The first early transition metal perfluorovinyl complexes: The synthesis of Cp2M(CF=CF2)nX2-n (Cp: Η5-C5H5-; M=Ti, Zr; X=Cl or F) and structures of Cp2Ti(CF=CF2)nX2-n (X=Cl, F) via Ti K-edge EXAFS studies

Article abstract of DOI:10.1016/S0022-328X(99)00073-X

A new route to perfluorovinyl compounds, recently reported by us, has been used to prepare the first examples of early transition metal complexes of the type Cp₂M(CF=CF₂)_nX_n-2 (Cp: η⁵-C₅H₅^-; M=Ti, Zr; X=Cl or F). These compounds are obtained in high yield from the two-stage, one-pot, reaction of HFC-134a (CF₃CH₂F) with two equivalents of BuLi, followed by addition of Cp₂MX₂ (M=Ti, Zr, X=F, Cl). For two of the titanium-containing compounds Ti K-edge EXAFS data have been recorded from which distances for the titanium-carbon bond of the perfluorovinyl group of 2.033(12) and 2.050(18) A in Cp₂Ti(CF=CF₂)₂ and Cp₂Ti(CF=CF₂)F are obtained. This is the first report of structural data for any perfluorovinyl organometallic compound, and the distances obtained are consistent with the perfluorovinyl group binding in a simple sigma fashion.

Full text of DOI:10.1016/S0022-328X(99)00073-X

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 582 (1999) 301–309
The first early transition metal perfluorovinyl complexes: the
5
−
synthesis of Cp M(CFꢀCF ) X
(Cp: h -C H ; M=Ti, Zr;
2
2 n 2−n
5
5
X=Cl or F) and structures of Cp Ti(CFꢀCF ) X
(X=Cl, F)
2
2 n 2−n
via Ti K-edge EXAFS studies
Kulbinder K. Banger, Alan K. Brisdon *
Department of Chemistry, UMIST, PO Box 88, Manchester M60 1QD, UK
Received 15 December 1998
Abstract
A new route to perfluorovinyl compounds, recently reported by us, has been used to prepare the first examples of early
5
−
transition metal complexes of the type Cp M(CFꢀCF ) X
(Cp: h -C H ; M=Ti, Zr; X=Cl or F). These compounds are
2
2 n n−2
5
5
obtained in high yield from the two-stage, one-pot, reaction of HFC-134a (CF CH F) with two equivalents of BuLi, followed by
3
2
addition of Cp MX (M=Ti, Zr, X=F, Cl). For two of the titanium-containing compounds Ti K-edge EXAFS data have been
2
2
recorded from which distances for the titanium–carbon bond of the perfluorovinyl group of 2.033(12) and 2.050(18) A
Cp Ti(CFꢀCF ) and Cp Ti(CFꢀCF )F are obtained. This is the first report of structural data for any perfluorovinyl organometal-
,
in
2
2 2
2
2
lic compound, and the distances obtained are consistent with the perfluorovinyl group binding in a simple sigma fashion. © 1999
Elsevier Science S.A. All rights reserved.
Keywords: Perfluorovinyl; Titanium; Zirconium; Synthesis; EXAFS
metal centres, this situation is not matched either in
range, or stability, of reagents for the synthesis of
metal–fluorocarbon species.
1
. Introduction
The replacement of hydrogen for fluorine in organic
The introduction of the perfluorovinyl (1,1,2 trifl-
uorovinyl) group onto metal centres is one such area
where a lack of methodology has limited the number of
complexes which have been synthesised. Although
much attention was focused in this area in the 1960s
and early 1970s there were only two practical synthetic
routes. The first of these was based on the incorpora-
fragments results in moieties which are often sterically
non-perturbed compared with their perprotio ana-
logues, but which possess very different electronic prop-
erties [1,2]. These factors are reflected in significantly
different physical and chemical properties for related
C–H and C–F containing compounds and in no area is
this more obvious than in the field of organometallic
chemistry. Transition metal organometallic compounds
containing fluorinated organic ligands are frequently
more thermally stable than their perprotio analogues,
and they often undergo quite different reactions. This
is, in part, due to the very much stronger C–F bond
compared with the C–H linkage. However, while there
exists a large arsenal of reagents available for the
introduction of alkyl and related perprotio groups onto
tion of C F as a p-bound ligand on a coordinatively
2
4
unsaturated late transition-metal centre followed by
2
heating the h -C
sults in a vinyllic rearrangement to generate the s-
bound –CFꢀCF complexes [3]. The second method
F -containing complexes, which re-
2 4
2
relied on generation of a perfluorovinyl lithium or
Grignard reagent, usually based on bromotrifl-
uoroethene [4]. These two routes accounted for the
successful synthesis of a number of main-group and late
transition metal complexes containing the pe-
rfluorovinyl ligand [5]. However, both of these methods
*
Corresponding author. Fax: +44-161-228-7040.
E-mail address: alan.brisdon@umist.ac.uk (A.K. Brisdon)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00073-X

302
K.K. Banger, A.K. Brisdon / Journal of Organometallic Chemistry 582 (1999) 301–309
have their limitations; the first is generally restricted to
coordinatively unsaturated late transition metal com-
plexes whilst the formation of Grignard and lithium
reagents rely on chloro- or bromo-substituted fluoro-
carbon starting materials, the availability of many of
which is now severely limited, at least for industrial
applications, because of their impact on the ozone
layer. This combination of factors has resulted, to date,
in the synthesis of main-group and late transition metal
perfluorovinyl compounds but no examples of early
transition metal complexes.
This lack of early transition metal fluoro–
organometallic complexes is unfortunate since these
metals provide some of the most active organometallic
centres with, in particular, the chemistry of Group 4
bis-cyclopentadienyl dihalide complexes having been
widely studied because of their potential range of appli-
cations in catalysis [6], anti-cancer drugs [7] and as
reagents in organic synthesis [8]. Work in this area has
resulted in the production of a number of organometal-
lic complexes with a variety of derivatised cyclopentadi-
which contrary to previous reports [4], we have found
to be stable for up to 24 h under anaerobic conditions
and at low temperature, is added the Group 4 bis(cy-
clopentadienyl)metal dihalides dissolved in cold diethyl
ether or THF. The solution is stirred and maintained at
low temperature for at least 1 h before slowly being
allowed to warm to room temperature (r.t.) when the
formation of an off-white precipitate becomes obvious.
Analysis of this material confirms it to be a mixture of
lithium halides.
In all experiments, prior to working-up the reaction
mixture, samples of the organic phase were withdrawn
and were monitored via NMR studies to determine the
19
extent of reaction. The F-NMR spectra of these solu-
tions demonstrated that the complex multiplet signals
due to HFC-134a at l −64.9 and −226.5 ppm had
been replaced by three sets of doublets of doublets
typical of the patterns previously observed for pe-
rfluorovinyl metal complexes [16].
Although aqueous work-ups have been utilised be-
fore for late transition metal perfluorovinyl complexes
enyl-based ligands [9]. Although
a
number of
[4], the use of such methods for these systems resulted
alkyl-substituted complexes exist, there are relatively
few alkenyl-containing titanocene complexes. Those
in complete decomposition of the products. Instead, a
large volume of hexane is added to the reaction mixture
to ensure complete precipitation of the lithium salts
followed by filtration under a dinitrogen atmosphere.
Removal of the volatile solvent, under reduced pres-
sure, resulted in solid products which were analytically
pure. Thus, the reaction of one equivalent of pe-
rfluorovinyllithium with Cp TiX (X=F,Cl) resulted in
that
have
been
fully
characterised
include
Cp TiX(C(Ph)ꢀCMe ) X=Br and Cl [10], the oxygen-
2
2
bridged bis-cyclopentadienyl(1,1,1,4,4,4 hexafluorobut-
en-3-yl) compound [11] and Cp*TiF(CHꢀCH ) [12].
2
2
The vinyl-substituted bis(pentamethylcyclopentadienyl)
complexes in particular have been the subject of much
recent work because of the range of reactivities and
variety of novel complexes and structures that are
produced, and this area has recently been reviewed [13].
We have recently reported a new route for the one-
pot synthesis of perfluorovinyl-containing compounds
in high yields based on the commercial CFC-replace-
ment HFC-134a (CF CH F). The high efficiency and
2
2
Cp TiX(CFꢀCF ) [compound 2 X=F, 3 X=Cl] and
2
2
when slightly more than two equivalents of pe-
rfluorovinyllithium was used Cp Ti(CFꢀCF ) , com-
2
2 2
pound 4 was obtained. In all cases yields greater than
8
5% were obtained.
The F-NMR spectrum obtained from compound 4
19
3
2
dissolved in CDCl is shown in Fig. 1 and the data
wide-ranging nature of this method was demonstrated
by the synthesis of examples of main-group and transi-
tion metal perfluorovinyl complexes [14]. Here, for the
first time, we describe the synthesis of titanium(IV)-
and zirconium(IV)-bis-cyclopentadienyl perfluorovinyl
complexes. We also report the first structural data for
perfluorovinyl–organometallic complexes via a series of
Ti K-edge EXAFS studies.
3
obtained for all the compounds is presented in Table 1.
The fluorine NMR spectra of all the perfluorovinyl-
containing complexes exhibit signals for the fluorine
2. Results and discussion
2.1. Synthesis and characterisation
The slow addition of two equivalents of n-butyl-
lithium to a diethyl ether solution of the CFC-replace-
ment HFC-134a (CF CH F) at −78°C results in the
3
2
−
+
formation of the thermally unstable CF ꢀCF Li
reagent (1) in good yields [14,15]. To a solution of 1,
2
Fig. 1. 19F-NMR spectrum of Cp Ti(CFꢀCF ) dissolved in CDCl3.
2
2 2

K.K. Banger, A.K. Brisdon / Journal of Organometallic Chemistry 582 (1999) 301–309
303
Table 1
For all three compounds the proton NMR spectra
exhibited a single peak between 6.4 and 6.5 ppm corre-
sponding to the equivalent protons of the Cp rings.
19
F-NMR data for the compounds Cp TiX2−n(CFꢀCF ) (X=F,Cl;
n=1,2)
2
2 n
13
l 19F (ppm) a ꢀJꢀ (Hz)
C-NMR spectra showed a signal within the range
16–119 ppm which is assigned to the carbons of the
Cp rings. The C-NMR spectrum of a concentrated
Compound
Assignment
1
13
Cp TiCl
−97.7(dd)
36(F , F ), 76(F , F )
Fa
2
a
c
a
b
(CFꢀCF2) −110.2(dd)
76(F , F ), 107(F , F ) Fb
a b b c
solution of Cp Ti(CFꢀCF ) dissolved in CDCl also
2
2 2
3
−
130.9(dd)
36(F , F ), 107(F , F ) Fc
a c b c
exhibits a complex multiplet at ca. 156.9 ppm, which by
virtue of the number of couplings observed must be due
to the two carbon nuclei of the perfluorovinyl ligand.
However, it was not possible to obtain good-quality
Cp TiF
64.3(s)
–
F
2
(CFꢀCF2)
−101.6(dd)
36(F , F ), 62(F , F ) Fa
a c a b
−
−
105.2(dd)
131.7(dd)
62(F , F ), 105(F , F ) Fb
a b b c
39(F , F ), 105(F , F ) Fc
a
c
b
c
13
data for the perfluorovinyl part of the C-NMR spec-
tra for the complexes due to their low solubility, the
number of resonances involved and the rate of sample
decomposition in common solvents, see below.
Cp Ti
−101.8(dd)
CFꢀCF2)2 −105.0(dd)
131.9(dd)
34(F , F ), 61(F , F ) Fa
a c a b
2
(
61(F , F ), 105(F , F ) Fb
a b b c
−
34(F , F ), 105(F , F ) Fc
a c b c
a
Chemical shift values reported are for CDCl3 solutions with
The IR spectra of the complexes are consistent with
the anticipated structures and are assigned on the basis
of previous vibrational spectroscopic studies of metal-
locene dihalides [20] and perfluorovinyl metal com-
plexes [21]. The w(CꢀC) vibrational mode of the
respect to external CFCl3.
nuclei of the perfluorovinyl ligand in three distinct
regions l −97 to −102, −105 to −110 and −131 to
−
132 ppm and each signal shows doublet of doublet
perfluorovinyl group is assigned to the intense peak
coupling patterns typical of an AMX spin system. The
two signals observed between −97 and −110 ppm for
compounds 2–4 are assigned to the two fluorine nuclei
of the terminal CF group and the lower frequency
resonance to the unique a-fluorine nucleus of the pe-
rfluorovinyl ligand (F , Fig. 1). This is in accord with
−1
observed between 1637 and 1653 cm
tions at ca. 1250, 1010 and 965 cm
the three w(C–F) modes.
and the absorp-
are assigned to
−1
2
UV–vis studies of the complexes in acetonitrile solu-
tion gave rise to a number of absorptions of which
those around 380–390 and 310–340 nm may be as-
c
previous assignments for other perfluorovinyl-contain-
ing compounds [16] in which the signals for nuclei Fa
signed to the Cp Ti fragment of the molecule on the
2
basis of previous studies of Cp TiX (X=halide) [22].
2
2
and F occur within a small chemical shift region whilst
b
The symmetry allowed p–p* transition of the pe-
rfluorovinyl ligand is expected around 200 nm accord-
ing to the work of Lacher et al. on chloro- and
fluoro-substituted ethylenes [23] and therefore, the in-
the signal for the F nucleus shows a large variation in
position, ranging from −205 ppm for CF ꢀCFH [17]
to −138 ppm for [CpFe(CO) (CFꢀCFCF )] [18]. As-
c
2
2
3
3
−1
signment of the two sets of signals between l −97 to
102 and l −105 to −110 to F and F is made on
tense peak observed at 210 nm (m=19 000 dm mol
−
1
−
a
b
cm ) in the UV spectrum of compound 4 is assigned
to this transition.
the basis of the magnitude of the coupling constants
1
9
19
between all the fluorine nuclei. The F– F coupling
constants observed in fluoroolefins are typically within
the range 20–90 Hz for gem-coupling, 30–60 Hz for
syn-coupling and 110–130 Hz for anti-coupling [17].
Although there is some overlap between the coupling
constant ranges for syn- and gem-couplings the larger
anti-coupling allows straightforward assignment of the
signals observed between −105 and −110 ppm to Fb,
A number of attempts were made to synthesise the
analogous zirconium complexes but these were always
19
less successful. F-NMR spectra obtained prior to
work-up procedures again showed consumption of the
starting hydrofluorocarbon and the presence of new
resonances which are consistent with those obtained for
the titanium perfluorovinyl-containing analogues. How-
ever, the materials decomposed rapidly as the tempera-
ture of the solution was raised towards r.t.
Decomposition was also evident for isolated solid prod-
ucts over a period of ca. 1 h. Because of this decompo-
sition it did not prove possible to obtain satisfactory
elemental analyses for any of the zirconium-containing
compounds. In contrast the isolated titanium complexes
are stable as solids, for example in a dry box; however,
in solution they too decompose, but at varying rates.
The time for complete decomposition in solution ranges
from minutes to many days depending on the solvent
used and the compound in question. In the hydrocar-
bon solvent systems that we have investigated the order
the fluorine nucleus anti to F , and those peaks between
c
−
97 and −102 ppm to F . For complex 2,
a
Cp Ti(CFꢀCF )F, an additional singlet is observed in
2
2
1
9
the F-NMR spectrum at 64.3 ppm which is assigned
to the single fluoride coordinated to the titanium centre
on the basis of spectra recorded for other titanium
fluoride species [17]. Although it is possible to observe
3
the J coupling between the cyclopentadienyl protons
and the fluoride nuclei in Cp TiF it is small (1.7 Hz
2
2
[19]) and we were not able to resolve an equivalent
coupling for complex 2 under similar spectroscopic
conditions.

304
K.K. Banger, A.K. Brisdon / Journal of Organometallic Chemistry 582 (1999) 301–309
of stability for the titanium species appears to be
parisons can only be made with the results of a more
recent X-ray diffraction study which shows an asym-
metric unit containing two titanocene dichloride
molecules but with essentially similar distances for the
titanium–chlorine and titanium–carbon bonds within
both molecules [d(Ti–Cl)av=2.364(3) and d(Ti–
Cp TiCl(CFꢀCF ) ꢀ Cp Ti(CFꢀCF ) B Cp TiF(CFꢀ
2
2
2
2 2
2
CF ) and the ultimate fate of the perfluorovinyl ligand
2
is the generation of CF CFH. Interestingly, the same
2
order of reactivity towards thermal decomposition is
not observed for the perprotio-vinyl analogues of the
titanium and zirconium complexes, in this case the
zirconium compounds are the more stable whilst
Cp Ti(CHꢀCH ) rapidly decomposes at −30°C to
C)av=2.370(9) A] [29]. Our EXAFS results also sug-
,
gest similar, but slightly longer, Ti–Cl and Ti–C
distances. However, the differences are small, ca. 1%
for the titanium–chlorine distance and within experi-
mental error for the titanium–carbon shell. It is most
likely that the two similar distances result in a poorer
distinction of the two shells than one might normally
expect and that the much smaller back-scattering con-
tribution of the carbon atoms compared with that
arising from the chlorine shell results in larger than
usual uncertainties in the parameters for the carbon
shell.
2
2 2
ultimately generate vinylidene or metallacyclobutane
complexes [24].
2.2. EXAFS studies
Because of the solution-phase decomposition of
these products, it has proved impossible to obtain
crystals suitable for characterisation by single-crystal
X-ray diffraction methods for any of these complexes.
However, we have been able to record room-tempera-
ture titanium K-edge EXAFS data for two of the
The Fourier transforms of the EXAFS spectra of
Cp TiF , Cp TiF(CFꢀCF ) and Cp Ti(CFꢀCF ) are
2
2
2
2
2
2 2
shown in Fig. 2(b,c,d), and in all cases a peak at ca.
perfluorovinyl-containing
materials
Cp TiF (CFꢀ
2
n
2
.4 A is observed which is assigned to shell of ten
,
CF2)2−n (n=0, 1) mulled in boron nitride. For com-
parison we have also recorded the EXAFS data for
Cp TiCl and Cp TiF .
carbon atoms of the two cyclopentadienyl ligands. In
the spectra of the fluoride-containing compounds
2
2
2
2
(
1
Cp TiF and 2) a peak is also observed at around
,
.8–1.9 A which must correspond to the Ti–F dis-
2
2
Data collection, averaging, background subtraction
and modelling of the Fourier transforms of the EX-
AFS for Cp TiCl , Cp TiF and compounds 2 and 4
tance. Modelling of the data for Cp TiF in this way
2
2
2
2
2
2
resulted in an R-factor of 20.2% and final bond dis-
tances of d(Ti–F)=1.855(6) and d(Ti–C)=
.378(12) A. For compound 2 modelling the data
with two shells (1F, 10C) resulted in a titanium–
fluoride bond distance of 1.812(7) A, a Ti–C distance
of 2.404(10) A and an R-factor of 27.9%. Inclusion
were carried out via standard methods [25]. The EX-
AFS spectra of all these compounds exhibit a small,
sharp peak just below the absorption edge which may
be assigned to the formally electron-dipole forbidden
A
,
2
,
,
1s“3d transition of the metal complex. The presence
,
of such a feature is indicative of a non-centrosymmet-
ric local environment such as that found in tetrahe-
dral or pseudo-tetrahedral geometry around the
central metal atom [26].
of a third shell (1C), corresponding to the Ti–C dis-
tance of the bound perfluorovinyl ligand, resulted, af-
ter iteration, in a drop in the R-factor to 23.1% and
a Ti–Cpfv distance of 2.050(18) A. The validity of
,
Background subtraction of the averaged data for
including this shell is unambiguously supported by
the statistical tests of Joyner et al. [30] at the 1%
level. Mapping of the occupation numbers of these
two shells is consistent with there being one fluoride
and one perfluorovinyl ligand coordinated to the tita-
nium metal centre, with a minimum in the R-factor
corresponding to occupation numbers of 1.0 F and
Cp TiCl ,
Cp TiF ,
Cp TiF(CFꢀCF )
and
2
2
2
2
2
2
Cp Ti(CFꢀCF ) resulted in the EXAFS spectra
2
2 2
shown in Fig. 2(a–d). Analysis of the primary coordi-
nation shells for the compound Cp TiCl , as a stan-
2
2
dard, was undertaken using a model consisting of
one-shell of two chlorine atoms and one-shell of ten
carbon atoms. Refinement of the model resulted in
1
.1 C. It should, however, be noted that in general
d(Ti–Cl)=2.389(5) and d(Ti–C)=2.379(16) A. De-
,
EXAFS is not particularly sensitive to occupancy lev-
els, typically confidence limits of 910–20% being ac-
cepted. Further shells were added to the model
corresponding to the non-bonded Ti···F and T···C
distances of the perfluorovinyl ligand based on geo-
metric calculations assuming CꢀC and C–F bond
spite the widespread applications of this complex it
has only been the subject of a few structural determi-
nations, with conflicting results. An early single-crys-
tal X-ray determination [27] reported distances to two
decimal places and provided no error estimates on the
derived distances of d(Ti–C) =2.36 and d(Ti–Cl)=
lengths of 1.3 and 1.35 A, respectively [31], and 120°
,
av
2
.37 A
study [28] suggested that the titanium–chlorine dis-
tance was significantly shorter (2.24 A) than the tita-
nium–carbon distance (2.38 A) but again no error
estimates were provided. Therefore, meaningful com-
,
. At a similar time an electron diffraction
bond angles. This resulted in a reduction in the R-
factor, but not at a statistically high enough level to
be included in the final model and they are, by con-
vention [32], omitted from the parameters which are
given in Table 2.
,
,

K.K. Banger, A.K. Brisdon / Journal of Organometallic Chemistry 582 (1999) 301–309
305
Fig. 2. The Fourier transformed EXAFS spectra (—, experimental; – – –, theoretical) of (a) Cp TiCl , (b) Cp TiF , (c) Cp TiF(CFꢀCF ) and
2
2
2
2
2
2
3
3
(
d) Cp Ti(CFꢀCF ) and (e) the background subtracted Ti K-edge EXAFS spectra (—, experimental data×k ; – – –, theory×k ) for
2 2 2
Cp Ti(CFꢀCF ) in boron nitride.
2
2 2

306
K.K. Banger, A.K. Brisdon / Journal of Organometallic Chemistry 582 (1999) 301–309
Table 2
,
Cpfv distance of 1.808(12) A which is essentially the
EXAFS derived distances for the primary coordination shells of the
compounds Cp TiX2−n(CFꢀCF2)n (X=F, Cl; n=0,1,2)
same as that found for the P–C
distance [1.807(8)
vinyl
2
A] recorded for the analogous complexes containing
,
Compound
Shell
Distance Debye-Waller R-factor c
PPh (CHꢀCH ) [37]. For the two structurally character-
2
2
a
−2 b
(
A
,
)
(A
,
)
ised examples of titanium perprotio–vinyl com-
plexes (Cp Ti(CHꢀCH )(OC(CH )C H ) and Cp*Ti-
2
2
2
6
11
2
Cp TiCl2
2.2×Cl 2.389(5)
0.009(2)
19.7
20.2
23.1
2
(
CHꢀCH )F) (Cp*=C Me ) the Ti–C
distances are
2
5
5
vinyl
9
.7×C 2.379(16) 0.016(14)
2
.143(4) and 2.098(6) A, respectively [38,39]. The EX-
,
Cp TiF2
2.1×F 1.855(6)
0.006(1)
2
AFS-derived titanium–perfluorovinylcarbon bond
lengths determined for compounds 2 [2.050(18) A] and
4 [2.033(12) A] are similar and both are slightly shorter
9
.7×C 2.378(12) 0.019(2)
,
Cp TiF(CFꢀCF ) 1.0×F 1.812(7)
0.001(1)
.1×C 2.050(18) 0.007(7)
.7×C 2.404(10) 0.016(2)
,
2
2
1
9
(
ca. 4% compared with Cp*Ti(CHꢀCH )F) than those
2
2
observed for the related vinyl complexes.
Cp Ti(CFꢀCF )
1.9×C 2.033(12) 0.019(4)
.2×C 2.416(4) 0.011(1)
19.0
2
2 2
These two Ti–Cpfv distances represent the first re-
ported estimates of this parameter for any metal-bound
perfluorovinyl complex. We note that in both cases the
9
a
This work, standard deviations (2|) are given in parentheses,
systematic errors in bond distances arising from data collection and
obtained distances are similar to 2.03 A
covalent radii for Ti(IV) (1.36 A) and sp hybridised
carbon (0.67 A) [40]. This suggests that the pe-
,
, the sum of the
2
analysis procedures are estimated as ca.90.02 A
,
.
,
b
Debye–Waller factor.
R=[ꢁ(
,
c
Theory
Expt.
3
Expt.
3
−
)k dk/ꢁ 
=k dk]×100%, obtained af-
rfluorovinyl group is bound in a simple s-fashion and
that there is no obvious p-delocalisation even though
the metal is electron poor. This, however, is not surpris-
ing since there is also no evidence for p-donation in the
ter modelling of primary coordination shells only.
Modelling the Fourier transform of the EXAFS data
for the bis-substituted complex 4 to a one-shell (2Cp,
Cp*TiF(CHꢀCH ) system [d(Ti–C )=2.099 A] de-
,
2
2
vinyl
10C) model resulted in an R-factor of 35.6%, whilst
spite the vinyl ligand presumably being a better poten-
inclusion of a second shell containing two carbon back-
scatterers corresponding to the two perfluorovinyl-car-
bons followed by iteration resulted in a reduction of the
R-factor to 19.0% and a Ti–Cpfv distance of 2.033(12)
tial p-donor than the fluorinated analogue.
A. Once again, weaker features are observed at longer
,
3
. Experimental
distances in the radial distribution plot and inclusion of
these shells arising from the other atoms in the pe-
rfluorovinyl ligand at distances similar to those ob-
tained from the previous compound resulted in a
further reduction in the R-factor, but these parameters
are not well defined and so not reported here. Fig. 2(e)
HFC-134a (ICI Klea), butylithium (2.5 M in hexane,
Aldrich), titanocenedichloride (Lancaster Synthesis)
were used as supplied after verification of purity using
spectroscopic methods. Diethyl ether (BDH) and THF
(
BDH) were dried by standing over sodium wire for ca.
day and subsequently refluxed over sodium/ben-
zophenone under a dinitrogen atmosphere. Hexane
Cannon Scientific) was stored over sodium wire prior
3
shows the background subtracted k weighted EXAFS
1
data for compound 4 and its fit to the theoretically
3
calculated k EXAFS.
(
There are relatively few data with which to directly
compare these distances. The Ti–F and Ti–C distances
are consistent with those observed in related, struc-
turally characterised, L TiF systems. For example
to use. Fluorine and proton NMR spectra were
recorded on solutions of samples on a Bruker AC200
instrument at 188.3 and 200.2 MHz and referenced
against CFCl and TMS, respectively, using the high-
frequency-positive convention. C-NMR spectra were
recorded on a Bruker AC300 machine at 75.47 MHz
and referenced against TMS. Elemental analyses were
performed by the analytical service in the Department.
IR spectra were recorded on a Nicolet PC5 instrument
and mass spectra were recorded by the Michael Barber
Mass Spectrometry centre, UMIST. All reactions were
carried out under anaerobic and anhydrous conditions.
All glassware was flame dried prior to use, and mois-
ture sensitive reagents were handled under an argon
atmosphere in a dry-box (Belle Technology, UK). All
recorded reaction temperatures are uncorrected internal
temperatures.
2
2
3
5
5
when L=(h -C H (SiMe )) [33] and L=(h -
C H (SiMe ) ) [34] d(Ti–F)=1.832(2) and 1.855(1) A
13
5
4
3
,
5
3
3 2
5
and
the
average
Ti–C
distance
in
(h -
C H (SiMe ) ) TiF is 2.407(3) A. There is, however, no
,
5
3
3 2 2
2
published structural work for any metal-bound pe-
rfluorovinyl group and only one crystal structure for a
metal–perhalovinyl compound [3,4,7,8 tetramethyl-1,
10-phenanthroline-N,N%)-(bis(trichlorovinyl))-mercury]
[35], but this does not allow for meaningful compari-
son. We have recently obtained crystallographic data
for some complexes containing perfluorovinyl–phos-
phorus(III) ligands. For cis-platinum(II) complexes
containing PPh (CFꢀCF ) [36] we find an average P–
2
2

K.K. Banger, A.K. Brisdon / Journal of Organometallic Chemistry 582 (1999) 301–309
307
3.1. Preparation of bis(cyclopentadienyl)titaniumdi-
8.04 mmol) in diethyl ether (180 ml, −80°C). After ca.
fluoride
2 h Cp TiCl (2.00 g, 8.04 mmol), dissolved in THF
2
2
(
250 ml, −80°C), is added slowly to the reaction
This was prepared based on literature methods [4] by
mixture which is held at −110°C. After the reaction is
reacting sodium fluoride (1.68 g, 40.00 mmol) dissolved
in water (15 ml) with a suspension of bis-(cyclopentadi-
enyl) titanium dichloride (5.00 g, 20.00 mmol) dissolved
in 100 ml of water in a single neck round bottom flask.
The reaction is vigorously stirred for 3 h yielding a
yellow solid, which is subsequently filtered and dried
overnight.
complete it is worked up as previously described result-
ing in a red–orange coloured material. Yield 2.05 g,
1
87%. m.p. (uncorrected) 150(dec.) °C. lC{ H} (CDCl ),
3
−
1
116.5 [m, C H ]; wmax/cm
1653 (CꢀC), 1653, 1234,
5
5
+
1005, 966, 819 (nujol mull); m/z (CI NH ) 312 ([M+
4
+
+
NH ] , 5%), 213 (100, [M−C F ] ), 197 (35, [M−
C F Cl] ); UV–vis umax/nm (MeCN) 389, 248 (m/dm
4
2 3
+
3
2
2
−
1
−1
mol
cm
3550 and 16 550).
5
3
.2. Fluoro(perfluoro6inyl)bis(p -cyclopentadienyl)-
5
titanium(IV) 2
3.4. Bis(perfluoro6inyl)bis(p -cyclopentadienyl)titanium-
(IV) 4
A 1 l 3-neck flask held at −80°C is equipped with a
magnetic stirrer, a rubber septum and a silicon oil
bubbler and maintained under a positive flow of dini-
trogen gas. The flask is charged with pre-cooled diethyl
In a similar procedure to that outlined for compound
2, to cold liquid HFC 134a (4.06 cm , 48.19 mmol) in
3
hexane (400 ml) is added butyllithium (2.5 M in hexane,
3
3
ether (200 ml, −50°C) and liquid HFC 134a (0.20 cm ,
38.55 cm , 96.33 mmol) over a 0.5 h period. After 2 h
2
.32 mmol) in diethyl ether (50 ml, −80°C) is added.
the temperature of the reaction mixture is lowered to
−110°C and bis-cyclopentadienyl titanium dichloride
(4.00 g, 16.06 mmol), dissolved in THF (400 ml,
−80°C), is added slowly. After warming to r.t. the
solvent volume is reduced and hexane is added. The
mixture is filtered under a dinitrogen atmosphere and
the volatile organic solvents are removed in vacuo. The
3
Butyllithium (2.5 M in hexane, 1.85 cm , 4.63 mmol)
was added slowly to the stirred solution over a 0.5 h
period. Once addition of the BuLi is complete the
reaction temperature is maintained between −55 and
−
+
−
80°C for 2 h to ensure generation of CF ꢀCF Li .
2
The reaction mixture temperature is lowered to
110°C and bis-cyclopentadienyl titanium difluoride
0.50 g, 2.32 mmol), dissolved in THF (200 ml,
80°C), is added slowly. The reaction is left to warm
3
−
(
−
orange solid is washed with hexane (4×10 cm ), and
dried under vacuum for 30 min. to afford 4 as a light
orange coloured material. Yield 4.8 g, 88%, m.p. (un-
corrected) 131°C.
to −35°C over a period of a few hours and then
allowed to attain r.t. by removal of the slush bath. The
solvent volume is reduced in vacuo to half and hexane
(Found: C, 49.2; H, 3.2; F, 33.5; Ti, 14.4%.
(C H ) Ti(CFꢀCF ) requires: C, 49.4; H, 2.9; F, 33.5;
5
5 2
2 2
1
(
300 ml) is added, resulting in the precipitation of
Ti, 14.1%). lH(CDCl ), 6.40 (s, C H ); lC{ H}
3 5 5
lithium salts, from the organic phase. The mixture is
allowed to settle before being carefully filtered through
a No. 4 sinter under a dinitrogen atmosphere. The
solvent is then removed in vacuo to leave a pastel
(CDCl ), 156.9 [m, CFꢀCF ], 118.1 [m, C H ]; wmax/
−1
3
2
5
5
cm
(nujol mull) 1637, (CꢀC), 1262, 1009, 966 (C–F);
+ +
m/z (CI NH ) 358 ([M+NH ] , 30%), 276 (100,
4
4
+
+
[M+NH –C F ] ), 214 (70, [M+NH –C F ] );
4
2
3
4
4 5
orange solid which is subsequently washed with hexane
UV–vis u /nm (MeCN) 468, 394, 344, 235(sh), 210
max
−1
3
3
−1
(
4×10 cm ), and dried under vacuum for 30 min to
(m/dm mol
cm
1075, 2065, 1830, 15 100 and
afford 2 as a yellow–orange coloured material Yield
.56 g, 88%. m.p. (uncorrected) 135(dec.) °C. (Found:
C, 50.5; H, 4.1; F, 25.2%. (C H ) Ti(CFꢀCF )F re-
19 000).
0
5
3.5. Bis(perfluoro6inyl)bis(p -cyclopentadienyl)-
zirconium(IV) 5
5
5 2
2
1
quires: C, 51.8; H, 3.6; F, 27.3%). lC{ H} (CDCl ),
3
−
1
1
1
2
19.0 [m, C H ]; wmax/cm
1637 (CꢀC), 1636, 1233,
009, 962, 827 (nujol mull); m/z (CI NH ) 276 ([M−
H] , 100%), 259 (10%, [M−F] ), 195 (20, [M−2H-
C F ] ); UV–vis umax/nm (MeCN) 462, 378, 312, 243
5
5
+
4
A preparative route similar to that for 2 outlined
above was used. BuLi (2.5 M, 20.0 cm , 0.050 mol) is
added to a solution of HFC 134a (2.16 cm , 0.026 mol)
in diethyl ether (180 cm , −80°C). After ca. 5 h
+
+
3
+
3
2
3
3
−1
−1
3
(
m/dm mol
cm
650, 1750, 3950 and 14 800).
3
Cp ZrCl (3.00 g, 0.010 mol) dissolved in THF (25 cm ,
2
2
5
3
.3. Chloro(perfluoro6inyl)bis(p -cyclopentadienyl)-
−80°C) is added slowly to the reaction mixture which
is held at −110°C. The reaction is left to warm slowly
to −35°C and then allowed to attain r.t. by removing
the slush bath. The solvent volume is reduced in vacuo
by 80 ml and hexane (100 cm ) is added which results in
the separation of dark polymeric material and precipi-
titanium(IV) 3
Compound 3 was prepared using a similar prepara-
3
3
tive method to that for 2. BuLi 2.5 M (6.44 cm , 16.08
3
mmol) is added to a solution of HFC 134a (0.68 cm ,

308
K.K. Banger, A.K. Brisdon / Journal of Organometallic Chemistry 582 (1999) 301–309
tation of the lithium salts. The mixture is allowed to
settle before being filtered through a No. 4 sinter under
a dinitrogen atmosphere. The solvent is then removed
in vacuo to leave an oily brown residue. A light brown
precipitate is extracted by washing with 2×20 cm of
hexane followed by filtration under a dinitrogen atmo-
sphere. Yield 1.45 g, 38%, m.p. (uncorrected) 131°C,
number, of backscattering atoms around the titanium
centre are relatively low the amount of backscattering is
small and the data has a poor signal to noise ratio at
high k-values, even after averaging a number of data-
sets; for this reason modelling of the data was typically
confined to the region k=3.5 to k=12.5. Modelling of
3
3
the background subtracted k weighted EXAFS used
dec. lF(CDCl ), −92.3 [1F, dd, J(FF) 34.4, 80.7 Hz,
curved-wave theory with phase shifts calculated using
the default ab initio method of the program EXCURVE
[42]. The refinement process involved iteration of the
distances and Debye–Waller factors for each shell as
3
CFꢀCFF], −115.4 [1F, dd, J(FF) 80.7, 105.9 Hz,
CFꢀCFF], −161.6 [1F, dd, J(FF) 34.4, 105.9 Hz,
1
CFꢀCF ); lH(CDCl ), 6.4 [s, C H ]; lC{ H} (CDCl ),
2
3
5
5
3
−
1
1
1
11.0 [m, C H ]; wmax/cm
(KBr disc) 3100 (C–H),
well as the Fermi energy difference (E ) against the
5
5
f
665 (CꢀC), 1233, 1015, 968 (C–F).
background subtracted data. After the lowest R-factor
was obtained in this way the shell occupation numbers
5
3
.6. Chloro(perfluoro6inyl)bis(p -cyclopentadienyl)-
were iterated against the shell radii and E value. Dur-
f
zirconium(IV) 6
ing modelling all shells were tested for statistical signifi-
cance according to the usual methods [30] and only
those that passed at the 95% confidence limits, or
better, are included.
A similar preparative method to that for compound 2
was used. BuLi (2.5 M, 9.50 cm , 0.024 mol) is added to
3
3
a solution of HFC 134a (1.0 cm , 0.012 mol) in diethyl
3
ether (200 cm , −80°C). After ca. 5h Cp ZrCl (3.51 g,
2
2
3
0.012 mol) dissolved in THF (50 cm , −80°C) is added
Acknowledgements
to the reaction mixture which is held at −110°C. The
reaction is slowly allowed to warm to r.t. overnight and
then worked up as described previously. 1.26 g, 31%.
m.p. (uncorrected) 150°C dec. lF(CDCl ), −97.65 [1F,
dd, J(FF) 36 Hz, J(FF) 76 Hz, CFꢀCFF], −110.2 [1F,
dd, J(FF) 76 Hz J(FF) 107 Hz, CFꢀCFF], −130.9
The authors wish to thank ICI Klea for providing
samples of HFC-134a, and the Director for provision
of facilities at Daresbury SRS, UK. The authors thank
Dr H. Clark (University of Leicester) for assistance in
recording EXAFS data. The financial support of
UMIST is gratefully acknowledged.
3
[
1F, dd, J(FF) 107 Hz, J(FF) 36 Hz, CFꢀCF );
2
1
lH(CDCl ), 6.3 [s, C H ]; lC{ H} (CDCl ), 114.0 [m,
C H ]; wmax/cm
3
5
5
3
−
1
(KBr disc) 3105 (C–H), 1667 (CꢀC),
5
5
1
3
232, 1013, 966 (C–F).
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