In organic chemistry, atoms other than carbon and hydrogen are generally referred to as heteroatoms. The most common heteroatoms are nitrogen, oxygen and sulfur. Now I present to you an article called A novel nickel(II) complex adopting a cis-configuration: solvothermal synthesis and crystal structure of [NiL2(H2O)4] (L = 1,4-dihydropyrazine-2,3-dione-5,6-dicarboxylate), published in 2002-07-31, which mentions a compound: 56413-95-7, mainly applied to nickel pyrazinedionedicarboxylate complex preparation structure; crystal structure nickel pyrazinedionedicarboxylate complex; pyrazinedicarbodinitrile reaction cadmium nickel perchlorate hydrate, Product Details of 56413-95-7.
Under solvothermal reaction conditions, the reaction of 5,6-dichloropyrazine-2,3-dicarbonitrile and [Ni(ClO4)2]·6H2O produces a novel cis-Ni(II) complex [NiL2(H2O)4] (1) (L = 1,4-dihydropyrazine-2,3-dione-5,6-dicarboxylate), whereas only hydrated 1,4-dihydropyrazine-2,3-dione-5,6-dicarboxylic acid (2) was obtained as a single phase when [Cd(ClO4)2]·6H2O was used instead of [Ni(ClO4)2]·6H2O. The crystal structure of 1 was determined
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Reference:
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate