NHC-manganese(i) complexes as carbene transfer agents

Article abstract of DOI:10.1039/b906450h

Tautomerization of coordinated azoles to their corresponding N-heterocyclic carbenes (NHCs) has been carried out by reaction of complexes fac-[Mn(L)(CO)₃(dppe)]⁺ (L = N-phenylimidazole) and fac-[Mn(L)(CO)₃(bipy)]⁺

Full text of DOI:10.1039/b906450h

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N-Heterocyclic Carbenes
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Published in issue 35, 2009 of Dalton Transactions
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www.rsc.org/dalton | Dalton Transactions
NHC–manganese(I) complexes as carbene transfer agents†
´
Javier Ruiz,* Angela Berros, Bernabe´ F. Perandones and Maril´ın Vivanco
Received 1st April 2009, Accepted 29th May 2009
First published as an Advance Article on the web 3rd July 2009
DOI: 10.1039/b906450h
Tautomerization of coordinated azoles to their corresponding N-heterocyclic carbenes (NHCs) has
been carried out by reaction of complexes fac-[Mn(L)(CO)3(dppe)]+ (L = N-phenylimidazole) and
fac-[Mn(L)(CO)3(bipy)]+ (L = N-methylbenzimidazole, benzoxazole, benzothiazole) with KOtBu and
subsequent protonation of the azolyl intermediates with NH4PF6. Several NHC–manganese(I)
complexes bearing an N–H residue of general formula fac-[Mn(NHC)(CO)3(dppe)]+ and
fac-[Mn(NHC)(CO)3(bipy)]+ have been tested as carbene transfer agents to the gold fragments [Au(L)]+
(L = PPh3, CNPh, CNXylyl), allowing isolation or spectroscopic detection of various Mn(I)/Au(I)
heterometallic intermediates containing azolyl bridging ligands, which liberate the gold(I) carbene
complexes [Au(NHC)(L)]+ by means of acid hydrolysis. By contrast, when using the silver(I) fragment
[Ag(PPh3)]+ as carbene acceptor no transmetallation process occurred but instead inverse
tautomerization of the NHC to the corresponding imidazole ligand was observed.
Introduction
Several methods are known to accomplish the synthesis of NHC
transition metal complexes.1 Out of them those consisting of
in situ deprotonation of imidazolium salts or direct reaction
of free NHC with the appropriate metallic fragment have been
extensively used. The first approach have been successfully applied
by Lin and co-workers to obtain NHC–Ag(I) complexes through
reaction of Ag2O with a variety of imidazolium cations.2 The
silver carbenes are of remarkable interest as carbene transfer
agents for the preparation of NHC complexes of other metals by
transmetallation reactions.3 Isocyanide complexes are also useful
starting materials for the synthesis of NHC metal complexes, either
by intermolecular or intramolecular coupling. Thus, reaction of
coordinated isocyanides with haloamines leads to the formation
of cyclic diaminocarbenes,4 whereas intramolecular cyclization of
amino-functionalized isocyanides to afford benzannulated NHC
complexes has also been described in the literature.5
We have recently reported two new methods for the generation
of NHC ligands assisted by coordination of the precursor species
to manganese(I). As summarized in Scheme 1, one of them implies
the coupling of isocyanides with propargylamines (compound I),6
whereas the other one is based on tautomerization reactions of
N-coordinated imidazoles (compound II).7 Preliminary results
on the use of these complexes as carbene transfer agents have
also been described.7 In this paper, we report the extension of
the tautomerization methodology to the synthesis of new NHC
complexes of manganese(I), including benzannulated ones, as well
as an account of the scope and limitations of the use of NHC–
Mn(I) complexes in transmetallation processes of the NHC ligand.
Scheme 1 Formation of NHCs by reaction of isocyanides with propar-
gylamine (I) and by tautomerization of imidazoles (II), in manganese
complexes. [Mn] = fac-[Mn(CO)3(bipy)]+.
Results and discussion
The tautomerization process observed in imidazole ligands
N-coordinated in manganese(I) complexes containing bipy chelat-
ing ligand7 (Scheme 1), also takes place when a more strongly
donating and bulkier chelating ligand such as dppe is present
in the complex (Scheme 2). The precursor compound fac-
[Mn(L)(CO)3(dppe)]ClO4 ([2]ClO4: L = N-phenylimidazole) is
readily obtained by reaction of fac-[Mn(OClO3)(CO)3(dppe)] with
N-phenylimidazole in CH2Cl2 at room temperature. Complex
2 is transformed into the corresponding imidazolin-2-ylidene
tautomer 4 by treatment with KOtBu and subsequent protonation
of the imidazolyl intermediate 3 with NH4PF6 (Scheme 2).8
The acid–base promoted tautomerization of coordinated
azoles to NHCs is also feasible when using benzannu-
lated derivatives (Scheme 3). The precursor compounds fac-
[Mn(L)(CO)3(bipy)]ClO4 ([6a]ClO4: L = N-methylbenzimidazole,
[6b]ClO4: L = benzoxazole, [6c]ClO4: L = benzothiazole) were
prepared using the same experimental procedure as for compound
2. The azole ligands in complexes 6a–c are N-coordinated, but
in the case of 6c a little amount (20%) of the S-coordinated
isomer is present in the isolated product, as detected by 1H NMR
spectroscopy (see Experimental).
Departamento de Qu´ımica Orga´nica e Inorga´nica, Facultad de Qu´ımica,
Universidad de Oviedo, 33006, Oviedo, Spain. E-mail: jruiz@uniovi.es;
Fax: +34 985103446; Tel: +34 985102977
† CCDC reference numbers 725955–725958 for compounds 8, 11a, 13 and
18. For crystallographic data in CIF or other electronic format see DOI:
10.1039/b906450h
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The Royal Society of Chemistry 2009
Dalton Trans., 2009, 6999–7007 | 6999
©

Scheme 3 Synthesis of benzannulated azolin-2-ylidene complexes 8a–c.
Scheme 2 Synthesis of the imidazolin-2-ylidene carbene complex 4.
Reaction of 6a–c with KOtBu followed by treatment with
NH4PF6 yields the carbene complexes 8a–c (Scheme 3). Formation
of the carbene complexes 4 and 8a–c appears to be based
on the preferential C-binding versus N-binding (or occasionally
S-binding) in the azolyl intermediate species 3 and 7a–c. It is worth
noting that the tautomerization reaction is highly selective, even in
the case of 6c, which indicates that both the N- and S-coordinated
isomers undergo the same tautomerization process. The two step
generation of carbene complexes 4 and 8a–c was monitored by IR
spectroscopy (Table 1); a strong shift to lower frequencies in the
n(CO) bands of the carbonyl ligands is observed on passing from 2
and 6a–c to the azolyl intermediates 3 and 7a–c, and a new change
to higher frequencies when forming the NHC complexes 4 and
8a–c on protonation. The lower n(CO) frequencies of 4 and
Table 1 Selected spectroscopic data (IR and NMR) for compounds 2–18
1
1
Compound IR (CH2Cl2/cm-1) n(CO)a
1H NMRb d
13C { H} NMR,bc
d
31P { H} NMRb d
=
2
3
4
2031 vs, 1959 s, 1941 s
2002 vs, 1922 s, 1911 sh
2022 vs, 1946 s
6.99 (1 H, s, CH), 6.93
(1 H, s, CH), 6.04 (1 H, s, CH)
—
74.6 (s, dppe)
84.2 (s, dppe)
75.9 (s, dppe)
=
=
6.73 (1 H, d, 3JHH = 1.0 Hz, CH),
169.2 (t, 2JCP = 20 Hz)
=
6.21 (1 H, d, 3JHH = 1.0 Hz, CH)
=
8.10 (1 H, s, NH), 6.80 (1 H, s, CH), 180.6 (t, 2JCP = 19 Hz)
=
6.58 (1 H, s, NH)
6a
6b
6c
7a
7b
7c
8a
8b
8c
9a
2038 vs, 1947 s, 1937 s
2044 vs, 1958 s, 1943 s
2042 vs, 1956 s, 1942 s
2009 vs, 1918 s, 1901 s
2018 vs, 1921 s
3.67 (3 H, s, NCH3)
7.45 (1 H, s, N CH)
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
=
=
8.06 (1 H, s, N CH)
—
—
—
2014 vs, 1922 s
2033 vs, 1952 s, 1924 s
2040 vs, 1963 s, 1939 s
2037 vs, 1960 s, 1936 s
2028 vs, 1944 s, 1925 s
4.11 (3 H, s, NCH3), 9.00 (1 H, s, NH) 197.2 (s)
11.84 (1 H, s, NH)
11.47 (1 H, s, NH)
9.76 (1 H, s, NH), 6.94 (1 H, s, CH), 184.7 (s)
1.74 (3 H, s, CH3)
235.2 (s)
236.2 (s)
=
9b
2029 vs, 1945 s, 1923 s
10.02 (1H, s, NH), 7.02 (1H, s, =CH), 184.7 (s)
—
1.79 (3H, s, CH3)
=
11a
11b
11c
11d
12a
2030 vs, 1936 s, 1927 s
2030 vs, 1937 s, 1926 s
5.84 (1 H, s, CH), 1.78 (3 H, s, CH3) 190.4 (s)
41.0 (s, PPh3)
40.9 (s, PPh3)
—
—
=
5.89 (1 H, s, CH), 1.82 (3 H, s, CH3) 191.4 (s)
=
2030 vs, 1933 s, 2217 w n(CN),
5.88 (1 H, s, CH), 1.78 (3 H, s, CH3)
—
—
=
2030 vs, 1939 s, 1928 s, 2207 w n(CN) 5.86 (1 H, s, CH), 1.83 (3 H, s, CH3)
11.40 (1 H, s, NH), 7.23 (1 H, s, CH), 184.4 (d, 2JCP = 184 Hz) 40.6 (s, PPh3)
2.18 (3 H, d, 4JHH = 0.6 Hz, CH3)
=
—
12b
12d
13
15a
15b
16a
16b
17
—
11.37 (1 H, s, NH), 2.17 (3 H, s, CH3)
11.54 (1 H, s, NH), 2.16 (3 H, s, CH3)
—
—
40.5 (s, PPh3)
—
2218 w n(CN)
6.25 (1 H, s, CH), 5.14 (1 H, s, CH) 192.2 (d, 2JCP = 135 Hz) 75.0 (s, dppe), 40.5 (s, PPh3)
=
=
2023 vs, 1950 s, 1927 s
2023 vs, 1939 s, 1913 s
2030 vs, 1949 s, 1917 s
2031 vs, 1938 s, 1928 sh
2037 vs, 1947 s, 1938 sh
2029 vs, 1937 s, 1925 s
4.12 (3 H, s, NCH3)
—
—
—
—
—
30.7 (s, PPh3)
31.2 (s, PPh3)
40.7 (s, PPh3)
39.1 (s, PPh3)
12.4 (s, PPh3)
—
3.92 (3 H, s, NCH3)
—
5.81 (1 H, s, =CH), 1.80 (3 H, d,
4JHH = 1.0 Hz, CH3)
7.16 (1 H, d, 3JHH = 1.1 Hz, N CH),
—
—
=
18
2030 vs, 1939 s, 1928 s
=
6.18 (1 H, s, CH), 1.94 (3 H, s, CH3)
a Abbreviations: vs = very strong, s = strong, w = weak, sh = shoulder. b NMR spectra recorded in CD2Cl2. c Ccarbene
.
7000 | Dalton Trans., 2009, 6999–7007
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The Royal Society of Chemistry 2009
©

8a–c with respect to those of 2 and 6a–c reflect the stronger
donor capability of the NHC ligands in comparison with their
corresponding azole ligands. It must be pointed out that, though
the azolyl species 3 and 7a–c where spectroscopically detected,
only compound 3 is stable enough to be isolated as a pure sample.
The NMR data are in agreement with the proposed carbene nature
of compounds 4 and 8a–c (Table 1), specially the appearance of a
1
low field singlet signal in the 13C{ H} NMR spectra assigned to
the carbene carbon atom, together with the presence of a low field
N–H signal in the 1H NMR spectra. Additionally, for 8a an X-ray
diffraction study has been carried out (Fig. 1).
Scheme 4 Transmetallation process of NHC ligands to obtain the gold(I)
carbene complexes 12a,b,d. [Mn] = fac-[Mn(CO)3(bipy)].
imidazolyl bridging ligands, but alternatively can be considered as
N-metalated NHC complexes of gold(I).
The heterometallic derivative 13, analogous to 11a–d but
containing the diphosphine dppe as chelating ligand, was prepared
in a slightly different way, involving direct reaction of 3 with
[AuCl(PPh3)] in the presence of TlPF6 (Scheme 5). The need of
the Tl(I) salt as chloride abstractor for the reaction to take place
is probably due to the high steric hindrance of the dppe ligand,
which diminishes the nucleophilicity of the deprotonated complex
3 with respect to the bipy counterpart.
Fig. 1 Molecular structure of the complex 8a, shown with 50% thermal
ellipsoids. Hydrogen atoms of the bipy ligand◦are omitted for clarity.
˚
Selected interatomic distances (A) and angles ( ): Mn1–C2 = 2.060(4),
N1–C2 = 1.358(4), C2–N3 = 1.358(4), N3–C4 = 1.388(4), C4–C5 =
1.384(5), C5–N1 = 1.395(4); Mn1–C2–N1 = 132.7(3), Mn1–C2–N3 =
122.8(3), N1–C2–N3 = 104.3(3), C2–N3–C4 = 112.4(3), N3–C4–C5 =
105.4(3), C4–C5–N1 = 106.4(3), C5–N1–C2 = 111.5(3).
Scheme 5 Formation of the NHC–Au(I) complex 14 through transmet-
allation reaction from complex 3.
In preliminary results we have shown that NHC complexes of
Mn(I) can be used as carbene transfer agents to Au(I). We have
now found that the designed transmetallation route can be applied,
with some limitations that we will comment below, to any NHC–
Mn(I) complex bearing a N–H residue in the carbene ligand, and
that this transferring process involves translocation of Mn(I) and
Au(I)metal ions inheterometallic intermediate species. Reaction of
9a,b with the gold(I) triphenylphosphine or isocyanide complexes
[AuCl(L)] (L = PPh3 or CNR) in the presence of KOH leads to
the formation of the heterometallic derivatives 11a–d (Scheme 4).
As shown in the scheme, apart from the target substitution of
the proton by the isolobal [Au(L)]+ fragment, which would afford
complexes 10a–d, an additional structural change has occurred so
that the nitrogen atom of the imidazolyl ligand is now coordinated
to manganese, whereas the carbon atom is bonded to gold.
Considering the soft and hard character of carbon and nitrogen
atoms in the heterocyclic ligand, respectively, this translocation
process of the metal ions appears to be promoted by the
softer character of Au(I) with respect to Mn(I). The assumed
intermediate species 10a–d were not detected during the reaction
course, even by performing the reaction at low temperature. Note
that 11a–d are Mn(I)/Au(I) heterometallic complexes containing
The new heterometallic compounds 11a–d and 13 where fully
analytically and spectroscopically characterized (Table 1). The
1
13C{ H} NMR spectra show a low field doublet signal (at about
190 ppm) for the carbene carbon atom, which is coupled with
the PPh3 phosphorus atom. The PPh3 ligand gives rise to a
1
characteristic singlet signal in the 31P{ H} NMR spectra at about
40 ppm. An X-ray diffraction study has been carried out for
complexes 11a (Fig. 2) and 13 (Fig. 3). Both structures are similar,
the main differences arising from the distinct steric requirements
of the chelating ligand, which lead to a different orientation of
the gold fragment with respect to the manganese coordination
sphere in each complex. In particular, the bulky dppe ligand forces
the plain of the imidazolyl ligand to be locked between the two
diphenylphosphine groups in complex 13.
The treatment of 11a,b,d and 13 with HBF4 or HClO4 in CH2Cl2
leads to the cleavage of the Mn–N linkage affording a mixture of
the gold(I) carbene complexes 12a,b,d and 14, and the starting
manganese(I) complexes 5 and 1, respectively, (see Schemes 4
and 5). The low solubility of compound 5 allows separation and
purification of the NHC–Au(I) complexes 12a,b,d, which were
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 6999–7007 | 7001
©

transmetallation reactions from NHC–Ag(I) complexes have been
extensively used.3,12 This method, requiring deprotonation of
imidazolium salts by Ag2O, can only be applied when both
nitrogen atoms in the carbene are substituted. In this sense, the
transmetallation route from NHC–Mn(I) derivatives described
herein can be an option for obtaining NHC–Au(I) complexes bear-
ing N–H residues. An alternative method consisting of treatment
of lithiated azoles with chloro-gold(I) complexes and subsequent
protonation of the azolyl derivatives has been described in the
literature.13
Benzannulated azolin-2-ylidene carbene complexes 8a,b were
also tested as carbene transfer agents. No reaction was found
by following the one-pot procedure involving treatment of 8a,b
with [AuCl(PPh3)]/KOH, so the alternative route consisting of
the reaction of azolyl derivatives 7a,b with [AuCl(PPh3)] in
the presence of TlPF6 was used (Scheme 6). The reaction was
performed at 0 ◦C, allowing in this case the spectroscopic detection
of the intermediate species 15a,b previous to the translocation
process of the metal ions to afford 16a,b occurring at room
temperature, thus clarifying the full reaction pathway for the
formation of these heterometallic species. Compounds 15a,b
Fig. 2 Molecular structure of the complex 11a, shown with 50% thermal
ellipsoids. Hydrogen atoms of the bipy and Ph groups are omitted for
◦
˚
clarity. Selected interatomic distances (A) and angles ( ): Mn1–N3 =
2.060(7), N1–C2 = 1.339(10), C2–N3 = 1.386(10), N3–C4 = 1.366(10),
C4–C5 = 1.352(11), C5–N1 = 1.390(11), C5–C6 = 1.508(12), Au1–C2 =
2.027(9), Au1–P1 = 2.286(2); Mn1–N3–C2 = 128.4(6), Mn1–N3–C4 =
125.9(6), N1–C2–N3 = 107.8(8), C2–N3–C4 = 105.6(7), N3–C4–C5 =
111.9(8), C4–C5–N1 = 104.0(8), C5–N1–C2 = 110.7(8), N1–C2–Au1 =
123.2(7), N3–C2–Au1 = 129.0(7), C2–Au1–P1 = 172.9(3).
1
and 16a,b are easily distinguished by IR and 31P{ H} NMR
spectroscopy (Table 1). The n(CO) bands of the benzimidazolyl
derivative 16a are almost identical with those of the analogous
imidazolyl complexes 11a,b, whereas the bands corresponding to
15a appear at lower frequencies (7 cm-1 on average), which reflects
the stronger donor capability of the carbon atom in comparison
with the nitrogen atom in the benzimidazolyl ligand. Similarly,
the n(CO) frequencies for the benzoxazolyl complex 15b are lower
1
than for 16b. On the other hand, the 31P{ H} NMR spectra of
16a,b show a singlet close to 40 ppm, that is in the expected region
for a PPh3 ligand located trans to the carbene carbon atom (see
data of 11a,b in Table 1), whereas those of 15a,b reveal the presence
of a singlet near to 30 ppm for the PPh3 ligand, which has now a
nitrogen atom in the trans position.14 Unfortunately compounds
16a,b slowly decompose during the work-up, precluding either the
isolation of these species as pure samples or the proper hydrolysis
reaction to complete the transmetallationn process of the carbene
ligands to gold.
Fig. 3 Molecular structure of the complex 13, shown with 50% thermal
ellipsoids. Hydrogen atoms of the bipy and Ph groups are omitted for
clarity. Ph groups of the dppe ligand are reduced◦to their Cipso for clarity
˚
too. Selected interatomic distances (A) and angles ( ): Mn1–N3 = 2.101(6),
N1–C2 = 1.372(9), C2–N3 = 1.334(9), N3–C4 = 1.387(9), C4–C5 =
1.318(10), C5–N1 = 1.380(9), Au1–C2 = 2.038(7), Au1–P1 = 2.292(2);
Mn1–N3–C2 = 125.1(5), Mn1–N3–C4 = 127.8(5), N1–C2–N3 = 107.8(6),
C2–N3–C4 = 106.9(6), N3–C4–C5 = 110.4(7), C4–C5–N1 = 106.2(7),
C5–N1–C2 = 108.6(6), N1–C2–Au1 = 121.9(5), N3–C2–Au1 = 129.9(6),
C2–Au1–P1 = 174.9(2).
Scheme 6 Translocation process of Mn(I) and Au(I) ions in benzannulated
azolyl bridging ligands. [Mn] = fac-[Mn(CO)3(bipy)].
isolated as white solids. This is not the case for compounds 1
and 14, which show a similar solubility in most organic solvents,
precluding isolation of the NHC–Au(I) complex 14 by this way.
This result highlights the importance of the ancillary ligands in
the starting manganese(I) complex for the synthetic viability of the
present experimental approach to obtain NHC–Au(I) derivatives.
This observation has also been pointed out by other authors
when using group 6 metal complexes in NHC transfer reactions
between transition metal ions.9 NHC gold complexes have recently
attracted renewed attention due to their applications in catalysis10
and medicine.11 For the preparation of NHC–Au(I) complexes
Assuming that the translocation process of the metal ions that
allows transformation of the NHC–Mn(I) complexes into NHC–
Au(I) complexes is favored with soft metal centers, we performed
the reaction of complex 9a, previously transformed into its depro-
tonated form by treatment with KOtBu, with [Ag(OClO3)(PPh3)]
(Scheme 7). Formation of the expected Mn(I)/Ag(I) heterometallic
derivative 17 readily takes place, as confirmed by the spectroscopic
data of the complex (see Table 1).
7002 | Dalton Trans., 2009, 6999–7007
This journal is
The Royal Society of Chemistry 2009
©

means of acid–base treatments. We have also shown herein that
NHC–Mn(I) complexes bearing an N–H residue in the carbene
ligand can be used as carbene transfer agents, allowing the
isolation of several NHC–Au(I) complexes by this way. The
mechanism of the transmetallation process, which includes a
key step involving translocation of Mn(I) and Au(I) metal ions,
has been elucidated by spectroscopic detection and/or isolation
of Mn(I)/Au(I) heterometallic intermediates containing azolyl
bridging ligands. When trying to use silver(I) ion as carbene
acceptor the transmetallation process was not completed but
instead inverse tautomerization of the NHC to the corresponding
imidazole ligand occurred.
Scheme 7 “Inverse” tautomerization of NHC ligand to N-coordinated
imidazole through the Mn(I)/Ag(I) heterometallic intermediate 17. [Mn] =
fac-[Mn(CO)3(bipy)].
Compound 17 slowly undergoes spontaneous hydrolysis by
standing in solution, probably due to the presence of traces of
water. The hydrolysis of 17 is fully completed by addition of
KOH. This process did not result in the formation of the target
silver(I) carbene complex, but instead the N-coordinated imidazole
manganese(I) complex 18 was obtained (Scheme 7). This means
that in 17 the scission of the C–Ag bond is easier than the scission
of the N–Mn bond, in contrast to that occurring in the analogous
Mn(I)/Au(I) heterometallic species. The structure of 18 was con-
firmed by X-ray diffraction analysis (Fig. 4). Note that in overall,
the reaction depicted in Scheme 7 supposes tautomerization of
an N-heterocyclic carbene to the corresponding imidazole ligand,
which is the inverse process to that drawn in Schemes 2 and 3. To
our knowledge, such a process has only been observed once in the
literature.15
Experimental
General
All reactions and manipulations were carried out under a nitrogen
atmosphere using standard Schlenk techniques. Solvents were
distilled over appropriate drying agents under dry nitrogen
prior to use. Compounds fac-[Mn(OClO3)(CO)3(dppe)] (1),16
fac-[Mn(OClO3)(CO)3(bipy)] (5),17 [9a]ClO4 and [9b]ClO4 were
prepared according to reported protocols. NMR spectra were
recorded on Bruker 300 and 400 MHz spectrometers. NMR
multiplicities are abbreviated as follows: s = singlet, d = doublet,
ddd = doublet of doublet of doublets, t = triplet, td = triplet of
doublets, m = multiplet. Coupling constants J are given in Hz.
6
6
Safety note. Perchlorate salts of metal complexes with organic
ligands are potentially explosive. Only small amounts of such
materials should be prepared and these should be handled with
great caution.
For the NMR spectra the atom labelling in 2,2¢-bipyridine
ligands is as follows:
Synthesis of [2]ClO4. To a solution of 1 (0.10 g, 0.16 mmol) in
CH2Cl2 (10 mL) 1-phenylimidazole (0.030 mL, d = 1.14 g mL-1,
0.24 mmol) was added and the solution stirred for 12 h. After
this period of time the solution was concentrated to 4 mL. Slow
addition of hexane (10 mL) gave a yellow solid, which was filtered
off and dried under vacuum (0.11 g, 90%). (Found: C 58.2, H 4.2,
Fig. 4 Molecular structure of the complex 18, shown with 50% thermal
ellipsoids. Hydrogen atoms of the bipy and Ph groups are omitted for
◦
˚
clarity. Selected interatomic distances (A) and angles ( ): Mn1–N3 =
2.067(1), N1–C2 = 1.358(2), C2–N3 = 1.318(2), N3–C4 = 1.386(2),
C4–C5 = 1.356(2), C5–N1 = 1.391(2), C5–C6 = 1.489(2); Mn1–N3–C2 =
127.9(1), Mn1–N3–C4 = 126.2(1), N1–C2–N3 = 110.9(2), C2–N3–C4 =
105.8(1), N3–C4–C5 = 110.5(2), C4–C5–N1 = 105.1(1), C5–N1–C2 =
107.7(1).
N 3.7 C38H32ClMnN2O7P2 requires C 58.4, H 4.1, N 3.6%). IR
1
n
max/cm-1 2031 vs, 1959 s, 1941 s (CO). 31P{ H} NMR (CD2Cl2)
d/ppm: 74.6 (s, dppe). 1H NMR (CD2Cl2) d/ppm: 7.66–7.52 (23
H, m, Harom Ph), 6.52–6.50 (2 H, m, Harom Ph), 6.99 (1 H, s, CH),
6.93 (1 H, s, CH), 6.04 (1 H, s, CH), 3.37–3.28 (4 H, m, CH2).
=
=
=
Synthesis of 3. To a solution of [2]ClO4 (0.10 g, 0.13 mmol)
in CH2Cl2 (10 mL) KOtBu (0.029 g, 0.26 mmol) was added. The
mixture was stirred for 15 min and then filtered off to give a
yellow solution, which was concentrated to 3 mL. Addition of
hexane (15 mL) afforded a pale yellow solid, which was filtered
off and dried under vacuum (0.070 g, 80%). (Found: C 66.8, H
Conclusions
In this paper we have shown that azole molecules (L) N-
coordinated in the manganese(I) complexes fac-[Mn(L)(CO)3-
(dppe)]+ (L = N-phenylimidazole) and fac-[Mn(L)(CO)3(bipy)]+
(L = N-methylbenzimidazole, benzoxazole, benzothiazole) can
be transformed into their corresponding NHC tautomers by
4.3, N 3.85 C38H31MnN2O3P2 requires C 67.1, H 4.6, N 4.1%). IR
1
n
max/cm-1 2022 vs, 1946 s (CO). 31P{ H} NMR (CD2Cl2) d/ppm:
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 6999–7007 | 7003
©

1
84.2 (s, dppe). H NMR (CD2Cl2) d/ppm: 7.46–7.25 (25 H, m,
not distinguished from those of the corresponding N-coordinated
isomer.
3
3
=
Ph), 6.73 (1 H, d, JHH = 1.0 Hz, CH), 6.21 (1 H, d, JHH
=
1.0 Hz, CH), 3.76 (2 H, m, CH2), 2.79 (2 H, m, CH2). 13C{ H}
1
=
Synthesis of [8a]PF6. To a solution of [6a]ClO4 (0.10 g,
0.19 mmol) in CH2Cl2 (10 mL) KOtBu (0.043 g, 0.40 mmol) was
added. The mixture was stirred for 45 min and then filtered off
to give an orange solution corresponding to 7a. Then, NH4PF6
(0.062 g, 0.40 mmol) was added and the resulting suspension
stirred for 1 h. The solution was then filtered off and concentrated
to 5 mL. Addition of hexane (15 mL) gave a yellow solid, which
was filtered off and dried under vacuum (0.081 g, 75%). (Found:
C 43.9, H 2.6, N 9.7 C21H16F6MnN4O3P requires C 44.05, H 2.8,
NMR (CD2Cl2) d/ppm: 223.4 (s, CO), 216.6 (s, CO), 169.2 (t,
2
=
JCP = 20 Hz, Ccarbene), 143.2–127.7 (m, Carom Ph), 127.3 (s, CH),
2
=
123.6 (s, CH), 27.1 (t, JCP = 19 Hz, CH2).
Synthesis of [4]PF6. To a solution of [2]ClO4 (0.10 g,
0.13 mmol) in CH2Cl2 (10 mL) KOtBu (0.029 g, 0.26 mmol) was
added. The mixture was stirred for 15 min, after which complex
3 was formed, as detected by IR spectroscopy. Then the solution
was filtered off and NH4PF6 (0.042 g, 0.26 mmol) added. The
resulting suspension was stirred for 2 h. Then the solution was
filtered off and concentrated to 5 mL. Hexane (15 mL) was added
dropwise affording a white solid, which was filtered off and dried
under vacuum (0.051 g, 48%). (Found: C 54.9, H 3.6, N 3.5
C38H32F6MnN2O3P3 requires C 55.2, H 3.9, N 3.4%). IR nmax/cm-1
1
N 9.8%). IR nmax/cm-1 2033 vs, 1952 s, 1924 s (CO). H NMR
3
(CD2Cl2) d/ppm: 9.07 (2 H, d, JHH = 5.7 Hz, HA bipy), 9.00 (1
3
H, s, NH), 8.42 (2 H, d, JHH = 8.0 Hz, HD bipy), 8.19 (2 H, t,
3JHH = 7.5 Hz, HC bipy), 7.65 (2 H, t, 3JHH = 6.6 Hz, HB bipy), 7.52
(1 H, d, 3JHH = 7.7 Hz, Harom C6H4), 7.41 (1 H, d, 3JHH = 7.7 Hz,
Harom C6H4), 7.32 (1 H, d, 3JHH = 7.4 Hz, Harom C6H4), 7.25 (1 H, d,
2022 vs, 1946 s (CO). 31P{ H} NMR (CD2Cl2) d/ppm: 75.9 (s,
1
1
3JHH = 7.4 Hz, Harom C6H4), 4.11 (3 H, s, NCH3). 13C{ H} NMR
1
dppe). H NMR (CD2Cl2) d/ppm: 8.10 (1 H, s, NH), 7.61–7.41
(23 H, m, Harom Ph), 7.21 (2 H, d, 3JHH = 6.7 Hz, Ho Ph), 6.80 (1
d/ppm: 221.6 (s, CO), 212.9 (s, CO), 197.2 (s, Ccarbene), 155.3 (s, C1
bipy), 153.9 (s, C2 bipy), 139.9 (s, C3 bipy), 135.6 (s, Carom C6H4),
133.8 (s, Carom C6H4), 127.9 (s, C4 bipy), 124.8 (s, C5 bipy), 124.6
(s, Carom C6H4), 124.0 (s, Carom C6H4), 112.9 (s, Carom C6H4), 110.0 (s,
Carom C6H4), 34.9 (s, NCH3).
=
=
H, s, CH), 6.58 (1 H, s, CH), 3.35 (2 H, m, CH2), 3.03 (2 H, m,
CH2). 13C{ H} NMR (CD2Cl2): 220.1 (s, CO), 216.4 (s, CO), 180.6
1
(t, 2JCP = 19 Hz, Ccarbene), 140.2 (s, Cipso NPh), 134.4–128.4 (m, Carom
1
=
=
Ph), 125.8 (s, CH), 120.9 (s, CH), 26.2 (t, JCP = 20 Hz, CH2).
Synthesis of [8b]PF6. The procedure was analogous to that
described above, using [6b]ClO4 (0.10 g, 0.19 mmol), KOtBu
(0.044 g, 0.39 mmol) (30 min of stirring) and NH4PF6 (0.127 g,
0.78 mmol) (12 h of stirring) (0.075 g, 69%). (Found: C 42.75, H
2.4, N 7.4 C20H13F6MnN3O4P requires C 42.95, H 2.3, N 7.5%). IR
Synthesis of [6a]ClO4. To a solution of 5 (0.10 g, 0.24 mmol) in
acetone (10 mL) 1-methylbenzimidazole (0.038 g, 0.28 mmol) was
added and the resulting mixture stirred for 2 h. The solution was
concentrated to 5 mL. Addition of hexane (15 mL) gave a yellow
solid, which was filtered off and dried under vacuum (0.113 g,
91%). (Found: C 47.8, H 3.1, N 10.7 C21H16ClMnN4O7 requires C
47.9, H 3.1, 10.6%). IR nmax/cm-1 2038 vs, 1947 s, 1937 s (CO). 1H
n
max/cm-1 2040 vs, 1963 s, 1939 s (CO). 1H NMR (CD2Cl2) d/ppm:
11.84 (1 H, s, NH), 9.30 (2 H, d, 3JHH = 5.4 Hz, HA bipy), 8.22 (2 H,
d, 3JHH = 8.0 Hz, HD bipy), 8.14 (2 H, td, 3JHH = 7.4 Hz, 4JHH
=
3
NMR (CD2Cl2) d/ppm: 9.18 (2 H, d, JHH = 5.5 Hz, HA bipy),
1.0 Hz, HC bipy), 8.06–8.01 (1 H, m, Harom C6H4), 7.76–7.63 (3 H,
m, HB bipy y Harom C6H4), 7.53–7.46 (1 H, m, Harom C6H4), 7.41–
8.47 (2 H, d, 3JHH = 7.7 Hz, HD bipy), 8.20 (2 H, td, 3JHH = 7.7 Hz,
4JHH = 1.4 Hz, HC bipy), 8.00 (1 H, m, Harom C6H4), 7.67 (2 H, ddd,
3JHH = 7.7 Hz, 3JHH = 5.0 Hz,4JHH = 1.4 Hz, HB bipy), 7.46–7.40
1
7.34 (1 H, m, Harom C6H4). 13C{ H} NMR (CD2Cl2) d/ppm: 235.2
(s, Ccarbene), 220.3 (s, CO), 213.8 (s, CO), 155.3 (s, C1 bipy), 154.4 (s,
=
(3 H, m, Harom C6H4), 6.98 (1 H, s, CH), 3.67 (3 H, s, CH3).
=
=
C2 bipy), 146.1 (s, OC C), 139.8 (s, C3 bipy), 134.1 (s, NC C),
128.1 (s, C4 bipy), 127.8 (s, Carom C6H4), 125.6 (s, Carom C6H4), 123.6
(s, C5 bipy), 121.4 (s, Carom C6H4), 116.2 (s, Carom C6H4).
Synthesis of [6b]ClO4. The procedure was completely analo-
gous to that described above, using 5 (0.10 g, 0.24 mmol) and
benzoxazole (0.034 g, 0.28 mmol). Reaction time: 3 h (0.089 g,
71%). (Found: C 46.6, H 2.7, N 8.1 C20H13ClMnN3O8 requires C
46.8, H 2.55, N 8.2). IR nmax/cm-1 2044 vs, 1958 s, 1943 s (CO).
1H NMR (CD2Cl2) d/ppm: 9.20 (2 H, d, 3JHH = 5.4 Hz, HA bipy),
Synthesis of [8c]PF6. The procedure was similar that the
synthesis of [8a]PF6, using [6c]ClO4 (0.10 g, 0.19 mmol), KOtBu
(0.042 g, 0.37 mmol) (30 min of stirring) and NH4PF6 (0.123 g,
0.75 mmol) (12 h of stirring) (0.076 g, 70%). (Found: C 42.0, H
2.4, N 7.5 C20H13F6MnN3O3PS requires C 41.8, H 2.3, N 7.3). IR
8.51 (2 H, d, 3JHH = 8.0 Hz, HD bipy), 8.23 (2 H, t, 3JHH = 7.2 Hz,
3
max/cm-1 2037 vs, 1960 s, 1936 s (CO). 1H NMR (CD2Cl2) d/ppm:
HC bipy), 8.06–8.03 (1 H, m, Harom C6H4), 7.72 (2 H, t, JHH
=
n
3
6.4 Hz, HB bipy), 7.67–7.55 (3 H, m, Harom C6H4), 7.45 (1 H,
11.47 (1 H, s, NH), 9.18 (2 H, d, JHH = 5.1 Hz, HA bipy), 8.21
=
3
3
s, CH).
(2 H, d, JHH = 7.7 Hz, HD bipy), 8.10 (2 H, t, JHH = 7.7 Hz,
HC bipy), 7.67–7.59 (3 H, m, HB bipy and Harom C6H4), 7.47–7.29
Synthesis of [6c]ClO4. This compound was prepared in a simi-
lar way to [6a]ClO4, using 5 (0.10 g, 0.24 mmol) and benzothiazole
(0.031 mL, d = 1.246 g mL-1, 0.28 mmol). Reaction time: 3 h
(0.111 g, 89%). (Found: C 45.6, H 2.7, N 7.75 C20H13ClMnN3O7S
requires C 45.3, H 2.5, N 7.9%). IR nmax/cm-1 2042 vs, 1956 s,
(3 H, m, Harom C6H4). 13C{ H} NMR (CD2Cl2) d/ppm: 236.2 (s,
1
Ccarbene), 220.1 (s, CO), 213.8 (s, CO), 155.3 (s, C1 bipy), 154.4 (s, C2
=
=
bipy), 145.4 (s, SC C), 139.9 (s, C3 bipy), 133.9 (s, NC C), 128.2
(s, C4 bipy), 128.0 (s, Carom C6H4), 125.8 (s, Carom C6H4), 123.6 (s, C5
bipy), 121.4 (s, Carom C6H4), 116.0 (s, Carom C6H4).
1
1942 s (CO). H NMR (CD2Cl2) N-coordinated isomer (80%)
d/ppm: 9.17 (2 H, d, 3JHH = 4.8 Hz, HA bipy), 8.56 (2 H, d, 3JHH
=
Synthesis of [11a]ClO4. To a solution of [9a]ClO4 (0.10 g,
0.18 mmol) in CH2Cl2 (20 mL), [AuCl(PPh3)] (0.107 g, 0.22 mmol)
and KOH (0.20 g, 3.56 mmol) were added and the mixture stirred
for 10 min. The solution was then filtered off and concentrated to
3 mL. Addition of diethyl ether (15 mL) gave a yellow solid, which
3
8.5 Hz, HD bipy), 8.29 (2 H, t, JHH = 6.7 Hz, HC bipy), 8.06
(1 H, s, =CH), 8.02–7.99 (2 H, m, Harom C6H4), 7.79–7.59 (4 H,
m, HB bipy y Harom C6H4) S-coordinated isomer (20%) d/ppm:
3
9.27 (2H, d, JHH = 5.7 Hz, HA bipy), the rest of the signal are
7004 | Dalton Trans., 2009, 6999–7007
This journal is
The Royal Society of Chemistry 2009
©

was filtered off and dried under vacuum (0.142 g, 78%). (Found: C
48.9, H 2.9, N 5.4 C41H32AuClMnN4O7P requires C 48.7, H 3.2, N
to 3 mL and hexane (10 mL) added to obtain a white solid, which
was filtered off and dried under vacuum (0.050 g, 71%). (Found:
C 47.95, H 3.5, N 3.8 C28H25AuBF4N2P requires C 47.75, H 3.6, N
1
5.5%). IR nmax/cm-1 2030 vs, 1936 s, 1927 s (CO). 31P{ H} NMR
(CD2Cl2) d/ppm: 41.0 (s, PPh3). 1H NMR (CD2Cl2) d/ppm: 9.15
(2 H, d, 3JHH = 4.6 Hz, HA bipy), 8.33 (2 H, d, 3JHH = 6.8 Hz, HD
bipy), 8.07 (2 H, t, 3JHH = 7.5 Hz, HC bipy), 7.56–7.22 (20 H, m,
4.0%). 31P{ H} NMR (CD2Cl2) d/ppm: 40.6 (s, PPh3). 1H NMR
1
(CD2Cl2) d/ppm: 11.40 (1 H, s, NH), 7.63–7.43 (20 H, m, Harom
1
Ph), 7.23 (1 H, s, =CH), 2.18 (3 H, d, 4JHH = 0.6 Hz, CH3). 13C{ H}
3
2
Harom C6H5), 7.13 (2 H, t, JHH = 5.8 Hz, HB bipy), 5.84 (1 H, s,
NMR (CD2Cl2) d/ppm: 184.4 (d, JCP = 184 Hz, Ccarbene), 138.1
1
CH), 1.78 (3 H, s, CH3). 13C{ H} NMR (CD2Cl2) d/ppm: 221.0
(s, Cipso Ph), 134.7–129.7 (m, Carom Ph), 129.3 (s, Cipso Ph), 128.5 (s,
=
=
(s, CO), 217.4 (s, CO), 190.6 (s, Ccarbene), 155.8 (s, C1 bipy), 153.4
(s, C2 bipy), 139.9 (s, C3 bipy), 139.4 (s, Cipso Ph), 134.1–128.0 (m,
C1), 127.8 (s, Carom Ph), 117.4 (s, CH), 10.4 (s, CH3).
Synthesis of [12b]BF4. This was similarly prepared from
[11b]ClO4 (0.10 g, 0.09 mmol) and HBF4 (0.026 mL, 0.19 mmol).
(0.052 g, 73%). (Found: C 50.8, H 3.7, N 3.5 C32H27AuBF4N2P
=
Carom C6H5), 126.8 (s, C4 bipy), 126.4 (s, CH), 123.7 (s, C5 bipy),
9.9 (s, CH3).
1
requires C 50.95, H 3.6, N 3.7%). 31P{ H} NMR (CD2Cl2) d/ppm:
Synthesis of [11b]ClO4. The procedure was completely analo-
gous to that described above, using [9b]ClO4 (0.10 g, 0.17 mmol),
[AuCl(PPh3)] (0.090 g, 0.18 mmol) and KOH (0.20 g, 3.56 mmol).
Reaction time: 30 min (0.140 g, 80%). (Found: C 51.2, H 3.0, N
1
40.5 (s, PPh3). H NMR (CD2Cl2) d/ppm: 11.37 (1 H, s, NH),
8.01–7.97 (3 H, m, Harom C10H7), 7.87 (1 H, d, 3JHH = 7.4 Hz, Harom
C10H7), 7.67–7.41 (7 H, m, Harom Ph, C10H7), 7.27–7.23 (13 H, m,
5.1 C45H34AuClMnN4O7P requires C 51.0, H 3.2, N 5.3%). IR
=
Harom Ph, CH), 2.17 (3 H, s, CH3).
1
n
max/cm-1 2030 vs, 1937 s, 1926 s (CO). 31P{ H} NMR (CD2Cl2)
1
d/ppm: 40.9 (s, PPh3). H NMR (CD2Cl2) d/ppm: 9.17 (2 H, d,
Synthesis of [12d]BF4. The procedure was analogous to the
synthesis of [12a]BF4, using [11d]ClO4 (0.10 g, 0.11 mmol) and
HBF4 (0.024 mL, 0.17 mmol) (0.050 g, 77%). (Found: C 40.1, H
3.3, N 7.55 C19H18AuBF4N3 requires C 39.9, H 3.2, N 7.3%). IR
3JHH = 5.1 Hz, HA bipy), 8.37 (2 H, d, JHH = 7.3 Hz, HD bipy),
3
3
8.09 (2 H, t, JHH = 6.7 Hz, HC bipy), 7.88–7.78 (3 H, m, Harom
C10H7), 7.68 (1 H, d, 3JHH = 7.8 Hz, Harom C10H7), 7.51–7.46 (4 H,
m, HB bipy Harom C10H7), 7.34–7.11 (16 H, m, Harom Ph and C10H7),
n
max/cm-1 2218 w (CN). 1H NMR (CD2Cl2) d/ppm: 11.54 (1 H, s,
1
5.89 (1 H, s, =CH), 1.82 (3 H, s, CH3). 13C{ H} NMR (CD2Cl2)
NH), 7.62–7.60 (3 H, m, Harom Ph), 7.49–7.47 (2 H, m, Harom Ph),
d/ppm: 221.0 (s, CO), 217.4 (s, CO), 191.4 (s, Ccarbene), 155.8 (s, C1
bipy), 153.4 (s, C2 bipy), 139.8 (s, C3 bipy), 136.8 (s, Cipso C10H7),
133.9–127.0 (m, Carom Ph and C10H7), 126.8 (s, C4 bipy), 125.9 (s,
7.38 (1 H, t, 3JHH = 8 Hz, Hp Xylyl), 7.24–7.20 (3 H, m, Harom Xylyl,
=
CH), 2.44 (6 H, s, CH3 Xylyl), 2.16 (3 H, s, CH3).
Synthesis of [13]PF6. To a solution of 3 (0.10 g, 0.15 mmol)
in CH2Cl2 (10 mL), [AuCl(PPh3)] (0.073 g, 0.15 mmol) and TlPF6
(0.103 g, 0.29 mmol) were added and the resulting suspension
stirred for 45 min. Then the mixture was filtered off and
concentrated to 3 mL. Addition of hexane (10 mL) gave a pale
yellow solid which was filtered off and dried under vacuum. Re-
crystallization from CH2Cl2/hexane afforded colourless crystals of
the compound suitable for X-ray crystallography (0.089 g, 47%).
(Found: C 52.1, H 3.8, N 2.0 C56H46AuF6MnN2O3P4 requires C
52.35, H 3.6, N 2.2%). IR nmax/cm-1 2023 vs, 1950 s, 1927 s (CO).
=
CH), 123.7 (s, C5 bipy), 9.9 (s, CH3).
Synthesis of [11c]ClO4. To a solution of [9a]ClO4 (0.10 g,
0.18 mmol) in CH2Cl2 (20 mL) [AuCl(CNPh)] (0.067 g, 0.20 mmol)
and KOH (0.20 g, 3.56 mmol) were added and the mixture stirred
for 1 h. Then the solution was filtered off and concentrated to
4 mL. Addition of a hexane/diethyl ether (1 : 1) (15 mL) gave
a yellow solid, which was filtered off and dried under vacuum
(0.114 g, 74%). (Found: C 42.1, H 2.55, N 8.0 C30H22AuClMnN5O7
requires C 42.3, H 2.6, N 8.2%). IR nmax/cm-1 2217 w (CN), 2030
vs, 1933 s (CO). 1H NMR (CD2Cl2) d/ppm: 9.38 (2 H, d, 3JHH
=
1
31P{ H} NMR (CD2Cl2) d/ppm: 75.0 (s, dppe), 40.5 (s, PPh3).
5.1 Hz, HA bipy), 8.36 (2 H, d, 3JHH = 8.3 Hz, HD bipy), 8.19 (2 H,
t, 3JHH = 7.1 Hz, HC bipy), 7.62–7.51 (4 H, m, Harom Ph HB bipy),
1H NMR (CD2Cl2) d/ppm: 7.59–7.33 (40 H, m, Harom Ph), 6.25
=
=
(1 H, s, CH), 5.14 (1 H, s, CH), 3.26–3.22 (4 H, m, CH2).
=
1
13C{ H} NMR d/ppm: 220.1 (s, CO), 216.2 (s, CO), 192.2 (d,
7.41–7.18 (8H, m, Harom Ph), 5.88 (1 H, s, CH), 1.78 (3H, s, CH3).
2
=
JCP = 134.8 Hz, Ccarbene), 140.0–126.1 (m, Carom Ph), 125.9 (s, CH),
Synthesis of [11d]ClO4. This was similarly prepared starting
from [9a]ClO4 (0.10 g, 0.18 mmol), KOH (0.20 g, 3.56 mmol) and
[AuCl(CNXylyl)] (0.072 g, 0.20 mmol) (0.100 g, 63%). (Found: C
43.6, H 2.8, N 7.9 C32H26AuClMnN5O7 requires C 43.7, H 3.0, N
8.0%). IR nmax/cm-1 2207 w (CN), 2030 vs, 1939 s, 1928 s (CO).
1H NMR (CD2Cl2) d/ppm: 9.42 (2 H, d, 3JHH = 5.3 Hz, HA bipy),
8.44 (2 H, d, 3JHH = 7.8 Hz, HD bipy), 8.25 (2 H, t, 3JHH = 7.6 Hz,
HC bipy), 7.70 (2 H, t, 3JHH = 5.9 Hz, HC bipy), 7.52–7.40 (4 H, m,
Harom Ph Xylyl), 7.28–7.25 (4 H, m, Harom Ph Xylyl), 5.86 (1 H, s,
1
=
120.0 (s, CH), 27.0 (t, JCP = 19.3 Hz, CH2).
Synthesis of 18. To a solution of [9a]ClO4 (0.10 g, 0.18 mmol)
in CH2Cl2 (10 mL) KOtBu (0.041 g, 0.18 mmol) was added and
the mixture stirred for 30 min. Then the solution was filtered off
and [Ag(OClO3)(PPh3)] (0.085 g, 0.18 mmol) added producing
an immediate change in the colour of the solution from red to
yellow owing to the formation of complex 17. Then KOH (0.20 g,
3.56 mmol) was added and the mixture stirred for 1 h. The solution
was then filtered off and concentrated to 3 mL. Addition of diethyl
ether (15 mL) gave a yellow solid, which was filtered off and dried
under vacuum (0.056 g, 56%). (Found: C 49.8, H 3.25, N 10.2
C23H18ClMnN4O7 requires C 50.0, H 3.3, N 10.1%). IR nmax/cm-1
2030 vs, 1939 s, 1928 s (CO). 1H NMR (CD2Cl2) d/ppm: 9.21 (2
=
CH), 2.47 (6 H, s, Xylyl), 1.83 (3 H, s, CH3).
Synthesis of [12a]BF4. To a solution of [11a]ClO4 (0.10 g,
0.10 mmol) in CH2Cl2 (10 mL) HBF4 (0.027 mL, d = 1.18 g mL-1,
54% in diethyl ether, 0.20 mmol) was added and the mixture
stirred for 15 min. The solvent was removed under vacuum and
the remaining yellow dissolved in CH2Cl2 (10 mL). Addition of
hexane (10 mL) gave a yellow solid corresponding to 5, which was
eliminated by filtration. The remaining solution was concentrated
3
3
H, d, JHH = 5.1 Hz, HA bipy), 8.47 (2 H, d, JHH = 8.0 Hz, HD
bipy), 8.24 (2 H, t, 3JHH = 7.4 Hz, HC bipy), 7.71 (2 H, t, 3JHH
=
6.6 Hz, HC bipy), 7.48–7.46 (3 H, m, Harom Ph), 7.16 (1 H, d,
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 6999–7007 | 7005
©

Table 2 Crystallographic data for 8a, 11a, 13 and 18
8a
11a
13
18
Formula
C21H16F6MnN4O3P
C41H32AuClMnN4O7P
4(C56H46AuF6MnN2O3P4),
3(CH2Cl2), 4(H2O)
5465.79
C23H18ClMnN4O7
FW/g mol-1
572.29
1011.04
552.80
Colour/habit
Colourless
0.28 ¥ 0.20 ¥ 0.02
Orthorhombic
Pccn
17.9823(7)
20.1857(9)
12.4699(5)
90
90
90
4526.4(3)
8
100(2)
1.680
0.736
2304.0
1.52–26.41
61 187
4653/0.1034
2859
4653/0/330
0.0434/0.083
0.1034/0.1073
1.016
Yellow
Yellow
Yellow
Crystal dimensions/mm3
Crystal system
Space group
0.11 ¥ 0.07 ¥ 0.03
Monoclinic
P21/c
13.6998(3)
16.4964(2)
34.3632(8)
90
95.510(2)
90
7730.1(3)
8
100(2)
1.737
4.285
3984.0
1.37–26.03
69 647
15 238/0.1049
10 969
15 238/928/873
0.0634/0.1026
0.0931/0.1049
1.989
0.36 ¥ 0.32 ¥ 0.25
Monoclinic
P21/c
19.1731(8)
34.8321(17)
17.7003(9)
90
106.796(2)
90
11 316.7(9)
2
100(2)
1.639
3.091
5526.0
1.17–26.02
101 972
22 254/0.1591
15 792
22 254/70/1221
0.0586/0.1486
0.0940/0.1591
1.579
0.23 ¥ 0.08 ¥ 0.08
Triclinic
¯
P1
˚
a/A
8.9537(2)
10.4298(2)
13.1270(3)
79.323(2)
80.763(1)
73.754(1)
11 48.84(4)
2
100(2)
1.598
0.745
564.0
1.59–27.1
35 256
5040/0.0755
4476
5040/0/334
0.0301/0.0734
0.035/0.0755
1.055
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
V/A
Z
T/K
3
˚
D
calcd/g cm-3
m/mm-1
F(000)
q range/◦
No. of reflections collected
No. of independent reflections/Rint
No. of observed reflections (I > 2s(I))
No. of data/restraints/parameters
R1/wR2 (I > 2s(I))a
R1/wR2 (all data)a
GOF (on F2)a
-3
˚
Largest diffraction peak and hole (e A )
+0.542/-0.38
+2.884/-1.830
+4.207/-2.895
+0.607/-0.494
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2
2
1/2
a R1 = (ꢀFo| - |Fcꢀ)/ |Fo|; wR2 = { [w(Fo - Fc2)2]/ [w(Fo2)2]}1/2; GOF = { [w(Fo - Fc2)2]/(n - p)}
.
3
=
JHH = 1.1 Hz, N CH), 7.13–7.10 (2 H, m, Harom Ph), 6.18 (1 H,
Notes and references
=
s, CH), 1.94 (3 H, s, CH3).
1 Selected reviews: F. E. Hahn and M. C. Jahnke, Angew. Chem., Int. Ed.,
2008, 47, 3122; R. H. Crabtree, D. Bourissou, O. Guerret, F. P. Gaba¨ı
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Kro¨cher, Angew. Chem., Int. Ed. Engl., 1997, 36, 2162.
X-Ray crystallography
2 H. M. J. Wang and I. J. B. Lin, Organometallics, 1998, 17, 972.
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8 For other tautomerization processes of imidazoles to NHCs see: K. L.
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Suitable single crystals of 8a (yellow), 11a (yellow), 13 (colourless)
and 18 (yellow) for the X-ray diffraction study were selected.
The data collection was carried out at 100(2) K. The crystals
were mounted on a Smart-CCD-1000 BRUKER single crystal
diffractometer equipped with a graphite-monochromated Mo Ka
18
˚
radiation (l = 0.71073 A). Multi-scan absorption correction
procedures were applied to the data. The structures were solved,
using the WINGX package.19 by direct methods (DIRDIF-
99)20 and refined by using full-matrix least-squared against F2
(SHELXL-97).21 All non-hydrogen atoms were anisotropically
refined. Hydrogen atoms were geometrically placed and left
riding on their parent atoms except for the hydrogen atoms
on: N3 in compound 8a, C2 and C4 in compound 18. Full-
matrix least-squares refinements were carried out by minimizing
ꢀ
w(Fo - Fc )2 with the SHELXL-97 weighting scheme and
stopped at shift/error < 0.001. The final residual electron density
maps showed no remarkable features. (Table 2)
2
2
9 S. Liu and K. R. Reddy, Chem. Soc. Rev., 1999, 28, 315; R. Ku, J. Huang,
J. Cho, F. Kiang, K. R. Reddy, Y. Chen, K. Lee, J. Lee, G. Lee, S. Peng
and S. Liu, Organometallics, 1999, 18, 2145; F. Kessler, N. Szesni, C.
Maabb, C. Hohberger, B. Weibert and H. Fischer, J. Organomet. Chem.,
2007, 692, 3005.
10 M. Marion and S. P. Nolan, Chem. Soc. Rev., 2008, 37, 1776.
11 P. J. Barnard and S. J. Berners-Price, Coord. Chem. Rev., 2007, 251,
1889.
Acknowledgements
This work was supported by the Spanish Ministerio de Ciencia
e Innovacio´n (PGE and FEDER funding, Project CTQ2006–
10035). B. F. P. Thanks the MICINN for a FPU grant (PGE
and European Social Fund).
7006 | Dalton Trans., 2009, 6999–7007
This journal is The Royal Society of Chemistry 2009
©

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and S. Cronje, Chem. Soc. Rev., 2008, 37, 1998.
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17 R. Uso´n, V. Riera, J. Gimeno and M. Laguna, Transition Met. Chem.
(London), 1997, 2, 123.
18 SOTARV–R. H. Blessing, Acta Crystallogr., Sect. A: Fundam. Crystal-
logr., 1995, 51, 33.
19 L. J. Farrugia, J. Appl. Crystallogr., 1999, 32, 837.
20 P. T. Beurskens, G. Beurskens, W. P. Bosman, R. de Gelder, S. Garc´ıa-
Granda, R. O. Gould, R. Israel and J. M. M. Smits, DIRDIF96
Program System, Technical Report of the Crystallography Laboratory,
University of Nijmegen, The Netherlands, 1996.
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Williams, J. Am. Chem. Soc., 2006, 128, 13702.
21 G. M. Sheldrick, SHELXL-97, Program for refinement of crystal
structures, University of Go¨ttingen, Germany, 1997.
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 6999–7007 | 7007
©