www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 582 (1999) 282 – 285
A simple route to essential tricarbollides. A high-yield synthesis of
7-amine-nido -7,8,9-tricarbaundecaboranes(10), 7-L-nido -7,8,9-C
3
B
8
H
10
(where L = H
3
N, Me
2
NH, Me
3
N, and Bu
t
H
2
N)
Bohumil S tı ´br
a,b,
*, Josef Holub
a,b
, Jaromı ´r Ples ek
a
, Toma ´s Jelı ´nek
a
,
Bohumı ´r Gru ¨ ner
a,b
, Francesc Teixidor
b
, Clara Vin ˜as
b
a
Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, 250 68 R ez , Czech Republic
b
Institute of Material Sciences, CSIC, Campus UAB, 08193 Bellaterra, Spain
Received 1 December 1998
Abstract
Reported is an improved synthesis of essential starting compounds for the development of tricarbollide and metallatricarbollide
chemistry. Evaporation of a solution of Na
+
[5,6-C
2
B
8
H
11
]
-
(1
-
) in neat Bu
t
NC, followed by acidification, led to the isolation
of 7-(Bu
t
H
2
N)-nido -7,8,9-C
3
B
8
H
10
(2a) in a 90% yield. This was converted into the 7-(H
3
N)-nido -7,8,9-C
3
B
8
H
10
(2b) derivative via
reaction with AlCl
3
in refluxing benzene (yield 77%). Methylation of 2b with Me
2
SO
4
in an alkaline solution gave the
7-(Me
3
N)-nido -7,8,9-C
3
B
8
H
10
(2c) derivative in essentially quantitative yield. The reaction of 2c with sodium in liquid ammonia
resulted in the formation of highly pure compounds 7-(Me
2
HN)-nido -7,8,9-C
3
B
8
H
10
(2d) (yield 71%) and nido -7,8,9-C
3
B
8
H
12
(3)
(yield 19%). © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Boron clusters; Carboranes; Tricarbaboranes; Tricarbollides; Syntheses
1. Introduction
Our first venture into the area of the 11-vertex nido
tricarbaborane (tricarbollide) chemistry was the synthe-
sis of ligand derivatives of the general formula 7-L-
nido -7,8,9-C
3
B
8
H
10
(2) (where L =amines) [1], which
are zwitterionic derivatives of the parent tricarbollide
anion [nido -7,8,9-C
3
B
8
H
11
]
-
[1,2]. Total synthesis of
these first representatives of this class of compounds is
based on a reaction sequence using commercially avail-
able o -carborane as the starting material (for the first
two reaction steps see references [3,4]).
1,2-C
2
B
10
H
12
OH
-
, ROH
95%
[7,8-C
2
B
9
H
12
]
-
Fe
3 +
,H
3
O
+
45%
5,6-C
2
B
8
H
12
1. CN
-
,H
2
O
2. OH
-
, Me
2
SO
4
28%
7-(Me
3
N)-7,8,9-C
3
B
8
H
10
2c
(total yield 12%) (1)
The most significant reaction step of the synthesis is the
conversion of 5,6-C
2
B
8
H
12
into the Me
3
N derivative of
type 2c, via monocarbon insertion. Another variation
of the tricarbollide synthesis was that of 2a using a
dilute solution of Bu
t
NC as the carbon-insertion agent
[1]. The Bu
t
H
2
N derivative thus formed was converted,
in a lower yield, into the Me
3
N derivative 2c by methyl-
ation as in Eq. (2):
[5,6-C
2
B
8
H
11
]
-
+Bu
t
NC
1. Bu
t
NC, RT, glyme, 2 -4 days
2. protonation
45 -60%
7-(Bu
t
H
2
N)-7,8,9-C
3
B
8
H
10
2a
MeI, NaH, glyme, reflux
38%
7-(Me
3
N)-
7,8,9-C
3
B
8
H
10
(total yield 7–10%)
2c
(2)
Dedicated to Dr Stanislav Her ma ´nek on the occassion of his 70th
birthday. All boron chemists know him as an NMR rule-maker and
creator of the progressive seco-systemization of cluster-boron com-
pounds.
* Corresponding author. Fax: +42-02-20941502.
E-mail address: stibr@uachr.iic.cas.cz (B. S tı ´br)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII:S0022-328X(99)00068-6