New cationic palladium (II) and rhodium (I) complexes of [Ph 2PCH2C(Ph)=N(2,6-Me2C6H 3)]

Article abstract of DOI:10.1016/j.jorganchem.2005.01.016

Treatment of the bulky iminophosphine ligand [Ph₂PCH ₂C(Ph)=N(2,6-Me₂C₆H₃)] (L) with [M(CH₃CN)₂(ligand)]⁺ⁿ, where for M = Pd(II): ligand = η³-allyl, n = 1, and for M = Rh(I), ligand: 2(C ₂H₄), 2(CO) or cod, n = 0, yields the mono-cationic iminophosphine complexes [Pd(η³-C₃H ₅)(L)][BF₄] (1), [Rh(cod)(L)][BF₄] (2), [Rh(CO)(CH₃CN)(L)][BF₄] (3), and cis-[Rh(L) ₂][BF₄] (4). All the new complexes have been characterised by NMR spectroscopy and X-ray diffraction. Complex 1 shows moderate activity in the copolymerisation of CO and ethene but is inactive towards Heck coupling of 4-bromoacetophenone and n-butyl acrylate.

Full text of DOI:10.1016/j.jorganchem.2005.01.016

Journal of Organometallic Chemistry 690 (2005) 1645–1658
www.elsevier.com/locate/jorganchem
New cationic palladium (II) and rhodium (I) complexes
of [Ph2PCH2C(Ph)@N(2,6-Me2C6H3)]
*
*
Sofia I. Pascu , Karl S. Coleman, Andrew R. Cowley, Malcolm L.H. Green ,
Nicholas H. Rees
Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
Received 6 December 2004; accepted 14 January 2005
Abstract
Treatment of the bulky iminophosphine ligand [Ph2PCH2C(Ph)@N(2,6-Me2C6H3)] (L) with [M(CH3CN)2(ligand)]+n, where for
M = Pd(II): ligand = g3-allyl, n = 1, and for M = Rh(I), ligand: 2(C2H4), 2(CO) or cod, n = 0, yields the mono-cationic iminophos-
phine complexes [Pd(g3-C3H5)(L)][BF4] (1), [Rh(cod)(L)][BF4] (2), [Rh(CO)(CH3CN)(L)][BF4] (3), and cis-[Rh(L)2][BF4] (4). All the
new complexes have been characterised by NMR spectroscopy and X-ray diffraction. Complex 1 shows moderate activity in the
copolymerisation of CO and ethene but is inactive towards Heck coupling of 4-bromoacetophenone and n-butyl acrylate.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Rhodium(I); Pd(II)-allyl; Iminophosphines; CO ethylene copolymerisation; Heck reactions
1. Introduction
ity and selectivity of Group 10 complexes [66], it is sur-
prising that no Rh(I) complexes of ligands combining
tertiary phosphine donors and (sp2)N-aryl donors with
bulky ortho substituents have been structurally investi-
gated. To date, no Rh(I) complexes of bulky iminophos-
phines such as [Ph2PCH2C(Ph)@N(2,6-R2C6H3)] (where
R = H, alkyl, aryl) are known.
We have been interested in studying neutral and cat-
ionic group 10 complexes of hybrid hemi-labile ligands,
and particularly featuring a bulky iminophosphine and
a diphenylphosphino group. The present work continues
our study on the synthesis, reactivity and catalysis of
neutral Ni(II), Pd(II) and Pt(II) complexes of enolisable
iminophosphine ligands with flexible backbone such as
[Ph2PCH2C(Ph)@N(2,6-R2C6H3)] (where R = H, Me,
iPr) [67]. Herein, we are reporting the synthesis and
spectroscopic studies of new organometallic cationic
Pd(II) and Rh(I) complexes of [Ph2PCH2C(Ph)@N-
(2,6-Me2C6H3)] (L). The activity of a new Pd(II) g3-allyl
complex in typical C–C coupling reactions, such as CO/
ethylene copolymerisation and the Heck coupling of an
activated olefin with an aryl-bromide, was tested.
Cationic four-coordinate Pd(II) and Rh(I) complexes
incorporating tertiary phosphines and olefins (such as
allyl or 1,5-cod) are of widespread interest as catalysts
precursors in organic synthesis and species such as
[Rh(L2)2]+ (where L2 is a bidentate nitrogen–phospho-
rus ligand) [1–4] have been shown to catalyse decarb-
onylation of aldehydes. Furthermore, there is
considerable current interest in hybrid P/N ligands and
a search in the Cambridge Structure Database revealed
that although a vast number of Groups 9–10 complexes
with nitrogen and phosphorus ligands have been charac-
terised structurally, only a relatively small number of
Pd(II) cations [5–53] and Rh(I) cations [54–65] contain-
ing bidentate N(sp2)–P(sp3) donors are reported. Since
bulky substituents at the aryl groups of N(sp2) donors
have been found to strongly influence the catalytic activ-
*
Corresponding authors. Present address: Department of Chemis-
try, University of Cambridge, Lensfield Road, CB2 1EW, UK (S.I.
Pascu). Tel.: +1223 336317; fax: +1223 3363017.
E-mail address: sip22@cam.ac.uk (S.I. Pascu).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.01.016

1646
S.I. Pascu et al. / Journal of Organometallic Chemistry 690 (2005) 1645–1658
2. Results and discussions
2.1. Syntheses
spectra of complexes 2–4 (in CD2Cl2) showed bands at
1539 (2), 1538 (3) and 1559 cmꢀ1 (4) assignable to mC@N
.
For 3, a broad band at 2304 cmꢀ1 indicated the presence
of coordinated CH3CN and the band at 2004 cmꢀ1 was
assigned to theCO stretching vibration. The presence of
CH3CN and CO ligands was also confirmed by 13C{1H}
NMR spectroscopy. In all cases, IR spectra (CD2Cl2)
showed broad bands in the region 1220 cmꢀ1 corre-
sponding to [BF4]ꢀ.
Bridge cleavage reactions of dimeric g3-allyl com-
plexes such as [Pd(g3-allyl)(l-Cl)]2 are known to leave
the palladium-p-allyl groups intact [68]. The cationic
g3-allyl complex [Pd(g3-allyl)(L)][BF4] (1) was obtained
by the reaction between [Pd(g3-allyl)(MeCN)2][BF4]
(prepared in situ, after reacting [Pd(g3-allyl)Cl]2 with
one equivalent of AgBF4 in CH3CN) and one equivalent
of the compound [Ph2PCH2C(Ph)@N(2,6-Me2C6H3)]
(L) (Scheme 1). Complex 1 is stable in the solid state
and can be exposed to air for up to 2 h without any
apparent decomposition. However, solutions in haloge-
nated solvents at room temperature lead to slow decom-
position but they are stable for weeks at ꢀ20 ꢁC under
N2. The complexes [Rh(cod)(L)][BF4] (2), [Rh(CO)-
(CH3CN)(L)][BF4] (3) and [Rh(L)2][BF4] (4) (Scheme
1) were made using a 1:2:2 ratio of Rh-precursor
[RhCl(cod)]2 (in case of 2), [RhCl(CO)2]2 (in case of 3)
or [RhCl(C2H4)2]2 (in case of 4), AgBF4 and the ligand
L, in CH3CN solutions at room temperature.
[Rh(cod)(L)][BF4] (2) was isolated in 75% yield. When
the precursor [RhCl(CO)2]2 was used, the complex
[Rh(CO)(CH3CN)(L)][BF4] (3) was isolated in 62% yield
and not the expected compound [Rh(CO)2(L)][BF4]. If
the complex [Rh(CO)2(L)][BF4] formed initially as an
intermediate, a trans effect of the PPh2 ligand moiety
in the metal complex would lead to the weakening of
the corresponding M–CO bond. This could be responsi-
ble for the lability (in the CH3CN solution) of the CO
group. With [RhCl(C2H4)2]2, AgBF4 and L in CH3CN,
a small amount of red crystals were obtained, together
with an unidentifiable mixture of products. The red crys-
The 31P{1H} NMR spectrum (CD2Cl2) of [Pd(g3-
allyl)(L)][BF4] (1) exhibited a singlet at d 37.5, consistent
with the coordination of the phosphine group to the pal-
ladium (II) centre (31P NMR resonance for the Z isomer
of the free ligand is d ꢀ19.8) [67]. The temperature
dependence of the NMR spectra of g3-allyl Pd(II) com-
plexes both in the presence and absence of coordinating
ligands has been described [68,69]. In accordance, the
allyl complex [Pd(g3-allyl)(L)][BF4] (1) was found ste-
1
reochemically non-rigid in CD2Cl2. The H NMR spec-
trum of
1 (room temperature, CD2Cl2) showed
diastereotopic methylene protons of the ligand as a pair
of doublet of doublets at d 4.57 and 4.34 (JHP = 10.7 Hz,
JHH = 7.4 Hz). The two methyl groups of Me2C6H3 are
also inequivalent, and the corresponding resonances
were observed as singlets at d 2.10 and 2.02. The aro-
matic protons were found as complex multiplets be-
1
tween d 7.77 and d 6.98. The H NMR spectrum, of
ABCDX type, exhibited five resonances assigned to
the g3-allyl group between 30 and ꢀ80 ꢁC (Table 1).
1
The assignment of the H NMR spectrum was assisted
by 1H –1H COSY and nOe difference experiments
Strong nOes of H5a with H2 and H3, as well as with the
o-PPh2 protons of the ligand were observed. Irradiating
H1a at room temperature and +30 ꢁC, the exchange be-
tween H1a and H2a is observed (negative nOe) as well as
nOeꢀs and transferred nOeꢀs with the PPh2 protons, Ha5
and H4a. Exchange between H1 and H2 is observed at
+30, +20 and + 10 ꢁC. Between 0 and ꢀ80 ꢁC, no
H1a=H2a exchange nOe is observed, however, the complete
freezing of exchange processes could not be achieved
even upon cooling to ꢀ80 ꢁC. For square-planar allyl
complexes of mixed hard and soft donor ligands, it is
documented that the syn–anti interchange of the allyl
protons takes place through the g3-g1-g3 interconver-
sion process (Scheme 2) [24,70,71]. The PPh2 group
weakens the trans Pd–CH2 bond. Therefore, the opening
of the allyl ring is promoted and the interchange of the
syn–anti protons Ha3 and H4a occurs due to rotation
about the r bonds, as suggested by VT ROESY
experiments.
1
tals were shown by H NMR spectroscopy and X-ray
diffraction to be cis-[Rh(L)2][BF4] (4). There was no evi-
dence for the expected products [Rh(C2H4)2(L)][BF4] or
[Rh(CH3CN)(C2H4)(L)][BF4]. The reaction was re-
peated using [RhCl(C2H4)2]2, AgBF4 and L in a 1:2:4 ra-
tio, and led to similar observation. Complex 4 was
formed in 35% yield. Finally, reaction between
[Rh(CO)(CH3CN)(L)][BF4] (3) and one equivalent of
free L was performed in CH2Cl2, and again gave only
the cis isomer of [Rh(L)2][BF4] (4).
2.2. Spectroscopic investigations
The complexes 1–4 have been characterised by ele-
mental analysis, mass spectrometry (FAB), infrared
1
and H, 13C{1H} and 31P{1H} NMR spectroscopy (in
CD2Cl2). Full assignments are given in Table 1.
The 13C{1H} NMR spectrum of 1 exhibited doublet
resonances at d 181.7 (2JPC = 7.9 Hz) and d 46.3
(1JPC = 28 Hz), which were assigned to the C@N and
methylene carbons of the iminophosphine ligand,
respectively. The chemical shift of the C@N function is
shifted compared to the chemical shift for the free ligand
The IR spectrum of 1 (in CD2Cl2) showed a mC@N
band at 1572 cmꢀ1, which is significantly shifted from
1634 cmꢀ1 for the free ligand [67], indicating that the
iminophosphine is chelated to the metal centre. The IR

S.I. Pascu et al. / Journal of Organometallic Chemistry 690 (2005) 1645–1658
1647
Ph
Cl
Cl
N
PPh2
i, ii
Pd(η3-allyl)
(η3-allyl)Pd
Pd
[BF4]
1
Ph
N
i, ii
[RhCl(cod)]2
PPh2
Rh
[BF4]
2
Ph
N
PPh2
Rh
i, ii
CO
OC
[BF4]
Ph
N
[RhCl(CO)2]2
i, ii
PPh2
PPh2
Ph
iii
Rh
PPh2
N
Rh
N
H3CCN
CO
[BF4]
PPh2
PPh2
[BF4]
Ph
4
3
Ph
Ph
PPh2
N
N
or
Rh
Rh
i, ii
H3CCN
[BF4]
[BF4]
[RhCl(C2H4)2]2
i, ii
Ph
N
Rh
N
PPh2
[BF4]
Ph
4
Scheme 1. Formation of compounds 1–4. (i) AgBF4, CH3CN; (ii) [Ph2PCH2C(Ph)@N(2,6-Me2C6H3)] (L), CH3CN; (ii) [Ph2PCH2C(Ph)@N(2,6-
Me2C6H3)] (L), CH2Cl2.
(d 167.2) and is consistent with coordination through the
nitrogen. Peaks at d 18.7 and 18.6 were assigned to the
carbons of the Me2C6H3 unit and peaks at d 52.7
(2JPC = 4 Hz), d 84.1 (2JPC = 30 Hz), and d 122.9
(2JPC = 6) to g3-allyl ligands (terminal trans to PPh2,
terminal cis to PPh2 and central, respectively).
The 31P{1H} NMR spectrum (CD2Cl2) of complex 2
showed a doublet at d 46.9 with the Rh–P coupling
1JRhP = 154 Hz, which is typical for [Rh(cod)(PR3)2]+
1
and [Rh(cod)(N/P)2]+ compounds [63,72,73]. H NMR
studies of 2 showed equivalent methylene protons of
the ligand as a doublet at d 4.50 (JHP = 11.0 Hz). The

Table 1
Data characterising compounds 1–4
Compound data
NMR data (CD2Cl2)
1
[Pd(g3-allyl){P2PCH2C(Ph)@N(2,6-Me2C6H3)}][BF4],
31H31BF4NPPd, Mw 641.79. Air and moisture sensitive yellow powder.
1H NMR data (500 MHz): 2.02 (s, 3H, Me2C6H3, 12H), 2.10 (s, 3H, Me2C6H3, 12H), 4.34 (d, 1H, HCH–P,
2
2
C
2JPH = 10.7, JHH = 7.4), 4.57 (d, 1H, HCH–P, 2JPH = 10.7, JHH = 7.4), 5.83 (b, 1H, H5a, central allyl-H), 3.15 (b,
1H, H1a; anti-Ha5, terminal allyl-H), 4.13 (b, 1H, Ha2; syn-Ha5, terminal allyl-H), 3.61 (b, 1H, Ha3; syn-H5a, terminal
allyl-H), 3.70 (b, 1H, H4a; anti-Ha5, terminal allyl-H), 6.99 (m, 3H, m + p-H of Me2C6H3), 7.10 (m, 2H, o-H of Ph),
7.26 (m, 2H, m-H of Ph), 7.43 (m, 1H, p-H of Ph), 7.62 (m, 6H, p + m-H of PPh2), 7.76 (m, 4H, o-H of PPh2);
31P{1H} NMR data (202.4 MHz): 37.5 (s);
E.A.% Found (Calc.) C 57.8 (58.0), H 4.5 (4.9), H 1.8 (2.2).
FAB+: m/z 554.2 (100) [M ꢀ BF4].
IR (CsI): mC@N 1572–1596 cmꢀ1 (broad) mBF4 1061 cmꢀ1 (broad).
11B{1H} NMR data (160.4 MHz): ꢀ0.6 (s);
19F NMR data (282.45 MHz): ꢀ152.5 (s);
1
13C{1H} NMR data (125.7 MHz): 18.7 (s, Me2C6H3N), 18.6 (s, Me2C6H3N), 46.3 (d, CH2P, JPC = 28), 52.7 (d,
2
2
terminal allyl-C, trans-PPh2, JPC = 4), 84.1 (d, terminal allyl-C, cis-PPh2, JPC = 30), 122.9 (d, central allyl-C,
2JPC = 6), 128.8, 128.7 (s, o-, o0-C of Me2C6H3N), 127.6 (s, m-C of Me2C6H3N), 127.4 (s, p-C of Me2C6H3N), 181.7
(d, N@C, 2JPC = 7.9), 132.2 (s, o-C of Ph), 132.5 (s, m-C of Ph), 127.3 (s, p-C of Ph), 133.3 (b, i-C of PPh2), 132.9
2
(d, o-C of PPh2, JPC = 12), 129.9 (d, m-C of PPh2, 3JPC = 11)
2
3
4
[Rh(cod){Ph2PCH2C(Ph)@N(2,6-Me2C6H3)}][BF4],
1H NMR data (500 MHz): 2.07 (m, 2H, cod-CH2, vicinal to cod-CH trans to PPh2), 2.11 (s, 6H, Me2C6H3, 2.23 (m,
2H, cod-CH2, vicinal to cod-CH cis to PPh2), 2.32 (m, 2H, cod-CH2, vicinal to cod-CH trans to PPh2), 2.43 (m,
2H, cod-CH2, vicinal to cod-CH cis to PPh2), 4.19 (b, 2H, cod-(CH@CH) trans to PPh2), 4.34 (b, 2H, cod-
(CH@CH) cis to PPh2), 4.50 (d, CH2P, 2H, 2JPH = 11), 6.96 (m, 3H, m + p-H of Me2C6H3), 7.2 (m, 4H, o + m-H of
Ph), 7.4 (m, 1H, p-H of Ph), 7.75 (m, 4H, o-H of PPh2), 7.70 (m, 2H, p-H of PPh2), 7.58 (m, 4H, m-H of PPh2);
C
36H38BF4NPRh, Mw 705.38. Air and moisture sensitive orange powder.
E.A.% Found (Calc.) C 61.2 (61.3), H 5.5 (5.4), N 2.00 (1.9).
FAB+ 618.2 (100) [M ꢀ BF4]+, 510.4 (40) [M ꢀ BF4–C8H12]+.
IR (CD2Cl2) mC@N 1539 cmꢀ1, mBF4 1000 cmꢀ1 (broad).
1
31P{1H} NMR data (202.4 MHz): 46.9 (d, JRhP = 154);
11B{1H} NMR data (160.4 MHz): 1.0 (s);
19F NMR data (282.45 MHz): ꢀ151.4 (s);
1
13C{1H} NMR data (125.7 MHz): 19.1 (s, Me2C6H3), 28.5, 32.1 (s, cod-CH2, 45.7 (d, CH2P, JPC = 24), 78.8 (b,
cod-CH trans to PPh2), 109.7 (b, cod-CH cis to PPh2), 183.8 (d, N@C, 2JPC = 9), 145.2 (s, i-C of Me2C6H3), 127.6
(s, m-C of Me2C6H3N), 128.4, 128.2, 129.0 (s, o-m-, p-C of Ph), 133.1 (d, o-C of PPh2, 2JPC = 12), 129.8 (d, m-C of
3
PPh2 JPC = 10), 134.2 (b, i-C of PPh2)
[Rh(CO)(CH3CN){Ph2PCH2C(Ph)@N(2,6-Me2C6H3)}][BF4],
1H NMR data (500 MHz): 1.88 (b, 3H, CH3CN, trans-P), 2.09 (s, 6H, Me2C6H3), 4.47 (d, 2H, CH2–P,
2JPH = 11.1), 7.07 (m, 2H, m-H of Me2C6H3), 7.02 (m, 1H, p-H of Me2C6H3), 7.14 (m, 2H, o-H of Ph), 7.27 (m, 2H,
m-H of Ph), 7.41 (m, 1H, p-H of Ph), 7.60 (m, 4H, m-H of PPh2, 4JPH = 2.7), 7.66 (m, 2H, p-H of PPh2, 5JPH = 2.2),
C
31H29BF4NPORh, Mw 666.27. Air and moisture sensitive orange powder.
% Found (Calc.) C 55.25 (55.9), H 4.99 (4.4), N 3.27 (4.2).
FAB+ m/z 582.1 (30) [M ꢀ BF4]+, 538.0 (100) [M ꢀ BF4–CH3CN]+.
3
7.81 (m, 4H, o-H of PPh2, JPH = 12.9);
IR (CD2Cl2) mC@N 1538 cmꢀ1, mCO 2004 cmꢀ1, mCH CN 2304 cmꢀ1, mBF4 1221 cmꢀ1
.
31P{1H} NMR data (202.4 MHz): 60.1 (d, JRhP = 160 Hz);
1
3
11B{1H} NMR data (160.4 MHz): ꢀ1.0 (s);
19F NMR data (282.45 MHz): ꢀ153.0 (s);
13C{1H} NMR data (125.7 MHz): 1.1 (d, CH3CN trans-P, JRhC = 12), 18.2 (s, Me2C6H3), 47.7 (d, CH2–P,
3
1JPC = 29), 122.4 (b, CH3CN), 129..35 (s, o-C of Me2C6H3N), 130.5 (s, p-C of Me2C6H3N), 130.3 (s, m-C of
Me2C6H3N), 186.4 (d, N@C, 2JPC = 13), 189.3 (dd, CO, 2JPC = 18, 1JRhC = 73), 129.1 (s, i-C of Ph), 134.1 (s, o-C of
Ph), 134.3 (s, m-C of Ph), 130.8 (s, p-C of Ph), 129.7 (b, i-C of PPh2), 134.7 (d, o-C of PPh2,2JPC = 20), 131.4 (d,
3
m-C of PPh2, JPC = 12), 134.6 (b, p-C of PPh2)
2
[Rh{Ph2PCH2C(Ph)@N(2,6-Me2C6H3)}2][BF4],
1H NMR data (500 MHz): 2.05 (s, 12 H, Me2C6H3, 4.20 (d, 4H, CH2P, JPH = 12.4), 6.50 (m, 6H, m-H of
C56H52BF4N2P2Rh, Mw 1004.70. Air and moisture sensitive red crystals.
% Found (Calc.) C 66.7 (66.9), H 4.19 (5.2), N 2.2 (2.8).
FAB+m/z 917.6 (100) [M ꢀ BF4]+.
Me2C6H3), 6.57 (m, 6H, p-H of Me2C6H3), 6.84 (m, 4H, p-H of Ph), 7.05 (m, 8H, m-H of Ph), 7.30 (m, 8H, o-H of
3
4
Ph), 7.42 (m, 8H, o-H of PPh2, JPH = 15.6), 7.19 (m, 8H, m-H of PPh2, JPH = 8.1), 7.27 (m, 4H, p-H of PPh2);
1
31P{1H} NMR data (202.4 MHz): 61.9 (d, JRhP = 176);
IR (CD2Cl2) mC@N 1559 cmꢀ1
.
11B{1H} NMR data (160.4 MHz): ꢀ0.6 (s);
19F NMR data (282.45 MHz): ꢀ155.7 (s);
13C{1H} NMR data (125.7 MHz): 20.1 (s, Me2C6H3N), 48.2 (b, C2 P), 129.2 (s, p-C of Me2C6H3), 128.8 (s, m-C of
Me2C6H3N), 146.2 (s, i-C of Me2C6H3N), 126.3 (s, o-C of Me2C6H3N), 133.2 (d, o-C of PPh2,2JPC = 12), 128.2 (d,
m-C of PPh2,3JPC = 10), 134.2 (b, i-C of PPh2), 179.8 (b, C@N)

S.I. Pascu et al. / Journal of Organometallic Chemistry 690 (2005) 1645–1658
1649
1
Ha2
Ha
1
Ha
N
P
N
Ha2
Pd
4
3
Pd
Ha
5
Ha
5
Ha
P
Ha
4
Ha
3
Ha
5
Ha
N
2
Ha
Pd
4
1
Ha
Ha
P
3
Ha
Scheme 2. g3-g1-g3 interconversion process in Pd-allyl complexes with N/P ligands.
two methyl groups of Me2C6H3 are also equivalent, and
the corresponding resonances were observed as singlet at
d 2.10. The aromatic protons were found as complex
multiplets between d 7.75 and d 6.96 and could be fully
protons of the ligands are equivalent (d 2.05) and the li-
gand backbone CH2 proton resonances were found as a
broad doublet, at d 4.2 (2JPH 12.5 Hz) and the aromatic
protons as a complex multiplet between d 7.85 and 6.46.
Broadening can be indicative of fluxionality, but no con-
vincing evidence was found for the presence of other iso-
1
assigned with the help of integration and of a H–1H
COSY experiment. NOe difference experiments allowed
the assignment of the cod olefinic protons. The reso-
nances belonging to olefinic protons trans to phospho-
rus overlap, e.g., broad multiplets at d 4.34 (2H) were
observed, while those trans relative to nitrogen (also
coinciding) appeared at higher field as broad multiplets
(d 4.04, 2H). NOe difference experiments suggest a slow
exchange of the four 1,5-cod olefinic protons, i.e., the
protons at C(4) and C(3) with C(7) and C(6), at room
mers by VT 1H and 31P{1H} NMR. The 31P{1H} NMR
1
(CD2Cl2) resonance in 4 (doublet at d = 61.9, JRhP
=
176 Hz) is shifted downfield from that of the free ligand
[Ph2PCH2C(Ph)@N(2,6-Me2C6H3)] (L) (isomer Z,
d = ꢀ19.8). A shift of this magnitude is typical for
Rh(I) complexes incorporating chelating N/P ligands
[74–77]. In addition, the magnitude of the Rh–P cou-
pling constant is typical for square planar complexes
with a trans N–Rh–P coordination [74].
temperature, at a time-scale estimated to be <0.5 sꢀ1
.
NOe difference experiments indicate that [Rh(cod)(L)]+
cation is ꢁdynamicꢀ, via a mechanism involving breaking
of the Rh–N bond with the apparent rotation of the 1,5-
cod, analogous with that described earlier [57].
2.3. X-ray data
Crystals suitable for single-crystal X-ray structural
determination were grown for 1–4, as detailed in Sec-
tion 5. ORTEP diagrams for compounds are presented
in Figs. 1–4 and relevant molecular parameters are
listed in Table 2. In all cases, molecular structural
determinations are consistent with the observations
made by NMR spectroscopy. The cations, anions
and solvent molecules are all well separated and there
are no unusually short intermolecular contacts. X-ray
structural determination confirmed the bidentate coor-
dination of the ligand and the square planar geometry
of the metal centre (but slightly distorted due to steric
crowding). In complex [Pd(g3-allyl)(L)][BF4] (1), where
L = [Ph2PCH2C(Ph)@N(2,6-Me2C6H3)], the bite angle
P(1)–Pd(1)–N(1) is 82.60(12)ꢁ, close to that found in
[Pd(g3-C3H5)(L0)][Br] (L0 = 2-(diisopropylphosphinom-
ethyl)-1-methylimidazole), of 83.2(2)ꢁ [70]. When coor-
dinated to an allyl ligand in the symmetric g3 bonding
The 1H NMR spectrum (CD2Cl2) of 3 shows a broad
signal at d 1.80, assignable to the protons of the MeCN
group trans to phosphorus. This resonance is in the ex-
pected ratio (by relative integration) to those corre-
sponding to the ligand, which were found at d 2.09
(singlet assigned to Me2C6H3), d 4.47 (a doublet, as-
2
signed to the CH2 backbone, JPH 11.1 Hz) and in the
range d 7.84–6.99 (the aromatic proton resonances).
31P{1H} NMR spectroscopy (CD2Cl2) showed a single
1
doublet at d 60 with a coupling constant of JRhP
160 Hz.
The 1H NMR spectrum of 4 showed no indication of
Rh-coordinated C2H4 groups. We believe that the com-
plex cis-[Rh(L)2][BF4] (4) was formed in this process,
and NMR confirmed complete conversion to a new spe-
cies where L is chelated to Rh(I), with loss of both C2H4
groups. NMR studies show that the Me2C6H3 methyl

1650
S.I. Pascu et al. / Journal of Organometallic Chemistry 690 (2005) 1645–1658
Fig. 1. Molecular structure of 1. ORTEP diagram shows the cation of
molecule 1 only. The asymmetric unit contains two independent
molecules of [Pd(g3-allyl)(L)][BF4].
Fig. 3. Molecular structure of the complex 3. ORTEP diagram of the
cation of molecule only. The asymmetric unit contains two
1
independent molecules of [Rh(CO)(CH3CN)(L)][BF4], one molecule
of benzene and one molecule of CH2Cl2.
mode, the metal atom sits above the C3 plane approx-
imately equidistant from each carbon atom. In 1, the
torsion angle Pd(1)–C(5)–C(3)–N(1) is ca. 4ꢁ. Usually,
a small exo or endo distortion of the central allyl car-
bon is observed in the solid state relative to the coor-
dination plane which can be defined (for Molecule 1
of 1) by P(1), N(1), C(3) and C(5). The deviation of
the central carbon atom, C(4), of the allyl ligand from
the coordination plane can be measured by the torsion
angle C(4)–C(5)–P(1)–N(1) (ca. 26ꢁ). The torsion angle
C(1)–P(1)–C(3)–C(5), of 20ꢁ, measures the deviation of
the backbone carbon atom C(1) of the iminophos-
phine ligand, residing below this plane, on the same
side as the central allyl carbon. The distances from
the two terminal allyl carbon atoms to palladium
are significantly different due to the different trans
influences of the phosphorus and nitrogen atoms.
˚
These are 2.125(5) A (Pd(1)–C(5)) and 2.214(5) A
˚
˚
(Pd(1)–C(3)) in molecule 1 and 2.208(5) A (Pd(2)–
˚
C(34)) and 2.144(5) A (Pd(2)–C(36)) in molecule 2.
˚
The Pd–P distances (2.2672(15) A in molecule 1 and
˚
2.2686(15) A in molecule 2) are within the expected
range and close to the values determined for complex
3
0
˚
[PdMe2(L)] (2.273(3) A) [67] and [Pd(g -C3H5)(L )][Br]
0
˚
of 2.292(2) A (L = 2-(diisopropylphosphinomethyl)-1-
methylimidazole) [70]. This separation is considerably
longer than the corresponding distance found in the
Fig. 4. Molecular structure of the complex 4. ORTEP diagram of the
cation of molecule 1 only. The asymmetric unit contains two
Fig. 2. Molecular structure of 2. ORTEP diagram shows the cation of
molecule 1 only. The asymmetric unit contains two independent
molecules of [Rh(cod)(L)][BF4] and two molecules of toluene.
independent molecules of [Rh(L)2][BF4] and three molecules of
CH2Cl2.

S.I. Pascu et al. / Journal of Organometallic Chemistry 690 (2005) 1645–1658
1651
Table 2
Selected bond lengths and angles for complexes 1–4
˚
Bond lengths (A)
Compound
Bond angles (ꢁ)
1
Molecule 1
Pd(1)–N(1)
Pd(1)–P(1)
Pd(1)–C(3)
Pd(1)–C(4)
Pd(1)–C(5)
N(1)–C(2)
N(1)–C(6)
P(1)–C(1)
P(1)–C(20)
P(1)–C(26)
C(1)–C(2)
C(3)–C(4)
C(4)–C(5)
2.123(4)
2.2672(15)
2.214(5)
2.162(5)
2.125(5)
1.290(6)
1.448(7)
1.840(5)
1.820(5)
1.803(5)
1.517(7)
1.388(8)
1.411(8)
N(1)–Pd(1)–P(1)
N(1)–Pd(1)–C(3)
P(1)–Pd(1)–C(3)
N(1)–Pd(1)–C(4)
P(1)–Pd(1)–C(4)
C(3)–Pd(1)–C(4)
N(1)–Pd(1)–C(5)
P(1)–Pd(1)–C(5)
C(3)–Pd(1)–C(5)
C(4)–Pd(1)–C(5)
C(3)–C(4)–C(5)
82.60(12)
104.82(18)
168.52(15)
137.6(2)
138.58(17)
37.0(2)
170.4(2)
103.67(16)
67.9(2)
38.4(2)
120.0(5)
Molecule 2
Pd(2)–N(2)
Pd(2)–P(2)
Pd(2)–C(34)
Pd(2)–C(35)
Pd(2)–C(36)
N(2)–C(32)
N(2)–C(37)
P(2)–C(33)
P(2)–C(51)
P(2)–C(57)
C(32)–C(33)
C(34)–C(35)
C(35)–C(36)
2.139(4)
2.2686(15)
2.208(5)
2.169(5)
2.144(5)
1.294(7)
1.426(7)
1.831(5)
1.815(5)
1.821(5)
1.491(8)
1.386(8)
1.421(8)
N(2)–Pd(2)–P(2)
N(2)–Pd(2)–C(34)
P(2)–Pd(2)–C(34)
N(2)–Pd(2)–C(35)
P(2)–Pd(2)–C(35)
C(34)–Pd(2)–C(35)
N(2)–Pd(2)–C(36)
P(2)–Pd(2)–C(36)
C(34)–Pd(2)–C(36)
C(35)–Pd(2)–C(36)
C(34)–C(35)–C(36)
82.46(12)
105.24(19)
169.32(16)
138.14(19)
137.99(16)
36.9(2)
169.7(2)
103.72(17)
67.6(2)
38.5(2)
119.3(5)
2
Molecule 1
Rh(1)–P(1)
Rh(1)–N(1)
Rh(1)–C(3)
Rh(1)–C(6)
Rh(1)–C(7)
Rh(1)–C(10)
P(1)–C(2)
2.2361(6)
2.138(2)
2.272(3)
2.140(3)
2.151(2)
2.230(3)
1.833(3)
1.812(2)
1.820(2)
1.296(3)
1.444(3)
1.501(3)
1.489(3)
1.518(4)
1.365(4)
1.525(5)
1.511(4)
1.394(4)
1.522(4)
1.532(5)
1.511(4)
P(1)–Rh(1)–N(1)
P(1)–Rh(1)–C(3)
N(1)–Rh(1)–C(3)
P(1)–Rh(1)–C(6)
N(1)–Rh(1)–C(6)
C(3)–Rh(1)–C(6)
P(1)–Rh(1)–C(7)
N(1)–Rh(1)–C(7)
C(3)–Rh(1)–C(7)
C(6)–Rh(1)–C(7)
P(1)–Rh(1)–C(10)
N(1)–Rh(1)–C(10)
C(3)–Rh(1)–C(10)
C(6)–Rh(1)–C(10)
C(7)–Rh(1)–C(10)
80.93(6)
167.81(8)
99.69(9)
94.41(8)
161.76(9)
81.21(11)
95.73(7)
159.61(9)
87.8(1)
P(1)–C(30)
P(1)–C(31)
N(1)–C(1)
N(1)–C(11)
C(1)–C(2)
C(1)–C(19)
C(3)–C(4)
C(3)–C(10)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
C(7)–C(8)
C(8)–C(9)
C(9)–C(10)
37.9(1)
156.82(8)
93.58(9)
35.28(11)
97.22(11)
81.58(11)
Molecule 2
Rh(101)–P(101)
Rh(101)–N(101)
Rh(101)–C(103)
Rh(101)–C(106)
Rh(101)–C(107)
Rh(101)–C(110)
P(101)–C(102)
P(101)–C(130)
P(101)–C(131)
N(101)–C(101)
N(101)–C(111)
2.2335(6)
2.145(2)
2.252(3)
2.146(3)
2.150(2)
2.240(3)
1.828(3)
1.811(3)
1.814(3)
1.298(3)
1.447(3)
P(101)–Rh(101)–N(101)
P(101)–Rh(101)–C(103)
N(101)–Rh(101)–C(103)
P(101)–Rh(101)–C(106)
N(101)–Rh(101)–C(106)
C(103)–Rh(101)–C(106)
P(101)–Rh(101)–C(107)
N(101)–Rh(101)–C(107)
C(103)–Rh(101)–C(107)
C(106)–Rh(101)–C(107)
P(101)–Rh(101)–C(110)
80.79(6)
161.21(8)
100.69(9)
91.90(8)
162.59(9)
81.3(1)
97.35(8)
158.19(9)
88.1(1)
38.1(1)
163.47(8)
(continued on next page)

1652
S.I. Pascu et al. / Journal of Organometallic Chemistry 690 (2005) 1645–1658
Table 2 (continued)
˚
Bond lengths (A)
Compound
Bond angles (ꢁ)
C(101)–C(102)
C(101)–C(119)
C(103)–C(104)
C(103)–C(110)
C(104)–C(105)
C(105)–C(106)
C(106)–C(107)
C(107)–C(108)
C(108)–C(109)
C(109)–C(110)
1.504(3)
1.485(4)
1.508(4)
1.357(4)
1.527(4)
1.512(4)
1.402(4)
1.523(4)
1.529(5)
1.514(4)
N(101)–Rh(101)–C(110)
C(103)–Rh(101)–C(110)
C(106)–Rh(101)–C(110)
C(107)–Rh(101)–C(110)
94.1(1)
35.16(11)
97.03(11)
81.53(11)
3
Molecule 1
Rh(1)–P(1)
Rh(1)–N(1)
Rh(1)–N(2)
Rh(1)–C(3)
P(1)–C(1)
2.2149(15)
2.109(5)
2.087(5)
1.836(9)
1.844(8)
1.819(6)
1.818(6)
1.140(9)
1.302(7)
1.453(6)
1.139(7)
1.515(7)
P(1)–Rh(1)–N(1)
P(1)–Rh(1)–N(2)
N(1)–Rh(1)–N(2)
P(1)–Rh(1)–C(3)
N(1)–Rh(1)–C(3)
N(2)–Rh(2)–C(3)
80.60(13)
168.12(19)
90.44(19)
94.57(18)
174.9(2)
P(1)–C(19)
P(1)–C(25)
O(1)–C(3)
N(1)–C(2)
N(1)–C(5)
N(2)–C(4)
C(1)–C((2)
94.1(2)
Molecule 2
Rh(101)–P(101)
Rh(101)–N(101)
Rh(101)–N(102)
Rh(101)–C(103)
P(101)–C(101)
P(101)–C(119)
P(101)–C(125)
O(101)–C(103)
N(101)–C(102)
N(101)–C(105)
N(102)–C(104)
C(101)–C(102)
2.2074(16)
2.115(5)
2.086(5)
1.820(9)
1.826(8)
1.804(9)
1.807(6)
1.138(9)
1.296(7)
1.460(6)
1.139(7)
1.526(7)
P(101)–Rh(101)–N(101)
P(101)–Rh(101)–N(102)
N(101)–Rh(101)–N(102)
P(101)–Rh(101)–C(103)
N(101)–Rh(101)–C(103)
N(102)–Rh(101)–C(103)
81.63(13)
173.48(17)
92.10(19)
92.06(19)
173.0(2)
94.3(2)
4
Molecule 1
Rh(1)–P(1)
Rh(1)–P(2)
Rh(1)–N(1)
Rh(1)–N(2)
P(1)–C(1)
2.1934(11)
2.1957(13)
2.209(4)
2.229(3)
1.825(5)
1.821(5)
1.825(5)
1.296(5)
1.442(5)
1.292(6)
1.444(6)
1.504(6)
1.514(6)
P(1)–Rh(1)–P(2)
P(1)–Rh(1)–N(1)
P(2)–Rh(1)–N(1)
P(1)–Rh(1)–N(2)
P(2)–Rh(1)–N(2)
N(1)–Rh(1)–N(2)
98.62(4)
79.64(9)
176.2(1)
177.7(1)
79.1(1)
P(1)–C(9)
102.69(13)
P(1)–C(15)
N(1)–C(2)
N(1)–C(21)
N(2)–C(30)
N(2)–C(49)
C(1)–C(2)
C(29)–C(30)
Molecule 2
Rh(2)–P(3)
Rh(2)–P(4)
Rh(2)–N(3)
Rh(2)–N(4)
P(3)–C(57)
P(3)–C(65)
P(3)–C(71)
P(4)–C(85)
P(4)–C(93)
P(4)–C(99)
N(3)–C(58)
N(3)–C(77)
2.2018(11)
2.1938(11)
2.200(3)
2.176(3)
1.841(4)
1.817(4)
1.831(5)
1.850(4)
1.818(5)
1.826(4)
1.292(5)
1.442(5)
P(3)–Rh(2)–P(4)
P(3)–Rh(2)–N(3)
P(4)–Rh(2)–N(3)
P(3)–Rh(2)–N(4)
P(4)–Rh(2)–N(4)
N(3)–Rh(2)–N(4)
98.71(4)
80.87(9)
167.80(9)
170.5(1)
81.4(1)
101.07(13)

S.I. Pascu et al. / Journal of Organometallic Chemistry 690 (2005) 1645–1658
1653
Table 2 (continued)
˚
Bond lengths (A)
Compound
Bond angles (ꢁ)
N(4)–C(86)
N(4)–C(105)
C(57)–C(58)
C(85)–C(86)
1.303(5)
1.445(5)
1.496(6)
1.508(6)
˚
˚
monohalide complex [PdMeCl(L)] (2.1925(9) A) and
in the dihalide complexes of the same ligand studied
by us earlier [67]. The Pd–N distances (2.123(4) and
Rh–CO bond lengths are 1.836(9) and 1.820(9) A (mol-
ecules 1 and 2, respectively), which are slightly shorter
˚
than the average value of 1.847 A, and similar to those
2.139(4) A) are similar to those found for Pd(II) com-
plexes in the same series. The C–C bond lengths with-
found in N/P complexes of the type [RhCl(CO)(L00)],
where L00 = chiral ferrocenyl chelating ligands, contain-
ing a tertiary phosphine and a pyrazole moiety
[56,62,79–81]. The CO group of [Rh(CH3CN)(CO)(L)]
[BF4] (3) was shown to be coordinated cis to the phos-
phine group of the ligand. These observations are in
agreement with previous findings whereby the com-
plexes [PdMe(PPh3)(L)] have been shown to exhibit a
mutual cis-arrangement of the phosphine ligands [67].
The relative cis-arrangement of the phosphines was
found in [Rh(L)2][BF4] (4). These observations are also
consistent with previous literature reports, which sug-
gested that the mutual trans positioning (in square pla-
nar complexes) of two phosphorous ligands, or of a
phosphorus and a carbon ligand, would lead to the
weakening of the corresponding M–P bonds [71,82].
˚
˚
in the allyl groups of 1 are: 1.388(8) A (C(3)–C(4))
˚
and 1.411(8) A (C(4)–C(5)) (molecule 1) and 1.386(8)
˚
˚
A (C(34)–C(35)) and 1.421(8) A (C(35)–C(36)). The
C(3)–C(4) (molecule 1) and C(34)–C(35) distances
show somewhat more double-bond character, proba-
bly again as a consequence of different donor proper-
ties of the P–N ligand.
For complexes 2–4, the chelating ligand N–Rh–P bite
angles are 80.93(6)ꢁ and 80.79(6) (for 2, molecules 1 and
2, respectively), 80.60(13)ꢁ and 81.63(13)ꢁ (for 3, mole-
cules 1 and 2, respectively), 79.64(9)ꢁ and 79.1(1)ꢁ (mol-
ecule 1 of 4) and 80.87(9)ꢁ and 81.4(1)ꢁ (molecule 2 of 4).
These values indicate slight deviations from ideal square
planar geometry. The lengths of the carbon–nitrogen
double bonds are all within the expected range, and
˚
are shown in Table 2. These values average 1.297 A,
and are slightly longer than that of the free ligand
3. Catalysis
˚
[Ph2PCH2C(Ph)@N(2,6-Me2C6H3)] (L) (1.273(2) A).
The Schiff-base character of the coordinated ligand is
thus confirmed. As with other Group 10 complexes of
this ligand the carbon–carbon backbone distances for
complexes 2–4 are comparable with that of the free li-
3.1. CO–ethylene copolymerisation test
The ability of [Pd(g3-allyl)(L)] (1) to catalyse the
copolymerisation of ethylene and CO was tested in the
absence of additional Lewis acid activators or transfer-
able alkyl groups such as MoOH. Complex 1 was found
inactive in the CO/ethylene copolymerisation reaction
performed under mild conditions (room temperature,
2 bar 1:1 ethylene). Braunstein et al. [83] found that in
CH2Cl2, temperatures as high as 60–90 ꢁC and pressures
of ca. 40 bar CO/ethylene mixture are needed when
methyl-Pd(II) complexes incorporating chelating phos-
phinemethyl–oxazoline ligands are used as pre-catalysts.
Therefore, the compound 1 was also tested under these
less mild conditions. A solution of [Pd(g3-allyl)(L)][BF4]
(1) was stirred for 12 h in CH2Cl2 at 90 ꢁC in the pres-
ence of 40 bar 1:1 ethylene:CO in a sealed Parr auto-
clave. No significant reduction in the pressure of the
autoclave was observed. Subsequently, the autoclave
was allowed to cool to room temperature before the
remaining C2H4/CO mixture was vented. A sample from
the solution was collected for GC–MS analysis that indi-
cated the formation of a mixture of oligomers, –[CO–
C2H4]n– with n = 2–8. After quenching, a small amount
of grey solid obtained was separated by filtration,
˚
gand (1.504(2) A) (Table 2).
For all Rh(I) complexes, the puckering of the chelates
(measured as the deviation of the methylene group of
the ligand backbone from the best nitrogen–rhodium–
phosphorus plane) ranges 20–31ꢁ, differing significantly
for the two molecules within the same asymmetric unit
(by ca. 10ꢁ). For complex 4, the rhodium–phosphorus
˚
˚
distances are 2.1934(11) A and 2.1957(13) A (molecule
˚
1) and 2.2018(11) and 2.1938(11) A (molecule 2), which
are shorter than those of the literature N/P complexes
with the P-atoms mutually trans (typical values 2.30–
˚
2.34 A) [78]. The Rh–P distances in complex 4 are short
due to the weak trans influence of nitrogen compared
with that of phosphorus. The rhodium–phosphorus dis-
˚
˚
tances in 2 are 2.2361(6) A (molecule 1) and 2.2335(6) A
(molecule 2), whereas in 3 these distances are 2.2149(15)
˚
and 2.2074(16) A. These values reflect the relative trans
influences of phosphines, nitriles and olefins. The rho-
dium–nitrogen bond lengths are all within the same
˚
range, for example: 2.138(2) A (in 2), 2.109(5) A (in
˚
˚
3), 2.209(4) and 2.229(3) A (in 4). In 3, the observed

1654
S.I. Pascu et al. / Journal of Organometallic Chemistry 690 (2005) 1645–1658
washed with methanol and dried in vacuum, to yield
CO/ethylene copolymer with a productivity of 110 g
polymerx mol Pdꢀ1 · hꢀ1(0.03 g yield). The resultant
product was characterised by solution IR, 1H and
13C{1H} NMR spectroscopies in a 1:1 mixture of
1,1,1,3,3,3-hexafluoro-isopropanol and C6D6. The 1H
NMR spectra of the copolymer contained a single band
of resonances in the region d 2.39–2.41, which can be as-
signed to the methylene protons –[CH2CH2CO]n–. The
13C{1H} NMR spectra showed singlet resonances for
the methylene and carbonyl carbons at d 35.3 and 212,
respectively. The presence of end-groups could not be
unambiguously detected by 1H or 13C{1H} NMR. Spec-
troscopic data suggest the formation of a perfectly alter-
nating copolymer, probably with the formula
[CH2@CHCH2(O)[CH2CH2C(O)]nH]. Simple melting
point determinations for the resulting copolymers were
in the range 249–259 ꢁC, suggesting that n > 400
[84,85]. For more accurate Tm results, differential scan-
ning calorimetry (DSC) data of the copolymer were per-
formed by Chisso Petrochemical Corporation (Japan).
In order to obtain reproducible Tm, the polymers were
first melted and cooled before the actual measurement.
DSC spectra for copolymer showed a major peak at
241 ꢁC. These indicate that the sample consisted mainly
of alternating CO/ethylene copolymers. This is in accord
with the NMR spectra of the copolymer, which showed
no detectable signals in the region expected for a double
insertion fault of ethylene into the copolymer structures.
However, a further minor peak in the DSC spectra was
observed at 150 ꢁC, suggesting that the sample also con-
tained a small amount of homo-polyethylene. Accurate
molecular weight determinations were not obtained
due to the poor solubility of the copolymers in common
organic solvents. In addition, GS–MS analysis of the
yellow solution prior to quenching showed the presence
of oligomers of the type [CH2=CHCH2C(O){CH2CH2-
C(O)}nH], where n = 1 (retention time 0.5–3.5 min), 2
(retention time 15–20 min) and 3 (retention time
29 min). In situ formation of active cationic species
was shown by mass spectrometry (ES) of the liquid
phase, which exhibited peaks with m/z = 624 (5% inten-
sity) and the isotopic pattern indicative for the
[Pd{(C2H4)2(CO)2}(L)]+ ion, where L = [Ph2PCH2C-
(Ph)@N(2,6-Me2C6H3)]. 1H and 31P{1H} NMR spec-
troscopy of the oligomer solutions also showed a
mixture of species, among which metal-coordinated imi-
nophosphine species was observed. Formation of a me-
tal-bound polymer along with Pd-oligomers [59,86] has
been reported. Although the structure of the catalyst
resting state could not be assigned these observations
are indicative of a ꢁlivingꢀ copolymerisation process.
During this study, Liu and co-workers [6] reported
several five-membered chelate complexes, incorporating
phosphorus and nitrogen donor ligands with rigid back-
bones, which are active towards ethylene/CO copoly-
merisation and our results on catalyst activity are
within the same range.
3.2. Heck coupling test
The compound [Pd(g3-allyl)(L)][BF4] (1) was tested
as a pre-catalyst for the Heck coupling of 4-bromoace-
tophenone with n-butyl acrylate. A mixture of 4-bromo-
acetophenone and 1.4 equivalents n-butyl acrylate was
heated at 130 ꢁC for 20 h, under N2 and in the absence
of air and moisture in dry N,N-dimethylacetamide, in
the presence of a base (sodium acetate) and 0.5 mol%
pre-catalyst. ½nBu4Nꢁ½OAcꢁ was also added to the reac-
tion mixture, since it has been shown that the presence
of a soluble base such as tetrabutylammonium acetate
significantly reduced the induction time required to form
the catalytically active species [87]. Although no Heck
coupled product was observed by GC–MS, surprisingly,
peaks at much higher retention times indicated the for-
mation of di- and tri-N-butyl acrylate oligomers with
m/z 254 and m/z 382, respectively.
4. Conclusions
Studies of the synthesis of cationic Pd(II) and Rh(I)
complexes have led to the isolation and characterisation
of the new mono-cationic complexes [Pd(3-allyl)(L)]-
[BF4] (1), [Rh(cod)(L)][BF4] (2), [Rh(CH3CN)(CO)(L)]-
[BF4] (3) and [Rh(L}2][BF4] (4), where L = [Ph2PCH2C-
(Ph)@N(2,6-Me2C6H3)]. These have been characterised
spectroscopically and structures confirmed by X-ray dif-
fraction. Complex 1 exhibits moderate activity towards
CO/ethylene copolymerisation and no activity in the
Heck coupling reaction between 4-bromoacetophenone
and n-butyl acrylate.
5. Experimental details
5.1. General
All manipulations of air and/or moisture sensitive
materials were performed under an inert atmosphere
of pure Ar or dry N2 using standard Schlenk line tech-
niques or in an inert atmosphere dry box. Inert gases
were purified firstly by passage through columns filled
with activated molecular sieves (4 A) and then either
manganese (II) oxide suspended on vermiculite, for the
Schlenk line, or BASF catalyst, for the dry box. Celite
filtration aid was purchased from Fluka Chemie and
oven-dried at 150 ꢁC prior to use. Solvents were pre-
dried over activated 4 A molecular sieves and then dis-
tilled under N2 from Na/K alloy (light petroleum ether
b.p. 40–60 ꢁC, diethyl ether, pentane), from sodium (tol-
uene), from potassium (THF), or from calcium hydride

S.I. Pascu et al. / Journal of Organometallic Chemistry 690 (2005) 1645–1658
1655
(dichloromethane). Deuterated NMR solvents (Aldrich,
Goss Scientific) were refluxed and distilled from potas-
sium metal (d8-toluene) or stirred overnight with cal-
cium hydride (CD2Cl2) prior to use. Microanalyses
were performed by the microanalytical laboratory of
the Inorganic Chemistry Laboratory, University of Ox-
ford and FAB+ mass-spectra by the EPSRC National
Mass Spectrometry Service Centre, University of Wales,
Swansea, UK.
NMR spectra were recorded using either a Varian
Mercury-vx 300 (1H 300 MHz, 13C 75.5 MHz, 19F
282.3 MHz, 31P 121.6 MHz) or a Varian UNITYplus
(1H 500 MHz, 11B 160.4 MHz, 13C 125.7 MHz, 31P
202.4 MHz) spectrometer and are at room temperature
unless otherwise stated. The spectra were referenced
internally relative to the residual protio-solvent (1H)
and solvent (13C) resonances relative to tetramethylsi-
lane (1H, 13C, d = 0) or externally to BF3 Æ Et2O (11B,
d = 0); H3PO4 (31P, d = 0) or CFCl3 (19F, d = 0). Chem-
ical shifts (d) are expressed in ppm and coupling con-
stants (J) in Hz.
GC–MS chromatographs and spectra were recorded
using a Hewlett–Packard 5890 Gas Chromatograph fit-
ted with a non-polar column connected to a Trio-1000
Mass Spectrometer operating Electron Impact (70 eV)
and Chemical Ionisation (CI) mode (NH3) and detecting
positively charged species. The temperature profile for
the GC is: 100 ꢁC (3 min), then 10 ꢁC/min ramp until
280 ꢁC (held for 10 min).
The compounds [RhCl(C2H4)2]2 [88,89], [RhCl-
(CO)2]2 [88,89], and [RhCl(cod)]2 [90], were prepared
according to the literature methods, [Pd(allyl)Cl]2 was
purchased from Aldrich and used as received. The
ligand L was prepared as described by us elsewhere [67].
The mixture was stirred at room temperature and the
colourless precipitate formed was removed by filtration.
To the filtrate, a CH3CN (50 mL) solution of
[Ph2PCH2C(Ph)@N(2,6-Me2C6H3)] (L) (0.12 g, 0.285
mmol) was added whilst stirring. The mixture was left
stirring in darkness for 10 h at room temperature. The
volatiles were removed under reduced pressure, and
the residue washed with a cold mixture of toluene and
pentane (30 mL, 1:4 ratio). The resulting orange solid
was recrystallised from a 1:4 mixture of CH2Cl2 and
pentane to afford orange crystals of [Rh(cod)(L)}][BF4]
(2). Yield: 0.15 g, 75%.
(NB. Elemental analysis given in Table 1 has been
performed on the crushed, high vacuum dried crystals).
5.2.3. [Rh(CO)(CH3CN)(L)][BF4] (3)
AgBF4 (0.04 g, 0.205 mmol) was added to a CH3CN
(50 mL) solution of [RhCl(CO)]2 (0.05 g, 0.102 mmol).
The mixture was stirred at room temperature and the
colourless precipitate formed was removed by filtration.
To the filtrate, a CH3CN (50 mL) solution of
[Ph2PCH2C(Ph)@N(2,6-Me2C6H3)] (L) (0.08 g, 0.0205
mmol) was added whilst stirring. The mixture was left
stirring for 10 h at room temperature in darkness. The
solvent was removed under reduced pressure and the
residue washed with a cold mixture of benzene and pen-
tane (20 mL, 1:4 ratio). The resulting orange solid was
recrystallised from a 1:4 mixture of CH2Cl2 and pentane
to afford orange crystals of [Rh(CO)(CH3CN)(L)][BF4]
(3). Yield 0.84 g, 62%.
(NB. Elemental analysis given in Table 1 has been
performed on the crushed, high vacuum dried crystals).
5.2.4. [Rh(L)2][BF4] (4)
AgBF4 (0.08 g, 0.41 mmol) was added to a CH3CN
(50 mL) solution of [RhCl(C2H4)]2 (0.10 g, 0.202 mmol).
The mixture was stirred at room temperature and the
colourless precipitate formed was removed by filtration.
To the filtrate, a CH3CN (50 mL) solution of
[Ph2PCH2C(Ph)@N(2,6-Me2C6H3)] (L) (0.17 g, 0.405
mmol) was added whilst stirring. The mixture was left
stirring for 10 h at room temperature in darkness. The
solvent was removed under reduced pressure and the
residue washed with 20 mL cold pentane. The resulting
red solid was recrystallised from a 1:4 mixture of
CH2Cl2 and pentane to afford red crystals characterised
as cis-[Rh(L)2][BF4] (4) by X-ray diffraction.
5.2. Preparations
5.2.1. [Pd(g3-allyl)(L)][BF4] (1)
The solids [Pd(g3-allyl)Cl]2 (0.10 g, 0.273 mmol) and
AgBF4 (145 mg, 0.547 mmol) were mixed in a Schlenk
tube and 50 mL CH3CN was added. The mixture was
stirred at room temperature for 30 min and formation
of a white precipitate was observed. A solution of
[Ph2PCH2C(Ph)@N(2,6-Me2C6H3] (L) in 50 mL
CH3CN was added to the reaction mixture whilst stir-
ring. Subsequently, the reaction mixture was left stirring
in darkness for 10 h and then the solids removed by fil-
tration. The filtrate was concentrated to 5 mL, layered
with pentane and stored at ꢀ20 ꢁC. Light-yellow crys-
tals of [Pd(g3allyl)(L)][BF4] (1) were formed, isolated
by filtration and dried under reduced pressure. Yield:
0.27 g, 69.5%.
The reaction was subsequently repeated using
[RhCl(C2H4)]2 (0.10 g, 0.20 mmol), AgBF4 (0.08 g,
0.40 mmol) and L (0.33 g, 0.81 mmol) in a 1:2:4 ratio.
Yield cis-[Rh(L)2][BF4] (4): 0.04 g, 35%.
5.2.5. Reaction between [Rh(CO)(CH3CN)(L)][BF4]
(3) and L
The solids [Rh(CO)(CH3CN)(L)][BF4] (3) (0.03 g,
0.075 mmol) and [Ph2PCH2C(Ph)@N(2,6-Me2C6H3)]
5.2.2. [Rh(cod)(L)][BF4] (2)
AgBF4 (0.08 g, 0.41 mmol) was added to a CH3CN
(50 mL) solution of [RhCl(cod)]2 (0.07 g, 0.203 mmol).

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S.I. Pascu et al. / Journal of Organometallic Chemistry 690 (2005) 1645–1658
(L) (0.05 g, 0.075 mmol) were mixed in a Schlenk tube
and 50 mL CH2Cl2 added dropwise. The mixture was
stirred for 10 h. The volatiles were removed under re-
duced pressure, and a red-brown solid was isolated
and recrystallised from a 1:4 mixture of CH2Cl2 and
pentane at ꢀ20 ꢁC to afford cis-[Rh(L)2][BF4] (4). Yield:
0.05 g, 69%.
solution) prior to quenching showed the presence of
a mixture of oligomers.
5.4. Heck coupling of 4-bromo-acetophenone and n-butyl
acrylate using complexes 1 as a catalyst
Sodium acetate (2.25 g, 27.4 mmol), 4-bromo-ace-
tophenone (4.97 g, 25.0 mmol), di-ethyleneglycol di-n-
butylether (0.50 g, 2.9 mmol, G.C. standard), n-butyl
acrylate (4.486 g, 35.0 mmol) and a N,N-dimethylaceta-
mide solution (10 mL) of the pre-catalyst (0.5 mol%,
based on 4-bromo-acetophenone) were added to N,N-
dimethylacetamide (20 mL) in a 100-mL 3-necked flask
equipped with a thermometer and reflux condenser,
against a counterflow of nitrogen. Tetrabutylammonium
acetate (2.26 g, 7.5 mmol) was also added to the reaction
mixture, as a completely soluble base. The mixture was
degassed and purged with nitrogen to ensure an inert
reaction atmosphere, then refluxed at the appropriate
reaction temperature for 20 h. The reaction mixture
was added at room temperature to an excess of water,
extracted with diethyl ether and dried with magnesium
sulphate. The extraction was analysed by GC–MS.
Complex 1 does not show significant activity as a
catalyst in this process as shown by integration of the
5.3. Copolymerisation test
The Pd pre-catalyst compound 1 in 50 mL CH2Cl2
was transferred using a glove-box into a dried 200 mL
Parr autoclave fitted with a Teflon liner and equipped
with a stirrer bar. The autoclave was charged with
40 bar 1:1 C2H4:CO mixture, sealed, and allowed to
reach 90 ꢁC. The mixture was stirred at this tempera-
ture for a further 12 h. Subsequently, the autoclave
was allowed to cool to room temperature before the
remaining C2H4/CO mixture was vented. The grey
precipitate obtained was separated by filtration,
washed with methanol and dried in vacuum (yield
30 mg, 110 g polymerx mol Pdꢀ1 · hꢀ1). Infrared
spectroscopy of the products showed the characteristic
carbonyl stretch of poly(C2H4-alt-CO) at 1692 cmꢀ1
.
GS–MS analysis of the filtrate (a yellow coloured
Table 3
Crystallographic data for compounds 1–4
1
2
3
4
Empirical formula
Formula weight
Crystal system
C
62H62B2F8N2P2Pd2 C100H108B2F8N2P2Rh2 C68H64B2F8N4O2P2Rh2 C115H110B2C16F8N4P4Rh2
1283.55
Monoclinic
P21/c
1779.4
Triclinic
1410.61
Triclinic
2264.09
Triclinic
ꢀ
ꢀ
ꢀ
Space group
Unit cell dimensions
P1
P1
P1
˚
a (A)
19.4136(7)
9.5339(3)
31.8889(11)
90
12.3670(3)
18.9460(3)
19.3170(5)
79.3020(10)
80.1090(10)
87.1860(10)
4380.61(7)
2
12.1572(4)
16.6137(6)
16.6600(6)
81.3903(12)
79.7375(14)
78.699(2)
3223.8(2)
4
13.3345(1)
20.1143(2)
20.6864(2)
102.1839(6)
90.8488(4)
101.8863(5)
52926.9
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
101.0869(13)
90
3
˚
Volume (A )
5792.1(3)
4
1.472
Z
4
1.419
Density (calculated) (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
Crystal size (mm3)
h Range for data collection
Index ranges
1.35
0.48
1.45
0.63
)
0.743
2608
0.588
2324
1848
0.3 · 0.3· 0.3
0–26.5
1436
0.20 · 0.30 · 0.40
1–27
0.20 · 0.20 · 0.20
5–23.5
0.20 · 0.20 · 0.40
4–28.4
0 6 h 6 21,
0 6 k 6 9,
ꢀ35 6 l 6 34
8560
0 6 h 6 15,
ꢀ23 6 k 6 23,
ꢀ23 6 l 6 24
23643
ꢀ6 6 h 6 6,
ꢀ21 6 k 6 21,
ꢀ21 6 l 6 21
8022
ꢀ17 6 h 6 17,
ꢀ26 6 k 6 26,
ꢀ27 6 k 6 26
46486
Reflections collected
Independent reflections
8011 [Rint = 0.04]
0.86 and 0.86
703
16715 [Rint = 0.02]
0.87, 0.87
1045
4345 [Rint = 0.03]
0.88 and 0.83
793
25647 [Rint = 0.04]
0.89 and 0.89
1271
Maximum and minimum transmission
Parameters
Goodness-of-fit
1.0625
0.9808
1.1616
1.0688
Final R indices
[I>3r(I)]
Largest difference peak and hole (e A
R1 = 0.0456
wR2 = 0.0503
ꢀ0.75 and +0.90
R1 = 0.0460
wR2 = 0.0508
ꢀ0.89, 1.26
R1 = 0.0401
wR2 = 0.0471
ꢀ0.40 and 0.61
R1 = 0.0540
wR2 = 0.0601
ꢀ0.92 and 3.28
ꢀ3
˚
)

S.I. Pascu et al. / Journal of Organometallic Chemistry 690 (2005) 1645–1658
1657
chromatograph peak for the product against the 4-bro-
mo-acetophenone and against the GC standard peak for
the di-ethyleneglycol di-n-butylether.
this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2005.01.016.
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