Synthesis and structure of di-µ-oxo nitridotechnetium(VI) dimers and a monomeric nitridotechnetium(V) mixed-ligand complex

Abstract

The di-µ-oxo technetium(VI) complexes [{TcN(S₂CNEt₂)}₂(µ-O)₂]1, [{TcN(S₂CNC₄H₈)}₂(µ-O)₂]2, [AsPh₄]₂[{TcN(CN)₂}₂(µ-O)₂]4 and [AsPh₄]₂[{TcN(edt)}₂(µ-O)₂]5(H₂edt = ethane-1,2-dithiol) have been prepared either by reaction of [{TcN(OH₂)₃}₂(µ-O)₂]²⁺ or Cs₂[TcNCl₅] in Na₄P₂O₇ solution with the appropriate ligand. The ESR spectra of solutions of 1 and 2 in SOCl₂ and of 4 in MeCN with added AsPh₄Cl·HCl showed that cleavage of the dimer occurs to give the nitridotechnetium(VI) monomers [TcNCl₂(S₂CNR₂)](R = Et or R₂= C₄H₈) or [TcNCl₂(CN)₂]^–. Reaction of [Tc^VINCl₂(S₂CNEt₂)] with K₂[SCOCOS] gave the mixed-ligand complex [AsPh₄][Tc^VN(S₂CNEt₂)(SCOCOS)]3. Single-crystal X-ray structures (Cu-Kα radiation) were determined for 1, 2 and 3. Complexes 1 and 2 are dimeric and are best described as two edge-sharing square pyramids, with TcN and Tc–Tc distances of 1.623(4), 1.624(4), 2.543(1), and 1.65(2), 1.59(2) and, 2.542(2)Å for 1 and 2 respectively. Complex 3 is monomeric with the technetium atom having a square pyramidal geometry, and a TcN distance of 1.54(2)Å.