Toward absolute asymmetric synthesis of coordination polymers with bidentate sulfide ligands

In search for sulfide-containing coordination polymers that crystallize as conglomerates, five new copper(I) complexes with prochiral sulfide ligands have been prepared and characterized by single crystal X-ray structure determination. Three unsymmetrical sulfides have been used: phenyl propargyl sulfide (Sprop), allyl methyl sulfide (Sally), and 2,5-dithiahexane (SS). In [CuCl(Sprop)]n (1), layers are formed via π-coordination of propargyl groups to copper(I). In [Cu2Br2(Sprop)4] (2), discrete dimers form with non-coordinating propargyl groups. In [CuCl(Sally)]n (3), layers are formed via π-coordination of allyl groups to copper(I), but disordered Sally ligands are also found. The mesitylcopper complex [Cu4(Mes)4(Sally)2] (4) is chiral but discrete. In [Cu4(Mes)4(SS)]n (5), racemic chains are formed by the SS ligand. Three out of five complexes prepared thus form coordination polymers, and all of the five complexes (1–5) exhibit terminal sulfide ligands that could be oxidized selectively when incorporated in an enantiopure polymer. Unfortunately none of 1–5 crystallized as a conglomerate, but whether this reflects an inherent tendency in this system is too early to say.

Graphical abstractNew chiral copper coordination polymers with prochiral sulfide ligands have been prepared and crystallized in search for total spontaneous resolution and enantioselective oxidation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► New chiral copper coordination polymers. ► Prochiral sulfide ligands for enantioselective oxidation. ► Toward absolute asymmetric synthesis.