Organometallic cyclisation reactions. Part II. Formation of molybdenum arsine complexes containing five-membered rings

Abstract

A reductive cyclisation reaction occurs when complexes of the type [Mo(η-C₅H₅)(CO)₂I(L)](L is a halogen-substituted tertiary arsine) react with sodium amalgam in tetrahydrofuran giving cyclic molybdenum–arsine complexes. The stereochemical non-rigidity of the ring systems in solution has been interpreted in terms of a square-pyramidal–trigonal-bipyramidal isomerisation process. The cyclic complex dicarbonyl (η-cyclopentadienyl)(3-dimethylarsinopropyl-C¹As) molybdenum(II) readily undergoes hydride abstraction to form a cationic derivative of chelated allyldimethylarsine.