06. Found: C, 46.28; H, 4.77; N, 4.90%. IR
(Nujol mulls, cmꢄ1): 1046, 771, 697, 690, 682. 1H-NMR
ꢄ
/
3.2.3. (NBu4)2[Pd2(m-dmpz)2R4] (2)
(300.13 MHz, (CD3)2CO, 293 K) dꢁ
Me3), 5.45 (d, Jꢁ1.8 Hz, 2H, H4), 7.34 (d, JH4,H5
Hz, 2H, H5); HH 2.16 (s, 6H, Me3), 5.42 (d, Jꢁ
1.8 Hz,
2H, H4), 6.96 (d, JH4,H5 1.8 Hz, 2H, H5). Ratio HT/
HHꢁ
10:1. 19F-NMR (282.35 MHz, (CD3)2CO, 220 K)
dꢁHT ꢄ80.12 (m, Nꢁ 81.42 (m,
51.5 Hz, 2F, F2), ꢄ
Nꢁ 86.00 (d, JF,F
51.5 Hz, 2F, F2), ꢄ 6.0 Hz, 2F, F6),
88.46 (d, JF,F
6.0 Hz, 2F, F6), ꢄ123.92 (s, 2F, F4),
124.24 (s, 2F, F4); HH ꢄ
77.88 (m, Nꢁ
F2), ꢄ80.20 (partially overlapped, F2), ꢄ
F6), ꢄ86.88 (s, 2F, F6), ꢄ
2F, F4). LM ((CH3)2CO, 5.0ꢅ
182.2 Compound 4: yield: 85%.
cm2 molꢄ1
/
HT 1.88 (s, 6H,
A 40% aqueous solution of NBu4OH (262 ml, 0.400
mmol) was added to a solution of cis-[PdR2(Hdmpz)2]
(279 mg, 0.399 mmol) in acetone (15 ml). After 30 min
of constant stirring the solution obtained was concen-
trated until 2 ml and isopropanol (10 ml) was added.
The white solid obtained was filtered off, washed with
isopropanol (5 ml) and vacuum-dried. Yield: 75%.
C66H86F12Cl8N6Pd2 (1687.866): Calc.: C, 46.97; H,
5.14; N, 4.98. Found: C, 46.63; H, 4.94; N, 4.88%. IR
(Nujol mulls, cmꢄ1): 1530, 1048, 773, 697, 684. 1H-
/
ꢁ/1.8
/
ꢁ
/
/
/
/
/
/
/
/
ꢁ
/
ꢄ
/
ꢁ
/
/
ꢄ
/
/
/74.8 Hz, 2F,
/
/
83.72 (s, 2F,
/
/
123.74 (s, 2F, F4), ꢄ
/123.80 (s,
NMR (300.13 MHz, (CD3)2CO, 293 K) dꢁ
12H, Me3, Me5), 5.14 (s, 2H, H4). 19F-NMR (282.35
MHz, (CD3)2CO, 195 K) dꢁ
76.02 (s, 4F, F2),
82.83 (s, 4F, F6), 124.10 (s, 4F, F4). LM
((CH3)2CO, 5.0ꢅ
10ꢄ4 M, 298.15 K)ꢁ168.6 S cm2
molꢄ1
/2.12 (s,
/
10ꢄ4 M, 298.15 K)ꢁ
/
S
.
/
ꢄ
/
C70H82F12Cl8N6Pd2 (1731.879): Calc.: C, 48.55; H,
4.77; N, 4.85. Found: C, 48.54; H, 4.60; N, 4.75%. IR
(Nujol mulls, cmꢄ1): 1207, 908, 807, 759, 697, 691, 683.
ꢄ
/
ꢄ
/
/
/
.
1H-NMR (300.13 MHz, (CD3)2CO, 293 K) dꢁ
/
HT 6.57
8.0, 6.6, 1.0 Hz, 2H, H5 indz), 6.75 (ddd,
8.6, 6.6, 1.0 Hz, 2H, H6 indz), 7.34 (dt, JH,H
8.0, 1.0 Hz, 2H, H4 indz), 7.47 (dc, JH,H
8.6, 1.0 Hz,
2H, H7 indz), 8.10 (d, JH,H 1.0 Hz, 2H, H3 indz)
(ddd, JH,H
ꢁ
/
3.2.4. (NBu4)2[Pd2(m-dmpz)(m-OH)R4] (5)
JH,H
ꢁ
/
ꢁ
/
A 40% aqueous solution of NBu4OH (525 ml, 0.801
mmol) was added to a solution of Hdmpz (38.5 mg,
0.400 mmol) in methanol (200 ml). After 5 min of
ꢁ
/
ꢁ
/

R. de la Cruz et al. / Journal of Organometallic Chemistry 663 (2002) 108ꢂ
/117
115
constant stirring, the complex [PdR2(COD)] (492 mg,
0.801 mmol) was added and the mixture was stirred for 8
h. The solvent was then partially evaporated under
vacuum until precipitation of a white solid, which was
separated by filtration, washed with methanol (5 ml)
and vacuum-dried. Yield: 70%. C61H80Cl8F12N4OPd2
(1609.749): Calc.: C, 45.52; H, 5.01; N, 3.48. Found: C,
45.30; H, 4.80; N, 3.36%. IR (Nujol mulls, cmꢄ1): 3623
part of an ABX system, JF,F
ꢁ
/
62.6, 13.0 Hz, 1F, F2b),
ꢄ
/
79.53 (m, B part of an ABY system, JF,F
Hz, 1F, F2d), ꢄ 112.6 Hz, 1F, F2a), ꢄ
80.15 (d, JF,F
81.54 (d, JF,F 84.86 (d, JF,F
37.6 Hz, 1F, F6c), ꢄ
10.6, 1F, F6a), ꢄ 37.6 Hz, 1F, F6d), ꢄ
85.22 (d, JF,F
88.62 (d, JF,F
10.6 Hz, 1F, F6b), ꢄ123.29 (s, 1F, F4),
123.53 (s, 1F, F4), ꢄ123.65 (s, 1F, F4), ꢄ
123.79 (s,
1F, F4). LM ((CH3)2CO, 5.0ꢅ10ꢄ4 M, 298.15 K)ꢁ
158.8 S cm2 molꢄ1
ꢁ/62.6, 5.8
/
ꢁ
/
/
ꢁ
/
/
ꢁ
/
/
ꢁ
/
/
ꢁ
/
/
ꢄ
/
/
/
/
/
(m, st Oꢀ
MHz, CDCl3, 293 K) dꢁ
6H, Me), 5.30 (s, 1H, H4). 19F-NMR (282.35 MHz,
CDCl3, 293 K) dꢁ 84.32 (s, 4F,
83.89 (s, 4F, F2,6), ꢄ
F2,6), ꢄ123.08 (s, 2F, F4), ꢄ124.28 (s, 2F, F4). LM
((CH3)2CO, 5.0ꢅ
10ꢄ4 M, 298.15 K)ꢁ126.7 S cm2
molꢄ1
/
H), 1040, 771, 696, 684. 1H-NMR (300.13
1.64 (s, 1H, OH), 1.55 (s,
.
/
ꢄ
/
3.3. X-ray crystallography
/
ꢄ
/
/
/
/
Suitable single crystals of compound HT-4 were
mounted in glass fibers, and diffraction measurements
/
/
.
were made using a Bruker SMART CCD area-detector
˚
Ka radiation (lꢁ0.71073 A)
diffractometer with Moꢂ
/
/
3.2.5. (NBu4)2[Pd2(m-dmpz)(m-LL)R4] (LLꢁ
indz, 7)
/
mpz, 6;
[18]. Intensities were integrated from several series of
exposures, each exposure covering 0.38 in v, the total
data set being a hemisphere [19]. Absorption corrections
were applied, based on multiple and symmetry-equiva-
lent measurements [20]. The crystal was poor diffracting
and the reflections with 2u higher than 41.648 were
rejected. The structure was solved by direct methods and
refined by least-squares on weighted F2 values for all
H(LL) (0.311 mmol) was added to a solution of
(NBu4)2[Pd2(m-dmpz)(m-OH)R4] (500 mg, 0.31 mmol) in
acetone (50 ml). After 2 h of constant stirring the
solution obtained was concentrated until 2 ml and
isopropanol (10 ml) was added. The white solid pre-
cipitated was filtered off, washed with isopropanol (5
ml) and vacuum-dried. Compound 6: yield: 75%.
C65H84Cl8F12N6Pd2 (1673.839): Calc.: C, 46.64; H,
5.06; N, 5.02. Found: C, 46.37; H, 5.09; N, 4.92%. IR
(Nujol mulls, cmꢄ1): 1587, 1048, 771, 687, 679. 1H-
Table 5
Crystal data and structure refinement for HT-4
Empirical formula
Formula weight
Temperature (K)
C70H82Cl8F12N6Pd2
1731.82
293(2)
NMR (300.13 MHz, (CD3)2CO, 293 K) dꢁ
Me dmpz), 2.00 (s, 3H, Me3 mpz), 2.30 (s, 3H, Me
dmpz), 5.19 (s, 1H, H4 dmpz), 5.39 (d, Jꢁ
1.7 Hz, 1H,
H4 mpz), 7.38 (d, JH4,H5 1.7 Hz, 1H, H5 mpz). 19F-
NMR (285.35 MHz, (CD3)2CO, 195 K) dꢁ 74.88
(ddd, JF,F 78.91 (m, A
105.0, 16.3, 5.0 Hz, 1F, F2c), ꢄ
part of an ABX system, JF,F
59.5, 16.3 Hz, 1F, F2b),
79.33 (m, B part of an ABY system, JF,F 59.5, 5.0
Hz, 1F, F2d), ꢄ 105.0 Hz, 1F, F2a),
80.13 (d, JF,F
81.55 (d, JF,F 84.86 (d, JF,F
35.5 Hz, 1F, F6c), ꢄ
9.7, 1F, F6a), ꢄ 35.5 Hz, 1F, F6d),
85.33 (d, JF,F
88.07 (d, JF,F
9.7 Hz, 1F, F6b), ꢄ123.79 (s, 2F, F4),
124.11 (s, 1F, F4), ꢄ124.24 (s, 1F, F4). LM
((CH3)2CO, 5.0ꢅ
10ꢄ4 M, 298.15 K) 164.8 S cm2
/
1.80 (s, 3H,
˚
Wavelength (A)
0.71073
Orthorhombic
Ibca
/
Crystal system
Space group
Unit cell dimensions
ꢁ
/
/
ꢄ
/
ꢁ
/
/
˚
a (A)
24.914(3)
25.063(3)
26.023(3)
˚
ꢁ
/
b (A)
˚
c (A)
ꢄ
/
ꢁ
/
a (8)
b (8)
g (8)
90
90
/
ꢁ
/
ꢄ
/
ꢁ
/
/
ꢁ
/
90
16249(4)
3
/
ꢁ
/
˚
Volume (A )
Z
Dcalc (Mg mꢄ3
ꢄ
/
ꢁ
/
/
8
1.416
)
ꢄ
/
/
Absorption coefficient (mmꢄ1
F(000)
Crystal size (mm)
)
0.775
7040
/
molꢄ1. Compound 7: yield: 77%. C68H84Cl8F12N6Pd2
(1709.873): Calc.: C, 47.77; H, 4.95; N, 4.91. Found: C,
47.67; H, 4.90; N, 4.91%. IR (Nujol mulls, cmꢄ1): 1206,
1048, 771, 697, 680. 1H-NMR (300.13 MHz, (CD3)2CO,
0.25ꢅ0.21ꢅ0.08
u Range for data collection (8)
Index ranges
1.57ꢂ20.82
/
05h 524, 05k 525,
05l 526
29810
Reflections collected
293 K) dꢁ
dmpz), 5.16 (s, 1H, H4 dmpz), 6.54 (ddd, JH,H
1.0 Hz, 1H, H5 indz), 6.76 (ddd, JH,H
8.5, 6.6, 1.0 Hz,
1H, H6 indz), 7.29 (dt, JH,H 8.1, 1.0 Hz, 1H, H4 indz),
7.72 (dc, JH,H
8.5, 1.0 Hz, 1H, H7 indz), 8.12 (d,
JH,H
1.0 Hz, 1H, H3 indz) (coupling constants in the
indz ring: JH6,H7 8.5 Hz, JH4,H5 8.1 Hz, JH5,H6 6.6
Hz, JH3,H7 JH4,H6 JH4,H7 JH5,H7
1.0 Hz). 19F-
NMR (282.35 MHz, (CD3)2CO, 195 K) dꢁ 75.60
(ddd, JF,F 78.95 (m, A
112.6, 13.0, 5.8 Hz, 1F, F2c), ꢄ
/1.83 (s, 3H, Me dmpz), 2.23 (s, 3H, Me
Independent reflections
Completeness to uꢁ20.828
Absorption correction
Max/min transmission
Refinement method
4254 [Rintꢁ0.0827]
100.0%
ꢁ
/
8.1, 6.6,
ꢁ
/
SADABS
ꢁ
/
1.000000, 0.724544
Full-matrix least-squares on F2
4254/0/447
ꢁ
/
Data/restraints/parameters
Final R indices [I ꢀ2s(I)]
R indices (all data)
Goodness-of-fit on F2
ꢁ
/
R1ꢁ0.0521, wR2ꢁ0.1694
R1ꢁ0.0886, wR2ꢁ0.1908
1.061
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
/
ꢄ
/
Largest difference peak and hole (e 1.072 and ꢄ0.289
ꢄ3
˚
A
)
ꢁ
/
/

116
R. de la Cruz et al. / Journal of Organometallic Chemistry 663 (2002) 108ꢂ117
/
Organometallics 19 (2000) 4968;
reflections (see Table 5) [21]. All non-hydrogen atoms
were assigned anisotropic displacement parameters and
refined without positional constraints. Hydrogen atoms
were taken into account at calculated positions and their
positional parameters were refined. Refinement pro-
References without activation parameters: (e) C. Tejel, M.A.
Ciriano, A.J. Edwards, F.J. Lahoz, L.A. Oro, Organometallics 16
(1997) 45;
(f) C. Tejel, M.A. Ciriano, J.A. Lo´pez, F.J. Lahoz, L.A. Oro,
Organometallics 19 (2000) 497;
(g) C. Tejel, M.A. Ciriano, L.A. Oro, A. Tiripicchio, F. Ugozzoli,
Organometallics 20 (2001) 1676.
ceeded smoothly to give R1ꢁ
/
0.0521 based on the
reflections with I ꢀ2s(I). Complex neutral-atom scat-
/
[4] P. Espinet, A.M. Gallego, J.M. Mart´ınez-Ilarduya, E. Pastor,
Inorg. Chem. 39 (2000) 975.
tering factors were used [22].
[5] (a) P. Espinet, J.M. Mart´ınez-Ilarduya, C. Pe´rez-Briso, A.L.
Casado, M.A. Alonso, J. Organomet. Chem. 551 (1998) 9;
(b) A.L. Casado, P. Espinet, Organometallics 17 (1998)
954;
4. Supplementary material
(c) A.L. Casado, J.A. Casares, P. Espinet, Inorg. Chem. 37 (1998)
4154;
Crystallographic data (excluding structure factors) for
this structure have been deposited with the Cambridge
Crystallographic Data Centre as Supplementary pub-
lication no. CCDC-185911. Copies of the data can be
obtained free of charge on application to The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(d) A.L. Casado, P. Espinet, J. Am. Chem. Soc. 120 (1998) 8978;
(e) A.L. Casado, J.A. Casares, P. Espinet, Organometallics 16
(1997) 5730.
[6] Selected references about FꢀF through-space coupling: (a) J.E.
/
Peralta, V. Barone, R.H. Contreras, D.G. Zaccari, J.P. Snyder, J.
Am. Chem. Soc. 123 (2001) 9162;
(Fax:
ac.uk or www: http://www.ccdc.cam.ac.uk).
ꢃ44-1223-336033; e-mail: deposit@ccdc.cam.
/
(b) L. Ernst, K. Ibrom, K. Marat, R.H. Mitchell, G.J. Bodwell,
G.W. Bushnell, Chem. Ber. 127 (1994) 1119;
(c) C.G. Giribet, M.C. Ruiz de Azu´a, R.H. Contreras, R.
Lobayan de Bonczok, G.A. Aucar, S.J. Go´mez, Mol. Struc. 300
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Acknowledgements
(d) P. Szczecinski, J. Zachara, J. Organomet. Chem. 447 (1993)
241;
We are very grateful for financial support by the
Direccio´n General de Ensenanza Superior (Project
˜
(e) F.B. Mallory, C.W. Mallory, M.B. Baker, J. Am. Chem. Soc.
112 (1990) 2577;
(f) R.S. Matthews, J. Fluorine Chem. 48 (1990) 7;
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(1985) 457.
BQU2001-2015) and the Junta de Castilla y Leo´n
(Project VA120/01). The Ministerio de Educacio´n y
Cultura is gratefully acknowledged for a fellowship to
A.M.G.
[7] M.A. Alonso, J.A. Casares, P. Espinet, J.M. Mart´ınez-Ilarduya,
C Pe´rez-Briso, Eur. J. Inorg. Chem. (1998) 1745.
[8] G. Lo´pez, J. Ruiz, C. Vicente, J.M. Mart´ı, G. Garc´ıa, P.A.
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(e) S. Trofimenko, Chem. Rev. 93 (1993) 943;
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Xortho
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117
[18] SMART V5.051 diffractometer control software, Bruker Analytical
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