Mono- and bimetallic silver(I) complexes with bridging and terminal-bound organic chelating ligands

Article abstract of DOI:10.1016/S0020-1693(02)01500-1

The synthesis of the mononuclear and homobimetallic silver(I) complexes [P(C₆H₄CH₂NMe₂-2) ₃]AgL₂ [L₂=acetylacetonate, acac (5a); tropolonate, trop (5b); 3-hydroxy-2-methyl-γ-pyranoate, pyro (5c)], [P(C₆H₄CH₂NMe₂-2) ₃]AgOC(O)Me (8) and [P(C₆H₄CH ₂NMe₂-2)₃]Ag-L₄-Ag[P(C ₆H₄CH₂NMe₂-2)₃] [L ₄=2,5-dihydroxy-p-benzochinoate, benz (6a); 1,4-dihydroxy- anthrachinoate, anthra (6b)] can be achieved by the reaction of the silver(I) salts [AgL₂] [L₂=acac (3a), trop (3b), pyro (3c)], [Ag₂L₄] [L₄=benz (3d), anthra (3e)] or [AgCO₂Me] (7) with P(C₆H₄CH₂NMe ₂-2)₃ (4) in a 1:1 or 1:2 molar ratio. The respective silver(I) salts 3a-3e are accessible by treatment of [AgNO₃] (1) with HL₂ or H₂L₄ (2a-2d), respectively. In 5a-5c, 6a and 6b the silver atom possesses a pseudotetrahedral environment caused by the chelate-bound ligands acac, trop, pyro, benz or anthra and the bidentate coordinated phosphane 4. In homobimetallic 6a and 6b the appropriate transition metals are spanned by the benz or anthra units, respectively. While in 5a-5c, 6a and 6b the silver metal possesses the coordination number 4, in 8 a T-shaped arrangement is set-up with a linear P-Ag-O unit. The chemical and physical behaviour of complexes 5a-5c, 6a, 6b and 8 is reported. Spectroscopic studies reveal that on the NMR time-scale the phosphane group with its Me ₂NCH₂ built-in arms is dynamic.

Full text of DOI:10.1016/S0020-1693(02)01500-1

Inorganica Chimica Acta 350 (2003) 114Á120
/
www.elsevier.com/locate/ica
Mono- and bimetallic silver(I) complexes with bridging and
terminal-bound organic chelating ligands
M. Leschke, M. Melter, H. Lang *
Technische Universitat Chemnitz, Fakultat fur Naturwissenschaften, Institut fur Chemie, Lehrstuhl Anorganische Chemie, Straße der Nationen 62,
¨ ¨ ¨ ¨
D-09111 Chemnitz, Germany
Received 17 May 2002; accepted 15 November 2002
Dedicated to Professor Pierre Braunstein.
Abstract
The synthesis of the mononuclear and homobimetallic silver(I) complexes [P(C6H4CH2NMe2-2)3]AgL2 [L2ꢀ
acac (5a); tropolonate, trop (5b); 3-hydroxy-2-methyl-g-pyranoate, pyro (5c)], [P(C6H4CH2NMe2-2)3]AgOC(O)Me (8) and
[P(C6H4CH2NMe2-2)3]AgꢀL4ꢀAg[P(C6H4CH2NMe2-2)3] [L4ꢀ2,5-dihydroxy-p-benzochinoate, benz (6a); 1,4-dihydroxy-anthra-
chinoate, anthra (6b)] can be achieved by the reaction of the silver(I) salts [AgL2] [L2ꢀacac (3a), trop (3b), pyro (3c)], [Ag2L4] [L4ꢀ
benz (3d), anthra (3e)] or [AgCO2Me] (7) with P(C6H4CH2NMe2-2)3 (4) in a 1:1 or 1:2 molar ratio. The respective silver(I) salts 3aÁ
3e are accessible by treatment of [AgNO3] (1) with HL2 or H2L4 (2aÁ2d), respectively. In 5aÁ5c, 6a and 6b the silver atom possesses
/acetylacetonate,
/
/
/
/
/
/
/
/
a pseudotetrahedral environment caused by the chelate-bound ligands acac, trop, pyro, benz or anthra and the bidentate
coordinated phosphane 4. In homobimetallic 6a and 6b the appropriate transition metals are spanned by the benz or anthra units,
respectively. While in 5aÁ/5c, 6a and 6b the silver metal possesses the coordination number 4, in 8 a T-shaped arrangement is set-up
with a linear PꢀAgꢀO unit. The chemical and physical behaviour of complexes 5aÁ
/
/
/5c, 6a, 6b and 8 is reported. Spectroscopic
studies reveal that on the NMR time-scale the phosphane group with its Me2NCH2 built-in arms is dynamic.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: b-Diketonate; Carboxylate; Chelate; Chinoate; Phosphane; Silver(I)
1. Introduction
2)3]Cu(m-X)CuX (Xꢀ/Cl, Br), could be prepared in
which one copper atom possesses a distorted trigonal-
bipyramidal environment, while the other one is almost
square-pyramidal coordinated [3]. In the latter homo-
bimetallic transition metal complex a contact ion pair
between Cuꢁ and CuX2ꢂ exists [3].
These mono- and bimetallic low-aggregated copper(I)
species play an important role, as, for example, catalysts
in organic and organometallic synthesis as well as model
compounds to study intramolecular electron transfer
Recently, it could be shown that the hypervalent
triaryl-phosphane P(C6H4CH2NMe2-2)3 enables the
successful synthesis of diverse copper(I) and copper(II)
species with copper in different coordination spheres
[1,2]. In the solid-state, the structure of these complexes
is dominated by the coordination number 3 (trigonal-
planar), 4 (distorted tetrahedral or square-pyramidal) or
5 (trigonal-bipyramidal) of the copper atom [1,2].
Besides such mononuclear copper(I) complexes [1] a
new type of a dicopper structure, [P(C6H4CH2NMe2-
processes [1Á5].
/
In view of our earlier studies in this area, we report
here on the synthesis of silver(I) transition metal
complexes, based on oxygen containing mono-, bi- and
tetradentate organic ligands and the phosphane
P(C6H4CH2NMe2-2)3 as multidentate ligand.
* Corresponding author. Tel.: ꢁ
1833.
E-mail address: heinrich.lang@chemie.tu-chemnitz.de (H. Lang).
/
49-371-531 1200; fax: ꢁ49-371-531
/
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0020-1693(02)01500-1

M. Leschke et al. / Inorganica Chimica Acta 350 (2003) 114Á
/
120
115
2. Experimental
2.3. Synthesis of 3d and 3e
2.1. General methods
Experimental conditions and work-up were identical
to the preparation of 3c. Experimental details: Synthesis
of 3d: 1.2 g (7.1 mmol) of [AgNO3] (1), 0.49 g (3.5 mmol)
of 2,5-dihydroxy-p-benzochinone (2d) and 1 ml (0.72 g)
of NEt3. Synthesis of 3e: 1.2 g (7.1 mmol) of [AgNO3]
(1), 0.84 g (3.5 mmol) of 1,4-dihydroxy-anthrachinone
(2e) and 1 ml (0.72 g) of NEt3.
All reactions were carried out under an atmosphere of
purified nitrogen (O2 traces: Cu catalyst, BASF AG,
˚
Ludwigshafen; H2O: molecular sieve 4 A) using stan-
dard Schlenk techniques. Tetrahydrofuran, diethyl ether
and n-pentane were purified by distillation from
sodiumÁ
ified by distillation from P2O5. Infrared spectra were
Elmer FT-IR 1000 spectrometer.
1H NMR were recorded on a Bruker Avance 250
spectrometer operating at 250.130 MHz or on a Bruker
AC 200 spectrometer operating at 200.13 MHz in the
Fourier transform mode; 13C {1H} NMR spectra were
recorded at 62.895 MHz or at 50.323 MHz. Chemical
shifts are reported in d units (parts per million) down-
/
benzophenone ketyl; dichloromethane was pur-
After appropriate work-up, 3d and 3e could be
isolated as brown solids.
recorded on a PerkinÁ
/
2.3.1. Compound 3d
Yield: 1.2 g (3.39 mmol, 96% based on 1). M.p.:
132 8C (dec.). IR (KBr) (cmꢂ1): nCO
Calc. for C6H2Ag2O4 (353.812): C, 20.37; H, 0.57.
Found: C, 20.05; H, 0.52%.
ꢀ1531 (vs). Anal.
/
field from tetramethylsilane with the solvent as the
1
2.3.2. Compound 3e
Yield: 1.55 g (3.41 mmol, 96% based on 1). M.p.:
reference signal (CDCl3: H NMR, dꢀ
/
7.26; 13C{1H}
NMR, dꢀ
101.255 MHz or at 81.015 MHz in CDCl3 with
P(OMe)3 (dꢀ139.0 ppm) as external reference relative
to H3PO4 (dꢀ0.0 ppm). Melting points were deter-
/
77.0). 31P{1H} NMR were recorded at
122 8C (dec.). IR (KBr) (cmꢂ1): nCO(asym)ꢀ
/
1577 (vs),
1446 (s). Anal. Calc. for C14H6Ag2O4
(453.928): C, 37.04; H, 1.33. Found: C, 36.79; H, 1.20%.
nCO(sym)ꢀ
/
/
/
mined using sealed capillaries on a Buchi MP 510
¨
2.4. Synthesis of mononuclear 5aÁ5c
/
melting point (m.p.) apparatus. Microanalyses were
performed by the Department of Organic Chemistry at
Chemnitz, University of Technology or the Institute of
Organic Chemistry, University of Heidelberg, Heidel-
berg.
To 400 mg (0.92 mmol) of P(C6H4CH2NMe2-2)3 (4)
dissolved in 50 ml of tetrahydrofuran equimolar
amounts of the silver(I) salts 3aÁ3c (3a: 190 mg; 3b:
/
210 mg; 3c: 215 mg) were added in one portion in the
dark at 25 8C. After 2 h of stirring at this temperature
the reaction mixture was filtrated through a pad of
Celite. All volatiles were removed in oil-pump vacuo
and the remaining yellow to brown solids were washed
three times with 10 ml portions of n-pentane. Complexes
Commercial available [AgNO3] (1), 3-hydroxy-2-
methyl-g-pyranone (H-pyro) (2c), 2,5-dihydroxy-p-ben-
zochinone (H-benz) (2d), 1,4-dihydroxyanthrachinone
(H-anthra) (2e) and [AgCO2Me] (7) were used without
further purification. P(C6H4CH2NMe2-2)3 (4) [6], [Aga-
cac] (3a) [7] and [Agtrop] (3b) [9] were prepared
according to literature procedures.
5aÁ5c were obtained as brown (5a) or pale yellow (5b,
/
5c) solids, which gradually darken on exposure to light.
2.2. Synthesis of 3c
2.4.1. Compound 5a
Yield: 550 mg (0.86 mmol, 93% based on 4). M.p.:
[AgNO3] (1) (0.6 g, 3.53 mmol) was dissolved in
acetonitrile (2 ml) and ethanol (50 ml). To this solution
0.445 g (3.53 mmol) of 3-hydroxy-2-methyl-g-pyranone
(2c) dissolved in triethylamine (0.5 ml, 0.36 g) and 30 ml
of ethanol is added dropwise in the dark at 25 8C. After
2 h of stirring the white precipitate NEt3ꢁNO3ꢂ was
separated by filtration and washed three times with 10
ml portions of cold ethanol. All volatiles were removed
from the filtrate in oil-pump vacuo leaving the silver(I)
salt 3c as a colourless solid, which gradually darkens on
exposure to light. Yield: 0.8 g (3.43 mmol, 97% based on
1).
129 8C (dec.). 1H NMR (200.13 MHz, CDCl3): dꢀ
/
1.88
(s, 6 H, CH3/acac), 2.10 (s, 18 H, CH3/NMe2), 3.74 (bs, 6
H, CH2), 5.12 (s, 1 H, CH/acac), 6.83 (pt, JHH 7.7 Hz,
3 H, C6H4), 7.1Á
7.5 (m, 9 H, C6H4). 13C{1H} NMR
ꢀ
/
/
(50.323 MHz, CDCl3): dꢀ
/
29.6 (CH3/acac), 45.2 (CH3/
67.0 Hz, CH2), 94.8 (CH/acac),
3
NMe2), 63.2 (d, JPC
ꢀ
/
3
127.1 (d, JPC
ꢀ5.0 Hz, C6H4), 129.4 (C6H4), 130.9
/
1
(C6H4), 131.8 (d, JPC
(C6H4), 143.0 (C6H4), 189.9 (CO/acac). 31P{1H} NMR
(80.015 MHz, CDCl3): dꢀ 626 Hz,
26.9 (d, 1J107
1J109
727 Hz). Anal. Calc. for C32H43AgN3O2P
ꢀ
/
36.9 Hz, iC/C6H4), 133.6
/
ꢂ
/
/
ꢀ
/
Ag31P
/
ꢀ
/
Ag31P
M.p.: 165 8C (dec.). IR (KBr) (cmꢂ1): nCO(asym)ꢀ
1624 (vs), nCO(sym)ꢀ1581 (s). Anal. Calc. for
C6H5AgO3 (232.970): C, 30.93; H, 2.16. Found: C,
/
(640.523): C, 60.00; H, 6.77; N, 6.56. Found: C, 60.96;
H, 7.13; N, 6.66%; please notice, due to rapid decom-
position no satisfactory elemental analysis could be
obtained.
/
30.49; H, 2.08%.

116
M. Leschke et al. / Inorganica Chimica Acta 350 (2003) 114Á120
/
3
44.6 (CH3/NMe2), 62.6 (d, JPC
2.4.2. Compound 5b
Yield: 560 mg (0.85 mmol, 92% based on 4). M.p.:
dꢀ
/
ꢀ
/
14.9 Hz, CH2),
3
99.5 (benz), 126.4 (d, JPC
ꢀ
/
5.0 Hz, C6H4), 128.6
2
110 8C (dec.). IR (KBr) (cmꢂ1): nCO(asym)ꢀ
/
1503 (vs),
1427 (s). H NMR (200.13 MHz, CDCl3):
2.05 (s, 18 H, CH3), 3.78 (s, 6 H, CH2), 6.88 (pt,
JHH 7.9 Hz, 3 H, C6H4), 7.1Á7.4 (m, 14 H, C6H4/
45.9
13.0 Hz, CH2), 119.9 (trop), 123.6
5.6 Hz, C6H4), 129.6 (C6H4),
26.8 Hz,
(C6H4), 130.4 (d, JPC
ꢀ7.7 Hz, C6H4), 131.2 (d,
/
1
nCO(sym)ꢀ
/
1JPC
2JPC
ꢀ
/
26.2 Hz, iC/C6H4), 132.9 (C6H4), 141.8 (d,
dꢀ
/
ꢀ
/
16.3 Hz, C6H4), 179.1 (CO/benz). 31P{1H}
1
ꢀ
/
/
NMR (101.255 MHz, CDCl3): dꢀ
/
ꢂ
/29.5 (d, J107
/
Ag31P
trop). 13C{1H} NMR (50.323 MHz, CDCl3): dꢀ
/
ꢀ
/
549 Hz, J109
/
ꢀ634 Hz). Anal. Calc. for
/
1
Ag31P
(CH3), 63.5 (d, 3JPC
ꢀ
/
C60H74Ag2N6O4P2 (1220.91): C, 59.02; H, 6.11; N,
6.88. Found: C, 58.89; H, 6.02; N, 6.95%.
3
(trop), 127.3 (d, JPC
ꢀ
/
131.3 (d, 2JPC
ꢀ
/
9.4 Hz, C6H4), 132.2 (d, 1JPC
ꢀ
/
iC/C6H4), 133.9 (C6H4), 135.6 (trop), 142.8 (d, JPC
ꢀ
/
2
15.6 Hz, C6H4), 181.0 (CO/trop). 31P{1H} NMR (80.015
2.5.2. Compound 6b
Yield: 570 mg (0.43 mmol, 94% based on 4). M.p.:
1
MHz, CDCl3): dꢀ
/
ꢂ
/
26.9 (d, J107
737 Hz). Anal. Calc. for C34H41AgN3O2P
/
ꢀ641 Hz,
/
Ag31P
1J109
/
ꢀ
/
84 8C (dec.). IR (KBr) (cmꢂ1): nCO(asym)ꢀ
/
1629 (vs),
1451 (s). H NMR (250.130 MHz, CDCl3):
2.10 (s, 36 H, CH3/NMe2), 3.59 (bs, 12 H, CH2),
6.85 (pt, JHH 8.0 Hz, 6 H, C6H4), 7.3Á7.4 (m, 18 H,
Ag31P
(662.527): C, 61.63; H, 6.24; N, 6.34. Found: C, 61.61;
H, 6.78; N, 6.43%.
1
nCO(sym)ꢀ
/
dꢀ
/
ꢀ
/
/
2.4.3. Compound 5c
Yield: 580 mg (0.87 mmol, 95% based on 4). M.p.:
C6H4), 7.5 (m, 2 H, anthra), 7.85 (m, 2 H, anthra), 8.35
(s, 2 H, anthra). 13C{1H} NMR (62.895 MHz, CDCl3):
82 8C (dec.). IR (KBr) (cmꢂ1): nCO(asym)ꢀ
/
1619 (vs),
1452 (s). H NMR (250.130 MHz, CDCl3):
2.20 (s, 18 H, CH3/NMe2), 2.35 (s, 3 H, CH3/pyro),
3.57 (bs, 3 H, CH2), 3.67 (bs, 3 H, CH2), 6.40 (d, 3JHH
5.5 Hz, 1 H, pyro), 6.85 (pt, JHH 7.9 Hz, 3 H, C6H4),
3
45.1 (CH3/NMe2), 61.7 (d, JPC
dꢀ
/
ꢀ21.1 Hz, CH2),
/
1
nCO(sym)ꢀ
/
112.7 (anthra), 126.6 (C6H4), 128.1 (C6H4), 129.1 (d,
dꢀ
/
1JPC
134.4 (anthra), 136.8 (anthra), 137.0 (anthra), 143.3 (d,
2JPC
22.6 Hz, C6H4), 157.7 (anthra), 186.8 (CO/
anthra). 31P{1H} NMR (101.255 MHz, CDCl3): dꢀ
ꢀ/37.7 Hz, C/C6H4), 133.3 (C6H4), 134.1 (C6H4),
i
ꢀ
/
ꢀ
/
ꢀ
/
3
7.3Á
/
7.5 (m, 9 H, C6H4), 7.70 (d, JHH
pyro). 13C{1H} NMR (62.895 MHz, CDCl3): dꢀ
ꢀ5.5 Hz, 1 H,
/
/
ꢂ
/
/
14.6
1
1
29.1 (d, J107
/
ꢀ
/
562 Hz, J109
/
ꢀ641 Hz). Anal.
/
3
(CH3/pyro) 45.1 (CH3/NMe2), 64.1 (d, JPC
3
CH2), 113.6 (pyro), 128.3 (d, JPC
Ag31P
Ag31P
ꢀ
/
9.6 Hz,
Calc. for C68H78Ag2N6O4P2 (1321.022): C, 61.82; H,
5.95; N, 6.36. Found: C, 62.01; H, 5.86; N, 6.29%.
ꢀ5.6 Hz, C6H4),
/
2
129.9 (C6H4), 131.0 (d, JPC
1JPC 17.8 Hz, iC/C6H4), 133.4 (C6H4), 142.1 (d,
2JPC
ꢀ12.4 Hz, C6H4), 143.7 (pyro), 149.1 (pyro),
ꢀ
/
8.6 Hz, C6H4), 132.4 (d,
ꢀ
/
/
153.7 (pyro), 171.2 (CO/pyro). 31P{1H} NMR (101.255
2.6. Synthesis of 8
1
MHz, CDCl3): dꢀ
/
ꢂ
/
29.6 (d, J107
/
ꢀ566 Hz,
/
Ag31P
1J109
/
ꢀ
/
640 Hz). Anal. Calc. for C33H41AgN3O3P
Experimental conditions and work-up are identical to
those for the preparation of 5. In this respect 400 mg
(0.92 mmol) of P(C6H4CH2NMe2-2)3 (4) were reacted
with 155 mg (0.92 mmol) of [AgCO2Me] (7). After
appropriate work-up complex 8 could be isolated as a
very light-sensitive, brown solid. Yield: 510 mg (0.85
mmol, 93% based on 4).
Ag31P
(666.516): C, 59.46; H, 6.20; N, 6.31. Found: C, 59.35;
H, 6.26; N, 6.31%.
2.5. Synthesis of 6a and 6b
To 400 mg (0.92 mmol) of P(C6H4CH2NMe2-2)3 (4)
dissolved in 50 ml of tetrahydrofuran the silver(I) salts
3d or 3e, respectively, were added in one portion in a
molar ratio of 2:1 (3d: 160 mg, 0.46 mmol; 3e: 210 mg,
0.46 mmol) in the dark at 25 8C. After 3 h of refluxing,
the red solution was filtrated through a pad of Celite
and all volatiles were removed in oil-pump vacuo. The
thus obtained solids were washed three times with 10 ml
portions of n-pentane to give 6a and 6b as red solids.
M.p.: 121 8C (dec.). IR (KBr) (cmꢂ1): nCO
ꢀ1570
/
1
(vs), nCO
dꢀ
CO2Me), 3.51 (d, JHH
2JHH
8.8 Hz, 3 H, CH2), 6.85 (pt, JHH
C6H4), 7.1Á
7.4 (m, 9 H, C6H4). 13C{1H} NMR (50.323
MHz, CDCl3): dꢀ23.2 (CH3/CO2Me), 45.6 (CH3/
ꢀ/1393 (s). H NMR (200.13 MHz, CDCl3):
/
2.07 (s, 18 H, CH3/NMe2), 2.18 (s, 3 H, CH3/
2
ꢀ/8.8 Hz, 3 H, CH2), 3.77 (d,
ꢀ
/
ꢀ/7.1 Hz, 3 H,
/
/
3
NMe2), 64.4 (d, JPC
3JPC
4.6 Hz, C6H4), 129.5 (C6H4), 131.9 (d, JPC
8.3 Hz, C6H4), 132.6 (d, JPCꢀ27.8 Hz, C6H4), 134.2
ꢀ10.2 Hz, CH2), 127.5 (d,
/
2
ꢀ
/
ꢀ
/
1
2.5.1. Compound 6a
Yield: 520 mg (0.43 mmol, 93% based on 4). M.p.:
/
3
2
(d, JPC
ꢀ
/
3.7 Hz, C6H4), 142.3 (d, JPC
C6H4), 177.8 (CO/CO2Me). 31P{1H} NMR (80.015
MHz, CDCl3): dꢀ
ꢀ17.5 Hz,
/
163 8C (dec.). IR (KBr) (cmꢂ1): nCO
ꢀ
/
1525 (vs). 1H
1
NMR (250.130 MHz, CDCl3): dꢀ
NMe2), 3.38 (bs, 6 H, CH2), 3.65 (bs, 6 H, CH2), 6.15 (s,
2 H, benz), 6.85 (pt, JHH 7.8 Hz, 6 H, C6H4), 7.2Á7.5
(m, 18 H, C6H4). 13C{1H} NMR (62.895 MHz, CDCl3):
/2.20 (s, 36 H, CH3/
/
ꢂ
/
26.2 (d, J107
/
ꢀ610 Hz,
/
Ag31P
1J109
/
ꢀ
/
707 Hz). Anal. Calc. for C29H39AgN3O2P
Ag31P
ꢀ
/
/
(600.49): C, 58.01; H, 6.55; N, 7.00. Found: C, 58.13; H,
6.76; N, 6.88%.

M. Leschke et al. / Inorganica Chimica Acta 350 (2003) 114Á
/
120
117
3. Results
Table 1
Synthesis of the mono- and homobimetallic silver(I) salts 3aÁ
/
3e
Phosphane-stabilised organo silver(I) complexes of
Compound
L2/L4
References
type XAgR (Xꢀ
/
Lewis-base, Rꢀorganic group) can be
/
a
3a
3b
3c
3d
3e
acac
[7,13]
[9]
prepared by following synthetic strategies: the reaction
of XAgNO3 with CH-acidic substrates, or treatment of
[AgNO3] with Rꢂ and then with X [8]. It appeared that
the latter reaction is the most favoured one and hence,
we used this method in the synthesis of the title
complexes 5, 6 and 8.
trop b
pyro c
benz d
anthra e
this work
this work
this work
a
acacꢀ
/
acetylacetonate, C5H7O2.
tropolonate, C7H5O2.
b
c
tropꢀ
/
The, therefore, necessary silver(I) salts [AgL2] [L2ꢀ
/
pyroꢀ
benzꢀ
anthraꢀ
/
3-hydroxy-2-methyl-g-pyronate, C6H5O3.
2,5-dihydroxy-p-benzochinoate, C6H2O4.
d
e
acetylacetonate, acac (3a); [7] tropolonate, trop (3b); 3-
hydroxy-2-methyl-g-pyranoate, pyro (3c)] and [Ag2L4]
/
/
1,4-dihydroxy-anthrachinoate, C14H6O4.
[L4ꢀ2,5-dihydroxy-p-benzochinoate, benz (3d); 1,4-di-
/
solubility, which might favour multinuclear structures,
complexes 3aÁ3e could only be characterised by IR
spectroscopy, elemental analysis and, for example,
hydroxy-anthrachinoate, anthra (3e)] were prepared
either by reacting [AgNO3] (1) with equimolar amounts
/
of the corresponding b-diketones HL2 [HL2ꢀ
/acetyla-
melting point determinations (Section 2).
cetone, H-acac (2a); tropolone, H-trop (2b); 3-hydroxy-
2-methyl-g-pyranone, H-pyro (2c)] (synthesis of the
As typical for b-diketonate complexes two character-
istic frequencies are found in the vibrational spectra
between 1500 and 1650 cmꢂ1 which can be assigned to
the asymmetrical and symmetrical CO streching fre-
quencies [9,10]. The respective CO frequencies are
90 cmꢂ1, indicating that in 3aÁ
3e
symmetrical chelate-bound diketonates are present
[9,10].
Since, 3b is somewhat better soluble as the other
species, additional 1H and 13C{1H} NMR spectroscopic
studies could be carried out, which reveal to the
proposed structure with a symmetrical chelate-bound
trop ligand [11].
silver(I) salts 3aÁ
/3c), or with the chinones H2L4
[H2L4ꢀ2,5-dihydroxy-p-benzochinone, H2-benz (2d);
/
1,4-dihydroxy-anthrachinone, H2-anthra (2e)] in a 2:1
molar ratio (synthesis of homobimetallic 3d and 3e) in
presence of NEt3 in ethanol solutions (Eqs. (1) and (2)).
separated by 40Á
/
/
After appropriate work-up the silver(I) salts 3aÁ3e can
be isolated as light-sensitive solids in excellent yield
(Table 1).
/
Complexes 3aÁ3e are colourless (3a, 3b), yellow (3c)
/
or brown solids (3d, 3e), which are poorly soluble in
most common polar organic solvents, such as dimethyl-
sulfoxide or dimethylformamide. Due to this low
The silver salts 3aÁ
synthesis of mononuclear 5aÁ
and 6b. Treatment of equimolar amounts of 3aÁ
/
3e can successfully be used in the
5c and homobimetallic 6a
3c with
/
/
P(C6H4CH2NMe2-2)3 (4) in tetrahydrofuran at 25 8C
produces the silver(I) complexes [P(C6H4CH2NMe2-
2)3]AgL2 [L2ꢀacetylacetonate (5a), tropolonate (5b),
/
3-hydroxy-2-methyl-g-pyranoate (5c)] in very good yield
(Eq. (3)). However, it is advisable to run the respective
reactions in the dark since otherwise decomposition
upon formation of colloidal silver takes place.
(1)
ð3Þ
(2)

118
M. Leschke et al. / Inorganica Chimica Acta 350 (2003) 114Á120
/
Homobimetallic
[P(C6H4CH2NMe2 - 2)3]Agꢀ
2)3] [L4ꢀ2,5-dihydroxy-p-benzochinoate (6a), 1,4-dihy-
droxy-anthrachinoate (6b)] in which the [P(C6H4CH2-
NMe2-2)3]Ag moieties are spanned by chinoate units are
accessible, when 3d or 3e, respectively, are reacted with 4
in a 1:2 molar ratio in tetrahydrofuran under reflux for 3
h (Eq. (4)). Complexes 6a and 6b can be isolated in 93 or
94% yield.
silver(I)
species
of
type
colloidal silver. Therefore, it is advisable to store these
species in the dark.
/
L4ꢀ
/
Ag[P(C6H4CH2NMe2-
Carboxylates can act as mono- or bidentate or
bridging ligands in transition metal chemistry [12]. Out
of this reason we reacted P(C6H4CH2NMe2-2)3 (4) with
1 equiv. of [AgCO2Me] (7) in tetrahydrofuran at 25 8C
(Eq. (5)). After appropriate work-up, complex 8 could
be obtained as a pale brown solid in 93% yield. When
compared with 5 and 6 mononuclear 8 is very light-
/
(4)
Complexes 5 and 6 are yellow (5b, 5c), brown (5a) or
sensitive and, for example, rapidly decomposes in
solution to afford a silver mirror on the Schlenk tube
walls.
red (6a, 6b) solids, which are, when compared with 3aÁ
/
3e, much better soluble, e.g. in dichloromethane, diethyl
(5)
ether or tetrahydrofuran. While solid 5 and 6 are fairly
stable to light, it appeared that solutions containing
these species start to decompose on formation of
Nevertheless, from IR spectroscopic studies it is
obvious that the acetate building block is only uni-
dentate-bound to the silver atom, which clearly is

M. Leschke et al. / Inorganica Chimica Acta 350 (2003) 114Á
/
120
119
evidenced from the separation of the stretching vibra-
tions of the CO units (see below), and could indepen-
dently be confirmed by X-ray structure analysis of e.g.
[P(C6H4CH2NMe2-2)3]Ag[OC(O)CF3] and [P(C6H4-
CH2NMe2-2)3Ag[OC(O)CF2CF3], respectively [13].
Complexes 5, 6 and 8 were fully characterised by
elemental analysis and spectroscopic studies (1H,
13C{1H} and 31P{1H} NMR).
Special features for 5, 6 and 8 are the singlet for the
six methyl groups, an AB pattern for the diasteretopic
methylene protons and a pseudotriplett due to the
aromatic proton in ortho-position to the phosphorus
nucleus. The assignments have been supported by
1H{31P} NMR decoupling experiments.
The 13C{1H} NMR spectra of 5, 6 and 8 in CDCl3 are
well defined and comprise sharp resonance signals. At
25 8C for the CH3 and CH2 units singlets are observed
which is in agreement with the equivalence of the three
built-in arms Me2NCH2 attributed to fast dynamic
processes [2,3].
A noticeable feature in the IR spectra of these species
is that two very distinct CO stretching vibrations (with
exception of 6a) appear between 1400 and 1650 cmꢂ1
depending on the organic b-diketonate, chinoate or
carboxylate building block present. While the separation
for 5b (Dnꢀ
/
76 cmꢂ1) points to a symmetrical-bound
tropolonate unit, in 5c and 6b Dn differs by 167 or 178
cmꢂ1, assembling asymmetric coordinated moieties
[10,12].
The difference of the CO vibrations in 8 corresponds
to a unidentate bonding situation of the carboxylic
fragment to the Group-11 transition metal atom [12]. A
similar behaviour was found in isostructural
[P(C6H4CH2NMe2-2)3]Ag[OC(O)CF3] in which, as re-
sult from X-ray structure analysis, a distinct T-shaped
Acknowledgements
This work was supported in part by the Deutsche For-
schungsgemeinschaft, the Fonds der Chemischen Indus-
trie. M.L. is grateful to the State of Saxony (SMWK) for
a Ph.D. fellowship (Landesgraduiertenstipendium).
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/
Agꢀ
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