Two dinuclear pyrophosphate-bridged copper(II) complexes displaying unusually strong Osingle bondHsingle bondO interactions

The crystal and molecular structures of two copper(II) dinuclear complexes bridged by the inorganic pyrophosphate tetraanion, namely, [Cu(bipy)(cis-H2P2O7)]2·3H2O 1 and [Cu2(terpy)2(HP2O7)]·2H2O(OH) 2, are reported (bipy = 2,2′-pyridine; terpy = 2,2′:6′,2″-terpyridine). Both compounds are characterized by two very strong Osingle bondHsingle bondO interactions which play a fundamental role in their crystal structure building. Compound 1 is identical to the recently reported compound 1a (Marino et al. Inorg. Chem. 50 (2011) 378–389), except for the supramolecular interaction which is revised in the present communication. Analysis of our data for 1 reveals the existence of a strong double well Osingle bondH⋯O′ ↔ O⋯(Hsingle bondO)′ interaction around an inversion center (Osingle bondO: 2.433(2) Å), which binds dinuclear units together into [100] polymeric chains. Dinuclear compound 2 is monoclinic, halved by a twofold axis bisecting it through the central O atom of the bridge. The extreme disorder found in the solvates in 2 prevented an accurate description of the solvato content, and a detailed analysis of the H-bonding scheme. However, the extremely short O⋯O = 2.473(2) Å intermolecular distance points to a (quasi) symmetrical Osingle bondHsingle bondO interaction.