Template- and pH-Directed Assembly of Diruthenium Diphosphonates with Different Topologies and Oxidation States

In the presence of organic templates, six diruthenium diphosphonates, namely, [H₃N(CH₂)₃NH₃]₂[Ru₂(hedp)₂] (1), [H₃N(CH₂)₄NH₃]₂[Ru₂(hedp)₂]·4H₂O (2), [H₃N(CH₂)₅NH₃]₂[Ru₂(hedp)₂]·4H₂O (3), [H₃N(CH₂)₃NH₃][Ru₂(hedp)(hedpH)]·H₂O (4), [H₃N(CH₂)₄NH₃][Ru₂(hedpH_0.5)₂]·2H₂O (5), and [H₃N(CH₂)₅NH₃]₂{[Ru₂(hedp)₂][Ru₂(hedpH)₂]} (6) [hedp = 1-hydroxyethylidenediphosphonate, CH₃C(OH)(PO₃)₂] have been synthesized under hydrothermal conditions. Compounds 1−3 contain homovalent paddlewheel cores of Ru₂^II,II(hedp)₂^4- that are connected through edge-sharing of the {RuO₅Ru} octahedra, resulting in infinite linear chains. Compounds 4−6 contain mixed-valent diruthenium(II,III) phosphonate paddlewheel cores of Ru₂^II,III(hedpH_n)₂^(3-2n)- that are connected by phosphonate oxygen atoms, forming distorted square-grid layers in 4 and 6 or a kagomé lattice in 5. Both the templates and the pH values are found to play important roles in directing the final products with particular topologies and oxidation states of the diruthenium unit. The magnetic studies show that weak antiferromagentic interactions are propagated between the homovalent diruthenium units in compounds 1−3. For compounds 4−6, weak ferromagnetic interactions are observed.