The syntheses and structures of mono- and di-bromovinylidenes

Article abstract of DOI:10.1016/j.jorganchem.2009.08.027

Reactions of metal acetylide complexes M(C{triple bond, long}CAr)(PP)Cp′ (M = Fe, Ru; Ar = C₆H₅, C₆H₄Me-4; PP = (PPh₃)₂, dppe; Cp′ = Cp, Cp*; not all combinations), or the analogous vinylid

Full text of DOI:10.1016/j.jorganchem.2009.08.027

Journal of Organometallic Chemistry 694 (2009) 4042–4048
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
The syntheses and structures of mono- and di-bromovinylidenes
*
Neil J. Brown, Mark A. Fox, Mark E. Smith, Dmitry S. Yufit, Judith A.K. Howard, Paul J. Low
Department of Chemistry, Durham University, South Rd., Durham DH1 3LE, UK
a r t i c l e i n f o
a b s t r a c t
Reactions of metal acetylide complexes M(C„CAr)(PP)Cp0 (M = Fe, Ru; Ar = C6H5, C6H4Me-4; PP = (PPh3)2,
dppe; Cp0 = Cp, Cp*; not all combinations), or the analogous vinylidene, wiꢀth cyanogen bromide yield
monobromovinylidene complexes [M{C@C(Br)Ar}(PP)Cp0]+, isolated as PF6 salts. The trimethylsilyl-
capped acetylides M(C„CSiMe3)(PP)Cp0 react with cyanogen bromide to give [M(C@CBr2)(PP)Cp0]+, the
first examples of metal complexes containing a terminal dihalovinylidene ligand, which can be isolated
as the BF4 salts. Molecular structures of representative mono- and di-bromovinylidene complexes are
reported, together with those of Ru(C„CSiMe3)(PPh3)2Cp and Ru(C„CSiMe3)(dppe)Cp*.
Ó 2009 Elsevier B.V. All rights reserved.
Article history:
Received 16 July 2009
Received in revised form 13 August 2009
Accepted 19 August 2009
Available online 23 August 2009
ꢀ
Keywords:
Ruthenium
Iron
Vinylidene
1. Introduction
(R = Ph, But) are also known, having been formed from closely
related reactions of I2 or [I(py)2]BF4 with Fe(C„CR)(dppm)Cp [7].
The chemistry of terminal vinylidene complexes has been
extensively developed since the first reports of such species in
the early 1970s [1], with studies of the synthesis, structure, bond-
ing and stoichiometric reactions of vinylidenes [2] leading to the
development of synthetically useful metal-catalysed reaction cy-
cles based on the formation and reaction of a vinylidene species
[3]. The development of convenient synthetic routes to vinylidene
complexes from the re-arrangement of a terminal alkyne within
the coordination sphere of an appropriate metal complex (Scheme
1), or from the addition of an electrophile to Cb of a metal acetylide
(Scheme 2), has greatly assisted the development of the chemistry
of this fascinating unsaturated carbene ligand.
The recent preparation of [{Ru{C@CI(H)}(dppe)Cp*]BF4 from
Ru(C„CH)(dppe)Cp* and [I(py)2]BF4, and subsequent deprotona-
tion to afford the iodoacetylide complex Ru(C„CI)(dppe)Cp* is
worthy of particular note [8]. However, aside from these few
flurries of activity, the chemistry of halovinylidenes has remained
largely undeveloped for much of the last 20 years.
Iwasawa’s demonstration of the synthetic utility of iodo-viny-
lidenes generated in situ from 1-iodoalkynes and W(thf)(CO)5 [9]
has generated something of a surge of interest in the chemistry
of halovinylidene complexes [10]. In the course of surveying condi-
tions for the cyanation of acetylide ligands [11] we investigated the
reactions of cyanogen bromide (BrCN) with metal acetylides, and
found this reagent suitable instead for the bromination of the
acetylide ligand under mild conditions. In this short report we
describe the use of cyanogen bromide in the preparation of mono-
and di-bromovinylidene complexes.
Although 1-haloalkynes have found considerable application in
synthetic organic chemistry, halovinylidenes remain relatively
rare. The first halogenated vinylidene complexes were prepared
by re-arrangement of 1-haloalkynes or dihaloalkynes upon a binu-
clear Co framework (Scheme 3) [4]. The difluorovinylidene ligand
has also been stabilised onꢀa bimetallic scaffold from reaction of
2. Results and discussion
CF2(COCl)2 with [Fe3(CO)11
] [5].
A more general route to halovinylidenes has been developed by
Bruce and co-workers who have demonstrated electrophilic addi-
tion of halogens (Cl2, Br2, I2) to half-sandwich ruthenium and os-
mium acetylide complexes to give a series of terminal mono-
halovinylidenes (Scheme 4), although in the case of reaction be-
tween Ru(C„CPh)(PPh3)2Cp and Br2, bromination of the acetylide
phenyl substituent para to the Cb carbon was also observed [6].
The related iron iodovinylidene complexes [Fe{C@C(I)R}(dppm)Cp]I
CARE: the likely evolution of cyanide ions and potentially HCN
as by-products in the reactions described herein necessitates
extreme care in their conduct.
The reaction of Fe(C„CAr)(dppe)Cp (Ar = Ph 1a, C6H4Me-4 1b)
with an excess of cyanogen bromide, BrCN, in the presence of
NH4PF6 in CH2Cl2 resulted in the ready formation of the dark green
bromovinylidene complexes [Fe{C@CBr(Ar)}(dppe)Cp]PF6 (Ar = Ph
[2a]PF6, C6H4Me-4 [2b]PF6) in good (ca. 60%) yield (Scheme 5).
The complexes were readily characterised on the basis of the solu-
tion spectroscopic data, which included a triplet at ca. 350 ppm
* Corresponding author. Tel.: +44 (0)191 334 2114; fax: +44 (0)191 384 4737.
E-mail address: p.j.low@durham.ac.uk (P.J. Low).
(JCP = 33 Hz) for the vinylidene C carbon, a clear bromine isotope
a
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.08.027

N.J. Brown et al. / Journal of Organometallic Chemistry 694 (2009) 4042–4048
4043
Scheme 5. The bromination of metal acetylides by cyanogen bromide.
Scheme 1. The formation of vinylidene complexes by the re-arrangement of
terminal alkynes within the coordination sphere of a metal centre.
Reactions of BrCN with Ru(C„CPh)(PPh3)2Cp (1c) and NH4PF6
in THF, CH2Cl2 or toluene solutions gave green solutions from
which
the
bromovinylidene
[Ru{C@C(Br)Ph}(PPh3)2Cp]PF6
([2c]PF6) could be isolated in low yield, with traces of the cyanov-
inylidene [Ru{C@C(CN)Ph}(PPh3)2Cp]PF6 also being observed in the
reaction mixture by 1H NMR and IR spectroscopy [for a closely re-
lated compound see 11a]. After exploration of a range of reaction
solvents, times and temperatures, [2c]PF6 was isolated in ca. 60%
yield, free of the cyanovinylidene, simply from reaction of the
vinylidene [Ru{C@C(H)Ph}(PPh3)2Cp]PF6 ([3]PF6) with excess BrCN
and NH4PF6 in CH2Cl2 solution (Scheme 6). In contrast to the reac-
tion of 1c with Br2, there was no sign of bromination of the phenyl
ring of the vinylidene ligand [6]. The relatively electron-rich acet-
ylide complex Ru(C„CC6H4Me-4)(dppe)Cp* (1d) reacted with
BrCN in the presence of NH4PF6 to give the monobromovinylidene
[2d]PF6. Although the fine details of the mechanism leading to the
formation of the bromovinylidene complexes [2]PF6 have not been
investigated, the presence of NH4PF6 during the bromination step
is important to these reactions, with significantly decreased yields
being obtained in its absence.
Scheme 2. The formation of a vinylidene from electrophilic addition to a metal
acetylide.
With a view to exploring the scope of the reaction we consid-
ered the prospects of forming di-bromovinylidene complexes
directly from a terminal metal acetylide or synthon, and two
equivalents of BrCN. The metal acetylide complex Fe(C„CH)(dp-
pe)Cp has been prepared from reactions of [Fe(dppe)Cp]BF4 with
LiC„CH.en [13], whilst related complexes featuring the C„CH
ligand, such as, Fe(C„CH)(dppe)Cp* [14], Ru(C„CH)(PPh3)2Cp
[15], and Ru(C„CH)(dppe)Cp* [16] are prepared by deprotonation
of the corresponding cationic vinylidenes [M(C@CH2)(PP)Cp0]+, ob-
tained in turn from MCl(PP)Cp0 (4) and HC„CSiMe3 [17] [18]. The
trimethylsilyl-capped acetylide complex Fe(C„CSiMe3)(dppe)Cp
(5a), which is a masked version of Fe(C„CH)(dppe)Cp, is obtained
rather more directly from FeCl(dppe)Cp (4a) and HC„CSiMe3 in
THF/NEt3 solutions containing NaBF4 [11c] and both Ru(C„CSiMe3)
(PPh3)2Cp (5b) and Ru(C„CSiMe3)(dppe)Cp* (5c) can be obtained
in entirely analogous fashion from RuCl(PPh3)2Cp (4b) and
RuCl(dppe)Cp* (4c), respectively (Scheme 7). The route described
in Scheme 7, which we find to be convenient, complements exist-
ing routes to similar half-sandwich ruthenium complexes based on
trapping Ru(C„CLi)(PP)Cp0 with SiClMe3 [17,18], but without the
complication of competing sites of lithiation reported by Kawata
and Sato in the case of the preparation of 5b [18].
Scheme 3. The formation of a bimetallic complex featuring a dihalovinylidene
ligand (not all combinations).
Scheme 4. Formation of terminal mono-halovinylidene complexes from reaction of
halogens with metal acetylide complexes (not all combinations).
pattern in the molecular ion (ES-MS), and the observation of the
vinylidene m )
(C@C) band ([2a]PF6 1614 cmꢀ1, [2b]PF6 1644 cmꢀ1
Reaction of the trimethylsilyl-capped acetylide complexes 5a,
5b, and 5c with excess BrCN were found to afford the di-bromo-
vinylidene cations [Fe(C@CBr2)(dppe)Cp]+ ([6a]+), [Ru(C@CBr2)-
(PPh3)2Cp]+ ([6b]+) and [Rꢀu(C@CBr2)(dppe)Cp*]+ ([6b]+), which
could be isolated as the BF4 salts. In each case, the reaction pro-
ceeded without NH4PF6, and is apparently driven by the formation
in the IR spectra. Whilst relatively stable as solids and in solution
under an inert atmosphere, on standing in air solutions of the
bromovinylidenes gradually oxidise to the carbonyl cation
[Fe(CO)(dppe)Cp]+ [12]. The presence of the carbonyl complex in
solution is easily determined by the strong
m(CO) band at
1979 cmꢀ1 and the carbonyl 13C resonance at 190 ppm.

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N.J. Brown et al. / Journal of Organometallic Chemistry 694 (2009) 4042–4048
Scheme 6. The formation of 2c from the vinylidene complex 3.
Scheme 7. The formation of the trimethylsilyl-capped acetylide complexes 5 and the di-bromovinylidenes [6] BF4.
of Me3SiCN. Each of [6a–c]BF4 exhibited the characteristically low
electron-withdrawing vinylidene ligand: the longer Ru(1)–P(2)
bond in [2c]+ is eclipsed relative to the C(2)–Br(1) bond (torsion
angle Br(1)C(2)Ru(1)P(2) 9.0°) whilst in [2d] the longer Ru(1)–
field C resonance associated with the strongly deshielded car-
a
bene-like carbon, and a [M+H]+ or [M]+ ion in the ES-MS displaying
the characteristic isotope pattern associated with the presence of
two bromine atoms. The iron complex also featured the vinylidene
m
(C@C) band at 1604 cmꢀ1. The ruthenium di-bromovinylidene
complexes [6b]BF4 and [6c]BF4 proved to be rather sensitive in
solution, possibly because of the significant ligand character in
the frontier orbitals of ruthenium vinylidene complexes [11a],
and the IR spectra of these species were always contaminated with
the carbonyl cation. Although the sensitivity of the samples made
accurate micro-analyses difficult to obtain, high resolution mass
spectrometry data were consistent with the proposed structures
(Supplementary material).
2.1. Molecular structures
The structures of [2c]PF6 (Fig. 1) and [2d]PF6 (Fig. 2) were deter-
mined from a crystal grown from acetone and hexane (Table 1),
and, unsurprisingly, are similar to those of [Ru{C@C(X)C6H4R-
4}(PPh3)2Cp][X3] (X = Br, R = Br; X = I, R = H) determined in the
earlier Bruce studies [6]. The Ru(PPh3)2Cp fragment exhibits the
usual approximately octahedral geometry. The parameters
associated with the Ru@C@C(Br)Ar fragment clearly establish the
vinylidene character of the ligand, with the characteristically short
0
0
Ru(1)–C(1) (1.835(6)AÅ) and C(1)–C(2) (1.303(7)AÅ) indicative of
Ru@C and C@C double bonds. The average Ru(1)–C(cp) distance
in the cation [2c]+ (2.360 Å) is similar to that found in
[Ru{C@C(Br)C6H4Br-4}(PPh3)2Cp]+ (2.366(5) Å), with the longest
distance associated with the carbon approximately trans to the
Fig. 1. The cation [2c]+ in [Ru{C@C(Br)C6H5}(PPh3)2Cp]PF6. In this and subsequent
figures hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and
angles (°): Ru(1)–P(1,2) 2.3461(13), 2.3729(13); Ru(1)–C(1) 1.835(6); C(1)–C(2)
1.303(7); C(2)–C(3) 1.492(7); C(2)–Br(1) 1.909(5); P(1)–Ru(1)–P(2) 101.34(4);
P(1)–Ru(1)–C(1) 87.76(15); P(2)–Ru(1)–C(1) 95.91(15); Ru(1)–C(1)–C(2) 173.3(4);
C(1)–C(2)–C(3) 122.1(5); C(1)–C(2)–Br(1) 118.9(4).
vinylidene ligand. The Ru(1)–P(1, 2) bond lengths in the cation
0
[2c]+ [Ru(1)–P(1, 2) 2.3461(13), 2.3729(13)AÅ] are arguably longer
than those in [Ru{C@C(Br)C6H4Br-4}(PPh3)2Cp]+ (2.337(2),
2.356(2) Å). The non-equivalence of the Ru–P bond lengths in both
[2c]+ and [2d]+ seems to be related to the orientation of the

N.J. Brown et al. / Journal of Organometallic Chemistry 694 (2009) 4042–4048
4045
Fig. 2. The cation [2d]+ in [Ru{C@C(Br)C6H4Me–4}(dppe)Cp*]PF6. Selected bond
lengths (Å) and angles (°): Ru(1)–P(1,2) 2.3049(2), 2.3176(5); Ru(1)–C(1) 1.851(2);
C(1)–C(2) 1.303(3); C(2)–C(3) 1.484(3); C(2)–Br(1) 1.937(2); P(1)–Ru(1)–P(2)
82.244(19); P(1)–Ru(1)–C(1) 83.13(6); P(2)–Ru(1)–C(1) 92.92(6); Ru(1)–C(1)–C(2)
173.31(16); C(1)–C(2)–C(3) 128.64(19); C(1)–C(2)–Br(1) 114.74(15).
Fig. 3. The molecular structure of 5b showing the atom labelling scheme. Selected
bond lengths (Å) and angles (°): Ru(1)–P(1,2) 2.2841(5), 2.2811(6); Ru(1)–C(1)
2.004(2); C(1)–C(2) 1.218(3); C(2)–Si(1) 1.806(2); P(1)–Ru(1)–P(2) 100.205(19);
P(1)–Ru(1)–C(1) 90.20(6); P(2)–Ru(1)–C(1) 87.01(6); Ru(1)–C(1)–C(2) 174.39(19);
C(1)–C(2)–Si(1) 176.9(2).
P(2) bond is almost eclipsed relative to the C(2)–C(3) bond of the
vinylidene ligand (corresponding torsion angle C(3)C(2)Ru(1)P(2)
–30.6°).
which features the Ru(PPh3)2Cp fragment, the longer Ru–P dis-
tances are likely due to steric effects between the bulky PPh3 and
Cp fragments, and is comparable with other examples of this type
[19]. The small differences in bond lengths along the linear Ru–
C(1)„C(2)–Si chain are not statistically significant, and the bond-
ing parameters are largely indistinguishable from those associated
with the phenylacetylide analogues [19b,20].
The trimethylsilyl-capped precursors 5b and 5c crystallised
readily from THF/CDCl3 and slow evaporation of NCMe/hexane
solutions, respectively. Aside from the differences imposed by the
different supporting phosphine and cyclopentadienyl ligands, the
key metric parameters of 5b and 5c are broadly similar. Thus, com-
pound 5c has somewhat shorter Ru–P bonds due to the enhanced
metal to phosphine back-bonding brought about by the more elec-
tron-rich pentamethylcyclopentadienyl ligand. In the case of 5b
The iron di-bromovinylidene [6a]BF4 was sufficiently stable to
permit recrystallisation, which afforded yellow–orange coloured
Table 1
Crystal data and refinement details.
Complex
[2c]PF6
[2d]PF6
5b
5c
[6a]BF4
Empirical formula
Formula weight
T (K)
C49H40BrP2Ru ꢁ PF6 ꢁ C3H6O
C45H46P2BrRu ꢁ PF6
974.71
120(2)
C46H44RuP2Si ꢁ 0.5 C4H8O
823.96
120(2)
C41H48SiP2Ru
731.89
120(2)
C34H31Br2FeCl2P2 ꢁ BF4 ꢁ CH2Cl2
1074.78
120(2)
874.91
120(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
Orthorhombic
P bca
18.0476(2)
14.2539(2)
35.9566(4)
90
Monoclinic
P21/n
10.4118(3)
20.8537(7)
19.5593(6)
90
Monoclinic
P21/n
10.4778(9)
22.480(2)
17.3638(15)
90
Monoclinic
P21/c
17.6283(4)
12.9530(3)
16.1175(3)
90
Monoclinic
P21/n
11.7249(4)
23.3677(7)
13.4513(4)
90
a
(°)
b (°)
90
90
90.966(10)
90
4246.2(2)
1.525
98.786(2)
90
4041.9(6)
1.354
92.80(2)
90
3675.86(14)
1.323
104.984(10)
90
3560.13(19)
1.632
c
(°)
V (Å3)
9249.79(19)
1.544
qc (g cmꢀ3
)
Z
l
8
4
4
4
4
(Mo K
a
) (mmꢀ1
)
5.270
1.481
0.531
0.574
2.954
Ntot
36641
44754
54624
45758
52890
N (Rint
R1
wR2
GOOF
)
6558 [0.0823]
0.0553
0.1534
1.110
11,829 [0.0469]
0.0480
0.0695
10,746 [0.0548]
0.0518
0.0795
10,244 [0.0249]
0.0345
0.0785
9457 [0.0747]
0.0634
0.1858
0.962
1.061
1.027
1.019

4046
N.J. Brown et al. / Journal of Organometallic Chemistry 694 (2009) 4042–4048
single crystals suitable for X-ray diffraction. The crystallographi-
cally determined structure of [6a]BF4 (Fig. 5) reveals the usual
approximately octahedral coordination geometry around the iron
centre. The Fe(1)–C(1) is relatively long (1.823(6) Å), and the
C(1)–C(2) bond is notably short (1.192(8) Å) in comparison with
related bond lengths in other vinylidene complexes containing
the Fe(dppe)Cp moiety in which these bonds fall in the range
1.74–1.76 Å [Fe–C(1)] and 1.31–1.33 Å [C(1)–C(2)] [21]; similar
ranges are also associated with vinylidenes derived supported by
the more electron-rich Fe(dppe)Cp* fragment [22]. The inductively
electron-withdrawing bromine substituents on the vinylidene C
a
likely cause these bond length variations by polarising the C@C
bond, hence introducing a larger electrostatic component to the
C@C bond.
3. Conclusion
This work has described the preparation and crystallographic
characterisation of mono- and di-bromo vinylidenes from the reac-
tions of cyanogen bromide with metal acetylides, or vinylidenes.
The use of cyanogen bromide in the presence of NH4PF6 as a mild
brominating agent avoids side reactions such as electrophilic aro-
matic halogenation reactions encountered when bromine is used
as the halogenating agent. The complexes [6a–c]BF4 are the first
examples of complexes bearing terminal dihalovinylidene ligands,
and have been obtained under mild conditions from double halo-
genation of readily synthesised precursors bearing trimethylsilyl
acetylide ligands, and thereby avoiding the use of dihaloacetylenes.
With these synthetic routes in hand, the chemistry of the dihalo-
vinylidene ligand may now be explored with greater convenience.
Fig. 4. The molecular structure of 5c showing the atom labelling scheme. Selected
bond lengths (Å) and angles (°): Ru(1)–P(1, 2) 2.2745(4), 2.2539(4); Ru(1)–C(1)
2.0104(16); C(1)–C(2) 1.224(2); C(2)–Si(1) 1.8184(18); P(1)–Ru(1)–P(2) 83.38(2);
P(1)–Ru(1)–C(1) 86.17(4); P(2)–Ru(1)–C(1) 81.15(4); Ru(1)–C(1)–C(2) 179.65(15);
C(1)–C(2)–Si(1) 164.15(15).
4. Experimental
All reactions were carried out under an atmosphere of nitrogen
using standard Schlenk techniques as a matter of routine, although
no special precautions were taken to exclude air or moisture dur-
ing work-up. Dichloromethane was purified and dried using an
Innovative Technology SPS-400, and degassed before use. Diethyl
ether, hexane and acetone were the best available commercial
grade, and used without further purification. The compounds
Fe(C„CPh)(dppe)Cp [23], [Fe(C„CC6H4Me-4)(dppe)Cp] [23],
[Fe(C„CSiMe3)(dppe)Cp] [11c], Ru(C„CC6H4Me-4)(dppe)Cp*
[23], [Ru(C@CHPh)(PPh3)2Cp]PF6 [24], FeCl(dppe)Cp [25],
RuCl(PPh3)2Cp [26] and RuCl(dppe)Cp* [16] were prepared by the
literature methods. Cyanogen bromide was purchased (Aldrich)
and sublimed at atmospheric pressure under nitrogen immediately
prior to use. Other reagents were purchased and used as received.
NMR spectra were recorded on
a
Bruker Avance (1H
400.13 MHz, 13C 100.61 MHz, 31P 161.98 MHz) spectrometer from
CDCl3 solutions unless otherwise indicated, and referenced against
solvent resonances (CDCl3 1H 7.26 13C 77.0; d6-acetone 1H 2.05, 13
C
29.8 ppm; CD2Cl2 1H 5.31, 13C 53.8) or external H3PO4 31P). See
(
Figs. 1–5 for the atom labelling schemes used in the NMR assign-
ments. IR spectra (CH2Cl2) were recorded using a Nicolet Avatar
spectrometer from cells fitted with CaF2 windows. Electrospray
ionisation mass spectra were recorded using Thermo Quest Finni-
gan Trace MS-Trace GC or WATERS Micromass LCT spectrometers.
Samples in dichloromethane (1 mg/mL) were 100 times diluted in
either methanol or acetonitrile, and analysed with source and
desolvation temperatures of 120 °C, with cone voltage of 30 V. Ele-
mental analyses were carried out within the Department of Chem-
istry at Durham University.
Fig. 5. The molecular structure of the cation [6a]+ from [Fe(C@CBr2)(dppe)Cp]BF4.
Selected bond lengths (Å) and angles (°): Fe(1)–P(1, 2) 2.2229(14), 2.2164(14);
Fe(1)–C(1) 1.823(6); C(1)–C(2) 1.192(8); C(2)–Br(1, 2) 1.923(6), 1.927(6); P(1)–
Fe(1)–P(2) 84.30(5); P(1)–Fe(1)–C(1) 92.97(15); P(2)–Fe(1)–C(1) 89.12(15); Fe(1)–
C(1)–C(2) 179.1(5); C(1)–C(2)–Br(1, 2) 122.9(5), 125.3(5).
Single crystal X-ray data for all structures were collected on a
Bruker SMART CCD 6000 (compounds [2c]PF6ꢂMe2CO, [2d]PF6
and 5c) or 1 K (5b.0.5THF and [6a]BF4ꢂCH2Cl2) diffractometers

N.J. Brown et al. / Journal of Organometallic Chemistry 694 (2009) 4042–4048
4047
equipped with a Cryostream (Oxford Cryosystems) cooling devices
at 120 K using kMo K or kCu K
4.4. Preparation [Ru{C@CBr(C6H4Me-4)}(dppe)Cp*]PF6 ([2d]PF6)
a
a
([2c]PF6ꢂMe2CO) radiation. All the
structures were solved by direct methods and refined by full-ma-
trix least squares on F2 for all data using SHELXTL software. All or-
dered non-hydrogen atoms were refined with anisotropic
displacement parameters, H-atoms were placed into calculated
positions and refined in a ‘‘riding” mode. The crystallographic data
and parameters of refinement are given in Table 1.
A
solution
of
Ru(C„CC6H4Me-4)(dppe)Cp*
(0.068 g,
0.090 mmol), NH4PF6 (0.037 g, 0.23 mmol) and cyanogen bromide
(0.037 g, 0.23 mmol) in CH2Cl2 (20 cm3) was stirred for 2 h, after
which time the solvent was removed. The residue was redissolved
in the minimum volume of CH2Cl2 and filtered through a small
plug of celite or cotton-wool into Et2O. The solution was then taken
to dryness to yield the product (0.055 g, 63%). IR (cmꢀ1):
m(C@C)
1649. 1H NMR: d 1.68 (s, 15H, C5Me5), 2.24 (s, 3H, Me), 2.74 (m,
2H, dppe), 3.08 (m, 2H, dppe), 6.60 (d, JHH = 6 Hz, 2H, C6H4), 6.73
(d, JHH = 6 Hz, 2H, C6H4), 7.02–7.54 (m, 20H, Ph). 13C NMR: d 10.4
(s, C5Me5), 21.4 (s, Me), 28.8 (m, dppe), 104.7 (s, C5Me5), 122.4 (s,
C2); 125.3 (C3), 129.1 (C4 overlap with 129.1 multiplet), 129.6
4.1. Preparation of [Fe{C@CBr(Ph)}(dppe)Cp]PF6 ([2a]PF6)
To a solution of Fe(C„CPh)(dppe)Cp (0.100 g, 0.161 mmol) and
NH4PF6 (0.060 g, 0.40 mmol) in CH2Cl2 (15 cm3), cyanogen bro-
mide (0.043 g, 0.40 mmol) was added and the reaction mixture al-
lowed to stir overnight. The resulting solution was concentrated,
filtered and purified by preparative TLC (80:20, acetone/hexane).
The major green band afforded the title compound (0.065 g, 58%)
as a deep green solid after precipitation (CH2Cl2/Et2O). IR (cmꢀ1):
2
4
0
(C5), 138.6 (C6); 129.1 (dd, JCP, JCP ꢃ 5 Hz, Cm,m ), 130.9, 133.2
2
4
0
0
0
(m, Ci,i ), 131.5, 132.2 (Cp,p ), 132.8, 133.3 (dd, JCP, JCP ꢃ 5 Hz, Co,o ),
332.4 (t, JCP = 17 Hz, C1). 31P NMR: d 74.5 (s, dppe), 165.6 (septet,
PF6). ES(+)-MS (m/z): 829.13041 [M]+; calculated 829.12961 amu.
m
(C'C) 1614. 1H NMR: d 3.10 (m, 2H, dppe); 3.15 (m, 2H, dppe);
4.5. Preparation of Ru(C„CSiMe3)(PPh3)2Cp (5b)
5.30 (s, 5H, Cp); 6.75–7.45 (m, 25H, Ph). 13C NMR: 28.6 (m, dppe);
90.7 (s, Cp); 127.2 (C4), 128.1 (C3), 128.2 (C6), 128.8 (C5); 128.9,
A
solution of RuCl(PPh3)2Cp (1.00 g, 1.38 mmol), NaBPh4
3
5
0
0
129.4 (dd, JCP
,
JCP ꢃ 5 Hz, Cm,m ); 131.5, 131.5 (Cp,p ); 131.3,
(0.567 g, 1.66 mmol) and HC„CSiMe3 (1.66 g, 16.9 mmol) in a
50:50 THF/NEt3 solution (75 cm3 total volume) was heated at re-
flux for 3 h. After this time, the solution was filtered and the sol-
vent removed. The residue was extracted with hot hexane to give
a yellow solution, from which the product was isolated by removal
2
4
0
0
132.3 (dd, JCP, JCP ꢃ 5 Hz, Co,o ); 132.9, 134.9 (m, Ci,i ); 137.8 (s,
C2); 348.4 (t, JCP = 33 Hz, C1). 31P NMR: 93.6 (s, dppe); –143.1
2
(septet, PF6). ES(+)-MS (m/z): 699.06761, [M]+; calculated
699.06631 amu.
of the solvent (0.98 g, 90%). IR (cmꢀ1): (C„C) 1994 cmꢀ1. 1H NMR:
m
d -0.03 (s, 9H, SiMe3), 4.19 (s, 5H, C5H5), 7.02 (apparent-t, 24H, Hm),
4.2. Preparation of [Fe{C@CBr(C6H4Me-4)}(dppe)Cp]PF6 ([2b]PF6)
7.14 (apparent-t, 12H, Hp), 7.53 (m, 24H, Ho). 13C NMR: d 1.7
3
(SiMe3); 85.4 (s, Cp); 118.7 (s, C2); 127.5 (dd, JCP
,
5JCP ꢃ 5 Hz,
2
4
A solution of Fe(C„CC6H4Me-4)(dppe)Cp (0.100 g, 0.158 mmol)
and NH4PF6 (0.064 g, 0.39 mmol) in CH2Cl2 (15 cm3) was treated
with cyanogen bromide (0.041 g, 0.39 mmol) and stirred overnight.
Concentration of the solution, filtration, and purification by pre-
parative TLC (45:55, acetone/hexane) gave a green band, which
upon isolation by precipitation from CH2Cl2/Et2O, gave the title
Cm); 128.3 (Cp); 133.9 (dd, JCP, JCP ꢃ 5 Hz, Co); 138.9 (m, Ci);
139.6 (t, JCP = 24 Hz, C1). 31P NMR: d 51.2.
Found: ES(+)ꢀMS (m/z) 789.18110 [M]+; calculated for Ru-
SiP2C46H44: 789.18362.
4.6. Preparation of Ru(C„CSiMe3)(dppe)Cp* (5c)
compound as a deep green solid (0.067 g, 59%). IR (cmꢀ1):
m(C@C)
1609. 1H NMR: d 2.26 (s, 3H, CH3); 3.10 (m, 4H, dppe); 5.29 (s,
5H, Cp); 6.66 (d, JHH = 7 Hz, C6H4), 6.80 (d, JHH = 7 Hz, C6H4);
7.04–7.63 (m, 20H, Ph). 13C NMR: 21.1 (s, CH3), 28.5 (m, dppe);
90.6 (s, Cp); 124.8 (C3), 127.4 (C4), 129.4 (C5 overlap with multi-
A solution of RuCl(dppe)Cp* (0.100 g, 0.149 mmol), NaBPh4
(0.061 g, 0.18 mmol) and HC„CSiMe3 (0.181 g, 1.84 mmol) in a
50:50 THF/NEt3 (20 cm3 total volume) solution was heated under
reflux for 2 h, after which time the solution is filtered and the sol-
vent removed. The residue was extracted with hot hexane to give a
yellow solution, from which the product could be isolated by re-
moval of the solvent (0.049 g, 45%). Although the resulting yellow
solid turns green upon prolonged exposure to air, NMR analysis re-
veals little change and the discoloured samples are suitable for fur-
plet at 129.4), 138.3 (C6); 128.9, 129.4 (dd, 3JCP, 5JCP ꢃ 5 Hz, Cm,m );
0
2
4
0
0
131.5, 131.5 (Cp,p ); 131.2, 132.4 (dd, JCP, JCP ꢃ 5 Hz, Co,o ); 133.0,
135.1 (m, Ci,i ); 137.6 (s, C2); 349.2 (t, JCP = 33 Hz, C1). 31P NMR:
2
0
94.0 (s, dppe); –143.1 (septet, PF6). ES(+)-MS (m/z): 713.08313,
[M]+; calculated 713.08196 amu.
ther reaction. IR (cmꢀ1):
SiMe3), 1.52 (s, 15H, C5Me5), 2.05 (m, 2H, dppe), 2.75 (m, 2H, dppe),
7.12 (m, 4H, Ph), 7.22 (m, 4H, Ph), 7.30 (m, 8H, Ph), 7.78 (m, 4H,
Ph). 13C NMR: d 1.4 (s, SiMe3); 9.9 (s, C5Me5); 29.1 (m, dppe);
m
(C„C) 1996. 1H NMR: d ꢀ0.18 (s, 9H,
4.3. Preparation of [Ru{C@CBr(Ph)}(PPh3)2Cp]PF6 ([2c]PF6)
2
4
A
solution
of
[Ru{C@C(H)Ph}(PPh3)2Cp]PF6
(0.100 g,
92.4 (s, C5Me5); 112.1 (s, C2); 126.9, 127.3 (dd, JCP, JCP ꢃ 5 Hz,
2 4
0 0 0
0.107 mmol), NH4PF6 (0.0383 g, 0.235 mmol) and cyanogen bro-
mide (0.310 g, 0.293 mmol) in CH2Cl2 (10 cm3) was stirred for 14
h. The resulting dark green solution was concentrated, and filtered
into rapidly stirred Et2O, causing precipitation of the product as a
dark green solid, which was recrystallised from acetone and hex-
Cm,m ); 128.7, 128.7 (Cp,p ); 133.2, 133.9 (dd, JCP, JCP ꢃ 5 Hz, Co,o );
136.9, 138.8 (m, Ci,i ); 152.5 (t, JCP = 23 Hz, C1). 31P NMR: d 81.6.
0
ES(+)ꢀMS (m/z) 733.1 [M+H]+.
4.7. Preparation of [Fe{C@CBr2}(dppe)Cp]BF4 ([6a]BF4)
ane (0.066 g, 61%). IR (cmꢀ1): (C@C) 1652. 1H NMR (d6-acetone):
m
d 5.62 (s, 5H, Cp), 7.12–7.52 (m, 35H, Ph). 13C NMR (d6-acetone): d
A
stirred solution of Fe(C„CSiMe3)(dppe)Cp (0.060 g,
96.3 (s, Cp), 123.9 (s, C2), 128.4 (s, C4), 129.4 (overlapped C3, C5),
0.097 mmol) in CH2Cl2 (6 cm3) was treated with cyanogen bromide
(0.07 mg, 0.66 mmol) to immediately give a dark purple solution,
which was stirred for 5 min before the solvent was removed
in vacuo. The residue dissolved in acetone (5 cm3) and treated with
NaBF4 (0.05 g, 0.455 mmol). After stirring for 2 h, the crude product
was treated with diethyl ether to afford a brown precipitate, which
was purified by preparative TLC (3:7 acetone/hexane). A dark col-
129.7 (s, C6); 128.9 (dd, 3JCP, 5JCP ꢃ 5 Hz, Cm,m ); 131.4 (Cp,p ); 131.3,
0
0
2
4
0
0
133.8 (m, Ci,i ); 134.0 (dd, JCP, JCP ꢃ 5 Hz, Co,o ); 340.7 (t,
JCP = 16 Hz, C1). 31P NMR (d6-acetone) d 40.9 (s, PPh3), –143.1 (sep-
tet, PF6). ES(+)-MS (m/z): 872.9, [M+H]+; 918.2 [M+2Na]+. Elemen-
tal Anal. Calc. for RuC49H36F6P3Br: C, 57.87; H, 3.97. Found: C,
58.10; H, 4.29%.

4048
N.J. Brown et al. / Journal of Organometallic Chemistry 694 (2009) 4042–4048
oured band was collected and recrystallised by slow diffusion of
hexane into a dichloromethane solution to give yellow–orange
crystals of the product suitable for X-ray crystallography
References
[1] (a) R.B. King, M.S. Saran, J. Chem. Soc., Chem. Commun. (1972) 1053;
(b) R.B. King, Coord. Chem. Rev. 248 (2004) 1533.
[2] (a) M.I. Bruce, Chem. Rev. 91 (1991) 197;
(0.056 g, 73 %). IR (cmꢀ1): (C@C) 1609. 1H NMR: d 2.98 (m, 2H,
m
dppe); 3.26 (m, 2H, dppe); 5.32 (s, 5H, Cp); 7.10 (m, 4H, dppe),
(b) M.I. Bruce, Chem. Rev. 98 (1998) 2797;
7.41 (m, 16H, dppe). 13C NMR: d 29.0 (m, dppe); 91.8 (s, Cp);
(c) M.I. Bruce, in: C. Bruneau, P.H. Dixneuf (Eds.), Metal Vinylidenes and
Allenylidenes in Catalysis, Wiley-VCH, Weinham, Germany, 2008, pp. 1–60;
(d) M.C. Puerta, P. Valerga, Coord. Chem. Rev. 193–195 (1999) 977.
[3] (a) B.M. Trost, A. McClory, Chem. Asian J. 3 (2008) 164;
(b) C. Bruneau, P.H. Dixneuf, Angew. Chem., Int. Ed. 45 (2006) 2176.
[4] (a) I.T. Horváth, G. Pályi, L. Markó, J. Chem. Soc., Chem. Commun. (1979) 1054;
(b) I.T. Horváth, G. Pályi, L. Markó, G.D. Andreetti, Inorg. Chem. 22 (1983)
1049.
3
5
0
111.2 (s, C2); 129.4, 129.7 (dd, JCP
,
JCP ꢃ 5 Hz, Cm,m ); 131.6,
2
4
0
0
131.8 (Cp,p ); 131.4, 132.9 (dd, JCP, JCP ꢃ 5 Hz, Co,o ); 132.9, 134.3
(m, Ci,i ); 341.6 (t, JCP = 34 Hz, C1). 31P NMR: d 91.1 (s, dppe).
0
ES(+)-MS 703.0, [M]+.
[5] W. Schulze, K. Seppelt, Inorg. Chem. 27 (1988) 3872.
[6] (a) M.I. Bruce, M.G. Humphrey, G.A. Koutsantonis, B.K. Nicholson, J.
Organomet. Chem. 296 (1985) C47;
4.8. Preparation of [Ru(C@CBr2)(PPh3)2Cp]BF4 ([6b]BF4)
(b) M.I. Bruce, M.G. Humphrey, G.A. Koutsantonis, B.K. Nicholson, J.
Organomet. Chem. 320 (1987) 217.
[7] M.P. Gamasa, J. Gimeno, E. Lastra, B.M. Martin, A. Anillo, A. Tiripicchio,
Organometallics 11 (1992) 1373.
[8] M.I. Bruce, M. Jevric, C.R. Parker, W. Patalinghug, B.W. Skelton, A.H. White, N.N.
Zaitseva, J. Organomet. Chem. 693 (2008) 2915.
[9] (a) T. Miura, N. Iwasawa, J. Am. Chem. Soc. 124 (2002) 518;
(b) T. Miura, H. Murata, K. Kiyota, H. Kusama, N. Iwasawa, J. Mol. Catal. A:
Chem. 213 (2004) 59.
A solution of Ru(C„CSiMe3)(PPh3)2Cp (0.100 g, 0.151 mmol),
cyanogen bromide (0.048 g, 0.45 mmol) and NaBF4 (0.033 g,
0.30 mmol) in CH2Cl2 (15 cm3) was stirred for 4 h, after which time
the solvent removed and the product extracted into the minimum
amount of CH2Cl2. The deep purple product was precipitated into
rapidly stirring hexane, collected by filtration and dried (0.020 g,
15%). 1H NMR (CD2Cl2): d 4.35 (s, 5H, Cp), 7.05–7.80 (m, 30H,
[10] (a) A. Allen, K. Villeneuve, N. Cockburn, E. Fatila, N. Riddell, W. Tam, Eur. J. Org.
Chem. (2008) 4178;
3
Ph). 13C NMR (CD2Cl2): 96.5 (s, Cp), 109.9 (s, C2), 129.1 (dd, JCP
,
2
5JCP ꢃ 5 Hz, Phm), 131.7 (s, Php), 133.0 (m, Phi), 133.8 (dd, JCP,
(b) M.-Y. Lin, S.J. Maddirala, R.-S. Liu, Org. Lett. 7 (2005) 1745;
(c) A.W. Sromek, M. Rubina, V. Gevorgyan, J. Am. Chem. Soc. 127 (2005)
10500;
4JCP ꢃ 5 Hz, Pho), 337.9 (t, JCP = 15 Hz, C1).
P NMR (CD2Cl2) d
31
38.5 (s, PPh3). ES(+)ꢀMS (m/z): 874.95885, [M]+; calculated:
(d) V. Mamane, P. Hannen, A. Fürstner, Chem. Eur. J. 10 (2004) 4556.
[11] (a) N.J. Brown, P.K. Eckert, M.A. Fox, D.S. Yufit, J.A.K. Howard, P.J. Low, Dalton
Trans. (2008) 433;
874.95983 amu.
(b) R.L. Cordiner, M.E. Smith, A.S. Batsanov, D. Albesa-Jove, F. Hartl, J.A.K.
Howard, P.J. Low, Inorg. Chim. Acta 359 (2006) 946;
(c) M.E. Smith, R.L. Cordiner, D. Albesa-Jove, D.S. Yufit, F. Hartl, J.A.K. Howard,
P.J. Low, Can. J. Chem. 84 (2006) 154;
(d) R.L. Cordiner, D. Corcoran, D.S. Yufit, A.E. Goeta, J.A.K. Howard, P.J. Low,
Dalton Trans. (2003) 3541.
4.9. Preparation of [Ru(C@CBr2)(dppe)Cp*]BF4 ([6c]BF4)
A
solution
of
Ru(C„CSiMe3)(dppe)(C5Me5)
(0.100 g,
0.137 mmol), cyanogen bromide (0.043 g, 0.41 mmol) and NaBF4
(0.030 g, 0.27 mmol) in CH2Cl2 (15 cm3) was stirred for 4 h, after
which the solvent removed and the product extracted into the
minimum amount of CH2Cl2. The deep purple product was precip-
itated into rapidly stirring hexane and collected by filtration
(0.105 g, 94%). 1H NMR (CD2Cl2) d 1.75 (s, 15H, C5Me5); 2.72 (m,
2H, dppe); 2.86 (m, 2H, dppe); 7.09–7.63 (m, 20H, Ph). 13C NMR
(CD2Cl2) d 10.3 (s, C5Me5); 28.9 (m, dppe); 80.2 (s, C5Me5); 105.7
[12] S.G. Davies, J. Hibberd, S.J. Simpson, S.E. Thomas, O. Watts, J. Chem. Soc., Dalton
Trans. (1984) 701.
[13] A. Davison, J. Selegue, J. Am. Chem. Soc. 100 (1978) 7763.
[14] N. Le Narvor, L. Toupet, C. Lapinte, J. Am. Chem. Soc. 117 (1995) 7129.
[15] M.I. Bruce, G.A. Koutsantonis, Aust. J. Chem. 44 (1991) 207.
[16] M.I. Bruce, B.G. Ellis, P.J. Low, B.W. Skelton, A.H. White, Organometallics 22
(2003) 3184.
[17] L. Dahlenburg, A. Weiß, M. Moll, J. Organomet. Chem. 535 (1997) 195.
[18] Y. Kawata, M. Sato, Organometallics 16 (1997) 1093.
[19] (a) M. Sato, Y. Kawata, H. Shintate, Y. Habata, S. Akabori, K. Unoura,
Organometallics 16 (1997) 1693;
(b) M.I. Bruce, B.C. Hall, N.N. Zaitseva, B.W. Skelton, A.H. White, J. Chem. Soc.,
Dalton Trans. (1998) 1793.
[20] (a) M.I. Bruce, M.G. Humphrey, M.R. Snow, E.R.T. Tiekink, J. Organomet. Chem.
314 (1986) 213;
2
4
0
0
(s, C2); 129.2, 128.6 (dd, JCP, JCP ꢃ 5 Hz, Cm,m ); 130.5 (m, Ci,i );
0
0
132.1, 132.4 (s, Cp,p ); 133.1 (m, Co,o ), 329.3 (t, JCP = 17 Hz, C1).
31P NMR (CD2Cl2) d 73.0 (s, dppe). ES(+)ꢀMS (m/z): 818.99261,
[M]+; calculated 818.99113 amu.
(b) J.M. Wisner, T.J. Bartczak, J.A. Ibers, Inorg. Chim. Acta 100 (1985) 115;
(c) F. Paul, B.G. Ellis, M.I. Bruce, L. Toupet, T. Roisnel, K. Costuas, J.-F. Halet, C.
Lapinte, Organometallics 25 (2006) 649.
Acknowledgements
[21] (a) J.P. Selegue, J. Am. Chem. Soc. 104 (1982) 119;
(b) R.S. Iyer, J.P. Selegue, J. Am. Chem. Soc. 109 (1987) 910;
(c) Y.-S. Yen, Y.-C. Lin, Y.-H. Liu, Y. Wang, Organometallics 26 (2007) 1250.
[22] (a) M.I. Bruce, P.A. Humphrey, M. Jevric, G.J. Perkins, B.W. Skelton, A.H. White,
J. Organomet. Chem. 692 (2007) 1748;
We thank the EPSRC and the University of Durham for financial
support.
(b) M. Akita, Y. Tanaka, M. Takeshita, A. Inagaki, M.-C. Chung, Organometallics
25 (2006) 5261;
(c) G. Argouarch, P. Thominot, F. Paul, L. Toupet, C. Lapinte, C.R. Chim. 6 (2003)
209.
Appendix A. Supplementary material
CCDC 740208, 740209, 7402010, 7402011 and 7402012 contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2009.08.027.
[23] W.M. Khairul, M.A. Fox, N.N. Zaitseva, M. Gaudio, D.S. Yufit, B.W. Skelton, A.H.
White, J.A.K. Howard, M.I. Bruce, P.J. Low, Dalton Trans. (2009) 610.
[24] M.I. Bruce, C. Hameister, A.G. Swincer, R.C. Wallis, Inorg. Synth. 21 (1982) 78.
[25] M.J. Mays, P.L. Sears, J. Chem. Soc., Dalton Trans. (1973) 1873.
[26] M.I. Bruce, C. Hameister, A.G. Swincer, R.C. Wallis, Inorg. Synth. 28 (1990) 270.