Boryl- and Silyl-Substituted Mixed Sandwich Compounds of Scandium

An improved, one-pot synthesis of the linear sandwich compound [Sc(η⁵ -C₅ H₅ )(η⁸ -C₈ H₈ )] is presented. The synthetic procedure is amenable to boryl- and silyl-substituted cyclopentadienyl and cyclooctatetraenyl ligands, thereby yielding the first functionalized derivatives. We found that the synthesis of the silyl-substituted mixed sandwich complexes produces higher yields when the ligand exchange is carried out stepwise, by isolating the intermediate trimethylsilylated half-sandwich complex [Sc(η⁸ -C₈ H₇ SiMe₃ )Cl(THF)] (THF=tetrahydrofuran). The molecular structures of the parent complex, as well as of its mono-boryl-substituted derivatives, have been determined by single-crystal X-ray diffraction. In addition, the optical and electrochemical properties of the mixed sandwich complexes are reported.