Coordination chemistry and diphenylacetylene hydrogenation catalysis of planar chiral ferrocenylphosphane-thioether ligands with cyclooctadieneiridium(I)

Article abstract of DOI:10.1002/ejic.200600065

The reaction of the P,S ligands CpFe{1,2-C₅H ₃(PPh₂)(CH₂SR)}, (1-R; R = Et, Ph, tBu), with 0.5 equivalents of [Ir(COD)Cl]₂ (metal/ligand = 1:1) furnishes the stable mononuclear adducts [Ir(COD)Cl(1-R)], 2-R, in high yields. The molecular structures of the three complexes 2-R have been determined by single-crystal X-ray diffraction. Compounds 2-Et and 2-Ph have similar five-coordinate molecular structures, with an intermediate coordination geometry between a distorted trigonal-bipyramid and a distorted square-pyramid. In the solid state, the sulfur atom chirality (R group exo, lone pair endo and parallel to the Cp-Fe axis) as well as the iridium chirality (Cl atom exo relative to the ferrocene group) is controlled by the ligand planar chirality. In solution, only one diastereoisomer is observed in both cases, indicating that the geometries observed in the solid state are maintained in solution, or that the different species are in rapid exchange on the NMR time scale. Complex 2-tBu, on the other hand, shows a four-coordinate square-planar molecular structure with a dangling thioether moiety, probably for steric reasons. For metal/ligand ratios greater than 1, the compounds [Ir(COD){κ²-P:S-(1-R)}] ⁺[Ir(COD)Cl₂]^- (3-R) are obtained, resulting from the chloride abstraction by the excess iridium metal on complex 2-R. The structure of 3-Ph was confirmed by single-crystal X-ray diffraction. A rapid equilibration between 2-R and 3-R gives rise to only one set of NMR signals for each metal/ ligand ratio. For the ligand 1-tBu, a similar equilibration between 2-tBu and 3-tBu is again observed, in addition to a slower equilibration with a third product, [Ir(COD)Cl](μ-1-R)[Ir(COD)Cl] (4-tBu), which is proposed to contain a bridging P,S ligand spanning two Ir centres. Complex 2-Ph reacts with [Rh(COD)Cl]₂ to give only the heterometallic ionic pair [Ir(COD){κ²-P:S-(1-Ph)}][Rh(COD)Cl₂] without transfer of ligand 1-Ph from Ir to Rh. Furthermore, the rhodium complex RhCl(COD)(1-Ph) reacts quantitatively with [Ir(COD)Cl]₂ at room temp, to yield 2-Ph and [Rh(COD)Cl]₂, thereby illustrating the much stronger affinity of ligands 1-Ph for iridium compared to rhodium. Finally, the complexes 2-tBu and 2-Ph were found to be efficient catalysts for the diphenylacetylene hydrogenation, affording a mixture of monohydrogenation [both (E)- and (Z)-stilbene] and dihydrogenation (1,2-diphenylethane) products. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejic.200600065

FULL PAPER
DOI: 10.1002/ejic.200600065
Coordination Chemistry and Diphenylacetylene Hydrogenation Catalysis of
Planar Chiral Ferrocenylphosphane-Thioether Ligands with
Cyclooctadieneiridium( )
I
Raluca Malacea,[a] Eric Manoury,*[a] Lucie Routaboul,[a] Jean-Claude Daran,[a]
Rinaldo Poli,[a] John P. Dunne,[b] Adrian C. Withwood,[b] Cyril Godard,[b] and
Simon B. Duckett[b]
Keywords: Ferrocenylphosphane ligands / Hemilability / Hydrogenation / Iridium / Planar chirality / Thioether ligands
The reaction of the P,S ligands CpFe{1,2-C5H3(PPh2)(CH2SR)}, 2-R. The structure of 3-Ph was confirmed by single-crystal X-
(1-R; R = Et, Ph, tBu), with 0.5 equivalents of [Ir(COD)Cl]2
(metal/ligand = 1:1) furnishes the stable mononuclear ad-
ducts [Ir(COD)Cl(1-R)], 2-R, in high yields. The molecular
structures of the three complexes 2-R have been determined
by single-crystal X-ray diffraction. Compounds 2-Et and 2-
Ph have similar five-coordinate molecular structures, with an
intermediate coordination geometry between a distorted tri-
gonal-bipyramid and a distorted square-pyramid. In the solid
state, the sulfur atom chirality (R group exo, lone pair endo
and parallel to the Cp-Fe axis) as well as the iridium chirality
(Cl atom exo relative to the ferrocene group) is controlled by
the ligand planar chirality. In solution, only one diastereoiso-
mer is observed in both cases, indicating that the geometries
observed in the solid state are maintained in solution, or that
the different species are in rapid exchange on the NMR time
ray diffraction. A rapid equilibration between 2-R and 3-R
gives rise to only one set of NMR signals for each metal/
ligand ratio. For the ligand 1-tBu, a similar equilibration be-
tween 2-tBu and 3-tBu is again observed, in addition to a
slower equilibration with a third product, [Ir(COD)Cl](µ-1-
R)[Ir(COD)Cl] (4-tBu), which is proposed to contain a bridg-
ing P,S ligand spanning two Ir centres. Complex 2-Ph reacts
with [Rh(COD)Cl]2 to give only the heterometallic ionic pair
[Ir(COD){κ2-P:S-(1-Ph)}][Rh(COD)Cl2] without transfer of li-
gand 1-Ph from Ir to Rh. Furthermore, the rhodium complex
RhCl(COD)(1-Ph) reacts quantitatively with [Ir(COD)Cl]2 at
room temp. to yield 2-Ph and [Rh(COD)Cl]2, thereby illustrat-
ing the much stronger affinity of ligands 1-Ph for iridium
compared to rhodium. Finally, the complexes 2-tBu and 2-Ph
were found to be efficient catalysts for the diphenylacetylene
scale. Complex 2-tBu, on the other hand, shows a four-coordi- hydrogenation, affording a mixture of monohydrogenation
nate square-planar molecular structure with a dangling thio- [both (E)- and (Z)-stilbene] and dihydrogenation (1,2-diphen-
ether moiety, probably for steric reasons. For metal/ligand
ratios greater than 1, the compounds [Ir(COD){κ2-P:S-
(1-R)}]+[Ir(COD)Cl2]– (3-R) are obtained, resulting from the
chloride abstraction by the excess iridium metal on complex
ylethane) products.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
substitution.[29–40] Furthermore, the largest scale industrial
enantioselective catalytic process involves an iridium-based
hydrogenation step in the synthesis of chiral herbicide (1S)-
Metolachlor.[41,42] Although many catalytic systems are
generated in situ by the ligand addition to the readily avail-
Introduction
The coordination chemistry of iridium has been widely
studied during the last few decades, in part because of nu-
merous applications that have been found in various cata-
lytic systems[1] since the pioneering work of Crabtree et al.[2]
In particular, iridium has been successfully applied to asym-
metric catalyses, such as olefin hydrogenation,[3–12] C=N hy-
drogenation,[13–21] transfer hydrogenation[22–28] and allylic
able chloro(cycloocta-1,5-diene)iridium dimer,
a good
number of ligand adducts have been isolated and crystallo-
graphically characterized. When the supporting ligand (L-
LЈ) is bidentate, several species can be envisaged depending
on the ability of the ligand to act in a monodentate or bi-
dentate fashion, and on the competition between the donor
atoms and the chloride ion for the metal center. These spe-
cies correspond to five-coordinate [Ir(κ2-L-LЈ)(COD)Cl],
four-coordinate neutral [Ir(κ1-L-LЈ)(COD)Cl] with a dan-
gling L or LЈ donor atom, and four-coordinate ionic [Ir(κ2-
L-LЈ)(COD)]+Cl–. Whereas several solid-state structures are
available for five-coordinate complexes[43–47] and an exam-
[a] Laboratoire de Chimie de Coordination, UPR-CNRS 8241,
205 Route de Narbonne, 31077 Toulouse Cedex, France
Fax: +33-5-61553131
E-mail: manoury@lcc-toulouse.fr
[b] Department of Chemistry, University of York,
YO10 5DD, United Kingdom
E-mail: sbd3@york.ac.uk
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
Eur. J. Inorg. Chem. 2006, 1803–1816
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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E. Manoury et al.
FULL PAPER
ple is also reported for neutral four-coordinate structure
with a dangling phosphanyl ester ligand,[48] no examples
are known, to the best of our knowledge, of four-coordinate
ionic [Ir(κ2-L-LЈ)(COD)]+ complexes with chloride as coun-
terion (though they are known for rhodium).[49–51] Whether,
for a given metal/ligand combination, the solid-state struc-
ture is maintained in solution and whether it is solvent de-
pendent, or whether equilibria between different structures
are established, has not been the subject of detailed studies
to the best of our knowledge. In addition, how the ligand
stereoelectronic properties may influence this structural
choice is also an obscure point.
(1)
The products 2-R have been characterized by analytical
and spectroscopic (1H, 31P, 13C NMR) methods. The NMR
properties are shown in Table 1. These are spectra recorded
on solutions obtained upon redissolving the isolated crys-
tals, but correspond to complex equilibria between different
species, as will be discussed in detail after the description
of the structures. The three compounds show grossly similar
physical (color, solubility) and spectroscopic properties in
solution, but have different structures in the solid state.
Whereas 2-Et and 2-Ph proved to be five-coordinate with a
κ2-P,S coordination mode for the bidentate ligand, their 2-
tBu analogue is only four-coordinate, with a κ1-P coordina-
tion mode and a dangling thioether functionality (see X-
ray structures below).
Another remarkable feature has been observed during
the crystallization of the crude product obtained from the
reaction of 1-Ph and [Ir(COD)Cl]2 (2:1 ratio). Whereas
crystals of 2-Ph were obtained from dichloromethane/hex-
ane, when the same procedure was followed for a toluene/
hexane, crystals of a different compound, namely [Ir(COD)-
(P,SPh)][Ir(COD)Cl2] (3-Ph) were produced. In fact, a
CDCl3 solution of 3-Ph gave a 31P resonance at 9.1 ppm,
quite different from the value observed for 2-Ph (–3.1 ppm).
As will be shown later, this resonance results from an equi-
librium mixture of 2-Ph and 3-Ph. When the synthesis was
repeated for a 1:1 ratio of 1-Ph and [Ir(COD)Cl]2 (1-Ph/Ir =
2), the resulting orange solid displayed solution-state NMR
properties in close correspondence with those of the iso-
lated crystals of 3-Ph. However, this solid also yielded crys-
tals of 2-Ph when recrystallized from dichloromethane/hex-
ane. It seems therefore that the choice of crystallization sol-
vent dictates the nature of the isolated product, indicating
a possible equilibrium between 2-Ph and 3-Ph [Equation
(2)]. A more detailed study of this equilibrium will be de-
scribed below.
The coordination chemistry of sulfur-containing li-
gands,[52,53] as well as their potential in homogeneous catal-
ysis[54,55] have recently attracted much interest, amongst
other things because the sulfur atom could become asym-
metric upon coordination to a metal. We have recently re-
ported the synthesis of a family of planar-chiral P,S ligands,
namely (R/S)-2-diphenylphosphanyl-[R-thiomethyl)ferro-
cenes (1-R), for instance with R = Et, tBu, Ph, which
proved to be very efficient in palladium-based asymmetric
allylic alkylation.[56] As a first step toward the development
of iridium-based catalytic systems, we wished to explore the
iridium coordination chemistry of such ligands, with a par-
ticular focus on the stoichiometry, stereochemistry, poten-
tial (hemi)lability, etc. In this paper, we describe the synthe-
sis and structure of a family of iridium complexes produced
upon reaction of the racemic 1-R (R = Et, tBu, Ph) ligands
with the cyclooctadieneiridium() moiety. We place particu-
lar emphasis on probing the relationship between the solu-
tion behaviour, the solid-state structure, and the nature of
the R substituent on the ferrocenyl thioether function. New
structural features and an unsuspected complex solution
behaviour have been found through these investigations.
Preliminary results on the catalytic diphenylacetylene hy-
drogenation reaction are also reported. Although the COD
ligand is replaced by other ligands or substrates under most
catalytic conditions (e.g. it is hydrogenated to cyclooctane
under hydrogenation conditions) the structural and dy-
namic features observed for the pre-catalyst (i.e., the coordi-
nation stereoselectivity, the hemilability) are potentially rel-
evant to the behaviour that one may expect under catalytic
conditions.
(2)
Results
(b) X-ray Structures
(a) Syntheses
Views of the molecular geometries of compounds 2-Et,
2-tBu and 2-Ph are presented in Figure 1. It is immediately
Addition of the 2 equivalents of the bidentate ligands evident that the Et and Ph derivatives are five-coordinate
[CpFe{1,2-C5H3(PPh2)(CH2SR)}] (1-R, R = Et, tBu, Ph), because the S atoms are within reasonable bonding dis-
which will be abbreviated as (P,SR), to complex [Ir(COD)- tances from the Ir centers [2.3928(17) Å and 2.3835(12) Å,
Cl]2 [i.e. 1 equiv. of (P,SR) to Ir] causes the splitting of the respectively], whereas the tBu derivative is only four-coordi-
chloride-bridged dinuclear structure of the iridium precur- nate (the S···Ir distance is 5.13 Å). A comparable Ir–S
sor and formation of mononuclear products, according to bonding distances [2.3594(15) Å] has been reported for a
the stoichiometry of Equation (1).
[(COD)Ir(P,StBu)]+ complex containing a chiral phosphin-
1804
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 1803–1816

Chlorocyclooctadieneiridium()–Ferrocenylphosphane–Thioether Ligand Adducts
Table 1. NMR properties of compounds 2-R (R = Et, tBu, Ph) in CDCl3 solution.[a]
FULL PAPER
2-Et
2-tBu
2-Ph
1H
PPh2
8.25 (m, 2 H)
7.58 (m, 3 H)
7.24 (s, 3 H)
7.05 (m, 2 H)
8.02 (m, 2 H)
7.50–7.46 (m, 5 H)
7.37–7.35 (m, 3 H)
8.01 [d, 2 H (7)]
7.66–7.61 (m, 4 H)[e]
7.46–7.41 (m, 3 H)[e]
7.27 (m, 4 H)[e]
7.12–7.09 (m, 2 H)[e]
5.55 [d, 1 H (12)]
4.09 (br. s, 2 H)[f]
4.44 (br. s, 1 H)
4.25 [t, 1 H (2.5)]
4.09 (br. s, 2 H)[f]
3.82
SCH2
C3H5
4.69 [d, 1 H (12)]
3.97 [d, 1 H (12)]
4.49 (s, 1 H)
4.22 (s, 1 H)
4.00 (s, 1 H)
4.09 [d, 1 H (13)]
3.87 [d, 1 H (13)]
4.64 [d, 1 H (2)]
4.39 [t, 1 H (2.5)]
4.28 (br. s, 1 H)
4.11
Cp
COD(CH)
3.83
3.48–3.53 (m, 4 H)[b]
2.96 (m, 1 H)
2.86 (m, 1 H)
2.62 (m, 2 H)
2.04 (m, 4 H)
1.40 (m, 5 H)[c]
3.7 (broad, 4 H)
3.32 {t, 2 H (7)}
3.09 (m, 2 H)
COD(CH2)
2.33–2.28 (m, 2 H)
2.13–2.11(m, 2 H)
1.80–1.77 (m, 2 H)
1.60–1.57 (m, 2 H)
1.42 (s, 9 H)
2.61–2.55 (m, 2 H)
2.01–1.93 (m, 4 H)
1.35–1.32 (m, 2 H)
[e]
SR
3.48–3.53 (m, 4 H)[b]
1.40 (m, 5 H)[c]
13C
Ph-ipso
135.1 [d (30)]
133.3 [d (51)]
135.4 [d, 2 C (13)]
132.0 [d, 2 C (9)]
130.6 [d, 1 C (2)]
129.0 (1 C)
127.8 [d, 2 C (10)]
127.2 [d, 2 C (9)]
70.6
133.8 [d (52)]
132.6 [d (50)]
134.8 [d (46)]
134.0 [d (51)]
132.3 [d, 2 C (9)]
130.7 [d, 2 C (2)]
128.9 [d, 2 C (2)]
127.9 [d, 2 C (10)]
127.0 [d, 2 C (9)]
Ph-o,m,p
135.2 [d, 2 C (11)]
134.2 [d, 2 C (10)]
130.1 [d, 1 C (2)]
129.7 [d, 1 C (2)]
127.6 [d, 2 C (10)]
127.4 [d, 2 C (10)]
71.0
Cp
70.7
C5H3
88.0 [d, 1 C (18)]
72.6 [d, 1 C (7)]
72.5 (s, 1 C)
70.3 [d, 1 C (38)]
68.7 [d, 1 C (5)]
30.9
90.0 [d, 1 C (14)]
74.9 [d, 1 C (8)]
74.4 [d, 1 C (50)]
71.3 [d, 1 C (17)]
69.7 [d, 1 C (7)]
28.7
88.7 [d, 1 C (18)]
72.3 (s, 1 C)
72.0 [d, 1 C (7)]
71.0 [d, 1 C (43)]
69.0 [d, 1 C (5)]
37.3
135.9 [d, iC (11)]
132.1 (s, 2 C)
129.8 (s, 1 C)
129.0 (s, 2 C)
67.4 (s, 2 C)
65.1 [d, 2 C (15)]
35.5 (s, 2 C)
28.7 (s, 2 C)
SCH2
SR
66.8 (CH2)
13.5 (CH3)
43.6 [C (CH3)]
30.9 [C(CH3)]
[d]
COD(CH)
COD(CH2)
64.5 [d, 2 C (13)]
29.8 [d, 2 C(5)]
35.8 (s, 2 C)
32.6 (s, 2 C)
30.6 (s, 2 C)
28.6 (s, 2 C)
31P
–3.1
15.7
–4.2
[a] Chemical shifts are reported as measured, for solutions containing ca. 10–2 mol/L of the isolated crystals. [b] Overlap between
COD(CH) and SEt (CH2) resonances. [c] Overlap between COD(CH2) and SEt (CH3) resonances. [d] Not visible (see text). [e] Overlap
between the PPh2 and SPh resonances. [f] Overlap between one SCH2 and one C5H3 resonance.
ite–thioether donor.[57] Other significant bonding param- mid and a distorted square-pyramid. In the distorted trigo-
eters are shown in Table 2 for the five-coordinate com- nal-bipyramidal view, the center of one C=C donor func-
pounds and in Table 3 for the four-coordinate one. When tion of the COD ligand (CO2) and the S1 donor atom de-
considering the coordination sites as corresponding to the fine the axial positions [angles of 168.1(4) and 166.703(18)°,
midpoints of the COD C–C double bonds, the geometry of respectively]. However, the equatorial angles deviate se-
2-tBu corresponds quite closely to an ideal square plane, verely from the ideal 120° value, for instance the CT01–
the Ir atom being only 0.0206(2) Å away from the least- Ir(1)–P(1) angle in the two compounds is 153.2(4) and
squares coordination plane. The coordination geometries of 156.06(2)°, respectively, whereas the P(1)–Ir(1)–Cl(1) angle
compounds 2-Et and 2-Ph, on the other hand, may be best is 91.33(7) and 90.03(3). In the alternative distorted square-
viewed as intermediate between a distorted trigonal-bipyra- pyramidal view, the axial ligand would be the Cl(1) ligand,
Eur. J. Inorg. Chem. 2006, 1803–1816
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1805

E. Manoury et al.
FULL PAPER
although a few of the Cl(1)–Ir–X angles [X = P(1), S(1),
CO1 and CO2] are relatively close to 90°. It is interesting
to note that in both 2-Et and 2-Ph, the Ir is located off the
basal square plane by 0.363(8) Å and 0.3506(3) Å respec-
tively, moreover the Ir is displaced toward the Cl atom. The
distance from Cl to the square plane is 2.875(6) Å and
2.850(2) Å respectively. In fact, it would seem possible to
view the structure as derived from that of the corresponding
square planar [Ir(COD)(P,SR)]+ by addition of Cl–, re-
sulting in a minimal perturbation of the square-planar ge-
ometry. Structures of five-coordinate [IrX(COD)L2] (X =
any halogen) are not uncommon. They comprise examples
with L2 = diphosphanes[43,44] including a ferrocenyl-func-
tionalized diphosphane,[45] diimines,[46,47] and also with L =
monodentate phosphane.[58] The compounds reported here
are the first such examples containing a bidentate P,S-type
framework. More importantly, they illustrate the delicate
Table 2. Selected bond lengths [Å] and angled [°] for the pentacoor-
dinate compounds 2-R (R = Et, Ph).
2-Et
2.026(8)
2-Ph
2.0216(9)
2.0433(8)
1.445(4)
Ir(1)–CT01
Ir(1)–CT02
C(30)–C(31)
C(34)–C(35)
Ir(1)–P(1)
Ir(1)–S(1)
Ir(1)–Cl(1)
P(1)–C(1)
P(1)–C(111)
P(1)–C(121)
S(1)–C(21)
S(1)–C(211)
2.030(7)
1.441(10)
1.407(11)
2.3322(15)
2.3928(17)
2.5739(19)
1.796(7)
1.843(7)
1.819(7)
1.809(8)
1.842(7)
1.496(9)
85.118(19)
153.2(4)
90.69(6)
90.3(3)
168.1(4)
88.48(7)
115.4(3)
103.0(4)
91.33(7)
88.84(8)
99.6(4)
103.4(3)
104.0(3)
118.06(19)
113.2(2)
116.4(3)
94.5(3)
110.7(3)
108.8(3)
126.8(4)
126.5(5)
123.2(6)
128.8(6)
114.8(5)
118.9(6)
121.8(6)
119.9(6)
122.4(6)
1.395(4)
2.3289(13)
2.3835(12)
2.5576(12)
1.807(3)
1.835(3)
1.837(3)
1.826(3)
1.790(3)
1.488(4)
85.298(8)
156.06(2)
91.583(19)
90.020(18)
166.703(18)
87.66(2)
113.814(19)
102.980(19)
90.03(3)
C(2)–C(21)
CT01–Ir(1)–CT02
CT01–Ir(1)–P(1)
CT02–Ir(1)–P(1)
CT01–Ir(1)–S(1)
CT02–Ir(1)–S(1)
P(1)–Ir(1)–S(1)
CT01–Ir(1)–Cl(1)
CT02–Ir(1)–Cl(1)
P(1)–Ir(1)–Cl(1)
S(1)–Ir(1)–Cl(1)
C(1)–P(1)–C(111)
C(1)–P(1)–C(121)
C(111)–P(1)–C(121)
C(1)–P(1)–Ir(1)
C(111)–P(1)–Ir(1)
C(121)–P(1)–Ir(1)
C(21)–S(1)–C(211)
C(211)–S(1)–Ir(1)
C(21)–S(1)–Ir(1)
C(2)–C(1)–P(1)
C(5)–C(1)–P(1)
C(3)–C(2)–C(21)
C(1)–C(2)–C(21)
C(2)–C(21)–S(1)
C(116)–C(111)–P(1)
C(112)–C(111)–P(1)
C(126)–C(121)–P(1)
C(122)–C(121)–P(1)
C(216)–C(211)–S(1)
C(212)–C(211)–S(1)
90.30(2)
100.46(13)
103.36(12)
101.25(12)
117.07(9)
114.85(10)
117.31(9)
98.62(13)
112.14(9)
108.09(10)
127.2(2)
126.0(2)
123.1(2)
128.7(2)
111.23(18)
121.6(2)
120.1(2)
118.9(2)
122.1(2)
122.7(2)
Figure 1. ORTEP views of the molecular structures of compounds
2-Et (a); 2-tBu (b) and 2-Ph (c). Ellipsoids are drawn at the 50%
probability level and hydrogen atoms are omitted for clarity.
116.9(2)
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Eur. J. Inorg. Chem. 2006, 1803–1816

Chlorocyclooctadieneiridium()–Ferrocenylphosphane–Thioether Ligand Adducts
Table 3. Selected bond lengths [Å] and angles [°] for the square planar compound 2-tBu.
FULL PAPER
Ir(1)–CT01
2.0859(6)
Ir(1)–CT02
1.9988(5)
Ir(1)–C(30)
Ir(1)–C(31)
Ir(1)–P(1)
P(1)–C(1)
P(1)–C(111)
S(1)–C(22)
2.204(2)
2.194(2)
2.3312(9)
1.811(3)
1.831(3)
1.828(3)
Ir(1)–C(34)
Ir(1)–C(35)
Ir(1)–Cl(1)
S(1)–C(21)
P(1)–C(121)
C(30)–C(31)
C(34)–C(35)
P(1)–Ir(1)–Cl(1)
CT02–Ir(1)–P(1)
CT02–Ir(1)–Cl(1)
C(1)–P(1)–C(121)
C(111)–P(1)–Ir(1)
C(121)–P(1)–Ir(1)
C(221)–C(22)–S(1)
C(223)–C(22)–S(1)
C(222)–C(22)–S(1)
C(1)–C(2)–C(21)
2.131(3)
2.110(3)
2.3625(8)
1.818(3)
1.835(3)
1.392(4)
1.418(4)
92.49(2)
93.369(19)
172.601(17)
100.70(12)
116.53(8)
114.22(8)
111.1(2)
110.5(2)
104.3(2)
128.0(2)
CT02–Ir(1)–CT01
CT01–Ir(1)–P(1)
CT01–Ir(1)–Cl(1)
C(1)–P(1)–C(111)
C(111)–P(1)–C(121)
C(1)–P(1)–Ir(1)
C(21)–S(1)–C(22)
C(5)–C(1)–P(1)
C(2)–C(1)–P(1)
C(3)–C(2)–C(21)
C(2)–C(21)–S(1)
C(116)–C(111)–P(1)
C(112)–C(111)–P(1)
86.434(11)
177.594(17)
87.904(18)
105.28(11)
101.02(12)
116.81(9)
103.56(13)
124.1(2)
127.77(18)
124.5(2)
109.91(18)
120.86(19)
120.18(19)
C(126)–C(121)–P(1)
C(122)–C(121)–P(1)
120.8(2)
120.8(2)
control exerted by the ligand structure on the coordination accompanies this coordination number increase. This obser-
geometry. This control is unlikely to have an electronic ori- vation gives credence to the hypothesis that the Ir–Cl bond
gin, as the Et and tBu substituents impart analogous elec- in the five-coordinate complexes is highly polarized, espe-
tronic effects, and different from those of the Ph substitu- cially when comparing it with the insignificant change of
ent. A steric effect appears more likely, because the tBu the Ir–P distance [2.3322(15) Å and 2.3289(13) Å in five-
group is more encumbering than either the Et or the Ph coordinate 2-Et and 2-Ph, respectively; 2.3312(9) Å in four-
group and thus prevents the compound to attain the five- coordinate 2-tBu] and Ir–CT distances [CT = center of the
coordinate geometry (Figure 1).
The S coordination step is interesting from the stereo- 2.032(10) Å for 2-Ph and 2.04(4) Å for 2-tBu].
chemical point of view. Coordination renders the S atom The structure of compound 3-Ph contains discrete
COD C=C bond; averages are 2.028(8) Å for 2-Et,
and the Ir atom asymmetric. In combination with the square-planar [Ir(COD)(κ2-P,SPh)]+ and [Ir(COD)Cl2]–
planar chirality of the substituted ferrocene moiety, eight anions. An interstitial toluene molecule completes the crys-
possible stereoisomers, namely four diastereomeric pairs of tal packing. One H atom of a CH2 group of the COD li-
enantiomers, can be obtained. There is, however, no indica- gand in the cation is located at a relatively short intermo-
tion from the NMR spectrum for the formation of more lecular contact (2.759 Å) above the Ir atom in the anion,
than one compound. Either the diastereoisomers have sig- see Figure 2, a location which places it in an approximately
nificantly different energies such that only one is present at ideal axial position. Indentification of such an interaction
equilibrium, or the isomerization proceeds through a low in solution by NMR spectroscopy was precluded by the
energy barrier (for instance by decoordination and recoor- complex redistribution equilibria (see below). However, the
dination through a four-coordinate square planar interme- Ir atom in each ion sits very close to the ideal square place
diate), or finally there may be a combination of both effects. defined by the middle of the C=C bonds and the P,S or Cl
Other observations, shown below, indicate that these com- donors, respectively [0.0158(5) Å in the cation, 0.0066(5) Å
pounds undergo dynamic rearrangements very rapidly. In in the anion]. Structures of four-coordinate cationic com-
the solid state, the compounds 2-Et and 2-Ph show the S plexes of type [Ir(COD)L2]+ are quite common in the litera-
atom with the same configuration relative to the ferrocene ture with various types of bidentate L2 and monodentate L
unit (R group exo, lone pair endo and parallel to the Cp– ligands, including two precedents with a chelating P,S-type
Fe axis), and the Cl ligand is located on the same side (exo) ligand, Ph2PO(1,2-cyclo-C6H10)StBu and Ph2PCH2P-
relative to the ferrocene group. The Ir–Cl distances of (tBu)2S.[57,60] All these previously reported salts contain
–
–
–
–
2.5739(19) and 2.5576(12) Å compare with those in other BF4 , PF6 , SbF6 , CF3SO3 , or tetraarylborates as coun-
five-coordinate [IrCl(COD)L2] derivatives with chelating terions. None contains the [Ir(COD)Cl2]– anion. In fact,
ligands, for instance 2.549 Å in [IrCl(COD)L2] [L2
=
this quite simple anion does not appear to have previously
(2R,3R)-2,3-O-isopropylidene-1,4-bis(5H-dibenzophos- been crystallographically characterized. This situation dif-
phol-5-yl)-2,3-butanediol],[43]
and
2.585(3) Å
in fers considerably from that of the rhodium congeners, for
[IrCl(COD)(dppp)].[44] However, these distances are longer which several structure of salts of type [Rh(COD)-
relative to neutral four-coordinate complexes [e.g. L2][Rh(COD)Cl2] have been reported.[61–65]
2.363(1) Å in Ir(COD)[= C(NCH2-p-Tol)2C2H2]Cl,[59] and
Selected bonding parameters for compounds 3-Ph are
2.3625(8) Å in complex 2-tBu]. A lengthening of ca. 0.2 Å shown in Table 4. Both ions exhibit a relatively undistorted
Eur. J. Inorg. Chem. 2006, 1803–1816
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E. Manoury et al.
FULL PAPER
Figure 2. ORTEP view of the molecular structures of compounds 3-Ph. Ellipsoids are drawn at the 50% probability level and hydrogen
atoms are omitted for clarity.
square-planar geometry when considering the center of the above, attesting to the importance of back-bonding for the
COD C=C bonds (CT) as defining the coordination posi- Ir–COD interaction. The Ir–P and Ir–S bond lengths in the
tions. The Ir–CT distances are significantly shorter in the cation are shorter than those in the neutral complexes, irre-
anion [average 1.976(5) Å] than in the cation [average spective of their coordination number. This effect can be
2.09(4) Å], and the latter are marginally longer than in the attributed to the metal ion contraction on going from the
4- and five-coordinate neutral complexes 2-R discussed neutral to the charged system, because of an increase of
Table 4. Selected bond lengths [Å] and angles [°] for compounds 3-Ph.
Ir(1)–CT01
Ir(1)–CT02
Ir(1)–C(30)
Ir(1)–C(31)
Ir(1)–C(34)
Ir(1)–C(35)
Ir(1)–P(1)
Ir(1)–S(1)
C(30)–C(31)
C(34)–C(35)
P(1)–C(1)
P(1)–C(111)
2.1242(2)
2.0518(2)
2.239(5)
2.228(5)
2.171(5)
2.164(5)
2.2820(13)
2.3280(12)
1.381(7)
1.397(7)
1.806(5)
1.828(5)
1.823(5)
85.612(7)
173.43(3)
89.93(3)
92.99(3)
170.56(3)
92.35(4)
102.6(2)
105.2(2)
114.86(16)
122.4(4)
126.4(4)
121.5(4)
119.1(4)
100.5(2)
108.55(17)
121.5(4)
Ir(2)–CT03
Ir(2)–CT04
Ir(2)–C(40)
Ir(2)–C(41)
Ir(2)–C(43)
Ir(2)–C(44)
Ir(2)–Cl(1)
Ir(2)–Cl(2)
C(40)–C(41)
C(43)–C(44)
1.9807(2)
1.9708(2)
2.094(6)
2.113(6)
2.086(5)
2.101(5)
2.3644(13)
2.3706(13)
1.415(8)
1.414(8)
P(1)–C(121)
S(1)–C(211)
1.824(5)
1.786(5)
88.285(9)
90.96(4)
177.05(4)
177.63(3)
90.72(3)
90.14(5)
103.6(2)
118.79(17)
110.19(16)
129.0(4)
111.9(3)
117.9(4)
123.2(4)
117.7(4)
115.67(17)
C(21)–S(1)
CT02–Ir(1)–CT01
CT01–Ir(1)–P(1)
CT01–Ir(1)–S(1)
CT02–Ir(1)–P(1)
CT02–Ir(1)–S(1)
P(1)–Ir(1)–S(1)
C(1)–P(1)–C(111)
C(121)–P(1)–C(111)
C(1)–P(1)–Ir(1)
C(2)–C(1)–P(1)
C(1)–C(2)–C(21)
C(112)–C(111)–P(1)
C(116)–C(111)–P(1)
C(211)–S(1)–C(21)
C(211)–S(1)–Ir(1)
C(212)–C(211)–S(1)
CT04–Ir(2)–CT03
CT03–Ir(2)–Cl(1)
CT04–Ir(2)–Cl(1)
CT03–Ir(2)–Cl(2)
CT04–Ir(2)–Cl(2)
Cl(1)–Ir(2)–Cl(2)
C(1)–P(1)–C(121)
C(121)–P(1)–Ir(1)
C(111)–P(1)–Ir(1)
C(5)–C(1)–P(1)
C(2)–C(21)–S(1)
C(122)–C(121)– P(1)
C(126)–C(121)–P(1)
C(216)–C(211)–S(1)
C(21)–S(1)–Ir(1)
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Chlorocyclooctadieneiridium()–Ferrocenylphosphane–Thioether Ligand Adducts
FULL PAPER
effective nuclear charge, and agrees with a predominant σ- two CH resonances in the corresponding 13C NMR spec-
bonding component for the Ir–P and Ir–S interactions.
trum is upfield shifted by ca. 15 ppm relative to the same
resonance in the other two compounds. The chemical shift
of the single H resonance of the unsubstituted Cp ligand
1
(c) NMR Spectroscopy of Compounds 2-R
is also significantly different for 2-tBu relative to the other
two compounds, and a slight difference is even observable
Given the subtle structural difference observed for com-
pounds 2 in the solid state depending on R, one might won-
der whether the same structural dichotomy is maintained
in solution. A detailed analysis of the NMR properties
seems to suggest that this is the case. The 31P resonance
chemical shift is essentially identical for compounds 2-Et
and 2-Ph, whereas it is significantly shifted downfield for 2-
tBu (see Table 1), in apparent agreement with donation
from the phosphorus atom to a less electron-rich metal in
the latter case. This observation is the strongest indication
in favor of a similar structure in the solid state and in chlo-
roform solution for compounds 2. Given the planar chiral-
ity of the functionalized Cp ring of the ferrocene moiety,
1
for the 13C resonance of the same group. The H and 13C
resonances of the CH2 group linking the S donor to the
ferrocene unit, on the other hand, seem sensitive to the elec-
tronic nature of the SR group, because they are similar for
the Et and tBu derivatives and different for the Ph deriva-
tive. In conclusion, the overall NMR behaviour suggests
that the solution structures of compounds 2 may be iden-
tical to those observed in the solid state.
(d) Study of Solution Equilibria
Solutions obtained by mixing the complexes [Ir(COD)Cl]2
all COD proton and carbon nuclei are magnetically in- and the free ligand 1-Ph in various ratios were investigated
1
equivalent in both types of structure, although a higher de- by H and 31P NMR spectroscopy. Only one set of reso-
gree of inequivalence could be expected for the five-coordi- nances was observed for all ratios up to 1-Ph/Ir = 1:1, but
nate structures where there is coordination-induced chiral- several individual resonances of this set (notably the 31P
ity at both the S and Ir atoms. The NMR spectra are, how- resonance and the 1H resonances of the ferrocene unsubsti-
ever, deceptively simple as only two sets of 13C resonances tuted Cp, of one of the substituted Cp protons, and of the
are observed for both the CH and the CH2 nuclei for all two CH2 protons) exhibited a continuous variation of the
three compounds. For compound 2-tBu, the CH resonances chemical shift as a function of the 1-Ph/Ir ratio (see Fig-
1
could not be identified, even by an H–13C HMQC experi- ure 3). The COD resonances were too broad to allow their
ment at temperatures down to 213 K. On the other hand, accurate monitoring. For 1-Ph/Ir ratios greater than 1, the
these peaks were visible when the spectrum was recorded in resonances of the free ligand 1-Ph (mostly evident from the
[D8]toluene solution (see Exp. Sect.). The pairs of C atoms 31P NMR spectrum) also appeared.
with distinct chemical shifts are probably associated to the
The behaviour illustrated in Figure 3 can be rationalized
different coordination positions (i.e. trans to P and trans to on the basis of Scheme 1, where rapid site exchange be-
S/Cl), whereas the asymmetry above and below the square tween the species participating in the equilibrium is re-
coordination plane has a negligible effect on the chemical quired. A similar equilibrium has previously been proposed
1
shift. Only for the H CH (COD) resonances in compound for an analogous system with the hemilabile N,O ligand 3-
2-Et was a slight asymmetry detected in the corresponding dimethylamino-1-(2Ј-pyridyl)-2-propen-1-one.[64] The reso-
NMR spectra due to this asymmetry. This observation nances did not decoalesce into those of the individual spe-
alone is not sufficient to confirm the difference in coordina- cies upon cooling to 213 K for a solution containing a 1-Ph/
tion geometry within the three compounds. However, the Ir ratio of 0.6. The first ligand–metal equilibrium leading
chemical shifts of the CH(COD) 1H and 13C resonances to 3-Ph must be essentially quantitative, because the NMR
change significantly on going from 2-Et and 2-Ph. In par- signals of free 1-Ph appear immediately after consumption
ticular, the CH resonances in the 1H NMR spectrum of one equivalent of the ligand per Ir dimer, whereas they
proved to be more spread apart in 2-tBu, while one of the are not visible before this ratio is attained.
Figure 3. Dependence of the chemical shift of a few resonance for the [Ir(COD)Cl]2/1-Ph system on the 1-Ph/Ir ratio. (a) 31P resonance;
1
(b) H resonances: unsubstituted Cp (5 H, diamonds); substituted Cp (1 H, circles); CH2 (1 H, squares; 1 H, triangles). The solid lines
are obtained by fitting the data according to Scheme 1 (see text).
Eur. J. Inorg. Chem. 2006, 1803–1816
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1809

E. Manoury et al.
FULL PAPER
out in this case. In contrast, treatment of complex [Ir-
(COD)Cl]2 with various amounts of 1-tBu in CDCl3 led to
the observation of two new 31P NMR resonances. Whereas
one of these (at δ = 17.5 ppm) exhibited the same chemical
shift at all 1-tBu/Ir ratios, the other one shifted continu-
ously from ca. δ = 14.6 at 1-tBu/Ir = 0.2 to ca. 15.7 at 1-tBu/
Ir = 1, see Figure 4 (a). In addition, the relative intensity of
these two resonances changed in favor of the second one
upon increasing the 1-tBu/Ir ratio, until the first one com-
pletely disappeared at the point when 1-tBu/Ir = ca. 1, see
Figure 4 (b). Further additions of the free ligand no longer
moved the δ = 15.7 resonance, although, a new resonance
due to the excess of free 1-tBu started to appear at δ =
–20.0 ppm. This observed behaviour suggests the presence
of at least three P-containing Ir complexes: two that are
in rapid exchange on the NMR time scale, generating the
resonance that is shifting in the δ = 14.6–15.7 ppm range,
and a third one giving the δ = 17.5 ppm resonance. The
latter species exchanges slowly on the NMR timescale, or
not at all, with the other two. In addition, the appearance
of the free 1-tBu resonance immediately after attaining the
1-tBu/Ir ratio of 1, suggested an essentially quantitative first
addition of 1-tBu to [Ir(COD)Cl]2 to generate 3-tBu, like
for the case of the 1-Ph addition.
Scheme 1.
Under the assumption of a first quantitative addition of
1-Ph to [Ir(COD)Cl]2, the individual concentrations of 2-
Ph and 3-Ph for each measured solution were obtained
from the equilibrium expression denoted in Equation (3), R
= Ph, using K as an adjustable parameter. These concentra-
tions were then used to calculate, for each resonance, the
chemical shifts according to Equation (4) (R = Ph). Fitting
to the experimental data yielded a reasonable agreement,
using the same value of the equilibrium constant (0.008) for
all resonances, as shown in Figure 3. The full fitting pro-
cedure and the values of δ2–Ph and δ3–Ph for each reso-
nance, as obtained from the fittings, are given in the Sup-
porting Information (for details see the footnote on the first
page of this article).
It seems logical to assume, on the basis of the results
shown above for the 1-Ph/Ir system, that the shifting reso-
nance is due to the rapidly equilibrating mixture of com-
pounds 2-tBu and the salt [Ir(COD)(κ2-P,StBu)]+[Ir-
(COD)Cl2]–, 3-tBu [equilibrium of Equation (2)]. The chem-
ical shift observed at low 1-tBu/Ir ratio [Figure 4 (a), ca. δ
(3)
(4)
When a sample of 1-Et was added to [Ir(COD)Cl]2 in a = 14.5 ppm] is close to that observed at low 1-Ph/Ir ratio
1:1 molar ratio in CDCl3 (i.e. a 1-Et/Ir ratio of 0.5), a single (Figure 3, ca. δ = 11 ppm) and attributed to compound 3-
31P NMR resonance was observed at δ = 10.9 ppm. The Ph. For the 1-Ph/Ir system, addition of the free ligand leads
isolated complex 2-Et (having a 1-Et/Ir ratio of 1), on the to an upfield shift toward the resonance of five-coordinate
other hand, yielded a 31P resonance at δ –4.2 under the 2-Ph (ca. δ = –3 ppm), whereas for the 1-tBu/Ir system,
same conditions (see Table 1), whereas the resonance of the addition of the free ligand leads to a downfield shift toward
free ligand 1-Et is at –20. Addition of an excess of ligand the resonance of four-coordinate 2-tBu (ca. δ = 15.5 ppm).
1-Et shifted this resonance further to δ = –4.6 ppm. We This proposition is in agreement with the observed behav-
therefore presume that the solution behaviour of “Ir(COD)- iour of the same system in C6D6: the lower polarity of this
Cl” in the presence of 1-Et is the same as with the 1-Ph solvent is expected to disfavor formation of the ionic system
ligand. A more detailed equilibrium study was not carried and, indeed, the resonance does not shift significantly by
Figure 4. Chemical shift (a) and relative ratio (b) of the 31P NMR resonances for the [Ir(COD)Cl]2/1-tBu system as a function of the 1-
tBu/Ir ratio. Squares: rapidly equilibrating mixture of 2-tBu and 3-tBu; triangles: 4-tBu; diamonds: 1-tBu. The solid line in (a) is the data
fit to the model of Scheme 2 (see text).
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Eur. J. Inorg. Chem. 2006, 1803–1816

Chlorocyclooctadieneiridium()–Ferrocenylphosphane–Thioether Ligand Adducts
FULL PAPER
Scheme 2.
varying the 1-tBu/Ir ratio in the 0 to Ͼ 1 range (δ always in ratio should be independent on the 1-tBu/Ir ratio. This ratio
the 15.68–15.71 range). can be estimated from the extrapolated relative intensities
We now need to assign the δ = 17.5 ppm resonance and of the δ = 14.6 and 17.5 ppmpeaks as 1-tBu/Ir Ǟ 0 (ca.
to rationalize the fact that it is observed only for the 1-tBu/ 42.3:57.7), from Figure 4 (b). This number can in turn be
Ir system. The most reasonable proposal that we are able used to estimate the individual concentrations of 2-tBu and
to advance involves a neutral dinuclear complex with a 3-tBu at each 1-tBu/Ir ratio. At this point, the concentration
bridging P,StBu ligand (4-tBu), see Scheme 2. Precedents of each iridium-containing species can be calculated solving
for this type of structural arrangement exist for P,N li- the equilibrium relationship [Equation (3), R = tBu], using
gands.[66,67] As the equilibrium between the five-coordinate K as an adjustable parameter. These concentrations were
and the four-coordinate isomers of 2-R lies strongly in favor then used to calculate the 31P chemical shift according to
of the latter when R = tBu, the pendant StBu arm is avail- Equation (4) (R = tBu). Fitting of the simulated and experi-
able to coordinate the Ir center in the unsaturated [Ir- mental data yielded a reasonable agreement for an equilib-
(COD)Cl] complex, which is in equilibrium with the rium constant of 0.036, as shown in Figure 4 (a). Thus, K
dichloro-bridged dimer. It is rather remarkable, however, is greater for R = tBu (0.036) than for R = Ph (0.008). The
that this process is slower than the addition of the chloride release of steric pressure upon transforming the chelating
anion to the same position. We presume that this is so for P,StBu ligand into a dangling one (whereas the P,SPh ligand
steric reasons. The reversible association/dissociation pro- remains chelating in compound 2-Ph) may provide an ex-
cess of the pendant StBu arm leading from 2-tBu to 3-tBu is planation of this difference.
fast because it is intramolecular. The reason why analogous
compounds 4-Ph and 4-Et are not observed would then be
(e) Comparison with Rh Coordination Chemistry and
related to the preferred sulfur coordination to the same Ir
Mixed Rh–Ir Studies
center, in the five-coordinate geometry of 2-Ph and 2-Et.
According to this proposal, compound 4 has an identical
When samples of 1-R (R = Ph, Et, tBu) were treated with
stoichiometry to compound 3. Therefore, the 3-tBu/4-tBu [Rh(COD)Cl]2 in a 2:1 molar ratio, a single 31P resonance,
Eur. J. Inorg. Chem. 2006, 1803–1816
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1811

E. Manoury et al.
Table 5. 31P resonances assigned to the products of 1:1 and 2:1 ligand 1-R addition to [M(COD)Cl]2 (solvent = CDCl3).
FULL PAPER
δ = 31P (JPRh
M = Rh
)
Complex
1-R/M ratio
M = Ir[a]
M(COD)Cl(P,SEt)
M(COD)Cl(P,StBu)
M(COD)Cl(P,SPh)
[M(COD)(P,SPh)][M(COD)Cl2]
1:1
1:1
1:1
1:2
5-Et: 25.2 (142 Hz)
5-tBu: 24.5 (147 Hz)
5-Ph: 22.2 (143 Hz)
6-Ph: 24.0 (143 Hz)
2-Et: –4.6
2-tBu: 15.6
2-Ph: –2.9
3-Ph: 11.0
[a] Following the chemical shift analysis as a function of 1-R/M ratio, as outlined in the text and described in detail in the Supporting
Information.
split into a doublet by a rhodium coupling, was observed same 31P NMR resonance (δ = –0.21 ppm) was obtained
in each case in the NMR spectrum. This resonance is there- by adding 1/2 mol of [Ir(COD)Cl]2 and 1/2 mol of
fore assigned to
a product with the stoichiometry [Rh(COD)Cl]2 simultaneously to one mol of 1-Ph. How-
RhCl(COD)(P,SR) (5-R) see Table 5. The very similar val- ever, complex 2-Ph cannot be the only species in solution,
ues of the chemical shifts and coupling constants, in con- because its resonance is shifted relative to that assigned to
trast to the behaviour observed for the Ir complexes, pure 2-Ph. From the observed NMR behaviour of complex
strongly indicates the same coordination mode for the three 2-Ph in the presence of variable amounts of [Ir(COD)Cl]2
ligands with respect to RhI.
(see Figure 3 and related discussion above), we can presume
When a sample of 1-Ph in CDCl3 was treated with that the reaction mixture also contains equilibrium
[Rh(COD)Cl]2 in a 1:1 molar ratio, a doublet resonance was amounts of complex [Ir(COD)(κ2-P,SPh)][Rh(COD)Cl2],
observed at δ = 24 ppm (143 Hz) in the 31P NMR spectrum. 3Ј, obtained by transfer of the chloride ligand to the dinu-
Both the chemical shift and the coupling constant of this clear rhodium complex as shown in Equation (6).
resonance are very close, but not identical, to those ob-
tained using a 2:1 ratio. Therefore, we presume that the
compound formed under these conditions (6-Ph) has the
same structure as the iridium analogue 3-Ph, namely
[Rh(COD)(P,SPh)][Rh(COD)Cl2]. As for compounds 5-R,
there are two possibilities: an ionic structure
[Rh(COD)(P,SR)]+Cl–, and a neutral structure with a dan-
(5)
gling thioether function, [RhCl(COD)(κ1-P,SR)], as seen for
the iridium analogue 2-tBu. In both cases, the rhodium
complexes are consistently four-coordinate, in agreement
with the lower propensity of RhI, relative to IrI, to give
five-coordinate geometries with the involvement of the dz2
orbital. A few examples of four-coordinate [Rh(COD)L2]+
complexes having Cl– as the counterion have been charac-
terized by X-ray crystallography, namely [Rh(COD)-
(6)
(bipy)2]+,[49] [Rh(COD)L2]+ (L = 1,3-dimethylimidazolin-2-
ylidene),[50] and a chelated version of the latter {L2
=
It is interesting to remark that the resonance observed
[MeNC3H2N-(CH2)3-NC3H2NMe]}.[51] However, addition
of the 1-R ligands to [Rh(COD)Cl]2 in C6D6 generated sol-
uble products whose 31P NMR resonances [5-Et: 21.8
(147 Hz); 5-tBu: 23.6 (148 Hz); 5-Ph: 21.6 (148 Hz)] turned
out to be essentially identical to those recorded in CDCl3.
This result strongly suggests that the adducts are neutral.
In conclusion, the IrI center has a greater tendency to coor-
dinate both the thioether function and the Cl– ion. The lat-
ter, however, is rather weakly coordinated as shown by the
long Ir–Cl distances in the X-ray structures (vide supra).
Subsequent mixing experiments were carried out in order
to probe the relative stability of RhI and IrI complexes with
the coordinated P,SR ligands. The addition of [Ir(COD)-
for this mixture (ca. –0.2 ppm), which contains
a
P,SPh:(Rh+Ir) ratio of 0.5, is much closer to the resonance
of 2-Ph than that of a solution with the same P,SPh to me-
tal ratio, but containing only Ir (ca. 8 ppm, see Figure 3).
This observation shows that [Ir(COD)Cl]2 is a stronger
chloride scavenger than its rhodium analogue. Another ob-
vious conclusion of this study is that the iridium ion forms
stronger bonds with the phosphorus and sulfur atoms of
the P,SPh ligand than does the rhodium ion.
(f) Catalytic Studies
Complexes 2 were tested as catalyst for the hydrogena-
Cl]2 to a sample of 5-Ph in a 1:2 molar ratio made the 31P tion of diphenylacetylene. The results are presented in
NMR resonance of the starting Rh complex and the P–Rh Table 6. Under 30 bar of dihydrogen pressure at room tem-
coupling disappear, yielding a new resonance (singlet) at δ perature with 1 mol-% of precatalyst, compound 2-tBu gave
= –0.25 ppm. From the observed chemical shift (cf. Table 5) a quantitative conversion after 6 h, whereas complex 2-Ph
and the absence of Rh coupling, we propose that the reac- was less active, yielding only a 59% conversion. In both
tion leads to complex 2-Ph, according to Equation (5). The cases, significant amounts of 1,2-diphenylethane were de-
1812
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 1803–1816

Chlorocyclooctadieneiridium()–Ferrocenylphosphane–Thioether Ligand Adducts
Table 6. Diphenylacetylene hydrogenation in presence of complexes 2-Ph and 2-tBu.
FULL PAPER
Entry
Complex
Reaction time
Conversion[a,b] Yield of cis-stilbene[b]
Yield of trans-stilbene[b] Yield of 1,2-diphenylethane[b]
1
2
2-Ph
2-tBu
6 h
6 h
59%
100%
79%
64%
8%
14%
13%
22%
[a] Reaction run with 1 mmol of diphenylacetylene, 0.01 mmol of complex 2 (1 mol-%) in 2 mL CH2Cl2 at room temperature under 30
bars of dihydrogen. [b] Determined by GC.
tected by GC (alkenes/alkane ratio is 92:8 for 2-Ph and coordination, probing the greater affinity of P,SR ligands
78:22 for 2-tBu). Compared to other hydrogenation systems for the heavier metal. The same solution is obtained
for the selective transformation of alkynes into alkenes, whether the P,SR ligand is initially bonded to Rh or Ir,
these systems perform rather poorly.[68–75]
indicating a high lability for such systems.
Furthermore, the stereoselectivity of the reaction, espe-
Complexes 2-R catalyse the hydrogenation of diphenyla-
cially with compound 2-tBu, is also quite poor (cis-stilbene/ cetylene at room temperature, paving the way to the appli-
trans-stilbene ratio is 91:9 for 2-Ph and 82:18 for 2-tBu). cation of such complexes to other hydrogenation reactions.
The presence of (E)-alkenes after hydrogenation of alkynes Our particular attention is devoted to asymmetric hydro-
is commonly explained by the isomerisation of (Z)-alkenes, genation, taking advantage of the availability of the chiral
which are the primary products arising from the syn-ad- ligands 1-R in optically pure form. Further studies in this
dition of H2 to the C–C triple bonds.[76–78] In order to de- direction are currently in progress in our laboratories.
termine whether similar reasons are involved in our system,
we carried out the reaction of cis-stilbene with dihydrogen
Experimental Section
in presence of complexes 2-Ph or 2-tBu under the same con-
ditions described in Table 6 for diphenylacetylene. Isomeris-
ation to trans-stilbene as well as hydrogenation to 1,2-di-
phenylethane did occur, although the rate of this transfor-
mation was slower than the direct formation of these two
products from diphenylacetylene. This result suggests that
the isomerization and further hydrogenation processes
probably occur mostly from the vinyl intermediate, before
the primary cis-stilbene product is formed by reductive eli-
mination. However, recoordination of the cis-stilbene fol-
lowed by both isomerization and further hydrogenation are
also possible.
General: All reactions were carried out under an argon using stan-
dard Schlenk techniques. Solvents were carefully dried by conven-
tional methods and distilled under argon before use. The (R/S)-2-
diphenylphosphanyl-(R-thiomethyl)ferrocene ligands (1-R, R = Et,
tBu, Ph) were prepared according to a published procedure[56] from
racemic 2-(diphenylthiophosphanylferrocenyl)methanol.[79] NMR
spectra were recorded with Bruker AC200 and Bruker Avance 500
FT-NMR spectrometers. The resonances were calibrated relative to
the residual solvent peaks and are reported with positive values
downfield from TMS. The NMR spectra of the new compounds 2-
R (R = Et, tBu, Ph) are collected in Table 1.
Synthesis of [IrCl(COD)(P,SEt)] (2-Et): In a Schlenk tube, under
argon, ligand 1-Et (69 mg, 0.155 mmol) was dissolved in dichloro-
methane (3 mL) and [Ir(COD)Cl]2 (52 mg, 0.077 mmol) was added.
After 1 h of stirring, the addition of pentane (10 mL) yielded a
yellow precipitate, which was filtered off to give [IrCl(COD)(P,SEt)]
(104 g, 86% yield). C33H37ClFeIrPS (780.21): calcd. C 50.80, H
4.78; found C 50.64, H 5.05.
Conclusion
The use of the ferrocenyl phosphane–thioether ligands 1-
R (R = Et, Ph, tBu) has allowed to reveal that the coordina-
tion geometry of chlorocyclooctadieneiridium() ligand ad-
ducts, both in the solid state and in solution, is delicately
controlled by the nature of the R substituent, yielding five-
coordinate complexes 2-R for R = Et, Ph and a four-coordi-
nate one for R = tBu, the latter featuring a dangling thio-
ether group. The ligand chirality controls the geometry at
the sulfur and iridium atoms, producing single dia-
stereomers.
Synthesis of IrCl(COD)(P,StBu) (2-tBu): In a Schlenk tube, under
nitrogen, ligand 1-tBu (272 mg, 0.576 mmol) was dissolved in
dichloromethane (3 mL) and [Ir(COD)Cl]2 (193 mg, 0.288 mmol)
was added. The solution was stirred for 2 h at room temperature
and 10 mL of hexane was the added to form a yellow precipitate.
The precipitate was filtered off under nitrogen and washed with
hexane, to give [IrCl(COD)(P,StBu)] (416 mg, 89% yield).
C35H41ClFeIrPS·CH2Cl2 (893.13): calcd. C 48.41, H 4.85; found C
48.62, H 4.70. The presence of dichloromethane was evident from
The solid state geometries appear to be maintained in
solution. However, complex equilibria between various the NMR spectrum recorded on a solution of the single crystals.
1H NMR (500 MHz, [D8]toluene: δ = 8.33 (dd, JHH = 10 Hz, JHP
structures are established. The chloride ligand is loosely
= 12 Hz, 2 H, Ph), 7.38 (dd, JHH = 10 Hz, JHP = 12 Hz, 2 H, Ph),
bound to iridium in the five-coordinate complexes 2-R,
7.19 (m, 2 H, Ph), 7.17 (m, 1 H, Ph), 6.97 (m, 2 H, Ph), 6.95 (m,
leading to its scavenging by excess metal complex and to a
1 H, Ph), 4.67 (s, sCp), 4.58 (d, JHH = 13 Hz, 1 H, CH2), 4.24 (d,
rapid equilibration between the complexes 2-R and ionic
JHH = 13 Hz, 1 H, CH2), 4.18 (s, sCp), 4.16 (s, 5 H, Cp), 4.13 (t,
[Ir(COD)(κ2-P,SR)]+[Ir(COD)Cl2]– (3-R). Salt-like com-
JHH = 2 Hz, sCp), 3.88 (br., COD), 2.30 (m, COD), 2.08 (m, COD),
pounds of type [Ir(COD)(k2-L-LЈ)][Ir(COD)X2]– have not
1.65 (m, COD), 1.49 (m, COD), 1.44 (s, 9 H, tBu) ppm. 13C NMR
been structurally characterized previously for any L-LЈ or
X, though they are quite common for the Rh congener.
Furthermore, competitive coordination reactions between
(500 MHz, [D8]toluene): δ = 136.05 (d, JCP = 12 Hz, 2 C, Ph),
135.0 (d, JCP = 50 Hz, quat. Ph), 133.70 (d, JCP = 12 Hz, 2 C, Ph),
133.4 (d, JCP = 50 Hz, quat. Ph), 130.00 (d, JCP = 3 Hz, 1 C, Ph),
rhodium and iridium for ligand 1-Ph lead only to iridium 129.05 (d, Ph, JCP = 2 Hz, 1 C), 127.40 (d, JCP = 6 Hz, 2 C, Ph),
Eur. J. Inorg. Chem. 2006, 1803–1816
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1813

E. Manoury et al.
FULL PAPER
Table 7. Crystal data and structure refinement for all compounds.
Identification code
2-Et
2-Ph
2-tBu
3-Ph
Empirical formula
Formula weight
Temperature [K]
Wavelength [Å]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C33H37ClFeIrPS·CH2Cl2
865.08
180(2)
0.71073
monoclinic
P21
11.6753(13)
10.9974(9)
12.7284(13)
90.0
100.717(13)
90.0
1605.8(3)
2
1.789
C37H37ClFeIrPS·CH2Cl2
913.12
180(2)
0.71073
triclinic
¯
P1
10.177(5)
12.983(5)
13.676(5)
102.045(5)
93.653(5)
102.670(5)
1712.8(12)
2
1.771
4.674
904
0.20 × 0.12 × 0.055
3.30 to 32.05
18279
C35H41ClFeIrPS·CH2Cl2
893.13
115(2)
0.71073
orthorhombic
Pbca
14.778(5)
19.216(6)
24.110(8).
90.0
90.0
90.0
C45H49Cl2FeIr2PS·(C7H8)0.5
1210.09
105(2)
0.71073
triclinic
¯
P1
10.1650(8)
13.4775(11)
16.7698(13)
81.296(2)
72.575(2)
78.406(2)
2137.1(3)
2
1.881
6.792
1178
0.22 × 0.19 × 0.07
2.10 to 28.32
22207
γ [°]
Volume [Å]3
Z
6847(4)
8
1.733
4.675
Density (calcd) [Mg/m3]
Absorption coefficient [mm–1
F(000)
]
4.980
856
0.22 × 0.17 × 0.01
2.17 to 26.14
12676
3552
Crystal size [mm3]
Theta range [°]
Reflections collected
0.35 × 0.12 × 0.03
1.93 to 28.40°.
66063
Independent reflections [R(int)]
Completeness [%]
6263 (0.0500)
98.5
10876 (0.0311)
90.3
8540 (0.0483)
99.2
10541 (0.0312)
98.8
Absorption correction
Max., min. transmission
Refinement method
multi-scan
0.6451 and 0.5709
F2
analytical
0.64910 and 0.24012
F2
SADABS
1.000 and 0.724635
F2
SADABS
1.0 and 0.812
F2
Data:restraints:parameters
Goodness-of-fit on F2
Final R indices [I Ͼ 2σ(I)]
6263/395/372
0.967
10876/0/406
0.914
R1 = 0.0304,
wR2 = 0.0494
R1 = 0.0415,
wR2 = 0.0516
8540/0/391
1.031
R1 = 0.0241,
wR2 = 0.0534
R1 = 0.0335
wR2 = 0.0569
10541/55/498
1.041
R1 = 0.0358, wR2 = 0.0815
R1 = 0.0326,
wR2 = 0.0682
R1 = 0.0437,
wR2 = 0.0714
0.571(7)
R indices (all data)
R1 = 0.0456, wR2 = 0.0855
4.945 and –1.048
Absolute structure parameter
Largest diff. peak and hole [e·Å–3
]
1.141 and –0.817
2.188 and –1.362
1.831 and –0.749
126.95 (d, JCP = 10 Hz, 2 C, Ph), 91.02 (d, JCP = 16 Hz, quat. Cp),
74.8 (d, JCP = 50 Hz, quat. Cp), 74.42 (d, JCP = 6 Hz, 1 C, sCp),
treated as riding models. As indicated by the refinement of the
Flack’s parameter,[82] compound 2-Et is twinned by inversion (“ra-
cemic twin”). In compound 3 a toluene solvent molecule is statistic-
71.37 (s, Cp), 71.24 (d, JCP = 7.4 Hz, 1 C, sCp), 69.7 (d, JCP
=
6.5 Hz, 1 C, sCp), 52 (COD), 43.05 [s, S-C (CH3)]. 30.75 (COD), ally disordered around an inversion center. The drawing of the
32.72 (COD), 30.7 [s, S-C(CH3)], 29.1 (s, CH2) ppm. 31P NMR molecules was realised with the help of ORTEP32.[83] Crystal data
(500 MHz, [D8]toluene): δ = 11.8 ppm.
and refinement parameters are shown in Table 7.
CCDC-283190 to -283193 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Synthesis of IrCl(COD)(P,SPh) (2-Ph): In a Schlenk tube, under
nitrogen, ligand 1-Ph (240 mg, 0.488 mmol) was dissolved in
dichloromethane (4 mL) and solid [Ir(COD)Cl]2 (163 mg,
0.244 mmol) was subsequently added. After 10 min of stirring, a
yellow precipitate was formed. Hexane (10 mL) was added to com-
plete the precipitation and the yellow solid was filtered off to yield
[IrCl(COD)(P,SPh)] (347 g, 86% yield). C37H37ClFeIrPS·CH2Cl2
(913.12): calcd. C 53.66, H 4.50; found C 53.83, H 4.53.
Supporting Information (see also the footnote on the first page of
this article): Procedures for fitting the equilibrium constant of
Equation (1) to the experimental NMR spectroscopic data (Ir/1-
Ph and Ir/1-tBu systems).
X-ray Crystallography: Yellow single crystals of complexes 2-R
(R = Et, tBu, Ph) were obtained by slow diffusion of light hydro-
carbon vapors (pentane for Et, hexane for tBu and Ph) into a
CH2Cl2 solution. Diffusion of hexane vapors into a toluene solu-
tion of 2-Ph gave yellow crystals of compound 3-Ph. A single crys-
tal of each compound was mounted under inert perfluoropolyether
on the tip of glass fibre and cooled in the cryostream of either an
Oxford-Diffraction XCALIBUR CCD diffractometer for 2-Ph, a
Stoe IPDS diffractometer for 2Et or a Bruker SMART CCD dif-
fractometer for 2-tBu and 3. Data were collected using the mono-
chromatic MoKα radiation (λ = 0.71073). The structures were
solved by direct methods (SIR97)[80] and refined by least-squares
procedures on F2 using SHELXL-97.[81] All H atoms attached to
carbon were introduced in calculation in idealised positions and
Acknowledgments
We are grateful to the EPSRC, the CNRS, and the European Union
for funding under the Hydrochem network (contract HPRN-CT-
2002-00176).
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1814
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Eur. J. Inorg. Chem. 2006, 1803–1816

Chlorocyclooctadieneiridium()–Ferrocenylphosphane–Thioether Ligand Adducts
FULL PAPER
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