Chandra Tilak, Allred Russell A, Kraft Brian J, Berreau Lisa M, Zaleski Jeffrey M
Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
Inorg Chem. 2004 Jan 26;43(2):411-20. doi: 10.1021/ic030218x.
The syntheses and Bergman cyclization temperatures of disubstituted tetradentate enediyne ligands based on a dibenzylethylenediamine backbone are reported relative to the corresponding Cu(II) and Zn(II) analogues. For these compounds, the R-groups dimethylamine (dma), pyridine (py), quinoline (quin), and 3-oxypyridine (pyO) have been symmetrically and asymmetrically incorporated at the alkyne termini positions directly (0:0) or via a methylene spacer (1:0, 0:1, 1:1). Electron paramagnetic resonance (EPR) reveals that all Cu(II) complexes are monomeric with near axial symmetry and g-values (g(x) approximately 2.04, g(y) approximately 2.09 g(z) approximately 2.25) representative of tetragonal Cu(II) geometries. The hyperfine splitting parameter A(z) values are approximately 170 x 10(-)(4) cm(-)(1), which is consistent with distorted 4-coordinate, or weakly 6-coordinate, structures. In contrast, solution conductivity measurements show that Zn(II) complexes with rigid py or quin ligands (e.g., py-py 0:0, py-quin 0:0) behave as 1:4 electrolytes indicative of dimeric, bridging enediyne structures. Consequently, these Zn(II) complexes have very high Bergman cyclization temperatures (>290 degrees C), while their less rigid, 1:1 analogues (<185 degrees C) and monomeric Cu(II) counterparts (110-136 degrees C) have markedly lower cyclization temperatures. The results underscore the important consequences metal center structure plays in influencing Bergman cyclization temperatures of metalloenediynes.
报道了基于二苄基乙二胺骨架的二取代四齿烯二炔配体相对于相应的铜（II）和锌（II）类似物的合成及伯格曼环化温度。对于这些化合物，R基团二甲胺（dma）、吡啶（py）、喹啉（quin）和3 - 氧代吡啶（pyO）已直接（0:0）或通过亚甲基间隔基（1:0、0:1、1:1）对称和不对称地引入到炔烃末端位置。电子顺磁共振（EPR）表明，所有铜（II）配合物均为近轴向对称的单体，其g值（g(x)约为2.04，g(y)约为2.09，g(z)约为2.25）代表四方铜（II）几何结构。超精细分裂参数A(z)值约为170×10⁻⁴ cm⁻¹，这与扭曲的四配位或弱六配位结构一致。相比之下，溶液电导率测量表明，具有刚性py或quin配体的锌（II）配合物（例如，py - py 0:0、py - quin 0:0）表现为1:4电解质，表明其为二聚体桥连烯二炔结构。因此，这些锌（II）配合物具有非常高的伯格曼环化温度（>290℃），而其刚性较小的1:1类似物（<185℃）和单体铜（II）对应物（110 - 136℃）的环化温度则明显较低。结果强调了金属中心结构在影响金属烯二炔的伯格曼环化温度方面所起的重要作用。
