Reactions of sterically congested secondary silanes with iron carbonyls. Formation of μ-silylene complexes Fe₂(CO)₈(μ-SiR₂) (R = mesityl and O(2,6-ⁱPr₂C₆H₃))

Reaction of dimesitylsilane with enneacarbonyldiiron in hot hexane yielded octacarbonyl(μ-dimesitylsilylene)diiron as thermally stable yellow crystals, for which the average bond lengths determined by X-ray crystallography are FeFe 2.721(2) and FeSi 2.404(2) Å, and the ²⁹Si NMR chemical shift of the bridging silylene is 145.1 ppm. Similarly, the reaction of bis(2,6-diisopropylphenoxy)silane with dodecacarbonyltriiron in refluxing toluene afforded octacarbonyl{μ-bis(2,6-diisopropylphenoxy)silylene}di-iron, whereas a similar treatment of the slightly bulkier bis(2,6-di-tert-butylphenoxy)silane with enneacarbonyldiiron or dodecacarbonyltriiron did not give the corresponding μ-silylene complex.