Organometallics
Article
suspended in the same solvent (3 mL). The mixture was sealed and
warmed at 120 °C in a silicone oil bath. After 24 h, the heating was
stopped and the solution was filtered through a 2 cm column of
alumina, yielding a yellow solution. After solvent evaporation a yellow
solid was obtained, which was vacuum-dried for 6 h. 1H NMR: δ 8.5−
8.45 (m, 1H), 7.443−7.180 (m, 2H), 7.05−6.95 (m,1H), 6.9−6.85(m,
1H), 6.75−6.7(m,2H), 2.5−1.5 (br m, 4H), 1.5−1.2 (m 4H), (m, 24 H).
31P{1H} (C6D6, 121.32 MHz): δ 71.597 (1JPt−P = 1941 Hz), 55.29
(1JPt−P = 2473 Hz). IR [cm−1]: 1269m, 1079s, 1022s. [FAB+]: m/z
675. Mp: 141−142 °C; dec above 180 °C. Anal. Calcd: C 49.35, H 6.9.
Found: C 49.13, H 6.80. Yield: 80%.
Thermolysis of complex 4 confirms the production of a
sulfur-free biphenyl moiety (complex 7) and the extrusion of
sulfur as SO2 (complex 9). The release of SO2 turned out to be
an irreversible process under the explored reaction conditions.
EXPERIMENTAL SECTION
■
General Considerations. All procedures were carried out using
standard Schlenk and glovebox techniques, using an MBraun glovebox
(<1 ppm H2O, O2) under high-purity argon (Praxair, 99.998%). THF
(J.T. Baker) was dried using an MBraun MB-SPS solvent purification
system. Toluene (J.T. Baker) was dried over sodium and distilled
under an inert atmosphere. Superhydride Li(BEt3)H (1.0 M, THF
solution), n-BuLi (2.5 M, hexanes solution), and SO2 (gas, 99.9%)
were supplied by Aldrich. Deuterated solvents were purchased from
Cambridge Isotope Laboratories and stored over 3 Å molecular sieves
in the glovebox, for at least 24 h prior to use. DBT, MeDBT, and
Me2DBT were purchased from Aldrich and were used as received to
prepare the corresponding sulfones: DBTO2, MeDBTO2, and
Me2DBTO2, which were dried in vacuo prior to their use.36 The
chelating bisphosphine ligand, dippe, was prepared from 1,2-
bis(dichlorophosphino)ethane (Aldrich) and the corresponding
isopropylmagnesium chloride solution (2.0 M, in THF solution,
Aldrich).37 [(dippe)Pt(μ-H])]2 was prepared as reported38 from
[(dippe)PtCl2] using a Na/Hg amalgam in 1 atm of H2 in a THF
solution at room temperature. Neutral alumina and silica were heated
at 200 °C under vacuum for 2 d and stored in the glovebox. All other
chemicals and filter aids were reagent grade and were used as received.
Isolated complexes were purified by crystallization or column
Compounds 5 (yield 76%) and 6 (yield 43%) were prepared and
monitored in a completely similar way. Key 31P{1H} signals in C6D6
(121.32 MHz): δ 54.54, 1JPt−P = 2426 Hz, 69.73, 1JPt−P = 1932 Hz, for
1
1
5; 54.54, JPt−P = 2426 Hz, 69.73, JPt−P = 1932 Hz, for 6.
Thermolysis Reaction for Complex 4. A NMR tube with a
J. Young valve was loaded with 0.04 g of complex 4 and 0.75 mL of
benzene-d6, monitored every 4 h for 10 d, heating from room
temperature to 120 °C. The relative yields of 7 (60%), 8 (10%), and 9
(30%) were obtained by integration of the characteristic signals by
31P{1H} NMR. An authentic sample of 7 was prepared as described
(vide infra). Crystals for 9 were obtained on cooling the reaction
mixture at −20 °C in the freezer within the drybox.
Preparation of [Pt(dippe)(η2-(C,C-C12H8)] (7). A stirred solution
of 2,2′-dibromobiphenyl (0.05 g, 0.16 mmol) in 10 mL of THF was
reacted by dropwise addition of n-buthyllithium (0.147 mL of a 2.5 M
solution of THF) in an ice/acetone bath. Then the mixture was
warmed to room temperature and stirred for 1 h. A suspension of
[(dippe)PtCl2] (0.84 g, 0.16 mmol) in THF (3 mL) was then added,
and the resulting solution was stirred at room temperature for 2 h and
the solvent was then removed under vacuum. The resulting residue
was extracted with toluene and filtered. Toluene was then evaporated
under vacuum, and the residue yielded a yellow powder. Yield: 87%.
31P{1H} NMR (C6D6, 121.32 MHz): δ 63.32 (1JPt−P = 1676 Hz).
Reactivity of Complex 7 with SO2. A benzene-d6 solution of 7
(0.039 g, 0.06.8 mmol) was bubbled with SO2 (caution, poisonous
gas!) at −70 °C for 10 min. Then the system was sealed and gently
heated from room temperature to 120 °C during 10 days without any
changes in the reaction mixture, monitored by 31P{1H} NMR (C6D6,
121.32 MHz): δ 63.32 (1JPt−P = 1676 Hz).
1
chromatography. H and 31P{1H} NMR spectra were determined at
room temperature in benzene-d6. 1H chemical shifts (δ, ppm) are
reported relative to the residual proton resonances in the
corresponding deuterated solvent. 31P{1H} NMR spectra were
recorded relative to external 85% H3PO4. All spectra were carried
out using thin-wall (0.38 cm) WILDMAD NMR tubes with J. Young
valves. Catalytic experiments were carried out in a 100 mL Parr,
T315SS stainless steel reactor. Elemental analyses (EAs) were also
performed by USAI-UNAM using a Perkin-Elmer 2400 microanalyzer.
Unless otherwise stated, EAs of pure compounds showed variable
inconsistencies due to their high oxygen sensitivity and were not
reported; however, most of them displayed satisfactory MS-EI+. Mass
spectrometry determinations (MS-EI+) of pure compounds were
performed by USAI-UNAM using a Thermo-Electron DFS.
X-ray Structure Determination. The crystals for compounds 4
and 9 were first cryoprotected using Paratone-N and mounted on glass
fibers; immediately, the crystals were cooled at 193(2) K using a
Cryojet cryostream (Oxford Cryosystems device). Diffraction data
were collected on an Oxford Diffraction Gemini diffractometer with a
CCD-Atlas area detector using a graphite-monochromated radiation
source, λMo κα = 0.71073 Å. CrysAlisPro and CrysAlis RED software
packages39a were used for data collection and data integration. All data
sets consisted of frames of intensity data collected with a frame width
of 1° in ω, a counting time of 27 to 30 s/frame, and a crystal-to-
detector distance of 55.00 mm. The double pass method of scanning
was used to exclude any noise. The collected frames were integrated by
using an orientation matrix determined from the narrow frame scans.
Final cell constants were determined by a global refinement; collected
data were corrected for absorbance by using analytical numeric
absorption correction39b using a multifaceted crystal model based on
expressions of the Laue symmetry using equivalent reflections.
Structure solution and refinement were carried out with the
programs SHELXS97 and SHELXL97; for molecular graphics,
ORTEP-3 for Windows was used.39d The software used to prepare
material for publication was WinGX.39e
Catalytic Deoxydesulfurization of Sulfones of Dibenzothio-
phene. A typical experiment was performed as follows: in the
glovebox, a 50 mL Schlenk flask was charged with [Pt(dippe)H]2
(0.002 g, 0.0031 mmol) and DBTO2 (0.067 g, 0.31 mmol), added in a
10:2 v/v mixture of toluene (10 mL) and THF (2 mL). The resulting
solution was stirred for 30 min at room temperature, venting all the
released gases in the drybox. After this time, a 3.0 M solution of
MeMgBr (0.62 mL, 1.86 mmol) was added to the mixture, a color
change being observed from red to orange. The reaction mixture was
then heated to reflux for 4 days under argon in a Schlenk line. A blend
of precipitates (beige to brown) was observed to form gradually. After
that time, the reaction mixture was then acid-hydrolyzed at room
temperature. A strong effervescence was observed upon addition of
mineral acid (HCl, 10 mL, 10% vol), due to the release of H2S
(caution poisonous gas!), which was bubbled into a trap with a
Pb(CH3COO)2 solution, thereby precipitating PbS as a black solid.
After venting all gases, the remaining mixture was extracted with
CH2Cl2 (3 × 7 mL), and the organic layers were separated, dried, and
analyzed by GC-MS. To note, if a characterization of the solid was
required, acid hydrolysis was avoided and the reaction mixture was
centrifuged and washed with hexanes and acetone. The solid was dried
for 4 h under high vacuum and analyzed by powder-XRD, confirming
the presence of MgO, MgBr2, and MgS.
Full-matrix least-squares refinement was carried out by minimizing
2
(Fo − Fc2)2. All non-hydrogen atoms were refined anisotropically. H
atoms attached to C atoms were placed in geometrically idealized
positions and refined as riding on their parent atoms, with C−H =
0.95−1.00 Å and Uiso(H) = 1.2Ueq(C) or 1.5Ueq(C) for aromatic,
methylene, methyne, and methyl groups. Crystal data and
experimental details of the structure determination are listed in the
Supporting Information.
Preparation of [Pt(dippe)(η2-(C,S-DBTO2)] (4). A representative
experiment was carried out as follows: in a drybox a Schlenk tube with
a Teflon valve was charged with [(dippe)PtH]2 (0.04 g, 0.0436 mmol)
dissolved in 1 mL of benzene and DBTO2 (0.018 g, 0.0872 mmol)
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dx.doi.org/10.1021/om3002729 | Organometallics 2012, 31, 4039−4045
Oviedo, Alberto
