Rhenium and technetium complexes with tridentate N-[(N',N'-dialkylamino)(thiocarbonyl)]-N'-substituted benzamidine ligands

N-(Dialkylamino)(thiocarbonyl)]benzimidoyl chlorides react with functionalized amines such as 2-aminophenol, 2-methylaminopyridine, and 2-aminobenzoic acid in clean and high-yield procedures with the formation of the novel tridentate N-(N', N'-dialkylamino)(thiocarbonyl)]- N'-substituted benzamidine ligands H2L1, HL2, and H2L3. By starting from (NBu4)MOCl4] (M = Re, Tc) or ReOCl3(PPh3)2] and H2L1, a series of oxorhenium(V) and oxotechnetium(V) complexes of the composition MOCl(L1)] were synthesized and characterized by spectroscopic methods and X-ray crystallography. The monomeric, five-coordinate compounds are air-stable and bind (L1)(2-) tridentate in the equatorial coordination sphere. Dimeric products of the compositions (ReOCl(L2))2O] and ReOCl(L3)]2 were isolated during reactions with HL2 and H2L3. While dimerization in (ReOCl(L2))2O] is established via an oxo bridge, the metal atoms in ReOCl(L3)]2 are connected by the carboxylic group of the ligand, and the product represents the first example of a high-oxidation state rhenium complex displaying such a bonding feature.