Structure of [N,N′-bis(3,5-di-t-butyl-salicylidene)-2-benzyl-1,3- propanediaminato]nitridotechnetium(V) complex, TcN(bzdbsalpn), and nitrido-bridged linear polymeric chains in crystalline syn-isomer

A novel nitridotechnetium(V) complex with a tetradentate Schiff base ligand, TcN(bzdbsalpn), was synthesized by the reaction of TcNCl ₂(PPh₃)₂ and N,N′-bis(3,5-di-t-butyl- salicylidene)-2-benzyl-1,3-propanediamine (H₂bzdbsalpn). Both the syn- and anti-isomers of TcN(bzdbsalpn) were formed in the solution, but recrystallization of a mixture of syn- and anti-TcN(bzdbsalpn) gave a single crystal only for the syn-isomer. X-ray crystallography showed that the syn-TcN(bzdbsalpn) was in a distorted octahedral structure. The planar tetradentate bzdbsalpn ligand coordinates to the technetium atom in an O-N-N-O equatorial plane and the six-membered N_imine-N_imine chelate ring that includes the propylene group adopts a chair conformation. The nitrido ligand (Tc≡N) is at an apical position and the Tc≡N triple bond length is 1.6 Å. Interestingly, the crystal of syn-TcN(bzdbsalpn) has a nitrido-bridged linear polymeric structure (⋯Tc≡N⋯ Tc≡N⋯) running along the 2₁ screw axes parallel to the b axis. The intermolecular N⋯Tc distance in the syn-TcN(bzdbsalpn) crystal (∼2.8 Å) is fairly long compared with that reported for Cr(V) and Mn(V) nitrido complexes with analogous Schiff base ligands (∼2.5 Å).