Neopentyl- and trimethylsilylmethylpalladium chemistry: Synthesis of reagents for organopalladium chemistry and the crystal structure of the neopentyl(phenyl)palladium(IV) complex [Pd(mq)(CH2CMe3)Ph(bpy)]Br (mq =8-methylquinolinyl, bpy =2,2′-bipyridine)

Article abstract of DOI:10.1016/S0020-1693(02)00978-7

Synthetic routes to neopentyl and trimethylsilylmethyl complexes of Pd(II) are reported, Pd(CH₂EMe₃)Ph(tmeda) [E=C (1), Si (3); tmeda=N,N,N′,N′-tetramethylethylenediamine] and Pd(CH₂EMe₃)Ph(bpy) [E=C (2), Si (4); bpy=2,2′-bipyridine]. Complexes 1 and 3 are formed on the reaction of PdIPh(tmeda) with LiCH₂EMe₃, and they react with bpy to give 2 and 4. Oxidative addition reactions of 8-(bromomethyl)quinoline (mqBr) with Pd(CH₂EMe₃)Ph(bpy) result in the formation of octahedral Pd(IV) complexes [Pd(mq)(CH₂EMe₃)Ph(bpy)]Br [E=C (5), Si (6)]. An X-ray structural analysis for 5, the first example of a stable cationic arylpalladium(IV) complex, shows a fac-PdC₃N₃ configuration with the neopentyl group trans to the quinoline nitrogen donor atom.

Full text of DOI:10.1016/S0020-1693(02)00978-7

Inorganica Chimica Acta 338 (2002) 94ꢁ98
/
www.elsevier.com/locate/ica
Neopentyl- and trimethylsilylmethylpalladium chemistry:
synthesis of reagents for organopalladium chemistry and the
crystal structure of the neopentyl(phenyl)palladium(IV) complex
[Pd(mq)(CH2CMe3)Ph(bpy)]Br (mqꢀ
/
8-methylquinolinyl,
bpyꢀ2,2?-bipyridine)
/
Allan J. Canty a,*, Marten J.G. Hettinga a, Jim Patel a, Michel Pfeffer b, Brian
W. Skelton c, Allan H. White c
a School of Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia
b Laboratory of Metal-Mediated Synthesis, UMR 7513 du CNRS, 4, rue Blaise Pascal, 67000 Strasbourg Cedex, France
c Department of Chemistry, University of Western Australia, Nedlands, Western Australia 6009, Australia
Received 17 December 2001; accepted 27 March 2002
Abstract
Synthetic routes to neopentyl and trimethylsilylmethyl complexes of Pd(II) are reported, Pd(CH2EMe3)Ph(tmeda) [Eꢀ
/C (1), Si
(3); tmedaꢀN,N,N?,N?-tetramethylethylenediamine] and Pd(CH2EMe3)Ph(bpy) [EꢀC (2), Si (4); bpyꢀ2,2?-bipyridine].
/
/
/
Complexes 1 and 3 are formed on the reaction of PdIPh(tmeda) with LiCH2EMe3, and they react with bpy to give 2 and 4.
Oxidative addition reactions of 8-(bromomethyl)quinoline (mqBr) with Pd(CH2EMe3)Ph(bpy) result in the formation of octahedral
Pd(IV) complexes [Pd(mq)(CH2EMe3)Ph(bpy)]Br [EꢀC (5), Si (6)]. An X-ray structural analysis for 5, the first example of a stable
/
cationic arylpalladium(IV) complex, shows a fac-PdC3N3 configuration with the neopentyl group trans to the quinoline nitrogen
donor atom.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Organopalladium; Intramolecular coordination; Neopentyl; Trimethylsilylmethyl; Palladium(IV); 8-Methylquinolinyl
1. Introduction
chemistry, including in recent reports of palladium
chemistry [3ꢁ8]. In the absence to date of ambient
/
Hydrocarbylpalladium(IV) complexes are a well-es-
tablished feature of the organometallic chemistry of
palladium and, prior to the first account of such
complexes [1], there were several reports that are
indicative of the formation of unstable Pd(IV) com-
plexes that could not be detected spectroscopically.
Among these reports is the observation that
temperature stable arylpalladium(IV) species, the po-
tential roles of arylpalladium(IV) species in catalysis,
and the interesting observation of Diversi et al., we have
developed syntheses of Pd(CH2EMe3)Ph(bpy) (EꢀC,
/
Si) and examined their reactivity toward 8-bromo-
methylquinoline (mqBr) in view of the enhanced stabi-
lity for Pd(IV) complexes expected to be imparted by the
presence of an intramolecular [Cꢀ
syntheses of potentially widely useful new alkyl(aryl)pal-
ladium(II) substrates Pd(CH2EMe3)Ph(L2) [EꢀC, Si;
L2ꢀtmeda (N,N,N?,N?-tetramethylethylenediamine),
/
N]ꢂ group [9,10]. The
Pd(CH2CMe3)2(bpy) (bpyꢀ
benzyl bromide to form PdBr(CH2CMe3)(bpy) and
PhCH2ꢀCH2CMe3 [2]. The neopentyl and the closely
/
2,2?-bipyridine) reacts with
/
/
related trimethylsilylmethyl groups have played an
important role in the development of organometallic
/
bpy] are reported, together with an X-ray structural
analysis for the octahedral Pd(IV) complex
[Pd(mq)(CH2CMe3)Ph(bpy)]Br.
* Corresponding author. Fax: ꢃ61-3-6226 2858
/
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 0 9 7 8 - 7

A.J. Canty et al. / Inorganica Chimica Acta 338 (2002) 94ꢁ
/
98
95
2. Experimental
yellow solution was allowed to warm slowly to ambient
temperature, then stored at ꢂ40 8C. Yellowꢁred crys-
tals formed over several days (58 mg, 58%). H NMR
/
/
1
The reagents PdIPh(tmeda) [11] and 8-(bromo-
methyl)quinoline [12] were prepared as described. Neo-
pentyllithium and trimethylsilylmethyllithium were
prepared as described [13], except that hexane was
used as a solvent and reflux undertaken for 2 days.
Alkyllithium reagents were purified by means of sub-
limation [LiCH2CMe3 (110 8C, 0.01 mmHg), LiCH2-
SiMe3 (95 8C, 0.01 mmHg)] prior to use. All reactions
and manipulations of air and moisture sensitive com-
pounds were carried out under an argon atmosphere
using glovebox and Schlenk techniques. Solvents were
purified and dried in the usual manner [14]. Other
reagents were purchased and used without further
purification. 1H NMR and 13C NMR spectra were
recorded on a Varian Unity Inova 400 WB spectrometer
operating at 100.587 (13C) or 399.703 (1H) MHz.
Chemical shifts are reported in ppm relative to SiMe4.
Microanalyses were performed by the Central Science
Laboratory, University of Tasmania.
3
(acetone-d6): d 9.15 (‘d’, Jꢀ5.6 Hz, 1, H6-bpy), 8.52
/
3
3
(‘d’, Jꢀ
/
8.0 Hz, 1, H3-bpy), 8.48 ( ‘d’, Jꢀ
7.8 Hz, 4Jꢀ
1.6 Hz, 1, H4?-bpy),
5.6 Hz,1, H6?-bpy), 8.12 (dt, Jꢀ
1.6 Hz, 1, H4-bpy), 7.80 (ddd, 3Jꢀ5.6 Hz, 3Jꢀ
Hz, 4Jꢀ1.2 Hz, 1, H5?-bpy), 7.60 (dd, 3Jꢀ8.0 Hz, 4Jꢀ
1.2 Hz, 2, H2,6-Ph), 7.50 (ddd, 3Jꢀ7.6 Hz, 3Jꢀ
5.2 Hz,
4Jꢀ
1.2 Hz, 1, H5?-bpy), 6.95 (m, 2, H3,5-Ph), 6.82 (tt,
3Jꢀ
1.6 Hz, H4-Ph), 1.72 (s, 2, CH2CMe3),
/
8.0 Hz, 1,
H3?-bpy), 8.24 (dt, 3Jꢀ
/
/
3
3
8.16 (d, Jꢀ
/
/
7.8 Hz,
5.2
4Jꢀ
/
/
/
/
/
/
/
/
/
/
7.2 Hz, 4Jꢀ
/
0.92 (s, 9, CH2CMe3). 13C{1H} NMR (acetone-d6): d
155.6, 149.7, 149.1, 139.3, 138.4, 123.5, 122.7, 122.3,
121.1, 117.0, 38.1, 35.1, 34.6. Anal. Calcd. for
C21H24N2Pd: C, 61.39; H, 5.89; N, 6.82. Found: C,
61.38; H,5.92; N, 6.88%.
2.1.3. [Pd(CH2SiMe3)Ph(tmeda)] (3)
A suspension of PdIPh(tmeda) (0.57 g, 1.3 mmol) in
diethyl ether (10 ml) was cooled to ꢂ80 8C, and
/
transferred by cannula to a flask containing LiCH2-
SiMe3 (0.25 g, 2.7 mmol), which had been pre-cooled to
2.1. Synthesis of complexes
ꢂ
/
80 8C. The resulting suspension was stirred for 0.5 h
2.1.1. [Pd(CH2CMe3)Ph(tmeda)] (1)
A suspension of PdIPh(tmeda) (0.31 g, 0.73 mmol) in
while it was allowed to warm slowly to ꢂ30 8C. The
solution was then warmed quickly to 0 8C, and ice-cold
water (5 ml) was added. The mixture was stirred for a
/
diethyl ether (10 ml) was cooled to ꢂ
transferred by cannula to flask containing
LiCH2CMe3 (66 mg, 0.85 mmol) which had been pre-
cooled to ꢂ80 8C. The resulting suspension was stirred
for 0.5 h while it was allowed to warm slowly to ꢂ
40 8C. The mixture was stirred at ꢂ40 8C for 0.5 h,
/
80 8C and
a
few minutes, then rapidly cooled to ꢂ40 8C. The
/
diethyl ether solution was separated by decantation,
and the water layer was washed twice with diethyl ether
(20 ml). The combined organic layers were dried over
sodium sulfate, at 0 8C, and filtered through cotton-
wool/Celite. All volatiles were removed in a vacuum
/
/
/
then warmed slowly to 0 8C. Water (2 ml) at 0 8C was
added, yielding a black suspension which was stirred for
leaving a yellow solid, and crystallisation from acetone
1
a short period at 0 8C, then rapidly cooled to ꢂ
/
40 8C.
at ꢂ
(acetone-d6, ꢂ
/
60 8C gave white crystals (0.35 g, 69%). H NMR
3
The clear yellow organic layer was separated by
decantation, and the water layer was washed twice
with diethyl ether (10 ml). The combined organic
extracts were dried over sodium sulfate at 0 8C and
filtered through cottonwool/Celite. All volatiles were
removed in a vacuum leaving a yellow solid. Crystal-
/
20 8C) d 7.88 (d, Jꢀ6.79 Hz, 2, H2,6-
/
3
3
Ph), 6.79 (t, Jꢀ
Hz, 1, H4-Ph), 2.65 (s-broad, 4, (CH2)2), 2.49 (s, 6,
NMe2), 2.21 (s, broad, 6, NMe2), ꢂ0.29 (s, 2,
CH2SiMe3) ꢂ
0.44 (s, 9, CH2SiMe3). 13C{1H} NMR
(acetone-d6, ꢂ20 8C) d 161.6, 138.3, 125.6, 120.9, 59.7,
59.4, 48.2 (broad), 3.1, ꢂ1.59. Anal. Calcd. for
/
7.59 Hz, 2, H3,5-Ph), 6.68 (t, Jꢀ
/7.20
/
/
/
lisation from acetone at ꢂ
/
40 8C gave white crystals
(0.22 g, 82%). H NMR (acetone-d6, ꢂ20 8C): d 7.42
(m, 2, Ph), 6.66ꢁ6.80 (m, 3, Ph), 2.49ꢁ2.66 (broad,
/
1
/
C16H32N2SiPd: C, 49.67; H, 8.34; N, 7.24. Found: C,
50.52; H, 8.46; N, 7.24%.
/
/
overlapping, 10, NMe2 and (CH2)2), 2.13 (s-broad, 6,
NMe2), 1.11 (s, 2, CH2CMe3), 0.72 (s, 9, CH2CMe3).
2.1.4. [Pd(CH2SiMe3)Ph(bpy)] (4)
A solution of [Pd(CH2SiMe3)Ph(tmeda)] (3) (0.28 g,
13C{1H} NMR (acetone-d6, ꢂ
/
20 8C): d 164.3, 138.6,
125.4, 120.6, 59.8, 58.8, 48.0, 34.6. Anal. Calcd. for
C17H32N2Pd: C, 55.06; H, 8.70; N, 7.55. Found: C,
55.13; H 8.71; N, 7.56%.
0.74 mmol) in acetone (2 ml) was cooled to ꢂ
mixed with a solution of 2,2?-bipyridine (0.23 g, 1.47
mmol) in acetone (2 ml) at ꢂ40 8C. The mixture was
warmed slowly to ꢂ10 8C and the resultant yellow
solution was concentrated to ꢂ0.5 ml and stored at ꢂ
20 8C. Yellow crystals formed over several days (0.12 g,
38%). 1H NMR (acetone-d6) d ꢂ8.86 (d, 3Jꢀ
4.4 Hz, 1,
8.0 Hz, 1, H3-bpy), 8.47 (d, Jꢀ
8.0 Hz, 1, H3-bpy), 8.24 (dt, 3Jꢀ7.9 Hz, 4Jꢀ
1.8 Hz, 1,
/
40 8C and
/
/
2.1.2. [Pd(CH2CMe3)Ph(bpy)] (2)
A solution of Pd(CH2CMe3)Ph(tmeda) (1) (91 mg,
/
/
0.25 mmol) in acetone (1 ml) was cooled to ꢂ
mixed with a solution of 2,2?-bipyridine (53 mg, 0.37
mmol) in acetone (2 ml) at ꢂ80 8C. The resultant
/
40 8C and
/
/
3
3
H6-bpy), 8.52 (d, Jꢀ
/
/
/
/
/

96
A.J. Canty et al. / Inorganica Chimica Acta 338 (2002) 94ꢁ98
/
H4-bpy), 8.15ꢁ
/
8.11 (m, 2, H4-bpy and H6-bpy), 7.79
(d, 3Jꢀ
3Jꢀ
7.6 Hz, 1, H4-mq), 7.54 (m, 1, H3-mq), 7.43-7.37
(m, 2, H6-mq and H5-bpy), 7.18 (m, 2, Ph), 7.05 (m, 3,
/
7.2 Hz, 1, H2-mq), 7.74 (m, 1, H5-bpy), 7.66 (d,
3
3
4
(ddd, Jꢀ
7.49ꢁ7.52 (overlapping, 3, H2,6-Ph and H5-bpy), 6.96
(m, 2, H3,5-Ph), 6.83 (tt, 3Jꢀ7.2 Hz, 4Jꢀ
1.6 Hz, 2, H4-
/
7.5 Hz, Jꢀ
/
5.3 Hz, Jꢀ/1.2 Hz, 1, H5-bpy),
/
/
/
/
Ph), 4.46 (d, 2Jꢀ
Hz, 1, CH2-mq), 1.60 (d, Jꢀ
1.58 (d, 2Jꢀ
/
14.0 Hz, 1, CH2-mq), 4.20 (d, 2Jꢀ
/
14.0
3
Ph), 0.30 (s, 2, CH2SiMe3), 0.16 (s, 9, CH2SiMe3).
13C{1H} NMR (acetone-d6): d 162.8, 155.6, 154.7,
149.7, 148.7, 139.0, 138.9, 138.4, 126.5, 126.2, 126.1,
122.7, 122.4, 121.5, 2.92, ꢂ8.14. Anal. Calcd. for
C20H24N2SiPd: C, 56.27; H, 5.67; N, 6.56. Found: C,
56.33; H, 5.76; N, 6.60%.
/
12.8 Hz, 1, CH2SiMe3),
/
12.8 Hz, 1, CH2SiMe3), ꢂ0.46 (s, 9,
/
CH2SiMe3). 13C{1H} NMR (acetone-d6): d 154.1,
153.7, 149.1, 146.9, 146.4, 143.8, 142.2, 141.7, 139.3,
134.4, 134.1, 130.5, 129.3, 129.1, 128.9, 128.4, 127.8,
127.4, 127.0, 126.3, 125.9, 123.3, 43.1, 1.14, 0.92. Anal.
Calcd. for C29H32BrN3SiPd: C, 55.52; H, 4.97; N, 6.48.
Found: C, 54.27; H, 6.26; N, 5.25%.
/
2.1.5. [Pd(mq)(CH2CMe3)Ph(bpy)]Br (5)
A solution of Pd(CH2CMe3)Ph(bpy) (2) (15 mg, 0.04
mmol) in acetone (1 ml) was mixed with a solution of 8-
(bromomethyl)quinoline (8.7 mg, 0.04 mmol) and
stirred for 5 min. Diethyl ether was added dropwise
until the solution became cloudy, then refrigerated.
After 12 h crystals had formed, the solution was
2.2. X-ray structure determination for 5
Crystals were obtained from a concentrated solution
of the complex in acetone at 0 8C. A full sphere of CCD
area-detector diffractometer data as measured (2umax
decanted and the crystals washed with pentane (3ꢄ5
/
ꢀ
/
1
ml) and dried in a vacuum (14 mg, 61%). H NMR
(CDCl3) d 9.56 (d, 3Jꢀ8.0 Hz, 1, H3-bpy), 9.52 (d, 3Jꢀ
8.0 Hz, 1, H3-bpy), 8.58 (d, 3Jꢀ
4.4 Hz, 1, H6-bpy), 8.51
588, v scan mode, monochromatic Mo Ka radiation,
/
/
˚
lꢀ
tions, these being merged to 6769 unique after ‘empiri-
cal’/multiscan absorption correction, 5420 with F ꢀ
/
0.71073 A; T Â
/
150 K) yielding 13 468 total reflec-
/
3
3
(t, Jꢀ
bpy), 8.20 (t, Jꢀ
Hz, 1, H5-mq), 7.93 (d, Jꢀ
7.71 (m, 2, H2-mq and H5-bpy), 7.59 (d, Jꢀ
/
7.8 Hz, 1, H4-bpy), 8.37 (d, Jꢀ5.2 Hz, 1, H6-
/
/
3
3
/
7.8 Hz, 1, H4-bpy), 8.11 (d, Jꢀ
/
8.4
4s(F) being considered ‘observed’ and used in the full-
matrix least-squares refinement. Anisotropic thermal
parameters were refined for the non-hydrogen atoms,
3
/
4.4 Hz, 1, H7-mq), 7.77ꢁ
/
3
/
8.0 Hz, 1,
3
3
H4-mq), 7.49 (t, Jꢀ
/
7.6 Hz, 1, H3-mq), 7.38 (dd, Jꢀ
8.4 Hz, 1, H6-mq), 7.30 (t, Jꢀ
/
(x, y, z, Uiso H
tional residuals R, Rw were 0.055, 0.044, reflection
weights being (s2(F)ꢃ0.0004F2)ꢂ1. Neutral atom com-
) being constrained at estimates. Conven-
3
3
4.8 Hz, Jꢀ
/
/6.4 Hz, 1,
H5-bpy), 7.22 (d, 3Jꢀ
/
8.0 Hz, 2, H2,6-Ph), 7.06-7.00 (m,
2
/
3, H3,4,5-Ph), 4.52 (d, Jꢀ13.8 Hz, 1, CH2-mq), 4.01
/
plex scattering factors were employed and computation
used the XTAL 3.7 program system [15].
2
3
(d, Jꢀ
/
13.8 Hz, 1, CH2-mq), 2.79 (d, Jꢀ
/9.8 Hz, 1,
2
CH2CMe3), 2.70 (d, Jꢀ
/
9.8 Hz, 1, CH2CMe3), 0.60 (s,
Crystal data: C31H32BrN3Pd, Mꢀ
/
632.9, Triclinic,
8.748(2), bꢀ10.063(2), cꢀ
99.214(4), bꢀ99.762(4), gꢀ
1380 A , Dcalc (Zꢀ2)ꢀ1.523
640, specimen 0.09ꢄ0.05ꢄ0.04 mm,
21.4 cmꢂ1, ‘T’min,max
0.57, 0.84.
9, CH2CMe3). 13C{1H} NMR (acetone-d6): d 154.6,
154.0.150.4, 149.5, 146.9, 146.8, 146.1, 144.1, 142.0,
141.5, 138.9, 133.3, 129.9, 129.0, 128.1, 127.7, 127.3,
127.0, 126.1, 125.9, 123.1, 121.8, 59.4, 43.9, 36.8, 31.0.
Anal. Calcd. for C30H32BrN3Pd: C, 58.03; H, 5.70; N,
6.77. Found: C, 58.15; H, 5.32; N, 6.55%.
¯
space group
P
/
1; aꢀ
17.398(4) A, aꢀ
109.821(3)8, Vꢀ
cmꢂ3; F(000)ꢀ
mMo
/
/
/
˚
/
/
/
3
˚
/
/
/
g
/
/
/
ꢀ
/
ꢀ
/
Selected structural data are given in Table 1 and a
view of the complex is shown in Fig. 1.
2.1.6. [Pd(mq)(CH2SiMe3)Ph(bpy)]Br (6)
A solution of Pd(CH2SiMe3)Ph(bpy) (4) (25 mg, 0.058
mmol) and 8-(bromomethyl)quinoline (13 mg, 0.058
mmol) was stirred in acetone (2 ml) at 0 8C for 15 min.
3. Results and discussion
The solvent was reduced to ꢂ
pentane was added to the solution until cloudiness
developed. The solution was stored at ꢂ20 8C, giving
/0.5 ml in a vacuum and
/
a colourless microcrystalline product after 3 days (26
mg, 69%); despite the crystalline nature of this complex
and its complete dissolution to give high quality NMR
spectra, microanalyses from several preparations differ
slightly from expected values (see below). 1H NMR
3.1. Synthesis of complexes
The new arylpalladium(II) complexes Pd(CH2CMe3)-
Ph(tmeda) and Pd(CH2SiMe3)Ph(tmeda) have been
obtained (Eq. (1)) and converted to bpy derivatives
(Eq. (2)). Yields of 1 and 3 were maximised by addition
of suspensions of PdIPh(tmeda) to excess solid Li-
CH2EMe3 at low temperature, rather than addition of
LiCH2EMe3 to solutions or suspensions of PdIPh(t-
meda).
(CDCl3) d 9.43 (d, 3Jꢀ
/
7.6 Hz, 1, H3-bpy), 9.32 (d, 3Jꢀ
4.0 Hz, 1, H6-bpy), 8.49
/
8.0 Hz, 1, H3-bpy), 8.63 (d, 3Jꢀ
/
3
4
3
(dt, Jꢀ
4.0 Hz, 1, H6-bpy), 8.20ꢁ
bpy), 7.83 (dd, 3Jꢀ4.8 Hz, 4Jꢀ
/
7.9 Hz, Jꢀ
/
2.0 Hz, 1, H4-bpy), 8.28 (d, Jꢀ
8.17 (m, 2, H5-mq and H4-
1.2 Hz, 1, H7-mq), 7.81
/
/
/
/

A.J. Canty et al. / Inorganica Chimica Acta 338 (2002) 94ꢁ
/
98
97
Table 1
Selected
[Pd(mq)(CH2CMe3)Ph(bpy)]Br (5)
˚
(A)
bond
distances
and
angles
(8)
for
Bond distances
PdꢀC(01)
PdꢀC(1)
PdꢀC(81)
2.031(5) PdꢀN(1)
2.085(6) PdꢀN(11)
2.030(5) PdꢀN(11?)
2.193(5)
2.181(5)
2.206(5)
Bond angles
C(01)ꢀPdꢀC(1)
C(01)ꢀPdꢀC(81)
C(1)ꢀPdꢀC(81)
C(01)ꢀPdꢀN(1)
C(01)ꢀPdꢀN(11)
C(01)ꢀPdꢀN(11?)
C(1)ꢀPdꢀN(1)
C(1)ꢀPdꢀN(11)
C(1)ꢀPdꢀN(11?)
N(1)ꢀPdꢀN(11)
N(1)ꢀPdꢀN(11?)
N(11)ꢀPdꢀN(11?)
N(11)ꢀPdꢀC(81)
N(11?)ꢀPdꢀC(81)
N(1)ꢀPdꢀC(81)
PdꢀC(01)ꢀC(02)
85.5(2) PdꢀC(01)ꢀC(06)
89.0(2) PdꢀC(1)ꢀC(11)
89.5(2) PdꢀC(81)ꢀC(8)
92.1(2) PdꢀN(1)ꢀC(2)
113.7(4)
122.4(4)
109.0(3)
130.7(4)
110.1(3)
115.3(4)
125.6(4)
113.2(3)
125.6(4)
112.4(5)
104.6(5)
113.2(4)
107.8(4)
110.1(5)
108.4(5)
98.4(2) PdꢀN(1)ꢀC(8a)
168.6(2) PdꢀN(11)ꢀC(12)
171.9(2) PdꢀN(11)ꢀC(16)
91.4(2) PdꢀN(11?)ꢀC(12?)
104.4(2) PdꢀN(11?)ꢀC(16?)
96.6(2) C(1)ꢀC(11)ꢀC(111)
78.8(2) C(1)ꢀC(11)ꢀC(112)
76.1(2) C(1)ꢀC(11)ꢀC(113)
172.6(2) C(111)ꢀC(11)ꢀC(112)
96.5(2) C(111)ꢀC(11)ꢀC(113)
82.7(2) C(112)ꢀC(11)ꢀC(113)
127.6(3)
Fig. 1. Projection of the cation in [Pd(mq)(CH2CMe3)Ph(bpy)]Br (5).
Thermal ellipsoids (50%) are shown for non-hydrogen atoms, and
˚
hydrogen atoms have been given an arbitrary radius of 0.1 A.
PdIPh(tmeda)ꢃLiCH2EMe2
0 Pd(CH2EMe3)Ph(tmeda)ꢃLiI
1 : EꢀC (82%) 3 : EꢀSi (69%)
(1)
3.2. X-ray structural study of
[Pd(mq)(CH2CMe3)Ph(bpy)]Br (5)
Pd(CH2EMe3)Ph(tmeda)ꢃbpy
0 Pd(CH2EMe3)Ph(bpy)ꢃtmeda
2 : EꢀC (58%) 4 : EꢀSi (38%)
The cation has a distorted octahedral fac-PdC3
configuration with the neopentyl group trans to the
quinoline nitrogen donor atom (Fig. 1, Table 1), and
(2)
angles at palladium in the range 85.5(2)ꢁ98.4(2)8. The 8-
methylquinolinyl-N,C group forms an essentially planar
chelate ring in which the palladium and benzylic carbon
/
Reactions of 2 and 4 with 8-bromomethylquinoline as
a potential oxidant were productive in terms of detecting
Pd(IV) chemistry in NMR reactions in acetone-d6, with
isolation of complexes also subsequently achieved (Eq.
(3)). Acetone-d6 was chosen as a solvent in view of the
instability of the diorganopalladium(II) reagents in
chlorinated solvents, as commonly observed for such
complexes. For Pd(CH2CMe3)Ph(bpy), crystals of
[Pd(mq)(CH2CMe3)Ph(bpy)]Br (5) suitable for an X-
˚
atoms deviate by 0.328(5) and 0.509(9) A from the mq
mean planes; the pyridine rings form a dihedral angle of
19.0(2)8, and the Pd atom lies 0.012(8), 0.280(8),
˚
0.662(8) and 0.328(5) A from the mean planes of the
Ph, py, py?, and mq groups respectively.
The phenyl ring is skewed away from the C(1)PdC(81)
plane, such that the PdC(01)C(06) angle is Â148 smaller
/
1
ray structural analysis were obtained (Fig. 1). H NMR
spectra show very low intensity resonances indicating
than PdC(01)C(02). This would appear to result from
close contacts between the ortho-hydrogen atom H(02)
and the hydrogen atoms of the methylene groups of mq
the presence of a minor isomer (ꢂ5%) for 5 and 6,
/
presumably resulting from interchange of CH2EMe3
and phenyl group positions to retain the fac-PdC3
configuration.
and
CH2CMe3,
H(02)Á Á ÁH(81a)
2.23
and
˚
H(02)Á Á ÁH(1b),C(1) 2.15, 2.75 A, respectively, where
the latter contact may be related to a preferred staggered
configuration for CH2ꢀ
/
CMe3 in concert with orienta-
Pd(CH2EMe3)Ph(bpy) (2; 4)ꢃmqBr
tion of the CMe3 group to minimise methylÁ Á Ápy?
0 [Pd(mq)(CH2EMe3)Ph(bpy)]Br
5 : EꢀC; 6 : EꢀSi
(3)
interactions.
Ambient temperature stable arylpalladium(IV) com-
plexes are formed on the interaction of 8-(bromo-

98
A.J. Canty et al. / Inorganica Chimica Acta 338 (2002) 94ꢁ98
/
methyl)quinoline with neopentyl and trimethylsilyl-
methyl complexes of Pd(II), and are more stable than
complexes decomposing at or below ambient tempera-
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We thank the Australian Research Council for
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one month Visiting Professorship (to A.J.C.) and the
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Re´seau Franco-Australien de Chimie Mole´culaire.
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