First synthesis of 1,1′-ferrocene bis-aminophosphonic esters

Article abstract of DOI:10.1016/j.jorganchem.2004.01.012

The series of aminophosphonates bearing the 1,1′ -bis-substituted ferrocenyl moiety was obtained by the addition of dialkyl phosphites to an azomethine bond of Schiff bases derived from 1,1′-ferrocene-bis-carboxaldehyde. This addition led to both diastereoisomeric forms demonstrating its behaviour to be contrary to the addition to terephthalic Schiff bases, which led exclusively to a meso -form.

Full text of DOI:10.1016/j.jorganchem.2004.01.012

Journal of Organometallic Chemistry 689 (2004) 1265–1270
www.elsevier.com/locate/jorganchem
First synthesis of 1,10-ferrocene bis-aminophosphonic esters
*
ꢀ
ꢀ
Jarosław Lewkowski , Monika Rzezniczak, Romuald Skowronski
Department of Organic Chemistry, University of Łꢀodꢀz, Narutowicza 68, 90-136 Łꢀodꢀz, Poland
Received 12 June 2003; accepted 3 January 2004
Abstract
The series of aminophosphonates bearing the 1,10-bis-substituted ferrocenyl moiety was obtained by the addition of dialkyl
phosphites to an azomethine bond of Schiff bases derived from 1,10-ferrocene-bis-carboxaldehyde. This addition led to both dia-
stereoisomeric forms demonstrating its behaviour to be contrary to the addition to terephthalic Schiff bases, which led exclusively to
a meso-form.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: 1,10-Ferrocenedicarboxaldehyde; Schiff bases; Aminophosphonates; Asymmetrical induction; 1,10-bis-substituted ferrocene moiety
1. Introduction
ters bearing ferrocenyl moiety [32,33]. In this paper,
we present the first synthesis of variously N-substituted
1,10-ferrocene-bis-aminomethane phosphonates using the
addition to the azomethine bond [4]. These compounds
can be converted into various bis-aminophosphonates
O-substituted with polyglycols, steroids or nucleosides,
which might be interesting analogues of ferrocene com-
pounds already described in the literature [34,35].
After the first preparation of aminophosphonic acids
and esters [1–3], the great development of their chem-
istry was observed in the aspect of the synthesis [4–6],
the stereochemistry [7–9], biochemical properties [10,11]
and their applications in various fields of agriculture and
medicine [12–14].
Because ferrocene-derived compounds are character-
ized by their ability to make metal-centred redox sys-
tems to generate oxidized or reduced form of different
properties they have been widely employed in various
fields such as: molecular recognition as biosensors [15–
19], in asymmetric catalysis [20], in polymer science as
red-ox active polymers and dendrimers [21], in non-
linear optics [22], in synthesis of complex photochemical
systems [23] and in pharmacology [24]. Successful at-
tempts of the synthesis of amino acids bearing ferrocene
moiety have been also performed [25–31]. Ferrocenyl
amino acids found their application in food chemistry as
a possible substitute for phenylalanine in the commer-
cial sweetener aspartame [30].
2. Results and discussion
1,10-Ferrocene-bis-aminophosphonates were synthe-
sized by the addition of dialkyl phosphites to the
azomethine bond of Schiff bases. As the model com-
pounds, diethyl, dibenzyl and diphenyl phosphites were
chosen.
Schiff bases of 1,10-ferrocenedicarboxaldehyde 2a–d
were prepared following the known methodology [6,32].
They were characterised by means of elemental analyses
1
and H NMR spectroscopy.
The phosphite additions were carried out in toluene or
in acetonitrile at a boiling temperature for 5–7 h (Scheme
1). Tetraethyl esters 3a, 3d and 3j were isolated from the
post-reaction mixture by the multiple washing with ether
of their ethanol-aqueous acidic solution and by sub-
sequent extraction of the alkaline aqueous mixture with
dichloromethane. Resulting crude tetraethyl esters de-
composed on silica gel and on neutral aluminium oxide,
Regarding all above, we wanted to combine proper-
ties of mentioned groups of compounds and recently
we have reported the synthesis of aminophosphonic es-
* Corresponding author. Tel.: +48-426784731; fax: +48-426786583.
E-mail address: jlewkow@krysia.uni.lodz.pl (J. Lewkowski).
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.01.012

1266
J. Lewkowski et al. / Journal of Organometallic Chemistry 689 (2004) 1265–1270
PO3R'2
CHO
HP(O)(OR')2
NHR
RNH2
NR
NR
Fe
Fe
Fe
PO3R'2
CHO
NHR
1
2
a-d
3
a-l
2a: R = CH2Ph; 2b: R = CH2Fur; 2c: R = CHPh2; 2d: R = CH(CH3)Ph
3a: R = CH2Ph, R' = Et; 3b: R = CH2Ph, R' = CH2Ph; 3c: R = CH2Ph, R' = Ph;
3d: R = CH2Fur, R' = Et; 3e: R = CH2Fur, R' = CH2Ph; 3f: R = CH2Fur, R' = Ph;
3g: R = CHPh2, R' = Et; 3h: R = CHPh2, R' = CH2Ph; 3i: R = CHPh2, R' = Ph;
3j: R =(R)-CH (CH3)Ph, R' = Et; 3k: R = (R)-CH (CH3)Ph, R' = CH2Ph;
3l: R = (R)-CH (CH3)Ph, R' = Ph;
Fur =
O
Scheme 1.
that is why they were purified by the column chroma-
tography on cellulose powder. Tetrabenzyl esters 3b, 3e,
3h and 3k could not be treated in this way, as their hy-
drochlorides are not soluble in ethanol–water mixture
and cellulose powder was not a suitable adsorbent to
purify them. They were isolated and purified by the col-
umn chromatography on neutral aluminium oxide but
partial decomposition of esters on aluminium oxide was
observed, which resulted in their very moderate yields. In
this way, we have obtained N-substituted diethyl and
dibenzyl 1,10-ferrocene-bis-aminomethanephosphonates
3a–b, 3d–e, 3h and 3j–k. The 1H and 31P NMR spectros-
copy, the mass spectrometry and the elemental analysis
confirmed their identity and their purity.
Tetraphenyl bis-aminophosphonates 3c, 3f, 3i, 3l de-
composed in the above-described conditions. Their pu-
rification was then very troublesome and their structure
was confirmed only by the NMR spectroscopy and the
mass spectrometry measurements of crude products.
Because the intensity of their mass peaks mostly did not
exceed 5%, the high-resolution mass spectrometry
(HRMS) measurements could not be performed. Their
data are quoted in Section 3.
10-ferrocene-bis-(carbaldehyde-N-diphenylmethylimine)
(2c) with diethyl phosphite occurred in a small de-
gree – its conversion rate was 33%, as estimated from
NMR measurements. The reaction was repeated
many times, we were changing the duration, the ratio
of substrates and solvent (acetonitrile and toluene)
and none of them improved the conversion rate of
the reaction. The isolation of the product from the
post-reaction mixture was therefore impossible, so
the occurring ester product was identified only by the
NMR spectroscopy and mass spectrometry measure-
ments. We have no idea why such a phenomenon
occurred, especially that initial applied conditions
were the same as in all other cases of the synthesis of
ethyl esters 3a, 3d, 3j. Nothing seems to explain such
a low conversion rate of reaction in the ester 3g
synthesis.
The addition of phosphites to achiral Schiff bases of
1,10-ferrocenedicarbaldehyde was not stereoselective at
all or the stereoselectivity occurred in a very small degree.
The addition of phosphites to ferrocene-bis-carbimines
2a–c led to the formation of two diastereoisomeric forms
(the meso form and the raceme mixture) of 1,10-ferrocene-
bis-methanephosphonate 3a–i in a 1:1, 1:2 or 3:2 ratio,
which was demonstrated by means of the 1H and
31P NMR spectroscopy. The addition of a phosphite
to the chiral 1,10-ferrocene-bis-(carbaldehyde-N-(R)-a-
methylbenzylimine) (2d) led to the formation of three
diastereoisomers in a 1:3:1 ratio. Unfortunately, diaste-
reoisomers were not separated due to their fragility to
silica gel and neither applied cellulose powder nor
aluminium oxide were found to be efficient enough to
provide a good resolution of diastereoisomers.
It is not the exception that aminophosphonic phenyl
ester demonstrate less stability than alkyl or alkyl-aryl
ones. The same case was discussed for ferrocene-derived
mono-aminophosphonates [32,33] and similar situation
occurred in case of (2-furyl)-N-tritylamino-phosphonic
esters [36], which diphenyl ester could not be obtained
because of its instability [37].
A
very interesting matter occurred in a case
of tetraethyl 1,10-ferrocene-bis-(N-diphenylmethyl-
aminomethanephosphonate) (3g). The reaction of 1,

J. Lewkowski et al. / Journal of Organometallic Chemistry 689 (2004) 1265–1270
1267
The addition of phosphites to terephthalic and
isophthalic imines is in 100% stereoselective [38–40]
leading to the formation of a meso-form and we sug-
gested [39] that this stereoselective addition to completely
achiral compounds originated from intermolecular in-
teractions between two molecules of the mono-addition
intermediate products and two phosphite molecules
(Scheme 2(a)). In case of ferrocene derivative, it takes the
most probably the conformation as in Scheme 2(b),
which seems to be the most convenient one. This con-
formation makes the formation of the similar dimer more
difficult. In addition, we suggest the probable occurrence
of interactions between iron in ferrocene and oxygen
from phosphonic group as presented in Scheme 2(c).
These phenomena make the attack of a phosphite mol-
ecule on an azomethine bond possible from both sides.
All attempts to cleave ethyl esters 3a, 3d, 3g and 3j
failed. We tried to use acidic cleavage with aqueous
hydrochloric acid as well as the known [6] method with
trimethylsilyl bromide. Both methods led to the variety
of products, among which, we identified phosphoric
acid derivatives and 1,10-bis-(aminomethyl)ferrocene. It
would suggest that the retro-addition reaction occurred.
But as the rest of products remained unidentified, the
retro-addition is not the exclusive reaction.
ophosphonates [32], title bis-esters 3a–l behave similarly
to former ones, but they are more fragile.
3. Experimental
All solvents (POCh-Poland) were routinely distilled
and dried prior to use [41]. Amines (Aldrich), phosphites
(Aldrich) and 1,10-ferrocenedicarboxaldehyde (Aldrich)
were used as received. Cellulose powder was provided by
Aldrich. All NMR spectra were recorded on a Varian
Gemini 200 BB spectrometer operating at 200 MHz for
1H NMR and at 81 MHz for 31P NMR. Elemental
analyses and mass spectra were performed in the Centre
of Molecular and Macromolecular Studies (Polish
ꢀ ꢀ
Academy of Science) in Łodz.
3.1. Schiff bases of 1,10-ferrocenedicarboxaldehyde (2a–d)
To a solution of ferrocenecarboxaldehyde (0.107 g,
0.5 mmol) in methanol (10 ml), an amine (1mmol) was
added. The mixture was then stirred for 20 h at a room
temperature, then the mixture was evaporated, the solid
residue dissolved in benzene and precipitated with hex-
ane to give a pure product. In a case of non-crystalline
product, the residue was dissolved in benzene and fil-
tered through a cellulose pad and then evaporated to
give a pure product.
Our aim and perspective for the future is to find the
way to obtain various ferrocene-derived bis-aminophos-
phonic acids, as they are of interest as the starting ma-
terial for the synthesis of ferrocene-bearing macrocycles,
bis-phosphonosteroids or bis-phosphono-nucleosides.
The best method is the cleavage of title bis-esters 3a–l,
but as we showed, it is not a simple task. It is to remark
that, in comparison to ferrocene-derived mono-amin-
3.1.1. 1,10-ferrocene-bis-(carbaldehyde-N-benzylimine)
(2a)
Yield ¼ 0.20 g (95%); (brown crystals); mp ¼ 56–
58 °C.
(a)
(b)
OR'
R'O
P
NHR
OR'
O
H
RN
H
OR'
OR'
O
P
NR
OR'
P
P
Fe
H
R'O
R'O
O
RN
NR
H
O
O
RN
P
OR'
R'O
NHR
OR'
(c)
OR'
P
Fe
O
RN
Scheme 2.

1268
J. Lewkowski et al. / Journal of Organometallic Chemistry 689 (2004) 1265–1270
1H NMR (CDCl3, 200 MHz): d 8.11 (s, CH@N, 2H);
3.2.1. Tetraethyl 1,10-ferrocene-bis-(N-benzylaminometh-
anephosphonate) (3a)
7.32 (m, PhH, 10 H); 4.67 (narrow m, Cp, 4H); 4.60 (s,
CH2Ph, 4H); 4.37 (narrow m, Cp, 4H).
Elemental analysis: Anal. Found: C, 74.42; H, 5.64;
N, 6.53. Calc. for C26H24FeN2: C, 74.29; H, 5.76; N,
6.66%.
Yield ¼ 0.25 g (71%).
1H NMR (CDCl3, 200 MHz): d 7.36 (m, PhH, 10H);
4.22–3.96 (m, CH2CH3, CH2Ph, Cp, 20H); 3.69 and
2
3.66 (2d, JPH ¼ 10:8 Hz, CHP, 2H); 1.94 (large s, NH,
2H); 1.27 and 1.25 (2t, J ¼ 6:9 Hz, CH2 CH3, 12H). 31
NMR (CDCl3, 81 MHz): d 22.22 and 22.16 (1:1).
P
3.1.2. 1,10-ferrocene-bis-(carbaldehyde-N-furfurylimine)
(2b)
EI-MS: m=z ¼ 696.3 [Mþ]; 420.2 [Mþ)2HOP(OEt)2];
238.1 [Fc(CHNH)2]; 91.1 [þCH2Ph]; 65.0 [Cp].
Elemental analysis: Anal. Found: C, 58.25; H, 6.60;
N, 3.99. Calc. for C34H46FeN2O6P2: C, 58.63; H, 6.66;
N, 4.02%.
Yield ¼ 0.17 g (89%); (dense oily liquid).
1H NMR (CDCl3, 200 MHz): d 8.12 (s, CH@N, 2H);
7.40 (m, Hf5ur, 2H); 6.35 (m, H3fur, 2H); 6.27 (m, H4fur
,
2H); 4.66 (narrow m, Cp, 4H); 4.59 (s, CH2 Fur, 4H);
4.37 (narrow m, Cp, 4H).
Elemental analysis: Anal. Found: C, 66.18; H, 5.15;
N, 6.91. Calc. for C22H20FeN2O2: C, 66.02; H, 5.04; N,
7.00%.
3.2.2. Tetrabenzyl 1,10-ferrocene-bis-(N-benzylaminomet-
hanephosphonate) (3b)
Yield ¼ 0.23 g (48%).
1H NMR (CDCl3, 200 MHz): d 7.29 (m, PhH, 30H);
4.91 (m, OCH2Ph, 8H); 4.18–3.88 (m, Cp, CH2Ph, 12H);
3.73 and 3.69 (2d, 2JPH ¼ 8:8 Hz, CHP, 2H); 1.92 (large
s, NH, 2H). 31P NMR (CDCl3, 81 MHz): d 23.48 and
23.38 (1:1).
3.1.3. 1,10-ferrocene-bis-(carbaldehyde-N-diphenylmeth-
ylimine) (2c)
Yield ¼ 0.28 g (97%); (brown crystals); mp ¼ 130–132
°C.
1H NMR (CDCl3, 200 MHz): d 8.00 (s, CH@N, 2H);
7.33 (m, PhH, 20H); 5.30 (s, CHPh2, 2H); 4.61 (narrow
m, Cp, 4H); 4.27 (narrow m, Cp, 4H).
Elemental analysis: Anal. Found: C, 79.89; H, 5.71;
N, 5.04. Calc. for C38H32FeN2: C, 79.72; H, 5.63; N,
4.89%.
EI-MS: m=z ¼ 945.1 [Mþ]; 682.4 [Mþ)HOP(O
CH2Ph)2]; 420.8 [Mþ)2 HOP(OCH2Ph)2]; 238.3
[Fc(CHNH)2]; 107.1 [þOCH2Ph]; 91.1 [þCH2Ph]; 65.0
[Cp].
Elemental analysis: Anal. Found: C, 68.78; H, 5.72;
N, 2.74. Calc. for C54H54FeN2O6P2: C, 68.65; H, 5.76;
N, 2.96%.
3.1.4. 1,10-ferrocene-bis-(carbaldehyde-N-(R)-a-meth-
ylbenzylimine) (2d)
3.2.3. Tetraphenyl 1,10-ferrocene-bis-(N-benzylaminome-
thanephosphonate) (3c)
Yield ¼ 0.21 g (95%) (dense oily liquid).
1H NMR (CDCl3, 200 MHz): d 8.04 (s, CH@N, 2H);
7.32 (m, PhH, 10 H); 4.67 (narrow m, Cp, 4H); 4.56
(narrow m, Cp, 4H); 4.30 (quart, J ¼ 6:6 Hz, CHPh,
2H); 1.55 (d, J ¼ 6:6 Hz, CH3, 6H).
Conversion rate ¼ 75% estimated by NMR.
1H NMR (CDCl3, 200 MHz): d 7.23–6.80 (m, PhH,
30H); 4.49–4.09 (m, Cp, CH2Ph, 12H); 3.71 and 3.67
2
(2d, JPH ¼ 8:8 Hz, CHP, 2H); 1.99 (large s, NH, 2H).
Elemental analysis: Anal. Found: C, 75.19; H, 6.41;
N, 6.12. Calc. for C28H28FeN2: C, 75.00; H, 6.29; N,
6.25%.
31P NMR (CDCl3, 81 MHz): d 14.91 and 14.59 (1:2).
FAB-MS: m=z ¼ 945.1 [Mþ]; 421.4 [Mþ)2 HOP
(OPh)2]; 238.0 [Fc(CHNH)2]; 93.1 [þOPh]; 91.1
[þCH2Ph]; 65.0 [Cp].
3.2. Dialkyl N-alkylaminoferrocenemethanephosphonates
(3a–l)
3.2.4. Tetraethyl 1,10-ferrocene-bis-(N-furfurylaminomet-
hanephosphonate) (3d)
To a solution of an imine (0.5 mmol) in toluene (10
ml), dialkyl phosphite (1 mmol) was added. The solution
was refluxed for seven days. In case of ethyl derivatives
3a, 3d and 3j the solvent was evaporated, the residue was
dissolved in the 10% aqueous HCl–ethanol (4:1), washed
with ether (3 ꢀ 20 ml), the aqueous layer extracted with
dichloromethane (3 ꢀ 25 ml), the organic layers dried
and evaporated to give an appropriate product. The
product was purified by means of column chromatog-
raphy on cellulose powder. In case of benzyl derivatives
3b, 3e, 3h, 3k, a crude product was chromatographed on
aluminium oxide without previous extraction. Phenyl
derivatives decomposed in above mentioned conditions.
Yield ¼ 0.23 g (66%).
1H NMR (CDCl3, 200 MHz): d 7.36 (m, Hf5ur, 2H);
6.26 (m, Hf3ur, 4H); 4.26–3.93 (m, CH2CH3,CH2Ph, Cp,
20H); 3.89 and 3.73 (2d, 2JPH ¼ 9:8 Hz, CHP, 2H); 1.75
(large s, NH, 2H); 1.26 and 1.25 (2t, J ¼ 6:9 Hz,
CH2CH3, 12H).31P NMR (CDCl3, 81 MHz): d 22.61
and 22.50 (1:1).
EI-MS: m=z ¼ 676.1 [Mþ]; 538.1 [Mþ)HOP(OEt)2];
400.1 [Mþ)2HOP(OEt)2]; 238.2 [Fc(CHNH)2]; 81.0
[þCH2Fur]; 65.0 [Cp].
Elemental analysis: Anal. Found: C, 52.94; H, 5.91;
N, 4.49. Calc. for C30H42FeN2O8P2: C, 53.27; H, 6.26;
N, 4.14%.

J. Lewkowski et al. / Journal of Organometallic Chemistry 689 (2004) 1265–1270
1269
3.2.5. Tetrabenzyl 1,10-ferrocene-bis-(N-furfurylaminom-
ethanephosphonate) (3e)
Elemental analysis: Anal. Found: C, 72.29; H, 5.95;
N, 2.50. Calc. for C66H62FeN2O6P2: C, 72.26; H, 5.70;
N, 2.55%.
Yield ¼ 0.22 g (47%).
1H NMR (CDCl3, 200 MHz): d 7.29 (m, PhH, H5fur
,
22H); 6.26 (m, H3fur, 2H); 6.15 (m, Hf4ur, 2H); 4.89 (m,
OCH2Ph, 8H); 4.14–4.04 (m, Cp, CH2Fur, 12H); 3.73
3.2.9. Tetraphenyl 1,10-ferrocene-bis-(N-diphenylmethyl-
aminomethanephosphonate) (3i)
2
and 3.69 (2d, JPH ¼ 8:8 Hz, CHP, 2H); 2.05 (large s,
Conversion rate ¼ 78% estimated by NMR.
1H NMR (CDCl3, 200 MHz): d 7.32 (m, PhH, 40H);
5.61 and 5.54 (2s, CHPh2, 2H); 4.46–4.05 (m, Cp, 8H);
3.73 and 3.69 (2d, 2JPH ¼ 8:8 Hz, CHP, 2H); 2.05 (large
s, NH, 2H). 31P NMR (CDCl3, 81 MHz): d 15.10 and
14.94 (2:1).
FAB-MS: m=z ¼ 1040.6 [Mþ]; 807.4 [Mþ)HOP
(OPh)2]; 573.4 [Mþ)2HOP(OPh)2]; 238.9 [Fc(CHNH)2];
233.8 [þP(O)(OH)(OCH2Ph)]; 167.1 [þCHPh2]; 93.1
[þOPh]; 65.0 [Cp].
NH, 2H). 31P NMR (CDCl3, 81 MHz): d 23.12 and
22.85 (3:2).
EI-MS: m=z ¼ 924.3 [Mþ]; 662.2 [Mþ)HOP
(OCH2Ph)2]; 400.1 [Mþ)2 HOP(OCH2Ph)2]; 238.0
[Fc(CHNH)2]; 107.1 [þOCH2Ph]; 91.1 [þCH2Ph]; 81.1
[þCH2Fur]; 65.0 [Cp].
Elemental analysis: Anal. Found: C, 65.12; H, 5.67;
N, 3.21. Calc. for C50H50FeN2O8P2: C, 64.94; H, 5.45;
N, 3.03%.
3.2.10. Tetraethyl 1,10-ferrocene-bis-(N-N-(R)-a-meth-
ylbenzylaminomethanephosphonate) (3j)
3.2.6. Tetraphenyl 1,10-ferrocene-bis-(N-furfurylaminom-
ethanephosphonate) (3f)
Yield ¼ 0.21 g (59%).
1H NMR (CDCl3, 200 MHz): d 7.38 (m, PhH, 10H);
4.41–3.78 (m, CH2CH3, CHPh, Cp, 18H); 3.64, 3.34 and
Conversion rate ¼ 70% estimated by NMR.
1H NMR (CDCl3, 200 MHz): d 7.26 (m, PhH, H5fur
,
22H); 6.31 (m, H3fur, Hf4ur, 4H); 4.40–4.10 (m, Cp,
2
3.51 (3d, JPH ¼ 10:4 Hz, CHP, 2H); 1.90 (large s, NH,
2
CH2Fur, 12H); 3.73 and 3.69 (2d, JPH ¼ 8:8 Hz, CHP,
2H); 1.47 (d, J ¼ 6:6 Hz, CHCH3, 6H); 1.26 and 1.24
(2t, J ¼ 7:0 Hz, CH2CH3, 12H). 31P NMR (CDCl3, 81
MHz): d 23.53, 22.40 and 23.14 (1:3:1).
2H); 2.05 (large s, NH, 2H). 31P NMR (CDCl3, 81
MHz): d 14.81 and 14.63 (1:1).
FAB-MS: m=z ¼ 868.3 [Mþ]; 634.2 [Mþ)HOP
(OPh)2]; 400.1 [Mþ)2 HOP(OPh)2]; 238.0 [Fc
(CHNH)2]; 93.1 [þOPh]; 81.1 [þCH2Fur]; 65.0 [Cp].
EI-MS: m=z ¼ 724.1 [Mþ]; 586.2 [Mþ)HOP(OEt)2];
448.2 [Mþ)2HOP(OEt)2]; 238.1 [Fc(CHNH)2]; 105.0
[þCH(CH3)Ph]; 65.0 [Cp].
Elemental analysis: Anal. Found: C, 60.01; H, 6.88;
N, 3.91. Calc. for C36H50FeN2O6P2: C, 59.67; H, 6.96;
N, 3.87%.
3.2.7. Tetraethyl 1,10-ferrocene-bis-(N-diphenylmethyla-
minomethanephosphonate) (3g)
Conversion rate ¼ 33% estimated by NMR.
1H NMR (CDCl3, 200 MHz): d 7.32 (m, PhH, 20H);
5.59 and 5.52 (2s, CHPh2, 2H); 4.37–3.90 (m, CH2CH3,
Cp, 16H); 3.77 and 3.76 (2d, 2JPH ¼ 15:0 Hz, CHP, 2H);
2.05 (large s, NH, 2H); 1.26 and 1.25 (2t, J ¼ 6:6 Hz,
CH2CH3, 12H). 31P NMR (CDCl3, 81 MHz): d 23.02
and 22.83 (1:1).
EI-MS: m=z ¼ 849.1 [Mþ]; 711.1 [Mþ)HOP(OEt)2];
573.2 [Mþ)2HOP(OCH2Ph)2]; 238.0 [Fc(CHNH)2];
167.1 [þCHPh2]; 65.0 [Cp].
3.2.11. Tetrabenzyl 1,10-ferrocene-bis-(N-N-(R)-a-meth-
ylbenzylaminomethanephosphonate) (3k)
Yield ¼ 0.22 g (45%).
1H NMR (CDCl3, 200 MHz): d 7.29 (m, PhH, 30H);
4.88 (m, OCH2Ph, 8H); 4.34, 4.16 and 4.05 (3quart,
J ¼ 6:8 Hz, 2H); 3.87 and 3.75 (2m, Cp, 8H); 3.80, 3.69
2
and 3.53 (3d, JPH ¼ 8:8 Hz, CHP, 2H); 2.03 (large s,
NH, 2H). 31P NMR (CDCl3, 81 MHz): d 24.15, 23.95
and 23.70 (1:3:1).
EI-MS: m=z ¼ 973.1 [Mþ]; 882.3 [Mþ)CH2Ph]; 448.2
[Mþ)2HOP(OCH2Ph)2]; 238.0 [Fc(CHNH)2]; 171.0
[þP(O)(OH)(OCH2Ph)]; 107.1 [þOCH2Ph]; 105.1
[þCH(CH3)Ph]; 65.0 [Cp].
3.2.8. Tetrabenzyl 1,10-ferrocene-bis-(N-diphenylmethyl-
aminomethanephosphonate) (3h)
Elemental analysis: Anal. Found: C, 69.35; H, 5.99;
N, 2.65. Calc. for C56H58FeN2O6P2: C, 69.14; H, 6.01;
N, 2.88%.
Yield ¼ 0.26 g (47%).
1H NMR (CDCl3, 200 MHz): d 7.27 (m, PhH, 40H);
5.57 and 5.49 (2s, CHPh2, 2H); 4.89 (m, OCH2Ph, 8H);
2
4.30–4.06 (m, Cp, 8H); 3.77 and 3.76 (2d, JPH ¼ 13:6
3.2.12. Tetraphenyl 1,10-ferrocene-bis-(N-N-(R)-a-meth-
ylbenzylaminomethanephosphonate) (3l)
Hz, CHP, 2H); 2.05 (large s, NH, 2H). 31P NMR
(CDCl3, 81 MHz): d 23.70 and 23.47 (3:2).
EI-MS: m=z ¼ 1097.1 [Mþ]; 572.2 [Mþ)2HOP
(OCH2Ph)2]; 238.0 [Fc(CHNH)2]; 171.0 [þP(O)(OH)
(OCH2Ph)]; 167.1 [þCHPh2]; 107.1 [þOCH2Ph]; 65.0
[Cp].
Conversion rate ¼ 74% estimated by NMR.
1H NMR (CDCl3, 200 MHz): d 7.25 (m, PhH, 30H);
4.36–3.94 (m, Cp, CHCH3, 10H); 3.73 and 3.69 (2d,
2JPH ¼ 8:8 Hz, CHP, 2H); 2.05 (large s, NH, 2H). 31P

1270
J. Lewkowski et al. / Journal of Organometallic Chemistry 689 (2004) 1265–1270
[17] P.D. Beer, J.E. Nation, M.E. Harman, M.B. Hursthouse, J.
Organomet. Chem. 441 (1992) 465.
NMR (CDCl3, 81 MHz): d 15.44, 15.37 and 15.27
(1:3:1).
FAB-MS: m=z ¼ 917.3 [Mþ]; 683.3 [Mþ)HOP-
(OPh)2]; 449.2 [Mþ)2HOP(OPh)2]; 238.0 [Fc(CHNH)2];
105.1 [þCH(CH3)Ph]; 93.1 [þOPh]; 65.0 [Cp].
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