Synthesis, characterization, and crystal structure of aqua­bis­(4,4′-dimeth­oxy-2,2′-bi­pyridine)[μ-(2R,3R)-tartrato(4−)]dicopper(II) octa­hydrate

Typical electroless copper baths (ECBs), which are used to chemically deposit copper on printed circuit boards, consist of an aqueous alkali hydroxide solution, a copper(II) salt, formaldehyde as reducing agent, an l-(+)-tartrate as complexing agent, and a 2,2′-bi­pyridine derivative as stabilizer. Actual speciation and reactivity are, however, largely unknown. Herein, we report on the synthesis and crystal structure of aqua-1κO-bis­(4,4′-dimeth­oxy-2,2′-bi­pyri­dine)-1κ(2) N,N′;2κ(2) N,N′-[μ-(2R,3R)-2,3-dioxidosuccinato-1κ(2) O (1),O (2):2κ(2) O (3),O (4)]dicopper(II) octa­hydrate, [Cu(2)(C(12)H(12)N(2)O(2))(2)(C(4)H(2)O(6))(H(2)O)]·8H(2)O, from an ECB mock-up. The title compound crystallizes in the Sohncke group P2(1) with one chiral dinuclear complex and eight mol­ecules of hydrate water in the asymmetric unit. The expected retention of the tartrato ligand’s absolute configuration was confirmed via determination of the absolute structure. The complex mol­ecules exhibit an ansa-like structure with two planar, nearly parallel bi­pyridine ligands, each bound to a copper atom that is connected to the other by a bridging tartrato ‘handle’. The complex and water mol­ecules give rise to a layered supra­molecular structure dominated by alternating π stacks and hydrogen bonds. The understanding of structures ex situ is a first step on the way to prolonged stability and improved coating behavior of ECBs.