Preparation and crystal structures of silyl-substituted potassium cyclooctatetraenides

Abstract

Cyclooctatetraenyl complexes of potassium are readily available by the reaction of silyl-substituted cyclooctatrienes C8H8-1,4-(SiR3)2 (SiR3 = SiMe3, SiMe2tBu, SiPh3) with potassium hydride or potassium metal. While C8H8-1,4-(SiMe3)2 gave a mixture of K2{C8H6-1,3-(SiMe3)2} (1a) and K2{C8H7-SiMe3} (1b), the substitution pattern on the COT ring remained unchanged in the case of C8H8-1,4-(SiMe2tBu)2 and C8H8-1,4-(SiPh3)2. [{K2{C8H6-1,4-(SiMe2tBu)2}(PhMe)}∞] (2) crystallizes in the absence of DME, featuring a μ4-bridging COT ring, while in [K2(C8H6-1,4-(SiPh3)2)(DME)4] (3) the substituted COT ligand adopts a highly symmetric μ-η8:η8-coordination, resulting in an “inverse sandwich” architecture. Compound 3 could be oxidized by treatment with iodine to give the corresponding neutral cyclooctatetraene derivative C8H6-1,4-(SiPh3)2 (4).