Coordination chemistry of diphenylphosphinoferrocenylthioethers on cyclooctadiene and norbornadiene rhodium(i) platforms

Article abstract of DOI:10.1039/c2dt30993a

Complexes [RhCl(diene)(P,SR)] with chiral ferrocenyl phosphine-thioethers ligands (diene = norbornadiene, NBD, 1^R, or 1,5-cyclooctadiene, COD, 3^R; P,SR = CpFe(1,2-η⁵-C₅H ₃(PPh₂)(CH₂

Full text of DOI:10.1039/c2dt30993a

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PAPER
Coordination chemistry of diphenylphosphinoferrocenylthioethers on
cyclooctadiene and norbornadiene rhodium(I) platforms†‡
Ekaterina M. Kozinets,a,b,c Oleksandr Koniev,a,b Oleg A. Filippov,c Jean-Claude Daran,a,b Rinaldo Poli,a,b,d
Elena S. Shubina,c Natalia V. Belkova*c and Eric Manoury*a,b
Received 7th May 2012, Accepted 30th July 2012
DOI: 10.1039/c2dt30993a
Complexes [RhCl(diene)(P,SR)] with chiral ferrocenyl phosphine–thioethers ligands (diene =
norbornadiene, NBD, 1R, or 1,5-cyclooctadiene, COD, 3R; P,SR = CpFe(1,2-η5-C5H3(PPh2)(CH2SR);
R = tBu, Ph, Bz, Et) and the corresponding [Rh(diene)(P,SR)][BF4] (diene = NBD, 2R; COD, 4R) have
been synthesized from [RhCl(diene)]2 and the appropriate P,SR ligand. The molecular structure of the
cationic complexes 2tBu, 4Ph and 4Bz, determined by single-crystal X-ray diffraction, shows the expected
slightly distorted square planar geometry. For the neutral chloride complexes, a combination of
experimental IR and computational DFT investigations points to an equally four coordinate square planar
geometry with the diene ligand, the chlorine and the phosphorus atoms in the coordination sphere and
with a dangling thioether function. However, a second isomeric form featuring a 5-coordinated square
planar geometry with the thioether function placed in the axial position is easily accessible in some cases.
Introduction
Since the development by Noyori and coworkers of efficient cat-
alytic systems for the asymmetric hydrogenation of non-functio-
nalized ketones,1–3 much effort has been devoted to the
asymmetric hydrogenation of polar substrates,4 ketones5 but also
Scheme 1 General structure of the (P,SR) ligands used in this study.
imines6–9 or heteroarenes,10 because of their great scientific and
practical importance, which includes industrial applications.11,12
Scheme 1.18–22 The use of these ligands (particularly for R = Et,
Most of the catalysts used so far are based on ruthenium,
rhodium and iridium with phosphorus and nitrogen-containing
ligands.
Ph, Bz and tBu) has led to a number of catalytic applications in
asymmetric allylic substitution23,24 asymmetric methoxycarbo-
nylation25 and asymmetric hydrogenation.26 Although other
kinds of ligands based on P and S donor atoms have already
been used in CvC hydrogenations,27–30 we reported the first
application of these types of ligands, to the best of our knowl-
edge, to the hydrogenation of ketones, promising results being
obtained in the ionic hydrogenation of various acetophenones.26
In combination with [IrCl(COD)]2 (COD = 1,5-cycloocta-
diene), these ligands have yielded the corresponding IrCl(COD)-
(P,SR) adducts, of which those with R = Et, Ph and Bz adopt a
5-coordinate square pyramidal geometry (axial Cl) in the solid
state and in solution, whereas the tBu derivative is square planar
with a dangling thioether function.31 These iridium complexes
were shown to be excellent precatalysts for the hydrogenation of
aromatic ketones in the presence of a strong base such as
NaOMe in methanol and other alcohols, leading to quantitative
hydrogenations in less than two hours at room temperatures
under 30 bar of H2 and with only 0.05% of catalyst loading and
with enantiomeric excesses that reached >99% (at 0 °C) for
selected substrates.26
Our group has worked extensively on the chiral ligand plat-
form built around the planar chirality of ferrocene, mostly with
asymmetric 1,2 substitution, but also 1,2,3 trisubstitution and
1,2,3,1′ tetrasubstitution.13–17 Our interest in recent years has
focused on chiral ligands based on P and S donor atoms with the
development of the 1,2-substituted ferrocenes (P,SR) shown in
aCNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de
Narbonne, BP 44099, F-31077 Toulouse Cedex 4, France.
E-mail: eric.manoury@lcc-toulouse.fr; Fax: +33-561553003;
Tel: +33-561333174
bUniversité de Toulouse, UPS, INPT, F-31077 Toulouse Cedex 4, France
cA. N. Nesmeyanov Institute of Organoelement Compounds, Russian
Academy of Sciences, Vavilov Street 28, 119991 Moscow, Russia.
E-mail: nataliabelk@ineos.ac.ru; Fax: +7-499-1355085;
Tel: +7-499-1356448
dInstitut Universitaire de France, 103, bd Saint-Michel, 75005 Paris,
France
†Dedicated to Professor David Cole-Hamilton on the occasion of his
retirement and for his outstanding contribution to transition metal
catalysis.
‡Electronic Supplementary Information (ESI) available. CCDC 872062
for 2tBu, 872063 for 4Bz, 872064 for 4tBu. For ESI and crystallographic
data in CIF or other electronic format see DOI: 10.1039/c2dt30993a
Specific stoichiometric investigations of the precatalyst hydro-
genation in methanol, yielding partial hydrogenation of the
This journal is © The Royal Society of Chemistry 2012
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RhCl(NBD)(P,StBu) (1tBu, yield: 97%). 1H NMR (500 MHz,
CDCl3): δ 8.48 (m, 2H, Ph); 7.53 (m, 3H, Ph); 7.3–7.2 (m, 3H,
Ph); 6.93 (br dd, 2H, Ph, JHH = 7.2 Hz, JHP = 9.7 Hz); 5.06
(d (AB), 1H, CH2Fc, JHH = 13.8 Hz); 4.56 (s, 1H, subst. Cp);
4.30 (s, 1H, subst. Cp); 4.14 (s, 1H, subst. Cp); 3.90 (s, 5H, Cp);
3.84 (d (AB), 1H, CH2Fc, JHH = 13.8 Hz); 3.78 (s, 2H,
CH NBD); 3.61 (s, 2H, CH NBD); 3.57 (s, 2H, CH NBD); 1.51
(s, 9H, tBu) 1.23 (s, 2H, CH2 NBD). 13C{1H} NMR (125 MHz,
cyclooctadiene to cyclooctene (experimentally observed by
GC-MS) and presumably leading at least initially to Ir(P,SR)-
(OMe)(MeOH), have not so far allowed the isolation or spectro-
scopic observation of a catalytically active species. It is known
from elegant work by Heller et al. that the hydrogenation of
diene ligands in complexes such as [M(diene)(L2)]+ (L2 being
typically a diphosphine ligand a M = Rh) in methanol yields
[M(L2)(MeOH)2]+ adducts and that such derivatives are less
easily generated and less stable when M = Ir.32–35 With the goal
of generating more stable model complexes of the above men-
tioned iridium catalysts, we have therefore turned out attention to
analogous Rh complexes. We report in this contribution the syn-
thesis and characterization of a variety of adducts of the (P,SR)
ligands in Scheme 1 with [RhCl(COD)]2 and [RhCl(NBD)]2
(NBD = norbornadiene). This includes an IR study and a DFT
investigation to elucidate the structure of the compound in the
solid state and in solution. Related cationic complexes [Rh-
(COD)(P,SR)]+ and [Rh(NBD)(P,SR)]+ have also been isolated
and structurally characterized. We also report preliminary investi-
gations of acetophenone hydrogenation using these rhodium
complexes as precatalysts. It will be shown that, albeit the cataly-
tic activity is lower, these complexes are good structural and
functional models of the corresponding Ir precatalysts.
CDCl3): δ 136.3 (d, Ph, JCP = 12.8 Hz); 135.3 (d, quat Ph, JCP
45.6 Hz); 133.8 (d, quat Ph, JCP = 45.6 Hz); 132.3 (d, Ph, JCP
9.2 Hz); 130.4 (d, Ph, JCP = 2.2 Hz); 128.7 (d, Ph, JCP
1.8 Hz); 127.7 (d, Ph, JCP = 10.4 Hz); 127.2 (d, Ph, JCP
=
=
=
=
9.2 Hz); 91.3 (d, quat Cp, JCP = 18.6 Hz); 73.3 (s, subst. Cp);
71.9 (d, subst. Cp, JCP = 7.6 Hz); 71.5 (d, quat Cp, JCP
=
7.6 Hz); 71.0 (s, Cp); 69.0 (d, subst. Cp, JCP = 5.2 Hz); 61.4
(s, CH2 NBD); 60.2(br s, CH NBD); 55.9 (br s, CH NBD); 48.5
(s, CH NBD); 46.0(s, S-C(CH3)); 31.3 (s, S-C(CH3)); 28.8
(CH2Fc). 31P{1H} NMR (202 MHz, CDCl3): δ 23.6 (d, JP–Rh
159 Hz). MS (ESI) m/z: 667.081 (M − Cl−, 100%).
=
RhCl(NBD)(P,SPh) (1Ph, yield: 98%). 1H NMR (500 MHz,
CDCl3): δ 8.52 (m, 2H, Ph); 7.73 (br d, JHH = 7.5 Hz, 2H, Ph);
7.58 (m, 3H, Ph); 7.4–7.1 (m, 6H, Ph); 6.62 (m, 2H, Ph); 5.37
(br d (AB), 1H, CH2Fc, JHH = 13 Hz); 4.45 (br s, 1H, subst.
Cp); 4.28 (br d (AB), 1H, CH2Fc, JHH = 13 Hz); 4.24 (br s, 1H,
subst. Cp); 4.03 (br s, 1H, subst. Cp); 3.88 (s, 5H, Cp); 3.54
(s, 4H, CH NBD); 3.40 (s, 2H, CH NBD); 1.17 (s, 2H, CH2
Experimental section
General
NBD). 13C{1H} NMR (125 MHz, CDCl3): δ 136.2 (d, Ph, JCP
=
13.0 Hz); 135.3 (d, quat Ph, JCP = 46.8 Hz); 135.1 (quat Ph);
133.3 (d, quat Ph, JCP = 46.0 Hz); 131.6 (d, Ph, JCP = 9.3 Hz);
130.6 (d, Ph, JCP = 2.2 Hz); 130.3 (Ph); 129.0 (Ph); 128.6 (d,
Ph, JCP = 1.8 Hz); 127.9 (d, Ph, JCP = 10.5 Hz); 127.5 (Ph);
127.2 (d, Ph, JCP = 9.4 Hz); 89.0 (d, quat Cp, JCP = 18.6 Hz);
72.6 (s, subst. Cp); 72.4 (d, subst. Cp, JCP = 7.7 Hz); 71.0 (s,
All reactions were carried out under an argon atmosphere using
standard Schlenk techniques. Solvents were carefully dried by
conventional methods and distilled under argon before use. The
(R/S)-2-diphenylphosphanyl-(R-thiomethyl)ferrocene
ligands
(R = Et, tBu, Ph, Bz) were prepared according to a published
procedure from racemic 2-(diphenylthiophosphanylferrocenyl)-
methanol.36 Compounds [RhCl(COD)]2,[RhCl(NBD)]2 and[Rh-
(COD)2]BF4 were purchased from Strem Chemicals and used as
received.1H, 13C{1H} and 31P{1H} NMR spectra were recorded
with a Bruker Avance 500 FT-NMR spectrometer. The reson-
ances were calibrated relative to the residual solvent peaks and
are reported with positive values downfield from TMS. For all
Cp); 70.8 (d, quat Cp, JCP = 40 Hz); 69.1 (d, subst. Cp, JCP
5.0 Hz); 60.8 (d, JCRh = 5.3 Hz, CH2 NBD); 59.1(d, JCRh
=
=
7.6 Hz, CH NBD); 54.2 (br s, CH NBD); 48.2 (s, CH NBD);
34.1 (CH2Fc). 31P{1H} NMR (202 MHz, CDCl3): δ 23.8 (d,
J
P–Rh = 154 Hz). MS (ESI) m/z: 687.049 (M − Cl−, 100%).
RhCl(NBD)(P,SBz) (1Bz, yield: 99%). 1H NMR (500 MHz,
1
characterized compounds, the peak assignments in the H and
13C NMR spectra were based on COSY, HSQC and HMBC 2D
experiments. HRMS were obtained from dichloromethane solu-
tions with a Xevo G2 Q TOF spectrometer by the electrospray
method. IR spectra were recorded at room temperature with a
Nicolet 6700 spectrometer in the solid state (as nujol mulls)
using polyethylene cells for the low frequency region. The
optical purity and the conversions for the hydrogenation experi-
ments were determined by chiral GC (Supelco BETA
DEX™ 225).
CDCl3): δ 8.46 (m, 2H, Ph); 7.59 (m, 3H, Ph); 7.45–7.25
(m, 8H, Ph); 6.88 (m, 2H, Ph); 4.32 (br s, 1H, subst. Cp); 4.25
(br s, 1H, subst. Cp); 4.13 (br d (AB), 1H, CH2Fc, JHH
=
12 Hz); 4.08 (s, 1H, subst. Cp); 4.00 (m, 1H CH2Fc + 1H
CH2Ph); 3.73 (s, 5H, Cp); 3.70 (d (AB), 1H, CH2Ph); 3.52 (br s,
4H, NBD); 3.42 (br s, 2H, NBD); 1.19 (s, 2H, CH2 NBD).
13C{1H} NMR (125 MHz, CDCl3): δ 143.4 (quat Ph); 136.0 (d,
Ph, JCP = 13.3 Hz); 135.5 (d, quat Ph, JCP = 43.8 Hz); 134.6
(d, quat Ph, JCP = 44.8 Hz); 131.4 (d, Ph, JCP = 9.4 Hz); 130.5
(d, Ph, JCP = 2.0 Hz); 129.5 (Ph); 128.71 (Ph); 128.66 (d, Ph,
JCP = 1.8 Hz); 127.9 (d, Ph, JCP = 10.4 Hz); 127.7 (Ph); 127.4
(d, Ph, JCP = 9.1 Hz); 88.6 (d, quat Cp, JCP = 19.7 Hz); 72.6 (s,
subst. Cp); 72.5 (d, subst. Cp, JCP = 7.6 Hz); 70.7 (s, Cp); 70.4
(d, quat Cp, JCP = 38.9 Hz); 69.1 (d, subst. Cp, JCP = 4.7 Hz);
60.4 (s, CH2 NBD); 53.8 (br s, CH NBD); 49.9 (br s, CH NBD);
48.1 (s, CH NBD); 40.6 (CH2Ph); 31.3 (CH2Fc). 31P{1H} NMR
(202 MHz, CDCl3): δ 20.3 (d, JP–Rh = 147 Hz). MS (ESI) m/z:
701.067 (M − Cl−, 100%).
General procedure for the synthesis of RhCl(NBD)(P,SR),
1. In
a
Schlenk tube, under nitrogen, ligand (P,SR)
(0.793 mmol) was dissolved in dichloromethane (5 mL) and
[RhCl(NBD)]2(183 mg, 0.396 mmol) was added. The solution
was stirred for 4 h at room temperature and 15 mL of pentane
was then added to yield a yellow precipitate. The precipitate was
filtered under argon and washed with pentane to give
RhCl(NBD)(P,SR).
Dalton Trans.
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RhCl(NBD)(P,SEt) (1Et, yield: 99%). 1H NMR (500 MHz,
CDCl3): δ 8.44 (m, 2H, Ph); 7.59 (m, 3H, Ph); 7.27 (m, 3H, Ph);
6.87 (m, 2H, Ph); 4.52 (s, 1H, subst. Cp); 4.37 (br d (AB), 1H,
CH2Fc, JHH = 12 Hz); 4.29 (s, 1H, subst. Cp); 4.14 (s, 1H,
subst. Cp); 4.06 (br d (AB), 1H, CH2Fc, JHH = 12 Hz); 3.83 (s,
5H, Cp); 3.60 (br m, 4H, CH NBD); 3.42 (br s, 2H, CH NBD);
2.81 (m, 1H, CH2CH3); 2.57 (m, 1H, CH2CH3); 1.38 (t, 3H,
CH3, JHH = 6.7 Hz); 1.22 (s, 2H, CH2 NBD). 13C{1H} NMR
(125 MHz, CDCl3): δ 135.9 (d, Ph, JCP = 13.2 Hz); 135.5 (d,
quat Ph, JCP = 44.3 Hz); 134.2 (d, quat Ph, JCP = 44.8 Hz);
131.4 (d, Ph, JCP = 9.5 Hz); 130.5 (d, Ph, JCP = 2.2 Hz); 128.7
(d, Ph, JCP = 1.8 Hz); 127.9 (d, Ph, JCP = 10.4 Hz); 127.5 (d,
Ph, JCP = 9.2 Hz); 88.8 (d, quat Cp, JCP = 19.4 Hz); 72.7 (s,
subst. Cp); 72.5 (d, subst. Cp, JCP = 7.7 Hz); 70.8 (s, Cp); 70.2
(d, quat Cp, JCP = 38 Hz); 69.0 (d, subst. Cp, JCP = 4.8 Hz);
60.7 (s, CH2 NBD); 55.3 (br s, CH NBD); 51.2 (br s, CH NBD);
48.2 (s, CH NBD); 30.8 (CH2Fc); 29.7 (d, JCRh = 3.4 Hz,
CH2CH3); 13.4 (CH3). 31P{1H} NMR (202 MHz, CDCl3):
δ 21.3 (d, JP–Rh = 148 Hz). MS (ESI) m/z: 639.049 (M − Cl−,
100%).
(AB), 1H, CH2Fc, JHH = 12.9 Hz); 2.48 (m, 2H, CH2 cod); 2.32
(m, 2H, CH2 cod); 1.99 (m, 2H, CH2 cod); 1.87 (m, 2H, CH2
cod); 1.41 (s, 9H, tBu). 13C HNMR (125 MHz, CDCl3): δ 135.1
(d, Ph, JCP = 11.9 Hz); 134.4 (d, quat Ph, JCP = 43.6 Hz); 133.9
(d, Ph, JCP = 10.5 Hz); 133.2 (d, quat Ph, JCP = 43.4 Hz); 130.1
(d, Ph, JCP = 1.7 Hz); 129.5 (Ph); 127.7 (d, Ph, JCP = 10.0 Hz);
127.5 (d, Ph, JCP = 9.6 Hz); 90.6 (d, quat Cp, JCP = 14.1 Hz);
74.6 (d, subst. Cp, JCP = 7.6 Hz); 74.3 (d, quat Cp, JCP
=
42.2 Hz); 71.3 (d, subst. Cp, JCP = 6.9 Hz); 71.1 (s, Cp); 69.8
(d, subst. Cp, JCP = 7.2 Hz); 43.0 (s, S-C(CH3)); 31.9 (v. br s,
CH2 cod); 31.1 (s, S-C(CH3)); 30.3 (v. br s, CH2 cod), 28.6 (br
s, CH2Fc). 31P NMR (202 MHz, CDCl3): δ 21.0 (d, JP–Rh
=
148 Hz). MS (ESI) m/z: 683.112 (M − Cl−, 100%).
Essential spectroscopic parameters for the other compounds:
R = Ph: δ 28.0 (d, JP–Rh = 166 Hz). R = Bz: δ 31.1 (d, JP–Rh
170 Hz). R = Et: δ 22.8 (d, JP–Rh = 144 Hz).
=
General procedure for the synthesis of [Rh(COD)(P,SR)]BF4,
4. In Schlenk tube, under nitrogen, ligand (P,SR)
a
(0.305 mmol) was dissolved in dichloromethane (5 mL) and
[Rh(COD)2]BF4(124 mg, 0.305 mmol) was added. The solution
was stirred for 30 min at room temperature and 15 mL of
pentane was then added to yield a yellow precipitate. The pre-
cipitate was filtered under argon and washed with pentane to
give [Rh(COD)(P,SR)]BF4.
Synthesis of [Rh(NBD)(P,StBu)]BF4, 2tBu. In a Schlenk tube,
under nitrogen, complex RhCl(NBD)(P,StBu) (0.148 mmol) was
dissolved in dichloromethane (5 mL) and 5 ml of a water solu-
tion of NaBF4(20 mg, 0.178 mmol) was added. The organic
phase was separated and dried over anhydrous sodium sulfate.
After solvent evaporation, [Rh(NBD)(P,StBu)]BF4 was obtained
[Rh(COD)(P,StBu)]BF4 (4tBu
,
yield 99%). 1H NMR
(500 MHz, CDCl3): δ 7.60–7.35 (m, 10H, Ph); 5.78 (br s, 2H,
CH COD); 4.78 (br s, 1H, subst. Cp); 4.64 (s, 5H, Cp); 4.48 (br
s, 1H, subst. Cp); 4.12 (br s, 1H, subst. Cp); 4.00–3.95 (m, 2H,
1H CH cod + 1H CH2Fc); 3.85 (br s, 1H, CH COD); 2.87 (m,
1H, CH2 COD); 2.71 (m, 1H, CH2 COD); 2.69 (d (AB), 1H,
CH2Fc, JHH = 12.2 Hz); 2.59 (m, 1H, CH2 COD); 2.49 (m, 1H,
CH2 COD); 2.39 (m, 1H, CH2 COD); 2.30 (m, 1H, CH2 COD);
2.07 (m, 1H, CH2 COD); 1.96 (m, 1H, CH2 COD); 1.37 (s, 9H,
1
as a yellow solid. H NMR (500 MHz, CDCl3): δ 7.69 (m, 2H,
Ph); 7.55–7.50 (m, 6H, Ph); 7.40 (m, 2H, Ph); 5.85–5.65 (br m,
2H, CH NBD); 4.77 (s, 1H, subst. Cp); 4.64 (s, 5H, Cp); 4.49
(m, 1H, subst. Cp); 4.35–4.30 (br s, 3H, CH NBD); 4.12 (m,
1H, subst. Cp); 3.96 (d (AB), 1H, CH2Fc, JHH = 12.2 Hz);
3.90–3.70 (br s, 1H, CH NBD); 2.81 (d (AB), 1H, CH2Fc, JHH
= 12.2 Hz); 1.69 (br s, 2H, CH2 NBD); 1.37 (s, 9H, tBu). 13C
{1H} NMR (125 MHz, CDCl3): δ 134.0 (d, Ph, JCP = 13.2 Hz);
132.1 (d, Ph, JCP = 2.2 Hz); 131.7 (d, Ph, JCP = 9.9 Hz); 131.3
(d, Ph, JCP = 2.4 Hz); 129.6 (d, quat Ph, JCP = 45.8 Hz); 129.5
(d, Ph, JCP = 10.6 Hz); 129.0 (d, Ph, JCP = 10.8 Hz); 126.0 (d,
quat Ph, JCP = 52.3 Hz); 85.9 (d, quat Cp, JCP = 18.5 Hz); 83.8
(br s, CH NBD); 75.8 (d, subst. Cp, JCP = 6.8 Hz); 72.2 (s,
subst. Cp); 72.0 (s, CH NBD); 71.0 (s, Cp); 70.0 (br s, CH
NBD); 68.9 (d, subst. Cp, JCP = 5.7 Hz); 67.8 (d, CH2 NBD,
JC-Rh = 4.4 Hz); 64.7 (d, quat Cp, JCP = 55.2 Hz); 54.8 (s,
S-C(CH3)); 31.0 (s, S-C(CH3)); 29.1 (d, CH2Fc, JCP = 5.3 Hz.
31P NMR (202 MHz, CDCl3): δ 26.1 (d, JP–Rh = 158 Hz). MS
(ESI) m/z: 667.081 (M − BF4−, 100%).
tBu). 13C{1H} NMR (125 MHz, CDCl3): δ 133.9 (d, Ph, JCP
=
12.7 Hz); 132.3 (d, Ph, JCP = 2.0 Hz); 132.1 (d, Ph,
JCP = 9.0 Hz); 131.6 (d, Ph, JCP = 2.2 Hz); 130.0 (d, ipso Ph,
JCP = 44.4 Hz); 129.5 (d, Ph, JCP = 10.4 Hz); 128.8 (d, Ph,
JCP = 10.0 Hz); 125.9 (d, ipso Ph, JCP = 50.6 Hz); 104.4 (dd,
CH COD, JCP = 9.7 Hz, JCRh = 7.1 Hz); 102.1 (dd, CH COD,
JCP = 9.4 Hz, JCRh = 6.1 Hz); 85.5 (d, ipso Cp, JCP = 17.7 Hz);
82.1 (d, CH COD, JCRh = 11.3 Hz); 81.3 (d, CH COD, JCRh
=
12.6 Hz); 76.1 (d, subst. Cp, JCP = 6.7 Hz); 73.1 (s, subst. Cp);
71.0 (s, Cp); 69.2 (s, subst. Cp, JCP = 5.7 Hz); 63.2 (d, ipso Cp,
JCP = 56.1 Hz); 55.7 (s, S-C(CH3)); 35.7 (s, CH2 COD); 31.5
(CH3); 31.0 (s, CH2 COD); 29.2 (s, CH2Fc); 28.7 (s, CH2 COD);
27.0 (s, CH2 COD). 31P{1H} NMR (202 MHz, CDCl3): δ 23.8
(d, JP–Rh = 143 Hz). MS (ESI) m/z: 683.112 (M − BF4−, 100%).
General procedure for the synthesis of RhCl(COD)(P,SR),
3. In
a Schlenk tube, under nitrogen, ligand (P,StBu)
(0.797 mmol) was dissolved in dichloromethane (5 mL) and
[RhCl(COD)]2(196 mg, 0.397 mmol) was added. The solution
was stirred for 4 h at room temperature and 15 mL of pentane
was then added to form a yellow precipitate. The precipitate was
filtered under nitrogen and washed with pentane, to give [RhCl-
(COD)(P,SR). Only in the case of R = tBu, the product could be
isolated in a pure state. Yield: 64%. R = tBu. 1H NMR
(500 MHz, CDCl3): δ 8.06 (m, 2H, Ph); 7.55–7.25 (m, 8H, Ph);
4.64 (br s, 1H, subst. Cp); 4.36 (br s, 1H, subst. Cp); 4.35–4.20
(m, 2H, 1 subst. Cp + 1 CH2Fc); 4.09 (s, 5H, Cp); 3.91 (br d
[Rh(COD)(P,SPh)]BF4 (4Ph
,
yield: 80%). 1H NMR
(500 MHz, CDCl3): δ 7.80–7.35 (m, 15H, Ph); 5.17 (m, 1H, CH
COD); 4.72 (br s, 1H, subst. Cp); 4.70 (s, 5H, Cp), 4.49 (br s,
1H, subst. Cp); 4.29 (m, 1H, CH COD); 4.17 (d (AB), 1H,
CH2Fc, JHH = 12.3 Hz); 4.12 (m, 1H, CH COD); 4.09 (br s, 1H,
subst. Cp); 4.01 (m, 1H, CH COD); 3.04 (d (AB), 1H, CH2Fc,
JHH = 12.3 Hz); 2.80 (m, 1H, CH2 COD); 2.68 (m, 1H, CH2
COD), 2.46 (m, 2H, CH2 COD); 2.36 (m, 1H, CH2 COD); 2.14
(m, 1H, CH2 COD) 2.04 (m, 1H, CH2 COD) 1.96 (m, 1H, CH2
COD). 13C{1H} NMR (125 MHz, CDCl3): δ 134.1 (d, Ph, JCP
=
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12.7 Hz); 132.7 (Ph); 131.9 (d, Ph, JCP = 9.4 Hz); 131.7 (Ph);
131.3 (Ph); 130.4 (Ph); 130.4 (d, ipso Ph, JCP = 45.1 Hz); 129.9
(d, Ph, JCP = 10.1 Hz); 125.9 (d, ipso Ph, JCP = 49.5 Hz); 107.0
(br s, CH COD); 103.3 (dd, CH COD, JCP = 9.0 Hz, JCRh = 6.0
Hz); 86.2 (d, CH COD, JCRh = 11.8 Hz); 84.8 (d, ipso Cp,
JCRh = 16.9 Hz); 84.1 (d, CH COD, JCRh = 10.8 Hz); 75.9 (d,
subst. Cp, JCP = 6.2 Hz); 72.9 (br s, subst. Cp); 71.3 (br s, Cp);
69.1 (d, subst. Cp, JCP = 5.8 Hz); 64.6 (d, ipso Cp, JCP = 55.9
Hz); 37.9 (d, CH2Fc, JCP = 4.6 Hz); 34.4 (s, CH2 COD); 30.3 (s,
CH2 COD); 30.0 (s, CH2 COD); 27.1 (s, CH2 COD). 31P{1H}
NMR (202 MHz, CDCl3): δ 22.1 (d, JP–Rh = 144 Hz). MS (ESI)
m/z: 703.081 (M − BF4−, 100%).
15.0 (CH3). 31P{1H} NMR (202 MHz, CDCl3): δ 22.9 (d, JP–Rh
= 144 Hz). MS (ESI) m/z: 655.081 (M − BF4−, 100%).
X-ray crystallography. A single crystal of each compound
was mounted under inert perfluoropolyether on the tip of a cryo-
loop and cooled in the cryostream of either an Oxford-Diffrac-
tion XCALIBUR SAPPHIRE-I CCD diffractometer or an
Agilent Technologies GEMINI EOS CCD diffractometer. Data
were collected using the monochromatic Mo Kα radiation (λ =
0.71073). The structures were solved by direct methods
(SIR97)37 and refined by least-squares procedures on F2 using
SHELXL-97.38 All H atoms attached to carbon were introduced
in idealised positions and treated as riding on their parent atoms
in the calculations. The drawing of the molecules was realised
with the help of ORTEP3.39,40 Crystal data and refinement para-
meters are shown in Table 1.
[Rh(COD)(P,SBz)]BF4 (4Bz, yield 42%). 1H NMR (500 MHz,
CDCl3): δ 7.70 (m, 2H, Ph); 7.60–7.50 (m, 8H, Ph); 7.34 (m,
5H, Ph); 5.57 (m, 2H, CH COD); 4.54 (br s, 6H, Cp + 1H,
subst. Cp); 4.42 (br s, 1H, subst. Cp); 4.19 (d (AB), 1H, CH2Ph,
JHH = 13.8 Hz); 4.13 (br s, 1H, subst. Cp); 4.03 (d (AB), 1H,
CH2Ph, JHH = 13.8 Hz); 3.97 (m, 2H, CH COD); 3.50 (d (AB),
1H, CH2Fc, JHH = 12.5 Hz); 2.92 (m, 1H, CH2 COD), 2.76 (m,
1H, CH2 COD); 2.67 (d (AB), 1H, CH2Fc, JHH = 12.5 Hz); 2.60
(m, 2H, CH2 COD); 2.48 (m, 1H, CH2 COD) 2.36 (m, 1H, CH2
COD) 2.13 (m, 2H, CH2 COD). 13C{1H} NMR (125 MHz,
CDCl3): δ 134.2 (d, Ph, JCP = 12.9 Hz); 133.7 (quat Ph); 132.3
(d, Ph, JCP = 9.8 Hz); 132.1 (d, Ph, JCP = 2.3 Hz); 131.4 (d, Ph,
JCP = 2.3 Hz); 130.2 (d, quat Ph, JCP = 46.2 Hz); 129.8 (d, Ph,
Crystallographic data (excluding structure factors) have been
deposited with the Cambridge Crystallographic Data Centre -
CCDC 872062 for 2tBu, CCDC 872063 for 4Bz, CCDC 872064
for 4tBu
.
Computational details. Calculations were performed with the
Gaussian 09 package41 using the B3LYP hybrid functional42,43
under the DFT approach, since it performs better in frequency
calculations. All carbon and hydrogen atoms were described
with the 6-31G(d,p) basis set, whereas the 6-31++G(d,p) basis
set was applied to the P, S, B, F and Cl atoms. Effective core
potentials (ECP) and its associated SDD basis set44–47 sup-
plemented with f-polarization functions (SDD(f))48 were applied
for the Rh, Ir and Fe atoms. Geometry optimizations were per-
formed for the neutral NBD and COD complexes 1 and 3 with
R = Ph and tBu without any ligand simplification. Calculations
were also carried out on the isolated cation of 2Ph and on the
iridium analogue IrCl(COD)(P,StBu). No scaling factors were
applied to the calculated low-frequency vibrations. Since the
inclusion of anharmonicity effects in the case of 3tBu did not
lead to any significant change in the Rh–Cl frequency values
(see ESI, Table S1‡), this method was not applied to the other
calculations.
JCP = 10.5 Hz); 129.5 (Ph); 129.1 (Ph); 128.8 (d, Ph, JCP
=
10.11 Hz); 127.9 (d, Ph, JCP = 10.4 Hz); 128.4 (Ph); 127.2 (d,
quat Ph, JCP = 49.6 Hz); 105.8 (dd, CH COD, JCP = 9.6 Hz,
JCRh = 7.1 Hz); 102.7 (dd, CH COD, JCP = 9.9 Hz, JCRh = 6.5
Hz); 85.3 (d, CH COD, JCRh = 10.9 Hz); 85.1 (d, CH COD,
JCRh = 11.6 Hz); 75.4 (br s, subst. Cp); 72.6 (br s, subst. Cp);
71.4 (br s, Cp); 69.2 (br s, subst. Cp); 42.6 (CH2Ph); 34.2 (d,
CH2 COD, JCP = 3.5 Hz); 31.5 (d, CH2Fc, JCP = 4.6 Hz); 31.0
(d, CH2COD, JCP = 3.5 Hz); 29.7 (d, CH2 COD, JCP = 3.5 Hz);
27.6 (d, CH2 COD, JCP = 3.5 Hz). 31P{1H} NMR (202 MHz,
CDCl3): δ 21.8 (d, JP–Rh = 144 Hz).
[Rh(COD)(P,SEt)]BF4 (4Et, yield: 76%). 1H NMR (500 MHz,
CDCl3): δ 7.77–7.62 (m, 2H, Ph); 7.61–7.35 (m, 8H, Ph); 5.43
(m, 1H, CH COD); 5.33 (m, 1H, CH COD); 4.74 (br s, 1H,
subst. Cp); 4.65 (s, 5H, Cp); 4.48 (m, 1H, subst. Cp); 4.12 (br s,
1H, subst. Cp); 4.06–3.82 (m, 3H, 2H CH cod + 1H CH2Fc);
2.99 (m, 1H, CH2CH3); 2.92–2.80 (m, 1H, CH2 COD);
2.80–2.25 (m, 6H, 5H CH2 COD + 1H CH2CH3); 2.70 (d (AB),
1H, CH2Fc, JHH = 12.6 Hz); 2.20–2.00 (m, 2H, CH2 COD);
1.32 (t, 3H, CH3, JHH = 7.2 Hz). 13C{1H} NMR (125 MHz,
CDCl3): δ 134.2 (d, Ph, JCP = 13.0 Hz); 132.3 (d, Ph, JCP = 2.2
Hz); 132.0 (d, Ph, JCP = 9.5 Hz); 131.5 (d, Ph, JCP = 2.4 Hz);
130.2 (d, quat Ph, JCP = 45.4 Hz); 129.6 (d, Ph, JCP = 10.5 Hz);
128.8 (d, Ph, JCP = 10.0 Hz); 129.1 (Ph); 126.5 (d, quat Ph, JCP
= 49.3 Hz); 104.7 (dd, CH COD, JCP = 9.6 Hz, JCRh = 7.3 Hz);
103.3 (dd, CH COD, JCP = 10.0 Hz, JCRh = 6.2 Hz); 85.8 (d,
quat Cp, JCP = 16.1 Hz); 84.9 (d, CH COD, JCRh = 11.7 Hz);
83.9 (d, CH COD, JCRh = 10.9 Hz); 75.7 (d, subst. Cp, JCP = 5.9
General procedure of asymmetric hydrogenation
Solution of 6.4 × 10−3 mmol of catalyst, 3.2 × 10−2 mmol of
CH3ONa (5 equiv.) and 3.2 mmol of acetophenone (500 equiv.)
in 2 ml of isopropanol was transferred into a 5 ml glass vial
which was then placed under argon into a stainless steel auto-
clave. The reaction vessel was pressurized to the 30 bar of H2
pressure and stirred with magnetic bar for 1 h at room temp-
erature. The reaction was stopped by release of pressure. The
crude materials were obtained by purification reaction mixture
by chromatography on silica using dichloromethane as an eluent.
The product was finally analyzed by chiral GC.
Results and discussion
Hz); 72.6 (s, subst. Cp); 71.2 (s, Cp); 69.0 (s, subst. Cp, JCP
=
(a) Syntheses
5.4 Hz); 64.9 (d, quat Cp, JCP = 55.6 Hz); 34.6 (d, CH2 COD,
JCP = 3.5 Hz); 32.8 (CH2CH3); 30.9 (s, CH2 COD); 30.3 (d,
CH2Fc, JCP = 5.1 Hz); 29.5 (s, CH2 COD); 27.3 (s, CH2 COD);
The addition of the (P,SR) ligand (1 equiv per Rh atom) to a
dichloromethane solution of [RhCl(NBD)]2 or [RhCl(COD)]2
Dalton Trans.
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Table 1 Crystal data and structure refinement parameters
2tBu
4Ph
4Bz
Empirical formula
Formula weight
Temperature, K
Wavelength, Å
Crystal system
Space group
a, Å
b, Å
c, Å
α, °
β, °
C34H37FePRhS, BF4
754.24
180(2)
0.71073
Orthorhombic
P212121
10.663
16.983
17.435
90
90
90
3157.3
4
1.587
1.146
1536
C37H37FePRhS, BF4, CH2Cl2
875.19
180(2)
0.71073
Orthorhombic
Pca21
26.321(5)
9.652(5)
14.209(5)
90
90
90
C38H39FePRhS, BF4, CH2Cl2
889.22
180(2)
0.71073
Triclinic
ˉ
P1
11.5390(8)
12.8367(8)
13.5655(8)
108.445(6)
101.880(5)
98.703(5)
1813.9(2)
2
1.628
1.154
904
0.43 × 0.22 × 0.16
3.12 to 26.37
14 216
γ, °
Volume, Å3
Z
3610(2)
4
1.610
1.158
Density (calc), Mg m−3
Abs. coefficient, mm−1
F(000)
1776
Crystal size, mm3
Theta range, °
Reflections collected
0.54 × 0.47 × 0.18
3.02 to 27.10
12 237
0.56 × 0.22 × 0.07
2.98 to 26.36
19 753
Indpt reflections (Rint
Completeness, %
)
6118 (0.0344)
98.5
7239 (0.0342)
99.8
7393 (0.0506)
99.8
Absorption correction
Max. and min. transm.
Refinement method
Data/restr./param.
Multi-scan
1.0 and 0.619
F2
6118/24/388
1.094
0.0381, 0.0926
0.0461, 0.0954
0.08(3)
0.959 and −1.030
Multi-scan
1.0 and 0.7726
F2
7250/1/442
1.037
0.0340, 0.0833
0.0399, 0.0857
−0.005(18)
0.752 and −0.587
Multi-scan
1.0 and 0.77764
F2
7408/24/478
1.039
0.0453, 0.1227
0.0555, 0.1297
Goodness-of-fit on F2
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
Flack’s parameter
Residual density, e Å−3
0.868 and −1.678
2
Table 2 31P NMR data for the Rh complexes (δ in ppm with the JPRh
in Hertz in parentheses)
1R
2R
3R
4R
R = tBu
R = Ph
R = Bz
R = Et
23.6 (159)
23.8 (154)
20.3 (147)
21.3 (148)
26.1 (158)
21.0 (148)
28.0 (166)
31.1 (170)
22.8 (144)
23.8 (143)
22.1 (144)
21.8 (144)
22.9 (144)
BF4, 2tBu, in sufficient purity. The complete series of the BF4
salts containing the COD ligand, [Rh(COD)(P,SR)]BF4, 4R, on
the other hand, was more conveniently obtained by addition of
(P,SR) to a solution of compound [Rh(COD)2]BF4. All these
were isolated in a pure state.
(b) Characterization of the [Rh(diene)(P,SR)]+ salts 2 and 4
Scheme 2 Summary of the synthetic work and compounds numbering
scheme.
We begin the characterization section with the salts 2 and 4, for
which the analysis is more straightforward. The NMR spectra
show standard 1H, 13C and 31P chemical shifts and coupling pat-
terns for the expected square planar coordination around the RhI
center. In particular, Rh coupling is visible for selected 13C
resonances of the diene ligand and for the phosphine 31P resonance
(the latter is collected in Table 2 for all compounds).
yielded the corresponding adducts RhCl(NBD)(P,SR), 1R, and
RhCl(COD)(P,SR), 3R, see Scheme 2. For the NBD reagent, the
complete series with R = tBu, Ph, Bz and Et was obtained as
pure derivatives as shown by the NMR and HRMS analyses.
Concerning the COD series, although all compounds could be
obtained in solution as shown by the spectroscopic analyses,
only the tBu derivative 3tBu could be isolated as a pure product.
Starting from 1tBu, addition of NaBF4 in dichloromethane led to
the precipitation of NaCl and formation of [Rh(NBD)(P,StBu)]-
The molecular geometry of compounds 2tBu, 4Ph and 4Bz was
confirmed by single crystal X-ray diffraction. Whereas com-
pound 2tBu contains only the cation and the anion in the crystal,
compounds 4Ph and 4Bz crystallize with one molecule of
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dichloromethane per ion pair. Views of the three cations are
shown in Fig. 1 and relevant bond distances and angles for the
three compounds are compared in Table 3. The geometry is
typical of [Rh(diene)(L1L2)]+ complexes where L1L2 is a chelat-
ing ligand, of which over 1000 are reported in the literature. The
two midpoints of the donating ene functions and the P and
S donor atoms define an approximate square planar configur-
ation, which is quite typical of d8 RhI. As a matter of fact,
the geometry is nearly for 4Ph, with trans angles quite close to
180° (P–Rh–X1 and S–Rh–X2 = 178.6(3) and 174.69(6)°,
respectively; X = midpoints of the CvC bonds, see Table 3),
whereas it is more distorted for 4Bz. A close inspection of the
structure of 4Bz shows that this distortion is related to a twist of
the COD ligand, which is caused by a van der Waals repulsion
between one of the COD CHvCH donating groups (C11–C12)
and the CH2 group of the benzyl substituent on sulfur (C22). A
similar van der Waals repulsion, namely a 2.16 Å contact between
the H atoms on one of the tBu methyl groups (C23) and on atom
C12 of the NBD ligand, explains the even larger distortion
observed in 2tBu (P–Rh–X1 and S–Rh–X2 = 163.54(4) and
166.20(4)°, respectively; see Table 3). As expected, the X1–Rh–
X2 angle is much smaller for the NBD ligand with a value of
69.943(11)°, similar to the angle observed in related com-
pound.29 Another peculiar geometrical feature is that the sulfur
substituent is placed anti relative to the CpFe moiety of the ferro-
cene group for the three complexes. Upon coordination, the
sulfur atom becomes chiral and therefore two different diastereo-
isomers could be obtained in principle, with the sulfur substitu-
ent either syn or anti to the CpFe moiety. Similarly to all
previously reported complexes containing ligands of this family,
without exception,31,49–51 a single compound is obtained in solu-
tion and the sulphur substituent is placed on the side opposite
(anti) to the FeCp group with respect to the S–C–C–C–P
chelate. Consequently, the observed diastereomer has the
configuration (Sfc, SS) or (Rfc, RS) for 2tBu and for 4Ph and (Rfc,
SS) or (Sfc, RS) for 4Bz. The two Cp rings are roughly eclipsed
with the largest twist angle, τ, 7.5(4)° for 4Bz.
A few other [Rh(diene)(P,S)]n+ complexes of d8 RhI have been
previously described, some being cationic with a phosphine–
thioether28,29,52–55 or phosphine–phosphine sulfide56,57 ligand,
others being neutral with a phosphine–thiolato ligand,56,58,59 but
the Rh–S distance does not appear to be too sensitive to this
modification. The Rh–P and Rh–S distances found for 4Ph and
4Bz (see Table 3) compare quite well with the average in the
above mentioned examples (Rh–P: 2.29(3) Å and Rh–S:
2.36(3) Å). Whereas the Rh–P distances are quite similar for the
three compounds, the Rh–S distance is significantly shorter in
4Bz, suggesting a better binding ability of the benzyl derivative,
and longer in 2tBu, probably reflecting the greater steric bulk of
the sulphur substituent which is also responsible for the greater
geometry distortion (vide supra). There are no reasons to
doubt that the solution structures of the other 4R compounds are
identical to the solid state structure found for 4Ph and 4Bz.
DFT/B3LYP geometry optimizations were carried out for the
cations of 2R and 4R with R = tBu and Ph. The results are also
reported in Table 3. For compounds 2tBu and 4Ph, the optimized
geometry reproduced quite well the experimentally observed
one, except for a slight overestimation of the Rh–P, R h –S and
Rh–C distances (by 0.08 Å on average for Rh–S and Rh–P,
0.04 Å for Rh–C). Whereas the calculated Rh–P distance is
essentially the same in all four compounds, the Rh–S distance
increases from Ph to the more bulky tBu substituent, in agree-
ment with the experimental evidence. Views of all optimized
geometries are provided in the ESI, Fig. S1.‡
(c) Characterization of the chloride complexes 1 and 3
Fig. 1 Molecular views of the cationic complexes in compounds 2tBu
(a), 4Ph (b) and 4Bz (c) with the atom-labelling scheme. Displacement
ellipsoids are drawn at the 30% probability level. The BF4 counterion
and H atoms have been omitted for clarity.
Concerning the neutral chlorido complexes, the solution and
solid state structures cannot be assigned as easily because of the
presence of five potentially coordinating ligands. We were unfor-
tunately unable to obtain single crystals for any of these
−
Dalton Trans.
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Table 3 Selected experimental (from X-ray diffraction) and computed (by DFT optimizations) bond lengths [Å] and angles [°] in compounds 2R and
4R
2tBu
4Bz
2Ph
4tBu
4Ph
X-ray
DFT
DFT
DFT
X-ray
DFT
X-ray
Distancesa
Rh–P
Rh–S
Rh–X1
Rh–X2
Rh–C11
Rh–C12
Rh–C15
Rh–C16
C11–C12
C15–C16
2.2587(13)
2.3641(13)
2.1231(3)
2.0066(4)
2.229(5)
2.229(5)
2.118(5)
2.127(5)
1.358(8)
1.384(8)
2.331
2.452
2.165
2.032
2.263
2.283
2.159
2.141
1.409
1.383
2.343
2.402
2.145
2.047
2.260
2.248
2.169
2.159
1.404
1.385
2.354
2.508
2.179
2.062
2.302
2.270
2.173
2.183
1.408
1.384
2.2858(15)
2.3378(11)
2.119(2)
2.040(5)
2.227(4)
2.227(4)
2.169(4)
2.142(4)
1.368(8)
1.391(7)
2.354
2.421
2.184
2.069
2.310
2.271
2.182
2.188
1.404
1.385
2.2796(10)
2.3194(10)
2.1198(3)
2.0199(3)
2.210(4)
2.240(4)
2.127(5)
2.142(5)
1.352(8)
1.380(11)
Anglesa
P–Rh–S
P–Rh–X1
P–Rh–X2
S–Rh–X1
S–Rh–X2
X1–Rh–X2
92.64(5)
92.2
165.6
97.6
102.0
163.5
69.2
92.6
168.8
99.6
98.5
166.1
69.6
90.3
175.8
92.5
93.1
171.6
84.4
92.30(3)
178.6(3)
93.01(6)
88.83(12)
174.69(6)
85.87(17)
90.9
177.2
93.5
91.0
172.6
84.9
93.24(4)
168.29(3)
91.59(3)
90.95(3)
168.21(3)
86.423(13)
163.54(4)
93.84(13)
103.01(3)
166.20(4)
69.943(11)
a X1 and X2 are the midpoints of the coordinating COD CvC functions, C11–C12 and C14–C15 (for the NBD complexes) or C15–C16 (for the
COD complexes), respectively.
cannot be totally excluded, because a handful of compounds
with the RhX(diene)(L1L2) stoichiometry feature indeed a free
halide anion. In these structures, the cationic complex is charac-
terized by strongly binding neutral ligands such as two mono-
dentate N-heterocyclic carbenes (NHC),60
a bidentatebis-
NHC,61–63 a 2,2′-bipyridine,64 or a 2,2′-dipyridylmethane.65 All
the other structures of this type contain, like those of 4Ph and
4Bz, non-coordinating X− anion (mostly PF6−, BF4−, CF3SO3
−
and ClO4−). A 5-coordinate geometry of type II also appears
unlikely because it is much less common for RhI than for IrI, but
again it cannot be excluded. Rare examples of 5-coordinate
RhX(diene)(L1L2), with COD or NBD and including a halide
ligand in the coordination geometry are limited to complexes
where L1L2 is bipyridine,64 2-phenylazopyridine,64 2-pyridyl-
imines,66 or an NHC–oxazoline.67–69 It is also relevant to
compare pairs of related [Rh(diene)(L1L2)]+X− and RhY(diene)-
(L1L2) structures (X = non-coordinating anion, Y = halide),
where the weaker partner of the chelating L1L2 donor set dis-
sociates to let the halide enter the coordination sphere on going
from the former to the latter. Examples of this situation include
bidentate ligands L1L2 such as phosphine–amines,70,71 phos-
phine–ethers,72 or phosphine–phosphine oxides.73,74 Clearly, all
these examples involve a relatively strong donor (e.g. a phos-
phine) and a weaker one (N or O donor) giving the bidentate
Scheme 3 Possible molecular geometries for MCl(diene)(L1L2) com-
plexes (M = Rh, Ir).
compounds, preventing us to determine the solid state structure.
Interestingly, the structure adopted by the related iridium com-
plexes IrCl(COD){CpFe[1,2-C5H3(PPh2)(CH2SR)]} depends
on the nature of the thioether substituent.31 For R = tBu, the
molecule adopts a square planar geometry with a (COD)ClP
coordination environment and a dangling thioether function
(i.e. structure I in Scheme 3), whereas the compounds with R =
Et, Ph and Bz prefer a pentacoordinated square pyramidal geo-
metry with a loosely bonded axial Cl ligand (structure II). These
structural motifs seem to be maintained in solution, according to
observed differences in the NMR properties, notably the 31P
resonance.31 The Rh complexes 1R and 3R could also conceiva-
bly adopt structure I or II, but a third possibility (III) with a che-
lating (P,S) ligand and an outer sphere chloride ion, related to
those observed for 2tBu, 4Ph and 4Bz by simple replacement of
the BF4− ion with Cl−, can also be imagined.
ligand
a
pronounced hemilability character. Apparently,
examples of this type for phosphine–thioethers have not yet been
described. Since no suitable single crystals for a diffraction
analysis could be obtained for any of compounds 1 and 3,
their structure was addressed by a combination of spectroscopic
techniques (IR, NMR) and DFT calculations.
As shown in Table 2, the 31P chemical shift and Rh coupling
for compounds 1 and 3 do not greatly differ from those of the
BF4− salts 2 and 4. This is an expected occurrence if the chloride
complexes adopted structure III. It should be remarked that the
Inspection of the previously published X-ray structures of
related rhodium complexes suggests that III is unlikely but
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Table 4 Selected 1H (Δδ in parentheses) and 13C NMR (in italics) data for the FcCH2S group in complexes 1–4 (δ in ppm)
1R
2R
3R
4R
(P,SR)a
(S = P,SR)a
R = tBu
R = Ph
R = Bz
R = Et
5.06, 3.84 (1.22)
28.8
5.37, 4.2 (1.09)
34.1
4.13, 4.00 (0.13)
31.3
4.37, 4.06 (0.31)
30.8
3.96, 2.81 (1.15)
29.1
ca. 4.2, 3.91 (ca. 0.3)
28.6
ca. 4.0, 2.69 (ca. 1.3)
29.2
4.17, 3.04(1.15)
37.9
3.50, 2.67 (0.83)
31.5
ca. 4.0, 2.70 (ca. 1.3)
30.3
3.80, 3.63 (0.17)
27.4
4.17, 4.09 (0.08)
34.2
3.72, 3.65 (0.07)
31.1
3.74, 3.74 (0.00)
30.9
3.99, 3.96 (0.04)
26.7
4.42, 4.35 (0.07)
33.3
4.14, 3.77 (0.37)
30.5
4.09, 3.87 (0.22)
30.3
a Data from ref. 23.
31P chemical shift in the [IrCl(COD)(P,SR)] and [Ir(COD)-
(P,SR)]+ compounds was found diagnostic for discriminating
structures of type I (δ −4.2 for R = Ph and −3.1 for R = Et), II
(δ 15.7 for R = tBu) and III (δ 11.0 for R = Ph and 14.5 for R =
tBu).31 In particular, the 31P resonance is rather similar for the Ir
complexes of type II and III and different relative to those with
structure I. Therefore, the similarity between the resonances of
the chloride complexes 1 and 3 with those of the BF4 salts 2 and
4 that are known to adopt structure III would appear to point to
a structure of type II or III for the chloride complexes. This
argument, however, can in no way be considered conclusive
because the metal nature may have a different effect on the
chemical shift of the different structural types.
Fig. 2 Solid state IR spectra (lower fingerprint region) of 3tBu (red
line), 4tBu (blue line), 1tBu (pink line), 2tBu (cyan line) and IrCl(COD)-
(P,StBu) (green line).
Another useful comparison comes from the detailed analysis
of the 1H spectra. Most protons (i.e. diene, PPh2) are not
expected to greatly respond to the structural type. The FcCH2S
protons, on the other hand, may be sensitive to the thioether
coordination, namely discriminate between I and II/III. The two
protons of this group, whether the S atom is coordinated or not,
are diastereotopic and therefore always give rise to an AB
pattern. This feature was also observed for the free ligands and
for the sulfur-protected version of the free ligand, (S = P,SR),23
the 1H and 13C resonances of which are collected in Table 4
together with those of the isolated compounds 1–4. It can be
noted that the two doublets of the AB pattern in the 1H NMR are
very close to each other in the (P,SR) and (S = P,SR) molecules
(Δδ < 0.4 ppm). This difference is systematically much greater
Since the NMR analysis does not allow an unambiguous
assignment of the chemical structure for the chlorido derivatives,
additional studies were carried out by solid state IR spectroscopy,
although limited to the COD-(P,StBu) and NBD-(P,StBu) deriva-
tives. Spectra in the lower fingerprint region (600–250 cm−1
)
were measured for 1tBu, 2tBu, 3tBu, 4tBu and IrCl(COD)(P,StBu)
in the solid state and the results are reported in Fig. 2. The M–Cl
stretching region shows various bands, the most intense one
having a higher frequency for the iridium compound IrCl(COD)-
(P,StBu) (295 cm−1) than for the rhodium compounds 1tBu and
3tBu (271 and 288 cm−1, respectively). The assignment of these
bands to the Ir–Cl and Rh–Cl stretching vibrations, respectively,
was confirmed by the calculations (vide infra). On going to the
tetrafluoroborate salts 2tBu and 4tBu, the major band disappears
in agreement with the removal of the Cl− ligand from the metal
coordination sphere. These observations are in favor of a coordi-
nation geometry of type I or II (Scheme 3).
−
for the cationic complexes in the BF4 salts where the S atom is
coordinated to the Rh centre (0.83 ppm in 4Bz and >1 ppm for
all other examples). It can be argued that the enantioselective
sulfur coordination makes a further magnetic discrimination of
the two CH2 protons, thereby increasing their chemical shift
difference. Considering now the chlorido derivatives, we note
that three of them exhibit a small chemical shift difference (0.13
for 1Bz, 0.31 for 1Et, ca. 0.3 for 3tBu), whereas the Δδ values are
much greater for the other two compounds (1.22 for 1tBu, 1.09
for 1Ph) and comparable to those of the cationic complexes.
These results would tend to suggest that the thioether function is
not coordinated to the Rh center in complexes 1Bz, 1Et and 3tBu
(e.g. structure I), whereas coordination might occur for the other
two derivatives. Analysis of the FcCH2S 13C chemical shift does
not bring any additional clarification, since this resonance
appears to be very little sensitive to the chemical environment as
shown in Table 4.
Geometry optimizations for all three types of structures were
carried out at the same computational level as for the cationic
complexes described above. The calculations were carried out
for complexes 1R and 3R for R = tBu and Ph in order to evaluate
the effect of the R substituent and the diene ligand. The geome-
try of the iridium analogue IrCl(COD)(P,StBu) was also opti-
mized and was found to agree quite well with that obtained
experimentally in the solid state.31 A table with the most signifi-
cant metric parameters for all optimized structures is reported in
the ESI (Table S2‡). All attempts to optimize the geometry of
Dalton Trans.
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Fig. 3 DFT(B3LYP) optimized geometries of 1Ph with relative ener-
gies in parentheses in kcal mol−1. Hydrogen atoms are omitted for
clarity.
Fig. 4 Calculated IR spectra (lower fingerprint region) of 3tBu (red
line), 4tBu (blue line) and IrCl(COD)(P,StBu) (green line).
[Rh(diene)(P,SR)]+ with Cl− as a counteranion (e.g. a geometry
of type III in Scheme 3) led to the dissociation of the thioether
arm to allow formation of the rhodium–chloride bond (i.e. an
optimized geometry of type I in Scheme 3). The geometry of the
only local energy minimum obtained for 3tBu is quite similar to
that of the iridium analogue, with the sulfur atom far away from
the Rh center (5.556 Å).31 Similar optimized geometries are also
adopted by the other complexes (1Ph, 1tBu, 3Ph). Replacement of
the S atom in the coordination sphere of 2R or 4R by the Cl
atom in 1R or 3R systematically lengthens the M–P bond by
ca. 0.05 Å (cf. Table 3 and Table S2‡).
A second, higher energy minimum was also found for com-
plexes 1Ph, 1tBu and 3Ph. In these structures, the sulfur donor
function has rearranged to place itself along the z direction per-
pendicularly to the square plane defined by the other four
ligands, loosely interacting with the metal center, defining a
pseudo pentacoordinated square-pyramidal geometry like that of
II in Scheme 3, except that the axial coordination position of the
square pyramid is occupied by the sulfur atom instead of the
Cl atom (type II′). An example is shown in Fig. 3 for compound
1tBu (all other optimized geometries are available in the ESI
section, Fig. S2‡). The Rh–S distance is too long to be con-
sidered an interaction for compound 3Ph (3.674 Å), whereas it
signals a genuine 5-coordinate geometry for 1Ph (2.824 Å) and
1tBu (2.702 Å), when considering that the axial interaction for
5-coordinate square pyramidal d8 complexes is lengthened by
the dz2 electron pair. The shorter Rh–S separation for the tBu
derivative may be related to the greater donating power of the
StBu donor function. On the other hand, this geometry is more
destabilized relative to the square planar global minimum for
1tBu (by 8.2 kcal mol−1) than for 1Ph (3.1 kcal mol−1). The
greater steric bulk of the tBu group may be responsible for this
difference. All attempts to optimize a type II geometry led to
one of the above mentioned minima. Therefore, the geometry
optimizations are in favor of a structure of type I for compounds
1 and 3, irrespective of the nature of the R substituent (at least
for Ph and tBu).
Fig. 5 Calculated IR spectra (lower fingerprint region) of 1tBu type I
(green line), 1Ph type I (red line), 1tBu type II′ (pink line) and 1Ph type
II′ (blue line).
the COD compound 3tBu and for the iridium analogue, since
only a minimum of type I was optimized. The computed spectra
for these two compounds, as well as for the salt 4tBu, are shown
in Fig. 4. These spectra match rather closely those experimentally
observed, confirming the type I structure. The calculated
maximum absorption for the strongest M–Cl stretching band is
at 279 cm−1 for the Ir complex and at 277 cm−1 for the Rh
complex 3tBu, whereas the spectrum of 4tBu does not show any
strong band in this region. The adoption of a structure of type I
1
by compound 3tBu is also in line with the suggestion of the H
NMR spectrum (AB pattern of the CH2StBu moiety, vide supra).
The calculated spectra for the type I and type II′ minima of
compounds 1tBu and 1Ph are shown in Fig. 5. It can be seen that
the Rh–Cl stretching band for the type I minima is very similar
to that of compound 3tBu (286 and 273 cm−1 for the strongest
absorption). On the other hand, the Rh–Cl vibration is shifted to
much lower frequencies in the type II′ minima of 1Ph
(247 cm−1), and especially of 1tBu (208 cm−1). This effect can
obviously be attributed to the coordination of the sulfur atom,
which provides additional electron density to the metal center
and labilizes the Rh–Cl bond, an effect which is stronger for the
It is now of interest to analyze the calculated IR spectrum of
the observed minima and compare it with the experimental ones
reported in Fig. 2. The M–Cl stretching vibration is coupled with
M-(diene) stretches in all rhodium complexes and contributes
mostly to two intense bands, which exhibit a greater frequency
difference in the COD series. The analysis is rather simple for
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Dalton Trans.

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tBu derivative where the Rh–S distance is shorter. In agreement
with this argument, the Rh–Cl distance is shorter for the type I
minima of compounds 1tBu and 1Ph (2.382 and 2.390 Å, respect-
ively) and longer for the type II′ geometries of 1Ph (2.459 Å)
and particularly 1tBu (2.572 Å). The difference between the
calculated Rh–Cl frequencies for the type I and II′ minima (Δν)
is 78 cm−1 for 1tBu and 26 cm−1 for 1Ph. On the other hand, the
experimental Rh–Cl stretching frequency in 1tBu is only 17 cm−1
lower than that of compound 3tBu. Therefore, we conclude that
the structure adopted by compound 1tBu is most likely of type I
in the solid state, like that of compound 3tBu. However, the large
chemical shift difference for the CH2StBu AB resonances in the
1H NMR spectrum suggests that a structure of type II′ might be
more favorable in solution for this compound. If this is the case,
are only slightly lower. A full description of the catalytic per-
formance of these complexes, including the effect of the sulphur
substituent, reaction temperature, and substrate, which is
currently being investigated, will be reported in due course.
Conclusions
Rhodium complexes associating chiral ferrocenyl phosphine–
thioethers and diene (COD or NBD) ligands have been syn-
thesized and fully characterized. For the neutral chlorido
complexes, for which X-ray structural analyses could not be
carried out, combination of NMR and IR spectroscopy and DFT
calculations indicates that they adopt a square planar geometry
with a dangling thioether function. A second, pentacoordinated
structure with a square pyramidal geometry and the thioether
function placed in the axial position is however easily accessible.
The cationic complexes, on the other hand adopt a standard
square planar bis-chelated structure. These rhodium complexes
are not only good structural models for our previously published
iridium-based hydrogenation catalysts but have also been tested
in the asymmetric hydrogenation of acetophenones and proved
to be efficient precatalysts.
the difference is certainly
a consequence of the lower
steric encumbrance of the norbornadiene ligand relative to
cyclooctadiene.
The calculated spectra of compounds 1Ph and 3Ph (shown in
the ESI, Fig. S3‡) exhibit similar features, with the major bands
in the 260–280 cm−1 range for the type I structures and in the
240–270 cm−1 range for the type II′ structures.
(d) Catalytic studies
Because iridium complexes of diphenylphosphinoferrocenyl
thioether ligands were shown to be excellent precatalysts for the
hydrogenation of acetophenone in the presence of NaOMe in
isopropanol at room temperature under 30 bar of H2 and with
only 0.2% of catalyst, we decided to study the catalytic proper-
ties of corresponding rhodium complexes in the same conditions
and compare the activity of the complexes (Scheme 4). For these
preliminary investigations, we selected only the complexes with
t-butyl substituent on sulfur. The results are shown in Table 5.
All the tested rhodium complexes are active precatalysts for
the hydrogenation of acetophenone supporting our hypothesis
that the rhodium complexes are not only structural but also func-
tional models of the iridium analogues. All these rhodium com-
plexes exhibit a rather similar catalytic activity, which is however
significantly lower than that of the corresponding iridium
complex IrCl(COD)(P,StBu), whereas their enantioselectivities
Acknowledgements
We are grateful to the CNRS (Centre National de la Recherche-
Scientifique) and the RFBR (Russian Foundation for Basic
Research) for support through the GDRI (Groupe de Recherche
Internationale) “Homogeneous catalysis for Sustainable Devel-
opment” and a France–Russia (RFBR–CNRS) bilateral grant.
We are also grateful to the IUF (Institut Universitaire de France)
for additional funding and to the CINES (Centre Informatique
National de l’Enseignement Supérieur) and the CICT (Centre
Interuniversitaire de Calcul de Toulouse, project CALMIP) for
granting free computational time. EMK thanks the Embassy of
France in Moscow for a Ph.D. grant.
Notes and references
1 M. Kitamura, T. Ohkuma, S. Inoue, N. Sayo, H. Kumobayashi,
S. Akutagawa, T. Ohta, H. Takaya and R. Noyori, J. Am. Chem. Soc.,
1988, 110, 629–631.
2 T. Ohkuma, H. Ooka, S. Hashiguchi, T. Ikariya and R. Noyori, J. Am.
Chem. Soc., 1995, 117, 2675–2676.
3 R. Noyori and T. Ohkuma, Angew. Chem., Int. Ed., 2001, 40, 40–73.
4 H. U. Blaser, C. Malan, B. Pugin, F. Spindler, H. Steiner and M. Studer,
Adv. Synth. Catal., 2003, 345, 103–151.
5 R. Malacea, R. Poli and E. Manoury, Coord. Chem. Rev., 2010, 254,
729–752.
6 W. Tang and X. Zhang, Chem. Rev. (Washington, DC, US), 2003, 103,
3029–3069.
7 T. C. Nugent and M. El-Shazly, Adv. Synth. Catal., 2010, 352, 753–819.
8 N. Fleury-Bregeot, V. de la Fuente, S. Castillon and C. Claver,
ChemCatChem, 2010, 2, 1346–1371.
Scheme 4 Asymmetric hydrogenation of acetophenone.
Table 5 Catalytic activity of the complexes
9 J. H. Xie, S. F. Zhu and Q. L. Zhou, Chem. Rev., 2011, 111, 1713–1760.
10 D.-S. Wang, Q.-A. Chen, S.-M. Lu and Y.-G. Zhou, Chem. Rev.
(Washington, DC, US), 2012, 112, 2557–2590.
11 H.-U. Blaser, Adv. Synth. Catal., 2002, 344, 17–31.
12 H. U. Blaser, B. Pugin, F. Spindler and M. Thommen, Acc. Chem. Res.,
2007, 40, 1240–1250.
Catalyst
Time [h]
Conversion [%]
ee (S) [%]
(S)-IrCl(COD)(P,StBu)
(S)-RhCl(COD)(P,StBu)
(S)-RhCl(NBD)(P,StBu)
(S)-Rh(COD)(P,StBu)BF4
(S)-Rh(NBD)(P,StBu)BF4
1
1
1
1
1
93
11
12
12
8
61
67
46
51
49
13 G. Iftime, J. Daran, E. Manoury and G. Balavoine, Organometallics,
1996, 15, 4808–4815.
Dalton Trans.
This journal is © The Royal Society of Chemistry 2012

View Online
14 G. Iftime, C. MoreauBossuet, E. Manoury and G. Balavoine, Chem.
Commun., 1996, 527–528.
15 G. Iftime, J. Daran, E. Manoury and G. Balavoine, Angew. Chem., Int.
Ed., 1998, 37, 1698–1701.
16 E. Manoury, J. Fossey, H. Ait-Haddou, J. Daran and G. Balavoine,
Organometallics, 2000, 19, 3736–3739.
17 J. Chiffre, Y. Coppel, G. Balavoine, J. Daran and E. Manoury, Organo-
metallics, 2002, 21, 4552–4555.
18 A. M. Masdeu-Bulto, M. Dieguez, E. Martin and M. Gomez, Coord.
Chem. Rev., 2003, 242, 159–201.
19 M. Mellah, A. Voituriez and E. Schulz, Chem. Rev., 2007, 107,
5133–5209.
G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels,
Ö. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski and D. J. Fox,
Gaussian 09, Revision A.02, Gaussian, Inc., Wallingford CT, 2009.
42 A. D. Becke, J. Chem. Phys., 1993, 98, 5648–5652.
43 C. T. Lee, W. T. Yang and R. G. Parr, Phys. Rev. B, 1988, 37, 785–789.
44 D. Andrae, U. Haussermann, M. Dolg, H. Stoll and H. Preuss, Theor.
Chim. Acta, 1990, 77, 123–141.
45 U. Haussermann, M. Dolg, H. Stoll, H. Preuss, P. Schwerdtfeger and
R. M. Pitzer, Mol. Phys., 1993, 78, 1211–1224.
46 W. Kuchle, M. Dolg, H. Stoll and H. Preuss, J. Chem. Phys., 1994, 100,
7535–7542.
47 T. Leininger, A. Nicklass, H. Stoll, M. Dolg and P. Schwerdtfeger,
J. Chem. Phys., 1996, 105, 1052–1059.
20 H. Pellissier, Tetrahedron, 2007, 63, 1297–1330.
21 R. Malacea and E. Manoury, in Phosphorus Ligands in Asymmetric
Catalysis, ed. A. Börner, Wiley-VCH, Weinheim, Germany, 2008, vol.
1–3, pp. 749–784.
48 A. W. Ehlers, M. Bohme, S. Dapprich, A. Gobbi, A. Hollwarth, V. Jonas,
K. F. Kohler, R. Stegmann, A. Veldkamp and G. Frenking, Chem. Phys.
Lett., 1993, 208, 111–114.
22 F. L. Lam, F. Y. Kwong and A. S. C. Chan, Chem. Commun., 2010, 46,
4649–4667.
49 R. Malacea, E. Manoury, J.-C. Daran and R. Poli, J. Mol. Struct., 2008,
890, 249–254.
23 L. Routaboul, S. Vincendeau, J.-C. Daran and E. Manoury, Tetrahedron:
Asymmetry, 2005, 16, 2685–2690.
50 R. Malacea, L. Routaboul, E. Manoury, J.-C. Daran and R. Poli, J. Orga-
nomet. Chem., 2008, 693, 1469–1477.
24 L. Routaboul, S. Vincendeau, C. O. Turrin, A. M. Caminade,
J. P. Majoral, J. C. Daran and E. Manoury, J. Organomet. Chem., 2007,
692, 1064–1073.
25 L. Diab, M. Gouygou, E. Manoury, P. Kalck and M. Urrutigoity, Tetra-
hedron Lett., 2008, 49, 5186–5189.
26 E. Le Roux, R. Malacea, E. Manoury, R. Poli, L. Gonsalvi and
M. Peruzzini, Adv. Synth. Catal., 2007, 349, 309–313.
27 E. Hauptman, R. Shapiro and W. Marshall, Organometallics, 1998, 17,
4976–4982.
28 E. Hauptman, P. J. Fagan and W. Marshall, Organometallics, 1999, 18,
2061–2073.
29 S. Gladiali, F. Grepioni, S. Medici, A. Zucca, Z. Berente and L. Kollar,
Eur. J. Inorg. Chem., 2003, 556–561.
30 E. Guimet, M. Dieguez, A. Ruiz and C. Claver, Dalton Trans., 2005,
2557–2562.
31 R. Malacea, E. Manoury, L. Routaboul, J.-C. Daran, R. Poli, J. P. Dunne,
A. C. Withwood, C. Godard and S. B. Duckett, Eur. J. Inorg. Chem.,
2006, 1803–1816.
51 L. Diab, J. C. Daran, M. Gouygou, E. Manoury and M. Urrutigoity, Acta
Crystallogr., Sect. C: Cryst. Struct. Commun., 2007, 63, m586–M588.
52 F. Teixidor, R. Benakki, C. Vinas, R. Kivekas and R. Sillanpaa, Organo-
metallics, 1998, 17, 4630–4633.
53 D. A. Evans, F. E. Michael, J. S. Tedrow and K. R. Campos, J. Am.
Chem. Soc., 2003, 125, 3534–3543.
54 N. Khiar, R. Navas, E. Alvarez and I. Fernandez, ARKIVOC, 2008,
211–224.
55 N. Khiar, R. Navas, B. Suarez, E. Alvarez and I. Fernandez, Org. Lett.,
2008, 10, 3697–3700.
56 J. Browning, G. W. Bushnell, K. R. Dixon and R. W. Hilts, J. Organomet.
Chem., 1993, 452, 205–218.
57 J. W. Faller, S. C. Milheiro and J. Parr, J. Organomet. Chem., 2008, 693,
1478–1493.
58 J. Browning, K. R. Dixon, N. J. Meanwell and F. Wang, J. Organomet.
Chem., 1993, 460, 117–126.
59 H. S. Lee, J. Y. Bae, D. H. Kim, H. S. Kim, S. J. Kim, S. Cho, J. Ko and
S. O. Kang, Organometallics, 2002, 21, 210–219.
32 H. J. Drexler, W. Baumann, A. Spannenberg, C. Fischer and D. Heller,
J. Organomet. Chem., 2001, 621, 89–102.
33 A. Preetz, H. J. Drexler, C. Fischer, Z. Dai, A. Borner, W. Baumann,
A. Spannenberg, R. Thede and D. Heller, Chem.–Eur. J., 2008, 14,
1445–1451.
60 A. Neveling, G. R. Julius, S. Cronje, C. Esterhuysen and
H. G. Raubenheimer, Dalton Trans., 2005, 181–192.
61 J. A. Mata, A. R. Chianese, J. R. Miecznikowski, M. Poyatos,
E. Peris, J. W. Faller and R. H. Crabtree, Organometallics, 2004, 23,
1253–1263.
34 A. Preetz, C. Fischer, C. Kohrt, H. J. Drexler, W. Baumann and
D. Heller, Organometallics, 2011, 30, 5155–5159.
35 I. D. Gridnev, E. Alberico and S. Gladiali, Chem. Commun., 2012, 48,
2186–2188.
36 T. Hayashi, T. Mise, M. Fukushima, M. Kagotani, N. Nagashima,
Y. Hamada, A. Matsumoto, S. Kawakami, M. Konishi, K. Yamamoto and
M. Kumada, Bull. Chem. Soc. Jpn., 1980, 53, 1138–1151.
37 A. Altomare, M. Burla, M. Camalli, G. Cascarano, C. Giacovazzo,
A. Guagliardi, A. Moliterni, G. Polidori and R. Spagna, J. Appl. Crystal-
logr., 1999, 32, 115–119.
62 M. V. Baker, S. K. Brayshaw, B. W. Skelton, A. H. White and
C. C. Williams, J. Organomet. Chem., 2005, 690, 2312–2322.
63 R. J. Lowry, M. K. Veige, O. Clement, K. A. Abboud, I. Ghiviriga and
A. S. Veige, Organometallics, 2008, 27, 5184–5195.
64 J. J. Robertson, A. Kadziola, R. A. Krause and S. Larsen, Inorg. Chem.,
1989, 28, 2097–2102.
65 M. Toganoh, N. Harada and H. Furuta, J. Organomet. Chem., 2008, 693,
3141–3150.
66 H. F. Haarman, F. R. Bregman, J. M. Ernsting, N. Veldman, A. L. Spek
and K. Vrieze, Organometallics, 1997, 16, 54–67.
38 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 2007,
64, 112–122.
67 L. H. Gade, V. César and S. Bellemin-Laponnaz, Angew. Chem., Int. Ed.,
2004, 43, 1014–1017.
39 M. N. Burnett and C. K. Johnson, ORTEPIII, Report ORNL-6895, Oak
Ridge National Laboratory, Oak Ridge, Tennessee, U.S., 1996.
40 L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565.
41 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb,
J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson,
H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov,
J. Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota,
R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, T. Vreven, J. A Montgomery Jr., J. E. Peralta, F. Ogliaro,
M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov,
R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant,
S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, N. J. Millam, M. Klene,
J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts,
R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli,
J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski,
68 V. César, S. Bellemin-Laponnaz and L. H. Gade, Eur. J. Inorg. Chem.,
2004, 3436–3444.
69 V. César, S. Bellemin-Laponnaz, H. Wadepohl and L. H. Gade,
Chem.–Eur. J., 2005, 11, 2862–2873.
70 M. Stradiotto, J. Cipot and R. McDonald, J. Am. Chem. Soc., 2003, 125,
5618–5619.
71 A. D. Phillips, S. Bolaño, S. S. Bosquain, J.-C. Daran, R. Malacea,
M. Peruzzini, R. Poli and L. Gonsalvi, Organometallics, 2006, 25,
2189–2200.
72 M. Ahlmann and O. Walter, J. Organomet. Chem., 2004, 689,
3117–3131.
73 A. M. Z. Slawin, M. B. Smith and J. D. Woollins, J. Chem. Soc., Dalton
Trans., 1996, 1283–1293.
74 A. M. Z. Slawin, M. B. Smith and J. D. Woollins, J. Chem. Soc., Dalton
Trans., 1996, 4575–4581.
This journal is © The Royal Society of Chemistry 2012
Dalton Trans.