C.K. Barik, et al.
InorganicaChimicaActa512(2020)119833
4.3. Preparation of [Ru2(CO)4(PPh3)2(µ-OOCCH2OSi(OEt)3)2] (2a)
4.9. Control experiment
A sample of triethyl amine (6 µl, 0.03 mmol) and chlorotriethox-
ysilane (6 µl, 0.03 mmol) were added into a solution of 1 (15 mg,
0.015 mmol) in tetrahydrofuran (5 mL). The resulting mixture was
stirred for 1 h at 25 °C, filtered and evaporated under vacuum to afford
2a as a yellow powder. Yield: 10 mg, 0.007 mmol, 47%. IR (di-
chloromethane, cm−1): νCO 2027 (s), 1983 (m), 1955 (s), νC=O 1597
(s). 1H NMR (400 MHz, CDCl3): δ 7.58–7.54 (m, 6H, arom-H),
7.39–7.37 (m, 9H, arom-H), 3.93 (s, 4H, CH2), 3.65–3.59 (m, 6H, CH2),
1.06–1.03 (t, 9H, J = 1.8 Hz, CH3). 31P{1H} NMR (162 MHz, CDCl3): δ
12.3 ppm. 13C{1H} NMR (100 MHz, CDCl3): δ 204.9, 184.9, 133.8,
133.4, 129.6, 128.2, 62.5, 59.1, 18.0 ppm. HRMS (m/z): 1315.1321,
calculated for C56H65O16Si2P2100Ru102Ru [M + H]+: 1315.1341.
A sample of triethyl amine (0.14 mL, 1.02 mmol) and chloro-
triethoxysilane (0.20 mL, 1.02 mmol) were added in EtOH (20 mL),
then H2O (15 mL) was added to the above solution. The resulting
mixture was stirred at room temperature for 30 min under vigorous
stirring. The pH of the reaction mixture was around 7.5 at this point,
which was adjusted to ca. 12 by the addition of NH3 (2 mL) solution,
stirred for another 12 h at room temperature, and then heated at 60 °C
for 72 h. The white gel was recovered by centrifugation at 4000 rpm,
washed several times with water followed by ethanol, dichloromethane
and dried under vacuum overnight. The species so obtained (10 mg)
was used as catalyst in a reaction between styrene (2.3 mL, 20 mmol)
and ethyl diazoacetate (0.25 mL, 2 mmol) in dichloroethane (10 mL) as
above. Analysis by 1H NMR spectroscopy showed that no product was
formed.
4.4. Preparation of [Ru2(CO)4(PPh3)2(µ-OOCCH2OH)2] (2b)
4.10. Crystallographic studies
A sample of compound 3 was prepared using an analogous proce-
dure except that the crude product was purified by column chromato-
graphy with DCM as eluent. This afforded 2b as a yellow powder. Yield:
29 mg, 0.02 mmol, 84%. IR (dichloromethane, cm−1): νCO 2026 (s),
1985 (m), 1953 (s), νC=O 1597 (s). 1H NMR (400 MHz, CDCl3): δ
7.58–7.54 (m, 6H, arom-H), 7.39–7.35 (m, 9H, arom-H), 3.73 (s, 2H,
CH2), −0.17 (s, 9H, CH3). 31P{1H} NMR (162 MHz, CDCl3): δ
Diffraction-quality crystals of 1 and 2a were grown from di-
chloromethane, and 2b was grown from acetonitrile at 0 °C and
mounted on quartz fibers. X-ray diffraction data were collected at
103(2) K on a Bruker X8 APEX system, using Mo Kα radiation, with the
SMART suite of programs [18]. Data processing and correction were
made for Lorentz and polarization effects with SAINT [19], and for
adsorption effects with SADABS [20]. Structural solution and refine-
ment were carried out with the SHELXTL suite of programs [21]. The
structures were solved by direct methods to locate the heavy atoms,
followed by successive difference maps for the light, non-hydrogen
atoms.
12.8
ppm.
HRMS
(m/z):
1135.0651,
calculated
for
C
50H53O10Si2P2100Ru102Ru [M + H]+: 1135.0707.
4.5. Preparation of A
A sample of complex 2a (200 mg, 0.15 mmol) was dissolved in
EtOH (20 mL), then H2O (15 mL) was added to the above solution. The
resulting mixture was stirred at room temperature for 30 min under
vigorous stirring. The pH of the reaction mixture was around 7.5 at this
point, which was adjusted to ca. 12 by the addition of NH3 (2 mL)
solution, stirred for another 12 h at room temperature, and then heated
at 60 °C for 72 h. The brown colored gel (55 mg) was recovered by
centrifugation at 4000 rpm, washed several times with water followed
by ethanol, dichloromethane and dried under vacuum for overnight. IR
(KBr, cm−1): νCO 1938 (s), 1886 (s), νC=O 1640 (br), 1534 (w).
Solvates were found for the crystals of 2a (DCM) and 2b (MeCN).
The MeCN solvate in the latter exhibited disorder which was modelled
with four alternative sites; the occupancies refined to a total of ~ 0.66.
There was disorder (~5%) of the ruthenium atom positions in 1, which
were modelled with two alternative positions each. Appropriate re-
straints were placed on all disordered parts.
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
4.6. Calcination of A
A sample of A (170 mg) was calcined at 450 °C under vacuum for
2 h to afford a black crystalline powder of B (128 mg). Similar calci-
nation of 2a (200 mg) afforded a black crystalline powder of C
(112 mg).
Acknowledgements
This work was supported by Nanyang Technological University and
the Ministry of Education (Research Grant No. M4012079). The assis-
tance of Dr Deblin Jana with acquisition of the electron micrographs
and associated spectra, and GC analyses is acknowledged.
4.7. Synthesis of D
Appendix A. Supplementary data
A sample of MCM-41 (120 mg) was added to a solution of 2a
(30 mg) in toluene (5 mL). The resulting mixture was refluxed for 12 h,
which afforded gel type yellow solid. This was recovered by cen-
trifugation at 4000 rpm, washed several times with dichloromethane
and dried overnight under vacuum. IR (KBr, cm−1): νCO 2020 (s), 1975
(m), 1951 (s).
Supplementary data to this article can be found online at https://
References
4.8. General procedure for catalytic reactions
In a typical experiment, styrene (2.3 mL, 20 mmol), ethyl diazoa-
cetate (0.25 mL, 2 mmol) and 2a (10 mol %)/A-D (55 mg) were added
into dichloroethane (10 mL). The resulting mixture was then stirred at
50 °C for 2 d. After cooling to room temperature, the solution was se-
parated by centrifugation, solvent removed, and the product identified
by 1H NMR spectroscopy and GCMS.
5