Polyhedral monocarbaborane chemistry: Reactions of the [6-Ph-nido-6-CB 9H11]- anion with two-electron donors to yield a series of neutral arachno and closo ten-vertex monocarbaborane derivatives

Article abstract of DOI:10.1016/j.jorganchem.2005.02.038

Reaction of the ten-vertex [6-Ph-nido-6-CB₉H₁₁] ^- anion (1) with two-electron donor ligands L, where L is SMe ₂, NH₂Ph, NC₅H₅, NC ₅H₄-para-CH₂Ph, NC₅H ₄-para-Ph or NC₉H₇ (where NC₉H ₇ is quinoline) in the presence of {FeCl₃(OH ₂)₆} gives the six neutral arachno ten-vertex monocarbaboranes [6-Ph-9-L-arachno-6-CB₉H₁₂], compounds 2, 3, 4, 7, 9 and 11, respectively, isolatable in yields of up to 63%. On prolonged treatment with {FeCl₃(OH₂)₆} oxidative cluster closure of the four compounds 4, 7, 9 and 11 that have pyridine-type ligands gives the neutral closo ten-vertex monocarbaboranes [1-Ph-6-L-closo-1-CB₉H₈], compounds 6, 8, 10 and 12, respectively, in yields of 49-92%. All new species 2, 3, 4, 6, 7, 8, 9, 10, 11 and 12 are characterised by single-crystal X-ray diffraction analysis and NMR spectroscopy. [This paper is an annotated exposition of parts of an oral presentation at the Third Pan-European Meeting of Boron Chemists, EUROBORON-3, Pruhonice, The Czech Republic, September 2004, of which the proceedings constitute this volume of Journal of Organometallic Chemistry.]

Full text of DOI:10.1016/j.jorganchem.2005.02.038

Journal of Organometallic Chemistry 690 (2005) 2815–2828
www.elsevier.com/locate/jorganchem
q
Polyhedral monocarbaborane chemistry
Reactions of the [6-Ph-nido-6-CB9H11]ꢀ anion with two-electron
donors to yield a series of neutral arachno and closo ten-vertex
monocarbaborane derivatives
a
Neil J. Bullen , Andreas Franken , Colin A. Kilner , Simon J. Teat ,
a
a
b
a,
William Clegg b,c, John D. Kennedy
*
a
The School of Chemistry of the University of Leeds, Leeds LS2 9JT, UK
CCLRC Daresbury Laboratory, Keckwick Lane, Daresbury, Warrington WA4 4A, UK
b
c
The School of Natural Sciences (Chemistry) of the University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, UK
Received 10 December 2004; accepted 17 February 2005
Available online 14 April 2005
Abstract
Reaction of the ten-vertex [6-Ph-nido-6-CB9H11]ꢀ anion (1) with two-electron donor ligands L, where L is SMe2, NH2Ph, NC5H5,
NC5H4-para-CH2Ph, NC5H4-para-Ph or NC9H7 (where NC9H7 is quinoline) in the presence of {FeCl3(OH2)6} gives the six neutral
arachno ten-vertex monocarbaboranes [6-Ph-9-L-arachno-6-CB9H12], compounds 2, 3, 4, 7, 9 and 11, respectively, isolatable in
yields of up to 63%. On prolonged treatment with {FeCl3(OH2)6} oxidative cluster closure of the four compounds 4, 7, 9 and 11
that have pyridine-type ligands gives the neutral closo ten-vertex monocarbaboranes [1-Ph-6-L-closo-1-CB9H8], compounds 6, 8,
10 and 12, respectively, in yields of 49–92%. All new species 2, 3, 4, 6, 7, 8, 9, 10, 11 and 12 are characterised by single-crystal
X-ray diffraction analysis and NMR spectroscopy. [This paper is an annotated exposition of parts of an oral presentation at the
Third Pan-European Meeting of Boron Chemists, EUROBORON-3, Pruhonice, The Czech Republic, September 2004, of which
the proceedings constitute this volume of Journal of Organometallic Chemistry.]
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Boron-containing cluster compounds; Monocarbaboranes; closo Ten-vertex monocarbaboranes; arachno Ten-vertex monocarbaboranes;
Ligand adducts of moncarbaboranes; Single-crystal X-ray diffraction analysis; Crystal and molecular structure; NMR spectroscopy
1. Introduction
atom in the cluster – is relatively unexplored in compar-
ison to the flanking fields of binary boranes – boron hy-
dride cluster compounds that contain only boron atoms
in the cluster – and dicarbaboranes – boron hydride
cluster compounds that also contain two carbon atoms
in the cluster. In the past this was mainly due to the lack
of convenient syntheses of these compounds. The rela-
tively recent discovery of the Brellochs reaction, between
nido-B10H14 and aldehydes in alkaline solution, for the
generation of {CB9} cluster species, now offers a conve-
nient one-step entry into monocarbaborane chemistry,
with the choice of aldehyde making a variety of
The chemistry of the monocarbaboranes – boron hy-
dride cluster compounds that also contain one carbon
q
This article was freely submitted for publication without royalty.
By acceptance of this paper, the publisher and/or recipient acknowl-
edges the right of the authors to retain non-exclusive, royalty-free
license in and to any copyright covering this paper, along with the right
to reproduce all or part of the copyrighted paper.
*
Corresponding author. Tel.: +44 113 343 6414; fax: +44 113 343
6401.
E-mail address: johnk@chem.leeds.ac.uk (J.D. Kennedy).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.02.038

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N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
C-substituted monocarbaboranes available [1–6]. There
is some ongoing interest in the synthesis of species that
combine carbaborane units with organyl systems to gen-
erate interesting molecular frameworks, for example in
the construction of rod-like units, due in part to their
potential applicability in areas such as nanoarchitectural
construction [7–13] and effect chemistry such as liquid-
crystal behaviour [14,15]. As a contribution to these
areas, we report here on a potentially generic route to
neutral monocarbaborane derivatives that is afforded
by the reaction of the [6-Ph-nido-6-CB9H11]ꢀ anion 1
with two-electron donor species, which we here exem-
plify principally by pyridine-type species. Anion 1 is
the product of the Brellochs reaction between nido-
B10H14 and PhCHO. The commercial availability of
many pyridine derivatives that can be used as two-elec-
tron donors permits the ready synthesis of systematically
related series of compounds. The resulting neutral spe-
cies described, of which the molecules have an extended
bent aspect, complement recently reported monoanionic
and dianionic rod-like species that are also constructed
from combinations of monocarbaborane and organic
units [16].
A previous study of a number of neutral pyridine-
borane compounds, specifically a series with general
formulation [6,9-(NC5H4R)2-arachno-B10H12], made
use of KitaigorodskiiÕs Aufbau Principle (KAP) for
the systematic analysis and visualisation of any similar-
ities or variations among their extended crystal struc-
tures [17,18]. This method of approach to the
delineation of crystal packing allows trends in packing
behaviour and specific lower-energy intermolecular so-
lid state interactions of interest to be identified easily
and systematically. The cumulative effect of such lower-
energy interactions is one of the principal driving forces
behind the supramolecular assembly of larger mole-
cules, an area of currently expanding interest and activ-
ity. One intention behind this present work is that the
generation and crystallographic analysis of systematic
sequences of structurally related smaller compounds
that are suitable for such systematic KAP analyses will
better enable the study and understanding of such
weaker interactions.
6-CB9H12] (4). Note that, for convenience in this text,
we use the formulation {FeCl3(OH2)6} to describe iro-
n(III) chloride hexahydrate, rather than the more exact,
but more cumbersome, solid-state formulation [Fe-
Cl2(OH2)4]Cl(OH2)2; we acknowledge an (inexact) com-
ment from a referee about this. We have been able to
obtain compounds 2 and 3 in yields of 88% and 58%,
respectively, although it has so far only been possible to
obtain the NC5H5 compound 4 in a yield of 14% in a pure
state due to its very ready further reaction under the con-
ditions used (see below). The crystallographically deter-
mined molecular structures are shown in Fig. 1. Each
of the compounds 2, 3 and 4 exhibits the expected ten-
vertex arachno monocarbaborane structural framework,
i.e., that based on the parent binary borane model, the
[arachno-B10H14]2ꢀ dianion, with the phenyl and ligand
groups bound exo to the cluster in the C(6)- and B(9)-
positions, respectively. Characterisation of these com-
1
pounds was further substantiated by 11B and H NMR
spectroscopy. These three arachno compounds 2, 3 and
4 have similar 11B NMR spectra, with six resonances cor-
responding to the chemically inequivalent sets of atoms
B(1,3), B(2), B(4), B(5,7), B(8,10) and B(9). Full assign-
ments for both 11B and 1H NMR spectra are given in Sec-
tion 4.
The crystallographically determined molecular struc-
ture of [6-Ph-9-(NC5H5)-arachno-6-CB9H12] (4) was
found to be 50:50 disordered as a result of pseudo-sym-
metry across the molecular framework. In the crystallo-
graphic solution, the disorder results in an averaging of
the interatomic distances associated with the C(6) and
B(9) positions in the monocarbaborane cluster. These
distances are therefore in this case averaged in the crys-
tallographic solution, even though carbon-to-boron
connectivities in carbaborane cluster compounds are
generally shorter than their corresponding boron-to-
boron connectivities. For comparison, Table 1 tabulates
relevant cluster-connectivity lengths for compounds 2, 3
and 4 and for the closely related series of analogous
substituted monocarbaboranes [6-Ph-9-(NC5H4-para-
CH2Ph)-arachno-6-CB9H12] (7), [6-Ph-9-(NC5H4-para-
Ph)-arachno-6-CB9H12] (9) and [6-Ph-9-(NC9H7)-ara-
chno-6-CB9H12] (11) (where NC9H7 is quinoline).
Compounds 7, 9 and 11 are synthesised and character-
ised as described below. One consequence of the disorder
in the crystal of compound 4 is that the crystallograph-
ically derived molecular structure is very similar to that
of the long-known isostructural species [6,9-(NC5H5)2-
arachno-B10H12] (5) [18,19]. In accord with this molecu-
lar similarity, the overall three-dimensional crystal
structures of compounds 4 and 5 are also very much
alike, and essentially isomorphous, as reflected in very
similar unit-cell dimensions for both species (Table 2).
If the {FeCl3(OH2)6} is present in excess in the reac-
tion with pyridine, an oxidation of the initially formed
2. Results and discussion
The [6-Ph-nido-6-CB9H11]ꢀ anion (1) was prepared
via the Brellochs reaction from nido-B10H14 and benzal-
dehyde according to the literature methods [1,2]. We
now report that, in the presence of iron(III) chloride
hexahydrate – {FeCl3(OH2)6} – anion 1 reacts with
two-electron donor species such as dimethylsulfide,
aniline and pyridine to form compounds such as
[6-Ph-9-(SMe2)-arachno-6-CB9H12] (2), [6-Ph-9-(NH2Ph)-
arachno-6-CB9H12] (3) and [6-Ph-9-(NC5H5)-arachno-
[6-Ph-9-(NC5H5)-arachno-6-CB9H12] species
4
can

N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
2817
Fig. 1. ORTEP diagrams illustrating the crystallographically determined molecular structures of (top) [6-Ph-9-(SMe2)-arachno-6-CB9H12] (2),
(centre) [6-Ph-9-(NH2Ph)-arachno-6-CB9H12] (3) and (bottom) [6-Ph-9-(NC5H5)-arachno-6-CB9H12] (4). Anisotropic displacement parameters are
shown at the 50% probability level. There are two crystallographically independent molecules of [6-Ph-9-(SMe2)-arachno-6-CB9H12] in the
˚
asymmetric unit; but both have similar intramolecular dimensions, therefore only one is shown here. Selected interatomic distances (in A) are as
follows: for 2, B(5)–C(6) 1.771(4), C(6)–B(7) 1.725(4), B(7)–B(8) 1.889(4), B(8)–B(9) 1.870(4), B(9)–B(10) 1.853(4), B(10)–B(5) 1.861(4), C(6)–C(61)
1.508(4) and B(9)–S(91) 1.912(3); for 3, B(5)–C(6) 1.739(2), C(6)–B(7) 1.758(2), B(7)–B(8) 1.873(3), B(8)–B(9) 1.890(3), B(9)–B(10) 1.890(3), B(10)–
B(5) 1.863(3), C(6)–C(61) 1.495(2) and B(9)–N(91) 1.604(2); and for 4, B(5)–C(6) 1.822(4), C(6)–B(7) 1.792(4), B(7)–B(8) 1.876(4), B(8)–B(9) 1.811(4),
B(9)–B(10) 1.805(4), B(10)–B(5) 1.873(4), C(6)–C(61) 1.543(3) and B(9)–N(91) 1.547(3).
occur. Specifically, a four-electron oxidation results in
closure of the monocarbaborane cluster, to yield the
corresponding closo congener [1-Ph-6-(NC5H5)-closo-1-
CB9H8] (6). Overall, the {FeCl3(OH2)6} first facilitates
the binding of the two-electron donor species to the
monocarbaborane cluster to yield the [6-Ph-9-
(NC5H5)-arachno-6-CB9H12] species 4, and thence, when
present in excess, it oxidises this arachno monocarbabo-
rane cluster to the closo congener 6 (Scheme 1).
Stoichiometries as in Eqs. (1) and (2) can be written
for the reaction of anion 1 with pyridine and for the sub-
sequent oxidation of the intermediate arachno species 4
to the final closo product 6. Under conditions that we have
attempted so far, we have not been able to induce cluster

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N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
Table 1
Comparison of connectivity distances for the disordered [6-Ph-9-(NC5H5)-arachno-6-CB9H12] structure (compound 4) with those for related species
[6-Ph-9-L-arachno-6-CB9H12], where L is SMe2 (compound 2), NH2Ph (compound 3), NC5H4-para-CH2Ph (compound 7), NC5H4-para-Ph
(compound 9) and NC9H7 (quinoline, compound 11)
˚
Distance (in A) for [6-Ph-9-L-arachno-6-CB9H12
Connection
]
L = NC5H5 (4)
L = SMe2 (2)
L = NH2Ph (3)
L = NC5H4CH2Ph (7)
L = NC5H4Ph (9)
L = NC9H7 (11)
C,B(6)–B(2)
C,B(9)–B(4)
C,B(6)–B(5)
C,B(9)–B(10)
C,B(6)–B(7)
C,B(9)–B(8)
C,B(6)–C,N(61)
C,B(9)–C,N(91)
1.688(4)
1.685(5)
1.822(4)
1.809(4)
1.795(4)
1.813(4)
1.541(4)
1.545(4)
1.672(4), 1.673(4)
1.737(4), 1.730(4)
1.771(4), 1.732(4)
1.853(4), 1.852(4)
1.725(4), 1.763(4)
1.870(4), 1.886(4)
1.508(4), 1.501(4)
1.912(3)a, 1.909(3)a
1.674(2)
1.721(2)
1.734(2)
1.890(3)
1.758(2)
1.890(3)
1.495(2)
1.604(2)
1.673(3)
1.745(3)
1.759(3)
1.871(3)
1.732(3)
1.874(3)
1.503(2)
1.580(3)
1.667 (2)
1.733(2)
1.740(2)
1.901(2)
1.752(2)
1.867(2)
1.508(2)
1.569(2)
1.672(2)
1.736(2)
1.736(2)
1.890(2)
1.755(2)
1.895(2)
1.504(2)
1.580(2)
Standard uncertainties are given in parentheses.
a
Note: The atoms involved in this instance are B(9) and S(91), therefore the distance is greater.
Table 2
Comparison of unit-cell dimensions for the two isostructural species [6-
Ph-9-(NC5H5)-arachno-6-CB9H12] (compound 4), and [6,9-(NC5H5)2-
arachno-B10H12] (compound 5) [18,19]a
a
Compound 4
Compound 5
Space group
C2/c
8
C2/c
8
Z
a
b
c
15.3090(4)
13.6837(4)
15.7206(5)
100.874(1)
15.1401(5)
13.7539(3)
15.6420(5)
101.582(2)
b
Standard uncertainties are given in parentheses.
a
Note: Compound 5 can also be induced to crystallise with P21/c
morphology [18,19].
closure from arachno to closo for the SMe2 and NH2Ph
species 2 and 3. It is not clear at present why the pyridine
species should undergo closure the more readily.
½6-Ph-nido-6-CB9H11ꢁꢀ þ H2O þ NC5H5
Fig. 2. ORTEP diagram illustrating the crystallographically deter-
mined molecular structure of [1-Ph-6-(NC5H5)-closo-1-CB9H8] (com-
pound 6). Anisotropic displacement parameters are shown at the 50%
! 6-Ph-9-ðNC5H5Þ-arachno-6-CB9H12 þ OHꢀ
ð1Þ
Although the stoichiometry of Eq. (1) does not involve
an iron(III) species, the reaction nevertheless does not
proceed in the absence of the added {FeCl3(OH2)6}. It
is not evident to us what the role of the {FeCl3(OH2)6}
˚
probability level. Selected interatomic distances (in A) are as follows:
C(1)–C(11) 1.4871(16), C(1)–B(2) 1.6105(17), C(1)–B(3) 1.6082(17),
B(2)–B(3) 1.8431(18), B(2)–B(6) 1.7988(18), B(3)–B(6) 1.8047(18) and
B(6)–N(61) 1.5501(16).
H
H
H
N
C
C
H
C
H
H
NC5H5
[FeCl3(OH2)6]
[FeCl3(OH2)6]
N
[6-Ph-nido-6-CB9H11]− anion
[1-Ph-6-NC5H5-closo-1-CB9H8]
[6-Ph-9-NC5H5-arachno-6-CB9H12
]
Scheme 1. Schematic diagram exemplifying the formation of arachno and closo monocarbaborane products from the reaction of the [6-Ph-nido-6-
ꢀ
CB9H11
]
anion (1) with pyridines.

N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
2819
might be, whether perhaps as a Lewis acid catalyst –
which is unlikely as the metal centre will be coordin-
atively unsaturated in its hydrated form, or perhaps as
a generator of mild protic acidity under the quasi-
aqueous conditions, which may assist the reaction in
some way. An interesting quasi-converse of this type
of phenomenon is involved in the reaction of the nido
ten-vertex [PhCB9H11]ꢀ anion (1) to give the closo ten-
vertex [PhCB9H9]ꢀ anion by ostensibly simple dihydro-
gen loss, which we have found proceeds best with the
presence of elemental sodium metal [2], which is odd be-
cause the closure is a formal oxidation, whereas elemen-
tal sodium is a strong reducing agent.
The crystallographically determined molecular struc-
ture of 6 is shown in Fig. 2. It can be seen that the phe-
nyl-substituted carbon atom is at the apical 1-position,
with the pyridine unit bound to the boron atom in the
6-position. As with all new compounds reported in this
paper, this crystallographically determined structure is
1
consistent with the 11B and H NMR spectra recorded
Fig. 3. ORTEP diagrams illustrating the crystallographically determined molecular structures of (top) [6-Ph-9-(NC5H4-para-CH2Ph)-arachno-6-
CB9H12] (compound 7), (centre) [6-Ph-9-(NC5H4-para-Ph)-arachno-6-CB9H12] (compound 9), and (bottom) [6-Ph-9-(NC9H7)-arachno-6-CB9H12
]
˚
(compound 11). Anisotropic displacement parameters are shown at the 50% probability level. Selected interatomic distances (in A) are as follows: for
7, B(5)–C(6) 1.759(3), C(6)–B(7) 1.732(3), B(7)–B(8) 1.867(3), B(8)–B(9) 1.874(3), B(9)–B(10) 1.871(3), B(10)–B(5) 1.870(3), C(6)–C(61) 1.503(2) and
B(9)–N(91) 1.580(3); for 9, B(5)–C(6) 1.7396(19), C(6)–B(7) 1.7523(19), B(7)–B(8) 1.875(2), B(8)–B(9) 1.867(2), B(9)–B(10) 1.901(2), B(10)–B(5)
1.863(2), C(6)–C(61) 1.5077(17) and B(9)–N(91) 1.5685(17); and for 11, B(5)–C(6) 1.7361(18), C(6)–B(7) 1.7554(19), B(7)–B(8) 1.870(2), B(8)–B(9)
1.895(2), B(9)–B(10) 1.890(2), B(10)–B(5) 1.876(2), C(6)–C(61) 1.5036(17) and B(9)–N(91) 1.5789(17).

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N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
for the bulk sample, confirming that the single crystals
selected for the X-ray work were representative. Thus,
this closo ten-vertex monocarbadecaborane [1-Ph-6-
(NC5H5)-closo-1-CB9H8] (6) shows six resonance centres
in its 11B NMR spectrum, arising from the inequivalent
B(2,3), B(4,5), B(6), B(7,9), B(8) and B(10) positions. As
expected, the B(6) resonance for the pyridine-substituted
position appears as a singlet in the 11B NMR spectrum,
whereas the other signals appear as doublets arising
NC9H7 (quinoline, compounds 11 and 12, respectively),
have been prepared in reasonable yields, isolated and
fully characterised. All compounds were synthesised by
the reaction of [NEt4][6-Ph-nido-6-CB9H11], i.e., the
[NEt4]+ salt of anion 1, with the appropriate pyridine
or quinoline derivative in the presence of {FeCl3(OH2)6}
as oxidant. The crystallographically determined molecu-
lar structures are shown in Figs. 3 and 4, and prepara-
tive details are given in Section 4. The arachno
compounds 7, 9 and 11 all have characteristic 11B
NMR spectra very similar to that of the simple parent
(i.e., unsubstituted) pyridine derivative [6-Ph-9-
(NC5H5)-arachno-6-CB9H12] (4) described above. Like-
wise, the closo species 8, 10 and 12 exhibit 11B NMR
spectra analogous to that of [1-Ph-6-(NC5H5)-closo-1-
CB9H8] (6), also described above. Assignments for all
1
from couplings J(11B–1H).
Pyridine-substitution on the lower belt of boron
atoms, i.e., those more distal from the C(1) cluster
carbon centre, is in accord with observations made in
previous studies of substitution reactions of ten-vertex
monocarbaboranes, such as in reactions of the [closo-
1-CB9H10]ꢀ and [1-Ph-closo-1-CB9H9]ꢀ anions. For
example, it has been reported that halogenation of these
two anions occurs also initially at the 6-position
[2,20,21].
1
11B and H NMR spectra are given in Section 4.
The compounds [6-Ph-9-(NC5H4-para-CH2Ph)-ara-
chno-6-CB9H12] (7), [6-Ph-9-(NC5H4-para-Ph)-arachno-
6-CB9H12] (9), [1-Ph-6-(NC5H4-para-CH2Ph)-closo-1-
CB9H8] (8) and [1-Ph-6-(NC5H4)-para-Ph)-closo-1-
CB9H8] (10) can be envisaged as being rod-like in
character, having tip-to-tip van der Waals lengths rang-
6-Ph-9-ðNC5H5Þ-arachno-6-CB9H12 þ 4Fe3þ
! 1-Ph-6-ðNC5H5Þ-closo-6-CB9H8 þ 4Fe2þ þ 2H2
ð2Þ
˚
ing from ca. 14.9 to 17.5 A, and approximate along-the-
˚
molecule lengths ranging from ca. 17.5 to 19.7 A (see
In this reaction of the [6-Ph-nido-6-CB9H11]ꢀ anion (1)
with pyridine, the second step (Eq. (2)) of the overall
reaction occurs very readily, and, under conditions that
we have used so far, proceeds before the first step (Eq.
(1)) is complete. It is only when the concentration of
{FeCl3(OH2)6} is relatively low, e.g., ca. 0.9 mol equiv-
alents relative to 1 mol of the [NEt4]+ salt of anion 1,
that the [6-Ph-9-(NC5H5)-arachno-6-CB9H12] species 4
is observed as a major reaction product, and even then
significant quantities of [1-Ph-6-(NC5H5)-closo-1-
CB9H8] (6) (from step 2) are present. The mixture of
compounds 4 and 6 was not easily separable into its
components by recrystallisation and chromatography,
although ultimately we did manage successfully to
obtain a pure sample of the arachno compound 4 and
characterise it by NMR spectroscopy and a single-crys-
tal X-ray diffraction analysis. The closo species 6 is much
easier to obtain in a pure state because reaction with an
excess of {FeCl3(OH2)6} drives the second step to com-
pletion, and the arachno species 4 is then not present in
the final product mixture. The second step (Eq. (2)) does
not occur so readily with the substituted pyridines that
we have investigated as part of this work, and all the
other closo and arachno monocarbaboranes reported be-
low can thence be isolated more easily as individual ma-
jor reaction products.
Table 3). In contrast to other reported rod-like mono-
carbaborane derivatives, such as those based on the
icosahedral {CB11} cluster [16], the species presented
here have an inherent degree of angularity. In the cases
of the closo compounds this angularity arises from the
mutual ÔmetaÕ-type positionings of the C(1)-phenyl
and B(6)-pyridyl(ene) groupings: the angles between
the C(1)–C(11) and B(6)–N(61) bonding vectors for
all the closo compounds 6, 8, 10, and 12 are given in
Table 4. For the arachno species, the angularity arises
from the non-colinearity of the exo-terminal bonding
vectors at the cluster C(6) and B(9) positions; the
relevant angles between the C(6)–C(61) and B(9)–
N(91) vectors for the arachno species 4, 7, 9 and 11
are given in Table 5. The two para-benzylpyridine spe-
cies 7 and 8 have additional angularity associated with
them, arising from the tetrahedral {CH2} methylene
group present.
3. Conclusion
The new neutral monocarbaborane derivatives 2–4
and 6–12 reported here and characterised as summa-
rised above are readily synthesised. As well as having
interesting molecular frameworks that may have poten-
tial interest from a standpoint of nanoarchitectural
construction, they also constitute series of compounds
that vary systematically in that they have successively
more condensed aromatic residues in the nitrogen-do-
Thus, utilising the same reaction, but using a series of
substituted pyridines, two series of compounds with gen-
eral formulae [6-Ph-9-L-arachno-6-CB9H12] and [1-Ph-6-
L-closo-1-CB9H8], where L = NC5H5 (compounds 4 and
6, respectively), NC5H4-para-CH2Ph (7 and 8, respec-
tively), NC5H4-para-Ph (9 and 10, respectively) and

N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
2821
Fig. 4. ORTEP diagrams illustrating the crystallographically determined molecular structures of (top) [1-Ph-6-(NC5H4-para-CH2Ph)-closo-1-CB9H8]
(compound 8), (centre) [1-Ph-6-(NC5H4-para-Ph)-closo-1-CB9H8] (compound 10) and (bottom) [1-Ph-6-(NC9H7)-closo-1-CB9H8] (compound 12).
Anisotropic displacement parameters are shown at the 50% probability level. There are two crystallographically independent molecules of [1-Ph-6-
(NC5H4-para-Ph)-closo-1-CB9H8] (10) in the asymmetric unit; however, both have similar intramolecular dimensions, therefore only one is shown
˚
here. Selected interatomic distances (in A) are as follows: for 8, C(1)–C(11) 1.4868(18), C(1)–B(2) 1.6121(18), C(1)–B(3) 1.6126(19), B(2)–B(3)
1.847(2), B(2)–B(6) 1.808(2), B(3)–B(6) 1.800(2) and B(6)–N(61) 1.5507(16); for 10, C(1)–C(11) 1.4908(19), C(1)–B(2) 1.606(2), C(1)–B(3) 1.6023(19),
B(2)–B(3) 1.845(2), B(2)–B(6) 1.795(2), B(3)–B(6) 1.799(2) and B(6)–N(61) 1.5438(18); and for 12, C(1)–C(11) 1.490(2), C(1)–B(2) 1.609(2), C(1)–B(3)
1.608(2), B(2)–B(3) 1.845(3), B(2)–B(6) 1.805(3), B(3)–B(6) 1.811(3) and B(6)–N(61) 1.556(2).
nor ligands bonded to the monocarbaborane cluster.
Specifically, there is an effective condensation that pro-
gresses from the para-benzylpyridine derivatives, in
which the non-pyridyl aromatic ring is bound to the
pyridyl {NC5} skeleton by a {CH2} link, through
para-phenylpyridine, which has the non-pyridyl aro-

2822
N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
Table 3
˚
The overall tip-to-tip van-der-Waals lengths (in A) of the rod-like compounds [6-Ph-9-(NC5H4-para-CH2Ph)-arachno-6-CB9H12] (compound 7), [6-
Ph-9-(NC5H4-para-Ph)-arachno-6-CB9H12] (compound 9), [1-Ph-6-(NC5H4-para-CH2Ph)-closo-1-CB9H8] (compound 8) and [1-Ph-6-(NC5H4-para-
Ph)-closo-1-CB9H8] (compound 10): first column, through space; second column, approximately along the spine of the molecule
Compound
Length
Length
7
[6-Ph-9-(NC5H4-para-CH2Ph)-arachno-6-CB9H12
[6-Ph-9-(NC5H4-para-Ph)-arachno-6-CB9H12]
]
19.93
19.82
22.07
20.49
9
8
10
[1-Ph-6-(NC5H4-para-CH2Ph)-closo-1-CB9H8]
[1-Ph-6-(NC5H4-para-Ph)-closo-1-CB9H8]
18.07
17.29, 17.72
21.51
19.95, 19.96
Table 4
Angles (in degrees) between the C(1)–C(11) and B(6)–N(61) bonding vectors for compounds [1-Ph-6-(NC5H5)-closo-1-CB9H8] (compound 6), [1-Ph-
6-(NC5H4-para-CH2Ph)-closo-1-CB9H8] (compound 8), [1-Ph-6-(NC5H4-para-Ph)-closo-1-CB9H8] (compound 10), and [1-Ph-6-(NC9H7)-closo-1-
CB9H8] (compound 12)
Compound
Angle C(1)–C(11) / B(6)–N(61)
6
[1-Ph-6-(NC5H5)-closo-1-CB9H8]
109.32
109.23
8
[1-Ph-6-(NC5H4)-para-CH2Ph)-closo-1-CB9H8]
[1-Ph-6-(NC5H4)-para-Ph)-closo-1-CB9H8]
[1-Ph-6-(NC9H7)-closo-1-CB9H8]
10
12
107.15 and 111.56
107.68
Table 5
Angles (in degrees) between the C(6)–C(61) and B(9)–N(91) bonding vectors for compounds [6-Ph-9-(NC5H5)-arachno-6-CB9H12] (compound 4),
[6-Ph-9-(NC5H4-para-CH2Ph)-arachno-6-CB9H12
(NC9H7)-arachno-6-CB9H12] (compound 11)
]
(compound 7), [6-Ph-9-(NC5H4-para-Ph)-arachno-6-CB9H12
]
(compound 9), and [6-Ph-9-
Compound
Angle C(6)–C(61) / B(9)–N(91)
4
[6-Ph-9-(NC5H5)-arachno-6-CB9H12
[6-Ph-9-(NC5H4-para-CH2Ph)-arachno-6-CB9H12
[6-Ph-9-(NC5H4-para-Ph)-arachno-6-CB9H12
[6-Ph-9-(NC9H7)-arachno-6-CB9H12
]
144.29
151.68
145.89
149.93
7
]
9
11
]
]
matic ring more intimately linked by a direct sigma-
bond, to quinoline in which the second benzenoid
group is now very intimately fused to the {NC5} pyr-
idyl residue with two atoms in common. As mentioned
in the Introduction, one intent behind the work is the
generation of systematic sequences of such structurally
related smaller molecular species that are suitable for a
systematic study of variations of solid-state packing
patterns to assess weaker intermolecular interaction
modes. In this context, we currently explore for the syn-
thesis of other closely related systematic series, for exam-
ple the series with general formula [1-Ph-6-(NC5H4-para-
R)-closo-1-CB9H8], where R = H, Me, Et, isoPr and tert-
Bu, which exhibits incremental increase of steric bulk at
the pyridine para-site. The factors that influence solid-
state crystal packing are not very well understood, and
so these systematic synthetic studies, combined with a
methodical stepwise crystallographic analysis, for exam-
ple by the KAP approach, should result in a better appre-
ciation of a range of weaker solid state interactions that
could have useful implications for designed crystal engi-
neering that involves boron-containing clusters [22]. We
hope to report on our applications of this approach when
we have crystallographically substantiated a larger li-
brary of compounds.
4. Experimental
4.1. General
Reagents and solvents were obtained commercially;
solvents were dried and deoxygenated before use, and
reagents were used as obtained commercially. As
mentioned above, we use {FeCl3(OH2)6} conveniently
to describe iron(III) chloride hexahydrate, rather than
the more exact, but more cumbersome, solid-state formu-
lation [FeCl2(OH2)4]Cl(OH2)2. The [NEt4]+ salt of the
[6-Ph-nido-6-CB9H11]ꢀ anion (1) was prepared by the
Brellochs reaction between nido-B10H14 and PhCHO as
described in the literature [2,23]. Reactions were carried
out under dry dinitrogen, with subsequent manipulations
conducted in air. Thin-layer chromatography (TLC) was
carried out using 1 mm layers of silica gel GF254 on glass
plates of dimensions 20 · 20 cm, made from aqueous slur-
ries followed by drying in air at 80 ꢁC. Criteria of identity

N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
2823
and purity for new species were clean 11B and 1H NMR
spectra together with, in most cases, elemental analytical
data and single-crystal X-ray diffraction analysis for the
crystal and molecular structures, and also in most cases
by mass-spectrometric confirmation of molecular weight
and empirical formula, although the arachno species de-
scribed generally exhibited double dihydrogen loss from
the parent ion. Single-resonance NMR spectroscopy,
and one-dimensional and two-dimensional double reso-
nance correlation NMR spectroscopy, were generally
performed at 294–299 K and at ca. 5.9 T (the field B0 cor-
responding to 1H frequencies at ca. 250 MHz), although
some work was done at ca. 11.8 T (the field B0 corre-
sponding to 1H frequencies at ca. 500 MHz), as indicated.
Commercially available instrumentation was used, with
techniques and procedures as adequately described and
enunciated elsewhere [24–28]. Chemical shifts d are given
in ppm relative to N = 100 MHz for d(1H) ( 0.05 ppm)
(nominally TMS) and N = 32.083972 MHz for d(11B)
( 0.5 ppm) (nominally [BF3(OEt2)] in CDCl3) [28]. N is
as defined by McFarlane [29]. Resonance-line separations
arising from couplings J are given in Hz. Separations of
the doublets observed for BH units in the 11B spectra
are given 4 Hz, although it should be pointed out that
these experimentally observed splittings will generally be
lower than the actual coupling constants 1J(11B–1H), par-
ticularly in cases of overlap of proximate resonance lines
+2.99, H(2); +2.80, H(4); +2.76, H(5,7); +2.57, s,
H(92,93); +1.60, H(8,10); +0.91, H(1,3); +0.50, H(9);
ꢀ0.18, H(6); ꢀ3.19, Hl. Microanalyses: values for C
and H were found to be consistently low for this species;
typically found values were C, 40.4; H, 8.0%; C9H23B9S
requires C, 41.5; H, 8.9%; however, NMR spectroscopy
showed no impurities, and the single-crystal X-ray work
showed no solvent in the crystal matrix.
4.3. Preparation of [6-Ph-9-(NH2Ph)-arachno-6-
CB9H12] (compound 3)
[NEt4][6-Ph-nido-6-CB9H11] (500 mg, 1.5 mmol) was
dissolved in CHCl3 (40 cm3), and aniline (NH2Ph,
4.5 cm3, 49 mmol) and {FeCl3(OH2)6} (1.4 g, 5.2 mmol)
were added. The reaction mixture was stirred at reflux
temperature under a nitrogen atmosphere for 72 h,
and then allowed to cool. Evaporation of CHCl3 re-
sulted in a brown residue which was acidified with aque-
ous hydrochloric acid (5%, 50 cm3). The aqueous
mixture was extracted with diethyl ether (3 · 30 cm3),
and the ethereal layers were combined and evaporated,
leaving a pale brown residue containing mostly the [6-
Ph-9-NH2Ph-arachno-6-CB9H12] product 3 (260 mg,
0.89 mmol, 58%). Preparative TLC (CH2Cl2:hexane,
7:3) yielded pure 3 as a white crystalline solid (220 mg,
0.75 mmol, 49%, RF = 0.15). Slow evaporation of a solu-
tion of 3 in CHCl3 yielded single crystals (m.p.
189–191 ꢁC) suitable for study by single-crystal X-ray
diffraction analysis. NMR data: d(11B) (CDCl3): +0.9,
d(135), B(4); ca. ꢀ8.2, B(2); ca. ꢀ8.6, d(113), B(2) and
B(5,7); ꢀ15.2, d(96), B(9); ꢀ26.9, d(123), B(8,10);
ꢀ39.6, d(147), B(1,3). d(1H) (CDCl3): +7.50, m, H(63-
65); +7.37, d, H(62,66); +7.15, m, H(93,97,95); +7.08,
m, H(94,96); +5.98, s, H(91); ca. +2.70, H(4); ca.
+2.65, H(2); ca. +2.57, H(5,7); +1.35, H(8,10); ca.
+0.68, H(1,3) and H(9); ꢀ0.48, H(6); ꢀ3.47, Hl. Micro-
analysis: C13H24B9N requires C, 53.5; H, 8.3; N, 4.8;
found C, 53.6; H, 8.3; N, 4.8%. Mass spectrometry: m/
z = 286.9, envelope maximum, [M]+ ꢀ 4H.
1
[28]. For the non-cluster H NMR data, numberings of
the non-cluster hydrogen atoms are according to those
used for the crystallographic data.
4.2. Preparation of [6-Ph-9-(SMe2)-arachno-6-CB9H12]
(compound 2)
[NEt4][6-Ph-nido-6-CB9H11] (300 mg, 0.92 mmol) and
{FeCl3(OH2)6} (0.5 g, 1.8 mmol) were dissolved in
CH2Cl2 (20 cm3). Dimethyl sulfide (2 cm3, 27 mmol)
was added and the reaction mixture was stirred at room
temperature under an N2 atmosphere for 18 h. The reac-
tion mixture was then evaporated, and the resultant yel-
low-brown residue was acidified with aqueous
hydrochloric acid (5%, 50 cm3) and the aqueous layer
extracted with diethyl ether (3 · 30 cm3). The ethereal
layers were combined and evaporated, and the solid
washed with n-hexane (20 cm3) and dried to yield [6-
Ph-9-(SMe2)-arachno-6-CB9H12] (2) as a white crystal-
line solid (0.21 g, 0.81 mmol, 88%). Crystals (m.p./dec.
120–122 ꢁC) suitable for single-crystal X-ray work were
obtained by the overlayering of a concentrated solution
of compound 2 in CH2Cl2 in a 5 mm tube with a ten-
fold excess of hexane, and allowing slow diffusion.
NMR data: d(11B) (CDCl3): +1.5, d(130), B(4); ꢀ4.0,
d, B(2); ꢀ8.7, d(150), B(5,7); ꢀ20.2, d(118), B(9);
ꢀ26.1, d(132), B(8,10); ꢀ38.6, d(149), B(1,3). d(1H)
(CDCl3): +7.22, m, H(62,63,65,66); +7.12, m, H(64);
4.4. Formation and isolation of [6-Ph-9-(NC5H5)-
arachno-6-CB9H12] (compound 4)
[NEt4][6-Ph-nido-6-CB9H11] (250 mg, 0.76 mmol) was
dissolved in CH2Cl2 (40 cm3), and pyridine (NC5H5,
4 cm3, 49 mmol) and {FeCl3(OH2)6} (180 mg,
0.67 mmol) were added. The reaction mixture was stirred
at room temperature under a dinitrogen atmosphere for
72 h. The dichloromethane and excess pyridine were re-
moved under vacuum, and the resulting brown residue
was acidified with aqueous hydrochloric acid (5%,
30 cm3). The aqueous mixture was extracted with diethyl
ether (3 · 30 cm3), and the ethereal layers were combined
and evaporated, leaving a pale brown solid (110 mg). 11
B

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N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
NMR spectroscopy showed that this solid contained
both the closo and arachno pyridine species [1-Ph-6-
(NC5H5)-closo-1-CB9H8] (6) and [6-Ph-9-(NC5H5)-
arachno-6-CB9H12] (4), along with [4-Ph-arachno-4-
CB8H13] arising from acidification of the [NEt4][6-Ph-
nido-6-CB9H11] starting material [2] and also the
[1-Ph-closo-1-CB9H9]ꢀ anion [2], in approximately
2:3:1:1 molar ratio. Preparative TLC (CH2Cl2: hexane,
4:1) was carried out, and the mixture of compounds 4
and 6 (49 mg, RF = 0.67) was separated from the other
products. In a 5 mm tube, slow diffusion of hexane across
a benzene interface into a solution of this mixture in
CH2Cl2 thence yielded single crystals of 4 (m.p./dec.
200–205 ꢁC) suitable for study by single-crystal X-ray
diffraction analysis and for NMR spectroscopy. NMR
data: d(11B, 160.5 MHz) (CDCl3): +1.3, d(131), B(4);
ꢀ7.1, d(148), B(2); ꢀ9.1, d(147), B(5,7); ꢀ12.2, d(123),
B(9); ꢀ25.3, d(119), B(8,10); ꢀ39.1, d(147), B(1,3).
d(1H) (CDCl3): +8.87, d, H(92,96); +8.12, t, H(94);
+7.66, t, H(93,95); +7.24, d, H(62,66); +7.20, t,
H(63,65); +7.11, t, H(64); +2.77, H(2); ca. +2.66, H(4)
and H(5,7) accidentally coincident; +1.54, H(8,10);
+1.38, H(9); +0.75, H(1,3); ꢀ0.22, H(6); ꢀ3.14, Hl.
Microanalysis: C13H24B9N requires C 51.9, H 8.0, N
values being high; however, NMR spectroscopy showed
no impurities, and the single-crystal X-ray work showed
no solvent in the crystal matrix, and the m.p. was
constant.
4.6. Preparation of [6-Ph-9-(NC5H4-para-CH2Ph)-
arachno-6-CB9H12] (compound 7)
[NEt4][6-Ph-nido-6-CB9H11] (500 mg, 1.5 mmol) was
dissolved in CH2Cl2 (30 cm3), and para-benzylpyridine
NC5H4-para-CH2Ph, (10 cm3, 63 mmol) and {Fe-
Cl3(OH2)6} (1.5 g, 5.5 mmol) were added. The reaction
mixture was stirred at room temperature under a dinitro-
gen atmosphere for 96 h, and subsequent evaporation
yielded a brown residue which was then acidified with
aqueous hydrochloric acid (5%, 50 cm3). The aqueous
mixture was extracted with diethyl ether (3 · 30 cm3),
and the ethereal layers were combined and evaporated.
The resulting residue was washed with hexane, leaving
a pale yellow solid containing mostly the [6-Ph-9-
(NC5H4-para-CH2Ph)-arachno-6-CB9H12] product (7)
(74 mg, 0.20 mmol, 13%). In a 5 mm tube, slow diffusion
of hexane across a benzene interface into a solution of
this residue in CH2Cl2 yielded single crystals of 7 (m.p./
dec. 199–204 ꢁC) suitable for study by single-crystal
X-ray diffraction analysis. NMR data: d(11B) (CDCl3):
+0.9, d(111), B(4); ca. ꢀ.6, B(2); ca. ꢀ.2, d(127),
B(5,7); ꢀ12.3, d, B(9); ꢀ25.5, d(120), B(8,10); ꢀ39.3,
d(146), B(1,3). d(1H) (CDCl3): +8.69, d, H(92,96);
+7.35, m, unresolved ArH; +7.10, m, unresolved ArH;
+4.14, s, H(97); ca. +2.75, H(4); ca. +2.62, H(2) and
H(5,7) accidentally coincident; +1.48, H(8,10); +1.30,
H(9); +0.71, H(1,3); ꢀ0.24, H(6); ꢀ3.21, Hl. Microanal-
ysis: C19H28B9N requires C 62.1, H 7.7, N 3.8; found C
61.9, H 7.6 and N 3.7%. Mass spectrometry: m/
z = 363.3, envelope maximum, [M]+ ꢀ 4H.
5.1; found
C
51.7,
H
7.8 and
N
5.1%.
Mass spectrometry: m/z = 273.3, envelope maximum,
[M]+ ꢀ 4H.
4.5. Preparation of [1-Ph-6-(NC5H5)-closo-1-CB9H8]
(compound 6)
[NEt4][6-Ph-nido-6-CB9H11] (350 mg, 1.07 mmol) and
{FeCl3(OH2)6} (1 g, 3.7 mmol) were dissolved in
CH2Cl2 (20 cm3). Pyridine (2 cm3, 25 mmol) was added
and the reaction mixture was stirred at room tempera-
ture under an N2 atmosphere for 96 h. The reaction mix-
ture was then evaporated, and the resultant brown
residue was acidified with aqueous hydrochloric acid
(5%, 50 cm3) and the aqueous layer extracted with
diethyl ether (3 · 30 cm3). The ethereal layers were
combined and evaporated. The yellowish solid was
recrystallised from CH2Cl2/n-hexane, to yield [1-Ph-6-
(NC5H5)-closo-1-CB9H8] (6) as a white crystalline solid
(270 mg, 0.99 mmol, 92%). In a 5 mm tube, slow diffu-
sion of hexane into a solution of 6 in CH2Cl2 yielded sin-
gle crystals (m.p. 195–198 ꢁC) suitable for study by
single-crystal X-ray diffraction analysis. NMR data:
d(11B) (CDCl3): +25.2, d(156), B(10); ꢀ5.1, s, B(6);
ꢀ11.1, d(155), B(4,5); ꢀ16.6, d(154), B(2,3); ꢀ20.3,
d(145), B(7,9); ꢀ24.8, d(142), B(8). d(1H) (CDCl3):
+8.58, d, H(62,66); +8.15, t, H(64); +7.93, d, H(11,16);
+7.66, t, H(63,65); +7.41, t, H(13,15); +7.35, t, H(14);
+5.38, H(10); +2.29, H(4,5); +2.17, H(2,3); +1.87,
H(7,9); +1.09, H(8). Microanalyses: over several at-
tempts, values for C and H and N were found to be con-
sistently erratic for this species, usually with found
4.7. Preparation of [1-Ph-6-(NC5H4-para-CH2Ph)-
closo-1- CB9H8] (compound 8)
[NEt4][6-Ph-nido-6-CB9H11] (1 g, 3.1 mmol) was dis-
solved in CHCl3 (40 cm3), and 4-benzylpyridine
(NC5H4-para-CH2Ph, 12.5 cm3, 79 mmol) and {Fe-
Cl3(OH2)6} (3 g, 0.011 mol) were added. The reaction
mixture was stirred at reflux temperature under a dini-
trogen atmosphere for 14 days, and then allowed to
cool. The CHCl3 was removed under vacuum, and the
resulting brown residue was acidified with aqueous
hydrochloric acid (5%, 50 cm3). The aqueous mixture
was extracted with diethyl ether (4 · 30 cm3), and the
ethereal layers were combined and evaporated, leaving
a pale yellow solid consisting mostly of [1-Ph-6-
(NC5H4-para-CH2Ph)-closo-1-CB9H8] (8) (720 mg,
2.0 mmol, 64%). Preparative TLC (CH2Cl2:hexane,
3:2) thence yielded pure 8 as a white crystalline solid
(650 mg, 1.8 mmol, 58%, RF = 0.45). In a 5 mm tube,

N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
2825
slow diffusion of hexane, across a benzene interface, into
a solution of 8 in CH2Cl2 yielded single crystals (m.p.
151–152 ꢁC) suitable for study by single-crystal X-ray
diffraction analysis. NMR data: d(11B) (CDCl3): +25.0,
d(155), B(10); ꢀ5.3, s, B(6); ꢀ11.1, d(143), B(4,5);
ꢀ16.7, d(154), B(2,3); ꢀ20.1, d(141), B(7,9); ꢀ24.9,
d(140), B(8). d(1H) (CDCl3): +8.42, d, H(62,66); +7.92,
d, H(12,16); +7.4, m, H(13-15,63,65,70-72); +7.13, d,
H(69,73); +5.34, H(10); +4.11, s, H(67); +2.24, H(4,5);
+2.08, H(2,3); +1.80, H(7,9); +1.03, H(8). Microanaly-
sis: C19H24B9N requires C, 62.8; H, 6.7; N, 3.9; found
C, 62.6; H, 6.7; N, 3.6%. Mass spectrometry: m/z =
364.3, envelope maximum, [M]+
14 days, and then allowed to cool. The CHCl3 was re-
moved under vacuum, and the resulting brown residue
was acidified with aqueous hydrochloric acid (5%,
70 cm3). The aqueous mixture was extracted with diethyl
ether (3 · 40 cm3), and the ethereal layers were com-
bined and evaporated, leaving a pale yellow solid
consisting principally of [1-Ph-6-(NC5H4-para-Ph)-clo-
so-1-CB9H8] (10) (540 mg, 1.5 mmol, 63%). Preparative
TLC (CH2Cl2:hexane, 3:2) thence yielded pure 10 as a
white crystalline solid (420 mg, 1.2 mmol, 49%,
RF = 0.6). In a 5 mm tube, slow diffusion, across a ben-
zene interface, between hexane and a solution of 10 in
CH2Cl2 yielded single crystals (m.p. 177–179 ꢁC) suit-
able for study by single-crystal X-ray diffraction analy-
sis. NMR data: d(11B) (CDCl3): +25.0, d(155), B(10);
ꢀ5.2, s, B(6); ꢀ11.0, d(142), B(4,5); ꢀ16.6, d(155),
B(2,3); ꢀ20.1, d(139), B(7,9); ꢀ24.8, d(141), B(8).
d(1H) (CDCl3): +8.57, d, H(62,66); +7.97, d, H(12,16);
+7.79, d, H(63,65); +7.67, m, H(68,72); +7.59, m,
H(69-71); +7.38, m, H(13-15); +5.41, H(10); +2.27,
H(4,5); +2.14, H(2,3); +1.85, H(7,9); +1.07, H(8).
Microanalysis: C18H22B9N requires C, 61.8; H, 6.3; N,
4.0; found C, 61.8; H, 6.2; N, 4.0%. Mass spectrometry:
m/z = 349.3, envelope maximum, [M]+.
4.8. Preparation of [6-Ph-9-(NC5H4-para-Ph)-
arachno-6-CB9H12] (compound 9)
[NEt4][6-Ph-nido-6-CB9H11] (500 mg, 1.5 mmol) and
4-phenylpyridine (NC5H4-para-Ph, 3.2 g, 21 mmol) were
dissolved in CHCl3 (40 cm3), and {FeCl3(OH2)6} (1.2 g,
4.4 mmol) was added. The reaction mixture was stirred
at reflux temperature under a dinitrogen atmosphere
for 28 h, and then allowed to cool. The CHCl3 was re-
moved under vacuum, and the resulting brown residue
was acidified with aqueous hydrochloric acid (5%,
50 cm3). The aqueous mixture was extracted with
CH2Cl2 (3 · 30 cm3), and the organic layers were
combined and evaporated, leaving a pale yellow solid
consisting mostly of [6-Ph-9-(NC5H4-para-Ph)-arachno-
6-CB9H12] (9) (300 mg, 0.84 mmol, 56%). Preparative
TLC (CH2Cl2:hexane, 4:1) thence yielded pure 9 as a
white crystalline solid (230 mg, 0.65 mmol, 43%,
RF = 0.5). In a 5 mm tube, slow diffusion of hexane,
across a benzene interface, into a solution of 8 in
CH2Cl2 yielded single crystals (m.p./dec. 231–240 ꢁC)
suitable for study by single-crystal X-ray diffraction
analysis. NMR data: d(11B) (CDCl3): +0.9, d(122),
B(4); ca. ꢀ.2, B(2); ca. ꢀ.2, d(129), B(5,7); ꢀ12.4, d,
B(9); ꢀ25.4, d(115), B(8,10); ꢀ39.2, d(146), B(1,3).
d(1H) (CDCl3): +8.84, d, H(92,96); +7.81, d, H(93,95);
+7.72, m, H(62,66); +7.60, m, H(63-65); +7.20, m,
H(99-101); +7.09, d, H(98,102); ca. +2.80, H(2); ca.
+2.73, H(4); ca. +2.66, H(5,7); +1.54, H(8,10); +1.36,
H(9); +0.75, H(1,3); +0.19, H(6); ꢀ3.13, Hl. Microanal-
ysis: C18H26B9N requires C 61.1, H 7.4, N 4.0; found C
60.9, H 7.7 and N 4.1%. Mass spectrometry: m/z =
349.4, envelope maximum, [M]+ ꢀ 4H.
4.10. Preparation of [6-Ph-9-(NC9H7)-arachno-6-
CB9H12] (compound 11)
[NEt4][6-Ph-nido-6-CB9H11] (0.4 g, 1.22 mmol) was
dissolved in CHCl3 (80 cm3), quinoline (2 cm3,
17 mmol) and {FeCl3(OH2)6} (0.4 g, 1.48 mmol) were
added, and the reaction mixture was stirred at reflux
temperature under an atmosphere of dinitrogen for
24 h, then allowed to cool to room temperature. The
reaction mixture was acidified with aqueous hydrochlo-
ric acid (5%, 50 cm3) and extracted with CH2Cl2
(3 · 30 cm3). The organic layers were combined and
evaporated, yielding a yellow residue. Preparative
TLC (CH2Cl2:hexane, 4:1) yielded pure [6-Ph-9-
(NC9H7)-arachno-6-CB9H12] (11) as a white crystalline
solid (190 mg, 48%, RF = 0.7). Single crystals of 11
(m.p./dec. 226–228 ꢁC) suitable for study by single-crys-
tal X-ray diffraction analysis were grown by slow diffu-
sion of n-hexane into a concentrated solution of 11 in
CH2Cl2 in a 5 mm tube. NMR data: d(11B) (CDCl3):
+1.7, d(128), B(2); ca. ꢀ.4, B(4); ca. ꢀ.7, d, B(5,7);
ꢀ14.0, d, B(9); ꢀ25.2, d(117), B(8,10); ꢀ38.9, d(147),
B(1,3). d(1H) (CDCl3): +9.41, d, H(99); +9.35, d,
H(92); +8.63, d, H(94); +8.10, t, H(98); +8.08, m,
H(96); +7.85, t, H(97); +7.70, t, H(93); +7.33, d,
H(62,66); +7.23, t, H(63,65); +7.13, t, H(64); ca.
+2.80, H(2) and H(4) accidentally coincident; +2.75,
H(5,7); +1.56, H(8,10); +1.53, H(9); +0.78, H(1,3);
+0.01, H(6), ꢀ2.98, Hl. Microanalysis: C16H24B9N re-
quires C, 58.7; H, 7.4; N, 4.3; found C, 58.5; H, 7.5;
N, 4.1%.
4.9. Preparation of [1-Ph-6-(NC5H4-para-Ph)-
closo-1-CB9H8] (compound 10)
[NEt4][6-Ph-nido-6-CB9H11] (800 mg, 2.4 mmol) and
4-phenylpyridine (NC5H4-para-Ph, 5 g, 032 mmol) were
dissolved in CHCl3 (40 cm3), and {FeCl3(OH2)6} (2 g,
7.40 mmol) was added. The reaction mixture was stirred
at reflux temperature under a dinitrogen atmosphere for

2826
N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
4.11. Preparation of [1-Ph-6-(NC9H7)-closo-1-CB9H8]
(compound 12)
of reference. Diagrams in Figs. 1–4 were prepared with
the aid of the ORTEP-3 program [36].
[NEt4][6-Ph-nido-6-CB9H11] (0.32 g, 0.976 mmol) was
dissolved in CHCl3 (40 cm3), quinoline (NC9H7,
3.5 cm3, 30 mmol) and {FeCl3(OH2)6}] (0.85 g,
3.14 mmol) were added, and the reaction mixture stirred
at reflux temperature under an atmosphere of dry nitro-
gen for 12 days. The reaction mixture was then cooled
and evaporated, acidified with aqueous hydrochloric
acid (5%, 30 cm3), and then extracted with CH2Cl2
(3 · 30 cm3). The CH2Cl2 extracts were combined and
evaporated, to yield a pale brown residue. Preparative
TLC (CH2Cl2:hexane, 3:1) yielded [1-Ph-6-(NC9H7)-
closo-1-CB9H8] (12) as a white crystalline solid (154 mg,
49%; RF = 0.74). Slow diffusion of hexane into solution
of compound 12 in CH2Cl2, held in a 5 mm tube, thence
yielded single crystals (m.p. 81–83 ꢁC) suitable for study
by single-crystal X-ray diffraction analysis. NMR data:
d(11B) (CDCl3): +25.9, d(148), B(10); ꢀ5.5, s, B(6);
ꢀ10.9, d(147), B(4,5); ꢀ15.4, d(148), B(2,3); ꢀ19.9,
d(137), B(7,9); ꢀ24.9, d(140), B(8). d(1H) (CDCl3):
+8.72, d, H(62); +8.63, d, H(69); +8.55, d, H(64);
+8.00, d, H(66); +7.95, t, H(68); +7.89, d, H(12,16);
+7.79, t, H(67); +7.63, t, H(63); +7.37, t, H(13,15);
+7.30, t, H(14); +5.30, H(10); +2.32, H(4,5); +2.26,
H(2,3); +2.12, H(7,9); +1.21, H(8). Microanalyses: over
several attempts, values for C and H and N were found
to be consistently erratic for this species; however,
NMR spectroscopy showed no impurities, and the sin-
gle-crystal X-ray work showed no solvent in the crystal
matrix, and the m.p. was consisitent. Mass spectrometry:
m/z = 322.0, envelope maximum, [M]+.
5.1. [6-Ph-9-(SMe2)-arachno-6-CB9H12] (compound 2)
C9H23B9S, M = 260.62, monoclinic, space group
˚
P21/c, a = 12.8311(2), b = 16.0183(3), c = 19.4141(3) A,
3
A ,
˚
b = 128.993(1)ꢁ,
U = 3101.29(9)
Dcalc =
˚
1.116 Mg mꢀ3
,
Z = 8, Mo Ka, k = 0.71073 A,
l = 0.183 mmꢀ1, T = 150(2) K, R1 = 0.0629 for 5452
reflections with I > 2r(I), and wR2 = 0.1566 for all
6079 unique reflections; CCDC 254031.
5.2. [6-Ph-9-(NH2Ph)-arachno-6-CB9H12]
(compound 3)
C13H24B9N, M = 291.62, orthorhombic, space group
˚
Pna21, a = 10.4683(3), b = 10.1286(3), c = 16.3132(5) A,
3
U = 1729.68(9) A , Dcalc = 1.12 Mg mꢀ3, Z = 4, Mo
˚
Ka, k = 0.71073 A, l = 0.056 mmꢀ1, T = 150(2) K,
˚
R1 = 0.0378 for 3002 reflections with I > 2r(I), and
wR2 = 0.0895 for all 3322 unique reflections; CCDC
254032.
5.3. [6-Ph-9-(NC5H5)-arachno-6-CB9H12]
(compound 4)
C12H22B9N, M = 277.6, monoclinic, space group
C2/c, a = 15.3090(4), b = 13.6837(4), c = 15.7206(5)
3
˚
˚
˚
A,b = 100.874(1)ꢁ, U = 3234.08(16) A , Dcalc = 1.14 Mg
mꢀ3, Z = 8, Mo Ka, k = 0.71073 A, l = 0.057 mm
,
ꢀ1
T = 150(2) K, R1 = 0.0719 for 2758 reflections with
I > 2r(I), and wR2 = 0.1624 for all 3167 unique reflec-
tions; CCDC 254033.
5. Single-crystal X-ray diffraction analyses
5.4. [1-Ph-6-(NC5H5)-closo-1-CB9H8] (compound 6)
C12H18B9N, M = 273.56, orthorhombic, space group
For all compounds except 7, a conventional sealed-
tube X-ray source was used. Obtainable crystals for
compound 7 were small and required use of higher-
intensity synchrotron-generated X-radiation to achieve
sufficient diffraction intensity for crystallographic analy-
sis [30–32]. Otherwise, methods and programs were
standard [33–35]. Selected crystallographic data are gi-
ven below. Full data for all the previously crystallo-
graphically unreported species discussed in this present
paper are deposited at the Cambridge Crystallographic
Data Centre, CCDC. The CCDC deposition numbers
for the individual compounds are as indicated in data
summaries below. These data can be obtained free of
charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or
from the Cambridge Crystallographic Data Centre, 12,
Union Road, Cambridge CB2 1EZ, UK; fax: (internat.)
+44-1223/336-033; E-mail: deposit@ccdc.cam.ac.uk].
Data for compound 8 are previously reported and
deposited [16], but are included here for convenience
˚
Pbca, a = 13.5552(3), b = 14.6399(4), c = 15.5854(5) A,
3
U = 3092.87(15) A , Dcalc = 1.175 Mg mꢀ3, Z = 8, Mo
Ka, k= 0.71073 A, l = 0.059 mmꢀ1, T = 150(2) K, R1 =
0.0419 for 2657 reflections with I > 2r(I), and wR2 =
0.113 for all 3028 unique reflections; CCDC 254034.
˚
˚
5.5. [6-Ph-9-(NC5H4-para-CH2Ph)-arachno-6-
CB9H12] (compound 7)
C19H28B9N, M = 367.71, orthorhombic, space group
˚
P212121, a = 7.9947(9), b = 12.8714(13), c = 20.585(2) A,
3
U = 2118.3(4) A , Dcalc = 1.153 Mg mꢀ3
,
Z = 4,
˚
˚
k = 0.684 A [wiggler-generated from 2-GeV electrons
at 150-250 mA on the synchrotron radiation source
(SRS) at station 9.8, CCLRC, Daresbury, UK] [28–
30], l = 0.059 mmꢀ1, T = 150(2) K, R1 = 0.0475 for
3759 reflections with I > 2r(I), and wR2 = 0.116 for all
4666 unique reflections; CCDC 254035.

N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
2827
5.6. [1-Ph-6-(NC5H4-para-CH2Ph)-closo-1-CB9H8]
(compound 8)
Acknowledgements
We thank the UK EPSRC for financial support
(Grant Nos. J/56929, K/05818, L/49505, M/83360 and
R/61949), and for a contribution towards a research
DTA to N.J.B., and we thank the EPSRC and CCLRC
for a beam-time allocation at the UK SRS Daresbury,
Station 9.8. We also thank the UK DTI for support,
and Dr. Richard Taylor of Dow Corning Ltd for his
interest and good offices.
C19H24B9N, M = 363.68, monoclinic, space group
˚
P21/c, a = 9.9181(2), b = 10.8545(3), c = 19.3643(4) A,
3
˚
b = 97.272(1)ꢁ, U = 2067.91(8) A , Dcalc = 1.168 Mg
ꢀ1
mꢀ3, Z = 4, Mo Ka, k = 0.71073 A, l = 0.06 mm
,
˚
T = 150(2) K, R1 = 0.0434 for 3360 reflections with
I > 2r(I), and wR2 = 0.1216 for all 4050 unique reflec-
tions; CCDC 204007.
5.7. [6-Ph-9-(NC5H4-para-Ph)-arachno-6-CB9H12]
(compound 9)
References
[1] B. Brellochs, in: M.G. Davidson, T.B. Marder, K. Wade (Eds.),
Contemporary Boron Chemistry, Royal Society of Chemistry,
Cambridge, UK, 2000, p. 212.
C18H26B9N, M = 353.69, monoclinic, space group
˚
P21/c, a = 10.8914(2), b = 10.6922(2), c = 18.8063(3) A,
3
˚
[2] A. Franken, C.A. Kilner, M. Thornton-Pett, J.D. Kennedy,
Collect. Czech. Chem. Commun. 67 (2002) 869.
b = 113.952(1)ꢁ, U = 2001.46(6) A , Dcalc = 1.174 Mg
ꢀ1
mꢀ3, Z = 4, Mo Ka, k = 0.71073 A, l = 0.06 mm
,
˚
[3] I.B. Sivaev, S. Sjoberg, V.I. Bregadze, in: Abstracts Eleventh
International Meeting on Boron Chemistry (IMEBORON XI),
Moscow, Russia, 2002, p. 69.
T = 150(2) K, R1 = 0.0415 for 3200 reflections with
I > 2r(I), and wR2 = 0.1096 for all 3922 unique reflec-
tions; CCDC 254036.
[4] I.B. Sivaev, S. Sjoberg, V.I. Bregadze, in: Yu.N. Bubnov (Ed.),
Boron Chemistry at the Beginning of the 21st Century, Editorial
URSS, Moscow, Russia, 2003, p. 334.
[5] I.B. Sivaev, in: Abstracts Third European Meeting on Boron
Chemistry(EUROBORON3), Pruhonice, Czech Republic, 2004, p.
O 52.
5.8. [1-Ph-6-(NC5H4-para-Ph)-closo-1-CB9H8]
(compound 10)
ˇ
[6] B. Brellochs, J. Backovsky, B. Stıbr, T. Jelınek, J. Holub, M.
ˇ
´ ˇ
Bakardjiev, D. Hnyk, M. Hofmann, I. Cısarova, B. Wrackmeyer,
´
´
´
ꢀ
´
C18H22B9N, M = 349.66, triclinic, space group P1,
a = 10.7917(1), b = 12.0346(1), c = 17.3083(3) A, a =
˚
Eur. J. Inorg. Chem. (2004) 3605.
ˇ
[7] U. Scho¨berl, J. Miller, K. Base, M. Ibrahim, P.N. Ibrahim, T.F.
76.450(1), b = 88.690(1), c = 65.703(1)ꢁ, U = 1984.89(4)
Magnera, D.E. David, J. Michl, Polym. Reprints 43 (1993) 81.
[8] P. Schwab, M.D. Levin, J. Michl, Chem. Rev. 99 (1999) 1863.
[9] H.M. Colquhoun, P.L. Herbertson, K. Wade, I. Baxter, D.J.
Williams, Macromolecules 31 (1998) 1694.
3
1.17 Mg mꢀ3, Z = 4, Mo Ka, k =
˚
A , Dcalc
=
0.71073 A, l = 0.06 mmꢀ1, T = 150(2) K, R1 = 0.0434
for 6381 reflections with I > 2r(I), and wR2 = 0.1184
for all 7773 unique reflections; CCDC 254037.
˚
[10] E.S. Alexseyava, M.A. Fox, J.A.K. Howard, J.A.H. Macbride,
K. Wade, Appl. Organomet. Chem. 17 (2003) 499.
[11] H. Yao, R.N. Grimes, Organometallics 22 (2003) 4539.
[12] M.F. Hawthorne, Z. Zheng, Acc. Chem. Res. 30 (1997) 267.
[13] M.D. Mortimer, W. Jiang, Z. Zheng, R.R. Kane, I.T. Chizhevsky,
C.B. Knobler, M.F. Hawthorne, in: J. Michl (Ed.), Modular
Chemistry, Kluwer Academic Press, Dordrecht, Netherlands, 1997,
p. 551.
5.9. [6-Ph-9-(NC9H7)-arachno-6-CB9H12]
(compound 11)
C16H24B9N, M = 327.65, monoclinic, space group
˚
P21/c, a = 11.7278(2), b = 11.4555(2), c = 14.3034(3) A,
[14] P. Kaszynski, S. Pakhomov, V.G. Young, Collect. Czech. Chem.
Commun. 67 (2002) 1061.
3
˚
b = 106.469(1)ꢁ, U = 1842.79(6) A , Dcalc = 1.181 Mg
[15] J. Thomas, M.F. Hawthorne, J. Chem. Soc., Chem. Commun.
(2001) 1884.
ꢀ1
mꢀ3, Z = 4, Mo Ka, k = 0.71073 A, l = 0.06 mm
,
˚
T = 150(2) K, R1 = 0.0423 for 2953 reflections with
I > 2r(I), and wR2 = 0.1169 for all 3608 unique reflec-
tions; CCDC 254038.
[16] N.J. Bullen, A. Franken, C.A. Kilner, J.D. Kennedy, J. Chem.
Soc., Chem. Commun. (2003) 1684.
[17] C. OÕDowd, J.D. Kennedy, M. Thornton-Pett, J. Organomet.
Chem. 657 (2002) 20.
[18] C. OÕDowd, Structural and synthetic studies on the bis(pyridine)-
arachno-decaborane species, Ph.D. Thesis, University of Leeds,
2001.
5.10. [1-Ph-6-(NC9H7-closo-1-CB9H8] (compound 12)
C16H20B9N, M = 323.62, monoclinic, space group
[19] T.M. Polyanskaya, V. Volkov, E.A. Ilinchik, Izv. Akad. Nauk
Gruz. SSR, Ser. Khim. 8 (1989) 298.
˚
P21/c, a = 14.2254(3), b = 10.5672(2), c = 12.9679(2) A,
[20] S.V. Ivanov, J.J. Rockwell, S.M. Miller, O.P. Anderson, K.A.
Solntsev, S.H. Strauss, Inorg. Chem. 35 (1996) 7882.
´
[21] Z. Xie, D.J. Liston, T. Jelınek, V. Mitro, R. Bau, C.A. Reed, J.
3
˚
b = 114.1070(10)ꢁ, U = 1779.35(6) A , Dcalc = 1.208 Mg
ꢀ1
mꢀ3, Z = 4, Mo Ka, k = 0.71073 A, l = 0.062 mm
,
˚
Chem. Soc., Chem. Commun. (1993) 384.
[22] See, for example, together with references cited therein: A. Franken,
T = 150(2) K, R1 = 0.0615 for 2810 reflections with
I > 2r(I), and wR2 = 0.1681 for all 3482 unique reflec-
tions; CCDC 254039.
´
N.J. Bullen, T. Jelınek, M. Thornton-Pett, S.J. Teat, W. Clegg,
J.D. Kennedy, M.J. Hardie, New J. Chem. 28 (2004) 1499.

2828
N.J. Bullen et al. / Journal of Organometallic Chemistry 690 (2005) 2815–2828
´
[23] T. Jelınek, C.A. Kilner, M. Thornton-Pett, J.D. Kennedy, J.
Chem. Soc., Chem. Commun. (2001) 1790.
[30] R.J. Cernik, W. Clegg, C.R.A. Catlow, G. Bushnell-Wye, J.V.
Flaherty, G.N. Greaves, I. Burrows, D.J. Taylor, S.J. Teat, M.
Hamichi, J. Synchrotron Rad. 4 (1997) 279.
[24] M.A. Beckett, M. Bown, X.L.R. Fontaine, N.N. Greenwood,
J.D. Kennedy, M. Thornton-Pett, J. Chem. Soc., Dalton Trans.
(1988) 1969.
[31] J. Bould, W. Clegg, J.D. Kennedy, S.J. Teat, M. Thornton-Pett,
J. Chem. Soc., Dalton Trans. (1997) 2005.
[25] G. Ferguson, J.D. Kennedy, X.L.R. Fontaine, Faridoon, T.R.
Spalding, J. Chem. Soc., Dalton Trans. (1988) 2555.
[26] D. Reed, Chem. Soc. Rev. 22 (1993) 109.
[32] W. Clegg, M.R.J. Elsegood, S.J. Teat, C. Redshaw, V.C. Gibson,
J. Chem. Soc., Dalton Trans. (1998) 3037.
[33] Z. Otwinowski, W. Minor, Methods Enzymol. 276 (1997) 307.
[34] COLLECT, Data Collection Software, Nonius, Delft, Netherlands,
1998.
ˇ
´
[27] S. Hermanek, Inorg. Chim. Acta 289 (1999) 20.
[28] J.D. Kennedy, in: J. Mason (Ed.), Multinuclear NMR,
Plenum Press, New York and London, USA and UK, 1987,
p. 221.
[35] SMART, SAINT, SADABS, SHELXTL, Bruker AXS Inc., Madison, WI,
USA, 1997–2001.
[29] W. McFarlane, Proc. Roy. Soc. Lond. Ser. A 306 (1968) 185.
[36] ORTEP-3, L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.