Syntheses, Crystal Structures, and Conversion of Three Linkage Isomers of Di-2-pyridyl Ketone in Dichlorobis(dimethyl sulfoxide-S)ruthenium(II) and Chlorobis(dimethyl sulfoxide-S)ruthenium(II) Complexes: [RuCl2(dpk-κ2N,O)(dmso-S)2], [RuCl2(dpk-κ2N,N′)(dmso-S)2], and [RuCl(dpk-OH-κ3N,O,N′)(dmso-S)2

Abstract

Abstract The reaction between trans-[RuCl2(dmso-S)4] (dmso = dimethyl sulfoxide) and di-2-pyridyl ketone (dpk) in H2O at room temperature afforded trans(Cl),cis(S)-[RuCl2(dpk-κ2N,O)(dmso-S)2] (1) in high yield, while the reaction between cis(Cl),fac(S)-[RuCl2(dmso-S)3(dmso-O)] and dpk in EtOH–DMSO at reflux afforded cis(Cl),cis(S)-[RuCl2(dpk-κ2N,N′)(dmso-S)2] (2). Reaction of 1 with Ag+ and OH− afforded the one-dimensional Ru–Ag coordination polymer trans(Cl),cis(S)-[AgRuCl2(dpk-OH-κ3N,O,N′)(dmso-S)2]n (3), which, as shown by X-ray crystallographic analysis, was in an “arrested” state of chloride ion abstraction. Reaction of 3 in DMSO afforded a mixture of two isomers containing dpk-OH-κ3N,O,N′: trans(Cl,O),cis(S)- and cis(Cl,O),cis(S)-[RuCl(dpk-OH-κ3N,O,N′)(dmso-S)2] (4a and 4b, respectively). The trans(Cl,O),cis(S)-isomer 4a was selectively synthesized by reaction of 1 with OH− in H2O, while the cis(Cl,O),cis(S)-isomer 4b was selectively synthesized by reaction of 2 with OH− in H2O. The isomerization reaction between 4a and 4b in DMSO solution was found to be reversible, and 4b was favored over 4a, with K4ab = [4b]/[4a] = 1.5 ± 0.1. The crystal structures of 1 and 2 showed that the geometry of the RuCl2(dmso-S)2 unit caused selective formation of the κ2N,O- and κ2N,N′-coordination modes of the dpk ligand. In 4a, the flexibility of the κ3N,O,N′-coordination mode of the (dpk-OH)− ligand mitigates the steric hindrance caused by the RuCl(dmso-S)2+ unit.