Synthesis, characterisation and reactivity of ruthenium bis-bifluoride, ruthenium hydride bifluoride and ruthenium hydride fluoride complexes

Article abstract of DOI:10.1039/b101007g

Bifluoride complexes, trans-[Ru(depe)₂H(FHF)] (1), trans-[Ru(dppe)₂H(FHF)] (2), trans-[Ru(dppp)₂H(FHF)] (3) and cis-[Ru(PMe₃)₄(FHF)₂] (4) (depe = Et₂PCH₂CH₂PEt₂, dppe = Ph₂PCH₂CH₂PPh₂, dppp = Ph₂PCH₂CH₂CH₂PPh₂) were synthesised from the reactions of the corresponding cis-dihydride complexes with NEt₃·3HF in THF. The characteristic features of the low temperature NMR spectra of the bifluoride complexes include ¹⁹F resonances at ca. δ -300 for the proximal fluorine and ca. δ -165 for the distal fluorine. The acidic protons resonate at ca. δ 13. The value of J(HF) for the distal fluorine lies in the range 300-400 Hz. The bifluoride ligands exhibit characteristic vibrations at ca. 2300 cm^-1 and ca. 2430 cm^-1 in the IR spectrum. All the complexes exhibit dynamic exchange processes, probably due to dissociation of FHF^-. In addition, complex 3 undergoes a ring flipping process that is suppressed at low temperature. The X-ray crystal structure of 3 has been obtained. The bifluoride ligand is disordered over two positions about the inversion centre. The Ru-F distance is 2.351(5) A and the F···F distance is 2.290(8) A, the Ru-F···F angle is 149.7°. The X-ray crystal structure for 4 reveals that the Ru-F distances are 2.149(5) A and 2.150(4) A, the F···F bond lengths are 2.323(8) A and 2.329(8) A, with Ru-F···F angles of 128.5(3)° and 138.4(3)°. The two bifluoride ligands are cis to each other. Reaction of 1 and 3 with [NMe₄]F yields trans-[Ru(depe)₂(H)F] 5 and trans-[Ru(dppp)₂(H)F] 6. Reaction of 2 with Me₃SiX (X = N₃, OTf) yields trans-[Ru(dppe)₂(H)N₃] and [Ru(dppe)₂(H)]OTf. Reactions with several halo-organic compounds yields trans-[Ru(dppe)₂(H)X] (X = Cl, Br and I). The organic products from CH₃I, CH₃COCl and C₆H₅COCl were identified as CH₃F, CH₃COF and C₆H₅COF respectively.

Full text of DOI:10.1039/b101007g

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Synthesis, characterisation and reactivity of ruthenium
bis-bifluoride, ruthenium hydride bifluoride and ruthenium
hydride fluoride complexes
Naseralla A. Jasim, Robin N. Perutz,* Simon P. Foxon and Paul H. Walton
Department of Chemistry, University of York, Heslington, York, UK YO10 5DD.
E-mail: rnp1@york.ac.uk
Received 30th January 2001, Accepted 15th April 2001
First published as an Advance Article on the web 10th May 2001
Bifluoride complexes, trans-[Ru(depe)2H(FHF)] (1), trans-[Ru(dppe)2H(FHF)] (2), trans-[Ru(dppp)2H(FHF)] (3)
and cis-[Ru(PMe3)4(FHF)2] (4) (depe = Et2PCH2CH2PEt2, dppe = Ph2PCH2CH2PPh2, dppp = Ph2PCH2CH2CH2-
PPh2) were synthesised from the reactions of the corresponding cis-dihydride complexes with NEt3ؒ3HF in THF.
The characteristic features of the low temperature NMR spectra of the bifluoride complexes include 19F resonances
at ca. δ Ϫ300 for the proximal fluorine and ca. δ Ϫ165 for the distal fluorine. The acidic protons resonate at ca. δ 13.
The value of J(HF) for the distal fluorine lies in the range 300–400 Hz. The bifluoride ligands exhibit characteristic
vibrations at ca. 2300 cmϪ1 and ca. 2430 cmϪ1 in the IR spectrum. All the complexes exhibit dynamic exchange
processes, probably due to dissociation of FHFϪ. In addition, complex 3 undergoes a ring flipping process that
is suppressed at low temperature. The X-ray crystal structure of 3 has been obtained. The bifluoride ligand is
disordered over two positions about the inversion centre. The Ru–F distance is 2.351(5) Å and the F ؒ ؒ ؒ F distance
is 2.290(8) Å, the Ru–F ؒ ؒ ؒ F angle is 149.7Њ. The X-ray crystal structure for 4 reveals that the Ru–F distances
are 2.149(5) Å and 2.150(4) Å, the F ؒ ؒ ؒ F bond lengths are 2.323(8) Å and 2.329(8) Å, with Ru–F ؒ ؒ ؒ F angles
of 128.5(3)Њ and 138.4(3)Њ. The two bifluoride ligands are cis to each other. Reaction of 1 and 3 with [NMe4]F
yields trans-[Ru(depe)2(H)F] 5 and trans-[Ru(dppp)2(H)F] 6. Reaction of 2 with Me3SiX (X = N3, OTf) yields
trans-[Ru(dppe)2(H)N3] and [Ru(dppe)2(H)]OTf. Reactions with several halo-organic compounds yields trans-
[Ru(dppe)2(H)X] (X = Cl, Br and I). The organic products from CH3I, CH3COCl and C6H5COCl were identified
as CH3F, CH3COF and C6H5COF respectively.
inatively unsaturated metal complexes.13 Insertion of small
organic molecules, such as C2F4 or CS2, into metal–fluorine
Introduction
Doherty and Hoffman have reviewed a wide range of examples
of low-valent fluoro-organometallic species with carbonyl,
phosphine and stilbene ligands.1 Roesky et al. described
transition-metal complexes containing fluorine–metal and
carbon–metal bonds.2 The combination of “soft” metals with
“hard” ligands is well established and known to yield interest-
ing and often unusual synthetic chemistry and many potential
catalytic applications.3,4 Recently, Togni et al. reported the syn-
thesis and crystal structure of five-coordinate [Ru(dppp)2F]PF6,
trans-[Ru(dppp)2F(CO)] and cis-[Ru(dppp)2F2] complexes.5 The
coordinatively unsaturated complex [Ru(dppp)2F]PF6 reacts
with activated haloalkenes R–X (X = Cl, Br) in a 1 : 1 molar
ratio to give fluorinated organic derivatives.6 Bergman et al.
reported the synthesis and the crystal structure of [(η5-C5H5)Ir-
(PMe3)(Ph)F].7 The syntheses of ruthenium fluorides such as
[(η5-C5H5)RuF(CO)(PCy3)]8 and [(η5-C5H5)RuF(AsPh3)(PPh3)]
have been reported, as have bis-(chelating-phosphine)fluoro
complexes of the form [RuF(CO)L2]X, (L = dppm, dppe and
X = BF4, PF6) in which the fluoro ligand is trans to the CO.9
Hope et al. have shown that XeF2 can be used to introduce
fluorine oxidatively into low-valent Ru, Os and Ir complexes
or via reaction of Ru() and Os() hydrides with anhydrous
HF.10 A related trifluoro-bridged diruthenium cation [Ru2F3-
(PMe2Ph)6]+ has also been reported.11
bonds has also been detected.14 The Ir() hydride fluoride
[Ir(H)2F(PtBuPh)2] complex reacts with trimethylsilyl com-
pounds (TMS–X) to give a quantitative transfer of the X-group
to Ir (X = OTf, NCS, NCO, OCOCH3, OCOCF3, N3, SPh).15
The F–H–F ligand has now been established at a variety of
metals: Mo, W, Ru, Ni, Pd and Pt.16 We have reported the
synthesis and reactivity of trans-[Pt(PR3)2H(FHF)] (R = Cy or
iPr). At ambient temperature, fluxional behaviour is observed
which is principally associated with intermolecular exchange of
HF between platinum centres. The distal fluoride of the bifluor-
ide ligand undergoes exchange between two platinum centres
and exchange of HF between platinum centres occurs similarly.
(We refer to the fluorine bound directly to the metal as proximal
and the fluorine bound via the hydrogen bond as distal.) The
bifluoride ligand can be replaced easily by anionic ligands
(e.g. OTfϪ) or neutral ligands such as PPh3 or pyridine. Parkin
et al. reported the bifluoride complexes, [M(PMe3)4H2F(FHF)]
M = Mo and W, synthesised with aqueous HF.17 Earlier studies
of bifluoride complexes17–20 are summarised in ref. 16.
Of particular relevance to this paper is the ruthenium bifluor-
ide complex, trans-[Ru(dmpe)2H(FHF)], that we characterised
in solution and solid state.20 This complex was prepared by the
reaction of cis-[Ru(dmpe)2H2] either with fluoroarenes (C6F6,
C5F5H or others), or by reaction with NEt3ؒ3HF. The 1H NMR
spectrum of the ruthenium complex shows coupling constants
J(HFdistal) = 274 Hz while J(HFproximal) < 30 Hz. The NMR and
IR parameters suggest the presence of an asymmetric bifluoride
ligand with predominant M–F ؒ ؒ ؒ H–F character. It was
proposed that the reaction of the transition metal dihydride
with C6F6 yields trans-[Ru(dmpe)2(C6F5)H] with release of HF
Holloway and Hope have shown that the reactivity of
organometallic fluorides is controlled by the metal–fluorine
bond (the addition of Lewis bases results in either addition
reactions or ligand substitution reactions).12 Weaker metal–
fluorine bonds allow reaction at the fluoride ligand, either F–Cl
exchange or Lewis acid abstraction of fluoride, to form coord-
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J. Chem. Soc., Dalton Trans., 2001, 1676–1685
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b101007g

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Table 1 NMR data for complexes 1–6 and trans-[Ru(dmpe)2H(FHF)] in [2H8]-THF at room temperature (δ, J/Hz)
Complex
δ (1H) acidic
δ (1H) hydride
δ (19F)
δ (31P)
J(PF)
J(PH)
J(HhydrideF)
1
2
3
4
13.3
12.0
12.0
13.2
Ϫ24.3 quin
Ϫ25.8 quin
Ϫ22.8 quin
—
Ϫ352
Ϫ167
Ϫ326
Ϫ167.5
Ϫ355
Ϫ162
Ϫ291
Ϫ160.3
Ϫ416
Ϫ415
65.0
65.1
20.8
—
—
—
25
21.5
20
—
—
—
—
20
3.5 t
25.4 dt
65.1 d
18
—
5
—
—
13.8
Ϫ23.6 dquin
Ϫ20.8 dquin
Ϫ25.9 quin
13
—
—
20
19
21
57
46
—
6
trans-[Ru(dmpe)2H(FHF)]20
46.3
which reacts with cis-[Ru(dmpe)2H2] to form the bifluoride
complex.
Crystal structures of bifluoride complexes show that the bi-
fluoride ligand is not coordinated linearly to the metal centre but
exhibits an M–F ؒ ؒ ؒ F angle of 128–156Њ (see Table 8).17,19,20
The F ؒ ؒ ؒ F separation in each of these complexes is consider-
ably less than twice the van der Waals radius of fluorine (1.4
Å).21 The metal–fluorine bond lengths are long, probably as a
result of weakening through the hydrogen bond to the distal
fluorine. In trans-[Ru(dmpe)2H(FHF)] the lengthening is
accentuated by the hydride ligand trans to bifluoride.
We report the synthesis of a series of ruthenium bifluoride
complexes and examine their structures, spectroscopy, reac-
tivity and dynamics.
Results
The dihydrides, cis-[Ru(PP)2H2] (PP = depe, dppe, dppp) and
cis-[Ru(PMe3)4H2] react immediately with NEt3ؒ3HF in THF
solution at room temperature to give hydrogen, trans-
[Ru(PP)2H(FHF)] 1–3 and cis-[Ru(PMe3)4(FHF)2] 4 respect-
ively. Effervescence in the first few minutes provides evidence
for the evolution of hydrogen from the reactions. This method
was satisfactory for 2–4, but gave an impure product with 1.
The dmpe analogue had originally been made by the C–F
activation method (see above). Reaction of cis-[Ru(depe)2H2]
with C6F5H yielded trans-[Ru(depe)2(4-C6F4H)H] and trans-
[Ru(depe)2H(FHF)] 1. The C–F activation product was separ-
ated by fractional crystallisation and is not discussed further
here. It is analogous to the dmpe species described in ref. 20.
There was no evidence for aromatic C–H bond activation. By
this method we were able to obtain satisfactory samples of 1,
but corresponding attempts at C–F activation with the other
ruthenium hydrides did not yield any reaction at all. All
Fig. 1 1H NMR spectra (500.13 MHz) of the hydride region of trans-
[Ru(dppe)2H(FHF)] 2 in [2H8]-THF (a) at room temperature, (b) at 193
K, (c) at 193 K with 31P broad band decoupling.
1
products were characterised by H, 19F and 31P NMR spec-
troscopy, IR spectroscopy, mass spectrometry and elemental
analysis (C,H). Complexes 3 and 4 were also characterised by
X-ray crystallography.
Hz for 1, J(HF) = 306 Hz for 2, J(HF) = 317 Hz for 3 and
J(HF) = 339 Hz for 4 and J(HF) < 40 Hz for the small coup-
ling. This resonance is assigned to the hydrogen of the FHF
ligand. The large coupling is associated with the distal fluorine
of the bifluoride ligand (Fig. 2). The magnitude of this coupling
provides additional evidence to support the suggestion of
weakened hydrogen bonding relative to that of the bifluoride
NMR spectroscopy
The 1H NMR spectra of 1–3 are similar to each other. A reson-
ance at δ ca. Ϫ24 appears as a quintet (J(PH) = ca. 20 Hz)
at room temperature and is assigned to the hydride ligand
(Fig. 1a). The NMR spectrum is very similar to that of trans-
[Ru(dmpe)2H(FHF)].20 On cooling, the hydride resonance
resolves into a doublet of quintets (Fig. 1b), which collapses
into a doublet on phosphorus decoupling with J(HF) ca. 60 Hz
(Fig. 1c). The coupling between the proximal fluorine and the
hydride proton in 1–3 was not observed at room temperature in
the ruthenium bifluoride complexes, because of exchange
processes (see below). Complex 4 exhibits no hydride resonance
in this region.
1
anion. For comparison, the H NMR spectrum of the free
bifluoride anion shows a triplet with J(HF) = 120 Hz. The
value of J(HF) for free HF is solvent dependent; in MeCN
J(HF) = 479 Hz, in DMSO J(HF) = 440 Hz and in the liquid
phase J(HF) = 529 Hz. Thus, the value of J(HF) in the
ruthenium complexes (306–392 Hz), lies between those for the
bifluoride anion and HF.22 The NMR parameters are listed in
Tables 1 and 2.
The 31P{1H} NMR spectrum shows a singlet at δ 67.0 for 1
which is unresolved at low temperature. A singlet at δ 65.1 at
room temperature for 2 is resolved into a doublet at low
temperature (J(PF) = 17 Hz). However the singlet at δ 20.8 for
A broad, low-field resonance found at δ 12.0–13.3 splits into
a doublet resonance and shifts up to 0.6 ppm to lower field on
cooling with unresolved shoulders on the inside, J(HF) = 392
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Fig. 2 1H NMR spectra (500.13 MHz) of the acidic region of trans-
[Ru(dppe)2H(FHF)] 2 in [2H8]-THF (a) at room temperature, (b) at 193
K.
3 resolves into a sharp triplet at δ 13.8 and a triplet of doublets
at δ 27.1 (J(PP) = 42, J(PF) = 10 Hz) at low temperature
(Fig. 3). It is proposed that the 31P{1H} NMR spectrum splits
into two inequivalent resonances at low temperature because
the two six-membered rings are locked in different conform-
ations, one pointing up to the bifluoride, the other pointing
down to the hydride (see crystal structure). Each of these two
phosphorus nuclei will be coupled to the other two phosphorus
nuclei to give an [AX]2 system which simplifies to yield apparent
triplets with a splitting of 42 Hz.
The room temperature 31P{1H} NMR spectrum for complex
4 shows two resonances, a triplet at δ 3.5 and a doublet of
triplets at δ 25.4. At low temperature, the former splits into a
triplet of triplets. The two mutually cis phosphorus atoms are
magnetically inequivalent. Low temperature 31P{1H} J-resolved
NMR experiments showed that J(PF) = 25 Hz for the mutually
trans phosphine ligands, and |J(PFcis) + J(PFtrans)| = 189 Hz for
the mutually cis phosphine ligands, while J(PP) = 32 Hz.
The 19F NMR spectra at room temperature of 1–3 contain
two resonances. The broad resonance at ca. δ Ϫ350 is assigned
to the proximal fluorine. On cooling, this resonance broadens
for complexes 1 and 2 and splits into a doublet for 3 and 4.
The second resonance at ca. δ Ϫ165 is broad at room tem-
perature. On cooling this resonance sharpens to a doublet of
doublets, e.g. J(FF) = 164 Hz and J(HF) = 317 Hz for 3
(Fig. 4). The observation of matching values of J(HF) in the
proton and fluorine NMR spectra supports the proposal
that HF is hydrogen bonded in the FHF ligand. The coupling
constant networks are summarised in Fig. 5 and Tables 1 and 2.
31P{1H} NMR spectra of trans-[Ru(dppp)2H(FHF)] 3 were
recorded over a temperature range of 178–253 K in CD2Cl2.
The rate constant k for the ring flipping dynamic process was
calculated by simulation using the program g-NMR.23 Fig. 3
shows an overlay of the experimental and the calculated vari-
able temperature 31P{H} NMR spectra; Fig. 6 shows the Eyring
plot. The resulting kinetic data are listed in Table 3, yielding
∆H‡ = 30 3 kJ molϪ1, ∆S‡ = Ϫ48 9 J KϪ1 molϪ1 and
∆G‡ = 41 3 kJ molϪ1 at 233 K.
Infrared spectroscopy
IR spectra of the dihydride and the bifluoride complexes
were recorded over the range 4000–200 cmϪ1 as Nujol mulls,
(samples were prepared under argon). The ν(M–H) bands for
the dihydride starting materials at 1700–1872 cmϪ1 were
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Fig.
5
Coupling constants and postulated structures of trans-
[Ru(depe)2H(FHF)] 1, trans-[Ru(dppe)2H(FHF)]
2
and trans-
[Ru(dppp)2H(FHF)] 3 at low temperature.
Fig. 3 Variable temperature 31P{1H} NMR spectra in CD2Cl2 (121.49
MHz) overlaid with simulated spectra for trans-[Ru(dppp)2H(FHF)] 3.
Fig. 6 Eyring plot for ring flipping of trans-[Ru(dppp)2H(FHF)] 3.
Table 3 Simulated rate constants for ring flipping of 3 at low
temperature
T/K
k/s–1
178
193
213
233
253
1.97 × 101
8.96 × 101
5.26 × 102
2.90 × 103
1.13 × 104
replaced by new bands on formation of the bifluoride com-
plexes. The complexes 1–3 show three absorption bands (Table
4); for instance, for 2 there are two broad bands at 2315 cmϪ1
and 2450 cmϪ1, assigned to ν(HF) of the bifluoride (Fig. 7).
These values are higher than that of the bifluoride ion in its
various salts (ν(HF) = 1250–1750 cmϪ1).24 The third sharper
absorption of 2 at 1893 cmϪ1 was assigned as the ν(Ru–H)
Fig. 4 19F NMR spectra (470.4 MHz) for trans-[Ru(dppe)2H(FHF)]
in [2H8]-THF showing the distal fluorine resonance at 193 K.
J. Chem. Soc., Dalton Trans., 2001, 1676–1685
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Fig. 7 IR spectra (Nujol mull) of trans-[Ru(dppe)2H(FHF)] 2 and cis-
[Ru(dppe)2H2].
Table 4 IR data (ν/cm–1) for 1–4 and for corresponding dihydride
complexes
Complexes
Vibration mode
1
2
3
4
MH2
M(H)(FHF)
ν(M–H)
ν(M–H)
ν(HF)
1868
1889
2310
2450
1872
1893
2315
2450
1870
1900
2316
2463
1822
—
2290
2399
ν(HF)
Fig. 8 Top: the crystal structure (ORTEP28 diagram) of trans-
[Ru(dppp)2H(FHF)] 3ؒ2THF (thermal ellipsoids at the 50% probability
level). Hydrogen atoms and THF are not shown. Bottom: with the
phenyl groups removed, but with the second disordered bifluoride
shown pale. Each bifluoride site has 50% occupancy.
vibration. In general, as the hydrogen bond interaction
increases, ν(HF) is reduced from the value observed for free HF
(gas phase 3960 cmϪ1).25 Complexes of HF with a variety of
non-metal bases have been studied by IR spectroscopy in
matrices. For the majority of bases, the HF stretching mode
lies above 3000 cmϪ1, even with strong bases such as NMe2H
it lies no lower than 2760 cmϪ1.26 Our observed bands for the
HF stretching modes of the coordinated bifluoride complex lie
in an intermediate region and are indicative of a weakened
hydrogen bonding interaction. The position of the lower
frequency band in each case was found to be close to that
observed for ν(RuH) in trans-[Ru(PR3)4(H)Cl].27
Table 5 Selected bond distances (Å) and angles (Њ) for 3
Ru(1)–F(1)
Ru(1)–P(1A)
Ru(1)–P(1)
Ru(1)–P(2A)
Ru(1)–P(2)
2.351(5)
F(1) ؒ ؒ ؒ F(2)
2.290(8)
180.00
93.72(5)
86.28(5)
149.7(3)
2.3653(14)
2.3653(14)
2.3798(14)
2.3798(14)
P(1A)–Ru(1)–P(1)
P(1A)–Ru(1)–P(2)
P(1)–Ru(1)–P(2)
Ru(1)–F(1) ؒ ؒ ؒ F(2)
Complex 4 shows two broad absorption bands at 2290 cmϪ1
and 2399 cmϪ1 which are close to the values of ν(HF) for the
ruthenium hydride bifluoride complexes and assigned to the
ν(HF) of the bifluoride. No hydride band was seen in the IR for
this complex.
trans-[Ru(dmpe)2H(FHF)], but significantly shorter than the
F ؒ ؒ ؒ F separation (2.352(8) Å) found for [Mo(PMe3)4H2F-
(FHF)]. The F ؒ ؒ ؒ F separation in trans-[Ru(dppp)2H(FHF)]
is considerably less than twice the van der Waals radius (1.4
Å).21
The Ru–F bond length, 2.351(5) Å, is even longer than that
(2.284(5) Å) found for trans-[Ru(dmpe)2H(FHF)] and is sub-
stantially longer than found in any conventional ruthenium
fluoride complexes, typically 2.01–2.07 Å.3,5,6,20 The long Ru–F
bond probably results from a combination of the trans influence
of the hydride and the hydrogen bonding in the FHF unit.
The crystal structure helps to understand the variable tem-
perature 31P{1H} NMR behaviour. The six-membered rings are
locked in different conformations, one pointing up to the bi-
fluoride, the other pointing down to the hydride. In solution,
the two rings will be flipping and the bifluoride ligand rotating
about the Ru–F bond faster than the NMR time scale.
Crystal structure of complex 3
The crystal structure of 3ؒ2THF was determined by single
crystal X-ray crystallography. The bifluoride complex 3 was
crystallised from THF at Ϫ20 ЊC. During the refinement, the
ruthenium ion was automatically constrained to lie on the
inversion centre. The asymmetric unit contains exactly one half
¯
of the molecule. Applying the symmetry operator of P1 (about
the centre of inversion) reveals the full structure, but results in
disorder of the bifluoride (FHF) unit over two positions about
the metal centre. Refinement of the site occupation factor of
each bifluoride unit against a free variable reveals that the
occupation of both sites is equal to ca. 0.5, excluding the altern-
ative formulation, [Ru(dppp)2(FHF)2]. The hydrogen atoms in
the bifluoride, hydride and solvent of crystallisation were not
located.
Crystal structure of complex 4
Complex 4 was crystallised from THF at Ϫ20 ЊC. The structure
(Fig. 9, Table 6) shows the presence of two bifluoride ligands
coordinated to the ruthenium centre and lying cis to each other
in two different planes. The Ru–F ؒ ؒ ؒ F angles of 128.5(3)Њ and
138.4(3)Њ are comparable to the values of 129.9(3)Њ reported for
trans-[Ru(dmpe)2H(FHF)].20 The F ؒ ؒ ؒ F bond lengths,
2.323(8) Å and 2.329(8) Å, are longer than those of trans-
[Ru(dppp)H(FHF)] 3 (2.290(8) Å) but the difference is on the
borderlines of significance. The Ru–F bond lengths of 2.149(4)
ORTEP28 diagrams of the crystal structure are shown in
Fig. 8. The structure (Table 5) shows the presence of bifluoride,
F–H–F, coordinated to ruthenium lying trans to the hydride
(which was not located). The Ru–F ؒ ؒ ؒ F angle, 149.7(3)Њ, is
larger than that of trans-[Ru(dmpe)2H(FHF)].20 The F ؒ ؒ ؒ F
distance of 2.290(8) Å is similar to those found in the bifluoride
salts, MFHF (M = Na+, K+, NH4 ),29 pyridine(HF)n,30 and in
+
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Table 7 NMR data for complexes trans-[Ru(dppe)2(H)X] (X = Cl, Br,
I, N3) and [Ru(depe)2H]OTf in [2H8]-THF
Complex
δ (1H)
δ (31P)
J(PH)/Hz
trans-[Ru(dppe)2(H)Cl]
trans-[Ru(dppe)2(H)Br]
trans-[Ru(dppe)2(H)I]
[Ru(dppe)2H]OTf
Ϫ18.9
Ϫ17.6
Ϫ15.6
Ϫ11.9
Ϫ18.7
63.4
62.7
62.5
52.6
65.7
20
20
20
20
19
trans-[Ru(dppe)2(H)(N3)]
[Mo(PMe3)4H2F(FHF)].17 It was suggested above that the
interaction between HF and RuF in the bifluoride complexes
consisted of a normal hydrogen bond between Ru–F and HF.
Attempts to remove HF from the ruthenium bifluoride com-
plexes with pyridine, triethylamine and lithium diisopropyl-
amide gave new products which have not been characterised.
However, reaction of 1 and 3 with dry [NMe4]F in THF under
argon was more successful. The products 5 and 6 were studied
by IR and NMR spectroscopy and identified as trans-
[Ru(depe)2(H)F] 5 and trans-[Ru(dppp)2(H)F] 6. The IR spec-
trum from the reaction of 3 no longer contained the ν(HF)
bands belonging to the bifluoride complex of 3 at 2316 cmϪ1
and 2463 cmϪ1 and the hydride band shifted from 1900 cmϪ1 to
1925 cmϪ1.
1
The H NMR spectrum shows a resonance at δ Ϫ23.6 for 5
and at δ Ϫ20.8 for 6. Both show a doublet of quintets pattern
that simplifies to a doublet when phosphorus decoupled
(J(HF) = 46 Hz and J(PH) = 19 Hz) for 6. No resonances due
to the acidic proton were seen at low field, providing evidence
that the compound is not a bifluoride complex. The HF
coupling is very clear in the proton NMR spectra at room
temperature.
Fig.
9
Top: the crystal structure (ORTEP28 diagram) of cis-
[Ru(PMe3)4(FHF)2] 4. Hydrogen atoms have been omitted. The
thermal ellipsoids are shown at the 50% probability level. Bottom: with
the methyl groups removed.
The 31P{1H} NMR spectrum for complex 5 shows a doublet
resonance at δ 65.1 (J = 13 Hz) at room temperature. Complex 6
shows a singlet resonance at δ 18. On cooling, this resonance
splits into two resonances, a triplet at δ 12.4 (J(PP) = 43 Hz)
and a triplet of doublets at δ 23.9 (J(PF) = 13 Hz and
J(PP) = 43 Hz), in a similar way to the bifluoride complex with
the same phosphine. Notice that P–F coupling is only detected
to one pair of 31P nuclei.
Table 6 Selected bond distances (Å) and angles (Њ) for 4
Ru(1)–F(1)
Ru(1)–F(3)
Ru(1)–P(1)
Ru(1)–P(2)
Ru(1)–P(3)
Ru(1)–P(4)
F(1) ؒ ؒ ؒ F(2)
F(3) ؒ ؒ ؒ F(4)
2.150(5)
2.149(4)
2.394(3)
2.370(4)
2.258(3)
2.264(2)
2.323(8)
2.329(8)
Ru(1)–F(1) ؒ ؒ ؒ F(2)
Ru(1)–F(3) ؒ ؒ ؒ F(4)
P(3)–Ru(1)–P(1)
P(1)–Ru(1)–P(2)
P(3)–Ru(1)–P(4)
F(1)–Ru(1)–P(1)
F(3)–Ru(1)–P(3)
F(1)–Ru(1)–P(4)
F(3)–Ru(1)–P(1)
128.5(3)
138.4(3)
98.59(11)
163.16(7)
96.68(8)
82.75(17)
89.02(15)
91.52(15)
85.23(15)
The 19F NMR spectrum of 6 shows only one broad reson-
ance at δ Ϫ415 at room temperature which broadens at low
temperature. The lack of a resonance at ca. δ Ϫ167 due to the
distal fluorine of the bifluoride ligand gives further evidence
that the ligand is a fluoride and that the reaction products are
trans-[Ru(dppp)2(H)F] and trans-[Ru(depe)2(H)F] (eqns. (1)
and (2)). It should be noted that we cannot distinguish whether
the reaction involves replacement of bifluoride by fluoride, or
removal of HF.
Å and 2.150(5) Å lie between those in conventional ruthenium
fluoride complexes (2.01–2.07 Å)14 and those of trans-
[Ru(dmpe)2H(FHF)] and complex 3. The absence of a strong
trans directing ligand evidently results in a much shorter Ru–F
bond.
The angle between the plane containing the F(2) ؒ ؒ ؒ F(1)–Ru
unit and the P(3)–P(4)–Ru plane is 1.9Њ, the angle between the
F(4) ؒ ؒ ؒ F(3)–Ru plane and the P(3)–P(4)–Ru plane is 29.1Њ.
Thus, the bifluoride ligand F(1) ؒ ؒ ؒ F(2) is in approximately the
same plane as the two phosphine ligands P(3) and P(4), while
the second bifluoride ligand F(3) ؒ ؒ ؒ F(4) lies in a different
plane.
(1)
(2)
The F ؒ ؒ ؒ F separation in both 3 and 4 indicates that the
bifluoride ligand is involved in a weaker hydrogen bonding
interaction than that of the free bifluoride anion, which can be
described as hydrogen bonding of HF to the proximal fluorine
Ru–F ؒ ؒ ؒ HF. The low temperature NMR spectra support this
description. cis-[Ru(PMe3)4(FHF)2] is the first ruthenium bis-
bifluoride complex to be characterised in solution and in the
solid state.
(b) Replacement of bifluoride. In the ruthenium bifluoride
complexes, the bifluoride ligand can also be replaced easily by
other halides or cyanide. The bifluoride ligand of 2 exchanges
rapidly with XϪ in aqueous MX (XϪ = ClϪ, BrϪ, IϪ and CNϪ) to
give trans-[Ru(dppe)2(H)X] (Scheme 1) in low yield. The NMR
parameters of trans-[Ru(dppe)2(H)X] are listed in Table 7.
The bifluoride complex trans-[Ru(dppe)2H(FHF)] abstracts
halides from the reaction with halo-organic compounds (CH3I,
CHCl3, CHBr3, CH2Cl2, 2-bromopyridine, C6H5X [X = Cl, Br
and I], CH3COCl, C6H5COCl) in THF to yield the correspond-
ing trans-[Ru(dppe)2(H)X] complex (X = Cl, Br and I) in good
yields. The bifluoride complex can also fluorinate some halo-
Reactivity of bifluoride complexes
(a) Conversion of bifluoride to fluoride complexes. Parkin et al.
extracted HF from [Mo(PMe3)4H2F2](HF)2 by adding 1/3 of an
equivalent of [Mo(PMe3)5N2] which reacts with HF to yield
J. Chem. Soc., Dalton Trans., 2001, 1676–1685
1681

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Scheme 1 Ligand replacement and reactivity of trans-[Ru(dppe)2-
H(FHF)].
Fig. 10 Variable temperature 1H NMR spectra (300.13 MHz) of a
mixture of [NBu4]FHF and trans-[Ru(dppe)2H(FHF)] in [2H8]-THF.
organics (CH3I, CH3COCl and C6H5COCl to produce CH3F,
CH3COF and C6H5COF) (Scheme 1). The 19F NMR spectra
show the disappearance of the distal and the terminal fluorine
resonances of the bifluoride ligand. In the reaction of the bi-
fluoride complex with CH3I and CH3COCl the fluorine
resonances for CH3F and CH3COF were observed. NMR data
are summarised in Table 7.
δ 12.0 at room temperature. On cooling, this resonance separ-
ates and sharpens into a doublet at (Tc ca. 253 K). The hydride
resonance is a quintet at room temperature, which changes
into a doublet of quintets at low temperature. In the 19F NMR
spectra, the resonance of the proximal fluorine at ca. δ Ϫ326
is broad at room temperature and broadens further on cooling.
The resonance of the distal fluorine is broad at room temper-
ature and resolves into a doublet of doublets on cooling. A
similar observation was found in all the other ruthenium bi-
fluoride complexes. The change in the hydride resonance is
different from that in the platinum bifluoride complex reported
in our previous work in which coupling to the proximal fluorine
was retained at room temperature.16 The proximal fluorine
coupling is very clear in the hydride resonance of the ruthenium
complex at low temperature, but disappeared at room temper-
ature. The disappearance of the hydride–fluorine coupling
suggests that the bifluoride ligand is dissociating from the com-
plex at room temperature, but remains bound at low temper-
ature (eqn. (4)). This behaviour would also account for the
change in chemical shift of the acidic proton on cooling.
The complexes 1, 2 and 4 show identical dynamic behaviour
in the 1H and 19F NMR spectra and may therefore undergo the
same exchange processes. However, the poor resolution of the
spectra and the complexity of the system prevent us from carry-
ing out additional kinetic analysis.
Dynamic behaviour was observed on addition of
[NBu4]FHF. The behaviour of solutions of [NBu4]FHF alone
was described in ref. 16. At room temperature, the bifluoride
proton is observed as the expected triplet at δ 16.1 (J(HF) =
120 Hz), but on cooling the outer resonances of the triplet
broaden and weaken without change in frequency. This
behaviour probably originates in ion-pair formation. A spec-
trum of a mixture of [NBu4]FHF and 2 at 193 K corresponded
simply to the spectra measured for the components alone.
However, warming caused the resonances of the bifluoride
complex and free bifluoride to coalesce into one resonance at
δ 15.0 (Fig. 10). The exchange process is shown in eqn. (5).
Ruthenium bifluoride complexes can also react with Me3SiX
(X = N3 or OTf) in THF, to produce [Ru(dppe)2(H)X] in good
yield. These reactions were initially carried out in an NMR
tube, then scaled up. The ν(HF) band of the bifluoride was
absent from the IR spectrum of all these products. In the azide
complex, two bands were found; a sharp band at 2036 cmϪ1
assigned to the ν(N3) stretching vibration and a shoulder at
2013 cmϪ1 assigned to ν(Ru–H). In the triflate complex a strong
and sharp band located at 2147 cmϪ1 was assigned to the
ν(Ru–H) stretching vibration and two bands found at 1261
cmϪ1 and 1161 cmϪ1 were assigned to ν(SO3) and ν(CF3) of the
OTf respectively. The hydride resonance of the triflate lies at
δ Ϫ11.9, compared with ca. δ Ϫ17 to Ϫ18 for most of the
other trans-[Ru(dppe)2(H)X] complexes (Table 7). The ν(Ru–H)
mode in the IR spectrum and the hydride resonance in the
NMR spectrum for the triflate complex are quite distant from
those of other complexes. The IR spectra of five-coordinate
ruthenium hydride salts show ν(Ru–H) vibrations at higher
frequencies than for other hydride complexes.31 Five-coordinate
salts have been reported in which the hydride resonates between
δ Ϫ8.02 and Ϫ11.62,32 close to the hydride resonance observed
for the triflate complex. It is suggested that the triflate complex
is a five-coordinate salt [RuH(dppe)2](OTf), while the azide
complex is six-coordinate trans-[Ru(dppe)2(H)(N3)].
Exchange with free bifluoride and dynamic behaviour of
bifluoride complexes
The fluxionality is very clear in the variable temperature NMR
spectra of all the bifluoride complexes. The extraction of HF
from these complexes suggests that the HF in the bifluoride
ligand might dissociate HF in solution (eqn. (3)), but the lack
of etching on the glass, even on prolonged standing, excludes
this mechanism.
M–F–H–F + F*–H*–F*Ϫ
M–F*–H*–F* + F–H–FϪ (5)
M–F–H–F
MF + H–F
(3)
Discussion
Spectroscopic analysis has enabled us to characterise four
ruthenium bifluoride complexes. These complexes illustrate the
scope for direct hydrogen bonding to metal-bound fluorine—
the importance of hydrogen bonding in the metal coordination
sphere is recognised for its influence on bonding, structure
and reactivity.33 The crystal structures for 3 and 4 were also
determined. The spectroscopic and X-ray data make it evident
that the hydrogen bond is far from symmetric and could be
Free bifluoride anion was detected during the synthesis which
indicates that the bifluoride complex may also dissociate FHFϪ
in solution (eqn. (4)).
M–F–H–F
M+ + F–H–FϪ
(4)
We now turn to the effect of cooling on the NMR spectra of
2. The acidic proton resonance appears as a broad singlet at
1682
J. Chem. Soc., Dalton Trans., 2001, 1676–1685

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Table 8 Low temperature coupling constants, bond lengths and angles of bifluoride complexes
Complex
J(FF)/Hz
J(MFHF)/Hz
J(MFHF)/Hz
F ؒ ؒ ؒ F distance/Å
M–F distance/Å
M–F ؒ ؒ ؒ F angle/Њ
trans-[Ru(depe)2H(FHF)] 1
trans-[Ru(dppe)2H(FHF)] 2
trans-[Ru(dppp)2H(FHF)] 3
trans-[Ru(dmpe)2H(FHF)]20
cis-[Ru(PMe3)4(FHF)2] 4
162
125
164
152
153
36
<30
<30
<30
—
392
306
317
274
339
—
—
2.290(8)
2.276(8)
2.323(8)
2.329(8)
—
—
—
2.351(5)
2.2846(5)
2.149(5)
2.150(5)
—
—
—
149.7(3)
129.9(3)
128.5(3)
138.4(3)
—
—
134
156
—
trans-[Pt(PCy3)2H(FHF)]16
trans-[Pt(PiPr3)2H(FHF)]16
[MoF(PMe3)4(H)2(FHF)]17
[W(PMe3)4F(H)2(FHF)]17
[Ni(C4N2F2H)(PEt3)2(FHF)]19
[Ni(C5NF4)(PEt3)2(FHF)]19
HF
103
103
—
—
—
≈85
—
—
48
43
—
—
—
41
410–530
120
412
393
410
430
427
424
—
—
—
2.351(8)
2.389(6)
2.404(5)
—
2.124(3)
2.117(5)
1.909(3)
—
—
—
—
—
—
—
FHFϪ
2.24–2.28
described as containing a Ru–F ؒ ؒ ؒ H–F moiety. The appear-
ance of the hydride–fluorine coupling at low temperature and
its disappearance at room temperature suggests that the bifluor-
ide ligand dissociates from the complex at room temperature,
but remains bound at low temperature. The weakly bound bi-
fluoride ligand in trans-[Ru(dppe)2H(FHF)] exchanges with
free bifluoride anion in [2H8]-THF solution at low temperature.
We also found that the FHFϪ ligand is weakly coordinated and
benzene, [2H8]-toluene and [2H8]-tetrahydrofuran solvents
(Goss Scientific) were dried over potassium and vacuum dis-
tilled prior to use. All NMR tubes (Wilmad 528-PP) were either
fitted with a Young’s tap to allow sealing under argon atmos-
phere, or were flame sealed under vacuum.
Most NMR spectra were recorded on a Bruker MSL300 (1H
recorded at 300.13 MHz, 19F at 282.35 MHz, 31P at 121.49
MHz) or Bruker AMX500 spectrometers (1H recorded at
500.13 MHz, 19F at 470.4 MHz, 31P at 202.46 MHz). 19F NMR
spectra with 1H decoupling were recorded on a Bruker
DRX400 spectrometer, as were 1H spectra with 19F decoupling.
Simulations were carried out with g-NMR.23 Mass spectra were
recorded on a VG Autospec instrument and are quoted for
102Ru. IR spectra were measured on a Mattson-Unicam
Research Series instrument fitted with a CsI beamsplitter.
Chemicals were obtained from the following sources RuCl3ؒ
xH2O (Aldrich), trimethylphosphine (PMe3) (Strem); bis-
(dimethylphosphino)methane (dmpe), bis(diethylphosphino)-
ethane (depe), bis(diphenylphosphino)ethane (dppe) and
bis(diphenylphosphino)propane (dppp) (Aldrich or Lancaster).
[NMe4]F and NEt3ؒ3HF were supplied by Aldrich, Me3SiOTf
was obtained from Gelest and Me3SiN3 was synthesised by
standard methods. KCl, KBr, KI, NaOH, KPF6, KOH, KCN,
Mg, MgSO4, P2O5 and iodine were supplied by Fisons and
sodium dispersion by Strem. [NMe4]F was dried and dry
[NBu4](FHF) was synthesised according to the literature.16 The
Ϫ
can be replaced with XϪ (XϪ = ClϪ, BrϪ, IϪ, N3 and OTf Ϫ).
It can also be used to fluorinate some organic compounds
(CH3Cl, CH3COCl and C6H5COCl yielding CH3F, CH3COF
and C6H5COF respectively). The overall reaction is a halide
metathesis that yields trans-[Ru(PP)2(H)X]. The preparative
methods described in this paper can also be used to introduce
the fluoride ligand selectively under mild conditions by sequen-
tial reaction with NEt3ؒ3HF and [NMe4]F.
Table 8 summarises the HF coupling constants of the distal
fluorine for the bifluoride and key geometric parameters
reported in our previous paper,16 the current work and some
bifluoride complexes from the literature. The F ؒ ؒ ؒ F distance
in the bifluoride complexes ranges from 2.276(8) to 2.404(5) Å,
appreciably longer than the F ؒ ؒ ؒ F distance in the bifluoride
anion (2.24–2.28 Å). There is good correlation (correlation
coefficient 0.96) between the F ؒ ؒ ؒ F distance and J(HF) for
the distal fluorine, suggesting that the magnitude of J(HF)
increases as the hydrogen bond weakens.
Brammer et al. have shown that hydrogen bonds at metal
fluoride complexes are shorter than for other metal halide com-
plexes. They have also found that M–F ؒ ؒ ؒ H angles lie in the
range 130–160Њ compared to 90–130Њ for their analogues with
other halides.34 Our bond angles Ru–F ؒ ؒ ؒ F fall within the
range suggested by Brammer, but as yet we cannot compare
our geometric parameters for those with analogues in which
fluorine is replaced by other halogens.
In this paper, we have characterised a bis-bifluoride complex
in which the bifluoride ligand lies trans to one PMe3 and cis to
another. In the remainder of the ruthenium bifluoride com-
plexes, the bifluoride lies trans to hydride. It is now apparent
that the complexes of type trans-[Ru(PP)2(H)(FHF)] have a
Ru–F bond length between 0.13 and 0.2 Å longer than that in
cis-[Ru(PMe3)4(FHF)2]. The magnitude of J(PF) increases
from 10–20 Hz with a cis-disposition of phosphines and bifluor-
ide to ca. 190 Hz for a trans-disposition.
36
dihydrides Ru(depe)2H2,35 Ru(dppe)2H2,35 Ru(dppp)2H2 and
Ru(PMe3)4H2 37 were synthesised by standard methods.
Syntheses
Synthesis of trans-[Ru(depe)2H(FHF)] (1). cis-[Ru(depe)2H2]
(0.2 g, 0.361 mmol) was dissolved in THF (30 mL) in a Schlenk
tube and a two-fold excess of C6F5H (0.13 g, 0.773 mmol) was
added to the solution. The mixture was stirred at room tem-
perature for 1 h. The solvent was removed under vacuum. The
residue was extracted with hexane, and the extract filtered
through a cannula. The filtrate was reduced to 3 mL and cooled
to Ϫ30 ЊC to form crystals of trans-[Ru(depe)2H(C6F5)]. The
supernatant was filtered off and the solvent removed under
vacuum to yield yellow trans-[Ru(depe)2H(FHF)]. (Found: C,
44.06; H, 9.7. Calc. for C20F2H50P4Ru: C, 43.39; H, 9.10%). The
C,H analysis figures are slightly higher than calculated which is
consistent with some loss of HF as was observed with the dmpe
analogue.
Experimental
IR (Nujol, cmϪ1): 2450 (m, b), 2310 (m, b), 1889 (m), 1567
(w), 1372 (w), 1259 (s), 1043 (s), 1028 (s), 939 (m), 808 (m), 788
(m), 738 (w), 721 (w), 532 (w), 481 (m), 391 (w), 352 (vw).
Mass spectra (FAB-MS): m/z 514 (100%, M+ Ϫ 2HF).
All syntheses and manipulations were carried out under argon
using standard Schlenk (vacuum 10Ϫ2 mbar) and high vacuum
techniques (vacuum 10Ϫ4 mbar), or in a glove box. Diethyl
ether, toluene, benzene, hexane, tetrahydrofuran (Fison AR or
HPLC grade) were dried over sodium–benzophenone and dis-
tilled under argon. The dried solvents were stored under argon
in ampoules fitted with a Young’s ptfe tap. All deuterated, [2H6]-
Synthesis of trans-[Ru(dppe)2H(FHF)] (2). cis-[Ru(dppe)2H2]
(1.0 g, 1.11 mmol) was dissolved in THF (50 mL) in a Schlenk
tube and a three-fold excess of NEt3ؒ3HF (0.537 g, 3.33 mmol)
J. Chem. Soc., Dalton Trans., 2001, 1676–1685
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was added to the solution. The mixture was stirred at room
temperature for 1 h. The solvent was removed under vacuum.
The residue was extracted with benzene, filtered through a
cannula, and pumped to dryness. Recrystallisation from THF–
hexane at Ϫ30 ЊC afforded yellow crystals (yield 85%). (Found:
C, 66.03; H, 5.57. Calc. for C52F2H50P4Ru: C, 66.58; H, 5.37%).
IR (Nujol, cmϪ1): 2450 (m, b), 2315 (m, b), 1893 (m), 1233
(vw), 1190 (w), 884 (vw), 877 (w), 751 (s), 664 (m), 646 (m), 520
(s), 452 (m), 425 (w), 355 (w), 327 (vw).
Crystal data. C62H70F2P4O2Ru, M = 1110.13, triclinic, space
group P1 (no. 2), a = 11.812(5), b = 12.060(6), c = 11.379(5) Å,
¯
α = 112.51(3), β = 96.17(4), γ = 109.18(3)Њ, U = 1362.9(10) Å3,
T = 150 K, Z = 1, µ(MoKα) = 0.455 mmϪ1, 5371/5062
measured/unique data, Rint = 0.0518. The structure was solved
by direct methods using SAPI,38 and expanded using Fourier
techniques with DIRDIF,39 and refined against F2 (SHELXL
97).40 Hydrogen atoms on the phosphine ligands were placed in
idealised positions, but hydrogen atoms on the bifluoride, the
hydride position and the THF were not included. The
ruthenium atom sits on the centre of symmetry. The bifluoride
was disordered about the two positions generated by the
crystallographic inversion operation. When the site occupations
of the two fluorine atoms were allowed to refine freely, they
converged to 52%, clearly excluding the structure [Ru-
(dppp)2(FHF)2]. This formula was also excluded as follows.
When the site occupation factors of F(1) and F(2) were set at
100% and the structure allowed to refine, the Uiso values for F(1)
and F(2) increased significantly, the R values were raised and a
hole formed close to F(1). Final R1, wR2 on all data 0.0710,
0.1279; R1, wR2 on [Io > 2σ(Io)] 0.0445, 0.1162.
Mass spectra (FAB-MS): m/z 898 (100%, M+ Ϫ 2HF).
Synthesis of trans-[Ru(dppp)2H(FHF)] (3). This complex was
prepared in an identical fashion to trans-[Ru(dppe)2H(FHF)].
The product was recrystallised from THF at Ϫ30 ЊC to afford
yellow crystals (yield 82%). (Found: C, 66.72; H, 5.89. Calc. for
C54F2H54P4Ru: C, 67.14; H, 5.63%).
IR (Nujol cmϪ1): 2463 (b, m), 2316 (b, m), 1900 (s), 1124 (w),
1072 (m), 984 (w), 949 (m), 917 (m), 843 (s), 795 (w), 759 (w),
739 (s), 645 (w), 545 (m), 513 (s), 498 (s), 465 (w), 422 (m), 379
(vw), 330 (w).
Mass spectra (FAB-MS): m/z 927 (M+ Ϫ FHF).
Structure determination for complex 4
Synthesis of cis-[Ru(PMe3)4(FHF)2] (4). cis-[Ru(PMe3)4H2]
(0.50 g, 1.04 mmol) was dissolved in THF (50 mL) in a Schlenk
tube. The solution was cooled to 0 ЊC and a two-fold excess of
NEt3ؒ3HF (0.335 g, 2.07 mmol) added. The mixture was stirred
for 1 h until yellow crystals formed. The solvent was removed
under vacuum. The residue was extracted with benzene, filtered
through a cannula, and dried under vacuum. The product was
recrystallised from THF at Ϫ30 ЊC to afford yellow crystals
(yield 85%). (Found: C, 29.76; H, 7.90. Calc. for C12F4H38P4Ru:
C, 29.75; H, 7.91%).
Yellow block-shaped crystals were obtained from a solution
of 4 in THF at Ϫ20 ЊC. Diffraction data were collected for a
crystal with dimensions 0.5 × 0.5 × 0.5 mm.
Crystal data. C12H38F4P4Ru, M = 483.37, monoclinic, space
group Cc (no. 9), a = 16.435(14), b = 8.819(3), c = 17.826(18)
Å, β = 123.46(5)Њ, U = 2155(3) Å3, T = 150 K, Z = 4,
µ(MoKα) = 1.408 mmϪ1, 2379/1761 measured/unique data,
Rint = 0.0294. The structure was solved by direct methods using
SAPI,38 and expanded using Fourier techniques with
DIRDIF,39 and refined against F2 (SHELXL 97).40 Hydrogen
atoms on the phosphine ligands were placed in idealised
positions, but hydrogen atoms on the bifluoride were not
included. Final R1, wR2 on all data 0.0396, 0.1024, R1, wR2 on
[I > 2σ(I)], 0.0368, 0.0990.
IR (Nujol, cmϪ1): 2399 (m, b), 2290 (m, b), 1313 (w), 1255
(w), 955 (m), 940 (m), 865 (w), 723 (s), 670 (w), 635 (w), 471
(vw), 380 (w), 360 (w).
Mass spectra (FAB-MAS): m/z 425 (M+ Ϫ HF3).
Abstraction of HF from bifluoride complexes. trans-
[Ru(depe)2(H)(FHF)] (0.1 g, 0.11 mmol) or trans-[Ru(dppp)2-
(H)(FHF)] (0.1 g, 0.106 mmol) was dissolved in THF (50 mL)
in a Schlenk tube. The solution was added to excess solid
[NMe4]F (0.1 g, 1.1 mmol) under argon. The resulting suspen-
sion was stirred at room temperature for 2 h and the solvent was
then removed under vacuum. The product was extracted with
benzene (60 mL) and then dried under vacuum to yield a yellow
product.
CCDC reference numbers 157681 and 157682.
See http://www.rsc.org/suppdata/dt/b1/b101007g/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
We would like to acknowledge discussions and experimental
assistance from Dr S. B. Duckett and Prof. W. Levason, and the
University of York and the EPSRC for financial assistance.
Synthesis of trans-[Ru(dppe)2(H)N3]. cis-[Ru(dppe)2H(FHF)]
(0.1 g, 0.106 mmol) was dissolved in THF (20 mL) in a Schlenk
tube and (CH3)3SiN3 (0.012 g, 0.106 mmol) was added to the
solution. The mixture was stirred at room temperature for 1 h.
The solvent was removed under vacuum and the solid residue
was extracted with benzene and dried under vacuum. Recrystal-
lisation from THF–hexane at Ϫ30 ЊC afforded yellow crystals
(yield 78%). (Found: C, 66.97; H, 5.5; N: 4.1. Calc. for C52H49-
N3P4Ru: C: 66.31; H, 5.23; N, 4.46%).
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Synthesis of [Ru(dppe)2(H)]OTf. This complex was
synthesised using the same method as described for trans-
[Ru(dppe)2(H)N3].
IR (Nujol, cmϪ1): 2174 (s), 1261 (m), 1161(m), 895 (vw), 888
(vw), 783 (w sh), 722 (m), 640 (w), 580 (vw), 514 (w).
Structure determination for complex 3
Yellow block-shaped crystals of 3ؒ2THF were obtained from a
solution of 3 in THF at Ϫ20 ЊC. Diffraction data were collected
for a crystal with dimensions 0.4 × 0.3 × 0.2 mm.
1684
J. Chem. Soc., Dalton Trans., 2001, 1676–1685

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