Synthesis, Structure, and Characterizations of a Volatile/Soluble Heterometallic Hexanuclear Precursor [NaMn 2 (thd) 4 (OAc)] 2 .

The paper describes a hetero bi metallic mixed-ligand hexanuclear precursor [NaMn 2 (thd) 4 (OAc)] 2 ( 1 ) (thd = 2,2,6,6-tetramethyl-3,5-heptadionate; OAc = acetate) that was designed based on its lithium homoleptic analogue, [LiMn 2 (thd) 5 ], by replacing one of the thd ligands with an acetate group in order to accommodate 5-coordinated sodium instead of tetrahedral lithium ion. The complex, which is highly volatile and soluble in a variety of common solvents, has been synthesized by both the solid-state and solution methods. The unique "dimer-of-trimers" heterometallic structure consists of two trinuclear [NaMn II 2 (thd) 4 ] + units firmly bridged by two acetate ligands. X-ray diffraction techniques, DART mass spectrometry, ICP-OES analysis, and IR spectroscopy have been employed to confirm the structure and composition of the hexanuclear complex. Similar to the Li counterpart forming LiMn 2 O 4 spinel material upon thermal decomposition, the title Na:Mn = 1:2 compound was utilized as the first single-source precursor for the low-temperature preparation of Na 4 Mn 9 O 18 tunnel oxide. Importantly, four Mn sites in the hexanuclear molecule can be potentially partially substituted by other transition metals, leading to hetero tri - and tetra metallic precursors for the advanced quaternary and quinary Na-ion oxide cathode materials.