Additions and intramolecular migrations of nucleophiles in cationic diruthenium μ-allenyl complexes

Article abstract of DOI:10.1016/j.jorganchem.2007.06.029

The diruthenium μ-allenyl complex [Ru₂(CO)(NCMe)(μ-CO){μ-η¹:η²-C(H){double bond, long}C{double bond, long}C(Me)(Ph)}(Cp)₂][BF₄], 3b, reacts with halide anions to yield the neutral derivatives [Ru₂(CO)₂(X){μ-η¹:η²-C(H){double bond, long}C{double bond, long}C(Me)(Ph)}(Cp)₂] [X = Cl, 4b; X = Br, 4c; X = I, 4d]. Complex 4b undergoes isomerization to the unprecedented bridging vinyl-chlorocarbene species [Ru₂(CO)(μ-CO){μ-η¹:η³- C(Cl)C(H){double bond, long}C(Me)(Ph)}(Cp)₂], 10, upon filtration of a CH₂Cl₂ solution through an alumina column. Complex 3b reacts with an excess of NaBH₄ to give five products: the allene complex [Ru₂(CO)₂{μ-η²:η²- CH₂{double bond, long}C{double bond, long}C(Me)(Ph)}(Cp)₂], 5; the hydride species trans-[Ru₂(CO)₂(μ-H){μ-η¹:η²-CH{double bond, long}C{double bond, long}C(Me)(Ph)}(Cp)₂], 6, and cis-[Ru₂(CO)₂(μ-H){μ-η¹:η²-CH{double bond, long}C{double bond, long}C(Me)(Ph)}(Cp)₂], 8; the vinyl-alkylidene [Ru₂(CO)(μ-CO){μ-η¹:η³- C(H)C(H){double bond, long}C(Me)(Ph)}(Cp)₂], 9; and the cluster [Ru₃(CO)₃(μ-H)₃(Cp)₃], 7. Studies on the thermal stabilities of 5, 6, 8 and 9 have suggested a plausible mechanism for the formation of these complexes and for the synthesis of 10.

Full text of DOI:10.1016/j.jorganchem.2007.06.029

Journal of Organometallic Chemistry 692 (2007) 4119–4128
www.elsevier.com/locate/jorganchem
Additions and intramolecular migrations of nucleophiles
in cationic diruthenium l-allenyl complexes
a
b, ,1
*
Selby A.R. Knox , Fabio Marchetti
a
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
Dipartimento di Chimica e Chimica Industriale, Via Risorgimento 35, 56126 Pisa (I), Italy
b
Received 23 April 2007; received in revised form 19 June 2007; accepted 19 June 2007
Available online 26 June 2007
Abstract
The diruthenium l-allenyl complex [Ru2(CO)(NCMe)(l-CO){l-g1:g2-C(H)@C@C(Me)(Ph)}(Cp)2][BF4], 3b, reacts with halide
anions to yield the neutral derivatives [Ru2(CO)2(X){l-g1:g2- C(H)@C@C(Me)(Ph)}(Cp)2] [X = Cl, 4b; X = Br, 4c; X = I, 4d]. Complex
4b undergoes isomerization to the unprecedented bridging vinyl-chlorocarbene species [Ru2(CO)(l-CO){l-g1:g3- C(Cl)C(H)@
C(Me)(Ph)}(Cp)2], 10, upon filtration of a CH2Cl2 solution through an alumina column.
Complex 3b reacts with an excess of NaBH4 to give five products: the allene complex [Ru2(CO)2{l-g2:g2- CH2@C@
C(Me)(Ph)}(Cp)2], 5; the hydride species trans-[Ru2(CO)2(l-H){l-g1:g2-CH@C@C(Me)(Ph)}(Cp)2], 6, and cis-[Ru2(CO)2(l-H){l-
g1:g2-CH@C@C(Me)(Ph)}(Cp)2], 8; the vinyl-alkylidene [Ru2(CO)(l-CO){l-g1:g3- C(H)C(H)@C(Me)(Ph)}(Cp)2], 9; and the cluster
[Ru3(CO)3(l-H)3(Cp)3], 7.
Studies on the thermal stabilities of 5, 6, 8 and 9 have suggested a plausible mechanism for the formation of these complexes and for
the synthesis of 10.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Diruthenium complexes; Allenyl; Bridging vinyl-chlorocarbene; Bridging hydride; Hydride migration
1. Introduction
ion, with coordination through the Ca and Cb carbons
[1a,6]; however, alternative modes of coordination have
been reported [1a,2d,7].
Allenyl ligands ½ꢀCaðRÞ@Cb@CcðR0ÞðR00Þꢁ coordinated
in mono- [1], di- [1a,2] and poly-nuclear complexes [1a,3]
have been the subject of much interest in recent years. In
particular, di- and poly-nuclear species have attracted con-
siderable attention: the unsaturated C3 chain readily under-
goes coupling reactions with organic fragments [4],
providing an easy route for the synthesis of new multi-
site-bound hydrocarbyl ligands [1a,2b,4,5].
Common methods of synthesis include nucleophilic sub-
stitution on propargyl halides [8] and C–C bond formation
by reaction with diazocompounds [9]. A further strategy
for the preparation of l-g1:g2 allenyl complexes was
recently reported [10], whereby the diruthenium com-
plexes [Ru2(CO)(l-CO){l-g1:g3-Ca(H)CbCc(OH)(Me)(R)-
C(O)}(Cp)2] [R = Me, 1a; R = Ph, 1b], prepared from the
cyclopentenone adduct [Ru2(CO)(l-CO){l-g1:g3-C(Ph)-
C(Ph)C(O)}(Cp)2] by alkyne exchange [11], are treated
with HBF4, resulting in formation of the allenyl [Ru2-
(CO)2(l-CO){l-g1: g2-Ca(H)@Cb@Cc(Me)(R)}(Cp)2][BF4]
[R = Me, 2a; R = Ph, 2b] (Scheme 1) [12].
Allenyls display a variety of coordination modes. The
most common in dinuclear complexes is the [l-g1:g2] fash-
*
Corresponding author. Tel.: +39 050 2219245.
Preliminary studies on the chemistry of 2 have shown
that the allenyl ligand is reactive towards neutral organic
E-mail address: fabmar@dcci.unipi.it (F. Marchetti).
Born in 1974 in Bologna, Italy.
1
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.06.029

4120
S.A.R. Knox, F. Marchetti / Journal of Organometallic Chemistry 692 (2007) 4119–4128
molecules such as alkynes and diazocompounds [12].
Moreover, compounds 2a–b react readily with CH3CN/
Me3NO to give the acetonitrile adducts [Ru2(CO)(NC-
Me)(l-CO){l-g1:g2-C(H)@C@C(Me)(R)}(Cp)2][BF4]
[R = Me, 3a; R = Ph, 3b], see Scheme 1.
2. Results and discussion
2.1. Reactivity of acetonitrile derivatives of diruthenium
allenyl complexes with NaBH4
The chemistry of the derivatives 3 offers promise in
that acetonitrile often acts as a labile ligand in organome-
tallic chemistry. For dinuclear species acetonitrile removal
is a crucial step in allowing coordination, at one of
the two metal centres, of either anionic nucleophiles
such as hydride, halides and pseudo-halides [13], or neu-
tral organic fragments [14]. In a number of cases this sub-
stitution is the precursor of an intramolecular coupling
reaction involving the species introduced and the pre-
existing bridging hydrocarbyl ligand; these reactions, par-
ticularly those leading to carbon–carbon bond formation,
have attracted interest because they may act as models for
heterogeneously catalyzed processes occurring on metal
surfaces [14a,14e].
It has been previously demonstrated that complex 3a
undergoes nucleophilic substitution under mild conditions
by chloride ion, towards which 2a–b are completely unreac-
tive, affording the neutral allenyl derivative [Ru2(CO)2-
(Cl){l-g1:g2-C(H)@C@CMe2}(Cp)2], 4a (Scheme 1), the
structure of which has been determined by X-ray diffrac-
tion [12]. We report herein our studies on the reactivity of
3b towards hydride and halide ions, aimed at exploring
the possibility of coupling reactions between the allenyl
ligand and species introduced to the metal centre by nitrile
removal.
The acetonitrile compound [Ru2(CO)(NCMe)(l-CO)-
{l-g1:g2-C(H)@C@C(Me)(Ph)}(Cp)2][BF4], 3b, is obtained
rapidly by treating a dichloromethane solution of 2b with
1 equiv. of Me3NO dissolved in acetonitrile (Scheme 2).
Complex 3b was characterized by IR spectroscopy and
used in situ for subsequent reactions with nucleophiles.
The IR spectrum of 3b (in CH2Cl2 solution) shows two
bands at 2005 and 1870 cmꢀ1, corresponding to the pres-
ence of one terminal and one semi-bridging carbonyl
ligands, respectively. Complex 3b probably exists as mix-
tures of interconverting isomers, due to r, p and cis/trans
fluxionality [10,12], allowing the NCMe ligand to be bound
at either ruthenium atom.
The reaction of 3b, in THF solution, with NaBH4 was
investigated. IR spectroscopy revealed, after 1 h, the complete
disappearance of the starting material, and subsequent
removal of the solvent gave a yellow-brown residue. The IR
spectrum of this (in CH2Cl2 solution) exhibited two absorp-
tions at 1981 cmꢀ1 (s) and 1919 cmꢀ1 (vs). The residue was
chromatographed on an alumina column maintained at
ꢀ35 ꢁC, leading to the separation of five products (see Scheme
3): [Ru2(CO)2{l-g2:g2-CH2@C@C(Me)(Ph)}(Cp)2], 5; trans-
[Ru2(CO)2(l-H){l-g1:g2-CH@C@C(Me)(Ph)}(Cp)2], 6;
[Ru3(CO)3(l-H)3(Cp)3], 7; cis-[Ru2(CO)2(l-H){l-g1:g2-
CH@C@C(Me)(Ph)}(Cp)2], 8; and [Ru2(CO)- (l-CO){l-
g1:g3-C(H)C(H)@C(Me)(Ph)}(Cp)2], 9. Complex 7, the
formation of which appears to be the consequence of some
fragmentation (yield 7%), is a known species [15], and was
identified by IR spectroscopy and mass spectrometry, in
addition to its characteristic deep blue colour. The new
compounds 5, 6, 8 and 9 have been fully characterized by
IR and NMR spectroscopy, elemental analysis and mass
spectrometry.
+
R
Me
Cγ(Me)(R)(OH)
Cγ
H
Cβ
H
Cβ
O
Cα
Ru
Cα
Ru
C
O
O
O
C
C
HBF4
C
Ru
Ru
Complex 5 is the formal result of nitrile displacement
and hydride attack on the Ca Carbon of the allenyl unit
of 3b. The complex consists of a [Ru2(Cp)2(CO)2] core,
with the two carbonyls occupying terminal sites at each
metallic centre, and an allene ligand which is coordinated
to the ruthenium atoms through its p bonds. Dinuclear
C
C
O
O
R
Me
Ph
1a
1b
2a
2b
MeCN, Me3NO
+
+
R
R
+
Ph
Cγ
Ph
Cγ
Me
Me
Cγ
Me
Cγ
Me
H
H
Cβ
Cβ
H
Cβ
H
Cβ
LiCl
Cα
Ru
Cα
Cα
Ru
Cα
Ru
O
O
NCMe
Cl
O
C
MeCN
O
C
C
O
C
MeCN
C
Ru
Ru
Ru
Ru
Ru
Me3NO
C
C
C
C
O
O
O
O
4a R = Me
3a R = Me
2b
3b
Scheme 1.
Scheme 2.

S.A.R. Knox, F. Marchetti / Journal of Organometallic Chemistry 692 (2007) 4119–4128
4121
Ph
Me
Cγ
H
Ph
Cγ
H
Cβ
Cα
OC
Cα
Me
H
Cβ
Ru
Ru
OC
CO
Ru
Ru
H
CO
6 (15 %)
5 (9 %)
+
Ph
Cγ
Me
H
Cβ
Cα
Ru
CO
H
MeCN
Cp
CO
H
+ H −
Ru
H
Ru
Ru
Cp
Cp
C
Cβ
OC
H
O
Cγ(Ph)(Me)
Cα
OC
H
3b
Ru
Ru
Ru
CO
7 (7 %)
C
O
9 (11 %)
Ph
Cγ
Me
H
Cβ
Cα
CO
OC
Ru
Ru
H
8 (36 %)
Scheme 3.
compounds containing the l-g2:g2 allene moiety have been
described [16], some containing the [M2(Cp)2(CO)2] skele-
ton (M = Ru [17], Fe [18]). Furthermore, the same g2:g2
allene ligand has also been reported to be coordinated in
poly-nuclear species [19].
The spectroscopic data for 5 are characteristic of its
diiron and diruthenium analogues. The IR spectrum (in
CH2Cl2 solution) exhibits two carbonyl bands, at 1933
and 1915 cmꢀ1. The 1H NMR spectrum shows the presence
in solution of two isomers in comparable amounts. In anal-
ogous compounds the only configuration exhibited by the
Cp ligands is trans, and it is likely that this is also the case
here. For example, the complex [Ru2(CO)2{l-g2:g2-
in 5a Ph is axial and Me is equatorial, whereas in 5b the
opposite configuration is adopted. Indeed, in the 1H
NMR spectrum of 5a the methyl group (d 1.82 ppm) is
shielded compared with that in 5b (d 2.17 ppm), while the
opposite trend is seen for the Cp resonances [5a: d 5.04,
4.87 ppm; 5b d 4.65, 4.35 ppm]. These features indicate that
the Me group is close to the Ru–Ru axis in 5a while in 5b it
is oriented away from it (Scheme 4).
The Ca–H protons of 5 resonate as doublets at ca. 3.6
and 2.7 ppm, with a coupling constant of ca. 4 Hz. In the
13C NMR spectrum, the Ca resonance is shifted signifi-
cantly upfield (e.g. for 5b at 29.7 ppm) with respect to com-
plex 2b [12], as a consequence of the loss of alkylidene
character. The Cb and Cc resonances occur at ca. 190
and 60 ppm.
Ca(H)(CO2Et)@Cb@Cc(H)(CO2Me)}(Cp)2]
has
been
shown to exist in two trans forms, both characterized by
X-ray diffraction [17]. The two forms differ in the orienta-
tions of the substituents at Cc, with one isomer having
the CO2Me group and the Ca–H in axial and equatorial
sites, respectively, with regard to the Ru–Ru bond axis,
while in the other the CO2Me and the Ca–H lie in equato-
rial and axial positions, respectively. In both isomers, the
CO2Et function is in an axial position. On this basis, it is
likely that the two isomers of 5 have the structures 5a
and 5b, in which the orientations of the Cc substituents
Me
Cγ
H
Ph
Cγ
H
Cα
Ph
Cα
Me
Cβ
H
Cβ
H
OC
OC
Ru
Ru
Ru
Ru
CO
CO
5b
5a
1
(Ph and Me) are different. The H NMR data suggest that
Scheme 4.

4122
S.A.R. Knox, F. Marchetti / Journal of Organometallic Chemistry 692 (2007) 4119–4128
Complexes 6 and 8, the latter being the highest yield
C
C
C
product (36%), derive from 3b by nitrile displacement with
hydride ion, followed by rearrangement without involving
the allenyl ligand.
The IR spectrum of 6 exhibits two carbonyl bands, at
1972 and 1918 cmꢀ1, with the second more intense than
the first. Conversely, the IR spectrum of 8 shows bands
at 1984 and 1921 cmꢀ1, with the latter being less intense
than the former.
C
C
C
C
C
C
OC
Cp
OC
Cp
OC
Cp
M
M
M
M
M
M
Cp
Cp
C
C
Cp
C
O
O
O
III
II
I
Scheme 5.
The NMR spectra of 6 and 8 reveal the absence of fluxi-
onality and contain single sets of resonances. In the H
NMR spectra, the bridging hydrides are at typically high
band due to terminal Ru–H stretching is observable at
ca. 1960 cmꢀ1 [22a,22c]. No such band is observed in the
IR spectra of 6 and 8.
1
field chemical shifts, at ꢀ13.73 ppm (6) and ꢀ14.20 ppm
Compound 9 (and its analogue 11, see later) belongs to a
large class of diruthenium and diiron complexes which
have been reported in the literature. Such complexes con-
sist of a cis-[M2(Cp)2(CO)(l-CO)] core (M = Ru, Fe) and
a bridging l-g1:g3-vinyl-alkylidene ligand (Scheme 5,
structure I), which has been alternatively described as l-
g1:g3-allylidene (Scheme 5, structure II) or 1,2-dimetalla-
cyclo-pent-3-ene (Scheme 5, structure III) [23].
1
(8). The salient H and 13C NMR features of 6 and 8 do
not differ significantly from the data available for the par-
ent 2b. Thus, the Ca–H proton resonates as a quartet (due
to coupling with Cc-Me) at 8.80 ppm (6) and 9.12 ppm (8).
Moreover, the Ca, Cb and Cc carbons are observed at ca.
115, 165 and 110 ppm respectively. The CO carbons reso-
nate at values typical of terminal carbonyl ligands (e.g.
for 6 at 202.4 and 203.1 ppm).
The spectroscopic characteristics of 9 are consistent with
those of the analogous species. The IR spectrum (in CH2-
Complexes 6 and 8 are isomers, which could arise from
either cis–trans arrangements of the Cp ligands or from
axial and equatorial orientations of the Cc substituents.
The former is the most likely on the basis of the IR and
NMR data. cis and trans isomers of complexes containing
the [M2(Cp)2(CO)2] unit (M = Fe, Ru) in several cases have
distinctive frequencies for their higher carbonyl stretching
vibration, the latter being at higher values in cis isomers
than in the trans forms [13c,13d,13e,20]. On this basis, a
cis configuration is attributable to complex 8 and a trans
configuration to complex 6. This attribution is supported
Cl2 solution) shows two bands at 1951 and 1774 cmꢀ1
,
accounting for terminal and bridging carbonyls, respec-
1
tively. In the H NMR spectrum, which has a single set
of resonances, the Ca–H proton resonates as a doublet
(J 7.2 Hz), due to coupling with Cb–H, at the typically
low field (d 10.75 ppm) expected for a proton bound to a
bridging alkylidene carbon; Cb–H is seen at d 4.71 ppm.
In the 13C NMR spectrum, the resonances of the Ca, Cb
and Cc carbons are found at d 155.4, 82.7 and 71.1 ppm,
respectively. These values are consistent with the alkylidene
character of Ca and with the olefin-bound-to-metal nature
of Cb and Cc.
1
by comparing the H NMR resonances of the Cp ligands
of 6 and 8 with those of the cis and trans isomers of the par-
ent complex 2b [12], and by the order in which compounds
6 and 8 are eluted from the chromatographic column. Thus
6, which is expected to be less polar than 8, is eluted with a
less polar solvent. Moreover, the Cc-Me resonances for 6
2.2. Studies on the thermal stabilities of the products of the
reaction of 3b with NaBH4
1
and 8, in both the H and 13C NMR spectra, are very
The IR spectrum of the mixture formed in the reaction
of 3b with NaBH4 (see above) indicates that the mixture
contains mainly compounds 6 and 8, and suggests that
the other products isolated by chromatography might
derive from 6 and 8 through subsequent intramolecular
rearrangements.
In order to investigate this possibility, solutions of
complexes 5, 6, 8 and 9 were heated and monitored via IR
and NMR spectroscopies (see Table 1). These studies have
suggested a plausible mechanism for the formation of 6, 5
1
similar (e.g. in the H NMR spectra: for 6, d 2.25 ppm;
for 8, d 2.24 ppm), while the Ca resonances in the 13C
NMR spectra differ significantly (for 6: d = 113.5 ppm;
for 8: d = 118.1 ppm). The opposite trends should be
apparent if compounds 6 and 8 have different orienta-
tions of the methyl and phenyl groups at Cc and the
same arrangement of the Cp ligands. In 6 and 8 the Cc
substituents are expected to adopt the same orienta-
tions found in the precursor 2b, where the hindered phenyl
group points away from the Cp rings, lying in an axial
position.
Table 1
The structures shown in Scheme 3, with bridging rather
than terminal hydride, are as expected for compounds 6
and 8. Hydrides are usually found acting as bridging
ligands in diruthenium complexes [14a,21], and examples
of terminal coordination are rare [22]. IR spectroscopy is
strongly diagnostic in determining which coordination is
adopted by hydride in a diruthenium complex, since the
Relevant 1H NMR resonances for the compounds involved in the
reactions shown in Scheme 6
Complex
8
6
5b
9
l-H
Ca–H
Cb–H
ꢀ14.20
ꢀ13.73
9.12
8.80
3.72, 2.85
10.75
4.71

S.A.R. Knox, F. Marchetti / Journal of Organometallic Chemistry 692 (2007) 4119–4128
4123
Ph
Me
Cγ
H
Cβ
Cα
CO
OC
Ru
Ru
H
n-heptane reflux, 30 min.
8
Ph
Cγ
Me
H
H
Cβ
Cβ
Cα
H
Cγ(Ph)(Me)
OC
Cα
OC
Ru
Ru
Ru
Ru
CO
H
C
O
6
9
Me
Cγ
H
n-heptane reflux, 7 h
n-heptane reflux, 42 h
Cα
Ph
Cβ
H
OC
Ru
Ru
CO
5b
Scheme 6.
and 9 shown in Scheme 6. Moreover, it has been possible to
deduce a scale of thermodynamic stability, with the vinyl-
alkylidene species 9 as the most stable product. This result
is in accordance with previous findings, which indicate that
l-allenyl complexes undergo nucleophilic additions prefer-
entially at the central carbon (Cb) of the C3 chain [24],
although examples of additions at Ca have also been
reported [5a,25].
Compound 8 is the main fraction collected by chroma-
tography, in spite of the fact it is not stable in boiling
n-heptane solution. This abundance is probably due to
the following kinetic reasons: (i) complex 8 results directly
from 3b by nitrile substitution with hydride; and (ii) the
configuration of the Cp ligands (cis) is that presumably
favoured in the parent cationic allenyl complexes [12]. In
other words, the synthesis of 8 consists of simple substitu-
tion at the metal centres and would not require a rear-
rangement of the Cp rings.
conditions, contrary to what was found after chromatogra-
phy at low temperature. It may be concluded that 5b is
thermodynamically more stable than 5a. Formation of 5a
in significant amounts at low temperature is probably
because it has the same arrangement of the Cc substituents
as the allenyl precursor (see Scheme 4). The rearrangement
which leads from 6 to 5b consists of hydride migration
from the metal site to the Ca carbon of the allenyl moiety.
It is probable that, both on the alumina column and in
boiling heptane, compounds 5a,b derive from 6 (and not
from 8) since this route does not require any modification
of the arrangement of the Cp ligands.
Finally, if an n-heptane solution of 5b is heated for 42 h,
formation of 9 occurs, accompanied by some decomposi-
tion, as a result of hydrogen migration from Ca to Cb,
together with trans-to-cis isomerisation. Compound 9 is
stable in boiling heptane solution upon further heating
(7 h).
Complex 8 undergoes clean and complete cis-to-trans
isomerisation after 30 min in heptane at reflux temperature,
to give 6. cis–trans isomerizations are common in dinuclear
complexes of ruthenium and iron. Adams and Cotton pro-
posed a mechanism for the cis–trans isomerization of
[Fe2(l-CO)2(CO)2(Cp)2] which is now a fundamental
example of the dynamic behaviour of metal carbonyl com-
pounds [26]. Moreover, cis–trans interconversion has been
investigated in [Ru2(l-CO)2(CO)2(Cp)2] [27] and related
dinuclear complexes [23d,28].
2.3. Reactivity of acetonitrile derivatives of diruthenium
allenyl complexes with halides
The possibility of introducing simple anions at the metal
sites of the diruthenium species 3, and observing subsequent
migration to the allenyl ligand, led us to investigate the reac-
tivity of 3b with halides. The reactions of 3b with Clꢀ (from
LiCl), Brꢀ (from LiBr) and Iꢀ (from KI) occur rapidly in the
presence of a large excess of the salt in THF solution,
to afford the neutral products [Ru2(CO)2(X){l-g1:g2-Ca-
(H)@Cb@Cc(Me)(Ph)}(Cp)2] [X = Cl, 4b; X = Br, 4c;
X = I, 4d] (Scheme 7).
Compound 6 transforms cleanly, in boiling heptane over
7 h, into the l-g2:g2 allene species 5b. It is noteworthy that
complex 5b is obtained in the absence of 5a under these

4124
S.A.R. Knox, F. Marchetti / Journal of Organometallic Chemistry 692 (2007) 4119–4128
+
Ph
Cγ
Ph
Ph
H
Me
Me
Me
C
C
γ
γ
Cβ
Cl
H
Cγ (Ph)(Me)
Cβ
H
H
C
C
β
β
Cα
O
Cα
Ru
CH2Cl2
C
C
C
−
α
α
O
Cl
X
C
X
O
O
MeCN
C
C
Ru
Ru
Ru
Ru
Ru
Ru
Ru
γ-Al2O3
− NCMe
C
O
C
C
C
O
O
O
4b
10
X
Cl
Br
I
3b
4b
4c
4d
Scheme 8.
Scheme 7.
filtration through the alumina used for chromatographic
separations. Thus, passing a CH2Cl2 solution of 4b through
an alumina column (see Section 4) results in clean forma-
tion of an orange product which has been identified as
[Ru2(CO)(l-CO){l-g1:g3-Ca(Cl)Cb(H)@Cc(Me)(Ph)}(Cp)2],
10, an isomer of 4b (Scheme 8).
Compounds 4b–d were purified by quick filtration
through alumina and fully characterized by IR and NMR
spectroscopy, elemental analysis and mass spectrometry.
The molecular structures of 4b–d are likely to resemble that
determined in the solid state for [Ru2(CO)2(Cl){l-g1:
g2- C(H)@C@C(Me)2}(Cp)2], 4a; this latter complex,
which has a trans geometry for the Cp rings, contains
two carbonyls, one terminally bonded to one ruthenium
atom, and one semi-bridging. The X-ray structure of 4a
revealed that the allenyl ligand bridges the two ruthenium
atoms in an identical fashion to that found for 2b [12], with
a r bond to one metal and a p bond to the other. More-
over, the chloride ligand is bound to the ruthenium which
is r-bound to the allenyl.
Evidence for terminal and symmetrically bridging car-
bonyls in 10 is provided by IR absorptions at 1985 and
1
1832 cmꢀ1, respectively. The H NMR spectrum displays
resonances for the phenyl protons (7.80–7.05 ppm), the ole-
finic Cb–H (5.59 ppm), the Cp rings (5.26, 4.57 ppm), and
the Cc-Me group (1.48 ppm), respectively. In particular,
the absence of a low-field signal, attributable to an alkylid-
ene proton, suggests the modification of the allenyl moiety
present in the starting compound 4b. Unfortunately, com-
plex 10 is not sufficiently soluble to record a satisfactory
13C NMR spectrum, or to grow crystals suitable for
X-ray analysis. However, elemental analysis for C, H and
Cl, and the mass spectrum confirmed the identity of 10.
According to the sequence shown in Scheme 6, the
bridging vinyl-chlorocarbene ligand of complex 10 might
be the result of chloride migration from the metal to the
Ca carbon of the allenyl ligand, followed by hydrogen
migration from Ca to Cb. Nonetheless, attempts to convert
4b into 10 upon heating in solution were unsuccessful: com-
plex 4b is unaltered after 15 h in boiling toluene. This
experimental evidence suggests that the possibility that
complex 10 forms by a reaction of 4b with CH2Cl2 on alu-
mina, rather than by intramolecular rearrangements of 4b,
should not be excluded. Somewhat surprisingly, the trans-
formation depicted in Scheme 8 is limited to compound 4b,
since the analogous species 4a, 4c–d are stable upon pas-
sage through alumina. Terminal halocarbene ligands are
well-known species [30], however only a few cases of bridg-
ing halocarbenes have been reported, and they usually
involve the CF2 unit bridging between two metal centres
[31]. Compound 10 contains the first example of a bridging
vinyl-chlorocarbene ligand.
The mono-halide species 4b–d show very similar spectro-
scopic patterns, analogous to that of 4a. The IR spectra (in
CH2Cl2 solution) exhibit two bands at ca. 1985 and
1890 cmꢀ1, corresponding to one terminal and one semi-
1
bridging carbonyl, respectively. The H NMR spectra of
the compounds, recorded at room temperature, show the
absence of fluxionality. Moreover, the NMR spectra of
4b contain two sets of signals, in ca. 4:1 ratio. It is proposed
that the two sets are due to cis and trans isomers, in agree-
ment with what was reported for 4a, although it is difficult
1
to deduce which set of resonances is which. The salient H
and 13C NMR features of 4b–d do not significantly differ
from the data available for 4a, 2b, 6 and 8. Thus, a reso-
nance at ca. 10 ppm is seen for the Ca–H proton, while
the carbons of the allenyl chain resonate, for example in
the case of 4d, at d 120.7 (Ca), 160.4 (Cb) and 113.7 (Cc)
ppm. Moreover, the resonances of the carbonyl ligands
are found at ca. 202 and 213 ppm, in accord with the termi-
nal and semi-bridging coordination modes, respectively,
suggested by IR data.
The substitution of one nitrile ligand by halides has been
previously described for dinuclear complexes containing
the unit [M2Cp2(CO)2], M = Fe, Ru [13b,13c,13d,13e].
The reaction which leads to 4c is accompanied by
fragmentation, since small amounts (12%) of the known
monomer [Ru(Cp)(CO)2(Br)] [29] were isolated upon
chromatography.
3. Conclusions
The substitution of a carbonyl ligand by an acetonitrile
molecule in cationic diruthenium allenyl complexes allows
the introduction of hydride and halide ions to the metal
sites under mild conditions.
More interestingly, we have observed that compound
4b, in dichloromethane solution, is not stable upon slow

S.A.R. Knox, F. Marchetti / Journal of Organometallic Chemistry 692 (2007) 4119–4128
4125
The resulting products undergo successive rearrange-
ments which involve the bridging allenyl ligand. These can
be promoted by: (i) thermal treatment, (ii) filtration through
alumina, and (iii) both. Hydride migration from the metal
site to the Ca carbon of the allenyl moiety provides a
l-g2:g2 allene adduct. The latter can be isolated and charac-
terized, but it is further convertible into a more stable vinyl-
alkylidene derivative, by hydrogen migration from Ca to Cb.
Likewise, an unprecedented example of a bridging vinyl-
chlorocarbene species might be the result of chloride migra-
tion from the ruthenium centre to the Ca carbon of the alle-
nyl ligand, occurring simultaneously with hydrogen
migration from Ca to Cb.
was dissolved in THF (30 mL) and treated with NaBH4
(240 mg, 6.34 mmol). The mixture was stirred for 1 h, then
the solvent was removed under reduced pressure. The
resulting residue was introduced to an alumina column
(15 · 2.5 cm) and chromatographed at ꢀ35 ꢁC. The follow-
ing products were collected by using varying amounts of n-
hexane and CH2Cl2 as eluent and isolated as powders upon
removal of the solvent under vacuum.
4.3. [Ru2(CO)2{l-g2:g2-CaH2@Cb@Cc(Me)(Ph)}(Cp)2]
(5a–b)
(Eluent: hexane/CH2Cl2 95:5; colour: pale yellow.)
Yield: 30 mg, 9.1%. Anal. Calc. for C22H20O2Ru2: C,
50.96; H, 3.89. Found: C, 50.80; H, 4.00%. FAB-MS: 520
1
m/z. IR (CH2Cl2) m(CO) 1933 (m, sh), 1915 (s) cmꢀ1. H
4. Experimental
NMR (CD2Cl2, 298 K) 5a: d 7.72–6.63 (5H, Ph); 5.04,
2
4.1. General data
4.87 (s, 10H, Cp); 3.52, 2.60 (d, JHH = 4.0 Hz, 2H,
CaH2); 1.82 (s, 3H, Me); 5b: d 7.72–6.63 (5H, Ph); 4.65,
2
All reactions and general manipulations were carried
out under a nitrogen atmosphere, using solvents dried by
distillation from appropriate drying agents. Chromato-
graphic separations were carried out on columns of deacti-
vated alumina (6% w/w water), at ꢀ35 ꢁC. All reactions
were monitored by IR spectroscopy. IR spectra were
recorded on a Perkin–Elmer 1710 FT-IR spectrometer,
using calcium fluoride cells of 1 mm path length. EI and
FAB mass spectra were recorded on a Fisons Autospec
instrument. Elemental analyses were performed by the
Microanalytical laboratory of the School of Chemistry,
University of Bristol. All NMR measurements were per-
formed on JEOL GX 400 spectrometer, operating in Fou-
4.35 (s, 10H, Cp); 3.72, 2.85 (d, JHH = 4.3 Hz, 2H,
CaH2); 2.17 (s, 3H, Me). 5a/5b ratio 6:5. 13C{1H} NMR
(CD2Cl2, 298 K) 5a: d 210.1, 206.5 (CO); 189.9 (Cb);
149.7 (ipso-Ph); 128.5, 127.7, 126.4 (Ph); 88.0, 86.1 (Cp);
62.1 (Cc); 28.8 (Me); 25.0 (Ca); 5b: d 208.0, 207.1 (CO);
187.8 (Cb); 150.7 (ipso-Ph); 127.7, 125.4, 124.5 (Ph); 87.3,
84.0 (Cp); 56.9 (Cc); 31.3 (Me); 29.7 (Ca).
4.4. trans-[Ru2(CO)2(l-H){l-g1:g2-CaH@Cb@Cc(Me)-
(Ph)}(Cp)2] (6)
Eluent: hexane/CH2Cl2 90:10; colour: yellow. Yield:
50 mg, 15%. Anal. Calc. for C22H20O2Ru2: C, 50.96; H,
3.89. Found: C, 50.79; H, 3.95%. FAB-MS: 520 m/z. IR
1
rier transform mode. The chemical shifts for H and 13C
(CH2Cl2) m(CO) 1972 (m), 1918 (s) cmꢀ1
.
1H NMR
were referenced to internal TMS. All the reagents were
commercial products of the highest purity available and
used as received, except for [Ru2(CO)2(l-CO){l-g1:g2-
C(H)@C@C(Me)(Ph)}(Cp)2][BF4], 2b, which was prepared
according to the published method [12].
5
(CD2Cl2, 298 K) d 8.80 (q, JHH = 2.5 Hz, 1H, CaH);
8.43–6.98 (5H, Ph); 5.16, 4.76 (s, 10H, Cp); 2.25 (d,
5JHH = 2.5 Hz, 3H, Me); ꢀ13.73 (s, 1H, l-H). 13C{1H}
NMR (CD2Cl2, 298 K) d 203.1, 202.4 (CO); 162.7 (Cb);
140.1 (ipso-Ph); 128.4, 126.4, 125.0 (Ph); 113.5 (Ca); 110.9
(Cc); 85.2, 85.0 (Cp); 22.2 (Me).
4.2. Synthesis of [Ru2(CO)(NCMe)(l-CO)-
{l-g1:g2-C(H)@C@C(Me)(Ph)}(Cp)2] [BF4] (3b)
4.5. [Ru3(CO)3(l-H)3(Cp)3] (7)
Complex [Ru2(CO)2(l-CO){l-g1:g2-C(H)@C@ C(Me)-
(Ph)}(Cp)2][BF4], 2b (200 mg, 0.316 mmol), was dissolved
in CH2Cl2 (20 mL) and treated with a solution of Me3NO
in MeCN (3.3 mL, 0.33 mmol). The mixture was stirred for
15 min. The solvent was then removed under reduced pres-
sure, giving a brown residue. The IR spectrum of the resi-
due, dissolved in CH2Cl2, indicated clean formation of 3b
[m(CO) 2005 (vs), 1870 (s) cmꢀ1].
Eluent: hexane/CH2Cl2 90:10; colour: blue. Yield:
39 mg, 7.0% [15].
4.6. cis-[Ru2(CO)2(l-H){l-g1:g2-CaH@Cb@Cc(Me)-
(Ph)}(Cp)2] (8)
Eluent: hexane/CH2Cl2 80:20; colour: yellow. Yield:
117 mg, 36%. Anal. Calc. for C22H20O2Ru2: C, 50.96; H,
3.89. Found: C, 51.10; H, 3.77%. FAB-MS: 520 m/z. IR
4.2.1. Reaction of [Ru2(CO)2(NCMe){l-g1:g2-
(CH2Cl2) m(CO) 1984 (vs), 1921 (s) cmꢀ1
.
1H NMR
C(H)@C@C(Me)(R)}(Cp)2][BF4], 3b, with NaBH4
Complex [Ru2(CO)(l-CO)(NCMe){l-g1:g2-C(H)@C@
C(Me)(Ph)}(Cp)2][BF4], 3b, freshly prepared by reacting
[Ru2(CO)2(l-CO){l-g1:g2-C(H)@C@C(Me)(Ph)}(Cp)2][BF4],
2b (400 mg 0.633 mmol), with Me3NO in MeCN solution,
5
(CD2Cl2, 298 K) d 9.12 (q, JHH = 2.5 Hz, 1H, CaH);
7.81–6.57 (5H, Ph); 5.14, 5.06 (s, 10H, Cp); 2.24 (d,
5JHH = 2.5 Hz, 3H, Me); ꢀ14.20 (s, 1H, l-H). 13C{1H}
NMR (CD2Cl2, 298 K) d 202.6, 201.7 (CO); 162.7 (Cb);

4126
S.A.R. Knox, F. Marchetti / Journal of Organometallic Chemistry 692 (2007) 4119–4128
141.1 (ipso-Ph); 128.2, 126.5, 125.0 (Ph); 118.1 (Ca); 112.3
(Cc); 84.7, 84.1 (Cp); 22.3 (Me).
133 mg, 76%. Anal. Calc. for C22H19ClO2Ru2: C, 47.78;
H, 3.46; Cl, 6.41. Found: C, 47.65; H, 3.23; Cl, 6.19%.
EI-MS: 554 m/z. IR (CH2Cl2)m(CO) 1989 (vs), 1887 (s)
4.7. [Ru2(CO)(l-CO){l-g1:g3-Ca(H)Cb(H)@Cc(Me)-
(Ph)}(Cp)2] (9)
cmꢀ1
.
1H NMR (CDCl3, 298 K) Major isomer: d 9.80
5
(q, JHH = 1.9 Hz, 1H, CaH); 7.77–7.24 (5H, Ph); 5.30,
5
4.78 (s, 10H, Cp); 2.28 (d, JHH = 1.9 Hz, 3H, Me); Minor
5
Eluent: hexane/CH2Cl2 80:20; colour: yellow. Yield:
37 mg, 11%. Anal. Calc. for C22H20O2Ru2: C, 50.96; H,
3.89. Found: C, 51.14; H, 3.79%. FAB-MS: 520 m/z. IR
isomer: d 9.87 (q, JHH = 1.9 Hz, 1H, CaH); 7.77–7.24
5
(5H, Ph); 5.21, 4.84 (s, 10H, Cp); 1.92 (d, JHH = 1.9 Hz,
3H, Me). Isomer ratio 4:1. 13C{1H} NMR (CDCl3, 298 K)
d 213.0 (s-CO); 201.0 (CO); 158.4 (Cb); 138.6 (ipso-Ph);
130.5 (Ca); 128.3, 126.2 (Ph); 114.6 (Cc); 88.3, 86.1 (Cp);
22.6 (Me).
(CH2Cl2) m(CO) 1951 (vs), 1774 (s) cmꢀ1
.
1H NMR
3
(CD2Cl2, 298 K) d 10.75 (d, JHH = 7.2 Hz, 1 H, CaH);
7.58–6.50 (5 H, Ph); 5.08, 4.88 (s, 10H, Cp); 4.71 (d,
3JHH = 7.2 Hz, 1H, CbH); 1.59 (s, 3H, Me). 13C{1H}
NMR (CD2Cl2, 298 K) d 239.4 (l-CO); 200.5 (CO); 155.4
(Ca); 146.8 (ipso-Ph); 128.0, 127.7, 125.6 (Ph); 88.6, 85.7
(Cp); 82.7 (Cb); 71.1 (Cc); 38.9 (Me).
Compounds 4c–d were prepared by the same procedure
described for 4b, by reacting 3b with the appropriate halide
salt (LiBr, KI).
4c (yield: 85%; colour: orange). Anal. Calc. for
C22H19BrO2Ru2: C, 44.23; H, 3.21; Br, 13.37. Found: C,
44.35; H, 3.15; Br, 13.12%. FAB-MS: 598 m/z. IR
4.8. Studies on the thermal stabilities of 5, 6, 8 and 9
1
(CH2Cl2) m(CO) 1986 (vs), 1890 (s) cmꢀ1. H NMR (d8-
5
Complex 8 (150 mg, 0.289 mmol) was dissolved in
n-heptane (15 mL) and the solution was heated at reflux
temperature for 30 min. The solution was then cooled to
room temperature and the solvent was removed under vac-
uum, giving a yellow powder. IR and NMR spectroscopic
data indicated complete conversion into complex 6. The
latter was purified by filtration on alumina. Yield:
130 mg, 87%. The residue was then dissolved in n-heptane
(15 mL), and heated at reflux temperature for 7 h. The
solution was then cooled and powdery 5b was cleanly
obtained upon removal of the solvent. The identity of 5b
toluene, 298 K) d 9.80 (q, JHH = 2.0 Hz, 1H, CaH);
7.70–7.19 (5H, Ph); 4.80, 4.60 (s, 10H, Cp); 2.02 (d,
5JHH = 2.0 Hz, 3H, Me). 13C{1H} NMR (d8-toluene,
298 K) d 210.5 (s-CO); 201.9 (CO); 160.1 (Cb); 138.9
(ipso-Ph); 129.0 (Ca); 128.1, 127.9, 126.0 (Ph); 113.9 (Cc);
88.1, 86.4 (Cp); 29.0 (Me).
4d (yield: 89%; colour: orange). Anal. Calc. for
C22H19IO2Ru2: C, 41.00; H, 2.97; I, 19.69. Found: C,
41.09; H, 3.06; I, 19.84% FAB-MS: 646 m/z. IR
1
(CH2Cl2)m(CO) 1984 (vs), 1891 (s) cmꢀ1. H NMR (d8-tol-
uene, 298 K) d 9.82 (q, 5JHH = 2.2 Hz, 1H, CaH); 7.54–6.63
1
5
was established by IR and H NMR spectroscopy. Yield:
(5H, Ph); 4.47, 4.28 (s, 10H, Cp); 1.97 (d, JHH = 2.2 Hz,
120 mg, 80%. The yellow complex was dissolved in n-hep-
tane (15 mL) and heated at reflux. IR spectroscopy
revealed progressive formation of 9 and consumption of
5b, which was completed after 42 h. The final mixture
was chromatographed on an alumina column and a yellow
band was collected by using a mixture of CH2Cl2 and
n-hexane (1:1 v:v) as eluent. Removal of the solvent gave
a yellow powder, which was identified as complex 9 by
IR and 1H NMR spectroscopy. Yield: 79 mg, 53%. Finally,
a solution of complex 9 was boiled in n-heptane (10 mL)
for 7 h, but no variation was detected via IR.
3H, Me). 13C{1H} NMR (d8-toluene, 298 K) d 209.2 (s-
CO); 202.9 (CO); 160.4 (Cb); 140.0 (ipso-Ph); 128.6,
126.5, 126.1 (Ph); 120.7 (Ca); 113.7 (Cc); 88.2, 86.9 (Cp);
30.4 (Me).
4.10. Synthesis of [Ru2(CO)(l-CO){l-g1:g3-Ca(Cl)-
Cb(H)@Cc (Me)(Ph)}(Cp)2] (10)
Complex [Ru2(CO)2(Cl){l-g1:g2-C(H)@C@ C(Me)(Ph)}
(Cp)2], 4b (120 mg, 0.217 mmol), was dissolved in dichloro-
methane (15 mL) and introduced to an alumina column
(15 · 2.5 cm). An orange band corresponding to 10 was
collected by using neat CH2Cl2 as eluent. Compound 10
was obtained as an air stable orange powder upon
removal of the solvent under reduced pressure. Yield:
85 mg, 71%. Anal. Calc. for C22H19ClO2Ru2: C, 47.78;
H, 3.46; Cl, 6.41. Found: C, 47.62; H, 3.29; Cl, 6.30%.
EI-MS: 554 [M+], 526 [M+ꢀCO], 519 [M+ꢀCl] m/z. IR
4.9. Synthesis of [Ru2(CO)2(X){l-g1:g2-Ca(H)@
Cb@Cc(Me)(Ph)}(Cp)2] [X = Cl, 4b; X = Br, 4c; X = I,
4d]
To a THF solution (20 mL) of complex [Ru2(CO)(NC-
Me)(l-CO){l-g1:g2-C(H)@C@C(Me)(Ph)}(Cp)2][BF4], 3b,
freshly prepared from [Ru2(CO)2(l-CO){l-g1:g2-C(H)@
C@C(Me)(Ph)}(Cp)2][BF4], 2b (200 mg 0.316 mmol), LiCl
(260 mg, 6.13 mmol) was added. The resulting mixture
was stirred for 1 h, then it was introduced to a short alu-
mina column (3 · 2.5 cm). Quick filtration with a mixture
of THF and methanol (95:5 v:v) afforded an orange solu-
tion of 4b, which gave an ochre yellow powder upon
removal of the solvent under reduced pressure. Yield:
(CH2Cl2) m(CO) 1985 (vs), 1832 (s) cmꢀ1 1H NMR
.
(CD2Cl2, 298 K) d 7.80–7.05 (5H, Ph); 5.59 (s, 1H, CbH);
5.26, 4.57 (s, 10H, Cp); 1.48 (s, 3H, Me).
Acknowledgements
The authors thank Philip J. King and James N.L. Den-
nett for assistance with NMR characterizations.

S.A.R. Knox, F. Marchetti / Journal of Organometallic Chemistry 692 (2007) 4119–4128
4127
(c) L. Busetto, F. Marchetti, S. Zacchini, V. Zanotti, J. Braz. Chem.
Soc. 14 (2003) 902;
Appendix A. Supplementary material
(d) L. Busetto, F. Marchetti, S. Zacchini, V. Zanotti, Inorg. Chim.
Acta 358 (2005) 1204;
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/
j.jorganchem.2007.06.029.
(e) V.G. Albano, L. Busetto, F. Marchetti, M. Monari, S. Zacchini,
V. Zanotti, Z. Naturforsch. B 62b (2007) 427.
[14] (a) M. Akita, R. Hua, S.A.R. Knox, Y. Moro-oka, S. Nakanishi,
M.I. Yates, J. Organomet. Chem. 569 (1998) 71;
(b) M. Akita, R. Hua, S.A.R. Knox, Y. Moro-oka, S. Nakanishi,
M.I. Yates, Chem. Commun. (1997) 51;
References
(c) V.G. Albano, L. Busetto, F. Marchetti, M. Monari, S. Zacchini,
V. Zanotti, Organometallics 22 (2003) 1326;
[1] (a) A. Wojcicki, Inorg. Chem. Commun. 5 (2002) 82, and references
therein;
(d) J.N.L. Dennett, S.A.R. Knox, J.P.H. Charmant, A.L. Gillon,
A.G. Orpen, Inorg. Chim. Acta 354 (2003) 29;
(e) M. Akita, R. Hua, S. Nakanishi, M. Tanaka, Y. Moro-oka,
Organometallics 16 (1997) 5572.
(b) A. Wojcicki, C.E. Shuchart, Coord. Chem. Rev. 105 (1990) 35;
(c) R.P. Hughes, R.B. Larichev, L.N. Zakharov, A.L. Rheingold,
Organometallics 25 (2006) 3943;
(d) A. Asensio, M.L. Buil, M.A. Esteruelas, E. Onate, Organomet-
˜
[15] N.J. Forrow, S.A.R. Knox, M.J. Morris, A.G. Orpen, J. Chem. Soc.
Chem. Comm. (1983) 234.
[16] (a) I.Y. Wu, T.W. Tseng, C.T. Chen, M.C. Cheng, Y.C. Lin, Y.
Wang, Inorg. Chem. 32 (1993) 1539;
allics 23 (2004) 5787;
(e) H. Werner, F. Kukla, P. Steinert, Eur. J. Inorg. Chem. 6 (2002)
1377.
[2] (a) M.J. Chetcuti, S.R. McDonald, Organometallics 21 (2002)
3162;
(b) R.D. Adams, G. Chen, L. Chen, J. Yin, Organometallics 12
(1993) 2644;
(c) S. Ogoshi, T. Nishida, K. Tsutsumi, M. Ooi, T. Shinagawa, T.
Akasaka, M. Yamane, H. Kurosawa, J. Am. Chem. Soc. 123 (2001)
3223;
(b) S. Doherty, G. Hogarth, M. Waugh, W. Clegg, M.R.J.
Elsegood, Organometallics 19 (2000) 5696;
(c) R.R. Willis, C.E. Shuchart, A. Wojcicki, A.L. Rheingold, B.S.
Haggerty, Organometallics 19 (2000) 3179;
(d) J.H. Huang, Y.T. Lee, D.C. Swenson, L. Messerle, Polyhedron
25 (2006) 559.
(d) L. Busetto, F. Marchetti, S. Zacchini, V. Zanotti, Eur. J.
Inorg. Chem. 16 (2005) 3250.
[17] P.J. King, PhD Thesis, University of Bristol, 1996.
[18] E.L. Hoel, G.B. Ansell, S. Leta, Organometallics 5 (1986) 585.
[19] K. Lee, J.R. Shapley, Organometallics 17 (1998) 4030.
[20] V.G. Albano, L. Busetto, F. Marchetti, M. Monari, S. Zacchini, V.
Zanotti, J. Organomet. Chem. 689 (2004) 528.
[21] (a) H. Yan, A.M. Beatty, T.P. Fehlner, J. Am. Chem. Soc. 25 (2003)
16367;
[3] (a) M. Soleilhavoup, C. Saccavini, C. Lepetit, G. Lavigne, L.
Maurette, B. Bruno, R. Chauvin, Organometallics 21 (2002)
871;
(b) M.I. Bruce, N.N. Zaitseva, B.W. Skelton, A.H. White, J. Chem.
Soc., Dalton Trans. 8 (2002) 1678.
[4] See for example: (a) S. Doherty, M.R.J. Elsegood, W. Clegg,
N.H. Rees, T.H. Scanlan, M. Waugh, Organometallics 16 (1997)
3221;
(b) R.R. Willis, M. Calligaris, P. Faleschini, J.C. Gallucci, A.
Wojcicki, J. Organomet. Chem. 593–594 (2000) 465.
[5] See for example: (a) S. Doherty, G. Hogarth, M. Waugh, T.H.
Scanlan, W. Clegg, M.R. Elsegood, Organometallics 18 (1999)
3178;
(b) K.I. Tada, M. Oishi, H. Suzuki, M. Tanaka, Organometallics 15
(1996) 2422;
(c) B.S. Kang, U. Koelle, U. Thewalt, Organometallics 10 (1991)
2569;
(d) R.E. Colborn, A.F. Dyke, S.A.R. Knox, K.A. Mead, P.
Woodward, J. Am. Chem. Soc., Dalton Trans. (1983) 2099.
[22] (a) T. Iwasa, H. Shimada, A. Takami, H. Matsuzaka, Y. Ishii, M.
Hidai, Inorg. Chem. 38 (1999) 2851;
(b) S. Doherty, G. Hogarth, M. Waugh, W. Clegg, M.R.J.
Elsegood, Organometallics 19 (2000) 4557;
(b) A. Inagaki, T. Takemori, M. Tanaka, H. Suzuki, Angew Chem.,
Int. Ed. 39 (2000) 404;
(c) S. Doherty, M. Waugh, T.H. Scanlan, M.R.J. Elsegood, W.
Clegg, Organometallics 18 (1999) 679.
(c) R. Abbel, K. Abdur-Rashid, M. Faatz, A. Hadzovic, A.J. Lough,
R.H. Morris, J. Am. Chem. Soc. 127 (2005) 1870.
[23] (a) L. Busetto, F. Marchetti, S. Zacchini, V. Zanotti, Organometallics
23 (2004) 3348;
[6] See for example: (a) P. Blenkiron, J.F. Corrigan, N.J. Taylor, A.J.
Carty, Organometallics 16 (1997) 297;
(b) V.G. Albano, S. Bordoni, L. Busetto, F. Marchetti, M. Monari,
V. Zanotti, J. Organomet. Chem. 684 (2003) 37.
[7] N. Carleton, J.F. Corrigan, S. Doherty, R. Pixner, Y. Sun, N.J.
Taylor, A.J. Carty, Organometallics 13 (1994) 4179.
[8] D. Seyferth, G.B. Womack, C.M. Archer, J.C. Dewan, Organomet-
allics 8 (1989) 430.
(b) A.F. Dyke, S.A.R. Knox, P.J. Naish, G.E. Taylor, J. Chem. Soc.,
Chem. Commun. (1980) 803;
(c) C.P. Casey, G.P. Niccolai, Organometallics 13 (1994) 2527;
(d) L. Busetto, F. Marchetti, S. Zacchini, V. Zanotti, J. Organomet.
Chem. 691 (2006) 2424;
[9] (a) D. Nucciarone, N.J. Taylor, A.J. Carty, Organometallics 5 (1986)
1179;
(e) L. Busetto, V. Zanotti, J. Organomet. Chem. 690 (2005) 5430.
[24] (a) S.M. Breckenridge, N.J. Taylor, A.J. Carty, Organometallics 10
(1991) 837;
(b) P. Blenkiron, G.D. Enright, N.J. Taylor, A.J. Carty, Organomet-
allics 15 (1996) 2855.
(b) S. Doherty, M.R.J. Elsegood, W. Clegg, M. Waugh, Organomet-
allics 15 (1996) 2688.
[25] S. Doherty, M.R.J. Elsegood, W. Clegg, T.H. Scanlan, N.H. Rees,
Chem. Commun. (1996) 1545.
[10] J.N.L. Dennett, S.A.R. Knox, K.M. Anderson, J.P.H. Charmant,
A.G. Orpen, J. Chem. Soc., Dalton Trans. (2005) 63.
[11] A.F. Dyke, S.A.R. Knox, P.J. Naish, G.E. Taylor, J. Chem. Soc.,
Dalton Trans. (1982) 1297.
[26] (a) F.A. Cotton, G. Wilkinson, in: Advanced inorganic Chemistry,
fifth ed., Wiley, New York, 1988, p. 1325;
[12] C.P. Mc Ardle, PhD Thesis, University of Bristol, 1998. The syntheses
details and data for complexes 1a–b, 2a–b, 3a, 4a, and the cif files
related to the X-ray structures of 2b Æ [BPh4] and 4a have been
enclosed as Supplementary material.
(b) R.D. Adams, F.A. Cotton, J. Am. Chem. Soc. 95 (1973)
6589.
[27] J.G. Bullitt, F.A. Cotton, T.J. Marks, Inorg. Chem. 11 (1972)
672.
[13] (a) K. Boss, M.G. Cox, C. Dowling, A.R. Manning, J. Organomet.
Chem. 612 (2000) 18;
[28] (a) C.P. Casey, K.P. Gable, D.M. Roddick, Organometallics 9 (1990)
221;
(b) V.G. Albano, L. Busetto, M. Monari, V. Zanotti, J. Organomet.
Chem. 606 (2000) 163;

4128
S.A.R. Knox, F. Marchetti / Journal of Organometallic Chemistry 692 (2007) 4119–4128
(b) N.C. Schroeder, R. Funchess, R.A. Jacobson, R.J. Angelici,
Organometallics 8 (1989) 521;
(c) A.F. Dyke, S.A.R. Knox, M. Morris, P.J. Naish, J. Chem. Soc.,
Dalton Trans. (1983) 1417.
[30] (a) J.A. Lopez, K. Mereiter, M. Paneque, M.L. Poveda, O. Serrano,
S. Trofimenko, E. Carmona, Chem. Commun. 37 (2006) 3921;
(b) P.J. Brothers, W.R. Roper, Chem. Rev. 88 (1988) 1293.
[31] (a) A.M. Crespi, M. Sabat, D.F. Shriver, Inorg. Chem. 27 (1988) 812;
(b) W. Petz, F. Weller, A. Barthel, C. Mealli, J. Reinhold, Z. Anorg.
All. Chem. 627 (2001) 1859.
[29] G.C. Bruce, B. Gangnus, S.E. Garner, S.A.R. Knox, A.G. Orpen,
A.J. Phillips, J. Chem. Soc., Chem. Commun. 19 (1990) 1360.