Coordination properties of N2S (1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane) or N2S2 (1,8-bis(3,5-dimethyl-1-pyrazolyl)-3, 6-dithiaoctane or 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl) -2-thiapropyl]benzene) donor ligands toward Rh(I)

Article abstract of DOI:10.1016/j.jorganchem.2004.02.014

The 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane ligand (bdtp) reacts with [Rh(COD)(THF)₂][BF₄] to give [Rh(COD)(bdtp)][BF₄] ([1][BF₄]), which is fluxional in solution on the NMR time scale. Its further treatment with carbon monoxide leads to a displacement of the 1,5-cyclooctadiene ligand, generating a mixture of two complexes, namely, [Rh(CO)₂(bdtp)][BF₄] ([2][BF₄]) and [Rh(CO)( bdtp -κ³ N, N, S )][BF₄] ([3][BF₄]). In solution, [2][BF₄] exists as a mixture of two isomers, [Rh(CO)₂(bdtp -κ² N, N)]⁺ ([2a]⁺) and [Rh(CO)₂(bdtp -κ³ N, N, S)]⁺ ([2b]⁺; major isomer) rapidly interconverting on the NMR time scale. At room temperature, [2][BF₄] easily loses one molecule of carbon monoxide to give [3][BF₄]. The latter is prone to react with carbon monoxide to partially regenerate [2][BF₄]. The ligands 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-thiapropyl]benzene (bddf) and 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) are seen to react with two equivalents of [Rh(COD)(THF)₂][BF₄] to give the dinuclear complexes [Rh₂(bddf)(COD)₂] [BF₄]₂ ([4][BF₄]₂) and [Rh₂(bddo)(COD)₂][BF₄]₂ ([5][BF₄]₂), respectively. In such complexes, the ligand acts as a double pincer holding two rhodium atoms through a chelation involving S and N donor atoms. Bubbling carbon monoxide into a solution of [4][BF₄]₂ results in loss of the COD ligand and carbonylation to give [Rh₂(bddf)(CO)₄] [BF₄]₂ ([6][BF₄]₂). The single-crystal X-ray structures of [3][CF₃SO₃], [5][BF₄]₂ and [6][BF₄]₂ are reported.

Full text of DOI:10.1016/j.jorganchem.2004.02.014

Journal of Organometallic Chemistry 689 (2004) 1599–1608
www.elsevier.com/locate/jorganchem
Coordination properties of N2S
(1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane) or N2S2
(1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane or
1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-thiapropyl]benzene)
donor ligands toward Rh(I)
a,b
Jordi Garcıa-Anton , Rene Mathieu , Noel Lugan , Josefina Pons Picart
a,
a
b,
*
*
ꢀ
ꢀ
ꢀ
€
,
b
Josep Ros
a
Laboratoire de Chimie de Coordination du CNRS, 205 Route de Narbonne, 31077 Toulouse Cedex 4, France
Departament de Quꢀımica, Facultat de Ciꢁencies – Edifici C sn, Universitat Autꢁonoma de Barcelona, 08193-Bellaterra-Cerdanyola, Barcelona, Spain
b
Received 13 January 2004; accepted 10 February 2004
Abstract
The 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane ligand (bdtp) reacts with [Rh(COD)(THF)2][BF4] to give [Rh(COD)(bdtp)]-
[BF4] ([1][BF4]), which is fluxional in solution on the NMR time scale. Its further treatment with carbon monoxide leads to a
displacement of the 1,5-cyclooctadiene ligand, generating a mixture of two complexes, namely, [Rh(CO)2(bdtp)][BF4] ([2][BF4]) and
[Rh(CO)(bdtp-j3N,N,S)][BF4] ([3][BF4]). In solution, [2][BF4] exists as a mixture of two isomers, [Rh(CO)2(bdtp-j2N,N)]þ ([2a]þ)
and [Rh(CO)2(bdtp-j3N,N,S)]þ ([2b]þ; major isomer) rapidly interconverting on the NMR time scale. At room temperature, [2][BF4]
easily loses one molecule of carbon monoxide to give [3][BF4]. The latter is prone to react with carbon monoxide to partially re-
generate [2][BF4]. The ligands 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-thiapropyl]benzene (bddf) and 1,8-bis(3,5-dimethyl-1-pyraz-
olyl)-3,6-dithiaoctane (bddo) are seen to react with two equivalents of [Rh(COD)(THF)2][BF4] to give the dinuclear complexes
[Rh2(bddf)(COD)2][BF4]2 ([4][BF4]2) and [Rh2(bddo)(COD)2][BF4]2 ([5][BF4]2), respectively. In such complexes, the ligand acts as a
double pincer holding two rhodium atoms through a chelation involving S and N donor atoms. Bubbling carbon monoxide into a
solution of [4][BF4]2 results in loss of the COD ligand and carbonylation to give [Rh2(bddf)(CO)4][BF4]2 ([6][BF4]2). The single-
crystal X-ray structures of [3][CF3SO3], [5][BF4]2 and [6][BF4]2 are reported.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Rhodium(I); N,S-ligands; Pyrazole; Hemilabile ligands
1. Introduction
which can be more readily displaced from the metal
centre, thereby leaving a vacant site or stabilizing tran-
sition states. The different types of hemilability have
been reviewed by Braunstein and Naud [3].
Pyrazole-containing molecules are attractive poten-
tial hemilabile ligands since they are relatively easy to
prepare; moreover their steric and electronic properties
can be tuned in a straightforward manner [4]. In recent
years, we have studied and reported the synthesis and
characterization of ligands combining a pyrazolyl group
with some other functions containing N (amine) [5], P
(phosphine) [6], O (alcohol or ether) [7], and S (thiol or
The chemistry of transition metal complexes incor-
porating hemilabile ligands has been widely studied in
recent years [1]. The term hemilabile ligand, first intro-
duced by Jeffrey and Rauchfuss [2], refers to polydentate
ligands possessing both strong donor groups, anchoring
the ligand to the metal centre, and weaker donor groups,
* Corresponding authors. Tel.: +34935812895; fax: +34935813101.
E-mail addresses: mathieu@lcc-toulouse.fr (R. Mathieu),
josefina.pons@uab.es (J. Pons Picart).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.02.014

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1600
thioether) [8] as donor atoms. In particular, we have
investigated the hemilabile properties of the 1,5-bis(3,5-
dimethyl-1-pyrazolyl)-3-thiapentane (bdtp) and 1,8-bis-
(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) ligands
in their association with Pd(II) [8d]. Various examples of
bdtp coordination to Co(II) [9], Zn(II) [10], Cd(II) [10],
Cu(I) [9,11,12] and Ag(I) [9] are available from the lit-
erature. The ligand generally acts as tridentate (NSN) –
except for [ZnCl2(bdtp)], in which it acts as bidentate
(NN) – as also observed in our previously reported
Pd(II) complexes. On the other hand, bddo was previ-
ously shown to behave either as bidentate (NN) in
Cu(II) and Zn(II) complexes [13,15], or as tretraden-
tate (NSSN) in a Ni(II) complex [15], or even as a bis-
bidentate NS ligand in a Cd(II) complex [15]. We have
found the two first of these coordination modes in the
case of Pd(II) [8a].
We have extended this study to Rh(I)/bdtp complexes
and in this paper the results of our investigations are
compared with those recently obtained with Rh(I)
complexes of bis[(3,5-dimethyl-1-pyrazolyl)methyl]eth-
ylamine (LN) [5a] and bis[2-(3,5-dimethyl-1-pyraz-
olyl)ethyl]ether (LO) ligands (Scheme 1) [7c]. We also
describe the synthesis of the new 1,2-bis[3-(3,5-dimethyl-
1-pyrazolyl)-2-thiapropyl]benzene ligand (bddf) and the
results of our investigation on the bonding properties of
both the bddo and the bddf toward Rh(I).
2. Results and discussion
2.1. Case of the 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thia-
pentane (bdtp) ligand
The bdtp ligand reacts with [Rh(COD)(THF)2][BF4] –
generated in situ via reaction of [Rh(COD)Cl]2 with
AgBF4 in THF – to give a complex whose elemental
analyses are in agreement with the formula
[Rh(bdtp)(COD)][BF4] ([1][BF4]). The room temperature
1H NMR spectrum shows sharp resonances for the CH
and CH3 groups of the pyrazolyl cycles, and broad
resonances at 4.57 and 4.49 ppm for the NCH2 group of
the bdtp ligand and the olefinic hydrogens of the 1,5-
cyclooctadiene suggesting the occurrence of a fluxional
phenomenon. By lowering the temperature to 183 K, a
splitting of the resonances of the CH3 groups of the
pyrazolyl cycle into four somewhat broad signals at
2.55, 2.27, 2.21 and 2.12 ppm is observed. Intricate
broad overlapping resonances are observed in the 3–5
ppm region. It is, however, clearly apparent that most of
these resonances result from the splitting of the broad
resonances observed at room temperature at 4.57 and
4.49 ppm. This shows that the olefinic protons of the
1,5-cyclooctadiene and the NCH2 protons are no longer
equivalent at low temperature. However, the fluxional
phenomenon is not frozen at 183 K.
Let us now recall the behavior of the parent Rh(I)
complexes of the LN or LO ligands (Scheme 1). Two
situations have been encountered. In the case of complex
[Rh(LN)(COD)][BF4], there is a thermodynamic equi-
librium in solution between two isomers, one (the minor
isomer) in which the ligand is j3-bonded and the other
one in which the ligand is j2-bonded [5a]. For complex
[Rh(LO)(COD)][BF4], there is only a weak interaction
between the rhodium and the oxygen, but the complex is
not fluxional [7c]. On this basis, the fluxional behavior
of complex [1]þ likely results from a combination of two
phenomena, namely: (i) a dynamic equilibrium between
two isomers in which the ligand bdtp would be either j2
or j3-bonded, which would render the olefinic protons
of 1,5-cyclooctadiene non-equivalent at low temperature
(Scheme 2) and (ii) a chelate ring-flipping process within
the j3-bonded isomer, which would render the methy-
N
N
N
N
N
LN
LO
N
N
N
N
N
N
O
S
bdtp
N
N
Scheme 1.
+
+
S
N
N
N
N
N
N
N
S
Rh
Rh
N
[1]+
Scheme 2.

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1601
Table 1
lene and methyl resonances of the bdtp ligand magneti-
cally inequivalent.
þ
ꢂ
Selected bond lengths (A) and angles (ꢁ) for [3] with estimated
standard deviations in parentheses
Bubbling carbon monoxide into a solution of [1][BF4]
in dichloromethane at room temperature leads to a
mixture of complexes. The infrared spectrum of the
solution in the m(CO) region indeed shows a set of two
weak bands at 2103 and 2043 cmꢀ1 and a set of two
strong bands at 2078 and 2003 cmꢀ1 attributable to a
first complex, [2]þ, present as a mixture of isomers (vide
infra), and a strong band at 2003 cmꢀ1 attributable to a
second complex, [3]þ. Evaporation of the solution and
crystallization led to [3]þ only as a solid.
The observation of a single peak at 2003 cmꢀ1 in the
m(CO) stretching region for [3]þ is consistent with a j3
bonding mode of the bdtp ligand. As it was not possible
to obtain suitable crystals for an X-ray structure deter-
[3]þ
Rh(1)–C(1)
Rh(1)–N(2)
Rh(1)–N(12)
Rh(1)–S(1)
1.828(2)
2.043(2)
2.045 (2)
2.3938(5)
C(1)–Rh(1)–N(2)
C(1)–Rh(1)–N(12)
N(12)–Rh(1)–N(2)
C(1)–Rh(1)–S(1)
N(12)–Rh(1)–S(1)
N(2)–Rh(1)–S(1)
92.34(8)
90.99(8)
176.14(6)
172.23(7)
87.64(5)
89.32(4)
mination, we repeated the reaction with AgCF3SO3 in-
stead of AgBF4. Suitable crystals of [3][CF3SO3] could
then be obtained. The structure of [3]þ is shown in Fig. 1
and a list of selected bond distances and angles is given
in Table 1. The rhodium atom is bound to the two ni-
trogen and to the sulfur atoms of the bdtp ligand, and
also to a carbon monoxide ligand, in a slightly distorted
ꢂ
square-planar geometry. The Rh atom lies 0.05 A above
the mean plane formed by the atoms C1, N2, N12 and
ꢂ
S1. The Rh–N (2.0432(15) and 2.0454(16) A) and Rh–C
ꢂ
(1.8281(19) A) bond distances are similar to those found
in the [Rh(LN)(CO)][BPh4] [5a] and [Rh(LO)(CO)][BF4]
ꢂ
[7c] complexes, 2.015(3)–2.042(4) A and 1.795(5)–
ꢂ
1.809(4) A for Rh–N and Rh–C bonds, respectively. No
other complex with RhCN2S core (C carbonyl, S thio-
ether) could be found in the literature. The Rh–S bond
ꢂ
distance (2.3938(5) A) is in the upper limit of the Rh–
Fig. 1. ORTEP drawing of the cation [Rh(bdtp)(CO)]þ ([3]þ) showing
the numbering scheme (ellipsoids are shown at the 50% probability
level).
Fig. 2. The 400 MHz 1H NMR (above) and gNMR simulated spectra for the NCH2CH2S fragment of [Rh(bdtp)(CO)]þ ([3]þ), including (a) the
numbering and (b) the dihedral angles for the NCH2CH2S fragment.

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1602
S(thioether) bonds found in the literature (2.262–2.390
ꢂ
having NOE interaction with H4, shows strong NOE
interaction with the doublets of doublets of doublets at
4.79 ppm and was assigned to CH3(7). From the X-ray
crystal structure (Fig. 1), it can be seen that the nearest
proton to CH3(7) is H9R and therefore it is the one that
should present NOE interaction. This information al-
lowed us to assign H9R to the doublets of doublets of
doublets at 4.79 ppm, and H9S to the signal at 5.16 ppm.
Coupling constants obtained from the gNMR [17] gen-
ꢂ
A range; mean bond distance of 2.322 A) [16].
The 1H NMR spectrum of [3]þ in CDCl3 is in
agreement with the solid-state structure. The two pro-
tons of each CH2 of the pz–CH2–CH2–S chain are
diastereotopic, thus leading to four groups of signals
(Fig. 2), and each group of signals can be assigned as a
doublet of doublets of doublets. This happens due to the
rigid conformation of the bdtp ligand in its j3 bonding
mode. This behavior had been previously observed by
some of us in similar pyrazole-thioether or pyrazole-
thiolate Pd(II) complexes [8]. An HMQC experiment
(Fig. 3) was performed to assign protons H10R and H10S
to the two doublets of doublets of doublets of lower d,
and H9R and H9S to those of higher d. NOESY experi-
ments (Fig. 4) allowed us to differentiate H9R from H9S
and CH3(6) from CH3(7): the singlet that appears at
2.52 ppm shows NOE interaction only with H4 and was
assigned to CH3(6). The singlet at 2.32 ppm, besides
1
erated H NMR simulated spectra (Fig. 2) helped us to
differentiate H10R and H10S. These coupling constants
agree with the conformation of the S–CH2–CH2–N
2
3
chain as seen in Fig. 1. Geminal J and ffi 180ꢁ J cou-
pling constants have indeed significantly higher values
3
than ffi 30ꢁ and ffi 60ꢁ J coupling constants [18]. Thus,
H10R should correspond to the doublet of doublets of
doublets at 2.81 ppm and H10S to the one at 3.86 ppm.
Coming back now to the ([2][BF4])/([3][BF4]) mix-
ture in solution, the infrared spectrum shows, in ad-
dition to the single band due to [3]þ, two weak
absorption bands at 2103 and 2043 cmꢀ1 (isomer
[2a]þ) and two strong absorption bands at 2078 and
2003 cmꢀ1 (isomer [2b]þ). By analogy with the related
[Rh(CO)2LN]þ and [Rh(CO)2LO]þ complexes [5a,7c],
we attribute to the minor isomer [2a]þ a 16 valence-
electron structure in which the bdtp ligand is j2N,N-
bonded to Rh(I), and to the major isomer [2b]þ a 18
valence-electron isomer with the ligand j3N,N,S-bon-
ded to Rh(I). It is worth noting that the [2a]þ/[2b]þ/
[3]þ mixture can be regenerated upon bubbling carbon
monoxide through a solution of pure [3]þ in dichlo-
romethane. However, it is worth noting that even
under a carbon monoxide atmosphere, it was not
possible to crystallize the di-carbonyl compounds out
of the solution.
1
In addition to the signals due to [3]þ, the 293K H
Fig. 3. The 250 MHz 2D HMQC spectrum of [Rh(bdtp)(CO)]þ ([3]þ).
NMR spectrum of the [2a]þ/[2b]þ/[3]þ mixture shows for
the CH2 groups one broad peak at 3.99 ppm and one
broad triplet at 3.18 ppm in a 1:1 ratio that gives evi-
dence for a fluxional process in solution. At the same
temperature, sharp resonances at 2.27, 2.34, and 6.08
ppm are observed for the methyl and CH groups of the
pyrazolyl cycles, respectively. Lowering the temperature
to 183 K induces a progressive splitting of the 3.99 ppm
resonance into three broad resonances at 4.65, 4.16, and
1.81 ppm, in a 1:2:1 ratio. Concomitantly, the signal at
3.18 ppm splits into four broad resonances at 3.73, 3.19,
2.93, and 2.50 ppm, in the 1:1:1:1 ratio. In the same
temperature range, the methyl resonances at 2.27 and
2.34 ppm evolve to give four resonances of equal in-
tensity centred at 2.61, 2.38, 2.16, and 1.69 ppm. There is
no significant change observable for the 6.08 ppm res-
onance, except a slight broadening and a slight shift to
6.03 ppm. From these results it is clear that, as for [1]þ,
the fluxional behavior of [2b]þ implies a conformational
equilibrium of the six-membered chelate rings. This is
Fig. 4. The 250 MHz 2D NOESY spectrum of [Rh(bdtp)(CO)]þ ([3]þ).

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1603
+
+
+
N
S
N
OC
OC
N N
OC
OC
N N
-
CO
CO
S
Rh
Rh
OC Rh
S
+
N
N
N
N
N
N
[2a]+
[2b]+
[3]+
Scheme 3.
corroborated by a low DGz value of ca. 50 kJ molꢀ1 as
deduced from the coalescence behavior of each of the
methylene and methyl proton resonances [19]. A similar
fluxional behavior has recently been evidenced in a
Rh(I) complex of the closely related LO ligand [7c], and
in Pd(II) complexes of tridentate pyrazole-based ligands
with a NOS-donor set [8d]. Our observations are sum-
marized in Scheme 3.
In summary, the bonding modes of the bdtp ligand,
and the LN and LO ligands toward Rh(I) are very similar
since j2 and j3 bonding modes have been evidenced in
the three complexes. For the dicarbonyl Rh(I) species, in
which there is little steric crowding around Rh, the j3
bonding mode of the pyrazole-based ligand is the most
abundant. In addition, it appears that the
[Rh(bdtp)(CO)2]þ dicarbonyl complex decarbonylates
more easily than its LN and LO analogues. This is cer-
tainly the result of the softer donor character of the
sulfur atom compared to nitrogen and oxygen in amine
or ether functions. This is supported by the m(CO)
stretching frequency values of the resulting monocar-
bonyl complexes: 2003 cmꢀ1 (bdtp), 1997 cmꢀ1 (LN) [5a],
1994 cmꢀ1 (LO) [7c], which decrease with the increase of
the hardness of the heteroatom donor centre.
2
2
N
N
SH
2 BuLi
Br
Br
N
N
+
Li+
S
N
N
N
N
S
S
bddf
Scheme 4.
2.2. Case of the 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-
thiapropyl]benzene (bddf) and 1,8-bis(3,5-dimethyl-1-
pyrazolyl)-3,6-dithiaoctane (bddo) ligands
The 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-thiapro-
pyl]benzene (bddf) was obtained in good yield by
treatment of the lithium thiolate salt of N-(2-merca-
ptoethyl)-3,5-dimethylpyrazole and a; a0-dibromo-o-
xylene in refluxing tetrahydrofurane (Scheme 4).
The reaction of [Rh(COD)(THF)2][BF4] with bddf
and 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane
(bddo) gives, regardless of the initial metal to ligand
ratio (from 1:1 to 2:1) is, [Rh2(bddf)(COD)2][BF4]2
([4][BF4]2) and [Rh2(bddo)(COD)2][BF4]2 ([5][BF4]2),
respectively. The room temperature 1H NMR spectra of
complexes [4]2þ and [5]2þ are little informative since,
except for the sharp resonances of the pyrazolyl cycles,
only broad resonances are observed.
Fig. 5. ORTEP drawing of the cation [Rh2(bddo)(COD)2]2þ ([5]2þ
)
showing the numbering scheme (ellipsoids are shown at the 50%
probability level).

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1604
The solid-state structure of [5][BF4]2 was established
bridging or trans chelating NN ligand (Cu(II), Zn(II)
[13–15] or Pd(II) [8a] complexes), or as tetradentate
N2S2 ligands (Ni(II) [15] and Pd(II) [8a] complexes). In
the latter Pd(II) complex, stepwise coordination of the
ligand as a tetradentate toward one metal center was
found to involve an intermediate bearing two pyrazolyl
fragments in trans position, followed by isomerization,
and coordination of the sulfur atoms, which are weaker
donors. The differences observed in the present case may
be due to the fact that after coordination of the first
pyrazolyl group, the bulky cyclooctadiene ligand blocks
the trans position, thus preventing the second pyrazolyl
ligand to enter the same coordination sphere.
by X-ray diffraction. It consists of a bimetallic dicationic
unit of [Rh2(bddo)(COD)2]2þ (Fig. 5) associated with
two BFꢀ4 anions. The cation possesses a crystallographic
inversion centre located in the middle of the C12–C12*
bond. Each half of the bddo ligand is coordinated to a
Rh(I) atom through the nitrogen atom of the pyrazolyl
ring and the sulfur atom of the thioether group. The
coordination sphere of each metal atom is completed by
a 1,5-cyclooctadiene ligand. Table 2 lists selected bond
distances and angles for [5]2þ. The Rh(I) atom lies 0.057
ꢂ
A above the mean plane formed by the centroid of C21–
C22 and C25–C26 bonds, N2, and S1. The Rh–N
ꢂ
ꢂ
(2.092(3) A) and Rh–S (2.366(2) A) bond distances are
similar to those found in the literature for complexes
Bubbling carbon monoxide into a solution of [4][BF4]2
gives [Rh2(bddf)(CO)4][BF4]2 ([6][BF4]2; Scheme 5). A
similar reaction carried out from [5][BF4]2 led to the
precipitation of an intractable white material. The IR of
[6]2þ shows, in the m(CO) region, two peaks at 2106 and
2041 cmꢀ1 indicating the formation of a dicarbonyl Rh(I)
complex. Noticeably, the m(CO) absorptions bands ap-
pear at almost the same frequency as in [2a]þ.
The structure of [6][BF4]2 was established by an X-
ray diffraction study. It consists of a cationic unit of
[Rh2(bddf)(CO)4]2þ (Fig. 6) associated to two BFꢀ4 an-
ions. Each half of the bddf ligand is coordinated to a
Rh(I) atom through one nitrogen of the pyrazolyl cycle
and one sulfur of the thioether groups. Two carbonyls
ligands in cis position complete a slightly distorted
square-planar environment around the metal centre.
Each Rh(I) centre has 16 valence electrons, consistent
with the IR data. Table 2 lists a selection of bond dis-
ꢂ
with Rh–N(pz) (2.015–2.141 A range; mean bond dis-
ꢂ
tance of 2.085 A) and Rh–S(thioether) (2.262–2.39 A
ꢂ
range; mean bond distance of 2.322 A), respectively [16].
ꢂ
Attempts to get some insight into the dynamic be-
havior of complexes [4][BF4]2and [5][BF4]2 by 1H NMR
remained inconclusive. Changes in the NMR spectra
were indeed observed in the 273 –183 K temperature
range but, due to the overlap of the signals, they could
not be rationalized.
The solid-state structure of [5][BF4]2 shows that po-
tentially tetradentate N2S2 bddf and bddo ligands act as
bis-NS bidentate donors in these Rh(I) complexes. A
similar coordination mode had previously been en-
countered in the case of a Cd(II) complex [15]. In other
cases, the bddo ligand has been found to behave as
Table 2
Selected bond lengths (A) and angles (ꢁ) for [5] and [6]2þ with esdÕs in
2þ
ꢂ
[4]2+
parentheses
[5]2þ
[6]2þ
Rh(1)–C(21)
Rh(1)–C(22)
Rh(1)–C(25)
Rh(1)–C(26)
Rh(1)–N(2)
Rh(1)–S(1)
2.158(4)
2.121(4)
2.174(5)
2.154(5)
2.092(3)
2.366(2)
Rh(1)–C(29)
Rh(1)–C(30)
Rh(2)–C(31)
Rh(2)–C(32)
Rh(1)–N(2)
Rh(2)–N(12)
Rh(1)–S(8)
1.91(2)
1.86(2)
1.89(2)
1.86(2)
2.09(1)
2.07(1)
2.38(4)
2.38(3)
S
N
S
N
N
N
Rh
Rh
Rh(2)–S(18)
N(2)–Rh(1)–C(22)
N(2)–Rh(1)–C(26)
N(2)–Rh(1)–C(21)
N(2)–Rh(1)–C(25)
N(2)–Rh(1)–S(1)
C(22)–Rh(1)–S(1)
C(26)–Rh(1)–S(1)
C(21)–Rh(1)–S(1)
C(25)–Rh(1)–S(1)
C(22)–Rh(1)–C(26)
C(22)–Rh(1)–C(21)
C(26)–Rh(1)–C(21)
C(22)–Rh(1)–C(25)
C(26)–Rh(1)–C(25)
C(21)–Rh(1)–C(25)
154.7(1)
95.0(2)
167.5(1)
95.4(2)
86.3(1)
93.5(1)
149.7(2)
90.8(1)
173.0(2)
97.7(2)
37.6(2)
81.4(2)
82.1(2)
37.1(2)
89.1(2)
C(30)–Rh(1)–C(29)
C(30)–Rh(1)–N(2)
C(29)–Rh(1)–N(2)
C(30)–Rh(1)–S(8)
C(29)–Rh(1)–S(8)
N(2)–Rh(1)–S(8)
C(32)–Rh(2)–C(31)
89.0(8)
170.7(6)
94.4(7)
89.7(5)
172.7(6)
88.0(3)
85.6(7)
CO
[6]2+
C(32)–Rh(2)–N(12) 177.0(5)
C(31)–Rh(2)–N(12) 93.6(6)
S
N
S
N
N
C(32)–Rh(2)–S(18)
C(31)–Rh(2)–S(18)
N(12)–Rh(2)–S(18)
90.5(5)
175.7(5)
90.2(3)
N
Rh
Rh
OC
Scheme 5.
CO
OC
CO

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J. Garcıa-Anton et al. / Journal of Organometallic Chemistry 689 (2004) 1599–1608
1605
thiapentane (bdtp) [8d], bis(3,5-dimethyl-1-pyrazolyl)-
3,6-dithiaoctane (bddo) [15] and [RhCl(COD)]2 [20] have
been prepared according to the published procedures.
Elemental analyses (C, N, H, S) were performed on a
Carlo Erba CHNS EA-1108 instrument. Infrared spec-
tra were recorded on a Perkin–Elmer 2000 FT spectro-
photometer either in KBr pellets or in CH2Cl2 solution
in CaF2 cells. The NMR spectra were obtained on
Bruker AC200, WM250, AMX400, or DRX500 instru-
ments. Chemical shifts (d) were referenced to the resid-
ual signals of the deuterated solvent and are given in
ppm. Mass spectra were obtained with an Esquire 3000
ion trap mass spectrometer from Bruker Daltonics.
Fig. 6. ORTEP drawing of the cation [Rh2(bddf)(CO)4]2þ ([6]2þ
)
4.2. Synthesis of 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-
thiapropyl]benzene (bddf)
showing the numbering scheme (ellipsoids are shown at the 30%
probability level).
7.2 ml of butyl lithium 1.6 M in hexane (11.5 mmol)
were added dropwise to a solution of 1.62 g (10.4 mmol)
of N-(2-mercaptoethyl)-3,5-dimethylpyrazole in THF
(10 ml) keeping the Schlenk flask in an ice-water bath.
Precipitation of the lithium thiolate was observed and
then 1.41 g (5.1 mmol) of a; a0-dibromo-o-xylene 96% in
THF (5 ml) were added. The solution was heated under
reflux for 5 h. After cooling to room temperature the
solvent was evaporated to dryness. Dichloromethane (25
ml) was added and the precipitated LiCl was filtered off.
The solution was washed with distilled water (3 · 20 ml).
The organic layer was then dried over anhydrous so-
dium sulphate and the solvent was removed in vacuum
to give bddf as a white solid.
ꢂ
tances and angles. The Rh1 atom lies 0.012 A above the
mean plane formed by the atoms C29, C30, N2 and S8,
ꢂ
whereas Rh2 atom lies 0.046 A above the plane formed
by C31, C32, N12 and S18. The Rh–N (2.074(11) and
ꢂ
ꢂ
2.094(13) A) and Rh–S (2.376(4) and 2.375(3) A) dis-
tances are similar to those found in the parent complex
[5]2þ (vide supra).
3. Conclusion
This study complements our project aimed at evalu-
ating the bonding properties of N2X tridentate pyraz-
olyl-based ligands (X ¼ N, O, S) toward Rh(I). It
appears that when no steric strain is imposed by other
ligands, these pyrazole-based ligands show a hemilabile
character with a good propensity to adopt a j3 bonding
mode, in equilibrium with a j2 bonding mode in low
concentration.
The different behavior observed with the bddf and
bddo ligands, both acting as j2 N,S ligands toward two
Rh(I) centres, is probably the consequence of the pres-
ence of the bulky 1,5-cyclooctadiene which remains in
the coordination sphere of the metal, thus preventing
the j2N,N-bonding mode due to steric crowding.
bddf: yield: 1.62 g (77%) – C22H30N4S2 (414.63): C,
63.73; H, 7.29; N, 13.51; S, 15.47. Found: C, 63.58; H,
7.15; N, 13.64; S, 15.73%. IR (KBr, cmꢀ1): m(C–H)al
2925, m(C@C), m(C@N) 1552, d(C–H)oop 780-763. 1H
NMR (250 MHz, CDCl3) d ¼ 2:22 (s, 12H, 4 Me), 2.86
3
(t, J ¼ 7 Hz, 4H, S–CH2–CH2), 3.64 (s, 4H, S–CH2–
3
ph), 4.08 (t, J ¼ 7 Hz, 4H, pz–CH2–CH2), 5.78 (s, 2H,
pz–CH), 7.19 (b, 4H, C6H4). - 13C{1H} NMR (63 MHz,
CDCl3) d ¼ 11:3 (Me), 13.6 (Me), 32.0 and 33.6 (S–
CH2–ph and CH2–CH2–S), 48.7 (pz–CH2–CH2), 105.2
(pz–CH), 127.6–136.2 (C6H4), 139.4 and 147.9 (pz–C).
MS (ESI): m/z (%) ¼ 415 (100) [M + Hþ].
4. Experimental
4.3. Synthesis of [Rh(bdtp)(COD)][BF4] ([1][BF4])
and [Rh(bdtp)(COD)][CF3SO3] ([1][CF3SO3])
4.1. Generals remarks
A solution of 0.081 g (0.416 mmol) of AgBF4 [or
0.107 g (0.416 mmol) of AgCF3SO3] in methanol (5 ml)
was added dropwise and under vigorous stirring to a
solution of 0.102 g (0.207 mmol) of [RhCl(COD)]2 in
THF (15 ml). The reaction was carried out in the dark to
prevent reduction of Ag(I) to Ag(0). The solution turned
from an initial orange color to yellow, and AgCl pre-
cipitated. After 30 min the solution was filtered through
The syntheses were performed using usual vacuum
line and Schlenk techniques. All reagents were com-
mercial grade chemicals and were used without further
purification. Diethyl ether, tetrahydrofuran, and di-
chloromethane solvent used for the syntheses, were
dried and distilled by standard methods and stored
under nitrogen. 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-

ꢀ
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J. Garcıa-Anton et al. / Journal of Organometallic Chemistry 689 (2004) 1599–1608
1606
a Celite pad and 0.116 g (0.417 mmol) of bdtp were
added. After stirring for 3 h solution was evaporated to
dryness and the desired product [1][BF4] [or
[1][CF3SO3]] was crystallized in a dichloromethane/di-
ethyl ether mixture.
[1][BF4]: Yield: 0.219 g (92%) – C22H34BF4N4RhS
(576.30): C, 45.85; H, 5.95; N, 9.72; S, 5.56. Found: C,
45.63; H, 5.87; N, 9.63; S 5.65%.
[3][CF3SO3]: Yield: 0.068 g (98%) – C16H22F3N4
O4RhS2 (558.40): C, 34.41; H, 3.97; N, 10.03; S, 11.46.
Found: C, 34.58; H, 3.83; N, 10.07; S, 11.21%.
[3]þ: IR (KBr, cmꢀ1): m(C–H)ar 3129–3018, m(C–H)al
2968–2924, m(CO) 1995, m(C@C), m(C@N) 1551,
d(CH3)as 1462, d(C–H)oop 822-793. 1H NMR (250 MHz,
CDCl3) d ¼ 2:32 (s, 6H, Me), 2.52 (s, 6H, Me), 2.81
(ddd, 2H, CH2–CHH–S, 2J ¼ 14:7 Hz, 3J ¼ 3:3 Hz,
3J ¼ 2:2 Hz), 3.86 (ddd, 2H, CH2–CHH–S, 2J ¼ 14:7
Hz, 3J ¼ 12:1 Hz, 3J ¼ 1:6 Hz), 4.79 (ddd, 2H, pz-
CHH-CH2, 2J ¼ 15:6 Hz, 3J ¼ 2:2, 3J ¼ 12:1), 5.16
(ddd, 2H, pz-CHH-CH2, 2J ¼ 15:6 Hz, 3J ¼ 3:3 Hz,
3J ¼ 1:6 Hz), 5.98 (s, 2H, pz–CH). 13C{1H} NMR (63
MHz, CDCl3) d ¼ 12:3 (Me), 16.1 (Me), 38.7 (CH2–
CH2–S), 51.7 (pz–CH2–CH2), 108.0 (pz–CH), 143.3,
[1][CF3SO3]: Yield: 0.246 g (93%) – C23H34F3N4
O3RhS2 (638.57): C, 43.26; H, 5.37; N, 8.77; S, 10.04.
Found: C, 43.33; H, 5.25; N, 8.67; S, 9.86%.
[1]þ: IR (KBr, cmꢀ1): m(C–H)al 2924, m(C@C),
m(C@N) 1558, m(CH3)as 1466. 1H NMR (400 MHz,
CD2Cl2) d ¼ 2:02 (b, 4H, CHHendo COD), 2.28 (s, 6H,
Me), 2.38 (s, 6H, Me), 2.42-2.66 (b, 8H, CHHexo COD,
pz–CH2–CH2), 4.49, 4.57 (b, 8H, CH COD, pz–CH2–
CH2), 5.98 (s, 2H, pz–CH). 13C{1H} NMR (63 MHz,
CDCl3) d ¼ 11:4 (Me), 14.3 (Me), 32.3 (b, CH2 COD),
35.9 (CH2–CH2–S), 48.6 (pz–CH2–CH2), 85.7 (b, CH
COD), 107.5 (pz–CH), 142.6, 152.2 (pz–C).
1
152.6 (pz–C), 181.8 (d, J ¼ 81:1 Hz, CO).
4.6. Complexes [Rh2(bddf)(COD)2][BF4]2 ([4][BF4]2)
and [Rh2(bddo)(COD)2][BF4]2 ([5][BF4]2)
A solution of 0.069 g (0.354 mmol) of AgBF4 in
THF (5 ml) was added dropwise and under vigorous
stirring to a solution of 0.088 g (0.179 mmol) of
[RhCl(COD)]2 in THF (15 ml). The reaction was
carried out in the dark to prevent reduction of Ag(I)
to Ag(0). Solution turned from an initial orange color
to yellow, and AgCl precipitated. After 30 min the
solution was filtered through a Celite pad and 0.073 g
(0.177 mmol) of bddf [or 0.060 g (0.177 mmol) of bddo]
were added. After stirring for 3 h solution was evap-
orated to dryness and the desired product [4][BF4]2 [or
[5][BF4]2] was crystallized in a dichloromethane/diethyl
ether mixture.
4.4. Synthesis of [Rh(bdtp)(CO)2][BF4] ([2][BF4])
or [Rh(bdtp)(CO)2][CF3SO3] ([2][CF3SO3])
Carbon monoxide was bubbled through a solution of
0.075 g (0.130 mmol) of [1][BF4] or 0.079 g (0.124 mmol)
of [1][CF3SO3] in CH2Cl2 (15 ml) for 1 h. The solution
was then evaporated to dryness in vacuum to eliminate
both the solvent and the COD ligand. The residue was
dissolved in CH2Cl2 (15 ml) and carbon monoxide was
bubbled again. This solution contains a mixture of [2]þ
and [Rh(bdtp)(CO)]þ ([3]þ) but attempts to isolate the
dicarbonyl complexes by crystallization failed even un-
der carbon monoxide atmosphere. The complexes have
been identified by IR and NMR spectroscopy, sub-
tracting the data of [3]þ.
[4][BF4]2: Yield: 0.161 g (90%) – C38H54B2F8N4
Rh2S2 (1010.41): C, 45.17; H, 5.39; N, 5.54; S, 6.35.
Found: C, 44.90; H, 5.25; N, 5.39; S, 6.02%. IR (KBr,
cmꢀ1): m(C–H)al 2947, m(C@C), m(C@N) 1554, m(B–F)
[2]þ: IR (CH2Cl2, cmꢀ1): isomer [2a]þ m(CO) 2103
1
(w), 2043 (w); isomer [2b]þ m(CO) 2078 (s), 2003 (s). H
1
1057. H NMR (200 MHz, CD2Cl2) d ¼ 2:32 (b, 8H,
NMR (250 MHz, CD2Cl2, 293 K) d ¼ 2:29 (s, 6H, Me),
2.35 (s, 6H, Me), 3.18 (b, 4H, CH2–CH2–S), 3.99 (b, 4H,
pz–CH2–CH2), 6.05 (s, 2H, pz–CH). 13C{1H} NMR (63
MHz, CDCl3, 293 K) d ¼ 11:7 (Me), 15.0 (Me), 34.9
(CH2–CH2–S), 47.9 (pz–CH2–CH2), 107.7 (pz–CH),
CH2(COD)), 2.41 (s, 6H, Me), 2.64 (s, 6H, Me), 4.93 (b,
4H, CH(COD)), 6.14 (s, 2H, pz–CH), 7.63 (b, 4H,
C6H4). 13C{1H} NMR (50 MHz, CD2Cl2) d ¼ 12:3
(Me), 16.0 (Me), 29.2, 33.6 (b, CH2(COD)) 36.1, 40.3
(CH2–CH2–S, S–CH2–ph), 50.3 (pz–CH2–CH2–S), 82.8,
88.5, 96.0 (b, CH(COD)), 109.8 (pz–CH), 130.4, 132.6,
133.8 (C6H4), 144.6, 150.7 (pz–C).
1
144.3, 151.2 (pz–C), 185.0 (d, J ¼ 71:4 Hz, CO).
4.5. Rh(bdtp)(CO)][BF4] ([3][BF4]) and [Rh(bdtp)
(CO)][CF3SO3] ([3][CF3SO3])
[5][BF4]2: Yield: 0.152 g (92%) – C32H50B2F8N4
Rh2S2 (934.31): C, 41.14; H, 5.39; N, 6.00; S, 6.86.
Found: C, 40.88; H, 5.51; N, 5.81; S, 6.68%. IR (KBr,
cmꢀ1): m(C–H)al 2920–2836, m(C@C), m(C@N) 1556,
m(B–F) 1054. 1H NMR (200 MHz, CD2Cl2) d ¼ 2:17 (b,
8H, CHHendo COD), 2.35 (s, 6H, Me), 2.44 (s, 6H, Me),
2.50 (b, 12H, CHHexo COD, SCH2–CH2S), 3.06 (b, 4H,
pz–CH2–CH2), 4.60 (b, 4H, CH COD), 5.00 (b, 4H, pz–
CH2–CH2), 5.99 (s, 2H, pz–CH). 13C{1H} NMR (50
MHz, CD2Cl2) d ¼ 12:1 (Me), 15.3 (Me), 29.2, 33.7 (b,
The solution obtained in the preparation of [2]þ is
evaporated to dryness and [3]þ is obtained quantita-
tively and crystallized in a dichloromethane/diethyl
ether mixture.
[3][BF4]: Yield: 0.064 g (99%) – C15H22BF4N4ORhS
(496.13): C, 36.31; H, 4.47; N, 11.29; S, 6.46. Found: C,
36.25; H, 4.42; N, 11.42; S, 6.33%.

ꢀ
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J. Garcıa-Anton et al. / Journal of Organometallic Chemistry 689 (2004) 1599–1608
1607
CH2(COD)) 35.6 (pz–CH2–CH2–S, S–CH2–CH2–S), 50.6
(pz–CH2–CH2–S), 85.3 (b, CH(COD)), 109.4 (pz–CH),
144.8, 151.2 (pz–C).
130.4, 132.0, 132.7 (C6H4), 145.6, 152.4 (pz–C), 178.6
(bd,1J ¼ 71:0 Hz, CO), 182.1 (bd,1J ¼ 71:0 Hz, CO).
4.8. X-ray crystallographic study
4.7. Complex [Rh2(bddf)(CO)4][BF4]2 ([6][BF4]2)
Crystals of [3][CF3SO3], [5][BF4]2, and [6][BF4]2 suit-
able for X-ray diffraction experiments were obtained
through re-crystallization from dichloromethane/diethyl
ether mixtures. Data were collected on an STOE IPDS
diffractometer at 160 K for [3][CF3SO3] and [5][BF4]2, and
at 293 K for [6][BF4]2. Full crystallographic data for the
three complexes are gathered in Table 3. All calculations
wereperformed on a personal computer using the WinGX
Carbon monoxide was bubbled through a solution of
0.075 g (0.074 mmol) of [4][BF4]2 in CH2Cl2 (15 ml) for
1 h. The solution was then evaporated to dryness in
vacuum to eliminate both the solvent and the COD li-
gand. The residue was dissolved in CH2Cl2 (15 ml) and
carbon monoxide was bubbled again. The desired
product [6][BF4]2 was crystallized in a dichloromethane/
diethyl ether mixture.
system [21]. The structures were solved by using the SIR
-
[6][BF4]2: Yield: 0.048 g (71%) – C26H30B2F8N4
O4Rh2S2 (906.09): C, 34.46; H, 3.34; N, 6.18; S, 7.08.
Found: C, 34.42; H, 3.25; N, 6.14; S, 7.25. IR (CH2Cl2
solution, cmꢀ1): m(CO) 2105, 2046. IR (KBr, cmꢀ1):
m(C–H)ar 3140–3010, m(CO) 2106, 2041, m(C@C),
m(C@N) 1551, m(B–F) 1056. 1H NMR (200 MHz,
CD2Cl2 solution) d ¼ 2:41 (s, 6H, Me), 2.52 (s, 6H, Me),
3.18 (m, 4H, CH2–CH2–S), 4.07 (s, 4H, S–CH2–ph), 4.65
(m, 4H, pz–CH2–CH2), 6.20 (s, 2H, pz–CH), 7.41–7.51
(m, 4H, C6H4). 13C{1H} NMR (50 MHz, CD2Cl2 so-
lution) d ¼ 11:6 (Me), 15.3 (Me), 33.4, 40.4 (CH2–CH2–
S, S–CH2–ph), 49.2 (pz–CH2–CH2–S), 108.8 (pz–CH),
92 program [22], which revealed in each instance the po-
sition of most of the non-hydrogen atoms. All remaining
non-hydrogen atoms were located by the usual combi-
nation of full-matrix least-squares refinement and differ-
ence electron density syntheses by using the SHELXL-97
program [23]. Atomic scattering factors were taken from
the usual tabulations. Anomalous dispersion terms for
Rh atoms were included in Fc. All non-hydrogen atoms
were allowed to vibrate anisotropically. All the hydrogen
atoms were set in idealized position (R3CH, C–H ¼ 0.96
2
ꢂ
ꢂ
ꢂ
A; R2CH2, C–H ¼ 0.97 A; RCH3, C–H ¼ 0.98 A; C(sp )–
ꢂ
H ¼ 0.93 A; Uiso 1.2 or 1.5 time greater than the Ueq of the
Table 3
Crystallographic data for crystal structures [3][CF3SO3], [5][BF4]2 and [6][BF4]2
Compound
[3][CF3SO3]
[5][BF4]2
[6][BF4]2
Empirical formula
Molecular mass (g)
T (K)
Crystal system
Space group
C16H22F3N4O4RhS2
558.41
160(2)
C32H50B2F8N4Rh2S2
934.31
160(2)
C26H30B2F8N4O4Rh2S2
906.09
293(2)
Monoclinic
Cc
Triclinic
ꢃ
Monoclinic
P21=c (No. 14)
P1
Unit cell dimensions
ꢂ
a (A)
8.8473(5)
9.0397(5)
14.5691(8)
103.828(5)
101.877(5)
95.474(5)
1094.3(1)
2
9.259(5)
14.021(5)
14.590(5)
25.531(5)
7.873(5)
17.415(5)
ꢂ
b (A)
ꢂ
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
100.993(5)
96.425(5)
3
ꢂ
V (A )
1859.3(14)
4
1.669
3479(3)
4
1.730
Z
Dcalc (g cmꢀ3
)
1.695
1.026
l (mmꢀ1
F ð000Þ
)
1.070
948
1.149
1800
564
0.5 · 0.4 · 0.3
3.09–30.22
Crystal size (mm)
h range (ꢁ)
0.1 · 0.1 · 0.2
2.03–26.18
0.4 · 0.2 · 0.04
2.70–26.09
Reflexions collected
Total, independent
Data/restraints/parameters
Goodness-of-fita
Final R1, wR2
9636, 5760
5760/0/275
1.030
14 273, 3661
3661/0/228
0.997
12 936, 6581
6581/2/437
1.003
0.0260, 0.0621
0.0312, 0.0644
0.520 and )1.023
0.0383, 0.0732
0.0658, 0.0818
0.532 and )0.427
0.0793, 0.2173
0.0949, 0.2390
1.252 and )1.048
0.06(7)
R1 (all data), wR2
ꢀ3
ꢂ
Residual electron density (e A
Absolute structure parameters
)
P
2
2
2
2
2
a The function minimized was
wðjFojÞ ꢀ jFcj Þ , where w ¼ ½r2ðIÞ þ ðaPÞ2Šꢀ1, and P ¼ ðjFoj þ 2jFcj Þ=3.

ꢀ
ꢀ
J. Garcıa-Anton et al. / Journal of Organometallic Chemistry 689 (2004) 1599–1608
1608
ꢀ
[6] (a) R. Tribo, J. Pons, R. Yanez, J.F. Piniella, A. Alvarez-Larena,
ꢀ
J. Ros, Inorg. Chem. Commun. 3 (2000) 545–549;
ꢀ~
carbon atom to which the hydrogen atom is attached).
The final R (on F ) factor and xR (on F 2) values, as well as
the numbers of parameters refined and other details
concerning the refinement of the crystal structure are
presented in Table 3.
ꢀ~
(b) G. Esquius, J. Pons, R. Yanez, J. Ros, R. Mathieu, B.
Donnadieu, N. Lugan, J. Organomet. Chem. 667 (2003) 126–134.
[7] (a) A. Boixassa, J. Pons, A. Virgili, X. Solans, M. Font-Bardia, J.
Ros, Inorg. Chim. Acta 340 (2002) 49–55;
(b) A. Boixassa, J. Pons, X. Solans, M. Font-Bardia, J. Ros,
Inorg. Chim. Acta 346 (2003) 151–157;
(c) A. Boixassa, J. Pons, J. Ros, R. Mathieu, N. Lugan, J.
Organomet. Chem. 682 (2003) 233–239;
5. Supplementary material
(d) A. Boixassa, J. Pons, X. Solans, M. Font-Bardia, J. Ros,
Inorg. Chim. Acta 355 (2003) 254–263;
CCDC-223820 for [3][CF3SO3], CCDC-223821 for
[5][BF4]2 and CCDC-223822 for [6][BF4]2 contain the
supplementary crystallographic data for this paper.
These data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html [or from the
Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK; fax: (internat.) +44-
1223-336-033; e-mail: deposit@ccdc.cam.ac.uk].
(e) A. Boixassa, J. Pons, X. Solans, M. Font-Bardia, J. Ros,
Inorg. Chim. Acta 357 (2004) 733–738.
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[8] (a) J. Garcıa-Anton, J. Pons, X. Solans, M. Font-Bardia, J. Ros,
Eur. J. Inorg. Chem. (2002) 3319–3327;
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