Ligand redox non-innocent behaviour in ruthenium complexes of ethynyl tolans

Article abstract of DOI:10.1016/j.ica.2011.02.043

A small series of half-sandwich bis(phosphine) ruthenium acetylide complexes [Ru(C≡CC₆H₄C≡CSiMe ₃)(L₂)Cp′] and [Ru(C≡CC₆H ₄C≡CC₆H₄R-4)(L₂)Cp′] (R = OMe, Me,

Full text of DOI:10.1016/j.ica.2011.02.043

Inorganica Chimica Acta 374 (2011) 461–471
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Ligand redox non-innocent behaviour in ruthenium complexes of ethynyl tolans
Wan M. Khairul a,b, Mark A. Fox a, Phil A. Schauer a, David Albesa-Jové a, Dmitry S. Yufit a,
Judith A.K. Howard a, Paul J. Low a,
⇑
a Department of Chemistry, Durham University, South Rd, Durham DH1 3LE, UK
b Department of Chemical Sciences, Faculty of Science and Technology, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Malaysia
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 26 February 2011
A small series of half-sandwich bis(phosphine) ruthenium acetylide complexes [Ru(C„CC6H4C„CSiMe3)
(L2)Cp0] and [Ru(C„CC6H4C„CC6H4R-4)(L2)Cp0] (R = OMe, Me, CO2Me, NO2; L2 = (PPh3)2, Cp0 = Cp;
L2 = dppe; Cp0 = Cp⁄) have been synthesised. One-electron oxidations of these complexes gave the corre-
sponding radical cations, which were significantly more chemically stable in the case of the Ru(dppe)Cp⁄
derivatives. The representative complex [Ru(C„CC6H4C„CC6H4OMe-4)(dppe)Cp⁄] was further examined
by spectroelectrochemical (IR and UV–Vis–NIR) methods. The results of the spectroelectrochemical stud-
ies, supported by DFT calculations, indicate that the hole is largely supported by the ‘RuC„CC6H4’ moiety
in a manner similar to that described previously for simple aryl ethynyl complexes, rather than being
more extensively delocalized along the entire conjugated ligand.
Dedicated to Professor Wolfgang Kaim,
scholar, teacher and friend, in celebration of
his outstanding contributions to Chemistry.
Keywords:
Ruthenium
Alkynyl
Tolan
Ó 2011 Elsevier B.V. All rights reserved.
Spectroelectrochemistry
DFT
1. Introduction
tures. Spectroelectrochemical methods, supported by DFT calcula-
tions, have been used to examine the effects of one-electron
Metal complexes containing ‘carbon-rich’ ligands have been
extensively investigated over the last 20 years, with many studies
focusing on, for example, the synthesis, reactions and electronic
structure of complexes bearing extended cumulated ligands
(allenylidenes, butatrienylidenes and higher culumenic ligands)
[1–3], the synthesis, physical and electronic structures of metal–
polyynyl and polyyndiyl complexes [4–14], NLO properties of
metal complexes bearing carbon-rich ligands [15], and the
potential for carbon-rich ligands to mediate electron transfer pro-
cesses in both solution state studies [16–20] and in metal|mole-
cule|metal junctions [21–23]. In the context of many of these
areas, the recognition of the varying degrees of redox non-inno-
cence [24–28] of the carbon rich ligand as a convoluted function
of metal, supporting ligands and ligand substituents has provided
a new framework within which to consider the electrochemical,
electronic and optical properties of this vibrant area of ‘carbon-
rich’ organometallic chemistry [29–32].
oxidation on the physical and electronic structure of these
complexes, revealing the important role of the tolan ligand,
especially the metal-coordinated ethynyl phenylene fragment, in
supporting the unpaired electron.
2. Results and discussion
2.1. Syntheses
The complex [Ru(C„CC6H4C„CSiMe3)(PPh3)2Cp] (1a), which
can be considered as one of the simplest examples of a metal com-
plex bearing a phenylene ethynylene ligand extended beyond a
phenyl acetylide, was reported some time ago from the desilyla-
tion/metallation reaction of [RuCl(PPh3)2Cp] with 1,4-bis(trimeth-
ylsilylethynyl)benzene in the presence of KF (Scheme 1) [37].
Although the mechanism of the desilylation/metallation reaction
has not been elucidated, an intermediate silylvinylidene may be in-
volved, with nucleophilic cleavage of the activated silylvinylene
and precipitation of the monometallic acetylide product occurring
before activation of the second trimethylsilyl ethynyl moiety [38–
40]. The analogous complex [Ru(C„CC6H4C„CSiMe3)(dppe)Cp⁄]
(1b) was prepared here in a similar fashion from 1,4-bis(trimethyl-
silylethynyl)benzene and [RuCl(dppe)Cp⁄] for reference purposes.
However, attempts to prepare the tolan complexes
[Ru(C„CC6H4C„CC6H4R-4)(L2)Cp0] [R = OMe (2), Me (3), CO2Me
(4), NO2 (5); L2 = (PPh3)2, Cp0 = Cp (series a); L2 = dppe; Cp0 = Cp⁄
The oligo(phenylene ethynylene) moiety is one member of the
family of ‘carbon-rich’ ligands that has attracted recent interest
particularly from the point of view of their NLO [33–35] and redox
[29,36] properties. In this report we describe the preparation of a
series of metal complexes bearing 1-ethynyl-4-(aryl ethynyl)-
benzene (i.e. tolan) ligands, and representative molecular struc-
⇑
Corresponding author. Tel.: +44 191 334 2114; fax: +44 191 384 4737.
E-mail address: p.j.low@durham.ac.uk (P.J. Low).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.02.043

462
W.M. Khairul et al. / Inorganica Chimica Acta 374 (2011) 461–471
Scheme 1. The preparation of 1a, 1b and related complexes.
(series b)] from the various trimethylsilyl-protected ethynyl tolan
precursors Me3SiC„CC6H4C„CC6H4R were often inconsistent, or
gave the desired complexes only in low yield. Only in the case of
2a did the ‘KF’ route yield consistently acceptable results. It is pos-
sible to speculate on the possible formation of the various isomeric
vinylidene side products that might intercept the reaction pathway
en route to the desired products, given the surprisingly facile for-
mation of vinylidene complexes from internal alkynes [41–43].
However, further discussions must await a more detailed study of
the migratory aptitude of the various fragments that comprise these
apparently simple alkyne derivatives, Me3SiC„CC6H4C„CC6H4R,
within the coordination environment of half-sandwich ruthenium
centres. The complexes 2b and 3–5 were therefore prepared
from the parent ethynyl tolans via the intermediate protio-
vinylidenes and deprotonation in situ and isolated in acceptable
yield (Scheme 2) [44,45]. The preparation of similar complexes by
Sonogashira cross-coupling of [Ru(C„CC6H4C„CH)(PPh3)2Cp] with
iodobenzene has been described elsewhere (Scheme 1) [46].
Complex 1a may also be prepared from [RuCl(PPh3)2Cp] and
HC„CC6H4C„CSiMe3 (Scheme 1), albeit in lower yield (33%) than
that reported earlier from the bis(silyl) precursor (64%).
together with the structures of 3a and 4a. Representative plots of
3a, 4a and 5a are given in Fig. 1, with bond lengths and angles sum-
marised in Table 1.
The most immediately apparent structural feature in the series
relates to the relative disposition of the aromatic rings within the
tolan ligand fragment, and the orientation of the C(3)–C(8) ring with
respect to the half-sandwich metal moiety. The Ru(PR3)2Cp frag-
ment offers two almost degenerate, high-lying d
priate symmetry to conjugate with the orthogonal
p
orbitals of appro-
-components of
p
an acetylide ligand. There are therefore two possible orientations of
the phenylene ring which will lead to a degree of conjugation with
the metal centre, one in which the ring plane bisects the P–Ru–P an-
gle and therefore lies approximately ‘perpendicular’ to the Cp plane,
and the other, orthogonal conformation in which the plane of the
aromatic portion of the ligand is closer to ‘parallel’ to the plane of
the Cp ligand. Whilst gas-phase calculations usually favour the ‘par-
allel’ conformation [12,31] the difference in energy between the
conformations is small (0.3–0.4 kcal molꢀ1) [32]. In the solid state
both perpendicular [32,47–49] and parallel [32,50–52] conforma-
tions have been observed, with both forms having been structurally
characterised in the case of the parent system Ru(C„CPh)(PPh3)2Cp
[53,54]. In the case of 3a, 4a and 5a the observed conformation ap-
pears to be influenced by intermolecular contacts.
The structural data from 3a, 4a and 5a (at both 296 and 120 K)
can be compared with those of the related phenyl acetylide com-
plexes [Ru(C„CC6H4R-4)(PPh3)2Cp] (R = H [53,54], CN [51], NO2
[49]) and trends established from the series [Ru(C„CC6H4R-
4)(dppe)Cp⁄] (R = NH2 [55], F [55], OMe [55], Me [56], H [55], CN
[55], NO2 [55]) (Table 2). As has been noted elsewhere, a small
back-bonding contribution leads to shorter Ru–C1 bonds in the
case of acetylide ligands bearing electron withdrawing groups,
Within each series (1a–5a, 1b–5b), the spectroscopic properties
associated with the Ru(PP)Cp0 fragment are remarkably invariant
with the Cp (dH = 4.33–4.50; dC = 85.5–85.6 ppm), Cp⁄ (dH = 1.56–
1.62; dC = 92.5–92.6 ppm), PPh3 (dP = 51.3 ppm) and dppe (dP =
81.8 ppm) resonances falling in a narrow range across the relevant
series. The IR spectra are characterised by two distinct
m(C„C)
bands, one associated with the metal-coordinated (2058–
2064 cmꢀ1) acetylide moiety, the other with the pendant group
(2153 (1a), 2149 (1b), 2202–2215 (2–5) cmꢀ1). In the case of the
Ru(dppe)Cp⁄ containing complexes 1b–5b the pseudo doublets
(AB spin system) associated with the phenylene rings were usually
resolved, with the proton resonances on the pendent ring being
influenced by the electronic nature of the substituent in the usual
fashion.
whilst
p-donating substituents generally lead to elongations of
the same bond [55,57,58]. The Ru–P and C1„C2 bond lengths gen-
erally display little significant variation, although variations in the
precision of data and the temperature of data collection may mask
small underlying trends (Table 2). The relatively high precision of
the structure determinations from the tolan complexes 3a, 4a
and 5a reveal identical Ru–C1 and C1„C2 bond lengths, with a
contraction of the Ru–P bond lengths associated with 4a and 5a
that falls at the borderline of statistical significance (Table 1). It
2.2. Molecular structures
The structures of 1a [37] and 5a [45] have been previously re-
ported. The structure of 5a has been re-determined here at 120 K

W.M. Khairul et al. / Inorganica Chimica Acta 374 (2011) 461–471
463
Scheme 2. The preparation of complexes 2–5.
would appear that the small trends in bond lengths in the coordi-
nation sphere of the metal centre as a function of acetylide substi-
tuent are even less prevalent in the structures of the tolan
derivatives determined here.
these subsequent oxidation events were not investigated further
in the present study. However, the most striking feature of these
data is the remarkable consistency of the anodic half-wave poten-
tials, which span only 50 mV, despite the variation in the tolan li-
gand substituent, R ranging from relatively strongly electron
donating OMe to electron withdrawing NO2. This compares with
the ca. 250 mV difference in formal oxidation potential of the anal-
ogous acetylide complexes [Ru(C„CC6H4R)(dppe)Cp⁄] (R = OMe,
NO2) [55].
Given the greater stability of the redox couples based on the
Ru(dppe)Cp⁄ systems evidenced by these electrochemical data,
and the greater solubility of the complexes 1b–5b as compared
with 1a–5a, complex 2b was chosen as a representative system
for spectroelectrochemical investigation [59]. The characteristic
2.3. Electrochemistry and IR spectroelectrochemistry
Typically, half-sandwich ruthenium acetylides undergo a single
electron oxidation in common solvents to give the corresponding
radical cations, the electrode potential and chemical stability of
which are sensitive to both the supporting ligands on the ruthe-
nium centre and the acetylide substituent. The additional steric
bulk and enhanced donor properties of the supporting ligand set
leads to more facile oxidation (i.e. oxidation at less positive poten-
tials) of [Ru(C„CC6H4R)(dppe)Cp⁄] complexes in comparison to
those based on [Ru(C„CC6H4R)(PPh3)2Cp] and generally greater
chemical stability of the oxidation products [31,55]. These general
trends are reproduced in the tolan series 2–5 (Table 3). Each com-
plex in the series underwent a well defined oxidation event, with
the chemical instability of the radical cations [Ru(C„CC6H4R)
(PPh3)2Cp]+ being evidenced by ipc: ipa < 1; in the case of 5a the cur-
rent ratio and shape of the voltammetric waves points to deposi-
tion of the cation on the electrode surface, and subsequent
stripping behaviour. The radical cations [Ru(C„CC6H4R)(dppe)
Cp⁄]+ were more stable on the timescale of the CV experiments,
although the substantial peak to peak separations indicate sluggish
electron transfer kinetics. The nitro containing complexes also
exhibited a reduction wave near ꢀ0.85 V (versus SCE). In all cases,
a large, multi-electron wave near the anodic limit of the solvent
was also apparent. The chemical complications that accompany
m(C„C) band in metal acetylide complexes has proven to be a use-
ful diagnostic tool for the evaluation of the extent to which the
acetylide fragment contributes to redox processes [30,31,60]. The
characteristic m(C„C) band of the metal coordinated acetylide in
4b was found at 2072 cmꢀ1, and decreased in frequency on oxida-
tion. A product species with IR bands at 1925 and 1576 cmꢀ1 was
observed as the oxidation proceeded, and assigned as [4b]+ (Table
4, Fig. 2). In the neutral state the m(C„C) band of the non-coordi-
nated alkyne moiety (C9„C10) was also observed at 2207 cmꢀ1
(Table 4); this latter band changes little in the band frequency dur-
ing oxidation. On the basis of these IR data, it can be surmised that
the hole generated as
a result of oxidation resides on the
RuC„CC6H4– moiety with little contribution from the more ex-
tended portion of the tolan ligand. These suggestions can be ad-
dressed further with reference to calculations of the electronic
structures of related model systems (see below).

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W.M. Khairul et al. / Inorganica Chimica Acta 374 (2011) 461–471
Fig. 1. Molecular structures of 3a (top), 4a (middle) and 5a (bottom) showing the atom labelling scheme. The different ring orientations observed in the crystals are likely due
to crystal packing effects.
Table 1
Bond distances for 3a, 4a and 5a.
3a
4a
5a (120 K)
5a (296 K)a
R = Me
R = CO2Me
R = NO2
R = NO2
Ru(1)–C(1)
2.0051(19)
2.000(3)
2.009(2)
1.986(4)
Ru(1)–P(1)
2.3020(5)
2.2866(7)
2.2894(6)
2.283(1)
Ru(1)–P(2)
2.3020(5)
2.2862(7)
2.2976(6)
2.300(1)
C(1)–C(2)
1.215(3)
1.217(4)
1.218(3)
1.211(6)
C(2)–C(3)
1.429(3)
1.422(4)
1.432(3)
1.440(6)
C(3)–C(4, 8)
C(4)–C(5), C(7)–C(8)
C(6)–C(5, 7)
1.406(2), 1.403(3)
1.379(3), 1.382(3)
1.397(3), 1.396(3)
1.439(3)
1.393(4), 1.416(4)
1.379(4), 1.408(4)
1.401(4), 1.375(4)
1.437(4)
1.397(3), 1.407(3)
1.382(3), 1.400(3)
1.396(3), 1.385(3)
1.445(3)
1.379(6), 1.387(6)
1.361(6), 1.385(6)
1.391(6), 1.383(7)
1.449(6)
C(6)–C(9)
C(9)–C(10)
1.204(3)
1.195(4)
1.193(3)
1.167(6)
C(10)–C(11)
C(11)–C(12, 16)
C(12)–C(13), C(16)–C(15)
C(14)–C(13, 15)
1.436(3)
1.433(4)
1.446(3)
1.433(6)
1.384(3), 1.396(3)
1.386(3), 1.383(3)
1.375(3), 1.385(3)
1.403(5), 1.386(4)
1.372(5), 1.394(4)
1.383(4), 1.389(4)
1.397(4), 1.390(4)
1.393(3), 1.378(4)
1.369(4), 1.389(4)
1.389(7), 1.372(7)
1.398(8), 1.373(7)
1.333(8), 1.366(8)
a
From [45].
2.4. Electronic structure calculations
in Table 6 with those most relevant to the discussions of electronic
structure and spectroscopic properties below being illustrated in
Figs. 3–5. The labelling scheme for the electronic calculation stud-
ies follows that employed in the crystallographic section.
The Ru–C1, Ru–P, C1„C2 and C2–C3 bond lengths in 2-H are
comparable with those found for the simple phenyl acetylide
derivative 6-H at similar levels of theory (Table 5) [31]. At the level
of theory employed, the aromatic rings of the tolan ligand in 2-H
For calculations at the DFT level, the model system
[Ru(C„CC6H4C„CC6H4OMe)(PH3)2Cp] (2-H) was used together
with the corresponding radical cation [2-H]+. The discussion which
follows refers to results obtained from calculations at the B3LYP/3-
21G⁄ level of theory with no symmetry constraints (Table 5). Ener-
gies and composition of selected frontier orbitals are summarised

W.M. Khairul et al. / Inorganica Chimica Acta 374 (2011) 461–471
465
Table 2
Selected bond lengths from a series of reference compounds Ru(C„CC6H5R-4)(L2)Cp0 [(L2)Cp0 = (PPh3)2Cp; (dppe)Cp⁄]. See Fig. 1 for atom labelling scheme.
Ru–C
Ru–P(1, 2)
C1„C2
C2–C3
References
Ru(C„CC6H4R-4)(PPh3)2Cp
H
CN
NO2
2.016(3)
2.011(2)
1.994(5)
2.285(1), 2.303(1)
2.3031(5), 2.3134(5)
2.297(2), 2.301(2)
1.215(4)
1.219(3)
1.202(8)
1.456(4)
1.432(3)
1.432(7)
[53,54]
[51]
[49]
Ru(C„CC6H4R-4)(dppe)Cp⁄
NH2
F
OMe
Me
H
2.026(3)
2.014(3)
2.015(2)
2.0205(19)
2.011(4)
2.2625(11), 2.2622(11)
2.2715(7), 2.2583(7)
2.2652(2), 2.2643(6)
2.2621(5), 2.2622(5)
2.2622(12), 2.2563(12)
2.2755(6), 2.2639(5)
1.202(4)
1.209(4)
1.216(3)
1.211(3)
1.215(5)
1.209(3)
1.221(8)/1.225(8)
1.444(4)
1.445(4)
1.433(3)
1.437(3)
1.431(5)
1.434(3)
1.437(8)/1.413(8)
[55]
[55]
[55]
[56]
[55]
[55]
[55]
CN
NO2
2.004(2)
1.997(6)/2.004(6)
2.2639(14)/2.2676(14), 2.2747(14)/2.2650(15)
Table 3
Electrochemical data for complexes 2–5.
a
b
a
E(1/2)oxd
D
Ep
ipc/ipa
E(1/2)red
2a
3a
4a
5a
2b
3b
4b
5b
0.59
0.60
0.63
0.64
0.39
0.37
0.41
0.42
113
127
171
156
83
103
135
149
0.9
0.8
0.8
1.4
1.0
1.0
1.0
1.0
ꢀ0.85
ꢀ0.84
a
All E values in Volt vs. SCE. Conditions: CH2Cl2 solvent, 0.1 M [NBu4]PF6 elec-
trolyte, Pt working, counter and pseudo-reference electrodes,⁄
m
= 100 mV sꢀ1 at
20 °C. The decamethyl ferrocene/decamethyl ferrocenium (Fc /Fc⁄+) couple was
used as an internal reference for potential measurements (Fc⁄/Fc⁄+ taken as ꢀ0.02 V
vs. SCE in CH2Cl2/0.1 M [NBu4]PF6).
b
D
Ep = |Epa ꢀ Epc|.
Table 4
Spectroelectrochemical IR data (m(C„C)/m(Aryl)) for complex 2b, with calculated
Fig. 2. The IR spectra of 2b (solid line) and [2b]+ (broken line) collected from a
vibrational frequencies from the models [2-H]n+ a,b
.
spectroelectrochemical experiment (CH2Cl2/0.1 M [NBu4]PF6). The small band at
1970 cmꢀ1 is
m(CO) from a
small amount of [Ru(CO)(dppe)Cp⁄]+ formed by
0
+1
decomposition of the sample in solution prior to measurement.
m
(CC)
m(Aryl)
m
(CC)
m(Aryl)
2b
2207w
2060s
2208w
2091s
1592m
2206m
1923s
2153m
2002 m
1577s
localised on the C11–C16 ring comprises the LUMO+4. The frontier
orbital order therefore more closely resembles that of the 9-anthryl
derivative Ru(C„CC14H10)(PH3)2Cp (7-H) than the phenylacetylide
analogue (6-H) (Fig. 6) [31].
[2-H]+
1561m
1554m
a
m
(Aryl) =
m(CC) of the C6H4OMe ring, weakly coupled with C6H4.
b
A scaling factor of 0.95 has been applied to all calculated frequencies [61].
The a
- and b-spin frontier orbitals of [2-H]+ are of similar com-
position to the frontier orbitals described for 2-H with a small
change in relative ordering. The geometry differences calculated
for 2-H and [2-H]+ (Table 5) are entirely in keeping with the orbi-
tals characteristics of the HOMO in 2-H and the b-LUSO in [2-H]+
(Table 6, Figs. 3 and 5). The metal–phosphine bond lengths are sen-
are co-planar (C7–C6ꢁꢁꢁC11–C16 ꢀ0.005°) and lie in the plane
approximately perpendicular to the Cp ring (C0–RuꢁꢁꢁC3–C8
ꢀ0.023°, C0 is the centroid of the Cp ring) and bisecting the
P–Ru–P angle. The OMe group lies in the plane of the associated
phenylene ring (C15–C18–O–CH3 0.002°), the geometry with a
C15–C18–O–CH3 torsion angle of 180° being virtually isoenergetic
(0.002 kcal molꢀ1). The conformational characteristics of [2-H]+ are
similar (C7–C6ꢁꢁꢁC11–C16 0.014°; C0–RuꢁꢁꢁC3–C8 0.063°). The
HOMO and [HOMOꢀ1] of 2-H are approximately orthogonal and
sitive to the net electron density available for p-back bonding and
consequently are elongated in [2-H]+ relative to 2-H, reflecting a
decrease in the net electron density at the metal centre as the mol-
ecule is oxidised. The elongation of the acetylide C1„C2 bond in
[2-H]+ when compared with 2-H is consistent with a decrease in
the net acetylide
p-bonding character and the character of the b-
derived from mixing the metal d and C1„C2 acetylide
with the HOMO containing appreciable contributions from the to-
lan -system, especially the C1„C2 moiety (25%) and C3–C8 phe-
nylene ring (27%) (Table 6, Fig. 3). Occupied orbitals with more
C11–C16 phenyl ring
p
-systems,
LUSO. There is a greater distortion towards a cumulenic structure
in the C3–C8 phenylene ring in [2-H]+ than in [6-H]+, although
the structural distortion in the C11–C16 ring is far less pronounced.
The spin density distribution calculated for [2-H]+ is informa-
tive when considered alongside similar calculations for [6-H]+
and [7-H]+ (Table 7). Taking the phenyl acetylide complex [6-H]+
as a point of reference, the net spin density on the metal centre
p
p
- (HOMOꢀ2), and metal and Cp (HOMOꢀ3)
character are found only slightly lower in the orbital manifest. The
LUMO can be described in terms of a p⁄ orbital with considerable
character derived from the C3–C8 phenylene ring and lies below
a nest of empty orbitals (LUMO+1, LUMO+2, LUMO+3) associated
with the Ru(PH3)2Cp fragment. A p⁄ orbital more significantly
decreases as the ligand p-system is extended, with a concomitant
increase in the spin density on the conjugated ligand. The tolan
complex [2-H]+ follows the trend established by [6-H]+ and

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W.M. Khairul et al. / Inorganica Chimica Acta 374 (2011) 461–471
[7-H]+, with the total spin density on the metal (0.251) and tolan
ligand (0.495) clearly indicating the substantive role of the conju-
gated ligand in supporting the hole generated on oxidation [26].
The spin density is not distributed evenly throughout the tolan li-
gand, with the C1„C2 ethynyl moiety and C3–C8 ring bearing
some +0.47e as compared with +0.26e for C9„C10 and the
C6H4OMe fragments (Table 7, Fig. 7).
Table 5
Optimised bond lengths (Å) for [2-H]n+, [6-H]n+ and [7-H]n+ (n = 0, 1).
2.5. TD DFT and UV–Vis–NIR spectroelectrochemistry
2-H
[2-H]+
D
6-H
[6-H]+ 7-H
[7-H]+
Ru–P(1, 2) 2.2799 2.3108
+0.0309 2.278 2.324
–0.0605 2.018 1.944
+0.0157 1.228 1.247
2.280 2.309
2.013 1.954
1.230 1.246
1.420 1.385
1.425 1.448
1.444 1.437
1.400 1.407
The calculated electronic structure of the model systems can
also be related to the experimental system through a combination
of TD DFT calculations and electronic spectroscopy. UV–Vis–NIR
spectroelectrochemical studies were conducted to give access to
the electronic spectra of both 2b and [2b]+ (Fig. 8), with assign-
ments made on the basis of comparison with the spectra of
[Ru(C„CC6H4Me-4)(dppe)Cp⁄]n+ (n = 0, 1) and TD DFT calculations
of [2-H]n+ (Table 8). The electronic spectrum of 2b is characterised
Ru–C1
C1„C2
C2–C3
2.0145 1.9540
1.2286 1.2443
1.4205 1.3928 ꢀ0.0277 1.426 1.400
C3–C4
1.4144 1.4280 +0.0136 1.412 1.423
C4–C5
C5–C6
C6–C7
1.3872 1.3759 ꢀ0.0113 1.392 1.386
1.4119 1.4249
1.4120 1.4248
+0.0130 1.398 1.403
+0.0128
C7–C8
C8–C3
C6–C9
1.3873 1.3757 ꢀ0.0116
1.4144 1.4285 +0.0141
1.4207 1.3980 ꢀ0.0227
1.2153 1.2226 +0.0073
1.4213 1.4032 ꢀ0.0181
1.4145 1.4220 +0.0075
by a pronounced
near 26000 cmꢀ1, which is not present in the spectra of simple me-
tal acetylides based on the Ru(dppe)Cp⁄ moiety, and a d p⁄
p–
p–
p⁄ transition characteristic of the tolan ligand
C9„C10
C10–C11
C11–C12
C12–C13
C13–C14
C14–C15
C15–C16
C16–C11
C14–OMe
(pseudo-MLCT) band at higher energy (32100 cmꢀ1) [31]. On oxi-
dation, these transitions which involve the ligand p⁄ system (i.e.
LUMO) as an acceptor shift to higher energy (Table 8, Fig. 3). In
addition, three new, much weaker bands are observed at 21 800,
12 600 and 7500 cmꢀ1. The lowest energy of these bands in [2b]+
are attributed to the symmetry forbidden ‘dd’-type transitions,
1.3842 1.3768 ꢀ0.0074
1.4042 1.4123
1.3987 1.4067
+0.0081
+0.0080
1.3932 1.3847 ꢀ0.0085
1.4071 1.4160 +0.0089
1.3841 1.3625 ꢀ0.0216
Table 6
Energy (eV) and composition (%) of selected orbitals from 2-H and [2-H]+.
eV
Cp
P(1)H3
P(2)H3
Ru
C1
C2
ArC3–C8
C9
C10
ArC11–C16
OMe
2-H
LUMO+4
LUMO+3
LUMO+2
LUMO+1
LUMO
0.17
0
4
16
24
1
4
5
4
24
9
0
10
6
13
0
1
2
1
6
0
10
6
13
0
1
2
1
6
0
74
62
50
2
18
55
19
41
22
0
0
1
8
0
7
11
10
1
10
8
0
0
0
0
0
14
24
8
11
0
0
0
0
0
0
0
0
8
3
0
12
0
0
0
0
0
0
10
8
0
3
0
4
99
0
0
0
0
0
0
2
2
0
11
0
11
0
ꢀ0.06
ꢀ0.23
ꢀ0.86
ꢀ0.88
ꢀ4.63
ꢀ5.40
ꢀ5.51
ꢀ5.95
ꢀ6.48
ꢀ6.60
0
0
41
27
2
8
1
28
10
0
33
0
HOMO
HOMOꢀ1
HOMOꢀ2
HOMOꢀ3
HOMOꢀ4
HOMOꢀ5
[2-H]+
2
0
2
0
24
100
18
0
0
0
0
0
0
Alpha (a)
LUSO+5
LUSO+4
LUSO+3
LUSO+2
LUSO+1
LUSO
ꢀ2.57
ꢀ2.69
ꢀ2.70
ꢀ3.44
ꢀ4.09
ꢀ4.21
ꢀ7.79
ꢀ8.58
ꢀ8.83
ꢀ9.17
ꢀ9.55
ꢀ9.66
1
2
0
20
26
1
2
7
6
31
3
1
15
0
8
13
0
1
2
2
5
1
15
0
8
13
0
1
2
2
5
4
68
0
55
48
3
6
0
0
9
0
11
6
3
8
8
3
0
0
1
0
1
6
13
24
9
18
0
100
0
9
0
0
0
0
5
9
4
0
0
1
1
0
0
0
0
0
11
7
0
0
0
54
0
0
0
0
16
29
24
0
0
82
30
3
0
0
0
0
2
9
11
0
0
0
51
22
10
2
1
5
HOSO
8
HOSOꢀ1
HOSOꢀ2
HOSOꢀ3
HOSOꢀ4
HOSOꢀ5
Beta (b)
LUSO+6
LUSO+5
LUSO+4
LUSO+3
LUSO+2
LUSO+1
LUSO
23
55
41
3
1
2
1
2
1
4
0
0
2
8
3
9
14
11
19
ꢀ2.38
ꢀ2.56
ꢀ2.69
ꢀ3.36
ꢀ3.96
ꢀ4.01
ꢀ6.67
ꢀ8.05
ꢀ8.73
ꢀ9.11
ꢀ9.27
ꢀ9.53
1
0
2
19
2
25
4
3
5
30
8
0
1
0
15
8
0
13
1
1
2
6
2
1
0
15
8
0
13
1
1
2
6
2
5
0
68
56
5
47
19
15
55
44
17
1
4
0
0
9
10
0
9
0
9
7
2
0
0
1
0
0
13
8
26
7
0
14
100
0
0
44
1
25
10
3
1
24
1
6
0
0
0
4
0
4
11
0
0
0
0
0
0
12
0
7
1
0
0
63
0
0
0
19
0
13
35
0
0
18
97
2
0
0
0
2
0
3
14
0
0
HOSO
HOSOꢀ1
HOSOꢀ2
HOSOꢀ3
HOSOꢀ4
6
0
1
0
9
0
13
0
0
0
0

W.M. Khairul et al. / Inorganica Chimica Acta 374 (2011) 461–471
467
Fig. 4. The (a) a-HOSO and (b) a
-LUSO of [2-H]+.
Fig. 3. The (a) HOMOꢀ2, (b) HOMOꢀ1, (c) HOMO, (d) LUMO, (e) LUMO+1, (f)
LUMO+2, (g) LUMO+3, (h) LUMO+4 from 2-H. In this and all subsequent figures,
orbitals are plotted with contour values at 0.04 (e/bohr3)1/2
.
which, given the mixing of metal and ethynyl orbitals that charac-
terise the occupied frontier orbitals of ruthenium acetylide com-
plexes, should probably be described as a dp/dp transition. The
Fig. 5. The (a) b-[HOSOꢀ6], (b) b-[HOSOꢀ1], (c) b-HOSO, (d) b-LUSO, (e) b-
[LUSO+1], (f) b-[LUSO+2] of [2-H]+.

468
W.M. Khairul et al. / Inorganica Chimica Acta 374 (2011) 461–471
Table 8
Summary of observed electronic transition in 2 and [2]+ from spectroelectrochemical
studies (CH2Cl2/0.1 M [NBu4]PF6), and results of TD DFT calculations on the models 2-
H and [2-H]+.
2
2-H
Electronic transitions (cmꢀ1) (Molar extinction coefficient / Mꢀ1 cmꢀ1 or
calculated oscillator strength)
HOMO ? LUMO
HOMOꢀ2 ? LUMO
26 200 (18 000)
34 100 (19 900)
[2]+
28 000 (1.6306)
34 700 (0.2996)
[2-H]+
Fig. 6. The model complexes 6-H and 7-H [26].
b-HOSOꢀ1 ? b-LUSO
b-HOSO ? b-LUSO
7500 (60)
12 600 (1300)
21 800 (1890)
7700 (0.000)
Table 7
9700 (0.7137)
21 900 (0.5118)
23 000 (0.3181)
26 400 (0.3980)
Calculated spin density distribution in the model radical cations [2-H]+, [6-H]+ and [7-
H]+ (B3LYP/3-21G⁄) [31].
a
-HOSO ?
b-HOSOꢀ6 ? b-LUSO
b-HOSO ? b-LUSO+2
a-LUSO
32 100 (18 700)
[2-H]+
[6-H]+
[7-H]+
Cp
P
Ru
C1
0.030
0.003
0.251
0.083
0.148
0.234
ꢀ0.020
0.111
0.170
0.041
0.000
0.413
0.043
0.269
0.246
0.021
0.000
0.220
0.079
0.114
0.598
dic redox character of these complexes is not well described in
terms of simple Ru(II/III) pairs, but rather descriptions of the oxida-
tive electrochemistry should acknowledge the involvement of the
conjugated carbon-rich ligand in the oxidation process.
C2
C6H4/C6H5/C14H9
C9
C10
C6H4OMe
4. Experimental
4.1. General conditions
All reactions were carried out under an atmosphere of nitrogen
using standard Schlenk techniques. Reaction solvents were puri-
fied and dried using an Innovative Technology SPS-400, and de-
gassed before use. No special precautions were taken to exclude
air or moisture during work-up. The compounds [RuCl(PPh3)2Cp]
[62], [RuCl(dppe)Cp⁄] [63] and the ligand precursors Me3SiC„
CC6H4C„CSiMe3 [64], HC„CC6H4C„CSiMe3 [65], HC„CC6H4C„
CC6H4R (R = Me, NO2, CO2Me, OMe) and their trimethylsilyl pro-
tected analogues were prepared by literature routes [66,67]. Other
reagents were purchased and used as received. All E values in Volt
versus SCE from CH2Cl2 solutions containing 0.1 M [NBu4]PF6 elec-
trolyte, using an air-tight three-electrode cell with Pt working,
Fig. 7. A plot of the spin density calculated for [2-H]+.
counter and pseudo-reference electrodes,
m
= 100 mV sꢀ1 at 20 °C.
The decamethyl ferrocene/decamethyl ferrocenium (Fc⁄/Fc⁄+) cou-
ple was used as an internal reference for potential measurements
(Fc⁄/Fc⁄+ taken as ꢀ0.02 V versus SCE in CH2Cl2/0.1 M [NBu4]PF6)b
D
Ep = |Epa ꢀ Epc|. Spectroelectrochemical experiments in CH2Cl2/
0.1 M [NBu4]PF6 were conducted in a manner similar to that de-
scribed elsewhere [30,31].
NMR spectra were recorded on
400.13 MHz, 13C 100.61 MHz, 31P 161.98 MHz) or Varian Mercury
31P 161.91 MHz) spectrometers from CDCl3 solutions and refer-
enced against solvent resonances (1H, 13C) or external H3PO4
31P). IR spectra were recorded using a Nicolet Avatar spectrometer
a
Bruker Avance (1H
(
(
from Nujol mull suspended between NaCl plates. Electrospray ion-
isation mass spectra were recorded using Thermo Quest Finnigan
Trace MS-Trace GC or WATERS Micromass LCT spectrometers.
Samples in dichloromethane (1 mg/mL) were 100 times diluted
in either methanol or acetonitrile, and analysed with source and
desolvation temperatures of 120 °C, with cone voltage of 30 V.
High resolution spectra were recorded using a Thermo Electron
Finnigan LTQ FT mass spectrometer with capillary temperature
275 °C and capillary voltage 100 V.
Fig. 8. The UV–Vis–NIR spectra of 2b (solid line) and [2b]+ (broken line) collected
from a spectroelectrochemical experiment (CH2Cl2/0.1 M NBu4PF6).
12 600 cmꢀ1 band has significant b-HOSO ? b-LUSO character, and
is an LMCT-like transition, whilst the band at 21 800 cmꢀ1 has
p–
p⁄ character. The band at 32 100 cmꢀ1 retains the d p⁄ (pseudo
p–
MLCT) character noted for 2-H, and is shifted somewhat to lower
energy as a result of the significant tolan ligand-character in the re-
dox and acceptor orbitals.
4.2. Preparative work
3. Conclusion
4.2.1. Alternative preparation of [Ru(C„CC6H4C„CSiMe3)(PPh3)2Cp]
(1a)
The combination of crystallographic, spectroscopic and compu-
tational work demonstrates that the tolan ligand in complexes
such as 2–5 has significant redox non-innocent character. The ano-
A
solution of [RuCl(PPh3)2Cp] (103 mg, 0.142 mmol),
HC„CC6H4C„CSiMe3 (37 mg, 0.18 mmol) and NH4PF6 (48 mg,

W.M. Khairul et al. / Inorganica Chimica Acta 374 (2011) 461–471
469
0.30 mmol) in MeOH (10 ml) was heated at reflux for 3.5 h. Treat-
4.2.5. Preparation of [Ru(C„CC6H4C„CC6H4Me)(PPh3)2Cp] (3a)
ment of the dark solution with four drops of DBU gave a fine yellow
precipitate which was collected by filtration, washed with MeOH
(5 ml), and air-dried to afford 1a as a yellow solid (42 mg,
A
solution of [RuCl(PPh3)2Cp] (100 mg, 0.14 mmol),
HC„CC6H4C„CC6H4Me (44 mg, 0.15 mmol) and KF (1.2 mg,
0.021 mmol) in MeOH (10 ml) was heated at reflux for 20 min to
form a bright yellow precipitate, which was collected by filtration,
washed with MeOH (3 ml), and air-dried to afford a yellow solid
(82 mg, 0.090 mmol, 63%). Recrystallisation from CH2Cl2/MeOH
0.047 mmol, 33%). IR: m
(C„C) 2080, 2153 cmꢀ1.1H NMR: d 0.26
(s, 9H, SiMe3); 4.34 (s, 5H, Cp); 6.99–7.49 (m, 34H, Ar). 31P{1H}
NMR: d 51.3 (s, PPh3). ES(+)-MS (m/z): 888, [M+H]+.
gave bright yellow crystals of 3a. IR:
m .
(C„C) 2063, 2212 cmꢀ1
1H NMR: d 2.36 (s, 3H, Me); 4.33 (s, 5H, Cp); 7.03–7.49 (m, 38H,
Ar). 13C{1H} NMR: d 21.7 (Me), 85.5 (Cp); 89.6, 90.2 (C9, C10);
115.4, 117.4, 121.0 (C2, C3, C6); 123.2 (t, JCP = 25 Hz, C1); 127.5
4.2.2. Preparation of [Ru(C„CC6H4C„CSiMe3)(dppe)Cp⁄] (1b)
A
suspension of [RuCl(dppe)Cp⁄] (102 mg, 0.15 mmol),
(dd, JCP/6JCP ꢃ5 Hz, Cm); 128.7 (Cp); 128.8 (C11); 129.3, 130.3,
Me3SiC„CC6H4C„CSiMe3 (54 mg, 0.20 mmol), and KF (10 mg,
0.17 mmol) in MeOH (10 ml) was heated at reflux for 3.5 h under
a nitrogen atmosphere. The yellow precipitate formed was col-
lected by filtration, washed with MeOH and hexanes, and air-dried
to afford 1b as a yellow powder (57 mg, 0.068 mmol, 45%). IR:
3
131.1, 131.5 (C4, C5, C12, C13); 134.0 (dd, JCP/5JCP ꢃ5 Hz, Co);
2
137.9 (C14); 139.0 (dd, JCP/4JCP ꢃ11 Hz Ci). 31P{1H} NMR: d 51.3
1
(s, PPh3). ES(+)-MS (m/z): 906, M+; 691 [MꢀC17H11]+. Found: C,
76.17; H 5.03%. C58H46P2Ru requires: C, 76.91; H, 5.08%.
m
(C„C) 2058, 2149 cmꢀ1 1H NMR: d 0.29 (s, 9H, SiMe3); 1.62 (s,
.
15H, Cp⁄); 2.21 (2 ꢂ dd, 2H, JHP = JHH = 7 Hz); 2.83 (2 ꢂ dd, 2H,
JHP = JHH = 7 Hz); 6.65 (pseudo-d, JHH = 8 Hz, 2H, C6H4); 7.10 (pseu-
do-d, JHH = 8 Hz, 2H, C6H4); 7.18–7.79 (m, 20H, Ar). 13C{1H} NMR: d
4.2.6. Preparation of [Ru(C„CC6H4C„CC6H4Me)(dppe)Cp⁄] (3b)
A
solution of [RuCl(dppe)Cp⁄] (100 mg, 0.15 mmol),
HC„CC6H4C„CC6H4Me (32 mg, 0.15 mmol) and NH4PF6 (24 mg,
0.15 mmol) in MeOH (10 ml) was heated at reflux for 30 min to
form a bright yellow precipitate in red-coloured solution, at which
point 2–3 drops of DBU were added to form more yellow precipi-
tate which was collected by filtration, washed with cold MeOH
(3 ml), and air-dried to afford 3b as a yellow solid (84 mg,
0.14 (s, SiMe3); 10.0 (Me at Cp); 29.4 (dd, JCP CCP
89.3, 90.6 (C9, C10); 92.6 (Cp); 106.7, 110.9, 116.1 (C2, C3, C6);
/
ꢃ23 Hz, CH2);
127.0, 127.3 (dd, JCP CCP
/
ꢃ5 Hz, Cm;m0); 128.7 (Cp;p0); 129.3,
130.3 (C4, C5); 133.4, 133.1 (dd, JCP CCP
/
ꢃ5 Hz, Co;o0); 135.6 (t,
JCP = 25 Hz, C1); 138.4, 138.7 (m, Ci;i0). 31P{1H} NMR: d 81.8 (s,
dppe). ES(+)-MS (m/z): 833, [M+H]+.
0.099 mmol, 66%). IR: m .
(C„C) 2062, 2206 cmꢀ1 1H NMR: d 1.56
(s, 15H, Cp⁄); 2.08 (2 ꢂ dd, 2H, JHP = JHH = 8 Hz); 2.68 (2 ꢂ dd, 2H,
JHP = JHH = 8 Hz); 3.82 (s, 3H, Me); 6.70 (pseudo-d, JHH = 8 Hz, 2H,
C6H4); 6.86 (pseudo-d, JHH = 8 Hz, 2H, C6H4); 7.16–7.34 (m, 20H
Ar); 7.43 (pseudo-d, JHH = 8 Hz, 2H, C6H4); 7.75 (pseudo-d,
JHH = 8 Hz, 2H, C6H4). 13C{1H} NMR: d 10.3 (Me at Cp); 21.7 (Me);
4.2.3. Preparation of [Ru(C„CC6H4C„CC6H4OMe)(PPh3)2Cp] (2a)
A
solution of [RuCl(PPh3)2Cp] (100 mg, 0.14 mmol),
HC„CC6H4C„CC6H4OMe (44 mg, 0.21 mmol) and NH4PF6
(44 mg, 0.14 mmol) in MeOH (10 ml) was heated at reflux for
30 min to form a bright yellow precipitate in red-coloured solution,
2–3 drops of DBU was added to form more yellow precipitate
which was collected by filtration, washed with cold MeOH (3 ml),
and air-dried to afford 2a as a yellow solid (101 mg, 0.11 mmol,
78%). Recrystallisation from CHCl3/hexane yields bright yellow
29.6 (dd, JCP CCP
/
ꢃ23 Hz, CH2); 89.3, 90.4 (C9, C10); 92.9 (Cp);
111.1, 116.7, 121.1 (C2, C3, C6); 127.7, 127.5 (dd, JCP CCP
/
ꢃ5 Hz,
Cm;m0); 128.8 (Cp;p0); 129.4 (C11); 129.3, 130.3, 131.1, 131.5 (C4,
C5, C12, C13); 133.2, 133.5 (dds, JCP CCP
/
ꢃ5 Hz, Co;o0); 135.6 (t,
JCP = 25 Hz, C1); 137.9 (C14); 138.4, 138.7 (m, Ci;i0). 31P{1H} NMR:
d 81.8 (s, dppe). ES(+)-MS (m/z): 851, [M+H]+.
crystals of 2a. IR: m
(C„C) 2064, 2215 cmꢀ1.1H NMR (400 MHz): d
3.99 (s, 3H, OMe), 4.50 (s, 5H, Cp), 7.03–7.64 (m, 38H, Ar).
13C{1H} NMR (125.7 MHz): d 55.5 (OMe), 85.5 (Cp); 89.3, 89.5
(C9, C10); 114.2 (C13); 115.4, 116.3, 117.5 (C2, C3, C6); 122.8 (t,
4.2.7. Preparation of [Ru(C„CC6H4C„CC6H4CO2Me)(PPh3)2Cp] (4a)
A
solution of [RuCl(PPh3)2Cp] (100 mg, 0.14 mmol),
3
HC„CC6H4C„CC6H4CO2Me (54 mg, 0.21 mmol) and NH4PF6
(44 mg, 0.27 mmol) in MeOH (10 ml) was heated at reflux for
30 min to form a bright yellow precipitate in red-coloured solution,
at which point the addition of 2–3 drops DBU to form more yellow
precipitate which was collected by filtration, washed with cold
MeOH (3 ml), and air-dried to afford 4a as a yellow solid (95 mg,
0.01 mmol, 71%). Recrystallisation from CHCl3/hexane giving
JCP = 25 Hz, C1); 127.5 (dd, JCP/6JCP ꢃ5 Hz, Cm); 128.7 (Cp); 130.6,
2
131.2, 133.1 (C4, C5, C12); 131.3 (C11); 134.1 (dd, JCP/5JCP ꢃ5 Hz,
1
Co); 139.0 (dd, JCP/4JCP ꢃ11 Hz Ci); 159.5 (C14). 31P{1H} NMR: d
51.3 (s, PPh3). ES(+)-MS (m/z): 945, [M+Na]+; 923, [M+H]+; 691,
[MꢀC17H11O]+.
4.2.4. Preparation of [Ru(C„CC6H4C„CC6H4OMe)(dppe)Cp⁄] (2b)
bright yellow crystals of 4a. IR: m(C„C) 2064, 2202; (C@O)
A
solution of [RuCl(dppe)Cp⁄] (100 mg, 0.15 mmol),
1724 cmꢀ1 1H NMR: d 3.92 (s, 3H, OMe); 4.33 (s, 5H, Cp); 7.05–
.
HC„CC6H4C„CC6H4OMe (35 mg, 0.15 mmol) and NH4PF6
(24 mg, 0.15 mmol) in MeOH (10 ml) was heated at reflux for
30 min to form a bright yellow precipitate in red-coloured solution,
at which point 2–3 drops of DBU were added to form more yellow
precipitate which was collected by filtration, washed with cold
MeOH (3 ml), and air-dried to afford 2b as a yellow solid (81 mg,
8.01 (m, 38H, Ar). 13C{1H} NMR: d 52.4 (OMe); 85.5 (Cp); 89.0,
94.3 (C9, C10); 115.6, 116.5 (C2, C3); 125.1 (t, JCP = 25 Hz, C1);
3
127.5 (dd, JCP/6JCP ꢃ5 Hz, Cm); 128.8 (Cp); 129.0, 129.1, 132.3
(C6, C11, C14); 129.7, 130.4, 131.5, 131.5 (C4, C5, C12, C13);
2
1
134.0 (dd, JCP/5JCP ꢃ5 Hz, Co); 138.9 (dd, JCP/4JCP ꢃ11 Hz, Ci);
166.9 (C@O). 31P{1H} NMR: d 51.3 (s, PPh3). ES(+)-MS (m/z): 950,
M+; 691, [MꢀC18H11O2]+.
0.094 mmol, 63%). IR: m .
(C„C) 2061, 2206 cmꢀ1 1H NMR: d 1.56
(s, 15H, Cp⁄); 2.09 (2 ꢂ dd, 2H, JHP = JHH = 6 Hz); 2.68 (2 ꢂ dd, 2H,
JHP = JHH = 6 Hz); 3.30 (s, 3H, OMe); 6.68 (pseudo-d, JHH = 8 Hz,
2H, C6H4); 7.11 (pseudo-d, JHH = 8 Hz, 2H, C6H4); 7.17–7.75 (m,
4.2.8. Preparation of [Ru(C„CC6H4C„CC6H4CO2Me)(dppe)Cp⁄] (4b)
A
solution of [RuCl(dppe)Cp⁄] (100 mg, 0.15 mmol),
24H Ar). 13C{1H} NMR: d 10.0 (Me at Cp); 29.5 (dd, JCP CCP
/
HC„CC6H4C„CC6H4CO2Me (39 mg, 0.15 mmol) and NH4PF6
(24 mg, 0.15 mmol) in MeOH (10 ml) was heated at reflux for
20 min to form a bright yellow precipitate in red-coloured solution,
at which point 2–3 drops of DBU were added to form more yellow
precipitate which was collected by filtration, washed with cold
MeOH (3 ml), and air-dried to afford 4b as a yellow solid (66 mg,
ꢃ23 Hz, CH2); 55.5 (s, OMe); 89.1, 89.6 (C9, C10); 92.5 (Cp);
111.0, 114.1, 116.4 (C2, C3, C6); 114.2 (C13), 127.7, 127.5 (dd,
JCP CCP
/
ꢃ5 Hz, Cm;m0); 128.8 (Cp;p0); 130.3, 131.0, 133.0 (C4, C5,
C12); 131.4 (C11); 133.8, 133.2 (dd, JCP CCP
/
ꢃ5 Hz, Co;o0); 135.3
(t, JCP = 25 Hz, C1); 137.1, 139.0 (m, Ci;i0); 159.4 (C14). 31P{1H}
NMR: d 81.8 (s, dppe). ES(+)-MS (m/z): 867, [M+H]+.
0.074 mmol, 49%). IR: m .
(C„C) 2061, 2208; (C@O) 1717 cmꢀ1 1H

470
W.M. Khairul et al. / Inorganica Chimica Acta 374 (2011) 461–471
NMR: d 1.56 (s, 15H, Cp⁄); 2.08 (2 ꢂ dd, 2H, JHP = JHH = 6 Hz); 2.68
(2 ꢂ dd, 2H, JHP = JHH = 6 Hz); 3.92 (s, 3H, OMe); 6.70 (pseudo-d,
JHH = 8 Hz, 2H, C6H4); 7.19–7.74 (m, 22H, Ar); 7.52 (pseudo-d,
JHH = 8 Hz, 2H, C6H4); 7.98 (pseudo-d, JHH = 8 Hz, 2H, C6H4).
l . Reflections (32 842) were collected yielding
= 0.516 mmꢀ1
11 440 unique data (Rmerg = 0.0420). Final wR2(F2) = 0.1091 for all
data (568 refined parameters), conventional R1 (F) = 0.0488 for
10 246 reflections with I ꢄ 2r, GOF = 1.152.
13C{1H} NMR: d 10.0 (Me at Cp); 29.5 (dd, JCP CCP
/
ꢃ23 Hz, CH2);
52.4 (s, OMe); 88.8, 94.6 (C9, C10); 92.5 (Cp); 111.4, 115.8 (C2,
4.3.2. Crystal data for 4a
ꢃ5 Hz, Cm;m0); 128.9, 129.1, 132.3
ꢀ
C3); 127.2, 127.7 (dd, JCP CCP
/
C
59H46O2P2Ru ꢂ 2CHCl3, M = 1188.70, triclinic, space group P1,
(C6, C11, C14); 129.7, 130.7, 131.3, 131.4 (C4, C5, C12, C13);
a = 8.8607(14), b = 16.062(3), c = 20.357(3) Å,
99.969(3),
Dcalc = 1.477 mg mꢀ3 = 0.698 mmꢀ1. Reflections (26 680) were
l
a
= 108.503(3), b =
128.8 (Cp;p0); 133.2, 133.8 (dd, JCP CCP
/
ꢃ5 Hz, Co;o0); 137.8 (t,
c
= 95.193(3)°, U = 2673.0(7) Å3, F(0 0 0) = 1212, Z = 2,
JCP = 25 Hz, C1); 137.1, 139.0 (m, Ci;i0); 167.0 (C@O). 31P{1H}
NMR: d 81.8 (s, dppe). ES(+)-MS (m/z): 895, [M+H]+.
,
collected yielding 12 781 unique data (Rmerg = 0.031). Final
wR2(F2) = 0.2104 for all data (636 refined parameters), conven-
4.2.9. Preparation of [Ru(C„CC6H4C„CC6H4NO2)(PPh3)2Cp] (5a) [45]
tional R1 (F) = 0.0825 for 11 206 reflections with I ꢄ 2
r, GOF =
A
solution of [RuCl(PPh3)2Cp] (100 mg, 0.14 mmol),
1.124.
HC„CC6H4C„CC6H4NO2 (51 mg, 0.21 mmol) and NH4PF6 (44 mg,
0.14 mmol) in MeOH (10 ml) was heated at reflux for 30 min to
form a bright red precipitate. The addition of 2–3 drops DBU gave
more red precipitate, which was collected by filtration, washed
with cold MeOH (3 ml), and air-dried to afford 5a as a red solid
(87 mg, 0.093 mmol, 66%). Recrystallisation from CHCl3/MeOH
4.3.3. Crystal data for 5a
C57H43O2P2Ru, M = 936.93, monoclinic, space group P21/c,
a = 8.9330(11), b = 26.063(3), c = 18.991(2) Å, b = 91.754(3)°, U =
4419.5(9) Å3, F(0 0 0) = 1928, Z = 4, Dcalc = 1.408 mg mꢀ3
, l = 0.473
mmꢀ1. Reflections (36 023) were collected yielding 13 273 unique
data (Rmerg = 0.0401). Final wR2(F2) = 0.0998 for all data (568 re-
fined parameters), conventional R1 (F) = 0.0422 for 9945 reflections
gave bright red crystals of 5a. IR: m .
(C„C) 2063, 2200 cmꢀ1 1H
NMR: d 4.34 (s, 5H, Cp); 7.08–8.52 (m, 38H, Ar). 13C{1H} NMR: d
85.6 (Cp); 88.2, 97.1 (C9, C10); 115.8, 115.9 (C2, C3); 123.9
with I ꢄ 2r, GOF = 1.029.
3
(C13); 126.9 (t, JCP = 25 Hz, C1); 127.5 (dd, JCP/6JCP ꢃ5 Hz, Cm);
128.8 (Cp); 130.8, 131.3 (C6, C11); 131.7, 132.1, 132.6 (C4, C5,
C12); 134.1 (dd, 2JCP/5JCP ꢃ5 Hz, Co); 138.9 (dd, 1JCP/4JCP ꢃ11 Hz Ci);
146.7 (C14). 31P{1H} NMR: d 51.3 (s, PPh3). ES(+)-MS (m/z): 938,
[M+H]+; 691, [MꢀC16H8NO2]+.
Acknowledgements
We thank the EPSRC, ONENorthEast and Durham University for
funding this work. W.M.K. held scholarships from the Human Re-
sources Development in Science and Technology Programme, Min-
istry of Science, Technology and Innovation, Malaysia. P.J.L. holds
an EPSRC Leadership Fellowship.
4.2.10. Preparation of [Ru(C„CC6H4C„CC6H4NO2)(dppe)Cp⁄] (5b)
A
solution of [RuCl(dppe)Cp⁄] (100 mg, 0.15 mmol),
HC„CC6H4C„CC6H4NO2 (37 mg, 0.15 mmol) and NH4PF6 (24 mg,
0.15 mmol) in MeOH (10 ml) was heated at reflux for 30 min to
form a bright red precipitate, 2–3 drops of DBU were added to form
more red precipitate which was collected by filtration, washed
with cold MeOH (3 ml), and air-dried to afford 5b as a red solid
Appendix A. Supplementary material
CCDC 811043, 811044, 811045 contain the supplementary crys-
tallographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
http://www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version, at
doi:10.1016/j.ica.2011.02.043.
(66 mg, 0.075 mmol, 50%). IR: m .
(C„C) 2063, 2207 cmꢀ1 1H NMR:
d 1.56 (s, 15H, Cp⁄); 2.10 (2 ꢂ dd, 2H, JHP = JHH = 6 Hz, CH2), 2.69
(2 ꢂ dd, 2H, JHP = JHH = 6 Hz, CH2); 6.72 (pseudo-d, JHH = 8 Hz, 2H,
C6H4); 7.20–7.34 (m, 20H, Ar); 7.60 (pseudo-d, JHH = 9 Hz, 2H,
C6H4); 7.74 (pseudo-d, JHH = 8 Hz, 2H, C6H4); 8.20 (pseudo-d,
JHH = 9 Hz, 2H, C6H4). 13C{1H} NMR: d 10.0 (Me at Cp); 29.5 (dd,
References
JCP CCP
/
ꢃ23 Hz, CH2); 87.8, 97.1 (C9, C10); 92.5 (Cp); 111.6, 114.8
(C2, C3); 123.6 (C13); 127.5, 127.2 (dd, JCP CCP
/
ꢃ5 Hz, Cm;m0);
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