Structural and Redox Variations in Technetium Complexes Supported by <i>m</i>-Terphenyl Isocyanides

Abstract

A series of technetium complexes with the sterically encumbered m-terphenyl isocyanides CNArDipp2 (Dipp = 2,6-diisopropylphenyl) and CNArMes2 (Mes = 2,4,6-trimethylphenyl) has been prepared. The products span three different oxidation states (+1, +3, and +5) of the radioactive transition metal and comprise carbonyl, nitrosyl, chloride, and nitrido complexes. All members of this series (trans,mer-[TcI(CO)3Cl(CNArDipp2)], trans-[TcI(NO)Cl2(PPh3)(CNArDipp2)2], [TcIIICl3(PMe2Ph)2(L)] (L = CNArDipp2, CNArMes2), trans-[TcVNCl2(CNArDipp2)2], cis-[TcVNCl2(CNArMes2)2(L)] (L = H2O, MeOH), cis-[TcVNBr2(CNArMes2)2], and trans-[TcV(NPh)X2(CNArDipp2)2] (X = Cl, Br)) are stable under ambient conditions. The νCN IR frequencies measured for the complexes frequently appear at wavenumbers higher than those for the uncoordinated isocyanides, which suggests a low degree of back-donation into the CN π* orbitals of these ligands.