Synthesis, spectroscopic and redox properties of ruthenium complexes with selenoether macrocycles: crystal structures of cis-[RuCl2([16]aneSe4)] and trans-[RuCl(PPh3)([16]aneSe4)]PF6 ([16]aneSe4 = 1,5,9,13-tetraselenacyclohexadecane)

Abstract

Reaction of [Ru(dmf)₆]Cl₃ (dmf = dimethylformamide) with 1 molar equivalent of [16]aneSe₄ (1,5,9,13-tetraselenacyclohexadecane) or 2 molar equivalents of [8]aneSe₂ (1,5-diselenacyclooctane) in refluxing EtOH yielded cis-[RuCl₂([16]aneSe₄)] or cis-[RuCl₂([8]aneSe₂)₂]. Reaction of [Ru(dmf)₆][CF₃SO₃]₃ with [16]aneSe₄ in the presence of either LiBr or NaI in refluxing EtOH yielded cis-[RuBr₂([16]aneSe₄)] or [RuI₂([16]aneSe₄)] respectively. The cis arrangements have been confirmed in solution by ⁷⁷Se-{¹H} NMR studies on the dichloro and dibromo derivatives, and in the solid state by a single-crystal structure determination on cis-[RuCl₂([16]aneSe₄)]. Refluxing cis-[RuX₂([16]aneSe₄)] (X = Cl or Br) in MeNO₂ yielded the trans-dihalogeno species exclusively. The compounds [MCl₂(PPh₃)₃] (M = Ru or Os) react with [16]aneSe₄ to give trans-[MCl(PPh₃)([16]aneSe₄)]⁺ which can be isolated by addition of PF₆^– counter ion. The single-crystal structure of [RuCl(PPh₃)([16]aneSe₄)]⁺ confirms the trans chlorophosphine arrangement, with the Se-based lone pairs of the macrocycle adopting the all-up configuration, such that the methylene groups of the ligand backbone are all directed to the opposite side of the RuSe₄ plane from the PPh₃ ligand. Electrochemical studies on the metal(II) compounds have been conducted, and the macrocyclic complexes all exhibit reversible M^II–M^III redox couples. The ruthenium(III) species [RuBr₂([16]aneSe₄)]Br has been prepared by Br₂ oxidation and isolated. These are the first macrocyclic selenoether complexes involving Ru^II, Os^II or Ru^III.