In search of tris(trimethylsilylcyclopentadienyl) thorium†
Reduction of Cp′3ThCl, Cp′3ThBr, and Cp′3ThI (Cp′ = C5H4SiMe3) with potassium graphite generates dark blue solutions with reactivity and spectroscopic properties consistent with the formation of Cp′3Th. The EPR and UV-visible spectra of the solutions are similar to those of crystallographically-characterized tris(cyclopentadienyl) Th(III) complexes: [C5H3(SiMe3)2]3Th, (C5Me4H)3Th, (C5tBu2H3)3Th, and (C5Me5)3Th. Density functional theory (DFT) analysis indicates that the UV-visible spectrum is consistent with Cp′3Th and not [Cp′3ThBr]1−. Although single crystals of Cp′3Th have not been isolated, the blue solution reacts with Me3SiCl, I2, and HCCPh to afford products expected from Cp′3Th, namely, Cp′3ThCl, Cp′3ThI, and Cp′3Th(CCPh), respectively. Reactions with MeI give mixtures of Cp′3ThI and Cp′3ThMe. Evidence for further reduction of the blue solutions to a Cp′-ligated Th(II) complex has not been observed. The crystal structures of Cp′3ThMe and (Cp′3Th)2(μ-O) were also determined as part of these studies.