Silver(I) ferrocenylcarboxylate: Reactivity and reaction behavior toward phosphines and phosphites

Article abstract of DOI:10.1016/j.jorganchem.2012.12.007

Silver(I) ferrocenylcarboxylate [Fe(η⁵-C₅H ₄CO₂Ag)(η⁵-C₅H₅)] (1) subsequently decarboxylates either in boiling dichloromethane or tetrahydrofuran to give biferrocene [Fe(η⁵-C₅H ₄)(η⁵-C₅H₅)]₂ (2) and elemental silver. Phosphine silver(I) ferrocenylcarboxylates of type [Fe(η⁵-C₅H₄CO₂Ag(PR ₃)_n)(η⁵-C₅H₅)] (R = Ph: 4a, n = 1; 4b, n = 2; 4c, n = 3. R = n-Bu: 5a, n = 1; 5b, n = 2; 5c, n = 3. R = OMe: 6a, n = 1; 6b, n = 2; 6c, n = 3) are accessible by treatment of 1 with PR₃ (3a, R = Ph; 3b, R = n-Bu; 3c, R = OMe) in the ratio of 1:n. With dppe (7) tetrametallic [Fe(η⁵-C₅H₄CO ₂Ag(μ-dppe))(η⁵-C₅H₅)] ₂ (8) (dppe = Ph₂PCH₂CH₂PPh ₂) was formed. The structures of 4b and 8 in the solid state have been determined by single X-ray structure determination. In 4b the silver(I) ion possesses a pseudo-tetrahedral environment, whereby the four coordination sites are occupied by the chelated FcCO₂ unit and two datively-bonded PPh₃ ligands. Compound 8 forms in the solid state a dimer setup by a [Ag(μ-dppe)]₂ central building block. The FcCO₂ groups are chelated to Ag(I) thus resulting in a pseudo-tetrahedral coordination sphere at silver. The solution behavior of 4-6 was analyzed by temperature-dependent ³¹P{¹H} NMR studies indicating ligand exchange processes.

Full text of DOI:10.1016/j.jorganchem.2012.12.007

Journal of Organometallic Chemistry 725 (2013) 60e67
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Silver(I) ferrocenylcarboxylate: Reactivity and reaction behavior
toward phosphines and phosphites
*
Janett Kühnert, Harald Hahn, Tobias Rüffer, Bernhard Walfort, Heinrich Lang
Chemnitz University of Technology, Faculty of Natural Sciences, Institute of Chemistry, Department of Inorganic Chemistry, Straße der Nationen 62, 09111 Chemnitz, Germany
a r t i c l e i n f o
a b s t r a c t
Silver(I) ferrocenylcarboxylate [Fe(h h
5-C5H4CO2Ag)(
boiling dichloromethane or tetrahydrofuran to give biferrocene [Fe(
elemental silver. Phosphine silver(I) ferrocenylcarboxylates of type [Fe(
5-C5H5)] (1) subsequently decarboxylates either in
5-C5H4)( 5-C5H5)]2 (2) and
5-C5H4CO2Ag(PR3)n)( 5-C5H5)]
Article history:
Received 2 October 2012
Received in revised form
4 December 2012
h
h
h
h
(R ¼ Ph: 4a, n ¼ 1; 4b, n ¼ 2; 4c, n ¼ 3. R ¼ n-Bu: 5a, n ¼ 1; 5b, n ¼ 2; 5c, n ¼ 3. R ¼ OMe: 6a, n ¼ 1; 6b,
n ¼ 2; 6c, n ¼ 3) are accessible by treatment of 1 with PR3 (3a, R ¼ Ph; 3b, R ¼ n-Bu; 3c, R ¼ OMe) in the
Accepted 5 December 2012
ratio
of
1:n.
With
dppe
(7)
tetrametallic
[Fe(h
5-C5H4CO2Ag(
m
-dppe))(
h
5-C5H5)]2
(8)
Keywords:
Silver
Carboxylate
Ferrocene
Solid-state structure
(dppe ¼ Ph2PCH2CH2PPh2) was formed. The structures of 4b and 8 in the solid state have been deter-
mined by single X-ray structure determination. In 4b the silver(I) ion possesses a pseudo-tetrahedral
environment, whereby the four coordination sites are occupied by the chelated FcCO2 unit and two
datively-bonded PPh3 ligands. Compound 8 forms in the solid state a dimer setup by a [Ag(m-dppe)]2
central building block. The FcCO2 groups are chelated to Ag(I) thus resulting in a pseudo-tetrahedral
coordination sphere at silver. The solution behavior of 4e6 was analyzed by temperature-dependent
31P{1H} NMR studies indicating ligand exchange processes.
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
features both in solution and in the solid state. Very recently, the
use of 10-(diphenylphosphanyl)-1-ferrocenecarboxylic acid (Hdpf)
Ferrocenecarboxylic acid is known since quite some time and
its reactivity and reaction chemistry, respectively, has been viewed
in terms of cluster synthesis [1,2], surface modification and bio-
inorganic applications including biosensors [3], and, for example,
catalysis [4], since the ferrocene backbone is a brilliant building
block for the construction of new molecules and materials with
tailor-made properties, due to its robustness, well-established
synthesis methodologies, and excellent redox properties. On the
other hand, silver(I) carboxylates of type [AgO2CR] and
[AgO2CR(Ln)], respectively, (R ¼ single-bonded organic ligand)
gained recently interest because they can be used as precursors in,
for example, metallization processes using Chemical Vapor
Deposition (CVD), Atomic Layer Deposition (ALD) [5,6], spin-
coating [7], inkjet printing [8] or combustion-CVD [9] techniques
to obtain silver films as well as patterns on different substrate
materials. In addition, they are of importance as building blocks in
the preparation of hetero(multi)nuclear transition metal
complexes [10]. However, only less is known about their structural
in the synthesis of silver(I)-based heterooligometallic complexes
was reported, because the appropriate coordination sites within
these species allowed to prepare complexes of higher nuclearity
[11]
With this in mind and as a continuation of our research in the
field of synthesizing (hetero)multimetallic complexes using ferro-
cene derivatives as structural building block motifs [10], we here
describe the physical and chemical behavior of the silver(I) ferro-
cenylcarboxylate [Fe(h h
5-C5H4CO2Ag)( 5-C5H5)]. The solid-state
structure of two samples is reported as well.
2. Results and discussion
The thermal behavior of the silver(I) ferrocenylcarboxylate
[Fe(
Fe(
h h
5-C5H4CO2Ag)( 5-C5H5)] (1), accessible by the reaction of
h
5-C5H4CO2H)( 5-C5H5) with [AgNO3] in presence of NEt3 [10a],
h
was studied. Therefore, 1 was suspended in either dichloromethane
or tetrahydrofuran and the corresponding reaction mixture was
heated to reflux. It was observed that in the higher boiling solvent
the decomposition occurred more rapidly, as expected (Experi-
mental Part). Upon thermolysis, a brownish slurry was formed,
whereby silver precipitated in form of a silver mirror on the Schlenk
* Corresponding author. Tel.: þ49 (0)371 531 21210; fax: þ49 (0)371 531 21219.
E-mail address: heinrich.lang@chemie.tu-chemnitz.de (H. Lang).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.12.007

J. Kühnert et al. / Journal of Organometallic Chemistry 725 (2013) 60e67
61
Ag
CO2
Fe
T
Fe
+
+
Ag
(1)
2 CO2
2
x2
Fe
1
Scheme 1.
tube walls. From the slurry, orange biferrocene (2) could be isolated
by subsequent crystallization. The release of CO2 was proven by
passing the gaseous components through a barium hydroxide
solution, whereby precipitation of barium carbonate was observed.
The isolation of 2 together with elemental Ag shows that 1
decomposes in a consecutive process including decarboxylation as
well as homolytic bond cleavage and bond coupling reactions. In
summary, this thermal behavior enriches the synthesis methodol-
ogies for preparing biferrocene [12]. In general, the thermal
decomposition of silver(I) carboxylates of formula [AgO2CR]
(R ¼ organic ligand) to afford R2 was studied by Fields and
Meyerson [13]
against air and moisture are. Better solubility of the corresponding
complexes can be achieved by increasing the number of Lewis-
bases at silver(I). For example, complexes possessing three phos-
phine or phosphite ligands, respectively, or featuring the dppe
chelating moiety, can safely be handled for a short period of time in
air without significant decomposition or oxidation of the appro-
priate phosphines or phosphites. However, it must be emphasized
that 4e6 and 8 should best be stored in the dark and that all
chemical manipulations should be performed with exclusion of
light, otherwise decomposition upon formation of elemental
silver is observed. Concerning the overall stability of 4e6
following trend can be seen 4 > 5 > 6, whereby complexes 4aec
are the most stabile species.
The identity of 4e6 and 8 has been confirmed by elemental
analysis as well as IR and NMR (1H, 13C{1H}, 31P{1H})
spectroscopy. The molecular structures of 4b and 8 in the solid
state were additionally determined by single X-ray structure
analysis, thus confirming the structural assignments made from
spectroscopic analysis.
It is established that non-soluble coordination oligomers and
polymers can be converted to, for example, lower aggregated or
even mononuclear species upon addition of 2- or 4-electron Lewis-
base molecules including phosphines, phosphites, amines or sul-
fanes. Thus, we reacted 1 with PR3 (3a, R ¼ Ph; 3b, R ¼ n-Bu; 3c,
R ¼ OMe) in the ratio of 1:n (n ¼ 1, 2, 3) and with dppe (7)
(diphenylphosphinoethane), respectively, in tetrahydrofuran as
solvent at ambient temperature. Within these reactions the ferro-
Most characteristic in the IR spectra of 4e6 and 8 are their nCO2
vibrations (Experimental Part). The strong nCO2 absorptions of the
carboxylato units are observed between 1330 and 1460 (ns(CO2))
cenylcarboxylato silver(I) phosphines [Fe(h -
5-C5H4CO2Ag(PR3)n)(h5
C5H5)] (R ¼ Ph: 4a, n ¼ 1; 4b, n ¼ 2; 4c, n ¼ 3. R ¼ n-Bu: 5a, n ¼ 1;
5b, n ¼ 2;5c, n ¼ 3. R ¼ OMe: 6a, n ¼ 1; 6b, n ¼ 2; 6c, n ¼ 3) and
and 1540e1590 cmꢀ1
(
na(CO2)) (ns ¼ symmetric, na ¼ anti-
symmetric OeCeO stretching mode), which is typical in transi-
tion metal chemistry [14]. Whereas the anti-symmetric (CO2)
tetrametallic [Fe(h m-dppe))(h
5-C5H4CO2Ag( 5-C5H5)]2 (8) were
formed in yields between 90 and 95% (Experimental Part) (Schemes
1 and 2). Within all of these reactions soluble species were formed
which, after appropriate work-up, could be isolated as pale yellow
to orange colored solids (4a, 4b, 8), waxy materials (5a) or liquids
(4c, 5b, 5c, 6aec). It is obvious that the more Lewis-base ligands are
available at silver(I), the more stable the organometallic complexes
n
bands can always be detected, the respective symmetric vibrations
only at times, which is attributed to additional ligand absorptions in
this region, i.e. for the respective phosphite derivatives only na could
be observed. The Dn value (Dn
carboxylic anions bind in a mono-, bi-dentate or chelating fashion
¼
na
ꢀ
ns) gives a first hint if the
CO2Ag(PR3)n
Fe
PR3 (3)
4
: R = Ph, n = 1-3
n
5
: R = Bu, n = 1-3
CO2Ag
6: R = OMe, n = 1-3
Fe
1
Ph2P
PPh2
AgO2C
Ag
dppe (7)
CO2
Ph2P
PPh2
Fe
Fe
8
Scheme 2. Synthesis of 4e6 and 8 by phosphine or phosphite treatment of 1.

62
J. Kühnert et al. / Journal of Organometallic Chemistry 725 (2013) 60e67
observed, i. e. 3a, ꢀ6.4; 4a, 15.7 ppm (Experimental Part). In
addition, the 31P{1H} NMR spectra of these complexes are of
some more interest because they show in solution ligand
exchange processes (Experimental Part, Fig. 1). Similar observa-
tions were made for comparable phosphine or phosphite silver(I)
complexes [15] and [(R3P)Ag carboxylates] [16]. For the appropriate
phosphine and phosphite silver(I) carboxylates two super-imposed
doublets are observed at low temperature (1J107Ag31P and 1J109Ag31P),
due to coupling of the 31P nucleus with the 107Ag and 109Ag isotopes
having natural abundances of 52 and 48%, respectively (Experi-
mental Part) [17]. At ambient temperature the 31P{1H} spectra are
characterized by either broad doublets or broad signals. Exemplary,
the temperature-dependent 31P{1H} NMR spectra of 6a in the
temperature range of 213e298 K are shown in Fig. 1. This behavior
corresponds to related silver(I) organic species, for a detailed
discussion see references [15] and [16]. As it can be seen from Fig. 1,
1
1
representative J107Ag31P and J109Ag31P coupling constants of 685
and 790 Hz are characteristic. Furthermore, it could be demon-
strated that the exchange process becomes faster in the presence of
an excess of phosphine or phosphite [16].
The molecular structures of 4b and 8 in the solid state were
established by single X-ray crystallographic studies. Single crystals
of 4b were obtained by slow diffusion of petroleum ether into
a tetrahydrofuran solution containing 4b at ꢀ20 ꢁC, while crystals
of 8 were accessible from a concentrated dichloromethane solu-
ꢁ
ꢀ
tion at ꢀ20 C. ORTEP diagrams, selected bond distances (A) and
angles (ꢁ) are given in Fig. 2 (complex 4b) and 3 (8). Selected
crystal and structure refinement data are given in the Experi-
mental Part. Molecules 4b and 8 crystallize in the triclinic space
group P1.
The overall structural feature of 4b in the solid state is that the
Ag(I) ion possesses a pseudo-tetrahedral AgP2O2 environment
setup by two PPh3 ligands and one chelate-bonded carboxylic
ꢁ
group with bond angles ranging from 53.68(12) to 126.80(12)
(Fig. 2). The silver-oxygen and silver-phosphorus bond distances
correspond
to
structurally
related
complexes,
i.e.
[Ag(O2CR)(PPh3)2] with R ¼ H, Me, CF3 [16,18]. The C5H4CO2Ag
unit of 4b is nearly planar, as revealed from a calculation of mean
plane of the atoms Ag1, O1, O2 C6eC11 (root-mean-square (rms)
ꢀ
deviation from planarity: 0.102 A, highest deviation from planarity
ꢀ
observed for Ag1 with 0.201(2) A). As expressed by the torsion
Fig. 1. Temperature-dependent 31P{1H} NMR spectra of 4a (in CDCl3, temperature
range 213e298 K).
angle of, e.g. C2eFe1eC6eC11 with ꢀ8.9(6) ꢁ, the cyclopentadienyl
ligands at the iron atom exhibit an almost eclipsed conformation.
The FeeD distances are as expected.
Complex 8 forms a centrosymmetric dimer in the solid state
(Fig. 3) with a central Ag2P4C4 ten-membered ring. The dppe
ligands are acting as bridging units between two [AgO2CFc] moie-
ties, giving rise to pseudo-tetrahedral AgP2O2 arrangements at
Ag(I). The dppe ligands occupying two of the four coordination sites
and the ferrocenylcarboxylate anions are chelate-bonded through
both oxygen atoms to the third and fourth site. In this respect,
tetrametallic 8 closely resembles bimetallic 4b (Fig. 2). The range of
the angles around Ag1 is 53.59(7) to 133.13(3) ꢁ, the Ag1eO1 and
to a transition metal atom [14]. Within our studies the Dn values
were calculated for 4e6 and 8 indicating that the carboxylic units
are chelate/bidentate-bonded to silver(I) with exception of 6aec,
respectively (Experimental Part).
Additionally, NMR spectroscopic studies were carried out to
characterize all new complexes (Experimental Part). The
appropriate 1H and 13C{1H} NMR spectra consist of well-
resolved resonance signals and show the respective coupling
patterns for the organic building blocks present (Experimental
Part).
ꢀ
Ag1eO2 distances with 2.393(2) and 2.546(2) A differ from each
other more pronounced as observed for 4b, indicating a more
unsymmetrical binding of the carboxylato ligand to Ag1. As
observed for 4b, the C5H4CO2Ag unit of 8 is nearly planar. A
calculated mean plane of the atoms Ag1, O1, O2 C6eC11 gives an
Appreciable resonance signals in the 1H NMR spectra of all
complexes are the proton resonances of the cyclopentadienyl
ligands
h
5-bonded to iron. In this respect, the ferrocenyl cyclo-
ꢀ
pentadienyl ring protons always appear as a singlet (C5H5 unit) and
two pseudo-triplets (C5H4 moiety, JHH ¼ ca. 1.8 Hz) in the range of
4.0e5.0 ppm (Experimental Part).
rms deviation from planarity of 0.058 A with the highest deviation
ꢀ
from planarity observed for Aꢁg1 with 0.110(1) A. The torsion angle
C1eFe1eC6eC11 with 2.3(3) indicates that the cyclopentadienyl
ligands at iron possess more precisely the eclipsed conformation as
compared to 4b (see above). Thus, related structural features of 8
are very similar to those of 4b and other phosphine-stabilized Ag(I)
carboxylato complexes [16,18]
31P{1H}) spectroscopy is even suitable to monitor the progress of
the reaction of 1 with 3aec and 7, respectively, to give 4e6 and 8
(Experimental Part). Upon coordination of PR3 (R ¼ Ph, n-Bu,
OMe) or dppe to silver(I) an representative shift to lower field is

J. Kühnert et al. / Journal of Organometallic Chemistry 725 (2013) 60e67
63
ꢁ
ꢀ
Fig. 2. ORTEP diagram (25% probability level) of 4b with the atom numbering scheme (hydrogen atoms are omitted for clarity). Selected bond distances (A) and angles ( ): Ag1eP1
2.4720(12), Ag1eP2 2.4180(12), Ag1eO1 2.450(4), Ag1eO2 2.419(3), O1eC11 1.251(6), O2eC11 1.251(6), Fe1eD1 1.658(3), Fe1eD2 1.648(3); D1eFe1eD2 179.6(2), P1eAg1eP2
123.19(4), O1eAg1eO2 53.68(12), P1eAg1eO1 95.26(11), P1eAg1eO2 111.02(9), P2eAg1eO1 126.80(12), O1eC11eO2 123.1(5), C11eO1eAg1 90.6(3), C11eO2eAg1 92.1(3)
(D1 ¼ centroid of C1eC5, D2 ¼ centroid of C6 e C10). Standard uncertainties are given in the last significant figure(s) in parenthesis.
Fig. 3. ORTEP diagram (25% probability level) of 8 with the atom numbering scheme (hydrogen atoms and dichloromethane solvent molecules were omitted for clarity). Selected bond
ꢁ
ꢀ
distances(A) and angles( ):Ag1eP12.4195(7), Ag1eP22.4275(7), Ag1eO12.393(2), Ag1eO2 2.546(2), O1eC111.270(4), O2eC111.252(4), Fe1eD11.650(1), Fe1eD21.644(1); D1eFe1eD2
178.2(2), P1eAg1eP2133.13(3), O1eAg1eO253.59(7), P1eAg1eO1117.80(6), P1eAg1eO2102.63(5), P2eAg1eO1109.03(6), O1eC11eO2124.3(3), C11eO1eAg194.30(18), C11eO2eAg1
87.70(18) (D1 ¼ centroid of C1 e C5, D2 ¼ centroid of C6 e C10). Symmetry code “A”: ex, ey, ez. Standard uncertainties are given in the last significant figure(s) in parenthesis.

64
J. Kühnert et al. / Journal of Organometallic Chemistry 725 (2013) 60e67
3. Conclusion
(0.24 mmol, 80% based on 1). The spectroscopic data of 2 are
identical with the one reported in reference [12].
Heating the organometallic ferrocenyl silver(I) carboxylate
[Fe(
hydrofuran produced in a redox reaction biferrocene [Fe(h5
C5H4)(
5-C5H5)]2 along with elemental silver and CO2, which is
a common feature of silver(I) salts of organic carboxylic acids [13].
As intermediate formation [Fe(
5-C5H4Ag)( 5-C5H5)] can be
considered which was formed by initial decarboxylation. Ferrocene
[Fe(
5-C5H4CO2Ag)( 5-C5H5)] can be stabilized by the addition of 2-
electron donors like PR3 (R ¼ Ph, n-Bu, OMe). Thus available
h
5-C5H4CO2Ag)(
h
5-C5H5)] in boiling dichloromethane or tetra-
4.3. Synthesis of [AgO2CFc(PPh3)] (4a)
-
h
Complex 1 (127 mg, 0.377 mmol) was suspended in 20 mL of
tetrahydrofuran and slowly 100 mg (0.377 mmol) of PPh3 (3a) were
added, whereby a clear orange colored reaction solution was ob-
tained. After stirring it for 45 min at ambient temperature it was
filtered through a pad of Celite. After removal of all volatiles in oil-
pump vacuum the title compound was obtained as a yellow solid in
a yield of 208 mg (0.347 mmol, 92% based on 1).
h
h
h
h
phosphine/phosphite silver(I) ferrocenylcarboxylates [Fe(h5
-
C5H4CO2Ag(PR3)n)(
h
5-C5H5)] (n ¼ 1, 2, 3) are more stable than
C29H24AgFeO2P (599.17) calc. C, 58.13, H, 4.04; found C, 58.49, H,
[Fe( h
h
5-C5H4CO2Ag)( 5-C5H5)], however, exposure to light induced
3.96%. Mp. 75 ꢁC. IR (KBr) [cmꢀ1]: nCO(as) 1541 (vs), nCO(s) 1460 (s). 1H
the formation of elemental silver. While these molecules are most
likely aggregated depending on the number of phosphine or
phosphite present, which is a common feature for such type of
complexes, the use of the chelating ligand dppe (Ph2PCH2CH2PPh2)
NMR (CDCl3)
d
4.21 (s, 5 H, C5H5), 4.27 (pt, 3JHH ¼ 1.9 Hz, 2 H, C5H4),
4.78 (pt, 3JHH ¼ 1.9 Hz, 2 H, C5H4), 7.3e7.5 (m, 15 H, C6H5). 13C{1H}
NMR (CDCl3) d
69.5 (C5H5), 70.1 (CH/C5H4), 70.7 (CH/C5H4), 76.3 (iC/
C5H4), 129.3 (d, JCP ¼ 10.6 Hz, CH/C6H5), 130.3 (d, JCP ¼ 38.9 Hz, iC/
C6H5), 131.2 (d, JCP ¼ 2.4 Hz, CH/C6H5), 134.0 (d, JCP ¼ 16.3 Hz, CH/
produced tetrametallic [Fe(
This species is setup by a [Ag( -dppe)]2 core unit, the FcCO2 groups
are chelated to Ag(I) thus resulting in a pseudo-tetrahedral coor-
dination sphere at silver. The solution behavior of [Fe(h5
h m-dppe))(h
5-C5H4CO2Ag( 5-C5H5)]2.
m
C6H5), 179.4 (CO2). 31P{1H} NMR (CDCl3)
d 15.7. ESI-MS [m/z]:
[Mþ ꢀ FcCO2 þ PPh3 þ H] 633.
-
C5H4CO2Ag(PR3)n)(
h
5-C5H5)] was analyzed by temperature-
4.4. Synthesis of [AgCO2CFc(PPh3)2] (4b)
dependent 31P{1H} NMR studies indicating ligand exchange
processes as characteristic for similar, for example, phosphine sil-
The synthesis and appropriate work-up is identical to that one of
4a (see above). Following compounds were reacted: 163 mg
(0.484 mmol) of 1 and 254 mg (0.968 mmol) of PPh3 in 20 ml of
tetrahydrofuran. Complex 4b was isolated as a yellow solid in
a yield of 385 mg (0.446 mmol, 92% based on 3).
ver(I) carboxylates and b-diketonates, respectively [15,16]
4. Experimental Part
4.1. Starting materials, reaction conditions and instrumentation
C47H39AgFeO2P2 (861.43) calc. C, 65.52, H, 4.56; found C, 65.34,
H, 4.74%. Mp. 87 ꢁC. IR (KBr) [cmꢀ1
] nCO(as) 1542 (vs), nCO(s) 1461 (s).
3
All reactions were carried out under an atmosphere of purified
nitrogen (4.6) using standard Schlenk techniques. Tetrahydrofuran,
diethyl ether and n-hexane were purified by distillation from
sodium/benzophenone ketyl; dichloromethane was purified by
distillation from calcium hydride. Celite (purified and annealed,
Erg. B.6, Riedel de Haen) was used for filtrations. The silver(I) fer-
rocenylcarboxylate 1 was prepared according to a published
procedure [10a]. Infrared spectra were recorded with a Perkin
Elmer FT-IR spectrometer Spectrum 1000. 1H NMR spectra were
recorded with a Bruker Avance 250 spectrometer at 298 K oper-
ating at 250.130 MHz in the Fourier transform mode; 13C{1H} NMR
spectra were recorded at 62.860 MHz. Chemical shifts are reported
1H NMR (CDCl3)
d
4.07 (s, 5 H, C5H5), 4.20 (pt, JHH ¼ 1.7 Hz, 2 H,
C5H4), 4.78 (pt, 3JHH ¼ 1.7 Hz, 2 H, C5H4), 7.2e7.5 (m, 30 H, C6H5). 13
C
{1H} NMR (CDCl3)
d 69.3 (C5H5), 69.3 (CH/C5H4), 70.5 (CH/C5H4),
79.6 (iC/C5H4), 128.9 (d, JCP ¼ 9.6 Hz, CH/C6H5), 130.1 (d, JCP ¼ 1.4 Hz,
i
CH/C6H5), 132.7 (d, JCP ¼ 25.8 Hz, C/C6H5), 134.1 (d, JCP ¼ 16.8 Hz,
CH/C6H5), 176.8 (CO2). 31P{1H} NMR (CDCl3)
d 7.3. ESI-MS [m/z]:
[Mþ ꢀ FcCO2] 631.
4.5. Synthesis of [AgO2CFc(PPh3)3] (4c)
The synthesis and respective work-up, is identical with the
synthesis of 4a (see earlier). In this respect, 178 mg (0.528 mmol) of
1 were reacted with 415 mg (1.584 mmol) of 3a in 20 mL of
tetrahydrofuran. Complex 4c could be obtained as a yellow liquid in
a yield of 552 mg (0.491 mmol 93% based on 1).
in
the solvent as reference signal (CDCl3: 1H NMR
NMR
77.16). 31P{1H} NMR spectra were recorded at
d units (parts per million) downfield from tetramethylsilane with
d
¼ 7.26; 13C{1H}
d
¼
101.255 MHz in CDCl3 with P(OMe)3 as external standard
C65H54AgFeO2P3 (1123.72) calc. C, 69.47, H, 4.84; found C, 68.44,
(
d
¼ 139.0) rel. to 85% H3PO4 (
d
¼ 0.00). The ESI-TOF (Electro-Spray-
H, 5.00%. Mp. 153 ꢁC. IR (KBr) [cmꢀ1
] nCO(as) 1590 (vs), nCO(s) 1331 (s).
3
Ionization e Time-of-Flight) mass spectra were determined using
a Mariner Biospectrometry Workstation 4.0 (Applied Biosystems).
Microanalysis was performed by using a Thermo FLASHEA 1112
Series instrument.
1H NMR (CDCl3)
d
4.08 (s, 5 H, C5H5), 4.22 (pt, JHH ¼ 1.8 Hz, 2 H,
C5H4), 4.79 (pt, 3JHH ¼ 1.8 Hz, 2 H, C5H4), 7.2e7.4 (m, 45 H, C6H5). 13
C
{1H} NMR (CDCl3)
d 69.4 (C5H5), 69.5 (CH/C5H4), 70.5 (CH/C5H4),
128.8 (d, JCP ¼ 9.1 Hz, CH/C6H5), 129.7 (d, JCP ¼ 1.4 Hz, CH/C6H5),
134.1 (d, JCP ¼ 17.8 Hz, CH/C6H5), 134.2 (d, JCP ¼ 14.9 Hz, iC/C6H5); iC/
C5H4 could not be detected under the measurement conditions
4.2. Thermal decomposition of 1, synthesis of biferrocene 2
applied. 31P{1H} NMR (CDCl3)
d 3.5. ESI-MS [m/z (rel. intens)]:
200 mg (0.594 mmol) of 1 were suspended either in dichloro-
methane or tetrahydrofuran (50 mL) and the reaction mixture was
heated to reflux, whereby it turned from a yellow to a brownish
slurry, and a silver mirror was formed on the Schlenk tube walls.
After 6 h (dichloromethane) or 4 h (tetrahydrofuran) the reaction
mixture was filtered through a pad of Celite and all volatiles were
removed in oil-pump vacuum. The residue was dissolved in
dichlormethane and subsequent crystallization at ambient
temperature gave orange 2. Yield (from dichlormethane): 74 mg
(0.18 mmol, 67% based on 1); yield (from tetrahydrofuran): 88 mg
[Mþ ꢀ FcCO2 ꢀ PPh3] 631 (100), [Mþ ꢀ FcCO2] 893 (90).
4.6. Synthesis of [AgO2CFc(PnBu3)] (5a)
The synthesis and work-up of 5a follows the procedure
described for 4a (see earlier). In this respect, 95 mg (0.282 mmol) of
1 were reacted with 57 mg (0.282 mmol, 0.07 mL) of 3b in 20 mL of
tetrahydrofuran. Stirring for 45 min at ambient temperature
resulted in the formation of an almost clear reaction solution,
which was filtered through a pad of Celite. Removal of all volatiles

J. Kühnert et al. / Journal of Organometallic Chemistry 725 (2013) 60e67
65
in oil-pump vacuum gave 5a as yellow oil, which after 8 h drying in
4.10. Synthesis of [AgO2CFc(P(OMe)3)2] (6b)
oil-pump vacuum resulted in the formation of a dark yellow waxy
material. Yield: 140 mg (0.260 mmol, 92% based on 1).
Complex 6b was synthesized in an analogous manner as
described for 4a by reacting 200 mg (0.60 mmol) of 1 and 148 mg
(1.194 mmol, 0.14 mL) of 3c in 20 mL of tetrahydrofuran at ambient
temperature. After appropriate work-up, 6b was isolated as dark
orange oil, which slowly starts to decompose after 8 h of storing.
Yield: 320 mg (0.55 mmol, 92% based on 1).
C23H36AgFeO2P (539.20) calc. C, 51.23, H, 6.73; found C, 50.15, H,
6.59%. IR (KBr) [cmꢀ1 nCO(as) 1556 (vs), nCO(s) 1458 (s). 1H NMR
]
(CDCl3)
d
0.96 (t, JHH ¼ 7.0 Hz, 9 H, CH3/nBu), 1.3 - 1.7 (m, 18 H,
CH2/nBu), 4.21 (s, 5 H, C5H5), 4.27 (pt, 3JHH ¼ 1.8 Hz, 2 H, C5H4), 4.76
(pt, 3JHH ¼ 1.8 Hz, 2 H, C5H4), 7.3 - 7.5 (m, 15 H, C6H5). 13C{1H} NMR
(CDCl3)
d
13.8 (CH3/nBu), 24.4 (d, JCP ¼ 15.4 Hz, CH2/nBu), 25.2 (d,
C17H27AgFeO8P2 (585.04) calc. C, 34.90, H, 4.65; found C, 35.62,
JCP ¼ 22.6 Hz, CH2/nBu), 28.0 (CH2/nBu), 69.6 (C5H5), 70.2 (CH/C5H4),
H, 4.32%. IR (KBr) [cmꢀ1 nCO(as) 1551 (vs). 1H NMR (CDCl3)
] d 3.69 (d,
i
70.7 (CH/C5H4); the signals for C and CO2 could not be assigned
JPH ¼ 13.1 Hz, 18 H, CH3), 4.18 (s, 5 H, C5H5), 4.2 - 4.3 (m, 2 H, C5H4),
under the measurement conditions applied. 31P{1H} NMR (CDCl3)
4.7e5.0 (m, 2 H, C5H4). 13C{1H} NMR (CDCl3)
d
51.3 (d, 2JCP ¼ 4.8 Hz,
d
ꢀ0.2 (d, J107Ag31P ¼ 670.8 Hz), ꢀ0.2 (d, J109Ag31P ¼ 776.9 Hz).
CH3), 69.3 (C5H5), 69.8 (CH/C5H4), 70.4 (CH/C5H4), 177.7 (CO2), the
i
signal for C/C5H4 could not be detected under the measurement
conditions applied. 31P{1H} NMR (CDCl3)
d 132.6.
4.7. Synthesis of [AgO2CFc(PnBu3)2] (5b)
4.11. Synthesis of [AgO2CFc(P(OMe)3)3] (6c)
Yellow 5b was synthesized in an analogous manner as described
for 4a. Thus, 107 mg (0.317 mmol) of 1 were treated with 128 mg
(0.634 mmol, 0.16 mL) of 3b in 20 mL of tetrahydrofuran. Yield:
214 mg (0.289 mmol, 91% based on 1).
Complex 6c was synthesized as described for 4a: 168 mg
(0.499 mmol) of 1 and 186 mg (1.497 mmol, 0.17 mL) of 20 mL of
tetrahydrofuran. The title complex could be isolated as orange oil in
a yield of 324 mg (0.457 mmol, 92% based on 1).
C35H63AgFeO2P2 (741.51) calc. C, 56.69, H, 8.56; found C, 56.77, H,
8.51%. IR (KBr) [cmꢀ1
]
nCO(as) 1560 (vs), nCO(s) 1342 (s). 1H NMR
C20H36AgFeO11P3 (709.11) calc. C, 33.87, H, 5.11; found C, 34.37,
3
(CDCl3)
d
0.84 (t, JHH ¼ 7.1 Hz, 18 H, CH3/nBu), 1.2e1.5 (m, 36 H,
H, 4.50%. IR (KBr) [cmꢀ1 nCO(as) 1538 (s). 1H NMR (CDCl3)
] d 3.65 (d,
CH2/nBu), 4.09 (pt, 3JHH ¼ 1.8 Hz, 2 H, C5H4), 4.11 (s, 5 H, C5H5), 4.67
JPH ¼ 13.1 Hz, 27 H, CH3), 4.14 (s, 5 H, C5H5), 4.20 (pt, 3JHH ¼ 1.4 Hz,
(pt, 3JHH ¼ 1.8 Hz, 2 H, C5H4). 13C{1H} NMR (CDCl3)
d
13.8 (CH3/nBu),
2 H, C5H4), 4.70 (pt, 3JHH ¼ 1.4 Hz, 2 H, C5H4). 13C{1H} NMR (CDCl3)
24.5 (d, JCP ¼ 13 Hz, CH2/nBu), 25.3 (d, JCP ¼ 11 Hz, CH2/nBu), 27.5 (d,
d
51.4 (d, JCP ¼ 5.3 Hz, CH3), 69.3 (C5H5), 69.9 (CH/C5H4), 70.5 (CH/
i
JCP ¼ 4.3 Hz, CH2/nBu), 68.9 (CH/C5H4), 69.1 (C5H5), 70.3 (CH/C5H4),
C5H4), 177.6 (CO2); the resonance signal for C/C5H4 could not be
80.7 (iC/C5H4), 175.0 (CO2). 31P{1H} NMR (CDCl3)
d
ꢀ9.0. ESI-MS [m/
detected under the measurement conditions applied. 31P{1H} NMR
z] [Mþ ꢀ FcCO2 þ H] 511.
(CDCl3) d 132.7.
4.12. Synthesis of [AgFcCO2(dppe)]2 (8)
4.8. Synthesis of [AgO2CFc(PnBu3)3] (5c)
1,2-Bis(diphenylphosphino)ethane (7) (161 mg, 0.405 mmol)
was dissolved in 30 mL of tetrahydrofuran and 136 mg
(0.405 mmol) of 1 were added in a single portion at ambient
temperature. After 1.5 h of stirring at this temperature all volatile
materials were removed in oil-pump vacuum leaving a yellow solid
material. Washing the residue twice with 5 mL portions of chlo-
roform gave the title complex in analytical pure form. Yield: 270 mg
(0.184 mmol, 91% based on 1).
Complex 5c was synthesized in an analogous manner as
described for 4a. In this respect, 138 mg (0.409 mmol) of 1 and
248 mg (1.226 mmol, 0.31 mL) of 3b in 20 mL of tetrahydrofuran
were reacted. After appropriate work-up, yellow oily 5c was ob-
tained. Yield: 316 mg (0.375 mmol, 92% based on 1).
C47H90AgFeO2P (843.81) calc. C, 59.80, H, 9.61; found C, 60.03, H,
9.43%. IR (KBr) [cmꢀ1
]
nCO(as) 1568 (vs), nCO(s) 1341 (s). 1H NMR
3
(CDCl3)
d
0.86 (t, JHH ¼ 6.8 Hz, 27 H, CH3/nBu), 1.2e1.6 (m, 54 H,
C74H66Ag2Fe2O4P4 (1470.59) calc. C, 60.43, H, 4.52; found C,
CH2/nBu), 4.1e4.2 (m, 2 H, C5H4), 4.13 (s, 5 H, C5H5), 4.7e4.8 (m, 2 H,
59.99, H, 4.60%. Mp. 210 ꢁC (decomp.). IR (KBr) [cmꢀ1]: nCO(as) 1543
C5H4). 13C{1H} NMR (CDCl3)
d
13.8 (CH3/nBu), 24.5 (d, JCP ¼ 13.0 Hz,
(vs), nCO(s) 1460 (s). 1H NMR (CD2Cl2)
d
2.82 (s, 8 H, CH2/dppe), 3.83
3
CH2/nBu), 25.7 (d, JCP ¼ 7.7 Hz, CH2/nBu), 27.7 (d, JCP ¼ 6.7 Hz,
(s, 10 H, C5H5), 4.19 (pt, JHH ¼ 1.8 Hz, 4 H, C5H4), 4.71 (pt,
CH2/nBu), 68.9 (CH/C5H4), 69.1 (C5H5), 70.3 (CH/C5H4), 80.7 (iC/
3JHH ¼ 1.8 Hz, 4 H, C5H4), 7.2e7.4 (m, 24 H, C6H5), 7.6e7.7 (m, 16 H,
C5H4), 175.0 (CO2). 31P{1H} NMR (CDCl3)
d
ꢀ13.6.
C6H5). 13C{1H} NMR (CD2Cl2)
d 69.7 (C5H5), 69.8 (CH/C5H4), 71.3
i
(CH/C5H4), 129.6 (CH/C6H5), 130.9 (CH/C6H5), 134.0 (CH/C6H5), C/
i
C5H4, C/C6H5); the signals for CO2 and CH2 could not be detected
4.9. Synthesis of [AgO2CFc(P(OMe)3)] (6a)
unequivocally. 31P{1H} NMR (CD2Cl2)
d 5.3 (pt). ESI MS [m/z]:
[Mþ ꢀ 2 FcCO2 ꢀ Ag] 905.
Complex 6a was synthesized analogously as described for 4a. In
this respect, 234 mg (0.694 mmol) of 1 and 86 mg (0.694 mmol,
0.08 mL) of 3c in 20 mL of tetrahydrofuran were reacted. After
appropriate work-up, complex 6a could be isolated as orange oil in
a yield of 296 mg (0.642 mmol, 93% based on 1.
4.13. Crystallography. Crystal data for 4b and 8. 4b
C47H39AgFeO2P2, Mr
¼ 0.71073 A, a ¼ 9.8684(10), b ¼ 11.2491(11), c ¼ 19.191(2) A,
¼
861.44
g
molꢀ1
,
triclinic, P1,
ꢀ
ꢀ
l
3
ꢀ
ꢁ
C14H18AgFeO5P (460.96) calc. C, 36.48, H, 3.94; found C, 36.62, H,
a
¼ 73.295(2),
b
¼ 83.865(2),
g
¼ 72.357(2) , V ¼ 1944.1(3) A ,
4.45%. IR (KBr) [cmꢀ1
]
nCO(as) 1553 (vs). 1H NMR (CDCl3)
d
3.66 (d,
Z ¼ 2, rcalcd ¼ 1.472 g cmꢀ3
,
m
¼ 1.472 mmꢀ1, T ¼ 298(2) K,
Q
JPH ¼ 13.1 Hz, 9 H, CH3), 4.16 (s, 5 H, C5H5), 4.23 (pt, 3JHH ¼ 1.7 Hz,
range ¼ 1.97e27.10ꢁ, reflections collected: 22,241, independent:
2 H, C5H4), 4.73 (pt, 3JHH ¼ 1.7 Hz, 2 H, C5H4). 13C{1H} NMR (CDCl3)
8539 (Rint ¼ 0.0741), R1 ¼ 0.0684, wR2 ¼ 0.1855 [I > 2
s
(I)]. 8:
triclinic,
¼ 0.71073 A, a ¼ 11.3939(10), b ¼ 13.3777(12), c ¼ 14.1922(13)
d
51.5 (d, 2JCP ¼ 4.8 Hz, CH3), 69.4 (C5H5), 70.0 (CH/C5H4), 70.5 (CH/
C78H74Ag2Cl8Fe2O4P4, Mr
¼
1810.29
g
molꢀ1
,
,
i
ꢀ
C5H4), 177.9 (CO2); the resonance signal for C/C5H4 could not be
l
3
ꢀ
detected under the measurement conditions applied. 31P{1H} NMR
A,
a
¼ 74.392(1),
b
¼ 69.374(1),
g
¼ 74.451(1) , V ¼ 1913.5(3) A ,
ꢁ
ꢀ
(CDCl3)
d
131.3. ESI-MS [m/z (rel. intens.)]: [Mþ ꢀ FcCO2 þ H] 233
Z ¼ 1, rcalcd ¼ 1.571 g cmꢀ3
,
m
¼ 1.288 mmꢀ1, T ¼ 183(2) K,
Q
(62), [Mþ ꢀ P(OMe)3 þ H þ K] 377 (100).
range ¼ 1.56e26.37ꢁ, reflections collected: 21,861, independent:

66
J. Kühnert et al. / Journal of Organometallic Chemistry 725 (2013) 60e67
(k) M. Colombari, B. Baltarin, I. Carpani, L. Guadagnini, A. Mignani, E. Scavetta,
D. Tonelli, Electroanalysis 19 (2007) 2321;
7813 (Rint ¼ 0.0376), R1 ¼ 0.0370, wR2 ¼ 0.0937 [I > 2
s(I)]. Data
were collected with a Bruker Smart CCD diffractometer. Both
structures were solved by direct methods and refined by full-
matrix least-squares methods on F2 with the SHELXTL-97
program package [19]
(l) P. Wipawakaru, H. Ju, D.K.Y. Wong, Anal. Bioanal. Chem. 402 (2012) 2817;
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Crystallographic data of 4b and 8 as CIF files are available free of
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of 4b and 8 are also available from the Cambridge Crystallographic
Database as file no. CCDC 901847 and CCDC 901846.
Acknowledgment
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