414 Organometallics, Vol. 25, No. 2, 2006
Helfer et al.
alcohols gave η3-allyl complexes with no aldehyde products but
pH measurements were performed using a Fischer Scientific
Accumet basic pH meter by Denver Instruments Inc. with a
semimicro glass pH electrode with a silver/silver chloride reference
electrode. The pH electrode was calibrated at pH 4, 7, and 10 using
pH buffers.
with formation of tetrahydrofuran derivatives that produced a
2-
Pd hydride complex.23 Two studies of PdCl4 also suggest
formation of a Pd hydride prior to η3-allyl formation.15a,24 Our
reaction is consistent with these prior studies, except that in
water with PtCl2(TPPTS)2, the alkene can be nucleophilically
attacked and generate the Pt(Cl)(H)(TPPTS)2 through a â-hy-
dride elimination (Figure 2). The clean formation of monodeu-
terated oxidation product provides good evidence for â-hydride
elimination and dissociation of the enol from platinum with the
deuterium added in the enol f keto rearrangement. No
deuterium is incorporated into the isomerization products.
Synthesis of [Pt(η3-C3H5)(TPPTS)2]Cl. Into a 25 mL Schlenk
flask was placed 0.1217 g (0.458 mmol) of PtCl2, 0.5709 g (0.917
mmol) of TPPTS, and a small stir bar. The flask was evacuated
and back-filled with N2 three times, after which 10 mL of triply
distilled water was added to the flask via airtight syringe. The flask
was immersed in a preheated oil bath at 70 °C. After about 1.5 h,
the solid PtCl2 had completely dissolved and 500 µL of allyl alcohol
(7.35 mmol) was added to the flask. The resulting solution was
stirred at 70 °C for 15 h. After the allotted time, the contents of
the flask were added to a 250 mL round-bottom flask containing
∼100 mL of EtOH. A white solid immediately precipitated. The
solvent was removed in vacuo, and the white solid was collected
and placed into a glass vial. Yield: 0.521 g (75% based on moles
of PtCl2). The mass spectrum shows the molecular ion for the cation
centered around 1373 amu with the usual platinum distribution.
195Pt NMR (D2O, room temperature): δ -5391 (t, 1JPt-P ) 4014
Conclusion
We have detailed the formation of [Pt(η3-allyl)(TPPTS)2]+
species from the reaction of cis-Pt(Cl)2(TPPTS)2 with various
hydroxyl-functionalized alkenes. The characterizations of these
species agree very well with those of their PPh3 analogues. A
mechanism was proposed which explains the observations made
throughout, such as formation of a Pt-H species, characteriza-
tion of alkene oxidation products, effect of added chloride, etc.
Since allylic compounds are important in a variety of reactions,
i.e., allylic alkylation, such traditional organic reactions may
take place in water as a result,1b providing an example of benign
synthesis.
Hz). 31P{1H} NMR (D2O, room temperature): δ 18.90 (s, 1JPt-P
)
4014 Hz). 1H NMR (D2O, room temperature): δ 7.8-7.0 (m, [Pt-
(η3-C3H5)(TPPTS)2]Cl, 24H), 5.47 (m, meso H, 1H), 3.90 (br, syn
H’s, 2H), 3.00 (m, anti H’s, 2H).
Reaction Performed in Carius Tubes. These reactions were
conducted in 10 mL Carius tubes, modified with a 14/20 glass joint.
(a) Reaction of cis-Pt(Cl)2(TPPTS)2 with Excess Allyl Alcohol.
Into a 10 mL modified Carius tube was placed 0.1264 g (0.0836
mmol) of cis-Pt(Cl)2(TPPTS)2, a small stir bar, and 1.0 mL of triply
distilled water. Upon complete dissolution of the solid, 20 drops
of an alkenol was added to the solution. The tube was then attached
to the high-vacuum line and subjected to three freeze-pump-thaw
cycles, after which the tube was flame-sealed under vacuum. The
sealed tube was placed into a constant-temperature bath at 82 °C
and stirred at this temperature for 3 h. After the allotted time, a 0.5
mL aliquot of the resulting solution was placed into an NMR tube
and analyzed by 195Pt and 31P NMR spectroscopy. Results are given
in Tables 1 and 2.
Experimental Section
Materials. All substrates (allyl alcohol, 3-buten-1-ol, 2-buten-
1-ol (mixture of isomers), 3-buten-2-ol, 4-penten-1-ol, 1-penten-
3-ol, 4-penten-2-ol, and 3-penten-2-ol (predominately trans)) were
purchased from Aldrich Chemical Co. and were used as received.
D2O and d8-THF were purchased from Cambridge Laboratory
17b
Isotopes and used as received. cis-Pt(Cl)2(TPPTS)2 and cis-Pt-
25
(Cl)2(P(p-tolyl)3)2 were synthesized according to literature pro-
cedures.
Solvents. Water was triply distilled and degassed with N2 prior
to use. Diethyl ether and THF were purchased from VWR; the THF
was dried by refluxing over Na/benzophenone overnight, followed
by distilling under N2. Absolute EtOH was purchased from Pharmco
and used as received.
To isolate the allyl product, the contents of the tube were
transferred to a 100 mL round-bottom flask containing ∼50 mL of
EtOH. An off-white precipitate was immediately formed. The flask
was attached to the rotary evaporator and the solvent removed in
vacuo. The residue was redissolved in 1.0 mL of triply distilled
water and precipitated again as described. After removal of the
solvent, the off-white residue was dissolved in 0.5 mL of D2O and
pH Buffers. The pH 4 buffer was composed of a 0.05 M solution
of sodium biphthalate. The pH 7 buffer was composed of a solution
of 0.021 M NaH2PO4 and 0.029 M Na2HPO4. The pH 10 buffer
was composed of a solution of 0.025 M NaHCO3 and 0.025 M
Na2CO3. All three buffers were purchased from VWR and diluted
to the appropriate volume using triply distilled water.
1
analyzed by 31P and H NMR spectroscopy. Results are given in
Tables 1 and 2. Discussion of the NMR results is given in the
Supporting Information.
1
Methods. H , 31P, and 195Pt NMR spectra were recorded on a
(b) Reaction of cis-Pt(Cl)2(P(p-tolyl)3)2 with 3-Buten-1-ol at
Room Temperature. In the drybox, 0.0560 g (0.0640 mmol) of
cis-Pt(Cl)2(P(p-tolyl)3)2 was placed into a 15 mL Schlenk flask,
along with a small stir bar. To the flask was then added 4.0 mL of
dry THF. Upon stirring, a suspension was produced. To the
suspension was added 3 drops of 3-buten-1-ol from a glass pipet.
The flask was sealed with a rubber septum and stirred at room
temperature for 21.5 h. After the allotted time, a 0.5 mL aliquot of
the resulting solution was placed into an NMR tube and analyzed
1
1
Varian XL 400 NMR spectrometer. 1D H TOCSY and 2D H
COSY NMR were recorded on a 500 MHz Varian NMR spec-
trometer. 31P NMR spectra (161.89 Hz) were proton decoupled and
referenced to an external standard of 85% phosphoric acid in D2O.
195Pt NMR (85.75 MHz) spectra were referenced to an external
standard of 0.2 M K2PtCl4 (in 0.4 M KCl/D2O), which was set at
-1627 ppm.26 A coaxial inner cell filled with d6-DMSO was used
to take NMR spectra in H2O.
A mass spectrum of [Pt(η3-C3H5)(TPPTS)2]Cl was recorded by
the Mass Spectrometry and Proteomics Facility of Ohio State
University using Q-TOF 2 nanospray.
1
by 31P and H NMR spectroscopy.
31P{1H} NMR (THF, d8-THF insert, room temperature): δ 27.0
(s, OP(p-tolyl)3, 1.5%), 19.9 (s, trans-Pt(Cl)2(P(p-tolyl)3)2, 16%),
14.2 (s, cis-Pt(Cl)2(P(p-tolyl)3)2, 82.5%).
(23) Hosokawa, T.; Tsuji, T.; Mizumoto, Y.; Murahashi, S.-I. J.
Organomet. Chem. 1999, 574, 99.
(24) Pietropaolo, R.; Uguagliati, P.; Boschi, T.; Crociani, B.; Belluco,
U. J. Catal. 1970, 18, 338.
(25) Casey, C. P.; Chung, S.; Ha, Y.; Powell, D. R. Inorg. Chim. Acta
1997, 265, 127.
(26) Hollis, L. S.; Lippard, S. J. J. Am. Chem. Soc. 1983, 105, 3494.
(c) Reaction of cis-Pt(Cl)2(P(p-tolyl)3)2 with 3-Buten-1-ol at
60 °C. In the drybox, 0.0580 g (0.0663 mmol) of cis-Pt(Cl)2(P(p-
tolyl)3)2, a small stir bar, and 4.0 mL of dry THF were placed into
a 10 mL modified Carius tube. To the mixture was added 3 drops
of 3-buten-1-ol from a glass pipet. The tube was fitted with an
Helfer, Derrik S.
