Synthesis and properties of novel substituted 4,5,6,7-tetrahydroindenes and selected metal complexes

The synthesis of a complete series of substituted 4,5,6,7-tetrahydroindenes (4,5,6,7-tetrahydroindene, 1; 1-methyl-, 1,3-dimethyl- and 1,2,3-trimethyl-4,5,6,7-tetrahydroindene, 2-4) is reported. The synthesis of ferrocenes (8-11) from these substituted cyclopentadienes is described. The electrochemistry of these ferrocenes indicates that these complexes are more readily oxidized than ferrocene and that the effect of methyl or alkyl substituents on the ease of oxidation is additive. A single crystal X-ray structure of two of the ferrocenes, bis(1,3-dimethyl-4,5,6,7-tetrahydroindenyl)iron(II), 10, and bis(1,2,3-trimethyl-4,5,6,7-tetrahy-droindenyl)iron(II), 11, indicates that steric hindrance causes the alkyl substituents to be bent away from the plane of the cyclopentadienyl ring. However, the structures differ in that the cyclopentadienyl rings in 10 are staggered wheras those in 11 are eclipsed. The synthesis of the cyclopentadienyltricarbonylmethyl compounds of molybdenum and tungsten from 3 and 4 is also described.