Synthesis and Characterization of Allyl(β-ketoimmato)palladium(II) Complexes: New Precursors for Chemical Vapor Deposition of Palladium Thin Films

Article abstract of DOI:10.1021/om980728c

Treatment of β-ketoiminates with [(allyl)Pd(μ-Cl)]₂ affords volatile, air-stable allyl(β-ketoiminato)palladium(II) complexes. The structure of [(methallyl)Pd(Phacac)] (Phacac = MeCOCHCMeNPh) was determined by single-crystal X-ray diffraction. In solution ¹H NMR analyses indicate either a direct rotation of a planar allyl ligand about the allyl-palladium axis or a solvent-assisted exchange process involving the transient formation of a monodentate ketoiminato ligand. The physical properties of the complexes were modified by altering the β-ketoiminato or the η³-allyl ligands. Some derivatives are liquid at room temperature and were known to be suitable for chemical vapor deposition of Pd thin films.

Full text of DOI:10.1021/om980728c

864
Organometallics 1999, 18, 864-869
Syn th esis a n d Ch a r a cter iza tion of
Allyl(â-k etoim in a to)p a lla d iu m (II) Com p lexes: New
P r ecu r sor s for Ch em ica l Va p or Dep osition of P a lla d iu m
Th in F ilm s
Yeng-Lien Tung,† Wen-Cheng Tseng,† Chi-Young Lee,† Peng-Fu Hsu,†
Yun Chi,*,† Shie-Ming Peng,‡ and Gene-Hsiang Lee‡
Department of Chemistry and Material Research Center, National Tsing Hua University,
Hsinchu 30043, Republic of China, and Department of Chemistry and Instrumentation Center,
National Taiwan University, Taipei 10764, Taiwan, Republic of China
Received August 28, 1998
Treatment of â-ketoiminates with [(allyl)Pd(µ-Cl)]2 affords volatile, air-stable allyl(â-
ketoiminato)palladium(II) complexes. The structure of [(methallyl)Pd(Phacac)] (Phacac )
1
MeCOCHCMeNPh) was determined by single-crystal X-ray diffraction. In solution H NMR
analyses indicate either a direct rotation of a planar allyl ligand about the allyl-palladium
axis or a solvent-assisted exchange process involving the transient formation of a mono-
dentate ketoiminato ligand. The physical properties of the complexes were modified by
altering the â-ketoiminato or the η3-allyl ligands. Some derivatives are liquid at room
temperature and were known to be suitable for chemical vapor deposition of Pd thin films.
The preparation of thin films of palladium by metal
nate ligands, which allow for organic functional group
variation on the imine nitrogen as a possible way to fine-
tune physical and chemical properties. In this article,
we report the synthesis and characterization of such
â-ketoiminato complexes and a preliminary investiga-
tion of their application in the generation of Pd films.
organic chemical vapor deposition (CVD) is becoming
increasingly attractive for the fabrication of electronic
devices1 because such films have potentially useful
applications in replacing gold as electrical contacts in
integrated circuits and in making gas sensors, magne-
tooptical data storage devices, etc.2 The largest obstacle
to CVD of Pd films has been the lack of suitable
precursors, as most volatile Pd complexes suffer from
poor stability in air and moisture.3 Recently, this
problem was partially overcome by Puddephatt, who
reported the preparation of volatile allyl(â-diketonato)-
palladium(II) complexes, which are liquid and stable at
room temperature and are excellent CVD precursors for
Pd films.4 In view of these results, we felt it desirable
to investigate analogous complexes having â-ketoimi-
Exp er im en ta l Section
Gen er a l In for m a tion a n d Ma ter ia ls. Infrared spectra
were recorded on a Perkin-Elmer 2000 FT-IR spectrometer.
1H and 13C NMR spectra were recorded on a Bruker AM-400
or AMX-300 instrument. Mass spectra were obtained on a
J EOL SX-102A instrument operating in fast atom bombard-
ment (FAB) mode. Thermogravimetric analyses were made
with a Seiko TG/DTA 300 instrument. Melting points were
determined using Seiko SSC 5000 differential scanning calo-
rimetry. Elemental analyses were performed at the NSC
Regional Instrumentation Center at National Cheng Kung
University, Tainan, Taiwan.
SEM micrographs of palladium films were obtained using
a Hitachi S-4000 scanning electron microscope. Resistivities
of films were measured using a LR-400 four-wire AC resistance
bridge, manufactured by Linear Research Inc. XPS spectra of
films were recorded with a Physical Electronics PHI 1600
ESCA instrument with an Al/Mg dual anode X-ray source. The
surface compositions in atomic percentage deduced from XPS
spectra were determined after 1-2 min sputtering with argon
at 4 keV until a constant composition was obtained. AES
spectra for surface scanning and depth profile were recorded
on a Physical Electronics PHI 670 Xi Auger instrument after
sputtering with argon at 3 keV. XPS is most useful for
detection of carbon (detection limit, ca. 0.5%), while Auger
spectra are useful to detect oxygen and fluorine in the presence
* To whom correspondence should be addressed. FAX: (886) 3 572-
0864. E-mail: ychi@chem.nthu.edu.tw.
† National Tsing Hua University.
‡ National Taiwan University.
(1) (a) Bhaskaran, V.; Hampden-Smith, M. J .; Kodas, T. T. Chem.
Vap. Deposition 1997, 3, 85. (b) Zhang, Y.; Chio, S. W.-K.; Puddephatt,
R. J . J . Am. Chem. Soc. 1997, 119, 9295. (c) Sordelli, L.; Martra, G.;
Psaro, R.; Dossi, C.; Coluccia, S. J . Chem. Soc., Dalton Trans. 1996,
765. (d) Thomas, R. R.; Park, J . M. J . Electrochem. Soc. 1989, 136,
1661. (e) Feurer, E.; Suhr, H. Thin Solid Films 1988, 157, 81. (f) Kudo,
T.; Yamaguchi, A. J pn. Pat. J P62 207 868, 1987.
(2) (a) Gliem, R.; Schlamp, G. Met. Technol. 1987, 41, 34. (b) Dubin,
V. M.; Lopatin, S. D.; Sokolov, V. G. Thin Solid Films 1993, 226, 94.
(c) Dossi, C.; Psaro, R.; Bartsch, A.; Brivio, E.; Galasco, A.; Losi, P.
Catal. Today 1993, 17, 527. (d) Hierso, J .-C.; Serp, P.; Feurer, R.; Kalck,
P. Appl. Organomet. Chem. 1998, 12, 161.
(3) (a) Gozum, J . E.; Pollina, D. M.; J ensen, J . A.; Girolami, G. S. J .
Am. Chem. Soc. 1988, 110, 2688. (b) Yuan, Z.; J iang, D.; Naftel, S. J .;
Sham, T.-K.; Puddephatt, R. J . Chem. Mater. 1994, 6, 2151.
(4) (a) Yuan, Z.; Puddephatt, R. J . Adv. Mater. 1994, 6, 51. (b) Yuan,
Z.; Puddephatt, R. J . Chem. Vap. Deposition 1997, 3, 81. (c) Zang, Y.;
Yuan, Z.; Puddephatt, R. J . Chem. Mater. 1998, 10, 2293.
10.1021/om980728c CCC: $18.00 © 1999 American Chemical Society
Publication on Web 02/05/1999

Allyl(â-ketoiminato)palladium(II) Complexes
Organometallics, Vol. 18, No. 5, 1999 865
of palladium. In all cases analyses are corrected for relative
sensitivities of each element.
Calcd for C15H19NOPd: C, 43.89; H, 6.28; N, 5.12. Found: C,
44.27; H, 6.21; N, 5.28.
Com p lex 4, [P d (η3-CH2CMeCH2)(Mea ca c)]. MS (FAB,
107Pd): m/z 273 (M+). 1H NMR (300 MHz, CDCl3, 293 K): δ
5.31-5.21 (m, 1H), 4.74 (s, 1H), 3.70-3.60 (m, 1H), 3.45 (s,
3H), 3.00 (d, 1H, J HH ) 6.7 Hz), 2.46 (d, 1H, J HH ) 11.5 Hz),
1.94 (s, 3H), 1.90 (s, 3H), 1.29 (d, 3H, J HH ) 6.3 Hz). 13C NMR
(75 MHz, CDCl3, 293 K): δ 177.1, 165.4, 114.3, 97.7, 75.6, 49.3,
49.1, 26.9, 21.2, 16.1. Anal. Calcd for C10H17NOPd: C, 43.89;
H, 6.26; N, 5.12. Found: C, 44.20; H, 6.12; N, 5.22.
Complex 5, [P d (η3-CH2CMeCH2)(Moa ca c)]. MS (FAB,
107Pd): m/z 317 (M+). 1H NMR (300 MHz, CDCl3, 293 K): δ
5.31-5.21 (m, 1H), 4.93 (s, 1H), 3.96-3.87 (m, 1H), 3.85-3.76
(m, 1H), 3.71-3.61 (m, 1H), 3.50 (t, 2H, J HH ) 6.6 Hz), 3.29
(s, 3H), 2.93 (d, 1H, J HH ) 6.5 Hz), 2.44 (d, 1H, J HH ) 11.6
Hz), 1.93 (s, 3H), 1.91 (s, 3H), 1.31 (d, 3H, J HH ) 6.2 Hz). 13C
NMR (75 MHz, CDCl3, 293 K): δ 177.8, 165.3, 133.7, 98.1,
76.2, 73.5, 59.3, 59.0, 48.8, 27.1, 21.2, 16.0. Anal. Calcd for
Allylpalladium complexes with the empirical formula
[(allyl)Pd(µ-Cl)]2 were prepared according to literature proce-
dures.5 Ketoimines were prepared from the direct condensation
of acetylacetone and amines at room temperature,6 or from
reaction of hexafluoroacetylacetone and amines using mont-
morillonite K10 as a catalyst.7 Abbreviations used for the
â-ketoiminate ligands are as follows: Mehfac ) CF3COCHCCF3-
NMe, Buhfac ) CF3COCHCCF3NnBu, Mohfac ) CF3COCHC-
CF3NCH2CH2OMe, Alhfac ) CF3COCHCCF3NCH2CHdCH2,
Phacac ) MeCOCHCMeNPh, Meacac ) MeCOCHCMeNMe,
Moacac ) MeCOCHCMeNCH2CH2OMe, Alacac ) MeCOCHC-
MeNCH2CHdCH2. Two typical synthetic procedures for the
preparation of â-ketoiminato Pd complexes are described
below, together with spectral and analytical data for the
compounds prepared. Due to thermal instability or physical
state, some compounds did not give satisfactory elemental
analyses. 1H NMR spectra for these complexes (2, 6, 8-11,
13, 14) have been deposited in the Supporting Information.
[P d (η3-CH2CMeCH2)(P h a ca c)] (1). A mixture of distilled
water (40 mL), NaOH (250 mg), and PhacacH (175 mg, 1.00
mmol) was stirred at 45 °C for 30 min to give a homogeneous
solution, which was then added to a suspension of [Pd(η3-CH2-
CMeCH2)(µ-Cl)]2 (217 mg, 0.55 mmol) in diethyl ether (20 mL).
The mixture was stirred for 10 min, and the ether layer was
separated, washed with distilled water (3 × 10 mL) and dried
over sodium sulfate; then the solvent was evaporated to give
the product [Pd(η3-CH2CMeCH2)(Phacac)] as a yellow solid
(yield, 289 mg, 86%). Single crystals of 1 suitable for an X-ray
diffraction study were obtained from recrystallization in
saturated acetone solution at room temperature.
[P d (η3-CH2CMeCH2)(Meh fa c)] (15). A mixture of diethyl
ether (30 mL), NaOMe (200 mg), and MehfacH (450 mg, 2.04
mmol) was stirred at room temperature for 30 min to give a
homogeneous solution, which was then added to a mixture of
[Pd(η3-CH2CMeCH2)(µ-Cl)]2 (400 mg, 1.02 mmol) and NaOH
(250 mg) in water (50 mL). The mixture was vigorously stirred
for 10 min; the ether layer was separated, washed with
distilled water (3 × 10 mL), and dried over sodium sulfate.
Then the solvent was evaporated to give the product [Pd(η3-
CH2CMeCH2)(Mehfac)] as a yellow solid (yield, 740 mg, 95%).
Sp ectr oscop ic Da ta for â-Ketoim in a to Com p lexes.
Com p lex 1, [P d (η3-CH2CMeCH2)(P h a ca c)]. MS (FAB,
107Pd): m/z 335 (M+). 1H NMR (300 MHz, CDCl3, 293 K): δ
7.24 (t, 2H, J HH ) 7.5 Hz), 7.00 (t, 1H, J HH ) 7.5 Hz), 6.88 (br,
1H), 4.97 (s, 1H), 3.52 (d, 1H, J HH ) 2.8 Hz), 2.73 (s, 1H), 2.34
(s, 1H), 2.03 (s, 3H), 1.98 (s, 3H), 1.92 (d, 1H, J HH ) 2.8 Hz),
1.64 (s, 3H). 13C NMR (75 MHz, CDCl3, 293 K): δ 178.7, 163.9,
156.9, 130.5, 128.5 (2C), 123.7 (2C), 122.8, 97.3, 58.8, 57.1, 27.1,
23.3, 22.9. Anal. Calcd for C15H19NOPd: C, 53.67; H, 5.70; N,
4.17. Found: C, 53.19; H, 5.65; N, 4.30.
C
12H21NO2Pd: C, 45.37; H, 6.66; N, 4.41. Found: C, 45.80; H,
6.56; N, 4.60.
Com p lex 6, [P d (η3-CH2CMeCH2)(Ala ca c)]: MS (FAB,
107Pd): m/z 299 (M+). 1H NMR (300 MHz, CDCl3, 293 K): δ
5.91-5.79 (m, 1H), 5.14-5.07 (m, 2H), 4.80 (s, 1H), 4.36-4.33
(m, 2H), 3.56 (d, 1H, J HH ) 2.8 Hz), 2.86 (d, 1H, J HH ) 2.8
Hz), 2.82 (s, 1H), 2.60 (s, 1H), 2.08 (s, 3H), 1.96 (s, 3H), 1.88
(s, 3H). 13C NMR (75 MHz, CDCl3, 293 K): δ 176.8, 165.5,
135.6, 130.6, 114.6, 98.0, 62.0, 58.4, 54.5, 26.7, 23.2, 21.0.
Com p lex 7, [P d (η3-CH2CMeCHMe)(Mea ca c)]: MS (FAB,
107Pd): m/z 287 (M+). 1H NMR (300 MHz, CDCl3, 293 K): δ
5.06 (dd, 1H, J HH ) 12.0, 7.1 Hz), 4.72 (s, 1H), 3.45 (s, 3H),
3.00 (d, 1H, J HH ) 7.1 Hz), 2.64 (d, 1H, J HH ) 12.0 Hz), 1.89
(s, 3H), 1.84 (s, 3H), 1.40 (s, 3H), 1.20 (s, 3H). 13C NMR (75
MHz, CDCl3, 293 K): δ 177.8, 165.6, 108.5, 97.5, 88.7, 49.1,
46.7, 27.2, 25.0, 21.0, 20.9. Anal. Calcd for C11H19NOPd: C,
45.93; H, 6.66; N, 4.87. Found: C, 46.66; H, 6.46; N, 4.95.
Com p lex 8, [P d (η3-CH2CH CMe2)(Moa ca c)]. MS (FAB,
107Pd): m/z 331 (M+). 1H NMR (300 MHz, CDCl3, 293 K): δ
5.09 (dd, 1H, J HH ) 12.0 Hz, 7.2 Hz), 4.74 (s, 1H), 3.97-3.80
(m, 2H), 3.54 (t, 2H, J HH ) 3 Hz), 3.33 (s, 3H), 2.96 (dd, 1H,
J HH ) 7.3 Hz, 1.3 Hz), 2.63 (dd, 1H, J HH ) 12.0, 1.3 Hz), 1.93
(s, 3H), 1.92 (s, 3H), 1.44 (s, 3H), 1.22 (s, 3H). 13C NMR (75
MHz, CDCl3, 293 K): δ 178.6, 165.5, 108.1, 98.1, 86.6, 73.5,
59.3, 59.1, 46.2, 27.4, 25.1, 21.1, 21.0.
Com plex 9, [P d(η3-CH2CMeCMeCH2OMe)(Moacac)]: MS
(FAB, 107Pd): m/z 375 (M+). 1H NMR (300 MHz, CDCl3, 293
K): δ 4.74 (s, 1H), 3.87 (t, 2H, J HH ) 6.3 Hz), 3.64 (d, 1H, J HH
) 10.6 Hz), 3.51 (t, 2H, J HH ) 6.3 Hz), 3.32 (s, 3H), 3.16 (s,
3H), 3.10 (d, 1H, J HH ) 10.6 Hz), 2.96 (d, 1H, J HH ) 1.1 Hz),
2.86 (d, 1H, J HH ) 1.1 Hz), 2.11 (s, 3H), 1.92 (s, 3H), 1.91 (s,
3H), 1.40 (s, 3H). 13C NMR (75 MHz, CDCl3, 293 K): δ 178.3,
165.4, 123.5, 98.0, 80.7, 73.4, 73.0, 59.1 (2C), 57.3, 51.6, 27.2,
21.2 (2C), 17.1.
Com p lex 2, [P d (η3-CH2CHCH2)(Mea ca c)]. 1H NMR (300
MHz, CDCl3, 293 K): δ 5.67-5.54 (m, 1H), 4.80 (s, 1H), 3.78
(d, 1H, J HH ) 6.9 Hz), 3.49 (s, 3H), 3.22 (d, 1H, J HH ) 6.6 Hz),
3.01 (d, 1H, J HH ) 12.5 Hz), 2.71 (d, 1H, J HH ) 11.7 Hz), 2.00
(s, 3H), 1.95 (s, 3H). 13C NMR (75 MHz, CDCl3, 293 K): δ
175.8, 165.4, 115.1, 97.8, 60.0, 53.2, 49.1, 26.3, 21.5.
Com p lex 3, [P d (η3-CH2CHCHMe)(Mea ca c)]. MS (FAB,
107Pd): m/z 273 (M+). 1H NMR (300 MHz, CDCl3, 293 K): δ
4.78 (s, 1H), 3.54 (d, 1H, J HH ) 2.6 Hz), 3.45 (s, 3H), 2.96 (d,
1H, J HH ) 2.6 Hz), 2.84 (s, 1H), 2.62 (s, 1H), 2.10 (s, 3H), 1.91
(s, 3H), 1.86 (s, 3H). 13C NMR (75 MHz, CDCl3, 293 K): δ
176.1, 165.4, 130.7, 97.7, 58.5, 53.5, 49.1, 26.5, 23.4, 21.5. Anal.
Com p lex 10, [P d (η3-CH2CMeCMeCH2OMe)(Meh fa c)].
MS (FAB, 107Pd): m/z 439 (M+). 1H NMR (300 MHz, CDCl3,
293 K): δ 5.60 (s, 1H), 3.74 (d, 3H, J HH ) 2.0 Hz), 3.62 (d, 1H,
J HH ) 10.7 Hz), 3.32 (s, 1H), 3.18 (s, 3H), 3.12 (d, 1H, J HH
)
10.7 Hz), 3.11 (s, 1H), 2.17 (s, 3H), 1.39 (s, 3H). 13C NMR (75
MHz, CDCl3, 293 K): δ 166.1 (q, CO, J CF ) 32 Hz), 155.6 (q,
CN, J CF ) 26 Hz), 126.9, 120.1 (q, CF3, J CF ) 282 Hz), 120.0
(q, CF3, J CF ) 286 Hz), 87.5, 84.9, 73.7, 58.3, 55.1, 50.7, 21.6,
18.2.
Com p lex 11, [P d (η3-CH2CMeCMeCH2OMe)(Moh fa c)].
1H NMR (300 MHz, CDCl3, 293 K): δ 5.61 (s, 1H), 4.10-4.03
(m, 2H, J HH ) 6.9 Hz), 3.65-3.57 (m, 3H), 3.38 (d, 1H, J HH
)
10.6 Hz), 3.35 (s, 3H), 3.19 (s, 3H), 3.13 (s, 1H), 3.10 (d, 1H,
J HH ) 10.6 Hz), 2.19 (s, 3H), 1.40 (s, 3H). 13C NMR (75 MHz,
CDCl3, 293 K): δ 166.4 (q, CO, J CF ) 32 Hz), 156.1 (q, CN,
J CF ) 26 Hz), 126.6, 120.0 (q, CF3, J CF ) 286 Hz), 119.9 (q,
CF3, J CF ) 279 Hz), 87.6, 85.2, 74.6, 73.6, 60.8, 59.8, 58.4, 55.6,
21.5, 18.2.
(5) (a) Robinson, S. D.; Shaw, B. L. J . Chem. Soc. 1963, 4806. (b)
Sakakibara, M.; Takahashi, Y.; Sakai, S.; Ishii, Y. J . Chem. Soc., Chem.
Commun. 1969, 396. (c) Akermark, B.; Hansson, S.; Krakenberger, B.;
Vitagliano, A.; Zetterberg, K. Organometallics 1984, 3, 679.
(6) Greenhill, J . V. J . Chem. Soc. Rev. 1977, 6, 277.
(7) Braibante, M. E. F.; Braibante, H. S.; Missio, L.; Andricopulo,
A. Synthesis 1994, 898.

866 Organometallics, Vol. 18, No. 5, 1999
Tung et al.
Ta ble 1. Cr ysta l Da ta for th e X-r a y Diffr a ction
Com p lex 12, [P d (η3-CH2CH CH2)(Meh fa c)]. MS (FAB,
107Pd): m/z 367 (M+). 1H NMR (300 MHz, CDCl3, 293 K): δ
5.82-5.67 (m, 1H), 5.67 (s, 1H), 4.07 (d, 1H, J HH ) 6.8 Hz),
Stu d ies of Com p lex 1
formula: C15H19NOPd
cryst syst: orthorhombic
mol wt: 335.72
3.78 (s, 3H), 3.53 (d, 1H, J HH ) 6.5 Hz), 3.24 (d, 1H, J HH
)
12.4 Hz), 2.94 (d, 1H, J HH ) 11.8 Hz). 13C NMR (75 MHz,
CDCl3, 293 K): δ 165.6 (q, CO, J CF ) 33 Hz), 155.6 (q, CN,
J CF ) 27 Hz), 120.2 (q, CF3, J CF ) 282 Hz), 120.0 (q, CF3, J CF
) 286 Hz), 117.8, 87.5, 63.3, 57.1, 50.9. Anal. Calcd for C9H9-
NOF6Pd: C, 29.41; H, 2.47; N, 3.81. Found: C, 30.30; H, 2.64;
N, 4.05.
space group: Pbca
a ) 9.0500(20) Å
b ) 19.2745(20) Å
c ) 16.681(14) Å
V ) 2910(3) Å3
Z ) 8
Com p lex 13, [P d (η3-CH2CHCH2)(Bu h fa c)]. 1H NMR (300
MHz, CDCl3, 293 K): δ 5.81-5.68 (m, 1H), 5.64 (s, 1H), 4.07
(d, 1H, J HH ) 6.7 Hz), 3.89-3.79 (m, 2H), 3.41 (d, 1H, J HH
Dc ) 1.533 g/cm3
F(000) ) 1351
)
2θ(max) ) 50°
6.7 Hz), 3.22 (d, 1H, J HH ) 12.2 Hz), 2.94 (d, 1H, J HH ) 12.2
Hz), 1.71 (m, 2H, J HH ) 7.2 Hz), 1.34 (m, 2H, J HH ) 7.2 Hz),
0.93 (t, 3H, J HH ) 7.2 Hz). 13C NMR (75 MHz, CDCl3, 293 K):
δ 165.6 (q, CO, J CF ) 32 Hz), 154.5 (q, CN, J CF ) 26 Hz), 120.2
(q, CF3, J CF ) 277 Hz), 120.1 (q, CF3, J CF ) 286 Hz), 117.1,
87.4, 63.4, 62.3, 56.6, 36.5, 20.9, 14.5.
Com p lex 14, [P d (η3-CH2CH CH2)(Moh fa c)]. MS (FAB,
107Pd): m/z 411 (M+). 1H NMR (300 MHz, CDCl3, 293 K): δ
5.82-5.68 (m, 1H), 5.66 (s, 1H), 4.08 (m, 2H, J HH ) 6.7 Hz),
4.09-4.06 (m, 1H), 3.61 (t, 1H, J HH ) 6.7 Hz), 3.53 (d, 1H,
J HH ) 6.1 Hz), 3.33 (s, 3H), 3.21 (d, 1H, J HH ) 12.4 Hz), 2.95
(d, 1H, J HH ) 11.9 Hz). 13C NMR (75 MHz, CDCl3, 293 K): δ
166.3 (q, CO, J CF ) 34 Hz), 156.1 (q, CN, J CF ) 27 Hz), 120.0
(q, 2CF3, J CF ) 287 Hz), 117.3, 87.6, 74.4, 63.4, 61.1, 59.8, 57.4.
Anal. Calcd for C11H13NO2F6Pd: C, 32.09; H, 3.18; N, 3.40.
Found: C, 30.89; H, 3.07; N, 3.30.
h, k, l ranges: 0-10, 0-22, 0-19
cryst size: 0.50 × 0.45 × 0.25 mm
µ(Mo KR) ) 12.47 cm-1
transmissn: 0.688 (max), 0.437 (min)
no. of unique data: 2554
no. of data with I > 2σ(I): 1911
no. of atoms, params: 37, 164
max ∆/σ ratio: 0.0006
RF; Rw: 0.028; 0.028
GOF: 1.82
D-map, max/min: 0.60/-0.74 e/Å3
Ch a r t 1
Com p lex 15, [P d (η3-CH2CMeCH2)(Meh fa c)]. MS (FAB,
107Pd): m/z 381 (M+). 1H NMR (300 MHz, CDCl3, 293 K): δ
5.65 (s, 1H), 3.84 (d, 1H, J HH ) 2.2 Hz), 3.77 (q, 3H, J HF ) 2.0
Hz), 3.30 (d, 1H, J HH ) 2.2 Hz), 3.08 (s, 1H), 2.84 (s, 1H), 2.19
(s, 3H). 13C NMR (75 MHz, CDCl3, 293 K): δ 165.5 (q, CO,
J CF ) 32 Hz), 155.4 (q, CN, J CF ) 26 Hz), 134.0, 120.2 (q, CF3,
J CF ) 282 Hz), 120.0 (q, CF3, J CF ) 285 Hz), 87.4, 61.7, 57.0,
50.8, 23.9. Anal. Calcd for C10H11NOF6Pd: C, 31.47; H, 2.91;
N, 3.67. Found: C, 32.15; H, 2.90; N, 3.88.
RCA cleaning method; SiO2 substrates were placed in dilute
HF solution for 12 h, and then washed with deionized water
and dried at 120 °C for 10 min. The flow rate of carrier gas
was adjusted to 20-40 mL/min. The duration of deposition
was typically between 30 min and 1 h.
Com p lex 16, [P d (η3-CH2CMeCH2)(Alh fa c)]. MS (FAB,
107Pd: m/z 407 (M+). 1H NMR (300 MHz, CDCl3, 293 K): δ
5.96-5.84 (m, 1H), 5.68 (s, 1H), 5.20 (d, 1H, J HH ) 10.2 Hz),
5.12 (d, 1H, J HH ) 18.0 Hz), 4.57 (s, 2H), 3.84 (d, 1H, J HH
)
Resu lts a n d Discu ssion
2.7 Hz), 3.18 (d, 1H, J HH ) 2.7 Hz), 3.18 (s, 1H), 2.82 (s, 1H),
2.12 (s, 3H). 13C NMR (75 MHz, CDCl3, 293 K): δ 166.2 (q,
CO, J CF ) 32 Hz), 155.4 (q, CN, J CF ) 26 Hz), 136.4, 133.6,
120.2 (q, CF3, J CF ) 282 Hz), 120.1 (q, CF3, J CF ) 286 Hz),
116.6, 87.3, 66.5, 63.4, 58.3, 23.5. Anal. Calcd for C12H13NOF6-
Pd: C, 35.36; H, 3.21; N, 3.44. Found: C, 35.97; H, 3.14; N,
3.61.
Syn th esis a n d Ch a r a cter iza tion of P r ecu r sor s.
The synthesis of â-ketoimine ligands involved the simple
condensation of acetylacetone and a primary amine (H2-
NR1; R1 ) Ph, Me, Bun, methoxyethyl, allyl) in an
aromatic solvent.6 After the mixture was stirred at room
temperature for 2 days, the free â-ketoimine was then
isolated in 75-89% yields. The preparations involving
hexafluoroacetylacetone (hfacH) utilized K-10 mont-
morillonite as a catalyst7 to afford the analogous
fluorine-substituted â-ketoimine ligand in 60-85% yield
upon heating in CHCl3 solvent for 2 days (Scheme 1).
X-r a y Cr ysta llogr a p h y. The X-ray diffraction measure-
ment was carried out on a Nonius CAD-4 diffractometer at
room temperature. Lattice parameters were determined from
25 randomly selected high-angle reflections. Three standard
reflections were monitored every 3600 s. No significant varia-
tion in intensities (e1%) was observed during the course of
all data collection. Intensities of diffraction signals were
corrected for Lorentz, polarization, and absorption effects (ψ
scans). The structure was solved with the NRCC-SDP-VAX
package. All non-hydrogen atoms had anisotropic temperature
factors, while hydrogen atoms of organic substituents were
placed at calculated positions with UH ) UC + 0.1. The
crystallographic refinement parameters of complex 1 are
summarized in Table 1.
Formation of the ammonium salt [hfac][NH3R],8
a
kinetic product obtained by direct mixing of hexafluo-
roacetylacetone with amine, was not observed. The
latter synthetic procedure is effective for the large-scale
generation of the required bis(trifluoromethyl)-substi-
tuted â-ketoimine ligands.
CVD P r oced u r es. Thermal CVD reactions were conducted
in a horizontal hot-wall Pyrex reactor, consisting of a Pyrex
tube of internal diameter 25 mm, placed within an electric
temperature-controlled tube furnace, as described in Chart 1.
Precursors were loaded in the glass container. The carrier gas
was introduced through a side arm of the container and
became saturated with vapors of palladium precursors before
entering the hot zone. Si substrates were cleaned using the
Sch em e 1

Allyl(â-ketoiminato)palladium(II) Complexes
Organometallics, Vol. 18, No. 5, 1999 867
Ta ble 2. Str u ctu r es a n d Meltin g P oin ts of P a lla d iu m P r ecu r sor s 1-16
compd no.
R
R1
R2
R3
R4
yield (%)
mp (°C)
1
2
3
4
5
Me
Me
Me
Me
Me
Me
Me
Me
Ph
Me
H
Me
H
H
H
H
H
Me
Me
Me
H
H
H
H
Me
Me
Me
Me
Me
CH2OMe
CH2OMe
CH2OMe
H
H
H
Me
Me
H
H
H
H
H
H
Me
Me
Me
Me
Me
H
H
H
H
H
86
61
80
86
90
80
90
87
73
90
75
95
87
88
95
80
129-132
unstable
79-81a
89-91a
49-51a
liquid
Me
Me
Me
CH2CH2OMe
CH2CHdCH2
Me
CH2CH2OMe
CH2CH2OMe
Me
6
7
70-72a
liquid
8b
9b
10b
11b
12
13
14
15
16
Me
liquid
liquid
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CH2CH2OMe
Me
79-81
118-120
60-62
71-73
87-89
89-91
Bun
H
H
H
H
CH2CH2OMe
Me
CH2CHdCH2
a
b
Sample decomposed upon melting. Selected for CVD experiments.
Sch em e 2
changing the substituents R on the ketoimine ligand
from Me to CF3, increasing the numbers of methyl
substituents on the η3-allyl ligand, or attaching a bulky
or long-chain hydrocarbon, such as an n-butyl, meth-
oxyethyl, or allyl group to the nitrogen of the ketoimi-
nato ligand. Evidently, steric interactions on both the
η3-allyl and â-ketoiminate ligands is the principal factor
that stabilizes these complexes. The presence of a
methoxy and a second allyl pendant also seems to
improve the thermal stability.
The complexes [(allyl)Pd(µ-Cl)]2 were prepared ac-
cording to literature methods.5 Five allyl complexes
were synthesized; their molecular structures are
The volatility and thermal stability of the Pd com-
pounds were investigated, since these are important in
CVD applications. Using thermogravimetric analysis
(TGA) it was found that Pd complexes with ketoimine
ligands derived from acetylacetone are less thermally
stable. This effect is best seen from the TGA of 8, which
exhibits a sudden weight loss of 68% between 146 and
182 °C and which leaves a black residue nearly equiva-
lent to the theoretical weight of Pd metal. In contrast,
complexes derived from hexafluoroacetylacetone are
more volatile and robust under conditions of TGA
experiments. Thus, most of these fluorine-substituted
complexes partially evaporated and partially decom-
posed, producing a small amount of metallic Pd residue.
Of particular interest is the TGA of 10, which showed
a simple one-step loss of nearly 100% within the
temperature range 139-175 °C. This observation is
consistent with highly effective transportation of Pd
metal into the gas phase without decomposition.
The physical properties, such as the melting point,
of the Pd complexes can be modified by changing the
ligand environment to give liquid CVD precursors
having distinct advantages in applications due to their
reproducible and steady rates of evaporation.9 As indi-
cated in Table 2, complexes 4-12 possess fairly low
melting points and show potential for CVD application
as liquid precursors, while complexes 8-10 exist as
slightly viscous liquid materials at room temperature.
Str u ctu r e of Ketoim in a to Com p lexes. Confirma-
tion of the molecular structure was provided by a single-
crystal X-ray analysis of the N-substituted phenyl
complex 1. As can be seen from Figure 1, the Pd atom
possesses a distorted-square-planar coordination envi-
ronment consisting of O and N atoms of the â-ketoimi-
nate ligand and C(1) and C(3) of the allyl ligand. The
Pd-O distance (2.056(3) Å) is nearly equal to that of
Our synthetic strategy was to select congested, highly
substituted allyl ligands while avoiding unnecessarily
large organic substituents which could reduce the
volatility of the palladium complexes.
In the synthesis of allyl(â-ketoiminato)palladium(II)
complexes, the â-ketoimine ligand is first converted to
the â-ketoiminate salt on treatment with a slight excess
of NaOH in aqueous media or NaOMe in diethyl ether.
Mixing this solution with a second solution containing
[(allyl)Pd(µ-Cl)]2 in equal proportion generates the allyl
â-ketoiminato complexes (allyl ) C3H5, C3H4Me, C3H3-
Me2, C3H2Me2(CH2OMe); Scheme 2). The â-ketoiminato
Pd complexes prepared during this study are listed in
Table 2, along with their structural properties, reaction
yields, and melting points.
The physical properties of the â-ketoiminate com-
plexes differ substantially: 1 possesses the highest
melting point and is relatively nonvolatile at room
temperature, while 2 is unstable at room temperature
and even decomposes to form a Pd film on the wall of
the reaction flask during workup. Complexes 1, 8-10,
and 14-16 can be stored at room temperature for long
periods, whereas other less stable analogues have to be
kept below 0 °C to avoid decomposition. The thermal
stability of the Pd complexes can be improved by
(8) Shin, H.-K.; Hampden-Smith, M. J .; Kodas, T. T.; Rheingold, A.
L. J . Chem. Soc., Chem. Commun. 1992, 217.
(9) (a) Maury, F. J . Phys. IV 1995, C5, 449. (b) Maury, F. Chem.
Vap. Deposition 1996, 2, 113.

868 Organometallics, Vol. 18, No. 5, 1999
Tung et al.
F igu r e 2. Variable-temperature 13C NMR spectra (d6-
DMSO) of 6, showing the olefinic protons of the methallyl
ligand.
F igu r e 1. Molecular structure of complex 1, emphasizing
the coordination environment about Pd and showing the
atomic numbering scheme. Relevant bond distances (Å):
Pd-O ) 2.056(3), Pd-N ) 2.066(3), N-C(8) ) 1.308(5),
O-C(6) ) 1.275(5), C(6)-C(7) ) 1.372(6), C(7)-C(8) )
1.407(6), Pd-C(1) ) 2.097(4), Pd-C(2) ) 2.116(4), Pd-C(3)
) 2.139(4), C(1)-C(2) ) 1.410(6), C(2)-C(3) ) 1.399(6).
Bond angles (deg): O-Pd-N ) 91.2(1), N-Pd-C(1) )
101.5(2), O-Pd-C(3) ) 99.3(2).
ature. These four signals are assigned to syn, anti, syn,
4
and anti protons on the basis of the pattern of J HH
coupling observed. When the temperature is raised to
343 K, all signals broadened substantially, indicating
the onset of chemical exchange. This behavior was
1
confirmed by a H NMR spin saturation transfer experi-
ment conducted on complex 3 in CDCl3 solution at room
temperature. In the latter experiment, irradiation of one
anti proton signal led to the complete suppression of the
second anti signal but gave no obvious diminution of
the syn proton signals. The same observation was noted
on irradiation of the syn proton signals under similar
conditions. These 1H NMR SST experiments clearly
indicate the presence of a dynamic process that causes
the pairwise exchange between pairs of anti protons and
syn protons but produces no scrambling among the anti
and syn protons.
the Pd-N distance (2.066(3) Å), while the N-C(8)
distance (1.308(5) Å) and its adjacent C(7)-C(8) distance
(1.407(6) Å) are also similar to the O-C(6) distance
(1.275(5) Å) and the respective C(6)-C(7) distance
(1.372(6) Å), indicating formation of evenly distributed
and delocalized π-interactions on the ketoiminato ligand.
The Pd-C distances and the N-Pd-C(1) and O-Pd-
C(3) angles, respectively, are within the limits of
experimental error of the related ketoiminate complex,
but the latter contains a nondelocalized ketoiminato
ligand.10
For compounds that contain an asymmetric η3-allyl
ligand, only one set of 1H NMR proton signals were
observed for all examples at even lower temperature.
Thus, only one isomer is present in solution for the
asymmetric η3-allyl complexes, in which the non-
hydrogen substituents are believed to be located at the
position trans to the nitrogen atom of the â-ketoiminate
ligand, because of reduced steric interaction.
F lu xion a l Beh a vior in Solu tion . The allyl(â-ke-
toiminato)palladium complexes possess novel dynamic
behavior in solution, as revealed from the variable-
temperature 1H NMR studies of methallyl complexes
3, 6, 15, and 16 in CDCl3, toluene, or DMSO. For
instance, olefinic proton signals of the methallyl ligand
in complex 6 appear at δ 3.48 (J HH ) 2.8 Hz), 2.72, 2.58
(J HH ) 2.8 Hz), and 2.33 in d8-toluene at room temper-
The fluxional behavior was observed to be more rapid
in a polar organic solvent. This is best exemplified by
1
the variable-temperature H NMR studies of complex
6 in d6-DMSO. As seen in Figure 2, the syn protons at
δ 3.41 and 2.87 and the anti protons at δ 2.75 and 2.61
observed at room temperature broaden substantially
when the temperature is increased. When the temper-
ature is raised to 353 K, the anti protons produce a
broad signal at δ 2.71, while the syn protons completely
merge into the baseline; no coalescence of syn protons
was observed at this temperature because their chemi-
cal shifts differ greatly. Moreover, the 1H NMR spec-
trum of 16 in d6-DMSO at room temperature exhibits
only two signals: one is a broad signal at δ 3.62 and
the second is a relatively sharp signal at δ 3.07 due to
syn and anti protons, which is in marked contrast to
observation of four distinct olefinic signals of η3-allyl
ligand in CDCl3 or d8-toluene solution, confirming the
(10) Claverini, R.; Ganis, P.; Pedone, C. J . Organomet. Chem. 1973,
50, 327.

Allyl(â-ketoiminato)palladium(II) Complexes
Organometallics, Vol. 18, No. 5, 1999 869
Ta ble 3. Dep osition Con d ition s a n d Th in -F ilm
P r op er tiesa
Sch em e 3
atom %
sample
deposition
O2 flow
precursor temp (°C) temp (°C) rate (mL/min) Pd
C
F
8
8
8
70
70
70
70
25
60
60
60
300
300
200
250
200
200
300
200
10.0
40.0
40.0
40.0
34.0
25.0
35.0
25.0
95 4.2
98 1.5
98 2.0
98 1.2
97 1.5 1.4
97 1.4 1.6
97 1.2 1.2
97 1.4 2.1
9
10
10
11
11
a
All experiments were carried out under a pressure of (1-3) ×
10-2 Torr, depending on the O2 flow rate; substrates were broken
Si wafers.
impurities.14 Although experimental conditions were not
optimized, the Pd films obtained were shiny and mir-
rorlike. They adhered well to silicon substrates but
poorly to SiO2, as tested by scratch or adhesive-tape
tests. Preliminary XPS and Auger spectroscopy identify
the films prepared from 8 and 9 as g98% Pd with e2%
of carbon and no nitrogen contamination, while films
from 10 and 11 differ in that detectable amounts (<2%)
of residual fluorine are retained, when the deposition
experiments were conducted at 200-300 °C. However,
when the deposition temperature is increased to 300 °C
and the flow rate of oxygen carrier gas to 40 mL/min,
the amount of carbon impurities dropped to ∼1%, which
represents the best film we obtained in this work. A
summary of typical experimental conditions, together
with analytical data for palladium films, is given in
Table 3. Electrical conductivity measurement of films
in one example give a resistivity of 1.6 × 10-5 Ω cm,
slightly higher than that of bulk Pd metal (1.1 × 10-5
Ω cm). Again, this effect is attributed to incorporation
of carbon impurities in the Pd films.
Con clu sion . Allyl(â-ketoiminato)palladium(II) com-
plexes can serve as precursors for chemical vapor
deposition of Pd thin films. Unlike diketonato com-
pounds reported previously,4 which require fairly ex-
pensive fluorinated diketonato ligands, the compounds
discussed herein can be prepared in good yields from
easily accessible and inexpensive commercially available
materials. Furthermore, the melting points and thermal
stabilities of these precursors can be tailored by sys-
tematic modification of the η3-allyl or â-ketoiminato
group. After appropriate adjustment of substituents,
some complexes display excellent thermal stability and
volatility at or above room temperature. In the case of
complexes 8-10, stable liquid phases are obtained: they
are among the best CVD precursors for Pd thin films
reported to date.
existence of a similar, but much faster, pairwise ex-
change of syn and anti protons.
The lack of interchange between syn and anti protons
in all experiments clearly shows that the fluxional
process is not due to a η3-η1-η3 interconversion of the
allyl ligand.11 Other likely explanations would be 180°
rotation of the planar η3-allyl ligand about the allyl-
palladium axis12 and the formation of a solvent-
coordinated intermediate that contains either an O-
bound or a N-bound monodentate ketoiminato ligand,
followed by interchange of the solvent molecule and the
ketoiminato ligand (Scheme 3), as both latter processes
would average the environment of syn-syn and anti-
anti protons, but not interchange syn and anti protons.
Direct rotation of the allyl ligand seems to be the process
occurring in chloroform or toluene, as these nonpolar
solvents coordinate poorly to the Pd atom. However, on
altering the solvent to DMSO, incorporation of the
solvent molecule into the coordination sphere of the
palladium atom is more facile; thus, the solvent-assisted
pathway becomes the dominant exchange process in
solution. Interestingly, this exchange pathway is mecha-
nistically similar to that observed in palladium com-
plexes [(allyl)PdClL], generated by the addition of
DMSO, phosphine, or arsine ligand, to allylpalladium
chloride complexes [(allyl)Pd(µ-Cl)]2.13
CVD of P a lla d iu m . CVD experiments were con-
ducted in a horizontal hot wall reactor with selected
ketoiminato precursors 8-11 at reduced pressure. Other
complexes were not tested in CVD experiments because
of low volatility and poor thermal stability. The experi-
ments were carried out at 200-300 °C and precursor
samples were kept between 25 and 70 °C, with oxygen
as carrier gas (20-40 mL/min) to suppress carbon
Ack n ow led gm en t. We thank the National Science
Council of the Republic of China for financial support
(Grant No. NSC 87-2113-M007-027-COM).
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates and anisotropic thermal parameters for complex
1 and 1H NMR spectra for complexes 2, 6, 8-11, 13, and 14.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(11) (a) Cotton, F. A.; Faller, J . W.; Musco, A. Inorg. Chem. 1967, 6,
179. (b) van Leeuwen, P. W. N. M.; Praat, A. P. J . Chem. Soc., Chem.
Commun. 1970, 365.
(12) (a) Davison, A.; Rode, W. C. Inorg. Chem. 1967, 6, 2124. (b)
Faller, J . W.; Incorvia, M. J . Inorg. Chem. 1968, 7, 840. (c) Faller, J .
W.; Incorvia, M. J .; Thomsen, M. E. J . Am. Chem. Soc. 1969, 91, 518.
(13) Ramey, K. C.; Statton, G. L. J . Am. Chem. Soc. 1966, 88, 4387.
OM980728C
(14) Hierso, J .-C.; Satto, C.; Feurer, R.; Kalck, P. Chem. Mater. 1996,
8, 2481.