Molecular Thorium Compounds with Dichalcogenide Ligands: Synthesis, Structure, 77Se NMR Study, and Thermolysis

Article abstract of DOI:10.1021/acs.inorgchem.8b02555

A series of dimeric thorium disulfides and diselenides have been prepared with sterically undemanding ancillary ligands. Five complexes, (py)₆Th₂I₄(μ₂-S₂)₂, (py)₆Th₂Br₂(SC₆F₅)₂(μ₂-S₂)₂, (py)₆Th₂I₄(μ₂-Se₂)₂, (py)₆Th₂I₂(SC₆F₅)₂(μ₂-Se₂)₂, and (py)₆Th₂Br₂(SC₆F₅)₂(μ₂-Se₂)₂, were isolated in high yields by first reducing mixtures of I₂, F₅C₆SSC₆F₅, PhSeSePh, or PhSSPh, and PhSeBr with elemental Th, followed by in situ ligand-based redox reactions with elemental sulfur or selenium. These are the first examples of thorium compounds with bridging dichalcogenide ligands. Attempts to prepare chloride derivatives gave mixtures of (py)₄ThCl₄ and either (py)₆Th₂Cl₂(SC₆F₅)₂(μ₂-S₂)₂ or (py)₈Th₄Se₄(SePh)₄(SC₆F₅)₄. All products were characterized by single-crystal and powder X-ray diffraction and IR, UV-visible, and NMR spectroscopy. A computational analysis of experimental ⁷⁷Se NMR chemical shifts reveals that the solvated dimeric structures with two bridging dichalcogenides are maintained in solution. Thermolysis of (py)₆Th₂I₄(μ₂-Se₂)₂ leads to reduction of the bridging Se₂^2- moieties, oxidation of the I^- ligand, and formation of solid-state ThSe₂ and I₂.

Full text of DOI:10.1021/acs.inorgchem.8b02555

Article
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Molecular Thorium Compounds with Dichalcogenide Ligands:
77
Synthesis, Structure, Se NMR Study, and Thermolysis
†
†
,‡,§
Anna Y. Kornienko,† Thomas J. Emge,†
́
Wen Wu, David Rehe, Peter Hrobarik,*
and John G. Brennan*,†
†Department of Chemistry and Chemical Biology, Rutgers, the State University of New Jersey, 610 Taylor Road, Piscataway,
New Jersey 08854-8087, United States
‡Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, SK-84215 Bratislava, Slovakia
§Institut fu
̈
r Chemie, Technische Universitat Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany
̈
S
* Supporting Information
ABSTRACT: A series of dimeric thorium disulfides and diselenides
have been prepared with sterically undemanding ancillary ligands.
Five complexes, (py)6Th2I4(μ2-S2)2, (py)6Th2Br2(SC6F5)2(μ2-S2)2,
(py)6Th2I4(μ2-Se2)2, (py)6Th2I2(SC6F5)2(μ2-Se2)2, and
(py)6Th2Br2(SC6F5)2(μ2-Se2)2, were isolated in high yields by first
reducing mixtures of I2, F5C6SSC6F5, PhSeSePh, or PhSSPh, and
PhSeBr with elemental Th, followed by in situ ligand-based redox reac-
tions with elemental sulfur or selenium. These are the first examples of
thorium compounds with bridging dichalcogenide ligands. Attempts to
prepare chloride derivatives gave mixtures of (py)4ThCl4 and either (py)6Th2Cl2(SC6F5)2(μ2-S2)2 or (py)8Th4Se4(SePh)4(SC6F5)4.
All products were characterized by single-crystal and powder X-ray diffraction and IR, UV−visible, and NMR spectroscopy.
A computational analysis of experimental 77Se NMR chemical shifts reveals that the solvated dimeric structures with two
bridging dichalcogenides are maintained in solution. Thermolysis of (py)6Th2I4(μ2-Se2)2 leads to reduction of the bridging
Se2 moieties, oxidation of the I− ligand, and formation of solid-state ThSe2 and I2.
2−
prepare increasingly large polymetallic compounds in order to
monitor size-dependent physical properties,11 sterically demand-
ing ligands can be a liability, and it becomes advantageous to
work with sterically undemanding ancillaries.
INTRODUCTION
■
Understanding the complicated nature of bonding in actinide
(An) systems remains one of the great challenges in inorganic
chemistry, given our incomplete understanding of how much
the radially extended 5f orbitals are involved in covalent inter-
actions. In the quest to prepare and characterize appropriately
insightful An molecules with significant covalent bonding char-
acter, ligands with fewer electronegative chalcogen (E; E = S,
Se, Te)-based anions are particularly attractive synthetic
targets. Actinide compounds with An−E bonds are also appeal-
ing from a reactivity perspective, because these bonds are rela-
tively weak and thus a potential source of controllable reactivity.
Compounds with An−E bonds are found with RE−,1 E2−,1b−d,2
and (En)2− ligand systems, and of the three, the polychalcogenides
(En2−, n = 2,2e−i,3 3,1g,2n,3b,4 4,2i,5 56) are the least well developed
molecular class. Recent work has explored chemistry with
sterically demanding ancillary ligands (i.e., silylamides,1g,2h,3b−d,7
substituted cyclopentadienyls,1k−p,2c,k,l,3e,6,8 pyrazolylborates,1q,r,3f,9
branched alkoxides1p), because these ancillaries impart solu-
bility in polar solvents that facilitates crystallization and because
their steric bulk inhibits ligand redistribution reactions. Control
of steric properties within the primary and secondary coor-
dination sphere in actinide molecules is critical to the
preparation of synthetically challenging motifs: i.e., the recent
preparation of remarkable compounds with terminal AnE
bonds.3d,7d,10 In contrast, when it becomes interesting to
Polychalcogenide chemistry is particularly attractive because
E−E bonds are readily reduced, providing chemists with a
potential source of reactivity for rationally building larger
clusters or heterometallic compounds. Actinide compounds
2−
with E2 ligands can be prepared with less congested coor-
dination environments, although success in this area has thus
far has been restricted to compounds of uranium. The first
example of an actinide molecule with a dichalcogenide ligand
was the dioxouranate UO2(thiocarbamate)2(S2)2−, prepared
by the thermal decomposition of a uranyl thiocarbamate
methoxide precursor.3a This report was eventually followed by
the successful synthesis of [U(Se2)4]4−,12 [UO2(S2)3]4−,13 and
the imido analogue [(Bu2bipyridine)U(NBu)2I]2Se4.5
Related chemistry with thorium is important, because dia-
magnetic Th(IV) affords an opportunity to probe solution
structure, speciation, and reactivity, particularly with com-
pounds of selenium, since the large NMR chemical shift
dispersion of 77Se has been useful3d,14 for correlating solution
and solid-state structure/dynamics in both Th(SeR)4 molecules
Received: September 7, 2018
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.8b02555
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Article
(broad, 2H, py), 6.94 (m, 1H, py), 6.64 (m, 2H, py). 19F NMR
(toluene-d8): −138 (m, 2F), −159 (t, 1F), −162 (m, 2F).
and cubane clusters.1b,s This work outlines the synthesis and
characterization of six dichalcogenido bridged thorium dimers,
formed in the ligand-based redox reactions of thorium
selenolates with elemental chalcogen. A powerful combination
of 77Se NMR and relativistic DFT calculations is used to show
that the well-defined solid-state structures are maintained in
solution, and an investigation into the thermal decomposition
reactions of the halogenated materials shows that ThE2, rather
than ternary solid-state compounds, are produced.
Synthesis of (py)6Th2Cl2(SC6F5)2(S2)2 (3). Th (0.232 g,
1.00 mmol), PhSSPh (0.109 g, 0.50 mmol), F5C6SSC6F5 (0.199 g,
0.50 mmol), and PhSeCl (0.192 g, 1.00 mmol) were combined in pyri-
dine (10 mL) with a catalytic amount of Hg (0.010 g, 0.05 mmol), and
the mixture was stirred for 12 h until the thorium metal was completely
consumed to give a pale yellow solution. Sulfur (0.064 g, 2.00 mmol)
and toluene (10 mL) were added, and the mixture was stirred for an
additional 45 min. The yellow solution was filtered to remove a light
gray powder, concentrated to 15 mL, and layered with hexanes
(15 mL) to give colorless crystals, one of which was identified by
single-crystal diffraction as (py)6Th2Cl2(SC6F5)2(S2)2·1.5py (3).
PXRD of the powdered product revealed that this reaction
cocrystallizes as a number of products, including 3 and monomeric
(py)4ThCl4 (7).
EXPERIMENTAL SECTION
■
General Methods. All syntheses were carried out under ultrapure
nitrogen (Welco Praxair), using conventional drybox or Schlenk
techniques. Pyridine and hexane (Aldrich) were purified with a dual-
column Solv-Tek solvent purification system and collected immedi-
Synthesis of (py)6Th2I4(Se2)2·2py (4). Th (0.232 g, 1.00 mmol),
PhSeSePh (0.312 g, 1.00 mmol), and I2 (0.254 g, 1.00 mmol) were
combined in pyridine (20 mL) with a catalytic amount of Hg (0.010 g,
0.05 mmol). The mixture was stirred for 12 h until the thorium metal
was consumed to give a yellow solution and trace black powder.
Elemental selenium (0.158 g, 2.00 mmol) was added, and the mixture
was stirred for an additional 30 min. The yellow solution was filtered,
concentrated to 10 mL, and layered with hexanes (15 mL) to form
yellow crystals (0.53 g, 61%) that melt at 252 °C and decompose
(turn black) at 384 °C. IR: 2924 (s), 2853 (s), 1598 (w), 1463 (m),
1365 (s), 1261 (w), 1220 (w), 1067 (w), 1037 (w), 801 (m),
722 (w), 700 (w), 489 (w) cm−1. UV−vis: this compound shows an
absorption plateau at ca. 440 nm, but a well-defined maximum was
not observed (see Figure S22 in the Supporting Information). Anal.
Calcd for C40H40N8Th2I4Se4: C, 25.0; H, 2.10; N, 5.84 (lattice
pyridine removed C30H30N6Th2I4Se4: C, 20.5; H, 1.72; N, 4.77).
Found: C, 25.1; H, 2.29; N, 5.64. 1H NMR (benzene-d6): 8.98
(broad, 2H, py), 6.88 (m, 1H, py), 6.62 (m, 2H, py). 77Se NMR
(pyridine-d5): 241 (s).
Synthesis of (py)6Th2I2(SC6F5)2(Se2)2·py (5). Th (0.232 g,
1.00 mmol), PhSeSePh (0.312 g, 1.00 mmol), F5C6SSC6F5 (0.199 g,
0.50 mmol), and I2 (0.127 g, 0.50 mmol) were combined in pyridine
(20 mL) with a catalytic amount of Hg (0.010 g, 0.05 mmol), and the
mixture was stirred for 12 h until the metal was completely consumed
to give a yellow solution. Elemental selenium (0.158 g, 2.0 mmol) was
added, and the mixture was stirred for 1 h. The pale orange solution
was filtered, concentrated to 15 mL, and layered with hexanes
(15 mL) to give orange crystals (0.30 g, 31%) that became deep
orange and melt at 181 °C and decompose at 290 °C. IR: 2924 (s),
2854 (s), 1601 (w), 1460 (s), 1376 (s), 1261 (w), 1221(w), 1152 (w),
1038 (w), 969 (m), 859 (w), 833 (w), 802 (w), 722 (m), 698 (w),
623 (w) cm−1. UV−vis: this compound shows an absorption plateau
at ca. 400 nm. Anal. Calcd for C47H35N7Th2F10I2S2Se4: C, 28.4;
H, 1.78; N, 4.94 (lattice pyridine removed C42H30N6Th2F10I2S2Se4:
C, 26.5; H, 1.59; N, 4.41). Found: C, 28.2; H, 1.97; N, 4.47. 1H NMR
(toluene-d8): 8.71(broad, 2H, py), 6.91 (m, 1H, py), 6.63 (m, 2H,
py). 19F NMR (toluene-d8): −138 (d, 2F), −159 (t, 1F), −162
(m, 2F). 77Se NMR (pyridine-d5): 332 (s).
15
ately prior to use. F5C6SSC6F5 was prepared according to literature
procedures. PhSeSePh (Aldrich) was purchased and recrystallized
from hexanes. PhSSPh (Acros), sulfur, selenium, and iodine
(Aldrich), thorium chips (International Bioanalytical Industries
Inc.), and mercury (Strem Chemicals) were purchased and used as
received. Melting points were recorded in sealed capillaries and are
uncorrected. IR spectra were recorded on a Thermo Nicolet Avatar
360 FTIR spectrometer from 4000 to 400 cm−1 as Nujol mulls on CsI
plates. UV−vis absorption spectra were recorded on a Shimadzu
UV-3600 double-beam spectrophotometer with the samples dissolved
in pyridine. Gas chromatography−mass spectrometry (GC-MS) data
were collected on a Varian Saturn 2100T instrument fitted with a
capillary column (30 mm length, 0.25 mm i.d., 0.25 mm film thickness).
All NMR data were collected on a Varian VNMRS 500 spectrometer
at 25 °C with the compounds dissolved in deuterated solvents. 1H and
19F NMR spectra were obtained at 499 and 476 MHz, respectively;
77Se NMR spectra were acquired with a longer relaxation delay (7.0 s)
in hydrogen- or fluorine-decoupled mode at 95 MHz using PhSeSePh
as an external standard. Elemental analyses were performed by
Quantitative Technologies, Inc. (Whitehouse, NJ).
Synthesis of (py)6Th2I4(S2)2·2py (1). Th (0.232 g, 1.00 mmol),
PhSSPh (0.218 g, 1.00 mmol), and I2 (0.254 g, 1.00 mmol) were
combined in pyridine (20 mL) with a catalytic amount of Hg (0.010 g,
0.05 mmol). The mixture was stirred for 12 h until all Th metal was
completely consumed to give a yellow solution with trace black
powder. Sulfur (0.064 g, 2.00 mmol) and toluene (10 mL) were
added, and the mixture was stirred for 1 h to give a yellow solution
that was filtered to remove a pale yellow powder, concentrated to
20 mL, and layered with hexanes (15 mL) to form colorless crystals
(0.36 g, 46%) that melt at 181 °C and decompose (turn black) at
291 °C. IR: 2924 (w), 2852 (w), 1598 (m), 1463 (m), 1365 (m),
1219 (m), 1151 (w), 1065 (m), 1037 (m), 1002 (m), 738 (s),
695 (s), 623 (s), 542 (m), 466 (w), 417 (m) cm−1. Anal. Calcd for
C40H40I4N8S4Th2: C, 27.7; H, 2.33; N, 6.47 (without lattice pyridine
C30H30N6I4Th2S4: C, 22.9; H, 1.92; N, 5.34). Found: C, 23.0;
H, 2.06; N, 5.24. 1H NMR (toluene-d8): 8.48 (d, J = 4.8 Hz, 2H, py),
7.00 (m, 1H, py), 6.67 (t, J = 6.0 Hz, 2H, py).
Synthesis of (py)6Th2Br2(SC6F5)2(Se2)2·2py (6). Th (0.232 g,
1.00 mmol), PhSeSePh (0.156 g, 0.50 mmol), F5C6SSC6F5 (0.199 g,
0.50 mmol), and PhSeBr (0.236 g, 1.00 mmol) were combined in
pyridine (20 mL) with a catalytic amount of Hg (0.010 g,
0.05 mmol), and the mixture was stirred for 12 h until the thorium
metal was consumed to give a yellow solution. Elemental selenium
(0.158 g, 2.00 mmol) was added, and the mixture was stirred for an
additional 10 min. The pale orange solution was filtered, concentrated
to 15 mL, and layered with hexanes (10 mL) to give orange crystals
(0.40 g, 44%) that melt at 145 °C and decompose at 416 °C.
IR: 2923 (s), 2854 (s), 1601 (m), 1503 (w), 1463 (s), 1376 (s),
1262 (w), 1221 (m), 1151 (w), 1079 (w), 1069 (w), 1038 (m),
1003 (m), 969 (m), 860 (s), 752 (m), 698 (s), 623 (s) cm−1. Anal.
Calcd for C52H40F10Br2N8S2Se4Th2: C, 31.7; H, 2.05; N, 5.69 (lattice
pyridine removed C42H30F10Br2N6S2Se4Th2: C, 27.83; H, 1.67; N, 4.64).
Found: C, 31.6; H, 2.11; N, 5.63. 1H NMR (toluene-d8): 8.72 (broad,
Synthesis of (py)6Th2Br2(SC6F5)2(S2)2 (2). Th (0.232 g,
1.00 mmol), PhSSPh (0.109 g, 0.50 mmol), F5C6SSC6F5 (0.199 g,
0.50 mmol), and PhSeBr (0.236 g, 1.00 mmol) were combined in
pyridine (10 mL) with a catalytic amount of Hg (0.010 g,
0.05 mmol), and the mixture was stirred for 12 h until the thorium
metal was completely consumed to give a yellow solution. Sulfur
(0.064 g, 2.00 mmol) and toluene (10 mL) were added, and the
mixture was stirred for an additional 30 min. The bright yellow
solution was filtered to remove a light gray powder, concentrated to
15 mL, and layered with hexanes (15 mL) to give colorless crystals
(0.29 g, 36%) that melt at 213 °C and decompose at 273 °C.
IR: 2924 (s), 2854 (s), 1630(w), 1601 (m), 1462 (s), 1365 (s),
1261 (m), 1222 (m), 1153 (w), 1079 (w), 1037 (w), 967 (s), 859 (s),
801(s), 741 (s), 694 (s), 624 (m), 578 (w), 482 (w), 419 (w) cm−1.
Anal. Calcd for C42H30N6Th2F10Br2S6: C, 31.0; H, 1.86; N, 5.17.
Found: C, 31.0; H, 1.91; N, 5.17. 1H NMR (toluene-d8): 8.54
B
DOI: 10.1021/acs.inorgchem.8b02555
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Article
2H, py), 6.89 (broad, 1H, py), 6.58 (broad, 2H, py). 19F NMR
(toluene-d8): −138(m, 2F), −159 (t, 1F), −162 (m, 2F). 77Se NMR
(pyridine-d5): 309 (s).
operating at 40 kV and 50 mA and equipped with a three-circle Azlan
goniometer. The system used 1.0 mm pinhole collimation and a
Rigaku Osmic parallel-mode (e.g., primary beam dispersion less than
0.01° in 2θ) mirror monochromator (Cu Kα; λ = 1.5418 Å). Data
were collected at room temperature (20 °C) with a sample to detector
distance of approximately 32 cm. Spatial calibration and flood-field
correction for the area detector were performed prior to data collec-
tion. The 2048 × 2048 pixel images were collected at a fixed detector
(2θ) angle of 15° for approximately 10 min with ω fixed and with
continuous rotation in ϕ (capillary axis) of about 1°/s. For the
intensity versus 2θ plots (see the Supporting Information),28 back-
ground levels, modeled as amorphous scattering from air, capillary,
and sample, were subtracted and integrations in χ (Bruker GADDS)29
were performed. No other corrections to the PXRD data were made.
PXRD patterns of ground samples were compared with the calculated
diffraction pattern of the respective compound. To account for the
temperature difference in the PXRD (T = 293 K) and single-crystal
(T = 120 K) patterns, a wavelength of 1.51 Å was used for the
calculated PXRD patterns. In addition, it appeared that the intensity
and d spacings of low-angle PXRD data were much less affected by
evaporation of lattice solvent. Thus, the 4° < 2θ < 12° PXRD data
provided an excellent region for the phase verification performed here.
Diagrams of the PXRD data are available in the Supporting Information.
Single-Crystal X-ray Structure Determination. Data for 1−7
were collected on a Bruker Smart APEX CCD diffractometer with
graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) at 120 K.30
Crystals were immersed in Paratone oil and examined at low tem-
peratures. The data were corrected for Lorentz effects, polarization,
and absorption, the last by a face-based numerical method.30 The
structures were solved by direct methods.31 All non-hydrogen atoms
Attempt To Prepare (py)6Th2Cl2(SC6F5)2(Se2)2. Th (0.232 g,
1.00 mmol), PhSeSePh (0.156 g, 0.50 mmol), F5C6SSC6F5 (0.199 g,
0.50 mmol), and PhSeCl (0.192 g, 1.00 mmol) were combined in
pyridine (15 mL) with a catalytic amount of Hg (0.010 g,
0.05 mmol), and the mixture was stirred for 12 h until the metal
was completely consumed to give an orange solution. Elemental
selenium (0.158 g, 2.00 mmol) was added, and the mixture was then
stirred for 10 min. The pale orange solution was filtered, concentrated
to 15 mL, and layered with hexanes (15 mL) to give crystals that were
ground and identified by PXRD as a mixture of the (py)4ThCl4 (7)
and (py)8Th4Se4(SePh)4(SC6F5)4.1b
Computational Details. All structures were fully optimized at the
PBE0 level of theory,16 including an atom-pairwise correction for dis-
persion forces via Grimme’s D3 model17 with Becke-Johnson (BJ)18
damping in the Turbomole program.19 Quasirelativistic energy-
consistent small-core pseudopotential (effective-core potential,
ECP)20 along with corresponding Gaussian-type orbital valence
basis sets of def2-TZVP quality were used for metals (Th, Hf, Zr) and
iodine, respectively, while all other atoms were treated with an
all-electron def2-TZVP basis set.21 Relativistic all-electron DFT
calculations of the nuclear shielding were performed using the
Amsterdam Density Functional (ADF) program suite,22 employing a
customized PBE0 exchange-correlation functional with 40% exact-
exchange admixture (PBE0-40HF)23 in conjunction with Slater-type
orbital basis sets of triple-ζ doubly polarized (TZ2P) quality.
An integration accuracy of 5 was used. Both scalar and spin−orbit
relativistic effects were treated by the two-component zeroth-order
regular approximation (ZORA).24 Bulk solvent effects were simulated
by the conductor-like screening model (COSMO)25 as implemented
self-consistently in ADF, considering pyridine as the solvent. The
computed 77Se nuclear shieldings were converted to chemical shifts
(δ, in ppm) relative to the shielding of Me2Se, computed at the same
level. Where applicable, the calculated shieldings were averaged over
the magnetically equivalent nuclei. QTAIM (quantum theory of
atoms in molecules) delocalization indices (DI) were evaluated at the
ZORA scalar relativistic PBE0/TZ2P level using utilities implemented
in the ADF package.22 The DI integrates the electron density in the
bonding region between two atoms in question and serves thus as a
quantitative descriptor of the bond covalency.3d,26 The ADF code was
also used for energy decomposition analysis (EDA)27 of the total
bonding energy into steric and electronic (attractive orbital) inter-
actions and for time-dependent DFT calculations of excitation
energies.
were refined31 on the basis of Fo . All hydrogen atom coordinates
2
were calculated with idealized geometries. All structures were drawn
using the Mercury 3.8 program.32 Crystallographic data and final
R indices for 1−7 are given in Table S1 of the Supporting Information.
The CIF files for 1−7 have been deposited with the Cambridge
Structural Database with CCDC numbers 1853617−1853623,
respectively. Thermal ellipsoid diagrams for 1−6 are shown in
Figures 1 and 2, and the thermal ellipsoid diagram for 7 is shown in
Thermolysis. A ground sample of 4 (ca. 200 mg) was placed in a
quartz thermolysis tube under a nitrogen atmosphere; the tube was
evacuated and purged with argon three times, sealed under vacuum,
and placed into a Model 847 Lindberg tube furnace. The initially
empty “cold” end of the glass tube was held at −196 °C by immersion
in liquid nitrogen. The sample was heated to 850 °C at a ramp rate of
10 °C/min and then held at 850 °C for 6 h, at which time it was
cooled to 25 °C at a rate of 3.5 °C/min. The gray-black powder that
was formed at the sample end of the quartz tube was placed in a glass
Figure 1. Thermal ellipsoid (ORTEP) diagram of (py)6Th2I4(E2)2,
where E = S (1), Se (4). Orange denotes S or Se, purple I, light blue
Th, dark blue N, and gray C. H atoms are removed for clarity, and
ellipsoids are at the 50% probability level. Significant bond length
averages are given in Table 1.
10
capillary and identified as ThSe2 by PXRD (space group Pmnb
(No. 62), Z = 4, PDF# 74-0978). GC-MS analysis of the volatile
products identified py (m/z 79) and I2 (m/z 253.8).
Scanning Electron Microscopy (SEM). Field-emission scanning
electron microscopy (FE-SEM, ZEISS Sigma) and energy-dispersive
X-ray spectroscopy (EDS, silicon drift detector from Oxford
Instruments) were employed to record the morphological character-
istics of the pyrolysis materials. Imaging and EDS were completed
using 5 and 15 keV electron beam voltages, respectively. All samples
were covered with a 20 nm Au coating using a rotary-pumped sputter
coating system (EMS150R, Electron Microscopy Sciences) and
placed on carbon adhesive tape with a specimen holder (Ted Pella).
Polycrystalline X-ray Diffraction (PXRD). PXRD data for
compounds 1−4, 6, and 7 were obtained with a Bruker Vantec-500
area detector and a Bruker FR571 rotating-anode X-ray generator
Figure S26. Complete crystallographic details for 1−7 are given in the
Supporting Information.
RESULTS AND DISCUSSION
■
Ligand-based redox reactions of thorium halide/chalcogeno-
lates with elemental E give high yields of bimetallic thorium
compounds with bridging (E2)2− ligands. Addition of elemental E
to solutions of “ThIn(EPh)4−n” or “ThXn(SC6F5)m(EPh)4−(n+m)
”
(E = S, Se; X = I, Br, and n = 1−4) leads to the reduction of E to
give (E2)2−, oxidation of EPh− to give PhEEPh, and the formation
C
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Figure 2. (a) ORTEP diagram of (py)6Th2X2(SC6F5)2(S2)2, where X = Br (2), Cl (3). (b) ORTEP diagram of (py)6Th2X2(SC6F5)2(Se2)2, where
X= I (5), Br (6). Green denotes F, yellow S, orange Se, red halogen(X), light blue Th, dark blue N, and gray C. H atoms are removed for clarity,
and ellipsoids are at the 50% probability level. Significant bond length averages are given in Table 1.
Scheme 1. Synthesis of Dichalcogenido-Bridged Thorium
Dimers with Terminal Iodides
chloride derivative 3 and iodide 5 with fluorothiolates that
crystallize in the space group P1
̅
.
Related compounds in the literature are limited. There exists
a thorium dimer with two bridging sulfido ligands, {[η5-1,2,4-
(Me3C)3C5H2]2Th}2(μ-S)2,2c and there are two examples of
monometallic thorium compounds with terminally bound η2-E2
units, Cp*2Th(DMAP)(S2)3e and [Th(Se2){N(SiMe3)2}3]−.3d
In contrast, there is a more extensive uranium literature,
including monometallic species with η2-E2 ligands1e,2e,3a−c,f,g
and bimetallic compounds with one or two bridging E2
ligands.2b,e,h,i,3c,4
Bond geometries for all six compounds summarized in Table 1
are consistent with prior literature, with values reflecting the sizes
of the atomic/ionic components. In all six compounds, there
are three pyridine molecules bound to thorium(IV), with two
of these pyridines (N(1), N(3)) having Th−N bond lengths
(2.68−2.72 Å) consistent with the wide range of previously
reported Th−N(pyridine) bond lengths: i.e., 2.62−2.72 Å in
monomeric (py)xTh(ER)4,1a (x = 3, 4; E = S, Se; R = Ph,
C6F5), 2.63−2.71 Å in a group of cubane clusters,1b,s and 2.730 Å
in (py)2Th2(μ-OEt2)2(OEt2)6.34 Pyridines opposite to the EE
bridges have a slightly longer Th−N(2) bond length (2.73−
2.78 Å). The difference in Th−N(1),(3) and Th−N(2) bond
lengths within one molecule are about 0.03 Å (compounds 1
and 3), 0.09 (2), 0.01 Å (4), 0.07 Å (5), and 0.06 Å (6).
Thorium−sulfur(thiolate) distances are equally consistent
with previous literature values: compare the Th−S(C6F5) in
nine-coordinate 2 (2.892(2) Å), 3 (average 2.900(9) Å),
5 (average 2.885(4) Å), and 6 (2.884(3) Å) with the Th−
S(C6F5) bonds in the eight-coordinate cubane clusters
(py)8 Th4 S4 (SPh)4 (SC6 F5 )4 (2.900(2) Å)1b and
(py)8Th4Se4(SePh)4(SC6F5)4 (2.889(2) Å)1b and the Th−S
of (py)6Th2I4(E2)2 (Scheme 1) or (py)6Th2X2(SC6F5)2(E2)2
(Scheme 2).
A similar redox approach to the synthesis of the disulfide
compounds in the presence of chloride ion led to the formation
of a product mixture, which includes (py)6Th2Cl2(SC6F5)2(S2)2
(3) and (py)4ThCl4 (7) (Scheme 3). The latter structure has
considerable literature precedence.33
Similarly, attempts to make a diselenido thorium dimer with
terminal fluorothiolate and chloride led to the isolation of a
crystalline mixture containing (py)4ThCl4 and the thorium
1b
heterocubane (py)8Th4Se4(SePh)4(SC6F5)4 (Scheme 4).
Compounds 1−6 were characterized by spectroscopic
methods and low-temperature single-crystal X-ray diffraction.
Figure 1 shows an ORTEP diagram of the common molecular
structure of 1 and 4, and Figure 2 shows an ORTEP diagram of
the common molecular structure of 2, 3, 5, and 6 from a
variety of orientations, with significant bond lengths and angles
for 1−6 given in Table 1. These are the first examples of
1a
bonds in monometallic seven coordinate (py)3Th(SC6F5)4
(2.811−2.825(10) Å).
In all compounds the halide ligands are terminally bound.
There are four iodides in 1 (3.174(1), 3.179(1) Å) and 4
(3.197(1), 3.201(1) Å) and two iodides in 5 (average 3.205(1) Å)
with nearly identical Th−I bond lengths that are consistent
with previously published Th−I distances: i.e., 3.172(1) Å in
(C5Me5)2[iPrNC(Me)NiPr-κ2N,N′]ThI,35 3.171(1) Å in
2−
thorium compounds with bridging E2 ligands.
All six compounds have similar structures containing a
central Th2(μ2‑E2)2 core region, with the primary coordination
sphere of each thorium saturated by two additional mono-
dentate anions and three neutral pyridine ligands. The molec-
ular site symmetry of the individual dimer molecules for four of
the six compounds is P21/n, with the exception being the
36
ThI3[O(CH2)4I](THF)3, and 3.226(1) Å in ThI(OCH
i-Pr2)3(py)2.37 Similarly, complexes 2 and 6 contain terminal
bromide ligands with Th−Br bond lengths that are also similar
to those in previously reported examples: i.e., 2.895(1) Å in mono-
meric (η5-Cp)2ThBr2(THF)38 and 2.885(2) Å in heterometallic
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Scheme 2. Synthesis of Dichalcogenido-Bridged Thorium Dimers with Ancillary Halides and Fluorinated Thiolates
Scheme 3. Synthetic Attempt To Prepare a Disulfide-Bridged Thorium Dimer with Terminally Bound Chloride and
Fluorothiolate Ligands
Scheme 4. Synthetic Attempt To Prepare a Diselenido-Bridged Thorium Dimer with Fluorothiolate and Chloride Terminal
Ligands
[(η5-C5Me5)2Th(Br)N(mesityl)Cu(DMAP))].39 In the single
chloride derivative 3, the Th−Cl bond lengths (average
2.733(8) Å) are again similar to literature values: i.e., 2.755(1) Å
in monomeric Th(TMTAA)Cl2(THF)240 and 2.737(1) Å in
ThCp*(TMTAA)Cl40 (TMTAA = tetramethyltetraazaannulene),
among others.14d,39,41
Disulfido bonds in 1−3 are in the range 2.076−2.090(3) Å,
consistent with the terminal S2 unit in the thorium disulfide
complex (η5-C5Me5)2ThS2(DMAP), which contains a 2.088 Å3e
sulfur−sulfur bond. Comparable distances42 have also been
noted in uranium,2e,f,h lanthanide,43,44 and transition-metal
chemistry.45 Similarly, dimers 4−6 contain Se−Se bonds
within a narrow range of bond lengths (2.342−2.350(3) Å)
that are almost identical with the 2.397(1) Å for the terminally
bound diselenido ligand in [K(18-crown-6)][Th(η2-E2)(NR2)3]3d
and fall within the range of expected values for diselenide moieties
bound to lanthanides46 and transition metals.45h,47
The molecular conformation of the [(py)3ThX(SC6F5)E2]2
dimers 2, 3, 5, and 6 can be viewed as having an equatorial
plane containing the Th(IV) ions, the centroids of all the py
ligands, and the two μ2-E2 bridging ligands. In this scheme, the
halide and SC6F5 ligands extend out of the equatorial plane,
such that the X2S2 plane is nearly perpendicular to the equa-
torial plane. This motif makes available a variety of close
contacts that are indicative of prevalent intramolecular hydro-
gen bonding to halogen, chalcogen, and nitrogen acceptor
atoms. Further, the py ligands are rotated around their Th−N
bonds and this situation brings their α-H atoms into proximity
with H-bond acceptors.
in Table 2 for comparison. In all of these compounds, intra-
molecular interactions, which are indicated by distances
shorter than vdW radii sums, are found for all α-H on py
ligands. For example, in 2, H(7)···F(5) for py(N1), H(12)···
S(1) for py(N2), and H(21)···Br(1) for py(N3) are 0.21, 0.29,
and 0.18 Å less than vdW, respectively (Figure 3); in 5,
H(11)···S(1) for py(N1), H(16)···S(1) for py(N2), and
H(17)···S(1) for py(N3) are 0.18, 0.25, and 0.27 Å less than
vdW, respectively, and in 6, H(7)···F(1) for py(N1), H(12)···
S(1) for py(N2), and H(21)···Br(5) for py(N3) are 0.18, 0.27,
and 0.10 Å less than vdW, respectively. Two of these are
expected, since F and Br are good electronegative H-bond
acceptors. For H···S, the extreme shortness of this contact
likely has both the electrostatic basis of the H-bond and the
proximity basis of these two atoms more or less confined to a
plane perpendicular to the aforementioned equatorial plane of
the dimer. As was mentioned earlier, Th(1)−N(2) bonds are
much longer (0.09 Å in 2, 0.07 Å in 5, and 0.06 Å in 6) than
Th(1)−N(1) and Th(1)−N(3) bonds, and this is consistent
with py(N2) having a close contact on only one side of the
ligand, versus py(N1) and py(N3) having close contacts on
both sides of the py ligand. The situation in 3 is unique.
H(12)···S(3) and H(16)···Cl(1) for py (N2) are 0.20 and
0.27 Å less than vdW, respectively. These close contacts from
both sides of the py ligand are also consistent with the fact that
the Th bond to N(2) is closer than the distance between Th
bonds to N(1) and N(3), namely 2.727(8) Å versus 2.720(8)
and 2.694(8) Å, in comparison with 2, 5, and 6.
If unit cell packing is viewed along crystallographic c axis, the
arrangement of neighboring molecules of 6 in the crystallo-
graphic ab plane is shown in Figure S27. A nearly one
Table 2 summarizes close contacts in the compounds 2, 3, 5,
and 6. The van der Waals radii sums (vdW)48 are also included
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a
Table 2. Summary of H···Y (Y = N, E, or X) Distances (Å) in 2, 3, 5, and 6
b
c
(py)6Th2Br2(SC6F5)2S4 (2)
(py)6Th2Cl2(SC6F5)2S4 (3)
(py)6Th2I2(SC6F5)2Se4 (5)
(py)6Th2Br2(SC6F5)2Se4 (6)
Contacts from py (N1)
H(7)···S(1) 2.95
H(7)···F(5) 2.46
H(11)···Br(1) 2.84
H(7)···S(3) 2.80
H(7)···F(1) 2.54
H(11)···Cl(1) 2.82
Contacts from py (N2)
H(11)···S(1) 2.82
H(11)···F(1) 2.71
H(7)···I(1) 3.06
H(7)···Se(2) 2.90
H(7)···F(1) 2.49
H(11)···Br(1) 2.90
H(12)···S(1) 2.71
H(12)···N(1) 2.91
H(16)···Br(1) 3.01
H(16)···N(3) 2.76
H(12)···S(3) 2.80
H(12)···N(3) 2.86
H(16)···Cl(1) 2.68
H(16)···N(1) 2.89
H(16)···S(1) 2.75
H(16)···N(1) 2.75
H(12)···I(1) 3.09
H(12)···N(3) 2.68
H(12)···S(1) 2.73
H(12)···N(1) 2.69
H(16)···Br(1) 3.00
H(16)···N(3) 2.69
Contacts from py (N3)
H(17)···S(1) 2.78
H(17)···F(1) 2.67
H(21)···Br(1) 2.87
H(21)···S(2) 3.27
H(17)···S(3) 3.09
H(17)···F(5) 2.99
H(21)···Cl(1) 2.75
H(21)···S(2) 3.54
H(17)···S(1) 2.73
H(17)···F(5) 2.64
H(21)···I(1) 3.28
H(21)···Se(2) 2.96
H(21)···S(1) 2.82
H(21)···F(5) 2.56
H(17)···Br(1) 2.95
H(17)···Se(2) 3.14
Values shorter than the sum of van der Waals radii are given in boldface type. The van der Waals radii sums:48 2.75 Å for H···N, 3.00 Å for H···S,
a
b
3.10 Å for H···Se, 2.67 Å for H···F, 2.95 Å for H···Cl, 3.05 Å for H···Br, and 3.18 Å for H···I. S(1) is a terminal atom, and S(2) and S(3) are
c
bridging atoms. S(1) and S(2) are bridging atoms, and S(3) is a terminal atom.
Table 3. Experimental and Computed 77Se NMR Chemical
Shifts (in ppm vs Me2Se) in Selected Thorium Diselenide
a
Complexes
calcd
exptl
c
b
δ(77Se) δ(77Se)
complex
Th2I4(μ2-Se2)2 (fully desolvated 4) 2.948
d(Th−Se) DI(Th−Se) (ppm) (ppm)
0.520
0.456
0.437
0.421
469
272
267
233
(py)6Th2I4(μ2-Se2)2 (4)
(py)6Th2Br4(μ2-Se2)2
(py)6Th2Cl4(μ2-Se2)2
2.981
2.994
3.008
241
(py)6Th2I2(SC6F5)2(μ2-Se2)2 (5)
(py)6Th2Br2(SC6F5)2(μ2-Se2)2 (6) 2.997
2.993
0.443
0.436
328
318
332
309
Figure 3. Asymmetric structural unit of compound 2, with short
contacts inside the molecule highlighted.
(py)3ThI2(μ2-Se2)
(py)4ThI2(μ2-Se2)
(py)3ThI (SC6F5)(μ2-Se2)
(py)4ThI (SC6F5)(μ2-Se2)
2.775
2.796
2.788
2.804
0.794
0.738
0.770
0.725
656
497
678
520
dimensional (1D) void channel of coordinating py and solvate py
molecules along the c axis is sandwiched by Th2Se4Br2(SC6F5)2
regions. There are also a few intermolecular interactions: i.e.,
H···F (2.508(1) Å) and H···Se (2.930(1) Å).
[K(18-crown-6)]Th(Se2)(NR2)3
2.914
0.529
273
3023e
a
DFT optimized Th−Se bond lengths, d(Th−Se) (in Å), and
DFT Calculations and 77Se NMR Study of Solution
Structures. 77Se NMR spectroscopy combined with rela-
tivistic DFT calculations and analysis of the measured chemical
shifts provides unique insight into the solution structure of
diselenido compounds 4−6. Establishing speciation for these
molecules is important to fully understand the chemistry of the
An−E bond and to realize the ultimate goal of being able to
rationally design synthetic approaches to construct increasingly
large cluster compounds. Solution and solid-state structures are
not necessarily the same, given that strong bases such as
pyridine can potentially fragment polymetallic compounds to
give products with reduced nuclearity, as illustrated in ionic
systems by the reaction of (THF)14Ln10S6(Se2)6I6 with
pyridine to give (py)6Ln2(Se0.2S0.8)(Se2)I2.46a
QTAIM delocalization indices of the Th−Se bonds, DI(Th−Se), are
b
also given. 2c-ZORA(SO)/PBE0−40HF/TZ2P results using a
COSMO solvation model (cf. Computational Details). Note that
the trends in 77Se NMR shifts are dominated by paramagnetic
shielding contributions (cf. Table S55 in the Supporting Information).
c
NMR spectra recorded in pyridine-d5 at room temperature.
Chemical shift calculations were done at the two-component
ZORA relativistic level, including spin−orbit (SO) coupling,
using the user-customized hybrid PBE0-40HF functional, which
was shown to perform very well for a series of monomeric Th
selenolates, thorium cubanes (py)8Th4(μ3-E)4(μ2-E′Ph)4(η-
E′Ph)4 (E, E′ = S, Se), and various organoselenides.1s The
investigated structures were fully optimized at the DFT level
(PBE0-D3(BJ)/ECP/def2-TZVP) using quasi-relativistic small-
core pseudopotentials for thorium and iodine, along with atom-
pairwise corrections for dispersion forces (see Computational
Details). First, we note an excellent agreement between X-ray
and DFT optimized structures of complexes 1−6, with dif-
ferences in Th−E, E−E, and Th−X (E = S, Se; X = Br, I, S)
bond lengths of less than 0.03 Å (cf. Table 1 and Table S51 in
The experimental 77Se NMR shifts for complexes 4−6, along
with those computed for these and other hypothetical thorium
dichalcogenide species that could potentially be present in
pyridine-d5 solution, are collected in Table 3. Compounds 4−6
show single 77Se NMR resonances at 241, 332, and 309 ppm,
respectively (Table 3), all in the range expected for diselenides
bridging two Th(IV) ions.
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the Supporting Information). Interestingly, one pyridine mole-
cule on each Th atom opposite to the E22− bridges (equatorial
position with respect to the Th2X2 plane) has a notably longer
Th−N bond length than the others (by more than 0.07 Å),
consistent with the Th−N bond asymmetry observed for axial
and equatorial nitrogen atoms in solid-state structures of 1−6,
although this inequality is less pronounced in X-ray structures
of complexes 1 and 4 (see Table 1 and discussion above).
Energy decomposition analysis (EDA) suggests that the longer
Th−Npy bonds in the equatorial position have an electronic
origin resulting from weaker Th−N orbital attractive inter-
actions rather than from steric effects (the latter is comparable
with that for axial Th−Npy bonds; cf. Table S52 in the Sup-
porting Information). In addition, similar Th−N bond asym-
metry for equatorial and axial pyridine ligands is computed for
isoelectronic group 4 (Ti, Zr, Hf) congeners of complex 4
(cf. Table S53 in the Supporting Information), showing that
this phenomenon is not related to Th(5f) orbitals but to a
trans influence of bridging E22− moieties, and it also appears in
monomeric Th dichalcogenide species (i.e., Th−N bonds in a
experimental data for complexes 5 and 6. This can be
rationalized by stronger π-donating abilities within the row
I− < Br− < Cl−, which in turn weakens the Th−Se bond
covalency in mixed Th chalcogenide−halide complexes on going
up the halogen group, and might be the reason for the lower
stability of dimeric Th2E4 species with terminal Cl− ligands.
UV−Vis Absorption Spectra. In contrast to colorless
compounds 1−3, complexes 4−6 are yellow to yellow-orange
in the solid-state as well as in pyridine solution. The UV−vis
absorption spectrum of compound 4 is given in Figure S22 of
the Supporting Information, showing the strongest absorption
band at about 310 nm, followed by an intense absorption
without a distinct maximum reaching a plateau at about
440 nm and a steadily decreasing absorption within the wave-
length range of 400−500 nm. To understand the nature of the
electronic transitions, we performed time-dependent DFT calcu-
lations of excitation energies (see Table S56 and Figure 28 in
the Supporting Information) for isostructural compounds 1
(colorless (py)6Th2I4(μ2-S2)2) and 4 (yellow (py)6Th2I4-
(μ2-Se2)2). The profile of the TD-DFT simulated absorption
spectrum of 4 agrees well with experiment (cf. Figures S22
and S28 in the Supporting Information) and thus allows
assignment of the most intense bands (cf. Table S56 and
Figure S29 in the Supporting Information). Hence, it is clear
that the strongest peak in the UV region (∼310 nm) can be
primarily assigned to excitations from nonbonding lone pairs
on the bridging selenium atoms (HOMO-1) to predominantly
metal-centered MOs with a large Th(5f) contribution (LUMO
+13, LUMO+17), followed by less intense excitations from the
Se lone pairs to pyridine ligands (∼350 nm, HOMO-1 →
LUMO+7 transition). The absorption in the visible (violet)
region (370−410 nm) is primarily related to transitions from
the Th−Se bonding MOs (HOMO, HOMO-2) and non-
bonding Se lone pairs (HOMO-1) to selenium antibonding
MOs (LUMO+3). Since the latter excitation energies corre-
sponding to the n(E22−) → π*(E22−) transition are shifted
hypsochromically in disulfide complexes, these appear as
colorless. We note in passing that the yellow color is also
observed for some lanthanide di- and triselenide complexes46a,49
that can be similarly related to n(Se22−) → π*(Se22−) transitions
and that the behavior of related telluride compounds50 is also
consistent with this interpretation.
2−
position trans to the centroid of E2 ligands are elongated
more than those in the cis position). Adding more pyridine
ligands to the first Th coordination sphere in (py)6Th2I4(μ2-
Se2)2 and (py)4ThI4(μ2-Se2) and optimization of these struc-
tures at the DFT level results in detachment of these extra py
molecules from the metal center, demonstrating the saturated
metal coordination environment in isolated dichalcogenide
complexes 1−6. In contrast, removal of pyridine ligands leads
to somewhat shorter Th−E bonds and elongated E−E contacts
(cf. Table S51 in the Supporting Information).
Experimentally observed 77Se NMR shifts for pyridine-d5
solutions of complexes 4−6 match very well with the DFT
computed values and are consistent with the dimeric structures
being maintained in solution. Not surprisingly, “desolvated”
species (with no pyridine ligands attached to thorium) are
absent in solution; these hypothetical molecules are computed
to be deshielded by about 200 ppm relative to their pyridine-
solvated congeners (cf. Table 3), but no 77Se resonance signal
in the region 350−1000 ppm was detected. Similarly, 77Se
NMR shifts for corresponding monomeric Th species with
terminal dichalcogenide ligands are predicted to appear within
the range 490−680 ppm (depending on the number of coor-
dinated py molecules; cf. Table 3), thus excluding the dissoci-
ation of dimers in solution. In this regard, the dissociation of
thorium dimers, Th2(μ2-Se2), with two bridging dichalcoge-
nide ligands into monomeric species is computed to be
strongly endoergic; specifically, the Gibbs free energies, ΔG°r,
for the dissociation of complex 4 to (py)3ThI2(μ2-Se2) or
(py)4ThI2(μ2-Se2) (concomitant with coordination of addi-
tional pyridine molecules in the latter case) were calculated to
be 30 and 27 kcal/mol, respectively (the PBE0-D3(BJ)/ECP/
def2-TZVP result; cf. Table S54 in the Supporting Infor-
mation). We note further that although 77Se NMR shifts
observed herein for dimeric structures resemble the value
measured for a thorium complex with a “terminal” Se22− ligand,
[K(18-crown-6)][Th(Se2)(NR2)3] (δ(77Se) 302 ppm in
pyridine-d5),3d this coincidence can be attributed to the
anionic nature of the latter, which is reflected in its elongated
Th−Se bonds and reduced Th−Se covalency in comparison to
neutral mononuclear Th diselenides (cf. Table 3). Replacing
iodide ligands with lighter analogues (Br−, Cl−) leads to
slightly longer Th−Se distances that are also reflected in
small but notable upfield 77Se shifts, as are also evident from
Thermolysis. Thermolysis1a,51 of carefully designed molec-
ular precursors is potentially useful as a low-temperature
synthesis approach to metastable solid-state materials, with
compounds 1 and 4 presenting an opportunity to explore the
low-temperature preparation of ternary solid-state materials.
Of the two, the I/SeSe combination found in 4 was the most
promising candidate to form a ternary phase at elevated tem-
peratures because of the relative electronegativity of I and Se.
Compounds with fluorinated thiolate ligands are complicated
by the tendency of Th to abstract F and form ThF4, and the
more electronegative sulfur in 1 favors the formation of ThS2
rather than ThI2S or ThI2(S2). Thermolysis of 4 was per-
formed under the same conditions as previously reported for1a
52
(py)3Th(SePh)4. The PXRD analysis revealed that ThSe2 is
the only solid-state product, with no evidence for the forma-
tion of any ternary ThISe phases. The surface morphology of
the resulting powder of the thermal residual is shown in Figure 4
by SEM, and this ThSe2 stoichiometry was also confirmed by
EDS (Figure S25), with trace (<3%) iodide present. GC/MS
analysis of the volatile products identified both pyridine and
elemental iodine (Scheme 5).
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ACKNOWLEDGMENTS
■
This material is based upon work supported by the National
Science Foundation under CHE-1464887. The computational
work has been supported by the Ministry of Education,
Science, Research and Sport of the Slovak Republic and by the
Slovak Research and Development Agency under contracts
1/0712/18 (VEGA) and APVV-17-0324, respectively. P.H.
also acknowledges funding from the European Union’s Horizon
2020 research and innovation program under the Marie
Skłodowska-Curie Grant No. 752285.
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thermolysis of compound 4.
Scheme 5. Thermal Decomposition of (py)6Th2I4(Se2)2.
CONCLUSIONS
Remarkably simple chalcogen-rich Th dimers containing E2
■
2−
(E = S, Se) bridging ligands can be prepared with a range of
sterically undemanding ancillary ligands, including both
halogens and fluorinated thiolates. These compounds are
fundamentally important starting materials for our ultimate
goal of rationally approaching increasingly large actinide and
heterometallic actinide/transition-metal cluster compounds.
The solution 77Se NMR spectra are consistent with the dimeric
structure being maintained in pyridine solution. Thermolysis of
the dimer containing both I− and Se2 ligands resulted in
2−
reductive cleavage of the Se−Se bond, oxidative elimination of
I2, and formation of solid-state ThSe2.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the ACS
Publications website at DOI: 10.1021/acs.inorgchem.8b02555.
■
S
Calculated and observed PXRD profiles for 1−7,
crystallographic data for 1−7, IR and NMR spectra, and
calculated 77Se NMR shieldings and their decomposition
into individual contributions (PDF)
Cartesian coordinates of the DFT-optimized structures
(XYZ)
Accession Codes
CCDC 1853617−1853623 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
*E-mail for J.G.B.: bren@rci.rutgers.edu.
*E-mail for P.H.: peter.hrobarik@uniba.sk.
■
ORCID
́
Peter Hrobarik: 0000-0002-6444-8555
John G. Brennan: 0000-0002-3994-221X
Notes
The authors declare no competing financial interest.
I
DOI: 10.1021/acs.inorgchem.8b02555
Inorg. Chem. XXXX, XXX, XXX−XXX

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