SYNTHESIS AND STRUCTURE OF DI-MU-OXO NITRIDOTECHNETIUM(VI) DIMERS AND A MONOMERIC NITRIDOTECHNETIUM(V) MIXED-LIGAND COMPLEX

The di-mu-oxo technetium(VI) complexes [{TcN(S2CNEt2)}2(mu-O)2] 1, [{TcN(S2CNC4H8)}2(mu-O)2] 2, (AsPh4]2[{TcN(CN)2}2(mu-O)2] 4 and [AsPh4]2[{TcN(edt)}2(mu-O)2] 5 (H-2edt = ethane-1,2-dithiol) have been prepared either by reaction of [{TcN(OH2)3}2(mu-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 [TcVINCl2(S2CNEt2)] with K2[SCOCOS] gave the mixed-ligand complex [AsPh4][TcVN(S2CNEt2)(SCOCOS)] 3. Single-crystal X-ray structures (Cu-Kalpha 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 Tc=N 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) angstrom for 1 and 2 respectively. Complex 3 is monomeric with the technetium atom having a square pyramidal geometry, and a Tc=N distance of 1.54(2) angstrom.