3950 J. Am. Chem. Soc., Vol. 123, No. 17, 2001
Sommer et al.
mL flask was flame dried under a continuous stream of argon.
Anhydrous acetonitrile (23 mL) was placed in the flask and was
degassed for 20 min by bubbling argon through the liquid. Then
palladium sponge (0.200 g 1.88 mmol) and nitrosonium hexafluoro-
phosphate (0.704 g, 4.02 mmol) were added, forming a pale green-
colored solution. The mixture was heated to 60 °C using an oil bath
and was maintained at this temperature for 4 h. During this time, the
color changed to yellow, and a steady evolution of NO gas was
observed. After this time, a small amount of palladium sponge remained,
and the evolution of NO had ceased. The reaction was filtered under
argon through a dried Schlenk filter. To the yellow solution was then
added 50 mL of anhydrous ether dropwise which resulted in the
crystallization of the product. The mixture was then Schlenk filtered
again under argon to collect the product as nearly white crystals. The
crystals were washed with anhydrous ether (15 mL) followed by pentane
(5 mL) and were dried under vacuum. The white crystals are somewhat
moisture-sensitive, decomposing over a period of several hours in the
air (0.95 g, 90%). The complex was stored under argon at -25 °C. 1H
NMR (CD3NO2, 500 MHz): δ 2.65 (s). 13C NMR (CD3NO2, 125
MHz): δ 3.75, 126.12. Anal. Calcd for C8H12F12N4P2Pd: C, 17.14; H,
2.16; N, 9.99. Found: C, 16.96; H, 2.18; N, 9.98.
J ) 1.75, 1H), 7.88 (dd, J1 ) 1.97, J2 ) 7.64, 2H), 8.01 (t, J ) 7.36,
4H), 8.06 (br, 4H), 8.14 (d, J ) 7.81, 4H), 8.44 (s, 4H), 9.00 (d, J )
1.93, 2H). ΛM ) 235 Ω-1 cm2 mol-1. Anal. Calcd for C65H55Cl2F12N7P2-
Pd2: C, 51.78; H, 3.68; N, 6.50. Found: C, 51.39; H, 3.48; N, 6.81.
Molecular Rectangle formed with [(16)Pd2(CH3CN)2](PF6)2 and
4,4′-Dipyridyl. A 50 mL flask was charged with [(16)Pd2(CH3CN)2]-
(PF6)2 (0.194 g, 0.107 mmol) dissolved in acetonitrile (20 mL), forming
a yellow solution. To this was added 4,4′-dipyridyl (0.0168 g, 0.107
mmol) as a solid, in one portion. Upon addition, the intensity of the
yellow color lightened slightly. The reaction was stirred at room
temperature for 1 h, and the solvent was removed under reduced
pressure to leave a yellow powder. This was slurried in 10:1 pentane:
acetone (11 mL) and was filtered. The powder was washed with
methanol (5 mL) tetrahydrofuran (5 mL), ether (5 mL), and pentane
1
(2.5 mL) (0.188 g, 98.4%). The H NMR spectrum of the molecular
rectangle is highly symmetrical. Both the spacer-chelators and the 4,4′-
dipyridyl groups of the rectangle have identical chemical shifts
1
consistent with a D2h point group on the NMR time scale. H NMR
(CD3CN, 500 MHz): δ 1.40 (s, 36H), 2.80 (t, J ) 7.08, 8H), 3.08 (t,
J ) 7.09, 8H), 7.18 (d, J ) 1.75, 4H), 7.59 (d, J ) 4.69, 8H), 7.61 (t,
J ) 1.78, 2H), 7.68-7.71 (m, 12H), 8.06 (dd, J1 ) 2.06, J2 ) 6.66,
4H), 8.38 (d, J ) 6.57, 8H), 8.42 (td, J1 ) 1.37, J2 ) 8.86, 8H), 8.47
(d, J ) 7.75, 8H), 8.76 (s, 8H), 9.28 (d, J ) 6.44, 8H), 9.43 (d, J )
1.97, 4H). ΛM ) 527 Ω-1 cm2 mol-1. Anal. Calcd for C150H126F48N18P8-
Pd4: C, 47.84; H, 3.37; N, 6.69. Found: C, 47.99; H, 3.36; N, 6.80.
ESI-MS: a series of peaks were observed consistent with [M-n-
(PF6)]n+‚m(CH3CN) (n ) 1-7, m ) 0,2): for example, 1110.3
[(16)Pd2(CH3CN)2](PF6)4. A 10 mL flask was flame dried under a
continuous stream of argon. The flask was charged with tetrakis-
(acetonitrile)palladium(II) hexafluorophosphate (0.0600 g, 0.108 mmol)
which was dissolved in anhydrous acetonitrile (4 mL), forming a pale
yellow solution. To this was added the ligand, 16, (0.0500 g 0.0535
mmol) as a solid. The ligand rapidly dissolved, and the color changed
to an orange-yellow. The reaction was stirred at room temperature for
5 h, during which time the color lightened. The reaction was then vapor-
diffused with ether, causing the product to precipitate as a yellow
powder. The product was collected by filtration and was washed with
ether (10 mL), followed by pentane (5 mL) (0.928 g, 95.9%). Many of
[M-3(PF6)]3+
.
Molecular Rectangle formed with [(17)Pd2(CH3CN)2](PF6)2 and
4,4′-Dipyridyl. [(17)Pd2(CH3CN)2](PF6)2 (0.0500 g, 0.02770 mmol)
was dissolved in acetonitrile (10 mL) in a 25 mL flask, forming a yellow
solution. To this solution was added 4,4′-dipyridyl (0.00433 g, 0.0277
mmol) in one portion, as a solid. The dipyridyl rapidly dissolved, and
the intensity of the color lightened somewhat. The reaction was stirred
at room temperature for 1 h. Half of the acetonitrile was removed in
vacuo, and the solution was vapor-diffused with ether to yield the
product as small yellow needles (0.0481 g, 92.3%). The 1H NMR
spectrum of the molecular rectangle is highly symmetrical. Both the
spacer-chelators and the 4,4′-dipyridyl groups of the rectangle have
identical chemical shifts consistent with a D2h point group on the NMR
1
the H NMR signals for this complex remain broad even when the
1
temperature is elevated to 57 °C or the solution is diluted. H NMR
(CD3CN, 500 MHz): δ 1.38 (s, 18H), 1.96 (s, 6H), 2.80 (t, J ) 7.25,
4H), 3.06 (t, J ) 7.07, 4H), 7.15 (d br, 2H), 7.60 (t, J ) 1.68, 1H),
7.63 (d, J ) 7.96, 2H), 7.95 (br, 4H), 8.02 (br d, J ) 7.18, 4H), 8.32-
8.40 (br m, 6H), 8.50-8.17 (br m, 8H), 9.32 (br d, J ) 1.85, 2H). ΛM
) 334 Ω-1 cm2 mol-1. Anal. Calcd for C69H61F24N9P4Pd2: C, 45.81;
H, 3.40; N, 6.97. Found: C, 46.10; H, 3.64; N, 6.91.
1
[(17)Pd2(CH3CN)2](PF6)4. A 10 mL flask was flame dried under a
continuous stream of argon. The flask was charged with tetrakis-
(acetonitrile)palladium(II) hexafluorophosphate (0.0603 g, 0.108 mmol)
which was dissolved in anhydrous acetonitrile (4 mL), forming a pale
yellow solution. To this was added the fully oxidized ligand, 17, (0.0500
g 0.0538 mmol) as a solid. The ligand dissolved during the first minutes
of reaction, and the color became light yellow. The reaction was stirred
at room temperature for 4 h, after which time the reaction solution
was vapor-diffused with ether, causing the product to crystallize as
small yellow needles. The crystals were collected and were washed
time scale. H NMR (CD3CN, 500 MHz): δ 1.50 (s, 36H), 7.54 (d, J
) 1.74, 4H), 7.78-7.82 (m, 16H), 7.90 (t, J ) 1.72, 2H), 7.94 (d, J )
9.15, 4H), 8.05 (d, J ) 9.32, 4H), 8.42 (d, J ) 8.25, 4H), 8.48 (dd, J1
) 1.81, J2 ) 7.67, 4H), 8.54-8.59 (m, 16H), 8.65 (d, J ) 7.73, 8H),
9.10 (s, 8H), 9.49 (d, J ) 6.34, 8H), 10.57 (d, J ) 1.94, 4H). ΛM
)
511 Ω-1 cm2 mol-1. Anal. Calcd for C150H118F48N18P8Pd4: C, 47.94;
H, 3.16; N, 6.71. Found: C, 47.23; H, 3.13; N, 6.76. ESI-MS: a series
of peaks were observed consistent with [M-n(PF6)]n+‚m(CH3CN) (n )
1-7, m ) 0,2): for example, 402.4 [M-7(PF6) +2(CH3CN)].
Bis(8-hydroxyquinolinato)palladium(II) (27). Palladium(II) acetate
(0.112 g, 0.499 mmol) was dissolved in tetrahydrofuran (5 mL) and
was filtered through Celite into a 25 mL flask. The resulting solution
was concentrated under vacuum to a volume of 5 mL. 8-Hydroxy-
quinoline (0.145 g, 1.03 mmol) was dissolved in tetrahydrofuran (2
mL) and was added dropwise to the stirred solution of the acetate. Upon
addition of the ligand, the color of the solution gradually lightened.
After 2 min of stirring, the product began to precipitate as fine, yellow-
orange crystals. The reaction was stirred for 15 min. Then, triethylamine
(140 µL, 1.00 mmol) was added to the reaction mixture. The reaction
was stirred for 10 min. The reaction was then cooled to 0 °C and was
filtered. The crystals were washed with cold tetrahydrofuran (5 mL),
methanol (5 mL), ether (5 mL), and pentane (5 mL). The crystals were
then dissolved in nearly boiling dimethylformamide (35 mL) and
filtered. Upon cooling, the product deposited as lustrous, orange blades.
The crystals were collected by filtration and were washed with 10 mL
each of methanol, ether, and pentane (0.140 g, 71.1%). 1H NMR
(CD2Cl2, 400 MHz): δ 6.97 (dd, J1 ) 0.89, J2 ) 7.92, 2H), 7.02 (dd,
J1 ) 0.79, J2 ) 8.03, 2H), 7.42-7.48 (m, 4H), 8.33 (dd, J1 ) 1.37, J2
) 8.45, 2H), 8.48 (dd, J1 ) 1.39, J2 ) 4.89, 4H). Anal. Calcd for
C18H12N2O2Pd2: C, 54.77; H, 3.06; N, 7.10. Found: C, 54.68; H, 2.83;
N, 7.15.
1
with ether (10 mL), followed by pentane (10 mL) (0.092 g, 95%). H
NMR (CD3CN, 400 MHz): δ 1.44 (s, 18H), 1.96 (s, 6H), 7.46 (d, J )
1.80, 2H), 7.80 (t, J ) 1.80, 1H), 7.82 (d, J ) 9.25, 2H), 7.95-8.04,
(m, 6H), 8.36 (d, J ) 8.33, 2H), 8.43-8.49 (m, 10H), 8.56 (d, J )
3.82, 4H), 8.88 (s, 4H), 10.67 (d, J ) 1.76, 2H). ΛM ) 384 Ω-1 cm2
mol-1. Anal. Calcd for C69H57F24N9P4Pd2: C, 45.91; H, 3.18; N, 6.98.
Found: C, 45.96; H, 3.04; N, 6.83
[(16)Pd2Cl2](PF6)2. In a 50 mL flask, [(16)Pd2(CH3CN)2](PF6)4
(0.181 g, 0.100 mmol) was dissolved in acetonitrile (12 mL), forming
an orange-yellow solution of the complex. To this was added, dropwise,
tetraethylammonium chloride (0.0332 g 0.200 mmol) dissolved in
methanol (2 mL). Upon addition of the chloride, the color of the solution
lightened to a pale yellow. The reaction was stirred at room temperature
for 1 h. The solvent was then removed under reduced pressure to yield
a yellow powder. This was slurried in methanol (10 mL) and was
filtered; the solid was washed with excess methanol followed by ether
(10 mL) and pentane (10 mL). The yellow solid was dissolved in a
minimum amount of hot acetone and was vapor-diffused with ether to
1
yield small yellow crystals (0.146 g, 96.7%). H NMR (CD3CN, 500
MHz): δ 1.47 (s, 18H), 2.97 (t, J ) 7.24, 4H), 3.12 (t, J ) 7.15, 4H),
7.29 (d, J ) 1.76, 2H), 7.31 (br, 4H), 7.68 (d, J ) 7.71, 2H), 7.73 (t,