Novel 1,3,2-diazabora-[3]ferrocenophanes and a 1,4,2,3-diazadibora-[4] ferrocenophane

Article abstract of DOI:10.1016/j.ica.2004.07.059

N,N′-Dilithiated 1,1′-bis(trimethylsilylamino)ferrocene (2) reacts with boron halide adducts (HBBr₂-SMe₂; BF ₃-OEt₂ and BBr₃-SMe₂), boron halides (BCl₃, BBr₃, BCl₂(OPh) and BCl ₂(Ph)) and 1,1-bis(dimethylamino)dichlorodiborane(4) to give the corresponding 1,3-bis(trimethylsilyl)-1,3,2-diazabora-[3]ferrocenophanes (3)-(8) and the 2,3-bis(dimethylamino)-1,4-bis(trimethylsilyl)-1,4,2,3-diazadibora-[4] ferrocenophane (9). All new complexes were characterised by multinuclear magnetic resonance spectroscopy in solution, and the solid-state molecular structures of the hydride (3), fluoride, chloride (4, 5), and of the phenoxy and phenyl derivatives (7, 8) were determined by X-ray analysis.

Full text of DOI:10.1016/j.ica.2004.07.059

Inorganica Chimica Acta 358 (2005) 1420–1428
www.elsevier.com/locate/ica
Novel 1,3,2-diazabora-[3]ferrocenophanes and a
1,4,2,3-diazadibora-[4]ferrocenophane
*
Bernd Wrackmeyer , Elena V. Klimkina, Wolfgang Milius,
*
Oleg L. Tok, Max Herberhold
Lab. fur Anorganische Chemie II, Universita¨t Bayreuth, Universita¨tsstr. 30, NW 1, D-95440 Bayreuth, Germany
Received 18 June 2004; accepted 17 July 2004
Dedicated to Professor F. Gordon A. Stone on the occasion of his 80th birthday
Abstract
N,N0-Dilithiated 1,10-bis(trimethylsilylamino)ferrocene (2) reacts with boron halide adducts (HBBr2–SMe2; BF3–OEt2 and
BBr3–SMe2), boron halides (BCl3, BBr3, BCl2(OPh) and BCl2(Ph)) and 1,1-bis(dimethylamino)dichlorodiborane(4) to give the cor-
responding 1,3-bis(trimethylsilyl)-1,3,2-diazabora-[3]ferrocenophanes (3)–(8) and the 2,3-bis(dimethylamino)-1,4-bis(trimethylsilyl)-
1,4,2,3-diazadibora-[4]ferrocenophane (9). All new complexes were characterised by multinuclear magnetic resonance spectroscopy
in solution, and the solid-state molecular structures of the hydride (3), fluoride, chloride (4, 5), and of the phenoxy and phenyl deriv-
atives (7, 8) were determined by X-ray analysis.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Ferrocenes; Boron; NMR-multinuclear; X-ray
1. Introduction
nitrogen atoms. Recently, we have reported on the
first 1,3,2-diazabora-[3]ferrocenophanes (1) [6], in
which the boron atom bears an exocyclic amino
group, N(R)R0. Depending on the nature of the amino
group, either endocyclic (1b) or exocyclic BN(pp)p
interactions (1a) dominate. This became evident by dy-
namic NMR measurements in solution as well as by
significant differences in the solid-state molecular
structures [6].
The 1,10-bis(trimethylsilylamido)ferrocene ligand
possesses attractive chelating ability, which has already
been demonstrated for magnesium, titanium [1,2], zir-
conium [1], tin [3,4] and phosphorus derivatives [5].
The ring closure to the 1,3,2-diazahetero-[3]ferroceno-
phane system enforces an approximately perpendicular
orientation of the lone electron pairs at both nitrogen
atoms with respect to the p system of the cyclopenta-
dienyl rings, and if a trigonal-planar coordinated bor-
on atom occupies the position between the two amido
nitrogen atoms, efficient BN(pp)p interaction can take
place, involving the lone electron pairs at the two
SiMe3
N
1
a
b
B
N(R)R´
Fe
R
Et Et
*
N
Corresponding authors. Fax: +49 921 552157.
E-mail addresses: b.wrack@uni-bayreuth.de (B. Wrackmeyer),
max.herberhold@uni-bayreuth.de (M. Herberhold).
R´ Et Ph
SiMe3
0020-1693/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.07.059

B. Wrackmeyer et al. / Inorganica Chimica Acta 358 (2005) 1420–1428
1421
In the present work, we report on our attempts to
prepare 1,3,2-diazabora-[3]ferrocenophanes 3–8 analo-
gous to 1 with other functional groups at boron (e.g.,
H, F, Cl, Br, OPh and Ph), and a 1,4,2,3-diazadibora-
[4]ferrocenophane (9). Except of the hydride, the func-
tionalities at the boron atom in 3–8 can be regarded as
more or less strong p electron donors, and this property
should be reflected by the molecular structure of the
respective ferrocenophane. We have therefore deter-
mined the molecular structures in the solid state by
X-ray analysis, and have also characterised the com-
of moisture. They are readily soluble in benzene, tolu-
ene, CDCl3 or CD2Cl2, and the solutions can be kept
for prolonged periods in sealed tubes at ꢀ18 ꢁC.
The structure of 9 follows from a consistent set of
NMR data (vide infra). Attempts to enforce the poten-
tial rearrangement of 9 into 10 (Scheme 2) were not suc-
cessful. Heating of 9 in toluene for several hours at 80
ꢁC induced decomposition and NMR signals for 10
could not be assigned.
2.2. NMR spectroscopic results
1
plexes by H, 11B, 13C and 29Si NMR measurements in
solution.
Relevant 11B, 13C and 29Si NMR data for 3–9 are
listed in Table 1, and 1H NMR data are given in Section
1
4. The H and 13C NMR spectra of 3–8 are simple, as
2. Results and discussion
expected for a plane of symmetry passing through the
atoms B, N, C1, C10 and Fe. The ferrocene system gives
1
rise to two multiplets in the H NMR spectrum for the
2.1. Syntheses
H2,5 and H3,4 nuclei and three 13C NMR signals for
Both the N,N0 dilithiated-1,10-bis(trimethylsilyl-
amino)ferrocene (2) and the corresponding N,N0-magne-
sium derivative [1,3] are useful starting materials for the
reaction with boron halides [6]. In this work, we have al-
ways used freshly prepared 2, which reacted with either
boron halides or adducts of boron halides to give the de-
sired aminoboranes 3–9 in moderate to good yields
(Scheme 1). The compounds 3–8 could be isolated as
yellow or orange solids or oils, which were purified by
crystallisation to give single crystals suitable for X-ray
analysis in the cases of 3, 4, 5, 7 and 8. The diborane(4)
derivative 9 was obtained as an orange oil which so far
did not crystallise. The aminoboranes 3–9, in particular
the boron halides 4, 5 and 6, are sensitive towards traces
C1, C2,5 and C3,4. The 1H(BH) NMR signal for 3 is read-
1
ily detected by a H{11B} double resonance experiment.
All 11B NMR signals (Table 1) are found in a narrow
range expected [7] for such surroundings where the
boron atom is trigonally planar surrounded by two
nitrogen atoms and an additional other substituent.
Similarly, there is only one 29Si NMR signal for each
compound (Table 1) and the 29Si resonance is hardly af-
fected by the substituent at the boron atom. In compar-
ison with 1a, where the exocyclic NEt2 group acts as a
strong p donor, causing a significant distortion of endo-
cyclic BN(pp) bonding [6], the 29Si NMR signals in 3–9
are shifted to higher frequencies by ca. 10 ppm. The 19F
1
NMR signal of 4 is broad, similar to the H(BH) NMR
SiMe3
N
Li
Fe
Li
N
+ HBBr2-SMe2
Me2N
NMe2
SiMe3
2
+
B
B
+ 3 BF3-OEt2
+ BBr3-SMe2
Cl
Cl
+ BCl3
+ BBr3
SiMe3
SiMe3
+ BCl2(OPh)
+ BCl2(Ph)
NMe2
NMe2
N
N
N
B
B
Fe
B
R
Fe
N
SiMe3
SiMe3
9
3
4
5
6
7
8
R
H
F Cl Br OPh Ph
Scheme 1. Synthesis of the 1,3,2-diazabora-[3]ferrocenophanes (3)–(8) and of the 1,4,2,3-diazadibora-[4]ferrocenophane (9).

1422
B. Wrackmeyer et al. / Inorganica Chimica Acta 358 (2005) 1420–1428
SiMe3
SiMe3
80 ˚C
toluene
N
N
N
N
NMe2
NMe2
B
B
B
B(NMe2)2
Fe
Fe
(6 h)
SiMe3
SiMe3
10
9
Scheme 2. Heating of 9 does not induce rearrangement but leads to decomposition.
Table 1
11B, 13C and 29Si NMR dataa of the 1,3-bis(trimethylsilyl)-2-R-1,3,2-diazabora-[3]ferrocenophanes and of 2,3-bis(dimethylamino)-1,4-bis(trimeth-
ylsilyl)-1,4,2,3-diazadibora-[4]ferrocenophane (9)
Compound
3
R = H
4
R = F
5
R = Cl
6
R = Br
7
R = OPh
8
R = Ph
9
1a 1b
R = NEt2 R = N(Et)Ph
d13C(N–SiMe3) 1.2 (57.2)
0.9 [3.6] (57.5)
99.7 [8.7]
69.4 [1.0]
67.9
d19F (CDCl3):
ꢀ114.3
2.54 (58.0) 3.3 (58.5)
1.4 (57.7)
100.0
69.1
2.8 (57.7)
103.3
68.7
0.9 (57.0) 1.4 (57.0) 2.2 (57.7)
d13C(fc–C1)
d13C(fc–C2,5
d13C(fc–C3,4
R
101.7
69.3
67.8
d1H:
101.4
68.6
67.8
102.0
68.9
68.2
104.3
96.3
101.2
68.8
67.9
)
)
69.5, 67.9 67.0 (br)
65.8, 65.2 67.0 (br)
67.5
d13C:
117.7 (Co)
67.7
d13C:
126.8 (Cm)
b
b
d13C:
39.3 (br)
40.9 (br)
4.31 (br)
120.1 (Cp) 127.6 (Cp)
129.4 (Cm) 134.3 (Co)
156.8 (Ci)
29.4
142.0 (br)(Ci)
36.9
13.8 (59.2) 10.2 (57.6) 10.4 (57.4)
d11
B
32.6
11.1 (57.3) 11.1 {4.7}(57.6) 12.9
27.0
31.1
29.2
39.0 27.8
0.7 (57.0) 1.0
31.0
8.4 (57.7)
d29Si
a
Measured in C6D6 (1a), CD2Cl2 (3, 4, 6 and 9), CDCl3 (5, 7, 8 and 1b); coupling constants ( 0.5 Hz) 1J(29Si,13C) are given in parentheses;
nJ(19F,13C) in brackets; 3J(29Si,19F) in braces.
b
Ref. [6].
signal of 3, as a result of partially relaxed 19F–11B spin–
spin coupling. The presence of the B–F bond in 4 is also
indicated by the doublet splitting of the 1H(SiMe3)
tional changes which, together with restricted rotation
about the exocyclic B–NMe2 bonds, leads to loss of
molecular symmetry. Therefore, as shown by the 13C
NMR spectrum (Fig. 1), the surroundings of the C2,5
and C3,4 nuclei become different. This is further illus-
trated by two favourable conformations, 90 and 900(Fig.
2), for which the optimised geometries were calculated.
Similar to many other diborane(4) derivatives [8], the
four nitrogen atoms avoid to become part of a plane
1
NMR signal (5J(19F, B, N, Si, C, H) = 1.8 Hz), of var-
ious 13C NMR signals, and also by the doublet in the
29Si NMR spectrum due to 19F–13C and 29Si–19F spin–
spin coupling, respectively.
The complex 9 is a more special case, since the N–B–
B–N bridge in the [4]ferrocenophane causes conforma-
Fig. 1. 62.9 MHz 13C{1H} NMR spectrum of the [4]ferrocenophane (9) (the 29Si satellites for 1J(29Si,13CMe) = 57.0 Hz are marked by asterisks).

B. Wrackmeyer et al. / Inorganica Chimica Acta 358 (2005) 1420–1428
1423
changes by which magnetisation transfer takes place be-
tween H2 and H5 and also between H3 and H4.
2.3. Molecular structures of the [3]ferrocenophanes
Selected structural parameters of the molecular
structures of 3, 4, 5, 7 and 8 are given in Table 2.
These [3]ferrocenophanes possess typical structures, as
shown in Fig. 4(a) for the hydride 3 (view on the top
of the ferrocene system) and in Fig. 4(b) for the fluo-
ride 4 (side view; the molecular structure of the chlo-
ride 5 is exactly analogous). The cyclopentadienyl
rings are in eclipsed positions within the experimental
error, and the atoms Fe, C1, N, B, N and C10 are ar-
ranged in one plane.
Fig. 2. Models of two favourable conformers of the [4]ferrocenophane
(9). The geometries were optimised [18] by calculations [B3LYP/6-
311+G(d,p) level of theory], and almost identical energies for 90 and 900
were found.
The molecular structures of the phenoxy and the phe-
nyl derivative (7 and 8) are shown in Figs. 5(a) and (b),
respectively. Again, the cyclopentadienyl rings are in
eclipsed positions: the twist angles s (cf. [11]) are small
(<1ꢁ). The planes including the phenoxy substituent in
7 and the phenyl ring in 8 are oriented almost perpendic-
ular to the NBN plane (81.9ꢁ and 81.8ꢁ, respectively),
and therefore p interactions between boron and the
respective exocyclic substituent are unlikely.
The B–N bond lengths are found in the usual
range, typical of significant BN(pp)p interactions
[12,13]. In all [3]ferrocenophanes studied here, the
planes of the cyclopentadienyl rings are slightly bent
towards each other in the direction of the bridge;
the angles a (cf. [11]) are in the range of 10–16ꢁ (Table
2). The C1–N and C10–N bond vectors deviate also
slightly from the C5 planes, again towards the boron
around both boron atoms. However, the rotational bar-
rier about the B–B bond is small. A solid-state molecu-
lar structure showing a conformation corresponding to
that of 90 has been determined for 2,3-bis(dimethyl-
amino)-1,4,2,3-dithiadibora-[4]ferrocenophane [9].
The fluxional character of 9 becomes apparent from
1D and 2D NOESY/EXSY NMR experiments [10]
using different mixing times (Fig. 3). Since the
1
1H(SiMe3) and the H(NMe2) transitions exhibit differ-
ent NOE off-diagonal intensities with the different H2,5
nuclei, it appears that the structure analogous to 900 is fa-
voured. When the mixing time was increased from 0.5 to
0.8 s, off-diagonal intensities due to exchange could be
identified by their phase being identical with that of
the diagonal signals (see the 1D experiments shown in
Fig. 3). This points towards slow conformational
Fig. 3. 400 MHz 1D 1H/1H NOE-difference spectra (gradient enhanced; mixing time 0.8 s) of 9. The irradiated resonance signals are marked by
arrows; the resulting intensities arsing from NOE or EXchange are marked. The differential effects observed indicate the preference of the
conformation shown (corresponding to 900 in Fig. 2), and at the same time also a fluxional character is revealed, since magnetisation transfer takes
0
0
0
0
place between H2;2 and H5;5 , and H3;3 and H4;4 , respectively.

1424
B. Wrackmeyer et al. / Inorganica Chimica Acta 358 (2005) 1420–1428
Table 2
Selected bond lengths [pm] and angles [ꢁ]a of the 1,3-bis(trimethylsilyl)-2-R-1,3,2-diazabora-[3]ferrocenophanes 3, 4, 5, 7, 8, 1a and 1b
b
3
R = H
4
R = F
5
R = Cl
7
R = OPh
8
R = Ph
1a [6}
R = NEt2
1b [6]
R = NEt(Ph)
B–N
142.1(5)
141.6(5)
141.6(5)
141.8(6)
136.5(5)
177.1(3)
177.2(3)
258.1
145.6(11)
141.7(11)
181.6(8)
177.1(7)
177.7(6)
262.6
142.5(10)
140.9(10)
142.9(9)
177.4(6)
178.1(6)
256.9
143.2(6)
146.5(6)
159.0(6)
179.8(4)
177.8(4)
258.1
147.0 (9)
151.2(9)
140.1(9)
171.9(5)
170.7(5)
259.6
1.446(3)
B–R
N–Si
149.2(6)
179.2(3)
176.7(3)
176.3(3)
256.9
Nꢁ ꢁ ꢁN
258.1
292.0
C(1)ꢁ ꢁ ꢁC(10)
Feꢁ ꢁ ꢁB
296.1
333.7
129.8(4)
296.2
332.1
293.7
334.5
292.3
334.5
289.4
342.9
303.9
316.4
342.6
126.7(4)
116.6(2)
N–B–N(endo)
N–B–R
131.3(4)
115.1(4)
113.6(4)
116.3(3)
116.3(3)
121.9(3)
122.0(3)
121.8(3)
121.6(3)
0 (mirror plane)
12.6
132.1(7)
112.8(6)
115.1(6)
114.9(5)
114.1(5)
119.2(6)
120.9(6)
125.9(5)
120.9(6)
0 (mirror plane)
13.8
130.0(7)
115.9(7)
113.8(7)
110.6(4)
114.4(5)
120.8(6)
122.5(6)
128.5(5)
123.1(5)
2.9
126.0(4)
118.5(4)
115.5(4)
111.5(3)
110.9(3)
124.0(4)
122.3(4)
124.5(3)
126.1(3)
1.4
121.0(6)
120.4(7)
118.5(7)
116.0(4)
120.7 (4)
113.6(5)
109.8(5)
129.3(4)
127.8(4)
61.7
C(1)–N–Si
C(10)–N–Si
B–N–C(1)
B–N–C(10)
B–N–Si
116.6(2)
117.5(2)
123.1(3)
122.9(3)
120.3(3)
119.7(2)
0 (mirror plane)
12.9
108.5(2)
123. 2(3)
127.9(2)
c
Fe–Cð1Þ–N–B–N–Cð10ÞD ðpmÞ
1.4
15.0
C5/C5(a)
13.8
15.5
10.8
C5/N(b)
C5–Fe–C5(c)
C5/C5(twist) (s)
Fe–C5(centre)
1.7 2.2
171.1
1.5 2.0
171.8
1.3 0.4
171.3
0.3 2.4
170.5
0.4
0.9 2.5
169.6
0.5
4.5 3.8
170.6
0.7
0.9
170.3
0 (symmetry)
163.3
0 (symmetry)
163.0
163.2
0 (symmetry)
163.1
162.7
0 (symmetry)
162.3
162.6
162.2
162.6
163.1
162.9
163.0
163.7
a
The definition of the angles a, b, c and s is given in [11].
b
The C-atoms corresponding to C(1) are – independently of their crystallographic labels – named C(10). (The crystallographic labels of C(10) is
C(4) in 3, 4, and 5, C(6) in 7 and 8, C(1A) in 1b and C(16) in 1a.)
c
Mean deviation from plane.
atom; the angles b (cf. [11]) are small (<5ꢁ; Table 2).
All these structural features reflect a compromise in
order to accommodate the planar C–N–B–N–C unit
without an extremely wide endocyclic N–B–N angle.
This angle is wider than in most other cyclic aminobo-
rane structures and the data show an apparently
unsystematic variation (126.0–132.1ꢁ). Table 2 also
contains the structural data for the diethylamino
Fig. 4. Molecular structures of 3 (a) (ball and stick model) and 4 (b) (ORTEP plot, 50% probability), see Table 2 for structural parameters.

Table 3
Crystallographic data of the 1,3-bis(trimethylsilyl)-2-R-1,3,2-diazabora-[3]ferrocenophanes 3, 4, 5, 7 and 8
3
R = H
4
R = F
5
R = Cl
7
R = OPh
8
R = Ph
Formula
Crystal
C
16H27BFeN2Si2
C16H26BFFeN2Si2
yellow prism
0.16 · 0.15 · 0.12
monoclinic
C16H26BClFeN2Si2
yellow prism
0.14 · 0.12 · 0.12
monoclinic
C22H31BFeN2OSi2
yellow-orange prism
0.18 · 0.16 · 0.12
monoclinic
C22H31BFeN2Si2
orange prism
0.12 · 0.11 · 0.08
triclinic
yellow needle
0.18 · 0.16 · 0.08
monoclinic
P2(1)/m
Dimensions (mm)
Crystal system
Space group
Lattice parameters
P2(1)/m
P2(1)/m
P2(1)/n
P1
a (pm)
b (pm)
968.4(2)
1074.7(3)
1065.8(2)
961.31(9)
1066.20(13)
1064.84(11)
970.89(19)
1055.4(2)
1069.0(2)
1961.6(9)
662.9(2)
2091.8(5)
1019.7(2)
1137.1(2)
1233.4(3)
101.54(3)
111.69(3)
108.18(3)
2
c (pm)
a (ꢁ)
b (ꢁ)
c (ꢁ)
Z
114.879(15)
114.318(8)
113.75(3)
116.57(2)
2
0.866
Siemens P4
2
0.886
Siemens P4
2
1.004
STOE IPDS I
4
0.733
Siemens P4
Absorption coefficient l (mmꢀ1
Diffractometer
)
0.751
STOE IPDS I
Mo Ka, k = 71073 pm, graphite monochromator
Measuring range (#) (ꢁ)
Reflections collected
2–26
7064
2.1–25.0
2187
1686
2.1–26.1
7009
2059
2.2–22.5
3860
2913
1.9–26.0
8307
4293
Independent reflections (I > 2r(I))
Absorption correctiona
Refined parameters
2044
none
none
133
none
121
none
262
none
253
127
0.110/0.045
0.469/ꢀ0.253
wR2/R1(I > 2r(I))
0.113/0.041
0.332/ꢀ0.483
0.108/0.053
0.353/ꢀ0.347
0.146/0.062
0.408/ꢀ0.308
0.1012/0.047
0.535/ꢀ0.292
Maximum/minimum residual electron density (e pmꢀ3 · 10ꢀ6
)
a
Absorption correction did not improve the data set.

1426
B. Wrackmeyer et al. / Inorganica Chimica Acta 358 (2005) 1420–1428
Fig. 5. Molecular structures of 7 (a) and 8 (b) (ORTEP plots, 50% probability); see Table 2 for structural parameters.
compound 1a [6], where exocyclic BN(pp)p bonding is
important. The data of 1a are clearly different from
those of the other [3]ferrocenophanes studied here.
ferrocene [1,6], N,N0-dilithio-1,10-bis(trimethylsilyl-
amino)ferrocene (fc(NSiMe3)2Li2) (2) [6], Br3B–SMe2
from Br3B and SMe2 (molar ratio 1:1) in hexane–
CH2Cl2, BCl2(OPh) from B(OPh)3 and BCl3 (molar
ratio 1:2) in hexane [15], 1,2-bis(dimethylamino)dibo-
ron dichloride [16]. Other starting materials were pur-
3. Conclusions
chased from Aldrich [n-butyllithium (1.6
M
M in
hexane), boron tribromide (1.0 in hexane),
NMR spectroscopic and direct structural evidence
points towards strong endocyclic BN(pp)p interactions
in most 1,3,2-diaza-[3]ferrocenophanes, such as 3–8.
The deviations from the ideal ferrocene-like arrange-
ment are caused by the trigonal-planar geometry at the
boron atom, avoiding a too wide endocyclic N–B–N
bond angle. Molecular symmetry is lost in the 1,4,2,3-
diazadibora-[4]ferrocenophane (9). The access to the
boron hydride 3 and to the boron halides 4–6 opens
the route to numerous further transformations, includ-
ing oxidative additions in transition metal chemistry
[14]. Similarly, the chemistry of the diborane(4) deriva-
tive 9 needs to be explored.
HBBr2–SMe2 (1.0 M in CH2Cl2)], Acros [boron tri-
chloride (1.0 M in hexane)], Fluka [phenylboron
dichloride] and Frontier Scientific, Inc. [tetra-
kis(dimethylamino)diborane(4)], and used without fur-
ther purification.
NMR measurements: Bruker ARX 250 and DRX
500: 1H, 13C, 11B, 29Si NMR (refocused INEPT [17]
2
1
based on J(29Si,1H) = 7 Hz); Varian INOVA 400: H,
13C NMR; Bruker Avance 360: 19F NMR. Chemical
shifts are given with respect to Me4Si [d1H(CHCl3/
CDCl3) = 7.24; (CHDCl2) 5.33; d13C(CDCl3) = 77.0,
(CD2Cl2) = 53.5; d29Si = 0 for N(29Si) = 19.867184
MHz; d11B = 0 for external BF3–OEt2 with
N(11B) = 32.083971 MHz; d19F = 0 for external CFCl3
with N(19F) = 94.094003 MHz]. EI-MS spectra: Finni-
gan MAT 8500 spectrometer (ionisation energy 70 eV)
4. Experimental
1
4.1. General
with direct inlet; the m/z data refer to the isotopes H,
12C, 14N, 11B, 28Si, and 56Fe. The melting points (uncor-
rected) were determined using a Buchi 510 melting point
¨
All syntheses and the handling of the samples were
carried out observing necesarry precautions to exclude
traces of air and moisture. Carefully dried solvents
and oven-dried glassware were used throughout. The
deuterated solvents CD2Cl2 and CDCl3 were distilled
over CaH2 in an atmosphere of argon. All other solvents
were distilled from Na metal in an atmosphere of argon.
The starting materials were prepared as described
in the literature, i.e., 1,10-bis(trimethylsilylamino)-
apparatus.
4.2. Properties of 1,2-bis(dimethylamino)diboron
dichloride
B.p. 41–42 ꢁC/0.2 Torr (cf. [15]: b.p. 38-42 ꢁC/10–14
1
mm). H NMR (250.1 MHz; CD2Cl2; 25 ꢁC): d = 2.87
(s, 6H, NCH3), 2.90 (s, 6H, NCH3). 13C NMR (62.9

B. Wrackmeyer et al. / Inorganica Chimica Acta 358 (2005) 1420–1428
1427
MHz, CD2Cl2; 25 ꢁC): d = 38.0 (NCH3), 42.3 (NCH3).
11B NMR (80.3 MHz; CD2Cl2; 25 ꢁC): d = 37.6.
fc(NSiMe3)2Li2 (2) and BBr3 (1.33 mL of a 1.0 M solu-
tion in hexane, 1.33 mmol) to give 100 mg (17%) of 6 as
a yellow-orange oil.
4.3. Synthesis of the 1,3-bis(trimethylsilyl)-2-R-1,3,2-
diazabora-[3]ferrocenophanes
4.3.4.2. Method B. A solution of freshly prepared Br3B–
SMe2 (0.62 mmol) in hexane–CH2Cl2 was used in the
reaction with 2 (231 mg, 0.62 mmol) to give 131 mg
(47%) of 6 as a yellow-orange oil. 1H NMR (250.1
MHz; CD2Cl2,0 25 ꢁC): d = 0.22 (s, 18H, Me3Si), 3.86
4.3.1. 1,3-Bis(trimethylsilyl)-2-hydro-1,3,2-diazabora-[3]
ferrocenophane (3)
Freshly prepared fc(NSiMe3)2Li2 (2) (357 mg, 0.96
mmol) was taken up in hexane (20 mL); the suspension
was cooled to ꢀ70 ꢁC and HBBr2–SMe2 (0.96 mL of a
1.0 M solution in CH2Cl2, 0.96 mmol) was injected
slowly through a syringe. After stirring the reaction mix-
ture for 2 h at ꢀ70 ꢁC and then for 2 h at ambient tem-
perature, insoluble materials were seperated by
centrifugation and the clear liquid was collected. Vola-
tile materials were removed in vacuo (0.01 Torr) and
the resulting oil was dissolved in hexane (18 mL). After
filtration, the solvent was removed in vacuo to give 170
mg (48%) of 3 as a yellow solid. After 2 weeks at ꢀ30 ꢁC,
a few yellow needles of 3 crystallised at the glass wall.
These crystals (m.p. 65–67 ꢁC) were suitable for X-ray
structure determination. 1H{11B} NMR (250.1 MHz;
CD2Cl2; 25 ꢁC): d = 0.13 (s, 18H, Me3Si), 3.86 (m, 4H,
0
0
0
(m, 4H, H2;2 ;5;5 ), 4.00 (m, 4H, H3;3 ;4;4 ).
4.3.5. 1,3-Bis(trimethylsilyl)-2-phenoxy-1,3,2-diazabora-
[3]ferrocenophane (7)
The synthesis was carried out in the same way as for
3, starting from 380 mg (1.02 mmol) of fc(NSiMe3)2Li2
(2) and a solution of freshly prepared BCl2(OPh) (1.02
mmol) in hexane (4 mL) to give 240 mg (51%) of 7 as
a yellow-orange oil. Crystallisation from hexane at
ꢀ20 ꢁC gave yellow-orange crystals of 7 (m.p. 102–103
1
ꢁC). H NMR (250.1 MHz; CDCl3, 25 ꢁC): d = ꢀ0.05
0
0
(s, 18H, Me3Si), 3.95 (m, 4H, H2;2 ;5;5 ), 4.05 (m, 4H,
0
0
H3;3 ;4;4 ), 6.80 (m, 2H, Ph(Ho)), 6.93 (m, 1H, Ph(Hp)),
7.28 (m, 2H, Ph(Hm)).
0
0
0
0
H2;2 ;5;5 ), 3.99 (m, 4H, H3;3 ;4;4 ), 4.31 (br) (s, 1H, B–H).
4.3.6. 1,3-Bis(trimethylsilyl)-2-phenyl-1,3,2-diazabora-
[3]ferrocenophane (8)
4.3.2. 1,3-Bis(trimethylsilyl)-2-fluoro-1,3,2-diazabora-[3]
ferrocenophane (4)
The synthesis was carried out as described for 3 (2: 340
mg, 0.91 mmol; BCl2(Ph): 145 mg, 0.91 mmol) to give 220
mg (54%) of 8 as a orange oil. Crystallisation from hexane
at ꢀ30 ꢁC gave orange crystals of 8 (m.p. 148–150 ꢁC). 1H
NMR (250.1 MHz; CDCl3, 25 ꢁC): d = ꢀ0.32 (s, 18H,
The same procedure as for 3 was used (2: 214 mg,
0.57 mmol; BF3–OEt2, freshly distilled: 0.22 mL, 1.72
mmol). The resulting oil was dissolved in hexane (18
mL). After filtration from LiBF4, the solvent was re-
moved in vacuo to give 73 mg (33%) of 4 as a yellow so-
lid. Crystallisation from hexane, after 2 weeks at ꢀ30
ꢁC, gave yellow crystals of 4, m.p. 132–134 ꢁC (decom-
position). 1H NMR (250.1 MHz; CD2Cl2, 25 ꢁC):
0
0
0
0
Me3Si), 3.83 (m, 4H, H2;2 ;5;5 ), 4.02 (m, 4H, H3;3 ;4;4 ),
7.29 (m, 3H, Ph(Hm,p)), 7.42 (m, 2H, Ph(Ho)).
4.4. Synthesis of the 2,3-bis(dimethylamino)-1,4-bis(tri-
methylsilyl)-1,4-diaza-2,3-dibora-[4]ferrocenophane (9)
5
d = 0.090 (d, 18H, Me3Si, J(19F,1H) = 1.8 Hz), 3.89 (m,
0
0
0
4H, H2;2 ;5;5 ), 3.97 (m, 4H, H3;3 ;4;4 ).
The synthesis was carried out in analogy to that of 3,
starting from 342 mg (0.92 mmol) of fc(NSiMe3)2Li2 (2)
and 170 mg (0.92 mmol) of 1,2-bis(dimethylamino)dibo-
ron dichloride to give 268 mg (62%) of 9 as a red-orange
4.3.3. 1,3-Bis(trimethylsilyl)-2-chloro-1,3,2-diazabora-
[3]ferrocenophane (5)
1
The synthesis was carried out in analogy to that of 3,
starting from 120 mg (0.32 mmol) of fc(NSiMe3)2Li2 (2)
and BCl3 (0.32 mL of a 1.0 M solution in hexane, 0.32
oil. H NMR (250.1, 400 and 500.1 MHz; CDCl3; 25
ꢁC): d = 0.04 (s, 18H, Me3Si), 2.78 (br) (s, 6H, NCH3),
0
2.83 (br) (s, 6H, NCH3), 3.71 (m, 2H, H5;5 ), 3.83 (m,
0
0
0
1
mmol) to give 95 mg (73%) of 5 as a yellow oil. H
2H, H3;3 ), 3.89 (m, 2H, H4;4 ), 4.03 (m, 2H, H2;2 ). EI-
MS (70 eV) for C20H38N4B2Si2Fe (468.22): m/z
(%) = 468 (100) [M+], 351 (95) [M+ ꢀ (CH3)3-
SiN(CH3)2], 308 (13), 102 (15), 73 (19).
NMR (250.1 MHz; CDCl3, 25 ꢁC): d = 0.18 (s, 18H,
0
0
0
0
Me3Si), 3.83 (m, 4H, H2;2 ;5;5 ), 3.99 (m, 4H, H3;3 ;4;4 ). A
small amount of crystalline material of 5 with identical
NMR parameters had been obtained previously [6] as
a side product, which was characterised by X-ray analy-
sis in this work.
4.5. Crystal structure determinations of the 2-R-1,3,2-
diazabora-[3]ferrocenophanes
4.3.4. 1,3-Bis(trimethylsilyl)-2-bromo-1,3,2-diazabora-
[3]ferrocenophane (6)
4.3.4.1. Method A. The synthesis was carried out in anal-
ogy to that of 3, starting from 494 mg (1.33 mmol) of
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.

1428
B. Wrackmeyer et al. / Inorganica Chimica Acta 358 (2005) 1420–1428
(d) A. Moezzi, M.M. Olmstead, R.A. Bartlett, P.P. Power,
Organometallics 11 (1992) 2383;
5. Supplementary information
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Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre as sup-
plementary publications no. CCDC-242924 (3), CCDC-
242925 (4), CCDC-242922 (5), CCDC-242923 (7) and
CCDC-242921(8). Copies ofthe data can be obtained free
of charge on application to CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK [fax (internat.): +44 (0)1223/336033;
e-mail: deposit@ccdc.cam.ac.uk].
(b) J.K.M. Sanders, B.K. Hunter, Modern NMR Spectroscopy,
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Acknowledgement
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(d) G. Schmid, R. Boese, D. Blaeser, Z. Naturforsch., Teil B
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