High-spin carboxylate polymers [M(OOCCMe3)2]n of group VIII 3d metals

A coordination polymer of the general formula [Co(OOCCMe3)2]n (2) was prepared by mild thermolysis of the coordination polymer of variable composition [(HOOCCMe3)xCo(OH)n(OOCCMe3)2−n]m, the dinuclear cobalt complex Co2(μ-H2O)(OOCCMe3)4(HOOCCMe3)4, the tetranuclear cobalt cluster Co4(μ3-OH)2(OOCCMe3)6(HOEt)6, and the hexanuclear cluster [Co6(μ4-O)2(μn-OOCCMe3)10(C4H8O)3(H2O)]·1.5(C4H8O) (7) in organic solvents. In the crystal, the polymer has a chain structure. Unlike thermolysis of cobalt pivalates, thermolysis of the dinuclear complex Ni2(μ-H2O)(OOCCMe3)4(HOOCCMe3)4 gave rise to the hexanuclear complex Ni6(μ2-OOCCMe3)6(μ3-OOCCMe3)6 (3). The magnetic properties of compound 2 are substantially different from those of 3. Compound 2 undergoes the magnetic phase transition into the ordered state at Tc = 3.4 K (H = 1 Oe), whereas compound 3 exhibits antiferromagnetic properties. Solid-state decomposition of polymeric cobalt carboxylate 2 (below 350 °C) afforded the octanuclear cluster Co8(μ4-O)2(μ2-OOCCMe3)6(μ3-OOCCMe3)6 (9) as the major product, which sublimes without decomposition. Decomposition of 3 gave nickel oxide as the final product. Pivalates 2 and 3 reacted with 2,3-lutidine in acetonitrile at 80 °C to form the isostructural dinuclear complexes (2,3-Me2C5H3N)2M2(μ-OOCCMe3)4 (M = Co or Ni). The structures of compounds 3 and 7 were established by X-ray diffraction. The structure of polymer 2 was determined by powder X-ray diffraction analysis.