Diphenylphosphino(phenyl pyridin-2-yl methylene)amine palladium(II) complexes: Chemoselective alkene hydrocarboxylation initiators

Article abstract of DOI:10.1016/j.jorganchem.2005.04.032

The heteroditopic, P-N-chelating ligand diphenylphosphino(phenyl pyridin-2-yl methylene)amine (1) has been synthesised via a simple 'one-pot' procedure and its donor characteristics assessed. The neutral [MX(Y)(1-κ²-P-N)] (3, M = Rh, X = Cl, Y

Full text of DOI:10.1016/j.jorganchem.2005.04.032

Journal of Organometallic Chemistry 690 (2005) 5264–5281
www.elsevier.com/locate/jorganchem
Diphenylphosphino(phenyl pyridin-2-yl methylene)amine
palladium(II) complexes: Chemoselective alkene
hydrocarboxylation initiators
a,b,
b
b,1
Philip W. Dyer
*, John Fawcett , Martin J. Hanton
a
Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, UK
Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, UK
b
Received 1 February 2005; received in revised form 18 April 2005; accepted 20 April 2005
Available online 16 June 2005
Abstract
The heteroditopic, P–N-chelating ligand diphenylphosphino(phenyl pyridin-2-yl methylene)amine (1) has been synthesised via a
simple ꢀone-potꢁ procedure and its donor characteristics assessed. The neutral [MX(Y)(1-j2-P–N)] (3, M = Rh, X = Cl, Y = CO; 4,
M = Pd, X = Y = Cl; 5, M = Pd, X = Cl, Y = Me; 6, M = Pt, X = Y = Cl; 7, M = Pt, X = Cl, Y = Me; 8, M = Pt, X = Y = Me) and
cationic [Pd(Me)(MeCN)(1-j2-P–N)][Z] (9, Z = B{3,5-(CF3)2-C6H3}4; 10, Z = PF6) complexes of 1 have been prepared and charac-
terised. The solid-state structures of complexes 3, 4, 6 and 7 have been established by X-ray crystallography. Reactions of
t
[PdCl(Me)(1-j2-P–N)] towards CO and BuNC have been investigated, affording the corresponding g1-acyl (12) and -iminoacyl
(14) complexes, respectively. Similar insertion chemistry is observed for the cationic derivative 9. Treatment of the acyl complex
12 with ethene at elevated pressure establishes an equilibrium between the starting material and the product resulting from insertion,
13. Under catalytic conditions, combination of palladium(II) with 1 in MeOH affords a selective initiator for the formation of 4-oxo-
hexanoic acid methyl ester (15) from CO/ethene (38 bar, 90 ꢀC).
ꢁ 2005 Elsevier B.V. All rights reserved.
Keywords: P–N ligands; Palladium; Polyketone; Hydrocarboxylation
1. Introduction
wide range of variously substituted donor units into
the coordination sphere of metals.
There is continued interest in the application of hete-
roditopic ligands to a variety of catalytic processes, with
bidentate P–N derivatives having been the focus of par-
ticular attention [1]. The asymmetry present in systems
of this type offers a degree of selectivity in reactions
occurring at the metal centre, due to the electronic and
steric disparity between the two different donor groups.
Furthermore, they provide a means of introducing a
One area in which P–N ligands have received com-
paratively little attention is that of the production of
low molecular weight oxygenates from CO and alkenes
via co-oligomerisation, despite the extensive application
of both P–P and N–N bidentate ligands [2–5]. Such reac-
tions are of significant industrial interest. Since they can
be tuned to provide routes to carboxylic acids, diacids,
polyketones and esters, all valuable organic building
blocks. In particular, shorter chain alkene–CO oligo-
mers (oxygenates) have found widespread use as sol-
vents, in part because of their low cost, but also as a
result of their low environmental impact [3].
*
Corresponding author. Tel.: +44 191 334 2150; fax: +44 191 384
4737.
E-mail address: p.w.dyer@durham.ac.uk (P.W. Dyer).
Current address: Sasol Technology UK Research Laboratory,
Purdie Building, North Haugh, St. Andrews, Fife KY16 9ST, UK.
1
For a number of years we have been interested in the
preparation of chelating phosphorus–nitrogen scaffolds
0022-328X/$ - see front matter ꢁ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.04.032

P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
5265
and have focussed our attention upon systems that
could be prepared through the formation of a P–N bond
[6,7]. This methodology is attractive not only because
such reactions are generally easily achieved, but also be-
cause the resulting aminophosphine component is an
electronically and sterically flexible donor moiety in its
own right [8–10].
Here, we report the synthesis and coordination chem-
istry of readily prepared diphenylphosphino(phenyl
pyridin-2-yl methylene)amine, an attractive ligand that
combines an aminophosphine fragment in a potentially
6-membered chelate-forming system. Emphasis is placed
on the preparation, characterisation and reactivity of
the palladium(II) complexes of this ligand, prior to dem-
onstrating their utility for the selective oligomerisation
of CO/C2H4. It was of particular interest to probe the
reactivity of the palladium methyl complex 5, since the
insertion of carbon monoxide into palladium–alkyl
bonds is of considerable relevance in a range of catalytic
processes [11–13,23].
magnitudes of the three-bond couplings to phosphorus
exhibited by C5 (3JPC = 6 Hz) and C7 (3JPC = 11 Hz),
analysis by a modified Karplus relationship suggests
that the imine bond adopts a Z configuration with re-
spect to the pyridyl ring [16].
2.2. Assessment of the donor characteristics of the
P-component of ligand 1
Iminopyridyl phosphine 1 reacts cleanly and quanti-
tatively with elemental selenium upon sonication to af-
ford the corresponding mono-selenide 2 [31P{1H}
NMR d: +42.6 (1JSeP = 769 Hz)] (Scheme 2). This deriv-
ative can be used to assess the donor characteristics of
the P-component of 1, since there exists a well-estab-
1
lished correlation between the magnitude of JPSe cou-
pling constants and the basicity of phosphines: the
1
greater the value of JPSe, the greater the s-character
of the P lone pair and hence the poorer its donating abil-
ity [17]. The magnitude of 1JPSe obtained for 2 is consis-
tent with the P-component of 1 being a comparatively
poor r-donor (comparable with other diarylaminophos-
phines) [8]. This is presumed to be a consequence of
both partial delocalisation of the P lone pair into the
conjugated p-system of the ligand backbone and the
electronegativity of nitrogen.
2. Results and discussion
2.1. Synthesis of ligand 1
The heteroditopic P–N ligand 1 is prepared in two
steps using a straightforward ꢀone-potꢁ procedure start-
ing from 2-cyanopyridine (Scheme 1) and isolated fol-
lowing purification by Soxhlet extraction with hexane
(45% yield). Air and moisture sensitive compound 1 is
stable for several hours as a dry solid under air, but
for only minutes in solution if non-dried solvents are
employed.
The
rhodium
carbonyl
chloride
complex
[RhCl(CO)(1-j2-P–N)] (3) is formed quantitatively upon
treating a CDCl3 solution of 1 with 0.5 equivalents of
[RhCl(CO)2]2 under a CO atmosphere (Scheme 2). The
31P{1H} NMR spectrum of 3 [d: +84.5 (1JRhP = 167 Hz)]
reveals a doublet with a downfield coordination chemi-
cal shift (Dd) of ꢀ43 ppm compared to unbound 1.
1
The magnitude of the JRhP coupling constant is indica-
The somewhat low yield of 1 is presumed to result
from competitive ring deprotonation of 2-cyanopyridine
by PhLi. In an attempt to alleviate this problem, less ba-
sic PhMgBr was used in the place of the organolithium
reagent. However, in this case only a trace of 1 was ob-
tained according to the 31P{1H} NMR spectrum of the
crude reaction mixture.
The 31P{1H} NMR spectrum of 1 shows a single
sharp resonance at a chemical shift typical of a diaryla-
minophosphine, +41.9 ppm {CD2Cl2} [8,14]. In the
13C{1H} NMR spectrum, a signal readily attributable
to the imine carbon (C6) is observed at a characteristic
chemical shift (d: 171.8), exhibiting a small two-bond
coupling to P (2JPC = 7 Hz) [6,15]. Given the relative
tive of the geometry at Rh being CO cis to P as would be
expected on thermodynamic grounds, and is comparable
in size to that observed for similar systems [18–20]. The
value of JRhP is consistent with the P-component of 1
being a relatively poor donor (vide supra). IR spectros-
1
copy shows
a single strong carbonyl stretch at
2010 cmꢁ1. This value is consistent with that determined
for a recently reported, related P–N chelate, possessing a
pyridyl moiety and an aminophosphine bound to rho-
dium [21]. Although the use of the carbonyl stretching
frequency of trans-[RhCl(CO)L2] complexes as a mea-
sure of the donor behaviour of L is well-established
[8,22], the relationship for cis-chelating bidentate ligands
is less clear. However, the value determined here for 3 is
Scheme 1. The synthesis of ligand 1 (with spectroscopic numbering scheme).

5266
P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
Scheme 2. Reactions of ligand 1 with selenium and complexes of Rh(I), Pd(II) and Pt(II).
still indicative of poor r-donor/high p-acceptor charac-
ter, and is in line with the deduction made from the 1JPSe
coupling constant (vide supra).
P–N)] (6), [PtCl(Me)(1-j2-P–N)] (7), [PtMe2(1-j2-P–
N)] (8) were all obtained from the reaction of 1 with
the appropriate [Pt(X)(Y)(COD)] precursor in excellent
yields of ca. 90% (Scheme 2).
2.3. Synthesis of neutral palladium(II) and neutral
platinum(II) complexes of ligand 1
2.4. NMR characterisation of neutral palladium(II) and
platinum(II) complexes of ligand 1
Due to their relevance in carbon monoxide/alkene
copolymerisation, palladium(II) complexes of ligand 1
were attractive targets [23]. The complexes [PdCl2(1-
j2-P–N)] (4) and [PdCl(Me)(1-j2-P–N)] (5) were pre-
pared by reaction of a slight excess of 1 with
[PdCl2(COD)] and [PdCl(Me)(COD)], respectively, in
CH2Cl2 at RT and isolated in excellent yields of 94%
and 87% (Scheme 2). Using analogous reaction condi-
tions, the related platinum(II) complexes [PtCl2(1-j2-
Each of the complexes 4–8 shows a single resonance
by 31P{1H} NMR spectroscopy at a shift indicative of
a metal-coordinated diarylaminophosphine, with a
downfield coordination chemical shift (Dd), except for
6, where Dd = ꢁ2.4 ppm (Table 1) [8,24]. For complexes
6–8, the 31P {1H} NMR spectral data reveal the ex-
1
pected trend in the magnitudes of the JPtP coupling
constants, the smallest value being observed for
Table 1
Selected NMR spectroscopic data for ligand 1 and complexes 3–10
Compound
d
31P {1H}a
d
1H
d
13C {1H}
M–CH3
C6@N
M–CH3
1
3
4
5
6
7
8
+41.9
+84.5 (1JRhP 167 Hz)
+66.8
–
171.8 (2JPC 7 Hz)a
176.5b
181.6a (2JPC 5 Hz)
177.3b (2JPC 4 Hz)
180.7b (2JPC 5 Hz)
177.4b (2JPC 5 Hz)
175.0b (3JPtC 27 Hz)
–
–
–
–
–
+72.9
0.54b (3JPH 3.2 Hz)
ꢁ0.7b
+39.5 (1JPtP 3806 Hz)
+46.9 (1JPtP 4800 Hz)
+65.3 (1JPtP 1259 Hz)
–
–
0.53b (3JPH 3.7, JPtH 79.9 Hz)
ꢁ16.7 (2JPC 5, JPtC 677 Hz)b,c
2
1
0.53b (3JPH 7.9, JPtH 90.6 Hz)
10.9b,d (2JPC 111, JPtC 340 Hz)
2
1
0.77b (3JPH 7.9, JPtH 65.4 Hz)
ꢁ21.6b,c (2JPC 4, JPtC 759 Hz)
2
1
9
10
a
+73.7b
+73.4 (m1/2 = 14.3 Hz)b,e
0.35b (3JPH 2.3 Hz)
178.5b (2JPC 6 Hz)
178.1b (2JPC 6 Hz)
0.7
1.2
0.38b (br, m1/2 = 4.2 Hz)
Measured in CD2Cl2 at 300 K.
Measured in CDCl3 at 300 K.
Me cis P.
b
c
d
e
Me trans P.
Cation only.

P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
5267
dimethyl complex 8 (1JPtP = 1259 Hz) in which there is a
strongly trans-influencing methyl ligand trans to the P-
donor fragment [25].
1
The H NMR spectra of complexes 4–8 are broadly
similar to those of 1, but reveal downfield values of Dd
(ꢂ1 ppm) for the C1–H resonances, which also exhibit
four-bond coupling to P (4JPH ꢂ 1 Hz), consistent with
bidentate P–N binding. Additionally, the C1–H reso-
nances for complexes 7 and 8 also show a 3JPtH coupling
of 15.4 and 21.9 Hz, respectively. Discrimination of the
cis- and trans-methyl resonances of 8 was achieved
1
through a H NOESY NMR experiment; assignment
based solely on coupling constants is unreliable [28].
By 13C{1H} NMR spectroscopy, a downfield shift of
ca. 5–10 ppm for the imine carbon C6, compared to un-
bound 1, was observed for each of the complexes.
The spectroscopic data obtained for complex 5 con-
firm its regioselective formation, a single resonance being
observed by 31P {1H} NMR spectroscopy {d: +72.9},
1
with one Pd–CH3 resonance appearing in both the H
Fig. 1. Thermal ellipsoid plot (50% probability) of [RhCl(CO)(1-j2-P–
N)] (3), hydrogen atoms and molecule of CDCl3 omitted for clarity.
and 13C NMR spectra {1H, d: 0.54 (3JPH = 3.2 Hz);
13C, d: ꢁ0.71}. These data are consistent with the forma-
tion of the thermodynamic isomer in which the methyl
group occupies a position cis to the P donor fragment,
the small coupling observed being comparable to that
observed in other similar systems [26–28].
2.5. X-ray crystallographic investigation of complexes of
ligand 1
Crystals suitable for study by X-ray diffraction were
obtained for 3, 4, 6 and 7 by slow diffusion of hexane
into a chlorocarbon solution of the appropriate com-
plex. The molecular structures of 3, 4, 6 and 7 are pre-
sented in Figs. 1–4, respectively. Tables 2 and 3 list
selected bond distances and bond angles and Table 5
gives selected crystal data and refinement details.
The gross molecular structures of complexes 3, 4, 6
and 7 confirm both the square planar geometry about
the metal centres and the bidentate P–N binding mode
of ligand 1. In each case, the chelate ring adopts a ꢀdis-
torted-boatꢁ conformation, which presumably results
from the inclusion of the aromatic ring and the imine
double bond within the chelate that resist being twisted
out-of-plane. The imine carbon C6 is essentially planar
in each structure, as expected. The plane of the pyridyl
ring is twisted out of the square coordination plane
about the metal {angle between planes in the range
25.6 (7) to 39.6o (6)} for all four complexes. This reflects
a degree of flexibility associated with the P–N chelate
ring, something further exemplified by the variation of
the ligand bite angle with values ranging from 82.71(4)
(3) to 85.29(8)ꢀ (7).
Fig. 2. Thermal ellipsoid plot (50% probability) of 4, hydrogen atoms
and molecule of CD2Cl2 omitted for clarity.
of the P moiety compared to that of the pyridyl N-atom
˚
[29]. For complex 4, a pronounced elongation (ꢀ0.11 A)
of the Pd(1)–Cl(1) bond compared to the Pd(1)–Cl(2)
bond is observed. A similar situation occurs for complex
6, where two inequivalent Pt(1)–Cl bond distances are
˚
identified that differ by ꢀ0.08 A.
The molecular structures of the rhodium complex 3
and the platinum complex 7 are entirely consistent with
those inferred from NMR spectroscopy (vide infra).
They confirm that 3 adopts the thermodynamic isomer
The heteroditopic nature of ligand 1 influences both
the synthesis and the resulting structures of its com-
plexes, as a consequence of the greater trans-influence

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P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
Table 2
Selected bond lengths and angles for [RhCl(CO)(1-j2-P–N)] (3) and
[PdCl2(1-j2-P–N)] (4)
Complex 3
Complex 4
˚
Bond distances (A)
Rh(1)–C(25)
Rh(1)–N(1)
Rh(1)–P(1)
Rh(1)–Cl(1)
O(1)–C(25)
P(1)–N(2)
P(1)–C(13)
P(1)–C(19)
N(2)–C(6)
C(6)–C(5)
C(5)–N(1)
N(1)–C(1)
1.814(2)
2.1475(16)
2.1905(5)
2.3802(5)
1.145(3)
1.7018(16)
1.812(2)
1.815(2)
1.274(3)
1.500(3)
1.358(3)
1.341(3)
Pd(1)–N(1)
Pd(1)–P(1)
Pd(1)–Cl(1)
Pd(1)–Cl(2)
P(1)–N(2)
P(1)–C(13)
P(1)–C(19)
N(2)–C(6)
C(6)–C(5)
C(5)–N(1)
N(1)–C(1)
2.0610(14)
2.1983(5)
2.3813(4)
2.2728(5)
1.6984(15)
1.7992(18)
1.8032(18)
1.288(2)
1.503(2)
1.355(2)
1.346(2)
Bond angles (ꢀ)
C(25)–Rh(1)–P(1)
N(1)–Rh(1)–P(1)
C(25)–Rh(1)–Cl(1)
N(1)–Rh–Cl(1)
93.83(7)
82.71(4)
93.46(7)
N(1)–Pd(1)–P(1)
P(1)–Pd(1)–Cl(2)
N(1)–Pd(1)–Cl(1)
Cl(2)–Pd(1)–Cl(1)
N(1)–Pd(1)–Cl(2)
P(1)–Pd(1)–Cl(1)
N(2)–P(1)–Pd(1)
C(6)–N(2)–P(1)
C(5)–C(6)–N(2)
N(1)–C(5)–C(6)
C(1)–N(1)–C(5)
83.78(4)
93.530(17)
91.28(4)
90.21(4)
92.021(16)
173.10(4)
172.287(17)
104.60(5)
120.39(13)
124.00(16)
119.77(15)
118.62(15)
Fig. 3. Thermal ellipsoid plot (50% probability) of 6, hydrogen atoms
and molecule of CH2Cl2 omitted for clarity.
C(25)–Rh(1)–N(1)
P(1)–Rh(1)–Cl(1)
O(1)–C(25)–Rh(1)
N(2)–P(1)–Rh(1)
C(6)–N(2)–P(1)
N(2)–C(6)–C(5)
N(1)–C(5)–C(6)
C(1)–N(1)–C(5)
175.40(8)
171.768(19)
179.2(2)
105.40(6)
122.30(14)
123.96(18)
118.76(17)
117.84(17)
Table 3
Selected bond lengths and angles for [PtCl2(1-j2-P–N)] (6) and
[PtCl(Me)(1-j2-P–N)] (7)
Complex 6
Complex 7
˚
Bond distances (A)
Pt(1)–N(1)
Pt(1)–P(1)
Pt(1)–Cl(1)
Pt(1)–Cl(2)
P(1)–N(2)
2.056(4)
2.1898(12)
2.3601(12)
2.2817(12)
1.684(4)
1.805(5)
1.798(5)
1.285(6)
1.489(6)
1.353(6)
1.343(6)
Pt(1)–N(1)
Pt(1)–P(1)
Pt(1)–Cl(1)
Pt(1)–C(25)
P(1)–N(2)
P(1)–C(13)
P(1)–C(19)
N(2)–C(6)
C(6)–C(5)
C(5)–N(1)
N(1)–C(1)
2.174(3)
2.1643(9)
2.3613(9)
2.040(4)
1.694(3)
1.813(4)
1.808(3)
1.289(4)
1.504(5)
1.350(5)
1.345(4)
P(1)–C(13)
P(1)–C(19)
N(2)–C(6)
C(6)–C(5)
C(5)–N(1)
N(1)–C(1)
Fig. 4. Thermal ellipsoid plot (50% probability) of 7, hydrogen atoms
omitted for clarity.
Bond angles (ꢀ)
N(1)–Pt(1)–P(1)
P(1)–Pt(1)–Cl(2)
N(1)–Pt(1)–Cl(1)
Cl(2)–Pt(1)–Cl(1)
N(1)–Pt(1)–Cl(2)
P(1)–Pt(1)–Cl(1)
N(2)–P(1)–Pt(1)
C(6)–N(2)–P(1)
C(5)–C(6)–N(2)
N(1)–C(5)–C(6)
C(1)–N(1)–C(5)
84.50(11)
94.55(4)
N(1)–Pt(1)–P(1)
P(1)–Pt(1)–C(25)
N(1)–Pt(1)–Cl(1)
C(25)–Pt(1)–Cl(1)
N(1)–Pt(1)–C(25)
P(1)–Pt(1)–Cl(1)
N(2)–P(1)–Pt(1)
C(6)–N(2)–P(1)
C(5)–C(6)–N(2)
N(1)–C(5)–C(6)
C(1)–N(1)–C(5)
85.29(8)
93.78(12)
91.95(8)
89.91(11)
91.15(4)
with the CO ligand located cis to the P-donor fragment,
and for complex 7 that the pyridyl ring adopts a position
trans to the methyl group, in accord with the relative
trans-influences of each of the ligands. Furthermore,
the difference in the Pt(1)–N(1) bond distances {6:
89.42(11)
173.80(14)
174.87(3)
107.47(10)
123.7(3)
178.26(11)
173.15(4)
104.81(15)
122.2(4)
123.6(4)
120.6(4)
118.8(4)
124.1(3)
119.2(3)
117.8(3)
˚
˚
2.0564(4) A; 7: 2.1643(9) A}, clearly reflects the greater
trans-influence of a methyl versus a chloride ligand [18].
The P(1)–N(2) bond distances for the complexes 3, 4,
˚
6 and 7 lie in the range 1.684(4)–1.7018(16) A. Although
shorter than the values normally attributed to P–N sin-
gle bonds, the possibility of a degree of phosphorus–
nitrogen multiple bond character can be ruled out since
the orientation of the imine N atom precludes N ! P
retro-donation [30]. Indeed, this metric parameter is

P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
5269
generally an extremely poor indicator of P–N bond or-
der. Consistent with the lack of P–N multiple bonding
are the imine N(2)–C(6) and C(6)–C(5) bond distances,
which are in accord with an imine and C–C single bond,
respectively [6,31].
NMR spectra (CDCl3), while the resonance for the
1
Pd–CH3 group appeared slightly broadened in the H
NMR spectrum at ambient temperature. This is sugges-
tive of reversible association/dissociation of MeCN at a
rate comparable with the NMR timescale, possibly as a
result of a competitive metal-binding interaction by the
PFꢁ6 anion. No such process is observed for 9 since the
[B{3,5-(CF3)2-C6H3}4]ꢁ anion is known to be essentially
non-coordinating, and hence does not compete with
MeCN for binding to the metal centre [33].
3. Reactivity of palladium(II) complexes of 1
3.1. Cationic palladium(II) methyl complexes of ligand 1
In attempts to study the dynamic process associated
1
With a view to exploring the reactivity of the palla-
dium methyl bond of complex 5 toward CO and ethene,
it was of interest to prepare the corresponding cationic
Pd systems. Thus, the palladium-methyl salts [PdMe-
with 10, H and 31P {1H} NMR spectra were obtained
over the temperature range 300–230 K (10 K intervals;
CDCl3). No resonance attributable to MeCN (bound
1
or free) was detectable according to H NMR spectros-
(MeCN)(1-j2-P–N)][Z]
9
{Z = B{3,5-(CF3)2-C6H3}4}
copy (even at 230 K), while the Pd–CH3 resonance
actually broadened slightly [m1/2(300 K) = 4.2 Hz, m1/2
(230 K) = 6.0 Hz]. However, examination of the
31P{1H} NMR spectra obtained on cooling the sample
to 230 K, revealed that the broad resonance sharpened
{m1/2(300 K) = 14.3 Hz, m1/2(230 K) = 3.5 Hz}, presum-
ably due to a slowing in the rate of exchange of the
MeCN. No variation was observed in the 31P{1H}
NMR spectra for the resonance associated with the
PFꢁ6 anion, which remained a septet over the tempera-
ture range 300–230 K.
and 10 {Z = PF6} were prepared by reacting acetonitrile
solutions of 5 with the sodium salts of the desired anion
at RT for 4 and 3 days, respectively (Scheme 3). The two
complexes were isolated as their acetonitrile adducts in
good yields (91% and 81%, respectively). Selected
NMR data for complexes 9 and 10 are presented in
Table 1.
The 31P{1H} NMR spectrum of 9 exhibits a single,
sharp resonance, whereas the spectrum of 10 features a
broadened signal (vide infra). For both complexes only
a very small change in 31P NMR chemical shift
(ꢀ0.5 ppm) is observed following chloride abstraction.
In their 13C{1H} NMR spectra a significant shift of
the resonance for the Pd–CH3 group is observed, from
d ꢁ0.71 (5) to d +0.71 and d +1.24 for 9 and 10, respec-
tively. This is believed to result from the more electron
deficient metal centre de-shielding the carbon of the
methyl group. In both complexes, as with 5, the Pd–
CH3 resonance appears as a singlet, indicating a Me
cis to P geometry at palladium [32].
3.2. Insertion reactions of neutral palladium(II) methyl
complexes of ligand 1
The preparation of [PdCl{g1-C(@O)Me}(1-j2-P–N)]
(12), from a CDCl3 solution of 5 under an atmosphere
of CO at RT was carried out (Scheme 4). On following
this reaction by 31P{1H} NMR spectroscopy, a single
new species 12 {d: +56.1} was observed to form, the ini-
tially yellow solution slowly turning bright red; complete
conversion was achieved in 2 days. The identity of this
new product 12 as the corresponding g1-acyl derivative
Sharp resonances corresponding to bound MeCN are
1
observed in both the H and 13C{1H} NMR spectra of
9. In contrast, for the PFꢁ6 salt 10 no resonances could
is clear from both 1H {–C(O)Me d: 2.04 (4JPH
1.7 Hz)} and 13C{1H} NMR spectroscopies {–C(O)Me
=
be observed for MeCN in either the 1H or 13C{1H}
Scheme 3. Synthesis of cationic palladium(II) methyl complexes of ligand 1.

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P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
Scheme 4. Insertion reactions of neutral palladium complex 5.
1
d: 227.0 (2JPC = 9 Hz)} and from IR spectroscopy,
which reveals a characteristic carbonyl stretch at
1696 cmꢁ1 [26,34–36]. The small magnitude of the value
by 31P NMR spectroscopy. In the H NMR spectrum
(Fig. 5) the methyl group of 13 appears as a singlet
(d), the b-CH2 protons (c) as a pseudo-triplet of dou-
blets, and the a-CH2 protons (b) appear as a multiplet.
It is proposed that the 13 forms via ethene insertion
and halide displacement, resulting in an intramolecu-
larly-coordinating ketone moiety [Pd{CH2CH2C-
(@O)Me-j2-C–O}(1-j2-P–N)][Cl] (13) {31P NMR d:
+72.9}.2 This is in accord with considerable literature
precedent in favour of the j2-C–O isomer over the
non-chelating b-ketoalkyl form [13,21,41]. Although,
no mechanistic detail may be inferred for this process
without detailed kinetic studies, the reluctance for eth-
ene insertion is likely to result from a combination of
steric inhibition of initial substrate binding (consider-
ably less facile for C2H4 compared with CO) and neces-
sary isomerisation post insertion [18,41]. As expected on
thermodynamic grounds, insertion of CO into the acyl
bond of 13 could not be detected.
No further changes were observed by NMR spectros-
copy over a period of 18 h at RT. Venting the over pres-
sure of ethene led to the clean regeneration of 12 and the
disappearance of 13. Together, these observations sug-
gest that an equilibrium situation has been achieved.
Although, both the insertion of ethene into palla-
dium–acyl bonds [13,42,43] and the insertion of carbon
monoxide into palladium–alkyl bonds [44] are known
to be facile, the rates of these processes (and those of
the corresponding de-insertion reactions) are known to
differ significantly. This is reflected in this study by the
2
for JPC is indicative of a ꢀC cis to Pꢁ geometry at palla-
dium, which is expected from trans-influence arguments
[32]. The carbon of the methyl group of the acyl moiety
appears as a doublet [d: 39.0 (3JPC = 25 Hz)] at a shift
consistent with that observed for other acyl complexes
[26,34].
A number of pathways for the formation of 12 from 5
are possible, all of which involve migratory insertion
and isomerisation, but that differ in the nature of the ini-
tially formed CO complex: (a) via a 5-coordinate CO ad-
duct; (b) through halide displacement followed by CO
binding; and (c) following opening of the P–N chelate
and subsequent CO coordination [35,37,38]. Since no
intermediate species were observed by 31P{1H} NMR
spectroscopy at room temperature (the necessary inser-
tion reactions are known to be rapid [39]) and no de-
tailed kinetic study was undertaken, no conclusion as
to the mechanism for the formation of the acyl complex
12 may be made.
The insertion of ethene into the palladium–acyl bond
of 12 represents another important step in the catalytic
cycle of carbon monoxide/ethene copolymerisation
[23,40]. To study this type of reaction with systems
involving ligand 1, a CDCl3 solution of 12 was placed
under an atmosphere of ethene and the reaction moni-
1
tored by H and 31P{1H} NMR spectroscopies. After
3 days no reaction had occurred. Consequently, the
pressure of ethene was increased to ten atmospheres,
which led to the rapid formation of a new species 13
in a near 1:1 ratio with the starting acyl complex 12,
2
Although IR spectroscopy would distinguish between the two
possible isomers of 13, high pressure facilities were not available to us.

P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
5271
Fig. 5. 1H (250.13 MHz, CDCl3) NMR spectrum of the reaction of [PdCl{g1-C(@O)Me}(1-j2-P–N)] (12) with C2H4 (10 atm) and proposed
structure of 13.
relative ease of formation of 12 from 5 (pCO = 1 atm)
compared with that of 13 from 12 (pC2H4 = 10 atm). In-
deed, studies of CO/C2H4 copolymerisation have identi-
fied that the rate of copolymerisation is dependent upon
ethene pressure, with ethene insertion being the rate-
determining step [23,45].
Capitalising on the successful formation of the acyl
complex 12, it was of interest to explore the related
insertion of isonitriles (isoelectronic with CO). Thus,
the iminoacyl complex [PdCl{g1-C(@NBut)Me}(1-j2-
P–N)] (14), was synthesised through addition of one
equivalent of CNBut to a CDCl3 solution of 5; complete
conversion to the product 14 occurred within 1 h at RT.
This much higher rate of insertion of isonitrile compared
with CO (conversion of 5 to 12, 2 days) is in line with
previous observations [46,47].
The 31P{1H} NMR spectrum of 14 shows a single
sharp resonance at a chemical shift {d: +57.9} almost
identical to that for the acyl complex 12. The arrange-
ment about the palladium centre is proposed as being
iminoacyl cis to P on trans-influence grounds, the mod-
erate magnitude of two-bond coupling to the iminoacyl
C@N being supportive of this assignment {d: 148.9
(2JPC = 24 Hz)} [32]. The methyl group of the iminoacyl
moiety appears at characteristic shifts in the 1H and
13C{1H} NMR spectra {1H, d: 2.85 (4JPH = 2.1 Hz);
13C, d: 34.9 (3JPC = 4 Hz)}. The 13C{1H} NMR shift
of the C@N fragment is entirely consistent with an g1-
iminoacyl {d: 148.92 (2JPC = 23.5 Hz)} [36].
Complexes of g1-iminoacyls normally show a strong
C@N stretch in the region 1580–1630 cmꢁ1 [36], with N-
tert-butyl-substituted variants often appearing at the
lower end of this scale [48]. However, since only a single
C–N band was observed in the IR spectrum of 14 at
1593 cmꢁ1 (cf. 1587 cmꢁ1 for 1), it seems reasonable to
suggest that both the bands due to bound 1 and the
C@N stretch of the g1-iminoacyl are coincident.
Although CO double insertion is precluded on thermo-
dynamic grounds, multiple isonitrile insertion is possible
[47]. Here, addition of two equivalents of CNBut to 5 gave
a number of new products according to 1H and 31P{1H}
NMR spectroscopies, which were not readily identifiable.
However, complete consumption of 5 was clear, with no
evidence for the formation of 14. This is consistent with
multiple CNBut insertion having indeed taken place.
3.3. Reactions of cationic palladium(II) methyl
complexes of ligand 1
A
CDCl3 solution of [PdMe(MeCN)(1-j2-P–
N)][B{3,5-(CF3)2-C6H3}4] (9) was placed under one
atmosphere of CO. Complete conversion to the corre-
sponding acyl derivative [Pd{C(@O)Me}(MeCN)(1-j2-
P–N)][B{3,5-(CF3)2-C6H3}4] (11) was achieved after 6 h

5272
P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
at RT (Scheme 3). Clearly, this reaction is considerably
faster than that for the formation of the neutral acyl
complex 12 from 5 (2 days, RT). This is consistent
with the proposal that the rate-limiting step in these
insertion reactions is believed to be initial binding
of the substrate to the metal, something that will be
facilitated for the coordinatively unsaturated cationic
palladium systems.
The 31P{1H} NMR spectrum of 11 shows a single res-
onance (d: +57.8) at a shift similar to that of the neutral
g1-acyl palladium species 12 (d: +56.1). In the 13C{1H}
NMR spectrum the carbonyl carbon of the acyl group
appears as a downfield singlet with a chemical shift char-
acteristic for an g1-acyl complex (d: 222.8), the multi-
plicity indicating that the acyl lies cis to phosphorus
[32]. As with the precursor complex 9, MeCN is tightly
bound to palladium, sharp resonances appearing in the
1H and 13C{1H} NMR spectra for this ligand {1H, d:
2.15; 13C, d: +2.50}. The methyl group of the acyl moi-
ety gives rise to a resonance at d: 38.0 ppm, consistent
with that observed for 12 and other g1-acyl complexes.
FAB mass spectrometry supports the assignment of 11
as the acetonitrile adduct, clearly showing loss of both
the acyl and MeCN ligands [m/z: 515 (M–CH3CN)+,
472 (M–CH3CN-acyl)+].
3.4. Catalytic CO/ethene copolymerisation testing
Although homoditopic N–N [49–52] and P–P [23,53–
55] ligand systems have received the most attention for
CO/ethene copolymerisation, there is a growing body
of evidence that heteroditopic P–N ligands are also effec-
tive [21,56–58]. For polyketone synthesis, a bite angle
dependency has been noted for both P–P- and P–N-
based scaffolds, 6-membered chelate systems being pref-
erential in terms of activity, selectivity, and polymer
molecular weight [23,58–60]. Thus, the combination of
the size of chelate formed and the reactivity demon-
strated (vide supra) by ligand 1 in partnership with pal-
ladium toward CO and ethene, made this an intriguing
system to explore for this type of polymerisation
reaction.
The behaviour of both preformed complex [PdCl2(1-
j2-P–N)] (4) (entries 1–3, Table 4) and systems gener-
ated in situ from Pd(OAc)2 and ligand 1, in a 1:1.5 ratio
(entries 4–6), were explored at both 30 and 90 ꢀC under
38 bar pressure of pre-mixed 1:1 CO:C2H4. All tests
were performed in dry methanol with 4 equivalents of
methanesulphonic acid as an activator, conditions repre-
sentative of those generally used for the formation of
polyketones [23].
The IR spectrum of 11 shows an acyl CO band at
1653 cmꢁ1. This is at a significantly lower frequency to
that observed for 12 (1696 cmꢁ1) and is likely to result
from some slight interaction between the acyl oxygen
and the cationic metal centre, although this is insufficient
to displace MeCN. It is well recognised that true
g2-acyl complexes show mCO bands at lower frequencies
Contrary to expectations, none of the reactions (en-
tries 1–6) led to the formation of polyketone. Indeed,
no new carbon-containing species could be detected
from reactions performed at 30 ꢀC (entries 1 and 4). In
contrast, for tests carried out at 90 ꢀC in the presence
of the acid activator (entries 2 and 5), 4-oxo-hexanoic
acid methyl ester (15) was obtained as the only
organic product, with an activity of ca. 8–9 g
{mol Pd}ꢁ1 barꢁ1 hꢁ1 (Scheme 5). Although these val-
ues are only moderate, they are of a comparable magni-
tude to the activities for the formation of CO/C2H4
copolymers by other P–N ligand-based catalyst systems:
9 g (mol Pd)ꢁ1 barꢁ1 hꢁ1 by Green et al. [56];
148 g (mol Pd)ꢁ1 barꢁ1 hꢁ1 by Fryzuk et al. [57]; and
224 g (mol Pd)ꢁ1 barꢁ1 hꢁ1 by Liu et al. [58].
than their g1-acyl counterparts (usually DmCO > 50 cmꢁ1
)
[36].
In contrast, attempts to bind and subsequently insert
ethene into the Pd–Me bond of 11 proved elusive. Under
1 atmosphere of ethene no reaction was observed to
1
occur by either H or 31P NMR spectroscopy (as for
the neutral system). In contrast, at elevated temperatures
or pressures, rapid decomposition of 11 occurred, with
the generation of palladium ꢀblackꢁ and other intractable
products.
Notably, analysis of the organic phase isolated after
each catalytic test revealed that no methyl propionate
Table 4
Summary of ethene/carbon monoxide oligomerisation chemistry catalysed by preformed complex 4 or by an initiator generated in situ from
[Pd(OAc)2] and 1a
Entry
Initiator
[Pd] (Mol · 10ꢁ4
)
Activatorc
Temperature (ꢀC)
Oligomer yield (g)
Activity for oligomersd
1
2
3
4
5
6
a
4
1.80
1.80
1.80
1.82
1.82
1.82
MeSO3
MeSO3
None
H
H
30
90
90
30
90
90
0
0.166
0
4
8.0
0
4
0
Pd(OAc)2/1b
Pd(OAc)2/1b
Pd(OAc)2/1b
MeSO3
MeSO3
None
H
H
0
0
0.180
0
8.7
0
Reaction conditions: MeOH (60 mL) solvent, stirring rate (900 rpm), 1:1 ethene:carbon monoxide (38 bar), 3 h.
Ratio [Pd(OAc)2]:1 = 1:1.5.
b
c
Pd:MeSO3H = 1:4.
g (mol Pd)ꢁ1 barꢁ1 hꢁ1
d
.

P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
5273
Scheme 5. Formation of 4-oxo-hexanoic acid methyl ester (15) from CO/C2H4/MeOH.
had been formed via mono-hydromethoxycarbonyla-
tion. This side product is often observed to form with
poorly active polyketone initiators [23]. Irrespective of
the reaction conditions, a large amount of colloidal ꢀpal-
ladium blackꢁ was found at the end of each run.
MeOH solvent (equations 1 and 2); such mechanisms
are well established for polyketone synthesis [23,45,61].
Chain termination by methanol can occur via proton-
ation of the b-ketoalkyl (cycle A) or by nucleophilic at-
tack at the acyl complex (cycle B), however the structure
of 15 cannot be used to distinguish these two processes.
As would be expected from the proposed mechanisms
for the formation of 15, no organic products are ob-
tained when anhydrous dichloromethane is used in the
place of MeOH as solvent. Although there is no evi-
dence here in preference of either pathway A or B,
methyl propionate formation is generally believed to
result from a palladium hydride-based cycle [62]. How-
ever, the unique selectivity for the formation of keto-
ester 15 via palladium-catalysed copolymerisation of
CO/C2H4 with ligand 1 merits further comment, since
a Schulz–Flory distribution of oligomeric products
would normally be expected [2,3].
For palladium-based initiators bearing chelating P–P
and N–N donors it is well documented that the nature of
the ligand (bite angle {bridge length}, steric bulk, bridge
substituents and basicity) has a considerable impact
upon the polymerisation process (especially activity
and product distribution) [2,3,45,63,64]. Not only is it
reasonable to suggest that these types of effect are also
likely to play an important role for heteroditopic li-
gands, but that the electronic asymmetry (differences
in trans effect) in the chelate will also be significant
[18,65]. Although the formation of polyketone is often
favoured over lower molecular weight oxygenates for
P–P-based ligands that adopt 6-membered chelates
[23], there are notable exceptions [2,61,66].
The nature of the catalytically active species gener-
ated in situ (entries 4–6) was probed through investiga-
tion of the reaction between Pd(OAc)2 and 1 (1:1) in
MeOH. After 30 min at room temperature, a vivid
red-orange solution had been formed, which was found
to contain five new species all with chemical shifts char-
acteristic of metal-bound aminophosphines (D: +58 to
+82 ppm), in addition to a small quantity of unbound
1, according to 31P {1H} NMR spectroscopy. Although
this mixture remained unchanged over a period of 18 h
at RT, its complexity precluded further analysis. Subse-
quent heating of the solution at reflux for a further 18 h
led to the formation of ꢀpalladium blackꢁ and a green
solution, which showed no signal by 31P {1H} NMR
spectroscopy. Although not revealing the identity of
the active catalytic species, these observations confirm
both the partial resilience of unbound 1 and its com-
plexes in MeOH, despite the presence of a potentially
reactive polar P–N linkage, in line with previous obser-
vations regarding the stability of metal-bound amino-
phosphines [7,8].
Pd2þ þ MeOH ! ½Pd-OMeꢃþ þ Hþ
ð1Þ
ð2Þ
½Pd-OMeꢃþ ! ½Pd-Hꢃþ þ HCðOÞH
It is believed that keto-ester 15 results from either a
catalytic cycle based upon an initial Pd-hydride or Pd–
OMe species (Scheme 6), generated in situ from the
Scheme 6. ꢀCarbomethoxyꢁ (A) and ꢀhydrideꢁ (B) catalytic cycles for the formation of keto-ester (15) from CO/C2H4/MeOH.

5274
P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
Ligand 1 is somewhat flexible and can readily accom-
strates a weak secondary Pd–carbonyl interaction. The
robustness of the inherent P–N linkage of 1 has been
established.
A highly selective, but moderately active hydrocarb-
oxylation catalyst system is obtained on combining li-
modate P–N bite angles of 90ꢀ or 120ꢀ. This feature is
important since 1 can bind to both square planar and
trigonal bipyramidal complexes, something that is
known to influence not only migratory insertion path-
ways, but also dictate between oligomerisation and
polymerisation [67]. The ꢀdistorted boatꢁ conformation
that 1 adopts provides a degree of steric hindrance
above and below the square coordination plane of palla-
dium, which could slow insertion reactions. Consider-
ation of the molecular structure of 4 (Fig. 2) indicates
that the orientation of P(1) locates one of its phenyl sub-
stituents in reasonable proximity to Cl(2). In solution,
rotation about the P(1)–C(13) bond would further en-
hance this effect. As has been demonstrated, the amino-
phosphine component of 1 is a somewhat poor r-donor,
something that will enhance the nucleophilicity of the
palladium to which it is bound. Under the catalytic con-
ditions employed, this will favour attack of methanol at
the acyl generated during the ꢀhydride cycleꢁ B, leading
to more rapid chain termination and hence lower molec-
ular weight products.
gand
1
with palladium(II) in the presence of
methanesulphonic acid. 4-Oxo-hexanoic acid methyl es-
ter (15) is obtained as the only organic product from the
reaction of CO with C2H4 (38 bar, 90 ꢀC) in methanol.
The unusual selectivity of palladium(II) complexes of 1
for the formation of 15 is attributed to a combination
of a significant steric demands, low basicity, and flexible
P–N bite angle of this ligand framework.
Further variants of 1 have been prepared and optimi-
sation of the hydrocarboxylation behaviour of palla-
dium complexes of these types of ligand is being
actively investigated.
4. Experimental
4.1. General considerations
An informative comparison may be drawn with a re-
lated P–N ligand based on an aza-N-indolyl skeleton, re-
ported recently by Burrows and co-workers [21]. Like 1,
this system combines an aromatic N- and an N-bound
PPh2-donor fragment, but differs in the constitution of
the ligand backbone and in the formation of 5- rather
a 6-membered metallacycle, with a slightly more elec-
tron-donating phosphine moiety. In contrast to 1, when
bound to palladium, Burrowsꢁ ligand leads exclusively to
polyketone. The observed ꢀreversedꢁ selectivity obtained
with 1 compared to that of Burrowsꢁ system is believed
to result from a the greater flexibility of the former
(rotation being possible about the C(5)–C(6) and the
P(1)–N(2) bonds), compared with planar aromatic aza-
indole backbone.
All manipulations of air and/or water sensitive
materials were performed under an atmosphere of
nitrogen using standard Schlenk and cannula tech-
niques or in a conventional nitrogen-filled glove box
(unless stated otherwise). Solvents were freshly distilled
under nitrogen from sodium/benzophenone (tetrahy-
drofuran, diethyl ether, toluene, dme), from calcium
hydride (dichloromethane), from sodium (hexane, pen-
tane, 40–60 PE), from magnesium/iodine (MeOH), or
from P2O5 (CD2Cl2, C6D6 and CDCl3) and degassed
prior to use. Elemental analyses were performed by
S. Boyer at London Metropolitan University. NMR
were recorded on a Bruker AM 250, AMX 300, or
AMX 400; chemical shifts were referenced to residual
protio impurities in the deuterated solvent (1H), to
the deuterated solvent (13C), or to external aqueous
85% H3PO4 (31P). Chemical shifts are reported in
ppm and coupling constants in Hz. All spectra were
obtained at ambient probe temperature (298 K) unless
stated otherwise. For 1H NMR spectra, 31P coupled
3.5. Conclusion
A versatile ꢀone-potꢁ synthesis of a 6-membered che-
lating P–N ligand 1 has been described via addition of
phenyl lithium to 2-cyanopyridine and subsequent
quenching with chlorodiphenyl phosphine. This ligand
readily coordinates to rhodium(I), palladium(II) and
platinum(II) in a predictable manner, as indicated both
spectroscopically in solution and by X-ray crystallogra-
phy in the solid state. The neutral palladium methyl
1
resonances were verified by obtaining H {31P} spectra.
13C NMR spectra were assigned with the aid of DEPT
135. Infrared spectra were recorded (Nujol mulls [KBr
windows], KBr discs, or in solution [KBr windows]) on
a Perkin–Elmer 1600 spectrophotometer; Nujol was
dried over sodium wire. FAB (3-nitrobenzyl alcohol
matrix) and EI mass spectra were recorded on a Kra-
tos Concept 1H instrument and are reported in (m/z).
GC–MS were performed using a Perkin–Elmer Auto-
system XL GC machine (PE-5MS 30 m coil, internal
diameter = 0.25 mm, film thickness = 0.25 lm) coupled
to a Perkin–Elmer Turbomass mass spectrometer.
Sonication was achieved by suspending the desired
t
complex 5 readily inserts CO and BuNC to yield the
corresponding g1-acyl (12) and -iminoacyl (14) com-
plexes, respectively. Under an elevated pressure of eth-
ene, an equilibrium is established between 12 and the
product resulting from insertion, 13. Similar, but more
rapid CO insertion chemistry has been established for
the cationic methyl palladium(II) complex 9, which af-
fords an essentially g1-acyl complex 11, that demon-

P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
5275
reaction vessel in a water-filled Grant Ultrasonic Bath
XB2.
Palladium, platinum and rhodium salts were used on
CH). 13C {1H} NMR (100.61 MHz, CDCl3):
d
2
3
[ppm] = 171.8 (d, JPC = 7, C6), 156.9 (d, JPC = 6, C5),
3
149.3 (s, C1), 141.9 (d, JPC = 11, C7), 139.6 (d,
loan from Johnson Matthey. BArF3 was a gift from the
Asahi Glass Corporation. Gaseous reagents were from
BOC and all other chemicals from Aldrich. All solid re-
agents were used as received, except 2-CN-pyridine
which was distilled from CaH2 under reduced pressure.
Where appropriate, liquid reagents were dried, distilled
and deoxygenated prior to use. Gases were passed
through a drying column (silica/CaCO3/P2O5) prior to
use. cis-[Mo(CO)4(pip)2] [68], [RhCl(CO)2]2 [69],
[PdCl2(MeCN)2] [70], [PdCl(Me)(COD)] [71], [PdMe2(T-
MEDA)] [72], [PtCl2(COD)] [73], [PtCl(Me)(COD)] [74],
[PtMe2(COD)] [75], and [NaB(3,5-(CF3)2C6H4)4] [76]
were prepared according to literature procedures. All
other chemicals were obtained commercially and used
as received. Melting points were obtained in sealed glass
tubes under nitrogen, using a Gallenkamp Melting Point
apparatus and are uncorrected.
1JPC = 6, {i-C6H5}2P), 136.1 (s, C3), 132.1 (d,
2JPC = 21, {o-C6H5}2P), 130.2 (s, C10), 128.7
(d,4JPC = 3, {p-C6H5}2P), 128.6 (s, C8), 128.3 (s, C9),
3
128.3 (d, JPC = 2, {m-C6H5}2P), 123.8 (s, C2), 123.5
4
(d, JPC = 2, C4). 31P {1H} NMR (101.26 MHz, C6D6):
d [ppm] = +37.6 (s); (101.26 MHz, CD2Cl2) d: +41.9
(s). MS (FAB+): 366 M+, 289 (M–Ph)+. IR (KBr, CDCl3
solution): m(C@N) = 1584 cmꢁ1. Anal. Found C, 78.78;
H, 5.35; N, 7.52%. Calc. for C24H19N2P (366.39): C,
78.67; H, 5.23; N, 7.65%.
4.3. Diphenylphosphino selenide (phenyl pyridin-2-yl-
methylene) amine (2)
A Youngꢁs tap NMR tube was charged with Se
(19 mg, 2.36 · 10ꢁ4 mol) and
1
(72 mg, 1.97 ·
10ꢁ4 mol) and the tube sealed, before transferring to a
Schlenk line. CDCl3 (0.75 mL) was added and the tube
freeze/thaw degassed, back-filled with N2 and sealed.
The tube was then sonicated for 18 h. The yellow solu-
tion turned green. Excess Se was removed via filtration,
to leave a transparent dark green solution of 2. 31P {1H}
NMR (101.26 MHz, CDCl3): d [ppm] = +42.6 (s with
4.2. Diphenylphosphino(phenyl pyridin-2-yl-
methylene)amine (1)
To a stirred, cooled (ꢁ78 ꢀC) solution of dried 2-cya-
no-pyridine (4.00 g, 3.84 · 10ꢁ2 mol) in diethyl ether
(300 mL) was added dropwise PhLi (1.8 M, cyclohex-
ane/diethyl ether, 21.4 mL, 3.84 · 10ꢁ2 mol), and the
vessel left to stir at this temperature for 4 h, yielding a
dark red solution. An ethereal solution (50 mL) of
Ph2PCl (6.9 mL, 3.84 · 10ꢁ2 mol) was added dropwise
via cannula. The mixture was allowed to stir at
ꢁ78 ꢀC for 1 h before being left to warm to RT with stir-
ring for 18 h, resulting in a brown solution and white
precipitate. The solid was removed by filtration through
a glass frit and washed with diethyl ether (2 · 50 mL) to
leave a transparent brown solution. The solvent was
removed in vacuo to leave a brown solid, which was
subsequently extracted with hexane (300 mL) using a
Soxhlet apparatus. Upon cooling, the resultant red
solution precipitated 1 (Fig. 6) as a powdery yellow-
orange solid, which was recovered by cannula filtration
1
satellites, JSeP = 769).
4.4. Diphenylphosphino(phenyl pyridin-2-yl-
methylene)amine rhodium carbonyl chloride,
[RhCl(CO)(1-j2-P–N)] (3)
A Youngꢁs tap NMR tube was charged with 1
(51 mg,
1.39 · 10ꢁ4 mol),
[Rh(CO)2Cl]2
(27 mg,
6.95 · 10ꢁ5 mol) and sealed, before transferring to a
Schlenk line. CDCl3 (0.75 mL) was added and the tube
freeze/thaw degassed, back-filled with N2 and sealed.
After 30 min, when gas evolution had finished, the solu-
tion was freeze/thaw degassed, back-filled with an atmo-
sphere of CO, sealed and left to stand at RT for 1 h,
resulting in a deep red solution. Layering petroleum
ether 40–60 on top of the CDCl3 solution, yielded crys-
tals of 3 suitable for an X-ray structure determination,
after standing for 1 week. A CO atmosphere was found
to be necessary to prevent decomposition of 3 in solu-
(6.29 g,
45%,
m.p. = 99–101 ꢀC).
1H
NMR
(250.13 MHz, C6D6): d [ppm] = 8.52 (1 H, m, C1H),
7.93–7.85 (5H, m, PyH + C6H5), 7.66 (1H, dt,
3JHH = 7.8, JHH = 1.2, CH), 7.34–7.14 (11H, m,
3
PyH + C6H5), 6.75 (1H, dd, JHH = 4.8, JHH = 1.1,
tion, as has been reported previously3 [22]. H NMR
3
1
3
(301.24 MHz, CDCl3):
d
[ppm] = 9.60 (1H, d,
3JHH = 5.2, C1H), 7.69–7.19 (17H, m, PyH + C6H5),
3
7.13 (1H, d, JHH = 7.9, CH). 13C {1H} NMR
(75.75 MHz, CD2Cl2):
= 48 Hz, Rh–CO), 176.5 (s, C6), 154.7 (s, C1), 147.7 (d,
d
[ppm] = 188.1 (br, m1/2
3
3JPC = 20, C5), 139.0 (s, C3), 138.7 (d, JPC = 16, C7),
3
Complex 3 is stable in solution under an atmosphere of CO for
Fig. 6. General numbering scheme for 1 for NMR assignment.
weeks.

5276
P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
1
135.4 (dd, JPC = 61, JRhC = 2.0, {i-C6H5}2P), 132.6 (s,
2
(301.24 MHz, CDCl3):
4
d
[ppm] = 9.76 (1H, dd,
3JHH = 5.4, JPH = 1.0, C1H), 7.67–7.20 (17H, m,
C10), 132.0 (d, JPC = 13, {o-C6H5}2P), 131.1 (d,
2
4JPC = 3, {p-C6H5}2P), 129.9 (s, C8), 128.7 (s, C9),
3
PyH + C6H5), 7.08 (1H, d, JHH = 7.6, CH), 0.54 (3H,
3
3
128.5 (d, JPC = 11, {m-C6H5}2P), 127.4 (s, C2), 126.8
d, JPH = 3.2, Pd–CH3). 13C {1H} NMR (75.75 MHz,
(s, C4). 31P {1H} NMR (121.94 MHz, CDCl3): d
CDCl3): d [ppm] = 177.3 (d, JPC = 4, C6), 153.6 (s,
2
1
3
3
[ppm] = +84.5 (d, JRhP = 167). MS (FAB+): 497 (M–
C1), 148.1 (d, JPC = 16, C5), 139.2 (d, JPC = 16, C7),
Cl)+, 469 (M–Cl–CO)+. IR (KBr, CDCl3 solution):
m(CO) = 2010 cmꢁ1; m(C@N) = 1608, 1589 cmꢁ1. Anal.
Found C, 56.30; H, 3.55; N, 5.21%. Calc. for
C25H19N2OPClRh (532.76): C, 56.36; H, 3.59; N, 5.26%.
138.2 (s, C3), 132.7 (d, JPC = 60, {i-C6H5}2P), 132.7
1
2
(d, JPC = 13, {o-C6H5}2P), 132.5 (s, C10), 131.2 (d,
4JPC = 2, {p-C6H5}2P), 130.0 (s, C8), 128.6 (d,
3JPC = 4, {m-C6H5}2P), 128.4 (s, C9), 127.5 (s, C2),
127.0 (s, C4), ꢁ0.7 (s, Pd–CH3). 31P {1H} NMR
(121.94 MHz, CDCl3): d [ppm] = +72.9 (s). MS (FAB+):
507 (M–Me)+, 487 (M–Cl)+, 472 (M–Me–Cl)+. IR (KBr,
CDCl3 solution): m(C@N) = 1608, 1589, 1564 cmꢁ1. Anal.
Found C, 57.26; H, 4.15; N, 5.20%. Calc. for
C25H22N2PClPd (523.30): C, 57.38; H, 4.24; N, 5.35%.
4.5. Diphenylphosphino(phenyl pyridin-2-yl methylene)-
amine palladium dichloride, [PdCl2(1-j2-P–N)] (4)
A Schlenk was charged with 1 (365 mg, 9.97 ·
10ꢁ4 mol) and PdCl2(COD) (271 mg, 9.49 · 10ꢁ4 mol).
The vessel was stirred and cooled (ꢁ78 ꢀC), as CH2Cl2
(40 mL) was added dropwise, then left to stir and warm
to RT over 18 h. The CH2Cl2 was removed under re-
duced pressure to leave 4 as a yellow powder, which
was washed with diethyl ether (3 · 30 mL) and dried in
vacuo (484 mg, 94%). Yellow needle-like crystals of 4,
suitable for an X-ray structure determination, were
grown from a CD2Cl2 solution layered with hexane.
1H NMR (250.13 MHz, CD2Cl2): d [ppm] = 9.94 (1H,
4.7. Diphenylphosphino(phenyl pyridin-2-yl methylene)-
amine platinum dichloride, [PtCl2(1-j2-P–N)] (6)
A Schlenk was charged with 1 (145 mg, 3.96 ·
10ꢁ4 mol) and PtCl2(COD) (144 mg, 3.85 · 10ꢁ4 mol).
The solids were stirred, as CH2Cl2 (10 mL) was added
dropwise. The vessel was sealed and left to stir for 4 days
at RT, the initially orange solution turned yellow. The
solution was filtered and the solvent removed under re-
duced pressure to leave 6 as a vivid yellow powder,
which was washed with diethyl ether (3 · 10 mL) and
dried in vacuo (219 mg, 90%). Yellow needle-like crys-
tals of 6, suitable for an X-ray structure determination,
were grown from a CH2Cl2 solution layered with hex-
3
4
dd, JHH = 5.8, JPH = 1.2, C1H), 7.81–7.27 (18H, m,
PyH + C6H5). 13C {1H} NMR (75.75 MHz, CD2Cl2): d
[ppm] = 181.6 (d, JPC = 5, C6), 157.4 (s, C1), 145.3 (d,
2
3JPC = 21, C5), 140.4 (s, C3), 138.1 (d, JPC = 19, C7),
3
134.2 (s, C10), 133.3 (d, JPC = 11, {o-C6H5}2P), 132.7
2
4
(d, JPC = 3, {p-C6H5}2P), 130.9 (s, C8), 129.9 (d,
1JPC = 70, {i-C6H5}2P), 129.6 (s, C9), 129.4 (s, C2),
ane. H NMR (301.24 MHz, CD2Cl2): d [ppm] = 10.10
1
129.1 (d, JPC = 12.0, {m-C6H5}2P), 128.6 (s, C4). 31P
(1H, dd, JHH = 5.9, JPH = 1.3, C1H), 7.99 (1H, m,
3
3
4
{1H} NMR (101.26 MHz, CD2Cl2): d [ppm] = +66.8
(s). MS (FAB+): 544 M+, 509 (M–Cl)+, 472 (M–2Cl)+.
IR (KBr, CDCl3 solution): m(C@N) = 1608, 1587,
1560 cmꢁ1. Anal. Found C, 53.13; H, 3.43; N, 4.98%.
Calc. for C24H19N2PCl2Pd(543.72): C, 53.02; H, 3.52;
N, 5.15%.
CH), 7.79–7.35 (18H, m, PyH + C6H5). 13C {1H}
NMR (75.75 MHz, CD2Cl2):
d [ppm] = 180.7 (d,
2JPC = 5, C6), 156.7 (s, C1), 144.3 (d, JPC = 19, C5),
3
140.1 (s, C3), 138.3 (d, JPC = 19, C7), 133.7 (s, C10),
3
2
4
133.2 (d, JPC = 11, {o-C6H5}2P), 132.5 (d, JPC = 2,
{p-C6H5}2P), 130.5 (s, C8), 129.2 (s, C9), 129.1 (d,
1JPC = 76, {i-C6H5}2P), 129.0 (s, C2), 128.8 (d,
3JPC = 12.0, {m-C6H5}2P), 127.7 (s, C4). 31P {1H}
NMR (121.94 MHz, CD2Cl2): d [ppm] = +39.5 (s +
4.6. Diphenylphosphino(phenyl pyridin-2-yl methylene)-
amine palladium methyl chloride, [PdCl(Me)-
(1-j2-P–N)] (5)
1
satellites, JPtP = 3806). MS (FAB+): 597 (M–Cl)+, 561
(M–2Cl)+. IR (KBr, CDCl3 solution): m(C@N) = 1608,
1590, 1560 cmꢁ1. Anal. Found C, 45.67; H, 3.08; N,
4.58%. Calc. for C24H19N2PCl2Pt (632.38): C, 45.58; H,
3.03; N, 4.43%.
A Schlenk was charged with 1 (457 mg, 1.25 ·
10ꢁ3 mol) and PdCl(Me)(COD) (321 mg, 1.21 · 10ꢁ3
mol). The vessel was cooled to ꢁ78 ꢀC and the solids
stirred, as CH2Cl2 (20 mL) was added dropwise. Subse-
quently, the vessel was kept at a constant 15 ꢀC (cold
water bath) and stirred for 2 days, with all light ex-
cluded. The resulting mixture was filtered to remove col-
loidal palladium, giving a transparent yellow solution.
The CH2Cl2 was removed under reduced pressure to
leave 5 as an orange-yellow powder, which was washed
with hexane (3 · 30 mL) and dried in vacuo to leave a
vivid yellow powder (551 mg, 87%). 1H NMR
4.8. Diphenylphosphino(phenyl pyridin-2-yl methylene)-
amine platinum methyl chloride, [PtCl(Me)(1-j2-P–N)]
(7)
A Youngꢁs tap NMR tube was charged with 1
(37 mg, 1.01 · 10ꢁ4 mol) and PtCl(Me)(COD) (36 mg,
1.01 · 10ꢁ4 mol). CDCl3 (0.75 mL) was added and the
tube freeze/thaw degassed, back-filled with N2, sealed

P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
5277
and left to stand at RT for 18 h. The solvent was
removed under reduced pressure to leave 7 as a yellow
powder, which was washed with hexane (3 · 5 mL)
and dried in vacuo (56 mg, 90%). Yellow crystals of 7
suitable for an X-ray structure determination were
1589, 1560 cmꢁ1. Anal. Found: C, 52.87; H, 4.18; N,
4.66%. Calc. for C26H25N2PPt (591.54): C, 52.79; H,
4.26; N, 4.74%.
4.10. Diphenylphosphino(phenyl pyridin-2-yl methylene)-
amine methyl acetonitrile palladium (II) tetrakis(3,5-
bis(trifluoromethyl)phenyl)borate, [PdMe(MeCN)-
(1-j2-P–N)][B{3,5-(CF3)2-C6H4}4] (9)
1
grown from CH2Cl2/petroleum ether 40–60. H NMR
(250.13 MHz, CDCl3) d: 9.94 (1H, dd + satellites,
4
3
3JHH = 5.5, JPH = 0.9, JPtH = 15.4, C1H), 7.76–7.17
(18H, m, PyH + C6H5), 0.53 (3H, d + satellites,
2
3JPH = 3.7, JPtH = 79.9, Pt–CH3). 13C {1H} NMR
A
Schlenk was charged with
5
(127 mg,
(75.75 MHz, CDCl3) d: 177.4 (d, JPC = 5, C6), 153.6
2
2.42 · 10ꢁ4 mol), Na[B{3,5-(CF3)2-C6H3}4] (221 mg,
2.49 · 10ꢁ4 mol), acetonitrile (40 mL) and sealed. The
vivid yellow solution was stirred at RT for 4 days, then
filtered to remove a small amount of white precipitate
that had formed. Removal of solvent under reduced
pressure left a yellow solid, which was dissolved in
CH2Cl2 (20 mL) and the solution filtered. Removal of
the solvent and drying in vacuo afforded 9 as a vivid yel-
low solid (296 mg, 91%, m.p. = 70–71 ꢀC).
(s, C1), 145.7 (d, JPC = 15, C5), 139.3 (d, JPC = 17,
3
3
C7), 137.9 (s, C3), 132.8 (d + satellites, JPC = 12,
2
3JPtC = 41, {i-C6H5}2P), 132.4 (s, C10), 131.3 (d,
1JPC = 74, {i-C6H5}2P), 131.3 (d, 4JPC = 3, {p-
C6H5}2P), 130.0 (s, C8), 128.6 (s, C9), 128.3 (d,
3JPC = 11, {m-C6H5}2P + C2 obscured here), 127.8 (s,
2
1
C4), ꢁ16.7 (d + satellites, JPC = 5, JPtC = 677, Pt–
CH3). 31P {1H} NMR (101.26 MHz, CDCl3) d: +46.9
(s + satellites, JPtP = 4800). MS (FAB+): 597 (M–
1
1H (301.24 MHz, CDCl3): d [ppm] = 8.68 (1H, dd,
Me)+, 576 (M–Cl)+. IR (KBr, CDCl3 solution):
m(C@N) = 1610, 1590 cmꢁ1. Anal. Found C, 49.15; H,
3.56; N, 4.47%. Calc. for C25H22N2PClPt (611.96): C,
49.07; H, 3.62; N, 4.58%.
4
3JHH = 4.7, JPH = 0.6, C1H), 7.64–7.18 (30H, m,
PyH + C6H5 + C6H3(CF3)2), 2.12 (3H, s, CH3CN),
0.35 (3H, d, 3JPH = 2.3, Pd–CH3). 13C {1H}
2
(100.61 MHz, CDCl3): d [ppm] = 178.5 (d, JPC = 6,
1
C6), 161.9 (q, JBC = 50, i-C6H3(CF3)2), 151.1 (s, C1),
4.9. Diphenylphosphino(phenyl pyridin-2-yl-
methylene)amine platinum dimethyl, [PtMe2(1-j2-P–
N)] (8)
3
148.5 (d, JPC = 16, C5), 139.7 (s, C3), 138.2 (d,
3JPC = 17, C7), 135.0 (br s, o-C6H3(CF3)2), 133.8 (s,
2
C10), 132.6 (d, JPC = 13, {o-C6H5}2P), 132.4 (d,
4JPC = 3, {p-C6H5}2P), 130.4 (d, 1JPC = 66, {i-
A
Schlenk was charged with
1
(156 mg,
3
C6H5}2P), 130.2 (s, C9), 129.5 (d, JPC = 11, {m-
4.26 · 10ꢁ4 mol) and PtMe2(COD) (138 mg, 4.14 ·
10ꢁ4 mol). The solids were stirred, as CH2Cl2 (10 mL)
was added dropwise. The vessel was sealed and left to
stir for 2 days at RT, the initially orange solution stayed
orange. The solution was filtered and the solvent re-
moved under reduced pressure to leave 8 as a vivid or-
ange powder, which was washed with hexane
(3 · 10 mL) and dried in vacuo (203 mg, 83%). 1H
(301.24 MHz, CDCl3): d [ppm] = 9.30 (1H, dd + satel-
C6H5}2P), 129.4 (m, m-C6H3(CF3)2), 129.2 (s, C8),
3
129.3 (d, JPC = 6, {m-C6H5}2P), 128.5 (s br, CH3CN),
1
128.3 (s, C9), 124.7 (q, JFC = 270, CF3), 119.9 (br,
CH3CN), 117.7 (m, p-C6H3(CF3)2), 2.6 (s, CH3CN),
0.7 (s, Pd–CH3). 31P {1H} (121.94 MHz, CDCl3): d
[ppm] = +73.7 (s). MS (FAB+): 487 M+, 472 (M–Me)+.
MS (FABꢁ): 863 (B{C6H3(CF3)2}4)ꢁ. IR (KBr, CDCl3
solution): m(C@N) = 1610, 1594 cmꢁ1
.
Anal. Found: C, 51.08; H, 2.52; N, 2.95%. Calc. for
C59H37N3BPF24Pd (1392.11): C, 50.90; H, 2.68; N,
3.02%.
3
4
3
lites, JHH = 5.7, JPH = 1.1, JPtH = 21.9, C1H), 7.70–
7.00 (18H, m, PyH + C6H5), 0.77 (3H, d + satellites,
2
3JPH = 7.9, JPtH = 65.4, Pt–CH3 {trans-P}), 0.53 (3H,
3
2
d + satellites, JPH = 7.9, JPtH = 90.6, Pt–CH3 {cis-P}).
13C {1H} (75.75 MHz, CDCl3): d [ppm] = 175.0 (s + sat-
4.11. Diphenylphosphino(phenyl pyridin-2-yl methylene)-
amine methyl acetonitrile palladium (II)
hexafluorophosphate, [PdMe(MeCN)-
(1-j2-P–N)][PF6] (10)
3
2
ellites, JPtC = 27, C6), 152.5 (s + satellites, JPtC = 14,
C1), 147.5 (d, JPC = 14, C5), 139.8 (d, JPC = 14, C7),
3
3
137.2 (s, C3), 134.2 (d, JPC = 46, {i-C6H5}2P), 132.5
1
(m, {o-C6H5}2P), 131.8 (s, C10), 130.1 (d, JPC = 2, {p-
4
C6H5}2P), 129.6 (s, C8), 128.4 (s, C9), 128.1 (d,
3JPC = 10, {m-C6H5}2P), 127.5 (s + satellites, 3JPtC = 18,
A
Schlenk was charged with
5
(306 mg,
5.84 · 10ꢁ4 mol), NaPF6 (101 mg, 6.01 · 10ꢁ4 mol), ace-
tonitrile (60 mL) and sealed. The vivid yellow solution
was stirred at RT for 3 days, then filtered to remove
the slight white precipitate that had formed. Removal
of solvent under reduced pressure left a yellow solid,
which was dissolved in CH2Cl2 (30 mL) and the solution
filtered. Removal of the solvent and drying in vacuo left
C2), 126.2 (s, C4), 10.9 (d + satellites, JPC = 111,
2
1JPtC = 340, Pt–CH3 {trans-P}), ꢁ21.6 (d + satellites,
2JPC = 4, JPtC = 759, Pt–CH3 {cis-P}). 31P {1H}
1
(121.94 MHz, CDCl3): d [ppm] = +65.3 (s + satellites,
1JPtP = 1259). MS (FAB+): 576 (M–Me)+, 561 (M–
2Me)+. IR (KBr, CDCl3 solution): m(C@N) = 1605,

5278
P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
10 as a vivid yellow solid (298 mg, 81%, m.p. = 97 ꢀC
colour change, yellow to black, 157–158 ꢀC melted).
1H (250.13 MHz, CDCl3): d [ppm] = 9.37 (1H, br d,
3JHH = 3.5, C1H), 7.77–7.06 (18H, m, PyH + C6H5),
0.38 (3H, br s, m1/2 = 6.0 Hz, Pd–CH3). 13C {1H}
added, the tube freeze/thaw degassed, then back-filled
with CO and sealed. After standing at RT for 2 days,
with periodic vigorous shaking, the initially yellow solu-
tion became bright red. 1H NMR (301.24 MHz, CDCl3):
3
4
d [ppm] = 9.54 (1H, dd, JHH = 5.0, JPH = 1.1, C1H),
2
(75.75 MHz, CDCl3): d [ppm] = 178.1 (d, JPC = 6, C6),
7.69–7.21 (17H, m, PyH + C6H5), 7.08 (1H, d,
4
3
152.9 (s, C1), 147.9 (d, JPC = 16, C5), 139.3 (s, C3),
3JHH = 7.9, CH), 2.04 (3H, d, JPH = 1.7, Pd–
3
138.8 (d, JPC = 18, C7), 133.1 (s, C10), 132.6 (d,
C{@O}CH3). 13C {1H} NMR (75.75 MHz, CDCl3): d
2JPC = 12, {o-C6H5}2P), 131.7 (s, {p-C6H5}2P), 130.3
[ppm] = 227.0 (d, JPC = 9, Pd–C{@O}CH3), 176.3 (d,
2
1
3
(s, C8), 129.8 (d, JPC = 40, {i-C6H5}2P), 128.9 (s, C9),
2JPC = 3, C6), 153.3 (s, C1), 149.3 (d, JPC = 13, C5),
3
3
128.8 (d, JPC = 11, {m-C6H5}2P), 128.0 (s, C2), 127.6
139.4 (d, JPC = 16, C7), 138.5 (s, C3), 133.6 (d,
(s, C4), 1.2 (s, Pd–CH3). 31P {1H} (101.26 MHz, CDCl3):
d [ppm] = +73.4 (br s, m1/2 = 14.3 Hz, Ph2P {2-IP}),
1JPC = 55, {i-C6H5}2P), 132.7 (s, C10), 132.1 (d,
4
2JPC = 14, {o-C6H5}2P), 131.3 (d, JPC = 2, {p-
1
ꢁ144.5 (sept, JPF = 716, PF6). MS (FAB+): 487 M+,
C6H5}2P), 130.1 (s, C8), 128.9 (s, C9), 128.7 (d,
3JPC = 4, {m-C6H5}2P), 127.5 (s, C2), 127.1 (s, C4),
472 (M–Me)+. MS (FABꢁ): 145 (PF6)ꢁ. IR (KBr,
CH2Cl2 solution): m(C@N) = 1606, 1588, 1564 cmꢁ1
Anal. Found: C, 47.98; H, 3.60; N, 5.98%. Calc. for
C27H25N3P2F6Pd (673.87): C, 48.12; H, 3.74; N, 6.24%.
.
39.00 (d, JPC = 25, Pd–C{@O}CH3). 31P {1H} NMR
3
(121.94 MHz, CDCl3):
d
[ppm] = +56.1 (s). MS
(FAB+): 515 (M–Cl)+, 507 (M-acyl)+, 487 (M–Cl-
Me)+, 472 (M–Cl-acyl)+. IR (KBr, CDCl3 solution):
4.12. Diphenylphosphino(phenyl pyridin-2-yl methylene)-
amine g1-acyl acetonitrile palladium (II)
tetrakis(3,5-bis(trifluoromethyl)phenyl)borate,
[Pd{C(@O)Me}(MeCN)(1-j2-P–N)]-
[B{3,5-(CF3)2-C6H4}4] (11)
m(C@O) = 1696 cmꢁ1; m(C@N) = 1610, 1588, 1565 cmꢁ1
.
4.14. Reaction of [PdCl{C(@O)Me}(1-j2-P–N)] (12)
with CH2@CH2, formation of 13
In a thick-walled Youngꢁs tap NMR tube, a CDCl3
(0.5 mL) solution of 7 (6 mg, 1.09 · 10ꢁ5 mol) prepared
as previously described, was freeze/thaw degassed, back-
filled with CH2@CH2 and sealed. After standing at RT
for 3 days, no reaction was evident by 31P {1H} NMR
spectroscopy. After raising the pressure of CH2@CH2
in the tube to ꢀ10 atmospheres, 1H and 31P {1H}
NMR spectroscopies showed a new peak corresponding
to the product resulting from insertion (within 10 min of
CH2@CH2 being added), in addition to a peak for the
acyl starting material, in a 1:1 ratio. Standing at RT
for 18 h caused no change according to 1H and 31P
{1H} NMR spectroscopies. 31P {1H} NMR
(101.26 MHz, CDCl3): d [ppm] = +72.1 (s, 13), +56.1
(s, 12).
A Youngꢁs tap NMR tube was charged with 9 (19 mg,
1.36 · 10ꢁ5 mol). CDCl3 (0.5 mL) was added, the tube
freeze/thaw degassed, then back-filled with CO and
sealed. After standing at RT for 6 h, with periodic vigor-
ous shaking, the initially yellow solution became orange.
1H (301.24 MHz, CDCl3): d [ppm] = 8.73 (1 H, br,
C1H), 7.71–7.23 (30H, m, PyH + C6H5 + C6H3(CF3)2),
4
2.15 (3H, s, CH3CN), 2.03 (3H, d, JPH = 1.8, Pd–
C(@O)CH3). 13C {1H} (75.75 MHz, CDCl3):
d
2
[ppm] = 222.8 (s, Pd–C{@O}CH3), 177.6 (d, JPC = 6,
1
C6), 161.9 (q, JBC = 50, i-C6H3(CF3)2), 151.1 (s, C1),
3
149.9 (d, JPC = 14, C5), 139.9 (s, C3), 138.2 (d,
3JPC = 18, C7), 135.0 (br s, o-C6H3(CF3)2), 133.9 (s,
4
C10), 132.5 (d, JPC = 2, {p-C6H5}2P), 132.1 (d,
1
1
2JPC = 13, {o-C6H5}2P), 131.20 (d, JPC = 60, {i-
Data for complex 13 only: H NMR (250.13 MHz,
[ppm] = 9.66 (1H, dd, 3JHH = 5.0,
3
C6H5}2P), 130.2 (s, C8), 129.5 (d, JPC = 11.0, {m-
CDCl3):
4JPH = 0.9, C1H), 7.71–7.19 (18H, m, PyH + C6H5),
d
C6H5}2P), 129.2 (s, C9), 129.2 (m, CF3), 128.5 (s, C4),
1
3
4
127.9 (s, C2), 124.7 (q, JFC = 273, CF3), 119.5 (br,
2.30 (2H, pseudo-td, JHH = 8.2, JPH = 3.2, Pd–CH2–
CH2–C{@O}CH3), 1.70 (3H, s, Pd–CH2–CH2–
C{@O}CH3), 1.54 (2H, m, Pd–CH2–CH2–C{@O}CH3).
3
MeCN), 117.7 (m, p-C6H3(CF3)2), 38.0 (d, JPC = 30,
Pd–C(@O)CH3), 2.5 (s, CH3CN). 31P {1H}
(101.26 MHz, CDCl3): d [ppm] = +57.8 (s). MS (FAB+):
515 (M–CH3CN)+, 472 (M–CH3CN-acyl)+. MS (FABꢁ):
863 (B{C6H3(CF3)2}4)ꢁ. R (KBr, CH2Cl2 solution):
4.15. Diphenylphosphino(phenyl pyridin-2-yl-
methylene)amine palladium N-tert-butyl-g1-iminoacyl-
chloride, [PdCl{g1-C(@NBut)Me}(1-j2-P–N)] (14)
m(C@O) = 1653 cmꢁ1; m(C@N) = 1610, 1590 cmꢁ1
.
4.13. Diphenylphosphino(phenyl pyridin-2-yl methylene)-
amine palladium g1-acyl chloride,
A Youngꢁs tap NMR tube was charged with 12
(15 mg, 2.87 · 10ꢁ5 mol). CDCl3 (0.5 mL) was added
and the tube freeze/thaw degassed. ButNC
(2.87 · 10ꢁ5 mol) was then added via vacuum transfer
using a gas/vapour addition bulb and Hg manometer,
the tube back-filled with N2 and sealed. After standing
[PdCl{g1-C(@O)Me}(1-j2-P–N)] (12)
A thick-walled Youngꢁs tap NMR tube was charged
with 5 (51 mg, 9.75 · 10ꢁ5 mol). CDCl3 (0.5 mL) was

P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
5279
at RT for 1 h the initially yellow solution turned deep
red. 1H NMR (250.13 MHz, CDCl3): d [ppm] = 9.84
using graphite monochromated Mo-Ka X-radiation
(k = 0.71073 A). Data collection and reduction were
˚
3
4
(1H, dd, JHH = 5.6, JPH = 1.0, C1H), 7.96–7.21 (18H,
conducted using the SMART and SAINT programs [77],
respectively. All further calculations were performed
using the SHELXTL package [78] and programs therein.
Structures were solved using Patterson methods. All
structures were refined using full-matrix least squares
based on F2. An empirical absorption correction was ap-
plied to all data using SADABS [79]. All non-hydrogen
atoms were refined anisotropically, then hydrogen
atoms included at idealised positions and refined as rigid
groups.
4
m, PyH + C6H5), 2.85 (3H, d, JPH = 2.1, Pd–
C{@NC(CH3)3}CH3), 1.43 (9H, s, Pd–C{@NC-
(CH3)3}CH3). 13C {1H} NMR (75.75 MHz, CDCl3): d
2
[ppm] = 179.5 (d, JPC = 4, C6), 154.8 (s, C1), 148.9 (d,
2JPC = 24,
Pd–C{@NC(CH3)3}CH3),
147.0
3
(d,
3JPC = 18.0, C5), 140.4 (s, C3), 138.0 (d, JPC = 18.0,
C7), 133.9 (s, C10), 133.23 (d, JPC = 3, {p-C6H5}2P),
4
2
3
132.8 (d, JPC = 13, {o-C6H5}2P), 131.5 (d, JPC = 12,
{m-C6H5}2P), 130.5 (s, C8), 129.2 (s, C9), 128.4 (s, C2),
128.3 (s, C4), 60.0 (s, Pd–C{@NC(CH3)3}CH3), 34.9 (d,
3JPC = 4, Pd–C{@NC(CH3)3}CH3), 29.2 (s, Pd–
C{@NC(CH3)3}CH3). {i-C6H5}2P was not observed.
31P {1H} NMR (101.26 MHz, CDCl3): d [ppm] = +57.9
(s). MS (FAB+): 606 (MH)+, 570 (M–Cl)+, 473 (M–Cl–
C{@NC(CH3)3}CH3)+. IR (KBr, CH2Cl2 solution):
4.17. Catalytic testing
Catalyst testing was undertaken in a custom-made
HEL Automate autoclave system (stainless steel) under
computer control. Stirring was achieved using a magnet-
ically driven paddle stirrer. Temperature control was
achieved using both an internal heater coil and an exter-
nal heater jacket and monitored both inside and out.
Autoclave dried under flow of N2 at elevated tempera-
ture. Procatalysts were introduced into the autoclave
quickly under air and the system rapidly purged with
nitrogen. Solvent (dry MeOH) was added to the reaction
1593 (C@N) cmꢁ1
.
4.16. X-Ray crystal structure analyses
X-ray diffraction data (Table 5) were collected on a
Bruker Apex 2K CCD area detector diffractometer
equipped with an Oxford Cryostream N2 cooling device,
Table 5
Crystallographic data for the complexes 3, 4, 6, and 7
Complex
3 Æ CDCl3
4 Æ CD2Cl2
6 Æ CH2Cl2
7
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C
653.13
25H19N2OPClRh Æ CDCl3 C24H19N2PCl2Pd Æ CD2Cl2 C24H19N2PCl2Pt Æ CH2Cl2 C25H22N2PClPt
630.62
717.30
611.96
150(2)
Monoclinic
P2(1)/n
150(2)
Triclinic
150(2)
Monoclinic
P2(1)/n
150(2)
Orthorhombic
P2(1)2(1)2(1)
9.6133(4)
12.0936(4)
20.3218(7)
90
ꢀ
P1
9.0218(4)
˚
a (A)
12.9589(5)
12.2356(4)
17.8924(6)
90
12.5494(6)
12.3151(6)
17.6121(8)
90
˚
b (A)
10.8340(5)
14.3981(7)
75.3150(10)
83.4430(10)
68.9620(10)
1270.17(10)
2
˚
c (A)
a (ꢀ)
b (ꢀ)
c (ꢀ)
102.035(1)
90
100.8050(10)
90
90
90
3
˚
Volume (A )
2774.66(17)
4
1.563
2673.6(2)
4
1.782
2362.60(15)
4
1.720
Z
Dcalc (mg/m3)
1.649
1.232
Absorption coefficient (mmꢁ1
Crystal size (mm3)
h-range (ꢀ)
)
1.081
5.724
6.134
0.42 · 0.37 · 0.34
1.78 to 26.00
21045
0.34 · 0.30 · 0.14
1.46 to 26.00
9969
0.340.28 · 0.26
1.84 to 27.00
22078
0.39 · 0.24 · 0.21
1.96 to 28.00
20653
Reflections collected
Independent reflections
5437
4929
5843
5577
[R(int) = 0.0155]
26.00ꢀ/99.9%
Empirical
0.86 and 0.75
5437/0/316
1.044
[R(int) = 0.0146]
26.00ꢀ/98.9%
Empirical
0.93 and 0.76
4929/0/298
1.047
[R(int) = 0.0289]
27.00ꢀ/100.0%
Empirical
0.86 and 0.50
5843/0/298
1.146
[R(int) = 0.0423]
28.00ꢀ/99.1%
Empirical
0.75 and 0.34
5577/0/272
1.020
Completeness to h
Absorption correction
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R1 = 0.0251
wR2 = 0.0672
R1 = 0.0267
wR2 = 0.0680
–
R1 = 0.0214
wR2 = 0.0576
R1 = 0.0227
wR2 = 0.0582
–
R1 = 0.0324
wR2 = 0.1049
R1 = 0.0341
wR2 = 0.1056
–
R1 = 0.0216
wR2 = 0.0465
R1 = 0.0224
wR2 = 0.0467
0.002(5)
R indices (all data)
Absolute structure parameter
˚
Largest differential peak and hole (e A
ꢁ3
)
1.103 and ꢁ0.999
0.463 and ꢁ0.637
3.136 and ꢁ1.289
1.121 and ꢁ0.778
Standard deviations are given in parentheses.

5280
P.W. Dyer et al. / Journal of Organometallic Chemistry 690 (2005) 5264–5281
and Cooligomers, Kluwer Academic Publishers, Dordrecht,
2003, pp. 37–82 (Chapter 3).
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appropriate, activator (MeSO3H) was also added via
syringe under a flow of nitrogen. The reactor vessel
was saturated with CO:C2H4 (1:1, 38 bar) at ambient
temperature prior to rapid warming of the vessel to
the desired reaction temperature.
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5. Supplementary material
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC, Nos. CCDC 261271–261274 for
3, 4, 6, and 7, respectively. Copies of this information
may be obtained free of charge from The Director, 12
Union Road, Cambridge, CB2 1EZ, UK (fax: +44
1223 336 033: e-mail deposit@ccdc.cam.ac.uk or www:
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The Royal Society and The Nuffield Foundation are
thanked for grants to PWD. Johnson Matthey Plc. is
thanked for the loan of platinum group metal salts.
Financial support from the EPSRC (PWD {JREI GR/
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