Photochemical synthesis of a palladium dichloromethyl complex, {(hexyl)HC(N-methyl-imidazol-2-yl)2}Pd(CHCl2)Cl. X-ray molecular structures of {(hexyl)HC(N-methylimidazolyl-2-yl)2} Pd(X)Cl, X=Cl, and CHCl2

Article abstract of DOI:10.1016/S0022-328X(03)00693-4

The reaction of (hexyl)HC(mim)₂ (1, mim= N -methyl-imidazol-2-yl) with (cod)PdMeCl in C₆H₆ yields {(hexyl)HC(mim)₂}Pd(Me)Cl (3). The photochemical reaction of 3 with CH₂Cl₂ at 23 °C in ambient room light yields {(hexyl)HC(mim)₂}Pd(CHCl₂)Cl (4). It is proposed that this reaction proceeds by homolytic scission of the Pd-Me bond of 3.

Full text of DOI:10.1016/S0022-328X(03)00693-4

Journal of Organometallic Chemistry 683 (2003) 240Á248
/
www.elsevier.com/locate/jorganchem
Photochemical synthesis of a palladium dichloromethyl complex,
{(hexyl)HC(N-methyl-imidazol-2-yl)2}Pd(CHCl2)Cl.
X-ray molecular structures of {(hexyl)HC(N-methylimidazolyl-2-
yl)2}Pd(X)Cl, Xꢀ
/
Cl, and CHCl2
Christopher T. Burns, Han Shen, Richard F. Jordan *
Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, IL 60637, USA
Received 7 April 2003; received in revised form 3 July 2003; accepted 14 July 2003
Abstract
The reaction of (hexyl)HC(mim)2 (1, mimꢀ
yl)HC(mim)2}Pd(Me)Cl (3). The photochemical reaction of 3 with CH2Cl2 at 23 8C in ambient room light yields {(hex-
Me bond of 3.
/N-methyl-imidazol-2-yl) with (cod)PdMeCl in C6H6 yields {(hex-
yl)HC(mim)2}Pd(CHCl2)Cl (4). It is proposed that this reaction proceeds by homolytic scission of the PdÃ
/
# 2003 Elsevier B.V. All rights reserved.
Keywords: Photochemical synthesis; Palladium dichloromethyl complexes; Molecular structures
1. Introduction
{(hexyl)HC(mim)2}Pd(CHCl2)Cl (mimꢀ
dazol-2-yl). Metal alkyls containing a-halogen substitu-
ents are quite common [3Á5]. In particular, transition
metal MCHCl2 complexes [6Á16] and main group
MCHCl2 compounds [17Á19] have been synthesized
previously, typically by oxidative addition of CHCl3 to
low valent precursors or by alkylation of metal halides
by LiCHCl2 [20].
/
N-methyl-imi-
Metal-catalyzed insertion polymerization of vinyl
halides is a challenging goal. Previously we showed
that single-site olefin polymerization catalysts based on
early or late transition metals undergo facile net 1,2
insertion of vinyl chloride (VC), but the resulting
LnMCH2CHRCl species undergo rapid b-Cl elimination
to form LnMCl products and CH2Ä
precludes insertion polymerization [1]. Similar 1,2 inser-
tion/b-X elimination reactions of CH2ÄCHX (XꢀF,
/
/
/
/
CHR olefins, which
/
/
Cl, Br) with metal hydrides or discrete or in situ-
generated metal alkyl species have been reported [2].
An alternative approach to the insertion polymerization
of VC would involve chain growth by 2,1 insertion, so
that intermediate a-Cl-substituted LnMCHClCH2R al-
kyl species are generated. As part of an effort to assess
the viability of 2,1 VC insertion polymerization, we are
studying the chemistry of metal alkyls with a-halogen
substituents. Here we describe the synthesis and struc-
2. Results and discussion
2.1. Ligand synthesis
The neutral bis-imidazole ligand (hexyl)HC(mim)2 (1)
was prepared as shown in Scheme 1. Deprotonation of
N-methylimidazole (mim) with n-BuLi at ꢁ65 8C
followed by addition of diethyl carbonate yields
(mim)2CO [21]. Reduction of (mim)2CO to (mim)2CH2
/
ture of
a
new Pd dichloromethyl complex
with KOH in H2NNH2×
nation with n-BuLi (ꢁ78 8C, 2 h) and quenching with 1-
iodohexane (ꢁ78Á23 8C) produces 1 as a white solid in
92% yield [23].
/
H2O [22], followed by deproto-
/
* Corresponding author. Tel.:
37020805.
E-mail address: rfjordan@uchicago.edu (R.F. Jordan).
ꢂ
/
1-77-37026429; fax:
ꢂ/1-77-
/
/
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00693-4

C.T. Burns et al. / Journal of Organometallic Chemistry 683 (2003) 240Á
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241
Scheme 1.
2.2. Synthesis of {(hexyl)HC(mim)2}PdCl2 and
{(hexyl)HC(mim)2}PdClMe
The reaction of 1 with (cod)PdCl2 (codꢀ1,5-cyclooc-
/
tadiene) in CH2Cl2 yields {(hexyl)HC(mim)2}PdCl2 (2,
Scheme 2) as an orange solid. In contrast to earlier
bis(imidazolyl)methane complexes, 2 is highly soluble in
CH2Cl2 due to the hexyl substituent [24]. Similarly, the
reaction of 1 with (cod)Pd(Me)Cl in benzene yields
{(hexyl)HC(mim)2}Pd(Me)Cl (3, Scheme 2) as an off-
white solid. Complex 3 is soluble in CH2Cl2 and
CH2ClCH2Cl, sparingly soluble in C6H5Cl, and insolu-
ble in benzene and toluene.
2.3. Molecular structure of {(hexyl)HC(mim)2}PdCl2
(2)
Fig. 1. Two views of the molecular structure of {(hex-
yl)HC(mim)2}PdCl2 (2). Hydrogen atoms are omitted.
The molecular structure of 2 was determined by X-ray
diffraction. ORTEP views of 2 are shown in Fig. 1. The
crystallographic data and a list of selected bond
distances and angles for 2 are given in Tables 1 and 2,
respectively. Compound 2 adopts a square planar
88.2(2)8), and the other angles at Pd are close to 908.
The chelate ring adopts a boat conformation. The angle
structure about palladium as expected. The sum of the
˚
between the NÃ
C(22)ÃC(18)ÃN(5)/N(5)Ã
the angle between the NÃ
(N(6)ÃC(22)ÃC(18)ÃN(5)/C(18)Ã
/
CÃ
/
CÃ
/
N and NÃ
Pd(2)ÃN(6)) is 161.468, and
CÃCÃ
/
PdÃ
/
N planes (N(6)Ã
/
angles at Pdꢀ360.08, and the Pd lies 0.01 A out of the
/
/
/
/
/
NÃ
/
NÃ
/
ClÃ
/
Cl plane. The (N(5)Ã
/
PdÃ/N(6) angle is
/
/
/
N and CÃ
C(24)ÃC(22))
/
CÃ
/
C planes
/
/
/
/
/
is
147.208. Overall, the structure 2 is very similar to those
of the bis(pyrazolyl)methane complexes {Me2C(pz)2}-
PdCl2 and {Ph2C(pz)2}PdCl2 [25,26].
The 1H-NMR spectrum of 2 at 25 8C contains one set
of imidazolyl H4 (d 7.43) and H5 (d 6.88) resonances
and one set of hexyl resonances, which is consistent with
the Cs-symmetric structure observed in the solid state.
The NOESY spectrum of 2 contains crosspeaks between
the imidazolyl NÃ
/
Me resonance and the bridgehead
methine resonance, which is consistent with placement
of the hexyl group in the apical position, as observed in
the solid state. This conformation minimizes steric
repulsion between the NÃ/Me groups and the hexyl
group. Previously, Canty proposed an analogous struc-
ture for {MeHC(mim)2}PdMe2 based on NMR and
molecular modeling studies [27].
Scheme 2.

242
C.T. Burns et al. / Journal of Organometallic Chemistry 683 (2003) 240Á248
/
Table 1
Crystal data and structure refinement for 2 and 4
Table 2
˚
Selected bond lengths (A) and angles (8) for 2
Complex
2×
/
2 CH2Cl2
4
Bond lengths
Cl(3)Ã
N(5)Ã
N(5)Ã
/
Pd(2)
2.308(6) Cl(4)Ã
2.014(5) N(6)Ã
1.336(8) N(6)Ã
/
Pd(2)
2.290(1)
2.009(5)
1.334(8)
1.503(9)
Empirical formula
C30H48Cl4N8Pd2ꢂ
2CH2Cl2
/
C16H25Cl3N4Pd
/
Pd(2)
/
Pd(2)
/
C(18)
/
C(22)
Formula weight
Temperature (K)
1021.04 (including sol- 486.15
vent)
C(18)Ã
Bond angles
N(5)ÃPd(2)Ã
N(5)ÃPd(2)Ã
N(6)ÃPd(2)Ã
N(5)ÃPd(2)Ã
N(6)ÃPd(2)Ã
Cl(3)ÃPd(2)Ã
C(16)ÃN(5)ÃC(18)
/C(24)
1.499(9) C(22)ÃC(24)
/
100
130
MoÁ
Monoclinic
P21/n
/
/
N(6)
Cl(3)
Cl(3)
Cl(4)
Cl(4)
88.2(2) C(16)Ã
90.8(2) C(18)Ã
178.0(2) N(5)ÃC(18)Ã
178.8(2) N(5)ÃC(18)Ã
90.6(2) N(7)ÃC(18)Ã
90.4(7) C(20)ÃN(6)Ã
107.2(6) C(20)ÃN(6)Ã
/
N(5)Ã
/
Pd(2)
Pd(2)
N(7)
127.1(5)
125.7(5)
109.1(6)
125.8(6)
125.0(6)
106.4(5)
126.8(4)
˚
Wavelength (A)
MoÁ
Monoclinic
P21/c
/Ka, 0.71073
/Ka, 0.71073
/
/
/
N(5)Ã
/
Crystal system
Space group
/
/
/
/
/
/
/
/
C(24)
C(24)
C(22)
Pd(2)
˚
a (A)
16.355(5)
13.834(4)
19.066(6)
93.475(6)
4306(2)
4
9.650(2)
15.865(3)
12.751(2)
94.440(3)
1946.4(6)
4
/
/
/
/
˚
b (A)
/
/Cl(4)
/
/
˚
c (A)
/
/
/
/
b (8)
3
V (A )
˚
Z
Dcalc (mg mꢁ3
m, mmꢁ1
)
1.575
1.326
1.659
1.371
Crystal size (mm)
2u range (8)
Limiting indices
0.45ꢃ
1.82Á25.03
195h 5
k 513, ꢁ195
/
0.20ꢃ
/
0.07
0.15ꢃ
2.48Á25.03
65h 511, ꢁ
k 518, ꢁ155l 5
/
0.10ꢃ
/
0.10
/
/
ꢁ/
/
/15, ꢁ
/165
/
ꢁ/
/
/
/185
/
/
/
/
l 5
/
22
/
/
/
/
15
Reflections collected 20 562
Independent reflec- 7586
tions
9723
3433
Rint
0.0294
Refinement method Full-matrix least-
0.0205
Full-matrix least-
squares on F2
3433/0/220
squares on F2
7586/0/462
Data/restraints/
parameters
Adsorption correc- SADABS based on re- SADABS based on
tion
dundant diffractions
redundant diffrac-
tions
Final R indices [I ꢀ
2s(I)]
/
R1ꢀ
0.1720
0.0749, wR2ꢀ
/
0.0689, wR2ꢀ
/
R1ꢀ
0.1482
R1ꢀ0.0536, wR2ꢀ
/
0.0527, wR2ꢀ
/
R indices (all data) R1ꢀ
/
/
/
/
0.1754
Goodness-of-fit on 1.152
F2
0.1489
1.196
Scheme 3.
Largest difference
peak and hole (e
2.911 and ꢁ
/0.986
1.073 and ꢁ1.330
/
The 1H- and 13C-NMR spectra of 4 establish that the
two mim rings are inequivalent. In the 1H-NMR
ꢁ3
˚
A
)
Diffractometer
Bruker SMART APEX Bruker SMART
APEX
spectrum, the PdÃ
6.34, which is the only singlet in the downfield region. In
the 13C-NMR spectrum, the PdÃ
CHCl2 resonance is
/
CHCl2 resonance is identified at d
/
2.4. Generation of {(hexyl)HC(mim)2}Pd(CHCl2)Cl
(4)
identified at d 62.1, which is the only methine carbon
resonance other than the CH(mim)2(hexyl) resonance
according to DEPT-135 and DEPT-90 NMR experi-
Complex 3 is stable in CH2Cl2 at 23 8C, but only if
protected from light through the use of amberized
glassware or storage of the solution in the dark.
Exposure of a CH2Cl2 solution of 3 to ambient room
light for 68 h at 23 8C results in complete disappearance
of 3 and formation of a 95/5 mixture of {(hex-
yl)HC(mim)2}Pd(CHCl2)Cl (4) and dichloride complex
2 (Scheme 3) [28]. Small amounts of crystalline 4 were
obtained by recrystallization of the product mixture
ments. These chemical shifts are close to those of the Ã
/
CHCl2 unit of (dppe)Pd(CHCl2)Cl (1H d 5.98; 13C{1H}
d 72.3) [14]. The positive ion ESI mass spectrum [29] of
4 in CH2Cl2ÁMeCN contains peak envelopes with
/
isotope distributions that match calculated patterns for
{(hexyl)HC(mim)2}Pd(CHCl2)ꢂ, {(hexyl)HC(mim)2}-
Pd(CHCl2)(MeCN)ꢂ
and
Pd(CHCl2)]2(m-Cl)ꢂ, which are expected products of
ionization of the PdÃCl bond of 4 in CH3CN. Observed
[{(hexyl)HC(mim)2}-
/
from CH2Cl2Ápentane, which enabled X-ray crystal-
/
and calculated molecular ion envelopes from ESIMS
lographic analysis of 4. Further exposure of the solution
to room light results in complete conversion to 2.
spectra of 4 are shown in Fig. 2.

C.T. Burns et al. / Journal of Organometallic Chemistry 683 (2003) 240Á
/248
243
Fig. 2. Observed (top) and calculated (bottom) molecular ion envelopes from ESI mass spectra of cations derived from 4: (a)
{(hexyl)HC(mim)2}Pd(CHCl2)ꢂ; (b) {(hexyl)HC(mim)2}Pd(CHCl2)(MeCN)ꢂ; (c) [{(hexyl)HC(mim)2}Pd(CHCl2)](m-Cl)ꢂ
.
2.5. Molecular structure of 4
The molecular structure of 4 was determined by X-ray
diffraction. ORTEP views of 4 are shown in Fig. 3. The
crystallographic data and a list of selected bond
distances and angles for 4 are given in Tables 1 and 3,
respectively.
The core structure of 4 is very similar to that of 2. The
geometry at Pd is square planar, with the sum of the
˚
angles at Pd being 360.18, and the Pd lies 0.03 A out of
the N(1)Ã
/
N(2)Ã
/
C(1)Ã
/
Cl(1) plane. The (N(1)Ã
/
PdÃ/N(2)
angle is 86.4(2)8), and the other angles at Pd are close to
908. The chelate ring adopts a boat conformation which
is very similar to that of 2. The NÃ
dihedral angle (N(1)ÃC(5)ÃC(9)ÃN(2)/C(9)Ã
C(5)ꢀ144.48) is similar to that in 2, while the NÃ
CÃN/NÃPdÃN dihedral angle (N(1)ÃC(5)ÃC(9)ÃN(2)/
N(1)ÃPdÃN(2)ꢀ153.08) is ca. 88 smaller than the
/
CÃ
/
CÃ
/
N/CÃ
C(10)Ã
CÃ
/
CÃ
/
C
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
corresponding dihedral angle in 2. This difference is
ascribed to greater steric repulsion between the CHCl2
group and the (hexyl)HC(mim)2 ligand in 4, versus the
smaller Cl and the (hexyl)HC(mim)2 ligand in 2. The
˚
Pd(1)Ã
than Pd(1)Ã
that the CHCl2 ligand has a higher trans influence than
/N(2) bond length (2.095(5) A) is slightly longer
˚
/
N(1) bond length (2.055(5) A), which shows
˚
chloride. The Pd(1)Ã
/
C(1) (2.035(6) A) and Pd(1)Ã
(2.314(2) A) distances are both shorter than the corre-
sponding distances in (dppe)Pd(CHCl2)Cl (PdÃC:
Cl: 2.356(1) A). The two chloride atoms
CHCl2 unit both point away from the PdÃCl(1)
unit, which minimizes steric crowding between those
groups. The same orientation of the ÃCHCl2 unit was
/
Cl(1)
˚
/
˚
˚
2.105(5) A; PdÃ
/
of the Ã
/
/
Fig. 3. Two views of the molecular structure of {(hex-
yl)HC(mim)2}Pd(CHCl2)Cl (4). Hydrogen atoms are omitted.
/

244
C.T. Burns et al. / Journal of Organometallic Chemistry 683 (2003) 240Á248
/
Table 3
2.6. Reaction mechanism
˚
Selected bond lengths (A) and angles (8) for 4
Compound 3 is stable in CH2Cl2 solution at ambient
temperature for days, but only if protected from light. If
a CH2Cl2 solution of 3 is exposed to ambient room light
in the absence of O2, the formation of 4 is observed
within 4 h and is complete within 68 h. Previous studies
show that photolysis of Pd(II), Pt(II), Pt(IV) and other
Bond lengths
C(1)Ã
C(1)Ã
N(2)Ã
N(2)Ã
C(9)Ã
/
Pd(1)
2.035(6)
1.665(8)
2.095(5)
1.323(8)
1.506(8)
C(1)Ã
N(1)Ã
N(1)Ã
C(5)Ã
Cl(1)Ã
/
Cl(2)
1.840(7)
2.055(5)
1.318(8)
1.504(8)
2.314(2)
/Cl(3)
/
Pd(1)
/
Pd(1)
C(9)
/
C(5)
/
/C(10)
/C(10)
/Pd(1)
Bond angles
Cl(2)ÃC(1)Ã
Cl(2)ÃC(1)Ã
C(5)ÃN(1)Ã
C(9)ÃN(2)Ã
C(1)ÃPd(1)Ã
N(1)ÃPd(1)Ã
metal alkyls can result in MÃ
/
R bond homolysis [38].
/
/Cl(3)
111.9(4)
105.5(3)
123.5(4)
122.8(4)
89.3(2)
Cl(3)Ã
N(1)ÃC(5)Ã
N(2)ÃC(9)Ã
N(1)ÃPd(1)Ã
C(5)ÃC(10)Ã
N(2)ÃPd(1)Ã
/
C(1)Ã
/
Pd(1)
C(10)
C(10)
122.7(4)
125.4(5)
124.8(5)
86.4(2)
Thus, it is likely that the conversion of 3 to 4 involves
photolysis of 3 to generate a Pd(I) species and CH3+, H
atom abstraction from the solvent by CH3+, and
coupling of the Pd(I) and +CHCl2 intermediates, as
shown in Scheme 4. Consistent with this mechanism,
exposure of a solution of 3 in CD2Cl2 to ambient light
resulted in the formation of CDH3 (identified by the
/
/Pd(1)
/
/
/
/Pd(1)
/
/
/
/Pd(1)
/
/N(2)
/
/
Cl(1)
/
/C(9)
110.3(5)
91.1(1)
/
/
C(1)
93.3(2)
/
/Cl(1)
observed in (dppe)Pd(CHCl2)Cl [14]. This orientation
results in a close HÁ Á ÁCl contact between the PdÃCHCl2
and PdÃCl atoms which raises the possibility of
characteristic 1:1:1 triplet (JHD
1H-NMR
spectrum, and
ꢀ
/
2.0 Hz) at d 0.18 in the
/
{(hexyl)HC(mim)2}Pd
(CDCl2)Cl (4-d1), which was confirmed by the char-
/
CCl2HÁ Á ÁCl hydrogen bonding [30]. The possibility of
an interaction between the hydrogen of the CHCl2
group and the chlorine atom on Pd was investigated
1
acteristic Pd(CDCl2) resonance (1:1:1 triplet, JCD
ꢀ29
/
Hz) at d 62.1 in the 13C-NMR spectrum. The mechan-
ism of the conversion of 4 to 2 is unknown at this time.
Similar reactivity for 3 was found in CD2ClCD2Cl
and CDCl3. In CD2ClCD2Cl solution, 3 converts to 2 in
the presence of ambient room light over the course of 45
days. No intermediate species, e.g. {(hexyl)HC
(mim)2}Pd(CDClCD2Cl)Cl, were detected although
CDH3 was observed. In this case, it is expected that
the methyl radical produced by homolysis of 3 reacts
with the solvent to form CDH3, while the palladium
radical couples with the resulting solvent-derived radical
to form {(hexyl)HC(mim)2}Pd(CDClCD2Cl)Cl. This
species was not detected, possibly due to fast b-Cl
elimination to form 2 [1e]. The reaction of 3 in CDCl3 in
ambient room light is fast and produces 2 along with
CH4, CDH3, CH3CDCl2, CH3CCl3, and CH3Cl, which
are formed by coupling of radical intermediates [38]. In
contrast, 3 decomposes to Pd0 in C6D5Cl solution,
apparently by a non-photochemical process.
by 13C-NMR and IR measurements. For 4, the Ã
/
CHCl2
13C resonance appears as a doublet at d 62.1 with a 1JCH
1
value of 182 Hz. This JCH value is similar to values for
organic compounds containing CHCl2 groups, such as
1,1,2,2-tetrachloroethane (180 Hz) [31], and dichloro-
methane (178 Hz) [32]. The IR spectrum of 4 shows a
nCH stretch for the Ã
2227 cmꢁ1 for (hexyl)HC(mim)2Pd(CDCl2)Cl (4-d1)),
which is similar to that for Cl2CHCHCl2 (2985 cmꢁ1
/
CHCl2 group at 2956 cmꢁ1 (nCD
ꢀ
/
)
[33]. Thus there is no compelling NMR or IR evidence
for hydrogen bonding in 4.
˚
The PdÃ
to PdÃ
plexes, in which the Me group is trans to a neutral N-
donor ligand, e.g. (C(ÄO)(N-methylbenzimidazol-2-
/
CHCl2 bond distance (2.035(6) A) is similar
/
Me bond distances in related L2Pd(Me)Cl com-
/
˚
yl)2}Pd(Me)Cl (2.030(4) A) [34] and {8-(2-pyridyl)qui-
˚
noline)}Pd(Me)Cl (2.031(5) A) [35]. The close similarity
of PdÃCHCl2 and PdÃMe distances in those systems
reflects a balance of electronic and steric effects. It is
well established that MÃCF3 bonds are shorter (typi-
cally by 0.05 A) than corresponding MÃMe bonds. This
difference has been ascribed to hybridization effects,
increased ionic character in MÃCF3 versus MÃCH3
/
/
/
˚
/
/
/
bonds and, more controversially, to d-sꢄCÃF backbonding
[36]. The presence of the two electron withdrawing a-Cl
substituents in a PdÃ
/
CHCl2 complex might be expected
to shorten the PdÃ
/
C bond for the same reasons that MÃ
/
CF3 bonds are short. However, due to the large Cl
radius, this effect will be attenuated by steric crowding.
In fact, in complex 4 there is a close contact between one
˚
Cl(3): 2.692 A), which
is shorter than the sum of van der Waals radii of H and
a-Cl and a mim hydrogen (H(2)Ã
/
˚
Cl (2.95 A) [37], indicative of steric crowding between
these ligands.
Scheme 4.

C.T. Burns et al. / Journal of Organometallic Chemistry 683 (2003) 240Á
/248
245
3. Conclusions
4.2. Preparations
The reaction of {(hexyl)HC(mim)2}Pd(Me)Cl (3) in
CH2Cl2 in ambient room light yields {(hex-
yl)HC(mim)2}Pd(CHCl2)Cl (4). This reaction proceeds
4.2.1. (Hexyl)HC(mim)2 (1)
A slurry of (mim)2CH2 (1.51 g, 8.60 mmol) in THF
(150 ml) at ꢁ78 8C was prepared and n-BuLi (2.5 M in
/
by homolysis of the PdÃ
structure of 4 has been determined by X-ray diffraction
C bond length falls in the range observed
for related LnPd(Me)Cl complexes, reflecting a balance
of electronic and steric effects.
/
Me bond of 3. The molecular
hexanes, 3.78 ml, 9.45 mmol) was added over 5 min
while the mixture was stirred. A clear deep yellow
and the PdÃ
/
solution formed. The solution was stirred at ꢁ78 8C
/
for 2 h, and 1-iodohexane (2.15 g, 10.1 mmol) was added
by syringe. The mixture was allowed to warm to 25 8C
over 12 h while stirring was maintained. The volatiles
were removed under vacuum and the resulting clear oil
was dissolved in CH2Cl2 (200 ml). The CH2Cl2 solution
was washed with H2O (300 ml), NaHCO3 (300 ml), and
brine (300 ml), and finally dried over Na2SO4. The
Na2SO4 was filtered off and the volatiles were removed
from the filtrate under vacuum to afford a clear oil. The
oil was suspended in pentane (50 ml) and the pentane
4. Experimental
4.1. Starting materials and general conditions
4.1.1. General comments
was removed under vacuum to give a yellowÁ
/
white
All manipulations were performed using dry box or
Schlenk techniques under an N2 atmosphere, or on a
high-vacuum line unless otherwise indicated. Solvents
were distilled from appropriate drying/deoxygenating
agents (THF: sodium benzophenone ketyl; CH2Cl2:
CaH2; CDCl3, CD2Cl2, C6D5Cl, and CD2ClCD2Cl:
P4O10). Pentane, hexanes, benzene and toluene were
purified by passage through columns of activated
alumina and BASF R3-11 oxygen removal catalyst.
Nitrogen was purified by passage through columns
containing activated molecular sieves and Q-5 oxygen
scavenger. (cod)Pd(Me)Cl [39], (mim)2CO [21], and
(mim)2CH2 [22] were prepared as described in the
literature. All other chemicals were purchased from
Aldrich and used without further purification. Elemen-
tal analyses were performed by Midwest Microlabs
(Indianapolis, IN) and Galbraith Laboratories (Knox-
ville, TN).
solid. The solid was extracted with hexanes (3ꢃ200 ml).
/
The clear extracts were combined and taken to dryness
under vacuum to yield a white, fluffy solid (2.04 g, 92%).
1H-NMR (CD2Cl2): d 6.85 (s, 2H, H4-mim), 6.76 (s,
2H, H5-mim), 4.33 (t, Jꢀ
/
8, 1H, CH), 3.44 (s, 6H,
), 1.28 (m, 8H,
6.5, 3H,
NCH3), 2.25 (q, Jꢀ8, ÃCHCH2CH2Ã
/
/
/
CHCH2CH2CH2CH2CH2CH3), 0.86 (t, Jꢀ
/
CH2CH3). 13C NMR (CD2Cl2): d 147.1, 127.0, 121.9,
38.9, 33.0, 32.1, 31.7, 29.4, 28.0, 23.0, 14.2. Anal. Calc.
for C15H24N4: C, 69.19; H, 9.29; N, 21.51. Found: C,
68.88; H, 8.85; N, 21.18%.
4.2.2. {(Hexyl)HC(mim)2}PdCl2 (2)
A solution of (cod)PdCl2 (0.536 g, 1.88 mmol) and
(mim)2CH(hexyl) (0.500 g, 1.92 mmol) in CH2Cl2 (50
ml) was stirred for 12 h at 25 8C. The clear orange
solution was concentrated to 25 ml under vacuum and
cooled to ꢁ
of an orange crystalline solid. The solid was collected by
filtration, washed with Et2O (3ꢃ30 ml) and hexanes
(3ꢃ30 ml) and dried under vacuum yielding an orange
powder (0.560 g, 68%). H-NMR (CD2Cl2): d 7.43 (s,
2H, H4-mim), 6.88 (s, 2H, H5-mim), 4.25 (t, Jꢀ7.5, 1H,
CH), 3.76 (s, 6H, NCH3), 2.40 (m, 2H, CH2), 1.36 (m,
7,
/
78 8C for 4 h, resulting in the precipitation
NMR spectra were recorded on Bruker DMX-500 or
DRX-400 spectrometers, in Teflon-valved tubes, at
/
1
23 8C unless otherwise indicated. H- and 13C-chemical
/
1
shifts are reported versus SiMe4 and were determined by
reference to residual 1H- and 13C-solvent signals. All
coupling constants are reported in Hz. DEPT (Distor-
tionless Enhancement by Polarization Transfer) spectra
were acquired and processed using standard Bruker
programs.
Electrospray mass spectra were recorded on freshly
prepared samples (ca. 1 mg mlꢁ1 in CH2Cl2) using an
Agilent 1100 LC-MSD spectrometer incorporating a
/
4H, CH2CH2), 1.29 (m, 4H, CH2CH2), 0.87 (t, Jꢀ
/
3H, CH2CH3). 13C NMR (CD2Cl2): d 143.5, 128.7,
121.2, 38.1, 34.8, 34.6, 31.9, 29.2, 27.7, 22.9, 14.1. Anal.
Calc. for C15H24Cl2N4Pd: C, 41.16; H, 5.05; N, 12.80.
Found: C, 41.09; H, 5.51; N, 12.55%.
quadrupole mass filter with a m/z range of 0Á
/3000. A 5
4.2.3. {(Hexyl)HC(mim)2}Pd(Cl)Me (3)
ml sample was injected by flow injection (MeCN) using
an autosampler. Purified nitrogen was used as both the
nebulizing and drying gas. Typical instrumental para-
meters: drying gas temperature 350 8C, nebulizer pres-
sure 35 psi, drying gas flow 12.0 l minꢁ1, fragmentor
voltage 70 V.
A solution of (cod)Pd(Cl)Me (0.40 g, 1.5 mmol) and
(mim)2CH(hexyl) (0.41 g, 1.6 mmol) in benzene (30 ml)
was stirred for 2 h at 25 8C. A white solid precipitated
immediately. The solid was isolated by filtration, rinsed
with benzene (2ꢃ
/20 ml), and dried under vacuum (0.60
1
g, 94%). H-NMR (CD2Cl2): d 7.23 (d, Jꢀ1, 1H, H4/
/

246
C.T. Burns et al. / Journal of Organometallic Chemistry 683 (2003) 240Á248
/
H5-mim), 6.99 (d, Jꢀ
1, 1H, H4/H5-mim), 6.81 (d, Jꢀ
4.17 (t, Jꢀ7.6, 1H, CH), 3.74 (s, 3H, NCH3), 3.69 (s,
3H, NCH3), 2.43 (m, 1H, CHCH2), 2.27 (m, 1H,
7, 3H,
CH2CH3), 0.61 (s, 3H, PdCH3). 13C{1H}-NMR
(CD2Cl2): d 146.0, 144.2, 127.5, 127.4, 121.1, 121.0,
38.1 (CH2), 34.5 (NCH3), 34.0 (CH), 33.8 (NCH3),
31.9, (CH2), 29.2 (CH2), 27.7 (CH2), 22.8 (CH2), 14.1
/
1, 1H, H4/H5-mim), 6.90 (d, Jꢀ
/
and slowly cooling the mixture down to ꢁ80 8C. Single
crystals of 4 were obtained after 3 days.
/
/1, 1H, H4/H5-mim),
/
CHCH2), 1.22 (m, 8H, (CH2)4), 0.85 (t, Jꢀ
/
5. Supplementary material
Crystallographic data for the structural analyses have
been deposited at the Cambridge Crystallographic Data
Centre, and allocated the deposition numbers CCDC
no. 207054 for 2 and 207053 for 4. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2 1EZ,
(CH2CH3),
ꢁ6.4 (PdCH3). Anal. Calc. for
/
C16H27ClN4Pd: C, 46.05; H, 6.52; N, 13.43. Found: C,
45.81; H, 6.49; N, 13.08%.
UK (Fax: ꢂ44-1223-336033; e-mail: deposit@ccdc.
cam.ac.uk or http://www.ccdc.cam.ac.uk).
/
4.2.4. {(Hexyl)HC(mim)2}Pd(CHCl2)Cl (4)
A
Schlenk flask was charged with {(hex-
yl)HC(mim)2}Pd(Me)Cl (110 mg, 0.264 mmol) and
CH2Cl2 (10 ml) was added by cannula transfer. The
pale yellow solution was stirred at 23 8C in the presence
of ambient room light for 68 h to yield a clear, more
intensely yellow solution. The volatiles were removed
under vacuum to afford a pale yellow solid (112 mg,
88%). 1H-NMR spectrum showed that the sample
Acknowledgements
We thank Dr Ian Steele and Rory Waterman for
assistance with X-ray diffraction analyses and Dr
Chang-Jin Qin for assistance with ESIMS experiments.
This work was supported by the Edison Polymer
Innovation Corporation and the Department of Energy
(DE-FG02-00ER15036).
contained ca. 5% {(hexyl)HC(mim)2}PdCl2 (2, vide
1
supra). H-NMR (CD2Cl2): d 7.82 (d, Jꢀ
/
2, 1H), 7.23
2, 1H), 6.82 (d, Jꢀ2, 1H),
6.34 (s, 1H, PdCHCl2), 4.18 (dd, Jꢀ9, 7, (CH2)4CH),
3.75 (s, 3H, NÃCH3), 3.69 (s, 3H, NÃCH3), 2.68 (m, 1H,
CHCHH), 2.31 (m, 1H, CHCHH), 1.36Á1.26 (m, 8H,
(CH2)4), 0.86 (t, Jꢀ
7, 3H, CH2CH3). 13C{1H}-NMR
(d, Jꢀ
/
2, 1H), 6.96 (d, Jꢀ
/
/
/
/
/
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