at Ϫ20 ЊC the product crystallised over 48 h as a colourless
was cooled to Ϫ60 ЊC and methyl triflate (2.7 µL, 0.024 mmol)
solid. Yield: 23 mg, 74%.
added. The mixture was warmed to Ϫ40 ЊC and stirred for
about 30 min until a clear yellow solution was obtained. It was
then again cooled to Ϫ60 ЊC, an equimolar amount of the
phosphine added, the mixture transferred to a NMR tube and
placed in a precooled NMR spectrometer (Ϫ60 ЊC). The reac-
tion was monitored by 1H NMR spectroscopy starting at
Ϫ60 ЊC and warming the solution to room temperature in 20 ЊC
intervals. In all cases quantitative formation of the pal-
ladium() complexes [PdMe3(2,2Ј-bipy)(phosphine)][O3SCF3]
was observed at Ϫ60 ЊC; decomposition of the complexes via
reductive elimination of ethane and formation of [PdMe(2,2Ј-
bipy)(phosphine)][O3SCF3] took place at different temperatures
indicated below.
[PdMe3(phen)(PMe2Ph)][O3SCF3] 6. Methyl triflate (7.9 µL,
0.069 mmol) was added to a solution of [PdMe2(phen)] (22 mg,
0.069 mmol) in dichloromethane at (4 mL) Ϫ60 ЊC. The solu-
tion was warmed to Ϫ40 ЊC and stirred for 15 min during which
time it changed from bright orange to yellow; PMe2Ph (9.9 µL,
0.069 mmol) was added and the solution concentrated to ≈2 mL
below 0 ЊC. The product was obtained as colourless crystals,
suitable for X-ray crystallography, by slow diffusion of diethyl
ether into the solution at Ϫ20 ЊC. Yield: 29 mg, 68%.
[PtMe3(2,2Ј-bipy)(PMePh2)][O3SCF3] 9. This complex was
isolated as a yellow oil by a similar procedure to that for the
dimethylphenylphosphine analogue above using methyl triflate
(5.9 µL, 0.052 mmol), [PtMe2(2,2Ј-bipy)] (20 mg, 0.052 mmol)
and PMePh2 (9.8 µL, 0.052 mmol). Several attempts to purify
the product by crystallisation were unsuccessful. Yield: 28 mg,
72%.
[PdMe3(2,2Ј-bipy)(PPh3)][O3SCF3] 1. Decomposition starts
at Ϫ20 ЊC. [PdMe(2,2Ј-bipy)(PPh3)][O3SCF3] 1a: 1H NMR
(acetone-d6) very broad resonances for 2,2Ј-bipy, δ 7.86 (m, 6 H,
Ph), 7.67 (m, 3 H, Ph), 7.60 (m, 6 H, Ph) and 0.85 (s, 3 H,
PdCH3); 31P-{1H} NMR (acetone-d6) δ 40.7.
[PtMe3(2,2Ј-bipy)(PMe2Ph)][O3SCF3] 10. Methyl triflate (5.6
µL, 0.050 mmol) was added to a solution of PtMe2(2,2Ј-bipy)
(19 mg, 0.050 mmol) in tetrahydrofuran (5 mL) at room tem-
perature. The resulting yellow solution was stirred for 30 min,
PMe2Ph (7.1 µL, 0.050 mmol) added and the mixture stirred for
30 min. The solvent was removed in a vacuum, the oily residue
washed with pentane and diethyl ether (3 mL) and dissolved in
tetrahydrofuran (3 mL). Pentane was added until the solution
became cloudy and the mixture stored at Ϫ20 ЊC overnight,
after which time the product had precipitated as a pale yellow,
crystalline solid. Yield: 21 mg, 61%.
[PdMe3(2,2Ј-bipy)(PMePh2)][O3SCF3] 2. Decomposition
starts at 0 ЊC. [PdMe(2,2Ј-bipy)(PMePh2)][O3SCF3] 2a: 1H
NMR (acetone-d6) very broad resonances for 2,2Ј-bipy, δ 7.86
2
(m, 4 H, Ph), 7.60 (m, 6 H, Ph), 2.38 (d, J(HP) = 10.0, 3 H
3
PCH3) and 0.91 (d, J(HP) = 2.8 Hz, 3 H, PdCH3); 31P-{1H}
NMR (acetone-d6) δ 25.4.
[PdMe3(2,2Ј-bipy)(PCy3)][O3SCF3] 4. Decomposition starts
at 0 ЊC. [PdMe(2,2Ј-bipy)(PCy3)][O3SCF3] 4a: 1H NMR
(acetone-d6) very broad resonances, could not be assigned;
31P-{1H} NMR (acetone-d6) δ 28.9.
Synthesis of the palladium(II) complex [PdMe(2,2Ј-bipy)(PMe2-
Ph)][O3SCF3] 3a
[PdMe3(2,2Ј-bipy){P(OMe)3}][O3SCF3] 5. Decomposition
starts at Ϫ20 ЊC. [PdMe(2,2Ј-bipy){P(OMe)3}][O3SCF3] 5a: H
1
Methyl triflate (6.8 µL, 0.060 mmol) was added to a solution
of [PdMe2(2,2Ј-bipy)] (18 mg, 0.060 mmol) in tetrahydrofuran
(4 mL) at Ϫ60 ЊC and the solution warmed and stirred at
Ϫ40 ЊC for 30 min giving a pale yellow solution; PMe2Ph (8.6
µL, 0.060 mmol) was added at this temperature and the solu-
tion warmed to room temperature and stirred at this temper-
ature for 2 h. The solvent was removed in a vacuum, the residue
dissolved in the minimum amount of dichloromethane, and the
product crystallised on slow diffusion of diethyl ether into the
NMR (acetone-d6) very broad resonances for 2,2Ј-bipy, δ 3.93
3
(d, J(HP) = 13.2 Hz, 9 H POCH3) and 1.02 (s, 3 H, PdCH3);
31P-{1H} NMR (acetone-d6) δ 122.9.
[PdMe3(tmen)(PMe2Ph)][O3SCF3] 7. Methyl triflate (3.6 µL,
0.032 mmol) was added to a solution of [PdMe2(tmen)] (8.1 mg,
0.032 mmol) in acetone-d6 (0.3 mL) at Ϫ60 ЊC. After stirring for
20 min PMe2Ph (4.6 µL, 0.032 mmol) was added and the solu-
tion transferred to a NMR tube. The reaction was monitored
by 1H NMR from Ϫ60 ЊC to room temperature in 20 ЊC
intervals. Decomposition starts at Ϫ40 ЊC. [PdMe(tmen)-
(PMe2Ph)][O3SCF3] 7a: 1H NMR (acetone-d6, 0 ЊC) δ 7.92
(m, 2 H, Ph), 7.56 (m, 3 H, Ph), 2.95 (broad, 2 H, NCH2), 2.81
1
solution at Ϫ20 ЊC over 48 h. Yield: 30 mg, 89%. H NMR
(CDCl3, Ϫ30 ЊC): δ 8.64 (m, 1 H, H6A bipy), 8.62 (m, 1 H, H3A
bipy), 8.55 (m, 1 H, H3B bipy), 8.28 (m, 1 H, H4A bipy), 8.08
(m, 1 H, H4B bipy), 7.81 (m, 2 H, Ph), 7.71 (m, 1 H, H5A bipy),
7.55 (m, 3 H, Ph), 7.37 (m, 1 H, H6B bipy), 7.20 (m, 1 H,
4
(broad, 2 H, NCH2), 2.66 (d, J(HP) = 2.0, 6 H, NCH3), 2.49
2
H5B bipy), 1.89 (d, J(HP) = 10.0, 6 H, PCH3) and 0.91 (d,
2
(s, 6 H, NCH3), 1.83 (d, J(HP) = 10.0, 6 H, PCH3) and 0.31
3J(HP) = 3.2 Hz, 3 H, PdCH3). 31P-{1H} NMR (CDCl3,
Ϫ30 ЊC): δ 10.5 (Found: C, 42.58; H, 4.00; N, 5.00. C20H22F3-
N2PPdS requires C, 42.53; H, 3.93; N, 4.96%).
(d, 3J(HP) = 3.6 Hz, 3 H, PdCH3); 31P-{1H} NMR (acetone-d6,
0 ЊC) δ 8.0.
[{PdMe3(2,2Ј-bipy)}2(depe)][O3SCF3]2 11. Decomposition
starts at Ϫ20 ЊC giving a complex mixture of products.
Decomposition of the isolated palladium(IV) complexes 3 and 6
The complexes were dissolved in acetone-d6 at Ϫ20 ЊC. As the
solutions were warmed to room temperature, decomposition
was monitored by 1H NMR spectroscopy. In both cases
reductive elimination of ethane was observed at 20 ЊC.
[PdMe(phen)(PMe2Ph)][O3SCF3] 6a: 1H NMR (acetone-d6,
20 ЊC) very broad resonances for phen, δ 8.10 (m, 2 H, Ph), 7.61
[{PdMe3(2,2Ј-bipy)}2(Et3[12]aneP3)][O3SCF3]2
12
and
[PdMe3(2,2Ј-bipy)(Et3[12]aneP3)][O3SCF3] 13. The ligand (7.6
mg, 0.025 mmol) was added to a solution of [PdMe3(2,2Ј-
bipy)(O3SCF3)] in acetone-d6 (0.3 mL) at Ϫ60 ЊC. The phos-
phine has low solubility and was partly precipitated. Complex
1H NMR spectra were obtained, containing several 2,2Ј-bipy
and Et3[12]aneP3 environments. Minor products included 13,
and the major product was 12. When this reaction was
repeated, with addition of Et3[12]aneP3 in chloroform-d3 to
retain solubility for the ligand, 12 was formed as a minor prod-
uct with 13 being the major product. The mixture of complexes
2
(m, 3 H, Ph), 2.11 (d, J(HP) = 10.4, 6 H, PCH3) and 1.14
(d, 3J(HP) = 2.9 Hz, 3 H, PdCH3); 31P-{1H} NMR (acetone-d6,
20 ЊC) δ 10.4.
1H NMR studies of the formation of palladium(IV) complexes of
monodentate phosphine and depe in solution at low temperatures:
general procedure
1
decomposes above 0 ЊC to give ethane and complex H NMR
[PdMe2(2,2Ј-bipy)] (7.0 mg, 0.024 mmol) in acetone-d6 (0.3 mL)
spectra.
J. Chem. Soc., Dalton Trans., 2000, 3325–3330
3329
Bayler, Angela
