2-Pyridyl substituents enhance the activity of palladium-phospha-adamantane catalysts for the methoxycarbonylation of phenylacetylene

Article abstract of DOI:10.1039/c6dt03983a

The synthesis of a series of CgPAr ligands is reported, where CgP is the 6-phospha-2,4,8-trioxa-1,3,5,7-tetramethyladamant-6-yl moiety and Ar = 2-pyridyl (L₂), 3-pyridyl (L₃), 2-pyrimidyl (L₄), 4-R-2-pyridyl [R = Me (L_5a), CF₃ (L_6a), SiMe₃ (L_7a)] or 6-R-2-pyridyl [R = Me (L_5b), CF₃ (L_6b), SiMe₃ (L_7b). Testing of these ligands in the Pd-catalysed methoxycarbonylation of phenylacetylene reveals that the activity and branched selectivity of the catalysts derived from these ligands varies as a function of the N-heterocycle, with the catalyst derived from L_5b being the most active of those tested. This, together with the poor performance of catalysts derived from L₃ supports the hypothesis that the catalysis proceeds by a “proton shuttling” mechanism, an idea that previously had only been applied to arylphosphines. Reaction of [PtCl₂(cod)] with L where L = L₂ or L_4-7 yields a rac/meso mixture of the trans-[PtCl₂(L)₂] (1a-h) complexes, three of which are structurally characterised. ³¹P NMR spectroscopy shows that reaction of L₃ with [PtCl₂(cod)] gives a mixture of mononuclear and binuclear metal complexes in solution. The complex trans-[PdCl₂(L₂)₂] (4) reacts with AgBF₄ to give the [PdCl(κ¹-L₂)(κ²-L₂)]BF₄ (5) with spectroscopic and structural characterisation confirming the presence of a P,N-chelate. ¹H and ³¹P NMR evidence supports the assignment of a pyridyl-protonated species being formed upon treatment of 4 with TsOH·H₂O in CD₂Cl₂; both the protonated species and chelate 5 are observed when the reaction is carried out in MeOH.

Full text of DOI:10.1039/c6dt03983a

Dalton
Transactions
View Article Online
View Journal
PAPER
2-Pyridyl substituents enhance the activity of
palladium–phospha-adamantane catalysts for the
methoxycarbonylation of phenylacetylene†
Cite this: DOI: 10.1039/c6dt03983a
Timothy A. Shuttleworth, Alexandra M. Miles-Hobbs, Paul G. Pringle* and
Hazel A. Sparkes
The synthesis of a series of CgPAr ligands is reported, where CgP is the 6-phospha-2,4,8-trioxa-1,3,5,7-
tetramethyladamant-6-yl moiety and Ar = 2-pyridyl (L2), 3-pyridyl (L3), 2-pyrimidyl (L4), 4-R-2-pyridyl
[R = Me (L5a), CF3 (L6a), SiMe3 (L7a)] or 6-R-2-pyridyl [R = Me (L5b), CF3 (L6b), SiMe3 (L7b). Testing of these
ligands in the Pd-catalysed methoxycarbonylation of phenylacetylene reveals that the activity and
branched selectivity of the catalysts derived from these ligands varies as a function of the N-heterocycle,
with the catalyst derived from L5b being the most active of those tested. This, together with the poor
performance of catalysts derived from L3 supports the hypothesis that the catalysis proceeds by a “proton
shuttling” mechanism, an idea that previously had only been applied to arylphosphines. Reaction of
[PtCl2(cod)] with L where L = L2 or L4–7 yields a rac/meso mixture of the trans-[PtCl2(L)2] (1a–h)
complexes, three of which are structurally characterised. 31P NMR spectroscopy shows that reaction of L3
with [PtCl2(cod)] gives a mixture of mononuclear and binuclear metal complexes in solution. The
complex trans-[PdCl2(L2)2] (4) reacts with AgBF4 to give the [PdCl(κ1-L2)(κ2-L2)]BF4 (5) with spectroscopic
1
and structural characterisation confirming the presence of a P,N-chelate. H and 31P NMR evidence sup-
Received 17th October 2016,
Accepted 30th November 2016
ports the assignment of a pyridyl-protonated species being formed upon treatment of 4 with TsOH·H2O
in CD2Cl2; both the protonated species and chelate 5 are observed when the reaction is carried out in
MeOH.
DOI: 10.1039/c6dt03983a
www.rsc.org/dalton
the branched product, methyl methacrylate (MMA) which is a
precursor to poly(methyl methacrylate).3 The methoxy-
Introduction
The palladium-catalysed methoxycarbonylation of alkynes carbonylation of phenylacetylene (Scheme 1, R = Ph) produces
(Scheme 1) is an atom-efficient way of producing branched or methyl atropate (branched product), a precursor to ibuprofen2
linear α,β-unsaturated esters from readily available feedstocks.1,2
or methyl cinnamate (linear product), which has applications
The methoxycarbonylation of propyne (Scheme 1, R = Me) in the perfume and flavouring industries.4
has been extensively studied owing to the industrial interest in
The activity, selectivity and stability of the palladium cata-
lyst for methoxycarbonylation depend critically on the ligand.
Drent et al. reported that changing the ligand from PPh3 to
Ph2P(2-py) (L1) led to an increase in rate of three orders of
magnitude for propyne and an increase in branched selectivity
from 89% to 99%.3 It was postulated that a “non-classical”
carbomethoxy mechanism involving P,N-chelates was in
operation and the greater catalyst activity was a result of the
Ph2P(2-py) acting as a “proton messenger”,3 by bringing the
proton into close proximity to the metal and thereby promot-
ing the protonolysis of the proposed vinyl-palladium inter-
mediate as shown in Scheme 2.
Scheme 1
School of Chemistry, University of Bristol, Cantock’s Close, Bristol, BS8 1TS, UK.
E-mail: Paul.Pringle@bristol.ac.uk
Recently, Bühl et al. reported a computational study of
several possible pathways for methoxycarbonylation.5 Drent’s
original mechanism was challenged, as it was found that the
postulated, selectivity-determining transition state would
†Electronic supplementary information (ESI) available: Crystal structures of
ligands L2–7 and crystal structure and refinement details. CCDC
1497885–1497898. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c6dt03983a
This journal is © The Royal Society of Chemistry 2016
Dalton Trans.

View Article Online
Paper
Dalton Transactions
from Ph2P(2-py) have been shown to be excellent for phenyl-
acetylene methoxycarbonylation (Scheme 1, R = Ph).3,6
It has also been observed that substituents on the 2-pyridyl
ring have a pronounced effect upon the performance of the
catalyst; moreover Ph2P(3-py) and Ph2P(4-py) give catalysts of
much lower activity.3 Palladium complexes of other monophos-
phines with the potential to form heterodonor P,L-chelates
(e.g. pyrimidylphosphines,7 iminophosphines,8 phosphinoqui-
nilines,9 furylphosphines10 and so called TROPPs11) have been
shown to be efficient methoxycarbonylation catalysts. It is
notable that in all of these ligands an Ar2P moiety is present.12
Ligands incorporating the 6-phospha-2,4,8-trioxa-1,3,5,7-
tetramethyladamant-6-yl (CgP) moiety are effective for a range
t
of Pd-catalysed carbonylation reactions.13 CgPR and Bu2PR
are comparable in terms of bulk but very different in
σ/π-bonding characteristics: the donor properties of CgPR are
comparable to a (PhO)2PR.14 It was therefore of interest to
investigate CgP(2-py) (L2) and its derivatives as ligands for
Pd-catalysed methoxycarbonylation of phenylacetylene. We
show here that the Pd–L2 catalysts are active and that 4- and
6-substituents on the 2-pyridyl affect the performance of the
catalyst. The platinum and palladium coordination chemistry
of these ligands has been explored which has given some
insight into the function of L2 and related ligands.
Scheme 2 Drent’s non-classical carbomethoxy mechanism.3
favour the formation of linear product (methyl crotonate) over
the branched product (MMA). Instead, an alternative cycle
involving labile P,N-chelates was proposed which proceeded by
an in situ base mechanism (Scheme 3)5 closely related to that
described by Scrivanti et al.6 This was suggested to be the
most plausible mechanism due to it having surmountable bar-
riers congruent with the high turnover and selectivity observed
experimentally with L1. Common to the Drent and Bühl
mechanisms (Schemes 2 and 3) is the chelation of the P,N
ligand which acts to stabilise the catalyst. Catalysts derived
Results and discussion
Ligand synthesis
The synthesis of CgP(2-py) (L2) has previously been reported
via a Pd-catalysed P-arylation of CgPH15 and we have extended
the route to the preparation of cage phosphines containing
3-pyridyl (L3), 2-pyrimidyl (L4), 4-substituted-2-pyridyl (L5–7a
)
and 6-substituted-2-pyridyl (L5–7b) (Scheme 4). These air-stable
ligands were purified by column chromatography and have
been fully characterised. Crystals of all of the ligands L2–7 suit-
able for X-ray crystallography have been obtained. The struc-
tures are very similar to each other and so only L2, as a
representative structure, is shown in Fig. 1 along with its main
metrical parameters; the structures of L3–7 are given in the
ESI.†
Methoxycarbonylation catalysis
In order to draw comparisons in performance among the
ligands, the methoxycarbonylation of phenylacetylene (eqn (1))
has been carried out in the presence of L1–7, PPh3 and CgPPh
under the same reaction conditions and the results are pres-
ented in Table 1.
Scheme 3 Bühl’s in situ base mechanism.5
Dalton Trans.
This journal is © The Royal Society of Chemistry 2016

View Article Online
Dalton Transactions
Paper
Table 1 Catalytic methoxycarbonylation of phenylacetylenea
% Conversionb
Entry
ligand
4.5 h
1 h
% Branchedc
1
2
3
4
5
6
7
8
PPh3
CgPPh
L1
13
72
100
89
63
100
92
32
89
87
14
—
—
100
59
34
95
64
21
55
34
—
47
—
96
82
99
81
91
95
84
87
73
94
99
86
—
L2
L5a
L5b
L6a
L6b
L7a
L7b
L3
9
10
11
12
13
L4
—
75
<2
a Reaction conditions: 5.5 mmol of phenylacetylene, 5.5 × 10−3 mmol
of Pd(OAc)2, 2.2 mmol of p-tolylsulfonic acid monohydrate, 1.1 mmol
of ligand, 1.5 cm3 of MeOH, 45 bar of CO, 60 °C. b Conversion and
selectivity determined by 1H NMR (see Experimental for details). Each
result is an average of 2 or more runs. c The rest of the product was the
linear isomer.
Ligand L2 (entry 4) produced a higher activity catalyst than
CgPPh (entry 3) indicating that the 2-pyridyl group has a posi-
tive effect within the CgPAr series of ligands. This is reinforced
by the low activity observed with the 3-pyridyl isomer L3 (entry
11). The pyrimidyl group in ligand L4 (entry 12) led to a catalyst
with lower activity than L2.
Scheme 4
The results for the catalysts derived from L5–7a and L5–7b
show that substituents Me, CF3 and SiMe3 at the 4- and 6-posi-
tions in the 2-pyridyl ring can, in some cases, have a signifi-
cant effect on the conversion compared to the unsubstituted
L2. However, there appears to be no consistent trends associ-
ated with the stereoelectronic effect of the substituents.
Relative to L2: (1) the 4-Me ligand L5a (entry 5) gives a signifi-
cantly lower conversion while the 6-Me ligand L5b (entry 6)
gives a significantly higher conversion; (2) the 4-CF3 and
4-SiMe3 ligands, L6a (entry 7) and L7a (entry 9), perform simi-
larly to L2 while the 6-CF3 and 6-SiMe3 ligands, L6b (entry 8)
and L7b (entry 10), produce catalysts of lower activity than L2.
In terms of branched selectivity, there is some evidence that
the 6-substituted 2-pyridyl ligands L5–7b give more branched-
selective catalysts than their 4-substituted isomers L5–7a
(entries 5–10). Others have reported similar observations with
4- and 6-substituted pyridyl derivatives of L1; that is, greater
branched selectivity was obtained with 6-substituted than with
4-substituted pyridyl ligands.4
Fig. 1 Crystal structure of L2. Hydrogen atoms omitted for clarity.
Thermal ellipsoids at 50% probability. Selected bond lengths (Å) and
bond angles (°): P1–C1 1.8857(12), P1–C4 1.8734(12), P1–C11 1.8395(12);
C1–P1–C4 92.71(5), C1–P1–C11 101.83(5), C4–P1–C11 106.34(5).
Under the conditions we used for the catalysis, the PPh3
catalyst produced low and inconsistent conversions (entry 1)
ð1Þ
In order to elucidate the function of the 2-pyridyl in the Pd-
catalysis, the coordination chemistry of L2–7 with Pt and Pd
has been investigated.
and at the end of the runs, copious amounts of black deposit,
presumably metallic palladium, was observed indicating that
the catalyst was not stable. As previously reported,4 the very
high activity of the catalyst derived from L1 (entry 3) contrasts
Coordination chemistry
sharply with that of the isosteric PPh3 analogue (entry 1). The Ligands L2–7 have been reacted with [PtCl2(cod)] (cod = 1,5-
CgPPh is superior to PPh3 in producing a moderately active cyclooctadiene) in CH2Cl2. With the exception of the reaction
catalyst (entry 2) that shows no evidence of decomposition to with L3 (see below), products of the type trans-[PtCl2(L)2] (1a–h)
metallic Pd during the catalytic runs.
were obtained (Scheme 5) which have been fully characterised.
This journal is © The Royal Society of Chemistry 2016
Dalton Trans.

View Article Online
Paper
Dalton Transactions
Scheme 5
The 31P NMR spectra of the products in each case showed two
closely spaced singlets with 195Pt satellites (1JP–Pt values are
typical of trans-[PtCl2(PR3)2] complexes) consistent with the
presence of rac and meso diastereomers resulting from the
chirality of the cage ligands.14
Crystals suitable for X-ray crystallography of 1c, 1d, 1e and
1g (meso isomers in each case) were grown by slow diffusion of
hexane into a CH2Cl2 solution of a rac/meso mixture of the
corresponding complex. As shown in Fig. 2–5, in each case,
the ligands adopt an anti conformation, with the C(pyridyl)–
P–P–C(pyridyl) torsion angle of 180°.
Fig. 3 Crystal structure of meso-1d, showing the anti–trans confor-
mation adopted by the ligands. Hydrogen atoms omitted for clarity.
Atoms suffixed with a dash (’) are related by symmetry operation (−x,
1−y, −z). Thermal ellipsoids at 50% probability. Selected bond lengths (Å)
and angles (°): Pt1–Cl1 2.3119(6), Pt1–P1 2.3198(6), P1–C1 1.883(3),
P1–C4 1.878(3), P1–C11 1.845(3); C1–P1–C4 93.99(11), C1–P1–C11
103.98(12), C4–P1–C11 111.54(12).
The reaction of [PtCl2(cod)] with the 3-pyridyl ligand L3 gave
different results from those for all of the 2-pyridyl ligands L2,
and L4–7. The 31P NMR spectrum of the products of the reac-
tion of [PtCl2(cod)] with 2 equiv. of the 3-pyridyl ligand L3
showed four signals with 195Pt satellites, as well as free ligand
(δP −29.5 ppm). Two of the signals were assigned to rac/meso-
[PtCl2(L3)2] (1i) because of the similarity of their 31P NMR data
(δP −2.6 ppm, 1JP,Pt = 2703 Hz; δP −2.8 ppm, 1JP,Pt = 2710 Hz) to
those of the analogues 1a–h. The remaining two signals were
assigned to binuclear complexes of the type [Pt2Cl2(L3)2(μ-Cl)2]
Fig. 4 Crystal structure of meso-1e, showing the anti–trans confor-
mation adopted by the ligands. Hydrogen atoms omitted for clarity.
Atoms suffixed with a dash (’) are related by symmetry operation (−x,
1−y, −z). Thermal ellipsoids at 50% probability. Selected bond lengths (Å)
and angles (°): Pt1–Cl1 2.3056(5), Pt1–P1 2.3227(5), P1–C1 1.877(2),
P1–C4 1.886(3), P1–C11 1.842(2); C1–P1–C4 94.43(10), C1–P1–C11
105.04(13), C4–P1–C11 109.69(10).
on the basis of their large 1JP,Pt values (δP 8.3 ppm, 1JP,Pt = 4592
1
Hz; δP 7.9 ppm JP,Pt = 4608 Hz). Two types of isomerism (syn/
anti and rac/meso) would be expected for [Pt2Cl2(L3)2(μ-Cl)2]; in
view of the 0.4 ppm difference in their δP values, we tentatively
assign the two observed 31P NMR signals to syn- and anti-2
(Scheme 6) with the signals expected for the rac and meso
Fig. 2 Crystal structure of meso-1c showing the anti–trans confor- isomers unresolved. Mixtures of mononuclear and binuclear
mation adopted by the ligands. Hydrogen atoms omitted for clarity.
Atoms suffixed with a dash (’) are related by symmetry operation (−x, −y,
−z). Thermal ellipsoids at 50% probability. Selected bond lengths (Å) and
angles (°): Pt1–Cl1 2.3125(7), Pt1–P1 2.3259(7), P1–C1 1.884(3), P1–C4
products were also reported in the reaction of [PtCl2(cod)] with
2 equiv. CgPPh14 and so the observation of exclusive formation
of mononuclear complexes 1a–h appears to be an effect of the
2-pyridyl group. It is tempting to associate this with weak
Pt⋯N interactions stabilising the mononuclear complexes
1.879(3), P1–C11 1.837(3); C1–P1–C4 94.10(13), C1–P1–C11 109.47(13),
C4–P1–C11 105.41(13).
Dalton Trans.
This journal is © The Royal Society of Chemistry 2016

View Article Online
Dalton Transactions
Paper
Scheme 7
value of 1JP,Pt for the chelate-P is consistent with the ring strain
being relieved by lengthened Pt–P bonds; the crystal structure
of the Pd analogue 5[BF4] (see below) supports this inference.
In a similar manner to that described above for the Pt ana-
logues, reaction of [PdCl2(cod)] with 2 equiv. of L2 yielded
trans-[PdCl2(L2)2] (4) which has been fully characterised.
Treatment of 4 with 1 equiv. of AgBF4 gave a product assigned
the structure 5[BF4], the Pd analogue of 3[BF4] (Scheme 8).
Crystals of 5[BF4] suitable for X-ray crystallography were
obtained and its crystal structure determined (Fig. 6) which
confirmed the cis orientation of the two P-donors. The chelate
ring strain is apparent from the acute P–Pd–N angle of 69.0°.
The Pd–P length within the chelate is longer (by ca. 0.02 Å)
Fig. 5 Crystal structure of meso-1g, showing the anti–trans confor-
mation adopted by the ligands. Disordered atoms in CgP moiety and
hydrogen atoms omitted for clarity. Atoms suffixed with a dash (’) are
related by symmetry operation (1−x, −y, −z). Thermal ellipsoids at 50%
probability. Selected bond lengths (Å) and angles (°): Pt1–Cl1 2.3022(5),
Pt1–P1 2.3193(5), P1–C1 1.877(2), P1–C4 1.875(2), P1–C11 1.833(2); C1–
P1–C4 94.23(9), C1–P1–C11 103.66(8), C4–P1–C11 111.82(9).
Scheme 8
Scheme 6
although in the solid state at least, no such interactions were
detected in complexes 1c–e and 1g (see Fig. 2–5).
The ability of 2-pyridylphosphines to switch between
P-monodentate and P,N-bidentate coordination has been
invoked as part of the explanation for the high activity of Pd-
complexes of 2-pyridylphosphines in methoxycarbonyla-
tion.3,5,6 It was therefore of interest to investigate if 2-pyridyl-
phosphine L2 could form 4-membered P,N-chelates. Treatment
of the trans complex 1a with 1 equiv. of AgBF4 gave a precipi-
tate of AgCl and a solution whose 31P{1H} NMR spectrum was
Fig. 6 Crystal structure of 5[BF4]. The [BF4]− counterion, hydrogen
consistent with the formation of the monochelate 3[BF4] atoms and CH2Cl2 solvent molecule are omitted for clarity. Thermal
(Scheme 7). Two doublets were observed at −48.1 ppm (1JP,Pt
=
ellipsoids at 50% probability. Selected bond lengths (Å) and angles (°):
2
Pd1–Cl1 2.2989(10), Pd1–P1 2.3170(10), Pd1–P2 2.2779(10), Pd1–N1
2.073(3), P1–C11 1.829(4), P2–C26 1.819(4); P1–Pd1–P2 112.44(3), P1–
Pd1–N1 68.95(9), P1–C11–N1 101.9(3), P2–Pd1–Cl1 86.17(4), P1–Pd1–
Cl1 161.35(4), P2–Pd1–N1 176.87(9), C1–P1–C4 95.33(17), C16–P2–C19
2728 Hz) and +0.8 ppm (1JP,Pt = 3514 Hz) with a small JP,P of
11 Hz typical of cis coordinated phosphines. The signal at
−48.1 ppm is assigned to the P,N-chelate since its high field
shift is characteristic of a 4-membered chelate.16 The lower 94.48(16).
This journal is © The Royal Society of Chemistry 2016
Dalton Trans.

View Article Online
Paper
Dalton Transactions
than that for the monodentate ligand perhaps reflecting the similar to L1 shown in Schemes 1 and 2. Tellingly, the 31P{1H}
ring strain. NMR spectrum of the mixture obtained after catalysis runs
The 31P{1H} NMR spectrum of 5[BF4] in CHCl2CHCl2 involving Pd and L2 showed, amongst other peaks, a promi-
showed a slightly broadened (w1/2 ∼ 8 Hz) signal at 28.8 ppm, nent signal at −37.8 ppm, reminiscent of the peak observed at
corresponding to the monodentate ligand, and a sharp −42.1 ppm for the cation 5, suggesting that a four-membered
doublet at −42.7 ppm (2JP,P = 3.2 Hz), assigned to the P,N- Pd chelate is present.
chelate. The signals remain distinct but broaden as the temp-
erature is raised (e.g. w1/2 ∼ 70 Hz at 100 °C in CHCl2CHCl2)
indicating that cation 5 is fluxional, which is associated with
intramolecular interchange of chelating and non-chelating P,N
Conclusions
ligands. Iggo et al. have shown that the complex [PdCl{κ1-Ph2P A series of substituted pyridyl-functionalised phospha-ada-
(2-py)}{κ2-Ph2P(2-py)}]BF4 (an analogue of 5[BF4]) is fluxional mantyl ligands L2–7 have been made and fully characterised. It
but with a coalescence temperature for the 31P NMR signals of was found that, in some cases, substituents on the pyridyl ring
−30 °C which is at least 150 °C lower than for cation 5.17 The had a marked effect on the rate of Pd-catalysed methoxycarbo-
high barrier to exchange in 5 can be rationalised in terms of nylation of phenylacetylene. The 6-methyl substituted ligand
steric hindrance to Pd–P bond rotation which may be required L5b showed good activity and selectivity for the branched
in order for the pyridyl-nitrogen in the κ1-L2 to coordinate. product albeit lower than that of the well-known Ph2P(2-py)
Energy barriers to M–P bond rotation in complexes containing (L1). The catalytic performance is a function of the substitu-
cis-M(CgPH)2 moieties have previously been shown18 to be of ents on the pyridine consistent with the idea that a mechan-
the order of 50 kJ mol−1
Complex is only sparingly soluble in CD2Cl2 but operating.
addition of 1.1 equiv. of TsOH·H2O to a suspension of 4 in The Pt and Pd coordination chemistry of L2–7 has been
.
ism involving P,N-chelation and “proton shuttling” may be
4
CD2Cl2 gave a homogenous yellow solution. The 31P NMR spec- probed and the ability of the ligands to form P,N-chelates has
trum showed two broad peaks at 6.0 and 3.7 ppm (w1/2 ∼ 57 Hz been established in solution from the characteristic 31P NMR
and 53 Hz respectively), which are tentatively assigned to spectra and in the solid state by the crystal structure of a palla-
diastereoisomers of protonated species such as 6 (Scheme 9) dium complex containing L2 ligands bound in a κ1- and
with rapid proton exchange rendering the 31P NMR signals κ2-mode. Moreover protonation of the pyridyl-N in a Pd-L2
1
equivalent on the NMR timescale. In the H NMR spectrum of complex has been observed in solution. In contrast to the
6 a broad signal centred at 6.55 ppm is assigned to the exchan- CgP(2-py) ligands, the CgP(3-py) ligand L3 gives binuclear
ging N–H. When a suspension of 4 in MeOH was treated with Pt complexes in a similar fashion to the CgPPh.
TsOH, the 31P NMR spectrum of the resulting solution dis-
The methoxycarbonylation activity with catalysts derived
played two broad signals at 6.3 and 4.5 ppm (assigned to 6) from CgP(2-py) and its derivatives demonstrates that the
but in addition, two signals at 28.8 and −42.2 ppm are 2-pyridyl effect is not restricted to Ph2P(2-py) and its deriva-
present, suggesting that the P,N-chelate 5[OTs] is also gener- tives. The CgP and Ph2P moieties has very different stereoelec-
ated (Scheme 9).
tronic effects and therefore the results presented hold out the
The Pd and Pt coordination chemistry of L2 has shown that prospect that other R2P(2-py) ligands may be useful for alkyne
the ligand can be monodentate (κ1) or chelating (κ2) and the methoxycarbonylation catalysis.
pyridyl-N can be protonated by TsOH. These properties are
essential for the catalyst to be able to function in a manner
Experimental
General procedures
All reactions were carried out under an atmosphere of dry
nitrogen, unless otherwise stated, using standard Schlenk line
techniques and oven dried (200 °C) glassware. CH2Cl2 and
hexane were collected from a Grubbs type solvent purification
system, and deoxygenated by bubbling with N2 for 30 minutes.
Xylene and CD2Cl2 were dried over activated 4 Å molecular
sieves for 72 hours and deoxygenated by successive freeze–
pump–thaw cycles. MeOH was purchased as anhydrous, stored
over 3 Å molecular sieves and deoxygenated by bubbling with
N2 for 30 minutes. Other commercial reagents were used as
supplied unless otherwise stated. [PtCl2(cod)],19 [PdCl2(cod)],20
1,3,5,7-tetramethyl-4,6,8-trioxa-2-phospha-adamantane (CgPH),21
CgPPh,14 Ph2P(2-py)22 (L1) 2-bromo-4-(trimethylsilyl)pyridine,23
Scheme 9
and 2-bromo-6-(trimethylsilyl)pyridine24 were synthesised accord-
Dalton Trans.
This journal is © The Royal Society of Chemistry 2016

View Article Online
Dalton Transactions
Paper
ing to literature procedures. 1H, 11B, 13C, 19F and 31P NMR
CgP(2-pyrm) (L4). Purification by flash column chromato-
spectra were recorded at ambient temperature unless otherwise graphy (20% EtOAc/hexane) yielded the product as a white
stated, on Jeol ECP (Eclipse) 300, Jeol ECS 300, Jeol ECS 400, solid (0.679 g, 80%). Crystals suitable for X-ray diffraction were
Varian 400-MR, Varian VNMRS 500 spectrometers and a Bruker grown by slow evaporation of a CH2Cl2 solution of the product.
3
Avance III HD 500 spectrometer equipped with a 13C-observe 1H NMR (500 MHz, CDCl3): δH 8.69 (d, JH,H = 4.9 Hz, 2H, ArH
3
(DCH) cryogenic probe. Chemical shifts δ are given in parts per (H-4 and H 6)), 7.13 (t, JH,H = 4.9 Hz, 1H, ArH (H-5)), 2.19 (d,
1
2
million (ppm) and coupling constants J are in Hz. H and 13C 2JH,H = 13.3 Hz, 1H, CgP CH2), 2.14 (dd, JH,H = 13.1 Hz, 3JH,P
=
chemical shifts were referenced to residual solvent peaks. 11B, 19
F
6.7 Hz, 1H, CgP CH2), 1.92 (dd, 3JH,P = 25.2 Hz, 2JH,H = 13.3 Hz,
and 31P chemical shifts were referenced to BF3·OEt2, CFCl3 and 1H, CgP CH2), 1.78 (d, JH,P = 12.0 Hz, 3H, CgP CH3), 1.72 (d,
3
85% H3PO4 respectively. Mass Spectra were recorded by the 3JH,P = 12.7 Hz, 3H, CgP CH3), 1.66 (dd, JH,H = 13.3 Hz, JH,P
=
2
3
University of Bristol Mass Spectrometry Service on VG Analytical 4.7 Hz, 1H, CgP CH2), 1.42 (s, 3H, CgP CH3), 1.27 (s, 3H, CgP
1
Autospec (EI) or VG Analytical Quattro (ESI) spectrometers. CH3). 13C{1H} NMR (126 MHz, CDCl3): δC 174.8 (d, JC,P
=
2
Elemental Analysis was carried out by the Microanalytical 9.7 Hz, ArC (C-2)), 156.1 (d, JC,P = 5.0 Hz, ArC (C-4 and C-6)),
Laboratory of the School of Chemistry, University of Bristol. X-ray 119.3 (s, ArC (C-5)), 96.6 (s, CgP quat. C), 96.4 (s, CgP quat. C),
1
1
crystallography was performed by the University of Bristol X-ray 74.4 (d, JC,P = 24.8 Hz, CgP quat. C), 73.9 (d, JC,P = 6.9 Hz,
2
2
Analytical Service using Bruker AXS Microstar or Bruker Kappa CgP quat. C), 45.6 (d, JC,P = 17.1 Hz, CgP CH2), 38.5 (d, JC,P
=
2
Apex II diffractometers. Thin Layer Chromatography (TLC) was 1.9 Hz, CgP CH2), 28.7 (d, JC,P = 19.3 Hz, CgP CH3), 28.1 (s,
performed using Merck Kieselgel 60 F254 (Merck) aluminium CgP CH3), 27.9 (s, CgP CH3), 27.6 (d, 2JC,P = 10.2 Hz, CgP CH3).
backed plates (0.25 mm layer of silica). Flash column chromato- 31P{1H} NMR (162 MHz, CDCl3): δP −18.5 (s, CgP). HRMS (EI):
graphy was performed using a Biotage Isolera Spektra One m/z calc. for C14H19N2O3P [M]+ = 294.1133; obs. = 294.1137.
Chromatographic Isolation system. Elem. Anal. found (calc. for C14H19N2O3P): C, 57.10 (57.14); H,
General procedure for the synthesis of pyridyl-functionalised 6.53 (6.51); N, 9.33 (9.52).
phospha-adamantyl ligands. A Schlenk flask was charged with
CgP(4-Me-2-py) (L5a). Purification by flash column chromato-
a suspension of CgPH (1 equiv.), K2CO3 (3 equiv.) and graphy (40% diethyl ether/hexane) yielded the product as a
[Pd(PPh3)4] (3 mol%) in xylene (6 cm3). The desired ArBr white solid (0.343 g, 74%). Crystals suitable for X-ray diffrac-
(1.2 equiv.) was added and the mixture heated to 110 °C and tion were grown by slow diffusion of hexane into a CH2Cl2
stirred for 24 h. The mixture was then allowed to cool and, in solution of the product. 1H NMR (400 MHz, CDCl3): δH 8.53 (d,
air, passed through silica, eluting with Et2O. Removal of the 3JH,H = 5.0 Hz, 1H, ArH (H-6)), 7.77 (s, 1H, ArH (H-3)), 7.02 (d,
solvents in vacuo yielded the crude product.
3JH,H = 5.0 Hz, 1H, ArH (H-5)), 2.34 (s, 3H, Ar–CH3), 2.07 (dd,
3
3
CgP(2-py) (L2). Prepared according to a literature pro- 2JH,H = 13.2 Hz, JH,P = 6.7 Hz, 1H, CgP CH2), 1.91 (dd, JH,P
=
cedure.14 Crystals suitable for X-ray diffraction were grown by 23.4 Hz, 2JH,H = 13.3 Hz, 1H, CgP CH2), 1.83 (d, 2JH,H = 13.2 Hz,
slow diffusion of hexane into a CH2Cl2 solution of the product. 1H, CgP CH2), 1.57 (d, JH,P = 12.4 Hz, 3H, CgP CH3), 1.50 (dd,
3
3
Spectroscopic data the same as those reported.
2JH,H = 13.3 Hz, JH,P = 4.1 Hz, 1H, CgP CH2), 1.41 (s, 3H, CgP
3
CgP(3-py) (L3). Purification by flash column chromatography CH3), 1.40 (d, JH,P = 12.4 Hz, 3H, CgP CH3), 1.37 (s, 3H, CgP
(20% EtOAc/hexane) yielded the product as a white solid CH3). 13C{1H} NMR (101 MHz, CDCl3): δC 160.4 (d, JC,P = 12.7
1
3
(0.432 g, 71%). Crystals suitable for X-ray diffraction were Hz, ArC (C-2)), 149.9 (d, JC,P = 14.2 Hz, ArC (C-6)), 146.5 (d,
grown by slow diffusion of hexane into a CH2Cl2 solution of 3JC,P = 1.8 Hz, ArC (C-4)), 130.2 (d, JC,P = 10.5 Hz, ArC (C-3)),
2
1
the product. H NMR (400 MHz, CDCl3): δH 8.93–8.92 (m, 1H, 124.0 (s, ArC (C-5)), 96.9 (s, CgP quat. C), 96.3 (s, CgP quat. C),
1
1
ArH (H-2)), 8.61–8.59 (m, 1H, ArH (H-6)), 8.19–8.15 (m, 1H, 73.5 (d, JC,P = 9.9 Hz, CgP quat. C), 73.1 (d, JC,P = 22.9 Hz,
2
2
2
ArH (H-4)), 7.31–7.26 (m, 1H, ArH (H-5)), 2.05 (dd, JH,H
=
CgP quat. C), 45.2 (d, JC,P = 16.7 Hz, CgP CH2), 37.5 (d, JC,P =
13.3 Hz, 3JH,P = 7.3 Hz, 1H, CgP CH2), 1.94 (dd, 3JH,P = 25.1 Hz, 2.1 Hz, CgP CH2), 28.2 (s, CgP CH3), 28.0 (s, CgP CH3), 27.9 (d,
2JH,H = 13.3 Hz, 1H, CgP CH2), 1.66 (d, 2JH,H = 13.5 Hz, 1H, CgP 3JC,P = 20.6 Hz, CgP CH3), 27.3 (d, JC,P = 11.7 Hz, CgP CH3),
3
2
3
CH2), 1.51 (dd, JH,H = 13.4 Hz, JH,P = 4.3 Hz, 1H, CgP CH2), 21.4 (s, Ar–CH3). 31P{1H} NMR (162 MHz, CDCl3): δP −24.5 (s,
1.49 (d, JH,P = 12.8 Hz, 3H, CgP CH3), 1.41 (s, 6H, CgP CH3), CgP). HRMS (EI): m/z calc. for C16H22NO3P [M]+ = 307.1337;
3
1.25 (d, 3JH,P = 13.3 Hz, 3H, CgP CH3). 13C{1H} NMR (101 MHz, obs. = 307.1331. Elem. Anal. found (calc. for C16H22NO3P): C,
2
CDCl3): δC 155.6 (d, JC,P = 26.4 Hz, ArC (C-2)), 150.5 (s, ArC 62.32 (62.53); H, 7.25 (7.22); N, 4.54 (4.56).
(C-6)), 142.3 (d, JC,P = 14.5 Hz, ArC (C-4)), 130.6 (d, JC,P
32.4 Hz, ArC (C-3)), 123.6 (d, JC,P = 4.4 Hz, ArC (C-5)), 97.0 (s, atography (5% EtOAc/hexane) yielded the product as a white
CgP quat. C), 96.2 (s, CgP quat. C), 73.3 (d, 1JC,P = 21.6 Hz, CgP solid (0.578 g, 82%). Crystals suitable for X-ray diffraction were
quat. C), 73.2 (d, JC,P = 7.3 Hz, CgP quat. C), 45.3 (d, JC,P
2
1
=
CgP(6-Me-2-py) (L5b). Purification by flash column chrom-
3
1
2
=
grown by slow evaporation of a CHCl3 solution. 1H NMR
2
3
17.7 Hz, CgP CH2), 36.4 (d, JC,P = 1.9 Hz, CgP CH2), 28.1 (s, (400 MHz, CDCl3): δH 7.78 (d, JH,H = 7.7 Hz, 1H, ArH (H-3)),
CgP CH3), 27.9 (s, CgP CH3), 27.5 (d, 2JC,P = 22.2 Hz, CgP CH3), 7.51 (t, JH,H = 7.7 Hz, 1H, ArH (H-4)), 7.06 (d, JH,H = 8.2 Hz,
3
2
26.9 (d, JC,P = 11.1 Hz, CgP CH3). 31P{1H} NMR (162 MHz, 1H, ArH (H-5)), 2.54 (s, 3H, Ar–CH3), 2.07 (dd, JH,H = 13.2 Hz,
2
2
CDCl3): δP −29.5 (s, CgP). HRMS (EI): m/z calc. for C15H20NO3P 3JH,P = 6.7 Hz, 1H, CgP CH2), 1.89 (dd, JH,P = 23.1 Hz, JH,H
=
3
2
[M]+ = 293.1184; obs. = 283.1174. Elem. Anal. found (calc. for 13.2 Hz, 1H, CgP CH2), 1.82 (d, JH,H = 13.3 Hz, 1H, CgP CH2),
2
2
3
C15H20NO3P): C, 61.78 (61.43); H, 6.94 (6.87); N, 5.00 (4.78).
1.48 (dd, JH,H = 13.3 Hz, JH,P = 4.1 Hz, 1H, CgP CH2), 1.55
This journal is © The Royal Society of Chemistry 2016
Dalton Trans.

View Article Online
Paper
Dalton Transactions
3
3
1
1
(d, JH,P = 12.3 Hz, 3H, CgP CH3), 1.41 (d, JH,P = 12.5 Hz, 3H, CgP quat. C), 73.8 (d, JC,P = 9.0 Hz, CgP quat. C), 73.1 (d, JC,P
CgP CH3), 1.40 (s, 3H, CgP CH3), 1.35 (s, 3H, CgP CH3). 13C{1H} = 23.3 Hz, CgP quat. C), 45.1 (d, 2JC,P = 16.9 Hz, CgP CH2), 37.7
NMR (126 MHz, CDCl3): δC 160.1 (d, 1JC,P = 10.7 Hz, ArC (C-6)), (d, JC,P = 2.0 Hz, CgP CH2), 28.0 (s, CgP CH3), 27.9 (s, CgP
2
158.9 (d, 3JC,P = 14.4 Hz, ArC (C-2)), 135.6 (d, 3JC,P = 1.2 Hz, ArC CH3), 27.8 (d, 2JC,P = 20.0 Hz, CgP CH3), 27.4 (d, 2JC,P = 11.4 Hz,
(C-4)), 126.2 (d, JC,P = 8.4 Hz, ArC (C 3)), 122.6 (s, ArC (C-5)), CgP CH3). 19F NMR (377 MHz, CDCl3): δF −68.1 (s, Ar–CF3). 31
P
2
1
96.9 (s, CgP quat. C), 96.3 (s, CgP quat. C), 73.6 (d, JC,P
=
{1H} NMR (162 MHz, CDCl3): δP −23.6 (s, CgP). HRMS (EI): m/z
9.9 Hz, CgP quat. C), 73.1 (d, 1JC,P = 22.9 Hz, CgP quat. C), 45.2 calc. for C16H19F3NO3P [M]+ = 361.1055; obs. = 361.1058. Elem.
2
2
(d, JC,P = 16.7 Hz, CgP CH2), 37.6 (d, JC,P = 2.1 Hz, CgP CH2), Anal. found (calc. for C16H19F3NO3P): C, 53.32 (53.19); H, 5.38
2
28.2 (s, CgP CH3), 28.0 (s, CgP CH3), 27.9 (d, JC,P = 20.4 Hz, (5.30); N, 3.75 (3.88).
2
CgP CH3), 27.3 (d, JC,P = 11.8 Hz, CgP CH3), 24.3 (s, Ar–CH3).
CgP(4-SiMe3-2-py) (L7a). Purification by flash column chrom-
31P{1H} NMR (162 MHz, CDCl3): δP −24.9 (s, CgP). HRMS (ESI): atography (10% EtOAc/hexane) yielded the product as a white
m/z calc. for C16H23NO3P [M + H]+ = 308.1410; obs. = 308.1404. solid (0.390 g, 56%). Crystals suitable for X-ray diffraction were
Elem. Anal. found (calc. for C16H22NO3P): C, 62.44 (62.53); H, grown by slow evaporation of a CH2Cl2 solution of the product.
3
7.27 (7.22); N, 4.57 (4.56).
1H NMR (500 MHz, CDCl3): δH 8.64 (d, JH,H = 4.7 Hz, 1H, ArH
3
CgP(4-CF3-2-py) (L6a). Purification by flash column chrom- (H-3)), 8.11 (br s, 1H, ArH (H-6)), 7.30 (d, JH,H = 4.7 Hz, 1H,
2
3
atography (20% diethyl ether/hexane) yielded the product as a ArH (H-5)), 2.10 (dd, JH,H = 13.3 Hz, JH,P = 6.6 Hz, 1H, CgP
3
2
white solid (0.673 g, 80%). Crystals suitable for X-ray diffrac- CH2), 1.92 (dd, JH,P = 23.4 Hz, JH,H = 13.2 Hz, 1H, CgP CH2),
2
3
tion were grown by slow diffusion of hexane into a CH2Cl2 1.80 (d, JH,H = 13.3 Hz, 1H, CgP CH2), 1.57 (d, JH,P = 12.4 Hz,
solution of the product. 1H NMR (500 MHz, CDCl3): δH 8.88 (d, 3H, CgP CH3), 1.51 (dd, 2JH,H = 13.3 Hz, 3JH,P = 4.1 Hz, 1H, CgP
3JH,H = 5.0 Hz, 1H, ArH (H-6)), 8.23 (s, 1H, ArH (H-3)), 7.43 (d, CH2), 1.42 (s, 3H, CgP CH3), 1.41 (d, JH,P = 12.6 Hz, 3H, CgP
3
3JH,H = 5.0 Hz, 1H, ArH (H-5)), 2.08 (dd, JH,H = 13.3 Hz, JH,P
=
CH3), 1.37 (s, 3H, CgP CH3), 0.32 (s, 9H, Si(CH3)3). 13C{1H}
2
3
6.9 Hz, 1H, CgP CH2), 1.94 (dd, 3JH,P = 23.6 Hz, 2JH,H = 13.3 Hz, NMR (126 MHz, CDCl3): δC 159.6 (d, 1JC,P = 13.5 Hz, ArC (C-2)),
2
2
1H, CgP CH2), 1.69 (d, JH,H = 13.4 Hz, 1H, CgP CH2), 1.59 (d, 149.8 (s, ArC (C-4)), 149.1 (d, JC,P = 13.4 Hz, ArC (C-3)), 133.9
3JH,P = 12.5 Hz, 3H, CgP CH3), 1.54 (dd, JH,H = 13.3 Hz, JH,P
4.2 Hz, 1H, CgP CH2), 1.43 (s, 3H, CgP CH3), 1.42 (d, JH,P
=
=
(d, JC,P = 9.1 Hz, ArC (C-6)), 127.3 (s, ArC (C-5)), 96.9 (s, CgP
2
3
3
quat. C), 96.3 (s, CgP quat. C), 73.5 (d, 1JC,P = 9.7 Hz, CgP quat.
3
12.8 Hz, 3H, CgP CH3), 1.36 (s, 3H, CgP CH3). 13C{1H} NMR C), 73.1 (d, JC,P = 22.7 Hz, CgP quat. C), 45.2 (d, JC,P = 16.7
1
2
(126 MHz, CDCl3): δC 163.5 (d, 1JC,P = 18.1 Hz, ArC (C-2)), 150.9 Hz, CgP CH2), 37.5 (d, JC,P = 2.1 Hz, CgP CH2), 28.2–27.8 (m,
2
3
2
2
(d, JC,P = 13.1 Hz, ArC (C-6)), 137.8 (q, JC,F = 33.9 Hz, ArC CgP CH3), 27.3 (d, JC,P = 11.6 Hz, CgP CH3), 1.6 (s, Si(CH3)3).
(C-4)), 124.8 (dq, JC,P = 10.0 Hz, JC,F = 3.5 Hz, ArC (C-3)), 31P{1H} NMR (162 MHz, CDCl3): δP −26.9 (s, CgP). HRMS (ESI):
2
3
122.9 (q, JC,F = 273.5 Hz, Ar–CF3), 118.4 (q, JC,F = 3.5 Hz, ArC m/z calc. for C18H29NO3PSi [M + H]+ = 366.1649; obs. =
1
3
1
(C-5)), 97.0 (s, CgP quat. C), 96.3 (s, CgP quat. C), 73.6 (d, JC,P 366.1662. Elem. Anal. found (calc. for C18H28NO3PSi): C, 59.55
1
= 9.7 Hz, CgP quat. C), 72.0 (d, JC,P = 22.8 Hz, CgP quat. C), (59.15); H, 7.89 (7.72); N, 4.02 (3.83).
2
2
44.9 (d, JC,P = 16.5 Hz, CgP CH2), 37.6 (d, JC,P = 2.0 Hz, CgP
CgP(6-SiMe3-2-py) (L7b). Purification by flash column chrom-
atography (10% EtOAc/hexane) yielded the product as a white
2
CH2), 28.0 (s, CgP CH3), 27.7 (s, CgP CH3), 27.8 (d, JC,P
=
20.6 Hz, CgP CH3), 27.3 (d, 2JC,P = 11.4 Hz, CgP CH3). 19F NMR solid (0.424 g, 42%). Crystals suitable for X-ray diffraction were
(377 MHz, CDCl3): δF −64.8 (s, Ar–CF3). 31P{1H} NMR grown by slow evaporation of a CH2Cl2 solution of the product.
3
(162 MHz, CDCl3): δP −24.2 (s, CgP). HRMS (EI): m/z calc. for 1H NMR (400 MHz, CDCl3): δH 7.71 (d, JH,H = 7.9 Hz, 1H, ArH
C16H19F3NO3P [M]+ = 361.1055; obs. = 361.1057. Elem. Anal. (H-3)), 7.50 (t, JH,H = 7.7 Hz, 1H, ArH (H-4)), 7.38 (d, JH,H
=
3
3
2
found (calc. for C16H19F3NO3P): C, 53.01 (53.19); H, 5.37 (5.30); 7.5 Hz, 1H, ArH (H-5)), 2.15 (d, JH,H = 13.2 Hz, 1H, CgP CH2),
2.10 (dd, JH,H = 13.2 Hz, JH,P = 6.5 Hz, 1H, CgP CH2), 1.91
CgP(6-CF3-2-py) (L6b). Purification by flash column chrom- (dd, JH,P = 23.5 Hz, JH,H = 13.2 Hz, 1H, CgP CH2), 1.57–1.51
2
3
N, 3.96 (3.88).
3
2
3
atography (10% EtOAc/hexane) yielded the product as a white (m, 3H, CgP CH3 and 1H CgP CH2), 1.47 (d, JH,P = 12.5 Hz,
solid (0.633 g, 76%). Crystals suitable for X-ray diffraction were 3H, CgP CH3), 1.42 (s, 3H, CgP CH3), 1.33 (s, 3H, CgP CH3),
grown by slow evaporation of a CH2Cl2 solution of the product. 0.30 (s, 9H, Si(CH3)3). 13C{1H} NMR (126 MHz, CDCl3):
3
1H NMR (400 MHz, CDCl3): δH 8.06 (d, JH,H = 7.9 Hz, 1H, ArH δC 167.0 (d, 3JC,P = 10.0 Hz, ArC (C-6)), 160.5 (d, 1JC,P = 13.4 Hz,
3
3
3
2
(H-3)), 7.81 (t, JH,H = 8.2 Hz, 1H, ArH (H-4)), 7.58 (d, JH,H
=
ArC (C-2)), 133.0 (d, JC,P = 3.2 Hz, ArC (C-4)), 128.4 (d, JC,P =
7.8 Hz, 1H, ArH (H-5)), 2.09 (dd, 2JH,H = 13.1 Hz, 3JH,P = 6.8 Hz, 17.2 Hz, ArC (C-3)), 127.4 (s, ArC (C-5)), 96.9 (s, CgP quat. C),
1H, CgP CH2), 1.95 (dd, JH,P = 23.9 Hz, JH,H = 13.3 Hz, 1H, 96.4 (s, CgP quat. C), 73.7 (d, JC,P = 8.7 Hz, CgP quat. C), 73.2
3
2
1
2
3
1
2
CgP CH2), 1.94 (d, JH,H = 13.4 Hz, 1H, CgP CH2), 1.57 (d, JH,P (d, JC,P = 23.4 Hz, CgP quat. C), 45.3 (d, JC,P = 16.8 Hz, CgP
2
= 12.5 Hz, 3H, CgP CH3), 1.58–1.54 (m, 1H CgP CH2), 1.48 (d, CH2), 37.7 (d, JC,P = 2.0 Hz, CgP CH2), 28.1 (s, CgP CH3), 28.0
3JH,P = 12.8 Hz, 3H, CgP CH3), 1.42 (s, 3H, CgP CH3), 1.34 (s, (s, CgP CH3), 27.9 (d, JC,P = 19.9 Hz, CgP CH3), 27.4 (d, JC,P
=
2
2
3H, CgP CH3). 13C{1H} NMR (126 MHz, CDCl3): δC 162.4 (d, 11.6 Hz, CgP CH3), 1.6 (s, Si(CH3)3). 31P{1H} NMR (162 MHz,
1JC,P = 21.0 Hz, ArC (C-2)), 148.6 (qd, JC,F = 34.6 Hz, JC,P
=
CDCl3): δP −26.9 (s, CgP). HRMS (ESI): m/z calc. for
2
3
10.8 Hz, ArC (C-6)), 136.6 (d, 3JC,P = 2.4 Hz, ArC (C-4)), 131.9 (d, C18H29NO3PSi [M + H]+ = 366.1649; obs. = 366.1651. Elem.
2JC,P = 13.7 Hz, ArC (C-3)), 121.5 (q, JC,F = 274.5 Hz, Ar–CF3), Anal. found (calc. for C18H28NO3PSi): C, 59.29 (59.15); H, 7.79
1
119.4 (q, 3JC,F = 2.7 Hz, ArC (C-5)), 96.6 (s, CgP quat. C), 96.4 (s, (7.72); N, 3.87 (3.83). (The stability of this ligand was tested by
Dalton Trans.
This journal is © The Royal Society of Chemistry 2016

View Article Online
Dalton Transactions
Paper
heating in MeOH (ca. 0.5 cm3) with TsOH·H2O (2 equiv.) and (s) and 27.6 (s) (CgP CH3), 27.4 (vir t, JC,P = 2.4 Hz) and 27.3
Pd(OAc)2 (0.1 equiv.) for 24 h and no decomposition was (vir t, JC,P = 2.4 Hz) (CgP CH3), 26.7 (br s) and 26.6 (br s) (CgP
1
observed.)
CH3). 31P{1H} NMR (162 MHz, CD2Cl2): δP −0.8 (s, JP,Pt = 2707
1
[PtCl2(L2)2] (1a). A solution of L2 (0.157 g, 0.537 mmol) in Hz) and −0.9 (s, JP,Pt = 2706 Hz) (CgP). HRMS (ESI): m/z calc.
CH2Cl2 (2 cm3) was added to a solution of [PtCl2(cod)] for C28H38ClN4O6P2Pt [M − Cl]+ = 818.1600; obs. = 818.1606.
(0.100 g, 0.267 mmol) in CH2Cl2 (2 cm3) and stirred for Elem. Anal. found (calc. for C28H38Cl2N4O6P2Pt): C, 39.66
24 hours. In air, the product was then precipitated in hexane (39.35); H, 4.57 (4.48); N, 6.34 (6.56).
(ca. 25 cm3). After the mixture was allowed to settle, the super-
[PtCl2(L5a)2] (1c). A solution of L5a (0.018 g, 0.058 mmol) in
natant was removed using a pipette and the residual solvent CH2Cl2 (1 cm3) was added to a solution of [PtCl2(cod)]
removed in vacuo to give the product as a pale yellow solid (0.010 g, 0.027 mmol) in CH2Cl2 (1 cm3) and stirred for
(0.184 g, 81%). rac : meso compounds observed in 3 : 2 ratio. 1H 24 hours. In air, the product was then precipitated in hexane
NMR (500 MHz, CD2Cl2): δH 8.76 (d, JH,H = 4.9 Hz) and 8.76 (ca. 25 cm3). After the mixture was allowed to settle, the super-
3
3
(d, JH,H = 4.9 Hz) (total 2H, ArH (H-6)), 8.04–8.01 (m, 2H, ArH natant was removed using a pipette and the residual solvent
(H-3)), 7.70–7.64 (m, 2H, ArH (H-4)), 7.32–7.26 (m, 2H, ArH removed in vacuo to give the product as a pale yellow solid
2
(H-5)), 3.04 (dt, 2JH,H = 13.6 Hz, JH,P = 2.3 Hz) and 2.95 (dt, JH,H (0.022 g, 86%). Crystals suitable for X-ray diffraction were
= 13.6 Hz, JH,P = 2.3 Hz) (total 2H, CgP CH2), 1.98–1.86 (m, 3H, grown by slow diffusion of hexane into a CH2Cl2 solution of
CgP CH2), 1.85 (vir t, JH,P = 6.2 Hz) and 1.80 (vir t, JH,P = 6.2 Hz) the product. rac : meso compounds observed in 3 : 2 ratio.
3
(total 6H, CgP CH3), 1.74 (vir t, JH,P = 6.7 Hz) and 1.69 (vir t, 1H NMR (500 MHz, CD2Cl2): δH 8.60 (d, JH,H = 5.0 Hz) and
3
JH,P = 6.7 Hz) (total 6H, CgP CH3), 1.66–1.59 (m, 1H, CgP CH2), 8.58 (d, JH,H = 5.0 Hz) (total 2H, ArH (H-6)), 7.89 (br s) and
3
1.39 (s) and 1.34 (s) (total 6H, CgP CH3), 1.27 (s) and 1.26 (s) 7.86 (br s) (total 2H, ArH (H-3)), 7.14 (d, JH,H = 4.7 Hz) and
3
(total 6H, CgP CH3). 13C{1H} NMR (126 MHz, CD2Cl2): δC 154.2 7.10 (d, JH,H = 5.0 Hz) (total 2H, ArH (H-5)), 3.05 (d of vir t,
2
(vir t, JC,P = 154.1 Hz, ArC (C-2)), 149.6 (app q, JC,P = 8.4 Hz, 2JH,H = 13.6 Hz, JH,P = 2.1 Hz) and 2.95 (d of vir t, JH,H = 13.6
ArC (C-6)), 134.7 (app q, JC,P = 3.3 Hz, ArC (C-4)), 130.7 (app q, Hz, JH,P = 2.1 Hz) (total 2H, CgP CH2), 2.38 (s) and 2.35 (s)
JC,P = 8.3 Hz, ArC (C-3)), 123.9 (s, ArC (C-5)), 96.4–96.2 (m, CgP (total 6H, Ar–CH3), 2.05–2.02 (m, 1H, CgP CH2), 1.98–1.88 (m,
quat. C), 74.9 (vir t, JC,P = 14.1 Hz) and 74.7 (vir t, JC,P
=
2H, CgP CH2), 1.84 (vir t, JH,P = 6.2 Hz) and 1.80 (vir t, JH,P =
14.1 Hz) (CgP quat. C), 73.8 (vir t, JC,P = 11.1 Hz) and 73.7 6.2 Hz) (total 6H, CgP CH3), 1.73 (vir t, JH,P = 6.6 Hz) and 1.68
(vir t, JC,P = 11.1 Hz) (CgP quat. C), 42.2 (vir t, JC,P = 3.8 Hz) and (vir t, JH,P = 6.6 Hz) (total 6H, CgP CH3), 1.65–1.56 (m, 3H, CgP
42.1 (vir t, JC,P = 3.8 Hz) (CgP CH2), 41.9–41.8 (m, CgP CH2), CH2), 1.39 (s) and 1.34 (s) (total 6H, CgP CH3), 1.27 (s) and
27.9 (s, CgP CH3), 27.7 (s, CgP CH3), 27.6 (br s) and 27.2 (br s) 1.26 (s) (total 6H, CgP CH3). 13C{1H} NMR (126 MHz, CD2Cl2):
(CgP CH3), 26.0 (vir t, JC,P = 2.0 Hz) and 25.8 (vir t, JC,P = 2.5 δC 159.3 (vir t, JC,P = 34.6 Hz, ArC (C-2)), 149.8 (vir t, JC,P = 8.7
Hz) (CgP CH3). 31P{1H} NMR (162 MHz, CD2Cl2): δP −0.6 (s, Hz) and 149.6 (vir t, JC,P = 8.7 Hz) (ArC (C-6)), 146.9–146.7 (br
1JP,Pt = 2740 Hz) and −1.1 (s, 1JP,Pt = 2727 Hz) (CgP). HRMS (ESI): s, ArC (C-4)), 132.2 (vir t, JC,P = 8.7 Hz) and 132.0 (vir t, JC,P
=
m/z calc. for C30H40ClN2O6P2Pt [M − Cl]+ = 816.1695; obs. = 8.7 Hz) (ArC (C-3)), 125.6 (s, ArC (C-5)), 96.9 (s, CgP quat. C),
816.1690. Elem. Anal. found (calc. for C30H40Cl2N2O6P2Pt): C, 96.8 (s) and 96.7 (s) (CgP quat. C), 75.5 (vir t, JC,P = 14.0 Hz)
42.64 (42.26); H, 5.13 (4.73); N, 3.44 (3.29).
and 75.3 (vir t, JC,P = 14.0 Hz) (CgP quat. C), 74.4 (vir t, JC,P =
[PtCl2(L4)2] (1b). A solution of L4 (0.033 g, 0.110 mmol) in 11.1 Hz) and 74.3 (vir t, JC,P = 11.1 Hz) (CgP quat. C), 42.9 (app
CH2Cl2 (1 cm3) was added to a solution of [PtCl2(cod)] q, JC,P = 4.1 Hz, CgP CH2), 42.4 (s) and 42.3 (s) (CgP CH2), 27.8
(0.020 g, 0.053 mmol) in CH2Cl2 (1 cm3) and stirred for (s, CgP CH3), 27.64 (s) and 27.56 (s) (CgP CH3), 27.5 (br s) and
24 hours. In air, the product was then precipitated in hexane 27.4 (br s) (CgP CH3), 26.1 (vir t, JC,P = 2.2 Hz) and 25.9 (vir t,
(ca. 25 cm3). After the mixture was allowed to settle, the super- JC,P = 2.4 Hz) (CgP CH3), 21.7 (s) and 21.6 (s) (Ar–CH3). 31P{1H}
1
natant was removed using a pipette and the residual solvent NMR (162 MHz, CD2Cl2): δP −0.6 (s, JP,Pt = 2738 Hz) and −1.0
1
removed in vacuo to give the product as a pale yellow solid (s, JP,Pt
= 2729 Hz) (CgP). HRMS (ESI): m/z calc. for
(0.043 g, 95%). rac : meso compounds observed in 1 : 1 ratio. 1H C32H44ClN2O6P2Pt [M − Cl]+ = 844.2009; obs. = 844.1993.
NMR (500 MHz, CD2Cl2): δH 8.76 (d, JH,H = 4.9 Hz) and 8.75 Elem. Anal. found (calc. for C32H44Cl2N2O6P2Pt): C, 43.47
3
3
(d, JH,H = 4.9 Hz) (total 4H, ArH (H-4 and H-6)), 7.25–7.22 (m, (43.64); H, 5.07 (5.04); N, 3.19 (3.18).
2
2H, ArH (H-5)), 3.16 (d of vir t, JH,H = 13.7 Hz, JH,P = 1.8 Hz)
[PtCl2(L5b)2] (1d). A solution of L5b (0.017 g, 0.055 mmol) in
and 3.13 (d of vir t, JH,H = 13.6 Hz, JH,P = 2.3 Hz) (total 2H, CH2Cl2 (1 cm3) was added to a solution of [PtCl2(cod)]
CgP CH2), 2.29 (d, 3JH,H = 13.8 Hz) and 2.21 (d, 3JH,H = 13.8 Hz) (0.010 g, 0.027 mmol) in CH2Cl2 (1 cm3) and stirred for
(total 2H, CgP CH2), 1.92–1.83 (m, 12H, CgP CH3), 1.82–1.70 24 hours. In air, the product was then precipitated in hexane
(m, 4H, CgP CH3), 1.37 (s) and 1.35 (s) (total 6H, CgP CH3), (ca. 25 cm3). After the mixture was allowed to settle, the super-
1.20 (s, 6H, CgP CH3). 13C{1H} NMR (126 MHz, CD2Cl2): natant was removed using a pipette and the residual solvent
2
δC 168.0 (vir t, JC,P = 46.1 Hz, ArC (C-2)), 156.2 (vir t, JC,P
=
removed in vacuo to give the product as a pale yellow solid
5.6 Hz) and 156.1 (vir t, JC,P = 5.6 Hz) (ArC (C-4 and C-6)), 121.3 (0.020 g, 78%). Crystals suitable for X-ray diffraction were
(s, ArC (C-3)), 97.0 (s) and 96.96 (s) (CgP quat. C), 96.94 (s) and grown by slow diffusion of hexane into a CH2Cl2 solution of
96.92 (s) (CgP quat. C), 75.8–75.5 (m, CgP quat. C), 42.9–42.8 the product. rac : meso compounds observed in 3 : 2 ratio.
(m, CgP CH2), 42.6–42.4 (m, CgP CH2), 27.9 (s, CgP CH3), 27.7 1H NMR (500 MHz, CD2Cl2): δH 7.87–7.84 (m, 2H, ArH (H-3)),
This journal is © The Royal Society of Chemistry 2016
Dalton Trans.

View Article Online
Paper
Dalton Transactions
7.58–7.53 (m, 2H, ArH (H-4)), 7.16–7.12 (m, 2H, ArH (H-5)), = 952.1443; obs. = 952.1479. Elem. Anal. found (calc. for
2
3.09 (d of vir t, JH,H = 13.6 Hz, JH,P = 2.1 Hz) and 2.99 (d of vir C32H38Cl2F6N2O6P2Pt): C, 38.66 (38.88); H, 3.89 (3.87); N, 2.85
2
t, JH,H = 13.6 Hz, JH,P = 2.1 Hz) (total 2H, CgP CH2), 2.62 (s) (2.83).
2
and 2.57 (s) (total 6H, Ar–CH3), 2.17 (d, JH,H = 13.7 Hz, 1H,
[PtCl2(L6b)2] (1f). A solution of L6b (0.040 g, 0.110 mmol) in
CgP CH2), 1.90–1.87 (m, 2H, CgP CH2) 1.85 1.70 (m, 12H, CgP CH2Cl2 (1 cm3) was added to a solution of [PtCl2(cod)]
CH3), 1.64–1.60 (m, 3H, CgP CH2), 1.37 (s) and 1.34 (s) (total (0.020 g, 0.053 mmol) in CH2Cl2 (1 cm3) and stirred for
6H, CgP CH3), 1.25 (s, 6H, CgP CH3). 13C{1H} NMR (126 MHz, 24 hours. In air, the product was then precipitated in hexane
CD2Cl2): δC 159.3 (vir t, JC,P = 8.6 Hz) and 159.0 (vir t, JC,P = 8.6 (ca. 25 cm3). After the mixture was allowed to settle, the super-
Hz) (ArC (C-6)), 153.7 (vir t, JC,P = 34.8 Hz) and 153.6 (vir t, JC,P natant was removed using a pipette and the residual solvent
= 35.6 Hz) (ArC (C-2)), 135.4–135.3 (m, ArC (C-4)), 128.7 (vir t, removed in vacuo to give the product as an off-white solid
JC,P = 9.3 Hz) and 128.5 (vir t, JC,P = 8.2 Hz) (ArC (C-3)), 124.2 (0.044 g, 84%). rac : meso compounds observed in 2 : 1 ratio. 1H
3
(s) and 124.1 (s) (ArC (C-5)), 97.0 (s) and 96.9 (s) (CgP quat. C), NMR (500 MHz, CD2Cl2): δH 8.30 (d, JH,H = 8.0 Hz) and 8.25
3
3
96.8 (s) and 96.7 (s) (CgP quat. C), 75.6 (vir t, JC,P = 14.0 Hz) (d, JH,H = 8.0 Hz) (total 2H, ArH (H-3)), 7.90 (t, JH,H = 8.0 Hz)
3
3
and 75.4 (vir t, JC,P = 14.0 Hz) (CgP quat. C), 74.5 (vir t, JC,P
=
and 7.85 (d, JH,H = 8.0 Hz) (total 2H, ArH (H-4)), 7.68 (d, JH,H
11.1 Hz) and 74.2 (vir t, JC,P = 11.1 Hz) (CgP quat. C), 42.9 (vir = 7.9 Hz) and 7.63 (d, 3JH,H = 7.9 Hz) (total 2H, ArH (H-5)), 3.08
2
t, JC,P = 3.8 Hz) and 42.7 (vir t, JC,P = 3.8 Hz) (CgP CH2), 42.5 (s) (d of vir t, JH,H = 13.7 Hz, JH,P = 2.2 Hz) and 3.01 (d of vir t,
and 42.4 (s) (CgP CH2), 27.9 (s, CgP CH3), 27.8 (s) and 27.6 (s) 2JH,H = 13.8 Hz, JH,P = 2.2 Hz) (total 2H, CgP CH2), 2.16 (d, 2JH,H
2
(CgP CH3), 27.7 (br s) and 27.4 (br s) (CgP CH3), 26.4 (vir t, JC,P = 13.8 Hz) and 2.14 (d, JH,H = 13.8 Hz) (total 2H, CgP CH2),
= 2.4 Hz) and 26.0 (vir t, JC,P = 2.4 Hz) (CgP CH3), 24.8 (s) and 1.95–1.84 (m, 2H, CgP CH2), 1.78–1.68 (m, 14H, CgP CH3 and
24.7 (s) (Ar–CH3). 31P{1H} NMR (162 MHz, CD2Cl2): δP −1.2 (s, CH2), 1.41 (s) and 1.36 (s) (6H, CgP CH3), 1.27 (br s, 6H, CgP
1
1JP,Pt = 2731 Hz) and −1.5 (s, JP,Pt = 2723 Hz) (CgP). HRMS CH3). 13C{1H} NMR (126 MHz, CD2Cl2): δC 156.1 (vir t, JC,P
=
(ESI): m/z calc. for C32H44ClN2O6P2Pt [M − Cl]+ = 844.2009; 32.0 Hz) and 156.0 (vir t, JC,P = 32.5 Hz) (ArC (C-2)), 148.1 (vir t,
obs. 844.2012. Elem. Anal. found (calc. for JC,P = 7.3 Hz) and 147.8 (vir t, JC,P = 7.8 Hz) (ArC (C-6)), 136.7
C32H44Cl2N2O6P2Pt): C, 43.73 (43.64); H, 5.12 (5.04); N, 3.24 (vir t, JC,P = 5.6 Hz, ArC (C-4)), 134.2 (vir t, JC,P = 9.5 Hz, ArC
=
1
1
(3.18).
(C-3)), 121.9 (q, JC,F = 274.0 Hz) and 121.8 (q, JC,F = 274.4 Hz)
[PtCl2(L6a)2] (1e). A solution of L6a (0.020 g, 0.055 mmol) in (Ar–CF3), 121.2 (br s) and 121.1 (br s) (ArC (C-5)), 97.1 (s) and
CH2Cl2 (1 cm3) was added to a solution of [PtCl2(cod)] 97.05 (s) (CgP quat. C), 97.03 (s) and 96.9 (s) (CgP quat. C),
(0.010 g, 0.027 mmol) in CH2Cl2 (1 cm3) and stirred for 75.7 (vir t, JC,P = 14.4 Hz) and 75.6 (vir t, JC,P = 14.4 Hz) (CgP
24 hours. In air, the product was then precipitated in hexane quat. C), 74.8–74.5 (m, CgP quat. C), 42.7–42.6 (m, CgP CH2),
(ca. 25 cm3). After the mixture was allowed to settle, the super- 42.4 (s) and 42.3 (s) (CgP CH2), 27.8 (s, CgP CH3), 27.7 (s) and
natant was removed using a pipette and the residual solvent 27.6 (s) (CgP CH3), 27.2 (s) and 27.71 (s) (CgP CH3), 26.2 (br s,
removed in vacuo to give the product as a pale yellow solid CgP CH3). 19F NMR (470 MHz, CD2Cl2): δF −68.4 (s) and −68.5
1
(0.019 g, 72%). Crystals suitable for X-ray diffraction were (s) (Ar–CF3). 31P{1H} NMR (202 MHz, CD2Cl2): δP 0.2 (s, JP,Pt
=
grown by slow diffusion of hexane into a CH2Cl2 solution of 2756
Hz,
CgP).
HRMS
(ESI): m/z
calc.
for
=
the product. rac : meso compounds observed in 3 : 1 ratio. 1H C32H38Cl2F6N2NaO6P2Pt [M
+
Na]+
= 1010.1029; obs.
3
NMR (500 MHz, CD2Cl2): δH 8.96 (d, JH,H = 5.0 Hz) and 8.93 1010.1027. Elem. Anal. found (calc. for C32H38Cl2F6N2O6P2Pt):
(d, 3JH,H = 5.0 Hz) (total 2H, ArH (H-6)), 8.29 (br s) and 8.26 (br C, 38.92 (38.88); H, 4.08 (3.87); N, 2.75 (2.83).
s) (total 2H, ArH (H-3)), 7.53 (d, 3JH,H = 4.4 Hz) and 7.50 (d, 3JH,H
[PtCl2(L7a)2] (1g). A solution of L7a (0.040 g, 0.110 mmol) in
2
= 4.7 Hz) (total 2H, ArH (H-5)), 3.02 (d of vir t, JH,H
=
CH2Cl2 (1 cm3) was added to a solution of [PtCl2(cod)]
2
13.7 Hz, JH,P = 2.3 Hz) and 2.93 (d of vir t, JH,H = 13.7 Hz, JH,P (0.020 g, 0.053 mmol) in CH2Cl2 (1 cm3) and stirred for
= 2.4 Hz) (total 2H, CgP CH2), 1.98–1.86 (m, 4H, CgP CH2), 24 hours. In air, the product was then precipitated in hexane
1.84–1.71 (m, 12H, CgP CH3), 1.69–1.67 (m, 2H, CgP CH2), 1.41 (ca. 25 cm3). After the mixture was allowed to settle, the super-
(s) and 1.36 (s) (total 6H, CgP CH3), 1.28 (s, 6H, CgP CH3). natant was removed using a pipette and the residual solvent
13C{1H} NMR (126 MHz, CD2Cl2): δC 156.9 (vir t, JC,P = 33.7 Hz, removed in vacuo to give the product as a pale yellow solid
ArC (C-2)), 151.0 (vir t, JC,P = 8.2 Hz, ArC (C-6)), 137.3 (q of vir t, (0.035 g, 66%). Crystals suitable for X-ray diffraction were
2JC,F = 33.9 Hz, JC,P = 3.6 Hz, ArC (C-4)), 126.8–126.6 (m, ArC grown by slow diffusion of hexane into a CH2Cl2 solution of
1
3
(C-3)), 123.2 (q, JC,F = 273.5 Hz, Ar–CF3), 118.4 (q, JC,F
=
the product. rac : meso compounds observed in 1 : 1 ratio. 1H
3
3.5 Hz, ArC (C-5)), 97.0–96.9 (m, CgP quat. C), 75.7 (vir t, NMR (500 MHz, CD2Cl2): δH 8.69 (d, JH,H = 4.7 Hz) and 8.66
3
JC,P = 14.0 Hz, CgP quat. C), 74.5 (vir t, JC,P = 11.0 Hz, CgP (d, JH,H = 4.7 Hz) (total 2H, ArH (H-3)), 8.19–8.17 (m) and
quat. C), 42.6 (vir t, JC,P = 4.0 Hz, CgP CH2), 42.5 (s, CgP CH2), 8.15–8.13 (m) (total 2H, ArH (H-6)), 7.40 (d, 3JH,H = 4.6 Hz) and
3
27.9 (s, CgP CH3), 27.7 (s) and 27.6 (s) (CgP CH3), 27.5 (br s) 7.36 (d, JH,H = 4.7 Hz) (total 2H, ArH (H-5)), 3.07 (d of vir t,
and 27.4 (br s) (CgP CH3), 26.0 (vir t, JC,P = 2.5 Hz) and 25.9 2JH,H = 13.6 Hz, JH,P = 2.3 Hz) and 2.97 (d of vir t, JH,H
=
=
2
(vir t, JC,P = 2.5 Hz) (CgP CH3). 19F NMR (377 MHz, CD2Cl2): 13.6 Hz, JH,P = 2.3 Hz) (total 2H, CgP CH2), 2.04 (d, JH,H
2
δF −65.13 (s) and −65.16 (s) (Ar–CF3). 31P{1H} NMR (162 MHz, 13.7 Hz) and 1.93 (d, JH,H = 13.5 Hz, 2H, CgP CH2), 1.92–1.85
2
1
1
CD2Cl2): δP 1.2 (s, JP,Pt = 2759 Hz) and 0.7 (s, JP,Pt = 2750 Hz) (m, 2H, CgP CH2), 1.82 (vir t, JH,P = 6.2 Hz) and (vir t, JH,P
=
(CgP). HRMS (ESI): m/z calc. for C32H38ClF6N2O6P2Pt [M − Cl]+ 6.1 Hz) (total 6H, CgP CH3), 1.72 (vir t, JH,P = 6.6 Hz) and 1.68
Dalton Trans.
This journal is © The Royal Society of Chemistry 2016

View Article Online
Dalton Transactions
Paper
(vir t, JH,P = 6.6 Hz) (total 6H, CgP CH3), 1.74–1.67 (m, 6H, CgP which was added to hexane to precipitate the product. After
CH3), 1.64–1.58 (m, 2H, CgP CH2), 1.40 (s) and 1.34 (s) (total the mixture was allowed to settle, the supernatant was
6H, CgP CH3), 1.26 (s) and 1.25 (s) (total 6H, CgP CH3), 0.30 (s) removed using a pipette and the residual solvent removed
and 0.28 (s) (total 18H, Si(CH3)3). 13C{1H} NMR (126 MHz, in vacuo to give the product as an off-white solid (0.010 g,
1
CD2Cl2): δC 153.5 (vir t, JC,P = 33.7 Hz, ArC (C-2)), 149.8–149.7 74%). H NMR (400 MHz, CD2Cl2): δH 9.26–9.06 (m, 1H, ArH),
(m, ArC (C-4)), 149.0–148.8 (m, ArC (C-3)), 135.7–135.5 (m, ArC 8.84–8.78 (m, 1H, ArH), 8.53–8.48 (m, 1H, ArH), 8.18–8.08 (m,
(C-6)), 128.9 (br s, ArC (C-5)), 96.9–96.7 (m, CgP quat. C), 75.5 1H, ArH), 7.97–7.91 (m, 2H, ArH), 7.84 7.78 (m, 1H, ArH),
(vir t, JC,P = 13.9 Hz) and 75.3 (vir t, JC,P = 13.9 Hz) (CgP quat. 7.45–7.41 (m, 1H, ArH), 2.47–1.27 (m, 32H, CgP CH3 and CgP
C), 74.5–74.2 (m, CgP quat. C), 42.9 (m, CgP CH2), 42.4 CH2). 11B{1H} NMR (128 MHz, CD2Cl2): δB −2.1 (s, BF4).
(m, CgP CH2), 28.0 (s, CgP CH3), 27.8 (s) and 27.7 (s) (CgP 19F NMR (377 MHz, CD2Cl2): δF −152.8 (s, BF4). 31P{1H} NMR
2
1
CH3), 27.6 (br s) and 27.5 (br s) (CgP CH3), 26.1 (br s) and 25.9 (162 MHz, CD2Cl2): δP 0.8 (d, JP,P = 11.8 Hz, JP,Pt = 3514 Hz,
2
1
(br s) (CgP CH3), −1.59 (s) and −1.62 (s) (Si(CH3)3). 31P{1H} monodentate CgP), −48.1 (d, JP,P = 11.6 Hz, JP,Pt = 2947 Hz,
NMR (162 MHz, CD2Cl2): δP −0.8 (s, JP,Pt = 2728 Hz) and −1.3 chelate CgP). HRMS (ESI): m/z calc. for C30H40ClN2O6P2Pt [M]+
1
1
(s, JP,Pt
=
2647 Hz) (CgP). HRMS (ESI): m/z calc. for = 816.1695; obs. = 816.1691.
[PdCl2(L2)2] (4). A solution of L2 (0.103 g, 0.350 mmol) in
Elem. Anal. found (calc. for C36H56Cl2N2O6P2PtSi2): C, 43.61 CH2Cl2 (2 cm3) was added to a solution of [PdCl2(cod)]
(43.37); H, 5.80 (5.66); N, 2.95 (2.81).
(0.050 g, 0.175 mmol) in CH2Cl2 (2 cm3) and stirred for
C36H56ClN2O6P2PtSi2 [M − Cl]+ = 960.2484; obs. = 960.2490.
[PtCl2(L7b)2] (1h). A solution of L7b (0.040 g, 0.110 mmol) in 24 hours. In air, the product was then precipitated in hexane
CH2Cl2 (1 cm3) was added to a solution of [PtCl2(cod)] (ca. 25 cm3). After the mixture was allowed to settle, the super-
(0.020 g, 0.053 mmol) in CH2Cl2 (1 cm3) and stirred for natant was removed using a pipette and the residual solvent
24 hours. In air, the product was then precipitated in hexane removed in vacuo to give the product as a yellow solid (0.129 g,
(ca. 25 cm3). After the mixture was allowed to settle, the super- 96%). rac : meso compounds observed in 1 : 1 ratio. 1H NMR
3
natant was removed using a pipette and the residual solvent (500 MHz, CD2Cl2): δH 8.73 (d, JH,H = 4.3 Hz) and 8.71 (d,
removed in vacuo to give the product as a pale yellow solid 3JH,H = 4.4 Hz) (total 2H, ArH (H-6)), 8.01 (d, 3JH,H = 4.4 Hz, 2H,
(0.044 g, 83%). rac : meso compounds observed in 1 : 1 ratio. ArH (H-3)), 7.70–7.66 (m, 2H, ArH (H-4)), 7.29 (appq, 3JH,H = 4.4
3
2
1H NMR (500 MHz, CD2Cl2): δH 7.96 (d, JH,H = 8.0 Hz) and Hz, 2H, ArH (H-5)), 3.04 (d of vir t, JH,H = 13.6 Hz, JH,P = 2.3
7.88 (d, JH,H = 8.0 Hz) (total 2H, ArH (H-3)), 7.60–7.52 (m, 2H, Hz) and 2.96 (d of vir t, 2JH,H = 13.6 Hz, JH,P = 2.3 Hz) (total 2H,
3
3
3
ArH (H-4)), 7.48 (d, JH,H = 7.4 Hz) and 7.44 (d, JH,H = 7.4 Hz) CgP CH2), 2.24 (s) and 2.35 (s) (total 1H, CgP CH2), 1.99–1.89
(total 2H, ArH (H-5)), 3.10–3.04 (m, 2H, CgP CH2), 2.29 (d, 2JH,H
=
(m, 3H, CgP CH2), 1.84 (vir t, JH,P = 6.3 Hz) and 1.80 (vir t,
2
13.6 Hz) and 2.18 (d, JH,H = 13.6 Hz) (total 2H, CgP CH2), JH,P = 6.3 Hz) (total 6H, CgP CH3), 1.73 (vir t, JH,P = 6.8 Hz) and
1.87–1.58 (m, 16H, CgP CH3 CH2), 1.36 (s) and 1.33 (s) (total 1.70 (vir t, JH,P = 6.6 Hz) (total 6H, CgP CH3), 1.59–1.54 (m, 2H,
6H, CgP CH3), 1.26 (s) and 1.25 (s) (total 6H, CgP CH3), 0.33 (s) CgP CH2), 1.38 (s) and 1.35 (s) (total 6H, CgP CH3), 1.27 (s, 6H,
and 0.32 (s) (total 18H, Si(CH3)3). 13C{1H} NMR (126 MHz, CgP CH3). 13C{1H} NMR (126 MHz, CD2Cl2): δC 155.6 (vir t, JC,P
CD2Cl2): δC 169.0 (br s) and 168.8 (br s) (ArC (C-6)), 155.1 (s) = 30.4 Hz) and 156.0 (vir t, JC,P = 29.7 Hz) (ArC (C-2)), 150.1
and 155.0 (s) (ArC (C-2)), 133.0–132.8 (m, ArC (C-4)), 130.4 (app q, JC,P = 8.0 Hz, ArC (C-6)), 135.4 (br s, ArC (C-4)), 131.1
(vir t, JC,P = 10.2 Hz) and 130.2 (vir t JC,P = 9.7 Hz) (ArC (C-3)), (vir t, JC,P = 8.7 Hz) and 130.1 (vir t, JC,P = 8.2 Hz) (ArC (C 3)),
128.9 (s) and 128.8 (s) (ArC (C-5)), 96.9–96.8 (m, CgP quat. C), 124.5 (s, ArC (C-5)), 97.0–96.8 (m, CgP quat. C), 76.3 (vir t,
75.6–75.3 (m) and 74.7–74.3 (m) (CgP quat. C), 42.9 (vir t, JC,P
=
JC,P = 10.9 Hz) and 76.2 (vir t, JC,P = 10.8 Hz) (CgP quat. C), 75.0
3.8 Hz) and 42.8 (vir t, JC,P = 3.9 Hz) (CgP CH2), 42.4 (s) and (vir t, JC,P = 7.1 Hz) and 74.8 (vir t, JC,P = 7.0 Hz) (CgP quat. C),
42.3 (s) (CgP CH2), 28.0 (s, CgP CH3), 27.8 (s) and 27.7 (s) (CgP 43.2–43.1 (m, CgP CH2), 42.5–42.4 (m, CgP CH2), 28.2 (br s)
CH3), 27.4 (br s) and 27.3 (br s) (CgP CH3), 26.4 (br s) and 26.3 and 28.1 (br s) (CgP CH3), 27.8 (s, CgP CH3), 27.73 (s) and
(br s) (CgP CH3), −1.56 (s) and −1.57 (s) (Si(CH3)3). 31P{1H} 27.68 (s) (CgP CH3), 26.8 (vir t, JC,P = 2.5 Hz) and 26.6 (vir t,
1
NMR (202 MHz, CD2Cl2): δP −1.6 (s, JP,Pt = 2722 Hz) and −1.9 JC,P = 2.7 Hz) (CgP CH3). 31P{1H} NMR (162 MHz, CD2Cl2):
1
(s, JP,Pt
= 2724 Hz) (CgP). HRMS (ESI): m/z calc. for δP 4.4 (s) and 4.3 (s) (CgP). HRMS (ESI): m/z calc. for
C36H57Cl2N2O6P2PtSi2 [M + H]+ = 996.2251; obs. = 996.2247. C30H40ClN2O6P2Pd [M − Cl]+ = 727.1088; obs. = 727.1103.
Elem. Anal. found (calc. for C36H56Cl2N2O6P2PtSi2): C, 43.54 Elem. Anal. found (calc. for C30H40Cl2N2O6P2Pd): C, 47.16
(43.37); H, 5.77 (5.66); N, 3.18 (2.81).
[PtCl2(L3)2] (1i). The solution of L3 (0.020 g, 0.068 mmol)
(47.17); H, 5.29 (5.28); N, 3.85 (3.67).
[PdCl(κ1-L2)(κ2-L2)]BF4 (5[BF4]). AgBF4 (0.008 g, 0.039 mmol)
was added to a solution of [PtCl2(cod)] (0.012 g, 0.034) in was added to a CH2Cl2 solution (3 cm3) of 4 (0.030 g,
CH2Cl2 (1 cm3) and the mixture stirred. The reaction was 0.039 mmol) and stirred overnight. The cloudy mixture was
monitored over 24 hours by 31P NMR spectroscopy (see text for then filtered through Celite to give a yellow solution, which
details).
was added to hexane to precipitate the product. After the
[PtCl(κ1-L2)(κ2-L2)]BF4 (3[BF4]). AgBF4 (0.003 g, 0.015 mmol) mixture was allowed to settle, the supernatant was removed
was added to a CH2Cl2 solution (2 cm3) of 1a (0.013 g, using a pipette and the residual solvent removed in vacuo to
0.015 mmol) and stirred overnight. The cloudy mixture was give the product as a yellow solid (0.024 g, 76%). Crystals suit-
then filtered through Celite to give a colourless solution, able for X-ray diffraction were grown by slow evaporation of a
This journal is © The Royal Society of Chemistry 2016
Dalton Trans.

View Article Online
Paper
Dalton Transactions
1
CH2Cl2 solution of the product. H NMR (500 MHz, CD2Cl2): set to 1 before being fixed at the refined values. Restraints
δH 8.92–8.89 (m, 1H, ArH), 8.79–8.78 (m, 1H, ArH), 8.41–8.36 were applied to the bond lengths and the thermal parameters
(m, 1H, ArH), 8.06–8.02 (m, 2H, ArH), 7.87–7.79 (m, 2H, ArH), of pairs of disordered atoms on almost the same site were con-
7.79–7.47 (m, 1H, ArH), 2.43–1.27 (m, 32H, CgP CH3 and CgP strained to be equal. The structure of 5 was twinned and
−
CH2). 11B{1H} NMR (128 MHz, CD2Cl2): δB −2.2 (s, BF4). refined as a 2-component twin. In addition, the BF4 counter-
19F NMR (377 MHz, CD2Cl2): δF −152.8 (s, BF4). 31P{1H} NMR ion displayed disorder in the fluorine positions, the sum of
(121 MHz, CD2Cl2): δP 28.8 (br s, monodentate CgP), −42.1 (d, the occupancies were set to equal 1 and refined before being
2JP,P = 3.2 Hz, chelate CgP). 31P{1H} NMR (121 MHz, CD2Cl2, fixed at the refined values. Restraints were applied to maintain
2
−90 °C): δP 28.8 (d, JP,P = 3.2 Hz, monodentate CgP), −42.0 sensible thermal parameters and B–F distances. Crystal struc-
(br s, chelate CgP). HRMS (ESI): m/z calc. for ture and refinement details are given in Tables S1–S3 in ESI.†
C30H40ClN2O6P2Pd [M]+ = 727.1088; obs. = 727.1118. Elem. Crystallographic data for the compounds have been deposited
Anal. found (calc. for C30H40BClF4N2O6P2Pd·CH2Cl2): C, 41.79 with the Cambridge Crystallographic Data Centre as sup-
(41.36); H, 4.86 (4.70); N, 3.20 (3.11) (the presence of CH2Cl2 plementary publication, CCDC 1497885–1497898.
was confirmed by 1H NMR spectroscopy and was observed
in the crystal structure).
Acknowledgements
Protonation studies
TsOH·H2O (0.003 g, 0.015 mmol) was added to a suspension The Bristol Chemical Synthesis Centre for Doctoral Training
of 4 (0.010 g, 0.013 mmol) in CD2Cl2 (0.7 cm3), upon which (BCS CDT) funded by the Engineering and Physical Sciences
the solution became homogeneous, yielding species assigned Research Council (EPSRC) (EP/G036764/1) and the University
to the protonated species 6. 31P{1H} NMR (121 MHz, CD2Cl2): of Bristol are thanked for a PhD studentship (to T. A. S.).
δP 6.0 (br s, CgP) and 3.7 (br s, CgP). An analogous procedure
in MeOH (0.7 cm3) also gave a homogenous solution, assigned
to be a mixture of 6 and a P,N-chelate species related to 5[OTs].
References
31P{1H} NMR (121 MHz, CD2Cl2): δP 28.8 (br s, monodentate
CgP), 6.3 (br s, CgP) and 4.5 (br s, CgP), −42.2 (br s, chelate
CgP).
1 G. Kiss, Chem. Rev., 2001, 101, 3435–3456.
2 (a) A. Brennführer, H. Neumann and M. Beller,
ChemCatChem, 2009, 1, 28–41 and references therein;
(b) P. Kalck and M. Urrutigoïty, Inorg. Chim. Acta, 2015,
431, 110–121 and references therein.
Phenylacetylene methoxycarbonylation
Adapted from previously reported procedure.9 Catalysis was
performed using a Baskerville Multi-Cell autoclave. The ligand
(0.11 mmol) was added to the autoclave and the system put
under an atmosphere of N2. Solutions of Pd(OAc)2
(0.0055 mmol) in MeOH (0.5 cm3) and TsOH·H2O (0.22 mmol)
in MeOH (0.5 cm3) were then added, followed by phenyl-
acetylene (5.5 mmol). This was then washed in using MeOH
(0.5 cm3) and the autoclave flushed with three cycles of CO (ca.
10 bar). The autoclave was then pressurised to 45 bar and
heated to 60 °C. After 1 hour or 4.5 hours, the autoclave was
transferred to an ice bath and once cooled, the system was
vented. A small amount of each sample was dissolved in CDCl3
and analysed by 1H NMR spectroscopy. Conversion and selecti-
vity was determined by integration of the phenylacetylene
alkynyl proton (δH 3.10 ppm) and the methyl atropate (δH 6.38
and 5.90 ppm) and methyl cinnamate (δH 7.71 and 6.42 ppm)
alkenyl protons.
3 (a) E. Drent, P. Arnoldy and P. H. M. Budzelaar,
J. Organomet. Chem., 1993, 455, 247–253; (b) E. Drent,
P. Arnoldy and P. H. M. Budzelaar, J. Organomet. Chem.,
1994, 475, 57–63; (c) E. Drent and D. H. L. Pello, World
Patent, WO95/03269, 1995; (d) E. Drent, W. W. Jager and
J. C. L. J. Suykerbuyk, World Patent, WO1995005357, 1995;
(e) E. Drent and W. W. Jager, US Patent, US5719313, 1998.
4 A. Viña and E. Murillo, J. Braz. Chem. Soc., 2003, 14, 744–749.
5 (a) L. Crawford, D. J. Cole-Hamilton, E. Drent and M. Bühl,
Chem. – Eur. J., 2014, 20, 13923–13926; (b) L. Crawford,
D. J. Cole-Hamilton and M. Bühl, Organometallics, 2015,
34, 438–449.
6 A. Scrivanti, V. Beghetto, E. Campagna, M. Zanato and
U. Matteoli, Organometallics, 1998, 17, 630–635.
7 M. T. Reetz, R. Demuth and R. Goddard, Tetrahedron Lett.,
1998, 39, 7089–7092.
8 A. Scrivanti, U. Matteoli, V. Beghetto, S. Antonaroli,
R. Scarpelli and B. Crociani, J. Mol. Catal. A: Chem., 2001,
170, 51–56.
X-ray crystallography
All of the X-ray diffraction data were collected at 100 K on a
Bruker Apex II diffractometer with CCD area detector using
Mo-Kα radiation (λ = 0.71073 Å). Absorption corrections were
carried out using SADABS.25 All of the structures were solved
9 M. L. Clarke, D. J. Cole-Hamilton, D. F. Foster,
A. M. Z. Slawin and J. D. Woollins, J. Chem. Soc., Dalton
Trans., 2002, 1618–1624.
using Superflip26,27 and refined by full matrix least squares on 10 (a) A. Scrivanti, V. Beghetto, M. Zanato and U. Matteoli,
F2 using ShelXL28,29 within Olex2.30 The structure of meso-1g
displayed disorder in the cage, the occupancies of the dis-
ordered atoms were refined with the sum of the occupancies
J. Mol. Catal. A: Chem., 2000, 160, 331–336; (b) A. Scrivanti,
V. Beghetto, E. Campagna and U. Matteoli, J. Mol. Catal. A:
Chem., 2001, 168, 75–80.
Dalton Trans.
This journal is © The Royal Society of Chemistry 2016

View Article Online
Dalton Transactions
Paper
11 L. Bettucci, C. Bianchini, W. Oberhauser, M. Vogt and
J. F. Bickley and A. Steiner, Dalton Trans., 2010, 39, 7921–
H. Grützmacher, Dalton Trans., 2010, 39, 6509–6517.
7935.
12 Propyne methoxycarbonylation catalysts based on RR′P(2-py) 18 P. Jankowski, C. L. McMullin, I. D. Gridnev, A. G. Orpen
where R or R′ ≠ Ph have been claimed in patents: (a) E. Drent
and P. H. M Budzelaar, Eur. Patent, EP0386834B1, 1993;
(b) E. Drent, US Patent, US005166411A, 1992.
and P. G. Pringle, Tetrahedron: Asymmetry, 2010, 21, 1206–
1209.
19 J. X. McDermott, J. F. White and G. M. Whitesides, J. Am.
Chem. Soc., 1976, 98, 6521–6528.
13 (a) P. G. Pringle and M. B. Smith, in Phosphorus(III) Ligands
in Homogeneous Catalysis: Design and Synthesis, ed. P. C. J. 20 C. T. Bailey and G. C. Lisensky, J. Chem. Educ., 1985, 62,
Kamer and P. W. N. M. van Leeuwen, John Wiley & Sons, 896.
Ltd, Chichester, UK, 2012; (b) J. C. L. J. Suykerbuyk, 21 M. Epstein and S. A. Buckler, J. Am. Chem. Soc., 1961, 83,
E. Drent and P. G. Pringle, World Patent, WO9842717, 1998; 3279–3282.
(c) R. I. Pugh, P. G. Pringle and E. Drent, Chem. Commun., 22 H. Schmidbaur and Y. Inoguchi, Z. Naturforsch., B: Anorg.
2001, 1476–1477; (d) G. R. Eastham, World Patent, Chem. Org. Chem., 1980, 35, 1329–1334.
WO2004024322, 2004; (e) G. R. Eastham and N. Tindale, 23 C. Y. Kim, D.-G. Ha, H. H. Kang, H.-J. Yun, S.-K. Kwon,
World Patent, WO2005079981, 2005; (f) G. R. Eastham,
World Patent, WO2005118519, 2005; (g) M. Slany,
J.-J. Kim and Y.-H. Kim, J. Mater. Chem., 2012, 22, 22721–
22726.
M. Schäfer and M. Röper, German Patent, DE10228293, 24 S. D. Bull, S. G. Davies, D. J. Fox, M. Gianotti, P. M. Kelly,
2001; (h) M. Schäfer, M. Slany, E. Zeller, M. Röper,
M. Schultz and G. Grimm, World Patent, WO0226382, 2002;
C. Pierres, E. D. Savory and A. D. Smith, J. Chem. Soc.,
Perkin Trans. 1, 2002, 1858–1868.
(i) E. Drent, P. G. Pringle and R. I. Pugh, World Patent, 25 G. M. Sheldrick, SADABS V2012/1, University of Göttingen,
WO0128972, 2001. Germany.
14 R. A. Baber, M. L. Clarke, K. M. Heslop, A. C. Marr, 26 L. Palatinus and G. Chapuis, J. Appl. Crystallogr., 2007, 40,
A. G. Orpen, P. G. Pringle, A. Ward and D. E. Zambrano-
Williams, Dalton Trans., 2005, 1079–1085.
15 T. Brenstrum, D. A. Gerristma, G. M. Adjabeng,
786–790.
27 L. Palatinus, S. J. Prathapa and S. van Smaalen, J. Appl.
Crystallogr., 2012, 45, 575–580.
C. S. Frampton, J. Britten, A. J. Robertson, J. McNulty and 28 G. M. Sheldrick, Acta Crystallogr., Sect. A: Fundam.
A. Capretta, J. Org. Chem., 2004, 69, 7635–7639. Crystallogr., 2008, 64, 112–122.
16 V. K. Jain, V. S. Jakkal and R. Bohra, J. Organomet. Chem., 29 G. M. Sheldrick, Acta Crystallogr., Sect. C: Cryst. Struct.
1990, 389, 417–426. Commun., 2015, 71, 3–8.
17 J. Liu, C. Jacob, K. J. Sheridan, F. Al-Mosule, B. T. Heaton, 30 O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard
J. A. Iggo, M. Matthews, J. Pelletier, R. Whyman,
and H. Puschmann, J. Appl. Crystallogr., 2009, 42, 339–341.
This journal is © The Royal Society of Chemistry 2016
Dalton Trans.