Well-Defined, Molecular Bismuth Compounds: Catalysts in Photochemically Induced Radical Dehydrocoupling Reactions

Article abstract of DOI:10.1002/chem.202002219

A series of diorgano(bismuth)chalcogenides, [Bi(di-aryl)EPh], has been synthesised and fully characterised (E=S, Se, Te). These molecular bismuth complexes have been exploited in homogeneous photochemically-induced radical catalysis, using the coupling of silanes with TEMPO as a model reaction (TEMPO=(tetramethyl-piperidin-1-yl)-oxyl). Their catalytic properties are complementary or superior to those of known catalysts for these coupling reactions. Catalytically competent intermediates of the reaction have been identified. Applied analytical techniques include NMR, UV/Vis, and EPR spectroscopy, mass spectrometry, single-crystal X-ray diffraction analysis, and (TD)-DFT calculations.

Full text of DOI:10.1002/chem.202002219

Accepted Article
Accepted Article
Title: Well-defined, molecular bismuth compounds: catalysts in
photochemically-induced radical dehydrocoupling reactions
Authors: Jacqueline Ramler, Ivo Krummenacher, and Crispin
Lichtenberg
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Link to VoR: https://doi.org/10.1002/chem.202002219
01/2020

10.1002/chem.202002219
Chemistry - A European Journal
COMMUNICATION
Well-defined, molecular bismuth compounds: catalysts in
photochemically-induced radical dehydrocoupling reactions
Jacqueline Ramler,[a] Ivo Krummenacher,[a,b] and Crispin Lichtenberg*[a]
[a]
[b]
J. Ramler, Dr. I. Krummenacher, Priv.-Doz. Dr. C. Lichtenberg
Institute of Inorganic Chemistry
Julius-Maximilians-University Würzburg
Am Hubland, 97074 Würzburg, Germany
E-mail: crispin.lichtenberg@uni-wuerzburg.de
Dr. I. Krummenacher
Institute of Sustainable Chemistry & Catalysis with Boron
Am Hubland, 97074 Würzburg, Germany
Supporting information for this article is given via a link at the end of the document.
Abstract: A series of diorgano(bismuth)chalcogenides, [Bi(aryl)EPh],
has been synthesised and fully characterised (E = S, Se, Te). These
molecular bismuth complexes have been exploited in homogeneous
photochemically-induced radical catalysis, using the coupling of
silanes with TEMPO as a model reaction (TEMPO = (tetramethyl-
piperidin-1-yl)-oxyl). Their catalytic properties are complementary or
superior to those of known catalysts for these coupling reactions.
Catalytically competent intermediates of the reaction have been
identified. Applied analytical techniques include NMR, UV/vis, and
EPR spectroscopy, mass spectrometry, single-crystal X-ray
diffraction analysis, and (TD-)DFT calculations.
Scheme 1. Well-defined, molecular bismuth compounds for catalysed radical
reactions: species applied in thermally- vs. photochemically-induced
transformations.
Covalent bonds Z–X with a heavy p-block element Z as one of the
bonding partners show low homolytic bond dissociation energies
due to inefficient spatial and energetic overlap of the relevant
atomic orbitals.[1] This allows access to reversible homolytic bond
dissociations (Z–X ⇄ Z● + X●) under mild reaction conditions,
which is a key feature for potential catalytic applications via radical
pathways.[2] For instance, equilibrium scenarios have been
reported for the homolysis of the Sn≡Sn bond in (SnAr)2 and the
Pn–Pn bonds in (Pn(CSiMe3CH2)2)2 (Ar = C6H3-2,6-(C6H3-2,6-
iPr2)2; Pn = Sb, Bi).[3,4] Such findings have paved the way for new
catalytic applications of well-defined, molecular complexes of
heavy p-block elements in radical reactions.[2c] Among potential
catalysts of this kind, bismuth compounds in particular are
attractive synthetic targets due to characteristics such as low cost,
(relatively) low toxicity, and prospects for recyclability.[5,8a] In this
context, the radical dehydrocoupling of SiPhH3 and TEMPO with
[Bi(NONDipp)]● and the radical cyclo-isomerization of δ-iodo-olefins
with Ph2Bi–Mn(CO)5 have recently been reported (Scheme 1;
include the degradation of organic dyes such as methyl orange,[9]
antibiotics such as tetracycline,[10] and biocides such as
triclosan,[8b] as well as CH activation of aliphatic and aromatic
hydrocarbons,[11]
transfer
(de)hydrogenation
of
alcohols/ketones,[12] and olefin polymerisation.[8a] These
applications of bismuth compounds in heterogeneous catalysis
suggest that photochemical strategies might also be applicable
for well-defined, molecular bismuth compounds under
homogeneous conditions. Indeed, the light-sensitivity of
molecular bismuth complexes such as organobismuthanes,
dibismuthanes, bismuth amides, and related species has been
phenomenologically reported in some cases.[13] The direct
involvement of bismuth functional groups in visible light
absorption has been demonstrated through TD-DFT calculations
and UV/vis spectroscopy for the bismuth radical [Bi(NONDipp)]●, a
dibismuthane, and
a cationic bismuth carbamoyl ([RBi–
TEMPO
=
(tetramethylpiperidin-1-yl)-oxyl;
NONDipp
=
C(O)NR’2]+).[4a,14,15,16] However, applications of well-defined
molecular bismuth compounds in photochemically-initiated,
catalysed radical reactions have not been reported to date.
We show here that an easily accessible, storable, molecular
organo(bismuth) thiolate is catalytically active in photochemically-
induced radical dehydrocoupling reactions.
O(SiMe2NDipp)2, Dipp = 2,6-iPr2C6H3).[6,7] While these reactions are
thermally-initiated, photochemically-induced transformations
represent an important complementary approach to radical
catalysis. Indeed, a range of inorganic bismuth compounds such
as (nanostructured) oxides (Bi2O3),[8] titanates (Bi4Ti3O12),[9]
vanadates (BiVO4),[10] halide perovskites (Cs3Bi2Br9),[11] and an
oxybromide (Bi24O31Br10(OH)δ)[12] have been exploited in
photocatalytic transformations. Catalysed types of reactions
We recently reported preliminary results on the synthesis of
the diorgano(bismuth)thiolate 2-SPh from transition metal
bismuthane 1-Mn(CO)5 and diphenyldisulfide, (SPh)2 (Scheme 2,
1
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Scheme 2. Synthesis of compounds 2-EPh via routes A and B and molecular
structures of 2-SePh and 2-TePh in the solid state. Cp = C5H5. Displacement
parameters are drawn at the 50% probability level. Selected bond lengths (Å)
and angles (°): 2-SePh: Bi1–C1, 2.284(11); Bi1–C14, 2.303(10); Bi1–Se1,
2.7285(11); Bi1–S1, 2.966(3); C1–Bi1–C14, 97.9(3); C1–Bi1–Se1, 90.0(3); S1–
Bi1–Se1, 157.23(6). 2-TePh: Bi1–C1, 2.288(3); Bi1–C14, 2.289(3); Bi1–Te1,
2.9296(3); Bi1–S1, 3.0007(7); C1–Bi1–C14, 96.98(9); C1–Bi1–Te1, 93.92(7);
S1–Bi1–Te1, 161.818(14).
Figure 1. Experimental UV/vis spectrum of 2-SPh in THF (solid black line), five
lowest energy calculated transitions (blue bars), and molecular orbitals involved
in the two calculated absorptions with highest intensity (A1 and A4). Iso-value =
0.03.
Route A).[6] Here, we extend this approach to the heavier
homologues 2-SePh and 2-TePh, which could be obtained in high
yields (>90%, Supp. Inf.). In addition, compounds 2-EPh were
also synthesised in a straightforward, transition-metal-free salt
elimination protocol via Route B and fully characterised (Scheme
2, Supp. Inf., E = S, Se, Te). Single-crystal X-ray diffraction
analysis of 2-SePh and 2-TePh confirmed Bi1–Se1 and Bi1–Te1
bond length in the expected ranges[17] and bonding interactions
between Bi1 and the sulphur atom of the ligand backbone, S1, as
recently reported for the sulphur analogue 2-SPh.[6,18] According
to NBO analyses, these Bi1∙∙∙S1 interactions are realised through
n(S1)→σ*(Bi–EPh) bonding with the corresponding deletion
energies ranging from 18.2 to 21.3 kcal∙mol–1 (Supp. Inf.). In order
to evaluate the potential of compounds 2-EPh to be applied in
photochemical reactions, they were analysed by UV/vis
spectroscopy and (TD-)DFT calculations. The results are
qualitatively identical and discussed here for 2-SPh (for details
see Supp. Inf.). The experimental UV/vis spectrum of 2-SPh in
THF shows two absorption features centred around 307 and 264
nm with an onset at ca. 380 nm (Figure 1). These absorption
bands were correlated with five singlet-singlet transitions T1-T5,
three of which show larger oscillator strengths (T1 (315 nm), T2
(296 nm), T4(266 nm)). T1, T2, and T4 correspond to a
HOMO/LUMO (T1, 88%), HOMO/LUMO+1 (T2, 78%), and
HOMO-1/LUMO (T4, 59%) transition, respectively (Figure 1 and
Supp. Inf.). While the HOMO and the HOMO-1 show contributions
to Bi–SPh σ-bonding,[19] the LUMO and LUMO+1 show
contributions to Bi–SPh σ*-antibonding interactions. These
analyses suggest that compounds 2-EPh should be susceptible
to photochemical Bi–EPh bond cleavage, rendering them
candidates for photocatalytic applications.
80 °C, small amounts of the coupling product P1 were detected,
but the product formations are in agreement with stoichiometric
regimes (entries 4-6). Following our UV/vis spectroscopic and
(TD-)DFT analyses of compounds 2-EPh, these bismuth
chalcogenides were also tested as dehydrocoupling catalysts
under photochemical conditions. Indeed, 2-EPh proved to be
catalytically active under irradiation with a mercury vapour lamp
Table 1. Bismuth species in the catalysed dehydrocoupling reaction of TEMPO
with PhSiH3 (S1) or Ph2SiH2 (S2).
#
cat.
silane (R or R2)
S1 (Ph)
n
1
1
1
1
1
1
1
1
1
1
2
1
2
2
2
2
1
1
1
1
cond.
23 °C
23 °C
23 °C
80 °C
80 °C
80 °C
h∙ν
conversion [%]a
<1 (P1)
1
2-SPh
2-SePh
2-TePh
2-SPh
2-SePh
2-TePh
None
2-SPh
2-SePh
2-TePh
2-SPh
2-SPh
2-SPh
2-SPh
2-SPh
2-SPh
4
2
S1 (Ph)
<1 (P1)
3
S1 (Ph)
<1 (P1)
4
S1 (Ph)
3 (P1)
5
S1 (Ph)
9 (P1)
6
S1 (Ph)
9 (P1)
7
S1 (Ph)
10 (P1)
8
S1 (Ph)
h∙ν
93 (53% P1, 20% P1’)
65 (39% P1, 13% P1’)
13 (P1)
9
S1 (Ph)
h∙ν
10
11
12
13
14
15
16
17
18
19
20
S1 (Ph)
h∙ν
S1 (Ph)
h∙ν
94 (13% P1, 87% P1’)
S3 (Ph2)
S3 (Ph2)
S2 (nHex)
S4 (Ph/Me)
S5 (tBu2)
S1 (Ph)
h∙ν
63 (P3)
97 (P3)b
h∙ν
h∙ν
64 (69% P2, 29% P2’)
54 (P4)b
h∙ν
We thus turned our attention towards the dehydrocoupling
of phenylsilane (S1) with TEMPO to give siloxides P1 and P1’
(see reaction scheme in Table 1). This reaction has recently been
investigated as a model reaction for thermally-initiated radical
catalysis with main group compounds in pivotal studies by the
groups of Hill[20] and Coles.[7] In benzene solution at 23 °C with a
reaction time of 1 d, 10 mol% of compounds 2-EPh proved to be
not catalytically active (entries 1-3). At an elevated temperature of
h∙ν
0 (P5)
23 °C
h∙ν
4 (P1)
>99(52%P1,24%P1’)c
4
S1 (Ph)
5
S1 (Ph)
23 °C
h∙ν
<1 (P1)
5
S1 (Ph)
48 (P1)
a: conversion of TEMPO, determined by 1H NMR spectroscopic analysis of
silanes S1-S5 and P1-P4 (also see Supp. Inf.).[20] b: conversion of S3 and S4 to
P3 and P4. c: the TEMPO that is part of 4 is also fully converted (Supp. Inf.).
2
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(entries 7-10). While the background reaction and the tellurium
compound 2-TePh only led to low yields of the desired coupling
products, good (65%) and excellent conversions (93%) could be
obtained with the homologous selenium (2-SePh) and sulphur
species (2-SPh). This trend was ascribed to the photosensitivity
of 2-EPh, which increases with increasing atomic numbers of E,
and to the higher reactivity of selenium and tellurium containing
by-products (with the potential to undergo unselective side
reactions).[21] The by-product dihydrogen, H2, was detected by 1H
NMR spectroscopy. With 2-SPh as a catalyst and two equivalents
of TEMPO, 94% conversion was obtained in 1 d reaction time,
necessarily with a clear preference for the double substitution
product P1’ (entry 11). 2-SPh is also active as a catalyst for
dehydrocoupling of the less reactive substrate Ph2SiH2 (S3): with
one equivalent of TEMPO, 63% yield of P3 were obtained under
standard photochemical conditions (entry 12). Near-quantitative
conversion of S3 to P3 in 1 d was obtained by using n = 2
equivalents of TEMPO (entry 13). These results demonstrate for
the first time the high potential of well-defined molecular bismuth
compounds for the exploitation in photochemically-induced
catalytic bond forming events via radical pathways. In terms of
catalytic activity, the bismuth thiolate 2-SPh clearly outperforms
the bismuth radical compound [Bi(NONDipp)]●, which was recently
reported to catalyse the reaction of S1 with TEMPO in a thermally-
induced transformation (e.g.: 10 mol% [Bi(NONDipp)]●, 70 °C, 1.7
d reaction time, 10% conversion (formation of P1);[22] cf. entries 8,
11).[7] Furthermore, the catalytic activity of 2-SPh can compete
with that of the magnesium amide Mg{N(SiMe3)2}2(thf)2, which has
been shown to catalyse thermally-initiated dehydrocoupling
reactions of S1 and S3 with TEMPO: while Mg{N(SiMe3)2}2(thf)2
is catalytically more selective in addressing only one Si–H bond
of PhSiH3, i.e. reaction of S1 with 1 equiv. TEMPO (10 mol% cat.,
60 °C 1 d, 99% yield of P1; cf. entry 8), 2-SPh is catalytically more
active in addressing Si–H bonds of secondary silanes, i.e. in the
overall reaction of S1 or S3 with two equiv. TEMPO (S1: 10 mol%
Mg{N(SiMe3)2}2(thf)2, 80 °C, 6 d, 96% yield, S3: 10 mol%
Mg{N(SiMe3)2}2(thf)2, 80 °C, 4 d, 99% yield; cf. entries 11, 13).
Concerning the mode of initiation of the reaction (thermally vs.
photochemically), our approach is complementary to those
previously reported for the dehydrocoupling of TEMPO with
silanes.[7,20]
Scheme 3. a) Synthesis of compounds 4 and 5; i: Na(OTEMP), r.t. THF, 2 h; ii:
PhSiH3, 60 °C, benzene, 4 d. b,c) Molecular structures of 4 and 5 in the solid
state. Displacement parameters are drawn at the 50% probability level.
Selected bond lengths (Å) and angles (°): 4: Bi1–C1, 2.274(8); Bi1–C14,
2.271(9); Bi1–O1, 2.184(5); Bi1–S1, 2.936(2); N1–O1, 1.459(8); C1–Bi1–C14,
91.5(3); C1–Bi1–O1, 92.3(3); Bi1–O1–N1, 106.1(4); S1–Bi1–O1, 159.76(15);
ƩC/O–N1–C/O, 333.9(6). 5: Bi1–C1, 2.262(7); Bi1–C14, 2.289(7); Bi1–Bi1‘,
3.0211(5); C1–Bi1–C14, 104.8(3); C1–Bi1–Bi1‘, 91.59(18); C1–Bi1–Bi1‘–C1‘,
180.
3b).[3b,7,24,25] This is also in agreement with the presence of a
Bi1∙∙∙S1 bonding interaction, which is expected for a sufficiently
electronegative
anionic
substituent
X–
bound
to
[Bi(C6H4CH2)2S]+.[6,18] EPR spectroscopic investigations revealed
a very weak resonance indicating the presence of trace amounts
(0.3%) of TEMPO in solution. Since the NMR spectroscopic and
elemental analysis of 4 gave no hints at the presence of impurities,
the
postulation
of
an
equilibrium
scenario
TEMPO●,
[Bi(C6H4CH2)2S(OTEMP)]
⇌
[Bi(C6H4CH2)2S]●
+
appeared tempting.[3b,7] However, powder EPR spectra of 4 and
the temperature-dependence of the EPR signals of 4 in solution
clearly ruled out an equilibrium scenario in the range of –60 to
+20 °C,[26] indicating that it is in fact due to trace impurities of
TEMPO in the sample, which could not be removed by repeated
re-crystallisations (Figure S12, Supp. Inf.).
Preliminary investigations into the substrate scope of this
reaction show reduced catalytic activities for silanes bearing one
or more alkyl substituents (entries 14-16 and Supp. Inf.).
In order to identify potential intermediates of the catalysed
reactions, a reaction mixture obtained under our standard
catalytic conditions (e.g. entry 8) was analysed by high-resolution
mass spectrometry. Signals of m/z = 578.1922 and 843.1000
were detected (Supp. Inf.).[23] This corresponds to species with
the sum formulae [C23H31BiNOS]+ (calc. m/z = 578.1925) and
[C28H25Bi2S2]+ (calc. m/z = 843.1000), which were assigned to
Compound 5 was obtained as a red solid from the reaction
of 4 with PhSiH3. NMR spectroscopic reaction monitoring
revealed the formation of PhSiH2(OTEMP) and H2, suggesting a
mechanism
via
the
short-lived
bismuthane
[HBi(C6H4CH2)2S].[27,28] Once compound 5 is precipitated, its
solubility in common organic solvents is very poor. NMR
spectroscopic data could only be obtained at elevated
temperature in pyridine (Supp. Inf.).[29] Single-crystal X-ray
diffraction analysis confirmed the expected molecular structure
with Ci symmetry and a non-polar Bi–Bi bond (3.02 Å), resulting
in the absence of Bi1∙∙∙S1 interactions (Scheme 3c).[6]
protonated
[Bi(C6H4CH2)2S(OTEMP)]
derivatives
of
(4)
the
and
bismuth
the
tempoxide
dibismuthane
[Bi(C6H4CH2)2S]2 (5), respectively. Both compounds were
synthesised in independent approaches, isolated, and fully
characterised (Scheme 3). Compound 4 was obtained as a
colourless solid from the reaction of 3 with in-situ-generated
Na(OTEMP). Single-crystal X-ray diffraction analysis revealed X–
O1 bond lengths (Bi1–O1, 2.18 Å; N1–O1, 1.46 Å) and an angle
sum around N1 (333.9°), which point towards this complex being
best described as a bismuth tempoxide species (Scheme
Combined UV/vis spectroscopic and (TD-)DFT analyses of
and 5 suggest that they should be susceptible to
4
photochemically-induced Bi–O/Bi–Bi bond cleavage (Supp. Inf.).
In agreement with these results, isolated compounds 4 and 5
proved to be catalytically competent in the photochemically-
induced dehydrocoupling of S1 with TEMPO (Table 1, entries 17-
20). While quantitative yields were obtained with 4, the lower yield
of 48% obtained with 5 was ascribed to the poor solubility of the
3
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presented in this work is certainly complex and potentially
involves resting states and parallel reaction pathways. In order to
rationalise the catalytic reaction, a tentatively suggested catalytic
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catalytic experiments is shown in Scheme 4 (for further details,
see Supp. Inf.).
[2]
[3]
[4]
For isolable bismuth radicals see: a) R. J. Schwamm, J. R. Harmer, M.
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TEMPO to give P1, catalysed by 2-SPh (for further details see Supp. Inf.). [Bi]
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accessible
and
storable
diorgano(bismuth)thiolate
[Bi(C6H4CH2)2S(SPh)] (2-SPh) allows for the first application of a
well-defined molecular bismuth compound as a catalyst in a
homogeneous photochemical approach. In the radical
dehydrocoupling of silanes with TEMPO, 2-SPh shows a much
higher catalytic activity than previously reported bismuth
compounds and is competitive with a previously reported
magnesium species. The new approach is complementary to
existing ones in terms of reaction initiation (thermal vs.
photochemical), opening up perspectives for orthogonal synthetic
strategies. TD-DFT calculations gave insights into the initiating
step of the reaction and catalytically competent intermediates
have been isolated and characterised.
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1988, 27, 3730-3733; b) P. Šimon, R. Jambor, A. Růžička, L. Dostál,
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Eur. J. 2020, DOI: 10.1002/chem.202001674.
Acknowledgements
Funding through the Fonds der Chemischen Industrie, the
Universitätsbund Würzburg, the University of Würzburg, and the
Deutsche Forschungsgemeinschaft is gratefully acknowledged. C.
L. thanks Prof. Holger Braunschweig for continuous support.
[18] Also see: A. Toma, C. I. Raţ, A. Silvestru, T. Rüffer, H. Lang, M. Mehring,
J. Organomet. Chem. 2016, 806, 5-11.
[19] There are also significant contributions of a sulphur-centred lone pair to
the HOMO and the HOMO-1.
[20] D. J. Liptrot, M. S. Hill, M. F. Mahon, Angew. Chem. Int. Ed. 2014, 53,
6224-6227.
Keywords: bismuth • chalcogens • radical reactions •
dehydrocoupling • photocatalysis
[21] a) J.-J. Aleman-Lara, E. Block, S. Braverman, M. Cherkinsky, M. B. C.
de la Plata, Sulfur, Selenium, and Tellurium, Science of Synthesis, vol.
39, Houben-Weyl, 2014; b) S. M. Horvat, C. H. Schiesser, New J. Chem.
2010, 34, 1692-1699.
[1]
a) Y.-R. Luo, Bond Dissociation Energies. In CRC Handbook of
Chemistry and Physics, 89th ed.; Ed.: D. R. Lide, CRC Press/Taylor and
Francis: Boca Raton, FL, 2009; b) S. J. W. Price and A. F. Trotman-
Dickenson, Trans. Faraday Soc. 1958, 54, 1630-1637; c) D. P.
Mukhopadhay, D. Schleier, S. Wirsing, J. Ramler, D. Kaiser, E. Reusch,
[22] Data read out from Figure S7 of ref. [7].
[23] Bismuth radicals are challenging to detect EPR spectroscopically, which
has been ascribed to fast relaxation as a result of large spin-orbit
coupling (ref. [2b]). For example, the bismuth radical that is formed in the
4
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10.1002/chem.202002219
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equilibrium reaction [Bi(CSiMe3CH2)2]2 ⇌ 2 [Bi(CSiMe3CH2)2]● could not
be detected by EPR spectroscopy (ref. [2b]). The EPR spectroscopic
detection of a bismuth radical that may be a reactive species in the
catalytic experiments presented in this work would thus be surprising,
since it would be expected to be very short-lived and present only in very
low concentrations. Nevertheless, attempts to detect bismuth radical
species by irradiating 2-SPh or 4 during EPR spectroscopic experiments
were undertaken, but proved to be unsuccessful (for details see Supp.
Inf.).
[24] G. C. Forbes, A. R. Kennedy, R. E. Mulvey, P. J. A. Rodger, Chem.
Commun. 2001, 1400-1401.
[25] Z. Turner, Inorg. Chem. 2019, 58, 14212-14227.
[26] This equilibrium scenario may well be accessible at elevated
temperatures, since the homolytic cleavage of the Bi–O bond in 4 is only
mildly endergonic (ΔG = +12.0 kcal∙mol–1) according to DFT calculations
(Supp. Inf.).
[27] a) G. Balázs, H. J. Breunig, E. Lork, Organometallics 2002, 21, 2584-
2586; b) G. Balázs, H. J. Breunig, E. Lork, Z. Naturforsch. 2005, 60b,
180-182; c) R. J. Schwamm, M. Lein, M. P. Coles, C. M. Fitchett, Angew.
Chem. Int. Ed. 2016, 55, 14798-14801.
[28] A sole example of an isolable secondary bismuthane has been reported:
N. J. Hardman, B. Twamley, P. P. Power, Angew. Chem. Int. Ed. 2000,
39, 2771-2773.
[29] A poor solubility of the related species [Bi(C6H4CH2)2NMe]2 is suggested
by the use of 100 mL THF for the extraction of 59 mg of this compound:
S. Shimada, J. Maruyama, Y.-K. Choe, T. Yamashita, Chem. Commun
2009, 6168-6170.
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Entry for the Table of Contents
Insert graphic for Table of Contents here.
Well-defined molecular bismuth with Bi–EPh functional groups are catalytically active in the photochemical dehydrocoupling of silanes
with TEMPO (E = S, Se, Te). Their properties are complementary or superior to those of other main group catalysts for these reactions.
Institute and/or researcher Twitter usernames: @Uni_WUE
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