Inorganic Chemistry
Article
1H NMR (500 MHz, C6D6): δ 6.98 (s, 1H, C(O)CHC(O)), 7.08
(t, 3JHH = 7.4 Hz, 4H, CH), 7.13 (d, 3JHH = 7.2 Hz, 2H, CH), 8.02 (d,
EXPERIMENTAL SECTION
■
Materials and Instrumentation. Caution! Beryllium compounds
are highly toxic and should be handled using appropriate safety
precautions.
3JHH = 7.6 Hz, 4H, CH). 9Be NMR (42 MHz, C6D6): δ 6.2 (s, ω1/2
=
14.6 Hz). 13C NMR (126 MHz, C6D6): δ 94.81 (s, C(O)CHC(O)),
128.47 (s, CH), 128.56 (s, CH), 132.22 (s, CH), 137.85 (s,
CC(O)CH), 185.73 (s, C(O)). FT-IR (cm−1): 3064 (vw), 3053 (vw),
3029 (vw), 1591 (m), 1544 (m), 1522 (vs), 1477 (s), 1454 (s), 1440
(m), 1377 (vs), 1334 (s), 1301 (s), 1226 (s), 1177 (m), 1156 (m),
1079 (s), 1026 (m), 1001 (m), 959 (s), 861 (m), 828 (s), 816 (m),
791 (m), 753 (s), 726 (s), 683 (vs), 718 (m), 589 (s), 518 (s), 453
(m), 430 (m), 404 (m).
Aqueous solutions of beryllium sulfate for ESI MS analysis were
prepared by dissolving the required amount of BeSO4·4H2O (BDH)
in high-purity distilled and deionized water to obtain a stock solution
of concentration 2.2 × 10−3 mol L−1. This stock solution was further
diluted to obtain a dilution series of BeSO4 solutions ranging from 2.2
× 10−4 to 2.2 × 10−5 mol L−1. In order to reduce manipulation of the
beryllium salt, stock solutions of the various ligands and aluminum
sulfate (BDH) were prepared to match the concentration of the
beryllium sulfate employed in ESI MS competition studies, i.e., 2.2 ×
10−3 mol L−1. All ligands were purchased commercially and used
without further purification. Stock solutions of these ligands were
prepared by dissolving the required amount of ligand in a very small
volume of dichloromethane, followed by dilution to the required
volume with methanol.
Synthesis of Be(tta)2. Amounts of 8.3 mg (0.10 mmol) of BeCl2
and 46.6 mg (0.21 mmol) of thenoyltrifluoroacetylacetone (Htta)
were weighed into a Schlenk tube equipped with a PTFE valve, and 5
mL of benzene was added via cannula. Vigorous gas evolution was
observed immediately after the addition of the solvent. When no more
gas evolution was observed, the tube was sealed, and the colorless
solution was stirred overnight at ambient temperature. After removal
of the solvent in vacuo, Be(tta)2 was obtained as a colorless,
microcrystalline powder in quantitative yield.
In order to investigate speciation of the Be2+ cation with these
ligands in a systematic manner, aliquots of the above stock solutions
were combined in a range of metal: ligand ratios (see the Results and
Discussion). The pH was unadjusted. The initial mass spectra were
obtained immediately after preparation, after 24 h, and finally after 3−
21 days in order to ensure that the systems had attained equilibrium.
The relative ion intensities did not change significantly over this
period; precipitation was also not an issue in these systems because of
the very low concentrations used.
1H NMR (500 MHz, C6D6): δ 6.26 (s, 1H, C(O)CHC(O)), 6.32
(dd, 3JHH = 4.9 Hz, 3JHH = 3.9 Hz, 1H, CH), 6.71 (dd, 3JHH = 4.9 Hz,
4JHH = 1.1 Hz, 1H, CH), 6.93 (dd, 3JHH = 3.9 Hz, 4JHH = 1.1 Hz, 1H,
CH). 9Be NMR (42 MHz, C6D6): δ 5.0 (s, ω1/2 = 7.2 Hz). 13C NMR
1
(126 MHz, C6D6): δ 94.15 (s, C(O)CHC(O)), 119.39 (q, JCF
=
281.3 Hz, CF3), 128.57 (s, CH), 134.34 (s, CH), 136.13 (s, CH),
141.04 (s, CC(O)CH), 172.07 (q, 2JCF = 35.4 Hz, C(O)CF3), 184.14
(s, C(O)). 19F NMR (283 MHz, C6D6): δ −74.76 (s, CF3). FT-IR
(cm−1): 3116 (vw), 1615 (w), 1572 (s), 1548 (s), 1513 (m), 1444
(w), 1407 (s), 1367 (m), 1352 (s), 1330 (s), 1303 (m), 1256 (s),
1234 (m), 1191 (s), 1165 (m), 1132 (vs), 1087 (m), 1068 (m), 1042
(w), 1026 (w), 955 (s), 865 (m), 848 (w), 812 (s), 789 (vs), 753
(m), 718 (s), 685 (s), 634 (s), 606 (m), 585 (m), 559 (m), 520 (w),
504 (s), 455 (m).
Synthesis of BeCl2(benzil). Amounts of 14.3 mg (0.18 mmol) of
BeCl2 and 38.7 mg (0.18 mmol) of benzil were weighed into a
Schlenk tube equipped with a PTFE valve, and 5 mL of
dichloromethane was added via cannula. The tube was sealed and
the suspension stirred overnight at ambient temperature. After
removal of the solvent in vacuo, BeCl2(benzil) was obtained as a
yellow, microcrystalline powder in quantitative yield.
General experimental details regarding the mass spectrometry
instrumentation used were described previously.13,23 The studies used
a Bruker MicrOTOF instrument, having a range of m/z 50−3000 and
a mass accuracy of 5 ppm. The CEV was varied between 40 and 180 V
to vary the degree of fragmentation. Data analysis was performed with
Data Analysis software (version 3.4, Bruker Daltonics) and mMass
(version 5.5.0)61,62 used in the confirmation of all ESI MS
assignments by a comparison of the observed and predicted isotope
patterns.
NMR Spectroscopy. 1H, 9Be, and 13C NMR spectra were
recorded on Bruker Avance III HD 300 and Avance III 500 NMR
spectrometers. The latter was equipped with a Prodigy Cryo-Probe.
1H NMR (300/500 MHz) and 13C NMR (126 MHz) chemical shifts
are given relative to the solvent signal for C6D6 (7.16 and 128.1
1H NMR (300 MHz, CD2Cl2): δ 7.54 (t, 3JHH = 7.7 Hz, 4H, CH),
7.71 (t, 3JHH = 7.3 Hz, 2H, CH), 7.97 (d, 3JHH = 7.5 Hz, 4H, CH). 9Be
NMR (42 MHz, C6D6): δ 6.6 (s, ω1/2 = 22.7 Hz). 13C NMR (126
MHz, CD2Cl2): δ 129.62 (s, CH), 130.53 (s, CH), 133.38 (s,
CC(O)), 135.74 (s, CH), 195.22 (s, C(O)). FT-IR (cm−1): 3065
(vw), 3053 (vw), 3031 (vw), 1591 (m), 1544 (m), 1522 (vs), 1477
(s), 1454 (s), 1440 (m), 1377 (vs), 1334 (s), 1316 (m), 1301 (s),
1226 (s), 1177 (m), 1156 (m), 1099 (w), 1079 (m), 1026 (m), 999
(w), 987 (w), 959 (s), 930 (w), 859 (m), 828 (s), 816 (s), 791 (m),
753 (s), 726 (s), 695 (m), 683 (vs), 618 (m), 589 (s), 518 (s), 453
(m), 430 (m), 404 (m).
X-ray Structure Determinations on Be(dbm)2 and
BeCl2(benzil). Crystals suitable for X-ray diffractometry of Be(dbm)2
were received by layering of a saturated benzene solution with
pentane and allowing it to stand over several days. Heating a
suspension of BeCl2(benzil) in o-difluorobenzene to 100 °C in a
sealed tube led to the formation of single crystals suitable for X-ray
diffractometry at the wall of the vessel above the solvent interface.
Single crystals were selected under exclusion of air in perfluorinated
polyether (Fomblin YR 1800, Solvay Solexis) and mounted using the
MiTeGen MicroLoop system. X-ray diffraction data were collected
using the monochromated Cu Kα radiation of a Stoe StadiVari
diffractometer equipped with a Xenocs Microfocus source and a
Dectris Pilatus 300 K detector. The diffraction data were reduced with
the X-Area software.67 The structure was solved using direct methods
(SHELXS-2013/1) and refined against F2 (SHELXL-2016/4) using
the ShelXle software package.68 All atoms were located by difference
Fourier synthesis and non-H atoms refined anisotropically. H atoms
9
ppm)/CD2Cl2 (5.32 and 53.8 ppm), while Be (42 MHz) used 0.43
[M] BeSO4 in D2O and 19F (283 MHz) used neat CFCl3 as an
external standard. NMR spectra were processed with the MestReNova
software.63
IR Spectroscopy. IR spectra were recorded on a Bruker α Fourier
transform infrared (FT-IR) spectrometer equipped with a diamond
attenuated total reflectance unit in an argon-filled glovebox.
Processing of the spectra was performed with the OPUS software
package64 and OriginPro2017.65
General Synthetic Remarks. All manipulations were performed
either under solvent vapor pressure or dry argon using glovebox and
Schlenk techniques. Dichloromethane was dried by refluxing over
CaH2 and benzene over sodium and subsequent distillation under
argon, respectively. CD2Cl2 was dried over CaH2 and C6D6 over Na/
K alloy and vacuum-transferred directly into the J. Young NMR tubes.
BeCl2 was prepared according to literature procedures.66 Because of
the expected extreme toxicity of the beryllium compounds, no
elemental analysis could be performed. The purity of the isolated
compounds was therefore determined by NMR and IR spectroscopy.
Synthesis of Be(dbm)2. Amounts of 7.7 mg (0.10 mmol) of BeCl2
and 43.3 mg (0.19 mmol) of Hdbm were weighed into a Schlenk tube
equipped with a poly(tetrafluoroethylene) (PTFE) valve, and 5 mL of
benzene was added via cannula. Vigorous gas evolution was observed
immediately after the addition of the solvent. When no more gas
evolution was observed, the tube was sealed, and the colorless
solution was stirred overnight at ambient temperature. After removal
of the solvent in vacuo, Be(dbm)2 was obtained as a colorless,
microcrystalline powder in quantitative yield.
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Inorg. Chem. XXXX, XXX, XXX−XXX