Coordination chemistry of 2,6-dixylyl-4-phenylphosphabarrelene with selected transition metals

Article abstract of DOI:10.1039/b816499a

The 2,6-dixylyl-4-phenylphosphabarrelene has been synthesised from the parent phosphinine and its properties as a ligand explored through the preparation and characterisation of the complexes W(CO)₅(L), Re(CO)₄(L)Cl, (η⁶-c

Full text of DOI:10.1039/b816499a

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Coordination chemistry of 2,6-dixylyl-4-phenylphosphabarrelene with
selected transition metals†
Christopher Wallis,a Peter G. Edwards,*a Martin Hanton,b Paul D. Newman,a Andreas Stasch,a
Cameron Jones‡a and Robert P. Toozeb
Received 22nd September 2008, Accepted 8th December 2008
First published as an Advance Article on the web 4th February 2009
DOI: 10.1039/b816499a
The 2,6-dixylyl-4-phenylphosphabarrelene has been synthesised from the parent phosphinine and its
properties as a ligand explored through the preparation and characterisation of the complexes
6
5
W(CO)5(L), Re(CO)4(L)Cl, (h -cymene)RuCl2(L), [(h -Me3SiC5H4)Fe(CO)2(L)]PF6,
Rh(1,5-COD)(L)Cl, Ir(1,5-COD)(L)Cl, and cis-Pt(L)2Cl2, where L = 4-phenyl-2,10-bis-(2,4-
5
dimethylphenyl)-4H-1,4-ethenophospholine (xPB), cymene = 4-isopropyltoluene, h -Me3SiC5H4 =
trimethylsilylcyclopentadienyl and 1,5-COD = 1,5-cyclooctadiene. The new complexes were
5
characterised by spectroscopic and analytical techniques and, for [(h -Me3SiC5H4)Fe(CO)2(L)]PF6
6
and Ru(h -cymene)(L)Cl2, by single-crystal X-ray structure determination. The coordination
properties of the phosphabarrelene have been established and compared with analogous complexes of
triarylphosphines and triarylphosphites. Most spectroscopic and structural indicators suggest that
the phosphabarrelene has coordination behaviour similar to that of simple triarylphosphines such
as PPh3.
properties of phosphabarrelenes by examining Rh(CO)(L)2Cl
Introduction
complexes of several phosphabarrelene derivatives. For Rh(I)
complexes, this study indicated that the phosphabarrelenes had
donor properties best described as lying somewhere between those
of triarylphosphines and phosphites.4
Phosphabarrelenes, originally reported by Markl,1 remain a
relatively unexplored class of organophosphorus compound. Breit
was the first to investigate metal complexes of phosphabarre-
lenes during his studies of Rh(I) systems as potential isomeri-
sation/hydroformylation catalysts.2 Latterly, Le Floch and co-
workers have examined the coordination chemistry of heterodonor
bi- and tridentate phosphine sulfide phosphabarrelene derivatives
in an effort to exploit the perceived unique donor properties of
the phosphabarrelenes in catalysis.3 In addition to the study of
this ligand type in the rhodium-catalysed hydroformylation of
internal alkenes,4 Breit and co-workers have recently synthesised
chiral, bidentate phosphite-phosphabarrelene ligands and applied
them to rhodium-based asymmetric hydrogenation.5 Much of this
recent focus on phosphabarrelene ligands has been driven by
a desire to find ligands that behave similarly to phosphites (or
phosphonites) but are less prone to degradation under the reaction
conditions commonly required for carbonylation and/or other
types of catalysis. Breit identified phosphabenzenes (from which
phosphabarrelenes are derived) as good potential candidates to
replace phosphites or more traditional tertiary phosphines in
rhodium-catalysed hydroformylation.6 Based on these studies, it
was suggested that the phosphinines were more p-acidic than
tertiary phosphines and were, therefore, more akin to phosphites
in their electronic properties. Breit also investigated the donor
These studies aside, there are few examples of fully characterised
k coordinated phosphabarrelene-transition metal complexes. We
1
have an interest in examining the coordination properties of
heterocyclic phosphines and have recently investigated aspects
of the coordination chemistry of a series of halo-substituted
arylphosphinines.7 As an extension of this work and in order to ob-
tain a more general understanding of the relative donor properties
of phosphabarrelenes, we have conducted a systematic survey of
1
the coordination chemistry of a k coordinated triarylphosphabar-
relene with a number of transition metal centres. To allow a more
direct comparison of phosphabarrelene coordination behaviour
for different metals, we have restricted our study to the coordina-
tion chemistry of the 2,6-dixylyl-4-phenylphosphabarrelene ligand
(xPB) originally reported by Breit.4 The nature of the phosphorus–
metal bond has been examined and compared with analogous
complexes of triarylphosphines and triarylphosphites and these
details are presented here.
Results and discussion
Tungsten
aSchool of Chemistry, Main Building, Park Place, Cardiff, UK CF10 3AT.
E-mail: edwardspg@cardiff.ac.uk
The mono-phosphabarrelenepentacarbonyltungsten(0) complex
W(CO)5(xPB), 1, was formed by the reaction of dixylylphos-
phabarrelene with the precursor W(CO)5THF (Scheme 1). Com-
plex 1 was isolated after recrystallisation and was fully charac-
terised by spectroscopic means. The coordination of the ligand
bSasol Technology (UK) Ltd., Purdie Building, North Haugh, St. Andrews,
UK KY16 9ST
† CCDC reference numbers 703036 & 703037. For crystallographic data
in CIF or other electronic format see DOI: 10.1039/b816499a
‡ Present address: School of Chemistry, Monash University, P. O. Box 23,
Victoria, 3800, Australia.
1
was confirmed by a downfield shift in the 31P{ H} NMR spectrum
of the complex with a singlet being observed at dP -7.2 ppm
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Scheme 1
(compared to dP -58 ppm for the free ligand, DdP = 50.8 ppm)
be 75 kJ mol-1,7 hence a greater barrier is associated with
W(CO)5(dixylylphosphinine) compared to W(CO)5(xPB). The
explanation for this resides in the nature of the two donors,
the phosphabarrelene being non-planar with a sp3 hybridised
phosphorus compared to a sp2 hybridised phosphorus centre
in the planar phosphinine. Consequently, the dixylyl groups are
“pulled back” away from the metal centre in the phosphabarrelene
complex alleviating steric congestion and allowing more freedom
of rotation than in the dixylylphosphinine complex.
1
with tungsten satellites (183W, 15% abundant, JP–W = 265 Hz).
Interestingly, and unlike the analogous complex of the parent
1
phosphinine, only one peak is seen in the 31P{ H} NMR spectrum
of the complex at room temperature. However, upon cooling the
sample to -34 ◦C this single peak starts to split until two distinct
singlets are resolved at dP 7.8 and 7.6 ppm at low temperature.
As with the analogous phosphinine complex, this observation
can be explained by rotamer isomerisation as shown in Fig. 1.
The cis isomer is defined as that where both ortho-methyl groups
of the xylyl rings are on the same side of the phosphabarrelene
phenyl ring while the trans isomer has the two ortho-methyl
groups on opposite sides of the phosphabarrelene ring. When both
isomers are observed at low temperature the relative ratios are not
1 : 1 but approximately 60 : 40 resembling the situation observed
with related dihaloarylphosphinine complexes.7 Thus, one of the
rotamers appears to be thermodynamically more stable but it is
not possible to determine from the NMR data alone which one
this is. The free energy of activation (DG‡) for this rotation was
determined to be 48 kJ mol-1 (from variable temperature NMR
studies), a value within the range established for M–P rotation in
cis-Pt(L)2Cl2 systems (L = 1-tert-butylphosphinane).8
To understand further the nature of the tungsten–phosphorus
1
bond in W(CO)5(xPB), the JP–W and the carbonyl stretching
frequencies of 1 were compared with analogous complexes of
phosphines and phosphites. The correlation between the s-donor/
p-acceptor abilities of phosphorus ligands and their 1JP–W values,
and/or their n(CO) stretching frequencies in W(CO)5(PR3) com-
plexes has been studied by Grim and co-workers9 who showed
that there was a correlation between the most intense carbonyl
1
stretching frequency (the E mode) and JP–W in phosphine and
phosphite complexes of pentacarbonyltungsten.10 Fig. 2 displays
this data in comparison to that of the analogous W(CO)5(xPB).
1
The values of the JP–W coupling constant and the n(CO) (E
mode) are 265 Hz and 1942 cm-1 for 1 placing xPB between
triphenylphosphine and tri-4-tolylphosphine in terms of donor
ability. Grim argued that better p-acceptor ligands give a higher
1
n(CO) and a larger JP–W coupling constant as increased p back-
bonding to the phosphorus has the effect of shortening the
metal–phosphorus bond consequently strengthening the metal–
phosphorus s-bond. Larger 1JP–W coupling constants were thus in-
terpreted as reflecting a greater p-bonding component in the M–P
bond. On this basis, the position of xPB in the series suggests that
it has p-acceptor abilities (and s-donor properties) most closely
similar to those of simple triarylphosphines. Steric differences
x
between triphenylphosphine and PB might be anticipated and
Fig. 1 Rotamers of W(CO)5xPB (1).
these two influences could be expected to work in opposition. The
pendant xylyl groups at the 2 position of the phosphabarrelene
core may serve to lengthen and weaken the M–P bond thus
reducing 1JW–P. Crystallographic studies (herein) indicate that
The DG‡ value for this cis ↔ trans interconversion in
the W(CO)5(dixylylphosphinine) complex was determined to
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Fig. 2 E mode stretching frequencies (n) vs. P–W coupling constants (J) in W(CO)5L complexes.
triphenylphosphine may, however, be more sterically bulky. Steric
influences will also be expected to influence JP–W coupling con-
coupling constant of around 14 Hz. The unique carbonyl trans to
the chloride is observed as a broad singlet.
1
stants if such interactions result in compression or expansion of the
C–P–C angles. Due to the cyclic nature of the phosphabarrelene
ligand, some of the C–P–C bonds are restricted at angles less
than 100◦ (vide infra) and it might be anticipated that the lone
pair in xPB has greater ‘s’ character than in PPh3 giving rise
The infrared spectrum of 2 shows four carbonyl stretching fre-
quencies, which agrees with data observed with related complexes
of this type11 and is consistent with a cis configuration for the
complex.10 Comparison of 2 with the analogous triphenylphos-
phine complex reveals a very similar pattern with n(CO) at 2109,
2023, 2005 and 1922 cm-1 in W(CO)5(xPB) and 2106, 2018, 2002
and 1945 cm-1 for W(CO)5(PPh3). Thus, the carbonyl stretching
frequencies seem to show that the phosphorus-rhenium bond in
2 is again, in terms of s-donor and p-acceptor properties, very
similar to triphenylphosphine.
1
to a larger JP–W coupling constant in W(CO)5(xPB) compared
to W(CO)5(PPh3). In balance, caution is required in interpreting
1
donor properties by these methods, but it is clear that JP–W for
W(CO)5(xPB) is appreciably smaller than for phosphite complexes.
Rhenium
Iron and ruthenium
To the best of our knowledge there are no reported complexes
of phosphabarrelenes with any of the transition metals of group
7 prompting us to investigate their chemistry. Complex 2 was
prepared by refluxing a solution of xPB with chloropentacarbonyl-
rhenium(I) in dichloromethane (Scheme 1); the desired complex
5
The cationic [(h -Me3SiC5H4)Fe(CO)2(xPB)]+ complex (3) was
synthesised as its hexafluorophosphate salt by the addition
of the phosphabarrelene to a solution of [(h -Me3SiC5H4)-
5
Fe(CO)2(CH3CN)]PF6 in dichloromethane (Scheme 1). Yellow
crystals suitable for X-ray crystallography were obtained by
vapour diffusion of diethyl ether to an ethanolic solution of the
complex salt; the structure of the cation is shown in Fig. 3. The
complex has the three legged piano stool structure common to sys-
tems of this type. Comparison with the related [CpFe(CO)2PPh3]+
1
being obtained as a microcrystalline yellow solid. The 31P{ H}
NMR spectrum of 2 is a singlet (d -23 ppm) showing the
characteristic downfield shift (Dd = 35 ppm) upon coordination of
the phosphabarrelene ligand. In addition, the 1H NMR spectrum
shows a downfield shift for the doublet of doublets associated
with the proton at the C-8 position. This is characteristic of
coordination of phosphabarrelenes to most transition metal
centres, although the magnitude of the coordination shift varies
species reveals some differences, notably in the Fe–P bond lengths
of 2.2165(12) A in 3 and 2.2380(15) A in [CpFe(CO)2PPh3] .12 This
shorter bond between the phosphabarrelene and the iron centre
relative to triphenylphosphine could reflect a slight increase in
the p-acceptor properties of the phosphabarrelene (as remarked
by Breit4) relative to triphenylphosphine although the observed
difference may also be due to steric influences of the bulkier PPh3.
It is noteworthy that the analogous trimethylphosphite complex
+
˚
˚
1
(vide infra). Three carbonyl resonances are observed in the 13C{ H}
NMR spectrum as expected for the two carbonyls cis to the
phosphabarrelene and trans to one another, the carbonyl trans
to the phosphabarrelene, and the carbonyl trans to the chloride.
The carbonyl trans to the phosphabarrelene is identified by a large
2JC–P coupling constant of 64 Hz, whereas the CO ligands cis to the
˚
exhibits a phosphorus-iron bond length of 2.164 A, significantly
shorter than in 3.13 The internal C–P–C bond angles of PB in 3
2
x
phosphabarrelene and trans to one another have a smaller JC–P
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31P{ H} NMR spectrum. These observations suggest rotamer iso-
merisation as was observed with the tungsten carbonyl complex 1;
DG of activation for the rotation was estimated from the
NMR experiments to be 60 kJ mol-1. It is noteworthy that
the peak at d 4.5 ppm is considerably more intense than the
peak at d -7.7 ppm suggesting that one of the rotamers is
thermodynamically favoured over the other as was the case in
the (xPB)pentacarbonyltungsten(0) complex, 1. These rotamers
result from restricted rotation around the phosphorus–ruthenium
bond, where, in one of the isomers, the benzene ring of the
phosphabarrelene core points towards the cymene ring, while
in the other rotamer it points away from the cymene group.
Thus, if the cymene is free to rotate on the ruthenium at these
temperatures, it is reasonable to suggest that a greater degree of
steric relief occurs when the benzene ring points away from the
cymene group and it would appear that this configuration would be
thermodynamically favoured. This is indeed the orientation seen
in the crystal structure of 4 shown in Fig. 4. The complex exhibits a
three legged pianostoolgeometry that is consistent with complexes
of this type. Comparison of the phosphorus–ruthenium bond
lengths with analogous complexes of tri(meta-tolyl)phosphine16
1
Fig. 3 ORTEP view of the cation (3). Hydrogen atoms have been
omitted for clarity. Thermal ellipsoids are drawn at 30% occupancy
˚
level. Selected bond lengths (A): Fe(1)–P(1) 2.2165(12); P(1)–C(21)
and triphenylphosphite17 gives values of 2.3619 A for complex 4,
˚
1.832(4); P(1)–C(1) 1.852(4); P(1)–C(5) 1.847(4); Fe(1)–C(43) 1.774(5);
Fe(1)–C(42) 1.780(5); O(1)–C(42) 1.143(5); O(2)–C(43) 1.138(5). Se-
lected bond angles (◦): C(21)–P(1)–Fe(1) 119.14(13); C(1)–P(1)–Fe(1)
119.77(14); C(5)–P(1)–Fe(1) 121.39(14); C(43)–Fe(1)–P(1) 92.27(15);
C(42)–Fe(1)–P(1) 95.22(15); O(1)–C(42)–Fe(1) 176.0(4); O(2)–C(43)–
Fe(1) 177.1(4).
6
˚
˚
2.379 A for (h -cymene)RuCl2{P(m-tol)3} and 2.264 A for
6
(h -cymene)RuCl2{P(OPh)3}. These values follow a similar trend
to that noted for the iron(II) systems and reinforces the notion that
the phosphabarrelene is similar in behaviour to a triarylphosphine
but is not as powerful a p-acid as related phosphites.
average 97◦, a value very close to that (96◦) observed by Breit in
the trans-Rh(CO)Cl(xPB)2 complex.4 This constraint contributes
to the reduced cone angle of 141.4◦ for the ligand in the current
complex (using the method of Mingos).14
1
The 31P{ H} NMR spectrum of the iron complex, 3, shows a
1
characteristic upfield coordination shift to d 10.6 ppm. The H
NMR spectrum was broad at room temperature but sharpened
sufficiently upon cooling to -50 ◦C to allow assignments to be
1
made. The temperature dependence of the H NMR spectrum
suggests there is some form of fluxional process present even
1
though no noticeable broadening is observed in the 31P{ H} NMR
spectrum at room temperature indicating that the fluxional process
does not involve phosphine exchange at the iron centre and is
1
likely due to restricted rotation of the ligands. The 13C{ H} NMR
spectrum of 3 is consistent with the structure although assignment
of the CO and two of the quaternary carbons was compromised
by weak signal intensity. The infrared data for 3 again compare
well with the analogous triphenylphosphine complex; 3 exhibits
two carbonyl stretching bands at 2055 and 2013 cm-1, whereas the
triphenylphosphine complex has two bands at 2052 and 2008 cm-1,
respectively,15 indicating that the phosphabarrelene again exhibits
electronic properties similar to those of triphenylphosphine in
these iron complexes.
Fig. 4 ORTEP view of (4). Hydrogen atoms have been omitted for
clarity. Thermal ellipsoids are drawn at 30% occupancy level. The
molecule of dichloromethane has been omitted for clarity. Selected bond
˚
lengths (A): P(1)–Ru(1) 2.3619(12); Cl(1)–Ru(1) 2.4043(12); Cl(2)–Ru(1)
2.4044(12); P(1)–C(1) 1.846(4); P(1)–C(5) 1.852(5); P(1)–C(7) 1.862(4).
Selected bond angles (◦): P(1)–Ru(1)–Cl(1) 84.15(5); P(1)–Ru(1)–Cl(2)
88.78(5); C(1)–P(1)–Ru(1) 123.09(13); C(5)–P(1)–Ru(1) 121.56(14);
C(7)–P(1)–Ru(1) 118.87(14).
6
The (h -cymene)RuCl2(xPB) complex, 4, was prepared from the
reaction of the [(h -cymene)RuCl2]2 dimer with two mol equiv.
The crystallographic cone angle of 145.3◦ for the phosphabarre-
lene in complex 4 compares to that calculated for the iron complex
3 but is somewhat smaller than the value of 161◦ quoted for the
trans-Rh(CO)Cl(xPB)2 complex 4. Although direct comparison
with PPh3 complexes may be inappropriate as PPh3 shows cone
angle values that extend from approximately 129◦ to around
168◦, it is noteworthy that a large number of triphenylphosphine
6
of the phosphabarrelene in dichloromethane (Scheme 1). The
1
31P{ H} NMR spectrum of 4 is very broad at room temperature
with two peaks centred around 2 ppm. Upon heating to 80 ◦C
these two peaks sharpen to a single peak at d -5.4 ppm;
coalescence occurs at 60 ◦C. Upon cooling, at -50 ◦C two
sharp peaks at d 4.5 ppm and d -7.7 ppm are observed in the
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complexes have cone angles of ~145◦. All these values are lower
than the ~175◦ cone angle of the directly comparable di(o-
tolyl)phenylphosphine largely as a consequence of the ‘tied-back’
C–P–C bond angles in the constrained phosphabarrelene. It would
appear therefore that xPB has steric and electronic properties
similar to those of triarylphosphines (particularly PPh3).
Rhodium and iridium
The Rh(1,5-COD)(xPB)Cl complex 5 was synthesised by addition
of 2 equiv. of the phosphabarrelene ligand to [Rh(1,5-(COD)Cl]2 in
dichloromethane (Scheme 1). Complex 5 was isolated as a yellow
1
Fig. 5 JP–Pt coupling constants for complexes of the type cis-(L)2PtCl2.
1
solid and characterised by spectroscopic means. The 31P{ H}
In common with the rhodium complex 5, the phosphorus–metal
coupling constant in complex 7 is slightly higher at 3860 Hz
than the analogous triphenylphosphine complex where a value
of 3673 Hz is observed. The magnitude of 1JP–M coupling is largely
dominated by the Fermi contact term and hence the extent of s
orbital character in the M–P bond. Furthermore, there tends to
be, in the absence of complicating steric effects,21 an increase in the
absolute value of 1JP-M as the M–P bond length decreases.22 Thus
the higher p-acceptor ability of the phosphabarrelene combined
with a greater degree of s orbital character in the phosphorus lone
NMR spectrum shows a downfield shifted doublet at d -17.5 ppm,
1
with a JP–Rh coupling constant of 160 Hz. Again, coordination
is confirmed in the 1H NMR spectrum by the characteristic
downfield shift (from d 7.82 ppm to d 8.77 ppm) of the C-8
1
proton. The JP–Rh coupling constant in 5 compares with a value
of 152 Hz for the analogous triphenylphosphine complex.18 The
analogous iridium(I) complex Ir(1,5-COD)(xPB)Cl, 6, was made
in the same way as the rhodium complex 5 (Scheme 1). The
1
31P{ H} NMR spectrum of the yellow compound gives a singlet
x
1
at d -24.1 ppm, and the 1H NMR spectrum shows the downfield
shifted doublet of doublets for the proton on the C-8 position of
the phosphabarrelene ring at d 8.76 ppm. These data aside, the
remaining spectroscopic details are unremarkable.
pair of PB results in the enhanced JP–Pt coupling constant for
7. The former point is supported by the work of Grim and co-
workers23 who postulate that there is a trend in the 1JP–Pt coupling
constants on going from alkyl to aryl phosphines. Thus, they
state that for PRnPh3-n as n decreases the absolute value of the
1JP–Pt coupling constant increases, i.e. p-acidity increases as more
phenyl groups are introduced on the phosphine and the values
Platinum
1
The cis-Pt(xPB)2Cl2 complex 7 was synthesised by reaction of
2 equiv. of the phosphabarrelene ligand with Pt(NCPh)2Cl2 in
dichloromethane (Scheme 1). Complex 7 is, to the best of our
knowledge, the first phosphabarrelene complex of its type to
of the observed JP–Pt coupling constant increase accordingly.
There remains, however, a marked distinction between the absolute
1
values of the JP–Pt coupling constants for phosphines (including
xPB) compared to typical phosphites which are larger as a
consequence of shorter M–P bond lengths and increased ‘s’
electron density in the bonds.24,25
1
be characterised by spectroscopic means. The 31P{ H} NMR
spectrum exhibits the coordinated downfield singlet at -27.8 ppm,
with corresponding 195Pt satellites (1JP–Pt coupling constant of
In conclusion, several complexes of the di-xylylphos-
phabarrelene, xPB, have been synthesised and characterised.
Spectroscopic indicators suggest that xPB behaves in a similar
fashion to triarylphosphines as a donor to metal centres. A close
1
3860 Hz.) The H NMR spectrum also shows the characteristic
coordination shift for the C-8 proton on the phosphabarrelene
1
ring from d 7.82 ppm to d 8.60 ppm. The 13C{ H} NMR spectrum
x
comparison between the data for the PB complexes and related
alludes to the cis configuration of the complex. This reasoning is
based upon two observations; firstly the C-2 and C-6 carbons on
the phosphabarrelene ring appear as doublets rather than triplets
and, secondly they show an increased JC–P coupling constant of
38 Hz. Further evidence for the cis assignment for complex 7
comes from comparison of the 1JP–Pt coupling constant in 7 with
related phosphine complexes. It is reported that, for any given
phosphine, the magnitude of this coupling constant is sensitive to
the geometry of the complex. For example, cis-Pt{P(p-tolyl)3}2Cl2
has a 1JP–Pt coupling constant of 3627 Hz, whereas in trans-Pt{P(p-
tolyl)3}2Cl2 it is 2650 Hz.19 This highlights an established trend for
phosphine complexes of the type Pt(PR3)2Cl2, where 1JP–Pt values
are characteristically in the order of 1000 Hz greater in the cis
isomer compared to the trans form, which relates to the higher
trans influence of a phosphine donor relative to chloride. Hence,
PPh3 complexes is noted, although cone angles for the more rigid
xPB ligand from two crystal structures are less than those observed
at the higher extreme for the more rotationally free PPh3 system.
Experimental
The new compounds were synthesised under nitrogen using
standard inert atmosphere (Schlenk) techniques. Complexes 1–7
were handled as air and moisture sensitive compounds for
manipulation. Solvents were freshly distilled from sodium or
calcium hydride under nitrogen before use. The 31P{ H} NMR
1
spectra were recorded on Jeol Eclipse 300 and Bruker DPX500
spectrometers operating at 121.7 and 202.5 MHz, respectively, and
1
referenced to 85% H3PO4 (d = 0 ppm). H (400.8 MHz) spectra
1
as the JP–Pt coupling constant of complex 7 (3860 Hz) is close
were obtained on a Bruker DPX400 spectrometer except in some
cases where a Bruker DPX500 NMR spectrometer was used as
to the values recorded for cis-Pt{P(p-tolyl)3}2Cl2 (3627 Hz), and
cis-Pt(PPh3)2Cl2 (3673 Hz),20 it can be concluded that the likely
geometry of 7 is cis. See Fig. 5 for comparison of the current
complex with known phosphine systems.
indicated. 13C{ H} (125.8 MHz) NMR spectra were obtained on
1
a Bruker DPX500 spectrometer and are referenced to tetram-
ethylsilane (d = 0 ppm). Infrared spectra were recorded either in
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solution or as Nujol Mulls on a Nicolet 510 FT-IR spectropho-
tometer. Accurate mass spectra were recorded on a Waters LCT
Premier XE mass spectrometer, the protonated form of leucine
enkephalin C28H38N5O7 (MW 556.2271) was used as the lock
mass/internal standard. 4-phenyl-2,10-bis-(2,4-dimethylphenyl)-
4H-1,4-ethenophospholine (xPB) was prepared by the method of
Breit.4 All other chemicals were of reagent grade and used as
supplied unless otherwise stated. All new compounds have been
characterised by a combination of spectroscopic and high resolu-
tion mass spectrometry. Microanalyses were performed by Medac
Ltd UK. The accuracy of the analytical data was impaired by the
presence of a persistent non-phosphorus containing by-product
that was carried through from the ligand synthesis. Exhaustive
crystallisation and/or chromatography of the complexes did
remove much of this unwanted material and the resultant micro-
analytical data are somewhat outside the usual limits. In addition,
compounds 3 and 4 have been characterised crystallographically.
2H, Ar–H), 7.41 (d, 2H, J = 7.2 Hz, Ar–H), 7.48 (t, 2H, J =
7.4 Hz, Ar–H), 7.55 (d, 2H, J = 7.4 Hz, Ar–H), 7.79 (d, 2H, J =
19.3 Hz, CH3/5), 8.48 (b dd, 1H, JH–P = 9.25 Hz, CH-8) ppm.
1
13C{ H} NMR (CDCl3): d = 20.09 (s br, CH3), 60.75 (d, J =
10.1 Hz, C), 123.47 (d, J = 12.6 Hz, CH), 124.03 (s, CH), 126.86
(s, CH), 127.09 (s, CH), 127.44 (s, CH), 127.58 (s, CH), 128.01
(s, CH), 130.22 (s, CH), 132.02 (d, J = 12.6 Hz, CH), 137.62 (s,
CH), 138.32 (s, CH), 146.08 (br, C), 148.13 (br, C), 148.46 (br,
C), 148.63 (br, C), 150.63 (br, C), 151.14 (br, C), 178.29 (s br,
CO), 180.89 (d, J = 64.2 Hz, trans-CO), 182.31 (d, J = 13.8 Hz,
cis-CO) ppm. IR (hexane): 2109.8 (m, CO), 2023.9 (s, CO), 2005.6
(s, CO), 1922.7 (s, b, CO), 1261.2, 1096.3, 1014.4, 734.8 cm-1.
ES mass spectrum: (m/z) 755.1363 [M - Cl]+. Anal. calcd for
C37H29O4PClRe: C 56.23, H 3.71%. Found: C 54.9, H 3.4%.
(g5-Trimethylsilylcyclopentadienyl)[4-phenyl-2,10-bis-(2,4-
dimethylphenyl)-4H-1,4-ethenophospholine]-dicarbonyliron(II)
hexafluorophosphate, 3
[4-Phenyl-2,10-bis-(2,4-dimethylphenyl)-4H-1,4-
ethenophospholine]-pentacarbonyltungsten(0), 1
5
To a solution of (h -trimethylsilylcyclopentadienyl)(dicarbonyl)-
(acetonitrile)-iron(II) hexafluorophosphate (96 mg, 0.22 mmol) in
dichloromethane (10 mL) was added PB (0.1 g, 0.22 mmol) in
A solution of xPB (0.1 g, 0.22 mmol) in THF (5 mL) was added to a
solution of W(CO)5THF (70 mg, 0.22 mmol) in THF (10 mL) and
the reaction mixture stirred at room temperature for 18 h. After
removing the solvent in vacuo the crude material was washed with
cold 40 : 60 petroleum ether and the residue recrystallised from
x
dichloromethane (10 mL) and the reaction mixture stirred for
18 h. After removing the volatile materials in vacuo, the desired
compound was isolated from the solid residue by crystallisation via
vapour diffusion of diethyl ether into an ethanolic solution of the
1
40 : 60 petroleum ether to give 1 as a yellow solid. Yield = 0.15 g
crude product. Yield = 40 mg (21%). 31P{ H} NMR (202.5 MHz,
1
-
(87%). 31P{ H} NMR (202.5 MHz, CDCl3): d = -7.23 (s with 183
W
CDCl3): d = 10.59 (s), -144.17 (septet, JP–F = 713 Hz, PF6 ) ppm.
1
1
satellites, JP–W = 265 Hz) ppm. H NMR (400.8 MHz, CDCl3):
d = 2.21 (s, 12H, CH3), 6.52 (d, 1H, J = 7.7 Hz, Ar–H), 6.91 (m,
5H, Ar–H), 7.01 (t, 1H, J = 7.6 Hz, Ar–H), 7.16 (m, 2H, Ar–H),
7.39 (t, 1H, J = 7.3 Hz, Ar–H), 7.48 (t, 2H, J = 7.9 Hz, Ar–H),
7.56 (d, 2H, J = 7.5 Hz, Ar–H), 7.73 (d, 2H, J = 17.3 Hz, CH3/5),
1H NMR (500.1 MHz, CDCl3, 223 K): d = 0.15 (s, 9H, SiMe3),
2.16 (s, 6H, CH3), 2.31 (s, 6H, CH3), 4.07 (br, 2H, Cp–H), 4.37
(br, 2H, Cp–H), 6.62 (br, m, 1H, Ar–H), 6.89 (br, m, 1H, Ar–H),
7.10 (br, m, 8H, Ar–H), 7.60 (br, m, 6H, Ar–H), 8.00 (br, m,
1H, Ar–H) ppm. 13C{ H} NMR (125.8 MHz, CDCl3): d = 1.04
1
7.97 (dd, 1H, JH–H = 4.0 Hz, JH–P = 12.0 Hz, CH-8) ppm. 13C{ H}
(s, SiMe3), 20.92 (s, CH3), 21.02 (s, CH3), 21.13 (s, CH3), 21.15 (s,
CH3), 65.90 (s, C, Cp), 71.10 (s, CH, Cp), 72.80 (s, CH, Cp), 123.93
(s, CH), 124.07 (s, C), 126.46 (s, CH), 126.61 (s, CH), 127.46 (s,
CH), 128.93 (s, CH), 129.01 (s, CH), 129.28 (s, CH), 131.01 (s,
CH), 131.17 (s, CH), 135.25 (s, C), 136.38 (s, C), 136.98 (s, C),
138.17 (s, C), 149.68 (d, J = 4.0 Hz, C), 150.91 (br, CH) ppm.
IR (dichloromethane): 2054.8 (CO), 2013.3 (CO), 1261.2, 1095.4,
1019.2, 734.8 cm-1. ES mass spectrum: (m/z) 705.2022 [M]+. Anal.
calcd for C43H42O2P2SiF6Fe: C 60.70, H 4.99%. Found: C 60.4,
H 4.9%.
1
NMR (125.8 MHz, CDCl3): d = 21.13 (s, CH3), 61.79 (d, J =
8.8 Hz, C), 124.66 (d, J = 12.6 Hz, CH), 124.86 (d, J = 3.8 Hz,
CH), 126.30 (s, C), 126.44 (s, CH), 127.70 (s, CH), 127.97 (s, CH),
128.70 (s, CH), 128.86 (s, C), 129.02 (s, CH), 129.23 (s, CH), 131.02
(s, CH), 131.16 (s, CH), 131.53 (d, J = 18.9 Hz, CH), 134.90 (d,
J = 13.8 Hz, C), 136.09 (s, C), 138.32 (s, C), 139.86 (s, C), 150.23
(s, C), 191.15 (d, J = 62.9 Hz, trans-CO), 194.88 (d, J = 7.5 Hz,
cis-CO) ppm. IR (hexane): 2073.9 (w, CO), 1985.7 (w, CO), 1941.6
(s, CO), 1261.0, 1099.1, 1016.4, 858.0, 739.7 cm-1. Anal. calcd for
C38H29O5PW: C 58.47, H 3.75%. Found: C 57.5, H 3.5%.
(g6-Cymene)[4-phenyl-2,10-bis-(2,4-dimethylphenyl)-4H-1,4-
[4-Phenyl-2,10-bis-(2,4-dimethylphenyl)-4H-1,4-
ethenophospholine](dichloro)ruthenium(II), 4
ethenophospholine]-tetracarbonyl(chloro)-rhenium(I), 2
6
To
a
solution of bis(h -cymene)tetrachlorodiruthenium(II)
To
a
solution of chloropentacarbonyl-rhenium(I) (80 mg,
(134 mg, 0.22 mmol) in dichloromethane (10 mL) was added xPB
(0.2 g, 0.44 mmol) in dichloromethane (10 mL) and the reaction
mixture allowed to stir at room temperature for 18 h. Subsequently,
the solution was evaporated to dryness in vacuo, washed with
40 : 60 petroleum ether and the resulting yellow solid crystallised
0.22 mmol) in dichloromethane (10 mL) was added the
phosphabarrelene (0.1 g, 0.22 mmol) in dichloromethane (10 mL)
and the reaction mixture subsequently refluxed for 18 h. After
cooling the volatile materials were removed in vacuo and the
desired compound extracted into 40 : 60 petroleum ether (20 mL).
After filtering, the desired complex was precipitated as a yellow
from dichloromethane–methanol. Yield = 0.25 g (74%). 31P{ H}
1
NMR (121.7 MHz, CDCl3, 353 K): d = -5.46 (s) ppm. 1H
NMR (500.1 MHz, CDCl3): d = 1.01 (s, 3H, CH3), 1.16 (d, 3H,
J = 6.7 Hz, CH3), 1.21 (d, 3H, J = 6.8 Hz, CH3), 2.08 (s, 3H,
CH3), 2.24 (s, 6H, CH3), 2.85 (septet, 1H, J = 6.9 Hz, CH), 5.26
(d, 2H, J = 5.9 Hz, CH), 5.40 (d, 2H, J = 6.0 Hz, CH), 6.34 (d,
solid upon cooling. Yield = 83 mg (48%). 31P{ H} NMR
1
(121.7 MHz, CDCl3): d = -21.90 (s) ppm. 1H NMR (500.1 MHz,
CDCl3): d = 2.21 (s, 12H, CH3), 6.52 (d, 1H, J = 8.0 Hz, Ar–H),
6.91 (m, 3H, Ar–H), 7.00 (t, 2H, J = 7.6 Hz, Ar–H), 7.13 (m,
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1H, J = 6.5 Hz, Ar–H), 6.82 (t, 1H, J = 6.5 Hz, Ar–H), 6.93
(m, 6H, Ar–H), 7.37 (t, 2H, J = 7.1 Hz, Ar–H), 7.45 (t, 2H, J =
7.6 Hz, Ar–H), 7.53 (d, 2H, J = Ar–H), 7.69 (d, 2H, J = 17.5 Hz,
CDCl3): d = 21.19 (s, CH3), 21.44 (s, CH3), 28.45 (s, CH2), 33.58
(s, CH2), 52.51 (s, CH), 60.98 (d, J = 11.3 Hz, C), 93.60 (d, J =
15.1 Hz, CH), 124.02 (d, J = 12.6 Hz, CH), 124.85 (d, J = 1.3 Hz,
CH), 126.13 (s, CH), 127.14 (s, CH), 127.83 (s, CH), 128.68 (s,
CH), 129.15 (s, CH), 129.60 (d, J = 5.0 Hz, CH), 130.47 (s, CH),
132.71 (s, C), 133.85 (d, J = 16.4 Hz, CH), 135.75 (d, J = 3.8 Hz,
C), 136.03 (d, J = 12.6 Hz, C), 137.43 (t, J = 15.1 Hz, C), 140.14
(s, C), 149.51 (d, J = 26.4 Hz, C2/6), 152.28 (d, J = 2.5 Hz,
CH), 153.31 (d, J = 3.8 Hz, C) ppm. IR (hexane): 1260.3, 1091.9,
1019.0, 803.3, 722.2 cm-1. ES mass spectrum: (m/z) 798.2815
[M - Cl + CH3CN]+. Anal. calcd for C41H41PClIr: C 62.14,
H 5.23%. Found: C 61.8, H 5.3%.
1
CH3/5), 8.85 (s, 1H, Ar–H) ppm. 13C{ H} NMR (125.8 MHz,
CDCl3): d = 19.25 (s, CH3), 21.27 (s, CH3), 21.52 (s, CH3), 22.30
(s, CH3), 30.69 (s, CH3), 60.64 (s, C), 80.77 (s, CH), 81.48 (s, CH),
96.82 (s, C), 101.25 (s, C), 123.35 (d, J = 10.1 Hz, CH), 123.60
(s, CH), 126.13 (s, CH), 126.68 (s, CH), 127.81 (s, CH), 128.69 (s,
CH), 129.12 (s, CH), 130.90 (s, CH), 135.82 (s, C), 136.88 (s, CH),
137.60 (s, C), 140.18 (s, C), 151.10 (s, C), 153.56 (s, CH) ppm.
IR (Nujol): 1260.3, 1093.4, 1027.9, 806.1, 724.1 cm-1. ES mass
spectrum: (m/z) 768.2087 [M - Cl + CH3CN]+. Anal. calcd for
C43H43PCl2Ru: C 67.70, H 5.69%. Found: C 66.4, H 5.4%.
cis-Di[4-phenyl-2,10-bis-(2,4-dimethylphenyl)-4H-
1,4-ethenophospholine]dichloroplatinum(II), 7
(1,5-Cyclooctadiene)[4-phenyl-2,10-bis-(2,4-dimethylphenyl)-4H-
1,4-ethenophospholine]chloro-rhodium(I), 5
To a solution of bis-(benzonitrile)dichloroplatinum(II) (0.10 g, 0.
22 mmol) in dichloromethane (10 mL) was added xPB (0.2 g,
0.44 mmol) and the reaction mixture stirred for 18 h. After
evaporation of volatile materials in vacuo, the resulting yellow
material was recrystallised from THF to yield 7 as a white solid.
Yield = 0.13 g (57%). 31P NMR (121.7 MHz, CDCl3): d = -27.78
(s with 195Pt satellites, 1JP–Pt = 3860 Hz) ppm. 1H NMR (CDCl3):
d = 1.97 (s, 12H, CH3), 2.24 (s, 12H, CH3), 6.46 (d, 2H, J = 7.2 Hz,
Ar–H), 6.73 (d, 4H, J = 7.4 Hz, Ar–H), 6.82 (m, 4H, Ar–H), 6.97
(m, 8H, Ar–H), 7.29 (d, 4H, J = 7.3 Hz, Ar–H), 7.40 (m, 10H,
To a solution of [Rh(1,5-COD)Cl]2 (0.15 mg, 0.22 mmol) in
dichloromethane (10 mL) was added PB (0.2 g, 0.44 mmol) in
x
dichloromethane (10 mL) and the reaction mixture stirred for
18 h. After removal of all volatile materials in vacuo, the resulting
yellow solid was washed with cold 40 : 60 petroleum ether. The
desired compound was obtained as a bright yellow solid upon
crystallisation from 40 : 60 petroleum ether. Yield = 70 mg (40%).
1
31P{ H} NMR (202.5 MHz, CDCl3): d = -17.52 (d, JP–Rh = 160.8
Hz) ppm. 1H NMR (500.1 MHz, CDCl3): d = 1.66 (m, 4H, CH2),
2.12 (s, 6H, CH3), 2.23 (s, 6H, CH3), 2.41 (m, 4H, CH2), 3.27 (s,
2H, CH), 5.13 (s, 2H, CH), 6.39 (d, 1H, J = 7.8 Hz, Ar–H), 6.95
(m, 3H, Ar–H), 7.06 (dt, 1H, J = 7.3 Hz, 2.1 Hz, Ar–H), 7.18
(m, 3H, Ar–H), 7.38 (m, 2H, Ar–H), 7.46 (t, 2H, J = 8.0 Hz,
Ar–H), 7.54 (d, 2H, J = 7.7 Hz, Ar–H), 7.58 (d, 2H, J = 16.3 Hz,
1
Ar–H), 8.60 (dd, 2H, J = 12.1 Hz, 7.5 Hz, CH-8) ppm. 13C{ H}
NMR (125.8 MHz, CDCl3): d = 20.99 (s, CH3), 21.60 (s, CH3),
60.95 (d, J = 16.4 Hz, C), 124.26 (d, J = 5.0 Hz, CH), 124.58
(d, J = 12.6 Hz, CH), 126.80 (s, CH), 128.49 (s, CH), 128.83
(s, CH), 129.13 (s, C), 129.31 (s, CH), 131.05 (s, CH), 132.97 (s,
CH), 134.38 (s, C), 134.47 (s, CH), 135.32 (s, CH), 135.93 (s, C),
138.30 (s, C), 139.16 (s, C), 147.21 (d, J = 37.7 Hz, C2/6), 151.46
(s, C), 152.61 (s, CH) ppm. IR (Nujol): 1260.3, 1096.3, 1022.1,
806.1, 761.7, 701.0 cm-1. Anal. calcd for C66H58P2Cl2Pt: C 67.22,
H 4.97%. Found: C 66.1, H 4.6%.
1
CH3/5), 8.77 (dd, 1H, J = 9.7 Hz, 7.8 Hz, CH-8) ppm. 13C{ H}
NMR (125.8 MHz, CDCl3): d = 21.18 (s, CH3), 21.40 (s, CH3),
28.03 (s, CH2), 32.67 (s, CH2), 43.48 (s, CH), 69.24 (d, J = 12.6 Hz,
C), 103.99 (d, J = 12.6 Hz, CH), 123.96 (s, CH), 124.03 (s, CH),
126.25 (s, CH), 127.06 (s, CH), 127.77 (s, CH), 128.69 (s, CH),
129.12 (s, CH), 129.62 (d, J = 5.0 Hz, CH), 130.56 (s, CH), 131.21
(s, C), 134.32 (d, J = 18.9 Hz, CH), 135.59 (s, C), 136.19 (d, J =
13.8 Hz, C), 137.47 (s, C), 140.24 (s, C), 149.59 (d, J = 18.9 Hz,
C2/6), 151.81 (d, J = 3.8 Hz, CH), 152.50 (s, C) ppm. IR (hexane):
1260.6, 1096.9, 1020.1, 801.8, 722.3 cm-1. ES mass spectrum: (m/z)
708.2251 [M - Cl + CH3CN]+. Anal. calcd for C41H41PClRh: C
70.03, H 5.89%. Found: C 69.0, H 5.5%.
Crystallography
All single-crystal X-ray data was collected at 150 K on
a Bruker/Nonius Kappa CCD diffractometer using graphite
˚
monochromated MoKa radiation (l = 0.71073 A), equipped
with an Oxford Cryostream cooling apparatus. The data was
corrected for Lorentz and polarization effects and for absorption
using SORTAV.26 Structure solution was achieved by Patterson
methods (Dirdiff-99 program system27) and refined by full-matrix
least-squares on F2 (SHELXL-9728) with all non-hydrogen atoms
assigned anisotropic displacement parameters. Hydrogen atoms
attached to carbon atoms were placed in idealised positions
and allowed to ride on the relevant carbon atom. In the final
cycles of refinement, a weighting scheme that gave a relatively flat
analysis of variance was introduced and refinement continued until
convergence was reached. Molecular structures in the figures were
drawn with Ortep 3.0 for Windows (version 1.08).29 Data collection
and refinement parameters: Compound 3: C43H42FeO2PSi·PF6,
(1,5-Cyclooctadiene)[4-phenyl-2,10-bis-(2,4-dimethylphenyl)-4H-
1,4-ethenophospholine]chloroiridium(I), 6
The Ir complex, 6, was synthesised as for the rhodium complex
above using [Ir(1,5-COD)Cl]2 (0.15 mg, 0.22 mmol) and xPB (0.2 g,
0.44 mmol) in dichloromethane (20 mL). The desired compound
was isolated as a yellow solid. Yield = 70 mg (40%). 31P NMR
(202.5 MHz, CDCl3): d = -24.09 (s) ppm. 1H NMR (500.1 MHz,
CDCl3): d = 1.21 (m, 4H, CH2), 1.52 (m, 4H, CH2), 2.09 (s, 6H,
CH3), 2.22 (s, 6H, CH3), 2.93 (dd, 2H, J = 6.6 Hz, 3.4 Hz, CH),
4.73 (m, 2H, CH), 6.42 (d, 1H, J = 7.6 Hz, Ar–H), 6.92 (m,
4H, Ar–H), 7.10 (d, 2H, J = 7.6 Hz, Ar–H), 7.37 (t, 2H, J =
7.2 Hz, Ar–H), 7.45 (t, 3H, J = 7.5 Hz, Ar–H), 7.53 (d, 2H, J =
7.8 Hz, Ar–H), 7.63 (d, 2H, J = 18.3 Hz, CH3/5), 8.76 (dd, 1H,
-1
˚
FW = 850.65 g mol , T = 150(2) K, l = 0.71073 A, orthorhombic,
˚
˚
˚
Pna21, a = 17.285(4) A, b = 18.104(4) A, c = 12.811(3) A, V =
3
-3
˚
4008.8(14) A , Z = 4, r(calcd) = 1.409 Mg m , crystal size =
J = 10.5 Hz, 7.3 Hz, CH-8) ppm. 13C{ H} NMR (125.8 MHz,
0.25 ¥ 0.22 ¥ 0.20 mm3, reflections collected = 21 094, independent
1
2176 | Dalton Trans., 2009, 2170–2177
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The Royal Society of Chemistry 2009
©

View Article Online
reflections = 7708, R(int) = 0.045, Parameters = 504, R1 [I>2
s (I)] = 0.053, wR2 [I>2 s (I)] = 0.13, R1 (all data) = 0.066,
wR2 (all data) = 0.13, Flack parameter = 0.01(2). Compound 4:
C43H43Cl2PRu·0.5(CH2Cl2), FW = 805.18 g mol-1, T = 150(2) K,
4 B. Breit and E. Fuchs, Chem. Commun., 2004, 694; E. Fuchs, M. Keller
and B. Breit, Chem.–Eur. J., 2006, 12, 6930.
5 B. Breit and E. Fuchs, Synthesis, 2006, 13, 2121.
6 B. Breit, R. Winde, T. Mackewitz, R. Paciello and K. Harms,
Chem.–Eur. J., 2001, 7, 3106.
7 C. Wallis, PhD Thesis, Cardiff University, 2007.
8 R. A. Baber, M. F. Haddow, A. J. Middleton, A. G. Orpen, P. G. Pringle,
A. Haynes, G. L. Williams and R. Papp, Organometallics, 2007, 26,
713.
9 R. J. Angelici and M. D. Malone, Inorg. Chem., 1967, 6, 1731; S. O.
Grim, D. A. Wheatland and W. McFarlane, J. Am. Chem. Soc., 1967,
89, 5573; R. L. Keiter and J. G. Verkade, Inorg. Chem., 1969, 8, 2115;
J. G. Verkade, Coord. Chem. Rev., 1972, 9, 1; C. A. Tolman;, Chem.
Rev., 1977, 77, 313.
¯
˚
˚
˚
l = 0.71073 A, triclinic, P1, a = 10.238(2) A, b = 13.693(3) A,
◦
◦
◦
˚
c = 16.451(3) A, a = 107.20(3) , b = 103.59(3) , g = 106.38(3) ,
3
-3
˚
V = 1982.2(7) A , Z = 2, r(calcd) = 1.349 Mg m , crystal size =
0.35 ¥ 0.25 ¥ 0.15 mm3, reflections collected = 13 631, independent
reflections = 7520, Rint = 0.035, parameters = 458, R1 [I > 2s(I)] =
0.053, wR2 [I > 2s(I)] = 0.14, R1 (all data) = 0.067, wR2 (all
data) = 0.15.
10 S. O. Grim, P. R. McAllister and R. M. Singer, Chem. Commun., 1969,
38.
Conclusions
11 F. Zingales, U. Sartorelli, F. Canziani and M. Raveglia, Inorg. Chem.,
1966, 6, 154.
We have surveyed the coordination chemistry of 2,6-dixylyl-4-
phenylphosphabarrelene (xPB) with a number of transition metals,
hence extending the range of known phosphabarrelene-transition
metal complexes. We report for the first time a number of isolated
phosphabarrelene complexes ranging from group 6 to group
11. The coordination chemistry of the phosphabarrelene ligand
has been established, identifying it as electronically similar to
triarylphosphine analogues but sterically slightly less bulky; cone
angles have been established in two cases. Rotameric isomerism is
observed in a number of complexes and appears to be common.
12 P. E. Riley and R. E. Davies, Organometallics, 1983, 2, 286.
13 U. B. Eke, Y. H. Liao, Y. S. Wen and L. K. Lu, J. Chin. Chem. Soc.
(Taipei), 2000, 47, 109.
14 T. E. Miller and D. M. Mingos, Transition Met. Chem., 1995, 20, 533.
15 Y. T. Fu, P. C. Chao and L. K. Liu, Organometallics, 1998, 17, 221.
16 A. Hafner, A. Muhlebach and P. A. van der Schaaf, Angew. Chem., Int.
Ed., 1997, 36, 2121.
17 E. Hodson and S. J. Simpson, Polyhedron, 2004, 23, 2695.
18 O. Niyomura, T. Iwasawa, N. Sawada, M. Tokunaga, Y. Obora and Y.
Tsuji, Organometallics, 2005, 24, 3468.
19 E. Matern, J. Pikies and G. fritz, Z. Anorg. Allg. Chem., 2000, 626, 2136.
20 F. Ramos-Lima, A. Quiroga, J. Perez, M. Font-Bardia, X. Solano and
C. Navarro, Eur. J. Inorg. Chem., 2003, 1591.
21 P. B. Hitchcock, B. Jacobson and A. Pidcock, J. Chem. Soc., Dalton
Trans., 1977, 2038.
Acknowledgements
22 G. G. Mather, A. Pidcock and G. J. N. Rapsey, J. Chem. Soc., Dalton
Trans., 1973, 2095.
We would like to thank EPSRC and Sasol Technology (UK)
Ltd. for funding (C. W.) and the EPSRC for support for NMR
spectroscopy and mass spectrometry facilities. We are very grateful
to Dr R. L. Jenkins and Mr R. Hicks for help in collecting
spectroscopic data.
23 S. O. Grim, R. L. Keiter and W. McFarlane, Inorg. Chem., 1967, 6,
1133.
24 Q.-B. Bao, S. J. Geib, A. L. Rheingold and T. B. Brill, Inorg. Chem.,
1987, 26, 3453.
25 C. J. Cobley and P. G. Pringle, Inorg. Chim. Acta, 1997, 265, 107.
26 R. H. Blessing, Acta Crystallogr., Sect. A: Found. Crystallogr., 1995,
51, 33.
27 P. T. Beurskens, G. Beurskens, R. de Gelder, S. Garcia-Granda, R. O.
Gould, R. Israel and J. M. M. Smits, Crystallography Laboratory,
University of Nijmegen, The Netherlands, 1999.
28 G. M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal
Structures, University of Go¨ttingen, Germany, 1997.
29 L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565.
Notes and references
1 G. Markl and F. Lieb, J. Chem. Soc., Chem. Commun., 1971, 1249.
2 B. Breit and E. Fuchs, Chem. Commun., 2004, 694.
3 O. Piechaszyk, M. Doux, L. Ricard, Y. Jean and P. Le Floch,
Organometallics, 2005, 24, 1204.
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 2170–2177 | 2177
©