Iron cyclopentadienone complexes derived from C2-symmetric bis-propargylic alcohols; Preparation and applications to catalysis

Article abstract of DOI:10.1039/c5dt04610f

A series of complexes containing the iron-cyclopentadienone structure were prepared by cyclising bis-propargylic alcohols and their derivatives with iron pentacarbonyl. The resulting complexes were characterised and tested in the catalysis of ketone reduction and alcohol oxidation. The complexes are competent catalysts for ketone reduction and alcohol oxidations.

Full text of DOI:10.1039/c5dt04610f

View Article Online
View Journal
Dalton
Transactions
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: R. C. Hodgkinson,
A. Del Grosso, G. J. Clarkson and M. Wills, Dalton Trans., 2016, DOI: 10.1039/C5DT04610F.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/dalton

Page 1 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
Iron cyclopentadienone complexes derived from C2-symmetric bis-propargylic alcohols;
preparation and applications to catalysis.
Roy Hodgkinson,+ Alessandro Del Grosso,+ Guy Clarkson and Martin Wills.*
Department of Chemistry, Warwick University, Coventry, CV4 7AL, UK. +44 24 7652 3260.
Email m.wills@warwick.ac.uk
+ RH and ADG contributed equally.
Abstract. A series of complexes containing the iron-cyclopentadienone structure were
prepared by cyclising bis-propargylic alcohols and their derivatives with iron pentacarbonyl.
The resulting complexes were characterised and tested in the catalysis of ketone reduction
and alcohol oxidation. The complexes are competent catalysts for ketone reduction and
alcohol oxidations.
Keywords: Asymmetric, iron, cyclopentadienone, catalysis, ketone, reduction.
Introduction
There is a growing interest in the application of iron-based complexes for the catalysis of
asymmetric transformations, primarily due to its relative low cost and toxicity relative to
more commonly used catalysts based on precious metals.1 Iron cyclopentadienone complexes
(general structure 1) have recently emerged as promising reagents for hydrogenation
reactions and for hydrogen transfer processes.2-13 Key to their application in this capacity is
the formation of the derived hydrides of general structure 2, which can be achieved in situ
using a number of activating agents, or through formation and isolation of the hydride prior to
use. Complex 2 can transfer two atoms of hydrogen to an acceptor such as a ketone or imine
and in doing so is converted to the unsaturated form 3. Complex 2 can be regenerated from 3
using a reducing agent such as formic acid or an alcohol (in the case of asymmetric transfer
hydrogenation – ATH) or hydrogen gas (as in the case of asymmetric pressure hydrogenation
– APH). The hydrogen transfers are believed to take place through a cyclic transition state as
depicted in Figure 1.13 The complexes have also been used in alkyne and alkene reductions,
using a derivative in which the OH bond on the Cp ring is modified.14
1

Dalton Transactions
Page 2 of 32
View Article Online
DOI: 10.1039/C5DT04610F
Figure 1. Proposed mode of hydride transfer from iron hydride complexes to ketone.
Iron cyclopentadienone complexes were reported in detail by Schrauzer in 1959, through the
cyclisation of two alkynes with an iron carbonyl complex,2a and this approach remains the
most common one.2-13 Intramolecular cyclisation of a 1,7-dialkyne can be used to form
complexes such as 4a and 4b. The formation and isolation of the iron hydride 5 was reported
by Knölker in 1999,3b and this hydride was demonstrated in 2007 by Casey and Guan, to be
effective catalysts for the hydrogenation of a series of ketones.4 The iron hydride species can
also be generated in situ from an iron tricarbonyl complex using an activating agent such as
Me3NO (TMAO) or a close derivative,15 or K2CO3 (in an aqueous environment)7b or through
the use of photoactivation, in the presence of a hydrogen source.5 Apart from reductions, the
hydrogen-transfer properties of the catalyst have allowed it to be applied to what can be
regarded as formal oxidations of alcohols (using acetone as a hydrogen acceptor),9 reductive
amination,10 ‘hydrogen borrowing’ reactions in which a C-N bond is formed between an
alcohol and an amine12a-c and to conversion of an amide to a nitrile.12d Table 1 summarises
recent applications of the catalysts, together with the catalyst derivatives commonly
employed.
2

Page 3 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
Table 1. Synthetic applications of iron cyclopentadienone tricarbonyl catalysts.
Entry Application
Author, year
Casey et al. 2007 and 2009 4
Catalyst used
Activator
n/a
1
2
3
4
C=O hydrogenation
5
6
C=O hydrogenation
C=O reduction
Berkessel et al. 2011 5
6a
uv light.
Wills et al. 2012
.
7 and derivatives. TMAO
C=O reduction –
aldehyde and ketone
C=O reduction –using
formaldehyde and H2O
C=O reduction
Beller et al. 2012 7a, 7b
.
K2CO3
4
5
Wu et al. 2015 11
Na2CO3
4
6
7
8
9
Gennari et al. 2015 8
Funk et al. 2010 9a
Guan et al. 2010 9b
TMAO
8
CHOH oxidn
4 and derivatives
TMAO
n/a
CHOH oxidn
5
CHOH oxidn
Williams et al. 2009 9c
1 (all R = Ph) and H2O
9.
10
11
12
CHOH oxidn
Wills et al. 2011 6b
1 (all R=Ph) and
TMAO
derivatives of 7
Reductive amination
Quintard et al. 2012,2013, 10b,
10c, 10e
4, and derivatives TMAO
of 7, 9, 10, 11
C=O and C=N
reduction
Renaud et al. 2013 10d
Cationic
TMAO
derivatives of 11
13
14
C=N reduction
Reductive hydroamina- Beller et al. 2012 7e
Beller et al. 2013, 2011, 7c,d
Phosphonic acid
Phosphonic acid
5
5
.
tion of alkynes
15
‘hydrogen borrowing’
Feringa et al. 2014 12a
4, derivative of 4
TMAO
Zhao et al. 2015 12c
Wills et al. 2015 12b
Nakazawa et al. 2014 14
16
17
‘hydrogen borrowing’
Alkene and alkyne
reduction
1 (all R = Ph)
TMAO
Derivative of 5.
n/a OH of Cp is
alkylated
TMAO
18
19
Alkylation of beta-
ketoester
Quintard et al. 2013 10a
Sortais et al. 2015 12d
4
Amide to nitrile
NHC-containing
complex
Uv light
Very few examples of asymmetric modifications of iron(cyclopentadienone) complexes have
been published to date. Berkessel et al. reported the use of complex 6, in which one CO
ligand was replaced by the chiral monodonor ligand MONOPHOS, thus rendering the iron
3

Dalton Transactions
Page 4 of 32
View Article Online
DOI: 10.1039/C5DT04610F
hydride chiral and offering the potential for this asymmetric to be relayed in the hydrogen-
transfer step.5 Using this catalyst, products with up to 32% ee were obtained for
acetophenone reduction. We reported the application of the asymmetric complex 7 and close
derivatives to ketone reduction by transfer hydrogenation, with a maximum ee of 25%.6 In a
recent example Gennari et al. created a cleverly designed catalyst 8 derived from a binapthyl-
scaffold, and this gave the highest asymmetric inductions so far recorded for ketone reduction
with this class of complex; up to 77% in one case.8 In this paper we describe the synthesis and
applications of a series of asymmetric iron(cyclopentadienone) complexes derived from C2-
symmetric diols, which represent a new derivative class of these complexes.
Results and discussion.
In earlier unrelated work, we demonstrated an efficient route to the synthesis of diol 12 in
high enantioselectivity through the asymmetric reduction of the precursor diketone.16
Treatment of 12 with Fe(CO)5 (130 °C, 20 h, sealed tube) resulted in the formation of
complex 13 in 76% yield. The breaking of the C2-symmetry of the substrate was clear in the
1
product, with distinct signals in the H-NMR spectrum observed for each of the methine
protons adjacent to the hydroxyl groups. In addition a racemic/meso mixture of diols was
prepared by reduction of the precursor diketone with NaBH4. When this was cyclised in the
same manner, the peaks of the racemic product could be observed but in addition the
presence of the meso product was confirmed by the observation of extra methine resonances
(Supporting Information). A complex with a hydroxyl group in the fused ring has been
reported by Pearson et al.2c In addition, it was possible to prepare each of the O-protected
ethers 14-17 and to convert these to the corresponding complexes 18-21 in the same manner
(Scheme 1). Each of the catalysts were characterised by NMR, MS and IR analysis, following
purification by chromatography on silica gel, to which the complexes are stable. As expected,
1
characteristic peaks were observed in the H-NMR spectrum for the diastereoisomeric
protecting groups. In addition, taking the OBn and OTBDMS derivatives as substrates, it was
possible to substitute one CO for MONOPHOS using the TMAO-activated process described
by Berkessel.5 Both diastereomeric combinations of the resulting complexes 22-25 were
formed, i.e. derived from both enantiomers of MONOPHOS, in order to examine the
possibility of matched and mismatched stereocontrol in subsequent applications.
Scheme 1. Synthesis of iron(cyclopentadienone) catalysts.
4

Page 5 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
.
Reagents and conditions: i) NaH, THF, BnBr, tBu4NI, rt, 24h (for 14); TBDMSCl, Imidazole,
DMF, o/n, rt (for 15); TIPSCl, imidazole, DMF; o/n, rt (for 16); TBDPSCl, imidazole, DMF,
o/n, rt (for 17). ii) 3.0 eq. Fe(CO)5, toluene, 130 °C, 20h. iii) MONOPHOS (2.0 eq.), TMAO
(2.0 eq.), toluene, 60 °C, o/n.
Although complexes 22 and 23 appeared to be single isomers, each diastereoisomer of
complexes 24 and 25 bearing OTBDMS groups were found to contain a ca. 10% of the other
diastereoisomer. This suggested that either racemisation of the BINOL component during the
preparation of MONOPHOS or during its subsequent complexation had taken place.
Racemisation of the diether ligand prior to or during complexation seems unlikely as this
would have been expected to lead to formation of some of the meso isomer, but this was not
observed. The lack of diastereoisomeric impurities in 22 and 23 may be the result of
purification from the minor diastereoisomers during the isolation procedure.
The complexes 13, 18-21 were first applied to the asymmetric reduction of the
representative substrate acetophenone, using both asymmetric transfer hydrogenation (ATH)
and pressure hydrogenation (APH) conditions. The complexes were also used in the
oxidation of racemic 1-phenylethanol using acetone as a hydrogen acceptor. In all cases the
active catalyst was generated in situ using methods previously reported, and in some cases
comparisons with the unfunctionalised catalyst 4b2b were also made.2-12,15 In the ATH
reactions (Table 2 shows selected results, further results are given in the Supporting
Information, Table S1), at 60 °C using a 5:2 (molar) formic acid:triethylamine azeotrope
(FA/TEA) and 10 mol% catalyst, full conversion was observed in several cases however the
asymmetric inductions were extremely low and a significant amount of formate co-product
was also formed, presumably through formylation of the initial alcohol product (confirmed to
5

Dalton Transactions
Page 6 of 32
View Article Online
DOI: 10.1039/C5DT04610F
be of the same absolute configuration as the alcohol).6a TMAO was added to ensure full
activation of the catalysts efficiently although, as demonstrated using unsubstituted 4b, it
could be omitted from the reaction6a at the cost of a slower activation; a reaction complete in
24h using TMAO reached just 52% conversion in the same time without TMAO (entries 1-
3). In this respect, however the diol complex 13 appeared to be less sensitive to the additive
(entries 4-7). Although the enantioselectivities were low, the OH and OBn complexes gave
products of opposite configurations to those observed with the O-silylated complexes (entries
8-15). The use of lower catalyst loadings (5%, 1%) gave much lower conversions, as did
lowering the temperature to 40 °C (Supporting Information). Another clear trend was the
observation of improved ees when using the more hindered silyl-substituted complexes, for
both the alcohol and formate products.
Table 2. ATH of acetophenone reduction using iron catalysts 13, 18-21.a
Entry Catal- Loading Activa- Time
Alcohol Formate Alcohol Formate
yst
4b
4b
4b
13
13
13
13
18
18
19
19
20
20
21
21
/mol%
10
10
10
10
10
10
10
5
tor
None
None
TMAO 24 h
TMAO 5 h
TMAO 24 h
/%
44
78
87
19
78
69
83
13
65
29
86
24
76
24
79
/ %
8
22
13
5
14
10
14
33
22
54
12
5
ee / %
-
-
ee/ %
-
-
1 b
2 b
3 b
4
24 h
5 days
-
-
9 (S)
8 (S)
8 (S)
8 (S)
2 (S)
3 (S)
18 (R)
17 (R)
23 (R)
22 (R)
21 (R)
24 (R)
6 (S)
8 (S)
8 (S)
9 (S)
3 (S)
1 (R)
16 (R)
5
6 b
7 b
8
None
24 h
TMAO 24 h
TMAO 24 h
TMAO 24 h
TMAO 24 h
TMAO 24 h
TMAO 24 h
TMAO 24 h
TMAO 24 h
TMAO 24 h
9
10
5
10
5
10
5
10
10
11
12
13
14
15
16 (R)
c
23
26
12
24 (R)
22 (R)
18 (R)
a. reaction conditions; [S] = ca. 1.0 M, TMAO (1 eq. relative to complexes) unless otherwise indicated, %
conversions are given and the balance is unreduced ketone. b. [S] = 1.45M. c. not determined.
A similar pattern emerged for the pressure hydrogenation reactions (APH; Table 3),
although some unusual observations were made with respect to the method of activation.
Control reactions run under nitrogen indicated that significant background transfer
6

Page 7 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
hydrogenation was also operating (entries 4-6, 12-14), however the conversions were lower.
The similar ees (for 13) observed in the absence of hydrogen gas indicated that the catalyst
was still operating in the reaction. Initially, unsubstituted complex 4b was tested and this
gave 100% conversion under 30 bar hydrogen pressure at 80 °C in 24 h in an iPrOH/water
solvent mixture, provided that an activator; either K2CO3 or TMAO,15 was added (entries
7a,b
1-3). Given this precedent, K2CO3 was used in all the subsequent tests. Unfortunately, the
substituted catalysts were not as active as 4b, giving much lower conversions under the same
conditions (entries 8, 17, 24, 30). No advantage was gained from running the reactions at the
higher temperature of 100 °C (entries 9, 18, 21, 25, 30); catalyst decomposition was
suspected) or for a longer time (72 h) at a lower temperature of 60 °C (entries 16, 20, 23, 28).
Whilst most of the other complexes behaved in a similar manner to 4b, requiring some form
of activation for best results, for diol-containing complex 13, omission of the K2CO3 (and no
other activator) resulted in full acetophenone reduction (entry 7), as did the use of 1 mol% of
TMAO (entry 10). The use of 1.5 mol% of TMAO, however, gave a lower conversion,
possibly due to partial catalyst decomposition (entry 11). The use of 1 mol% of TMAO also
proved to be the most effective way to activate the other catalysts where tested (entries 19,
26, 31). The asymmetric induction was not improved in either case however and remained
modest, not exceeding 20% ee in any case, although again the more hindered silylated
complexes gave the best enantioselectivities. This may reflect the distant separation of the
chiral centres from the likely reduction centre, which requires some further optimisation to
extend its influence to the transition state of the reduction; the trend in the results suggests
that a further increase in the steric hindrance of the groups on the ‘bridging C-4’ unit could
provide a route to such improvements.
Table 3. APH of acetophenone using iron catalysts 13, 18-21.a
Entry
1b
Catalyst Activator
Time / h T / ºC Conv./%
Eeb /%
None
K2CO3 (5%)
18
18
18
18
18
18
18
80
80
80
80
80
80
80
11
-
-
-
-
4b
2 b
100
100
1
51
69
4b
4b
4b
4b
4b
13
3 b
TMAO (1%)
None
4 b,c
5 b,c
6 b,c
7 b
K2CO3 (5%)
TMAO (1%)
None
-
-
5 (S)
100
7

Dalton Transactions
Page 8 of 32
View Article Online
DOI: 10.1039/C5DT04610F
8 b
9
K2CO3 (5%)
K2CO3 (5%)
TMAO (1%)
TMAO (1.5%)
None
K2CO3 (5%)
TMAO (1%)
None
K2CO3 (5%)
K2CO3 (5%)
K2CO3 (5%)
TMAO (1%)
K2CO3 (5%)
K2CO3 (5%)
None
18
24
18
18
18
18
18
18
72
18
24
18
72
24
18
72
18
24
18
18
72
18
24
18
80
100
80
80
80
80
80
18
7
100
79
52
6
53
55
29
93
18
100
34
31
42
8
9 (S)
3 (S)
8 (S)
6 (S)
8 (S)
7 (S)
8 (S)
7 (S)
9 (S)
8 (S)
6 (S)
7 (S)
13 (R)
11 (R)
14 (R)
19 (R)
15 (R)
13 (R)
13 (R)
20 (R)
19 (R)
18 (R)
6 (R)
13
13
13
13
13
13
13
18
18
18
18
18
19
19
20
20
20
20
20
21
21
21
21
21
10 b
11 b
12 b,c
13 b,c
14 b,c
15 b
16
80
60
17 b
18
19 b
20
21
22
80
100
80
60
100
80
23
24
K2CO3 (5%)
K2CO3 (5%)
K2CO3 (5%)
TMAO (1%)
None
K2CO3 (5%)
K2CO3 (5%)
K2CO3 (5%)
TMAO (1%)
60
80
59
9
25
26
100
80
100
31
25
34
12
72
27
28
29
30
80
60
80
100
80
31
15 (R)
a. Reaction conditions; 1 mol% catalyst, [S] = ca. 1.0 M unless otherwise indicated, 30 bar H2, iPrOH/H2O (0.5
mL/0.2 mL) used as solvent, b. [S] = 1.9 M. c. control reaction run under nitrogen (1 atm) with no hydrogen
present.
Given the unexpected result obtained when K2CO3 was omitted from the reaction with diol
catalyst 13, we questioned whether the addition of water to a dry solvent could reproduce this
effect. This proved to be the case; in dry THF, 31% reduction of acetophenone was observed
after 18h at 80 °C, possibly due to trace amounts of adventitious water, however as increasing
amounts of water were added, the conversion increased, reaching 99% when 100 mol% (1
eq.) relative to substrate, and 100% when a 5/2 THF/water solvent mixture was used –
1
although no change to the ee was observed (Supporting Information, Table S2). A H-NMR
study of the reaction revealed the formation of an iron hydride complex, suggesting that
water was initiating the formation of the active species. A similar effect, although to a lesser
extent, created by addition of water was also observed when toluene was used as solvent
(Supporting Information, Table S3).
Reductions of acetyl cyclohexane (ATH or APH) and of 3,3-dimethyl-2-butanone
(
pinacolone, ATH) also worked using 10 mol% catalyst although the products were racemic
or of low ee (see Supporting Information, Tables S5 and S6). In the APH of 3,3-dimethyl-2-
8

Page 9 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
butanone, using 1 mol% of catalyst 13 and 18-21, (60 °C, 72 h, 30 bar H2), conversions were
generally low (Supporting Information, Table S7). Due to the low conversions, accurate ees
could not be determined, however these were generally in the range of 30-38%.
The complexes proved to be efficient at the catalysis of alcohol oxidation using acetone as
hydrogen acceptor, a process which has been reported for a number of iron(cyclopentadienyl)
catalysts.6b,9 However both enantiomers of substrate were oxidised with little selectivity
(Table 4), although with excellent conversions, particularly when 10 mol% of catalyst was
used. The catalyst loading could be reduced to 5 mol% in some cases although at 1 mol%
loading, incomplete conversion was observed (Supporting Information, Table S4). The
observed enantiomeric excesses indicated that no significant level of kinetic resolution was
taking place in the oxidations.
Table 4. Oxidation of 1-phenylethanol using iron catalysts 13, 18-21.a
Entry
Catalyst Loading Time Alcohol Ketone Alcohol
/ mol% / h
/ %
53
4
15
0
12
3
0
/ %
47
96
85
100
88
97
100
50
100
96
32
92
100
18
ee / %
8 (R)
28 (R)
12 (R)
n/a
20 (R)
31 (S)
n/a
1
2
3
4
5
8
9
10
11
14
15
17
18
19
20
10
10
10
10
5
5
24
5
24
5
13
13
18
18
18
19
19
19
19
20
20
21
21
21
21
10
10
5
5
24
5
50
0
6 (S)
n/a
5
24
24
24
5
24
5
10
5
10
10
5
4
68
8
0
82
0
5 (R)
5 (S)
45 (S)
n/a
2 (S)
n/a
5
24
100
a. Reaction conditions; 60 °C, [S] = 0.19M, acetone solvent, TMAO (1 eq. relative to complexes).
The design of the MONOPHOS-containing catalysts 22-25 was anticipated to be capable of
delivering improved results since; i) MONOPHOS is known to be compatible with
complexes of this type and ii) the additional element of chirality in the ligand could be
matched or mismatched to that on the cyclohexyl ring.5 In the event, 22-25 exhibited very
9

Dalton Transactions
Page 10 of 32
View Article Online
DOI: 10.1039/C5DT04610F
low activity in the applications in which they were tested, despite the use of several methods
to activate them. Results for the ATH of acetophenone and 3,3-dimethyl-2-butanone with the
MONOPHOS complexes are given in the Supporting Information (Table S8). Using 10 mol%
catalyst, for 24 h at 25-60 °C, and activation with TMAO, conversions were below ca. 7%.
Performing the reaction using TMAO (in the dark or in the presence of light), or blue or uv
light (365 nm) to activate the precatalyst, no improvement was observed. In one case, the use
of the OTBDMS 24 catalyst (60 °C, 24 h) in the reduction of acetophenone gave 12.2%
alcohol (18.0 % ee) and 8.9% formate (12.4 % ee), both of R configuration. The same
outcome was observed in pressure hydrogenation tests. Using 1 mol% catalyst, 60 °C, 72 h,
gave < 5% conversion and ees of less than 10% (Supporting Information, Table S9).
To examine the effect of a phosphine we added increasing amounts of
triphenylphosphine to 1 mol% of 13 under APH conditions (Supporting Information, Table
S10). In this case, as the amount of PPh3 increased, the conversion (80 °C, 18h) decreased
and with 2% PPh3 relative to 1 mol% catalyst 13, no reduction was achieved. This may
indicate the formation of a less reactive phosphine-containing species similar to 22—25. This
study was also carried out using MONOPHOS as an additive and a similar reduction in
activity was observed although the enantioselectivity was not significantly changed
(Supporting Information, Table S11). Funk and Moyer have described closely related
complexes which demonstrate lower activity towards hydrogen transfer when a CO ligand
was replaced by a phosphine, and our results mirror these.9a
The X-ray crystallographic structures of complexes 4b2b (Figure 2), 22 (Figure 3) and 23
(Figure 4) were obtained (see Supporting Information for full details). In the case of 23, two
independent molecules of similar conformation were observed (see Supporting Information
for full detail of each structure). Both complexes 22 and 23 are quite congested and hindered,
particularly in comparison with 4b, which benefits from a more ‘open’ structure. This may
account for the observed low reactivity of the derived hydride from the MONOPHOS-
containing complexes, not only in comparison with 4b, but also compared to complex 6
reported by Berkessel, which does not contain substituents on the carbon backbone.
10

Page 11 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
Figure 2. The X-ray crystallographic structure of 4b (CCDC 1431241).
Figure 3. The X-ray crystallographic structure of complex (SS,S)-22 (CCDC 1431242).
11

Dalton Transactions
Page 12 of 32
View Article Online
DOI: 10.1039/C5DT04610F
Figure 4. The X-ray crystallographic structure of complex (SS,R)-23 (CCDC 1431243).
In order to investigate in more detail the reasons for the slow reactivity of 22-25 an 1H-NMR
experiment was carried out using catalyst 24 under hydrogenation conditions in a sealed
NMR tube (Scheme 2). Upon irradiation over a period of 4h, a major signal for an iron
hydride 26 was observed at -12.11 ppm (J = 88.6 Hz) and a minor doublet at -12.18 ppm (J =
80.1 Hz) in ratio of ca 12:1 which are tentatively assigned as diastereoisomers at the Fe atom
based on analogy with Berkessel’s observations.5 There was also a further doublet at -11.40
ppm tentatively assigned to the hydride from complex 25 present in 24. This was
subsequently confirmed by independent formation of the hydride from complex 25 (see
Supporting Information).
Scheme 2. Generation of hydride from iron(cyclopentadienone) catalyst 24.
TBDMSO
TBDMSO
TBDMSO
TBDMSO
Ph
OH
Ph
Ph
O
Ph
CO
i)
ca 12:1 mixture,
Major stereochemistry at Fe not determined
Fe
Fe
OC
L
OC
L
H
26
24
L= (S)-MONOPHOS
L= (S)-MONOPHOS
Reagents and conditions: i) irradiation (365 nm), 4h, sealed tube, 4 bar H2 gas.
12

Page 13 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
In our case the high ratio of Fe isomers did not translate into a high enantioselectivity in the
reduction. However a sample of added acetophenone was not significantly reduced in the
reaction after heating the reaction to 80 °C for 3 days, whilst the peak at -12.18 ppm became
the major species, together with some additional peaks which corresponded to 24 although
this was not reisolated (see Supporting Information). This strongly indicates that whilst an
iron hydride does form in the reaction, the transfer of hydrogen from the complex to the
substrate is very slow. Likewise the high level of steric hindrance created in the complex
through the introduction of a bulky phosphine may also explain the observed dramatic
reduction in reactivity upon addition of triphenylphosphine in the APH tests described above.
However, electronic effects could also be important; a computational study on this class of
complex13c has revealed that increasing the acidity of the CpOH group can contribute to
greater activity. Hence replacement of the electron-withdrawing CO with either PPh3 or
MONOPHOS could reduce the acidity of the CpOH and hence reduce catalytic activity. The
authors of the computational study indicated that phosphines containing electron-donating
groups, of moderate steric size, could potentially increase the CpOH acidity and hence the
activity, and this remains the subject of future studies. Similar observations have been made
in experimental studies on the ruthenium analogues of the iron catalysts used in this study; in
particular the rapid and reversible formation of a bond from the substrate carbonyl to the OH
of the CpOH has been shown to be the first step of the catalytic mechanism.17
In conclusion, we have prepared a series of enantiomerically-pure (cyclopentadienone)iron
complexes through the cyclisation of a C2-symmetric diol and its derivatives. Replacement of
a CO with a phosphorus-donor ligand has also been achieved. The complexes are competent
catalysts for the reduction of ketones under a range of conditions and for alcohol oxidation
however no significant enantiomeric inductions were achieved in these transformations. An
ideal catalyst might benefit from a balance between the size of the phosphorus-donor and any
groups on the other part of the complex.
Experimental section:
General; Solvents and reagents for the synthesis of complexes and catalytic reactions were
degassed prior to use and all reactions were carried out under either a nitrogen or argon
atmosphere. All heated experiments were conducted using thermostatically controlled oil
baths. Reactions were monitored by TLC using aluminum backed silica gel 60 (F254) plates,
13

Dalton Transactions
Page 14 of 32
View Article Online
DOI: 10.1039/C5DT04610F
visualized using UV 254 nm and phosphomolybdic acid (PMA), potassium permanganate or
vanillin dips as appropriate. Flash column chromatography was carried out routinely using 60
micrometer silica gel. Reagents were used as received from commercial sources unless
1
otherwise stated. H NMR spectra were recorded on a Bruker DPX (300, 400 or 500 MHz)
spectrometer. Chemical shifts are reported in
δ units, parts per million relative to the singlet
at 7.26 ppm for chloroform and 0.00 ppm for TMS. Coupling constants (J) are measured in
Hertz. IR spectra were recorded on a Perkin-Elmer Spectrum One FT-IR Golden Gate. Mass
spectra were recorded on a Bruker Esquire2000 or a Bruker MicroTOF mass spectrometer.
Melting points were recorded on a Stuart Scientific SMP 1 instrument and are uncorrected.
GC analysis was performed using a Hewlett Packard 5890. Dry solvents were purchased and
used as received.
(3S,6S)-1,8-Diphenylocta-1,7-diyne-3,6-diol 12.16
In a flask 1,8-diphenylocta-1,7-diyne-3,6-dione16 (2.66 g, 9.79 mmol, 1 eq.) was added and
dissolved in DCM (9.8 mL) and azeotrope formic acid/triethylamine (5:2 mixture; 6.5 mL).
To this mixture was added (S,S)-Teth-TsDpen RuCl 16 (62 mg, 0.10 mmol, S/C: 100:1) and
the mixture was heated to 35 ºC and stirred for 20 h. The reaction was cooled to rt and a
saturated solution of sodium hydrogen carbonate (50 mL) was added and the reaction was
extracted with DCM (3 x 50 mL). The organic extracts were dried over Na2SO4 and
concentrated under reduced pressure. The crude material was further purified by column
chromatography in 20% to 40% EtOAc/petroleum ether to yield (S,S)-12 as a orange oil,
which was recrystallized from heptane to give a off-white solid (2.71 g, 9.33 mmol, 95%, ee:
99%, de: 97.6%). mp: 74-76 ºC, (lit: 79-80 ºC); IR(neat) 3211, 3054, 2960, 2924, 2069, 2005,
1979, 1662, 1653, 1597, 1559, 1489, 1456, 1442, 1337, 1268, 1177, 1157, 1070, 1041, 1026,
1010 cm−1; δH (500 MHz, CDCl3) 7.42-7.45 (4H, m, ArH), 7.28-7.33 (6H, m, ArH), 4.76
(2H, s, CHOH), 2.35 (1H, br. s, OH), 2.34 (1H, br. s, OH), 2.05-2.15 (4H, m, CH2); δC (125
MHz, CDCl3) 131.7 (4C), 128.5 (2C), 128.3 (4C), 122.5 (2C), 89.5 (2C), 85.3 (2C), 62.5
(2C), 33.4 (2C); m/z (ESI+) 313.1 (M + Na, 100%).
14

Page 15 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
Tricarbonyl ((4S,7S)-4,7-dihydroxy-1,3-diphenyl-4,5,6,7-tetrahydro-2H-inden-2-one) iron 13.
In a pressure tube (3S,6S)-1,8-diphenylocta-1,7-diyne-3,6-diol 12 (500 mg, 1.72 mmol, 1.00
eq.) and iron pentacarbonyl (1.01 g, 0.7 mL, 5.16 mmol, 3.00 eq.) were dissolved in
anhydrous toluene (5 mL), the mixture was then degassed (bubbling nitrogen, 10 minutes)
and the tube was sealed. The mixture was heated to 130 ºC for 20h. After cooling to rt, the
mixture was diluted with EtOAc (10mL) and passed through a celite plug washing through
with EtOAc (100 mL). The solvent was removed and the product was purified by column
chromatography in 5% to 10% EtOAc/petroleum ether to yield the product 13 as an orange
24
D
solid (600 mg, 1.31 mmol, 76%). [
α]
= +244 (c 0.008 in CHCl3); mp: 97-99 ºC (dec.);
(found (EI): M+ + H, 459.0533. C24H19FeO6 requires M, 459.0526); IR(neat) 3051, 2951, 2064,
1990, 1702, 1657, 1539, 1500, 1441, 1358, 1262, 1217, 1189, 1096, 1069, 1029 cm−1; δH
(500 MHz, CDCl3) 7.85-7.87 (2H, m, ArH), 7.78-7.79 (2H, m, ArH), 7.35-7.7.42 (6H, m,
ArH), 5.09 (1H, br q, J = 4.7 Hz, CHOH), 4.83 (1H, br q, J = 3.4 Hz, CHOH), 2.37-2.42 (1H,
m, CHH), 2.37 (1H, d, J = 3.1 Hz, OH), 2.28-2.33 (1H, m, CHH), 2.28 (1H, d, J = 3.4 Hz,
OH), 1.85-1.90 (1H, m, CHH), 1.70-1.75 (1H, m, CHH); δC (125 MHz, CDCl3) 208.0 (3C),
169.7, 131.2, 130.7, 129.9 (2C), 129.3 (2C), 129.0 (2C), 128.8 (2C), 128.5, 128.4, 102.4,
102.2, 82.2, 80.2, 63.0, 61.9, 28.3, 26.8; m/z (ESI+) 481.0 (M + Na, 100%), 459.0 (80%).
((3S,6S)-3,6-Bis(benzyloxy)octa-1,7-diyne-1,8-diyl)dibenzene 14.
A suspension of (3S,6S)-1,8-diphenylocta-1,7-diyne-3,6-diol 12 (300 mg, 1.03 mmol, 1.0 eq.)
and sodium hydride (60% dispersion in mineral oil, 86 mg, 2.16 mmol, 2.1 eq.) in THF (10
mL) was stirred at rt for 30 min.. Then benzyl bromide (369 mg, 257
ꢀL, 2.16 mmol, 2.1 eq.)
15

Dalton Transactions
Page 16 of 32
View Article Online
DOI: 10.1039/C5DT04610F
and tetrabutylammonium iodide (192 mg, 0.52 mmol, 0.5 eq.) were added and the mixture
was stirred at rt for 24h. The reaction was quenched using a saturated ammonium chloride
solution (50 mL) and extracted with EtOAc (3 x 50 mL) and the combined organic extracts
were washed with brine (3 x 50 mL). The crude material was purified by column
chromatography on silica gel in petroleum ether to 15% EtOAc/petroleum ether to yield the
product 14 as a yellow oil (448 mg, 0.95 mmol, 92%). [ ]
24: -119 (c 0.54 in CHCl3);
D
α
HRMS: (found (EI): M+ + Na, 493.2135. C34H30NaO2 requires M, 493.2138); IR(neat) 3062,
3030, 2927, 2856, 1598, 1572, 1489, 1453, 1442, 1389, 1370, 1332, 1280, 1254, 1226, 1203,
1178, 1149, 1086, 1066, 1026 cm−1; δH (500 MHz, CDCl3) 7.45-7.47 (4H, m, ArH), 7.39-
7.41 (4H, m, ArH), 7.35-7.37 (3H, m, ArH), 7.30-7.34 (9H, m, ArH), 4.86 (2H, AB, JAB
=
11.8 Hz, CHHPh), 4.60 (2H, AB, JAB = 11.8 Hz, CHHPh), 4.38-4.40 (2H, m, CHO), 2.07-
2.17 (4H, m, CH2); δC (125 MHz, CDCl3) 138.0, (2C), 131.8 (4C), 128.4 (4C), 128.4 (2C),
128.3 (2C), 128.1 (4C), 127.7 (4C), 122.8 (2C), 88.0 (2C), 86.2 (2C), 70.8 (2C), 68.8 (2C),
31.7 (2C); m/z (ESI+) 493.2 (M+ Na, 100%), 509.2 (M+K-H, 45%).
Tricarbonyl (4S,7S)-4,7-bis(benzyloxy)-1,3-diphenyl-4,5,6,7-tetrahydro-2H-inden-2-one iron
18.
In a pressure tube ((3S,6S)-3,6-bis(benzyloxy)octa-1,7-diyne-1,8-diyl)dibenzene 14 (450 mg,
0.96 mmol, 1.00 eq.) and iron pentacarbonyl (564 mg, 0.38 ꢀL, 2.88 mmol, 3.00 eq.) were
dissolved in anhydrous toluene (5 mL), the mixture was then degassed (bubbling nitrogen, 10
minutes) and the tube was sealed. The mixture was heated to 130 ºC for 20h. After cooling to
rt and dilution with EtOAc (10mL) it was passed through a celite plug washing through
EtOAc (100 mL). Solvent was removed under reduced pressure and then the product was
purified by column chromatography on silica gel in 5% to 20 % EtOAc/petroleum ether to
yield the product 18 as an orange solid (420 mg, 0.66 mmol, 69 %). [α]
24 = +321 (c 0.007 in
D
CHCl3); mp: 66-68 ºC (dec.); (found (EI): M+ + H, 639.1472. C38H31FeO6 requires M,
639.1465); IR(neat) 3059, 3030, 2928, 2860, 2063, 2009, 1984, 1635, 1540, 1498, 1439, 1393,
1363, 1319, 1213, 1081, 1051, 1026 cm−1; δH (500 MHz, CDCl3) 7.79-7.82 (2H, m, ArH),
16

Page 17 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
7.71-7.74 (2H, m, ArH), 7.35-7.43 (7H, m, ArH), 7.29-7.32 (3H, m, ArH), 7.24-7.26 (2H, m,
ArH), 7.19-7.20 (2H, m, ArH), 6.93-6.95 (2H, m, ArH), 4.69 (1H, br. s, CHO), 4.58 (1H,
ABq, JAB = 10.7 Hz, CHH), 4..41 (1H, ABq, JAB = 10.7 Hz, CHH), 4.38 (1H, ABq, JAB = 10.7
Hz, CHH) 4.36 (1H, br. s, CHO), 4.12 (1H, ABq, JAB = 10.6 Hz, CHH), 2.13-2.23 (3H, m,
CHHCH2), 2.08-2.11 (1H, m, CHH); δC (125 MHz, CDCl3) 208.2 (3C), 170.2, 137.0, 136.9,
131.4, 131.0, 130.1 (2C), 130.0 (2C), 128.4 (2C), 128.4 (2C), 128.4 (2C), 128.3 (2C), 128.0
(2C), 128.0 (4C), 127.9 (2C), 100.7, 99.9, 83.3, 81.8, 72.3, 71.7, 70.2, 67.8, 21.7, 21.5; m/z
(ESI+) 661.1 (M + Na, 100%), 639.2 (43%).
((3S,6S)-3,6-Bis(tert-butyldimethylsilyloxy)octa-1,7-diyne-1,8-diyl)dibenzene.15.
In a flask (3S,6S)-1,8-diphenylocta-1,7-diyne-3,6-diol 12 (500 mg, 1.72 mmol, 1.0 eq.) was
dissolved in DMF (20 mL). To the mixture were added imidazole (293 mg, 4.30 mmol, 2.5
eq.) and tert-butyl(chloro)dimethylsilane (648 mg, 4.30 mmol, 2.5eq.) and the mixture was
stirred overnight at rt. The reaction was quenched with water (100 mL) and diluted with
EtOAc (150 mL) and the organic fraction was washed with water (3 x 50 mL) and brine (3 x
50 mL) then dried using Na2SO4 then concentrated under reduced pressure. Purification by
column chromatography on silica gel using 5% to 10% EtOAc/petroleum ether yielded the
product 15 as a yellow oil (850 mg, 1.64 mmol, 95%). [ ]
23: -34 (c 0.48 in CHCl3); HRMS:
D
α
(found (EI): M+ + Na, 541.2931. C32H46NaO2Si2 requires M, 541.2929); IR(neat) 2954, 2928,
2885, 2855, 1598, 1471, 1462, 1443, 1407, 1388.9, 1361, 1338, 1281, 1251, 1188, 1083,
1004 cm−1; δH (500 MHz, CDCl3) 7.42-7.44 (4H, m, ArH), 7.29-7.32 (6H, m, ArH), 4.66-
t
4.69 (2H, m, CHOC), 1.94-2.03 (4H, m, CH2), 0.95 (18H, s, Bu), 0.20 (6H, s, CH3), 0.17
(6H, s, CH3); δC (125 MHz, CDCl3) 131.6 (4C), 128.2 (4C), 128.1 (2C), 123.1 (2C), 90.8
(2C), 84.3 (2C), 63.2 (2C), 34.4 (2C), 25.9 (6C) 18.3 (2C), -4.3 (2C), -4.9 (2C); m/z (ESI+)
541.3 (M + Na, 100%).
Tricarbonyl ((4S,7S)-4,7-bis((tert-butyldimethylsilyl)oxy)-1,3-diphenyl-4,5,6,7-tetrahydro-
17

Dalton Transactions
Page 18 of 32
View Article Online
DOI: 10.1039/C5DT04610F
2H-inden-2-one) iron 19.
In a pressure tube ((3S,6S)-3,6-bis(tert-butyldimethylsilyloxy)octa-1,7-diyne-1,8-diyl)di
benzene 15 (500 mg, 0.96 mmol, 1.0 eq.) and iron pentacarbonyl (564 mg, 0.38 L, 2.88
ꢀ
mmol, 3.0 eq.) were dissolved in anhydrous toluene (5 mL). The mixture was then degassed
(bubbling nitrogen, 10 minutes) and the tube was sealed. The mixture was heated to 130 ºC
for 20h. After cooling to rt and dilution with EtOAc (10 mL) and passed through a celite plug
washing through with EtOAc (100 mL), solvent was removed under reduced pressure and the
product purified by column chromatography on silica gel using 5% to 10% EtOAc/petroleum
ether to yield the product 19 as an orange solid (430 mg, 0.63 mmol, 65%). [α]
24 = +321 (c
D
0.007 in CHCl3); mp: 73-75 ºC (dec.); (found (EI): M+ + H, 687.2265. C36H47FeO6Si2
requires M, 687.2256); IR(neat) 2953, 2928, 2883, 2855, 2063, 2011, 1984, 1500, 1470, 1439,
1361, 1253, 1198, 1099, 1055, 1005 cm−1; δH (500 MHz, CDCl3) 7.72-7.74 (2H, m, ArH),
7.62-7.64 (2H, m, ArH), 7.40-7.43 (3H, m, ArH), 7.35-7.40 (2H, m, ArH), 7.29-7.34 (1H, m,
ArH), 5.01-5.02 (1H, m, CHOTBDMS), 4.88-4.90 (1H, m, CHOTBDMS), 2.28-2.38 (2H, m,
CHHCHH), 1.83-1.87 (1H, m, CHH), 1.76-1.80 (1H, m, CHH), 0.86 (9H, s, tBu), 0.71 (9H, s,
tBu), 0.09 (3H, s, CH3), -.006 (3H, s, CH3), -0.34 (3H, s, CH3), -0.58 (3H, s, CH3); δC (125
MHz, CDCl3) 208.6 (3C), 170.6, 131.2, 130.9, 130.7 (2C), 130.0 (2C), 128.5 (2C), 128.4
(2C), 128.1, 128.0, 103.6, 102.2, 83.9, 80.7, 63.4, 61.7, 27.5, 26.1, 26.1 (3C), 25.7 (3C), 18.3,
18.0, -4.4, -4.5, -5.1, -5.8; m/z (ESI+) 709.2 (M + Na, 100%), 678.2 (54%). 1018..
((3S,6S)-3,6-Bis(triisopropylsilyloxy)octa-1,7-diyne-1,8-diyl)dibenzene 16.
In a flask (3S,6S)-1,8-diphenylocta-1,7-diyne-3,6-diol 12 (500 mg, 1.72 mmol, 1.0 eq.) was
dissolved in DMF (20 mL). To this solution was added imidazole (293 mg, 4.30 mmol, 2.5
eq.) and triisopropyl(chloro)silane (829 mg, 920
ꢀL, 4.30 mmol, 2.5 eq.) and the mixture was
18

Page 19 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
left to stir overnight at rt. The reaction was quenched with water (50 mL) and diluted with
EtOAc (50 mL) and the organic fraction was washed with water (3 x 50 mL) and brine (3 x
50 mL). The organic fraction was dried using Na2SO4 and concentrated under reduced
pressure. Purification by column chromatography on silica gel using 2% to 3%
EtOAc/petroleum ether yielded the product 16 as a yellow oil (620 mg, 1.03 mmol, 60%).
23
D
[
α]
: -5 (c 0.46 in CHCl3); HRMS: (found (EI): M+ + Na, 625.3876. C38H58NaO2Si2
requires M, 625.3868); IR(neat) 2941, 2891, 2865, 1598, 1489, 1444, 1384, 1366, 1338, 1253,
1171, 1093, 1059, 1012 cm−1;
H (500 MHz, CDCl3) 7.39-7.41 (4H, m, ArH), 7.28-7.30 (6H,
δ
m, ArH), 4.80 (2H, br. s, CHOSi), 2.06-2.07 (4H, m, CH2), 1.15-1.20 (6H, m, CH(CH3)2),
1.12 (18H, d, J = 9.8 Hz, CH(CH3)2), 1.11 (18H, d, J = 9.8 Hz, CH(CH3)2); δC (125 MHz,
CDCl3) 131.6 (4C), 128.2 (4C), 128.0 (2C), 123.2 (2C), 91.1 (2C), 84.2 (2C), 63.2 (2C), 34.4
(2C), 18.1 (12C), 12.3 (6C); m/z (ESI+) 625.4 (M + Na, 100%), 595.4 (65%).
Tricarbonyl
((4S,7S)-1,3-diphenyl-4,7-bis((triisopropylsilyl)oxy)-4,5,6,7-tetrahydro-2H-
inden-2-one) iron 20.
In a pressure tube ((3S,6S)-3,6-bis(triisopropylsilyloxy)octa-1,7-diyne-1,8-diyl)dibenzene 16
(500 mg, 0.83 mmol, 1.00 eq.) and iron pentacarbonyl (488 mg, 0.33 ꢀL, 2.49 mmol, 3.00
eq.) and dissolved in anhydrous toluene (5 mL), the tube was then degassed (bubbling
nitrogen, 10 minutes) and the tube was sealed. The tube was heated to 130 ºC for 20h, then
cooled to rt and diluted with EtOAc (10mL). The solution was passed through a celite plug
washing through EtOAc (100 mL). The solvent was removed under reduced pressure and the
product was purified by column chromatography on silica gel in 5% to 30%
EtOAc/petroleum ether to yield the product20 as a yellow solid (326 mg, 0.42 mmol, 51%).
[ ]
29: -136 (c 0.028 in CHCl3); mp: 57-59 ºC (dec.); (found (EI): M+ + Na, 793.3019.
D
α
C42H58FeNaO6Si2 requires M, 793.3015); IR(neat) 2942, 2890, 2865, 2063, 2012, 1982, 1650,
1501, 1462, 1446, 1364, 1136, 1104, 1054, 1014 cm−1;
H (500 MHz, CDCl3) 7.64-7.66 (2H,
δ
m, ArH), 7.51-7.53 (2H, m, ArH), 7.29-7.38 (6H, m, ArH), 5.24 (1H, t, J = 4.6 Hz,
CHOTIPS), 5.21 (1H, t, J = 3.7 Hz, CHOTIPS), 2.32-2.45 (2H, m, CHHCHH), 1.90-1.96
19

Dalton Transactions
Page 20 of 32
View Article Online
DOI: 10.1039/C5DT04610F
(1H, m, CHH), 1.81-1.87 (1H, m, CHH), 0.93-0.94 (9H, m, TIPS), 0.86-0.90 (30H, m, TIPS),
0.61 (3H, sept, J = 7.5 Hz, CH(CH3)); δC (125 MHz, CDCl3) 208.5 (3C), 170.8, 131.3 (2C),
131.1, 131.0, 130.1 (2C), 128.4 (2C), 128.2 (2C), 128.0, 127.8, 104.4, 102.8, 85.3, 80.7, 63.8,
63.1, 29.0, 28.4, 18.3 (6C), 18.0 (6C), 13.1 (3C), 12.9 (3C);m/z (ESI+) 793.3 (M + Na,
100%), 771.3 (86%).
((3S,6S)-3,6-Bis(tert-butylphenylsilyloxy)octa-1,7-diyne-1,8-diyl)dibenzene 17.
In a flask (3S,6S)-1,8-diphenylocta-1,7-diyne-3,6-diol 12 (500 mg, 1.72 mmol, 1.0 eq.) was
added and dissolved in DMF (20 mL). To the solution was added imidazole (293 mg, 4.30
mmol, 2.5 eq.) and tert-butyl(chloro)diphenylsilane (1.18 g, 1.15 mL, 4.30 mmol, 2.5 eq.)
and the mixture was left to stir overnight at rt. The reaction was quenched with water (50 mL)
and diluted with EtOAc (50 mL) and the organic fraction was washed with water (3 x 50 mL)
and brine (3 x 50 mL). The organic extract were dried using Na2SO4 and concentrated under
reduced pressure. Purification by column chromatography on silica gel using 5% to 6%
EtOAc/petroleum ether yielded the product 17 as a yellow oil (939 mg, 1.22 mmol, 71%).
[ ]
23: -94 (c 0.7 in CHCl3); (found (EI): M+ + Na, 789.3558. C52H54NaO2Si requires M,
D
α
789.3555); IR(neat) 3070, 3048, 2957, 2929, 2889, 2855, 1589, 1489, 1471, 1443, 1427, 1390,
1361, 1341, 1306, 1261, 1189, 1106, 1082, 1028, 1006 cm−1; δH (500 MHz, CDCl3) 7.78
(4H, d, J = 6.7 Hz, ArH), 7.71 (4H, d, J = 6.7 Hz, ArH), 7.37-7.40 (7H, m, ArH), 7.30-7.34
(6H, m, ArH), 7.21-7.27 (5H, m, ArH), 7.17-7.18 (4H, m, ArH), 4.62 (2H, br. s, CHOSi),
2.01-2.03 (4H, m, CH2), 1.10 (18H, s, C(CH3)3); δC (125 MHz, CDCl3) 136.1 (4C), 135.9
(4C), 133.9 (2C), 133.7 (2C), 131.5 (2C), 129.7 (2C), 129.5 (2C), 128.1 (2C), 128.0 (2C),
127.6 (4C), 127.4 (2C), 123.1 (2C), 90.5 (2C), 85.0 (2C), 64.0 (2C), 33.9 (2C), 27.0 (6C),
19.4 (2C); m/z (ESI+) 789.4 (M + Na, 100%), 805.3 (50%).
Tricarbonyl-((4S,7S)-4,7-bis((tert-butyldiphenylsilyl)oxy)-1,3-diphenyl-4,5,6,7-tetrahydro-
2H-inden-2-one) iron 21.
20

Page 21 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
In a pressure tube ((3S,6S)-3,6-bis(dimethylphenylsilyloxy)octa-1,7-diyne-1,8-diyl)dibenzene
17 (500 mg, 0.65 mmol, 1.00 eq.) and iron pentacarbonyl (382 mg, 0.26 L, 1.95 mmol, 3.00
ꢀ
eq.) was dissolved in anhydrous toluene (5 mL), the tube was then degassed (bubbling
nitrogen, 10 minutes) and the tube was sealed. The tube was heated to 130 ºC for 20h. After
cooling to rt and diluted with EtOAc (10mL) the solution was passed through a celite plug
washing through EtOAc (100 mL). The solvent was removed under reduced pressure and the
product purified by column chromatography on silica gel in 5% to 20% EtOAc/petroleum
ether to yield the product 21 as an orange solid (220 mg, 0.24 mmol, 36%). [ ]
23: -39 (c
D
α
0.018 in CHCl3); mp: 80-82 ºC (dec); (found (EI): M+ + Na, 957.2710. C56H54FeNaO6Si2
requires M, 957.2702); IR(neat) 3050, 2930, 2893, 2856, 2063, 2011, 1985, 1645, 1589, 1500,
1488, 1471, 1444, 1427, 1391, 1362, 1188, 1104, 1042, 1006 cm−1; δH (500 MHz, CDCl3)
7.60 (2H, d, J = 7.0 Hz, ArH), 7.44-7.50 (5H, m, ArH), 7.27-7.41 (17H, m, ArH), 7.21-7.25
(3H, m, ArH), 7.14-7.19 (3H, m, ArH), 5.21 (1H, t, J = 4.2 Hz, CHOSi), 4.93 (1H, t, J = 4.8
Hz, CHOSi), 1.95-2.01 (1H, m, CHH), 1.83-1.89 (1H, m, CHH), 1.50-1.55 (1H, m, CHH),
t
t
1.45-1.48 (1H, m, CHH), 0.73 (9H, s, Bu), 0.64 (9H, s, Bu); δC (125 MHz, CDCl3) 208.4
(3C), 170.5, 135.9 (2C), 135.7 (2C), 135.7 (2C), 135.7 (2C), 134.4, 133.6, 133.0, 132.9,
131.2 (2C), 131.0, 131.0, 129.9, 129.8, 129.7 (2C), 129.7, 129.6 128.6 (2C), 128.2 (2C),
128.2, 127.7, 127.7 (2C), 127.5 (2C), 127.5 (2C), 127.4 (2C), 104.6, 101.7, 84.5, 80.5, 65.0,
64.5, 28.3, 27.5, 27.1 (3C), 26.6 (3C), 19.0, 18.9; m/z (ESI+) 935.3 (M + H, 100%), 957.3
(75%).
(S)-N,N-Dimethyldinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepin-4-amine
((S)-
MONOPHOS). 18
21

Dalton Transactions
Page 22 of 32
View Article Online
DOI: 10.1039/C5DT04610F
An oven dried flask, cooled under N2, fitted with a reflux condenser was charged with (S)-
BINOL (2.35 g, 8.2 mmol, 1 eq.) and flushed with N2. To this solid, toluene (50 mL) was
added followed by P(NMe2)3 (3.08 g, 3.4 mL, 12.5 mmol, 1.5 eq.). The reaction mixture was
refluxed for 9 hours, after cooling to rt the toluene was removed and the product passed
through a silica plug using 200 mL of 20% EtOAc/petroleum ether then washing the plug
with 200 mL of DCM which contained the product as a white solid (2.84 g, 7.9 mmol, 96%).
o
[
α]
31 : +552 (c 0.68 in CHCl3); mp: 198-200 C (lit: 190-191 oC); IR(neat) 3056, 3013, 2976,
D
2923, 2896, 2840, 2798, 1616, 1588, 1502, 1482, 1458, 1446, 1429, 1407, 1357, 1324, 1294,
1267, 1229, 1203, 1184, 1151, 1142, 1124, 1067 cm−1;
H (500 MHz, CDCl3) 7.95 (1H, d, J
δ
= 8.9 Hz, ArH), 7.88-7.91 (3H, m, ArH), 7.50 (1H, d, J = 8.9 Hz, ArH), 7.33-7.42 (5H, m,
ArH), 7.22-7.28 (2H, m, ArH), 2.55 (6H, d, JPH = 10.0 Hz, CH3); δC (125 MHz, CDCl3)
150.0 (2C), 149.5, 132.9, 132.6, 131.4, 130.8, 130.3, 128.4, 128.3, 127.0, 126.9, 126.1 (2C),
124.8, 124.6, 124.0, 122.8, 122.1, 36.0;
H, 100%), 382.0 (45%).
δP (202 MHz, CDCl3) 162.2, m/z (ESI+) 360.0 (M +
(R)-N,N-Dimethyldinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepin-4-amine
((R)-
MONOPHOS).18
Prepared as described above using (R)-BINOL (2.35 g, 8.2 mmol, 1 eq.) and P(NMe2)3 (3.08
g, 3.4 mL, 12.5 mmol, 1.5 eq.) to give the product as a white solid (2.80 g, 7.8 mmol, 95%).
o
o
[α]
30 = -674 (c 0.23 in CHCl3); mp: 196-198 C (lit: 190-191 C); IR(neat) 3056, 3013, 2975,
D
2923, 2896, 2841, 2806, 1615, 1588, 1503, 1482, 1459, 1446, 1430, 1407, 1357, 1324, 1295,
1267, 1229, 1204, 1184, 1152, 1142, 1067 cm−1;
H (500 MHz, CDCl3) 7.97 (1H, d, J = 8.9
Hz, ArH), 7.89-7.92 (3H, m, ArH), 7.50 (1H, d, J = 8.9 Hz, ArH), 7.33-7.42 (5H, m, ArH),
7.22-7.28 (2H, m, ArH), 2.54 (6H, d, JPH = 10.0 Hz, CH3); C (125 MHz, CDCl3) 150.0 (2C),
δ
δ
149.5, 132.8, 132.6, 131.4, 130.7, 130.3,130.0, 128.3, 128.3, 127.0, 126.9, 126.1 (2C), 124.8,
124.6, 122.8, 122.1, 122.0, 36.0; δP (202 MHz, CDCl3) 162.1, m/z (ESI+) 360.0 (M + H,
100%).
22

Page 23 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
Dicarbonyl-((4S,7S)-4,7-bis(benzyloxy)-1,3-diphenyl-4,5,6,7-tetrahydro-2H-inden-2-one-(S)-
N,N-dimethyldinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepin-4-amine) iron 22.
To a degassed and foil-covered flask a solution of tricarbonyl (4S,7S)-4,7-bis(benzyloxy)-1,3-
diphenyl-4,5,6,7-tetrahydro-2H-inden-2-one iron 18 (620 mg, 0.97 mmol, 1 eq.) and (S)-N,N-
dimethyldinaphtho[2,1-d:1',2'-f][1,3,2]dioxa phosphepin-4-amine (698 mg, 1.94 mmol, 2 eq)
in anhydrous toluene (20 mL) was added trimethylamine-N-oxide (146 mg, 1.94 mmol, 2 eq.)
at rt. The reaction was heated to 60 ºC overnight, the reaction was cooled to rt and the toluene
was removed. The material was passed through a silica plug using initially 10%
EtOAc/pentane and flushing the plug with 30% EtOAc/pentane to give 22 as a yellow solid
(554 mg, 0.80 mmol, 65%). [
α
]
29: +120 (c 0.19 in CHCl3); mp: 97-99 ºC (dec.); (found (EI):
D
M+, 970.2596. C59H49FeNO7PSi2 requires M,970.2592);
δH (500 MHz, CDCl3) 8.29 (2H, d, J
= 7.2 Hz, ArH), 7.90 (1H, d, J = 8.1 Hz, ArH), 7.84 (1H, d, J = 8.2 Hz, ArH), 7.81 (1H, d, J =
8.9 Hz, ArH), 7.70 (1H, d, J = 8.9 Hz, ArH), 7.81 (2H, d, J = 7.3 Hz, ArH), 7.42-7.46 (5H,
m, ArH), 7.35-7.40 (5H, m, ArH), 7.17-7.22 (4H, m, ArH), 7.07-7.16 (4H, m, ArH), 6.94
(1H, d, J = 8.9 Hz, ArH), 6.91 (1H, d, J = 7.3Hz, ArH), 6.82 (2H, t, J = 7.6 Hz, ArH), 6.58
(2H, d, J = 6.9 Hz, ArH), 4.87 (1H, br. s, CH), 4.70 (1H, ABq, JAB = 11.3 Hz, CH2Ph), 4.64
(1H, ABq, JAB = 11.3 Hz, CH2Ph), 4.25 (1H, ABq, JAB = 10.1 Hz, CH2Ph), 4.20 (1H, br. s,
CH), 3.92 (1H, ABq, JAB = 10.1 Hz, CH2Ph), 2.24-2.30 (1H, m, CHH), 2.14 (6H, d, J = 10.0
Hz, NCH3), 1.95-2.09 (3H, m, CHHCH2); δC (125 MHz, CDCl3) 214.9 (d, JPC = 19.1), 211.0
(d, J = 25.1 Hz), 166.1 (d, J = 4.0 Hz), 149.5 (d, J = 12.1 Hz), 147.9 (d, J = 6.0 Hz), 137.9,
137.4, 134.4, 134.5, 132.8, 132.6, 131.3, 131.1, 130.1, 128.9 (2C), 129.1 (2C), 128.3 (2C),
128.3, 128.1 (2C), 128.1 (2C), 128.0 (2C), 127.6 (2C), 127.3, 127.2, 126.9 (2C), 126.7 (2C),
126.2 (2C), 125.9 (2C), 125.0 (2C), 122.9 (2C), 122.5 (d, JPC = 3.0 Hz), 122.3 (d, JPC = 2.0
Hz), 120.9 (2C), 97.3, 93.6, 81.3, 80.4, 72.6, 71.3, 71.0, 69.0, 37.2, 37.1, 21.1, 20.4; δP (242
MHz, CDCl3) 188.6; m/z (ESI+) 970.2 (M + H, 100%). The compound was assumed to be
light sensitive and was stored in the dark.
23

Dalton Transactions
Page 24 of 32
View Article Online
DOI: 10.1039/C5DT04610F
Dicarbonyl-((4S,7S)-4,7-bis(benzyloxy)-1,3-diphenyl-4,5,6,7-tetrahydro-2H-inden-2-one-(R)-
N,N-dimethyldinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepin-4-amine) iron 23.
To a degassed and foil-covered flask a solution of tricarbonyl (4S,7S)-4,7-bis(benzyloxy)-1,3-
diphenyl-4,5,6,7-tetrahydro-2H-inden-2-one iron 18 (560 mg, 0.88 mmol, 1 eq.) and (R)-N,N-
dimethyldinaphtho[2,1-d:1',2'-f][1,3,2]dioxa phosphepin-4-amine (633 mg, 1.76 mmol, 2 eq.)
in anhydrous toluene (20 mL) was added trimethylamine-N-oxide (132 mg, 1.76 mmol, 2 eq.)
at rt. The reaction heated to 60 ºC overnight, the reaction was cooled to rt and the toluene was
removed. The material was passed through a silica plug using initially using 10%
EtOAc/pentane and flushing the plug with 30% EtOAc/pentane to isolated as a yellow solid
(572 mg, 0.59 mmol, 67%). [
α]
29: +300 (c 0.08 in CHCl3); mp: 117-119 ºC (dec.);
H (500
δ
D
MHz, CDCl3) 8,37 (2H, d, J = 7.3 Hz, ArH), 8.16 (2H, d, J = 8.6 Hz, ArH), 7.84 (3H, dd, J =
6.1 Hz, ArH), 7.59 (1H, d, J = 8.9 Hz, ArH), 7.14-7.49 (21H, m, ArH), 6.91-6.93 (2H, m,
ArH), 5.91 (1H, d, J = 8.9 Hz, ArH), 5.12 (1H, br. s, CH), 4.69 (1H, ABq, JAB = 11.0 Hz,
CH2Ph), 4.58 (1H, ABq, JAB = 10.4 Hz, CH2Ph), 4.54 (1H, ABq, JAB = 11.0 Hz, CH2Ph),
4.40 (1H, ABq, JAB = 10.4 Hz, CH2Ph), 4.15 (1H, br. s, CH), 2.20-2.32 (2H, m, CH2), 2.13
(3H, s, NCH3), 2.11 (3H, s, NCH3), 2.08 (2H, br. s, CH2); δC (125 MHz, CDCl3) 212.9 (d, JPC
=23.1 Hz), 211.6 (d, JPC = 24.1 Hz), 165.2 (d, JPC = 4.0 Hz), 149.4 (d, JPC = 10.0 Hz), 147.9,
137.7, 137.5, 134.7, 134.3, 133.4, 132.7, 132.5, 131.2 (d, JPC =15.1 Hz), 131.4, 130.8, 130.4,
130.2, 129.9, 129.8, 129.5, 129.0, 128.8, 128.6, 128.6, 128.5, 128.4, 128.3 (3C), 128.1, 128.0,
127.7, 127.5, 127.1, 127.0, 126.8, 126.3, 125.9, 125.2, 125.0, 124.3, 124.0, 123.1 (d, JPC
=
3.0 Hz), 120.9, 117.8, 97.3, 97.2, 93.9, 81.9, 71.9, 71.8, 71.2, 69.4, 37.2 (2C), 20.9, 20.2; δP
(242 MHz, CDCl3) 193.6; m/z (ESI+) 970.2 (M + H, 100%). The compound was assumed to
be light sensitive and was stored in the dark. The sample contained ca 5% EtOAc by mass.
Dicarbonyl-((4S,7S)-4,7-bis((tert-butyldimethylsilyl)oxy)-1,3-diphenyl-4,5,6,7-tetrahydro-
2H-inden-2-one-(S)-N,N-dimethyldinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepin-4-amine)
iron 24.
24

Page 25 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
To a degassed solution of tricarbonyl((4S,7S)-4,7-bis((tert-butyldimethylsilyl)oxy)-1,3-
diphenyl-4,5,6,7-tetrahydro-2H-inden-2-one) iron 19 (600 mg, 0.90 mmol, 1 eq.) and (S)-
N,N-dimethyl dinaphtho[2,1-d:1',2'-f][1,3,2]dioxa phosphepin-4-amine (647 mg, 1.80 mmol,
2 eq.) in anhydrous toluene (50 mL) was added trimethylamine-N-oxide (135 mg, 1.80 mmol,
2 eq.) at rt. This was degassed and heated to 60 ºC overnight, then cooled to rt and toluene
was removed under reduced pressure. This was further purified by column chromatography
using 10% to 30 % EtOAc/pentane to yield a orange solid (570 mg, 0.56 mmol, 62%). mp:
>150 ºC (dec.); [
requires M, 1018.3383); IR(neat) 2952, 2927, 2854, 2008, 1952, 1713, 1591, 1500, 1253, 1227,
1156, 1099, 1050, 1004, 800, 772, 749, 671, 565 cm−1;
H (500 MHz, CDCl3) 8.43 (2H, d, J
α
]
30: +97 (c 0.08 in CHCl3); (found (EI): M+, 1018.3381. C57H65FeNO7PSi2
D
δ
= 7.4 Hz, ArH), 7.90 (2H, d, J = 8.3 Hz, ArH), 7.82 (1H, d, J = 8.2 Hz, ArH), 7.78 (1H, d, J =
8.9 Hz, ArH), 7.73 (1H, d, J = 9.2 Hz, ArH), 7.52 (2H, d, J = 7.4 Hz, ArH), 7.36-7.48 (6H,
m, ArH), 7.14-7.22 (3H, m, ArH), 7.07 1H, d, J = 8.6 Hz, ArH), 6.99 (1H, d, J = 8.9 Hz,
ArH), 6.73 (1H, t, J = 7.3 Hz, ArH), 6.64 (2H, t, J = 7.6 Hz, ArH), 5.11 (1H, s, CHOSi), 4.62
(1H, s, CHOSi), 2.36-2.43 (1H, m, CH2), 2.17-2.27 (1H, m, CH2), 2.10 (6H, d, J = 10.0 Hz,
N(CH3)2), 1.74-1.79 (2H, m, CH2), 0.98 (9H, s, C(CH3)3), 0.58 (9H, s, C(CH3)3), 0.25 (3H, s,
SiCH3), 0.19 (3H, s, SiCH3), -0.13 (3H, s, SiCH3), -0.78 (3H, s, SiCH3); δC (125 MHz,
CDCl3) 215.0 (d, JPC = 16.9 Hz), 211.6 (d, JPC = 24.9 Hz), 166.4 (d, JPC = 3.9 Hz), 149.4 (d,
JPC = 11.9 Hz), 148.0 (d, JPC = 6.9 Hz), 134.5, 134.1, 132.9, 132.6, 131.3, 131.1, 130.1, 130.0
(2C), 129.8, 129.5 (2C), 128.2, 128.0, 127.9, 127.3, 127.1 (2C), 126.9, 126.7, 126.1, 126.0,
125.8, 125.0 (2C), (d, JPC = 2.5 Hz, ArH), 122.4 (d, JPC = 3.0 Hz, ipso), 122.3, 120.9, 100.3,
95.2, 81.2, 79.5 (d, JPC = 2.0 Hz, CpH), 64.2, 63.4, 37.0 (d, J = 5.9 Hz), 27.2, 26.3 (3C), 25.7
(3C), 25.3, 18.8, 18.0, -3.3, -4.7, -4.9, -5.9; δP (242 MHz, CDCl3) 187.8; m/z (ESI+) 1018.2
(M+, 100%). The compound was found to be light sensitive and decomposed in solution. The
1H-NMR spectrum and subsequent hydride formation experiments indicated the presence of
ca 10% of the diastereomer 25 (see Supporting Information) and traces of other impurities.
25

Dalton Transactions
Page 26 of 32
View Article Online
DOI: 10.1039/C5DT04610F
Dicarbonyl-((4S,7S)-4,7-bis((tert-butyldimethylsilyl)oxy)-1,3-diphenyl-4,5,6,7-tetrahydro-
2H-inden-2-one-(R)-N,N-dimethyldinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepin-4-amine)
iron 25.
TBDMSO
Ph
O
Fe(CO)2(R-MONOPHOS)
Ph
TBDMSO
To a degassed solution of tricarbonyl (4S,7S)-4,7-bis(benzyloxy)-1,3-diphenyl-4,5,6,7-
tetrahydro-2H-inden-2-one iron 19 (600 mg, 0.90 mmol, 1 eq.) and (R)-N,N-dimethyl
dinaphtho[2,1-d:1',2'-f][1,3,2]dioxa phosphepin-4-amine (647 mg, 1.80 mmol, 2 eq.) in
anhydrous toluene (50 mL) was added trimethylamine-N-oxide (135 mg, 1.80 mmol, 2 eq.) at
rt. This was degassed and heated to 60 ºC overnight, then cooled to rt and toluene was
removed under reduced pressure. The product was further purified by column
chromatrography using 10% to 30% EtOAc/pentane yielding a orange solid (550 mg, 0.54
mmol, 60%) mp:>150 ºC (dec.); [
2010, 1957, 1608, 1591, 1500, 1463, 1446, 1292, 1253, 1155, 1100, 1052, 980, 850, 826,
720, 562 cm−1;
H (500 MHz, CDCl3) 8.28-8.30 (4H, m, ArH), 7.83-7.86 (3H, m, ArH), 7.62
α
]
30: +142 (c 0.05 in CHCl3); IR(neat) 2950, 2927, 2854,
D
δ
(1H, d, J = 8.8 Hz, ArH), 7.41-7.46 (3H, m, ArH), 7.36-7.40 (3H, m, ArH), 7.31-7.34 (3H, m,
ArH), 7.14-7.24 (4H, m, ArH), 6.09 (1H, d, J = 9.0 Hz, ArH), 5.40 (1H, br. s, CHOSi), 4.60
(1H, br. s, CHOSi), 2.42 (1H, t, J = 13.7 Hz, CH2), 2.23 (1H, t, J = 13.9 Hz, CH2), 2.07 (6H,
d, J = 9.7 Hz, N(CH3)2), 1.86 (1H, d, J = 13.7 Hz, CH2), 1.78 (1H, d, J = 8.8 Hz, CH2), 0.94
(9H, s, C(CH3)3), 0.67 (9H, s, C(CH3)3), 0.27 (3H, s, SiCH3), 0.16 (3H, s, SiCH3), 0.07 (3H,
s, SiCH3), -0.37 (3H, s, SiCH3); δC (125 MHz, CDCl3) 213.1 (d, J = 20.9 Hz), 212.3 (d, JPC =
23.9 Hz), 165.6 (d, J = 3.9 Hz), 165.6 (d, J = 3.99 Hz), 149.4 (d, J = 9.9 Hz), 148.0 (d, J =
6.9 Hz), 134.9, 134.5, 132.7, 132.5, 131.2, 131.1, 130.0, 129.8, 129.6 (2C), 128.3, 128.2,
128.0, 127.7 (2C), 127.1, 126.9, 126.8, 126.3, 125.9, 125.2, 125.0, 123.1, 122.7 (2C), 121.7,
120.9, 99.4, 96.8, 82.0, 76.9, 64.9, 63.7, 37.1 (2C, d, JPC = 5.0 Hz), 27.4, 26.4 (3C), 25.8
(3C), 25.7, 18.8, 18.1, -3.2, -4.4, -4.9, -5.3; δP (242 MHz, CDCl3) 193.4; m/z (ESI+) 1018.2
(M+, 100%). The compound was found to be light sensitive and decomposed in solution. The
1H-NMR spectrum and subsequent hydride formation experiments indicated the presence of
ca 10% of the diastereomer 24 (see Supporting Information).
26

Page 27 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
Procedure for reduction of ketones with formic acid/triethylamine (FA/TEA).
Acetophenone (100 mg, 0.83 mmol, 1.0 eq), Catalyst (0.10 eq. / 10 mol%) and FA/TEA (5:2
azeotrope, 830 L) were added to a flask under nitrogen, degassed and stirred for 10 min.
ꢀ
TMAO (0.1 eq. / 10 mol%) was added to the reaction and the mixture was heated at the
temperature indicated for the time stated. At the end of this time the reaction was allowed to
cool to rt and EtOAc:hexane (1:4, ca 10 mL) was added to dilute the sample. This solution
was passed through celite and then silica gel. The residue was taken up in EtOAc:hexane
(1:4, ca 10 mL x 2) and the solutions filtered passed through celite and then silica gel. This
served to remove residues of catalyst to give the product in quantitative conversion as
assessed by the mass balance. Removal of solvent gave the product which was analyzed by
GC and NMR.6a A sample of the formate derivative of known major configuration was
prepared and this is described below. When following conversion over time, a small sample
was taken from the reaction and treated as described above. An authentic (commercial)
sample of the reduction product of 3,3-dimethyl-2-butanone was used to establish the GC
conditions. Chiral GC analysis; i) for reacemic 1-phenylethanol (CP-Chiralsil-Dex-Cβ 25m x
o
0.25mm x 0.25µm, T = 110 C, P = 18 psi, He gas) (R) isomer 12.95 min, (S) isomer 14.24
min. The ketone has a RT of 6.03 min (features in the asymmetric sample of 32% ee). 1-
o
25m x 0.25mm x 0.25µm, T = 110 C,
Phenylethyl formate (racemic); CP-Chiralsil-Dex-C
β
P = 18 psi, He gas) (S) isomer; 7.62 min, (R) isomer; 8.55 min. 3,3-Dimethyl-2-butanol. 70
°C, Racemic CP-Chiralsil-Dex-C
25m x 0.25mm x 0.25µm, T = 110 oC, P = 18 psi, He gas)
β
(R) isomer; 8.41 min, (S) isomer; 8.77 min.
Procedure for reduction of ketones with hydrogen gas.
Illustration with acetophenone: acetophenone (100 mg, 0.83 mmol), catalyst (0.01 eq. / 1
mol%), and iPrOH (0.5 mL) were added to a small test tube containing a stirrer bar. A
solution of K2CO3 (5.8 mg, 0.042 mmol) in water (0.2 mL), or TMAO (1 mol%) was added,
then the test tube was sealed in a Parr hydrogenator and charged with hydrogen to 30 bar,
venting once. The sealed vessel was heated to the temperature indicated and stirred for the
time given in the table. At the end of this time, the reaction was allowed to cool to rt, the
pressure was carefully released and the sample was worked up and analyzed as previously
described.
27

Dalton Transactions
Page 28 of 32
View Article Online
DOI: 10.1039/C5DT04610F
Procedure for oxidation of alcohols with acetone as the hydrogen acceptor.
Acetophenone (100 mg, 0.83 mmol, 1.0 eq), Catalyst (0.10 eq. / 10 mol%) and acetone (4.3
mL) were added to a pressure tube, degassed and stirred for 10 min. TMAO (0.1 eq. / 10
mol%) was added, the reaction tube was sealed and the mixture was heated at the temperature
indicated for the time stated. At the end of this time the reaction was allowed to cool to rt and
the sample was worked up and analyzed as previously described.
Synthesis of (S)-1-phenylethyl formate via a Mitsunobu reaction.
To an oven dried flask was added acetophenone (250 mg, 243 ꢀL, 2.08 mmol, 1eq.) and
formic acid triethylamine azeotrope (5:2) (1.39 mL). To this solution was added 3C-(R,R)-
Teth-TsDpenRuCl catalyst16 (2.5 mg, 0.004 mmol, S/C: 500:1) and the mixture was heated to
40 ºC overnight. The reaction was cooled to rt and diluted in EtOAc and passed through a
silica plug, the solvent was removed to yield a yellow oil (250 mg, 2.05 mmol). To this
solution was added formic acid (94 mg, 77
(538 mg, 2.05 mmol, 1 eq.) as a anhydrous THF (10 mL) solution. The reaction was cooled to
0 ºC and DIAD (415 mg, 404 L, 2.05 mmol, 1 eq.) as a single portion. The reaction was
ꢀL, 2.05 mmol, 1 eq.) and triphenylphosphine
ꢀ
allowed to warm to rt and left overnight. The THF was removed and the water was added
and the aqueous solution was extracted with DCM (3 x 50 mL). The organic solvent was
dried with Na2SO4 and the solvent was removed under reduced pressure to yield a yellow oil.
This contained diisopropyl hydrazine-1,2-dicarboxylate (20% by NMR) no further
purification was attempted. On GC this showed peak 1 at 7.72 (75.4%, S) and peak 2 at 8.75
(24.6%, R) (ee = 51%). δH (400MHz, CDCl3) 8.07 (1H, s, C(O)H), 7.27-7.36 (5H, m, ArH),
6.00 (1H, q, J = 6.7 Hz, CH(O)CH3), 1.58 (3H, d, J = 6.5 Hz, CH3). This data was consistent
with that previously reported.6b A racemic sample was prepared according to the procedure in
this reference.
28

Page 29 of 32
Dalton Transactions
View Article Online
DOI: 10.1039/C5DT04610F
Acknowledgements.
We thank the Leverhulme Trust (Grant no. RPG-374) for financial support to RH, the EPSRC
(Grant no. EP/M006670/1) for financial support to ADG and Johnson Matthey Catalysis and
Chiral Technologies for a gift of Teth-TsDpenRuCl catalyst. The X-ray diffraction instrument
was obtained through the Science City Project with support from the AWM and part funded
by the ERDF.
References.
1) (a) C. Bolm, J. Legros, J. Le Paih, and L. Zani, Chem. Rev. 2004, 104, 6217-6254. (b) S.
Enthaler, K. Junge, and M. Beller, Angew. Chem. Int. Ed. 2008, 47, 3317–3321. (c) S.
Gaillard and J.-L. Renaud, ChemSusChem 2008, 1, 505-509. (d) G. Bauer and K. A.
Kirchner, Angew. Chem. Int. Ed. 2011, 50, 5798-5800. (e) K. Junge, K. Schroder and M.
Beller, Chem. Commun. 2011, 47, 4849-4859. (f) M. Darwish and M. Wills, Catal. Sci.
Technol. 2012, 2, 243 – 255. (g) K. Gopalaiah, Chem.Rev. 2013, 113, 3248–3296. (h) A.
Quintard and J. Rodriquez, Angew Chem. Int. Ed. 2014, 53, 4044-4055. (h) I. Bauer and H.-J.
Knölker, Chem. Rev. 2015, 115, 3170-3387.
2) (a) G. N. Schrauzer, J. Am. Chem. Soc. 1959, 81, 5307-5310. (b) A. J. Pearson, R. J.
Shively Jr and R. A. Dubbert, Organometallics 1992, 11, 4096-4104. (c) A. J. Pearson and R.
J. Shively Jr, Organometallics 1994, 13, 578-584. (d) A. J. Pearson and J. B. Kim, Org. Lett.
2002, 4, 2837-2840. (e) E. Weiss, R. G. Merenyl and W. Huber, Chem and Industry 1960,
407-408.
3) (a) H.-J. Knölker, J. Heber and C. H. Mahler, Synlett 1992, 1002-1004. (b) H.-J. Knölker,
E. Baum, H. Goesman and R. Klauss, Angew. Chem. Int. Ed. 1999, 38, 2064-2066. (c) H.-J.
Knölker, E. Baum, H. Goesmann and R. Klauss, Angew. Chem. Int. Ed. 1999, 38, 702-705.
(d) T. N. Plank, J. L. Drake, D. K. Kim and T. W. Funk, Adv. Synth. Catal. 2012, 354, 597-
601.
4) (a) C. P. Casey and H. Guan, J. Am. Chem. Soc. 2007, 129, 5816-5817. (b) C. P. Casey and
H. Guan, J. Am. Chem. Soc. 2009, 131, 2499-2507.
5) (a) A. Berkessel, S. Reichau, A. Von der Höh, N. Leconte and J.-M. Nordörfl,
Organometallics 2011, 30, 3880-3887.
ChemCatChem, 2011, 3, 861-867.
(b) A. Berkessel and A. Van der Höh,
6) (a) J. P. Hopewell, J. E. D. Martins, T. C. Johnson, J. Godfrey and M. Wills, Org. Biomol.
Chem. 2012, 10, 134-145. (b) T. C. Johnson, G. J. Clarkson and M. Wills, Organometallics
2011, 30, 1859-1868.
29