Syntheses and reactivity studies of solvated dirhenium acetonitrile complexes

Abstract

Fully and partially solvated triply-bonded [Re₂]⁴⁺ complexes have been synthesized and their X-ray structures are described. A fully solvated dirhenium salt with BAr_f [tetrakis(3,5-bis(trifluoromethyl)phenyl)borate] as the counter anion [Re₂(CH₃CN)₁₀][BAr_f]₄ (1) has been characterized. The solubility of the complex in CH₂Cl₂ and THF in addition to CH₃CN offers the possibility of improved reactivity. The structure of [Re₂(µ-O)(CH₃CN)₁₀][BF₄]₄ (2) that possesses a linear [Re^III–O–Re^III]⁴⁺ unit is reported. Protonation reactions of cis-Re₂Cl₂(dppm)₂(O₂CCH₃)₂ and trans-Re₂Cl₄(dppm)₂ with HBF₄·Et₂O in acetonitrile afforded cis and trans [Re₂(dppm)₂(CH₃CN)₆][BF₄]₄ (3 and 4), respectively. Prolonging the reaction time, however, does not lead to fully solvated complex [Re₂(CH₃CN)10][BF₄]₄. The neutral nitrogen donor ligands pynp (2-(2-pyridyl)-1,8-naphthyridine) and tznp (2-(2-thiazolyl)-1,8-naphthyridine) react readily with [Re₂(CH₃CN)₁₀][BF₄]₄ to provide trans-[Re₂(pynp)₂(CH₃CN)₄][BF₄]₄ and trans-[Re₂(tznp)₂(CH₃CN)₄][BF₄]₄. The X-ray structures trans-[Re₂(pynp)₂(CH₃CN)₄][BF₄]₄ (5) and trans-[Re₂(tznp)₂(CH₃CN)₄][BF₄]₃[PF₆] (6) have been determined.