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 MII–MIII 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 RuII, OsII or RuIII.