Synthesis and Hydrogenation of Heavy Homologues of Rhodium Carbynes: [(Me3P)2(Ph3P)Rh≡E-Ar*] (E=Sn, Pb)

Article abstract of DOI:10.1002/anie.202015725

Tetrylidynes [(Me₃P)₂(Ph₃P)Rh≡SnAr*] (10) and [(Me₃P)₂(Ph₃P)Rh≡PbAr*] (11) are accessed for the first time via dehydrogenation of dihydrides [(Ph₃P)₂RhH₂SnAr*] (3) and [(Ph₃P)₂RhH₂PbAr*] (7) (Ar=2,6-Trip₂C₆H₃, Trip=2,4,6-triisopropylphenyl), respectively. Tin dihydride 3 was either synthesized in reaction of the dihydridostannate [Ar*SnH₂]^? with [(Ph₃P)₃RhCl] or via reaction between hydrides [(Ph₃P)₃RhH] and (Formula presented.) [(Ar*SnH)₂]. Homologous lead hydride [(Ph₃P)₂RhH₂PbAr*] (7) was synthesized analogously from [(Ph₃P)₃RhH] and (Formula presented.) [(Ar*PbH)₂]. Abstraction of hydrogen from 3 and 7 supported by styrene and trimethylphosphine addition yields tetrylidynes 10 and 11. Stannylidyne 10 was also characterized by ¹¹⁹Sn M?ssbauer spectroscopy. Hydrogenation of the triple bonds at room temperature with excess H₂ gives the cis-dihydride [(Me₃P)₂(Ph₃P)RhH₂PbAr*] (12) and the tetrahydride [(Me₃P)₂(Ph₃P)RhH₂SnH₂Ar*] (14). Complex 14 eliminates spontaneously one equivalent of hydrogen at room temperature to give the dihydride [(Me₃P)₂(Ph₃P)RhH₂SnAr*] (13). Hydrogen addition and elimination at stannylene tin between complexes 13 and 14 is a reversible reaction at room temperature.

Full text of DOI:10.1002/anie.202015725

Angewandte
Research Articles
Chemie
How to cite: Angew. Chem. Int. Ed. 2021, 60, 5882–5889
International Edition:
German Edition:
doi.org/10.1002/anie.202015725
doi.org/10.1002/ange.202015725
Rhodiumhydrides
Synthesis and Hydrogenation of Heavy Homologues of Rhodium
ꢀ
Carbynes: [(Me3P)2(Ph3P)Rh E-Ar*] (E = Sn, Pb)
Max Widemann, Klaus Eichele, Hartmut Schubert, Christian P. Sindlinger, Steffen Klenner,
Rainer Pçttgen, and Lars Wesemann*
ꢀ
Abstract: Tetrylidynes [(Me3P)2(Ph3P)Rh SnAr*] (10) and
by Power and co-workers in 1996.[1] The nucleophilic anion
[CpMo(CO)3]À was reacted with the electrophile Ar’GeCl at
508C in THF (Ar’ = 2,6-Mes2C6H3-, Mes = 2,4,6-trimethyl-
ꢀ
[(Me3P)2(Ph3P)Rh PbAr*] (11) are accessed for the first time
via dehydrogenation of dihydrides [(Ph3P)2RhH2SnAr*] (3)
and [(Ph3P)2RhH2PbAr*] (7) (Ar* = 2,6-Trip2C6H3, Trip =
2,4,6-triisopropylphenyl), respectively. Tin dihydride 3 was
either synthesized in reaction of the dihydridostannate
phenyl). After elimination of a CO ligand the germylyne
[1]
ꢀ
complex [Cp(CO)2Mo GeAr’] was isolated as red crystals.
Following this procedure the analogous chromium and
tungsten complexes featuring a triple bond with germanium
were isolated. However, in these cases the stepwise formation
of the germylyne was observed with the metalloorganoger-
mylene [Cp(CO)3M-GeAr*] (M = Cr, W) (Ar* = 2,6-
Trip2C6H3, Trip = 2,4,6-triisopropylphenyl) being an inter-
mediate.[2] Filippou et al. reported a variety of compounds
exhibiting a triple bond between a transition metal (M = Nb,
Cr, Mo, W, Mn, Re, Fe, Ni, Pt) and a heavy element of the
Group 14 (E = Si, Ge, Sn, Pb).[3] Three synthetic strategies for
the synthesis of these carbyne homologues were reported:
nucleophilic substitution at organotetrel halides by nucleo-
philic transition metal complexes;[1,2,3c,i] elimination of N2/
PMe3 ligands and oxidative addition of organotetrel halides at
transition metal complexes[3f,g,k–q] and formation of haloyli-
dene complexes followed by halide abstraction.[3d,e] Hashi-
moto, Tobita and co-workers have synthesized tungsten
germylyne and tungsten silylyne complexes by dehydrogen-
ation using mesityl isocyanate, nitriles or stepwise proton and
hydride abstraction with the hydrido hydrogermylene and
hydrido hydrosilylene as starting materials.[4] Tilley and co-
workers reported cationic silylyne complexes of molybdenum
and osmium.[5] An amino germylyne complex of molybdenum
was published by Jones et al.[6] Most recently Power et al.
presented with the metathetical exchange between metal-
metal triple bonds of transition metal molybdenum and main
group metals Ge, Sn and Pb a very elegant synthetic method
[Ar*SnH2]À with [(Ph3P)3RhCl] or via reaction between
1
hydrides [(Ph3P)3RhH] and = [(Ar*SnH)2]. Homologous
2
lead hydride [(Ph3P)2RhH2PbAr*] (7) was synthesized anal-
ogously from [(Ph3P)3RhH] and 1= [(Ar*PbH)2]. Abstraction
2
of hydrogen from 3 and 7 supported by styrene and
trimethylphosphine addition yields tetrylidynes 10 and 11.
Stannylidyne 10 was also characterized by 119Sn Mçssbauer
spectroscopy. Hydrogenation of the triple bonds at room
temperature with excess H2 gives the cis-dihydride [(Me3P)2-
(Ph3P)RhH2PbAr*] (12) and the tetrahydride [(Me3P)2-
(Ph3P)RhH2SnH2Ar*] (14). Complex 14 eliminates sponta-
neously one equivalent of hydrogen at room temperature to
give the dihydride [(Me3P)2(Ph3P)RhH2SnAr*] (13). Hydro-
gen addition and elimination at stannylene tin between
complexes 13 and 14 is a reversible reaction at room temper-
ature.
Introduction
The first example for a synthesis of a higher homologue of
transition metal carbynes Cp(CO)2Mo Ge-Ar’ was reported
ꢀ
[*] M. Widemann, Dr. K. Eichele, Dr. H. Schubert, Prof. Dr. L. Wesemann
Institut für Anorganische Chemie,
Eberhard Karls Universität Tübingen
Auf der Morgenstelle 18, 72076 Tübingen (Germany)
E-mail: lars.wesemann@uni-tuebingen.de
ꢀ
for the synthesis of carbyne homologues (Cp(CO)2Mo E-
Dr. C. P. Sindlinger
Ar*, E = Ge, Sn, Pb).[7] Known homologues of transition
metal carbyne complexes and new entries reported in this
contribution are summarized in Figure 1.[8]
Institut für Anorganische Chemie,
Georg-August Universität Gçttingen
Tammannstrasse 4, 37077 Gçttingen (Germany)
S. Klenner, Prof. Dr. R. Pçttgen
Institut für Anorganische und Analytische Chemie,
Universität Münster
Corrensstrasse 30, 48149 Münster (Germany)
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
https://doi.org/10.1002/anie.202015725.
ꢀ 2021 The Authors. Angewandte Chemie International Edition
published by Wiley-VCH GmbH. This is an open access article under
the terms of the Creative Commons Attribution Non-Commercial
NoDerivs License, which permits use and distribution in any
medium, provided the original work is properly cited, the use is non-
commercial and no modifications or adaptations are made.
Figure 1. Known homologues of transition metal carbyne complexes
[8]
ꢀ
[LnM E-R] and new entries reported in this contribution.
5882
ꢀ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 5882 –5889

Angewandte
Research Articles
Chemie
Scheme 1. Synthesis of hydride bridged rhodium tin and lead complexes 3, 7; Elimination of hydrogen and formation of the stannylidyne 10 and
plumbylidyne 11. [Trip=2,4,6-tri(isopropyl)phenyl].
We are interested in hydrogen transfer of heavy group 14
elements and studied the reactivity of organoelement trihy-
drides of germanium and tin.[9] The base induced reductive
elimination of hydrogen was investigated.[9a–c,10] Chemistry of
cationic hydrides was explored after hydride abstraction from
organoelement trihydrides.[9d,11] Deprotonation of trihydrides
yields the highly reactive organoelement dihydrido anions of
germanium and tin.[9e,f] Herein we report the use of anions
[Ar*EH2]À (E = Ge, Sn) and lead hydride [(Ar*Pb-H)2] to
synthesize rhodium element dihydrides [(Ph3P)nRhH2EAr*]
of Ge (n = 1) (Scheme 5), Sn and Pb (n = 2) (Scheme 1).[12]
The tin and lead dihydride complexes were dehydrogenated
in reaction with styrene to yield after PMe3 addition the first
examples for triple bonds between rhodium and tin or lead
The hydride-bridged complexes 3 and 7 were character-
ized by NMR spectroscopy, elemental analyses and crystal
structure determination. The molecular structure of 7 is
shown in Figure 2. Details of the structure analyses and an
ORTEP of the essentially isostructural molecular structure of
3 were placed in the Supporting Information.
In coordination compounds 3 and 7 two triphenylphos-
phine and two hydride ligands are square planar cis coordi-
nated at rhodium with slightly shorter interatomic Rh-P and
Rh-H distances in the tin case. The Rh-P distances [2.2741(7)–
2.2897(9) Š] lie in the range of square planar coordinated
(Ph3P)2Rh(I) fragments stabilized by closo-borates via BH-
interaction or Cp2WH2 hydride coordination [2.2192(6)–
2.2391(6) Š].[13] The hydride positions in 3 and 7 were
localized using X-ray difference Fourier maps and refined
with distance restraints. Budzelaar et al. studied the oxidative
ꢀ
ꢀ
Rh E (E = Sn, Pb). Hydrogenation of the triple bonds Rh E
is also presented.
Results and Discussion
To further evaluate the nucleophilicity of the aryldihy-
dridostannate (1) we explored the reactivity of this anion in
reaction with tris(triphenylphosphine)rhodium chloride 2
(Scheme 1). In the product complex, a triphenylphosphine
ligand and the chloride substituent at the rhodium atom were
displaced by the dihydridostannate nucleophile. The hydride
substituents were transferred from the tin atom to the
rhodium and exhibit a contact to the tin atom. Following an
alternative protocol, the Rh coordination compound 3 was
synthesized in high yield (93%) reacting the low valent
organotin hydride [(Ar*SnH)2] 4 with rhodium hydride
[(Ph3P)3RhH] 5 (Scheme 1). Since a lead homologue of
stannate 1 is unknown the rhodium hydride route (Scheme 1)
was used to synthesize a rhodium-lead complex. Due to
thermal instability of the low valent lead hydride [(Ar*PbH)2]
6 the reaction with the rhodium hydride was carried out at
À408C. The rhodium-lead dihydride 7 forms the same
structural motif as the Rh-Sn compound 3. However, this
Rh-Pb complex decomposes at room temperature and must
be stored below 08C.
Figure 2. ORTEP of the molecular structure of 7. Ellipsoids at 50%
probability. iPr groups, phenyl rings of the PPh3 ligand except the ipso-
C atoms and CH hydrogen atoms are omitted for clarity. Interatomic
distances in [Š] and angles [deg]: Pb–Rh 2.6361(3), Pb–H1 2.37(5),
Pb–H2 2.15(4), Pb–C1 2.327(3), Rh–H1 1.71(5), Rh–H2 1.65(4), Rh–P1
2.2897(9), Rh–P2 2.2824(8), C1-Pb-Rh 114.0(1), C1-Pb-H2 97.6(12),
C1-Pb-H1 83.0(12), H2-Pb-H1 63.0(17), P1-Rh-P2 104.17(3), P2-Rh-H2
82.1(15), P1-Rh-H2 171.1(15), P2-Rh-H1 171.0(17), P1-Rh-H1 84.3(17),
H2-Rh-H1 90(2), Pb-Rh-H2 54.4(15), Pb-Rh-H1 62.0(17), Rh-Pb-H2
38.7(11), Rh-Pb-H1 39.4(12).[36]
Angew. Chem. Int. Ed. 2021, 60, 5882 –5889
ꢀ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH www.angewandte.org
5883

Angewandte
Research Articles
Chemie
addition of H-SnnBu3 at b-diiminate complexes of rhodium
and found a Rh-Sn distance of 2.563(1) Š, Sn-H 2.27(4) Š
and Rh-H 1.47(4) Š.[14] To compare, in complex 3 the
observed Rh-Sn distance is 2.5262(3) Š, Sn-H 2.11(4) Š and
Rh-H 1.59(4) Š long. In the lead case the Rh-Pb distance of
2.6361(3) Š can be compared with an example of PbCl2
coordination [2.7561(7) Š] or plumbole coordination at
a phenyl moiety of the terphenyl substituent in compounds 8
and 9 double sets of 1H and 13C NMR signals were found for
the trip-substituents of the terphenyl group. This type of
terphenyl-rhodium coordination is already known in the
literature.[21] Both heteroelement NMR signals were found at
high frequencies (119Sn NMR 8, 3112 ppm; 207Pb NMR 9,
11269 ppm) in comparison to known organometallostanny-
lenes or plumbylenes.[7,17,18,22] Cationic complex [Cp*W-
(CO)3Sn(NHC)][Al(OC(CF3)3)4] exhibits a 119Sn NMR signal
at very high frequency (3318 ppm).[17b]
1
rhodium [2.7601(5), 2.7712(5) Š].[15] The H NMR signals of
the hydride substituents were found for 3 at À4.13 ppm (JRh-
H = 22 Hz, JSn-H = 220 Hz) and for 7 at 3.62 ppm (JRh-H
=
21 Hz, JPb-H = 124 Hz). The high frequency shift of the Rh-H
signal of the lead derivative 7 can be explained with the
influence of the heavy atom lead on the chemical shift of light
atoms. The relativistic effects on NMR chemical shifts by
spin-orbit coupling has been investigated by quantum chem-
ical methods.[16] The 119Sn NMR signal of 3 found at 1728 ppm
points toward an aryl rhodostannylene. Metallostannylenes of
metals Cr, Mo and Wexhibit signals at high frequencies in the
range of 2116–3318 ppm.[17] The shift to lower frequency of
compound 3 (1728 ppm) might be interpreted as an indicator
for an increased coordination number caused by hydride Sn
contacts. The same reasoning can be applied in the case of the
207Pb NMR signal of derivative 7: the signal was found at
8195 ppm and should be compared with metalloplumbylenes
In the tin case besides hydrogen transfer to styrene
coordination of styrene was ascertained in solution with high
concentrations of styrene (see Supporting Information for
data of styrene complexes). Furthermore, in reaction with
hydrogen and PPh3 the stannylene complex 8 was transferred
back to the hydride complex 3. However, this oxidative
addition of H2 proceeds very slowly (Scheme 1).
To further investigate the hydrogen transfer products,
reactions with trimethylphosphine were studied. Remarkably,
as products of PMe3 coordination in both cases the first
examples for triple bond formation between rhodium and
heavy Group 14 elements Sn and Pb were found (Scheme 1).
Both tetrylidyne complexes were crystallized from hexane
at À408C as black-brown crystals in moderate yield (10, 61%;
investigated by Powerꢀs group [Cr, Mo, W: 9374– 11, 46%). The molecular structure in the solid state was
9563 ppm].[18]
Using the nucleophilic substitution procedure (Scheme 1)
determined in both cases by single crystal X-ray diffraction
(Figures 3 and 4).
À
ꢀ
as the method to synthesize complex 3 two Sn H bonds were
Both Rh E (E = Sn 2.3856(2), E = Pb 2.4530(2) Š) bond
activated, and the hydrides transferred to rhodium (for the
transfer back to tin vide infra, Scheme 4). This reaction should
be compared with the Ga-H activation studied by Aldridge
and co-workers at rhodium (I).[19] The 1,2-hydrogen migration
from tin, germanium and silicon to transition metals (Ru, Os,
Mo, Hf) was studied intensively by Tilley and co-workers.[20]
They discussed the equilibrium of hydride transfer between
hydrido-metallostannylene (HM-Sn-R) and hydridostanny-
lene (M–SnHR) with tin favouring energetically the hydri-
dometallostannylene.[20a]
lengths are by far the shortest bonds between these elements
(CCDC search). The angles at tin or lead are close to linearity
[Sn 174.6(1), Pb 174.2(1)8]. In both cases 10 and 11 the
Examples for heavy Group 14 element metal dihydride
complexes like [(Ph3P)2RhH2EAr*] (E = Sn 3; E = Pb 7) are
precedented in the literature for the following element
combinations: Ge-Ru,[20e,h] Mo,[20i] W,[4d] Rh;[14] Sn-Os,[20g]
Ru[20a,b] Hf,[20f] Rh;[14] Pb-Ru.[20a]
The rhodium dihydride 3 reacts at room temperature with
deuterium to give the dideuteride complex (see Supporting
Information, Figures S11, S12). Both dihydrides 3 and 7 show
reductive elimination of hydrogen and formation of the ylene
complexes Ar*E-Rh(PPh3) [E = Sn (8), E = Pb (9)] upon
storage in solution at rt. However, in the tin case this
hydrogen elimination is a very slow reaction and the lead
compound also exhibits decomposition and formation of
Ar*H. To selectively synthesize these ylene coordination
compounds transfer of hydrogen from 3 and 7 to styrene was
investigated (Scheme 1). Whereas the tin hydride 3 reacts
overnight completely with styrene the lead hydride 7 shows
the higher reactivity and the transfer is finished after 2 h. Both
complexes 8 and 9 could be characterized as a mixture with
PPh3 which could not be separated from the rhodium
complexes. Due to coordination of the rhodium atom at
Figure 3. ORTEP of the molecular structure of 10. Ellipsoids at 50%
probability. Hydrogen atoms are omitted for clarity. Interatomic
distances in [Š] and angles [deg]: Rh–Sn 2.3856(2), Sn–C1 2.197(2),
Rh–P1 2.2714(6), Rh–P2 2.2630(6), Rh–P3 2.2805(6), C1-Sn-Rh 174.6-
(1), P2-Rh-P1 106.9(1), P2-Rh-P3 104.3(1), P1-Rh-P3 106.3(1), P2-Rh-Sn
108.7(2), P1-Rh-Sn 117.5(2), P3-Rh-Sn 112.3(2).[36]
5884
www.angewandte.org ꢀ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 5882 –5889

Angewandte
Research Articles
Chemie
Figure 5. 119Sn Mçssbauer spectrum of complex 10. The green
(d=0.54(2) mmsÀ1, 6(1) %) and ocher (d=3.73(4) mmsÀ1, 5(1) %)
sub-signals correspond to minor SnIV and SnII impurity phases.
out.[23] A sample of the rhodium stannylidyne 10 was also
investigated by 119Sn Mçssbauer spectroscopy to get further
insight into the oxidation state of the tin atom. In Figure 5 the
119Sn Mçssbauer spectrum of compound 10 is presented
together with a simulation (d = 2.63(1) mmsÀ1, DEQ = 2.47-
(1) mmsÀ1, G = 0.82(1) mmsÀ1). The isomer shift found for 10
and the quadrupole splitting are close to the values found for
stannylidyne complexes of molybdenum and tungsten (d:
2.38–2.50 mmsÀ1; DEQ: 1.81–2.82 mmsÀ1). Furthermore, the
Figure 4. ORTEP of the molecular structure of 11. Ellipsoids at 50%
probability. Hydrogen atoms are omitted for clarity. Interatomic
distances in [Š] and angles [deg]: Rh–Pb 2.4530(2), C1–Pb 2.2758(18),
P3–Rh 2.2792(6), P1–Rh 2.2646(5), Rh–P2 2.2598(6), C1-Pb-Rh 174.2-
(1), P2-Rh-P1 107.4(1), P2-Rh-P3 105.0(1), P1-Rh-P3 106.9(2), P2-Rh-Pb
108.2(2), P1-Rh-Pb 116.7(1), P3-Rh-Pb 111.9(2).[36]
ꢀ
isomer shift of distannyne (Ar*Sn SnAr*, d: 2.69, DEQ: 3.73)
lies also in this range, which was interpreted as tin in oxidation
state (II).[23,24] The differences in the quadrupole splitting can
be attributed to the varying geometry at the transition metal
since in all examples the tin atoms are further substituted by
a terphenyl substituent. The largest DEQ points toward a less
symmetrical substituent on the transition metal.[23,24] The
anisotropy of the tin atom was further investigated by 119Sn
CP/MAS NMR spectroscopy (see in the Supporting Infor-
mation Figure S51).
rhodium atom is nearly tetrahedrally coordinated by the three
phosphines and the Group 14 ligand. The Group 14 elements
show signals in the 119Sn and 207Pb NMR spectra at 1149 ppm
1
2
(10: ddt, J119Sn-103Rh = 762 Hz, 2J119Sn-31P = 294 Hz, J119Sn-31P
=
185 Hz) and 5729 ppm (11: d, 1J207Pb-103Rh = 1050 Hz). The
chemical shifts of the tetrylidynes lie in the range of
ꢀ
complexes featuring triple bonds with molybdenum Mo E
ꢀ
(Sn: 1021 ppm, Pb 9660 ppm) or niobium Nb Sn
829.7 ppm.[3c,7] In the 13C{1H} NMR spectra the signals for
the ipso carbon atom connected at tin or lead exhibit the
signal at highest frequency (Sn: 188.0 ppm, Pb 274.7 ppm).
The shift to high frequencies of the plumbylidyne can be
compared with the plumbylidynes published by Filippou et al.
exhibiting signals at 280.6, 279.1, 278.7 ppm.[3l,m] The shift of
the 13C NMR signals to high frequencies can be rationalized
by the influence of the heavy atom lead on the chemical shift
of the neighbouring atom.[16]
Since the presented [Rh] Sn-Ar* and [Rh] Pb-Ar*
complexes were synthesized in a reductive elimination
sequence of hydrogen (Scheme 1) the reactivity of these
compounds 10 and 11 towards hydrogen was of interest and
the results are shown in Scheme 2.
ꢀ
ꢀ
Both compounds show an addition reaction of hydrogen
at rt. The stannylidyne 10 adds two equivalents of hydrogen
whereas the plumbylidyne 11 reacts with one equivalent.
Hydrogenation of higher homologues of transition metal
carbynes is, to the best of our knowledge, so far an unknown
reaction.[8,25] Power and co-workers studied the reactivity of
unique heavy element alkyne homologues of germanium and
Probing the electronic structure including NBO analyses
suggests the E-Rh bonding to be primarily composed of two
p-type bonds that constitute from filled Rh d-orbitals
donating into a set of empty p-orbitals at the tetrel element.
NBO analyses further suggest that the s-interactions stem
from a strongly E-located near pure s-orbital pair of electrons
that, according to second order perturbation analysis strongly
donates into an empty Rh 5s-orbital. The extent of this
donation is significantly stronger for Sn (162 kcalmolÀ1) than
for Pb (108 kcalmolÀ1). An only partial contribution of
a triple-bond Lewis structure description is in line with
Lçwdin bond indices for E-Rh pairs of ca. 2(Æ 0.1). (See
Supporting Information for further information)
†
†
tin.[26] Digermyne [Ar Ge GeAr ] exhibits a hydrogenation
ꢀ
†
†
=
at rt to give a mixture of dihydride [Ar GeH GeHAr ] and
tetrahydride [Ar†GeH2-GeH2Ar†] (Ar† = C6H3-2,6(C6H3-2,6-
iPr2)2),[27] whereas the distannyne [Ar Sn SnAr ] shows
a reversible addition and elimination of one equivalent of
hydrogen at 808C.[28] The addition of hydrogen at amido-
distannyne and amido-digermyne was presented by Jones
et al.[29]
†
†
ꢀ
Based on NMR spectroscopy in the process of the
formation of tetrahydride 14, the addition product of one
equivalent hydrogen complex 13 is an intermediate
(Scheme 2), which could also be synthesized by reacting the
In the case of the stannylidyne complexes of molybdenum
and tungsten Mçssbauer spectroscopic studies were carried
Angew. Chem. Int. Ed. 2021, 60, 5882 –5889
ꢀ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH www.angewandte.org
5885

Angewandte
Research Articles
Chemie
Scheme 2. Hydrogenation of the rhodium tetrylidyne complexes 10 and 11 at rt.
Scheme 3. Selective synthesis of the intermediate dihydride 13.
dihydride complex 3 with two equivalents of trimethylphos-
phine (Scheme 3).
The tetrahydride 14 shows a spontaneous reductive
elimination of hydrogen at rt. However, this elimination is
a slow reaction and by NMR spectroscopy the reversibility of
!
the hydrogen elimination and addition (13 14) was probed
!
and confirmed experimentally (Scheme 2, Supporting Infor-
mation Figures S7–10). Hydrogenation of the metallostanny-
lene 13 can be compared with the addition of hydrogen at
a metallosilylene or germylene.[3d,30] The described reversible
hydrogenation is a rare case for a stannylene exhibiting
a reversible room temperature hydrogenation reaction.
Reversible addition and elimination of hydrogen is known
for the well-studied distannyne. The equilibrium between
hydrogen, distannyne and low valent dihydride was studied at
808C.[28] Pµpai, Ashley and co-workers investigated the base
induced reversible hydrogenation of diorganostannylene [Sn-
{CH(SiMe3)2}2]. Hydrogenation was observed at 4 bar H2 in
the presence of Et3N acting as a catalyst and the elimination
of H2 was demonstrated at room temperature in reaction of
the dihydride with DBU.[31] Bis(boryl) substituted stannylene
was shown to add hydrogen at rt by Aldridge and co-
workers.[32]
Figure 6. ORTEP of the molecular structure of 14. Ellipsoids at 50%
probability. Hydrogen atoms and iPr groups are omitted for clarity.
Only Rh-H and Sn-H hydride atoms are shown. Interatomic distances
in [Š] and angles [deg]: Rh–Sn 2.5797(1), Sn–C1 2.212(1), P1–Rh
2.3084(3), Rh–P2 2.3295(4), Rh–P3 2.3323(4), Sn–H3 1.891(15), Sn–
H4 1.891(15), Rh–H1 1.57(2), Rh–H2 1.54(3), C1-Sn-Rh 118.2(1), P1-
Rh-P2 106.18(1), P1-Rh-P3 106.18(1), P2-Rh-P3 96.61(1), P1-Rh-Sn1
143.53(1), P2-Rh-Sn 101.27(1), P3-Rh-Sn 93.82(1).[36]
Hydrogenation products 12, 13 and 14 were characterized
by single crystal X-ray diffraction and NMR spectroscopy. In
Figures 6 and 7 an ORTEP of the molecular structures of 12
and 14 is presented (see Supporting Information for an
ORTEP of the molecular structure of 13).
À
Figure 7. ORTEP of the molecular structure of 12. Ellipsoids at 50%
probability. Hydrogen atoms and iPr groups are omitted for clarity.
Only Rh-H hydride atoms are shown. Interatomic distances in [Š] and
angles [deg]: Rh–Pb 2.6697(2), Pb–C1 2.316(2), P3–Rh 2.3080(7), Rh–
P2 2.3286(7), Rh–P1 2.3329(6), Rh–H1 1.33(4), Rh–H2 1.58(4), C1-Pb-
Rh 115.14(6), P3-Rh-P2 100.19(3), P3-Rh-P1 103.57(2), P2-Rh-P1
103.37(2), P3-Rh-Pb 97.16(2), P2-Rh-Pb 88.28(2), P1-Rh-Pb 153.82-
(2).[36]
The Rh Sn bond length of 2.5797(1) Š found in 14 is
much longer than the triple bond (Table 1) and can be
compared with single bonds between these elements.[15,33] The
signal for the RhH2 moiety was found in the 1H NMR
spectrum at À11.24 ppm and the SnH2 group shows a signal at
4.31 ppm. Both ranging in the chemical shift range typical of
Rh-H and Sn-H signals.[9b,c,34] The RhH2 unit of 13 shows
5886
www.angewandte.org ꢀ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 5882 –5889

Angewandte
Research Articles
Chemie
ca. 350 Hz)] the 119Sn NMR signal of 15 was found at lower
Table 1: Selected data of compounds 3, 7–14.
frequencies in the typical area for higher coordination
numbers at tin [-325 ppm (dt (br), 1J119Sn-103Rh = 392 Hz,
1J119Sn-1H = 740 Hz)]. The increased Sn-H coupling constant
in 15 is another proof for the hydrogen transfer to form a sp3-
tin atom (Scheme 4). An ORTEP of the molecular structure
of 15 was placed in the Supporting Information.
Rh–Sn [Š]
Rh–Pb [Š] d (119Sn)[a] d (207Pb)[a] d (103Rh)[a]
3
7
8
2.5262(3)
1727
3112
1149
À8503
À8057
2.6361(3)
8195
9
11269
10
11
12
2.3856(2)
2.4530(2)
2.6697(2)
5729
11733
À8321
À8529
À9440
13 2.59289(17)
14 2.5797(1)
3296
À244
[a] in ppm.
Scheme 4. Hydrogen transfer to tin.
a signal at À8.60 ppm in the typical range for transition metal
hydrides and the signal of the tin atom was found at 3296 ppm
(d, 1J119Sn-103Rh = ca. 350 Hz) in the 119Sn NMR spectrum
(Table 1).[17,34a]
Finally, the homologous germate anion [Ar*GeH2]À was
also reacted with the rhodium electrophile 2 to give
(Ph3P)RhGeH2Ar* (16) (Scheme 5 and Supporting Informa-
tion for ORTEP of the reaction product). In this complex
À
The Rh Pb bond length of 2.6697(2) Š found in 12 is
À
longer than the triple bond and slightly shorter than Rh Pb
single bonds found in the literature.[15a,35] The signal for the
protons of the RhH2 group was found in the 1H NMR
spectrum at À6.71 ppm. For the lead atom a signal at very
high frequency 11733 ppm was found in the 207Pb NMR
spectrum (Table 1). Compound 9 exhibits also a signal at very
high frequency (9, 11269 ppm). Both resonances lie at
exceptionally high frequencies and only few examples in this
chemical shift range were found: metalloplumbylenes Cp-
(CO)3MPbAr* (M = Cr, 9563 ppm; Mo, 9659 ppm; W,
9374 ppm).[18] Furthermore the 31P NMR signal of the PPh3
ligand in trans-position to the plumbylene ligand was found at
À
a Ge Rh bond was formed; the hydride substituents stay at
the germanium atom and a phenyl moiety of the terphenyl
substituent shows h6-coordination at rhodium. Obviously, due
À
to the higher stability of the Ge H bond the hydride
substituents were not transferred to rhodium and a complex
comparable with the dihydrides 3 and 7 was not formed.
Furthermore, in comparison to the stannate anion 1, the
germate anion is the stronger element-centered nucleo-
phile.[9e]
1
2
very high frequency 321.6 ppm (dt, J103Rh-31P = 103 Hz, J31P-
31P = 6.5 Hz, PPh3). In comparison compound 13 exhibits for
the PPh3 ligand a signal at 93.1 and compound 14 at 47.1 ppm.
This substantial high frequency NMR chemical shift found in
12 is likely to be attributed to the influence of the plumbylene
ligand. This is another example for the HALA effect
discussed for heavy atoms due to spin-orbit coupling.[16] In
contrast the effect of the plumbylene exerted on the directly
bonded rhodium, expressed by the 103Rh chemical shift is
Scheme 5. Reaction of [Ar*GeH2]À with [(Ph3P)3RhCl].
relatively small (compare 103Rh NMR data for compounds 3, Conclusion
7 and 12, 13 in Table 1). In the series of compounds analyzed
by 103Rh NMR spectroscopy a deshielding effect of ca.
1000 ppm of the Group 14 ligand at rhodium was observed:
low valent ligand (plumbylene, stannylene À8057 to
À8529 ppm) versus germyl and stannyl (À9131 to
À9440 ppm) (Supporting Information Table S4).
Following a sequence of hydride transfer from tin or lead
to rhodium and reductive elimination of hydrogen from the
rhodium dihydride complexes tin and lead tetrylidynes
ꢀ
ꢀ
featuring a Rh Sn or Rh Pb triple bond were synthesized.
The polar triple bonds of the rhodium tetrylidynes add one
(Pb case) or two (Sn case) equivalents of hydrogen at room
temperature. The addition of two equivalents of hydrogen in
the tin case is a stepwise procedure, with the hydrogenation of
the rhodium and formation of a metallostannylene as the first
hydrogenation. The second hydrogenation is a room temper-
ature reversible reaction between stannylene tin and hydro-
gen.
With the formation of rhodium dihydride 13 (Scheme 3)
the sequence of hydride transfer from the tin atom of the
dihydridostannate 1 into the bridging position in compound 3
to the rhodium atom was completed. Transfer of both hydride
substituents from the transition metal back to the tin atom
was realized in reaction with chelating phosphine dmpe
[dmpe: bis(dimetyhlphosphino)ethane]. This intramolecular
hydrogen transfer is a remarkable example for a reductive
elimination at a transition metal in combination with an
oxidative addition of a ligand in the first coordination sphere.
In comparison to 3 [1727 ppm (dt, 1J119Sn-103Rh = ca. 150 Hz,
2J119Sn-1H = ca. 240–250 Hz)] and 13 [3296 ppm (d, 1J119Sn-103Rh
=
Angew. Chem. Int. Ed. 2021, 60, 5882 –5889
ꢀ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH www.angewandte.org
5887

Angewandte
Research Articles
Chemie
[5] a) B. V. Mork, T. D. Tilley, Angew. Chem. Int. Ed. 2003, 42, 357 –
360; Angew. Chem. 2003, 115, 371 –374; b) P. G. Hayes, Z. Xu, C.
Beddie, J. M. Keith, M. B. Hall, T. D. Tilley, J. Am. Chem. Soc.
2013, 135, 11780 –11783.
[6] J. Hicks, T. J. Hadlington, C. Schenk, J. Li, C. Jones, Organo-
metallics 2013, 32, 323 –329.
[7] J. D. Queen, A. C. Phung, C. A. Caputo, J. C. Fettinger, P. P.
Power, J. Am. Chem. Soc. 2020, 142, 2233 –2237.
[8] S. Saini, A. Agarwal, S. K. Bose, Dalton Trans. 2020, 49, 17055 –
17075.
Acknowledgements
The authors acknowledge support by the state of Baden-
Württemberg through bwHPC and the German Research
Foundation (DFG) trough grant no INST 40/467-1 FUGG
(JUSTUS 1 cluster), INST 40/575-1 FUGG (JUSTUS 2
cluster) as well as WE 1876/13-1. Open access funding
enabled and organized by Projekt DEAL.
[9] a) C. P. Sindlinger, L. Wesemann, Chem. Sci. 2014, 5, 2739 –
2746; b) C. P. Sindlinger, A. Stasch, H. F. Bettinger, L. Wese-
mann, Chem. Sci. 2015, 6, 4737 –4751; c) C. P. Sindlinger, W.
Grahneis, F. S. W. Aicher, L. Wesemann, Chem. Eur. J. 2016, 22,
7554 –7566; d) F. Diab, F. S. W. Aicher, C. P. Sindlinger, K.
Eichele, H. Schubert, L. Wesemann, Chem. Eur. J. 2019, 25,
4426 –4434; e) J.-J. Maudrich, F. Diab, S. Weiß, M. Widemann, T.
Dema, H. Schubert, K. M. Krebs, K. Eichele, L. Wesemann,
Inorg. Chem. 2019, 58, 15758 –15768; f) J.-J. Maudrich, M.
Widemann, F. Diab, R. H. Kern, P. Sirsch, C. P. Sindlinger, H.
Schubert, L. Wesemann, Chem. Eur. J. 2019, 25, 16081 –16087.
[10] a) J.-J. Maudrich, C. P. Sindlinger, F. S. W. Aicher, K. Eichele, H.
Schubert, L. Wesemann, Chem. Eur. J. 2017, 23, 2192 –2200;
b) F. S. W. Aicher, K. Eichele, H. Schubert, L. Wesemann,
Organometallics 2018, 37, 1773 –1780.
[11] C. P. Sindlinger, F. S. W. Aicher, L. Wesemann, Inorg. Chem.
2017, 56, 548 –560.
[12] a) S. Weiß, H. Schubert, L. Wesemann, Chem. Commun. 2019,
55, 10238 –10240; b) J. Schneider, C. P. Sindlinger, K. Eichele, H.
Schubert, L. Wesemann, J. Am. Chem. Soc. 2017, 139, 6542 –
6545.
[13] a) E. Molinos, S. K. Brayshaw, G. Kociok-Kçhn, A. S. Weller,
Organometallics 2007, 26, 2370 –2382; b) A. Rifat, N. J. Patmore,
M. F. Mahon, A. S. Weller, Organometallics 2002, 21, 2856 –
2865; c) N. W. Alcock, O. W. Howarth, P. Moore, G. E. Morris,
Chem. Commun. 1979, 1160 –1162.
Conflict of interest
The authors declare no conflict of interest.
Keywords: hydrogenation ·leadhydride ·rhodiumhydride ·
tetrylidyne ·tinhydride
[1] R. S. Simons, P. P. Power, J. Am. Chem. Soc. 1996, 118, 11966 –
11967.
[2] L. Pu, B. Twamley, S. T. Haubrich, M. M. Olmstead, B. V. Mork,
R. S. Simons, P. P. Power, J. Am. Chem. Soc. 2000, 122, 650 –656.
[3] a) P. Ghana, M. I. Arz, U. Chakraborty, G. Schnakenburg, A. C.
Filippou, J. Am. Chem. Soc. 2018, 140, 7187 –7198; b) P. Ghana,
M. I. Arz, G. Schnakenburg, M. Straßmann, A. C. Filippou,
Organometallics 2018, 37, 772 –780; c) A. C. Filippou, D.
Hoffmann, G. Schnakenburg, Chem. Sci. 2017, 8, 6290 –6299;
d) A. C. Filippou, B. Baars, O. Chernov, Y. N. Lebedev, G.
Schnakenburg, Angew. Chem. Int. Ed. 2014, 53, 565 –570;
Angew. Chem. 2014, 126, 576 –581; e) A. C. Filippou, P. Ghana,
U. Chakraborty, G. Schnakenburg, J. Am. Chem. Soc. 2013, 135,
11525 –11528; f) A. C. Filippou, U. Chakraborty, G. Schnaken-
burg, Chem. Eur. J. 2013, 19, 5676 –5686; g) A. C. Filippou, A.
Barandov, G. Schnakenburg, B. Lewall, M. van Gastel, A.
Marchanka, Angew. Chem. Int. Ed. 2012, 51, 789 –793; Angew.
Chem. 2012, 124, 813 –817; h) A. C. Filippou, O. Chernov, G.
Schnakenburg, Chem. Eur. J. 2011, 17, 13574 –13583; i) A. C.
Filippou, O. Chernov, K. W. Stumpf, G. Schnakenburg, Angew.
Chem. Int. Ed. 2010, 49, 3296 –3300; Angew. Chem. 2010, 122,
3368 –3372; j) A. C. Filippou, N. Weidemann, G. Schnakenburg,
Angew. Chem. Int. Ed. 2008, 47, 5799 –5802; Angew. Chem.
2008, 120, 5883 –5886; k) A. C. Filippou, N. Weidemann, A. I.
Philippopoulos, G. Schnakenburg, Angew. Chem. 2006, 118,
6133 –6137; l) A. C. Filippou, N. Weidemann, G. Schnakenburg,
H. Rohde, A. I. Philippopoulos, Angew. Chem. Int. Ed. 2004, 43,
6512 –6516; Angew. Chem. 2004, 116, 6674 –6678; m) A. C.
Filippou, H. Rohde, G. Schnakenburg, Angew. Chem. 2004, 116,
2293 –2297; n) A. C. Filippou, P. Portius, A. I. Philippopoulos, H.
Rohde, Angew. Chem. Int. Ed. 2003, 42, 445 –447; Angew. Chem.
2003, 115, 461 –464; o) A. C. Filippou, A. I. Philippopoulos, G.
Schnakenburg, Organometallics 2003, 22, 3339 –3341; p) A. C.
Filippou, P. Portius, A. I. Philippopoulos, Organometallics 2002,
21, 653 –661; q) A. C. Filippou, A. I. Philippopoulos, P. Portius,
D. U. Neumann, Angew. Chem. Int. Ed. 2000, 39, 2778 –2781;
Angew. Chem. 2000, 112, 2881 –2884.
[14] N. Zhang, R. S. Sherbo, G. S. Bindra, D. Zhu, P. H. M. Budzelaar,
Organometallics 2017, 36, 4123 –4135.
[15] a) A. K. Swarnakar, M. J. Ferguson, R. McDonald, E. Rivard,
Dalton Trans. 2016, 45, 6071 –6078; b) M. Saito, M. Nakada, T.
Kuwabara, R. Owada, S. Furukawa, R. Narayanan, M. Abe, M.
Hada, K. Tanaka, Y. Yamamoto, Organometallics 2019, 38,
3099 –3103.
´
[16] J. Vícha, J. Novotny, S. Komorovsky, M. Straka, M. Kaupp, R.
Marek, Chem. Rev. 2020, 120, 7065 –7103.
[17] a) B. E. Eichler, A. D. Phillips, S. T. Haubrich, B. V. Mork, P. P.
Power, Organometallics 2002, 21, 5622 –5627; b) Y. N. Lebedev,
U. Das, G. Schnakenburg, A. C. Filippou, Organometallics 2017,
36, 1530 –1540.
[18] L. Pu, P. P. Power, I. Boltes, R. Herbst-Irmer, Organometallics
2000, 19, 352 –356.
[19] J. A. B. Abdalla, A. Caise, C. P. Sindlinger, R. Tirfoin, A. L.
Thompson, A. J. Edwards, S. Aldridge, Nat. Chem. 2017, 9,
1256 –1262.
[20] a) P. W. Smith, R. C. Handford, T. D. Tilley, Organometallics
2019, 38, 4060 –4065; b) H.-J. Liu, M. S. Ziegler, T. D. Tilley,
Angew. Chem. 2015, 127, 6722 –6726; c) H.-J. Liu, J. GuihaumØ,
T. Davin, C. Raynaud, O. Eisenstein, T. D. Tilley, J. Am. Chem.
Soc. 2014, 136, 13991 –13994; d) M. E. Fasulo, E. Calimano, J. M.
Buchanan, T. D. Tilley, Organometallics 2013, 32, 1016 –1028;
e) M. E. Fasulo, T. D. Tilley, Chem. Commun. 2012, 48, 7690 –
7692; f) J. GuihaumØ, C. Raynaud, O. Eisenstein, L. Perrin, L.
Maron, T. D. Tilley, Angew. Chem. Int. Ed. 2010, 49, 1816 –1819;
Angew. Chem. 2010, 122, 1860 –1863; g) P. G. Hayes, C. W.
Gribble, R. Waterman, T. D. Tilley, J. Am. Chem. Soc. 2009, 131,
4606 –4607; h) P. G. Hayes, R. Waterman, P. B. Glaser, T. D.
[4] a) T. P. Dhungana, H. Hashimoto, M. Ray, H. Tobita, Organo-
metallics 2020, 39, 4350 –4361; b) T. Fukuda, T. Yoshimoto, H.
Hashimoto, H. Tobita, Organometallics 2016, 35, 921 –924; c) H.
Hashimoto, T. Fukuda, H. Tobita, M. Ray, S. Sakaki, Angew.
Chem. Int. Ed. 2012, 51, 2930 –2933; Angew. Chem. 2012, 124,
2984 –2987; d) H. Hashimoto, T. Tsubota, T. Fukuda, H. Tobita,
Chem. Lett. 2009, 38, 1196 –1197; e) T. Watanabe, H. Hashimoto,
H. Tobita, Angew. Chem. Int. Ed. 2004, 43, 218 –221; Angew.
Chem. 2004, 116, 220 –223.
5888
www.angewandte.org ꢀ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 5882 –5889

Angewandte
Research Articles
Chemie
Tilley, Organometallics 2009, 28, 5082 –5089; i) A. Shinohara, J.
[29] a) C. Jones, T. J. Hadlington, Chem. Commun. 2014, 50, 2321 –
McBee, T. D. Tilley, Inorg. Chem. 2009, 48, 8081 –8083.
[21] K. M. Krebs, S. Freitag, J. J. Maudrich, H. Schubert, P. Sirsch, L.
Wesemann, Dalton Trans. 2018, 47, 83 –95.
[22] a) B. Wrackmeyer, in Annual Reports on NMR Spectroscopy,
Vol. 38 (Ed.: G. A. Webb), Academic Press, San Diego, 1999,
pp. 203 –264; b) B. Wrackmeyer, K. Horchler, in Ann. Rep.
NMR Spec., Vol. 22 (Ed.: G. A. Webb), Academic Press, San
Diego, 1990, pp. 249 –306.
2323; b) J. Li, C. Schenk, C. Goedecke, G. Frenking, C. Jones, J.
Am. Chem. Soc. 2011, 133, 18622 –18625.
[30] K. Inomata, T. Watanabe, Y. Miyazaki, H. Tobita, J. Am. Chem.
Soc. 2015, 137, 11935 –11937.
[31] R. C. Turnell-Ritson, J. S. Sapsford, R. T. Cooper, S. S. Lee, T.
Fçldes, P. A. Hunt, I. Pµpai, A. E. Ashley, Chem. Sci. 2018, 9,
8716 –8722.
[32] A. V. Protchenko, J. I. Bates, L. M. A. Saleh, M. P. Blake, A. D.
Schwarz, E. L. Kolychev, A. L. Thompson, C. Jones, P. Mount-
ford, S. Aldridge, J. Am. Chem. Soc. 2016, 138, 4555 –4564.
[33] a) M. Kilian, H. Wadepohl, L. H. Gade, Organometallics 2008,
27, 524; b) M. Kilian, H. Wadepohl, L. H. Gade, Eur. J. Inorg.
Chem. 2008, 1892 –1900; c) J. Martincovµ, R. Dostµlovµ, L.
[23] H. Rohde, M. Menzel, F. Renz, A. C. Filippou, Hyperfine
Interact. 2008, 185, 129 –132.
[24] G. H. Spikes, J. R. Giuliani, M. P. Augustine, I. Nowik, R. H.
Herber, P. P. Power, Inorg. Chem. 2006, 45, 9132 –9136.
[25] T. Chu, G. I. Nikonov, Chem. Rev. 2018, 118, 3608 –3680.
[26] a) L. Pu, B. Twamley, P. P. Power, J. Am. Chem. Soc. 2000, 122,
3524 –3525; b) P. P. Power, Acc. Chem. Res. 2011, 44, 627 –637;
c) Y. Peng, X. Wang, J. C. Fettinger, P. P. Power, Chem.
Commun. 2010, 46, 943 –945; d) Y. Peng, B. D. Ellis, X. Wang,
J. C. Fettinger, P. P. Power, Science 2009, 325, 1668 –1670; e) Y.
Peng, M. Brynda, B. D. Ellis, J. C. Fettinger, E. Rivard, P. P.
Power, Chem. Commun. 2008, 6042 –6044; f) P. P. Power,
Organometallics 2007, 26, 4362 –4372; g) C. Cui, M. M. Olm-
stead, J. C. Fettinger, G. H. Spikes, P. P. Power, J. Am. Chem. Soc.
2005, 127, 17530 –17541; h) C. Cui, M. M. Olmstead, P. P. Power,
J. Am. Chem. Soc. 2004, 126, 5062 –5063; i) L. Pu, A. D. Phillips,
A. F. Richards, M. Stender, R. S. Simons, M. M. Olmstead, P. P.
Power, J. Am. Chem. Soc. 2003, 125, 11626 –11636; j) A. D.
Phillips, R. J. Wright, M. M. Olmstead, P. P. Power, J. Am. Chem.
Soc. 2002, 124, 5930 –5931; k) M. Stender, A. D. Phillips, R. J.
Wright, P. P. Power, Angew. Chem. Int. Ed. 2002, 41, 1785 –1787;
Angew. Chem. 2002, 114, 1863 –1865.
˚
Dostµl, A. Ruzicka, R. Jambor, Organometallics 2009, 28, 4823 –
4828.
[34] a) C. Cheng, J. F. Hartwig, J. Am. Chem. Soc. 2014, 136, 12064 –
12072; b) L. Turculet, J. D. Feldman, T. D. Tilley, Organometal-
lics 2004, 23, 2488 –2502.
[35] G. Thiele, Y. Franzke, F. Weigend, S. Dehnen, Angew. Chem. Int.
Ed. 2015, 54, 11283 –11288; Angew. Chem. 2015, 127, 11437 –
11442.
[36] Deposition Number(s) 2042784 (for 3), 2042791 (for 7), 2042794
(for 8b), 2042785 (for 8), 2042787 (for 10), 2042786 (for 11),
2042790 (for 12), 2042792 (for 13), 2042789 (for 14), 2042788 (for
15), and 2042793 (for 16) contain(s) the supplementary
crystallographic data for this paper. These data are provided
free of charge by the joint Cambridge Crystallographic Data
Centre and Fachinformationszentrum Karlsruhe Access Struc-
tures service www.ccdc.cam.ac.uk/structures.
[27] G. H. Spikes, J. C. Fettinger, P. P. Power, J. Am. Chem. Soc. 2005,
127, 12232 –12233.
[28] S. Wang, T. J. Sherbow, L. A. Berben, P. P. Power, J. Am. Chem.
Soc. 2018, 140, 590 –593.
Manuscript received: November 25, 2020
Accepted manuscript online: January 13, 2021
Version of record online: February 1, 2021
Angew. Chem. Int. Ed. 2021, 60, 5882 –5889
ꢀ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH www.angewandte.org
5889