Room-temperature cyclometallation of amines, imines and oxazolines with [MCl2Cp*]2 (M = Rh, Ir) and [RuCl2(p-cymene)]2

Article abstract of DOI:10.1039/b303737a

N,N-Dimethylbenzylamine, alkyl and aryl imines derived from benzaldehyde, and 2-phenyl-4,4-dimethyloxazoline all undergo cyclometallation with [IrCl₂Cp*]₂ (Cp_* = η-C₅Me₅) when treated with NaOAc in dichloromethane at room temperature. The imines are also cyclometallated by [RhCl₂Cp*]₂ under the same conditions whilst only N-alkyl imines are cyclometallated by [RuCl₂(p-cymene)]₂. The role of acetate in the cyclometallation is more than just as a base. X-Ray structures of cyclometallated complexes [MCl{C₆H₄-2-C(H)=NCH₂CH₂OMe-κC ,N}(η-ring)] (M = Ir, Rh ring = Cp* M = Ru, ring = p-cymene), [MCl{C₆H₄-2-C(H)=NCH₂CH₂OMe-κC ,N}Cp*](M = Ir, Rh). [RuCl(η²-O₂CMe)(p-cymene)] and [IrCl₂(NH₂Ph)Cp*] are reported.

Full text of DOI:10.1039/b303737a

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Room-temperature cyclometallation of amines, imines and
oxazolines with [MCl2Cp*]2 (M ؍ Rh, Ir) and
[RuCl2(p-cymene)]2 †
David L. Davies,* Omar Al-Duaij, John Fawcett, Marco Giardiello, Stephen T. Hilton and
David R. Russell
Department of Chemistry, University of Leicester, Leicester, UK LE1 7RH.
E-mail: dld3@le.ac.uk
Received 3rd April 2003, Accepted 3rd June 2003
First published as an Advance Article on the web 22nd September 2003
N,N-Dimethylbenzylamine, alkyl and aryl imines derived from benzaldehyde, and 2-phenyl-4,4-dimethyloxazoline all
undergo cyclometallation with [IrCl2Cp*]2 (Cp* = η-C5Me5) when treated with NaOAc in dichloromethane at room
temperature. The imines are also cyclometallated by [RhCl2Cp*]2 under the same conditions whilst only N-alkyl
imines are cyclometallated by [RuCl2(p-cymene)]2. The role of acetate in the cyclometallation is more than just as a
base. X-Ray structures of cyclometallated complexes [MCl{C H -2-C(H)᎐NCH CH OMe-κC,N}(η-ring)](M = Ir,
᎐
6
4
2
2
Rh ring = Cp*; M = Ru, ring = p-cymene), [MCl{C H -2-C(H)᎐NCH CH OMe-κC,N}Cp*](M = Ir, Rh),
᎐
6
4
2
2
[RuCl(η2-O2CMe)(p-cymene)] and [IrCl2(NH2Ph)Cp*] are reported.
To our knowledge there are only two papers reporting com-
plexes of Cp*M with a cyclometallated nitrogen donor ligand,
both with iridium. Activation of an aryl C–H bond occurs in
the cyclometallation of phenyl oxazolones, using [IrCl2Cp*]2
and NaOAc,15 whilst reaction of a diimine with [IrCl2Cp*]2
leads to activation of a methyl group.16
Introduction
C–H activation is an extremely important process because of its
potential for producing functionalised hydrocarbons.1 Intra-
molecular C–H activation can lead to cyclometallated com-
plexes;2 such complexes of the platinum metals were first
reported in 19653 and have since shown promise in several fields
of chemistry particularly catalysis.4 Though the chemistry of
cyclometallation is well established new synthetic routes to such
species which only require mild conditions and do not require
an M–C bond in the starting material are still desirable.
In addition, there is scope to widen the range of metal
species that can undergo this process. As part of our research
on half-sandwich complexes we were interested in preparing
areneruthenium and Cp*M (M = Ir, Rh) complexes with
cyclometallated ligands containing nitrogen donor atoms.
Arene ruthenium complexes containing cyclometallated
N,N-dimethylbenzylamine (dmbaH) are known.5 Such com-
plexes show interesting reactivity particularly in C–C bond
forming reactions with ethene,6 and alkynes.5 Recently η1-aryl
ruthenium complexes have been shown to be intermediates in a
catalytic Heck type coupling.7 In addition, [RuCl(dmba)(C6H6)]
has been used as an intermediate in the synthesis of a
ruthenium complex for bioelectrochemical applications.8 Arene
ruthenium dmba complexes have traditionally been made by
transmetallation with mercury reagents,5,9 though a C–H activ-
ation route using NaOH as a base has recently been reported.10
Other arene ruthenium complexes with a cyclometallated azo-
benzene have also been made from mercury reagents.11 Cyclo-
metallation of benzylideneaniline has been reported with
[RuCl2(PMe3)(C6Me6)] in the presence of AgBF4.12 More
Cyclometallation in palladium chemistry is very well estab-
lished and Pd(OAc)2 is known to be preferable to PdCl2 as a
precursor. Indeed, in some cases addition of acetate to a pal-
ladium chloride complex can induce cyclometallation of the
ligand.17 We have therefore investigated the use of NaOAc to
promote cyclometallation of nitrogen donor ligands in arene
ruthenium and Cp*M (M = Rh, Ir) complexes. All new com-
1
pounds were characterised by H and 13C NMR, FAB mass
spectrometry and elemental analysis and X-ray diffraction in
selected cases.
Results
Our intial studies used N,N-dimethylbenzylamine since the
cyclometallated areneruthenium complexes with this ligand are
known.5,9 Reaction of [IrCl2Cp*]2 with N,N-dimethylbenzyl-
amine in dichloromethane at room temperature in the presence
of NaOAc as base led to formation of complex 1a in good
yield. The 1H NMR spectrum of 1a clearly shows that co-
ordination and cyclometallation of the ligand has occurred.
Thus, the NMe2 group gives rise to two singlets at δ 2.90 and
3.03 and the benzyl protons are also inequivalent giving two
mutually coupled doublets at δ 3.26 and 4.38. The phenyl group
shows four inequivalent protons as expected for the orthometal-
lated product. The 13C NMR spectrum shows only four arene
carbons with protons attached and two signals for the NMe2
group as expected for 1a. The inequivalence of the methyls of
the NMe2 is consistent with the chiral centre at the metal.
Moreover, it demonstrates that epimerisation at the metal and
decoordination of the nitrogen must be slow on the NMR
timescale.
recently cyclometallation of
a benzodiazepine has been
achieved with [RuCl2(p-cymene)]2 at room temperature in di-
chloromethane using NEt3 as a base in the presence of
NaBPh4.13 Cyclometallated nitrogen containing ligands with
Cp*M (M = Rh, Ir) are much rarer, though cyclometallated
phosphorus containing ligands have often been identified in
C–H activation studies with Cp*M (M = Rh, Ir) complexes.14
† Based on the presentation given at Dalton Discussion No. 6, 9–11th
September 2003, University of York, UK.
Electronic supplementary information (ESI) available: Characteris-
ation and crystallographic data for [IrCl2(NH2Ph)Cp*] (6), and Figures
showing the structures of 3b, 5b and 6. See http://www.rsc.org/
suppdata/dt/b3/b303737a/
D a l t o n T r a n s . , 2 0 0 3 , 4 1 3 2 – 4 1 3 8
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
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The corresponding reactions were also attempted with
[RhCl2Cp*]2 and [RuCl2(p-cymene)]2, but in neither case was
the corresponding product 1b or 1c formed. Work up of the
reaction mixtures and washing the solids formed with hexane
left species which showed no signals due to N,N-dimethyl-
benzylamine in the 1H NMR spectra. In both cases the starting
dimers had reacted so the reactions of the dimers with NaOAc
were investigated. Reaction of [RhCl2Cp*]2 with NaOAc leads
to a solid which shows broad signals in the 1H NMR spectrum
which can be assigned to Cp* protons and to acetate protons.
However, the chemical shifts of the signals are not consistent
between all samples, neither is their relative integration. Indeed,
the integration is often not a simple ratio equivalent to one or
two acetates per Cp*. In one case we were able to isolate crystals
suitable for X-ray diffraction which were determined to be
[Rh(OH2)(η1-O2CMe)2Cp*]ؒH2O. This complex has previously
been isolated by reaction of [RhCl2Cp*]2 with AgOAc.18,19
However, the 1H NMR spectrum of this batch of crystals
showed no evidence for water, as found by Merola and co-
workers,18 and the mass spectra of these samples often contain
dimeric species (m/z 605) corresponding to [Rh2(O2CMe)-
Cl2Cp*2] showing that they still contain chloride. We believe
that the solid is a mixture which, in solution, may be in dynamic
equilibrium allowing exchange of chloride and acetate through
dimeric species and we have made no further attempts to
characterise these products.
To test the generality of the cyclometallation with Cp*Ir and
further explore ligands that might cyclometallate with arene
ruthenium and Cp*Rh we have tested a number of imines.
Reaction of 3 or 4 with [IrCl2Cp*]2 in the presence of NaOAc
led to formation of 3a and 4a, respectively in good yields. The
1H NMR spectra of 3a and 4a both show singlets at δ 1.72 and
ca. δ 3.35 due to Cp* and OMe, respectively, with the imine
proton being observed at δ 8.37 or 8.31 for 3a or 4a, respect-
ively. In both complexes the NCH2 protons are inequivalent,
hence epimerisation at the metal is slow on the NMR timescale.
Both complexes show the expected signals for an orthometal-
lated phenyl group; in the 13C NMR spectra the metallated
carbons are observed at δ 168.73 or 168.59, for 3a or 4a, respect-
ively, approximately 33 ppm downfield from the corresponding
signals in the free ligands. The ν(C᎐N) decreases by about
᎐
50 cmϪ1 compared with the free ligand as expected for co-
ordination of the imine. The X-ray structure of 3a has been
determined and is discussed below.
In the case of ruthenium, the reaction of [RuCl2(C6H6)]2 with
a large excess of NaOAc has been reported previously to give
[RuCl(O2CMe)(C6H6)] and the corresponding p-cymene com-
plex was also synthesised by a different method.20 The 1H NMR
spectrum of the product from the reaction of [RuCl2-
(p-cymene)]2 with NaOAc shows the presence of acetate and
p-cymene in a 1 : 1 ratio and agrees with the data reported for
[RuCl(O2CMe)(p-cymene)]. The mass spectrum also shows a
peak at m/z 295 corresponding to [Ru(O2CMe)(p-cymene)];
however there are additional peaks at m/z 601 due to a dimer,
[Ru2Cl2(OAc)(p-cymene)2]. We have managed to crystallise the
product and the X-ray structure shows it to be [RuCl(η2-O2-
CMe)(p-cymene)] with a bidentate acetate as proposed pre-
viously.20 The structure with selected bond lengths and angles is
shown in Fig. 1.
The influence of the nature of the imine substituent on the
course of the cyclometallation was also probed by using benzyl-
ideneaniline (5). In this case reaction with [IrCl2Cp*]2 in the
presence of NaOAc led to formation of a mixture of products.
1
The H NMR spectrum suggested the presence of the cyclo-
metallated imine 5a contaminated with another complex
containing a non-metallated phenyl which we subsequently
identified as the aniline complex [IrCl2(NH2Ph)Cp*] 6.21 Thus,
during the course of the reaction some of the initial imine
had hydrolysed and the resulting amine complexed to the
[IrCl2Cp*]2 to form 6. We reasoned that if the imine is hydrolys-
ing to form benzaldehyde and aniline then addition of excess
benzaldehyde may reverse this reaction and prevent the form-
ation of significant amounts of aniline and hence 6. Thus, the
reaction was repeated in the presence of benzaldehyde. This led
to formation of solely 5a which could be isolated in 84% yield.
The structure of 5a has been determined by X-ray diffraction
and is discussed below.
Having found that imines derived from benzaldehyde cyclo-
metallated easily with [IrCl2Cp*]2 we examined the reactions of
these ligands with [RhCl2Cp*]2 and [RuCl2(p-cymene)]2. In
these cases hydrolysis of the ligands seemed to be more of a
problem so excess benzaldehyde was used in many cases. The
alkyl imines 3 and 4 cyclometallated with both rhodium and
ruthenium forming 3b,c and 4b,c in good yields. In each case
the cyclometallation was obvious from the observation of only
1
four protons in the phenyl region in the H NMR spectra and
only four carbons with protons attached in the phenyl region of
the 13C spectra. The NCH2 protons are inequivalent, as are all
four aromatic protons of the p-cymene in 3c and 4c, consistent
with the chiral metal centre. As found for [IrCl2Cp*]2, reaction
of benzylidene aniline with [RhCl2Cp*]2 and NaOAc in the
presence of excess benzaldehyde led to isolation of the cyclo-
metallated product 5b. However, the same reaction with
ruthenium led only to formation of 2 by reaction with acetate.
The structures of 3a–c and 5a–b have been determined by
X-ray crystallography and selected bond distances and angles
are listed in Table 1. The structures of 3a, 3c and 5a are shown
in Figs. 2–4, respectively (structures of 3b and 5b are in the
ESI†). The complexes show the expected piano-stool type
Fig. 1 Molecular structure and atom numbering scheme for 2 with
50% displacement ellipsoids and all H atoms omitted for clarity.
Selected bond distances (Å) and angles (Њ): Ru–O(1) 2.166(2), Ru–O(2)
2.151(2), Ru–Cl 2.389(1), O(1)–C(1) 1.266(3), O(2)–C(1) 1.266(3),
C(1)–C(2) 1.495(4); O(2)–Ru–O(1) 60.31(7), O(1)–Ru–Cl 84.92(5),
O(2)–Ru–Cl 85.75(5).
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Table 1 Selected bond distances (Å) and angles (Њ) for 3a–c and 5a–b
3a
3b
3ca
5a
5b
M–C(1)
M–N(1)
M–Cl
C(1)–C(6)
C(6)–C(7)
C(7)–N(1)
2.036(3)
2.078(3)
2.397(1)
1.399(5)
1.431(5)
1.290(5)
2.027(2)
2.089(2)
2.398(1)
1.407(3)
1.437(3),
1.283(3)
2.043(2)
2.080(2)
2.418(1)
1.418(3)
1.440(3)
1.284(3)
2.042(3)
2.088(2)
2.403(1)
1.412(4)
1.433(4)
1.292(4)
2.032(3)
2.115(3)
2.399(1)
1.399(5)
1.434(4)
1.281(4)
M–C(π-ring)b
2.148(3)
2.155(4)
2.159(4)
2.252(3)
2.279(4)
2.147(2)
2.153(2)
2.166(2)
2.250(2)
2.278(2)
2.171(2)
2.177(2)
2.186(2)
2.200(2)
2.284(2)
2.288(2)
2.153(3)
2.168(3)
2.171(3)
2.231(3)
2.254(3)
2.123(3)
2.149(4)
2.150(3)
2.250(3)
2.250(3)
C(1)–M–N(1)
C(1)–M–Cl
Cl–M–N(1)
77.84(13)
85.53(11)
86.09(8)
78.73(7)
86.03(5)
88.41(4)
77.85(7)
85.37(5)
87.84(5)
77.60(11)
87.12(8)
86.15(7)
78.33(12)
89.64(10)
92.06(8)
a Average values for two independent molecules. b M–C distances to Cp* (3a, 3b, 5a, 5b) or to p-cymene (3c).
Fig. 4 Molecular structure and atom numbering scheme for 5a with
50% displacement ellipsoids and all H atoms omitted for clarity.
Fig. 2 Molecular structure and atom numbering scheme for 3a with
in related Cp*Ir cyclometallated diazabutadiene complexes16
though the Ir–C distances are slightly shorter in 3a and 5a con-
sistent with a bond to an sp2 carbon rather than sp3. The Ru–C
and Ru–N bond lengths are similar to those in the related
(p-cymene)ruthenium complex with a cyclometallated benzo-
diazepine.13 Complex 3c shows two independent molecules in
the unit cell, the only major difference between these being the
orientation of the (CH2)2OMe chain and a lengthening of the
Ru–Cl bond in one molecule. In 5a the phenyl substituent on
nitrogen is rotated out of the plane of the cyclometallated
fragment (dihedral angle C(7)–N(1)–C(8)–C(9) = 128.6Њ) and
is approximately parallel to the Cp*; presumably this is to
minimise unfavourable steric interactions with the Cp*. The
rhodium complex 5b shows a similar orientation. All the com-
plexes show significant variations in the M–C bond lengths to
the π-bound ring. Thus, the Cp* complexes (3a,b and 5a,b)
show an η3–η2 coordination with three short M–C bonds:
2.123(3)–2.171(3) Å, and two longer ones: 2.231(3), 2.279(4) Å.
Similarly the p-cymene ruthenium complex shows an η4–η2 dis-
tortion with four short bonds: 2.171(2)–2.200(2) Å, and two
longer bonds: 2.284(2)–2.288(2) Å. In all cases the longer bonds
are approximately trans to the M–C σ-bond.
50% displacement ellipsoids and all H atoms omitted for clarity.
Fig. 3 Molecular structure and atom numbering scheme for one of the
independent molecules of 3c with 50% displacement ellipsoids and all
H atoms omitted for clarity.
We have also examined cyclometallation of phenyl oxazoline
7. Reaction of 7 with [IrCl2Cp*]2 and NaOAc led to formation
of 7a. The 1H NMR spectrum shows two singlets at δ 1.50 and
1.53, two mutually coupled doublets at δ 4.43 and 4.55 due to
the oxazoline and only four protons in the phenyl region as
expected for cyclometallation. Similar reactions with [RhCl2-
Cp*]2 and [RuCl2(p-cymene)]2 at room temperature failed to
geometry. The M–C(aryl) bond lengths [range 2.027(2)–2.043(2)
Å], the M–N bond lengths [range 2.078(3)–2.115(3) Å] and the
chelate bite angles [range 77.60(11)–78.73(7)Њ] are similar in
all the complexes. The Ir–N distances are the same as those
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Scheme 1 Proposed mechanism
give cyclometallated products. This is not due to lack of
different requirements for electron density at the metal. Elec-
stability of the product, at least for ruthenium, since we
have previously synthesised this compound via a mercury
reagent.22
trophilic attack is favoured by electron poor metal centres
whilst oxidative addition is favoured by electron-rich metal
centres. The failure of 1, a good σ-donor ligand but with no
π-acceptor character, to cyclometallate with [RhCl2Cp*]2 and
[RuCl2(p-cymene)]2 would be consistent with an electrophilic
mechanism. In agreement with that, cyclometallation of 1 is
possible starting with a more electrophilic, cationic ruthenium
complex, though with a stronger base viz. NaOH;10 and is more
efficient with [RuCl2(C6H6)]2 rather than the more electron
donating p-cymene dimer.5 However, Bergman et al. have
shown that intermolecular C–H activation with [IrMe(OTf )-
(L)Cp*] (L = PMe3 or P(OMe)3) proceeds via dissociation of
triflate which is favoured by electron donating ligands, i.e. the
rate with PMe3 is faster than with P(OMe)3.24 Similar increased
rates of C–H activation with more electron donating substi-
tuents have been observed for platinum diimine systems.25 This
is in agreement with our observations that the alkyl-substituted
imines 3 and 4 cyclometallate more easily than the aryl-substi-
tuted one 5, and with the reduced reactivity of the oxazoline 7
containing the electron withdrawing oxygen atom. Thus, elec-
tron donating ligands may help in promoting loss of an anion
and creating a vacant coordination site, however too much
donation may then be detrimental in reducing the electro-
philicity of the metal for the C–H activation step. Further
studies to probe the electronic requirements of the ligands to
facilitate C–H activation, the precise role(s) of acetate and C–C
bond forming reactivity of some of the resultant complexes are
currently under investigation.
Discussion
The results described above show that acetate can promote
cyclometallation of amines, imines and oxazolines with [IrCl2-
Cp*]2 even at room temperature. The corresponding reactions
work for fewer substrates with Cp*Rh and fewer still with
areneruthenium under the same conditions. The greater facility
for cyclometallation with Cp*Ir rather than rhodium has been
noted previously for benzoate complexes.23 The detailed mech-
anism and role(s) of acetate in these reactions is not yet clear,
however, some key intermediates are presented in Scheme 1 and
are discussed further below.
Our attempts to isolate a complex of type B (Scheme 1) by
direct reaction of the dimers with these ligand have so far failed;
there is no reaction or in the case of imines hydrolysis occurs to
give primary amine complexes e.g. 6. Notably, there is no reac-
tion between 1 and [IrCl2Cp*]2 using NEt3 as base in place of
NaOAc. This suggests that acetate may help facilitate break up
of the dimer and exchange of a chloride ligand. This is further
evidenced by the fact that all the dimers will react with acetate.
In the case of ruthenium we isolated the known complex 2, a
species of type A (Scheme 1), which can cyclometallate 3 to
form 3c in the absence of added acetate. Another special feature
of acetate may be its ability to act as an intramolecular base as
has been proposed in palladium cyclometallation reactions.1c
The intramolecular hydrogen bonding observed in [Rh(OH2)-
(η1-O2CMe)2Cp*]ؒH2O shows this may also be possible for
these half-sandwich cyclometallations.
Experimental
Dichloromethane, N,N-dimethylbenzylamine, benzylidene-
aniline and sodium acetate were used as supplied. The dimers
[MCl2Cp*]2 (M = Rh, Ir)26 or [RuCl2(p-cymene)]2,27 and oxazol-
ine 728 were prepared by literature methods. The methoxy-alkyl
imines 3 and 4 were prepared by the same procedure as a similar
hydroxyethyl imine.29 The reactions described were carried
out under nitrogen; however, once isolated as pure solids the
compounds are air-stable and precautions for their storage
are unnecessary. 1H and 13C NMR spectra were obtained
using Bruker spectrometers, at 250 MHz in CDCl3 unless
stated otherwise, chemical shifts were recorded in ppm
(referenced to tetramethylsilane or residual protons in the
NMR solvent). FAB mass spectra were obtained on a Kratos
Concept mass spectrometer using an NOBA matrix. Infrared
spectra were run as solids in a diamond ATR cell using a Perkin
Elmer Spectrum 1 instrument. Microanalyses were performed
by the elemental analysis service of the University of North
London.
In order for C–H activation to occur a vacant site is needed
therefore loss of an anion from C is likely to be necessary as
found in a related Cp*Ir system.24 The two most likely mechan-
isms for the C–H activation step are; oxidative addition of the
aryl C–H bond to give MV (M = Ir, Rh) or RuIV cations followed
by reductive elimination of HX (i.e. via D1), or electrophilic
attack of the metal on the arene (i.e. via a Wheland intermedi-
ate D2) followed by loss of a proton. These two alternatives have
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General procedure for cyclometallation reactions
ClNORh: C, 55.12, H, 6.24, N, 3.21. Found: C, 54.92, H, 6.39,
N, 3.15%. H NMR: δ 1.66 (s, 15H, Cp*), 3.38 (s, 3H, OMe),
1
Sodium acetate and the appropriate dimer [MCl2Cp*]2 (M =
Rh, Ir) or [RuCl2(p-cymene)]2 were added to a solution of the
ligand in dichloromethane (15–20 ml). The mixture was stirred
for several hours, then filtered through Celite. The filtrate was
evaporated to dryness and then washed with hexane to remove
excess ligand to give the cyclometallated products. These were
usually pure at this stage but the compounds could be recrystal-
lised from dichloromethane–hexane. Details of individual
reactions are shown below.
3.87 (m, 2H, CH2O), 4.01 (m, 1H, NCHHЈ), 4.20 (m, 1H,
NCHHЈ), 7.00 (dt, 1H, J 7.5, 1, H4), 7.21 (dt, 1H, J 7.5, 1.5, H5),
7.42 (dd, 1H, J 7.5, 1.5, H3), 7.77 (d, 1H, J 7.5, H6), 8.16 (d, 1H,
JRhH 4, HC᎐N). 13C NMR: δ 9.49 (C5Me5), 59.11 (OMe), 60.75
᎐
(CH2O), 70.62 (NCH2), 96.03 (d, JRhC 6, C5Me5), 122.67,
128.46, 130.95, 136.01 (C3, C4, C5, C6), 145.49 (C2), 173.97
(HC᎐N), 184.03 (d, J
33, C1Rh). MS (FAB): m/z 435 [M]ϩ,
᎐
RhC
400 [M Ϫ Cl]ϩ. IR: ν(C᎐N) 1606 cmϪ1
.
᎐
[RuCl{C H -1-C(H)᎐N(CH ) OCH -ꢀC,N}(p-cymene)] (3c)
᎐
6
4
2
2
3
[IrCl{C6H4-2-CH2NMe2-ꢀC,N}Cp*] (1a)
This was prepared from NaOAc (67 mg, 0.82 mmol), [RuCl2-
(p-cymene)]2 (200 mg, 0.33 mmol), and imine 3 (107 mg, 0.66
mmol) and benzaldehyde (35 mg, 0.33 mmol); after stirring for
5 h, 3c was isolated as a brown solid (230 mg, 82%). Calc. for
C20H26ClNORu: C, 55.48, H, 6.05, N, 3.24. Found: C, 55.54, H,
6.05, N, 3.29%. 1H NMR: δ 0.83 (d, 3H, J 7, CHMeMeЈ), 1.06
(d, 3H, J 7, CHMeMeЈ), 2.07 (s, 3H, Cy-Me), 2.49 (sept, 1H, J 7
Hz, CHMeMeЈ), 3.39 (s, 3H, OMe), 3.98 (m, 2H, CH2O), 4.26
(m, 2H, NCH2), 4.82 (d, 1H, J 6, Cy), 4.99 (d, 1H, J 6, Cy), 5.58
(d, 1H, J 6, Cy), 5.62 (d, 1H, J 6, Cy), 6.95 (t, 1H, J 7, H4), 7.12
(dt, 1H, J 7.5, 1.5, H5), 7.41 (dd, 1H, J 7.5, 1, H3), 8.05 (s, 1H,
This was prepared from NaOAc (50 mg, 0.61 mmol), [IrCl2-
Cp*]2 (200 mg, 0.25 mmol), and N,N-dimethylbenzylamine
(85 mg, 0.63 mmol); after stirring for 20 h, 1a was isolated as an
orange precipitate (177 mg, 71%). Calc. for C19H27ClIrN: C,
45.91, H, 5.47, N, 2.82. Found: C, 45.87, H, 5.56, N, 2.79%. 1H
NMR: δ 1.63 (s, 15H, Cp*), 2.90 (s, 3H, NMe), 3.03 (s, 3H,
NMeЈ), 3.26 (d, 1H, J 13, NCH), 4.38 (d, 1H, J 13, NCHЈ), 6.86
(dt, 1H, J 7, 1, H4), 6.98 (t, 1H, J 7, H5), 7.05 (d, 1H, J 7, H3),
7.61 (d, 1H, J 7, H6). 13C NMR: δ 9.47 (C5Me5), 51.81, 57.47
(2 × NMe), 73.72 (NCH2), 87.61 (C5Me5), 121.56, 122.38,
126.47, 134.65 (C3, C4, C5, C6), 148.30 (C2), 151.38 (C1Ir). MS
(FAB): m/z 497 [M]ϩ, 460 [M Ϫ Cl Ϫ H2]ϩ.
HC᎐N), 8.12 (d, 1H, J 7.5, H6). 13C NMR: δ 18.96 (MeC6H4),
᎐
21.42 (CH(iPr)), 23.21, 31.04 (2 × Me(iPr)), 58.97 (OMe), 65.30
(CH2O), 70.69 (NCH2), 80.17, 80.89, 90.07, 91.24 (CH (C6H4
Cy)), 101.89, 102.62 (C (C6H4 Cy)), 122.33, 128.90, 129.71,
Reaction of N,N-dimethylbenzylamine with [RhCl2Cp*]2
A mixture of N,N-dimethylbenzylamine (87 mg, 0.65 mmol),
NaOAc (55 mg, 0.67 mmol), and [RhCl2Cp*]2 (200 mg, 0.32
mmol), was stirred in dichloromethane for 20 h. The mixture
139.07 (C3, C4, C5, C6), 145.38 (C2), 173.69 (HC᎐N), 188.48
᎐
(C1Ru). MS (FAB): m/z (%) 433 [M]ϩ, 398 [M Ϫ Cl]ϩ. IR:
ν(C᎐N) 1601 cmϪ1
.
᎐
1
was filtered through Celite and evaporated to dryness. The H
NMR spectrum showed a broad resonance at ca. δ 1.7 due to
Cp* and another signal at ca. δ 1.95. The mass spectrum
showed ions at m/z 237 [RhCp*], 297 [Rh(OAc)Cp*], 545
[Rh2Cl2Cp*2 Ϫ H], 581 [Rh2Cl3Cp*2], 605 [Rh2Cl2(OAc)Cp*2].
Crystals were grown by diffusion of hexane into a dichloro-
methane solution. The X-ray structure showed the crystals to
be [Rh(OH2)(η1-O2CMe)2Cp*]ؒH2O.
[IrCl{C H -2-C(H)᎐N(CH ) OCH -ꢀC,N}Cp*] (4a)
᎐
6 4 2 3 3
This was prepared from NaOAc (70 mg, 0.85 mmol), [IrCl2-
Cp*]2 (200 mg, 0.25 mmol), and imine 4 (90 mg, 0.50 mmol);
after stirring for 5 h, 4a was isolated as an orange precipitate
(260 mg, 96%). Calc. for C21H29ClIrNO: C, 46.78, H, 5.42, N,
1
2.60. Found: C, 46.80, H, 5.46, N, 2.68%. H NMR: δ 1.72 (s,
15H, Cp*), 2.17 (m, 2H, CH2), 3.33 (s, 3H, OMe), 3.43 (m, 2H,
CH2O), 4.13 (m, 2H, NCH2), 6.98 (dt, 1H, J 7.5, 1, H4), 7.16
(dt, 1H, J 7.5 and 1.5, H5), 7.52 (dd, 1H, J 7.5, 1, H3), 7.76 (d,
Reaction of N,N-dimethylbenzylamine with [RuCl2(p-cymene)]2
A mixture of N,N-dimethylbenzylamine (88 mg, 0.66 mmol),
NaOAc (67 mg, 0.82 mmol), and [RuCl2(p-cymene)]2 (200 mg,
0.33 mmol), was stirred in dichloromethane for 20 h. The mix-
ture was filtered through Celite and evaporated to dryness. The
1H NMR spectrum showed the presence of [RuCl(η2-O2CMe)-
(p-cymene)] (2) by comparison with literature data.20 This was
further characterised by X-ray diffraction.
1H, J 7.5, H6), 8.31 (s, 1H, HC᎐N). 13C NMR: δ 9.20 (C5Me5),
᎐
29.02 (CH2), 58.75 (OMe), 59.81 (CH2O), 69.75 (NCH2), 88.87
(C5Me5), 121.96, 128.16, 131.61, 134.73 (C3, C4, C5, C6), 146.27
(C2), 168.59 (C1Ir), 175.55 (HC᎐N); MS (FAB): m/z 539 [M]ϩ,
᎐
502 [M Ϫ Cl Ϫ H ]ϩ. IR: ν(C᎐N) 1593 cmϪ1
.
᎐
2
[RhCl{C H -2-C(H)᎐N(CH ) OCH -ꢀC,N}Cp*] 4b
᎐
6
4
2
3
3
This was prepared from NaOAc (66 mg, 0.81 mmol), [RhCl2-
Cp*]2 (200 mg, 0.32 mmol), and imine 4 (115 mg, 0.65 mmol);
after stirring for 5h, 4b was isolated as a red solid (275 mg,
95%). Calc. for C21H29ClNORh: C, 56.07, H, 6.50, N, 3.11.
[IrCl{C H -2-C(H)᎐N(CH ) OCH -ꢀC,N}Cp*] (3a)
᎐
6
4
2
2
3
This was prepared from NaOAc (70 mg, 0.85 mmol), [IrCp*-
Cl2]2 (200 mg, 0.25 mmol), and imine 3 (80 mg, 0.50 mmol);
after stirring for 5 h, 3a was isolated as an orange precipitate
(255 mg, 96%). Calc. for C20H27ClIrNO: C, 45.75, H, 5.18, N,
1
Found: C, 55.98, H, 6.44, N, 3.15%. H NMR (300 MHz):
δ 1.66 (s, 15H, Cp*), 2.21 (m, 2H, –CH2), 3.32 (s, 3H, OMe),
3.44 (m, 2H, –CH2O), 3.93 (m, 1H, NCHHЈ), 4.12 (m, 1H,
NCHHЈ), 7.01 (dt, 1H, J 7.5, 1, H4), 7.22 (dt, 1H, J 7.6, 1.5, H5),
7.41 (dd, 1H, J 7.5, 1.5, H3), 7.77 (d, 1H, J 7, H6), 8.11 (d, 1H,
1
2.67. Found: C, 45.65, H, 5.18, N, 2.62%. H NMR: δ 1.72 (s,
15H, Cp*), 3.37 (s, 3H, OMe), 3.85 (m, 2H, CH2O), 4.19 (m,
2H, NCH2), 6.97 (dt, 1H, J 7.5, 1, H4), 7.15 (dt, 1H, J 7.5, 1.5,
H5), 7.52 (dd, 1H, J 7.5, 1 Hz, H3), 7.76 (d, 1H, J 7.5, H6), 8.37
JRhH 4, HC᎐N). 13C NMR: δ 9.41 (C5Me5), 29.32 (CH2), 58.64
᎐
(s, 1H, HC᎐N). 13C NMR: δ 9.25 (C5Me5), 59.00 (OMe), 61.89
(CH2O), 58.75 (OMe), 69.72 (NCH2), 95.98 (d, JRhC 6, C5Me5),
᎐
(CH2O), 70.34 (NCH2), 88.88 (C5Me5), 121.97, 128.52, 131.71,
122.62, 128.08, 130.81, 136.01 (C3, C4, C5, C6), 145.32 (C2),
134.71 (C3, C4, C5, C6), 146.42 (C2), 168.73 (C1Ir), 176.31 (HC᎐
172.97 (HC᎐N), 183.93 (d, JRhC 33, C1Rh). MS (FAB): m/z 449
᎐
᎐
N). MS (FAB): m/z 525 [M]ϩ, 490 [M Ϫ Cl]ϩ. IR: ν(C᎐N) 1596
[M]ϩ, 414 [M Ϫ Cl]ϩ, 412 [M Ϫ Cl Ϫ H ]ϩ. IR: ν(C᎐N) 1604
᎐
᎐
2
cmϪ1
.
cmϪ1
.
[RhCl{C H -2-C(H)᎐N(CH ) OMe-ꢀC,N}Cp*] (3b)
[RuCl{C H -1-C(H)᎐N(CH ) OCH -ꢀC,N}(p-cymene)] 4c
᎐
6 4 2 3 3
᎐
6
4
2
2
This was prepared from NaOAc (33 mg, 0.40 mmol),
[RhCl2Cp*]2 (100 mg, 0.16 mmol), imine 3 (53 mg, 0.32 mmol)
and benzaldehyde (33 mg, 0.31 mmol); after stirring for 5 h, 3b
was isolated as a red solid (125 mg, 89%). Calc. for C20H27-
This was prepared from NaOAc (35 mg, 0.43 mmol), [RuCl2-
(p-cymene)]2 (100 mg, 0.16 mmol), and imine 4 (58 mg, 0.33
mmol) and benzaldehyde (18 mg, 0.17 mmol); after stirring for
5 h, 4c was isolated as a red solid (123 mg, 84%). Calc. for
D a l t o n T r a n s . , 2 0 0 3 , 4 1 3 2 – 4 1 3 8
4136

View Article Online
C21H28ClNORu: C, 56.43, H, 6.31, N, 3.13. Found: C, 56.61, H,
6.22, N, 3.13%. 1H NMR: δ 0.80 (d, 3H, J 7, CHMeMeЈ), 1.06
(d, 3H, J 7, CHMeMeЈ), 2.10 (s, 3H, Cy–Me), 2.37 (m, 2H,
CH2), 2.49 (sept, 1H, J 7, CHMeMeЈ), 3.36 (s, 3H, OMe), 3.47
(m, 2H, CH2O), 4.17 (m, 2H, NCH2), 4.82 (d, 1H, J 6.5, Cy),
4.95 (d, 1H, J 6, Cy), 5.64 (d, 2H, J 6.5, Cy), 6.96 (dt, 1H, J 7.5,
1, H4), 7.13 (dt, 1H, J 7.5, 1.5, H5), 7.41 (dd, 1H, J 7.5, 1, H3),
8.01 (s, 1H, HC᎐N), 8.12 (d, 1H, J 7.5, H6). 13C NMR: δ 18.98
᎐
(MeC6H4), 21.23 (CH (iPr)), 23.49 (Me (iPr)), 29.53 (CH2),
31.04 (Me (iPr)), 58.83 (OMe), 62.97 (CH2O), 69.82 (NCH2),
79.58, 81.26, 89.79, 91.71 (CH (C6H4 Cy)), 101.21, 103.31 (C
(C6H4 Cy)), 122.34, 128.61, 129.68, 139.07 (C3, C4, C5, C6),
145.19 (C2), 172.77 (HC᎐N), 188.31 (C1Ru). MS (FAB): m/z 447
᎐
[M]ϩ, 410 [M Ϫ Cl Ϫ H ]ϩ. IR: ν(C᎐N) 1602 cmϪ1
.
᎐
2
[IrCl{C H -2-C(H)᎐NPh-ꢀC,N}Cp*] 5a
᎐
6
4
This was prepared from NaOAc (13 mg, 0.16 mmol), [IrCl2-
Cp*]2 (50 mg, 0.06 mmol), dibenzylideneaniline (23 mg, 0.13
mmol) and benzaldehyde (7 mg, 0.07 mmol); after stirring for
5 h, 5a was isolated as a red precipitate (57 mg, 84%). Calc. for
C23H25ClIrN: C, 50.86, H, 4.64, N, 2.58. Found: C, 50.78, H,
1
4.68, N, 2.59%. H NMR: δ 1.47 (s, 15H, Cp*), 7.02 (dt, 1H,
J 7.5, 1, H4), 7.20 (dt, 1H, J 7.5, 1.5, H5), 7.30 (m, 1H, Ph), 7.40
(t, 2H, J 7.5, Ph), 7.57 (m, 2H, Ph), 7.62 (dd, 1H, J 7.5, 1, H3),
7.85 (d, 1H, J 7.5, H6), 8.31 (s, 1H, HC᎐N). 13C NMR: δ 8.90
᎐
(C5Me5), 89.39 (C5Me5), 122.14, 122.67, 127.43, 129.16, 129.75,
132.62, 135.29 (C3, C4, C5, C6 and Ph), 147.15 (C2), 152.00 (Ph),
170.68 (C1Ir), 175.58 (HC᎐N). MS (FAB): m/z 543 [M]ϩ, 508
᎐
[M Ϫ Cl]ϩ. IR: ν(C᎐N) 1582 cmϪ1
.
᎐
[RhCl{C H -2-C(H)᎐NPh-ꢀC,N}Cp*] 5b
᎐
6
4
This was prepared from NaOAc (66 mg, 0.80 mmol), [RhCl2-
Cp*]2 (200 mg, 0.32 mmol), dibenzylideneaniline (120 mg, 0.65
mmol) and benzaldehyde (35 mg, 0.33 mmol); after stirring for
5 h, 5b was isolated as a red precipitate (178 mg, 71%). Calc. for
C23H25ClNRh: C, 60.87, H, 5.55, N, 3.09. Found: C, 60.63, H,
1
5.85, N, 3.00%. H NMR: δ 1.43 (s, 15H, Cp*), 7.06 (t, 1H,
J 7.5, H4), 7.27 (t, 1H, J 7.5, H5), 7.30 (t, 1H, J 7.5, Ph), 7.42 (t,
2H, J 7.5, Ph), 7.54 (dd, 1H, J 7.5, 1, H3), 7.62 (d, 2H, J 8, Ph),
7.85 (d, 1H, J 8, H6), 8.18 (d, 1H, JRhH 4, HC᎐N). 13C NMR:
᎐
δ 9.10 (C5Me5), 96.42 (d, JRhC 6.5, C5Me5), 122.32, 122.89,
127.42, 129.28, 129.58, 131.64, 136.58 (C3, C4, C5, C6 and Ph),
146.32 (C2), 151.24 (Ph), 172.50 (HC᎐N), 185.55 (d, J
33,
᎐
᎐
RhH
C1Rh). MS (FAB): m/z 453 [M]ϩ, 418 [M Ϫ Cl]ϩ. IR: ν(C᎐N)
1598 cmϪ1
.
[IrCl{C6H4-2-Me2oxaz)-ꢀC,N}Cp*] 7a
This was prepared from NaOAc (16 mg, 0.20 mmol),
[IrCl2Cp*]2 (63 mg, 0.08 mmol), and oxazoline 7 (28 mg, 0.16
mmol); after stirring for 5 h, 7a was isolated as an orange pre-
cipitate (62 mg, 74%). Calc. for C21H27ClIrNO: C, 46.96, H,
1
5.07, N, 2.61. Found: C, 46.72, H, 4.89, N, 2.54%. H NMR:
δ 1.50 (s, 3H, Me), 1.53 (s, 3H, Me), 1.79 (s, 15H, Cp*), 4.43 (d,
1H, J 8, OCHHЈ), 4.55 (d, 1H, J 8, OCHHЈ), 6.99 (dt, 1H, J 7.5,
1, H4), 7.24 (dt, 1H, J 7.5, 1.5, H5), 7.42 (dd, 1H, J 7.5, 1, H3),
7.75 (d, 1H, J 7.5, H6). 13C NMR: δ 10.14 (C5Me5), 26.54 (Me),
28.87 (Me), 67.51 (CMe2), 82.95 (OCH2), 88.05 (C5Me5),
121.89, 126.51, 132.35, 135.37 (C3, C4, C5, C6), 162.81 (C2),
178.17 (C1Ir). MS (FAB): m/z. 537 [M]ϩ, 502 [M Ϫ Cl]ϩ. IR:
ν(C᎐N) 1623 cmϪ1
.
᎐
X-Ray crystal structure determinations
Details of the structure determinations of crystals of 2, 3a–c
and 5a–b are given in Table 2, those for 6 are in the ESI.† Data
were collected on a Bruker Apex 2000 CCD diffractometer
using graphite monochromated Mo-Kα radiation, λ = 0.7107 Å
at 150 K. The data were corrected for Lorentz and polarisation
effects and empirical absorption corrections (SADABS)30 were
D a l t o n T r a n s . , 2 0 0 3 , 4 1 3 2 – 4 1 3 8
4137

View Article Online
7 E. J. Farrington, J. M. Brown, C. Barnard and E. Rowsell,
Angew. Chem., Int. Ed., 2002, 41, 169.
8 A. D. Ryabov, V. S. Sukharev, L. Alexandrova, R. Le Lagadec and
M. Pfeffer, Inorg. Chem., 2001, 40, 6529.
9 S. Attar, J. H. Nelson, J. Fischer, A. Decian, J. P. Sutter and
M. Pfeffer, Organometallics, 1995, 14, 4559.
10 S. Fernandez, M. Pfeffer, V. Ritleng and C. Sirlin, Organometallics,
1999, 18, 2390.
11 R. K. Rath, S. G. Valavi, K. Geetha and A. R. Chakravarty,
J. Organomet. Chem., 2000, 596, 232.
12 G. Martin and J. Boncella, Organometallics, 1989, 8, 2968.
13 J. Perez, V. Riera, A. Rodriguez and D. Miguel, Organometallics,
2002, 21, 5437.
14 For example: (a) W. D. Jones and F. J. Feher, J. Am. Chem. Soc.,
1985, 107, 620; (b) P. Diversi, S. Iacoponi, G. Ingrosso, F. Laschi, A.
Lucherini, C. Pinzino, G. Uccello-Barretta and P. Zanello,
Organometallics, 1995, 14, 3275; (c) A. H. Janowicz and R. G.
Bergman, J. Am. Chem. Soc., 1983, 105, 3929.
applied in all cases. The structures were solved by Patterson
methods and refined by full-matrix least squares on F 2 using
the program SHELXTL-PC.31 All hydrogen atoms bonded to
carbon were included in calculated positions (C–H = 0.96 Å)
using a riding model. All non-hydrogen atoms were refined
with anisotropic displacement parameters without positional
restraints. Complex 3c has two independent molecules in the
unit cell the only significant differences are the orientation of
the CH2CH2OMe chain and the Ru–Cl bond distance.
CCDC reference numbers 207506–207512.
See http://www.rsc.org/suppdata/dt/b3/b303737a/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
We thank the Saudi Arabian government (O. A-D.) for a
studentship and Johnson Matthey for a loan of platinum
metal salts.
15 W. Bauer, M. Prem, K. Polborn, K. Sunkel, W. Steglich and W. Beck,
Eur. J. Inorg. Chem., 1998, 485.
16 B. J. Wik, C. Romming and M. Tilset, J. Mol. Catal. A Chem., 2002,
189, 23.
17 X. Riera, A. Caubet, C. Lopez, V. Moreno, E. Freisinger,
M. Willermann and B. Lippert, J. Organomet. Chem., 2001, 629,
97.
18 P. Boyer, C. Roy, J. Bielski and J. Merola, Inorg. Chim. Acta, 1996,
245, 7.
19 J. W. Kang, K. Moseley and P. M. Maitlis, J. Am. Chem. Soc., 1969,
91, 5970.
20 D. A. Tocher, R. O. Gould, T. A. Stephenson, M. A. Bennett,
J. P. Ennett, T. W. Matheson, L. Sawyer and V. K. Shah, J. Chem.
Soc., Dalton Trans., 1983, 1571.
References and notes
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21 Details, including the X-ray structure determination are in the
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22 A. J. Davenport, D. L. Davies and M. Giardiello, unpublished work.
23 J. Kisenyi, G. Sunley, J. Cabeza, A. Smith, H. Adams, N. Salt and
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31 G. M. Sheldrick, in SHELXTL-PC, Madison, WI, 1990.
D a l t o n T r a n s . , 2 0 0 3 , 4 1 3 2 – 4 1 3 8
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