Synthesis and characterization of transition metal stabilized carbocations of the types [Cp*(CO)2Fe{μ-(Cn H2n-1}M(CO)xCp]PF6 (x = 2, M = Fe or Ru; x = 3, M = W, Cp* = η5-C5(CH3)5; Cp = η5-C5H5; n = 3-6) and [Cp(CO)2Ru{...

Article abstract of DOI:10.1016/j.jorganchem.2007.02.016

Title full: Synthesis and characterization of transition metal stabilized carbocations of the types [Cp^*(CO)₂Fe{μ-(C_nH _2n-1}M(CO)_xCp]PF₆ (x = 2, M = Fe or Ru; x = 3, M = W, Cp^* = η⁵-C₅(CH₃)₅; Cp = η⁵-C₅H₅; n = 3-6) and [Cp(CO)₂Ru{μ-(C_nH_2n-1)}W(CO) ₃Cp]PF₆ (n = 3-5) and the crystal structures of the complexes [Cp^*(CO)₂Fe(CH₂)₃Ru(CO )₂Cp], [Cp^*(CO)₂Fe(CH₂)₅Ru(CO )₂Cp], [Cp^*(CO)₂Fe-(CH₂)₅W(CO )₃Cp], and [Cp(CO)₂Ru(CH₂)₅W(CO)₃Cp]. The mixed-ligand complexes [Cp^*(CO)₂Fe(CH₂)_nM(CO) _xCp] (x = 2, M = Fe or Ru; x = 3, M = W, Cp^* = η⁵-C₅(CH₃)₅; Cp = η⁵-C₅H₅; n = 3-6), type I, react with one equivalent of the hydride abstractor Ph₃CPF₆ to give the transition metal-stabilized carbocation complexes [Cp^*(CO)₂Fe{μ-(C_nH _2n-1)}M(CO)_xCp]PF₆. Similarly the new heterobimetallic complexes [Cp(CO)₂Ru{μ-(C_nH_2n-1)}W(CO) ₃Cp], type II, react with Ph₃CPF₆ to give the carbocation complexes [Cp(CO)₂Ru{μ-(C_nH_2n-1)}W(CO) ₃Cp]PF₆. Spectroscopic data show that hydride abstraction selectively takes place from the methylene group β to the metal atom attached to the Cp^* ligand in type I complexes. In type II complexes, the reaction is totally metalloselective with hydride abstraction occurring at the CH₂ β to the ruthenium metal centre. All products have been characterized by IR, ¹H,¹³C NMR spectroscopy and elemental analysis. ¹H and ¹³C NMR data clearly show that in the carbocation complexes one metal is σ-bonded to the alkanediyl carbocation while the other is bonded to the cationic end in a η²-fashion forming a chiral metallacylopropane type structure. The molecular structures of the cationic metallacyclic complexes [Cp^*(CO)₂Fe{μ-(C₃H₅ )}Fe(CO)₂Cp]PF₆ [E.O. Changamu, H.B. Friedrich, M. Rademeyer, Acta Crystallogr., Sect. E 62 (2006) m442.] and [Cp^*(CO)₂Fe(μ-C₃H₅) Ru-(CO)₂Cp]PF₆ [H.B. Friedrich, E.O. Changamu, M. Rademeyer, Acta Crystallogr., Sect. E 62 (2006) m405.] have been confirmed by single crystal X-ray crystallography and reported elsewhere. The structures of the precursor complexes [Cp^*(CO)₂Fe(CH₂)₃Ru-(C O)₂Cp] (1), [Cp^*(CO)₂Fe(CH₂)₅Ru-(C O)₂Cp] (2), [Cp^*(CO)₂Fe(CH₂)₅W(CO) ₃Cp] (3), and [Cp(CO)₂Ru (CH₂)₅W(CO)₃Cp] (4), have been confirmed by single crystal X-ray crystallography. The structure of [Cp^*(CO)₂Fe(CH₂)₃Ru(CO )₂Cp] is compared with that of its corresponding cationic complex, [Cp^*(CO)₂Fe{μ-(C₃H₅ )}Ru(CO)₂Cp]PF₆.

Full text of DOI:10.1016/j.jorganchem.2007.02.016

Journal of Organometallic Chemistry 692 (2007) 2456–2472
www.elsevier.com/locate/jorganchem
Synthesis and characterization of transition metal stabilized
carbocations of the types [Cp*(CO)2Fe{l-(CnH2nꢀ1}M(CO)xCp]PF6
(x = 2, M = Fe or Ru; x = 3, M = W, Cp* = g5-C5(CH3)5;
Cp = g5-C5H5; n = 3–6) and [Cp(CO)2Ru{l-(CnH2nꢀ1)}W(CO)3Cp]PF6
(n = 3–5) and the crystal structures of the complexes
[Cp*(CO)2Fe(CH2)3Ru(CO)2Cp], [Cp*(CO)2Fe(CH2)5Ru(CO)2Cp],
[Cp*(CO)2Fe-(CH2)5W(CO)3Cp], and [Cp(CO)2Ru(CH2)5W(CO)3Cp]
a
a,
b
Evans O. Changamu , Holger B. Friedrich *, Melanie Rademeyer
a
School of Chemistry, University of KwaZulu-Natal, Durban 4041, South Africa
School of Chemistry, University of KwaZulu-Natal, Private Bag X01, Scottsville, Pietermaritzburg 3209, South Africa
b
Received 13 December 2006; received in revised form 11 February 2007; accepted 15 February 2007
Available online 21 February 2007
Abstract
The mixed-ligand complexes [Cp*(CO)2Fe(CH2)nM(CO)xCp] (x = 2, M = Fe or Ru; x = 3, M = W, Cp* = g5-C5(CH3)5; Cp = g5-
C5H5; n = 3–6), type I, react with one equivalent of the hydride abstractor Ph3CPF6 to give the transition metal-stabilized carbocation
complexes [Cp*(CO)2Fe{l-(CnH2nꢀ1)}M(CO)xCp]PF6. Similarly the new heterobimetallic complexes [Cp(CO)2Ru{l-(CnH2nꢀ1)}-
W(CO)3Cp], type II, react with Ph3CPF6 to give the carbocation complexes [Cp(CO)2Ru{l-(CnH2nꢀ1)}W(CO)3Cp]PF6. Spectroscopic
data show that hydride abstraction selectively takes place from the methylene group b to the metal atom attached to the Cp* ligand
in type I complexes. In type II complexes, the reaction is totally metalloselective with hydride abstraction occurring at the CH2 b to
1
1
the ruthenium metal centre. All products have been characterized by IR, H,13C NMR spectroscopy and elemental analysis. H and
13C NMR data clearly show that in the carbocation complexes one metal is r-bonded to the alkanediyl carbocation while the other
is bonded to the cationic end in a g2-fashion forming a chiral metallacylopropane type structure. The molecular structures of the cationic
metallacyclic complexes [Cp*(CO)2Fe{l-(C3H5)}Fe(CO)2Cp]PF6 [E.O. Changamu, H.B. Friedrich, M. Rademeyer, Acta Crystallogr.,
Sect. E 62 (2006) m442.] and [Cp*(CO)2Fe(l-C3H5)Ru-(CO)2Cp]PF6 [H.B. Friedrich, E.O. Changamu, M. Rademeyer, Acta Crystal-
logr., Sect. E 62 (2006) m405.] have been confirmed by single crystal X-ray crystallography and reported elsewhere. The structures of
the precursor complexes [Cp*(CO)2Fe(CH2)3Ru-(CO)2Cp] (1), [Cp*(CO)2Fe(CH2)5Ru-(CO)2Cp] (2), [Cp*(CO)2Fe(CH2)5W(CO)3Cp]
(3), and [Cp(CO)2Ru (CH2)5W(CO)3Cp] (4), have been confirmed by single crystal X-ray crystallography. The structure of [Cp*(CO)2-
Fe(CH2)3Ru(CO)2Cp] is compared with that of its corresponding cationic complex, [Cp*(CO)2Fe{l-(C3H5)}Ru(CO)2Cp]PF6.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Alkanediyl carbocation, Mixed-ligand; Heterobimetallic; Metallacyclopropane; Hydride abstraction
1. Introduction
Whereas mononuclear complexes of the types
[Cp(CO)2M(g2-CH2@CHR)]X (M = Fe or Ru) and
[Cp*(CO)2Fe(g2-CH2@CHR)]X(Cp = g5-C5H5,Cp* = g5-
*
Corresponding author. Tel.: +27 31 2603107; fax: +27 31 2603091.
C5(CH3)5, R = alkyl or aryl group, X = BF4 or PF6) have
E-mail address: friedric@ukzn.ac.za (H.B. Friedrich).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.02.016

E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
2457
been fairly well studied [3–11], there are very few reports of
their bimetallic analogues in which both Cp and Cp*
ligands are present in the same molecule. Furthermore,
there are very few reports of heterodinuclear organometal-
lic carbocations in the literature that have no metal–metal
bonds [1,2,12].
α
γ
β
Cp*(CO)2Fe CH2 CH2 CH2 CH2 M(CO)xCp
n
x = 2, M = Fe or Ru
x = 3, M = W
n = 0, 1, 2, 3
α
CH2
γ
β
+
CH CH2 CH2 M(CO)xCp
Transition metal stabilized carbocations were believed
to be cationic metal olefin complexes [6,7,10,12–15], which
are strongly activated towards nucleophilic attack [16].
This phenomenon plays a key role in many important cat-
alytic processes [17]. Transition metal olefin complexes are
also considered to be models for catalytic intermediates in
important industrial processes like metathesis, oligomeriza-
tion and polymerization of alkenes and alkynes, hydration
and oxidation of olefins and hydroformylation. Further-
more, there are reports that heterobimetallic catalysts are
considered superior to their monometallic analogues in
activity and selectivity [18]. A deeper understanding of
the nature of the bonding in the reactive intermediates of
these processes should give more insight into the mecha-
nisms of the catalytic reactions.
Cp*(CO)2Fe
n
Fig. 1. Structural formula of (a) alkanediyl complex (b) transition metal-
stabilized metallacyclic carbocation complex showing the labeling of
carbon positions of the hydrocarbon ligand.
observed in side-on bonded ligands in which there is free
rotation around the metal–ligand axis and the Cb–Cc bond
(see Fig. 1). Furthermore, X-ray diffraction studies have
shown that the molecular geometries of the complexes
[Cp*(CO)2Fe{l-(C3H5)}Fe(CO)2Cp]PF6 and [Cp*(CO)2-
Fe{l-(C3H5)}Ru(CO)2Cp]PF6 (Cp* = g5-C5Me5) are sig-
nificantly distorted at the b-CHd+ position to allow for
greater interaction between the metal centre and the b-
CHd+ carbon resulting in the formation of chiral metalla-
cyclopropane type structures [1,2].
The bonding between unsaturated hydrocarbons and
transition metals is usually treated as donor–acceptor in
nature and is mostly described in terms of the Dewar–
Chatt–Duncanson (DCD) model [19,20]. The validity of
the DCD model has been supported by both experiment
and theory [21–23], but more recent studies suggest that
the model is not suited to quantify the distortion of the
ligand in the complex or to predict the details of the
bonding properties of different ligands [24]. For example,
it does not distinguish between a p-bonded complex and
a metallacycle as an alternative description of the three-
membered cyclic structure. The latter is suggested to be
prevalent in high oxidation state organometallic com-
plexes [25]. Very recent experimental and theoretical
studies by Scherer et al. on valence shell charge concen-
trations in olefin complexes of nickel also suggest that
the nature of bonding between olefins and transition met-
als may be more complex than portrayed by the DCD
model [26].
We now report on a series of the mixed-ligand transition
metal alkanediyl complexes [Cp*(CO)2Fe(CH2)nM(CO)x-
Cp] (where n = 3–6; x = 2, M = Fe, or Ru, x = 3, M = W)
and [Cp(CO)2Ru(CH2)nW(CO)3Cp] (n = 3–5) and their
reactions with Ph3CPF6 to give the transition metal-stabi-
lized carbocations [Cp*(CO)2Fe{l-(CnH2nꢀ1)}M(CO)x-
Cp]PF6 (where n = 3–6; x = 2, M = Fe, or Ru, x = 3,
M = W) and [Cp(CO)2Ru{l-(CnH2nꢀ1)}W(CO)3Cp]PF6
(n = 3–5). The precursor complexes [Cp*(CO)2Fe(CH2)nM-
(CO)xCp] (where x = 2, n = 3, M = Fe, n = 3–5, M = Ru)
have been reported previously [28], but the rest are new.
2. Results and discussion
2.1. Preparation of the complexes [Cp*(CO)2Fe-
{l-(CnH2nꢀ1)}M(CO)xCp]PF6 (n = 3–6; x = 2, M = Fe
or Ru; x = 3, M = W)
Our recent NMR studies on the complexes [{Cp(CO)2-
Fe}2(l-CnH2nꢀ1)]PF6 (n = 4–10) and [{Cp(CO)2Fe}2(l-
CnH2nꢀ2)](PF6)2 (n = 5–10) showed that the metals form
metallacyclopropane type structures with the cationic end
of the alkanediyl carbocation and that the positive charge
is distributed mainly within the metallacycle [27]. These
studies demonstrated that NMR spectroscopy may be used
to distinguish between the traditional side-on bonding
between unsaturated hydrocarbons and transition metals
and the three-membered metallacycle. The metallacyclo-
propane complexes are chiral, with the b-CH carbon being
Reactions of the neutral complexes [Cp*(CO)2Fe(CH2)n-
M(CO)xCp] (M = Fe, W or Ru, n = 3–6) with Ph3CPF6 in
CH2Cl2 gave deep red solutions from which the carbocat-
ion complexes [Cp*(CO)2Fe{l-(CnH2nꢀ1)}M(CO)xCp]PF6
were obtained by precipitation with diethyl ether in good
yields (32–89%). The solutions of tungsten containing com-
plexes appeared bluish-green indicating partial decomposi-
tion. The complexes where n = 3 were precipitated as
orange microcrystalline solids, while the rest of the com-
plexes separated as red oils upon addition of diethyl ether
to the CH2Cl2 solutions. The red oils swelled up into pale
yellow, almost clear, spongy solids, which were found to
be analytically pure after drying under reduced pressure.
These have low melting points reminiscent of ionic liquids,
as they consist of large cations, [Cp*(CO)2Fe{l-
(CnH2nꢀ1)}MLy]+, associated with a relatively small coun-
ter anion PFꢀ6 .
1
the chiral centre. The chirality is observed in the H NMR
spectra in which the protons of the methylene groups
attached to the chiral centre (c-CH2) are observed to be
diastereotopic [1,2,6,27]. In some complexes this effect is
also observed in the protons of the methylene group that
is b to the chiral centre [6,27]. This effect is unlikely to be

2458
E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
The complexes where n = 3 are fairly stable in air at
selectively from the CH2 group b to the Fe attached to the
Cp* ligand. For example, the characteristic triplet in the
spectra of the neutral precursors, [Cp*(CO)2Fe(CH2)nM-
(CO)xCp] (x = 2, M = Fe or Ru; x = 3, M = W; n = 3–
6), at around 0.9 ppm due to the equivalent protons of
the CH2 a to the Cp*(CO)2Fe group is absent from the
spectra of the carbocation complexes. The position of the
peak assignable to the Cp protons in the carbocation com-
plexes is also not significantly different from the one
observed in the neutral complexes. Apart from the iron
and ruthenium-containing complexes where n = 3, all the
complexes show two characteristic sharp doublets at about
2.82 ppm (J ꢁ 8.1 Hz) and 3.05 ppm (J ꢁ 14.4 Hz) assign-
5 ꢁC. For example, a sample of [Cp*(CO)2Fe{l-(C3H5)}-
Fe(CO)2Cp]PF6 was kept in the fridge at 5 ꢁC for seven
months with minimal decomposition. However, they
decompose in solution to brown solids, especially if the sol-
vents are not nitrogen-saturated. The complexes where
n > 3 darken and become sticky when exposed to air, but
are stable for several months under nitrogen at ꢀ15 ꢁC.
They are more soluble in halogenated solvents than the
complexes where n = 3 and solubility increases with
increase carbocation chain length. All the compounds have
1
been characterized by H and 13C NMR spectroscopy, IR
spectroscopy and elemental analysis and data are given in
Tables 1–3. The structures of [Cp*(CO)2Fe{l-(C3H5)}Fe-
(CO)2Cp]PF6 and [Cp*(CO)2Fe{l-(C3H5)}Ru(CO)2Cp]-
PF6 have been confirmed by single crystal X-ray crystallog-
raphy and have been reported elsewhere [1,2]. The
structures show significant distortion in the molecular
geometry resulting from enhanced interaction between
the metal attached to the Cp* ligand and the b-CH+ group.
The 13C NMR data also support this observation and are
discussed in Section 2.1.3.
able to the diastereotopic CH2 protons
a to the
Cp*(CO)2Fe group. These protons do not show geminal
coupling. In all the complexes the c-CH2 protons show sep-
arate multiplets in the spectra. This is expected because
they are in the neighbourhood of a chiral centre (the b-
CH carbon). Similarly, the d-CH2 (see Fig. 1) protons show
separate multiplets in the spectra as would be expected for
protons in the neighbourhood of a prochiral centre (the c-
CH2). These assignments were confirmed by 2D NMR
experiments including HSQC, COSY and NOESY. The
spectra are similar to those of [Cp*(CO)2Fe{l-(C3H5)}Fe-
(CO)2Cp]PF6 recorded at ꢀ50 ꢁC, where the molecule is
expected to be static (see Fig. 3, Section 2.4). The molecular
structures of the complexes [Cp*(CO)2Fe{l-(C3H5)}Fe-
(CO)2Cp]PF6 [2] and [Cp*(CO)2Fe{l-(C3H5)}Ru(CO)2-
Cp]PF6 [1] show that the metal attached to the Cp* ligand
is coordinated to the alkanediyl carbocation in a g2-fash-
ion forming metallacyclopropane type structures, with the
2.1.1. IR spectroscopy
The IR spectral data are summarized in Table 1. The
complexes show two bands in the C–O stretching region
within the range 2053–2013 cmꢀ1, which are assignable to
the cationic Cp*(CO)2Fe carbonyls. These values are in
agreement with reported data for related mononuclear
complexes [6]. Two other expected bands lie within the
range 2003–1946 cmꢀ1, with positions characteristic of
the metal to which the CO groups are attached [28]. In this
range some of the compounds show only one strong and
broad band, probably because of band overlap.
˚
˚
bond Fe–Cb being 2.302(6) A and 2.291(3) A, respectively.
The data, therefore, suggest that the same type of bonding
prevails in the longer chain complexes.
In the spectrum of [Cp*(CO)2Fe{l-(C3H5)}W(CO)3-
Cp]PF6 the diastereotopic FeCH2 protons show sharp
and well-resolved doublets with J ꢂ 7.9 and 14.7 Hz,
respectively. The sharpness of these signals and the cou-
1
2.1.2. H NMR spectroscopy
The 1H NMR spectroscopic data are summarized in
Table 2. The data show that hydride abstraction took place
Table 1
Data for [Cp*(CO)2Fe(CnH2nꢀ1)MLy]PF6
n
MLy
Yield (%)
Mp. (ꢁC)
IR m(CO)/(cmꢀ1 a
)
Elemental analysis
C: Found (calculated)
H: Found (calculated)
3
4
5
6
3
4
5
6
3
4
5
5b
6
CpFe(CO)2
CpFe(CO)2
CpFe(CO)2
CpFe(CO)2
CpRu(CO)2
CpRu(CO)2
CpRu(CO)2
CpRu(CO)2
CpW(CO)3
CpW(CO)3
CpW(CO)3
CpW(CO)3
CpW(CO)3
82
80
60
64
89
82
32
68
51
78
57
80
63
130–133
48–51
44–47
94–96
119–120
38–40
40–42
68–70
88–90
65–67
62–63
150–152
46–48
2042m, 2016m, 1966m
2053m, 2011m, 1949m
2051m, 2024m, 1945s
2055m, 2016m, 2003s, 1942m
2042m, 2025m, 2000s, 1970s
2052s, 2015s, 1952s
43.3 (43.2)
44.1 (44.2)
45.4 (45.1)
45.7 (46.0)
39.7 (40.3)
40.9 (41.3)
42.3 (42.1)
43.3 (43.1)
35.8 (36.1)
36.6 (36.9)
38.4 (37.8)
58.1 (58.5)
38.6 (38.9)
4.1 (4.1)
4.2 (4.3)
4.3 (4.5)
4.6 (4.8)
3.8 (3.6)
4.0 (4.0)
4.3 (4.2)
4.6 (4.6)
3.3 (3.3)
3.5 (3.5)
3.4 (3.7)
5.0 (4.9)
3.9 (3.9)
2054s, 2014s, 1948s
2055s, 2016s, 2003sh, 1941s
2045s, 2021s, 2004sh, 1920sbr
2053s, 2018s, 1972m, 1915sbr
2055s, 2013s, 1911s
2055, 2014, 1912
2055s, 2012s, 1910s
a
Measured in CH2Cl2.
b
Counter ion is BPhꢀ4 ; s = strong, sbr = strong and broad, sh = shoulder, m = medium.

Table 2
1H NMR data for [Cp*(CO)2Fe(CnH2nꢀ1)MLy]PF6
e
n
MLy
CpM
Cp*Fe
cis-FeCH2(3JHH
)
trans-FeCH2
FeCH2CH
FeCH2CHCH2
MCH2
MCH2CH2
MCH2CH2CH2
a
c
c
a
c
3
CpFe(CO)2
5.16 (5H, s)
1.97 (15H, s)
2.58 (1H, m)
3.05 (1H, d, 12.8)
5.48 (1H, m)
2.52 (1H, m),
1.65 (1H, m)
1.75 (1H, m),
1.08 (1H, m)
1.35 (2H, m)
4
CpFe(CO)2
CpFe(CO)2
CpFe(CO)2
CpFe(CO)2
4.78 (5H, s)
4.76 (5H, s)
4.94 (5H, s)
4.72 (5H, s)
5.61 (5H, s)
5.37 (5H, s)
5.25 (5H, s)
5.22 (5H, s)
5.82 (5H, s)
5.44 (5H, s)
5.42 (5H, s)
5.65 (5H, s)
5.38 (5H, s)
1.87 (15H, s)
1.88 (15H, s)
2.10 (15H, s)
1.88 (15H, s)
1.96 (15H, s)
1.86 (15H, s)
1.88 (15H, s)
1.88 (15H, s)
1.98 (15H, s)
1.88 (15H, s)
1.89 (15H, s)
2.04 (15H, s)
1.88 (15H, s)
2.75 (1H, d, 7.9)
2.85 (1H, d, 8.1)
3.15 (1H, d, 8.2)
2.83 (1H, d, 8.1)
2.54 (1H, m)
3.03 (1H, d, 14.4)
3.11 (1H, d, 14.5)
3.44 (1H, d, 14.4)
3.08 (1H, d, 14.7)
2.97 (1H, m)
4.02 (1H, m)
3.92 (1H, m)
4.30 (1H, m)
3.89 (1H, m)
5.66 (1H, m)
4.02 (1H, m)
3.92 (1H, m)
3.89 (1H, m)
5.23 (1H, m)
4.06 (1H, m)
3.98 (1H, m)
4.29 (1H, m)
3.92 (1H, m)
1.22(1H, m),
2.26 (1H, m)
2.35 (1H, m),
1.15 (1H, m)
2.47 (1H, m),
1.32 (1H, m)
2.30 (1H, m),
1.23 (1H, m)
5
1.45 (1H, m),
1.69 (1H, m)
1.52 (1H, m),
1.86 (1H, m)
1.46 (2H, m)
5d
6
1.45 (2H, m)
1.38 (2H, m)
1.69 (1H, m),
1.34 (1H, m)
a
b
c
3
CpRu(CO)2
CpRu(CO)2
CpRu(CO)2
CpRu(CO)2
2.21 (2H, m),
2.90 (2H, m)
1.44 (1H, m),
1.95 (1H, m)
1.52 (2H, m)
4
2.80 (1H, d, 8.1)
2.84 (1H, d, 7.9)
2.83 (1H, d, 8.1)
2.62 (1H, d, 7.8)
2.80 (1H, d, 8.0)
2.86 (1H, d, 6.5)
3.16 (1H, d, 8.2)
2.84 (1H, d, 8.2)
3.14 (1H, d, 14.4)
3.11 (1H, d, 14.3)
3.08 (1H, d, 14.3)
3.19 (1H, d, 14.6)
3.03 (1H, d, 14.4)
3.14 (1H, d, 14.4)
3.45 (1H, d, 13.4)
3.11 (1H, d, 14.5)
2.41 (1H, m),
1.50 (1H, m)
2.33 (1H, m),
1.13 (1H, m)
2.29 (1H, m),
1.32 (1H, m)
5
1.88 (1H, m),
1.52 (1H, m)
1.58 (2H, m)
c
6
1.58 (2H, m)
1.58 (1H, m),
1.32 (1H, m)
a
c
c
a
c
3
CpW(CO)3
CpW(CO)3
CpW(CO)3
CpW(CO)3
CpW(CO)3
2.94 (1H, m),
1.96 (1H, m)
1.75 (1H, m),
1.21 (1H, m)
1.63 (1H, m),
1.15 (1H, m)
1.62–1.79
4
2.38 (1H, m),
1.30 (1H, m)
2.33 (1H, m)
5
1.63 (2H, m)
1.55 (2H, m)
5d
6
2.46 (1H, m),
1.42 (1H, m)
2.31 (1H, m),
1.23 (1H, m)
(4H, m)
1.44 (2H, m)
1.61 (1H, m),
1.36 (1H, m)
a
Recorded in acetone-d6.
Recorded in CD3CN.
Recorded in CDCl3.
Counter ion is BPhꢀ4 .
J values are given in Hz.
b
c
d
e

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E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
pling constants suggest that the chirality of the b-carbon is
maintained even in solution and that this compound does
not undergo a detectable dynamic process in solution.
Similar observations have been made in the heterobimetal-
lic complex [Cp(CO)2Ru{l-(C3H5)}W(CO)3Cp]PF6 (Sec-
tion 2.2.2).
2.1.3. 13C NMR spectroscopy
The 13C NMR data are summarized in Table 3 and they
support the conclusion that hydride abstraction occurred
selectively from the CH2 that is b to the Cp*(CO)2Fe in
spite of the steric demands of the bulky Ph3C+ and Cp*
groups. For example, the signal observed at around
14 ppm assignable to the carbon atom of the CH2 a to
Cp*(CO)2Fe in the spectra of the starting materials,
[Cp*(CO)2Fe(CH2)nM(CO)xCp] (x = 2, M = Fe or Ru;
x = 3, M = W; n = 3–6), is significantly shifted to about
57 ppm in the spectra of the carbocation complexes. Fur-
thermore, the signals assignable to the Cp(CO)2M carbonyl
and Cp carbon atoms are similar to those reported for
related neutral complexes [28], whilst the signals assignable
to the Cp*(CO)2Fe group carbonyl and Cp* carbon atoms
are shielded and deshielded, respectively. These data agree
closely with those reported for related cationic mononu-
clear complexes [6]. This further confirms that hydride
abstraction occurred from the CH2 group b to the bulky
Cp*(CO)2Fe group. This is not unexpected given the elec-
tron releasing ability of the methyl groups of the Cp*
ligand, which increases the p-donor ability of the Fe atom
to which it is attached. The increased p-donor ability of the
metal labilises the b-CH2 hydride more than the metal
atom attached to the Cp ligand on the other end of the
alkyl bridge, making it to be more readily abstracted by
the Ph3C+ electrophile. In the product, the increased p-
donor ability of the metal and the increased acceptor abil-
ity of the hydrocarbon ligand favour strong interaction
between the two. This may lead to the distortion of the
hydrocarbon ligand and formation of a strong bond. This
distortion has been observed [1,2] and is discussed along-
side the structure of the neutral complex [Cp*(CO)2Fe-
(CH2)3Ru(CO)2Cp] in Section 2.3.
The position of the signal assignable to the b-CH+ car-
bon shifts to higher field as the chain length of the alka-
nediyl carbocation increases. The shift is most significant
when the alkanediyl carbocation chain length increases
from n = 3 to n = 4. Thus, in the complex where n = 3
the b-CH+ carbon atoms resonate at about 118, while in
the complex where n = 4 the b-CH+ carbon atoms resonate
at about 90 ppm i.e. shielding of about 28 ppm by just
increasing the alkanediyl carbocation chain length by one
methylene group. In the complexes where n > 4, the
b-CH+ carbons resonate at about 88 ppm corresponding
to shielding of about 2 ppm relative to the complexes where
n = 4. As the alkanediyl carbocation chain length increases
there is reduced steric interaction between the Cp and Cp*
ligands, which allows the metal and the b-CH+ carbon to
approach each other more closely resulting in a stronger

E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
1
2461
interaction, which is probably responsible for the increase
2.2.2. H NMR spectroscopy
in the shielding experienced by the b-CH+ carbon.
The 1H NMR spectroscopic data are summarized in
Table 5. The data show that hydride abstraction occurred
at the ruthenium side of the alkyl chain. In general the
spectra show the same pattern as those of the mixed-ligand
complexes. The main difference is in the positions of the
chemical shifts assignable to the RuCH2 protons. In these
complexes the protons that show cis coupling with the
b-CH proton (the proton of the CH2 a to Ru) are more
deshielded than those that show trans coupling. In con-
trast, in the mixed-ligand complexes (Section 2.1.3) these
positions are reversed. The spectrum of the complex where
n = 3 is significantly different from those of its mixed-
ligand analogues [Cp*(CO)2Fe{l-(C3H5)}Fe(CO)2Cp]PF6
and [Cp*(CO)2Fe{l-(C3H5)}Ru(CO)2Cp]PF6, in that the
diastereotopic RuCH2 protons show sharp and well-
resolved doublets with J values of 4.8 and 14.3 Hz, respec-
tively. In this respect, it is similar to the mixed-ligand
tungsten-containing analogue [Cp*(CO)2Fe{l-(C3H5)}-
W(CO)3Cp]PF6. The sharpness of these signals suggests
that the chirality of the b-carbon is maintained even in
solution and that this complex is more static than some
of its mixed-ligand analogues.
Another remarkable observation is the very small degree
of deshielding experienced by the carbon atom of the c-
CH2 group (see Fig. 1b). For example, in the neutral com-
plex [Cp*(CO)2Fe(CH2)3Fe(CO)2Cp], the carbon of the
CH2 a to Fe(CO)2Cp (c to Cp*(CO)2Fe) resonates at
9.4 ppm (in CDCl3) [28], while in the cationic metallacyclic
complex [Cp*(CO)2Fe{l-(C3H5)}Fe(CO)2Cp]PF6 it reso-
nates at 9.8 ppm (in CDCl3). Thus, it is deshielded by only
0.4 ppm relative to the starting material. In contrast, the b-
CH2 carbon is deshielded by about ꢁ74 ppm, while the
carbon of CH2 a to Cp*(CO)2Fe is deshielded by 26 ppm
relative to the neutral complex. In the complex [Cp*(CO)2-
Fe(CH2)4Fe(CO)2Cp], the c-CH2 carbon resonates at
43.6 ppm (see Section 4.3), while in the cationic metallacy-
clic complex [Cp*(CO)2Fe{l-(C4H7)}Fe(CO)2Cp]PF6 it
resonates at 44.6 ppm. Thus, it is deshielded by only
1 ppm relative to the neutral complex. In contrast, the
b-CH2 carbon is deshielded by about 44 ppm, while the
a-CH2 carbon is deshielded by about 42 ppm relative to
the neutral complex. This trend is observed in all the other
complexes and can only be attributed to increased back-
donation from the metal atom to the b-CH+, which effec-
tively diminishes the negative inductive effect on the
c-CH2 carbon. This also indicates that the positive charge
is distributed mainly among the groups forming the metal-
lacyclopropane ring. This further supports the representa-
tion of the bonding between the metal centre and the
alkanediyl carbocation as shown in Fig. 1(b), rather than
the traditional side-on DCD model [19,20].
2.2.3. 13C NMR spectroscopy
These data are summarized in Table 6. They support the
conclusion that hydride abstraction took place selectively
at the Ru side of the alkyl chain. For example, the signal
assignable to the carbon of the CH2 a to the Cp(CO)2W
metal appears only slightly deshielded in the spectra of
the cationic metallacyclic complexes relative to the corre-
sponding neutral complexes, [Cp(CO)2Ru(CH2)nW-
(CO)3Cp]. On the other hand, the a and b carbon atoms
on the Ru side are significantly deshielded in the cationic
metallacyclic complexes relative to the neutral starting
materials, which strongly suggests that the positive charge
is located on the Ru side of the molecule. This may be
attributed to the ruthenium centre being less sterically
crowded than the tungsten centre. Hence, the ruthenium
is likely to interact more strongly with the b-CH2 than
the tungsten and thus labilise a hydride, which is then
abstracted by the trityl salt, resulting in the formation of
a distorted tetragonal pyramidal structure.
2.2. Preparation of the complexes [Cp(CO)2Ru-
{l-(CnH2nꢀ1)}W(CO)3Cp]PF6(n = 3–5)
The new neutral Ru–W heterobimetallic complexes
[Cp(CO)2Ru(CH2)nW(CO)3Cp] were prepared by reacting
the ruthenium complexes [Cp(CO)2Ru(CH2)nI] (n = 3–5)
with the salt Na[Cp(CO)3W] in THF. The characterization
data of these new compounds are reported in Section 4.9.
They were reacted with Ph3CPF6 in CH2Cl2 to give orange
red solutions from which the corresponding cationic
metallacyclic complexes [Cp(CO)2Ru{l-(CnH2nꢀ1)}W-
(CO)3Cp]PF6 were precipitated as pale yellow, air-stable
microcrystalline solids by the addition of diethyl ether.
These complexes are insoluble in most hydrocarbon sol-
vents such as hexane and halogenated solvents such as
chloroform. They are, however, fairly soluble in acetone,
nitromethane and THF.
2.3. The molecular structure of the neutral complex
[Cp*(CO)2Fe(CH2)3Ru(CO)2Cp] (1)
The molecular structure of 1 in Fig. 2 shows two crystal-
lographically independent molecules found in the asym-
metric unit. In each molecule, the Fe and Ru atoms are
coordinated in a pseudo-octahedral fashion, with the Fe
atom coordinated by two carbonyls, the g5-pentamethylcy-
clopentadienyl ligand and the alkyl chain. The Ru atom is
coordinated by two carbonyls, a g5-cyclopentadienyl
ligand and the bridging alkyl chain. The alkyl chain adopts
the energetically favoured all-trans conformation. With
respect to the Fe attached to the Cp* ligand the b-carbon
2.2.1. IR spectroscopy
The IR spectral data are summarized in Table 4. These
complexes show four C–O stretching bands: two in the range
2084–2041 cmꢀ1, assignable to cationic Ru–CO carbonyls,
and two others in the range 2011–1911 cmꢀ1, assignable to
the neutral W–CO carbonyls. These values are in close agree-
ment with reported data for related compounds [12,28,29].

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E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
Table 4
Data for [Cp(CO)2Ru(CnH2nꢀ1)W(CO)3]PF6
n
Yield (%)
Decomposing temperature (ꢁC)
IR m(CO)/(cmꢀ1) in CH2Cl2
Elemental analysis
C: Found (calculated)
H: Found (calculated)
3
4
5
59
52
54
>118
>107
>95
2069, 2024, 1924
2084, 2054, 2015, 1913
2083, 2041, 2011, 1911
29.7 (29.2)
30.4 (30.2)
31.7 (31.2)
2.1 (2.0)
2.5 (2.3)
2.8 (2.5)
of the alkyl chain lies in a conformation between the two
CO ligands, while with respect to the ruthenium centre it
lies in a conformation between a CO ligand and the Cp
ligand. This conformational preference with respect to
the Cp* ligand has been observed in reported mononuclear
complexes containing the Cp* ligand [30,31]. The confor-
mation with respect to the Cp ligand is common with alkyl
and alkanediyl Cp containing complexes [29,32,33]. The
direct consequence of this conformations in the same
molecule is that the Cp* ligand is approximately perpendic-
ular to the alkyl chain, while the Cp on the Ru atom is par-
allel to the same alkyl chain plane. In this way the rings are
far apart, thus reducing steric interaction.
1a. Thus, there is significant distortion in the molecular
geometry after hydride abstraction, resulting in stronger
interaction between the metal and the b-CH+ carbon.
The foregoing observations confirm the suggestions
made by Cais et al. that organometallic carbocations are
stabilized by the delocalization of the positive charge and
the ability of the molecule to undergo geometrical changes,
which result in enhanced bonding interaction between the
metal atom and the formally positive ligand moiety [35].
2.4. Variable temperature NMR studies on
[Cp*(CO)2Fe{l-(C3H5)}Fe(CO)2Cp]PF6
1
The H NMR spectrum of the complex [Cp*(CO)2Fe-
˚
˚
The Fe–Ca bond lengths of 2.06(3) A and 2.11(2) A of
the independent molecules in the asymmetric unit of com-
{l-(C3H5)}Fe(CO)2Cp]PF6 showed five broad peaks
assignable to the five protons of the C3H5 moiety (Table
2). The broadening of the peaks in the spectrum was possi-
bly due to the molecule undergoing a dynamic process in
solution. Fig. 3a shows a stacked plot of some of the spec-
tra recorded at various temperatures. It can be seen that all
the signals assignable to the a-CH2 protons of the C3H5
moiety (Htrans, Hcis, Ha and Hb) broadened and then col-
lapsed into the baseline at temperatures above 40 ꢁC.
Below 15 ꢁC the peaks assignable to the protons of the
CH2 group a to the Cp*(CO)2Fe group (Htrans and Hcis)
resolve into sharp doublets. The separate peaks assigned
to the protons of the CH2 group a-to the Cp(CO)2Fe group
(Ha and Hb) resolved into a multiplet at 2.55 ppm and a
doublet of doublets at 1.65 ppm, respectively. There was
no further change observed in the spectrum at tempera-
tures below 0 ꢁC. This showed that the dynamic process
responsible for peak broadening was ‘‘frozen out’’ rather
easily by lowering the temperature of the solution slightly
below room temperature. At all the temperatures the Cp*
and Cp ligand peaks remained sharp singlets. We had
hoped that the diasteriotopic a-CH2 protons would coa-
lesce into doublets at a temperature above room tempera-
ture but the compound decomposed before this was
observed.
˚
˚
pound 1 are similar to 2.057 A and 2.069 A reported for
Cp*(CO)2Fe(CH2)3Br [30] and Cp*(CO)2Fe(n-C5H11) [31],
˚
respectively. The Ru–Ca bond lengths of 2.13(2) A and
2.17(2) A in compound 1 are within the range of 2.142–
2.179 A reported for [Cp(CO)2Fe(CH2)3Ru(CO)2Cp] [29]
˚
˚
and [Cp(CO)2Ru(CH2)5Ru(CO)2Cp] [34]. Important bond
lengths and angles are summarized in Table 7.
The torsion angles Fe1–C11–C12–C13 = 177.2(17)ꢁ,
Ru1–C13–C12–C11 = ꢀ161.6(18)ꢁ, C33–C34–C35–Ru2 =
162.8(17)ꢁ are close to 180ꢁ, confirming that the metals are
r-bonded to the alkyl chain [33].
In Table 8 selected bond angles and bond lengths of the
neutral complex 1 (molecule A) are compared with those of
the corresponding cationic metallacyclic complex,
[Cp*(CO)2Fe{l-(C3H5)}Ru(CO)2Cp]PF6 (1a). It can be
seen that there is significant distortion in the molecular
geometry around the Fe centre in compound 1a. For exam-
ple, in going from compound 1 to 1a, the angle C12–C11–
Fe (i.e. Cb–Ca–Fe) decreased from 117.5(18)ꢁ to 76.51(14)ꢁ.
On the other hand, the angle C11–C12–Fe (i.e. Ca–Cb–Fe)
increased from the non-bonded 36.85ꢁ to the bonded
67.23ꢁ. The Fe–C12 (i.e. Fe–Cb) bond distance decreased
˚
from the non-bonded 3.05 A in
1 to the bonded
˚
˚
2.291(3) A in 1a. This is significantly shorter than 2.59 A
and 2.72 A reported for the carbocation complex
˚
At temperatures above room temperature, the signal at
5.5 ppm (assignable to the b-CH+ proton) sharpened and
resolved into an almost binomial quintet (see Fig. 4). This
suggested that the metallacyclopropane ring observed in
solution at room temperature and in the solid state may
have opened. At temperatures below room temperature,
this multiplet became broad and less resolved.
[{Cp(CO)2Fe}2{l-C3H5)}]PF6 [32]. These observations
suggest a significant shortening of the Fe–C12 (i.e. Fe–
Cb) distance and hence strong interaction between the
metal centre and the b-CH+ carbon. The bond length
˚
Fe–C11 (i.e. Fe–Ca) increased from 2.06(3) A in 1 to
˚
2.173(2) A in 1a. The C11–C12–C13 bond angle of the
alkyl group increased from the more tetrahedral 114ꢁin 1
to the distorted 125ꢁ in the cationic metallacyclic complex
To further probe the changes in the spectra at tempera-
tures above room temperature, the solvent was changed

E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
2463
from acetone-d6 to dimethylformamide-d7 (DMF). The
spectra obtained at all temperatures were the same as those
observed in acetone, apart from insignificant changes in the
chemical shift positions. However, it was observed that
when the temperature was raised above 70 ꢁC, even the sig-
nal assignable to the b-CH+ proton disappeared, suggest-
ing that the compound may have decomposed or the
carbocation may have been displaced by the coordinating
DMF solvent. Solvent coordination and subsequent olefin
displacement has been reported involving acetonitrile as
the solvent in hydride abstraction reactions [7]. In the pres-
ent case the spectra show some evidence to support the
presence of [Cp(CO)2FeCH2CH@CH2] in solution. For
example, a new multiplet at about 6.00 ppm assignable to
the @CH proton in [Cp(CO)2FeCH2CH@CH2], two dou-
blets between 4.46 and 4.78 ppm assignable to the @CH2
protons and a doublet at 2.10 ppm assignable to FeCH2
protons appeared. Resonances assignable to the dimers
[Cp*(CO)2Fe]2 and [Cp(CO)2Fe]2 were also observed at
1.78 ppm and 4.96 ppm, respectively, but not any deriva-
tives of the C3H5 moiety. Any cyclopropane or propene
formed from the decomposition or displacement may have
left the solution and hence not been detected by NMR,
because of the high operating temperatures.
The position of the multiplet assignable to the b-CH+ pro-
ton shifts to higher field as the temperature is lowered
(Fig. 4). This observed shielding may be due to increasing
back-donation of electron density from the metal centre into
the formally positively charged b-CH+, leading to the
strengthening of the metallacyclopropane structure. At
lower temperatures (below 0 ꢁC) there is increased interac-
tion between the metal centre and the b-CH+ carbon result-
ing in increased back-donation and hence shielding of the
proton. At high temperatures (>50 ꢁC) increased molecular
vibration leads to opening of the metallacyclopropane ring.
2.5. Reactions of the mixed-ligand complexes
[Cp*(CO)2Fe{l-(C5H9)}M (CO)2Cp]PF6 (M = Fe, Ru)
with NaI and CD3OD
The reactions of the compound [Cp*(CO)2Fe{l-
(C5H9)}Ru(CO)2Cp]PF6 with both NaI and deuterated
methanol, as well as the reaction between [Cp*(CO)2-
Fe{l-(C5H9)}Fe(CO)2Cp]PF6 and NaI, were studied as
illustrations of the reactions between the mixed-ligand car-
bocation complexes with nucleophiles. The reactions were
followed by proton NMR spectroscopy. Both the methox-
ide and iodide anions attack the Fe attached to the Cp*
ligand, giving [Cp*(CO)2FeOCD3] and [Cp*(CO)2FeI],
respectively. In addition, the new ruthenium g1-alkenyl
complex [Cp(CO)2Ru(CH2)3CH@CH2] was obtained
from [Cp*(CO)2Fe{l-(C5H9)}Ru(CO)2Cp]PF6, while the
previously reported iron g1-alkenyl complex [Cp(CO)2-
Fe(CH2)3CH@CH2] [36] was obtained from [Cp*(CO)2-
Fe{l-(C5H9)}Fe(CO)2Cp]PF6. No addition products were
observed in solution. The reactions did not go to comple-
tion after 40 min and were found to be slower that those

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E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
Table 6
13C NMR data for [Cp(CO)2Ru(CnH2nꢀ1)W(CO)3Cp]PF6 in CDCl3
n
RuCO
WCO
CpRu
CpW
RuCH2
RuCH2CH
RuCH2CHCH2
WCH2
WCH2CH2
3
4
5
N.O.
197.1, 195.4
197.0, 195.4
230.2, 220.1
229.6, 219.9
230.6, 219.9
93.9
93.4
93.3
91.9
92.2
92.3
40.6
50.1
51.8
115.8
89.1
86.1
ꢀ2.2
ꢀ6.6
45.1
44.0
ꢀ11.8
41.1
N.O. = not observed.
O7
C43
X-ray quality crystals. The reaction with NaBPh4 was
carried out in a bid to raise the melting points and the sta-
bility of these complexes. It was found that the complexes
[Cp*(CO)2Fe{l-(C5H9)}W(CO)3Cp]BPh4 and [Cp*(CO)2-
Fe{l-(C5H9)}Fe(CO)2Cp]BPh4 readily form when the pre-
cursors are dissolved together in acetone and stirred briefly.
They precipitate as yellow plates upon addition of diethyl
ether to the CH2Cl2 solutions. They melt at 150–152 ꢁC,
which is significantly higher when compared with the 62–
63 ꢁC of the PFꢀ6 salts.
C41
C40
C39
C42
C44
O8
Ru2
C38
C18
C19
C20
O3
C35
C22
C21
C17
O4
C34
Ru1
C16
C13
C33
C37
O5
O2
C15
C36
Fe2
O6
C30
C12
C11
O1
C25
C14
C29
C24
Fe1
C26
C27
C8
C4
C10
C23
C28
C7
C2
C9
C3
C32
2.7. Molecular structure of the neutral complexes
[Cp*(CO)2Fe(CH2)5Ru(CO)2Cp] (2),
[Cp*(CO)2Fe(CH2)5W(CO)3Cp] (3) and
[Cp(CO)2Ru(CH2)5W(CO)3Cp] (4)
C6
C1
C5
Molecule B
Molecule A
Fig. 2. The Molecular structures of the crystallographically independent
molecules (A and B) in the asymmetric unit of 1 showing atom-numbering
scheme.
The above complexes are precursors to some of the car-
bocation complexes discussed in Sections 2.1 and 2.2.
Determination of their structures by crystallography is an
important step towards understanding the source of the
stability exhibited by the carbocation complexes, as well
as their structures. Obtaining X-ray quality crystals of
the carbocation complexes remains a challenge, as they
behave like ionic liquids, but a change of counter ion has
shown some promising results.
Table 7
Selected bond lengths and angles for compound 1
˚
Bond length (A)
Bond angle (ꢁ)
C14–Fe1
C15–Fe1
Fe1–C11
C13–C12
C13–Ru1
C22–Ru1
C21–Ru1
C37–Fe2
C33–C34
C33–Fe2
Ru2–C44
Ru2–C43
Ru2–C35
C11–C12
C36–Fe2
C34–C33
C34–C35
1.78(3)
1.74(2)
2.06(3)
1.57(3)
2.13(2)
1.85(3)
1.84(3)
1.74(3)
1.52(4)
2.11(2)
1.88(3)
1.91(3)
2.17(2)
1.49(4)
1.78(3)
1.52(4)
1.54(3)
C15–Fe1–C14
C15–Fe1–C11
C14–Fe1–C11
C12–C11–Fe1
C34–C33–Fe2
C21–Ru1–C22
C21–Ru1–C13
C22–Ru1–C13
C21–Ru1–C19
C37–Fe2–C36
C37–Fe2–C33
C36–Fe2–C33
C44–Ru2–C43
C44–Ru2–C35
C43–Ru2–C35
C34–C35–Ru2
C11–C12–C13
98.8(12)
91.1(11)
85.8(12)
117.5(18)
116.4(17)
88.9(12)
87.1(11)
85.6(11)
101.6(12)
96.5(13)
87.9(12)
90.2(11)
91.5(13)
87.7(11)
87.4(11)
111.4(15)
114.0(2)
The molecular structure of [Cp*(CO)2Fe(CH2)5Ru-
(CO)2Cp] (2), shown in Fig. 5 is broadly similar to that
of compound 1, the major difference being the length of
the alkyl bridge between the metal centres. Compound 2
has a C5 alkyl bridge, while compound 1 has a C3 alkyl
bridge between the metal centres. The bond length Fe–
˚ ˚ ˚
C
(alkyl) = 2.063(5) A is similar to 2.06(3) A and 2.11(2) A
observed in the two independent molecules of 1, respec-
˚
tively. The bond length Ru–C(alkyl) = 2.161(5) A in com-
˚
˚
pound 2 is similar to 2.13(2) A and 2.17(2) A observed in
compound 1. Selected bond angles and bond lengths are
given in Table 9.
The torsion angles C11–C12–C13–C14 = 177.6(4)ꢁ,
of the corresponding symmetrical complexes [{Cp(CO)2-
Fe}2{l-(CnH2nꢀ1)}]PF6 [27]. This is attributable to stabil-
ization by the electron releasing Cp* ligand that enhances
the p-donor ability of the Fe to the b-CH carbon.
C15–C14–C13–C12 = 173.1(4)ꢁ,
C13–C12–C11–Fe =
165.6(3)ꢁ, C13–C14–C15–Ru = ꢀ176.8(3)ꢁ confirm that
the alkyl chain is fully saturated and r-bonded to both met-
als [33].
The molecular structure of [Cp*(CO)2Fe(CH2)5W-
(CO)3Cp] (3) is shown in Fig. 6. The compound differs
from compound 2 in that it contains tungsten instead of
ruthenium as the second metal centre. The geometry at
the tungsten atom is distorted tetragonal pyramidal in
which the base is made up of the three carbonyl ligands
2.6. Reactions of [Cp*(CO)2Fe{l-(C5H9)}M(CO)xCp]-
PF6 with NaBPh4 (x = 2, M = F; x = 3, M = W)
The complexes [Cp*(CO)2Fe{l-(CnH2nꢀ1)}M(CO)xCp]-
PF6 (where n = 4–6) are low melting solids and did not give

E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
2465
Table 8
Comparison between the bond distances of complex 1 and the carbocation complex 1a
1
1aa
1
1aa
˚
Bond length (A)
Bond angle (ꢁ)
C11–C12–Fe
C12–C11–Fe
C11–Fe–C12
C14–Fe–C15
C11–C12–C13
C12–C13–Ru
C21–Ru–C22
a
36.85
117.50 (18)
25.68
98.80(12)
114(2)
115.9(16)
88.9(12)
67.23(14)
76.51(14)
36.26(8)
92.51(11)
125.2(2)
107.23(15)
92.96(12)
Fe–C11
Fe–C12
Fe–C14
Fe–C15
O2–C14
O1–C15
C11–C12
2.06(3)
3.05
2.17(2)
2.29(3)
1.78(3)
1.79(3)
1.13(3)
1.14(3)
1.39(3)
1.78(3)
1.74(2)
1.13(4)
1.16(3)
1.49(4)
Data obtained from the CIF file of Ref. [2].
a
b
H
Cp*(CO)Fe
Fe(CO)2Cp
C
C
+
H
H
C
b
a
Hcis
Htrans
3b
Fig. 3. (a) The stacked plot of selected 1H NMR spectra of the a-CH2 protons of C3H5 portion of [Cp*(CO)2Fe{l-(C3H5)}Fe(CO)2Cp]PF6 recorded
between ꢀ50 and 50 ꢁC. Labeling of protons is shown in the structure on the right side (b).
and C15 of the alkyl chain and the apex is the metal capped
for related compounds [30]. W–C(CO) vary from 1.960(6)–
1.981(6) A and are within the ranges reported for related
compounds [30]. Selected bond angles and bond lengths
are given in Table 9.
˚
with the cyclopentadienyl ligand. The bond length Fe–
˚
C
(alkyl) = 2.067(5) A is similar to the values observed in 1
˚
and 2. The bond length W–C(alkyl) = 2.321(6) A is within
the range expected for W–C(alkyl) bond distances reported
Compounds 2 and 3 are precursors to the cationic
metallacyclic
complexes
[Cp*(CO)2Fe{l-(C5H9)}Ru-
(CO)2Cp]PF6 and [Cp*(CO)2Fe{l-(C5H9)}W(CO)3Cp]PF6.
Even though the structures of the cationic metallacyclic
complexes have not been confirmed by X-ray crystallogra-
phy, 13C NMR data of the cationic metallacyclic complexes
C9
O1
O2
C8
C19
C16
C20
C4
C17
Fe
C3
C5
C18
C24
C21
C22
C10
C12
C14
C2
C1
C11
Ru
O4
C13
C15
C7
C23
C6
O3
Fig. 4. The stacked plot of selected 1H NMR spectra of the b-CH proton
of [Cp*(CO)2Fe{l-(C3H5)}Fe(CO)2Cp]PF6 recorded between ꢀ50 and
50 ꢁC.
Fig. 5. The molecular structure of [Cp*(CO)2Fe(CH2)5Ru(CO)2Cp] (2)
showing the atom numbering scheme.

2466
E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
Table 9
˚
Selected bond lengths (A) and bond angles (ꢁ) of compounds 2, 3 and 4
2
3
4
2
3
4
˚
Bond length (A)
Bond angle (ꢁ)
Fe–C11
Fe–C16
Fe–C17
C16–O2
C17–O1
Ru–C15
Ru–C23
Ru–C24
C23–O4
C24–O3
2.063(5) Fe1–C11 2.067(5) C20–Ru1 1.85(2)
1.754(6) Fe1–C16 1.760(6) C21–Ru1 1.847(19) C17–Fe–C11
1.745(5) Fe1–C17 1.747(6) C10–Ru1 2.138(16) C16–Fe–C11
C17–Fe–C16
97.3(3) C17–Fe1–C16
88.3(2) C17–Fe1–C11
90.0(2) C16–Fe1–C11
93.9(3) C21–Ru1–C20
89.4(2) C21–Ru1–C10
90.2(2) C20–Ru1–C10
92.3(7)
85.9(7)
87.9(8)
116.5(12)
113.2(14)
113.4(14)
113.4(13)
75.3(6)
1.160(6) C16–O1
1.149(7) C17–O2
2.161(5) W1–C15 2.321(6) C13–W1
1.851(6) W1–C23 1.960(6) C6–W1
1.859(6) W1–C24 1.981(6) O5–C21
1.154(6) W1–C25 1.979(6) O4–C20
1.141(7) C11–W1
1.157(7) C12–W1
1.968(16) C12–C11–Fe
117.2(3) C12–C11–Fe1 118.4(4) C9–C10–Ru1
1.992(18) C11–C12–C13 114.6(4) C11–C12–C13 115.0(4) C6–C7–C8
1.969(17) C12–C13–C14 112.2(4) C12–C13–C14 110.1(5) C7–C8–C9
2.320(16) C13–C14–C15 114.0(4) C13–C14–C15 113.3(5) C10–C9–C8
1.16(2)
1.15(2)
C14–C15–Ru
C23–Ru–C24
C23–Ru–C15
C24–Ru–C15
114.4(3) C14–C15–W1 115.4(4) C11–W1–C6
90.5(2) C23–W1–C25 103.9(2) C13–W1–C6
89.4(2) C23–W1–C24
85.9(2) C25–W1–C24
C23–W1–C15
73.1(6)
1.148(7) O3–C23
1.167(7) O3–C13
1.154(6) O2–C12
1.140(7) O1–C11
1.15(2)
1.15(2)
1.16(2)
76.9(2) C12–W1–C6
79.8(2) C11–W1–C13
74.2(2) C11–W1–C12
131.4(7)
105.3(7)
75.6(7)
C12–C11 1.519(6) O4–C24
C12–C13 1.525(6) O5–C25
C14–C13 1.517(6) C11–C12 1.515(8) C6–C7
C14–C15 1.520(6) C13–C12 1.533(8) C7–C8
C13–C14 1.538(8) C9–C8
1.529(16)
1.530(15)
1.537(16)
1.532(16)
C24–W1–C15 134.1(2) C13–W1–C12
C25–W1–C15 73.6(2) C7–C6–W1
78.1(8)
118.1(10)
C14–C15 1.536(8) C9–C10
as the polymethylene-bridged cobaloximes [37,38]. It has
also been reported in the alkyl substituent of the imidazo-
lium salt 1,10-[1,10-decyl]bis[3-methyl-1H-imidazolium-1-
yl]hexafluorophosphate [39].
C7
O2
C8
C2
C3
C17
O3
O5
O4
C23
C25
C11
C15
C13
C1
˚
The bond length Ru–Ca(alkyl) = 2.138(16) A falls within
C4
Fe
C12
˚
C9
the range 2.13(2)–2.17(2) A observed in compounds 1 and
C6
C14
C24
C5
C6
W
˚
˚
2. The Ru–CCO bonds are 1.85(2) A and 1.847(19) A and
C16
˚
are within the range 1.84(4)–1.91(3) A observed in com-
C21
C19
C22
C18
C20
O1
pounds
1 and 2. The bond length W–Ca(alkyl) =
˚
2.320(16) A is the same as that observed in compound 3.
˚
Similarly, the W–CCO distances of 1.968(16) A, 1.992(18)
Fig. 6. The molecular structure of [Cp*(CO)2Fe(CH2)5W(CO)3Cp] (3)
showing the atom numbering scheme. Note that the methyl groups on the
Cp* ligand are disordered.
˚
˚
˚
A and 1.969(17) A, respectively, fall within the range
1.960(6)–1.981(6) A observed in compound 3. The C–C
bond distances within the alkyl chain are similar to those
within the alkyl chain in compound 3, but slightly longer
than those in compound 2. The Cp ligands are oriented
almost perpendicular to one another, with the angle
between the ring planes being 81ꢁ. Selected bond angles
and bond distances are given in Table 9.
suggest that similar geometry distortion as that observed in
[Cp*(CO)2Fe{l-(C3H5)}Ru(CO)2Cp]PF6 (1a), may have
occurred upon hydride abstraction. Efforts are being made
to obtain X-ray quality crystals of the carbocation com-
plexes. Crystal data and experimental details of data collec-
tion and refinement are given in Table 10.
The torsion angles associated with the alkyl bridge are
W–C6–C7–C8 = ꢀ168.9(11)ꢁ,
C6–C7–C8–C9 = 70(2)ꢁ,
C10–C9–C8–C7 = 175.4(16)ꢁ, and C8–C9–C10–Ru1 =
ꢀ178.2(13)ꢁ. The significantly reduced angle C6–C7–C8–
C9 = 70(2)ꢁ reflects the unusual kink in the alkyl chain.
The torsion angles C12–C13–C14–C15 = 170.1(5)ꢁ,
Fe1–C11–C12–C13 = 178.1(4)ꢁ,
C14–C13–C12–C11 =
175.8(5)ꢁ, and C13–C14–C15–W1 = 167.6(4)ꢁ confirm that
the alkyl chain is fully saturated and r-bonded to both
transition metals.
3. Conclusions
The molecular structure of [Cp(CO)2Ru(CH2)5W-
(CO)3Cp] (4) shown in Fig. 7 can be compared with both
compounds 2 and 3. It contains a ruthenium centre coordi-
nated in the same way as in compound 2 and is linked to a
tungsten centre by a pentanediyl chain in the same manner
as in compound 3. It differs from both complexes by having
a ‘‘kink’’ in the alkyl chain (see Fig. 7). This strained
gauche conformation has been observed in other organo-
metallic complexes involving long chain alkyl groups such
We have shown, by 1H and 13C NMR spectroscopy, that
in the mixed-ligand complexes [Cp*(CO)2Fe(CH2)nM-
(CO)xCp] (n > 3, x = 2, M = Fe, Ru; x = 3, M = W),
hydride abstraction takes place selectively from the CH2
group b to Fe attached to the Cp* ligand. In the Ru–W
complexes [Cp(CO)2Ru(CH2)nW(CO)3Cp] where n = 4, 5
hydride abstraction was totally metalloselective, always
taking place at the CH2 group b to the Ru metal centre.

E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
2467
Table 10
Crystal data and experimental details for complexes 1, 2, 3 and 4
Compound
1
2
3
4
Empirical formula
Formula weight (g/mol)
Lattice
C22H26FeO4Ru
511.36
Monoclinic
P21/c
C24H30FeO4Ru
539.40
Monoclinic
C2/c
C25H30FeO5W
650.21
Monoclinic
P21/c
C25H30O5RuW
695.43
Monoclinic
P21/c
Space group
˚
a (A)
26.57(2)
8.482(4)
20.862(11)
90.00
112.35(6)
90.00
4348(5)
4
1.562
30.739(5)
8.2029(12)
23.649(4)
90.00
127.992(10)
90.00
4699.5(12)
8
1.525
12.5991(4)
12.4843(3)
15.6910(5)
90.00
105.798(3)
90.00
2455.75(13)
4
1.759
22.241(9)
7.747(2)
11.506(4)
90.00
99.89(3)
90.00
1953.0(12)
4
2.127
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Dcalc (Mg mꢀ3
)
Temperature (K)
Crystal size (mm)
F(000)
l (Mo Ka) (mmꢀ1
Wavelength (k)
150(2)
0.3 · 0.3 · 0.3
2080
1.385
0.71073 A
120(2)
0.2 · 0.2 · 0.05
2208
1.286
0.71073 A
150(2)
0.2 · 0.15 · 0.05
1280
5.303
0.71073 A
120(2)
0.4 · 0.4 · 0.4
1192
6.686
0.71073 A
)
˚
˚
˚
˚
Reflections for cell parameters
Crystal description
620
plate
1003
plate
852
plate
1037
plate
Crystal colour
Collected data of 2h range (ꢁ)
Transmission factors (Tmin
Yellow
4.15–29.67
0.6814, 0.6814
Yellow
4.20–31.87
0.7830, 0.9385
Yellow
3.60–34.34
0.4168, 0.7774
Pale yellow
4.42–29.92
0.1751; 0.1751
,
Tmax
)
Measured reflections
Independent reflections
Observed reflections with
31194
11304
10192
23427
7528
5324
39720
9268
4583
18899
4981
4752
I > 2r(I)
Internal fit
Rint = 0.0835
ꢀ36 ! 23
Rint = 0.0615
ꢀ45 ! 35
Rint = 0.0553
ꢀ18 ! 18
Rint = 0.0665
ꢀ28 ! 30
h
k
l
ꢀ11 ! 11
ꢀ11 ! 12
ꢀ17 ! 19
ꢀ9 ! 10
ꢀ27 ! 28
ꢀ29 ! 33
ꢀ24 ! 24
ꢀ13 ! 15
Final R indices [F2 > 2r(F2)]
R1 = 0.2515,
wR(F2) = 0.5441
1.124
R1 = 0.0619,
wR(F2) = 0.1448
1.208
R1 = 0.0501,
wR(F2) = 0.1254
0.899
R1 = 0.0956,
wR(F2) = 0.2203
1.147
Goodness-of-fit on F2(S)
Parameters
280
276
294
244
Maximum shift
(D/r)max = 0.011
Dqmax = 6.602
(D/r)max = 0.001
Dqmax = 1.203
(D/r)max = 0.063
Dqmax = 5.453
(D/r)max = 0.001
Dqmax = 6.674
Largest difference in peak
ꢀ3
˚
(e A
)
ꢀ3
˚
Largest hole (e A
)
Dqmin = ꢀ5.814
Dqmin = ꢀ0.503
Dqmin = ꢀ0.918
Dqmin = ꢀ6.480
O5
between one metal centre and the formally positive
b-CH+ carbon, resulting in the formation of a metallacy-
clopropane type of structure. The carbocation com-
plexes are chiral with the b-CH carbon being the chiral
C8
O1
C11
C21
C10
C7
C9
C16
1
centre according to H and 13C NMR data. This is fur-
C6
Ru1
C20
ther strong evidence supporting the proposed metallacyclo-
propane bonding model. 13C NMR data have also shown
that the positive charge in the cationic metallacyclic com-
plexes is delocalized mainly within the metallacyclopro-
pane ring.
The cationic metallacyclic complexes [Cp*(CO)2Fe-
{l-(CnH2nꢀ1)}MLy]PF6 where n > 3 behave like ionic
liquids. They collect as red oils upon addition of diethyl ether
to their CH2Cl2 solutions and attempts to dry them under
reduced pressure leads to the formation of low melting
spongy solids. This is not unexpected given the fact that
the cations, [Cp*(CO)2Fe{l-(CnH2nꢀ1)}MLy]+, are large,
while the associated counter anion PFꢀ6 is relatively small.
C13
C12
W1
C3
C15
O2
O4
C17
O3
C19
C2
C1
C18
C4
C5
Fig. 7. The molecular structure of [Cp(CO)2Ru(CH2)5W(CO)3Cp] (4)
showing the atom numbering scheme. Note that the methyl C10 and C21
are disordered.
Single crystal X-ray crystallography data have also
revealed that hydride abstraction leads to distortion of
the molecular geometry to allow increased interaction

2468
E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
4. Experimental
4.1. General
rated n-decane (30 mL) in a Schlenk tube. The mixture
was refluxed for 24 h at 160 ꢁC and then allowed to cool
to room temperature over several hours. A shiny black
solid precipitated and was filtered off in air, washed with
hexane (10 mL) and dried under reduced pressure. It was
extracted several times with dichloromethane until the
extracts were clear (about 150 mL) and a dark maroon
solution was obtained. The solvent was removed under
reduced pressure to give a maroon solid, which was found
to be analytically pure, and its IR spectrum in CH2Cl2 and
elemental analysis data matched those of an authentic sam-
ple (Strem Chemicals).
All reactions were carried out under inert atmosphere
(UHP or HP nitrogen) using standard Schlenk tube tech-
niques. Heptane (Rochelle >98%) was distilled from
sodium/benzophenone ketyl and stored over sodium wire.
Decane and diglyme were dried over sodium wire and used
˚
without distillation. The molecular sieves 4 A (Merck AR)
were dried in a tube furnace at 250 ꢁC for 10 h and cooled
in a dessiccator before use. The other solvents were treated
as previously reported [27].
Dicyclopentadiene (Fluka 95%), iron pentacarbonyl
(Aldrich), pentamethylcyclopentadiene (Aldrich 95%),
RuCl3 Æ xH2O (Johnson Matthey), tungsten hexacarbonyl
(Acros 99%), pentane, ferric sulfate (Merck AR), glacial
acetic acid (Kleber 99.5%), mercury (Associated Chemical
Enterprises, triple distilled AR), 1,3-dibromopropane
(Aldrich 99%), 1,4-dibromobutane (Fluka 98%), 1,5-dib-
romopentane (Aldrich 97%), and 1,6-dibromohexane
(Aldrich 98%) were used as purchased. Sodium iodide
was dried under reduced pressure at 100 ꢁC for 8 h before
use. Alumina (Merck, aluminium oxide 90 neutral, active)
was deactivated with deionized water and dried in an oven
kept at 110 ꢁC before use. Melting points were recorded on
an Ernst Leitz Wetzlar hot-stage microscope and are
uncorrected. Elemental analyses were performed on a
LECO CHNS-932 elemental analyzer. Infrared spectra
were recorded on a Nicolet Impact 400D 5DXFT-spectro-
photometer between 4000–400 cmꢀ1, either in solution
using liquid cell, NaCl windows (Aldrich 99.99%) or KBr
(Aldrich 99.99%) discs. NMR spectra were recorded on
Varian Gemini 300 MHz and Varian Inova 400 MHz spec-
trometer. Variable temperature NMR spectra were
recorded on a Varian Inova 500 MHz spectrometer. The
solvents, CDCl3 (Aldrich, 99.8%), acetone-d6 (Aldrich,
99.5%), acetonitrile-d3 (Aldrich, 99.8%), and N,N-dimeth-
ylformamide-d7 (Aldrich, 99.5%) were used as purchased
or occasionally dried over type 4A molecular sieves. Solu-
tions for NMR spectroscopy were always prepared under
nitrogen gas using nitrogen-saturated solvents.
4.3. Preparation of [Cp*(CO)2Fe(CH2)nFe(CO)2Cp]
(n = 3–6)
These were prepared by the modified literature method
[28]. For example, a solution of Na[Cp*(CO)2Fe] (1.5
mmol) in THF was added to a stirred solution of [Cp-
(CO)2Fe{(CH2)3I}] (0.76 g, 2.1 mmol) in THF at ꢀ78 ꢁC.
The mixture was stirred at this temperature for 20 min
and then allowed to attain room temperature, while moni-
toring the reaction by IR spectroscopy (m(CO)). When the
reaction was judged complete (after 5 h), the solvent was
removed under reduced pressure leaving a brown solid.
This solid was extracted three times with 20 mL portions
of hexane and the solution concentrated under reduced
pressure to about 10 mL. A yellow solid formed. The
mother liquor was syringed off, the solid washed once with
3 mL ice-cold hexane and dried under reduced pressure.
Analytical and spectroscopic data matched that of the
reported compound [28]. The complexes where n = 4–6
were prepared in a similar manner. These are new and their
characterization data are reported here.
[Cp*(CO)2Fe(CH2)4Fe(CO)2Cp]: Yield = 54% based
on the haloalkyl complex, IR m(CO) (hexane): (cmꢀ1
)
2008s, 1987s, 1953s, 1932s. Anal. Calc. for C23H28Fe2O4:
1
C, 57.53; H, 5.87. Found: C, 56.97; H, 5.77%. H NMR
(CDCl3): [d] 4.70s (5H, CpFe), 1.70s (15H, Cp*Fe), 1.33–
1.43m (6H, CpFeCH2CH2CH2), 0.91t (2H, Cp*FeCH2),
13C NMR (CDCl3): [d] 219.7 (Cp*FeCO), 217.9 (CpFeCO),
94.7 (C5(CH3)5), 85.3 (CpFe), 45.1 (Cp*FeCH2CH2), 43.6
(Cp*FeCH2CH2CH2), 14.1 (Cp*FeCH2), 4.1 (CpFeCH2).
[Cp*(CO)2Fe(CH2)5Fe(CO)2Cp]: Yield = 64% based
The precursors Ru3(CO)12 [40], [Cp(CO)2Fe]2 [41],
[Cp(CO)2Ru]2 [42], and [Cp(CO)3W]2 [43] were prepared
by the literature methods. [Cp*(CO)2Fe]2 was either pur-
chased from Strem chemicals or prepared by the modified
literature method [44]. The halogenoalkyl complexes
[Cp(CO)2Fe{(CH2)nX}] (X = Br, I; n = 3–6) [45],
[Cp(CO)2Ru{(CH2)nX}] (X = Br, I, n = 3–6) [46], and
[Cp(CO)3W{(CH2)nX}] (X = Br, I; n = 3–6) [47] were pre-
pared by the literature methods and used to prepare the
mixed-ligand alkanediyl complexes.
on the haloalkyl complex, IR m(CO) (hexane): (cmꢀ1
)
1
2008s, 1985s, 1955s, 1938s; H NMR (CDCl3): [d] 4.69s
(5H, CpFe), 1.70s (15H, Cp*Fe), 1.34–1.43m (8H,
CpFeCH2CH2CH2CH2), 0.91t (2H, Cp*FeCH2); 13C
NMR (CDCl3): [d] 219.7(Cp*FeCO), 217.8 (CpFeCO),
94.7 (C5(CH3)5), 85.3 (CpFe), 41.3 (Cp*FeCH2CH2CH2),
38.4 (Cp*FeCH2CH2), 37.7 (CpFeCH2CH2), 14.2 (FeCH2),
9.3 (C5(CH3)5), 4.1 (CpFeCH2).
4.2. Preparation of [Cp*(CO)2Fe]2
[Cp*(CO)2Fe(CH2)6Fe(CO)2Cp] was only identified
by its IR (hexane) data (2008, 1986, 1953, 1932) and used
for the preparation of the cationic metallacyclic complex
without further characterization.
Pentamethylcyclopentadiene (1 mL) was added to a
solution of iron pentacarbonyl (2 mL) in nitrogen-satu-

E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
2469
4.4. Preparation of [Cp*(CO)2Fe{l-
(CnH2nꢀ1)}Fe(CO)2Cp]PF6 (n = 3–6)
Ru(CO)2Cp] (Section 4.5), using the salt Na[Cp*(CO)2Fe]
and the tungsten iodoalkyl complexes [Cp(CO)3W-
{(CH2)nI}]. The molecular structure of [Cp*(CO)2Fe-
{l-(CH2)5}W(CO)3Cp] has been confirmed by single crys-
tal X-ray crystallography. The complexes have been char-
acterized by IR and NMR spectroscopy and elemental
analysis as follows:
A filtered solution of Ph3CPF6 (0.38 g, 0.95 mmol) in
CH2Cl2 (10 mL) was added to a solution of [Cp*(CO)2Fe-
(CH2)3Fe(CO)2Cp] (0.44 g, 0.95 mmol) in CH2Cl2 (2 mL)
in a Schlenk tube and the mixture allowed to stand overnight
under nitrogen at room temperature. The resultant deep
orange solution was filtered through a cannula into a pre-
weighed Schlenk tube. Dry nitrogen-saturated diethyl ether
was added to the solution until precipitation just started.
The mixture was allowed to stand for about 1 h in the dark
during which time a microcrystalline orange solid precipi-
tated. The mother liquor was syringed off and the solid dried
under reduced pressure. The rest of the complexes were pre-
pared in the same manner, but instead of adding diethyl
slowly and leaving the mixture for 1 h, the diethyl ether
was added rapidly, during which time the compounds sepa-
rated out as red oils. The mother liquor was syringed off and
the compounds dried under reduced pressure. As soon as the
vacuum was applied the red oils swelled up to spongy pale
yellow solids, which were found to be analytically pure.
Yields and other characterization data are given in Table 1.
[Cp*(CO)2Fe(CH2)3W(CO)3Cp]:
Yield = 72%,
Decomposes >120 ꢁC, IR (CH2Cl2): (cmꢀ1) 2005, 1976,
1918; 1H NMR (CDCl3): [d] 5.61s (5H, CpW), 1.77s
(15H, C5Me5Fe), 1.69m (4H, WCH2CH2), 0.99t (2H,
FeCH2); 13C NMR (CDCl3): [d] 218.4 (Cp*Fe–CO),
219.6, 229.7 (CpW–CO), 91.9 (CpW), 94.8 (C5Me5Fe),
18.9 (FeCH2), 44.9 (FeCH2CH2), ꢀ4.7 (WCH2), 8.2 (C5
(CH3)5Fe).
[Cp*(CO)2Fe(CH2)4W(CO)3Cp]:
Yield = 56%;
M.p. = 126–128 ꢁC; IR (hexane): (cmꢀ1) 2014, 1987,
1929, 1761. Anal. Calc. for C24H28FeO5W: C, 45.31; H,
1
4.44. Found: C, 45.35; H, 4.46%. H NMR (CDCl3): [d]
5.35s, (5H, CpW), 1.70s (15H, C5Me5Fe), 1.55m (4H,
WCH2 and FeCH2CH2), 1.43m (2H, WCH2CH2), 0.99t
(2H, FeCH2); 13C NMR (CDCl3): [d] 219.6, 229.7 (CpW–
CO), 218.4 (Cp*Fe–CO), 94.8 (C5Me5Fe), 91.9 (CpW),
44.9 (FeCH2CH2), 18.9 (FeCH2), 8.2 (C5 (CH3)5Fe), ꢀ4.7
(WCH2).
4.5. Preparation of [Cp*(CO)2Fe(CH2)nRu(CO)2Cp]
(n = 3–6)
[Cp*(CO)2Fe(CH2)5W(CO)3Cp]:
Yield = 82%,
M.p. = 125–127 ꢁC; IR (hexane): (cmꢀ1) 2008, 1978,
These compounds were prepared following the same
procedure described in Section 4.3, using the salt Na[Fe-
(CO)2Cp*] and the iodoalkyl ruthenium complexes
[Cp(CO)2Ru(CH2)nI]. The characterization data of the com-
plexes where n = 3–5 matched the literature data [28]. The
molecular structure of [Cp*(CO)2Fe{l-(CH2)5}Ru(CO)2Cp]
has been confirmed by single crystal X-ray crystallography.
The complex [Cp*(CO)2Fe(CH2)6Ru(CO)2Cp] is new and
thus its characterization data are reported here.
1916. Anal. Calc. for C25H30FeO5W: C, 46.18; H, 4.65.
1
Found: C, 46.22 H 4.59%. H NMR (CDCl3): [d] 5.34s,
(5H, CpW), 1.70s (15H, C5Me5Fe), 1.53m (2H, WCH2)
1.31m (2H, WCH2CH2), 0.99t (2H, FeCH2), 1.43m
(FeCH2CH2CH2), 13C NMR (CDCl3): [d] 219.7, 229.4
(CpW–CO), 217.4 (Cp*Fe–CO), 94.8 (C5Me5Fe), 91.5
(CpW), 42.2 (FeCH2CH2CH2), 37.3 (FeCH2CH2), 36.9
(WCH2CH2), 14.2 (FeCH2), 9.3 (C5 (CH3)5Fe), ꢀ4.7
(WCH2).
Yield = 57% based on the iodoalkyl complex, IR (hexane):
(cmꢀ1) 2018s, 1988s, 1959s, 1933s; 1HNMR(CDCl3): [d]5.20s
(5H, CpRu), 1.70s (15H, Cp*Fe), 1.54m (2H, RuCH2), 1.43m
(2H, RuCH2CH2CH2), 1.31m (2H, FeCH2CH2), 1.34m (2H,
FeCH2CH2CH2), 1.31m (2H, RuCH2CH2), 0.91t (2H,
[Cp*(CO)2Fe{l-(CH2)6}W(CO)3Cp] was only identi-
fied by its IR m(CO) (hexane) data (2009, 1975,
1915 cmꢀ1) and converted to the cationic metallacyclic
complex.
13
FeCH2); C NMR (CDCl3): [d] 219.7(Cp*FeCO), 202.6
4.8. Preparation of [Cp*(CO)2Fe{l-
(RuCO), 94.7 (C5(CH3)5), 88.6 (CpM), 40.0 (RuCH2CH2-
CH2), 37.9 (FeCH2CH2CH2), 35.5 (FeCH2CH2), 34.4 (Ru-
CH2CH2), 9.3 (C5(CH3)5), 14.2 (FeCH2), ꢀ2.9 (RuCH2).
(CnH2nꢀ1)}W(CO)3Cp]PF6 (n = 3–5)
These reactions were carried out in a similar manner to
those of the mixed-ligand heterobimetallic complexes of
iron and ruthenium described in Section 4.4.
4.6. Preparation of [Cp*(CO)2Fe{l-
(CnH2nꢀ1)}Ru(CO)2Cp]PF6 (n = 3–6)
4.9. Preparation of [Cp(CO)2Ru{l-(CH2)n}W(CO)3Cp]
(n = 3–6)
All the reactions were carried out by following the pro-
cedure described in Section 4.4.
The preparation of the complex [Cp(CO)2Ru(CH2)3W-
(CO)3Cp] will be described to illustrate the general method
used in the preparation of these new compounds. A
solution of Na[Cp(CO)2Ru] (0.80 mmol) in THF (15 mL)
was added to a solution of the iodoalkyl complex
[Cp(CO)3W{(CH2)3I}] (0.4 g, 0.80 mmol) in THF (3 mL)
4.7. Preparation of [Cp*(CO)2Fe(CH2)nW(CO)3Cp]
(n = 3–6)
These new compounds were prepared in a similar man-
ner as the iron-ruthenium complexes [Cp*(CO)2Fe(CH2)n-

2470
E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
at ꢀ30 ꢁC over a period of 10 min. The solution was stirred
at this temperature for 20 min and then allowed to attain
room temperature (1 h) and stirred for a further 8 h. The
solution was the concentrated at reduced pressure to leave
a brown solid. This was extracted three times with a 1:1
mixture of hexane and CH2Cl2 (3 · 20 mL) and a pale yel-
low solution was obtained. The solvent was concentrated
under reduced pressure to about a third of the original vol-
ume and then cooled to ꢀ78 ꢁC, when a pale yellow solid
precipitated. The mother liquor was syringed off and the
solid dried under reduced pressure. The complexes where
n = 4, 5 were prepared similarly. The molecular structure
of [Cp(CO)2Ru(CH2)5W(CO)3Cp] has been confirmed by
single crystal X-ray crystallography. The complexes where
n = 3–5 have been characterized by IR, NMR spectroscopy
and elemental analysis as follows:
4.11. Reactions of some of the complexes [Cp*(CO)2Fe-
{l-(C5H9)}M(CO)2Cp]PF6 (M = Fe or Ru) with sodium
iodide
Approximately 10 mg of a given complex was dissolved
in N2-saturated deuterated acetone in an NMR tube and its
1H NMR spectrum recorded. About 10 mg of NaI was
added to the solution in the NMR tube and the reaction
followed by recording spectra at 5-min intervals until there
was no further change observed in the spectra. [Cp*(CO)2-
Fe{l-(C5H9)}Fe(CO)2Cp]PF6 gave Cp*(CO)2FeI and the
previously reported [Cp(CO)2FeCH2(CH2)2CH@CH2]
1
[36], as recognized by their H NMR spectra as follows:
Cp*(CO)2FeI: [d] 2.01s (C5(CH3)5).
[Cp(CO)2FeCH2(CH2)2CH@CH2]: [d] 4.92s (Cp),
1.45m (Fe(CH2)3CH2), 2.06m (Fe(CH2)3CH2), 5.04m
(FeCH2(CH2)2CH@CH2), 5.82m (FeCH2(CH2)2CH@
CH2). Unreacted [Cp*(CO)2Fe{l-(C5H9)n}Fe(CO)2Cp]PF6
was also observed in solution.
[Cp(CO)2Ru(CH2)3W(CO)3Cp]: Yield = 50% based
on the haloalkyl precursor; IR(CH2Cl2): (cmꢀ1) 2007m,
1943m, 1910s; M.p. = 125–127 ꢁC. Anal. Calc. for
C18H16O5RuW: C, 36.20; H, 2.70. Found: C, 36.25; H,
2.73%. 1H NMR (CDCl3): [d] 5.35s (5H, CpW), 5.21s
(5H, CpRu), 1.72m (2H, RuCH2CH2), 1.68m (2H,
RuCH2), 1.56t (WCH2); 13C NMR(CDCl3): [d] 229.3,
217.6 (WCO), 202.6 (RuCO), 91.3 (CpW), 88.5 (CpRu),
47.2 (RuCH2CH2), 2.4 (RuCH2), ꢀ5.5 (WCH2).
[Cp*(CO)2Fe{l-(C5H9)n}Ru(CO)2Cp]PF6 gave Cp*(CO)2-
FeI and the new r-alkenyl complex [Cp(CO)2RuCH2-
1
(CH2)2CH@CH2], as recognized by its H NMR spectrum
as follows: [d] 5.42s (CpRu), 1.58m (Ru(CH2)3CH2), 2.20m
(Ru(CH2)3CH2), 4.91m (RuCH2(CH2)2CH@CH2), 5.80m
(RuCH2(CH2)2CH@CH2). Unreacted [Cp*(CO)2Fe{l-
(C5H9)}Ru(CO)2Cp]PF6 was also observed in solution.
[Cp(CO)2Ru(CH2)4W(CO)4Cp]: Yield = 39% based
on the haloalkyl precursor; IR(CH2Cl2): (cmꢀ1) 2009m,
1944m, 1911s; M.p. = 120–122 ꢁC. Anal. Calc. for C19H18-
4.12. Reaction of [Cp*(CO)2Fe{l-(C5H9)}-
Ru(CO)2Cp]PF6 with CD3OD
1
O5RuW: C, 37.33; H, 2.97. Found: C, 37.34; H, 2.93%. H
NMR (CDCl3): [d] 5.35s (5H, CpW), 5.20s (5H, CpRu),
1.66m (2H, RuCH2), 1.53m (6H, WCH2CH2CH2); 13C
NMR (CDCl3): [d] 229.3, 217.5 (WCO), 202.6 (RuCO),
91.5 (CpW), 88.6 (CpRu), 46.2 (RuCH2CH2), 42.4
(RuCH2CH2CH2), ꢀ3.7 (RuCH2), ꢀ9.8 (WCH2).
Approximately 10 mg of the complex was dissolved in
N2-saturated deuterated methanol in an NMR tube and
its H NMR spectrum recorded. About 10 mg of Na2CO3
1
was added to the solution in the NMR tube and the reac-
tion followed by recording spectra at 5-min intervals until
there was no further change observed in the spectra. Most
of the complex had reacted after 40 min, but the reaction
did not go to completion. Four compounds were observed
in solution: [Cp*(CO)2Fe]2, [Cp*(CO)2FeOCD3], unreacted
[Cp*(CO)2Fe{l-(C5H9)}Ru(CO)2Cp]PF6 and the new
complex [Cp(CO)2RuCH2(CH2)2CH@CH2], as identified
[Cp(CO)2Ru(CH2)5W(CO)3Cp]: Yield = 56% based
on the haloalkyl; IRm(CO)/CH2Cl2: (cmꢀ1
) 2009m,
1944m, 1911s; M.p. = 68–70 ꢁC. Anal. Calc. for C20H20O5-
1
RuW: C, 38.42; H, 3.22. Found: C, 37.98, H 3.48%. H
NMR (CDCl3): [d] 5.35s (5H, CpW), 5.21s (5H, CpRu),
1.66m (2H, RuCH2), 1.52m (2H, RuCH2CH2); 1.53m
(RuCH2CH2CH2), 1.53m (WCH2), 1.25m (WCH2CH2)
13C NMR (CDCl3): [d] 229.3, 217.5 (WCO), 202.6 (RuCO),
91.5 (CpW), 88.6 (CpRu), 41.2 (RuCH2CH2), 39.5
(RuCH2CH2CH2), 36.8 (WCH2CH2) ꢀ9.8 (WCH2), ꢀ3.2
(RuCH2).
1
by their H NMR spectra as follows: [Cp*(CO)2Fe]2:
1.77s (C5(CH3)5); [Cp*(CO)2FeOCD3], 1.80s (C5(CH3)5),
[Cp(CO)2RuCH2(CH2)2CH@CH2]: [d] 5.36s (CpRu),
1.68m {Ru(CH2)3CH2}, 2.08m {Ru(CH2)3CH2}, 5.01m
{RuCH2(CH2)2CH@CH2}, 5.82m (RuCH2(CH2)2CH@CH2).
[Cp(CO)2Ru(CH2)6W(CO)3Cp] was only identified
by its IR(CH2Cl2) (cmꢀ1) data (2009, 1975, 1915 cmꢀ1
)
and converted to the cationic metallacyclic complex with-
out further characterization.
4.13. Reactions of the complexes [Cp*(CO)2Fe{l-
(C5H9)}W(CO)3Cp]PF6 and [Cp*(CO)2Fe{l-
(C5H9)}Fe(CO)2Cp]PF6 with NaBPh4
4.10. Preparation of [Cp(CO)2Ru{l-
(CnH2nꢀ1)}W(CO)3Cp]PF6 (n = 3–6)
The complex [Cp*(CO)2Fe{l-(C5H9)}W(CO)3Cp]PF6
(0.038 g, 0.048 mmol) and NaBPh4 (0.016 g, 0.085 mmol)
were weighed into a Schlenk tube followed by 10 mL ace-
tone. The mixture was stirred for 10 min. The solvent
was removed under reduced pressure to leave a yellow
These were carried out in a similar manner as explained
in Section 4.4. Pale yellow microcrystalline solids were
obtained.

E.O. Changamu et al. / Journal of Organometallic Chemistry 692 (2007) 2456–2472
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diffractometer (CrysAlis CCD 170) using Mo Ka radiation
˚
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graphic data and the procedures used for data collection
and reduction information for compounds 1–4 are given
in Table 10.
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Acknowledgements
We acknowledge financial support from NRF, THRIP,
and UKZN (URF). One of us (E.O.C.) thanks Kenyatta
University, Kenya, for study leave to carry out this work.
We thank Drs. A.W.F. Kamdem (University of Douala,
Cameroun), G.E.M. Maguire (UKZN) and H.G. Kruger
(UKZN) for fruitful NMR discussions.
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E 60 (2004) m551.
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Chem. 587 (1999) 28.
Appendix A. Supplementary material
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Organomet. Chem. 112 (1976) 309.
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181.
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(1978) 5554, and references cited therein.
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659.
CCDC 630865, 630866, 630867 and 630868 contain the
supplementary crystallographic data for compounds 1, 2, 3
and 4. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or
e-mail: deposit@ccdc.cam.ac.uk. Supplementary data asso-
ciated with this article can be found, in the online version,
at doi:10.1016/j.jorganchem.2007.02.016.
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