metal-organic compounds
Ê
bond [1.147 (6) A], being somewhat longer than the corre-
sponding bonds found in the complexes listed in Table 3,
approaches the structural features of the bond in the free
coordination with a small ꢂ back-donation contribution,
owing to ꢂ-bonding between the metal d orbitals and the ꢂ*
orbital of the CN group. The complex shows an intense broad
visible absorption band at ꢆmax = 435 nm in chloroform. This
absorption could be attributed to a d±ꢂ* metal-to-ligand
charge-transfer (MLCT) transition from the Fe centre to the
nitrile ligand. Such low-energy MLCT bands are typically
associated with large molecular quadratic NLO responses
(Garcia, Robalo, Dias et al., 2001; Garcia et al., 2002).
In the solid state, complex (I) crystallizes in the monoclinic
centrosymmetric space group P21/c, thus destroying our hopes
of obtaining dipole supramolecular alignment. The molecular
structure of the cation is presented in Fig. 1. The coordination
geometry can be described as a pseudo-octahedral three-
legged piano stool on the assumption that the cyclopenta-
dienyl group takes up three coordination sites. This geometry,
similar to that of other compounds of the same family (Garcia,
Robalo, Teixeira et al., 2001), is con®rmed by the angles
around the metal centre, which are all close to 90ꢀ (Table 1), as
well as by the remaining XÐFeÐCp(centroid) angles [P1Ð
Fe1ÐCp(centroid) = 124.62 (6)ꢀ, P2ÐFe1ÐCp(centroid) =
122.67 (6)ꢀ and N1ÐFe1ÐCp(centroid) = 123.4 (1)ꢀ]. As
expected, all angles involving the Cp centroid are considerably
larger than those involving the phosphite, phosphine and
nitrile ligands.
Ê
imine [1.155 (15) A; Higashi & Osaki, 1997]. These values,
altogether with the bond angles Fe1ÐN1 C1 and N1 C1Ð
C2 [175.4 (4) and 173.7 (5)ꢀ, respectively], show that, in the
solid state, the nitrile group departs somewhat from the
expected linear geometry, and there is no evidence of any
appreciable ꢂ back-donation contribution. These results
con®rm the spectroscopic data found for (I), since only a small
ꢂ back-donation effect was noticed. According to this beha-
viour, which can be correlated with the donor ability of the
metal centre, we can identify the [Fe(Cp)(PMe3){P(OPh)3}]+
fragment as a weak ꢂ-donor towards the nitrile ligand when
compared with other fragments (Table 3).
In recent publications, the importance of intermolecular
interactions involving halogens, in particular F atoms, as a
possible tool in crystal engineering has been studied in great
detail (Chopra et al., 2005). The three-dimensional packing of
(I) shows a supramolecular organometallic zigzag chain of
aligned cations (of the same conformational isomer) in an up±
down con®guration, obtained via a network of CÐHÁ Á ÁFꢃ
interactions (Table 2) involving the F atoms of the anions and
H atoms of the nitrile [H7Á Á ÁF6i; symmetry code: (i) 1 x, y,
1
z], phosphine (H33AÁ Á ÁF6i) and phosphite [H42Á Á ÁF5ii;
1
2
In the molecule of (I), we observe the well known
contraction of the FeÐP bond when using a phosphite ligand
instead of phosphine. Thus, the observed value of
symmetry code: (ii) x,
y, z 12] (Fig. 2), generating in this
way a one-dimensional chain along the b axis. We have taken
into account the criteria used by Reichenbacher et al. (2005),
Ê
Ê
2.1206 (14) A, which is shorter than that of the trimethyl-
where HÁ Á ÁF distances up to 2.9 A can be considered as weak
Ê
phosphine ligand [2.2332 (15) A], can be attributed to the
intermolecular interactions. These interactions organize the
complex cations into pairs through the spherical anion, in such
a way that their dipole moments and second-order polariz-
abilities cancel. A weaker interaction of the type CÐ
HÁ Á ÁC(ꢂ), between a C atom of the benzene ring attached to
presence of the oxygen as the ꢇ atom of the pendent groups on
the triphenylphosphite. This value agrees with the values
observed for Fe(phosphine) and Fe(phosphite) derivatives in
the Cambridge Structural Database (CSD, Version 5.25; Allen,
2002), presented in Table 3, where FeÐN and N C distances
are also included for comparison.
the nitrile and a phenyl H atom of the phosphite ligand [C34Ð
H34Á Á ÁC4iii; symmetry code: (iii) x,
y, z + 12], gives rise to
1
2
Ê
The FeÐN distance [1.871 (4) A] in (I) is somewhat shorter
than that found in [Fe(Cp)(CO){P(OPh)3}(4-NCC6H4NO2)]-
the formation of a two-dimensional aggregation of chains of
different optical isomers of the complex cation parallel to the
(101) plane.
Ê
BF4 [1.878 (10) A; Garcia, Robalo, Teixeira et al., 2001], while
it is very similar to that observed in [Fe(Cp)(dppe)(4-
Ê
NCC6H4NO2)]PF6 [1.874 (11) A; dppe is (diphenylphos-
Experimental
phino)ethane; Garcia, Robalo, Dias et al., 2001]. The N
C
TlPF6 (0.40 mmol) was added to
a solution of [Fe(Cp)-
{P(OPh)3}(PMe3)I] (0.40 mmol) and 4-nitrobenzonitrile (0.72 mmol)
in dichloromethane (40 ml) at room temperature. The mixture was
stirred at room temperature for 22 h. A colour change was observed
from dark brown to red, with simultaneous precipitation of thallium
iodide. The red solution was ®ltered, evaporated under vacuum to
dryness, and washed several times with diethyl ether and n-hexane to
remove the excess of nitrile. The dark-red residue was further puri-
®ed by vapour diffusion of diethyl ether into a concentrated
dichloromethane solution, affording dark-red crystals of (I) (yield
47%; m.p. 435±436 K). Analysis calculated for C33H33F6FeN2O5P3: C
49.49, H 4.16, N 3.50%; found: C, 49.44, H 4.12, N 3.31%. IR (KBr,
cm 1): ꢄ(N C) 2221, ꢄ(NO2) 1526 and 1345; H NMR (300 MHz,
1
Figure 2
CD3COCD3): ꢃ 1.85 (d, 9H, J = 9.0 Hz, PMe3), 4.64 (s, 5H, ꢀ5-C5H5),
7.23 [m, 3H, P(OPh)3:H-para], 7.34±7.42 [m, 12H, P(OPh)3:H-ortho
and H-meta], 8.05 (d, 2H, J = 9.0 Hz, H2, H6), 8.41 (d, 2H, J = 9.0 Hz,
A view of the two-dimensional layer of zigzag chains formed by different
optical isomers of the complex cation. H atoms not involved in hydrogen
bonding have been omitted. Broken lines indicate CÐHÁ Á ÁF and CÐ
HÁ Á ÁC(ꢂ) interactions.
H3, H5); 13C{1H} NMR (75 MHz, CD3COCD3): ꢃ 18.85 (d, JCP
=
ꢁ
Acta Cryst. (2005). C61, m386±m389
Duarte et al.
[Fe(C5H5)(C7H4N2O2)(C18H15O3P)(C3H9P)]PF6 m387
Duarte, M. Teresa
