Use of organomolybdenum compounds for promoted hydrolysis of phosphoester bonds in aqueous media

Article abstract of DOI:10.1002/ejic.201402071

The dissolution of the indenyl (Ind) complex [{(η⁵-Ind) Mo(CO)₂(μ-Cl)}₂] (1) in N,N'-dimethylformamide (DMF) gives the ring-slipped complex [(η³-Ind)Mo(CO) ₂Cl(DMF)₂] (2). The aerial oxidat

Full text of DOI:10.1002/ejic.201402071

FULL PAPER
DOI:10.1002/ejic.201402071
Use of Organomolybdenum Compounds for Promoted
Hydrolysis of Phosphoester Bonds in Aqueous Media
[
a]
[b,c]
[a]
Ana C. Gomes, Carla A. Gamelas,
José A. Fernandes,
[a]
[d]
[a]
Filipe A. Almeida Paz, Patrique Nunes, Martyn Pillinger,
Isabel S. Gonçalves, Carlos C. Romão, and Marta Abrantes*
[a]
[b]
[d]
Keywords: Indenyl ligands / Molybdenum / Coordination modes / Oxido ligands / Phosphoesters / Hydrolysis
5
The dissolution of the indenyl (Ind) complex [{(η -Ind)-
drolysis in para-nitrophenylphosphate (pNPP), which was
used as a model substrate. The reactions were performed in
aqueous solution at 55 °C and followed by 1H NMR spec-
troscopy. For assays performed with 30–100 mol-% of 1 or 3
relative to pNPP, both compounds promote the production of
para-nitrophenol (pNPh) from pNPP. Compound 3 is espe-
cially active in promoting the hydrolytic cleavage of the
phosphoester bond (t1/2 Ͻ 80 min).
Mo(CO)
gives the ring-slipped complex [(η -Ind)Mo(CO)
2). The aerial oxidation of 2 leads to the formation of the
dinuclear oxomolybdenum(V) chloride [Mo (DMF)
μ-O) Cl ] (3). The structures of 2 and 3·DMF have been de-
2 2
(μ-Cl)} ] (1) in N,NЈ-dimethylformamide (DMF)
3
2
2
Cl(DMF) ]
(
2
O
2
4
-
(
2
2
termined by single-crystal X-ray diffraction. Compounds 1
and 3 were examined as promoters of phosphoester bond hy-
Introduction
transition metals to phosphoester bond hydrolysis has been
[
4]
[5,6]
[7–10]
studied for a few examples, such as Ti, V,
Mn,
Organophosphate pesticides are the most significant
cause of severe toxicity and death from acute poisoning
worldwide and are responsible for more than 200000 deaths
[
11]
[12–23]
Zr, and Mo,
but still remains largely unexplored.
Molybdenum is an essential trace element for plant
growth, and molybdenum oxides are commonly used as fer-
tilizers to avoid molybdenum deficiencies in soils world-
each year in developing countries.[
1,2]
Moreover, their ac-
cumulation in the environment is a recognized ecological
threat and they have harmful effects on human beings and
other mammalian species owing to possible long-term ex-
[
24]
wide; therefore, molybdenum compounds are interesting
candidates for the metal-promoted hydrolysis of phospho-
esters. The use of molybdenum compounds as hydrolysis-
promoting agents of phosphoesters has been reported with
posure to sublethal doses.[
3]
Chemically, organophosphate pesticides are esters of
phosphoric acid (phosphoesters). Hydrolysis products of
organophosphate pesticides are either nontoxic or have a
molybdenocene derivatives [CpЈ MoCl ] (CpЈ = substituted
2
2
[
12–15]
cyclopentadienyl),
[MoO Cl L] and [MoO Me L]
2 2 2 2
[
3]
complexes (L = no ligand, mono-, or bidentate li-
substantially lower toxicity than the original substrates.
[
22,23]
[16–20]
gands),
molybdates,
polyoxometalate deriva-
Thus, hydrolysis is considered to be a possible strategy to
eliminate organophosphate pesticides. In the absence of a
catalyst or enzyme, phosphoester hydrolysis may be ex-
tremely slow under normal conditions. For this reason, over
[
17,21,22]
tives,
ganic hybrids.
The effect of molybdates on phosphoester hydrolysis was
and molybdenum oxide based inorganic–or-
[
23]
time, a growing interest in the metal-promoted hydrolysis originally studied in the context of analytical colorimetric
of phosphoesters has arisen. The application of group 4–7 methods for organic phosphate estimation during the
[
25–27]
1950s.
To study the analytical interferences between
[
[
a] Department of Chemistry, CICECO, University of Aveiro,
Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
b] Instituto de Tecnologia Química e Biológica da Universidade
Nova de Lisboa,
organic and inorganic phosphates, these studies were con-
ducted on a wide variety of substrates. More recently, a
growing interest in the biological activity of molybdenum
compounds and their interactions with phosphate-contain-
ing biomolecules has arisen. These studies are typically con-
Av. da República, Estação Agronómica Nacional, 2780-157
Oeiras, Portugal
[
[
c] Escola Superior de Tecnologia, Instituto Politécnico de Setúbal,
2
910-761 Setúbal, Portugal
ducted with model substrates such as para-nitrophenylphos-
d] Centro de Química Estrutural, Complexo Interdisciplinar,
Instituto Superior Técnico, Universidade de Lisboa,
[12,13,18,22,23]
phate (pNPP),
2-hydroxypropyl-4-nitrophenyl
[
20]
[18]
1
049-001 Lisbon, Portugal
phosphate (HPNP),
phenylphosphate,
bis(para-nitro-
E-mail: marta.abrantes@ist.utl.pt
[12]
[15]
phenyl)phosphate, and dimethylphosphate. Reports of
studies performed with biological substrates are limited to
http://cqe.ist.utl.pt/pages/marta_abrantes.php
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201402071.
[
16,17,21]
adenosine triphosphate (ATP).
Eur. J. Inorg. Chem. 2014, 3681–3689
3681
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
As part of our ongoing work to explore molybdenum DMF molecule. The NMR spectra obtained shortly after
complexes for the promoted hydrolysis of phosphoesters, we dissolving 1 in [D ]DMF show only the presence of 2. At
7
1
have now studied the performance of the dimeric chloride room temperature, the H NMR spectrum shows rather
5
complex [{(η -Ind)Mo(CO) (μ-Cl)} ] (1; Ind = indenyl) as broad peaks, which suggests that there are extensive dy-
2
2
a hydrolysis-promoting agent of pNPP in aqueous media. namic structural interconversions (Figure lb). The broaden-
Compound 1 is of interest for this reaction owing to its ing of the signals is even more pronounced at 55 °C (Fig-
possession of Cl ligands, which are prone to hydrolysis and ure 1a). At –10 °C (Figure 1c), the spectrum becomes well
substitution by oxygen ligands. Furthermore, indenyl com- resolved, and sharp resonances are observed for the indenyl
plexes are potentially interesting as catalyst precursors ow- protons 1-H and 3-H (doublet), 2-H (triplet), and 5-H/8-H
ing to the propensity of this ligand to undergo haptotropic
5
3
shifts (i.e., ring slippage from η to η hapticity) induced by
electrochemical reduction or ligand addition. This hapto-
flexibility plays an important role in many catalytic pro-
[
28–30]
cesses.
In this study, we further report that the dissolution of
1
in N,N-dimethylformamide (DMF) gives the ring-slipped
3
complex [(η -Ind)Mo(CO) Cl(DMF) ] (2), which sub-
2
2
sequently can undergo aerial oxidation to give the dinuclear
oxomolybdenum(V) chloride [Mo O (DMF) (μ-O) Cl ] (3).
2
2
4
2
2
Compound 3 was also examined as a hydrolysis-promoting
agent, and the results are compared with those obtained for
Mo(CO) and [MoO Cl (DMF) ].
6
2
2
2
Results and Discussion
Synthesis
5
The indenyl complex [{(η -Ind)Mo(CO) (μ-Cl)} ] (1)
2
2
was synthesized in nearly quantitative yield by the reaction
Scheme 1. Synthesis of 2 and 3 from 1.
5
3
of [(η -Ind)Mo(η -C H )(CO) ] with HCl (1 m in diethyl
3
5
2
ether) in dichloromethane at room temperature. The
method is particularly attractive as the allyl precursor is
3
conveniently available from [Mo(η -C H )Cl(CO) -
3
5
2
[31,32]
(
NCMe) ] and KInd in almost quantitative yield.
Re-
2
cently, Honzí cˇ ek et al. isolated dimeric 1 after bubbling
5
gaseous HCl through
a
solution of [(η -Ind)Mo-
3
[33]
(
η -C H )(CO) ].
Under similar reaction conditions,
3 5 2
bubbling gaseous HCl through the solution at a high flow
rate instead of HCl (1 m in diethyl ether) in a more con-
5
trolled reaction produces [(η -Ind)Mo(CO) Cl ] in excellent
2
3
[
34]
yield.
In the solid state, 1 is stable to air and moisture
1
3
for several hours. The solid-state C cross-polarization
magic angle spinning (CP MAS) NMR spectrum presents
the indenyl signals with chemical shifts characteristic of the
η -coordination mode, which are similar to those observed
for other η -indenyl ligands such as those in [(η -Ind)-
5
5
5
2
[35]
5
3
Mo{κ -S P(OEt) }(CO) ]
(
and [(η -Ind)Mo(η -C H )-
2
2
2
3 5
[
36]
CO)2].
Compound 1 can be dissolved in DMF to give a brown
solution. The color change is due to the immediate forma-
3
tion of [(η -Ind)Mo(CO) Cl(DMF) ] (2, Scheme 1). Ac-
2
2
cordingly, the addition of diethyl ether, pentane, or n-hex-
ane to the freshly prepared (30 min) solution results in the
immediate precipitation of 2 as a brown solid rather than
the dimeric complex 1. The IR spectrum of 2 shows two
–
1
strong ν(CO) absorptions at 1830 and 1934 cm (cf. 1851
1
Figure 1. H NMR spectra recorded at (a) 55 °C, (b) room tem-
–
1
–1
and 1954 cm for 1) and a very strong band at 1638 cm
for the carbonyl stretching vibration of the coordinated in [D
perature, and (c) –10 °C of the solution obtained after dissolving 1
7
]DMF.
Eur. J. Inorg. Chem. 2014, 3681–3689
3682
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
and 6-H/7-H (two multiplets). The pattern of signals for the 2.2268(10) Å ranges, respectively, and the unique Mo–Cl
3
indenyl protons is very similar to that found for [(η -Ind)- distance is significantly longer at 2.4747(4) Å (see Figure 2
[37]
3
Mo(CO) (DMF) ]BF . The η -coordination mode of the and Table S1). The cis and trans octahedral angles are in
2
3
4
indenyl ligand in these complexes is evident mainly from the 75.91(6)–105.42(5)° and 171.10(5)–173.8° ranges,
the resonance of the proton in the 2-position. For 2, this respectively. The wide distribution of the former angles with
signal appears at lower field (δ = 7.10 ppm) than the signals respect to the ideal value is attributed to the very distinct
of the protons of the six-membered ring of the indenyl li- nature and steric impediment of the various organic ligands
5
gand (5-H to 8-H: δ = 6.28, 6.36 ppm), whereas η -indenyl that compose the metal coordination sphere, which ulti-
molybdenum compounds have the signal of 2-H at higher mately lead to a diversity of angles to minimize mutual ste-
[
35]
field.
ric repulsion.
In a separate experiment, compound 1 was dissolved in
The hinge angle (HA), fold angle (FA), and ΔMo–C are
DMF, and the solution was layered with pentane and important parameters to characterize the coordination
II
[40,41]
diethyl ether. After storage in a fridge for 3 d under air, mode of the indenyl ligand to the Mo metal center.
red crystals of the known dinuclear oxomolybdenum(V) For 2, these parameters were calculated as HA = 23.23(16)°,
chloride [Mo O (DMF) (μ-O) Cl ] (3) were obtained FA = 24.13(15)°, and ΔMo–C = 0.764 Å and clearly sup-
2
2
4
2
2
3
(
Scheme 1). Compound 3 was previously isolated by Agu- port the η -hapticity of the indenyl ligand. Each pair of
ado et al. after slow diffusion of diethyl ether into a solution neutral CO and DMF ligands is mutually cis in the equato-
[38]
II
of [MoO Cl (DMF) ] and PPh in DMF.
The isolation rial positions in the coordination octahedron of Mo . The
2
2
2
3
of 3 is in line with a previous report by Sarkar and co- geometric orientations of the DMF ligands are different
3
workers in which the aerial oxidation of [Mo(η -C H )- from each other, mainly because of distinct supramolecular
3
5
Cl(CO) (L)] [L = bis(3,5-dimethylpyrazolyl)methane] gave contacts: one DMF ligand is not engaged in any structur-
2
the dimeric oxomolybdenum(V) complex [Mo O (L) (μ-O) - ally relevant contacts, whereas the other participates both
2
2
2
2
[
39]
Cl2]. We may conclude that the dissolution of 1 in DMF in C–H···O and in C–H···π interactions (see Table S1).
initially gives 2, which slowly transforms into 3 in the pres- A remarkable feature of 2 concerns the unusual metal
ence of oxygen. Accordingly, the H NMR spectrum of an coordination environment. A search in the literature reveals
1
aged (4 d) solution of 1 in [D ]DMF showed no signals for that only three other monometallic structures of the type
7
5
n
the η -indenyl group and the appearance of several weak [CpЈMoL X] (CpЈ is any substituted cyclopentadienyl, L is
signals between δ = 6.4 and 7.6 ppm, which may be assigned any neutral κ ligand, and X is any halogen; no restrictions
4
1
[
42]
to indene.
on the value of n) exist.
Among the compounds of this
type, 2 stands out because it is neutral and is the first to
3
have carbonyl or indenyl ligands and η -hapticity for the
CpЈ ring.
Crystal-Structure Descriptions
As for 2, 3 also crystallizes in the centrosymmetric tri-
Compound 2 crystallizes in the centrosymmetric triclinic
space group P1, and the asymmetric unit is composed of a
¯
clinic space group P1, and the asymmetric unit is composed
of whole dimeric molecular unit formulated as
Mo O (DMF) (μ-O) Cl ] (see Figure S2). In addition, the
¯
a
3
whole [(η -Ind)Mo(CO) Cl(DMF) ] molecular complex, as
2
2
[
3
2
2
4
2
2
depicted in Figure 2. Considering the center of the η -group
as a coordination site, the coordination environment
around the metal center is best envisaged as a highly dis-
torted octahedron. The Mo–Ccarbonyl and Mo–O distances
are in the 1.9383(15)–1.9504(15) Å and 2.2223(10)–
asymmetric unit contains a free DMF molecule, which is
disordered over two distinct crystallographic sites (rates of
occupancy of 0.80:0.20) that share the same position for the
nitrogen atom. Complex 3 has already been described by
Aguado et al. in a crystal structure without the presence of
[
38]
the solvent molecule of crystallization.
Indeed, the two
dimeric [Mo O (DMF) (μ-O) Cl ] complexes are structur-
2
2
4
2
2
ally very similar (see Table S2 for geometrical details of the
coordination environments), and small differences only
occur in the conformations of the coordinated DMF mol-
ecules (to accommodate the disordered solvent molecule of
crystallization in the crystal structure). Except for a large
number of weak hydrogen-bonding interactions of the type
C–H···O and C–H···Cl, the crystal structure of 3·DMF is
devoid of noticeable supramolecular interactions (see Table
S3).
Crystal packing diagrams for 2 and 3·DMF are given in
the Supporting Information (Figures S1 and S3).
Figure 2. The asymmetric unit of 2. Non-hydrogen atoms are repre-
sented as thermal ellipsoids drawn at the 50% probability level,
and hydrogen atoms are represented as small spheres with arbitrary
Phosphoester Bond Hydrolysis
II
Sodium para-nitrophenylphosphate (pNPP) was used as
radii. For selected bond lengths and angles of the Mo coordina-
tion sphere, see Table S1.
a model substrate for the phosphoester bond hydrolysis re-
Eur. J. Inorg. Chem. 2014, 3681–3689
3683
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
1
action (Scheme 2). Initially, 1 was used as the hydrolysis- 30 h. Over time, the H NMR spectra of the reaction solu-
promoting agent (30–100 mol-% relative to pNPP), and the tions show that the amount of pNPP (doublets at δ = 8.21
1
reactions were followed by H NMR spectroscopy as de- and 7.31) decreases with the concomitant increase of the
scribed recently for the study with [MoO Cl L] and hydrolysis product para-nitrophenol (pNPh, doublets at δ =
2
2
[
22,23]
[
MoO Me L] derivatives.
The reaction progression can 8.15 and 6.89; Figure 4). Peaks relative to the promoter are
2
2
[18]
be monitored by UV/Vis spectroscopy,
NMR spec- not easily distinguished in the studied spectra owing to its
In this work, NMR low solubility in the reaction medium (a biphasic solid–li-
[
12,15–18,20–23]
[16]
troscopy,
and HPLC.
spectroscopy was chosen owing to its ability to provide in- quid system is formed). Interestingly, a peak at δ ≈ 7.20 ppm
formation not only about the pNPP decay and correspond- is present after 43.7 h of reaction (marked with an asterisk
ing reaction products but also about the molybdenum pro- in Figure 4). The singular character of this peak led us to
moter.
think that it may correspond to a transitory reaction species
as previously reported for [MoO Cl (DMF) ] and Na -
2
2
2
2
[
22]
MoO (transitory peak at δ = 7.80 ppm).
4
Scheme 2. Hydrolysis of para-nitrophenylphosphate (pNPP) to give
para-nitrophenol (pNPh).
At 55 °C and with D O as solvent, 30 mol-% of 1 pro-
2
motes the hydrolysis of pNPP (Figure 3). Although it was
not possible to fit a simple kinetic model to our experimen-
tal data, t1/2 can be estimated as ca. 100 h under these reac-
tion conditions. An increase in the amount of promoter
from 30 to 100 mol-% has a beneficial impact on the hydrol-
ysis reaction rate. In this case, t1/2 is estimated to be ca.
1
Figure 4. H NMR spectra of the hydrolysis of pNPP in the pres-
ence of 100 mol-% of 1 relative to pNPP. Reaction conditions:
2
55 °C, D O, dioxane as internal standard.
A comparison of the reaction profiles with that of the
blank reaction (performed in the absence of any metal com-
plex) at 55 °C clearly shows that the hydrolysis reaction is
accelerated by the presence of the molybdenum complex 1
(Figure 3). The blank reaction progresses slowly, and a
modest hydrolysis of 10% is achieved even after 13 d.
Mo(CO) was also tested as a hydrolysis promoter. How-
6
ever, its activity is equivalent to that for the blank reaction.
In comparison to the promoter [MoO Cl (DMF) ],
2
2
2
which is one of the best-performing representatives of the
MoO Cl L] complexes previously studied in our
[
2
2
[
22,23]
Figure 3. Hydrolysis profile of pNPP either in the absence of pro- group,
moter (ϫ) or with 100 mol-% of Mo(CO) (᭝), 30 (᭺) or 100 (+) moting the hydrolytic cleavage of the phosphoester bond
mol-% of 1, 100 mol-% of [MoO Cl (DMF)
of 3 (᭛). Reaction conditions: 55 °C, D O, dioxane as internal
standard. Reaction pD values: 7.41 for the blank reaction and
Mo(CO) , 6.41 for 30 mol-% of 1, 5.41 for 100 mol-% of 1, 1.41
for [MoO Cl (DMF) ] and 3.
compound 1 is two times more efficient in pro-
6
2
2
2
] (ᮀ), or 100 mol-%
{
6
1: t1/2 ≈ 30 h; endpoint ≈ 175 h; [MoO Cl (DMF) ]: t
≈
2
2
2
1/2
2
0 h; endpoint ≈ 350 h; Figure 3). However, it is important
to mention that the mol-% of molybdenum for 1 is two
6
2
2
2
times higher than in the case of [MoO Cl (DMF) ].
2
2
2
Eur. J. Inorg. Chem. 2014, 3681–3689
3684
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
[
Mo O (DMF) (μ-O) Cl ] (3) is a very efficient hydrolysis molybdate anions, namely, [Mo O
]2– (m = 17–22),[43,44]
3m+1
2
2
4
2
2
m
promoter with t1/2 Ͻ 80 min (remaining pNPP after 80 min which indicates that 1 is prone to hydrolysis of the indenyl
of reaction = 37%). Over time, and especially after hydroly- and Cl ligands and subsequent water condensation reac-
sis of 80% of pNPP, the reaction rate for the dimeric system tions. The positive ESI mass spectrum of 1b exhibits a peak
+
clearly slows down, and its profile merges with that for at m/z = 115, which is characteristic of [C H ] , a typical
9
7
metal-free ion in the mass spectra of indenyl derivatives.[
45]
[
MoO Cl (DMF) ].
2
2
2
These results are interesting in the context of the pre- In the positive ESI mass spectrum, a mixture of peaks with
viously reported data with group 4–7 transition metals. Al- a characteristic isotopic distribution for monomeric Mo-
though comparison of performance with promoters studied containing species is also present. Further studies will be
in different research groups is very difficult owing to the needed to unambiguously identify these species.
variability between substrates, reaction conditions, and out-
put measures, some qualitative considerations can still be phasic brown system. In addition to peaks for pNPP and
Phosphoester hydrolysis assays with 3 lead to a mono-
1
made.
pNPh, the H NMR spectrum of the hydrolysis reaction
One important advantage of the system described here is shows peaks of DMF, which originate from the metal pro-
the amount of promoter used (60–200 mol-% of Mo relative moter (δ = 7.93, 3.02, and 2.86 ppm). Over time, a new set
to pNPP). Previous studies of phosphoester hydrolysis of of singlets appears at δ = 8.24 and 2.72 ppm, which can be
pNPP promoted by group 4–7 transition metals have gen- assigned to formic acid (FA) and the dimethylammonium
erally been performed with a large excess of metal in rela- (DMA) cation, respectively. The appearance of these peaks
4
5
tion to the substrate: between 1.1ϫ10 and 3.3ϫ10 mol- had already been reported in our previous work with
+
[12,15]
[22]
%
of Mo relative to pNPP for [CpЈ Mo(OH)(H O)] ,
[MoO Cl (DMF) ].
Both [MoO Cl (DMF) ] and com-
2
2
2
2
2
2 2 2
3
4
between 6.8ϫ10 and 3.4ϫ10 mol-% of Mo relative to pound 3 lead to acidic solutions with a pD of 1.41, which
[27]
between 4ϫ103 and can be attributed to the hydrolysis of the Mo–Cl bonds and
pNPP for [(NH ) (MoO )],
6
4
2
4
3
ϫ10 mol-% of Ti relative to pNPP for titanocene deriva- the formation of HCl. Under these conditions, the degrada-
[
4]
3
tives (CpЈ TiCl ), 1ϫ10 mol-% of V relative to pNPP for tion of DMF to give FA and DMA ions is likely ac-
2
2
4
–
5–
6– [5,6]
polyoxovanadates ([V O ] , [V O ] , and [V O ] ),
celerated. Interestingly, the appearance of the NMR peaks
4
4
12
5
15
4
10 28
and between 1.4ϫ10 and 3.6ϫ10 mol-% Mn relative to of FA and DMA ions (starting at 44 h) coincides with the
[
7]
pNPP for MnO2. Exceptions, in which the reactions were slowing down of the reaction. The negative-ion ESI mass
performed with catalytic or equimolar amounts of metal spectrum of a solution obtained after stirring 3 with water
compound relative to pNPP include (1) the reports by Pa- at 55 °C for 48 h shows, among others, multiple peaks of
rac-Vogt and co-workers with 70 mol-% of Mo with poly- polymeric Mo-containing species, namely, a series of poly-
[
18]
2–
oxomolybdates
and (2) our reports with 10–100 mol-% oxomolybdate [Mo O3m+1] anions (m = 15–22), similar to
m
of Mo with [MoO X L] derivatives (X = Cl, Me) for the 1b.
2
2
[
22,23]
substrate pNPP.
Very recently, Hupp et al. reported the
use of the Zr-based metal–organic framework (MOF) UiO-
6 for the hydrolysis of a methylated version of pNPP Conclusions
6
(
methyl paraoxon) with an exceptionally low load of access-
We have reported that the dissolution of the dimeric
ible metal (0.27 mol-% of Zr) derived from the use of
3
5
chloride complex [{(η -Ind)Mo(CO) (μ-Cl)} ] (1) in DMF
6 mol-% of Zr relative to methyl paraoxon.[
11]
2
2
3
gives the ring-slipped complex [(η -Ind)Mo(CO) Cl-
2
The best results with molybdenum were obtained for re-
(
DMF) ] (2). The mild aerial oxidation of 2 leads to the
2
actions performed with molybdenocenes at 20 °C, which af-
forded half-times in the same range as that obtained with 3
dinuclear oxomolybdenum(V) chloride [Mo O (DMF) -
2
2
4
(
μ-O) Cl ] (3). Complexes 1 and 3 can be used directly as
[
12,13,15]
2 2
(t1/2 Ͻ 1 h).
However, in addition to high Mo/pNPP
precursors to hydrolytically active species for the phospho-
ester bond cleavage of para-nitrophenylphosphate in aque-
ous solution to give inorganic phosphate and para-nitro-
phenol as the products of hydrolysis. The mechanism and
the scope of this reaction are being investigated in detail
4
5
molar ratios (between 1.1ϫ10 and 3.3ϫ10 mol-% rela-
tive to pNPP), the molybdenocenes have an imperative
requirement for an inert atmosphere (no reaction occurs
under air). This inert atmosphere requirement does not ex-
ist for all the other reported systems including ours.
To understand the stability and reactivity of 1 and 3 in
the reaction medium (water), stability tests were also per-
formed (see Experimental Section for details). After 48 h of
stirring 1 in the presence of water at 55 °C for 48 h, a bi-
phasic solid–liquid system was obtained [solid (1a), liquid
(
for example, with other substrates such as toxic organo-
phosphate esters) and will be reported in due course. The
behavior of 1 upon dissolution in other solvents is also be-
ing further investigated.
(
1
1b)]. The solid 1a was identified by FTIR spectroscopy as
in 70% yield, which indicates that 1 has a low solubility
Experimental Section
in water (as already detected in the hydrolysis assays) and Materials and Methods
that the solid is not moisture sensitive. The solution 1b was
Microanalyses (CHN) were obtained with a Truspec instrument at
analyzed by ESI mass spectrometry. The negative-ion the University of Aveiro by M. Marques, and the Mo contents
ESI mass spectrum of 1b exhibits one series of polyoxo- were determined by inductively coupled plasma optical emission
Eur. J. Inorg. Chem. 2014, 3681–3689
3685
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
1
3
1
spectroscopy (ICP-OES) at C.A.C.T.I., University of Vigo, Spain.
FTIR and FTIR (ATR) spectra were recorded with a Bruker Ten-
7
[D ]DMF, 263 K): δ C/δ H = 123.8/6.28 (C-5, C-8/C-6, C-7),
117.2/6.36 (C-5, C-8/C-6, C-7), 104.4/7.10 (C-2), 73.5/4.86 (C-1,
C-3) ppm.
–1
sor 27 spectrophotometer in the 350–4000 cm range with 256
scans and 4 cm–1 resolution. FT-Raman spectra were recorded with
a Bruker RFS 100 spectrometer with a Nd:YAG coherent laser (λ
3
[
(η -Ind)Mo(CO)
2
Cl(DMF)
2
] (2): Compound 1 (0.1 g, 0.17 mmol)
was dissolved in DMF (5 mL), and the solution was stirred for
0 min at room temperature under nitrogen. To the brown solution,
a layer of diethyl ether was added (10 mL), followed by pentane
30 mL) and n-hexane (30 mL). After 10 min, the colorless solution
was filtered, and the brown residue was washed with pentane (3ϫ
0 mL) and vacuum-dried. Yield: 0.14 g (90%). C17 21ClMoN
448.75): calcd. C 45.50, H 4.72, N 6.24; found C 44.98, H 4.41, N
1
13
1
1
1
1
13
=
1064 nm). H, C{ H}, H– H COSY and H– C heteronuclear
3
multiple quantum coherence (HMQC) NMR spectra were recorded
with Bruker Avance II+ 300 and 400 MHz (UltraShieldTM Mag-
(
1
3
net) spectrometers. Solid-state magic angle spinning (MAS)
C
NMR spectra were recorded at 100 MHz with a Bruker Avance
2
H
2 4
O
1
4
00 spectrometer with 3 μs H 90° pulses, 2 ms contact time, a spin-
(
ning rate of 10 kHz, and 3 s recycle delays. Chemical shifts are
quoted in parts per million from tetramethylsilane. Electrospray
ionization (ESI) mass spectra were obtained with a 500-MS quad-
rupole ion trap mass spectrometer (Varian Inc., Palo Alto, CA,
USA). Samples were introduced into the ESI ion source by using
a syringe pump set to a flow rate of 20 μL/min. The ion spray
voltage was set at Ϯ5 kV, the capillary voltage was 60–80 V, and
the radio frequency (RF) loading was 80%. Nitrogen was used as
the nebulizing and drying gas at pressures of 35 and 10 psi, respec-
tively; the drying gas temperature was 350 °C. The spectra were
recorded in the range 100–1000 Da. The spectra typically corre-
spond to the average of 20–35 scans. The samples were dissolved
in Millipore deionized water immediately prior to the analysis.
5
1
.90. FTIR (ATR): ν˜ = 2935 (w), 1934 [vs, ν(CO)], 1830 [vs, ν(CO)],
638 (vs), 1494 (w), 1432 (m), 1421 (m), 1378 (m), 1365 (s), 1310
(
9
w), 1250 (w), 1150 (w), 1113 (m), 1060 (w), 1047 (m), 1014 (w),
65 (m), 915 (w), 885 (w), 778 (m), 747 (m), 687 (s), 579 (m), 551
–
1 1
(
w), 506 (m), 393 (s), 370 (s) cm . H NMR (300 MHz, [D
63 K): δ = 8.02 (s, CH), 7.10 (t, J = 6.2 Hz, 1 H, 2-H), 6.36 (m, 2
H, 5-H, 8-H/6-H, 7-H), 6.28 (m, 2 H, 5-H, 8-H/6-H, 7-H), 4.86 (d,
J = 6.2 Hz, 2 H, 1-H, 3-H), 2.95 (s, CH ), 2.78 (s, CH ) ppm.
7
]DMF,
2
3
3
Orange crystals of 2 suitable for X-ray diffraction were obtained
by slow diffusion of diethyl ether into a solution of 1 in DMF
under nitrogen.
2 2 4 2 2
[Mo O (DMF) (μ-O) Cl ] (3): Compound 1 (0.08 g, 0.13 mmol)
was dissolved in DMF (10 mL), and to this solution was added a
pentane (20 mL) layer followed by another layer of diethyl ether
Air-sensitive operations were performed by standard Schlenk tech-
niques under a nitrogen atmosphere. Solvents were dried by stan-
dard procedures [tetrahydrofuran (THF), diethyl ether, and n-hex-
ane over Na/benzophenone ketyl; dichloromethane over CaH ] and
2
distilled under nitrogen. 1 m HCl in diethyl ether (Sigma–Aldrich),
N,NЈ-dimethylformamide (DMF, 99%, Sigma–Aldrich), pentane
(
20 mL). The solution was kept in a fridge for 3 d under air; this
resulted in the formation of red crystals, which were identified as
. Yield: 0.05 g, 60%. C12 Mo (619.16): calcd. C 23.28,
H 4.56, N 9.05; found C 22.96, H 4.68, N 8.85. FTIR (ATR): ν˜ =
939 (w), 1632 (vs), 1439 (w), 1438 (m), 1366 (m), 1357 (m), 1250
3
H28Cl
2
2 4 8
N O
2
(
99%, Sigma–Aldrich), n-hexane (99%, Sigma–Aldrich), D
2
O
(
(
m), 1157 (w), 1122 (w), 1062 (w), 958 (vs), 940 (m), 868 (w), 802
w), 741 (m), 721 (m), 699 (m), 684 (s), 498 (m), 490 (m), 470 (m),
(
99.9%, Euroisotop), [D ]DMF (99.5%, Sigma–Aldrich), and 4-
7
nitrophenyl phosphate disodium salt hexahydrate (pNPP, 98%,
–1
3
84 (vs) cm . FT-Raman: ν˜ = 2939 (w), 1546 (m), 959 (m), 787
Alfa Aesar) were purchased from commercial sources and used as
–1
1
(
2
vs), 446 (w), 215 (m) cm . H NMR (300 MHz, [D
63 K): δ = 8.01 (s), 2.94 (s, CH ), 2.77 (s, CH ) ppm.
7
]DMF,
5
3
3 5 2
received. [(η -Ind)Mo(η -C H )(CO) ] was prepared as previously
reported.
3
3
[
31b]
Single-Crystal X-ray Diffraction
5
[
6
(
{(η -Ind)Mo(CO)
2
(μ-Cl)}
2
] (1): HCl (1 m) in diethyl ether (6.0 mL,
5
Single crystals of compounds 2 and 3·DMF were manually har-
vested from the crystallization vials and immediately immersed in
highly viscous FOMBLIN Y perfluoropolyether vacuum oil (LVAC
.00 mmol) was added dropwise to a solution of [(η -Ind)Mo-
η -C H )(CO) ] (0.51 g, 1.67 mmol) in CH Cl , and the reaction
3 5 2 2 2
3
mixture was stirred for 2 h at room temperature. The resultant red
brown precipitate was collected by filtration, washed with diethyl
140/13, Sigma–Aldrich) to avoid degradation caused by the evapo-
[46]
ration of the solvent.
The crystals were mounted on Hampton
ether, and vacuum dried. Yield: 0.49 g (98%). C22
605.13): calcd. C 43.66, H 2.33, Mo 31.71; found C 43.39, H 2.32,
Mo 32.09. FTIR (KBr): ν˜ = 3097 (w), 2056 (w), 1961 [vs, ν(CO)],
2 2 4
H14Cl Mo O
Research CryoLoops with the help of a Stemi 2000 stereomicro-
scope equipped with Carl Zeiss lenses. The data were collected with
a Bruker X8 Kappa APEX II CCD area-detector diffractometer
(
1862 [vs, ν(CO)], 1602 (w), 1542 (m), 1479 (m), 1446 (m), 1376 (m),
(
Mo-K
trolled by the APEX2 software package
Oxford Cryosystems Series 700 cryostream monitored remotely by
α
graphite-monochromated radiation, λ = 0.71073 Å) con-
1330 (m), 1240 (w), 1220 (w), 1153 (w), 1099 (w), 1037 (m), 984
[47]
and equipped with an
(
4
3
m), 902 (m), 829 (s), 745 (vs), 601 (m), 592 (m), 561 (m), 517 (m),
96 (m), 470 (w), 453 (m), 443 (s), 387 (w) cm . FT-Raman: ν˜ =
095 (w), 3070 (w), 3049 (w), 1951 (w), 1842 (m), 1545 (w), 1447
–1
[48]
using the software interface Cryopad.
Images were processed
with SAINT+,[ and the data were corrected for absorption by
49]
(w), 1376 (w), 1328 (vs), 1240 (w), 1160 (w), 1038 (w), 1006 (w),
[
50]
the multiscan semi-empirical method implemented in SADABS.
9
08 (w), 738 (w), 594 (w), 562 (w), 520 (w), 496 (m), 458 (w), 390
–
1
13
The structures were solved by using the Patterson synthesis algo-
(
m), 284 (m), 262 (w), 184 (w), 165 (s), 122 (vs), 106 (vs) cm .
CP MAS NMR: δ = 265.7 (CO), 259.2 (CO), 130.2 (C-8, C-9),
29.0 (C-5, C-6), 123.9 (C-4, C-7), 89.9 (C-2), 76.4 (C-1, C-3) ppm.
C
rithm implemented in SHELXS-97,[ which allowed the immedi-
51]
II
V
ate location of the crystallographically independent Mo or Mo
1
centers and most of the heaviest atoms. The remaining non-
hydrogen atoms were located from difference Fourier maps calcu-
lated from successive full-matrix least-squares refinement cycles on
The NMR spectroscopic data for a freshly prepared solution of 1
3
in [D
Cl(DMF)
7 2
]DMF showed only the presence of [(η -Ind)Mo(CO) -
1
2
[51b,52]
2
] (2). H NMR (300 MHz, [D
t, J = 6.2 Hz, 1 H, 2-H), 6.36 (m, 2 H, 5-H, 8-H/6-H, 7-H), 6.28
m, 2 H, 5-H, 8-H/ 6-H, 7-H), 4.86 (d, J = 6.2 Hz, 2 H, 1-H, 3-H) with an occupancy ratio of 0.8:0.2. The two disordered components
7
]DMF, 263 K): δ = 7.10 F by SHELXL-97.
The DMF molecule of crystallization in
(
(
3·DMF was disordered over two distinct crystallographic positions
1
3
1
7
ppm. C{ H} (126 MHz, [D ]DMF, 263 K): δ = 232.7 (CO), 148.3 were refined with isotropic displacement parameters for the non-
(
1
C-4, C-9), 123.8 (C-5, C-8/C-6, C-7), 117.2 (C-5, C-8/C-6, C-7),
hydrogen atoms, and the N–C, C–O, and C···C distances were re-
strained to be similar by using the SHELXL command SADI. Ad-
03.4 (C-2), 72.5 (C-1, C-3) ppm. 13C, H HSQC (126/300 MHz,
1
Eur. J. Inorg. Chem. 2014, 3681–3689
3686
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
ditionally, the central nitrogen atoms were found to be very close
and, therefore, were set to be coincident. All non-hydrogen atoms
composing the dimetallic neutral cluster were successfully refined
with anisotropic displacement parameters.
tacts in 2 and 3·DMF are summarized in Tables S1–S3 (Supporting
Information).
CCDC-963360 (for 2) and -963361 (for 3·DMF) contain the sup-
plementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Most of the hydrogen atoms bound to carbon atoms were placed
at their idealized positions by using appropriate HFIX instructions
in SHELXL: 33 for the –CH
groups of the aromatic rings and the N–CH–O groups. The
hydrogen atoms bound to the carbon atoms of the C ring of the
3
methyl group and 43 for the CH
Hydrolysis Reactions: Sodium para-nitrophenylphosphate (pNPP,
4
0
.0 mg, 0.01 mmol) and dioxane (internal standard, 1.2 mg,
.013 mmol) were dissolved in deuterated water in a 5 mm NMR
5
indenyl ligand in 2 appeared to adopt inaccurate positions when
the HFIX 43 command was used. Therefore, the positions of these
atoms were refined with C–H distances restrained to 0.95(1) Å.
When the HFIX instruction 33 was used for atom C-9 of 3·DMF,
a large electron density near the carbon atom remained unassigned.
Therefore, the HFIX 123 command (corresponding to two pairs of
hydrogen atoms with a mutual displacement of 60° and occupanc-
ies equal to 0.5) was used instead. All hydrogen atoms were in-
cluded in subsequent refinement cycles with isotropic thermal dis-
placement parameters (Uiso) fixed at 1.2ϫUeq (CH groups) or
tube containing a magnetic stirring bar and heated to 55 °C. The
molybdenum compound (variable amounts in the range 30–
1
00 mol-% relative to pNPP) was added, and the progression of
1
the reaction was monitored over time by H NMR spectroscopy.
Attention: The magnetic stirring bar was removed immediately be-
fore the NMR measurement, and then reintroduced immediately
after the measurement. The relative amounts of pNPP and para-
nitrophenol (pNPh) in the reaction medium were followed by quan-
tification of the respective areas in comparison to the area of the
internal standard. The pH of the solution was measured at the
described reaction temperature. The pD value of the solution was
obtained by adding 0.41 to the pH reading. Before the addition of
the catalyst, the reaction medium had a pD of 7.4. The addition of
1.5ϫUeq (methyl groups) of the parent carbon atoms.
The last difference Fourier map synthesis showed for 2 that the
–3
highest peak (0.402 eÅ ) was located at 0.73 Å from C9 (center of
–3
the indenyl ligand) and the deepest hole (–0.439 eÅ ) at 0.70 Å the metal complexes studied caused significant differences in the
–
3
from Mo1; for 3·DMF the corresponding peak (0.464 eÅ ) and
pD of the reaction medium. The reactions were not buffered so
that the real impact of each compound per se in the hydrolysis
reaction could be understood. The authors are aware that the pD
may influence the performance of the systems and that it is difficult
to distinguish between the effect of pH and the effect of metal
promoter. However, we would like to recall that it is the behavior
–3
hole (–0.525 eÅ ) were found at 1.79 Å from C18 and 1.11 Å from
Mo1, respectively. Information concerning the crystallographic
data collection and structure refinement details is summarized in
Table 1. The most relevant geometrical parameters of the molybd-
enum coordination environments and of the supramolecular con-
Table 1. Crystal data and structure refinement details.
Compound
2
3·DMF
Formula
M
Temperature/K
Crystal system
Space group
a/Å
b/Å
c/Å
C
17
H
21ClMoN
2
O
4
C
12
H
28Cl
2
Mo
2
N
4
O
8
·C
3
H
7
NO
448.75
150(2)
triclinic
692.26
180(2)
triclinic
P1
9.6781(14)
11.0819(15)
14.128(2)
85.079(9)
75.962(9)
69.251(9)
1374.7(3)
2
¯
¯
P1
8.6448(6)
10.7816(9)
11.4577(9)
71.368(3)
72.342(2)
77.423(3)
955.59(13)
2
α/°
b/°
γ/°
Volume/Å3
Z
D
calcd./gcm–3
1.560
0.849
1.672
1.155
μ(Mo-K
α
)/mm–1
Crystal size/mm
Crystal type
θ range /°
0.11ϫ0.06ϫ0.02
red plate
1.94–29.26
0.10ϫ0.08ϫ0.06
orange block
3.32–25.35
–11Յ hՅ 11
–13Յ kՅ 13
–17Յ lՅ 17
25419
Index ranges
–11Յ hՅ 11
–
–
14Յ kՅ 14
14Յ lՅ 15
Reflections collected
Independent reflections
Data completeness
19118
5139 [Rint = 0.0235]
98.8% (to θ = 29.26°)
R1 = 0.0207
wR2 = 0.0469
R1 = 0.0249
wR2 = 0.0484
m = 0.0199
5033 [Rint = 0.0678]
99.7% (to θ = 25.35°)
R1 = 0.0385
wR2 = 0.0699
R1 = 0.0656
wR2 = 0.0799
m = 0.276
Final R indices [IϾ2σ(I)][
a,b]
Final R indices (all data) [a,b]
Weighting scheme[c]
n = 0.2981
0.402, –0.439
n = 0.7390
0.464, –0.525
Largest diff. peak and hole/ eÅ–3
|. [b] wR2 = {Σ[w(F 2
– F
2)2]/Σ[w(F
2 2
) ]} . [c] w = 1/[σ (F
1/2
2
2
) + (mP) + nP], where P = (F
2
2
+ 2F
c
2)/3.
[
a] R1 = Σ||F
o
| – |F
c
||/Σ|F
o
o
c
o
o
o
Eur. J. Inorg. Chem. 2014, 3681–3689
3687
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
of the metal promoter in deuterated water that defines the pD of
the system and that buffering the system would “mask” this reac-
tivity and, thus, the possible availability of species in solution. The
blank reaction was performed without molybdenum compound.
[11] M. J. Katz, J. E. Mondloch, R. K. Totten, J. K. Park, S. T.
Nguyen, O. K. Farha, J. T. Hupp, Angew. Chem. Int. Ed. 2014,
5
3, 497–501; Angew. Chem. 2014, 126, 507–511.
[
[
12] M. J. Kuo, S. Kuhn, D. Ly, Inorg. Chem. 1995, 34, 5341–5345.
13] L. Y. Kuo, L. A. Barnes, Inorg. Chem. 1999, 38, 814–817.
Stability Test for 1: Compound 1 (0.25 g, 0.41 mmol) and H
2
O
[14] L. Y. Kuo, N. M. Perera, Inorg. Chem. 2000, 39, 2103–2106.
(
35 mL) were added to a Schlenk tube. The resultant suspension
[15] T. J. Ahmed, L. N. Zakharov, D. R. Tyler, Organometallics
2
007, 26, 5179–5187.
was stirred at 55 °C for 48 h. The brown precipitate was isolated,
washed with water, and vacuum dried to afford the solid 1a. The
remaining pale orange filtrate was designated as 1b. The solid 1a
was characterized by FTIR spectroscopy and identified as [{(η -
Ind)Mo(CO)
[
[
16] E. Ishikawa, T. Yamase, J. Inorg. Biochem. 2006, 100, 344–350.
17] E. Cartuyvels, K. V. Hecke, L. V. Meervelt, C. Görller-Wal-
rand, T. N. Parac-Vogt, J. Inorg. Biochem. 2008, 102, 1589–
5
1
598.
18] E. Cartuyvels, G. Absillis, T. N. Parac-Vogt, Chem. Commun.
008, 85–87.
19] G. Absillis, R. V. Deun, T. N. Parac-Vogt, Inorg. Chem. 2011,
0, 11552–11560.
2 2
(μ-Cl)} ] (1). Yield: 0.18 g (70%). The filtrate 1b was
[
[
[
analyzed by ESI-MS.
2
Stability Test for 3: Compound 3 (0.6 g, 0.9 mmol) was deaerated,
and H O (10 mL) was added. The resultant solution was stirred for
8 h at 55 °C to afford the solution 3a, which was analyzed by ESI-
MS.
5
2
20] G. Absillis, E. Cartuyvels, R. V. Deun, T. N. Parac-Vogt, J. Am.
Chem. Soc. 2008, 130, 17400–17408.
4
[
[
21] E. Ishikawa, T. Yamase, Eur. J. Inorg. Chem. 2013, 1917.
22] C. Tomé, M. C. Oliveira, M. Pillinger, I. S. Gonçalves, M. Abr-
antes, Dalton Trans. 2013, 42, 3901–3907.
23] A. C. Gomes, M. Pillinger, P. Nunes, I. S. Gonçalves, M. Abr-
antes, J. Organomet. Chem. 2014, 760, 42–47.
24] U. C. Gupta (Ed.), Molybdenum in Agriculture, Cambridge
University Press, Cambridge, 1997.
Supporting Information (see footnote on the first page of this arti-
cle): Tables of selected bond lengths and angles for 2 and 3, geomet-
rical details of supramolecular contacts, crystal packing diagrams
for 2 and 3, the molecular structure of 3.
[
[
[
[
[
[
25] H. Weil-Malherbe, R. H. Green, Biochem. J. 1951, 49, 286–292.
26] H. Weil-Malherbe, Biochem. J. 1953, 55, 741–745.
27] L. Lutwak, J. Sacks, J. Biol. Chem. 1953, 200, 565–569.
28] M. J. Calhorda, C. C. Romão, L. F. Veiros, Chem. Eur. J. 2002,
8, 868–875.
Acknowledgments
This work was partly financed by FEDER (Fundo Europeu de
Desenvolvimento Regional) through COMPETE (Programa Op-
eracional Factores de Competitividade) and by national funds
through the FCT (Fundação para a Ciência e a Tecnologia) with
the projects CICECO (Centre for Research in Ceramics and Com-
posite Materials) – FCOMP-01-0124-FEDER-037271 (FCT ref.
[29] C. A. Bradley, I. Keresztes, E. Lobkovsky, P. J. Chirik, Organo-
metallics 2006, 25, 2080–2089.
[30] a) S. M. Bruno, C. A. Gamelas, A. C. Gomes, A. A. Valente,
M. Pillinger, C. C. Romão, I. S. Gonçalves, Catal. Commun.
2
012, 23, 58–61; b) S. M. Bruno, A. C. Gomes, C. A. Gamelas,
PEst-C/CTM/LA0011/2013),
FCOMP-01-0124-FEDER-029779
M. Abrantes, M. C. Oliveira, A. A. Valente, F. A. Almeida Paz,
(FCT ref. PTDC/QEQ-SUP/1906/2012, including the research
M. Pillinger, C. C. Romão, I. S. Gonçalves, New J. Chem. 2014,
grant with ref. BPD/UI89/4864/2013 to A. C. G.) – and the Centro
de Química Estrutural (PEst-OE/QUI/UI0100/2013). We further
wish to thank the FCT for specific funding towards the purchase
of the single-crystal diffractometer and for the postdoctoral grant
SFRH/BPD/63736/2009 (to J. A. F.). The authors are grateful to
M. C. Oliveira for the ESI-MS analysis. The NMR spectrometers
are part of The National NMR Network (REDE/1517/RMN/
38, 3172–3180.
[
31] a) J. R. Ascenso, C. G. Azevedo, I. S. Gonçalves, E. Herdtweck,
D. S. Moreno, C. C. Romão, J. Zühlke, Organometallics 1994,
13, 429–431; b) J. R. Ascenso, C. G. Azevedo, I. S. Gonçalves,
E. Herdtweck, D. S. Moreno, M. Pessanha, C. C. Romão, Or-
ganometallics 1995, 14, 3901–3919.
[
[
[
[
32] J. W. Faller, C.-C. Che, M. J. Mattina, A. Jakubowski, J. Or-
ganomet. Chem. 1973, 52, 361–387.
33] J. Honzí cˇ ek, J. Vinklárek, M. Erben, J. Lodinský, L. Dostál,
Z. Pad e˘ lková, Organometallics 2013, 32, 3502–3511.
34] M. G. B. Drew, V. Félix, I. S. Gonçalves, C. C. Romão, B.
Royo, Organometallics 1998, 17, 5782–5788.
2005), supported by POCI 2010 (Programa Operacional Ciência e
Inovação 2010) and the FCT. The authors also thank the Portug-
uese NMR Network (Instituto Superior Técnico Center) (RECI/
QEQ-QIN/0189/2012) for providing access to the NMR facilities.
35] M. J. Calhorda, C. A. Gamelas, I. S. Gonçalves, E. Herdtweck,
C. C. Romão, L. F. Veiros, Organometallics 1998, 17, 2597–
[
[
[
[
[
[
[
[
[
[
1] S. V. Kumar, M. Fareedullah, Y. Sudhakar, B. Venkateswarlu,
E. A. Kumar, Archiv. Appl. Sci. Res. 2010, 2, 199–215.
2] M. Eddleston, N. A. Buckley, P. Eyer, A. H. Dawson, Lancet
2611.
[
36] S. S. Braga, I. S. Gonçalves, A. D. Lopes, M. Pillinger, J. Ro-
cha, C. C. Romão, J. J. C. Teixeira-Dias, J. Chem. Soc., Dalton
Trans. 2000, 2964–2968.
2008, 371, 597–607.
3] M. Sirotkina, I. Lyagin, E. Efremenko, Int. Biodeterior. Biodeg-
rad. 2012, 68, 18–23.
[37] J. R. Ascenso, I. S. Gonçalves, E. Herdtweck, C. C. Romão, J.
Organomet. Chem. 1996, 508, 169–181.
4] A. Erxleben, J. Claffey, M. Tacke, J. Inorg. Biochem. 2010, 104,
[38] R. Aguado, J. Escribano, M. R. Pedrosa, A. D. Cian, R. Sanz,
F. J. Arnáiz, Polyhedron 2007, 26, 3842–3848.
390–396.
5] N. Steens, A. M. Ramadan, T. N. Parac-Vogt, Chem. Commun.
009, 965–967.
2
[39] V. S. Joshi, M. Nandi, H. Zhang, B. S. Haggerty, A. Sarkar,
Inorg. Chem. 1993, 32, 1301–1303.
[40] V. Cadierno, J. Díez, M. P. Gamasa, J. Gimeno, E. Lastra, Co-
ord. Chem. Rev. 1999, 147, 193–195.
[41] HA = angle between the medium planes subtended between
planes (C1–C3) and (C1, C3, C8, C9); FA = angle between the
medium planes subtended between planes (C1–C3) and (C4–
C9); ΔM–C = 0.5ϫ(dM–C8 + dM–C9) – 0.5ϫ(dM–C1 + dM–
C3).
6] N. Steens, A. M. Ramadan, G. Absillis, T. N. Parac-Vogt, Dal-
ton Trans. 2010, 39, 585–592.
7] D. S. Baldwin, D. R. Jones, L. M. Coleman, J. K. Beattie, Envi-
ron. Sci. Technol. 2001, 35, 713–716.
8] X. Jia-Qing, C. Yong, L. Ci, Z. Jiu-Jin, H. Wei, Z. Xian-Cheng,
J. Dispersion Sci. Technol. 2005, 26, 693–699.
9] W. Jiang, B. Xu, Q. Lin, J. Li, F. Liu, X. Zang, H. Chen, Col-
loids Surf. A 2008, 315, 103–109.
10] W. D. Jiang, B. Xu, J. Z. Li, J. Q. Xie, H. Y. Fu, H. Chen, X. C.
Zeng, J. Dispersion Sci. Technol. 2006, 27, 869–877.
[42] a) A. C. Filippou, W. Grünleitner, E. Herdtweck, J. Organomet.
Chem. 1989, 373, 325–342; b) C. J. Adams, K. M. Anderson,
Eur. J. Inorg. Chem. 2014, 3681–3689
3688
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
I. M. Bartlett, N. G. Connelly, A. G. Orpen, T. J. Paget, H.
Phetmung, D. W. Smith, J. Chem. Soc., Dalton Trans. 2001,
[48] Cryopad, Remote monitoring and control, Version 1.451, Oxford
Cryosystems, Oxford, 2006.
1284–1292; c) G. R. Willey, T. J. Woodman, M. G. B. Drew, J. [49] SAINT+, Data Integration Engine, version 7.23a, Bruker AXS,
Organomet. Chem. 1996, 510, 213–217.
Madison, 1997–2005 .
[50] G. M. Sheldrick, SADABS, version 2.01, Bruker AXS, Madi-
son, 1998.
[
[
43] D. K. Walanda, R. C. Burns, G. A. Lawrance, E. I. Von Nagy-
Felsobuki, J. Chem. Soc., Dalton Trans. 1999, 311–322.
44] L. Vilà-Nadal, E. F. Wilson, H. N. Miras, A. Rodríguez-
Fortea, L. Cronin, J. M. Poblet, Inorg. Chem. 2011, 50, 7811–
[
51] a) G. M. Sheldrick, SHELXS-97, Program for Crystal Struc-
ture Solution, University of Göttingen, 1997; b) G. M. Sheld-
rick, Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, 64,
7819.
112–122.
[
[
[
45] R. B. King, Can. J. Chem. 1969, 47, 559–568.
46] T. Kottke, D. Stalke, J. Appl. Crystallogr. 1993, 26, 615–619.
47] APEX2 Data Collection Software, Version 2.1-RC13, Bruker
AXS, Delft, 2006 .
[
52] G. M. Sheldrick, G. SHELXL-97, Program for Crystal Struc-
ture Refinement, University of Göttingen, Germany, 1997.
Received: February 17, 2014
Published Online: July 7, 2014
Eur. J. Inorg. Chem. 2014, 3681–3689
3689
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim