Towards a new type of heterometallic system based on a paddle-wheel Ru2 dimer: first results derived from the use of a high spin diruthenium(iii,iii) building block

Abstract

A new facile strategy has been reported for the synthesis of homovalent diruthenium(III,III) phosphates. On assembling the homovalent Ru₂ units and Cu²⁺ in the presence of K⁺, new trimetallic phosphates, K₂[{Cu(H₂O)}₂Ru₂(PO₄)₄(H₂O)₂] (1), were formed. In compound 1, the Ru₂ dimer showed a Ru–Ru double bond distance of 2.3400 Å with a high spin ground state S = 2, and neighboring [Ru₂(PO₄)₄(H₂O)₂]⁶⁻ units were linked via distorted tetragonal pyramid Cu(H₂O)²⁺ ions, forming the negative layer [{Cu(H₂O)}₂Ru₂(PO₄)₄(H₂O)₂]_n²ⁿ⁻. Antiferromagnetic coupling was mediated between Ru₂⁶⁺ and Cu²⁺via O–P–O bridges. Detailed magnetism measurements demonstrated that compound 1 exhibited a two-step relaxation in oscillation susceptibilities, and an order below 14 K with a large coercive field of H_c = 24.9 kOe at 1.8 K. It is the highest T_c and H_c for the non-carboxylate diruthenium compounds reported to date.