Synthesis and structures of homo- and heterobimetallic rhodium(i) and/or iridium(i) complexes of binucleating bis(1-pyrazolyl)methane ligands

Article abstract of DOI:10.1039/c1dt10499c

The synthesis of a series of Rh(i) and Ir(i) homobimetallic complexes using three different linking scaffolds is described. The cyclooctadiene (COD) complexes [M₂(COD)₂(L_scaffold)][BAr ^F₄]₂ (2-7) where M = Rh(i) or Ir(i), and L _scaffold = bis(1-pyrazolyl)methane ligands, p-C₆H ₄[CH(pz)₂]₂ (1a), m-C₆H ₄[CH(pz)₂]₂ (1b) and the anthracene-bridged 1,8-C₁₄H₈[CH(pz)₂]₂ (1c) were synthesized. The COD co-ligands of 2-7 were replaced with the carbonyl co-ligands to form the analogous homobimetallic complexes, [M ₂(CO)₄(L_scaffold)][BAr^F ₄]₂ (8-13). The solid-state structures of the dicationic homobimetallic complexes 2, 3, 5, 6, 9, and 10, as well as cationic monometallic complexes 15 and 22 of ligands 1b and 1c respectively, were characterized using X-ray crystallography. The solid-state XRD structures of the resulting dirhodium and diiridium complexes with the para- and meta-phenylene and anthracene scaffolds show that there are distinct differences between structures of complexes 2-10 due to the variation in the scaffold structures, in particular the relative positions of the two metal centres. Heterobimetallic RhIr complexes of the m-C₆H₄[CH(pz)₂] ₂ ligand were also synthesized using a stepwise approach, and the observed exchange of the metal centres in the heterobimetallic complexes was found to be dependent on the nature of the coligand.

Full text of DOI:10.1039/c1dt10499c

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PAPER
Synthesis and structures of homo- and heterobimetallic rhodium(I) and/or
iridium(I) complexes of binucleating bis(1-pyrazolyl)methane ligands†
Joanne H. H. Ho,a Jo¨rg Wagler,b Anthony C. Willisc and Barbara A. Messerle*a
Received 24th March 2011, Accepted 9th August 2011
DOI: 10.1039/c1dt10499c
The synthesis of a series of Rh(I) and Ir(I) homobimetallic complexes using three different linking
scaffolds is described. The cyclooctadiene (COD) complexes [M2(COD)2(Lscaffold)][BArF ]2 (2–7)
4
where M = Rh(I) or Ir(I), and Lscaffold = bis(1-pyrazolyl)methane ligands, p-C6H4[CH(pz)2]2 (1a),
m-C6H4[CH(pz)2]2 (1b) and the anthracene-bridged 1,8-C14H8[CH(pz)2]2 (1c) were synthesized. The
COD co-ligands of 2–7 were replaced with the carbonyl co-ligands to form the analogous
homobimetallic complexes, [M2(CO)4(Lscaffold)][BArF ]2 (8–13). The solid-state structures of the
4
dicationic homobimetallic complexes 2, 3, 5, 6, 9, and 10, as well as cationic monometallic complexes
15 and 22 of ligands 1b and 1c respectively, were characterized using X-ray crystallography. The
solid-state XRD structures of the resulting dirhodium and diiridium complexes with the para- and
meta-phenylene and anthracene scaffolds show that there are distinct differences between structures of
complexes 2–10 due to the variation in the scaffold structures, in particular the relative positions of the
two metal centres. Heterobimetallic RhIr complexes of the m-C6H4[CH(pz)2]2 ligand were also
synthesized using a stepwise approach, and the observed exchange of the metal centres in the
heterobimetallic complexes was found to be dependent on the nature of the coligand.
likely to lead to enhanced reactivity. These linking scaffolds can
range in structure from linear to bent, and vary in their degree of
rigidity.1,4,5,6
Introduction
In recent years, bimetallic complexes have been used in ho-
mogeneous catalysis as an effective tool for promoting organic
transformations.1,2 Bimetallic catalysts can display cooperative in-
teractions, also known as synergistic effects, between the proximate
metal centres leading to reactivities and selectivities that cannot be
attained using their corresponding monometallic counterparts.1,3
Bimetallic complexes as well as metal clusters in which the metal
pairs are held in close proximity through direct metal–metal bonds
have been widely studied.4 However, these metal–metal bonds are
often more labile than other chemical bonds commonly found in
organic substrates, and during catalysis these bimetallic complexes
typically undergo fragmentation leading to monometallic species.1
To take advantage of the unique potential of bimetallic complexes
for catalysis, those bimetallic complexes which contain bridging
organic ligands that can stabilize the bimetallic system are most
The use of binucleating ligands with ligand isolated donor
sets (Fig. 1) is one of the more recent developments where
two metal centres are held in close proximity to coopera-
tively catalyze a given organic transformation.6,7,8,9,10 Cooper-
ativity effects that have been observed in bimetallic systems
usually occur through electronic and/or spatial interactions.
Electronic cooperativity11 occurs most often when the metal
centres are electronically coupled through a conjugated p-
electron system, while cooperativity due to spatial factors1,4,7
occurs when the two metals are held in close proximity through
space by a rigid binucleating ligand. Stanley and co-workers
reported a highly selective and active dirhodium hydroformyla-
tion catalyst, Rh2(norbornadiene)(P4), where P4 is the binucleat-
ing tetraphosphine-based ligand, (Et2PCH2CH2)(Ph)PCH2P(Ph)
(CH2CH2PEt2),12 while the bimetallic dicyclopentadienyl titanium
aSchool of Chemistry, University of New South Wales, Kensington, NSW
2052, Australia. E-mail: b.messerle@unsw.edu.au; Fax: +61 2 9662 1697;
Tel: +61 2 9385 4683
bInstitut fu¨r Anorganische Chemie, Technische Universita¨t Bergakademie
Freiberg, 09596, Freiberg, Germany
cSchool of Chemistry, Australian National University, Canberra, ACT 0200,
Australia
† Electronic supplementary information (ESI) available: (1) NMR data,
(2) Extensive crystallographic information, and (3) crystallographic infor-
mation files (CIF) of compounds 1c, 2, 3, 5, 6, 9, 10, 15 and 22. CCDC
reference numbers 798119–798127. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/c1dt10499c
Fig. 1 Structures of binucleating ligands with isolated donor sets.
Dalton Trans., 2011, 40, 11031–11042 | 11031
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complex of Marks et al. showed far better reactivity than its
monometallic analogue in the copolymerization of ethylene with
styrene.6,13,14
We have recently reported that a dual metal catalyst system
(Rh and Ir) using cationic Rh(I) and Ir(I) complexes of the
type [M(bpm)(CO)2]BArF (where M = Rh or Ir, bpm = bis(1-
4
pyrazolyl)methane, and BArF = tetrakis[3,5-bis(trifluoromethyl)-
Scheme 1
4
phenyl]borate) is a highly efficient catalyst for the two step
intramolecular dihydroalkoxylation reaction of alkyne diols in
the formation of spiroketals.15 The two metal centres worked
cooperatively to provide greater efficiencies than the individual
monometallic complexes for the concurrent cyclization of alkyne
diols.
analogous to the synthetic route reported for 1a and 1b (Scheme 1).
The cobalt-catalyzed reaction of 1,8-diformylanthracene8 with the
in situ formation of thionyl dipyrazole led to the isolation of LAnt
(1c) as a brown solid in moderate yield (62%).
Preparation of homobimetallic complexes. A series of the
homobimetallic dirhodium and diiridium complexes with binu-
cleating ligands, (Lscaffold = Lp (1a), Lm (1b), and LAnt (1c)), were
prepared by the reaction of one equivalent of the ligand with two
Herein we describe the synthesis and structural studies of a series
of homo- and heterobimetallic complexes where the two metal cen-
tres are held at well-defined distances from each other using three
different linking scaffolds. The binucleating ligands include the
para- and meta-phenylene linked bis(1-pyrazolyl)methane ligands,
p-C6H4[CH(pz)2]2 (1a) and m-C6H4[CH(pz)2]2 (1b) (Fig. 2), previ-
ously reported by Reger et al.9 A newly designed and synthesized
binucleating ligand where the two bidentate ligands are held on
an anthracene scaffold 1,8-C14H8[CH(pz)2]2 (1c) is also described,
with the aim of providing a more rigid scaffold for holding the
ligand pair. The synthesis of the cyclooctadiene (COD) complexes
equivalents of the respective metal precursors, [M(COD)2]BArF
4
(M = Rh, Ir), in THF at room temperature (Scheme 2). All of
the dicationic complexes [M2(COD)2(Lscaffold)][BArF ]2 (2–7) were
4
isolated in excellent yields (84–96%) as bright yellow solids. Each
of these complexes was found to be air and moisture stable in both
solid form and in solution.
[M2(COD)2(Lscaffold)][BArF ]2 (2–7) where M = Rh(I) or Ir(I),
4
and Lscaffold = p-C6H4[CH(pz)2]2 (1a), m-C6H4[CH(pz)2]2 (1b) and
1,8-C14H8[CH(pz)2]2 (1c) is described, as well as the synthesis of the
analogous homobimetallic complexes, [M2(CO)4(Lscaffold)][BArF ]2
4
(8–13). The solid-state structures of the dicationic homobimetallic
complexes 2, 3, 5, 6, 9, and 10, as well as the cationic monometallic
complexes 15 and 22 of ligands 1b and 1c respectively, were
characterized using X-ray crystallography, and the structures
are discussed. Approaches to the synthesis of heterobimetallic
Scheme 2
The cyclooctadiene co-ligands of [M2(COD)2(Lscaffold)][BArF ]2
(2–7) were readily replaced with the carbonyl co-
ligands to form the analogous homobimetallic complexes,
[M2(CO)4(Lscaffold)][BArF ]2 (8–13) by placing dichloromethane
complexes of the general formula [(MAX)(MBX¢)(Lm)][BArF ]2
4
4
(MA, MB = Rh or Ir; X, X¢ = COD or (CO)2), (18–21) are also
described, and the exchange processes of the heterobimetallic
systems investigated using NMR spectroscopy.
4
solutions of 2–7 under an atmosphere of carbon monoxide
(Scheme 3). In each case, the colour of the reaction mixture
changed from yellow to pale yellow after a few minutes and
n-pentane was added slowly to afford the carbonyl complexes
8–13 as solid precipitates. In order to ensure complete reaction
for each of the desired carbonyl complexes, the carbonylation
procedure was repeated once. The dicationic carbonyl complexes
[M2(CO)4(Lscaffold)][BArF ]2 (8–13) were isolated as pale yellow
4
solids in high yields (67–95%). All of these complexes are air and
moisture stable in both the solid form and in solution, with the
exception of the Ir(I) complex on the anthracene scaffold 13 which
was found to be mildly air-sensitive and decomposed slowly upon
prolonged exposure to air.
Fig. 2 Binucleating ligands, p-C6H4[CH(pz)2]2 (1a), m-C6H4[CH(pz)2]2
(1b), and 1,8-C14H8[CH(pz)2]2 (1c).
Results and discussion
Preparation of binucleating ligands
Reger and co-workers have previously reported the synthesis
of the binucleating ligands, p-C6H4[CH(pz)2]2 (Lp, 1a) and m-
C6H4[CH(pz)2]2 (Lm, 1b) (Fig. 1), using a straightforward method
to add the bis(1-pyrazolyl)methane units to the different linking
scaffolds.9 The novel anthracene-bridged binucleating ligand, 1,8-
C14H8[CH(pz)2]2, (LAnt, 1c) was prepared through a procedure
Scheme 3
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Spectroscopic studies of complexes 2–13
All of the homobimetallic complexes 2–13 were fully characterized
using both one and two-dimensional NMR spectroscopy, mass
spectrometry and elemental analysis. The highly symmetric nature
of the para- and meta-phenylene bridged dirhodium and diiridium
complexes (2–5 and 8–11) is reflected in their simple, well-resolved
1
1H and 13C NMR spectra. At room temperature, the H NMR
spectra of the para- and meta-phenylene bridged homobimetallic
complexes in CD2Cl2 each contain only one set of resonances due
to the pyrazole protons. In addition both the resonances due to
the four phenylene protons of the para-phenylene complexes and
the two aromatic protons 4-H and 6-H of the meta-phenylene
complexes, are equivalent, which suggests a C2-symmetry in these
complexes.
Fig.
4
1H NOESY (600 MHz, CD2Cl2, 258 K) spectra of
[Rh2(CO)4(LAnt)][BArF
] (12) at two different regions, (a) 8.0–9.0 ppm,
2
4
and (b) 6.0–6.6 ppm, showing the exchange peaks H5–H4, and between
the four protons H4a–d (marked by the double-headed arrow).
The 1H NMR spectrum of the dirhodium cyclooctadiene
anthracene complex 6 shows that the structure of the complex
is fluxional in CD2Cl2 at room temperature on the NMR time
resonances attributed to protons H4a, H4b, H4c and H4d of the
four pyrazolyl donors. The exchange cross peaks observed indicate
there are two exchange processes occurring—one with exchange
between the positions of the two bis(1-pyrazolyl)methane ligands,
and one with exchange between the pairs of pyrazole substituents
within each bis(1-pyrazolyl)methane ligand. This was attributed
to slow rotation of the two bis(1-pyrazolyl)methane ligands about
1
scale (Fig. 3), and a variable-temperature H NMR (VT-NMR)
study in the temperature range 258–298 K showed that at lower
temperatures, the complex becomes unsymmetrical with reduced
1
fluxionality (Fig. 3). On the other hand, the H NMR spectrum
of the analogous diiridium complex, 7, contains sharp resonances
at ambient temperature with resonances observed for two sets of
bispyrazolyl ligand protons, which indicates that the complex is
not fluxional and unsymmetrical at ambient temperature. This was
attributed to the steric bulk of the cyclooctadiene co-ligands which
restricts the free rotation of the pairs of bis(1-pyrazolyl)methane
motifs.
1
the anthracene–methine bond. The H NMR spectrum of the
diiridium analogue (13) of 12 at 243 K contains only one set
of resonances that can be attributed to pyrazole protons, which
indicates that, in solution, complex 13 is effectively symmetrical.
The 13C NMR spectra of the homobimetallic carbonyl com-
plexes support the presence of carbonyl ligands bound to the
rhodium and iridium centers, with carbonyl resonances observed
at ~181 ppm (1JRh–C = 70 Hz) and ~169 ppm for each of the
dirhodium and diiridium carbonyl complexes, respectively. In
addition, the solid-state IR spectra of the homobimetallic carbonyl
complexes each show two intense absorption bands for the metal
bound carbonyls between 2101–2115 cm-1, comparable to similar
Rh(I) and Ir(I) bis(1-pyrazolyl)methane complexes previously
reported. The dirhodium complexes were found to have higher
carbonyl stretching frequencies than their analogous diiridium
complexes, which is indicative of a lower electron density on the
rhodium center and reduced metal–CO back-donation for the
dirhodium complexes. This is consistent with the periodic trend
that third row transition metals are better p-bases than those of
the second row.10
Molecular structures of complexes 2, 3, 5, 6, 9, 10
The molecular structures of [Rh2(COD)2(Lp)][BArF ]2, 2,
Fig.
3
1H NMR (600 MHz, CD2Cl2) spectra of [Rh2(COD)2-
4
(LAnt)][BArF4]2 (6) at (a) 298 K, (b) 273 K, and (c) 258 K.
[Ir2(COD)2(Lp)][BArF ]2 3, [Ir2(COD)2(Lm)][BArF ]2·CH2Cl2 5,
4
4
[Rh2(COD)2(LAnt)][BArF ]2 6, [Ir2(CO)4(Lp)][BArF ]2 9, and
4
4
The dirhodium and diiridium carbonyl anthracene complexes
12 and 13 were both found to be fluxional in CD2Cl2 at
ambient temperature, with broadened resonances in the 1H NMR
spectra, and NMR studies at lowered temperatures showed a
slowing of the rotation. For complex 12, the unresolved broad
resonances observed at room temperature sharpened considerably
[Rh2(CO)4(Lm)][BArF ]2 10 (Fig. 5 and 6) show that each com-
4
plex has a slightly distorted square-planar geometry about the
metal centre, with bite angles N–M–N (M = Rh, Ir) of 85.30–
87.19◦. Each metal centre is bound to one bidentate bis(1-
pyrazolyl)methane unit, which provides two N-atoms as well as
either two C-atoms of carbon monoxide or two centres of the
1
at 258 K. The H NOESY spectrum (Fig. 4) of 12 recorded at
C C bonds of 1,5-cyclooctadiene as the co-ligands. Each of the
258 K contains cross-peaks due to the exchange of the H4 and H5
of the anthracene group. In addition, cross-peaks were observed
in the 1H NOESY spectrum indicating exchange between the
six-membered M–N–N–C–N–N (where M = Rh/Ir) metallacycles
adopt a distorted boat-like configuration. The average M–N
and M–C (M = Rh/Ir) bond distances are also comparable to other
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Fig.
6
ORTEP views of the cationic fragments of the homo-
Fig. 5 ORTEP views of the cationic fragments of the homobimetallic
complexes (a) [Ir2(COD)2(Lp)][BArF4]2 3, (b) [Rh2(COD)2(Lp)][BArF4]2 2,
with thermal ellipsoids at the 30% probability level.
bimetallic complexes (a) [Ir2(COD)2(Lm)][BArF4]2·CH2Cl2 5, and (b)
[Rh2(COD)2(LAnt)][BArF
bility level.
] 6, with thermal ellipsoids at the 30% proba-
2
4
Table 1 Selected bond lengths of the inner coordination sphere
of [Rh2(COD)2(Lp)][BArF4]2, 2, [Ir2(COD)2(Lp)][BArF
]
3, [Ir2(COD)2-
centres are directed away from each other. In the case of the meta-
phenylene scaffold (Fig. 6), the metal units of diiridium complex
5 are each oriented away from each other on opposite sides of the
phenylene ring (Fig. 6(a)). This can be attributed to steric crowding
caused by the bulky 1,5-cyclooctadiene co-ligands.
4
2
(Lm)][BArF4]2·CH2Cl2, 5·CH2Cl2, and [Rh2(COD)2(LAnt)][BArF4]2, 6
Atoms
(M = Rh, Ir)
2
3
5·CH2Cl2 Atoms (M = Rh)
6
˚
˚
Bond lengths (A)
2.102(2) 2.085(2) 2.083(3) Rh(1)–N(1)
2.095(2) 2.083(2) 2.089(3) Rh(1)–N(3)
Bond lengths (A)
M(1)–N(1)
M(1)–N(3)
In considering the complexes bound to the anthracene-scaffold,
the structure of the dirhodium COD complex 6 (Fig. 6(b)) reveals
that one of the Rh-bound bis(1-pyrazolyl)methane moieties is
aligned vertically above the anthracene bridge while the second
Rh-bound moiety is oriented away from the first so that the two
Rh(I) centres are well separated, with a Rh ◊ ◊ ◊ Rh distance of
2.117(3)
2.109(3)
Rh(1) ◊ ◊ ◊ Rh(2) 8.371(1)
M(2)–N(5)
M(2)–N(7)
2.095(3) Rh(2)–N(5)
2.086(3) Rh(2)–N(7)
2.095(3)
2.075(3)
˚
rhodium/iridium bis(1-pyrazolyl)methane structures reported in
literature.15,16 Direct metal–metal bonds are absent in the solid-
state structures of the dicationic homobimetallic complexes (2, 3,
8.371(1) A. This also has significant impact on the structure of
the anthracene ring system, which is no longer absolutely planar
in this structure. This is likely due to the close interaction of the
two rhodium moieties which distort the anthracene backbone.
The solid-state structures of the carbonyl homobimetallic
complexes 9 and 10 were also confirmed using X-ray diffraction
˚
5, 6, 9, and 10), where intermetallic distances greater than 5.2 A
were observed in all cases (Table 1).
A comparison of the single-crystal X-ray structural analyses of
the cyclooctadiene homobimetallic complexes 2, 3, 5 and 6 (Fig. 5
and 6) reveals a very different structural relationship between the
pairs of metal complexes for each of the three complexes with
different linking scaffolds. In the case of the pair of iso-structural
para-phenylene complexes 2 and 3 (Fig. 5), each of the two cationic
metal complex substituents lie about an inversion centre at the
(Fig. 7, Table 2). The homobimetallic dication of 9 has a centre
-
of inversion, thus, only half of the dicationic unit and one BArF
4
anion are present in the asymmetric unit. In comparison to the
analogous 1,5-cyclooctadiene complex 3, the Ir–N bond lengths
of complex 9, which contains carbonyl co-ligands, are much
shorter. In addition, the Ir–C bond lengths of the CO ligands
in 9 are also shorter than the Ir–C bond lengths (two centres of
the C C bonds) of the cyclooctadiene in 3. This is expected as
centroid of the phenylene ring, with the asymmetric unit consisting
-
of half a dication and a BArF anion. In addition, the two metal
4
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Table 2 Selected bond lengths and angles of the inner coordination
sphere of [Ir2(CO)4(Lm)][BArF4]2, 9, and [Rh2(CO)4(Lm)][BArF4]2, 10
No metal–metal interaction is present, with a Rh ◊ ◊ ◊ Rh separa-
tion of 5.223(1) A (corresponds to the second molecule in the
˚
asymmetric unit). Another interesting feature is an intramolecular
Atoms (M = Ir)
Atoms (M = Rh)
CH ◊ ◊ ◊ p interaction between the meta-phenylene 2-H atom and
˚
˚
Bond lengths (A)
9
Bond lengths (A)
10
˚
the neighbouring pyrazolyl rings. The 2.92 A separation between
Ir(1)–N(1)
Ir(1)–N(3)
Ir(1)–C(1)
Ir(1)–C(2)
2.058(3)
2.067(5)
1.847(4)
1.855(4)
Rh(1)–N(1)
Rh(1)–N(3)
Rh(2)–N(5)
Rh(2)–N(7)
Rh(1)–C(1)
Rh(1)–C(2)
Rh(2)–C(16)
Rh(2)–C(17)
Rh(1) ◊ ◊ ◊ Rh(2)
Bond angles (◦)
N(1)–Rh(1)–N(3)
N(5)–Rh(2)–N(7)
2.068(4)
2.084(4)
2.071(3)
2.081(4)
1.852(7)
1.884(6)
1.860(5)
1.878(6)
5.806(1)
the phenylene-2-H ◊ ◊ ◊ Ct (Ct = centroid) as well as the angles
of approximately 115◦ suggest the shielding observed for this
phenylene 2-H in the 1H NMR spectrum could possibly be a
result of the proximity of the p clouds to the pyrazolyl rings. This
observation was also previously reported for similar structures
with the meta-phenylene scaffold.9
Bond angles (◦)
N(1)–Ir(1)–N(3)
Stepwise preparation and characterization studies of
heterobimetallic Rh–Ir complexes
85.30(4)
88.04(15)
88.32(14)
The heterobimetallic complexes with the bis(1-pyrazolyl)methane
derived ligands were prepared in a stepwise fashion as out-
lined in Scheme 4. Two different approaches were taken
for the preparation of the desired heterobimetallic com-
plex, [Rh(CO)2Ir(CO)2(Lm)][BArF ]2. Each approach proceeds
4
through the formation of the monometallic intermediates, MAL+,
where MA
=
Rh/Ir occupies one of the two bis(1-
pyrazolyl)methane motifs, followed by the subsequent addition
of the second metal precursor which results in the complexation
of MB = Rh/Ir to the other vacant bis(1-pyrazolyl)methane motif.
Fig. 7 ORTEP views of the cationic fragments of the homobimetallic
complexes [Ir2(CO)4(Lp)][BArF4]2 9 (a) and [Rh2(CO)4(Lm)][BArF4]2 10 (b),
with thermal ellipsoids at the 30% probability level.
carbon monoxide is a much more strongly binding ligand than
1,5-cyclooctadiene.
The molecular structure of [Rh2(CO)4(Lm)][BArF ]2 (10) consists
4
of two chemically identical but crystallographically independent
molecules in the asymmetric unit. In comparison to its iridium
cyclooctadiene analogue (5), the dirhodium complex with car-
bonyl co-ligands, 10, revealed a different relative orientation of
the two metal complexes, with the two bis(1-pyrazolyl)methane
sites both oriented on the same side of the phenylene scaffold
with the two rhodium units pointing towards each other (Fig. 7).
Scheme 4
Monometallic rhodium(I) and iridium(I) complexes of the
general formula [MA(COD)(Lm)]BArF4 (MA = Rh, 14; MA = Ir, 15)
were each prepared by the reaction of an equivalent of ligand Lm
(1b) with 0.90–0.94 equivalents of the respective metal precursors,
[M(COD)2]BArF (M = Rh, Ir) (Scheme 4). The amount of
4
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˚
Table 3 Selected bond lengths [A] of the inner coordination sphere of
metal precursor added in this step is critical for the selective
synthesis of the monometallic compound. An excess amount of the
metal precursor resulted in the formation of the homobimetallic
complex. To obtain analytically pure 14 unreacted ligand was
removed using column chromatography through alumina leading
to a moderate yield (48%). On the other hand, crystals of the
pure mono-iridium analogue 15 were obtained in 49% yield by the
careful layering of n-pentane onto a dichloromethane solution of
[Ir(COD)(Lm)]BArF4, 15 and [Ir(COD)(LAnt)]BArF4, 22
Atoms (M = Ir)
15
22
Ir(1)–N(1)
Ir(1)–N(3)
2.100(4)
2.066(5)
2.1002(15)
2.0721(15)
with a N(1)–Ir(1)–N(3) bond angle of 86◦. The Ir center shows
a square-planar configuration, with Ir–N bond lengths of 2.07–
2.10 A, which is in the range of bond lengths observed for the
15. The monometallic carbonyl complexes [MA(CO)2(Lm)][BArF ]
4
(MA = Rh, 16; Ir, 17) were prepared by stirring dichloromethane
solutions containing the respective complexes 14 and 15 under an
atmosphere of carbon monoxide (Scheme 4). 16 and 17 were each
obtained as pale yellow solids in 80 and 62% yields respectively.
The monometallic complexes 16 and 17 were found to be air and
moisture stable in both the solid form and in solution, as were the
complexes 14 and 15.
˚
equivalent Ir cyclooctadiene complexes described herein.
Synthesis of heterobimetallic complexes
Approach 1. Treatment of a dichloromethane solution of
the mono-iridium complex, [Ir(COD)(Lm)]BArF , 15 with 0.98
4
1
All of the H NMR spectra of the monometallic complexes
equivalents of the rhodium precursor, [Rh(COD)2]BArF , at
4
14–17 recorded at room temperature contain two different sets
of resonances due to pyrazolyl protons, one corresponding to the
protons of the metal bound bis(1-pyrazolyl)methane and the other
to those of the free bis(1-pyrazolyl)methane motif.
room temperature resulted in the formation of a mixture of the
heterobimetallic complex, [Rh(COD)Ir(COD)(Lm)][BArF ]2 (18)
4
and the homobimetallic complexes, [Rh2(COD)2(Lm)][BArF ]2 (4)
4
and [Ir2(COD)2(Lm)][BArF ]2 (5) in a total yield of 92%. The
4
To confirm the identity of the monometallic iridium(I) cyclooc-
mixture of bimetallic products is evident in the 1H NMR spectrum
where, for example, the resonances due to the aromatic phenylene
protons, Hd and Hf, appear as three sets of doublets in a ratio of 25,
50 and 25% for the three species 4, 18 and 5 respectively (Fig. 9).
Furthermore, the positive ion ESI mass spectrum substantiates
the presence of this mixture with molecular ion peaks observed at
tadiene complex (15), the structure of [Ir(COD)(Lm)]BArF , 15,
4
was determined using X-ray crystallography (Fig. 8). In addition,
the X-ray crystal structure of the monometallic complex with
the anthracene scaffold, [Ir(COD)(LAnt)]BArF , 22, was analyzed
4
and the structure is shown in Fig. 8. Selected bond lengths of 15
and 22 are shown in Table 3. The molecular structures confirmed
that the respective monocationic complexes each contain only one
metal unit on the binucleating ligand (1b or 1c). In both structures,
the single Ir metallacycle adopts a distorted boat conformation,
1655.0, 1745.0 and 1833.1, where each corresponds to [M-BArF ]+
4
where M is the complete dication of 4, 18, and 5 respectively. These
results confirm that the metal centers undergo exchange between
binding sites during the second addition of the metal precursor,
resulting in the formation of not only the heterobimetallic species
18, but also the homobimetallic complexes 4 and 5.
Fig. 9 1H NMR (600 MHz, CD2Cl2, 298 K) spectra (selected region,
Fig. 8 ORTEP view of the cationic fragment of the monometallic
complexes [Ir(COD)(LAnt)]BArF 22 (a) and [Ir(COD)(Lm)]BArF 15 (b)
6.5–8.2 ppm) of the mixture of [Rh(COD)Ir(COD)(Lm)][BArF
] (18),
4 2
[Rh2(COD)2(Lm)][BArF
] ] (5) (above)
(4), and [Ir2(COD)2(Lm)][BArF
2 4 2
4
4
4
with thermal ellipsoids at the 30% probability level.
and expanded spectra of selected regions (below).
11036 | Dalton Trans., 2011, 40, 11031–11042
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The reaction conditions were varied, using different tempera-
tures (e.g. 40 and -85 ◦C) and solvents (e.g. THF and CH2Cl2). The
results showed that the ratio of the bimetallic complexes formed
is not affected by the reaction conditions with the same mixture
of the homo- and heterobimetallic products being formed in each
case.
at d 169.17 ppm in the 13C NMR spectrum, characteristic of an
iridium-bound carbonyl group. This indicates that the CO and
COD co-ligands do not undergo exchange during the exchange
of the metal centers, so that the formation of the mixture results
purely from exchange of the two metals at the pyrazolyl ligand,
with the co-ligand remaining bound to the metal.
To better understand how the exchange of the metal centers
occurs during the addition of the second metal precursor, the
two homobimetallic complexes 4 and 5 were dissolved in CD2Cl2
and added together into a Young’s NMR tube. No indication of
the formation of the heterobimetallic complex was observed even
after a few days, even with heating. Hence, the homobimetallic
complexes are stable once formed and no exchange of the metal
centers to form the heterobimetallic species 18 occurs even in
solution.
Carbonylation to form mixture of 19¢, 10¢ and 11¢
The carbonyl complexes, [Rh(13CO)2Ir(13CO)2(Lm)][BArF ]2 (19¢),
4
[Rh2(13CO)4(Lm)][BArF ]2 (10¢) and [Ir2(13CO)4(Lm)][BArF ]2 (11¢)
4
4
were prepared in situ in a Young’s NMR tube by bubbling
13C labelled carbon monoxide (13CO) into the dichloromethane
solution of the mixture of [Rh(COD)Ir(CO)2(Lm)][BArF ]2 (21),
4
[Rh2(COD)2(Lm)][BArF ]2 (4), and [Ir2(CO)4(Lm)][BArF ]2 (11)
4
4
(Scheme 4).
1
The H and 13C NMR spectra of the mixture (19¢, 10¢, and
11¢) contain only resonances due to the metal bound carbonyl
complexes and free cyclooctadiene. The 13C NMR spectrum was
used to identify the products (Fig. 11). Carbonyl ligands (13CO)
bound to iridium and rhodium appear as a single resonance at
d 169.00 ppm and as a doublet at 181.39 ppm (1JRh–C = 69.3 Hz)
respectively in the 13C NMR spectrum (Fig. 11(a)). In addition,
the four singlets which lie between 75.00–76.00 ppm in the 13C
NMR spectrum (Fig. 11(b)) correspond to the four different sets
of proton signals due to the CH(Pz)2, which confirms the presence
of three different species in the mixture.
Approach 2. An alternative route for the synthesis of
the pure heterobimetallic complex was attempted where the
monometallic complex, [Ir(COD)Lm]BArF , 15 was first converted
4
to [Ir(CO)2Lm]BArF , 17, before the addition of the second
4
metal precursor, [Rh(COD)2]BArF . However, treatment of a
4
dichloromethane solution of 17 with an equimolar quantity of
[Rh(COD)2]BArF at room temperature gave a mixture of the
4
heterobimetallic complex, [Rh(COD)Ir(CO)2(Lm)][BArF ]2 (21)
4
and the two homobimetallic complexes, [Rh2(COD)2(Lm)][BArF ]2
4
(4) and [Ir2(CO)4(Lm)][BArF ]2 (11), in a total yield of 98%.
4
The mixture of both the homo- and heterobimetallic products
1
1
is evident in the H NMR spectrum, where the H-13C HSQC
NMR spectrum in Fig. 10 confirms that the four singlets which
appeared at 7.46, 7.48, 7.65 and 7.67 ppm were assigned to the
four different proton signals of CH(Pz)2 of complexes 4, 11 and
21. This suggests that the metal centers undergo exchange during
the second addition of the metal precursor, regardless of the nature
of the starting monometallic complex used.
1
Fig. 11 13C{ H} NMR (150.9 MHz, CD2Cl2, 223 K) spectrum of the
mixture of 19¢, 10¢ and 11¢ at selected regions, (a) carbonyl and (b) CH(Pz)2
regions.
Co-ligand exchange
Surprisingly, when the order of addition of the second metal
was switched around (Scheme 5), where [Ir(COD)2]BArF was
4
added to [Rh(CO)2Lm]BArF (16), both metal and co-ligand
4
Fig. 10 A section of the 1H-13C HSQC NMR (600 MHz, CD2Cl2, 298 K)
spectra (selected region) of the mixture of [Rh(COD)Ir(CO)2(Lm)][BArF
(21), [Ir2(CO)4(Lm)][BArF4]2 (11), and [Rh2(COD)2(Lm)][BArF4]2 (4).
]
2
4
In the mixture of the homo- and heterobimetallic products
formed here, the CO ligands remain attached only to the iridium
center since the carbonyl region shows only a single resonance
Scheme 5
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exchange were observed. Using IR and 13C NMR spec-
troscopy, the mixture of complexes formed was identified to be
[Rh(COD)Ir(CO)2(Lm)][BArF ]2 (21), [Ir2(CO)4(Lm)][BArF ]2 (11),
The heterobimetallic complexes of the general formula
[(MAX)(MBX¢)(Lm)][BArF ]2 (MA, MB = Rh or Ir; X, X¢ =
4
COD or (CO)2), (18–21) have also been synthesized through the
selective preparation of the monometallic complexes. However,
in each case, mixtures of the hetero- and the homobimetallic
complexes were obtained. Two approaches for the synthesis of
the pure heterobimetallic complexes were attempted and they
involved the selective preparation of the monometallic com-
4
4
and [Rh2(COD)2(Lm)][BArF ]2 (4), the same mixture observed with
4
reverse order of addition. The 13C NMR spectrum confirms the
presence of the mixture of products, with four singlets appearing
at the region for the resonances of the CH(Pz)2 (Fig. 12(b)). On
the other hand, in the 13C NMR spectrum, only one carbonyl
resonance at d 169.04 ppm (which corresponds to Ir bound
CO) was observed (Fig. 12(a)). In addition, the v(CO) stretching
frequencies for the mixture of products of 2101 and 2038 cm-1
further support the presence of the Ir(CO)2 fragment.
plexes, [MA(COD)(Lm)]BArF (MA = Rh, 14; MA = Ir, 15) and
4
[MA(CO)2(Lm)]BArF (MA = Rh, 16; Ir, 17) followed by the
4
addition of a second metal precursor. Both methods result in
metal exchange during the addition of the rhodium precursor
to each of the mono-iridium complexes. Switching the addition
order of the metal precursor (iridium precursor to the mono-
rhodium complex) leads to exchange of metal, as well as ex-
change of the co-ligands. These findings suggest that binucleating
ligand, m-C6H4[CH(pz)2]2 (1b), which contains two N,N-bis(1-
pyrazolyl)methane motifs, is not suitable for the selective prepara-
tion of the pure Rh(I)/Ir(I) heterobimetallic complexes. Stronger
binding ligands such as P-donor ligands and N-heterocyclic
carbenes might be more suitable donors in order to stop the metal
exchange process. The heterobimetallic complexes, although not
yet accessible in pure form, are also being tested for their catalytic
performance. As shown by NMR the mixtures contain 50 percent
of the heterobimetallic complex, and these mixtures might indeed
exhibit much better catalytic performance than the equimolar
mixtures of the two homo-bimetallic complexes.
1
Fig. 12 13C{ H} NMR (150.9 MHz, CD2Cl2, 298 K) spectrum of a
mixture of [Rh(COD)Ir(CO)2(Lm)][BArF
] ]
(21), [Ir2(CO)4(Lm)][BArF
2 4 2
4
(11) and [Rh2(COD)2(Lm)][BArF
and (b) CH(Pz)2 regions.
] (4) at selected regions, (a) carbonyl
2
4
This indicates that the co-ligands undergo exchange such that
the dicarbonyl ligands on the initial rhodium complex (16) move
to the iridium center with 100% yield upon addition of the second
precursor (Scheme 5). This suggests that in this particular case, the
rhodium center binds preferentially to the cyclooctadiene rather
than the carbonyl co-ligands.
Experimental section
General procedures
All manipulations of metal complexes and air sensitive reagents
were carried out using standard Schlenk techniques or in
a dinitrogen/argon-filled glovebox. All solvents were distilled
under dinitrogen/argon from a drying agent prior to use:
sodium benzophenone ketyl (diethyl ether, tetrahydrofuran, hex-
ane, and pentane) or calcium hydride (dichloromethane). 1,8-
Conclusions
A new binucleating ligand with the anthracene scaffold, LAnt
(1c) has been synthesized and fully characterized. A series
of novel homobimetallic dirhodium(I) and diiridium(I) com-
plexes containing two bis(1-pyrazolyl)methane motifs bridged by
three different well-defined rigid aromatic scaffolds, ligands m-
C6H4[CH(pz)2]2, Lm (1a), p-C6H4[CH(pz)2]2, Lp (1b), and 1,8-
C14H8[CH(pz)2]2, LAnt (1c), have been synthesized and fully char-
acterized.
17
Diformylanthracene,8 [Rh(COD)2]BArF and [Ir(COD)2]BArF
4
4
were prepared according to literature procedures. Ligands p-
C6H4[CH(pz)2]2 (1a) and m-C6H4[CH(pz)2]2 (1b) were synthesized
by literature methods.9
1
1
1H, 13C{ H}, 19F{ H} NMR spectra were recorded on Bruker
The nature of the three different types of scaffolds has a direct
influence on the relative position of the two metal centers in
the solid-state XRD structures of the bimetallic complexes. The
binucleating ligand with the anthracene scaffold (1c) holds the
two metals of the homobimetallic complexes on the same side
of the scaffold, while the two metals with the meta-phenylene
scaffold (1b) can face towards the same side or face towards
opposite sides of the phenylene ring. The two rhodium units
DPX300, DMX400, DMX500 or DPX600 spectrometers. All
1
spectra were recorded at 298 K, unless otherwise stated. H and
13C NMR chemical shifts are referenced to internal solvent shifts.
J values are given in Hz. Infrared spectra were obtained using an
Avatar 370 FT-IR (Thermo Nicolet) spectrometer. ESI-MS were
carried out by the Biological Mass Spectrometry Facility (BMSF),
University of New South Wales, Australia. Microanalyses were
carried out at the Campbell Analytical Laboratory, University
of Otago, New Zealand. Single crystal X-ray analyses were
performed by Dr Jo¨rg Wagler at Institut fu¨r Anorganische
Chemie, TU Bergakademie Freiberg, Germany (1c, 2, 3, 9, 10,
15, and 22) and Dr Anthony C. Willis at the Research School
of Chemistry, Australian National University, Australia (5, 6).
X-ray diffraction data were collected in phi and omega scans
on a Nonius KappaCCD diffractometer (5, 6) and a Bruker X8
APEX2-CCD diffractometer (1c, 2, 3, 9, 10, 15, and 22) using
of [Rh2(CO)4(Lm)][BArF ]2 (10) are pointed towards each other,
and display the shortest Rh ◊ ◊ ◊ Rh distance of 5.223 A for all of
4
˚
the solid-state structures obtained for the bimetallic complexes.
In contrast, the two metal centers of the complexes with the
para-phenylene scaffold (1a) are all oriented on opposite sides
of the linking phenylene ring. The efficiency of these complexes as
catalysts for the dihydroalkoxylation of alkyne diols is currently
under investigation.
11038 | Dalton Trans., 2011, 40, 11031–11042
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Mo-Ka radiation. The structures were solved with direct methods
(SHELXS97) and refined by full-matrix least-squares refinement
of F2 using SHELXL97.
d 8.05 (d, 3J(H5–H4) = 2.7 Hz, 4H, H5), 7.72 (br s, 16H, ortho-CH
3
of BArF ), 7.60 (s, 2H, CH(Pz)2), 7.59 (d, J(H3–H4) = 2.3 Hz,
4
4H, H3), 7.55 (s, 8H, para-CH of BArF ), 6.80 (s, 4H, Hb), 6.60
4
(t, 3J(H4-H3/H5) = 2.5 Hz, 4H, H4), 4.34 (m, 4H, CH of COD),
3.76 (m, 4H, CH of COD), 2.53 (m, 4H, CH2 of COD), 1.89 (m,
4H, CH2 of COD), 1.77 (m, 4H, CH2 of COD), 1.53 (m, 4H, CH2
of COD) ppm.
Synthesis of [1,8-bis(bis(1-pyrazolyl)methyl)anthracene], LAnt (1c)
A suspension of sodium hydride (0.816 g, 20.4 mmol) in 30 mL of
THF was cooled in an ice bath for an hour. Pyrazole (1.42 g, 20.8
mmol) was added slowly over 5 mins and the resulting solution
stirred at 0 ◦C for an additional hour. Subsequently, the dropwise
addition of thionyl chloride (1.22 g, 10.3 mmol) was carried out
Diiridium(I) dicyclooctadiene complex with p-C6H4[CH(pz)2]2
ligand (Lp, 1a), [Ir2(COD)2(Lp)][BArF ]2 (3)
4
◦
at 0 C over 5 mins. The ice bath was removed and the resulting
Bright yellow solid. Yield: 0.100 mmol, 93%, m.p. 249–
◦
251 C. ESI-MS (Acetone), m/z (%): 1835.4 ([M-BArF ]+, 100).
suspension was allowed to stir at RT for an extra hour. Anhydrous
cobalt chloride (0.0330 g, 0.251 mmol) was added, followed by the
addition of 1,8-diformylanthracene1 (0.600 g, 2.56 mmol). The
mixture was heated at reflux for 20 h. After cooling to room
temperature, 50 mL of water was added and the mixture was
stirred for 15 mins. CH2Cl2 was added (3 ¥ 50 mL) and the organic
layer extracted and washed with water (100 mL) and dried over
MgSO4. The solvent was removed in vacuo and a yellow solid was
obtained. The crude product was washed with hot ethanol and 1c
was obtained after recrystallization from CH2Cl2/n-pentane as a
yellow solid. Crystals suitable for a single crystal structure analysis
were obtained by slow evaporation of a mixture of CH2Cl2 and
toluene solution of 1c (Fig. 1, ESI†).
4
Anal. Calcd. C100H66B2F48Ir2N8: C, 44.52; H, 2.47; N, 4.15; found:
C, 44.43; H, 2.70; N, 3.84%. 1H NMR (600 MHz, CD2Cl2, 298 K):
d 8.11 (d, 3J(H5–H4) = 2.7 Hz, 4H, H5), 7.77 (d, 3J(H4-H3/5) =
2.4 Hz, 4H, H3), 7.72 (br s, 16H, ortho-CH of BArF ), 7.58 (s,
4
3
2H, CH(Pz)2), 7.55 (s, 8H, para-CH of BArF ), 6.69 (t, J(H4-
4
H3/H5) = 2.6 Hz, 4H, H4), 6.65 (s, 4H, Hb), 4.10 (br s, 4H, CH of
COD), 3.49 (br s, 4H, CH of COD), 2.31 (br s, 4H, CH2 of COD),
1.764(m, 12H, CH2 of COD), 1.38 (br s, 4H, CH2 of COD) ppm.
Dirhodium(I) dicyclooctadiene complex with m-C6H4[CH(pz)2]2
ligand (Lm, 1b), [Rh2(COD)2(Lm)][BArF ]2 (4)
4
Yield: 0.750 g (2.13 mmol), 62%. mp 249–251 ◦C (dec). ES-
MS m/z (%): 471.7 (100) [L + 2H+]+. Anal. Calcd. C28H22N8:
C, 49.53; H, 2.69; N, 4.28; found: C, 49.37; H, 2.90; N, 4.09%.
1H NMR (400 MHz, CDCl3, 298 K): d 8.49 (s, 1H, H10), 8.16
Bright yellow solid. Yield: 0.0735 mmol, 91%, m.p. 248–
◦
250 C. ESI-MS (CH2Cl2), m/z (%):1654.9 (67) [M - BArF ]+.
4
Anal. Calcd. C100H66B2F48N8Rh2: C, 47.68; H, 2.64; N, 4.45; found:
C, 47.85; H, 2.90; N, 4.05%. 1H NMR (600 MHz, CD2Cl2, 298 K):
d 7.92 (d, 3J(H5–H4) = 2.5 Hz, 4H, H5), 7.88 (t, 3J(He–Hd and f) =
3
(s, 2H, CH(Pz)2), 8.10 (s, 1H, H9), 8.01 (d, J(H4/5-H3/6) =
7.9 Hz, 1H, He), 7.73 (s, 16H, ortho-CH of BArF ), 7.56 (s, 12H,
8.4 Hz, 2H, H4,5), 7.71 (d, 3J(H3¢-H4¢) = 1.6 Hz, 4H, H3¢), 7.58
4
para-CH of BArF and H3 of Pz), 7.46 (s, 2H, CH(Pz)2), 6.96
3
3
4
(d, J(H5¢-H4¢) = 2.4 Hz, 4H, H5¢), 7.40 (dd, J(H3/6-H2/7) =
(d, 3J(Hd and f -He) = 7.9 Hz, 2H, Hd and f), 6.55 (t, 3J(H4-H3/H5) =
2.4 Hz, 4H, H4), 5.46 (s, 1H, Hb), 4.34, 3.71 (each m, 4H, CH of
COD), 2.53, 1.90, 1.79, 1.62 (each m, 4H, CH2 of COD) ppm.
3
3
6.8 Hz, J(H3/6-H4/5) = 8.4 Hz, 2H, H3,6), 6.79 (d, J(H2/7-
H3/6) = 6.8 Hz, 2H, H2,7), 6.38 (dd, 3J(H4¢-H3¢) = 1.6 Hz, 3J(H4¢-
H5¢) = 2.4 Hz, 4H, H4¢). 13C{ H} NMR (100.6 MHz, CDCl3, 298
1
K): d 141.22 (s, C3¢), 131.94 (s, C1 and C8), 131.57 (s, quat C of
anthracene), 130.51 (s, C4 and C5), 130.29 (s, C5¢), 128.81 (s, C10),
128.73 (2 s, quat C of anthracene), 125.87 (s, C2 and C7), 125.10
(s, C3 and C6), 116.134 (s, C9), 106.99 (s, C4¢), 76.09 (s, CH(Pz)2).
Diiridium(I) dicyclooctadiene complex with m-C6H4[CH(pz)2]2
ligand (Lm, 1b), [Ir2(COD)2(Lm)][BArF ]2 (5)
4
Bright yellow solid. Yield: 0.0780 mmol, 96%, m.p. 156–
◦
159 C. ESI-MS (CH2Cl2), m/z (%): 1833.0 (58) [M-BArF ]+.
4
General procedure for the synthesis of homobimetallic dirhodium(I)
and diiridium(I) dicyclooctadiene complexes, [Rh2(COD)2(Lp/Lm/
LAnt)][BArF ]2/[Ir2(COD)2(Lp/Lm/LAnt)][BArF ]2 (2–7)
Anal. Calcd. C100H66B2F48Ir2N8: C, 44.52; H, 2.47; N, 4.15; found:
C, 44.43; H, 2.70; N, 3.84%.
4
4
A mixture of the respective binucleating ligand, Lp (1a),9 Lm (1b),9
Dirhodium(I) dicyclooctadiene complex with 1,8-C6H4[CH(pz)2]2
or LAnt (1c), (0.0810 mmol) and [M(COD)2]BArF (M = Rh, Ir;
ligand (LAnt, 1c), [Rh2(COD)2(LAnt)][BArF ]2 (6)
4
4
0.164 mmol) in THF (5 mL) was stirred for 30 mins at RT. The
solvent was removed in vacuo. The crude product was redissolved
in CH2Cl2 and n-pentane was added slowly to afford a yellow
solid which was collected by filtration and further washed with
n-pentane (3 ¥ 5 mL). The solid was recrystallized from CH2Cl2/n-
pentane, yielding the respective complexes (2–7).
Yellowish-brown solid. Yield: 0.0840 mmol, 92%, 136–
◦
140 C. ESI-MS (CH2Cl2), m/z (%):1755.1 (26) [M - BArF ]+.
4
Anal. Calcd. C112H86B2F48N8Rh2: C, 49.53; H, 2.69; N, 4.28; found:
C, 49.37; H, 2.90; N, 4.09%. 1H NMR (600 MHz, CD2Cl2, 258 K):
3
d 8.89 (s, 1H, H10), 8.39 (d, J(H4–H3) = 8.3 Hz, 1H, H4), 8.34
3
3
(d, J(H5–H6) = 8.3 Hz, 1H, H5), 8.06 (d, J(H7–H6) = 6.6 Hz,
1H, H7), 7.87 (s, 1H, CH(Pz)2 at C8), 7.72 (br s, 16H, ortho-CH
Dirhodium(I) dicyclooctadiene complex with p-C6H4[CH(pz)2]2
of BArF ), 7.67–7.62 (m, 2H, H3 and H6), 7.58 (br s, 2H, H3b of
Pz), 7.52 (s, 8H, para-CH of BArF ), 7.47 (s, 1H, CH(Pz)2 at C1),
ligand (Lp, 1a), [Rh2(COD)2(Lp)][BArF ]2 (2)
4
4
4
Bright yellow solid. Yield: 0.0715 mmol, 88%, m.p. 249–
7.22 (br s, 4H, H3a and H5a of Pz), 7.10 (s, 1H, H9), 6.98 (br s,
2H, H5b of Pz), 6.45 (d, 3J(H2–H3) = 6.6 Hz, 1H, H2), 6.37 (br s,
2H, H4a), 6.24 (br s, 2H, H4b); for COD(b): 4.60, 4.42 (each br s,
2H, CH), 2.62, 2.52 (each br s, 2H, CH2), 2.09 (m, 4H, CH2); for
◦
252 C. ESI-MS (CH2Cl2), m/z (%):1655.1 (30) [M - BArF ]+.
4
Anal. Calcd. C100H66B2F48N8Rh2: C, 47.68; H, 2.64; N, 4.45; found:
C, 47.74; H, 2.56; N, 4.41%. 1H NMR (600 MHz, CD2Cl2, 298 K):
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1
5.51 (s, 1H, Hb) ppm. 13C{ H} NMR (150.9 MHz, CD2Cl2, 298
COD(a): 4.05,3.32 (each br s, 2H, CH), 2.34, 1.71 (each br s, 2H,
CH2), 1.71, 1.39 (each m, 2H, CH2),1.79 (m, 2H, CH2) ppm.
K): d 181.58 (d, 1J(Rh–CO) = 69.8 Hz, CO). IR (KBr disc) vCO
=
2115, 2055 (s) cm-1.
Diiridium(I) dicyclooctadiene complex with 1,8-C6H4[CH(pz)2]2
ligand (LAnt, 1c), [Ir2(COD)2(LAnt)][BArF ]2 (7)
Diiridium(I) tetracarbonyl complex with m-C6H4[CH(pz)2]2 ligand
4
(Lm, 1a), [Ir2(CO)4(Lm)][BArF ]2 (11)
4
Yellowish-brown solid. Yield: 0.0890 mmol, 84%, 124–
◦
126 C. ESI-MS (CH2Cl2), m/z (%):1935.3 (26) [M - BArF ]+.
Pale yellow solid. Yield: 0.0474 mmol, 88%, m.p. 191–193 ◦C. ESI-
4
MS (CH2Cl2), m/z (%): 1731.9 (33) [M - BArF ]+. Anal. Calcd.
Anal. Calcd. C112H86B2F48Ir2N8: C, 46.36; H, 2.52; N, 4.01; found:
C, 46.10; H, 2.58; N, 3.79%.
4
C88H42B2F48Ir2N8O4: C, 40.69; H, 1.79; N, 4.31; found: C, 41.00;
1
H, 1.98; N, 4.18%. 13C{ H} NMR (150.9 MHz, CD2Cl2, 298 K):
d 169.00 (s, CO). IR (KBr disc) vCO = 2101, 2037 (s) cm-1.
General procedure for the synthesis of homobimetallic dirhodium(I)
and diiridium(I) tetracarbonyl complexes, [Rh2(CO)4(Lp/Lm/
LAnt)][BArF ]2/[Ir2(CO)4(Lp/Lm/LAnt)][BArF ]2 (8–13)
4
4
Dirhodium(I) tetracarbonyl complex with 1,8-C6H4[CH(pz)2]2
ligand (LAnt, 1c), [Rh2(CO)4(LAnt)][BArF ]2 (12)
4
Each of the complexes 2–7 (0.0500 mmol) was dissolved in CH2Cl2
(5 mL). The solution was degassed using three cycles of freeze-
pump-thaw and treated under an atmosphere of carbon monoxide
using a balloon for 15 mins. The solution changed in colour from
bright yellow to pale yellow. n-Pentane was slowly added to the
reaction mixture under an argon atmosphere and a pale yellow
solid was obtained. At times when a yellow oil was obtained, the
carbonylation step was repeated and n-pentane was added slowly
at 0 ◦C to afford a pale yellow solid which was collected by filtration
and washed with n-pentane (3 ¥ 5 mL) and dried under vacuum.
The crude product was recrystallized from CH2Cl2/n-pentane and
each of the complexes (8–11) was isolated.
Pale yellow solid. Yield: 0.0620 mmol, 78%, m.p. 132–135 ◦C. ESI-
MS (CH2Cl2), m/z (%): 1655.2 (18) [M - BArF ]+ + H+. Anal.
4
Calcd. C96H46B2F48N8O4Rh2: C, 45.85; H, 1.84; N, 4.46; found:
1
C, 46.06; H, 1.99; N, 4.41%. H NMR (600 MHz, CD2Cl2, 258
3
K): d 8.87 (s, 1H, H10), 8.42 (d, J(H5–H6) = 8.3 Hz, 1H, H5),
8.26 (d, 3J(H4–H3) = 8.6 Hz, 1H, H4), 8.07 (s, 1H, H3a/b of Pz),
3
8.00 (d, J(H7–H6) = 6.7 Hz, 1H, H7), 7.93, 7.84 (m, 3H, H3a
and Hb of Pz), 7.70 (br s, 20H, CH(Pz)2 at C8 and ortho-CH of
BArF and H6 and H3a/b and H5a/b), 7.55 (m, 1H, H3), 7.51
4
(br s, 9H, para-CH of BArF4 and CH(Pz)2 at C1), 7.39 (s, 1H, H9),
7.25, 7.17, 6.80 (m, 3H, H5a and Hb of Pz), 6.62 (br s, 1H, H2),
1
6.45, 6.42, 6.37, 6.11 (m, 4H, H4a and H4b) ppm. 13C{ H} NMR
(150.9 MHz, CD2Cl2, 258 K): d 181.25 (d, 1J(Rh–CO) = 70.4 Hz,
CO). IR (KBr disc) vCO = 2112, 2057 (s) cm-1.
Dirhodium(I) tetracarbonyl complex with p-C6H4[CH(pz)2]2 ligand
(Lp, 1a), [Rh2(CO)4(Lp)][BArF ]2 (8)
4
Yield: 0.0580 mmol, 88%, m.p. 175–178 ◦C. ESI-MS
Diiridium(I) tetracarbonyl complex with 1,8-C6H4[CH(pz)2]2
(CH2Cl2), m/z (%): 1550.9 (51) [M - BArF ]+. Anal. Calcd.
4
ligand (LAnt, 1c), [Ir2(CO)4(LAnt)][BArF ]2 (13)
4
C88H42B2F48N8O4Rh2: C, 43.70; H, 1.92; N, 4.63; found: C, 43.43;
1
Pale yellow solid. Yield: 0.0590 mmol, 82%, m.p. 110–113 ◦C. ESI-
H, 2.15; N, 4.51%. H NMR (600 MHz, CD2Cl2, 298 K): d 8.14
3
3
MS (CH2Cl2), m/z (%): 741.1 (52) [M - 2BArF - Ir - 2CO]+ +
(d, J(H5–H4) = 2.7 Hz, 4H, H5), 7.93 (d, J(H5–H4) = 2.2 Hz,
4H, H3), 7.71 (m, 18H, ortho-CH of BArF4 and CH(Pz)2), 7.55 (m,
4
Na+. Anal. Calcd. C96H46B2F48Ir2N8O4: C, 42.81; H, 1.72; N, 4.16;
8H, para-CH of BArF ), 6.72 (t, 3J(H4-H3/5) = 2.6 Hz, 4H, H4),
1
found: C, 42.72; H, 2.02; N, 4.14%. 13C{ H} NMR (150.9 MHz,
4
6.52 (s, 4H, Hb) ppm. 13C{ H} NMR (150.9 MHz, CD2Cl2, 298
1
CD2Cl2, 243 K): d 169.58 (s, CO). IR (KBr disc) vCO = 2101, 2041
K): d 181.56 (d, 1J(Rh–CO) = 69.9 Hz, CO). IR (KBr disc) vCO
=
(s) cm-1.
2113, 2061 (s) cm-1.
General procedure for the stepwise preparation of heterobimetallic
complexes with m-C6H4[CH(pz)2]2 ligand (Lm, 1a)
Diiridium(I) tetracarbonyl complex with p-C6H4[CH(pz)2]2 ligand
(Lp, 1a), [Ir2(CO)4(Lp)][BArF ]2 (9)
4
Synthesis of monometallic rhodium(I) and iridium(I) complexes,
with m-C6H4[CH(pz)2]2 ligand (Lm, 1a), (14–17)
Pale yellow solid. Yield: 0.0420 mmol, 67%, m.p. 175–178 ◦C. ESI-
MS (CH2Cl2), m/z (%): 1731.1 (35) [M - BArF ]+. Anal. Calcd.
4
Rhodium(I) cyclooctadiene complex, [Rh(COD)(Lm)]BArF (14)
C88H42B2F48Ir2N8O4: C, 40.69; H, 1.79; N, 4.31; found: C, 40.65;
4
1
H, 1.64; N, 4.26%. 13C{ H} NMR (150.9 MHz, CD2Cl2, 298 K):
A solution of [Rh(COD)2]BArF (0.174 g, 0.147 mmol) in 5 mL
d 168.95 (s, CO). IR (KBr disc) vCO = 2104, 2047 (s) cm-1.
4
of THF was added dropwise to a solution of 1b9 (0.0600 g, 0.162
mmol) in 10 mL of THF. The reaction mixture was stirred for
0.5 h at RT. The solvent was removed and the crude product
was redissolved in CH2Cl2. n-Pentane was slowly added to afford
a yellow solid which was collected by filtration and washed
with n-pentane (3 ¥ 5 mL). The crude product was purified by
chromatography on a short plug of neutral alumina using diethyl
ether followed by THF. Evaporation of the THF fraction under
reduced pressure, followed by recrystallization from CH2Cl2/n-
Dirhodium(I) tetracarbonyl complex with m-C6H4[CH(pz)2]2
ligand (Lm, 1a), [Rh2(CO)4(Lm)][BArF ]2 (10)
4
Pale yellow solid. Yield: 0.0480 mmol, 95%, m.p. 182–187 ◦C. ESI-
MS (CH2Cl2), m/z (%): 1550.7 (100) [M - BArF ]+. Anal. Calcd.
4
C88H42B2F48N8O4Rh2: C, 43.70; H, 1.92; N, 4.63; found: C, 43.59;
1
H, 2.21; N, 4.32%. H NMR (600 MHz, CD2Cl2, 298 K): d 8.05
(d, 3J(H5–H4) = 2.5 Hz, 4H, H5), 7.93 (d, 3J(H5–H4) = 2.31 Hz,
4H, H3), 7.74 (s, 16H, ortho-CH of BArF ), 7.66 (s, 2H, CH(Pz)2),
pentane afforded 14 as a yellow solid. Yield: 0.102 g (0.0706 mmol),
4
7.57 (m, 9H, para-CH of BArF4 and He), 6.71 (m, 6H, Hd and f, H4),
48%. ESI-MS (Acetone), m/z (%): 581.2 (100) [M - BArF ]+. H
1
4
11040 | Dalton Trans., 2011, 40, 11031–11042
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NMR (500 MHz, d8-THF, 298 K): d 8.27 (d, 3J(H5–H4) = 2.6 Hz,
Iridium(I) dicarbonyl complex, [Ir(CO)2(Lm)]BArF (17)
4
2H, H5), 8.19 (s, 1H, CH(Pz)2 at Ca), 7.95 (s, 1H, CH(Pz)2 at Cc),
7.84 (d, J(H3–H4) = 2.2 Hz, 2H, H3), 7.79 (s, 8H, ortho-CH of
Complex 15 (0.100 g, 0.0652 mmol) was dissolved in CH2Cl2
(5 mL). The solution was degassed using three cycles of freeze-
pump-thaw and treated under an atmosphere of carbon monoxide
for 5 min. An off-white precipitate was formed and the reaction
mixture stirred for an additional 10 mins. n-Pentane was added
and complex 17 was collected by filtration, washed with n-pentane
(3 ¥ 5 mL) and dried under vacuum. Yield: 0.0600 g (0.0405 mmol),
62%, m.p. 207–211 ◦C. Anal. Calcd. C54H30BF24IrN8O2: C, 43.77;
3
3
BArF ), 7.74 (d, J(H5¢-H4¢) = 2.3 Hz, 2H, H5¢), 7.57 (m, 5H,
4
para-CH of BArF and He), 7.48 (m, 2H, H3¢), 7.38 (d, J(Hd–
3
4
He) = 7.8 Hz, 1H, Hd), 6.64 (t, 3J(H4–H3 and H5) = 2.5 Hz, 2H,
H4), 6.53 (d, 3J(Hf–He) = 7.8 Hz, 1H, Hf), 6.28 (t, 3J(H4¢-H3¢ and
H5¢) = 2.0 Hz, 2H, H4¢), 5.95 (s, 1H, Hb), 4.44, 3.86 (each m, 2H,
CH of COD), 2.48, 1.92 (each m, 2H, CH2 of COD), 1.68 (m, 4H,
CH2 of COD) ppm.
1
H, 2.04; N, 7.56; found: C, 43.72; H, 2.14; N, 7.34%. H NMR
(600 MHz, CD2Cl2, 298 K): d 8.10 (br s, 2H, H5), 8.05 (d, 3J(H5–
H4) = 2.4 Hz, 2H, H5), 7.72 (br s, 8H, ortho-CH of BArF4 and H3),
Iridium(I) cyclooctadiene complex, [Ir(COD)(Lm)]BArF (15)
4
7.69 (s, 1H, CH(Pz)2 at Ca), 7.68 (s, 1H, CH(Pz)2 at Cc), 7.58–7.54
A solution of [Ir(COD)2]BArF (0.188 g, 0.147 mmol) in 5 mL of
3
4
(m, 8H, H3¢ and H5¢ and para-CH of BArF ), 7.52 (t, J(He–Hd
4
THF was added dropwise to a ice-cold solution of 1b9 (0.0600 g,
0.162 mmol) in 20 mL of THF. The reaction mixture was stirred
for 10 min in an ice bath. The solvent was removed and the crude
product was redissolved in CH2Cl2. n-Pentane was slowly added to
afford a yellow solid which was collected by filtration and washed
with n-pentane (3 ¥ 5 mL). Pure crystals of 15 were obtained
by the careful layering of n-pentane into a CH2Cl2 solution of
and Hf) = 7.7 Hz, 1H, He), 7.32 (d, 3J(Hd–He) = 7.7 Hz, 1H, Hd),
6.75 (t, 3J(H4–H3 and H5) = 2.8 Hz, 2H, H4), 6.41 (br s, 1H, Hf),
6.34 (t, 3J(H4–H3 and H5) = 2.2 Hz, 2H, H4¢), 5.74 (br s, 1H, Hb)
ppm. 13C{ H} NMR (150.9 MHz, CD2Cl2, 298 K): d 169.38 (s,
1
CO). IR (KBr disc) vCO = 2095, 2033 (s) cm-1.
Synthesis of heterobimetallic rhodium-iridium complexes, with
m-C6H4[CH(pz)2]2 ligand (Lm, 1a), (18–21)
the crude product. Yield: 0.110 g (0.0717 mmol), 49%, m.p. 228–
◦
232 C. ESI-MS (CH2Cl2), m/z (%): 672.1 (100) [M - BArF ]+.
4
Anal. Calcd. C60H42BF24IrN8: C, 46.98; H, 2.76; N, 7.30; found: C,
46.71; H, 2.98; N, 7.10%. 1H NMR (600 MHz, CD2Cl2, 298 K): d
8.04 (d, 3J(H5–H4) = 2.36 Hz, 2H, H5), 7.72 (s, 10H, ortho-CH of
BArF4 and H3), 7.67 (s, 1H, CH(Pz)2 at Cc), 7.57 (d, 3J(H5¢-H4¢) =
Rhodium-iridium dicyclooctadiene complex,
[Rh(COD)Ir(COD)(Lm)][BArF ]2 (18)
4
A CH2Cl2 solution of [Rh(COD)2]BArF (0.0578 g, 0.0489 mmol)
4
was added dropwise to a CH2Cl2 solution of complex 15 (0.0763 g,
0.0499 mmol). The reaction mixture was stirred for 0.5 h at RT.
n-Pentane was added slowly to afford a yellow solid which was
collected by filtration and washed with n-pentane (3 ¥ 5 mL).
The crude product was recrystallized from CH2Cl2/n-pentane to
form a mixture of products 18, 4 and 5 as a yellow solid. Yield:
0.117 g (0.0449 mmol), 92%. ESI-MS (CH2Cl2), m/z (%): 1655.0
([M - BArF ]+ of 3.4, 33), 1745.0 ([M - BArF ]+ of 3.20, 36), 1833.1
2.19 Hz, 2H, H5¢), 7.56 (br s, 4H, para-CH of BArF ), 7.54–7.49
4
3
(H3¢ and CH(Pz)2 at Ca and He), 7.33 (d, J(Hd–He) = 7.92 Hz,
1H, Hd), 6.66 (m, 2H, H4), 6.41 (d, 3J(Hf–He) = 7.59 Hz, 1H, Hf),
6.32 (m, 2H, H4¢), 5.74 (s, 1H, Hb), 4.06, 3.54 (each m, 2H, CH of
COD), 2.31, 1.72 (each m, 2H, CH2 of COD), 1.57–1.42 (m, 4H,
CH2 of COD) ppm.
4
4
([M - BArF ]+ of 3.5, 26). 1H NMR (600 MHz, CD2Cl2, 298 K):
Rhodium(I) dicarbonyl complex, [Rh(CO)2(Lm)]BArF (16)
4
4
3
d 8.00 (m, 4H, H5), 7.92 (m, 4H, H5¢), 7.86 (t, J(He–Hd and f) =
8.03 Hz, 1H, He of [Rh2]), 7.78 (t, 3J(He–Hd and f) = 8.03 Hz, 1H, He
Complex 14 (0.0608 g, 0.0421 mmol) was dissolved in CH2Cl2
(5 mL). The solution was degassed using three cycles of freeze-
pump-thaw and treated under an atmosphere of carbon monoxide
using a balloon for 10 min. The solution changed from a bright
yellow to a pale yellow solution. n-Pentane was slowly added
into the reaction mixture under a nitrogen atmosphere and a
yellow oil was obtained. The pentane layer was removed and the
carbonylation step was repeated, whereupon n-pentane was added
slowly to afford a very pale yellow solid which was collected by
filtration, washed with n-pentane (3 ¥ 5 mL) and dried under
vacuum to afford 16. Yield: 0.0470 g (0.0338 mmol), 80%. ESI-
of [RhIr]), 7.77 (m, 4H, H3), 7.72 (m, 17H, ortho-CH of BArF ,
4
He of [Ir2]), 7.55 (m, 12H, para-CH of BArF and H3¢), 7.47, 7.41
4
(2 s, 2H, CH of [RhIr]), 7.46 (s, 2H, CH of [Ir2]), 7.42 (s, 2H, CH
3
of [Rh2]), 6.96 (d, J(Hd and f–He) = 7.63 Hz, 2H, Hd and f of [Rh2]),
6.91, 6.87 (2d, 3J(Hd and f–He) = 7.39 Hz, 2H, Hd and f of [RhIr]), 6.82
3
3
(d, J(Hd and f–He) = 6.87 Hz, 2H, Hd and f of [Ir2]), 6.67 (t, J(H4-
3
H3/H5) = 2.45 Hz, 4H, H4), 6.57 (t, J(H4-H3/H5) = 2.34 Hz,
4H, H4¢), 5.46 (s, 1H, Hb of [Rh2]), 5.40 (s, 1H, Hb of [RhIr]), 5.35
(br s, 1H, Hb of [Ir2]); for [Rh]COD: 4.35, 3.70 (each m, 4H, CH),
2.54, 1.91, 1.79, 1.66 (each m, 4H, CH2); for [Ir]COD: 4.15, 3.44
(each m, 4H, CH), 2.35, 1.73, 1.60, 1.47 (each m, 4H, CH2) ppm.
MS (Acetone), m/z (%): 529.1 (44) [M - BArF ]+. Anal. Calcd.
4
C54H30BF24N8O2Rh: C, 46.57; H, 2.17; N, 8.05; found: C, 46.38;
H, 2.46; N, 7.75%. 1H NMR (500 MHz, d8-THF, 298 K): d 8.41 (s,
2H, H5), 8.33 (s, 1H, CH(Pz)2 at Ca), 8.26 (s, 2H, H3), 7.90 (s, 1H,
Rhodium(cyclooctadiene)-iridium(dicarbonyl) complex,
[Rh(COD)Ir(CO)2(Lm)][BArF ]2 (19)
4
CH(Pz)2 at Cc), 7.79 (s, 8H, ortho-CH of BArF ), 7.69 (s, 2H, H5¢),
4
7.57 (m, 4H, para-CH of BArF ) 7.50 (s, 2H, H3¢), 7.46 (t, 3J(He–
A n-pentane/CH2Cl2 solution of [Rh(COD)2]BArF (0.0239 g,
4
4
3
Hd and Hf) = 7.9 Hz, 1H, He), 7.25 (d, J(Hd–He) = 7.9 Hz, 1H,
0.0202 mmol) and complex 17 (0.0300 g, 0.0202 mmol) were
stirred at RT for 30 mins. n-Pentane was added slowly to afford a
yellow solid which was collected by filtration and washed with n-
pentane (3 ¥ 5 mL) to afford 19, 4, and 11 as a yellow solid. Yield:
0.0329 g (0.0194 mmol), 96%. ESI-MS (Acetone), m/z (%):1655.2
3
Hd), 6.79 (s, 2H, H4), 6.60 (d, J(Hf–He) = 7.2 Hz, 1H, Hf), 6.29
1
(s, 2H, H4¢), 5.89 (s, 1H, Hb) ppm. 13C{ H} NMR (150.9 MHz,
d8-THF, 298 K): d 183.16 (d, 1J(Rh–CO) = 70.0 Hz, CO). IR (KBr
disc) vCO = 2107, 2049 (s) cm-1.
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([M - BArF ]+ of 3.4, 45), 1693.2 ([M - BArF ]+ of 3.21, 100),
4
4
Notes and references
1731.2 ([M - BArF ]+ of 3.7, 45). H NMR (600 MHz, CD2Cl2,
1
4
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273 K): d 8.13–8.02 (m, 12H, H5 of [Ir2] and H5 of [RhIr]), 7.93–
7.90 (m, 8H, H5 of [Rh]2 and H5¢ of [RhIr]), 7.85 (m, 1H, He),
7.71 (m, He and ortho-CH of BArF ), 7.67, 7.65 (2 s, 2H, CH of
4
[Ir2] and CH of [IrRh]), 7.55 (m, 12H, para-CH of BArF and H3
4
of [Rh2] and H3¢ of [RhIr]), 7.48, 7.46 (2 s, 2H, CH of [Rh]2 and
3
CH of [RhIr]), 6.94 (d, J(Hd and f–He) = 7.6 Hz, 2H, Hd and f), 6.86
(2d, 3J(Hd and f–He) = 7.1 Hz, 2H, Hd and f), 6.80–6.74 (m, 4H, H4 of
[Ir2] and H4 of [IrRh]), 6.57 (m, 4H, H4¢ of [RhIr]), 6.55 (m, 4H,
H4 of [Rh2]), 5.70–5.37 (m, 2H, Hb), 5.22 (br s, 1H, Hb of [Ir2]);
for [Rh]COD: 4.33 (m, 4H, CH of), 3.82, 3.69 (each m, 2H, CH),
2.51, 1.89 (each m, 4H, CH2), 1.76, 1.60 (each m, 4H, CH2) ppm.
1
19F{ H} NMR (282.4 MHz, CD2Cl2, 298 K): d -63.17 ppm. IR
(KBr disc) vCO = 2100, 2037 (s) cm-1. IR (liquid, CH2Cl2) vCO
=
2097, 2033 (s) cm-1.
Rhodium-iridium 13C-labeled tetracarbonyl complex,
[RhIr(13CO)4(Lm)][BArF ]2 (20)
4
A dichloromethane-d2 (0.6 mL) solution of the mixture of
complexes 18, 4 and 5 was added into a Young’s NMR tube.
13C-Labelled carbon monoxide was bubbled into the mixture for
1 min and a mixture of complexes 20, 10 and 11 and free COD
were formed in situ. 1H NMR (600 MHz, CD2Cl2, 243 K): d 8.11
(s, 2H, H5 of [Ir2] and H5 of [RhIr]), 8.04 (s, 2H, H5 of [Rh]2 and
H5¢ of [RhIr]), 8.00–7.96 (m, 2H, H3 of [Ir2] and H3¢ of [IrRh]),
7.86–7.80 (m, 2H, H3 of [Rh2] and H3 of [RhIr]), 7.78–7.65 (m,
ortho-CH of BArF and CH of [Ir2] and CH of [IrRh]), 7.62, 7.61
4
(2 s, 2H, CH of [Rh]2 and CH of [RhIr]), 7.51 (br s, 8H, para-CH
of BArF ), 7.42–7.30 (m, 1H, He), 6.70 (m, 2H, H4 of [Ir2] and H4
4
of [IrRh]), 6.61 (m, 1H, H4¢ of [RhIr] and H4 of [Rh2]), 6.50–6.42
(m, 2H, Hd/f), 5.50 (CH of free COD), 5.26–5.19 (m, 1H, Hb), 2.29
11 A. Ceccon, S. Santi, L. Orian and A. Bisello, Coord. Chem. Rev., 2004,
248, 683.
12 (a) M. E. Broussard, B. Juma, S. G. Train, W.-J. Peng, S. A. Laneman
and G. G. Stanley, Science, 1993, 260, 1784; (b) R. C. Matthews, D. K.
Howell, W.-J. Peng, S. G. Train, W. D. Treleaven and G. G. Stanley,
Angew. Chem., Int. Ed. Engl., 1996, 35, 2253.
1
(m, CH2 of free COD) ppm. 19F{ H} NMR (282.4 MHz, CD2Cl2,
298 K): d -63.17 ppm. IR (KBr disc) vCO = 2100, 2037 (s) cm-1.
Iridium(I) cyclooctadiene complex, [Ir(COD)(LAnt)]BArF (22)
4
13 (a) H. Li and T. J. Marks, Proc. Natl. Acad. Sci. U. S. A., 2006, 103,
15295; (b) H. Li, C. L. Stern and T. J. Marks, Macromolecules, 2005,
38, 9015; (c) H. Li, L. Li, D. J. Schwartz, C. L. Stern and T. J. Marks,
J. Am. Chem. Soc., 2005, 127, 14756; (d) H. Li, L. Li and T. J. Marks,
Angew. Chem., Int. Ed., 2004, 43, 4937.
14 (a) H. Steinhagen and G. Helmchen, Angew. Chem., Int. Ed. Engl.,
1996, 35, 2339; (b) M. A. Esteruelas, M. P. Garcia, A. M. Lo´pez and
L. A. Oro, Organometallics, 1991, 10, 127.
15 J. H. H. Ho, R. Hodgson, J. Wagler and B. A. Messerle, Dalton Trans.,
2010, 39, 4062.
16 S. L. Dabb, J. H. H. Ho, R. Hodgson, B. A. Messerle and J. Wagler,
Dalton Trans., 2009, 634.
Complex 22 was synthesized according to the procedure of
15. Crystals suitable for a single crystal structure analysis were
obtained by the careful layering of n-pentane onto a CH2Cl2
solution of 22.
Acknowledgements
Financial support from the University of New South Wales is
gratefully acknowledged. J. H. H. Ho thanks the University of New
South Wales for a University International Postgraduate Award
(UIPA).
17 B. Guzel, M. A. Omary, J. P. Fackler, Jr. and A. Akgerman, Inorg.
Chim. Acta, 2001, 325, 45.
11042 | Dalton Trans., 2011, 40, 11031–11042
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The Royal Society of Chemistry 2011
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