Iron-Catalyzed Hydrosilylation of Aldehydes and Ketones under Solvent-Free Conditions

Article abstract of DOI:10.1021/acs.organomet.5b00630

Exposure of aldehyde or ketone to 1 mol % BIAN-Fe(C₇H₈) complex in the presence of diphenyl silane affords the corresponding protected alcohol in excellent yields, under mild reaction conditions. Aldehydes and ketones are reduced cleanly in the presence of a broad range of functional groups under solvent-free conditions.

Full text of DOI:10.1021/acs.organomet.5b00630

Article
pubs.acs.org/Organometallics
Iron-Catalyzed Hydrosilylation of Aldehydes and Ketones under
Solvent-Free Conditions
Francis S. Wekesa, Renzo Arias-Ugarte, Lydia Kong, Zachary Sumner, Gregory P. McGovern,
and Michael Findlater*
Texas Tech University, Department of Chemistry & Biochemistry, Lubbock, Texas 79409-1061, United States
S
* Supporting Information
ABSTRACT: Exposure of aldehyde or ketone to 1 mol %
BIAN-Fe(C7H8) complex in the presence of diphenyl silane
affords the corresponding protected alcohol in excellent yields,
under mild reaction conditions. Aldehydes and ketones are
reduced cleanly in the presence of a broad range of functional
groups under solvent-free conditions.
intermediates and has been widely employed in both academia
and industry.4 Complementary to carbonyl reduction protocols
employing molecular hydrogen or hydride transfer reagents,
hydrosilylation, followed by aqueous workup to cleave the Si−
O bond, has emerged as a safe and relatively mild protocol for
the synthesis of alcohols (Figure 1). Traditionally, protocols
INTRODUCTION
■
Metal complexes of the robust framework of bis(arylimino)-
acenaphthene (BIAN) involving the α-diimine fragment
conjugated with the naphthalene ring have found widespread
use in coordination chemistry and catalysis.1 The correspond-
ing iron complexes of BIAN are, however, limited to a relatively
few reports,2 and many of these are tridentate derivatives
generated by incorporation of a pendant donor arm into the
parent bidentate ligand.3 The structural rigidity, stereo-
electronic tunability based on the N-substitutents, and facile
successive electron-accepting feature of the BIAN collectively
make it an attractive ligand to design metal complexes suitable
for electron transfer processes and catalytic application.
In view of these desirable properties, herein, we report the
syntheses of two new iron complexes, BIAN-FeCl2 and BIAN-
Fe(C7H8) (Scheme 1, BIAN = 1,2-((bis-2,6-diisopropyl-
Figure 1. Strategies for catalytic hydrosilylation of carbonyl
compounds.
Scheme 1
based on precious metal catalysts, particularly ruthenium,
rhodium, and iridium, have seen the most widespread use.5
However, the high cost, low abundance, and toxicity of these
elements have prompted the development of alternative
methods of carbonyl reduction based upon first-row transition
metals such as iron and cobalt.6 Iron, in particular, is a
noteworthy substitute for this application since it is environ-
mentally benign, abundant, inexpensive, and, more significantly,
less toxic than the precious metals so often in use in
pharmaceutical applications. Highly effective iron-based cata-
lysts for carbonyl reduction have recently emerged based
around multidentate ligand architectures featuring both P- and
N-donor atoms.7 Transfer hydrogenation and direct H2
addition reactions have been reported by the Beller,8 Casey,9
and Morris10 groups.
phenyl)imino)acenaphthene), and the application of the
toluene complex in the chemoselective reduction of aldehydes
and ketones under mild and solvent-free hydrosilylation
conditions.
Because of their widespread use, ease of synthesis from
commercially available materials, and demonstrated success in
Selective hydrosilylation of carbonyl compounds is an
invaluable synthetic route to alcohols and silyl ether
Received: July 22, 2015
© XXXX American Chemical Society
A
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industrial processes, we sought to explore the application of
bidentate bis(imino) ligands in hydrosilylation reactions using
base metals such as iron. Despite the diversity of recent
contributions made toward the development of iron-catalyzed
hydrosilylation of carbonyl compounds,6 there is still a great
demand for practical and chemoselective methodologies.
RESULTS AND DISCUSSION
■
Stirring 1 equiv of the BIAN ligand with FeCl2 results in the
formation of 14-electron, paramagnetic BIAN-FeCl2, which, in
the solid-state, displays a tetrahedral geometry at the iron
center (Scheme 1). The solution magnetic moment was found
to be 5.93 B.M. (Evans method)11 in methylene chloride-d2
and is consistent with a tetrahedral, high-spin Fe(II) complex.
The isolated dichloride is reduced with excess 0.5% sodium
amalgam under an argon atmosphere to furnish the reduced
Fe(0) center, which may be conveniently trapped with an
aromatic solvent; shown in Scheme 1 is the 18-electron,
diamagnetic toluene complex, BIAN-Fe(C7H8). The molecular
structures of both complexes are presented with the iPr groups
removed for clarity (Figure 2).
Figure 3. 80 K Mossbauer spectrum of BIAN-Fe(C H ).
̈
7
8
redox noninnocent ligand systems, an excellent recent study by
Neidig and Milstein has emphasized the importance of
combining as many spectroscopic and computational methods
as possible in properly assigning metal oxidation state.14a At this
time, in the absence of further characterization studies
employing SQUID magnetometry, EPR, variable-temperature
Mossbauer spectroscopy, and computational (DFT) methods,
̈
we are hesitant to definitively assign an oxidation state to the
metal center in BIAN-Fe(C7H8).14b Some contribution from
an “ene-diamide” form is, however, likely.12b
Several commercially available silanes were screened in the
presence of the iron precatalyst for the hydrosilylation of
benzaldehye (Table 1). Initially, the benzaldehyde is converted
Table 1. Screening of Silanes in the Hydrosilylation of
a
Benzaldehyde
b
entry
silane (equiv)
[Fe] cat (mol %)
time (h)
yield (%)
1
2
3
4
5
6
7
8
Et3SiH (3.0)
1.0
1.0
1.0
1.0
1.0
5.0
3.0
none
18
18
18
1
0
>70
0
(EtO)3SiH (3.0)
Ph3SiH (2.0)
Ph2SiH2 (1.0)
Ph2SiH2 (3.0)
Ph2SiH2 (1.0)
PhSiH3 (1.0)
Ph2SiH2 (1.0)
c
>99
1
>99
>99
>99
0
1
Figure 2. Solid-state structures of BIAN-FeCl2 and BIAN-Fe(C7H8)
at 30% probability ellipsoids, H atoms and i-Pr groups removed for
clarity.
1
18
a
b
Reaction conditions: benzaldehyde (1.0 mmol), 70 °C. Yields were
determined by GC−MS analysis of crude reaction mixture using
Diimine chelates are well-known to behave in a redox
noninnocent manner, and important electronic structural
information can be gleaned via an inspection of chelate bond
distances. Thus, BIAN-FeCl2 exhibits C−C and C−N distances
of 1.506(6) and 1.283(6) Å, respectively. These values are
typical of C−C single and CN double bonds, indicating that
no charge transfer has occurred. In contrast, the BIAN-
Fe(C7H8) shows a significant shortening of the C−C bond
distance 1.400(4) Å and concomitant lengthening of the C−N
distance 1.343(3) Å. These values strongly suggest that a
reduction of the ligand has taken place; studies by Cowley,12a
Chirik,12b and Wieghardt12c in related systems do not allow an
unambiguous assignment of the nature of this reduction (i.e.,
0-, 1-, or 2-electrons) based solely on bond distances. To try to
gain further insight, BIAN-Fe(C7H8) was analyzed using 57Fe
c
mesitylene as the internal standard. Ph2Si(OCH2Ph2)2 was also
observed when the reaction mixture was stirred overnight (ratio of
35:65).
into a siloxy intermediate, which affords benzyl alcohol upon
workup. Among the silanes tested, triethoxysilane, diphenylsi-
lane, and phenylsilane gave good yields of benzyl alcohol
(Table 1, entries 2, 4−7). Neither triethylsilane nor
triphenylsilane displayed any considerable reactivity (Table 1,
entries 1 and 3). The observed differences in silane activity with
the bis(arylimino)acenaphthene iron complex are consistent
with earlier reports using bis(imino)pyridine iron complexes.15
Thus, the relatively inexpensive diphenylsilane was selected for
further investigation as it proved to be an ideal reductant, giving
product in almost quantitative yield in less than 1 h at catalyst
loadings as low as 1 mol % (Table 1, entry 4). Increased catalyst
loading (Table 1, entry 6) or addition of excess silane (Table 1,
Mossbauer spectroscopy (Figure 3). At 80 K, the Mossbauer
̈
̈
spectrum features a doublet with an isomer shift (δ) of 0.45
mm s−1 and a quadrupole splitting (ΔEq) of 0.41 mm s−1.13
While such parameters have been widely applied in the study of
B
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entry 5) afforded no significant difference in overall yield of
benzyl alcohol.
Table 2. Iron-Catalyzed Hydrosilylation of Aldehydes and
Ketones with BIAN-Fe(C7H8) and Ph2SiH2
a
After optimizing the reaction conditions and selecting our
silane reductant of choice, several aldehydes and ketones
(Table 2) were reduced to demonstrate the generality of the
catalytic hydrosilylation method under solvent-free conditions.
Importantly, BIAN-Fe(C7H8) is an effective precatalyst without
the need for an activator and with only 1 equiv of silane. In
most cases, the reaction was complete within 1 h. The progress
of the reaction was monitored by GC−MS or 1H NMR
spectroscopy by analysis of either the silyl ether or the
corresponding alcohol after treatment with TBAF.
A broad functional group tolerance is observed: aromatic
(Table 2, entries 1−8), aliphatic (Table 2, entries 9 and 10),
and heterocyclic (Table 2, entries 11 and 12) aldehydes are all
reduced in excellent yields. Similarly, aromatic (Table 2, entries
13−15), aliphatic (Table 2, entries 16−18), and heterocyclic
ketones (Table 2, entries 19 and 20) are also reduced in good
to excellent yields. The hydrosilylation of ketones is, in general,
slower than the corresponding reaction for aldehydes. This
could arise from an increased steric component; this is
supported by entries 16−18 in Table 2. In each case, lower
than expected yields are obtained for the sterically larger
aliphatic ketones, and in the case of 1r (Table 2, entry 18), an
extended reaction time, 18 h, is required to obtain an isolated
product yield of 85%.
To place these results into a proper context, it is worthwhile
to compare these data with some leading examples of
alternative first-row metal catalysts. For example, a recent
report by Stradiotto and Turculet disclosed an Fe complex that
displays TOFs of up to 393 min−1.7 In contrast, Tilley has
reported the structurally simple [Fe{N(SiMe3)2}2] to also
effectively catalyze the hydrosilylation of aldehydes and ketones
with TOFs of ∼10 min−1.16 It is also important to note that
both the Stradiotto and Tilley catalysts are active between 23
and 25 °C. Thus, the activity of BIAN-Fe(C7H8), TOF = 0.5
min−1 (acetophenone, Table 1, entry 13), is somewhat lower
than that of comparable Fe-based analogues.
The iron-catalyzed hydrosilylation of α,β-unsaturated
ketones was also examined (Figure 4). In contrast to the
extended reaction times required of ketones (Table 2, entries
13−20), hydrosilylation of cyclohexenone (3) with Ph2SiH2 in
the presence of 1 mol % of BIAN-Fe(C7H8) occurred smoothly
in just 30 min at 70 °C. The corresponding alcohol (4a), with
no evidence for alkene reduction, was obtained exclusively
following workup with TBAF hydrolysis. However, if the
reduction is allowed to proceed overnight, a 1:1 mixture of 4a
and cyclohexanone (4b) is obtained after workup. It is
tempting to envision the possibility that 4b arises from a
competing alkene hydrosilylation pathway. However, given that
we are aware of only one prior report of alkene hydrosilylation
occurring preferentially in the presence of a carbonyl moiety,17
we tend to discount this explanation. It is more likely that Fe-
catalyzed isomerization of the allyl-silylether occurs18 to
generate a protected enol, which, upon workup, tautomerizes
to form the ketone 4b (Figure 4).
In a similar fashion, we carried out the hydrosilylation of the
terpenoid citral (5; E:Z, 1:1.5, Scheme 2). Reduction occurred
exclusively at the carbonyl and with no erosion in stereo-
chemistry (the ratio of E:Z isomers remained 1:1.5; see the
Supporting Information, S29).
a
Reaction conditions: Substrate (1.0 mmol), BIAN-Fe(C7H8) (1.0
b
mol %), 70 °C. Isolated yield of purified product after column
chromatography.
C
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images spanning at least a hemisphere of reciprocal space. All the data
were corrected for Lorentz polarization effects. A multiscan absorption
correction was applied using SADABS19 or CrystalClear.20 Structures
were solved by direct methods and refined by full-matrix least-squares
against F2 (SHELXTL21). All hydrogen atoms were assigned riding
isotropic displacement parameters and constrained to idealized
geometries. Crystallographic data for the two structures are given in
the Supporting Information. CCDC-1044803 and CCDC-1044804
contain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from the Cambridge Crystallo-
graphic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif,
or from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, U.K.; fax: (+44) 1223-336-033; e-mail:
deposit@ccdc.cam.ac.uk.
BIAN Ligand. BIAN ligand was synthesized by refluxing a
suspension of acenaphthenequinone and 2,6-diisopropylaniline in the
presence of acetic acid, according to a literature procedure.22
Recrystallization of the crude ligand from hot toluene afforded air-
stable orange crystals, 85% yield, 1H NMR (400 MHz, CDCl3): δ 7.85
d, 8.2 Hz, 2H, (acenaphthene), 7.34 t, 7.8 Hz, 2 H, (acenaphthene),
7.27−7.22 (m, 6H, (Ar), 6.61, (d, 7.3 Hz, 2 H, (Aryl), 3.01 (sept, 6.9
Hz, 4 H(iPr-Me) 1.22 (d, 6.9 Hz, 12 H(iPr-Me), 0.95 (d, 6.9 Hz, 12
H(iPr-Me).
Figure 4. Hydrosilylation of cyclohexenone and potential isomer-
ization mechanism with BIAN-Fe(C7H8).
BIAN-FeCl2. To a 250 cm3 round-bottom flask was added BIAN
Ligand (4.222 g, 8.433 mmol), FeCl2 (0.822 g, 6.49 mmol), and THF
(150 cm3). The resulting solution was allowed to stir at ambient
temperature for 16 h, during which time the solution turned blue. The
solution was filtered over a pad of Celite, and the volatiles were
removed under vacuum to yield a solid residue. The solid was washed
with pentane to afford a paramagnetic blue solid, 86% yield. 1H NMR
(400 MHz, C6D6): δ −16.75, −2.02, 0.46, 0.94 (d, 5.2 Hz), 1.20 (d,
5.2 Hz), 2.48, 3.04, 6.61, 7.44, 7.91, 12.03. Anal. Calcd for
C36H40Cl2FeN2: C, 68.91, H, 6.43, N, 4.46. Found C, 69.84, H,
6.52, N, 3.87.
Scheme 2
CONCLUSIONS
■
In summary, readily accessed bis(imino)acenaphthene iron
arene complex, BIAN-Fe(C7H8), is an efficient precatalyst for
the hydrosilylation of aldehydes and ketones using Ph2SiH2.
This method exhibits broad functional group tolerance and
high activities at 70 °C under solvent-free conditions. Further
investigations into the scope, mechanism, and enantioselectivity
of these reactions are a continuing area of investigation in our
laboratory.
BIAN-Fe(C7H8). A 100 cm3 round-bottom flask was charged with
Hg (52.612 g, 262 mmol) and pentane (∼10 cm3). With vigorous
stirring, Na (0.264 g, 11.4 mmol) was added, and the amalgam was
stirred for 0.5 h. Subsequently, BIAN-FeCl2 (1.434 g, 2.285 mmol),
pentane (10 cm3), and toluene (10 cm3) were added. The resulting
solution was stirred for 48 h under ambient conditions to afford a red
solution. The reaction mixture was decanted away from the amalgam
and filtered through Celite. After solvent stripping from the filtrate,
BIAN-Fe(C7H8) was isolated as a red solid, 54% yield. 1H NMR (400
MHz, C6D6): δ 7.46 (t, 8 Hz, 2H), 7.39 (d, 8 Hz, 4H), 7.27, (d, 8 Hz,
2H), 6.81, (t, 7.4 Hz, 2H), 5.89, (t, 7.4 Hz, 1H, p-C6H5CH3), 5.72 (d,
6.9 Hz, 2H), 4.96 (d, 6.0 Hz, 2H), 4.80 (t, 6.0 Hz, 2H), 3.86 (sept, 6.9
Hz, 4 H(iPr-Me), 3.04 (s, tol, 3H) 1.59 (d, 6.9 Hz, 12 H(iPr-Me), 0.78
(d, 6.9 Hz, 12 H(iPr-Me). 13C NMR (101 MHz, C6D6): δ 19.899,
24.50, 25.59, 28.43, 80.61, 80.98, 82.17, 97.67, 118.95, 123.99, 124.03,
126.63, 128.29, 130.71, 132.64, 141.68, 152.08, 152.87. Elem. Anal.
Calcd for C43H48FeN2: C, 79.61, H, 7.46, N, 4.32. Found C, 79.10, H,
7.48, N, 4.69.
Reduction of Aldehydes under “Solvent-Free” Conditions.
In a glovebox, a 20 mL oven-dried scintillation vial containing a stir bar
was charged with BIAN-Fe(C7H8) (1.0 mol %, 6.49 mg).
Subsequently, substrate (1.0 mmol) and Ph2SiH2 (1.0 mmol, 184.3
mg) were added. The vial was sealed, and the reaction mixture was
transferred to the Schlenk line and stirred at 70 °C for 30 min. A
longer reaction time was required for aldehydes 1g and 1h (Table 2,
entries 7 and 8).
EXPERIMENTAL SECTION
■
General Synthetic Procedures. All reagents were purchased
from commercial vendors and were used without further purification
unless otherwise noted. CH3CN was distilled from CaH2. All
manipulations of oxygen- and moisture-sensitive materials were
conducted with a standard Schlenk technique or in a glovebox.
Flash column chromatography was performed using silica gel (230−
400 mesh). Analytical thin-layer chromatography (TLC) was
performed on 60 F254 (0.25 mm) plates, and visualization was
accomplished with UV light (254 and 354 nm) and/or an aqueous
alkaline KMnO4 solution, followed by heating. Proton and carbon
nuclear magnetic resonance spectra (1H NMR and 13C NMR) were
recorded on a JEOL 400 MHz spectrometer with Me4Si or solvent
resonance as the internal standard (1H NMR, Me4Si at 0 ppm, CHCl3
at 7.24 ppm; 13C NMR, Me4Si at 0 ppm, CDCl3 at 77.0 ppm). H
1
NMR data are reported as follows: chemical shift, multiplicity (s =
singlet, d = doublet, t = triplet, q = quartet, quint = quintet, sext =
sextet, sept = septet, br = broad, m = multiplet), coupling constants
(Hz), and integration. Gas chromatography−mass spectrometry
(GC−MS) and high-resolution mass spectrometry (HRMS) were
performed on an electron ionization time-of-flight (EI-TOF) mass
spectrometer. Melting points were recorded using a capillary melting
point apparatus and are uncorrected.
X-ray Crystallography. Data for BIAN-FeCl2 and BIAN-
Fe(C7H8) complexes were obtained on a Bruker Smart Apex II
CCD diffractometer. All data were collected at room temperature
using graphite-monochromated Mo−Kα radiation (λ = 0.71073 Å).
Intensity data were collected using ω-steps accumulating area detector
Reduction of Ketones under “Solvent-Free” Conditions. In a
glovebox, a 20 mL oven-dried scintillation vial containing a stir bar was
charged with BIAN-Fe(C7H8) (1.0 mol %, 6.49 mg). Subsequently,
substrate (1.0 mmol) and Ph2SiH2 (1.0 mmol, 184.3 mg) were added.
The vial was sealed, and the reaction mixture was transferred to the
Schlenk line and stirred at 70 °C for 3 h. A longer reaction time was
required for the ketone 1r (Table 2, entry 18).
Hydrolytic Workup and Purification of Alcohols. THF (2 mL)
was added, and the reaction mixture was cooled to 0 °C. The reaction
mixture was then quenched with TBAF, 1.0 M in THF (1 mL),
D
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allowed to warm up to room temperature, and stirred for 3 h. Solvent
was evaporated, and the residue was dissolved in diethyl ether (30 mL)
and washed with water (2 × 20 mL). The organic phase was separated,
dried over MgSO4, filtered, and concentrated under reduced pressure.
Hydrolysis products with high boiling points were purified by a short
silica gel column and washed with n-hexane/ethyl acetate (3:2) or
dichloromethane/methanol (99:1). Triethylamine was added in the
eluting solvent for heterocyclic substrates. Hydrolysis products with
low boiling points (1a, 1d, 1k, 1l, 1m,1n, 1q, 1s, 1t, and 3) were
purified by distillation.
NMR (101 MHz, CDCl3): δ 141.78, 134.32, 128.39, 125.83, 62.21,
34.17, 32.03.
2,4-Dimethylpentan-2-ol (2n). A colorless liquid (99 mg, 85%).
1H NMR (400 MHz, CH3OD): δ 2.96 (dt, 5.5 Hz, 1.3 Hz, 1 H), 1.70
(sept, 6.4 Hz, 2 H), 0.87(d, 6.4 Hz, 12H), 13C NMR (101 MHz,
CDCl3): δ 81.76, 30.48, 19.75, 16.84.
1-((4-Trifluoromethyl)benzyl)ethanol (2o). A colorless oil
1
(180.6 mg, 95%). H NMR (400 MHz, CDCl3): δ 7.55 (d, 8.5 Hz,
2 H), 7.41 (d, 5.8 Hz, 2 H), 4.86 (q, 3.6 Hz, 1 H), 1.43 (d, 1.4 Hz 3
H). 13C NMR (101 MHz, CDCl3): δ 149.63, 129.58 (q, JC‑F = 32.0
Hz), 125.60, 125.32 (d, JC‑F, 3.8 Hz), 122.61, 120.01, 69.69. 19F NMR
(376 MHz, CDCl3): δ −62.36.
Benzyl Alcohol (2a). A colorless oil (95 mg, 88%). 1H NMR (400
MHz, CDCl3): δ 7.31−7.36 (m, 5 H), 4.66 (s, 2 H), 2.42 (br s, 1 H).
13C NMR (101 MHz, CDCl3): δ 140.94, 128.55, 7127.62, 127.02,
65.21.
Diphenylmethanol (2p). A colorless solid, m.p, 68−70 °C (180.3
mg, 99%). 1H NMR (400 MHz, CDCl3): δ 7.40−7.30 (m, 8 H), 7.30−
7.24 (m, 2 H), 5.80 (d, 5.5 Hz, 1 H), 2.47 (d, 5.5 Hz, 1 H). 13C NMR
(101 MHz, CDCl3): δ 143.73, 128.42, 128.49, 126.49, 76.13.
4-Methoxybenzyl Alcohol (2b). A colorless oil (127 mg, 92%).
1H NMR (400 MHz, CDCl3): δ 7.25 (d, 2 H, 8.5 Hz), 6.86 (d, 2 H,
5.5 Hz), 4.53 (br s, 2 H), 3.78 (s, 3 H), 2.79 (br s, 1 H). 13C NMR
(101 MHz, CDCl3): δ 158.90, 133.06, 128.48, 113.73, 64.53, 55.12.
(4-N,N-Dimethylamino)benzyl Alcohol (2c). A colorless liquid
1
Cyclohexanol (2q). A colorless liquid (85 mg, 85%). H NMR
(400 MHz, CDCl3): δ 3.51 (s, 1 H), 2.37−2.35 (m, 1H), 1.82−1.79
(m, 2H), 1.67−1.62 (m, 2H), 1.49−1.45 (m, 1H), 1.22−1.18 (m, 5H).
13C NMR (101 MHz, CDCl3): δ 70.25, 35.49, 25.41, 24.10.
Dicyclohexylmethanol (2r). A colorless solid, mp 62 °C (147.2
mg, 75%). 1H NMR (400 MHz, CDCl3): δ 3.02 (dt, 5.5 Hz, 1.5 Hz, 1
H), 1.77−1.52 (m, 10H), 1.48−1.33 (m, 2H), 1.30−1.91 (m, 10H).
13C NMR (101 MHz, CDCl3): δ 80.41, 39.84, 29.98, 27.31, 26.53,
26.48, 26.16.
1
(149.5 mg, 99%). H NMR (400 MHz, CDCl3): δ 7.23 (d, 8.7 Hz, 2
H), 6.62 (d, 8.7 Hz, 2 H), 4.53 (s, 2 H), 2.93 (s, 6 H), 1.96 (br s, 1 H).
13C NMR (101 MHz, CDCl3): δ 150.24, 128.92, 128.52, 112.59,
65.13, 40.61.
(4-Trifluoromethyl)benzyl Alcohol (2d). A colorless oil (128.8
mg, 74%). 1H NMR (400 MHz, CDCl3): δ 7.59−7.61 (m, 2 H), 7.45−
7.47 (m, 2 H), 4.76 (d, 4.0 Hz, 2 H), 1.94 (br s, 1 H). 13C NMR (101
MHz, CDCl3): δ 144.69, 129.52 (q, JC‑F = 32.0 Hz), 126.81, 125.44 (d,
JC‑F = 3.0 Hz), 122.81, 64.46. 19F NMR (376 MHz, CDCl3): δ −62.39.
4-Nitrobenzyl Alcohol (2e). A colorless liquid (146.3 mg, 92%).
1H NMR (400 MHz, CDCl3): δ 8.17−8.19 (d, 2 H, 8.5 Hz), 7.49−
7.51 (d, 2 H, 5.8 Hz), 4.80 (s, 2 H), 2.14 (br s, 1 H). 13C NMR (101
MHz, CDCl3): δ 148.14, 134.27, 126.96, 123.700, 63.96.
Naphthalen-1-ylmethanol (2f). A colorless liquid (156.6 mg,
99%). 1H NMR (400 MHz, CDCl3): δ 8.08−8.06 (m, 1 H), 7.88−7.86
(m, 1 H), 7.80 (d, 8.2 Hz, 1H), 7.55−7.40 (m, 4 H), 5.07 (d, 5.5 Hz, 2
H), 2.18 (t, 6.0 Hz, 1 H). 13C NMR (101 MHz, CDCl3): δ 136.17,
128.57, 128.54, 126.24, 125.78, 125.31, 125.21, 123.56, 63.44.
2,2-Diphenylethanol (2g). A colorless liquid (193.3 mg, 96%).
1H NMR (400 MHz, CDCl3): δ 7.36−7.33 (m, 4 H), 7.30−7.23 (m, 6
H), 4.20−4.18 (m, 2 H), 4.15 (m, 1 H). 13C NMR (101 MHz,
CDCl3): δ 141.35, 134.29, 130.03, 128.62, 128.25, 128.66, 126.72,
66.01, 53.54.
1-(Thiophen-2-yl)ethanol (2s). A colorless liquid (116.6 mg,
1
91%). H NMR (400 MHz, CDCl3): δ 7.25 (d, 7.5 Hz, 1 H), 6.98 (t,
5.3 Hz, 2 H), 5.07 (m, 1 H), 1.60 (d, 4.5 Hz, 1H). 13C NMR (101
MHz, CDCl3): δ 149.82, 126.54, 124.28, 123.08, 66.06, 25.13.
1-(Pyridin-3-yl)ethanol (2t). A colorless liquid (96 mg, 88%). 1H
NMR (400 MHz, CDCl3): δ 8.36 (d, 33 Hz 1 H), 7.69 (s, 1 H), 7.21−
7.20 (m, 1H), 5.24−8.84 (br s, 1 H) 4.29 (br s, 1 H) 13C NMR (101
MHz, CDCl3): δ 148.00,147.00, 141.67, 133.45, 123.49, 67.46, 25.11.
1
2-Cyclohexen-1-ol (4a). A colorless liquid (91.2 mg, 93%). H
NMR (400 MHz, CDCl3): δ 5.85−5.76 (m, 1 H), 5.73−5.74 (m, 1H),
4.16 (br s, 1 H), 3.43 (q, 4.7 Hz, 1 H), 2.25−1.75 (m, 4 H), 1.74−1.65
(m, 2H), 1.64−1.45 (m, 2 H). 13C NMR (101 MHz, CDCl3): δ
130.51, 129.80, 65.81, 65.44, 31.93, 24.99, 18.89, 15.20.
trans-2-Phenyl-2-propen-1-ol (6). A colorless liquid (128.8 mg,
96%). 1H NMR (400 MHz, CDCl3): δ 7.39−7.41 (m, 2 H), 7.33−7.35
(m, 2 H), 7.25−7.27 (m, 1 H), 6.63 (d, 16.0 Hz, 1 H), 6.36 (dt, J =
15.9, 5.9 Hz, 1 H), 4.32 (dd, 4.6 Hz, 1.3 Hz, 2 H), 1.53 (t, 5.9 Hz, 1
H). 13C NMR (101 MHz, CDCl3): δ 136.61, 134.31, 131.01, 128.53,
128.43, 127.62, 126.41, 63.58.
2,6-Bis-methanol-bromobenzene (2h). A colorless solid (193.5
mg, 90%). 1H NMR (400 MHz, CDCl3): δ 7.36−7.33 (m, 4 H), 7.30−
7.23 (m, 6 H), 4.20−4.18 (m, 2 H), 4.15 (m, 1 H). 13C NMR (101
MHz, CDCl3): δ 141.35, 134.29, 130.03, 128.62, 128.25, 128.66,
126.72, 66.01, 53.54.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.5b00630.
3-Phenylpropan-1-ol (2i). A colorless liquid (106.2 mg, 78%). 1H
NMR (400 MHz, CDCl3): δ 7.36−7.33 (m, 4 H), 7.30−7.23 (m, 6
H), 4.20−4.18 (m, 2 H), 4.15 (m, 1 H). 13C NMR (101 MHz,
CDCl3): δ 141.35, 134.29, 130.03, 128.62, 128.25, 128.66, 126.72,
66.01, 53.54.
Complete experimental procedures and full character-
ization data for BIAN-FeCl2 and BIAN-Fe(C7H8)
(PDF)
1
1-Octanol (2j). A colorless liquid (128 mg, 99%). H NMR (400
MHz, CDCl3): δ 3.59 (t, 5.5 Hz, 2 H), 1.65 (br s, 1 H), 1.57 (m, 2 H),
1.30−1.19 (m, 10 H), 0.84 (t, J = 3 H). 13C NMR (101 MHz, CDCl3):
δ 62.97, 32.74, 31.78, 29.37, 29.24, 25.71, 22.61, 14.04.
Crystallographic data for BIAN-FeCl2 (CIF)
Crystallographic data for BIAN-Fe(C7H8) (CIF)
Thiophen-2-yl-methanol (2k). A colorless liquid (97 mg, 87%).
1H NMR (400 MHz, CDCl3): δ 7.27−7.25 (m, 1 H), 6.98−6.95 (m, 2
H), 4.77 (d, 5.5 Hz, 2 H), 2.27 (t, 6.0 Hz, 1 H). 13C NMR (101 MHz,
CDCl3): δ 144.04, 126.90, 125.57, 125.52, 59.68.
AUTHOR INFORMATION
Corresponding Author
*E-mail: michael.findlater@ttu.edu.
Notes
■
Pyridin-2-ylmethanol (2l). A colorless liquid (97.1 mg, 89%). 1H
NMR (400 MHz, CDCl3): δ 8.35 (d, 4.6 Hz, 1 H), 7.56 (dd, 7.8, 1.2
Hz, 1 H), 7.27 (d, 7.8 Hz, 1 H), 7.06 (dd, 5.5 Hz, 1.2 Hz, 1 H), 4.64
(s, 2 H). 13C NMR (101 MHz, CDCl3): δ 159.90, 148.15, 136.77,
122.05, 120.67, 64.19.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
1
We are grateful for financial support from the Robert A. Welch
Foundation (Grant D1807) and the National Science
Foundation (CRIF MU grant CHE-1048553) and to Dr.
1-Phenylethanol (2m). A colorless liquid (106.2 mg, 78%). H
NMR (400 MHz, CDCl3): δ 7.30−7.16 (m, 5 H), 3.66(t, 6.4 Hz, 2
H), 2.69 (q, 7.8 Hz, 2 H), 1.90−1.83 (m, 2 H), 1.50 (s, 1 H). 13C
E
DOI: 10.1021/acs.organomet.5b00630
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(19) Sheldrick, G. M. SADABS v2008/1; Bruker AXS Inc.: Madison,
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Guigen Li for the generous donation of several substrates, Dr.
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Dr. Paul Chirik for help in obtaining the Mossbauer spectrum
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(22) Dastgir, S.; Coleman, K. S.; Cowley, A. R.; Green, M. L. H.
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DOI: 10.1021/acs.organomet.5b00630
Organometallics XXXX, XXX, XXX−XXX