Triferrocenylphosphineiron carbonyls by substitution and disproportionation processes

Abstract Mono-(I), bis-(II), and tris-(triferrocenylphosphine)iron carbonyls (III) were obtained photochemically or thermally in high yields. The photochemical reaction of triferrocenylphosphine with iron pentacarbonyl was found to proceed only at elevated temperature, and it was discovered that I, first formed almost quantitatively, is converted to III by a disproportionation process. Complex II is not formed as an intermediate, notwithstanding the fact that II can be obtained by photochemically induced disproportion, as well as by thermally initiated substitution, from I as starting material. Several aspects of the reaction were explored, and a mechanism is suggested to account for the observed behavior. The product of the thermally initiated reaction of triferrocenylphosphine with butadieneiron tricarbonyl was characterized as a tris(phosphine)iron dicarbonyl (IV), structurally different from III. An examination of carbonyl stretching bands indicated that I and II are very probably trigonal bipyramidal in configuration with the phosphine ligand axially disposed. Consideration is given to possible structural configurations for III and IV.