Mononuclear metal phosphinates with ancillary pyrazole ligands. Synthesis and X-ray crystal structures of [M(Ph2PO2) 2(3,5-DMPZ)2] (M = Co, Zn)

Article abstract of DOI:10.1002/zaac.200500118

The reaction of diphenylphosphinic acid, [Ph₂P(O)(OH)], with CoCl₂ or ZnCl₂ and 3,5-dimethylpyrazole (DMPZ) in the presence of triethylamine affords the mononuclear phosphinates, M(Ph ₂PO₂)₂(DMPZ)₂ (M = Co(1), Zn(2)). The molecular structures of 1 and 2 reveal a tetrahedral environment around the metal. The phosphinate ligands are monoanionic and bind to the metal in a monodentate manner, while the pyrazole ligands act as neutral monodentate ligands. Intermolecular C-H - O and π-π interactions in 1 and 2 result in the generation of two dimensional supramolecular polymeric sheets in the solid state.

Full text of DOI:10.1002/zaac.200500118

Mononuclear Metal Phosphinates with Ancillary Pyrazole Ligands. Synthesis
and X-ray Crystal Structures of [M(Ph2PO2)2(3,5-DMPZ)2] (M ؍ Co, Zn)
Vadapalli Chandrasekhar*,a, Ramamoorthy Boomishankara, Palani Sasikumara, Loganathan Nagarajana, and
A. Wallace Cordesb
a Kanpur / India, Department of Chemistry, Indian Institute of TechnologyϪKanpur
b Fayetteville, Arkansas / U. S. A., Department of Chemistry and Biochemistry, University of Arkansas
Received March 10th, 2005.
Dedicated to Professor Herbert W. Roesky on the Occasion of his 70th Birthday
Abstract. The reaction of diphenylphosphinic acid, [Ph2P(O)(OH)],
with CoCl2 or ZnCl2 and 3,5-dimethylpyrazole (DMPZ) in the pre-
sence of triethylamine affords the mononuclear phosphinates,
M(Ph2PO2)2(DMPZ)2 (Mϭ Co(1), Zn(2)). The molecular structu-
res of 1 and 2 reveal a tetrahedral environment around the metal.
The phosphinate ligands are monoanionic and bind to the metal
in a monodentate manner, while the pyrazole ligands act as neutral
monodentate ligands. Intermolecular C-HϪO and πϪπ interac-
tions in 1 and 2 result in the generation of two dimensional supra-
molecular polymeric sheets in the solid state.
Keywords: Cobalt; Zinc; Diphenylphosphinic acid; Dimethylpyra-
zole; Phosphinates
Introduction
sition metal ions. Also, there has been increased interest in
the use of phosphinic acid R2P(O)OH for the formation of
molecular phosphinates [34Ϫ36]. Herein, we report in the
following, the synthesis and X-ray structural characteriz-
ation of two mononuclear metal phosphinates
[M(Ph2PO2)2(3,5-DMPZ)2] (where Mϭ CoII (1), ZnII (2);
DMPZ ϭ 3,5-dimethylpyrazole).
Transition metal phosphonates have been well-known for
some time and have been of interest from the point of view
of applications in diverse areas such as sorption [1], cataly-
sis [2, 3], sensors [4], radioactive waste water treatment
[5Ϫ7], non-linear optics [8, 9], etc. In view of the interest
of transition metal phosphonates, there have also been ef-
forts to assemble and study molecular metal phosphonates
[10Ϫ18]. The latter are soluble compounds and are amen-
able to study by a variety of techniques. One of the chal-
lenges is finding appropriate synthetic routes that can lead
to the formation of molecular assemblies containing phos-
phonate ligands. Recently, we have discovered that the use
of ancillary ligands such as 3,5-dimethylpyrazole enhances
the solubility of the transition metal phosphonates and al-
lows the isolation of lipophilic discrete molecular transition
metal phosphonates [19]. Thus, for example a dodecanulear
copper(II) phosphonate complex was isolated in the reac-
tion between copper(II) chloride, t-butylphosphonic acid
and 3,5-dimethylpyrazole [19]. Using analogous approaches
we have been able to assemble tetranuclear copper(II) [20],
hexanuclear and trinuclear zinc(II) [21] and trinuclear co-
balt(II) transition metal phosphonates [22]. There have also
been other reports on molecular phosphonates containing
ancillary ligands [23Ϫ26]. Recently there has also been
interesting work on the use of (t-BuO)2P(O)OH as a ligand
[27Ϫ33] for forming molecular phosphates containing tran-
Results and Discussion
We have shown previously that the reaction of
PhP(O)(OH)2 with ZnCl2 and 3,5-dimethylpyrazole leads to
the formation of a hexanuclear zinc(II) phosphonate [21]
(Scheme 1). On the other hand a similar reaction with t-
BuP(O)(OH)2 leads to the isolation of trinuclear zinc(II)
[21] and cobalt (II) phosphonates [22] (Scheme 2). The mo-
lecular structures of the hexa and trinuclear derivatives re-
veal that the phosphonate ligand (RPO3)2Ϫ acts as a trip-
odal ligand and is involved in bridging three adjacent metal
centers. We reasoned that the use of a phosphinate ligand
(R2PO2)Ϫ would lead to a reduction of the nuclearity of
metal phosphinates. Accordingly, the reaction of anhydrous
CoCl2 or ZnCl2 with diphenylphosphinic acid and 3,5-di-
methylpyrazole in the presence of triethylamine as hydrogen
chloride scavenger results in the formation of monomeric
metal complexes 1 and 2 (Scheme 3). It is of the interest
to note cobalt(II) and zinc(II) diphenylphosphinates in the
absence of ancillary ligands show various types of poly-
meric structures. Thus, Thompson and coworkers have re-
ported two polymeric structures for poly bis(µ-diphenyl-
phosphinato)cobalt(II) [37]. While the structure of the β
form was not elucidated, the δ-form contains tetrahedrally
coordinated cobalt(II) linked by two phosphinate bridges
to form a chain polymer. Fackler et al. have synthesized two
* Prof. V. Chandrasekhar
Department of Chemistry
Indian Institute of Technology-Kanpur
Kanpur-208 016, India
Tel: ϩ91-512-2597259
email: vc@iitk.ac.in
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DOI: 10.1002/zaac.200500118
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V. Chandrasekhar, R. Boomishankar, P. Sasikumar, L. Nagarajan, A. Wallace Cordes
Scheme 3 Synthesis of monomeric metal complexes 1 and 2
Scheme 1 Structure of hexanuclear zinc(II) phosphonate
Scheme 4 Polymeric structures of cobalt phosphinates 3 and 4
Scheme 2 Structure of trinuclear zinc(II) and cobalt(II) phosphon-
ates
X-ray crystal structures of [Co(Ph2PO2)2(DMPZ)2]
(1) and [Zn(Ph2PO2)2 (DMPZ)2] (2)
structural forms of [Co(OPPh2O)2]n [38]. One of these, 3,
consists of polymeric chains in which single and triple phos-
phinate groups alternate between tetrahedral cobalt atoms
(Scheme 4). The other isomer, 4, consists of cobalt atoms
with tetrahedral coordination geometry linked by double
phosphinate bridges. Although polymeric structures have
been deduced for [Zn(OPPh2O)2]n [39, 40] based on powder
XRD, confirmation from single crystal analysis is lacking.
In the present instance the molecular phosphinates 1 and
2 have been characterized by single crystal X-ray structural
analysis as well as by other analytical data (vide infra). The
31P NMR spectrum of 2 shows a single resonance at
ϩ25.3 ppm, confirming the equivalence of the phosphinate
ligands in solution.
The molecular structure of 1 is shown in Fig. 1. Some of
the important bond distance and bond angle data for this
compound are summarized in the caption of Fig. 1. The
molecular structure of 1 reveals a mononuclear CoII com-
plex. Thus, the ancillary ligand 3,5-dimethylpyrazole is ef-
fective in decomposing the polymeric structure into its sim-
ple molecular form. The immediate coordination environ-
ment around cobalt consists of two oxygens and two nitro-
gen atoms. Although the N1-Co1-N3 and O3-Co1-N1
angles are perfectly tetrahedral, the other bond angles devi-
ate from ideal tetrahedral values. Thus, the O3-Co1-O1
(113.8 (2)°) and O1-Co1-N3 (111.4 (3)°) angles are slightly
wider while O3-Co1-N3 (105.7 (2)°) and O1-Co1-N1 (106.4
(3)°) angles are slightly narrower. Interestingly the phosphi-
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Mononuclear Metal Phosphinates with Ancillary Pyrazole Ligands
˚
Fig. 3 DIAMOND View of 2. Important bond distances /A and
angles /° are
˚
Fig. 1 DIAMOND View of 1. Selected bond distances /A and
angles /° are
Zn1-O1 1.860 5), Zn1-O3 1.853 (5), Zn1-N1 1.956 (6), Zn1-N3 1.935 (6),
N1-N2 1.323 (9), N3-N4 1.320 (9), P1-O1 1.486 (5), P1-O2 1.460 (5), P2-O3
1.483 (5), P2-O4 1.457 (5), O1-Zn1-O3 108.1 (2), O1-Zn1-N1 108.9 (2), O1-
Zn1-N3 107.8 (2), O3-Zn1-N1 107.5 (2), O3-Zn1-N3 110.1 (2), N1-Zn1-N3
113.9 (3), Zn1-O1-P1 141.4 (3) and Zn1-O1-P1 136.4 (3).
Co1-O1 1.907(9), Co1-O3 1.912(7), Co1-N1 1.9597(9), Co1-N3 2.001(8), N1-
N2 1.372(12), N3-N4 1.374(11), P1-O1 1.520(8), P1-O2 1.496(8), P2-O3
1.530(7), P2-O4 1.483(5), O1-Co1-O3 113.8(2), O1-Co1-N1 106.4(3), O1-
Co1-N3 111.4(3), O3-Co1-N1 109.6(2), O3-Co1-N3 105.7(2), N1-Co1-N3
109.6(3), Co1-O1-P1 135.6(4) and Co1-O1-P1, 139.5(3).
The intramolecular hydrogen bonding parameters (bond length in
˚
A and bond angle in °) are
a) for N2-H2A...O2: N-H (0.860(7)), NϪ-O (2.595(8)), HϪ-O (1.755(5)), N-
HϪ-O (164.9 (5));
b) for N4-H4A...O4: N-H (0.860(7)), NϪ-O (2.500(8)), HϪ-O (1.760(5)), N-
HϪ-O (164.9(5))
Fig. 2 View of the 2D-sheet network formed in 1 by weak hydrogen
˚
bonding. The bond parameters (bond length in A and bond angle
in °) are
a) for C3-H3...O2: C-H (0.930(5)), CϪ-O (3.463(10)), HϪ-O (2.551(8)), C-
HϪ-O (166.87(33)) and the symmetry is Ϫx, 0.5ϩy, 1.5Ϫz;
b) for C16-H16...O2: C-H (0.930(12)), CϪ-O (3.448(17)), HϪ-O (2.587(9))
and C-HϪ-O (154.2 (8)) and the symmetry is x, 1.5Ϫy, Ϫ0.5ϩz.
Fig. 4 View of the 2D- sheet network formed in 2 by weak hydrogen
bonding. The bond parameters (bond length in A and bond angle
˚
in °) are
nate ligand, [Ph2PO2]Ϫ functions only as a monodentate li-
gand. Thus, in effect, the influence of the ancillary ligand
3,5-dimethylpyrazole is not to increase the coordination
number around cobalt but to decrease the hapticity of the
phosphinate ligand. The bond distances P1-O1 (1.520
a) C12-H12...O4: C-H (0.931 (9)), CϪ-O (3.232 (10)), HϪ-O (2.481 (4)), C-
HϪ-O (137.9 (6)) and the symmetry is x, 0.5Ϫy, Ϫ0.5ϩz; b) for C14-
H14...O2: C-H (0.930 (91)), CϪ-O (3.270(1)), HϪ-O (2.616(4)), C-HϪ-O
(127.83(6)) and the symmetry is x, 0.5Ϫy, Ϫ0.5ϩz; c) for C15-H15...O2: C-
H (0.930(89)), CϪ-O (3.335 (10)), HϪ-O (2.743(5)), C-HϪ-O (122.36 (6))
and the symmetry is x, 0.5Ϫy, Ϫ0.5ϩz; d) for C21-H21...O2: C-H (0.931
(11)), CϪ-O (3.398(11)), HϪ-O (2.737 (5)), C-HϪ-O (128.7 (6)) and the
symmetry is Ϫ0.5ϩx, 0.5Ϫy, 1Ϫz; and the distance between (Ar)π...π(Pz) is
˚
˚
(8) A) and P1-O2 (1.496 (8) A) are different. The P-O dis-
˚
3.497 (1) A and the symmetry is 0.5ϩx, 0.5Ϫy, 1Ϫz.
tances in the polymeric phosphinates 3 and 4 are 1.505 (6)
˚
and 1.521 (18) A respectively. In the present instance the
3,5-dimethylpyrazole ligand functions as a neutral monod-
entate ligand. The presence of the free ϪNH group facili-
tates its interaction in an intramolecular hydrogen bonding
with PϭO units. One of the phosphinate oxygen (O2) is also
involved in an intermolecular C-HϪO hydrogen bonding
interaction with two protons (H3 and H16) of two different
phenyl substituents of two different phosphinate groups.
The cumulative effect of these types of weak interactions
leads to the formation of a supramolecular two-dimen-
sional sheet-like network (Fig. 2).
The molecular structure of 2 is quite similar to that of 1
(Fig. 3). The metric parameters observed for this complex
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V. Chandrasekhar, R. Boomishankar, P. Sasikumar, L. Nagarajan, A. Wallace Cordes
Table 1 Crystal data and structure refinement parameters for 1 and 2
1
2
Empirical formula
Formula weight
Temperature
C40H42CoN4O4P2
763.65
C68H72N8O8P4Zn2
1383.96
293(2) K
293(2) K
˚
˚
Wavelength
0.71073 A
0.71073 A
Crystal system, space group
Unit cell dimensions
monoclinic, P21/c
a ϭ 21.540(5) A;
orthorhombic, Pbca
˚
˚
a ϭ 16.00(4) A
˚
˚
b ϭ 8.998(5) A; β ϭ 116.070(5)°
b ϭ 18.00(10) A;
˚
˚
c ϭ 22.260(5) A;
c ϭ 22.00(5) A;
6336.0(4) A
3
3
˚
˚
Volume
3875(2) A
Z, Calculated density
Absorption coefficient
F(000)
Crystal size
Theta range for data collection
Limiting indices
Reflections collected / unique
Completeness to theta
Absorption correction
Refinement method
Data / restraints / parameters
Goodness-of-fit on F2
Final R indices [I>2sigma(I)]
R indices (all data)
4, 1.309 Mg/m3
4, 1.451 Mg/m3
0.570 mmϪ1
0.922 mmϪ1
1596
2880
0.2 x 0.2 x 0.3 mm3
1.84 to 22.49°
0.24 x 0.24 x 0.03 mm3
2.25 to 26.89°
Ϫ23 Յ h Յ 23, Ϫ9 Յ k Յ 0, Ϫ23 Յ l Յ 23
10048 / 5042 [R(int) ϭ 0.1238]
99.7 % (θ ϭ 22.49°)
Not applied
Ϫ20 Յ h Յ 20, Ϫ22 Յ k Յ 22, Ϫ27 Յ l Յ 27
6799 / 6798 [R(int) ϭ 0.15]
99.3 % (θ ϭ 26.89°)
Empirical, (R.A.Jacobson, MS Corp, 1998)
Full-matrix least-squares on F2
6798 / 0 / 410
Full-matrix least-squares on F2
5042 / 0 / 446
0.980
0.987
R1 ϭ 0.0666, wR2 ϭ 0.1464
R1 ϭ 0.1798, wR2 ϭ 0.1922
0.314 and Ϫ0.390 e.A
R1 ϭ 0.0923, wR2 ϭ 0.1572
R1 ϭ 0.2290, wR2 ϭ 0.2040
0.366 and Ϫ0.520 e.A
Ϫ3
Ϫ3
˚
˚
Largest diff. peak and hole
was prepared by literature methods [50]. Diphenylphosphinic acid
(Aldrich), cobalt(II) chloride and zinc(II) chloride (Lancaster) were
purchased and used as such without any further purification. Melt-
ing points were measured using a JSGW melting point apparatus
and are uncorrected. Elemental analyses were carried out using a
Thermoquest CE instruments model EA/110 CHNS-O elemental
analyzer. Infrared spectra were recorded as KBr pellets on a FT-
IR Bruker-Vector Model. 1H, and 31P NMR spectra were obtained
on a JEOL-JNM LAMBDA 400 model spectrometer using CDCl3
solutions with shifts referenced to tetramethylsilane (for 1H) and
orthophosphoric acid (for 31P) respectively.
are summarized in the caption of Fig. 3. The coordination
geometry around zinc is slightly distorted from a perfect
tetrahedral geometry. The coordination environment
around zinc comprises of two oxygen atoms (derived from
two monodentate diphenyl phosphinate ligands) and two
nitrogen atoms (derived from two neutral 3,5-dimethylpyra-
zole ligands). The PϭO units on each phosphinate motif
are involved in intramolecular hydrogen bonding with the
N-H protons on the pyrazolyl ligand which is shown in Fig.
3. Further, each PϭO group is involved in a C-HϪO inter-
action with the aryl hydrogens of the diphenylphosphinate
moieties to generate a linear array of zinc atoms. Several
such linear arrays are linked to each other through the in-
tervening πϪ-π interactions between one of the pyrazolyl
rings and an aryl moiety on the phosphinate ligand
[41Ϫ43]. In addition, there is also an intermolecular C-HϪ-
O interaction between the aryl protons and the coordinated
oxygen atom O1 [44Ϫ49]. This interaction leads to the link-
ing of two linear zinc arrays to generate a two-dimensional
sheet (Fig. 4).
Preparation of [Co(Ph2PO2)2(DMPZ)2] (1)
To
a suspension of anhydrous cobalt(II) chloride (0.19 g,
1.46 mmol) in dichloromethane (15 mL), a solution of diphenyl
phosphinic acid (0.64 g, 2.93 mmol) and triethylamine (0.30 g,
2.96 mmol) in dichloromethane (20 mL) was added dropwise over
a period of 40 min. After the addition was over, a solution of 3,5-
dimethylpyrazole (0.28 g, 2.92 mmol) in dichloromethane (5 mL)
was added slowly. The solution was allowed to stir for 20 h; di-
chloromethane was evaporated to get a pale blue solid. The solid
was extracted with 40 mL of benzene and the resulting suspension
was filtered through a G4-frit to remove the precipitated triethyl-
amine hydrochloride. The clear blue solution was removed to get
an intense blue solid. Yield: 0.72 g (72 %); m.p. 141 °C. C, H, N
analysis: Anal. calcd. for C34H36O4N4P2Co (685.55): C 59.56, H
5.29; found: C 59.01, H 5.14 %.
Conclusion
The reaction of CoCl2 or ZnCl2 with diphenylphosphinic
acid and 3,5-dimethylpyrazole in the presence of triethyl-
amine leads to the formation of the mononuclear complexes
[M(Ph2PO2)2(DMPZ)2]. Each of these complexes contains
a tetrahedral coordination environment around the metal
(2O and 2N). This situation contrasts with the polymeric
structures reported for the cobalt(II) and zinc(II) phosphi-
nates [Co(Ph2PO2)2]n and [Zn (Ph2PO2)2]n.
IR (KBr, cmϪ1): 1207[s], 1163[s], 1125[s], 1045[m].
Preparation of [Zn(Ph2PO2)2(DMPZ)2] (2)
To a suspension of anhydrous zinc(II) chloride (0.16 g, 1.18 mmol)
in dichloromethane (15 mL), a solution of diphenylphosphinic acid
(0.52 g, 2.38 mmol) and triethylamine (0.24 g, 2.37 mmol) in di-
chloromethane (20 mL) was added dropwise over a period of
40 min. After the addition was over, a solution of 3,5-dimethylpyra-
Experimental Section
All the reactions were performed under a dry nitrogen atmosphere
by employing standard Schlenk techniques. 3,5-Dimethylpyrazole
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Mononuclear Metal Phosphinates with Ancillary Pyrazole Ligands
zole (0.23 g, 2.39 mmol) in dichloromethane (5 mL) was added
slowly. The solution was allowed to stir for 20 h; dichloromethane
was evaporated to get a white solid. The solid was extracted with
40 mL of benzene and the resulting suspension was filtered through
a G4-frit to remove the precipitated triethylamine hydrochloride.
The clear solution thus obtained was removed to get a crystalline
white solid. Yield: 0.70 g (86 %); m.p. 133 °C. C, H, N analysis:
Anal. calcd. for C34H36O4N4P2Zn (692.01): C 59.01, H 5.24; found:
C 59.34, H 5.07 %.
[12] G. Anantharaman, V. Chandrasekhar, M. G. Walawalkar, H.
W. Roesky, D. Vidovic, J. Magull, M. Notlemeyer, Dalton
Trans. 2004, 1271.
[13] M. G. Walawalkar, R. Murugavel, H. W. Roesky, H.-G.
Schmidt, Inorg. Chem. 1997, 36, 4202.
´
[14] M. G. Walawalkar, R. Murugavel, H. W. Roesky, I. Uson, R.
Kraetzner, Inorg. Chem. 1998, 37, 473.
[15] M. R. Mason, A. M. Perkins, R. M. Matthews, J. D. Fisher,
M. S. Mashuta, A. Vij, Inorg. Chem. 1998, 37, 3734.
[16] M. G. Walawalkar, R. Murugavel, A.Voigt, H. W. Roesky, H.-
G. Schmidt, J. Am. Chem. Soc. 1997, 119, 4656.
[17] M. R. Mason, M. S. Mashuta, J. F. Richardson, Angew. Chem.
Int. Ed. Engl. 1997, 36, 239.
IR (KBr, cmϪ1): 1262[s], 1165[s], 1126[s], 1046[s]. 1H NMR (400 MHz,
CDCl3): δ ϭ 2.2 (s, 12H, CH3), 5.7 (s, 2H, CH), 7.18-7.27 (m, 12H, phenyl),
7.69-7.74 (m, 8H, phenyl); 31P NMR (160 MHz, CDCl3): δ ϭ ϩ25.27 (s).
[18] W. Ouelette, B.-K Koo, E. Burkholder, V. Golub, C. J.
O’Connor, J. Zubieta, Dalton Trans. 2004, 1527.
[19] V. Chandrasekhar, S. Kingsley, Angew. Chem. Int. Ed. Engl.
2000, 39, 2320.
[20] V. Chandrasekhar, S. Kingsley, A. Vij, K. C. Lam, A. L.
Rheingold, Inorg. Chem. 2000, 39, 3238.
[21] V. Chandrasekhar, S. Kingsley, B. Rhatigan, M. K. Lam, A.
L. Rheingold, Inorg. Chem. 2002, 41, 1030.
[22] S. Kingsley, Ph. D Thesis, Indian Institute of Technology,
Kanpur, India, 2001.
[23] E. I. Tolis, M. Helliwell, S. Langley, J. Raftery, R. E. P. Win-
penny, Angew. Chem. Int. Ed. Engl. 2003, 42, 3804.
[24] E. K. Brechin, R. A. Coxall, A. Parkin, S. Parsons, P. A.
Tasker, R. E. P. Winpenny, Angew. Chem. Int. Ed. Engl. 2001,
40, 2700.
X-ray Crystallography
Single crystals of 1 and 2 suitable for X-ray diffraction studies were
obtained by the slow evaporation of benzene solution. The X-ray
data for the compound 1 was collected on Enraf Nonius CAD4
diffractomer at 293 K. The data set for 2 was collected on a Mer-
cury CCD - AFC8S at 293 K. The details pertaining to the data
collection and refinement for 1 and 2 are given in Table 1. The
structures were solved by direct methods using SHELXS-97 and
refined by full-matrix least squares on F2 using SHELXL-97 [51].
Due to the moderate quality of the data the reliable parameters for
compound 1 is high. All the hydrogen atoms were included in ideal-
ized positions, and a riding model was used. Non-hydrogen atoms
were refined with anisotropic displacement parameters.
Crystallographic data for the structures reported in this paper have
been deposited with the Cambridge Crystallographic Data Centre
as supplementary publication No. CCDC-265716 & 265717. Copies
of the data can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge CB21EZ, UK (fax: (.44) 1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk).
[25] S. Langley, M. Helliwell, J. Raftery, E. Tolis, R. E. P. Win-
penny, Chem. Comm. 2004, 142.
[26] A. Harrison, D. K. Henderson, P. A. Lovatt, A. Parkin, P. A.
Tasker, R. E. P. Winpenny, Dalton Trans. 2003, 4271.
[27] M. Sathiyendiran, R. Murugavel, Inorg. Chem. 2002, 41, 6404.
[28] R. Murugavel, M. Sathiyendiran, M. G. Walawalkar, Inorg.
Chem. 2001, 40, 427.
[29] R. Murugavel, M. Sathiyendiran, Chemistry Letters 2001, 84.
[30] R. Pothiraja, M. Sathiyendiran, R. Murugavel, R. J. Butcher,
Inorg. Chem. 2005, 44, 000.
Acknowledgments. We (VC, PS and LN) are thankful to the Council
of Scientific and Industrial Research (CSIR), New Delhi, India for
generous financial support.
[31] R. Murugavel, M. Sathiyendiran, R. Pothiraja, R. J. Butcher,
Chem. Comm. 2003, 20, 2546.
References
[32] R. Murugavel, M. Sathiyendiran, R. Pothiraja, M. G. Wala-
walkar, T. Mallah, E. Riviere, Inorg. Chem. 2004, 43, 945.
[33] R. Pothiraja, M. Sathiyendiran, R. J. Butcher, R. Murugavel,
Inorg. Chem. 2004, 43, 7585.
[1] F. Fredoueil, D. Massiot, P. Janvier, F. Gingl, M. B.-Doeuff,
M. Evian, A. Clearfield, B.Bujoli, Inorg. Chem. 1999, 38, 1831.
[2] B.-Z. Wan, R. G. Anthony, G.-Z. Peng, A. Clearfield, J. Catal.
1994, 19, 101.
[3] D. Deniaud, B. Schollorn, J. Mansury, J. Rouxel, P. Battion,
B. Bujoli, Chem. Mater. 1995, 7, 995.
[4] S. B. Ungashe, W. L. Wilson, H. E. Katz, G. R. Scheller, T.
M. Putvinski, J. Am. Chem. Soc. 1992, 114, 8717.
[5] A. Clearfield, Inorganic Ion Exchange Materials, CRC Press,
Boca Raton, Florida, 1982.
[6] G. Alberti, Acc. Chem. Res. 1978, 11, 163.
[7] J. D. Wang, A. Clearfield, G.-Z. Peng, Mater. Chem. Phys.
1993, 35, 208.
[34] P. Betz, A. Bino, Inorg. Chim. Acta. 1988, 147, 109.
´´
[35] T. Azaıs, L. B.-Coury, J. Vaissermann, P. Bertani, J. Hirsch-
inger, J. Maquet, C. Bonhomme, Inorg. Chem. 2002, 41, 981.
[36] S. Midolini, A. Orlandini, P. Rosa, L. Sorace, Inorg. Chem.
2005, 000.
[37] J.-L. Du, S. J. Rettig, R. C. Thompson, J. Trotter, Can. J.
Chem. 1991, 69, 277.
[38] S.-J. Liu, R. J. Staples, J. P. Fackler Jr, Polyhedron 1992, 11,
2427.
[39] S. H. Rose, B. P. Block, J. Polymer. Sci. A-1 1966, 4, 573.
[40] S. H. Rose, B. P. Block, J. Polymer. Sci. A-1 1966, 4, 583.
[41] C. Janiak, Dalton. Trans. 2000, 3885.
[42] L. J. Childs, N. W. Alcock, M. J. Hannon, Angew. Chem. Int.
Ed. Engl. 2001, 40, 1079.
[8] A. Cabeza, M. A. G. Aranda, S. Bruque, D. M. Poojary, A.
Clearfield, J. Sanz, Inorg. Chem. 1998, 37, 4168.
[9] B. Zhang, D. M. Poojary, A. Clearfield, Inorg. Chem. 1998,
37, 249.
[10] M. G. Walawalkar, H. W. Roesky, R. Murugavel, Acc. Chem.
Res. 1999, 32, 117.
[43] V. Chandrasekhar, R. Azhakar, J. F. Bickley, A. Steiner, Chem.
Comm. 2005, 459.
[11] G. Anantharaman, M. G. Walawalkar, R. Murugavel, B.
´
Gabor, R. H. Irmer, M. Baldus, B. Angerstein, H. W. Roesky,
[44] P. K. Thallapally, A. K. Katz, H. L. Carrell, G. R. Desiraju,
CrystEngComm 2003, 5, 87.
Angew. Chem. Int. Ed. Engl. 2003, 42, 4482.
Z. Anorg. Allg. Chem. 2005, 631, 2727Ϫ2732
zaac.wiley-vch.de
 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
2731

V. Chandrasekhar, R. Boomishankar, P. Sasikumar, L. Nagarajan, A. Wallace Cordes
[45] V. Chandrasekhar, S. Nagendran, S. Bansal, A. W. Cordes, A.
[49] V. Chandrasekhar, A. Athimoolam, N. Dastagiri Reddy, S.
Nagendran, A. Steiner, S. Zacchini, R. Butcher, Inorg. Chem.
2003, 42, 51.
[50] B. S. Furniss, A. J. Hannaford, P. W. G. Smith, A. R. Tatchell,
Vogel’s Text book of Practical Organic Chemistry, 5th edition,
ELBS and Longman: London, 1989.
[51] G. M. Scheldrick, SHELXL-97, Program for Crystal Structure
Analysis (release 97-2), University of Göttingen, Göttingen,
Germany, 1998.
Vij, organometallics. 2002, 15, 3297.
[46] G. R. Desiraju, T. Steiner, The Weak Hydrogen Bond In Struc-
tural Chemistry and Biology, Oxford University Press, Ox-
ford, 1999.
[47] M. Nishio, CrystEngComm 2004, 6, 130.
[48] M. Nishio, M., Hirota, Y. Umezawa, CH/π Interaction
(Evidence, Nature and Consequence), Wiley-VCH, New
York, 1998.
2732
 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
zaac.wiley-vch.de
Z. Anorg. Allg. Chem. 2005, 631, 2727Ϫ2732