Synthesis and characterisation of ferrocenyl-phosphonic and -arsonic acids

Article abstract of DOI:10.1016/S0022-328X(01)00908-1

The ferrocene-derived acids FcCH₂CH₂E(O)(OH)₂ [4, E=P; 10, E=As; Fc=Fe(η⁵-C₅H₅)(η⁵-C₅H₄)] have been synthesized by the reaction of FcCH₂CH_2<

Full text of DOI:10.1016/S0022-328X(01)00908-1

Journal of Organometallic Chemistry 637–639 (2001) 216–229
www.elsevier.com/locate/jorganchem
Synthesis and characterisation of ferrocenyl-phosphonic and
-arsonic acids
Steven R. Alley, William Henderson *
Department of Chemistry, Uni6ersity of Waikato, Pri6ate Bag 3105, Hamilton, New Zealand
Received 28 December 2000; received in revised form 15 March 2001; accepted 26 March 2001
Abstract
The ferrocene-derived acids FcCH2CH2E(O)(OH)2 [4, E=P; 10, E=As; Fc=Fe(h5-C5H5)(h5-C5H4)] have been synthesized by
the reaction of FcCH2CH2Br with either P(OEt)3 followed by hydrolysis, or with sodium arsenite followed by acidification.
Reaction of FcCH2OH with (EtO)2P(O)Na gave FcP(O)(OEt)(OH), which was converted to FcCH2P(O)(OH)2 (3) by silyl ester
hydrolysis using Me3SiBr–Et3N followed by aqueous work-up. Similarly, the known phosphonic acid FcP(O)(OH)2 and the new
derivatives 1,1%-Fc%[P(O)(OH)2]2 [Fc%=Fe(h5-C5H4)2] and 1,1%-Fc%[CH2P(O)(OH)2]2 (7) have been synthesized via their correspond-
ing esters. X-ray crystal structure determinations have been carried out on 3 and 7, and the hydrogen-bonding networks discussed.
Electrospray mass spectrometry has been employed in the characterization of the various acids. Phosphonic acids give the
expected [M–H]− ions and their fragmentation at elevated cone voltages has been found to be dependent on the acid.
FcP(O)(OH)2 fragments to [C5H4PO2H]−, but in contrast Fc(CH2)nP(O)(OH)2 (n=1, 2) give Fe{h5-C5H4(CH2)nP(O)O2]− ions,
which are proposed to have an intramolecular interaction between the Fe atom and the phosphonate group. In contrast, arsonic
acid (10), together with PhAs(O)(OH)2 for comparison, undergo facile alkylation (in methanol or ethanol solvent), and at elevated
cone voltages (e.g. \60 V) undergo carbon–arsenic bond cleavage giving [CpFeAs(O)(OR)O]− (R=H, Me, Et) and ultimately
[AsO2]− ions. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Ferrocene; Phosphonic acid; Arsonic acid; Crystal structures; Electrospray mass spectrometry
mately incorporate these redox-active molecules into
metal phosphonate materials. In this field, there has
been recent interest in phosphonic acids and phospho-
nates derived from the arene chromium tricarbonyl
moiety, where the carbonyl ligands provide a conve-
nient infrared spectroscopic handle for materials char-
acterization [7,8]. Since its discovery, there has been
intense interest in the chemistry of ferrocene and its
derivatives [9], however, in the area of organophospho-
rus derivatives, most work has focused on ferrocenyl–
phosphines as ligands [9,10]. Reports of phosphonic
acid derivatives of ferrocene are, surprisingly, extremely
rare. The phosphonic acid FcP(O)(OH)2 has been re-
ported in patent literature as an ingredient in explosives
[11] while the monoester FcCH2P(O)(OMe)(OH) has
been known for some time [12]. 6-Ferrocenylhexylphos-
phonic acid, Fc(CH2)6P(O)(OH)2, has been synthesized
by Me3SiBr-mediated hydrolysis of Fc(CH2)6-
P(O)(OEt)2 [13]. Synthesis of the phosphinic acid,
FcCH2P(O)(OH)(CH2OH) [14] and the phosphate salt,
1. Introduction
Phosphonic and arsonic acids are diprotic acids with
the general formula RE(O)(OH)2 (E=P, As; R=alkyl,
aryl). There has been recent intense interest in the
chemistry of phosphonic acids, particularly for the self-
assembly of their metal salts into two- and three-dimen-
sional structures, since the resulting phosphonate
materials have chemical properties which are highly
dependent on the nature of the organic moiety (R) on
the phosphonic acid [1]. Phosphonic acids containing
photo-active [2], acidic [3], basic [4], ion-selective [5]
and chiral [6] R groups have been prepared for incorpo-
ration into metal phosphonate materials.
The aim of this work was to synthesize phosphonic
acids derived from the ferrocene moiety, and to ulti-
* Corresponding author. Tel.: +64-7-838-4656; fax: +64-7-838-
4219.
E-mail address: w.henderson@waikato.ac.nz (W. Henderson).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00908-1

S.R. Alley, W. Henderson / Journal of Organometallic Chemistry 637–639 (2001) 216–229
217
Scheme 1.
FcCH2CH2OPO3Na2 [15] have recently been reported.
Arsonic acids, while weaker acids than phosphonic
acids, also form salts with metals [16] and have been
used widely as analytical reagents for certain metal ions
[17] though their structural chemistry has been studied
less widely [16]. Ferrocene–phosphonic (and arsonic)
acids have application in the fabrication of functional-
ized (electroactive) monolayers on metal and oxide
surfaces [13,18].
of phosphonate esters is a common technique for the
preparation of acid-sensitive phosphonic acids [8,13,24].
Acidification of the NaHCO3 solution resulted in the
precipitation of FcCH2P(O)(OH)2 (3) in high (91%)
yield (Scheme 1). The acid is a yellow crystalline mate-
rial, sparingly soluble in water and most organic sol-
vents, though appreciably soluble in lower alcohols and
Me2SO. The yellow colour of the solid slowly fades to
pale green upon prolonged exposure (several months)
to air at room temperature, characteristic of the fer-
ricinium ion formed as a result of the compound cata-
lyzing its own oxidation.
2. Results and discussion
2.1. Synthesis and spectroscopic characterisation of
ferrocenylphosphonic acids
Synthetic methods for the preparation of phosphonic
acids are well-developed and have been the subject of
several comprehensive reviews [19]. Phosphonic acids
can be prepared from aryl phosphonate esters by hy-
drogenolysis in the presence of platinum or palladium
catalysts [20]. Hydrogenolysis of the recently synthe-
sized FcCH2P(O)(OPh)2 [21] with H2–PtO2 led to the
isolation of the monoester FcCH2P(O)(OPh)OH (1),
rather than the desired phosphonic acid. We therefore
turned to the hydrolysis of alkyl esters, which has been
widely used in the synthesis of phosphonic acids. The
diethyl ester FcCH2P(O)(OEt)2 has been prepared by
reaction of FcCH2NMe3I with (EtO)2P(O)Na or
P(OEt)3 [22]. We find that the same product is pro-
duced in moderate yield (after chromatographic purifi-
cation) when FcCH2OH reacts with (EtO)2P(O)Na in
refluxing toluene. Using an excess of (EtO)2P(O)Na, the
monoester FcCH2P(O)(OEt)OH (2) was the principal
product. The preparation of monoesters by base hy-
drolysis is well-known [23], and in the present case it
seems likely that the excess (EtO)2P(O)Na is effecting
ester cleavage. Compound 2 is purified easily by extrac-
tion into an aqueous base, followed by acidification.
This compound is stable and conveniently prepared in
good yield (50–65%).
A similar synthetic method was applied to the prepa-
ration of ferrocenylethylphosphonic acid, FcCH2CH2-
P(O)(OH)2 (4) (Scheme 2). FcCH2CH2OH [which was
unreactive towards P(OPh)3 or (EtO)2P(O)Na] was
brominated using PBr3 to give stable FcCH2CH2Br,
which underwent Michaelis–Arbuzov [25] reaction in
refluxing P(OEt)3 to give FcCH2CH2P(O)(OEt)2 in high
yield. Silyl ester mediated hydrolysis of FcCH2-
CH2P(O)(OEt)2 proceeded smoothly to give the acid
FcCH2CH2P(O)(OH)2 (4) as a yellow powder in high
yield. The acid 4 is air stable, and is soluble in polar
solvents such as lower alcohols and Me2SO.
Three further ferrocenylphosphonic acids have been
prepared, the previously reported FcP(O)(OH)2 (5) [11]
and the novel 1,1%-ferrocenylbis(phosphonic acids), 1,1%-
Fc%[P(O)(OH)2]2 (6) and 1,1%-Fc%[CH2P(O)(OH)2]2 (7).
The acids 5 and 6 are related synthetically, both being
derived from reaction of lithiated ferrocene (FcLi or
Fc%Li2 for 5 and 6, respectively) with (EtO)2P(O)Cl
(Scheme 3). Reactions of lithiated ferrocenes with com-
pounds containing P–Cl bonds are well-established in
the synthesis of ferrocenyl–phosphorus compounds,
and the reaction of Fc%Li2 with (EtO)2PCl has been
reported in the literature [26]. The products in the
present case are the ferrocenylphosphonates FcP(O)-
The ferrocene moiety is prone to acid-catalysed oxi-
dation, so acidic hydrolysis of 2 was not undertaken.
Instead, 2 was silylated with Me3SiBr–Et3N, followed
by hydrolysis of the resulting silyl ester with 10%
NaHCO3 solution. Such silyl ester-mediated hydrolysis

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S.R. Alley, W. Henderson / Journal of Organometallic Chemistry 637–639 (2001) 216–229
Scheme 2.
Scheme 3.
(OEt)2 and 1,1%-Fc%[P(O)(OEt)2]2, which were purified
by flash column chromatography. Silyl ester-mediated
hydrolysis was complicated by the solubility of the
resulting acids 5 and 6 in water. Hydrolysis was there-
P(O)(OH)2 (3). Spectra recorded in alkaline D2O give
an upfield shift of ca. 5 ppm compared to spectra for
the free acids.
fore effected by
a
small excess of water in
2.2. Synthesis of diphenyl ferrocenylphosphonate esters
dichloromethane, rather than by
a
solution of
NaHCO3. FcP(O)(OH)2 is an air-stable, yellow crys-
talline compound, while 6 is also yellow, but the colour
fades with time. Both 5 and 6 are soluble in water and
polar organic solvents.
As part of this work, we have also synthesized and
characterized the phenyl ferrocenylphosphonate esters
FcP(O)(OPh)2 (8) and 1,1%-Fc%[P(O)(OPh)2]2 (9). The
reaction of (PhO)2P(O)Cl with FcLi and 1,1%-Fc%Li2
gave 8 and 9, respectively, in high yields. The crude
products were brown oils, easily purified by silica
column chromatography, using ethyl acetate as the
eluting solvent. The pure phenyl esters 8 and 9 are
orange crystalline solids, unlike the analogous ethyl
esters, which are brown oils. They are also appreciably
more stable than the analogous ethyl esters, which
discolour rapidly in air at room temperature. It was
found during the synthesis of 8 that the order of
addition of the FcLi and (PhO)2P(O)Cl had some bear-
ing on the outcome of the reaction. If FcLi is added to
a solution of (PhO)2P(O)Cl the reaction proceeded as
expected. However, the reverse order of addition led to
The synthesis of phosphonic acid 7 was accomplished
using similar chemistry. Reaction of 1,1%-dilithiofer-
rocene with paraformaldehyde gave the diol 1,1%-
Fc%(CH2OH)2 which was chlorinated with PCl3 in a
known procedure [27] to give the reactive dichloride
1,1%-Fc%(CH2Cl)2. This was reacted, without purifica-
tion, with excess refluxing P(OEt)3 to give 1,1%-
Fc%[CH2P(O)(OEt)2]2, which after silyl ester hydrolysis
gave 7 as a bright yellow powder which turns green
over a period of weeks in air, and is soluble in water
and polar organic solvents.
The phosphonic acids give single resonances in their
31P–{1H}-NMR spectra, e.g. at l 23.1 for FcCH2-

S.R. Alley, W. Henderson / Journal of Organometallic Chemistry 637–639 (2001) 216–229
219
Fig. 1. Molecular structure and atom numbering scheme of FcCH2P(O)(OH)2 (3); non-hydrogen atom ellipsoids are shown at the 50% probability
level.
Fig. 2. Molecular structure and atom numbering scheme of 1,1%-Fc%[CH2P(O)(OH)2]2 (7); non-hydrogen atom ellipsoids are shown at the 50%
probability level.
two products (in ca. 1:1 ratio by 31P-NMR) which were
isolated by chromatography and identified as the ex-
pected phenyl ester FcP(O)(OPh)2 (8) and a second
product characterized by 31P-NMR (l 31P 42.6) and
electrospray ionisation mass spectrometry [M+, m/z
510 (100%), MNa+, m/z 533 (76%)] as the phosphinate
ester Fc2P(O)(OPh).
numbering schemes. Selected bond lengths and angles
are given in Tables 1 and 2, respectively. Of particular
interest in both structures are the hydrogen-bonding
networks formed between the acid hydroxyl groups and
the hydrogen bond accepting PꢀO group.
The structure of 3 shows no exceptional bond lengths
or angles. The cyclopentadienyl rings of the ferrocenyl
group are eclipsed and the C(1)–C(11) bond lies in the
plane of the cyclopentadienyl rings, as seen in structures
of other Fc–CH2–P systems [14,21]. There is no inter-
action of the phosphonic acid group with the iron
atom. Indeed the phosphonic acid is heavily involved in
the anticipated hydrogen bonding interactions with ad-
jacent phosphonic acid groups. The compound crystal-
lizes with eight molecules in the unit cell and forms
two-dimensional ferrocenyl bi-layers in the crystallo-
graphic ab plane. Hydrogen bonding between phospho-
nic acid groups on the surface of these layers serves to
hold the structure together. Individual hydrogen bond-
ing interactions are shown in Fig. 3, while the overall
lattice is depicted in Fig. 4. Each phosphonic acid
2.3. X-ray crystal structure determinations of
FcCH2P(O)(OH)2 (3) and 1,1%-Fc%[CH2P(O)(OH)2]2 (7)
To fully characterize the acids 3 and 7, and compare
the differences in the structure of mono- and bis-substi-
tuted ferrocenylphosphonic acids, single crystal X-ray
diffraction analyses were carried out on both com-
pounds. There has been considerable interest recently in
structural features of metallocene-derived carboxylic
acids [28], and the structures of 3 and 7 are the first of
the ferrocenylphosphonic acids.
The molecular structures of 3 and 7 are shown in
Figs. 1 and 2, respectively, together with the atom

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S.R. Alley, W. Henderson / Journal of Organometallic Chemistry 637–639 (2001) 216–229
group bonds to the PꢀO oxygen of an adjacent phos-
phonic acid residue in the same plane along the b-
axis via an O(3)–H(3)···O(1%) bond. The second
hydroxyl group hydrogen bonds to a phosphonic acid
residue in an adjacent plane with the formation of an
O(2)–H(2)···O(1¦) bond. This second hydrogen bond
bridges the bi-layers and results in the formation of
eight-membered P–O–H rings (Fig. 3). Such rings are
a common feature of organophosphorus acid struc-
tures [29] and the chain of hydrogen-bonded eight-
membered rings is reminiscent of that observed
Table 1
Selected bond lengths a (A) and bond angles (°) for 3
,
Bond lengths
CpFe–C av
Range
CpC–C av
Range
C(1)–C(11)
C(1)–P(1)
P(1)–O(1)
2.054(16)
2.045–2.064
1.43(1)
1.422–1.432
1.514(2)
P(1)–O(2)
P(1)–O(3)
O(2)–H(2)
O(3)–H(3)
O(1)···H(2%)
O(1)···H(3%)
1.566(1)
1.568(1)
0.775(1)
0.783(1)
1.819(1)
1.829(1)
Fig. 3. Hydrogen bonding interactions involving 3, showing the
formation of eight-membered HO–PꢀO···HO–PꢀO rings.
1.805(1)
1.513(1)
Bond angles
C(11)–C(15)
range
C(21)–C(25)
range
C(15)–C(11)–C(1)
C(12)–C(11)–C(1)
C(11)–C(1)–P(1)
O(1)–P(1)–C(1)
O(2)–P(1)–C(1)
O(3)–P(1)–C(1)
previously in the structure of an aza-crown ether
functionalised phosphonic acid derivative [4c]. The
PꢀO group of each molecule of 3 accepts two hydro-
gen bonds, one from a neighbour in the same plane,
and the second from an adjacent plane (Fig. 3).
The two C5H4CH2P(O)(OH)2 units of 7 adopt an
anti orientation about the central iron atom. The iron
sits at a centre of symmetry and the asymmetric unit
contains only half of the molecule. As in the structure
of 3 the C(1)–C(11) bond lies in the plane of the
cyclopentadienyl ring and there is no indication of
any interaction between the iron atom and phospho-
nic acid groups.
The macrostructure of 7 can be described as infi-
nite chains of hydrogen bonded bisphosphonic acid
molecules. These chains run almost at right angles to
each other in the structure and are cross-linked by
further hydrogen bonding interactions, as shown in
Fig. 5. A similar infinite chain motif is found in the
crystal structures of the bisphosphonic acid series
(HO)2P(O)–(CH2)n–P(O)(OH)2 (n=1, [30] 2 [31] and
3 [32]). The structures adopted by these aliphatic bis-
phosphonic acids in the solid state are those which
maximise the hydrogen bonding interactions. Each
phosphonic acid group in the crystal of 7 is involved
in four hydrogen bonds, giving a total of eight hydro-
gen bonding interactions for each molecule. The PꢀO
bonds accept two hydrogen bonds, one from a neigh-
bour in the same chain, the second from a phospho-
nic acid in a neighbouring chain. Similarly, each
phosphonic acid group forms two donor hydrogen
bonds through the two OH groups.
107.57(12)
–108.54(12)
107.6(2)
O(1)–P(1)–O(2)
O(1)–P(1)–O(3)
113.28(6)
108.86(6)
–108.2(2)
126.97(12) O(2)–P(1)–O(3)
125.44(12) P(1)–O(2)–H(2)
112.18(9) P(1)–O(3)–H(3)
112.06(6) O(2)–H(2)–-O(1%) 175.92(7)
105.95(6) O(3)–H(3)--O(1%) 166.87(7)
108.25(7)
108.26(7)
119.05(7)
117.39(7)
a Non-bonded O···O distances: O(1)···O(2a) 2.5932, O(1)···O(3b)
,
2.5982 A.
Table 2
Selected bond lengths a (A) and bond angles (°) for 7
,
Bond lengths
CpFe–C av
Range
CpC–C av
Range
C(1)–C(11)
P(1)–C(1)
P(1)–O(1)
2.039(2)
2.037–2.042
1.420(3)
1.413–1.427
1.498(2)
1.785(2)
P(1)–O(3)
P(1)–O(2)
O(2)–H(2)
O(3)–H(3)
O(1)···H(2%)
O(1)···H(3%)
1.548(2)
1.551(1)
0.745(10)
0.661(10)
1.832(10)
1.923(10)
1.502(1)
Bond angles
C(11)–C(15)
Range
C(15)–C(11)–C(1) 126.4(2)
C(12)–C(11)–C(1) 126.2(2)
C(11)–C(1)–P(1)
C(1)–P(1)–O(2)
C(1)–P(1)–O(3)
C(1)–P(1)–O(1)
O(2)–P(1)–O(3)
108.37(8)
113.33(7)
108.98(8)
119.5(2)
116.6(2)
107.43–108.37 O(2)–P(1)–O(1)
O(3)–P(1)–O(1)
P(1)–O(2)–H(2)
P(1)–O(3)–H(3)
O(2)–H(2)···O(1%) 175.1(2)
O(3)–H(3)···O(1%) 164.5(2)
112.68(12)
106.14(9)
108.06(9)
111.77(7)
a Non-bonded O···O distances: O(1)···O(2a) (in chain) 2.5745;
O(1)···O(3b) (cross chain) 2.5662 A.
,

S.R. Alley, W. Henderson / Journal of Organometallic Chemistry 637–639 (2001) 216–229
221
FcCH2As(O)(OH)2. Instead only starting material and
FcCH2OH were obtained on work-up. Sodium arsenite
solution is strongly basic, and presumably effects hy-
drolysis of FcCH2NMe3+ and the reactive chloride
FcCH2Cl to FcCH2OH [35].
The reaction of FcCH2CH2Br with sodium arsenite
was more successful, with the arsonic acid
FcCH2CH2As(O)(OH)2 being isolated in a fair yield as
an air-stable yellow powder on acidification. The acid
did not decompose in air over time [though neither did
the phosphonic acid analogue FcCH2CH2P(O)(OH)2],
and unlike the phosphonic acids which decomposed on
melting, the arsonic acid had a clearly defined melting
point and did not decompose.
2.5. Electrospray ionization mass spectrometry (ESMS)
study of ferrocene-deri6ed phosphonic and arsonic acids
2.5.1. Phosphonic acids
ESMS is a versatile technique for the characterisation
of involatile and thermally sensitive compounds, and
there have been several studies applying the technique
to ferrocene-derived compounds [36]. Ferrocene and
some derivatives can be oxidised to the ferricinium ion
under electrospray conditions [37], while other deriva-
tives bearing protonatable groups show a variable
amount of protonation [21]. Phosphonic acids readily
deprotonate under ESMS conditions [38], and as ex-
pected, the negative ion ES spectra of the ferro-
cenylphosphonic acids 3, 4 and 5 were dominated at
low cone voltages by the [M–H]− ions.
Of interest are the differing fragmentation pathways
at elevated cone voltages. For FcP(O)(OH)2 (5) a peak
at m/z 128 appeared, assigned to the ion [C5H4PO2H]−
ion (formally formed by loss of neutral C5H5FeOH),
which is also observed in the negative ion spectrum of
6 at high cone voltages. No other fragmentation of 5 is
observed at cone voltages up to 180 V. Fig. 6(c) shows
the spectrum of 5 at a cone voltage of 100 V. The ES
spectra for 3 and 4 give a single major fragment ion at
high cone voltages (e.g. 100 V, Fig. 6(a,b)), at m/z 213
and 227, respectively, corresponding to loss of C5H6
from the pseudo-parent [M–H]− ion. The resulting
ions [Fe{h5-C5H4(CH2)nPO3}]− (n=1 or 2) (alterna-
tively written as [M–H–C5H6]−) might be stabilized by
interaction between the phosphonate group and the
exposed iron atom, structures 11 and 12. Evidence for
this comes from the far greater relative intensity of the
Fig. 4. The hydrogen bonded lattice of 3, showing ferrocene bi-layers
held together by hydrogen bonding.
2.4. Synthesis of the ferrocene-deri6ed arsonic acid
FcCH2CH2As(O)(OH)2 (10)
The Meyer reaction [33] has been used widely for the
synthesis of aliphatic arsonic acids, and involves the
reaction of sodium arsenite (Na3AsO3) with alkyl
halides, followed by acidification, whereupon the acid
separates out [34]. However, reactions of the ferrocenyl-
methylating agents FcCH2NMe3I or FcCH2OH with
sodium arsenite in refluxing aqueous solution, or
FcCH2Cl and sodium arsenite in water–dichloro-
methane at reflux did not produce the arsonic acid

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Fig. 5. The hydrogen bonding network in the structure of 7.
Fig. 6. Negative ion electrospray mass spectra of (a) 3, (b) 4, and (c) 5 at a cone voltage of 100 V, showing the relative intensities of the
[M–H–C5H6]− ions for 3 and 4 (see structures 11 and 12) and the formation of the [C5H4PO2H]− ion for 5.
[M–H–C5H6]− ion in the spectra of 4 when compared
to 3, as illustrated in Fig. 6 at a cone voltage of 100 V.
The extra CH2 spacer in 4 would enable the phospho-
nate to interact more easily with the iron; the analogous
ion is not observed in the spectra of 5. A similar,
though positively-charged ion, [Fe{h5-C5H4CH2P-
(O)(OPh)2}]+ was observed in high cone voltage spec-
tra of FcCH2P(O)(OPh)2, and is thought to be stabi-
lized by interaction of the PꢀO group with the iron
atom [21].
The ES spectra of the ferrocenylbis(phosphonic acid)
6 are dominated by the [M–H]− (m/z 345) and [M–
2H]2− (m/z 172) ions. At higher cone voltages, ions at
m/z 327 and 128 are observed; the former is formed by
loss of H2O from [M–H]− (possibly giving a cyclic
P–O–P anhydride) and the latter corresponds to the
[C5H4PO2H]− ion. Spectra for 7 are also dominated by
the [M–H]− ion (m/z 373) at low cone voltages, how-
ever the [M–2H]2− ion (m/z 186) was not observed. At
higher cone voltages (\120 V) a more complex frag-
mentation pattern emerges, though still dominated by
[M–H]−.
The monoesters 1 and 2 also gave strong [M–H]−
ions and weaker [2M–H]− ions at low cone voltages,
with pyridine added to aid ionization. At higher cone
voltages (\60 V), fragmentation occurs, with ions
[M–H–PhOH]− (m/z 261) and [M–H–PhH]− (m/z
277) observed for 1. Positive ion ES spectra of the
diester 8 gave both [M]+ and [M+H]+ ions (m/z 418
and 419, respectively), with the latter increasing in
intensity at higher cone voltages. At cone voltages
greater than 60 V the [M–C5H5]+ ion appeared and

S.R. Alley, W. Henderson / Journal of Organometallic Chemistry 637–639 (2001) 216–229
223
increased in intensity as the cone voltage was increased,
similar to the behaviour reported for FcCH2P(O)(OPh)2
[21]. Positive ion ES spectra of the bis(phosphonate
ester) (9) were dominated by the [2M+Li]+ (m/z 1307)
and [2M+Na]+ (m/z 1323) ions, even when no Li+ or
Na+ ions were added, showing the strong, but not
unexpected, propensity of this compound to coordinate
metal ions [38,39]. The [M]+ (m/z 650), [M+H]+ (m/z
651), [M+Li]+ (m/z 657) and [M+Na]+ (m/z 673)
ions were also observed. Phosphonate 9 may prove to
have an interesting coordination chemistry, given recent
interest in this field, such as the ability of [Fe{h5-
C5H4P(O)Ph2}2] to stabilize an unusual tetrahedral co-
ordination geometry for palladium(II) [40].
the parent acids. Esterification of arsenic acids is
known to be a facile process in alcoholic solutions [46].
Prompted by the lack of negative-ion ES studies of
organo-arsenic acids (especially arsonic acids), a brief
study of phenylarsonic acid was undertaken, using
methanol or ethanol as the solvent, with pyridine added
to aid ionisation. PhAs(O)(OH)2 methylated very read-
ily, such that at 20 V the only ion observed was
[PhAs(O)(OMe)O]− (m/z 215). Increasing the cone
voltage yielded [M–H]− (m/z 201), [M–OH]− (m/z
185), [AsO2+MeOH]− (m/z 139) and [AsO2]− (m/z
107), the latter being the base peak at cone voltages
greater than 60 V. Spectra in ethanol paralleled the
methanol spectra, confirming assignments.
2.5.2. FcCH2CH2As(O)(OH)2
The negative-ion ES spectrum of 10 at 20 V in
methanol with added pyridine resulted in observation
of the expected [M–H]− ion (m/z 337), together with
the [M–2H+Me]− ion, i.e. [FcCH2CH2As(O)-
(OMe)O]− at m/z 351, due to methylation by the
solvent. This behaviour is markedly different to that of
the analogous phosphonic acid 4, which showed no
methylation. When ethanol is used as the solvent, the
analogous [FcCH2CH2As(O)(OEt)O]− ion (m/z 365)
was observed. At elevated cone voltages, the spectra are
more complex; at 60 V for the methanol system the
base peak is [CpFeAsO2(OMe)]− (m/z 259) while sig-
nificant intensity ions [AsO2]− (m/z 107) [41] and
[AsO2+MeOH]− (m/z 139) are also observed. At very
low intensity, ions [M–H]− (m/z 337) and
[CpFeAsO2(OH)]− (m/z 245) are also observed. The
ions at m/z 245 and 259 are of interest, since they
require cleavage of the As–C bond; an analogous pro-
cess was not observed for the phosphonic acid analogue
4. At 100 V, the [AsO2]− ion was the sole ion observed;
as shown by studies described later in this section, this
behaviour appears typical of other arsonic acids.
Studies of the positive-ion ES behaviour of
organoarsenic acids tend to dominate the published
literature [41–43] which is rather surprising, given the
acidic nature of such compounds and the equal ability
of ES spectrometers to operate in positive or negative
ion modes. The acids however have been found to form
[M+X]+ (X=H, Na and K) ions under ES conditions
[41,42] and positive ion mode has been used in the
development of analytical techniques [43,44]. The use of
methanolic solvents is commonplace in the reported
studies, and methanol is added specifically to increase
sensitivity in one study [45]. The positive ion ES be-
haviour of six organoarsenic acids in a methanol–water
solvent system in the presence of acetic acid has been
studied [42]. In all cases, the protonated molecule was
the most intense ion, however, all spectra contained
weak ions due to the respective [M+H–H2O+
MeOH]+ ions, corresponding to monomethylation of
3. Experimental
3.1. Materials and methods
All solvents used were LR grade or better, and
(except for ethyl acetate) were distilled under a nitrogen
atmosphere from the appropriate drying agent prior to
use: THF and diethyl ether (sodium–benzophenone
ketyl), dichloromethane and petroleum spirits, boiling
range 60–80 °C (CaH2), toluene (sodium metal). Reac-
tions were carried out in air unless otherwise stated.
Platinum dioxide (BDH), sodium metal (BDH), n-
butyl lithium, 1.6 M in hexanes (Aldrich), t-butyl
lithium, 1.7 M in pentane (Aldrich), tetramethyl-
ethylenediamine (tmeda) (BDH), diethylphosphite
(Aldrich), triethylphosphite (BDH), PCl3 (Aldrich),
As2O3 (BDH), TMEDA (BDH), phenylarsonic acid
(BDH) and ferrocene (Strem) were used as supplied.
The compounds FcCH2P(O)(OPh)2 [21], FcCH2OH
[47], FcCH2CH2Br [48], FcLi [49], 1,1%-Fc%Li2 [50],
Me3SiBr [51], (PhO)2P(O)H [52], (RO)2P(O)Cl (R=Et,
Ph) [53] and FcCH2Cl [54] were prepared according to
literature procedures, or minor variations thereof. 1,1%-
Fc%(CH2OH)2 was prepared by reaction of 1,1%-Fc%Li2
with (CH2O)n, followed by aqueous work-up.
Melting points were measured using a Reichert Ther-
mopan melting point microscope and are uncorrected.
IR spectra were recorded using a Bio-Rad FTS-40
spectrometer. Samples of the phosphonic acids were
run as KBr disks, while samples of the esters, and the
arsonic acid were run in CH2Cl2 solution. ESMS were
obtained with a VG Platform II mass spectrometer.
Samples were dissolved in an appropriate solvent and
introduced into the spectrometer via a 10 ml sample
loop using a Thermo Separation Products SpectaSys-
tem P1000 LC pump at a flow rate of 0.01 ml min−1
.
Cone voltages were typically varied from 20 to 120 V to
maximise spectral quality. To aid ionisation, pyridine
was added to acidic samples. A Bruker AC300P spec-
trometer operating at 121.51 MHz was used to acquire

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S.R. Alley, W. Henderson / Journal of Organometallic Chemistry 637–639 (2001) 216–229
(s, br), 2926 (w), 1204 (s), 1105, (m), 1071 (w), 1039 (w),
1025 (w), 1000 (w), 985 (w), 923 (m).
3.3. Synthesis of FcCH2P(O)(OEt)(OH) (2)
(EtO)2P(O)Na was prepared by refluxing a mixture
of diethyl phosphite (6.97 ml, 0.054 mol) and sodium
metal (1.24 g, 0.054 mol) in dry toluene (80 ml) under
a nitrogen atmosphere until no trace of the metal was
observed (1–2 h). To the hot solution was added
FcCH2OH (5.85 g, 0.027 mol) in ꢀ1 g portions and
reflux continued for three hours. The reaction solution
was cooled and 60 ml of 10% NaHCO3 solution added.
The resulting two-phase system was stirred for 10 min
before the layers were separated.
Scheme 4. Atom labeling used in assignment of ferrocenyl NMR
signals; hydrogen atoms are numbered according to the carbon to
which they are bonded.
all 31P-NMR spectra; chemical shifts are relative to an
external reference of 85% orthophosphoric acid (l 0.0).
1
13C- and H-NMR spectra were obtained on a Bruker
AC300P (1H, 300.13 MHz; 13C 75.47 MHz) or a Bruker
DRX400 (1H, 400.17 MHz; 13C, 100.62 MHz) spec-
trometer and referenced to residual solvent lines. Sol-
vents were assigned the following chemical shift values
with respect to external SiMe4: CDCl3, 7.26 (1H), 77.06
(13C); Me2SO-d6, 2.6 (1H), 39.5 (13C); D2O, 3.5 (MeOH,
1H), 49.3 (MeOH, 13C). Acid samples were often dis-
solved in NaOD–D2O solution, prepared by reaction of
a small amount of Na (ꢀ1–3 mg) with excess D2O
(ꢀ2 ml). Two-dimensional NMR experiments were
used to unambiguously assign spectra for compounds 2,
3, 4, 8, and 9. Comparison of these results with other
spectra aided in full assignment of the rest of the
compounds. The atom labelling scheme used for assign-
ment of ferrocenyl NMR signals is given in Scheme 4.
The aqueous layer was washed with Et2O (40 ml),
acidified with concentrated HCl and extracted with
CH2Cl2 (3×30 ml). The combined CH2Cl2 fractions
were dried over MgSO4 and filtered. The solution was
concentrated (to ꢀ10 ml) and acetone added until no
further precipitation occurred. The precipitate was
filtered, washed with cold water (10 ml) followed by
acetone (5 ml), then air-dried to give 5.43 g (65%) of 2
as a microcrystalline yellow powder, m.p. 183 °C (dec).
Anal. Found: C, 50.3; H, 5.6. Calc. for C13H17FeO3P:
C, 50.7; H, 5.6%. 31P–{1H}-NMR (CDCl3): l 29.1.
3
13C–{1H}-NMR (CDCl3): l 16.33 (d, JC,P 6.4 Hz,
1
OCH2CH3), 28.24 (d, JC,P 142 Hz, CH2P), 61.56 (d,
2JC,P 6.9 Hz, OCH2CH3), 67.87 (s, C3), 68.91 (s, C4),
3
1
3.2. Synthesis of FcCH2P(O)(OPh)(OH) (1)
69.47 (d, JC,P 3.1 Hz, C2). H-NMR (CDCl3): l 1.24
(3H, t, 3JH,H 7.0 Hz, OCH2CH3), 2.85 (2H, d, 2JH,P 19.9
Hz, CH2P), 3.93 (2H, m, OCH2CH3), 4.09, (2H, d,
3JH,H 1.6 Hz, H3), 4.11 (5H, s, H4), 4.23 (2H, br s, H2),
6.7 (1H, br s, POH). ESMS: (MeCN–H2O, cone
voltage 20 V) m/z 307 ([M–H]−, 100%), 325 ([M–H+
H2O]−, 9%). IR (Solution in CH2Cl2) (cm−1): 3416 (w),
1221 (m), 1204 (s), 1104 (m), 1051 (s), 1024 (s), 966 (m),
806 (m), 609 (w), 493 (m), 475 (m).
To a solution of FcCH2P(O)(OPh)2 (0.55 g, 1.2
mmol), in MeOH (25 ml) was added a catalytic amount
(ca. 5 mg) of PtO2. This solution was placed under a
dihydrogen atmosphere (50 psi) and agitated for 4 days.
The dark green solution was allowed to slowly evapo-
rate resulting in the precipitation of dirty yellow crys-
tals of 1. The crystals were dissolved in CH2Cl2 (10 ml)
and extracted with 10% aqueous NaHCO3 (2×10 ml).
The combined aqueous fractions were washed with
CH2Cl2 (10 ml), acidified with concentrated HCl then
extracted with CH2Cl2 (2×10 ml). The combined or-
ganic fractions were dried over MgSO4 and filtered. The
product was precipitated by addition of petroleum spir-
its, filtered and air-dried to give 21.3 mg (4.6%) of 1 as
a yellow powder, m.p. 160 °C. Anal. Found: C, 57.4;
H, 4.9. Calc. for C17H17FeO3P: C, 57.3; H, 4.8%.
31P–{1H}-NMR (CDCl3): l 26.5. 13C–{1H}-NMR
3.4. Synthesis of FcCH2P(O)(OH)2 (3)
A solution of triethylamine (0.82 g, 8.1 mmol) and 2
(2.5 g, 8.11 mmol) in dry CH2Cl2 (50 ml) was placed
under a nitrogen atmosphere in an oven-dried flask.
Me3SiBr (6.2 g, 40 mmol) was added and the mixture
refluxed gently for 3 h. The reaction mixture was cooled
to room temperature (r.t.), saturated aqueous NaHCO3
solution (50 ml) added and the two-phase system stirred
vigorously for a further 3 h. The layers were separated,
the aqueous phase was washed with CH2Cl2 (2×25 ml)
and acidified with concentrated HCl. The yellow precip-
itate was filtered and washed with water (2×50 ml)
then air-dried to give 2.08 g (91%) of 3, m.p. 222–
228 °C (dec.). Anal. Found: C, 46.5; H, 4.7. Calc. for
C11H13FeO3P: C, 47.2; H, 4.7%. 31P–{1H}-NMR
(Me2SO): l 23.1. 13C–{1H}-NMR (Me2SO): l 29.68 (d,
2
(CDCl3): l 150.18 (d, JC,P 11 Hz, Ph, i-C), 129.62 (s,
Ph, m-C), 124.86 (s, Ph, p-C), 120.76 (s, Ph, o-C), 70.10
1
(s, C2), 69.43 (s, C4), 68.40, (s, C3), 27.67 (d, JC,P 140
1
Hz, CH2P). H-NMR (CDCl3): l 7.24–6.90 (5H, m,
Ph), 4.24 (2H, br s, H3), 4.13 (7H, br s, H2, H4), 2.95
2
(d, JH,P 21 Hz, CH2P). ESMS: (MeOH–H2O, cone
voltage 20V) m/z 355 ([M–H]−, 100%), 325 ([M–H+
MeOH]−, 10%). IR (solution in CH2Cl2) (cm−1): 3053

S.R. Alley, W. Henderson / Journal of Organometallic Chemistry 637–639 (2001) 216–229
225
1JP–C 134 Hz, CH2P), 67.16 (s, C3), 68.66 (s, C4), 69.24
(br s, C2), 80.26 (br s, C1). H-NMR (Me2SO): l 2.65
washed with H2O (2×20 ml) before being dried over
MgSO4, filtered and the solvent removed under vac-
uum. The residue was dissolved in EtOAc (ca. 2 ml)
and purified with alumina flash column chromatogra-
phy, using EtOAc as the eluting solvent. The resulting
red oil [FcP(O)(OEt)2, 0.45 g, 1.4 mmol] was dissolved
in CH2Cl2 (10 ml) and placed under a nitrogen atmo-
sphere. Freshly distilled Me3SiBr (0.64 g, 4.19 mmol)
was added and the solution stirred for 4 h. Solvent and
excess silane were removed under vacuum and replaced
with dry, distilled CH2Cl2 (5 ml). To this was added
H2O (0.10 g, 5.56 mmol). Precipitation of the acid
began within 5 min. After 30 min the product was
filtered and washed with CH2Cl2, then air-dried to give
0.31 g (24%) of 5 as a microcrystalline yellow solid,
m.p. 198–205 °C (dec.). Anal. Found: C, 44.5; H, 4.2.
Calc. for C10H11FeO3P: C, 45.2; H, 4.1%. 31P–{1H}-
NMR (Na salt in D2O): l 15.3. 13C–{1H}-NMR (Na
salt in D2O): l 69.76 (s, C4), 70.55 (d, 3JC,P 9.6 Hz, C3),
71.26 (d, 2JC,P 11.3 Hz, C2), 73.33 (d, 1JC,P 154 Hz, C1).
1H-NMR (Me2SO-d6): l 4.14 (2H, br s, H3), 4.21 (5H,
br s, H4), 4.28 (2H, br s, H2). ESMS: (MeCN–H2O,
cone voltage 40 V) m/z 265 ([M–H]−, 100%). IR (KBr
disc) (cm−1): 2796 (br, m), 1202 (s), 1130 (s), 1106 (m),
1039 (s), 1013 (s), 944 (s), 889 (w), 816 (w), 667 (w), 585
(m), 472 (m), 452 (m).
1
(2H, d, 2JP–H 19 Hz, CH2P), 4.00 (2H, s, H3), 4.07 (5H,
s, H4), 4.15 (2H, s, H2). ESMS: (MeCN–H2O, cone
voltage 60 V) m/z 279 ([M–H]−, 100%). IR (KBr disc)
(cm−1): 2753 (br, s), 1264 (m), 1225 (m), 1103 (s), 992
(s), 947 (s), 925 (m), 832 (m), 814 (m), 610 (w), 542 (w),
498 (m), 436 (m).
3.5. Synthesis of FcCH2CH2P(O)(OH)2 (4)
FcCH2CH2Br (0.85 g, 2.9 mmol) was dissolved in
triethylphosphite (5 ml) and heated to reflux under
nitrogen. After 5 h the solution was cooled and the
excess triethylphosphite removed by distillation (ca. 0.2
mmHg at r.t.). The residue1 was dissolved in CH2Cl2
(10 ml) and placed under a nitrogen atmosphere. Tri-
ethylamine (1.47 g, 14.5 mmol)2 and Me3SiBr (2.22 g,
14.5 mmol) were added and the reaction stirred for 4 h
at r.t. Sodium hydroxide (1 M, 20 ml) was added and
stirring continued for 30 min. The layers were separated
and the aqueous layer washed with CH2Cl2 (2×20 ml),
then acidified with concentrated HCl. The yellow pre-
cipitate was filtered, washed liberally with cold water
and air-dried to give 0.58 g (68%) of 4, m.p. 185–
190 °C (dec.). Anal. Found: C, 49.1; H, 5.3. Calc. for
C12H15FeO3P: C, 49.1; H, 5.1%. 31P–{1H}-NMR
(Me2SO-d6): l 26.6. 13C–{1H}-NMR (Me2SO-d6): l
3.7. Synthesis of 1,1%-Fc%[P(O)(OH)2]2 (6)
2
1
22.54 (d, JC–P 2 Hz CH2CH2P), 28.66 (d, JC–P 101
3
Hz, CH2P), 66.87 (s, C3), 67.33 (s, C2), 89.05 (d, JC–P
Ferrocene (0.93 g, 5 mmol) was dissolved in
16 Hz, C1). H-NMR (Me2SO-d6): l 1.84 (2H, d, JH–P
18 Hz, CH2P), 2.46 (2H, br s, CH2CH2P), 4.03 (2H, br
s, H3), 4.09 (9H, m, H2, H4), 7.22 (1.6H, br s, P–OH).
ESMS: (MeCN–H2O, cone voltage 20 V) m/z 293
([M–H]− 100%), 311 ([M–H+H2O]− 10%). IR (KBr
disc) (cm−1): 3414 (w), 2721 (br, m), 1230 (m), 1195
(m), 1112 (s), 1019 (s), 961 (m), 931 (s), 824 (m), 814
(m), 677 (m), 520 (m), 505 (m), 494 (m).
petroleum spirits (20 ml) under nitrogen. BuLi (6.24
ml, 1.6 M, 10 mmol) and tmeda (0.74 ml, 5 mmol) were
added and the reaction stirred for 12 h. The resulting
suspension was added slowly with stirring to a solution
of (EtO)2P(O)Cl (1.6 ml, 10 mmol) in petroleum spirits
(10 ml). The reaction was immediate, resulting in the
precipitation of a brown tar. The solvent was decanted
off and replaced with water (20 ml) and CH2Cl2 (20
ml). The phases were separated and the aqueous layer
further extracted with CH2Cl2 (2×20 ml). The com-
bined organic fractions were dried over MgSO4 and
evaporated to dryness. The residue was dissolved in
EtOAc (ca. 5 ml) and purified with alumina flash
column chromatography, using an EtOAc to MeOH
solvent gradient to give 2 g (88%) of 1,1%-ferrocenyl-
bis(diethylphosphonate) as a brown oil.
1
2
n
3.6. Synthesis of FcP(O)(OH)2 (5)
Ferrocene (0.93 g, 5 mmol) was dissolved in dry THF
t
(5 ml) and cooled to 0 °C under nitrogen. BuLi (0.6
ml, 1.7 M, 4.16 mmol) was added and the solution
stirred for 15 min. (EtO)2P(O)Cl (0.718 g, 4.16 mmol)
was added dropwise with stirring, and the solution
stirred for 1 h. The solvent was removed under reduced
pressure and replaced with H2O (20 ml) and CH2Cl2 (20
ml). The layers were separated and the organic phase
A solution of 1,1%-ferrocenyl-bis(diethylphosphonate)
(0.526 g, 1.15 mmol), in dry CH2Cl2 (10 ml) was placed
under nitrogen, freshly distilled Me3SiBr (0.88 ml, 9.2
mmol) added dropwise and the reaction mixture stirred
overnight. Water (0.3 ml, 0.016 mol) was added and
stirring continued until precipitation was complete (ca.
30 min). The microcrystalline yellow powder was
filtered and washed with acetone to give 0.35 g (89%) of
6, m.p. 235–238 °C (dec.). Anal. Found: C, 34.5; H,
3.3. Calc. for C10H12FeO6P2: C, 34.7; H, 3.5%. 31P–
1 Separation of the diethyl-ester intermediate [FcCH2CH2P-
(O)(OEt)2] by flash column chromatography (Al2O3, EtOAc to
MeOH solvent gradient) prior to hydrolysis did not improve the
overall yield.
2 The triethylamine can be omitted if the trimethylsilylbromide is
freshly distilled and glassware is dry.

226
S.R. Alley, W. Henderson / Journal of Organometallic Chemistry 637–639 (2001) 216–229
t
{1H}-NMR (Na salt in D2O): l 21.7. 13C–{1H}-NMR
(5 ml) under nitrogen and cooled to 0 °C. BuLi (2.9
1
(Na salt in D2O): l 72.09 (d, JC,P 149 Hz, C1), 72.52
ml, 1.7 M, 5 mmol) was added and the solution stirred
for 15 min. This solution was added dropwise to a
solution of (PhO)2P(O)Cl (1.34 g, 5 mmol) in THF (10
ml) and the solution stirred for 1 h. The solvent was
removed under reduced pressure and replaced with
H2O (20 ml) and CH2Cl2 (20 ml). The layers were
separated and the organic phase washed with H2O
(2×20 ml) before being dried over MgSO4. The solvent
was removed and the resulting brown oil purified by
silica flash column chromatography using petroleum
spirits:CH2Cl2:MeOH (48:50:2) as the eluting solvent.
This gave 0.83 g (40%) of 8 as a brown oil which
crystallised upon standing, m.p. 77–80 °C. Anal.
Found: C, 62.3; H, 4.7. Calc. for C22H19FeO3P: C, 63.2;
H, 4.6%. 31P–{1H}-NMR (CDCl3): l 20.6. 13C–{1H}-
3
2
1
(d, JC,P 10 Hz, C3), 72.71 (d, JC,P 12 Hz, C2). H-
NMR (Na salt in D2O): l 4.5–4.7 (8H, m, H2, H3),
8.80 (4H, br s, POH). ESMS: (MeCN, cone voltage 80
V) m/z 345 ([M–H]−, 100%), 327 ([M–H−H2O]−,
17%). IR (KBr disc) (cm−1): 2771 (br, m), 1198 (s),
1058 (s), 1036 (s), 1004 (s), 956 (s), 885 (m), 839 (m),
747 (m), 638 (m), 575 (s), 501 (m), 480 (m), 461 (m), 434
(w).
3.8. Synthesis of 1,1%-Fc%[CH2P(O)(OH)2]2 (7)
In a dry, nitrogen-flushed flask was placed THF (30
ml), 1,1%-ferrocenylbis(methanol) (0.80 g, 3.26 mmol),
pyridine (0.52 g, 6.52 mmol) and freshly distilled PCl3
(0.89 g, 6.52 mmol). The reaction mixture was stirred
until precipitation of pyridinium chloride was deemed
complete (ca. 1 h). The solution was filtered and the
solvent removed to give a bright yellow crystalline
material, crude 1,1%-Fc%(CH2Cl)2. Triethylphosphite (5
ml) was added and the solution refluxed for 2 h. Excess
triethylphosphite was distilled off under vacuum and
the resulting brown oil purified by alumina flash
column chromatography using an EtOAc to MeOH
solvent gradient. The 1,1%-ferrocenyl-bis-(diethyl
methylphosphonate) was isolated as a viscous brown oil
(1.03 g, 65%).
1
NMR (CDCl3): l 65.45 (d, JC,P 166 Hz, C1), 70.12 (s,
C4), 71.90 (dd, 2JC,P 12 Hz, 3JC,P 11 Hz, C2, C3), 120.73
3
(d, JC,P 3 Hz, o-C), 124.93 (s, p-C%), 129.72 (d, JC,P 10
Hz, m-C), 150.86 (d, JC–P 6 Hz, i-C). 1H-NMR
2
(CDCl3): l 4.25 (5H, s, H4), 4.46 (2H, s, H3), 4.62 (2H,
d, JC,P 1.2 Hz, H2), 7.1–7.4 (10H, m, Ph). ESMS:
2
(MeCN–H2O, positive ion, cone voltage 60 V) m/z 419
([M+H]+, 100%), 436 ([M+H2O]+, 31%), 460 ([M+
MeCN]+, 11%). IR (solution in CH2Cl2) (cm−1): 1591
(s), 1492 (s), 1188 (m), 1107 (m), 1071 (m), 1006 (m),
944 (s), 828 (m), 619 (m), 603 (m), 496 (s).
1,1%-Ferrocenyl-bis-(diethylmethylphosphonate) (0.53
g, 1.1 mmol) was dissolved in dry CH2Cl2 (10 ml) and
the solution placed under a nitrogen atmosphere.
Me3SiBr (1.32 g, 8.8 mmol) was added and the reaction
stirred for 3 h. Water (0.15 g, 8.8 mmol) was added
with stirring, resulting in precipitation of a dark green
powder. The solvent was removed and the residue
dissolved in 5 ml of 1 M NaOH solution. The green
solution was reduced to a yellow colour by the addition
of excess potassium metabisulfite, then acidified with
concentrated HCl. Slow evaporation over 3 days gave
dark brown crystals which were filtered and washed
with water (5 ml), then air-dried to give 0.173 g (42%)
of 7, m.p. darkens at 203 °C (dec.). Anal. Found: C,
37.4; H, 4.4. Calc. for C12H16FeO6P2: C, 38.5; H, 4.3%.
31P–{1H}-NMR (Na salt in D2O): l 19.0. 13C–{1H}-
NMR (Na salt in D2O): l 32.84 (d, 1JC,P 76 Hz, CH2P),
3.10. Synthesis of 1,1%-Fc[P(O)(OPh)2]2 (9)
Ferrocene (1 g, 5.4 mmol) was dissolved in petroleum
n
spirits (20 ml) under nitrogen. BuLi (6.72 ml, 1.6 M,
10.8 mmol) and freshly distilled tmeda (0.8 ml, 0.62 g,
5.4 mmol) were added and the reaction stirred for 12 h.
A solution of (PhO)2P(O)Cl (2.2 ml, 2.9 g, 10.8 mmol)
in diethyl ether (10 ml) was then added slowly with
stirring. The product precipitated as a brown tar. The
solvent was removed under vacuum and the residue
washed with petroleum spirits (2×10 ml). Water (20
ml) and CH2Cl2 (20 ml) were added and the flask
agitated until dissolution was complete. The layers were
separated and the organic phase washed with water
(2×20 ml), dried over MgSO4 and the solvent re-
moved. The resulting brown oil was purified by silica
flash column chromatography using
a
CH2Cl2:
2
69.64 (s, C2), 72.20 (s, C3), 86.50 (d, JC,P 2 Hz C1).
EtOAc:MeOH solvent gradient. The mono-substituted
byproduct, FcP(O)(OPh)2 eluted in EtOAc:CH2Cl2, 1:9,
while the desired product eluted in EtOAc:CH2Cl2, 3:7.
Removal of the solvent resulted in 2.45 g (66%) of
1,1%-Fc%[P(O)(OPh)2]2 (9) as yellow crystals, m.p. 120–
121.5 °C. Anal. Found: C, 62.7; H, 4.5. Calc. for
C34H29FeO6P2: C, 62.8; H, 4.3%. 31P–{1H}-NMR
(CDCl3): l 26.2. 13C–{1H}-NMR (CDCl3): l 73.53 (d,
2
1H-NMR (Na salt in D2O): l 2.49 (4H, d, JP,H 12.3
Hz, CH2P), 3.98 (4H, br s, H3), 4.12 (4H, br s, H2).
ESMS: (MeCN–H2O, cone voltage 20 V) m/z 373
([M–H]−, 100%). IR (KBr) (cm−1): 2749 (br, s), 1265
(m), 1225 (m), 995 (s), 946 (s), 920 (m), 829 (m), 607
(m), 483 (m), 432 (m).
3
3.9. Synthesis of FcP(O)(OPh)2 (8)
2JC,P 16 Hz, C2), 74.60 (d JC,P 14 Hz, C3), 120.63 (d
3JC,P 4 Hz, o-C), 125.14 (s, p-C), 128.66 (d, JC,P 61 Hz,
1
2
Ferrocene (0.93 g, 5 mmol) was dissolved in dry THF
C1), 129.74 (s, m-C), 150.59 (d, JC,P 8 Hz, i-C).

S.R. Alley, W. Henderson / Journal of Organometallic Chemistry 637–639 (2001) 216–229
227
voltage 40 V) m/z 351 ([M–2H+Me]−, 30%), 337
([M–H]−, 100%), 259 ([M–2H−CpCH2CH2+Me]+
6%), 245 ([M–H–CpCH2CH2), 10%). IR (solution in
CH2Cl2) (cm−1): 2743 (br, s), 2385 (br, m), 2303 (br,
m), 1252 (w), 1220 (w), 881 (s), 827 (m), 784 (m), 486
(m).
Table 3
Crystal data and analysis parameters for FcCH2P(O)(OH)2 (3) and
1,1%-Fc%[CH2P(O)(OH)2]2 (7)
Empirical formula
Crystal size (mm)
Formula weight (g mol−1
Crystal system
C11H13O3Pfe
0.34×0.29×0.21 Not recorded
C12H16O6P2Fe
)
280.03
Orthorhombic
9.859(3)
9.231(2)
25.017(7)
90
2276.7(1)
Pbca
8
1.634
1152
1.45
293(2)
2BqB27
374.04
Monoclinic
8.3415(2)
9.8376(1)
9.1540(2)
103.696(1)
729.82(2)
P21/c
,
a (A)
,
b (A)
3.12. X-ray crystal structure determinations for
FcCH2P(O)(OH)2 (3) and 1,1%-Fc%[CH2P(O)(OH)2]2 (7)
,
c (A)
i (°)
3
,
V (A )
Single crystals of 3 were obtained serendipitously
from a warm methanol solution which also contained
urea and zinc chloride in an attempt to prepare the zinc
salt of the acid. From this solution, small yellow crys-
tals of 3 precipitated over a period of 2–4 weeks.
Crystallographic data for 3 are given in Table 3. The
data set was collected on a Nicolet R3 diffractometer.
The structure was solved by direct methods and devel-
oped routinely using the SHELXL-97 program with full
least-squares refinement based on F2o. All non-hydrogen
atoms were refined using anisotropic temperature fac-
tors. All hydrogen atoms were found from peaks of
residual electron density in the penultimate electron
density map and refined in a riding model with
isotropic temperature factors. The largest residual elec-
Space group
Z
2
Dcalc (g cm−3
F(000)
)
1.702
384
1.28
293(2)
v(Mo–Ka) (mm−1
)
Temperature (K)
2q Range for data
collection (°)
Total reflections
Unique reflections
2BqB27
23529
2534
(Rint=0.0224)
0.726
1.000
0.0216
0.058 a
1.053
4242
1577
(Rint=0.016)
0.758
0.962
Tmin
Tmax
R1 [I\2|(I)]
wR2
Goodness-of-fit
0.024
0.0613 b
0.971
a w=[|2(Fo2)+(0.0313P2+1.2852]−1 where P=(Fo2+2F2c)/3.
b w=[|2(Fo2)+(0.0328P2+0.4962P]−1 where P=(Fo2+2F2c)/3.
tron density peaks in the final electron density map did
−3
,
not exceed +0.279 and −0.305 e A
.
1H-NMR (CDCl3): l 4.60 (4H, s, H3), 4.70 (4H, d,
3JH,P 1 Hz, H2), 7.1–7.4 (20H, m, Ph). ESMS: (positive
ion, MeOH, cone voltage 90 V) m/z 651 ([M+H]+,
100%), 673 ([M+Na]+, 19%). IR (solution in CH2Cl2)
(cm−1): 1591 (s), 1490 (s), 1189 (m), 1163 (m), 1071
(w), 1036 (m), 1025 (m), 1007 (w), 941 (s), 837 (w), 618
(w), 602 (m), 403 (m).
Crystals of 7 suitable for X-ray crystallographic anal-
ysis were obtained by evaporation of an aqueous solu-
tion which also contained potassium bisulfite as a
reducing agent. Crystallographic data for compound 7
are given in Table 3. The data set was collected on a
Siemens SMART CCD diffractometer and corrected
for absorption using SADABS [55]. The structure was
solved by direct methods and developed routinely using
the SHELXL-97 program with full-matrix least-squares
refinement based on F2o. All non-hydrogen atoms were
refined using anisotropic temperature factors. All hy-
drogen atoms were found from peaks of residual elec-
tron density in the penultimate electron density map
and were refined with isotropic temperature factors.
3.11. Synthesis of FcCH2CH2As(O)(OH)2 (10)
Arsenic(III) oxide (As2O3, 0.213 g, 1.07 mmol) was
dissolved in aqueous sodium hydroxide (1.3 ml, 4.98 M,
6.45 mmol) and made up to 5 ml with water.
FcCH2CH2Br (0.7 g, 2.4 mmol) in CH2Cl2 (5 ml) was
added, the CH2Cl2 removed under reduced pressure
and 0.5 ml of EtOH added as a co-solvent. The result-
ing solution was refluxed for 7 h. After cooling, the
reaction solution was extracted with CH2Cl2 to remove
any unreacted bromide. The aqueous layer was aci-
dified with 1 M HCl, the resulting yellow precipitate
filtered, washed with cold water, and dried to give 0.34
g (41%) of 10, m.p. 149–152 °C. Anal. Found: C, 42.7;
H, 4.7. Calc. for C12H15AsFeO3: C, 42.6; H, 4.5%.
13C–{1H}-NMR (Na salt in D2O): l 22.65 (s, CH2Cp),
31.21 (s, CH2As), 67.67 (s, C3), 68.02 (s, C2), 69.06 (s,
The largest residual electron density peaks in the final
−3
,
density map did not exceed +0.336 or −0.288 e A
.
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 158654 for complex 3 and
CCDC no. 158655 for complex 7. Copies of this infor-
mation may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
1
C4), 90.08 (s, C1). H-NMR (Na salt in D2O): l 2.30
(2H, m, CH2As), 2.85 (2H, m, CH2Cp), 4.24 (2H, br s,
H3), 4.46 (7H, br s, H2, H4). ESMS: (MeOH, cone

228
S.R. Alley, W. Henderson / Journal of Organometallic Chemistry 637–639 (2001) 216–229
Chem. Commun. (1995) 65;
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