The first 1,3,2-diazabora-[3]ferrocenophanes - Molecular structures and dynamic behaviour in solution

Article abstract of DOI:10.1016/j.ica.2003.09.039

Dilithiated 1,1^′-bis(trimethylsilylamino)ferrocene (1) reacts with aminoboron dihalides (2) X₂B-N(R^′)R [X=Br, R^′=R=Et (2a); X=Cl, R^′=Me, R=CH ₂Ph (2b), X=Cl, R^′=Et, R=Ph (2c)] to

Full text of DOI:10.1016/j.ica.2003.09.039

Inorganica Chimica Acta 357 (2004) 1703–1710
www.elsevier.com/locate/ica
The first 1,3,2-diazabora-[3]ferrocenophanes – molecular
structures and dynamic behaviour in solution
*
Bernd Wrackmeyer , Elena V. Klimkina, Heidi E. Maisel,
*
Wolfgang Milius, Max Herberhold
Laboratorium fu€r Anorganische Chemie, Universit€at Bayreuth, Lehrstuhl f. Anorganische Chemie II, Universitaetsstr. 30, NW 1,
Bayreuth D-95440, Germany
Received 6 June 2003; accepted 2 September 2003
Dedicated to Professor Helmut Werner on the occasion of his 70th birthday
Abstract
Dilithiated 1,10-bis(trimethylsilylamino)ferrocene (1) reacts with aminoboron dihalides (2) X2B-N(R0)R [X ¼ Br, R0 ¼ R ¼ Et
(2a); X ¼ Cl, R0 ¼ Me, R ¼ CH2Ph (2b), X ¼ Cl, R0 ¼ Et, R ¼ Ph (2c)] to give 2-amino-1,3,2-diazabora-[3]ferrocenophanes (3a–c) for
the first time. The steric constraints exerted by the [3]ferrocenophane unit and the presence of the N-SiMe3 groups cause rather
different B–N bonding situations in these tri(amino)boranes. The boron atom has the choice between three nitrogen atoms for
BN(pp)p bonding: in the cases of 3a and 3b, it prefers the NEt2 and the N(Me)CH2Ph group, respectively, over the N-SiMe3 groups,
whereas in 3c the N(Et)Ph group appears to be the weaker p-donor. This can be concluded from the X-ray structural analyses
1
carried out for 3a and 3c, and from the low temperature H, 13C, and 29Si NMR spectra of 3a–3c.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Ferrocene; Boron; NMR – multinuclear; X-ray
1. Introduction
the nature of the substituents R and R0 in the exocyclic
amino group, the boron atom may prefer either the
exocyclic BN(pp)p bonding (B) with considerable dis-
tortion of the [3]ferrocenophane structure or the endo-
cyclic BN(pp)p interactions (C), where the boron atom
lies in the plane formed by Fe, C(1), C(10) and the two
nitrogen atoms. The structure A with perfect BN(pp)p
bonding involving all three nitrogen atoms is unlikely,
since the bulky N-SiMe3 groups will prevent an appro-
priate orientation of the exocyclic amino group N(R)R0.
In the present work, we describe the synthesis of the first
three examples of 1,3,2-diazabora-[3]ferrocenophanes
and their structural characterisation.
Recently, the chelating ability of the 1,10-bis(tri-
methylsilylamino)ferrocene ligand has been established
for magnesium, titanium [1,2], zirconium [1], and tin
derivatives [3,4]. The ring closure to the 1,3,2-diazahet-
ero-[3]ferrocenophane system enforces an approxi-
mately perpendicular orientation of the lone electron
pairs at both nitrogen atoms with respect to the p system
of the cyclopentadienyl rings (Scheme 1; A–C). In this
context, a boron atom with trigonal planar surround-
ings in the central 2-position of the bridge could be an
attractive probe for studying p interactions of the boron
pz orbital with the lone pairs of electrons at the nitrogen
atoms [5–8], in particular if the boron atom is linked to a
third amino group as in A–C (Scheme 1). Depending on
2. Results and discussion
2.1. Synthesis of the 1,3,2-diazabora-[3]ferrocenophanes
* Corresponding authors. Tel.: +49-921-55-2542; fax: +49-921-55-
2157 (B. Wrackmeyer); fax: +49-921-55-2157 (M. Herberhold).
E-mail addresses: b.wrack@uni-bayreuth.de (B. Wrackmeyer),
max.herberhold@uni-bayreuth.de (M. Herberhold).
In general, dilithiation of 1,10-bis(trimethylsilyla-
mino)ferrocene proceeds readily [1,3,9] to give 1 which
0020-1693/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2003.09.039

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B. Wrackmeyer et al. / Inorganica Chimica Acta 357 (2004) 1703–1710
Scheme 1. BN(pp)p interactions in 2-amino substituted 1,3,2-diazabora-[3]ferrocenophanes.
may then react with element halides to afford the cor-
responding [3]ferrocenophanes. Although the magne-
sium derivative sometimes gives better results [1,3],
treatment of 1 with different aminoboron dihalides (2)
(Scheme 2) provides a fairly straightforward route to the
desired 1,3,2-diazabora-[3]ferrocenophanes (3).
The tri(amino)boranes (3) are orange solids (3a, 3c)
or an orange oil (3b) which are very sensitive towards
traces of moisture. Their solutions in benzene, toluene,
CDCl3 or CD2Cl2 cannot be kept for prolonged periods
at room temperature without decomposition. In con-
trast to 3a which is obtained in high yield and can be
readily purified by crystallisation, the formation of 3b
and 3c is accompanied by side reactions, and the crys-
tallisation of pure products is slow. The side reactions
involve the formation of bis(amino)boron chlorides
[R0(R)N]2B-Cl, and presumably also of the 2-chloro-
1,3,2-diazabora-[3]ferrocenophane [10]. Suitable crystals
for X-ray structural analysis were obtained for 3a and 3c
(vide infra). All three complexes 3a–3c were sufficiently
soluble in CDCl3, CD2Cl2 or toluene for NMR studies
at low temperature. These measurements revealed
structural details corresponding to the solid-state
structures in the cases of 3a and 3c, and in the case of 3b
at low temperature the bonding situation is comparable
to that found for 3a.
2.2. NMR spectroscopic results
Fig. 1 shows a typical one-dimensional NOE experi-
ment [11] carried out for 3a which confirms the assign-
ment of the 1H(C5H4) NMR signals. The broadened
Scheme 2. Synthesis of the 1,3,2-diazabora-[3]ferrocenophanes.
Fig. 1. The 500.13 MHz 1H/1H NOE difference spectrum of 3a (in C6D6 at 23 °C), using the gradient-enhanced version of the experiment [11b]. The
transitions of the N-SiMe3 groups are irradiated, and the response is indicated. Note the broad 1H2;5 NMR signals.

B. Wrackmeyer et al. / Inorganica Chimica Acta 357 (2004) 1703–1710
1705
1H2;5 NMR signal indicates a dynamic process, of which
the origin is not obvious at first glance. At lower tem-
sonable to assume efficient exocyclic BN(pp)p bonding
in both 3a and 3b.
perature, the pairwise degeneracy of the 1H2;5
,
1H3;4
Finally, the case of 3c is different, although at first
sight it might be tempting to assume a situation analo-
gous to that found for 3b. However, all NMR spectro-
scopic evidence in solution at low temperature indicates
that a plane of symmetry is present in the molecular
structure of 3c, in contrast to the situation in 3b. There is
and, better resolved, of the 13C2;5 and 13C3;4 NMR sig-
nals is lifted, giving rise to four signals instead of two in
1
both the H and 13C NMR spectra. At the lowest tem-
perature studied in the case of 3a ()70 °C), the signals of
the NEt2 group (1H, 13C NMR) and of the NSiMe3
groups (1H, 13C, 29Si NMR) remain unchanged. It can
be concluded, as in structure B, that rotation about the
exocyclic B–N bond is slow, and that the boron atom is
shifted out of the plane defined by Fe, C(1), C(10) and
the two nitrogen atoms, which explains the appearance
of the C5H4 NMR signals. Structure B requires that the
ethyl (NEt2) groups and the N-SiMe3 substituents re-
main equivalent, in agreement with the NMR spectra.
The activation energy of the hindered rotation about the
exocyclic B–N bond can be evaluated from the 13C
NMR spectra [12]. The magnitude of DG#ð0 °CÞ ¼ 58 ꢀ 1
kJ/mol is much higher than for other tri(amino)boranes
and lies in the range more typical of amino(diorg-
ano)boranes [13a,13b].
1
only one H, 13C and 29Si NMR signal for the two N-
1
SiMe3 groups in 3c, and there are four H and 13C(CH)
NMR signals, respectively, for the C5H4 groups (Fig. 2,
upper trace). This means that the boron atom lies in the
Fe, C(1), C(10), N, N plane as in structure C, and that
the amino group cannot freely rotate, most likely for
steric reasons. The observation of two 13C(ortho) and
two 13C(meta) signals for the N-Ph group at low tem-
perature is the result of hindered rotation about the N–
C(ipso) bond [13b,13c]. This particular structural feature
supports the assumption that the phenyl group com-
petes successfully as a p acceptor for the p electron
density at the exocyclic nitrogen atom. The electron
deficiency of the boron atom in 3c is then mainly com-
pensated, in contrast to the situation in 3a and 3b, by
endocyclic BN(pp)p interactions.
Inspection of the NMR spectra of 3b reveals broad-
ened signals at room temperature in all regions. At low
temperature, the signals become sharp, and the C5H4
groups exhibit 10 13C NMR signals (Fig. 2, lower trace).
Since there are also two 29Si NMR signals, we are
dealing again with a structure of type B. The hindered
rotation about the exocyclic B–N bond becomes ap-
parent from the complete loss of molecular symmetry, as
The d11B values of 3a–3c lie in the range typical of
tri(amino)boranes bearing N-SiMe3 and/or N-aryl
groups [14], and since they represent the sum of all in-
teractions, they cannot be used straightforwardly to
discuss differences in BN(pp)p bonding. There is no
systematic study of 29Si NMR data of N-silylamino-
boranes available. In the light of the present results such
measurements appear to be rewarding considering the
marked difference in 29Si nuclear shielding between 3a,
3b (d29Si ¼ 1.0, 1.9) on the one side and 3c (d29Si ¼ 8.4)
on the other side. In the former cases BN(pp)p bonding
is weak for the N-SiMe3 groups in contrast to the latter
1
indicated by the H and 13C NMR signals of the C5H4
groups and the observation of two 13C and 29Si NMR
signals for the N-SiMe3 groups. The presence of two
different substituents at nitrogen in 3b, in contrast to 3a,
leaves no doubt with regard to restricted rotation about
the exocyclic B–N bond in 3b, and it is therefore rea-
Fig. 2. Parts of the low temperature 62.9 MHz 13C{1H} NMR spectra of the [3]ferrocenophanes (3b) (lower trace) and (3c) (upper trace). Note the
complete loss of symmetry in the case of 3b [10 13C(C5H4) signals] in contrast to 3c [five 13C(C5H4) signals].

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B. Wrackmeyer et al. / Inorganica Chimica Acta 357 (2004) 1703–1710
Table 1
11B, 13C, and 29Si NMR dataa of the 2-amino-1,3-bis(trimethylsilyl)-1,3,2-diazabora-[3]ferrocenophanes (3)
Compound N(R)R0
3a, NEt2
23 °C
3b, N(Me)CH2Ph
23 °C
3c, N(Et)Ph
23 °C
)50 °Cb
)50 °C
)30 °C
d
d
d
13C(N-SiMe3)
1.4 (57.0)
1.2
1.5 (56.5)
0.7 (56.8)
0.8 (56.8)
2.2 (57.7)
2.0 (57.3)
13C(NR)
39.6, 13.7
39.6, 13.7
39.0, 13.5
39.0, 13.5
36.5
35.6
12.9
40.9 (br)
12.7
40.4
13C(NR0)
55.7 (CH2)
127.2
128.2
54.6 (CH2)
126.5 (Cp)
127.2
109.9 (br)
115.2
109.5 (Co)
114.5 (Cp)
115.8 (Co)
128.1 (Cm)
129.2 (Cm)
149.7 (Ci)
116.3 (br)
128.3 (br)
128.9 (br)
149.9
128.9
139.8
128.3
139.1 (Ci)
d
13C(fc-C1)
96.3
95.9
96.6
96.2, 95.6
101.2
68.8
100.9
d
13C(fc-C2;5
)
)
67.0 (br)
70.3, 67.8
66.8 (br)
70.1, 69.6
67.3, 67.0
68.7, 68.6
d
13C(fc-C3;4
67.0 (br)
66.3, 64.9
66.8 (br)
65.44, 65.36
65.1, 64.0
67.9
67.9, 67.7
d
d
11B
29Si
27.8
1.0
28.6
1.9 (56.8)
31.0
8.4 (57.7)
2.2 (56.6)
2.7 (56.4)
a Measured in C6D6 (3a), CD2Cl2 (3b), CDCl3 (3c); coupling constants J(29Si,13C) (ꢀ0.5 Hz) are given in parentheses.
b In [D8]toluene at )50 °C.
case. There are also considerable differences in the re-
spective B–N and N–Si bond lengths and in the bond
angles at the N(Si) atoms (vide infra) (see Table 1).
2.3. Molecular structures of the [3]ferrocenophanes (3a)
and (3c)
The molecular structures of complexes 3a and 3c are
shown in Figs. 3 and 4, respectively. Selected bond
lengths and angles are given in Table 2. The surround-
ings of the boron and nitrogen atoms are trigonal planar
Fig. 4. Molecular structure of 3c. The boron atom lies in the plane
formed by Fe, C(1), and N(1) as the result of efficient endocyclic
BN(pp) bonding (see Table 2) and perpendicular arrangement of the
NC(9)C(11) plane with respect to the N(1)BN(1A) plane.
within the experimental error. The shape of the ferroc-
enophane ring in 3a indicates weak endocyclic and
strong exocyclic BN(pp)p bonding, confirmed by the
presence of fairly long [7,8] endocylic B–N bonds and a
rather short [7,8] exocyclic B–N bond. The opposite
situation is found for the molecular structure of 3c,
where the endocyclic B–N bonds are short and the
exocyclic B–N bond is long, in agreement with the ar-
rangement of the plane of the exocyclic amino group
with respect to the ferrocenophane ring.
Fig. 3. Molecular structure of 3a showing the non-planar [3]ferroce-
nophane ring as the result of efficient exocyclic BN(pp)p bonding
which is also evident from the respective B–N bond lengths (Table 2).

B. Wrackmeyer et al. / Inorganica Chimica Acta 357 (2004) 1703–1710
1707
Table 2
Selected bond lengths (pm) and angles (°)a of the [3]ferrocenophanes (3a) (Fig. 3) and (3c) (Fig. 4)
3a
3c
C(11)–N(11)
C(16)–N(12)
142.3(7)
142.8(8)
147.0(9)
151.2(9)
140.1(9)
171.9(5)
170.7(5)
148.6(7)
146.5(8)
316.4
C(1)–N(1)
1.446(3)
1.446(3)
N(11)–B(1)
N(12)–B(1)
N(1)–B
N(13)–B(1)
N(11)–Si(11)
N(2)–B
N(1)–Si(1)
149.2(6)
179.2(3)
N(12)–Si(12)
N(13)–C(114)
N(13)–C(116)
N(2)–C(9)
N(2)–C(11)
Feꢁ ꢁ ꢁB
146.2(5)
138.7(5)
342.6
Fe(1)ꢁ ꢁ ꢁB(1)
C(11)–Fe(1)–C(16)
Fe(1)–C(11)–N(11)
Fe(1)–C(16)–N(12)
C(11)–N(11)–Si(11)
C(16)–N(12)–Si(12)
N(11)–B(1)–N(12))
N(11)–B(1)–N(13)
N(12)–B(1)–N(13)
C(114)N(13)C(116)/N(11)BN(12)
C5/C5 (a)
96.9(3)
122.5(4)
122.2(4)
116.0(4)
120.7(4)
121.0(6)
120.4(7)
118.5(7)
171.8
C(1)–Fe–C(1A)
Fe–C(1)–N(1)
94.8(2)
125.9(2)
C(1)–N(1)–Si(1)
108.5(2)
N(1)–B–N(1A)
N(1)–B–N(2)
126.7(4)
116.6(2)
C(11)N(2)C(9)/N(1)B(N(1A)
C5/C5 (a)
C5/N(1) (b)
90
10.8
4.5
15.0
0.9
C5/N(11) (b1)
C5/N(12) (b2)
C5–Fe(1)–C5 (c)
C5/C5 (twist) (s)
3.8
170.6
0.7
C5–Fe–C5 ðcÞ
170.3
0 (symmetry)
C5/C5 (twist) (s)
a The definition of the angles a; b; c and s is given in [16b,16c].
There are also marked differences in the N–Si bond
lengths in 3a and 3c, being short [15] in 3a and long in 3c.
It is tempting to relate these features to the availability of
the lone pairs of electrons at the N(Si) nitrogen atoms for
additional Si–N bonding interactions, since the degree of
BN(Si)(pp)p bonding is low in 3a and high in 3c.
The cyclopentadienyl rings in the structures of both
3a and 3c lie almost exactly in eclipsed positions, as in
many other [n]ferrocenophanes with n ¼ 1, 2 [16] and
n ¼ 3 [1–4,16], somewhat tilted against a parallel ar-
rangement (see angles a and c in Table 2) towards the
NBN unit. However, the mutual positions of the cy-
clopentadienyl rings (staggered, eclipsed or in between)
depend strongly on the geometry and nature of the
bridge, as is evident for the molecular structures of
various [3]ferrocenophanes [17]. As a result of the dif-
ferent ferrocenophane ring geometries, the non-bonding
Feꢁ ꢁ ꢁB distances differ markedly in 3a and 3c.
4. Experimental
4.1. General
The preparation and handling of all compounds were
carried out in an atmosphere of dry argon and carefully
dried solvents were used throughout. Starting materials
were prepared as described (1,10-bis(trimethylsilyla-
mino)ferrocene [1b]), diethylaminoboron dibromide (2a)
from BBr3 and B(NEt2)3 (molar ratio 2:1), ben-
zyl(methyl)aminoboron dichloride (2b) [18] and
ethyl(phenyl)aminoboron dichloride (2c) [18]). Other
starting materials were commercially available, such as n-
butyllithium (1.6 M in hexane) and boron trichloride (1.0
M in hexane). NMR measurements: Bruker ARX 250
and Bruker DRX 500: 1H, 11B, 13C, 29Si NMR (refocused
INEPT [19] based on 2J(29Si, 1H) ¼ 7 Hz); chemical
shifts are given with respect to Me4Si [d1H (CHCl3/
CDCl3) ¼ 7.24; d13C (CDCl3) ¼ 77.0, (CD2Cl2) ¼ 53.5,
(C6D6) ¼ 128.0, (C6D5CD3) ¼ 20.5; d29Si ¼ 0 for
N(29Si) ¼ 19.867184 MHz]; external BF3-OEt2 [d11B ¼ 0
for N(11B) ¼ 32.083971 MHz].
3. Conclusions
The molecular structures both in solution and in the
solid state of the first 1,3,2-diazabora-[3]ferroceno-
phanes (3a–c) depend on a remarkable manner on the
nature of the amino group in 2-position. Strong p do-
nors such as the NEt2 (3a) or N(Me)CH2Ph groups (3b)
enforce a nonplanar ferrocenophane ring whereas
weaker p donors such as a N(Et)Ph group induces effi-
cient endocyclic BN(pp)p bonding for which a planar
[3]ferrocenophane ring is required as in 3c.
4.2. Synthesis of the N,N0-dilithioamide 1 (fc(NSiMe3)2
Li2)
A solution of fc(NHSiMe3)2 (350 mg, 0.97 mmol) in
hexane (25 mL) was cooled ()60 °C), and n-BuLi was
added (1.21 mL of a 1.6 M solution in hexane, 1.94
mmol). The reaction mixture was stirred at )60 °C for 1

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B. Wrackmeyer et al. / Inorganica Chimica Acta 357 (2004) 1703–1710
h, then allowed to reach ambient temperature and kept
stirring for further 30 min. The formation of a red
precipitate was observed which was separated using a
centrifuge and decanting the supernatant liquid. The
solid was dried under vacuum to give 340 mg (94%) of 1
as an orange powder.
adding a solution of Et2NBBr2 (2a) (0.21 g, 0.8 mmol) in
hexane (10 mL), the mixture was warmed to room
temperature and kept stirring for 12 h. Insoluble mate-
rials were filtered off and the solvent was removed in
vacuo. The residue, a yellow oil which slowly became
solid, was dissolved in a small amount of hexane, and
the solution was stored at )18 °C for several days. Then
3a was obtained as orange crystals (0.31 g; 81%; m.p.
4.3. Properties of the aminoboron dichlorides (2b) and
(2c)
1
161 °C). H NMR (500.1 MHz; C6D6; 25 °C): d ¼ 0:43
(s, 18H, 0 Me3Si), 3.40, 1.10 (q, t, 10H, Et2N), 4.10 (br,
0
0
0
Benzyl(methyl)aminoboron dichloride (2b): b.p. 40–
42 °C/0.2 Torr ([20]: b.p. 68 °C/2 Torr). 1H NMR (250.1
MHz; CDCl3; 25 °C): d ¼ 2:89 (s, 3H, MeN), 4.51 (s,
2H, NCH2), 7.25–7.50 (m, 5H, Ph). 13C NMR (62.9
MHz, CDCl3; 25 °C): d ¼ 37:1 (MeN), 55.8 (NCH2),
127.6 (Co;p), 128.6 (Cm), 137.0 (Ci). 11B NMR (80.3
MHz; CDCl3; 25 °C): d ¼ 31:3.
4H, H2;2 ;5;5 ), 4.16 (m, 4H, H3;3 ;4;4 ).
2-Benzyl(methyl)amino-1,3-bis(trimethylsilyl)-1,3,2-
diazabora-[3]ferrocenophane (3b): A suspension of
fc(NSiMe3)2Li2 (1) (100 mg, 0.27 mmol) in hexane (15
mL) was cooled to )70 °C, and PhCH2(Me)NBCl2 (2b)
(54 mg, 0.27 mmol) was injected slowly through a sy-
ringe. After stirring the reaction mixture for 1 h at )70
°C and then for 3 h at ambient temperature, the mixture
was separated by centrifugation from insoluble materi-
als, and the liquid was collected. Volatile materials were
removed in vacuo (0.01 Torr), and the resulting oil was
dissolved in hexane (15 mL). After filtration the solvent
was removed in vacuo to give 85 mg (65%) of 3b as a
yellow-orange oil. 1H NMR (CDCl3, 25 °C): d ¼ 0.23 (s,
18H, Me3Si), 2.72 (s, 3H, MeN),0 3.83 (br), 3.90 (br) (m,
Ethyl(phenyl)aminoboron dichloride (2c): b.p. 38–39
1
°C/0.2 Torr ([21]: b.p. 67 °C/3 Torr). H NMR (250.1
MHz; CDCl3; 25 °C): d ¼ 3:73, 1.14 (q, t, 5H, EtN),
7.05–7.20 (m, 2H, Ph), 7.25–7.50 (m, 3H, Ph). 13C NMR
(62.9 MHz; CDCl3; 25 °C): d ¼ 49:4, 14.4 (EtN), 126.9
(Cp), 127.8 (Co), 129.2 (Cm), 144.8 (Ci). 11B NMR (80.3
MHz; CDCl3; 25 °C): d ¼ 31:4.
0
0
0
4.4. Synthesis of the 1,3-bis(trimethylsilyl)-2-amino-
1,3,2-diazabora-[3]ferrocenophanes (3a)–(3c)
4H, H2;2 ;5;5 ), 3.94 (m, 4H, H3;3 ; 4;4 ), 4.48 (br) (s, 2H,
NCH2), 7.2–7.5 (m, 5H, Ph).
2-Ethyl(phenyl)amino-1,3-bis(trimethylsilyl)-1,3,2-di-
azabora-[3]ferrocenophane (3c): The synthesis was car-
ried out in analogy to that of 3b, starting from 170 mg
(0.46 mmol) of fc(NSiMe3)2Li2 (1) and 92 mg (0.46
mmol) of Et(Ph)NBCl2 (2c), to give 130 mg (58%) of 3c
2-Diethylamino-1,3-bis(trimethylsilyl-1,3,2-diazabora-
[3]ferrocenophane (3a): Freshly prepared fc(NsiMe3)2
Li2 (1) (0.32 g, 0.86 mmol) was taken up in hexane (10
mL), and the suspension was cooled to )30 °C. After
Table 3
Crystallographic data of the [3]ferrocenophanes (3a) and (3c)
3a
3c
Formula
Crystal
C
20H36BN3Si2Fe
C24H36BN3Si2Fe
orange platelet
0.18 ꢂ 0.16 ꢂ 0.06
orthorhombic
Pnma
orange prism
0.18 ꢂ 0.15 ꢂ 0.12
triclinic
Dimensions (mm)
Crystal system
Space group
P1
Lattice parameters (pm, °)
a ¼ 1010:1ð2Þ
b ¼ 2508:4ð5Þ
c ¼ 3137:5ð6Þ
a ¼ 70:10ð3Þ
b ¼ 89:94ð3Þ
c ¼ 78:41ð3Þ
12
a ¼ 1547:2ð3Þ
b ¼ 1393:9ð3Þ
c ¼ 1223:6ð2Þ
Z
4
0.678
Absorption coefficient l (mmꢃ1
Diffractometer
)
0.728
STOE IPDS I (Mo Ka, k ¼ 71073 pm), graphite monochromator
Measuring range (e)
Reflections collected
2–26
48 042
2–26
18 381
Independent reflections (I > 2rðIÞ)
Absorption correction
Refined parameters
6658 (26 006 all)
nonea
1460
1130 (2612 all)
numerical
157
wR2=R1 (I > 2rðIÞ)
0.070/0.047
0.32/)0.19
0.079/0.038
0.40/)0.17
Maximum/minimum residual electron density (e pmꢃ3 10ꢃ6
)
a Absorption correction did not improve the data set.

B. Wrackmeyer et al. / Inorganica Chimica Acta 357 (2004) 1703–1710
1709
€
(c) H. Noth, H. Vahrenkamp, Chem. Ber. 100 (1967) 3353;
€
as a yellow oil. Crystallisation from hexane gave, after 2
months at )30 °C, orange crystals of 3c, m.p. 131–132
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°C. H NMR (CDCl3, 25 °C, J/Hz): d ¼ ꢃ0:12 (s, 18H,
Me3Si), 3.10, 1.40 (q, t, 5H, EtN), 3.83 (br), 3.90 (br) (m,
€
(b) H. Noth, R. Staudigl, W. Storch, Chem. Ber. 114 (1981) 3024;
0
0
0
0
4H, H2;2 ;5;5 ), 4.05 (m, 4H, H3;3 ;4;4 ), 6.55 (br) (m, 2H,
Ph-Ho), 6.62 (m, 1H, Ph-Hp), 7.17 (br) (m, 2H, Ph-Hm).
1H NMR (CDCl3, )30 °C): d ¼ ꢃ0:17 (s, 18H, Me3Si),
1.38 (t, 3H, CH3), 3.03 (q, 2H, NCH2), 3.78, 3.90 (m, m,
€
(c) H. Noth, Z. Naturforsch., Teil B 38 (1983) 692;
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0
0
0
0
2H, 2H, H2;2 ;5;5 ), 4.04 (m, 4H, H3;3 ;4;4 ), 6.42 (m, 2H,
€
(f) H. Noth, S. Weber, Chem. Ber. 117 (1984) 2504;
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€
399;
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4.5. Crystal structure determinations of the 2-amino-
1,3,2-diazabora-[3]ferrocenophanes (3a) and (3c)
(i) A. Hergel, H. Pritzkow, W. Siebert, Angew. Chem., Int. Ed.
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(j) H. Braunschweig, C.V. Koblinski, M. Mamuti, U. Englert, R.
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(k) A. Berenbaum, H. Braunschweig, R. Dirk, U. Englert, J.C.
Details pertinent to the crystal structure determina-
tions are listed in Table 3. Crystals of appropriate size
were sealed under argon in Lindemann capillaries. The
data collections were carried out at 20 °C.
€
Green, F. Jakle, A.J. Lough, I. Manners, J. Am. Chem. Soc. 122
(2000) 5765.
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65;
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512;
5. Supplementary information
€
(d) R. Koster, G. Seidel, B. Wrackmeyer, Chem. Ber. 122 (1989)
Crystallographic data (excluding structure factors)
for the structures reported in this paper have been de-
posited with the Cambridge Crystallographic Data
Centre as supplementary publications no. CCDC-
210104 (3a) and CCDC-210105 (3c). Copies of the data
can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge CB2 1EZ, UK [fax (inter-
nat.): +44 (0)1223/336033; deposit@ccdc.cam.ac.uk].
1825;
(e) R. Koster, G. Seidel, B. Wrackmeyer, D. Schlosser, Chem. Ber.
€
122 (1989) 2055;
€
(f) R. Koster, G. Seidel, C. Kruger, G. Muller, A. Jiang, R. Boese,
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€
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[9] B. Wrackmeyer, H.E. Maisel, M. Herberhold, J. Organomet.
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[10] B. Wrackmeyer, E.V. Klimkina, M. Herberhold, unpublished
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Acknowledgements
€
[12] J. Sandtsrom, Dynamic NMR Spectroscopy, Academic Press,
New York, 1982, p. 96.
This work was supported by the Deutsche Fors-
chungsgemeinschaft and the Fonds der Chemischen
Industrie.
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