Komine Nobuyuki, Buell René W, Chen Chun-Hsing, Hui Alice K, Pink Maren, Caulton Kenneth G
Department of Chemistry, Indiana University , 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States.
Inorg Chem. 2014 Feb 3;53(3):1361-9. doi: 10.1021/ic402120r. Epub 2014 Jan 10.
A new pincer ligand is synthesized to be dianionic, with the potential to be redox active. It has pyrrrole rings attached to both ortho sites of a pyridine, as the linking element. This H2L can be doubly deprotonated and then used to replace two chloride ligands in MCl2(NCPh)2, to form LM(NCPh) for M = Pd, Pt. The acid form H2L reacts with ZnEt2 with elimination of only 1 mol of ethane to yield (HL)ZnEt, a three-coordinate species with one pendant pyrrole NH functionality. This molecule binds the Lewis base p-dimethylaminopyridine (DMAP) to give first a simple 1:1 adduct that eliminates ethane on heating to form four-coordinate LZn(DMAP), which has an unusual structure due to the strong preference of the pincer ligand to bind in a mer (planar) geometry. A molecule with two HL(-) ligands each bonded in a bidentate manner to FeCl2 is synthesized and shown to contain four-coordinate iron with a flattened-tetrahedral structure. The electrochemistry of LM(NCPh) and (L)Zn(DMAP) shows three oxidation processes, which is interpreted to involve at least two oxidations of the pyrrolide arms.
一种新型钳形配体被合成为二阴离子型，具有氧化还原活性的潜力。它有吡咯环连接在吡啶的两个邻位上，作为连接元素。这种H₂L可以被双去质子化，然后用于取代MCl₂(NCPh)₂中的两个氯配体，形成LM(NCPh)，其中M = Pd、Pt。酸形式的H₂L与ZnEt₂反应，仅消除1摩尔乙烷，生成(HL)ZnEt，这是一种具有一个悬垂吡咯NH官能团的三配位物种。该分子与路易斯碱对二甲氨基吡啶(DMAP)结合，首先形成一个简单的1:1加合物，加热时消除乙烷，形成四配位的LZn(DMAP)，由于钳形配体强烈倾向于以面式(平面)几何构型结合，其结构不寻常。合成了一种分子，其中两个HL⁻配体均以双齿方式与FeCl₂键合，并显示含有具有扁平四面体结构的四配位铁。LM(NCPh)和(L)Zn(DMAP)的电化学显示出三个氧化过程，这被解释为至少涉及吡咯臂的两次氧化。
