Tungsten(0) and rhodium(I) complexes of a series of 2-(2′-halo) triarylphosphinines

Article abstract of DOI:10.1039/b816507f

A series of halo substituted triarylphosphinines have been synthesised and coordinated to tungsten(0) and rhodium(I) to give [(2-(2′-halo)- triarylphosphinine)W(CO)₅] and [(2-(2′-halo)- triarylphosphinine)Rh(COD)Cl] respectively. The complexes

Full text of DOI:10.1039/b816507f

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PAPER
www.rsc.org/dalton | Dalton Transactions
Tungsten(0) and rhodium(I) complexes of a series of
2-(2¢-halo)triarylphosphinines
Christopher Wallis,a David McGuinness,b Paul D. Newman,a Robert P. Toozeb and Peter G. Edwards*a
Received 22nd September 2008, Accepted 25th November 2008
First published as an Advance Article on the web 6th February 2009
DOI: 10.1039/b816507f
A series of halo substituted triarylphosphinines have been synthesised and coordinated to tungsten(0)
and rhodium(I) to give [(2-(2¢-halo)-triarylphosphinine)W(CO)5] and [(2-(2¢-halo)-
triarylphosphinine)Rh(COD)Cl] respectively. The complexes have been examined by NMR and IR
spectroscopy in an effort to elucidate the nature of the bonding between the phosphinines and the
respective metal centre. The W(CO)5(L) systems reveal restricted C–C bond rotation as evidenced by
1
temperature-dependent 31P{ H} NMR spectra. Thermodynamic barriers to the rotation are dependent
upon the nature of the halide with DG‡ values of 72.5 kJ mol-1 and 50.8 kJ mol-1 being obtained for the
chloro- and fluoro-derivatives, respectively; activation barriers for the iodo- and bromo- derivatives
were beyond the accessible temperature range of the NMR experiment.
have not appeared. As part of our interest in heterocyclic and
Introduction
macrocyclic phosphorus donors we sought a route to 2,2¢-dihalo-
Over the last few years the synthesis, coordination chemistry
substituted arylphosphinines for two main purposes. The first
and catalytic properties of phosphinines have been investigated
was to study their basic coordination properties in order to
by various groups.1 These broad-ranging studies include the
establish whether such ligands behave in a similar manner to
development of new synthetic routes,2 through the preparation
the unsubstituted analogues and the second, longer-term aim,
of functionalised phosphinines,3 to the generation of phosphinine
was a view to developing further functionalised systems. The
anions.4 Intrinsic to all these investigations has been a desire to
current paper deals with aspects of the coordination chemistry of
evaluate the properties of the phosphinines in order to establish
the dihalo substituted arylphosphinines highlighting similarities
the nature of this donor type with regard to more traditional P-
and differences between the current ligands, their unsubstituted
donors such as phosphines and phosphites. A concise account of
analogues and phosphines in general.
phosphinine chemistry up to 2007 is given in the review by Mu¨ller
and Vogt.5 Reported phosphinines include SPS pincer ligands,6
Results and discussion
heterodonor phosphino-phosphinines,7 tripodal phosphinines8
and macrocycles.9 Most of these studies highlight the fact that
phosphinines behave as good p-acceptors but relatively poor
s-donors; this latter property relates to the contracted lone pair
which is the HOMO-2 in phosphinines.
Compounds 1–4 were synthesised via a variation of a literature
procedure.11 The series of halide substituted pyrylium salts, which
are reported here for the first time, were obtained as air- and
moisture-stable, bright yellow solids in yields ranging from 5%
to 89% (Scheme 1). The very low yield for the iodo derivative
(5%) is somewhat anomalous, but it is not known why the
The strong p-acceptor nature of the phosphinines has attracted
interest from groups concerned with homogeneous catalysis. In
the area of hydroformylation, for example, phosphinines have been
touted as replacements for p-acceptor ligands such as phosphites
which are known to be good for stabilizing the low oxidation
states of the metal during the catalytic cycle. Much of the impetus
for the investigation of these heterocyclic phosphines stems from
a desire to supplant phosphites and phosphonites (which are
prone to decomposition under catalytic conditions) with more
robust ligands that mimic or better the performance of the
P(OR)3/RP(OR¢)2 systems.10
Even though triarylphosphinines are relatively common (2,4,6-
triphenyl phosphinine being the most widely used), systems
containing other heteroatoms, particularly potentially reactive
groups such as halide that may allow further functionalisation
aSchool of Chemistry, Cardiff University, Park Place, Cardiff, UK CF10
3AT. E-mail: edwardspg@cardiff.ac.uk; Fax: +44 (0)29 20874030; Tel: +44
(0)29 20874023
bSasol Technology UK, Purdie Building, North Haugh, St Andrews, Fife,
UK KY16 9ST
Scheme 1
2178 | Dalton Trans., 2009, 2178–2184
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isolated yield was so low. The corresponding phosphinines 5–8
were synthesised using a methodology introduced by Maerkl12
and further developed by Breit to negate the use of phosphine
gas.10 Thus, compounds 5–8 were synthesised from their respective
pyrylium salt by reaction with 2 equivalents of P(SiMe3)3 in
refluxing dimethoxyethane in yields ranging from 27% to 63%.
The use of DME is preferred to the acetonitrile originally
used by Maerkl as cleaner reactions were observed with the
former solvent; only the phosphinine and, on occasion, unreacted
The electronic changes at the phosphorus centre induced upon
coordination are not only evident in the 31P NMR chemical shifts,
but also in the absolute value of the coupling constants in the 1H
1
and 13C{ H} NMR spectra. In particular, the protons of the C-3
and C-5 positions on the phosphinine ring experience a change in
the 2JH–P coupling constant from around 6 Hz to >17 Hz and the
1JC–P coupling constants to the C-2 and C-6 carbons adjacent to
the phosphorus atom decrease from around 52 Hz to 15 Hz upon
coordination.
tris(trimethylsilyl)phosphine were observed in the 31P{ H} NMR
An interesting feature of these complexes arises in the 31P NMR
spectra where for the chloro-, bromo- and iodo- derivatives, two
peaks of unequal intensity are observed at room temperature.
This observation is tentatively assigned to the presence of two
rotameric isomers resulting from restricted P–C bond rotation
as a consequence of the bulk of the halide: the fluoro-derivative,
1
spectra of the reaction mixtures after reflux. Excess P(SiMe3)3was
removed as PH3 after decomposition with methanol at room
temperature. The phosphinines were all characterised by NMR
spectroscopy and high resolution mass spectrometry, and are, to
the best of our knowledge, the first reported phosphinines of their
type. The compounds are orange solids that can be crystallised
as feathery ‘herring bone’ type crystals, that were unsuitable
for analysis by single-crystal X-ray crystallographic techniques.
1
9, shows only one peak in the 31P{ H} NMR spectrum at room
temperature (see later). The two possible rotamers are assigned
as cis and trans according to the relative orientation of the halo-
aryl groups. The two peaks observed at room temperature in the
1
1
Comparison of the 31P{ H}, 1H and 13C{ H} spectra for the
1
phosphinines 5–8 reveals little difference in the spectra across the
31P{ H} NMR spectrum of the chloro-derivative were observed to
series. The 31P{ H} chemical shifts lie in a narrow range from
coalesce upon heating to 388 K, enabling the activation energy
of 72.5 kJ mol-1 for this rotation barrier to be determined.
For the bromo-, and iodo- derivatives however, coalescence was
not observed upon heating to 110 ◦C indicating, as expected,
substantially higher rotation barriers for these bulkier analogues.
1
192.2 to 193.1 ppm and the 1H NMR spectra are dominated
by aromatic resonances which often overlap making individual
assignment difficult. The carbon atoms adjacent to the phosphorus
atom in the phosphinine ring show little change in either shift
or coupling constant across the halophosphinine series. The only
notable difference is in compound 5 were the C-2¢ carbon is clearly
distinguished by its coupling to the fluorine atom.
1
Variable temperature 31P{ H} NMR spectroscopic studies of the
fluoroarylphosphinine complex 9, which gives a singlet at room
temperature, revealed the presence of two signals for the two
rotamers at low temperature (258 K, Fig. 1). Upon warming
these two resonances coalesce allowing the activation barrier of
50.8 kJ mol-1 to be determined. The equilibrium constant between
rotamers did not appear to be temperature dependent as the ratios
of the peaks in the 31P spectra remained constant (approximately
1:2). It seems reasonable to suggest that the major rotamer is the
trans isomer, as this would provide the greater steric relief in the
complex. The presence of two rotamers, leads to broadening and
this coupled with extensive overlap of peaks in the aromatic region
of the 1H NMR spectra of the complexes makes unequivocal
assignment of the peaks difficult to the extent that full assignment
was not possible in all cases. Similar problems were encountered
Compounds 9–12 (Scheme 2) were made by reacting the
appropriate halo-arylphosphinine with W(CO)5THF (made in situ
by the photolysis of W(CO)6 in THF) at room temperature. The
resulting phosphinine–tungsten complexes, W(CO)5(L), were fully
characterised by NMR spectroscopy and high resolution mass
spectrometry. Unlike with the majority of tertiary phosphines, the
coordination induced shifts (DdP) are upfield for phosphinines, an
anomaly partly ascribed to the phosphorus atom being a sp2 centre
compared to sp3 in a typical tertiary phosphine. The chemical shifts
in the 31P NMR spectra of the tungsten–phosphinine complexes
(9–12) are similar to related complexes reported by Mathey and
co-workers,13 where upfield shifts are observed upon coordination
albeit to a lesser extent than those observed here. This is not
surprising as the phosphinines of Mathey are significantly different
to the current ligands.
1
in the 13C{ H} NMR spectra.
The IR spectra of the phosphinine–tungsten complexes gives
insight into the nature of the W–P bond as the carbonyl stretching
frequencies are sensitive to the electronic nature of the phosphinine
ligands. Table 1 compares the current complexes with other phos-
phorus based ligand complexes of pentacarbonyltungsten(0). As
can be seen from Table 1, the phosphinines are most closely similar
to alkyl and aryl phosphites on this basis and in agreement with
the observations of Kozlowski et al.16 Although there seems to be
no difference between the iodo-, bromo-, and chloro- derivatives,
there is a small increase in the stretching frequencies with the
fluoro- derivative indicating increased p-acceptor behaviour as
might be expected with the enhanced electronegativity of the
halide. The major and minor rotamers in compounds 10–12 appear
indistinguishable in the IR spectra, as only the three carbonyl
stretches expected for a M(CO)5(L) complex are observed. The
1JP–W coupling constants for all the tungsten complexes were
281 Hz (Table 2). This compares with the value of 280 Hz for
W(CO)5(PPh3),17 but is significantly smaller than that of 404 Hz
Scheme 2
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Fig. 1 Variable temperature NMR study of the 2-fluorophosphinine complex, 9.
Table 1 Carbonyl stretching frequencies for complexes 9–12 and related
systems
Table 2 Selected NMR data for 5–8 and their metal complexes
Phosphinine (L)
L
LW(CO)5
166.9
LRh(COD)Cl
n(CO) cm-1
5
dP
193.1
186.9
(184.3)
8.1
(21.5)
(160.0)
2
1
L
A1
A1
E
Ref.
(JP–Rh
)
dH3/5
8.1
(5.9)
165.3
(52.8)
-117.2
8.1
P(NMe2)3
PMe3
PPh3
P(OMe)3
12
11
9
9
2067
2069
2071
2079
2076
2076
2076
2077
2083
2101
1942
1949
1942
1962
1983
1983
1983
1981
1968
2006
1933
1939
1942
1948
1954
1954
1954
1959
1959
1998
14
14
15
15
(JH–P
)
(17.4)
160.9
(15.1)
-113.2
dC2/6
(JC–P
dF
)
-116.2
6
7
8
dP
192.7
164.9
187.5
(186.3)
8.1
(15.9)
(157.2)
dH3/5
(JH–P
8.0
7.9
P(OPh)3
P(CF3)3
14
15
)
(6.0)
168.9
(52.8)
(17.6)
164.6
15.2()
dC2/6
(JC–P
dP
)
192.2
165.0
187.3
(186.3)
7.5
(7.7)
(147.5)
observed in W(CO)5{P(OPh)3}.18 Thus this data would appear
to support the notion that the current phosphinines are closely
similar to PPh3 in their bonding properties and taking the NMR
and IR spectroscopic data into account, it is reasonable to suggest
that the s-donor/p-acceptor properties of these phosphinines lie
closer to those of PPh3 than P(OPh)3.
dH3/5
(JH–P
dC2/6
(JC–P
8.0
7.9
)
(6.0)
168.9
(52.7)
(17.6)
166.5
(8.8)
)
dP
192.2
7.9
(6.2)
173.7
(52.8)
164.9
7.9
(17.6)
170.1
(8.8)
—
dH3/5
(JH–P
dC2/6
(JC–P
)
Complexes 13–15 were synthesised by stirring the relevant phos-
phinine with [(1,5-COD)RhCl]2 in dichloromethane (Scheme 2).
)
The formation of a Rh complex was confirmed by 31P{ H} NMR
1
spectroscopy in which, in each case, a doublet with a coordination
chemical shift of around 10 ppm was observed. The phosphorus-
rhodium coupling of around 185 Hz lies between that observed for
the analogous (1,5-COD)RhCl(PPh3) complex (1JP–Rh = 152 Hz)19
barrier was observed by 31P{ H} NMR spectroscopy, presumably
due to the complexes being square planar in geometry with a lower
steric restriction to P–C rotation than in the W(CO)5(L) complexes
above. The complexes were characterised by NMR spectroscopy
with the characteristic reduction in coupling constants for the
protons in the C-3 and C-5 positions being observed in the
1
and that for the (1,5-COD)RhCl{P(OPh)3} complex (1JP–Rh
=
273 Hz).20 As alluded to above, this appears to suggest that the
phosphinines have donor properties that lie somewhere between
arylphosphines and arylphosphites. No evidence of a rotational
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1H NMR spectra as noted for the tungsten complexes above.
Mulls on a Nicolet 510 FT-IR spectrophotometer. Accurate mass
spectra were recorded on a Micromass Q-Tof mass spectrometer
calibrated with sodium formate and leucine encephalin as internal
standards.
1
Unfortunately, the 13C{ H} NMR spectra were not sufficiently
well resolved to allow unequivocal assignment of the C-2 and C-6
carbons and only tentative assignments are given in Table 2. The
numbering scheme for NMR assignments is given in Fig. 2.
2,6-Bis-(2¢-fluorophenyl)-4-tolylpyrylium tetrafluoroborate (1)
Powdered NaOH (1.4 g 36 mmol), 2¢-fluoroacetophenone (5 g,
36 mmol) and p-tolylaldehyde (2.2 g, 18 mmol) were mixed
together with a pestle and mortar for 25 min. The highly viscous
yellow mixture was dissolved in ether (100 ml) and water, the
organic phase was separated and washed with water (3 ¥ 50 ml)
then brine (3 ¥ 50 ml) and dried over MgSO4. After filtration the
solvent was removed in vacuo and the resultant crude “diketone”
used directly for the synthesis of the pyrylium salt. Thus, under an
argon atmosphere, a mixture of “diketone” (950 mg, 1.9 mmol),
chalcone (395 mg, 1.9 mmol) and BF3.OEt2 (7 ml) was stirred at
100 ◦C for 2 h, then cooled to room temperature and diluted with
Et2O (10 ml). After 12 h the yellow precipitate was filtered off and
washed thoroughly with Et2O to yield 2,6-bis-(2¢-fluorophenyl)-4-
tolylpyrylium tetrafluoroborate (1) as a yellow solid. Yield = 2.8 g
(34%). 1H-NMR {(CD3)2CO}: d = 2.50 (s, 3H, CH3), 7.3–7.4 (m,
2H, Ar-H), 7.51 (t, J = 7.5 Hz, 4H, Ar-H), 7.7- 7.8 (m, 2H, Ar-H),
8.2–8.3 (m, 2H, Ar-H), 8.01 (d, J = 8.4 Hz, 2H, Ar-H), 8.72 (s, 2H,
Fig. 2 NMR assignment numbering scheme.
An iodo-phosphinine derivative of the rhodium complex was
not obtained as upon addition of the phosphinine to the yel-
low rhodium dimer solution, the solution immediately turned
1
black. There was no evidence of the desired complex in the H
1
CH 3/5) ppm. 13C{ H}NMR (125.8 MHz; (CD3)2CO): d = 21.9,
1
NMR spectrum and the 31P{ H} NMR spectrum was silent.
117.2, 117.7, 117.8, 117.9, 126.4, 129.4, 129.8, 130.7, 131.5, 137.6,
137.7, 149.2, 167.3 ppm. 19F NMR (282.8 MHz, (CD3)2CO): d =
-153.1 ppm.
No identifiable products could be isolated. This may suggest
that the phosphinine underwent cyclometallation at the iodo-
(C-2¢) position. It is reasonable to propose that C-X oxidative
addition might be more facile for the iodo-phosphinine and
that this may provide a decomposition pathway. Furthermore,
similar behaviour was observed on attempting to coordinate
phosphinines 5–8 to a number of palladium(II) precursors. No
2,6-Bis-(2¢-chlorophenyl)-4-tolylpyrylium tetrafluoroborate (2)
The synthesis of 2 was identical to that of 1 except that
2¢-chloroacetophenone was used. The reaction yielded 2,6-bis-
(2¢-chlorophenyl)-4-tolypyrylium tetrafluoroborate (2) as a yellow
solid in 62% yield. 1H-NMR {(CD3)2CO}: d = 2.58 (s, 3H, CH3),
7.6–7.9 (m, 8H, Ar-H), 8.30 (dt, J = 6.5, 1.2 Hz, 2H, Ar-H), 8.47
1
discrete complexes could be obtained and 31P { H} NMR spectra
of the reaction mixtures were silent. No decomposition products
could be identified. Phosphinine–palladium(II) complexes are
known,21 although none have a carbon-halide bond in such an
accessible position to the metal as in the current ligands.
1
(d, J = 8.5 Hz, 2H, Ar-H), 9.15 (s, 2H, CH 3/5) ppm. 13C{ H}
NMR (125.8 MHz; (CD3)2CO): d = 21.9, 121.2, 129.3, 129.8,
130.6, 131.4, 132.1, 132.5, 134.0, 136.1, 149.6, 167.2, 171.7 ppm.
Experimental
2,6-Bis-(2¢-bromophenyl)-4-tolylpyrylium tetrafluoroborate (3)
All compounds were synthesised under nitrogen using standard
inert atmosphere (Schlenk) techniques. Compounds 1–4 were ob-
tained and handled as air- and moisture-stable solids. Compounds
5–12 were handled and stored as air- and moisture-sensitive solids
while complexes 13–15 were handled as air- and moisture-sensitive
compounds for manipulation but were found to be air-stable as
solids. All solvents were freshly distilled from sodium or calcium
hydride under nitrogen before use. Tris(trimethylsilyl)phosphine
was prepared according to a literature route.22 All other chemicals
were of reagent grade and used as supplied unless otherwise stated.
The synthesis of 3 was identical to that of 1 except us-
ing 2¢-bromoacetophenone. The reaction yielded 2,6-bis-
(2¢-bromophenyl)-4-tolylpyrylium tetrafluoroborate (3) as
a
1
yellow solid in 89% yield. H-NMR (CD2Cl2): d = 2.56 (s, 3H,
CH3), 7.5–7.7 (m, 6H, Ar-H), 7.8–7.9 (m, 2H, Ar-H), 7.9–8.1 (m,
1
4H, CH 3/5), 8.70 (s, 2H, Ar-H) ppm. 13C{ H} NMR (125.8 MHz;
CD2Cl2): d = 22.3, 120.1, 122.3, 129.3, 129.5, 130.4, 130.5, 131.9,
133.3, 135.2, 135.4, 149.9, 166.4, 171.9 ppm.
1
The 31P{ H} NMR spectra were recorded on Jeol Eclipse 300 and
2,6-Bis-(2¢-iodophenyl)-4-tolylpyrylium tetrafluoroborate (4)
Bruker DPX500 spectrometers operating at 121.7 and 202.5 MHz
respectively, and referenced to 85% H3PO4 (d = 0 ppm). 1H spectra
were obtained on a Bruker DPX400 spectrometer (400.8 MHz) or
a Bruker DPX500 NMR spectrometer (500.1 MHz) and refer-
The synthesis of 4 was identical to that of 1 except that
2¢-iodoacetophenone was used. The reaction yielded 2,6-bis-
(2¢-iodophenyl)-4-tolylpyrylium tetrafluoroborate (4) as a yellow
solid in 5% yield. 1H-NMR (CD2Cl2): d = 2.53 (s, 3H, CH3), 7.2–
7.4 (m, 8H, Ar-H), 7.48 (d, J = 8.2 Hz, 2H, Ar-H), 7.6–7.7 (m, 2H,
Ar-H), 7.89 (dd, J = 7.8, 1.5 Hz, 2H, Ar-H), 8.0–8.1 (m, 2H, Ar-H),
1
enced to tetramethylsilane at dH = 0 ppm. 13C{ H} (125.8 MHz)
NMR spectra were obtained on a Bruker DPX500 spectrometer
and are referenced to tetramethylsilane (d = 0 ppm). Infrared
spectra were recorded either as a solution cell or as Nujol
1
8.51 (s, 2H, CH 3/5) ppm. 13C{ H} NMR (125.8 MHz; CD2Cl2):
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d = 22.4, 120.3, 129.7, 129.9, 130.6, 132.0, 133.0, 134.5, 135.1,
2,6-Bis-(2¢-iodophenyl)-4-tolylphosphinine (8)
141.9, 150.1, 166.2, 173.9 ppm.
Synthesis of 8 was the same as that of 5 except that 4 was used
as the pyrylium salt. The reaction gave 2,6-bis-(2¢-iodophenyl)-
2,6-Bis-(2¢-fluorophenyl)-4-tolylphosphinine (5)
4-tolylphosphinine (8) as an orange solid in 63% yield. 31P{ H}
1
1
NMR (202.5 MHz, CDCl3): d = 192.2 ppm. H NMR (CDCl3):
Tris(trimethylsilyl)phosphine (0.84 g, 3.35 mmol, 1.2 equiv.) was
added to a slurry of 1 (1.3 g, 2.79 mmol) in DME (40 ml) and the
resulting mixture refluxed for 16 h during which time the pyrylium
salt dissolved. The DME was then removed in vacuo to yield a
brown residue. The residue was dissolved in diethyl ether (20 ml),
filtered through a pad of neutral aluminium using a further 30 ml
of diethyl ether to complete elution of the desired product. The
solution was pumped to dryness to yield an orange residue which
was crystallised from 40/60 petroleum ether to give 2,6-bis-(2¢-
fluorophenyl)-4-tolylphosphinine (5) as an orange solid. Yield =
d = 2.28 (s, 3H, CH3), 6.95 (t, J = 7.6 Hz, 2H), 7.19 (d, J =
7.9 Hz, 2H), 7.2–7.4 (m, 4H), 7.52 (d, J = 8.1 Hz, 2H), 7.90 (d,
1
J = 6.2 Hz, 2H, CH 3/5) ppm. 13C{ H} NMR (CDCl3): d = 20.1
(s, CH3), 127.6 (s, CH), 128.0 (s, CH), 128.4 (d, J = 16.4 Hz, CH),
129.3 (d, J = 12.6 Hz, CH), 129.8 (s, CH), 130.4 (s, C), 134.0 (d,
J = 11.3 Hz, CH), 138.0 (s, C), 138.8 (s, C), 139.7 (d, J = 3.8 Hz,
CH), 140.5 (s, C), 147.5 (d, J = 22.6 Hz, C), 173.7 (d, J = 52.8 Hz,
C 2/6) ppm. IR (Nujol) cm-1: 1260.1; 1091.9; 1019.7; 800.9. Mass
Spec. (m/z): 590.9257; Calc Mass 590.9236.
1
0.7 g (56%.). 31P{ H} NMR (202.5 MHz, CDCl3): d = 193.1 ppm.
1H NMR (CDCl3): d = 2.29 (s, 3H, CH3), 7.0–7.2 (m, 6H), 7.23
(m, 2H), 7.42–7.45 (m, 4H), 8.09 (dd, J = 5.9 Hz, 1.5 Hz, 2H, CH
[2,6-Bis-(2¢-fluorophenyl)-4-tolylphosphinine]-
pentacarbonyltungsten(0) (9)
1
3/5) ppm. 13C{ H} NMR (CDCl3): d = 21.3 (s, CH3), 116.3 (d,
A solution of 5 (0.1 g, 0.27 mmol) in THF was added at room
temperature to a solution of W(CO)5THF (90 mg, 0.27 mmol)
in THF. The reaction mixture was stirred at room temperature
for 18 h, after which the solution was pumped to dryness. The
crude material was washed with 40/60 petroleum ether and the
resulting material was recrystallised from 40/60 petroleum ether to
give [2,6-bis-(2¢-fluorophenyl)-4-tolylphosphinine]pentacarbonyl
J = 22.6 Hz, CH), 124.5 (s, CH), 127.8 (d, J = 18.9 Hz, CH), 129.1
(s, CH), 129.8 (s, CH), 130.9 (dd, J = 0.2, 0.1 Hz, C), 131.7 (dd,
J = 13.2, 1.3 Hz, CH), 134.0 (dd, J = 46.5, 2.5 Hz, CH), 138.1 (s,
C), 138.9 (d, J = 2.5 Hz, C), 143.1 (d, J = 13.8 Hz, C), 159.1 (dd,
19
J = 246.6, 5.0 Hz, C-2¢), 165.3 (d, J = 52.8 Hz, C 2/6) ppm.
F NMR (282.2 MHz, CDCl3): d = -117.3 (d, J = 13.9 Hz) ppm.
IR (Nujol) cm-1: 1259.8; 1100.5; 1021.6; 802.6; 745.5. Mass Spec.
(m/z): Obs. Mass 375.1119; Calc. Mass 375.1114.
tungsten(0), 9, as an orange solid. Yield = 0.12 g (67%). 31P{ H}
1
NMR (202.5 MHz, CDCl3): d = 166.9 (s, 1JP–W = 280.8 Hz) ppm.
1H NMR (CDCl3): d = 2.31 (s, 3H, CH3), 7.1–7.2 (m, 6H), 7.3–7.4
2,6-Bis-(2¢-chlorophenyl)-4-tolylphosphinine (6)
(m, 6H), 7.98 (d, J = 17.4 Hz, 2H, CH 3/5) ppm. 13C{ H} NMR
1
(CDCl3): d = 21.3 (s, CH3), 116.3 (d, J = 21.4 Hz, CH), 124.4
(s, CH), 127.3 (s, CH), 129.0 (t, J = 15.1 Hz, C), 129.9 (s, CH),
130.8 (d, J = 8.8 Hz, C), 132.6 (d, J = 7.5 Hz, CH), 137.2 (d, J =
12.6 Hz, CH), 137.6 (d, J = 5.0 Hz, C), 138.4 (s, C), 140.3 (d, J =
22.6 Hz, C), 159.4 (dd, J = 240.3, 7.5 Hz, C-2¢), 160.9 (d, J =
15.1 Hz, C 2/6), 193.8 (d, J = 8.8 Hz, CO), 197.8 (d, J = 32.7 Hz,
CO) ppm. 19F NMR (282.2 MHz, CDCl3): d = -113.2 ppm. IR
(hexane) cm-1: 2077.0 (w, CO); 1980.7 (sh, CO); 1958.8 (st, CO);
1260.9; 1101.9; 1016.5; 809.1; 737.8. Mass Spec. (m/z): 643.0149;
Synthesis of 6 was the same as that of 5 except that 2 was used as
the pyrylium salt. The reaction gave 2,6-bis-(2¢-chlorophenyl)-4-
1
tolylphosphinine 6 as an orange solid in 43% yield. 31P{ H} NMR
(202.5 MHz, CDCl3): d = 192.7 ppm. 1H NMR (CDCl3): d = 2.30
(s, 3H, CH3), 7.0–7.2 (m, 6H), 7.4–7.5 (m, 6 H), 8.02 (d, 2H, J =
1
6.0 Hz, CH 3/5) ppm. 13C{ H} NMR (CDCl3): d = 21.2 (s, CH3),
127.0 (s, CH), 128.1 (s, CH), 129.4 (s, CH), 129.8 (d, J = 10.1 Hz,
CH), 130.2 (s, CH), 132.1 (d, J = 10.1 Hz, CH), 132.4 (d, J =
6.3 Hz, C), 134.1 (d, J = 11.3 Hz, CH), 141.6 (s, C), 141.7 (d,
J = 23.9 Hz, C), 142.1 (d, J = 13.8 Hz, C), 147.1 (s, C), 168.9 (d,
J = 52.8 Hz, C 2/6) ppm. IR (Nujol) cm-1: 1260.5; 1096.9; 1033.9;
801.9; 756.0. Mass Spec. (m/z): Obs Mass 407.0514; Calc. Mass
407.0523.
Calc Mass 643.0159 (M+ - 2CO); 614 (M+ - 3CO); 586 (M+
4CO); 558 (M+ - 5CO); 375 (L+).
-
[2,6-Bis-(2¢-chlorophenyl)-4-tolylphosphinine]
pentacarbonyltungsten(0) (10)
2,6-Bis-(2¢-bromophenyl)-4-tolylphosphinine (7)
Compound 10 was made by the same procedure as that
for complex except phosphinine was used. The re-
Synthesis of 7 was the same as that of 5 except that 3 was used
as the pyrylium salt. The reaction gave 2,6-bis-(2¢-bromophenyl)-
9
6
action gave [2,6-bis-(2¢-chlorophenyl)-4-tolylphosphinine]penta-
carbonyltungsten(0), 10, as an orange solid consisting of two
4-tolylphosphinine (7) as an orange solid in 27% yield. 31P{ H}
1
1
1
NMR (202.5 MHz, CDCl3): d = 192.2 ppm. H NMR (CDCl3):
rotamers. Yield = 0.12 g (65%). Major rotamer: 31P{ H} NMR
1
d = 2.33 (s, 3H, CH3), 7.1–7.2 (m, 2H), 7.33 (dt, J = 7.5, 0.8 Hz,
2H), 7.42 (d, J = 7.6 Hz, 2H), 7.53 (d, J = 8.1 Hz, 2H), 7.65 (dd,
J = 8.0, 0.7 Hz, 2H), 8.02 (d, J = 6.0 Hz, 2H, CH 3/5) ppm.
(202.5 MHz, CDCl3): d = 164.9 (s, JP–W = 280.9 Hz) ppm.
1H NMR (CDCl3): d = 2.28 (s, 3H, CH3), 7.13–7.16 (m, 4H), 7.27–
7.30 (m, 4H), 7.38–7.44 (m, 4H), 7.93 (d, J = 17.6 Hz, 2H, CH
1
1
13C{ H} NMR (CDCl3): d = 20.1 (s, CH3), 126.4 (s, CH), 126.5
3/5) ppm. 13C{ H} NMR (CDCl3): d = 21.23 (s, CH3), 126.90 (s,
(s, CH), 127.2 (s, CH), 128.1 (s, CH), 130.7 (d, J = 10.1 Hz, CH),
132.2 (s, CH), 132.9 (d, J = 11.3 Hz, CH), 136.9 (s, C), 137.6 (s,
C), 140.8 (d, J = 13.8 Hz, C), 142.5 (d, J = 22.6 Hz, C), 147.3 (s,
C), 168.9 (d, J = 52.7 Hz, C 2/6) ppm. IR (Nujol) cm-1: 1260.3;
1094.2; 1020.7; 801.3. Mass Spec. (m/z): Obs. Mass 495.9125; Calc
Mass 495.9119.
CH), 127.29 (s, CH), 129.91 (s, CH), 130.16 (d, J = 1.3 Hz, CH),
130.37 (s, CH), 132.74 (d, J = 7.5 Hz, CH), 133.67 (d, J = 8.8 Hz,
C), 137.08 (d, J = 11.3 Hz, CH), 137.64 (t, J = 6.3 Hz, C), 139.73
(d, J = 12.6 Hz, C), 143.41 (s, C), 147.06 (s, C), 164.62 (d, J =
15.1 Hz, C 2/6), 193.79 (d, J = 8.8 Hz, 1JC–W = 125.5 Hz, cis-CO),
197.74 (d, J = 32.7 Hz, trans-CO) ppm. IR (hexane) cm-1: 2076.4
2182 | Dalton Trans., 2009, 2178–2184
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(w, CO); 1983.1 (sh, CO); 1954.2 (st, CO); 1261.8; 1171.2; 1147.9;
[2,6-Bis-(2¢-fluorophenyl)-4-tolylphosphinine]-
chloro(COD)rhodium(I) (13)
1
815.5; 739.7. Minor rotamer (not all peaks were evident): 31P{ H}
NMR (202.5 MHz, CDCl3): d = 166.6 (s, 1JP–W = 280.9 Hz) ppm.
1H NMR (CDCl3): d = 2.25 (s, 3H, CH3), 7.13–7.16 (m, 4H),
7.27–7.30 (m, 4H), 7.38–7.44 (m, 4H), 7.90 (d, J = 17.5 Hz, 2H,
To
a solution of chloro(COD)rhodium(I) dimer (66 mg,
0.13 mmol) in DCM (10 ml) was added phosphinine 5 (0.1 g,
0.27 mmol) in DCM (10 ml). The reaction mixture was allowed
to stir at room temperature for 18 h and the solution pumped
to dryness. The resultant yellow solid was washed with cold
40/60 petroleum ether and recrystallised from 40/60 petroleum
ether to yield [2,6-bis-(2¢-fluorophenyl)-4-tolylphosphinine]-
chloro(COD)rhodium(I) (13) as a yellow solid. Yield = 0.11 g
1
CH 3/5) ppm. 13C{ H} NMR (CDCl3): d = 21.13 (s, CH3), 126.29
(s, CH), 127.03 (s, CH), 129.42 (s, CH), 129.69 (s, CH), 130.09 (s,
CH), 132.29 (d, J = 7.5 Hz, CH), 133.89 (d, J = 8.8 Hz, C), 191.20
(s, CO) ppm. Mass Spec. (m/z): Obs Mass 674.9567; Calc Mass
674.9554 (M+ - 2CO); 619 (M+ - 4CO); 590 (M+ - 5CO).
1
(67%). 31P{ H} NMR (202.5 MHz, CDCl3): d = 186.9 (d, J =
[2,6-Bis-(2¢-bromophenyl)-4-tolylphosphinine]-
pentacarbonyltungsten(0) (11)
184.3 Hz) ppm. 1H NMR (CDCl3): d 1.6–1.7 (m, 4H, COD-
aliphatic), 2.04 (m, 4H, COD-aliphatic), 2.33 (s, 3H, CH3), 3.35
(s, 2H, COD-olefin), 5.42 (s, 2H, COD-olefin), 6.96–7.11 (m, 4H,
Ar-H), 7.36 (m, 2H, Ar-H), 7.42 (m, 4H, Ar-H), 8.13 (d, J =
Compound 11 was made by the same procedure as that for com-
plex 9 except phosphinine 7 was used. The reaction gave [2,6-bis-
(2¢-bromophenyl)-4-tolylphosphinine]pentacarbonyl-tungsten(0),
11, as an orange solid that consists of two rotamers. Yield = 0.1 g
14.2 Hz, 2H, CH 3/5), 8.24 (t, J = 7.1 Hz, 2H, Ar-H) ppm. 13C{ H}
1
NMR (CDCl3): d = 21.2 (s, CH3), 28.7 (s, COD-aliphatic), 33.0
(s, COD-aliphatic), 71.3 (d, J = 12.6 Hz, COD-olefin), 106.4 (s,
COD-olefin), 115.7 (d, J = 22.6 Hz, CH), 124.3 (s, CH), 127.3 (s,
C), 127.5 (s, CH), 128.0 (s, C), 129.8 (s, CH), 130.3 (s, CH), 133.3
(s, CH), 137.2 (s, C), 138.0 (s, CH), 158.1 (s, C), 160.0 (s, C) ppm.
19F NMR (282.8 MHz, CDCl3): d = -116.6 ppm. IR (Nujol) cm-1:
1260.1, 1091.9, 1020.9, 801.5.
1
(63%). Major rotamer: 31P{ H} NMR (121.7 MHz, CDCl3): d =
164.98 (s, 1JP–W = 280.8 Hz) ppm. 1H NMR (500.1 MHz, CDCl3):
d = 2.25 (s, 3H, CH3), 7.03–7.07 (m, 2H), 7.15 (t, J = 7.4 Hz, 2H),
7.21 (t, J = 8.4 Hz, 2H), 7.34 (t, J = 7.3 Hz, 2H), 7.41 (t, J =
8.4 Hz, 2H), 7.62 (t, J = 8.2 Hz, 2H), 7.92 (d, J = 17.6 Hz, 2H, CH
1
3/5) ppm. 13C{ H} NMR (CDCl3): d = 21.44 (s, CH3), 127.26 (s,
CH), 127.49 (s, CH), 128.25 (s, CH), 129.04 (s, CH), 129.89 (t, J =
5.0 Hz, CH), 132.57 (d, J = 8.8 Hz, CH), 137.13 (d, J = 12.5 Hz,
CH), 138.32 (s, C), 139.86 (s, C), 141.57 (d, J = 13.8 Hz, C),
143.36 (s, C), 148.52 (s, C), 166.52 (d, J = 8.8 Hz, C 2/6), 193.76
(d, J = 8.8 Hz, cis-CO), 197.74 (d, J = 32.7 Hz, trans-CO) ppm.
IR (hexane) cm-1: 2076.4 (w, CO); 1983.1 (sh, CO); 1954.2 (st,
CO); 1261.8; 1171.2; 1147.9; 815.5; 739.7. Minor rotamer (some
[2,6-Bis-(2¢-chlorophenyl)-4-tolylphosphinine]-
chloro(COD)rhodium(I) (14)
Complex 14 was synthesised by the same procedure as
13 to yield [2,6,-bis-(2¢-chlorophenyl)-4-tolylphosphinine]chloro-
(COD)rhodium(I) (14) as an orange-yellow solid. Yield = 98 mg
1
(61%). 31P{ H} NMR (202.5 MHz, CDCl3): d = 187.5 (d, J =
1
peaks could not be assigned because of overlap): 31P{ H} NMR
1
1
1
186.3 Hz) ppm. H NMR (500.1 MHz, CDCl3): d 1.71–1.73 (m,
(121.7 MHz, CDCl3): d = 167.21 (s, JP–W = 280.8 Hz) ppm. H
NMR (500.1 MHz, CDCl3): d = 2.28 (s, 3H, CH3), 7.62 (t, J =
4H, COD-aliphatic), 1.9 (m, 4H, COD-aliphatic), 2.3 (s, 3H, CH3),
3.4 (s, 2H, COD-olefin), 5.3 (s, 2H, COD-olefin), 7.2 (d, J = 8.1 Hz,
4H, Ar-H); 7.3–7.4 (m, 4H, Ar-H), 7.5 (d, J = 7.9 Hz, 2H, Ar-H),
1
8.1 Hz, 2H), 7.88 (d, J = 17.5 Hz, 2H, CH 3/5) ppm. 13C{ H}
NMR (CDCl3): d = 21.13 (s, CH3), 127.08 (s, CH), 127.64 (s, CH),
128.18 (s, CH), 130.23 (s, CH), 131.91 (d, J = 7.5 Hz, CH), 136.74
(d, J = 11.3 Hz, CH), 141.80 (d, J = 12.6 Hz, C) ppm. Mass Spec.
(m/z):Obs Mass 819.8140; Calc Mass 819.8159; 736 (M+ - 3CO).
7.9 (m, 2H, Ar-H), 8.1 (d, J = 15.9 Hz, 2H, CH3/5) ppm. 13C{ H}
1
NMR (CDCl3): d = 20.1 (s, CH3), 28.7 (s, COD-aliphatic), 31.9
(s, COD-aliphatic), 70.4 (d, J = 12.6 Hz, COD-olefin), 105.9 (s,
COD-olefin), 125.8 (s, CH), 126.4 (s, CH), 127.7 (s, CH), 128.9 (s,
CH), 128.7 (s, CH), 128.8 (s, CH), 131.5 (d, J = 8.8 Hz, C), 132.7
(s, C), 136.4 (s, C), 137.0 (s, CH), 137.2 (s, C), 146.0 (s, C), 157.2
(s, C) ppm. IR (Nujol) cm-1: 1260.5, 1057.7, 1032.9, 816.6, 758.1.
[2,6-Bis-(2¢-iodophenyl)-4-tolylphosphinine]-
pentacarbonyltungsten(0) (12)
Compound 12 was made by the same procedure as that
for complex 9 except phosphinine 8 was used. The reaction
gave [2,6-bis-(2¢-iodophenyl)-4-tolylphosphinine]pentacarbonyl-
tungsten(0), 12, as an orange solid that contains two rotamers.
Yield = 79 mg (51%). Data was obtained for the major rotamer
[2,6-Bis-(2¢-bromophenyl)-4-tolylphosphinine]-
chloro(COD)rhodium(I) (15)
Complex 15 was synthesised by the same procedure as 13 to yield
[2,6-bis-(2¢-bromophenyl)-4-tolylphosphinine]chloro(COD)-rho-
dium(I) (15) as an orange-yellow solid. Yield = 76 mg (51%).
1
1
only. 31P{ H} NMR (202.5 MHz, CDCl3): d = 164.9 (s, JP–W
=
280.9 Hz) ppm. 1H NMR (CDCl3): d = 2.28 (s, 3H, CH3), 7.13–
7.16 (m, 4H), 7.27–7.30 (m, 4H), 7.38–7.44 (m, 4H), 7.93 (d, J =
1
31P{ H} NMR (202.5 MHz, CDCl3): d = 187.3 (d, J = 186.3 Hz)
1
17.6 Hz, 2H, CH 3/5) ppm. 13C{ H} NMR (CDCl3): d = 21.22
ppm. 1H NMR (500.1 MHz, CDCl3): d 1.7 (m, 4H, COD-
aliphatic), 2.3 (s, 3H, CH3), 2.4 (m, 4H, COD-aliphatic), 4.2 (s,
2H, COD-olefin), 5.1 (d, J = 3.7 Hz, 2H, COD-olefin), 7.07–7.10
(m, 4H, Ar-H), 7.15–7.2 (m, 2H, Ar-H), 7.3 (d, J = 8.0 Hz, Ar-H),
7.46 (dd, J = 7.7, 1.6 Hz, 2H, CH3/5), 7.49 (d, J = 7.3 Hz, 2H,
(s, CH3), 127.19 (d, J = 2.5 Hz, CH), 128.36 (s, CH), 128.50 (s,
CH), 129.88 (s, CH), 130.13 (s, CH), 130.50 (s, C), 131.33 (d, J =
7.5 Hz, CH), 136.85 (s, C), 137.30 (d, J = 12.6 Hz, C), 139.52 (s,
CH), 139.76 (s, C), 145.32 (s, C), 170.12 (d, J = 8.8 Hz, C 2/6),
193.69 (s, cis-CO) ppm. IR (hexane) cm-1: 2076.4 (w, CO); 1983.1
(sh, CO); 1954.2 (st, CO); 1261.8; 1171.2; 1147.9; 815.5; 739.7.
Mass Spec. (m/z): Obs Mass 774.8265; Calc Mass 774.8276 (M+ -
5CO).
1
Ar-H) ppm. 13C{ H} NMR (CDCl3): d = 20.1 (s, CH3), 29.9 (s,
COD-aliphatic), 40.3 (s, COD-aliphatic), 77.7 (d, J = 15.1 Hz,
COD-olefin), 104.3 (s, COD-olefin), 125.3 (s, C), 126.2 (s, CH),
127.1 (s, CH), 128.0 (s, C), 128.1 (s, C), 128.3 (s, CH), 128.9 (s, CH),
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130.0 (s, CH), 132.2 (s, CH), 135.3 (s, C), 135.5 (s, CH), 142.3 (s, C),
147.5 (s, C) ppm. IR (Nujol) cm-1: 1260.0, 1097.6, 1021.6, 803.8.
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We describe a new series of 2-(2¢-halo)-substituted phosphinine
ligands, and their tungsten and rhodium complexes. We have
established the relative s-donation/p-acceptor abilities of the
phosphinines based on comparison of carbonyl stretching fre-
quencies and/or 1JP–W or 1JP–Rh values for the W(CO)5(L) and (1,5-
COD)RhCl(L) complexes with related literature examples. Such
comparison suggests that the electronic properties of the halo-
arylphosphinines are more like triarylphosphines than phosphites.
The dihalo-arylphosphinines are also potentially useful systems
for the introduction of other functionalities through substitution
of the halides and efforts are ongoing in this vein in an attempt to
produce donor functionalised tridentate phosphinines.
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Acknowledgements
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We would like to thank EPSRC and Sasol Technology (U.K.)
Limited for funding. We are also grateful to EPSRC for the funding
enabling the purchase of a Bruker 500 MHz NMR Spectrometer
and Micromass Q-Tof Mass Spectrometer. Thanks are also due to
Dr R. L. Jenkins for his assistance in acquiring much of the data
in support of this paper.
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Notes and references
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2184 | Dalton Trans., 2009, 2178–2184
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The Royal Society of Chemistry 2009
©