Inorganica Chimica Acta 328 (2002) 254 – 258
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Note
Syntheses and crystal structures of mononuclear
[2.2]paracyclophane complexes of rhodium and iridium supported
by the pentamethylcyclopentadienyl ligand
[M(
6
-pcp)(
5
-C
5
Me
5
)](BF
4
)
2
(M = Rh and Ir)
Masahiko Maekawa
a,
*, Naoki Hashimoto
b
, Takayoshi Kuroda-Sowa
b
,
Yusaku Suenaga
b
, Megumu Munakata
b
a
Research Institute for Science and Technology, Kinki Uniersity, 3 -4 -1 Kowakae, Higashi -Osaka 577 -8502, Japan
b
Department of Chemistry, Kinki Uniersity, Kowakae, Higashi -Osaka 577 -8502, Japan
Received 13 July 2001; accepted 20 September 2001
Abstract
Mononuclear [2.2]paracyclophane complexes of Rh and Ir, [M(
6
-pcp)(
5
-C
5
Me
5
)](BF
4
)
2
(M=Rh (1) and Ir (2); pcp =
[2.2]paracyclophane) were crystallized and their structures were first characterized crystallographically. On both pcp complexes the
metal atom is bonded to the benzene ring on one side of the pcp ligand in the
6
-coordination mode. The metal atom is also
supported by the
5
-C
5
Me
5
ligand to afford a triple-decker sandwich structure. In Rh pcp complex 1 the average RhC(pcp) and
RhC(C
5
Me
5
) distances are 2.284(2) and 2.161(2) A , respectively. The average C(pcp)C(pcp) distance of 1.407(4) A with the Rh
atom is longer than that (1.388(4) A ) without a Rh atom. Similarly, the average IrC(pcp) and IrC(C
5
Me
5
) distances in Ir pcp
complex 2 are 2.275(3) and 2.174(3) A , respectively. The average C(pcp)C(pcp) distance of 1.410(4) A with the Ir atom is longer
than that (1.388(4) A ) without an Ir atom. It is interesting that the average interannular distances of 2.97 A for 1 and 2 between
two decks of the pcp ligand are shorter than that (3.09 A ) of the metal-free pcp ligand, indicative of the decrease of the repulsive
-interaction between benzene rings. The Rh pcp complex gave the well-resolved
1
H NMR signals of [Rh(
6
-pcp)(
5
-C
5
Me
5
)]
2 +
,
whereas the Ir pcp complex exhibited two kinds of
1
H NMR signals which were assigned as [Ir(
6
-pcp)(
5
-C
5
Me
5
)]
2 +
and
[Ir
2
(
6
-pcp)(
5
-C
5
Me
5
)
2
]
4 +
in (CD
3
)
2
CO at 23 °C. © 2002 Elsevier Science B.V. All rights reserved.
Keywords: Rhodium complexes; Iridium complexes; Cyclophanes; Cyclopentadienyls; Crystal structures;
1
H NMR
1. Introduction
Transition metal complexes of cyclophanes continue
to be a new and exciting area of organometallic chem-
istry [1 – 5]. There have been many publications dealing
with the synthesis and the spectroscopic characteriza-
tion of such complexes. Such studies are of interest,
because they can provide useful information about the
changes in the cyclophane skeleton due to metal
-bonding. Four possible coordination modes as metal
complexes of [2.2]paracyclophane (pcp) are illustrated
in Scheme 1. The pcp complexes of the coordination
mode (a) are most general [6–13], which have been
produced by the support of carbonyl, anime and cy-
clopentadienyl ligands as a stabilizing co-ligand (L). Cr
complex [Cr(
6
-pcp)(CO)
3
] [6] and Ru complex [Ru(
6
-
pcp)(C
5
H
5
N)
2
Cl] [9] with a piano stool structure and Fe
complex [Fe(
6
-pcp)(
5
-C
5
H
5
)](BF
4
)
2
[8] with a triple-
decker structure have been crystallographically charac-
terized. On the other hand, the pcp complexes of the
coordination mode (b) [7,14,15] and (c) [16,17] have
been relatively limited. The crystal structures of Ru
complexes [Ru
2
(
5
,
5
-pcp)(
6
-C
6
Me
6
)
2
](BF
4
)
2
[14] and
* Corresponding author. Fax: +81-6-6730 5896.
E-mail address: maekawa@rist.kindai.ac.jp (M. Maekawa).
0020-1693/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII:S0020-1693(01)00720-4