138353-40-9Relevant academic research and scientific papers
Synthesis of 2-ferrapyridine complexes and their use as precursors for substituted pyridinones and pyrroles
Snead, Thomas E.,Mirkin, Chad A.,Lu, Kuang-Lieh,Beckman, Heather L.,Geoffroy, Gregory L.,Rheingold, Arnold L.,Haggerty, Brian S.
, p. 942 - 954 (1992)
The 2-ferra-3-azetine complexes Fe2(μ-CHCH=NR)(CO)6, which form from the reaction of Fe2(μ-CH2)(CO)8 with phosphinimines, have been found to react photochemically with a variety of alkynes (R1C≡CR2) by inserting the alkyne into the four-membered metallacycle to give the 2-ferrapyridine complexes Fe2(μ-C(R1)C(R2)CHCH=NR)(CO)6. Two of the 2-ferrapyridine complexes have been crystallographically characterized and shown to consist of six-membered metallacycles having adjacent iron and nitrogen atoms with this metallacycle π-coordinated to the second iron atom by three carbon atoms and an Fe-Fe bond. Terminal alkynes (R1 = Me, Ph, But, SiMe3) undergo the insertion regioselectively to give only the 2-ferrapyridine isomer with the substituted carbon adjacent to the iron atom. Unsymmetrical internal alkynes insert to give generally a mixture of isomere which is influenced by the steric and electronic nature of the alkyne substituents. The 2-ferrapyridine complex Fe2(μ-C(Ph)CHCHCH=NBut)(CO)6 was shown to undergo a ring contraction when heated at 160°C under CO (500 psi) to give the new 2-ferra-3-azetine complex Fe2{μ-C[CH=C(Ph)(H)]CH=NR}(CO)6, which has also been crystallographically characterized and has a vinyl substituent attached to the 3-carbon of the 2-ferra-3-azetine ring. When heated, the 2-ferrapyridine complexes released 2-pyridinones and pyrroles with the ratio of these products dependent upon the ring substituents and the conditions employed. For example, the 2-ferrapyridine complexes prepared from terminal alkynes gave 2-pyridinones as the major products. The reaction of 2-ferrapyridine complexes prepared from internal alkynes gave mixtures of 2-pyridinones and pyrroles. The presence of electron-donating substituents on the 2-ferrapyridine ring favored the formation of 2-pyridinones, as did the presence of halide ion and an atmosphere of CO in the thermolysis reactions.
