Organophosphine/phosphite-stabilized silver(I) complexes bearing N-acetylbenzamide ligand: Synthesis, characterization and potential application in metal organic chemical vapor deposition

Article abstract of DOI:10.1002/aoc.2863

New N-silver(I) acetylbenzamide complexes of type L_n· AgNC₉H₈O₂ (L = PPh₃; n = 1, 2a; n = 2, 2b; n = 3, 2c; L = P(OEt)₃; n = 1, 2d; n = 2, 2e; n = 3, 2f) were prepared. These complexes were

Full text of DOI:10.1002/aoc.2863

Full Paper
Received: 3 January 2012
Revised: 17 March 2012
Accepted: 19 March 2012
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/aoc.2863
Organophosphine/phosphite-stabilized
silver(I) complexes bearing N-acetylbenzamide
ligand: synthesis, characterization and
potential application in metal organic
chemical vapor deposition
Xian Tao, Ke-Cheng Shen, Qing-Yun Tang, Meng Feng, Jiang-Tao Fang,
Yu-Long Wang and Ying-Zhong Shen*
New N-silver(I) acetylbenzamide complexes of type LnꢀAgNC9H8O2 (L = PPh3; n = 1, 2a; n = 2, 2b; n = 3, 2c; L = P(OEt)3; n = 1, 2d;
n = 2, 2e; n = 3, 2f) were prepared. These complexes were obtained in high yields and characterized by elemental analysis, 1H
NMR, 13C{H} NMR, 31P{H} NMR and IR spectroscopy, respectively. The molecular structure of 2b has been determined by X-ray
single-crystal analysis in which the silver atom is in a distorted tetrahedral geometry and crystallizes as cis–trans. New N-silver(I)
acetylbenzamide complexes have a four-membered ring, which could influence their chemical and physical properties and
modulate volatility. Metal organic chemical vapor deposition experiments were carried out successfully at 400ꢁC and 450ꢁC
using 2e as precursor for the deposition of silver films, respectively. The high-purity silver film obtained at 400ꢁC is dense
and homogeneous. Copyright © 2012 John Wiley & Sons, Ltd.
Supporting information may be found in the online version of this article.
Keywords: silver; N-acetylbenzamide; precursor; MOCVD
deposition temperature 523–623 K, system pressure 6.7 Pa;[25]
Introduction
[(fod)Ag(PMe3)] with carrier gas H2, deposition temperature
503–573 K, system pressure 13.3 Pa;[26] [(CF3COO)Ag(PnBu3)] with
With the enormous progress in microelectronic circuitry, such as
decreasing feature sizes and increasing chip speeds,[1] it is
carrier gas Ar, deposition temperature 480–590 K, system
pressure 101.3 Pa.[5] In our previous report, various organopho-
anticipated that there will be a need to change interconnect
materials to be suitable for reducing signal propagation delays.[2]
sphine-stabilized silver complexes, for example, silver methane-
sulfonates,[21,22,27,28] and silver succinimide[23,29,30] have been
In this respect, silver is an excellent choice because it has the low-
est resistivity and highest thermal conductivity of all metals at
room temperature.[1,3–5] Various methods have been used to
deposit silver thin films, such as sputtering,[6] thermal evapora-
tion,[7] electron-beam evaporation,[8] and chemical vapor deposi-
tion (CVD).[9] Of these techniques, metal organic chemical vapor
deposition (MOCVD) is a very effective technique for intercon-
tacts in ultra large-scale integration (ULSI) because of its high
deposition rates with good step coverage[10–13] and high aspect
ratio in the multilevel metallization structure.[14]
used as CVD precursors in a number of studies. Thus new classes
of silver(I) precursors are highly desirable. N-Acetylbenzamide has
a novel structure which may form the class of cyclic b-diketones
for good chelating ability, and there are only a few reports
about its metal complexes.[31] We report here the synthesis of
organophosphine/phosphite-stabilized N-silver(I) acetylbenza-
mide complexes which were used as precursor for the deposition
of silver by using MOCVD techniques for the first time. The single-
crystal structure of 2b has also been determined and discussed.
One of the major problems in silver MOCVD is the selection of
appropriate silver(I) precursors. The silver precursors most often
used are diverse inorganic and organometallic complexes, includ-
ing AgF,[15] [(C4F7)Ag]n,[16] (b-diketonato)Ag(PR3),[17,18] (hfac)Ag
(CNMe),[19] various organophosphine-stabilized silver carboxy-
lates,[20] silver methanesulfonates[21,22] and silver succinimide.[23]
The majority of silver salts and complexes are completely invola-
tile,[24] but it can be overcome by employing tertiary phosphines
as secondary ligands. Organometallic silver compounds with
tertiary phosphines are used as precursors in CVD for the deposition
of silver layers, e.g. [(hfac)Ag(PMe3)n] with no carrier gas,
*
Correspondence to: Ying-Zhong Shen, Applied Chemistry Department, School
of Material Science and Engineering, Nanjing University of Aeronautics and
Astronautics, Nanjing 210016, People’s Republic of China. E-mail: yz_shen@nuaa.
edu.cn
Applied Chemistry Department, School of Material Science and Engineering,
Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People’s
Republic of China
Appl. Organometal. Chem. 2012, 26, 323–329
Copyright © 2012 John Wiley & Sons, Ltd.

X. Tao et al.
d 7.2–7.5 (m, 18 H, PPh3ꢂ, Phꢂ), d 8.1 (d, 2H, Phꢂ, JHH = 7.4
Hz). 13C{H} NMR (CDCl3): d 25.7 (CH3), d 127.6 (C6H5), d 128.3
(C6H5), d 129.6 (C6H5), d 130.2 (C6H5), d 128.0 (C6H5/PPh3), d 129.4
(JPC = 10.7 Hz, C6H5/PPh3), d 131.4 (C6H5/PPh3), d 134.0 (JPC = 16.1
Hz, C6H5/PPh3), d 176.3 (C=O/C6H5C=O), d 180.7 (C=O/CH3C=O).
31P{H} NMR (CDCl3): d 15.2. IR (KBr) data (cmꢂ1): 3053 (m), 2925
(m), 1611 (s), 1598 (s), 1570 (s), 1480 (s), 1435 (s), 1371 (s), 1338 (s),
1267 (m), 1096 (m), 1016 (m), 899 (w), 745 (s), 693 (s), 677 (m), 518
(m), 504 (s), 441 (w).
Experimental
General Procedures
All operations were carried out under an atmosphere of purified
nitrogen with standard Schlenk techniques. The solvent dichloro-
methane (CH2Cl2) was purified by distillation from P2O5 under N2
before use. N-Acetylbenzamide was synthesized from benzamide
in acetic anhydride with two drops of concentrated sulfuric
acid.[32] 1H NMR were recorded on a Bruker Advance 300 spec-
trometer operating at 300.130 MHz in the Fourier transform
mode; 13C{H} NMR spectra were recorded at 75.467 MHz. Chemical
shifts are reported in d units (parts per million) downfield from
tetramethylsilane (d = 0.0 ppm) with the solvent as the reference
signal (1H NMR, CDCl3 d = 7.26; 13C{H} NMR, CDCl3 d = 77.55).
31P{H} NMR spectra were recorded with a Bruker Advance 300
spectrometer operating at 121.49 MHz, using the pulsed Fourier
transform mode. 31P{H} NMR spectra were run under conditions
of broad-band proton decoupling in CDCl3. All spectra were
referenced to external 85% H3PO4 at room temperature, with
the appropriate lock solvent. Infrared spectra were collected
on a Bruker Vector 22 Instrument in KBr at room temperature.
Elemental analysis was performed on a PerkinElmer 240 C
elemental analyzer. Thermogravimetry (TG) and differential scan-
ning calorimetry (DSC) studies were carried out with a NETZSCH
STA 409 PC/PG with a constant heating rate of 10ꢁC minꢂ1 under
N2 (30 cm3 minꢂ1). Melting points were observed in sealed capil-
laries and were uncorrected. MOCVD experiments were carried
out in a vertical quartz tube hot-wall MOCVD reactor of 60 mm
diameter. Heating was achieved by a resistively heated tube oven
(AICHUANG Co.). Scanning electron microscopy (SEM) and
energy-dispersive X-ray (EDX) analysis were carried out using a
Hitachi model S-4800 with scanning electron microscope
and EDX detector. Absorption spectra were recorded with a UV-
2550 UV ꢂ visible spectrophotometer.
Synthesis of (Ph3P)2ꢀAgNC9H8O2 (2b)
Complex 2b is obtained by following the above procedure, only
using triphenylphosphine (0.2623 g, 1 mmol), AgNO3 (0.0849 g,
0.5 mmol) and NaNC9H8O2 (0.0925 g, 0.5 mmol) instead. After ap-
propriate work-up (see above), complex 2b was obtained as a
white solid. Yield: 0.36 g (91% based on AgNO3); m.p. 216–
217ꢁC dec.. Anal. Calcd for C45H38O2AgNP2: C, 68.02; H, 4.82; N,
1
1.76. Found: C, 67.63; H, 4.43; N, 1.72%. H NMR (CDCl3): d 2.5 (s,
3 H, CH3ꢂ;), d 7.1–7.7 (m, 33 H, PPh3ꢂ, Phꢂ;), d 7.9 (d, 2 H,
Phꢂ, JHH = 7.2 Hz). 13C{H} NMR (CDCl3): d 25.3 (CH3), d 127.7
(C6H5), d 131.4 (C6H5), d 131.6 (C6H5), d 131.8 (C6H5), d 127.5
(C6H5/PPh3), d 128.5 (JPC = 9.8 Hz, C6H5/PPh3), d 129.9 (C6H5/
PPh3),
d 133.4 (JPC = 16.5 Hz, C6H5/PPh3), d 174.3 (C=O/
C6H5C=O), d 179.1 (C=O/CH3C=O). 31P{H} NMR (CDCl3): d 8.6. IR
(KBr) data (cmꢂ1): 3053 (m), 2925 (m), 1616 (m), 1586 (s), 1566 (s),
1479 (s), 1434 (s), 1369 (s), 1339 (s), 1263 (m), 1096 (s), 1010 (m),
898 (w), 747 (s), 722 (s), 693 (s), 679 (m), 516 (s), 503 (s), 440 (w).
Synthesis of (Ph3P)3ꢀAgNC9H8O2 (2c)
Complex 2c can be synthesized in the same manner as 2a (see
above). In this respect, triphenylphosphine (0.3935 g, 1.5 mmol)
and AgNO3 (0.0849 g, 0.5 mmol) reacted with NaNC9H8O2
(0.0925 g, 0.5 mmol). After appropriate work-up (see above),
complex 2c was obtained as a white solid. Yield: 0.49 g (93%
based on AgNO3); m.p. 221–223ꢁC dec.. Anal. Calcd for
C63H53O2AgNP3: C, 71.59; H, 5.05; N, 1.33. Found: C, 70.91; H,
Synthesis
1
4.73; N, 1.30 %. H NMR (CDCl3): d 2.5 (s, 3 H, CH3ꢂ), d 7.0–7.7
Synthesis of NaNC9H8O2 (1)
(m, 48 H, PPh3ꢂ, Phꢂ), d 7.9 (d, 2 H, Phꢂ, JHH = 7.4 Hz). 13C{H}
NMR (CDCl3): d 25.3 (CH3), d 127.6 (C6H5), d 131.6 (C6H5), d 131.7
(C6H5), d 132.1 (C6H5), d 127.5 (C6H5/PPh3), d 128.4 (JPC = 9.6 Hz,
C6H5/PPh3), d 129.7 (C6H5/PPh3), d 133.4 (JPC = 16.6 Hz, C6H5/
PPh3), d 171.1 (C=O/C6H5C=O), d 172.4 (C=O/CH3C=O). 31P{H}
NMR (CDCl3): d 8.0. IR (KBr) data (cmꢂ1): 3051 (m), 2925 (m),
1609 (m), 1586 (s), 1565 (s), 1479 (s), 1434 (s), 1369 (s), 1339 (s),
1263 (w), 1096 (s), 1009 (m), 898 (m), 748 (s), 722 (s), 693 (s),
679 (m), 516 (s), 503 (s), 440 (w).
Sodium hydride (0.3000 g, 10.00 mmol) as an approximately 80%
dispersion in mineral oil dissolved in 20 ml CH2Cl2 was added
dropwise to
a
stirred solution of N-acetylbenzamide[32]
(1.6300 g, 10.00 mmol) in 20 ml CH2Cl2 at 0ꢁC. The reaction mix-
ture was stirred for 1 h and a large amount of white precipitate
appeared. The suspension was filtered through a Büchner
funnel also under an atmosphere of purified nitrogen, and
was washed with 10 ml CH2Cl2 twice. A white solid product
was obtained after removing CH2Cl2 under oil-pump vacuum.
The product was stored under nitrogen. Yield: 1.55 g (84%,
based on N-acetylbenzamide).
Synthesis of (EtO)3PꢀAgNC9H8O2 (2d)
Complex 2d can be synthesized similar to a procedure used for
the synthesis of 2a (see above). In this respect, [(EtO)3P] (0.0831
g, 0.5 mmol) and AgNO3 (0.0849 g, 0.5 mmol) reacted with NaN-
C9H8O2 (0.0925 g, 0.5 mmol). After appropriate work-up, complex
2d can be isolated as a colorless liquid. Yield: 0.20 g (92% based
on AgNO3); m.p. 61–62ꢁC dec.. Anal. Calcd for C15H23O5AgNP: C,
41.31; H, 5.31; N, 3.21. Found: C, 41.16; H, 5.02; N, 3.15%. 1H
NMR (CDCl3): d 1.3 (t, 9 H, CH3/CH3CH2ꢂ, JHH = 7.1 Hz), d 2.5 (s,
3 H, CH3ꢂ), d 3.9 (qd, 6 H, JHH = 7.1 Hz, JPH = 2.8 Hz, CH2/
CH3CH2ꢂ), d 7.3–7.4 (m, 3 H, Phꢂ), d 8.0 (d, 2 H, Phꢂ, JHH = 7.3
Hz). 13C{H} NMR (CDCl3): d 15.7 (JPC = 6.2 Hz, CH3/CH3CH2ꢂ), d
25.0 (CH3), d 60.8 (JPC = 4.4 Hz, CH2/CH3CH2ꢂ), d 127.7 (C6H5), d
130.2 (C6H5), d 130.9 (C6H5), d 132.3 (C6H5), d 175.5 (C=O/C6H5C=O),
Synthesis of Ph3PꢀAgNC9H8O2 (2a)
A solution of triphenylphosphine (0.1312 g, 0.5 mmol) and
AgNO3 (0.0849 g, 0.5 mmol) dissolved in 20 ml CH2Cl2 was added
dropwise to a stirred solution of NaNC9H8O2 (0.0925 g, 0.5 mmol)
suspended in 20 ml CH2Cl2 at 0ꢁC. The clear solution was
obtained by filtration through a pad of celite after stirring the
reaction mixture for 6 h at 0ꢁC. A white solid product was
obtained after removing all the volatiles under oil-pump vacuum.
Yield: 0.24 g (90% based on AgNO3); m.p. 204–206ꢁC dec. Anal.
Calcd for C27H23O2AgNP: C, 60.92; H, 4.35; N, 2.63. Found: C,
1
60.36; H, 4.04; N, 2.58 %. H NMR (CDCl3): d 2.6 (s, 3 H, CH3ꢂ),
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Copyright © 2012 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2012, 26, 323–329

Organophosphine/phosphite-stabilized silver(I) complexes
d 179.1 (C=O/CH3C=O). 31P{H} NMR (CDCl3): d 123.8. IR (KBr) data
(cmꢂ1): 3061 (m), 2981 (s), 2934 (m), 2899 (m), 1673 (s), 1599 (s),
1573 (s), 1445 (m), 1391 (s), 1347 (s), 1275 (m), 1163 (m), 1097 (m),
1021 (s), 935 (s), 771 (m), 719 (m), 678 (m), 542 (m).
Metal Organic Chemical Vapor Deposition of 2e
The deposition of silver was conducted using a vertical quartz
tube hot-wall MOCVD reactor with 2e as precursor. As substrate
pieces of oxidized silicon were applied, the typical deposition
time was limited to 30 min. For each of MOCVD experiments,
approximately 500 mg 2e was charged into the sample reservoir,
maintained at 120ꢁC to ensure the generation of adequate partial
pressure of the sample. A stream of nitrogen was introduced,
with the flow rate adjusted to 20 sccm under a pressure of
60 Pa. The substrate susceptor was heated at a temperature
between 400ꢁC and 450ꢁC by a resistive heating element. The
deposition of Ag films was carried out in a reaction chamber
(a hot-wall vertical cylindrical reactor). No reducing agent such as
H2 was used in the deposition processes. The average film thick-
nesses at different temperatures were about 0.56 mm, 0.68 mm,
respectively.
Synthesis of [(EtO)3P]2ꢀAgNC9H8O2 (2e)
Complex 2e can be synthesized in the same manner as 2a
(see above). In this respect, [(EtO)3P] (0.1662 g, 1 mmol) and AgNO3
(0.0849 g, 0.5 mmol) reacted with NaNC9H8O2 (0.0925 g, 0.5 mmol).
After appropriate work-up (see synthesis of 1, above) complex 2e is
obtained as a colourless liquid. Yield: 0.27 g (90% based on AgNO3).
Anal. Calcd for C21H38O8AgNP2: C, 41.87; H, 6.36; N, 2.33. Found:
1
C, 41.57; H, 6.08; N, 2.26 %. H NMR (CDCl3): d 1.2 (t, 18 H, CH3/
CH3CH2ꢂ, JHH = 7.1 Hz), d 2.5 (s, 3 H, CH3ꢂ), d 3.9 (qd, 12 H, JHH = 7.1
Hz, JPH = 2.2 Hz, CH2/CH3CH2ꢂ), d 7.3–7.4 (m, 3 H, Phꢂ), d 8.0 (d, 2 H,
Phꢂ, JHH = 7.3 Hz). 13C{H} NMR (CDCl3): d 15.9 (JPC = 6.2 Hz, CH3/
CH3CH2ꢂ), d 22.6 (CH3), d 60.3 (JPC = 5.3 Hz, CH2/CH3CH2ꢂ),
d 127.1 (C6H5), d 127.9 (C6H5), d 131.1 (C6H5), d 133.1 (C6H5),
d 169.4 (C=O/C6H5C=O), d 178.4 (C=O/CH3C=O). 31P{H} NMR Results and Discussion
(CDCl3): d 128.6. IR (KBr) data (cmꢂ1): 3065 (s), 2981 (m), 2936 (m),
Synthesis and Characterization of Complexes 2a–2f
2896 (m), 1660 (s), 1625 (s), 1578 (s), 1449 (m), 1404 (s), 1385 (s),
1298 (m), 1123 (m), 1097 (m), 1024 (s), 939 (s), 790, (m), 771 (m),
686 (m), 636 (m), 532 (m), 415 (w).
Metalorganic silver precursors of type LnꢀAgNC9H8O2 (L = PPh3;
n = 1, 2a; n = 2, 2b; n = 3, 2c; L = P(OEt)3; n = 1, 2d; n = 2, 2e;
n = 3, 2f) were prepared and used for this work (Scheme 1).
Synthesis of [(EtO)3P]3ꢀAgNC9H8O2 (2f)
Table 1. Crystallographic data and analysis parameters for 2b
Complex 2f can be synthesized using a similar procedure to that
for 2a (see above). In this respect, [(EtO)3P] (0.2493 g, 1.5 mmol)
and AgNO3 (0.0849 g, 0.5 mmol) reacted with NaNC9H8O2
(0.0925 g, 0.5 mmol). After appropriate work-up, complex 2d
can be isolated as a colourless liquid. Yield: 0.34 g (88% based
on AgNO3). Anal. Calcd for C27H53O11AgNP3: C, 42.20; H, 6.95; N,
1.82. Found: C, 41.82; H, 6.59; N, 1.77%. 1H NMR (CDCl3): d 1.2
(t, 27 H, CH3/CH3CH2ꢂ, JHH =7.1 Hz), d 2.5 (s, 3 H, CH3ꢂ), d 3.9 (qd,
18 H, JHH =7.2 Hz, JPH =1.4 Hz, CH2/CH3CH2ꢂ), d 7.3–7.5 (m, 3 H,
Phꢂ), d 8.0 (d, 2 H, Phꢂ, JHH = 7.4 Hz). 13C{H} NMR (CDCl3):
d 16.5 (JPC = 6.0 Hz, CH3/CH3CH2ꢂ), d 25.5 (CH3), d 60.3 (JPC = 4.9
Hz, CH2/CH3CH2ꢂ), d 128.0 (C6H5), d 131.5 (C6H5), d 131.6 (C6H5),
d 133.6 (C6H5), d 169.5 (C=O/C6H5C=O), d 178.1 (C=O/CH3C=O).
31P{H} NMR (CDCl3): d 130.1. IR (KBr) data (cmꢂ1): 3064 (m),
2981 (s), 2935 (m), 2901 (m), 1682 (s), 1615 (s), 1575 (s), 1445
(m), 1392 (s), 1347 (s), 1272 (m), 1163 (s), 1097 (s), 1022 (s), 935
(s), 770 (s), 718 (m), 678 (m), 617 (w), 537 (m), 418 (w).
Formula
C
91H76Ag2Cl2N2O4P4
Formula weight
Space group
Crystal size (mm)
Crystal system
Z value
1672.06
C2/c
0.2 ꢃ 0.2 ꢃ 0.2
Monoclinic
4
a (Å)
19.652 (4)
b (Å)
17.297 (4)
c (Å)
24.326 (5)
a (ꢁ)
90
b (ꢁ)
110.29 (3)
g (ꢁ)
90
Dcalc (g cmꢂ3
)
1.432
Index ranges
ꢂ23 ≤ h ≤ 19, -17 ≤ k ≤ 20, -21≤ l ≤ 29
Crystal shape/color
Prism/colorless
3424
F (000)
m (Mo Ka) (mmꢂ1
l (Mo Ka) (Å)
Temperature (K)
θ range (ꢁ)
)
0.71
0.71073
153(2)
X-Ray Structure Determination
2.7–28.9
6471
A single crystal of 2b could be obtained by cooling a saturated
dichloromethane solution containing 2b to ꢂ20ꢁC. A suitable
crystal for X-ray determination was placed in glue under N2
because of its sensitivity to oxygen and moisture. X-ray structure
measurement was performed on a Bruker Smart Apex CCD detec-
tor equipped with graphite monochromatic Mo Ka radiation
(l = 0.71073 Å) at 153 K. Date collection and processing (cell
refinement, data reduction, and empirical absorption correction)
were performed using the CrystalClear program package.[33]
The structure was solved using direct methods and refined
by full-matrix least-squares procedures on F2 (SHELX-97).[34] All
of the non-hydrogen atoms were refined with anisotropic
displacement parameters. Crystallographic data and details on
refinement are presented in Table 1.
Independent reflections
[(I) > 2s(I)]
R1 [I > 2s(θ)]
wR2 [I > 2s(θ)]
Goodness-of-fit on F2c
0.031
0.071
1.04
Δrmax (eÅꢂ3
)
0.84
Δrmin (eÅꢂ3
)
ꢂ0.93
h
ꢂ
ꢃ
i
1=2
.
ꢀ
ꢁ
ꢀ
ꢁ
P
P
P
P
2
aR1 ¼ ðjjFoj ꢂ jFcjjÞ= jFoj;wR2 ¼
w F2o ꢂ F2c
=
wF4o
h
ꢂ
ꢃ
ꢂ
ꢃ
i
ꢂ
ꢃ
bw = 1 / s2 F2o
+
0.0357P 2 + 10.3555P , P = Fo2 + 2F2c /3.
h
i
P
cS =
w(F2o ꢂ Fc2)2 / (nꢂ p)1/2; n= number of reflections, p = parameters
used.
Appl. Organometal. Chem. 2012, 26, 323–329
Copyright © 2012 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

X. Tao et al.
Scheme 1. Synthesis of complexes 2a–2f
The complexes were isolated in high yield (88–93%) as white
solids (2a–2c) or colorless liquids (2d–2f), which were stable
under inert atmosphere for months at room temperature. On
exposure to air they all decomposed in days to form brown
products. Complexes 2a–2f were characterized by elemental
analysis, FT-IR, 1H NMR, 13C{H} NMR and 31P{H} NMR, respec-
tively (see Experimental section).
and can be compared with those of related compounds: [Ag2(pz)
2(PPh3)2] (Hpz = pyrazole) at d 9.87 [39] and [Ag2(pz)2(PPh3)3]
(Hpz = pyrazole) at d 6.13.[39]
Single-Crystal Structure of 2b
The bands assigned to N-H stretching vibrations in
N-acetylbenzamide (at 3270 and 1520 cmꢂ1) disappeared in the
spectra of the complexes, which indicates the deprotonation of
the nitrogen atom upon complexation with silver(I) ion.[35] In
the IR spectra of N-acetylbenzamide two bands at 1740 and
1680 cmꢂ1 were assigned to two C=O stretching vibrations.[35]
Compared to the free N-acetylbenzamide ligand (1740 and
1680 cmꢂ1), the displacement of the C=O stretching vibration shifted
to lower frequencies (about 58–115 cmꢂ1). These changes, which are
correlated with those found for the uracil moiety,[36] could be
ascribed to the delocalization of the anionic charge into the carbonyl
groups, thus decreasing the C=O bond order. Compared with
the free triethylphosphite (1030 cmꢂ1), the P=OꢂC linkage
stretching vibrations in the complexes shifted to lower frequencies
(1021–1024 cmꢂ1), which provides good evidence for the occurrence
of the organophosphine ligands coordinating to silver ion.[37]
The NMR spectra (1H, 13C{H} and 31P{H}) were recorded for all
six complexes at room temperature. In 1H NMR spectra, the
integration area ratios are consistent with the stoichiometries of
the complexes. The proton of ꢂCH3 in C9H8NO2ꢂ appeared at
2.5–2.6 ppm, which agrees well with a previous report.[35] The
protons of complexes 2a–2f in the aryl proton region were in
the range 7.0–8.1 ppm. The complexes (2d–2f) are easily
distinguished because the resonances of the protons of P(OEt)3
show two groups. In the 13C{H} NMR spectra, the chemical
shifts of all carbonyls are found in the range 169.5–180.7 ppm.
The aryl carbon resonances of 2a–2f are easily distinguished
(127.1–134.0 ppm) from the resonance of -CH3 on C9H8NO2ꢂ
(22.6–25.7 ppm).
A single crystal of complex 2b could be grown by slowly cooling
a saturated dichloromethane solution containing 2b to ꢂ20ꢁC.
The molecular structure of complex 2b is depicted in Fig. 1.
Selected bond distances (Å) and bond angles (ꢁ) are given in
Table 2.
Complex 2b crystallizes in the monoclinic space group C2/c,
and is composed of one molecule of [(Ph3P)2ꢀAgNC9H8O2] and
one molecule of dichloromethane (Fig. 1). In the complex, a
four-coordinated silver(I) ion is present with two PPh3 ligands
occupying two of the coordination sites (PP), a oxygen atom
and nitrogen atom of N-acetylbenzamide occupying the 3rd
and 4th sites, forming a distorted tetrahedral geometry around
silver.
In complex 2b, the N-acetylbenzamide molecule can be func-
tionalized as bidentate ligand, forming one short covalent nitro-
gen–silver bond and one longer coordinative oxygen–silver
bond. The root mean square (RMS) deviation of the atoms
(Ag(1)-N(1)-C(2)-C(1)-O(1)) from the best-fit least squares plane
is 0.0105 Å and the O(12) atom is 0.8054 Å above the plane.
The phosphorus resonance signals for complexes 2a–2c
appeared in the range 8.0–15.2 ppm, downfield shifted in
contrast to non-coordinated PPh3 (ꢂ5.3 ppm). However, the
phosphorus resonance signals for complexes 2d–2f shifted to
high field (123.8–130.1 ppm) compared with the free P(OEt)3
(137.6 ppm), which is typical in silver(I) phosphane chemistry.[27,38]
Complexes with only one equivalent phosphite ligand per silver(I)
center show a signal at higher field, while with addition of a
second and a third equivalent of P(OEt)3 subsequently, the signal
shifted to lower field, i.e. 2d: 123.8; 2e: 128.6; and 2f: 130.1 ppm
(Experimental section). The chemical shifts are similar to the
observed values for PPh3 ligands coordinated to silver(I)
Figure 1. Molecular structure and atom numbering scheme for 2b. The
hydrogen atoms and solvent molecules are omitted for clarity
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Appl. Organometal. Chem. 2012, 26, 323–329

Organophosphine/phosphite-stabilized silver(I) complexes
Table 2. Selected bond lengths (Å) and bond angles (ꢁ) for 2b
Bond lengths (Å)
Thermal Analysis
TG and DSC studies are required to optimize the temperature at
which the respective silver precursor should be maintained
during the CVD experiments. For example, the TG and DSC curves
of complex 2e are shown in Fig. 2.
Ag(1)–P(1)
Ag(1)–N(1)
O(1)–C(2)
O(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(8)–C(9)
2.445 (7)
2.306 (2)
1.237 (3)
1.230 (3)
1.504 (4)
1.391 (4)
1.381 (4)
1.381 (4)
Ag(1)–P(2)
Ag(1)–O(1)
N(1)–C(2)
N(1)–C(3)
C(2)–C(1)
C(4)–C(9)
C(8)–C(7)
C(6)–C(7)
2.435 (9)
2.635 (2)
1.361 (3)
1.363 (3)
1.501 (3)
1.396 (4)
1.376 (4)
1.386 (4)
It can be seen from the DSC curve that one apparent endother-
mic process from 125ꢁC to 400ꢁC with the peak temperature at
186ꢁC and the silver precursor decomposes in this temperature
range. Firstly, it may lose a triethylphosphite ligand between
125ꢁC and 177ꢁC with a corresponding weight loss of about
27.23%, which is close to the theoretical loss (27.60%). It loses
another P(OEt)3 and N-acetylbenzamide subsequently and it is
difficult to know the sequence of decomposition of P(OEt)3 and
N-acetylbenzamide. The final percentage of the residue is
22.17%, which is a little higher than the theoretical value of silver
(17.91%), which may be due to some impurities in the complex.
The complex exhibits an appropriate thermal decomposition
temperature, indicating that it could be a candidate for a
metal organic chemical vapor deposition (MOCVD) precursor for
growing silver films.
Bond angles (ꢁ)
N(1)–Ag(1)–P(2)
N(1)–Ag(1)–P(1)
P(1)–Ag(1)–P(2)
N(1)–Ag(1)–O(1)
P(2)–Ag(1)–O(1)
P(1)–Ag(1)–O(1)
C(2)–N(1)–Ag(1)
124.1 (5)
112.1 (6)
123.1 (3)
53.0 (6)
C(3)–N(1)–Ag(1)
C(2)–O(1)–Ag(1)
C(2)–N(1)–C(3)
O(1)–C(2)–N(1)
O(1)–C(2)–C(1)
N(1)–C(3)–C(4)
N(1)–C(2)–C(1)
133.8 (2)
88.6 (2)
122.7 (2)
117.8 (2)
118.7 (2)
114.4 (2)
123.4 (2)
106.5 (5)
113.6 (5)
100.5 (2)
MOCVD depositions
The dihedral angle between the least squares planes defined
by the six-membered ring (C(4)–C(9)) and the (Ag(1)-N(1)-C
(2)-C(1)-O(1)) plane is 138.4ꢁ. The imide fragment is not quite
planar in complex 2b, as indicated by the C-N-C-O torsion
angles of 163.7ꢁ and 6.8ꢁ.
In general, liquid precursor is better than solid precursor owing to
its constant vapor pressure. In addition, according to the thermal
properties obtained from TG and DSC studies, the complexes
decompose with release of the auxiliary ligands first. Therefore,
on the basis of the properties of complexes 2a–2f, we chose 2e
as a potential CVD precursor to grow silver films.
The surface morphology and composition of the silver films
were characterized by SEM and EDX analysis (Fig. 3). Their
morphologies exhibit obvious differences depending on their
deposition temperatures. The dense and homogeneous silver
layer was formed at 400ꢁC (Fig. 3a). The film is composed of many
The Ag–N distance [2.306(2) Å] is close to that of [(Ph3P)
3AgNC4H4O2] [2.313(4) Å] [23], but much longer than that of
[(MeO)3PAgNC4H4O2] [2.171(3) Å].[30] The Ag–P distances [2.435
(9), 2.445(7) Å] are close to the sum of covalent radio of P and
Ag atoms (2.44 Å)[40] and shorter than that of [(R3P)2AgPI] (PI =
C8H4NO2) [2.494(7) Å].[41] The angles of P–Ag–P [123.1(3)ꢁ] are
much smaller than that of [(Ph3P)2AgNC4H4O2] [145.4(4)ꢁ][23]
[42]
and that of [(Ph3P)2ꢀAgNC4H4O3] [135.6(3)ꢁ].
Symmetrical acyclic imides (R = R′) have three planar conforma-
tions (Scheme 2), cis–cis, cis–trans and trans–trans, differentiated
by the relative orientations of the carbonyl groups to the central
NH bond. In unsymmetrical imides (R ¼ R′), two cis–trans isomers
are possible. The cis–cis conformation has the highest energy due
to the steric overcrowding between R and R′, and is not observed
in solution or in the solid state for any known acyclic imides.[35]
The trans–trans conformation is destabilized by about 4 KJ molꢂ1
relative to the cis–trans conformation by the electrostatic
repulsion between the two relatively close carbonyl groups. The
cis–trans conformation is the most stable form and is observed
in solution for all simple acyclic imides except dipivalamide.[35]
The simple acyclic imide, N-acetylbenzamide, was found to crys-
tallize in cis–trans and trans–trans conformations.[35,43] Complex
2b crystallizes in the most stable form, cis–trans conformation,
which may be due to the steric hindrance effect.
Figure 2. TG and DSC curves of 2e (heating rate 10ꢁC minꢂ1, N2)
Scheme 2. Three planar conformations of acyclic imides
Appl. Organometal. Chem. 2012, 26, 323–329
Copyright © 2012 John Wiley & Sons, Ltd.
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X. Tao et al.
Figure 3. SEM images and EDX spectra of the films deposited from 2e using N2 as the carrier gas at temperatures of (a) 400ꢁC and (b) 450ꢁC
well-isolated, granular genuine pearls spreading all over the
substrate. The sizes of silver grains are in the range 50–150 nm.
Finally, upon further increasing the deposition temperature to
450ꢁC, the quality of the metal film was poor (Fig. 3b). This obser-
vation is consistent with the fact that the nuclear grown rate of
silver deposition is much greater than that of the formation of
the initial nucleation sites on the substrate, which then gives
much larger metal aggregation instead of giving better thin film
uniformity.[44] EDX analyses of the as-deposited films at 400ꢁC
and 450ꢁC show the presence of silver alone. Other light
elements, such as C and P, which might be present as impurities
or formed by surface oxidation of silver, are below the detection
limit.
The UV–visible absorption spectra of the silver films deposited
at 400ꢁC and 450ꢁC are shown in Fig. 4. The absorption spectra of
the as-deposited film at 400ꢁC shows a broad peak at 410 nm.
The absorption of the as-deposited film at 450ꢁC is red-shifted
towards 438 nm. The absorption peaks at ~405 nm are due to
the surface plasmon polariton resonance (SPPR) of Ag particles,
which are sensitive to the microstructure of the films.[45] The
peak broadness is due to dipole–dipole interactions of the
Ag particles.[46–48]
Conclusions
A series of Lewis-base stabilized silver(I) N-acetylbenzamidate
compounds have been prepared by reaction of [NaNC9H8O2]
with AgNO3 and triphenylphosphine or triethylphosphite in
1:1–3 molar ratio. Complex 2b is a monomer with a four-coordinated
silver atom and crystallizes as cis–trans. New N-silver(I) acetylbenza-
mide complex exhibits a novel structure with a four-membered ring,
which can influence its chemical and physical properties and modu-
late volatility. Complex 2e was used as precursor in the deposition of
silver using the MOCVD technique successfully, and the as-deposited
film at 400ꢁC is dense and homogeneous. It has been demonstrated
that the complex is a promising candidate as precursor for the
deposition of Ag.
Supporting Information
Supporting information may be found in the online version of
this article.
CCDC-820899 (for complex 2b) contains the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/datarequest/cif.
Acknowledgments
This work was supported by the Natural Science Foundation of
Jiangsu province (BK2007199). National Science and Technology
of Major Project (2009ZX02039-002), Funding of Jiangsu Innova-
tion Program for Graduate Education (CX10B_100Z) and Funding
for Outstanding Doctoral Dissertation in NUAA (BCXJ10-11) are
also acknowledged.
Figure 4. UV–visible spectra of the films deposited from 2e using N2 as
the carrier gas at temperatures of (a) 400ꢁC and (b) 450ꢁC
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Appl. Organometal. Chem. 2012, 26, 323–329

Organophosphine/phosphite-stabilized silver(I) complexes
[22] X. Tao, K. C. Shen, Y. Z. Shen, J. Organomet. Chem. 2011, 696, 2681.
[23] X. Tao, Y. Q. Li, H. H. Xu, N. Wang, F. L. Du, Y. Z. Shen, Polyhedron
2009, 28, 1191.
References
[1] R. Manepalli, F. Stepniak, S. A. Bidstrup-Allen, P. A. Kohl, IEEE Trans.
Adv. Packag. 1999, 22, 4.
[24] K. M. Chi, K. H. Chen, S. M. Peng, G. H. Lee, Organometallics 1996, 15,
2575.
[25] N. H. Dryden, J. J. Vittal, R. J. Puddephatt, Chem. Mater. 1993, 5,
765.
[2] R. Liu, C. S. Pai, E. Martinez, Solid State Electron. 1999, 43, 1003.
[3] T. T. Kodas, M. J. Hampden-Smith, The Chemistry of Metal CVD, VCH,
Weinheim, Germany, 1994.
[4] P. Piszczek, E. Sylyk, M. Chaberski, C. Taeschner, A. Leonhardt, W. Bala,
K. Bartkiewicz, Chem. Vap. Depos. 2005, 11, 53.
[5] H. Schmidt, Y. Shen, M. Leschke, T. Haase, K. Kohse-Höinghaus, H. Lang,
J. Organomet. Chem. 2003, 669, 25.
[26] Z. Yuan, N. H. Dryden, J. J. Vittal, R. J. Puddephatt, Chem. Mater. 1995,
7, 1696.
[27] X. Tao, K. C. Shen, M. Feng, Q. Y. Tang, J. T. Fang, Y. L. Wang, Y. Z. Shen,
Dalton Trans. 2011, 40, 9250.
[6] M. Hauder, W. Hansch, J. Gstootner, D. Schmitt-Landsiedel, Appl.
[28] X. Tao, K. C. Shen, M. Feng, Q. Y. Tang, J. T. Fang, Y. L. Wang, Y. Z. Shen,
Polyhedron 2011, 30, 2661.
Phys. Lett. 2001, 78, 838.
[7] J. Uchil, K. Mohan Rao, M. Pattabi, J. Phys. D: Appl. Phys. 1996, 29,
2992.
[29] X. Tao, K. C. Shen, Y. L. Wang, Y. Z. Shen, Z. Anorg. Allg. Chem. 2011,
637, 1394.
[8] A. C. Carter, W. Chang, S. B. Qadri, J. S. Horwitz, R. Leuchtner, D. B.
Chrisey, J. Mater. Res. 1998, 13, 1418.
[30] X. Tao, Y. L. Wang, K. C. Shen, Y. Z. Shen, Inorg. Chem. Commun. 2011,
14, 169.
[9] A. Grodzicki, I. Lakomska, P. Piszczek, I. Szymanska, E. Szlyk, Coord.
[31] P. H. Phua, S. P. Mathew, A. J. P. White, J. G. de Vries, D. G. Blackmond,
Chem. Rev. 2005, 249, 2232.
K. K. Hii, Chem. Eur. J. 2007, 13, 4602.
[10] A. Jain, K. Chi, T. T. Kodas, M. J. Hampden-Smith, J. Electrochem. Soc.
1993, 140, 1434.
[11] N. Awaya, Y. Arita, Proceedings of the 1991 Symposium on VLSI
[32] D. Hurd, A. G. Prapas, J. Org. Chem. 1959, 24, 388.
[33] Rigaku/MSC, CRYSTALCLEAR, Rigauk/MSC Inc., The Woodlands, TX,
2005.
Thchnology, Orso, Japan, 1991, pp. 37.
[34] G. M. Sheldrick, SHELX-97, Programs for Crystal Structure Analysis
(Release 97–2), University of Gottingen, Germany, 1997.
[35] M. C. Etter, S. M. Reutzal, J. Am. Chem. Soc. 1991, 113, 2586.
[36] T. Woldbaek, P. Klaeboe, D. H. Christensen, Acta Chem. Scand. 1976,
A30, 531.
[37] L. W. Daasch, D. C. Smith, Anal. Chem. 1951, 23, 853.
[38] R. Mothes, T. Rüffer, Y. Z. Shen, A. Jakob, B. Walfort, H. Petzold,
S. E. Schulz, R. Ecke, T. Gessner, H. Lang, J. Chem. Soc. Dalton
Trans. 2010, 39, 11235.
[12] J. E. Parmeter, G. A. Petersen, P. M. Smith, C. A. Apblett, J. S. Reid,
J. A. T. Norman, A. K. Hochberg, D. A. Roberts, T. R. Omstead, J.
Vac. Sci. Technol. 1995, B13, 130.
[13] G. Braeckelmann, D. Manger, A. Burke, G. G. Peterson, A. E. Kaloyeros,
C. Reidsema, T. R. Omstead, J. F. Loan, J. J. Sullivan, J. Vac. Sci. Technol.
1996, B14, 1828.
[14] S. Kim, D. J. Choi, K. R. Yoon, K. H. Kim, S. K. Koh, Thin Solid Films
1997, 311, 218.
[15] R. J. H. Voorhoeve, J. W. Merewether, J. Electrochem. Soc. 1972, 119, 364.
[16] P. M. Jeffries, S. R. Wilson, G. S. Girolami, J. Organomet. Chem. 1993,
449, 203.
[17] D. A. Edwards, R. M. Harker, M. F. Mahon, K. C. Molloy, J. Mater. Chem.
1999, 9, 1771.
[18] N. Wang, X. Tao, F. L. Du, M. Feng, L. N. Jiang, Y. Z. Shen, Polyhedron
2010, 29, 1687.
[19] Z. Yuan, N. H. Dryden, X. Li, J. J. Vittal, R. J. Puddephatt, J. Mater.
Chem. 1995, 5, 303.
[39] G. A. Ardizzoia, G. La Monica, A. Maspero, M. Moret, N. Masciocchi,
Inorg. Chem. 1997, 36, 2321.
[40] K. Teo, J. C. Calabrese, Inorg. Chem. 1976, 15, 2467.
[41] R. Whitcomb, M. Rajeswaran, J. Chem. Crytallogr. 2006, 36, 587.
[42] X. Tao, K. C. Shen, Q. Y. Tang, M. Feng, J. T. Fang, Y. L. Wang, Y. Z. Shen,
Appl. Organomet. Chem. 2011, 26, 67.
[43] M. C. Etter, D. Britton, S. M. Reutzel, Acta. Cryst. 1999, C47, 556.
[44] W. L. Gladfelter, Chem. Mater. 1993, 5, 1372.
[45] D. Evanoff Jr., G. Chumanov, Chem. Phys. Chem. 2005, 6, 1221.
[46] T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, P. A. Wolff, Nature
1998, 391, 667.
[20] D. A. Edwards, R. M. Harker, M. F. Mahon, K. C. Molloy, Inorg. Chim.
Acta 2002, 328, 134.
[21] Y. Y. Zhang, Y. Wang, X. Tao, N. Wang, Y. Z. Shen, Polyhedron 2008,
27, 2501.
[47] S. Link, M. A. El-Sayed, J. Phys. Chem. B 1999, 103, 8410.
[48] D. D. Evanoff Jr., G. Chumanov, J. Phys. Chem. B 2004, 108, 13957.
Appl. Organometal. Chem. 2012, 26, 323–329
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