Influence of the electronic effects of phosphine ligands upon the properties of cyclopalladated complexes containing a

Article abstract of DOI:10.1039/a801737i

The synthesis, characterization and study of the properties of the cyclopalladated compounds [Pd{(η⁵-C₅H₅)Fe[(η⁵-C ₅H₃)C(Me)=N(C₆H₄-4-Me)]}Cl(L)] and [Pd{(η⁵-C₅H₅)Fe[(η⁵-C ₅H₃)CH₂NMe₂]}Cl(L)] (L = PPh₃, PPh₂Et, PPhEt₂ or PEt₃) are reported. The comparison of the electrochemical and electronic properties of these compounds has allowed us to elucidate the influence of the phosphine and chelate ligands upon the environment of the Fe^II. As a first approach to clarify the factors affecting the properties of these complexes, molecular orbital (MO) calculations using the PM3(tm) semiempirical method were also undertaken. [Pd{(η⁵-C₅H₅)Fe[(η⁵-C ₅H₃)C(Me)=N(C₆H₄-4-Me)]}Cl(PPh ₃)] (3a) and [Pd{(η⁵-C₅H₅)Fe[(n⁵-C ₅H₃)CH₂NMe₂]} Cl(PPh₃)] (3b) have also been characterized structurally. Complex 3a is triclinic, space group P1, with a = 12.795(2), b = 11.534(2) and c = 11.267(2) A and α = 106.660(10)°, β = 98.660(10)° and γ = 94.500(10)°; compound 3b is monoclinic, space group P2₁/a, with a = 13.650(3), b = 19.678(4) and c = 10.169(2) A and α = γ = 90.0° and β = 94.69(2)°. In both cases the molecules contain a [5,5] bicyclic system formed by a five-membered palladacycle and the C₅H₃ ring of the ferrocenyl moiety.

Full text of DOI:10.1039/a801737i

View Article Online / Journal Homepage / Table of Contents for this issue
InÑuence of the electronic e†ects of phosphine ligands upon the
properties of cyclopalladated complexes containing a r(PdÈC 2,
sp
ferrocene)bond
X-Ray crystal structures of [Pd{(g5-C H )Fe[(g5-C H )C(Me)xN(C H -4-
5 5
5 3
6 4
3
Me)]}Cl(PPh )] and [Pd{(g5-C H )Fe[(g5-C H )CH NMe ]}Cl(PPh )]
3
5 5
5 3
2
2
Concepcion Lopez,*,a Ramon Bosque,a Xavier Solansb and Merce Font-Bardiab
a Departament de Qu•mica Inorganica, Facultat de Qu•mica, Universitat de Barcelona, Mart•
Franques 1-11, 08028 Barcelona, Spain
b Departament de Cristallograf•a, Mineralog•a i Diposits Minerals, Facultat de Geolog•a,
Universitat de Barcelona, Mart• Franques s/n, 08028 Barcelona, Spain
The synthesis, characterization and study of the properties of the cyclopalladated compounds [PdM(g5-
C H )Fe[(g5-C H )C(Me)xN(C H -4-Me)]NCl(L)] and [PdM(g5-C H )Fe[(g5-C H )CH NMe ]NCl(L)] (L \
5
5
5
3
6
4
5
5
5
3
2
2
PPh , PPh Et, PPhEt or PEt ) are reported. The comparison of the electrochemical and electronic properties
3
2
2
3
of these compounds has allowed us to elucidate the inÑuence of the phosphine and chelate ligands upon the
environment of the FeII. As a Ðrst approach to clarify the factors a†ecting the properties of these complexes,
molecular orbital (MO) calculations using the PM3(tm) semiempirical method were also undertaken. [PdM(g5-
C H )Fe[(g5-C H )C(Me)xN(C H -4-Me)]NCl(PPh )] (3a) and [PdM(g5-C H )Fe[(g5-C H )CH NMe ]N
5
5
5
3
6
4
3
5
5
5
3
2
2
Cl(PPh )] (3b) have also been characterized structurally. Complex 3a is triclinic, space group P1, with
3
a \ 12.795(2), b \ 11.534(2) and c \ 11.267(2) Ó and a \ 106.660(10)¡, b \ 98.660(10)¡ and c \ 94.500(10)¡;
compound 3b is monoclinic, space group P2 /a, with a \ 13.650(3), b \ 19.678(4) and c \ 10.169(2) Ó and
1
a \ c \ 90.0¡ and b \ 94.69(2)¡. In both cases the molecules contain a [5,5] bicyclic system formed by a
Ðve-membered palladacycle and the C H ring of the ferrocenyl moiety.
5
3
One of the areas of organometallic chemistry that has
attracted great interest during the last few years is that con-
cerning ferrocene derivatives containing heteroatoms with
good donor abilities (e.g., nitrogen, oxygen, sulfur, phos-
phorus, etc.) since the coordination of a metal to these hetero-
atoms produces polymetallic molecules.1,2 In compounds of
this kind the presence of proximal metals may a†ect the
properties of the iron(II). For instance, recent electrochemical
studies on ferrocene derivatives containing divalent transition
metals and N-donor ferrocenyl units has shown that the pro-
clivity of the iron(II) to oxidize depends on several factors,3h7
including the nature of the transition metal and the mode of
coordination of the ferrocenyl unit to it [i.e., as a mono-
dentate or bidentate (C\N)~ or (N\N) ligand]. For instance,
in the coordination compounds [MM(g5-C H )Fe[(g5-
For these reasons we decided to study the electrochemical
and spectroscopic properties of the cyclopalladated complexes
[Pd(C\N)Cl(L)], in which (C\N) stands for either ferro-
cenylimine M(g5-C H )Fe[(g5-C H )C(Me)xN(C H -4-Me)]N
5
5
5
4
6 4
(1a) or N,N-dimethylaminomethylferrocene(1b) which acts as
a monoanionic bidentate ligand, and the neutral L group is
PPh , PPh Et. PPhEt or PEt . These studies may allow us
3
2
2
3
to explain the inÑuence of these neutral ligands bound to the
5
5
C H )CHxNCH CH NMe ]NCl ],8 [PdM(g5-C H )Fe[(g5-
5
4
2
2
2
2
5 5
C H )CH NMe ]N Cl ], [PdM(g5-C H )Fe[(g5-C H )CHx
5
4
2
2
2
2
5
5
5 4
NNMe ]N Cl ]
or
[MM(g5-C H )Fe[(g5-C H )Nx
2
2
2
5
5
5 4
CH(C H -2-O)] N],4 (M \ Zn, Co, Cu or Ni) the FeII
4
4
2
is more resistant to oxidation than in the corresponding
free ligands, while in the cyclopalladated derivatives
[PdM(g5-C H )Fe[(g5-C H )CH NMe ]N(l-Cl)] or [PdM(g5-
5
5
5
3
2
2
2
C H )Fe[(g5-C H )CH NMe ]NCl(PR )], in which the ligand
5
5
5
3
2
2
3
acts as a (C\N)~ bidentate ligand, the iron(II) is more prone
to oxidize.9
Besides, previous electrochemical studies on cyclopalladated
complexes containing N-donor ferrocenyl moieties suggested
that the ligands bound to the palladium in the cyclopalladated
derivatives (at a distance of three bond lengths) could also
contribute to tune the redox ability of the FeII.9
* Tel 34 934 021 274; Fax 34 934 90 7 725;
E-mail: clopez=kripto.qui.ub.es
Scheme 1
New J. Chem., 1998, Pages 977È982
977

View Article Online
palladium upon the spectroscopic and electronic properties of
the ferrocenyl unit.
C(6) atom of the ferocenyl unit.¤ The two compounds contain
a bicyclic system, which is formed by the substituted pentag-
onal ring of the ferrocenyl fragment and a Ðve-membered
metallacycle. In 3a the metallacycle is practically planar and
its mean plane forms an angle of 1.5¡ with the plane of the
C H ring, while in 3b the palladacycle has an envelope-like
Results and Discussion
5
3
conformation.
Syntheses and characterization
The di-l-chloro-bridged cyclopalladated complexes [PdM(g5-
C H )Fe[(g5- C H )C(Me)xN(C H -4-Me)]N(l-Cl)] (2a)10
5
5
5
3
6
4
2
and [PdM(g5-C H )Fe[(g5-C H )CH NMe ]N(l-Cl)] (2b)11
5
5
5
3
2
2
2
react (in benzene and at room temperature) with a stoichio-
metric amount of the appropriate phosphine ligand, L, to
give the monomeric derivatives [PdM(g5-C H )Fe[(g5-
5
5
C H )C(Me)xN(C H -4-Me)]NCl(L)] (3È6a) and [PdM(g5-
5
5
3
5
6 4
C H )Fe[(g5-C H )CH NMe ]NCl(L)] (3È6b). All these com-
5
3
2
2
plexes are orange-red (3È6a and 3, 4b) or yellowish (5, 6b)
solids at room temperature and are highly soluble in the most
common solvents: chloroform, dichloromethane, acetonitrile,
acetone and benzene, but they are only poorly soluble in alco-
hols and practically insoluble in alkanes.
Elemental analyses of compounds 3È6a, b are consistent
with the proposed formulae (see Experimental). The infrared
spectra of complexes 3È6a showed a sharp intense band in the
range 1570È1590 cm~1, which is assigned to the asymmetric
Œ
stretching of the CxNw functional group. This absorption
†
appears at lower wavenumbers than in free ferro-
Œ
cenylketimine12 [m( CxNw): 1625 cm~1] owing to the
†
coordination of the nitrogen. Compounds 3–6a, b have been
also characterized by 1H and 13C NMR spectroscopy (see
Experimental). Phosphorus-31 NMR spectra of compounds
3È6 showed a singlet in the range 30È40 ppm (Table 1). The
position of the signal is consistent, according to the liter-
ature,10,12 with a trans arrangement between the phosphine
group and the nitrogen of the ferrocenyl Schi† base. The
X-ray crystal structures of compounds 3a and 3b described
below conÐrm this type of arrangement.
Fig. 1 Molecular structure and atom labelling scheme of [PdM(g5-
C H )Fe[(g5-C H )C(Me)xN(C H -4-Me)]NCl(PPh )] (3a)
5
5
5
3
6
4
3
Description of the crystal structures
The molecular structures of 3a and 3b, together with the atom
labelling schemes, are presented in Fig. 1 and 2, respectively,
and a selection of bond lengths and angles for these com-
pounds is given in Table 2.
The structures consist of discrete molecules of [PdM(g5-
C H )Fe[(g5-C H )C(Me)xN(C H -4-Me)]N Cl(PPh )] in 3a
5
5
5
3
6
4
3
or [PdM(g5-C H )Fe[(g5- C H )CH NMe ]NCl(PPh )] in 3b,
5
5
5
3
2
2
3
separated by van der Waals contacts. In the two cases the
palladium is in a slightly distorted square-planar environment,
bound to a chlorine, the phosphorus, the nitrogen and the
Table 1 pK of the phosphine ligands and 31P NMR data, halfwave
a
potentials referenced to ferrocene and UV/VIS absorption wave-
lengths for the compounds under study.
Compound
L
pK a
d 31P
E
(Fc)/mV
k /nm
k /nm
a
1@2
1
2
A. Cyclopalladated compounds derived from:
[PdM(g5-C H )Fe[(g5-C H )C(Me)xN(C H -4-Me)]NCl(L)] (3aÈ6a)
5
5
5
3
6
3
3a
4a
5a
6a
PPh
2.30
37.6
36.5
32.0
30.2
70
393
376
342
322
309
305
306
298
Fig. 2 Molecular structure and atom labelling scheme of [PdM(g5-
C H )Fe[(g5-C H )CH NMe NCl(PPh )] (3b)
3
PPh Et 2.52
58
45
23
2
5
5
5
3
2
2
3
PPhEt
6.25
8.69
2
PEt
3
¤ In compound 3a, the least-squares equation of the plane deÐned
by the atoms Pd, P, N, Cl and C(6) is
B. Cyclopalladated compounds of general formula:
[PdM(g5-C H )Fe[(g5-C H )CH NMe ]NCl(L)] (3bÈ6b)
5
5
5
3
2
2
39.7
3b
4b
5b
6b
PPh
2.30
[16
[18
[25
[33
399
385
370
352
316
312
305
307
(0.5884)XO [ (0.2024)YO ] (0.7829)ZO \ 1.6688. The deviations
from this plane are: Pd, ]0.050; Pd, [0.120; N, [0.143; Cl, 0.110;
C(6), 0.149 Ó. In complex 3b, the least-squares equation of the same
plane is (0.2303)XO ] (0.7220)YO [ (0.6524)ZO \ [1.3923. The
deviations from this plane are: Pd, [0.087; P [0.396; Cl, 0.083; N,
[0.011; C(6), 0.102 Ó.
3
PPh Et 2.52
38.6
34.4
32.6
2
PPhEt
6.25
8.69
2
PEt
3
a Data from ref. 13.
978
New J. Chem., 1998, Pages 977È982

View Article Online
proclivity of compounds 3È6a,b towards oxidation is strongly
dependent on the nature of the phosphine ligands bound to
the palladium. In particular, in our two families of compounds
Table 2 Selected bond lengths (in Ó) and angles (in degrees) for 3a
and 3b. Standard deviations are given in parentheses
the replacement of the PPh by a more basic phosphine
3a
3b
3
ligand13 produces a decrease in E (Fc), that is to say the
PdwC(6)
PdwN
1.998(3)
2.136(3)
2.2371(10)
2.3414(9)
1.446(4)
1.299(4)
1.428(4)
1.983(10)
2.170(10)
2.238(3)
2.395(3)
1.50(2)
1.48(2)
1.468(14)
1@2
iron becomes more prone to oxidation. Besides, the half-wave
potentials for compounds 3È6a spread over a wider range (ca.
50 mV) than for compounds 3È6b (ca. 17 mV) in which the
substituent directly bound to the metallated ring is an sp3-
hybridized carbon atom. These results are similar to those
reported by Silva et al.18 for monosubstituted ferrocene deriv-
atives of the type M(g5-C H )Fe[(g5-C H )C(X)xY]N (class A)
PdwP
PdwCl
C(10)wC(11)
NwC(11)
NwC(13)
NwPdwCl
93.02(7)
95.08(3)
80.25(12)
92.51(10)
113.5(3)
119.3(3)
90.1(3)
95.59(11)
82.6(4)
92.6(3)
109.4(9)
109.0(10)
5
5
5 4
PwPdwCl
or M(g5-C H )Fe[(g5-C H )CHYZ]N (class B). For these
5
5
5 4
C(6)wPdwN
C(6)wPdwP
C(10)wC(11)wN
C(11)wNwC(13)
systems, it has been postulated that the stronger substituent
e†ect of the wC(X)xY moiety in class A compounds could be
interpreted in terms of the interaction between the p system of
the ferrocenyl group and the p orbital of the sp2 carbon.
z
Several attempts to correlate UV/VIS spectroscopic data
and the half-wave potentials (E ) of the FeII in ferrocene
1@2
derivatives have been reported.18h21 Recent electrochemical
Œ
In compound 3a the CxNw functional group is endo-
†
studies for a large number of this type of compound have
shown that for derivatives having the general formula M(g5-
C H )Fe[(g5-C H )C(X)xY]N (class A),18 an increase of the
Œ
cyclic and the CxNw bond length [1.299(4) Ó] is similar to
†
that reported for the free ligand.12 The imine has an anti con-
formation as reÑected in the C(10)wC(11)wNwC(13) torsion
angle [178.5(4)¡]. The plane deÐned by the phenyl group
forms an angle of 63.5¡ with the C H of the ferrocenyl
5
5
5 4
electron-withdrawing nature of the R group was reÑected in
an increase of the E (Fc) value and a decrease in energy of
1@2
the dÈd transition energy.
5
3
moiety.
Since compounds 3È6a included here also contain an sp2
carbon atom attached to the ferrocenyl group, we decided to
check whether the relationship between the electrochemical
and UV/VIS spectroscopic data (k~1) obtained by Silva et
al.18 for the class A ferrocenes could also be extended to the
palladium(II) compounds 3È6a. UV/VIS spectral data for com-
pounds 3È6a,b are summarized in Table 1. Comparison of
these data reveals that for 3È6a the position of the band k is
more sensitive to changes introduced in the phosphine ligands
than for 3È6b. In addition, for compounds 3È6a an overall
gross tendency appears to occur between E and k~1, that is
to say an increase in the redox potential (this is usually
related19h22 to an increase of the electronic acceptor character
of the substituents) tends to correspond to a decrease in the
energy of the dÈd transition. These Ðndings are similar to
those reported for class A compounds.18
The distance between the Fe and the Pd is 3.592(2) Ó for 3a
and 3.558(2) Ó for 3b, thus suggesting that there is no direct
interaction between the two metals. In the two structures, the
average CwC bond lengths in the two pentagonal rings
[1.406(15) Ó for 3a and 1.42(2) Ó for 3b] are similar to the
values reported for other ferrocene derivatives.14 The
FewC(ring) bond distances range from 2.011(3) to 2.065(3) Ó
in 3a and from 2.015(11) to 2.087(10) Ó in 3b. The two pentag-
onal rings of the ferrocenyl moiety are planar,” nearly parallel
(tilt angle) of 1.0¡ for 3a and 3.1¡ for 3b. The twist angle is 2.0¡
in 3a and 6.7¡ in 3b.
1
1@2
1
Electrochemical studies and UV/VIS spectra
Electrochemical data for the compounds under study were
obtained from cyclic voltammetric studies of 10~3 M solu-
tions in acetonitrile (HPLC grade). Cyclic voltammograms of
compounds 3È6a,b exhibit an anodic peak with a reduction in
the reverse scan. The experiments were carried out at di†erent
scan rates from 0.05 to 1.0 V s~1 and the results were consis-
tent with those expected for a simple and reversible one-
electron transfer process.15,16 The half-wave potentials
Theoretical approaches to clarify the inÑuence of the phosphine
ligands and the chelating group upon the electronic environment
of the iron(II)
As a Ðrst attempt to understand the e†ect of the palladium
and its ligands upon the electronic environment of the fer-
rocenyl fragment, we decided to undertake molecular orbital
(MO) calculations on the ligands 1a and 1b, as well as on
some model cyclopalladated complexes of the general formula
[PdM(g5-C H )Fe[(g5- C H )C(Me) xN(C H - 4-Me)]NCl (L)]
referred to ferrocene [E (Fc)] are summarized in Table 1.
1@2
Comparison of the data reveals that the cyclopalladated com-
pounds are more prone to oxidize than the free ligands (138
mV for 1a15 and [10 mV for 1b16). A similar trend has also
been observed for other cyclopalladated and cycloplatinated
complexes containing ferrocenyl units.9,17 In addition, the
5
5
5
3
6 4
and [PdM(g5-C H )Fe [(g5-C H )CH NMe ]NCl(L)] (Fig. 1,
5
5
5
3
2
2
where L represents PPh , PPh Me, PPhMe , PMe or PH )
3
2
2
3
3
(3a, 4aºÈ7aº and 3b, 4È7bº). The main di†erence between these
model compounds and the complexes prepared in this work is
the replacement of the ethyl group by a methyl or a hydrogen.
This approach was undertaken in order to minimize the prob-
lems that may arise during the optimization of the geometry
of these complexes owing to the Ñexibility of the ethyl frag-
ments.
” In compound 3a the least-squares equation of the plane deÐned by
the set of atoms C(1)ÈC(5) is (0.6419)XO [ (0.2767)YO ]
(0.7151)ZO \ 4.9479. The deviations from this plane are: C(1), 0.001;
C(2), [0.003; C(3), 0.004; C(5), 0.001 Ó. The least-squares equation of
the plane deÐned by the set of atoms C(6)ÈC(10) is
(0.6551)XO [ (0.2741)YO ] (0.7041)ZO \ 1.6329. The deviations
from this plane are: C(6), [0.013; C(7), 0.013; C(8), [0.009; C(9),
0.003; C(10), 0.008 Ó.
In compound 3b, the least-squares equation of the plane deÐned by
the set of atoms C(1)ÈC(5) is (0.1430)XO ] (0.7875)YO [
(0.5955)ZO \ 2.4029. The deviations from this plane are: C(1), 0.004;
C(2). 0.003; C(3), [0.009; C(4), 0.011; C(5), [0.010 Ó. The least-
squares equation of the plane deÐned by the set of atoms C(6)ÈC(10) is
(0.1239)XO ] (0.8194)YO [ (0.5597)ZO \ [0.7655. The deviations
from this plane are: C(6), [0.019; C(7), 0.131; C(8), [0.003; C(9),
[0.009; C(10), 0.017 Ó.
All the calculations were carried out with the PM3(tm)
model of the SPARTAN 4.1 program22 and the geometries of
all the molecules used in this study were fully optimized
before the calculation of the molecular orbitals. In order to test
the validity of this program for the compounds under
study the geometries of the imines M(g5-C H )Fe[(g5-
5
5
C H )C(R)xNR@]N (with R \ H, R@ \ Ph and R \ Me,
5
4
New J. Chem., 1998, Pages 977È982
979

View Article Online
R@ \ Ph or C H -4-Me) and of the cyclopalladated complexes
1b). Besides, and although the phosphine ligand is not directly
involved in the HOMO, the energy of this level is sensitive to
the nature of the phosphine. For the two families of com-
pounds the energy of the HOMO increases according to the
sequence PPh \ PPh Me \ PPhMe \ PMe , and conse-
6
4
3a and 3b were optimized and compared with available X-ray
data.12 In all cases, the structural parameters (bond lengths,
bond angles and the relative orientation of the rings) in the
optimized geometries were in excellent agreement with the
structural data obtained by X-ray di†raction, thus suggesting
that for compounds of this kind the PM3(tm) method22 gives
fairly accurate optimized geometries. On this basis, it seemed
reasonable to assume that this semiempirical method could
also be used to optimize the geometries of the model complex-
es containing L \ PPh Me, PPhMe , PMe or PH , for
3
2
2
3
quently the proclivity of FeII towards oxidation in the cyclo-
palladated complexes should be higher for compounds
containing PMe than for those with L \ PPh . On the other
3
3
hand, an increase in the basicity of the phosphine produces a
destabilization of the palladium-based orbitals, which in turn
could result in a greater electron density on the ferrocenyl
moiety. These Ðndings are consistent with the variations
obtained for the half-wave potentials of compounds 3È6a,b
(Table 1).
2
2
3
3
which X-ray data are not available.
The MO calculation for the ferrocenylimine M(g5-
C H )Fe[(g5-C H )C(Me)xN(C H -4-Me)]N reveals that the
5
5
5
4
6 4
HOMO is mainly a combination of the p orbital of the fer-
rocenyl fragment and the p orbital of the functional group
Œ
CxNw, while the LUMO is mainly the p* orbital of the
Conclusions
†
Œ
CxNw group. In contrast, in the cyclopalladated complex-
†
The electrochemical studies show that the cyclopalladated
compounds [PdM(g5-C H )Fe[(g5-C H )C(Me)xN(C H -4-
Me)]NCl(L)] (L \ PPh , PPh Et, PPhEt or PEt , 3È6a)
es derived from the ferrocenylimine (3a and 4È7aº), the
HOMO is formed by a combination of the p* orbital of the
ferrocenyl moiety, a contribution from the orbitals of the chlo-
5
5
5
3
6 4
3
2
2
3
are more sensitive to changes introduced in the phosphine
ligands than those containing the ferrocenylamine 1b. In
addition, for the two families of compounds an increase in the
basicity of the phosphine ligand enhances the proclivity of the
FeII towards oxidation. MO calculations on the compounds
[PdM(g5-C H )Fe[(g5-C H )C(Me)xN(C H -4-Me)]NCl(L)]
rine ligand bound to the palladium, the d
palladium atom and a small contribution from the p orbital
of the imine nitrogen, while the LUMO is mainly formed by
combination of two p* orbitals: one of the ferrocenyl group
orbital of the
x2~y2
z
Œ
and the other of the CxNw group [Fig. 3(A)]. These Ðnd-
†
ings allow us to conÐrm the results obtained by Silva et al.,18
who postulated that the variations observed in the electro-
chemical and electronic properties of M(g5-C H )Fe[(g5-
5
5
5
3
6 4
(3È6a) and [PdM(g5- C H )Fe[(g5- C H )CH NMe ]NCl(L)]
5
5
5
3
2
2
(3È6b) revealed that in compounds 3È6a there is a certain
degree of conjugation between the p system of the functional
group and that of the ferrocenyl fragment, while in 3È6b,
where the carbon bound to the C H ring has an sp3 hybrid-
5
5
C H )C(X)xY]N [which contain an sp2-hybridized carbon
5
4
atom attached to the ferrocenyl group (class A)] could be
related to a certain degree of conjugation between the p
system of the ferrocenyl moiety and the wC(X)xY fragment.
In the cyclopalladated complexes [PdM(g5-C H )Fe[(g5-
5
4
ization, this kind of interaction cannot take place.
5
5
C H )CH NMe )]NCl(L)] (L \ PPh , PPh Me, PPhMe ,
5
3
3
2
2
3
2
2
Experimental
PMe or PH , 3b and 4È7bº) [Fig. 3(B)], the HOMO was very
3
similar to that mentioned for compounds 3a and 4È7aº (except
Elemental analyses (C, H and N) were carried out at the
Serveis CientiÐco-Tecnics de la Universitat de Barcelona.
Infrared spectra were obtained with a Nicolet Impact-400
spectrophotometer using KBr pellets. 1H and 13C NMR
spectra were recorded at ca. 20 ¡C on a Gemini 200 MHz
instrument using CDCl (99.9%) as solvent and SiMe as
for the absence of the contribution of the p orbital of the
z
amine nitrogen), while the LUMO was basically a p* orbital
of the ferrocenyl moiety.
For the two families of compounds, the formation of the
r(PdwC) bond increases the energy of the HOMO, which is
consistent with the fact that in the cyclopalladated complexes
the FeII is more prone to oxidation than in the free ligands (1a,
3
4
internal standard. 31P NMR spectra of compounds 3È6a,b
were obtained with a Bruker 250 DRX instrument using
CDCl as solvent and trimethylphosphite as reference
3
Md31P[P(OMe) ] \ 140.17N. UV/VIS spectra of the com-
3
pounds in CH Cl were recorded at 20 ¡C with a Shimadzu
instrument.
2
2
Methods and materials
The di-l-chloro-bridged cyclopalladated complexes [PdM(g5-
C H )Fe[(g5-C H )C(Me)xN(C H -4-Me)]N(l-Cl)]
(2a)
(2b)
5
5
5
3
6
4
2
and [PdM(g5-C H )Fe[(g5-C H )CH NMe ]N(l-Cl)]
5
5
5
3
2
2
2
were prepared as described previously.10,11 The phosphines
PPh Et and PPhEt were kindly provided by Dr. D. Panyella
(Univ. Barcelona). CHCl and CH Cl were distilled (over
2
2
3
2 2
CaO) before use. Some of the preparations described below
require the use of benzene, which should be handled with
CAUTION.
Syntheses of 3È6a
2a (100 mg, 0.11 mmol)10 was suspended in 20 ml of benzene
and then 0.220 mmol of the corresponding phosphine was
added. The resulting mixture was stirred at room temperature
for 1.5 h. The undissolved materials were Ðltered o† and dis-
carded, and the Ðltrate was concentrated to dryness on a
rotary evaporator. The residue was dissolved in the minimum
Fig. 3 HOMO and LUMO of (A) [PdM(g5-C H )Fe[(g5-
5
5
C H )C(Me)xN(C H -4-Me)]NCl(PH )] (7aº) and (B) [PdM(g5-
5
3
6
4
3
C H )Fe[(g5-C H )CH NMe ]NCl(PH )] (7bº)
5
5
5
3
2
2
3
980
New J. Chem., 1998, Pages 977È982

View Article Online
Table 3 Crystal data and details of the reÐnement of the crystal structures of [PdM(g5-
C H )Fe[(g5-C H )C(Me)xN(C H -4-Me)]NCl(PPh )]
(3a)
and
[PdM(g5-C H )Fe[(g5-
5
5
5
3
6
4
3
5
5
C H )CH NMe ]NCl(PPh )] (3b). Standard deviations are given in parentheses
5
3
2
2
3
3a
3b
Empirical formula
Formula weight
Temperature/K
Wavelength/Ó
Crystal system
Crystal size/(mm ] mm ] mm)
Space group
C
720.31
293(2)
0.71069
Triclinic
0.1 ] 0.1 ] 0.2
P1
a \ 12.795(2) Ó
b \ 11.534(2) Ó
c \ 11.267(2) Ó
a \ 106.660(10)¡
b \ 98.660(10)¡
c \ 94.500(10)¡
1561.8(5)
H
ClFeNPPd
C
646.24
293(2)
0.71069
H
ClFeNPPd
37 33
31 31
Monoclinic
0.1 ] 0.1 ] 0.2
P2 /a
1
Unit cell dimensions
a \ 13.650(3) Ó
b \ 19.678(4) Ó
c \ 10.169(2) Ó
a \ 90¡
b \ 94.69(2)¡
c \ 90¡
Volume/Ó3
2722.3(10)
4
Z
2
Density calcd/g cm~3
Absorption coefÐcient/mm~1
# range for data collection/deg
Index ranges
1.532
1.204
2.23È30.00
[17 O h O 17
[16 O k O 15
0 O l O 15
9087
1.577
1.371
3.70È24.98
[15 O h O 16
0 O k O 23
0 O l O 11
2550
No. of reÑections collected
No. of independent reÑections
ReÐnement method
9087 [R (on F) \ 0.000]
2424 [R (on F) \ 0.1372]
int
int
Full-matrix least-squares on F2
No. of data/restraints/parameters
Goodness-of-Ðt on F2
9036/0/479
0.884
2374/0/327
1.109
Final R indices [I [ 2r(I)]
R \ 0.0356
R \ 0.0483
1
1
wR \ 0.0694
wR \ 0.1272
2
2
R indices (all data)
R \ 0.0847
R \ 0.0571
1
1
wR \ 0.1538
2
wR \ 0.1944
2
Largest di†. peak, hole/e Ó~3
0.826, [1.337
0.851, [1.282
amount of CH Cl and then treated with 20 ml of n-hexane.
71.21 [C H ], 67.82 [C3], 67.52 [C4], 69.12 [C5], 183.16
†
2
2
5 5
Œ
The resulting mixture was stirred at room temperature for 30
min and the deep orange solids formed were collected by Ðl-
tration and air-dried. (Yields: 83, 72, 81 and 75% for 3È6a,
respectively).
[ CxNw].
Syntheses of 3È6b
3a: Anal. (%) calcd (found) for C
H
NFePPdCl: C, 61.69
These compounds were prepared using the same procedure as
described above for 3È6a but using 2b as the starting
material.11 (Yields: 78, 75, 69 and 72% for 3È6b, respectively).
37 33
(61.7); H, 4.62 (4.7); N, 1.94 (2.05). IR(KBr pellets):
Œ
m( CxNw) \ 1570 cm~1. 1H NMR (in ppm): 3.75 [C H ].
†
5
5
3.38 [H3], 4.13 [H4]. 4.47 [H5], 2.07 [wC(Me)xNw], 2.38
[Me], 7.10È7.90 [aromatic]. 13C NMR (selected data in ppm):
70.53 [C H ], 101.72 [C1], 90.12 [C2], 69.19 [C3], 67.06 [C4],
3b: Anal. (%) calcd (found) for C
H
NFePPdCl: C, 57.61
31 31
(57.7); H, 4.83 (4.9); N, 2.17 (2.1). 1H NMR (in ppm): 3.79
[C H ], 3.60 [H3], 3.75 [H4], 4.00 [H5], 3.54 and 3.00
5
5
5 5
Œ
69.09 [C5], 181.42 [ CxNw].
[wCH Nw], 2.57 and 2.60 [wN(Me) ], 7.20È7.95
†
2
2
4a: Anal. (%) calcd (found) for C
(58.8); H, 4.95 (4.95); N, 2.08 (2.1). IR (KBr pellets):
H
NFePPdCl: C, 58.96
[aromatic]. 13C NMR (selected data in ppm): 69.39 [C H ],
33 33
5 5
97.22 [C1], 95.17 [C2], 69.73 [C3], 65.30 [C4], 69.58 [C5],
Œ
m( CxNw) \ 1575 cm~1. 1H NMR (in ppm): 3.81 [C H ],
60.57 [wCH Nw], 51.23 [Me].
†
5
5
2
3.58 [H3], 4.13 [H4], 4.41 [H5], 2.04 [wC(Me)xNw], 2.36
4b: Anal. (%) calcd (found) for C
H
NFePPdCl: C, 54.21
27 31
[Me], 2.15È2.40 [wCH w], 0.9È1.40 [Me], 6.98 [Ha and
(54.3), H, 5.22 (5.2); N, 2.34 (2.3). 1H NMR (in ppm): 3.72
2
Ha@], 7.19 [Hb and Hb@], 7.10È7.90 [C H ]. 13C NMR
[C H ], 3.52 [H3], 3.76 [H4], 3.96 [H5], 3.57 and 3.18
6
5
5 5
(selected data in ppm): 70.81 [C H ], 101.61 [C1], 91.23 [C2],
[wCH Nw], 3.24 and 3.00 [wN(Me) ], 2.10È2.40
5
5
2
2
2
6 5
Œ
69.64 [C3], 67.33 [C4], 69.42 [C5], 182.95 [ CxNw].
[wCH w], 0.90È1.40 [wCH ], 7.30È8.00 [C H ]. 13C NMR
†
3
5a: Anal. (%) calcd (found) for C
H
NFePPdCl: C, 55.79
(selected data in ppm): 69.52 [C H ], 97.01 [C1], 95.42 [C2],
29 33
5 5
(55.7); H, 5.33 (5.3); N, 2.24 (2.2). IR (KBr pellets):
69.82 [C3], 65.54 [C4], 69.80 [C5], 61.40 [wCH Nw], 51.18
2
Œ
m( CxNw) \ 1583 cm~1. 1H NMR (in ppm): 3.99 [C H ],
[Me].
†
5
5
3.62 [H3], 4.18 [H4], 4.41 [H5], 2.03 [wC(Me)xNw], 2.36
5b: Anal. (%) calcd (found) for C
H
NFePPdCl: C, 50.21
23 31
[Me], 2.06È2.38 [wCH w], 1.02È1.50 [Me], 6.98 [Ha and
(49.8), H, 5.68 (6.6); N, 2.55 (2.45). 1H NMR (in ppm): 3.88
2
Ha@], 7.19 [Hb and Hb@], 7.36È8.10 [C H ]. 13C NMR
[C H ], 3.43 [H3], 3.08 [H4], 3.95 [H5], 3.50 and 3.42
6
5
5 5
(selected data in ppm): 71.20 [C H ], 101.46 [C1], 90.79 [C2],
[wCH Nw], 3.20 and 2.98 [2wN(Me) ], 2.00È2.45
5
5
2
2
6 5
Œ
68.32 [C3], 67.40 [C4], 69.32 [C5] 183.02 [ CxNw].
[wCH w], 1.00È1.40 [Me], 7.30È7.95 [C H ]. 13C NMR
†
2
6a: Anal. (%) calcd (found) for C
H
NFePPdCl: C, 52.11
(selected data in ppm): 69.40 [C H ], 97.12 [C1], 94.92 [C2],
25 33
5 5
(52.05); H, 5.77 (5.8); N, 2.43 (2.4). IR (KBr pellets):
69.31 [C3], 65.96 [C4], 69.85 [C5], 61.42 [wCH Nw], 50.02
2
Œ
m( CxNw) \ 1590 cm~1. 1H NMR (in ppm): 4.03 [C H ],
[Me].
†
5
5
4.35 [H3], 4.29 [H4], 4.40 [H5], 2.08 [wC(Me)xNw], 2.37
6b: Anal. (%) calcd (found) for C
H
NFePPdCl: C, 45.45
19 30
[Me], 2.00È2.30 [wCH w], 0.95È1.30 [Me], 6.85 [Ha and
(45.4); H, 6.22 (6.1); N, 2.79 (2.7). 1H NMR (in ppm): 3.90
2
Ha@], 7.02 [Hb and Hb@]. 13C NMR (selected data in ppm):
[C H ], 4.40 [H3], 4.01 [H4], 3.98 [H5], 3.51 and 3.05
5
5
New J. Chem., 1998, Pages 977È982
981

View Article Online
[wCH Nw], 3.20 and 2.95 [wN(Me) ], 2.00È2.30
Catalunya (Grants N. PB96-0164 and SGR-1997-00174) for
Ðnancial support. We are also grateful to Dr. C. Muller (Dpt.
Qu•mica-F•sica, Univ. Barcelona) for the facilities given to
undertake the electrochemical studies.
2
2
[wCH w], 0.95È1.30 [Me]. 13C NMR (selected data in
2
ppm): 69.25 [C H ], 68.86 [C3], 65.68 [C4], 69.70 [C5], 61.50
5
5
[wCH Nw], 50.93 [Me].
2
References
Electrochemical studies
1 Ferrocenes. Homogeneous Catalysis. Organic Synthesis. Material
Science, ed. A. Togni and T. Hayashi, VCH, Weinheim, Germany,
1995.
2 W. R. Cullen and J. D. Woolins, Coord. Chem. Rev., 1981, 39, 1.
3 A. Benito, J. Cano, R. Mart•nez-Manez, J. Soto, J. Paya, J. Lloret,
M. Julve and J. Faus, Inorg. Chem., 1993, 32, 1197.
4 M. Bracci, C. Ercolani, B. Floris, M. Bassetti, A. Chiesi-Vila and
C. Guastini, J. Chem. Soc., Dalton T rans., 1990, 1357.
5 A. Louati, M. Gross, L. Douce and D. Matt, J. Organomet. Chem.,
1992, 438, 167.
6 K. Hamamura, M. Kita, N. Nonoyama and J. Fujita, J.
Organomet. Chem., 1993, 463, 169.
7 C. Lopez, R. Bosque, X. Solans, M. Font-Bard•a, J. Silver and G.
Fern, J. Chem. Soc., Dalton T rans., 1995, 1839.
8 R. Bosque, A. Caubet, C. Lopez, E. Espinosa and E. Molins, J.
Organomet Chem., 1997, 544, 233.
Electrochemical data for the compounds under study were
obtained by cyclic voltammetry under argon at ca. 20 ¡C,
using acetonitrile (HPLC grade) as solvent and tetra-
butylammonium hexaÑuorophosphate as supporting electro-
lyte. The redox half-wave potentials were referred to an
Ag/AgNO (0.1 M, in acetonitrile) electrode separated from
3
the solution by a medium porosity fritted disc. A platinum
wire auxiliary electrode was used in conjunction with a plati-
num disk working electrode, Tacussel EDI rotatory electrode
(3.14 mm2). Cyclic voltammograms of 10~3 M solutions of the
samples in acetonitrile were recorded with a Versstat, EG&G
Princeton Applied Research potentiostat.
9 (a) R. Bosque, C. Lopez and J. Sales, Inorg. Chim. Acta, 1996, 244,
141. (b) J. C. Kotz, E. Getty and L. Lin, Organometallics, 1985, 4,
610.
Crystal structure resolution and reÐnement
Prismatic crystals of compounds 3a and 3b were selected and
mounted on a Philips-110 four-circle di†ractometer. Unit cell
parameters were determined from automatic centering of 24
reÑections in the range (8¡ \ # \ 21¡) and reÐned by the
least-squares method. Intensities were collected with graphite
monochromated MoKa radiation using x [ 2# scan tech-
nique. The reÑections (9087 for 3a and 2550 for 3b) were mea-
sured in the ranges of 2.23¡ O # O 30.0¡ for 3a and
3.70¡ O # O 24.98¡ for 3b. The number of independent reÑec-
tions in the two cases are given in Table 3. In both cases, three
reÑections were measured every two hours for orientation and
intensity control and no signiÐcant intensity decay was
observed. Lorentz polarization corrections were made, but
absorption corrections were not.
10 R. Bosque, C. Lopez, J. Sales, X. Solans and M. Font-Bard•a, J.
Chem. Soc., Dalton T rans., 1994, 735.
11 J. G. Gaunt and B. L. Shaw, J. Organomet. Chem., 1975, 102, 511.
12 (a) R. Bosque, C. Lopez, J. Sales and X. Solans, J. Organomet.
Chem., 1994, 483, 61. (b) R. Bosque, C. Lopez and J. Sales, J.
Organomet. Chem., 1995, 498, 147. (c) R. Bosque, C. Lopez, J. Sales,
X. Solans and J. Silver, J. Chem. Soc., Dalton T rans., 1996, 3195.
(d) C. Lopez and R. Bosque, J. Organomet. Chem., 1996, 524, 247.
(e) C. Lopez, R. Bosque, X. Solans and M. Font-Bard•a, New J.
Chem., 1996, 20, 1285. ( f ) C. Lopez, R. Bosque, X. Solans and M.
Font-Bard•a, T etrahedron: Asymmetry, 1996, 7, 2527. (g) C. Lo pez,
R. Bosque, X. Solans and M. Font-Bard•a, J. Organomet. Chem.,
1997, 547, 309. (h) C. Lopez, R. Bosque, X. Solans and M. Font-
Bard•a, J. Organomet. Chem., 1997, 539, 99. (i) C. Lopez and J.
Granell, J. Organomet. Chem., 1998, 555, 211. (j) C. Lopez, R.
Bosque, D. Sainz, X. Solans and M. Font-Bard•a, Organometallics,
1997, 16, 3261. (k) C. Lopez, J. Sales, R. Zquiak and X. Solans, J.
Chem. Soc., Dalton T rans., 1992, 2321. (l) R. Bosque, M. Font-
Bard•a, C. Lopez, J. Sales, J. Silver and X. Solans, J. Chem. Soc.,
Dalton T rans., 1994, 747. (m) R. Bosque, C. Lopez, X. Solans, M.
Font-Bard•a, J. Silver and G. Fern, J. Chem. Soc., Dalton T rans.,
1995, 4053.
The structures were solved by direct methods using
SHELX23 and reÐned by the full-matrix least-squares method
using SHELX93.24 The function minimized was ;wpF o2
0
[ o F o2 o2, where w \ [r2(I) ] 0.0995P2]~1 for 3a, w \
c
[r2(F2) ] (0.1254P)2 ] 2.1781P]~1 for 3b and P \ [o F o2
0
0
] 2 o F o2]/3. f, f @ and f A were taken from the literature.25
c
13 W. A. Henderson and C. A. Sreuli, J. Am. Chem. Soc., 1960, 82,
The C(13) atom for 3b gave an abnormal temperature factor
5791.
and the short NwC(13) bond length suggests a possible dis-
order in its localization. Twenty-seven hydrogen atoms in 3a
(and all hydrogen atoms in 3b) were located from a di†erence
synthesis. For complex 3a the remaining six hydrogen atoms
were computed. All the hydrogen atoms (in 3a and 3b) were
reÐned with an overall isotropic temperature factor using a
riding model for computed H atoms. The Ðnal R indices and
further details concerning the reÐnement of the structures are
summarized in Table 3. CCDC reference number 440/048.
14 T. H. Allen and O. Kennard, Chem. Design Automation News,
1993, 8, 146.
15 E. R. Brown and J. E. Sandifer, in Electrochemical Methods, ed. W.
Rossiter and J. F. Hamilton, Wiley, New York, 1986, vol. II, p.
273.
16 C. Lopez, R. Bosque, X. Solans, M. Font-Bard•a, D. Tramuns, G.
Fern and J. Silver, J. Chem. Soc., Dalton T rans., 1994, 3039.
17 (a) A. D. Ryabov, G. M. Kazankov, I. M. Payanshkina, O. V.
Grozovsky, O. G. Dyachenko, V. A. Polyakov and L. G.
KuzÏmina, J. Chem. Soc., Dalton T rans., 1997, 4385. (b) C. E. L.
Headford, R. Mason, P. R. Ranatunge-Bandarage, B. H. Robinson
and J. Simpson, J. Chem. Soc., Chem. Commun., 1990, 601.
18 M. E. N. Silva, A. J. L. Pombeiro, J. J. R. Frausto da Silva, R.
Herrmann, N. Deus and R. E. Bozak, J. Organomet. Chem., 1994,
480, 81.
19 R. Herrman, A. J. L. Pombeiro, M. E. N. P. Rodrigues and I. Ugi
Port. Electrochim. Acta, 1984, 2, 57.
20 H. Henning and O. Gurtler, J. Organomet. Chem., 1968, 11, 307.
21 N. F. Blom, E. W. Neuse and M. G. Thomas, T ransition Met.
Chem. (W einheim, Ger.), 1987, 12, 301.
22 SPART AN 4.1, Wavefunction Inc. Irvine, CA, 1995.
23 G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467.
24 G. M. Sheldrick, SHEL X93, A Computer Program for the Determi-
nation of Crystal Structures, University of Gottingen, Germany,
1994.
Computational details
The calculations were performed with the SPARTAN 4.1 suite
of programs22 using
a
Silicon Graphics workstation
(INDIGO-2 power XZ). The PM3(tm) method was used with
the default parameters provided by the program. Geometrical
restrictions were not imposed in any case. The calculations
were performed using the option SCF \ converge. The
number of geometry optimization cycles required was greater
than the default value. A minimum of 1500 cycles was neces-
sary in all cases.
25 International T ables of X-ray Crystallography, Kynoch Press, Bir-
mingham, 1974, vol. IV, pp. 99È101.
Acknowledgements
We are indebted to the Direccion General de Investigacio
Cient•Ðca y Technica (DGYCIT) and to the Generalitat de

n
Received in Montpellier, France, 2nd March 1998;
Paper 8/01737I
982
New J. Chem., 1998, Pages 977È982