Hydrothermal synthesis and structural characterization of a new 2D-layered vanadium diphosphinate: [VO(O2(C6H5)PCH2P(C6H5)O2)]

Article abstract of DOI:10.1016/j.inoche.2006.03.007

A new inorganic-organic hybrid [VO(pcp)], where pcp is the P,P′diphenylmethylenediphosphinate ligand, has been hydrothermally synthesized and structurally characterized. The X-ray analysis revealed an undulated 2D-layered structure, where VO₅ moieties are connected through bridging phosphinate groups. Magnetic measurements in the range 300-2 K have shown a weak ferromagnetic interaction between vanadyl groups.

Full text of DOI:10.1016/j.inoche.2006.03.007

Inorganic Chemistry Communications 9 (2006) 591–594
www.elsevier.com/locate/inoche
Hydrothermal synthesis and structural characterization of a new
2D-layered vanadium diphosphinate: [VO(O2(C6H5)PCH2P(C6H5)O2)]
a
b
b,
c
Ferdinando Costantino , Stefano Midollini , Annabella Orlandini *, Lorenzo Sorace
a
`
Laboratorio di Chimica Inorganica, Universita di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
Istituto di Chimica dei Composti Organometallici, ICCOM, CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy
b
c
`
Dipartimento di Chimica and UdR INSTM, Universita di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy
Received 9 February 2006; accepted 8 March 2006
Available online 22 March 2006
Abstract
A new inorganic–organic hybrid [VO(pcp)], where pcp is the P,P0diphenylmethylenediphosphinate ligand, has been hydrothermally
synthesized and structurally characterized. The X-ray analysis revealed an undulated 2D-layered structure, where VO5 moieties are con-
nected through bridging phosphinate groups. Magnetic measurements in the range 300–2 K have shown a weak ferromagnetic interac-
tion between vanadyl groups.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Oxovanadium complex; Phosphinate; Hydrothermal synthesis; Hybrid material
The synthesis of new inorganic–organic hybrids is cur-
rently booming. Indeed, the combination of the physical
and chemical properties of inorganic and organic compo-
nents can allow the achievement of solid materials for quite
varied applications in the fields of catalysis, ion exchange,
material science, optics, magnetism, etc. In this respect,
metal phosphonates or phosphinates can be considered as
prototypical hybrid materials because the structural modi-
fications are easily achieved by varying the steric require-
ments of the organic moiety and/or the tether length [1].
Numerous oxovanadium organophosphonate phases
have been recently prepared and characterized. Their struc-
tural chemistry is very rich, as it includes solid materials
exhibiting 1D, 2D and 3D arrangements and incorporating
single valence V(IV) or V(V) or mixed valence V(IV)/V(V)
sites. Moreover, a somewhat common feature of this class
of compounds is the trend of the V/P/O framework to
arrange itself about guest species, which can be neutral as
well as charged molecules. Differently, as far as we know,
no related phosphinate derivatives of oxovanadium have
been reported [2].
In this communication, we report the hydrothermal syn-
thesis, crystal structure and magnetic characterization of
the new inorganic–organic vanadium diphosphinate
hybrid, [VO(O2(C6H5)PCH2P(C6H5)O2)]. The P,P0diph-
enylmethylenediphosphinate ligand, pcp2ꢀ
, has been
recently found capable to afford metal hybrids with several
metal(II) ions, like Be [3], Mn [4], Co [4], Ni [4], Cu [5–7],
Zn [8], Pb [9], and Sn [6], with a variety of structural
arrangements and different dimensionalities.
Well shaped blue crystals of the complex [VO(pcp)] were
prepared from a mixture of H2pcp (40 mg), VOSO4.nH2O
(22 ml) and H2O (18 ml) in a 23 ml Teflon-lined autoclave,
under autogenous pressure, at 160 °C for 120 h (Yield: ca.
41% based on vanadium) [10].
The X-ray analysis [11] revealed that the asymmetric
unit [VO(pcp)] (Fig. 1) is repeated infinitely in a bidimen-
sional network, where VO5 moieties are connected through
bridging phosphinate groups. In particular, the V(IV) sites
exhibit distorted square pyramidal coordination, the dis-
tortion from the limit geometry being evident from the val-
ues of the trans basal angles of 145.1(4) and 148.2(2)° and
*
Corresponding author. Tel.: +39 55 5225 290; fax: +39 55 5225 203.
E-mail address: annabella.bianchi@iccom.cnr.it (A. Orlandini).
1387-7003/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2006.03.007

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F. Costantino et al. / Inorganic Chemistry Communications 9 (2006) 591–594
Fig. 2. View of the layer of [VO(pcp)], propagated in the xy plane. Phenyl
rings are omitted for the sake of clarity.
Fig. 1. Perspective view of the asymmetric unit of [VO(pcp)]. ORTEP
˚
drawing with 30% probability ellipsoids. Selected bond distances (A) and
angles (°): V1–O5 1.565(8), V1–O1 1.980(8), V1–O3 1.964(9), V1–O2#2
1.977(8), V1–O4#1 1.941(8), P1–O1 1.505(9), P1–O2 1.483(9), P2–O3
1.498(10), P2–O4 1.485(9), O5–V1–O1 104.0(5), O5–V1–O3 106.3(6), O5–
V1–O2#2 107.8(5), O5–V1–O4#1 108.5(6), O1–V1–O2#2 148.2(4), O3–
V1–O4#1 145.1(4), P1–O1–V1 140.2(6), P2–O3–V1 140.4(6). Symmetry
operations: #1 x ꢀ 1, y , z; #2 ꢀx + 1, y ꢀ 1/2, ꢀz + 3/2.
Fig. 3. View along the x direction of the undulated layer, showing the
projection of phenyl rings and oxo terminal groups.
the displacement of the metal from the basal plane of
0.56 A. The square pyramid is defined by an apical termi-
˚
nal oxo group and four oxygen donors from three different
pcp ligands, one of them in bidentate and the other two in
monodentate mode. It follows that each pcp ligand utilizes
all of its oxygen donors to link three metal centers, result-
ing an undulated bidimensional network, with alternating
six- and fourteen-membered cycles (types 1b and 7a of
the fundamental building blocks for 2D oxovanadium org-
ano-phosphonates and -diphosphonates, respectively as
schematized by Finn et al. [2]) (Fig. 2).
Each 2D layer, which propagates in the xy plane, is
shielded by the presence of the phenyl rings, which project
into the intersheet region, as do the terminal vanadyl oxo
groups (Fig. 3). The phenyl rings, belonging to the same
pcp2ꢀ ligand, project from opposite sides of the layer.
In Fig. 4, the complete packing diagram of [VO(pcp)]
with view along the x axis is reported. Bond distances in
the coordination sphere are in agreement with the literature
data [16].
the same building block unit but different structural char-
acteristics. As a matter of fact, the Cu, Sn and Pb deriva-
tives are all 1D monodimensional polymers, with
arrangements featuring ribbon ladder-like (Sn) or double
intersecting ribbons (Pb, Cu) structures. The [Zn(pcp)]
derivative appears the closest to the title complex, as it dis-
plays a corrugated 2D layered network. Nevertheless, also
the structure of the [Zn(pcp)] hybrid significantly differenti-
ates from that of the vanadyl polymer. Apart from the dif-
ference in the coordination sphere, with the zinc and the
vanadium centers being tetrahedral and square pyramidal
coordinated respectively, also the architecture of the
respective layers is different. Whereas the layers of the
[Zn(pcp)] complex show voids of various dimensions, as
there are six-, eight- and 24-membered rings, the title deriv-
ative features only six- and 14-membered rings. It is to be
noted that the presence of six-membered rings is constant
in all the polymers containing the pcp2ꢀ ligand, their for-
mation being actually the first step upon the chelation of
the metal center. Then different growing processes of
It appears of interest to compare the title compound
with the previously reported M(II)(pcp) (M = Cu [6], Sn
[6], Pb [9] and Zn [8]) hybrid compounds, which present

F. Costantino et al. / Inorganic Chemistry Communications 9 (2006) 591–594
593
The X-ray powder diffraction spectrum of a polycrystal-
line sample of [(VO)(pcp)] is in agreement with the data
derived from the single-crystal X-ray analysis, showing that
the bulk material consists of a single phase.
The magnetic susceptibility of the title complex was mea-
sured between 2 and 300 K [17]. vT vs T curve is reported in
Fig. 5. At room temperature the observed value of
0.351 emu K molꢀ1 is in the range expected for one S = 1/2
with g > 2.00, while the increase observed at low tempera-
ture clearly points to the presence of weak ferromagnetic
coupling between vanadyl paramagnetic centers. These fea-
tures are more clearly evidenced in the best fit parameters of
Curie–Weiss plot (inset of Fig. 5), C = 0.351 emu K molꢀ1
(corresponding to g = 1.94) and h = 0.56 K. By considering
the structural features of the compound, we can consider it
as a square planar 2D Heisenberg lattice of spins S = 1/2.
Accordingly, its susceptibility data were fitted using the
equation of Rushbrooke and Wood [18] with the exchange
parameter J (H = ꢀ2JRSi Æ Sj) as a unique adjustable
parameter:
Ng2b2
4kB
vT ¼
½1 ꢀ ð2=xÞ þ ð2=x2Þ ꢀ ð4=3x3Þ
þ ð0:4833=x5Þ þ ð0:003797=x6Þꢁꢀ1
ð1Þ
where x = kBT/J and g was kept fixed at 1.94. Best fit curve
(R2 = 0.987) was obtained with J = 0.25 0.02 cmꢀ1. The
ferromagnetic coupling observed for the title complex is of
comparable magnitude to that observed for a layered van-
adyl phosphate compound [19]. The small magnitude of the
exchange constant, transmitted by the O–P–O pathway,
should be attributed to an almost complete cancellation
of the ferromagnetic and antiferromagnetic contribution
to the coupling. In particular, the latter is governed by dif-
ferent structural and chemical parameters, as demonstrated
for the related phosphonate and phosphate layered com-
pounds [20,21].
Fig. 4. Packing diagram of [VO(pcp)] viewed down the x axis.
extended networks, depending on the nature of the metal,
can occur. In this framework, it is to be recalled that when
water molecules are present in the lattices of M/pcp hybrids
(M = Mn, Co, Ni [4], Cu [5]), 2D-layered structures are
formed, where hydrogen bonding interactions play a fun-
damental role, in extending the structure dimensionality.
Finally, a comparison with the corresponding biphosph-
onate [(VO)(HOO2PCH2PO2OH)]2ꢀ anion seems fair, as
the latter ligand presents the same skeleton of the title diph-
osphinate, unless the phenyl rings are substituted by OH
groups [16]. Thus, differently from the title compound, the
(OHO2PCH2PO2OH)2ꢀ anion forms an unexpected mono-
meric structure, where the vanadium center is octahedrally
coordinated by a terminal oxo group, a water molecule
and two biphosphonates in bidentate fashion. However, it
is difficult to attribute such a structural difference simply to
the replacement of the phenyl rings with the OH groups.
As a matter of fact, just the synthesis of a variety of 1D,
2D and 3D diphosphonates oxovanadium compounds sug-
gests that the phase dimensionality is not only controlled
by the tether length or in general by the steric requirements
of the ligand substituents, but also by a plethora of factors
such as the reaction conditions (pH, temperature, stoichiom-
etrices, concentration), the power of the hydrothermal syn-
thesis and the involvement of intercalate templates [16].
Fig. 5. vT vs T experimental data (full triangles) and best fit curve
obtained by use of the Rushbrooke–Wood model for 2D Heisenberg
systems. In the inset, the Curie–Weiss plot of susceptibility data and
corresponding best fit line is shown.

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F. Costantino et al. / Inorganic Chemistry Communications 9 (2006) 591–594
[10] Anal. Calcd. (found) for
3.35(3.40).
C13H12O5P2V: C, 43.24 (43.35); H,
Appendix A. Supplementary data
[11] Crystal data: C13H12O5P2V, M = 361.11, orthorhombic, space group
Crystallographic data have been deposited with the
Cambridge Crystallographic Data Centre with CCDC
No. 297364. Supplementary data associated with this arti-
cle can be found, in the online version, at doi:10.1016/
j.inoche.2006.03.007.
˚
P212121, a = 6.188(3), b = 11.281(7), c = 20.923(7) A, U = 1460.6(12)
3
A , Z = 4, dcalcd = 1.642 Mg mꢀ3, l(Mo Ka) = 0.915 mmꢀ1, F(000) =
˚
732. A total of 1513 reflections were collected with a Mo Ka radiation
on an Enraf Nonius CAD4 automatic diffractometer at 293 K. The
structure was solved by direct methods and refined by a full-matrix
least-squares technique based on F2 using the WINGX package [12],
with SIR97 [13], SHELX97 [14] and ORTEPIII [15] programs. R1 and
R2w are 0.055 and 0.109, respectively, for 101 parameters and 819
observed data [I > 2r(I)].
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