Synthesis and physical and structural characterization of Ag(I) complexes supported by non-fluorinated β-diketonate and related ancillary ligands

Article abstract of DOI:10.1016/S0277-5387(02)00980-4

A series of Ag(I) complexes, [Ag(X)L], where X is the anion of 2,2,6,6-tetramethyl-3,5-heptanedione (tmhdH), 2,2,7-trimethyl-3,5- octanedione (tmodH), 2-sila-2,2,6,6-tetramethyl-3,5- heptanedione (tmshdH), 5-mercapto-2,2,6,6-tetramethyl-4-hepten-3-one (S-tmhdH), 5-mercapto-2,2,7-trimethyl-4-octen-3-one (S-tmodH), or 5-amino-2,2,6,6-tetramethyl-4-hepten-3-one (N-tmhdH) and L = triphenylphosphine (PPh₃) or tri-n-butylphosphine (PBu₃), were prepared by treatment of silver nitrate with either the diketone derivative in the presence of a base or with the preformed sodium salt of the diketone derivative. The thermal properties of the new complexes were investigated for potential application in chemical vapor deposition (CVD) processes. Results of thermogravimetric analysis showed that the vast majority of the silver complexes have little promise for CVD, since the ligands dissociate at elevated temperatures without volatilization. The first ever reported single crystal X-ray diffraction studies of silver complexes, with simple, ancillary, non-fluorinated β-diketonate supporting ligands, revealed [Ag(tmhd)(PPh₃)] (1a) to be monomeric and [Ag(S-tmhd)(PPh₃)]₂ (4a) to be dimeric in the solid state, respectively.

Full text of DOI:10.1016/S0277-5387(02)00980-4

Polyhedron 21 (2002) 1289ꢁ1297
/
www.elsevier.com/locate/poly
Synthesis and physical and structural characterization of Ag(I)
complexes supported by non-fluorinated b-diketonate and related
ancillary ligands
Silvana C. Ngo, Kulbinder K. Banger, Paul J. Toscano *, John T. Welch *
Department of Chemistry and NYS Center for Advanced Thin Film Technology, The University at Albany, State University of New York, 1400
Washington Ave., Albany, NY 12222, USA
Received 9 January 2002; accepted 21 March 2002
Abstract
A series of Ag(I) complexes, [Ag(X)L], where X is the anion of 2,2,6,6-tetramethyl-3,5-heptanedione (tmhdH), 2,2,7-trimethyl-3,5-
octanedione (tmodH), 2-sila-2,2,6,6-tetramethyl-3,5- heptanedione (tmshdH), 5-mercapto-2,2,6,6-tetramethyl-4-hepten-3-one (S-
tmhdH), 5-mercapto-2,2,7-trimethyl-4-octen-3-one (S-tmodH), or 5-amino-2,2,6,6-tetramethyl-4-hepten-3-one (N-tmhdH) and
Lꢀtriphenylphosphine (PPh3) or tri-n-butylphosphine (PBu3), were prepared by treatment of silver nitrate with either the diketone
/
derivative in the presence of a base or with the preformed sodium salt of the diketone derivative. The thermal properties of the new
complexes were investigated for potential application in chemical vapor deposition (CVD) processes. Results of thermogravimetric
analysis showed that the vast majority of the silver complexes have little promise for CVD, since the ligands dissociate at elevated
temperatures without volatilization. The first ever reported single crystal X-ray diffraction studies of silver complexes, with simple,
ancillary, non-fluorinated b-diketonate supporting ligands, revealed [Ag(tmhd)(PPh3)] (1a) to be monomeric and [Ag(S-
tmhd)(PPh3)]2 (4a) to be dimeric in the solid state, respectively. # 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Silver(I) complexes; Non-fluorinated b-diketonate ligands; Monothio-b-ketonate; b-Ketoiminate; Chemical vapor deposition; Crystal
structures
1. Introduction
while the SrSꢁ/Ce couple provides a bluish green light
[3]. Unfortunately, the SrSꢁ/Ce couple is only a weak
Currently, there is ongoing interest in the search for
electroluminescent materials. Applications range from
lighting appliances, such as fluorescent tubes, to display
apparatus such as cathode ray tubes or projection
television [1]. One of the most rapidly advancing and
growing areas is the development of thin film electro-
luminescent displays. Inorganic phosphor materials
currently are widely used in these applications, while
research on organic phosphors is ongoing [2]. The most
blue emitter and as such, a need remains for the
development of brighter blue sources. Recent work
suggests SrSꢁ
blue emission with CIE color coordinates of xꢀ
and yꢀ0.23 [3,4]. Codoping of the SrSꢁCu couple with
Ag gave an even truer blue color with CIEx ꢀ0.17,
CIEy ꢀ0.13 [3,5]. However, the strategy for silver
/Cu is a suitable alternative, with a good
/0.15
/
/
/
/
doping is currently limited by a lack of suitable volatile
silver-containing precursors.
One of the techniques for preparation of thin films of
these phosphors is metallo-organic chemical vapor
deposition (MOCVD). As such, precursor volatility
and stability are important issues for doping strategy.
Research on the preparation of stable, yet volatile,
complexes is central to the development of new, more
efficient MOCVD precursors.
commonly employed phosphor, the ZnSꢁ
Ce combination, generates red and green output by
filtering the yellow emission from the ZnSꢁMn couple
/
Mn with SrSꢁ
/
/
* Corresponding authors. Tel.: ꢂ
/
1-518-442-3127; fax: ꢂ1-518-442-
/
3462.
E-mail addresses: ptoscano@csc.albany.edu (P.J. Toscano),
jwelch@uamail.albany.edu (J.T. Welch).
b-Diketonates and allied derivatives are among the
most common ancillary ligand types for the preparation
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 0 9 8 0 - 4

1290
S.C. Ngo et al. / Polyhedron 21 (2002) 1289ꢁ1297
/
of MOCVD precursors. Structural variations of the
supporting b-diketonate ligand can impart desired
chemical and physical properties to the precursor
complex as well as modulate the volatility. Introduction
of a second, supporting ligand in a ternary complex can
have complementary effects, while improving the stabi-
lity of the complex. Combination of both strategies
clearly can lead to highly desirable enhancements in
performance for MOCVD.
Previously, the preparation of silver b-diketonate
complexes for use in MOCVD have focused on fluori-
nated b-diketonate ligands, such as hfac (anion of
1,1,1,5,5,5-hexafluoro-2,4-pentanedione) and fod (anion
solvents obtained commercially were of reagent grade
and used as received unless otherwise noted. Tetrahy-
drofuran (thf), toluene, and anhydrous diethyl ether
(Et2O) were distilled from sodiumꢁ
under nitrogen. Pentane and hexane were distilled from
sodiumꢁbenzophenoneꢁdiglyme under nitrogen. The b-
/benzophenone ketyl
/
/
diketone tmshdH was prepared according to our
procedure [10], while tmodH was made analogously by
condensing 3-methylbutyryl chloride with pinacolone in
the presence of lithium diisopropylamide. The heteroa-
tom substituted b-diketone derivatives, S-tmhd [8], S-
tmod [8], and N-tmhd [9] were prepared by literature
procedures. The sodium salts of the b-diketonate
compounds were prepared by modification of the
literature procedure for Na(hfac) [11].
of
2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octane-
dione) [6]. While these ligands impart volatility to the
Ag complexes, a crucial property for applications in
MOCVD, fluoride ion contamination in the resultant
films is frequently observed. The initial aim of the
present study was to investigate alternatives to the use of
fluorinated silver b-diketonates for MOCVD applica-
tions. Although there were some previous studies that
indicated that silver complexes containing non-fluori-
nated b-diketonate ligands had limited volatility [7], we
decided to explore a much wider range of structural
alterations to the b-diketonate backbone, including
unsymmetrically substituted ligands, as well as those in
which silylated substituents were incorporated or in
which an oxygen donor atom was replaced by sulfur [8]
or imino nitrogen [9]. The replacement of one of the
oxygen donor atoms of the b-diketonate was investi-
gated, since such ancillary ligands might facilitate
reduction of oxygen contamination, which accompanies
the MOCVD processing of silver b-diketonates. We
report here the synthesis and physical characterization
of a series of binary and ternary silver complexes,
[Ag(X)] and [Ag(X)L], where X is the anion of 2,2,6,6-
tetramethyl-3,5-heptanedione (tmhdH), 2,2,7-trimethyl-
3,5-octanedione (tmodH), 2,2,6,6-tetramethyl-2-sila-3,5-
1H, 13C, and 19F NMR spectra were recorded on a
Gemini-300 MHz NMR spectrometer at 300, 75.46, and
282.3 MHz, respectively. TGA data were obtained on a
TA Instrument TGA 2050 Thermogravimetric Analy-
zer. Sample sizes were 1ꢁ
/
3 mg. The ramp rate was 5.08
minꢃ1 and the nitrogen purge rate was 100 cm3 minꢃ1
.
Elemental analyses were performed by MHW Labora-
tories.
2.2. [Ag(tmhd)] (1)
This complex was prepared following a slight mod-
ification of the literature procedure [12]. Under an inert
atmosphere, a stirring slurry of AgNO3 (0.42 g, 2.5
mmol) in acetonitrile (0.14 ml) and methanol (5 ml) was
cooled to 0 8C. To this slurry was added a solution of
tmhdH (0.55 ml, 2.6 mmol) and triethylamine (0.35 ml,
2.5 mmol) in methanol (5 ml). The mixture was stirred at
0 8C for 1 h and then filtered quickly. The white-
colored silver complex was washed with methanol and
dried in vacuo. Yield: 0.40 g (55%). Anal. Calc. for
C11H19AgO2: C, 45.38; H, 6.58. Found: C, 45.52; H,
1
6.39%. H NMR (C6D6): d 5.71 (s, 1H, C(O)CHC(O)),
heptanedione
(tmshdH),
5-mercapto-2,2,6,6-tetra-
1.06 (s, 18H, tBuÃ
/
CH3). 13C NMR (C6D6): d 201.6 (C Ä
O), 90.7 (C(O)CHC(O)), 39.4 (C(CH3)3), 27.4
/
methyl-4-hepten-3-one (S-tmhdH), 5-mercapto-2,2,7-
trimethyl-4-octen-3-one (S-tmodH), or 5-amino-
2,2,6,6-tetramethyl-4-hepten-3-one (N-tmhdH) and L
is triphenylphosphine (PPh3) or tri-n-butylphosphine
(PBu3). We also present structural results on the first
two non-fluorinated b-diketonate silver complexes char-
acterized by single crystal X-ray diffraction.
(C(CH3)3).
2.3. [Ag(tmhd)(PPh3)] (1a) (method A)
A stirred slurry of 1 (0.21 g, 0.72 mmol) and
triphenylphosphine (0.19 g, 0.71 mmol) in toluene (10
ml) was cooled to 0 8C. The mixture was stirred at 0 8C
for 1 h giving a clear solution. Removal of the solvent in
vacuo afforded the silver complex as an off-white solid.
Yield: 0.33 g (83%). Anal. Calc. for C29H34AgO2P: C,
2. Experimental
2.1. Materials and physical measurements
1
62.94; H, 6.19. Found: C, 62.78; H, 6.09%. H NMR
6.88 (m, 15H, C6H5), 6.06 (s, 1H,
CH3). 13C NMR
Unless otherwise noted, all experiments were per-
formed under an inert atmosphere of nitrogen utilizing
standard Schlenk techniques or in a Vacuum Atmo-
spheres drybox filled with nitrogen. Reagents and
(C6D6): d 7.28ꢁ
/
C(O)CHC(O)), 1.49 (s, 18H, tBuÃ
/
2
O), 134.3 (d, JCP
(C6D6): d 200.4 (C Ä
/
ꢀ17.0 Hz, o-C
/
1
Ph), 132.1 (d, JCP
ꢀ/35.8 Hz, ipso-C Ph), 130.4 (p-C

S.C. Ngo et al. / Polyhedron 21 (2002) 1289ꢁ
/1297
1291
Ph), 129.0 (3JCP
(O)), 42.4 (C(CH3)3), 29.4 (C(CH3)3).
ꢀ/10.4 Hz, m-C Ph), 88.5 (C(O)CHC-
the oily residue with pentane gave the silver complex as
a gray solid. Yield: 0.20 g (79%). Anal. Calc. for
C29H34AgO2P: C, 62.94; H, 6.19. Found: C, 62.77; H,
1
2.4. [Ag(tmhd)(PPh3)] (1a) (method B)
6.24%. H NMR (C6D6): d 7.28ꢁ
/
6.86 (m, 15H, C6H5),
i
5.82 (s, 1H, C(O)CHC(O)), 2.60ꢁ
CH), 2.41 (br s, 2H, iBuÃCH2), 1.47 (s, 9H, tBuÃ
6.0 Hz, iBuÃCH3). 13C
O), 134.3 (d,
36.8 Hz, ipso-
/
2.45 (m, 1H, BuÃ
/
Na(tmhd) (0.45 g, 2.2 mmol) was dissolved in Et2O
(15 ml) and added to a stirred slurry of AgNO3 (0.37 g,
2.2 mmol) and triphenylphosphine (0.57 g, 2.2 mmol) in
Et2O (15 ml). The mixture was allowed to react for 24 h
forming a gray slurry. The volatile components were
removed in vacuo affording the crude product. Extrac-
/
/
3
CH3), 1.12 (d, 6H, JHH
ꢀ
/
/
NMR (C6D6): d 199.9 (C Ä
/
O), 194.1 (C Ä
/
2JCP
ꢀ
/
16.9 Hz, o-C Ph), 131.9 (d, 1JCP
ꢀ
/
4
C Ph), 130.5 (d, JCP
ꢀ1.9 Hz, p-C Ph), 129.0 (d,
/
3JCP
(iBuÃ
CH), 23.3 (iBuÃ
ꢀ
/
10.7 Hz, m-C Ph), 94.3 (C(O)CHC(O)), 53.2
CH2), 41.9 (C(CH3)3), 29.3 (C(CH3)3), 27.2 (iBuÃ
CH3).
tion with toluene (2ꢄ/20 ml), followed by filtration and
/
/
evaporation in vacuo, gave the silver complex as a white
/
1
solid. Yield: 1.2 g (56%). The H NMR spectrum of the
product was identical to that formed via Method A.
2.8. [Ag(tmod)(PBu3)] (2b)
2.5. [Ag(tmhd)(PBu3)] (1b)
This complex was prepared by a similar method to
that for 1b, instead utilizing tri-n-butylphosphine (0.11
ml, 0.42 mmol) and 2 (0.13 g, 0.46 mmol). Yield of
Tri-n-butylphosphine (1.0 ml, 4.0 mmol) was added
to a stirred slurry of 1 (1.2 g, 4.0 mmol) in toluene (45
ml) at 0 8C. The mixture was stirred at 0 8C for 1 h
reddishꢁblack oily liquid: 0.20 g (97%). Anal. Calc. for
/
C23H46AgO2P: C, 55.98; H, 9.40. Found: C, 56.12; H,
1
9.30%. H NMR (C6D6): d 5.66 (s, 1H, C(O)CHC(O)),
giving a redꢁ/brown solution. Removal of the toluene in
vacuo afforded the silver complex as a reddish brown
oily liquid. Yield: 1.8 g (93%). Anal. Calc. for C23H46A-
gO2P: C, 55.98; H, 9.40. Found: C, 55.82; H, 9.29%. H
2.51ꢁ
1.38 (s, 9H, tBuÃ
PCH2CH2CH2CH3 and iBuÃ
3JHH 6.9 Hz, PCH2CH2CH2CH3). 13C NMR (C6D6):
199.3 (C ÄO), 193.5 (C ÄO), 93.9 (C(O)CHC(O)), 53.1
(iBuÃ
CH2), 41.6 (C(CH3)3), 29.2 (C(CH3)3), 27.9 (d,
3JCP
25.7 (d, JCP
2JCP
CH3),
/
2.36 (m, 1H, iBuÃ
/
CH,), 2.29 (br s, 2H, iBuÃ
/
CH2),
1.01 (complex, 24H,
CH3), 0.80 (t, 9H,
/
CH3), 1.21ꢁ
/
1
/
NMR (C6D6): d 5.82 (s, 1H, C(O)CHC(O)), 1.42 (s,
18H, tBuÃ
CH2CH3), 0.88 (t, 9H, JHH
ꢀ
/
/
CH3), 1.32ꢁ
/
1.22 (m, 18H, PCH2CH2-
6.9 Hz, PCH2CH2CH2-
/
/
3
ꢀ
/
/
CH3). 13C NMR (C6D6):
(C(O)CHC(O)), 42.1 (C(CH3)3), 29.5 (C(CH3)3), 27.9
d
198.9 (C ÄO), 87.2
/
ꢀ
/
5.6 Hz, PCH2CH2CH2CH3), 27.1 (iBuÃ
/
CH),
1
ꢀ
/
18.4 Hz, PCH2CH2CH2CH3), 24.4 (d,
3
(d, JCP
1
6.0 Hz, PCH2CH2CH2CH3), 25.9 (d, JCP
ꢀ
/
ꢀ
13.8 Hz,
/
ꢀ
/
14.2 Hz, PCH2CH2CH2CH3), 23.3 (iBuÃ
/
2
14.8 Hz, PCH2CH2CH2CH3), 24.7 (d, JCP
PCH2CH2CH2CH3), 14.0 (PCH2CH2CH2CH3).
ꢀ
/
13.8 (PCH2CH2CH2CH3).
2.9. [Ag(tmshd)] (3)
2.6. [Ag(tmod)] (2)
A mixture of AgNO3 (0.92 g, 5.4 mmol) in CH3CN
(0.5 ml) and CH3OH (11 ml) at 0 8C was transferred by
cannula to a cooled flask containing a stirring mixture
of tmshdH (1.15 g, 5.7 mmol), triethylamine (0.8 ml, 5.7
mmol), and CH3OH (11 ml) at 0 8C. Immediate
formation of white precipitate was observed. The
mixture was stirred at 0 8C for an hour, filtered and
the precipitates washed with minute amounts of cold
CH3OH. The pale colored precipitates darkened over
This complex was prepared using a similar procedure
as that for 1, starting with AgNO3 (0.51 g, 3.0 mmol)
and tmodH (0.59 g, 3.2 mmol). Yield of white solid: 0.57
g (66%). Anal. Calc. for C11H19AgO2: C, 45.38; H, 6.58.
Found: C, 45.58; H, 6.54%. 1H NMR (C6D6): d 5.43 (s,
i
1H, C(O)CHC(O)), 2.12ꢁ
/
1.96 (m, 1H, BuÃ
/
CH), 1.93
CH2), 1.05 (s,
i
i
(s, 1H, BuÃ
/
CH2), 1.91 (br s, 1H, BuÃ
/
t
3
i
9H, BuÃ
13C (C6D6): d 201.1 (C Ä
(C(O)CHC(O)), 47.7 (iBuÃ
CH2), 39.3 (C(CH3)3), 27.3
(C(CH3)3), 26.2 (iBuÃCH), 22.5 (iBuÃ
CH3).
/CH3), 0.80 (d, 6H, JHH
ꢀ
/
6.6 Hz, BuÃ
/CH3).
/
O), 194.1 (C Ä
/O), 95.9
time even at ꢃ25 8C and were used immediately for the
/
/
preparation of the ternary complex 3a. Yield: 0.33 g
(20%).
/
/
2.7. [Ag(tmod)(PPh3)] (2a)
2.10. [Ag(tmshd)(PPh3)] (3a)
This complex was prepared by a similar method to
that for the preparation of 1a (Method A). Triphenyl-
phosphine (0.12 g, 0.46 mmol) was added to a stirred
slurry of 2 (0.13 g, 0.46 mmol) in toluene (15 ml) at
0 8C. The mixture was stirred at 0 8C for 1 h, after
which the toluene was removed in vacuo. Trituration of
A mixture of 3 (0.14 g, 0.46 mmol) and triphenylpho-
sphine (0.12 g, 0.46 mmol) in Et2O (30 ml) was stirred at
0 8C for 3 h. Removal of the solvent at 0 8C gave a
light brown powder. Yield: 0.25 g (95%). Anal. Calc. for
C28H34AgO2PSi: C, 59.05; H, 6.02. Found: C, 59.27; H,
5.99%. 1H NMR (CDCl3): d 7.50ꢁ
7.34 (m, 15H, C6H5),
/

1292
S.C. Ngo et al. / Polyhedron 21 (2002) 1289ꢁ1297
/
5.80 (s, 1H, C(O)CHC(O)), 1.16 (s, 9H, tBuÃ
(s, 9H, SiÃCH3).
/CH3), 0.17
CH2CH3), 23.7 (d, 2JCP
13.1 (PCH2CH2CH2CH3).
ꢀ14.3 Hz, PCH2CH2CH2CH3),
/
/
2.14. [Ag(S-tmod)] (5)
2.11. [Ag(S-tmhd)] (4)
This complex was prepared by the same method as for
4, instead using AgNO3 (0.26 g, 1.5 mmol) and Na(S-
tmod) (0.34 g, 1.53 mmol). Yield of dark yellow brown
product: 0.36 g (76%). Anal. Calc. for C11H19AgOS: C,
A yellow slurry of AgNO3 (0.26 g, 1.5 mmol) and
Na(S-tmhd) (0.34 g, 1.5 mmol) in thf (20 ml) was stirred
for 24 h giving a dark gray mixture. The solvent was
removed in vacuo and the residue extracted with toluene
(20 ml). Filtration and removal of all volatiles in vacuo
gave the silver complex as a yellow brown solid. Yield:
0.38 g (81%). Anal. Calc. for C11H19AgOS: C, 43.01; H,
1
43.01; H, 6.23. Found: C, 43.18; H, 6.03%. H NMR
(CDCl3): d 6.48 (s, 1H, C(O)CHC(S)), 2.34 (s, 1H, iBuÃ
/
/
i
i
CH2), 2.32 (s, 1H, BuÃ
/
CH2), 2.24ꢁ
CH3), 0.85 (d, 6H, JHH
CH3). 13C NMR (CDCl3): d 204.8 (C Ä
120.7 (C(O)CHC(S)), 59.3 (iBuÃ
CH2), 43.6 (C(CH3)3),
27.8 (iBuÃCH), 27.0 (C(CH3)3), 22.4 (iBuÃ
CH3).
/
2.05 (m, 1H, BuÃ
t
3
1
CH), 1.09 (s, 9H, BuÃ
/
ꢀ
/6.3
6.23. Found: C, 42.91; H, 6.02%. H NMR (CDCl3): d
i
t
Hz, BuÃ
/
/
O),
6.74 (s, 1H, C(O)CHC(S)), 1.31 (s, 9H, BuÃ
/
CH3), 1.10
O),
S), 118.2 (C(O)CHC(S)), 44.7 (C(CH3)3), 42.
t
(s, 9H, BuÃ
/
CH3). 13C NMR (CDCl3): d 206.9 (C Ä
/
/
/
/
173.5 (C Ä
/
(C(CH3)3), 31.0 (C(CH3)3), 27.2 (C(CH3)3).
2.15. [Ag(S-tmod)(PPh3)] (5a)
2.12. [Ag(S-tmhd)(PPh3)] (4a)
This complex was prepared analogously to 4a using
AgNO3 (0.26 g, 1.5 mmol), Na(S-tmod) (0.33 g, 1.5
mmol) and triphenylphosphine (0.39g, 1.5 mmol). Yield
A slurry of AgNO3 (0.26 g, 1.5 mmol), Na(S-tmhd)
(0.33 g, 1.5 mmol) and triphenylphosphine (0.39 g, 1.5
mmol) in thf (20 ml) was stirred for 44 h giving a lemon
yellow slurry. The solvent was removed in vacuo and the
residue extracted with toluene (25 ml). Filtration and
removal of all volatiles in vacuo gave the silver complex
as a lemon yellow solid. Yield: 0.61 g (72%). Anal. Calc.
for C29H34AgOPS: C, 61.16; H, 6.02. Found: C, 61.32;
of yellowꢁ
C29H34AgOPS: C, 61.16; H, 6.02. Found: C, 61.34; H,
5.87%. 1H NMR (CDCl3): d 7.46ꢁ
7.26 (m, 15H, C6H5),
6.45 (s, 1H, C(O)CHC(S)), 2.33 (bs, 2H, BuÃ
/brown product: 0.71 g (83%). Anal. Calc. for
/
i
/
CH2),
i
t
2.27ꢁ
/
2.04 (m, 1H, BuÃ
/
CH), 1.01 (s, 9H, BuÃ
6.3 Hz, iBuÃ
O), 133.9 (2JCP
30.2 Hz, ipso-C Ph), 130.3 (p-C
10.0 Hz, m-C Ph), 117.6
CH2), 43.5 (C(CH3)3), 28.4
CH), 27.3 (C(CH3)3), 22.3 (iBuÃ
CH3).
/CH3),
3
0.82 (d, 6H, JHH
ꢀ
/
/
CH3). 13C NMR
(CDCl3): d 204.6 (C Ä
/
ꢀ16.6 Hz, o-C
/
H, 6.15%. 1H NMR (CDCl3): d 7.60ꢁ
C6H5), 6.85 (s, 1H, C(O)CHC(S)), 1.36 (s, 9H, BuÃ
/
7.30 (m, 15H,
t
1
Ph), 131.8 (d, JCP
ꢀ
/
3
/
Ph), 128.8 (d, JCP
ꢀ
/
t
CH3). 13C NMR (CDCl3): d
(C(O)CHC(S)), 59.7 (iBuÃ
(iBuÃ
/
CH3), 1.14 (s, 9H, BuÃ
/
2
O), 134.1 (d, JCP
205.5 (C Ä
/
ꢀ16.6 Hz, o-C Ph), 131.4
/
/
/
1
(d, JCP
4
34.6 Hz, ipso-C Ph), 130.6 (d, JCP
ꢀ
/
ꢀ
/
1.9 Hz,
3
p-C Ph), 128.9 (d, JCP
ꢀ/10.4 Hz, m-C Ph), 113.6
2.16. [Ag(S-tmod)(PBu3)] (5b)
(C(O)CHC(S)), 44.5 (C(CH3)3), 44.4 (C(CH3)3), 31.5
(C(CH3)3), 27.7 (C(CH3)3).
Na(S-tmod) (0.26 g, 1.2 mmol) was added to a
stirring slurry of AgNO3 (0.20 g, 1.2 mmol) and tri-n-
butylphosphine (0.30 ml, 1.1 mmol) in thf (20 ml). The
reaction mixture was allowed to react for 24 h, resulting
in a gray slurry. The volatile components were removed
in vacuo affording the crude product. Extraction with
toluene (20 ml) followed by filtration and evaporation in
vacuo gave the silver complex as an orange brown oily
liquid. Yield: 0.42 g (72%). Anal. Calc. for C23H46A-
gOPS: C, 54.22; H, 9.10. Found: C, 54.12; H, 9.27%. 1H
NMR (CDCl3): d 6.47 (s, 1H, C(O)CHC(S)), 2.33 (s,
2.13. [Ag(S-tmhd)(PBu3)] (4b)
A mixture of AgNO3 (0.20 g, 1.2 mmol), Na(S-tmhd)
(0.26 g, 1.2 mmol) and tri-n-butylphosphine (0.30 g, 1.1
mmol) in thf (20 ml) was stirred for 24 h giving a yellow
mixture. The solvent was removed in vacuo and the
residue extracted with toluene (20 ml). Filtration and
removal of all volatiles in vacuo gave the silver complex
as a yellow brown oil. Yield: 0.56 g (96%). Anal. Calc.
for C23H46AgOPS: C, 54.22; H, 9.10. Found: C, 54.42;
i
i
1H, BuÃ
/
CH2), 2.31 (s, 1H, BuÃ
1H, BuÃCH), 1.60ꢁ
CH2CH3), 1.07 (s, 9H, BuÃ
6.3 Hz, iBuÃ
/
CH2), 2.25ꢁ2.05 (m
/
i
H, 8.86%. 1H NMR (CDCl3):
C(O)CHC(S)), 1.61ꢁ1.32 (complex, 18H, PCH2CH2-
CH2CH3), 1.29 (s, 9H, BuÃ
d
6.74 (s, 1H,
/
/
1.31 (complex, 18H, PCH2CH2-
CH3), 0.80 (d, 6H, JHH
CH2), 0.79 (t, 9H, JHH
t
3
/
/
ꢀ
/
t
t
3
/
CH3), 1.07 (s, 9H, BuÃ
/
/
ꢀ7.2 Hz,
/
3
CH3), 0.85 (t, 9H, JHH
ꢀ
/
7.2 Hz, PCH2CH2CH2CH3).
PCH2CH2CH2CH3). 13C NMR (CDCl3): d 203.7 (C Ä
O), 179.2 (C Ä CH2),
S), 119.7 (C(O)CHC(S)), 59.8 (iBuÃ
43.3 (C(CH3)3), 28.7 (iBuÃ
5.6 Hz,
PCH2CH2CH2CH3), 27.4 (C(CH3)3), 25.5 (d, JCP
/
13C NMR (CDCl3): d 204.8 (C Ä
(C(O)CHC(S)), 43.7 (C(CH3)3), 43.5 (C(CH3)3), 30.8
/
O), 185.0 (C Ä
/
S), 113.4
/
/
3
/CH), 27.6 (d, JCP
ꢀ
/
3
(C(CH3)3), 27.2 (d, JCP
1
ꢀ
/
5.6 Hz, PCH2CH2CH2CH3),
18.8 Hz, PCH2CH2-
ꢀ
/
1
27.1 (C(CH3)3), 24.8 (d, JCP
2
ꢀ
/
13.6 Hz, PCH2CH2CH2CH3), 24.4 (d, JCP
ꢀ13.3 Hz,
/

S.C. Ngo et al. / Polyhedron 21 (2002) 1289ꢁ
/1297
1293
PCH2CH2CH2CH3),
(PCH2CH2CH2CH3).
22.5
(iBuÃ
/
CH3),
13.6
30%; yield of 4a: 75%). X-ray data were collected at
ambient temperature using a Bruker R3m diffract-
ometer in the v ꢁ
(3ꢁ
20 8 minꢃ1) and graphite monochromated Mo Ka
radiation (lꢀ
sured every 200 reflections during data collection and
gave no indication of crystal decay. Data were corrected
for background, attenuators, Lorentz and polarization
effects in the usual fashion [13]. A semi-empirical
absorption correction was applied to 4a using the C-
scan method.
Both structures were solved by direct methods and
refined by full matrix least-squares procedures on jF2j
with the SHELXTL Plus package of programs. All non-
hydrogen atoms were refined anisotropically; hydrogen
/
2u mode with variable scan speed
2.17. [Ag(N-tmhd)(PPh3)] (6a)
/
˚
0.71073 A). Check reflections were mea-
/
A stirring slurry of AgNO3 (0.13 g, 0.77 mmol) and
Na(N-tmhd) (0.16 g, 0.78 mmol) was dissolved in Et2O
(20 ml). A solution of triphenylphosphine (0.20 g, 0.76
mmol) in Et2O (40 ml) was added. The reaction mixture
was allowed to react for 24 h resulting in a gray slurry.
The volatile components were removed in vacuo afford-
ing the crude product as a black solid. Extraction with
toluene (2ꢄ20 ml) followed by filtration and evapora-
/
tion in vacuo gave the silver complex as a salmon pink
colored solid. Yield: 0.24 g (56%). Anal. Calc. for
C29H35AgNOP: C, 63.05; H, 6.39. Found: C, 63.22; H,
6.50%. 1H NMR (CDCl3): d 7.44ꢁ
7.16 (m, 15H, C6H5),
atom positions were calculated geometrically and fixed
˚
/
t
at a CÃ/H distance of 0.96 A and were not refined.
5.32 (s, 1H, C(O)CHC(NH)), 1.14 (s, 9H, BuÃ
1.12 (s, 9H, tBuÃCH3). 13C NMR (CDCl3): d 205.3 (C Ä
O), 173.5 (C ÄNH), 133.8 (d, JCP
29.2 Hz, ipso-C Ph), 130.1 (p-C Ph),
3JCP
9.8 Hz, m-C Ph), 86.4
/
CH3),
Crystal data and further data collection parameters are
summarized in Table 1.
/
/
2
/
ꢀ16.4 Hz, o-C Ph),
/
1
131.8 (d, JCP
128.6 (d,
ꢀ
/
ꢀ
/
(C(O)CHC(NH)), 41.9 (C(CH3)3), 35.9 (C(CH3)3),
28.7 (C(CH3)3), 27.8 (C(CH3)3).
Table 1
Crystallographic data and parameters for 1a and 4a
1a
4a
2.18. [Ag(N-tmhd)(PBu3)] (6b)
Formula
Formula weight
C
553.4
29H34AgO2P
C58H68Ag2O2P2S2
1138.9
A stirred mixture of AgNO3 (0.20 g, 1.18 mmol) and
(N-tmhd) (0.24 g, 1.18 mmol) was dissolved in thf (10
ml). Tri-n-butylphosphine (0.31 ml, 1.18 mmol) was
added and the mixture stirred for 18 h. All volatiles were
removed from the resulting greenish black mixture.
Crystal color, Habit Pale yellow, plate Pale yellow, rectangular
prism
Crystal dimensions
(mm)
Crystal system
0.15ꢄ0.30ꢄ0.45 0.15ꢄ0.20ꢄ0.45
monoclinic
P21/c
triclinic
¯
Space group
˚
P
/1/
Extraction of the residue with toluene (2ꢄ20 ml)
/
a (A)
˚
13.253(6)
11.756(3)
17.722(5)
90
11.194(3)
13.639(3)
20.431(5)
75.32(2)
78.61(2)
72.37(2)
2851.0(12)
2
followed by filtration and evaporation in vacuo gave
the silver complex as a reddish brown oil. Yield: 0.51 g
(88%). Anal. Calc. for C23H47AgNOP: C, 56.10; H, 9.62.
b (A)
˚
c, (A)
a (8)
b (8)
1
102.40(3)
90
Found: C, 55.95; H, 9.49%. H NMR (CDCl3): d 10.2
g (8)
˚
V A
(br s, 1H, NH), 5.18 (s, 1H, C(O)CHC(NH)), 1.53ꢁ1.21
/
3
t
2696.7(16)
4
1.363
(complex, 18H, PCH2CH2CH2CH3), 1.04 (s, 9H, BuÃ
/
Z
t
3
CH3), 0.75 (t, 9H, JHH
Dcalc (g cmꢃ3
)
1.327
8.54
CH3), 0.98 (s, 9H, BuÃ
/
ꢀ
/
6.9
Hz, PCH2CH2CH2CH3). 13C NMR (CDCl3): d 204.9
m (Mo Ka) (cmꢃ1
F(000)
)
8.29
1144
1176
45.0
(C Ä
/
O), 173.4 (C Ä
/
NH), 86.2 (C(O)CHC(NH)), 41.7
2u max (8)
Reflections collected 3698
45.0
(C(CH3)3), 35.8 (C(CH3)3), 28.6 (C(CH3)3), 27.7
3
7678
7427
(C(CH3)3), 27.4 (d, JCP
ꢀ
/
2.9 Hz, PCH2CH2CH2CH3),
16.6 Hz, PCH2CH2CH2CH3), 24.0 (d,
Hz, PCH2CH2CH2CH3), 13.3
(PCH2CH2CH2CH3).
Independent
reflections
3521
(Rintꢀ1.44%)
1
24.8 (d, JCP
2JCP
13.5
ꢀ
/
(Rintꢀ2.68%)
4351
ꢀ
/
Observed reflections 2081
(Fꢀ 6.0s(F))
N/A
(F ꢀ4.0s(F))
0.868/0.953
595
Tmin/Tmax
Number of
parameters
298
2.19. X-ray crystallography
a
R
0.0422
0.0437
1.19
0.0817
0.0826
1.51
a
Crystals of 1a and 4a suitable for X-ray diffraction
studies were obtained by dissolving the corresponding
complex in thf and layering pentane over the solution.
Rw
b
Goodness-of-fit
a
2 1/2
RꢀajjFojꢃjFcjj/ajFoj;
Rwꢀ[a w(jFojꢃjFcj)2/a wjFoj ]
;
The mixture was cooled to ꢃ35 8C, while allowing the
/
wꢀ1/s2(Fo)ꢂg(Fo)2; gꢀ0.001 and 0.002 for 1a and 4a, respectively.
b
GOFꢀ[a w(jFojꢃjFcj)2/(NOꢃNV)]1/2, where NO is the number
pentane to diffuse slowly through the mixture. Crystals
formed over a period of five to nine days (yield of 1a:
of observations and NV is the number of variables.

1294
S.C. Ngo et al. / Polyhedron 21 (2002) 1289ꢁ1297
/
3. Results and discussion
the carbonyl and CH carbon atoms in the 13C NMR
spectra, upon coordination of the phosphine ligands.
Although slight darkening occurred over long periods of
time, no changes were observed in the NMR spectra of
the compounds.
3.1. Synthesis
Two routes were employed for the syntheses of the
Complex 1a could also be obtained by direct reaction
of AgNO3 with Na(tmhd) in the presence of PPh3. This
method was employed successfully for the preparation
binary silver complexes, [Ag(X)]. For complexes 1 (Xꢀ
/
tmhd), 2 (Xꢀtmod), and 3 (Xꢀtmshd), a modification
/
/
of the method of Wakeshima [13] was employed. In this
approach, AgNO3 was reacted with the b-diketone in
of [Ag(X)L], Xꢀ
S-tmod, LꢀPPh3 5a or PBu3 5b. The complexes were
air-stable, yellow to yellowꢁbrown compounds, prob-
/
S-tmhd, Lꢀ
/
PPh3 4a or PBu3 4b; Xꢀ
/
/
the presence of a base (Eq. (1)). Alternatively for 4 (Xꢀ
/
/
1
S-tmhd) and 5 (XꢀS-tmod), the complexes were read-
/
ably due to the coloration of the ligands. The H NMR
resonance for the CH resonance of the monothio-b-
diketonate ligands in the silver complexes experienced a
downfield shift compared to the corresponding silver b-
diketonate complexes, a result previously noted by
Musso and coworkers for an analogous silver complex
[16]. We also observed a downfield shift of the CH
resonance in the 13C NMR spectra of the coordinated
ligands upon sulfur substitution.
ily formed by displacement of nitrate using the sodium
salt of the b-diketonate derivative (Eq. (2)) [14]. The
method described in Eq. (1) was somewhat preferable, in
that it afforded spectroscopically pure products, suitable
for further reaction with neutral coordinating ligands to
form ternary complexes (vide infra). On the other hand,
separation of the silver product obtained in Eq. (2) from
unreacted sodium b-diketonate was difficult due to the
similar solubilities of these substances in most solvents.
Attempts to prepare the complexes via reaction of Ag2O
with the b-diketone, as described for hfac [7], failed to
provide the desired compounds. This result may be
attributed to the decreased acidity of the nonfluorinated
b-diketones relative to the fluorinated analogs.
Attempts to isolate pure Ag(N-tmhd) proved unsuc-
cessful, perhaps due to ease of hydrolysis [17]. However,
[Ag(N-tmhd)L], LꢀPPh3 5a or PBu3 5b could be
/
prepared in acceptable yield by direct reaction of
AgNO3 with Na(N-tmhd) in the presence of the appro-
priate phosphine ligand. The CH resonance of the b-
diketoiminate ligands in 5a and 5b was slightly upfield
of the chemical shifts observed for the b-diketonate
analogs, 1a and 1b, in both the 1H and 13C NMR
spectra.
ð1Þ
3.2. Thermal studies
Thermogravimetric analysis was employed to deter-
mine the suitability of the silver complexes for MOCVD
processing. Experiments were conducted at atmospheric
pressure under a nitrogen purge. Typical temperatures
of maximum weight loss were in the range of 160ꢁ
/
240 8C. For most of the complexes, weight loss was
accompanied by residues in the TGA pan, the amount
of which was comparable to the theoretical percentage
of silver present in the complex. In fact in some cases,
the residue appeared to be a silver mirror. Evidently,
these complexes lose the ancillary ligands upon heating,
without significant volatilization of the intact complex.
One exception was 1b, which had maximum rate of
weight loss at 204 8C and a residue of only 11%
(theoretical %Ag, 22%). Thus, at atmospheric pressure,
the majority of the studied complexes showed little
utility for MOCVD applications.
ð2Þ
Ternary complexes, [Ag(X)L], were prepared in two
ways. In the first method, reaction of Ag(tmhd) 1,
Ag(tmod) 2, and Ag(tmshd) 3 with 1 equiv. of PPh3 or
PBu3 gave the corresponding desired complexes 1aꢁ
/3a
(LꢀPPh3) and 1bꢁ2b (LꢀPBu3) in ꢀ80% yield. The
/
/
/
/
complexes are air-stable; the PPh3 derivatives were white
to grayish-white in color, while the PBu3 compounds
were orange or reddish-brown viscous liquids, perhaps
due to slight amounts of oxidation products. In all cases,
good elemental analyses [15] and NMR spectroscopic
data were obtained, so contamination must have been
quite small. Slight downfield shifts of the CH resonance
of the b-diketonate ligands were observed in the 1H
NMR spectra, while slight upfield shifts were found for
3.3. X-ray diffraction studies
While numerous solid-state structures have been
reported for silver complexes supported by fluorinated
b-diketonate ligands [6a,6b,6c,6f,6h,6f,6h,7,17ꢁ
/23], we

S.C. Ngo et al. / Polyhedron 21 (2002) 1289ꢁ
/1297
1295
have determined the first structures of ternary silver
complexes containing either a non-fluorinated b-diketo-
nate or a monothio-b-diketonate ligand.
The asymmetric unit for [Ag(tmhd)(PPh3)] 1a con-
tains one molecule of the mononuclear complex. The
geometry is best described as highly distorted trigonal
planar (Fig. 1); selected bond lengths and angles are
summarized in Table 2. Ag(1), P(1), O(1), and O(2) are
Table 2
˚
Selected bond lengths (A) and angles (8) for 1a
Bond lengths
Ag(1)ÃP(1)
Ag(1)ÃO(1)
Ag(1)ÃO(2)
O(1)ÃC(1)
O(2)ÃC(3)
C(1)ÃC(2)
C(2)ÃC(3)
2.320(2)
2.176(5)
2.254(6)
1.260(8)
1.257(8)
1.385(11)
1.417(10)
˚ ˚
planar to within 90.066 A; the silver atom is 0.18 A out
/
of the plane defined by the three donor atoms of the
ligands.
Structural features for 1a are reminiscent to those
reported for similar, three-coordinate analogs, [Ag(h-
Bond angles
P(1)ÃAg(1)ÃO(1)
P(1)ÃAg(1)ÃO(2)
O(1)ÃAg(1)ÃO(2)
Ag(1)ÃO(1)ÃC(1)
Ag(1)ÃO(2)ÃC(3)
C(1)ÃC(2)ÃC(3)
152.3(2)
122.7(2)
82.5(2)
130.0(5)
128.8(5)
127.7(6)
fac)L], LꢀPMe3 [6a,6b,6c], MeNC [6f], and PPh3 [17].
/
Comparisons to the latter complex are probably most
fruitful. The silver atom in 1a is unsymmetrically
bonded to the tmhd ligand with the Ag(1)Ã
/
O(1) bond
˚
almost 0.08 A longer than Ag(1)Ã
ingly, the longer AgÃ
complex with the smaller PÃ
/
O(2). Not surpris-
of centrosymmetric dimers; thus, the triclinic unit cell
contains two dimers. Selected bond lengths and angles
are collected in Table 3. To our knowledge, 4a is the first
complex for which a monothio-b-diketonate serves as a
bridging ligand [24,25], though a weak, long-range
bridging interaction is observed in a Hg(II) monothio-
b-diketonate complex [9].
The two dimers of 4a have similar overall structures
(see Fig. 2 for dimer molecule 1). The S-tmhd ligands in
both 4a dimers can be considered to be bridging in a
m4:h2,h2 mode, that is analogous to that seen for the
hfac ligands in [Ag(hfac)L]2, where L is 1,5-dimethyl-
1,5-cyclooctadiene [18] or diglyme [19a]. The dihedral
angle between the planes defined by the bridging S-
tmhd ligands in each dimer is a crystallographically-
enforced 0.008. The Agꢀ ꢀ ꢀAg distances in the dimers are
/O bond occurs on the side of the
/
AgÃO angle (Table 2 and
/
Fig. 1). Similar results are observed for [Ag(hfac)(PPh3)]
[17]. The reasons for these distortions are not clear,
though sterics may play a part; the hfac ligand is more
symmetrically coordinated in [Ag(hfac)L], Lꢀ
[6a,6b,6c] and MeNC [6f]. The AgÃO bonds in 1a are
slightly shorter than those observed for [Ag(hfac)(PPh3)]
/PMe3
/
˚
(2.218 (5) and 2.341(5) A) [17], which can be attributed
to the absence of the electron-withdrawing trifluoro-
methyl substituents. However, no appreciable lengthen-
ing of the CÃ
/
O bonds of the tmhd ligand was observed
P bond length in 1a is comparable to
for 1a. The AgÃ
/
those in previously reported monomeric, three-coordi-
nate silver b-diketonate complexes [6a,6b,6c,6f,17]. The
packing diagram shows a head-to-tail stacking of b-
diketone ligands for adjacent molecules. Stacking of
phenyl rings is also observed for alternating molecules.
The asymmetric unit for [Ag(S-tmhd)(PPh3)] 4a
contains two crystallographically independent halves
Table 3
˚
Selected bond lengths (A) and angles (8) for 4a
Molecule 1
Ag(1)ÃP(1)
Ag(1)ÃS(1)
Ag(1)ÃO(1)
Ag(1)ÃS(1a)
Ag(1)ÃO(1a)
S(1)ÃC(1)
O(1)ÃC(3)
C(1)ÃC(2)
C(2)ÃC(3)
2.382(3)
2.540(4)
2.604(9)
2.608(4)
2.830(9)
1.720(13)
1.335(16)
1.364(21)
1.435(18)
P(1)ÃAg(1)ÃS(1)
P(1)ÃAg(1)ÃO(1)
S(1)ÃAg(1)ÃO(1)
P(1)ÃAg(1)ÃS(1a)
P(1)ÃAg(1)ÃO(1a)
S(1)ÃAg(1)ÃS(1a)
O(1)ÃAg(1)ÃO(1a)
Ag(1)ÃS(1)ÃC(1)
Ag(1)ÃO(1)ÃC(3)
132.6(1)
118.2(2)
75.9(2)
116.7(1)
126.0(2)
110.7(1)
114.9(2)
115.2(4)
119.6(7)
Molecule 2
Ag(1?)ÃP(1?)
Ag(1?)ÃS(1?)
Ag(1?)ÃO(1?)
Ag(1?)ÃS(1?a)
Ag(1?)ÃO(1?a)
S(1?)ÃC(1?)
O(1?)ÃC(3?)
C(1?)ÃC(2?)
C(2?)ÃC(3?)
2.372(3)
2.540(4)
2.575(9)
2.634(5)
2.750(9)
1.624(16)
1.499(18)
1.376(19)
1.446(17)
P(1?)ÃAg(1?)ÃS(1?)
P(1?)ÃAg(1?)ÃO(1?)
S(1?)ÃAg(1?)ÃO(1?)
P(1?)ÃAg(1?)ÃS(1?a)
P(1?)ÃAg(1?)ÃO(1?a)
S(1?)ÃAg(1?)ÃS(1?a)
O(1?)ÃAg(1?)ÃO(1?a)
Ag(1?)ÃS(1?)ÃC(1?)
Ag(1?)ÃO(1?)ÃC(3?)
130.7(1)
117.0(2)
77.4(2)
117.4(1)
128.2(2)
111.8(1)
114.1(2)
117.5(4)
115.7(7)
Fig. 1. Molecular structure and atom numbering scheme for 1a.

1296
S.C. Ngo et al. / Polyhedron 21 (2002) 1289ꢁ1297
/
In general at atmospheric pressure, the complexes
under study decompose without volatilization to give
silver via loss of the supporting ligands. One exception
was 1b, [Ag(tmhd)(PBu3)], which exhibited some ability
to volatilize before total decomposition. We note that
while our work was in progress, Edwards, et al. reported
on the utility of [Ag(X)(PPh3)] complexes for CVD
processes, where X is various b-diketonate or b-ketoi-
minate ligands [17]. This group found a significant
variation in volatility and quality of deposited silver
films as a function of X. While many silver b-diketonate
derivatives, [Ag(X)L], including those in the present
study, are either too ionic [22] or too unstable to be
employed for CVD applications, it appears that judi-
cious choice of X and L ancillary ligands will possibly
allow for useful complexes to be obtained [6f,17,20,21].
Fig. 2. Molecular structure for and atom numbering scheme for dimer
molecule 1 for 4a. Hydrogen atoms are omitted for clarity.
5. Supplementary material
˚
2.929(2) and 2.900(2) A, for dimer molecules 1 and 2,
respectively.
Full lists of crystallographic data for 1a (CCDC
169487) and 4a (CCDC 169488), including atomic
coordinates, bond lengths and angles, and anisotropic
thermal parameters have been deposited with the Cam-
bridge Crystallographic Data Center. Copies of this
information may be obtained from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
The AgÃ/S bond lengths for the dimers of 4a are
clearly within bonding range, but are somewhat longer
on average than those observed in silver clusters
containing bridging thiolate ligands [26] or for metal-
to-sulfur bond distances in comparable, monomeric
monothio-b-diketonate complexes involving metals
from the second and third transition series [9,24]. The
(fax: ꢂ44-1233-336033; e-mail: deposit@ccdc.cam.ac.uk
/
AgÃ
/
O distances are longer than the AgÃ/S bonds and
or www: http://www.ccdc.cam.ac.uk).
include one long and one very long interaction per silver
center from different bridging S-tmhd ligands. These
interactions are weak at best; if the longer interaction is
ignored, then the geometry about each silver ion is
distorted tetrahedral. On the other hand, each silver ion
can be considered to be distorted trigonal planar, if all
Acknowledgements
We gratefully acknowledge the generous support for
this study by Planar Systems, Inc. and thank Dr.
Richard Tuenge for helpful advice.
AgÃ
O bond distance is similar to that found in monomeric
[Hg(S-tmhd)2], a linear complex with two weak HgÃ
interactions [9]. The AgÃP bond distances in the 4a
/
O bonds are omitted. Interestingly, the shorter AgÃ
/
/O
/
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