四氯化钼催化丁二烯1,2-聚合体系的紫外可见光谱研究

对四价钼系催化丁二烯1,2-聚合中Mo(Ⅳ)络合物的紫外可见光谱进行了研究.MoCl₄乙酸乙酯溶液呈棕红色,显顺磁性.在光谱的紫区和红区共有3个自旋允许d-d跃迁吸收带.Mo(Ⅳ)八面体络合物上各种配体的交换对光谱吸收带位置无影响.Mo(Ⅳ)在512nm处的特征吸收带随Al(i-Bu)₃/Mo或Al(i-Bu)₂OPh/Mo增加而渐趋消失,这是Mo(Ⅳ)→Mo(Ⅲ)反应的标志.在MoCl_4-n·(OC₈H₁₇)_n-Bd-Al(i-Bu)₂OPh₃组分陈化体系中Mo(Ⅳ)的还原得到加快,催化聚合活性亦有提高。

UV-Vis Spectral Studies of 1,2-Polymerization System of Butadiene Catalized by Molybdenum Tetrachloride

MoCl₄in ethyl acetate is of a brown-red color and paramagnetism, which is the result of three absorption bands in the red and blue parts of the spectrum due to the d-d spin-allowed transtition. The change in the types of ligands attached to Mo(Ⅳ), such as C^-, C₈H₁₇O^-, PhO^-, Bd, C₈H₁₇OH, PhOH and CH₃COOC₂H₅, has no influence on the position of the absorption band. The peak-value of characteristic absorption band of Mo (Ⅳ) complex at 512 nm varies with the amount of cocatalyst added into Mo-Al system. The disappearance of the characteristic absorption band implies that Mo(Ⅳ) is reduced to a low-valency state Mo(Ⅲ). The reduction of Mo(Ⅳ) is improved and the catalytic activity is raised in the aging catalyst system MoCl₄-2(OC₈H₁₇)₂-Bd-Al(i-Bu)₂OPhCH₃.