21-vinyl-21-carbaporphyrin 90-Rh, creating the 21-vinyl unit from the
21-ethylidene one (Scheme 48) [25].
Gold(III) 22-methyl-m-benziporphyrin (29-Me)-Au has also been found to be
prone to contraction [24]. The reaction of 22-methyl-m-benziporphyrin 29-Me with
sodium tetrachloroaurate(III) in benzene gave a mixture of gold(III) 21-methyl-mbenziporphyrins 91-Au and 92-Au with an almost quantitative yield (95%) (Scheme
43) [24]. The insertion of gold(III) conducted in dichloromethane afforded solely
(29-Me)-Au, which readily transformed into 91-Au and 92-Au in the course of
column chromatography (Scheme 49).
92-Au converts to the weakly aromatic ketone derivative 93-Au, which is the
result of the formal substitution of a formyl group with a hydroxyl group. The
resulting species undergoes keto-enol tautomerization 94-Au–95-Au (Scheme 50)
[24].
N
N
N
Ph
Ph
Tol
Tol
Rh
CH 3
-[H2]
N
N
N
Ph
Ph
Tol
Tol
Rh
CH 3
N
N
N
Ph
Ph
Tol
Tol
Rh
CH 3
Cl
+
+H
+
base
N
N
N
Ph
Ph
Tol
Tol
Rh
CH 2
Cl
85-Rh
88-Rh
89-Rh
90-Rh
Scheme 48 Acid–base reactivity of rhodium(III) 21-(μ-ethylidene)-21-carbaporphyrins 85-Rh
N
N
N
Ph
Ph
Tol
Tol
Au
N
N
N
Ph
Ph
Tol
Tol
Au
N
N
N
Ph
Ph
Tol
Tol
Au
92-Au
2+
OHC
N
N
H
N
Ph
Ph
Tol
Tol
21-Me
(29-Me)-Au
91-Au
+
+
+
Al 2 O 3
Na[AuC l 4] 2H 2 O
.
Scheme 49 Reactivity of gold(III) m-benziporphyrin (29-Me)-Au
N
N
N
Ph
Ph
Tol
Tol
Au
N
N
N
Ph
Ph
Tol
Tol
Au
92-Au
93-Au
94-Au
95-Au
OHC
O
N
N
N
Ph
Ph
Tol
Tol
Au
HO
N
N
N
Ph
Ph
Tol
Tol
Au
O
H
+
OH
-
Scheme 50 Formation of gold(III) 2-oxy-21-carbaporphyrin and its tautomerization
A Pincer Motif Etched into a meta-Benziporphyrin Frame
217