Neutral molecular Pd6 hexagons using κ3-P 2O-terdentate ligands

Article abstract of DOI:10.1021/ic060629o

The one-step synthesis of three new P₂O-terdentate carboxylic acid ditertiary phosphines 2-{(Ph₂PCH₂) ₂N}-3-(X)C₆H₃CO₂H (X = OCH ₃, L1; X = OH, L2) and 2-{(Ph₂

Full text of DOI:10.1021/ic060629o

Inorg. Chem. 2006, 45, 6761−6770
Neutral Molecular Pd6 Hexagons Using
K
3-P2O-Terdentate Ligands
Mark R. J. Elsegood, Martin B. Smith,* and Paul M. Staniland
Department of Chemistry, Loughborough UniVersity, Loughborough, Leics LE11 3TU, U.K.
Received April 13, 2006
The one-step synthesis of three new P2O-terdentate carboxylic acid ditertiary phosphines 2-{(Ph2PCH2)2N}-3-
(X)C6H3CO2H (X
Mannich condensation reaction using Ph2PCH2OH and the appropriate amine in CH3OH is reported. Compounds
L1 L3 function as typical cycloocta-1,5-
2-P2-didentate ligands upon complexation to Pd(CH3)Cl(cod) (cod
diene), affording the neutral, mononuclear complexes Pd(CH3)Cl(L1 L3) (1 3). Metathesis of 1 with NaX (X Br,
I) gave the corresponding (methyl)bromopalladium(II) (4) and (methyl)iodopalladium(II) (5) complexes, respectively.
When chloroform or chloroform/methanol solutions of 1 3 (or 5) were allowed to stand, at ambient temperatures,
yellow crystalline solids were isolated in very high yields (71 88%) and were analyzed for the novel hexameric
palladium(II) compounds 6 9. All new compounds reported have been fully characterized by a combination of
) OCH3, L1; X ) OH, L2) and 2-{(Ph2PCH2)2N}-5-(OH)C6H3CO2H (L3) by a phosphorus-based
−
κ
)
−
−
)
−
−
−
spectroscopic (multinuclear NMR, Fourier transform IR, electrospray mass spectrometry, matrix-assisted laser
desorption ionization time-of-flight mass spectrometry) and analytical methods. The self-assembly reactions are
remarkably clean as monitored by 31P
determined for L1, 4, 7 17CDCl3 2Et2O, 8
planar palladium(II) metal centers comprise a
either a chloride or iodide ligand, leading to 48-membered metallomacrocycles (with outside diameters of ca. 2.5
nm). Whereas only intramolecular O ‚‚‚N hydrogen bonding between the hydroxy group and tertiary amine has
been observed in 7, strong intermolecular O ‚‚‚O hydrogen bonding of the type CO‚‚‚HO(CH3)‚‚‚HO, involving
a methanol solvate, has been found in 8, leading to an unprecedented three-dimensional network motif.
{
1H
}
and 1H NMR spectroscopy. Single-crystal X-ray structures have been
6CHCl3 8CH3OH, and 9 17CDCl3. In hexamers 7 9, all six square-
2-P2-chelating diphosphine, a 1-O-monodentate carboxylate, and
‚
‚
‚
‚
‚
−
κ
κ
−H
−H
Introduction
late-transition,10 lanthanide,11 or group 1412 metals have all
recently been described. However, to the best of our
Considerable recent attention has been directed toward
novel cyclic polynuclear1 metal complexes, e.g., metal
wheels,2 metallocrowns,3 cartwheels,4 and catenanes,5 not
only for their aesthetic appeal but also for their fascinating
properties and potential applications as molecular magnetic
storage6 or photosensitive devices and as catalysts.7 Various
strategies have been documented for preparing such diverse
supermolecular metal-based materials.7,8 Structurally char-
acterized molecular hexagons containing either six first-row,9
(2) (a) Abu-Nawwas, A.-A. H.; Cano, J.; Christian, P.; Mallah, T.;
Rajaraman, G.; Teat, S. J.; Winpenny, R. E. P.; Yukawa, Y. Chem.
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Mkami, H.; Overgaard, J.; Piligkos, S.; Rajaraman, G.; Rentschler,
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A.; Winpenny, R. E. P. Angew. Chem., Int. Ed. 2003, 42, 101-105.
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Angew. Chem., Int. Ed. 2001, 40, 152-154. (g) Frey, M.; Harris, S.
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R. E. P. Chem.sEur. J. 2000, 6, 1407-1415.
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* To whom correspondence should be addressed. E-mail: m.b.smith@
lboro.ac.uk. Tel: +44 (0)1509 222553. Fax: +44 (0)1509 223925.
(1) (a) Amijs, C. H. M.; van Klink, G. P. M.; van Koten, G. Dalton Trans.
2006, 308-327. (b) Rauterkus, M. J.; Krebs, B. Angew. Chem., Int.
Ed. 2004, 43, 1300-1303. (c) Lehaire, M.-L.; Scopelliti, R.; Herdeis,
L.; Polborn, K.; Mayer, P.; Severin, K. Inorg. Chem. 2004, 43, 1609-
1617. (d) Thue´ry, P.; Villiers, C.; Jaud, J.; Ephritikhine, M.; Masci,
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10.1021/ic060629o CCC: $33.50
Published on Web 07/18/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 17, 2006 6761

Elsegood et al.
knowledge, there remain very few reported13 examples of
hexanuclear metallomacrocycles incorporating six d8 pal-
ladium centers, although smaller homotetranuclear palladium
species are known.14
The assembly of highly organized architectures has com-
monly made use of simple ligands that incorporate group
15 or 16 donor sites. Many of these building blocks are
frequently based on nitrogen (e.g., pyridyl15 or pyridone16
derivatives) and/or oxygen (e.g., carboxylates,17 alkoxides,18
or phosphinates/phosphonates19) donor ligands as connectors
between metal centers. Considerably less has been docu-
mented with tertiary phosphines, which routinely fulfill the
role of spectator ligand only.20,21 Recent elegant self-
assembled gold(I) complexes using chelating ditertiary
phosphines have been documented by Puddephatt et al.5
While carboxylates have been widely used in the synthesis
of metal-organic frameworks22,23 and polynuclear com-
pounds,24 the use of hybrid ligands such as phosphino-
carboxylic acids as building blocks for self-assembly is
extremely rare.25 Furthermore, the use of carboxylic acid
functionalized ditertiary phosphines, bearing a “hard” oxygen
and two “soft” phosphorus donors, as building blocks for
the self-assembly of multimetallic cyclic structures has not
been explored. In contrast, Raymond and co-workers have
used hybrid tertiary phosphines with PO2 donor sets for the
metal-based assembly of various supramolecular clusters.26
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Herein we describe a general synthetic route to three new
modified ditertiary phosphines, bearing a carboxylic acid
group, that can be readily prepared from inexpensive
reagents. These highly functionalized compounds, in their
carboxylate form, serve as excellent bridging ligands for the
unprecedented syntheses of four neutral 48-membered hexa-
nuclear Pd6 metallomacrocycles. In addition, the incorpora-
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N-arene backbone can be used to construct a novel
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6762 Inorganic Chemistry, Vol. 45, No. 17, 2006

Neutral Molecular Pd6 Hexagons
L1 (0.156 g, 0.277 mmol). After stirring for 15 min, the solution
was passed through a small Celite plug and Et2O (10 mL) and
petroleum ether (bp 60-80 °C, 10 mL) were added. The solid 1
was collected by suction filtration and dried in vacuo (0.185 g,
92%). Selected spectroscopic data for 1: 31P{1H} NMR (36.2 MHz)
Experimental Section
Materials. All syntheses were conducted in air with the exception
of L1-L3, which were conducted under an atmosphere of dry,
oxygen-free nitrogen using standard Schlenk techniques. All
solvents were distilled prior to use. The palladium(II) starting
material Pd(CH3)Cl(cod) (cod ) cycloocta-1,5-diene) was prepared
according to a published procedure.27 All other reagents were
purchased from commercial suppliers and used as received.
Instrumentation. IR spectra were recorded as KBr pellets over
the range 4000-200 cm-1 using a Perkin-Elmer system 2000 FT
1
26.1, -7.1 ppm [2J(PP) ) 50.6 Hz]; H NMR (400 MHz) 7.87-
7.01 (m, 23H, aromatic H), 4.29 (m, 2H, CH2), 3.91 (m, 2H, CH2),
3
3.81 (s, 3H, OCH3), 0.75 (dd, 3H, J(PH) ) 8 and 4 Hz, CH3)
ppm; IR νCO 1712, νPdCl 296 cm-1; FAB MS m/z 705 (M - CH3).
Anal. Calcd for C35H34NO3P2PdCl: C, 58.34; H, 4.77; N, 1.94.
Found: C, 58.11; H, 4.54; N, 1.56. Compound 2 was observed, by
in situ NMR, upon reaction of Pd(CH3)Cl(cod) (0.007 g, 0.0264
mmol) with 1 equiv of L2 (0.015 g, 0.0273 mmol) in CDCl3 (0.5
mL). Selected spectroscopic data for 2 (CDCl3): 31P{1H} NMR
1
spectrometer. H NMR and 31P{1H} NMR spectra were recorded
on JEOL FX90Q, Bruker AC250, or DPX-400 FT spectrometers
with chemical shifts (δ) reported relative to external tetramethyl-
silane or H3PO4. All NMR spectra (90, 250, or 400 MHz) were
recorded in CDCl3 solutions unless otherwise stated. Matrix-assisted
laser desorption ionization time-of-flight mass spectrometry (MALDI-
TOF MS) was recorded on a Bruker Reflex III spectrometer
operated using the reflection mode [with dihydroxybenzoic acid
(DHB) as the matrix]. Elemental analyses (Perkin-Elmer 2400 CHN
elemental analyzer) were performed by the Loughborough Uni-
versity Analytical Service within the Department of Chemistry.
Preparation of Ligands. 2-{(Ph2PCH2)2N}-3-(OCH3)C6H3CO2H
(L1). To the solids Ph2PCH2OH (1.055 g, 4.88 mmol) and 2-H2N-
3-(OCH3)C6H3CO2H (0.410 g, 2.45 mmol) was added oxygen-free
CH3OH (15 mL). After the solution was stirred for ca. 16 h, the
volume was reduced in vacuo and the white solid L1 collected by
suction filtration. The solid was washed with CH3OH (5 mL) and
dried in vacuo (1.100 g, 80%). Selected spectroscopic data for L1:
31P{1H} NMR (36.2 MHz) -22.3 ppm; 1H NMR (400 MHz) 12.1
(s, 1H, OH), 7.88-6.47 (m, 23H, aromatic H), 4.20 (m, 4H, CH2),
3.43 (s, 3H, OCH3) ppm; IR νCO 1699 cm-1; fast atom bombard-
ment (FAB) MS m/z 564 (M). Anal. Calcd for C34H31NO3P2: C,
72.45; H, 5.56; N, 2.49. Found: C, 72.64; H, 5.35; N, 1.97.
2-{(Ph2PCH2)2N}-3-(OH)C6H3CO2H (L2). To the solids
Ph2PCH2OH (1.028 g, 4.75 mmol) and 2-H2N-3-(OH)C6H3CO2H
(0.364 g, 2.38 mmol) was added oxygen-free CH3OH (20 mL).
After the mixture was stirred for ca. 3 days, solid L2 was collected
by suction filtration, washed with CH3OH (5 mL), and dried in
vacuo (1.141 g, 87%). Selected spectroscopic data for L2 [(CD3)2SO]:
31P{1H} NMR (36.2 MHz) -18.3 ppm; 1H NMR (400 MHz) 16.02
(s, 1H, CO2H), 10.25 (s, 1H, OH), 7.44-6.78 (m, 23H, aromatic
H), 4.33 (s, 4H, CH2) ppm; IR νCO 1654 cm-1; FAB MS m/z 550
(M). Anal. Calcd for C33H29NO3P2: C, 72.12; H, 5.33; N, 2.55.
Found: C, 71.80; H, 5.26; N, 2.29.
1
(36.2 MHz) 26.3, -7.3 ppm [2J(PP) ) 48.4 Hz]; H NMR (400
MHz) 8.00-7.01 (m, 23H, aromatic H), 4.36 (CH2), 4.15 (CH2),
3
0.74 (dd, 3H, J(PH) ) 7.3 and 2.6 Hz, CH3) ppm. Compound 3
was prepared in a manner similar to that of 1 (97%) using L3.
Selected spectroscopic data for 3 [(CD3)2SO]: 31P{1H} NMR (36.2
MHz) 22.8, -11.0 ppm [2J(PP) ) 46.2 Hz]; 1H NMR (400 MHz)
13.00 (br, 1H, CO2H), 9.66 (s, 1H, OH), 7.79-5.60 (m, 23H,
aromatic H), 4.18 (s, 2H, CH2), 4.08 (s, 2H, CH2), 0.33 (dd, 3H,
3J(PH) ) 7.8 and 3.2 Hz, CH3) ppm; IR νCO 1691, νPdCl 285 cm-1
.
Anal. Calcd for C34H32NO3P2PdCl: C, 57.80; H, 4.57; N, 1.98.
Found: C, 57.68; H, 4.36; N, 1.81.
Pd(CH3)Br{2-{(Ph2PCH2)2N}-3-(OCH3)C6H3CO2H} (4). To
a suspension of 1 (0.078 g, 0.108 mmol) in acetone (10 mL) was
added NaBr (0.111 g, 1.09 mmol) in acetone/CH3OH (1.5:1.5 mL).
The mixture was stirred for 4 h and the solvent evaporated to
dryness under reduced pressure. The crude solid was extracted into
CH2Cl2 (15 mL) and passed through a Celite plug. The solvent
was concentrated to ca. 1 mL and Et2O (15 mL) added to give 4,
which was collected by suction filtration and dried in vacuo (0.068
g, 82%). Selected spectroscopic data for 4: 31P{1H} NMR (36.2
1
MHz) 23.7, -7.3 ppm [2J(PP) ) 50.6 Hz]; H NMR (400 MHz)
7.97-7.07 (m, 23H, aromatic H), 4.39 (m, 2H, CH2), 4.00 (m, 2H,
CH2), 3.89 (s, 3H, OCH3), 0.88 (dd, 3H, 3J(PH) ) 8.0 and 4.3 Hz,
CH3) ppm; IR νCO 1712 cm-1; FAB MS m/z 750 (M - CH3). Anal.
Calcd for C35H34NO3P2PdBr‚0.5H2O: C, 54.31; H, 4.57; N, 1.81.
Found: C, 54.03; H, 4.33; N, 1.74.
Pd(CH3)I{2-{(Ph2PCH2)2N}-3-(OCH3)C6H3CO2H} (5). To a
suspension of 1 (0.081 g, 0.112 mmol) in acetone (10 mL) was
added NaI (0.184 g, 1.23 mmol) in acetone/CH3OH (1.5:1.5 mL).
The pale-orange mixture was stirred for 2 h and the solvent
evaporated to dryness under reduced pressure. The crude solid was
extracted into CH2Cl2 (25 mL) and passed through a Celite plug.
The solvent was concentrated to ca. 1-2 mL and Et2O (15 mL)
added to give 5, which was collected by suction filtration and dried
in vacuo (0.073 g, 80%). Selected spectroscopic data for 5: 31P{1H}
2-{(Ph2PCH2)2N}-5-(OH)C6H3CO2H (L3). To the solids
Ph2PCH2OH (1.019 g, 4.71 mmol) and 2-H2N-5-(OH)C6H3CO2H
(0.365 g, 2.38 mmol) was added oxygen-free CH3OH (25 mL).
Both reagents dissolved to give a yellow solution followed by the
immediate formation of solid L3. After the mixture was stirred for
ca. 1 day, L3 was collected by suction filtration, washed with
CH3OH (5 mL), and dried in vacuo (0.982 g, 76%). Selected
spectroscopic data for L3 [(CD3)2SO]: 31P{1H} NMR (36.2 MHz)
1
NMR (36.2 MHz) 16.8, -8.8 ppm [2J(PP) ) 50.6 Hz]; H NMR
(400 MHz) 7.95-6.84 (m, 23H, aromatic H), 4.34 (m, 2H, CH2),
3
4.00 (m, 2H, CH2), 3.82 (s, 3H, OCH3), 0.99 (dd, 3H, J(PH) )
7.4 and 5.0 Hz, CH3) ppm; IR νCO 1711 cm-1; FAB MS m/z 796
(M - CH3). Anal. Calcd for C35H34NO3P2PdI‚2H2O: C, 49.62; H,
4.53; N, 1.65. Found: C, 49.66; H, 4.74; N, 1.61.
1
-20.2 ppm; H NMR (400 MHz) 15.41 (s, 1H, CO2H), 9.81 (s,
1H, OH), 7.48-6.72 (m, 23H, aromatic H), 4.17 (s, 4H, CH2) ppm;
IR νCO 1664 cm-1; FAB MS m/z 550 (M). Anal. Calcd for C33H29-
NO3P2: C, 72.12; H, 5.33; N, 2.55. Found: C, 71.97; H, 5.24; N,
2.41.
Synthesis of Palladium(II) Complexes. Pd(CH3)Cl{2-
{(Ph2PCH2)2N}-3-(OCH3)C6H3CO2H} (1). To a CH2Cl2 (3 mL)
solution of Pd(CH3)Cl(cod) (0.074 g, 0.279 mmol) was added solid
[PdCl{2-{(Ph2PCH2)2N}-3-(OCH3)C6H3CO2}]6 (6). Compound
1 (0.075 g, 0.104 mmol) was dissolved in CHCl3 (2 mL) to afford
a pale-yellow solution. After this solution was allowed to stand
for ca. 20 days, a bright-yellow crystalline solid was isolated and
dried in vacuo (0.057 g, 75%). Selected spectroscopic data for 6:
31P{1H} NMR 10.8, 9.5 ppm [2J(PP) ) 4.9 Hz]; IR νCO 1609, 1356,
ν
PdCl 305 cm-1. Anal. Calcd for C204H180N6O18P12Pd6Cl6‚1.5CHCl3:
(27) Ru¨lke, R. E.; Ernsting, J. M.; Spek, A. L.; Elsevier, C. J.; van Leeuwen,
P. W. N. M.; Vrieze, K. Inorg. Chem. 1993, 32, 5769-5778.
C, 56.02; H, 4.16; N, 1.91. Found: C, 55.77; H, 4.17; N, 1.70.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6763

Elsegood et al.
Table 1. Details of the X-ray Data Collections and Refinements for Compounds L1, 4, 7‚17CDCl3‚2Et2O, 8‚6CHCl3‚8CH3OH, and 9‚17CDCl3
compound
L1
4
7‚17CDCl3‚2Et2O
8‚6CHCl3‚8CH3OH
9‚17CDCl3
formula
C34H31NO3P2
C35H34BrNO3P2Pd
C223H188Cl57D17N6-
O20P12Pd6
6338.73
C
212H206Cl24N6-
O26P12Pd6
C
221H180Cl51D17I6N6-
O18P12Pd6
M
563.54
764.88
5114.67
6821.34
cryst dimens
cryst color
cryst syst
space group
a/Å
0.61 × 0.26 × 0.18
colorless
triclinic
0.35 × 0.26 × 0.16
pale yellow
monoclinic
P21/n
12.0845(6)
16.9539(9)
16.1707(8)
0.32 × 0.23 × 0.22
0.28 × 0.23 × 0.12
0.17 × 0.17 × 0.08
colorless
yellow
yellow
trigonal
R3h
50.9328(8)
50.9328(8)
27.6308(7)
trigonal
R3h
34.865(9)
34.865(9)
16.076(6)
trigonal
R3h
50.7094(13)
50.7094(13)
27.6292(10)
P1h
10.2346(5)
11.5379(6)
13.3608(7)
108.617(2)
102.451(2)
94.244(2)
1442.50(13)
2
b/Å
c/Å
R/deg
â/deg
97.919(2)
γ/deg
V/Å3
3281.4(3)
4
1.916
1.75-28.84
27 919
7807
62075(2)
9
1.061
0.80-25.00
148 201
24 302
17 161
0.0411
0.0511
0.1604
16924(9)
3
0.902
2.19-29.00
40 443
8949
61528(3)
9
1.688
0.80-29.15
182 777
33 687
21 112
0.0531
0.0547
0.1722
Z
µ/mm-1
0.187
1.66-28.84
12 570
6555
5790
0.0105
0.0321
θ range/deg
measd reflns
indep reflns
obsd reflns [F 2 > 2σ(F 2)]
Rint
6672
5413
0.0273
0.0480
0.1053
0.757, -1.173
0.0587
0.0470
0.1477
1.122, -0.768
R1 [F 2 > 2σ(F 2)]a
wR2 (all data)b
largest difference
map features/e Å-3
0.0899
0.343, -0.214
1.534, -0.898
1.392, -1.313
2
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑[w(Fo - Fc )2]/∑[w(Fo )2]]1/2
.
Routinely prepared crystalline bulk samples of 6 were shown, by
elemental analyses, to contain between 1 and 3 mol of CHCl3.
10 was collected by suction filtration and dried in vacuo (0.111 g,
93%). Selected spectroscopic data for 10: 31P{1H} NMR (36.2
MHz, CDCl3/CH3OH) 8.7 ppm; H NMR [400 MHz, (CD3)2SO)]
13.00 (s, 1H, CO2H), 8.05-6.88 (m, 23H, aromatic H), 4.17 (m,
4H, CH2), 2.88 (s, 3H, OCH3) ppm; IR νCO 1710, νPdCl 309, 298
cm-1; FAB MS m/z 704 (M - Cl). Anal. Calcd for C34H31NO3P2-
PdCl2: C, 55.11; H, 4.23; N, 1.89. Found: C, 54.33; H, 4.62; N,
1.65.
1
[PdCl{2-{(Ph2PCH2)2N}-3-(OH)C6H3CO2}]6 (7). The com-
pounds L2 (0.023 g, 0.042 mmol) and Pd(CH3)Cl(cod) (0.010 g,
0.038 mmol) were dissolved in CDCl3 (1 mL) to give a pale-yellow
solution. After this solution was allowed to stand for ca. 5 days, a
yellow crystalline solid deposited (0.025 g, 88%). Selected spec-
troscopic data for 7: 31P{1H} NMR (observed in situ) 15.6, 13.9
ppm [2J(PP) ) 6.5 Hz]; IR νCO 1612, 1355, νPdCl 304 cm-1. Anal.
Calcd for C198H168N6O18P12Pd6Cl6‚3CDCl3: C, 53.64; H, 3.84; N,
1.87. Found: C, 53.94; H, 4.07; N, 1.90. Routinely prepared
crystalline bulk samples of 7 were shown, by elemental analyses,
to contain between 1 and 3 mol of CHCl3. An X-ray study of 7
suggests considerably more CDCl3 in the lattice per hexamer.
X-ray Crystallography. Suitable crystals of L1 were grown by
allowing a CH3OH filtrate to stand for 8 days. Crystals of 4 suitable
for X-ray crystallography were obtained by allowing a CH2Cl2/
Et2O filtrate to stand for 7 days. For 7-9, suitable crystals were
obtained directly from either CDCl3 (7 and 9) or CHCl3/CH3OH
(8) solutions. All measurements were made on a Bruker AXS
SMART 1000 CCD area detector diffractometer, at 150 K, using
graphite-monochromated Mo KR radiation (λ ) 0.710 73 Å) and
narrow frame exposures (0.3°) in ω. Cell parameters were refined
from the observed (ω) angles of all strong reflections in each data
set. Intensities were corrected semiempirically for absorption, based
on symmetry-equivalent and repeated reflections. The structures
were solved by direct methods and refined on F 2 values for all
unique data by full-matrix least squares. Table 1 gives further
details. All non-hydrogen atoms were refined anisotropically. For
4, the bromo and methyl groups exhibit positional interchange
disorder, with the major component occupied 74.0(2)% of the time.
For 7 and 9, respectively 2 and 51/2 molecules of CDCl3 were
refined as point atoms, while a further 61/2 and 3 CDCl3 molecules
were badly disordered and were therefore modeled as diffuse regions
of electron density using the Platon “Squeeze” procedure.28 In 7,
there was also 1 unique molecule of Et2O that was rather diffuse
and refined with poor geometry. In 8, 1 molecule of CHCl3 was
disordered with two sets of Cl positions, with the major component
occupied 59.3(7)% of the time. Also in 8, a molecule of CH3OH
lies close to the 3h axis and was therefore refined at 1/3 occupancy.
These disordered solvent molecules in 8 were refined without
[PdCl{2-{(Ph2PCH2)2N}-5-(OH)C6H3CO2}]6 (8). The com-
pounds L3 (0.061 g, 0.111 mmol) and Pd(CH3)Cl(cod) (0.030 g,
0.113 mmol) were dissolved in CHCl3 (15 mL) and CH3OH (1
mL) to give a colorless solution. After this solution was allowed
to stand for ca. 14 days, a yellow crystalline solid deposited (0.063
g, 79%). Selected spectroscopic data for 8: IR νCO 1616, 1570,
1372, νPdCl 305 cm-1. Anal. Calcd for C198H168N6O18P12Pd6-
Cl6‚2CH3OH: C, 57.10; H, 4.23; N, 2.00. Found: C, 56.95; H,
3.88; N, 2.00.
[PdI{2-{(Ph2PCH2)2N}-3-(OCH3)C6H3CO2}]6 (9). Compound
5 (0.022 g, 0.0271 mmol) was dissolved in CDCl3 (0.5 mL) to
give an orange solution, which was allowed to stand for ca. 14
days. An orange crystalline solid was isolated and dried in vacuo
(0.016 g, 71%). Selected IR data for 9: νCO 1607, 1362 cm-1. Anal.
Calcd for C204H180N6O18P12Pd6I6‚2CDCl3: C, 49.34; H, 3.67; N,
1.68. Found: C, 49.32; H, 3.53; N, 1.70. An X-ray study of 9
suggests considerably more CDCl3 in the lattice per hexamer.
PdCl2{2-{(Ph2PCH2)2N}-3-(OCH3)C6H3CO2H} (10). To a
CH2Cl2 (25 mL) solution of PdCl2(cod) (0.046 g, 0.161 mmol) was
added solid L1 (0.091 g, 0.161 mmol). After stirring for 4 h, the
pale-yellow solution was concentrated under reduced pressure to
ca. 10 mL and Et2O (10 mL) added to induce precipitation. Solid
(28) Spek, A. L. Acta Crystallogr., Sect. A 1990, 46, C34.
6764 Inorganic Chemistry, Vol. 45, No. 17, 2006

Neutral Molecular Pd6 Hexagons
hydrogen atoms and with restraints on geometry and displacement
parameters. Programs used were Bruker AXS SMART and SAINT
for diffractometer control and frame integration,29 Bruker SHELXTL
for structure solution, refinement, and molecular graphics,30 Mercury
for molecular graphics,31 and local programs.
Results and Discussion
Ligand Synthesis. As part of continuing studies probing
the synthetic utility of Ph2PCH2OH as an excellent synthon
to functionalized tertiary phosphines,32 we prepared the new
P2O-terdentate ligands 2-{(Ph2PCH2)2N}-3-(X)C6H3CO2H (X
) OCH3, L1; X ) OH, L2) and 2-{(Ph2PCH2)2N}-5-(OH)-
C6H3CO2H (L3) (eq 1) in high yields (typically 80%) from
inexpensive, commercially available precursors. All three
phosphines L1-L3 are air-stable, colorless solids whose
compositions were deduced by their characteristic 31P NMR
resonance [L1, δ(P) -22.3 ppm (CDCl3); L2, δ(P) -18.3
ppm {(CD3)2SO}; L3, δ(P) -20.2 ppm {(CD3)2SO}].33 On
the basis of the reagent stoichiometry used here, the 1H NMR
spectra further support double condensation as inferred by
the absence of an NH signal that would be expected if single
substitution resulted. The IR spectra (KBr disk) of L1-L3
each showed an intense νCdO stretch in the region 1650-
1700 cm-1, while the νOH stretching vibration was not readily
discernible. Other characterizing data are given in the
Experimental Section.
Figure 1. Molecular structure of L1. All hydrogen atoms except on O(1)
have been omitted for clarity. Thermal ellipsoids are drawn at the 40%
probability level.
Table 2. Selected Bond Distances and Angles for Compounds L1
and 4
L1
4
Bond Length (Å)
1.8665(12)
1.8679(12)
1.4860(14)
1.4888(15)
1.3181(15)
1.2133(16)
P(1)-C(1)
P(2)-C(2)
C(1)-N(1)
C(2)-N(1)
C(9)-O(1)
C(9)-O(2)
Pd(1)-Br(1)a
Pd(1)-C(35)a
Pd(1)-P(1)
Pd(1)-P(2)
1.845(4)
1.836(4)
1.493(5)
1.487(5)
1.321(5)
1.213(5)
2.4527(9)
2.157(8)
2.3177(11)
2.2536(10)
Bond Angle (deg)
111.45(7)
P(1)-C(1)-N(1)
P(2)-C(2)-N(1)
C(1)-N(1)-C(2)
Br(1)-Pd(1)-P(1)a
Br(1)-Pd(1)-P(2)a
P(1)-Pd(1)-C(35)a
P(1)-Pd(1)-P(2)
Br(1)-Pd(1)-C(35)a
P(2)-Pd(1)-C(35)a
Pd(1)-P(1)-C(1)
C(2)-P(2)-Pd(1)
112.2(2)
112.6(2)
111.0(3)
89.79(4)
173.64(4)
172.8(2)
95.58(4)
88.5(2)
111.38(7)
111.91(9)
Suitable crystals of L1 were grown from CH3OH over 8
days, and its X-ray structure is shown in Figure 1. Structure
analysis clearly shows approximate pyramidal geometries
about both phosphorus centers (Table 2).33 It is noteworthy
that the dihedral angle (3.9°) between the carboxylic acid
and N-arene group reflects a near-planar arrangement,
presumably imposed by the strong intramolecular N‚‚‚H-O
hydrogen bond [N(1)‚‚‚O(1) 2.5597(13) Å, H(1)‚‚‚N(1) 1.77
Å, and N(1)‚‚‚H(1)-O(1) 155°], which also manifests itself
in the mononuclear complexes 1-5 (vida infra for the X-ray
structure of 4).
86.6(2)
117.67(12)
113.05(12)
a For the major disorder components.
Palladium(II) Chemistry. To elucidate whether L1-L3
could support a multinuclear array via terdentate coordina-
tion, we chose a suitable late-transition-metal precursor that
would κ2-P2-chelate yet also have the propensity to form a
stable M-O bond.14a Accordingly, reaction of 1 equiv of
L1-L3 with Pd(CH3)Cl(cod) in CH2Cl2 (or CDCl3) gave
Pd(CH3)Cl(κ2-P2-L1-L3) (1-3; Scheme 1), which displayed
the usual spectroscopic and analytical data. In all three
complexes, 31P{1H} NMR spectroscopy showed the expected
AX pattern for inequivalent 31P nuclei in the regions 22.8-
26.3 and -7.1 to -11.0 ppm [2J(PP) ) 46.2-50.6 Hz].
Metathesis of 1 with NaX (X ) Br, I) gave the analogous
(methyl)bromo 4 and (methyl)iodo 5 complexes, respectively
(Scheme 1). An X-ray structure of 4 confirmed the antici-
pated square-planar geometry about the palladium(II) metal
center (Figure 2 and Table 2) with typical Pd-P bond lengths
[Pd(1)-P(1) 2.3177(11) Å and Pd(1)-P(2) 2.2536(10) Å]
(29) SMART and SAINT software for CCD diffractometers; Bruker AXS
Inc.: Madison, WI, 2001.
(30) Sheldrick, G. M. SHELXTL User Manual, version 6.10; Bruker AXS
Inc.: Madison, WI, 2000.
(31) New software for searching the Cambridge Structural Database and
visualizing crystal structures. Bruno, I. J.; Edgington, P. R.; Kessler,
M. K.; MacRae, C. F.; McCabe, P.; Pearson, J.; Taylor, R. Acta
Crystallogr., Sect. B 2002, 58, 389-397.
(32) (a) Smith, M. B.; Dale, S. H.; Coles, S. J.; Gelbrich, T.; Hursthouse,
M. B.; Light, M. E. CrystEngComm 2006, 8, 140-149. (b) Coles, S.
J.; Durran, S. E.; Hursthouse, M. B.; Slawin, A. M. Z.; Smith, M. B.
New J. Chem. 2001, 25, 416-422. (c) Durran, S. E.; Smith, M. B.;
Slawin, A. M. Z.; Gelbrich, T.; Hursthouse, M. B.; Light, M. E. Can.
J. Chem. 2001, 79, 780-791. (d) Durran, S. E.; Smith, M. B.; Slawin,
A. M. Z.; Steed, J. W. J. Chem. Soc., Dalton Trans. 2000, 2771-
2778.
(33) Durran, S. E.; Elsegood, M. R. J.; Hawkins, N.; Smith, M. B.; Talib,
S. Tetrahedron Lett. 2003, 44, 5255-5257.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6765

Elsegood et al.
Scheme 1. Preparation of Compounds 1-9 from L1-L3a
a Reagents and conditions: (i) Pd(CH3)Cl(cod); (ii) NaBr or NaI; (iii) CHCl3 or CHCl3/CH3OH, room temperature.
Figure 2. Molecular structure of 4. Minor disorder components and all
hydrogen atoms except on O(1) and C(35) have been omitted for clarity.
Thermal ellipsoids are drawn at the 40% probability level.
and angles [P(1)-Pd(1)-P(2) 95.58(4)°]. The dihedral angle
between the carboxylic acid group and the N-arene in 4
(9.4°) deviates slightly more than that in L1. Like L1, there
also persists an intramolecular N‚‚‚H-O hydrogen bond
[N(1)‚‚‚O(1) 2.644(4), H(1)‚‚‚N(1) 1.86 Å, and N(1)‚‚‚H(1)-
O(1) 154°] with the OH group of the ortho-substituted
carboxylic acid.
Figure 3. Molecular structure of a single molecule of 9. Two phenyl groups
on each phosphorus, all hydrogen atoms, and the solvent of crystallization
have been omitted for clarity. Thermal ellipsoids are drawn at the 40%
probability level.
self-assembly in chloroform solution so reactions were
performed in situ using Pd(CH3)Cl(cod) and L3 in a mixed-
solvent system (CDCl3/CH3OH) without prior isolation of
3. This protocol was used for L2 although CH3OH was not
required to solubilze the ligand. After these solutions were
allowed to stand for 5-14 days, the (pale)-yellow solids 7
and 8 were isolated in excellent yields (routinely ∼80% in
both cases). The IR spectra were particularly diagnostic and
clearly indicated κ1-O-carboxylate coordination for L1-L3
from the shift to lower wavenumbers by ca. 100 cm-1 for
νCdO (with respect to 1-5). In contrast, our attempt to
observe the molecular ion of 6 by MALDI-TOF MS was
unsuccessful, although a relatively abundant cluster of ions
was observed at m/z 1410.145, which could be consistent
with a dimeric species whereby both palladium(II) centers
are bridged by L1 in its deprotonated form (remaining
coordination sites on both palladium centers occupied by L1/
Cl ligands).
When CDCl3 solutions of 1 were monitored by 31P{1H}
NMR spectroscopy over 3 days, a new species 6 with δ(P)
resonances at 10.8 and 9.5 ppm [2J(PP) ) 4.8 Hz] was
observed accompanied by diminishment of those δ(P) signals
attributed to 1. A second minor species at δ(P) 8.3 ppm was
also observed and assigned to PdCl2(κ2-P2-L1) (10) by
comparison with an authentic sample prepared from PdCl2(cod)
and L1. Preparatively, compound 6 could be obtained as a
yellow, thermally stable (decomposes at >212 °C) solid34
in excellent yield (75%) upon allowing a chloroform solution
of 1 to stand at room temperature for ca. 20 days (Scheme
1). Using a similar approach, crystalline samples of the
analogous iodo complex 9 were obtained from CDCl3
solutions. By contrast, the low solubility of L3 hampered
(34) A low-resolution X-ray diffraction data set for 6‚xCHCl3 has been
obtained that confirms this molecular hexagon arrangement: trigonal,
R3h, a ) 51.668(14) Å, c ) 27.498(7) Å, V ) 63573(50) Å3.
6766 Inorganic Chemistry, Vol. 45, No. 17, 2006

Neutral Molecular Pd6 Hexagons
Figure 4. (a) X-ray structure of 7. All solvent molecules have been omitted for clarity. Thermal ellipsoids are drawn at the 40% probability level. (b) X-ray
structure of 8. All solvents except the well-ordered CH3OH solvate have been omitted for clarity. Thermal ellipsoids are drawn at the 40% probability level.
Table 3. Selected Bond Distances and Angles for the Hexamers
7‚17CDCl3‚2Et2O, 8‚6CHCl3‚8CH3OH, and 9‚17CDCl3
Pd-O bond lengths are all broadly as anticipated. Ligand
L1 adopts a monoanionic form ligating through both
7‚17CDCl3‚
8‚6CHCl3‚
phosphorus atoms and a single oxygen-donor center from
the carboxylate group. The formation of a Pd-O bond [Pd-
O 2.068(3), 2.079(4), and 2.109(3) Å]14a in 9‚17CDCl3 is
further reflected by the change in the stretching frequency
(∆ν ca. 100 cm-1) of the carbonyl group of L1 (from IR
spectroscopy) in accordance with κ1-O-carboxylate coordina-
tion. Each of the PdP2C2N six-membered rings has ap-
proximately the same conformation. To accommodate the
hexameric ring structure, there are significant twists in the
carboxylate/N-arene dihedral angles (33.5-51.0°) relative
to those observed in L1 and 4 (<10°). An insight into the
internal size of the hexamer is gleaned from the nonbonding
Pd‚‚‚Pd separations,13a which vary from 6.63 Å (adjacent
palladium centers) to 13.62 Å (internal transannular pal-
ladium centers), although the cavity is self-filling with phenyl
groups (one from each ditertiary phosphine). An estimation
of the maximum external transannular distance (measured
between symmetry-related phenyl protons on opposite sides
of the ring) gives an outside diameter of ca. 2.63 nm. Of the
approximate 17 chloroform molecules of crystallization, six
interact with the hexamer via Cl3C-D‚‚‚OdC links to the
free carboxylate oxygen (see Supporting Information). The
remainder, some badly disordered, fill the voids and channels
between the hexameric rings.
2Et2O
8MeOH
9‚17CDCl3
Bond Length (Å)
2.2292(12)
2.2439(12)
2.2419(11)
2.2326(11)
2.2293(11)
2.2344(11)
2.3311(13)
2.3463(11)
2.3402(11)
Pd(1)-P(1)
Pd(1)-P(2)
Pd(2)-P(3)
Pd(2)-P(4)
Pd(3)-P(5)
Pd(3)-P(6)
Pd(1)-Cl(1)
Pd(2)-Cl(2)
Pd(3)-Cl(3)
Pd(1)-I(1)
2.2407(12)
2.2533(12)
2.2292(13)
2.2575(13)
2.2391(14)
2.2655(15)
2.2565(13)
2.2321(14)
2.3332(14)
2.6424(5)
2.6404(6)
2.6398(5)
2.109(3)
2.079(4)
2.068(3)c
Pd(2)-I(2)
Pd(3)-I(3)
Pd(1)-O(4)
Pd(2)-O(7)
Pd(1)/Pd(3)-O(1A)
2.067(3)
2.059(3)
2.074(3)a
2.076(3)b
94.95(4)
Bond Angle (deg)
94.06(4)
94.10(4)
93.79(4)
91.21(9)
P(1)-Pd-P(2)
P(3)-Pd-P(4)
P(5)-Pd-P(6)
O(4)-Pd-Cl(1)
O(7)-Pd-Cl(2)
O(1A)-Pd-Cl(1)/Cl(3)
O(4)-Pd-I(1)
93.51(5)
94.71(5)
92.92(5)
91.73(8)
91.20(8)a
91.95(9)
92.75(10)
90.16(10)
90.19(9)
O(7)-Pd-I(2)
O(1A)-Pd-I(3)
a Symmetry operators: -x + 5/3, -y + 1/3, -z + 4/3. b Symmetry
operators: x - y, x - 1, -z + 1. c Symmetry operators: -x + /3, -y +
2
4
1/3, -z + /3.
For 7‚17CDCl3‚2Et2Ã, the asymmetric unit comprises
three independent palladium molecules, while for 8‚
6CHCl3‚8CH3OH, only one palladium molecule is unique.
Both 7‚17CDCl3‚2Et2Ã and 9‚17CDCl3 are close to being
isomorphous (Table 1) but differ in the amount and nature
of the included solvent of crystallization. The former includes
diethyl ether and has the larger unit cell volume as a result,
while the latter does not. The coordination environment about
each metal center is composed of a chelating κ2-P2-didentate
Suitable X-ray-quality crystals of 7‚17CDCl3‚2Et2O, 8‚
6CHCl3‚8CH3OH, and 9‚17CDCl3 were obtained and all
three structures determined (Figure 3 for 9, parts a and b of
Figure 4 for 7 and 8, respectively, and Table 3). In all three
cases, the hexagon core geometries are essentially identical.
The X-ray structure of 9 reveals a hexamer on an inversion
center with three independent palladium atoms each with a
I/P2/O coordination environment. The Pd-I, Pd-P, and
Inorganic Chemistry, Vol. 45, No. 17, 2006 6767

Elsegood et al.
phosphine, one chloride, and a κ1-O-bound carboxylate.
Again isomeric L2 and L3 both function efficiently as κ3-
P2O-terdentate ligands. The Pd-O, Pd-P, and Pd-Cl
lengths are all typical and in the normal ranges expected.
There is little evidence for a trans influence in the Pd-P
bond distances [Pd-Pav 2.2383(11) Å (P trans to Cl) and
Pd-Pav 2.2321(11) Å (P trans to O) for 7; Pd-P 2.2533(12)
Å (P trans to Cl) and Pd-P 2.2407(12) Å (P trans to O)
respectively for 8]. Furthermore, the six-membered Pd-P-
C-N-C-P ring conformations in both of these structures
are best described as slightly flattened chairs in which the
PdP2 approaches planarity with the P2C2 plane. The overall
structures both comprise a hexamer containing alternate
palladium metal centers and deprotonated L2 (or L3)
arranged to give isomeric 48-membered metallomacrocyclic
rings. The closest nonbonding Pd‚‚‚Pd distance in 7 is 6.659
Å (6.804 Å in 8), while the furthest internal transannular
Pd‚‚‚Pd separation is 12.959 Å (12.884 Å in 8).13a The
nanoscopic size of 7 (and 8) is 2.53 nm (and 2.59 nm) when
the outside of the ring structure is examined (measured
between symmetry-related phenyl protons on opposite sides
of the ring). To accommodate these hexameric motifs, the
carboxylate group is again likewise twisted (dihedral angles
between 43 and 54° for 7 and at 39° for 8) with respect to
the N-arene group. Within the cavity, most of the available
space is occupied by one phenyl ring from each phosphorus
center (Figure 4b). The unprecedented ability of the flexible
κ3-P2O-terdentate ligand to act in this way, thus facilitating
self-assembly of the hexagons shown, is clearly demon-
strated, and we believe this to constitute a rare example of
such a self-assembled structure.
Figure 5. X-ray structure of 8 showing the hydrogen-bonding interactions
between adjacent hexamer units. Phenyl groups on phosphorus and solvent
molecules except the well-ordered CH3OH solvate have been omitted for
clarity.
The specific use of L2 and L3 allows further secondary
interactions to be realized. Hence, in the case of 7, bearing
an o-phenolic OH group with respect to the -N(CH2PPh2)2
unit, only intramolecular hydrogen bonding [N‚‚‚O 2.722(5)-
2.738(5) Å, H(1)‚‚‚N(1) 2.26-2.29 Å, and N(1)‚‚‚H(1)-
O(1) 112-117°] is observed. In contrast, 8 reveals significant
intermolecular hydrogen-bonding contacts. A crystallo-
graphically well-determined CH3OH hydrogen bonds to the
carbonyl group of the carboxylate [O‚‚‚O 2.648(5) and
2.676(5) Å, H‚‚‚O 1.81 and 1.88 Å, and O‚‚‚H-O 171° and
159°]. Each hexamer makes 12 hydrogen-bonding interac-
tions, arranged in pairs, to six adjacent hexamer rings (three
above and three below the hexamer plane). Hexamers are
linked through simultaneous hydrogen bonding using the
phenolic O-H group on the N-phenyl ring and CH3OH
Figure 6. Packing plot of 8 showing the three-dimensional network. All
phenyl groups on phosphorus and solvent molecules except the well-ordered
CH3OH solvate have been omitted for clarity.
have been able to monitor their in situ self-assembly in
1
CDCl3 (or CD2Cl2) by 31P{1H} (Figure 7) and H NMR
spectroscopy (Figure 8). For 7, this process can be monitored
over ca. 4-5 h, whereupon under these conditions 7
crystallizes from the NMR solvent and precludes any further
meaningful spectra. Upon immediate mixing, we observe
mononuclear 2 along with small amounts of PdCl2(L2) [δ(P)
10.5 ppm] presumably formed by protonation (trace amounts
of HCl) of the Pd-CH3 group. After 24 min, a new species
at δ(P) 15.6 and 13.9 ppm appears, and by 263 min, this
becomes the predominant species present in solution. Simi-
solvent, affording 34-membered [R4 (34) pattern]35 pseudo-
4
1
larly the H NMR spectra reflect the same trend, namely, a
rings (Figure 5). This unique combination of interactions
(symmetry-imposed) leads to the novel three-dimensional
architecture shown in Figure 6, which, we believe to the best
of our knowledge, has not been previously observed.
While the solubilities of 7 and 8 are extremely low in
common organic (e.g., dichloromethane, acetone, and tetra-
hydrofuran) and polar solvents (e.g., dimethyl sulfoxide), we
gradual disappearance of the Pd-CH3 signal [δ(H) 0.7 ppm]
over time and growth in the intensity of a new signal at δ(H)
0.20 ppm corresponding to CH4 formation.36 No other
attempts to identify CH4 were pursued. Although we have
not attempted to ascertain the exact integer value for n in
[PdCl{2-{(Ph2PCH2)2N}-3-(OH)C6H3CO2}]n and, moreover,
(36) (a) Jensen, M. P.; Wick, D. D.; Reinartz, S.; White, P. S.; Templeton,
J. L.; Goldberg, K. I. J. Am. Chem. Soc. 2003, 125, 8614-8624. (b)
Wick, D. D.; Reynolds, K. A.; Jones, W. D. J. Am. Chem. Soc. 1999,
121, 3974-3983. (c) Abraham, R. J.; Edgar, M.; Glover, R. P.; Warne,
M. A.; Griffiths, L. J. Chem. Soc., Perkin Trans. 2 1996, 333-341.
(35) (a) Bernstein, J.; Davis, R. E.; Shimoni, L.; Chang, N.-L. Angew.
Chem., Int. Ed. Engl. 1995, 34, 1555-1573. (b) Etter, M. C.;
MacDonald, J. C.; Bernstein, J. Acta Crystallogr., Sect. B 1990, 46,
256-262.
6768 Inorganic Chemistry, Vol. 45, No. 17, 2006

Neutral Molecular Pd6 Hexagons
Figure 7. 31P{1H} NMR spectra of L2/Pd(Me)Cl(cod) (1:1 ratio) recorded over time at 298 K.
Figure 8. 1H NMR spectra of L2/Pd(Me)Cl(cod) (1:1 ratio) recorded over time at 298 K. The displaced cod ligand appears as two resonances at ca. δ(H)
2.4 and 5.6 ppm.
whether the hexanuclear species actually predominates in
solution, it is clear that this reaction proceeds very cleanly.
We also find that 6, 8, and 9 self-assemble over longer
periods than that observed for 7, which may reflect the
importance of several criteria: the predisposition of the
phenolic group, the nature of the substituent (-OCH3 vs
-OH), the terminal halide present, and the ligand solubility
in the solvents used. Furthermore, while the formation of
6-9 proceeds under extremely mild conditions (i.e., ambient
temperature), efforts to synthesize Pt6 molecular hexagons
Inorganic Chemistry, Vol. 45, No. 17, 2006 6769

Elsegood et al.
by a similar self-assembly process have so far proven to be
unsuccessful despite using more forcing conditions (CDCl3,
50 °C, 14 days). This observation is not too surprising given
that palladium(II) complexes are generally known to be more
reactive than their platinum(II) counterparts.
on phosphorus or by incorporating other functional polar
groups on the N-arene backbone may permit other supra-
molecular architectures to be realized. Further ligand and
coordination studies are currently in progress and will be
reported in due course.
Concluding Remarks
Acknowledgment. We thank the EPSRC for funding
(P.M.S.), Johnson Matthey plc for the generous loan of
precious metal salts, and the EPSRC National Mass Spec-
trometry Service Centre at Swansea for support of this work.
In conclusion, we have demonstrated, using simple build-
ing blocks, the synthesis of four novel nanosized molecular
Pd6 hexagons using flexible carboxylic acid modified di-
tertiary phosphines. The observation of discrete hexameric
structures from three different κ3-P2O-terdentate ligands (and
with two different halide auxiliary ligands) is evidence that
the bulk samples in each case are indeed hexanuclear and
are formed during the reaction. The use of suitably disposed
polycarboxylated phosphines may enable new classes of
porous materials22 to be accessed in which the cavity size
can be regulated. Moreover, manipulating the substituents
Supporting Information Available: Tables of crystal data and
structure refinement, atomic coordinates, bond lengths and angles,
anisotropic displacement parameters, hydrogen coordinates (CIF
format), and ellipsoid plots for L1, 4, 7‚17CDCl3‚2Et2Ã, 8‚6CHCl3‚
8CH3ÃΗ, and 9‚17CDCl3. This material is available free of charge
via the Internet at http://pubs.acs.org.
IC060629O
6770 Inorganic Chemistry, Vol. 45, No. 17, 2006