Reactions of tetrachloro(cyclopentadienyl)niobium with arenedithiolates yielded products [NbCp(1,2-S2C6H3R-4)2] (Cp = η5-C5H5; R = H 1 or Me 2), characterised primarily by analysis, 1H NMR and mass spectroscopy. Cyclic voltammetric studies on 1 and 2 showed two consecutive, quasi-reversible, reduction processes; ESR spectra of the initial products of chemical reduction were typical of those from niobium(IV) species with an unpaired electron largely centred on the metal and assigned to the anions [NbCp(1,2-S2C6H3R-4)2]â. Similar tantalum derivatives were less tractable, although properties of the more soluble species [TaCpâ²(1,2-S2C6H4)2] (Cpâ²Â = η5-C5H4Me) are reported. Reactions of tetrachloro(methylcyclopentadienyl)-niobium or -tantalum with salts of ethane-1,2-dithiol (H2edt) were very susceptible to hydrolysis and the major isolable products of reactions using the sodium reagent (Na2edt) were [M2(µ-O)(µ-η2â¶Î·2-edt)Cpâ²2Cl4] (M = Nb 4 or Ta 5), containing oxo and symmetrical dithiolate bridges. Reaction of [NbCpâ²Cl4] with 2 molar equivalents of Tl2edt formed the unsymmetrical compound [Nb2(µ-η1â¶Î·2-edt)2Cpâ²2O(edt)] 6, containing a terminal oxide ligand, one chelating and two unsymmetrically bridging edt groups. Structures of compounds 4 and 6 have been determined in the solid state by X-ray crystallography; 1- and 2-D NMR spectra of the binuclear products support the retention of these structures in solution.
四
氯化(
环戊二烯基)
铌与芳基二
硫醇的反应产物为[NbCp(1,2-S2C6H3R-4)2](Cp = η5-
C5H5; R = H 1 或 Me 2),主要通过分析、1H NMR 和质谱进行表征。对 1 和 2 进行的循环伏安研究显示了两个连续的、准可逆的还原过程;
化学还原的初始产物的 ESR 光谱具有典型的
铌(IV)物种特征,其中未成对电子主要集中在
金属中心,并被指认为阴离子[NbCp(1,2-S2C6H3R-4)2]-。类似的
钽衍
生物较为难以处理,尽管报道了更易溶的物种[TaCp′(1,2-S2
C6H4)2](Cp′ = η5-C5H4Me)的性质。四
氯化(
甲基环戊二烯基)
铌或
钽与
乙烷-1,2-二
硫醇(H2edt)盐的反应非常容易
水解,主要可分离产物为使用了
钠试剂(Na2edt)反应得到的[M2(μ-O)(μ-η2∷η2-edt)Cp′2Cl4](M = Nb 4 或 Ta 5),含有氧桥和二
硫醇对称桥。[NbCp′Cl4]与2摩尔当量的Tl2edt反应形成了不对称化合物[Nb2(μ-η1∷η2-edt)2Cp′2O(edt)] 6,含有端氧
配体、一个螯合和一个二
硫醇不对称桥。化合物4和6的固体结构通过X射线晶体学确定;二核产物的1-D和2-D NMR光谱支持溶液中这些结构的保留。