Picolinamide as a Directing Group on Metal Sandwich Compounds: sp2 C-H Bond Activation and sp3 C-H Bond Oxidation

Article abstract of DOI:10.1021/acs.organomet.7b00143

Palladium catalyzed bis-arylations, -alkylations, and -allylations on the Cp ring of iron and cobalt sandwich compounds have been achieved using the bidentate picolinamide directing group. This directing group along with catalytic Pd(OAc)₂ was found to be highly efficient for C-H functionalization, giving up to 87% yields. The palladacyclic intermediate for the C-H activation of the Cp ring has been isolated and structurally characterized for the cobalt sandwich compound [η⁵-C₅H₅]Co(η⁴-C₄Ph₄). Attempted C-H annulation reactions using picolinamide-derived sandwich compounds did not yield the expected annulated products and instead oxidized the Cp- and picolinamide-bound CH₂ unit to aldehydes. Detailed studies on this novel and unprecedented oxidation indicated that this happens only with the assistance of the picolinamide directing group. We have also shown that the sp² C-H functionalization and the sp³ C-H oxidation can be effectively carried out as a one-pot reaction.

Full text of DOI:10.1021/acs.organomet.7b00143

Article
pubs.acs.org/Organometallics
Picolinamide as a Directing Group on Metal Sandwich Compounds:
2
3
sp C−H Bond Activation and sp C−H Bond Oxidation
Susanta Hazra, Mayukh Deb, Jatinder Singh, and Anil J. Elias*
Department of Chemistry, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110016, India
*
S Supporting Information
ABSTRACT: Palladium catalyzed bis-arylations, -alkylations, and -allyla-
tions on the Cp ring of iron and cobalt sandwich compounds have been
achieved using the bidentate picolinamide directing group. This directing
group along with catalytic Pd(OAc) was found to be highly efficient for
2
C−H functionalization, giving up to 87% yields. The palladacyclic
intermediate for the C−H activation of the Cp ring has been isolated and
5
structurally characterized for the cobalt sandwich compound [η -
4
C H ]Co(η -C Ph ). Attempted C−H annulation reactions using
5
5
4
4
picolinamide-derived sandwich compounds did not yield the expected
annulated products and instead oxidized the Cp- and picolinamide-bound
CH unit to aldehydes. Detailed studies on this novel and unprecedented
2
oxidation indicated that this happens only with the assistance of the
2
picolinamide directing group. We have also shown that the sp C−H
3
functionalization and the sp C−H oxidation can be effectively carried out as a one-pot reaction.
1
1a
INTRODUCTION
workers in 2007.
In addition, intermolecular C−H
■
functionalization of ferrocene derivatives was reported by
using a nonremovable directing group.
catalyzed intramolecular C−H arylation of ferrocene derivatives
was reported separately by You, Gu, and Liu using external
There has been a sustained interest in developing method-
ologies for multifunctionalization of the Cp ring of ferrocene
due to numerous applications of such derivatives in
11b,h
Recently, palladium-
1
2
3
pharmaceuticals, biosensors, and dendrimers as well as in
1
1i,l
4
5
ligands.
However, catalytic C−H activation using a
removable directing group has remained a challenge on metal
sandwich compounds, with only 8-aminoquinoline showing
some promise. Therefore, the development of new method-
ologies for functionalization of metal sandwich compounds
using readily available, inexpensive, and removable directing
groups is considered to be highly desirable.
The picolinamide directing group, first introduced by
Daugulis in 2005, demonstrated excellent directing abilities
that ensured a range of transformations on conventional
catalysis, electrochemistry, and materials science. Recently,
the design and development of ferrocene-based electroactive
materials such as semiconductors, conducting polymers, and
12
6
charge storage materials have been carried out. Due to its high
air and moisture stability and ease of synthesis, the cobalt
sandwich compound [η -C H ]Co(η -C Ph ) has become an
excellent competitor to ferrocene and other sandwich
compounds in many applications, especially in the design of
5
4
5
5
4
4
7
chiral ligands for asymmetric catalysis. In addition, the electron
5
4
donor capability of [η -RCp]Co(η -C Ph ) derivatives has also
4
4
13
aromatic as well as aliphatic organic compounds. In addition,
picolinamide-directed carbon−heteroatom bond formations
been utilized for realizing new luminescent materials and
8
photovoltaic devices.
14
have also been achieved. However, no attempts have been
made to introduce a picolinamide directing group on metal
sandwich compounds for C−H bond activation.
The conventional approaches for functionalization of
ferrocene include standard Friedel−Crafts and Vilsmeier
reactions and the use of organolithium and organomercury
2
9
Herein, we present a Pd-catalyzed sp C−H arylation and
reagents. These methods have some limitations, such as low
alkylation of iron and cobalt sandwich compounds using
picolinamide as the directing group (Scheme 1). We also
demonstrate the easy removal of the picolinamide directing
group by two methods: mainly, reductive cleavage by Zn/HCl
and by hydrolysis using NaOH in ethanol. More interestingly,
we report for the first time a novel methodology to remove the
functional group tolerance and requirement of excess reagent
1
1d,12b
(
RLi, RHg).
In the case of the sterically hindered cobalt
5
4
sandwich compound [η -C H ]Co(η -C Ph ), even these
5
5
4
4
methods were not found to be suitable for functionalization
9
j
of the Cp ring. In the last two decades, transition-metal-
catalyzed and directing-group-assisted highly site selective C−H
functionalization has become a powerful methodology for many
3
directing group via oxidation of an sp C−H bond to an
10
significant transformations in organic synthesis. These C−H
functionalization studies have been extended to ferrocene and
ruthenocene following the pioneering work by You and co-
Received: February 23, 2017
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.7b00143
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Scheme 1. Directing-Group-Assisted C−H Bond Activation
of Iron and Cobalt Sandwich Compounds
Figure 1. Molecular structure of compound 1. Thermal ellipsoids are
drawn at the 30% probability level. Hydrogen atoms have been
omitted for clarity.
Scheme 3. Synthesis of Palladacycle Intermediates for the Cp
C−H Activation of the Picolinamide-Derived Cobalt
Sandwich Compound
1
membered palladacycle 3. Although spectral studies such as H
13
and C NMR and IR on palladacycle 3 indicated the presence
of CH CN as a ligand, its identity could not be verified by X-ray
3
diffraction studies. On reaction of palladacycle 3 with an
equimolar amount of 3-bromopyridine, the new palladacycle 4
was obtained whose crystal structure indicated the presence of
aldehyde. To the best of our knowledge, this represents an
unprecedented use of a picolinamide directing group for the
3
-bromopyridine as the fourth ligand in the square-planar
3
oxidation of an sp CH unit bound to the Cp ring of metal
2
palladium center (Figure 2).
sandwich compounds.
RESULTS AND DISCUSSION
■
The acyl chloride derivative of picolinic acid was prepared and
reacted with the corresponding aminomethyl derivative of iron
and cobalt sandwich compounds, which resulted in the
formation of picolinamide-derived metal sandwich compounds
in 76−82% yields (Scheme 2). These are highly air and
Scheme 2. Synthesis of Picolinamides Based on Iron and
a
Cobalt Sandwich Compounds
Figure 2. Molecular structure of compound 4. Thermal ellipsoids are
drawn at the 30% probability level. Hydrogen atoms have been
omitted for clarity.
A reaction of the palladacycle 3 with methyl iodide at 80 °C
in dichloroethane as solvent gave the bis-methylated product 4a
in 18% yield. However, when the solvent was changed to tert-
amyl alcohol, the yield of 4a was found to increase to 86%. This
observation made us attempt the C−H activation reaction by
a
Isolated yields are given.
moisture stable compounds and are soluble in many polar
organic solvents. The cobalt sandwich derived picolinamide 1
was also structurally characterized (Figure 1).
using catalytic amounts of Pd(OAc) . It was observed that 20
2
To determine the possibility of C−H activation of the Cp
ring using the picolinamide directing group, we carried out the
reaction of compound 1 with an equimolar amount of
palladium acetate in a mixture of acetic acid and acetonitrile
at 60 °C (Scheme 3). This resulted in the formation of the five-
mol % of Pd(OAc) gave 4a with a maximum yield of 79%. The
2
effect of reaction parameters was also optimized (Table S1 in
the Supporting Information). On the basis of isolated yields, it
was observed that tert-amyl alcohol was the most appropriate
solvent for the reaction with Cs CO as base at 80 °C (Scheme
2
3
B
DOI: 10.1021/acs.organomet.7b00143
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). In the case of arylation, we observe that slightly better yields
Article
4
found to be unreactive under the optimized reaction
conditions. 2-Fluoroiodobenzene did react but gave poor yields
of the product 5i even after the reaction was carried out for 30
h (Chart 1). The syntheses of Cp-bis-alkylated iron and cobalt
sandwich compounds have also been successfully carried out,
the details of which are given in Chart 1. The compounds 4a
and 5e were also structurally charecterized, and their structures
are shown in Figures 3 and 4, respectively.
are obtained by increasing the reaction temperature to 100 °C:
Scheme 4. Optimization of Reaction Conditions for C−H
Functionalization
e.g., for 4d (87%). The reaction of palladacycle intermediates 3
and 4 with 4-iodoanisole also gave the bis-arylated product 4d
in 90% and 84% yields, respectively.
We were keen to explore the substrate scope for this C−H
activation reaction. The reaction was found to work well with
electron-rich iodoarenes as well as electron-poor iodoarenes
and showed good tolerance toward functional groups present
on the iodoarenes (Scheme 5). It was also observed that
Scheme 5. Removal of Picolinamide Directing Group
Figure 3. Molecular structure of compound 4a. Thermal ellipsoids are
drawn at the 30% probability level. Hydrogen atoms have been
omitted for clarity.
iodoarenes were more suitable than bromoarenes, as a reaction
using 4-bromoiodobenzene gave exclusively 4-bromo-substi-
tuted products (4e, 5e). Both meta- and para-substituted
iodoarenes gave the bis-arylated products in moderate to good
yields (Chart 1). It was observed that monosubstituted
products are also formed in the reaction, but in very low
yields (∼2%). On the other hand, substituted iodoarenes
having ortho substituents such as OMe, NO , and CO Me were
2
2
Chart 1. Substrate Scope with Regard to Alkyl and Aryl
Iodides for the C−H Functionalization Reaction Given in
Scheme 4
Figure 4. Molecular structure of compound 5e. Thermal ellipsoids are
drawn at the 30% probability level. Hydrogen atoms have been
omitted for clarity.
Two different methods were attempted for removing the
picolinamide directing group after C−H functionalization.
Selected examples of α,α-bis-alkylated and α,α-bis-arylated
sandwich compounds were treated with (A) Zn with 1.5 M
HCl at room temperature and (B) NaOH in ethanol at 80
13a,14f,h
°
C.
The removal of picolinamide groups was found to
readily occur, giving the substituted parent aminomethyl
derivatives in 62−90% yield (Scheme 5). The Zn/HCl method
gave better yields in comparison to the conventional NaOH/
EtOH method.
C
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Carretero and co-workers in 2015 effectively carried out C−
H olefination/annulation on aryl picolinamides using
With a view to see whether both sp2 C−H bond
3
functionalization and sp C−H bond oxidation could be carried
15
[
RhCp*Cl2]2 along with Cu(OAc)2 and alkynes. Under
out as a one-pot reaction, we performed C−H activation
similar reaction conditions but by using [RuCl (p-cym)] with
reactions with the picolinamides 1 and 2 using Pd(OAc) in
2
2
2
benzyl amine as the substrate, Urriolabeitia and co-workers also
tert-amyl alcohol under the optimized reaction conditions. After
16
2
successfully carried out an alkyne annulation reaction. With a
view to exploring an analogous alkyne annulation on our metal
sandwich derived picolinamides, we have carried out a reaction
completion of the sp C−H bond functionalization, which was
monitored by TLC, [RuCl (p-cym)] and Cu(OAc) were
2
2
2
added to the same reaction mixture and it was further heated to
80 °C for 10−12 h. Isolation and purification of the crude
products by coloumn chromatography afforded bis-substituted
aldehydes in 35−55% yields (Scheme 8). The molecular
structure of the α,α-bis-methylated aldehyde of cobalt sandwich
compound 8c was also determined by single-crystal X-ray
diffraction studies and is shown in Figure 5.
of picolinamide 2 with diphenylacetylene by using [RuCl (p-
2
cym)] as the catalyst along with Cu(OAc) . Quite surprisingly,
2
2
instead of formation of the annulated/olefinated product, we
observed the formation of a metal sandwich aldehyde as the
only product of this reaction. The reaction clearly indicated that
3
the sp CH unit bound to the Cp ring is oxidized under these
2
3
conditions (Scheme 6). A similar sp CH unit oxidation was
Mechanism for the C−H Functionalization of Metal
Sandwich Compounds. A possible mechanism for bis-
arylation of picolinamide-based iron and cobalt sandwich
compounds is depicted in Scheme 9. The presence of the
picolinamide group has been found to be essential for the
coordination of palladium with the substrates for C−H
functionalization of the Cp ring. The coordination of Pd(II)
through the nitrogen atom followed by elimination of AcOH
2
observed in the case of the picolinamide-derived cobalt
sandwich compound as well.
Scheme 6. Attempted C−H Olefination/Annulation
Reaction on Compound 2
12,13a
results in the formation of intermediate I.
In the presence
of appropriate solvent and base, the Cp C−H bond in the
vicinity of the Pd(II) center becomes activated, which results in
12,13a
the formation of palladacycle intermediate II.
Next,
oxidative addition of aryl iodide leads to the Pd(IV)
intermediate III. Reductive elimination generates Pd(II) with
transfer of the aryl group to the Cp ring (IV). C−H bond
activation of the mono-aryl-substituted Cp ring followed by
base-assisted elimination of HI and oxidative addition of a
second molecule of aryl iodide leads to the Pd(IV) intermediate
13g
(
VI). Repetition of the steps leads to the formation of the
bis-arylated products.
3
To the best of our knowledge, this type of sp C−H bond
3
Mechanism for sp C−H Bond Oxidation. To investigate
oxidation to an aldehyde using a directing group has never been
reported. This novel finding has the potential not only to
remove the directing group after C−H functionalization but
also to convert the aminomethyl derivatives to an aldehyde.
Detailed studies were carried out for optimizing the reaction
conditions and for maximizing the yields. It was found that
the possible reaction mechanism of the sp3 C−H bond
oxidation, we have carried out a few control experiments, which
are shown in Scheme 10.
Since single-electron transfer (SET) is a possible step in the
3
sp C−H oxidation reaction, we verified this possibility by the
addition of a radical inhibitor. When compounds 1 and 2 were
treated with 2,2,6,6-tetramethylpiperidine oxide (TEMPO)
under the optimized reaction conditions, the yields of the
aldehydes were found to decrease drastically, indicating that the
reaction probably proceeds by a free radical process.
[
RuCl (p-cym)] (5 mol %) along with Cu(OAc) (1 equiv)
2
2
2
gave maximum yields (45−57%) for Cp bis-alkyl- and bis-aryl-
substituted sandwich compounds (Scheme 7). Noticeble
decomposition was observed in these reactions, which led to
lesser than expected yields of the compounds.
Similar studies using TEMPO on C−C coupling reactions
involving picolinamide-derived amino acids also showed drastic
reduction in the yields.
Scheme 7. Directing-Group-Assisted Ru-Catalyzed
Oxidation of α,α-Bis-Substituted Picolinamides to the
Corresponding Aldehydes
18,19
A picolinamide directing group
does play a significant role in the oxidation reaction, as both the
aminomethyl derivative and the benzamide derivative of metal
sandwich compounds were found to be unreactive for the
oxidation reaction under identical conditions (Scheme 10). On
the basis of our observations and related studies from other
1
7−19
groups,
shown in Scheme 11. First, a redox reaction take place in which
a possible catalytic cycle has been proposed, as
2+
2+
3+
Cu oxidizes the Ru complex to Ru and itself becomes
reduced to Cu . Next, Ru is coordinated with picolinamide
+
17
3+
18
+
to yield the intermediate IM1. After that, Cu abstracts an
electron from C−H bond of IM1 to form the radical
intermediate IM2. Subsequently, the radical species IM2
undergoes an intramolecular single-electron transfer (SET) to
afford the iminium intermediate IM3, which undergoes
19
hydrolysis to give the corresponding aldehydes 8 and 9.
D
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Scheme 8. One-Pot Synthesis of α,α-Bis-Substituted Aldehydes of Metal Sandwich Compounds
CONCLUSIONS
■
In summary, the syntheses of Cp multiply substituted iron and
cobalt sandwich compounds have been efficiently carried out
using picolinamide as a directing group and by using Pd(OAc)2
as a catalyst. The palladacycle intermediate of this reaction for
the cobalt sandwich compound has been isolated and
structurally characterized. Aryl iodides containing electron-
donating as well as electron-withdrawing substituents were
equally suitable for the reaction. We have also demonstrated
the easy removal of the directing group after C−H
functionalization by hydrolysis and reductive cleavage. More
interestingly, for the first time, we report a novel methodology
3
Figure 5. Molecular structure of compound 8c. Thermal ellipsoids are
drawn at the 30% probability level. Hydrogen atoms have been
omitted for clarity.
to remove the directing group by oxidation of the sp C−H
bond to the corresponding aldehydes. This novel methodology
and catalyst system can be applied to a variety of aryl- and alkyl-
substituted sandwich compounds. We have also successfully
Scheme 9. Proposed Mechanism for Pd-Catalyzed Bis-Arylation of Metal Sandwich Compounds
E
DOI: 10.1021/acs.organomet.7b00143
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2
3
Scheme 10. Control Experiments for Ru-Catalyzed
Oxidation of sp C−H Bonds
combined the sp C−H functionalization and the sp C−H
3
3
bond oxidation as a one-pot reaction. Attempts to extend sp
C−H oxidation to aryl picolinamide under identical reaction
conditions were unsuccessful and will require more detailed
studies. Possible mechanisms have been proposed for the C−H
activation and the C−H oxidation, which need to be verified
further by detailed mechanistic studies.
EXPERIMENTAL SECTION
■
General Information. All manipulations of the compounds used
were carried out using standard Schlenk techniques under a nitrogen
atmosphere. All solvents were freshly distilled and used. Ferrocene-
carboxylic acid, ferrocenecarboxamide, ferrocenylmethylamine, the
sodium salt of carbomethoxycyclopentadiene, and tris-
(
triphenylphosphine)cobalt chloride, as well as carboxylic acid,
5
4
carboxamide, and aminomethyl derivatives of [η -C H ]Co(η -
C Ph ) were prepared according to literature procedures.
5
4
7
k,l,20
4
4
Dimethyl carbonate, triphenylphosphine, oxalyl chloride (Spectro-
chem), picolinic acid, palladium acetate (Alfa Aesar), iodoarenes, and
1
13
iodoalkenes were used as received. H and C NMR spectra were
recorded on a Bruker Spectrospin DPX-300 NMR spectrometer at 300
and 75.47 MHz, respectively. Mass spectra were recorded on a Bruker
Micro-TOF QII quadrupole time-of-flight (Q-TOF) mass spectrom-
eter. X-ray diffraction studies of crystals mounted on a capillary were
carried out on a Bruker AXS SMART-APEX diffractometer equipped
with CCD area detector (Kα = 0.71073 Å, graphite monochroma-
2
1,22
tor).
Frames were collected at T = 298 K by ω, ϕ, and 2θ rotation
with a full quadrant data collection strategy (four domains each with
2
3
6
00 frames) at 10 s per frame with SMART. The measured
2
intensities were reduced to F and corrected for absorption with
3
Scheme 11. Proposed Mechanism for Ru-Catalyzed sp C−H Bond Oxidation of Metal Sandwich Compounds
F
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2
3
SAINT. Structure solution and refinement were carried out with the
137.07, 135.84, 128.09−128.64 (m), 126.30, 125.82, 122.08, 115.48,
95.68, 83.23, 74.24, 33.32, 22.68, 14.09. HRMS: m/z 695.2470, calcd
24
SHELXTL package by direct methods. Non-hydrogen atoms were
refined anisotropically. All hydrogen atoms were included in idealized
positions, and a riding model was used for the refinement. Images were
+
for C H CoN O [M + H] 695.2467.
46
40
2
5
4
General Procedure for Bis-Arylation of [η -(CH R)C H ]Co(η -
2
5 4
25
created with the program Diamond.
C
4
Ph
compound derived picolinamide 1 (0.06 g, 0.10 mmol), Pd(OAc)
mol %), Cs CO (2 equiv), and aryl iodide (2.5 equiv) were added to
4
) (R = Picolinamido). One equivalent of cobalt sandwich
General Procedure for Synthesis of Picolinamides of Metal
Sandwich Compounds. Picolinic acid (0.18 g, 1.50 mmol) and
triethylamine (0.30 mL, 3.00 mmol) were dissolved in dry DCM (15
mL). The solution was cooled to 0 °C followed by addition of ethyl
chloroformate (0.16 g, 1.50 mmol). The solution was then stirred for
2
(20
2
3
tert-amyl alcohol in a screw-capped vial having a magnetic bead and
heated at 80−100 °C for 12−24 h. The reaction was monitored by
TLC, and after completion, the reaction mixture was dried under
vacuum and the crude product was purified through column
chromatography using silica and hexane/ethyl acetate (80/20) as
eluent.
1
5 min in an ice bath. Afterward, the aminomethyl derivative of iron
and cobalt sandwich compounds (1 mmol) were dissolved in dry
DCM and were added dropwise using a syringe into the reaction
mixture. The solution was warmed to room temperature and stirred
for 24 h. Afterward, the solution was concentrated under vacuum and
the crude product was purified through column chromatography on
neutral alumina using hexane/ethyl acetate (70:30) as eluent.
5
4
2,5-(4-OMeC
4d): red crystalline solid; yield 72 mg (87%). Mp: 144−145 °C. Anal.
Found: C, 78.45; H, 5.15; N, 3.42. Calcd for C H N CoO : C,
H ) -η -(CH R)C H ]Co(η -C Ph ) (R = picolinamido)
6 4 2 2 5 2 4 4
(
54 43
2
3
1
7
8.44; H, 5.24; N, 3.39. H NMR (300 MHz, CDCl ): δ 8.39 (s, 1H),
3
5
4
8.09−8.16 (m, 2H), 7.98 (m, 1H), 6.98−7.37 (m, 25H), 6.49−6.58
[
η -(CH R)C H ]Co(η -C Ph ) (R = picolinamido) (1): red crystalline
2 5 4 4 4
(
m, 4H), 5.07 (s, 2H), 4.39 (s, 2H), 3.79 (s, 6H). 13C NMR (75 MHz,
solid; yield 0.51 g (82%). Mp: 143−145 °C. Anal. Found: C, 78.25; H,
CDCl ): δ 163.59, 158.33, 147.98, 137.12, 135.17, 128.06−128.77,
126.27, 125.92, 113.60, 99.87, 83.01, 75.33, 55.32, 35.73. HRMS: m/z
8
5
(
.05; N, 4.62. Calcd for C H N CoO: C, 78.17; H, 5.08; N, 4.56. IR
3
40
31
2
−1
1
ν, cm ): 1677 (CO), 3387 (NH). H NMR (300 MHz, CDCl ):
3
+
49.2502, calcd for C H CoN O Na [M + Na] 849.2497.
2
δ 8.46 (s, 1H), 8.11−8.13 (d, J = 6 Hz, 1H), 7.76−7.83 (m, 2H),
54 43
2
3
5
4
,5-(4-BrC H ) -η -(CH R)C H ]Co(η -C Ph ) (R = picolinamido)
6 4 2 2 5 2 4 4
7
3
1
6
.37−7.49 (m, 9H), 7.16−7.25 (m, 12H), 4.67 (s, 2H), 4.61 (s, 2H),
.98 (s, 2H). 13C NMR (75 MHz, CDCl ): δ 164.02, 149.81, 147.91,
(4e): yellow solid; yield 57 mg (63%). Mp: 142−143 °C. Anal. Found:
C, 67.51; H, 4.08; N, 3.09. Calcd for C H N Br CoO: C, 67.55; H,
4.03; N, 3.03. H NMR (300 MHz, CDCl
(d, 1H), 7.91 (s, 1H), 7.78- 7.81 (t, 1H), 7.08−7.75 (m, 25H), 6.82−
6
3
5
2
37
2
2
37.24, 136.12, 122.21−128.8, 95.09, 83.02, 42.21. HRMS: m/z
15.1845, calcd for C H CoN O [M + H] 615.1841.
η -(CH R)C H ]Fe(η -C H ) (R = picolinamido) (2): yellow
crystalline solid; yield 0.20 g (76%). Mp: 136−138 °C. Anal. Found:
C, 63.75; H, 5.07; N, 8.78. Calcd for C H FeN O: C, 63.77; H, 5.04;
1
+
3
): δ 8.33 (s, 1H), 8.07−8.10
4
0
32
2
5
5
[
2 5 4 5 5
13
.85 (d, 4H), 5.06 (s, 2H), 4.30 (s, 2H). C NMR (75 MHz, CDCl ):
3
δ 163.68, 148.90, 137.52, 135.31, 128.06−128.37 (m), 126.17, 123.12,
17
16
2
−1
1
122.00, 99.39, 85.01, 35.43.
N, 8.75. IR (ν, cm ): 1657 (CO), 3339, 3491(NH). H NMR (300
5
4
2
,5-(4-CF C H ) -η -(CH R)C H ]Co(η -C Ph ) (R = picolinamido)
3 6 4 2 2 5 2 4 4
4f): yellow-orange solid; yield 62 mg (68%). Mp: 139−140 °C. Anal.
MHz, CDCl ): δ 8.56 (s, 1H), 8.21−8.36 (m, 2H), 7.84−7.86 (d, 1H),
3
(
13
7
.39−7.42 (m, 1H), 4.31 (s, 3H), 4.23 (s, 6H), 4.14 (s, 2H). C NMR
Found: C, 71.85; H, 4.18; N, 3.12. Calcd for C H N CoOF : C,
1.84; H, 4.13; N, 3.10. H NMR (300 MHz, CDCl ): δ 8.30 (s, 1H),
.2 (d, 2H), 8.05 (t, 1H) 7.22- 7.33 (m, 16H), 7.05−7.17 (m, 13H),
.18 (s, 2H), 4.37 (s, 2H). C NMR (75 MHz, CDCl ): δ 163.60,
47.90, 137.72, 134.31, 128.06−128.57 (m), 126.17, 125.12, 122.00,
9.09, 84.01, 35.73. HRMS: m/z 925.1998, calcd for
5
4
37
2
6
(
75 MHz, CDCl ): δ 163.50, 148.06, 137.32, 126.09, 122.24, 83.45,
1
3
7
8
5
1
9
3
8
[
2.42, 69.77, 35.73. HRMS: m/z 343.0490, calcd for C H FeN NaO
17 16 2
+
M + Na] 343.0504.
General Procedure for Bis-Alkylation of [η -(CH R)C H ]Co-
13
5
3
2
5
2
4
(
η -C Ph ) (R = Picolinamido). One equivalent of cobalt sandwich
4 4
compound derived picolinamide 1 (0.06 g, 0.10 mmol), Pd(OAc) (20
mol %), Cs CO (2 equiv), and alkyl iodide or allyl bromide (4 equiv)
+
2
C H CoN O F Na [M + Na] 925.2034.
5
4
2
37
2
1 6
2
3
5
4
,5-(4-NO C H ) -η -(CH R)C H ]Co(η -C Ph ) (R = picolinamido)
2 6 4 2 2 5 2 4 4
were added to tert-amyl alcohol in a screw-capped vial having a
magnetic bead and were heated at 80−90 °C for 12−24 h. The
reaction was monitored by TLC. After completion, the reaction
mixture was dried under vacuum and the crude product was purified
through column chromatography using silica and hexane/ethyl acetate
(
4g): orange-red solid; yield 55 mg (60%). Mp: 144−146 °C. Anal.
Found: C, 75.39; H, 4.58; N, 3.32. Calcd for C H N CoO : C,
5.36; H, 4.50; N, 3.38. H NMR (300 MHz, CDCl ): δ 8.35 (s, 1H),
.22 (d, 2H), 8.09 (t, 1H), 7.17- 7.29 (m, 16H), 7.11−7.21 (m, 13H),
.12 (s, 2H), 4.35 (s, 2H). C NMR (75 MHz, CDCl ): δ 163.64,
47.90, 137.72, 134.31, 128.16−128.67 (m), 126.17, 125.12, 122.06,
99.19, 84.11, 35.71.
5
2
37
2
5
1
7
8
5
1
3
13
3
(
90/10) as eluent.
5
4
2
,5-Bis(methyl)-η -(CH R)C H ]Co(η -C Ph ) (R = picolinamido)
2 5 2 4 4
(
4a): orange crystalline solid; yield 51 mg (79%). Mp: 135−137 °C.
5
4
2
,5-(3-CO MeC H ) -η -(CH R)C H ]Co(η -C Ph ) (R = picolinami-
2 6 4 2 2 5 2 4 4
Anal. Found: C, 78.45; H, 5.45; N, 4.40. Calcd for C H N CoO: C,
42
35
2
do) (4h): orange solid; yield 57 mg (58%). Mp: 140−142 °C. Anal.
Found: C, 76.15; H, 4.98; N, 3.13. Calcd for C H N CoO : C,
1
7
8
4
8.49; H, 5.49; N, 4.36. H NMR (300 MHz, CDCl ): δ 8.44 (s, 1H),
.13 (d, 1H), 7.81 (d, 2H), 7.40−7.76 (m, 9H), 7.22−7.36 (m, 12H),
.35 (s, 2H), 3.98 (s, 2H), 1.61 (s, 6H). C NMR (75 MHz, CDCl ):
δ 163.57, 147.90, 137.21, 135.96, 128.06−128.66 (m), 126.09, 125.94,
22.15, 93.05, 83.32, 74.05, 33.73, 10.37. HRMS: m/z 643.2152, calcd
for C H CoN O [M + H] 643.2154.
3
5
6
43
2
5
−1
7
6.18; H, 4.91; N, 3.17. IR (ν, cm ) 1721, 1673 (CO), 3446, 3396
13
1
3
(NH). H NMR (300 MHz, CDCl ): δ 8.38 (s, 1H), 8.10−8.16 (m,
2
2
3
H), 7.78−7.87 (m, 4H), 7.01- 7.57 (m, 26H), 5.24 (s, 2H), 4.5 (s,
1
13
H), 3.71 (s, 6H). C NMR (75 MHz, CDCl ): δ 165.53, 163.66,
3
+
42
36
2
150.03, 148.14, 141.72, 137.33, 129.23, 126.09, 125.14, 122.25, 93.80,
5
4
2
,5-Bis(ethyl)-η -(CH R)C H ]Co(η -C Ph ) (R = picolinamido)
2 5 2 4 4
1
85.38, 68.58, 52.37, 38.44. HRMS: m/z 905.2399, calcd for
(
4b): yellow semisolid; yield 28 mg (42%). H NMR (300 MHz,
+
C H CoN O Na [M + Na] 905.2396.
56
43
2
5
CDCl ): δ 8.43 (s, 1H), 8.14 (d, 1H), 7.76−7.81 (d, 2H), 7.40−7.46
5
3
General Procedure for Bis-Alkylation of [η -(CH R)C H ]Fe-
2 5 4
5 5
(
2
m, 9H), 7.21−7.33 (m, 12H), 4.50 (s, 1H), 4.42 (s, 1H), 3.99 (s,
5
(
η -C H ) (R = Picolinamido). One equivalent of picolinamide 2
13
H), 2.08−2.12 (q, 2H), 1.91−1.93 (q, 2H), 0.82 (t, 6H); C NMR
(
0.03 g, 0.10 mmol), Pd(OAc) (20 mol %), Cs CO (2 equiv), and
2 2 3
(
(
75 MHz, CDCl ): δ 163.57, 147.90, 137.21, 135.96, 128.06−128.66
3
alkyl iodide or allyl bromide (4 equiv) were added to tert-amyl alcohol
in a screw-capped vial having a magnetic bead and heated at 80−90 °C
for 5−10 h. The reaction was monitored by TLC. After completion,
the reaction mixture was dried under vacuum and the crude product
was purified through column chromatography using silica and hexane/
ethyl acetate (90/10) as eluent.
m), 126.09, 125.94, 122.15, 93.05, 83.32, 74.05, 33.73, 20.74, 10.29;
+
HRMS: m/z 671.2465, calcd For C H CoN O [M + H]
71.2467.
,5-Bis(allyl)-η -(CH R)C H ]Co(η -C Ph ) (R = picolinamido) (4c):
yellow solid; yield 25 mg (38%). Mp: 128−130 °C. Anal. Found: C,
9.55; H, 5.68; N, 4.02. Calcd for C H N CoO: C, 79.52; H, 5.66;
=
44
40
2
6
5
4
2
2
5
2
4
4
5
5
7
2,5-Bis(methyl)-η -(CH R)C H ]Fe(η -C H ) (R = picolinamido)
2 5 4 5 5
1
46
39
2
1
N, 4.03. H NMR (300 MHz, CDCl ): δ 8.42 (s, 1H), 8.09 (d, J = 9
(5a): yellow-orange semisolid; yield 26 mg (74%). H NMR (300
3
Hz, 1H), 7.79−7.82 (t, 2H), 7.42−7.59 (m, 9H), 7.25 (m, 12H), 5.58
MHz, CDCl ): δ 8.43 (s, 1H), 8.14−8.16 (dd, 2H), 7.76−7.78 (m,
3
(
(
q, 2H), 4.77 (dd, J = 15 Hz, 4H), 4.42 (s, 2H), 3.99 (d, 2H), 2.86
1H), 7.31−7.34 (d, J = 9 Hz, 1H), 4.36 (d, J = 9 Hz, 2H), 3.95−4.07
dd, J = 6 Hz, 4H). 13C NMR (75 MHz, CDCl ): δ 163.31, 147.89,
(m, 7H), 1.93 (s, 6H). C NMR (75 MHz, CDCl ): δ 163.50, 149.94,
13
3
3
G
DOI: 10.1021/acs.organomet.7b00143
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
5
5
1
1
48.06, 137.32, 126.09, 122.24, 83.45, 82.45, 69.77, 67.50, 35.73,
2,5-(2-FC H ) -η -(CH R)C H ]Fe(η -C H ) (R = picolinamido) (5i):
6 6 2 2 5 2 5 5
+
3.25. HRMS: m/z 348.0914, calcd for C H FeN O [M] 348.0919.
orange-red crystalline solid; yield 6 mg (12%). Mp: 135−137 °C. Anal.
Found: C, 68.59; H, 4.34; N, 5.60. Calcd for C H N FeOF : C,
68.52; H, 4.36; N, 5.51. H NMR (300 MHz, CDCl ): δ 8.43 (s, 1H),
1
9
20
2
5
5
2
,5-Bis(ethyl)-η -(CH R)C H ]Fe(η -C H ) (R = picolinamido) (5b):
2
5
4
5
5
29 22
2
2
1
1
yellow-orange semisolid; yield 17 mg (45%). H NMR (300 MHz,
3
CDCl ): δ 8.43 (s, 1H), 8.16 (d, J = 9 Hz, 1H), 8.00 (s, 1H), 7.76−
8.33 (s, 1H), 8.14−8.19 (m, 5H), 7.88 (t, 1H), 7.69−7.72 (m, 4H),
3
1
3
7
2
.79 (m, 1H), 7.31−7.34 (d, J = 9 Hz, 1H), 4.33 (d, J = 3 Hz,
7.41−7.43 (t, 1H), 4.84 (s, 2H), 4.67−4.69 (s, 2H), 4.23 (s, 5H); C
1
3
H),3.95−4.19 (m, 7H), 2.28−2.36 (q, 4H), 1.26−1.29 (t, 6H).
C
NMR (75 MHz, CDCl ): δ 163.84, 147.93, 141.56, 137.31, 129.23,
3
NMR (75 MHz, CDCl ): δ 163.70, 150.02, 148.15, 137.35, 126.11,
126.15 125.14, 122.10, 88.01, 80.12, 71.98, 69.89, 36.58.
3
1
3
22.27, 90.24, 85.36, 69.49, 67.85, 38.43, 20.74, 14.99. HRMS: m/z
General Procedure for the Removal of the Picolininamide
+
Directing Group. Bis-aryl or bis-alkyl picolinamides were dissolved in
99.1135, calcd for C H FeN ONa [M + Na] 399.1130.
2
1
24
2
5
5
a THF/H O (1/1) mixture and stirred at room temperature for 15
[
2,5-Bis(allyl)-η -(CH R)C H ]Fe(η -C H ) (R = picolinamido) (5c):
2
2
5
4
5 5
1
min. Afterward 0.1 mL of 1.5 M HCl and Zn dust (15 equiv) were
added to the solution and this mixture was then stirred at room
temperature for 2−3 h. The reaction was monitored by TLC, and after
completion, the mixture was extracted with aqueous NaOH solution,
yellow-orange semisolid; yield 15 mg (40%). H NMR (300 MHz,
CDCl ): δ 8.47 (s, 1H), 8.46 (d, J = 12 Hz, 1H), 8.00 (s, 1H), 7.72−
3
7
4
4
.79 (m, 1H), 7.29−7.33 (d, J = 12 Hz, 1H), 5.89 (q, 2H), 4.95 (d,
H), 4.33 (d, J = 3 Hz, 2H), 3.95−4.29 (m, 7H), 3.086 (d, J = 6 Hz,
+
the organic layer dried over Na SO , and the crude product purified
H). HRMS: m/z 400.1226, calcd for C H FeN O [M] 400.1233.
2
4
23
24
2
5
5
through column chromatography on basic aluminum oxide using
DCM/MeOH (95/5) as eluent. A NaOH/EtOH hydrolysis reaction
was also carried out (Scheme 5) on a selected example to compare the
yields.
General Procedure for Bis-Arylation of [η -(CH R)C H ]Fe(η -
2
5 4
C H ) (R = Picolinamido). One equivalent of ferrocenyl picolinamide
2
aryl iodide (2.5 equiv) were added to tert-amyl alcohol in a screw-
capped vial having a magnetic bead and heated at 80−110 °C for 12−
2
reaction mixture was dried under vacuum and the crude product was
purified through column chromatography using silica and hexane/
ethyl acetate (70/30) as eluent.
5
5
(0.03 g, 0.10 mmol), Pd(OAc) (20 mol %), Cs CO (2 equiv), and
2 2 3
5
4
2,5-(4-OMeC
solid; yield 22 mg (85%). Mp: 128−129 °C. Anal. Found: C, 78.09;
H, 6.05; N, 2.10. Calcd for C H NCoO : C, 78.05; H, 6.09; N, 2.12.
H ) -η -(CH NH )C H ]Co(η -C Ph ) (6a): orange
6 4 2 2 2 5 2 4 4
0 h. The reaction was monitored by TLC, and after completion, the
43 40
2
1
H NMR (300 MHz, CDCl
): δ 7.21−7.32 (m, 12H), 6.89−7.08 (m,
3
12H), 6.57−6.60 (dd, 4H), 4.86 (s, 2H), 3.86 (s, 6H), 3.61 (s, 2H),
5
5
13
2
,5-(4-OMeC H ) -η -(CH R)C H ]Fe(η -C H ) (R = picolinamido)
1.45 (br, 2H). C NMR (75 MHz, CDCl
): δ 158.55, 135.49,
3
6
4 2
2
5
2
5 5
1
(5d): red semisolid; yield 41 mg (77%). H NMR (300 MHz, CDCl ):
126.06−129.53, 113.62, 82.27, 75.02, 55.27, 30.33.
3
5
4
δ 8.42−8.44 (m, 2H), 8.16−8.19 (d, J = 9 Hz, 1H), 7.80−7.81 (m,
H), 7.47−7.50 (m, 5H), 6.80−6.83 (d, 4H) 4.55−4.61 (m, 4H), 4.19
s, 5H), 3.76 (s, 6H). 13C NMR (75 MHz, CDCl ): δ 163.44, 158.38,
2,5-Bis(methyl)-η -(CH NH )C H ]Co(η -C Ph ) (6b): orange solid;
2 2 5 2 4 4
1
(
yield 27 mg (87%). Mp: 128−130 °C. Anal. Found: C, 80.79; H, 5.69;
1
N, 2.60. Calcd for C H CoN: C, 80.73; H, 5.65; N, 2.62. H NMR
3
36 30
1
7
49.86, 148.03, 137.18, 130.13, 129.50, 125.98, 122.04, 89.05, 80.52,
(300 MHz, CDCl ): δ 7.25−7.28 (m, 12H), 7.39−7.48 (m, 8H), 4.64
3
13
1.54, 68.55, 55.27, 36.80. HRMS: m/z 532.1461, calcd for
(s, 2H), 4.58 (s, 6H), 1.61 (s, 6H). C NMR (75 MHz, CDCl ): δ
3
+
C H FeN O [M] 532.1444.
136.31, 126.28−128.73, 83.31, 82.79, 60.39, 30.20, 14.20. HRMS: m/z
3
1
2
28
2
3
5
5
+
,5-(4-BrC H ) -η -(CH R)C H ]Fe(η -C H ) (R = picolinamido)
521.1682, calcd for C36
H
30Co [M − NH
2
] 521.1674.
6
4 2
2
5
2
5 5
5
5
(
5e): orange crystalline solid; yield 35 mg (60%). Mp: 138−140 °C.
2,5-(4-OMeC H ) -η -(CH NH )C H ]Fe(η -C H ) (7a): orange solid;
6 4 2 2 2 5 2 5 5
Anal. Found: C, 55.29; H, 3.58; N, 4.40. Calcd for C H N FeOBr :
yield 18 mg (85%). Mp: 135−136 °C. Anal. Found: C, 70.05; H, 6.02;
29
22
2
2
1
1
C, 55.27; H, 3.52; N, 4.45. H NMR (300 MHz, CDCl ): δ 8.44 (s,
N, 3.12. Calcd for C H FeNO : C, 70.27; H, 5.90; N, 3.28. H NMR
3
25 25
2
1
4
1
H), 8.18 (s, 1H), 8.15 (d, J = 6 Hz, 1H), 7.84 (t, 1H), 7.40 (s, 9H),
(300 MHz, CDCl ): δ 7.50−7.53 (d, J = 9 Hz, 4H), 6.89−6.92 (d, J =
3
13
13
.60−4.62 (m, 4H), 4.19 (s, 5H). C NMR (75 MHz, CDCl ): δ
9 Hz, 4H), 4.47 (s, 2H), 4.08 (s, 5H), 3.84 (s, 6H). C NMR (75
3
63.69, 149.99, 148.16, 137.36, 126.13, 122.25, 85.34, 68.67, 38.44.
MHz, CDCl ): δ 158.38, 137.18, 130.13, 89.05, 80.52, 71.54, 68.55,
3
+
+
HRMS: m/z 627.9451, calcd for C H FeN OBr [M] 627.9443, [M
55.27, 30.33. HRMS: m/z 427.1239, calcd for C H FeNO [M]
29
22
2
2
25 25
2
+
2] 629.9430, [M + 4] 631.9407.
427.1229.
2,5-Bis(methyl)-η -(CH NH )C H ]Fe(η -C H ) (7b): yellow semi-
5
5
5
5
2
,5-(4-NO C H ) -η -(CH R)C H ]Fe(η -C H ) (R = picolinamido)
2
6
4 2
2
5
2
5
5
2
2
5
2
5 5
1
(
5f): red crystalline solid; yield 39 mg (57%). Mp: 140−142 °C. Anal.
solid; yield 17 mg (90%). H NMR (300 MHz, CDCl ): δ 3.90−3.93
3
13
Found: C, 61.73; H, 3.68; N, 9.73. Calcd for C H N FeO : C, 61.94;
(m, 7H), 3.66 (s, 2H), 1.96 (s, 6H); 1.43 (br, 2H). C NMR (75
2
9
22
4
5
−1
1
H, 3.94; N, 9.66. IR (ν, cm ): 1672 (CO), 1511, 1338 (NO ). H
MHz, CDCl ): δ 82.35, 69.56, 67.19, 38.44, 13.11. HRMS: m/z
2
3
+
NMR (300 MHz, CDCl ): δ 8.42 (d, 1H), 8.41 (s, 1H), 8.18 (d, 1H),
227.0519, calcd for C H Fe [M − NH ] 227.0517.
3
13 15
2
7
1
1
8
.82−7.84 (m, 1H), 7.54−7.71 (m, 4H), 7.40−7.42 (m, 4H), 7.38 (t,
General Procedure for the Removal of the Picolininamide
13
3
H) 4.67−4.74 (m, 4H), 4.26 (s, 5H). C NMR (75 MHz, CDCl ): δ
Directing Group via Oxidation of sp C−H Bond. Bis-aryl or bis-
3
63.84, 147.93, 141.56, 137.31, 129.23, 126.15, 125.14, 122.10, 88.01,
0.12, 71.98, 69.89, 36.56. HRMS: m/z 562.0923, calcd for
alkyl picolinamides were dissolved in tert-amyl alcohol and stirred at
room temperature for 15 min. Afterward [RuCl (p-cym)] (5 mol %)
2 2
+
C H FeN O [M] 562.0934.
and Cu(OAc) (1 equiv) were added to the solution, and this mixture
2
29
22
4
5
5
5
2
,5-Bis(4-CF C H ) -η -(CH R)C H ]Fe(η -C H ) (R = picolinamido)
was then heated at 80 °C for 10−12 h. The reaction was monitored by
TLC, and after completion, the mixture was dried over vacuum and
the crude product was purified through column chromatography on
silica gel using hexane/ethyl acetate (80/20) as eluent.
3
6
4 2
2
5
2
5 5
(
5g): orange crystalline solid; yield 41 mg (64%). Mp: 129−131 °C.
Anal. Found: C, 61.13; H, 3.68; N, 4.65. Calcd for C H N FeOF : C,
3
1
22
2
6
1
6
8
7
1.20; H, 3.65; N, 4.60. H NMR (300 MHz, CDCl ): δ 8.42 (d, 1H),
.41 (s, 1H), 8.18 (d, 1H), 7.82−7.84 (m, 1H), 7.54−7.71 (m, 4H),
.40−7.42 (m, 4H), 7.38 (t, 1H) 4.67−4.74 (m, 4H), 4.26 (s, 5H).
3
5
4
2,5-(4-OMeC H ) -[η -C H -CHO]Co(η -C Ph ) (8a): orange crystal-
6 4 2 5 2 4 4
13
C
line solid; yield 21 mg (50%). Mp: 158−160 °C. Anal. Found: C,
NMR (75 MHz, CDCl ): δ 163.84, 147.93, 141.56, 137.31, 129.23,
79.89; H, 5.34; N, 0.00. Calcd for C H CoO : C, 79.99; H, 5.17; N,
3
48 37
3
1
1
6
26.15 125.14, 122.10, 88.01, 80.12, 71.98, 69.89, 36.56. HRMS: m/z
08.0983, calcd for C H FeN OF [M] 608.0980.
0.00. H NMR (300 MHz, CDCl ): δ 9.67 (s, 1H), 7.28 (m, 4H),
3
+
7.22−7.28 (m, 7H), 7.04−7.14 (m, 13H), 6.66 (d, J = 9 Hz, 4H), 5.16
3
1
22
2
6
5
5
13
2
,5-(3-CO MeC H )-η -(CH R)C H ]Fe(η -C H ) (R = picolinamido)
(s, 2H), 3.84 (s, 6H). C NMR (75 MHz, CDCl
3
): δ 191.28, 158.87,
2
6
4
2
5
2
5 5
(
5h): orange crystalline solid; yield 36 mg (55%). Mp: 136−138 °C.
134.34, 130.87, 128.06−128.77 (m), 126.86, 125.18, 113.18, 103.14,
+
Anal. Found: C, 67.39; H, 4.84; N, 4.71. Calcd for C H N FeO : C,
87.65, 55.30. HRMS: m/z 721.2149, calcd for C H CoO [M + H]
33
28
2
5
48 38
3
1
6
7.36; H, 4.80; N, 4.76. H NMR (300 MHz, CDCl ): δ 8.33−8.38
721.2147.
3
5
4
(
4
m, 2H), 8.09−8.19 (m, 3H), 7.64−7.82 (m, 5H), 7.18−7.32 (m, 3H),
2,5-(4-BrC H ) -[η -C H −CHO]Co(η -C Ph ) (8b): orange solid;
6
4 2
5
2
4
4
13
.65−4.66 (s, 2H), 4.50−4.54 (s, 2H), 4.17 (s, 5H), 3.81(s, 6H).
C
yield 25 mg (57%). Mp: 165−167 °C. Anal. Found: C, 67.58; H,
1
NMR (75 MHz, CDCl ): δ 165.53, 163.66, 150.03, 148.14, 141.72,
4.06; N, 0.00. Calcd for C H CoOBr : C, 67.50; H, 3.82; N, 0.00. H
3
46 31
2
1
3
37.33, 129.23, 126.09 125.14, 122.25, 93.80, 85.38, 68.58, 52.37,
8.44.
NMR (300 MHz, CDCl ): δ 9.58 (s, 1H), 7.10−7.17 (m, 5H), 7.03−
3
13
7.06 (m, 19H), 6.85−6.88 (m, 4H), 5.11 (s, 2H). C NMR (75 MHz,
H
DOI: 10.1021/acs.organomet.7b00143
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
CDCl ): δ 191.12, 134.86, 129.28, 128.06−128.56 (m), 126.37, 92.54,
S.H., M.D., and J.S. thank the UGC of India for research
fellowships. We thank the DST-FIST and IIT D for funding the
single-crystal X-ray diffractometer and HRMS facilities at IIT
Delhi.
3
8
8.81, 76.73.
5
4
2
,5-Bis(methyl)-[η -C H −CHO]Co(η -C Ph ) (8c): orange solid;
5
2
4
4
yield 12 mg (56%). Mp: 161−162 °C. Anal. Found: C, 80.52; H,
.84; N, 0.00. Calcd for C H CoO: C, 80.59; H, 5.45; N, 0.00. IR (ν,
5
36
29
1
1
cm- ) 1670 (CO). H NMR (300 MHz, CDCl ): δ 9.63 (s, 1H),
3
7
.38−7.52 (m, 12H), 7.17−7.23 (m, 8H), 4.55 (s, 2H), 1.86 (s, 6H).
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1
3
C NMR (75 MHz, CDCl ): δ 191.62, 134.89, 130.01, 129.83−
3
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36
30
5
5
2
,5-(4-OMeC H ) -η -(CHO)C H ]Fe(η -C H ) (9a): red solid; yield
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1
0 mg (45%). Mp: 145−148 °C dec. Anal. Found: C, 70.49; H, 5.24;
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N, 0.00. Calcd for C H FeO : C, 70.44; H, 5.20; N, 0.00. H NMR
25
22
3
2
006, 75, 1178−1181. (d) van Staveren, D. R.; Metzler-Nolte, N.
(
300 MHz, CDCl ): δ 10.25 (s, 1H), 7.50−7.53 (d, J = 9 Hz, 4H),
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.89−6.92 (d, J = 9 Hz, 4H), 4.84 (s, 2H), 4.20 (s, 5H), 3.84 (s, 6H).
1
3
C NMR (75 MHz, CDCl ): δ 193.44, 159.46, 139.08, 133.46,
3
1
22.18, 82.24, 71.54, 68.55, 55.34. HRMS: m/z 449.0796, calcd for
+
C H FeNaO [M + Na] 449.0811.
25
22
3
5
5
2
,5-(4-BrC H ) -η -(CHO)C H ]Fe(η -C H ) (9b): orange-red solid;
6 4 2 5 2 5 5
2
94; Angew. Chem., Int. Ed. 2006, 45, 285−288.
yield 11 mg (55%). Mp: 157−158 °C. Anal. Found: C, 52.79; H, 3.08;
1
(2) (a) Sun, R.; Wang, L.; Yu, H.; Abdin, Z.; Chen, Y.; Huang, J.;
N, 0.00. Calcd for C H FeOBr : C, 52.72; H, 3.08; N, 0.00. H NMR
23
16
2
Tong, R. Organometallics 2014, 33, 4560−4573. (b) Miyaji, H.; Kim,
D. S.; Chang, B. Y.; Park, E.; Park, S. M.; Ahn, K. H. Chem. Commun.
(
(
300 MHz, CDCl ): δ 10.25 (s, 1H), 7.48 (s, 8H), 4.91 (s, 2H), 4.26
3
s, 5H). 13C NMR (75 MHz, CDCl ): δ 193.44, 139.05, 133.45, 92.05,
3
2
008, 753−755. (c) Xie, S.; Zang, J.; Yuan, Y.; Chi, Y.; Yuan, R. Chem.
8
9.05, 69.67, 68.55. HRMS: m/z 544.8806, calcd for C H FeBr NaO
23 16 2
+
Commun. 2015, 51, 3387−3390. (d) Arivazhagan, C.; Borthakur, R.;
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(
[
M + Na] 544.8812.
5
5
2
,5-Bis(methyl)-η -(CHO)C H ]Fe(η -C H ) (9c): red solid; yield 12
5 2 5 5
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mg (45%). Mp: 154−156 °C. Anal. Found: C, 64.65; H, 6.02; N, 0.00.
1
Calcd for C H FeO: C, 64.50; H, 5.83; N, 0.00. H NMR (300 MHz,
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13
CDCl ): δ 10.29 (s, 1H), 4.34 (s, 2H), 4.12 (s, 5H), 2.04 (s, 6H).
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3
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13
14
Crystal Structure Determination. Suitable crystals of com-
pounds were obtained by slow evaporation of their saturated solutions
in suitable solvent mixtures. Single-crystal diffraction studies were
carried out on a Bruker SMART APEX CCD diffractometer with a Mo
Kα (λ = 0.71073 Å) sealed tube. All crystal structures were solved by
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(
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ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.7b00143.
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*
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AUTHOR INFORMATION
Corresponding Author
E-mail for A.J.E.: eliasanil@gmail.com.
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*
ORCID
Anil J. Elias: 0000-0001-9980-5076
Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
The authors thank the DST of India for financial assistance in
the form of research grant to A.J.E (DST EMR/2015/000285).
■
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DOI: 10.1021/acs.organomet.7b00143
Organometallics XXXX, XXX, XXX−XXX