om950537z_si_001.pdf (1.37 MB)
Niobium−Carbon Functionalities Supported by meso-Octaethylporphyrinogen and Derived Macrocycles
journal contribution
posted on 1996-01-09, 00:00 authored by Sylviane Isoz, Carlo Floriani, Kurt Schenk, Angiola Chiesi-Villa, Corrado RizzoliThis report concerns the organometallic chemistry of niobium based
on a macrocyclic ligand.
To this purpose, the
(meso-octaalkylporphyrinogen)niobium(V) complex
[(η5:η1:η5:η1-Et8N4)NbCl], 2, has been used as an appropriate starting material.
The ionization of the Nb−Cl
bond by the use of AgSO3CF3 gave a
bifunctional acid−base system with an increased acidity
of the metal center in
[(η5:η1:η1:η1-Et8N4)Nb(THF)(O3SCF3)],
3. The alkylation of 2 with
LiMe
gave a quite stable Nb(V) organometallic derivative
[(η5:η1:η1:η1-Et8N4)Nb−Me],
4, which
undergoes a migratory insertion reaction with ButNC
leading to an η2-iminoacyl derivative
[(η5:η1:η1:η1-Et8N4)Nb(ButNC)(η2-C(Me)NBut)],
6 (νCN, 2217 and
1736 cm-1). Two steps
of the reaction have been identified. An attempt to functionalize
the NbO in
[(η5:η1:η1:η1-Et8(C4H2N)3(p-MeC5H2N)NbO],
7, by the use of LiMe led, on the contrary, to
[(η1:η1:η1:η1-Et7(CH-Me)(C4H2N)3(p-MeC5H2N)NbOLi(THF)3],
derived from the metalation of one of the
meso-ethyl groups in 9. While X-ray analysis
provided information on the solid state
structures of 3, 4, 6, and
9, NMR studies allowed us to establish a relationship
between the
bonding mode of the porphyrinogen in the solid state and in solution.