Isolation, X-ray Structural Characterization, and Reactivities of Diiodosamarium(II) Complexes Bearing Amide Compounds as Ligands

Abstract The structures of diiodosamarium(II) complexes with amide compounds have been investigated basing on single crystal X-ray structural analyses. The reaction of [SmI2(thf)2] with 2 equivalents of tetramethylurea (TMU) gave [SmI2(thf)2(tmu)2] (1). The three different kinds of ligands in 1 attach to the samarium atom in a trans orientation. [SmI2(thf)2] reacted with 4 equivalents of 1,3-dimethyl-2-imidazolidione (DMI) to afford [SmI2(dmi)4] (2), forming a typical hexa-coordinated octahedral structure. Diiodosamarium complex containing four N,N-dimethylacetamide (DMA) ligands [SmI2(dma)4] (3) was prepared by treatment of [SmI2(thf)2] with 4 equivalents of DMA. The reaction of [SmI2(thf)2] with 6 equivalents of 1,3-dimethyl-3,4,5,6-tetrahydro-2-(1H)-pyrimidinone (dimethylpropyleneurea (DMPU)) gave [Sm(dmpu)6]I2 (4) quantitatively. This complex experiences a unique coordination fashion, in which six DMPU ligands coordinate to the samarium atom to overlap each other. [SmI2(dmpu)3(thf)] (5) was isolated from the reaction of [SmI2(thf)2] with 2 equivalents of DMPU. The reducing ability of these complexes was evaluated by reactions with benzylacetone or 9-haloanthracene. The structural analyses and reactivity studies of these complexes indicate that DMPU and DMA ligands are the most effective among the amide compounds to enhance the reducing ability of samarium diiodide.