Reaction Control of Dynamic Complexes with Multiple Bonds of Heavy Group-14 Elements

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During the period of 2002-2004, our study was directed toward the creation of new types of doubly bonded compounds of heavier group-14 element, elucidation of their structure and properties, and control of their unique dynamic properties. The following are the major achievements : As the first compound having formally 5p-hybridized silicon atom, a stable trisilaallene was synthesized using a stable silylene that was synthesized by us in 1999. Related trigermaallene, β-digerrnasilaallene, and β-disilagermaallene were also synthesized. X-ray analysis of these allenes has shown tot in contrast to carbon allenes, all of them have a significantly bent skeleton. As the most remarkable dynamic behavior, trisilaallene and β-disilagermaallene showed temperature dependent dynamic disorder of the central heavy grouo-14 atom. The detailed investigation of the dynamic process both experimentally and theoretically revealed that the process is explained by the facile rotation of the central atom around the terminal two silicon atoms. The dynamic disorder was not observed in the trigermaallene and β-digermasilaallene because of the severe bending at the terminal germanium atoms. Thermally stable silicon-chalcogen doubly bonded compounds (silanethione, silaneseleone, and silanetellone) were synthesized, using our stable dialkylsilylene. The first systematic analysis of the X-ray and UV-vis spectra of a series of silicon-chalcogen doubly bonded compounds revealed the element dependence of the strength of the double bonds and n π^* and n π^* absorption bands. The first 14-electron disilene-palladium complex that was synthesized by the reaction of a bis (phosphine) palladium with a stable disilene was found by the X-ray analysis and theoretical calculations to have the strong jx-disilene complex character.