benziporphyrin (meso-tetraarylpyriporphyrin) 3 and meso-tetraaryl-3-aza-mbenziporphyrin (N-confused meso-tetraarylpyriporphyrin) 4, are of interest as well
[21, 22].
The occurrence of a carbon atom in the inner cavity of 5, 7, 8 provides the suitable
(CNNN) surrounding, which enables creating a specific interaction of embedded mphenylene with inserted diamagnetic or paramagnetic metal cations [4, 9]. Importantly, the properties of organometallic complexes are controlled by suitable choices
of electronic factors and steric protection provided by the cautiously selected
external substitution of 5. It has been revealed that the coordination chemistry of
m-benziporphyrins takes several routes, which differ in the role of the arene moiety
[2, 16, 23–26]. In the context of the general topic assigned to this volume, it is
essential to recall that the organometallic derivatives of m-benziporphyrin resemble
the well-developed family of pincer ligand complexes, in which the metal–arene
bond is supported by two amine, sulfide, or phosphine arms 9–11 (Scheme 2) [27–
30]. Transition metal complexes containing the pincer-type ligands have attracted
scientifically well-justified interest [31–44].
The peculiar properties of the metal centers have been efficiently enforced by
pincer ligands. In organometallic complexes containing a direct transition metal–
carbon bond, chelation leads to the formation of metallacycles, which provide the
H
N
N
N
H
N
Ar
Ar
Ar
Ar
H
N
N
N
Ar
Ar
Ar
Ar
H
N
N
N
N
Ar
Ar
Ar
Ar
4
5
H
N
N
N
N
Ar
Ar
Ar
Ar
N
NH
N
HN
Ar
Ar
Ar
Ar
N
NH
HN
Ar
Ar
Ar
Ar
1
2
3
N
N
H
N
Ar
Ar
Ar
Ar
H
N
N
N
N
Ar
Ar
6
7
8
Scheme 1 meso-Tetraarylporphyrin 1 and derivatives: meso-tetraaryl-2-aza-21-carbaporphyrin
(N-confused porphyrin) 2, meso-tetraaryl-21-carbaporphyrin 3 and their m-phenylene analogues:
meso-tetraaryl-p-benziporphyrin 4, meso-tetraaryl-m-benziporphyrin 5, meso-tetraaryl-22-aza-mbenziporphyrin (meso-tetraarylpyriporphyrin) 6, meso-tetraaryl-3-aza-m-benziporphyrin 7, and
meso-diaryl-3-aza-m-benziporphyrin 8
A Pincer Motif Etched into a meta-Benziporphyrin Frame
183
[21, 22].
The occurrence of a carbon atom in the inner cavity of 5, 7, 8 provides the suitable
(CNNN) surrounding, which enables creating a specific interaction of embedded mphenylene with inserted diamagnetic or paramagnetic metal cations [4, 9]. Importantly, the properties of organometallic complexes are controlled by suitable choices
of electronic factors and steric protection provided by the cautiously selected
external substitution of 5. It has been revealed that the coordination chemistry of
m-benziporphyrins takes several routes, which differ in the role of the arene moiety
[2, 16, 23–26]. In the context of the general topic assigned to this volume, it is
essential to recall that the organometallic derivatives of m-benziporphyrin resemble
the well-developed family of pincer ligand complexes, in which the metal–arene
bond is supported by two amine, sulfide, or phosphine arms 9–11 (Scheme 2) [27–
30]. Transition metal complexes containing the pincer-type ligands have attracted
scientifically well-justified interest [31–44].
The peculiar properties of the metal centers have been efficiently enforced by
pincer ligands. In organometallic complexes containing a direct transition metal–
carbon bond, chelation leads to the formation of metallacycles, which provide the
H
N
N
N
H
N
Ar
Ar
Ar
Ar
H
N
N
N
Ar
Ar
Ar
Ar
H
N
N
N
N
Ar
Ar
Ar
Ar
4
5
H
N
N
N
N
Ar
Ar
Ar
Ar
N
NH
N
HN
Ar
Ar
Ar
Ar
N
NH
HN
Ar
Ar
Ar
Ar
1
2
3
N
N
H
N
Ar
Ar
Ar
Ar
H
N
N
N
N
Ar
Ar
6
7
8
Scheme 1 meso-Tetraarylporphyrin 1 and derivatives: meso-tetraaryl-2-aza-21-carbaporphyrin
(N-confused porphyrin) 2, meso-tetraaryl-21-carbaporphyrin 3 and their m-phenylene analogues:
meso-tetraaryl-p-benziporphyrin 4, meso-tetraaryl-m-benziporphyrin 5, meso-tetraaryl-22-aza-mbenziporphyrin (meso-tetraarylpyriporphyrin) 6, meso-tetraaryl-3-aza-m-benziporphyrin 7, and
meso-diaryl-3-aza-m-benziporphyrin 8
A Pincer Motif Etched into a meta-Benziporphyrin Frame
183