Rhodium(III) and iridium(III) complexes with quinolyl-functionalized Cp ligands: Synthesis and catalytic hydrogenation activity

Article abstract of DOI:10.1002/ejic.200800217

Bis(ethene) complexes of rhodium(I) and iridium(I) with 8-quinolylcyclopentadienyl ligands (Cp^Q and Cp^Q*) were oxidized by a photochemically induced reaction with chlorine-containing solvents or by treatment with iodine. Upon this oxidation, the quinoline ring rotates and the N donor coordinates to the metal centers. Substitution of the halogenido ligands through acetato groups leads to highly soluble derivatives, in which the acetate moiety acts as a monodentate or bidentate ligand. The new Rh complexes were evaluated as catalysts for the hydrogenation of 1-hexene. The coordinatively saturated complexes show hydrogenation activity without the necessity of external bases. The catalytic activity is highest for the cationic complex [Cp^Q*Rh(O₂CCH₃)] ⁺PF₆^- (6b), which contains a bidentate acetato ligand. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejic.200800217

FULL PAPER
DOI: 10.1002/ejic.200800217
Rhodium(III) and Iridium(III) Complexes with Quinolyl-Functionalized Cp
Ligands: Synthesis and Catalytic Hydrogenation Activity
Gerald Kohl,[a] Hans Pritzkow,[a] and Markus Enders*[a]
Keywords: Rhodium / Iridium / Hemilabile ligands / Hydrogenation
Bis(ethene) complexes of rhodium(I) and iridium(I) with 8-
quinolylcyclopentadienyl ligands (CpQ and CpQ*) were oxid-
ized by a photochemically induced reaction with chlorine-
containing solvents or by treatment with iodine. Upon this
oxidation, the quinoline ring rotates and the N donor coordi-
nates to the metal centers. Substitution of the halogenido li-
gands through acetato groups leads to highly soluble deriva-
tives, in which the acetate moiety acts as a monodentate or
bidentate ligand. The new Rh complexes were evaluated as
catalysts for the hydrogenation of 1-hexene. The coordina-
tively saturated complexes show hydrogenation activity
without the necessity of external bases. The catalytic activity
is highest for the cationic complex [CpQ*Rh(O2CCH3)]+PF6
–
(6b), which contains a bidentate acetato ligand.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
activity of several RhIII complexes with 8-quinolylcyclopen-
tadienyl ligands that are coordinatively saturated due to the
intramolecular coordination of the 8-quinolyl unit.
Introduction
Cyclopentadienyl ligands with an attached neutral het-
eroatom donor were studied intensely in the past years due
to their ability to modify significantly the properties of
metal complexes relative to their analogues with conven-
tional cyclopentadienyl ligands.[1] In most cases, the Cp
moiety binds strongly to metals and, depending on the elec-
tronic and steric demand of the metal center, the donor
function may coordinate strongly or weakly. In the latter
case, the hemilabile ligand behavior can lead to reversible
protection of a reactive, vacant coordination site so that
the coordination and transformation of other molecules is
possible.[2] We have incorporated a C2 spacer as well as an
sp2 nitrogen atom into a rigid heterocycle by using quinolyl-
functionalized Cp ligands. Their predefined geometry al-
lows the coordination of the nitrogen atom to the cyclopen-
tadienyl-bonded metal center. As expected, hard metal cen-
ters in high oxidation states are strongly bound by the N
donor, whereas a much weaker or even no coordination is
observed for metal atoms in low oxidation states.[3] We
showed that coordinatively unsaturated CpRhI and CpIrI
complexes are stabilized by hemilabile 8-quinolylcyclopen-
tadienyl ligands and that such systems are catalysts for C–
H activation.[4] It is well known that CpRh and CpIr com-
plexes with the metal atoms in oxidation state +III are cata-
lytically active in the hydrogenation of α-olefins.[5] Most of
such compounds are dimeric and dissociation opens a vac-
ant coordination site that is necessary for their catalytic ac-
tivity. In this work we evaluated the catalytic hydrogenation
Results and Discussion
Recently we reported the synthesis of bis(η2-ethene)
complexes of rhodium(I) and iridium(I) with 8-quinolyl-
functionalized Cp ligands (1a–d, Scheme 1).[4] Dissolved in
aromatic or aliphatic solvents, these complexes lose one eth-
ene ligand upon irradiation with visible light. The resulting
mono-η2-ethene complexes are stabilized by coordination
of the hemilabile quinoline moiety. This interaction is very
weak, leading to high reactivity of the complexes. Deriva-
tives 2b–d react with aliphatic or aromatic solvents and H/
H (or H/D) exchange is catalyzed.[4] For this process an
oxidative addition of the solvent molecule is most probable.
However, we have not been able to isolate or identify such
a species.
When the irradiation of complexes 1a–d is performed in
the presence of Si(CH3)3Cl or in solvents like CHCl3 or
CH2Cl2, the metal centers are oxidized leading to
dichlorido RhIII (IrIII) derivatives 3a–d. The use of I2 as an
oxidation agent leads to the diiodido derivatives 4a–d.[6]
Whereas the interaction of the relatively hard N donor
with the electron rich d8-metal centers in 2a–d is very weak,
the N–M bonding is reinforced upon oxidation of the metal
atoms, leading to very stable compounds. In contrast to tet-
ramethyl-substituted compounds 3b/d and 4b/d, derivatives
3a/c and 4a/c are only sparingly soluble in common organic
solvents. In the 1H NMR spectra of the rhodium com-
plexes, the H2 proton, which is in the neighborhood of the
nitrogen atom, is observed with an additional coupling to
[a] Anorganisch-Chemisches Institut, Universität Heidelberg,
Im Neuenheimer Feld 270
Fax: +49-0-6221-541616247
E-mail: markus.enders@uni-hd.de
4230
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 4230–4235

RhIII and IrIII Complexes with Quinolyl-Functionalized Cp Ligands
shorter than the other Rh–C bonds, showing that the metal
atom is not centered below the five-membered ring but
slightly shifted towards the heterocycle.
The halogenido ligands in 3b and 4b can be substituted
by acetate groups upon reaction with silver acetate. This
substitution occurs while maintaining the coordination of
the nitrogen atom to the metal center. The introduction of
the acetato ligands has a great influence on the properties
of the metal complexes that is most obvious in the increased
solubility of the complexes in organic solvents like chloro-
form, dichloromethane or toluene. Compounds 5a and 5b
are even soluble in water (Scheme 2).
Scheme 1. Preparation of the rhodium(III) and iridium(III) com-
plexes.
Scheme 2. Preparation of (acetato)rhodium complexes 5a and 5b.
the 103Rh center [3J(Rh,H) = 1.7 Hz]. This coupling proves
the N–Rh coordination in solution.
The IR spectra of the acetato complexes display intense
Crystals from 3a suitable for X-ray analysis were ob- absorptions for the asymmetric valence vibrations of the
tained from a solution of 1a in chloroform that was irradi- carboxyl groups at 1616 (5a) and 1624 (5b) cm–1. The
ated with visible light (Figure 1). Due to the low solubility νsym(CO2) bonds are detected between 1309 and 1366 cm–1.
of related iodido complex 4a, crystallization of this com- This pattern is characteristic for monodentate carboxylato
pound was not possible, whereas crystals of tetramethyl de- ligands.[7] The Rh–N interaction in 5a and 5b is retained in
rivative 4b grew easily from a chloroform solution at room solution, as can be concluded from the Rh–H coupling in
1
temperature.
the H NMR spectra [3J(Rh,H) = 1.5 Hz].
X-ray analyses established the coordination of the nitro-
Crystals of 5b suitable for X-ray analysis could be ob-
gen atoms to the metal centers. The Rh–N distance does tained by concentrating a dichloromethane solution of the
not change significantly from dichlorido to diiodido com- complex (Figure 2). Due to the weaker bonding of the acet-
plexes [3b: 2.113(7) Å,[3f] 4b: 2.111(3) Å] but depends on the ato ligands, the Rh–N distance in 5b [2.079(2) Å] is shorter
substitution at the Cp ring [3a: 2.089(1) Å]. This can be by 0.03 Å than that in iodo complex 4b. In the same way,
explained by the difference in electron density at the metal the distances of the central metal to the carbon atoms of
center caused by the additional methyl groups on the Cp the five-membered ring are shorter than those in 4b. The
ring. The better donating ability of the tetramethyl Cp li- Rh–O bond lengths [2.104(2) and 2.098(2) Å, respectively]
gand leads to a somewhat weaker Rh–N interaction in 3b do not vary significantly from those in (C5Me5)Rh-
relative to that in 3a. The Rh–C10 distance is significantly (PMe3)(CH3COO)2 (Table 1).[7]
Figure 1. Solid-state molecular structure of 3a (left) and 4b (right).
Eur. J. Inorg. Chem. 2008, 4230–4235
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4231

G. Kohl, H. Pritzkow, M. Enders
FULL PAPER
genation catalyst upon the addition of a base (e.g., Et3N).
More recently, a detailed kinetic investigation by Finke and
Maitlis et al. proved that under mild conditions [Cp*RhCl2]2
is a homogeneous catalyst, whereas more drastic conditions
slowly lead to the formation of highly active Rh0 nano-
particles that are able to catalyze the hydrogenation of ben-
zene.[10]
The compounds described in this work are monomers
due to the intramolecular N coordination. This coordina-
tion leads to a higher stability of the complexes. Under mild
hydrogenation conditions, the formation of Rh0 species is
very unfavorable. We therefore studied their potential as hy-
drogenation catalysts at 40 °C, 5 bar H2 pressure within 2 h
reaction time. Rhodium complexes 3a, 4a, 4b, 5a, 5b, and
6b, as well as the previously described cluster 7,[3g] were
evaluated in the hydrogenation of 1-hexene. At the end of
the hydrogenation reaction, all volatiles were transferred
under reduced vacuum for analysis. Mass spectral analysis
of the residue showed the presence of starting material.
Figure 2. Solid-state molecular structure of 5b.
Table 1. Selected bond lengths [Å] and angles [°] for 3a, 4b, and 5b.
3a (X = Cl)
4b (X = I)
5b (X = OAc)
Rh–N
Rh–X1
Rh–X2
2.089(1)
2.396(1)
2.377(1)
2.084(2)
2.128(2)
2.190(2)
2.177(2)
2.117(2)
89.7(1)
2.111(3)
2.705(1)
2.704(1)
2.079(4)
2.152(4)
2.197(4)
2.207(4)
2.138(4)
92.6(1)
2.079(2)
2.104(2)
2.098(2)
2.067(2)
2.114(2)
2.177(2)
2.177(2)
2.123(2)
96.1(1)
Rh–C10
Rh–C11
Rh–C12
Rh–C13
Rh–C14
N–Rh–X1
N–Rh–X2
X1–Rh–X2
C2–N–Rh
91.3(1)
89.4(1)
113.3(1)
92.8(1)
93.7(1)
113.1(3)
93.4(1)
79.2(1)
113.1(1)
Finally, the reaction of 5b with KPF6 leads to the forma-
tion of η2-acetato[η5-2,3,4,5-tetramethyl-(8-quinolyl)yclop-
entadienyl]rhodium(III) (6b), as described for related com-
plexes.[7] The chelating coordination of the carboxylato
group is clearly shown by the IR spectrum, in which the
intense absorptions of the monodentate carboxylato ligands
are absent (Scheme 3).
The analysis of the reaction products was performed by
GC and GC–MS measurements. The results are listed in
Table 2. All complexes show activity in the hydrogenation
of 1-hexene. Beside the hydrogenation of the terminal ole-
fin, a rearrangement to an internal olefin is catalyzed by
the complexes. The highest activity in the catalytic hydro-
genation reaction was found in the case of monoacetato
complex 6b. This compound also shows the lowest amount
of the rearrangement product 2-hexene. This is probably
due to the bidentate coordination mode of the acetato li-
gand, which allows the generation of a free coordination
site without the decoordination of a ligand. With cluster 7,
Scheme 3. Synthesis of monoacetato compound 6b.
Catalytic Hydrogenation of 1-Hexene
Rhodium complexes play an important role as catalysts the rearrangement reaction of the terminal olefin to 2-hex-
in the hydrogenation of olefinic and aromatic substrates. ene dominates. This is probably due to a competitive re-
The first and most famous example is the well-studied Wil- arrangement reaction at the Rh centers within the Rh6 clus-
kinson catalyst [Rh{P(C6H5)3}3Cl].[8,9] The complex ter. Halogenido complexes 3a and 4a show very low solubil-
[Cp*RhCl2]2 was synthesized and studied by Maitlis et al.[5] ity in thf. Therefore, complete homogeneous reaction condi-
They showed that this compound becomes an active hydro- tions could not be achieved and their activities were found
4232
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Eur. J. Inorg. Chem. 2008, 4230–4235

RhIII and IrIII Complexes with Quinolyl-Functionalized Cp Ligands
3J(H,H) = 7.3 Hz, H6], 7.84 [dd, 3J(H,H) = 7.3 Hz, 4J(H,H) =
1.2 Hz, 1 H, H5 or H7], 7.96 [dd, 3J(H,H) = 8.1 Hz, 4J(H,H) =
to be the lowest of all tested compounds. However, a related
donor-functionalized cyclopentadienyl rhodium(III) com-
plex is described in the literature to be completely inac-
tive.[11]
1.3 Hz, 1 H, H5 or H7], 8.34 [dd, J(H4,H3) = 8.5 Hz, J(H4,H2) =
1.5 Hz, H4], 8.66 [dt, 3J(H2,H3) = 5.0 Hz, 4J(H2,H4) = 1.6,
3J(H,Rh) = 1.6 Hz, H2] ppm. MS (FAB+): m/z (%) = 330 (100)
[M – Cl]+, 295 (68) [M – 2 Cl]+. C14H10NRhCl2 (366.05): calcd. C
45.94, H 2.75, N 3.83, Cl 19.37; found C 45.65, H 2.87, N 3.82, Cl
19.33.
3
4
Table 2. Results of the hydrogenation reaction of 1-hexene with the
quinolyl-substituted complexes as catalysts.[a]
Catalyst
Amount
[mg] (mmol)
GC analysis [%][b]
[η5-2,3,4,5-Tetramethyl-1-(8-quinolyl)cyclopentadienyl]dichloridorho-
dium(III) (3b): A procedure analogous to that used for the synthesis
of 3a. Compound 1b (130 mg, 0.3 mmol) in CHCl3 (20 mL) af-
forded 3b (90 mg, 0.21 mmol, 71%) after 4 d of irradiation as a red
solid. 1H NMR (CDCl3): δ = 1.69 (s, 6 H, CH3), 1.86 (s, 6 H, CH3),
7.54 [dd, 3J(H3,H2) = 5.0 Hz, 4J(H3,H4) = 8.5 Hz, 1 H, H3], 7.73
[dd, 3J(H,H) = 7.6 Hz, 3J(H,H) = 7.1 Hz, 1 H, H6], 7.80 [dd,
3J(H,H) = 7.1 Hz, 4J(H,H) = 1.9 Hz, 1 H, H5 or H7], 7.97 [dd,
3J(H,H) = 7.6 Hz, 4J(H,H) = 1.7 Hz, 1 H, H5 or H7], 8.33 [dd,
hexane
1-hexene
2-hexene
3a
4a
4b
5a
5b
6b
7
8.2 (0.02)
11.2 (0.02)
12.0 (0.02)
6.6 (0.02)
9.3 (0.02)
8.2 (0.01)
37.7 (0.03)
9.0
91.0
90.0
62.7
41.9
29.2
44.1
26.6
–
–
10.1
26.6
32.9
4.6
10.0
27.1
31.5
37.9
51.3
13.2
60.2
[a] Solvent thf; no added base; glass autoclave pressurized with
5 bar H2; 40 °C; 2 h reaction time. [b] Peak area of flame ionization
detector.
4
3
3J(H4,H3) = 8.5 Hz, J(H4,H2) = 1.7 Hz, 1 H], 8.68 [dt, J(H2,H3)
= 4.9 Hz, J(H2,H4) = 1.7 Hz, J(H,Rh) = 1.7 Hz, 1 H, H2] ppm.
13C NMR (CDCl3): δ = 8.8, 9.2 (CH3); 89.5 [d, 1J(Rh,C) = 9.1 Hz,
quart. CCp]; 98.4 [d, 1J(Rh,C) = 6.6 Hz, quart. CCp]; 107.2 [d,
1J(Rh,C) = 9.1 Hz, quart. CCp]; 124.2, 127.8, 129.0, 131.0, 137.8,
154.6 (CHquinoline); 128.3, 129.7, 157.9 (quart. Cquinoline) ppm. MS
(EI): m/z (%) = 421 (1) [M]+, 386 (3) [M – Cl]+, 350 (3) [M –
Cl – HCl]+, 36 (100) [HCl]+, 35 (17) [Cl]+. HRMS (EI): calcd. for
4
3
Conclusions
8-Quinolylcyclopentadienyl ligands are ideally suited for
chelating coordination to RhIII and IrIII centers. The new
complexes are readily obtained by oxidation of the corre-
sponding RhI and IrI compounds. Preliminary hydrogena-
tion experiments show that all complexes are active in the
hydrogenation of 1-hexene. However, all studied com-
pounds also catalyze, to some extent, the isomerization of
C
18H18NRh35Cl2 420.98712; found 420.98622. C18H18NRhCl2
(422.16).
[η5-(8-Quinolyl)cyclopentadienyl]dichloridoiridium(III) (3c): A pro-
cedure analogous to that used for the synthesis of 3a. Compound
1c (20 mg, 0.045 mmol) in CHCl3 (10 mL) afforded 3c (21 mg,
1-hexene into internal hexenes. In comparison to the well- 0.045 mmol, 100%) after 3 d of irradiation as an orange-brown so-
1
lid. H NMR (CDCl3): δ = 5.77 (pt, 2 H, Cp-CH), 6.13 (pt, 2 H,
studied [Cp*RhCl2]2 complex, there is no need for the ad-
dition of an external base. The best complex in this study
is the acetato derivative 6b.
Cp-CH), 7.60–7.71 (m, 2 H, Hquinoline), 7.87–7.95 (m, 2 H,
H
quinoline), 8.38 [dd, 3J(H,H) = 8.3 Hz, 4J(H,H) = 1.4 Hz, 1 H, H4],
8.96 [dd, 3J(H2,H3) = 5.1 Hz, 4J(H2,H4) = 1.5 Hz, H2] ppm. MS
(FAB+): m/z (%) = 455 (27) [M]+, 420 (100) [M – Cl]+, 384 (24)
[M – Cl – HCl]+. HRMS (EI): calcd. for C14H10N193Ir35Cl2
454.9820; found 454.9811. C14H10NIrCl2 (455.37).
Experimental Section
All experiments were carried out under an atmosphere of dry ar-
gon. Solvents were dried by using standard procedures and distilled
prior to use. Complexes 1a–d were prepared according to literature
procedures.[4] All other reagents were used as purchased. NMR
spectroscopy was performed with a Bruker DRX 200 (200.13 MHz
for 1H, 50.32 MHz for 13C) instrument; 1H NMR spectra were cal-
ibrated by using signals of residual protons from the solvent refer-
[η5-2,3,4,5-Tetramethyl-1-(8-quinolyl)cyclopentadienyl]dichloridoiri-
dium(III) (3d): A procedure analogous to that used for the synthesis
of 3a. Compound 1d (30 mg, 0.06 mmol) in CHCl3 (15 mL) af-
forded 3d (30 mg, 0.06 mmol, 98%) as a orange-brown solid. 1H
NMR (CDCl3): δ = 1.64 (s, 6 H, CH3), 1.69 (s, 6 H, CH3), 7.57
[dd, 3J(H3,H2) = 5.1 Hz, 3J(H3,H4) = 8.5 Hz, 1 H, H3], 7.69 [dd,
3J(H,H) = 7.3 Hz, J(H,H) = 7.9 Hz, H6], 7.83–7.93 (m, 2 H, H5
3
1
enced to SiMe4. The numbering of the assigned H NMR signals
and H7), 8.35 [dd, J(H,H) = 8.5 Hz, J(H,H) = 1.5 Hz, 1 H, H4],
3
4
of the quinoline moiety starts with H2 for the position next to the
N atom. The 13C spectral chemical shifts are reported relative to
the 13C solvent signals (referenced to SiMe4). No useful 13C data
were obtained for the a and c derivatives due to the very-low solu-
bility of the complexes. MS was recorded with a Jeol JMS-700 and
VG ZAB-2F.
9.00 [dd, J(H2,H3) = 5.1 Hz, J(H2,H4) = 1.5 Hz, 1 H, H2] ppm.
3
4
C18H18NIrCl2 (511.47).
[η5-(8-Quinolyl)cyclopentadienyl]diiodidorhodium(III) (4a): I2
(354 mg, 1.40 mmol) was added to a solution of 1a (490 mg,
1.40 mmol) in toluene (20 mL). The reaction mixture was stirred
overnight, and the precipitated solid was recovered by filtration,
washed with toluene followed by hexane, and dried in vacuo. Yield:
717 mg (1.31 mmol, 94 %) as a dark-red powder. 1H NMR
(CDCl3): δ = 5.84 (pt, 2 H, Cp-CH), 5.97 (m, 2 H, Cp-CH), 7.46
[dd, 3J(H3,H2) = 5.2 Hz, 3J(H3,H4) = 8.4 Hz, 1 H, H3], 7.67 [dd,
3J(H,H) = 7.9 Hz, 3J(H,H) = 7.3 Hz, H6], 7.83 [dd, 3J(H,H) =
7.3 Hz, 4J(H,H) = 1.4 Hz, 1 H, H5 or H7], 7.89 [dd, 3J(H,H) =
[η5-(8-Quinolyl)cyclopentadienyl]dichloridorhodium(III) (3a): In a
Pyrex glass Schlenk tube a solution of 1a (100 mg) in CHCl3 or
CH2Cl2 (15 mL) was irradiated for 4 d with the light of a 150-W
Hg high-pressure lamp. After evaporation of the solvent, 3a was
obtained as a dark-red solid (90 mg, 0.25 mmol, 88%). Alterna-
tively, to the photochemically induced oxidation of 1a by the sol-
vent, (CH3)3SiCl (2 equiv.) in a benzene or toluene solution can be
used as oxidant during light irradiation. In the latter case, the prod-
8.1 Hz, J(H,H) = 1.3 Hz, 1 H, H5 or H7], 8.28 [dd, 3J(H4,H3) =
4
uct precipitates due to its low solubility. 1H NMR (CDCl3): δ =
8.5 Hz, 4J(H4,H2) = 1.5 Hz, H4], 9.24 [dt, 3J(H2,H3) = 5.1 Hz,
5.77 (m, 2 H, Cp-CH), 5.92 (pt, 2 H, Cp-CH), 7.61 [dd, J(H3,H2) 4J(H2,H4) = 1.5 Hz, 3J(H,Rh) = 1.6 Hz, H2] ppm. MS (EI): m/z
3
= 5.0 Hz, 3J(H3,H4) = 8.4 Hz, 1 H, H3], 7.70 [dd, 3J(H,H) = 7.9 Hz,
(%) = 549 (56) [M]+, 422 (100) [M – I]+, 295 (97) [M – 2 I].
Eur. J. Inorg. Chem. 2008, 4230–4235
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G. Kohl, H. Pritzkow, M. Enders
FULL PAPER
C14H10I2NRh (548.95): calcd. C 30.63, H 1.84, N 2.55; found C
31.10, H 2.01, N 2.60.
4J(H4,H2) = 1.5 Hz, 1 H, H4] ppm. 13C NMR (CDCl3): δ = 23.6
[d, 3J(Rh,C) = 1.5 Hz, OOC-CH3]; 75.9 [d, 1J(Rh,C) = 8.6 Hz, Cp-
CH]; 86.1 [d, 1J(Rh,C) = 6.9 Hz, Cp-CH]; 110.3 [d, 1J(Rh,C) =
8.1 Hz, quart. CCp]; 123.7 [d, J(Rh,C) = 1.0 Hz], 128.0, 128.6,
130.7, 138.6, 151.1 (quinoline-CH); 129.3 [d, J(Rh,C) = 1.2 Hz],
130.2, 158.6 [d, J(Rh,C) = 0.7 Hz, quart. Cquinoline); 177.9 (OOC-
CH3) ppm. MS (FD): m/z (%) = 413 (60) [M]+, 354 (100) [M –
OOC-CH3]+. C18H16NO4Rh2 (413.23).
[η5-2,3,4,5-Tetramethyl-1-(8-quinolyl)cyclopentadienyl]diiodidorho-
dium(III) (4b): A solution of iodine (230 mg, 0.91 mmol) in pentane
(10 mL) was slowly added to a solution of 1b (360 mg, 0.88 mmol)
in pentane (20 mL). After 2 h the dark-red precipitate was filtered,
washed with pentane (2ϫ8 mL), and dried in vacuo. Yield: 450 mg
(0.74 mmol, 85%) as a dark-red powder. 1H NMR (CDCl3): δ =
2.01 (s, 6 H, CH3), 2.18 (s, 6 H, CH3), 7.40 [dd, 3J(H3,H2) = 5.0 Hz,
Diacetato[η5-2,3,4,5-tetramethyl-1-(8-quinolyl)cyclopentadienyl]rho-
3J(H3,H4) = 8.5 Hz, 1 H, H3], 7.71 [dd, 3J(H,H) = 7.7 Hz, 3J(H,H) dium(III) (5b): A procedure analogous to that used for the synthesis
3
4
= 7.1 Hz, 1 H, H6], 7.79 [dd, J(H,H) = 7.3 Hz, J(H,H) = 1.8 Hz,
of 5a. Compound 4b (290 mg, 0.48 mmol) in CH2Cl2 (20 mL) and
1 H, H5 or H7], 7.92 [dd, J(H,H) = 7.7 Hz, J(H,H) = 1.8 Hz, 1 silver acetate (160 mg, 0.96 mmol) afforded 5b (216 mg, 0.46 mmol,
3
4
H, H5 or H7], 8.26 [dd, J(H4,H3) = 8.3 Hz, J(H4,H2) = 1.5 Hz, 1 96%) as an orange solid. IR (thf): ν = 1309 (s), 1359 (s), 1590 (m),
3
4
˜
H, H4], 9.18 [dt, 3J(H2,H3) = 5.0 Hz, 4J(H2,H4) = 1.7 Hz, 1624 (s) cm–1. H NMR (CDCl3): δ = 1.60 (s, 6 H, CH3), 1.75 (s,
1
3J(H2,Rh) = 1.7 Hz, 1 H, H2] ppm. 13C NMR (CDCl3): δ = 10.7,
12.0 (Cp-CH3); 92.5 [d, 1J(Rh,C) = 8.2 Hz, quart. CCp]; 97.8 [d,
1J(Rh,C) = 6.0 Hz, quart. CCp]; 108.6 [d, 1J(Rh,C) = 8.2 Hz, quart.
6 H, CH3), 2.04 (s, 6 H, OOC-CH3), 7.45 [dd, 3J(H3,H2) = 5.0 Hz,
3J(H3,H4) = 8.5 Hz, 1 H, H3], 7.60–7.72 (m, 2 H, H6 and H5 or
H7), 7.90 [dd, 3J(H,H) = 7.5 Hz, 4J(H,H) = 2.0 Hz, 1 H, H5 or H7],
C
Cp]; 124.0, 127.6, 129.0, 130.9, 137.3, 158.8 (quinoline-CH); 128.6,
8.12 [dt, 3J(H2,H3) = 5.0 Hz, 4J(H2,H4) = 1.5 Hz, 3J(H,Rh) =
130.0, 158.7 (quart. Cquinoline) ppm. MS (EI): m/z (%) = 605 (4) 1.5 Hz, H2], 8.26 [dd, 3J(H4,H3) = 8.4 Hz, J(H4,H2) = 1.5 Hz, H4]
4
[M]+, 478 (100) [M – I]+, 350 (35) [M – I – HI]+, 175.5 (17) [M – ppm. 13C NMR (CDCl3): δ = 9.6, 9.8 (Cp-CH3); 24.9 [d, J(Rh,C)
3
2 I]2+. HRMS (EI): calcd. for C18H18INRh 477.95392; found
477.95687. C18H18I2NRh (605.06).
= 1.7 Hz, OOC-CH3]; 87.8 [d, 1J(Rh,C) = 10.2 Hz, quart. CCp];
97.8 [d, 1J(Rh,C) = 7.3 Hz, quart. CCp]; 105.4 [d, 1J(Rh,C) =
9.6 Hz, quart. CCp]; 123.5, 127.5, 128.8, 130.6, 137.8, 151.9 (quino-
line-CH); 129.8 (2 C), 157.9 (quart. Cquinoline), 177.1 (OOC-CH3)
ppm. MS (FD): m/z (%) = 469 (51) [M]+, 410 (100) [M – OOC-
CH3]+. C22H24NO4Rh (469.34).
[η5-(8-Quinolyl)cyclopentadienyl]diiodidoiridium(III) (4c): A pro-
cedure analogous to that used for the synthesis of 4a. Compound
1c (40 mg, 0.09 mmol) and iodine (25 mg, 0.10 mmol) afforded 4c
(56 mg, 0.088 mmol, 98%) as an orange solid. MS (EI): m/z (%) =
639 (13) [M]+, 512 (100) [M – I]+, 384 (29) [M – I – HI]+, 191 (24)
[M – 2 I – H – Ir]+. C14H10I2IrN (638.27): calcd. C 26.35, H 1.58,
N 2.19, I 39.77; found C 26.36, H 1.98, N 2.31, I 40.01.
η2-Acetato[η5-2,3,4,5-tetramethyl-1-(8-quinolyl)cyclopentadienyl]-
rhodium(III) Hexafluorophosphate (6b):
A solution of KPF6
(85 mg, 0.46 mmol) in water (10 mL) was added to 5b (108 mg,
0.23 mmol) dissolved in water (20 mL). After 2 h at room tempera-
ture the mixture was extracted with dichloromethane (2ϫ). After
the removal of the solvent in vacuo, 6b was obtained as a dark-
[η5-2,3,4,5-Tetramethyl-1-(8-quinolyl)cyclopentadienyl]diiodidoiridi-
um(III) (4d): A solution of iodine (57 mg, 0.22 mmol) in toluene
(5 mL) was added to a solution of 1d (111 mg, 0.22 mmol) in tolu-
ene (50 mL). After 2 h at room temperature, the product was pre-
cipitated by the addition of hexane (50 mL), separated by filtration,
washed twice with a few mL of hexane, and dried in vacuo. Yield:
148 mg (0.21 mmol, 95%) as a orange powder. 1H NMR (CDCl3):
yellow solid. Yield: 120 mg (0.22 mmol, 94%). IR (thf): ν = 1379
˜
(w), 1412 (w), 1466 (s), 1507 (m) cm–1. 1H NMR (CDCl3): δ = 1.50
(s, 6 H, CH3), 1.86 (s, 6 H, CH3), 2.15 (s, 3 H, OOC-CH3), 7.66–
3
3
7.77 (m, 2 H, H2 and H3), 7.85 [dd, J(H,H) = 7.2 Hz, J(H,H) =
8.2 Hz, 1 H, H6], 8.13 [dd, J(H,H) = 8.4 Hz, J(H,H) = 1.2 Hz, 1
H, H5 or H7], 8.19 [dd, 3J(H,H) = 7.2 Hz, 4J(H,H) = 1.2 Hz, H5
or H7], 8.62 [dd, 3J(H4,H2) = 8.0 Hz, 4J(H4,H3) = 2.0 Hz, H4] ppm.
13C NMR (CDCl3): δ = 9.2, 9.3 (Cp-CH3); 23.8 (OOC-CH3); 90.6
3
4
3
δ = 1.88 (s, 6 H, CH3), 2.10 (s, 6 H, CH3), 7.40 [dd, J(H3,H2) =
3
3
5.2 Hz, J(H3,H4) = 8.4 Hz, 1 H, H3], 7.69 [dd, J(H,H) = 6.7 Hz,
3J(H,H) = 8.5 Hz, 1 H, H6], 7.84–7.91 (m, 2 H, H5 and H7), 8.31
[dd, 3J(H4,H3) = 8.4 Hz, 4J(H4,H2) = 1.4 Hz, 1 H, H4], 9.52 [dd,
1
1
[d, J(Rh,C) = 10.2 Hz, quart. CCp]; 100.7 [d, J(Rh,C) = 7.3 Hz,
quart. CCp]; 106.2 [d, 1J(Rh,C) = 9.0 Hz, quart. CCp]; 123.5, 129.4,
130.0, 134.1, 140.9, 150.0 (quinoline-CH); 126.8, 130.4, 157.3
(quart. Cquinoline), 189.4 (OOC-CH3) ppm. 19F NMR (CDCl3): δ =
3J(H2,H3) = 5.2 Hz, J(H2,H4) = 1.4 Hz, 1 H, H2] ppm. 13C NMR
4
(CDCl3): δ = 9.9, 11.6 (Cp-CH3); 83.7, 90.8, 99.7 (quart. CCp);
124.9, 128.1, 128.8, 132.0, 137.1, 158.8 (quinoline-CH); 129.5,
130.3, 162.2 (quart. Cquinoline) ppm. MS (EI): m/z (%) = 695 (15)
[M]+, 568 (100) [M – I]+. HRMS (EI): calcd. for C18H18I2N193Ir
694.9158; found 694.9123. C18H18I2NIr (694.38).
–73.3 (d, PF6 ) ppm. 31P NMR (CDCl3): δ = –144.5 (sept., PF6 )
ppm. MS (FAB): m/z (%) = 410 (31) [M – PF6]+, 350 (100) [M –
CH3CO2H – PF6]+. C20H21F6NO2PRh (555.26).
–
–
Diacetato[η5-(8-quinolyl)cyclopentadienyl]rhodium(III) (5a): To a
suspension of 4a (117 mg, 0.35 mmol) in CH2Cl2 (20 mL) was
added silver acetate (117 mg, 0.70 mmol). The resulting mixture
was protected against light and stirred for 15 h. The precipitated
AgI was removed by filtration and washed with a few mL of
CH2Cl2. After evaporation of the solvent, the residue was extracted
with toluene (3ϫ). The toluene was evaporated, and product 5a
was obtained as an orange solid. Yield 113 mg (0.27 mmol, 76%).
General Procedure of the Catalytic Hydrogenation of 1-Hexene: The
metal complex and thf (5 mL) were placed into a glass autoclave. A
solution of 1-hexene (250 mg, 2.97 mmol) in thf (5 mL) was further
added, the autoclave was warmed to 40 °C in a water bath, and the
hydrogen pressure was raised to 5 bar. After 2 h of stirring, the
solution was cooled down to room temperature, and the pressure
in the autoclave was slowly released. The solution was separated
from the catalyst by condensation in vacuo and analyzed by GC
and GC–MS measurements. For quantification, the peak areas
from the FI detection were used. The results of the GC–MS mea-
surements are given in Table 2.
IR (CH Cl ): ν = 1310 (s), 1366 (s), 1593 (m), 1616 (s) cm–1. 1H
˜
2
2
NMR (CDCl3): δ = 2.10 (s, 6 H, OOC-CH3), 5.89–5.95 (m, 2 H,
Cp-CH), 6.02–6.08 (m, 2 H, Cp-CH), 7.53 [dd, 3J(H3,H2) = 5.0 Hz,
3J(H3,H4) = 8.4 Hz, 1 H, H3], 7.65 [dd, 3J(H,H) = 7.3 Hz, 3J(H,H)
3
4
= 7.9 Hz, 1 H, H6], 7.81 [dd, J(H,H) = 7.2 Hz, J(H,H) = 1.2 Hz,
Crystal-Structure Determination of 3a, 4b, and 5b: Crystal data of
1 H, H5 or H7], 7.90 [dd, J(H,H) = 8.0 Hz, J(H,H) = 1.2 Hz, 1 3a and 5b were collected with a Bruker AXS area detector SMART
3
4
H, H5 or H7], 8.15 [dt, 3J(H2,H3) = 5.1 Hz, 4J(H2,H4) = 1.5 Hz,
3J(H,Rh) = 1.5 Hz, 1 H, H2], 8.32 [dd, 3J(H4,H3) = 8.4 Hz,
1000 and that of 4b with a Siemens Stoe AED2 diffractometer
(Mo-Kα radiation, ω-scan). The structures were solved by direct
4234
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 4230–4235

RhIII and IrIII Complexes with Quinolyl-Functionalized Cp Ligands
Table 3. Crystal data and experimental details.
Compound
3a
4b
5b
Empirical formula
Formula weight
Crystal system
Space group
Unit cell dimensions:
a [Å]
C14H10Cl2NRh
366.04
Monoclinic
P21/n
C18H18I2NRh
605.04
Monoclinic
P2(1)/c
C22H24NO4Rh·CH2Cl2
554.26
Monoclinic
P21/c
8.4793(5)
13.6075(7)
10.421(5)
13.707(7)
8.6340(4)
14.2376(7)
b [Å]
c [Å]
α [°]
10.8672(6)
90
12.761(6)
90
19.0586(9)
90
β [°]
γ [°]
94.545(1)
90
1249.94(12)
4
1.945
1.771
720
0.41ϫ0.13ϫ0.09
190
2.40 to 32.04
–12 Յ h Յ 12
0 Յ k Յ 20
0 Յ l Յ 16
92.58(2)
90
1820.9(15)
4
2.207
4.325
1136
0.40ϫ0.40ϫ0.30
295
1.96 to 27.99
–13 Յ h Յ 13
0 Յ k Յ 18
0 Յ l Յ 16
100.968(1)
90
2300.0(2)
4
1.601
1.005
1128
0.42ϫ0.30ϫ0.08
173
1.80 to 28.32
–11 Յ h Յ 11
0 Յ k Յ 18
0 Յ l Յ 25
Volume [Å3]
Z
Density (calcd.) [gcm–3]
Absorption coefficient [mm–1]
F(000)
Crystal size [mm3]
Temperature [K]
θ range for data collection [°]
Index ranges
Reflections collected
11715
4392
15619
Independent reflections
Max. and min. transmission
Parameters
4149 [R(int) = 0.0258]
1.0000 and 0.7891
203
4388 [R(int) = 0.0057]
0.787 and 0.603
272
5550 [R(int) = 0.0270]
0.8312 and 0.7270
384
Goodness-of-fit on F2
Final R indices [IϾ2σ(I)]
R indices (all data)
1.059
1.009
1.020
R1 = 0.0241, wR2 = 0.0595
R1 = 0.0286, wR2 = 0.0628
1.231 and –0.317
R1 = 0.0280, wR2 = 0.0552
R1 = 0.0440, wR2 = 0.0592
0.828 and –0.548
R1 = 0.0282, wR2 = 0.0710
R1 = 0.0397, wR2 = 0.0750
0.688 and –0.510
Largest diff. peak and hole [eÅ–3]
methods and refined by full-matrix least-squares against F2 with
all reflections by using the SHELXTL program system.[12] All non-
hydrogen atoms were refined anisotropically. Hydrogen atoms were
located and refined isotropically. Crystal data and experimental de-
tails are listed in Table 3.[13]
ganomet. Chem. 2001, 622, 66–73; f) M. Enders, G. Kohl, H.
Pritzkow, Organometallics 2004, 23, 3832–3839; g) M. Enders,
G. Kohl, H. Pritzkow, J. Organomet. Chem. 2004, 689, 3024–
3030.
[4] G. Kohl, R. Rudolph, H. Pritzkow, M. Enders, Organometallics
2005, 24, 4774–4781.
[5] a) J. W. Kang, K. Moseley, P. M. Maitlis, J. Am. Chem. Soc.
1969, 91, 5970–5977; b) C. White, D. S. Gill, J. W. Kang, H. B.
Lee, P. M. Maitlis, J. Chem. Soc., Chem. Commun. 1971, 734–
735; c) M. J. Russell, C. White, P. M. Maitlis, J. Chem. Soc.,
Chem. Commun. 1977, 427–428; d) P. M. Maitlis, Acc. Chem.
Res. 1978, 11, 301–307; e) D. S. Gill, C. White, P. M. Maitlis,
J. Chem. Soc., Dalton Trans. 1978, 617–626.
Acknowledgments
This work was supported by the Deutsche Forschungsgemeinschaft
(SFB 623). The authors thank Degussa AG for donation of rhodi-
um(III)chloride. G. K. thanks the Landesgraduiertenförderung Ba-
den-Württemberg for a scholarship.
[6] P. Jutzi, M. O. Kirsten, B. Neumann, H.-G. Stammler, Organo-
metallics 1994, 13, 3854–3861.
[7] K. Isobe, P. M. Bailey, P. M. Maitlis, J. Chem. Soc., Dalton
Trans. 1981, 2003–2008.
[8] a) C. Elschenbroich, A. Salzer, Organometallchemie, Teubner,
Stuttgart, 1993, 3rd ed.; b) L. S. Hegedus, Organische Synthese
mit Übergangsmetallen, VCH, Weinheim, 1995, p. 81.
[9] J. A. Osborn, F. H. Jardine, J. F. Young, G. Wilkinson, J. Chem.
Soc. A 1966, 1711–1732.
[10] C. M. Hagen, J. A. Widegren, P. M. Maitlis, R. G. Finke, J.
Am. Chem. Soc. 2005, 127, 4423–4432.
[11] H. Adams, N. A. Bailey, M. Colley, P. A. Schofield, C. White,
J. Chem. Soc., Dalton Trans. 1994, 1445–1451.
[1] Review articles: a) J. Okuda, Commun. Inorg. Chem. 1994, 16,
185–205; b) P. Jutzi, U. Siemeling, J. Organomet. Chem. 1995,
500, 175–185; c) P. Jutzi, T. Redeker, Eur. J. Inorg. Chem. 1998,
6, 663–674; d) C. Müller, D. Vos, P. Jutzi, J. Organomet. Chem.
2000, 600, 127–143; e) H. Butenschön, Chem. Rev. 2000, 100,
1527–1564; f) U. Siemeling, Chem. Rev. 2000, 100, 1495–1526.
[2] a) B. Cornils, W. A. Herrmann, R. Schlögl, C.-H. Wong, Catal-
ysis from A to Z, Wiley-VCH, Weinheim, 2000, p. 253; b) J. J.
Schneider, Nachr. Chem. 2000, 48, 614–620; c) C. S. Slone,
D. A. Weinberger, C. A. Mirkin, Prog. Inorg. Chem. 1999, 48,
233–350; d) E. Lindner, S. Pautz, M. Haustein, Coord. Chem.
Rev. 1996, 155, 145–162.
[12] G. M. Sheldrick, SHELXTL 5.1, Bruker AXS, Madison, WI,
USA, 1998.
[3] a) M. Enders, R. Rudolph, H. Pritzkow, Chem. Ber. 1996, 129,
459–463; b) M. Enders, R. Rudolph, H. Pritzkow, J. Or-
ganomet. Chem. 1997, 549, 251–256; c) M. Enders, G. Ludwig,
H. Pritzkow, Organometallics 2001, 20, 827–833; d) M. Enders,
P. Fernández, G. Ludwig, H. Pritzkow, Organometallics 2001,
20, 5005–5007; e) M. Enders, G. Kohl, H. Pritzkow, J. Or-
[13] CCDC-673536, -673537, and -673538 contain the supplemen-
tary crystallographic 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.
Received: March 3, 2008
Published Online: August 19, 2008
Eur. J. Inorg. Chem. 2008, 4230–4235
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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