Ruthenium alkynyl, carbene and alkenyl complexes containing pendant uracil groups: An investigation into the formation of alkenyl-phosphonio complexes

Article abstract of DOI:10.1039/b912855g

The vinylidene complex [Ru(η⁵-C₅H ₅)(PPh₃)₂(CCHUr)][X] (X = PF₆, OTf, Ur = uracil) is a versatile precursor for a range of organometallic complexes containing pendant uracil groups. Using a

Full text of DOI:10.1039/b912855g

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PAPER
www.rsc.org/dalton | Dalton Transactions
Ruthenium alkynyl, carbene and alkenyl complexes containing pendant uracil
groups: an investigation into the formation of alkenyl-phosphonio complexes†
Michael J. Cowley, Jason M. Lynam,* Robert S. Moneypenny, Adrian C. Whitwood and Alastair J. Wilson
Received 30th June 2009, Accepted 17th August 2009
First published as an Advance Article on the web 18th September 2009
DOI: 10.1039/b912855g
5
= =
The vinylidene complex [Ru(h -C5H5)(PPh3)2( C CHUr)][X] (X = PF6, OTf, Ur = uracil) is a
versatile precursor for a range of organometallic complexes containing pendant uracil groups. Using
appropriate conditions the vinylidene complex may be selectively transformed into alkynyl
5
5
≡
=
Ru(–C CUr)(h -C5H5)(PPh3)2, carbene [Ru(h -C5H5)(PPh3)2( C{OMe}–CH2Ur)][X] and
5
=
alkenyl-phosphonio species [Ru(E-CH C{PPh3}Ur)(h -C5H5)(PPh3)2][X]. The synthesis of the related
5
=
alkenyl-phosphonio complexes [Ru(E-CH C{PPh3}R)(h -C5H5)(PPh3)2][X] (R = Ph, C6H4-3-OMe) is
described; these undergo a further orthometallation reaction: the mechanism of this latter reaction
appears to proceed via dissociation of a ruthenium-bound PPh3 ligand.
As vinylidene complexes structurally related to 3a[X] have been
Introduction
shown to be versatile synthons for a range of organometallic
species,9,10 it was anticipated that a range of uracil-containing
complexes could be derived from 3a[X]. In particular, it is of
interest to explore the factors controlling the assembly of the
nucelobase-containing compounds in both the solid state and
solution and if the presence of a functionalised substituent
within the complex will have a pronounced effect on their
chemistry.
The structure and reactivity of transition metal complexes
containing vinylidene ligands continue to attract considerable
interest.1 Underlying the potential applications of these species
is the fact that many electron-rich transition metal complexes
may facilitate the isomerisation of terminal alkynes into their
vinylidene tautomers.2 The vinylidene ligands exhibit markedly
different reactivity patterns when compared to the parent terminal
alkynes3 – notably, the a-carbon of the vinylidene is susceptible to
nucleophilic attack and the b-carbon reacts with electrophiles.
This rich reactivity means that vinylidenes may act as synthons
to metal complexes which contain carbene, carbyne or carbonyl
ligands.4 In addition, the b-carbon of vinylidene ligands in
cationic complexes may be easily deprotonated to afford alkynyl
complexes,5 which are themselves important building blocks in,
for example, materials with interesting electronic and non-linear
optical properties.6
We now report that 3a[X] may act as a precursor to complexes
5
≡
containing alkynyl, Ru(–C CUr)(h -C5H5)(PPh3)2, 4a, carbene
5
=
[Ru(h -C5H5)(PPh3)2( C{OMe}-CH2Ur)][X], 5a[X] and alkenyl-
5
=
phosphonio,
[Ru(E-CH C{PPh3}Ur)(h -C5H5)(PPh3)2][X],
6a[X], ligands. Given the somewhat serendipitous isolation of
6a[X], we have also investigated the preparation of complexes
5
=
[Ru(E-CH C{PPh3}R)(h -C5H5)(PPh3)2][OTf] (R
=
Ph,
6b[OTf]; R = C6H4-3-OMe, 6c[OTf]). The synthesis and structure
of 5a[PF6] has been reported in a preliminary communication.11
We have recently been engaged in a programme of research
focused on utilising pendant nucleobase groups to direct the
self-assembly of inorganic compounds in both the solid state
and solution.7 For example we have demonstrated that the reac-
Results and discussion
The synthetic routes and structures of the complexes prepared in
this study are shown in Scheme 1. The structures of complexes
5a[OTf], 6a[OTf], 6b[OTf], and 6c[OTf] have been determined
by single crystal X-ray diffraction, selected bond lengths and
angles are given in Table 1 and details of the data collections
and structural refinements in Table 2. As part of this study the
structure of the novel complex 3c[OTf] was also determined: see
ESI.†
5
tion of RuCl(h -C5H5)(PPh3)2, 1, with the uracil(Ur)-substituted
≡
alkyne HC CUr, 2, in the presence of NH4X (X = BF4,
PF6, OTf) results in the formation of vinylidene complexes
5
8
= =
[Ru(h -C5H5)(PPh3)2( C CHUr)][X], 3a[X]. A related synthetic
procedure was employed to prepare the isoelectronic complex
7
= =
[Mo( C CHUr)(h -C7H7)(dppe)][BF4]. Importantly, the salts of
3a+ self-assemble in the solid state to form cyclic rosette containing
six ruthenium cations, the assembly being mediated by hydrogen
bonding interactions from the pendant uracil groups.
a. Preparation and characterisation of
5
≡
Ru(–C CUr)(g -C5H5)(PPh3)2, 4a
Department of Chemistry, University of York, Heslington, York, UK YO10
5DD. E-mail: jml12@york.ac.uk; Fax: +44 (0)1904 432516; Tel: +44
(0)1904 432534
Deprotonation of cationic ruthenium vinylidene complexes has
proven to be a general and versatile route for the synthesis of
1
† Electronic supplementary information (ESI) available: 31P{ H} NMR
≡
alkynyl (Ru–C C–R) complexes. We therefore believed that a
31
simulations for 6c[OTf] and 1H{ P} NMR experiments. CCDC reference
similar reaction of 3a+ could occur to give the neutral species
numbers 737832 (3c[OTf]), 737833 (5a[OTf]), 737834 (6a[OTf]), 737835
(6b[OTf]) and 737836 (6c[OTf]). For ESI and crystallographic data in CIF
or other electronic format see DOI: 10.1039/b912855g
5
9
≡
Ru(–C CUr)(h -C5H5)(PPh3)2, 4a. Although the two N–H
groups in the uracil could, in principle, also be deprotonated by
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Scheme 1 Synthetic pathways employed in this study. (i) +NH4X, +2, MeOH, -NH4Cl; (ii) +NaOMe, -NaX, MeOH; (iii) +H+; (iv) MeOH; (v) excess
PPh3, CH2Cl2, reflux; X = PF6, OTf.
◦
˚
Furthermore due to its poor solubility, complete purification of
4a proved troublesome, with the product always contaminated
with NaPF6.
The infra-red spectrum of 4a exhibits a band at 2073 cm-1 which
Table 1 Selected bond lengths (A) and angles ( ) for 5a[OTf], 6a[OTf],
6b[OTf], and 6c[OTf]; * indicates an intermolecular distance
5a[OTf]
6a[OTf]
6b[OTf]
6c[OTf]
≡
is in the region characteristic of the C C stretch of half-sandwich
Ru(1)–P(1)
Ru(1)–P(2)
Ru(1)–C(1)
Ru(1)–C(2)
Ru(1)–C(3)
Ru(1)–C(4)
Ru(1)–C(5)
Ru(1)–C(6)
C(6)–C(7)
C(6)–O(1)
C(7)–(P3)
2.3220(4)
2.3444(4)
2.3172(15) 2.3271(8) 2.3289(15)
2.3375(14) 2.3354(8) 2.3232(15)
ruthenium alkynyl complexes.9 Consistent with the formulation
of 4a, a peak was observed in the FAB mass spectrum at m/z
826. Importantly, the formation of 4a from 3a+ is reversible:
protonation with HCl or HBF4·OEt2 in MeOH solution simply
resulted in reformation of 3a+. Indeed, it proved possible to
perform several protonation/deprotonation cycles on 4a using
HBF4·OEt2/NaOMe with no apparent decomposition of the
products. In this respect 4a mirrors exactly the reactivity of Ru(–
2.2849(18) 2.239(5)
2.2345(18) 2.238(5)
2.2521(18) 2.265(5)
2.2480(17) 2.243(5)
2.2665(17) 2.238(5)
1.9541(17) 2.063(5)
2.242(3)
2.252(3)
2.254(3)
2.245(3)
2.257(2)
2.090(2)
1.357(3)
2.235(5)
2.242(6)
2.256(5)
2.241(5)
2.240(5)
2.070(5)
1.366(7)
1.527(2)
1.319(2)
1.377(6)
1.788(5)
2.796(5)
1.798(3)
1.791(5)
5
9
≡
C CPh)(h -C5H5)(PPh3)2.
N(2)–H(2A) ◊ ◊ ◊ O(3)* 2.862(2)
The H and 31P{ H} NMR spectra of 4a in CD2Cl2 solution
proved to be extremely complex—in the 1H NMR spectrum,
very broad resonances were observed in the aromatic region
(for the phenyl rings of the coordinated phosphines) and for the
1
1
P(1)–Ru(1)–P(2)
P(1)–Ru(1)–C(6)
P(2)–Ru(1)–C(6)
103.585(16) 102.06(5)
90.91(5)
88.33(5)
101.96(3) 101.98(5)
90.40(15)
89.23(13)
90.75(7)
90.06(7)
89.57(16)
91.14(14)
cyclopentadienyl ligand. The 31P{ H} NMR spectrum exhibited a
1
single very broad resonance. We suspected this broadness was due
to the aggregation of 4a in solution.
a strong base, it was anticipated that the vinylidene proton would
in fact be the most acidic in the system12 and that protection of
the N–H groups of the uracil would not be necessary. This proved
to be the case. Addition of 1 equivalent of NaOMe to a methanol
solution of 3a+ resulted in a rapid colour change from deep red to
bright yellow. Precipitation with hexane afforded a bright yellow
microcrystalline complex, 4a, which proved to be air stable in both
the solid state and solution.
An NMR study employing CD2Cl2 solutions of 4a prepared at
a range of concentrations supported this argument. The 31P{ H}
1
NMR spectrum of a 21.8 mM CD2Cl2 solution exhibited a single
extremely broad resonance at d 49.61 (w 1 = 1430 Hz). Sys-
2
tematically decreasing the concentration of this solution resulted
in a narrowing of the resonance (Table 3). However, even at a
concentration of 1.0 mM a linewidth of 917 Hz was observed.
The NH resonances were not observed at any concentrations
employed.
Complex 4a was characterised by NMR and infra-red spec-
troscopy coupled with mass spectrometery: to date a single crystal
suitable for study by X-ray diffraction has not been obtained.
9530 | Dalton Trans., 2009, 9529–9542
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Table 2 Crystallographic data for complexes 3c[OTf]·0.75CH2Cl2·0.25Et2O, 5a[OTf]·C7H8, 6a[OTf], 6b[OTf]·CH2Cl2, 6c[OTf]·0.625CH2Cl2
3c[OTf]·0.75CH2Cl2·
0.25Et2O
5a[OTf]·C7H8
6a[OTf]
6b[OTf]·CH2Cl2
6c[OTf]·0.56CH2Cl2
Empirical formula
Formula weight
T/K
Wavelength/A
Crystal system
C52.75H47Cl1.50F3O4.25P2RuS C56H51F3N2O6P2RuS
C66H54F3N2O5P3RuS C69H58Cl2F3O3P3RuS
C69.56H59.11Cl1.11F3O4P3RuS
1281.43
110(2)
0.71073
Triclinic
¯
P1
10.3173(14)
14.380(2)
20.203(3)
82.335(3)
88.087(3)
80.744(3)
2931.7(7)
2
1054.15
110(2)
1100.06
150(2)
1238.15
110(2)
1289.09
110(2)
˚
0.71073
Monoclinic
P21/n
0.71073
Triclinic
P1
0.71073
Monoclinic
P21/n
0.71073
Triclinic
P1
¯
¯
Space group
˚
a/A
12.3192(10)
12.4402(10)
31.194(3)
90
94.150(2)
90
11.6129(5)
14.4787(6)
15.9001(6)
95.010(1)
92.914(1)
108.150(1)
2522.10(18)
2
13.375(2)
18.319(3)
23.489(4)
90
101.392(4)
90
10.2678(14)
14.522(2)
20.112(3)
82.415(3)
88.372(3)
80.570(3)
2932.5(7)
2
˚
b/A
˚
c/A
a [◦]
b [◦]
g [◦]
Volume/A
Z
3
˚
4768.1(7)
4
5641.5(16)
4
Density (calculated) 1.468
1.449
1.458
1.460
1.459
[Mg m-3]
Absorption
0.582
0.480
0.464
0.535
0.496
coefficient [mm-1]
F(000)
2160
0.21 ¥ 0.12 ¥ 0.09
1132
0.20 ¥ 0.19 ¥ 0.15
1.49 to 30.02
2544
0.18 ¥ 0.04 ¥ 0.03
1.42 to 25.09
1324
0.30 ¥ 0.12 ¥ 0.01
1.86 to 28.35
1318.2
0.20 ¥ 0.05 ¥ 0.03
1.02 to 22.61
Crystal size/mm
Theta range for data 1.31 to 28.32
collection [◦]
Index ranges
-16 ≤ h ≤ 16
-16 ≤ k ≤ 16
-41 ≤ l ≤ 41
-16 ≤ h ≤ 16
-19 ≤ k ≤ 20
-22 ≤ l ≤ 22
38454
-15 ≤ h ≤ 15
-21 ≤ k ≤ 21
-27 ≤ l ≤ 22
31806
-13 ≤ h ≤ 13
-18 ≤ k ≤ 19
-26 ≤ l ≤ 26
26119
-11 ≤ h ≤ 11
-15 ≤ k ≤ 15
-21 ≤ l ≤ 21
18538
Reflections collected 48327
Independent
reflections
Completeness (to
theta)
Absorption
correction
Max. and min.
transmission
Refinement method
Data/restraints/
parameters
11871 [R(int) = 0.0386]
99.8 (to 28.32◦)
14406 [R(int) = 0.0207] 9957 [R(int) = 0.1291] 14178 [R(int) = 0.0354] 7692 [R(int) = 0.0670]
97.7 (to 30.02◦)
99.4 (to 25.09◦)
Semi-empirical from equivalents
0.986 and 0.789
96.8 (to 28.35◦)
98.9 (to 22.61◦)
0.950 and 0.843
0.977 and 0.848
0.950 and 0.687
0.985 and 0.880
Full-matrix least-squares on F2
11871/4/635
1.057
14406/12/738
1.035
9957/0/730
14178/0/739
1.003
7692/1/779
1.044
Goodness-of-fit on
0.954
F2
Final R indices
[I > 2s(I)]
R1 = 0.0334
R1 = 0.0351
R1 = 0.0530
R1 = 0.0428
R1 = 0.0503
wR2 = 0.0767
R1 = 0.0447
wR2 = 0.0889
R1 = 0.0411
wR2 = 0.0951
R1 = 0.1234
wR2 = 0.0959
R1 = 0.0716
wR2 = 0.1093
R1 = 0.0784
R indices (all data)
wR2 = 0.0810
0.660 and -0.523
wR2 = 0.0924
1.083 and -0.625
wR2 = 0.1175
0.736 and -0.971
wR2 = 0.1062
1.311 and -1.017
wR2 = 0.1213
0.675 and -0.652
Largest diff. peak
-3
˚
and hole/e A
1
Table 3 Effect of concentration on the appearance of the 31P{ H} NMR
solvent, therefore the 1H and 31P{ H} NMR spectra of a 6.0 mM
solution of 4 in a range of d6-DMSO/CD2Cl2 solvent mixtures was
studied. As can be seen from Table 4, even in 75% CD2Cl2/25% d6-
DMSO the linewidth is much narrower, indicating that aggregation
is significantly reduced. On increasing the proportion of d6-DMSO
to 50%, two overlapping broad singlets were observed at d 49.58
and d 49.51. These singlets persisted, with changes in chemical
shift, in the 75% d6-DMSO solvent mixture. The presence of two
separate resonances means that under these conditions there are
at least two different hydrogen-bonded species in slow exchange,
although each resonance could be due to many species in fast
exchange. The fact that a single, sharp resonance is observed in
pure d6-DMSO is consistent with the presence of a monomeric
species.
1
spectra of CD2Cl2 solutions of 4a
[4a]/mM
Linewidth/Hz
1.0
4.4
10.9
21.8
917
1025
1241
1430
Employing d6-DMSO as solvent resulted in spectra which were
considerably sharper. For example, in the 1H NMR spectrum
distinct resonances were observed for the cyclopentadienyl, phenyl
and uracil groups, however, once again the NH resonances could
not be observed. A singlet at d 49.44 in the 31P{ H} NMR spectrum
1
These results clearly indicate that the degree of aggregation
of 4a occurring in CD2Cl2 solution is considerable. The possible
complementary hydrogen bonding patterns available to the uracil
was assigned to the PPh3 ligands.
The fact that dissolution in DMSO afforded sharp resonances
is consistent with little or no aggregation effects occurring in this
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1
Table 4 Effect of solvent on the appearance of the 31P{ H} NMR spectra
The solid state structure of both 5a[PF6]11 and 5a[OTf] have
been confirmed by single crystal X-ray diffraction. Slow cooling
of a methanol–toluene solution of the salts allowed for isolation of
crystals of the complexes as toluene solvates suitable for study by
X-ray diffraction. The resulting structural determination (Fig. 2)
illustrated that 5a[PF6] and 5a[OTf] are essentially isostructural.
The bond lengths and bond angles within the 5a+ cationic units
of solutions of 4a (6.0 mM)
% CD2Cl2/d6-DMSO
d
Linewidth/Hz
100/0
75/25
50/50
25/75
0/100
49.2
1160
29
—
49.58, 49.51
49.64, 49.56
49.44
—
=
are essentially identical and show, for example, short Ru C
49.44
6
˚
˚
distances (5a[PF6] = 1.946(3) A, 5a[OTf] = 1.9541(17) A).
The cationic units in these species form hydrogen-bonded
dimers involving a symmetric donor/acceptor interaction between
group in dimeric species, along with the labelling scheme for the
uracil group, are illustrated in Fig. 1. In the case of the vinylidene
complex 3a+ we were able to obtain evidence that aggregation
occurred to give dimeric species and the possible occurrence of all
the potential hydrogen bonding aggregates A–F.8 These data point
to a more complex behaviour in the case of 4a which, due to our
inability to observe the N–H resonances in the 1H NMR spectra,
we have been unable to deconvolute further.
=
N–H(2A) and C O(3) with slightly shorter NH ◊ ◊ ◊ O distance
in 5a[OTf] (5a[PF6] = 2.897(3) A, 5a[OTf] = 2.862(2) A). In
˚
˚
both cases the N–H(1) group is engaged in hydrogen bonding
˚
to the respective anions (N–H ◊ ◊ ◊ OTf 2.861(2) A, N–H ◊ ◊ ◊ FPF5
˚
3.005(3) A). The OTf anion in 5a[OTf] is disordered over two sites
which differ in their arrangement relative to the plane containing
the two hydrogen-bonded uracil groups.
The extent of the similarity between the structures observed for
5a[PF6] and 5a[OTf] demonstrates that the formation of hydrogen
bonds between pendant uracils on adjacent molecules is a general
structural feature of these compounds and not just a consequence
of crystal packing in a single example.
Evidence for the formation of aggregates of 5a+ in solution was
obtained from the N–H resonances in 1H NMR spectra. In CD2Cl2
solution these resonances exhibit significant concentration11 and
temperature dependence (Fig. 3). In general, an increase in the
concentration of the solution or a decrease in the temperature
both result in a shift of the N–H protons to lower field, behaviour
b. Preparation and characterisation of
5
=
[Ru(g -C5H5)(PPh3)2( C{OMe}–CH2Ur)][X], 5[X]
Heating a methanol solution of 3a[X] results in near quantitative
conversion to the corresponding carbene complexes 5a[X]. Indeed
the conversion of 3a[X] to 5a[X] is extremely facile and even occurs
in the solid state: mild heating of crystals of 3a[X] (which are
obtained as a MeOH solvate)8 results in conversion to 5a[X]. The
most convenient synthesis of 5a[X] is to perform prolonged (16 h)
reactions of 1 with 2 and NH4X in MeOH solution.
=
Fig.
1
Dimeric hydrogen-bonding patterns in solution. “C O(4)
–
≡
N–H(1)” refers to the hydrogen bonded motif exhibited by the
5
+
5
5
+
uracil groups. [Ru]+ = [Ru(h -C5H5)(PPh3)2(
C
C{H})] (3a), Ru(–C C)(h -C5H5)(PPh3)2 (4a), [Ru(h -C5H5)(PPh3)2( C{OMe}–CH2)] (5a+),
=
=
=
5
+
=
[Ru(CH C{PPh3})(h -C5H5)(PPh3)2] (6a).
9532 | Dalton Trans., 2009, 9529–9542
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that is typical of the formation of hydrogen-bonded aggregates. In
general, the lower field N–H proton in unsubstituted uracil groups
is assigned to N–H(3), the higher field N–H proton to N–H(1).13
As may be observed in Fig. 3, increasing the concentration (or
decreasing the temperature) of samples of 5a[X] results in the
resonances for both N–H(1) and N–H(3) moving to lower field,
consistent with enhanced aggregation occurring. In addition,
the resonance for N–H(1) shows a relatively smaller change
in chemical shift when compared with N–H(3), implying that
hydrogen bonding principally occurs through binding modes such
as A–C (Fig. 1) with a smaller contribution from D–F.
c. Preparation and characterisation of b-alkenyl-phosphonio salts
5
=
[Ru(E-CH C{PPh3}R)(g -C5H5)(PPh3)2][X], 6a[X]
Identification of the b-alkenyl-phosphonio complex 6a[OTf].
During our attempts to develop the synthesis of 5a[OTf], we
serendipitously discovered that the b-alkenyl-phosphonio complex
6a[OTf] was a minor product formed in the reaction of 1 with 2
and NH4OTf in MeOH at reflux. On one occasion, crystallisation
of the reaction mixture afford a small crop of yellow crystals
which a single crystal X-ray diffraction study demonstrated were
5
=
the alkenyl-phosphonio complex [Ru(E-CH C{PPh3}Ur)(h -
C5H5)(PPh3)2][OTf], 6a[OTf].
The resulting structure determination (Fig. 4) demonstrated
5
that the complex contains a half sandwich ruthenium Ru(h -
C5H5)(PPh3)2 fragment coordinated to a alkenyl ligand, which
is substituted at the b-position with both PPh3 and Ur groups;
the stereochemistry at the alkenyl ligand is E, i.e. with a trans
disposition of Ru and PPh3 groups. The bond metrics within
the alkenyl fragment are discussed below. The uracil groups
forms symmetric dimers, mediated by hydrogen bonding between
=
N–H(3) and C O(4). This motif is essentially identical to that
Fig. 2 (a) Structure of the cation of 5a[OTf]. Selected thermal ellipsoids
shown at the 50% probability level and selected hydrogen atoms omitted
for clarity. (b) Hydrogen bonding motif observed in the solid state, only
one orientation of the OTf anion shown.
shown by the carbene cations 5a+: however, the interaction
between the nucleobases appears to be stronger in the case of 6a+
than 5a (N–H ◊ ◊ ◊ O distance in 5a[OTf] = 2.862(2) A compared
+
˚
Fig. 3 (a) N–H region of 1H NMR spectra of 5a[OTf] recorded at various temperatures.
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6a–c[OTf], in excellent yield (Scheme 1). The structure of these
species was determined by NMR spectroscopy, elemental analysis
and single crystal X-ray diffraction. As demonstrated by X-ray
crystallography, complexes 6a–c[OTf] (Fig. 4, 5, 6) form an
isostructural series with a similar series of bond lengths and angles.
Indeed, the metrical parameters for the alkenyl-phosphonio ligand
within these species and those previously reported in the literature
(Table 5) are closely related, although the M–Ca bond lengths
within the Cp-ligated complexes reported in this study do appear
to be somewhat longer that the related p-cymene and indenyl-
substituted species. Within this series of complexes the most
5
marked structural difference is in the orientation of the [Ru(h -
+
=
Ind¢)(EE-CH C{PPh3}Ph)(CO)(PPh3)] the alkenyl-phosphonio
ligand is essentially parallel to the indenyl ring, whereas in
6a+ it is perpendicular. The electronic effects which govern the
orientation of alkenyl ligands within organometallic complexes
have been extensivily studied17–19 and demonstrate a preference for
Fig. 4 (a) ORTEP representation of the structure of the cation of 6a[OTf].
Selected thermal ellipsoids shown at the 50% probability level. Hydrogen
atoms omitted for clarity. (b) Packing diagram showing hydrogen bonding
interactions.
+
˚
to 2.796(5) A in 6a[OTf]). Also, as in the case of 5a , N–H(1)
Fig. 5 Structure of the cation of 6b[OTf]. Selected thermal ellipsoids
shown at the 50% probability level. Hydrogen atoms, except H(6), omitted
for clarity.
is involved in hydrogen bonding to the OTf anion (N–H ◊ ◊ ◊ O =
˚
2.796(5) A).
General synthesis and characterisation of alkenyl-phosphonio
complexes. Having identified 6a[OTf] as a minor product in
the reaction of 1 with 2 and NH4OTf in MeOH a gen-
eral synthetic route to complexes of this type was sought.
Related ruthenium complexes with alkenyl-phosphonio ligand
have been reported which contain indenyl14,15 and cymene
5
groups.16 In addition, isoelectronic species [M(h -C5Me5)(E-
+
=
C(H) C{PPh3}Ph)(PR3)(Cl)] (M = Rh or Ir), have been
described.16 The synthesis of these species involves either the
reaction of an isolated vinylidene complex or the reaction between
a metal complex with a terminal alkyne and PPh3. To the
best of our knowledge, the corresponding complexes [Ru(E-
CH C{PPh3}R)(h -C5H5)(PPh3)2], 6 , have not been observed
previously. Therefore the development of a suitable synthetic route
to these species with a range of substituents was an important goal
so that the precise effects of the uracil group could be quantified.
5
+
=
5
Reaction of the vinylidene complexes [Ru(h -C5H5)(PPh3)2-
= =
( C CH{R})][OTf] (R = Ur, 3a[OTf]; R = Ph, 3b[OTf];
R = C6H4-3-OMe, 3c[OTf]) with ten equivalents of PPh3 in
Fig. 6 Structure of the cation of 6c[OTf]. Selected thermal ellipsoids
shown at the 50% probability level. Hydrogen atoms, except H(6), omitted
for clarity. The OMe group is disordered over two positions.
CH2Cl2 at reflux resulted in the formation of the corresponding
5
=
vinyl complexes [Ru(E-CH C{PPh3}R)(h -C5H5)(PPh3)2][OTf],
9534 | Dalton Trans., 2009, 9529–9542
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◦
a
˚
Table 5 Comparison of bond lengths (A) and angles ( ) in alkenyl-phosphonio complexes
Cen–M–
Ca–Cb
Complex
M–Ca
Ca–Cb
Cb–Pc
M–Ca–Cb Ca–Cb–Pc Ca–Cb-R R–Cb–Pc
Ref.
5
+
=
=
[Ru(h -C9H7)(E-CH C{PPh3}{C CHcyhex})(PPh3)2] 2.045(6) 1.371(7) 1.790(6) 135.9(4)
117.5(4)
120.4(6)
120.5(6)
115.9(2)
115(1)
116(1)
118.2(4)
129.6(5) 112.5(4)
125.2(7) 114.4(6)
124.9(7) 114.5(5)
128.5(3) 115.5(2)
4.5
40.8
107.0
58.6
61.1
60.2
1.9
14
15
15
16
16
5
+
=
=
[Ru(h -C9H7)(E-CH C{PPh3}CH CHFc)(PPh3)2]
2.039(8) 1.354(11) 1.783(8) 133.5(7)
2.039(7) 1.344(10) 1.801(7) 135.6(6)
2.053(3) 1.343(4) 1.801(2) 131.3(2)
1.99(2) 1.42(3) 1.80(2) 133(1)
1.99(2) 1.36(3) 1.84(2) 137(1)
2.063(5) 1.377(6) 1.788(5) 135.0(4)
5
+
=
[Ru(h -Ind¢)(EE-CH C{PPh3}Ph)(CO)(PPh3)]
6
+
=
[Ru(h -p-cymene)(E-CH C{PPh3}Ph)Cl(PPh3]
5
+
=
[Ir(h -C5Me5)(E-CH C{PPh3}Ph)Cl(PPh3)]
129(1)
127(2)
115(1)
115(1)
5
+
=
[Rh(h -C5H5)(E-CH C{PPh3}Ph)Cl(PPh3)]
16
[6a]+
[6b]+
[6c]+
128.1(5) 113.7(3)
b
b
b
2.090(2) 1.357(3) 1.798(3) 133.59(19) 120.63(19) 128.2(2) 110.96(17) 23.9
2.070(5) 1.366(7) 1.791(5) 133.6(4) 121.0(4) 128.0(5) 110.7(4) 24.6
a Abbreviations used cyhex = cyclohex-1-enyl; Cen= centroid of aromatic ligand, Ind¢ = 1,2,3-Me3C9H4. b This work.
orientation in which d–p*-backbonding is maximised. However,
given that the stabilisation provided by this interaction is only ca.
28 kJ mol-1 and in the phosphonio-substituted complexes alkenyl
ligands are observed in plane with both p-base and p-acid ligands
it is likely that the precise geometry in these complexes is dictated
by steric effects, given the bulky groups present.
Clearly the mirror plane which exists in 6b[OTf] is not present
in 6a[OTf] or 6c[OTf] due to the presence of the unsymmetrical
substituent (Ur, or C6H4-3-OMe) on the alkenyl ligand. Any
rotation of this group must be slow on the NMRtimescale ensuring
that the two ruthenium-bound PPh3 ligands remain inequivalent.
1
The aromatic region of the H NMR spectra for 6a–c[OTf]
The 1H NMR spectrum of 6b[OTf] exhibited a downfield
also showed significant and essentially identical temperature
dependence. In the case of 6b[OTf] three broad resonances between
d = 7.37 and d = 6.99 were observed: these peaks overlapped with
other, sharp, resonances in the phenyl region. Cooling the sample
to 195 K led to these broad peaks sharpening significantly, with
six new resonances observed at d = 7.62, 7.50, 7.28, 6.85, 6.47 and
6.25. This observation is consistent with the phenyl groups in the
two ruthenium-coordinated phosphines becoming inequivalent.
This assignment was supported by a series of selectively decoupled
3
3
resonance at d 10.71 (dt, JPP = 36.9 Hz, JPP = 9.2 Hz), in
conjunction with a resonance at d 204.4 (dt, 2JPC = 16.1 Hz, 2JPC
=
1
6.4 Hz) in the 13C{ H} NMR spectrum confirming the presence of
the alkenyl ligand: similar resonances were observed in the case of
6a[OTf] and 6c[OTf]. The positioning of the PPh3 groups within
1
6b[OTf] was demonstrated in the 31P{ H} spectrum by a doublet
4
resonance at d 47.68 (d, JPP = 5.7 Hz) for the Ru-bound PPh3
ligands with a corresponding triplet for the PPh3 bonded to the
4
31
alkenyl ligand at d 17.46 (t, JPP = 5.7 Hz): the appearance of
1H{ P} NMR experiments (700 MHz, 260 K).
1
this spectrum did not alter with temperature. The 31P{ H} NMR
The broad nature of the phenyl resonances from the ruthenium-
bound phosphines at 300 K indicates that rotation around the
Ru–P bond is becoming slow on the NMR timescale. Presumably
phosphine rotation is being hindered by a steric interaction. A
1H-1H NOESY experiment revealed a strong nOe interaction
between the proton in the a-position of the alkenyl ligand and
the protons on the phenyl rings of the ruthenium-coordinated
triphenylphosphine. Examination of the crystal structures of
6a–c[OTf] reveals that this hydrogen sits in a “pocket” between
the two phosphine ligands. The NMR spectra demonstrate that
this is also the case in solution, with the hydrogen atom being
forced down into the pocket and presumably hindering phosphine
rotation.
spectra of 6a[OTf] and 6c[OTf] were somewhat more complex.
1
In the case of 6a[OTf] the 31P{ H} NMR spectrum in CD2Cl2
4
exhibited a resonance at d 16.1 (t, JPP = 5.6 Hz) for the PPh3
group coordinated to the alkenyl group, and two further peaks for
the PPh3 groups coordinated to the ruthenium were observed as
4
an AB pattern at d 46.8 (dd, 2JPP = 35.2 Hz, JPP = 5.6 Hz) and
2
4
d 46.3 (dd, JPP = 35.2 Hz, JPP = 5.6 Hz). The appearance of
these later resonances altered markedly with temperature (Fig. 7).
Similar behaviour was observed for 6c[OTf]: at 300 K a resonance
at d 17.3 (apparent triplet,4JPP = 5.6 Hz) for the PPh3 bonded to
the alkenyl group was observed: two further peaks, for the PPh3
ligands coordinated to the ruthenium, were observed as an AB
pattern at d 47.68 (apparent d, 5.6 Hz) and d 47.67 (apparent d,
5.6 Hz). On cooling the solution to 235 K the AB pattern becomes
an apparent triplet at d 47.84. At 195 K the spectrum appears
as would be expected on the basis of the crystal structure: the
upfield resonance at d = 17.8 remains a triplet (4JPP = 5.5 Hz) but
the downfield resonance can be seen as two separate doublet of
The poor solubility of 6a[OTf] in CD2Cl2 precluded us from
studying the concentration dependence of the NMR spectra
of this species. Although the complex was more soluble in
d4-MeOD, facile H/D exchange in this solvent meant the N–H
resonances were not observable. However, the N–H region of
the 1H NMR spectrum of 6a[OTf]–in common with that of
5a[OTf], displays significant temperature dependence, with both
N–H resonances moving downfield as the temperature is decreased
(Fig. 8). In this case, the N–H(3) proton show smaller changes in
chemical shift than N–H(1) which is consistent with aggregation
processes occurring in solution principally via motifs D–E (Fig. 1).
4
doublets at d = 48.26 (2JPP = 35.0 Hz, JPP = 5.4 Hz) and d =
48.02 (2JPP = 35.0 Hz, 4JPP = 5.4 Hz). Simulations of the spectra†
reveal that the changes in lineshape of the resonances may be
modeled by changes of chemical shift of these two resonances
with temperature, rather than the effects of a dynamic process.
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Fig. 7 Variable temperature 31P{1H} NMR spectrum of 6a[OTf] in CD2Cl2 solution. Only the resonances for the ruthenium-bound PPh3 ligands are
displayed. Spectra recorded at 20 K intervals with the foremost spectrum at 300 K, and the rearmost at 220 K.
Fig. 8 The N–H region of the 1H NMR spectrum of 6a[OTf] in CD2Cl2 solution recorded at various temperatures.
9536 | Dalton Trans., 2009, 9529–9542
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Mechanism of formation of b-alkenyl phosphonio salts. In-
termolecular nucleophilic addition of PPh3 to the a-carbon
of vinylidene ligands has been proposed in the formation of
5
+ 20
=
[Fe(C{PPh3} CH2)(h -C5H5)(CO)(PPh3)] , and in the reaction
5
+
= =
of [Ru(h -C5R5)(PPh3)2( C CH2)] (R = H, Me) with tertiary
phosphines.21 However, this does not appear to be a viable pathway
for the formation of the salts of 6+ from 3+ as, for example, there
is no obvious mechanism for how this would explain the observed
stereochemistry in the product.
A more plausible mechanism for the formation of 6+ is shown
in Scheme 2. The vinylidene 3+ is proposed to be in equilibrium
with the h (2e)-alkyne complex 7+. Nucleophilic attack by PPh3
2
onto the substituted carbon atom provides a simple rationale for
the formation of 6+. It is proposed that attack at the a-carbon
is prohibited for steric reasons as in the examples above where
such a reaction pathway is observed the vinylidene ligand is
unsubstituted. Presumably the reaction is under thermodynamic
control as the nucleophilic attack at the other alkyne carbon
atom will place the more bulky aryl group a to the metal,
which is anticipated to be less favoured: a kinetic preference for
the formation of 6+ based on electronic arguments cannot be
discounted.
Scheme 3 Exchange of coordinated alkyne ligands (i) + PhC 13CH,
≡
- PhC CH; + PhC CH, - PhC 13CH.
≡
≡
≡
was observed. These results are consistent with the formation of
5
13
+
+ 13
=
[Ru(h -C5H5)(PPh3)2( C CHPh)] , 3b - C and after 5 days, ap-
proximately 46% of the vinylidene complex possessed a 13C-label.
These results therefore provide further circumstantial evidence
for the presence of 7+ in equilibrium with 3+. A mechanism for
the alkyne/vinylidene exchange based on loss of a phosphine
ligand from 3b+ may also be possible. In this case a putative
5
2
13
+
≡
=
intermediate [Ru(h -C5H5)(h -H C CPh)(C C{Ph}H)(PPh3)]
may be proposed that could allow for the incorporation of the
13C label. However, under the conditions employed no evidence
for the formation of dimers of the alkyne was obtained which
might be expected if this were indeed the case.
Further reactions of 6b[OTf] and 6c[OTf]. After leaving a
CD2Cl2 solutions of 6c[OTf] to stand at room temperature for
approximately five weeks, it was observed that the solution had
undergone a colour change from bright yellow to deep red.
1
1H and 31P{ H} NMR spectroscopy revealed that 60% of the
6c[OTf] present in the original sample had been converted into
a new product, 8c[OTf]. Complex 8c[OTf] could be conveniently
prepared by heating a C2H2Cl4 solution of 6c[OTf] at 100 ◦C for
1 h. Although we have not been able to unambiguously determine
the structure of 8c[OTf] by a single crystal X-ray diffraction
study, the complex was characterised by a combination of NMR
Scheme 2 Mechanism of formation of 6+.
Although Gimeno et al. have demonstrated that the alkyne-form
of related half-sandwich ruthenium complexes may be observed
with the correct combination of ligands and indeed reacts with
PPh3 to give alkenyl-phosphoino complexes,15 this is, to the best
of our knowledge, the first experimental evidence for the presence
of 7+ in solutions of the vinylidene complex, 3+.
1
spectroscopy and mass spectrometry. The H NMR spectrum of
8c[OTf] exhibited a resonance at d 4.77 for a cyclopentadienyl
ligand and, in addition to a series of resonances in the aromatic
3
In an attempt to obtain further evidence for a significant equilib-
region, two distinctive multiplets at d 4.61 (ddd, JPaH = 22.0,
3
3
3
rium between 3+ and 7+ a CD2Cl2 solution of 3b[PF6] was treated
2JHH = 3.8, JPbH = 1.5 Hz) and 2.17 (ddd, JPaH = 22.1, JPbH
=
3
with an excess of PhC 13CH. We reasoned that if 7+ was present
in solution it might be possible to exchange the h -coordinated
18.2, JHH = 3.8 Hz), integrating to one proton each, relative
≡
2
to the cyclopentadienyl resonance. The nature of the couplings
1
31
alkyne, furthermore the use of the labelled phenylacetylene would
ensure that the process was essentially degenerate (Scheme 3).
Exchange of free and coordinated alkyne does indeed take place:
were assigned on the basis of selective and broad-band H{ P}
NMR experiments. The 31P{ H} NMR revealed two resonances,
1
mutually coupled doublets at d 52.38 (d, JPP = 3.5 Hz, Pa) and
46.92 (d, JPP = 3.5 Hz, Pb). The small size of the coupling constant
between the two phosphorus atoms strongly suggested that the
compound did not retain the two cis phosphine ligands of 6c[OTf].
These data also indicated that a PPh3 group had been lost in the
in the 31P{ H} NMR spectrum a new doublet resonance (d
1
42.68, JPC = 15.4 Hz) is observed to grow, whilst in the 1H
2
NMR spectrum the doublet resonance for the alkyne proton
13
≡
≡
of PhC CH decreases in intensity and a singlet for PhC CH
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1
3
3
formation of 8c[OTf]. A H-13C HMQC experiment revealed a
6b[OTf] was observed at d 10.75 (dt, JHP = 37.1 Hz, JHP
=
resonance at d 43.51 (t, J = 8.2 Hz) correlated to the two multiplets
9.1 Hz) as well as a resonance for a new species, 9b[OTf] at
1
3
3
seen at d 4.61 and 2.17 in the H NMR spectrum. A DEPT-
d 10.61 (dd, JHP = 34.7 Hz, JHP = 11.3 Hz). A resonance
for the cyclopentadienyl ligand in 9b[OTf] was observed at d
135 experiment confirmed that this resonance was due to a CH2
group. Complex 6b[OTf] underwent a related reaction to give a
product 8b[OTf] which exhibited a similar series of resonance in
its NMR spectra to 8c[OTf], although prolonged heating resulted
in decomposition in this case.
4.23. The 31P{ H} NMR revealed, in addition to the resonances
1
4
for 6b[OTf], two new resonances at d 61.01 (d, JPP = 6.3 Hz)
4
and d 14.43 (d, JPP = 6.3 Hz). These data indicated that
9b[OTf] has been formed by phosphine loss from 6b[OTf] and, as
5
=
The ESI mass spectrum of 8c[OTf] contained two major peaks:
such, 9b[OTf] is assigned the formula [Ru(E-CH C{PPh3}Ph)(h -
the first at m/z 823.1843 was assigned to the molecular ion 8c+,
C5H5)(NCMe)(PPh3)][OTf]. The ratio of 9b[OTf] to 6b[OTf] was
1 : 5, however, on heating the sample at 60 ◦C for 4 h, the
relative amount of 9b[OTf] decreased (ratio 9b[OTf] : 6b[OTf]
1 : 33) and resonances for 8b[OTf] were now observed, which
corresponded to approximately 4% conversion. After heating the
sample for a further six days, the yield of 8b[OTf] had increased to
approximately 20%. The quantity of 9b[OTf] relative to 6b[OTf]
had decreased still further: they were now present in a 1 : 45
ratio. In addition a further doublet resonance was observed
confirming the loss of a PPh3 group from 6c+ and, critically, a peak
+
=
at m/z 395, assigned to [(C6H4-3-OMe)(PPh3)C CH2] .
Two structures (G and H, Scheme 4) which vary in which PPh3
group has undergone the cyclometallation reaction were consid-
ered for 8+. Compound G (in which R = H) has been prepared
5
by Onitsuka and co-workers from the reaction between [Ru(h -
+
1
C5H5)( C CH2)(PPh3)2] with PPh3.21 The 1H and 31P{ H} NMR
= =
data of 8+ and the compounds with structure G are closely related.
+
3
=
However, our observation of [(C6H4-3-OMe)(PPh3)C CH2] in
at d 9.01 (d, JHP = 28.8 Hz) which was assigned to [Ru(E-
the mass spectrum suggest structure H for 8+. In addition, the
formation of the CH2 group in 8c[OTf] is contradictory to the
elegant deuterium labelling experiments performed by Onitsuka
et al., which would suggest that, if structure G had been formed,
the PPh3 group in the alkene ligand should be geminal to one of
the two protons: this is clearly not the case in 8c+. The difference in
behaviour may be explained by the different sites of nucleophilic
attack in the substituted and un-substituted vinylidene complexes.
In the case of the un-substituted species, Onitsuka et al. obtained
evidence for nucleophilic attack by both PPh3 and PMe2Ph at
the a-carbon of the vinylidene ligand. In the case of our aryl-
substituted complexes we believe that this pathway is inhibited for
steric reasons and thus favour structure H.
CH C{PPh3}Ph)(h -C5H5)(NCMe)2][OTf], 10b[OTf].
5
=
The rapid initial consumption of 9b[OTf] upon heating of the
solution indicates that it may be an intermediate along the path
to form the phosphonio-alkene complex 8b[OTf]. Furthermore,
because 9b[OTf] remains at a low concentration relative to the
starting material once the solution is heated and formation of
8b[OTf] begins, it would seem that loss of phosphine from 6[OTf]
is the rate determining step in the reaction to form 8[OTf].
These results are directly relevant to the formation 8b[OTf]
and 8c[OTf] in CD2Cl2 and tetrachloroethane. When a sample
of 6c[OTf] in CD2Cl2 solution was allowed to stand at room
temperature for several days, 1H NMR spectroscopy revealed
resonances similar to those observed for 9b[OTf] in acetonitrile,
for the product of phosphine loss.
The following mechanism for the formation for the cations
8+ (with structure H) is proposed (Scheme 5). Initial loss of
a phosphine ligand from 6+ results in the formation of vacant
coordination site at the metal to give I. This species may then
react with NCMe to give 9+ and subsequently 10+ or an ortho-
metallation reaction may occur to give a hydride-containing inter-
mediate J. Subsequent reduction elimination of the phosphonio-
substituted alkene may then occur to give 8+. Related ortho-
metallation reactions have been observed by Bruce and co-workers
5
in the Ru(h -C5H5)Me(PPh3)2 system.22
Conclusions
It is somewhat remarkable that the synthetic chemistry employed
to prepare the uracil-containing complexes is essentially identical
to that when more simple aromatic groups are present. Indeed,
the only significant difference in behaviour that is observed
appears to be that the nucleobase-containing species are far less
soluble, an observation which we rationalise in terms of enhanced
aggregation effects. These results indicate that even in the presence
of the functionalised uracil substituent the core chemistry of the
cyclopentadienyl ruthenium fragment remains unchanged.
Scheme 4 Possible structures for 8+.
Mechanistic study into the formation of 8b[OTf]. Monitoring
the reaction of 6b[OTf] in CD3CN solution gave insight into the
mechanism by which 8b[OTf] was formed. This study revealed
that even at room temperature, loss of a PPh3 ligand from the
ruthenium was occurring. In the 1H NMR spectrum, the resonance
for the proton attached to the a-carbon of the alkenyl ligand of
The solid state structure of both 5a[OTf], 5a[PF6] and 6a[OTf]
all exhibit the same hydrogen bonding motif, viz a symmetric
=
dimer employing N–H(3) and C O(4): N–H(1) engages in hy-
drogen bonding to the anion. The same pattern is observed in
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Scheme 5 (i) - PPh3; (ii) + NCMe; (iii) - NCMe; (iv) - PPh3, + NCMe; (v) + PPh3, - NCMe.
7
= =
[Mo( C CHUr)(h -C7H7)(dppe)][BF4]. This is in contrast to the
solid state structure of the cations of 3+ which forms a hexagonal
rosette. The origin of the differences in structure may be traced
back the geometries of the individual cations involved. In 3a+, the
uracil and cyclopentadienyl ligand are almost co-planar and the
nucleobase is also remote from the other ligands of the complex.
In contrast in 5a[OTf], 5a[PF6] and 6a[OTf] and the molybdenum
complex, the uracil group is perpendicular to the p-ligand ensuring
that the uracil is more crowded by the PPh3 or dppe ligands hence
restricting the aggregation in the solid state.
NMR spectra were acquired on a Bruker AV 500 spectrometer
(operating frequencies 1H 500.13 MHz, 31P 202.47 MHz, 13C
125.77 MHz) or a Bruker Avance 700 Spectrometer (operating
1
frequencies H 700.13 MHz, 31P 283.46 MHz). Solution NMR
studies were performed using standard CD2Cl2 solutions of 4a
made to the appropriate concentrations by using serial dilution.
Simulations of NMR spectra were performed with the gNMR
suite of programmes.25 IR spectra were acquired using a Mattson
Research Series FTIR spectrometer as a KBr disk. Mass spectrom-
etry measurements were performed on Fisons Analytical (VG)
Autospec (Fast Atom Bombardment) and Thermo-Electron Corp
LCQ Classic (ESI) instruments.
A similar argument provides a convenient explanation for the
pronounced aggregation effects observed in 4a when compared to
the carbene and b-alkenyl-phosphoino complexes. In the structure
of 4a the uracil group will be remote from the PPh3 ligands and
hence there will be fewer steric constraints on the formation of
the aggregates. A complementary explanation for the enhanced
aggregation is that 4a is neutral and as such it would be expected
that any Columbic repulsions present in, for example, 3a+ and 5a+
would not be present.
We have also developed a convenient route to the synthesis of
cyclopentadientyl-substituted b-alkenyl phosphonio complexes of
type 6+. It appears that this reaction proceeds via the less favourable
alkyne isomer of the vinylidene complex and that phosphine loss
from these species is facile, possibly due to the presence of three
PPh3 groups in close proximity.
5
= =
Synthesis of [Ru(g -C5H5)(PPh3)2( C CH-
{C6H4-3-OMe})][OTf], 3c[OTf]
5
RuCl(h -C5H5)(PPh3)2 (489 mg, 0.67 mmol) and NH4OTf (225 mg,
1.34 mmol) were placed in a Schlenk tube and suspended in
methanol (20 mL). 3-Methoxyphenylacetylene (178 mg, 205 ml,
1.34 mmol) was added to the solution, which was heated at reflux
for 10 min (until turning deep red). The solvent was removed
in vacuo and the red solid extracted with dichloromethane (2 ¥
10 mL). The extracts were reduced in volume to 10 mL and
triturated with ether to give a red powder, which was isolated
by filtration. The red solid was washed with ether (3 ¥ 10 mL).
Yield 589 mg, 90%. The structure of 3c[OTf] was also confirmed
by single crystal X-ray diffraction: see ESI.† 1H NMR: (CD2Cl2,
300 K) d = 7.42 (m, 6H, PPh3), 7.24 (m, 12H, PPh3), 7.19 (t,
1H C6H4-3-OMe), 7.05 (m, 12H PPh3), 6.69 (m, 2H, C6H4-3-
Experimental
All experimental procedures were performed under an atmosphere
of dinitrogen or argon using standard Schlenk line and glove
box techniques. Solvents were purified by distillation under argon
prior to use from appropriate drying agents (MeOH from Mg/I2;
CH3CN and CH2Cl2 from CaH2; Et2O from Na wire; acetone
from Drierite). The CD2Cl2 used for NMR experiments was
dried over CaH2 and degassed with three freeze-pump-thaw
cycles. The compounds RuCl(h -C5H5)(PPh3)2, 1,23 HC CUr, 2,
and [Ru(h -C5H5)(PPh3)2( C CHUr)][OTf], 3a[OTf], [Ru(h -
C5H5)(PPh3)2( C CHPh)(PPh3)2][OTf], 3b[OTf], were prepared
according to published procedures.
4
OMe), 6.62 (m, 1H, C6H4-3-OMe), 5.41 (t, JHP = 2.5 Hz, 1H,
= =
C C(H) C6H4-3-OMe), 5.27 (s, 5H, C5H5), 3.60 (s, 3H, C6H4-
1
3-OMe). 31P{ H} NMR: (CD2Cl2, 300 K) d = 42.43 (s, PPh3).
1
2
13C{ H} NMR: (CD2Cl2, 300 K) d = 353.85 (t, JPC = 15.4 Hz,
1
3
=
Ru C), 160.02 (s, C-OMe), 133.57 (dd, JPC = 51.7 Hz, JPC
=
9.6 Hz, PPh3 C-1), 133.56, 133.13, 131.15, 129.93, 128.73, 128.61
(multiplets, Ph), 121.14 (q, 1JCF = 321.4 Hz CF3), 119.66, 119.55
(multiplets, Ph), 112.72 (d, 3JPC = 32.3 Hz C-b), 95.05 (s, C5H5),
55.14 (s, OCH3). FAB mass spectrum: m/z = 823 [M+], m/z =
691 [M+ - HC2C6H4-3-OMe], m/z = 561 [M+ - PPh3], m/z = 429
5
24
≡
5
8
5
= =
9
= =
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The Royal Society of Chemistry 2009
Dalton Trans., 2009, 9529–9542 | 9539
©

View Article Online
[M+ - PPh3, HC2C6H4-3-OMe]. Elemental Analysis: Expected for
C69H58F3O4P3RuS: C 67.15% H 4.74%; Found: C 66.94% H 4.82%.
d = 46.11 (dd, 2JPP = 35.1 Hz, 4JPP = 5.9 Hz, RuPPh3), d = 45.54
(dd, 2JPP = 35.1 Hz, 4JPP = 5.0 Hz, RuPPh3), d = 15.28 (t, 4JPP
=
=
1
3
5.6 Hz); 13C{ H} NMR (CD3CN, 300 K): d = 211.56 (t, JPC
5
=
=
≡
16.4 Hz Ru–C), d 165.59 (s, C O), d 151.16 (s, C O), d 142.75
(d, 3JPC 5.0 Hz, Uracil C6), 138.2 (br), 134.37, 134.02 (br), 133.41,
133.07, 129.72, 129.56 (br), 129.25, 128.21, 127.92 (multiplets, Ph),
122.14 (d, 1JP–C = 83.0 Hz, C-b), 114.40 (d, 2JPC = 20.0 Hz, Uracil
C5), 85.71 (s, C5H5). FAB mass spectrum: m/z = 1089 [M+], m/z =
827 [M+ -PPh3], m/z = 565 [M+ - 2PPh3], m/z = 429 [M+ - 2PPh3,
HC2Ur]. Elemental Analysis: Expected for C66H54F3N2O5P3RuS:
C 64.02% H 4.40% N 2.26% Found C 62.29% H 4.29% N 2.35%.
Synthesis of Ru(-C CUr)(g -C5H5)(PPh3)2, 4a
5
RuCl(h -C5H5)(PPh3)2 (500 mg, 0.68 mmol), ethynyluracil
(185 mg, 1.35 mmol) and NH4PF6 (230 mg, 1.41 mmol) were
suspended in methanol (30 mL) and heated (with stirring) at 60 ◦C
for 2 h, after which time the solution had turned a deep red colour.
The solution was filtered and 1 M NaOMe in MeOH (0.7 mL)
was added. The solution underwent an immediate colour change
from red to bright yellow. Addition of hexane to the solution
resulted in the formation of a yellow microcrystalline solid which
was isolated by filtration. 1H NMR (d6-DMSO, 6.0 mM) d = 4.12
(s, C5H5); 31P NMR (d6-DMSO, 6.0 mM) d = 49.44 (s, PPh3).
5
=
Synthesis of [Ru(E-CH C{PPh3}Ph)(g -C5H5)(PPh3)2][OTf],
6b[OTf]
5
+
≡
Mass spectrum: m/z = 849 [Ru(C CUr)(h -C5H5)(PPh3)2]+Na ,
5
RuCl(h -C5H5)(PPh3)2 (250 mg, 0.34 mmol) and NH4OTf (63 mg,
5
+
5
≡
m/z = 826 [Ru(C CUr)(h -C5H5)(PPh3)2] , m/z = 719 [Ru(h -
0.37 mmol) were suspended in methanol (20 mL). Phenylacetylene
(60 ml, 55 mg, 0.34 mmol) was added to the reaction mixture, which
was heated at reflux for 10 min (until turning red). Upon cooling,
the reaction mixture was filtered and the solvent removed in vacuo.
The red solid so obtained was extracted with dichloromethane
(2 ¥ 10 mL). Addition of ether to the dichloromethane extract
resulted in the formation of a pale pink solid that was isolated by
filtration. This solid was dissolved in dichloromethane (20 mL)
and PPh3 (0.9 g, 3.44 mmol) was added to the solution, which was
then heated at reflux for 72 h. After cooling to room temperature
the yellow solution was reduced to dryness and the solid residue
washed with toluene (2 ¥ 10 mL). The yellow solid was dissolved
in dichloromethane and layered with hexane to give bright yellow
C5H5)(PPh3)2CO]+, m/z = 691 [Ru(h -C5H5)(PPh3)2]+, m/z = 429
5
[Ru(h -C5H5)(PPh3)]+. IR: (CH2Cl2 cm-1) 3435 (br, N–H), 2073
5
≡
=
(m, C C), 1618 (br, C O).
5
=
Synthesis of [Ru(g -C5H5)(PPh3)2{ C(OMe)-CH2Ur}][OTf],
5a[OTf]
5
RuCl(h -C5H5)(PPh3)2 (250 mg, 0.34 mmol), ethynyluracil (90 mg,
0.66 mmol) and NH4OTf (55 mg, 0.33 mmol) were suspended in
methanol (30 mL) and heated, with stirring, at reflux for 16 h.
During this time the colour of the solution changed from orange to
yellow. After cooling to room temperature the solution was filtered
and the volume of the filtrate reduced until precipitation began to
occur. Toluene (2 mL) was added to the solution. On standing,
1
crystals. Yield 246 mg, 77%. H NMR: (CD2Cl2) d = 10.74 (dt,
3
3JHP = 37.0 Hz, JHP = 9.4 Hz, 1H, Ru–CH=C{Ph}PPh3), 7.24
1
yellow crystals formed. Yield 232 mg, 68%. H NMR: (CDCl3)
1
(m, 50H, PPh3, Ph), 3.98 (s, 5H, C5H5). 31P{ H} NMR: (CD2Cl2)
d = 10.05 (s, 1H, NH), 8.62 (s, 1H, NH), 7.46 (t, J = 7.5 Hz, 6H
Ph), 7.33 (t, J = 7.5 Hz, 12H Ph), 7.17 (s, 1H, Uracil CH), 7.01 (t,
J = 8.4 Hz, 12H, Ph), 4.91 (s, 5H, C5H5), 4.30 (s, 2H, CH2), 3.38 (s,
4
4
1
d = 47.68 (d, JPP = 5.8 Hz), 17.46 (t, JPP = 5.8 Hz). 13C{ H}
2
NMR: (CD2Cl2, 300 K) d = 204.47 (td, JPC = 15.8 Hz, 6.8 Hz,
Ru–C), 141.53 (d, 1JPC = 21.1 Hz, C–PPh3 C1), 138.03 (s, br, Ru–
PPh3 C1), 134.03, 133.43, 132.98, 129.52, 129.39, 128.98, 128.52,
127.86 (multiplets, Ph), 121.13 (q, 1JCF 321.5 Hz CF3), 121.61 (d,
1JPC = 84.4 Hz, C-b), 116.87 (d, 2JPC = 62.9 Hz, Ph C-b C1), 85.64
(s, C5H5). FAB mass spectrum: m/z = 1055 [M+], m/z = 793 [M+ -
PPh3], m/z = 531 [M+ - 2PPh3], m/z = 429 [M+ - 2PPh3, HC2Ph].
Elemental Analysis: Expected for C68H58F3O3P3RuS: C 67.82% H
4.69%; Found: C 67.48% H 4.69%.
1
1
3H, OCH3). 31P{ H} NMR: (CDCl3) d = 45.32 (s, PPh3) 13C{ H}
NMR: (CDCl3): d = 305.4 (t, 2JPC = 12.1 Hz, Ru C), 163.66 (s,
=
=
CO), 150.03 (s, CO), 142.64 (s, HC C), 137.91 (s, HC=C), 135.71
(d, J = 45.4 Hz PPh3, C1), 133.45 (vt, |2JPC+4JPC| = 5.1 Hz, PPh3,
C2), 132.16 (d, J = 9.9 Hz, PPh3, C3), 131.99 (d, J = 3.0 Hz, PPh3,
C4), 91.54 (s, C5H5), 63.61 (s, OCH3), 30.97 (s, CH2).
5
=
Synthesis of [Ru(E-CH C{PPh3}Ur)(g -C5H5)(PPh3)2][OTf],
6a[OTf]
5
=
Synthesis of [Ru(E-CH C{PPh3}C6H4-3-OMe)(g -
5
RuCl(h -C5H5)(PPh3)2 (500 mg, 0.68 mmol) and NH4OTf (126 mg,
C5H5)(PPh3)2][OTf], 6c[OTf]
0.74 mmol) were suspended in methanol (30 mL). Ethynyl-uracil
(185 mg, 1.36 mmol) was added to the reaction mixture, which was
heated at reflux for 2 h, during which time the solution became red.
Upon cooling, the reaction mixture was filtered and the solvent
removed in vacuo. The red solid so obtained was extracted with
dichloromethane (3 ¥ 20 mL). The combined extracts were heated
at reflux with PPh3 (1.64 g, 6.80 mmol) for 72 h. After cooling to
room temperature, the yellow solution was reduced to dryness and
the solid residue washed with toluene (2 ¥ 10 mL). The yellow solid
was dissolved in dichloromethane and layered with hexane to give
bright yellow crystals. Yield 484 mg, 73%. 1H NMR (CD2Cl2) d =
10.75 (ddd, 3JHP = 35.2 Hz, 3JHP = 9.5 Hz, 3JHP = 7.8 1H, Ru-CH),
d = 10.48, (s, br, NH), d = 8.35 (s, br, NH), d = 7.15 (46H, Ph,
Uracil CH), d = 4.31 (s, 5H, C5H5). 31P NMR (CD2Cl2, 300 K)
5
= =
[Ru(h -C5H5)(PPh3)2( C CH{C6H4-3-OMe})][OTf] (128 mg,
0.13 mmol) and PPh3 (345 mg, 1.31 mmol) were placed in a Schlenk
tube and dissolved in dichloromethane (20 mL). The solution was
heated at reflux for 96 h until it became bright yellow. The solvent
was removed in vacuo and the yellow solid residue so obtained was
washed with toluene (3 ¥ 10 mL). The yellow solid was dissolved
in dichloromethane and layered with ether to give bright yellow
1
crystals. Yield 111 mg, 69%. H NMR: (CD2Cl2) d = 10.71 (dt,
3JHP = 36.9 Hz, JHP = 9.2 Hz, 1H, Ru–CH), 7.23 (50H, PPh3,
3
C6H4-3-OMe), 4.06 (s, 5H, C5H5), 3.77 (s, 3H, OMe). 31P NMR:
(CD2Cl2, 300 K) d = 47.67 (apparent dd, 4JPP = 1.9 Hz), 17.33 (t,
4JPP = 5.6 Hz); (CD2Cl2, 195 K) d = 48.26 (dd, JPP = 35.0 Hz,
2
4JPP = 5.4 Hz), 48.02 (dd, JPP = 35.0 Hz, JPP = 5.4 Hz), 17.87
4
4
9540 | Dalton Trans., 2009, 9529–9542
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The Royal Society of Chemistry 2009
©

View Article Online
1
(at, 4JPP = 5.5 Hz). 13C{ H} NMR: (CD2Cl2, 300 K): d = 204.15
refinement at calculated positions. In the case of the crystals of
6c[OTf]·0.56CH2Cl2 diffraction was only observed upto an angle
of 22.61◦ using Mo-Ka radiation which may be due to the disorder
observed in the structural solution.
2
4
(td, JPC = 15.4 Hz, 4.18 Hz, Ru–C), 159.95 (d, JPC = 1.6 Hz,
COMe), 142.62 (d, 1JPC = 20.6 Hz, CPPh3 C-1), 138.02 (br, Ru–
PPh3, C1), 134.02, 133.44, 129.51, 129.38, 127.84 (multiplets, Ph),
130.01, 125.07, 119.26, 113.20 (doublets, C6H4-3-OMe), 121.60 (d,
1JPC = 83.6 Hz, C-b), 120.96 (q, JCF 323.8 Hz CF3), 116.52 (d,
1
2JPC = 61.8 Hz, C b-Ph C1), 85.72 (s, C5H5), 55.34 (s, OCH3). FAB
mass spectrum: m/z = 1085 [M+], m/z = 823 [M+ - PPh3], m/z =
561 [M+ - 2PPh3], m/z = 429 [M+ - 2PPh3, HC2PhOMe]. Elemental
Analysis: Expected for C70H60Cl2F3O4P3RuS: C 63.73%, H 4.58%;
Found: C 62.47%, H 4.74%.
Acknowledgements
With thank the EPSRC and University of York for funding (DTA
award to MJC).
Notes and references
5
2
=
Preparation of [Ru(g -C5H5){g -H2C CPh(PPh3)}-
1 (a) M. I. Bruce, Chem. Rev., 1991, 91, 197; (b) H. Werner, J. Organomet.
Chem., 1994, 475, 45; (c) M. C. Puerta and P. Valerga, Coord. Chem.
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Rev., 2004, 248, 1627; (f) A. B. Antonova, Coord. Chem. Rev., 2007,
251, 1521.
2 For recent references see: (a) D. B. Grotjahn, X. Zeng and A. L. Coosky,
J. Am. Chem. Soc., 2006, 128, 2798; (b) D. B. Grotjahn, X. Zeng,
A. L. Cooksy, W. S. Kassel, A. G. DiPasquale, L. N. Zakharov and
A. L. Rheingold, Organometallics, 2007, 26, 3385; (c) M. J. Cowley,
J. M. Lynam and J. M. Slattery, Dalton Trans., 2008, 4552; (d) J. M.
Lynam, C. E. Welby and A. C. Whitwood, Organometallics, 2009, 28,
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3 (a) C. Bruneau and P. H. Dixneuf, Acc. Chem. Res., 1999, 32, 311;
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Int. Ed., 2006, 45, 2176; (d) B. M. Trost and A McClory, Chem.–Asian J.,
2008, 3, 164.
4 For reviews of this area see: (a) M. K. Whittlesey, in Comprehensive
Organometallic Chemistry III, ed. R. H. Crabtree, D. M P. Mingos and
M. I. Bruce, Elsevier, Oxford, U.K., 2006, vol. 6, chapter 6.12; (b) J.
Gimeno and V. Cadierno in Comprehensive Organometallic Chemistry
III, ed. R. H. Crabtree, D. M P. Mingos and M. I. Bruce, Elsevier,
Oxford, U.K., 2006, vol. 6, chapter 6.15.
(C6H4PPh2)][OTf], 8b[OTf]
6b[OTf] (ca. 20 mg) was placed in an NMR tube and dissolved
in C2D2Cl4 (0.5 mL). The solution was heated at 363 K for
30 min. 8b[OTf] was formed in approximately 50% yield (as shown
by 31P{ H} NMR spectroscopy). It was not possible to isolate
1
this complex however characterisation was performed by NMR
1
spectroscopy. H NMR (C2D2Cl4) d = 4.78 (s, C5H5, 5H), 4.64
3
2
3
(ddd, JHP = 22.3 Hz, JHH = 3.8 Hz, JHP = 2.5 Hz), 2.29 (atd,
3JHP = 17.3 Hz, JHH = 3.8 Hz). 31P{ H} (C2D2Cl4, 373 K) d =
2
1
51.48 (d, J = 3.2 Hz), 46.97 (d, J = 3.2 Hz).
5
2
=
Preparation of [Ru(g -C5H5){g -H2C C(C6H4-3-OMe)(PPh3)}-
(C6H4PPh2)][OTf], 8c[OTf]
6c[OTf] (ca. 20 mg) was placed in an NMR tube and dissolved
in C2D2Cl4 (0.5 mL). The solution was heated at 363 K for
30 min. 8c[OTf] was formed in approximately 50% yield (as shown
by 31P{ H} NMR spectroscopy). It was not possible to isolate
1
this complex however characterisation was performed by NMR
spectroscopy. 1H NMR (C2D2Cl4) d = 6.57 (m, 3H, C6H4-3-OMe),
6.88 (m, 1H, C6H4-3-OMe), 4.77 (s, 5H, C5H5), 4.61 (ddd, 3JHP
=
5 (a) F. Paul, B. G. Ellis, M. I. Bruce, L. Toupet, T. Roisnel, K. Costuas,
J.-F. Halet and C. Lapinte, Organometallics, 2006, 25, 649; (b) C. Bitcon
and M. W. Whiteley, J. Organomet. Chem., 1987, 336, 385; (c) N. J. Long
and C. K. Williams, Angew. Chem., Int. Ed., 2003, 42, 2586; (d) W. M.
Khairul, M. A. Fox, N. N. Zaitseva, M. Gaudio, D. S. Yufit, B. W.
Skelton, A. H. White, J. A. K. Howard, M. I. Bruce and P. J. Low,
Dalton Trans., 2009, 610.
22.0, 2JHH = 3.8, 3JHP = 1.5 Hz, =CH2), 3.57 (s. 3H, OMe), 2.17
(ddd, 3JHP = 22.1, 3JHP = 18.2, 2JHH = 3.8 Hz), 31P{ H} d = 52.38
1
(d, JPP = 3.5 Hz), 46.92 (d, JHP = 3.5 Hz) 13C{ H} d = 173.94
3
3
1
(dd, 2JPC = 32.9 Hz, 3JPC = 17.0 Hz) 158.7 (s, C6H4-3-OMe, C3),
2
1
143.7 (d, JCP = 6.4 Hz, C6H4-3-OMe, C1), d 137.36 (d, JPC
=
114.4 Hz, PPh2, C1), 132.72 (d, 1JPC 103.4 Hz, PPh3 C1), 128.8 (s,
C6H4-3-OMe, C6), 122.9 (s, C6H4-3-OMe, C4), 116.1 (s, C6H4-3-
OMe, C5), 112.8 (s, C6H4-3-OMe, C6), 92.52 (s, C5H5), 54.97 (s,
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OMe) 43.51 (at, 2JPC = 8.2 Hz, CH2).
=
Details of X-ray diffraction experiments
Pertinent data concerning the structural determinations reported
are collected in Table 2. Diffraction data were collected at 110 K on
a Bruker Smart Apex diffractometer with Mo-Ka radiation (l =
˚
0.71073 A) using a SMART CCD camera. Diffractometer control,
7 J. M. Lynam, Dalton Trans., 2008, 4067.
data collection and initial unit cell determination was performed
using “SMART” (v5.625 Bruker-AXS). Frame integration and
unit-cell refinement software was carried out with “SAINT+”
(v6.22, Bruker AXS). Absorption corrections were applied by
SADABS (v2.03, Sheldrick). Structures were solved by direct
methods using SHELXS-97 (Sheldrick, 1997) and refined by
full-matrix least squares using SHELXL-97 (Sheldrick, 1997).
All non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were placed using a “riding model” and included in the
8 M. J. Cowley, J. M. Lynam and A. C. Whitwood, Dalton Trans., 2007,
4427.
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The Royal Society of Chemistry 2009
Dalton Trans., 2009, 9529–9542 | 9541
©

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9542 | Dalton Trans., 2009, 9529–9542
This journal is
The Royal Society of Chemistry 2009
©