Synthesis of new donor/acceptor η5-cyclopentadienyl and η5-indenyliron(II) complexes with p-benzonitrile derivatives. Crystal structures of [Fe(η5-C5H5)(CO)(P(OC6H 5)3

Article abstract of DOI:10.1016/S0022-328X(01)01039-7

New complexes of the type [Fe(η⁵-Cp or Ind)(L)(L′)(p-NCR)][BF₄] (L, L′=CO, P(OC₆H₅)₃, P(C₆H₅)₃; R=C₆H₄N(CH₃)₂, C₆

Full text of DOI:10.1016/S0022-328X(01)01039-7

Journal of Organometallic Chemistry 632 (2001) 145–156
www.elsevier.com/locate/jorganchem
Synthesis of new donor/acceptor h5-cyclopentadienyl and
h5-indenyliron(II) complexes with p-benzonitrile derivatives.
Crystal structures of
[Fe(h5-C5H5)(CO)(P(OC6H5)3)(p-NCC6H4NO2)][BF4]·CH2Cl2 and
[Fe(h5-C9H7)(CO)(P(OC6H5)3)(p-NCC6H4NO2)][BF4]
M. Helena Garcia a,b, M. Paula Robalo a,c,*, Anto´nio P.S. Teixeira a,c, A.R. Dias a,
M. Fa´tima M. Piedade a,b, M. Teresa Duarte a
a Centro de Qu´ımica Estrutural, Instituto Superior Te´cnico, A6. Ro6isco Pais, 1049-001 Lisbon, Portugal
b Departamento de Qu´ımica e Bioqu´ımica, Faculdade de Cieˆncias da Uni6ersidade de Lisboa, Campo Grande, 1749-016 Lisbon, Portugal
Departamento de Qu´ımica, Uni6ersidade de E6ora, Cole´gio Lu´ıs Anto´nio Verney, Rua Roma˜o Ramalho n 59, 7000-671 E6ora, Portugal
c
o
´
Received 26 February 2001; accepted 22 April 2001
On the occasion of the 60th birthday of Professor Alberto Roma˜o Dias
Abstract
New complexes of the type [Fe(h5-Cp or Ind)(L)(L%)(p-NCR)][BF4] (L, L%=CO, P(OC6H5)3, P(C6H5)3; R=C6H4N(CH3)2,
C6H4NO2, (E)-C(H)ꢀC(H)C6H4NO2, (E)-C(H)ꢀC(H)C6H4N(CH3)2) have been synthesised and characterised. Spectroscopic data
were analysed in order to evaluate the tuning of the electronic density at the metal centre and the extension of the p-delocalisation
on the molecule, due to the presence of coligands with different acceptor/donor abilities. The structures of two complexes
[Fe(h5-C5H5)(CO)(P(OC6H5)3)(p-NCC6H4NO2)][BF4] and [Fe(h5-C9H7)(CO)(P(OC6H5)3)(p-NCC6H4NO2)][BF4] were determined
(
by X-ray crystallographic analysis. The compounds crystallised in the centrosymmetric space groups P1 and P21/n, respectively.
Bond distances within the nitrile ligand are discussed in order to evaluate the nature of iron–nitrile bonding in these complexes.
© 2001 Elsevier Science B.V. All rights reserved.
Keywords: Iron complexes; Benzonitrile derivatives; Cyclopentadienyl; Indenyl; Crystal structures
1. Introduction
molecular hyperpolarisability i. A further enhancement
of molecular polarisation can be introduced, at the
design stage, by the use of different metal centres which
can be extremely electron-rich or electron-deficient de-
pending on their oxidation states and on their ligand
environment [1–3]. In addition, new bonding ge-
ometries, interacting with aromatic and nonaromatic
coligands, can tune molecular hyperpolarisabilities,
since they may change the energies of the occupied and
unoccupied metal d orbitals that interact with the p
electron orbitals of the conjugated chromophore.
Therefore, transition metal compounds are expected to
be excellent acceptor or donor partners.
Organometallic chemistry has emerged as a promis-
ing research area to explore new variables for the
engineering of nonlinear optical hyperpolarisabilities
and for the development of new materials with poten-
tial nonlinear optical (NLO) applications. It is well
known that molecular polarisation, due to metal-to-lig-
and or ligand-to-metal charge transfer bands in the
UV–vis spectrum, is responsible for high values of
* Corresponding author. Tel.: +351-21-8419317; fax: +351-21-
8464455.
In our earlier studies, we identified the fragments
E-mail
addresses:
lena.garcia@ist.utl.pt
(M.H.
Garcia),
i044@alfa.ist.utl.pt (M.P. Robalo).
[M(h5-C5H5)(P P)]+ (M=Fe(II), Ru(II); P P=
–
–
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01039-7

146
M.H. Garcia et al. / Journal of Organometallic Chemistry 632 (2001) 145–156
bidentate phosphine) as good donor groups to built
donor-p-system-acceptor molecules for second and
third nonlinear optical effects [4–6], where the p-system
was a p-benzonitrile derivative. Compound [Fe(h5-
C5H5)(DPPE)(p-NCC6H4NO2)][PF6] showed a signifi-
cant molecular hyperpolarisability i of 410×10−30 esu
[6]. The main structural feature of this family of com-
pounds is the existence of the metal centre in the same
plane of the chromophore, thus allowing metal–ligand
p-backdonation via the dmetal–p* NC ligand.
Spectroscopic data were evaluated in order to under-
stand the contribution of all these variables on the
donor–acceptor ability of the iron(II) centre and the
extension of p-delocalisation on the molecule as well.
These studies were complemented with the discussion of
the structures, determined by X-ray diffraction, for
compounds [Fe(h5-C5H5)(CO)(P(OC6H5)3)(p-NCC6H4-
NO2)][BF4] (5) and [Fe(h5-C9H7)(CO)(P(OC6H5)3)(p-
NCC6H4NO2)][BF4] (16).
Our continuing interest on the understanding of
NLO properties — structural features, prompted us to
extend our studies on this type of molecules in order to
explore the possibility of fine tuning the NLO proper-
ties through some structural changes.
2. Results and discussion
2.1. Preparation and characterisation of the complexes
[Fe(p5-C5H5)(L)(L%)(p-NCR)][BF4] and
[Fe(p5-C9H7)(L)(L%)(p-NCR)][BF4]
With the aim to modify the electronic richness of the
metallic centre, the h5-cyclopentadienyl ligand was sub-
stituted by h5-indenyl. Also, the bidentate phosphine
coligand (DPPE) was replaced by ligands possessing
different acceptor/donor abilities, such as CO (good
p-acceptor), phosphite (medium p-acceptor) and the
monodentate triphenylphosphine (poor p-acceptor).
This work presents an extensive study on the synthe-
sis and characterisation of the family of compounds
Treatment of the starting materials [Fe(h5-
C5H5)(L)(L%)(I)] or [Fe(h5-C9H7)(L)(L%)(I)] (L, L%=CO,
P(C6H5)3, P(OC6H5)3) with AgBF4 and a slight excess
of the appropriate nitrile in dichloromethane or ben-
zene at room temperature afforded the cationic nitrile
complexes with different coligands.
After workup, complexes of the type [Fe(h5-Cp or
Ind)(L)(L%)(p-NCR)][BF4] (L, L%=CO, P(C6H5)3,
P(OC6H5)3; R=C6H4NO2, C6H4N(CH3)2, (E)-CHꢀ
CHC6H4NO2 and (E)-CHꢀCHC6H4N(CH3)2) (1–18)
(see Fig. 1) were obtained in ca. 30–80% yield. The
compounds are fairly stable towards oxidation in air
and moisture in both the solid state and solution. The
formulation is supported by analytical data, IR and
1H-, 13C- and 31P-NMR spectra (see Section 4).
The IR spectra of the derivatives reveal the presence
of the different coligands: cyclopentadienyl and indenyl
groups (: 3060 cm−1), the P(OC6H5)3 ligand (PꢁO
stretching modes as a clear triplet in the region 1150–
1220 cm−1), the CO ligand (in the range 1980–2070
cm−1) and the coordinated nitrile (w(CN)) (in the range
2230–2270 cm−1).
[Fe(h5-C5H5)(L)(L%)(p-NCR)][BF4]
P(OC6H5)3, P(C6H5)3 with
(L,
L%=CO,
R=C6H4N(CH3)2,
C6H4NO2, (E)-CHꢀCHC6H4N(CH3)2, (E)-CHꢀCHC6-
H4NO2) and [Fe(h5-C9H7)(L)(L%)(p-NCR)][BF4] (L,
L%=CO, P(OC6H5)3, and R=C6H4N(CH3)2, C6H4-
NO2, (E)-CHꢀCHC6H4NO2) where the organometallic
fragment has been systematically enriched or depleted
by changing the ligands L and L%. Also, the length of
the spacer has been varied in order to maximise the
delocalisation on the p-system.
Analysis of the w(CN) stretching bands of the new
complexes shows a general increase of the w(CN) upon
coordination, this shift being more pronounced for
complexes [Fe(h5-Cp)(CO)2(p-NCC6H4N(CH3)2)]+ (2)
(+46 cm−1
)
and [Fe(h5-Ind)(CO)2(p-NCC6H4N-
(CH3)2)]+ (15) (+42 cm−1). The extension of this
effect is virtually independent of the h5-group (cy-
clopentadienyl or indenyl) and seems to be affected by
the presence of the carbonyl and/or the phosphorus
coligands. For example, in the series [Fe(h5-
Cp)(L)(L%)(p-NCC6H4N(CH3)2)]+ (L=L%=P(OC6H5)3
(12), L=CO, L%=P(OC6H5)3 (6) and L=L%=CO (2),
the increasing values of Dw(CN) +21 (12), +29 (6)
and +46 cm−1 (2) are in agreement with the electronic
depletion at the iron centre. This enhancement of
w(CN) seems to be consistent with a nitrile s-type
coordination where the presence of p-backdonation
Fig. 1. Structural formulae of complexes [Fe(h5-C5H5 or
C9H7)(L)(L%)(p-NCR)][BF4] (1–18).

M.H. Garcia et al. / Journal of Organometallic Chemistry 632 (2001) 145–156
147
owing to p-bonding between the metal d orbitals and
the p* orbital of the CN group does not contribute
essentially to describe the metal nitrile interaction.
The IR spectra of the [Fe(h5-Cp or Ind)(CO)(L%)(p-
NCR)]+ (L%=P(OC6H5)3, P(C6H5)3, R=C6H4N-
(CH3)2, C6H4NO2, etc.) derivatives are also character-
ised by one strong carbonyl stretching absorption cor-
responding to the terminal CO group. These w(CO)
bands show lower values than those of the parent
dicarbonyl compounds. Regarding the series [Fe(h5-
ceptor groups relative to the same coordinated
chromophores. For example, a deshielding of +0.15
ppm (upon coordination) was found for the ortho pro-
tons relative to NC group of complex [Fe(h5-
Cp)(CO)2(p-NCC6H4N(CH3)2)][BF4] (2), and a smaller
value of +0.03 ppm for the corresponding [Fe(h5-
Cp)(CO)(P(OC6H5)3)]+ derivative (6). Moreover, in
these dimethylamino derivatives this effect is followed
by a deshielding of the methyl protons of the amino
group (+0.06 ppm for complex 2), indicating that this
group is acting as an electron donor upon coordination
to the organometallic centre. Although in most cases
the 1H-NMR shift values might be insignificant, a trend
is observed and is consistent with the IR results. Never-
theless, the [Fe(h5-Cp)(CO)(P(C6H5)3)]+ fragment (7–
10) behaves as a weak p-donor group, in spite of the
presence of the CO ligand, since small shieldings were
observed on the same protons (an effect more promi-
nent for the nitro derivatives). This p-donor behaviour
reflects an overall effect of p-backdonation towards the
nitrile ligand, due to the presence of the triphenylphos-
phine coligand.
Cp)(CO)(L%)(p-NCC6H4N(CH3)2)]+,
with
L%=
P(C6H5)3 (8), L%=P(OC6H5)3 (6) and L%=CO (2) we
found the values 1993, 2007 and 2015 cm−1, respec-
tively. These differences are consistent with the en-
hancement of p bonding between the metal and the
remaining terminal carbonyl group, due to the replace-
ment of one CO in [Fe(h5-Cp or Ind)(CO)2(p-NCR)]+
by the more basic and poorer p-acceptor phosphine or
phosphite. This effect of phosphorus ligands on the
w(CO) frequency values in these complexes seems to be
more pronounced in the h5-indenyl derivatives consis-
tent with a stronger donor character of indenyl com-
plexes relative to the corresponding cyclopentadienyl
derivatives.
Comparison of these spectroscopic data with our
previous results on [Fe(h5-Cp)(P P)]+ (P P=biden-
–
–
1H-NMR chemical shifts for the cyclopentadienyl
ring in the complexes [Fe(h5-Cp)(L)(L%)(p-NCR)][BF4]
are in the range usually observed for monocationic
iron(II) complexes, and seem to be affected by all the
other coligands. In fact, substitution of CO with the
more electron donating phosphite or phosphine leads to
a shift on Cp resonances upfield owing to the increased
electron density at the metal centre. Replacement of the
donor group (p-N(CH3)2) by the acceptor group (p-
NO2) on the nitrile benzene ring gives a deshielding
effect on the Cp resonance, as it was observed previ-
ously for analogous iron(II) complexes [4,7]. The pres-
ence of triphenylphosphine and triphenylphosphite are
also confirmed by their respective signals in the corre-
sponding ranges of the spectra. However, in contrast to
the effect observed for Cp ring, the phosphine and
phosphite signals are shown to be relatively insensitive
to the nature of the aromatic nitrile.
tate phosphines) fragments suggests that the substitu-
tion of phosphine by coligands with different
acceptor/donor abilities contribute to the tuning of the
donor/acceptor capacity of the iron(II) moiety towards
the nitrile ligand. Actually, it is possible to classify the
studied complexes in two groups:
1. organometallic moieties acting as acceptor groups
([Fe(h5-Cp)(CO)2]+ and [Fe(h5-Cp)(CO)(P(OC6-
H5)3)]+);
2. organometallic moiety acting as a p-donor group
([Fe(h5-Cp)(CO)(P(C6H5)3)]+) to be added to the
former fragment [Fe(h5-Cp)(P P)]+.
–
Moreover, within each group we can also recognise
different strengths on the acceptor ability: [Fe(h5-
Cp)(CO)(P(OC6H5)3)]+B[Fe(h5-Cp)(CO)2]+ and in the
donor capacity: [Fe(h5-Cp)(CO)(P(C6H5)3)]+B[Fe(h5-
Cp)(P P)]+.
–
The 13C-NMR spectroscopic data is also valuable in
assessing the donor/acceptor properties of the phos-
phine or phosphite, in the derivatives [Fe(h5-
Cp)(CO)(L%)(p-NCR)]+, since the 13CO resonance of
the carbonyl group in these complexes should reflect
these properties. Analysis of the carbonyl chemical shift
data for [Fe(h5-Cp)(CO)(L%)(p-NCR)]+derivatives indi-
cate a net donation of the electron density from L% to
the Fe centre showing the increasing order: CO
(209.11)BP(OC6H5)3 (213.50)BP(C6H5)3 (217.09)
Our previous studies for complexes [Fe(h5-Cp)(P
–
P)(p-NCR)]+ (P P=bidentate phosphines; R=donor
–
and acceptor aromatic nitriles) [4,7] suggested that IR
and NMR spectroscopic data could be used as a tool to
predict the nonlinear optical behaviour of the com-
pounds in solution. A good correlation was found for
the shift of the w(CN) to lower frequencies and a
1
simultaneous upfield shift in the H-NMR spectra for
the ortho protons of the nitrile aromatic ring, with high
values for molecular hyperpolarisabilities (i) [7]. Ac-
cording to this behaviour, which reflects the donor
found
for
the
series
[Fe(h5-Cp)(CO)(L%)(p-
NCC6H4NO2)]+ (L%=CO (1); P(OC6H5)3 (5); P(C6H5)3
(7)) and which could be extended for the other nitrile
chromophores.
ability of the [Fe(h5-Cp)(P P)]+ fragment, we were
–
able to identify in the present work the role of [Fe(h5-
Cp)(CO)2]+ and [Fe(h5-Cp)(CO)(P(OC6H5)3)]+ as ac-

148
M.H. Garcia et al. / Journal of Organometallic Chemistry 632 (2001) 145–156
Table 1
indenyl protons H(4–7) give rise to four separate sig-
nals of the type AA%BB%, or in the case of [(h5-
Ind)Fe(CO)(P(OC6H5)3)(p-NCC6H4NO2)]+ (16), two
doublets for the protons 4, 7 and two triplets for the
protons 5, 6; the three protons H(1–3) give rise to three
Optical spectral data for complexes [Fe(h5-L)(L%)(L¦)(p-NCR)][BF4]
in chloroform solutions at room temperature, concentration ca. 2.0×
10−5 mol dm−3
1
separate multiplets or singlets. These H-NMR patterns
were already described in the literature [8] for com-
pounds [(h5-Ind)Fe(CO)(L)(CO2R)]+ (L=phosphines
or phosphites; R=CHMe2, Me).
The hapticity of the indenyl ligand can be evaluated
spectroscopically by comparing the 13C-NMR chemical
shifts of the ring junction carbons (C3a, C7a) in the
metal complex with those of the sodium indenyl: larger
distortions from h5 coordination result in larger
downfield shifts [9–11]. According to this procedure,
the parameter Dl(C-3a,7a)=l(C-3a,7a (h-indenyl
complex))−l(C-3a,7a (sodium indenyl)) has been pro-
posed as an indication of the indenyl distortion, having
values in the range −20 to −40 ppm for planar
h5-indenyl, −10 to −20 ppm for a partially slipped
h5-indenyl and +5 to +30 ppm for h3-indenyl ligands
[12]. For all the indenyl complexes obtained in this
work we found upfield shifts, Dl(C-3a,7a): −21 ppm
for the dicarbonyl derivatives 14 and 15 and : −23
ppm for the carbonyltriphenylphosphite complexes 16–
18, consistent with a indenyl ligand coordinated in a h5
fashion. Analysis of the spectroscopic data of h5-in-
denyl derivatives, when compared with the h5-cyclopen-
tadienyl analogues, shows a similar trend and also both
fragments [Fe(h5-Ind)(CO)2]+ and [Fe(h5-Ind)(CO)-
(P(OC6H5)3)]+ behaved as accepting groups relatively
to the coordinated chromophores.
Optical absorption spectra of complexes [Fe(h5-
Cp)(L)(L%)(p-NCR)][BF4] and [Fe(h5-Ind)(L)(L%)(p-
NCR)][BF4] were recorded in ca. 2.0×10−5 mol dm−3
in chloroform, in the wavelength range of 230–800 nm
(Table 1). For all the complexes, the spectra are charac-
terised by one or two bands in the UV region that
could be attributed to electronic transitions on the
nitrile ligand. In addition, it was generally found for
cyclopentadienyliron or indenyliron derivatives the exis-
tence of a very weak CT band in the visible region, with
exception for the [Fe(h5-Cp or Ind)(CO)2]+ (1), (3),
(14) derivatives, containing the p-nitrobenzonitrile lig-
and, where no CT band was observed.
The solvatochromic response of some complexes of
this series was studied, using solvents of different polar-
ity, and results reveal that the position of all the
absorption bands remain almost unchanged.
2.2. Crystallographic studies
For [(h5-Ind)Fe(CO)(P(OC6H5)3)(p-NCR)]+ com-
plexes, 1H- and 13C-NMR spectra show that all the
protons and carbons of indenyl ligand are nonequiva-
lent reflecting the asymmetry of the molecule. The four
We were able to obtain good quality crystals, grown
from dichloromethane/diethylether solutions, for X-ray
diffraction work for the complexes [Fe(h5-C5H5)(CO)-
(P(OC6H5)3)(p-NCC6H4NO2)][BF4] (5) and [Fe(h5-

M.H. Garcia et al. / Journal of Organometallic Chemistry 632 (2001) 145–156
149
Table 2
C9H7)(CO)(P(OC6H5)3)(p-NCC6H4NO2)][BF4]
(16).
These X-ray structural studies allowed us to obtain
structural data about the coordinated metal centre and
especially on the geometrical parameters of the nitrile
ligand.
Selected bond lengths (A) and angles (°) for [Fe(h5-
Cp)(CO)(P(OC6H5)3)(p-NꢂCC6H4NO2)][BF4]·CH2Cl2 (5) and [Fe(h5-
Ind)(CO)(P(OC6H5)3)(p-NꢂCC6H4NO2)][BF4] (16)
,
5
16
The molecular diagrams of the cations [Fe(h5-
C5H5)(CO)(P(OC6H5)3)(p-NꢂCC6H4NO2)]+ and [Fe-
Bond lengths
Fe(1)ꢁN(1)
Fe(1)ꢁC(11)
Fe(1)ꢁC(12)
Fe(1)ꢁC(13)
Fe(1)ꢁC(14)
Fe(1)ꢁC(15)
Fe(1)ꢁC(1%)
Fe(1)ꢁC(2%)
Fe(1)ꢁC(3%)
Fe(1)ꢁC(3%a)
Fe(1)ꢁC(7%a)
FeꢁCp or Ind (centroid)
Fe(1)ꢁC(51)
C(51)ꢁO(51)
Fe(1)ꢁP(1)
N(1)ꢁC(1)
C(1)ꢁC(2)
C(2)ꢁC(3)
C(3)ꢁC(4)
C(4)ꢁC(5)
C(5)ꢁC(6)
C(6)ꢁC(7)
C(5)ꢁN(2)
C(7)ꢁC(2)
1.878(10)
2.074(12)
2.078(12)
2.079(12)
2.113(12)
2.110(12)
1.900(8)
(h5-C9H7)(CO)(P(OC6H5)3)(p-NꢂCC6H4NO2)]+
are
shown in Figs. 2 and 3, respectively, along with the
atomic numbering scheme. Values of selected bond
lengths and angles are given in Table 2. The structural
studies confirm the presence of the BF−4 anion and
reveal the presence of a CH2Cl2 crystallisation solvent
molecule in the case of compound 5.
2.072(11)
2.076(12)
2.086(10)
2.193(9)
2.193(10)
1.745(20)
1.793(12)
1.133(11)
2.139(3)
In both complexes, the metal is coordinated to the
h5-cyclopentadienyl ring, one phosphorus atom of the
phosphite ligand, one carbon atom of the carbonyl
ligand and to the nitrile nitrogen atom of the p-
NCC6H4NO2 ligand. The coordination geometry
around the iron atom is best described as pseudo-octa-
hedral, three-legged piano stool, on the assumption that
the cyclopentadienyl (5) and indenyl (16) groups take
up three coordination sites. This pseudo-octahedral ge-
1.718(20)
1.796(14)
1.136(14)
2.158(3)
1.139(14)
1.463(16)
1.374(15)
1.378(16)
1.370(16)
1.333(16)
1.378(17)
1.498(15)
1.369(15)
1.211(13)
1.202(13)
1.156(12)
1.439(13)
1.401(13)
1.370(14)
1.354(14)
1.380(13)
1.377(13)
1.464(13)
1.351(13)
1.210(12)
1.220(12)
N(2)ꢁO(1)
N(2)ꢁO(2)
Bond angles
P(1)ꢁFe(1)ꢁCp(centroid)
N(1)ꢁFe(1)ꢁCp(centroid)
C(51)ꢁFe(1)ꢁCp(centroid)
N(1)ꢁFe(1)ꢁP(1)
N(1)ꢁFe(1)ꢁC(51)
P(1)ꢁFe(1)ꢁC(51)
Fe(1)ꢁN(1)ꢁC(1)
N(1)ꢁC(1)ꢁC(2)
O(1)ꢁN(2)ꢁO(2)
O(1)ꢁN(2)ꢁC(5)
O(2)ꢁN(2)ꢁC(5)
O(51)ꢁC(51)ꢁFe(1)
127.8(6)
122.6(4)
120.9(6)
91.6(3)
94.5(5)
90.4(4)
175.0(9)
178.3(12)
124.9(13)
117.2(12)
117.8(12)
177.1(12)
120.3(5)
124.2(6)
120.5(8)
97.1(2)
98.1(4)
89.5(3)
173.7(8)
175.3(11)
122.9(11)
118.8(12)
118.3(10)
174.3(9)
Fig. 2. ORTEP diagram for [Fe(h5-C5H5)(CO)(P(OC6H5)3)(p-
NCC6H4NO2)]+, with 20% thermal ellipsoids, showing the atomic
labelling scheme. Hydrogen atoms have been omitted for clarity.
ometry is confirmed by the NꢁFeꢁC, PꢁFeꢁC and
NꢁFeꢁP angles around the iron atom, which are all
close to 90° to (see Table 2) for both complexes and the
remaining C(h5-centroid)ꢁFeꢁX (with X=N, C or P)
angles which are 122.6(4), 120.9(6), 127.8(6)° and
120.3(5), 120.5(8), 124.2(6)°, respectively, for complexes
5 and 16.
The slip-fold distortion of the indenyl ligand can be
described by the following parameters: the slip parame-
ter, D, and both the ‘fold’ angle (FA) and ‘hinge’ angle
(HA), representing the bending of the indenyl ligand at
C(1), C(3) and C(3a), C(7a), respectively [12,13]. Ac-
cordingly, indenyl complexes are considered to be h5-
coordinated with an HA lower than 10° and D less than
Fig. 3. ORTEP diagram for [Fe(h5-C9H7)(CO)(P(OC6H5)3)(p-
NCC6H4NO2)]+, with 20% thermal ellipsoids, showing the atomic
labelling scheme. Hydrogen atoms have been omitted for clarity.
,
0.25 A. For complex 16, we found the values FA=

150
M.H. Garcia et al. / Journal of Organometallic Chemistry 632 (2001) 145–156
Table 3
Structural data for Fe derivatives containing nitrile, phosphine or carbonyl groups
a
,
,
,
, , ,
FeꢁN (A) NꢂC (A) NCꢁC (A) FeꢁNꢁC (°) NꢂCꢁC (°) Refs.
Compound
FeꢁC (A) FeꢁP (A) FeꢁC (A)
[Fe(Cp)(CO)2(NCCH3)][BF4] 2.030–2.112
1.746–1.770 1.914
1.200
1.137
1.494
1.457
175.676
179.791
175.045
178.592
14a
[14b]
[Fe(Cp)(CO)(PC6H5)3)-
(NCCH3)][BF4]
2.061–2.124 2.227
1.762
1.916
1.911
1.874
1.878
1.900
[Fe(Cp)(CO)(PC6H5)3)-
(NCCH(COOH)tBu)][BF4]
[Fe(Cp)(DPPE)-
(p-NCC6H4NO2)][PF6]
[Fe(Cp)(CO)(P(OC6H5)3)-
(p-NCC6H4NO2)][BF4]
[Fe(Ind)(CO)(P(OC6H5)3)-
(p-NCC6H4NO2)][BF4]
p-NCC6H4NO2
2.070–2.132 2.235
2.063–2.090 2.209
2.074–2.113 2.158
2.072–2.193 2.139
1.772
1.116
1.129
1.139
1.156
1.155
1.480
1.42
174.329
176.6
[14c]
177.4
178.3
175.3
179.2
[7]
1.796
1.793
1.463
1.439
1.438
175.0
This work
This work
[14d]
173.7
a FeꢁC (Cp, Ind) range.
,
5.1(1)°; HA=5.4(1)°; D=0.11(1) A, consistent with an
contribute to describe the FeꢁNꢂC bond in the solid
state, although this effect could be supported by the
almost linear geometry of nitrile ligand in both com-
pounds (see Table 2). These results are in agreement
with IR spectroscopic studies which show an increase in
nitrile stretching frequency upon coordination, indicat-
ing that the NꢁC bond is apparently strengthened
rather than weakened.
h5-indenyl coordination.
In Table 3, we present a comparison between the
coordination geometry about the Fe atom for the re-
ported structures as well as other related complexes
with an iron nitrile bonding. The FeꢁC (of the Cp ring)
distances obtained in both structures are within the
expected values for Fe(II) compounds of this type
,
(2.072–2.193 A range), even for the indenyl derivative
16, which also indicates an h5-coordination for the
indenyl ligand. The phosphite geometric data are simi-
lar to the other compounds containing the phosphite
ligand [15]. The well-known contraction of the FeꢁP
bond, due to the presence of the oxygen as a-atom of
the pendent groups on triphenylphosphite, when com-
pared with analogous triphenylphosphine derivatives, is
also observed in these complexes.
3. Concluding remarks
IR and NMR spectroscopic data for this family of
complexes, also supported by the X-ray structural stud-
ies, indicate that coordination of nitrile ligand to the
metal centre has essentially a s-type character, the
metal–ligand p-backdonation being less significant.
These data identify the fragments [Fe(h5-Cp or
Ind)(CO)2]+ and [Fe(h5-Cp or Ind)(CO)(P(OC6H5)3)]+
as acceptor groups relative to the coordinated benzoni-
Our previous studies [7] on complexes of the type
[Fe(h5-Cp)(P P) (P P=bidentate phosphine) contain-
–
–
ing the p-nitrobenzonitrile chromophore showed that
the remarkable structural features found in X-ray dif-
fraction studies, namely FeꢁN and NꢂC bond lengths
and the retention of aromaticity on the benzonitrile
ring, did not corroborate the existence of p-backdona-
tion from the metal to the nitrile ligand, in the solid
state, although this effect was found in solution from
IR and NMR spectroscopic data.
trile
derivatives.
Conversely,
[Fe(h5-Cp)(CO)-
(P(C6H5)3)]+ acts as a weak p donor group, reflecting
an overall effect of p-backdonation towards the nitrile
ligand.
In addition to our previous work where the iron(II)
centre [Fe(h5-Cp)(P P)]+ was identified as a good p-
–
donor group, these results show that it can also behaves
as an acceptor or a weak p-donor group towards the
coordinated p-substituted benzonitrile, depending on
the coligands environment.
For the reported compounds (5 and 16), the FeꢁN
,
bond lengths (1.878(10) and 1.900(8) A, respectively),
are relatively shorter (within crystallographic errors)
than the corresponding distance found in iron(II) com-
plexes with the acetonitrile ligand and similar to the
FeꢁN bond length of the [Fe(h5-Cp)(DPPE)(p-
NCC6H4NO2)][PF6]. This feature is associated with
NꢂC bond lengths in the same range of the correspond-
ing length on the free p-NCC6H4NO2 ligand, particu-
larly in the case of 16, and the retention of aromaticity
on the benzonitrile ring. These observations altogether
suggest that the metal-to-nitrile back-donation does not
4. Experimental
4.1. General procedures
All experiments were carried out under dinitrogen by
use of standard Schlenk techniques. Solvents were dried
according to the usual published methods [16]. [Fe(h5-

M.H. Garcia et al. / Journal of Organometallic Chemistry 632 (2001) 145–156
151
was recrystallised from Me2CO–Et2O or CH2Cl2–
Et2O.
Cp)(CO)2(I)]
[17],
[Fe(h5-Cp)(CO)(P(OC6H5)3)(I)],
[Fe(h5-Cp)(CO)(P(C6H5)3)(I)] and [Fe(h5-Cp)(P(OC6-
H5)3)2(I)] [18] were prepared using different irradiation
times following the literature procedures. (E)-p-
NCCHꢀCHC6H4NO2 [19], [Fe(h5-Ind)(CO)2]2 [20],
4.2.1. [Fe(p5-Cp)(CO)2(p-NCC6H4NO2)][BF4] (1)
Yellow crystals; 72% yield, m.p. 156.3–156.4 °C.
Anal. Found: C, 40.99; H, 2.15; N, 6.64. Calc. for
C14H9N2O4FeBF4: C, 40.83; H, 2.20; N, 6.80%. IR
(KBr, cm−1): w(CO) 2072 and 2017, w(NꢂC) 2267,
[Fe(h5-Ind)(CO)2(I)]
[21]
and
[Fe(h5-Ind)(CO)-
(P(OC6H5)3)(I)] [17] were prepared according to the
procedures described in the literature. All the other
starting materials were used as purchased from Aldrich
Chemical Co.
1
w(NO2) 1524 and 1346. H-NMR ((CD3)2CO): 5.81 (s,
5H, h5-C5H5); 8.26 (d, 2H, JHH=9.0 Hz, H2, H6); 8.44
(d,
J
HH=9.0 Hz, 2H, H3, H5). 13C{1H}-NMR
Solid state IR spectra were recorded on a Perkin–
Elmer Paragon 1000 PC FTIR spectrophotometer in
KBr pellets; only significant bands are cited in the text.
1H-, 13C- and the 31P-NMR spectra were recorded on a
Varian Unity 300 spectrometer at probe temperature
((CD3)2CO): 88.42 (h5-C5H5); 117.32 (C1); 125.02 (C3,
C5); 134.15 (NC); 136.16 (C2, C6); 151.89 (C4); 209.11
(CO).
4.2.2. [Fe(p5-Cp)(CO)2(p-NCC6H4N(CH3)2)][BF4] (2)
Golden crystals; 60% yield, m.p. 142.7–143.3 °C.
Anal. Found: C, 46.33; H, 3.69; N, 6.53. Calc. for
C16H15N2O2FeBF4: C, 46.88; H, 3.69; N, 6.83%. IR
(KBr, cm−1): w(CO) 2065 and 2015, w(NꢂC) 2256.
1H-NMR ((CD3)2CO): 3.09 (s, 6H, N(CH3)2); 5.73 (s,
5H, h5-C5H5); 6.79 (d, 2H, JHH=9.3 Hz, H3, H5); 7.61
1
using acetone-d6 as solvent. The H and 13C chemical
shifts are reported in parts per million downfield from
internal Me4Si and the 31P-NMR spectra are reported
in parts per million downfield from external 85%
H3PO4 standard. Spectral assignments follow the num-
bering scheme shown in Fig. 4.
The UV–vis spectra were recorded on Hitachi U-
2001 and Shimadzu 1603 spectrophotometers. Micro-
analyses were performed in our laboratories using a
Fisons Instruments EA1108 system with data acquisi-
tion, integration and handling performed using a PC
with the EAGER-200 software package (Carlo Erba
Instruments). Melting points were obtained on a Leica
Galen III instrument and are not corrected.
(d, 2H,
J
HH=9.0 Hz, H2, H6). 13C{1H}-NMR
((CD3)2CO): 39.87 (N(CH3)2); 87.98 (h5-C5H5); 94.76
(C1); 112.21 (C3, C5); 135.29 (C2, C6); 138.62 (NC);
154.66 (C4); 209.81 (CO).
4.2.3. [Fe(p5-Cp)(CO)2((E)-p-NCCHꢀCHC6H4NO2)]-
[BF4] (3)
Yellow crystals; 58% yield, m.p. 129.7–131.0 °C.
Anal. Found: C, 43.65; H, 2.45; N, 6.34. Calc. for
C16H11N2O4FeBF4: C, 43.88; H, 2.53; N, 6.40%. IR
(KBr, cm−1): w(CO) 2079 and 2022, w(NꢂC) 2262,
4.2. Preparation of [Fe(p5-Cp)(CO)2(p-NCR)][BF4]
All the complexes were prepared by the process
described below. The appropriate nitrile p-NCR (R=
C6H4NO2, (E)-CHꢀCHC6H4NO2, C6H4N(CH3)2, (E)-
CHꢀCHC6H4N(CH3)2) (1.3 mmol) was added to a
solution of [Fe(h5-Cp)(CO)2(I)] (1 mmol) and one
equivalent of AgBF4 in CH2Cl2 (40 ml) at room tem-
perature (r.t.) and the mixture was stirred overnight. A
change was observed from dark brown to light orange
with simultaneous precipitation of AgI. The orange
solution was filtered, evaporated under vacuum to dry-
ness and washed several times with Et2O. The residue
1
w(NO2) 1518 and 1343. H-NMR ((CD3)2CO): 5.77 (s,
5H, h5-C5H5); 6.77 (d, 1H, JHH=16.5 Hz, H8); 7.95 (d,
2H, JHH=8.7 Hz, H2, H6); 7.98 (d, 1H, JHH=16.5 Hz,
H7); 8.32 (d, 2H, JHH=8.7 Hz, H3, H5). 13C{1H}-NMR
((CD3)2CO): 88.24 (h5-C5H5); 100.65 (C8); 124.96 (C3,
C5); 130.15 (C2, C6); 135.45 (C1); 139.86 (NC); 150.35
(C4); 153.51 (C7); 209.30 (CO).
4.2.4. [Fe(p5-Cp)(CO)2((E)-p-NCCHꢀCHC6H4N-
(CH3)2)][BF4] (4)
Yellow crystals; 81% yield, m.p. 149.4–151.3 °C.
Anal. Found: C, 48.77; H, 4.31; N, 5.82. Calc. for
C18H17N2O2FeBF4: C, 49.59; H, 3.93; N, 6.43%. IR
(KBr, cm−1): w(CO) 2077, 2037 and 1989 (sh), w(NꢂC)
2250. 1H-NMR ((CD3)2CO): 3.08 (s, 6H, N(CH3)2);
5.71 (s, 5H, h5-C5H5); 6.07 (d, 1H, JHH=16.5 Hz, H8);
6.79 (d, 2H, JHH=8.4 Hz, H3, H5); 7.49 (d, 2H, JHH
=
9.3 Hz, H2, H6); 7.65 (d, 1H, JHH=16.5 Hz, H7).
13C{1H}-NMR ((CD3)2CO): 40.40 (N(CH3)2); 87.01
(C8); 88.06 (h5-C5H5); 113.00 (C3, C5); 122.35 (C1);
131.08 (C2, C6); 138.30 (NC); 153.80 (C4); 156.31 (C7);
209.77 (CO).
Fig. 4. Numbering scheme for NMR spectral assignments.

152
M.H. Garcia et al. / Journal of Organometallic Chemistry 632 (2001) 145–156
4.3. Preparation of [Fe(p5-Cp)(CO)(P(OC6H5)3)-
(p-NCR)][BF4]
C6H4NO2, (E)-CHꢀCHC6H4NO2, C6H4N(CH3)2, (E)-
CHꢀCHC6H4N(CH3)2) (1.3 mmol) was added to a
solution of [Fe(h5-Cp)(CO)(P(C6H5)3)(I)] (1 mmol) and
one equivalent of AgBF4 in CH2Cl2 (40 ml) at r.t. and
the mixture was stirred for 6 h. A change of colour was
observed from dark green to deep red with simulta-
neous precipitation of AgI. The deep red solution was
filtered, evaporated under vacuum to dryness and
washed several times with Et2O. The residue was recrys-
tallised from CH2Cl2–Et2O.
All the complexes were prepared by the process
described below. The appropriate nitrile p-NCR (R=
C6H4NO2, C6H4N(CH3)2) (1.3 mmol) was added to a
solution of [Fe(h5-Cp)(CO)(P(OC6H5)3)(I)] (1 mmol)
and AgBF4 (1 mmol) in C6H6 or CH2Cl2 (40 ml) at r.t.
The mixture was stirred overnight at r.t. A change of
colour was observed from dark brown to orange with
simultaneous precipitation of AgI. After filtration, the
solution was evaporated under vacuum to dryness and
washed several times with Et2O to remove the excess of
nitrile. The residue was recrystallised from CH2Cl2–
Et2O.
4.4.1. [Fe(p5-Cp)(CO)(P(C6H5)3)(p-NCC6H4NO2)][BF4]
(7)
Red crystals; 63% yield, m.p. 176.8–178.6 °C. Anal.
Found: C, 57.61; H, 3.82; N, 4.25. Calc. for
C31H24N2O3FePBF4: C, 57.62; H, 3.74; N, 4.34%. IR
(KBr, cm−1): w(CO) 1974, w(NꢂC) 2247, w(NO2) 1528
4.3.1. [Fe(p5-Cp)(CO)(P(OC6H5)3)(p-NCC6H4NO2)]-
[BF4] (5)
1
and 1347. H-NMR ((CD3)2CO): 5.25 (s, 5H, h5-C5H5);
7.51–7.62 (m, 15H, PPh3); 7.67 (d, 2H, JHH=9.0 Hz,
H2, H6); 8.33 (d, 2H, JHH=9.0 Hz, H3, H5). 13C{1H}-
NMR ((CD3)2CO): 86.52 (h5-C5H5); 117.32 (C1);
124.88 (C3, C5); 130.25 (d, 3JCP=9.8 Hz, PPh3,C-
meta), 132.42 (PPh3, C-para); 133.15 (NC), 134.19 (d,
2JCP=9.8 Hz, PPh3, C-ortho); 135.32 (C2, C6); 151.42
(C4); 217.09 (d, 2JCP=28.1 Hz, CO). 31P{1H}-NMR
((CD3)2CO): 67.80 (s).
Golden crystals; 34% yield, m.p. 135.9–136.9 °C.
Anal. Found: C, 53.62; H, 3.40; N, 3.89. Calc. for
C31H24N2O6FePBF4: C, 53.64; H, 3.48; N, 4.04%. IR
(KBr, cm−1): w(CO) 2012, w(NꢂC) 2257, w(NO2) 1528
1
and 1347. H-NMR ((CD3)2CO): 5.12 (s, 5H, h5-C5H5);
7.30–7.35 and 7.46–7.53 (m, 15H, OPh); 8.10 (d, 2H,
J
HH=9.3 Hz, H2, H6); 8.45 (d, 2H, JHH=9.3 Hz, H3,
H5). 13C{1H}-NMR ((CD3)2CO): 85.93 (h5-C5H5);
4
117.14 (C1); 121.94 (d, JCP=4.4 Hz, OPh, C-meta);
4.4.2. [Fe(p5-Cp)(CO)(P(C6H5)3)(p-NCC6H4N-
(CH3)2)][BF4] (8)
Deep red crystals; 72% yield, m.p. 193.0–193.6 °C.
Anal. Found: C, 61.01; H, 5.02; N, 4.08. Calc. for
C33H30N2OFePBF4: C, 61.52; H, 4.69, N, 4.35%. IR
(KBr, cm−1): w(CO) 1993, w(NꢂC) 2249. 1H-NMR
125.06 (C3, C5); 127.13 (OPh, C-para); 131.40 (OPh,
C-ortho); 134.36 (NC); 135.09 (C2, C6); 151.50 and
151.62 (C4 and OPh, C-ipso), 213.50 (d, 2JCP=43.1 Hz,
CO). 31P{1H}-NMR ((CD3)2CO): 164.83.
4.3.2. [Fe(p5-Cp)(CO)(P(OC6H5)3)(p-NCC6H4N-
(CH3)2)][BF4] (6)
((CD3)2CO): 3.04 (s, 6H, N(CH3)2); 5.12 (d, 5H, JCP
=
1.2 Hz, h5-C5H5); 6.66 (d, 2H, JHH=9.0 Hz, H3, H5);
7.06 (d, 2H, JHH=9.0 Hz, H2, H6); 7.49–7.60 (m, 15H,
PPh3). 13C{1H}-NMR ((CD3)2CO): 39.82 (N(CH3)2);
85.88 (h5-C5H5); 95.38 (C1); 112.03 (C3, C5); 130.04 (d,
Orange solid; 33% yield, m.p. 125.4–127.1 °C. Anal.
Found: C, 56.57; H, 4.48; N, 3.67. Calc. for
C33H30N2O4FePBF4: C, 56.27; H, 4.37; N, 4.05%. IR
(KBr, cm−1): w(CO) 2007, w(NꢂC) 2242. 1H-NMR
((CD3)2CO): 3.11 (s, 6H, N(CH3)2); 4.97 (s, 5H, h5-
C5H5); 6.81 (d, 2H, JHH=8.1 Hz, H3, H5); 7.34–7.50
(m, 15H, OPh)); 7.49 (d, 2H, H2, H6).1 13C{1H}-NMR
((CD3)2CO): 39.92 (N(CH3)2); 85.25 (h5-C5H5); 95.07
4
3JCP=9.7 Hz, PPh3, C-meta); 132.16 (d, JCP=1.2 Hz,
PPh3, C-para); 133.25 (d, 1JCP=46.1 Hz, PPh3, C-ipso);
2
134.01 (d, JCP=9.7 Hz, PPh3, C-ortho); 134.61 (C2,
2
C6); 138.99 (NC); 154.27 (C4); 217.87 (d, JCP=29.2
Hz, CO). 31P{1H}-NMR ((CD3)2CO): 67.88 (s).
4
(C1); 112.37 (C3, C5); 121.97 (d, JCP=3.38 Hz, OPh,
4.4.3. [Fe(p5-Cp)(CO)(P(C6H5)3)((E)-p-NCCHꢀ
CHC6H4NO2)][BF4] (9)
C-meta); 127.06 (OPh, C-para); 131.33 (OPh, C-ortho);
2
135.05 (C2, C6); 138.90 (NC); 151.56 (d, JCP=8.0 Hz,
2
OPh, C-ipso); 154.58 (C4); 214.45 (d, JCP=40.2 Hz,
Red crystals; 75% yield, m.p. 161.9–163.1 °C. Anal.
Found: C, 58.85; H, 3.99; N, 4.14. Calc. for
C33H26N2O3FePBF4: C, 58.96; H, 3.90; N, 4.17%. IR
(KBr, cm−1): w(CO) 1993, w(NꢂC) 2243, w(NO2) 1523
CO). 31P{1H}-NMR ((CD3)2CO): 166.68 (s).
4.4. Preparation of
[Fe(p5-Cp)(CO)(P(C6H5)3)(p-NCR)][BF4]
1
and 1345. H-NMR ((CD3)2CO): 5.16 (s, 5H, h5-C5H5);
6.46 (d, 1H, JHH=16.5 Hz, H8); 7.19 (d, 1H, JHH
=
All the complexes were prepared by the process
described below. The appropriate nitrile p-NCR (R=
16.5 Hz, H7); 7.51–7.64 (m, 15H, PPh3); 7.81 (d, 2H,
J
HH=8.4 Hz, H2, H6); 8.26 (d, 2H, JHH=8.1 Hz, H3,
H5). 13C{1H}-NMR ((CD3)2CO): 86.27 (h5-C5H5);
1 Signal obscured by the aromatic protons of triphenylphosphite.
100.75 (C8); 124.96 (C3, C5); 129.88 (C2, C6); 130.19

M.H. Garcia et al. / Journal of Organometallic Chemistry 632 (2001) 145–156
153
4.5.2. [Fe(p5-Cp)(P(OC6H5)3)2(p-NCC6H4N-
(CH3)2)][BF4] (12)
Orange crystals; 57% yield, m.p. 120.1–121.6 °C.
Anal. Found: C, 61.92; H, 4.85; N, 2.79. Calc. for
C50H45N2O6FeP2BF4: C, 61.63; H, 4.65; N, 2.87%. IR
(KBr, cm−1): w(NꢂC) 2231. 1H-NMR ((CD3)2CO): 3.12
(s, 6H, N(CH3)2); 4.39 (s, 5H, h5-C5H5); 6.86 (d, 2H,
(d, 3JCP=10.0 Hz, PPh3, C-meta); 132.32 (PPh3, C-
1
para); 132.96 (d, JCP=46.4 Hz, PPh3, C-ipso); 134.15
2
(d, JCP=10.0 Hz, PPh3, C-ortho); 135.79 (C1); 139.80
2
(NC); 150.20 (C4); 151.60 (C7); 217.36 (d, JCP=27.8
Hz, CO). 31P{1H}-NMR ((CD3)2CO): 67.30 (s).
4.4.4. [Fe(p5-Cp)(CO)(P(C6H5)3)((E)-p-NCCHꢀ
CHC6H4N(CH3)2)][BF4] (10)
J
HH=9.3 Hz, H3, H5); 7.25–7.41 (m, 30H, OPh); 7.48
(d, 2H,
J
HH=9.3 Hz, H2, H6). 13C{1H}-NMR
Red crystals; 51% yield, m.p. 180.7–182.6 °C. Anal.
Found: C, 62.50; H, 4.89; N, 4.08. Calc. for
C35H32N2OFePBF4: C, 62.72; H, 4.81; N, 4.18%. IR
(KBr, cm−1): w(CO) 1983, w(NꢂC) 2248. 1H-NMR
((CD3)2CO): 3.04 (s, 6H, N(CH3)2); 5.09 (s, 5H, h5-
C5H5); 5.78 (d, 1H, JHH=16.5 Hz, C8); 6.72 (d, 2H,
((CD3)2CO): 40.35 (N(CH3)2); 81.54 (h5-C5H5); 97.07
(C1); 113.24 (C3, C5); 122.03 (OPh, C-meta); 126.35
(OPh, C-para); 130.93 (OPh, C-ortho); 134.64 (C2, C6);
138.73 (NC); 152.33 (OPh, C-ipso); 153.96 (C4).
31P{1H}-NMR ((CD3)2CO): 164.84 (s).
J
HH=8.7 Hz, H3, H5); 6.81 (d, 1H, JHH=16.5 Hz, C7);
4.5.3. [Fe(p5-Cp)(P(OC6H5)3)2((E)-p-NCCHꢀ
7.34 (d, 2H, JHH=8.4 Hz, H2, H6); 7.48–7.66 (m, 15H,
PPh3). 13C{1H}-NMR ((CD3)2CO): 40.16 (N(CH3)2);
85.91 (h5-C5H5); 88.03 (C8); 112.66 (C3, C5); 121.76
CHC6H4N(CH3)2)][BF4] (13)
Orange crystals; 60% yield, m.p. 81.6–83.0 °C. Anal.
Found: C, 62.35; H, 4.77; N, 2.78. Calc. for
C52H47N2O6FeP2BF4: C, 62.42; H, 4.73; N, 2.80%. IR
(KBr, cm−1): w(NꢂC) 2223. 1H-NMR ((CD3)2CO): 3.09
(s, 6H, N(CH3)2); 4.37 (s, 5H, h5-C5H5); 6.15 (d, 1H,
3
(C1); 130.72 (C2, C6); 130.81 (d, JCP=9.7 Hz, PPh3,
1
C-meta); 132.20 (PPh3, C-para), 133.23 (d, JCP=46.1
Hz, PPh3, C-ipso); 134.11 (d, 2JCP=9.7 Hz, PPh3,
C-ortho); 138.62 (NC); 153.79 (C4); 154.58 (C7); 217.82
(d, 2JCP=28.0 Hz, CO). 31P{1H}-NMR ((CD3)2CO):
67.82 (s).
JHH=16.2 Hz, H8); 6.80 (d, 2H, JHH=8.7 Hz, H3, H5);
7.24–7.44 (m, 31H, H7 and OPh); 7.49 (d, 2H, JHH
=
9.0 Hz, H2, H6). 13C{1H}-NMR ((CD3)2CO): 40.48
(N(CH3)2); 81.62 (h5-C5H5); 89.27 (C8); 113.09 (C3,
C5); 122.13 (OPh, C-meta); 126.37 (OPh, C-para);
130.18 (C1); 130.90 (C2, C6); 130.96 (OPh, C-ortho);
138.52 (NC); 154.35 (t, J=5.7 Hz, OPh, C-ipso);
154.29 (C7); (C4)2. 31P{1H}-NMR ((CD3)2CO): 164.78
(s).
4.5. Preparation of
[Fe(p5-Cp)(P(OC6H5)3)2(p-NCR)][BF4]
All the complexes were prepared by the process
described below. The appropriate nitrile p-NCR (R=
C6H4NO2, C6H4N(CH3)2, (E)-CHꢀCHC6H4N(CH3)2)
(1.3 mmol) was added to a solution of [Fe(h5-
Cp)(P(OC6H5)3)2(I)] (1 mmol) and AgBF4 (1 mmol) in
C6H6 (40 ml) at r.t. The mixture was stirred at r.t. for
2 days. A change of colour was observed from dark
brown to orange with simultaneous precipitation of
AgI. After filtration, the solution was evaporated under
vacuum to dryness and washed several times with Et2O
to remove the excess of nitrile. The residue was recrys-
tallised from CH2Cl2 or Me2CO–Et2O.
4.6. Preparation of [Fe(p5-Ind)(CO)2(p-NCR)][BF4]
All the complexes were prepared by the following
process: the appropriate nitrile p-NCR (R=C6H4NO2,
C6H4N(CH3)2) (1.3 mmol) was added to a solution of
[Fe(h5-Ind)(CO)2(I)] (1 mmol) and one equivalent of
AgBF4 in CH2Cl2 (40 ml) at r.t. and the mixture was
stirred overnight. A change of colour was observed
from reddish brown to red with simultaneous precipita-
tion of AgI. The red solution was filtered, evaporated
under vacuum to dryness and washed several times with
Et2O. The residue was recrystallised from CH2Cl2–
Et2O.
4.5.1. [Fe(p5-Cp)(P(OC6H5)3)2(p-NCC6H4NO2)][BF4]
(11)
Orange crystals; 63% yield, m.p. 104.0–105.5 °C.
Anal. Found: C, 58.90; H, 4.01; N, 2.88. Calc. for
C48H39N2O8FeP2BF4: C, 59.04; H, 4.03; N, 2.87%. IR
(KBr, cm−1): w(NꢂC) 2238, w(NO2) 1525 and 1345.
1H-NMR ((CD3)2CO): 4.60 (s, 5H, h5-C5H5); 7.20–7.25
(m, 6H, OPh), 7.34–7.41 (m, 24H, OPh); 8.01 (d, 2H,
4.6.1. [Fe(p5-Ind)(CO)2(p-NCC6H4NO2)][BF4] (14)
Red crystals; 29% yield, m.p. (dec.) 130.0 °C. Anal.
Found: C, 46.88; H, 2.32; N, 6.12. Calc. for
C18H11N2O4FeBF4: C, 46.80; H, 2.40; N, 6.06%. IR
(KBr, cm−1): w(CO) 2038 and 1986, w(NꢂC) 2274,
JHH=9.0 Hz, H2, H6); 8.45 (d, 2H, JHH=8.7 Hz, H3,
H5). 13C{1H}-NMR ((CD3)2CO): 82.58 (h5-C5H5);
117.63 (C1); 121.95 (OPh, C-meta); 125.38 (C3, C5);
126.47 (OPh, C-para); 131.03 (OPh, C-ortho); 134.30
(NC); 135.24 (C2, C6); 151.26 (C4); 152.30 (OPh, C-
ipso). 31P{1H}-NMR ((CD3)2CO): 163.19 (s).
1
w(NO2) 1528 and 1350. H-NMR ((CD3)2CO): 5.96 (s,
1H, Ind:H2%); 6.14 (d, 2H, JHH=2.4 Hz, Ind:H1%,H3%);
2 Signal obscured by the aromatic carbons of triphenylphosphite.

154
M.H. Garcia et al. / Journal of Organometallic Chemistry 632 (2001) 145–156
7.82–7.85 (m, A2B2, 2H, Ind:H4%,H7%); 8.06–8.09 (m,
A2B2, 2H, Ind:H5%,H6%); 8.20 (d, 2H, JHH=8.7 Hz, H2,
H6); 8.44 (d, 2H, JHH=8.7 Hz, H3, H5). 13C{1H}-NMR
((CD3)2CO): 73.66 (Ind:C1%,C3%); 90.40 (Ind:C2%);
109.00 (Ind:C3%a,C7%a); 116.91 (C1), 124.99 (C3, C5);
127.41 (Ind:C4%,C7%); 132.87 (NC); 134.83 (Ind:C5%,C6%);
136.02 (C2, C6); 151.79 (C4); 209.52 (CO).
121.87 (OPh, C-meta); 125.14 (C3, C5); 126.38, 127.67
(Ind:C4%, C7%); 127.17 (OPh, C-para); 131.40 (OPh,
C-ortho); 132.46, 133.49 (Ind:C5%, C6%); 133.19 (NC);
135.81 (C2, C6); 151.44 (d, 2JCP=8.6 Hz, OPh, C-ipso);
2
151.61 (C4), 213.45 (d, JCP=40.95 Hz, CO). 31P{1H}-
NMR ((CD3)2CO): 166.62 (s).
4.7.2. [Fe(p5-Ind)(CO)(P(OC6H5)3)(p-NCC6H4N-
(CH3)2)][BF4] (17)
4.6.2. [Fe(p5-Ind)(CO)2(p-NCC6H4N(CH3)2)][BF4] (15)
Deep red crystals; 70% yield, m.p. (dec.) 121.0 °C.
Anal. Found: C, 52.24; H, 3.84; N, 6.09. Calc. for
C20H17N2O2FeBF4: C, 52.22; H, 3.72; N, 6.09%. IR
(KBr, cm−1): w(CO) 2067, 2031 and 1988, w(NꢂC)
2252. 1H-NMR ((CD3)2CO): 3.09 (s, 6H, N(CH3)2);
Deep red crystals; 54% yield, m.p. 106.7–108.5 °C.
Anal. Found: C, 59.75; H, 4.48; N, 3.68. Calc. for
C37H32N2O4FePBF4: C, 59.87; H, 4.35; N, 3.77%. IR
(KBr, cm−1): w(CO) 1993, w(NꢂC) 2239. 1H-NMR
((CD3)2CO): 3.11 (s, 6H, N(CH3)2); 4.15 (s, 1H, Ind:H1%
or H3%); 5.50 (m, JHH=3.0 Hz, 1H, Ind:H2%); 5.59 (s,
1H, Ind:H1% or H3%); 6.79 (d, 2H, JHH=9.0 Hz, H3, H5);
7.33–7.62 (m, 19H, Ind:H4%–H7% and OPh); 7.41 (d, 2H,
H2, H6)3. 13C{1H}-NMR ((CD3)2CO): 39.95 (N(CH3)2);
63.46 and 77.40 (Ind:C1,C3); 88.17 (Ind:C2%); 94.92
(C1); 104.27, 111,16 (Ind:C3%a,C7%a); 112.43 (C3, C5);
5.84 (t, 1H, JHH=2.4 Hz, Ind:H2%); 6.07 (d, 2H, JHH
=
2.4 Hz, Ind:H1%,H3%); 6.78 (d, 2H, JHH=9.0 Hz, H3,
H5); 7.53 (d, 2H, JHH=8.4 Hz, H2, H6); 7.77–7.81 (m,
A2B2, 2H, Ind:H4%,H7%), 7.98–8.02 (m, A2B2, 2H,
Ind:H5%,H6%).
13C{1H}-NMR
((CD3)2CO):
39.82
(N(CH3)2); 73.20 (Ind:C1%,C3%); 89.54 (Ind:C2%); 94.45
(C1); 109.26 (Ind:C3%a,C7%a); 112.21 (C3, C5); 127.35
(Ind:C4%,C7%); 133.94 (Ind:C5%,C6%); 135.14 (C2, C6),
137.45 (NC); 154.60 (C4), 210.35 (CO).
4
121.93 (d, JCP=4.6 Hz, OPh, C-meta); 126.15, 127.84
(Ind:C4%,C7%); 127.15 (OPh, C-para), 131.35 (OPh, C-
ortho); 132.01, 133.059 (Ind:C5% and C6%); 133.94 (NC);
134.98 (C2, C6); 151.54 (d, 2JCP=8.7 Hz, OPh, C-ipso);
4.7. Preparation of
2
154.64 (C4), 214.31 (d, JCP=43.5 Hz, CO). 31P{1H}-
[Fe(p5-Ind)(CO)(P(OC6H5)3)(p-NCR)][BF4]
NMR ((CD3)2CO): 168.77 (s).
All the complexes were prepared by the process
described below. The appropriate nitrile p-NCR (R=
C6H4NO2, (E)-CHꢀCHC6H4NO2, C6H4N(CH3)2, (E)-
CHꢀCHC6H4N(CH3)2) (1.3 mmol) was added to a
solution of [Fe(h5-Ind)(CO)(P(OC6H5)3)(I)] (1 mmol)
and AgBF4 (1 mmol) in CH2Cl2 (40 ml) at r.t. The
mixture was stirred overnight at r.t. A change in colour
was observed from dark brown to red with simulta-
neous precipitation of AgI. After filtration, the solution
was evaporated under vacuum to dryness and washed
several times with Et2O to remove the excess of nitrile.
The residue was recrystallised from CH2Cl2–Et2O.
4.7.3. [Fe(p5-Ind)(CO)(P(OC6H5)3)((E)-p-NCCHꢀ
CHC6H4NO2)][BF4] (18)
Orange crystals; 36% yield, m.p. 149.0–149.5 °C.
Anal. Found: C, 57.55; H, 3.73; N, 3.56. Calc. for
C37H28N2O6FePBF4: C, 57.70; H, 3.66; N, 3.64%. IR
(KBr, cm−1): w(CO) 2010, w(NꢂC) 2243, w(NO2) 1519
and 1341. 1H-NMR ((CD3)2CO): 4.21 (s, 1H, Ind:H1% or
H3%); 5.56 (m, JHH=3.0 Hz, 1H, Ind:H2%); 5.63 (s, 1H,
Ind:H1% or H3%); 6.68 (d, 1H, JHH=16.8 Hz, H8), 7.38 (t,
3H, JHH=7.2 Hz, OPh, C-para); 7.47 (d, 6H, JHH=7.8
Hz, OPh, C-ortho); 7.55 (t, 6H, JHH=7.8 Hz, OPh,
C-meta); 7.67 (d, 1H, JHH=8.7 Hz, Ind:H4% or H7%);
7.71 (d, 1H, JHH=8.7 Hz, Ind:H4% or H7%); 7.76 (d, 1H,
4.7.1. [Fe(p5-Ind)(CO)(P(OC6H5)3)(p-NCC6H4NO2)]-
[BF4] (16)
J
HH=16.8 Hz, H7), 7.83 (d, 2H, JHH=8.1 Hz,
Ind:H5%,H6%); 7.96 (d, 2H, JHH=8.1 Hz, H2, H6); 8.31
(d, 2H,
HH=8.1 Hz, H3, H5). 13C{1H}-NMR
Red crystals; 51% yield, m.p. 143.4–144.6 °C. Anal.
Found: C, 56.65; H, 3.58; N, 3.70. Calc. for
C35H26N2O6FePBF4: C, 56.49; H, 3.52; N 3.76%. IR
(KBr, cm−1): w(CO) 1997, w(NꢂC) 2254, w(NO2) 1523
J
((CD3)2CO): 63.83, 77.92 (Ind:C1%,C3%); 88.68 (Ind:C2%);
100.59 (C8); 104.53, 110.69 (Ind:C3%a, C7%a); 122.99 (d,
4JCP=4.1 Hz, OPh, C-meta); 124.93 (C3, C5); 126.41,
127.62 (Ind:C4%,C7%); 127.21 (OPh, C-para); 129.08
(C1); 130.22 (C2, C6); 131.43 (OPh, C-ortho); 132.32,
133.36 (Ind:C5%,C6%); 134.48 (NC); 150.34 (C4); 151.50
1
and 1346. H-NMR ((CD3)2CO): 4.35 (bs, 1H, Ind:H1%
or H3%); 5.62 (dt, JHH= :3.0 Hz; 1H, Ind:H2%); 5.81
(bs, 1H, Ind:H1% or H3%); 7.31–7.36 (m, 3H, OPh);
7.44–7.54 (m, 12H, OPh); 7.60, 7.69 (t, JHH=7.35 Hz,
1H, Ind:H5% and H6%); 7.78 (d, 1H, JHH=8.7 Hz,
Ind:H4% or H7%); 7.86 (d, 1H, JHH=8.4 Hz, Ind:H4% or
H7%); 8.05 (dt, JHH=8.4 and 2.1 Hz, 2H, H2, H6); 8.42
(dt, JHH=8.4 and 2.1 Hz, 2H, H3, H5) 13C{1H}-NMR
((CD3)2CO): 64.45, 77.98 (Ind:C1% and C3%); 88.75
(Ind:C2%); 104.62, 110.65 (Ind:C3%a, C7%a); 116.76 (C1);
2
(d, JCP=8.7 Hz, OPh, C-ipso); 152.79 (C7); 213.79 (d,
2JCP=40.5 Hz, CO). 31P{1H}-NMR ((CD3)2CO):
167.74 (s).
3 Signal obscured by the aromatic protons of triphenylphosphite.

M.H. Garcia et al. / Journal of Organometallic Chemistry 632 (2001) 145–156
155
4.8. X-ray structures of [Fe(p5-C5H5)(P(OC6H5)3)-
(CO)(p-NꢂCC6H4NO2)][BF4]·CH2Cl2 and
mode. The structures were solved by direct methods
with SHELXS-97 [23] and refined by the full-matrix
least-squares method with SHELXL-97 [24].
[Fe(p5-C9H7)(P(OC6H5)3)(CO)(p-NꢂCC6H4NO2)][BF4]
Nonhydrogen atoms were anisotropically refined, ex-
cept for the atoms of the solvent molecule in compound
5. All hydrogen atoms were inserted in calculated posi-
tions and refined isotropically with a thermal parameter
equal to 1.2× those of the carbon atoms to which they
are bonded. The solvent molecule, CH2Cl2, was found
to be disordered over two positions. The occupation
factors refined to 0.50 and 0.50, in the last cycle of
refinement. In the disorder model the CꢁCl distances
Diffraction data for [Fe(h5-Cp)(POPh3)(CO)(p-
NꢂCC6H4NO2)][BF4]·CH2Cl2 (5) and [Fe(h5-Ind)-
(POPh3)(CO)(p-NꢂCC6H4NO2)][BF4] (16) were col-
lected at 293(2) K on an Enraf–Nonius TURBOCAD4
diffractometer with Cu–Ka radiation. The unit cell
dimensions and orientation matrix was obtained by
least-squares refinement of 25 centred reflections with
15.37BqB23.92° for 5 and by least-squares refinement
of 23 centred reflections with 15.99BqB23.15° for 16.
Using the CAD4 software [22], data were corrected for
Lorentz and polarisation effects and using c-scans for
absorption. Intensities of 6048 reflections for 5 and
8225 reflections for 16 were measured by the ꢀ–2q scan
,
were restrained to 1.75 A. The thermal parameters of
the O31 and O41 of the phosphite ligand in complex 5
were also refined with ISOR (estimated S.D. of 0.01).
The thermal parameters of the oxygen atoms of the
nitrile ligand in the same complex were also restrained
(estimated S.D. 0.01). The accuracy of the data allows
comparison of the structural parameters; although the
relatively high estimated S.D., due to the poor diffrac-
tion power of the crystals, preclude some conclusions
when interpreting the data. The illustrations were
drawn with program ORTEP-III [25] implemented in
OSCAIL8 [26]. The atomic scattering factors and anoma-
lous scattering terms were taken from International
Tables [27]. Other details of data collection and refine-
ment are given in Table 4.
Table 4
Crystal data and structure refinement for complexes [Fe(h5-
Cp)(CO)(P(OC6H5)(p-NꢂCC6H4NO2)][BF4]·CH2Cl2 (5) and [Fe(h5-
Ind)(CO)(P(OC6H5)(p-NꢂCC6H4NO2)][BF4] (16)
Complex
5
16
Empirical formula
C
32H24BCl2F4FeN2- C35H26BF4FeN2O6P
O6P
Formula weight
Temperature (K)
777.95
293(2)
1.54184
Triclinic
744.21
293(2)
1.54184
Monoclinic
P21/n
,
Wavelength (A)
Crystal system
Space group
(
P1
5. Supplementary material
Unit cell dimensions
,
a (A)
9.7881(7)
10.6358(9)
18.640(3)
94.603(9)
96.51(1)
115.420(6)
1723.3(3)
2
10.000(2)
11.500(1)
29.362(3)
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 157903 and 157904 for com-
pounds 5 and 16, respectively. Copies of this informa-
tion may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ UK
(Fax: +44-1223-336033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk).
,
b (A)
,
c (A)
h (°)
i (°)
95.70(2)
k (°)
3
,
V (A )
3359.9(9)
4
1.471
4.672
Z
Dcalc (Mg m−3
Absorption
)
1.521
5.982
coefficient (mm−1
)
F(000)
Index ranges
800
1520
−15h510;
−115k511;
−205l520
−115h51;
−135k51;
−355l535
7841
Acknowledgements
Financial support was given by Junta Nacional de
Reflections collected 6048
Independent
reflections
Reflections observed 2898
(\2|)
5006 [Rint=0.1141] 5979 [Rint=0.0723]
Investigac¸a˜o Cient´ıfica e Tecnolo´gica (JNICT) actually
Fundac¸a˜o para
a
Cieˆncia
e
Tecnologia (FCT)
2648
(PRAXIS/PCEX/C/QUI/0096/96).
Data/restraints/
parameters
Final R indices
[I\2|(I)]
5006/27/432
5979/0/452
R1=0.1036
References
R1=0.1105
R indices (all data)
Goodness-of-fit on
F2
R1=0.1739
1.043
R1=0.2020
1.031
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0.809 and −0.782
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,
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