Cobaltocene reductions of multiply bonded dirhenium complexes. II. The isolation of the paramagnetic species [(η5-C5H5)2Co][Re2(hp)4X2] (hp = anion of 2-hydroxypyridine; X = Cl,Br, or I)

Reaction of the quadruply bonded dirhenium(III) complexes (n-Bu₄N)₂Re₂X₈ (X = Cl, Br, or I) with 2-hydroxypyridine (Hhp) in refluxing n-pentanol gives Re₂(hp)₄X₂ in high yield (>;90%). These complexes are reduced by cobaltocene to yield the paramagnetic salts (η⁵-C₅H₅)₂Co]Re₂(hp)₄X₂]. The spectroscopic (electronic absorption and infrared) and electrochemical properties of these sets of complexes are in accord with them possessing σ²π⁴δ²(Re₂⁶⁺) or σ²π⁴δ²δ*¹(Re₂⁵⁺ ground state electronic configurations.