This HOT Article, describes the structural analysis of four new compounds and of known structures of related compounds revealing preferred
interaction geometries between tris-ethylenediamine metal cations and the oxalate dianion. These components have a mismatch in shape: the H-bond donor having three D–H groups and a three-fold character, while the acceptor can only present two accepting groups and has a two-fold character. This
clear conflict of symmetry between the H-bond donor and the H-bond acceptor moieties results in a compromised interaction in which we frequently observe a side-on interaction with the oxalate and the formation of uncommon bifurcated H-bonds. This interaction ranges from being quite symmetric with two similar H…O interactions, to an asymmetric situation with one short and one long H…O interaction.
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Recurrent H-bond graph motifs between metal tris-ethylenediamine cations and uncoordinated oxalate anions: Fitting a three pin plug into a two pin socket
Tony D. Keene, Michael B. Hursthouse and Daniel J. Price
CrystEngComm, 2011, Advance Article