Synthesis, X-ray structural determination and Moessbauer characterization of Schiff bases bearing ferrocene groups, their reduced analogues and related complexes

Article abstract of DOI:10.1016/S0020-1693(98)00413-7

[1+1], [1+2], [2+1] or [3+1] acyclic and [1+1] or [2+2] cyclic Schiff bases (L_AL_S), containing ferrocene moieties, have been prepared by reaction of formyl- or 1,1′-diformylferrocene and the appropriate amines. Formyl- and 1,1-diformylferrocene form respectively the acyclic [2+1] L_W and [2+2]_n L_Z compounds by reaction with 1,4-diaminomethylbenzene. Similar compounds (L_TL_V) have been obtained by condensation of aminomethylferrocene and 2,6-diformylpyridine, 2,6-diformyl-4-chlorophenol and 3-methoxy-2-hydroxybenzaldehyde. By reduction of these compounds with NaBH₄ the corresponding ferrocene-amine derivatives (L′) have been synthesized. All these compounds have been characterized by physico-chemical measurements (IR, NMR, Moessbauer spectroscopy and FAB mass spectrometry) and L_H, derived by the condensation of ferrocene-aldehyde and 1,5-diamino-3-oxa-pentane, also by an X-ray structural determination. The X-ray analysis of crystals of L_H, grown from a diethyl ether solution, shows that two independent molecules are present in the asymmetric unit; these two molecules are chemically equivalent with the ferrocenyl groups in the eclipsed form. The coordination ability of these compounds towards d metal ions as copper(II), nickel(II), platinum(II) and rhodium(III) was investigated; while the Schiff bases (L) may suffer hydrolysis, their reduced analogues (L′) form stable, well-defined complexes of the type M(L′)(Cl)_n (n=2, 3). The Moessbauer spectra of the prepared compounds show signals with δ at 0.44 and ΔE_Q 2.30 mm s^-1 for the Schiff bases L_AL_S and 0.52 and 2.40 mm s^-1 for the reduced analogues and hence may be diagnostic of the presence of Fe-CH=N- or Fe-CH₂-NH- groups. The signals with δ at 0.51-0.55 and ΔE_Q at 2.34-2.38 mm s^-1 for the Schiff bases L_TL_V, having Fe-CH₂-N=CH groups, resemble those of the reduced analogues.

Full text of DOI:10.1016/S0020-1693(98)00413-7

Inorganica Chimica Acta 287 (1999) 117–133
Synthesis, X-ray structural determination and Mo¨ssbauer
characterization of Schiff bases bearing ferrocene groups, their
reduced analogues and related complexesꢀ
E. Bullita a, U. Casellato a, F. Ossola a, P. Tomasin a, P.A. Vigato a,*, U. Russo b
a Istituto di Chimica e Tecnologie Inorganiche e dei Materiali A6anzati, Area della Ricerca Corso Stati Uniti 4, I-35127 Padua, Italy
b Dipartimento di Chimica Inorganica, Organometallica ed Analitica, Uni6ersita` di Pado6a Via Loredan 4, I-35100 Padua, Italy
Received 22 July 1998; accepted 9 November 1998
Abstract
[1+1], [1+2], [2+1] or [3+1] acyclic and [1+1] or [2+2] cyclic Schiff bases (LA···LS), containing ferrocene moieties, have
been prepared by reaction of formyl- or 1,1%-diformylferrocene and the appropriate amines. Formyl- and 1,1-diformylferrocene
form respectively the acyclic [2+1] LW and [2+2]n LZ compounds by reaction with 1,4-diaminomethylbenzene. Similar
compounds (LT···LV) have been obtained by condensation of aminomethylferrocene and 2,6-diformylpyridine, 2,6-diformyl-4-
chlorophenol and 3-methoxy-2-hydroxybenzaldehyde. By reduction of these compounds with NaBH4 the corresponding fer-
rocene–amine derivatives (L%) have been synthesized. All these compounds have been characterized by physico–chemical
measurements (IR, NMR, Mo¨ssbauer spectroscopy and FAB mass spectrometry) and LH, derived by the condensation of
ferrocene–aldehyde and 1,5-diamino-3-oxa-pentane, also by an X-ray structural determination. The X-ray analysis of crystals of
LH, grown from a diethyl ether solution, shows that two independent molecules are present in the asymmetric unit; these two
molecules are chemically equivalent with the ferrocenyl groups in the eclipsed form. The coordination ability of these compounds
towards d metal ions as copper(II), nickel(II), platinum(II) and rhodium(III) was investigated; while the Schiff bases (L) may
suffer hydrolysis, their reduced analogues (L%) form stable, well-defined complexes of the type M(L%)(Cl)n (n=2, 3). The
Mo¨ssbauer spectra of the prepared compounds show signals with l at 0.44 and DEQ 2.30 mm s−1 for the Schiff bases LA···LS
and 0.52 and 2.40 mm s−1 for the reduced analogues and hence may be diagnostic of the presence of Fe–CHꢀN– or
Fe–CH2–NH– groups. The signals with l at 0.51–0.55 and DEQ at 2.34–2.38 mm s−1 for the Schiff bases LT···LV, having
Fe–CH2–NꢀCH groups, resemble those of the reduced analogues. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Crystal structures; Ferrocene complexes; Schiff base complexes
multielectron redox mediators which could transfer sev-
eral electrons simultaneously at the same potential [4,5].
Compounds with ferrocene groups attached at the pe-
riphery of their coordinating moiety contain redox cen-
ters far enough from one another to have the same
potential and still close enough to provide all the
electrons at the same substrate site [4,5]. Their use as
ligands for suitable metal ions makes these receptors
quite good candidates as redox-catalytic systems capa-
ble of promoting redox reactions on a coordinate
substrate.
1. Introduction
Ferrocene containing compounds have been widely
studied owing to their potential in catalysis, material
science, molecular devices, hydrometallurgy, etc. [1–4].
Variously substituted ferrocene derivatives, bearing lig-
ating groups with different donor atoms, have been
proposed and successfully tested [5,6]. Several efforts
have been directed towards the design and synthesis of
ꢀ This article was partially presented at the 5th Meeting on Synthe-
ses and Methodologies in Inorganic Chemistry: New Compounds and
Materials, Bressanone, Italy, 2–7 October, 1994.
* Corresponding author. Tel.: +39-049-829 5962; fax: +39-049-
870 2911.
Macrocyclic and/or macroacyclic ligands containing
a redox-active center in close proximity to the coordi-
nation binding site are currently studied as molecular
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(98)00413-7

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E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
sensory devices [4–16]. These systems can electro-
chemically recognize the binding of any charged or
neutral inorganic or organic guest molecule, by either
interactions or communication via various bond link-
ages between the receptor site and the redox center
[4]. Systems bearing such reactive groups, based on
Schiff bases, exhibit appropriate physico–chemical
properties and can offer a valid chance to their use as
redox catalysts or as binding blocks for the prepara-
tion of molecular devices or as switching agents in
the cation transport. Selective separation of metal
ions from complex mixture is of paramount impor-
tance in the treatment of industrial wastes and by
products such as electron scrap, ashes of metallurgical
processes, effluent streams, etc. Specific extractants as
crown–ethers, cryptands, polyaza- or polyether-
macrocycles and other related derivatives are cur-
rently used for these separations.
ferrocene with the appropriate amine in alcohol or
acetonitrile solution (LA···LS), quite often followed
by a reduction of the resulting Schiff base with
NaBH4 (L% , L% , L%, L% , L% , L% ). Similar Schiff bases
have been obtained by reaction of aminomethylfer-
rocene with the appropriate formyl- or diformyl-
derivatives (LT···LV). Finally the acyclic discrete
[2+1] (Lw) or polymeric [2+2] (LZ) compounds have
been prepared by condensation of 1,4-diaminomethyl-
benzene respectively with formyl- or 1,1%-diformylfer-
rocene.
F
G
J
K
M
Q
More recently macrocyclic and/or macroacyclic
switching ligands have been proposed as different,
very promising alternative systems for the selective
recognition, transport and separation of metal ions
[5]. A chemical switching ligand is designed and syn-
thesized in such a way that complexing behaviour
and selectivity can be reversibly controlled by chang-
ing the pH, by photochemical or redox processes. In
the ferrocene-containing compounds, the key design
principle is that ferrocene has a readily accessible re-
dox ability such that neutral ferrocene can be easily
oxidized into ferrocenium cation. Therefore these sys-
tems can act as chemical switches [5].
Over the last few years, several Schiff bases con-
taining ferrocene groups have been prepared and their
coordination behaviour studied by means of different
physico–chemical measurements such as IR, NMR
and electrochemical data and their structure was de-
termined by single crystal X-ray diffractometric inves-
tigations. In these studies, Mo¨ssbauer spectroscopy
was also employed and revealed its important role for
a better understanding of the properties of the pre-
pared compounds [4–16].
Recently, we have undertaken studies aimed at the
design and synthesis of appropriate systems contain-
ing redox active center in close proximity to a host
binding site, capable to detect electrochemically the
complexation of any charged inorganic and organic
guest species, either through space electrostatic inter-
action, or via various bond linkages [16]. In particu-
lar we have prepared Schiff bases containing
ferrocene groups and studied their physico–chemical
and coordination properties together with their ability
to favour ion transfer at the liquid/liquid interface
[16].
In the present paper, we refer to the preparation of
a variety of cyclic or acyclic ferrocene-containing
compounds by condensation of formyl- or diformyl-

E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
119
1
was checked by elemental analyses, IR and H NMR
spectroscopy and FAB mass spectrometry.
In particular, the syntheses of 1,1%-diformylferrocene
were carried out in nitrogen-filled glove-boxes with the
rigorous exclusion of oxygen and moisture. In the
preparation of 1,1%-diformylferrocene, particular atten-
tion must be paid to the purity of DMF; in fact,
impurities in DMF cause the presence of by-products in
the final product (as unreacted ferrocene, formylfer-
rocene, etc.), which make the purification step by crys-
tallization from cyclohexane longer, thus lowering the
yield. The best DMF purification procedure turned out
to be the use of molecular sieve followed by distillation
under reduced pressure.
Also, the [2+2] Schiff base LH and the reduced
analogue LN% have been prepared following literature
procedure [11].
The elemental analyses of the prepared ligands and
complexes are reported in Table 1.
The yield is 25–40% for the Schiff bases, 50–55% for
the reduced analogues and 70–80% for the complexes.
The ligands melt with decomposition at the tempera-
ture reported below while the complexes decompose
above 300°C. FAB mass spectrometry evidences the
parent peak [M+H]+ at the appropriate m/z value for
all the prepared ligands, accompanied by the [M+
Na]+ peak especially for the polyamine derivatives. IR
and NMR data are reported and discussed in Section 3.
These compounds have been designed with the aim
to verify their coordination ability towards transition
metal ions, with respect to the presence of a progres-
sively increasing number of ferrocene units within the
coordination sites, the planar or 3-D geometry of the
ligands, the acyclic or cyclic coordinating systems con-
taining different donor atoms or groups, the distance of
the ferrocene groups from the coordination moieties,
the presence of conjugated systems, etc. Also, the func-
tionalization of these Schiff bases by the insertion of
crown–ether moieties was successfully tested.
Attention was devoted also to the chelating proper-
ties of these ferrocene derivatives towards transition
metal ions such as copper(II), nickel(II), palladium(II),
platinum(II) and rhodium(III). Preliminary data on
these systems have been presented already [16]. It was
verified that the Schiff bases can form unstable com-
plexes which suffer hydrolytic processes, with the conse-
quent formation of non-defined species. Only in some
cases the hydrolytic products have been identified. On
the contrary, well-defined and stable complexes have
been obtained with the reduced ligands (L%).
2.2. Schiff bases
2.2.1. Preparation of LA and LB
2-Aminomethyl-pyridine (2 mmol) dissolved in
CH3CN or MeOH (25 ml) was added to formylfer-
rocene (2 mmol) dissolved in 25 ml of the same solvent.
The red–brown solution was refluxed for 1 h, then
stirred at room temperature (r.t.) for a further 2 h and
finally reduced in volume. By addition of diethyl ether,
LA was obtained as a red–brown precipitate in a low
yield; it was washed with diethyl ether and dried in
vacuo (m.p.\300°C).
2. Experimental
2.1. Materials
LB was obtained as an oil by a similar procedure, by
reaction of equimolecular amounts of H2N(CH2)2-
S(C6H5) and formylferrocene. The red–brown reaction
solution was refluxed for 1 h and stirred at r.t. for 2 h,
then it was evaporated to dryness. The red–brown oil
obtained, soluble in almost all the organic solvents, was
treated three times with n-hexane and dried in vacuo.
The final product, obtained as a red–brown oil, was
dried in vacuo.
Formylferrocene, the amines H2NR [R=(CH2)2-
C6H4N; (CH2)2SC6H5; -benzo-5-crown-5], H2NRNH2
[R=(CH2)2; (CH2)3; (CH3)2CCH2; CH2C(CH3)2CH2;
CH2CH(OH)CH2; (CH2)2X(CH2)2 where X=NH,
NCH3, N(CH2)11CH3, O, S; (CH2)2O(CH2)2O(CH2)2],
tris-(2-aminoethyl)amine,
N,N%-bis-(3-aminopropyl)-
piperazine, 1,3-diaminomethylbenzene, 1,4-diamino-
methylbenzene, n-BuLi, the salts and the solvents were
commercial products (Aldrich) used without further
purification. Et2O and DMF were purified by standard
methods [17] and used immediately after distillation.
1,1%-Diformylferrocene [18] and aminomethylferrocene
[19] were prepared according to literature. Their purity
2.2.2. Preparation of LC–LJ
The appropriate polyamine (1 mmol) dissolved in
MeOH or CH3CN (25 ml) was added to a methanolic
or acetonitrile solution (25 ml) of ferrocenealdehyde (2
mmol). The red solution was refluxed for 1 h, then

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E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133

E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
121
Table 1
Elemental analyses of the prepared Schiff bases, their reduced analogues and related complexes
Compounds
Calc.
C
Found
C
H
N
S
H
N
S
LA
LC
LD
LE
LF · H2O
LG
LH
LI
LJ
67.13
65.03
65.62
61.44
58.89
63.68
62.94
62.25
64.89
63.79
62.90
58.76
59.18
59.76
62.35
63.02
65.96
68.40
62.27
64.72
62.15
67.07
68.40
5.30
5.87
6.11
5.37
5.70
6.13
5.68
5.96
6.80
5.76
5.71
6.53
5.67
6.63
6.83
7.81
5.53
5.45
4.70
5.24
5.76
5.44
5.45
9.21
67.12
64.57
65.75
61.98
58.46
63.26
61.91
62.29
64.46
64.20
62.99
58.61
59.40
59.25
62.00
63.11
66.37
68.21
62.35
64.65
62.36
67.28
68.38
5.37
5.53
5.83
5.10
5.22
6.14
5.56
6.07
6.79
6.10
5.30
6.49
5.32
7.84
6.50
8.05
5.79
5.66
4.68
5.38
5.85
5.32
5.62
8.87
5.83
5.67
5.97
5.28
8.25
5.64
5.18
9.46
7.63
12.22
3.43
9.86
10.25
10.10
12.78
5.13
7.98
4.48
7.81
3.81
5.21
7.98
5.37
5.24
5.39
5.45
8.12
5.46
5.20
9.33
6.05
6.15
LK
7.82
LL · 2H2O
LM · 2.5H2O
LN · 2H2O
LO · 3H2O · CH3CN
LP · 2H2O · CH3CN
LQ · MeOH
LR · H2O
LS · H2O
LT
12.46
3.52
10.36
10.69
10.30
12.43
5.22
7.81
4.55
7.63
3.92
5.48
7.86
LU · 0.5H2O
L
V · H2O
LW · 0.5H2O
LZ · 2H2O
LF%
LG% · H2O
LJ%
LM% · H2O
LQ%
60.49
61.04
64.45
60.68
64.39
6.24
7.01
7.43
6.18
8.34
5.43
7.91
9.39
10.11
13.65
6.21
60.02
61.30
64.32
60.60
64.42
6.46
6.95
7.52
6.75
8.55
5.37
8.00
9.45
9.81
13.24
6.30
Cu(LH)(ClO4)2 · H2O
Ni(LH)(ClO4)2 · H2O
Pt(LF)(Cl)2 · 3H2O
40.21
38.74
46.62
40.09
3.89
5.19
4.66
4.44
3.61
6.02
4.18
6.68
40.49
38.90
46.65
40.06
4.29
4.40
4.56
4.51
4.90
5.40
4.54
7.02
Ni(LK)(ClO4)2 · 2.5H2O
Cu(LG% )(Cl)2 · H2O
Ni(LG% )(Cl)2
49.01
50.45
45.47
40.61
46.41
39.26
48.86
48.95
51.33
50.44
48.21
48.76
45.49
40.42
5.02
5.48
5.28
4.16
5.24
4.30
5.46
5.79
6.19
6.34
5.94
5.14
6.59
5.85
6.35
6.54
4.08
3.51
4.16
3.52
5.84
5.85
7.48
7.35
7.03
7.29
9.65
8.57
49.31
50.02
45.34
41.31
46.27
39.02
48.52
48.52
51.51
50.65
48.41
48.60
45.38
40.37
5.63
5.45
4.86
4.41
5.16
4.98
5.15
5.15
6.36
6.85
6.63
4.71
6.80
6.12
6.29
6.42
3.95
4.07
4.11
5.29
6.42
6.42
7.34
7.12
7.04
7.09
10.21
8.72
Cu(LF% )(Cl)2 · 2H2O
Cu(LF% )(ClO4) · CHCl3
Ni(LF% )(Cl)2 · 2H2O
Pt(LF% )(Cl)2 · H2O
Cu(LK% )(Cl2) · 5H2O
Ni(LK% )(Cl2) · 5H2O
Cu(LJ%)(Cl2) · H2O
Ni(LJ%)(Cl2) · 2H2O
Pd(LJ%)(Cl2) · 1.5H2O
Pt(LJ%)(Cl2) · C6H5CN
Cu(LQ% )(Cl2) · 2H2O
Rh(LQ% )(Cl3) · 2H2O
4.67
4.01
4.32
3.73
4.03
3.18
stirred at r.t. for 2 h, and finally reduced in volume or
evaporated to dryness. The solution or the obtained
residue was treated with diethyl ether and precipitated
with n-pentane or n-hexane. The orange–red or ochre
compound so obtained was filtered, washed with n-hex-
ane or n-pentane and dried in vacuo. The compounds
have been obtained as orange–yellow or red–brown
solids (m.p.: LC=105–107°C, LD=105–108°C, LE=
107–109°C, LF=98–100°C, LG=94–95°C, LH=
110–111°C, LI=110–112°C, LJ=110–112°C).
2.2.3. Preparation of LK
Tris-2(aminoethyl)amine (1 mmol) in methanol (10
ml) was added to a methanolic solution of ferrocene-
aldehyde (3 mmol). The red solution was stirred for 1 h,
then allowed to stand for 1 h. The solution was evapo-

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E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
rated to dryness under reduced pressure and the ob-
tained oil was treated with diethyl ether (30 ml). The oil
slowly turned into a yellow–ochre solid that was
filtered, washed with diethyl ether and dried in vacuo
(m.p.=142–144°C).
2.2.8. Preparation of LT, LU and LV
Aminomethylferrocene (1 mmol) in methanol (25 ml)
was added to 2,6-diformyl-4-chlorophenol (0.5 mmol),
2,6-diformylpyridine (0.5 mmol) or 3-methoxy-2-hy-
droxybenzaldehyde (1 mmol) in methanol (50 ml), re-
spectively. The resulting orange–red solution was
refluxed for 2 h, reduced in volume and treated with
diethyl ether. The yellow precipitate obtained was col-
lected by filtration, washed with a methanol/diethyl
ether and dried in vacuo (m.p.: LT=165–168°C, LU=
124–125°C, LV=106–107°C).
2.2.4. Preparation of LL and LM
The appropriate amine (2 mmol) in CH3CN (30 ml)
was added dropwise under nitrogen to an acetonitrile
solution (30 ml) of 1,1%-diformylferrocene (1 mmol).
The dark-red solution was stirred in the dark for 4 h,
then evaporated to dryness, the obtained oil was dis-
solved in CHCl3. The addition of diethyl ether gave rise
to a dark-red precipitate, which was filtered, washed
with diethyl ether and dried in vacuo (m.p.: LL=142–
144°C, LM=122–125°C).
2.2.9. Preparation of LW and LZ
1,4-Diaminomethylbenzene (1 mmol) in chloroform
(25 ml) was added respectively to a chloroform solution
(25 ml) of formylferrocene (2 mmol) or 1,1%-diformyl-
ferrocene (1 mmol). The resulting dark red solution was
refluxed for 2 h, then reduced in volume and allowed to
stand. The obtained red–brown precipitate was col-
lected by filtration, washed with a diethyl ether solution
and dried in vacuo (m.p.: LW=110–111°C, LZ\
300°C).
2.2.5. Preparation of LO and LP
The appropriate diamine (2 mmol) in CH3CN (30 ml)
was added dropwise under nitrogen to a CH3CN solu-
tion (30 ml) of 1,1%-diformylferrocene (2 mmol). The
solution was stirred in the dark for 4 h, then reduced in
volume ($5 ml). The obtained precipitate was col-
lected by filtration and dried in vacuo.
2.3. Ferrocene containing amines
Additional product may be obtained from the
mother liquor. This was evaporated to dryness and the
residue treated with diethyl ether. The precipitate
obtained was filtered, washed with diethyl ether and
dried in vacuo (m.p.: LO=127–129°C, LP=125–
126°C).
2.3.1. Preparation of the reduced polyamines L% , L% ,
F
G
L%, L% , L%M and L%
J
K
Q
The appropriate Schiff base (2 mmol) in THF (LF,
LG, LJ, LK) or (50 ml) methanol (LM and LQ) was
treated, under a nitrogen atmosphere, with LiAlH4 or
NaBH4 (4–5 mmol), respectively. The resulting mixture
was refluxed for 30 min (when THF was used,
methanol (5 ml) was added). The resulting suspension
was clarified twice by filtration. The yellow solution
was evaporated to dryness and the obtained oil was
dissolved in CH2Cl2/isooctane. The yellow solid ob-
tained by slow evaporation of this solution was filtered,
washed with isooctane and dried in vacuo.
2.2.6. Preparation of LQ
The tetramine N,N%-bis-(3-aminopropyl)-piperazine
(1 mmol) in MeOH (50 ml) was added dropwise to a
methanol/chloroform solution (100 ml) of 1,1%-di-
formylferrocene (1 mmol). The dark-red solution was
refluxed for 30 min, then stirred at r.t. for 4 h. The
resulting solution was evaporated to dryness and the
obtained oil treated with diethyl ether (50 ml). The oil
slowly turned into a black–red solid which was filtered,
washed with diethyl ether and dried in vacuo (m.p.\
300°C).
Using this procedure L% was obtained as an oil. For
K
L% and L% , the residue was treated with water (50 ml)
J
M
and the yellow solid so obtained was filtered, washed
with water and dried in vacuo (m.p.: L% =60–62°C,
F
L% =35–38°C, L%J=50–52°C).
G
2.2.7. Preparation of LR and LS
2.4. Complexes with ferrocene containing polyamine
1,3- or 1,4-diaminomethylbenzene (1 mmol) in chlo-
roform (25 ml) was added to a chloroform solution (50
ml) of formylferrocene (2 mmol) or 1,1%-diformylfer-
rocene (1 mmol), respectively. The resulting orange–red
solution was refluxed for 2 h, then evaporated to
dryness. The residue was dissolved in CHCl3 (10 ml)
and allowed to stand overnight. The yellow–orange
precipitate obtained by addition of diethyl ether was
collected by filtration, washed twice with diethyl ether
and dried in vacuo (m.p.: LR=115–117°C, LS=117–
118°C).
2.4.1. Preparation of M(L%)(Cl)n (M=Cu2+, Ni2+
Pd2+, Pt2+, Rh3+, L%=L% , L% , L%, L% L% , n=2, 3)
,
F
G
J
K
Q
The appropriate metal chloride hydrate (CuCl2 ·
4H2O, NiCl2 · 4H2O or RhCl3 · 3H2O) or complex
(Pt(C6H5CN)2Cl2 or Pd(C6H5CN)2Cl2) (1 mmol) in
methanol (50 ml) was added dropwise to a methanolic
solution (50 ml) of the appropriate ferrocene containing
polyamine (L%) (1 mmol). The solution was stirred for 4
h, then reduced in volume and allowed to stand. The
precipitate obtained by slow evaporation of this solu-

E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
123
Table 3
tion or by addition of diethyl ether was collected by
filtration, washed with diethyl ether and dried in vacuo.
Fractional coordinates with equivalent isotropic thermal parameters
2
˚
(A )
a
2.5. X-ray crystallography
Atom
x
y
z
Ueq
Fe(1)
Fe(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10) −0.0215(4)
C(11)
N(1)
C(12)
C(13)
O(1)
C(14)
C(15)
N(2)
C(16)
C(18)
C(19)
C(20)
C(21)
C(17)
C(22)
C(23)
C(24)
C(25)
C(26)
Fe(3)
Fe(4)
C(27) −0.2409(5)
C(28) −0.1611(5)
C(29) −0.2016(5)
C(30) −0.3065(5)
C(31) −0.3308(5)
C(32) −0.4270(4)
C(33) −0.5191(4)
C(34) −0.4974(4)
C(35) −0.3920(4)
C(36) −0.3485(4)
C(37)
N(3)
C(38)
C(39)
O(2)
C(40)
C(41)
N(4)
C(42)
C(44)
C(45)
C(46)
C(47)
C(43)
C(48)
C(49)
C(50)
C(51)
C(52)
−0.03875(8)
0.21236(8)
−0.0109(7)
−0.0794(7)
−0.0030(7)
0.1128(7)
0.67040(6)
0.85583(6)
0.6183(5)
0.5375(5)
0.5281(5)
0.6032(5)
0.6589(5)
0.7770(4)
0.6999(4)
0.6967(4)
0.7719(4)
0.8215(4)
0.9002(4)
0.9431(4)
1.0232(4)
1.0001(5)
0.9119(3)
0.8898(5)
0.7909(5)
0.8038(4)
0.7516(4)
0.8271(3)
0.8127(3)
0.7362(3)
0.7033(3)
0.7595(3)
0.9385(4)
1.0041(4)
0.9895(4)
0.9149(4)
0.8834(4)
0.60143(6)
0.67431(7)
0.7149(3)
0.6579(3)
0.5521(3)
0.5437(3)
0.6443(3)
0.6728(2)
0.6046(2)
0.5029(2)
0.5082(2)
0.6132(2)
0.6483(5)
0.7360(5)
0.7627(6)
0.8588(6)
0.8894(4)
0.9847(6)
1.0190(5)
0.9508(5)
0.9011(5)
0.7665(4)
0.7005(4)
0.7194(4)
0.7970(4)
0.8261(4)
0.6564(5)
0.6294(5)
0.5488(5)
0.5261(5)
0.5925(5)
0.76155(6)
0.41820(5)
0.6466(3)
0.6938(3)
0.7709(3)
0.7713(3)
0.6944(3)
0.7368(3)
0.7887(3)
0.8655(3)
0.8611(3)
0.7815(3)
0.7493(4)
0.7948(3)
0.7571(4)
0.7652(4)
0.7139(3)
0.7169(4)
0.6686(4)
0.5778(3)
0.5455(4)
0.3955(3)
0.3191(3)
0.3334(3)
0.4186(3)
0.4569(3)
0.5240(2)
0.4591(2)
0.3870(2)
0.4074(2)
0.4921(2)
1.37292(5)
0.01102(6)
0.4541(3)
0.4210(3)
0.4431(3)
0.4897(3)
0.4965(3)
0.2774(3)
0.3199(3)
0.3150(3)
0.2694(3)
0.2461(3)
0.1974(4)
0.1651(4)
0.1174(5)
0.1462(6)
0.0956(3)
0.1222(6)
0.0614(5)
0.0617(4)
0.0486(3)
0.0449(3)
0.095(5)
0.097(4)
0.081(4)
0.072(3)
0.080(4)
0.067(3)
0.075(3)
0.071(3)
0.060(3)
0.050(2)
0.049(2)
0.051(2)
0.053(2)
0.058(3)
0.055(2)
0.058(3)
0.061(3)
0.054(2)
0.050(3)
0.051(2)
0.057(3)
0.060(3)
0.054(2)
0.049(2)
0.059(3)
0.061(3)
0.064(3)
0.061(3)
0.059(3)
0.0438(3)
0.0573(4)
0.070(3)
0.070(3)
0.066(3)
0.066(3)
0.073(3)
0.051(2)
0.054(2)
0.056(3)
0.053(2)
0.052(3)
0.059(3)
0.073(3)
0.085(4)
0.086(4)
0.081(2)
0.086(4)
0.077(3)
0.071(3)
0.062(3)
0.064(3)
0.079(4)
0.079(4)
0.064(3)
0.058(3)
0.095(4)
0.083(4)
0.095(4)
0.111(5)
0.110(4)
Data on crystals of LH, grown by slow evaporation
of a diethyl ether solution of the compound, were
collected at 298 K by a Philips PW 1100 (FEBO
System) four-circle diffractometer by using graphite-
˚
monochromated Mo Ka X-radiation (u=0.71069 A)
0.1079(7)
and the ꢀ/2q scan method. The structure was solved by
using heavy-atom methods with the SHELX86 program
[20] and refined by full-matrix least-squares methods
using the SHELXL package [21]. All non-hydrogen
atoms were refined anisotropically and the hydrogen
atoms were included in geometric positions. Crystal and
intensity data for the compound are reported in Table
2, atomic positional parameters with estimated stan-
dard deviations are listed in Table 3, and selected bond
distances and angles are reported in Table 4.
−0.1415(4)
−0.2068(4)
−0.1271(4)
−0.0126(4)
0.0756(6)
0.1756(5)
0.2674(6)
0.3964(6)
0.3939(4)
0.5152(6)
0.5043(6)
0.4749(5)
0.3696(6)
0.3824(3)
0.2984(3)
0.1890(3)
0.2053(3)
0.3248(3)
0.2023(4)
0.2527(4)
0.1604(4)
0.0528(4)
0.0788(4)
−0.34238(8)
0.36124(9)
2.6. Physico–chemical measurements
IR spectra were recorded as KBr pellets on a
1
Mattson FTIR 3000 spectrometer. H and 13C NMR
spectra were recorded at 200.132 MHz on a Bruker
AC200 spectrometer equipped with an Aspect 3000
computer at r.t. Some of the signals were assigned by
Table 2
Crystal and intensity data for LH
Compound
LH
Formula
C26H28N2OFe2
496.2
Formula weight
Cell parameters
˚
a (A)
10.992(4)
13.207(6)
15.909(6)
89.18(4)
96.78(4)
102.98(3)
2220(1)
1.48
˚
b (A)
˚
c (A)
0.7643(6)
0.7874(6)
0.8994(8)
0.9785(8)
1.0800(5)
1.1600(8)
1.2557(7)
1.3436(6)
1.3340(6)
0.3973(4)
0.4842(4)
0.5525(4)
0.5079(4)
0.4120(4)
0.1976(6)
0.2971(6)
0.3372(6)
0.2626(6)
0.1763(6)
h (°)
i (°)
k (°)
3
˚
Cell volume (A )
Dcalc. (g cm−3
F(000) (e)
System
)
1031
triclinic
¯
Space group
Z
P1 (no. 2)
−0.0051(5)
−0.0929(2)
−0.0825(2)
−0.0005(2)
0.0397(2)
−0.0174(2)
0.0708(5)
0.1259(5)
4 (2 independent molecules
in the asymmetric unit)
12.6
Absorption v (cm−1
(Mo Ka)
)
Data collected (2q limits)
Data with I\3|(I)
No. of parameters
(observed per parameter)
Discrepancy factor R
GOF
4273 (5–55°)
4044
487 (8.3)
0.0863(5)
0.0067(5)
−0.0029(5)
0.040
1.602
0.019
0.52
Highest shift (e.s.d.)
a Ueq is defined as one third of the trace of the orthogonalized Uij
tensor.
−3
˚
Highest map residual (e A
)

124
E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
Table 4 (continued)
Table 4
˚
Selected bond lengths (A) and angles (°) for LF
C(2)–Fe(1)–C(4)
C(1)–Fe(1)–C(10)
C(1)–Fe(1)–C(8)
C(1)–Fe(1)–C(6)
C(1)–Fe(1)–C(4)
C(1)–Fe(1)–C(2)
C(24)–Fe(2)–C(26)
C(23)–Fe(2)–C(26)
C(23)–Fe(2)–C(24)
C(22)–Fe(2)–C(25)
C(22)–Fe(2)–C(23)
C(17)–Fe(2)–C(25) 157.3(2)
C(17)–Fe(2)–C(23) 121.2(2)
C(21)–Fe(2)–C(26) 108.1(3)
C(21)–Fe(2)–C(24) 158.2(2)
C(21)–Fe(2)–C(22) 123.3(2)
C(20)–Fe(2)–C(26) 126.4(3)
C(20)–Fe(2)–C(24) 122.4(2)
C(20)–Fe(2)–C(22) 161.6(3)
C(20)–Fe(2)–C(21)
C(19)–Fe(2)–C(25) 126.3(2)
C(19)–Fe(2)–C(23) 120.6(2)
C(19)–Fe(2)–C(17)
C(19)–Fe(2)–C(20)
C(18)–Fe(2)–C(25) 161.2(2)
C(18)–Fe(2)–C(23) 105.1(3)
C(18)–Fe(2)–C(17)
C(18)–Fe(2)–C(20)
Fe(1)–C(1)–C(5)
C(2)–C(1)–C(5)
C(1)–C(2)–C(3)
Fe(1)–C(3)–C(2)
Fe(1)–C(3)–C(4)
C(3)–C(4)–C(5)
C(1)–C(5)–C(4)
Fe(1)–C(5)–C(1)
Fe(1)–C(6)–C(7)
69.2(3)
120.0(3)
161.2(3)
105.9(2)
68.5(3)
41.0(3)
68.4(2)
68.5(2)
41.4(2)
68.2(2)
41.0(2)
C(2)–Fe(1)–C(3)
C(1)–Fe(1)–C(9)
C(1)–Fe(1)–C(7)
C(1)–Fe(1)–C(5)
C(1)–Fe(1)–C(3)
C(25)–Fe(2)–C(26)
C(24)–Fe(2)–C(25)
C(23)–Fe(2)–C(25)
C(22)–Fe(2)–C(26)
C(22)–Fe(2)–C(24)
C(17)–Fe(2)–C(26) 120.9(2)
C(17)–Fe(2)–C(24) 159.1(3)
C(17)–Fe(2)–C(22) 105.2(2)
C(21)–Fe(2)–C(25) 122.6(3)
C(21)–Fe(2)–C(23) 159.3(2)
41.5(3)
156.5(3)
124.1(3)
40.5(3)
69.2(3)
40.3(2)
40.9(2)
68.9(3)
40.3(2)
69.0(2)
˚
Bond length (A)
Fe(1)–C(1)
Fe(1)–C(3)
Fe(1)–C(5)
Fe(1)–C(7)
Fe(1)–C(9)
Fe(2)–C(18)
Fe(2)–C(20)
Fe(2)–C(17)
Fe(2)–C(23)
Fe(2)–C(25)
C(1)–C(2)
2.043(6)
2.003(7)
2.061(7)
2.054(5)
2.041(5)
2.050(4)
2.045(4)
2.002(4)
2.008(5)
2.052(5)
1.420(8)
1.420(8)
1.420(7)
1.420(6)
1.420(6)
1.444(7)
1.460(8)
1.425(8)
1.50(1)
1.255(7)
1.420(6)
1.420(5)
1.420(5)
1.420(6)
1.420(6)
2.062(5)
2.069(5)
2.016(5)
2.066(8)
2.010(6)
1.420(8)
1.420(6)
1.420(6)
1.420(6)
1.420(7)
1.246(9)
1.41(1)
Fe(1)–C(2)
Fe(1)–C(4)
Fe(1)–C(6)
Fe(1)–C(8)
Fe(1)–C(10)
Fe(2)–C(19)
Fe(2)–C(21)
Fe(2)–C(22)
Fe(2)–C(24)
Fe(2)–C(26)
C(1)–C(5)
2.007(6)
2.037(8)
1.997(5)
2.081(5)
1.988(5)
2.076(5)
1.999(4)
2.047(5)
2.011(5)
2.073(5)
1.420(9)
1.420(9)
1.420(6)
1.420(6)
1.420(6)
1.258(7)
1.50(1)
1.414(8)
1.458(8)
1.447(8)
1.420(6)
1.420(6)
1.420(6)
1.420(5)
1.420(5)
2.094(5)
2.021(5)
2.088(7)
2.017(7)
2.054(6)
1.420(7)
1.420(8)
1.420(6)
1.420(5)
1.420(5)
1.49(1)
C(2)–C(3)
C(4)–C(5)
C(6)–C(10)
C(8)–C(9)
C(3)–C(4)
C(6)–C(7)
C(7)–C(8)
C(21)–Fe(2)–C(17)
C(20)–Fe(2)–C(25) 109.8(2)
C(20)–Fe(2)–C(23) 157.0(2)
41.6(2)
C(9)–C(10)
C(11)–N(1)
C(12)–C(13)
O(1)–C(14)
C(15)–N(2)
C(16)–C(17)
C(18)–C(17)
C(20)–C(21)
C(22)–C(23)
C(23)–C(24)
C(25)–C(26)
Fe(4)–C(45)
Fe(4)–C(47)
Fe(4)–C(48)
Fe(4)–C(50)
Fe(4)–C(52)
C(27)–C(31)
C(29)–C(30)
C(32)–C(33)
C(33)–C(34)
C(35)–C(36)
N(3)–C(38)
C(39)–O(2)
C(40)–C(41)
N(4)–C(42)
C(44)–C(43)
C(46)–C(47)
C(48)–C(49)
C(49)–C(50)
C(51)–C(52)
C(10)–C(11)
N(1)–C(12)
C(13)–O(1)
C(14)–C(15)
N(2)–C(16)
C(18)–C(19)
C(19)–C(20)
C(21)–C(17)
C(22)–C(26)
C(24)–C(25)
Fe(4)–C(44)
Fe(4)–C(46)
Fe(4)–C(43)
Fe(4)–C(49)
Fe(4)–C(51)
C(27)–C(28)
C(28)–C(29)
C(30)–C(31)
C(32)–C(36)
C(34)–C(35)
C(37)–N(3)
C(38)–C(39)
O(2)–C(40)
C(41)–N(4)
C(44)–C(45)
C(45)–C(46)
C(47)–C(43)
C(48)–C(52)
C(50)–C(51)
C(20)–Fe(2)–C(17)
69.2(2)
41.1(2)
C(19)–Fe(2)–C(26) 163.0(2)
C(19)–Fe(2)–C(24) 108.0(2)
C(19)–Fe(2)–C(22) 155.6(3)
68.6(2)
40.3(2)
C(19)–Fe(2)–C(21)
68.6(2)
C(18)–Fe(2)–C(26) 155.8(2)
C(18)–Fe(2)–C(24) 123.1(3)
C(18)–Fe(2)–C(22) 119.7(3)
41.0(2)
68.3(2)
70.4(3)
108.0(5)
108.0(6)
69.4(4)
70.7(5)
108.0(6)
108.0(6)
69.1(4)
71.7(4)
C(18)–Fe(2)–C(21)
C(18)–Fe(2)–C(19)
Fe(1)–C(1)–C(2)
Fe(1)–C(2)–C(1)
Fe(1)–C(2)–C(3)
C(2)–C(3)–C(4)
Fe(1)–C(4)–C(3)
Fe(1)–C(4)–C(5)
Fe(1)–C(5)–C(4)
Fe(1)–C(6)–C(10)
C(7)–C(6)–C(10)
69.1(2)
40.3(2)
68.1(3)
70.8(4)
69.1(4)
108.0(5)
68.2(5)
70.6(4)
68.8(4)
68.8(3)
108.0(4)
1.43(1)
1.50(1)
1.24(1)
1.420(6)
1.420(8)
1.420(9)
1.42(1)
1.401(8)
1.46(1)
1.420(8)
1.420(5)
1.420(7)
1.42(1)
the spin decoupling technique. All the examined sam-
ples were dissolved in CDCl3 that was used also as an
internal reference.
The homogeneity of the ligands containing iron and
sulfur or of the complexes was checked by using a
Philips XL40 model scanning electron microscope
equipped with an EDAX PV99 X-ray energy dispersive
spectrometer. Metal or iron:sulfur ratios were deter-
mined by energy dispersive X-ray spectrometry (EDX)
[22].
1.42(1)
1.42(1)
Bond angle (°)
C(9)–Fe(1)–C(10)
C(8)–Fe(1)–C(9)
C(7)–Fe(1)–C(9)
C(6)–Fe(1)–C(10)
C(6)–Fe(1)–C(8)
C(5)–Fe(1)–C(10)
C(5)–Fe(1)–C(8)
C(5)–Fe(1)–C(6)
C(4)–Fe(1)–C(9)
C(4)–Fe(1)–C(7)
C(4)–Fe(1)–C(5)
C(3)–Fe(1)–C(9)
C(3)–Fe(1)–C(7)
C(3)–Fe(1)–C(5)
C(2)–Fe(1)–C(10)
C(2)–Fe(1)–C(8)
C(2)–Fe(1)–C(6)
41.2(2)
40.3(2)
68.2(2)
41.8(2)
68.6(2)
105.8(3)
157.6(2)
122.7(2)
107.4(3)
158.2(2)
40.5(3)
124.0(2)
122.2(3)
68.8(3)
C(8)–Fe(1)–C(10)
C(7)–Fe(1)–C(10)
C(7)–Fe(1)–C(8)
C(6)–Fe(1)–C(9)
C(6)–Fe(1)–C(7)
C(5)–Fe(1)–C(9)
C(5)–Fe(1)–C(7)
C(4)–Fe(1)–C(10)
C(4)–Fe(1)–C(8)
C(4)–Fe(1)–C(6)
C(3)–Fe(1)–C(10)
C(3)–Fe(1)–C(8)
C(3)–Fe(1)–C(6)
C(3)–Fe(1)–C(4)
C(2)–Fe(1)–C(9)
C(2)–Fe(1)–C(7)
C(2)–Fe(1)–C(5)
68.7(2)
69.2(3)
40.2(2)
69.4(2)
41.0(2)
121.5(3)
160.2(2)
122.6(3)
122.8(2)
159.6(3)
160.1(3)
108.5(2)
157.2(3)
41.1(3)
The solvent content (H2O or MeOH) was evaluated
by thermal analysis curves by using a Netzsch STA 429
thermoanalytical equipment. The tests were performed
in a nitrogen atmosphere (flux rate 250 ml min−1
;
heating rate 5°C min−1) and in air under the same
conditions. Neutral alumina (Carlo Erba product) was
used as reference material.
All mass spectrometric measurements were per-
formed on a VG ZAB 2F instrument (VG Analytical
Ltd.) operating in electron impact (EI) (70 eV, 200 mA,
156.2(2)
124.9(3)
120.3(3)
161.2(2)
107.6(3)
68.8(3)
(continued)

E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
125
Scheme 1.
ion source temperature 200°C) and fast atom bombard-
ment (FAB) (8 KeV Xe atom bombarding a thioglyc-
erol/acetic acid solution of the sample) conditions [23].
Mo¨ssbauer spectra were obtained at 80 K on a
conventional constant-acceleration spectrometer, which
utilizes a room-temperature rhodium matrix cobalt-57
source. The spectra were fitted to Lorentzian line
shapes by using a standard least-squares computer min-
imization technique [24].
mamide. As reported in Section 2, particular care must
be devoted to the purity of dimethylformamide to avoid
the formation of by-products. Formyl- and diformylfer-
rocene are respectively yellow and dark red solids, very
soluble in the common organic solvents that can be
recrystallized from hydrocarbons.
The acyclic Schiff bases LA···LK bearing a progres-
sively increasing number of ferrocene groups have been
prepared by condensation in acetonitrile or methanol of
the appropriate amine and formylferrocene according
to Scheme 1.
3. Results and discussion
The synthetic pathways in Scheme 1 show that
formylferrocene forms, with amines bearing only one
NH2 group (as 2-aminomethyl-pyridine or 2-amino-
ethylthiophenol), the [1+1] condensation products LA
and LB while a [2+1] condensation reaction takes
place when formylferrocene is reacted with the diamines
H2N–R–NH2 in a 2:1 molar ratio. By this procedure
LC–LJ have been obtained. Finally a [3+1] condensa-
tion, with the formation of LK, occurs when the amine
precursor tris-(2-aminoethyl)amine is condensed with
formylferrocene in a 1:3 molar ratio. By a similar
synthetic procedure the macroacyclic (LL and LM)
or macrocyclic compounds (LO, LP, LQ and LS) of
Scheme 2 have been obtained by condensation of 1,1%-
3.1. Schiff bases bearing ferrocene groups
Formylferrocene and 1,1%-diformylferrocene are ex-
cellent precursors in the preparation of acyclic and
cyclic Schiff bases containing redox active groups in
close proximity to the coordinating moieties. While
formylferrocene is commercially available, 1,1%-di-
formylferrocene must be prepared, following literature
procedure [18], by reaction of ferrocene with n-BuLi in
the presence of N,N-tetramethylethylenediamine and
converting the resulting 1,1%-dilithiumferrocene com-
pound into the diformyl-derivatives with dimethylfor-

126
E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
Scheme 2.
diformylferrocene and the appropriate amine in a 1:2
and 1:1 molar ratio, respectively. While for the acyclic
complexes only a [1+2] condensation occurs, a [2+2]
or [1+1] cyclization may take place when polyamines of
the type H2N–R–NH2 are used, the type of cyclization
strongly depending on the nature of R. In fact it was
already reported that, when 1,1%-diformylferrocene is
reacted with diamines as 1,2-diaminoethane (or 1,3-di-
aminopropane), [2+2] cyclic compounds as LN are
obtained [11], while with amines containing longer
aliphatic chains the [1+1] cyclic compounds are formed
[25]. Thus, using the tetramine N,N%-bis-(3-amino-
propyl)-piperazine, the [1+1] cyclic compound LQ was
found while, when 1,2-diamino-2-methylpropane or 1,3-
diamino-2,2-dimethylpropane or 1,3-diamino-methyl-
benzene are the diamine precursors, respectively, the
[2+2] macroacycles LO, LP and LS are formed.
In these Schiff bases (LA···LS) the ferrocene groups are
in close proximity to the coordinating site; this can cause
hydrolysis when reacted with metal ions. In order to
avoid this behaviour and maintain the coordinating
ability of the Schiff base, aminomethylferrocene was
prepared [18] and reacted with the appropriate formyl-
or diformyl-precursors. In this amine precursor and
hence in the related Schiff base derivatives a CH2 spacer
was inserted between the amine or imine and the fer-
rocene groups. Aminomethylferrocene was prepared by
reaction of {[tris-(methylammonium)methyl]ferrocene}-
iodide with sodium azide followed by the reduction of
the resulting ferrocene azide by means of NaBH4 [19].
Very recently it has been conveniently prepared by
initially converting formylferrocene into its oxime by
condensation with hydroxylamine followed by the re-
duction of the resulting product with LiAlH4 in THF
[26]. Aminomethylferrocene is very soluble in the com-
mon organic solvents; its IR spectrum shows the charac-
teristic (NH2 at 3290 and 3250 cm−1). The condensation
reaction of aminomethylferrocene respectively with 2,6-
diformylpyridine, 2,6-diformyl-4-chlorophenol in a 2:1
molar ratio and with 3-methoxy-2-hydroxybenzaldehyde
in a 1:1 molar ratio produces the acyclic compounds
LT···LV as shown in Scheme 3.
Finally, 1,4-diaminomethylbenzene was used as amine
precursor in the condensation reaction with formylfer-
rocene and 1,1%-diformylferrocene to yield respectively
the [2+1] condensation product (LW) and the [2+2]n
oligomeric or polymeric species (LZ) (Scheme 4a). It
must be noted that 1,3-diaminoxylylbenzene reacts with
the 1,1%-diformylferrocene to form the cyclic [2+2]
compound LS and not the polymeric [2+2]n. This was
confirmed by mass spectra where the parent peak due
to the cyclic species has been obtained. Of course,
formylferrocene, by reaction with 1,3-diaminoxylylben-
zene, forms the [2+1] acyclic compound LR (Scheme
4b).

E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
127
Scheme 3.
The prepared compounds LA···LZ are orange–red
solids (only LB is a red–brown oil), very soluble in the
most common organic solvents including hydrocarbons.
In the compounds containing sulfur, the homogeneity
and the correct 2:1 (LF) or 1:1 (LB) Fe:S ratio was
ascertained by SEM and EDX analyses. In addition, 1H
NMR, IR and mass spectrometry agree with the formu-
Furthermore, the absence in the IR spectra of the
Schiff bases of the w CꢀO, which lies in the formylfer-
rocene at $1680 cm−1, and the simultaneous presence
of a strong peak at 1650–1635 cm−1 due to w CꢀN add
further evidences that the condensation reaction was
successful. Moreover, additional IR peaks, due to spe-
cific groups present in the Schiff bases, are easily de-
tectable; for example, in the compounds containing
etheric or crown–ether moieties (LH, LJ and LN),
strong absorptions at 1310 cm−1 due to w C–O–C
group have been observed and in those containing
pyridine (LA and LM) characteristic peaks at 1600 and
735 cm−1 have been detected.
Mass spectrometry has proved to be a particularly
valid analytical tool for the characterization of these
systems. In the FAB mass spectra of almost all the
prepared compounds, the parent peak [M+H]+ was
detected at the appropriate m/z value; moreover, the
fragmentation patterns are consistent with the proposed
structure. A specific and detailed mass spectrometry
investigation on some of the prepared compounds was
carried out and published elsewhere [16].
1
lation proposed. In particular in the H NMR spectra
in CDCl3 a characteristic peak at 8.15–8.07 ppm due to
the CHꢀN iminic protons can be detected; it must be
noted that the peaks due to the formyl protons CHꢀO
lie at 9.93 and 9.91 ppm, respectively, in the formyl-
and diformylferrocene derivatives. However, they com-
pletely disappear in the Schiff base derivatives, suggest-
ing that the designed condensation takes place. As
significant examples of the prepared Schiff bases, the
1H NMR spectra of LF, LG and LJ are discussed in
1
detail. The H NMR spectrum of LF shows the iminic
protons at 8.12 ppm, the cyclopentadienyl protons at
4.60, 4.34 and 4.18 ppm and the ethylenic protons as
coupled triplets at 3.66 and 2.84 ppm. For LG the
iminic protons lie at 8.11 ppm, the cyclopentadienyl
protons at 4.60, 4.33 and 4.15 ppm, the ethylenic
protons at 3.58 and 2.71 ppm, and the methylenic
The coordination properties of these compounds
have also been studied; when reacted with transition
metal salts (i.e. copper(II), or nickel(II) chloride, ni-
trate, acetate or perchlorate), they form complexes that,
according to elemental analyses, IR, SEM and EDX
investigations, may be formulated as M(L)(X)2 (L=
LD···LK) (X=Cl−, ClO4−). For instance, the com-
1
protons at 2.38 ppm. Similarly in the H NMR spec-
trum of LJ, the peaks due to the iminic protons occur at
8.08 ppm, the cyclopentadienyl protons at 4.60, 4.32
and 4.14 ppm and the ethylenic protons at 3.40, 2.49,
2.39 and 1.81 ppm, respectively.

128
E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
Scheme 4.
plexes Pd(LF)(Cl)2, Cu(LH)(H2O)(ClO4)2, Ni(LI)-
(ClO4)2 · 4H2O and Ni(LK)(ClO4)2 have been isolated: a
correct elemental analysis and a metal:iron:chloride ra-
tio of 1:2:2 for the first three complexes and 1:3:2 for
the fourth complex was ascertained by SEM and EDX
investigations, respectively. When dissolved for crystal-
lization, they quite often suffer additional reactions.
These complexes are not very stable in solution and
easily give rise to hydrolytic products with the conse-
quent formation of complexes apparently of the type
base complex; this may explain why we were only able
to isolate a few complexes with the prepared Schiff
bases. The formulation of these hydrolytic compounds
is proposed on the basis of their elemental analyses,
SEM and EDX investigations and IR spectroscopy.
Thus, during the experimental procedure to obtain
purify or recrystallize the di- or tri-imine complexes,
the monoimine Cu(LF–NH2)2(CH3COO)2H2O, Ni(LG–
NH2)2(CH3COO)2 · 2H2O, Ni(LH–NH2)2(ClO4)2 · 2H2O
and the diamine derivatives Ni(LK–NH2)(ClO4)2 ·
4.5H2O and Pt(LK–NH2)(Cl)2 have been isolated.
Again the atomic ratios and the homogeneity of the
–
–
M(L NH2)X2 or M(LKNH2)X2. Quite often the hy-
drolytic process occurs before the isolation of the Schiff

E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
129
complexes as determined by SEM and EDX investiga-
tions support the proposed formulations.
ment of the etheric–iminic chain that connects the
ferrocenyl groups. In molecule B (containing Fe(3) and
Fe(4)), the chain is more elongated than that in
molecule
A
(containing Fe(1) and Fe(2)). The
˚
Fe(1)···Fe(2) distance is, in fact, 6.592(2) A while the
Fe(3)···Fe(4) distance is 10.008(2) A. The N–C–C–O
˚
torsion angles are very similar (around 968–69°)
apart from the case of the N(3)–C(38)–C(39)–O(2)
chain that presents a torsion angle of −174.8°.
All the distances and angles are normal. The iminic
˚
CꢀN distances range between 1.27 and 1.28 A, while
˚
the etheric C–O bond distances are in the 1.40–1.43 A
range. The ferrocenyl groups are in the eclipsed form
and no relevant intra- or intermolecular interactions are
present.
The crystal packing (Fig. 2) shows a columnar ar-
rangement of the molecules along the a-direction.
The presence in the IR spectra of these complexes of
bands at about 3300–3200 cm−1 due to w NH2, sug-
gests that the ligand has suffered hydrolytic process
while the strong IR band at 1650–1640 cm−1, due to w
CꢀN, confirms the presence of iminic bonds. Finally,
the absorptions due to the presence of the counter-
anions are clearly detectable; these groups seem to be
coordinated in the case of the chloride, w M–Cl at
about 330–315 cm−1, and ionic in the case of the
perchlorate (a band centered at 1150 cm−1 due to w
ClO4−).
3.3. Ferrocene containing amines
In order to overcome the hydrolytic problems en-
countered especially during the complexation reactions,
the Schiff bases have been reduced to the corresponding
acyclic or cyclic polyamines by reaction with NaBH4 in
THF; the same reactions have also been successfully
carried out in methanol and water (Schemes 1 and 2).
The obtained compounds are generally yellow solids
stable both in air and solution. They do not suffer
hydrolysis and give rise, when treated with a variety of
transition metal salts such as copper(II), nickel(II),
palladium(II) and rhodium(III), to stable, well-defined
complexes.
3.2. The structure of LH
In order to confirm that the condensation reactions
proposed above really occur, an X-ray structural deter-
mination of LF was carried out. Yellow–ochre crystals
of the Schiff base, suitable for diffractometric investiga-
tion, were obtained by slow evaporation of a diethyl
ether solution of the compound.
Two molecules are present in the asymmetric unit
and are reported in Fig. 1 together with the numbering
scheme. The two molecules are chemically equivalent
and the most relevant difference is the spatial develop-
Again, IR and NMR are diagnostic that the reaction
does occur. In the IR spectra of these polyamines the
strong peak at $1640–1635 cm−1 (w CꢀN), present in
the related Schiff bases, disappears and bands at 3312–
3257 cm−1, due to w NH, can be detected. The NMR
spectra in CDCl3 show the peaks due to the methylenic
protons of the NH–CH2–Cp groups at 3.50–3.45 ppm,
while the peaks due to the CHꢀN iminic protons,
clearly detectable in the corresponding Schiff bases, are
completely absent. As a significant example of the
prepared amine derivatives, the 1H NMR spectra of L% ,
F
L% and L% are discussed in detail and compared with
G
J
those related to LF, LG and LH reported earlier in this
report. For L%F, the cyclopentadienyl protons lie at 4.15,
4.11 and 4.08 ppm, the methylenic HN–CH2–Cp pro-
tons at 3.49 ppm and the ethylenic protons at 2.80 and
2.65 ppm. For L% , the cyclopentadienyl protons occur
G
at 4.16, 4.08 and 4.07 ppm, the methylenic protons
HN–CH2–Cp at 3.49 ppm, the ethylenic –CH2CH2–
protons at 2.68 and 2.46 ppm and the methylic proton
1
(CH3) at 2.14 ppm. Finally in L%J, the H NMR spec-
trum reveals peaks at 4.14, 4.08 and 4.07 ppm (cy-
clopentadienyl protons), at 3.47 ppm (methylenic
protons), and at 2.63, 2.43, 2.35 and 1.68 ppm
Fig. 1. ORTEP plots at the 50% probability ellipsoid for the two
molecules (a and b) present in the asymmetric unit together with the
numbering scheme.

130
E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
Fig. 2. Crystal packing along the a-direction.
(ethylenic and propylenic protons). In all the prepared
compounds there is a shift towards lower ppm for the
same protons on going from the Schiff bases to the
corresponding reduced amine derivatives as a conse-
quence of the different deshielding ability of the iminic
–CHꢀN– and the aminic –CH2–NH– groups.
Moreover, in the Schiff bases and in the reduced
homologues derived from ferrocenedialdehyde, only one
peak at 4.10–4.14 ppm due to the protons of the
non-substituted cyclopentadienyl groups is observed.
This peak lies at 4.25 ppm for formylferrocene; thus the
reduction does not cause any significant shift on this
signal. On the contrary, significative shifts are observed
for the protons in the 2-, 5- and 4-positions of the
cyclopentadienyl rings bearing the imine or amine
groups. The peaks due to these protons, at 4.77 and 4.58
ppm in the formylferrocene, lie at 4.60 ppm and 4.34–
4.32 ppm in the Schiff bases, and are located at 4.15–
4.07 ppm in the reduced analogues.
The potentially tridentate L% and L% or tetradentate
F G
L% ligands react with the appropriate metal salts (cop-
J
per(II), nickel(II), and rhodium(III) chloride) to form
the 1:1 complexes M(L%)(Cl)n (n=2 or 3) (Scheme 1).
SEM and EDX analyses evidence the homogeneity of
the prepared samples, the iron:metal:chloride:sulfur ra-
tio 2:1:2:1 for Ni(L% )(Cl)2 or Cu(L% )(Cl)2 and the
F
F
iron:metal:chloride ratio 2:1:2 for Cu(L% )(Cl)2. More-
G
over, [Cu(CH3CH4)]ClO4 reacts in CHCl3/CH3CN with
L% to give the brown complex [Cu(L% )]ClO4; for this
F
F
complex, an iron:copper:chloride:sulfur ratio of 2:1:1:1
was deduced. The tripodal ligand L% also forms with
K
copper(II) and nickel(II) chloride the complexes
M(L% )(Cl)2 and with nickel(II) perchlorate Ni(L% )-
K
K
(ClO4)2; moreover L% , when treated with rhodium(III)
Q
chloride, gives rise to Rh(L% )(Cl)3. SEM and EDX
Q
investigations give atomic ratios which fully agree with
these formulations. The prepared complexes are solids,
stable in air and in solution, moderately soluble in the
most common organic solvents. Their IR spectra show
peaks at 3275–3130 cm−1 due to w NH; these absorption
peaks are ca. 100 cm−1 lower than those observed in the
corresponding reduced ligands.
The FAB mass spectra give further useful information
on their structure. They show the parent peaks at the
appropriate m/z value accompanied by the [M+Na]+
cations; in particular, for the cyclic compounds, they
further support the [2+2] nature of L% and L% and the
O
P
[1+1] nature of L% .
3.4. Mo¨ssbauer spectra
R
These reduced ferrocene–amines do not suffer hydrol-
ysis as a consequence of the reaction with the appropri-
ate metal salts and easily form the related complexes in
which the metal:ligand ratio depends on the shape of the
ligand and also on the experimental conditions; for
instance it was found that bidentate ligands favour the
formation of [M(L)2]2+ complexes [5].
The Mo¨ssbauer spectra at 80 K (Table 5) of all the
complexes present a single quadrupole split doublet
with a narrow linewidth that indicates the presence of a
single iron site deriving from the electronic and struc-
tural identity of the iron atoms in the two or three
ferrocene groups present in the same compound. The

E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
131
Table 5
eventual presence of a second metal in the molecule.
The isomer shift values for the Schiff base com-
pounds are smaller than that of the parent FeCp2
(0.52 mm s−1), meaning that the s electron density at
the iron nucleus is affected by the presence of the
imine function, while the reduction of that function
increases the isomer shift towards values comparable
with FeCp2. The reason for this may be found in the
electron withdrawing capability of the CꢀN moiety
that enhances the metal-to-ligand charge transfer and
indirectly increases the s electron density at the iron
nucleus.
As already observed, the imine function of the
Schiff base behaves as an electron buffer that com-
pletely isolates the cyclopentadienyl ring from the in-
fluence of any other group eventually bonded to the
nitrogen atoms. In fact, the Mo¨ssbauer parameters of
LQ–LT, in which the CꢀN double bond is on the
opposite side with respect to the nitrogen atom, cor-
roborate this statement: the isomer shift values are in
full agreement with those of the reduced compounds.
Finally, the reduction of the double bond of the
Schiff base gives the ferrocene moiety the same elec-
tronic structure of a normal FeCp2 derivative, as
proved by the values of the isomer shift.
The behaviour of the quadrupole splitting can be
explained in a similar way; compared to the FeCp2
compound, the presence of the Schiff base on the Cp
rings causes a small but significant decrease, while the
reduction of the CꢀN double bond increases its value
toward that of FeCp2. The rigidity imposed to the
structure by the iminic function compared to the
aminic one can cause the loss of the parallelism be-
tween the two Cp rings and so to an imbalance of
the iron to Cp bonds that affect the quadrupole split-
ting in an opposite way giving rise to an overall de-
crease in its value. In general the coordination of a
metal causes a slight decrease in the quadrupole split-
ting that may be due to very small variations in the
crystal structure of these compounds.
Some compounds display unexpected parameters:
LI, LL and LO present values perfectly in line with
those of the reduced compounds. It is possible that
reduction takes place during the many and long
operations required to obtain a suitable purity for
these compounds. This reduction process has been
observed already for the [2+2] cyclic Schiff base ob-
tained by condensation of 2,6-diformyl-4-chlorophenol
and 1,2-diaminobenzene ascertained also by single
crystal X-ray diffractometric data [30]. However, it
must be noted that Mo¨ssbauer parameters compara-
ble with those found for the reduced species, have
been reported in the recent literatures [27–29] for
mono- or bis-aldimine derivatives of the following
type:
Mo¨ssbauer effect parameters collected at 80 K
Compound
la (mm s−1
)
DEQ (mm s−1
)
Y (mm s−1
)
LA
LA%
0.444
0.522
0.518
0.519
0.522
0.439
0.520
0.523
0.518
0.439
0.438
0.512
0.518
0.513
0.517
2.294
2.411
2.349
2.352
2.369
2.288
2.410
2.392
2.385
2.288
2.292
2.360
2.387
2.380
2.383
0.282
0.270
0.286
0.252
0.259
0.343
0.280
0.277
0.254
0.302
0.296
0.264
0.357
0.340
0.264
Cu(LF% )(ClO)4
Cu(LA% )Cl2
Ni(LA% )Cl2
LB
LB%
Cu(LB% )Cl2
Ni(LB% )Cl2
LC
LE
LE%
Cu(LE% )Cl2
Pd(LE% )Cl2
Ni(LE% )Cl2
LF
LF%
0.435
0.538
0.520
0.512
2.308
2.387
2.281
2.246
0.323
0.291
0.408
0.363
Cu(LF% )Cl2
Ni(LF% )(ClO)4
LH
LH%
Ni(LH% )Cl2
LG%
0.431
0.511
0.509
0.509
2.218
2.361
2.343
2.214
0.328
0.331
0.262
0.423
Fe-amb
LL
0.555
0.507
0.508
0.514
2.375
2.348
2.335
2.35
0.372
0.340
0.445
0.42
LM
Fe-azb
a l is referred to r.t. a-Fe.
b Fe-am, ferrocene-methylamine; Fe-az, ferrocene-azide.
parameters are typical for ferrocene derivatives con-
taining low spin iron(II)1. It is usually assumed that
compounds of this type present isomer shift values
virtually independent from the presence of ring sub-
stituents and close to that of FeCp2 and quadrupole
splittings, depending slightly on their electron-donor
abilities [27–29]. In partial disagreement with these
statements, the present compounds can be easily di-
vided into two groups according to the respective val-
ues of the isomer shift. The first group with l around
0.44 mm s−1, is formed by the Schiff bases (L), while
the second, with l around 0.52 mm s−1, contains the
reduced analogues (L%) and the related complexes.
Within each group, l is rather constant i.e. 0.4389
0.004 and 0.51790.007 mm s−1, respectively. It is
evident that the Mo¨ssbauer parameters for these com-
pounds are mainly governed by the ferrocene–imine
function and that virtually no role is played by the
nature of the central atom, N, O, or S, or by the
1 The Mo¨ssbauer spectrum of LH collected at 298 K, gives the same
parameters as those at 80 K, as expected for ferrocene derivatives
containing low spin iron(II).

132
E. Bullita et al. / Inorganica Chimica Acta 287 (1999) 117–133
towards a few transition metal ions and the complexes
formed between them exhibited intermediate stability,
which is important for the stripping processes when the
ligand is oxidized to release the metal ion.
The results so far obtained are very promising and
further studies are currently in progress on the possibil-
ity of setting up new separation technologies or new
molecular devices based on ferrocene derivatives.
Also, for these compounds, which closely resemble,
respectively, LA or LB and LL or L% ; X-ray structural
M
5. Supplementary material
investigations demonstrate the occurrence of the de-
signed imine derivatives. Further studies are currently
in progress over a variety of substituted Schiff bases
bearing ferrocene groups to completely evaluate the
electronic contribution of the different groups on the
Mo¨ssbauer parameters.
Atomic coordinates, bond distances and angles, and
thermal parameters are available upon request from the
authors.
Finally, it may be interesting to note that formylfer-
rocene and 1,1%-diformylferrocene give Mo¨ssbauer
parameters in line with those of the reduced ferrocene
amine compounds but not with those of the related
imine derivatives. These results may be ascribed to the
differences in electronegativity between the iminic and
formyl groups (i.e. the iminic nitrogen or the formylic
oxygen).
Acknowledgements
The authors would like to thank A. Aguiari, O.
Biolo, A. Moresco and C. Everti for their technical
assistance and the Progetto Strategico-CNR ‘Tecnolo-
gie Chimiche Innovative’ and the EEC (contract no.
BRPR-CT95-0010) for financial support.
References
4. Conclusions
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In conclusion, a synthetic route is described to obtain
Schiff bases bearing up to three ferrocene moieties,
their reduction by NaBH4 to the corresponding amine
derivatives and the related complexes. The amine com-
pounds form stable, well-defined complexes, while the
corresponding imine derivatives easily suffer hydrolytic
processes.
The Mo¨ssbauer spectra of the prepared ligands and
complexes show the presence of a single iron site deriv-
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two or three ferrocene groups in the same compound
and may be diagnostic of the presence of Fc–HCꢀNR,
Fc–CH2–NꢀCHR or Fc–CH2–NHR groups. More-
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respect to the imine derivatives containing Fe–CHꢀN–
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