Reaction of [Re(CO)6]+ cation with cyclopentadienylthallium derivatives. Formation of cyclopentadienylrheniumtricarbonyl derivatives via [Re(CO)3L3]+ (L=solvent)

The reaction of [Re(CO)6]+ with cyclopentadienylthallium derivatives in DMSO or in DMF affords the corresponding cyclopentadienyltricarbonylrhenium derivatives with high yields. The cyclopentadienyl transfer from CpTl to [Re(CO)6][BF4] was also carried out in acetonitrile. However, in this case it is necessary to work in a sealed tube heated at 160 °C. Two compounds are obtained: the expected CpRe(CO)3 and a rhenium salt which was identified as [Re(CO)3(CH3CN)3][BF4]. The triacetonitrile tricarbonyl cation fac-[Re(CO)3(CH3CN)3]+ is also formed upon dissolution of [Re(CO)6][BF4] in acetonitrile and heating at 160 °C under pressure. It reacts afterwards with CpTl in acetonitrile to yield CpRe(CO)3 (32%). Thus, [Re(CO)3(CH3CN)3][BF4] can be considered as an intermediate for this ligand-transfer reaction.