Solution decomposition of platinum(II) fluoride cations; single-crystal structure of [Pt(PPh3)2(C6H4PPh 2)][SbF6]·CD2Cl2

Article abstract of DOI:10.1039/a709075g

An extended X-ray absorption fine structure (EXAFS) investigation of the metal co-ordination geometry in the cations [PtF(PR₃)₃]⁺ (R = Et or Ph) indicates that the Pt-F bond lengths are identical and only slightly longer t

Full text of DOI:10.1039/a709075g

View Article Online / Journal Homepage / Table of Contents for this issue
Solution decomposition of platinum(II) fluoride cations; single-crystal
structure of [Pt(PPh3)2(C6H4PPh2)][SbF6]ؒCD2Cl2
Howard C. S. Clark, John Fawcett, John H. Holloway, Eric G. Hope,* Lee A. Peck and
David R. Russell
Department of Chemistry, University of Leicester, Leicester, UK LE1 7RH
An extended X-ray absorption fine structure (EXAFS) investigation of the metal co-ordination geometry in the
cations [PtF(PR3)3]ϩ (R = Et or Ph) indicates that the Pt᎐F bond lengths are identical and only slightly longer
than those typical for low-valent metal fluoride complexes. The solution decomposition of the complexes,
[PtF(PPh3)3][X] (X = HF2, BF4 or SbF6), have been studied in both wet and dry chlorinated solvents and the only
reactions observed have been due to the presence of water, producing, initially, [Pt(OH)(PPh3)3]ϩ and subsequently
the ortho-metallated products [Pt(PPh3)3(C6H4PPh2)][X], which have been characterised by mass spectrometry,
multinuclear NMR spectroscopy and, when X = SbF6, by single-crystal X-ray crystallography.
Table 1 NMR spectral data for the cationic complexes 1–3a
Until fairly recently, in contrast to the extensive chemistry of
co-ordination compounds including chloride, bromide or
c
c
c
Complex
1ad
δ(31P)b
1JPtP
2JPP
δ(195Pt)b
Ϫ4270
1JPtF
iodide as ligands, the comparable research on species incorpor-
ating fluoride as a ligand has been sadly neglected.1 The
increased availability of a range of fluorinating agents, the
observation that low-valent metal–fluoride bonds are not
necessarily unstable, particularly in the presence of π-acceptor
ligands,2 and the appreciation that novel and potentially inter-
esting synthetic chemistry can be accomplished at the co-
ordinated fluoride ligand3 have revitalised this area. We have a
long-standing interest in transition-metal carbonyl fluoride
complexes4,5 and are currently attempting to evaluate the cri-
teria for metal–fluoride bond stability.
Early reports on low-valent platinum fluoride complexes,
which describe some poorly characterised derivatives, indicate
that, in these systems, the metal–fluoride bond is weak and
highly reactive. The best characterised platinum fluoride phos-
phine complexes are the [PtFL3][BF4] (L = PEt3, PMePh2 or
PPh3) species, prepared by halide metathesis or by the reaction
of PtL4 with anhydrous HF, for which 19F NMR and, when
L = PEt3, X-ray crystallography has confirmed the presence of
a platinum–fluorine bond.6–9
26.5(PA)
3.0(PB)
28.0(PA)
3.0(PB)
22.8(PC)
12.0(PD)
Ϫ68.0(PE)
21.0(PF)
16.8(PG)
2640
3701
2828
3455
2483
3644
2135
2835
2008
19
67
1be
2
19
19
Ϫ4405
—
250
—
3
366, 18
366, 18
18
Ϫ4450
—
a Assignments in parentheses. b In ppm. c In Hz. d δ(19F) = Ϫ232.0
(2JPaF = 39, JPbF = 139 Hz). e δ(19F) = Ϫ251.5 (2JPaF = 32, JPbF = 140
2
2
Hz).
+
+
+
PDPh3
PGPh3
PBR3
Pt
PFPh3
Pt
PCPh3
Pt
PAR3
Ph3PC
R3PA
Ph2PE
OH
F
2
3
1a R = Ph
1b R = Et
The various reports for low-valent platinum fluoride com-
plexes are under investigation and here we describe evidence for
reactivity in this class of complex and identify the decom-
position products of the [PtFL3]ϩ (L = phosphine) cations.
and fac-[PtCl3F3]2Ϫ, included in a compilation,11 have been
reported previously) and the data for the ‘P3F’ donor sets show
the standard shift to high frequency within a series of related
Results and Discussion
halide complexes.12 It has been noted that the JPtF coupling
1
The platinum fluoride phosphine complexes [PtFL3][X]
(L = PPh3 or PEt3; X = HF2, BF4 or SbF6) were prepared by the
literature routes, or modifications thereof.6,7 The [PtF-
(PEt3)3][BF4] complex was also obtained as the only product
from an attempted preparation of a platinum() phosphine
fluoride complex by the reaction of [Pt(PEt3)4][BF4]2 with XeF2
in acetonitrile. During the course of this work, a similar
fluorination of [Pt(py)4][BF4]2 with XeF2, was reported to give
a stable PtIV fluoride.10
constant for the triphenylphosphine complex is significantly
smaller than that for the triethylphosphine complex. This has
been used to suggest a weaker and more reactive Pt᎐F bond in
the former. Although the PEt3 complex is stable in solution over
extended periods and has been crystallographically character-
ised by one of us,9 all attempts to grow single crystals of the PPh3
complex resulted in decomposition (see below). It has been
shown that EXAFS spectroscopy can be a valuable tech-
nique for the determination of the metal–ligand interaction in
the absence of crystallographic data13 and we have investigated
the metal environment in these complexes by Pt LIII-edge
EXAFS.
The reliability of the data collection and treatment was con-
firmed by the collection and analysis of similar data for [PtF-
(PEt3)3][BF4] as a model compound (Table 2). The results of the
two-shell fit are in satisfactory agreement with the crystallo-
graphic data.9 For [PtF(PPh3)3][SbF6], transmission EXAFS
The 19F and 31P-{1H} NMR data for [PtFL3][BF4] (L = PEt3
1b[BF4] or PPh3 1a[BF4]) are in good agreement with those
reported previously12 whilst the 195Pt-{1H} NMR spectra,
reported for the first time, show the expected single resonances
(doublets of triplets of doublets) at ca. δ Ϫ4350 (Table 1). Sur-
prisingly, these represent the first 195Pt NMR data for a
platinum() fluoride complex (only the 195Pt NMR chemical
shift for [PtF2(py)4][BF4]210 and high frequency data for [PtF6]2Ϫ
J. Chem. Soc., Dalton Trans., 1998, Pages 1249–1252
1249

View Article Online
Table 2 EXAFS and crystal data for [PtF(PEt3)3][BF4] and EXAFS data for [PtF(PPh3)3][SbF6]a
[PtF(PEt3)3][BF4] [PtF(PPh3)3][SbF6]
Debye–Waller
factor
Debye–Waller
factor
X-Rayb
EXAFSc,d
EXAFSc,e
d(Pt᎐F)/Å
d(Pt᎐P)/Å
2.043(7)
2.239(3)
2.339(4)
2.335(4)
2.028(4)
2.308(3)
0.001(1)
0.011(1)
2.011(7)
2.294(3)
0.014(1)
0.014(1)
EF
Ϫ15.3(5)
Ϫ11.6(5)
a Standard deviations in parentheses. b Taken from ref. 9. c AFAC (a factor compensating for the reduction in amplitude due to multi-electron
processes) = 0.86 for all refinements. The systematic errors in bond distances arising from the data collection and analysis are ca. 0.02 Å for the first
co-ordination shells. d Fit index = Σi[(χT Ϫ χE)ki3]2 = 0.50 (where T is theoretical and E is experimental). R = [∫(χT Ϫ χE)k3 dk/∫χEk3 dk] = 0.203.
e Fit index = 0.22. R = 0.196.
data were collected to k = 15 ÅϪ1 (k = photoelectron wave vec-
tor) beyond the edge but, due to poor signal-to-noise at high k,
the data were truncated at k = 13 ÅϪ1. Five data sets were col-
lected, averaged and the data multiplied by k3 to compensate for
drop-off in intensity at higher k. No smoothing or Fourier fil-
tering was applied and the fit discussed below is compared with
the averaged raw (background-subtracted) EXAFS data. The
data were modelled to the same two shells of one fluorine atom
at r = ca. 2.03 Å and the three phosphorus atoms at r = ca. 2.27
Å. Each shell was added stepwise, iterated in the usual way, and
the best fits tested for statistical significance.14
Examination of the Fourier transforms indicated additional
features around 3.5 Å which, for both complexes, could be
modelled to backscattering from the carbon backbone. This
resulted in significant reductions to the fit index and R factor,
but we follow convention in not including these interactions in
our models.15 We note that fitting two shells at similar distance
may be dangerous. However, the validity of the fits we obtained
can be demonstrated by the level of correlation between the
data for the two shells (<0.6) and our attempts to fit the data to
chemically unreasonable single-shell or two-shell (2F, 2P)
models which give uncharacteristic Debye–Waller factors,
unreasonable bond lengths and markedly poorer fits (R > 30%).
Although the Pt᎐F bond length for 1a[SbF4] is slightly shorter
than that for 1b[BF4], the distances are the same within the
accuracy of the technique ( 0.02 Å), indicating that the
variation in the 1JPtF coupling constants results from changes in
the s character of the Pt᎐F bond in line with the differences in
basicity of the phosphine ligands. The increased reactivity of
the triphenylphosphine complex in solution, therefore, is likely
to occur as a result of other interactions in the complex.
We note that from the crystal structure, [PtF(PEt3)3]ϩ 1b shows
a marked tetrahedral distortion of the platinum co-ordination
resulting from or arising in short intramolecular H ؒ ؒ ؒ F
interactions which could markedly reduce the reactivity of the
fluoride ligand in this complex.
The complex [PtF(PPh3)3][X] decomposed over a period of
days in dichloromethane as evidenced by 31P NMR spec-
troscopy. After 2 h in CD2Cl2, in addition to the resonances
observed for the monofluorinated cationic starting material,
the formation of two, new, mutually-coupled resonances were
observed in the 31P-{1H} NMR spectrum apparently indicative
of substitution of fluoride on the metal for an alternative
anionic ligand. Despite the fact that these complexes have been
reported to undergo facile fluorine/chlorine exchange in chlori-
nated solvents, we find no evidence for fluoridation of the sol-
vents. This suggests that the new ligand on the platinum metal
centre is a hydroxide group, originating from traces of water in
the solvent, thus yielding [Pt(OH)(PPh3)3][SbF6] 2[SbF6]. Evi-
dence for this hypothesis has been provided by confirmatory
work in which separate samples of [PtF(PPh3)3][X] were dis-
solved in both rigorously dried and reagent grade CD2Cl2 and
studied, over a period of days, in a controlled manner by 31P-
{1H} NMR spectroscopy. The sample in the dry solvent dis-
played no evidence of decomposition, even after a period of
several weeks at room temperature, whereas the sample in wet
solvent was found to decompose rapidly following the same
decomposition pathway as previously described. This indicated
that (a) the product of this reaction is most probably a hydrox-
ide rather than a chloride derivative, (b) the reaction is
independent of the associated anion and (c) since both samples
were stored in the absence of light, the reaction is unlikely to
have proceeded via a radical mechanism.
During a further 2 week period, in addition to increasing
production of this new cationic species at the expense of the
initial monofluorinated derivative, the formation of a third
compound which displayed three mutually-coupled resonances,
all showing platinum satellites, could be observed. Resonances
attributed to the initial monofluorinated cation completely dis-
appeared over a further 2 week period and the signals due to
the monohydroxylated intermediates also decreased as those
of the third compound grew in intensity, ultimately resulting
in complete conversion to this new compound. The very low-
frequency 31P chemical shift for one resonance and the coup-
ling constant data allow assignment to [Pt(PPh3)2(C6H4PPh2)]ϩ
3, presumably formed by the standard ortho-metallation route
at the electron-rich metal centre followed by resulting elimin-
ation of H2O. In particular, δ(PF) is comparable to those
observed for cyclometallated phosphines trans to a second
1
phosphine;16 JPtP is characteristic of a phosphine ligand
G
trans to an aryl group17 and the unusually small 1JPtP (for phos-
E
phorus trans to phosphorus) is a consequence of distortion of
the angles at platinum and phosphorus. The formation of 3
offers further, indirect evidence that 2 is not a chloro species
since there have been no reports of the solution instability of
[PtCl(PPh3)3]ϩ in wet or dry solvents.
The ortho-metallated complex was isolated as a colourless
solid and crystals suitable for single-crystal X-ray crystallo-
graphic study were obtained by slow evaporation from CD2Cl2
solution. The unit cell of 3 contains two discrete, crystal-
lographically related, cation–anion pairs with no unusual con-
tacts between the ions and the two molecules of solvent. A
perspective view of the complex is shown in Fig. 1 and the
relevant bond lengths and angles are given in Table 3. As shown
in Fig. 1, the cation can be described as a pseudo-square planar
platinum() ion containing two normal PPh3 ligands and an
ortho-metallated PPh3 group. The PPh3 groups appear normal
and the Pt᎐P(1) and ᎐P(2) bond distances are comparable to
those reported for four-co-ordinate platinum() cations.18–20 In
the ortho-metallated ring the Pt᎐P(3) distance is similar to that
of the Pt᎐P(1) and ᎐P(2) bond distances, whilst the Pt᎐C(12)
distance [2.090(4) Å] is unusually long for an ortho-metallated
triphenylphosphine ligand.21,22 As observed in most ortho-
metallated phosphine ligands, the geometry around P(3) is sig-
nificantly distorted from that found in normal PPh3 ligands. As
a result of drawing ring 1 towards the metal, the C(11)᎐P(3)᎐Pt
angle is only 84.7(2)Њ, compared to an average of 114.5Њ for the
angles around P(1) and P(2), and the carbon–phosphorus dis-
1250
J. Chem. Soc., Dalton Trans., 1998, Pages 1249–1252

View Article Online
Experimental
Table 3 Selected bond lengths (Å) and angles (Њ) with estimated
standard deviations in parentheses for [Pt(PPh3)2(C6H4PPh2)][SbF6]ؒ
CD2Cl2
Fluorine-19 and 31P NMR spectroscopic studies were carried
out on a Bruker DRX400 spectrometer at 376.50 and 161.98
MHz and referenced to external CFCl3 and 85% H3PO4 respect-
ively, whilst the 195Pt NMR studies were recorded on a Bruker
AM300 spectrometer at 64.52 MHz, externally referenced to
[Na2PtCl6]–D2O. All spectra were recorded in CD2Cl2 and all
chemical shifts are reported using the high-frequency positive
convention.
Pt᎐C(12)
Pt᎐P(3)
2.090(4)
2.3126(13)
1.820(5)
1.829(5)
1.822(5)
1.800(5)
1.808(5)
1.398(7)
1.395(7)
1.389(8)
1.751(7)
Pt᎐P(1)
Pt᎐P(2)
2.3079(13)
2.3229(12)
1.820(5)
1.813(5)
1.830(5)
1.804(5)
1.381(7)
1.381(7)
1.400(8)
1.746(7)
1.869(3)
P(1)᎐C(71)
P(1)᎐C(91)
P(2)᎐C(51)
P(3)᎐C(11)
P(3)᎐C(31)
C(11)᎐C(12)
C(13)᎐C(14)
C(15)᎐C(16)
Cl(7)᎐C(1)
P(1)᎐C(81)
P(2)᎐C(41)
P(2)᎐C(61)
P(3)᎐C(21)
C(11)᎐C(16)
C(12)᎐C(13)
C(14)᎐C(15)
Cl(8)᎐C(1)
Sb᎐F (average)
Platinum LIII-edge extended X-ray absorption fine structure
spectra (EXAFS) were collected at the Daresbury synchrotron
radiation source operating at 2 GeV (ca. 3.2 × 10Ϫ10 J) with an
average current of 190 mA on station 7:1 using an order-
sorting Si(111) monochromator, offset to 50% of the rocking
curve for harmonic rejection. The EXAFS data were collected
in transmission mode at room temperature for samples diluted
in dry boron nitride and mounted between Sellotape strips in
1 mm aluminium spacers. The EXAFS data treatment utilised
the programs EX23 and EXCURV 92.24 Several data sets were
collected for each compound in k space, and averaged to im-
prove the signal-to-noise ratio. The pre-edge background was
removed by fitting the spectrum to a quadratic polynomial, and
subtracting this from the whole spectrum. The atomic contribu-
tion to the oscillatory part of the absorption spectrum was
approximated using polynomials, and the optimum function
judged by minimising the intensity of chemically insignificant
shells at low r in the Fourier transform. Curve fitting used single-
scattering curved-wave theory. Ground-state potentials of the
atoms were calculated using Von Barth theory and phase shifts
using Hedin–Lundqvist potentials. Two-shell (3P, 1F) models
were fitted in both cases. Refinements were also carried out
using other combinations and better fits were obtained with the
spectroscopically correct two-shell model. The distances and
Debye–Waller factors were refined for both shells, as well as the
Fermi energy difference. Fast atom bombardment mass spectra
were recorded on a Kratos Concept 1H mass spectrometer. All
preparative manipulations were carried out on a metal vacuum
line with facilities to connect Teflon and FEP (perfluoro-
ethylene–propylene co-polymer) reaction vessels. Hydrogen
fluoride (ICI) was purified by vacuum transfer, dried by
repetitive fluorination at room temperature and stored in
Kel-F tubes over dry BiF5.25 The complexes [PtF(PEt3)3][BF4],6
C(12)᎐Pt᎐P(1)
P(1)᎐Pt᎐P(3)
P(1)᎐Pt᎐P(2)
91.00(14)
158.54(4)
97.50(4)
101.1(2)
108.7(2)
123.5(2)
99.2(2)
114.8(2)
118.1(2)
104.8(2)
84.7(2)
C(12)᎐Pt᎐P(3)
C(12)᎐Pt᎐P(2)
P(3)᎐Pt᎐P(2)
68.4(2)
170.33(14)
102.59(4)
109.9(2)
101.2(2)
111.5(2)
110.3(2)
103.1(2)
110.3(2)
111.6(2)
107.1(2)
119.5(2)
C(71)᎐P(1)᎐C(91)
C(71)᎐P(1)᎐Pt
C(91)᎐P(1)᎐Pt
C(41)᎐P(2)᎐C(61)
C(41)᎐P(2)᎐Pt
C(61)᎐P(2)᎐Pt
C(11)᎐P(3)᎐C(31)
C(11)᎐P(3)᎐Pt
C(31)᎐P(3)᎐Pt
C(16)᎐C(11)᎐P(3)
C(71)᎐P(1)᎐C(81)
C(81)᎐P(1)᎐C(91)
C(81)᎐P(1)᎐Pt
C(41)᎐P(2)᎐C(51)
C(51)᎐P(2)᎐C(61)
C(51)᎐P(2)᎐Pt
C(11)᎐P(3)᎐C(21)
C(21)᎐P(3)᎐C(31)
C(21)᎐P(3)᎐Pt
125.0(2)
133.5(4)
C(16)᎐C(11)᎐C(12) 124.9(5)
C(13)᎐C(12)᎐C(11) 117.1(4)
C(11)᎐C(12)᎐Pt 104.8(3)
C(13)᎐C(14)᎐C(15) 122.0(5)
C(11)᎐C(16)᎐C(15) 117.2(5)
C(12)᎐C(11)᎐P(3)
C(13)᎐C(12)᎐Pt
C(12)᎐C(13)᎐C(14) 119.5(5)
C(16)᎐C(15)᎐C(14) 119.3(5)
101.1(3)
138.1(4)
C(22)᎐C(21)᎐P(3)
C(32)᎐C(31)᎐P(3)
Cl(8)᎐C(1)᎐Cl(7)
117.9(4)
118.5(4)
112.0(4)
C(26)᎐C(21)᎐P(3)
C(36)᎐C(31)᎐P(3)
121.7(4)
120.2(4)
[Pt(PEt3)4][BF4]2 and [PtF(PPh3)3][HF2]27 were prepared by
26
literature routes, whilst [PtF(PPh3)3][X] (X = BF4 or SbF6)
were prepared by modifications of the literature route.7
Tetrakis(triphenylphosphine)platinum(0) (Aldrich) (0.3 g, 0.25
mmol) was loaded into a prepassivated 6 mm external diameter
FEP tube fitted with a PTFE valve and NaBF4 (Fluorochem)
(0.026 g, 0.25 mmol) or NaSbF6 (Fluorochem) (0.028 g, 0.25
mmol) were loaded into a second passivated tube. After evacu-
ation on the metal line, anhydrous HF (ca. 1 cm3) was con-
densed onto the platinum complex at Ϫ196 ЊC. Upon warming,
effervescence was observed, necessitating quenching of the
reaction mixture in liquid nitrogen and venting off the hydro-
gen. When the reaction was complete, the anhydrous HF
solution of the metal complex was decanted onto NaBF4 or
NaSbF6 and, after 1 h at room temperature, the solvent was
removed in vacuo to yield brown solids.
Fig. 1 Molecular structure of [Pt(PPh3)2(C6H4PPh2)][SbF6]ؒCD2Cl2.
Displacement ellipsoids are shown at 30% probability level
tances around P(3) (average 1.804 Å) are shorter than those
around P(1) and P(2) (average 1.822 Å). Similarly, the angles
about C(11) deviate considerably from the usual value of 120Њ;
i.e. C(12)᎐C(11)᎐P(3) is 101.1(3)Њ and C(16)᎐C(11)᎐P(3) is
133.5(4)Њ. Comparable bond angle variations have been
reported for other ortho-metallated platinum()–triphenyl-
phosphine complexes.20 Additionally, the C(31)–P(3)᎐Pt angle
at 125.0(2)Њ is also outside the ‘standard’ range, which is a con-
sequence not of ortho-metallation, but steric interactions with
the aryl rings bound to P(2) which cause ring 3 to bend away
from this ligand. Rings 5,6,7 and 8 stagger themselves with
respect to the rings associated with the ortho-metallated
phosphine to minimise steric congestion. The anion is
unremarkable; the fluorines describe an almost perfect octa-
hedron around the antimony and there are no significant
cation–anion interactions.
The complex [Pt(PPh3)2(C6H4PPh2)][SbF6] was obtained as a
colourless solid following removal of the solvent after 3 months
from a sample used for the NMR decomposition studies (see
above). FAB mass spectrum: m/z 980 (Mϩ).
Crystal structure determination of [Pt(PPh3)2(C6H4PPh2)]-
[SbF6]ؒCD2Cl2
Crystal data: C55H44Cl2D2F6P3PtSb, M = 1303.57, triclinic,
a = 12.496(1), b = 13.045(2), c = 17.469(2) Å, α = 89.61(1),
β = 74.43(1), γ = 68.16(1)Њ, U = 2532.4(5) Å3, T = 190 K, space
group P1 (no. 2), Z = 2, µ(Mo-Kα) = 3.551 mmϪ1, 10 035 reflec-
¯
J. Chem. Soc., Dalton Trans., 1998, Pages 1249–1252
1251

View Article Online
13 See, for example, S. K. Harbron, S. J. Higgins, W. Levason, M. C.
tions measured, 8606 unique (Rint = 0.026) which were used in
all calculations. The final wR(F2) was 0.0711, R1 = 0.0325.
CCDC reference number 186/913.
See http://www.rsc.org/suppdata/dt/1998/1249/ for crystallo-
graphic files in .cif format.
Feiters and A. T. Steel, Inorg. Chem., 1986, 25, 1789; L. R. Hanton,
J. Evans, W. Levason and R. J. Perry, J. Chem. Soc., Dalton Trans.,
1991, 2039; M. J. Atherton, K. S. Coleman, J. Fawcett, J. H.
Holloway, E. G. Hope, A. Karaçar, L. A. Peck and G. C. Saunders,
J. Chem. Soc., Dalton Trans., 1995, 4029.
14 R. W. Joyner, K. J. Martin and P. Meehan, J. Phys. C, 1987, 20,
4005; N. Binstead, S. L. Cook, J. Evans, G. N. Greaves and R. J.
Price, J. Am. Chem. Soc., 1987, 109, 3667.
Acknowledgements
15 See, for example, N. R. Champness, W. Levason, D. Pletcher,
M. D. Spicer and M. Webster, J. Chem. Soc., Dalton Trans., 1992,
2201.
We would like to thank Dr. G. Eaton for recording the mass
spectra, Dr. A. K. Brisdon for assistance with the EXAFS data
acquisition, the Director of the Daresbury Laboratory for the
provision of facilities and the EPSRC (L. A. P., E. G. H. and
H. C. S. C.) and the Royal Society (E. G. H.) for financial
support.
16 P. S. Pregosin and R. W. Kunz, 31P and 13C NMR of Transition Metal
Phosphine Complexes, Springer-Verlag, Berlin, 1979.
17 P. S. Braterman, R. J. Cross, L. Manojlovic-Muir, K. W. Muir and
G. Young, J. Organomet. Chem., 1975, 84, C40.
18 P. S. Pregosin, R. Favez, R. Roulet, T. Boschi, R. A. Michelin and
R. Ros, Inorg. Chim. Acta, 1980, 45, L7.
19 R. Favez, R. Roulet, A. A. Pinkerton and D. Schwarzenbach, Inorg.
Chem., 1980, 19, 1356.
References
1 N. M. Doherty and N. W. Hoffman, Chem. Rev., 1991, 91, 553.
2 E. A. V. Ebsworth, N. Robertson and L. J. Yellowlees, J. Chem. Soc.,
Dalton Trans., 1993, 1031.
3 N. M. Doherty and S. C. Critchlow, J. Am. Chem. Soc., 1987, 109,
7906; J. E. Veltheer, P. Burger and R. G. Bergman, J. Am. Chem.
Soc., 1995, 117, 12 478.
4 S. A. Brewer, A. K. Brisdon, J. H. Holloway, E. G. Hope, L. A. Peck
and P. G. Watson, J. Chem. Soc., Dalton Trans., 1995, 2945.
5 C. J. Marshall, R. D. Peacock, D. R. Russell and I. L. Wilson, Chem.
Commun., 1970, 1643; S. A Brewer, J. H. Holloway and E. G. Hope,
J. Chem. Soc., Dalton Trans., 1994, 1067; S. A. Brewer, J. H.
Holloway, E. G. Hope and P. G. Watson, J. Chem. Soc., Chem.
Commun., 1992, 1577.
6 M. A. Cairns, K. R. Dixon and J. J. McFarland, J. Chem. Soc.,
Dalton Trans., 1975, 1159.
7 R. D. W. Kemmitt, R. D. Peacock and J. Stocks, J. Chem. Soc. A,
1971, 846.
8 K. R. Dixon and J. J. McFarland, J. Chem. Soc., Chem. Commun.,
1972, 1274.
9 D. R. Russell, M. A. Mazid and P. A. Tucker, J. Chem. Soc., Dalton
Trans., 1973, 1620.
20 A. G. Orpen, L. Brammer, F. H. Allen, O. Kennard, D. G. Watson
and R. Taylor, J. Chem. Soc., Dalton Trans., 1989, S1.
21 G. Perego, G. del Piero, M. Cesari, M. G. Clerici and E. Perotti,
J. Organomet. Chem., 1973, 54, C51; K. von Deuten and
L. Dahlenbury, Cryst. Struct. Commun., 1980, 9, 421; M. Cowie,
I. R. McKeer, S. J. Loeb and M. D. Gauthier, Organometallics,
1986, 5, 860.
22 N. C. Rice and J. D. Oliver, J. Organomet. Chem., 1978, 145, 121;
M. A. Bennett, D. E. Berry, S. K. Bhargava, E. J. Ditzel, G. B.
Robertson and A. C. Willis, J. Chem. Soc., Chem. Commun., 1987,
1613.
23 A. K. Brisdon, EX, A Program for EXAFS Data Reduction,
University of Leicester, 1992.
24 N. Binstead, S. J. Gurman and J. W. Campbell, EXCURV 92, SERC
Daresbury Laboratory Program, 1992.
25 K. O. Christe, W. E. Wilson and C. J. Schack, J. Fluorine Chem.,
1978, 11, 71.
26 D. J. Cole-Hamilton, J. Chem. Soc., Dalton Trans., 1984, 2249.
27 H. C. S. Clark, J. Fawcett, J. H. Holloway, E. G. Hope and L. A.
Peck, manuscript in preparation.
10 H.-H. Drews and W. Preetz, Z. Anorg. Allg. Chem., 1997, 623, 509.
11 P. L. Goggin and R. L. Goodfellow, NMR and the Periodic Table,
eds. R. K. Harris and B. E. Mann, Academic Press, London, 1978.
12 E. G. Hope, W. Levason and N. A. Powell, Inorg. Chim. Acta, 1986,
115, 187.
Received 18th December 1997; Paper 7/09075G
© Copyright 1998 by the Royal Society of Chemistry
1252
J. Chem. Soc., Dalton Trans., 1998, Pages 1249–1252