Solvent-free cyanosilylation of aromatic and heteroaryl aldehydes catalyzed by a cationic iron N-heterocyclic carbene complex at ambient temperature under UV irradiation

Article abstract of DOI:10.1016/j.ica.2019.119003

The cyanosilylation of aromatic aldehydes and heteroaryl aldehydes with trimethylsilyl cyanide (TMSCN) is efficiently catalyzed by an iron complex of the type {[3-isopropyl-1-(1R-phenylethyl)imidazol-2-ylidene]Fe(CO)₂}I (3) in presence of UV li

Full text of DOI:10.1016/j.ica.2019.119003

InorganicaChimicaActa495(2019)119003
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Research paper
Solvent-free cyanosilylation of aromatic and heteroaryl aldehydes catalyzed
by a cationic iron N-heterocyclic carbene complex at ambient temperature
under UV irradiation
Dharmendra Kumar, A.P. Prakasham, Manoj Kumar Gangwar, Prasenjit Ghosh
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India
A R T I C L E I N F O
A B S T R A C T
Keywords:
The cyanosilylation of aromatic aldehydes and heteroaryl aldehydes with trimethylsilyl cyanide (TMSCN) is
efficiently catalyzed by an iron complex of the type {[3-isopropyl-1-(1R-phenylethyl)imidazol-2-ylidene]Fe
(CO)2}I (3) in presence of UV light (λ = 294 nm) in moderate to excellent yields under ambient temperature.
The heteroaryl aldehydes exhibited higher yields than the aromatic ones, and the aromatic aldehydes, bearing
electron donating groups (EDG), exhibited higher yields over the ones with the electron withdrawing groups
(EWG). A proposed catalytic cycle initiates with an active species (A), formed by the dissociation from the iron
complex (3), and proceeds via an aldehyde activated species (B), and that upon reaction with TMSCN gives the
desired cyanosilylated product. Quite significantly, the initial active iron species (A) and the iron-bound α-
cyanobenzyloxy species (C) have been detected by mass spectrometry. Additionally, the formation of species (C)
was further corroborated by the observation of the formation of TMSI in 29Si NMR experiment.
Iron
N-Heterocyclic carbene (NHC)
Cyanosilylation
Homogeneous catalysis
Aromatic and heteroaryl aldehydes
1. Introduction
reaction of 1,3-dicarbonyl compounds with amines [47], and pro-
ceeding further along the line, we decided to study its application in
The realization of the potential of iron in chemical catalysis has
attracted attention lately, particularly from the viewpoint of its utility
as a substitute for the wide-spread applicability of expensive metals like
Pd [1], Rh [2], and Ir [3], based catalysts [4,5]. Iron being cheap, earth
abundant and environmentally benign readily fits as a viable alter-
native to the existing transition metal based catalysts [6,7]. Over the
years a formidable portfolio of iron catalysis [6–11] from CeH bond
activations [12–17], to reductions [18–22], to hydrosilylations [23–27]
to CeC [28] and CeO [29] cross-couplings [30], to olefin isomeriza-
tions [20] to even in the asymmetric synthesis [31–37] have emerged.
With our objective being the exploration of the potential of the
transition metal N-heterocyclic carbene complexes in biomedical ap-
plications [38–40] and in chemical catalysis [41–44], we became in-
terested in studying the catalytic potential of iron N-heterocyclic car-
bene complexes in chemical catalysis [45]. We rationalized that as the
N-heterocyclic carbenes are extremely successful as ligands in the do-
main of transition metal mediated homogeneous catalysis, the same is
well suited for exploring the potential of iron in catalysis. In this regard,
we have recently reported the utility of iron N-heterocyclic carbene
complexes in hydrosilylation reactions [45], in asymmetric Michael
addition reactions [46], and in the synthesis of β-enaminones from the
another important CeC bond forming reaction namely, the cyanosily-
lation reaction.
Our interest in cyanosilylation reaction arises primarily for its utility
in synthesizing industrially valuable and versatile intermediates like the
α-hydroxy, β-amino alcohols along with various other biologically ac-
tive compounds [48]. Specifically, the cyanosilylation reaction pro-
ceeds with the formation of cyanohydrin silylated ethers that can be
transformed to other value-added chemicals bearing different func-
tionalities. The cyanosilylation reaction has been extensively studied in
the areas of heterogeneous [49–51] and homogeneous catalysis
[52–57] including the Ligand Assisted Catalysis (LAC) [58,59], the
organocatalysis [60–62], by simple metal salts [63–65] and even under
catalyst-free conditions [66]. However, the studies on the use of well-
defined catalysts with focus on elucidating the catalytic cycle remains
comparatively few [10,53–55,67–75]. In the absence of any prior report
of the utility of iron N-heterocyclic carbene complexes in cyanosilyla-
tion reactions, we became interested in exploring the same as a part of
our continued interest in the reaction [67].
In this manuscript, we report the synthesis of an iron N-heterocyclic
carbene complex (3) of the type, {[3-isopropyl-1-(1R-phenylethyl)imi-
dazol-2-ylidene]Fe(CO)2}I (Fig. 1) that efficiently carried out the
E-mail addresses: dharam@chem.iitb.ac.in (D. Kumar), prakasham25@chem.iitb.ac.in (A.P. Prakasham), manojkg@chem.iitb.ac.in (M.K. Gangwar),
pghosh@chem.iitb.ac.in (P. Ghosh).
https://doi.org/10.1016/j.ica.2019.119003
Received 13 April 2019; Received in revised form 11 June 2019; Accepted 4 July 2019
Availableonline06July2019
0020-1693/©2019ElsevierB.V.Allrightsreserved.

D. Kumar, et al.
InorganicaChimicaActa495(2019)119003
benzimidazol-2-ylidene]Fe(CO)2}I
type
complexes
{R1 = Et
I
i-Pr
[1.972(5) Å], i-Pr [1.972(4) Å] and n-Bu [1.965(5) Å]} [45], and the
imidazole based {Cp[1-benzyl-3-R2-imidazol-2-ylidene]Fe(CO)2}PF6
type complexes {R2 = Me [1.9753(19) Å] and Et [1.977(4) Å]} [45],
{[1,3-diisopropylimidazol-2-ylidene]Fe(CO)2}PF6 [1.970(3) Å] [73],
{[1,3-diisopropylimidazol-2-ylidene]Fe(CO)2}I [1.9742(16) Å] [72]
N
N
Fe
CO
CO
Ph
( )
3
and
{[1,3-bis-2,6-diisopropylphenylimidazol-2-ylidene]Fe(CO)2}I
[1.990(2) Å] [72] Similarly, the two metal bound carbonyls showed
near equal Fe-CCO bond distances of 1.779(3) Å and 1.773(3) Å in the
iron complex (3) and were similar to that observed in the related
analogs namely, the benzimidazole based {Cp[1,3-di-R1-benzimidazol-
2-ylidene]Fe(CO)2}I type complexes {R1 = Et [1.765(5) Å and
1.780(5) Å], i-Pr [1.780(4) Å and 1.770(4) Å] and n-Bu [1.774(5) Å and
1.783(5) Å]} [45] and the imidazole based {Cp[1-benzyl-3-ethyl-imi-
Fig. 1. Iron complex (3) of an imidazole derived N-heterocyclic carbene.
cyanosilylation reaction of wide range of aromatic and heteroaryl al-
dehydes under ambient condition in presence of UV irradiation
(λ = 294 nm).
dazol-2-ylidene]Fe(CO)2}PF6 type complex [1.782(4)
Å
and
1.777(4) Å] [45],
{[1,3-diisopropylimidazol-2-ylidene]Fe(CO)2}I
2. Results and discussions
[1.7797(19) Å and 1.7801(19) Å] [72] and {[1,3-bis-2,6-diisopropyl-
phenylimidazol-2-ylidene]Fe(CO)2}I [1.780(3) Å and 1.781(3) Å] [72].
The two carbonyls moieties in the iron complex (3) are bound to the
metal centre at a right angle to each other [∠C20–Fe1–C1 91.0(2)]
(Table 1). The iodide anion remains non-bonded and was located at a
far off distance of 5.725 Å from the metal centre in the iron complex
(3).
With the intent of exploring the potential of the iron N-heterocyclic
carbene complexes as catalysts in the cyanosilylation of aldehydes, a
cationic iron complex (3) stabilized by 3-isopropyl-1-(1R-phenylethyl)
imidazol-2-ylidene was synthesized. Specifically, the reaction of the 3-
isopropyl-1-(1R-phenylethyl)imidazolium bromide (2) with the CpFe
(CO)2I in the presence of KN(SiMe3)2 gave the iron complex (3) in 37%
yield (Scheme 1) by following an earlier reported procedure for the
related iron N-heterocyclic carbene complexes [72,73,75–78]. The
imidazolium bromide salt (2) was conveniently synthesized by the al-
kylation reaction of 1-(1R-phenylethyl)imidazole (1) with isopropyl
bromide in 57% yield.
The iron complex (3) successfully carried out the cyanosilylation
reaction of aryl (Eq. (1)) and heteroaryl aldehydes (Eq. (2)) at 1 mol%
catalyst loading in good yields 28–93% at ambient temperature
(Table 2). Significant enhancement of the cyanosilylation reaction yield
of 10% was observed when the catalysis was carried out in presence of
UV irradiation at wavelength (λ = 294 nm) as opposed to the run
performed under the ordinary ambient daylight for the representative
substrates benzaldehyde and trimethylsilyl cyanide (TMSCN) (Table S2,
Supporting Information, entry 1). The exclusion of light under similar
condition yielded 54% of product yield for the same substrates (Table
S2, entry 1). Similar enhancement of the product yields for the iron
complex (3) by 36% and 61% respectively were observed with respect
to the control experiment performed with CpFe(CO)2I, exhibiting pro-
duct yield of 54%, and the blank experiment, exhibiting product yield
of 29%, (Table S2, entries 2 and 3) performed in absence of iron
complex (3) for the same two substrates. In particular, when cyanosi-
lylation of benzaldehyde was performed with the ligand precursor (2)
and also with a 1:1 mixture of iron complex (3) and ligand precursor (2)
at 1 mol% catalyst loading, then an yield of 39% and 88% (Table S2,
entries 4 and 6) respectively was observed. This indicates the vital role
played by the iron catalyst (3) in the cyanosilylation reaction. The
homogeneity of the reaction mechanism can be ascertained from the
mercury drop experiment performed for the two representative sub-
strates namely, benzaldehyde and TMSCN as catalyzed by the iron N-
heterocyclic carbene catalyst (3), and which showed comparable yields
of 88% as opposed to that of 90% when performed in the absence of Hg.
In this context, it must be noted that the mercury might not inhibit iron
nanoparticle based catalysts [82–84]. Lastly, the time-dependence
study gave an optimum reaction time of 6 h (Table S3).
The diamagnetic nature of iron complex (3) has been appropriately
characterized by various NMR spectroscopies. For instance, the char-
acteristic cyclopentadienyl (Cp) resonance appeared as a singlet at
5.38 ppm in 1H NMR and at 87.3 ppm in the 13C{1H} NMR spectrum
while the Fe–Ccarbene resonance observed at 164.1 ppm in the 13C{1H}
NMR. Likely, the infrared spectrum of the Fe-NHC complex (3) showed
two carbonyl stretching frequencies (νCO) at 2046 cm−1 and 1992 cm−1
and thereby specifies the presence of two CO ligands attached to the
iron centre, which are in the range of the νCO of the related Fe-NHC
complexes {[1,3-dimesitylimidazol-2-ylidene]Fe(CO)2}I [νCO at
2050 cm−1 and 2005 cm−1] [75], {[1,3-diisopropylimidazol-2-ylidene]
Fe(CO)2}I [νCO at 2049 cm−1 and 2001 cm−1] [73], and {[1-methyl-3-
picolylimidazol-2-ylidene]Fe(CO)2}I
[νCO
at
2049 cm−1
and
2002 cm−1) [73] and other reported related complexes [45,79–81]
(Table 1). Furthermore, the carbonyl moieties were appeared at highly
downfield region 210.1–211.1 ppm in the 13C{1H} NMR spectrum.
The molecular structure of iron N-heterocyclic carbene complex (3)
showed the metal centre in a “piano stool” geometry similar to that
reported for other related iron complexes (Table S1 and Fig. 2)
[45,79,80]. In particular, the iron centre is found bound to the cyclo-
pentadienyl moiety (Cp), the N-heterocyclic carbene ligand, 3-iso-
propyl-1-(1R-phenylethyl)imidazol-2-ylidene and two carbonyl moi-
eties in a tetrahedral environment. The Fe–Ccarbene bond distance of
1.976(3) in the iron complex (3) is similar to that observed in the re-
lated analogs namely, the benzimidazole based {[Cp[1,3-di-R1-
Quite significantly, a series of aromatic and heteroaryl aldehyde
Scheme 1. Synthetic route to the iron complex (3)
i-Pr
I
of an imidazole derived N-heterocyclic carbene li-
N
N
CpFe(CO)2I
gand.
+
i-PrBr
N
N
N
Fe
N
i-Pr
KN(SiMe3)2
Ph
CO
Ph
Br
CO
Ph
3
( )
2
( )
1
( )
2

D. Kumar, et al.
InorganicaChimicaActa495(2019)119003
Table 1
Structural comparison with literature data.
Complex
IR νCO cm−1
Fe–Ccarbene bond distance (Å)
1.976(3)
Fe–CCO bond distance (Å)
1.779(3) and 1.773(3)
∠CCO–Fe–CCO bond angle (°)
Refs.
2046 and 1992
91.0(2)
This work
2049 and 2001
2049 and 2006
1.9742(16)
1.990(2)
1.7797(19) and 1.7801(19)
1.780(3) and 1.781(3)
92.33(8)
[72,73]
[72]
90.97(14)
2038 and 1989
1.9753(19)
1.777(2) and 1.777(2)
93.86(9)
[45]
substrates successfully underwent cyanosilylation reaction in good to
excellent yields (Table 2, entry 1–13) under ambient condition. As ex-
pected, the aromatic aldehydes bearing electron donating groups (EDG)
cyanosilylated product (11–13) in low to moderate, 28–49% yields.
Quite interestingly, the heteroaromatic aldehydes namely, 2-picoli-
naldehyde, furfural and thiophene-2-aldehyde too gave cyanosilylated
products (14–16) in near quantitative yields 90–93%. It is noteworthy
that the heteroaryl aldehydes exhibited higher yields than the aromatic
ones, and the aromatic aldehydes, bearing electron donating groups
(EDG), exhibited higher yields over the ones with the electron with-
drawing groups (EWG). Unfortunately, no chiral induction was ob-
tained for any of the substrates.
namely,
benzaldehyde,
4-methylbenzaldehyde,
3-methox-
ybenzaldehyde, 4-methoxybenzaldehyde, 2,5-dimethoxybenzaldehyde,
3,4-dimethoxybenzaldehyde and 2,4,5-trimethoxybenzaldehyde gave
the cyanosilylated product (4–10) in moderate to good, 72–90% yields,
and along the same line, the aromatic aldehydes bearing electron
withdrawing groups (EWG) namely, 2-chlorobenzaldehyde, 4-ni-
trobenzaldehyde and 4-cyanobenzaldehyde substrates gave the
(1)
3

D. Kumar, et al.
InorganicaChimicaActa495(2019)119003
Table 2
Selected results for the solvent free cyanosilylation reaction of aromatic alde-
hydes including heteroaryl aldehydes and TMSCN substrates as catalyzed by the
Fe–NHC complex (3).
S. No
Aryl aldehydes
Products
yielda
90
1
2
3
81
77
Fig. 2. ORTEP of 3 ellipsoids are at 50% probability. All hydrogen atoms have
been omitted for clarity. Selected bond lengths (Å) and angles (°): Fe1–C1
1.977(3), Fe1–C20 1.781(4), Fe1–C21 1.778(4), O1–C20 1.137(4), O2–C21
1.138(4), N1–C1 1.366(4), N2–C1 1.354(4), C20–Fe1–C21 91.57(15),
C20–Fe1–C1 94.51(15), C21–Fe1–C1 95.73(15), N2–C1–Fe1 128.0(3),
N1–C1–Fe1 127.5(3), N2–C1–N1 104.4(3), O1–C20–Fe1 177.6(3), O2–C21–Fe1
176.6(3).
4
5
6
88
87
83
Eq. (1). General equation for the cyanosilylation reaction of aro-
matic aldehyde substrates catalyzed by Fe–NHC complex (3).
7
8
72
49
(2)
Eq. (2). General equation for the cyanosilylation reaction of het-
9
28
46
eroaryl aldehyde substrates catalyzed by Fe–NHC complex (3).
In the absence of any prior report of the use of the iron N-hetero-
cyclic carbene complexes in the cyanosilylation reaction, a comparison
of the catalysis results of the iron complex (3) is made with the handful
of iron catalysts known in literature for the cyanosilylation reaction
[63,69]. For example, a ferrocenium complex, Fe(Cp)2PF6 exhibited
93% of the cyanosilylated product yield for the reaction between ben-
zaldehyde and TMSCN at room temperature after 10 h of reaction time
at 2.5 mol% of catalyst loading under solvent-free conditions [69]
whereas, the iron complex (3) exhibited 90% of the product yield for
the same two substrates at room temperature after 6 h of reaction time,
at 1 mol% of catalyst loading also under solvent-free conditions under
UV irradiation (λ = 294 nm). Quite interestingly, the same Fe(Cp)2PF6
catalyst exhibited a lower yield of 65% in case of furfural and of 68% in
case of thiophene-2-aldehyde substrates for the cyanosilylation reaction
with TMSCN at room temperature after 10 h of reaction time at 2.5 mol
% of catalyst loading under solvent-free conditions [69], while the iron
complex (3) exhibited much superior yields of 93% in case of furfural
and of 90% in case of thiophene-2-aldehyde substrates with TMSCN at
room temperature after 6 h of reaction time at 1 mol% of catalyst
loading under solvent-free conditions in the presence of the UV irra-
diation (λ = 294 nm). Additionally another report exists of a FeCl3 salt,
for which the cyanosilylation followed by esterification were performed
to yield the cyanoester compounds in excellent yields [63]. Another
10
11
12
92
93
13
90
Reaction condition: aromatic aldehydes and hetero-aryl aldehydes (1.00 mmol),
TMSCN (0.297 g, 3.00 mmol), in presence of 1 mol% of catalyst. Reaction time
6 h at 27 °C.
a
Isolated yield.
4

D. Kumar, et al.
InorganicaChimicaActa495(2019)119003
I
regeneration of the iron N-heterocyclic carbene precatalyst (A). Ad-
ditionally, the cyanosilylation reaction of benzaldehyde with Zn(CN)2,
as cyanide source, and TMSI, as TMS source, was successfully catalyzed
by the iron N-heterocyclic carbene complex (3) yielding 2-phenyl-2-
trimethylsilyloxyacetonitrile (4) in CH2Cl2 (3 mL) both in the presence
and in the absence of UV irradiation (λ = 294 nm) in 6 h at 27 °C in
87% and 83% yields respectively (Table 3, entry 1) in agreement with
the proposed mechanism of the catalytic cycle. As expected, no product
formation was observed in absence of the pre-catalyst, iron N-hetero-
cyclic carbene complex (3) for the benzaldehyde, Zn(CN)2 and TMSI
(Table 3, entry 2).
i-Pr
N
N
Fe
CO
CO
Ph
(3)
hν
CO
I
i-Pr
N
N
Fe
CO
TMSO
O
3. Conclusion
CN
Ph
Ph
Ph
(4)
(A)
In summary, a cationic iron complex (3) stabilized over 3-isopropyl-
1-(1R-phenylethyl)imidazol-2-ylidene was synthesized and structurally
characterized. The iron complex (3) successfully performed the cya-
nosilylation of aromatic and heteroaryl aldehydes at 27 °C under sol-
vent free condition in good to excellent yields under UV irradiation
(λ = 294 nm). Significantly enough, the heteroaryl aldehydes exhibited
higher yields than the aromatic ones, and the aromatic aldehydes,
bearing electron donating groups (EDG), exhibited higher yields over
the ones with the electron withdrawing groups (EWG). However, no
chiral induction was obtained in the cyanosilylation reaction. In addi-
tion, the two catalytically relevant key intermediate species namely, the
initial active iron species (A) of the type {[3-isopropyl-1-(1R-pheny-
lethyl)imidazol-2-ylidene]Fe(CO)}I and iron-bound α-cyanobenzyloxy
species (C) have been detected in the mass spectrometry and along the
side the observation of TMSI in 29Si NMR also points towards the for-
mation of the iron-bound α-cyanobenzyloxy species (C) intermediates
in the catalytic cycle.
TMS
I
i-Pr
i-Pr
I
N
N
N
N
Fe
Fe
O
O
CN
CO
Ph
CO
Ph
Ph
(B)
Ph
(C)
TMS
I
i-Pr
CN
δ
δ
N
N
TMS
CN
TMS
I
Fe
CO
O
Ph
Ph
Scheme 2. Proposed mechanism for the iron N-heterocyclic carbene complex
(3) catalyzed cyanosilylation of benzaldehyde with TMSCN.
4. Experimental section
4.1. General procedures
report of the cyanosilylation of p-cyanobenzaldehyde and p-methyl-
benzaldehyde substrates exhibited near quantitative yield under cata-
lyst free condition [66].
All operations and handlings were carried out using glovebox and
standard Schlenk techniques. Purification of solvents have been per-
formed by using standard procedures. KN(SiMe3)2, from Sigma Alderich
(USA) were purchased and used without any further purification. 1-(1R-
phenylethyl)imidazole (1) [85] and CpFe(CO)2I [86,87], were synthe-
sized according to literature procedures. 1H, 13C{1H} and 29Si NMR
spectra were recorded on Bruker 400 MHz and 500 MHz NMR spec-
trometer. 1H NMR peaks are labeled as singlet (s), doublet (d), triplet
(t), quartet (q) broad (br), triplet of triplets (tt), doublet of doublets
(dd), multiplet (m), and septet (sept). Infrared spectra has been done on
the Elmer Spectrum One FT-IR spectrometer. Mass spectrometry ana-
lysis were being done on a Micromass Q-Tof and Bruker Maxis Impact
spectrometer. Optical rotation for compound (2–3) were being carried
out on Autopol IV, Serial #82083. Thermo Quest FLASH 1112 SERIES
(CHNS) Elemental Analyzer was used for collecting CHNS data. X-ray
diffraction data for Fe–NHC complex (3) was collected on a Rigaku Hg
724 + diffractometer and refinement parameters and crystal data col-
lection are summarized in Table S1. The structure was solved by using
direct methods and standard difference map techniques, and were re-
fined by full-matrix least-squares procedures on F2 with SHELXTL
(Version 6.10) [88,89]. The GCMS analysis for the catalysis runs were
performed by using Agilent Technologies 7890A GC systems with
5975C inert XL EI/CI MSD Triple-Axis detector and Agilent Technolo-
gies 7890A GC systems with CP-Chirasil-Dex CB chiral column was used
for the chiral GC resolutions.
A proposed mechanism for the cyanosilylation reaction of aromatic
and heteroaryl aldehydes as catalyzed by Fe-NHC complex (3) is out-
lined in Scheme 2. The dissociation of a CO moiety from the iron N-
heterocyclic carbene precatalyst (3) would yield an activated iron
species (A) which upon reaction with benzaldehyde would yield an iron
coordinated benzaldehyde species (B) and it upon reaction with TMSCN
would give an iron-bound α-cyanobenzyloxy species (C) along with
trimethylsilyl iodide (TMSI). Indeed, the 29Si NMR spectrum of the
reaction mixture obtained during the cyanosilylation of benzaldehyde
with TMSCN, showed the presence of TMSI resonance at 7.0 ppm as
verified independently by recording the 29Si NMR spectrum of TMSI
(Fig. 4, Supporting Information Figs. S109 and S111). As expected, the
29Si NMR spectrum also showed the presence of TMSCN resonance at
−11.5 ppm and of the silylether product namely, 2-phenyl-2-tri-
methylsilyloxyacetonitrile (4), at 24.5 ppm, and which too, were ver-
ified independently by comparing with the 29Si NMR spectrum of the
pure compounds (Fig. 4 and Supporting Information Figs. S109, S110
and S112).
The mass spectrometric study performed on two representative
substrates namely, benzaldehyde and TMSCN, as catalyzed by iron N-
heterocyclic carbene complex (3) provided valuable insight on the
catalyst mode of action. Significantly enough, iron N-heterocyclic car-
bene species (A) were detected as a [M]+ peak at m/z 363.1823 [Calcd.
363.1154] and also, the iron-bound α-cyanobenzyloxy species (C) were
detected as a [M]+ peak at m/z 495.1812 [Calcd. 495.1609] (Fig. 3 and
Supporting Information Figs. S108 and S109). Lastly, the reaction of the
intermediate species (C) with the trimethylsilyl iodide (TMSI) would
yield the desired cyanosilylated catalytic product (4) along with the
4.2. Synthesis of 3-isopropyl-1-(1R-phenylethyl)imidazol-3-ium bromide
(2)
A mixture of 1-(1R-phenylethyl)imidazole (1) (1.00 g, 5.81 mmol)
5

D. Kumar, et al.
InorganicaChimicaActa495(2019)119003
intermediate species
ESI-MS spectra
i-Pr
I
N
N
Fe
CO
Ph
(A)
i-Pr
N
Fe
O
N
CN
CO
Ph
Ph
(C)
Fig. 3. ESI-MS data of the activated precatalyst iron N-heterocyclic carbene species (A) and the iron-bound α-cyanobenzyloxy species (C), that were observed in the
iron N-heterocyclic carbene complex (3) catalyzed cyanosilylation of benzaldehyde with TMSCN.
(d, 1H, 3JH–H = 1 Hz, NCHCHN), 7.34–7.29 (m, 3H, C6H5CHCH3), 6.01
3
3
(q, 1H, JH–H = 7 Hz, C6H5CHCH3), 4.89 (sept, 1H, JH–H = 7 Hz, CH
3
(CH3)2), 1.97 (d, 3H, JH–H = 7 Hz, C6H5CHCH3), 1.57 (d, 6H,
3JH–H = 7 Hz, CH(CH3)2). 13C{1H} NMR (CDCl3, 100 MHz, 25 °C):
138.0 (C6H5CHCH3), 135.1 (NCHN), 129.4 (C6H5CHCH3), 129.3
(C6H5CHCH3), 127.1 (C6H5CHCH3), 120.7 (NCHCHN), 120.2
(NCHCHN), 59.7 (C6H5CHCH3), 53.4 (CH(CH3)2), 23.2 (CH(CH3)2),
23.1 (CH(CH3)2), 21.2 (C6H5CHCH3). IR data (cm−1) KBr pellet: 3087
(s), 2980 (s), 2424 (w), 2046 (m), 1665 (m), 1551 (s), 1495 (s), 1455
(m), 1388 (m), 1331 (m), 1283 (m), 1179 (s), 1158 (s), 1074 (m), 1015
(m), 851 (m), 776 (s), 715 (s), 654 (s), 541 (m), 458 (m). HRMS (ESI):
m/z 215.1559 [C14H19BrN2−Br]+, calcd. 215.1543. Anal. Calcd. for
C14H19BrN2: C, 56.96; H, 6.49; N, 9.49; Found: C, 56.78; H, 6.80; N,
25
Fig. 4. 29Si NMR of the reaction mixture showing the intermediate TMSI
formed from the cyanosilylation of benzaldehyde with TMSCN as catalyzed by
Fe-NHC complex (3) in CDCl3.
9.59%. [α]D +69.4 (c 1.00 in CHCl3).
4.3. Synthesis of [(3-isopropyl-1-(1R-phenylethyl)imidazol-2-ylidene)CpFe
(CO)2]I (3)
and isopropyl bromide (1.73 g, 14.3 mmol) was refluxed in CH3CN
(50 mL) for 24 h. All volatiles were then removed in vacuo and the re-
sidue was extracted with dry CH2Cl2 (4 × 25 mL), filtered through ce-
lite, evaporated, washed with EtOAc (4 × 15 mL) and finally dried in
vacuo to give product 2 as a reddish liquid (1.01 g, 59%). 1H NMR
(CDCl3, 400 MHz, 25 °C): 10.51 (s, 1H, NCHN), 7.55 (d, 1H,
3JH–H = 1 Hz, NCHCHN), 7.45 (d, 2H, 3JH–H = 6 Hz, C6H5CHCH3), 7.36
To
a solution of 3-isopropyl-1-(1R-phenylethyl)imidazol-3-ium
bromide (2) (0.400 g, 1.35 mmol) in THF (10 mL), a solution of KN
(SiMe3)2 (0.401 g, 2.01 mmol) in THF (15 mL) was added and the re-
sulting mixture was stirred for 1 h at 0 °C under N2 atmosphere. A so-
lution of CpFe(CO)2I (0.775 g, 2.54 mmol) was added to it and the re-
sultant mixture was stirred for another 16 h at room temperature. All
6

D. Kumar, et al.
InorganicaChimicaActa495(2019)119003
Table 3
trimethylsilyloxyacetonitrile (12) [94], 2-(4-cyanophenyl)-2-tri-
methylsilyloxyacetonitrile (13) [95], 2-(pyridin-2-yl)-2-trimethylsily-
loxyacetonitrile (14) [96], 2-(furan-2-yl)-2-trimethylsilyloxyacetoni-
trile (15) [69] and 2-(thiophen-2-yl)-2-trimethylsilyloxyacetonitrile
(16) [69] have been isolated by column chromatography under dif-
ferent condition as has been outlined in detail individually.
Cyanosilylation reaction of benzaldehyde with Zn(CN)2 as cyanide source and
TMSI as TMS source as catalyzed by Fe–NHC complex (3).
4.5. Procedure for the control experiment by using CpFe(CO)2I
For each catalysis run, a CpFe(CO)2I (0.003 g, 0.010 mmol, 1 mol
%), benzaldehyde (0.106 g, 1.00 mmol) and TMSCN (0.297 g,
3.00 mmol) were taken in a 3 mL quartz cuvette and the resulting so-
lution was irradiated for 6 h at 27 °C in presence of UV light
(λ = 294 nm). The crude product was further purified by column
chromatography using neutral Al2O3 as a stationary phase and eluting
with petroleum ether/EtOAc (v/v 99:1) to give the cyanosilylated
product 4 as a colorless liquid (0.110 g, 54%).
S. No.
1
Catalyst
Yielda in absence of
UV irradiation (%)
Yielda in presence of
UV irradiation (%)
83
87
4.6. General procedure for 29Si NMR spectroscopy
(3)
2
Without Fe–NHC (3)
ND
ND
In a typical run, a 3 mL quartz cuvette was charged with a mixture
of the iron N-heterocyclic carbene precatalyst (3) (0.005 g, 0.01 mmol),
benzaldehyde (0.106 g, 1.00 mmol) and TMSCN (0.297 g, 3.00 mmol)
and the resultant mixture was irradiated for 3 h in presence of UV light
(λ = 294 nm) at 27 °C. Then, 0.04 mL solution mixture in 3 mL CDCl3
were taken in NMR tube and the resultant solution was used for 29Si
NMR spectroscopy.
Reaction condition: benzaldehyde (0.106 g, 1.00 mmol), TMSI (0.240 g,
1.20 mmol) and Zn(CN)2 (0.234 g, 2.00 mmol) in presence of 3.8 mol % of
catalyst in CH2Cl2 (3.00 mL). Reaction time 6 h, 27 °C.
a
Isolated yields, ND = Not detected.
volatiles were then removed in vacuo to give the crude product as a
brown residue which was purified by column chromatography using
silica gel as a stationary phase and by eluting it with a CHCl3/MeOH
mixture (v/v 96:4) to give the product 3 as an yellow solid (0.251 g,
37%). 1H NMR (CDCl3, 500 MHz, 25 °C): δ 7.52 (s, 1H, NCHCHN), 7.41
(t, 2H, 3JH–H = 6 Hz, C6H5CHCH3), 7.36 (s, 1H, NCHCHN), 7.34 (t, 1H,
4.7. General procedure for mass spectrometry experiments
The molecular weights of the iron N-heterocyclic carbene complex
(3) and iron-bound α-cyanobenzyloxy specie (C) formed from the iron
N-heterocyclic carbene complex (3) were detected by DIESI-MS (Direct-
injection Electrospray Mass Spectrometry) studies done on a BRUKER
maxis impact. The mass analyses were being carried out in positive ion
detection modes on an ion trap mass spectrometer with an ESI source.
Parameters for the ESI-MS (Direct-injection Electrospray Mass
Spectrometry) study were taken according to previous reported method
[46] and were as follows: dry gas flow rate (4 L/min), dry gas tem-
perature (180 °C), nebulizer gas (N2, 0.3–0.5 bar), set charging voltage
(2000 V), spray shield voltage (500 V), capillary voltage (3700 V), set
APCI heater (0 °C) purge flow rate of 200.0 μL h−1 and syringe diameter
of 4.610 mm. The instrument data was attained within a mass range
from m/z 50 to 1500 and NaI-CsI mixture was used to calibrate the
spectrometer. Optimization of the formation of fragment ions by per-
forming several runs at various collision gas pressures and energies,
that aided in the explanation of spectra.
3
3JH–H = 6 Hz, C6H5CHCH3), 7.05 (d, 2H, JH–H = 6 Hz, C6H5CHCH3),
6.01 (q, 1H, 3JH–H = 6 Hz, C6H5CHCH3), 5.38 (s, 5H, C5H5), 5.10 (sept,
3
1H, JH–H = 6 Hz, CH(CH3)2), 1.96 (d, 3H, 3JH–H = 6 Hz, C6H5CHCH3),
3
3
1.63 (d, 3H, JH–H = 6 Hz, CH(CH3)2), 1.61 (d, 3H, JH–H = 6 Hz, CH
(CH3)2). 13C{1H} NMR (CDCl3, 100 MHz, 25 °C): 211.1 (CO), 210.1
(CO), 164.1 (NCN), 140.2 (C6H5CHCH3), 129.4 (C6H5CHCH3), 128.4
(C6H5CHCH3), 125.6 (C6H5CHCH3), 124.3 (NCHCHN), 122.6
(NCHCHN), 87.3 (C5H5), 59.9 (C6H5CHCH3), 54.1 (CH(CH3)2), 24.4
(CH(CH3)2), 23.9 (CH(CH3)2), 23.2 (C6H5CHCH3). IR data (cm−1) KBr
pellet (νCO): 2046 (s) and 1992 (s). HRMS (ESI): m/z 391.1103
[C21H23FeIN2O2−I]+
,
calcd.
391.1104.
Anal.
Calcd.
for
C21H
FeIN2O2: C, 48.68; H, 4.47; N, 5.41; Found: C, 48.97; H, 4.27; N,
23
25
5.48%. [α]D +65.0 (c 1.00 in CHCl3).
4.4. General procedure for cyanosilylation of aldehydes by using Fe–NHC
complex (3)
For each catalysis run, an Fe–NHC complex (3) (0.010 mmol), 1 mol
%), aryl aldehyde substrate (1.00 mmol) and TMSCN (3.00 mmol) were
taken in a 3 mL quartz cuvette and the resulting solution was irradiated
for 6 h at 27 °C in presence of UV light (λ = 294 nm). The crude product
was further purified by column chromatography using neutral Al2O3 as
a stationary phase and eluting with petroleum ether/EtOAc (v/v
99:1–70:30) to give the cyanosilylated product (4–16). The catalysis
products 2-phenyl-2-trimethylsilyloxyacetonitrile (4) [90], 2-(p-tolyl)-
2-trimethylsilyloxyacetonitrile (5) [90], 2-(3-methoxyphenyl)-2-tri-
methylsilyloxyacetonitrile (6) [69], 2-(4-methoxyphenyl)-2-tri-
methylsilyloxyacetonitrile (7) [69], 2-(2,5-dimethoxyphenyl)-2-tri-
methylsilyloxyacetonitrile (8) [91], 2-(3,4-dimethoxyphenyl)-2-
trimethylsilyloxyacetonitrile (9) [92], 2-(2,4,5-trimethoxyphenyl)-2-
trimethylsilyloxyacetonitrile (10) [93], 2-(2-chlorophenyl)-2-tri-
4.8. Procedure for the direct ionization ESI-MS detection of the iron-bound
α-cyanobenzyloxy species (C) formed from the iron N-heterocyclic carbene
precatalyst (3)
In a typical run, a 3 mL quartz cuvette was charged with a mixture
of the iron N-heterocyclic carbene precatalyst (3) (0.020 g,
0.038 mmol), benzaldehyde (0.050 g, 0.500 mmol) and TMSCN
(0.099 g, 1.00 mmol) and the resultant mixture was irradiated at room
temperature for 1 h in presence of UV light (λ = 294 nm) at 27 °C. The
reaction mixture was then diluted with 10 mL of CH3CN and an aliquot
of the sample solution was directly injected into the ESI/MS to obtain
the mass spectrometric data for the iron-bound α-cyanobenzyloxy
species (C).
methylsilyloxyacetonitrile
(11)
[94],
2-(4-nitrophenyl)-2-
7

D. Kumar, et al.
InorganicaChimicaActa495(2019)119003
4.9. General procedure for the reaction of benzaldehyde, TMSI and Zn
(CN)2 as catalyzed by Fe–NHC complex (3) yielding 2-phenyl-2-
trimethylsilyloxyacetonitrile (4) with and without UV irradiation at 294 nm
[26] D. Noda, A. Tahara, Y. Sunada, H. Nagashima, J. Am. Chem. Soc. 138 (2016)
2480–2483.
[27] B. Cheng, W. Liu, Z. Lu, J. Am. Chem. Soc. 140 (2018) 5014–5017.
[28] Y. Liu, J. Xiao, L. Wang, Y. Song, L. Deng, Organometallics 34 (2015) 599–605.
[29] W.-H. Wen, A.-N. Xie, H.-H. Wang, D.-X. Zhang, A. Ali, X. Ying, H.-Y. Liu,
Tetrahedron 73 (2017) 7169–7176.
A mixture of Fe–NHC complex (3) (0.020 g, 0.038 mmol, 3.8 mol%),
benzaldehyde (0.106 g, 1.00 mmol), Zn(CN)2 (0.234 g, 1.00 mmol) and
TMSI (0.240 g, 1.20 mmol) in CH2Cl2 (3.00 mL) was stirred for 6 h with
and without UV irradiation (λ = 294 nm) at 27 °C. The crude product
was further purified by column chromatography using neutral Al2O3 as
a stationary phase and eluting with petroleum ether/EtOAc (v/v 99:1)
to give the desired cyanosilylated product 4 as a colorless liquid
[(0.178 g, 87%) in the presence of UV irradiation and (0.170 g, 83%) in
the absence of UV irradiation].
[30] J.L. Kneebone, V.E. Fleischauer, S.L. Daifuku, A.A. Shaps, J.M. Bailey, T.E. Iannuzzi,
M.L. Neidig, Inorg. Chem. 55 (2016) 272–282.
[31] N.V. Tkachenko, O.Y. Lyakin, D.G. Samsonenko, E.P. Talsi, K.P. Bryliakov, Catal.
Commun. 104 (2018) 112–117.
[32] A. Dudek, J. Mlynarski, J. Org. Chem. 82 (2017) 11218–11224.
[33] M.N. Magubane, M.G. Alam, S.O. Ojwach, O.Q. Munro, J. Mol. Struct. 1135 (2017)
197–201.
[34] A. Mezzetti, Isr. J. Chem. 57 (2017) 1090–1105.
[35] W. Wang, Q. Sun, D. Xu, C. Xia, W. Sun, ChemCatChem 9 (2017) 420–424.
[36] S. Narute, R. Parnes, F.D. Toste, D. Pappo, J. Am. Chem. Soc. 138 (2016)
16553–16560.
[37] A. Zirakzadeh, K. Kirchner, A. Roller, B. Stoeger, M. Widhalm, R.H. Morris,
Organometallics 35 (2016) 3781–3787.
Acknowledgements
[38] A. Kumar, A. Naaz, A.P. Prakasham, M.K. Gangwar, R.J. Butcher, D. Panda,
P. Ghosh, ACS Omega 2 (2017) 4632–4646.
We thank the Department of Science and Technology (EMR/2014/
000254), New Delhi, India and Council of Scientific & Industrial
Research (CSIR) {01(2880)/17/EMR-II} New Delhi, India, for financial
support of this research. We are thankful to the National Single Crystal
X-ray Diffraction Facility and Sophisticated Analytical Instrument
Facility at IIT Bombay, India, for the crystallographic and other char-
acterization data. D.K. A.P.P. and M.K.G thank CSIR, New Delhi, India,
for research fellowships.
[39] S. Ray, J. Asthana, J.M. Tanski, M.M. Shaikh, D. Panda, P. Ghosh, J. Organomet.
Chem. 694 (2009) 2328–2335.
[40] S. Ray, R. Mohan, J.K. Singh, M.K. Samantaray, M.M. Shaikh, D. Panda, P. Ghosh, J.
Am. Chem. Soc. 129 (2007) 15042–15053.
[41] B. Ramasamy, P. Ghosh, Eur. J. Inorg. Chem. 2016 (2016) 1448–1465.
[42] A.P. Prakasham, P. Ghosh, Inorg. Chim. Acta 431 (2015) 61–100.
[43] A. Kumar, P. Ghosh, Eur. J. Inorg. Chem. (2012) 3955–3969.
[44] A. John, P. Ghosh, Dalton Trans. 39 (2010) 7183–7206.
[45] D. Kumar, A.P. Prakasham, L.P. Bheeter, J.-B. Sortais, M. Gangwar, T. Roisnel,
A.C. Kalita, C. Darcel, P. Ghosh, J. Organomet. Chem. 762 (2014) 81–87.
[46] A.P. Prakasham, M.K. Gangwar, P. Ghosh, J. Organomet. Chem. 859 (2018)
106–116.
Appendix A. Supplementary data
[47] A.P. Prakasham, M.K. Gangwar, P. Ghosh, Eur. J. Inorg. Chem. (2019) 295–313.
[48] R.J.H. Gregory, Chem. Rev. 99 (1999) 3649–3682.
[49] T. Kajiwara, H. Higashimura, M. Higuchi, S. Kitagawa, ChemNanoMat 4 (2018)
103–111.
The 1H NMR, 13C{1H} NMR, IR, HRMS and CHNS, data of the
compounds (1−3); 1H NMR, 13C{1H} NMR, CHNS, GC and GC-MS of
the catalysis products (4−16); the CIF file giving X-ray crystallographic
data of the iron complex (3) are available free of charge via the internet.
CCDC 1910128 (3) contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data center via http://www.ccdc.cam.ac.
uk/data_request/cif. Supplementary data to this article can be found
online at https://doi.org/10.1016/j.ica.2019.119003.
[50] W. Xi, Y. Liu, Q. Xia, Z. Li, Y. Cui, Chem. Eur. J. 21 (2015) 12581–12585.
[51] S. Zhao, Y. Chen, Y.-F. Song, Appl. Catal., A 475 (2014) 140–146.
[52] A.V. Gurbanov, G. Mahmoudi, M.F.C. Guedes da Silva, F.I. Zubkov,
K.T. Mahmudov, A.J.L. Pombeiro, Inorg. Chim. Acta 471 (2018) 130–136.
[53] V.S.V.S.N. Swamy, M.K. Bisai, T. Das, S.S. Sen, Chem. Commun. 53 (2017)
6910–6913.
[54] N. Kurono, T. Katayama, T. Ohkuma, Bull. Chem. Soc. Jpn. 86 (2013) 577–582.
[55] C.-Y. Chu, C.-T. Hsu, P.H. Lo, B.-J. Uang, Tetrahedron Asymmetry 22 (2011)
1981–1984.
[56] J. Li, T. Yu, M. Luo, Q. Xiao, W. Yao, L. Xu, M. Ma, J. Organomet. Chem. 874 (2018)
83–86.
[57] W. Wang, M. Luo, J. Li, S.A. Pullarkat, M. Ma, Chem. Commun. 54 (2018)
3042–3044.
References
[58] J.A. Vale, W.M. Faustino, P.H. Menezes, G.F. de Sa, J. Braz. Chem. Soc. 17 (2006)
829–831.
[1] R.D.J. Froese, C. Lombardi, M. Pompeo, R.P. Rucker, M.G. Organ, Acc. Chem. Res.
50 (2017) 2244–2253.
[59] M. Hatano, T. Ikeno, T. Miyamoto, K. Ishihara, J. Am. Chem. Soc. 127 (2005)
10776–10777.
[2] E. Peris, P. Lahuerta, Elsevier Ltd., 2007, pp. 121–236.
[3] S. Conejero, M. Paneque, M.L. Poveda, L.L. Santos, E. Carmona, Acc. Chem. Res. 43
(2010) 572–580.
[60] G.D. Yadav, D.S. Singh, ChemistrySelect 2 (2017) 4830–4835.
[61] J.J. Song, F. Gallou, J.T. Reeves, Z. Tan, N.K. Yee, C.H. Senanayake, J. Org. Chem.
71 (2006) 1273–1276.
[4] N. Sinha, F.E. Hahn, Acc. Chem. Res. 50 (2017) 2167–2184.
[5] M.P. Doyle, R. Duffy, M. Ratnikov, L. Zhou, Chem. Rev. 110 (2010) 704–724.
[6] C. Johnson, M. Albrecht, Coord. Chem. Rev. 352 (2017) 1–14.
[7] H. Nagashima, Bull. Chem. Soc. Jpn. 90 (2017) 761–775.
[8] A. Fuerstner, ACS Cent. Sci. 2 (2016) 778–789.
[62] Y. Suzuki, M.D. Abu Bakar, K. Muramatsu, M. Sato, Tetrahedron 62 (2006)
4227–4231.
[63] K. Iwanami, M. Aoyagi, T. Oriyama, Tetrahedron Lett. 46 (2005) 7487–7490.
[64] D.A. Evans, L.K. Truesdale, G.L. Carroll, J. Chem. Soc., Chem. Commun. (1973)
55–56.
[9] D. Bezier, J.-B. Sortais, C. Darcel, Adv. Synth. Catal. 355 (2013) 19–33.
[10] K. Riener, S. Haslinger, A. Raba, M.P. Hoegerl, M. Cokoja, W.A. Herrmann,
F.E. Kuehn, Chem. Rev. 114 (2014) 5215–5272.
[65] N. Kurono, M. Yamaguchi, K. Suzuki, T. Ohkuma, J. Org. Chem. 70 (2005)
6530–6532.
[66] W. Wang, M. Luo, W. Yao, M. Ma, S.A. Pullarkat, L. Xu, P.-H. Leung, ACS
Sustainable Chem. Eng. 7 (2019) 1718–1722.
[11] R. Shang, L. Ilies, E. Nakamura, Chem. Rev. 117 (2017) 9086–9139.
[12] B. Zhou, H. Sato, L. Ilies, E. Nakamura, ACS Catal. 8 (2018) 8–11.
[13] J. Norinder, A. Matsumoto, N. Yoshikai, E. Nakamura, J. Am. Chem. Soc. 130
(2008) 5858–5859.
[67] D. Kumar, A.P. Prakasham, S. Das, A. Datta, P. Ghosh, ACS Omega 3 (2018)
1922–1938.
[68] N. Kurono, K. Arai, M. Uemura, T. Ohkuma, Angew. Chem., Int. Ed. 47 (2008)
6643–6646.
[14] S. Asako, L. Ilies, E. Nakamura, J. Am. Chem. Soc. 135 (2013) 17755–17757.
[15] T. Matsubara, S. Asako, L. Ilies, E. Nakamura, J. Am. Chem. Soc. 136 (2014)
646–649.
[69] N.-U.H. Khan, S. Agrawal, R.I. Kureshy, S.H.R. Abdi, S. Singh, R.V. Jasra, J.
Organomet. Chem. 692 (2007) 4361–4366.
[16] T. Dombray, C.G. Werncke, S. Jiang, M. Grellier, L. Vendier, S. Bontemps, J.-
B. Sortais, S. Sabo-Etienne, C. Darcel, J. Am. Chem. Soc. 137 (2015) 4062–4065.
[17] N. Kimura, T. Kochi, F. Kakiuchi, J. Am. Chem. Soc. 139 (2017) 14849–14852.
[18] S.C. Bart, E. Lobkovsky, P.J. Chirik, J. Am. Chem. Soc. 126 (2004) 13794–13807.
[19] C.P. Casey, H. Guan, J. Am. Chem. Soc. 129 (2007) 5816–5817.
[20] D. Srimani, Y. Diskin-Posner, Y. Ben-David, D. Milstein, Angew. Chem., Int. Ed. 52
(2013) 14131–14134.
[70] H. Song, K. Ye, P. Geng, X. Han, R. Liao, C.-H. Tung, W. Wang, ACS Catal. 7 (2017)
7709–7717.
[71] F. Zhang, H. Song, X. Zhuang, C.-H. Tung, W. Wang, J. Am. Chem. Soc. 139 (2017)
17775–17778.
[72] D. Bezier, F. Jiang, T. Roisnel, J.-B. Sortais, C. Darcel, Eur. J. Inorg. Chem. (2012)
1333–1337.
[73] L. Mercs, G. Labat, A. Neels, A. Ehlers, M. Albrecht, Organometallics 25 (2006)
5648–5656.
[21] Y. Li, S. Yu, X. Wu, J. Xiao, W. Shen, Z. Dong, J. Gao, J. Am. Chem. Soc. 136 (2014)
4031–4039.
[74] A. Wacker, C.G. Yan, G. Kaltenpoth, A. Ginsberg, A.M. Arif, R.D. Ernst, H. Pritzkow,
W. Siebert, J. Organomet. Chem. 641 (2002) 195–202.
[75] P. Buchgraber, L. Toupet, V. Guerchais, Organometallics 22 (2003) 5144–5147.
[76] L. Mercs, A. Neels, H. Stoeckli-Evans, M. Albrecht, Dalton Trans. (2009)
7168–7178.
[22] Y. Sunada, H. Ogushi, T. Yamamoto, S. Uto, M. Sawano, A. Tahara, H. Tanaka,
Y. Shiota, K. Yoshizawa, H. Nagashima, J. Am. Chem. Soc. 140 (2018) 4119–4134.
[23] C. Johnson, M. Albrecht, Organometallics 36 (2017) 2902–2913.
[24] J.Y. Wu, B.N. Stanzl, T. Ritter, J. Am. Chem. Soc. 132 (2010) 13214–13216.
[25] D. Peng, Y. Zhang, X. Du, L. Zhang, X. Leng, M.D. Walter, Z. Huang, J. Am. Chem.
Soc. 135 (2013) 19154–19166.
[77] D. Bezier, G.T. Venkanna, L.C.M. Castro, J. Zheng, T. Roisnel, J.-B. Sortais,
8

D. Kumar, et al.
InorganicaChimicaActa495(2019)119003
C. Darcel, Adv. Synth. Catal. 354 (2012) 1879–1884.
[87] T.S. Piper, G. Wilkinson, J. Inorg. Nucl. Chem. 2 (1956) 38–45.
[78] S. Demir, Y. Gokce, N. Kaloglu, J.-B. Sortais, C. Darcel, I. Ozdemir, Appl.
Organomet. Chem. 27 (2013) 459–464.
[88] G.M. Sheldrick, Acta Crystallogr. Sect. A: Found. Crystallogr. 64 (2008) 112–122.
[89] L.J. Farrugia, J. Appl. Crystallogr. 45 (2012) 849–854.
[79] S. Warratz, L. Postigo, B. Royo, Organometallics 32 (2013) 893–897.
[80] V.V.K.M. Kandepi, J.M.S. Cardoso, E. Peris, B. Royo, Organometallics 29 (2010)
2777–2782.
[90] D.H. Ryu, E.J. Corey, J. Am. Chem. Soc. 126 (2004) 8106–8107.
[91] M.K. Sharma, S. Sinhababu, G. Mukherjee, G. Rajaraman, S. Nagendran, Dalton
Trans. 46 (2017) 7672–7676.
[81] B. Hildebrandt, S. Raub, W. Frank, C. Ganter, Chem. Eur. J. 18 (2012) 6670–6678.
[82] R. Xu, S. Chakraborty, S.M. Bellows, H. Yuan, T.R. Cundari, W.D. Jones, ACS Catal.
6 (2016) 2127–2135.
[92] S.A. Pourmousavi, H. Salahshornia, Bull. Korean Chem. Soc. 32 (2011) 1575–1578.
[93] F. Kurzer, A.A. Allen, J. Chem. Soc., Perkin Trans. 1 (1990) 2019–2026.
[94] A. Majhi, S.S. Kim, H.S. Kim, Appl. Organomet. Chem. 22 (2008) 407–411.
[95] S.M. Raders, J.G. Verkade, Tetrahedron Lett. 50 (2009) 5317–5321.
[96] J. Ternel, F. Agbossou-Niedercorn, R.M. Gauvin, Dalton Trans. 43 (2014)
4530–4536.
[83] R.H. Crabtree, Chem. Rev. 112 (2012) 1536–1554.
[84] J.A. Widegren, R.G. Finke, J. Mol. Catal. A: Chem. 198 (2003) 317–341.
[85] Y. Suzuki, J. Wakatsuki, M. Tsubaki, M. Sato, Tetrahedron 69 (2013) 9690–9700.
[86] R.J. Haines, A.L. Du Preez, J. Chem. Soc. A (1970) 2341–2346.
9