New group 10 complexes of the bulky iminophosphine ligands [Ph 2PCH2C(Ph)=N(2,6-R2C6H 3)], where R = Me, iPr

Article abstract of DOI:10.1039/b412391c

New neutral and cationic complexes [NiBr₂(L1)] (1), [NiBr ₂(OPHPh₂)(L1)] (2), [NiMe₂(L1)] (3), [NiBr(PMe₃)(L1)](Br) (4), [Ni(CH₃CN)(PMe ₃)(L1)](BF₄)₂ (5), [PdBr₂(L1)] (6), [PdI₂(L1)] (7), [PtMeCl(L1)] (8), [PtMe₂(L1)] (9), [Pt(CH₃CN)₂(L1)](BF₄)₂ (10), [Pt(L1)₂](X)₂ [X = Cl (11a), Br (11b)], [PtX(L1) ₂](X) [X = Cl (12a), Br (12b)], where L1: [Ph₂PCH ₂C(Ph)=N(2,6-Me₂C₆H₃)₂] and L2: [Ph₂PCH₂C(Ph)= N(2,6-ⁱPr ₂C₆H₃)₂], have been prepared and characterised. The molecular structures of 1, 2, 6, 7 and 9 have been determined. The complexes [PdBr₂(L2)] (6), [PdBr₂(L1)] and [PdMeCl(L1)] have been found to catalyse the Heck coupling of 4-bromoacetophenone with n-butyl acrylate under aerobic conditions. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2005.

Full text of DOI:10.1039/b412391c

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P A P E R
New group 10 complexes of the bulky iminophosphine ligands
i
[Ph PCH C(Ph) N(2,6-R C H )], where R = Me, Pr
Q
2
2
2
6
3
Sofia I. Pascu,*w Karl S. Coleman, A. R. Cowley, Malcolm L. H. Green* and
Nicholas H. Rees
Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford,
UK OX1 3QR
Received (in Toulouse, France) 10th August 2004, Accepted 28th September 2004
First published as an Advance Article on the web 17th January 2005
New neutral and cationic complexes [NiBr2(L1)] (1), [NiBr2(OPHPh2)(L1)] (2), [NiMe2(L1)] (3),
[NiBr(PMe3)(L1)](Br) (4), [Ni(CH3CN)(PMe3)(L1)](BF4)2 (5), [PdBr2(L2)] (6), [PdI2(L1)] (7), [PtMeCl(L1)]
(8), [PtMe2(L1)] (9), [Pt(CH3CN)2(L1)](BF4)2 (10), [Pt(L1)2](X)2 [X = Cl (11a), Br (11b)], [PtX(L1)2](X) [X
= Cl (12a), Br (12b)], where L1: [Ph PCH C(Ph) N(2,6-Me C H ) ] and L2: [Ph PCH C(Ph)
Q
Q
2
2
2
6
3 2
2
2
N(2,6-iPr2C6H3)2], have been prepared and characterised. The molecular structures of 1, 2, 6, 7 and 9 have
been determined. The complexes [PdBr2(L2)] (6), [PdBr2(L1)] and [PdMeCl(L1)] have been found to catalyse
the Heck coupling of 4-bromoacetophenone with n-butyl acrylate under aerobic conditions.
New neutral and cationic Group 10 complexes of bulky
heteroditopic N/P ligands have been prepared and are shown
in Schemes 1 and 2. All these complexes were characterised by
Introduction
Group 10 transition metals with diimine-based donor ligands
have been found to catalyse the polymerisation of ethene and
propene, giving rise to a new generation of polymers.1 Hybrid
N/P ligands containing phosphine and imine donor atoms can
exhibit hemi-labile character. Such behaviour is of interest in
homogeneous catalysis and in the activation of small molecules
since it facilitates the formation and stabilisation of intermedi-
ate species.2–7 The coordination chemistry and catalytic prop-
erties of N/P ligands with late transition metals continue to
attract attention owing to the possibility of tailoring the steric
and electronic properties of the different donor groups.8–23
Hybrid ligands are believed to enhance the catalytic activity for
Heck reactions by use of cooperative effects.24,25 However,
complexes containing mixed nitrogen and phosphorus ligands,
where the imine acts as a p acceptor and the phosphine as a
good s donor, have rarely been investigated as catalysts for the
Heck reaction.24
1
mass spectrometry (FAB), elemental analysis and H, 13C{1H}
and 31P{1H} NMR spectroscopy, with the aid of 1H{31P} NMR,
NOE difference, 1H-1H COSY, 1H-13C HSQC, and 1H-13C
HMBC experiments. 1H NMR spectra of all compounds show
resonances specific to metal-coordinated ligands L1 or L2 with
Here, we describe the preparation of neutral and cationic
Ni(II), Pd(II) and Pt(II) complexes of the chelating bidentate
iminophosphines [Ph PCH C(Ph) N(2,6-Me C H )] (L1)
2
Q
2
2
6
3
and [Ph PCH C(Ph) N(2,6-iPr C H )] (L2) (Scheme 1). We
Q
2
2
2
6
3
report that the Pd(II) complexes [PdBr2(L2)] 6, [PdBr2(L1)]26
and [PdMeCl(L1)]26 catalyse the Heck coupling of 4-bromoa-
cetophenone with n-butyl acrylate under aerobic conditions.
Results and discussion
The phosphine-imine ligands L1 and L2 were prepared using
established procedures.18,26 We have previously shown that
iminophosphine ligands of this family predominantly exist in
solution as the E isomer, although they are able to interconvert
between the E and Z isomers.26,27 Thus, ligand-exchange
reactions using [MMe2(L2)] complexes (where M = Ni, Pd
and Pt; L2 = a bidentate ligand such as bpy, tmeda or cod)
provide a convenient route to a large variety of dimethyl metal
complexes.28,29
Scheme
[NiBr (dme)], THF; (ii) Ph P(H) O, CH Cl ; (iii) [NiMe (tmeda)],
toluene; (iv) [3,5-(CF3)2C6H3]I, [Pd(dba)2], THF; (v) [PtMe2(cod)],
THF, ꢀ78 1C to room temperature; (vi) [PtMeCl(cod)], THF; (vii)
LDA, THF, ꢀ78 1C; (viii) Ph2PCl, THF, ꢀ78 1C to room temperature;
(ix) PdBr2.
1
Formation of neutral compounds 1–3 and 6–9: (i)
Q
2
2
2
2
2
w Current address: Department of Chemistry, University of Cam-
bridge, Lensfield Road, Cambridge, UK CB2 1EW.
T h i s j o u r n a l i s & T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 5
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7
385

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exposed to one equivalent of O PHPh in CH Cl , resulting
Q
2
2
2
in the formation of [NiBr (O PHPh )(Ph PCH C(Ph)
Q
Q
2
2
2
2
N(2,6-Me2C6H3)] (2) in low yields (o10%). Complex 2 was
identified by single-crystal X-ray diffraction. The Ni(II) mono-
cationic
complex
[NiBr(PMe ){Ph PCH C(Ph) N(2,6-
Q
3 2 2
Me2C6H3)}]Br (4) was prepared by reacting complex 1 with 2
equivalents of PMe3. Traces of L1 and [Ni(PMe3)2Br2] were
also identified by 1H and 31P{1H} NMR spectroscopy, suggest-
ing facile displacement of the N/P ligand by PMe3. The Ni(II)
dicationic complex [Ni(CH CN)(PMe ){Ph PCH C(Ph)
Q
N(2,6-Me2C6H3)}][BF4]2 (5) was obtained by reacting [Ni(-
3
3
2
2
MeCN)2(PMe3)2][BF4]2 with one equivalent of L1.
Palladium(II) complexes. The iminophosphine ligand L2 was
complex
reacted
with
PdBr2
Q
to
afford
the
{PdBr [Ph PCH C(Ph) N(2,6-iPr C H )]} (6). The neutral
2
2
2
2
6
3
complex {PdI [Ph PCH C(Ph) N(2,6-Me C H )]} (7) was
3
Q
2
2
2
2
6
prepared by an oxidative addition reaction between {[3,5-
(CF3)2C6H3]I} and [Pd(dba)2] (dba = dibenzylidenacetone)
in the presence of L1 (Scheme 1). Although Pd(II) complexes
of the type [PdRI(N/N)], where R = 3,5-(CF3)2C6H3) and
N/N = Me2N(CH2)2NMe2,30 or [PdRI(N/P)], where R = Me
or Ph and N/P = 2-(diisopropylphosphinomethyl)-1-methyli-
midazole,14 have previously been prepared by this method, no
traces of the monoaryl complex [PdI{3,5-(CF3)2C6H3}(L1)]
were found. The formation of dihalide complex 7 instead of
the expected complex [PdI{3,5-(CF3)2C6H3}(L1)] was presum-
ably a consequence of unfavourable steric interactions between
the iminophosphine ligand and the bulky aryl group 3,5-
(CF3)2C6H3 in the latter. Crystals of 6 and 7 suitable for
single-crystal X-ray diffraction were obtained from concen-
trated CH2Cl2 solutions layered with pentane and stored at
ꢀ20 1C.
Scheme 2 Formation of mono- and dicationic complexes 4, 5, 10, 11a,
11b and 12a, 12b: (i) 2 PMe3, THF; (ii) 2 AgBF4, CH3CN; (iii) L1,
CH3CN; (iv) [PtCl2(cod)]; (v) [PtBr2(CH3CN)2].
the correct integration ratios. Spectroscopic data for all new
compounds are given in Table 1 and the main NMR features
are discussed below. Complexes 1, 2, 6, 7 and 9 were also
characterised by X-ray diffraction and relevant molecular
parameters are given in Table 2.
Platinum(II) complexes. The neutral complexes [PtMeCl(L1)]
(8) and [PtMe2(L1)] (9) were isolated from the reaction of
[PtMeCl(cod)] (cod = 1,5-cyclooctadiene) and [PtMe2(cod)]
with L1, respectively. Crystals suitable for X-ray diffraction
studies were grown for 9 from a 1 : 4 mixture of toluene and
Compounds 1, 2, 6 and 7 are air-stable in the solid state and
moderately sensitive to oxygen and moisture in solutions. The
metal-alkyl systems 3, 8 and 9 and the mono- and dicationic
complexes 4, 5, 10, 11a, 11b and 12a, 12b are especially air- and
moisture-sensitive. Compound 2 was found thermally unstable
above 0 1C. All mono- and dicationic complexes are insoluble
in nonpolar solvents, relatively stable towards decomposition
in CH2Cl2 or THF, and decompose rapidly in MeOH and
CHCl3. Solutions of 9 in CD2Cl2 or d8-THF decompose upon
standing for ca. 2 h at room temperature. Although 9 is
somewhat more stable towards decomposition in solution
and the solid state than its analogous Ni and Pd complexes,
the low solubility and rapid decomposition at room tempera-
ture prevented characterisation by 13C{1H} NMR spectroscopy
and catalysis testing for Heck reactions.
pentane
at
ꢀ20
1C.
The
[Pt(CH CN) {Ph PCH C(Ph) N(2,6-Me C H )}][BF ] (10)
dicationic
complex
Q
3
2
2
2
2
6
3
4 2
was obtained by treating [Pt(CH3CN)4][BF4]2 with a CH3CN
solution of L1. Interestingly, reaction between [PtCl2(cod)] and
L1 carried out at room temperature in THF afforded a mixture
of two products in a 5 : 1 ratio as determined by 1H and
31P{1H} NMR spectroscopy. Similarly, the reaction between L1
and cis-[PtBr2(CH3CN)2] carried out in CH2Cl2 gave a mixture
of two products in the 3 : 2 ratio (as shown by integration in
the 1H NMR spectrum). In both cases, the products could not
be separated by crystallisation and chromatography on silica
led to decomposition. NMR, elemental analysis and FAB mass
spectrometry shown that, in each case, the products contained
two components, with the stoichiometry Pt : L1 : X of 1 : 2 :
2. Thus, the formation of complexes [Pt(L1)2][X]2, X = Cl
(11a) and Br (11b), and [PtX(L1)2]X, X = Cl (12a) and Br
(12b), are proposed. Variable temperature NMR experiments
in CD2Cl2 did not confirm the presence of an equilibrium
between the two complexes.
Syntheses
Nickel(II) complexes. The complexes [NiX2(L1)], where X =
Br (1) and Me (3), were prepared via reaction of [NiBr2(dme)]
and [NiMe2(tmeda)], respectively, with L1 (Scheme 1). Red
crystals of 1, suitable for X-ray structure determination, were
obtained by allowing a concentrated CH2Cl2 solution to stand
for 1 week at ꢀ20 1C, under a nitrogen atmosphere. Both
nickel(II) complexes 1 and 3 are sensitive to moisture. However,
3 is additionally thermally sensitive and decomposes (presum-
ably through elimination) to afford the free ligand L1, after
storage for 12 h at room temperature under N2, as shown by
1H and 31P{1H} NMR spectroscopies. To further explore the
coordination chemistry of 1 under aerobic conditions, this was
NMR and magnetic data
1
Room temperature H NMR spectroscopy of 1 showed broad
signals between d ꢀ5 and 25. The 31P{1H} NMR spectrum
recorded at the same temperature showed no signal from the
phosphorus nucleus. This is indicative of a paramagnetic
complex, consistent with Ni(II) in a tetrahedral geometry.
The dynamic behaviour of this species in solution was studied
by variable temperature NMR spectroscopy. H- and 31P{1H}
NMR spectroscopy (CD2Cl2) at ꢀ80 1C and below showed
1
386
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7

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Table 1 Data characterising compounds L-2, 1–12
Compound data
NMR data
L2
[Ph PCH C(Ph) N(2,6-iPr (C H )]
1H NMR (500 MHz, CD2Cl2) Minor isomer (Z):1.02 (d, CH3CHCH3,
12H, 3JHH ¼ 6.8), 2.09 (h, CH3CHCH3, 2H), 3.80 (d, CH2-P, 2H, 2JPH
Q
2
2
2
6
3
C32H36NP
MW 463.60
¼
3
1); Major isomer (E): 1.44 (d, CH3CHCH3, 12H, JHH ¼ 6.6), 3.37 (h,
Air and moisture sensitive, oily light-yellow solid
nCQ 1640 cmꢀ1
CH3CHCH3, 2H, 3JHH ¼ 6.6), 3.43 (d, CH2-P, 2H, 2JPH ¼ 1.7), 7.96–7.10
(multiple resonances, aromatic protons)
31P{1H} NMR data (202.4 MHz, toluene): Minor isomer (Z): ꢀ19.2 (s),
Major isomer (E): ꢀ12.6 (s)
N
31P{1H} NMR (202.4 MHz, CD2Cl2): Minor isomer (Z): ꢀ21.0 (s), Major
isomer (E): ꢀ14.9 (s)
1
[NiBr {Ph PCH C(Ph) N(2,6-Me C H )}]
Q
1H NMR (500 MHz, CD2Cl2, ꢀ 90 1C) 2.24 (s, 6H, Me2C6H3), 4.09 (b,
CH2–P, 2H), 6.50 (b, 1H, p-H of Me2C6H3), 6.85 (b, 2H, m-H of
Me2C6H3), 7.15-7.40 (b, 5H, o, p, m-H of Ph), 7.57 (b, 4H, m-H of PPh2),
7.67 (b, 4H, p-H of PPh2), 7.99 (b, 2H, o-H of PPh2)
31P{1H} NMR (202.4 MHz, CD2Cl2, ꢀ90 1C): 41.9 (s)
2
2
2
2
6
3
C28H26Br2NNiP
MW 625.99
Air-stable red-brown crystals.
Elemental analysis: % calculated (found) C 53.47
(53.72), H 4.21 (4.18), N 2.23 (2.23), Ni 8.91 (9.38)
Mass spectrometry: FAB1: m/z 626.0 (15) [M]1, 546
(100) [M ꢀ Br]1
IR: nCQ 1584 cmꢀ1
N
2
[NiBr (O HPPh ){Ph PCH C(Ph) N(2,6-
Q
1H NMR (500 MHz, CD2Cl2) paramagnetic, 15 broad resonances between
Q
Me2C6H3)}]
2
2
2
2
d ꢀ4 and ꢀ21
C40H37Br2NNiOP
Mw 828.18
Air and moisture sensitive brown crystals
Elemental analysis % found (Calc.) C 57.34 (58.01), H
5.20 (4.50), N 1.63 (1.69)
Mass spectrometry: FAB1: m/z 829.0 (14) [M]1, 749.0
(20) [M-Br]1, 626.0 (100) [M-(OHPPh2)]1
IR: nCQ 1560 cmꢀ1, nPH 2370, 2340 cmꢀ1 , n
1238
Q
P O
N
cmꢀ1
[NiMe {Ph PCH C(Ph) N(2,6-Me C H )}]
3
1H NMR (500 MHz, d8-toluene): 0.06 (d, 3H, Ni-Me trans-P, 3JPH ¼ 4.7),
Q
2
2
2
2
6
3
3
C
30H32NNiP
MW 496.26
Air and moisture sensitive red powder
0.49 (d, 3H, Ni-Me, cis-P, JPH ¼ 12.3), 2.09 (s, 6H, Me2C6H3), 3.31 (d,
2
CH2-P, 2H, JPH ¼ 6.7), 7.9 (b, 4H, o-H of PPh2), 7.67 (b, 4H, m-H of
PPh2), 7.40 (b, 2H, p-H of PPh2), 7.4-6.6 (multiple resonances, 8H,
aromatic protons)
Elemental analysis: % Found (Calc.) C 69.1 (72.6), H 5.9
(6.5), N 2.3 (2.8)
Mass spectrometry: FAB1: m/z 496.3 (10) [M]1, 481.3
(30) [M ꢀ Me]1, 466.2 (100) [M ꢀ Ni ꢀ 2Me]1
31P{1H} NMR (202.4 MHz, d8-toluene) 30.8(s)
13C{1H} NMR (125.7 MHz, d8-toluene) ꢀ12.0 (d, Ni-Me, 2JPC ¼ 226), 3.8
2
1
(d, Ni-Me, JPC ¼ 89), 21.5 (s, Me2C6H3N), 39.7 (d, CH2-P, JPC ¼ 6),
3
142.2 (s, i-C of Me C H N), 169.4 (d, C N, J ¼ 15), 128.0 (d, i-C of
Q
2
6
3
PC
3
3
PPh2, JPC ¼ 27), 127.9 (d, m-C of PPh2, JPC ¼ 13), other aromatic C-
resonances 132.7, 127.5, 125.0, 124.4, 123.0, 122.3, 119.3
1H NMR (300 MHz, CD2Cl2) 1.16 (b, 9H, PMe3), 1.96 (s, 6H, Me2C6H3),
4
[NiBr(PMe ){Ph PCH C(Ph) N(2,6-Me C H )}][Br]
Q
3
2
2
2
6
3
2
C
31H35Br2NNiP2
MW 702.07
Air and moisture sensitive purple powder
4.67 (d, 2H, CH2-P, JPH ¼ 21.5), 6.88 (t, 1H, p-H of Me2C6H3), 7.18 (d,
2H, m-H of Me2C6H3), 7.00 (m, 2H, o-H of Ph), 7.09 (m, 2H, m-H of Ph),
7.17 (m, 1H, p-H of Ph), 7.46 (m, 4H, o-H of PPh2, 3JP–Pho ¼ 13.4), 7.93 (b,
4H, m-H of PPh2), 7.79 (b, 2H, p-H of PPh2)
Elemental analysis: % Found (Calc.) C 53.2 (53.0), H 5.2
(5.02), N 1.0 (2.00), Ni 8.0 (8.3), Br 26.1 (22.7)
Mass spectrometry: FAB1: m/z 619.2 (20) [M ꢀ Br]1,
546.1 (70) [M ꢀ Br ꢀ PMe3]1
31P{1H} NMR data (121.51 MHz, CD2Cl2): 34.2 (d, PPh2 , JPP ¼ 218)
2
2
ꢀ22.9 (d, PMe3 JPP ¼ 218)
13C{1H} NMR data (75.5 MHz, CD2Cl2): 14.5 (b, PMe3), 17.6 (s,
Me2C6H3N), 149.4 (s, i-C of Me2C6H3N), 125.2 (s, o-C of Me2C6H3N),
128.2 (s, m-C of Me C H N), 130.2 (s, p-C of Me C H N), 162.0 (b, N
Q
2
6
3
2
6
3
C), 138.8 (b, i-C of Ph), 131.0 (s, o-C of Ph), 130.2 (s, m-C of Ph), 128.0 (s,
p-C of Ph), 135.4 (b, i-C of PPh2), 131.6 (b, o-C of PPh2), 130.8 (b, m-C of
PPh2), 128.4 (b, p-C of PPh2)
2
5
[Ni(CH CN)(PMe ){Ph PCH C(Ph) N(2,6-
Q
1H NMR (500 MHz, CD2Cl2): 1.22 (dd, 9H, PMe3 cis-PPh2, JPH ¼ 12,
3
3
2
2
Me2C6H3)}][BF4]2
C33H38B2F8N2NiP2
MW 756.93
4JPH ¼ 1), 1.83 (dd, 3H, MeCN trans-PPh2, 2JPH ¼ 13.5, 4JPH ¼ 1), 2.17 (s,
6H, Me2C6H3), 4.51 (dd, 2H, CH2-P, 2JPH ¼ 12, 4JPH ¼ 1.5), 6.90 (t, 1H, p-
3
3
H of Me2C6H3, JHH ¼ 7.5), 6.97 (d, 2H, m-H of Me2C6H3, JHH ¼ 7.5),
Air and moisture sensitive orange powder
Elemental analysis: % Found (Calc.) C 51.5 (52.3), H
5.31 (5.06), N 3.7 (3.7)
7.18 (m, 2H, o-H of Ph), 7.02 (m, 2H, m-H of Ph), 7.34 (m, 1H, p-H of Ph),
7.99 (m, 4H, o-H of PPh2, 3JPH ¼ 12.9), 7.81 (m, 4H, m-H of PPh2, 4JPH
¼
5
2.5), 7.62 (m, 2H, p-H of PPh2, JPH ¼ 2)
Mass spectrometry: FAB1: m/z 583.4(70) [M ꢀ 2BF4]21
540.9(15) [M ꢀ 2BF4 ꢀ CH3CN]21, 507.2 (100) [M ꢀ
2BF4 ꢀ PMe3]21
,
31P{1H} NMR data (202.4 MHz, CD2Cl2) 51.2 (d, PPh2, 2JPP ¼ 102), ꢀ8.2
2
(d, PMe3, JPP ¼ 102)
11B{1H} NMR (160.4 MHz, CD2Cl2) ꢀ0.6 (s)
IR: nC¼N 1634, nBF 906 –1250 cmꢀ1 (broad), nCH CN
19F NMR (282.45 MHz, CD2Cl2) ꢀ146.3 (s)
3
2004–2300 cmꢀ1 (broad)
13C{1H} NMR (125.7 MHz, CD2Cl2): 14.7 (d, MeCN trans-P, 2JPC ¼ 71),
2
15.9 (d, PMe3 cis-P, JPC ¼ 36), 19.5 (s, Me2C6H3N), 48.2 (b, CH2-P),
145.3 (s, i-C of Me2C6H3N), 128.2 (s, m-C of Me2C6H3N), 128.6 (s, o-C of
Ph), 127.9 (s, m-C of Ph), 127.4 (s, p-C of Ph), 134.2 (b, i-C of PPh2), 133.5
(d, o-C of PPh2, 2JPC ¼ 11), 130.7 (d, m-C of PPh2, 3JPC ¼ 11), 130.9 (b, p-
C of PPh2), other aromatic C-resonances: 132.3, 127.4, 124.5
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7
387

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Table 1 (continued )
Compound data
[PdBr {Ph PCH C(Ph) N(2,6-iPr C H )}]
NMR data
6
1H NMR (500 MHz, CD2Cl2) 0.47 (d, CH3CHCH3, 6H, 2JHH ¼ 6.6), 1.40
Q
2
2
2
2
6
3
3
C32H36Br2NPPd
MW 731.85
(d, CH3CHCH3, 6H, JHH ¼ 6.6), 2.88 (h, CH3CHCH3, 6H, 3JHH ¼ 6.8),
2
i
4.45 (d, CH2-P, 2H, JPH ¼ 13.5), 7.01 (t, 1H, p-H of Pr2C6H3), 7.03 (d,
Air stable red-orange powder
Elemental analysis: % Found (Calc.) C 52.2 (52.2), H 5.2
(4.9), N 1.8 (1.9), Br 21.1 (21.8)
2H, m-H of iPr2C6H3), 7.05 (m, 2H, o-H of Ph), 7.21 (m, 2H, m-H of Ph),
3
7.37 (m, 1H, p-H of Ph), 7.90 (m, 4H, o-H of PPh2, JPH ¼ 8.5), 7.58 (m,
4
5
4H, m-H of PPh2, JPH ¼ 2.8), 7.68 (m, 2H, p-H of PPh2, JPH ¼ 2.5)
Mass spectrometry: FAB1: m/z 729(3) [M]1, 649(10) [M 31P{1H} NMR (202.4 MHz, CD2Cl2) 45.0 (s)
ꢀ Br]1, 567(20) [M ꢀ 2Br]1
13C{1H} NMR (75.47 MHz, CD2Cl2) 23.0 (s, CH3CHCH3), 24.5 (s,
IR: nCQ 1592 cmꢀ1
CH3CHCH3), 25.9 (s, CH3CHCH3), 48.4(d, CH2-P, 1JPC ¼ 18), 144.6 (s, i-
N
i
C of Pr2C6H3N), 140.0 (s, o-C of Pr2C6H3N), 128.3 (s, m-C of
i
iPr C H N), 124.1 (s, p-C of iPr C H N), 179.3 (b, N C), 132.9 (b, i-C of
Ph), 132.5(s, o-C of Ph), 129.6 (s, m-C of Ph), 128.9 (s, p-C of Ph), 126.4 (d,
Q
2
6
3
2
6
3
i-C of PPh2, 1JPC ¼ 34), 133.5 (d, o-C of PPh2, 2JPC ¼ 7), 129.7 (d, m-C of
3
PPh2, JPC ¼ 7), 133.1 (s, p-C of PPh2)
7
[PdI {Ph PCH C(Ph) N(2,6-Me C H )}]
Q
1H NMR (500 MHz, CD2Cl2) 2.03 (s, 6H, Me2C6H3), 4.35 (d, 2H, CH2-P,
2JPH ¼ 13.2), 6.81 (t, 1H, p-H of Me2C6H3), 6.89 (d, 2H, m-H of
Me2C6H3), 6.95 (m, 2H, o-H of Ph), 7.13 (m, 2H, m-H of Ph), 7.27 (m, 1H,
2
2
2
2
6
3
C28H26I2NPPd
MW 767.72
3
Air stable red-brown powder
Elemental analysis: % Found (Calc.) C 44.5 (43.8), H 3.7
(3.4), N 2.0 (1.8)
p-H of Ph), 7.90 (m, 4H, o-H of PPh2, JPH ¼ 12.7), 7.58 (m, 4H, m-H of
4
5
PPh2, JPH ¼ 2.7), 7.66 (m, 2H, p-H of PPh2, JPH ¼ 1.95)
31P{1H} NMR (202.4 MHz, CD2Cl2) 43.1 (s)
Mass spectrometry: FAB1: m/z 640.31 (100) [M ꢀ I]1,
13C{1H} NMR (125.7 MHz, CD2Cl2) 19.6 (s, Me2C6H3N), 49.8 (d, CH2-P,
407(20) [M ꢀ PdI2]1
1JPC ¼ 27), 180.6 (d, N C, 2J ¼ 7.6), 148.2 (s, i-C of Me2C6H3N), 133.4
Q
PC
(d, o-C of PPh2, 2JPC ¼ 10), 129.5 (d, m-C of PPh2, 3JPC ¼ 11), 132.9 (d, p-
IR: nCQ 1570 cmꢀ1
N
4
C of PPh2, JPC ¼ 3), other aromatic C-resonances, assignable to Ph-CN
and Me2C6H3N: 131.7, 130.4, 128.8, 128.1, 127.7, 127.4, 127.2
1H NMR data (500 MHz, CD2Cl2): 0.68 (d, 3H, Pt-Me cis-P, 3JPH ¼ 3.5,
8
[PtMeCl{Ph PCH C(Ph) N(2,6-Me C H )}]
Q
2
2
2
6
3
2
C
29H29ClNPPt
1JPtH ¼ 73), 2.08 (s, 6H, Me2C6H3), 3.97 (d, CH2-P, 2H, JPH ¼ 11), 6.92
MW 653.06
Air stable white-yellow powder
(d, 3H, m-H of Me2C6H3), 7.02 (t, 2H, p-H of Me2C6H3), 7.19 (m, 2H, o þ
m-H of Ph), 7.37 (m, 2H, p-H of Ph), 7.84 (m, 4H, o-H of PPh2), 7.55 (m,
4H, m-H of PPh2), 7.67 (m, 2H, p-H of PPh2)
Elemental analysis: % Found (Calc.) C 52.1 (53.3), H 4.7
(4.5), N 2.03 (2.1)
Mass spectrometry: FAB1: m/z 652.0(10) [M]1,
638.0(100) [M ꢀ Me]1, 617.1(30) [M ꢀ Cl]1, 601.1(50)
[M ꢀ Cl ꢀ Me]1
31P{1H} NMR data (202.4 MHz, CD2Cl2) 22.6 (1JPtP ¼ 4670)
13C{1H} NMR data (125.7 MHz, CD2Cl2) 1.0 (b, Pt-Me), 18.5 (s,
Me2C6H3N), 48.1 (d, CH2-P, 1JPC ¼ 37), 176.2 (b, N C), 135.6 (d, i-C of
Q
Ph, 3JPC ¼ 8), 145.7 (d, i-C of Me2C6H3, 1JPC ¼ 23), 133.2 (d, o-C of PPh2,
2JPC ¼ 12), 129.2 (d, m-C of PPh2, 3JPC ¼ 12), 131.1 (d, p-C of PPh2), other
aromatic C-resonances: 131.5, 130.6, 128.5, 127.5, 126.5, 126.3, 126.1
3
9
[PtMe {Ph PCH C(Ph) N(2,6-Me C H )}]
Q
1H NMR (500 MHz, CD2Cl2) ꢀ0.23 (d, 3H, Pt-Me trans-P, JPH ¼ 8.2,
2
2
2
2
6
3
C30H32NPPt
Mw 632.64
1JPtH ¼ 67.1), 0.84 (d, 3H, Pt-Me, cis-P, 3JPH ¼ 7.5, 1JPtH ¼ 89.5), 1.98 (s,
2
6H, Me2C6H3), 3.76 (d, 2H, CH2-P, JPH ¼ 8.8), 6.62 (b, 2H, m-H of
Air and moisture sensitive light-yellow powder
Elemental analysis: % Found (Calc.)
Me2C6H3), 6.85 (b, 1H, p-H of Me2C6H3), 6.93 (m, 2H, o-H of Ph), 7.15
(b, 4H, m þ p-H of Ph), 7.20 (b, 4H, m-H of PPh2), 7.62 (b, 4H, o-H of
PPh2), 7.70 (b, 2H, p-H of PPh2)
C 57.1 (56.9), H 5.2 (5.1), N 2.3 (2.2) m/z
Mass spectrometry: FAB1: m/z 632.3 (15) [M]1, 617.6
(15) [M ꢀ Me]1, 602.3 (100) [M ꢀ 2Me]1
31P{1H} NMR (202.4 MHz, d8-THF) 17.2 (s, JPtP ¼ 1995)
1
10
[Pt(CH CN) {Ph PCH C(Ph) N(2,6-
1H NMR (500 MHz, CD2Cl2) 1.95 (b, 3H, CH3CN trans-P), 2.19 (s, 6H,
Me2C6H3), 2.37 (b, 3H, CH3CN cis-P), 4.87 (d, 2H, CH2-P, 2JPH ¼ 12.7),
7.15 (t, 1H, p-H of Me2C6H3, 2JHH ¼ 7.3), 7.09 (d, 2H, m-H of Me2C6H3,
2JHH ¼ 7.3), 7.30 (m, 4H, o þ m-H of Ph), 7.46 (m, 1H, p-H of Ph), 7.99
(m, 4H, o-H of PPh2, 3JPH ¼ 8.5), 7.73 (m, 4H, m-H of PPh2, 4JPH ¼ 3.4),
Q
3
2
2
2
Me2C6H3)}][BF4]2
32H32B2F8N3PPt
MW 858.29
C
Air and moisture sensitive brown-yellow powder
Elemental analysis: % Found (Calc.) C 43.7 (44.7), H
4.03 (3.8), N 5.36 (4.9), P 3.20 (3.60), B 2.4 (2.5)
Mass spectrometry (FAB1): m/z 684.3 [M ꢀ 2BF4]1
5
7.82 (m, 2H, p-H of PPh2, JPH ¼ 2.2)
31P{1H} NMR (202.4 MHz, CD2Cl2) 18.3 (1JPtP ¼ 3613)
11B{1H} NMR (160.4 MHz, CD2Cl2) ꢀ0.9 (s)
19F NMR (282.45 MHz, CD2Cl2) ꢀ151.5 (s)
13C{1H} NMR data (125.7 MHz, CD2Cl2) 17.8 (s, Me2C6H3N),18.9 (b,
1
CH3CN trans-P), 30.8 (b, CH3CN cis-P), 45.7 (d, CH2-P, JPC
¼
107),144.8 (s, i-C of Me C H N), 195.9 (b, N C), 121.3 (d, CH CN cis-P,
Q
2
6
3
3
2JPC ¼ 72), 116.9 (b, CH3CN trans-P), 134.0 (d, i-C of PPh2, 1JPꢀPhi ¼ 55),
133.4 (d, o-C of PPh2, 2JPꢀPho ¼ 11), 131.3 (d, m-C of PPh2, 3JPꢀPhm ¼ 12),
130.3 (b, p-C of PPh2), other aromatic-C resonances 135.5, 134.8, 133.4,
130.4, 130.0, 129.9, 129.6, 129.3, 123.1
11a and
12a
C56H52Cl2NPtP2
cis-[Pt{Ph PCH C(Ph) N(2,6-Me C H )} ][Cl]
Q
2 2 2 6 3 2 2
1H NMR (CD2Cl2): 2.15 (s, Me2C6H3, 12H), 3.99 (d, CH2-P, 3JPH ¼ 11.5
Hz, 4H), 7.96 (m, o-Ph2P, 8H), 7.78 (m, p-Ph2P, 4H), 7.62 (m, m-Ph2P, 8H)
31P{1H}NMR (CD2Cl2): 14.2 (1JPPt ¼ 3781 Hz)
Air stable white powder
Elemental analysis:% found (Calc.) C 61.4 (62.2) H 4.3
(4.8) N 1.8 (2.6)
cis-[PtCl{Ph PCH C(Ph) N(2,6-Me C H )} ][Cl]
Q
2
2
2
6
3 2
Mass spectrometry (FAB): m/z 1045.1(65) [M ꢀ Cl]1,
1H NMR (CD2Cl2): 2.18 (b, Me2C6H3, 6H), 1.95 (b, Me2C6H3, 6H), 4.30
(broad d, CH2-P, 3JPH ¼ 11.0 Hz, 2H), 5.20 (broad d, CH2-P, 3JPH ¼ 11.0
Hz, 2H);
1008.2(90) [M ꢀ 2Cl]1
31P{1H} NMR (CD2Cl2):29.0 (d, 1JPPt ¼ 3683 Hz, 1JPP ¼ 15 Hz), ꢀ4.0 (d, 1JPPt
¼ 3683 Hz, 1JPP ¼ 15 Hz). 7.47–6.95 (multiple resonances of aromatic protons)
388
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7

View Article Online
Table 1 (continued )
Compound data
NMR data
11b and
12b
C56H52Br2NPtP2
cis-[Pt{Ph PCH C(Ph) N(2,6-Me C H )} ][Br]
Q
2 2 2 6 3 2 2
1H NMR (CD2Cl2): 2.23 (s, Me2C6H3, 12H), 4.01 (d, CH2-P, 3JPH ¼ 12.0
Air stable light yellow powder
Elemental analysis:% found (Calc.) C 56.2 (57.5) H 4.1
(4.5) N 1.9 (2.4)
Hz, 4H), 7.96 (m, o-Ph2P, 8H, 3JPH ¼ 13.2), 7.78 (m, m-Ph2P, 8H, 4JPH
¼
5
2.9 Hz), 7.66 (m, p-Ph2P, 4H, JP–H ¼ 2.0 Hz)
31P{1H}NMR (CD2Cl2): 18.4 (1JPPt ¼ 3653 Hz)
Mass spectrometry (FAB): m/z 1090.1 (5) [M ꢀ Br]1,
cis-[PtBr{Ph PCH C(Ph) N(2,6-Me C H )} ][Br]
Q
2
2
2
6
3 2
1010.2(15) [M ꢀ 2Br]1
1H NMR (CD2Cl2): 2.23 (s, Me2C6H3, 12H), 1.90 (b, Me2C6H3, 6H), 4.80
(broad d, CH2-P, 3JPH ¼ 11.0 Hz, 2H), 4.43 (broad d, CH2-P, 3JPH ¼ 11.0
Hz, 4H). 7.50–6.90 (multiple resonances of aromatic protons)
31P{1H}NMR (CD2Cl2): 34.2 (d, 1JPPt ¼ 3672 Hz, 2JPP ¼ 11 Hz), ꢀ4.0 (d,
1JPPt ¼ 3672 Hz, JPP ¼ 11 Hz)
2
resonances characteristic for a diamagnetic complex incorpor-
ating the ligand L1. The 1H resonances of 1 were still broad at
ꢀ90 1C and signals due to paramagnetic species are still
observable in the baseline. Below ꢀ80 1C, the 31P{1H} NMR
spectrum showed a broad signal at d 41.9, which sharpened up
upon further cooling. Surprisingly, single crystal X-ray diffrac-
tion (150 K) showed that the solid-state geometry of complex 1
is a distorted square-planar one (vide infra). It is known that
nickel dibromide complexes with chelating bulky diimines such
as[NiBr {(2,6-RR0C H )N C(R00)–C(R00) N(2,6-RR0C H )}],
where R, R0 = H, CH3, CF3, or C6H5, R00 = 1,8-naphthadiyl,
Et, Me, or Cy, are tetrahedral and paramagnetic in the solid
state.31 In contrast, with chelating bis-phosphines, nickel diha-
lide complexes can be either in a distorted square-planar or
tetrahedral geometry, depending on the nature of the phos-
phine ligand and/or the nature of the halides.32 Complexes
containing mixed alkyl and phenyl phosphines may either be in
a square-planar or tetrahedral geometry, depending on the
number of phenyl groups attached to the phosphorus atom.
The equilibrium between square-planar (diamagnetic) and
tetrahedral (paramagnetic) geometries of Ni(II) dihalides has
been studied extensively.33–40
We have investigated the magnetism of 1 in the solid state by
variable temperature SQUID magnetometry from 5–350 K,
and in solution by Evan’s method (between 190–293 K in
CD2Cl2). The magnetic moment estimated for 1 using the
SQUID and Evan’s method is ca. 2.5 B.M. Magnetic moments
of 0 (no unpaired electrons and square-planar geometry) or 3.3
BM (two unpaired electrons, tetrahedral) were expected. Inter-
mediate values indicate a mixture of the two forms in equili-
brium. Both methods point towards a spin-equilibrium system
whereby the diamagnetic (square-planar) form is favoured at
low temperature and the paramagnetic (tetrahedral) form is
favoured at high temperature. However, the transition is
gradual and there is an appreciable concentration of the
tetrahedral form at all of the temperatures studied, thus no
sharp spin-crossover point was observed. Variable temperature
(VT) NMR experiments in CD2Cl2, which followed the change
in chemical shift of both the paramagnetic and diamagnetic
sets of resonances with temperature, did not lead to meaningful
thermodynamic parameters for the tetrahedral/square-planar
equilibrium in solution. These observations support the pre-
sence of a dynamic equilibrium slower than the NMR time-
scale for 1, consistent with the presence in the NMR spectra of
two separate sets of resonances due to the diamagnetic and
paramagnetic isomers at all temperatures.
show any conclusive evidence to support diamagnetic-para-
magnetic dynamic behaviour for 2. The ability of Ni(II) to form
both charged and neutral pentacoordinate complexes is well-
documented in the literature.32 Thus, numerous high-spin
distorted trigonal-bipyramidal and square-pyramidal com-
plexes are known, usually containing hard donor sites.41
1
The H NMR spectroscopy of 3 showed doublets at d 0.06
(3JPH = 4.7 Hz) and at d 0.49 (3JPH = 12.3 Hz) assigned to the
NiCH3 protons trans and cis to the PPh2 moiety, respectively.
31P{1H} NMR spectroscopy in d8-toluene of 3 exhibited a
singlet at d 30.8, showing that the Ni-coordinated phosphine
is considerably deshielded compared to free L1.
Q
Q
2
6
3
6
3
The cationic complexes 4 and 5 are both diamagnetic, as
1
shown by H and 31P{1H} NMR spectroscopy in CD2Cl2. The
broad signal at d 1.16 in the 1H NMR spectrum of 4 was
assigned to the PMe3 protons. The cis arrangement of PMe3
relative to the PPh2 group of the chelating ligand was assigned
on the basis of a strong NOE between the methyl groups of the
PMe3 ligand and the ortho protons of the PPh2 unit. This
configuration is probably favoured since it minimizes the steric
repulsions between the 2,6-Me2C6H3 unit and the PMe3 group.
The 31P{1H} NMR spectrum of 4 showed two doublets of equal
intensity, at d 34.2 (assigned to the PPh2 group) and at d ꢀ22.9
(assigned to the PMe3 group), with the coupling constant
1
2JPP = 218 Hz. The H NMR spectrum (CD2Cl2) of 5 shows
4
a double doublet at d 1.83 (3JPH = 13.5 Hz, JPH = 1 Hz),
assignable to the protons of the CH3CN group trans to
phosphorus, and a double doublet at d 1.22 (3JPH = 12 Hz,
5JPH = 1 Hz) assigned to the P(CH3)3 group cis to the PPh2
moiety. A strong NOE between the P(CH3)3 and the Hortho
from Ph2P (d = 7.99) indicates a cis coordination of the PMe3
and PPh2 to the metal centre. 31P{1H} NMR spectroscopy
(CD2Cl2) of 5 showed two doublets of equal intensities, at d
51.2 (assigned to PPh2) and at d ꢀ8.2 (assigned to PMe3) with
2JPP = 102 Hz. As expected, the coordinated phosphorus
nuclei are considerably deshielded compared to those of the
free ligands.
1
The H NMR spectrum of 6 exhibits two doublets at d 0.47
and 1.40 (3JHH = 6.6 Hz), corresponding to the two prochiral
methyl groups and a heptet (d 2.88) for the two CH protons of
the equivalent Pr groups, but only one doublet for the CH2
i
2
protons of the ligand backbone (d 4.45, JPH = 13.5). This
indicates that rotation around the imine N–aryl bond is fast on
the NMR timescale. However in the X-ray diffraction of 6 one
iPr group is placed above the plane defined by the imine group
and the other below this plane, suggesting some degree of steric
hindrance against free rotation. For the analogous complex 7,
only one sharp resonance corresponding to the protons of the
2,6-Me2C6H3 unit was observed in the aliphatic region of the
1H spectrum (d 2.03), as well as one methine doublet (d 4.35 7,
The room temperature 1H NMR spectrum of 2 (CD2Cl2)
also showed broad resonances in the range d ꢀ4 to 21,
indicating that this complex is not diamagnetic in solution at
room temperature. Proton NMR spectroscopy of paramag-
netic pentacoordinate-Ni(II) N/P complexes usually shows
signals in the range d ꢀ14 to 20.13 The room temperature
31P{1H} NMR spectroscopy of 2 showed no resonances. A
variable temperature NMR between ꢀ80 and 20 1C did not
1
2JPH = 13.2 Hz). The effect of metal coordination on the H
NMR chemical shifts are especially noticeable in the case of the
CH2 resonances, which changed from d 3.80 (2JPH = 1 for the
free Z isomer of L2) or 3.81 (2JPH = 1.1 for the free Z isomer
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7
389

View Article Online
of L1). 31P NMR spectra (CD2Cl2) showed singlet resonances
at d 45.0 (for 6) and 43.1 (for 7), significantly downfield
compared to that of free L2 and L1, found at d ꢀ21.0 and
ꢀ19.8, respectively.
Table 2 Selected bond lengths (A) and angles (1) for complexes 1, 2, 6,
7 and 9
1
Ni(1)–Br(1)
Ni(1)–Br(2)
Ni(1)–P(1)
Ni(1)–N(1)
P(1)–C(1)
P(1)–C(3)
P(1)–C(9)
N(1)–C(2)
N(1)–C(21)
C(1)–C(2)
2
2.349(2)
2.315(2)
2.140(5)
1.925(11)
1.852(16)
1.78(2)
Br(1)–Ni(1)–Br(2)
Ni(1)–N(1)–C(2)
P(1)–C(1)–C(2)
93.09(9)
120.1(10)
105.9(10)
170.76(17)
86.07(13)
86.1(4)
The 1H NMR spectrum of 8 (CD2Cl2) showed a centred
doublet assignable to the MePt group at d 0.68 (3JPH = 3.5
Hz), with the corresponding satellites due to coupling with
195Pt (2JPtH = 75 Hz). The strong NOE between Pt–methyl
protons of 8 and the ortho protons of PPh2 indicated that this
methyl group is coordinated to the platinum cis to the phos-
phorus nuclei. NMR spectroscopy also confirmed that this is
the only isomer present in solution. The 31P{1H} NMR spec-
trum (CD2Cl2) of [PtMeCl(L1)] 8 showed a centred singlet at d
22.6. 195Pt satellites are observed and the coupling constant
(1JPtP = 4670 Hz) is larger than that observed for [PtMe2(L1)]
9 (d 17.2, 1JPtP = 1995 Hz). The 1H NMR spectrum (CD2Cl2)
of 9 showed a centred pair of doublets assignable to the MePt
groups at d 0.84 (cis to PPh2, 3JPH = 7.5) and d ꢀ0.23 (trans to
PPh2, 3JPH = 8.2). As expected, the Pt–H coupling is larger for
the MePt cis to PPh2 (2JPtH = 89.5) than for the MePt trans to
P (2JPtH = 67.0). The 1H NMR spectrum of 10 (CD2Cl2)
showed broad signals at d 1.95 and 2.37 assignable to the
protons of the MeCN groups trans and cis to phosphorus
respectively. The 31P{1H} NMR spectrum (CD2Cl2) of 10
showed a centred singlet with 195Pt satellites at d 18.3 (1JPtP
= 3613 Hz).
Br(1)–Ni(1)–P(1)
Br(2)–Ni(1)–P(1)
P(1)–Ni(1)–N(1)
Br(1)–Ni(1)–N(1)
Br(2)–Ni(1)–N(1)
Ni(1)–P(1)–C(1)
1.802(17)
1.304(19)
1.45(2)
95.9(4)
169.1(4)
99.5(6)
1.46(2)
Ni(1)–Br(1)
Ni(1)–Br(2)
Ni(1)–P(1)
Ni(1)–N(1)
Ni(1)–O(1)
P(1)–C(1)
P(1)–C(3)
P(1)–C(9)
N(1)–C(2)
N(1)–C(21)
C(1)–C(2)
2.4736(13)
2.4634(12)
2.329(2)
2.111(6)
2.041(5)
1.824(9)
1.839(6)
1.816(8)
1.295(8)
1.439(9)
1.518(11)
Br(1)–Ni(1)–Br(2)
Br(1)–Ni(1)–P(1)
Br(2)–Ni(1)–P(1)
Br(1)–Ni(1)–N(1)
Br(2)–Ni(1)–N(1)
P(1)–Ni(1)–N(1)
Br(1)–Ni(1)–O(1)
Br(2)–Ni(1)–O(1)
P(1)–Ni(1)–O(1)
N(1)–Ni(1)–O(1)
Ni(1)–O(1)–P(2)
O(1)–P(2)–C(29)
O(1)–P(2)–C(35)
C(29)–P(2)–C(35)
O(1)–P(2)–H(1)
113.38(5)
95.27(6)
93.56(6)
150.44(15)
96.04(15)
79.34(16)
89.86(15)
92.44(14)
169.84(15)
91.9(2)
122.4(3)
111.2(3)
113.7(3)
107.4(3)
116(4)
X-Ray data
6
Pd(1)–Br(1)
Pd(1)–Br(2)
Pd(1)–N(1)
Pd(1)–P(1)
N(1)–C(2)
N(1)–C(3)
P(1)–C(1)
P(1)–C(21)
P(1)–C(27)
C(1)–C(2)
7 (Molecule 1)
Pd(1)–I(1)
Pd(1)–I(2)
Pd(1)–P(1)
Pd(1)–N(1)
P(1)–C(2)
P(1)–C(17)
P(1)–C(23)
N(1)–C(1)
N(1)–C(3)
C(1)–C(2)
7 (Molecule 2)
Pd(2)–I(3)
Pd(2)–I(4)
Pd(2)–P(2)
Pd(2)–N(2)
P(2)–C(30)
P(2)–C(45)
P(2)–C(51)
N(2)–C(29)
N(2)–C(31)
C(29)–C(30)
9
2.5029(11)
2.4289(10)
2.095(5)
Br(1)–Pd(1)–Br(2)
Br(1)–Pd(1)–N(1)
Br(2)–Pd(1)–N(1)
Br(1)–Pd(1)–P(1)
Br(2)–Pd(1)–P(1)
N(1)–Pd(1)–P(1)
92.20(4)
94.89(14)
171.01(14)
173.08(5)
92.45(6)
ORTEP views of complexes 1 and 2 are shown in Figs. 1–3.
For both complexes 1 and 2, the N and P donors of the ligand
L1 are coordinated to the metal, forming 5-membered rings.
Single crystal X-ray diffraction showed that the structure of
[NiBr2(L1)] (1) in the solid state is in a distorted square-planar
2.2158(18)
1.293(9)
1.433(8)
81.00(15)
geometry. The geometry around the Ni centre in [NiBr (O
Q
PHPh2)(L1)] (2) is closer to a distorted square-pyramid than to
2
1.837(7)
1.814(7)
a trigonal bipyramid. In the latter complex, the P(1) centre is
pulled slightly towards Ni, the Br(2) atom is placed axial and
the pyramid base, formed by N(1), P(1), Br(1) and O(1), is
almost planar. The bite angle N(1)–Ni(1)–P(1) for compound 1
is 86.1(4)1, which is similar to those of numerous nickel(II)
chelating bis-phosphine complexes, which incorporate a two-
carbon atom, P,P0 linkage, such as 1,2-bis(diphenylphosphi-
no)ethane (dppe). In these latter complexes, angles are found in
the range 85–901.42 The corresponding N(1)–Ni(1)–P(1) bite
angle for compound 2 is 79.34(16)1, that is, considerably
smaller than that of 1, probably due to the more puckered
structure of the chelate ring. As a consequence of the differ-
ences in the overall geometries of the complexes, the Br(1)–Ni–
Br(2) angle for 1, 93.09(9)1, is considerably smaller than that
for 2 [113.38(5)1]. The sum of the angles at N(1) in complexes 1
and 2 are indicative of sp2 hybridisation. The geometry of the
1.820(8)
1.502(10)
2.6260(6)
2.5768(5)
2.2293(14)
2.110(5)
1.843(6)
1.808(6)
1.797(6)
1.282(7)
1.444(7)
1.501(8)
I(1)–Pd(1)–I(2)
I(1)–Pd(1)–P(1)
I(2)–Pd(1)–P(1)
I(1)–Pd(1)–N(1)
I(2)–Pd(1)–N(1)
P(1)–Pd(1)–N(1)
89.695(19)
173.17(4)
93.97(4)
95.72(12)
173.09(12)
81.08(12)
2.6334(5)
2.5803(5)
2.2276(13)
2.112(4)
1.833(5)
1.811(5)
1.802(5)
1.288(6)
1.440(6)
1.502(7)
I(3)–Pd(2)–I(4)
I(3)–Pd(2)–P(2)
I(4)–Pd(2)–P(2)
I(3)–Pd(2)–N(2)
I(4)–Pd(2)–N(2)
P(2)–Pd(2)–N(2)
93.525(16)
167.91(4)
92.77(4)
94.13(11)
169.72(11)
80.99(12)
Pt(1)–P(1)
Pt(1)–N(1)
Pt(1)–C(3)
Pt(1)–C(4)
P(1)–C(2)
P(1)–C(19)
P(1)–C(25)
N(1)–C(5)
N(1)–C(1)
C(1)–C(2)
2.2411(9)
2.162(3)
2.091(4)
2.057(4)
1.844(4)
1.822(4)
1.836(4)
1.443(4)
1.297(5)
1.522(5)
P(1)–Pt(1)–N(1)
P(1)–Pt(1)–C(3)
N(1)–Pt(1)–C(3)
P(1)–Pt(1)–C(4)
N(1)–Pt(1)–C(4)
C(3)–Pt(1)–C(4)
80.87(9)
174.03(12)
94.10(14)
98.50(13)
178.92(14)
86.59(17)
Fig. 1 ORTEP diagram of the molecular structure of complex 1.
390
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7

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Fig. 2 ORTEP diagram of the molecular structure of complex 2.
nickel atom in 1 is distorted square-planar, with the chelating
ligand inducing a cis arrangement of the bromine atoms. In 1,
the Ni(1)–Br(1) and Ni(1)–Br(2) distances are 2.349(2) A and
2.315(2) A, respectively, with the slightly elongated metal-
halide bond situated trans to the phosphine unit. The car-
bon-carbon distances C(1)–C(2) for the ligand backbones of
1.46(2) (1) and 1.518(11) (2) A are within the range expected
for the imine form of the ligand and close to the values
observed for Pd(II) complexes and for the free ligand L1,
reported by us earlier.26 The N(1)–C(2) separations [of
1.304(19) (1) and 1.295(8) (2) A] are slightly larger than that
found in the free ligand L1 [1.273(2) A]. The atom H(1) was
located, using a Fourier map during the structure refinement,
tures in the solid state and in solution, with the ligand in its
iminophosphine form and square-planar geometry at the Pd
centre. The N–Pd–P bite angles for [PdBr2(L2)] 6 is 81.00(15)1,
that is, somewhat smaller than that for the isostructural
[PdBr2(L1)], 82.91(6)1.26 This is due to the increased bulk of
the isopropyl groups serving to increase the distance of the N
(and P) donor atoms from the Pd centre, which in turn
decreases the bite angle. The palladium–halogen bond lengths
for 6 and 7 are in the range expected for Pd(II) complexes,42
with the longer metal–halogen bond always trans to the
phosphorus atom due to the greater trans influence. The Pd–
P
separation slightly increases across the series, from
2.1845(12) for
for [PdCl2(L1)]26 to 2.2119(19)
[PdBr2(L1)],26 2.2158(18)
for [PdBr2(L2)] (6), and
A
A
at the P(2) centre of the O P(H)Ph group, which exhibits a
2
A
Q
distorted tetrahedral geometry. This determination is also
supported by the infrared spectrum, which showed two bands,
assignable to nPH (at 2370 and 2340 cmꢀ1) and a broad band
Q
ORTEP diagrams of complexes 6 and 7 are shown in Figs. 4
and 5, respectively. These Pd(II) complexes have similar struc-
2.2293(14) and 2.2276(13) A for [PdI2(L1)] (7; molecules 1
and 2, respectively, since two independent molecules are pre-
sent in the asymmetric unit). This variation occurs as a result of
the increasing trans influence in the halide series: Cl o Br o I.
In general, little variation in the bond lengths of L1 can be
(at 1238 cmꢀ1) assignable to the P O stretch.
observed upon chelation to Pd(II), although the C N carbon–
Q
Fig. 3 Alternative view of the molecular structure of complex 2, showing the distorted square-pyramid geometry around the Ni(II) centre (for
clarity only the ipso carbons from the aryl rings are shown).
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7
391

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Fig. 4 ORTEP diagram of the molecular structure of complex 6.
nitrogen separation increases upon coordination, from 1.273(2)
Heck reaction tests
A for the free ligand to 1.282(7) A and 1.288(6) A for 7 (N.B.
two independent molecules in the asymmetric unit). The ligand
backbone carbon–carbon distances for complexes 6 and 7
(Table 2) are comparable with that of free L1 [1.504(2) A].
An ORTEP diagram of complex 9 is shown in Fig. 6. X-Ray
structure determination confirmed that this complex exhibits
the same structure in the solid state as in solution, and is
isostructural with [PdMe2(L1)].26 In the solid state, this com-
plex also exhibits a pseudo square-planar geometry around the
metal centre. The P(1)–Pt(1)–N(1) bite angle is 80.87(9)1, which
is only slightly larger than that of complex [PdMe2(L1)],26 at
80.2(2)1. The Pt–C bond length for the methyl group situated
trans to phosphorus is 2.091(4) A. This is close to that of the
methyl cis to PPh2 [2.057(4) A], although the slight increase is
expected because of the greater trans influence of phosphorus
compared to nitrogen. The difference between these intera-
tomic separations is comparable to that found between the
corresponding cis and trans Pd–Me distances of complex
[PdMe2(L1)] [2.045(11) and 2.09(1) A, respectively]. The ligand
backbone carbon–carbon distance for complex 9 [1.522(5) A] is
comparable to that of related Pd complexes and somewhat
larger than that of the free L1 [1.504(2) A].
In recent years, palladium complexes of hybrid nitrogen and
phosphorus ligands have received attention as Heck cata-
lysts,24 due to the possibility of enhanced reactivity by coop-
erative effects. However, to date, no estimation of the activity
in Heck processes of Pd complexes of ligands with a flexible
backbone, such as L1 and L2, has been reported. We have
shown that [PdMeCl(L1)] shows moderate activity in another
C–C coupling reaction, that is, the CO/ethylene copolymerisa-
tion reaction.26
The complex [PdBr2(L2)] (6), as well as two of our pre-
viously
reported
complexes,
[PdBr2(L1)]
and
[PdMeCl(L1)],26,27 were tested as pre-catalysts for the Heck
coupling of 4-bromoacetophenone with n-butyl acrylate under
aerobic conditions. A mixture of 4-bromoacetophenone and
1.4 equiv. of n-butyl acrylate was heated at 130 1C for 20 h in
N,N-dimethylacetamide in the presence of a base (sodium
acetate), and 0.5 mol % of the pre-catalyst. (n-Bu)4NOAc
was added, as it has been shown that the presence of a soluble
base significantly reduces the induction time required to form
the catalytically active species.43 For the catalysts used, quan-
titative conversion into the corresponding olefin was achieved
Fig. 5 ORTEP diagram of the molecular structure of complex 7.
392
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7

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Fig. 6 ORTEP diagram of the molecular structure of complex 9.
Experimental
Table 3 Yield percentages and TON from the Heck coupling of 4-
bromoacetophenone and n-butyl acrylate with different pre-catalysts
General methods and materials
Pre-catalyst
(130 1C, 20 h)
TON/mol product
per mol Pd
All manipulations of air- and/or moisture-sensitive materials
were performed under an inert atmosphere of pure argon or
dry N2 using standard Schlenk line techniques, or in an inert
atmosphere dry-box. Inert gases were purified firstly by pas-
sage through columns filled with activated molecular sieves (4
A) and then either manganese(II) oxide suspended on vermi-
culite, for the Schlenk line, or BASF catalyst, for the dry-box.
Celite was purchased from Fluka Chemie and oven-dried at
150 1C prior to use for filtration. Solvents were pre-dried over
activated 4 A molecular sieves and then distilled under N2
atmosphere from NaK alloy (light petroleum ether, b.p. 40–60
1C, diethyl ether, pentane), from sodium (toluene), from
potassium (THF), or from calcium hydride (dichloromethane).
Deuterated NMR solvents (Aldrich, Goss Scientific) were
refluxed and distilled from potassium metal (d8-toluene) or
from calcium hydride (CD2Cl2), distilled and degassed prior to
use. Microanalyses were performed by the microanalytical
laboratory of the Inorganic Chemistry Laboratory, University
of Oxford, and FAB+ mass spectra by the EPSRC National
Mass Spectrometry Service Centre, University of Wales, Swan-
sea, UK.
% Yield
None (blank run)
[PdBr2(L2)] (6)
[PdBr2(L1)]26,27
[PdMeCl(L1)]26,27
0
100
93
0
200
186
148
74
under the conditions used. Yields and TON are given in
Table 3. With [PdBr2(L1)], , the conversion yield (determined
by GC-MS, based on 4-bromoacetophenone) was 93% and
the turnover number 186 mol product per mol Pd. With
[PdBr2(L2)] (6), a 100% conversion yield (turnover number
200) was obtained. Using the pre-catalyst [PdMeCl(L1)],26,27
the yield (determined by GC-MS, based on 4-bromoacetophe-
none) was 74% and the turnover number 148 (estimated as mol
product per mol catalyst). In all cases, the reaction time was
20 h. The slightly lower yield could be explained by the thermal
decomposition of the methyl–Pd pre-catalyst during the induc-
tion period.
In all cases, although the yields were extremely high and
comparable to those obtained using Pd(II) complexes of the
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 UNITY plus (1H 500 MHz, 11B 160.4
MHz, 13C 125.7 MHz, 31P 202.4 MHz) spectrometer and were
at room temperature unless otherwise stated. The spectra were
referenced internally relative to the residual protio solvent (1H)
and solvent (13C) resonances relative to tetramethylsilane (1H,
13C, d = 0) or externally to BF3 ꢁ Et2O (11B, d = 0); H3PO3
(31P, d = 0) or CFCl3 (19F, d = 0). Chemical shifts (d) are
expressed in ppm and coupling constants (J) in Hz.
GC-MS chromatograms and spectra were recorded using a
Hewlett Packard 5890 gas chromatograph fitted with a non-
polar column connected to a Trio-1000 mass spectrometer
operating in electron impact (EI, 70 eV) and chemical ionisa-
tion (CI; NH3) modes and detecting positively charged species.
The temperature profile for the GC was: 100 1C for 3 min, then
10 1C minꢀ1 ramp to 280 1C (held for 10 min).
ligands o-[PPh C H NH ] and o-[PPh C H N CHPh)] under
Q
2
6
4
2
2
6
4
similar reaction conditions,24 the turnover numbers so far are
significantly lower and further studies to improve these are
under way.
Conclusions
New nickel(II), palladium(II) and platinum(II) cis-dimethyl and
monomethyl monohalide complexes of bulky iminophosphine
ligands have been prepared and characterised. In contrast to
the reaction of [PtX2(cod)] (X = Cl, Br) with L1, which leads
to a mixture of products, treatment of [PtMe2(cod)] or
[PtMeCl(cod)] with one equivalent of L1 affords in both cases
the corresponding chelating complexes cleanly. The pre-cata-
lysts [PdBr2(L2)] 6, [PdBr2(L1)] and [PdMeCl(L1)] have been
found to be active in the Heck coupling of 4-bromoacetophe-
none with n-butyl acrylate. The attractive features of these
catalytic systems—high yields and air and moisture stability—
approach those of industrial interest and open future pers-
pectives for their use in other palladium-catalysed organic
reactions.
The reagents n-BuLi, PMe3, [NiBr2(dme)], [Pd(dba)2],
AgBF4, PdBr2, [3,5-(CF3)2C6H3]I, 4-bromoacetophenone,
diethylene glycol, di-n-butyl ether, n-butyl acrylate and N,N-
dimethylacetamide were purchased from Aldrich and used as
i
received. Ph2PCl, Pr2NH and 2,6-iPr2C6H3NH2 were pur-
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7
393

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chased from Strem and purified by vacuum distillation before
use. The compounds [PtMe2(cod)],44 [PtClMe(cod)],45 [Ni-
Me2(tmeda)],46 [NiCl2(PMe3)2]47 and L118,26 were prepared
according to literature procedures.
[NiBr (O PHPh )(L1)] (2). The exposure of complex 1
Q
(0.05 g, 0.06 mmol) to one equivalent of O PHPh (0.012 g,
0.06 mmol) in 50 ml CH2Cl2 for 12 h at room temperature
resulted in the formation of a small amount of 2 as air and
moisture sensitive brown, square-shaped crystals (yield o
10%). The product was characterised by X-ray crystallography
2
2
Q
2
Syntheses
as [NiBr (O PHPh )(L1)) (2).
2
Q
2
Spectroscopic data for all new compounds are given in Table 1.
[NiMe2(L1)] (3): NMR-scale reaction between L1 and [Ni-
Me2(tmeda)]. d8-Toluene (0.6 ml) was condensed onto a solid
mixture of [NiMe2(tmeda)] (0.015 g, 0.086 mmol) and L1
(0.035 g, 0.0857 mmol) at ꢀ173 1C in a Young’s NMR tube
fitted with a Teflon valve. The mixture was warmed to ꢀ78 1C
and the reaction monitored by 1H NMR spectroscopy over 4 h,
allowing it to equilibrate at each of the following temperature
steps: ꢀ75, ꢀ50, ꢀ40, ꢀ30, ꢀ20, ꢀ10, 0, +10, +25 1C and
+25 1C after 24 h. 3 was identified between ꢀ10 and +25 1C
{1H NMR: d = ꢀ0.213 (d, 3H, PdCH3, cis-P, 3JPH = 3.5 Hz),
[PhMeC N(2,6-iPr C H )]. The synthesis was adapted
Q
2
6
3
from the method of Okamoto et al.48 A mixture of acetophe-
none (25.75 g, 21.45 mmol), 2,6-diisopropylphenylamine (36.98
g, 21.45 mmol) and p-tolylsulfonic acid (ca. 1 g) in a round-
bottomed flask fitted with a Soxhlet extractor containing about
20 g anhydrous CaSO4 was refluxed in 200 ml toluene for 24 h.
During this time, water was removed using activated molecular
sieves (4 A), which were contained in the round-bottomed
flask. The reaction mixture was subsequently filtered through
Celite. After removal of volatile compounds, the brown residue
was distilled under reduced pressure (0.6 ꢂ 10ꢀ3 bar). The
unreacted starting materials were collected between 80–115 1C,
and the imine was collected at 140 1C as a yellow oil, which
solidified at room temperature to give a yellow powder. Yield:
14.25 g, 24%. IR (CsI): nCQN = 1645 cmꢀ1. Anal. calcd (%): C
85.9, H 9.0, N 5.0; found: C 85.2, H 9.7, N 4.9.
3
0.222 (d, 3H, PdCH3, trans-P, JPH = 11.5 Hz), 1.879 [s, 6H,
3
(CH3)2C6H3], 3.062 (d, 2H, CH2P, JPH = 6 Hz), 7.427–6.443
(multiple resonances of aromatic protons, 18H). 31P{1H}
NMR: d = 30.75} at various low concentrations relative to
free tmeda [1H NMR: d = 1.94 (s, 12H), 5.24 (s, 4H)], the
formation of which was also only observed above ꢀ10 1C,
unreacted L1 and [NiMe2(TMEDA)] [1H NMR: d = ꢀ0.639
(s, 6H), 1.443 (s, 4H), 1.94 (s, 12H)]. After 24 h at +25 1C the
1
product [NiMe2(L1)] (3) could not be observed in the H and
31P{1H} NMR spectra.
[Ph PCH C(Ph) N(2,6-iPr C H )] (L2). To a pre-cooled
Q
2
2
2
6
3
i
solution of dry Pr2NH (1.81 g, 17.90 mmol) in 50 ml THF, a
1.6 M solution n-BuLi in hexanes (1.14 g, 17.90 mmol) was
added dropwise at ꢀ78 1C. The mixture was allowed to warm
up to room temperature and stirred for 30 min. A cold solution
of 13 (5.00 g, 17.90 mmol) in 25 ml THF was added dropwise at
ꢀ78 1C under stirring. The mixture was stirred for 2 h at
ꢀ78 1C and the formation of the lithium salt of the imine, a
bright yellow precipitate, was observed. A cold solution of
Ph2PCl (4.94 g, 17.9 mmol) in 25 ml THF was transferred to
the reaction mixture dropwise. The yellow precipitate gradu-
ally disappeared and the solution turned to a lighter yellow.
The mixture was stirred for 12 h at room temperature before
removal of the volatile compounds under reduced pressure.
The resulting white residue was extracted with 50 ml toluene,
and removal of the solvent under reduces pressure gave a
yellow oil. Attempts to purify the product by extraction with
pentane, 40–60 1C petroleum ether or 100–120 1C petroleum
ether were unsuccessful because of the high solubility of the
yellow oil in all these solvents. Recrystallisation from pentane
at ꢀ20 1C resulted in the formation of a crystalline material
shown by 1H and 31P{1H} NMR spectroscopy to be mainly the
[NiMe2(L1)] (3). The compounds [NiMe2(tmeda)] (0.065 g,
0.37 mmol) and L1 (0.15 g, 0.37 mmol) were mixed in a Schlenk
tube and 100 ml toluene was added. The mixture was stirred for
6 h at room temperature, after which volatile compounds were
removed under reduced pressure. The resulting red solid was
washed twice with pentane and residual volatiles were removed
under reduced pressure to yield 3 as an air- and moisture-
sensitive red microcrystalline solid. Yield: 0.05 g, 29%.
[NiBr(PMe3)(L1)][Br] (4), from the reaction of 1 with PMe3.
Compound 1 (0.40 g, 0.64 mmol) was dissolved in 50 ml THF
at room temperature and PMe3 (0.09 g, 1.28 mmol) in 20 ml
THF was added via a syringe. The solution turned blue after
addition and was left stirring for 5 h. Volatile compounds were
removed under reduced pressure to give a blue residue. Pentane
(20 ml) was added to the residue, giving a deep-blue precipitate
and a purple supernatant. The mixture was stirred for a further
30 min, prior to separation as described below.
Fraction 1: a deep-blue powder was isolated by filtration,
washed with pentane and the residual volatiles removed under
reduced pressure. The air- and moisture-sensitive powder was
identified as 4. Yield: 0.18 g, 63%.
Fraction 2. Volatile compounds were removed from the
purple pentane filtrate under reduced pressure and the resulting
purple residue was recrystallised from a 1 4mixture of toluene
and pentane at ꢀ20 1C. A small amount of white microcrystal-
line precipitate was isolated by filtration and identified as L1
(yield o 5%). Purple crystals of an additional product (ca.
0.040 g) were isolated from the filtrate and identified as
[NiBr2(PMe3)2].
expected product, [Ph PCH C(Ph) N(2,6-iPr C H )] (L2) as
Q
2
2
2
6
3
a mixture of the two E/Z isomers in a 2 : 1 ratio (by
integration), together with starting materials and oxidation
products. Attempts to separate the components of this mixture
by column chromatography (on Kieselgur, using mixtures of
Et2O and petroleum ether 40–60 1C, in various ratios) were
unsuccessful. Further attempts to isolate this ligand were not
undertaken. Instead, the ligand was prepared in situ and used
directly for the synthesis of 6.
[NiBr2(L1)] (1), from the reaction of L1 with [NiBr2(dme)]. L1
(1.00 g, 2.46 mmol) was dissolved in 50 ml THF and added to a
suspension of [NiBr2(dme)] (0.76 g, 2.46 mmol) in 50 ml THF.
The mixture was stirred for 12 h at room temperature. Volatile
compounds were removed under reduced pressure and the
resulting brown residue was washed with pentane. Recrystalli-
sation from CD2Cl2 and Et2O at ꢀ20 1C afforded air stable
dark-red needle-like crystals of 1, which were isolated by
filtration. Yield: 1.05 g, 70%.
[Ni(CH3CN)(PMe3)(L1)][BF4]2 (5). The solids [Ni(P-
Me3)2Cl2] (0.10 g, 0.35 mmol) and AgBF4 (0.14 g, 0.70 mmol)
were mixed in a Schlenk tube and 50 ml of CH3CN were added.
The mixture was stirred at room temperature under N2 for 30
min. Formation of a white precipitate and an orange super-
natant was observed. The orange supernatant was filtered into
a second Schlenk tube, which contained L1 (0.14 g, 0.35 mmol)
dissolved in 20 ml of CH3CN. The reaction mixture was stirred
394
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7

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for 12 h, filtered and the residual volatiles removed under
reduced pressure to give an orange residue. This was further
recrystallised from CH2Cl2 and pentane to give 5 as an air- and
moisture-sensitive orange powder. Yield: 0.09 g, 36%.
tube and 50 ml THF were added. After stirring at room
temperature for 12 h, no colour change occurred. Subse-
quently, volatiles were removed under reduced pressure. The
resulting yellow solid was recrystallised from a 1 : 4 mixture of
CH2Cl2 and pentane, which gave a light-yellow microcrystal-
line solid, identified as a mixture of 11a and 12a in a 5 : 1 ratio
by integration. Crude yield: 0.05 g, 43%.
[PdBr (L2)] (6). Reaction between the imine [PhMeC
2
Q
N(2,6-iPr2C6H3] (5.00 g, 17.90 mmol) and LDA (1.92 g, 17.9
mmol), prepared in situ, and Ph2PCl (4.94 g, 17.90 mmol) in
200 ml THF was performed as described above. The toluene
extract was added to a suspension of PdBr2 (4.76 g, 17.90
mmol) in 50 ml THF, and the reaction mixture immediately
turned red. After 10 min of stirring at ambient temperature, an
orange precipitate was formed, the colour of the supernatant
remaining red-brown. The mixture was stirred for a further 2 h,
the solid isolated by filtration, and the residual volatiles
removed under reduced pressure. The brown powder was
recrystallised from CH2Cl2 and pentane giving 6 as a micro-
crystalline air-stable red-orange solid. Yield: 7.20 g, 55%.
cis-[Pt(L1)2][Br]2 (11b) and cis-[PtBr(L1)2][Br] (12b), from the
reaction of L1 with [cis-PtBr2(CH3CN)2]. The solids [cis-
PtBr2(CH3CN)2] (0.10 g, 0.228 mmol) and L1 (0.093 g, 0.228
mmol) were mixed in a Schlenk tube and 100 ml CH2Cl2 were
added. After stirring for 12 h at room temperature, volatiles
were removed under reduced pressure and the resulting yellow
solid was recrystallised from CH2Cl2 at ꢀ20 1C, affording an
inseparable mixture containing 11b and 12b (3 : 2 ratio by
integration), as a light-yellow microcrystalline powder. Crude
yield: 0.047 g, 35%.
[PdI2(L1)] (7). To a stirred solution of [Pd(dba)2] (0.195 g,
0.21 mmol) in THF (50 ml), a THF (20 ml) solution of L1 (0.1
g, 0.21 mmol) was added dropwise. After stirring for 10 min,
0.5 ml of [3,5-(CF3)2C6H3]I in 20 ml THF was added and the
reaction mixture was refluxed for 2 h, then stirred at room
temperature for a further 2 h. The resulting solution was then
filtered in order to remove the trace amount of Pd black. The
solvent was removed from the filtrate under reduced pressure
and the brown residue washed several times with Et2O. Re-
crystallisation of the residual solid from CH2Cl2 and pentane
gave complex 7 as air-stable red block-shaped crystals. Yield:
0.049 g, 30%.
Heck coupling of 4-bromoacetophenone and n-butyl acrylate
using [PdBr2(L2)] (6), [PdBr2(L1)] and [PdClMe(L1)] as pre-
catalysts
Sodium acetate (2.25 g, 27.4 mmol), 4-bromoacetophenone
(4.98 g, 25.0 mmol), diethylene glycol di-n-butyl ether (0.50 g,
2.9 mmol, G.C. standard), n-butyl acrylate (4.486 g, 35.0
mmol) and a N,N-dimethylacetamide solution (10 ml) of the
pre-catalyst (0.5 mol %, based on 4-bromoacetophenone) were
added to N,N-dimethylacetamide (20 ml) in a 100 ml 3-necked
flask equipped with a thermometer and a reflux condenser.
Tetrabutylammonium acetate (2.26 g, 7.5 mmol) was also
added to the reaction mixture, as a completely soluble base.
The mixture was refluxed at the appropriate reaction tempera-
ture for 20 h. The reaction mixture was worked-up by adding it
at room temperature to an excess of water, extracting with
diethyl ether and drying with magnesium sulfate. The extracted
material was analysed by GC-MS. The yield was calculated by
integration of the chromatographic peak of the product against
4-bromoacetophenone and against the GC standard peak for
diethylene glycol di-n-butyl ether.
[PtClMe(L1)] (8). To a mixture of L1 (0.058 g, 0.14 mmol)
and [PtMeCl(cod)] (0.050 g, 0.14 mmol), 100 ml THF was
added under stirring. The reaction mixture was stirred for 12 h
at room temperature. The resulting white solid was isolated by
filtration, washed with 20 ml of cold pentane and the residual
volatiles removed under reduced pressure. The white powder
obtained was recrystallised from a 1 : 4 mixture of CH2Cl2 and
pentane at ꢀ20 1C to give 8 as air-stable white-yellow crystals.
Yield: 0.048 g, 52%.
Crystal structure determinationz
[PtMe2(L1)] (9). A ꢀ78 1C THF (20 ml) solution of L1 (50
mg, 0.150 mmol) was added to a ꢀ78 1C THF solution of
[PtMe2(cod)] and left to reach room temperature whilst stir-
ring. Volatiles were removed under reduced pressure and the
light-yellow residue was washed with 20 ml pentane. The
residual volatiles were removed under reduced pressure to give
a yellow powder. Yield of crude product: 60.7 mg, 64%.
Recrystallisation from a 1: 4 mixture of toluene and pentane
at ꢀ20 1C gave yellow crystals of 9.
Crystals were isolated by filtration, and a specimen crystal
selected under an inert atmosphere, covered with polyfluor-
oether, and mounted on the end of a nylon loop. Crystal data
are summarised in Table 4. All data were collected at 150 K
except for compound 9, which was collected at 190 K. Data
collection was performed on an Enraf-Nonius DIP2000 for 1
and 2, and on a Nonius KappaCCD for 6, 7 and 9, using
graphite-monochromated MoKa radiation (l = 0.71073 A).
The images were processed with the DENZO and SCALE-
PACK programs.49 The crystal structures were solved by direct
methods using the program SIR92.50 The refinement and
graphical calculations were performed using the CRYSTALS51
and CAMERON52 software packages. The structures were
refined by full-matrix least-squares procedure on F. All non-
hydrogen atoms were refined with anisotropic displacement
parameters. Hydrogen atoms were located in Fourier maps and
their positions adjusted geometrically (after each cycle of
refinement) with isotropic thermal parameters. Chebychev
weighting schemes and empirical absorption corrections were
applied.53
[Pt(CH3CN)2(L1)][BF4]2
(10).
The
solids
[cis-
PtBr2(CH3CN)2] (0.10 g, 0.23 mmol) and AgBF4 (89.24 mg,
0.457 mmol) were mixed in a Schlenk tube and 50 ml CH3CN
was added. The mixture was stirred at room temperature for 30
min. Formation of a white precipitate was observed. L1 (0.09
g, 0.23 mmol) was dissolved in 20 ml CH3CN and was added to
the mixture whilst stirring. The resulting orange-coloured
mixture was left stirring overnight in darkness. After isolating
the supernatant by filtration, volatiles were removed under
reduced pressure to give a dark-orange residue, which was
washed with 20 ml pentane to give 10 as an air- and moisture-
sensitive brown-yellow powder. Yield: 0.15 g, 76.5%.
For complex 1, the largest peaks and deepest troughs of the
difference Fourier map lie close to the Br atoms, suggesting
that these may be disordered. However, attempts to model this
cis-[Pt(L1)2][Cl]2 (11a) and cis-[PtCl(L1)2][Cl] (12a), from the
reaction of L1 with [PtCl2(cod)]. The solids [PtCl2(cod)] (0.09 g,
0.25 mmol) and L1 (0.10 g, 0.25 mmol) were mixed in a Schlenk
z CCDC reference numbers 236196 and 236200. See http://
www.rsc.org/suppdata/nj/b4/b412391c/ for crystallographic data in
.cif or other electronic format.
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7
395

View Article Online
Table 4 Summary of crystallographic data
1
2
6
7
9
Empirical formula
Formula weight
C28H26Br2NNiP
626.01
150
C40H37Br2NNiOP2 + 1.24CH2Cl2
936.10
150
C32H34Br2NPPd
729.81
150(2)
Orthorhombic
P21cn
C28H26I2NPPd
767.71
150
C30H32NPPt
632.66
190
Temperature/K
Crystal system
Monoclinic
P21/n
Orthorhombic
Pcab
Monoclinic
P21
Monoclinic
C2/c
Space group
a/A
11.576(1)
90
13.535(1)
90
9.9766(2)
90
10.4664(2)
90
39.359(1)
90
a/1
b/A
23.162(3)
117.85(1)
11.171(1)
90
23.464(2)
90
13.5588(3)
90
16.3356(3)
99.3449(9)
16.3526(3)
90
9.388(1)
107.83(1)
14.772(1)
90
b/1
c/A
27.850(3)
90
21.8426(7)
90
g/1
U/A3
2648.3
4
1.570
8844.7
8
1.406
2954.7
4
1.641
2758.8
4
1.848
5196.1
8
1.62
Z
r (calcd)/mg mꢀ3
Absorption coefficient/mmꢀ1
F(000)
3.827
1256
2.503
3.409
1456
2.985
1472
5.48
2488
3775.3
4.1 to 26.4
49653
8500
y range for data collection
Reflections collected
Independent reflections
Rint
2.0 to 26.7
9456
5338
1 to 27
6291
4082
5.0 to 27.5
44207
12405
1 to 27.5
47816
5063
0.110
0.087
0.093
0.046
0.03
Data/parameters
Goodness-of-fit
R [I 4 3s(I)]
wR [I 4 3s(I)]
2572/298
1.0865
0.1178
0.1040
3915/512
1.2474
0.0581
0.0658
4082/334
1.0579
0.0394
0.0344
10511/596
1.0807
0.0306
0.0336
5063/317
1.1085
0.0279
0.0328
did not lead to substantial improvements in the agreement of
calculated and observed structure factors. The large anisotro-
pic thermal parameters of several of the C atoms may also be
indicative of unresolved disorder, but in view of the paucity of
observed diffraction data, it is not possible to model this
meaningfully. For complex 2, three distinct solvent sites were
located in difference Fourier maps and the coordinates, aniso-
tropic thermal parameters and site occupancies of the C and Cl
atoms were subsequently refined. The P–H hydrogen atom was
located in a difference Fourier map and its coordinates and
isotropic thermal parameter subsequently refined.
14 M. A. Jalil, S. Fujinami and H. Nishikawa, J. Chem. Soc., Dalton
Trans., 2001, 1091.
15 O. Daugulis and M. Brookhart, Organometallics, 2002, 21, 9.
16 A. Baceiredo, G. Bertrand, P. Dyer, J. Kawcett, N. Griep-Ram-
ing, O. Guerret, M. J. Hanton, D. R. Russel and A.-M. William-
son, New J. Chem., 2001, 25, 591.
17 A. Apfelbacher, P. Braunstein, L. Brissieux and R. Welter,
J. Chem. Soc., Dalton Trans., 2003, 1669.
18 G. Muller, M. Klinga, P. Osswald, M. Leskela and B. Rieger,
Z. Naturforsch. B, 2002, 57, 803.
19 Z. Guan and W. J. Marshall, Organometallics, 2002, 21, 3580.
20 X. Liu, T. K. W. Ong, S. Selvaratnam, J. J. Vittal, A. J. P. White,
D. J. Williams and P.-H. Leung, J. Organomet. Chem., 2002, 643, 4.
21 M. Koprowski, R.-M. Sebastian, V. Maraval, M. Zablocka,
V. Cadiemo, B. Donnadieu, A. Igau, A.-M. Caminade and
J.-P. Majoral, Organometallics, 2002, 21, 4680.
Acknowledgements
22 D. B. Grotjahn, D. Combs, S. Van, G. Aguirre and F. Ortega,
Inorg. Chem., 2000, 39, 2080.
23 M. A. Jalil, S. Fujinami, H. Senda and H. Nishikawa, J. Chem.
Soc., Dalton Trans., 1999, 1655.
We thank Balliol College for a Dervorguilla Scholarship (SIP),
the Royal Society for a University Research Fellowship (KSC)
and EPSRC for support.
24 K. R. Reddy, K. Surekha, G. H. Lee, S. M. Peng and S. T. Liu,
Organometallics, 2000, 19, 2637.
25 D. Morales-Morales, R. Redon, Y. Zheng and J. R. Dilworth,
Inorg. Chim. Acta, 2002, 328, 39.
References
1
G. J. P. Britovsek, V. C. Gibson and D. F. Wass, Angew. Chem.,
Int. Ed., 1999, 38, 428.
E. Lindner, S. Pautz and M. Haustein, Coord. Chem. Rev., 1996,
155, 145.
A. Bader and E. Lindner, Coord. Chem. Rev., 1991, 108, 27.
W. Keim, Angew. Chem., Int. Ed. Engl., 1990, 29, 235.
W. Keim, New J. Chem., 1994, 18, 93.
P. Braustein, Y. Chauvin, S. Mercier, L. Saussine, A. DeCian and
J. Fischer, J. Chem. Soc., Chem. Commun., 1994, 2203.
J. Pietsch, P. Braunstein and Y. Chauvin, New J. Chem., 1998, 22,
467.
C. M. Killian, J. P. McDevitt, P. B. Mackenzie, L. S. Moody and
J. A. Ponasik, Jr., Catalyst composition for the polymerisation of
olefins, WO9840420, USA, 1998.
Z. Guan, Bidentate ligand catalysts for polymerisation of ethylene,
WO2000059956, USA, 2000.
26 K. S. Coleman, M. L. H. Green, S. I. Pascu, N. H. Rees, A. R.
Cowley and L. H. Rees, J. Chem. Soc., Dalton Trans., 2001, 3384.
27 S. I. Pascu, Nickel(II), Palladium(II), Platinum(II) and Rhodiu-
m(I) Complexes of Iminophosphine Ligands, D. Phil. Thesis,
University of Oxford, Oxford, 2002.
28 S. H. de Graaf, J. Boersma and G. van Koten, J. Organomet.
Chem., 1988, 358, 545.
29 S. H. de Graaf, J. Boersma, W. J. J. Smeets, S. A. L. and G. van
Koten, Organometallics., 1989, 8, 2907.
2
3
4
5
6
7
8
30 T. Yagyu, M. Hamada, K. Osakada and T. Yamamoto, Organo-
metallics, 2001, 20, 1087.
31 D. P. Gates, S. A. Svejda, E. Onate, C. M. Killian, L. K. Johnson,
P. S. White and M. Brookhart, Macromolecules, 2000, 33, 2320.
32 L. Sacconi, F. Mani and A. Bencini, in Comprehensive Coordina-
tion Chemistry, ed. G. Wilkinson, Pergamon Press, Oxford, 1987,
vol. 5, p. 116.
9
10 P. Braunstein, J. Pietsch, Y. Chauvin, S. Mercier, L. Saussine, A.
DeCian and J. Fischer, J. Chem. Soc., Dalton Trans., 1996, 3571.
11 V. C. Gibson, A. Tomov, A. J. P. White and D. J. Williams, Chem.
Commun., 2001, 719.
33 C. Ercolani, J. V. Quagliano and L. M. Vallarino, Inorg. Chim.
Acta, 1973, 9, 413.
34 L. H. Pignolet Jr., W. W. Horrocks and R. H. Holm, J. Am.
Chem. Soc., 1970, 92, 1855.
12 X. Liu, K. F. Mok and P.-H. Leung, Organometallics, 2001, 20,
3918.
13 M. A. Jalil, S. Fujinami and H. Nishikawa, J. Chem. Soc., Dalton
Trans., 1999, 3499.
35 R. G. Hayter and S. Humiec, Inorg. Chem., 1965, 4, 1701.
36 E. Alyea, G. Ferguson, B. L. Ruhl and R. Shakya, Polyhedron,
1965, 4, 1701.
37 J. C. Cloyd, Jr. and D. W. Meek, Inorg. Chim. Acta, 1972, 12, 607.
396
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7

View Article Online
38 G. Booth and J. Chatt, J. Chem. Soc., 1965, 3238.
39 L. Que, Jr. and L. H. Pignolet, Inorg. Chem., 1973, 12, 156.
40 K. K. Chow and C. A. MacAuliffe, Inorg. Chim. Acta, 1974,
10, 197.
41 L. Crociani, G. Bandoli, A. Dolmella, M. Basato and B. Corain,
Eur. J. Inorg. Chem., 1998, 1811.
47 O. Dahl, Acta Chem. Scand., 1969, 23, 2342.
48 H. Okamoto, K. Shozo, M. Ogasawara, M. Konnai and
T. Takematsu, Agric. Biol. Chem., 1991, 55, 2733.
49 Z. Otwinowski and W. Minor, in Methods in Enzymology, eds.
C. N. Carter, Jr. and R. M. Sweet, Academic Press, London, 1996,
vol. 276,p. 307.
42 F. H. Allen, J. E. Davies, J. J. Galloy, O. Johnson, O. Kennard,
C. F. Macrae, E. M. Mitchell, G. F. Mitchell, J. M. Smith and
D. G. Watson, J. Chem. Inf. Comput. Sci., 1991, 31, 187.
50 A. Altomare, G. Carascano, C. Giacovazzo and A. Guagliardi,
J. Appl. Crystallogr., 1993, 26, 343.
51 (a) D. J. Watkin, C. K. Prout, J. R. Carruthers and P. W.
Betteridge, CRYSTALS, Oxford, UK, 1996; (b) P. W. Betteridge,
J. R. Carruthers, R. I. Cooper, K. Prout and D. J. Watkin,
J. Appl. Crystallogr., 2003, 36, 1487.
43 W. A. Herrmann, M. Elison, J. Fischer, C. Kocher and G. R. J.
¨
Artus, Angew. Chem., Int. Ed. Engl., 1995, 34, 2371.
44 E. Costa, P. Pringle and M. Ravetz, Inorg. Synth., 1997, 31, 284.
45 F. T. Lapido and G. K. Anderson, J. Organomet. Chem., 1994, 13,
303.
52 D. J. Watkin, C. K. Prout and L. J. Pearce, CAMERON, Oxford,
UK, 1996.
46 W. Kaschube, K. R. Poerschke and G. Wilke, J. Organomet.
Chem., 1988, 355, 525.
53 N. Walker and D. Stuart, Acta Crystallogr., Sect. A., 1983,
39, 158.
N e w J . C h e m . , 2 0 0 5 , 2 9 , 3 8 5 – 3 9 7
397