From symmetrical to asymmetrical nitrido phosphino-thiol complexes: a new class of neutral mixed-ligand (99m)Tc compounds as potential brain imaging agents.

A general procedure is presented for the preparation of a new class of nitrido asymmetrical Tc-99m complexes containing two different bidentate ligands bound to the same [Tc(N)]2+ core that could be used to design either essential or target specific imaging agents. This procedure is based on the chemical properties of a new monosubstituted [Tc(N)(R2PS)Cl(PPh3)] species composed of a TcN multiple bond and an ancillary phosphine thiol ligand (R2PSH). This intermediate readily reacts with bidentate mononegative ligands (S--Y) containing soft pi-donor coordinating atoms to give neutral pentacoordinate asymmetrical complexes of the type [Tc(N)(R2PS)(S--Y)].

Synthesis of a Novel Class of Trigonal Bipyramidal Nitrido Tc(V) Complexes with Phosphino-Thiol Ligands. Crystal Structure of [(99g)Tc(N)(L(1))(2)] [L(1) = 2-(Diphenylphosphino)ethanethiolato] and [(99g)Tc(N)(L(5))(2)] [L(5) = 2-(Ditolylphosphino)propanethiolato].

Reactions of the precursor complexes [(99g)Tc(N)Cl(2)(PPh(3))(2)] and [(99g)Tc(N)Cl(4)](-) with phosphine-thiol ligands (HL(n)()) of the type R(2)PCH(2)CH(2)SH (R = phenyl, methoxypropyl), R(2)'PCH(2)CH(2)CH(2)SH (R' = phenyl, tolyl), and R(2)' 'P-o-C(6)H(4)SH (R' ' = phenyl) afforded the five-coordinated, disubstituted nitrido technetium(V) complexes [(99g)Tc(N)(L(n)())(2)]. The complexes were characterized by elemental analysis, (1)H and (31)P NMR spectroscopy, FT IR, and positive FAB MS spectra. Structural characterization of [(99g)Tc(N)(L(1))(2)] (1) [HL(1) = (C(6)H(5))(2)PCH(2)CH(2)SH] and [(99g)Tc(N)(L(5))(2)] (5) [HL(5) = (o-CH(3)C(6)H(4))(2)PCH(2)CH(2)CH(2)SH] showed that the bidentate phosphino-thiol ligands are coordinated to the technetium center through the neutral phosphorus atom and the deprotonated thiol sulfur atom.