Syntheses and properties of Re(III) complexes derived from hydrotris(1-pyrazolyl)methanes: Molecular structure of [ReCl 2(HCpz3)(PPh3)][BF4]

Article abstract of DOI:10.1016/j.jorganchem.2004.11.005

The complexes [ReCl₂{N₂C(O)Ph}(Hpz)(PPh ₃)₂] (1) (Hpz = pyrazole), [ReCl₂{N ₂C(O)Ph}(Hpz)₂(PPh₃)] (2), [ReCl ₂(HCpz₃)(PPh₃)][BF₄] (3) and [ReCl₂(3,5-Me₂Hpz)₃(PPh₃)]Cl (4) were obtained by treatment of the chelate [ReCl₂{η²-N, O-N₂C(O)Ph}(PPh₃)₂] (0) with hydrotris(1-pyrazolyl)methane HCpz₃ (1,3), pyrazole Hpz (1,2), hydrotris(3,5-dimethyl-1-pyrazolyl)methane HC(3,5-Me₂pz)₃ (4) or dimethylpyrazole 3,5-Me₂Hpz (4). Rupture of a C(sp ³)-N bond in HCpz₃ or HC(3,5-Me₂pz) ₃, promoted by the Re centre, has occurred in the formation of 1 or 4, respectively. All compounds have been characterized by elemental analyses, IR and NMR spectroscopy, FAB-MS spectrometry, cyclic voltammetry and, for 1 ? CH₂Cl₂ and 3, also by single crystal X-ray analysis. The electrochemical E_L Lever parameter has been estimated, for the first time, for the HCpz₃ and the benzoyldiazenide NNC(O)Ph ligands.

Full text of DOI:10.1016/j.jorganchem.2004.11.005

Journal of Organometallic Chemistry 690 (2005) 1947–1958
www.elsevier.com/locate/jorganchem
Syntheses and properties of Re(III) complexes derived from
hydrotris(1-pyrazolyl)methanes: molecular structure
of [ReCl2(HCpz3)(PPh3)][BF4]
a,c
Elisabete C.B. Alegria a,b, Lu´ısa M.D.R.S. Martins , M. Fatima C. Guedes da Silva
a,b
,
´
a,
*
Armando J.L. Pombeiro
a
´ ´
Centro de Quımica Estrutural, Complexo I, Instituto Superior Tecnico, Avenida Rovisco Pais, P1049-001 Lisboa, Portugal
b
´ ´
Departamento de Engenharia Quımica, ISEL, R. Conselheiro Emıdio Navarro, 1950-062 Lisboa, Portugal
c
´
Universidade Lusofona de Humanidades e Tecnologias, Campo Grande 376, 1749-024 Lisboa, Portugal
Received 3 November 2004; accepted 4 November 2004
Available online 15 December 2004
Conference on nitrogen ligands organised by Prof. Pettinari
Abstract
The complexes [ReCl2{N2C(O)Ph}(Hpz)(PPh3)2] (1) (Hpz = pyrazole), [ReCl2{N2C(O)Ph}(Hpz)2(PPh3)] (2), [ReCl2(HCpz3)-
(PPh3)][BF4] (3) and [ReCl2(3,5-Me2Hpz)3(PPh3)]Cl (4) were obtained by treatment of the chelate [ReCl2{g2-N,O–
N2C(O)Ph}(PPh3)2] (0) with hydrotris(1-pyrazolyl)methane HCpz3 (1,3), pyrazole Hpz (1,2), hydrotris(3,5-dimethyl-1-pyraz-
olyl)methane HC(3,5-Me2pz)3 (4) or dimethylpyrazole 3,5-Me2Hpz (4). Rupture of a C(sp3)–N bond in HCpz3 or HC(3,5-Me2pz)3,
promoted by the Re centre, has occurred in the formation of 1 or 4, respectively. All compounds have been characterized by ele-
mental analyses, IR and NMR spectroscopy, FAB-MS spectrometry, cyclic voltammetry and, for 1 Æ CH2Cl2 and 3, also by single
crystal X-ray analysis. The electrochemical EL Lever parameter has been estimated, for the first time, for the HCpz3 and the ben-
zoyldiazenide NNC(O)Ph ligands.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Rhenium; Hydrotris(1-pyrazolyl)methane; Pyrazole; Hydrazide; Diazenide; Electrochemistry
1. Introduction
tuted ones, in particular at Re centres, and in
contrast with the tris(1-pyrazolyl)borate chemistry
[10], has so far been reported only rarely [3,8,9]. The
underdevelopment of this chemistry results from the
relatively small number of such ligands currently avail-
able, the difficulties associated with their synthesis and
the usually low yields. The rhenium(V) tris(pyraz-
olyl)methane complex [ReOCl2(HCpz3)]+, analogous
to the tris(pyrazolyl)borate compound [ReOCl2-
(HBpz3)], was prepared and shown [8] to add PPh3
to give the phosphine oxide complex [ReCl2(HCpz3)-
(OPPh3)]+, whereas rhenium(I) tricarbonyl complexes
of tris(pyrazolyl)methane ligands have also been
reported [9].
The current growth of interest in the coordination
chemistry of N3 tripodal neutral tris(1-pyrazolyl)alk-
anes, isoelectronic with the tris(1-pyrazolyl)borates an-
ionic ligands, is related to their applications in
catalysis and synthetic inorganic, bioinorganic and
organometallic chemistries [1–4]. However, in spite of
their importance, the coordination chemistry of hydro-
tris(1-pyrazolyl)methanes [3,5–9], HCpz3 and substi-
*
Corresponding author. Tel.: +351 2184 19237; fax: +351 2184
64455.
E-mail address: pombeiro@ist.utl.pt (A.J.L. Pombeiro).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.11.005

1948
E.C.B. Alegria et al. / Journal of Organometallic Chemistry 690 (2005) 1947–1958
Within the search for a suitable starting material for
tal ion have been reported, namely the C–N bond cleav-
age in bis(pyrazolyl)propane (CH3)2Cpz2 by Pt(II)
complexes [18] such as PtCl2, [PtCl2(RCN)2] (R = Me
or Ph) or K2[PtCl4], observed also in the reaction of
Ru(II) species with 1-hydroxymethyl-3,5-dimethylpyraz-
ole resulting in 3,5-dimethylpyrazole complexes [19],
and the B–N bond rupture in K[HB(3,5-Me2pz)3] by
Ru(II) complexes [20] such as [Ru(g6-C6H6)Cl2]2. Such
a behaviour, to our knowledge, has not been previously
shown for rhenium. In all the reported cases, the way the
cleavage reaction occurs has not been established.
Complexes 1 and 4 are also obtained upon reaction of
[ReCl2{g2-N,O–N2C(O)Ph}(PPh3)2] (0) with pyrazole
or 3,5-dimethylpyrazole [Scheme 1, reactions (c) and
(g), respectively]. The former product 1 has previously
been obtained by others [21] by refluxing for 2 days a
methanol mixture or stirring at room temperature an
acetone suspension of the starting benzoylhydrazido
chelate and an excess (ca. 7:1) of pyrazole. In our case,
1 has been prepared [reaction(c)] by using a benzene
solution, at room temperature for 20 h, with stoichiom-
etric amounts of reagents, whereas 4 was prepared by
refluxing a methanol solution for 28 h.
the synthesis of Re complexes with such a class of li-
gands, we have chosen the benzoylhydrazido-Re(V) che-
late [ReCl2{g2-N,O–N2C(O)Ph}(PPh3)2] (0) which is a
very useful precursor for a variety of organodiazenide
and dinitrogen complexes in lower metal oxidation
states, containing usually phosphines [11], phosphites
or phosphonites [12,13] and, to a smaller extent,
amine-based [14] ligands. From the study of the reaction
of [ReCl2{g2-N,O–N2C(O)Ph}(PPh3)2] (0) with hydro-
tris(1-pyrazolyl)methanes, i.e. HCpz3 and HC(3,5-
Me2pz)3, we should be able to investigate not only the
coordination chemistry of these species at rhenium cen-
tres with an organodiazenide or a derived ligand, but
also to prepare novel types of complexes with such
classes of ligands and/or derived ones. We have thus
prepared new Re(III) complexes with hydrotris(1-
pyrazolyl)methane or benzoylhydrazide ligands and,
since in some cases we have observed the conversion
of the tris(pyrazolyl)methane into the corresponding
pyrazole, i.e. Hpz or 3,5-Me2Hpz, we have also per-
formed some reactions with the latter species for com-
parative purposes.
Moreover, by investigating the redox behaviour of
the obtained products, we have got an insight into the
net electron donor/acceptor ability of such ligands, in
particular the hydrotris(1-pyrazolyl)methane and the
benzoyldiazenide, and succeeded in the estimate, for
the first time, of the values of the electrochemical EL Le-
ver ligand parameter [15–17], a measure of that
character.
If the reaction of the benzoylhydrazido chelate is per-
formed in the presence of a high excess of pyrazole (35:1
molar ratio), the bispyrazole complex [Re-
Cl2{N2C(O)Ph}(Hpz)2(PPh3)] (2) is the obtained prod-
uct [Scheme 1, reaction (d)] which is also formed by
further reaction of the monopyrazole complex 1 with
an excess of pyrazole [Scheme 1, reaction (b)].
Complex 2, similarly to 1, is obtained either in a
refluxing methanol suspension of the starting ben-
zoylhydrazido chelate or in a benzene solution of this
complex (it is soluble in this solvente) at room
temperature.
2. Results and discussion
2.1. Synthesis and characterization
When the reaction of the starting chelate 0 with
HCpz3 (1:1) is carried out in the presence of Tl[BF4]
or Na[BF4], in C6H6/MeOH under reflux, one obtains
the hydrotris(1-pyrazolyl)methane dichloro complex
[ReCl2(HCpz3)(PPh3)][BF4] (3) [Scheme 1, reaction
(e)]. The formation of this product, with preservation
of the two chloride ligands, is surprising in view of the
well known ability of Tl+ to abstract such ligands. In
contrast, the formation of compound 3 involves the for-
mal replacement of the chelating benzoylhydrazide and
one of the phosphine ligands by the tri-hapto HCpz3.
All the above reactions involve a formal two-electron
reduction of Re(V) to Re(III). This is believed to result
from an intra-molecular redox process on account of the
involvement of the expected conversion of the dihapto
benzoylhydrazido(3ꢀ) ligand, g2-NNC(O)Ph(3ꢀ), into
the monohapto benzoyldiazenido(1ꢀ), g1-NNC(O)Ph-
(1ꢀ).
The attempt to synthesise a rhenium complex with
an hydrotris(1-pyrazolyl)methane ligand i.e. hydrotris-
(1-pyrazolyl)methane HCpz3 or the corresponding
disubstituted HC(3,5-Me2pz)3, from the reaction with
the benzoylhydrazido rhenium(V) chelate [ReCl2{g2-
N,O–N2C(O)Ph}(PPh3)2] (0) (in stoichiometric amount)
in refluxing methanol, led to the formation of the corre-
sponding pyrazole derivatives [ReCl2{N2C(O)Ph}(Hpz)-
(PPh3)2] (1) or [ReCl2(3,5-Me2Hpz)3(PPh3)]Cl (4)
[Scheme 1, reactions (a) and (f)]. In the formation of
1, the benzoylhydrazido behaves as a hemilabile ligand
with opening of the chelating ring leading to a monod-
entate benzoyldiazenide, g1-NNC(O)Ph, the vacant
coordination position being occupied by a pyrazole.
This ligand, as well as its 3,5-dimethyl derivative in the
case of the formation of 4, are derived from the rupture
of a C(sp3)–N bond in the corresponding hydrotris-
(1-pyrazolyl)methane compound. Other cases of rupture
of a carbon–nitrogen or boron–nitrogen bond by a me-
However, in spite of the latter ligand being a good
precursor for a ligated dinitrogen at related rhenium
centres [11–14], in our reactions we have failed to isolate

E.C.B. Alegria et al. / Journal of Organometallic Chemistry 690 (2005) 1947–1958
1949
H
N
PPh
Ph
3
N
(a) HCpz (1:1)
C
O
3
(b) Hpz (20:1)
N
III
Re
N
C H /MeOH (∆)
6
6
MeOH (∆) or C H
6
6
Cl
Cl
PPh
3
1
H
N
PPh
3
Ph
N
(c)Hpz (1:1)
III
Re
C
O
N
N
C H
6
6
Cl
Cl
N
NH
2
(d) Hpz (35:1)
C H /MeOH (∆)
6
6
PPh
3
3
Cl
Cl
N
N
V
Re
Ph
C
BF
4
O
PPh
N
N
Cl
PPh
III
Re
N
N
HC
0
3
(e)HCpz (1:1), Tl[BF ] or Na[BF ]
3
4
4
Cl
N
N
C H /MeOH ( ∆)
6
6
3
Cl
Me
Me
Me
HN
N
HN
(f) HC(3,5-Me pz) (2:1) or (g) 3,5-Me Hpz (5:1)
III
Re
2
3
2
Cl
N
Me
Cl
HN
N
MeOH (∆)
Me
PPh
Me
3
4
Scheme 1.
any N2 complex. The N2 ligand could be formed from a
ligated NNC(O)Ph upon nuceophilic attack of methanol
on the carbonyl carbon, leading also to the elimination
of methylbenzoate PhCOOMe upon N–C bond cleavage
[11]. This cleavage can also be homolytic upon heating
[11].
since a mixture of the products 1 and 2 was obtained
from the reaction of the benzoylhydrazido complex with
Hpz, in refluxing C6H6/MeOH, in the presence of the tri-
flate salt. This contrasts with the reported [14] formation
of various amine dinitrogen complexes of rhenium de-
rived from the reaction of the same benzoylhydrazido
complex with an amine in the presence of NaOTF, un-
der experimental conditions similar to ours.
Neither NaOTf nor TlOTF promote the conversion
of the benzoylhydrazido ligand into N2, in our cases,

1950
E.C.B. Alegria et al. / Journal of Organometallic Chemistry 690 (2005) 1947–1958
All the complex products have been characterized by
[M ꢀ N2COPh]+ are observed. In all the complexes, the
elimination of PPh3 from any of the starting complexes
is less favoured relatively to the loss of the other ligands
since the fragment [M ꢀ PPh3]+ is not visible.
elemental analyses, IR and NMR spectroscopy, FAB-
MS spectrometry, electrochemical methods and, in the
case of 1 Æ CH2Cl2 and 3, also by X-ray diffraction
analysis.
In the IR spectra, the pyrazole complexes 1, 2 and 4
exhibit a medium band at 3076, 3286 and 3118 cmꢀ1
2.2. Electrochemical studies
,
respectively, assigned to the m(NH) stretching mode of
the pyrazole ring(s). Moreover, complexes 1 and 2 exhi-
bit strong bands at 1593 and 1588 cmꢀ1, respectively, as-
signed to m(C@O) of the benzoyldiazenido ligand and to
m(C@C) of the ligating pyrazole, and in the 1565–1549
cmꢀ1 range, attributed to m(N@N) of the organodiazen-
ido moiety and to m(N@C) of the pyrazole ring. In other
rhenium complexes, such IR bands for g1-N–
NNC(O)Ph complexes appear at comparable values,
e.g. [ReCl2{N2C(O)Ph}(PPh3)(L1)(L2)] [11] [L1 = PPh3,
L2 = MeCN, py or L1 = Ph2PCH2CH2PPh2, Ph2AsCH2-
CH2AsPh2; m(C@O) 1640–1700; m(N@N) 1530–1580
Complexes 1–4 exhibit by cyclic voltammetry, at a
platinum electrode at 25 ꢁC in a 0.2 M [nBu4N][BF4]/
CH2Cl2 solution, a first single-electron partially revers-
ible 1–3 or irreversible 4 oxidation wave (wave Iox) at
IEo1=x2 ¼ 0:73 (1), 0.68 (2) and 0.54 (3) V versus SCE
ox
I
(Fig. 1 for 2) or Ep ¼ 0:86 4 V versus SCE, assigned
to the ReIII ! ReIV oxidation, which is followed, at a
higher potential, by a second one (IIox), irreversible for
1, 2 and 4 (IIEopx ¼ 1:65, 1.64 and 1.42 V, respectively),
but reversible for 3 (IIE1o=x2 ¼ 1:42 V), assigned to the
ReIV ! ReV oxidation. In the first oxidation process
(wave Iox) a new, yet unidentified, species is formed to
a certain extent as shown by the reduction wave at Ep
ca. 0.3 V detected upon scan reversal following the ano-
dic scan beyond wave Iox.
cmꢀ1
] and [ReCl2{N2C(O)Ph}{=C(CH2)n-CH(R)O}-
(PPh3)2] [11] [n = 1, R = H, Me; n = 2, R = H, Me;
m(C@O) 1648–1663; (N@N) 1537–1551 cmꢀ1]. Complex
3 exhibits a broad band at ca. 1532 cmꢀ1 attributed to
(N@C) of the pyrazole rings.
The complexes also exhibit one reduction wave (wave
Ired) (irreversible for 1 and 2 at Ep ¼ ꢀ1:56 or ꢀ1.51
red
I
red
I
The trans geometry of complex 1 is assigned on the
basis of the singlet observed in the 31P–{1H} NMR spec-
trum and confirmed by the X-ray analysis.
V, respectively; reversible for 3 and 4, at E1=2 ¼ ꢀ0:74
or ꢀ0.36 V, respectively) whereas complex 3 displays
also a second irreversible one (IIred) at a lower potential,
IIErped ¼ ꢀ1:53 V.
1
In the H NMR spectrum, the methine hydrogen of
compound 3 appears at d 9.66, i.e. slightly deshielded
from that observed for the uncomplexed ligand by
1.26, in accord with the reported observations for the
complexes [ReOCl2(HCpz3)][BF4] [8] and [Re(HCpz3)-
(CO)3][BF4] [9], suggesting a weak hydrogen-bonding
interaction with the [BF4]ꢀ counterion in solution. In
the 13C–{1H} NMR spectra, the three carbon atoms
from the pyrazole ring in all complexes appear as sing-
lets. Their resonances are very similar to those observed
[18] for Pt complexes such as cis or trans-[PtX2(Hpz)2] X
(X = I or Cl) or [Pt{NH@C(Ph)pz}]Cl2. All the other
resonances of the benzoylhydrazido and triphenylphos-
phine ligands have also been assigned (see Section 3)
The starting chelate 0 was also investigated and
shown to exhibit, by cyclic voltammetry, three irrevers-
ible oxidation waves at 0.93, 1.42 and 1.80 V. The values
of the first oxidation potential of the complexes 1–4 are
less anodic than that of complex 0, in accord with the
lower metal oxidation state of the former (III) in com-
parison with the latter (V).
The slightly lower first oxidation potential of 2 in
comparison with 1 is indicative of a slightly stronger
IIox
2
Iox
1
in the H, 13C–{1H} and 13C NMR spectra, including
1
those of the ipso-, orto-, meta- and para-atoms of the
phenyl rings.
The FAB+-MS spectra of the complexes exhibit the
molecular ion [M+ and the fragmentation pathways occur
by cleavage of the metal–ligand bonds and rupture of
bonds within the PPh3 and HCpz3 (complex 3) ligands.
Hence for 3 the fragments [M ꢀ Cl]+, M ꢀ Cl ꢀ pz]+,
and those derived upon further loss of pyrazolyl and phe-
nyl groups are detected. Coupling of pyrazolyl with metal
fragments has also been observed, e.g. [M ꢀ Cl + pz]+
and derivatives. In the chemical reactions (see above),
the pyrazole derived from HCpz3 can also bind the metal
centre. In the case of 1 and 2, the fragments [M ꢀ Hpz]+,
[M ꢀ Cl]+, [M ꢀ Hpz–Cl]+ and, to a less extent,
0
-1
Ired
-2
-2
-1
0
1
2
E / V vs.S.C.E.
Fig. 1. Cyclic voltammogram of [ReCl2{N2C(O)Ph}(Hpz)2(PPh3)] (2),
initiated by the anodic sweep, at a Pt electrode, in 0.2 M [nBu4N][BF4]/
CH2Cl2 solution (v = 200 mV/s). Complex concentration: 1.6 mM.

E.C.B. Alegria et al. / Journal of Organometallic Chemistry 690 (2005) 1947–1958
1951
electron-donor character of the pyrazole relatively to the
PPh3 ligand in accordance with the values [15–17] of the
electrochemical Lever EL parameter (the stronger that
character, the lower EL) for these ligands (0.20 and
0.39 V versus NHE, respectively). The considerable
lower first oxidation potential of complex 3 compared
to 1 and 2 suggests that the tri-hapto HCpz3 ligand be-
haves as a stronger electron-donor than NNC(O)Phꢀ +
Hpz + PPh3 (in 1) and than NNC(O)Phꢀ + 2Hpz (in 2).
The higher first oxidation potential of 4, relatively to 3,
is indicative of a stronger overall electron-donor ability
of HCpz3, in the latter, in comparison with the three 3,5-
Me2pz ligands in the former complex (see Table 1).
olyl)methane ligand, EL = 0.14 V versus NHE, obtained
from complex 3.
The latter EL value was confirmed by applying Eq. (1)
to the first reduction process (ReIII/ReII) of complex 3,
i.e. by considering the corresponding SM and IM values
[16] of 1.17 and ꢀ0.88 V versus NHE.
Since the EL parameter is a measure of the electron
donor character of a ligand (the lower the parameter,
the stronger is that character), one can conclude that
the NNC(O)Phꢀ ligand (EL = 0.11 V) is a slightly stron-
ger electron donor than each pyrazole ligand in HCpz3
(EL = 0.14 V) and the latter is comparable to benzyl-
amine (EL = 0.14 V) [16,17], di-R-alkyl-diazabutadienes
(EL = 0.14 V) [16,17], biimidazol (EL = 0.13 V) [16,17]
and imidazole (EL = 0.12 V) [16,17]. Interestingly, the
pyrazole ring (EL = 0.14 V) in HCpz3 presents a stronger
electron-donor ability than the Hpz ligand (EL = 0.20 V)
[16,17], suggesting an electron-donor character for the
methine HC group. Nevertheless, both are weaker elec-
tron-donors than e.g. ammonia (EL = 0.07 V) [16,17],
water (EL = 0.04 V) [16,17] or N-methylimidazole
(EL = 0.08) [16,17]. That is consistent with the reported
[3,22,23] moderately strong r-donor and weak p-donor
capacity of HCpz3.
2.2.1. Estimate of electrochemical ligand parameters
The measured first oxidation potential (IE1o=x2 for the
ReIII ! ReIV oxidation) of the complexes allows us to
estimate, for the first time, the electrochemical EL Lever
parameter for the benzoyldiazenide and the hydrotris(1-
pyrazolyl)methane HCpz3 ligands, by applying the lin-
ear relationship (1), valid for octahedral complexes, that
relates their redox potential (V versus NHE) with
P
the sum of the EL values for all the ligands ( EL). The
slope (SM) and intercept (IM) are dependent upon the
metal, redox couple, spin state and stereochemistry
[15,16].
2.3. Solid state structures
X
ox
1=2
E
¼ SMð
ELÞ þ IM V versus NHE:
ð1Þ
The molecular structures of the pyrazole complex 1
with dichloromethane of crystallization, 1 Æ CH2Cl2,
and of the hydrotris(1-pyrazolyl)methane complex 3
were determined by single-crystal X-ray diffraction anal-
ysis. They are depicted in Figs. 2 and 3. Crystallographic
details are given in Table 2 and selected bond distances
and angles in Table 3.
Although the molecular structure of [Re-
Cl2{N2C(O)C6H5}(Hpz)(PPh3)2] (1) is already known
[21] we present here the crystal structure of [Re-
Cl2{N2C(O)C6H5}(Hpz)(PPh3)2] Æ CH2Cl2, i.e. 1 crystal-
lized with a CH2Cl2 solvent molecule. Cell parameters
reflect the different crystal packing.
Hence, by using the reported [16] SM and IM values for
the ReIII/IV redox couple (0.86 and 0.51 V versus NHE,
respectively), the known [16,17] ligand EL values for the
PPh3, Hpz and Clꢀ ligands (0.39, 0.20 and ꢀ0.24 V ver-
ox
I
sus NHE, respectively), and E1=2 values of our com-
plexes (referred to the NHE, see Section 3), we have
estimated the following EL values. For the benzoyldiaze-
nide ligand, EL = 0.11 V versus NHE, as the average of
the values obtained from complexes 1 and 2; for each
coordinated pyrazole group in the hydrotris(1-pyraz-
In both molecules of 1 Æ CH2Cl2 and 3, the coordina-
tion around the rhenium atom assumes an octahedral
geometry. The least-square plane of the two chlorine
and the two nitrogen atoms in 1 are within a standard
Table 1
Cyclic voltammetric dataa for [ReCl2{g2-N,O–N2C(O)Ph}(PPh3)2] (0),
[ReCl2{N2C(O)Ph}(Hpz)(PPh3)2] (1), [ReCl2{N2C(O)Ph}(Hpz)2-
(PPh3)] (2), [ReCl2(HCpz3)(PPh3)2] (3) and [ReCl2(3,5-Me2Hpz)3-
(PPh3)]Cl (4)
˚
deviation of 0.0171 A with the Re atom lying in it. In
3 the standard deviation of an equivalent plane is of
red
IEp ð E1=2ÞðIox
Þ
IIEopx ðE ÞðIIox
Þ
IErped ðE ÞðI
Þ
ox
ox
ox
1=2
red
1=2
I
Complex
˚
˚
0.0095 A with the rhenium atom lying 0.1866(45) A
above it. The slight distortion in 3 with short N–Re–N
bond angles [ranging from 81.1(4)ꢁ to 85.4(4)ꢁ] is com-
mon [8,9], and is probably a consequence of the triden-
tate feature of the HCpz3.
0b
1c
2
3d
4
0.93
1.42
1.65
1.64
(1.42)
1.42
ꢀ1.41
(0.73)
(0.68)
(0.54)
0.86
ꢀ1.46
ꢀ1.51
(ꢀ0.74)
(ꢀ0.36)
a
Values in V 0.02 relative to SCE (see Section 3); scan rate of 200
mV sꢀ1. Values for reversible waves are given in brackets.
The Re–N(pz) bond distances in both structures
˚
range from 2.094(11) to 2.163(11) A and are within
the usual one found [24,25] in pyrazole or pyrazolyl
coordination compounds independently from the fact
that the pz ring is monodentate (as in 1) or is part
b
A third irreversible oxidation wave is observed at IIIEpox ¼ 1:80 V.
c
A third irreversible oxidation wave is observed at IIIEpox ¼ 1:99 V.
d
A
second irreversible reduction wave is observed at
IIErped ¼ ꢀ1:53 V.

1952
E.C.B. Alegria et al. / Journal of Organometallic Chemistry 690 (2005) 1947–1958
Fig. 2. Molecular structure of the neutral complex of [ReCl2{N2C(O)Ph}(Hpz)(PPh3)2] Æ CH2Cl2 1 Æ CH2Cl2, indicating the atom numbering scheme.
Fig. 3. Molecular structure of the cationic complex of [ReCl2(HCpz3)(PPh3)][BF4] (3), indicating the atom numbering scheme.

E.C.B. Alegria et al. / Journal of Organometallic Chemistry 690 (2005) 1947–1958
1953
Table 2
Crystal data and structure for [ReCl2{NNC(O)C6H5}(Hpz)(PPh3)2] Æ CH2Cl2 (1 Æ CH2Cl2) and ReCl2(HCpz3)(PPh3)][BF4] (3)
1 Æ CH2Cl2
47H41Cl4N4OP2Re
1067.78
3
Empirical formula
Formula weight
Crystal system
Space group
C
C28H25BCl2F4N6PRe
820.42
Monoclinic
P21/c
Monoclinic
P21/c
˚
a (A)
12.708(5)
18.081(5)
16.376(3)
10.0460(8)
19.337(3)
90.000(5)
104.469(12)
90.000(5)
3080.3(7)
293(2)
˚
b (A)
˚
c (A)
19.877(5)
90.000(5)
˚
a (A)
˚
b (A)
100.747(5)
90.000(5)
˚
c (A)
3
˚
V (A )
4487(2)
293(2)
T (K)
Z
4
1.581
4
1.769
Density (calculated) (g cmꢀ3
)
Absorption coefficient (mmꢀ1
F(000)
)
3.058
2128
1.53–27.02
4.225
1600
2.18–25.99
h range for data collection (ꢁ)
Index ranges
ꢀ16 6 h 6 15, ꢀ23 6 k 6 0, 0 6 l 6 25
10062/9779 [Rint = 0.0387]
99.6%
Full-matrix least-squares on F2
9779/0/677
0.944
ꢀ19 6 h 6 19, 0 6 k 6 11, ꢀ23 6 l 6 0
6166/5978 [Rint = 0.1080]
98.8%
Full-matrix least-squares on F2
5978/0/359
0.948
Reflections collected/unique
Completeness to h = 27.02
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
R1 = 0.0505, wR2 = 0.0748
R1 = 0.1111, wR2 = 0.0852
R1 = 0.0766, wR2 = 0.1527
R1 = 0.1629, wR2 = 0.1780
Table 3
of a chelating hydrotris(1-pyrazolyl)methane moiety
(as in 3). Moreover, the bond lengths within the pyr-
azole groups of the HCpz3 ligand in complex 3 are
identical to those observed for the pyrazole ligand in
complex 1. Such a type of similarity has been recog-
nized in other cases like [M(HCpz3)2]2+ (M@Ni, Co
or Zn] [23]. It has also previously been observed that
complexes of tris(1-pyrazolyl)methane or tris(1-pyraz-
olyl)borane have quite similar structural parameters
[8,9].
˚
Selected bond distances (A) and angles (ꢁ) for the complexes
[ReCl2(PPh3)2{NNC(O)C6H5}(Hpz] Æ CH2Cl2
ReCl2(HCpz3)(PPh3)][BF4] (3)
(1 Æ CH2Cl2)
and
1
3
Bond lengths
Re–N1
Re–N11
Re–Cl1
Re–Cl2
Re–P1
1.762(5)
2.149(6)
Re–N11
Re–N21
Re–N31
Re–P1
2.094(11)
2.121(12)
2.163(11)
2.467(5)
2.347(4)
2.357(4)
2.4410(19)
2.4006(18)
2.4773(19)
2.4660(19)
1.252(7)
Re–Cl1
Re–Cl2
Re–P2
For the benzoyldiazenide ligand in 1, the Re–N bond
˚
distance [1.762(5) A] is much shorter than that of Re–
N1–N2
N2–C1
C1–O1
C1–C2
1.307(8)
1.254(9)
1.499(9)
N(pz), being indicative of a double bond character,
and the coordination is essentially linear [Re–N(1)–
N(2) angle of 171.2(4)ꢁ]. The ligand is bent at N(2) with
the N(1)–N(2)–C(1) angle of 119.8(6)ꢁ. Hence, the ben-
zoyldiazenide ligand acts as a 3-electron donor (if con-
sidered in the neutral form a) or as a 4-electron donor
(negatively charged form) [26], thus giving an 18-elec-
tron configuration to the complex. A similar coordina-
tion mode is known for a variety of organodiazenide
rhenium complexes [11c,27–30].
Bond angles
Cl(1)–Re–Cl(2)
Cl(1)–Re–P(1)
Cl(1)–Re–P(2)
Cl(1)–Re–N(1)
Cl(1)–Re–N(11)
Cl(2)–Re–P(1)
Cl(2)–Re–P(2)
Cl(2)–Re–N(1)
Cl(2)–Re–N(11)
P(1)–Re–P(2)
P(1)–Re–N(1)
P(1)–Re–N(11)
P(2)–Re–N(1)
P(2)–Re–N(11)
N(1)–Re–N(11)
Re–N(1)–N(2)
N(1)–N(2)–C(1)
88.31(6)
90.29(5)
89.45(5)
94.49(14)
172.18(15)
86.36(6)
90.91(6)
177.06(16)
83.93(15)
177.27(5)
92.71(18)
90.19(15)
90.03(18)
89.69(15)
93.3(2)
Cl(1)–Re–Cl(2)
Cl(1)–Re–P(1)
92.52(14)
97.21(15)
169.8(3)
87.1(3)
Cl(1)–Re–N(11)
Cl(1)–Re–N(21)
Cl(1)–Re–N(31)
Cl(2)–Re–P(1)
89.2(3)
96.84(14)
91.3(3)
88.8(3)
Cl(2)–Re–N(11)
Cl(2)–Re–N(21)
Cl(2)–Re–N(31)
P(1)–Re–N(11)
P(1)–Re–N(21)
P(1)–Re–N(31)
N(11)–Re–N(21)
N(11)–Re–N(31)
N(21)–Re–N(31))
169.7(3)
91.8(3)
Ph
[Re]
N
N
172.7(3)
93.0(3)
83.4(4)
C
O
85.4(4)
81.1(4)
a
171.24(4)
119.8(6)
The average Re–Cl bond distance in compound 1
˚
[2.4208(19) A] is longer than that found in complex 3

1954
E.C.B. Alegria et al. / Journal of Organometallic Chemistry 690 (2005) 1947–1958
Fig. 4. View of the intermolecular (dotted line) interaction in 1.
˚
[2.352(4) A] what probably reflects the neutral and cat-
ionic nature of the compounds, respectively. Such an ef-
fect is not evident in the Re–P bond distances which are
essentially equivalent in both compounds.
standard procedures and freshly distilled immediately
prior to use.
The hydrotris(1-pyrazolyl)methane and hydro-
tris(3,5-dimethyl-1-pyrazolyl)methane were prepared
in accord with published procedures [31]. The first
one was further recrystallized from warm diethyl ether.
Infrared spectra (4000–400 cmꢀ1) were recorded on a
Nicolet Impact 400D spectrophotometer instrument
in KBr pellets; wavenumbers are in cmꢀ1; abbrevia-
tions: vs, very strong; s, strong; m, medium; w, weak;
There is an intramolecular H bond N12–H12ꢁ ꢁ ꢁO1
˚
(H12ꢁ ꢁ ꢁO1, 1.938 A) in 1 which implies the coplana-
rity of both the pyrazolyl and the organodiazenide
groups. Due to the weak intermolecular hydrogen
˚
bond C12–H12Cꢁ ꢁ ꢁO1 (C12–O1, 3.470 A) the mole-
cules form pseudo dimers as can be seen in Fig. 4.
The CH2Cl2 moieties occupy the voids between the
phenyl rings of the molecule without any short con-
tact. A few weak hydrogen-bonding interactions be-
tween the chlorine ligands and the phenyl hydrogens
of the phosphines could be found in both 1 and 3
structures. Moreover, short contact distances between
the rhenium atom and some phenyl hydrogens of
the phosphines (H102, H126, H202, H226) could be
found in structure 1 with the obtained distances rang-
1
br, broad. H, 31P and 13C NMR spectra were recorded
on a Varian Unity 300 spectrometer at ambient tem-
perature; d values are in ppm relative to SiMe4 (1H
or 13C) or H3PO4 (31P). In the 13C NMR data, assign-
ments and coupling constants common to the
13C–{1H} NMR spectra are not repeated. Coupling
constants are in Hz; abbreviations: s, singlet; d, dou-
blet, t, triplet; q, quartet; qt, quintet; m, complex mul-
tiplet; br, broad; dd, doublet or doublets; dt, doublet of
triplets, tm, triplet of complex multiplets. Atom label-
˚
ing from 3.26(6) to 3.43(8) A.
ling for the Hpz ligand: HN(1)N(2)C(3)HC(4)HC(5)H.
Positive-ion FAB mass spectra were obtained on a Trio
2000 spectrometer by bombarding 3-nitrobenzyl alco-
hol (NBA) matrices of the samples with 8 keV
(ca. 1.28 · 1015 J) Xe atoms. Mass calibration for data
system acquisition was achieved using CsI. The C, H,
3. Experimental
All manipulations and reactions were performed un-
der an atmosphere of dinitrogen using standard vacuum
and inert-gas flow techniques. Solvents were purified by
N
elemental analyses were carried out by the

E.C.B. Alegria et al. / Journal of Organometallic Chemistry 690 (2005) 1947–1958
1955
Microanalytical Service of the Instituto Superior
´
Tecnico.
The electrochemical experiments were performed on
an EG&G PAR 273A potentiostat/galvanostat con-
nected to personal computer through a GPIB interface.
C6H6. The crystal of complex 1 analysed by X-rays was
obtained by slow addition of Et2O to a dichloromethane
solution of 1.
IR (KBr pellet): 3076 [s, m(NH)], 1592.5 [vs, m(C@O)],
1564.5, 1554.8 [vs, m(N@N) N2C(O)Ph and/or m(N@C)
1
Cyclic voltammograms were obtained in 0.2
M
Hpz]. NMR: H (CD2Cl2), d 13.94 [s, 1H, H(1) Hpz],
7.75 [d, 2H, JHH = 8.3, o-C(O)Ph], 7.59–7.53 [m, 12H,
[nBu4N][BF4]/CH2Cl2, at a platinum disc working elec-
trode (d = 1 mm). Controlled-potential electrolyses
(CPE) were carried out in electrolyte solutions with
the above-mentioned composition, in a three-electrode
H-type cell. The compartments were separated by a sin-
tered glass frit and equipped with platinum gauze work-
ing and counter electrodes. For both CV and CPE
experiments, a Luggin capillary connected to a silver
wire pseudo-reference electrode was used to control
the working electrode potential. The CPE experiments
were monitored regularly by cyclic voltammetry (CV),
thus assuring no significant potential drift occurred
along the electrolyses. The oxidation potentials of the
complexes were measured by CV (see above) in the pres-
ence of ferrocene as the internal standard, and the redox
potential values are quoted relative to the SCE by using
3
(o or m)-PPh3], 7.35 [m, 1H, p-C(O)Ph], 7.31 [m, 2H,
m-C(O)Ph], 7.27–7.19 m, 18H, {(m or o) + p}-PPh3],
6.97 dd, 1H, JH,H = 2.4, H(3) or H(5) Hpz], 6.90 [dd,
1H, JH,H = 1.95, H(3) or H(5) Hpz], 5.63 [q, 1H,
JH,H = 2.3, H(4) Hpz]. 31P–{1H}(CD2Cl2), d-6.8 s. 13C–
{1H}(CD2Cl2), d 167.50 [s, C@O], 140.53 [s, C(3)
Hpz], 134.76 [s, Cp (COPh)], 134.57 [t, JCP = 5.3, Co
(PPh3)], 133.04 [s, C(5) Hpz], 131.57 [s, Co or Cm
(COPh)], 130.73 [s, Cm or Co (COPh)], 130.04 [s, Cp
(PPh3)], 128.52 [t, JCP = 8.0, Ci (PPh3)], 128.23
[t, JCP = 4.6, Cm (PPh3)], 127.46 [s, Ci (COPh)], 106.77
[s, C(4) Hpz]. 13C (CD2Cl2), 167.50, 140.53
[d, JCH = 187.3, C(3) Hpz], 134.76 [d, JCH = 158.1, Cp
(COPh)], 134.57 [dt, JCH = 161.2, Co (PPh3)], 133.04
[d, JCH = 160.2, C(5) Hpz], 131.57 [d, JCH = 165.4, Co
or Cm (COPh)], 130.73 [d, JCH = 171.2, Cm or Co
(COPh)], 130.04 [d, JCH = 160.05, Cp (PPh3)], 128.52,
128.23 [dt, J CH = 158.2, Cm (PPh3)], 127.46, 106.77
[d, JCH = 185.3, C(4) Hpz]. FAB+-MS: m/z 982 ([M]+),
915 ([M ꢀ Hpz]+), 880 ([M ꢀ Hpz–Cl]+), 877
([M ꢀ COPh+), 849 ([M ꢀ N2C(O)Ph]+). Found: C,
56.5; H, 4.0; N, 5.6%. ReC46H39N4P2OCl2 requires C,
56.2; H, 4.0; N, 5.7.
the [Fe(g5-C5H5)2]0/+ (Eox ¼ 0:55 V versus SCE) redox
1=2
couple in 0.2 M [nBu4N][BF4]/CH2Cl2. They are con-
verted to the NHE scale by addition of 0.245 V [15,16]
Intensity data for [ReCl2{NNC(O)C6H5}(Hpz)-
(PPh3)2] Æ CH2Cl2 1 Æ CH2Cl2 and [ReCl2(HCpz3)(PPh3)]-
[BF4] 3 were collected using a Enraf-Nonius CAD4
diffractometer and structures were solved by direct meth-
ods by using the SHELXS-97 package [32]. The structure
refinements were carried out with SHELXL-97 [33]. All
hydrogens, except H12 in the pyrazolyl ring of structure
1 Æ CH2Cl2, were inserted in calculated positions. The
maximum and minimum peaks in the final differenꢀce3
3.2. Synthesis of
[ReCl2{NNC(O)C6H5}(Hpz)2(PPh3)] 2
˚
˚
electron density map were of ꢀ0.845 and 0.864 e Aꢀ3
To a solution of compound 1 (101 mg, 0.103 mmol)
in benzene (15 cm3) was added a methanol (15 cm3)
solution of pyrazole (140 mg, 2.06 mmol) and the mix-
ture was stirred under reflux for ca. 29 h. Concentration
in vacuo of the dark green solution followed by slow
addition of Et2O resulted in the precipitation of com-
pound 2 as a dark green solid which was filtered-off,
washed with Et2O and dried in vacuo (0.047 g, 58%
yield). Complex 2 can also be obtained by treatment
of a benzene solution (20 cm3) of the green chelate
(127.9 mg, 0.14 mmol) with a methanol solution (20
cm3) of pyrazole (334 mg, 4.92 mmol) under reflux for
ca. 35 h. Concentration and addition of Et2O leads to
the precipitation of compound 2 (0.053 g, 48% yield).
IR (KBr pellet): 3286 [s, m(NH)], 1588 [s, m(C@O)],
1549 [vs, m(N@N) N2COPh and/or m(N@C) Hpz].
NMR: 1H (CD2Cl2), d 14.31 and 12.61 [s, 1H+1H,
for structure 1 Æ CH2Cl2 and of ꢀ2.198 and 2.755 e A
(close to the rhenium atom) for structure 3.
3.1. Synthesis of
[ReCl2{NNC(O)C6H5}(Hpz)(PPh3)2] 1
To
a
light green suspension of [Re{2-N–O–
N2C(O)Ph}(PPh3)2] (0) (green chelate) (156 mg, 0.171
mmol) in methanol (20 cm3), HCpz3 was added (44
mg, 0.206 mmol) and the mixture was heated under re-
flux during ca. 28 h. The obtained dark green powder
of complex 1 was filtered off, washed with Et2O and
dried in vacuo (0.11 g, 66% yield). Complex 1 was also
obtained by treatment of a benzene solution (15 cm3)
of the chelate complex (68 mg, 0.075 mmol) with HCpz3
(0.016 g, 0.075 mmol) at room temperature during ca. 8–
10 h. Concentration in vacuo, followed by slow addition
of Et2O, led to the precipitation of 1 as a green solid
which was washed with Et2O and dried in vacuo
(0.042 g, 57% yield). Complex 1 is insoluble in methanol
and diethyl ether but very soluble in CH2Cl2, acetone or
3
4
H(1) Hpz], 7.86 [dd, 2H, JHH = 8.1, JHH = 1.2, o-
COPh, 7.72 [m, 1H, H(3) or H(5) Hpz], 7.66 [m, 1H,
H(3) or H(5) Hpz], 7.63–7.51 [m, 6H, (o or m-PPh3)],
7.36 [m, 1H, p-COPh], 7.33 [m, 2H, m-COPh], 7.30
[s, 1H, H(3) or H(5) Hpz], 7.28–7.26 [m, 9H, {(o or

1956
E.C.B. Alegria et al. / Journal of Organometallic Chemistry 690 (2005) 1947–1958
3
H(5)], 8.36 [d, 1H, JHH = 2.8, H(3) or H(5)], 8.10 [d,
m)+p}-PPh3, 6.80 [m, 1H, H(3) or H(5) Hpz], 6.36 [m,
1H, H(4) Hpz], 6.14 [m, 1H, H(4) Hpz]. 31P–
{1H}(CD2Cl2), d ꢀ0.25 s. 13C–{1H}(CD2Cl2), d 169.92
[s, C@O], 141.49 and 140.80[s, C(3) Hpz], 134.49 [d,
JCP = 9.3, Co or Cm (PPh3)], 134.03 [s, Cp (COPh)],
133.20 and 132.79 [s, C(5) Hpz], 130.94 [s, Co or Cm
(COPh)], 130.34 [d, JCP = 2.5, Cp (PPh3)], 128.89 [d,
JCP = 9.4, Ci (PPh3)], 128.83 [s, Ci (COPh)], 128.78 [m,
Co or Cm (COPh)], 128.45 [d, JCP = 10.6, Co or Cm
(PPh3)], 107.62 and 107.19 [s, C(4) Hpz]. 13C (CD2Cl2)
169.92, 141.49 and 140.80 [d, JCH = 185.3 and 189.2,
C(3) Hpz], 134.49 [dd, JCH = 160.8, Co or Cm (PPh3)],
134.03 [d, JCH = 142.7, Cp (COPh)], 133.20 and 132.79
[d, JCH = 157.6 and 163.7, C(5) Hpz], 130.94
[d, JCH = 173.5, Co or Cm (COPh)], 130.34 [dd,
JCH = 159.1, Cp (PPh3)], 128.89, 128.83, 128.78
[dm, JCH = 150.8, Co or Cm (COPh)], 128.45 [dd,
JCH = 162.5, Co or Cm (PPh3)], 107.62 and 107.19 [d,
JCH = 184.6 and 187.4, C(4) Hpz]. FAB+-MS: m/z 787
([M]+), 719 ([M ꢀ Hpz]+), 683 ([M ꢀ Hpz–Cl] +), 654
([M ꢀ N2COPh]+). Found: C, 42.6; H, 3.3; N, 9.4%. Re-
C31H26N6POCl2 Æ 3/2CH2Cl2 requires C, 42.8; H, 3.2; N,
9.2.
3
3
1H, JHH = 2.7, H(3) or H(5)], 7.95 [d, 1H, JHH = 2.1,
H(3) or H(5)], 7.61–7.55 [m, 6H, o or m-PPh3], 7.44–
7.33 m, 9H, (o or m) + p-PPh3], 6.80 [d, 1H,
3
3JHH = 2.1, H(3) or H(5)], 6.55 [dd, 1H, JHH = 2.4,
3
H(4)], 6.49 [d, 1H, JHH = 2.7, H(3) or H(5)], 6.31 [dd,
3
3
1H, JHH = 2.6, H(4)], 6.10 [dd, 1H, JHH = 2.4, H(4)].
31P–{1H}(CD2Cl2), d 4.66 s. 13C–{1H}(CD2Cl2), d
149.71, 147.66 and 146.84 [s, C(3), HCpz3], 134.56 [d,
JCP = 9.4, Co or Cm (PPh3)], 133.90, 132.96 and 132.29
[s, C(5), HCpz3], 131.30 [d, JCP = 2.2, Cp (PPh3)],
129.28 [d, JCP = 9.4, Co or Cm (PPh3)], 129.00 [d,
JCP = 11.2, Ci (PPh3)], 109.77, 109.41 and 108.79 [s,
C(4), HCpz3], 75.81 [s, HCpz3]. 13C (CD2Cl2), d
149.71, 147.66 and 146.84 [d, JCH = 172.7, 162.2 and
171.0, C(3) HCpz3], 134.56 [dd, JCH = 162.5, Co or Cm
(PPh3)], 133.90, 132.96 and 132.29 [d, JCH = 168.2,
170.5 and 173.4, C(5), HCpz3], 131.30 [dd,
JCH = 160.7, Cp (PPh3)], 129.28 [dd, JCH = 155.1, Co or
Cm (PPh3)], 129.00, 109.77, 109.41 and 108.79 [d,
JCH = 179.5, 168.2 and 183.3, C(4), HCpz3], 75.81 [d,
JCH = 152.5, HC pz3]. FAB+-MS: m/z 733 ([M]+), 698
([M ꢀ Cl+), 630 ([M ꢀ Hpz]+), 766 ([M + Hpz]+).
FABꢀ-MS: m/z 87 ([BF4]ꢀ). Found: C, 39.6; H, 3.1;
N, 9.7%. ReC28H25N6PCl2BF4 Æ 1/2CH2Cl2 requires C,
39.7; H, 3.0; N, 9.8.
3.3. Synthesis of [ReCl2(HCpz3)(PPh3)][BF4] 3
A benzene solution (20 cm3) of the green chelate 0
(71.5 mg, 0.0785 mmol) was treated with a methanol
solution (ca. 10 cm3) of Tl[BF4] (34.3 mg, 0.118 mmol)
and stirred at room temperature for ca. 15–20 min.
where after HCpz3 (22.9 mg, 0.0785 mmol) was added.
The resulting solution was stirred and heated at reflux
for 5–6 h. During this time, the solution colour changed
from green to brown. The mixture was filtered trough
celite and the reddish brown filtered solution was con-
centrated in vacuo and Et2O was added slowly. Cooling
overnight at ꢀ18 ꢁC yielded complex 3 as a reddish
brown crystalline solid which was filtered-off, washed
with Et2O and dried in vacuo (31.5 mg, 49% yield).
Complex 3 is soluble in ethanol, CH2Cl2 and acetone.
The crystal of this complex analysed by X-rays was ob-
tained by slow addition of Et2O to a dicloromethane
solution of 3. Complex 3 could also be obtained by reac-
tion of a benzene (10 cm3) solution of the green chelate 0
(73.0 mg, 0.082 mmol) with a methanol (10 cm3) solu-
tion of NaBF4 (13.2 mg, 0.123 mmol) and HCpz3
(20.6 mg, 0.098 mmol). The mixture was stirred under
reflux for ca. 27 h. The brown solution was filtered
and concentrated. Et2O was then added and the solution
was taken to dryness. Dissolution in THF followed by
addition of n-pentane resulted in the precipitation of
complex 3 which was filtered-off, washed with n-pentane
and dried in vacuo (38 mg, 56% yield).
3.4. Synthesis of [ReCl2(3,5-MeHpz)3(PPh3)]Cl 4
Refluxing a suspension of the green chelate 0 (107
mg, 0.118 mmol) in methanol (20 cm3) with hydro-
tris(3,5-dimethyl-1-pyrazolyl)methane (70.0 mg, 0.236
mmol) during 28 h resulted in a dark brown solution
which was concentrated and Et2O added. The solution
was taken to dryness and the residue was dissolved in
THF. Addition of n-pentane lead to the precipitation
of a brown compound which was filtered-off, washed
with n-pentane and dried in vacuo (0.06 g, 59% yield).
Complex 4 can also be formed by refluxing a suspension
of the green chelate (134 mg, 0.147 mmol) in methanol
(20 cm3) with 3,5-dimethylpyrazole (70.7 mg, 0.735
mmol) during 29 h what leads to a dark brown solution.
This solution was concentrated almost to dryness in va-
cuo and Et2O was slowly added. The reddish-brown
compound 4 was filtered-off and dried in vacuo (0.08
g, 65% yield).
IR (KBr pellet): 3118 [s, m(NH)], 1572 [vs, m(N@C),
1
(3,5-Me2Hpz)]. NMR: H (CDCl3), d 15.67 [s, br, 3H,
H(1), (3,5-Me2Hpz)], 7.77–7.75 [m, 6H, (o or m)-PPh3],
7.44–7.42 [m, 9H, {(o or m) + p}-(PPh3)], 6.10 [s, 3H,
H(4) (3,5-Me2Hpz)], 2.53 [s, 18H, CH3 (3,5-Me2Hpz)].
31P–{1H}(CDCl3), d 21.27 s. 13C–{1H}(CDCl3), d
144.71 [s, C(3), 3,5-Me2pz], 134.68 [s, C(5), 3,5-Me2pz],
132.13 [d, JCP = 9.8, Co or Cm (PPh3)], 130.74 [d,
JCP = 14.3, Ci (PPh3)], 128.60 [s, Cp (PPh3)], 128.51 [d,
JCP = 13.2, Co or Cm (PPh3)], 106.22 [s, C(4), 3,5-
IR (KBr pellet): 3133 [s, m(CH)], 1532 [vs, m(N@C),
HCpz3], 1064 [vs, m(B–F), BF4] NMR: 1H (CD2Cl2),
9.66 [s, 1H, H Cpz3], 8.41 [d, 1H, JHH = 2.7, H(3) or
3

E.C.B. Alegria et al. / Journal of Organometallic Chemistry 690 (2005) 1947–1958
1957
Me2pz], 11.10 [s, CH3, 3,5-Me2pz]. 13C (CDCl3), d
144.71, 134.68, 132.13 [dd, JCH = 188.68, Co or Cm
(PPh3)], 130.74, 128.60 [d, JCH = 169.7, Cp (PPh3)],
128.51 [dd, JCH = 176.3, Co or Cm (PPh3)], 106.22 [d,
JCH = 179.9, C(4), 3,5-Me2pz], 11.10 [q, JCH = 130.3,
CH3, 3,5-Me2pz]. FAB+-MS: m/z 807 ([M] +), 711
([M ꢀ 3,5-Me2Hpz]+), 674 {[M ꢀ (3,5-Me2Hpz–Cl)]+},
521 (M ꢀ 2(3,5-Me2Hpz–Cl)]+). FABꢀ-MS: m/z 35
(Clꢀ). Found: C, 46.52; H, 4.67; N, 9.92%.
ReC33H39N6PCl3 requires C, 47.0; H, 4.63; N, 9.97.
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4. Supplementary material
Crystallographic data for the structural analysis has
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 253079 for compound
1 Æ CH2Cl2 and CCDC No. 253080 for compound 3.
Copies of this information may be obtained free charge
from The Director, CCDC, 12, Union Road, Cambridge
CB2 1EZ (fax: +44 1223 336 033) or e-mail: depos-
it@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk.
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Acknowledgements
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This work has been partially supported by the IPL/
ˆ
(d) S.D. Orth, J. Barrera, M. Sabat, W.D. Harman, Inorg. Chem.
33 (1994) 3026;
41/2003 project, the Fundac¸a˜o para a Ciencia e Tecnolo-
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