Preparation, structural studies, and magnetic properties of coordination complexes of bimetallic arylplatinum compounds and pyridyl nitronyl nitroxide radicals

Article abstract of DOI:10.1039/b104579m

Treatment of 1,3-C₆H₄I₂ with Pt(PEt₃)₄ in toluene leads to the isolation of [1,3-(Pt(PEt₃)₂I)₂ C₆H₄] (2). This complex has been characterized by ¹H, ¹³C and ³¹P NMR and elemental analysis. The structure of 2 as well as that of [1,4-(Pt(PEt₃)₂I)₂C₆H₄] (1) have been determined by single crystal X-ray analysis. As expected, the platinum centers of these derivatives adopt a square planar coordination geometry with the phosphine ligands in a trans arrangement. Treatment of compounds 1 and 2 with AgPF₆ and subsequent addition of two equivalents of NITpPy (NITpPy = [2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide]) results in the formation of [1,4-(Pt(PEt₃)₂(NITpPY))₂C₆H₄ ]²⁺[PF₆]^-₂ (3) and [1,3-(Pt(PEt₃)₂(NITpPy))₂C₆H₄ ]²⁺[PF₆]^-₂ (4), respectively. Compounds 3 and 4 have been characterized by +ESI/TOF, IR, UV and elemental analysis. Their structures have been determined by X-ray crystallography which confirmed the coordination of a NITpPy ligand at each platinum center. As in 1 and 2, the platinum centers adopt a square planar coordination geometry with the phosphine ligands in a trans arrangement. As shown by EPR spectroscopy and SQUID magnetometry, intramolecular magnetic coupling of the coordinated NITpPy moieties does not occur.

Full text of DOI:10.1039/b104579m

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Preparation, structural studies, and magnetic properties of
coordination complexes of bimetallic arylplatinum compounds and
pyridyl nitronyl nitroxide radicals
James R. Gardinier,a Rodolphe Cléracb and François P. Gabbaï*a
a Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, USA
b Centre de Recherche Paul Pascal, CNRS UPR 8641, Avenue du Dr. A. Schweitzer,
33600 Pessac, France
Received 23rd May 2001, Accepted 10th September 2001
First published as an Advance Article on the web 14th November 2001
Treatment of 1,3-C6H4I2 with Pt(PEt3)4 in toluene leads to the isolation of [1,3-(Pt(PEt3)2I)2C6H4] (2). This
complex has been characterized by 1H, 13C and 31P NMR and elemental analysis. The structure of 2 as well as
that of [1,4-(Pt(PEt3)2I)2C6H4] (1) have been determined by single crystal X-ray analysis. As expected, the
platinum centers of these derivatives adopt a square planar coordination geometry with the phosphine ligands
in a trans arrangement. Treatment of compounds 1 and 2 with AgPF6 and subsequent addition of two equivalents
of NITpPy (NITpPy = [2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide]) results in the formation
of [1,4-(Pt(PEt3)2(NITpPy))2C6H4]2ϩ[PF6]Ϫ2 (3) and [1,3-(Pt(PEt3)2(NITpPy))2C6H4]2ϩ[PF6]Ϫ2 (4), respectively.
Compounds 3 and 4 have been characterized by ϩESI/TOF, IR, UV and elemental analysis. Their structures
have been determined by X-ray crystallography which confirmed the coordination of a NITpPy ligand at each
platinum center. As in 1 and 2, the platinum centers adopt a square planar coordination geometry with the
phosphine ligands in a trans arrangement. As shown by EPR spectroscopy and SQUID magnetometry,
intramolecular magnetic coupling of the coordinated NITpPy moieties does not occur.
Introduction
Results and discussion
Bifunctional Lewis acids are an emerging class of supramole-
cular building blocks. Such compounds can be regarded as the
charge reverse analogs of Lewis basic spacers such as 4,4Ј-
bipyridyl or pyrazine. They usually feature diverging Lewis
acidic sites accessible to coordination by incoming Lewis basic
substrates. In addition to a few main group systems,1–3 a variety
of dinuclear organometallic complexes of late transition metals
have been investigated. In most cases, these complexes are cat-
ionic and incorporate palladium or platinum as binding sites.
Previous investigations have shown the potential of such species
for the preparation of self-assembled macrocycles,4 dendri-
mers5 and polymers.6 It occurred to us that such species could
also be useful for the preparation of materials with unusual
magnetic properties. In particular, we became intrigued by the
possible use of these derivatives for the modular assembly of
polyradical species. Thus, in the initial steps of an investigation
aimed at discovering new motifs for the mediation of magnetic
superexchange interactions, we have probed the ability of dinu-
clear platinum phenylene complexes to serve as linkers between
organic nitroxide radicals.
The study of magnetic properties of nitroxide free radicals
and their coordination complexes is of current interest owing
to their potential utility as molecular magnetic materials.7
Due to their ease of preparation and stability, nitronyl nitrox-
ides8,9 have often been used as ligands to transition metals.10,11
In this contribution, we report the synthesis and properties of
diradical derivatives obtained by coordination of NITpPy
molecules (NITpPy = [2-(4-pyridyl)-4,4,5,5-tetramethylimid-
azoline-1-oxyl-3-oxide])12 to the metallic centers of 1,3- and
1,4-diplatinum phenylene complexes.13
Syntheses and structures of the bis(iodobis(triethylphosphine)-
platinum)phenylene complexes
1,3-Bis(iodobis(triethylphosphine)platinum)phenylene (2) was
prepared by adapting the published procedure used for the
synthesis of the 1,4-isomer (1).14 Thus, treatment of 1,3-
diiodobenzene with Pt(PEt3)4 in toluene at 85 ЊC afforded 2
(Scheme 1). Due to the high solubility of 2 in Et2O, separation
Scheme 1
of this compound from reaction by-products required repeated
fractional crystallization from hexanes to afford a 53% yield of
analytically pure 2. The NMR spectroscopic features of 2 are
in agreement with a solution structure of C2v symmetry. The 31
P
NMR spectrum of 2 consists of a single resonance line with a
pair of platinum satellites. Furthermore, the 1H NMR spectrum
of 2 exhibits one set of resonances for the triethylphosphine
protons. Accordingly, the aromatic protons give rise to reson-
ances whose multiplicity is in agreement with a symmetrically
meta-disubstituted phenylene ring.
While 1 has been previously characterized,14 its crystal struc-
ture was not reported. In the course of this work, we were able
to obtain single crystals of this compound that were analyzed
DOI: 10.1039/b104579m
J. Chem. Soc., Dalton Trans., 2001, 3453–3458
This journal is © The Royal Society of Chemistry 2001
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Fig. 3 Structure of the dication in 3. Selected bond distances
[Å] and angles [Њ]: Pt(1)–C(1) 2.017(12), Pt(1)–N(3) 2.122(11),
Pt(1)–P(1) 2.282(3), Pt(1)–P(2) 2.310(4); C(1)–Pt(1)–N(3) 178.2(5),
C(1)–Pt(1)–P(1) 86.6(4), N(3)–P(1)–P(1) 91.8(3), C(1)–Pt(1)–P(2)
88.7(4), N(3)–Pt(1)–P(2) 92.9(3), P(1)–Pt(1)–P(2) 175.09(12).
Fig. 1 Molecular structure of 1. Selected bond distances [Å] and
angles [Њ]: Pt(1)–C(1) 2.021(5), Pt(1)–P(2) 2.2991(13), Pt(1)–P(1)
2.3002(12), Pt(1)–I(1) 2.7136(6); C(1)–Pt(1)–P(2) 89.11(13), C(1)–
Pt(1)–P(1) 87.80(13), P(2)–Pt(1)–P(1) 168.71(4), C(1)–Pt(1)–I(1)
176.32(13), P(2)–Pt(1)–I(1) 88.89(3), P(1)–Pt(1)–I(1) 94.74(3).
Fig. 4 View of a portion of the supramolecular structure of 3 showing
the short contacts occurring between the nitronyl nitroxide moieties.
soluble in either chloroform or hot methanol. The ϩESI/TOF
mass spectrum of each compound is characterized by a m/z
peak at 704.7 that can be assigned to the [(Pt(PEt3)2(NITp-
Py))2C6H4]2ϩ dication. The IR spectra of 3 and 4 exhibit
absorption bands at 1374 and 1375 cmϪ1, respectively, which
correspond to the N–O stretching vibration. With respect to the
free radical, the UV-vis spectra of 3 and 4 are characterized by
a bathochromic shift of the NITpPy-centered transitions below
400 nm. Only weak absorption bands were observed in the vis-
ible region of the spectra and were assigned to the forbidden
n
π* transitions (3: ε(λ = 655 nm) = 70; 4: ε(λ = 656 nm) = 105).16
Complex 3 crystallizes in the monoclinic space group P21/n
Fig. 2 Molecular structure of 2. Selected bond distances [Å] and
angles [Њ]: Pt(1)–C(1) 2.034(8), Pt(1)–P(2) 2.292(2), Pt(1)–P(1) 2.304(2),
Pt(1)–I(1) 2.7031(7); C(1)–Pt(1)–P(2) 90.7(2), C(1)–Pt(1)–P(1) 91.5(2),
P(2)–Pt(1)–P(1) 172.02(7), C(1)–Pt(1)–I(1) 175.8(2), P(2)–Pt(1)–I(1)
89.30(6), P(1)–Pt(1)–I(1) 89.04(5).
as a bis(methylene chloride) solvate (Fig. 3). The cation is
centrosymmetric. As expected, the coordination geometry at
platinum is square planar and the atoms that define the square
plane form an 81.2Њ angle with respect to the phenylene ring.
The Pt–N (2.12(1) Å), Pt–C (2.02(1) Å) and Pt–P (2.282(3),
2.310(4) Å) bond lengths are comparable to the distances found
in related compounds.17 There is a 15.6Њ deviation from
coplanarity between the pyridyl and phenylene moieties. Fur-
thermore, the planar O(1)–N(1)–C(21)–N(2)–O(2) fragment
and the mean plane of the pyridine ring form a 15.1Њ angle with
respect to each other, which is comparable to that found in Zn-
(hfac)2ؒ2NITpPy (15.9Њ) (Hhfac = 1,1,1,5,5,5-hexafluoropent-
ane-2,4-dione).18 It is of interest to note that metal–NITpPy
complexes which are bound solely through the pyridyl nitro-
gen19 typically exhibit larger angles which range from 24Њ
for Mn(N3)2ؒ4NITpPy20 to 33Њ for HgBr2ؒNITpPy.21 An exam-
ination of the extended structure of 3ؒ2CH2Cl2 reveals the
existence of linear chains of the dications. In these chains, the
shortest intermolecular distance involves a nitroxide oxygen
atom (O(2)) and a methyl group (C(24A)) of the neighboring
molecule related by the symmetry transformation Ϫx ϩ 1, Ϫy
ϩ 1, Ϫz. The resulting distance O(2) ؒ ؒ ؒ C(24A) (3.47 Å) is
similar to that observed in the crystal structures of a series
HgBr2/pyridyl nitronyl nitroxide Lewis adducts21 and indicates
the presence of a short O ؒ ؒ ؒ HC contact which can be estim-
ated to range from 2.3 to 2.6 Å based on the calculated position
of the hydrogen atoms (Fig. 4).18 The second shortest inter-
molecular distance occurs between the neighboring NO
moieties and results in a N(2) ؒ ؒ ؒ O(2A) distance of 4.44 Å
(Fig. 4). Such NO ؒ ؒ ؒ NO contacts are prevalent in the solid
state structures of nitronyl nitroxides. Typically, however, these
contacts are much shorter and fall in the 3.2–3.5 Å range.9
by X-ray diffraction. Compound 1 crystallizes in the mono-
clinic space group P21/n with two molecules in the unit cell
(Fig. 1). Molecules of 1 are centrosymmetric. As expected, the
coordination geometry about the platinum is square planar
with the two phosphine ligands in a trans-arrangement. The
platinum square plane forms a dihedral angle of 82.3Њ with the
plane of the phenyl group. Similar deviations from orthogon-
ality have been observed in related platinum aryls.15 Other bond
distances and angles within the platinum square plane are
reminiscent of those found in (4,4Ј-[Pt(PEt3)2(I)]2biphenyl)14
and do not warrant further discussion. Compound 2 crystal-
lizes in the tetragonal space group P43212 with four molecules in
the unit cell (Fig. 2). Molecules of 2 contain a crystallographic
two-fold axis that bisects the phenylene ring and passes through
C(3) and C(4). The dihedral angles formed between the
platinum square plane and the phenylene ring is 78.0Њ. This
deviation from orthogonality appears slightly larger than that
observed in the case of 1 which possibly reflects the dif-
ferent steric requirements imposed by the meta- rather than
para-substitution of the phenylene ring.
Syntheses and structures of the diradicals
The diradicals 3 and 4 (Scheme 2) were prepared in good yield
by activation of the corresponding platinum iodide complexes
with AgPF6 and subsequent addition of two equivalents of
NITpPy. Compounds 3 and 4 are soluble in methylene chloride,
insoluble in aliphatic and aromatic solvents, and only slightly
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Scheme 2
Fig. 5 Structure of the dication in 4. Selected bond distances [Å]
and angles [Њ]: Pt(1)–C(1) 2.023(6), Pt(1)–N(3) 2.134(5), Pt(1)–P(1)
2.3081(18), Pt(1)–P(2) 2.3203(18), Pt(2)–C(3) 2.028(7), Pt(2)–N(6)
2.127(5), Pt(2)–P(4) 2.3019(17), Pt(2)–P(3) 2.3065(17); C(1)–Pt(1)–N(3)
178.6(2), C(1)–Pt(1)–P(1) 92.06(19), N(3)–Pt(1)–P(1) 89.30(16), C(1)–
Pt(1)–P(2) 88.37(19), N(3)–Pt(1)–P(2) 90.31(16), P(1)–Pt(1)–P(2)
174.56(7), C(3)–Pt(2)–N(6) 175.7(2), C(3)–Pt(2)–P(4) 88.61(18), N(6)–
Pt(2)–P(4) 93.72(15), C(3)–Pt(2)–P(3) 86.59(18), N(6)–Pt(2)–P(3)
91.50(15), P(4)–Pt(2)–P(3) 171.91(6).
Fig. 6 χT vs. T plot for compound 3 (᭹) and 4 (᭺) at 1 T.
Complex 4 crystallizes in the monoclinic space group P21/n
as a water–methanol solvate (Fig. 5). The average Pt–N (av.
2.12 Å), Pt–C (av. 2.02 Å), Pt–P (av. 2.31 Å) bond distances are
similar to those observed in 3. The mean plane of the phenylene
moiety is nearly orthogonal to both platinum coordination
square planes (89.7Њ and 89.8Њ for Pt(1) and Pt(2), respectively).
The angle between the plane of the phenylene group and the
pyridyl group bound to Pt(1) is 5.5Њ whereas the corresponding
angle involving Pt(2) is 9.4Њ. The planar ONCNO fragments of
the nitronyl nitroxide five membered rings form a dihedral
angle of 20.4Њ and 25.2Њ with their corresponding pyridyl group.
The cations in 4ؒH2OؒCH3OH are arranged into zigzagging
chains. In these chains, the shortest intermolecular distances are
found between neighboring molecules related by the symmetry
operation x ϩ 1, y Ϫ 1, z. As in 3, the shortest distances occur
between the nitronyl nitroxide oxygen atoms and methyl groups
of neighboring nitronyl nitroxides (O(1) ؒ ؒ ؒ C(51A) 3.501 Å
and O(3) ؒ ؒ ؒ C(39A) 3.566 Å with associated O ؒ ؒ ؒ HC dis-
tances in the range 2.4–2.6 Å). The next shortest intermolecular
distances between the nitronyl nitroxide moieties of neighbor-
ing dications in 4ؒH2OؒCH3OH are those involving the NO
groups. In this case, however, the distances separating the
paramagnetic moieties are large (N(2) ؒ ؒ ؒ N(2A) distance of
5.66 Å).
coupling constant aN (7.4 G) is comparable to that observed in
various nitronyl nitroxide derivatives.22 The absence of coupling
to the 195Pt nuclei most likely results from the localization of the
SOMO on the nitronyl nitroxide part of the NITpPy mole-
cule.23 The ∆ms = 2 transitions associated with the existence of a
triplet state were never observed. The magnetic susceptibility of
each compound was measured in the range 2–300 K and a plot
of χT vs. T is given in Fig. 6. The χT value of 0.749 cm3
K molϪ1 found for each compound at 300 K is in close agree-
ment with the theoretical value of 0.75 cm3 K molϪ1 for two
uncoupled S = 1/2 spins. While the temperature dependence of
the magnetic susceptibility of 4ؒH2OؒCH3OH is very close to a
Curie Law between 300 and 2 K, the magnetic data of 3 reflect
weak antiferromagnetic interactions (θ = Ϫ0.3 K).
The HOMO of a square planar d8 metal complex is largely
dxy in character.24 As shown by investigations on the non-
linear optical properties of complexes such as p-nitro-
phenylbis(triethylphosphine)platinum halides, the d8 metal
readily conjugates with the aromatic π-system.25 Thus, in com-
pounds 3 and 4, the dxy orbitals of the platinum could enable
electronic communication between the phenylene and the
pyridyl π-systems.26 However, because of the negligible spin
density found at the pyridine nitrogen atom of NITpPy,23 it is
unlikely that intramolecular magnetic interactions occur. In
turn, it seems reasonable to assume that the weak antiferro-
magnetic interactions observed in the case of 3 results from
intermolecular interactions between proximal nitronyl nitroxide
moieties of neighboring complexes. In particular, since both
platinum derivatives were found to possess similar O ؒ ؒ ؒ HC
contacts, the difference between the magnetic properties of 3
and 4 may be attributed to the shorter NO ؒ ؒ ؒ NO distance
observed in 3.
Magnetic properties of the diradicals
The magnetic properties of 3 and 4 are consistent with an isol-
ated two S = 1/2 spin system rather than an interacting (either
an S = 1 or S = 0) spin system. Thus, the room temperature EPR
spectrum of 10Ϫ5 M CH2Cl2 solutions of each compound
exhibits a five line signal centered at g = 2.01. The multiplicity
of this signal indicates coupling of the electron spin with two
equivalent nitrogen nuclei. The magnitude of the hyperfine
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solution to Ϫ30 ЊC overnight, afforded after drying for 12 hours
at 60 ЊC a 53% yield (0.54 g) of 2 as colorless needles. It should
be noted that the drying procedure should be followed since an
X-ray structural study revealed that 2 readily crystallizes with
¹ mol hexane molecule per mol 2. Furthermore, the elemental
Conclusion
This work demonstrates that bifunctional cationic aryl-
platinum() species readily coordinate NITpPy radicals to form
diradical species. While the structures of the paramagnetic
complexes 3 and 4 have been confirmed by X-ray diffraction
methods, magnetic measurements indicate the absence of
significant intramolecular magnetic communication, which can
be rationalized by invoking the localization of the SOMO on
the nitronyl nitroxide part of the NITpPy ligand.23
¯
²
analytical data performed on several undried samples were con-
sistent with the partial loss of hexane from 2ؒ0.5C6H14. X-Ray
quality crystals of solvent-free 2 were formed by allowing hot
C6F6 solutions to cool to room temperature and allowing the
solutions to stand for several days. Compound 2 is soluble in
CHCl3, CH2Cl2, THF, acetone, benzene, and toluene, and
slightly soluble in Et2O, hexanes, pentane, and hot hexafluoro-
benzene; mp 180–185 ЊC, melts with decomp. Anal. Calcd. for
C30H64I2P4Pt2: C, 30.21; H, 5.41. Found: C, 30.42; H, 5.32%.
Experimental
General
1H NMR(CDCl3) 7.20 (s, 1H, 3JHPt = 68 Hz), 6.79 (d, 2H, JHH
=
All manipulations involving platinum(0) compounds were
carried out either in a nitrogen-filled drybox or by using Schlenk
techniques. In these cases, solvents were dried by typical
methods and distilled before use. K2PtCl4, silver salts, and
PEt3 were purchased from Strem Chemicals, halogenobenzenes
were purchased from Aldrich and all were used as received.
Pt(PEt3)4 27 and NITpPy were prepared according to published
procedures. Atlantic Microlab (Norcross, Georgia) performed
elemental analyses. Melting points were measured by using a
Mel-Temp II instrument on samples contained in flame sealed
capillaries and are uncorrected. 1H (300 MHz), 13C (75.4 MHz),
31P (121.43 MHz) NMR spectra were acquired on a Varian
VXR 300 instrument. All chemical shifts are reported in δ
(ppm) units and are referenced to SiMe4 δ 0.00 (1H, 13C) and to
CHCl3 at either δ 7.27 ppm (1H) or δ 77.23 (13C) whereas 31P
chemical shifts were externally referenced to 85% H3PO4 at
δ 0.00. IR spectra (KBr pellets) were obtained by using an
ATI Mattson Genesis Series FTIR instrument. UV-vis spectra
were acquired by using a HP 8453 spectrophotometer. EPR
measurements were recorded at X-band frequencies with a
Bruker ESP300 instrument.
7 Hz, 3JHPt = 68 Hz), 6.53 (t, 1H, JHH = 7 Hz, 4JHPt = 26 Hz), 1.86
(br, m, 24H), 1.02 (pseudo quint, 36H, JHH = 8 Hz). 13C NMR
(CDCl3) 144.76 (m, Cipso) 142.04 (m, C2), 132.07 (m, C4(6)),
128.00 (s, C5), 15.30 (pseudo quint, JCP = 17 Hz), 8.08 (pseudo t,
JCP = 13 Hz). 31P NMR (CDCl3) 9.61 (s, JPtP = 2807 Hz).
{1,4-[Pt(PEt3)2(NITpPy)]2C6H4}[PF6]2 (3). In a typical prep-
aration, a 50 mL Schlenk flask fitted with a magnetic stirring
bar was charged with 1 (0.26 g, 0.22 mmol) and CH2Cl2 (20 mL)
in the drybox. AgPF6 (0.11 g, 0.43 mmol) was added to the
resulting solution. After 30 min, the reaction mixture was
filtered and the resulting colorless solution was combined with
a solution of NITpPy (0.11g, 0.45 mmol) in CH2Cl2 (10 mL).
Upon mixing, an emerald green solution formed. After the
solution had been stirred for 12 h, the solvent was removed by
vacuum distillation at room temperature to leave a dark green
oily residue which was subsequently washed with three 10 ml
portions of toluene to remove any unreacted NITpPy. From
this point forward, all manipulations were carried out in air and
care was taken to avoid contact with metal surfaces (such as
spatula, aluminium weighing pans) that typically gave rise to
trace magnetic impurities. The green product was dissolved in
10 mL of CH2Cl2 and filtered through a Celite pad three times
to remove an unidentified gray insoluble solid thus affording an
emerald green solution. Crystalline compound 3 was obtained
in a 73% yield (0.27 g) after vapor diffusion of pentane into
the CH2Cl2 solution. Anal. Calcd. (Found) for C54H96F12-
N6O4P6Pt2: C, 38.21 (38.30); H 5.70 (5.94); N 4.95 (4.80%); mp
Syntheses
1,4-[Pt(PEt3)2(I)]2C6H4 (1). This compound was prepared
by an adaptation of the method described in the literature.14
1,4-Diiodobenzene (0.21 g, 0.65 mmol) and Pt(PEt3)4 (0.95 g,
1.43 mmol) were allowed to react in toluene (25 mL) at 80 ЊC for
30 h. Compound 1 was isolated in an 82% yield (0.64 g) after
removing solvent by vacuum distillation and washing the color-
less solid with three 2 mL aliquots of Et2O. Crystals suitable for
X-ray structural determinations were obtained either by cool-
ing a concentrated hot toluene solution to Ϫ30 ЊC overnight or
after allowing a layer of Et2O (1 mL) to slowly diffuse (2 d) into
a CH2Cl2 solution (1 mL). Compound 1 is soluble in CHCl3,
CH2Cl2, THF, acetone, slightly soluble in benzene, toluene,
and hot hexafluorobenzene and insoluble in Et2O, hexanes and
pentane, mp 210 ЊC decomp. Anal. Calcd. for C30H64I2P4Pt2: C,
192–195 ЊC decomp. IR (KBr, νN–O) 1374 cmϪ1. UV [10Ϫ5
M
CH2Cl2, λ/nm(log ε)] 265 (4.20), 309 (4.27), 369 (4.03), 385
(4.20), 655 (1.84).
{1,3-[Pt(PEt3)2(NITpPy)]2C6H4}[PF6]2 (4). Compound 4 was
prepared from 2 (0.43 g, 0.36 mmol), AgPF6 (0.18 g, 0.71 mmol)
and NITpPy (0.17 g, 0.73 mmol) by following the method used
for the synthesis of 3. Vapor diffusion of pentane into the
CH2Cl2 solution yielded an insoluble green viscous liquid that
was dissolved in CH2Cl2 (2 mL) and transferred to a Pasteur
pipette containing a 2Љ column of silica gel. The column was
first eluted with CH2Cl2 (5 mL). The resulting green fraction
was set aside. The column was then eluted with methanol (10
mL) to give a second green fraction which after evaporation of
the solvent yielded a green solid. The solid was dissolved in the
minimal amount of boiling methanol and quickly filtered
through a pipette containing a glass wool plug. The resulting
solution was allowed to cool to room temperature and yielded
after one day a 54% yield (0.34 g) of 4ؒH2OؒCH3OH. Add-
itional portions of 4ؒH2OؒCH3OH were obtained by repeating
this procedure with the mother liquor and the CH2Cl2 fraction
collected from the first chromatographic run. A yield of 72%
(0.45 g) of crystalline 4ؒH2OؒCH3OH was finally obtained.
Anal. Calcd. (Found) for C55H102F12N6O6P6Pt2: C, 37.80(37.65);
H, 5.88(5.68); N, 4.81(4.80%). mp 181–184 ЊC decomp. IR
(KBr, νN–O) 1375 cmϪ1. UV [10Ϫ5 M CH2Cl2, λ/nm (log ε)] 243
(4.56), 308 (4.26), 371 (4.04), 384 (4.19), 656 (2.02).
1
30.21; H, 5.41. Found: C, 30.43; H, 5.54%. H NMR(CDCl3)
3
5
6.82 (br, 4H, JHPt = 66 Hz, JHPt = 8 Hz), 1.77 (br, m, 24H),
1.02 (pseudo quint, 36H, JHH = 8 Hz). 13C NMR (CDCl3)
136.84 (m), 135.02 (m, ipso), 15.30 (pseudo quint, JCP = 17 Hz),
8.12 (pseudo t, JCP = 13 Hz). 31P NMR (CDCl3) 8.35 (s, JPtP
=
2787 Hz).
1,3-[Pt(PEt3)2(I)]2C6H4 (2). In the drybox, a 50 mL Schlenk
flask fitted with a magnetic stirbar was charged with 1,3-diiodo-
benzene (0.28 g, 0.86 mmol), Pt(PEt3)4 (1.15 g, 1.72 mmol), and
25 mL toluene. After heating the reaction mixture with an
external 85 ЊC oil bath for 24 h, the volatile components were
removed by vacuum distillation at room temperature to leave
a sticky light yellow solid. The solid was washed with hexanes
(4 mL) and the supernatant was separated from the insoluble
portion by cannula filtration. The washing/filtration procedure
was repeated twice until the remaining solid was colorless.
Recrystallization of the colorless solid by cooling a hot hexane
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Table 1 Crystal data, data collection, and structure refinement for 1, 2, 3 and 4
1
2
3ؒ2CH2Cl2
4ؒH2OؒCH3OH
Formula
Mr
C30H64I2P4Pt2
1192.67
C30H64I2P4Pt2
1192.67
C56H100Cl4F12N6O4P6Pt2
1867.22
C55H102F12N6O6P6Pt2
1743.43
Crystal size/mm
Crystal system
Space group
0.40 × 0.27 × 0.13
Monoclinic
P21/n
0.19 × 0.17 × 0.10
Tetragonal
P43212
0.19 × 0.11 × 0.06
Monoclinic
P21/n
0.19 × 0.08 × 0.07
Monoclinic
P21/n
a/Å
b/Å
c/Å
7.4670(15)
15.906(3)
16.692(3)
100.37(3)
1950.2(7)
2
10.2652(15)
10.2652(15)
38.177(8)
–
4022.9(12)
4
11.634(2)
23.791(5)
14.159(3)
107.15(3)
3745.0(13)
2
13.772(3)
14.307(3)
36.198(7)
93.30(3)
7121(2)
4
β/Њ
V Å3
Z
ρcalc/g cmϪ3
2.031
8.931
1.969
8.659
1.656
4.077
1.630
4.139
µ(Mo-Kα)/mmϪ1
T /K
150(2)
110(2)
110(2)
110(2)
R1,a wR2b [I > 2σ(I )]
0.0254, 0.0618a
0.0310, 0.0755a
0.0809, 0.1513b
0.0440, 0.1055a
a R1 = Σ(Fo Ϫ Fc)/ΣFo. b wR2 = {[Σw(Fo2 Ϫ Fc2)2]/[Σw(Fo )2]}1/2
.
2
5 B.-H. Huisman, H. Schonherr, W. T. S. Huck, A. Friggeri, H.-J. Van
Manen, E. Menozzi, G. J. Vancso, F. C. J. M. Van Veggel and D. N.
Reinhoudt, Angew. Chem., Int. Ed., 1999, 38, 2248; W. T. S. Huck,
L. J. Prins, R. H. Fokkens, N. M. M. Nibbering, F. C. J. M.
van Veggel and D. N. Reinhoudt, J. Am. Chem. Soc., 1998, 120,
6240; W. T. S. Huck, F. C. J. M. van Veggel and D. N. Reinhoudt,
Angew. Chem., Int. Ed. Engl., 1996, 35, 1213.
6 M.-C. Lagunas, R. A. Gossage, A. L. Spek and G. van Koten,
Organometallics, 1998, 17, 731; P. Steenwinkel, H. Kooijman,
W. J. J. Smeets, A. L. Spek, D. M. Grove and G. van Koten,
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7 See for example: V. I. Ovcharenko and R. Z. Sagdeev, Russ. Chem.
Rev. (Engl. Transl.), 1999, 68, 345; P. M. Lahti, Magnetic Properties
of Organic Materials, Marcel Dekker, New York, 1999; O. Kahn,
Magnetism: A Supramolecular Function, Kluwer Publishing Co.,
Dordrecht, 1996; E. Coronado, P. Delhaes, D. Gatteschi and J. S.
Miller, Molecular Magnetism: From Molecular Assemblies to the
Devices, Kluwer Academic Publishers, Dordrecht, 1996, vol.
321; O. Kahn, Molecular Magnetism, VCH, New York, 1993;
D. Gatteschi, Molecular Magnetic Materials, Kluwer Academic
Publishers, Amsterdam, 1991.
Crystal structure determination
Data were collected on a Siemens SMART-CCD area detector
diffractometer with Mo-Kα radiation (λ = 0.71069 Å). Speci-
mens of suitable size and quality were selected and mounted
onto a glass fiber with Apiezon grease. The structure was solved
by direct methods, which successfully located most of the
non-hydrogen atoms. Subsequent refinement on F 2 using the
SHELXTL/PC package28 allowed location of the remaining
non-hydrogen atoms. Further crystallographic details can be
found in Table 1.
CCDC reference numbers 171201–171204.
See http://www.rsc.org/suppdata/dt/b1/b104579m/ for crys-
tallographic data in CIF or other electronic format.
Magnetometry
The magnetic susceptibility data were measured with the use
of a Quantum Design SQUID magnetometer MPMS-XL.
Measurements were performed in the temperature range 2–300
K at 1 T on finely divided polycrystalline samples. Data were
corrected for the sample holder, and diamagnetic contributions
were calculated from Pascal constants.
8 E. F. Ullman and J. H. Osieckie, J. Am. Chem. Soc., 1968, 90, 1078.
9 M. Deumal, J. Cirujeda, J. Veciana and J. J. Novoa, Chem. Eur. J.,
1999, 5, 1631.
10 A. Caneschi, D. Gatteschi, R. Sessoli and P. Rey, Acc. Chem. Res.,
1989, 22, 392; P. Rey and D. Luneau, NATO ASI Ser., Ser. C, 1999,
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Acknowledgements
11 A. Caneschi, D. Gatteschi, J. Laugier, P. Rey, R. Sessoli and
C. Zanchini, J. Am. Chem. Soc., 1988, 110, 2795; C. Benelli,
A. Caneschi, D. Gatteschi and L. Pardi, Inorg. Chem., 1992, 31, 741;
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K. Awaga, Phys. Rev. B: Condens. Matter, 1997, 56, 14560; K. Fey,
D. Luneau, T. Ohm, C. Paulsen and P. Rey, Angew. Chem., Int. Ed.,
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and O. Kahn, New. J. Chem., 1999, 23, 1333; A. Marvilliers, Y. Pei,
J. Cano, K. E. Vostrikova, C. Paulsen, E. Rivière, J.-P. Audière and
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We thank the Texas A&M Energy Resource Program (Grant
99–29 and 2000–08) and the Robert A. Welch Foundation
(Grant A-1423) and the Department of Chemistry at Texas
A&M University for generous financial support. The purchase
of the X-ray diffractometer was made possible by a grant
from the National Science Foundation (CHE-98 07975). R. C.
thanks the Conseil Regional d’Aquitaine and the Centre
National de Recherche Scientifique for financial support as well
as for providing access to the SQUID magnetometer. We thank
Dr Reibenspies for his expert insights regarding part of the
crystallography.
12 R. Sayre, J. Am. Chem. Soc., 1955, 77, 6689.
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