Syntheses and structures of pyrazolylmethane complexes of rhenium(iii), (iv) and (v)

Abstract

Reaction of [ReOCl₃(PPh₃)₂] with HCpz₃ (pz = pyrazole) in dichloromethane leads to the formation of a new Re(IV) complex [ReCl₃(HCpz₃)]X (XCl, [ReO₄]) with loss of the rhenium-oxo group. We also report a convenient, high-yield synthetic route to complexes of the type [ReOX_n(L)]^{(3 − n)+} (XCl, Br, n = 2, 3) by the reaction of bis(pyrazolylmethane) and bis(pyrazolylacetate) ligands with [ReOCl₃(PPh₃)₂]. Dinuclear complexes containing the ORe–O–ReO group were also isolated and structurally characterised. We have also investigated the reactions of these ligands with diazenide precursors and isolated and characterised complexes of the type [ReCl_x(N₂Ph) (L)(PPh₃)] (x = 1,2). The potential applications of these complexes as radiopharmaeuticals is discussed.