Synthesis, X-ray structure, and theoretical studies of novel cationic mono-cyclopentadienyl complexes of Co(III): The orthometalation of trans-azobenzene

Article abstract of DOI:10.1016/S0022-328X(00)00948-7

New cationic mono-cyclopentadienyl complexes of Co(III) containing mono or bidentate nitrogen donor ligands of general formula [Co(η⁵-C₅H₅)(PPh₃)L₂] [BF₄]₂ (L=NC-CH_3, 2, and NC-Ph, 3) or [Co(η⁵-C₅H₅)(PPh₃)(L-L)][BF ₄]₂, [L-L=2,2′-bisimidazole (H₂biim) (4) and dipyridylamine [HN(NC₅H₅)₂] (5) have been synthesised by the stoichiometric reaction of the Co(III) complex Co(η⁵-C₅H₅)(PPh₃)I₂ (1), with Ag[BF₄] and the appropriate ligand in CH₂Cl₂. Under the same conditions and using trans-azobenzene as a ligand, an orthometalation reaction took place, giving the new compound [Co(η⁵-C₅H₅)(PPh₃)(κ-C,κ-N-C₆H₄N=NPh)][BF₄] (6) in high yield. The structural characterisation of compounds 4 and 6, and of the starting compound Co(η⁵-C₅H₅)(PPh₃)I₂ (1) was done by single-crystal X-ray diffraction studies. DFT calculations (ADF program) were performed in order to understand the orthometallation reaction.

Full text of DOI:10.1016/S0022-328X(00)00948-7

Journal of Organometallic Chemistry 625 (2001) 186–194
www.elsevier.nl/locate/jorganchem
Synthesis, X-ray structure, and theoretical studies of novel cationic
mono-cyclopentadienyl complexes of Co(III): the orthometalation
of trans-azobenzene
Teresa Avile´s a,*, Anto´nio Dinis a, Maria Jose´ Calhorda b,c, Patr´ıcia Pinto c,
Vitor Fe´lix d, Michael G.B. Drew e
a Departamento de Qu´ımica, Centro de Qu´ımica Fina e Biotecnologia, Faculdade de Cieˆncias e Tecnologia, Uni6ersidade No6a de Lisboa,
2825-114 Caparica, Portugal
b ITQB, UNL, Apartado 127, 2781-901 Oeiras, Portugal
c Dep. Qu´ımica e Bioqu´ımica, Faculdade de Cieˆncias, Uni6ersidade de Lisboa, 1749-016 Lisbon, Portugal
d Dep. Qu´ımica, Uni6ersidade de A6eiro, 3810-193 A6eiro, Portugal
e Department of Chemistry, Uni6ersity of Reading, Whitenights, Reading, RG6 2AD, UK
Received 1 November 2000; received in revised form 2 December 2000; accepted 2 December 2000
Abstract
New cationic mono-cyclopentadienyl complexes of Co(III) containing mono or bidentate nitrogen donor ligands of general
formula [Co(h5-C5H5)(PPh3)L2][BF4]2 (L=NC–CH3, 2, and NC–Ph, 3) or [Co(h5-C5H5)(PPh3)(L–L)][BF4]2, [L–L=2,2%-bisimi-
dazole (H2biim) (4) and dipyridylamine [HN(NC5H5)2] (5) have been synthesised by the stoichiometric reaction of the Co(III)
complex Co(h5-C5H5)(PPh3)I2 (1), with Ag[BF4] and the appropriate ligand in CH2Cl2. Under the same conditions and using
trans-azobenzene as a ligand, an orthometalation reaction took place, giving the new compound [Co(h5-C5H5)(PPh3)(k-C,k-N–
C6H4NꢀNPh)][BF4] (6) in high yield. The structural characterisation of compounds 4 and 6, and of the starting compound
Co(h5-C5H5)(PPh3)I2 (1) was done by single-crystal X-ray diffraction studies. DFT calculations (ADF program) were performed
in order to understand the orthometallation reaction. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Co(III) complexes; Orthometallation; DFT calculations; X-ray structures
the aim of understanding the factors responsible for the
structure of the solids, and mono or bidentate N-donor
ligands were considered. Some of the ligands might also
act as bridges between metals, leading to the formation
of binuclear species. The complex Co(h5-C5H5)(PPh3)I2
(1), shown to be a good precursor for the synthesis of
cationic species [2], was used for these studies, using
silver salts in the presence of the appropriate ligand.
The ligand 2,2%-bismidazole, for instance, may coordi-
nate through two nitrogen atoms, leaving two N–H
bonds available for donation towards hydrogen bond
receptors. Trans-azobenzene has been known for a long
time to undergo orthometallation reactions with transi-
tion metals [3], but, in the case of cobalt, the only
reactions described involve Co(I) complexes [4]. In
complex Co(h5-C5H5)(PMe3)(h2-PhNꢀNPh), trans-
azobenzene is coordinated in a h2-mode [5]. The reac-
1. Introduction
Organometallic complexes are very interesting pre-
cursors as building blocks for the design of solids,
owing to the variety of coordination environments and
oxidation states, among others, which they can provide
[1]. Cationic complexes allow the additional possibility
of changing counter ions. A differently charged anion
may lead to other stoichiometries of the salts and the
presence of donor/acceptor groups may induce the for-
mation of directional hydrogen bonds between ions.
The synthesis of cationic monocyclopentadienyl
cobalt(III) complexes has therefore been pursued, with
* Corresponding author. Fax: +351-21-2948550.
E-mail addresses: tap@dq.fct.unl.pt (T. Avile´s), mjc@itqb.unl.pt
(M.J. Calhorda), vfelix@dq.ua.pt (V. Fe´lix), m.g.b.drew@
reading.ac.uk (M.G.B. Drew).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00948-7

T. A6ile´s et al. / Journal of Organometallic Chemistry 625 (2001) 186–194
187
tion of Co(h5-C5H5)(PPh3)I2 with trans-azobenzene, us-
ing Ag[BF4] on the other hand, gave rise to an ortho-
metallation reaction, the new complex [Co(h5-
C5H5)(PPh3)(k-C,k-N–C6H4NꢀNPh)][BF4] (6) being
formed. It represents, to the best of our knowledge, the
first example of an orthometallation reaction accom-
plished by a Co(III) complex. Both, this orthometal-
lated complex, the 2,2%-bismidazole derivative, and the
starting material were structurally characterised by sin-
gle-crystal X-ray diffraction. Density functional theory
calculations [6], using the ADF program [7], were per-
formed in order to understand the driving force for the
orthometallation reaction.
The nitrile derivatives 2 and 3 are very hygroscopic
and it proves difficult to obtain crystals of good quality
for single-crystal X-ray structure determination. The
1H-NMR spectra of complexes 2 and 3 in CDCl3 are in
agreement with the proposed structures, as shown by
the singlet observed for the Cp protons at l 5.98, and
6.3 ppm, respectively. The 1H-NMR of complexes 4
and 5 in d6 acetone also exhibit a singlet for the Cp
protons at l 6,23, and 6.62 ppm, respectively, in accor-
dance with the proposed structures. These spectra also
show a series of complex peaks in the region for
aromatic protons (protons of the N-donor ligands and
of PPh3), while the 31P-NMR spectra show singlets at l
43.54 and 41.15, respectively, for the PPh3 phosphorus
atom of complexes 4 and 5. A crystal of 4, [Co(h5-
C5H5)(PPh3)(H2biim)][BF4]2, suitable for X-ray struc-
ture determination, was grown by slow vapour
diffusion of diethylether into an acetone solution of the
complex. Attempts to grow good quality crystals of 5
by the same procedure failed. Crystals of the starting
material 1 were obtained from CH2Cl2–petroleum
ether.
2. Results and discussion
2.1. Chemical studies
The reaction of Co(h5-C5H5)(PPh3)I2 (1) with 2 mol
of Ag[BF4] in CH2Cl2 and the stoichiometric amount of
the appropriate mono or bidentate nitrogen donor lig-
and, at room temperature, yields crystalline red com-
plexes of general formula [Co(h5-C5H5)(PPh3)L2][BF4]2,
where L=NCCH3 (2) and NCC6H5 (3), or [Co(h5-
C5H5)(PPh3)(L–L)][BF4]2, where L–L=2,2%-bisimida-
zole (H2biim) (4) and dipyridylamine [HN(NC5H5)2] (5)
in good yields (Scheme 1).
When the reaction of Co(h5-C5H5)(PPh3)I2 (1) with 2
mol of Ag[BF4] in CH2Cl2 is performed using trans-
azobenzene as a ligand, an orthometalation reaction
takes place, giving rise to the new compound [Co(h5-
C5H5)(PPh3)(k-C,k-N–C6H4NꢀNPh)][BF4] (6) in high
yield (Scheme 2). Good quality crystals of 6 were
obtained from CH2Cl2–petroleum ether.
Complex 6 was also fully characterised by multinu-
clear NMR spectroscopy. The 1H-NMR spectrum in
CD2Cl2 show a singlet for the Cp protons at l 5.47
ppm and a series of complex peaks in the aromatic
region for the protons of the trans-azobenzene and of
PPh3. In the 13C spectrum, besides the expected peaks
in the aromatic region (from l 133.7 to 122.85 ppm)
and the peak corresponding to the Cp carbons at l
90.92 ppm, four isolated peaks are observed, namely
one doublet at l 173.06 ppm and 172.8 ppm (J 13C–
31P=26.83 Hz) which can be assigned to the azoben-
zene carbon bound to Co [8], two peaks at l 167.75 and
156.21 ppm assigned to the N-substituted phenyl car-
bons, and a fourth peak at l 142.9 ppm, assigned to the
ipso-carbons of PPh3. The 31P-NMR spectrum shows a
singlet at 45.21 ppm. The liquid secondary ion mass
spectra (LSIMS+) shows the cation peak at m/z 567
[Co(h5-C5H5)(PPh3)(k-C,k-N–C6H4NꢀNPh)]+ (90%).
The IR spectra in Nujol mulls of compounds 2–6,
display strong absorption bands centered at ca. w 1050
cm−1 characteristic of the counter ion [BF4]−.
Scheme 1.
Compounds Co(h5-C5H5)(PPh3)I2 (1), [Co(h5-
C5H5)(PPh3)(H2biim)][BF4]2
(4),
and
[Co(h5-
C5H5)(PPh3)(k-C,k-N–C6H4NꢀNPh)][BF4] (6), were
structurally characterised by single-crystal X-ray dif-
fraction studies.
Scheme 2.

188
T. A6ile´s et al. / Journal of Organometallic Chemistry 625 (2001) 186–194
In the three structures the cobalt centre displays a
distorted pseudo tetrahedral co-ordination environment
containing one h5-C5H5 ring and one P from a PPh3
ligand. The two remaining positions of the metal co-or-
dination sphere are occupied by two iodine atoms in 1,
two nitrogen atoms from H2biim in 4, and one nitrogen
atom and one carbon atom from C6H4NꢀNPh− in 6.
The more significant distortion from the idealised tetra-
hedral geometry is reported for complexes 4 and 6 and
arises from the small bite angles of the bidentate lig-
ands. Thus the chelation of H2biim in
4 and
C6H4NꢀNPh− in 6 results in similar chelating angles
N–Co–N and N–Co–C of 82.3(2)° and 80.6(3)°, re-
spectively. In contrast, in the complex 1, where that
steric constraint is absent, a wider I–Co–I angle of
95.05(4)°, closer to the ideal value for a tetrahedron, is
observed. The remaining angles subtended at the
cobalt(III) centre are comparable in the three com-
plexes. On the other hand, the structural parameters
reported in Table 1 for complex 1 agrees well with
those found for related cobalt(III) pseudo tetrahedral
neutral species [Co(h5-C5H5)(PPh2CH2POPh2)I2] and
[{Co(h5-C5H5)I2}2(m2-PPh2(CH2)5PPh2)] [9], in which
two Co(h5-C5H5)I2 moieties are bridged by the
PPh2(CH2)5PPh2 ligand.
Fig. 1. A PLUTON view of Co(h5-C5H5)(PPh3)I2 (1), showing the
molecular geometry and the atomic notation scheme adopted. For
clarity only the atomic notation for the quoted atoms in the text is
included.
To the best of our knowledge, the structure of com-
plex 4 represents the first X-ray determination of a
cobalt complex containing the H2biim ligand. In fact,
no crystal structures of cobalt complexes with that
ligand were found in the Cambridge Data Base (CSD)
[10] and consequently it is not possible to establish any
structural comparison of the structure reported for
complex 4 with other related structures.
The two BF−4 anions are close to the complex cation
4 leading to F···H–N interactions between three
fluorine atoms and the two N–H groups of H2biim via
Fig. 2. A PLUTON view of [Co(h5-C5H5)(PPh3)(H2biim)][BF4]2 (4),
showing the molecular geometry, the hydrogen bonds N–H···F to the
BF4 anion, and the atomic notation scheme adopted. For clarity only
the atomic notation for the quoted atoms in the text is included.
2.2. Crystallographic studies of Co(p5-C5H5)(PPh3)I2
(1), [Co(p5-C5H5)(PPh3)(H2biim)][BF4]2 (4) and
[Co(p5-C5H5)(PPh3)(s-C,s-N–C6H4NꢀNPh)][BF4] (6)
The solid state structures of metal complexes Co(h5-
C5H5)(PPh3)I2 (1), [Co(h5-C5H5)(PPh3)(H2biim)][BF4]2
(4), and [Co(h5-C5H5)(PPh3)(k-C,k-N–C6H4NꢀNPh)]-
[BF4] (6), were determined by single-crystal X-ray dif-
fraction. PLUTON style diagrams showing the overall
geometry of the complexes 1, 4, and 6 and the atomic
notation scheme used are presented in Figs. 1–3, re-
spectively. Selected bond lengths and angles are given
in Table 1.
Fig. 3.
A
PLUTON view of [Co(h5-C5H5)(PPh3)(k-C,k-N–
C6H4NꢀNPh)]+ (6), showing the molecular geometry and the atomic
notation scheme adopted. For clarity only the atomic notation for the
quoted atoms in the text is included.

T. A6ile´s et al. / Journal of Organometallic Chemistry 625 (2001) 186–194
189
Table 1
a
,
Selected bond distances (A) and bond angles (°) for complexes 1, 4 and 6
Complex 1
Co–I(1)
Co–P
I(1)–Co–I(2)
P–Co–I(1)
Cp–Co–I(1)
P–Co–Cp
2.584(3)
2.242(3)
95.05(4)
92.04(6)
119.2
Co–I(2)
Co–Cp
2.607(3)
1.716
P–Co–I(2)
Cp–Co–I(2)
95.13(12)
120.7
126.8
Complex 4
Co–N(61)
Co–P
N(71)–Co–N(61)
N(61)–Co–P
N(61)–Co–Cp
P–Co–Cp
1.961(5)
2.270(2)
82.3(2)
91.4(2)
126.0
Co–N(71)
Co–Cp
1.946(6)
1.707
N(71)–Co–P
N(71)–Co–Cp
91.1(2)
126.1
126.9
Complex 6
Co–N(51)
Co–P
N(51)–C(61)
N(51)–N(52)
Cp–Co–N(51)
P–Co–Cp
1.925(6)
2.240(2)
1.424(9)
1.242(7)
130.3
Co–C(76)
Co–Cp
N(52)–C(71)
1.987(8)
1.722
1.476(9)
Co–Cp–N(76)
120.0
126.8
N(51)–Co–C(76)
N(51)–Co–P
N(51)–N(52)–C(71)
C(75)–C(76)–Co
C(61)–N(51)–Co
N(52)–N(51)–C(61)
80.7(3)
94.4(2)
110.1(5)
135.4(6)
129.8(5)
108.7(6)
C(76)–Co–P
90.6(2)
C(76)–C(71)–N(52)
C(71)–C(76)–Co
N(52)–N(51)–Co
117.4(6)
110.0(6)
121.4(5)
a Cp represents the centroid of the h5-C5H5 ring.
two hydrogen bonding bifurcated arrangements (Fig.
2). One fluorine atom of one BF−4 anion interacts
concomitantly with both nitrogen atoms of H2biim
Complex 7 exhibits an acute N–Co–N chelating angle
of 41.2(3)°, which is much narrower than the N–Co–C
chelating angle of 80.7(3)° in complex 6. This difference
is expected, owing to the different bite angles of the five
and three chelating member rings present in 6 and 7,
respectively.
,
[N(64)–H(64)···F(23) 2.284 A, 146.0° (−1/2+x, 1/2−
,
y, −1/2+z) and N(74)–H(74)···F(23) 2.289 A, 146.7°
(−1/2+x, 1/2−y, −1/2+z)] resulting in the forma-
tion of a seven member ring (counting the hydrogen
atoms). The other two hydrogen bonds involving these
donor atoms and fluorine atoms are N(64)–
The N,N-chelation of trans-azobenzene in 7 results in
,
a distance of 1.367(9) A between the two nitrogen
donor atoms, which is much longer than that of
,
H(64)···F(21) 2.130 A, 152.9° (−1/2+x, 1/2−y, −1/
,
1.242(7) A found for 6, where the NꢀN bond retains a
,
2+z) and N(74)–H(74)···F(14) 2.960 A, 126.2°
double character. Furthermore, in 7 the azobenzene
ligand is far away from planarity, so that the C–N–N–
C torsion angle is 138.3° and the dihedral angle be-
tween the two phenyl rings is 89.2°. These angles take
the values of 175.1(5)° and 23.3(4)° in 6 (see Fig. 3).
(3/2−x, −1/2+y, 1/2−z).
Complex 6 represents also the first X-ray determina-
tion of the structure of a cobalt(III) complex in which
the trans-azobenzene ligand is orthometalated. Indeed,
the structure of the neutral complex Co(h5-
C5H5)(PMe3)(h2-PhNꢀNPh) (7) [5] was the unique ex-
2.3. DFT studies
ample of
a
cobalt complex containing the
trans-azobenzene ligand retrieved from a search on the
CSD. In this complex, the trans-azobenzene is co-ordi-
nated to a Co(I) centre in a h2-fashion, with two Co–N
DFT calculations [6] using the ADF program [7] (see
Section 4 for details) were performed on models of
complexes 6 and 7, respectively [Co(h5-C5H5)(PH3)(k-
C,k-N–C6H4NꢀNPh)]+ and Co(h5-C5H5)(PH3)(h2-
PhNꢀNPh), where the phosphines were taken as PH3.
The geometries of the two complexes were fully
optimised.
,
bond distances of 1.965(5) and 1.913(6) A. The or-
thometalation of PhNꢀNPh in 6 leads to Co–N and
,
Co–C bond distances of 1.925(6) and 1.987(8) A, re-
spectively. The uncoordinated nitrogen donor N(52) in
,
6 is at a distance of 2.781(6) A from the cobalt atom.

190
T. A6ile´s et al. / Journal of Organometallic Chemistry 625 (2001) 186–194
azobenzene also leads to a weakening of the NꢀN
Some of the relevant distances are given in Scheme 3
for the h2-azobenzene complex 7. The numbers in
italics are those from the observed structure, while the
others are calculated. The agreement is very good. The
C–N–N–C torsion angle was calculated as 138°
(138.3° in the structure), with the two phenyl groups
moving away from the metal. The coordination of
bond, which becomes longer than in free trans-azoben-
zene, as a result of donation from the N–N p bond to
the metal and back donation into the empty p*. This
,
value was calculated to be 1.261 A by full optimisation
of free trans-azobenzene, and the X-ray determination
at 82 K showed two independent molecules with NꢀN
,
distances of 1.252 and 1.259 A [11]).
The geometry of the orthometallated complex 6 was
also optimised with the ADF program. Some relevant
distances and angles are given in Table 2 and can be
compared to those of the X-ray structure in Table 1
(same numbering scheme). The agreement between cal-
culated (model) and experimental structures is also very
good for this complex.
The next step consisted of calculating the comple-
mentary species, namely the h2-azobenzene complex of
Co(III), [Co(h5-C5H5)(PH3)(h2-PhNꢀNPh)]2+ (8), and
the orthometallated derivative of Co(I), [Co(h5-
C5H5)(PH3)(k-C,k-C6H4NꢀNPh)]− (9). Their geo-
metries were also fully optimised, without any symme-
try constraints. The relative energies are given in
Scheme 4.
Scheme 3.
Table 2
,
Relevant bond distances (A) and bond angles (°) calculated for the
model complex [Co(h5-C5H5)(PH3)(k-C,k-N–C6H4NꢀNPh)]+
The immediate conclusion from these results is that
Co(III) prefers to form the orthometallated complex
(by 144 kcal mol−1, while for Co(I) coordination of
azobenzene is more favoured (by 63 kcal mol−1). The
bonding energy (DEint) can be decomposed as the sum
of several terms, namely Pauli repulsion (DEPauli), elec-
trostatic (DEelec) and orbital interactions (DEoi), repre-
senting the Pauli repulsion between occupied orbitals of
the fragments, the electrostatic interaction between
fragments (an attractive term), and the two-electron
stabilising interactions between occupied levels of one
fragment and empty levels of the other [12] (Table 3).
The preference of the Co(III) fragment for or-
thometallation can be ascribed to the smaller Pauli
repulsion accompanied by very similar electrostatic and
orbital interactions. On the other hand, for Co(I),
although the same trend is observed for the Pauli
repulsion, the electrostatic and orbital interactions de-
crease considerably for orthometallation. In other
words, the high charges on the CoCp(PH3)2+ and
C6H4NꢀNPh− fragments with Co(III) lead to a fa-
vourable interaction, contrary to CoCp(PH3) and
C6H4NꢀNPh-for Co(I). For Co(I), the stronger cova-
lent bonds formed with azobenzene (the DEoi term)
mainly determine the preference.
Co–N(51)
Co–P
N(51)–C(61)
N(51)–N(52)
1.966
2.176
1.433
1.276
Co–C(76)
1.940
1.368
N(52)–C(71)
N(51)–Co–C(76)
N(51)–Co–P
N(51)–N(52)–C(71)
C(61)–N(51)–Co
81.9
92.0
114.0
129.3
C(76)–Co–P
89.2
118.1
109.2
116.3
C(76)–C(71)–N(52)
C(71)–C(76)–Co
N(52)–N(51)–Co
Scheme 4.
Table 3
The decomposition of the bonding energy (kcal mol−1) for the
possible complexes of Co(I) and Co(III)
Co(III)
Co(I)
h2-Azo-
benzene
Ortho-
metallation
h2-Azo-
benzene
Ortho-
metallation
3. Conclusions
DEPauli
22626.4
22412.1
22262.4
21978.6
Among the new Co(III) complexes synthesised, the
first orthometallation reaction of trans-azobenzene in
the presence of Co(III) was observed, although simple
coordination takes place when this ligand reacts with
DEelec
DEoi
DEint
−4961.3
−23009.8
−5344.7
−4957.6
−22943.2
−5488.7
−4916.1
−23047.1
−5700.8
−4839.4
−22777.4
−5638.2

T. A6ile´s et al. / Journal of Organometallic Chemistry 625 (2001) 186–194
191
similar Co(I) fragments. DFT calculations showed that
the experimental observations were consistent with the
relative energies of the possible species. The H2biim
ligand coordinates to the CoCp(PPh3) fragment, the
N–H groups being involved in hydrogen bonds with
fluorine atoms of the BF−4 counter ion in the solid.
NMR (400 MHz, CDCl3): l 7.56–7.38 (m, 15H, Ph),
5.98 (s, 5H, C5H5), 2.14 (s, 6H, NC–CH3), IR (nujol, w
(cm−1)): broad band centred at 1050 cm–1, BF4–.
4.3. Synthesis of
[Co(p5-C5H5)(PPh3)(NC–Ph)2][BF4]2·CH2Cl2 (3)
A solution of Co(h5-C5H5)(PPh3)I2 (0.39 g, 0.6
mmol) and benzonitrile (0.13 cm3, 1.26 mmol) in
CH2Cl2 (20 cm3) was added to a suspension of Ag[BF4]
(0.30 g, 1.5 mmol) in CH2Cl2 (20 cm3), magnetically
stirred at r.t. A colour change of the initial solution
from green to red was observed, and a precipitate
formed. The mixture was left stirring for about 20 min
filtered and the solvent was removed under vacuum.
The oily residue was washed several times with
petroleum ether (3×20 cm3). It was recrystallised from
CH2Cl2–toluene to give nice red crystals, which recov-
ered by filtration, washed with petroleum ether, and
dried in vacuum to give pure 3. Yield ca. 70%. (Found:
4. Experimental
4.1. General procedures and materials
All reactions and manipulations of solutions were
performed under an argon atmosphere using Schlenck
techniques. Solvents were reagent grade and were dried
according to literature methods Co2(CO)8 was pur-
chased from Fluka and Ag[BF4] was purchased from
Aldrich and they were used as supplied. The complexes
Co(h5-C5H5)(CO)2 [13], Co(h5-C5H5)(CO)I2 and Co(h5-
C5H5)(PPh3)I2 [14] were prepared as previously re-
ported. The petroleum ether used has a b.p. of 40–60°C
Infrared spectra were recorded as mulls on NaCl
plates using an ATI Mattson Genesis FTIR spectrome-
ter. Elemental analyses were performed at the microan-
alytical laboratory of the Universidade Te´cnica de
Lisboa, Portugal.
C,
53.53;
H,
3.92;
N,
3.18;
Calc.
for
C38H32CoN2PB2F8Cl2: C, 53.6; H, 3.76; N, 3.29%).
1H-NMR (400 MHz, CDCl3): l 7.64–7.43 (m, 25 H,
Ph), 6.31 (s, 5H, C5H5), IR ( nujol, w (cm−1)): broad
band centred at 1050 cm–1, BF4–.
Mass spectra were recorded on VG Autospec LSIMS
Technique using 3-nitrobenzylalcohol as a matrix and a
Caesium gun at the Instituto de Ciencias de Materiales
4.4. Synthesis of [Co(p5-C5H5)(PPh3)(H2biim)][BF4]2
(4)
de Aragon, Zaragoza, Spain. H-, 13C- and 31P-NMR
A solution of Co(h5-C5H5)(PPh3)I2 (0.4 g, 0.62
mmol) in CH2Cl2 (20 cm3) was added to a suspension
of Ag[BF4] (0.60 g, 3.0 mmol) and 2,2%-bisimidazole
(0.09 g, 0.62 mmol) in CH2Cl2 (30 cm3), magnetically
stirred at r.t. A colour change of the initial solution
from green to red was observed, and a precipitate
formed. The mixture was left stirring over night,
filtered, and the solvent was partially removed under
vacuum. Petroleum ether was added and a precipitate
was formed (a red crystalline powder together with
some oil was formed). Extraction with acetone followed
by addition of diethylether gave red crystals, which
were recovered by filtration, washed with petroleum
ether, and dried in vacuum to give pure 4. Yield ca.
70%. (Found: C, 50.11; H, 3.73; N, 7.87; Calc. for
C29H26CoN4PB2F8: C, 50.0; H, 3.73; N, 8.04%). 1H-
NMR (400 MHz, d6-acetone): l 11.79 (s, 2H, NH),
8.09–7.20 (m, 19 H, Ph), 6.23 (s, 5H, C5H5), 31P{1H}-
NMR (161.986 MHz, d6-acetone): l 43.54(s). IR (nujol,
w (cm−1)): broad band centred at 1050 cm–1, BF4–.
1
spectra were recorded on a Bruker ARX 400 spec-
1
trophotometer. H-NMR spectra were recorded using
TMS as internal reference, 31P shifts were measured
with respect to external 85% H3PO4, and 13C-NMR
spectra were referenced using the 13C resonance of the
solvent as internal standard.
4.2. Synthesis of [Co(p5-C5H5)(PPh3)(NCCH3)2][BF4]2
(2)
A solution of Co(h5-C5H5)(PPh3)I2 (0.6 g, 1.0 mmol)
in CH2Cl2 (50 cm3) was added to a suspension of
Ag[BF4] (0.50 g, 2.5 mmol) and acetonitrile (2 cm3 of a
1 M solution in CH2Cl2 2.0 mmol) in CH2Cl2 (20 cm3),
magnetically stirred at room temperature (r.t.). A
colour change of the initial solution from green to red
was observed, and a precipitate formed. The mixture
was left stirring for about 20 min, it was filtered, and
the solvent was removed under vacuum. The oily
residue was washed several times with petroleum ether
(3×20 cm3), and it was recrystallised from CH2Cl2–
petroleum ether, to give nice red crystals. They were
recovered by filtration, washed with petroleum ether,
and dried in vacuum to afford pure 2. Yield ca. 70%.
(Found: C, 50.74; H, 4.04; N, 4.19; Calc. for
4.5. Synthesis of
[Co(p5-C5H5)(PPh3){HN(NC5H5)2}][BF4]2 (5)
A solution of Co(h5-C5H5)(PPh3)I2 (0.34 g, 0.53
mmol) in CH2Cl2 (20 cm3) was added to a suspension
of Ag[BF4] (0.58 g, 2.9 mmol) and dipyridilamine (0.1
1
C27H26N2PCoB2F8: C, 50.51; H, 4.05 N, 4.36%). H-

192
T. A6ile´s et al. / Journal of Organometallic Chemistry 625 (2001) 186–194
Table 4
Crystal data and refinement details for cobalt(III) complexes 1, 4, and 6
Compound
1
4
6
Empirical formula
M
C23H20CoI2P
640.09
C
694.06
29H26B2CoF8N4P
C35H29BCoF4N2P
654.31
Crystal system
Space group
Unit cell dimensions
Monoclinic
C2/c
Monoclinic
P21/n
Monoclinic
P21/n
,
a (A)
22.176(27)
14.253(17)
17.735(21)
127.89(1)
4424(9)
13.315(16)
14.539(17)
15.713(19)
98.24(1)
3010(6)
4
1.531
0.701
1408
10.346(12)
13.350(15)
22.663(24)
100.79(1)
3071(6)
4
1.415
0.663
1344
,
b (A)
,
c (A)
i (°)
V (A )
3
,
Z
8
Dcalc (g cm−3
)
1.922
3.645
2448
v (mm−1
F(000)
)
q Range (°)
Index ranges hkl
1.84–.92
2.58–26.19
−165h50, −175k517,
−195l519
9815
5686 (Rint=0.0745)
404
2.38–26.03
−125h50, −155k516,
−275l527
10 370
5835 (Rint=0.0485)
390
05h527, −175k517,
−215l516
5158
3312 (Rint=0.0470)
245
Reflections collected
Unique reflections
Refined parameters
Goodness-of-fit on F2
R and Rw [I\2(I)]
(all data)
1.070
0.990
1.139
0.0515, 0.1516
0.0727, 0.1694
0.991 and −1.624
0.0832, 0.2137
0.1729, 0.2598
0.774 and −0.656
0.0995, 0.2452
0.1425, 0.2443
1.107 and −0.525
Largest difference peak and hole
−3
,
(e A
)
g, 0.53mmol) in CH2Cl2 (20 cm3), magnetically stirred
at r.t. A colour change of the initial solution from green
to red was observed, and a precipitate formed. The
mixture was left stirring for about 20 min, it was
filtered, concentrated and petroleum ether added. A
precipitate was formed, it was washed several times
with petroleum ether (3×20 cm3), and recrystallised
from a mixture of acetone diethylether, to give nice red
crystals, which were recovered by filtration, washed
with petroleum ether, and dried in vacuum to give pure
5. Yield ca. 70%. (Found: C, 52.27; H, 4.18; N, 4.92;
Calc. for C33H31N3PCoB2F8: C, 51.23; H, 4.01; N,
washed several times with petroleum ether (3×20 cm3).
This reaction was repeated a large number of times,
and sometimes it was difficult to solidify the oil, that
was achieved by washing the red oily residue with
water, followed by petroleum ether. It was recrystallised
from CH2Cl2–petroleum ether to give nice red crystals,
which were recovered by filtration, washed with
petroleum ether, and dried in vacuum to give pure 6:
1.11 g (88%) (Found: C, 63.13; H, 4.41; N, 4.05; Calc.
for C35H29N2PCoBF4: C, 64.24; H, 4.43; N, 4.28%).
1H-NMR (400 MHz, CD2Cl2): l 8.00–6.85 (m, 24 H,
Ph), 5.47 (s, 5H, C5H5), 13C{1H}-NMR (100.62 MHz,
CD2Cl2): l 173,06,172,8(d, J 13C–31P=26,83 Hz, C–
Co) 167.75 (s, C–Co), 156.21 (s, C–N), 142.90 (s, C
ipso, PPh3), 133.70–122.85 (m, Ph), 90.92 (s, Cp),
31P{1H}-NMR (161.986 MHz, CD2Cl2): l 45.21(s) IR
(nujol, w (cm−1)): broad band centred at 1050 cm–1,
BF4–.
1
5.43%). H-NMR (400 MHz, d6-acetone): l 10.42 (s,
1H, NH), 8.20–6.62 (m, 23 H, Ph), 6.28 (s, 5H, C5H5),
31P{1H}-NMR (161.986 MHz, d6-acetone): l 41.15(s).
IR (nujol, w (cm−1)): broad band centred at 1050 cm–1,
BF4–.
4.6. Synthesis of
[Co(p5-C5H5)(PPh3)(s-C,s-N–C6H4NꢀNPh)][BF4] (6)
4.7. Crystallography
A solution of Co(h5-C5H5)(PPh3)I2 (1.24 g, 1.94
mmol) and trans-azobenzene (0.36 g, 1.94 mmol) in
CH2Cl2 (20 cm3) was added to a suspension of Ag[BF4]
(0.78 g, 3.9 mmol), magnetically stirred at r.t. A colour
change of the initial solution from green to red was
observed, and a precipitate formed. The mixture was
left stirring for about 20 min, it was filtered, and the
solvent was removed by vacuum. The oily residue was
In the Table 4 are summarised the crystal data,
pertinent data collection parameters and refinement
details for complexes 1, 4 and 6.
The X-ray data for these three complexes were col-
lected on a MAR research plate system using graphite
MoꢁKa radiation at Reading University. The crystals
were positioned at 70 mm from the image plate.
Ninety-five frames were measured at 2° intervals using

T. A6ile´s et al. / Journal of Organometallic Chemistry 625 (2001) 186–194
193
a counting time between 2 and 10 min appropriate to
the crystal under study. Data analysis was carried out
with the XDS program [15]. Only the intensities of the
complex were corrected empirically for absorption ef-
fects, using a version of DIFABS modified for image
plate geometry [16]. The structures were solved by a
combination of the direct methods, Fourier-difference
syntheses and subsequent full-matrix least-squares
refinements on F2. All hydrogen atoms were introduced
in the refinement at the geometric idealised positions. In
complex 6 the BF−4 anions were disordered. Two sets of
tetrahedral fluorine atoms were found from difference
Fourier maps and were refined with occupancy factors
x and 1−x, being x refined to 0.56(1). All non-hydro-
gen atoms were refined with anisotropic thermal
parameters except the fluorine atoms of 6, which were
refined with group isotropic ones. The hydrogen atoms
were refined with isotropic thermal parameters equal to
1.2 times that of the parent atom.
Crystallographic Data Centre, CCDC no. 151552 for
compound 1, CCDC no. 151553 for compound 4 and
CCDC no. 151554 for compound 6. Copies of this
information 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 http://www.ccdc.cam.ac.uk).
Acknowledgements
This work was supported by PRAXIS XXI
under projects PRAXIS/PCNA/C/QUI/103/96 and
PRAXIS/PCNA/C/QUI/143/94. VF thanks British
Council and FCT for funding. The University of Read-
ing and EPSRC are thanked for funds for the Image
Plate system.
The residual electronic density found for all com-
plexes were within the expected values. All calculations
required to solve and refine the structures were carried
out with SHELXS and SHELXL from the SHELX-97 pack-
age [17]. Molecular diagrams and the analysis of hydro-
gen bonds were performed with the PLATON software
[18].
References
[1] (a) J.M. Lehn, Angew. Chem.Int. Ed. Engl. 29 (1990) 1304. (b)
D. Braga, F. Grepioni, Acc. Chem.Res. 27 (1994) 51. (c) M.J.
Calhorda, D. Braga, F. Grepioni, Transition Metal Clusters —
The Relationship between Molecular and Crystal Structure, in
P. Braunstein, L.A. Oro, P.R. Raithby (Eds.), Metal Clusters in
Chemistry, Wiley-VCH, Weinheim, 1999. (d) D. Braga, F. Gre-
pioni, A.G. Orpen (Eds.), Crystal Engineering: from Molecules
to Crystals, to Materials, Kluwer Academic Publishers, Dor-
drecht, 1999.
4.8. DFT calculations
Density functional calculations [6] were carried out
with the Amsterdam Density Functional (ADF) program
[7] developed by Baerends and coworkers (release 2.3)
[19]. Vosko and coworkers’ local exchange correlation
potential was used [20], with Becke’s non-local exchange
[21] and Perdew’s correlation corrections [22]. The ge-
ometry optimisation procedure was based on the method
developed by Versluis and Ziegler [23], using the non-lo-
cal correction terms in the calculation of the gradients,
together with non-local exchange and correlation correc-
tions. The structures of the complexes described above
and others referred in the text were used to prepare input
files for the optimisation of the geometry of the model
complexes. Full optimisations without symmetry con-
straints were always performed. In all the calculations,
a triple-z Slater-type orbital (STO) basis set was used for
Co 3s, 3p, 4s, 4p, 3d; triple-z STO augmented with a
single-z polarisation function was used for P 3s and 3p,
C 2s and 2p, N 2s and 2p, and H 1s. A frozen core
approximation was used to treat the core electrons of C
(1s), N (1s), P ([1–2]s, 2p) and Co ([1–2]s, 2p).
[2] (a)T. Avile´s, M.L.H. Green, J. Chem. Soc. Dalton Trans. (1979)
1116. (b) T. Avile´s, P. Royo, J. Organometal. Chem. 221 (1981)
333.
[3] (a) A.C. Cope, R.W. Siekman, J. Am. Chem.Soc. 87 (1965) 3272.
(b) M.I. Bruce, Angew. Chem. Int. Ed. Engl. 16 (1977) 73. (c)
G.W. Parshall, Acc. Chem. Res. 3 (1970) 139.
[4] R.F. Heck, J. Am. Chem. Soc. 85 (1963) 657.
[5] H-F. Klein, M. Helwig, U. Koch, U. Flo¨rke, H.-J. Haupt, Z.
Naturforsch. 48b (1993) 778.
[6] R.G. Parr, W. Yang, Density Functional Theory of Atoms and
Molecules, Oxford University Press, New York, 1989.
[7] Amsterdam Density Functional (ADF) Program, Release 2.3,
Vrije Universiteit, Amsterdam, The Netherlands, 1995.
[8] A.R. Garber, P.E. Garrou, G.E. Hartwell, M.J. Smas, J.R.
Wilkinson, L.J. Todd, J. Organomet. Chem. 86 (1975) 219.
[9] Q.-B. Bao, S.J. Landon, A.L. Rheingold, T.M. Haller, T.B. Brill,
Inorg. Chem. 24 (1985) 900.
[10] F.H Allen, J.E Davies, J.J Galloy, O. Johnson, O. Kennard, C.F
Mcrae, D.G. Watson, J. Chem. Inf. Comput. Sci. 31 (1991) 204.
[11] J. Harada, K. Ogawa, S. Tomoda, Acta Crystallogr. Sect. B 53
(1997) 662.
[12] (a) T. Ziegler, A. Rauk, Inorg. Chem. 18 (1979) 1755. (b) T.
Ziegler, A. Rauk, Inorg. Chem.. 18 (1979) 1758. (c) T. Ziegler,
A. Rauk, Theor. Chim. Acta 46 (1977) 1.
[13] M.D. Rausch, R.A. Genetti, J. Org. Chem. 35 (1970) 3888.
[14] R.B. King, Inorg. Chem. 5 (1966) 82.
[15] W. Kabsch, J. Appl. Crystallogr. 21 (1988) 916.
[16] N. Walker, D. Stuart, DIFABS, Acta Crystallogr. Sect. A 39
(1983) 158.
[17] G.M. Sheldrick, SHELX-97, University of Go¨ttingen, Germany,
1997.
5. Supplementary material
Crystallographic data for the structures reported in
this paper have been deposited with the Cambridge

194
T. A6ile´s et al. / Journal of Organometallic Chemistry 625 (2001) 186–194
[18] A.L. Spek, PLATON, A Multipurpose Crystallographic Tool,
Utrecht University, Utrecht, The Netherlands, 1999.
[19] (a) E.J. Baerends, D. Ellis, P. Ros, Chem. Phys. 2 (1973) 41. (b)
E.J. Baerends, P. Ros, Int. J. Quantum Chem. S12 (1978)169. (c)
P.M. Boerrigter, G. te Velde, E.J. Baerends, Int. J. Quantum
Chem. 33 (1988)87. (d) G. te Velde, E.J. Baerends, J. Comp.
Phys. 99 (1992) 84.
[20] S.H. Vosko, L. Wilk, M. Nusair, Can. J. Phys. 58 (1980)
1200.
[21] A.D. Beck, J. Chem. Phys. 88 (1987) 1053.
[22] (a) J.P. Perdew, Phys. Rev. B33 (1986) 8822. (b) J.P. Perdew,
Phys. Rev. B34 (1986) 7406.
[23] (a) L. Versluis, T. Ziegler, J. Chem. Phys. 88 (1988) 322. (b) L.
Fan, T. Ziegler, J. Chem. Phys. 95 (1991) 7401.
.