The Dimethylbismuth Cation: Entry Into Dative Bi?Bi Bonding and Unconventional Methyl Exchange

Article abstract of DOI:10.1002/anie.202109545

The isolation of simple, fundamentally important, and highly reactive organometallic compounds remains among the most challenging tasks in synthetic chemistry. The detailed characterization of such compounds is key to the discovery of novel bonding scenarios and reactivity. The dimethylbismuth cation, [BiMe₂(SbF₆)] (1), has been isolated and characterized. Its reaction with BiMe₃ gives access to an unprecedented dative bond, a Bi→Bi donor–acceptor interaction. The exchange of methyl groups (arguably the simplest hydrocarbon moiety) between different metal atoms is among the most principal types of reactions in organometallic chemistry. The reaction of 1 with BiMe₃ enables an S_E2(back)-type methyl exchange, which is, for the first time, investigated in detail for isolable, (pseudo-)homoleptic main-group compounds.

Full text of DOI:10.1002/anie.202109545

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Accepted Article
Title: The Dimethylbismuth Cation: Entry into Dative Bi–Bi Bonding and
Unconventional Methyl Exchange
Authors: Jacqueline Ramler, Felipe Fantuzzi, Felix Geist, Anna Hanft,
Holger Braunschweig, Bernd Engels, and Crispin Lichtenberg
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10.1002/anie.202109545
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The Dimethylbismuth Cation: Entry into Dative Bi–Bi Bonding and
Unconventional Methyl Exchange
Jacqueline Ramler,[a] Felipe Fantuzzi,[a,b] Felix Geist,[a] Anna Hanft,[a] Holger Braunschweig,[a] Bernd
Engels,[b] and Crispin Lichtenberg*[a]
Abstract: The isolation of simple, fundamentally important, and
highly reactive organometallic compounds remains among the most
challenging tasks in synthetic chemistry. The detailed
characterization of such compounds is key to the discovery of novel
bonding scenarios and reactivity. The dimethylbismuth cation,
[BiMe2(SbF6)] (1), has been isolated and characterized. Its reaction
with BiMe3 gives access to an unprecedented dative bond, a Bi→Bi
donor/acceptor interaction. The exchange of methyl groups
(arguably the simplest hydrocarbon moiety) between different metal
atoms is among the most principal types of reactions in
organometallic chemistry. The reaction of 1 with BiMe3 enables an
SE2(back) type methyl exchange, which is for the first time
investigated in detail for isolable, (pseudo-)homoleptic main group
compounds.
Figure 1. Compounds with a) different types of bismuth-bismuth bonding and
b) unidirectional E→E donor-acceptor bonding.
Contributions towards a detailed and profound understanding of
bonding interactions between heavier p-block elements E have
revived the field of main group chemistry in the last decades.[1]
E–E bonding interactions tend to become weaker with an
group 15 compounds, unidirectional E→E bonding can be
realized by combining
a
cationic complex fragment
increasing principal quantum number of E, because the relevant
atomic orbitals become larger and more diffuse. In this respect,
the investigation of species with bonding interactions between
bismuth (the heaviest element without significant radioactivity) is
especially challenging. While the first species with a Bi–Bi single
bond, Me2Bi–BiMe2 (A), was generated as early as 1935,[2] its
isolation and detailed re-investigation was achieved only about
50 years later (Figure 1a).[3],[4] Following these pioneering
contributions, different types of compounds featuring Bi–Bi
multiple bonds have been reported more recently. These include
dibismuthenes such as the pivotal TbtBi=BiTbt (B) (Tbt = 2,4,6-
[CH(SiMe3)2]3-C6H2),[5] Bi2 units in the coordination sphere of
transition metals (as in Bi2(W(CO)5)3 (C)),[6] [K(222-crypt)]2[Bi2]
containing naked [Bi2]2– anions (D),[7] and free Bi2 (E), which has
been generated and analyzed in the gas phase and in noble gas
matrices (Figure 1a).[8]
[PnR2]+,which contains one empty p-orbital at Pn, with a trivalent
species PnR3, which bears one lone pair at Pn (Pn = P-Bi).[11],[4e,
12]
In fact, E→E bonding has been achieved for all group 15
elements but bismuth.[11e] So why is the generation of E→E
dative bonding especially challenging in the case of the heaviest
congener? On the one hand, the accessibility of (e.g. nitrogen-
and aryl-substituted) bismuth cations is well-documented,[13],[14]
and they have recently been established as potent soft Lewis-
acids.[15] On the other hand, [BiR2]+ cations without extreme
steric stabilization or considerable Bi∙∙∙anion bonding remain
elusive.[14] In addition, compounds of type BiR3 are poor donors
due to the inert pair effect and relativistic effects.[16] Further
complications may arise from ligand scrambling,[17] when
targeting species of type R3Bi→BiR’2. Herein, we report the first
example of a mononuclear alkylbismuth cation, [BiMe2(SbF6)],
and its reactivity towards BiMe3, revealing unprecedented donor-
acceptor interactions and unconventional methyl exchange.
Reaction of BiMe2Cl with AgSbF6 in dichloromethane (DCM)
gave [BiMe2(SbF6)] (1), which was isolated as a yellow, light-
sensitive crystalline material in 75% yield (Figure 2a). Solution
In contrast, compounds featuring unidirectional Bi→Bi donor-
acceptor interactions have not been reported to date.
Unsupported E→E bonding has recently been documented, for
instance, in the low-valent silicon(II), germanium(II), and tin(II)
compounds F-H, in which the central atoms bear one lone pair
and one empty p-orbital (Figure 1b).[9],[10] In the chemistry of
1
NMR spectroscopy in CD2Cl2 revealed one singlet in the H (δ =
2.28 ppm) and the 13C NMR spectrum (δ = 64.4 ppm),
respectively. Compared to the neutral parent compound BiMe3,
these resonances experience a dramatic increase in chemical
shifts of Δδ = +1.17 ppm (1H) and Δδ = +71.2 ppm (13C), which
reflects the electron-deficient nature of 1.[18] The light-sensitivity
of 1 prompted us to perform UV/vis spectroscopic analyses. In
DCM solution, a broad absorption band with its maximum at 321
nm was observed, which stretches well into the visible region of
λ > 400 nm (Supp. Inf.). In good agreement with these data,
CAM-B3LYP-based calculations revealed a first electronically
[a]
[b]
Dr. J. Ramler, Dr. F. Fantuzzi, F. Geist, Dr. A. Hanft, Prof. Dr. H.
Braunschweig, Priv.-Doz. Dr. C. Lichtenberg
Institute of Inorganic Chemistry
Julius-Maximilians-University Würzburg
Am Hubland, 97074 Würzburg (Germany)
E-mai: crispin.lichtenberg@uni-wuerzburg.de
Dr. F. Fantuzzi, Prof. Dr. B. Engels
Institute of Physical and Theoretical Chemistry
Julius-Maximilians-University Würzburg
Am Hubland, 97074 Würzburg (Germany)
excited state (S1) with dominant contributions by
a
HOMO→LUMO transition (72%) at λcalc = 333 nm. The HOMO is
Supporting information for this article is given via a link at the end of
the document.
1
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10.1002/anie.202109545
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Inf.). Based on TD-DFT calculations and the natural transition
orbital (NTO) analysis using CAM-B3LYP, the S0→S1 excitation
(λcalc = 289 nm) was ascribed to an n(Bi2)→σ*(Bi1–Bi2)
transition with additional σ(Bi2–Me)→σ*(Bi1–Bi2) contributions
(Figure 3b and Supp. Inf.). In line with these results, geometry
optimization of the S1 state leads to dissociation of the Bi–Bi
bond as a consequence of populating the σ*(Bi1–Bi2) orbital.
Single-crystal X-ray diffraction analysis of compound 3
unambiguously confirmed the formation of an adduct between
BiMe3 and [BiMe2(SbF6)] (Figure 3c, monoclinic space group
P21/c, Z = 4). The Bi→Bi bond length amounts to the remarkably
small value of only 3.00 Å. This is well within the range of Bi–Bi
bond lengths that have been reported for dibismuthanes with
unsupported, covalent Bi–Bi single bonds, such as Bi2Et4, Bi2Ph4,
and Bi2Mes4 (2.98-3.09 Å).[20], [21] All Bi–C bond lengths are in the
range of 2.21-2.24 Å, ranging between those reported for the
single components of this compound (i.e. 1 and BiMe3). Both
bismuth atoms in 3 show a coordination number of four. Bi1
shows a distorted tetrahedral coordination geometry. This is
unusual for four-coordinate bismuthIII compounds,[22] in which the
bismuth center commonly acts as a Lewis acid resulting in
bisphenoidal coordination geometries. BiMe3 in particular has so
far only been coordinated as a donor to transition metal complex
fragments in [M(CO)5(BiMe3)] (M = Cr, W).[16c] The angle sums
C–Bi–C in these compounds (297.0-298.7°) are larger than in
non-coordinate BiMe3 (276.6°), but even larger in compound 3
(302.4°), suggesting a remarkably large degree of hybridization
between 6s and 6p bismuth atomic orbitals in the BiMe3 unit of 3.
The Bi2 atom in 3 shows the expected bisphenoidal coordination
geometry with [SbF6]– (Bi–F, 2.809 Å) and BiMe3 in the axial
positions. In line with these results, natural bond orbital (NBO)
analyses of 3 (Figure 3d) reveal an unusually large hybridization
between the 6s and 6p orbitals in Bi1 to give a hybrid orbital with
37% s- and 63% p-character (atom labeling is as in Figure 3).[23]
This occupied hybrid orbital of Bi1 and a vacant (“non-
hybridized”) p-orbital of Bi2 form the Bi→Bi donor-acceptor
interaction, which is strongly polarized towards Bi1 (localization
at Bi1: 79%). A Wiberg bond index (WBI) of 0.52 is associated
with this Bi→Bi interaction, which is reasonably large compared
to the WBIs of 0.24 that were found for the dative N→Bi
interactions in 2 (a WBI of 0.95 is obtained for the regular Bi–Bi
single bond in Me2Bi–BiMe2).
Figure 2. a) Synthesis of 1 and 2. b) Frontier orbitals (Kohn-Sham) of 1 at
isovalues of 0.04, as determined by DFT calculations. c) Molecular structure of
[BiMe2(SbF6)] (1) in the solid state, F3’ exceeds one formula unit and is shown
as a transparent ellipsoid.[31] Displacement ellipsoids are shown at the 50%
probability level. Hydrogen atoms are omitted for clarity. Selected bond
lengths (Å) and angles (°): Bi1–C1, 2.215(5); Bi1–C2, 2.223(5); Bi1–F1,
2.451(3); Bi1–F3’, 2.452(3); C1–Bi1–C2, 93.0(2); F1–Bi1–F3’, 169.73(11). d)
Molecular structure of [BiMe2(py)2][SbF6] (2) in the solid state.[31] Displacement
ellipsoids are shown at the 50% probability level. Bi1–C1, 2.235(12); Bi1–C2,
2.223(12); Bi1–N1, 2.519(7); C1–Bi1–C2, 92.3(5); N1–Bi1–N1’, 169.1(3).
associated with the occupied in-plane bismuth p-orbital, which is
partially delocalized into the Bi–C σ bonds, while the LUMO is
represented by an empty bismuth-centered p-orbital (Figure 2b).
Geometry optimization of the S1 state leads to a separation of
+
–
the BiMe2 and the SbF6 moieties, as a consequence of
populating the bismuth p-orbital oriented along the Bi–F axis. In
congruency with these findings, coordination of pyridine to
[BiMe2]+ blocks this transition, leading to the colorless compound
[BiMe2(py)2][SbF6] (2), which was isolated in 84% yield and fully
characterized (Figure 2a, py = pyridine).
Single-crystal X-ray diffraction analysis of 1 revealed the
formation of a contact ion pair in the solid state with Bi∙∙∙F
distances of 2.45 Å – interactions that are strong enough to
sufficiently stabilize 1, but weak enough to maintain a high
reactivity towards Lewis bases (Figure 2c, orthorhombic space
group Pbca with Z = 8). Each [BiMe2]+ unit interacts with two
fluorine atoms of neighboring [SbF6]– moieties, leading to a one-
dimensional coordination polymer along the crystallographic b-
axis in the solid state (Supp. Inf.). The bismuth atom adopts a
bisphenoidal coordination geometry with the fluorine atoms in
axial (F–Bi–F, 169.7°) and the carbon atoms in equatorial
positions (C–Bi–C, 93.0°). The Bi–C bonds (2.22 Å) are on
average and within one standard deviation shorter than those in
neutral BiMe3 (2.23-2.29 Å; average: 2.26 Å) or in the trinuclear
complex [(BiMe2)3(TmtBu)2]+ (2.24-2.27 Å; average: 2.25 Å TmtBu
The description of the Bi–Bi interaction in 3 as a Bi→Bi
dative bond is further corroborated by the intrinsic bond orbital
(IBO) analysis and the energy decomposition analysis combined
with the natural orbitals for chemical valence (EDA-NOCV)
method, the latter excluding the electron-sharing bond scenario
due to its larger (i.e. more negative) orbital interaction (ΔEorb
)
=
hydrotris(2-mercapto-1-tert-butylimidazolyl)borate),[19] and
component in comparison to that obtained for a Bi→Bi dative
bond (Figure 3d and Supp. Inf.). Furthermore, inspection of the
NOCV deformation densities reveals that ΔEorb is dominated by
σ donation from Bi1 to Bi2 (ΔEorb-σ = –29.9 kcal mol–1, 87% of
ΔEorb), and accounts for ca. 50% of all stabilizing contributions
between the BiMe3 and [BiMe2][SbF6] fragments in 3.
1H NMR spectroscopic analysis of 3 in CD2Cl2 at 25 °C gave
one broad resonance (FWHM = 42 Hz) for all five methyl groups
of the compound (Figure 3e (top)). A coalescence temperature
of 16 °C was determined, and splitting of the broad resonance
into two sharp signals with an intensity ratio of 2:3 was observed
at –40 °C with chemical shifts of δ = 1.97 (9H) and 2.21 (6H)
ppm. In line with the 1H NMR data, the 13C NMR spectrum at
similar to those in 2 (2.22-2.24 Å; average: 2.23 Å; Figure 2d).
Compounds 1 and 2 are the first examples of well-defined
mononuclear cationic bismuth alkyl complexes.
The soft Lewis acidic nature of compound 1, the absence of
neutral donor ligands, and its lack of extreme steric protection
prompted us to investigate its behavior towards the potential soft
Lewis base BiMe3, thereby targeting the formation of the hitherto
unknown Bi→Bi donor/acceptor bond. Reaction of 1 with BiMe3
in DCM gave pale yellow solutions, from which light yellow
crystals of the composition [BiMe2(BiMe3)(SbF6)] (3) were
isolated in 88% yield (Figure 3a). UV/vis spectroscopy in DCM
solution revealed a broad absorption band peaking at 302 nm
and reaching slightly into the visible region of λ > 400 nm (Supp.
2
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–40 °C shows two resonances at δ = 26.1 ppm (BiMe3) and 73.5
ppm (BiMe2). That is, the 13C NMR chemical shifts in 3
experience a considerable to strong shift to higher frequencies in
the case of the BiMe2 group (Δδ = 9.1 ppm) and the BiMe3
moiety (Δδ = 32.9 ppm), when compared to those of compounds
1 and free BiMe3, respectively. These findings demonstrate that
at low temperature in solution, 3 shows a quasi-static bonding
situation as indicated by the Lewis formula in Figure 3a with a
Bi→Bi bonding interaction. At ambient temperature in solution,
however, all methyl groups of compound 3 exchange rapidly on
the time scale of the NMR spectroscopic experiment. The VT
NMR spectroscopic data were subjected to line-shape analysis,
revealing activation parameters of ΔH‡ = 8.5 kcal∙mol–1, ΔS‡ = –
16.7 cal∙mol–1, ΔG‡(298 K) = 13.5 kcal∙mol–1, and k (298 K) =
1010 s–1 (Supp. Inf.). These results may be compared to
bonding situations in lighter group 15 homologs of compound 3.
[Me3P–PMe2][OTf] and related species are stable in solution,
where they show a static bonding situation without exchange
11b]
reactions at room temperature.[11a,
Compounds such as
[PhMe2As–AsPhMe][OTf] are stable in solution, but the
exchange of AsPhMe2 ligands (without exchange of the
hydrocarbon ligands) takes place at room temperature in
solution.[11d] [Me3Sb–SbMe2][SbMe2Br2] has been structurally
characterized in the solid state, but decomposes into mixtures of
mononuclear starting materials in solution, so that characteristic
spectroscopic features in solution have not been reported.[11c]
Similarly, the structure of [(Me2Sb)3][SbMe2Br2] has been
reported not to be preserved in solution.[24] Compound [Me3Sb–
SbMe2][GaCl4] was obtained in very small amounts and not as a
pure substance, which complicated its detailed spectroscopic
characterization.[25] Thus, the heaviest congener of this series,
[BiMe2(BiMe3)(SbF6)] (3), shows a remarkable combination of
being sufficiently stable in solution due to the pronounced and
soft Lewis acidity of cationic bismuth species[14-15] such as
[BiMe2]+ and a dynamic bonding situation due to rapid and
reversible Bi–C bond cleavage/formation in solution.
Methyl exchange reactions in organometallic main group
species have been reported in some detail for compounds such
as (AlMe3)2, for its Lewis base adducts, and for its mixtures with
other organometallic compounds such as GaMe3, InMe3, ZnMe2,
and LiMe.[26] Intra- as well as intermolecular exchange
mechanisms have been discussed, sometimes controversially,
as in the case of (AlMe3)2.[26] We performed DFT calculations in
order to elucidate the mechanism of methyl exchange in
compound 3 (Figure 4). A reaction pathway with an sp3-
hybridized methyl group bridging two cationic bismuth centers
(reminiscent of methyl exchange discussed for compounds such
as Al2Me6) was first considered (Figure 4). Surprisingly, a local
minimum structure 4 with a three-membered Bi2C ring as a key
structural motif was located on the potential energy surface
(PES). According to the IBO analysis, the Bi–(µ2-sp3-CH3)–Bi
motif can be described as a three-center-two-electron bond with
Bi–C (2×) and Bi–Bi bonding interactions (Supp. Inf.). However,
the free energy, ΔG, for the reaction 3 → 4 is +20.7 kcal∙mol–1.
This value does not yet include an (expectedly small) kinetic
barrier and is thus unlikely to solely account for the
experimentally observed process. Alternatively, Bi→Bi bond
dissociation was considered as the initiating step of the methyl
exchange reaction. This bond scission proceeds barrierless to
give the starting materials 1 and BiMe3 in a slightly endergonic
reaction (ΔG = +1.9 kcal∙mol–1). While an electrophilic attack of 1
Figure 3. a) Synthesis of [BiMe2(BiMe3)(SbF6)] (3). b) Natural transition
orbitals of the S0→S1 excitation of 3 at isovalues of 0.04, as determined by
(TD-)DFT calculations. c) Molecular structure of
3
in the solid state.[31]
Displacement ellipsoids are shown at the 50% probability level. Hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and angles (°): Bi1–C1,
2.219(18); Bi1–C2, 2.21(2); Bi1–C3, 2.223(18); Bi2–C4, 2.24(2); Bi2–C5,
2.24(2); Bi1–Bi2, 3.0005(11); Bi2∙∙∙F3, 2.809; C1–Bi1–C2, 97.7(7); C2–Bi1–C3,
103.1(8); C1–Bi1–C3, 101.6(7); C4–Bi2–C5, 94.2(8). d) investigation of Bi→Bi
bond in 3 with NBO, IBO and EDA-NOCV (charge flows from red to blue)
analyses (for details see Supp. Inf.); e) 1H VT-NMR spectra of 3 in CD2Cl2; red
(blue) numbers indicate chemical shift (integrals) of the respective signals.
3
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at the bismuth-centered lone pair of BiMe3 regenerates the
adduct 3, an electrophilic attack of 1 at the methyl group of
BiMe3 was also considered. It proceeds via a van der Waals
Methyl exchange along this pathway has rarely been discussed
to date, but has been suggested or shown for heterobimetallic
systems of late transition metal compounds[28] and for
hypothetical systems such as [Li2Me]+.[29] To the best of the
authors’ knowledge, the relevance of backside SE2-type methyl
exchange is now for the first time demonstrated for a simple,
intermediate
5
located 6.9 kcal∙mol–1 above 3, with the
corresponding transition state (TS1) lying 14.2 kcal∙mol–1 above
3. These results are in excellent agreement with the
experimentally determined value of ΔG‡(298 K) = 13.5 kcal∙mol–1, isolable, (pseudo-)homoleptic, and homometallic compound.
and the associative character of the reaction 1 + BiMe3 → 5 →
TS1 is in congruency with the negative activation entropy
delineated from line-shape analyses (ΔS‡ = –16.7 cal∙mol–1).
Remarkably, the resulting compound 6 was identified as a local
minimum on the PES. It shows an sp2-hybridized methyl group
with a coordination number of five, which is best described as a
methyl anion according to its natural charge of –1.20, bridging
The isolation of compounds featuring Al–(µ2-sp2-CH3)–Al
structural motifs suggests that this may well be a more general
phenomenon.[30]
In order to shed some light on the role of the pnictogen atom
in SE2 type methyl exchange reactions, model compounds
[Pn2Me5]+ (7-Pn) were studied by DFT calculations (Pn = N-Bi).
These investigations show that such transformations are most
favorable for the heaviest congener bismuth, underlining its
unique combination of soft Lewis acidity and relatively weak Pn–
Me bonding that allows for reversible Bi–C bond cleavage (Supp.
Inf.).
two bismuth atoms in
a
(quasi-)linear Bi–(µ2-sp2-CH3)–Bi
structural motif. Accordingly, NBO and IBO calculations on 6
indicate a Bi–(µ2-sp2-CH3)–Bi three-center-two-electron bond
and a lone pair at each bismuth center, which leads to a closed-
shell singlet system with a calculated HOMO–LUMO gap of 4.28
eV (Supp. Inf.). The reaction 3 → 6 is endergonic by only 7.1
kcal∙mol–1. Our findings suggest that the exchange of methyl
groups between the two bismuth atoms in 1 proceeds via a
In summary, [BiMe2(SbF6)] (1) has been synthesized, isolated,
and fully characterized and represents the first example of a
mononuclear dialkyl bismuth cation. Reaction of 1 with BiMe3
gives [BiMe2(BiMe3)(SbF6)] (3) featuring the unprecedented
structural motif of a BiIII→BiIII donor-acceptor interaction. Methyl
exchange in 3 is rapid at room temperature in solution and is
suggested to proceed via an initial Bi→Bi bond dissociation
followed by formation of an intermediate with a trigonal planar
(sp2-hybridized) methyl anion. This corresponds to an SE2 (back)
mechanism, which has been described for heterobimetallic late
transition metal complexes, but rarely been considered or even
been pinpointed as a concept for methyl exchange in main
group chemistry to date and may be more common than
previously anticipated. These findings highlight the unusual
properties of cationic bismuth species as Lewis acids with the
ability to undergo reversible Bi–C bond cleavage, which we aim
to exploit in future synthetic and catalytic applications.
Keywords: Bismuth • Lewis acidity • cationic species • methyl
exchange • electrophilic substitution
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Figure 4. Free energy (ΔG) profile of the proposed methyl exchange reaction
mechanism of 3. Disfavored reaction pathway is shown in red. Selected
calculated interatomic distances are given in Å.
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species featuring an unusual methyl anion with an sp2-
hybridized carbon atom bridging two Bi centers. These findings
are in agreement with the previously calculated low inversion
barrier of the methyl anion (1.50 kcal∙mol–1)[27] and demonstrate
its practical relevance in methyl anion exchange reactions of
organometallic p-block species. The methyl exchange reaction
[5]
[6]
BiMe2SbF6 + BiMe2Me* → 6 → BiMeMe*SbF6 + BiMe3
(eq. 1)
corresponds to a bimolecular electrophilic substitution reaction
(SE2 (back)), i.e. the electrophilic analog of the well-known
nucleophilic SN2 substitution reaction in organic chemistry.
[7]
a) L. Xu, S. Bobev, J. El-Bahraoui, S. C. Sevov, J. Am. Chem. Soc.
2000, 122, 1838-1839; b) D. Dai, M.-H. Whangbo, A. Ugrinov, S. C.
4
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Sevov, F. Wang, L. Li, A. Villesuzanne, A. B. Alekseyev, H.-P.
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10.1002/anie.202109545
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Entry for the Table of Contents
The dimethyl bismuth cation, [BiMe2(SbF6)], has been isolated and characterized. Reaction with BiMe3 allows access to the first
compound featuring Bi→Bi donor acceptor bonding. In solution, dynamic behavior with methyl exchange via an unusual SE2
mechanism is observed, underlining the unique properties of bismuth species as soft Lewis acids with the ability to undergo
reversible Bi–C bond cleavage.
Institute and/or researcher Twitter usernames: @LichtenbergLab
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