Bis(aqua)bis(η5-cyclopentadienyl)vanadium(IV) bis(trifluoromethanesulfonate) tetrahydrofuran solvate: Synthesis and characterization

Article abstract of DOI:10.1016/j.ica.2012.09.038

The reactivity pattern of [V(Cp)₂Cl₂] towards the weakly coordinating CF₃SO₃^- anion in the absence of chelating or bridging organic ligands has been investigated, where Cp^- is the η⁵

Full text of DOI:10.1016/j.ica.2012.09.038

Inorganica Chimica Acta 394 (2013) 747–751
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Note
Bis(aqua)bis(
g
5-cyclopentadienyl)vanadium(IV) bis(trifluoromethanesulfonate)
tetrahydrofuran solvate: Synthesis and characterization
a,b
a
c
c
Theocharis C. Stamatatos , Spyros P. Perlepes , Catherine P. Raptopoulou , Aris Terzis ,
Nikolaos Klouras
a
a,
⇑
Department of Chemistry, University of Patras, 265 04 Patras, Greece
Chemistry Department, Brock University, L2S 3A1 St. Catharines, Ontario, Canada
Institute of Materials Science, NCSR ‘‘Demokritos’’, 153 10 Aghia Paraskevi Attikis, Greece
b
c
a r t i c l e i n f o
a b s t r a c t
ꢀ
Article history:
Received 25 July 2012
Received in revised form 25 September
2 2 3 3
The reactivity pattern of [V(Cp) Cl ] towards the weakly coordinating CF SO anion in the absence of
ꢀ
5
ꢀ
chelating or bridging organic ligands has been investigated, where Cp is the
g
-C
H
5 5
ligand. The syn-
thesis, single-crystal X-ray structure and physical/spectroscopic characterization are reported for the
2
012
IV
product [V(Cp)
(H
2 2
O)
2
](CF
3
SO
)
3 2
ꢁTHF (1ꢁTHF). The coordination about the V atom, formed by the two
Accepted 26 September 2012
Available online 11 October 2012
H
2
O molecules and the centroids of the cyclopentadienyl rings, is distorted tetrahedral. The [V(Cp)
2
2
+
(H
2
O)
2
]
cation is connected to the triflate anions via hydrogen bonds. Magnetic susceptibility, EPR
and IR data are discussed in terms of the nature of bonding and the structure of the complex.
Keywords:
Bis(aqua)bis(
5-
Ó 2012 Elsevier B.V. All rights reserved.
g
cyclopentadienyl)vanadium(IV) cation
Crystal structure
Electron paramagnetic resonance spectra
Infrared spectra
Triflate anion
ꢀ
1
. Introduction
The first organometallic compounds of vanadium with a V-to-li-
mon oxidation state of the metal with Cp ligation is the + IV,
examples being the vanadocene dihalide and bis(pseudohalide)
complexes, [V(Cp)
2 2
X ] (X = Cl, Br, N
3
, NCS, NCO,. . .) [2,3]. Interest
ꢀ
gand
p
or
r
bond were characterized in 1953, [V(Cp)
2
X
2
] (X = Cl,
in V/Cp compounds with respect to potential applications arises
from their use as catalysts, employment in organic synthesis, anti-
tumor properties and their importance in bioinorganic chemistry.
Examples of catalytic processes using such species are the [V(Cp)
Cl ]/Al(Et) Cl systems in the Ziegler–Natta polymerization of ethyl-
ene [4]. The importance of V/Cp complexes in organic synthesis
has been demonstrated by the use of [V(Cp)(H)(CO)
aration of alkanes from alkyl bromides and of aldehydes from car-
bonic acid chlorides [5]. Complexes of the {V (Cp)
ꢀ
Br), and 1960, [V(Ph)Cl
pentadienyl(ꢀ1) ligand (C
3
], respectively [1], where Cp is the cyclo-
ꢀ
ꢀ
5
H ) and Ph is the phenyl group. Pro-
5
gress in this area had been relatively slow until the 1980s.
During the last two decades, organovanadium chemistry has expe-
rienced an explosive development and compounds covering the
2
2
2
ꢀ
3ꢀ
⁄
ꢀ
oxidation states ꢀIII, e.g. in [V(CO)
5
]
, to +V, e.g. in [VO(Cp )
3
]
in the prep-
⁄
ꢀ
(
[
Me)
2
], where Cp is the pentamethylcyclopentadienyl(ꢀ1) ligand
IV
2+
1], have been prepared.
2
}
moiety
An important class of organometallic V compounds consists of
exhibit antitumor and antiproliferative properties, both in vitro
and in vivo, primarily via oxidative damage [6]. A comparison test
in the human testicular cancer cell lines Tera-2 and Ntera-2, using
both 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bro-
mide assays and apoptosis assays, led to the conclusion that the
those containing one (half-sandwich complexes) or two (sandwich
ꢀ
and bent sandwich complexes) Cp groups or their analogs. The
5
ligands are usually coordinated in the
g
mode. Cp complexes exist
with the V center in oxidation numbers ꢀI to +V, e.g. compounds
ꢀ
I
ꢀ
0
+
7
[
C
[
V
(Cp)(CO)
3
] , [V (Cp)(Tp)] (Tp is the propylium cation,
g
-
[V(Cp)
2 2
(NCS) ] was most potent [7]. Very recently, in vitro experi-
+
I
II
III
IV
5
7
H
7
), [V (Cp)(CO)
4
], [V (Cp)
2
], [V (Cp)
2
Cl], [V (Cp)
2
(Me)
2
] and
ments of dichloridobis[(p-methoxybenzyl)(g -cyclopentadienyl]
V
⁄
V O(Cp )(Ph)
2
], demonstrating the versatility of valence electronic
vanadium(IV) and its diselenocyanate-derivative on the CAKI-1 cell
line showed impressive cytotoxic effects with IC50 values in the
nanomolar range, for the first time for metallocene anticancer drug
candidates [8a]. Further biological studies in structurally similar
compounds have also revealed the potential of this family of
configurations suitable for binding to this ligand. The most com-
⇑
Corresponding author. Tel.: +30 2610 997140; fax: +30 2610 997118.
E-mail address: n.klouras@chemistry.upatras.gr (N. Klouras).
0
020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.09.038

7
48
T.C. Stamatatos et al. / Inorganica Chimica Acta 394 (2013) 747–751
Elemental analyses (C, H, S) were conducted at the in-house
Microanalytical Service using an EA 1108 Carlo Erba analyser. IR
ꢀ1
spectra (4000–500 cm ) were recorded on a Perkin Elmer 16PC
FT spectrometer with samples prepared as KBr pellets. The mag-
netic susceptibility of the product was measured at 20 °C by the
Faraday method with a Cahn–Ventron RM-2 balance standardized
with [HgCo(SCN)
corr] for the diamagnetism of the constituent atoms using Pascal’s
constants. The effective magnetic moment, eff, was calculated
corrT] . The EPR spectrum in
4 M
]. The molar susceptibility was corrected [(v )-
l
1
/2
from the equation
M
leff = 2.83[(v )
DMSO solution was recorded on a Bruker ES200 X-band spectrom-
eter at room temperature (25 °C).
Scheme 1. The starting material dichloridobis( 5
or vanadocene dichloride, [V(Cp) Cl ].
g -cyclopentadienyl)vanadium(IV)
2
2
2
.2. Synthesis of [V(Cp)
(H
2 2
2
O) ](CF
3 3 2
SO ) ꢁTHF (1ꢁTHF)
compounds in the treatment of various cancer cell lines [8b–d].
Compound [V(Cp) (acac)](CF SO ) is a dual-function anticancer
agent with anti-angiogenic and anti-mitotic properties against
human cancer cells [9]. Finally, the crystal structure of the product
A colourless solution of Ag(CF
5 mL) was added to a green suspension of [V(Cp) Cl ] (0.126 g,
.5 mmol) in the same solvent (5 mL) under vigorous stirring. A
white precipitate of AgCl formed immediately and the colour of
the reaction mixture turned to deep green. After stirring for
10 min, AgCl was removed by filtration and the deep green filtrate
was stored for 24 h at room temperature in a covered tube filled with
Ar gas. X-ray quality green–brown, plate-like crystals of the product
were deposited on the walls of the tube. The crystals were collected
3
SO
3
) (0.257 g, 1.0 mmol) in THF
2
3
3
(
0
2
2
of the reaction between aqueous [V(Cp) ] and diphenyl phos-
2
Cl
2
phate, namely [V(Cp) (H O) ]{O P(OPh) } [10], shows that the
2
2
2
2
2 2
IV
interaction of V with phosphate is an outer-sphere process; this
structure offers a model for the interaction of the antitumor unit
2
+
{
V(Cp)
metrical parameters about the phosphate similar to those in DNA
10].
We have a long-standing interest in the reactivity chemistry of
2
}
with DNA in that diesterified phosphoric acids exhibit
by filtration, washed with Et
and kept under Ar (the product slowly decomposes in air). Yield:
0.105 g (36%). Anal. Calc. for C16 V: C, 31.71; H, 3.78; S,
0.92. Found: C, 31.92; H, 3.71; S, 11.07%. M.p. 104 °C. IR data (KBr
2
O (2 ꢂ 3 mL), dried in air for 15 min
[
ꢀ
⁄ꢀ
IV
IV
IV
IV
22 6 9 2
H F O S
Cp , Cp or other substituted derivatives of Ti , Zr , Hf and V
metallocenes) with either organic or inorganic ligands which
results in structurally interesting products [2,11–14]. For example,
we have reported that the reaction of [Ti(Cp) Cl ] and 2,6-bis(3,5-
1
(
ꢀ
1
pellet, cm ):
m = 3280, 3094, 1444, 1256, 1178, 1034, 880, 822,
ꢀ1
7
l
66, 646, 578, 520 cm . Effective magnetic moment (20 °C):
2
2
ꢀ4
ꢀ1
eff = 1.74 B.M. EPR (DMSO): g = 1.981(2), hAi = 67.8 ꢂ 10 cm
.
dimethylpyrazolyl-1-yl)pyridine (bdmpp) in acetone proceeds
with the complete substitution of the cyclopentadienyl ligands
IV
2
.3. Single-crystal X-ray crystallography
and affords complex [Ti Cl
2
(O
2
)(bdmpp)] containing the side-on
2
2ꢀ
(
g
) O
reaction of [Ti(Cp)
the trinuclear complex [Ti
gular, oxide-centered topology [14]. As part of a broad research
program to investigate the reactivity of [M(Cp) ] compounds
M = Ti, Zr, Hf, V; X = halide or pseudohalide), this report describes
2
group [11]. Also we have recently discovered that the
] with MeOH and H O surprisingly leads to
](I ) possessing a trian-
A green–brown, plate-like crystal of 1 THF (0.10 ꢂ 0.39 ꢂ
2
I
2
2
IV
0
.49 mm) was taken from the mother liquor and immediately
3
O(OMe)
6
(Cp)
3
3
2 2
X
Table 1
(
Crystallographic data for complex 1ꢁTHF.
the reaction of vanadocene dichloride (Scheme 1) with the weakly
ꢀ
Formula
16 22 6 9 2
C H F O S V
587.40
0.10 ꢂ 0.39 ꢂ 0.49
green–brown, plates
monoclinic
coordinating anion (WCA) CF
3
SO
3
in the absence of ancillary che-
M
r
lating or bridging organic ligands and the full characterization of
the product [V(Cp) (H O) ](CF SO . Reactions of metallocene
Crystal size (mm)
Colour, habit
Crystal system
Space group
2
2
2
3
3 2
)
complexes with WCAs are of current interest because their prod-
ucts are important in catalysis [15]. For example, complexes of
1
P2 /n
0
ꢀ
a
(Å)
8.1577(1)
21.0261(3)
13.4999(2)
90.936(2)
2315.26(6)
4
1.685
6.153
1196
160(2)
0
the type [M(Cp )
cyclopentadienyl) are utilized as catalysts for the polymerization
of alkenes CH @CHR (R = H, alkyl, aryl) [16]. It is universally
2
(Me)(WCA)] (M = Ti, Zr, Hf; Cp = substituted
b (Å)
c (Å)
b (°)3
V (Å )
Z
2
accepted that polymerization involves initial substitution of the
WCA by the alkene to generate a cationic alkene intermediate,
ꢀ
D
calcd (g cm 3
)
0
2
+
[
M(Cp )
2
(Me)(
g
-CH
2
@CHR)] , and that the latter then undergoes
ꢀ1
l
(Cu K ), (mm
a
)
0
1
migratory insertion to give an alkyl intermediate, [M(Cp )
CHMeR)] , with subsequent steps involving a series of similar
2
(g
-CH
2
F(000)
T (K)
h range (°)
Ranges
+
6.64–65.00
insertion reactions.
h
k
l
ꢀ9 ? 9
ꢀ17 ? 24
ꢀ15 ? 12
16123
2
. Experimental
Measured reflections
Unique reflections (Rint
)
3803 (0.0555)
3402
1.075
0.0396
0.1016
2.1. General and physical measurements
Reflections used [I > 2
Goodness-of-fit (GoF) on F
r(I)]
2
a
R
1
[I > 2
r
(I)]
[I > 2 (I)]
min (e Å
Most manipulations were performed under aerobic conditions
b
wR
2
r
q
using materials and solvents (Merck, Alfa Aesar) as received.
V(Cp) Cl ] was synthesized by the 1:2:2 reaction of VCl , CpH
and Bu Li in THF/petroleum ether under inert conditions (Ar atmo-
sphere) according to a published procedure [2].
ꢀ3
(
D
q
)max/(
D
)
)
0.339/ꢀ0.535
[
2
n
2
4
a
R1
=
R
(|F | ꢀ |F |)/
o
c
o
R(|F |).
b
2
2
2
[w(F 2)2]}1/2.
o
wR
2
= {
R
[w(F
o
ꢀ F
c
) ]/
R

T.C. Stamatatos et al. / Inorganica Chimica Acta 394 (2013) 747–751
749
cooled to ꢀ113 °C. Diffraction data were collected on a Rigaku
R-AXIS SPIDER Image Plate diffractometer equipped with
graphite monochromator utilizing Cu K radiation. Data collection
scans) and processing (cell refinement, data reduction and
Table 2
Selected bond lengths (Å) and angles (°) for complex 1ꢁTHF.
a
a
V–O(1W)
V–O(2W)
V–C(1)
V–C(2)
V–C(3)
V–C(4)
V–C(5)
V–Cp
V–C(6)
2.058(1)
2.072(2)
2.288(2)
2.257(2)
2.291(2)
2.297(2)
2.297(2)
1.950
V–C(7)
V–C(8)
V–C(9)
V–C(10)
V–Cp
Mean C–C
2.285(8)
(x
2.288(5)
2.286(5)
2.274(4)
1.958
1.401(7)
1.801(3)
1.319(3)
1.438(2)
empirical absorption correction) were performed using the
CRYSTALCLEAR program package [17]. Important crystal data and
parameters for data collection and refinement are listed in Table 1.
The structure was solved by direct methods using SHELXS-97 [18]
0
b
c
d
d
Mean C–S
Mean C–F
2
a
and refined by full-matrix least-squares techniques on F with
2.282(4)
Mean S–Od
SHELXS-97 [19]. The H atoms of the disordered molecules (see
below) were introduced at calculated positions as riding on bonded
atoms. All the rest H atoms were located by difference maps and
refined isotropically. All non-H atoms were refined anisotropically.
a
0
b
O(1W)–V–O(2W)
O(1W)–V–Cp
O(1W)–V–Cp
O(2W)–V–Cp
O(2W)–V–Cp
81.7(1)
109.0(2)
106.6(2)
106.9(2)
107.6(2)
Cp –V–Cp
Aver. C–C–C
Aver. F–C–Fd
133.1(2)
a
c
108.0(5)
107.5(2)
115.0(1)
111.4(2)
0
b
a
d
ꢀ
Aver. O–S–O
The C atoms of one of the two Cp rings [C(6)–C(10)] as well as the
0
b
Aver. F–C–Sd
C atoms of the lattice THF molecule were found disordered over
two orientations and refined with occupation factors summing
one.
a
b
c
Cp is the C(1)C(2)C(3)C(4)C(5) cyclopentadienyl ring centroid.
Cp is the C(6)C(7)C(8)C(9)C(10) cyclopentadienyl ring centroid.
These values refer to the Cp and Cp rings.
These values refer to the CF
0
0
d
ꢀ
3
SO
3
counterions.
3
. Results and discussion
.1. Brief synthetic comments and characterization studies
3
The 1:2 reaction between [V(Cp) Cl ] and Ag(CF SO ) in THF is
ꢀ1
especially to the 1300–1200 cm region and it was proposed that
splitting of the as(S–O) band is due to coordination in monoden-
tate or bidentate fashions. The CSO part of the free anion has a
3V point group symmetry. In this symmetry, two SO stretching
modes, (E) and (A ), and two SO deformation modes, (A
and (E), are expected [27]. In the IR spectrum of 1 THF, the bands
at 1256, 766, 646 and 520 cm are assigned [27] to the
(A ), (A ) and (E) modes, respectively. The number of the
3
m
3
2
2
3
C
3
accompanied by a colour change from green to deep green–brown
and quantitative precipitation of AgCl. Removal of the white pre-
cipitate by filtration and storage of the filtrate at room temperature
m
4
m
2
1
3
m
3
1
)
m
5
ꢀ1
4
m (E),
gives crystals of [V(Cp)
2
(H
2
O)
2
](CF
3
SO
3
)
2
ꢁTHF (1ꢁTHF) in moderate
m
2
1
m
3
1
m
5
yield. The aqua ligands most probably originate from the moisture
of the solvent which was not distilled. The preparation of the prod-
uct is summarized in the balanced Eq. (1).
bands indicate no evidence for reduction in symmetry below C3V
,
ꢀ
indicating the ionic character of CF
due to lowering of the symmetry to C
dentate or bidentate sulfonate coordination had occurred. The
3
SO
3
; splitting of the modes,
s
, would be expected if mono-
THF
½
VðCpÞ Cl
2
ꢃ þ 2AgðCF
3
SO
3
Þ þ 2H
2
O þ THF !
2
ꢀ1
band at 1178 cm most probably has a predominant C-F stretch-
ing character [26].
ꢂ ½VðCpÞ ðH
2
OÞ ꢃðCF
3
ꢁTHF
SO
3
Þ ꢁ THF þ 2AgCl
ð1Þ
2
2
1
The bulk magnetic susceptibility measurement on 1ꢁTHF gave a
value of eff = 1.74 B.M., which is very close to the spin-only value
l
3.2. Description of structure
1
for one unpaired electron (3d system) [3]. The room-temperature
EPR spectrum of 1ꢁTHF in DMSO solution consists of eight sharp
lines as expected from the coupling of the one electron spin with
Selected bond lengths and angles for complex 1ꢁTHF are listed
in Table 2, while parameters for the hydrogen bonding interactions
are summarized in Table 3. The molecular structure of the cation
5
1
that of the V nucleus (I = 7/2). The average g value is 1.981(2)
and a second order perturbation effect leads to a non-uniform line
spacing between the components (68–78 G), the same as for com-
2
+
[V(Cp)
2
(H O)
2 2
]
is shown in Fig. 1 and a small portion of one
zig-zag chain present in the crystal structure of the complex is de-
picted in Fig. 2.
2 3 3
plex [V(Cp) (acac)](CF SO ) [9]. The average hyperfine coupling
constant hAi, calculated using the equation given by Pake and Rog-
Complex 1ꢁTHF crystallizes in the monoclinic space group P2
1
/n.
cations,
ꢀ4
ꢀ1
2+
ers [20], is 67.8 ꢂ 10 cm , very similar to the values reported for
V(Cp) ] complexes (L = monodentate ligand) [21]. This result
Its structure consists of well-separated [V(Cp)
CF
(H
2 2
O)
2
]
ꢀ
[
L
2 2
3
SO
3
anions and lattice THF molecules; the latter will not be
2+
indicates that in 1ꢁTHF the single unpaired electron is in an orbital
further discussed. That the relatively ‘‘hard acid’’ {V(Cp)
2
}
moiety
IV
essentially localized on the V center [3,9]. It should be recalled at
prefers to bind to water and not triflate may be consistent with the
this point that the EPR sample was exclusively in the liquid phase
HSAB model, in that H
2
O is most probably a better ‘‘hard base’’
ꢀ
IV
(
25 °C). Under these conditions the anisotropy of the hyperfine and
than CF
3
SO
3
[10]. The V center adopts the familiar ‘‘bent sand-
-containing complexes
g-tensors averages due to fast molecular tumbling and the spec-
trum consists of 2I + 1 lines centered at gave and spaced by roughly
wich’’ geometry found in numerous V(Cp)
2
5
ꢀ
[2,9,10,30–32], being
p-bonded to two g Cp ligands and r-
Aave [22].
bonded to two H O molecules. If the ring centroids are considered
2
A characteristic feature in the IR spectrum of 1ꢁTHF is the
as coordination sites, the coordination polyhedron of the metal ion
ꢀ1
appearance of a medium intensity band at 3280 cm assignable
[
is a distorted tetrahedron, the other two coordination sites being
ꢀ
23] to
and relatively low wavenumber of this band are both indicative
of hydrogen bonding. The IR spectra of -bonded cyclopentadienyl
metal complexes have been studied in detail [12–14,24,25]. The
m(OH) of the coordinated H
2
O molecules. The broadness
occupied by the aqua ligands. The C
5
H
5
ligation shows unexcep-
tional metrical parameters. The average C-C distance [1.401(7) Å],
V–C distance [2.285(8) Å], V-centroid distance [1.954 Å] and cen-
troid-V-centroid angle [133.1(2)°] compare favorably with the cor-
responding metrical parameters in closely related molecules and
p
ꢀ1
bands at 3094, 1444, 1034, 822 and 578 cm can be assigned to
the (CH), (CC), d(CH) [overlapping with the (A ) mode, (CS),
(CH) and d(CCC) vibrational modes, respec-
ꢀ
m
m
m
1
1
m
cations [2,9,10,30–32]. The dihedral angle between the two Cp
of the triflate anion],
p
rings is 46.6°. The V–O bond lengths in 1 THF [mean value:
ꢀ
IV
tively. The CF
3
SO
3
ion has been the subject of numerous IR studies
2.065(2) Å] are typical for V –OH
2
bonds [33,34] and can be com-
to establish a correlation between vibrational frequencies and the
mode of coordination [26–29]. Much attention has been given
pared, for example, with the average distance of 2.074(3) Å ob-
2ꢀ
served in [V
2
O
2
F
(H
6 2
O)
2
]
[34]. The metrical parameters for the

7
50
T.C. Stamatatos et al. / Inorganica Chimica Acta 394 (2013) 747–751
Table 3
Hydrogen bonding interactions in the crystal structure of 1ꢁTHF.
Interactiona
DꢁꢁꢁA (Å)
HꢁꢁꢁA (Å)
D–HꢁꢁꢁA ( )
o
Symmetry operator of A
O(1W)–H(1WA)ꢁꢁꢁ O(14)
O(2W)–H(2WA) ꢁꢁꢁO(12)
O(2W)–H(2WB) ꢁꢁꢁO(16)
2.726
2.625
2.722
1.911
1.925
1.821
172.0
167.6
174.4
ꢀx, 1 ꢀ y, ꢀz
ꢀ1 + x, y, z
1/2 ꢀ x, 1/2 + y, 1/2 ꢀ z
a
3ꢀ
Atoms O(12), O(14) and O(16) belong to the two CF
3
SO counterions. A = acceptor; D = donor.
Table 4
2 2 2
Selected structural parameters for the cations of complexes [V(Cp) (H O) ]{O2-
a
P(OPh)
2
}
2
[9] and 1ꢁTHF.
Parameterb (Å) or (°)
[V(Cp)
(H
O)
1ꢁTHF
2.065
1.954
2.285
1.401
2
2
2
]{O
2
P(OPh)
2
}
2
V–Owater
V–Cp
V–C
2.050
1.963
2.297
1.402
C–C
O–V–O
Cp–V–Cp
84.2
133.0
81.7
133.1
a
The crystal structure of this complex is composed of two crystallographically
independent mononuclear cations and the parameters of both cations have been
taken into account for the comparison.
b
All values, except the O–V–O and Cp–V–Cp angles for 1ꢁTHF, are mean values.
Complex 1ꢁTHF is the second structurally characterized com-
Fig. 1. Labeled PovRay representation of the cation [V(Cp)
2
(H
2
O)
2
]2+ of complex
2+
IV
plex containing the cation [V(Cp)
[
2 2 2
(H O) ] ; the first one is
1
ꢁTHF with the atom numbering scheme. Colour scheme: V , olive green; O, red; C,
V(Cp) (H O) ]{O P(OPh) [10] mentioned in the introduction.
2
2
2
2
2 2
}
gray; H, purple. (For interpretation of the references to colour in this figure legend,
the reader is referred to the web version of this article.)
The molecular structures of the pseudotetrahedral cations of the
two compounds are very similar. Rather than discuss similarities,
we list in Table 4 typical structural parameters for the cations of
the two complexes. The remarkable similarity of the molecular
structures is clearly evident. Obviously, the replacement of
3ꢀ
CF
3
SO groups are typical for the uncoordinated triflate anion
[
26,28,35]. They adopt a staggered-ethane configuration about
the S-–C bond; as in other structures containing ionic triflates,
the O–S–O [average: 115.0(1)°] and F–C–S [average: 111.4(2)°] an-
gles are greater than 109°, while the F–C–F [average: 107.5(2)°]
and O–S–C [average: 103.2(1)°] are less than 109°.
ꢀ
ꢀ
CF
3
SO
3
by (OPh)
2
PO
2
has no effect on the structure of the
cations.
Two oxygen atoms of one triflate anion [O(14), O(16)] partici-
4. Concluding comments and perspectives
pate in hydrogen bonds to vanadium-bound water molecules
2+
[
O(1W), O(2W)] from two different [V(Cp)
ducing an infinite, zig-zag chain throughout the crystal lattice
Fig. 2). Their parameters are in the range of hydrogen bonds of
2
(H
2
O)
2
]
cations, pro-
The present work extends the body of results that emphasize
the fact that the reactivity chemistry of the compounds
[M(Cp) X ] (M = Ti, Zr, Hf, V; X = halide or pseudohalide) can lead
(
2
2
medium strength. Atom O(2W) also acts as a hydrogen bond donor
to an oxygen atom [O(12)] of the second triflate anion, thus provid-
ing a third indirect binding of the V atom to the triflate groups via
a water bridge. Finally, one of the bound water molecules [O(1W)]
forms a weak hydrogen bond with the heavily disordered oxygen
atom of the THF solvate molecule.
to interesting products. Compound 1ꢁTHF, described in this work,
2+
is only the second complex containing the cation [V(Cp) (H O) ]
2
2
2
.
IV
From the synthetic inorganic chemistry viewpoint, we have further
developed the use [35–37] of the THF-soluble salt Ag(CF SO ) for
3
3
IV
ꢀ
the preparation of M /Cp complexes containing coordinated
[35,36] or purely ionic [34] triflates.
Fig. 2. Capped stick representation of one 1D zig-zag chain created by hydrogen bonds in the crystal structure of 1 c˙ THF. Colour scheme: VIV, olive green; O, red; C, gray; S,
blue; F, yellow. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

T.C. Stamatatos et al. / Inorganica Chimica Acta 394 (2013) 747–751
751
As far as future perspectives are concerned, we currently try to
use 1ꢁTHF as a convenient starting material for reactions with
bridging organic ligands, including diols [38,39] and 2-pyridyl oxi-
mes [40], in an attempt to synthesize mixed organometallic/coor-
dination clusters of V. We are also performing reactions between
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II
II
1
ꢁTHF or [V(Cp)
2 2
Cl ] (the ‘‘metal’’) and mononuclear Ni or Co /2-
pyridyl oximate complexes containing free oxygen sites (the ‘‘li-
gand’’) [41] for the synthesis of V/Co and V/Ni clusters using the
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Appendix A. Supplementary material
[
[
[
[
CCDC 883853 contains the supplementary crystallographic data
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