Formation of N-methylated cyclic ligand systems from unusual reactions between trimethylamine N-oxide and acetylenes on Fe₃Te₂(CO)₉ and contrast with reactions on Fe₃E₂(CO)₉(E = S, Se)

Abstract

Activation of C-H bonds of N-methyl groups has been achieved on cluster support. Use of a noncoordinating solvent in the reaction of Me₃NO.2H₂O, acetylenes, and Fe₃Te₂(CO)₉ leads to activation of N-methyl groups of Me₃NO and formation of N,N-dimethyldihydropyrrole (1) and N,N'-dimethylhexahydropyrimidine (2) ring systems. The NMe₃ ligand, resulting from TMNO, is retained on the metal cluster due to the absence of a coordinating solvent and reacts with incoming acetylenes. In contrast, activation of the N-methyl groups of Me₃NO is not observed in the reaction using Fe₃S₂(CO)₉, which yields complexes with vinylferrocene (3) and 1,4-diferrocenylbuta-1,3-diene-2,3-dithio (4) units attached to Fe₂S₂(CO)₆. All new compounds have been structurally characterized by single-crystal X-ray diffraction studies.