Rhenium Tris(pyrazolyl)Borate Oxothiolate Complexes: Syntheses and Structures

Article abstract of DOI:10.1134/S1070328419080086

Abstract: The rhenium complexes TpReOCl(S^tBu) (I), TpReO(S^tBu)₂ (II), and TpReO(SⁿC₃H₇)₂ (III) are synthesized using two methods by analogy to the known thiophenyl complexes. Complexes I–III having more electron-donating alkylthiolate ligands are characterized by IR and NMR spectroscopy. The structures of complexes I–III are determined by X-ray diffraction analysis (СIF files CCDC nos. 1892096 (I), 1892097 (II), and 1892098 (III)). The temperature dependence of the spectra of the bis(thiolate) complexes allows one to determine the activation energy for the hindered rotation about the Re–thiolate ligand bond. The by-product of the reaction of TpReOCl₂ with NaS-tert-Bu, binuclear oxygen-bridged complex TpRe^IVCl(S-tert-Bu)O(S-tert-Bu)₂Re^IVTp, is isolated and structurally characterized (СIF file CCDC no. 1892099).

Full text of DOI:10.1134/S1070328419080086

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ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2019, Vol. 45, No. 8, pp. 539–547. © Pleiades Publishing, Ltd., 2019.
Russian Text © The Author(s), 2019, published in Koordinatsionnaya Khimiya, 2019, Vol. 45, No. 8, pp. 451–460.
Rhenium Tris(pyrazolyl)borate Oxothiolate Complexes:
Syntheses and Structures
I. V. Skabitskiia, *, S. G. Sakharova, A. A. Pasynskiia, †, and R. S. Eshmakova
aKurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia
*e-mail: skabitskiy@gmail.com
Received January 21, 2019; revised March 12, 2019; accepted March 14, 2019
Abstract—The rhenium complexes TpReOCl(StBu) (I), TpReO(StBu)2 (II), and TpReO(SnC3H7)2 (III) are
synthesized using two methods by analogy to the known thiophenyl complexes. Complexes I–III having
more electron-donating alkylthiolate ligands are characterized by IR and NMR spectroscopy. The structures
of complexes I–III are determined by X-ray diffraction analysis (СIF files CCDC nos. 1892096 (I), 1892097
(II), and 1892098 (III)). The temperature dependence of the spectra of the bis(thiolate) complexes allows one
to determine the activation energy for the hindered rotation about the Re–thiolate ligand bond. The by-prod-
uct of the reaction of TpReOCl2 with NaS-tert-Bu, binuclear oxygen-bridged complex TpReIVCl(S-tert-
Bu)O(S-tert-Bu)2ReIVTp, is isolated and structurally characterized (СIF file CCDC no. 1892099).
Keywords: rhenium complexes, thiolate complexes, tris(pyrazolyl)borate, hindered rotation, temperature-
dependent NMR
DOI: 10.1134/S1070328419080086
INTRODUCTION
particular, TpReOCl2 (Tp is HB(C3H3N2)3) [1] by ste-
ric and electronic characteristics resembles
C5Me5ReOCl2 synthesized in situ by the reaction of
Cp′ReCl4 with water [2]. The TpReOCl2 complex can
be obtained directly from ammonium perrhenate on
reflux in alcohol in the presence of hydrochloric acid
(blue crystalline powder, IR spectrum: Re–O and B–
The tris(pyrazolyl)borate anion is a tridentate six-
electron donor ligand forming stable complexes with
rhenium. The anion is strongly bound to the metal
and, hence, is not involved in ligand exchange reac-
tions, is not oxidized, and is not reduced even under
fairly drastic conditions. The tris(pyrazolyl)borate
complexes behave, to a considerable extent, as analogs
of the pentamethylcyclopentadienyl complexes. In H at 978 and 2528 cm–1, respectively [3]).
O
Cl
N
N
Re
EtOH, HCl
Cl
NH4ReO4 + TpNa
N
N
N
H
N
B
Chlorine atoms are readily substituted by thiolate The compounds with one and two phenyl- and eth-
groups in the reactions with thiols in the presence of
bases. For example, the TpReO(SC2H4S) chelate
ylthiolate ligands were obtained similarly. The consec-
utive substitution of the chloride ligands by one and
complex with the strongly shortened Re=O bond two phenylthiolates results in the shift of the vibration
(1.69 Å) was synthesized by the reaction of TpReOCl2
with HSC2H4SH in the presence of triethylamine [4].
band of the Re–O bond in the IR spectra of the com-
plexes (978, 956, and 945 cm–1, respectively) [5].
†
Deceased.
539

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540
SKABITSKII et al.
R
R
O
O
O
Cl
Cl
S
N
N
N
N
S
N
N
N
N
1 RSH
Base
2 RSH
Base
Re
Re
R
N
Re
S
Cl
N
N
N
H
N
H
N
N
H
N
N
B
B
N
B
R = C6H5, CH3CH2
R = C6H5, CH3CH2, 2-Py
The purpose of this work is the synthesis of the rhe- 3 days. The precipitated crystalline aggregates were
nium tris(pyrazolyl)borate oxo-tert-butylthiolate decanted, washed with pentane and cooled liquid
complexes as promising metal-containing ligands for nitrogen (4 times by 4 mL), and dried in vacuo. The
the preparation of heterometallic complexes in which yield was 13 mg (11%).
the tert-butylthiolate groups provide a higher solubility
and an easier thermal decomposition of the complexes
during the production of nanosized inorganic compo-
sitions.
TpReOCl(S-tert-Bu): TLC (CH2Cl2): green spot,
Rf 0.75; TpReO(S-tert-Bu)2: TLC (CH2Cl2): yellow-
brown spot Rf 0.67.
Synthesis of complexes I, II, and TpReCl(S-tert-
Bu)O(S-tert-Bu)2ReTp (IV). Procedure 2. Di-tert-
butyl disulfide (1.1 mL, 5.7 mmol) and diglyme
(0.5 mL) were added to a suspension of sodium
(0.23 g, 10 mmol) in THF (20 mL). The reaction mix-
ture was stirred for 24 h, and TpReOCl2 (2.08 g, 4.3
mmol) was added to the obtained white suspension.
The reaction mixture was heated at 65°C for 3 h. The
solvent was removed in vacuo, and the obtained dark
brown oil was extracted with heptane by portions of
60, 50, and 4 × 20 mL. The heptane extract was evap-
orated to 20 mL and chromatographed on a column
packed with silica gel (3 × 15 cm). Three fractions were
eluted: green (200 mL of a CH2Cl2–hexane (1 : 1)
mixture), brown (250 mL of a CH2Cl2–hexane (1 : 1)
mixture, and 50 mL of CH2Cl2), and violet (300 mL of
CH2Cl2) fractions.
After the green fraction was evaporated in vacuo, a
green powder of complex I was obtained in a yield of
65 mg (3%).
The brown fraction was evaporated to dryness, and
the residue was dissolved in hexane (12 mL). The solu-
tion was kept at –25°С for 24 h. The precipitated thin
needle-like crystals were filtered off at –70°C, washed
with pentane cooled to the freezing onset (–130°C) in
liquid nitrogen (3 times by 8 mL), and dried in vacuo.
The yield of complex II was 327.6 mg (13%).
EXPERIMENTAL
Commercial ammonium perrhenate, tert-butyl-
mercaptan, and di-tert-butyl disulfide (Acros organ-
ics) were used as received. The syntheses of TpReOCl2
[1] and TpNa [6] were carried out according to
described procedures. All procedures during the syn-
thesis and isolation of products were conducted in
anhydrous solvents under pure argon. Plates
(MERCK) of silica gel 60 F254 on the aluminum basis
were applied for thin-layer chromatography (TLC).
IR spectra were recorded on a Bruker Alpha spec-
1
trometer using a Platinum ATR attachment. H and
13C NMR spectra were measured on a Bruker AV 400
instrument, and chemical shifts are presented relative
to tetramethylsilane.
Synthesis of TpReOCl(S-tert-Bu) (I) and TpReO-
(S-tert-Bu)2 (II). Procedure 1. Diazabicycloundecene
(DBU) (80 μL, 0.54 mmol) and tert-butylmercaptan
(50 μL, 0.44 mmol) were added to a suspension of
TpReOCl2 (100 mg, 0.21 mmol) in toluene (15 mL).
The reaction mixture was stirred at 110°C in a sealed
Schlenk flask for 24 h. Volatile components of the
reaction mixture were removed in vacuo. The solid
residue was dissolved in dichloromethane (10 mL),
diluted with hexane (12 mL), and deposited on a chro-
matographic column (silica gel 14.5 × 1.5 cm), eluting
the green and brown zones with a dichloromethane–
hexane (1 : 1) system. The green eluate was evaporated
to dryness, and the residue was dissolved in a mixture
of dichloromethane (3 mL) and hexane (1.5 mL). The
resulting mixture was kept at –25°C for 24 h. The pre-
cipitated green powder was filtered off, washed with
pentane (4 times by 1.5 mL), and dried in vacuo. The
yield was 53 mg (48%).
The violet fraction was evaporated to dryness, and
the dark oil was extracted with hot hexane. The black-
violet crystals of complex IV formed on keeping the
extract at room temperature for 24 h were decanted,
washed with hexane (3 × 5 mL), and dried in vacuo.
The yield of complex IV was 1 mg (0.02%).
The residue that was not dissolved in heptane was
extracted with benzene (40 mL). The obtained extract
was kept at 5°С, and the formed brown precipitate was
The brown fraction was evaporated to dryness, dis- filtered off, washed with heptane (4 × 5 mL), and
solved in heptane (1.5 mL), and kept at –25°C for recrystallized from a mixture of dichloromethane
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY
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RHENIUM TRIS(PYRAZOLYL)BORATE OXOTHIOLATE COMPLEXES
541
(10 mL) and hexane (10 mL). The obtained green benzene extract was poured onto a 10-cm column
powder was dissolved in CH2Cl2 (30 mL) and filtered packed with silica gel and eluted with benzene
(150 mL). The brown solution was evaporated to
30 mL, and heptane (30 mL) was added. The obtained
solution was kept at 5°С, and the precipitated brown
crystals were decanted, washed with hexane (3 times
by 5 mL), and dried in vacuo. The yield of complex III
was 1.3 g (53%).
through a silica gel layer. Hexane (5 mL) was added to
the green solution, and the mixture was evaporated to
dryness and dried in vacuo. The yield of complex I was
211.5 mg (9%).
Complex I: TLC (CH2Cl2): green spot, Rf 0.75. IR
(ν, cm–1): 3144 vw, 3119 vw br, 2954 vw br, 2915 vw br,
2856 vw, 2516 vw br, 1502 w, 1474 vw, 1453 vw,
1405 m, 1388 w, 1360 vw, 1310 m, 1211 m, 1186 w,
1165 w, 1116 m, 1073 vw, 1046 vs, 991 w, 958 vs,
The mother liquor was evaporated to dryness, and
the residue was extracted with boiling heptane (4 times
by 10 mL). The crystals of complex III precipitated on
919 vw, 890 vw, 863 vw, 816 vw, 792 w, 763 vs, 737 w, keeping the heptane extract at –25°С were decanted,
710 s, 670 vw, 651 m, 613 m, 578 vw, 441 vw, 414 vw.
washed with hexane (3 times by 5 mL), and dried in
1H NMR (CDCl3), δ, ppm: 2.10 (s, 9H), 4.16 (br.m,
vacuo. The yield of complex III was 0.17 g (7%).
1H), 5.95 (dd, 3JH–H = 2.3 Hz, 1H), 6.45 (dd, 3JH–H
=
For C15H24BN6OS2Re (FW = 566)
2.3 Hz, 1H), 6.51 (dd, 3JH–H = 2.35 Hz, 1H), 7.31 (dd,
3JH–H = 2.35 Hz, 1H), 7.58 (dd, 3JH–H = 2.22 Hz, 1H),
7.79 (dd, 4JH–H = 0.60 Hz, 3JH–H = 2.35 Hz, 1H), 7.87
(dd, 4 JH–H = 0.6 Hz, 3JH–H = 2.35 Hz, 1H), 8.17 (dd,
3JH–H = 2.2 Hz, 1H), 8.43 (dd, 3JH–H = 2.35 Hz, 1H).
Anal. calcd., % C, 31.86 H, 4.28 N, 14.86 S, 11.34
Found, %
C, 32.58 H, 4.56 N, 14.52 S, 11.18
IR (ν, cm–1): 3146 vw, 3129 vw, 3109 vw, 2959 s,
2927 m, 2866 m, 2479 s, 1498 m, 1460 w, 1404 s,
1388 m, 1307 vs, 1222 m, 1205 s br, 1182 w, 1114 m,
1069 w, 1044 vs, 986 m, 938 s, 889 w, 854 vw, 814 vw,
13С{1H} NMR (CDCl3), δ, ppm: 63.47; 34.50; 105.77;
107.53; 108.46; 132.68; 163.70; 139.16; 144.03; 145.93;
145.81.
789 w, 766 s, 711 m, 669 vw, 651 w, 614 w, 419 vs.
Complex II: TLC (CH2Cl2): yellow-brown spot, Rf
3
1H NMR (CDCl3, 298 K), δ, ppm: 1.06 (t, JH–H
=
0.67. IR (ν, cm–1): 3108 vw br, 2954 w, 2915 w br,
2890 w, 2854 w, 2488 vw br, 1501 w, 1473 vw, 1453 w,
1406 m, 1390 m, 1358 w, 1309 m, 1217 m br, 1185 w,
1158 m, 1118 m, 1071 w, 1047 vs, 983 m, 936 vs, 890 w,
819 w, 794 w, 765 s, 756 s br, 713 s, 660 w, 617 m, 572 w,
7.26 Hz, 6H, SCH2CH2CH3), 1.91 (m, 4H,
SCH2CH2CH3), 2.97–5.04 (br.m, 5H, SCH2CH2CH3 +
3
3
BH), 5.94 (t, JH–H = 2.2 Hz, 1H), 6.43 (t, JH–H
=
2.2 Hz, 2H), 7.37 (dd, 3JH–H = 2.2 Hz, 4JH–H = 0.8 Hz,
3
3
1
1H), 7.67 d, JH–H = 1.9 Hz, 2H), 7.79 (d, JH–H
=
439 w, 417 w. H NMR (CDCl3), δ, ppm: 1.67 (br.s,
2.0 Hz, 1H), 8.32 (br.s, 2H). С{1H} NMR (CDCl3,
13
18H), 4.47 br.m; 5.99 (dd, 3JH–H = 2.2 Hz, 1H), 6.40
3
3
298 K), δ, ppm: 14.1, 26.2, 45.5 v.br, 106.0, 107.4,
(dd, JH–H = 2.3 Hz, 2H), 7.41 (dd, JH–H = 2.2 Hz,
1
4JH–H = 0.7 Hz), 7.70 (dd, JH–H = 2.4 Hz, JH–H
<
3
4
133.9, 136.8, 145.5, 147.9. H NMR (toluene-d8,
3
0.4 Hz, 2H) 7.96 (dd, 3JH–H = 2.2 Hz, 1H), 8.38 (br.s,
2H). 13С{1H} NMR (CDCl3), δ, ppm: 105.86; 107.10;
133.89; 136.78; 149.69; 145.67; 60.07; 34.34. 1H NMR
(toluene-d8, 233 K), δ, ppm: 1.33 (s, 9H, StBu), 2.41
233 K), δ, ppm: 0.96 (t, JH–H = 7.10 Hz, 3H,
SCH2CH2CH3), 1.27 (t, JH–H = 7.0 Hz, 3H,
3
SCH2CH2CH3), 1.79 (m, 1H, SCH2CH2CH3), 1.92
(m, 1H, SCH2CH2CH3), 2.31 (m, 3H,
SCH2CH2CH3+ SCH2CH2CH3), 3.45 (m, 1H,
SCH2CH2CH3), 4.25 (br.m, 1H, BH), 4.61 (m, 1H,
SCH2CH2CH3), 4.76 (m, 1H, SCH2CH2CH3), 5.38
(s, 9H, StBu), 4.23 (br.m, 1BH); 5.40 (m, 1H), 5.66
(m, 1H), 5.71 (m, 1H), 7.01 (m, 1H), 8.10 (m, 1H),
8.15 (m, 1H), 8.64 (m, 1H).
3
(t, JH-H = 2.1 Hz, 1H), 5.69 (br.s, 1H), 5.72 (br.s,
Complex IV: TLC (CH2Cl2): violet spot, Rf 0.38. IR
1H), 6.7 (d, 3JH–H = 1.7 Hz, 1H), 7.07 (br.m, 2H), 7.80
(ν, cm–1): 3144 m br, 3101 m, 2952 m, 2910 m,
1
(m, 1H), 7.82 (br.s, 1H), 8.58 (br.s, 1H). H NMR
2884 m, 2851 m br, 2482 m br, 1499 m, 1469 w, 1451 w,
1403 s br, 1357 m, 1307 s, 1269 m, 1207 s br, 1153 s, (toluene-d8, 353 K), δ, ppm: 1.06 (t, 3JH–H = 7.20 Hz,
1117 s, 1098 m, 1069 m, 10 43 vs, 983 s, 919 m, 887 m,
859 m, 838 m, 814 m, 788 m, 761 vs br, 733 s, 709 vs,
666 s, 648 s, 611 s, 574 m, 485 m, 436 m br.
Synthesis of complex III. Dipropyl disulfide
(1.5 mL, 9.6 mmol) was added to a suspension of
sodium (0.4 g, 17 mmol) in THF (20 mL). The reac-
tion mixture was stirred for 24 h, and TpReOCl2 (2.1 g,
4.3 mmol) was added to the obtained white suspen-
sion. The reaction mixture was stirred for 24 h, the sol-
6H, SCH2CH2CH3), 1.96 (m, 4H, SCH2CH2CH3),
3.43 (br.s, 2H, SCH2CH2CH3), 3.92 (br.m, 2H,
SCH2CH2CH3), 4.3 (br.m, 1H, BH), 5.51 (t, 3JH–H
=
3
2.2 Hz, 1H), 5.88 (t, JH–H = 2.3 Hz, 2H), 6.89 (m,
1H), 7.27 (m, 2H), 7.77 (m, 1H), 8.20 (br.s, 2H).
13С NMR (toluene-d8, 353 K), δ, ppm: 14.2, 26.9,
45.9 br, 105.9, 107.2, 133.7, 136.6, 146.1, 148.5.
X-ray diffraction analysis was carried out on a
vent was removed in vacuo, and the obtained dark Bruker APEX II CCD diffractometer. An absorption
brown oil was extracted with benzene (60 mL). The correction was applied by the method of multiple
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SKABITSKII et al.
Table 1. Crystallographic data and structure refinement parameters for complexes I–IV
Parameter
I
II
III
IV
Empirical formula
FW
Radiation (λ , Å)
C20H27BN6OSClRe C17H28BN6OS2Re
C15H24BN6OS2Re C31H47B2N12OS3Cl3Re2
631.99
593.58 565.53
MoKα (λ = 0.71073)
1200.35
Detection
150(2)
150(2)
120(2)
150(2)
temperature, K
Crystal system
Space group
а, Å
b, Å
c, Å
α, deg
β, deg
γ, deg
V, Å3
Triclinic
Monoclinic
Cc
15.5182(4)
15.3550(3)
29.1704(6)
90
92.9860(1)
90
6941.3(3)
Triclinic
Trigonal
P1
̅
P1
̅
R3̅
9.3684(8)
11.177(1)
12.715(1)
111.161(1)
93.553(1)
93.888(1)
1233.4(2)
7.668(1)
7.882(1)
27.782(1)
27.782(1)
29.663(2)
90
90
120
19828(2)
18.783(2)
82.805(2)
82.007(2)
65.269(2)
1018.3(2)
Z
2
12
2
18
calcd, g cm–3
1.702
1.704
1.844
1.809
ρ
μ, mm–1
5.143
5.451
6.188
5.855
F(000)
620.0
3504.0
552.0
10 512.0
Scan range, deg
Scan mode
4.17–53.056
4.036–55.78
4.392–63.996
4.36–61.026
ω
Independent
5087 (Rint = 0.0230) 16516 (Rint = 0.0419) 6683 (Rint = 0.0185)
13022 (Rint = 0.0458)
reflections (N1)
Reflections
with I > 2σ(I) (N2)
Number of refined
parameters
4620
284
15726
776
6446
237
10254
496
GOОF (F2)
R1 for N2
1.064
0.0296
1.037
0.268
1.057
0.0171
0.933
0.0248
wR2 for N1
0.0740
0.423
0.0391
0.0543
Δρmax/Δρmin, e Å–3
5.21/–0.98
0.91/–0.85
1.06/–1.12
2.14/–1.46
measurements of equivalent reflections using
Quantum chemical calculations were performed in
the SADABS program [7]. The structures of com- the framework of the density functional theory (DFT)
plexes I–IV were determined by a direct method and using the ORCA 4.01 program package [10]. The
refined by least squares relative to F2 in the anisotropic
approximation of non-hydrogen atoms using the
SHELX-2014 [8] and OLEX2 [9] program packages.
The positions of hydrogen atoms were calculated geo-
metrically. The crystallographic data and structure
refinement parameters for compounds I–IV are pre-
sented in Table 1. Selected bond lengths and bond
angles in complexes I–IV are given in captions to
Figs. 1–4. The coordinates of atoms and other param-
eters for the structures of complexes I–IV were depos-
ited with the Cambridge Crystallographic Data Centre
(CIF files CCDC nos. 1892096–1892099;
http://www.ccdc. cam.ac.uk/data_request/cif).
geometry optimization of the complexes and transi-
tion states was carried out using the PBE functional
[11, 12] with the double-split all-electron def2-SVP
basis set [13] and the D3BJ empirical correction to
dispersion interactions [14, 15]. The activation energy
was calculated using the PBE0 hybrid functional [16]
with the triple-split all-electron def2-TZVP basis
set [13].
RESULTS AND DISCUSSION
Complexes I and II were synthesized using two dif-
ferent procedures. The first synthesis was carried out
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