A new lead(II) inorganic-organic hybrid of the P,P′-diphenylmethylene-diphosphinate ligand: Synthesis and X-ray characterization of the [Pb(CH2(P(Ph)O2)2)] complex

Article abstract of DOI:10.1016/S1387-7003(03)00037-6

By reaction of lead(II) nitrate with P,P′-diphenylmethylenediphosphinic acid in water solution a new inorganic-organic hybrid of formula [Pb(CH₂(P(Ph)O₂)₂)] has been synthesized and structurally characterized. The complex displays a polymeric columnar structure, the column being formed by two intersecting sinusoidal ribbons of lead(II) ions bridged by bifunctional phosphinate ligands. The intersections of the ribbons are constituted by dimeric units of pentacoordinated lead(II) ions.

Full text of DOI:10.1016/S1387-7003(03)00037-6

Inorganic Chemistry Communications 6 (2003) 546–548
www.elsevier.com/locate/inoche
A new lead(II) inorganic–organic hybrid of the
P; P0-diphenylmethylene-diphosphinate ligand: synthesis
and X-ray characterization of the ½PbðCH2ðPðPhÞO2Þ ÞŠ complex
2
*
Franco Cecconi, Carlo A. Ghilardi , Stefano Midollini, Annabella Orlandini
Istituto di Chimica dei Composti Organometallici, ICCOM, CNR, Via J. Nardi, 39-50132 Firenze Italy
Received 9 December 2002; accepted 20 January 2003
Abstract
By reaction of lead(II) nitrate with P; P0-diphenylmethylenediphosphinic acid in water solution a new inorganic–organic hybrid
of formula ½PbðCH2ðPðPhÞO2Þ2ފ has been synthesized and structurally characterized. The complex displays a polymeric columnar
structure, the column being formed by two intersecting sinusoidal ribbons of lead(II) ions bridged by bifunctional phosphinate
ligands. The intersections of the ribbons are constituted by dimeric units of pentacoordinated lead(II) ions.
Ó 2003 Elsevier Science B.V. All rights reserved.
Keywords: Inorganic–organic hybrids; Crystal structures; Polymeric complexes; Lead complexes
Metal organophosphonate complexes are hybrid in-
organic/organic materials of growing interest, as they
can show structural typologies useful to various appli-
cations (molecular sieves, selective catalysts, absorbers,
ionic exchangers, matrices for electric and magnetic
devices) [1–7].
Already several years ago a number of monopho-
sphinates had been found to have a strong aptitude to
form metal coordination polymers, which have been
used in a variety of applications (coatings and grease
thickeners) [8]. Generally these metal monophosphinates
present extended chain polymeric structures with the
metals linked by variously bridging phosphinate groups
[9–16].
layered polymers, where the metal can be replaced by
another metal without changing the overall structure
(mixed metal polymers could be obtained indeed). In
this type of complexes the water molecules, both of
coordination and crystallization, play a determinant
role, as they are involved through hydrogen bonding
interactions in building of pluridimensional extended
networks. The removing of such water molecules could
represent an important challenge, in order to leave open
coordination sites on the metals for possible intercala-
tion or catalytic reactions.
Now we report the synthesis and the crystal structure
of a lead(II) hybrid coordination polymer with the li-
gand pcp, of formula [Pb(pcp)]. So far only very few
examples of lead(II) containing organo-phosphonates
[6,18,19] or -phosphinates [10,13] have been reported.
The [Pb(pcp)]complex has been synthesized by re-
acting equimolar amounts of H2pcp and PbðNO3Þ2 in
boiling water. Standing of the solution in a closed flask
for a day, at 353 K, afforded colorless needle-shaped
crystals suitable for an X-ray study. The compound is
insoluble in water and in both polar and apolar organic
solvents. (Yield, 50 mg, 63%. Anal. Calcd. for
C13H12O8P2Pb: C, 31.14; H, 2.41%. Found: C, 31.27;
H, 2.45%.)
Recently, we have reported a series of inorganic–or-
ganic hybrids of general formula ½MðH2OÞ3ðpcpފÁ H2O,
where M ¼ Mn2þ; Co2þ; Ni2þ and pcp is the bifunc-
tional P,P0-diphenylmethylenediphosphinate ligand [17].
These compounds constitute a series of isomorphous
* Corresponding author. Tel.: +39-055-243990; fax: +39-055-
24783666.
E-mail address: ghilardi@fi.cnr.it (C.A. Ghilardi).
1387-7003/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S1387-7003(03)00037-6

F. Cecconi et al. / Inorganic Chemistry Communications 6 (2003) 546–548
547
The X-ray analysis 1 of the title compound revealed a
polymeric structure, where the asymmetric unit is rep-
resented by the Pb(pcp) moiety. Fig. 1 shows the envi-
ronment about each lead atom, which displays a
pentacoordination geometry, being surrounded by five
oxygen atoms from four pcp ligands in a square pyra-
midal arrangement.
Unlike the structure of the series reported
) [17],
½MðH2OÞ3ðpcpފ Á H2O (M ¼ Mn2þ; Co2þ; Ni2þ
there are no water molecules in the sphere of coordi-
nation of the lead nor interspersed in the lattice. Here
the structure can be described as an infinite array of
ꢀ
dimers of lead atoms (PbÁ Á ÁPb 3.901 A) bridged by the
phosphinate arms of the pcp ligand. Each phosphinate
uses all of its four oxygen atoms to link four lead atoms
belonging to two contiguous dimers, thus creating a
subunit established by two pcp ligands and by two lead
dimers. Additionally one of the four pcp oxygen atom
bridges both the leads of a dimer, so that each pcp li-
gand displays five bonds. The propagation of the mono-
dimensional polymer along the b axis is represented in
Fig. 2. Ideally the structure can be viewed as two sinu-
soidal ribbons intersecting through the lead dimers. In
Fig. 3 is given the packing diagram with the view normal
to [1 0 0], with the phenyl rings excluded for sake of
clarity. In Fig. 4 the complete packing with view normal
to [0 1 0] evidences the shielding exerted by the organic
part of the ligand, namely the phenyl rings, which dis-
pose themselves outside the columnar array of the in-
tersecting ribbons.
Fig. 1. Perspective view of a portion of the polymer [Pb(pcp)], showing
the coordination environment of the lead atom. OrtepIII drawing with
ꢀ
30% probability ellipsoids. Important selected bond distances (A)
and angles (°): Pb1–O1 2.297(10), Pb1–O3 2.345(12), Pb1–O20
(ꢀx þ 3=2; ꢀy ꢀ 1=2; ꢀz) 2.401(10), Pb1–O4 (x; y þ 1; z) 2.488(11), Pb–
O10 (ꢀx þ 3=2; ꢀy þ 1=2; ꢀz) 2.678(11); O1–Pb1–O3 85.2(4), O1–Pb1–
O20 79.0(4), O3–Pb1–O20 85.9(5), O1–Pb1–O4 80.5(4), O3–Pb1–O4
92.6(4), O20–Pb1–O4 159.5(4), O1–Pb1–O10 77.0(4), O3–Pb1–O10
156,2(4), O20–Pb1–O10 75.4(4), O4–Pb1–O10 99.8(3); P1–O1 1.533(11),
P1–O2 1.498(11), P2–O3 1.498(12), P2–O4 1.487(12).
Concerning in particular the lead atom it is evident
that the square pyramidal arrangement leaves a void in
the sphere of coordination. Such hemileptic coordina-
tion with low coordination number with respect to the
large size of the metal is favouring the localization of the
Pb(II) lone pair [24], whose activity is exerted in a space
shielded by the phenyl rings of the adjacent molecules.
Accordingly the bond lengths Pb–O show a variety of
Fig. 2. Perspective view of some symmetry related units of [Pb(pcp)]
showing the propagation of the 1D polymer along the b axis. The
phenyl rings are omitted for sake of clarity. The unlabeled atoms
linked to lead represent oxygens.
ꢀ
values, as they range from 2.297(10) to 2.678(11) A with
the shortest Pb–O bond apical in the square pyramid
and opposite to the void [6].
On the same side of the lone pair the shortest con-
ꢀ
tacts to lead atom are those relative to O2(4.0 A) and
1
Crystal data: C13H12O4P2Pb; M ¼ 501:35, monoclinic, space group
ꢀ
C2/c, a ¼ 29:280ð7Þ; b ¼ 5:451ð3Þ; c ¼ 23:152ð5ÞA, b ¼ 128:56ð3Þ°,
ꢀ3
U ¼ 2889:5ð18ÞA ; Z ¼ 8; dcalcd ¼ 2:305 Mgmꢀ3; lðMo-KaÞ ¼ 11:907
mmꢀ1; F ð000Þ ¼ 1872. A total of 1762 reflections were collected on a
Enraf Nonius CAD4 automatic diffractometer with a Mo-Ka radia-
ꢀ
tion (k ¼ 0:7107 A) at 293 K. The structure was solved by direct
methods and refined by a full-matrix least-squares technique based on
2 using the WINGX package [20] with SIR97 [21], SHELX97 [22] and
F
ORTEPIII [23] programs. R1 and wR2 are 0.048 and 0.109 respectively
for 181 parameters and 1293 reflections [I > 2rðIÞ]. CCDC Ref. No.
202842.
Fig. 3. Packing diagram of [Pb(pcp)] with view normal to [1 0 0]. The
phenyl rings are excluded for sake of clarity.

548
F. Cecconi et al. / Inorganic Chemistry Communications 6 (2003) 546–548
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