The electron-poor phosphines P{C6H3(CF 3)2-3,5}3 and P(C6F 5)3 do not mimic phosphites as ligands for hydroformylation. A comparison of the coordination chemistry of P{C 6H3(CF3)2-3,5}3 and P(C6F5)3

Article abstract of DOI:10.1039/b418193j

The fluoroaryl phosphines P{C₆H₃(CF₃) ₂-3,5}₃ (L_a) and P(C₆F ₅)₃ (L_b) form the complexes trans-[MCl ₂(L_a)₂] and trans-[MCl₂(L _b)₂] (M = Pd or Pt) which have been isolated and fully characterised. ³¹P NMR studies of competition experiments show that the stability of trans-[PdCl₂L₂] is in the order L = L_b < L_a < PPh₃. The crystal structure of trans-[PtCl₂(L_a)₂] is reported and reveals that the Pt-P bond lengths in trans-[PtCl₂L₂] are in the order L = L_b < L_a < PPh₃. The equilibria established when [Pt(norbornene)₃] is treated with L_a or L_b are investigated by ³¹P and ¹⁹⁵Pt NMR spectroscopy and the species [PtL_n(norbornene)_3-n] (n = 1-3) identified. Ligands L_a and L_b appear to have similar affinities for platinum(0). The complexes trans-[MCl(CO)(L_a) ₂] and trans-[MCl(CO)(L_b)₂] (M = Rh or Ir) have been synthesised and fully characterised; the values of v_co are comparable with those for analogous phosphite complexes. The ligands L _a, L_b, P(C₆H₂F ₃-3,4,5)₃ (L_c), P{C₆H ₄(CF₃)-2}₃ (L_d), PPh₃ and P(OPh)₃ have been tested in rhodium-catalysed hydroformylation of 1-hexene and L_a, L_b, and PPh₃ have been tested in rhodium-catalysed hydroformylation of 4-methoxystyrene. Ligands L _a, and L_b, have been shown to be stable under the hydroformylation catalysis conditions. For the 1-hexene reaction, the activity and selectivity for L_a and L_c are very similar to the PPh₃ catalyst (TOF ca. 400 h^-1; n: iso 2.5-3.0) but for the sterically demanding L_b and L_d the activity and selectivity was much lower than with PPh₃ (TOF ca. 15, n: iso ratio 0.6). Thus, the yield of heptanals obtained with the catalyst derived from L_a is 94% while under the same conditions with L_b only 6%. The TOF for the L_a/Rh catalyst was 5 times lower than for the P(OPh)₃/Rh catalyst despite the superficially similar ligand electronic characteristics for L_a and P(OPh)₃. The Royal Society of Chemistry 2005.

Full text of DOI:10.1039/b418193j

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F U L L P A P E R
The electron-poor phosphines P{C6H3(CF3)2-3,5}3 and P(C6F5)3 do
not mimic phosphites as ligands for hydroformylation. A comparison
of the coordination chemistry of P{C6H3(CF3)2-3,5}3 and P(C6F5)3
and the unexpectedly low hydroformylation activity of their rhodium
complexes
Matthew L. Clarke,*†a Dianne Ellis,a Kate L. Mason,a A. Guy Orpen,a Paul G. Pringle,*a
Richard L. Wingad,a Damien A. Zahera and R. Tom Baker‡b
a School of Chemistry, University of Bristol, Cantocks Close, Bristol, UK BS8 1TS.
E-mail: Paul.pringle@bristol.ac.uk
b Du Pont Central Research and Development Laboratories, Wilmington, DE, USA
Received 2nd December 2004, Accepted 2nd February 2005
First published as an Advance Article on the web 28th February 2005
The fluoroaryl phosphines P{C6H3(CF3)2-3,5}3 (La) and P(C6F5)3 (Lb) form the complexes trans-[MCl2(La)2] and
trans-[MCl2(Lb)2] (M = Pd or Pt) which have been isolated and fully characterised. 31P NMR studies of competition
experiments show that the stability of trans-[PdCl2L2] is in the order L = Lb < La < PPh3. The crystal structure of
trans-[PtCl2(La)2] is reported and reveals that the Pt–P bond lengths in trans-[PtCl2L2] are in the order L = Lb < La <
PPh3. The equilibria established when [Pt(norbornene)3] is treated with La or Lb are investigated by 31P and 195Pt NMR
spectroscopy and the species [PtLn(norbornene)3− ] (n = 1–3) identified. Ligands La and Lb appear to have similar
n
affinities for platinum(0). The complexes trans-[MCl(CO)(La)2] and trans-[MCl(CO)(Lb)2] (M = Rh or Ir) have been
synthesised and fully characterised; the values of mCO are comparable with those for analogous phosphite complexes.
The ligands La, Lb, P(C6H2F3-3,4,5)3 (Lc), P{C6H4(CF3)-2}3 (Ld), PPh3 and P(OPh)3 have been tested in rhodium-
catalysed hydroformylation of 1-hexene and La, Lb, and PPh3 have been tested in rhodium-catalysed hydroformylation
of 4-methoxystyrene. Ligands La, and Lb, have been shown to be stable under the hydroformylation catalysis
conditions. For the 1-hexene reaction, the activity and selectivity for La and Lc are very similar to the PPh3 catalyst
(TOF ca. 400 h−1; n : iso 2.5–3.0) but for the sterically demanding Lb and Ld the activity and selectivity was much
lower than with PPh3 (TOF ca. 15, n : iso ratio 0.6). Thus, the yield of heptanals obtained with the catalyst derived
from La is 94% while under the same conditions with Lb only 6%. The TOF for the La/Rh catalyst was 5 times lower
than for the P(OPh)3/Rh catalyst despite the superficially similar ligand electronic characteristics for La and P(OPh)3.
According to their Tolman electronic parameters, the
Introduction
electron-poor phosphines P{C6H4(CF3)2-3,5}3, (La) and
The applications of Wilkinson’s [RhH(CO)(PPh3)3] hydroformy-
P(C6F5)3, (Lb) would be expected to have donor properties sim-
lation catalyst1 in synthesis has been one of the most impressive
ilar to phosphites.16 Moreover Lb has a cone angle comparable
successes of homogeneous catalysis over the last 30 years.2
with the bulkiest phosphites16 and therefore it was of interest to
Rhodium-phosphite hydroformylation catalysts are generally
investigate the potential of these commercially available ligands
more active3–6 than their phosphine analogues and very bulky
in hydroformylation catalysis. In this paper we report that
rhodium complexes of La and Lb have modest hydroformylation
catalytic activity and relate this to their coordination chemistry.
phosphites have found industrial application.2 However, one
limitation of the applications of phosphite ligands is the kinetic
lability of the P–O bonds which make them susceptible to
hydrolysis7 and therefore robust ligands that may mimic phos-
phites would be useful.8 Fluoroarylphosphines are attractive
in this regard because they are ostensibly similar donors to
phosphites9 and contain relatively inert P–C bonds.
It is well established that electron-withdrawing groups on
arylphosphines increase the activity of the derived rhodium hy-
droformylation catalysts.10–13 For example a fluoroaryl derivative
of bisbi has been shown13 to give a hydroformylation catalyst
Results and discussion
that is five times more active and even more selective (n : iso
up to 123 : 1) than the parent bisbi system. Hope and co-
Co-ordination chemistry of P{C6H4(CF3)2-3,5}3 and P(C6F5)3
workers have reported14 very active rhodium catalysts from para-
Complexes of Lb with late transition metals were first reported
substituted fluoroarylphosphines that can be used in fluorous
by Kemmitt et al.17 but the analogues with La have not been
biphasic systems or supercritical CO2 though recently, Erkey
previously described.
and Palo15 were unable to detect coordination of P(C6F5)3 to
rhodium in supercritical CO2.
Platinum and palladium. Treatment of [PtCl2(SMe2)2] or
[PtCl2(cod)] (cod = 1,5-cyclooctadiene) with La gave trans-
[PtCl2(La)2] (1a) which has been fully characterised (see Ex-
perimental) and its crystal structure has been determined (see
below). The formation of the trans isomer 1a reflects the steric
bulk of La (h = 160◦) since the reaction of [PtCl2(cod)] with PPh3
† Present address: School of Chemistry, University of St Andrews, St
Andrews, Fife, KY16 9ST.
‡ Present address: Chemistry Division, MS J582, Los Alamos National
Laboratory, NM 87545, USA.
1 2 9 4
D a l t o n T r a n s . , 2 0 0 5 , 1 2 9 4 – 1 3 0 0
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
©

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(h = 145◦) under similar conditions yields cis-[PtCl2(PPh3)2]
exclusively.
The structures of 3a, 4a and 5a were assigned on the basis of the
doublet, triplet or quartet observed in the 195Pt NMR spectra.
Addition of a large excess of La did not give any new platinum-
containing species such as [Pt(La)4], consistent with the large
steric bulk of La.19 Under similar conditions using Lb, complexes
3b and 4b were identified by 195Pt NMR spectroscopy but no
evidence was found for 5b even in the presence of a large excess
of ligand Lb. None of these platinum(0) species were isolated in
pure form but solids containing predominantly 3b or 4b were
obtained, as shown by 31P and 195Pt NMR spectroscopy.
Under the mild conditions used to make 1a above,
[PtCl2(SMe2)2] did not react with Lb; however, when a mixture
of [PtCl2(SMe2)2] and Lb was refluxed in toluene for 6 days, two
platinum-containing species in a 1 : 1 ratio along with free Lb
were detected by 31P NMR spectroscopy. One of the products
was identified as the known18 complex trans-[PtCl2(Lb)2] (1b)
from its 31P NMR data and the triplet in the 195Pt NMR
spectrum. The doublet 195Pt NMR signal observed for the
second product shows that it has one coordinated phosphine and
therefore could be [Pt2(l-Cl)2Cl2(Lb)2] or [PtCl2(SMe2)(Lb)] but
was not further characterised (see Experimental for the data).
The values of 1J(PtP) for the platinum complexes 3–5a,b and
their PPh3 analogues are in the order PPh3 < La < Lb which
1
is in agreement with the relationship between J(PtP) and the
electron richness of phosphorus(III) ligands on platinum(0).20
From the fact that 5a readily formed while 5b was not
observed, it might be concluded that La has a greater affinity for
platinum(0) than Lb. However, when 2 equivalents of La were
added to a toluene solution containing a mixture of 3b and 4b,
the main species present in the complicated mixture produced
was identified as the mixed species 4ab from the 31P NMR data:
1
2
d(Pa) 37.2 { J(PtPa) 3928 Hz, J(PaPb) 82 Hz} and d(Pb) 20.8
{ J(PtPb) not resolved, 2J(PaPb) 82}. This suggests that any
1
The palladium analogues 2a and 2b were prepared from
[PdCl2(NCPh)2] and have been fully characterised; complex 2a
has been previously reported.17 In order to probe the relative
affinities of La, Lb and PPh3 for palladium(II), the reactions
shown in Scheme 1 were monitored by 31P NMR spectroscopy.
Complex 2b was treated with 2 equivalents of La in CDCl3
and initially, the intermediate mixed ligand complex 2ab was
observed, identified from the characteristic AX pattern with
chemical shifts close to the symmetrical analogues 2a and 2b
difference in affinity between La and Lb for platinum(0) is small
which contrasts with the clear distinction for palladium(II) noted
above. The lack of evidence for the formation of 5b is likely a
consequence of the large bulk of Lb (h = 184◦).
2
(see Experimental for data) and a very large J(PP) of 641 Hz
consistent with inequivalent trans-PR3 ligands. After 1 h, no
further changes in the spectra were observed and the only species
detected were 2a and Lb. Treatment of the mixture of 2a and
Lb with 2 equivalents of PPh3 gave, within 10 min, exclusively
[PdCl2(PPh3)2] (as the trans isomer predominantly) with free La
and Lb.
Thus, under these conditions, the order of affinity for palla-
dium(II) is unambiguously established as Lb < La < PPh3 which
is the order of increasing ligand r-donor strength. It is also the
order of decreasing ligand bulk though it seems reasonable to
assume that steric considerations would be less important in
these trans complexes.
A mixture of platinum(0) species are formed upon addition of
La or Lb to [Pt(norbornene)3] which have been unambiguously
identified in solution by 31P and 195Pt NMR spectroscopy (see
Experimental for data). Thus when 1–3 equivalents of La was
added to a CH2Cl2 solution of [Pt(norbornene)3], mixtures
containing 3a, 4a, 5a and La were formed in varying proportions
indicating that the equilibria shown in Scheme 2 were present.
X-Ray crystal structure of trans-[PtCl2(La)2] (1a). The crystal
structure of trans-[PtCl2{P(C6H3(CF3)2-3,5)2}2] (1a) was deter-
¯
mined (Fig. 1). Complex 1a crystallises in space group P1 with
the platinum atom on a centre of inversion consistent with the
trans configuration of the complex. Selected bond lengths and
angles are given in Table 1. The mean P–C bond lengths (1.823(4)
21
˚
A in 1a) are close to those reported in trans-[PtCl2(PP◦h3)2]
˚
(1.820(2) A). The C–P–C angles range from 103.49(11) to
◦
a
˚
Table 1 Selected bond lengths (A) and angles ( ) for (1a)
Pt(1)–P(1)
Pt(1)–Cl(1)
2.3017(8)
2.3079(7)
Cl(1)–Pt(1)–P(1)
Cl(1A)–Pt(1)–P(1)
P(1A)–Pt(1)–Cl(1)
88.49(3)
91.51(3)
180.0(2)
a Symmetry transformation for 1A atoms −x, −y, −z.
Scheme 1
Scheme 2
D a l t o n T r a n s . , 2 0 0 5 , 1 2 9 4 – 1 3 0 0
1 2 9 5

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The complexes [Rh2Cl2(cyclooctene)4], [Rh(cod)2]SO3CF3
and [Rh(CO)2(acac*)] (acac* = ButC(O)CHC(O)But) react
smoothly with La to give the expected products 8a, 9a and
10a, respectively, which have all been characterised fully (see
Experimental). However under similar conditions, Lb reacts with
[Rh2Cl2(cyclooctene)4] or [Rh(CO)2(acac*)] to give mixtures of
products with complexes 8b and 10b identified in solution on the
basis of the 31P NMR data; no reaction was observed between
Lb and [Rh(cod)2]CF3SO3.
By modifying the literature procedures for [RhH(CO)-
(PPh3)3]25 and [IrH(CO)(PPh3)3]26 the syntheses of analogues
with La and Lb were attempted. However, treatment of rhodium
complexes 6a or 6b or iridum complexes 7a or 7b with NaBH4
in ethanol in the presence of La or Lb or by treatment of 6a with
H2 in the presence of La and NEt3 were unsuccessful; in each
case, only starting materials were detected with no evidence for
hydride formation from 1H NMR spectroscopy.
Fig. 1 Structure of trans-[PtCl2(La)2] (1a). Hydrogen atoms have been
omitted for clarity.
105.79(11)◦. The arrangement of the aryl groups with respect
to the PtP2Cl2 plane can be represented in terms of the three Cl–
Pt–P–C
torsion angles [71.3◦, −168.4◦ and −49.5◦] which
ipso
Hydroformylation catalysis
shows that one of the aryl groups is almost eclipsed with respect
to the chlorine atoms.
The phosphines La and Lb have been tested as ligands for
rhodium catalysed hydroformylation of 1-hexene (eqn. (1))
under standard2 conditions (see Experimental) and the results
compared with those for PPh3, P(OPh)3 and ligands Lc and Ld.
The catalysts were generated in situ, the product distributions
were determined by GC and the rates were determined by
measuring gas uptakes as a function of time at constant pressure.
Under the conditions used, in the absence of added phosphorus
ligand, only traces of aldehyde were detected.
The Pt–P bond length in 1a of 2.3017(8) is longer than
22
˚
in 1b (2.280(1) A) and shorter than in trans-[PtCl2(PPh3)2]
21
˚
(2.319(3), 2.316(3) A). The decrease in Pt–P bond lengths in
trans-[PtCl2(L)2] correlates well with increasing 1J(PtP): L = Lb
(3145 Hz) < La (2798 Hz) < PPh3 (2638 Hz). Short Pt–PR3 bond
1
lengths and large J(PtP) values are normally associated with
strong Pt–P r–bonding23 but the electronegative substituents in
La and Lb would surely make these poorer r–donors than PPh3.
The shorter Pt–P bond lengths are most likely a result of the
smaller covalent P radius in the electron-poor phosphines.
Iridium and rhodium chemistry. The sparingly soluble com-
plexes 6a,b and 7a,b were made from [Rh2Cl2(CO)4] and
[IrCl(CO)2(p-toluidine)], respectively, and fully characterised
(see Experimental); complexes 6b and 7b have been previously
reported.17,24 The value of m(CO) for trans-[MCl(CO)L2] is a
measure of the r/p-bonding characteristics of L. The values are
given in Table 2 for 6a,b and 7a,b together with the values for the
PPh3 and P(OR)3 analogues for comparison. From these data it
can be concluded that the order of decreasing r–donor and/or
increasing p-acceptor ability is PPh3 < La < Lb < P(OR)3.
(1)
The results are given in Table 3 (Entries 1–6). The PPh3 derived
catalyst efficiently converts 1-hexene to C-7 aldehydes with no
by-products and selectivity to the linear aldehydes is modest
(Entry 1). The P(OPh)3 derived catalyst shows over 5 times the
activity of the PPh3 catalyst under these conditions (Entry 2).
The catalysts derived from the electron-poor phosphines La
(Entry 3) and Lc (Entry 5) show similar activity to PPh3.
These catalysts also gave similarly modest selectivity (n : i
of 2–3) with 2-methylhexanal (and traces of 2-ethylpentanal)
accounting for the majority of the branched product. The bulky,
electron-poor phosphins Lb (Entry 4) and Ld (Entry 6) gave
low activity catalysts and a greater proportion of iso-products.
Of the branched aldehyde product (formed in 4% yield), about
one third is 2-ethylpentanal which is derived from 2-hexene
and indicates that isomerisation of 1-hexene to 2-hexene is a
competing reaction when using the bulky phosphine catalysts.
After the hydroformylation catalysis runs with La (Entry 3)
and Lb (Entry 4) the product solutions were investigated by
31P NMR spectroscopy which revealed strong signals for free
ligands (which were used in excess) showing that the ligands
were stable under the hydroformylation conditions; in addition
a weak doublet was observed in the solution with ligand Lb
Table 2 m(CO) for trans-[MCl(CO)L2]
L
M
m(CO)/cm−1
P(OPh)3
Lb
Rh
Rh
Rh
Rh
Ir
Ir
Ir
2016
2004
2000
1965
1993
1992
1987
1950
La
PPh3
P(OBun)3
Lb
La
PPh3
Ir
1 2 9 6
D a l t o n T r a n s . , 2 0 0 5 , 1 2 9 4 – 1 3 0 0

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Table 3 Hydroformylation catalysis
Entry
Substrate
Conditionsa
Ligand
hb/◦
145
128
160
184
145
>200
145
160
Conversionc
n : isoc
TOFd
1
2
3
4
5
6
7
8
9
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
4-methoxystyrene
4-methoxystyrene
4-methoxystyrene
i
i
i
ii
i
ii
iii
iii
iii
PPh3
P(OPh)3
La
95
92
94
6
94
6
100
100
25
2.9
2.6
3.0
0.6
2.5
0.6
0.13
0.20
0.29
380
2000
400
b
Lb
∼15
Lc
400
b
Ld
∼15
n.d.
n.d.
n.d.
PPh3
La
Lb
184
a Reaction conditions (see Experimental for more details): (i) at 60 ◦C, 20 bar, 0.2 mol% catalyst, L/Rh = 4.5, 3 h; (ii) at 100 ◦C, 5 mol%
catalyst, L/Rh = 4.5, 4 h; (iii) at 55 ◦C, 7 bar, 5 mol% catalyst, L/Rh = 5, 4 h. b Values from ref. 16 c In % as determined by GC. For 1-hexene
reactions, the conversions are based on 1-hexene consumed against biphenyl as an internal standard and selectivity to aldehydes is essentially 100%.
For the 4-vinylanisole hydroformylation in Entry 9, the by-product was polyvinylanisole. d Determined by monitoring gas uptake with time over the
first 2 h, except in the case of entries 4 and 6 which were determined by conversion h−1; n.d. = not determined
consistent with the presence of a rhodium(I) complex (d 28.4,
1J(RhP) 131 Hz).
Rhodium-catalysed hydroformylation of 4-vinylanisole (eqn.
(2)) with PPh3, La and Lb was investigated and the results are
presented in Table 3 (Entries 7–9).
175◦). Thus the low activity of the catalyst derived from Lb con-
trasts sharply with the exceptionally high activity of the catalyst
derived from the bulky monophosphite P(OC6H4But-2)3.4,29
The conclusion to be drawn is that despite superficial
stereoelectronic similarities, monodentate fluoroarylphosphines
do not mimic monophosphites in terms of delivering high-
activity hydroformylation catalysts. Further theoretical work is
in progress to understand why this is so.
(2)
Similar trends in activity to the 1-hexene reaction are appar-
ent: La and PPh3 give catalysts of similar activity while Lb gives
low activity. Of the aldehyde product obtained, the selectivity for
the more valuable (in terms of potential applications27) branched
aldehyde decreases in the order PPh3 > La > Lb.
Experimental
All preparations were carried out in a dry nitrogen atmosphere
using Schlenk techniques. Unless otherwise stated, the metal
complexes were found to be air stable in the solid state, so once
prepared were stored in air. All reaction solvents were dried by
refluxing over appropriate drying reagents (calcium hydride for
dichloromethane and acetonitrile, sodium/benzophenone for
diethylether, tetrahydrofuran, toluene, benzene, pentane, and
hexane, and anhydrous magnesium sulfate for acetone) and
distilled under nitrogen prior to use. Commercial reagents were
used as supplied and other reagents were prepared by litera-
ture methods: [PtCl2(cod)] and [PtCl2(SMe2)2];30 [IrCl(CO)2(p-
toluidine)];31 [Pt(norbornene)3];32 elemental analyses were car-
ried out in the Microanalytical Laboratory of the School of
Several features of the catalytic results are worthy of fur-
ther discussion. There is no doubt that phosphites generally
give more active rhodium catalysts for hydroformylation than
phosphines and our measurements of the rates obtained with
PPh3 and P(OPh)3 above concur with this. The explanation
given is that the r/p-bonding characteristics of the electron-
poor phosphites leads to weaker Rh–CO bonding which in
turn facilitates the rate-determining CO displacement by the
alkene substrate.2 For the same reasons, electron-withdrawing
substituents on phosphines would be expected to lead to higher
activity hydroformylation catalysts. Such activity enhancements
have been observed although many of these have been with
diphosphines2 for which other factors may complicate the
interpretation.28 For monophosphines Moser et al.10 showed,
using P(C6H4Z-4)3 (Z = H, Cl, F, CF3) as ligands in 1-hexene
hydroformylation, that electron-withdrawing substituents led to
increased catalytic activity; the most rapid (with P(C6H4CF3-4)3)
was a factor of 1.4 times faster than with PPh3. In the light of
this, the negligible difference in rate between PPh3 and La is un-
expected. The greater bulk of La (h = 160◦) than PPh3 (h = 145◦)
may be a factor although we also detected very little difference in
the rate with Lc. We conclude that for our PAr3 catalyst systems,
electronic effects are apparently not very significant.
The very bulky phosphines Lb and Ld gave low activity hy-
droformylation catalysts. The coordination chemistry described
above revealed that Lb is generally a poorer ligand than La for
late transition elements and thus it may be incomplete coordi-
nation of Lb to rhodium under the catalytic conditions that is
responsible for the low observed rate. The ligand Ld is apparently
an even poorer ligand than Lb since we have been unable to make
complexes of Ld with Pt, Pd or Rh using the conditions described
above for the synthesis of complexes of La and Lb.
The mCO values for [RhCl(CO)(Lb)2] given above and the
reported Tolman electronic parameter16 for Lb suggest that the
ligand properties of Lb are more similar to P(OAr)3 than PPh3.
Furthermore the Tolman cone angle for Lb (h = 184◦) is compa-
rable to that of the bulky monophosphite P(OC6H4But-2)3 (h =
Chemistry, Bristol University. H, 31P and 195Pt NMR spectra
1
were recorded on Jeol FX90Q, Jeol GX400, and Jeol ecp 300
NMR spectrometers with chemical shifts to high frequency
of TMS, 85% H3PO4, and N(Pt) 21.4 MHz respectively.
P{C6H3(CF3)2-3,5}3 (La, d(P) −2.0 in d8-thf) was purchased
from Fluorochem, P(C6F5)3 (Lb, d(P) −74.0, hpt, 3J(PF) 36 Hz
in d8-thf) was purchased from Aldrich and P{C6H4(CF3)-2}3
(Ld) was made by the literature method.33
Tris(3,4,5-trifluorophenyl)phosphine (Lc)
The Grignard reagent 3,4,5-C6H2F3MgBr was prepared by
gradually adding a solution of 1-bromo-3,4,5-trifluorobenzene
(7.07 g, 33.5 mmol) in Et2O (20 cm3) into a cooled suspension of
magnesium (0.81 g, 33.5 mmol) in Et2O (20 cm3). The mixture
was warmed to room temperature before the addition of a
solution of PCl3 (1.53 g, 11.2 mmol). After stirring overnight,
the solvents were removed in vacuo and the residue dissolved in
toluene and filtered through a sinterstick. The toluene solution
was washed with brine solution, dried with sodium sulfate and
the solvent was removed in vacuo to give Lc in high purity (3.1 g,
7.31 mmol, 65%) (This is an unoptimised yield as some product
was lost during the filtration stage). Elemental analysis (calc.):
C, 50.96 (50.96); H, 1.24 (1.43); MS (EI) m/z: 424 (M+); 31P{ H}
1
NMR (C6D6): d = −1.0; 19F NMR (C6D6): d = −132.4 (6F, dd,
3J(FF) = 20.8 Hz; 3J(FH) = 7.0 Hz), −156.0 (3F, tt, 3J(FF) =
4
1
20.8 Hz, J(FH) = 6.2 Hz); H NMR (C6D6): d = 6.5 (6H,
q. app., J = 6.8 Hz).
D a l t o n T r a n s . , 2 0 0 5 , 1 2 9 4 – 1 3 0 0
1 2 9 7

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trans-[PtCl2(La)2] (1a)
Reaction of [Pt(norbornene)3] with Lb
Ligand La (69 mg, 0.103 mmol) was added to a solution
of [PtCl2(SMe2)2] (20 mg, 0.052 mmol) in pentafluorobenzene
(5 cm3). This gave a yellow solution which was stirred at room
temperature for 24 h. The solvent was then removed in vacuo and
toluene (10 cm3) was added to form a yellow suspension which
was stirred for 30 min. The product was then filtered off under
nitrogen and washed with toluene (2 × 2 cm3) to give 1a as a
pale yellow solid (59 mg, 0.037 mmol, 72%). Elemental analysis
(calc.): C, 35.85 (35.90); H, 1.05 (1.15); MS (FAB) m/z: 1571
One equivalent (56 mg, 0.105 mmol), two equivalents (112 mg,
0.210 mmol), three equivalents (167 mg, 0.314 mmol) or four
equivalents (224 mg, 0.421 mmol) of Lb were added to a
solution of [Pt(norbornene)3] (50 mg, 0.105 mmol) in a,a,a-
trifluorotoluene (4 cm3). This gave a light brown solution
which was stirred at room temperature for 1 h. The solvent
was then removed in vacuo to give a light brown solid. In
1
each reaction 31P{ H} and 195Pt NMR spectroscopy showed
a mixture of uncoordinated Lb and complexes 3b and 4b in
1
1
(M+ − Cl), 1535 (M+ − 2Cl); 31P{ H} NMR (C6F5H/C6D6):
varying proportions. Spectroscopic data for 3b: 31P{ H} NMR
d = 22.9 (1J(PPt) = 2798 Hz); 195Pt NMR (C6F5H/C6D6): d =
393.4 (t); 19F NMR (CDCl3): d = −64.2 (s);1H NMR (CDCl3):
d = 8.11 (6H, s); 8.06 (12H, t, J(PH) = 5.5 Hz).
(CDCl3): d = −27.1 (s, 1J(PPt) = 3577 Hz); 195Pt NMR (CDCl3):
d = −958 (d);19F NMR (CDCl3): d = −128.1 (6F, o-F), −146.0
1
(3F, p-F), −157.8 (6F, m-F). Spectroscopic data for 4b: 31P{ H}
1
NMR (CDCl3): d = −23.3 (s, J(PPt) = 4006 Hz); 195Pt NMR
(CDCl3): d = −318 (t); 19F NMR (CDCl3): d = −130.3 (12F,
Reaction of [PtCl2(SMe2)2] with Lb
o-F), −148.2 (6F, p-F), −159.7 (12F, m-F).
Ligand Lb (100 mg, 0.19 mmol) was added to a solution of
[PtCl2(SMe2)2] (37 mg, 0.094 mmol) in toluene (20 cm3) to give a
yellow solution which was stirred and heated to reflux for 6 days.
31P NMR spectroscopy revealed the formation of two platinum-
containing products (see Results and discussion) one of which
Reaction of [Pt(norbornene)3] with La
This was carried out as above to give mixtures of 3a, 4a and 5a.
1
Spectroscopic data for 3a: 31P{ H} NMR (C6H5CF3/C6D6): d =
1
1
is trans-[PtCl2(Lb)2] (1b).18 31P{ H} NMR (C6H5CH3/C6D6):
32.8 (br, s, J(PPt) = 3523 Hz); 195Pt NMR (C6H5CF3/C6D6):
d = −25.8 (1J(PPt) = 3145 Hz); 195Pt NMR (C6H5CH3/C6D6):
d = 487.1 (t). The other species had parameters: d(P) = −30.7
(1J(PPt) = 3694 Hz); d(Pt) = 705.7 (d).
d = −1117.5 (d). Spectroscopic data for 4a: 31P{ H} NMR
1
(C6H5CF3/C6D6): d = 38.6 (s, 1J(PPt) = 3706 Hz); 195Pt NMR
(C6H5CF3/C6D6): d = −510.0 (t). Spectroscopic data for 5a:
1
31P{ H} NMR (C6F5H/C6D6): d = 53.2 (s, 1J(PPt) = 4551 Hz);
195Pt NMR (C6F5H/C6D6): d = 166 (q).
trans-[PdCl2(La)] (2a)
Ligand La (262 mg, 0.20 mmol) was added to a solution
of [PdCl2(NCPh)2] (75 mg, 0.20 mmol) in CH2Cl2 (15 cm3).
This gave a brown/orange solution which was stirred at room
temperature for 6 h. The solvent was then removed in vacuo and
toluene (10 cm3) was added to form a brown suspension. The
suspension was stirred for 30 min, filtered off under nitrogen and
washed with toluene (2 × 2 cm3) to give 2a17 as a light brown
solid (183 mg, 0.121 mmol, 62%). Elemental analysis (calc.): C,
37.55 (37.95); H, 1.20 (1.20); MS (FAB) m/z: 1446 (M+ − 2Cl);
Reaction of [Pt(norbornene)3] with Lb and La successively
Three equivalents of Lb (39.4 mg, 0.074 mmol) were added to a
solution of [Pt(norbornene)3] (12 mg, 0.025 mmol) in toluene
(0.7 cm3) in an NMR tube. The tube was shaken to give a
1
pale yellow solution. 31P{ H} NMR (C6H5CH3): d = −22.4
1
1
(s, J(PPt) = 4003 Hz, 4b), −26.4 (s, J(PPt) = 3577 Hz, 3b)
(ratio ∼ 1 : 4), −73.9 (hpt, 3J(PF) = 36 Hz, Lb). Three equivalents
of La (50 mg, 0.074 mmol) were added to this mixture and the
1
1
31P{ H} NMR (CDCl3): d = 24.8;19F NMR (CDCl3): d = −64.2
contents were shaken to give a cloudy solution. 31P{ H} NMR
(s); 1H NMR (CDCl3): d = 8.12 (6H, s); 8.05 (12H, t, 3J(PH) =
spectroscopy showed a complex mixture with the major species
1
2
5.1 Hz).
being 4ab. 31P{ H} NMR (C6H5CH3): d = 37.2 (d, J(PP) =
82 Hz, 1J(PPt) = 3928 Hz, Pa), 20.8 (d, 2J(PP) = 82 Hz, 1J(PPt)
not resolved, Pb).
trans-[PdCl2(Lb)2] (2b)
Ligand Lb (140 mg, 0.26 mmol) was added to a solution of
[PdCl2(NCPh)2] (50 mg, 0.13 mmol) in CH2Cl2 (10 cm3). This
gave an orange/brown solution which was stirred at room
temperature for 2 h. The solvent was then removed in vacuo and
toluene (4 cm3) was added followed by pentane (10 cm3). The
reaction mixture was left in the fridge for 24 h after which time a
yellow suspension was formed. The product was then filtered off
under nitrogen and washed with pentane (2 × 4 cm3) to give 2b
as a yellow solid (85 mg, 0.068 mmol, 52%). Elemental analysis
(calc.): C, 34.70 (34.85); MS (FAB) m/z: 1170 (M+ − 2Cl);
trans-[RhCl(CO)(La)2] (6a)
Ligand La (1.05 g, 1.54 mmol) was added to a solution of
[Rh2Cl2(CO)4] (150 mg, 0.39 mmol) in C6H6 (15 cm3). CO was
evolved and the yellow solution was stirred for 36 h. The solvent
was then removed under vacuum and CH2Cl2 (5 cm3) was added
to give a yellow suspension which was then stirred for 1 h
before filtering off the product under nitrogen. The solid was
washed with CH2Cl2 (2 × 5 cm3) to give 6a as a pale yellow solid
(256 mg, 0.170 mmol, 87%). Elemental analysis (calc., 6a·H2O):
31P{ H} NMR (CDCl3): d = −27.0 (br, s); 19F NMR (CDCl3):
C, 38.35 (38.60); H, 1.15 (1.30); MS (FAB) m/z: 1524 (M+
+
1
d = −126.2 (12F, o-F), −143.8 (6F, p-F), −158.8 (12F, m-F).
Reaction of trans-[PdCl2(Lb)2] (2b) with La and then PPh3
H2O), 1506 (M+), 1478 (M+ − CO), 1443 (M+ − CO − Cl); IR:
1
m(CO) 2000 cm−1; 31P{ H} NMR (C6H5CF3/C6D6): d = 33.0 (d,
1J(PRh) = 134.7 Hz); 19F NMR (C6D6): d = −62.8 (s); 1H NMR
(C6D6): d = 8.12 (m). The analogous complex 6b was made by
the literature method.17
Complex 2b (21.6 mg, 0.017 mmol) was dissolved in CDCl3
(0.7 cm3) in an NMR tube. La (23.3 mg, 0.035 mmol) was added
and the tube was shaken to give a yellow solution. The reaction
was monitored by 31P NMR spectroscopy which after 1 h showed
trans-[IrCl(CO)(La)2] (7a)
1
a mixture of predominantly complex 2a and ligand Lb. 31P{ H}
Ligand La (100 mg, 0.15 mmol) was added to a solution
of [IrCl(CO)2(p-toluidine)] (29 mg, 0.075 mmol) in toluene
(10 cm3). CO was evolved and a yellow solution was formed
which was stirred at room temperature for 24 h. After this
time a yellow suspension was formed and this was filtered off
under nitrogen and washed with toluene (2 × 4 cm3) to give
7a as a yellow solid (69 mg, 0.043 mmol, 58%). Elemental
analysis (calc.): C, 36.55 (36.90); H, 0.95 (1.15); MS (FAB) m/z:
NMR (CDCl3): d = 25.6 (s, 2a), −73.7 (hpt, 3J(PF) = 36 Hz, Lb)
(initially the mixed ligand complex 2ab was detected with d =
30.4 and −25.5 (2J(PP) = 641 Hz)). Triphenylphosphine (9.2 mg,
0.035 mmol) was then added to the mixture and the tube was
1
shaken to give a yellow solution. 31P{ H} NMR (CDCl3): d =
24.0 (s, trans-[PdCl2(PPh3)2]), 22.4 (s, cis-[PdCl2(PPh3)2]) (ratio
∼ 4 : 1), −3.6 (s, La) − 73.7 (hpt, 3J(PF) = 36 Hz, Lb).
1 2 9 8
D a l t o n T r a n s . , 2 0 0 5 , 1 2 9 4 – 1 3 0 0

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1
1596 (M+), 1568 (M+ − CO); IR: m(CO) 1987 cm−1; 31P{ H}
was evolved and a yellow solution was formed which was stirred
1
at room temperature for 4 h. 31P{ H} NMR spectroscopy and
NMR (C6F5H/C6D6): d = 27.8 (s); 19F NMR (THF/C6D6): d =
−61.6 (s).
FAB mass spectrometry showed the product to be a mixture of
[Rh(acac*)(Lb)2] (10b) and unreacted Lb which we were unable to
1
separate. 31P{ H} NMR (C6D6/CH2Cl2): d = −7.0 (d, 1J(PRh) =
trans-[IrCl(CO)(Lb)2] (7b)
200.0 Hz).
Ligand Lb (150 mg, 0.282 mmol) was added to a solution of
[IrCl(CO)2(p-toluidine)] (55 mg, 0.141 mmol) in C6H6 (15 cm3).
This gave a dark green solution which was stirred at room
temperature for 48 h. The solvent was then removed in vacuo and
CH2Cl2 (10 cm3) was added to form a yellow suspension in the
dark green solution. The product was filtered off under nitrogen
and washed with CH2Cl2 (2 × 4 cm3) to give 7b17 as a yellow
solid (56 mg, 0.042 mmol, 31%). Elemental analysis (calc.): C,
33.10 (33.70); MS (FAB) m/z: 788 (M+ − Lb), 768 (M+ − Lb −
Hydroformylation of 1-hexene
These experiments were conducted in a stainless steel autoclave
held at constant pressure and connected to a ballast vessel from
which 1 : 1 CO/H2 was fed. Reaction rates were determined
by measuring gas uptake over time up to 50% conversion, and
further confirmed by GC/MS analysis of the reaction products.
The identities of the reaction products were established by
comparison of retention times and mass spectra with authentic
samples. [Rh(acac)(CO)2] (5.0 mg, 0.019 mmol) and ligand
(0.90 mmol) in toluene (4 cm3) were added to the autoclave
which was then flushed with 1 : 1 CO/H2.◦The autoclave was
then pressurised (10 bar) and stirred at 60 C for 1 h to allow
the catalyst to form. 1-Hexene (1.2 cm3) was injected and the
pressure adjusted to 20 bar. The gas uptake was monitored as a
function of time.
1
CO), 725 (M+ − Lb − CO − Cl); IR: m(CO) 1992 cm−1; 31P{ H}
NMR (C6F5CF3/C6D6): d = −31.7 (s).
[Rh2(l-Cl)2(La)4] (8a)
A solution of La (280 mg, 0.42 mmol) in CH2Cl2 (5 cm3) was
added dropwise over 2 min to a solution of [Rh2Cl2(cyclo-
octene)4)] (75 mg, 0.11 mmol) in CH2Cl2 (5 cm3) and the resulting
bright red solution was stirred at room temperature for 24 h to
give a red suspension. The solid was filtered off under nitrogen
and washed with toluene (2 × 5 cm3) to give the product 8a
(268 mg, 0.091 mmol, 86%). Elemental analysis (calc): C, 38.75
Hydroformylation of 4-vinylanisole
In
a glove box under nitrogen, a solution of 4-vinyl-
(39.00); H, 1.35 (1.25); 31P{ H} NMR (C4D8O), d = 57.3 (d,
1
anisole (39 mg, 0.291 mmol), polydimethylsiloxane (21 mg,
0.290 mmol), [Rh(acac*)(CO)2] (5.0 mg, 0.015 mmol) and ligand
(5 equivalents with respect to Rh, 0.073 mmol) in C6D6 (3 cm3)
was prepared in a 10 cm3 vial. The mixture was then shaken,
pressurised to 7 bar with 1 : 1 CO/H2 and heated to 55 ◦C for
4 h. The solution was analysed by 1H NMR spectroscopy with
polydimethylsiloxane peak used as the standard to calculate the
yields of each product given in Table 3.
1J(PRh) = 195.8 Hz); 19F NMR (CD2Cl2): d = −63.4 (s); H
1
NMR (CD2Cl2): d = 8.20 (12H, s), 8.13 (24H, d, J = 12.5).
Reaction of [Rh2(l-Cl)2(cyclooctene)4] with Lb
A solution of Lb (100 mg, 0.19 mmol) in CH2Cl2 (5 cm3) was
added dropwise over 2 min to a solution of [Rh2Cl2(cyclo-
octene)2)] (34 mg, 0.047 mmol) in CH2Cl2 (5 cm3) and the
resulting bright red solution was stirred at room temperature
for 24 h. A mixture of products was obtained and one signal at
d(P) = 2.4 (d, 1J(PRh) = 261 Hz) was tentatively assigned to 8b.
X-Ray crystal structure of 1a
X ray diffraction experiments on trans-[PtCl2{P(C6H3(CF3)2-
3,5)2}2] (1a) were performed at −100 ◦C on a Bruker
SMART diffractometer using Mo Ka X-radiation, a
=
[Rh(cod)(La)2]O3SCF3 (9a)
˚
0.71073 A. Crystal data: trans-[PtCl2{P(C6H3(CF3)2-3,5)2}2]
Ligand La (100 mg, 0.15 mmol) was added to a solution of
[Rh(cod)2]O3SCF3 (34 mg, 0.075 mmol) in CH2Cl2 (10 cm3). This
gave a yellow solution which was stirred at room temperature
for 24 h. The solvent was then removed in vacuo and pentane
(10 cm3) was added to form a yellow suspension. The suspension
was stirred for 24 h, filtered off under nitrogen and washed
with pentane (2 × 5 cm3) to give 9a as a yellow solid (64 mg,
0.038 mmol, 51%). Elemental analysis (calc., 9a.CH2Cl2): C,
¯
(1a), C48H18Cl2F36P2Pt, M = 1606.55, triclinic, space group, P1
˚
(No. 2), a = 10.372(2), b = 11.649(2), c = 12.263(3) A, a =
◦
3
˚
69.43(2), b = 86.03(2), c = 85.14(2) , V = 1381.0(5) A , Z =
1, l = 2.853 mm−1, reflections measured, 6660, independent
reflections, 4735, Rint 0.0177, R1 = 0.019. Absorption corrections
were based on equivalent reflections and structures refined
2
against all Fo data with hydrogen atoms riding in calculated
positions. The fluorine atoms on carbons C(8) {F(4), F(5),
F(6)}, C(18) {F(10), F(11), F(12)} and C(27) {F(13), F(14),
F(15)} were disordered with occupancies 0.696(5) and assigned
constrained anisotropic displacement parameters.
CCDC reference number 257444.
See http://www.rsc.org/suppdata/dt/b4/b418193j/ for cry-
stallographic data in CIF or other electronic format.
38.80 (39.00); H, 2.05 (1.80); MS (FAB) m/z: 1443 (M+
−
1
cod − CF3SO3), 881 (M+ − La − cod − CF3SO3); 31P{ H}
NMR (CDCl3): d = 25.1 (d, J(PRh) = 160.4 Hz); 19F NMR
1
(CD2Cl2): d = −63.5 (36F, s), −79.2 (3F, s); 1H NMR (CD2Cl2):
d = 2.5 (8H, br, s, cod CH2), 5.5 (4H, br, s, cod CH), 8.0 (12H,
d, 3J(HP) = 10.1, ArH), 8.1 (6H, s, ArH).
[Rh(acac*)(La)2] (10a)
Acknowledgements
Ligand La (150 mg, 0.22 mmol) was added to a solution of
[Rh(CO)2(acac*)] (39 mg, 0.11 mmol) in CH2Cl2 (15 cm3). This
gave a yellow solution and CO was evolved. The reaction mixture
was stirred at room temperature for 5 h and then all volatiles were
removed in vacuo to give 10a as a bright yellow solid (142 mg,
0.087 mmol, 78%). Elemental analysis (calc., 10a·CH2Cl2): C,
We should like to thank EPSRC and DuPont for a CASE
studentship (to K. L. M.), Johnson-Matthey for the loan of
precious metal salts and the Leverhulme Trust for a Research
Fellowship (to P. G. P.).
42.10 (42.10); H, 2.20 (2.30); MS (FAB) m/z: 1626 (M+); 31P{ H}
1
References
NMR (C6D6/CH2Cl2): d = 59.2 (d, J(PRh) = 194.2 Hz); 19F
1
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