Synthesis of 2-Ferrapyridine Complexes and Their Use as Precursors for Substituted Pyridinones and Pyrroles

Thomas E. Snead, Chad A Mirkin*, Kuang Lieh Lu, Heather L. Beckman, Gregory L. Geoffrey, Arnold L. Rheingold, Brian S. Haggerty

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

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 isomers 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.

Original languageEnglish (US)
Pages (from-to)942-954
Number of pages13
JournalOrganometallics
Volume11
Issue number2
DOIs
StatePublished - Feb 1 1992

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

Fingerprint Dive into the research topics of 'Synthesis of 2-Ferrapyridine Complexes and Their Use as Precursors for Substituted Pyridinones and Pyrroles'. Together they form a unique fingerprint.

Cite this