醋酸铑(Ⅱ)与2-吡啶羧酸的反应研究

A Study on the Reaction Process of Dirhodium Tetraacetate and 2-Picolinic Acid

醋酸铑(Ⅱ)与2-吡啶羧酸在水溶液中反应,并没有生成与吡啶基团配位该有的紫色或红色产物,而是生成一种绿色混合物。绿色混合物的乙醇溶液在空气中静置2个月时,被空气中的氧气缓慢氧化成单核的三(2-吡啶羧酸)合铑。X衍射单晶测试表明,三(2-吡啶羧酸)合铑为经式结构,同时晶体中含有一个结晶水分子,水分子通过氢键将相邻的2个三(2-吡啶羧酸)合铑分子连接成一维链状超分子,链状分子间又进一步通过吡啶环之间的强烈π-π作用堆积成三维结构。

A green but not a purple or red product was obtained by reaction of dirhodium（Ⅱ） tetraacetate with 2-picolinic acid in an aqueous solution, indicated that the 2-picolinic acid are bound to the rhodium center through O atoms but not N atoms. While the ethanol solution of the green product was allowed to evaporate slowly in the air, it was oxidized to mer-rhodium（Ⅲ） trispicolinate, which was characterized by single-crystal X-ray diffraction, by the oxygen in the air within two months. There is one molecule of water of crystallization per molecule of rhodium（Ⅲ） trispicolinate complexes. The water molecule is hydrogen-bonded to two carboxylate oxygen atoms from two adjacent rhodium（Ⅲ） trispicolinate molecules, which links the rhodium（Ⅲ） trispicolinate molecules to form a chain supramolecular structure. The chains are further packed to a three-dimensional network by the π-π interactions of the rhodium（Ⅲ） trispicolinatemolecules between the neighboring pyridine rings.