Synthesis of N-substituted derivatives of the hypho-(amine)(amino)B8H11 system

Article abstract of DOI:10.1016/S0022-328X(00)00612-4

The chemistry of the hypho-(amine)(amino)B₈H₁₁ system is developed by the synthesis of several derivatives by three routes. [(Et₂HN)B₈H₁₁NEt₂] (4), characterised by single-crystal X-ray work, is prepared from the reaction between B₉H₁₃(SMe₂) and Et₂NH. Methylation of [(EtH₂N)B₈H₁₁NHEt] (1) using NaH and MeI gives, successively, [(EtMeHN)B₈H₁₁NHEt] (5), [(EtMe₂N)B₈H₁₁NHEt] (6) and [(EtMe₂N)B₈H₁₁NMeEt] (7). Alternatively, a displacement reaction with NHEt₂ on (1) or on [(MeH₂N)B₈H₁₁NHMe] (2) yields [(Et₂HN)B₈H₁₁NHEt] (8) or [(Et₂HN)B₈H₁₁NHMe] (9), and a displacement on (1) with pyridine yields [(C₅H₅N)B₈H₁₁NHEt] (10). Phosphine-containing derivatives [(Ph₃P)B₈H₁₁NHEt] (11) and [(PhMe₂P)B₈H₁₁NHEt] (12) can be isolated from interaction of (1) with PPh₃, [RhCl(PPh₃)₃] or [PtCl₂(PMe₂Ph)₂].

Full text of DOI:10.1016/S0022-328X(00)00612-4

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 614–615 (2000) 215–222
Synthesis of N-substituted derivatives of the
hypho-(amine)(amino)B8H11 system
Udo Do¨rfler a,*, Claudia Bauer a, Detlef Gabel a, Nigam P. Rath b, Lawrence Barton b,
John D. Kennedy c
a Department of Chemistry, Uni6ersity of Bremen, PO Box 330 440, 28334 Bremen, Germany
b Department of Chemistry, Uni6ersity of Missouri at St Louis, St Louis, MO 63121, USA
c School of Chemistry, Uni6ersity of Leeds, Leeds LS2 9JT, UK
Received 20 April 2000
It is a pleasure for the authors to be able to dedicate this paper to Professor Sheldon G. Shore on the occasion of his 70th birthday, in
recognition to his achievements and influence in inorganic chemistry.
Abstract
The chemistry of the hypho-(amine)(amino)B8H11 system is developed by the synthesis of several derivatives by three routes.
[(Et2HN)B8H11NEt2] (4), characterised by single-crystal X-ray work, is prepared from the reaction between B9H13(SMe2) and
Et2NH. Methylation of [(EtH2N)B8H11NHEt] (1) using NaH and MeI gives, successively, [(EtMeHN)B8H11NHEt] (5),
[(EtMe2N)B8H11NHEt] (6) and [(EtMe2N)B8H11NMeEt] (7). Alternatively, a displacement reaction with NHEt2 on (1) or on
[(MeH2N)B8H11NHMe] (2) yields [(Et2HN)B8H11NHEt] (8) or [(Et2HN)B8H11NHMe] (9), and a displacement on (1) with pyridine
yields [(C5H5N)B8H11NHEt] (10). Phosphine-containing derivatives [(Ph3P)B8H11NHEt] (11) and [(PhMe2P)B8H11NHEt] (12) can
be isolated from interaction of (1) with PPh3, [RhCl(PPh3)3] or [PtCl2(PMe2Ph)2]. © 2000 Elsevier Science B.V. All rights reserved.
Keywords: Boranes; Hypho cluster; Azaborane; N ligands; NMR spectroscopy; Crystal structure
thence structurally identified in 1963 [4], was initially
regarded as a unique compound. However, in 1997 it
1. Introduction
was reported that this route to the hypho-type
[(RH2N)B8H11NHR] structural motif is not limited to
Polyhedral boron-containing cage chemistry based
on eight boron atoms is relatively sparsely developed
the ethylamine system, but that other primary amine
because suitable eight-boron starting materials are gen-
derivatives, specifically n-butyl, isopropyl and tert-bu-
erally only available via multistep reactions from com-
tyl, could also readily be formed [5]. The synthesis was,
mercially available decaborane(14). The eight-boron
however, limited to primary amines only. In order
species [(EtH2N)B8H11NHEt] (1), available in high yield
further to develop the area of azametallaborane chem-
in two simple steps from nido-B10H14, has been shown
istry containing seven or eight boron atoms we have
to constitute a good entry into azacarbaborane [1] and
become interested in the synthesis of additional mem-
azametallaborane chemistry [2]. Its structure is based
bers of this eight-boron family as starting substrates.
on a cluster of hypho-type eight-vertex character that
bears two amine-derived residues, viz. one amine ligand
in an exo terminal position and one amino group in a
bridging position (Fig. 1). Compound 1, first synthe-
sized from [B9H13(SMe2)] and NHEt2 in 1962 [3], and
* Corresponding author. Tel.: +49-421-2182200; fax: +49-421-
2182871.
E-mail address: doerfler@chemie.uni-bremen.de (U. Do¨rfler).
Fig. 1. Schematic structure of compounds of the hypho-type family
[(RH2N)B8H11NHR].
0022-328X/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00612-4

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U. Do¨rfler et al. / Journal of Organometallic Chemistry 614–615 (2000) 215–222
We therefore report here the syntheses of nine further
species derived from the hypho-type (amine)-
(amino)B8H11 system. These were obtained by three
different approaches: (a) by the direct reaction of sec-
ondary amines with [B9H13(SMe2)]; (b) by the N-depro-
tonation and subsequent N-methylation of [(EtH2N)-
B8H11NHEt] (1); and (c) by ligand exchange on com-
pound (1) and also on [(MeH2N)B8H11NHMe] (2) in
which the exo-(NH2R) group is replaced by other
donor ligands.
Other eight-boron azaboranes are rare, and are lim-
ited to those in the nine-vertex nido and arachno {NB8}
systems [6–10], and the ten-vertex arachno {N2B8},
{CNB8} and {SNB8} systems [11–13]. Useful wider
accounts of azaborane chemistry are in Refs. [14,15].
Boron-containing cluster compounds in the hypho cate-
gory are not nearly as well represented as the better-
known closo, nido and arachno cluster species. In this
regard, and in view of the theme of this volume, it is
particularly apposite to note that the first hypho boron
hydride species, the [B5H12]− anion, and the Lewis-base
adducts L2B5H9, where L is a two-electron donor, were
discovered by Sheldon Shore over a quarter of a cen-
tury ago [16–18].
2.1.2. Alkylation of the nitrogen atoms
The low yield of the dialkylamine compound (4) by
direct synthesis from [B9H13(SMe2)] prompted us to
seek alternative routes for the generation of N-substi-
tuted derivatives. One approach is the replacement of
the N-bound hydrogen atoms on the NH2R group
and/or on the bridging {NHR} group by alkyl substitu-
tents. We have been able to demonstrate this using
[(EtH2N)B8H11NHEt] (1) as starting substrate. Thus, at
−78°C, treatment a solution of (1) in THF with a
slight excess of NaH, followed by reaction with MeI,
yields [(EtMeHN)B8H11NHEt] ((5), 37% yield) (Eq.
(3)), in which a monomethylation of the exo-NH2Et
group to give exo-NHMeEt has occurred.
(EtNH2)B8H11NHEt+NaH+MeI
1
“(EtMeNH)B8H11NHEt+H2+NaI
(3)
Under thes5e conditions no other products were ob-
served, and only one hydrogen atom was replaced,
specifically one of those on the NH2Et site. At room
temperature (r.t.), by contrast, the same reaction af-
forded the dimethylated species [(EtMe2N)B8H11NHEt]
(6), in a low yield. The starting material (1) was largely
recovered, and there was no evidence of formation of
the monomethylated compound (5). The yield of
dimethylated compound (6) was thence logically in-
creased by the use of two equivalents of NaH followed
by addition of two equivalents of MeI in the r.t.
reaction (Eq. (4)). This resulted in the isolation of
compound (6) in 45% yield. No nitrogen methylation at
the bridging {NHEt} residue was observed; presumably
steric crowding in the open face of the cluster [5]
inhibits any initial hydride attack at this site, and
reaction at the more accessible exo-NH2R unit is there-
fore exclusively preferred. However, the use of three
equivalents of NaH and MeI in the r.t. reaction does
result in the replacement of all three N-bound hydrogen
atoms by methyl, to give [(EtMe2N)B8H11NMeEt] ((7),
57% yield) (Eq. (5)). Under the same conditions, an
attempt to replace all of the N-bound hydrogen atoms
in [(isoPrH2N)B8H11NHisoPr] (3) failed, presumably be-
cause of inhibitory steric effects of the bulkier isopropyl
groups; use of an excess of NaH followed by MeI
resulted only in cluster decomposition.
2. Results and discussion
2.1. Preparati6e results
2.1.1. Direct synthesis
The eight-boron cluster family [(RH2N)B8H11NHR],
where RꢀEt (1) [3], Me (2) and isoPr (3) [5] can be
prepared from the reaction in refluxing benzene of
[B9H13(SMe2)] with the primary amines NH2Et,
NH2Me and NHi2soPr, respectively. The reaction pro-
ceeds stepwise. First, the SMe2 ligand is replaced by
amine to give [B9H13(NH2R)] (Eq. (1)), and then reac-
tion of additional amine with the [B9H13(NH2R)] af-
fords the {B8H11} cluster product by amine addition
and elimination of one boron vertex (Eq. (2)). The
resulting azaboranes can then be purified in reasonable
overall yields by recrystallization from ethanol–water.
B9H13(SMe2)+NH2R“B9H13(NH2R)+SMe2
B9H13(NH2R)+2NH2R
(1)
(EtH2N)B8H11NHEt+2NaH+2MeI
“(RH2N)B8H11NHR+BH3(NH2R)
(2)
1
“(EtMe2N)B8H11NHEt+2H2+2NaI
(4)
Under the same conditions no reaction was found
with secondary amines. However, we have now found
that use of a large, eightfold, excess of NHEt2 with
[B9H13(SMe2)] at a higher temperature, viz. +100°C in
toluene for 24 h can give the secondary amine ana-
logue. [(Et2HN)B8H11NEt2] ((4), 14% yield). Use of
other secondary amines, however, has so far exclusively
yielded only the amine-nonaborane species as in (Eq.
(1)).
6
(EtNH2)B8H11NHEt+3NaH+3MeI
1
“(EtMe2N)B8H11NMeEt+3H2+3NaI
(5)
7
2.1.3. Substitution of the exo-NH2R moiety by another
ligand
We have found that the exchange of the exo amine
ligand by another amine is an equally convenient route

U. Do¨rfler et al. / Journal of Organometallic Chemistry 614–615 (2000) 215–222
217
to new N-substituted derivatives of the hypho-
(amine)(amino)B8H11 system. For example, compound
(1) reacts with NHEt2 in refluxing benzene over 3 h to
give [(Et2HN)B8H11NHEt] (8) in 31% yield (Eq. (6)).
Under the same reaction conditions, the use of
[(MeH2N)B8H11NHMe] (2) in place of compound (1)
leads to the formation of [(Et2HN)B8H11NHMe] (9) in
the higher yield of 61%. The exo-NH2Me group there-
fore appears to be a better leaving group than NH2Et,
easily identified by NMR spectroscopy, as their 11B
NMR spectra present a characteristic shielding pattern
over the quite large range of ca. −55 to +5 ppm,
showing only minor differences in their overall 11B
cluster shielding patterns. A change of the ligands to a
secondary amine residue, or to pyridine or to a phos-
phine, however, shows significant substituent effects at
the substituted B(3) and bridged B(5) and B(6) sites,
although the shieldings at other sites remain largely
very similar to the primary amine models. Thus, when
the H atoms of the exo-NH2R group in compound (1)
are successively replaced by methyl groups, l(11B) for
B(3) is shifted progressively to lower shielding, from
−20.0 ppm in (1) to −15.5 ppm in (5) and thence to
−11.3 ppm in (6). Likewise, in compounds (4) and (7)
the resonances of the boron atoms B(5) and B(6) are
shifted by ca. 7 ppm to low field relative to (1) when the
hydrogen atom of the {NHR} bridge is substituted by
an alkyl group. Interestingly in this context, replace-
ment of the exo-amine ligand by pyridine, in compound
(10), has an effect on the B(3) chemical shift similar to
a secondary aliphatic amine: this atom gives a signal at
−15.4 ppm, comparable to that in compounds (4), (5),
(8) and (9). The phosphine substituents at B(3) in (11)
and (12) cause a shift to high-field of ca. 18 ppm, which
is within the range of established substituent effects for
although in this case
a
significant amount of
[H3B(NHMe2)] (identified by NMR spectroscopy) was
also isolated. When compound (1) was treated under
the same conditions with the tertiary amines Et3N and
NPh3, no exchange reaction was observed. Only unre-
acted starting compound (1) was recovered, even after
prolonged heating. Presumably steric effects hinder the
substitution of the NH2Et unit by these more bulky
amines.
(EtH2N)B8H11NHEt+NHEt2
1
“(Et2NH)B8H11NHEt+NH2Et
(6)
8
Other bases, such as pyridines and phosphines, simi-
larly react with compound (1). Thus pyridine replaces
the exo-NH2Et unit to give [(C5H5N)B8H11NHEt] (10,
61% yield), and PPh3 analogously gives the phosphine-
substituted species [(Ph3P)B8H11NHEt] (11, 40% yield).
It is not certain whether this last exchange happens
because the trivalent phosphine is kinetically a better
nucleophile than the amine, or whether it is more basic
to this particular boron site than the amines, even
though phosphines are more generally regarded as be-
ing less basic, for example in protic systems. In a direct
comparison with NPh3, which does not react, the small
nitrogen atom radius will increase the steric demands of
NPh3 compared to PPh3, and, in addition, the nitrogen
lone pair will be more significantly delocalized into the
aromatic rings. In attempts to generate metallated
derivatives of compound (1), we have found that phos-
phine-containing metal halide complexes can function
as another source of phosphine. Thus, in the reactions
of both [RhCl(PPh3)3] and [PtCl2(PMe2Ph)2] with (1),
exchange of the exo-ligand occurs, and, respectively,
[(Ph3P)B8H11NHEt] (11) and [(PhMe2P)B8H11NHEt]
(12) can be isolated in good yields. The formation of
1
phosphine-for-amine substitution [20]. In the H NMR
spectra, the N-bound H atoms of the exo-NH2R group
diagnostically resonate at ca. +4.0 ppm and those of
the bridging {NHR} group at ca. −1.4 ppm. Some
small deviations in these positions are observed in
compounds 4–12, as expected (Fig. 2).
2.3. Structural study of compound (4)
A single crystal of compound (4) was analysed by
X-ray diffraction analysis in order to establish whether
the cluster structure suffers any gross structural effects
as a result of the presence of the additional ethyl
groups. In particular, we were interested in any struc-
tural consequences from the introduction of the more
sterically demanding ethyl substituent endo on the
bridging nitrogen atom. An endo ethyl group might
disruptively impinge upon the cluster face, which, with
its concave nature and five bridging and endo hydrogen
atoms, could be regarded as crowded [5]. The molecular
structure derived from this study (Fig. 1) thence confi-
rms that 4 is architecturally a direct analogue of com-
pounds (1) and (3), for which crystallographically
determined structures have been previously reported
[4,5]. Selected geometric parameters for (4) are pre-
sented in Table 2, along with those of (1) and (3) for
comparison. Interboron distances in all three species
are essentially identical within experimental error, and
the additional N-bound ethyl groups, both exo, and,
more particularly, endo, do not therefore significantly
the
latter
contrasts
to
the
formation
of
[(PMe2Ph)2PtB7H10(NHEt)] from the same reagents in
the presence of NaH in CH2Cl2 solution 2(c).
2.2. NMR spectroscopic results
NMR data for compound (2), and for compounds
4–12, are given in Table 1. Assignments are readily
made by comparison with data reported previously, for
example for compounds (1) [19] and (3) [5]. The ‘primary
amine’ azaboranes of the type [(RH2N)B8H11NHR] are

218
U. Do¨rfler et al. / Journal of Organometallic Chemistry 614–615 (2000) 215–222
Table 1
Selected NMR parameters a for [(MeH2N)B8H11NHMe] (2), [(Et2HN)B8H11NEt2] (4), [(EtMeHN)B8H11NHEt] (5), [(EtMe2N)B8H11NHEt] (6),
[(EtMe2N)B8H11NMeEt] (7), [(Et2HN)B8H11NHEt] (8) [(Et2HN)B8H11NHMe] (9), [(C5H5N)B8H11NHEt] (10), [(Ph3P)B8H11NHEt] (11), and
[(PhMe2P)B8H11NHEt] (12)
B1
B2
B3
B4
B5,6
B7
B8
mH(4,5)
mH(6,7)
NH
NH2
l(11B)
l(11B)
l(11B)
l(11B)
l(11B)
l(11B)
l(11B)
[l(1H)]
[l(1H)]
[l(1H)]
[l(1H)]
[l(1H)]
[l(1H)]
[l(1H)]
[l(1H)]
[l(1H)]
2
−1.2
[+2.60]
−55.4
[−0.80]
−19.6
[+1.15]
−33.2
[+0.65]
−11.3/−10.4
[+2.42]
[+2.30]
−3.6
[+2.71]
[+2.80]
−10.6
[+2.46]
[+2.39]
−11.3
−34.4
[+0.65]
−31.4
b
[+0.65]
[−0.48]
−29.5
[+0.59]
[+0.55]
−31.2
[−2.02]
[−2.26]
[−0.80] c
[+5.57]
4
+5.5
[+2.95]
−55.7
[−0.49]
−15.7
−29.5
[+0.79]
−29.5
[+0.77]
[+1.63] d
[−2.62]
e
[–2.87]
[+1.38]
5
+1.7
[+2.62]
−54.8
[−0.64]
−15.5
−32.7
[+0.71]
−34.0
[+0.73]
[–0.68]
−34.2
[+1.21] f
[+0.57]
[−1.96]
[–2.19]
[−1.40] g
[+3.50]
6
−0.4
[+2.95]
−55.0
[−0.62]
−11.3
−32.9
[+0.69]
−31.4
[+1.01] h
[+2.42]
[+0.69]
[+0.52]
[−0.43]
–29.8
[+0.75]
[+0.59]
−31.3
[+0.54]
[−0.66]
−31.3
[+0.55]
[−0.67]
−29.2
[−1.98]
[−2.17]
[−1.40] i
7
+2.9
[+3.25]
–56.1
[−0.52]
–11.2
–29.8
[+0.75]
–3.5
–29.8
[+0.75]
[+1.73] j)
[+2.83]
[+2.81]
−10.8
[+2.45]
[+2.39]
−10.1
[+2.43]
[+2.36]
−11.2
[+2.43]
[+2.51]
−5.8/−10.3
[+2.62]
[+0.50]
−6.0/−10.6
[+2.62]
[+0.27]
[−2.57]
k
[–2.74]
8
+1.4
[+2.59]
−55.0
[−0.66]
−16.7
−32.8
[+0.69]
−34.1
[+0.69]
[+1.26] l
[−1.97]
[−2.18]
[−1.40] m
[+3.52]
9
+1.4
[+2.59]
−55.0
[−0.67]
−16.6
−32.9
[+0.69]
−34.4
[+0.69]
[+1.27] n
[−1.94]
[−2.12]
[−1.30] o
[+3.55]
10
11
12
+2.0
[+2.94]
−54.7
[−0.52]
−15.4
−29.2
[+0.92]
−32.3
[+0.92]
[+2.12] p
[+0.77]
[−0.24]
−27.7
[−1.72]
[−1.72]
[−1.15] q
[−0.73] s
[−0.96] u
+2.2
[+2.49]
−54.3
[−0.71]
−37.9
−27.7
[+1.11]
−27.7
[−0.23] r
[+2.52]
−38.7
[+0.80]
[−1.70]
−28.6
[+0.74]
[−1.87]
[+1.11]
[−1.60]
[−1.67]
+1.4
[+2.62]
−54.6
[−0.63]
−28.7
[+1.08]
−28.6
[+1.16]
[−0.21] t
[+2.40]
a In CDCl3 at +20°C.
b exo N-group: [d(1H)](CH3) +2.63.
c Bridging N-group: [d(1H)](CH3) +2.39.
d exo N-group: [d(1H)](CH3CH2) +3.35 and +3.10; [d(1H)](CH3CH2) +1.40 and +1.31.
e Bridging N-group: [d(1H)](CH3CH2) +2.70 and +1.40; [d(1H)](CH3CH2) +1.08 and +0.79.
f exo N-group: [d(1H)](CH3CH2) +2.99; [d(1H)](CH3CH2) +1.34; [d(1H)](CH3) +2.83.
g Bridging N-group: [d(1H)](CH3CH2) +2.62; [d(1H)](CH3CH2) +1.05.
h exo N-group: [d(1H)](CH3CH2) +3.21; [d(1H)](CH3CH2) +1.37; [d(1H)](CH3) +2.78 and +2.75.
i Bridging N-group: [d(1H)](CH3CH2) +2.66; [d(1H)](CH3CH2) +1.06.
j exo N-group: [d(1H)](CH3CH2) +3.21; [d(1H)](CH3CH2) +1.35; [d(1H)](CH3) +2.77 and +2.73.
k Bridging N-group: [d(1H)](CH3CH2) +2.68; [d(1H)](CH3CH2) +1.16; [d(1H)](CH3) +1.49.
l exo N-group: [d(1H)](CH3CH2) +3.32 and +3.17; [d(1H)](CH3CH2) +1.37 and +1.33.
m Bridging N-group: [d(1H)](CH3CH2) +2.61; [d(1H)](CH3CH2) +1.06.
n exo N-group: [d(1H)](CH3CH2) +3.35 and +3.15; [d(1H)](CH3CH2) +1.35 and +1.32.
o Bridging N-group: [d(1H)](CH3) +2.41.
p Pyridine substituent site: [d(1H)](NCHCHCH) +8.00; [d(1H)](NCHCHCH) +7.54; [d(1H)](NCHCHCH) +8.94.
q Bridging N-group: [d(1H)](CH3CH2) +2.73; [d(1H)](CH3CH2) +1.10.
r 1J(31P-11B) ca. 110 Hz,{Ph3P} substituent site: [d(1H)](Ph) +7.20 to +7.80.
s Bridging N-group: [d(1H)](CH3CH2) +2.71; [d(1H)](CH3CH2) +1.27.
t 1J(31P-11B) ca. 125 Hz, {PMe2 Ph} substituent site: [d(1H)](CH3) +1.72 and +1.68, 2J(31Pꢁ1H) ca. 10 Hz, [d(1H)](Ph) +7.18 to +7.84;
d(31P)=+2.0.
u Bridging N-group: [d(1H)](CH3CH2) +2.68; [d(1H)](CH3CH2) +1.07.

U. Do¨rfler et al. / Journal of Organometallic Chemistry 614–615 (2000) 215–222
219
effects are observed for the B(8)ꢁB(7)ꢁB(6) and
B(3)ꢁB(4)ꢁB(5) angles, which could be associated with
steric factors due to the additional ethyl groups on the
nitrogen atoms in compound (4).
perturb the gross structure. There are, however, small
but significant enlargements of the N(5,6)ꢁB(6)ꢁB(7)
and N(5,6)ꢁB(5)ꢁB(4) angles, of 5.93 and 8.00°, respec-
tively, at the bridging NEt2 site of compound (4) rela-
tive to the corresponding parameters in (3), and similar
3. Experimental
Reactions were carried out in dry solvents under dry
nitrogen but subsequent manipulatory and separatory
procedures were carried out in air. Preparative thin-
layer chromatography (TLC) was carried out using 0.75
mm layers of silica gel G (Merck, GF254) made from
water slurries on glass plates of dimensions 20×20
cm2, followed by drying in air at 100°C. [B9H13(SMe2)]
[3], [(EtH2N)B8H11NHEt] (1) [3], [(isoPrH2N)B8H11-
NHisoPr] (3) [5], [RhCl(PPh3)3] [21] and [PtCl2(PMe2-
Ph)2] [22] were prepared by literature methods and all
other reagents were obtained commercially. NMR spec-
troscopy was carried out on Bruker DPX200, AC250
and AM400 instruments operating at ca. 4.7, 5.9 and
9.4 T. Chemical shifts l are given in ppm relative to
]=100 MHz for l(1H) (nominally SiMe4), and ]=
32.083 972 MHz for l(11B) (nominally [F3BOEt2] in
CDCl3). ] is as defined in Ref. [23]. The mass spectra
were recorded on a Finnigan MAT 8200 spectrometer.
Fig. 2. An ORTEP [27] drawing of the crystallographically determined
molecular structure of [(Et2HN)B8H11NEt2] (4) with thermal ellip-
soids shown at the 50% probability. In the interest of clarity hydrogen
atoms are drawn as circles with an arbitrary small radius.
3.1. Synthesis of [(MeH2N)B8H11NHMe] (2)
Table 2
A solution of [B9H13(SMe2)] (1.20 g; 6.97 mmol) in
dry THF (40 ml) was heated to reflux with a fourfold
excess of NH2Me (28 mmol) for 3 h, after which time
the reaction mixture was cooled, and the resulting
crystalline precipitate filtered off. Recrystallization
from ethanol–water (1:1, ca. 10 ml) yielded pure azabo-
rane (2) (521 mg, 3.29 mmol, 48%) as white crystalline
solid; MS (FAB+) for compound (2): m/z=158 [M+,
25%].
,
Selected interatomic distances (A) and angles (°) for
[(EtH2N)B8H11NHEt]
(1);
data
from
reference
[4],
[(isoPrH2N)B8H11NHisoPr] (3); data from reference [5] and
[(Et2HN)B8H11NEt2] (4); this work
1
3
4
Bond interatomic distances
B(1)ꢁB(2)
B(1)ꢁB(3)
B(1)ꢁB(4)
B(1)ꢁB(7)
B(1)ꢁB(8)
B(2)ꢁB(4)
B(2)ꢁB(5)
B(2)ꢁB(6)
B(2)ꢁB(7)
B(3)ꢁB(4)
B(3)ꢁB(8)
B(4)ꢁB(5)
B(5)ꢁB(6)
B(6)ꢁB(7)
B(7)ꢁB(8)
B(3)ꢁN(3)
B(5)ꢁN(5,6)
B(6)ꢁN(5,6)
1.826(9)
1.819(2)
1.707(2)
1.762(2)
1.743(2)
1.718(2)
1.800(2)
1.767(2)
1.771(2)
1.803(2)
1.896(2)
1.927(2)
1.819(2)
1.963(2)
1.815(2)
1.926(2)
1.590(2)
1.557(2)
1.560(2)
1.807(3)
1.701(3)
1.762(2)
1.737(3)
1.727(3)
1.799(3)
1.764(3)
1.777(3)
1.798(3)
1.876(2)
1.923(3)
1.819(3)
1.987(3)
1.822(3)
1.919(3)
1.600(2)
1.571(2)
1.573(2)
1.709(10)
1.769(8)
1.741(8)
1.726(9)
1.812(9)
1.810(10)
1.793(7)
1.791(9)
1.919(9)
1.918(9)
1.841(9)
1.989(9)
1.825(8)
1.902(9)
1.578(7)
1.573(9)
1.572(9)
3.2. Synthesis of [(Et2HN)B8H11NEt2] (4)
[B9H13(SMe2)] (100 mg, 0.58 mmol) was dissolved in
toluene (10 ml), NHEt2 (0.5 ml, 4.80 mmol) added, and
the solution was refluxed for 24 h. The more volatile
components were removed in vacuo, the solid residue
was redissolved in CH2Cl2 and the products were sepa-
rated and purified by repeated preparative TLC, devel-
opment with CH2Cl2 giving two products. These were
[(Et2NH)B8H11NEt2] (4) (20 mg, 0.083 mmol, 14%, RF
0.8) and [B9H13(NHEt2)] (88 mg, 0.48 mmol, 82%, RF
0.9); MS (EI, 70 eV, 200°C) for compound (4): m/z=
242 [M+, 15%], 72 [Et2N+, 18%].
Bond angles
N(5,6)ꢁB(6)ꢁB(7)
N(5,6)ꢁB(5)ꢁB(4)
B(8)ꢁB(7)ꢁB(6)
B(3)ꢁB(4)ꢁB(5)
118.86(10)
119.67(10)
116.64(11)
116.62(10)
126.86(27)
125.60(26)
124.76(27)
124.93(12)
3.3. Synthesis of [(EtMeHN)B8H11NHEt] (5)
A solution of compound (1) (60 mg, 0.32 mmol) in
THF (5 ml), was cooled to −78°C and then NaH (12

220
U. Do¨rfler et al. / Journal of Organometallic Chemistry 614–615 (2000) 215–222
mg, 0.5 mmol) was added. The solution was stirred for
30 min at r.t., cooled to −78°C, and then MeI (72 mg,
0.55 mmol) was added. After stirring a further 1 h the
more volatile components were removed in vacuo, the
solid residue redissolved in CH2Cl2 and the products
separated and purified by repeated preparative TLC.
Development with hexane–CH2Cl2 (3:7) gave [(Et-
MeHN)B8H11NHEt] (5) (24 mg, 0.12 mmol, 37%, RF:
0.7) and [(EtH2N)B8H11NHEt] (1) (25 mg, 0.134 mmol,
42%, RF 0.4); MS (EI, 70 eV, 200°C) for compound (5):
m/z=200 [M+, 12%].
3.7. Synthesis of [(Et2HN)B8H11NHMe] (9)
A sample of compound (1) (50 mg, 0.31 mmol) was
dissolved in benzene (10 ml), and NHEt2 (65 ml, 0.62
mmol) was added. After 3 h at reflux temperature the
more volatile components were removed in vacuo, the
solid residue redissolved in CH2Cl2 and the products
separated and purified by repeated preparative TLC.
Development in CH2Cl2 gave [(Et2HN)B8H11NHMe]
(9) (38 mg, 0.19 mmol, 61%, RF 0.53) and
[BH3(NHEt2)] (5 mg, 0.006 mmol, 19%, RF 0.49); MS
(EI, 70 eV, 200°C) for compound (9): m/z=200 [M+,
34%].
3.4. Synthesis of (EtMe2N)B8H11NHEt] (6)
NaH (20 mg, 0.83 mmol) was added to a solution of
compound 1 (60 mg, 0.32 mmol) in THF (5 ml) at r.t.
The mixture was stirred for 30 min, and then MeI (119
mg, 0.83 mmol) was added. After stirring for 1 h the
more volatile components were removed in vacuo, the
solid residue redissolved in CH2Cl2 and the products
separated and purified by repeated preparative TLC.
3.8. Synthesis of [(C5H5N)B8H11NHEt] (10)
Pyridine (22 ml, 0.268 mmol) was added to a solution
of compound (1) (25 mg, 0.134 mmol) in benzene (10
ml), and the solution was then heated at reflux for 3 h.
The more volatile components were removed in vacuo,
the solid residue redissolved in CH2Cl2 and the prod-
ucts separated and purified by repeated preparative
TLC. Development in CH2Cl2 gave [(C5H5N)B8H11-
NHMe] (10) (38 mg, 0.08 mmol, 61%, RF 0.74) and
[BH3(NC5H5)] (2 mg, 0.02 mmol, 16%, RF 0.57); MS
(EI, 70 eV, 200°C) for compound (10): m/z=221
[M+, 22%], 217 [M+−3H, 30%].
Development
in
hexane–CH2Cl2
(3:7)
gave
[(EtMe2N)B8H11NHEt] (6) (31 mg, 0.144 mmol, 45%,
RF 0.82) and [(EtH2N)B8H11NHEt] (1) (13 mg, 0.7
mmol, 22%, RF 0.4); MS (EI, 70 eV, 200°C) for com-
pound (6): m/z=214 [M+, 20%], 73 [NEtMe+2 , 45%].
3.5. Synthesis of (EtMe2N)B8H11NMeEt] (7)
A sample of compound (1) (40 mg, 0.22 mmol) was
dissolved in THF (5 ml), and NaH (18 mg, 0.75 mmol)
was added. The solution was stirred for 30 min at r.t.,
and MeI (107 mg, 0.75 mmol) was added. After stir-
rings for a further 2 h, the more volatile components
were removed in vacuo, the solid residue redissolved in
CH2Cl2, and the products separated and purified by
repeated preparative TLC. Development in hexane–
CH2Cl2 (3:7) gave [(EtMe2N)B8H11NMeEt] (7) (28 mg,
0.12 mmol, 57%, RF 0.9) and [(EtH2N)B8H11NHEt] (1)
(4 mg, 0.18 mmol, 9%, RF 0.4); MS (EI, 70 eV, 200°C)
for compound (7): m/z=228 [M+, 11%].
3.9. Synthesis of [(Ph3P)B8H11NHEt] (11)
Route (a): PPh3 (140 mg, 0.53 mmol) was added to a
solution of [(EtH2N)B8H11NHEt] (1) (100 mg, 0.53
mmol) in toluene (10 ml). The solution was then heated
at reflux for 14 h. Examination of the product mixture
by integrated NMR spectroscopy revealed a ca. 40:60
mol% mixture of [(Ph3P)B8H11NHEt] (11) and
[(EtH2N)B8H11NHEt] (1). Route (b): [RhCl(PPh3)3]
(100 mg, 0.25 mmol) was added to a solution of com-
pound (1) (20 mg, 0.108 mmol) in toluene (10 ml), and
the mixture then was heated at reflux for 2 h. The more
volatile components were removed in vacuo, the solid
residue redissolved in CH2Cl2 and the products sepa-
rated and purified by repeated preparative TLC. Devel-
3.6. Synthesis of (Et2HN)B8H11NHEt] (8)
NHEt2 (56 ml, 0.54 mmol) was added to a solution of
compound (1) (50 mg, 0.27 mmol) in benzene (10 ml).
After heating at reflux for 8 h, the more volatile compo-
nents were removed in vacuo, the solid residue redis-
solved in CH2Cl2 and the products separated and
purified by repeated preparative TLC. Development
with CH2Cl2 gave [(Et2HN)B8H11NHEt] (8) (18 mg,
0.084 mmol, 31%, RF 0.50) and [(EtH2N)B8H11NHEt]
(1) (26 mg, 0.14 mmol, 52%, RF 0.3); MS (EI, 70 eV,
200°C) for compound (8): m/z=214 [M+, 28%], 199
[M+−Me, 5%].
opment
with
hexane–CH2Cl2
(3:7)
gave
[(Ph3P)B8H11NHEt] (11) (26 mg, 0.064 mmol, 60%, RF
0.55); MS (EI, 70 eV, 200°C) for compound (11):
m/z=392 [M+, 11%], 262 [PPh+3 , 22%].
3.10. Synthesis of [(PhMe2P)B8H11NHEt] (12)
[PtCl2(PMe2Ph)2] (30 mg, 0.05 mmol) was added to a
solution of compound 1 (10 mg, 0.053 mmol) in toluene
(10 ml) and the solution then was heated at reflux for 2

U. Do¨rfler et al. / Journal of Organometallic Chemistry 614–615 (2000) 215–222
221
Table 3
and SAINT software packages [24] were used for data
collection and data integration. Analysis of the inte-
grated data did not show any decay. Final cell con-
stants were determined by a global refinement of xyz
centroids of 8192 reflections (qB27.5°). Collected data
were corrected for systematic errors using SADABS
[25] based upon the Laue symmetry using equivalent
reflections. Crystal data, and data-collection and refine-
ment parameters, are listed in Table 3. Structure solu-
tion and refinement were carried out using the
Crystal data and details of refinement of [(Et2HN)B8H11NEt2] (4)
Empirical formula
Formula weight
Colour
Temperature (K)
Crystal system
Space group
C8H32B8N2
242.84
Colourless
223(2)
Triclinic
(
P1
Unit cell dimensions
,
a (A)
9.26470(10)
9.89090(10)
,
b (A)
,
c (A)
10.76610(10)
111.1930(10)
93.3870(10)
126.7710(10)
805.73(27)
SHELXTL
-
PLUS software package [26]. The structure was
h (°)
i (°)
k (°)
solved by direct methodsand refined successfully in the
(
space group P1. Full-matrix least-squares refinement
was carried out by minimising S w(F2o−Fc2)2. The non-
hydrogen atoms were refined anisotropically to conver-
gence. All cage and N-bound hydrogen atoms were
located from the difference Fourier synthesis and were
refined freely. The remaining hydrogen atoms were
treated using the appropriate riding model (AFIX m3).
3
,
V (A )
Z
2
Dcalc(M gm−3
)
1.001
0.051
v (mm−1
)
Crystal size (mm)
qmin, qmax (°)
Index ranges
0.20×0.20×0.40
2.09, 27.00
−125h512, −265k512,
05l527
Reflections collected
Independent reflections
Refinement method
17 127
3518 [Rint=0.05]
Full-matrix least-squares
on F2
4. Supplementary material
Complete listings of the atomic coordinates, geomet-
rical parameters and anisotropic displacement coeffi-
cients for non-hydrogen atoms, together with positional
and isotropic displacement coefficients for hydrogen
atoms, are deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC no. 146817. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: de-
posit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk). Tables of observed and calculated structure
factors are available in electronic format.
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices (observed data)
R indices (all data)
3497/0/211
1.055
R1=0.055, wR2=0.2628
R1=0.0828, wR2=0.1529
+0.217, −0.246
Largest difference map peak and
−3
,
hole (e A
)
h. The more volatile components were removed in
vacuo, the solid residue redissolved in CH2Cl2, and the
products separated and purified by repeated preparative
TLC. Development in hexane–CH2Cl2 (3:7) gave
[(PhMe2P)B8H11NHEt] (12) (10 mg, 0.035 mmol, 68%,
RF 0.6); MS (EI, 70 eV, 200°C) for compound (12):
m/z=279 [M+, 17%], 138 [PhPMe+2 , 26%].
Acknowledgements
3.11. Crystal structure determination of
[(Et2HN)B8H11NEt2] (4)
We thank the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie, the UK EPSRC for
support, and NSF Grant no. CHE-9309690 for funds
to purchase the X-ray diffractometer.
A crystal of appropriate dimension was mounted on
a glass fibre in a random orientation. Preliminary ex-
amination and data collection were performed using a
Siemens SMART CCD-Detector X-Ray diffractometer
and graphite-monochromated Mo–Ka radiation (u=
References
,
[1] U. Do¨rfler, J.D. Kennedy, D. Ormsby, R. Greatrex, Inorg.
Chim. Acta 304 (2000) 268.
0.71073 A). Preliminary unit-cell constants were deter-
mined with a set of 45 narrow-frame scans (0.3° in ‚).
A typical data set collected consisted of 4028 frames of
intensity data, collected with a frame width of 0.3° in ‚
and a counting time of 15 s per frame, at a crystal-to-
detector distance of 4.930 cm. The double-pass method
of scanning was used to exclude any noise. The col-
lected frames were integrated using an orientation ma-
trix determined from the narrow-frame scans. SMART
[2] (a) U. Doerfler, J.D. Kennedy, L. Barton, C.M. Collins. N.P.
Rath, J. Chem. Soc. Dalton Trans. (1997) 707. (b) U. Do¨rfler,
N.P. Rath, M Thornton-Pett, L. Barton, J.D. Kennedy, to be
submitted. (c) U. Do¨rfler, P.A. Salter, X.L.R. Fontaine, N.N.
Greenwood, J.D. Kennedy, M. Thornton-Pett, Collect. Czech.
Chem. Commun. 64 (1999) 947. (d) U. Do¨rfler, N.P. Rath, L.
Barton, J.D. Kennedy, to be submitted.
[3] B.M. Graybill, A.R. Pitochelli, M.F. Hawthorne, Inorg. Chem. 1
(1962) 626.

222
U. Do¨rfler et al. / Journal of Organometallic Chemistry 614–615 (2000) 215–222
Siebert (Ed.), Advances in Boron Chemistry, Royal Society of
Chemistry, Cambridge, UK, 1997, p. 399.
[4] R. Lewin, P.G. Simpson, W.N. Lipscomb, J. Chem. Phys. 39
(1963) 1532.
[16] A.V. Fratini, G.W. Sullivan, M.L. Denniston, R.K. Hertz, S.G.
Shore, J. Am. Chem. Soc. 96 (1974) 3013.
[17] R.J. Remmel, H.D. Johnson, II, S. Jaworiwsky, S.G. Shore, J.
Am. Chem. Soc. 97 (1975) 5395.
[18] M. Mangion, R.K. Hertz, M.L. Denniston, J.R. Long, W.R.
Clayton, S.G. Shore, J. Am. Chem. Soc. 98 (1976) 449.
[19] X.L.R. Fontaine, P. MacKinnon, J.D. Kennedy, P.A. Salter,
Collect. Czech. Chem. Commun. 61 (1996) 1773.
[20] (a) U. Do¨rfler, T.D. McGrath, P.A. Cooke, J.D. Kennedy, M.
Thornton-Pett, J. Chem. Soc. Dalton Trans. (1997) 4739. (b)
J.A. Albanese, D.E. Gingrich, C.D. Schaefer, Jr., J. Organomet.
Chem. 365 (1989) 23.
[5] U. Do¨rfler, M. Thornton-Pett, J.D. Kennedy, J. Chem. Soc.
Dalton Trans. (1997) 2547.
[6] K. Basˇe, J. Plesˇek,, S. Herma´nek, J. Huffman, P. Ragatz, R.
Schaeffer, J. Chem. Soc. Chem. Commun. (1975) 934.
&
[7] K. Basˇe, F. Hanousek, J. Plesˇek, B. St´ıbr, A. Lycka,. J. Chem.
Soc. Chem. Commun. (1981) 1162.
[8] K. Basˇe, Collect. Czech. Chem. Commun. 48 (1983) 2593.
&
[9] T. Jel´ınek, B. St´ıbr, J.D. Kennedy, Collect. Czech. Chem. Com-
mun. 59 (1994) 2244.
[10] M. Roth, P. Paetzold, Chem. Ber. 128 (1995) 1221.
&
[11] B. St´ıbr, J.D. Kennedy, T. Jel´ınek, J. Chem. Soc. Chem. Com-
[21] J.A. Osborn, G. Wikinson, Inorg. Synth. 28 (1990) 77.
[22] J.M. Jenkins, B.L. Shaw, J. Chem. Soc. Sect. A (1966) 770.
[23] W. McFarlane, Proc. R. Soc. Lond. Ser. A 39 (1968) 185.
[24] Siemens Analytical X-Ray, Madison, WI 1996.
[25] R.H. Blessing, Acta Crystallogr. Sect. A 51 (1995) 33.
[26] G.M. Sheldrick, Bruker Analytical X-Ray Division, Madison,
WI, (1998).
mun. (1990) 1309.
[12] J. Holub, T. Jel´ınek, J. Plesˇek, B. St´ıbr, S. Hermanek, J.D.
Kennedy, J. Chem. Soc. Chem. Commun. (1991) 1389.
[13] T. Jel´ınek, J.D. Kennedy, B. St´ıbr, J. Chem. Soc. Chem. Com-
mun. (1993) 1628.
[14] P. Paetzold, Pure Appl. Chem. 63 (1991) 345.
[15] W. Dirk, E. Leuschner, P. Lomme, P. Paetzold, M. Roth, in: W.
&
&
[27] P. McArdle, J. Appl. Crystallogr. 28 (1995) 65.
.