Terminal and bridging parent amido 1,5-cyclooctadiene complexes of rhodium and iridium

Article abstract of DOI:10.1002/chem.201204391

The ready availability of rare parent amido d⁸ complexes of the type [{M(μ-NH₂)(cod)}₂] (M=Rh (1), Ir (2); cod=1,5-cyclooctadiene) through the direct use of gaseous ammonia has allowed the study of their reactivity. Both complexes 1 and 2 exchanged the di-olefines by carbon monoxide to give the dinuclear tetracarbonyl derivatives [{M(μ-NH₂)(CO)₂}₂] (M=Rh or Ir). The diiridium(I) complex 2 reacted with chloroalkanes such as CH₂Cl ₂ or CHCl₃, giving the diiridium(II) products [(Cl)(cod)Ir(μ-NH₂)₂Ir(cod)(R)] (R=CH₂Cl or CHCl₂) as a result of a two-center oxidative addition and concomitant metal-metal bond formation. However, reaction with ClCH₂CH ₂Cl afforded the symmetrical adduct [{Ir(μ-NH₂)(Cl) (cod)}₂] upon release of ethylene. We found that the rhodium complex 1 exchanged the di-olefines stepwise upon addition of selected phosphanes (PPh₃, PMePh₂, PMe₂Ph) without splitting of the amido bridges, allowing the detection of mixed COD/phosphane dinuclear complexes [(cod)Rh(μ-NH₂)₂Rh(PR₃) ₂], and finally the isolation of the respective tetraphosphanes [{Rh(μ-NH₂)(PR₃)₂}₂]. On the other hand, the iridium complex 2 reacted with PMe₂Ph by splitting the amido bridges and leading to the very rare terminal amido complex [Ir(cod)(NH₂)(PMePh₂)₂]. This compound was found to be very reactive towards traces of water, giving the more stable terminal hydroxo complex [Ir(cod)(OH)(PMePh₂)₂]. The heterocyclic carbene IPr (IPr=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) also split the amido bridges in complexes 1 and 2, allowing in the case of iridium to characterize in situ the terminal amido complex [Ir(cod)(IPr)(NH ₂)]. However, when rhodium was involved, the known hydroxo complex [Rh(cod)(IPr)(OH)] was isolated as final product. On the other hand, we tested complexes 1 and 2 as catalysts in the transfer hydrogenation of acetophenone with iPrOH without the use of any base or in the presence of Cs ₂CO₃, finding that the iridium complex 2 is more active than the rhodium analogue 1. Tight connection: The reactivity and relative strength of NH₂ bridges in cyclooctadiene (cod) complexes of Rh and Ir of the type [{M(μ-NH₂)(cod)}₂] have been tested with a variety of donors. In general they are tightly bound to the metals. With the diiridium complex and selected ligands, the formation of terminal [Ir(d ⁸)-NH₂] species were observed (see scheme).

Full text of DOI:10.1002/chem.201204391

FULL PAPER
DOI: 10.1002/chem.201204391
Terminal and Bridging Parent Amido 1,5-Cyclooctadiene Complexes of
Rhodium and Iridium
Inmaculada Mena,[a] E. A. Jaseer,[b] Miguel A. Casado,*[a] Pilar Garcꢀa-OrduÇa,[a]
Fernando J. Lahoz,[a] and Luis A. Oro*[a, b]
Abstract: The ready availability of rare
plex 1 exchanged the di-olefines step-
wise upon addition of selected phos-
phanes (PPh3, PMePh2, PMe2Ph) with-
out splitting of the amido bridges, al-
lowing the detection of mixed COD/
terminal hydroxo
A
complex
[Ir-
parent amido d8 complexes of the type
[{M
G
N
clic carbene IPr (IPr=1,3-bis(2,6-diiso-
propylphenyl)imidazol-2-ylidene) also
split the amido bridges in complexes 1
and 2, allowing in the case of iridium
to characterize in situ the terminal
amido complex [Ir
However, when rhodium was involved,
the known hydroxo complex [Rh(cod)-
ACHTUNGTRENN(UNG IPr)(OH)] was isolated as final prod-
uct. On the other hand, we tested com-
plexes 1 and 2 as catalysts in the trans-
fer hydrogenation of acetophenone
with iPrOH without the use of any
base or in the presence of Cs2CO3,
finding that the iridium complex 2 is
more active than the rhodium analogue
1.
cod=1,5-cyclooctadiene) through the
direct use of gaseous ammonia has al-
lowed the study of their reactivity.
Both complexes 1 and 2 exchanged the
di-olefines by carbon monoxide to give
the dinuclear tetracarbonyl derivatives
phosphane
[(cod)Rh(m-NH2)2Rh
ly the isolation of the respective tetra-
phosphanes [{Rh(m-NH2)(PR3)2}2]. On
dinuclear
complexes
A
ACHTUNGTRENNUNG
ACHTUNGTREN(GNUN cod)ACHTNUTRGEG(NNUN IPr)ACHTUNGTRENNUNG(NH2)].
A
ACHTUNGTRENNUNG
[{M
N
the other hand, the iridium complex 2
reacted with PMe2Ph by splitting the
amido bridges and leading to the very
ACHTUNGTRENNUNG
The diiridium(I) complex 2 reacted
with chloroalkanes such as CH2Cl2 or
CHCl3, giving the diiridium(II) prod-
rare terminal amido complex [Ir
ACHTUNGTRNE(NUNG cod)-
ucts
[(Cl)
(cod)Ir
E
G
A
ACHTUNGTRENNUNG
(R=CH2Cl or CHCl2) as a result of a
two-center oxidative addition and con-
comitant metal–metal bond formation.
However, reaction with ClCH2CH2Cl
found to be very reactive towards
traces of water, giving the more stable
Keywords: cyclooctadienyl ligands ·
hydrogen transfer · iridium · parent
amido · rhodium
afforded the symmetrical adduct [{Ir
ACHTUNGERTN(NUNG m-
NH2)(Cl)(cod)}2] upon release of ethyl-
ACHTUNGTRENNUNG
ene. We found that the rhodium com-
Introduction
transfer hydrogenation to unsaturated substrates,[4] among
other organic transformations.[5] However, related work on
À
In general, the chemistry of amido late-metal complexes
parent amido late-metal complexes (M NH2) has been far
À
(M NHR; R=alkyl, aryl) has experienced a substantial
less developed, even though these complexes are thought to
be intermediates in catalytic homogeneous transformations
such as coupling between ammonia and aryl halides[6] or
boronic acids[7] to give primary aryl amines. More impor-
tantly, an isolated terminal parent amido complex of palladi-
evolution during the two past decades, from which reliable
methods of synthesis have been developed.[1] The main
reason behind these efforts lies in the crucial participation
of these species in relevant homogeneous catalytic processes
[3]
such as hydroamination,[2] C N coupling reactions, and
um has been reported to undergo C N reductive elimina-
À
À
tion to yield an aryl amine.[8]
The scarceness of methods to generate stable parent
amido late-metal species may be considered a factor of rele-
vance to explain the delayed study of the catalytic perform-
ance of parent amido late-metal complexes when compared
with the related aryl- or alkyl amido species. As a matter of
fact, it must be pointed out that these species are very rare
and no general synthetic methods have been developed for
their preparation.[9] So far, rational synthetic routes to these
compounds involve mainly salt metathesis reactions that dis-
place halogen ligands with amido nucleophiles,[10] dehydro-
halogenation of NH3 metallic adducts,[11] or deprotonation
of cationic NH3 adducts with strong bases.[12] Recently,
parent-amido-bridged complexes of ruthenium and iridium
[a] Dipl.-Chem. I. Mena, Dr. M. A. Casado, Dr. P. Garcꢀa-OrduÇa,
Prof. F. J. Lahoz, Prof. L. A. Oro
Instituto de Sꢀntesis Quꢀmica y Catꢁlisis Homogꢂnea ISQCH
Universidad de Zaragoza-CSIC
C/Pedro Cerbuna, 12, 50009 Zaragoza (Spain)
Fax : (+34)976-761-187
E-mail: mcasado@unizar.es
oro@unizar.es
[b] Dr. E. A. Jaseer, Prof. L. A. Oro
Centre of Research Excellence in Petroleum and Petrochemicals
King Fahd University of Petroleum & Minerals
Dhahran 31261 (Saudi Arabia)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201204391.
Chem. Eur. J. 2013, 19, 5665 – 5675
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5665

have been obtained by transfer hydrogenation to dinuclear
azido-bridged complexes with 2-propanol,[13] and a terminal
amido iridium complex has been isolated from the hydroge-
[14]
ꢀ
nation of a unique Ir N nitrido compound. It is important
to mention that none of these synthetic methods makes use
of ammonia as the source of “NH2” fragments, which we be-
lieve is a crucial factor to achieve further functionalization
of ammonia.[15]
In this line, there are some reports concerning the forma-
tion of amido complexes of Ir through oxidative addition
processes to afford parent-amido-bridged or terminal spe-
cies,[16] a phenomenon that was further confirmed by Hart-
wig et al., who reported on the formal oxidative addition of
ammonia to an electronic-rich IrI pincer system, leading to
the isolation of the first terminal amido hydrido IrIII com-
plex.[17] On the other hand, heterolytic splitting of ammonia
was very recently achieved with iridium[18] and ruthenium[19]
systems through metal–ligand cooperation. These methodol-
ogies lead to parent amido late-metal complexes by utilizing
NH3 as the direct source for the amido ligands, which we be-
lieve is the right approach to achieve further functionaliza-
tion of ammonia. Accordingly to this statement, we have re-
cently disclosed a novel strategy that allows the high-yield
access to parent-amido-bridged complexes of RhI and IrI
through heterolytic splitting of gaseous ammonia under very
mild conditions.[20]
Scheme 1. Synthesis of [{M
tetracarbonyl derivatives [{MAHCNUTGTRENNUNG
N
ACHTUNGERTN(NUNG cod)}2] (M=Rh (1), Ir (2)) and the
ity of complexes 1 and 2 in diethyl ether allowed their easy
isolation. Complexes 1 and 2 are quite sensitive towards
moisture; as a matter of fact, addition of stoichiometric
amounts of water to [D6]benzene solutions of 1 and 2 af-
forded the known hydroxo-bridged complexes [{M
(cod)}2] (M=Rh, Ir), upon release of ammonia, as con-
firmed by NMR measurements.
ACHTUNGTRENNUNG(m-OH)-
AHCTUNGTRENNUNG
The structure of complex 1 has been recently reported.[20]
In the present study, X-ray diffraction analysis of complex 2
confirms that both complexes exhibit similar structural fea-
tures. The main difference between them concerns their
asymmetric unit contents: two and three crystallographically
independent but chemically identical molecules for complex
1 and 2, respectively. Only one of those molecules of com-
plex 2 is depicted in Figure 1, and selected bond lengths and
angles are reported in Table 1. Both complexes are dinu-
The ready availability of these unusual species through
this protocol has allowed us to assess their reactivity towards
a variety of substrates. So far, the reactivity of terminal
parent amido complexes has been focused in proton ex-
12b, 21]
change processes with weak acids,[11a,
insertions of
and reductive
[10b]
À
carbon monoxide into the N H bond,
elimination of ammonia,[11b] a work that evidences a high ba-
sicity at the terminal amido nitrogen, which bears an ex-
posed and reactive free electron pair. The situation is quite
different in bridging parent amido complexes, in which the
lone electronic pair is usually tightly bounded in a dative
fashion to a second metal.[13,16a,b,f,18,24] In this context, a sig-
nificant contribution has been recently reported dealing
with the role of [Ir-NH2-Ir] linkages in catalytic transfer hy-
drogenation, enlightening a novel binuclear, outer-sphere
Noyori-like mechanism, in which the NH2 groups behave as
non-innocent ligands playing a key role in alcohol dehydro-
genation and imido formation.[25]
Figure 1. Molecular structure of complex 2.
Table 1. Selected bond lengths [ꢄ] and angles [8] for complex 2.[a]
À
À
Ir(1) N(1)
2.071(5)
2.074(5)
1.989(7)
1.985(5)
1.405(8)
1.397(9)
2.8146(3)
76.4(2)
Ir(2) N(1)
2.075(5)
2.081(5)
1.996(6)
1.993(7)
1.386(9)
1.377(10)
À
À
Ir(1) N(2)
Ir(2) N(2)
Results and Discussion
À
À
Ir(1) M(1)
Ir(2) M(3)
À
À
Ir(1) M(2)
Ir(2) M(4)
In a preliminary communication we reported on the facile
and high-yield access to RhI and IrI parent amido complexes
directly with gaseous ammonia.[20] In this way, bubbling NH3
to ethereal solutions of the methoxo-bridged complexes
À
À
C(1) C(2)
C(9) C(10)
À
À
C(5) C(6)
C(13) C(14)
Ir(1)···Ir(2)
N(1)-Ir(1)-N(2)
N(1)-Ir(1)-M(1)
N(1)-Ir(1)-M(2)
N(2)-Ir(1)-M(1)
N(2)-Ir(1)-M(2)
N(1)-Ir(2)-N(2)
N(1)-Ir(2)-M(3)
N(1)-Ir(2)-M(4)
N(2)-Ir(2)-M(3)
N(2)-Ir(2)-M(4)
76.2(2)
174.0(2)
97.5(3)
98.2(2)
172.1(2)
170.7(3)
97.3(2)
97.3(2)
[{M
at atmospheric pressure and low temperatures (À58C) af-
forded amido-bridged complexes of formulae [{M(m-NH2)-
(cod)}2] (M=Rh (1), Ir (2)) in excellent yields (Scheme 1).
Even though these reactions are reversible, the poor solubil-
ACHTUNGTRENNUNG(m-OMe)ACHTUNGTRENNUNG(cod)}2] (M=Rh, Ir; cod=1,5-cyclooctadiene)
AHCTUNGTRENNUNG
172.2(2)
ACHTUNGTRENNUNG
À
[a] M(1), M(2), M(3), and M(4) represent the midpoints of the C(1)
C(2), C(5) C(6), C(9) C(10), and C(13) C(14) bonds, respectively.
À
À
À
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Chem. Eur. J. 2013, 19, 5665 – 5675

Amido 1,5-Cyclooctadiene Complexes of Rhodium and Iridium
FULL PAPER
clear, formed by two “M
(cod)” fragments bridged by two
an ideal square-planar geometry than in 2, as it lies only
0.0401(2) ꢄ out of plane. The dihedral angle between the
NIrN planes (126.92(15)8) is slightly superior to that shown
in 2, therefore leading to a longer intermetallic distance of
2.9576(4) ꢄ, which compares well with that shown by the re-
amido groups. The metal atoms exhibit a distorted square-
planar coordination, involving two N atoms and the olefinic
bonds to which they are bonded in a h2-C=C fashion. An in-
dication of the distortion from an ideal square-planar coor-
dination in 2 comes from the fact that the iridium atoms lie
0.1081(3) and 0.0652(3) ꢄ out of the least-square plane
(formed by the two N atoms and the mid-points of the ole-
finic bonds) towards the other metal.
lated
amido-bridged
complex
[{IrACTHNGUTERNN(UG m-NH(p-
C6H4CH3))(CO)2}2] (2.933(1) ꢄ),[29] and follow the general
trend previously commented.
The amido groups behave as strong hydrogen donors to-
wards oxygen atoms of terminal carbonyls of adjacent mole-
cules, forming hydrogen-bond rings R22(10) (Table 3 and
Figure 3). Thus, hydrogen networks, along the c and a+c di-
rections, are established at a supramolecular level in the
crystalline structure of 4.
As in complex 1, the four-membered ring “IrNIrN” of
complex 2 shows a folded conformation; the dihedral angle
between the coordination planes defined by N(1)-Ir(1)-N(2)
and N(1)-Ir(2)-N(2) is 119.2(4)8, and consequently, a rela-
tively short metal–metal distance of 2.8146(3) ꢄ was ob-
served. This value, shorter than that found in the related
[{Ir
mean value found in dinuclear Ir compounds involving two
bridging atoms (2.584–2.968 ꢄ, mean value
ACHTUNGTRENNUNG(m-OEt)ACHTUNGTRENNUNG
(cod)}2] complex, 2.8958(11) ꢄ,[26] is close to the
Table 3. Bond lengths and angles for the hydrogen-bonding scheme in
complex 4.[a]
N
À
À
D H [ꢄ]
H···A [ꢄ]
D···A [ꢄ]
D H···A [8]
2.781(12) ꢄ).[27] In fact a deeper analysis of these “IrNIrN”
central cores revealed a direct relationship between the in-
termetallic distance and the four-membered-ring folding
(similar to that observed for “RhORhO” fragments).[28]
Values on the three independent molecules of compound 2
nicely follow the general trend (see the Supporting Informa-
tion).
À
N(1) H(2)···O
N
0.86(2)
0.86(4)
0.87(7)
2.52(5)
2.64(4)
2.84(8)
3.209(7)
3.325(5)
3.274(7)
137(2)
138(2)
112(5)
À
N(1) H(2)···O
v
À
N(1) H(1)···O(2 )
[a] Symmetry operation ’’) Àx, Ày+1, Àz; iv) xÀ1/2, 1/2Ày, zÀ1/2; v) Àx,
Ày, Àz.
Complexes 1 and 2 exchanged the di-olefines upon expo-
sure to carbon monoxide at atmospheric pressure, affording
complexes [{MACHTUNGTRENNUNG(m-NH2)(CO)2}2] (M=Rh (3), Ir (4)) as
yellow solids in moderate yields (Scheme 1). Yellow single
crystals of 4 were grown from a concentrated solution of the
complex in [D6]benzene at room temperature. The molecu-
lar structure of complex 4, very similar to the precursor
complex 2, is depicted in Figure 2. Selected geometrical pa-
rameters are reported in Table 2. Complex 4 is a dinuclear
Ir complex formed by two “Ir(CO)2” fragments related by a
crystallographic two-fold axis symmetrically bridged by two
amido groups. The metal coordination is less deviated from
Figure 3. One of the hydrogen-bonded network established in solid struc-
ture of 4. Symmetry operations: ’) Àx, y, 1/2Àz, ’’) Àx, 1Ày,Àz, ’’’) x, 1Ày,
zÀ1/2.
1
The H NMR spectra of the carbonyl the complexes 3 and
4 were featureless, showing a lone broad signal (d=À1.40
and À0.25 ppm for complexes 3 and 4, respectively) from
the amido ligands at all temperatures in [D8]toluene. These
amido protons correlated to the nitrogen resonances giving
signals at d=À45.0 and 5.1 ppm for 3 and 4, respectively, as
confirmed by 1H–15N HMBC measurements. The
13C{1H} NMR spectra were also very simple, because all the
carbonyls were found to be chemically equivalent. However,
IR data from solutions of complexes 3 and 4 in THF were
more informative; both spectra displayed a set of three
strong absorption bands for the terminal carbonyls, in agree-
ment with the bent conformation of the molecular frame-
Figure 2. Molecular structure of complex 4.
Table 2. Selected bond lengths [ꢄ] and angles [8] for complex 4.[a]
À
Ir(1)···Ir(2)
2.9577(4)
1.859(6)
75.0(2)
172.1(2)
97.7(2)
Ir(1) N(1)
Ir(1) C(2)
N(1’)-Ir(1)-C(1)
N(1’)-Ir(1)-C(2)
C(1)-Ir(1)-C(2)
2.082(4)
1.858(6)
97.4(2)
172.4(2)
89.8(2)
À
À
Ir(1) C(1)
N(1)-Ir(1)-N(1’)
N(1)-Ir(1)-C(1)
N(1)-Ir(1)-C(2)
[a] Primed atoms are related to the non-primed ones by Àx, y, 1/2Àz
symmetry operation.
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M. A. Casado, L. A. Oro et al.
work with C2v symmetry, as observed in the solid state for 4.
This structural information indicated that complexes 3 and 4
should be isostructural in solution. It is interesting to have a
close look to the n˜(CO) stretching frequencies of complexes
15N–1H HMBC, 13C–1H HSQC, and COSY bidimensional
techniques, mass spectrometry, IR spectroscopy, and ele-
mental analyses.
Red single crystals of complexes 5 and 7 were obtained
by allowing concentrated solutions of complex 2 to stand in
toluene with dichloromethane or dichloroethane for three
days, respectively. X-ray diffraction measurements con-
firmed the dinuclear nature of adducts 5 and 7, and revealed
the fact that the asymmetric unit of 7 is composed by two
crystallographically independent but very similar molecules
(together with two solvent toluene molecules). For clarity,
only one of them will be described in this manuscript, fur-
ther information can be found in the Supporting Informa-
tion.
The molecular structures of 5 and 7 are depicted in Fig-
ures 4 and 5, respectively. Selected bond length and angles
are given in Tables 4 and 5, respectively. Both complexes
show a similar dinuclear arrangement, with iridium centers
linked together by two parent amido groups. Without con-
sidering metal–metal bonds, the geometry around the metal
atoms is best described as a slightly distorted square pyra-
mid. In both complexes the pyramid base is formed by the
olefinic carbon atoms of the cyclooctadiene ligand (coordi-
3
(n˜ =2079, 2042, 1970 cmÀ1) and
4
(n˜ =2059, 2035,
1972 cmÀ1) and cross check them with those shown by struc-
turally related open-book complexes of the type [{M(m-
AHCTUNGTRENNUNG
L)(CO)2}2] (L=SR,[30] OR,[31] NHR[32]). The comparison
clearly shows that the tetracarbonyl parent amido complexes
3 and 4 display the more nucleophilic metallic centers
among these series. For instance, a 16 cmÀ1 shift towards
lower frequencies is observed in the IR spectra for com-
plexes 3 and 4 when compared to those shown by related
amido complexes [{MACTHNUTRGENNUG(m-NHACHTUNGTRNE{NUGN p-tolyl})(CO)2}2] (M=Rh,
Ir).[29] The simple and effective NH2-bridged bimetallic
system should be responsible by itself of the high basicity in-
duced to the metals.
This scenario has been explored by assessing the reactivity
of iridium complex 2 with chlorocarbons, which are known
to be relatively unreactive substrates and are indeed used as
solvents in many organometallic reactions. Rhodium com-
plex 1 was found to be very reactive towards chloroform
and dichloromethane giving, among unidentifiable mixtures
of COD-containing complexes and black insoluble solids,
yellow crystals of the mononuclear ammine adduct [Rh-
ACHTUNGTRENNUNG(cod)ClACHTUNGTRENNUNG(NH3)], which was fully characterized (see the Sup-
porting Information). More interestingly, the iridium com-
plex 2 reacted in a controlled way towards selected chloro-
carbons (CH2Cl2, CHCl3, and ClCH2CH2Cl), affording in
general dinuclear adducts that arise from a concerted dinu-
clear oxidative addition of the substrates.
NMR monitoring of the reaction of 2 with a tenfold
excess of dichloromethane or chloroform in [D6]benzene
solutions in the absence of light showed, after a few days,
the complete transformation to new species characterized as
the dinuclear adducts [(Cl)
N
N
ACHUTGTNNERNUG(cod)CAHTUNGTREN(NUNG CH2Cl)]
(5) and [(Cl)(cod)Ir(m-NH2)2Ir
G
E
N
ACHTUNGTRENNUNG
ly. However, when dichloroethane was used as substrate, the
clean formation of the symmetrical di-chloro complex [{Ir-
ACHTUNGTRENNUNG(m-NH2)ACHTUNGTRENNUNG(cod)(Cl)}2] (7) was observed, along with released
ethylene (Scheme 2). The diiridium adducts 5–7 were fully
Figure 4. Molecular structure of complex 5.
characterized by multinuclear NMR spectroscopy, including
Scheme 2. Synthesis of the dinuclear adducts 5–7; R=CH2Cl (5), CHCl2
(6).
Figure 5. Molecular structure of complex 7.
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Chem. Eur. J. 2013, 19, 5665 – 5675

Amido 1,5-Cyclooctadiene Complexes of Rhodium and Iridium
FULL PAPER
Table 4. Selected bond lengths [ꢄ] and angles [8] for complex 5.[a]
1
the cod=CH protons in the H NMR spectrum, clearly re-
flecting the C2v symmetry observed in the solid state, where-
as the non-symmetrical adducts 5 and 6 gave four distinct
À
À
Ir(1) Ir(2)
2.6794(3)
2.078(5)
2.064(5)
2.032(6)
2.044(6)
2.148(12)
1.403(8)
1.394(8)
83.44(16)
86.98(15)
78.2(2)
Ir(1) Cl(1A)
2.516(3)
2.043(5)
2.054(5)
2.037(6)
2.040(6)
1.819(12)
1.398(8)
1.397(8)
90.4(4)
93.8(3)
79.3(2)
167.2(2)
94.6(2)
96.8(2)
À
À
Ir(1) N(1)
Ir(2) N(1)
À
À
signals both in their H and their 13C{1H} NMR spectra, in
accordance with the Cs symmetry found in the molecular
structure of 5.
Some comments concerning the formation of the oxidized
species 5–7 should be underlined at this point. Although
two-center oxidative addition of chloro-containing sub-
strates is a process well recognized in some diiridium sys-
tems with highly basic ancillary such as isocyanides,[36] the
action of light (or ultraviolet light) is frequently needed.[37]
For the sake of comparison, the diiridium pyrazolyl complex
Ir(1) N(2)
Ir(2) N(2)
1
À
À
Ir(1) M(1)
Ir(2) M(3)
À
À
Ir(1) M(2)
Ir(2) M(4)
À
À
Ir(2) C
A
C
(17A) Cl(2A)
À
À
C(1) C(2)
C(9) C(10)
À
À
C(5) C(6)
C(13) C(14)
Cl(1A)-Ir(1)-N(1)
Cl(1A)-Ir(1)-N(2)
N(1)-Ir(1)-N(2)
N(1)-Ir(1)-M(1)
N(1)-Ir(1)-M(2)
N(2)-Ir(1)-M(1)
N(2)-Ir(1)-M(2)
C
C
(17A)-Ir(2)-N(1)
(17A)-Ir(2)-N(2)
N(1)-Ir(2)-N(2)
N(1)-Ir(2)-M(3)
N(1)-Ir(2)-M(4)
N(2)-Ir(2)-M(3)
N(2)-Ir(2)-M(4)
166.1(2)
98.2(2)
94.7(2)
168.1(2)
167.0(2)
[IrACTHNURTGENN(UG m-Pz)ACHTUNGTRENN(GUN cod)]2 is stable for weeks in dichloromethane or
À
[a] M(1), M(2), M(3), and M(4) represent the midpoints of the C(1)
dichloroethane; however, in the presence of visible irradia-
tion it undergoes a four-electron substrate reduction to give
well-defined oxidized species.[38]
À
À
À
C(2), C(5) C(6), C(9) C(10), and C(13) C(14) olefinic bonds, respec-
tively.
Table 5. Selected bond lengths [ꢄ] and angles [8] for complex 7.[a]
Amido phosphane and N-heterocyclic carbene complexes:
Encouraged by the lack of late d8 metal parent amido com-
plexes reported up to date, we took advantage of the ready
availability of amido complexes of RhI and IrI through our
original synthetic protocol to explore their reactivity. In par-
ticular, we chose different phosphanes and the N-heterocy-
clic carbene 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene
(IPr) as external ligands in an attempt to establish the
strength of the amido bridges in complexes 1 and 2.
The dirhodium complex 1 reacted with all selected phos-
phanes PR3 (PR3 =PPh3, PMePh2, PMe2Ph) by replacing the
cyclooctadiene ligands in a stepwise manner, without split-
ting of the amido bridges. NMR experiments allowed us to
observe, upon addition of two molar equivalents of the re-
spective phosphanes to 1, free COD and the formation of
mixed di-olefin/bis(phosphane) dinuclear species [(cod)Rh-
À
À
Ir(1) Cl(1)
2.4344(11)
2.060(3)
2.059(3)
2.045(4)
2.055(4)
Ir(2) Cl(2)
2.4565(10)
2.053(3)
2.062(4)
2.040(4)
2.035(5)
1.401(6)
1.396(6)
À
À
Ir(1) N(1)
Ir(2) N(1)
À
À
Ir(1) N(2)
Ir(2) N(2)
À
À
Ir(1) -M(1)
Ir(2)- M(3)
À
À
Ir(1) M(2)
Ir(2) M(4)
À
À
C(1) C(2)
1.392(6)
1.394(6)
C(9) C(10)
À
À
C(5) C(6)
C(13) C(14)
À
Ir(1) Ir(2)
2.6544(2)
87.13(10)
87.85(11)
78.88(14)
167.91(15)
96.17(15)
96.43(15)
167.66(15)
Cl(1)-Ir(1)-N(1)
Cl(1)-Ir(1)-N(2)
N(1)-Ir(1)-N(2)
N(1)-Ir(1)-M(1)
N(1)-Ir(1)-M(2)
N(2)-Ir(1)-M(1)
N(2)-Ir(1)-M(1)
Cl(2)-Ir(2)-N(1)
Cl(2)-Ir(2)-N(2)
N(1)-Ir(2)-N(2)
N(1)-Ir(2)-M(3)
N(1)-Ir(2)-M(4)
N(2)-Ir(2)-M(3)
N(2)-Ir(2)-M(4)
87.56(10)
89.74(11)
78.97(14)
167.80(15)
95.24(15)
96.24(16)
165.36(15)
À
[a] M(1), M(2), M(3), and M(4) represent the midpoints of the C(1)
À
À
À
C(2), C(5) C(6), C(9) C(10), and C(13) C(14) olefinic bonds, respec-
tively.
AHCNTURGENU(NG m-NH2)2RhCAHTUNGTRNEN(NGU PR3)2] (PR3 =PPh3 (8), PMePh2 (9), PMe2Ph
nated in their typical h2-C=C mode) and the nitrogen atoms
of the amido groups. The apical position of one of the iridi-
um atoms is occupied by a chlorine, whereas a carbon atom
of a chloromethylene fragment (5) or a chlorine (7) is locat-
ed at the apex of the other pyramid.
(10)), with an observed COD/PR3 ratio in their 1H NMR
spectra of 1:2 in all cases. The NMR pattern of the COD
protons and carbons at all ranges of temperature indicated
C2v symmetry, instead of the expected Cs symmetry related
with an open-book-like geometry (see the Experimental
Section). To fully understand the NMR spectra of complexes
8–10 one has to consider the known butterfly-like motion as-
sociated with dinuclear amido-bridged d8 complexes, which
consists of a four-membered metallacycle inversion, which is
very fast on the NMR time scale. This dynamic process pro-
The square pyramids of both metal atoms share the basal
edge defined by the two amido groups, allowing this way the
À
formation of iridium–iridium bonds (Ir(1) Ir(2): 2.6794(3)
and 2.6544(2) ꢄ for complex 5 and 7, respectively). These
short separations fall within the range of iridium–iridium
bond lengths, and are comparable to those observed in relat-
duces averaged NMR signals that reflect
a
planar
ed dinuclear, metal–metal bonded complexes such as [{Ir
StBu)(I)(CO)2}2] (2.638(1) ꢄ; tBu=tert-butyl),[33] [{Ir
(m-Pz)-
(m-StBu)(m-dmad)(P(OMe)3)2(CO)2}2] (2.614(2) ꢄ; Pz=pyr-
azolyl, dmad=dimethylacetylenedicarboxylate),[34] or [{Ir
(m-
NCPh2)Cl
(cod)}2] (2.6829(7) ꢄ).[35]
The presence of iridium–iridium bonds in these adducts
necessarily results too from an electronic perspective, be-
cause it accounts for their diamagnetism, as confirmed by
NMR measurements, and therefore can be formally consid-
ered as oxidized IrII–IrII entities. As a matter of fact, the
symmetrical complex 7 gave two different resonances for
G
“RhNRhN” core, a situation that has only been found for
two diarylamido-bridged rhodium complexes of the type
[{RhACHTUNGRTENNU(G m-NAr2)ACHTUNGTREN(NGNU cod)}2] (Ar=phenyl, p-tolyl), because it is the
most stable situation in terms of the avoidance of steric con-
tacts between the sterically demanding aryl amido and COD
ligands.[39]
Further addition of two extra molar equivalents of the re-
spective phosphanes afforded tetraphosphane complexes
AHCTUNGTRENNUNG
G
E
G
ACHTUNGTRENNUNG
[{RhACTHNURGTENN(GU m-NH2)CAHTUGNTERNN(GUN PR3)2}2] (PR3 =PPh3 (11), PMePh2 (12),
PMe2Ph (13)), which were isolated as brown–reddish solids
in fairly good yields (Scheme 3). The NMR spectra of 11–13
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5669

M. A. Casado, L. A. Oro et al.
spectrum for the symmetrical phosphanes in 14 together
with the information gathered from the 1H and
13C{1H} NMR spectra suggested a mononuclear penta-coor-
dinated complex with Cs symmetry, in principle coherent
with a trigonal-bipyramidal (tbp) structure. This information
was further confirmed by the micro-TOF mass spectrum of
14, which showed a peak at m/z 717.1997 with the exact iso-
Scheme 3. Synthesis of the mixed COD/phosphane complexes 8–10
(PR3 =PPh3 (8), PMePh2 (9), PMe2Ph (10)), and the tetraphosphane
complexes 11–13 (PR3 =PPh3 (11), PMePh2 (12), PMe2Ph (13)).
(PMePh2)2]+ ion.
topic distribution for the [IrACHTNUGTRNE(UNNG cod)ACHUTNRTGEG(NNNU NH2)ACHTNUGTRENNUGN
Although we were not able to locate the nitrogen signal
by 15N–1H HMBC experiments in the amido complex 14,
the presence of a NH2 group coordinated to iridium was
confirmed indirectly by its chemical reactivity: as expected,
addition of stoichiometric amounts of water to a solution of
14 in [D6]benzene gave rise to the clean transformation to
the hydroxo complex 15 and released ammonia. This conver-
sion was irreversible, because exposure of 15 to ammonia
does not revert back the reaction to the amido complex 14.
All the attempts made in order to isolate the amido complex
14 were fruitless, because it was found to be highly reactive
towards moisture (traces). Instead, we isolated the hydroxo
showed phosphane and amido resonances in a 2:1 ratio, and
their dinuclear nature was confirmed by mass spectrometry.
In all phosphane complexes 8–13, the NH2 resonances were
observed at high field (from d=À0.30 to À0.78 ppm) in the
1H NMR spectra, which correlated with amido nitrogen
atoms (dACHTUNGTRENNUNG
ative value corresponds to the more basic phosphane. Disap-
pointingly, no terminal amido complexes of rhodium of the
type [RhACHTUNGTRENNUNG(NH2)ACHTUNGTRENNUNG(PR3)3] were detected by NMR techniques,
regardless of the amount of added phosphane. This situation
is in marked contrast when aryl amido ligands are involved:
in these cases, the related dinuclear complexes [{Rh
G
analogue [IrACTHUNGRTENU(NG cod)(OH)CAHTUNGTRNE(NUNG PMePh2)2] (15), which is much more
NArH)2A(PEt3)2}2] (NArH=p-toluidine, p-anisidide, o-anisi-
dide, p-trifluoromethylanilide) do react with an excess of
G
stable than its amido precursor. The NMR spectra of 15
were virtually similar to those of the amido complex 14, so
both complexes should be isostructural. Furthermore, varia-
ble temperature NMR data of 15 indicated the existence of
a fluxional process that could be slowed down at À408C in
[D8]toluene, leading to the splitting of the =CH COD pro-
tons (as observed with the amido complex 14), in accord-
ance to the proposed penta-coordinated structure, as depict-
ed in Scheme 4: both symmetrical phosphanes are located at
the equatorial positions of a tbp, whereas the strong donor
OH (or NH2) group is located at the axial site, trans to one
of the C=C olefinic bonds. According to this, irradiation at
the hydroxo signal (d=À2.71 ppm) gave a strong positive
NOE effect with the equatorial =CH protons of the COD
ligand.
triethylphosphane to form the reactive terminal amido spe-
cies [RhACHTUNGTRENNUNG(NArH)ACHTUNGTRENNUNG
(PEt3)3].[40] This situation may be tentatively
explained by considering that NH2 ligands do not bear elec-
tron-withdrawing groups that could help to stabilize such
electron-rich terminal amido species, as it happens when
aryl amido ligands are involved.
Turning our attention to iridium, when complex 2 was re-
acted with PPh3, PMe2Ph, or even PMe3, insoluble intracta-
ble mixtures of phosphorous-containing complexes were
formed, which were not further characterized. Only when
the phosphane PMePh2 was reacted in situ with complex 2
in [D6]benzene, we observed the formation of a novel termi-
nal amido complex [Ir
amido derivative evolved to the hydroxo complex [Ir-
(cod)(OH)(PMePh2)2] (15) along with released ammonia in
ACHTUNGTRENNU(GN cod)ACHTNUTRGEGN(NNU NH2)ACHTNUGRTEN(UNNG PMePh2)2] (14). This
Having in mind the success on isolating the first terminal
parent amido complexes of rhodium by utilizing the elec-
tron-withdrawing di-olefin tetrafluorobenzobarrelene and
IPr as a voluminous and strong s-donor N-heterocyclic car-
bene ligand,[20] we explored in the same way the splitting of
the amido bridges in complexes 1 and 2 with IPr. When 1
was treated with two molar equivalents of IPr, a yellow mi-
crocrystalline solid was isolated in excellent yield. Further
A
ACHTUNGTRENNUNG
wet solvents, as observed by NMR techniques (Scheme 4).
1
inspection of its H NMR spectrum showed quite unexpect-
edly that it corresponded to the recently reported terminal
hydroxo complex [Rh
reaction of iridium complex 2 with IPr afforded the novel
hydroxo complex [Ir(cod)(IPr)(OH)] (17) in high yield,
(IPr)(OH)].[41] In the same way,
ACHUTGTNRENNUG(cod)ACHTUTGNRENNUGN
Scheme 4. Proposed structure for the terminal amido complex 14, and its
conversion to the terminal hydroxo complex 15.
N
ACHTUNGTRENNUNG
which was characterized by NMR spectroscopy, mass spec-
trometry, and elemental analysis.
1
The H NMR spectrum of 14 in [D6]benzene showed a sig-
nificant broad resonance at high field (d=À0.83 ppm) as-
signed to the NH2 group; whereas at room temperature the
=CH protons of the COD ligand were observed as a sole
resonance, at À408C they split into two distinct resonances.
Very importantly, the PMePh2/COD/NH2 ratio found was
2:1:1. The presence of a broad singlet in the 31P{1H} NMR
These terminal hydroxo species should have their origin
from hydrolysis of too reactive transient terminal amido spe-
cies [MACTHUNGRTENN(UNG cod)ACHNUTRTGEG(NNUN IPr)ACHTNUGTREN(NUNG NH2)] (Scheme 5). As a matter of fact,
NMR monitoring of the reaction of iridium complex 2 with
IPr at low temperatures allowed to detect the amido inter-
mediate [IrACHTNUGTERNNN(UG cod)ACHTUNRTGEG(NNUN IPr)ACHTGUNTREN(UNNG NH2)] (16), which was characterized
5670
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Chem. Eur. J. 2013, 19, 5665 – 5675

Amido 1,5-Cyclooctadiene Complexes of Rhodium and Iridium
FULL PAPER
octadiene parent amido complexes 2 and 1, in the absence
of any base and in the presence of cesium carbonate. The
addition of a weak base in the catalytic system was benefi-
cial in the case of the iridium catalyst 2, because in the pres-
ence of 3 mol% of cesium carbonate, almost quantitative
conversions to 1-phenylethanol was obtained after 24 h, this
was an improvement from 48% without base to 94% with
Cs2CO3. However, with the analogous rhodium complex 1,
conversions were less efficient and no positive effect was ob-
served with added Cs2CO3.
Scheme 5. Formation of the hydroxo complex 17 through the terminal
amido intermediate [IrACHTUNGTRENNUNG(cod)AHCTUNRTGEG(NNUN IPr)ACHTNUGTREN(NGUN NH2)] (16).
The time dependence for the transfer hydrogenation proc-
esses of acetophenone by using complexes 1 and 2 as cata-
lysts in the presence of 3 mol% Cs2CO3 was monitored
during 24 h. As illustrated in Figure 6, the iridium catalyst
was more active than the rhodium analogue, which showed
only moderate activity. As a matter of fact, the turn over
frequency at 50% conversion (TOF50)[23] for iridium catalyst
2 was approximately 1880 hÀ1, whereas the rhodium catalyst
1 gave a much lower TOF50 of 27 hÀ1.
1
in [D6]benzene: the pattern of the H NMR spectrum was
virtually identical to that of the hydroxo analogue 17, show-
ing two signals for the =CH COD protons and a broad reso-
nance for the NH2 protons, whereas the COD/IPr/NH2 ratio
found was 1:1:1. These amido species 16 gradually converted
to hydroxo complex 17 along with released ammonia within
several hours, a transformation that can be slowed down by
lowering the temperature. Nevertheless, even when using
carefully amalgam-dried solvents, the amido species proved
to be too reactive towards moisture to be isolated. In this
way, the splitting of the amido bridges in complexes 1 and 2
by IPr gives the expected terminal amido species [(cod)M-
ACHTUNGTRENNUNG(IPr)ACHTUNGTRENNUNG(NH2)], similarly to those reported with tfbb (tfbb =
tetrafluorobenzobarrelene); however, the COD ancillary
ligand is much less p acid than fluorinated tfbb, a situation
that helps to understand the sensitiveness of terminal amido
COD complexes towards hydrolysis. This phenomenon has
been already reported in some terminal amido ruthenium
complexes, a behavior sometimes compared to that of
strong basic alkaline amides.[1a]
Figure 6. Time dependence for the transfer hydrogenation of acetophe-
none by using 1 mol% of complexes 1 or 2 as catalysts at 808C and
3 mol% Cs2CO3 as external base.
Nevertheless, it is interesting to notice that reports of
stable terminal hydroxo late-metal complexes are rare,[22]
and quite often hydroxo alkali chemicals are required for
their preparation from chloro-containing metallic precursors.
The preparative method described here takes advantage of
the high tendency towards hydrolysis of terminal amido
complexes, and it could be the synthetic method of choice,
because it utilizes water as the hydroxo source and releases
gaseous ammonia as the only byproduct, avoiding this way
the use of strong bases and salt removal.
The role of the cesium carbonate is not really clear at this
point. We selected it because is a very weak base (as com-
pared with the strong base tBuOK, usually utilized in these
processes to deprotonate iPrOH) and therefore it is possible
to speculate about a conventional deprotonation of isopro-
panol to yield hydrido metal species that should be involved
in the classical hydrido mechanism, or alternatively the
cesium ion could interact with the iridium centers in the
pocket of the open-book dinuclear structure improving the
activity of the bimetallic species. In any case, the presence
of a weak base as cesium carbonate, considerably improves
the activity of the iridium catalyst for the transfer hydroge-
nations.
Catalytic activity of the cyclooctadiene complexes 1 and 2 in
the transfer hydrogenation of acetophenone: In a prelimina-
ry communication we reported that complex 2, at room tem-
perature and in absence of any base, was active as homoge-
neous catalysts for the transfer hydrogenation of acetophe-
none to 1-phenylethanol by using iPrOH as hydrogen
donor. Under such mild conditions a bimetallic mechanism
that allows a concerted net hydrogen transfer through a pro-
posed eight-membered dimetallacycle was proposed.[25]
However, the catalytic activity was relatively low and, in the
absence of acetophenone, or when its concentration was
substantially decreased, the formation of a stable imido clus-
Conclusion
In this contribution we have explored the chemistry around
unusual parent amido complexes of the type [{M
ACHTUNGTRENNUNG(m-NH2)-
ter of the formula [Ir
(cod)
E
G
ACHTUNGTRENNUNG
We have now tested, at 808C, the catalytic performance
for the hydrogen transfer of the iridium and rhodium cyclo-
tight bridges without compromising the dinuclear entity
such as in di-olefin replacement reactions with carbon mon-
Chem. Eur. J. 2013, 19, 5665 – 5675
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5671

M. A. Casado, L. A. Oro et al.
ued for 30 min, and then hexane (20 mL) was added to induce the precip-
itation of a dark green solid, which was collected by filtration through a
cannula. Recrystallization of the crude dark solid with benzene gave
oxide. The diiridium(I) complex [{IrACTHNUGTRENNUG(m-NH2)ACHTUNGTREN(NUGN cod)}2] acti-
vates chloroalkanes giving diiridium(II) products as a result
of a two-center oxidative addition and concomitant metal–
1
yellow crystals of 4 (0.06 g, 63%). H NMR (300 MHz, [D6]benzene): d=
À0.25 ppm (brs, 4H; NH2); 13C{1H} NMR (75 MHz, [D6]benzene): d=
175.8 ppm (s, CO); 15N–1H HMQC (40 MHz, [D6]benzene): d=5.1 ppm
(brs, NH2); ESI MS (m-TOF+): m/z: 266.5 [M+/2+H]; IR (THF): n˜ =
2059, 2035, 1972 (CO), 3393 cmÀ1 (NH2); elemental analysis calcd (%)
for C4H4Ir2N2O4: C 9.09, H 0.76, N 5.30; found: C 9.03, H 0.72, N 5.24.
metal bond formation. The [{MACHTNUTRGENNUG(m-NH2)ACHTUNGTREN(NNGU cod)}2] complexes
react with phosphanes; in the case of rhodium, phosphanes
are not able to split the amido bridges, allowing the detec-
tion of mixed COD/phosphane dinuclear complexes
[(cod)Rh
ACHTUNGTRENNUNG(m-NH2)2RhACHTGNUTRENNUNG
Synthesis of [(Cl)ACHTUGNTREN(UNNG cod)IrCAHTUTGNRENNUG(m-NH2)2IrACHTUNGERTN(GNUN cod)ACHTNGUERTN(NUGN CH2Cl)] (5): Complex 2 (0.10 g,
tive tetraphosphanes [{Rh
N
ACHTUNGTRENNUNG
0.16 mmol) was dissolved in toluene (10 mL) and then neat dichlorome-
thane (0.14 g, 104 mL, 1.64 mmol) was added through a microsyringe. The
deep red solution was stirred for a week at RT under dark. At this point,
the solution was filtered through a cannula and the solvent was removed
by vacuum to approximately 2 mL. Addition of hexane afforded a red
solid, which was collected by filtration, washed with hexane, and then
dried in vacuum (69 mg, 51%). 1H NMR (300 MHz, CDCl3): d=5.26 (s,
2H; CH2Cl), 3.98 (m, 2H), 3.81 (m, 2H), 3.70 (m, 2H), 3.55 (m, 2H; =
CH COD), 3.45 (brs, 2H; NH2), 2.75 (m, 2H; CH2 COD), 2.68 (brs, 2H;
NH2), 2.62 (m, 2H), 2.50 (m, 2H), 2.41 (m, 2H), 2.23 ppm (m, 8H; CH2
COD); 13C{1H} NMR (75 MHz, CDCl3): d=77.6 (s), 72.3 (s), 70.8 (s),
65.6 (s, =CH), 35.0 (s), 32.5 (s), 30.4 (s), 30.2 (s, CH2 COD), À2.4 ppm (s,
CH2Cl); 15N–1H HMQC (40 MHz, CDCl3): d=16.7 ppm (brs, NH2); ESI
MS (m-TOF+): m/z: 683.13 [M+ÀCl+H]; IR (solid): n˜ =3343 cmÀ1
(NH2); elemental analysis calcd (%) for C17H30Cl2Ir2N2: C 28.45, H 4.21,
N 3.90; found: C 28.64, H 4.01, N 3.92.
observed splitting of the amido bridges when iridium is in-
volved: this system efficiently generates a novel terminal
amido complex of IrI, which is too reactive to be isolated.
Likewise, the carbene IPr allowed the access to very reac-
tive terminal amido complexes, detectable only in the case
of iridium at low temperatures. These species evolve
through hydrolysis to stable terminal hydroxo complexes,
even with traces of moisture. The [{MACTHNUGTRENNUG(m-NH2)ACHTUNGTRENN(UGN cod)}2] com-
plexes are active homogeneous catalysts for the transfer hy-
drogenation of acetophenone to 1-phenylethanol by using
iPrOH as hydrogen donor, the iridium catalyst being more
active than the rhodium analogue, which showed only mod-
erate activity.
Synthesis of [(Cl)ACHTUGNETNR(UNNG cod)IrCAHUTGTNREN(NUG m-NH2)2IrACHTUNGERTNN(GUN cod)ACHTNUGRTEN(NUGN CHCl2)] (6): To a solution of
complex 2 (0.04 g, 0.06 mmol) in toluene (3 mL), neat chloroform (0.08 g,
51 mL, 0.63 mmol) was added through a microsyringe and the mixture
was allowed to stir overnight at room temperature in the absence of
light. The resulting deep brown solution was filtered through a cannula
and the solvent was removed in vacuum to approximately 2 mL. Addi-
tion of hexane afforded a yellow solid, which was collected by filtration,
washed with hexane, and then dried in vacuum (40 mg, 84%). 1H NMR
(300 MHz, CDCl3): d=7.58 (s, 1H; CHCl2), 4.09 (m, 2H), 3.95 (m, 2H),
3.90 (m, 2H), 3.68 (m, 2H) (CH2 COD), 3.40 (brs, 2H), 3.19 (brs, 2H;
NH2), 2.78 (m, 2H), 2.66 (m, 2H), 2.57 (m, 2H), 2.50 (m, 2H), 2.37 ppm
(m, 8H; CH2 COD); 13C{1H} NMR (75 MHz, CDCl3): d=80.1 (s), 74.4
(s), 72.7 (s), 70.9 (s, =CH), 34.8 (s), 33.7 (s), 30.8 (s), 29.8 ppm (s, CH2,
COD); 15N–1H HMQC (40 MHz, CD2Cl2): d=17.1 ppm (brs, NH2); ESI
MS (m-TOF+): m/z: 716.9 [M+ÀCl]; IR (solid): n˜ =3343 cmÀ1 (NH2); el-
emental analysis calcd (%) for C17H29Cl3Ir2N2: C 27.14, H 3.89, N 3.72;
found: C 27.79, H 4.00, N 3.87.
Experimental Section
General methods: All manipulations were performed under a dry argon
atmosphere by using Schlenk-tube techniques. Solvents were obtained
from a solvent purification system (Innovative Technologies) or were
dried by standard procedures and distilled under argon prior to use.
Complexes 1 and 2 were prepared by following the synthetic procedure
recently described.[20] Gaseous ammonia was purchased from Air Liquide
LTD. All the other chemicals used in this work have been purchased
from Aldrich Chemicals and were used as received. Carbon, hydrogen,
and nitrogen analyses were performed with a Perkin–Elmer 2400 CHNS/
O microanalyzer. Mass spectra were recorded on a VG Autospec double-
focusing mass spectrometer operating in the FAB+ mode. Ions were pro-
duced with the standard Cs+ gun at approximately 30 kV; 3-nitrobenzyl
alcohol (NBA) was used as matrix. ESI MS was recorded on a Bruker
Micro-Tof-Q by using sodium formiate as reference. 1H, 31P{1H}, and
13C{1H} NMR spectra were recorded on a Varian UNITY, a Bruker ARX
300, and a Bruker Avance 400 spectrometers operating at 299.95, 121.42,
and 75.47 MHz, 300.13, 121.49 and 75.47 MHz, and 400.13, 161.99 and
100.00 MHz, respectively. Chemical shifts are reported in [ppm] and ref-
erenced to Me4Si by using the residual signal of the deuterated solvent
(1H and 13C), H3PO4 as external reference (31P) and liquid NH3
(1H–15N HMQC). IR spectra were recorded in solution on a Perkin–
Elmer Spectrum One spectrometer by using a cell with NaCl windows.
Synthesis of [{IrCAHTUNGTRNE(NUG m-NH2)ACHTUGNTREN(UNNG cod)(Cl)}2] (7): A solution of 2 (0.04 g,
0.06 mmol) in toluene (3 mL) was treated with neat dichloroethane
(0.06 g, 50 mL, 0.63 mmol) through a microsyringe, and then allowed to
stir overnight at room temperature in the absence of light. The deep red
solution formed was filtered through a cannula and then the solvent was
removed in vacuum to approximately 2 mL. Addition of hexane afforded
a red solid, which was collected by filtration, washed with hexane, and
then dried in vacuum (40 mg, 89%). 1H NMR (300 MHz, CDCl3): d=
4.51 (m, 4H), 4.14 (m, 4H) (=CH COD), 3.87 (brs, 2H), 3.69 (brs, 2H;
NH2), 2.89 (m, 2H), 2.64 (m, 2H), 2.58 (m, 2H), 2.32 ppm (m, 2H; CH2
cod); 13C{1H} NMR (75 MHz, CDCl3): d=78.0 (s), 77.5 (s, =CH), 34.3 (s),
30.8 ppm (s, CH2, COD); 15N–1H HMQC (40 MHz, CDCl3): d=16.9 ppm
(brs, NH2); ESI MS (m-TOF+): m/z: 669.12 [M+ÀCl+H]; IR (solid): n˜ =
3343 cmÀ1 (NH2); elemental analysis calcd (%) for C16H28Cl2Ir2N2: C
27.31, H 4.01, N 3.98; found: C 26.93, H 3.81, N 3.74.
Synthesis of [{RhACHTUNGTRENNUNG(m-NH2)(CO)2}2] (3): Carbon monoxide was bubbled
through a yellow solution of 1 (0.18 g, 0.40 mmol) in toluene (10 mL) at
room temperature giving a brownish solution. The bubbling was contin-
ued for 30 min, and then hexane (20 mL) was added to induce the precip-
itation of a yellow solid, which was collected by filtration through a can-
nula, washed with hexane, and dried under vacuum (0.07 g, 50%).
1H NMR (300 MHz, [D6]benzene): d=À1.40 ppm (brs, 4H; NH2);
Synthesis of [(cod)RhACHTUNTRGENN(UG m-NH2)2RhACHTUNGTREN(NUNG PPh3)2] (8): An NMR tube was charg-
ed with complex 1 (13 mg, 0.03 mmol) and the solid was dissolved in de-
oxygenated [D6]benzene. Solid triphenylphosphane (44 mg, 0.17 mmol)
was added to this solution and then allowed to react for 1 h. At this
13C{1H} NMR (75 MHz, [D6]benzene): d=187.0 ppm (d, 1J
ACTHNUTRGNEU(GN C,Rh)=
64 Hz, CO); 15N–1H HMQC (41 MHz, [D6]benzene): d=À45.0 ppm (brs,
NH2); IR (THF): n˜ =2079, 2042, 1970 (CO), 3369 cmÀ1 (NH2); elemental
analysis calcd (%) for C4H4N2O4Rh2: C 13.73, H 1.15, N 8.01; found: C
14.56, H 1.07, N 7.75.
point, the conversion to
8
was quantitative. 1H NMR (300 MHz,
[D6]benzene): d=7.96 (m, 12H; Ho), 7.15 m, 18H; Hm + Hp, PPh3), 3.64
(m, 4H;=CH), 2.56 (m, 4H), 1.98 (m, 4H; CH2 COD), À0.78 ppm (brs,
4H; NH2); 31P{1H} NMR (121 MHz, [D6]benzene): d=51.3 ppm (d, 1J-
Synthesis of [{IrACHTUNGTRENNUNG(m-NH2)(CO)2}2] (4): Carbon monoxide was bubbled
through a red solution of 2 (0.10 g, 0.16 mmol) in toluene (10 mL) at
(P,Rh)=173 Hz); 13C{1H} NMR (75 MHz, [D6]benzene): d=138.0 (d, 1J-
ACHTUNGTRENNUNG
room temperature giving a deep green solution. The bubbling was contin-
CATHGNURTEN(UNGN C,Rh)=40 Hz, Cipso), 134.7 (m, Co), 128.8 (m, Cm + Cp, PPh3), 73.8 (d,
5672
www.chemeurj.org
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 5665 – 5675

Amido 1,5-Cyclooctadiene Complexes of Rhodium and Iridium
FULL PAPER
1J
(C,Rh)=12 Hz, =CH), 31.9 (s), 28.2 ppm (s, CH2 COD);
1J
C
ACHTUNGTRENNUNG
15N–1H HMQC (40 MHz, [D6]benzene): d=À5.1 ppm.
15N–1H HMQC (40 MHz, [D6]benzene): d=À17.8 (brs, NH2); MS
(ESI+): m/z: 395.0 [M+/2]; elemental analysis calcd (%) for
C32H48N2P4Rh2: C 48.62, H 6.12, N 3.54; found: C 48.11, H 6.02, N 3.23.
Synthesis of [(cod)RhACHTUNGTRENNUNG(m-NH2)2RhACHTUNTGREN(NGUN PMePh2)2] (9): An NMR tube was
charged with complex 1 (30 mg, 0.06 mmol) and the solid was dissolved
in deoxygenated [D6]benzene. Pure methyldiphenylphosphane (0.03 g,
25 mL, 0.13 mmol) was added to this solution through a microsyringe and
then allowed to stand for 5 min. At this point, the conversion to 9 was
quantitative. 1H NMR (300 MHz, [D6]benzene): d=7.78 (m, 8H; Ho),
7.18–6.97 (m, 12H; Hm + Hp, PPh2), 3.64 (m, 4H; =CH), 2.57 (m, 4H),
Synthesis of [IrACTHUGNTERN(NNGU cod)ACHTNURTEGNG(UNN NH2)ACHTNUGTERN(NUGN PMePh2)2] (14): Pure methyldiphenylphos-
phane (28 mg, 26 mL, 0.14 mmol) was slowly added through a syringe to a
solution of complex 2 (15 mg g, 0.023 mmol) in [D8]toluene (0.5 mL),
giving rise to a red solution. At this point, the conversion to complex 14
was found to be quantitative. 1H NMR (300 MHz, [D6]benzene): d=7.41
(m, 8H; Ho), 7.05 (m, 12H; Hm + Hp, PPh2), 3.14 (m, 4H; =CH), 2.01
(m, 4H; CH2), 1.90 (m, 4H; CH2 COD), 1.54 (m, 6H; CH3P), À0.83 ppm
2.00 (m, 4H, CH2 COD), 1.45 (m, 6H; PMe), À0.77 ppm (brs, 4H;
1
NH2); 31P{1H} NMR (121 MHz, [D6]benzene): d=31.1 ppm (d, J
G
167 Hz); 13C{1H} NMR (75 MHz, [D6]benzene): d=140.8 (m, Cipso), 132.8
1
1
(m, Co), 127.5–128.1 (m, Cm + Cp, PPh2), 73.7 (d, J
(P,Rh)=12 Hz, =CH),
(s, 2H, NH2); H NMR (300 MHz, [D8]toluene, À408C): d=7.35 (m, 6H;
31.9 (s), 28.2 (s, CH2 COD), 17.6 (d, 2J
(C,P)=14 Hz), 17.4 ppm (d, 2J-
Ho), 7.08 (m, 12H; Hm + Hp, PPh2), 3.81 (m, 2H), 2.85 (m, 2H; =CH
COD), 1.91 (m, 2H), 1.76 (m, 2H; CH2 COD), 1.37 (m, 6H; CH3P),
À1.34 ppm (s, 2H, NH2); 31P{1H} NMR (162 MHz, [D8]toluene): d=
À25.5 ppm (brs); 13C{1H} NMR (100 MHz, [D8]toluene, À408C): d=
(C,P)=14 Hz, PMe); 15N–1H HMQC (40 MHz, [D6]benzene): d=À8.8
(brs„ NH2); ESI MS (MALDI+): m/z: 635.7 [M+ÀCODÀ3H], 542.0
[M+ÀPMePh2À4H).
140.7 (d, 1J(C,P)=13 Hz, Cipso), 132.3 (d, 2J
ACTHNUTRGENNGU ACHTUGNTERN(NUGN C,P)=18 Hz, Co), 128.5 (s,
Synthesis of [(cod)RhACHTUNGTRENNUNG(m-NH2)2RhACHTUNTGREN(NGUN PMe2Ph)2] (10): Complex 10 was pre-
Cm), 128.3 (s, Cp, PPh2), 66.7 (s, =CH), 58.5 (m, =CH), 34.5 (s, CH2), 32.5
pared in situ by following the procedure described for complex 9, by re-
acting 1 (0.02 g, 0.05 mmol) and dimethylphenylphosphane (0.01 g, 16 mL,
0.11 mmol) in [D6]benzene. 1H NMR (300 MHz, [D6]benzene): d=8.10
(m, 4H; Co), 7.14–7.32 (m, 6H; Hm + Hp, PPh), 3.88 (m, 4H; =CH), 2.72
(m, 4H), 2.15 (m, 4H; CH2 COD), 1.31 (m, 12H; PMe2), À0.46 ppm
(brs, 4H; NH2); 31P{1H} NMR (121 MHz, [D6]benzene): d=13.4 ppm (d,
(s, CH2 COD), 12.3 (d, 1J
717.1997 [M+].
ACHTUNGTERNUN(NG C,P)=13 Hz, CH3P); MS (ESI+): m/z:
Synthesis of [IrACHTUNGTRENNUG(cod)(OH)AHCTUNGTREN(NUGN PMePh2)2] (15): A solution of complex 14
(0.02 g, 0.03 mmol) in THF (2 mL) was treated with water (0.02 g, 1.5 mL,
0.08 mmol) through a microsyringe. The resulting yellowish solution was
stirred for 10 min at room temperature and then the volatiles were re-
1J
1J
ACHTUNGTRENNUNG
A
moved under vacuum, affording a light brown solid (0.02 g, 99%).
Cm + Cp, PPh), 73.7 (d, 1J
G
1H NMR (400 MHz, [D8]toluene, À408C): d=7.91 (m, 6H; Ho), 7.48 (m,
2H; Ho), 7.42–7.28 (m, 12H; Hm + Hp, PPh2), 3.31 (m, 2H), 3.20 (m, 2H;
=CH COD), 2.27 (m, 2H; CH2 COD), 2.13 (m, 10H; CH2 COD +
CH3P), 1.97 (m, 2H; CH2 COD), À2.71 ppm (s, 1H, OH); 31P{1H} NMR
(162 MHz, [D8]toluene, À408C): d=À17.8 ppm (s); 13C{1H} NMR
COD), 19.0 (d, 2J(C,P)=13 Hz), 18.8 ppm (d, 2J
ACHTUNGTRENNUNG ACHUTNGTREN(NUGN C,P)=13 Hz, PMe2);
15N–1H HMQC (40 MHz, [D6]benzene): d=À11.6 ppm (brs, NH2); MS
(ESI+): m/z: 394.9 [M+ÀRhÀNH2ÀCOD].
Synthesis of [{RhACHTUNGTRENNUNG(m-NH2)ACHUTNTGREN(NUGN PPh3)2}2] (11): A solution of complex 1 (0.10 g,
(100 MHz, [D8]toluene, À408C): d=142.1 (d, 1J
ACHTUNGTRENNUNG
0.22 mmol) in toluene (9 mL) was treated with solid triphenylphosphane
(0.35 g, 1.32 mmol) and the resulting mixture was stirred for 2 h. The vol-
atiles were removed in vacuum leaving an orange solid, which was recrys-
tallized from toluene and hexane (0.19 g, 67%). 1H NMR (300 MHz,
[D6]benzene): d=7.75 (m, 24H; Ho), 7.02 (m, 24H; Hm), 6.81 (m, 12H;
Hp, PPh3), À2.01 ppm (br s, 4H; NH2); 31P{1H} NMR (121 MHz,
1J(C,P)=23 Hz), 138.2 (d, 1J(C,P)=14 Hz), 138.1 (d, 1J
ACHTUNGTRNEUNNG ACHUTNGTENRNUG ACTUHNGTRENNUGN
3
2
Cipso), 133.4 (m), 132.0 (m, Co), 131.2 (d, JACTHNUTRGEN(UNG C,P)=3 Hz, Cm), 130.8 (d, J-
AHCTUNGTERNNG(UN C,P)=10 Hz, Co), 129.3–128.0 (m, Cm + Cp, PPh2), 61.0 (s, =CH), 58.5
(m, =CH), 35.1 (s, CH2), 31.5 (s, CH2 COD), 11.7 (d, 1J
G
1
11.5 ppm (d, J
A
[D6]benzene): d=57.2 ppm (d, 1J
N
Synthesis of [Ir
N
N
ACHTUNGTRENNUNG
(75 MHz, [D6]benzene): d=139.2 (d, 1J
R
complex 2 (20 mg, 0.03 mmol), IPr (23 mg, 0.06 mmol), and carefully
dried [D6]benzene (0.4 mL), giving rise to a yellow solution within a
minute. At this point, the formation of the novel complex 16 was almost
quantitative. 1H NMR (300 MHz, [D6]benzene): d=7.41 (m, 8H; Ho),
7.05 (m, 12H; Hm + Hp, PPh2), 3.14 (m, 4H; =CH), 2.01 (m, 4H; CH2),
1.90 (m, 4H; CH2 COD), 1.54 (m, 6H; CH3P), À0.83 ppm (s, 2H, NH2);
1H NMR (300 MHz, [D8]toluene, À408C): d=7.29–6.98 (m, 6H; Ph IPr),
6.42 (s, 2H; =CH IPr), 3.91 (m, 2H; =CH COD), 2.92 (m, 4H; CH iPr),
2.55 (m, 2H; =CH), 2.00 (m, 4H; CH2), 1.55 (m, 4H; CH2 COD), 1.40
Co), 127.9–128.1 ppm (m, Cm + Cp, PPh3); 15N–1H HMQC (40 MHz,
[D6]benzene): d=À5.6 ppm; MS (ESI+): m/z: 643.5 [M+/2]; elemental
analysis calcd (%) for C72H64N2P4Rh2: C 67.19, H 5.01, N 2.18; found: C
67.01, H 4.89, N 2.09.
Synthesis of [{RhACHTUNGTRENNUNG(m-NH2)ACHTUGNTREN(NUNG PMePh2)2}2] (12): To a suspension of complex
1 (0.08 g, 0.17 mmol) in hexane (7 mL), pure methyldiphenylphosphane
(0.22 g, 199 mL, 1.06 mmol) was slowly added through a syringe, giving
rise to an orange solution, which was stirred for 40 min. Concentration of
the volume by reduced pressure to dryness afforded an orange solid. This
was washed repeatedly with hexane and then dried under vacuum
(0.12 g, 65%). 1H NMR (300 MHz, [D6]benzene): d=7.96 (m, 16H; Ho),
ACTHNUTRGNEUNG
(d, 3J(H,H)=6.6 Hz, 12H; CH3 iPr), 1.00 ppm (d, 3J (H,H)=6.9 Hz,
12H; CH3 iPr); 13C{1H} NMR (75 MHz, [D6]benzene): d=185.7 (s, C-Ir
IPr), 75.9, 46.6 (s, =CH), 34.9, 29.6 (s, CH2 COD), 28.5 (s, CH), 26.2, 24.5
(s, Me iPr); MS (ESI+): m/z: 717.1997 [M+].
7.13 (m, 24H; Hm + Hp, PPh2), 1.49 (m, 3H; PMe), À0.69 ppm (brs, 4H;
1
NH2); 31P{1H} NMR (121 MHz, [D6]benzene): d=30.2 ppm (d, J
G
Synthesis of [IrACTHNGUTRENNU(G cod)CAHTUNGTRNEN(UNG IPr)(OH)] (17): A solution of complex 2 (0.07 g,
165 Hz); 13C{1H} NMR (75 MHz, [D6]benzene): d=141.2 (d, 1J
35 Hz), 140.1 (d, 1J(C,Rh)=37 Hz), 139.8 (d, 1J
(C,Rh)=34 Hz, Cipso),
133.0 (m, Co + Cm), 131.0 (d, 3J(C,Rh)=3 Hz, Cm), 130.6 (d, 2J
(C,Rh)=
9 Hz, Co), 128.3 (d, 2J
(C,Rh)=12 Hz, Co), 127.3–127.9 (m, Cm + Cp,
PPh2), 17.8 (d, 2J
G
0.11 mmol) in toluene (5 mL) was treated with IPr (0.09 g, 0.23 mmol)
giving a yellow solution, and then with water (7 mL, 0.46 mmol), and the
resulting yellow mixture was stirred for 45 min. The volatiles were re-
moved in vacuum, and the addition of hexane (8 mL) afforded a yellow
solid, which was collected by filtration, washed with hexane, and then
dried in vacuum (0.15 g, 95%). 1H NMR (300 MHz, [D6]benzene): d=
7.29 (m, 2H; Hp), 7.25 (m, 4H; Hm, Ph IPr), 6.46 (s, 2H; =CH IPr), 3.78
E
ACHTUNGTRENNUNG
N
ACHTUNGTRENNUNG
m/z: 518.9 [M+/2].
(m, 2H; =CH COD), 2.90 (m, 4H; CH iPr), 2.71 (m, 2H; =CH), 1.94 (m,
Synthesis of [{RhACHTUNGTRENNUNG(m-NH2)ACHTUGNTREN(NUNG PMe2Ph)2}2] (13): Pure dimethylphenylphos-
3
4H; CH2), 1.45 (m, 2H; CH2 COD), 1.42 (d, J
G
phane (0.23 g, 235 mL, 1.65 mmol) was slowly added through a syringe to
a solution of complex 1 (0.12 g, 0.27 mmol) in toluene (3 mL), giving rise
to an orange solution, which was stirred for 30 min. Concentration of the
volume by reduced pressure to dryness afforded an orange solid. This
was washed repeatedly with hexane and then dried under vacuum
(0.18 g, 83%). 1H NMR (300 MHz, [D6]benzene): d=8.28 (m, 8H; Ho),
7.31–7.20 (m, 12H; Hm + Hp, PPh), 1.15 (m, 24H; PMe2), À0.30 ppm
(brs, 4H; NH2); 31P{1H} NMR (121 MHz, [D6]benzene): d=12.1 ppm (d,
3
iPr), 1.35 (m, 2H; CH2 COD), 1.01 ppm (d, J (H,H)=6.9 Hz, 12H; CH3
iPr); 13C{1H} NMR (75 MHz, [D6]benzene): d=186.3 (s, C-Ir), 146.6 (s,
Cq), 136.7 (s, Cq-N), 129.6 (s, Cm + Cp), 123.5 (s, =CHN IPr, 79.2, 45.5 (s,
=CH), 34.5, 29.2 (s, CH2 COD), 28.8 (s, CH), 26.1, 22.8 ppm (s, Me iPr);
MS (micro-TOF): m/z: 689.3487 [M+ÀOH].
General protocol for the catalytic transfer hydrogenation: In a Schlenk
tube, the catalyst (0.03 mmol), acetophenone (3 mmol), and an internal
Chem. Eur. J. 2013, 19, 5665 – 5675
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5673

M. A. Casado, L. A. Oro et al.
standard (mesitylene, 250 mL) and, when needed Cs2CO3 (0.09 mmol),
were dissolved in 2-propanol (3 mL). The reactor was then placed in a
thermostated oil bath at 808C with vigorous stirring. Conversions were
determined by gas chromatography techniques under the following con-
ditions: column temperature: 408C (2 min) to 80 at 58CminÀ1 at a flow
rate of 1 mLminÀ1 by using ultrapure He as carrier gas. The reaction
progress was monitored by GC analysis in order to calculate the time de-
pendence of the transfer hydrogenations of acetophenone. Aliquotes of
50 mL were taken in dichloromethane (1 mL) every 5 min for the first
30 min, every 10 min for the next 90 min, every 30 min for the next hour,
and finally another two samples were taken after 360 min and a final one
after 24 h from the beginning of the reaction. The samples were filtered
through a syringe filter.
mentary occupancy factors. Hydrogen atoms of the amido groups have
been refined with a common isotropic thermal parameter.
CCDC-913028 (2), CCDC-913029 (4), CCDC- (5), CCDC-913031 (7),
and CCDC-913032 contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif.
Acknowledgements
Financial support from CONSOLIDER INGENIO-2010 program under
the projects MULTICAT (CSD2009-00050) and Factorꢀa de Cristaliza-
ciꢆn (CSD2006-0015) and project CTQ2012-35665 is acknowledged.
P.G.O. acknowledges the CSIC “JAE-Doc” program, cofounded by the
ESF and Factorꢀa de Cristalizaciꢆn projects, for financial support. The au-
thors express their appreciation to the support from the Ministry of
Higher Education, Saudi Arabia, in establishment of the Center of Re-
search Excellence in Petroleum Refining & Petrochemicals at King Fahd
University of Petroleum & Minerals (KFUPM). The support of KFUPM
is also highly appreciated.
Crystal structure determination for complexes 2, 4, 5, and 7: X-ray dif-
fraction data were collected at 100(2) K on a Bruker SMART APEX
CCD (complexes 2 and 7) and on a Bruker APEX II (complexes 4 and
5) area detector diffractometers with graphite-monochromated MoKa ra-
diation (l=0.71073 ꢄ) by using narrow w rotations (0.38). Intensities
were integrated and corrected for absorption effects with SMART,[42]
SAINT+,[43] and SABABS[44] programs, included in APEX 2 package.
The structures were solved by direct methods with SHELXS-97,[45] and
refined by full-matrix least squares on F2 with SHELXL-97.[46] Hydrogen
atoms of the NH2 bridges have been observed in Fourier difference maps
À
and refined with a restraint in N H distances. Particular details concern-
ing the presence of solvent or static disorder are listed below.
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Crystal data for complex 2: 3(C16H28Ir2N2)·1.5(C6H6); M=2015.57;
orange prism; 0.22ꢅ0.19ꢅ0.13 mm3; triclinic; P1; a=9.2115(5), b=
¯
16.5730(8), c=19.9382(10) ꢄ; a=106.3240(10), b=90.6680(10), g=
104.2700(10)8;
14.139 mmÀ1
Z=2;
V=2820.2(2) ꢄ3; 1calcd =2.374 gcmÀ3
;
m=
,
min. and max. transmission factors: 0.115 and 0.196;
2qmax =56.968; 18548 reflections collected, 12330 unique [Rint =0.0178];
number of data/restraints/parameters: 12330/12/659; final GoF: 1.051,
R1 =0.0281 [10842 reflections, I>2s(I)], wR2=0.0691 for all data; larg-
est difference peak: 1.694 eꢄ3.
Crystal data for complex 4: C4H4Ir2N2O4; M=528.49; yellow needle;
0.34ꢅ0.12ꢅ0.07 mm3; monoclinic; C2/c; a=17.8094(12), b=4.0305(3),
c=14.1144(10) ꢄ; b=121.1610(10)8; Z=4; V=866.94(11) ꢄ3; 1cacld
=
4.049 gcmÀ3; m=30.644 mmÀ1, min. and max. transmission factors: 0.015
and 0.057; 2qmax =58.58; 5063 reflections collected, 1126 unique [Rint
=
[5] J. Choi, A. H. R. MacArthur, M. Brookhart, A. S. Goldman, Chem.
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0.0311]; number of data/restraints/parameters: 1126/1/63; final GoF:
1.118, R1 =0.0227 [1073 reflections, I>2s(I)], wR2=0.0594 for all data;
largest difference peak: 2.915 eꢄ3.
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Crystal data for complex 5: C17H30Cl2Ir2N2; M=717.73; red prism; 0.08ꢅ
0.05ꢅ0.02 mm3; monoclinic; C2/c; a=36.861(3), b=9.6577(7), c=
10.4390(7) ꢄ;
2.558 gcmÀ3; m=14.597 mmÀ1, min. and max. transmission factors: 0.465
and 0.604; 2qmax =60.028; 13405 reflections collected, 5107 unique [Rint
b=90.0340(10)8;
Z=8;
V=3716.2(4) ꢄ3;
1calcd =
=
0.0369]; number of data/restraints/parameters: 5107/4/249; final GoF:
0.999, R1 =0.0323 [4035 reflections, I>2s(I)], wR2=0.0651 for all data;
largest difference peak: 2.271 eꢄ3. Methylene chloride and chlorine
atoms bounded to the metals have been found disordered. They have
been included in the model in two sets of positions with complementary
occupancy factors (0.66/0.34). Hydrogen atoms of the amido groups have
been refined with a common isotropic thermal parameter. The highest re-
sidual density peak has been found close to an iridium atom. It has no
chemical sense.
Crystal data for complex 7: C16H28Cl2Ir2N2·C7H8; M=795.84; dark red
pyramidal; 0.18ꢅ0.16ꢅ0.15 mm3; triclinic; P1; a=11.0294(5), b=
¯
13.8433(7), c=16.0792(8) ꢄ; a=81.6060(10), b=84.1630(10), g=
77.1340(10)8;
11.497 mmÀ1
Z=4;
V=2361.6(2) ꢄ3;
1calcd =2.238 gcmÀ3
;
m=
,
min. and max. transmission factors: 0.188 and 0.283;
2qmax =57.428; 29063 reflections collected, 11077 unique [Rint =0.0235];
number of data/restraints/parameters: 11077/9/591; final GoF: 1.062,
R1 =0.0225 [9922 reflections, I>2s(I)], wR2=0.0536 for all data; largest
difference peak: 1.217 eꢄ3. The asymmetric unit contains two Ir atoms
and two solvent toluene molecules. One of the latter has been found to
be disordered; it has been modeled in two sets of positions with comple-
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Chem. Eur. J. 2013, 19, 5665 – 5675

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Received: December 10, 2012
Published online: March 15, 2013
Chem. Eur. J. 2013, 19, 5665 – 5675
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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5675