ReVN and TcVN complexes with a novel tetradentate hybrid benzamidine/thiosemicarbazone ligand

N-(diethylthiocarbamoyl)benzimidoyl chloride reacts with o-aminoacetophenone 4-methylthiosemicarbazone under formation of a novel N2S2 benzamidine/thiosemicarbazone ligand (H2L). The reaction of H2L with [ReNCl2(PPh3)2] yields a red complex of the composition [ReN(L)]. The molecular structure of [ReN(L)] reveals a square-pyramidal environment around the Re atom, in which the organic ligand occupies all four positions of the equatorial plane. The reaction of H2L with [TcNCl2(PPh3)2] results in a mixture of [TcN(L)] and a side-product of the composition [TcN(PPh3){Et2NC(S)NH}(L′)] (L′ = 1,10b-dimethyl-5-phenyl-1,10b-dihydro-[1,2,4]triazolo[1,5-c]quinazoline-2-thiolate). The formation of diethylthiourea and HL′ is the result of a metal-driven decomposition of H2L followed by cyclization.

The novel N2S2 benzamidine/thiosemicarbazone hybrid ligand H2L reacts with [TcNCl2(PPh3)2] under formation of a mixture of [TcN(L)] and a side-product containing two fragments of H2L, while with the analogous rhenium precursor [ReN(L)] is formed exclusively.Figure optionsDownload as PowerPoint slideHighlights
► A tetradentate benzamidine/thiosemisemicarbazone hybride ligand has been prepared.
► The novel ligand forms stable [MN(L)] complexes (M = Re, Tc).
► A metal-driven decomposition of H2L is observed with [TcNCl2(PPh3)2].
► The decomposition fragments of H2L coordinate to Tc.