Dimeric rhenium(I) carbonyl complexes with thiosemicarbazone backbone

Dimeric, neutral rhenium(l) complexes of the composition [Re-2(CO)(6)X(L-R)] (X = Cl or Br) are formed when [NEt4](2)[Re(CO)(3)Br-3] or [Re(CO)(3)Cl(CH3CN)(2)] react with 2,2'-dipyridylketone thiosemicarbazones (HLR, R = H, Ph). The thiosemicarbazones deprotonate during the reaction and connect two tricarbonylrhenium(I) units as formally pentadentate bridging ligands. This results in an extremely rare coordination mode, in which the two nitrogen atoms of the hydrazone unit bind to each one of the rhenium atoms. The bond lengths inside the thiosemicarbazonato backbone reflect a large degree of delocalization of electron density.