Lithiation of ferrocenylamines and vanadium dinitrogen chemistry

Article abstract of DOI:10.1016/S0022-328X(02)02018-1

The lithiation of ferrocenylamines [Fe(C₅H₅) (C₅H₄CH₂R)] (R = NMe₂, NEt₂, CH₂NMe₂, NC₄H₈O or NMeCH₂Ph) with organolithium reagents does not proceed with clean reaction at position 2 of the ring. Generally a range of products is formed, these sometimes difficult to separate. The electronic condition of the iron in these complexes as tested by M?ssbauer spectroscopy and electrochemistry, does not differ much between compounds. The crystal structures of several methylated derivatives of the ferrocenylamines are reported. All the ferrocenylamines seem to potentiate vanadium(II) to dinitrogen uptake, but the precise nature of the dinitrogen species formed could not be determined.

Full text of DOI:10.1016/S0022-328X(02)02018-1

Journal of Organometallic Chemistry 664 (2002) 245ꢂ257
/
www.elsevier.com/locate/jorganchem
Lithiation of ferrocenylamines and vanadium dinitrogen chemistry
Peter B. Hitchcock, G. Jeffery Leigh ꢀ, Maria Togrou
School of Chemistry, Physics and Environmental Science, University of Sussex, Falmer, Brighton BN1 9QJ, UK
Received 16 August 2002; accepted 24 September 2002
Abstract
The lithiation of ferrocenylamines [Fe(C5H5)(C5H4CH2R)] (Rꢁ/NMe2, NEt2, CH2NMe2, NC4H8O or NMeCH2Ph) with
organolithium reagents does not proceed with clean reaction at position 2 of the ring. Generally a range of products is formed, these
sometimes difficult to separate. The electronic condition of the iron in these complexes as tested by Mossbauer spectroscopy and
¨
electrochemistry, does not differ much between compounds. The crystal structures of several methylated derivatives of the
ferrocenylamines are reported. All the ferrocenylamines seem to potentiate vanadium(II) to dinitrogen uptake, but the precise nature
of the dinitrogen species formed could not be determined.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Ferrocenylaminates; Lithiation; Quaternisation; Vanadium(II); Dinitrogen uptake; X-ray structures; Mossbauer spectra; Cyclic
¨
voltammetry
1. Introduction
from the work of Gambarotta and co-workers [4], it was
postulated that incorporation of the ligand N,N-
dimethylaminomethylferrocenyl into dinitrogen-binding
compounds might provoke this kind of chemistry [6].
Derivatives of [Fe(C5H5)(C5H4CH2NMe2)], which can
be lithiated at a ring position adjacent to the dimethy-
laminomethyl group, can act as a ligand to titanium(IV)
[6], vanadium(III) [6] and especially to vanadium(II) [7].
In the last case, dinitrogen is taken up in a stoichiometry
approximating to that required to produce a bridging
dinitrogen complex, analogous to the compound ob-
tained first by Gambarotta and co-workers [4]. We
wished to extend these observations by using a range of
ferrocenyl derivatives to try to define the requirements
of a ferrocenyl ligand to potentiate vanadium(II) to
react with dinitrogen.
A monomeric lithiating agent seems to be essential for
the metallation of ferrocenes to be carried out smoothly
and in high yield [8]. The lithiation of N,N-dimethyla-
minomethylferrocene [9] is fast (ca. 1 h with LiBun in
anhydrous diethyl ether) and clean [10]. No X-ray
structural analysis has so far been carried out, but the
structure probably involves chelation of the carbon-
bound 2-lithium with the amine nitrogen.
Vanadium(II) has long been known to react with
dinitrogen, both in chemical systems and (presumably)
in the ironꢂvanadium nitrogenase [1]. Unlike the well
/
known range of molybdenum(0) and tungsten(0) dini-
trogen complexes, in which the supporting ligands are
phosphines, for vanadium(II) the ligands that may
support dinitrogen uptake are oxygen donors [2], sulfur
donors (as in nitrogenase) [3] or nitrogenꢂcarbon
donors [4]. The complex trans-[VCl2(tmen)2] (which
does not itself react with dinitrogen) reacts with
/
LiC6H4ꢀ
treatment with one equivalent of pyridine (py), a
bridging dinitrogen complex [{V(C6H4CH2N-
/
2-CH2NMe2 under dinitrogen to yield, after
Me2)2(py)}2(m-N2)], whose structure was determined by
X-ray crystallography [4]. This complex reacts with
acids to yield ammonia [5].
Additional redox-active centres not involved in dini-
trogen binding [6] might contribute electrons to any
protonation reaction of dinitrogen and thus affect the
mechanism and extent of protonation. Extrapolating
ꢀ Corresponding author. Tel.: ꢃ
67849
E-mail address: g.j.leigh@sussex.ac.uk (G.J. Leigh).
/
44-1273-606755; fax: ꢃ44-1273-
/
[Fe(C5H5)(C5H4CH2CH2NMe2)] is metallated with
LiBun in hexaneꢂ
Et2O at the 2-position of the ring in
/
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 2 0 1 8 - 1

246
P.B. Hitchcock et al. / Journal of Organometallic Chemistry 664 (2002) 245ꢂ257
/
good
yield,
but
at
half
the
rate
of
[Fe(C5H5)(C5H4CH2R)], and used their spectra to help
analyse the products isolated from the reactions of the
lithium reagent with iodomethane.
[Fe(C5H5)(C5H4CH2NMe2)] [9,11,12]. The longer reac-
tion times also appear to allow significant formation of
dilithiated species. The dimethylaminoethyl derivative of
benzene evidently cannot be metallated in this way
[11,13].
For Rꢁ
time in 1:1 [Fe(C5H5)(C5H4CH2R)]ꢂ
monolithiated product (VI, Fig. 1, Tables 1 and 2). For
RꢁNEt2, after 16 h reaction time in a 1:1 amineꢂ
LiBun
ratio, lithiation did not occur to any significant degree.
When
twofold excess of LiBun was used
[Fe(C5H5)(LiC5H3ꢀ2-CH2NEt2)] (II) formed in reason-
/
NMe2, the major product after 16 h reaction
/
LiBun ratio was the
/
/
2. Results and discussion
a
/
2.1. Lithiation of ferrocenylamines
able yield. X-ray analysis carried out on a sample
isolated from the reaction mixture after treatment with
MeI, showed only 30% replacement of a hydrogen at the
ring carbon atom C(7) by a methyl group, yielding
[Fe(C5H5){C5H3Me(CH2NMeEt2)}]I (VII). The struc-
ture was not well enough refined to warrant detailed
presentation, though the position of methylation was
unequivocally determined. Monolithiation had occurred
at the required ring position, but in rather low yield. The
compounds (VII) and [Fe(C5H5)(C5H4CH2NMeEt2)]I
(XII) co-crystallise, and we were unable to separate
them chromatographically, due to their high polarity.
However, compound XII was prepared independently
and characterised crystallographically (see below).
[Fe(C5H5)(C5H4CH2R)] (Rꢁ
CH2NMe2, NC4H8O or NMeCH2Ph)
/
NMe2, NEt2,
The compound with Rꢁ
1,2-derivative (I) with LiBun that precipitates from a
diethyl etherꢂhexane mixture [14]. However, the isola-
tion of the lithium derivatives [Fe(C5H5)(LiC5H3ꢀ2-
CH2R)] (RꢁNEt2 (II), CH2NMe2 (III), NC4H8O (IV)
/NMe2 gives a monolithiated
/
/
/
or NMeCH2Ph (V)) is difficult. They are highly soluble
in hexane, even at low temperatures. In order to
determine the yield and position of lithiation without
isolating the individual products, the lithium salts were
treated with D2O and the ring-deuterated products
examined by 1H-, 2H- and 13C{1H}-NMR spectro-
scopies. The presence of several deuterated materials in
each sample meant that the spectra were too complex to
analyse.
The lithiated mixtures were then treated with PhBr,
PriBr, or MeI, which have the potential both to
substitute the ring and to quaternise the amine nitrogen
to produce salts. Only MeI often yielded easily tractable
materials. The quaternised products were easier to
separate from the reaction mixtures, and were often
isolated in a crystalline form.
For Rꢁ/CH2NMe2, after 2 h we obtained a mixture
of monolithiated [Fe(C5H5)(LiC5H3ꢀ/2-CH2CH2NMe2)]
(III) and unlithiated starting material [Fe(C5H5)-
(C5H4CH2CH2NMe2)]. After 16 h, the presence of
polylithiated products was evident.
1
In the H- and 13C{1H}-NMR spectra of compounds
isolated after treating these metallation mixtures with
MeI, several peaks corresponding to methyl groups
attached to the Cp ring were present. For Rꢁ
NC4H8O, the amount of monolithiated material was
always exceeded by polylithiated product. For Rꢁ
/
/
In order to determine the optimum conditions under
which 2-lithiation of the ferrocenylamines occurs, com-
pounds [Fe(C5H5)(C5H4CH2R)] were allowed to react
with LiBun in 1:1, 1:1.5, 1:2 or 1:5 ratios with a range of
reaction times (1ꢂ5, 16 and 24 h). The reaction mixtures
/
were then treated in each case with a large excess of MeI.
The yellow precipitate formed in each experiment was
recrystallised from MeOHꢂEt2O and the materials were
/
characterised in solution by NMR spectroscopy and
found that mixtures of the quaternised salts
[Fe(C5H5){C5H3Me(CH2RMe)}]I
and
[Fe(C5H5)-
(C5H4CH2RMe)]I. Typical ring-substituted quaternised
products were [Fe(C5H5){C5H3Me(CH2RMe)-1,2}]I
(RꢁNMe2 (VI), NEt2 (VII), CH2NMe2 (VIII),
/
NC4H8O (IX) or NMeCH2Ph (X)). Attempts to separate
these products by recrystallisation and by various
chromatographic techniques were unsuccessful. Conse-
quently, we prepared [Fe(C5H5)(C5H4CH2RMe)]I (Rꢁ
/
NMe2 (XI), NEt2 (XII), CH2NMe2 (XIII), NC4H8O
(XIV) or NMeCH2Ph (XV)) individually by MeI
quarternisation of the corresponding ferrocenylamines
Fig. 1. Molecular structure of [Fe(C5H5){C5H3Me(CH2NMe3)}]I
(VI), showing the atom numbering scheme; the picture was drawn
with the use of the ORTEP program.

P.B. Hitchcock et al. / Journal of Organometallic Chemistry 664 (2002) 245ꢂ
/257
247
Table 1
Selected interatomic distances for [Fe(C5H5){C5H3Me(CH2NMe3)}]I
(VI)
and appear as a multiplet in the region dꢁ
/
2.87ꢂ
/
2.93
ppm. Because the asymmetry of the ferrocenyl entity
creates diastereotopic environments the NCH3 groups
of X are not equivalent. For the same reason, the
NCH2CH3 and NCH2CH3 protons in VII appear as
˚
Bond lengths (A)
Atoms
a
a
FeꢀM(1)
FeꢀM(2)
NꢀC(7)
NꢀC(8)
NꢀC(9)
NꢀC(10)
1.62(2)
1.65(2)
multiplets in the regions dꢁ
ppm, respectively. The PhCH2N protons in X are
isochronous and give rise to a singlet at dꢁ4.52 ppm.
/
1.33ꢂ
/
1.36 and 3.25ꢂ
/
3.36
1.535(19)
1.50(2)
/
The apparent equivalence of these protons is coinciden-
tal.
1.512(17)
1.53(2)
e.s.ds are in parentheses.
a
M(1) and M(2) are the centroids of the C(1)-to-C(5) and C(11)-to-
C(15) rings.
2.2. Mossbauer and cyclic voltammetry studies
¨
The cyclic voltammetry and Mossbauer spectroscopy
¨
of the ferrocenylamines [Fe(C5H5)(C5H4CH2R)] were
investigated, in order to determine whether they show
significantly different electronic conditions.
Table 2
Selected bond angles for complex [Fe(C5H5){C5H3Me(CH2NMe3)}]I
(VI)
The spectra obtained for the ferrocenylamines
[Fe(C5H5)(C5H4CH2R)] (Table 4) are sharp, as indi-
cated by the values of G (half-width at half maxima),
and there is no sign in the spectra of iron-containing
impurities. The isomer shifts (d) lie within a narrow
Atoms
Bond angles (8)
a
M(1)ꢀFeꢀM(2)
C(8)ꢀNꢀC(9)
C(8)ꢀNꢀC(10)
C(9)ꢀNꢀC(10)
C(8)ꢀNꢀC(7)
C(9)ꢀNꢀC(7)
C(10)ꢀNꢀC(7)
178.7(9)
109.7(13)
109.0(15)
109.0(14)
111.4(12)
107.5(11)
110.2(12)
range, 0.569
0.05 mm sꢄ1. Neither quaternisation with
/
MeI nor ring-substitution with methyl at a position
adjacent to the amine function induces major changes in
the spread of values. Considering that the isomer shift
(which measures the electron density on the Mossbauer
¨
e.s.ds are in parentheses.
a
atom) is determined mainly by the oxidation and spin
state of the iron atoms in the sample, which have not
been changed, this is disappointing but not surprising.
Furthermore, these values do not differ significantly
M(1) and M(2) are the centroids of the C(1)-to-C(5) and C(11)-to-
C(15) rings.
NMeCH2Ph, lithiation was generally very slow and
yields low. Preliminary X-ray crystal structure data for
the compound isolated from the reactions of
[Fe(C5H5)(C5H4CH2NMeCH2Ph)] after 16 h showed
the sample to be the ring methylated [Fe(C5H5){C5H3-
Me(CH2NMe2CH2Ph)-1,2}]I (X). The residuals of the
refinement are poor and the structure of this compound
will not be discussed further.
from those reported for [Fe(C5H5)(LiC5H3ꢀ
/
2-
CH2NMe2)], [V{Fe(C5H5)(C5H3CH2NMe2)}2Cl], sev-
eral titanium derivatives of [Fe(C5H5)(C5H4CH2NMe2)]
(dꢁ
0.54(1) mm sꢄ1 (mean value) at 77 K, referenced
against iron foil) [6], for some stannylated derivatives of
/
[Fe(C5H5)(C5H4CH2NMe2)] [15], or ferrocene itself
(dꢁ
0.51(5) mm sꢄ1 at 80 K, referenced against iron
/
Other lithium alkyls were also used as reagents in an
attempt to improve both selectivity and/or reaction rate,
but without appreciable success. Reaction with LiBut,
seemed to proceed faster, but always gave products
contaminated with polylithiated species.
foil) [16]. The lack of dependence of the isomer shifts on
the nature of the substituents on the rings is a common
feature of substituted ferrocenes [16].
Quadrupole splitting (q.s.) arises from the asymmetry
of the electron cloud around the nucleus [16]. The
quadrupole splittings for [Fe(C5H5)(C5H4CH2R)] lie
1H-NMR data for [Fe(C5H5){C5H3Me(CH2RMe)}]I
within a narrow range, 2.389
These values are very similar to that observed for
ferrocene itself (q.s.ꢁ
2.40(3) mm sꢄ1) [16]. The small
/
0.02 mm sꢄ1 (Table 4).
(RꢁNMe2 (VI), NEt2 (VII), CH2NMe2 (VIII) or
/
NMeCH2Ph (X)) are displayed in Table 3. These
assignments were supported by selective decoupling
/
1
and H{1H}-NOE experiments. We did not manage to
variation detected in the quadrupole splittings indicates
that, in the double-sandwich electronic environments,
the FeII orbitals are not very sensitive to the electron-
withdrawal or donation effects generated by the sub-
stituents on the ferrocenyl moieties. The quaternised
ferrocenylamines [Fe(C5H5){C5H3R?(CH2RMe)}]I (ex-
isolate a pure-enough sample of [Fe(C5H5){C5H3-
Me(CH2NMeC4H8O)}]I (IX) and1H-NMR data for
this compound are not reported. In the 1H-NMR
spectra of VI and X, the C5H3CH2 protons appear as
the expected two AB doublets [15]. In VII, the diaster-
eotopic C5H3CH2 protons are accidentally equivalent
cept for RꢁCH2NMe2) show somewhat lower values of
/
and give rise to a singlet at dꢁ/4.49 ppm. In VIII, the
q.s. (average 2.34 mm sꢄ1, Table 4). Probably the
positive charge on the nitrogen affects the electric field
C5H3CH2 protons are also chemically non-equivalent

248
P.B. Hitchcock et al. / Journal of Organometallic Chemistry 664 (2002) 245ꢂ257
/
Table 3
H1-NMR data for [Fe(C5H5){C5H3Me(CH2RMe)}]I (RꢁNMe2 (VI), NEt2 (VII), CH2NMe2 (VIII) or NMeCH2Ph (X)) in CD3OD (in ppm, d-
scale, room temperature)
Proton
Chemical shifts
VI
VII
VIII
X
NCH2CH3
C5H3CH3
ꢂ
/
1.33ꢂ
2.11 (s, 3H)
/
1.36 (m, 6H)
ꢂ
/
ꢂ
/
2.12 (s, 3H)
2.03 (s, 3H)
2.87ꢂ2.93 (m, 2H)
3.23 (s, 9H)
2.13 (s, 3H)
C5H3CH2CH2N
NCH3
ꢂ/
ꢂ/
/
ꢂ/
3.03 (s, 9H)
2.81 (s, 3H)
2.80 (s, 3H)
2.85 (s, 3H)
NCH2CH3
C5H3CH2CH2N
C5H5
ꢂ
ꢂ/
/
3.25ꢂ3.36 (m, 4H)
ꢂ/
4.19 (s, 5H)
4.29 (t, 1H)
4.35 (m, 1H)
4.46 (m, 1H)
/
ꢂ
/
ꢂ
ꢂ/
/
3.36ꢂ
4.10 (s)
/
3.47 (m, 2H)
4.18 (s, 5H)
4.30 (t, 1H)
4.36 (m, 1H)
4.48 (m, 1H)
4.19 (s, 5H)
4.34 (t, 1H)
C5H3
H5
C5H3
3.99 (t, 1H)
4.10 (m)
4.13 (m, 1H)
4.40 (m, 1H)
4.51 (m, 1H)
PhCH2N
C5H3CH2N
ꢂ
/
ꢂ
/
ꢂ
ꢂ/
/
4.52 (s, 2H)
4.62 (d, 1H, Jꢁ13.4 Hz)
4.71 (d, 1H, Jꢁ13.4 Hz)
4.52 (d, 1H, Jꢁ13.4 Hz)
4.61 (d, 1H, Jꢁ13.4 Hz)
4.49 (s, 2H)
Ph
ꢂ/
ꢂ/
ꢂ/
7.52ꢂ7.57 (m, 5H)
/
gradient at the iron. We conclude that the Mossbauer
¨
and in the ferrocenium ion is apparently localised on the
iron [18].
technique is unlikely to give us the desired information
on the relative electronic conditions, either of the
ferrocenylamines or of their lithiated derivatives.
We reached a similar conclusion from our electro-
chemical studies. Cyclic voltammetric measurements on
[Fe(C5H5)(C5H4CH2NMe2)] and a series of other ferro-
cenylamines have been previously reported [17]. Under
the same conditions, all the compounds [Fe(C5H5)-
When the potential range was extended beyond 1.1 V
an additional irreversible wave E was observed on the
first anodic scan with at least a one-electron transfer ca.
800 mV positive of A. An additional cathodic wave Cc
appears on the reverse sweep with the anodic compo-
nent Ca on subsequent scans. This suggests an EECE
mechanism where two successive electron transfers are
followed by a chemical reaction, the product of which is
also electroactive. Couple C, ca. 200 mV positive of A, is
assigned to a reversible one-electron oxidation of a new
ferrocenium species. A similar process was observed for
a range of ferrocenylamines reported by Duffy et al.
[17]. An irreversible wave E was attributed to the anodic
oxidation of the amine. The cation radical generated in
this manner abstracts a hydrogen from the solvent to
form an ammonium salt. This is probably also true for
the ferrocenylamines studied by us. The potential of E is
the only one dependent on the N-substituent.
(C5H4CH2R)] (RꢁNEt2, CH2NMe2, NMeCH2Ph or
/
NC4H8O) showed a single chemically and electrochemi-
cally reversible, one-electron couple A (see Table 5,
values referenced against decamethylferrocene) in their
cyclic voltammograms, due to the characteristic oxida-
tion of the ferrocene iron redox centre. Consistent with
other data [17], all non-protonated ferrocenylamines
oxidise at approximately the same potential as ferrocene
(0.48 V). The range of potentials is only 50 mV for five
compounds,
and
the
protonated
materials
[Fe(C5H5)(C5H4CH2RH)]BF4 display a similar small
range, though at potentials about 200 mV more positive,
a consequence of the higher Coulombic charge on the
salts as compared to the non-protonated ferrocenyla-
mines. Most of the electron density both in ferrocene
For the oxidation of the protonated ferrocenylamine
to the ferrocenium species; only a single reversible one-
electron couple was observed at the expected potential.
This is additional evidence that the electrochemistry of

P.B. Hitchcock et al. / Journal of Organometallic Chemistry 664 (2002) 245ꢂ
/257
249
Table 4
Mossbauer parameters (a) for [Fe(C H )(C H CH R)] and complexes
compounds is not influenced by the substituent on the
Cp ring.
¨
5
5
5
4
2
VIꢂ/XV (77 K, referenced against iron foil)
A
E
[FcCH2R] l[FcꢃCH2R] 0[FcꢃCH2RHꢃ]
b
c
d
Compound
d
q.s.
G
C
(mm s-1) (mm sꢄ1
)
(mm sꢄ1
)
l[FcꢃCH2RHꢃ]
[FcCH2NMe2]
[FcCH2NEt2]
0.53(1)
0.60(1)
0.54(1)
0.52(1)
0.61(1)
0.52(1)
2.40(1)
2.39(1)
2.39(1)
2.37(1)
2.39(1)
2.35(1)
2.36(1)
2.41(3)
0.15(1)
0.13(1)
0.11(1)
0.14(1)
0.17(1)
0.13(1)
0.15(1)
0.17(1)
[FcCH2CH2NMe2]
[FcCH2NC4H8O]
[FcCH2NMeCH2Ph]
[Fc?Me(CH2NMe3)]I (VI)
[Fc?Me(CH2NMeEt2)]I (VII) 0.53(1)
[Fc?Me(CH2CH2NMe3)]I
(VIII)
2.3. X-ray crystal structures
As most of the dialkylaminomethyl and aminoethyl-
ferrocenes are liquids, available X-ray structural data on
such compounds have been restricted mainly to their
ammonium salts or other derivatives with further
substitution on the cyclopentadienyl group [19,20]. We
0.53(2)
0.52(1)
0.51(1)
[Fc?Me(CH2NMeC4H8O)]I
(IX)
2.35(1)
2.32(1)
0.12(1)
0.06(1)
[Fc?Me(CH2NMe2CH2Ph)]I
(X)
studied
crystallographically
the
compounds
[Fe(C5H5){C5H3Me(CH2RMe)}]I derived by methyla-
tion of the products of the reaction of the corresponding
[Fe(C5H5)(LiC5H3CH2R)] with LiBun. As discussed
above, these compounds have the advantage that they
can be isolated as solids and are easier to crystallise.
[Fe(C5H5)(LiC5H3CH2NMe2)] (I) certainly is methy-
lated at a position adjacent to the ferrocenylamine side
chain. As mentioned earlier, the X-ray crystal structure
of [Fe(C5H5){C5H3Me(CH2NMe3)}]I (VI) is shown in
Fig. 1, and selected bond lengths and angles are listed in
Tables 1 and 2.
[FcCH2NMe3]I (XI)
[FcCH2NMeEt2]I (XII)
[FcCH2CH2NMe3]I (XIII)
[FcCH2NMeC4H8O]I (XIV)
[FcCH2NMe2CH2Ph]I (XV)
0.53(2)
0.54(1)
0.54(1)
0.53(1)
0.53(1)
2.33(3)
2.35(1)
2.41(1)
2.33(1)
2.35(2)
0.11(1)
0.12(1)
0.13(1)
0.13(1)
0.13(1)
a
Numbers in parentheses correspond to the experimental error in
the last significant figure.
b
Isomer shift.
Quadrupole splitting.
Half width at half height.
c
d
Table 5
Electrochemical data of ferrocenylamines [Fe(C5H5)(C5H4CH2R)] and
their N-protonated derivatives
As stated above, X-ray crystallographic data obtained
on a sample isolated from the reaction mixture of
[Fe(C5H5)(LiC5H3ꢀ
/
2-CH2NEt2)] (II) with LiBun after
a,b
b,c
treatment with MeI, showed only 30% replacement of a
hydrogen by a methyl group at the ring carbon atom
adjacent to the amino substituent. Attempts to obtain
the crystal structures of the ferrocenylamines [Fe(C5H5)-
{C5H3Me(CH2CH2NMe3)}]I (VIII) and [Fe(C5H5)-
{C5H3Me(CH2NMeC4H8O)}]I (IX) were fruitless, since
we could only isolate crystals of the non-ring methylated
derivatives [Fe(C5H5)(C5H4CH2CH2NMe3)]I (XIII) and
[Fe(C5H5)(C5H4CH2NMeC4H8O)]I (XIV) from the re-
action mixtures.
Substituent R E1/2 of [FcCH2R]
E1/2 of [FcCH2RH]BF4
NMe2
NEt2
0.48
0.49
0.46
0.51
0.50
0.69
0.69
0.56
0.70
0.69
CH2NMe2
NC4H8O
NMeCH2Ph
a
Half-wave
potentials
for
the
reaction
[Fcꢃ ꢀ
CH2R]ꢃeꢄ l[FcꢀCH2R] in volts; all potentials are referenced
against decamethylferrocene; potential for ferrocene under the same
conditions, 0.48 V.
b
Determined by cyclic voltammetry in MeCN solution with 0.1 M
(But N)BF4 electrolyte with a scan rate of 100 mV sꢄ1 at 20 8C.
As a cross-section, the X-ray crystal structures of the
4
compounds [Fe(C5H5)(C5H4CH2RMe)]I (Rꢁ
(XII), CH2NMe2 (XIII), NC4H8O (XIV) or NMeCH2Ph
(XV)) were determined (Figs. 2ꢂ5). Crystallographic
data and selected bond dimensions are displayed in the
Tables 6ꢂ13. Usually the compounds were crystallised
/
NEt2
c
Half-wave
potentials
for
the
reaction
[FcꢃCH2RHꢃ]ꢃeꢄ l[FcCH2RHꢃ] in volts; all potentials are refer-
enced against decamethylferrocene. The N-protonated derivatives of
the ferrocenylamines were obtained by addition of HBF4×Et2O to the
corresponding ferrocenylamines.
/
/
from a methanolic solution layered with Et2O as orange
needles or plates.
[Fe(C5H5)(C5H4CH2R)] involves a protonation reac-
tion.
The structures of the complexes VI, and XIIꢂXV
/
In summary, the observed electrochemistry of
[Fe(C5H5)(C5H4CH2R)] arises from an EECE mechan-
ism involving two reversible couples [FcꢃCH2R]/
[FcCH2R], [FcꢃCH2RHꢃ]/[FcCH2RHꢃ] similar to
those of ferrocene and an irreversible oxidation/proto-
nation of the amine function. It appears that the
oxidation of the ferrocene redox centre for this set of
showed similarities to those of the compounds
[Fe(C5H5)(C5H4CH2NMe3)]I [21], [Fe(C5H5)(C5H4-
CH2NMe3)]2B10H10,
[Fe(C5H5)(C5H4CH2NMe3)]2-
[Mo6O19] [22], [Fe(C5H5){C5H3PPh2(CHMeNMe2)-
1,2}] [20], [Fe(C5H5)(C5H4CH2NMe2Et)]2B20H18 [23],
[Fe(C5H5)(C5H4CH2NHMe2)]2[ZnCl4]×
/
H2O
[24],
[Fe(C5H5)(C5H4CH2NHCHO)] [25] and [Fe(C5H5)-

250
P.B. Hitchcock et al. / Journal of Organometallic Chemistry 664 (2002) 245ꢂ257
/
Fig. 2. Molecular structure of [Fe(C5H5)(C5H4CH2NMeEt2)]I (XII),
showing the atom numbering scheme; there are two independent
molecules differing only in the conformation about the Nꢀ
/
C(11) bond;
the picture was drawn with the use of the ORTEP program.
Fig. 4. Molecular structure of [Fe(C5H5)(C5H4CH2NMeC4H8O)]I
(XIV), showing the atom numbering scheme; the picture was drawn
with the use of the ORTEP program.
(C5H4CHMeNHMe2)](C4H5O6)×
/
2H2O [26]. Further-
[Fe(C5H5)-
more, the complex [{(m-Cl)PdL}2] (Lꢁ
/
{C5H2Me(CH2NMe2)-C,N}]) has been characterised
crystallographically [27]. The ferrocenylaminate ligand
in this compound contains a methyl substituent on the
Cp ring at a position adjacent to the amine function (cf.
groups differs by ca. 10.08 and the other by ca. 3.38 from
the fully eclipsed position. In XIII, a larger deviation
from the eclipsed arrangement is observed (ca. 16.48).
There is a perfectly eclipsed arrangement for the Cp
rings in XIV.
compound VI). In compound VI, the C(2)ꢀC(6) bond
˚
length is 1.44(2) A, which is slightly shorter than the
/
corresponding bond distance found in [{(m-Cl)PdL}2]
(1.510 A) [27].
˚
In the unit cell of XII there are two independent
molecules differing only in the conformation about the
2.4. N2 uptake experiments
Nꢀ
units of compounds VI, XIIꢂ
those in ferrocene itself [28]. The M(1)ꢀ
is nearly linear, varying only from 178.2 to 179.48 for
five compounds (‘M’ denotes the centroid of a Cp ring).
The cyclopentadienyl rings are planar within experi-
mental error, and approximately parallel and eclipsed.
The ferrocenyl group in VI is removed by ca. 5.28 from
the fully eclipsed position. In XII, one of the ferrocenyl
/
C(11) bond. The dimensions inside the ferrocenyl
XV are very similar to
FeꢀM(2) angle
[VCl2(tmen)2] reacts with LiC6H4ꢀ
dinitrogen to yield, after treatment with one equivalent
of pyridine (py) bridging dinitrogen complex
[{V(C6H4CH2NMe2)2(py)}2(m-N2)] [4]. A series of ex-
periments were carried out in order to determine
whether there is N2 uptake in the reaction of
[VCl2(tmen)2] with two molar equivalents of
/
2-CH2NMe2 under
/
/
/
a
[Fe(C5H5)(LiC5H3ꢀ
/
2-CH2R)] in THF (RꢁNMe2,
/
NEt2, CH2NMe2, NC4H8O or NMeCH2Ph). The dini-
Fig. 3. Molecular structure of [Fe(C5H5)(C5H4CH2CH2NMe3)]I×
/MeOH (XIII), showing the atom numbering scheme; the picture was drawn with
the use of the ORTEP program.

P.B. Hitchcock et al. / Journal of Organometallic Chemistry 664 (2002) 245ꢂ
/257
251
Table 8
Selected distances for [Fe(C5H5)(C5H4CH2CH2NMe3)]I×MeOH (XIII)
˚
Bond lengths (A)
Atoms
a
a
FeꢀM(1)
FeꢀM(2)
NꢀC(7)
NꢀC(8)
NꢀC(9)
NꢀC(10)
1.646(3)
1.655(3)
1.517(3)
1.506(3)
1.491(3)
1.498(3)
1.507(3)
1.518(3)
1.400(4)
C(1)ꢀC(6)
C(6)ꢀC(7)
C(16)ꢀO
e.s.ds are in parentheses.
a
M(1) and M(2) are the centroids of the C(1)-to-C(5) and C(11)-to-
C(15) rings.
Table 9
Selected bond angles for [Fe(C5H5)(C5H4CH2CH2NMe3)]I×MeOH
(XIII)
Fig. 5. Molecular structure of [Fe(C5H5)(C5H4CH2NMe2CH2Ph)]I
(XV), showing the atom numbering scheme; the picture was drawn
with the use of the ORTEP program.
Atoms
Bond angles (8)
Table 6
Selected interatomic distances for [Fe(C5H5)(C5H4CH2NMeEt2)]I
(XII)
a
M(1)ꢀFeꢀM(2)
C(9)ꢀNꢀC(10)
C(9)ꢀNꢀC(8)
C(10)ꢀNꢀC(8)
C(9)ꢀNꢀC(7)
C(10)ꢀNꢀC(7)
C(8)ꢀNꢀC(7)
178.5(2)
110.4(2)
109.0(2)
˚
Bond lengths (A)
Atoms
108.22(19)
110.95(19)
110.44(18)
107.73(17)
a
a
FeꢀM(1)
FeꢀM(2)
NꢀC(11)
NꢀC(12)
NꢀC(13)
NꢀC(15)
1.654(4)
1.642(4)
1.540(3)
1.494(3)
1.518(4)
1.508(4)
e.s.ds are in parentheses.
a
M(1) and M(2) are the centroids of the C(1)-to-C(5) and C(11)-to-
C(15) rings.
e.s.ds are in parentheses.
a
M(1) and M(2) are the centroids of the C(1)-to-C(5) and C(6)-to-
C(10) rings.
Table 10
Selected distances for compound [Fe(C5H5)(C5H4CH2NMeC4H8O)]I
(XIV)
˚
Bond lengths (A)
Atoms
Table 7
Selected bond angles for complex [Fe(C5H5)(C5H4CH2NMeEt2)]I
(XII)
a
a
FeꢀM(1)
FeꢀM(2)
NꢀC(6)
NꢀC(7)
NꢀC(8)
NꢀC(11)
1.642(5)
1.641(6)
1.524(6)
1.504(7)
1.517(7)
1.523(6)
Atoms
Bond angles (8)
a
M(1)ꢀFeꢀM(2)
C(12)ꢀNꢀC(15)
C(12)ꢀNꢀC(13)
C(15)ꢀNꢀC(13)
C(12)ꢀNꢀC(11)
C(15)ꢀNꢀC(11)
C(13)ꢀNꢀC(11)
178.4(2)
111.0(2)
111.4(2)
103.4(3)
107.2(2)
112.2(2)
111.8(2)
e.s.ds are in parentheses.
a
M(1) and M(2) are the centroids of the C(1)-to-C(5) and C(12)-to-
C(16) rings.
and that the dinitrogen complexes of this type are not
very stable and are difficult to characterise.
The N2 uptake was always very rapid, except for the
mixture of [VCl2(tmen)2] with [Fe(C5H5)(LiC5H3ꢀ
CH2NEt2)] for which zero uptake was observed. The
data are summarised below as dinitrogen actually taken
e.s.ds are in parentheses.
a
M(1) and M(2) are the centroids of the C(1)-to-C(5) and C(6)-to-
C(10) rings.
/2-
trogen uptake was always less than one molecule for
each two atoms of vanadium. No pure dinitrogen-
containing products were isolated, and this is perhaps
not surprising in view of the facts that the lithium
reagents were usually not pure (for reasons, see above),
up as a percentage of that required to form a Vꢂ
system: [Fe(C5H5)(LiC5H3ꢀ2-CH2R)] RꢁNMe2 (55%),
RꢁNEt2 (0%), RꢁCH2NMe2 (35%), RꢁNC4H8O
(30%) and RꢁNMeCH2Ph (40%). The fact that the
uptake was always less than what would be consistent
/
N2ꢂ
/
V
/
/
/
/
/
/

252
P.B. Hitchcock et al. / Journal of Organometallic Chemistry 664 (2002) 245ꢂ257
/
Table 11
Selected bond angles for [Fe(C5H5)(C5H4CH2NMeC4H8O)]I (XIV)
NC4H8O or NMeCH2Ph) gives monolithiated 1,2-deri-
vatives, but their isolation was difficult except for Rꢁ
NMe2. [VCl2(tmen)2] reacts with about two equivalents
/
Atoms
Bond angles (8)
of the lithium derivatives in THF with the concomitant
a
M(1)ꢀFeꢀM(2)
C(7)ꢀNꢀC(8)
C(7)ꢀNꢀC(11)
C(8)ꢀNꢀC(11)
C(7)ꢀNꢀC(6)
C(8)ꢀNꢀC(6)
C(11)ꢀNꢀC(6)
179.3(3)
112.6(4)
111.9(4)
107.3(4)
109.1(4)
109.2(4)
106.4(4)
uptake of N2 (except for RꢁNEt2). No dinitrogen-
/
a
containing complexes were isolated. If bridging N2
complexes are formed, there are certainly other reac-
tions occurring at the same time, which do not involve
N2 complexes. Neither Mossbauer spectroscopy nor
¨
cyclic voltammetry are suitable probes for the electronic
condition of the ferrocenyl nucleus. The use of these
techniques as indicators of the ability of the ferroceny-
laminates to potentiate vanadium for dinitrogen binding
is not promising.
e.s.ds are in parentheses.
a
M(1) and M(2) are the centroids of the C(1)-to-C(5) and C(12)-to-
C(16) rings.
Table 12
Selected interatomic distances for [Fe(C5H5)(C5H4CH2NMe2CH2Ph)]I
(XV)
3. Experimental
All operations were carried out under an inert atmo-
sphere in an Ar-filled drybox or with use of standard
Schlenk techniques. Solvents were dried by standard
procedures [29] and distilled under N2 prior to use. The
commercial products 2-bromobenzyl bromide, N-bro-
mosuccinimide, n-butyllithium (1.6 M solution in
C6H14), tert-butyllithium (1.7 M solution in C6H14), 2-
dimethylaminoethylchloride hydrochloride, 3-dimethy-
laminopropylchloride hydrochloride, N,N-dimethylben-
zylamine, ferrocene, were used without further
purification. Diallylamine, Et2NH, morpholine, benzyl-
methylamine (Aldrich) and N,N-dimethylaminomethyl-
ferrocene (Lancaster) were dried and distilled prior to
use.
˚
Bond lengths (A)
Atoms
a
a
FeꢀM(1)
FeꢀM(2)
NꢀC(6)
NꢀC(7)
NꢀC(8)
NꢀC(9)
1.641(2)
1.653(2)
1.536(3)
1.491(3)
1.496(3)
1.534(3)
e.s.ds are in parentheses.
a
M(1) and M(2) are the centroids of the C(1)-to-C(5) and C(16)-to-
C(20) rings.
Table 13
Selected bond angles for [Fe(C5H5)(C5H4CH2NMe2CH2Ph)]I (XV)
Microanalyses were carried out at the University of
Surrey using a Leenan CE 440 CHN elemental analyser,
or at MEDAC, Brunel Science Centre, Surrey. IR
Atoms
Bond angles (8)
a
M(1)ꢀFeꢀM(2)
C(7)ꢀNꢀC(8)
C(7)ꢀNꢀC(9)
C(8)ꢀNꢀC(9)
C(7)ꢀNꢀC(6)
C(8)ꢀNꢀC(6)
C(9)ꢀNꢀC(6)
178.2(1)
110.2(2)
spectra were recorded on a PerkinꢂElmer Spectrum
/
110.28(18)
110.47(19)
109.88(19)
109.64(18)
106.30(18)
One FT-IR spectrometer, from Nujol mulls prepared
under dinitrogen and spread on KBr plates. NMR
spectra were obtained in the appropriate deuterated
solvents using a Bruker 300 or 500 MHz instrument.
1
1
(13C, H)-HETCOR NMR, H{1H}-NOE and variable
e.s.ds are in parentheses.
a
M(1) and M(2) are the centroids of the C(1)-to-C(5) and C(16)-to-
C(20) rings.
1
temperature H-NMR experiments were carried out by
Dr Tony Avent, University of Sussex. Mass spectra were
taken by Dr Ali Abdul-Sada, at the University of
Sussex, using a Kratos M580RF instrument for FAB
spectra (and 3-nitrobenzyl alcohol as a matrix material),
with the formation of a bridging dinitrogen complex,
could be because the lithium-ferrocenylaminate starting
materials were not sufficiently pure. The lithiation
procedure needs to be improved, to ensure the 1:2
stoichiometric
[VCl2(tmen)2] and [Fe(C5H5)(LiC5H3ꢀ
and a Fisons VG Autospec for EI spectra. Mossbauer
¨
data were recorded at 77 K by Professor Jack Silver,
University of Greenwich. Spectra were referenced
against iron foil at 298 K. Cyclic voltammetry measure-
ments were performed under the supervision of Dr
Christopher J. Pickett at the John Innes Centre,
Norwich, using an EG&G PAR 362 scanning potentio-
stat. A three-electrode cell configuration was used, with
a Pt wire secondary electrode and a silver wire pseudo
reference electrode. The solvent used was MeCN with
proportion
for
the
2-CH2R)].
reactants
/
2.5. Conclusions
The
lithiation
of
the ferrocenylamines
NMe2, NEt2, CH2NMe2,
[Fe(C5H5)(C5H4CH2R)] (Rꢁ
/

P.B. Hitchcock et al. / Journal of Organometallic Chemistry 664 (2002) 245ꢂ
/257
253
0.1 M (But4N)BF4 as the supporting electrolyte. All
potentials were referenced against decamethylferrocene.
The measurements were carried out at room tempera-
ture (r.t.) under an atmosphere of purified dinitrogen.
3.2. Preparation of morpholinomethylferrocene [33]
As for the synthesis of N,N-diethylaminomethylfer-
rocene with ferrocene (41.8 g, 220 mmol), bis(morpho-
lino)methane (70.6 g, 380 mmol), phosphoric acid (39.0
g, 400 mmol) and AcOH (360 cm3). The reaction
mixture was heated on a steam bath for 20 h. Morpho-
X-ray crystal structure data were collected by the 2u ꢂ
/
v scan method at 173(2) K using an EnrafꢂNonius
/
CAD4 diffractometer. During processing, the data were
corrected for absorption by semi-empirical c-scan
methods. The structures were solved by direct methods
in SHELXS and refined by full-matrix least-square
methods in SHELXN [30]. All non-hydrogen atoms were
refined anisotropically. Diagrams of the molecular
structure of complexes were drawn with the ORTEP
package [31]. The crystallographic data are summarised
in Table 14.
linomethylferrocene was isolated as a reddishꢂ
solid (38.0 g, 133 mmol, 59%).
1H-NMR (CDCl3, ppm): d 2.27 (t, NCH2, 4H), 3.22
(s, C5H4CH2N, 2H), 3.53 (t, OCH2, 4H), 3.96ꢂ4.05 (m,
/
brown
/
C5H4, block of 9H), 4.00 (s, C5H5, block of 9H).
13C{1H}-NMR (CDCl3, ppm): d 52.63 (NCH2), 58.24
(C5H4CH2N), 66.29 (OCH2), 67.59 (C5H4), 68.02
(C5H5), 69.73 (C5H4), 81.82 (Cipso of C5H4).
A series of methylenediamines were prepared accord-
ing to literature methods [32]. These were subsequently
allowed to react with ferrocene (see below) in order to
prepare the corresponding ferrocenylamines [32,33].
3.3. Preparation of N-benzyl-N-
methylaminomethylferrocene [33]
[Fe(C5H5)(LiC5H3ꢀ
/
2-CH2NMe2)] (I) was prepared by
As for the synthesis of N,N-diethylaminomethylfer-
rocene with ferrocene (98.1 g, 530 mmol), N,N?-
dibenzyl-N,N?-dimethylmethylenediamine (229 g, 900
mmol), phosphoric acid (92.0 g, 940 mmol) and AcOH
(850 cm3). The reaction was performed at 100 8C for 24
h. The crude product was purified by high vacuum
distillation to give the N-benzyl-N-methylaminomethyl-
ferrocene as a dark red liquid (30.9 g, 97.2 mmol, 18%).
1H-NMR (CDCl3, ppm): d 2.10 (s, NCH3, 3H), 3.40
(s, PhCH2N and C5H4CH2N, 4H; coincidental overlap),
4.04 (s, C5H5, 5H), 4.08 (m, C5H4, 2H), 4.14 (m, C5H4,
2H), 7.28 (d, Ph, 5H).
literature methods [14,34].
3.1. Preparation of N,N-diethylaminomethylferrocene
[33]
The reported procedure [32] for the synthesis of N,N-
dimethylaminomethylferrocene was adopted for the
synthesis
of
N,N-diethylaminomethylferrocene.
N,N,N?,N?-tetraethylmethylenediamine (69.4 g, 440
mmol) was added dropwise to a well-stirred solution
of phosphoric acid (45.0 g, 460 mmol) in 416 cm3 of
AcOH in
a
three-necked round-bottomed flask
13C{1H}-NMR (CDCl3, ppm): d 41.53 (NCH3), 56.66
(PhCH2), 60.79 (C5H4CH2), 67.75 (C5H4), 68.31
(C5H5), 69.99 (C5H4), 82.99 (Cipso of C5H4), 126.69
(Ph), 128.02 (Ph), 128.78 (Ph), 139.10 (Cipso of Ph).
equipped with a condenser and a nitrogen inlet.
Ferrocene (48.3 g, 260 mmol) was then added and the
resulting suspension was heated on a steam bath for 16
h. The reaction mixture, a dark amber solution, was
allowed to cool to r.t. and was diluted with 550 cm3 of
water. The unreacted ferrocene was removed by extract-
ing the solution with three 325 cm3 portions of Et2O.
The aqueous solution was then cooled in an ice bath and
made alkaline by the addition of 245 g of NaOH pellets.
The tertiary amine separated from the alkaline solution
as an oil in the presence of some black tar. The mixture
was extracted with three 500 cm3 portions of Et2O. The
organic solution was washed with water and dried over
Na2SO4. Crude diethylaminomethylferrocene was ob-
tained as a dark red mobile liquid when the solvent was
removed under vacuum. Distillation of the crude
product under vacuum gave 30.5 g (110 mmol, 43%)
of the ferrocenylamine.
3.4. Preparation of N,N-dimethylaminoethylferrocene
N,N-Dimethylaminoethylferrocene was prepared by
rearrangement of N,N-trimethylaminomethylferrocene
iodide, using a method reported by Hauser et al. [35].
1H-NMR (CDCl3, ppm): d 2.26 (s, NCH3, 6H), 2.39ꢂ
/
2.52 (m, CH2, 4H), 4.03ꢂ
/
4.08 (m, C5H4, 4H), 4.10 (s,
C5H5, 5H).
13C{1H}-NMR (CDCl3, ppm): d 27.83 (C5H4CH2),
45.47 (NCH3), 60.85 (NCH2), 67.10 (C5H4), 67.98
(C5H4), 68.40 (C5H5), 86.63 (Cipso of C5H4).
3.5. Preparation of [Fe(C5H5)(LiC5H3ꢀ
/
2-CH2NEt2)]
(II)
1H-NMR (CDCl3, ppm): d 1.02 (t, CH3, 6H), 2.42 (q,
NCH2CH3, 4H), 3.48 (s, C5H4CH2, 2H), 4.08 (m, C5H4,
2H), 4.09 (s, C5H5, 5H), 4.14 (m, C5H4, 2H).
13C{1H}-NMR (CDCl3, ppm): d 11.87 (CH3), 46.01
(NCH2CH3), 51.63 (C5H4CH2), 67.65 (C5H4), 68.28
(C5H5), 70.00 (C5H4), 82.75 (Cipso of C5H4).
N,N-Diethylaminomethylferrocene (3.90 g, 14.4
mmol) was dissolved in 100 cm3 of Et2O and treated
dropwise with a 1.6 M solution of butyllithium in C6H14
(9.0 cm3, 14.4 mmol) over 10 min. Stirring was
continued for 16 h at r.t. The solvent was then removed

254
P.B. Hitchcock et al. / Journal of Organometallic Chemistry 664 (2002) 245ꢂ257
/
Table 14
Details of crystallographic structure determinations
Compound [Fe(C5H5){C5H3Me- [Fe(C5H5)(C5H4CH2N- [Fe(C5H5)(C5H4CH2CH2N- [Fe(C5H5)(C5H4CH2N- [Fe(C5H5)(C5H4CH2N-
(CH2NMe3)}]I (VI)
MeEt2)]I (XII)
Me3)]I×MeOH (XIII)
MeC4H8O)]I (XIV)
Me2CH2Ph)]I (XV)
Formula
M (g molꢄ1
C15H22FeIN
399.09
C16H24FeIN
413.11
C15H22FeIN×(CH4O)
431.13
C16H22FeINO
427.10
C20H24FeIN
461.15
)
Wavelength Moꢂ
/
Ka (mean)
0.71073
Orthorhombic
Moꢂ
0.71073
Monoclinic
/
Ka (mean)
Moꢂ
0.71073
Monoclinic
/
Ka (mean)
Moꢂ
0.71073
Orthorhombic
/
Ka (mean)
MoꢂKa (mean)
0.71073
Monoclinic
/
˚
(A)
Crystal
system
Space group Pbca (No. 61)
Unit cell di-
mensions
P21/c (No. 14)
P21/c (No. 14)
Pbca (No. 61)
P21/n (No. 14)
˚
a (A)
9.5787(8)
21.159(2)
16.154(2)
90
15.0030(3)
10.8778(3)
20.2922(5)
90
12.3565(3)
10.9342(3)
13.0520(5)
90
12.9152(5)
18.4478(8)
13.3985(3)
10.9172(2)
13.7018(4)
90
˚
b (A)
˚
c (A)
13.5502(5)
90
a (8)
b (8)
g (8)
90
90
91.844(2)
90
93.438(2)
90
90
90
112.848(1)
90
3
˚
V (A )
Z
3274.0(6)
8
1.62
3309.96(14)
8
1.66
1760.26(8)
4
1.63
3228.4(2)
1846.96(8)
4
1.66
8
1.76
Dcalc
(g cmꢄ3
)
Absorption 2.79
coefficient
2.77
2.61
2.84
2.49
(mmꢄ1
)
Data collec- 3.825u 521.99
tion range u
3.765u 530.04
3.735u 527.91
ꢄ125h 516,
ꢄ95k 514, ꢄ175l 517 ꢄ195k 521,
ꢄ165l 512
3.735u 525.04
ꢄ135h 515,
3.735u 527.85
(8)
Index ranges ꢄ105h 510,
ꢄ225k 522,
ꢄ175h 521,
ꢄ155k 514,
ꢄ285l 528
9449
ꢄ175h 514,
ꢄ115k 514,
ꢄ175l 518
4306
ꢄ175l 516
1957
Unique
4172
2789
reflections
Observed
reflections
[I ꢀ2s(I)]
Refined
1507
8128
3586
2426
3799
167
344
195
181
208
parameters
Final R1,
wR2
0.076; 0.187
0.036; 0.078
0.028; 0.060
0.044; 0.120
0.031; 0.073
[I ꢀ2s(I)]
R1, wR2 (all 0.097; 0.199
data)
0.045; 0.083
0.036; 0.064
0.051; 0.126
0.037; 0.077
under
vacuum,
leaving
[Fe(C5H5)(LiC5H3ꢀ
/
2-
stirred for ca. 5 h. The product [Fe(C5H5)(LiC5H3ꢀ
/2-
CH2NEt2)] as a dark amber oil (2.91 g, 10.5 mmol).
The product is very soluble even in non-polar solvents
such as C6H14, which makes the isolation and purifica-
tion of the lithium salt difficult. In subsequent reactions
of metal complexes with the lithium ligand, the reactions
were carried out directly, without Li-salt isolation.
CH2CH2NMe2)] was isolated as a dark amber oil (3.38
g, 12.9 mmol). The lithium salt is very soluble Et2O,
THF and in non-polar solvents such as C6H6 and
C6H14. In subsequent reactions of metal complexes
with the lithium reagent, the reactions were carried out
directly, without Li-salt isolation.
3.6. Preparation of [Fe(C5H5)(LiC5H3ꢀ
/
2-
3.7. Preparation of [Fe(C5H5)(LiC5H3ꢀ
/
2-
CH2CH2NMe2)] (III)
CH2NC4H8O)] (IV)
As for the synthesis of [Fe(C5H5)(LiC5H3ꢀ
/
2-
As for the synthesis of [Fe(C5H5)(LiC5H3ꢀ
/
2-
CH2NEt2)] with N,N-dimethylaminoethylferrocene
(4.69 g, 18.3 mmol) and butyllithium (1.6 M solution
in C6H14, 12 cm3, 19.2 mmol). The reaction mixture was
CH2NEt2)] with [Fe(C5H5)(C5H3CH2NC4H8O)] (8.12
g, 28.6 mmol) and butyllithium (1.6 M solution in
C6H14, 18 cm3, 28.8 mmol). An orange/brown precipi-

P.B. Hitchcock et al. / Journal of Organometallic Chemistry 664 (2002) 245ꢂ
/257
255
tate formed immediately after the addition of butyl-
lithium. Stirring was continued for 16 h at r.t. and the
resulting orange/brown solid was filtered off, washed
with C6H14 (20 cm3) and dried under vacuum for 2 h
(Yield: 2.02 g, 6.96 mmol, 24%).
3.11. Preparation of
[Fe(C5H5){C5H3Me(CH2CH2NMe3)}]I (VIII)
As for the synthesis of [Fe(C5H5){C5H3Me(CH2N-
MeEt2)}]I with [Fe(C5H5)(C5H4CH2CH2NMe2)] (1.21
g, 4.73 mmol), butyllithium (1.6 M, 3.0 cm3, 4.80 mmol)
and MeI (1.2 cm3, 2.67 g, 18.8 mmol). In this manner,
1.54 g of yellow crystals were isolated (3.74 mmol, 79%).
EI-MS m/z (%): 286 (10) [Fe(C5H5){C5H3Me-
(CH2CH2NMe3)}]ꢃ, 271 (45) [Fe(C5H5){C5H3Me-
(CH2CH2NMe2)}]ꢃ, 257 (26) [Fe(C5H5)(C5H4CH2-
CH2NMe2)]ꢃ (starting material), 213 (23) [Fe(C5H5)-
(C5H3MeCH2)]ꢃ, 121 (43) [Fe(C5H5)]ꢃ, 58 (100)
[CH2NMe2]ꢃ.
1H-NMR (C6D6, ppm): d 2.25 (m, NCH2, 4H), 3.16
(m, C5H3CH2N, 2H), 3.58 (m, OCH2, 4H), 3.96 (s,
C5H5, block of 8H), 3.91ꢂ4.11 (m, C5H3 block of 8H).
/
3.8. Preparation of [Fe(C5H5)(LiC5H3ꢀ
/
2-
CH2NMeCH2Ph)] (V)
As for the synthesis of [Fe(C5H5)(LiC5H3ꢀ
/
2-
CH2NEt2)] with [Fe(C5H5)(C5H3CH2NMeCH2Ph)]
(11.5 g, 36.2 mmol) and butyllithium (1.6 M solution
in C6H14, 23 cm3, 36.5 mmol). The product
3.12. Preparation of
[Fe(C5H5){C5H3Me(CH2NMeC4H8O)}]I (IX)
[Fe(C5H5)(LiC5H3ꢀ
/
2-CH2NMeCH2Ph)] was isolated
as a dark amber oil (8.52 g, 26.3 mmol). The lithium
salt is very soluble in Et2O and C6H14.
As for the synthesis of [Fe(C5H5){C5H3Me(CH2N-
MeEt2)}]I with [Fe(C5H5)(C5H4CH2NC4H8O)] (0.90 g,
3.17 mmol), butyllithium (1.6 M, 2.0 cm3, 3.20 mmol)
and MeI (0.8 cm3, 1.82 g, 12.8 mmol). In this manner,
0.71 g of yellow crystals were isolated (1.61 mmol, 51%).
The filtrate was evaporated to dryness yielding an amber
oil.
3.9. Preparation of
[Fe(C5H5){C5H3Me(CH2NMe3)}]I (VI)
This was prepared by direct reaction of MeI with (I)
in about 75% yield.
EI-MS m/z (%) on amber oil: 299 (25) [Fe(C5H5)-
{C5H3Me(CH2NC4H8O)}]ꢃ, 285 (95) [Fe(C5H5)(C5H4-
CH2NC4H8O)]ꢃ (starting material), 213 (36) [Fe(C5H5)-
(C5H3MeCH2)]ꢃ, 199 (100) [C11H11Fe]ꢃ, 121 (86)
[Fe(C5H5)]ꢃ.
3.10. Preparation of
[Fe(C5H5){C5H3Me(CH2NMeEt2)}]I (VII)
To an amber solution of [Fe(C5H5)(C5H4CH2NEt2)]
(1.52 g, 5.63 mmol) in Et2O (30 cm3), 1.6 M solution of
butyllithium in hexanes (3.5 cm3, 5.60 mmol) was added
carefully via a syringe. The reaction mixture was
allowed to stir for 16 h at r.t., after which time, a
solution of MeI (1.4 cm3, 3.18 g, 22.4 mmol) in Et2O was
added slowly. The reaction mixture was continued to
stir for a further 4 h, after which time, the yellow
precipitate formed was filtered off, washed with Et2O
and dried under vacuum. Recrystallisation of this solid
from a methanolic solution (5 cm3) layered with Et2O
(10 cm3) yielded yellow crystals (1.32 g, 3.10 mmol,
55%). The filtrate was evaporated to dryness yielding an
amber oil.
3.13. Preparation of
[Fe(C5H5){C5H3Me(CH2NMe2CH2Ph)}]I (X)
As for the synthesis of [Fe(C5H5){C5H3Me(CH2N-
MeEt2)}]I with [Fe(C5H5)(C5H4CH2NMeCH2Ph)] (0.75
g, 2.36 mmol), butyllithium (1.6 M, 1.5 cm3, 2.40 mmol)
and MeI (0.6 cm3, 1.33 g, 9.40 mmol). In this manner,
0.78 g of yellow crystals were isolated (1.65 mmol, 70%).
The filtrate was evaporated to dryness yielding an amber
oil.
EI-MS m/z (%) on amber oil: 333 (56) [Fe(C5H5)-
{C5H3Me(CH2NMeCH2Ph)}]ꢃ, 319 (100) [Fe(C5H5)-
(C5H4CH2NMeCH2Ph)]ꢃ (starting material), 213 (41)
[Fe(C5H5)(C5H3MeCH2)]ꢃ, 199 (83) [C11H11Fe]ꢃ, 134
(9) [CH2NMeCH2Ph]ꢃ, 121 (60) [Fe(C5H5)]ꢃ, 91 (45)
[CH2Ph]ꢃ.
EI-MS m/z (%) on amber oil: 285 (20) [Fe(C5H5)-
{C5H3Me(CH2NEt2)}]ꢃ, 213 (100) [Fe(C5H5)(C5H3Me-
CH2)]ꢃ, 199 (27) [C11H11Fe]ꢃ, 121 (64) [Fe(C5H5)]ꢃ,
73 (26) [HNEt2]ꢃ.
In order to determine the optimum reaction condi-
tions for the formation of [Fe(C5H5)(LiC5H3ꢀ
/
2-
3.14. Preparation of [Fe(C5H5)(C5H4CH2NMe3)]I
(XI)
CH2NEt2)], the same procedure was repeated with
[Fe(C5H5)(C5H4CH2NEt2)] and butyllithium in 1:1, 1:2
and 1:5 ratios, at a range of reaction times (1ꢂ
/
5, 10, 24
This was prepared by the method described in Ref.
[32].
1H-NMR (CD3OD, ppm): d 3.02 (s, NCH3, 9H), 4.28
(s, C5H5, 5H), 4.41 (m, C5H4, 2H), 4.52 (s, C5H4CH2N,
2H), 4.53 (m, C5H4, 2H).
and 48 h). The reaction mixture was treated in each case
with a large excess of MeI. The yellow precipitate
formed in each experiment was isolated and charac-
terised by NMR spectroscopy.

256
P.B. Hitchcock et al. / Journal of Organometallic Chemistry 664 (2002) 245ꢂ257
/
3.15. Preparation of [Fe(C5H5)(C5H4CH2NMeEt2)]I
(XII)
95%. Anal. Found: C, 51.25; H, 5.37; N, 3.07.
C20H24FeIN requires: C, 52.09; H, 5.25; N, 3.04%.
1H-NMR (CD3OD, ppm): d 2.84 (s, NCH3, 6H), 4.29
(s, C5H5, 5H), 4.44 (t, C5H4, 2H), 4.50 (s, PhCH2N, 2H),
4.57 (m, C5H4, 2H), 4.62 (s, C5H4CH2N, 2H), 7.55 (d,
Ph, 5H).
As for the synthesis of [Fe(C5H5)(C5H4CH2NMe3)]I,
with methyl iodide (0.4 cm3, 0.84 g, 5.55 mmol),
[Fe(C5H5)(C5H4CH2NEt2)] (1.01 g, 3.74 mmol) and
MeOH (5 cm3). Upon layering with 10 cm3 of Et2O
orange crystals formed, which were filtered, washed with
Et2O and dried under vacuum. Yield: 1.42 g, 3.44 mmol,
92%. Anal. Found: C, 46.14; H, 5.94; N, 3.41.
C16H24FeIN requires: C, 46.52; H, 5.86; N, 3.39%.
1H-NMR (CD3OD, ppm): d 1.37 (t, NCH2CH3, 6H),
3.19. Dinitrogen uptake experiments
The apparatus used consisted of a closable reaction
vessel connected to a gas burette. About two molar
equivalents of [Fe(C5H5)(LiC5H3ꢀ
/
2-CH2R)] (Rꢁ
/
2.89 (s, NCH3, 3H), 3.24ꢂ3.40 (m, NCH2CH3, 4H), 4.33
/
NMe2, NEt2, CH2NMe2, NC4H8O or NMeCH2Ph)
were then added. To a solution of [VCl2(tmen)2] in
THF under N2 at r.t. The reaction mixture changed
(s, C5H5, 5H), 4.43 (m, C5H4, 2H), 4.52 (s, C5H4CH2N,
2H), 4.57 (m, C5H4, 2H).
immediately from blue to deep redꢂbrown. The dinitro-
gen uptake was generally rapid, and complete within ca.
20 min.
/
3.16. Preparation of
[Fe(C5H5)(C5H4CH2CH2NMe3)]I (XIII)
As for the synthesis of [Fe(C5H5)(C5H4CH2NMe3)]I,
with methyl iodide (0.3 cm3, 0.72 g, 4.78 mmol),
[Fe(C5H5)(C5H4CH2CH2NMe2)] (0.82 g, 3.19 mmol)
and MeOH (5 cm3). Upon layering with 10 cm3 of
Et2O orange crystals formed, which were filtered,
washed with Et2O and dried under vacuum. Yield:
1.22 g, 3.06 mmol, 96%. Anal. Found: C, 45.09; H,
5.52; N, 3.50. C15H22FeIN requires: C, 45.14; H, 5.56;
N, 3.51%.
Acknowledgements
We acknowledge the award of an EPSRC studentship
to M.T.
References
1H-NMR (CD3OD, ppm): d 2.85ꢂ
2H), 3.19 (s, NCH3, 9H), 3.47ꢂ3.52 (m, NCH2, 2H),
4.13 (t, C5H4, 2H), 4.19 (s, C5H5, 5H), 4.22 (m, C5H4,
/2.91 (m, C5H4CH2,
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/
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[Fe(C5H5)(C5H4CH2NMeC4H8O)]I (XIV)
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[6] (a) P.B. Hitchcock, D.L. Hughes, G.J. Leigh, J.R. Sanders, J.S. de
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As for the synthesis of [Fe(C5H5)(C5H4CH2NMe3)]I,
with methyl iodide (0.2 cm3, 0.43 g, 2.85 mmol),
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