Symmetrical bis(acetylido)ruthenium(II) complexes

Article abstract of DOI:10.1002/ejic.201100322

Symmetrical, mononuclear bis(acetylido)ruthenium(II) complexes were prepared by the reaction of [trans-RuMe₂(dmpe)₂] [dmpe = 1,2-bis(dimethylphosphanyl)ethane] with terminal alkynes. The complexes were characterised by multinuclear N

Full text of DOI:10.1002/ejic.201100322

FULL PAPER
DOI: 10.1002/ejic.201100322
Symmetrical Bis(acetylido)ruthenium(II) Complexes
Leslie D. Field,*[a] Alison M. Magill,[a] Timothy K. Shearer,[a] Scott J. Dalgarno,[b] and
Mohan M. Bhadbhade[c]
Keywords: Ruthenium / Phosphanes / Metathesis / Alkyne ligands / Dimerisation
Symmetrical, mononuclear bis(acetylido)ruthenium(II) com-
plexes were prepared by the reaction of [trans-RuMe2-
(dmpe)2] [dmpe = 1,2-bis(dimethylphosphanyl)ethane] with
terminal alkynes. The complexes were characterised by mul-
tinuclear NMR spectroscopy and X-ray crystallography. In
some cases, the complexes catalyse the head-to-head dimer-
isation of terminal alkynes to yield organic butenynes. The
regiochemistry of this dimerisation depends on the solvent
used; methanol results in the isolation of (Z)-butenynes,
whereas toluene gives predominantly (E) isomers.
is less appealing, as the hydrogen byproduct of the reaction
can hydrogenate the terminal alkynes, resulting in contami-
nation of the desired alkynyl complexes with alkenyl com-
plexes. Symmetrical ruthenium bis(acetylide) complexes
bearing dmpe or 16-TMC (16-TMC = 1,5,9,13-tetramethyl-
1,5,9,13-tetraazacyclohexadecane) coligands have also been
prepared by the reaction of Ru(dmpe)2Cl2 or [Ru(16-
TMC)Cl2]Cl with terminal alkynes in the presence of so-
dium methoxide and zinc amalgam.[8] The role of the zinc
amalgam is not obvious; however, no reaction occurs in its
absence. The reaction possibly proceeds by reduction of the
RuII centre, which then undergoes reaction with the ter-
minal alkyne.
We have recently reported the development of a route to
mono- and bis(acetylido) complexes of ruthenium(II),[9] by
the reaction of terminal acetylenes with alkylruthenium
compounds (Scheme 1). The synthesis of a range of dinu-
clear and trinuclear acetylido-bridged ruthenium complexes
has now been demonstrated by using this route.[10] We re-
port here the synthesis of symmetrically substituted, mono-
Introduction
As a consequence of the potential applications of rigid-
rod (σ-alkynyl)transition-metal complexes as nonlinear op-
tical,[1] electronic communication (molecular wire),[1f,2] lu-
minescent[3] or liquid-crystalline materials,[4] complexes of
this type have been an active area of research in recent
years.[5] All of these potential applications depend on the
extended rigid linear structures, inherent stability and π-
electron configuration[5b] of the σ-alkynyl complexes.
Until recently, most (σ-alkynyl)transition-metal com-
plexes have been synthesised either by the reaction of an
alkali-metal alkynide or an alkaline earth-metal alkynide
RCϵCM (M = Li, Na, Mg, etc.) with a transition metal
halide LnMXnЈ (X = Cl, Br, I) or by the reaction of a ter-
minal alkyne with a transition-metal complex.[2c,5b]
Touchard et al.[3a] have developed an effective method
for the preparation of ruthenium acetylide complexes by
deprotonation of a vinylidene complex – a reaction pion-
eered by Dixneuf and co-workers.[6]
Some time ago, we reported a relatively clean synthesis
of ruthenium acetylide complexes, [trans-Ru(CϵCR)2-
(depe)2] [depe = 1,2-bis(diethylphosphanyl)ethane], by the
reaction of [trans-RuCl2(depe)2] with terminal alkynes in
the presence of NaOMe in methanol.[7] Attempts to prepare
analogous dmpe complexes by using the same technique
were unsuccessful, and until now, Ru(dmpe) acetylide com-
plexes have been traditionally prepared by the reaction of
[RuH2(dmpe)2] with terminal alkynes. This latter approach
[a] School of Chemistry, University of New South Wales,
Sydney 2052, Australia
Fax: +61-9385-8008
E-mail: L.Field@unsw.edu.au
[b] School of Engineering and Physical Sciences – Chemistry,
Heriot-Watt University,
Riccarton, Edinburgh EH14 4AS, UK
[c] Mark Wainwright Analytical Centre, University of New South
Wales,
Sydney 2052, Australia
Scheme 1.
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L. D. Field et al.
FULL PAPER
nuclear bis(acetylido)ruthenium complexes in high yields by ligand, which are observed at δ = 1.39 and 1.37 ppm,
the metathesis reaction of alkylruthenium(II) complexes respectively. Additionally, the Si(CH3)3 protons are evident
with terminal alkynes.
as a singlet resonance at δ = 0.25 ppm.
The 13C{1H} NMR spectrum of 3, and the symmetrical
bis(acetylides) in general, are relatively uncomplicated. The
spectrum of 3 displays two phosphorus-coupled quintets at
δ = 15.4 (2JPC = 7.4 Hz) and 30.1 ppm (2JPC = 13.3 Hz) due
to the CH3 and CH2 carbon atoms of the phosphane li-
gand, respectively, and two acetylide carbon resonances: a
singlet at δ = 110.9 and a phosphorus-coupled quintet at δ
= 155.5 ppm (2JPC = 14.2 Hz) due to the RuCϵC and
RuCϵC carbon atoms, respectively. Finally, the SiMe3 car-
bon atoms appear as a singlet resonance at δ = 2.45 ppm.
The 13C NMR shifts for the acetylene carbon atoms ap-
pear in Table 1, and – with the exception of 2 – the signal
of the ruthenium-bound acetylene carbon atom appears at
significantly lower field than that of the β-acetylene carbon
atom. For comparison, Table 1 also contains selected NMR
spectroscopic data for previously reported metal acetylide
complexes. The signals of the acetylene carbon atoms of all
of the bis(acetylido)iron complexes are shifted significantly
downfield compared to the shifts of their ruthenium ana-
logues. Additionally, there is only a slight change between
the 13C chemical shifts of the acetylene carbon atoms be-
tween analogous depe and dmpe complexes.
Results and Discussion
Ruthenium Bis(acetylides)
In benzene solution, the reaction between [trans-Ru-
Me2(dmpe)2] and phenylacetylene or tert-butylacetylene oc-
curs very slowly, even with heating or UV irradiation, and
typically requires several days to reach completion. The ad-
dition of a small quantity of methanol[10] to a benzene or
toluene solution of the starting materials resulted in com-
plete reaction at room temperature within several hours,
and the products were isolated in excellent yield and purity.
Neat methanol can also be employed as solvent.
A range of symmetrical bis(acetylide) complexes, [trans-
Ru(CϵCR)2(dmpe)2] [R = Ph (1), tBu (2), Me3Si (3), 4-
tBuC6H4 (4), 4-MeOC6H4 (5) and 3,5-(F3C)2C6H3 (6);
Scheme 2, yields in parentheses], was prepared. The meth-
anol-promoted reaction was found to be necessary for the
clean formation of complexes 4–6 (vide infra), whereas 1–3
could be successfully synthesised in the presence or absence
of methanol, albeit with longer reaction times in the latter
case.
Table 1. 31P{1H} and selected 13C{1H} NMR shifts [ppm] of a vari-
ety of symmetrical bis(acetylido)iron(II) and -ruthenium(II) com-
plexes.[a]
Complex
δP
δC
MCϵCR MCϵCR
1
2
40.8
40.6
38.7
40.6
40.8
39.5
51.3
52.3
131.4
103.2
155.5
127.2
125.6
143.5
130.6
104.6
136.9
140.0
121.9
165.7
147.2
111.3
113.7
110.9
108.5
108.6
109.3
112.8
115.8
113.7
117.1
111.9
118.8
117.7
3
4[b]
5[b]
6[b]
[trans-Ru(CϵCPh)2(depe)2][7]
[trans-Ru(CϵCtBu)2(depe)2][7]
[trans-Ru(CϵCC6H4-4-CϵCH)2(depe)2][7] 52.3
Scheme 2.
[trans-Fe(CϵCPh)2(dmpe)2][12]
[trans-Fe(CϵCtBu)2(dmpe)2][12]
[trans-Fe(CϵCSiMe3)2(dmpe)2][13]
68.6
69.4
66.2
The complexes were characterised by multinuclear NMR
and IR spectroscopy, mass spectrometry and, in some cases,
by X-ray crystallography. Complexes 1 and 2 have pre-
viously been prepared by the addition of the appropriate
terminal alkyne to [RuH2(dmpe)2][7] and the reaction of
[trans-RuCl2(dmpe)2] with phenylacetylene in the presence
[trans-Ru(CϵCC6H4-4-CϵCH)2(dmpe)2][12] 67.9
[a] NMR spectrum recorded in [D6]benzene unless otherwise
stated. [b] [D8]thf.
of Zn/Hg amalgam (complex 1 only),[2f] although character-
The IR spectroscopic data for the ruthenium bis(acetyl-
1
isation of 2 was limited to 31P and H NMR spectroscopy. ide) complexes 1–6 is summarised in Table 2, which also
Complexes 3–6 have not been previously reported.
contains data for related complexes found in the literature.
The 31P{1H} NMR spectra of all the complexes appear In general, the stretching frequency decreases as dmpe li-
as a single resonance at δ ≈ 40 ppm, confirming the mutu- gands are replaced by depe ligands and when RuII is re-
ally trans-axial positions of the acetylido ligands. The chem- placed by FeII. This may reflect the slightly stronger metal–
ical shift of the 31P resonance varies slightly depending on carbon bonding in FeII bis(acetylide) complexes relative to
the acetylide substitution. The 1H NMR spectra display res- their RuII analogues resulting in a weaker CϵC bond and
onances typical of symmetrically substituted [trans- a lower CϵC stretching frequency; depe is also a sterically
1
RuX2(dmpe)2] complexes.[7,9,11] The H NMR spectrum of more demanding ligand than dmpe resulting in weakening
3, for example, consists of two broad singlet resonances cor- of the metal–phosphorus bond and a corresponding
responding to the CH3 and CH2 protons of the phosphane strengthening of the metal–acetylide bond.
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Symmetrical Bis(acetylido)ruthenium(II) Complexes
Table 2. IR CϵC stretching frequencies [cm–1] for symmetrical
Table 3. Selected bond lengths [Å] and angles [°] for 2, 3 and 4.
bis(acetylido)ruthenium(II) and bis(acetylido)iron(II) complexes.
Bond
2
3
4
Complex
CϵC
Ru(1)–C(1)
Ru(1)–C(4)
C(1)–C(2)
C(4)–C(5)
C(2)–C(3)
C(5)–C(6)
Ru(1)–P(1)
Ru(1)–P(2)
2.067(2)
2.053(2)
2.057(3)
2.057(3)
1.223(4)
1.217(4)
1.439(4)
1.440(4)
2.3058(8)
2.3061(8)
2.3093(8)
2.3173(8)
1
2051
2070
1984
2049
2057
2044
2043
2062
2049
2
1.214(4)
1.476(3)
1.225(3)
3
4
5
6
1.796(2)[a]
2.2989(7)
2.3030(7)
2.3072(6)
2.3020(6)
[trans-Ru(CϵCPh)2(depe)2][7]
[trans-Ru(CϵCtBu)2(depe)2][7]
[trans-Ru(CϵCC6H4-4-CϵCH)2(depe)2]
[trans-Fe(CϵCtBu)2(dmpe)2][12]
[trans-Fe(CϵCPh)2(dmpe)2][12]
[trans-Fe(CϵCSiMe3)2(dmpe)2][13]
[trans-Fe(CϵCC6H4-4-CϵCH)2(dmpe)2][12]
Ru(1)–P(3)
Ru(1)–P(4)
2059
2037
1972
C(1)–Ru(1)–C(1)
C(1)–Ru(1)–C(4)
Ru(1)–C(1)–C(2)
Ru(1)–C(4)–C(5)
C(1)–C(2)–C(3)
C(4)–C(5)–C(6)
180.00(12)
178.4(2)
177.4(3)
180.00(13)
177.7(2)
179.20(11)
178.1(3)
176.4(2)
177.2(3)
175.5(3)
2037, 2016
172.0(2)[b]
[a] C(2)–Si(1) bond length. [b] C(1)–C(2)–Si(1) bond angle.
Crystals of 2 and 3 suitable for X-ray diffraction were
obtained by slow concentration of benzene solutions. Crys-
tals of 4 were deposited from a saturated benzene solution.
The complexes 2, 3 and 4 are isostructural (Figure 1,
Table 3), and their X-ray structures confirm the expected
octahedral geometry in which the acetylido ligands occupy
mutually trans positions. The structures of 2 and 3 have a
C2 centre of inversion about the metal centre.
tortion is even more pronounced in 3, where the C(1)–C(2)–
Si(1) bond angle of 172.0(2)° gives the complex a marked
bend.
Alkyne Dimerisation
Head-to-head dimerisation of terminal alkynes is an at-
tractive, atom-economical method of synthesising conju-
gated butenynes,[15] which are important as building blocks
in organic synthesis and components of biologically active
molecules.[16] Although many metal complexes, including
early and late transition metals and lanthanides, are known
to catalyse the dimerisation reaction of terminal alkynes,[17]
in most cases a mixture of regio- and stereoisomeric but-
enynes is obtained. To date there have been few reported
examples of highly selective catalysis.[16b]
A small number of ruthenium-based complexes have
proven valuable catalysts for the formation of specific but-
enynes.[18] For example, Rappert and Yamamoto[19] re-
ported the catalytic dimerisation of phenylacetylene to (Z)-
1,4-diphenyl-1-buten-3-yne using [cis-RuH(NH3)(PMe3)4]-
[PF6].
In the absence of methanol, heating of (4-tert-butyl-
phenyl)acetylene with 8 mol-% of [trans-Ru(CH3)2(dmpe)2]
at 60 °C in benzene solution afforded (E)-1,4-bis(4-tert-but-
ylphenyl)-1-buten-3-yne (E-7) (Scheme 3; Table 5, Run 1),
which precipitated from solution. Identical reactions involv-
ing (4-methoxyphenyl)acetylene and [3,5-bis(trifluorometh-
yl)phenyl]acetylene gave (E)-1,4-bis(4-methoxyphenyl)-1-
buten-3-yne (E-8) and (E)-1,4-bis[3,5-bis(trifluoromethyl)-
Figure 1. ORTEP plots of 2, 3 and 4. Thermal ellipsoids are shown
at the 50% probability level, some hydrogen atoms have been omit-
ted for clarity.
The Ru–C bond lengths at approximately 2.06 Å are phenyl]-1-buten-3-yne (E-9), respectively (Table 5, Runs 2
identical (within experimental error) and compare well with and 3). The butenynes produced crystallised directly from
those of previously reported bis(acetylido)ruthenium com- the reaction mixture or were isolated by evaporation of the
plexes.[7,8b,9,14] The CϵC bond lengths at approximately solvent followed by recrystallisation from pentane.
1.22 Å are also consistent with those of previously reported
Similarly, the reaction of [trans-RuMe2(dmpe)2] with
complexes. There is a slight deviation from colinearity in 20 equiv. of PhCCH in [D8]toluene at 60 °C for 16 h
the CϵC–Ru–CϵC acetylide backbones of 2 and 4, with (Table 5, Run 4) resulted in the formation of the known
Ru(1)–C(1)–C(2) and C(1)–C(2)–C(3) angles of ca. 178 and compound[20] (E)-1,4-diphenyl-1-buten-3-yne (E-10) in 64%
ca. 177°, respectively, differing slightly from 180°. This dis- yield (based on phenylacetylene). In all cases, the phos-
Eur. J. Inorg. Chem. 2011, 3503–3510
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L. D. Field et al.
FULL PAPER
of toluene solutions. ORTEP plots of E-7, E-8 and E-9 are
shown in Figure 2, and selected bond lengths and angles
given in Table 4. The crystal structures confirm the (E)
stereochemistry about the double bonds. The structures of
E-8 and E-9 are disordered over two positions around the
alkene and alkyne bridging units.
Table 4. Selected bond lengths [Å] and angles [°] for E-7, E-8 and
E-9.
E-7
E-8
E-9
Scheme 3.
C(10)–C(11)
C(9)–C(10)
C(8)–C(9)
C(7)–C(8)
C(4)–C(7)
C(9)–C(10)–C(11)
C(8)–C(9)–C(10)
C(7)–C(8)–C(9)
C(4)–C(7)–C(8)
1.442(2)
1.187(3)
1.421(3)
1.267(3)
1.472(2)
178.3(2)
175.0(2)
131.4(2)
131.6(2)
1.443(2)
1.107(3)
1.414(4)
1.376(3)
1.443(2)
176.9(2)
175.6(4)
128.7(3)
130.21(19)
1.454(3)
1.155(5)
1.427(6)
1.328(5)
1.454(3)
178.1(3)
175.9(5)
126.0(5)
128.2(3)
phorus-containing species present after the reaction were
mixtures of the mono- and bis(acetylido) complexes, [trans-
RuMe(CϵCR)(dmpe)2][9] and [trans-Ru(CϵCR)2(dmpe)2].
The 1H NMR spectra of the organic butenynes show two
vinyl proton resonances with a 3JHH coupling of ca. 16 Hz,
characteristic of a disubstituted double bond with (E)
stereochemistry.[21] For example, E-8 exhibits doublet reso-
nances at δ = 7.45 and 7.03 ppm with 16.4 Hz coupling.
The 13C{1H} NMR spectrum of E-9 shows two F3C car-
bon resonances as 19F-coupled quartets at δ = 124.0 and
The known butenynes Z-8,[22] Z-10[22] and Z-11[23] were
the exclusive dimerisation products resulting from the reac-
tion of the respective terminal alkynes with [trans-Ru-
Me2(dmpe)2] (5 mol-%) in neat [D3]MeOH at 60 °C over
16 h (Scheme 4; Table 5, Runs 5–8). The use of [D4]MeOD
as solvent in place of [D3]MeOH resulted in the formation
of a mixture of D0, D1 and D2 isotopologues of the (Z)-
butenyne product.
1
124.3 ppm with JCF = 272 Hz. The two F3CC carbon
atoms are observed as almost coincident quartets, with a
2
smaller JCF = 33 Hz coupling at δ = 132.8 ppm, and there
3
are JCF couplings of 4 Hz to the ArCH atoms.
Crystals of E-7 and E-9 suitable for X-ray diffraction
were obtained by recrystallisation of the compounds from
pentane. Crystals of E-8 were grown by slow concentration
Scheme 4.
1
When the reactions are monitored by 31P{1H} and H
NMR spectroscopy, it can be seen that, initially, there is
rapid formation of [trans-Ru(CϵCR)2(dmpe)2], and the bis-
(acetylido) complexes may be isolated at this stage if re-
quired. With continued heating, the terminal alkyne is con-
sumed completely, and the predominant phosphorus-con-
1
taining species displays 31P{1H} and H NMR resonances
consistent with butenynylruthenium complexes.[24] Organo-
metallic η1- and/or η3-butenynyl complexes are often ob-
served as intermediates in alkyne dimerisation reactions,
and their presence here is entirely consistent with the pro-
posed literature mechanism of the dimerisation reaction.[25]
Attempts to dimerise [3,5-bis(trifluoromethyl)phenyl]-
acetylene in [D3]MeOH were unsuccessful (Table 5, Run 8).
This failure may be attributed to the insolubility of [trans-
Ru[CϵCC6H3-3,5-(CF3)2]2(dmpe)2], which precipitates
from the reaction medium immediately after addition of the
terminal alkyne to [trans-RuMe2(dmpe)2].[26]
The choice of solvent clearly has a strong influence on
the geometry of the final butenyne compound obtained in
this reaction. Different mechanisms have been suggested for
the formation of (E)- and (Z)-butenynes from terminal al-
Figure 2. ORTEP plots of E-7, E-8 and E-9. Thermal ellipsoids are
shown at the 50% probability level; only one component of the
disorder is shown in E-8 and E-9.
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Symmetrical Bis(acetylido)ruthenium(II) Complexes
Table 5. Dimerisation of terminal alkynes by trans-RuMe2(dmpe)2.
Run
Substrate
Catalyst loading[a]
[mol-%]
Solvent
Time[b]
[h]
(E)/(Z)[c]
Conversion[c]
[%]
Yield[d]
[%]
1
2
3
4
5
6
7
8
4-tBuC6H4CCH
4-MeOC6H4CCH
3,5-(F3C)2C6H3CCH
PhCCH
4-MeOC6H4CCH
PhCCH
8
8
4
5
5
5
5
5
C6H6
C6H6
C6H6
16
16
100
16
16
16
16
16
Ͼ99:1
Ͼ99:1
Ͼ99:1
96:4
1:Ͼ99
1:Ͼ99
1:Ͼ99
n. a.
47
43
77
37
40
59
26
97
78
81
0
[D8]toluene
[D3]MeOH
[D3]MeOH
[D3]MeOH
[D3]MeOH
35
Ͼ99
Ͼ99
Ͼ99
trace
tBuCCH
3,5-(F3C)2C6H3CCH
[a] Catalyst loading = (mol catalyst/mol substrate)ϫ100. [b] Reactions carried out at 60 °C. [c] Determined by NMR spectroscopy. [d]
Isolated yield.
kynes;[27] formation of the (Z) isomer occurs by intramolec-
[trans-Ru(CϵCPh)2(dmpe)2] (1): Phenylacetylene (0.50 mL,
4.5 mmol) was added to a solution of [trans-Ru(CH3)2(dmpe)2]
ular addition of an alkynyl ligand onto the α-carbon atom
of a metal-bound vinylidene ligand.[18a,28] Conversely, (E)
(0.35 g, 0.81 mmol) in benzene (2 mL). The solution was heated
under nitrogen at 60 °C for 2 d. The volatile components were re-
moved under reduced pressure, and the residue was recrystallised
isomers result from the insertion of a π-bound alkyne into
an alkynyl–metal bond.[27] The use of methanol as a solvent
from benzene to give 1 as a yellow crystalline solid (0.23 g, 47%).
appears to favour the formation of a vinylidene complex as
the intermediate and the (Z) isomer as the product.
The NMR spectra are identical to reported data.[29] C28H42P4Ru
(603.596): calcd. C 55.72, H 7.01; found C 55.55, H 7.09. IR (KBr):
ν
= 2051 [ν(CϵC)] cm–1.
˜
max
[trans-Ru(CϵCtBu)2(dmpe)2] (2):[7] tert-Butylacetylene (0.50 mL,
4.0 mmol) was added to a solution of [trans-Ru(CH3)2(dmpe)2]
(0.26 g, 0.60 mmol) in benzene (0.5 mL). The solution was heated
under nitrogen at 60 °C for 14 d. The solvent was removed under
reduced pressure to give 2 as a white solid (0.33 g, 97%). Crystals
suitable for X-ray diffraction were obtained from a benzene solu-
tion. 31P{1H} NMR (121.51 MHz, [D6]benzene): δ = 40.64 (s) ppm.
1H{31P} NMR (300.13 MHz, [D6]benzene): δ = 1.45 (s, 24 H,
PCH3), 1.42 (s, 8 H, PCH2), 1.32 (s, 18 H, CCH3) ppm. 13C{1H,
31P} (161.98 MHz, [D6]benzene): δ = 113.7 (RuCϵC), 103.2
(RuCϵC), 33.8 (CCH3), 30.4 (PCH2), 29.8 (CCH3), 15.6 (PCH3)
ppm. C24H50P4Ru (563.62): calcd. C 51.14, H 8.94; found C 51.26,
H 9.03. ESI-MS: m/z (%) = 565 [M + H]+ (20), 523 (70), 494 (100),
441 (30), 401 [M – (CϵCtBu)2]+ (15). HRMS (ESI+, MeOH):
Conclusions
The reaction between terminal acetylenes and dimeth-
ylruthenium complexes was used as a viable alternative ap-
proach to synthesise a range of bis(acetylido)ruthenium
complexes. The effectiveness of this route has been demon-
strated, and a number of new symmetrically substituted
bis(acetylido)ruthenium complexes were isolated and char-
acterised. The bis(acetylido)ruthenium complexes also serve
as catalysts for the head-to-head dimerisation of terminal
acetylenes to butenynes and, depending on the reaction sol-
vent, the stereochemistry of the butenyne products can be
controlled to give predominately either (E) or (Z) isomers.
calcd. for [M + 1] 565.1979; found 565.1988. IR (KBr): νmax = 2070
˜
[ν(CϵC)] cm–1.
[trans-Ru(CϵCSiMe3)2(dmpe)2]
(3):
(Trimethylsilyl)acetylene
Experimental Section
(0.50 mL, 3.5 mmol) was added to a solution of [trans-Ru(CH3)2-
(dmpe)2] (0.22 g, 0.51 mmol) in benzene (0.5 mL). The solution was
heated under nitrogen at 60 °C for 14 d. The solvent was removed
under reduced pressure and the residue washed with ice-cold pen-
tane (2 mL) to give 3 (0.26 g, 86%) as a white solid, which required
no further purification. 31P{1H} NMR (121.51 MHz,
[D6]benzene): δ = 38.72 (s) ppm. 1H{31P} NMR (300.13 MHz,
[D6]benzene): δ = 1.39 (s, 24 H, PCH3), 1.37 (s, 8 H, PCH2), 0.25
(s, 18 H, SiCH3) ppm. 13C{1H,31P} (100.61 MHz, [D6]benzene): δ
= 155.5 (RuCϵC), 110.9 (RuCϵC), 30.1 (PCH2), 15.4 (PCH3), 2.45
(SiCH3) ppm. C22H50P4RuSi2 (595.78): calcd. C 44.35, H 8.46;
found C 44.63, H 8.72. ESI-MS: m/z (%) = 597 [M + H]+ (100),
539 (30), 524 (15), 441 (30), 401 [M – (CϵCSiMe3)2]+ (10). HRMS
(ESI+, MeOH): calcd. for [M + 1] 597.15174; found 597.15153. IR
General: All syntheses and manipulations involving air-sensitive
compounds were carried out by using standard vacuum-line and
Schlenk techniques under dry nitrogen or argon. Methanol, tolu-
ene, and benzene were dried and degassed by heating with standard
drying agents under dry nitrogen and were freshly distilled prior
to use. NMR spectra were recorded with Bruker Avance III 600
(operating at 600.13, 150.9 and 242.9 MHz for 1H, 13C and 31P,
respectively), Bruker DMX500 (operating at 500.13, 125.92, and
202.45 MHz for 1H, 13C and 31P, respectively), Bruker AVANCE
DRX400 (operating at 400.13, 125.76, and 161.98 MHz for 1H, 13
C
and 31P, respectively) or Bruker DPX300 (operating at 300.13 and
121.49 MHz for 1H and 31P, respectively) spectrometers at 300 K
1
unless otherwise stated. H and 13C NMR spectra were referenced
(KBr): ν
= 1984 [ν(CϵC)] cm–1.
˜
max
to residual solvent resonances, whereas 31P NMR spectra were ref-
erenced to external neat trimethyl phosphite (δ = 140.85 ppm). IR
spectra were recorded with a Shimadzu 8400 series FTIR spectrom-
eter. Where indicated, mass spectra were recorded by electrospray
ionization (ESI) with a Finnigan LCQ mass spectrometer. The
complex [trans-RuMe2(dmpe)2] was prepared as described.[9] Ter-
minal alkynes were purchased from Aldrich and used as received.
[trans-Ru(CϵCC6H4-4-tBu)2(dmpe)2] (4): (4-tert-Butylphenyl)-
acetylene (0.50 mL, 2.77 mmol) was added to a solution of [trans-
Ru(CH3)2(dmpe)2] (0.058 g, 0.134 mmol) in toluene (3 mL). Meth-
anol (1 mL) was added, and the solution was stirred at room tem-
perature for 45 min. The volatile compounds were removed under
reduced pressure, and the residue was washed with hexane (2ϫ
Eur. J. Inorg. Chem. 2011, 3503–3510
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3507

L. D. Field et al.
FULL PAPER
2 mL). The compound was dried in vacuo to give 4 as a pale yellow
ArCH=CHCϵC), 1.27 [s, 9 H, C(CH3)3], 1.18 [s, 9 H, C(CH3)3]
powder. Yield: 0.064 g (67%). 31P{1H} NMR (202 MHz, [D8]thf): ppm. Spectroscopic properties are identical to those reported by
δ = 40.6 ppm. 1H NMR (500 MHz, [D8]thf): δ = 7.01 (AAЈ of Eisen and co-workers.[30]
AAЈXXЈ, 4 H, ArH), 6.88 (XXЈ of AAЈXXЈ, 4 H, ArH), 1.71 (m,
(E)-1,4-Bis[3,5-bis(trifluoromethyl)phenyl]-1-buten-3-yne (E-8): 1-
8 H, PCH2), 1.59 (br. s, 24 H, PCH3), 1.23 [s, 18 H, C(CH3)3] ppm.
Ethynyl-3,5-bis(trifluoromethyl)benzene (1.0 mL, 5.6 mmol) was
13C{1H} NMR (125 MHz, [D8]thf): δ = 144.3 [s, ArCC(CH3)3],
added to a solution of [trans-Ru(CH3)2(dmpe)2] (0.10 g, 0.23 mmol)
in benzene (2 mL). The reaction mixture was heated under nitrogen
at 60 °C for 16 h and allowed to cool. Colourless crystals formed,
2
129.4 (s, ArCH), 128.6 (s, ϵCC), 127.2 (p, JCP = 15.2 Hz,
RuCϵC), 123.9 (s, ArCH), 108.5 (br. s, RuCϵC), 33.7 [s,
C(CH3)3], 30.8 [s, C(CH3)3], 30.0 (m, PCH2), 15.0 (m, PCH3) ppm.
which were isolated by filtration and washed with pentane to give
C36H58P4Ru (715.804): calcd. C 60.45, H 8.17; found C 60.22, H
1
E-8 (0.53 g, 40%). H NMR (300.13 MHz, [D6]acetone): δ = 8.26
8.26. IR (Fluorolube): ν
= 2049 [ν(CϵC)] cm–1.
˜
max
(s, 2 H, ArHCϵC), 8.12 (s, 2 H, ArHC=C), 8.08 (s, 1 H,
3
ArHCϵC), 8.00 (s, 1 H, ArHC=C), 7.45 (d, JHH = 16.4 Hz, 1 H,
[trans-Ru(CϵCC6H4-4-OMe)2(dmpe)2] (5): (4-Methoxyphenyl)-
acetylene (1 mL, 7.7 mmol) was added to a solution of [trans-
Ru(CH3)2(dmpe)2] (0.1615 g, 0.374 mmol) in methanol (10 mL).
The solution was stirred at room temperature for 90 min, during
which time a yellow solid precipitated. The volatile compounds
were removed under reduced pressure, and the residue was washed
with pentane (2ϫ 2 mL). The compound was dried in vacuo to give
5 as a pale yellow powder. Yield: 0.152 g (61%). 31P{1H} NMR
(161 MHz, [D8]thf): δ = 40.8 ppm. 1H NMR (400 MHz, [D8]thf): δ
= 6.86 (AAЈ of AAЈXXЈ, 4 H, ArH), 6.55 (XXЈ of AAЈXXЈ, 4 H,
ArH), 3.63 (s, 6 H, OCH3), 1.69 (m, 8 H, PCH2), 1.57 (br. s, 24 H,
PCH3) ppm. 13C{1H} NMR (125.7 MHz, [D8]thf): δ = 156.7 (s,
COCH3), 131.5 (s, ArCH), 125.6 (m, RuCϵC), 125.5 (s, ArCipso),
113.9 (s, ArCH), 108.6 (br. s, RuCϵC), 55.4 (s, OCH3), 31.0 (m,
PCH2), 16.1 (m, PCH3) ppm. C30H46O2P4Ru (663.659): calcd. C
ArCH=CH), 7.03 (d, 3JHH = 16.4 Hz, 1 H, ArCH=CHCϵC) ppm.
13C{1H} NMR (75.49 MHz, [D6]acetone): δ = 141.1 (ArC), 139.4
2
2
(ArC), 132.8 (q, JCF = 33 Hz, CCF3), 132.8 (q, JCF = 33 Hz,
3
3
CCF3), 132.5 (d, JCF = 4 Hz, ArCH), 127.8 (d, JCF = 4 Hz,
ArCH), 126.4 (s, CϵCC=C), 124.3 (q, JCF = 272 Hz, CF3), 124.0
(q, JCF = 272 Hz, CF3), 122.9 (q, JCF = 4 Hz, ArCH), 122.8 (q,
3JCF = 4 Hz, ArCH), 112.4 (s, CϵCC=C), 92.2 (s, CϵCC=C), 90.6
(s, CϵCC=C) ppm. C20H8F12 (476.264): calcd. C 50.44, H 1.69;
found C 50.40, H 1.81.
1
1
3
(E)-1,4-Bis(4-methoxyphenyl)-1-buten-3-yne
(E-9):
(4-Meth-
oxyphenyl)acetylene (1.50 mL, 11.6 mmol) was added to a solution
of [trans-Ru(CH3)2(dmpe)2] (0.40 g, 0.93 mmol) in benzene (2 mL).
The reaction mixture was heated under nitrogen at 60 °C for 16 h
and allowed to cool. Colourless crystals precipitated, and these
were isolated by filtration and washed with pentane to afford the
head-to-head dimer E-9 (0.9 g, 59%). 1H NMR (300.13 MHz,
[D6]benzene): δ = 7.49 (AAЈ of AAЈXXЈ, 2 H, ArH), 7.07 (AAЈ of
AAЈXXЈ, 2 H, ArH), 7.05 (d, 3JHH = 16.7 Hz, 1 H, CH=CH), 6.61
54.29, H 6.99; found C 54.58, H 7.26. IR (Fluorolube): νmax = 2057
˜
[ν(CϵC)] cm–1.
[trans-Ru[CϵCC6H3-3,5-(CF3)2]2(dmpe)2] (6): [3,5-Bis(trifluoro-
methyl)phenyl]acetylene (200 μL, 1.13 mmol) was added to a solu-
tion of [trans-RuMe2(dmpe)2] (0.0945 g, 0.219 mmol) in MeOH
(15 mL). The solution was stirred at room temperature for 4 h, then
concentrated under reduced pressure to ca. 3 mL. The supernatant
was decanted and the yellow residue dried in vacuo to give cis-6 as
a pale yellow powder. Yield: 0.141 g (73%). 31P{1H} NMR
(121.5 MHz, [D8]thf): δ = 40.2 (apparent t, splitting = 22.7 Hz),
30.0 (apparent t, splitting = 22.7 Hz) ppm. This compound was
taken up in [D8]thf and irradiated with a mercury-vapour lamp for
18 h. The solvent was removed under reduced pressure, and the
residue was crystallised from toluene to yield 6 as a pale yellow
powder. 31P{1H} NMR (242.93 MHz, [D8]thf): δ = 39.5 (s) ppm.
1H NMR (600.13 MHz, [D8]thf): δ = 7.41 (s, 2 H, p-ArH), 7.38 (s,
4 H, o-ArH), 1.78 (m, 8 H, PCH2), 1.60 (s, 24 H, PCH3) ppm.
13C{1H} NMR (150.9 MHz, [D8]thf): δ = 143.5 (p, 2JCP = 15.1 Hz,
RuC), 133.8 (s, ipso-C), 132.0 (q, 2JCF = 32.1 Hz, CCF3), 130.3 (br.
s, o-ArC), 125.0 (q, 1JCF = 269.7, CF3), 115.7 (sept, 3JCF = 3.8 Hz,
3
(m, XXЈ of AAЈXXЈ, 4 H, ArH), 6.30 (d, JHH = 16.7 Hz, 1 H,
CH=CH), 3.22 (s, 3 H, OCH3), 3.17 (s, 3 H, OCH3) ppm. 13C{1H}
NMR (75.49 MHz, [D6]benzene): δ = 160.2 (ArCOMe), 160.1 (Ar-
COMe), 140.6 (ArC), 138.0 (ArC), 133.2 (ArCH), 130.7 (ArCH),
130.3 (CϵCC=C), 114.5 (ArCH), 114.1 (ArCH), 105.6
(CϵCC=C), 96.1 (CϵCC=C), 88.3 (CϵCC=C), 54.7 (OCH3), 54.6
(OCH3) ppm. C18H16O2 (264.324): calcd. C 81.79, H 6.10; found
C 81.80, H 6.34. Spectroscopic properties are identical to those
reported by Bassetti and co-workers.[31]
General Procedure for the Dimerisation of Terminal Alkynes
In [D3]MeOH: [D3]MeOH (ca 0.7 mL) was vacuum-transferred
onto solid [trans-RuMe2(dmpe)2] (ca. 0.02 g). The mixture was
thawed and the terminal alkyne added through a syringe. The mix-
ture was heated to 60 °C and monitored periodically by 1H and
31P{1H} NMR spectroscopy. After the desired time, CDCl3 was
added and the mixture washed with water. The organic layer was
separated, dried with MgSO4 and subjected to NMR spectroscopic
analysis. The organic product was isolated from the CDCl3 solu-
tion.
1
p-ArC), 109.3 (s, RuCϵC), 30.9 (p, JCP = 13.4 Hz, PCH2), 16.0
(m, PCH3) ppm. C32H38F12P4Ru (875.604): calcd. C 43.89, H 4.37;
found C 44.18, H 4.66. IR (Fluorolube): ν
= 2044 [ν(CϵC)]
˜
max
cm–1.
In [D8]Toluene: [D8]Toluene (ca. 0.7 mL) was vacuum-transferred
onto solid [trans-RuMe2(dmpe)2] (ca. 0.02 g). The mixture was
thawed and the terminal alkyne added through a syringe. The mix-
ture was heated to 60 °C for the desired time with periodic monitor-
(E)-1,4-Bis(4-tert-butylphenyl)-1-buten-3-yne (E-7): (4-tert-Butyl-
phenyl)acetylene (1 mL, 5.5 mmol) was added to a solution of
[trans-Ru(CH3)2(dmpe)2] (0.20 g, 0.46 mmol) in benzene (2 mL).
The reaction mixture was heated under nitrogen at 60 °C for 16 h.
The mixture was allowed to cool, and the volatile components were
removed under reduced pressure. The residue was redissolved in
pentane from which colourless crystals of E-7 precipitated (0.32 g,
37%), which were isolated by filtration. 1H NMR (400.13 MHz,
1
ing by H and 31P{1H} NMR spectroscopy.
X-ray Structure Determinations: Single crystals of 2, 3 and E-8 were
attached, with Exxon Paratone N, to a short fibre supported on a
thin piece of copper wire inserted in a copper mounting pin. The
[D6]benzene): δ = 7.99 (AAЈ of AAЈXXЈ, 2 H, ArHCϵC), 7.49 crystal was quenched in a cold nitrogen gas stream from an Oxford
(AAЈ of AAЈXXЈ, 2 H, ArHC=C), 7.34 (XXЈ of AAЈXXЈ, 2 H, Cryosystems Cryostream. A Bruker kappa APEXII area detector
ArHCϵC), 7.17 (XXЈ of AAЈXXЈ, 2 H, ArHC=C), 6.52 (d, JHH diffractometer employing graphite-monochromated Mo-Kα radia-
3
3
= 11.7 Hz, 1 H, ArCH=CH), 5.85 (d, JHH = 11.7 Hz, 1 H,
tion generated from a fine-focus sealed tube was used for the data
3508
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 3503–3510

Symmetrical Bis(acetylido)ruthenium(II) Complexes
Table 6. Crystallographic data for 2, 3, 4, E-7, E-8 and E-9.
2
3
4
E-7
E-8
E-9
Empirical formula
Formula mass
Crystal system
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C24H50P4Ru
563.59
triclinic
C22H50P4RuSi2
595.75
triclinic
C36H58P4Ru
715.77
monoclinic
13.8356(10)
20.9962(14)
14.4248(10)
90
112.461(2)
90
3872.5(5)
296(2)
C24H28
316.46
monoclinic
12.707(4)
9.931(3)
15.273(5)
90
94.440(17)
90
1921.5(11)
123(2)
P21/c
C18H16O2
264.31
triclinic
C10H20F6
254.26
monoclinic
4.9195(14)
23.257(6)
8.262(2)
90
102.097(8)
90
924.2(4)
173(2)
P21/n
9.0968(5)
9.4867(5)
9.8880(6)
74.721(2)
70.786(2)
71.702(2)
752.73(7)
150(2)
9.3483(6)
9.9106(7)
10.1310(7)
70.680(3)
64.586(3)
72.539(3)
786.16(9)
150(2)
7.8575(8)
8.6286(9)
11.7457(13)
102.281(5)
99.895(5)
108.734(4)
711.65(13)
150(2)
γ [°]
V [Å3]
T [K]
Space group
¯
P1
¯
P1
¯
P1
P21/c
Z
1
6431
2627
0.0538
0.0319
0.0859
0.0329
0.0869
1
4
4
2
4
3638
1937
0.0265
0.0473
0.0972
0.0927
0.1133
No. of reflections measured
No. of independent reflections
Rint
Final R1 value [IϾ2σ(I)]
Final wR(F2) value [IϾ2σ(I)]
Final R1 value (all data)
Final wR(F2) value (all data)
11125
2750
0.0277
0.0253
0.0620
0.0295
0.0656
33663
8526
0.0568
0.0441
0.0894
0.0650
0.0978
44290
4203
0.0474
0.0609
0.1609
0.0759
0.1748
10251
2500
0.0422
0.0373
0.0966
0.0442
0.1024
f) K. A. Green, M. P. Cifuentes, T. C. Corkery, M. Samoc,
M. G. Humphrey, Angew. Chem. Int. Ed. 2009, 48, 7867–7870;
g) B. Babgi, L. Rigamonti, M. P. Cifuentes, T. C. Corkery,
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collection. Data were collected at 150(2) K. The data integration
and reduction were undertaken with APEX2,[32] and subsequent
computations were carried out with the X-Seed[33] graphical user
interface. The structures were solved by direct methods with
SHELXS-97[34] and extended and refined with SHELXL-97.[34]
The non-hydrogen atoms in the asymmetric unit were modelled
with anisotropic displacement parameters. A riding-atom model
with group-displacement parameters was used for the hydrogen
atoms. Single crystals of 4, E-7 and E-9 were mounted on glass
fibres. Data were collected with a Bruker Nonius X8Apex2 dif-
fractometer equipped with graphite-monochromated Mo-Kα radia-
tion (λ = 0.71073 Å) at 123(2) (4) or 100(2) K (E-7) or with a
Bruker SMART-CCD diffractometer equipped with graphite-mo-
nochromated Mo-Kα radiation (λ = 0.71073 Å) at 173(2) K (E-9).
The structures were solved by direct methods and full-matrix least-
squares refinements by using the SHELXTL-97 program pack-
age.[34] Hydrogen atoms were placed at calculated positions, and all
non-hydrogen atoms were refined anisotropically. All calculations
were performed by using the crystallographic and structure refine-
ment data summarised in Table 6. CCDC-800005 (for 2), -800006
(for 3), -800007 (for 4), -800008 (for E-7), -800009 (for E-8) and
-800010 (for E-9) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
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Published Online: June 29, 2011
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