Azanonaborane-pyridine derivatives Synthesis, structure and some molecular-orbital calculations

Article abstract of DOI:10.1016/S0022-328X(02)01420-1

The molecular structure of hypho-type [(RNH₂)B₈H₁₁NHR] is based on a {B₈} cluster with one nitrogen bridge and one exo amine ligand. In general these azanonaboranes are synthesized by the reaction of [B₉H₁₃(SMe₂)] with primary amines. Modifications of these azanonaboranes are possible by ligand-exchange reactions. Necessary conditions for ligand-exchange reactions of the azanonaboranes [(RNH₂)B₈H₁₁NHR], in which the exo-{NH₂R} group is replaced by other nitrogen-donor ligands, are reported. The nitrogen-donor ligands that have been examined include primary, secondary and tertiary amines as well as a series of substituted pyridines. The structures of the pyridine-containing azanonaboranes [(C₅H₅N)B₈H₁₁NHR] where R = methyl, ethyl, iso propyl or tertiary butyl, have been determined crystallographically, and are compared with the aliphatic azanonaboranes [(RNH₂)B₈H₁₁NHR]. The reactions of the various [(RNH₂)B₈H₁₁NHR] species with pyridine or the substituted pyridines give coloured products, contrasting with the colourless nature of the starting alkylamine species. The electronic interaction between the {B₈} hypho-type unit and the bonded pyridine units has been investigated by UV-vis spectroscopy and by AM-1 molecular-orbital calculations.

Full text of DOI:10.1016/S0022-328X(02)01420-1

Journal of Organometallic Chemistry 657 (2002) 205ꢁ216
/
www.elsevier.com/locate/jorganchem
Azanonaborane-pyridine derivatives [(R?C5H4N)B8H11NHRƒ]:
synthesis, structure and some molecular-orbital calculations
Claudia Bauer a, Detlef Gabel a, Tobias Borrmann a, John D. Kennedy b,
Colin A. Kilner b, Mark Thornton-Pett b, Udo Dorfler a,*
¨
a Department of Chemistry, University of Bremen, P.O. Box 330 440, 28334 Bremen, Germany
b Department of Chemistry, University of Leeds, Leeds, England LS2 9JT, UK
Received 15 October 2001; accepted 22 March 2002
Abstract
The molecular structure of hypho-type [(RNH2)B8H11NHR] is based on a {B8} cluster with one nitrogen bridge and one exo
amine ligand. In general these azanonaboranes are synthesized by the reaction of [B9H13(SMe2)] with primary amines. Modifications
of these azanonaboranes are possible by ligand-exchange reactions. Necessary conditions for ligand-exchange reactions of the
azanonaboranes [(RNH2)B8H11NHR], in which the exo-{NH2R} group is replaced by other nitrogen-donor ligands, are reported.
The nitrogen-donor ligands that have been examined include primary, secondary and tertiary amines as well as a series of
substituted pyridines. The structures of the pyridine-containing azanonaboranes [(C5H5N)B8H11NHR] where Rꢀmethyl, ethyl,
/
isopropyl or tertiary butyl, have been determined crystallographically, and are compared with the aliphatic azanonaboranes
[(RNH2)B8H11NHR]. The reactions of the various [(RNH2)B8H11NHR] species with pyridine or the substituted pyridines give
coloured products, contrasting with the colourless nature of the starting alkylamine species. The electronic interaction between the
{B8} hypho-type unit and the bonded pyridine units has been investigated by UVꢁ/vis spectroscopy and by AM-1 molecular-orbital
calculations. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Hypho cluster; Azanonaborane; N ligands; X-ray crystal structure; MO calculations
1. Introduction
amine-type residues attached to it, viz. one amino group
{NHEt} in a boronÃboron bridging position, and one
/
The azanonaboranes [(RNH2)B8H11NHR] are avail-
able via simple three- or four-step reactions from
commercially available nido-decaborane(14), B10H14.
[(EtNH2)B8H11NHEt] was the first compound of this
family to be reported [1,2]. [(EtNH2)B8H11NHEt] was
first synthesized in 1962 by the reaction of
[B9H13(SMe2)] with NH2Et [1], and the determination
of its structure and thence unequivocal constitution
followed in 1963 [2]. Some time later, the results of
NMR-spectroscopy were taken to suggest that the eight-
boron core cluster of this compound could be defined as
being in a hypho category [3]. Thus, its molecular
structure is based on a {B8} cluster [2] of interesting
hypho-type eight-vertex character [3] that has two
ligand unit NH2Et in an exo terminal position (Fig. 1).
The description of the eight-vertex borane cluster of
[(RNH2)B8H11NHR] in terms of hypho character can be
based on the WilliamsꢁWade formalism, often de-
/
scribed as ‘Wade’s rules’ [4]. This formalism classifies
the relationship between the skeletal structures of
boranes and the numbers of electron pairs that they
contain. Thus, a species with n skeletal atoms will adopt
a hypho structure if held together by (nꢂ4) electron
/
pairs. In the [(RNH2)B8H11NHR] cluster system the exo
amine NH2R is a two-electron-donor ligand to the eight-
boron central cluster, whereas the {NHR} group is an
electron-precise moiety that is formally attached to two
skeletal boron atoms via one normal covalent bond and
one dative bond. The {NHR} unit thereby gives three
electrons to the cage. The boron cage itself provides
nineteen cluster-bonding electrons to the framework.
Together with the total of five electrons from the two
* Corresponding author. Tel.: ꢂ
218-2871.
E-mail address: doerfler@chemie.uni-bremen.de (U. Dorfler).
/
49-421-218-2200; fax: ꢂ49-421-
/
¨
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 1 4 2 0 - 1

206
C. Bauer et al. / Journal of Organometallic Chemistry 657 (2002) 205ꢁ216
/
Fig. 1. Generalised schematic structure of compounds 5ꢁ/28 of the [(RNH2)B8H11NHR] family (BH exo hydrogen atoms are omitted for clarity).
The compounds may be regarded as hypho-type eight-vertex {B8} cluster species, or as arachno-type nine-vertex {B8N} cluster species.
nitrogen centres, 24 electrons (12 electron pairs) are,
therefore, available for the eight skeletal atoms. Conse-
quently, the [(RNH2)B8H11NHR] species fulfil the
conditions for being an eight-vertex member of the
hypho cluster family. In nine-vertex azanonaborane
terms, i.e. by inclusion of the bridging nitrogen atom
of the {NHR} grouping as a cluster constituent, then the
species will have nine-vertex arachno character [3], with
a {B8N} skeletal geometry that mimics that of the
arachno nine-vertex binary borane n-B9H15.
Subsequently, it was shown that this route into this
system is not limited to the reaction of [B9H13(SMe2)]
with NH2Et [5,6], but that other primary amines NH2R,
such as iso-propylamine, n-butylamine, tert-butylamine
[5] and methylamine [6] also generate their correspond-
ing [(RNH2)B8H11NHR] species. In some cases, it is also
possible to use secondary amines, as in the use of NHEt2
to give [(Et2NH)B8H11NEt2] [6], but in this case the
yield is not very high. In addition to these direct
syntheses from [B9H13(SMe2)], a second route to sec-
ondary-amine derivatives is via the modification of the
nitrogen-containing groups by N-deprotonation of the
[(RNH2)B8H11NHR] system and subsequent N-alkyla-
tion [6].
Compounds of this family constitute interesting
entries into azacarbaborane [7] and azametallaborane
chemistries [8,9] and also have interesting potential for
use as boron carriers for boron neutron-capture therapy
[10]. In order further to facilitate the development of this
new azanonaborane science, we have been investigating
other possible routes to and among these species. In this
context, we here report a ligand-exchange reaction in
which the exo-NH2R ligand is replaced by other
nitrogen-donor ligands, both aliphatic and aromatic.

C. Bauer et al. / Journal of Organometallic Chemistry 657 (2002) 205ꢁ
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207
During the course of our initial experiments, reactions
carried out with unsubstituted pyridine NC5H5 as donor
ligand gave a bright yellow [(C5H5N)B8H11NHEt]
product, contrasting with the colourless nature of the
starting alkylamine species. In view of this, a series of
substituted pyridines R?C5H4N, where R? is both
electron-donating and electron-withdrawing, e.g. 4-
NH2, 4-CHO and 3-Br, have also been used in the
ligand-exchange reactions with species [(RNH2)B8-
H11NHR], in order to investigate for variety of colour-
change differences in the products [(R?C5H4N)-
B8H11NHR]. Such colourations suggest that there is
an electronic interaction between the {B8} hypho-type
unit and the bonded pyridine units. This phenomenon
may be related to that found for other borane-pyridine
complexes, particularly those of the [6,9-L2-arachno-
temperatures have to be no less than 80 8C but not
higher than 150 8C. Decomposition occurs at 150 8C
and above. The aromatic solvents benzene, toluene and
xylene can be used, but attempts using the non-polar
non-aromatic solvent hexane were not productive. In
terms of more polar solvents, the ligand-exchange
reaction can be carried out in 1,4-dioxane, whereas use
of tetrahydrofurane was not successful, presumably
because of its lower boiling point (b.p.). Polar solvents
with hydroxyl groups, e.g. ethanol and propanol, cannot
be used for the ligand-exchange reaction because they
decompose the azanonaborane at these temperatures.
No reaction was observed in the polar aprotic solvent
acetonitrile, even though the b.p. is in principle high
enough.
Following this initial survey, we adopted benzene as
solvent of choice for subsequent investigation, and we
thence investigated primary, secondary and tertiary
aliphatic amines, together with pyridine and substituted
pyridines, for use in the ligand-exchange reaction.
Successful syntheses were obtained with primary amines
that contained either non-polar residues, or polar
residues distal to the amine site, to yield [(EtNH2)-
B10H12] constitution [11ꢁ13].
/
Thus, we report here on the synthesis and structure of
several new members of this family of azanonaboranes,
and also, with the pyridine and substituted pyridine
species, compare these experimental results with the
calculated structures and UVꢁvis spectra obtained from
/
semi-empirical AM-1 molecular-orbital calculations.
One ultimate calculational target here is to develop a
B8H11NHMe]
5,
[(isoPrNH2)B8H11NHMe]
6,
qualitative molecular-orbital model to explain the UVꢁ
/
[(terBuNH2)B8H11NHMe] 7, [{MeO(CH2)3NH2}B8H11-
NHMe] 8, [(HO(CH2)3NH2)B8H11NHMe] 9, and
[{OC4H8NH(CH2)2NH2}B8H11NHMe] 10. However,
the reaction did not proceed with the aromatic amine
aniline under corresponding conditions. Primary amines
with adjacent polar groups, such as 2-methoxyethyla-
mine, 2,2-diethoxy-ethylamine or N-acetylethylendia-
mine, similarly did not undergo the ligand-exchange
reactions. Empirically, for these substituted primary
amines, we found that there must be more than two
{CH2} groups between the {NH2} residue and the polar
functional group in the amine.
vis spectra of these azanonaboraneꢁpyridine derivatives
/
in terms of a dependence on the substituents on the
pyridine ring. In this regard, we also here compare
conclusions regarding the electronic interaction between
the pyridine moieties and the hypho-type {B8} clusters in
compounds of the [(R?C5H4N)B8H11NHR] series with
those previously reported [11ꢁ13] for the ten-vertex [6,9-
/
(R?C5H4N)2-arachno-B10H12] cluster system.
2. Results and discussion
Diethylamine and diallylamine, viz. secondary amines
with non-polar residues, also react with [(RNH2)-
B8H11NHR] to yield the corresponding products
2.1. Preparation
?
[(R2NH)B8H11NHR] [6]. Use of non-aromatic cyclic
We have found that the exchange of the exo amine
secondary amines also conveniently gives their corre-
sponding products. Both five-membered-ring species, as
with pyrrolidine in [(C4H8NH)B8H11NHMe] 11 and
[(C4H8NH)B8H11NHisoPr] 12, and six-membered-ring
species, as in the piperidine compound [(C5H10NH)-
B8H11NHMe] 13, can be prepared. Here it is of interest
to note that differences in the {NHR} residue that is
bonded to the bridging nitrogen atom also do not
significantly change the reactivity, with comparable
yields being obtained for the {NHMe} compound 11
and the {NHisoPr} compound 12. The reaction also
proceeds when there are ring heteroatoms in the cyclic
aliphatic amine, as with a nitrogen atom, as in
[(NHC4H8NH)B8H11NHisoPr] 14, or an oxygen atom,
as in [(OC4H8NH)B8H11NHCH3] 15. As with the
primary amines as discussed in the previous paragraph,
§
ligand NR?H2 for another amine NH2Rƒor NHR2
(equation 1 and 2, respectively) is a convenient route
for the formation of new N-substituted members of this
azanonaborane family, of general formulations
ƒ
[(R?NH2)B8H11NHR)] or [(R2HN)B8H11NHR], respec-
tively.
(R?H2N)B8H11NHRꢂNH2Rƒ
0 (RƒH2N)B8H11NHRꢂNH2R?
(1)
(2)
(R?H2N)B8H11NHRꢂNHR§
2
0 (R2§HN)B8H11NHRꢂNH2R?
In initial experiments, we investigated the dependence
of the ligand-exchange reaction on the solvent, using
[(EtNH2)B8H11NHEt] and pyridine as the test system.
The result of this investigation is that the necessary

208
C. Bauer et al. / Journal of Organometallic Chemistry 657 (2002) 205ꢁ216
/
the ligand-exchange reaction does not occur with some
examples of substituted secondary amines in which there
is only a short carbon chain between the substituent
group and the amine unit. These examples are dietha-
nolamine and N,N?,N?-trimethylethylendiamine. Pyr-
role as an aromatic amine does not undergo the
ligand-exchange reaction, presumably because the nom-
inally isolated electron pair of the nitrogen atom is part
of the aromatic p-electron system. The reaction with
imidazole does, however, occur, presumably now be-
cause its character is more basic than that of pyrrole:
imidazole contains two nitrogen atoms and only one of
the nitrogen electron pairs is needed for the aromatic p-
electron system. As a model for tertiary amines, reac-
tions were also tried with triethylamine, but no exchange
reaction occurred under our conditions, presumably
because of inhibitory steric effects.
Fig. 2. A drawing of the crystallographically determined molecular
structure of [(C5H5N)B8H11NHMe] 17, with thermal ellipsoids of non-
hydrogen atoms shown at 50% probability. For clarity hydrogen atoms
are drawn as circles with an arbitrary small radius.
The ligand exchange also occurs readily with pyridine
to yield the yellow product [(C5H5N)B8H11NHMe] 17.
We thence investigated for pyridine derivatives with a
range of electron-donating and electron-accepting sub-
stituents, firstly to establish whether the exchange also
occurs at extremes of donating and accepting substitu-
ent effect, and secondly to examine for differences of
colour in the products. The substituted pyridines used
were 4-dimethylaminopyridine, 4-aminopyridine, 4-ben-
zylpyridine, 4-phenylpyridine, 3-bromopyridine, 4-acet-
ylpyridine, 4-nitropyridine and chinoline. These
experiments resulted in the formation of [(C5H5N)-
B8H11NHMe] 17, [(C5H5N)B8H11NHEt] 18, [(C5H5N)-
B8H11NHisoPr] 19, [(C5H5N)B8H11NHterBu] 20, [(4-
NH2C5H4N)B8H11NHMe] 21, [(4-NMe2-C5H4N)B8H11-
NHMe] 22, [(4-PhCH2-C5H4N)B8H11NHMe] 23, [(4-
Ph-C5H4N)B8H11NHMe] 24, [(3-Br-C5H4N)B8H11NHi-
soPr] 25, [(4-MeCO-C5H4N)B8H11NHMe] 26 and [(4-
NO2-C5H4N)B8H11NHMe] 27. Both reactivity and yield
were both very similar for the pyridines with both donor
or acceptor substituents, and there was similarly little
variation between 3-substituted analogues and 4-sub-
stituted analogues. In all such cases the exchange
reaction worked very well. However, 2-substitution is
presumably sterically inhibitory, as we observed no
reaction when either 2,6-dimethylpyridine, or 2,2?-
dithiopyridine, or acridine, were used.
Fig. 3. A drawing of the crystallographically determined molecular
structure of one of the two independent molecules of
[(C5H5N)B8H11NHEt] 18, with thermal ellipsoids of non-hydrogen
atoms shown at 50% probability. For clarity hydrogen atoms are
drawn as circles with an arbitrary small radius.
2.2. Structural study
The four pyridine compounds [(C5H5N)B8H11NHMe]
17, [(C5H5N)B8H11NHEt] 18, [(C5H5N)B8H11NHisoPr]
19 and [(C5H5N)B8H11NHterBu] 20, were examined by
single-crystal X-ray diffraction analysis (Fig. 2, Fig. 3,
Fig. 4 and Fig. 5).
The results readily confirmed the identities of the
compounds, and were consistent with the results of
NMR spectroscopy (for details see Section 3), confirm-
ing that the crystals selected were representative of the
Fig. 4. A drawing of the crystallographically determined molecular
structure of [(C5H5N)B8H11NHiso Pr] 19, with thermal ellipsoids of
non-hydrogen atoms shown at 50% probability. For clarity hydrogen
atoms are drawn as circles with an arbitrary small radius.

C. Bauer et al. / Journal of Organometallic Chemistry 657 (2002) 205ꢁ
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209
{NHEt}0
/
{NHisoPr}0
/
{NHterBu}, but there is no
corresponding large systematic variation in any mole-
cular structural dimension, and, in any event, the
{NHterBu} species 20 is crystallographically not best
defined, which inhibits a fine intercomparison across the
whole of the series. The most significant variation, a
relatively minor one, is in intra-cluster folding (Table 1).
Thus, there is a small, but interesting, and apparently
systematic, change in the two intra-cluster fold-angles,
as manifested by changes in the hinge-angle within the
{B8} cluster, and the hinge angle between the {B8}
cluster and the {B2N} bridge triangle. Both these angles
decrease somewhat along the 170
/
180
/
19 {NHMe}0
/
{NHEt}0
/
{NHisoPr} sequence. This perhaps seems to
go in the opposite direction from that naively expected
from steric effects, which, it could be supposed instinc-
tively, would force a more open fold-angle as the steric
effect of the group increases. However, the groups are
on the ‘outside’ of the cluster, and so perhaps that is why
the opposite is observed. The effects are, however, small,
so there may also be an electronic contribution to this
effect. Alternatively, the observed variation could be a
fortuitous consequence of solid-state packing effects,
and not represent a systematic free-molecule effect. Here
it is of interest to note that the trend does appear to be
continued for the {NHterBu} analogue 20. However,
since the crystal structure of this last species exhibited
crystallographic disorder, and since the differences in
these fold angles are small, there must be circumspection
about the use of the derived dimensions of the molecular
structure for such detailed comparison.
Fig. 5. A drawing of the crystallographically determined molecular
structure of [(C5H5N)B8H11NHter Bu] 20, with thermal ellipsoids of
non-hydrogen atoms shown at 50% probability. For clarity hydrogen
atoms are drawn as circles with an arbitrary small radius. The crystal
exhibits a 1:1 crystallographic disorder across a quasi-mirror-plane
through N(5,6)B(6)B(1)B(3); one of the two similar derived molecules
is drawn here. The two disordered molecules differ principally in the
rotational orientations of the pyridine and tertiary-butyl moieties
about the B(3)Ã
/
N(31) and N(5,6)ÃC(61) linkages, respectively.
/
bulk samples. It is convenient to note here that the
general NMR characteristics of this hypho-azanonabor-
ane compound type have been adequately covered in the
previous literature [3ꢁ5]; all the new compounds re-
/
ported in this present work exhibit typical behaviour.
Of the crystal structures, it should be noted that the
{NHEt} species 18 contained two independent mole-
cules within the asymmetric unit of the unit cell, and
therefore, two independent molecular structures are
established for this compound. The {NHterBu} com-
pound 20, by contrast, was subject to a 1:1 crystal-
lographic disorder across a quasi-mirror-plane through
N(5,6)B(6)B(1)B(3): although the molecular geometry
for both forms was clearly established, including hydro-
gen-atom location, with clear parallels with the mole-
cular structures of compounds 17, 18 and 19, any
derived geometry may be insufficiently precise for
detailed intercomparisons with these other species. The
other two species, the {NHMe} and {NHisoPr} com-
pounds, 17 and 19, respectively, were crystallographi-
cally straightforward. The basic molecular structures of
compounds 17, 18, 19 and 20 are found to be very
similar, and similar in turn to those of the compounds in
this class that have been previously examined structu-
rally, viz. [(EtNH2)B8H11NHEt], [(isoPrNH2)B8-
H11NHisoPr], [(isoPrNH2)B8H11NHterBu] and [(Et2NH)-
B8H11NEt2] [2,4,5]. There is of course variation among
the substituent residues because that is how the com-
pounds differ. There is, in principle, a systematic
2.3. Molecular-orbital calculations
One aim of our theoretical research work is to explain
the colour of pyridineꢁazanonaborane complexes as
/
part of a general theoretical understanding of this
interesting and potentially important type of compound.
One ultimate target here is to develop a qualitative
molecular-orbital model to explain the UVꢁ
/
vis spectra
of these azanonaboraneꢁpyridine derivatives in terms of
/
a dependence on the substituents on the pyridine ring.
For this purpose we have chosen ground-state calcula-
tion at the semi-empirical AM-1 level of theory [16].
This type of calculation gives the HOMO and LUMO
energies, which we have used for interpretation. We did
not use electronic spectra calculations that are only
useful for directly comparing measured and calculated
spectra, rather than energy-level differences, and which,
therefore, do not allow any detailed view on how the
substituents may influence the absorption maxima. At
an initial empirical level, we were interested in an
explanation for the dependence of the colour described
by the longest wavelength absorption in terms of the
nature of the substituents on the pyridine rings. In order
to approach this, the AM-1 calculations were therefore,
inductive/steric trend in the sequence {NHMe}0
/

210
C. Bauer et al. / Journal of Organometallic Chemistry 657 (2002) 205ꢁ216
/
Table 1
Selected intra-cluster fold-angles B(3)ÃB(4)ÃB(5), B(6)ÃB(7)ÃB(8), B(4)ÃB(5)ÃN(5,6) and B(7)ÃB(6)ÃN(5,6) (8) in [(C5H5N)B8H11NHMe] 17,
[(C5H5N)B8H11NHEt] 18, [(C5H5N)B8H11NHiso Pr] 19, and [(C5H5N)B8H11NHter Bu] 20
Compound
B(3)ÃB(4)ÃB(5)
B(6)ÃB(7)ÃB(8)
B(4)ÃB(5)ÃN(5,6)
B(7)ÃB(6)ÃN(5,6)
17
18 (molecule 1)
18 (molecule 2)
Me
Et
116.7
114.9
114.8
113.2
107.0
117.65
116.2
115.7
116.0
114.5
118.9
117.5
117.4
116.9
116.4
119.4
116.9
116.0
116.5
109.1
Et
19
20
iso Pr
ter Bu
Note that, for compound 20, there is a 1:1 disorder of the molecule across the quasi-mirror-plane through N(5,6)B(6)B(1)B(3), which will render
derived interatomic distances for this molecule unreliable for detailed comparisons.
carried out on the pyridine and substituted-pyridine
species 17, 22, 24, 25, 26, 27, and 28. Orbital energies
after total geometry optimisation for the highest occu-
pied molecular orbital (HOMO, see Fig. 6) and the
lowest unoccupied molecular orbital (LUMO, again see
Fig. 6) are listed in Table 2.
differences being between 9 and 10 eV for the azanona-
boranes. Principal elements of the molecular-orbital
structure that are responsible for the colour can be
constructed qualitatively from combinations of frag-
ments of HOMO of the azanonaborane and the p-
LUMO of the pyridine (Fig. 8).
The orbital-energy differences DEHOMOꢁLUMO show
correlations with the experimental data for lmax as
The energy of the HOMO of the [(C5H5N)-
B8H11(NHR)] molecule is higher than that of the
HOMO of the {B8H11(NHR)} fragment, and is nearly
completely localised around the framework of the
cluster (Fig. 6). Concomitantly, the LUMO of the
molecule is localised exclusively on the pyridine frag-
ment (Fig. 6) and is lower in energy than the LUMO of
the pyridine fragment in pure pyridines (Fig. 8). The
resulting calculated orbital-energy difference of between
6 and 7 eV is responsible for the absorption in the visible
region. Due to the localisation of the LUMO of
[(C5H5N)B8H11(NHR)] molecule on the complexed
pyridine fragment, this orbital-energy difference and,
therefore, also the colour show a dependence on the
pyridine substituents. A p-donor leads to a blue shift
whereas a p-acceptor leads to a red shift. The dimethy-
laminopyridine compound 22, with the strongest donor
substituent on the pyridine ring, and [(4-NO2-
C5H4N)B8H11NHMe] 27, with the strongest acceptor
substituent, define the limits of the observed wavelength
determined from UVꢁ
Specifically, the plot
/
vis absorption spectroscopy.
of energy difference
DEHOMOꢁLUMO versus 1/lmax is linear (Fig. 7). The
only exception to this generality is [(4-NMe2-
C5H4N)B8H11NHMe] 22 which shows different beha-
viour: its datum is not coincident with the correlation
line to which the data points for the other compounds
are close. This exception perhaps arises because the
dimethylaminopyridine ligand in compound 22 is a
strong p-donor and thus not only affects the LUMO
but also the HOMO. One tentative explanation is that
the dimethylamino group acts as a concurrent p-donor
towards the azanonaborane unit.
The analysis of the results in Table 2 reveals that there
is only a small variation in HOMO, and so the
correlation in the DEHOMOꢁLUMO plot arises principally
from the larger variations in the LUMO. There is also a
parallel with the LUMO energies of the individual
uncomplexed pyridines. The starting aliphatic azanona-
boranes and the uncomplexed pyridines are both
originally colourless, with lmax for each smaller than
300 nm, and with the AM-1 calculated orbital-energy
range of 320ꢁ
compounds reported here are found. This range, corre-
sponding to 3.9ꢁ2.6 eV, represents the energy differ-
ences between ground and excited states of molecules,
/
480 nm, within which all the other
/
Fig. 6. AM1-calculated molecular orbitals of [(C5H5N)B8H11NHMe] 17: (a) LUMO and (b) HOMO.

C. Bauer et al. / Journal of Organometallic Chemistry 657 (2002) 205ꢁ
/216
211
Table 2
Orbital energies after total geometry optimisation for the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital
(LUMO) for the substituted pyridine species [(RC5H4N)B8H11(NHR)]
AM1
UVꢁ
/
vis absorption 1/l (cmꢃ1
)
HOMO (eV) LUMO (eV)
DE (LUMOꢁ/HOMO) (eV)
LUMO (isolated pyridine
derivatives) (eV)
Compound
22
17
25
24
28
26
27
3.13
2.75
2.56
2.41
2.08
2.60
2.32
ꢃ7.70
ꢃ7.97
ꢃ8.07
ꢃ7.91
ꢃ7.92
ꢃ8.08
ꢃ8.34
ꢃ0.63
ꢃ1.05
ꢃ1.30
ꢃ1.29
ꢃ1.46
ꢃ1.69
ꢃ2.32
7.07
6.92
6.77
6.62
6.46
6.39
6.02
ꢂ0.51
ꢂ0.17
ꢃ0.32
ꢃ0.35
ꢃ0.55
ꢃ0.66
ꢃ1.39
Fig. 7. Correlation of the energy differences DEHOMO ꢁ LUMO with 1/
lmax for the series of pyridne and substituted pyridine compounds 17ꢁ
28.
/
but is clearly much lower than the calculated HOMOꢁ
LUMO energy differences of between 6 and 7 eV. This is
as expected from this type of calculation, because any
Coulomb and exchange integrals and conformation
interactions, especially of the excited state, are not
considered, and these typically reduce the energy
differences. Compared with the unsubstituted pyridine
compound 17, the pyridine units of all the other
compounds except the dimethylamino compound 22
are acceptor-substituted. Within this series of acceptor-
substituted compounds, the LUMO energy can be
reduced for a variety of reasons. Thus, in the bromi-
nated compound 25 there is found to be a strong
inductive effect from the bromine substituent, in the 4-
phenylpyridine compound 24 the phenyl moiety acts as
a good p-acceptor, in the chinoline compound 28 the
extended p-system can be invoked, whereas in the acetyl
and nitro compounds 26 and 27 the involvement of the
p* orbitals of the carbonyl and nitro groups, respec-
tively, are the principal factors in the reduction of the
LUMO energy of the [(C5H5N)B8H11(NHR)] molecule
compared with the pure pyridine. In contrast to the
/
Fig. 8. Schematic picture of the energy difference DEHOMO ꢁ LUMO in
pure pyridine (left), in a [(C5H5N)B8H11(NHR)] molecule (centre) and
in a [(RNH2)B8H11(NHR)] molecule (right).
variations arising from changing the substituent on
pyridine, changing the residue R of the aliphatic group
on the bridging nitrogen atom does not show any
significant effect on the lmax value of the relevant
{NHMe}, {NHEt}, {NHisoPr} and {NHterBu} com-
pounds 17, 18, 19 and 20. Calculations (which are not
plotted in Fig. 6) reveal only a small variation among
their HOMO energies, from 6.92 to 6.87 eV. This
variation is too small to have any significant differential
effects on the colours of these species.
It has been shown previously [11] that the colours of
6,9-bis-pyridine-arachno-decaborane
[6,9-(C5H5N)2-
arachno-B10H12] and its ring-substituted derivatives
vary from a very pale yellow to a deep red, depending
on the substituent group on the pyridine ligand. In the
case of [6,9-(C5H5N)2-arachno-B10H12] and its ring-
substituted derivatives, electron-withdrawing substitu-
ents also shifted the absorption band at the longest wave

212
C. Bauer et al. / Journal of Organometallic Chemistry 657 (2002) 205ꢁ216
/
length towards red, whereas a p-donor substituent led to
a blue shift. The differences of cluster-structure char-
acter between ten-vertex arachno {B10} and eight-vertex
hypho {B8} would, therefore, appear to have no
significant differential influence on the colours of their
pyridine complexes, because the {B8} series shows very
similar colourations to the {B10} series [11]. In this
regard it may be noted that for both systems the local
structures at the point of pyridine attachment are very
similar: in each case the pyridine ligand is bound to a
cluster {BH(endo)} unit. It will clearly be of interest to
MHz) [14], J being as defined by McFarlane [15]. Mass
spectrometric data were measured using a Finnigan
MAT 8222 instrument, either (a) by fast-atom bom-
bardment ionisation (FAB) with glycerol or nitrobenzy-
lalcohol (NBA) as matrix, or (b) by 70 eV electron-
impact ionisation (EI) at 473 K. Only the signal with the
highest intensity of the boron isotopic pattern is listed.
UV data were measured on a Varian Cary 50 Bio
instrument. Molecular-orbital calculations [16] were
carried out with HYPERCHEM [17].
examine other pyridineꢁ
/
boranes in this respect: for
3.1. X-ray diffraction analysis
example, those involving the ligand endo-bound to an
open face {BH(exo)} unit, or exo to an open face boron
atom that is not associated with an inner-sphere
bridging or endo hydrogen atom, or bound exo to an
apical boron atom.
Crystal data for [(C5H5N)B8H11NHMe] 17,
[(C5H5N)B8H11NHEt] 18, [(C5H5N)B8H11NHisoPr] 19
and [(C5H5N)B8H11NHterBu] 20 are as follows: com-
pound 17, C6H20B8N2: Mꢀ
dichloromethane), 0.34ꢄ0.31ꢄ
9.4555(4), cꢀ
89.971(3), gꢀ106.3404(3)8, Uꢀ
644.13(6) A , Dcalc 2, MoꢁKa,
1.066 Mg mꢃ3, Zꢀ
0.054 mmꢃ1, Tꢀ
150(2) K, R1ꢀ
0.0455 for 2269 reflections with I ꢀ2s(I), and wR2ꢀ
0.1194 for all 2491 independent reflections; compound
18, C7H22B8N2: Mꢀ220.75, triclinic (from dichloro-
methane), 0.40ꢄ0.08ꢄ
10.2693(2), bꢀ11.9478(3), cꢀ
81.7440(11), bꢀ76.85960(10), gꢀ
1431.87(6) A , Dcalc
1.024 Mg mꢃ3, Zꢀ
0.052 mmꢃ1, Tꢀ
150(2) K, R1ꢀ
0.0683 for 3641 reflections with I ꢀ2s(I), and wR2ꢀ
0.1820 for all 5612 independent reflections; compound
19, C8H24B8N2: Mꢀ234.77, triclinic (from dichloro-
methane), 0.48ꢄ0.42ꢄ
7.1388(5), bꢀ9.1147(9), cꢀ
102.804(4), bꢀ103.586(5), gꢀ
747.32(12) A , Dcalc
1.043 Mg mꢃ3, Zꢀ
0.053 mmꢃ1, Tꢀ
150(2) K, R1ꢀ
0.0574 for 2229 reflections with I ꢀ2s(I), and wR2ꢀ
0.1683 for all 2926 independent reflections; compound
20, C9H26B8N2: Mꢀ248.79, monoclinic (from dichlor-
omethane), Space group P21/n, aꢀ6.9056(1), bꢀ
99.6579(6)8, Uꢀ
1.007 Mg mꢃ3, Zꢀ
4, MoꢁKa,
0.052 mmꢃ1, Tꢀ
150(2) K, R1ꢀ
0.0514 for 2568 reflections with I ꢀ2s(I), and wR2ꢀ
/206.72, triclinic (from
Due to the absence of crystallographic X-ray data for
/
/0.11 mm, Space group
˚
¯
the substituted pyridine derivatives 21ꢁ/27, it has not
P/
1; aꢀ
/
6.6798(4), bꢀ
/
/
11.4955(7) A, aꢀ
/
been possible to compare their calculated and experi-
mental geometries, especially for the conformation
111.494(3), bꢀ
/
/
/
3
˚
ꢀ
/
/
/
˚
about the BÃ
/
N(pyridine) bond, which is the most
lꢀ
/
0.71073 A, mꢀ
/
/
/
flexible point in the structure. Nevertheless, because
/
/
the results of our calculations suggest a strong depen-
vis spectra on
dence of the absorption maxima in UVꢁ
/
/
¯
the LUMO energy of the substituted pyridines, it seems
likely that changes in the rotamer conformation about
/
/
0.02 mm, Space group P
/
1; aꢀ
/
˚
/
/
12.12373(3) A, aꢀ
87.3380(10)8, Uꢀ
4, MoꢁKa,
/
the BÃ
/
N(pyridine) vector should not have a strong
/
/
/
3
˚
influence on the LUMO of the pyridine moiety and
therefore on the absorption maxima. Further calcula-
tions, especially of the dependence of the rotational
ꢀ
/
/
/
˚
lꢀ
/
0.71073 A, mꢀ
/
/
/
/
/
barrier about the BÃ
/
N(pyridine) vector, are needed to
test this hypothesis. Interesting in this regard would be
additional information about the different behaviour of
derivative 22, which contains a strong p-donor sub-
stituent and therefore, could act as a p-donor into the
{B8} cluster.
/
¯
/
/
0.10 mm, Space group P
/
1; aꢀ
/
˚
/
/
12.7128(13) A, aꢀ
103.573(5)8, Uꢀ
2, MoꢁKa,
/
/
/
/
3
˚
ꢀ
/
/
/
˚
lꢀ
/
0.71073 A, mꢀ
/
/
/
/
/
3. Experimental
/
Reactions were carried out in dry solvents. The
starting azanonaboranes [(RNH2)B8H11NHR], where
R is methyl 1, ethyl 2, isopropyl 3, and tertiary butyl
4, were prepared according to the literature [1,4,5], and
[B9H13(SMe2)] was also prepared by a literature method
[1]. Preparative thin-layer chromatography was carried
/
/
˚
32.4995(4), cꢀ
1640.79(3) A , Dcalc
/
7.4161(1) A, bꢀ
/
/
3
˚
ꢀ
/
/
/
˚
lꢀ
/
0.71073 A, mꢀ
/
/
/
/
/
0.1271 for all 3205 independent reflections. CCDC
reference numbers for compounds 17, 18, 19 and 20
are 172 012, 172 013, 172 014 and 172 015, respectively.
Methods and programs were standard [18].
out using 0.75 mm layers of silica-gel G (Merck GF254
made from water slurries on glass plates of dimensions
of 20ꢄ
20 cm2, followed by drying in air at 100 8C. All
)
/
other reagents were obtained commercially. NMR
spectroscopy was carried out at 4.7 T on commercially
available instrumentation. Chemical shifts d are given in
3.2. Preparation of compounds
1
ppm to high field (low frequency) of TMS for H (J
3.2.1. General procedure
The appropriate compound [(RNH2)B8H11NHR],
nominally 100 MHz) and 13C (J nominally 25.145004
MHz), and [BF3(OEt)] for 11B (J nominally 32.083971
where Rꢀmethyl 1, ethyl 2, isopropyl 3, or tert-butyl
/

C. Bauer et al. / Journal of Organometallic Chemistry 657 (2002) 205ꢁ
/216
213
4 (100 mmol) was dissolved in 10 ml benzene, and the
appropriate amine or pyridine for the ligand-exchange
reaction was added (100 mmol). After heating the
solution at reflux for 2 h, the solvent was removed
under reduced pressure. The residue, consisting of the
crude azanonaborane product, was then purified by
repeated thin-layer chromatography on silica gel using
dichloromethane as liquid phase. Criteria of purity and
3.2.2.4. [{MeO(CH2)3NH2}B8H11NHMe] 8. Com-
pound 1 reacts with 3-methoxypropylamine to give 8.
Chromatography: CH2Cl2/THF (9:1); RFꢀ
42% (9 mg, 42 mmol); NMR (CDCl3): BH(2) ꢃ
0.68]; BH(7) ꢃ33.6 [ꢂ0.70]; BH(4) ꢃ32.3 [ꢂ
BH2(8) ꢃ32.3 [endo ꢃ0.68, exo ꢂ0.48 ]; BH(3) ꢃ
20.5 [ꢂ1.13]; BH(5) and BH(6) both at ca. ꢃ9.8 [both
at ca. ꢂ2.38]; BH(1) ꢂ1.9 [ꢂ2.56]; mH(4.5)ꢀ 1.97;
mH(6.7)ꢀ 2.09; CH2OCH3 ꢂ73.1 [ꢂ3.62]; OCH3 ꢂ
59.2 [ꢂ3.37]; NH2CH2 ꢂ50.5 [ꢂ3.24]; NH2CH2CH2 ꢂ
27.6 [ꢂ1.93]; NHCH3 ꢂ38.4 [ꢂ2.38]; NH2(CH2)3OCH3
[ꢂ4.77]; NHCH3 [ꢃ1.32]; Mass spectrum: FAB (NBA):
m/z: 216 ([M]ꢂ, 10%), m/z: 216 ([M]ꢃ, 35%; 201
[MÃ
CH3]ꢃ, 40%).
/
0.77; Yield:
55.1 [ꢃ
0.70];
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
ꢃ
/
identity for this well-recognised molecular type [1ꢁ
/5]
/
ꢃ
/
/
/
/
were clean multinuclear NMR spectra consistent with
the molecular formulation, allied with corresponding
molecular ions in the mass spectrum, and also allied, in
the case of compounds 17, 18, 19 and 20 as representa-
tives, with all-atom molecular structures determined by
single crystal X-ray diffraction analysis as summarised
above.
/
/
/
/
/
/
/
/
/
/
3.2.2.5. [{HO(CH2)3NH2}B8H11NHMe] 9. Com-
pound 1 reacts with 3-hydroxypropylamine to give 9.
3.2.2. Primary amines
Chromatography: CH2Cl2/THF (9:1); RFꢀ
31% (6 mg, 31 mmol); NMR (CDCl3): BH(2) ꢃ
[ꢃ0.71]; BH(7) ꢃ32.4 [ꢂ0.67]; BH(4) ꢃ32.4 [ꢂ0.67];
BH2(8) ꢃ32.4 [endo ꢃ0.71, exo ꢂ0.43] BH(3); ꢃ20.4
[ꢂ1.11]; BH(5) and BH(6) both at ca. ꢃ9.7 [both at ca.
2.37]; BH(1) 1.7 [ꢂ2.49]; mH(4.5)ꢀ 2.00;
mH(6.7)ꢀ 2.11; CH2OH ꢂ63.0 [ꢂ3.90]; NH2CH2
50.1 [ꢂ3.24]; NHCH3 ꢂ38.5 [ꢂ2.38]; CH2CH2OH
29.0 [ꢂ1.94]; NH2(CH2)3OH [ꢂ4.95/ꢂ4.83]; NHCH3
[ꢃ
1.31]; Mass spectrum: FAB (NBA): m/z: 202 ([M]ꢂ,
45%), m/z: 202 ([M]ꢃ, 52%;188 [MÃ H]ꢃ, 43%).
CH3ꢂ
/
0.27; Yield:
/55.2
3.2.2.1. [(EtNH2)B8H11NHMe] 5. Compound 1 reacts
/
/
/
/
/
with ethylamine to give 5. RFꢀ
35 mmol); NMR (CDCl3): BH(2) ꢃ
33.3 [ꢂ0.50], BH(4) ꢃ33.1 [ꢂ0.50], BH2(8) ꢃ
[endo ꢃ0.77, exo ꢂ0.50], BH(3) ꢃ20.5 [ꢂ0.91], BH(5)
and BH(6) both at ca. ꢃ10.3 [both at ca. ꢂ2.23], BH(1)
1.4 [ꢂ2.39]; mH(4.5)ꢀ 2.15, mH(6.7)ꢀ
NH2CH2CH3 ꢂ44.9 [ꢂ2.84], NHCH3 ꢂ38.7 [ꢂ
NH2CH2CH3 13.9 [ꢂ1.71], NH2CH2CH3 [ꢂ
/
0.80. Yield: 35% (6 mg;
55.2 [ꢃ0.77], BH(7)
30.9
/
/
/
/
/
/
/
/
ꢃ
/
/
/
/
/
ꢂ
/
ꢂ
/
/
/
ꢃ
/
/
/
/
/
/
ꢃ
/
/
/
/
/
ꢂ
/
/
/
/
ꢂ
/
/
/
ꢃ
/
/
ꢃ
/
2.32;
ꢂ
/
/
/
/
/
/
/
/2.23],
/
ꢂ
/
/
/5.17]
/
/
and NHCH3 [ꢃ1.28]. Mass spectrum: FAB (NBA)
/
m/z 172 ([M]ꢂ, 20%), m/z 172 ([M]ꢃ, 17%).
3.2.2.6. [{OC4H8NH(CH2)2NH2}B8H11NHMe]
Compound 1 reacts with 4-(2-aminoethyl)morpholine
to give 10. Chromatography: CH2Cl2/THF (3:1); RFꢀ
0.66; Yield: 22% (7 mg, 22 mmol); NMR (CDCl3): BH(2)
55.2 [ꢃ0.69]; BH(4) and BH(7) ꢃ32.5 [ꢂ0.70];
BH2(8) ꢃ32.5 [endo ꢃ0.69, exo ꢂ0.47]; BH(3) ꢃ20.3
[ꢂ1.15]; BH(5) and BH(6) both at ca. ꢃ9.9 [both at ca.
2.35]; BH(1) 1.7 [ꢂ2.53]; mH(4.5)ꢀ 1.99;
mH(6.7)ꢀ 2.10; NCH2CH2O 66.8 [ꢂ
NH2CH2CH2N ꢂ54.9 [ꢂ2.59]; NCH2 ꢂ53.0 [ꢂ
NH2CH2CH2N ꢂ45.7 [ꢂ3.16]; NHCH3
10.
3.2.2.2. [(isoPrNH2)B8H11NHMe] 6. Compound 1 re-
/
acts with isopropylamine to give 6. RFꢀ
38% (7 mg, 38 mmol); NMR (CDCl3): BH(2) ꢃ
0.62]; BH(7) ꢃ34.2 [ꢂ0.76]; BH(4) ꢃ32.8 [ꢂ0.76]; ꢃ
30.9 [endo ꢃ0.62, exo ꢂ0.52] BH2(8); BH(3) ꢃ20.9 [ꢂ
1.23]; BH(5) and BH(6) both at ca. ꢃ10.2 [both at ca. ꢂ
2.42]; BH(1) ꢂ1.4 [ꢂ2.58]; mH(4.5)ꢀ 1.95; mH(6.7)ꢀ
2.09; NH2CH(CH3)2 ꢂ50.3 [ꢂ3.48]; NHCH3 ꢂ37.6
[ꢂ2.40]; NH2CH(CH3)2 20.7/ꢂ20.4 [ꢂ1.40];
1.34]; Mass
/0.76; Yield:
/
55.1 [ꢃ
/
ꢃ
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
ꢂ
/
ꢂ
/
/
/
ꢃ
/
/
/
/
ꢃ
/
/
/
ꢃ
/
ꢂ
/
/
3.76];
ꢃ
/
/
/
/
/
/
/
/
2.73];
/
ꢂ
/
/
/
/
/
ꢂ
/
38.4 [ꢂ
/
NH2CH(CH3)2 [ꢂ
/
3.98] and NHCH3 [ꢃ
/
2.41]; NH2CH2CH2N [ꢂ
/
4.85]; NHCH3 [ꢃ
/
1.33]; Mass
spectrum: FAB (NBA): m/z: 257 ([M]ꢂ, 25%), m/z: 257
spectrum: FAB (NBA): m/z: 186 ([M]ꢂ, 65%), m/z:
186 ([M]ꢃ, 18%)
([M]ꢃ, 38%).
3.2.2.3. [(terBuNH2)B8H11NHMe] 7. Compound 1
3.2.3. Secondary amines
reacts with tert-butylamine to give 7. RFꢀ
34% (7 mg, 34 mmol); NMR (CDCl3): BH(2) ꢃ
0.83]; BH(7) ꢃ34.6 [ꢂ0.37]; BH(4) ꢃ32.1 [ꢂ
BH2(8) ꢃ30.1 [endo ꢃ0.83, exo ꢂ0.27]; BH(3) ꢃ
[ꢂ0.84]; BH(5) and BH(6) both at ca. ꢃ10.4 [both at ca.
2.07]; BH(1) ꢂ0.6 [ꢂ2.26]; mH(4.5)/mH(6.7)ꢀ 2.30;
53.9; NHCH3 37.6 [ꢂ2.12];
27.2 [ꢂ1.17]; NH2C(CH3)3 [ꢂ4.96/ꢂ
1.38]; Mass spectrum: FAB (NBA):
m/z: 200 ([M]ꢂ, 100%; 352 ([Mꢂ 2H]ꢂ, 6%),
NBAÃ
m/z: 200 ([M]ꢃ, 40%).
/
0.89; Yield:
55.2 [ꢃ
0.37];
23.2
/
/
3.2.3.1. [(C4H8NH)B8H11NHMe] 11. Compound 1
/
/
/
/
reacts with pyrrolidine to give 11. RFꢀ
lisation EtOH/H2O 1:1; Yield: 45% (9 mg, 45 mmol);
NMR (CDCl3): BH(2) ꢃ55.0 [ꢃ0.68]; BH(4) and BH(7)
33.0 [ꢂ0.73]; BH2(8) ꢃ33.0 [endo ꢃ0.68, exo ꢂ0.53];
BH(3) ꢃ16.7 [ꢂ1.16]; BH(5) and BH(6) both at ca.
9.9 [both at ca. ꢂ2.59] [ꢂ2.59]; BH(1) ꢂ1.5 [ꢂ2.43];
mH(4.5)ꢀ 1.95; mH(6.7)ꢀ 2.13; NHCH2 ꢂ
56.4 [ꢂ3.57/ꢂ3.11]; NHCH3 34.4 [ꢂ
NHCH2CH2 24.4/ꢂ24.2 [ꢂ2.07]; NHCH2 [ꢂ
/
0.89; Recrystal-
/
/
/
/
/
/
/
/
ꢂ
/
/
/
/
ꢃ
/
ꢃ
/
/
/
/
/
NH2C(CH3)3
NH2C(CH3)3
ꢂ
/
ꢂ
/
/
/
/
ꢂ
/
/
/
/
ꢃ
/
/
/
/
/
4.80]; NHCH3 [ꢃ
/
/
ꢃ
/
/
ꢃ
/
/
56.9/ꢂ
/
2.39];
4.24];
/
/
/
/
ꢂ
/
/
ꢂ
/
/
/
/

214
C. Bauer et al. / Journal of Organometallic Chemistry 657 (2002) 205ꢁ216
/
NH [ꢃ
/
1.33]; Mass spectrum: FAB (NBA): m/z: 198
([M]ꢂ, 40%), m/z: 198 ([M]ꢃ, 30%).
NHCH2CH2O [ꢂ
/
5.25]; NHCH3 [ꢃ1.38]; Mass spec-
/
trum: FAB (NBA): m/z: 214 ([M]ꢂ, 28%), m/z: 214
([M]ꢃ, 5%).
3.2.3.2. [(C4H8NH)B8H11NHisoPr] 12. Compound 3
reacts with pyrrolidine to give 12. RFꢀ
lisation EtOH/H2O 1:1; Yield: 42% (10 mg, 42 mmol);
NMR (CDCl3): BH(2) ꢃ55.5 [ꢃ0.68]; BH(4) and BH(7)
32.7 [ꢂ0.76]; BH2(8) ꢃ32.7 [endo ꢃ0.68, exo ꢂ0.53];
BH(3) ꢃ16.9 [ꢂ1.21]; BH(5) and BH(6) both at ca.
11.2 [both at ca. ꢂ2.59]; BH(1) ꢂ1.4 [ꢂ2.43];
mH(4.5)ꢀ 2.02; mH(6.7)ꢀ 2.21; NHCH2 ꢂ56.9/ꢂ
56.5 [ꢂ3.58/ꢂ3.12]; NHCH 52.7 [ꢂ2.53];
NHCH2CH2 24.4/ꢂ24.3 [ꢂ2.07]; NHCH(CH3)2
21.3/ꢂ21.2 [ꢂ 1.65];
/
0.88; Recrystal-
3.2.3.6. [{CHNH(CH)2N}B8H11NHMe] 16. Com-
pound 1 reacts with imidazol to give 16. Chromatogra-
/
/
phy: CH2Cl2/THF (1:1); RFꢀ
mmol); NMR (d8-THF): BH(2) ꢃ
34.2 [endo ꢃ0.52, exo ꢂ0.50]; BH(4) and BH(7)
31.3 [ꢂ0.59]; BH(3) ꢃ20.8 [ꢂ1.70]; BH(5) and BH(6)
both at ca. ꢃ10.7 [both at ca. ꢂ2.24]; BH(1) ꢂ0.5 [ꢂ
2.69]; mH(4.5)/mH(6.7)ꢀ 1.99; NCHNH ꢂ136.1 [ꢂ
8.05]; NHCH ꢂ127.2 [ꢂ7.22]; NCH ꢂ117.6 [ꢂ6.91];
NHCH3 ꢂ38.9 [ꢂ 1.06]; NH [ꢂ12.3];
/0.78; Yield: 38% (7 mg, 38
ꢃ
/
/
/
/
/
/
55.1 [ꢃ0.73]; BH2(8)
/
/
/
ꢃ
/
/
/
ꢃ
/
/
/
/
ꢃ
/
/
/
/
/
ꢃ
/
/
ꢃ
/
/
/
/
/
/
/
/
/
ꢂ
/
/
/
ꢃ
/
/
/
ꢂ
/
/
/
ꢂ
/
/
/
/
/
/
/
1.06]; NHCH2 [ꢂ
/
4.20]; NH [ꢃ
/
/
/
2.24]; NHbridge [ꢃ
/
/
Mass spectrum: FAB (NBA): m/z: 226 ([M]ꢂ, 100%),
m/z: 226 ([M]ꢃ, 38%).
Mass spectrum: FAB (NBA): m/z: 195 ([M]ꢂ, 15%), m/
z: 195 ([M]ꢃ, 30%).
3.2.3.3. [(C5H10NH)B8H11NHMe] 13. Compound 1
reacts with piperidine to give 13. Chromatography:
3.2.4. Pyridine and pyridine derivatives
CH2Cl2/THF (10:1); RFꢀ
mmol); NMR (CDCl3): BH(2) ꢃ
33.6 [ꢂ0.70]; BH(4) ꢃ33.4 [ꢂ
[endo 0.74, exo 0.58]; BH(3) ꢃ
BH(5) and BH(6) both at ca. ꢃ10.1 [both at ca. ꢂ
2.45]; BH(1) 1.3 [ꢂ2.60]; mH(4.5)ꢀ 1.96;
mH(6.7)ꢀ 2.16; NHCH2CH2 55.5/ꢂ55.2 [ꢂ3.76/
2.80]; NHCH2CH2/NHCH2CH2CH2 25.3/ꢂ22.2
[ꢂ2.10 bis 1.40]; NHCH3 38.4 [ꢂ2.41];
1.34]; Mass
/
0.86; Yield: 50% (11 mg, 50
55.2 [ꢃ0.74]; BH(7) ꢃ
0.70]; BH2(8) ꢃ32.0
16.1 [ꢂ1.11];
3.2.4.1. [(C5H5N)B8H11NHMe] 17. Compound 1 re-
/
/
/
acts with pyridine to give 17. RFꢀ
mg, 40 mmol); NMR (CDCl3): BH(2) ꢃ
BH(7) ꢃ32.4 [ꢂ0.93]; BH(4) ꢃ29.3 [ꢂ0.93]; BH2(8) ꢃ
29.3 [endo ꢃ0.25, exo ꢂ0.77]; BH(3) ꢃ15.5 [ꢂ2.13];
BH(5) and BH(6) both at ca. ꢃ10.5 and ꢃ9.2 [both at
ca. 2.51/ꢂ2.43]; BH(1) 1.9 [ꢂ2.94]; mH(4.5)/
mH(6.7)ꢀ 1.69; NCHCHCH 147.5 [ꢂ8.97];
NCHCHCH ꢂ140.3 [ꢂ7.99]; NCHCHCH ꢂ125.2 [ꢂ
7.54]; NHCH3 38.5 [ꢂ2.48]; NH [ꢃ1.06]; Mass
spectrum: FAB (NBA, cosolvens: CH2Cl2): m/z: 206
([M]ꢂ, 89%); UV spectrum: lmax
364 nm (THF; 2.7ꢄ
10ꢃ4 mol lꢃ1; oꢀ
2259).
/0.64; Yield: 40% (8
/
/
/
/
/
54.6 [ꢃ0.49];
/
ꢃ
/
ꢂ
/
/
/
/
/
/
/
/
/
/
/
/
/
/
ꢂ
/
/
/
ꢃ
/
/
/
/
ꢃ
/
ꢂ
/
/
/
ꢂ
/
/
ꢂ
/
/
ꢂ
/
ꢂ
/
/
/
ꢃ
/
ꢂ
/
/
/
ꢂ
/
ꢂ
/
/
/
/
/
/
NHCH2CH2CH2CH2 [ꢂ
/
3.19]; NHCH3 [ꢃ
/
ꢂ
/
/
/
spectrum: FAB (NBA): m/z: 212 ([M]ꢂ, 60%), m/z: 212
([M]ꢃ, 18%).
ꢀ
/
/
/
3.2.3.4. [(NHC4H8NH)B8H11NHMe] 14. Compound
1 reacts with piperazine to give 14. Chromatography:
3.2.4.2. [(C5H5N)B8H11NHEt] 18. Compound 2 reacts
with pyridine to give 18. RFꢀ0.74; Yield: 59% (13 mg,
59 mmol); NMR (CDCl3): BH(2) ꢃ54.7 [ꢃ0.52]; BH(7)
32.3 [ꢂ0.92]; BH(4) ꢃ29.2 [ꢂ0.92]; BH2(8) ꢃ29.2
[endo ꢃ0.24, exo ꢂ0.77]; BH(3) ꢃ15.4 [ꢂ2.43]; BH(5)
and BH(6) both at ca. ꢃ11.2 [both at ca. ꢂ2.51/ꢂ2.43];
BH(1) 2.0 [ꢂ2.94]; mH(4.5)/mH(6.7)ꢀ 1.72;
NCHCHCH ꢂ147.5 [ꢂ8.94]; NCHCHCH ꢂ140.4 [ꢂ
8.00]; NCHCHCH ꢂ125.2 [ꢂ7.54]; NHCH2 ꢂ46.5 [ꢂ
2.69]; NHCH2CH3 ꢂ13.6 [ꢂ1.11]; NH [ꢃ1.15]; Mass
spectrum: FAB (NBA): m/z: 220 ([M]ꢂ, 44%); EI (70
eV, 473 K): m/z: 220 ([M]ꢂ, 20%), 217 ([MÃ3H]ꢂ,
30%); UV spectrum: lmax 364 nm (THF; 2.9ꢄ
10ꢃ4
mol lꢃ1; oꢀ
2034).
CH2Cl2/THF (1:1); RFꢀ
mmol); NMR (d8-THF): BH(2) ꢃ
and BH(7) ꢃ36.1 [ꢂ0.58]; BH2(8) ꢃ
exo ꢂ0.58]; BH(3) ꢃ17.9 [ꢂ1.00]; BH(5) and BH(6)
both at ca. ꢃ12.2 [both at ca. ꢂ2.26]; BH(1) ꢂ1.0 [ꢂ
2.51]; mH(4.5)ꢀ 2.14; mH(6.7)ꢀ 2.29; Cluster-
NHCH2 ꢂ55.5/ꢂ55.3 [ꢂ3.41/2.8]; ClusterNHCH2CH2
44.7/44.6 [ꢂ2.8ꢁ3.0]; NHCH3 ꢂ38.4 [ꢂ2.28]; Clus-
terNHCH2 [ꢂ5.19]; ClusterNHCH2CH2NH [ꢂ2.50];
/
0.84; Yield: 46% (10 mg, 46
57.2 [ꢃ0.63]; BH(4)
32.9 [endo ꢃ0.63,
/
/
/
/
/
/
/
/
/
ꢃ
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
ꢃ
/
/
ꢃ
/
ꢂ
/
/
/
ꢃ
/
/
/
/
/
/
/
/
ꢂ
/
/
/
/
/
/
/
/
/
/
/
/
/
/
NH [ꢃ0.79]; Mass spectrum: FAB (NBA): m/z: 213
/
([M]ꢂ, 35%), m/z: 213 ([M]ꢃ, 8%).
/
ꢀ
/
/
3.2.3.5. [(OC4H8NH)B8H11NHMe] 15. Compound 1
reacts with morpholine to give 15. Chromatography:
/
CH2Cl2/THF (15:1); RFꢀ
mmol); NMR (CDCl3): BH(2) ꢃ
and BH(7) ꢃ33.4 [ꢂ0.35]; BH2(8) ꢃ
exo ꢂ0.35]; BH(3) ꢃ15.9 [ꢂ0.81]; BH(5) and BH(6)
both at ca. ꢃ9.9 [both at ca. ꢂ2.15/ꢂ2.09]; BH(1) ꢂ1.2
[ꢂ2.37]; mH(4.5)ꢀ 2.24; mH(6.7)ꢀ 2.44;
NHCH2CH2O ꢂ64.3/ꢂ64.1 [ꢂ3.75/ꢂ3.70]; NHCH2
53.3/ꢂ53.1 [ꢂ3.16/ꢂ2.77]; NHCH3 ꢂ37.8 [ꢂ2.12];
/
0.79; Yield: 28% (6 mg, 28
54.9 [ꢃ0.90]; BH(4)
31.4 [endo ꢃ0.90,
3.2.4.3. [(C5H5N)B8H11NHisoPr] 19. Compound 3
reacts with pyridine to give 19. RFꢀ0.67; Yield: 47%
(11 mg, 47 mmol); NMR (CDCl3): BH(2) ꢃ55.0 [ꢃ
0.57]; BH(7) ꢃ32.2 [ꢂ0.92]; BH(4) ꢃ29.3 [ꢂ0.97];
BH2(8) ꢃ29.3 [endo ꢃ0.25, ꢂexo 0.76]; BH(3) ꢃ
[ꢂ2.11]; BH(5) and BH(6) both at ca. ꢃ11.8/ꢃ
[both at ca. ꢂ2.55/45]; BH(1) ꢂ1.8 [ꢂ
mH(6.7)ꢀ 1.76; NCHCHCH 147.6 [ꢂ
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
15.8
10.2
/
/
ꢃ
/
/
ꢃ
/
/
/
/
/
/
/
/
/
/
/
2.96]; mH(4.5)/
ꢂ
/
/
/
/
/
/
/
ꢃ
/
ꢂ
/
/
8.98];

C. Bauer et al. / Journal of Organometallic Chemistry 657 (2002) 205ꢁ
/216
215
NCHCHCH ꢂ
7.53]; NHCH ꢂ
21.2 [ꢂ1.11]; NH [ꢃ
m/z: 234 ([M]ꢂ, 20%); UV spectrum: lmax
(THF; 3.2ꢄ 1968).
10ꢃ4 mol lꢃ1; oꢀ
/
140.5 [ꢂ
52.9 [ꢂ
1.36]; Mass spectrum: FAB (NBA):
364 nm
/
7.99]; NCHCHCH ꢂ
2.53]; NHCH(CH3)2 ꢂ
/
125.2 [ꢂ
/
7.25ꢁ
NHCH3 ꢂ
FAB (NBA): m/z: 296 ([M]ꢂ, 45%), m/z: 296 ([M]ꢃ,
10%); UV spectrum: lmax 363 nm (THF; 1.0ꢄ
10ꢃ4
mol lꢃ1; oꢀ
6100).
/
7.45]; NHCH3 [ꢃ
/
1.30]; CH2
ꢂ
/
41.1 [ꢂ
/
4.09];
/
/
/
21.3/ꢂ
/
/
38.5 [ꢂ2.46]; NH [ꢃ
/
/1.06]; Mass spectrum:
/
/
ꢀ
/
ꢀ
/
/
/
/
/
3.2.4.4. [(C5H5N)B8H11NHterBu] 20. Compound 4
reacts with pyridine to give 20. RFꢀ0.69; Yield: 53%
(13 mg, 53 mmol); NMR (d8-THF): BH(2) ꢃ55.2 [ꢃ
0.56]; ꢃ31.9 [endo ꢃ0.19, exo ꢂ0.79] BH2(8); BH(4)
and BH(7) ꢃ29.1 [ꢂ0.98]; BH(3) ꢃ15.4 [ꢂ2.18]; BH(5)
and BH(6) both at ca. ꢃ11.3 [both at ca. ꢂ2.66/ꢂ2.58];
BH(1) 2.4 [ꢂ2.98]; mH(4.5)/mH(6.7)ꢀ 1.93;
NCHCHCH ꢂ147.6 [ꢂ8.99]; NCHCHCH ꢂ140.2 [ꢂ
8.01]; NCHCHCH ꢂ125.2 [ꢂ7.55]; NHC(CH3)3
53.3; NHC(CH3)3 ꢂ27.3 [ꢂ1.12]; NH [ꢃ1.12]; Mass
spectrum: FAB (NBA): m/z: 248 ([M]ꢂ, 100%), m/z:
249 ([M]ꢃ, 20%); UV spectrum: lmax
364 nm (THF;
2.6ꢄ 2307).
10ꢃ4 mol lꢃ1; oꢀ
3.2.4.8. [(4-PhÃ
1 reacts with 4-phenylpyridine to give 24. RFꢀ
Yield: 50% (14 mg, 50 mmol); NMR (THF): BH(2) ꢃ
55.0 [ꢃ0.76]; BH2(8) ꢃ32.9 [endo ꢃ0.50, exo ꢂ0.51];
BH(4) and BH(7) ꢃ29.8 [ꢂ0.66]; BH(3) ꢃ16.1 [ꢂ
BH(5) and BH(6) both at ca. ꢃ10.6 [both at ca. ꢂ
BH(1) ꢂ2.6 [ꢂ2.72]; mH(4.5)/mH(6.7)ꢀ
152.5; ꢂ147.7 [ꢂ8.63] (NCHCHC); Cphenyl
CCHCHCH ꢂ131.0 [ꢂ7.25ꢁ7.45]; CCHCHCH ꢂ
129.6 [ꢂ7.25ꢁ7.45]; CCHCHCH ꢂ127.2 [ꢂ7.25ꢁ
7.45]; NCHCHC ꢂ122.6 [ꢂ7.25ꢁ7.45]; NHCH3 [ꢃ
1.30]; Mass spectrum: FAB (NBA): m/z: 282 ([M]ꢂ,
35%), m/z: 283 ([M]ꢃ, 8%); UV spectrum: lmax
391
nm (THF; 6.6ꢄ 5000).
10ꢃ5 mol lꢃ1; oꢀ
/
C5H4N)B8H11NHMe] 24. Compound
/
/0.65.
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
1.83];
2.18];
/
/
/
/
/
ꢂ
/
/
/
ꢃ
/
/
/
/
ꢃ
/
1.94; Cpyridin
/
/
/
/
ꢂ
/
/
/
ꢂ
/
135.1;
/
/
ꢂ
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
ꢀ
/
/
/
ꢀ
/
/
/
3.2.4.5. [(4-NH2C5H4N)B8H11NHMe] 21. Compound
1 reacts with 4-aminopyridine to give 21. Chromato-
3.2.4.9. [(3-BrÃ
pound 3 reacts with 3-bromopyridine to give 25. RFꢀ
0.71; Yield: 45% (14 mg, 45 mmol); NMR (THF): BH(2)
/
C5H4N)B8H11NHisoPr] 25. Com-
graphy: CH2Cl2/THF (3:1); RFꢀ
mg, 47 mmol); NMR (THF): BH(2) ꢃ
BH(7) ꢃ35.8 [ꢂ0.63]; BH(4) ꢃ33.1 [ꢂ0.63]; BH2(8) ꢃ
32.9 [endo ꢃ0.35, exo ꢂ0.63]; BH(3) ꢃ17.6 [ꢂ1.85];
BH(5) and BH(6) both at ca. ꢃ12.3 [both at ca. ꢂ2.31];
BH(1) ꢂ0.6 [ꢂ2.71]; mH(4.5)/mH(6.7)ꢀ 1.96; CNH2
158.2; NCHCHC ꢂ150.7 [ꢂ8.23]; NCHCHC ꢂ109.8
[ꢂ6.51]; NHCH3 ꢂ39.1 [ꢂ2.31]; NH [ꢃ0.70]; NH2 [ꢂ
/0.68; Yield: 47% (10
/
/
56.8 [ꢃ0.68];
/
/
/
/
/
/
ꢃ
/
54.9 [ꢃ
BH(4) and BH(7) ꢃ
BH(5) and BH(6) both at ca. ꢃ
BH(1) ꢂ2.0 [ꢂ2.97]; mH(4.5)/mH(6.7)ꢀ
149.2 [ꢂ9.10]; NCHCHCH 146.5 [ꢂ
NCHCHCH ꢂ143.5 [ꢂ8.95]; NCHCHCH ꢂ126.4 [ꢂ
7.39]; NHCH(CH3)2 ꢂ52.9 [ꢂ2.63]; NHCH(CH3)2 ꢂ
21.3/ꢂ21.2 [ꢂ1.12]; NH [ꢃ1.06]; Mass spectrum: FAB
(NBA): m/z: 312 ([M]ꢂ, 35%); UV spectrum: lmax
385
nm (THF; 7.5ꢄ 5333).
10ꢃ5 mol lꢃ1; oꢀ
/
0.51]; BH2(8) ꢃ
/
31.7 [endo ꢃ
0.99]; BH(3) ꢃ
11.6 [both at ca. ꢂ
/
0.17, exo ꢂ
/
0.77];
2.09];
2.46];
/
/
/
/
/
28.7 [ꢂ
/
/
15.7 [ꢂ
/
/
/
/
/
/
/
/
ꢃ
/
/
/
/
ꢃ
/
1.75; NCHC
ꢂ
/
/
/
/
ꢂ
/
/
ꢂ
/
/
8.10];
/
/
/
/
/
/
/
/
/
6.61]; Mass spectrum: FAB: m/z (Glycerin, cosolvent
THF): 221 ([M]ꢂ, 10%), m/z (NBA): 221 ([M]ꢃ, 5%).
/
/
/
/
/
/
ꢀ
/
3.2.4.6. [(4-NMe2Ã
pound 1 reacts with 4-dimethylaminopyridine to give
22. RFꢀ0.67; Yield: 57% (14 mg, 57 mmol); NMR
(THF): BH(2) ꢃ54.7 [ꢃ0.58]; BH2(8) ꢃ33.6 [endo
0.42, exo ꢂ0.65]; BH(4) and BH(7) ꢃ30.6 [ꢂ
BH(3) ꢃ15.8 [ꢂ
10.1 [both at ca. ꢂ
mH(4.5)/mH(6.7)ꢀ 1.79; CN(CH3)2
CHC ꢂ146.2 [ꢂ8.34]); NHCHCHC ꢂ
N(CH3)2 ꢂ39.6 [ꢂ3.13]; NHCH3 ꢂ38.3 [ꢂ
[ꢃ
1.14]; Mass spectrum: FAB (NBA): m/z: 249 ([M]ꢂ,
18%); UV spectrum: lmax 320 nm (THF; 7.5ꢄ
10ꢃ5
mol lꢃ1; oꢀ
8400).
/
C5H4N)B8H11NHMe] 22. Com-
/
/
/
3.2.4.10. [(4-MeCOÃ
pound 1 reacts with 4-acetylpyridine to give 26. RFꢀ
0.6; Yield: 36% (9 mg, 36 mmol); NMR (CDCl3): BH(2)
/
C5H4N)B8H11NHMe] 26. Com-
/
/
/
/
ꢃ
/
/
/
/0.79];
/
/1.94]; BH(5) and BH(6) both at ca.
ꢃ
/
54.4 [ꢃ
BH(4) and BH(7) ꢃ
BH(5) and BH(6) both at ca. ꢃ
BH(1) ꢂ2.1 [ꢂ3.02]; mH(4.5)/mH(6.7)ꢀ
194.2; NCHCHC ꢂ148.2 [ꢂ9.10]; NCHCHC ꢂ
[ꢂ7.93]; NHCHCHC ꢂ144.9; COCH3 ꢂ26.8 [ꢂ2.70];
NHCH3 ꢂ38.6 [ꢂ2.50]; NH [ꢃ0.98]; Mass spectrum:
FAB (NBA): m/z: 248 ([M]ꢂ, 45%), m/z: 248 ([M]ꢃ,
15%); UV spectrum: lmax 431 nm (THF; 2.2ꢄ
10ꢃ4
mol lꢃ1; oꢀ
4000).
/
0.48]; BH2(8) ꢃ
/
31.7 [endo ꢃ
0.97]; BH(3) ꢃ
10.4 [both at ca. ꢂ
/
0.13, exo ꢂ
/
0.80];
2.09];
2.48];
ꢃ
/
/
2.42]; BH(1) ꢂ
/
0.9 [ꢂ
/
2.84];
/
28.6 [ꢂ
/
/
15.7 [ꢂ
/
/
ꢃ
/
ꢂ
/
155.1; NCH-
106.1 [ꢂ6.51];
2.42]; NH
/
/
/
/
/
/
/
/
/
ꢃ
/
1.64; CO ꢂ
/
/
/
/
/
/
/
/
123.2
/
/
/
/
/
ꢀ
/
/
/
/
/
/
ꢀ
/
/
3.2.4.7. [(4-PhCH2Ã
pound 1 reacts with 4-benzylpyridine to give 23. RFꢀ
0.67; Yield: 55% (16 mg, 55 mmol); NMR (THF): BH(2)
/
C5H4N)B8H11NHMe] 23. Com-
/
/
3.2.4.11. [(4-NO2Ã
pound 1 reacts with 4-nitropyridine to give 27. RFꢀ
0.81; Yield: 16% (4 mg, 16 mmol); NMR (CDCl3):
BH(2) ꢃ54.7 [ꢃ0.50]; BH2(8) ꢃ30.6 [endo ꢂ0.09, exo
0.85]; BH(4) and BH(7) ꢃ27.5 [ꢂ0.90]; BH(3) ꢃ15.4
[ꢂ2.13]; BH(5) and BH(6) both at ca. ꢃ10.2 [both at ca.
2.47]; BH(1) ꢂ2.4 [ꢂ3.00]; mH(4.5)/mH(6.7)ꢀ 1.66;
/
C5H4N)B8H11NHMe] 27. Com-
ꢃ
/
54.6 [ꢃ
BH(4) and BH(7) ꢃ
BH(5) and BH(6) both at ca. ꢃ
BH(1) ꢂ1.8 [ꢂ2.93]; mH(4.5)/mH(6.7)ꢀ
156.0; NCHCHC ꢂ146.9 [ꢂ8.76]; Cbenzyl
C6H4 ꢂ129.1/127.3 [7.45ꢁ7.18]; NCHCHC ꢂ
/
0.51]; BH2(8) ꢃ
/
32.6 [endo ꢃ
0.89]; BH(3) ꢃ
10.4 [both at ca. ꢂ
/
0.26, exo ꢂ
/
0.73];
2.06];
2.46];
/
/
29.6 [ꢂ
/
/
15.5 [ꢂ
/
/
/
/
/
/
/
/
/
/
ꢃ
/
1.69; Cpyridin
136.6;
125.3 [ꢂ
ꢂ
/
/
/
/
ꢂ
/
/
/
ꢂ
/
/
/
/
/
/
/
ꢂ
/
/
/
/
ꢃ
/

216
C. Bauer et al. / Journal of Organometallic Chemistry 657 (2002) 205ꢁ216
/
[2] R. Lewin, P.G. Simpson, W.N. Lipscomb, J. Chem. Phys. 39
(1963) 1532.
NCHCHC ꢂ
8.23]; NHCHCHC ꢂ
[ꢃ
0.98]; Mass spectrum: FAB (NBA): m/z: 251 ([M]ꢂ,
41%); UV spectrum: lmax 480 nm (THF; 6.8ꢄ
10ꢃ5
mol lꢃ1; oꢀ
7206).
/
150.7 [ꢂ
/
9.27]; NCHCHC ꢂ
/
119.4 [ꢂ
/
/
148.1; NCH3 ꢂ
/
38.5 [ꢂ2.46]; NH
/
[3] P. MacKinnon, X.L.R. Fontaine, J.D. Kennedy, P.A. Salter,
Collect. Czech. Chem. Commun. 61 (1996) 1773.
[4] (a) R.E. Williams, Inorg. Chem. 1 (1971) 210;
(b) K. Wade, J. Chem. Soc. Chem. Commun. (1971) 792;
(c) K. Wade, Adv. Inorg. Chem. Radiochem. 18 (1976) 1;
(d) R.E. Williams, Adv. Inorg. Chem. Radiochem. 18 (1976) 67.
/
ꢀ
/
/
/
3.2.4.12. [(C9H7N)B8H11NHisoPr] 28. Compound 3
reacts with chinoline to give 28. RFꢀ0.63; Yield: 53%
(15 mg, 53 mmol); NMR (CDCl3): BH(2) ꢃ54.6 [ꢃ
0.46]; BH2(8) ꢃ32.2 [ꢂ0.0 endo, exo ꢂ1.03]; BH(7)
29.4 [ꢂ1.03]; BH(4) ꢃ29.4 [ꢂ0.81]; BH(3) ꢃ17.0 [ꢂ
2.31]; BH(5) and BH(6) both at ca. ꢃ10.6 [both at ca. ꢂ
2.55/2.31]; BH(1) ꢂ2.9 [ꢂ3.07]; mH(4.5)/mH(6.7)ꢀ
1.66; C(1)H ꢂ150.0 [ꢂ9.60]; C(9) ꢂ143.1; C(3)H ꢂ
142.3 [ꢂ8.51]; C(7)H ꢂ132.5 [ꢂ7.99]; C(5)H ꢂ128.9
[ꢂ7.99]; C(4) ꢂ128.8; C(6)H ꢂ128.3 [ꢂ7.79]; C(2)H ꢂ
120.5 [ꢂ7.61]; C(8)H ꢂ124.7 [ꢂ9.51]; NHCH(CH3)2 ꢂ
52.9 [ꢂ2.63]; NHCH(CH3)2 ꢂ21.4/ꢂ21.3 [ꢂ1.20]; NH
[ꢃ1.12]; Mass spectrum: FAB (NBA): m/z: 283 ([M]ꢂ
22%), m/z: 285 ([M]ꢃ, 15%); UV spectrum: lmax
415
nm (THF; 1.98ꢄ 2326).
10ꢃ4 mol lꢃ1; oꢀ
[5] U. Dorfler, M. Thornton-Pett, J.D. Kennedy, J. Chem. Soc.
¨
Dalton Trans. (1997) 2547.
/
/
/
[6] U. Dorfler, C. Bauer, D. Gabel, N.P. Rath, L. Barton, J.D.
¨
Kennedy, J. Organomet. Chem. 614ꢁ615 (2000) 215.
/
/
/
/
[7] U. Dorfler, J.D. Kennedy, D. Ormsby, R. Greatrex, Inorg. Chim.
¨
Acta 304 (2000) 268.
ꢃ
/
/
/
/
/
/
/
/
[8] U. Dorfler, P.A. Salter, X.L.R. Fontaine, N.N. Greenwood, J.D.
¨
Kennedy, M. Thornton-Pett, Collect. Czech. Chem. Commun. 64
(1999) 947.
/
/
/
ꢃ
/
/
/
/
/
[9] U. Doerfler, J.D. Kennedy, L. Barton, C.M. Collins, N.P. Rath,
J. Chem. Soc. Dalton Trans. (1997) 707.
[10] See, for example, together with references cited therein: C. Bauer,
/
/
/
/
/
/
/
/
/
/
/
/
/
D. Gabel, U. Dorfler, Abstracts 2nd European Symposium on
¨
Boron Chemistry, EUROBORON 2, Dinard, France, September
/
/
/
/
/
/
,
2ꢁ6, 2001, Abstract no. O4; M. El-Zaria, U. Dorfler, D. Gabel,
/
¨
loc. cit., Abstract no. O8; D. Gabel, M. El-Zaria, U. Dorfler, loc.
¨
cit., Abstract no. O13; C. Bauer, J.D. Kennedy, M. Thornton-
ꢀ
/
/
/
Pett, T. Borrman, D. Gabel, U. Dorfler, loc. cit., Abstract no.
¨
P13; C. Bauer, U. Dorfler, D. Gabel, submitted to Eur. J. Med.
¨
Chem.
[11] B.M. Graybill, M.F. Hawthorne, J. Am. Chem. Soc. 83 (1961)
2673.
Acknowledgements
[12] T. Schaefer, R. Sebastian, R. Salman, Can. J. Chem. 59 (1981)
3026.
We thank the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie and the UK EPSRC
for support. We are also most grateful to M.B. Hurst-
house and S.J. Coles of the University of Southampton
for the collection of crystallographic X-ray diffraction
data for compound 18.
[13] M.G.S. Londesborough, C. Price, M. Thornton-Pett, W. Clegg,
J.D. Kennedy, Inorg. Chem. Commun. (1999) 298.
[14] J.D. Kennedy, Boron, in: J. Mason (Ed.), Multinuclear NMR
(Chapter 8), Plenum, New York and London, 1987, pp. 221ꢁ
[15] W. McFarlane, Proc. R. Soc. London Ser. A 39 (1968) 185.
[16] J.J.P. Stewart, J. Comp. Aided Molec. Des. 4 (1) (1990) 1ꢁ108.
/
258.
/
[17] HYPERCHEM 5.1, HyperCube Inc., Waterloo, Ontario Canada.
[18] Z. Otwinowski, W. Minor, DENZO-SMN, Processing of X-ray
Diffraction Data Collected in Oscillation Mode, Methods En-
zymol. 276 (1997) 307-326. C.W Carter, R.M. Sweet, (Eds.)
Academic Press; COLLECT, Data Collection Strategy Program,
Nonius, 1999.
References
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