Hu Xile, Castro-Rodriguez Ingrid, Meyer Karsten
Department of Chemistry and Biochemistry, Mail Code 0358, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0358, USA.
J Am Chem Soc. 2003 Oct 8;125(40):12237-45. doi: 10.1021/ja036880+.
Incorporation of a nitrogen functionality into a tripodal N-heterocyclic carbene ligand system affords the first N-anchored tetradentate tris-carbene ligands TIMEN(R) (R = Me (5a), t-Bu (5b), Bz (5c)). Treatment of the methyl derivatized H(3)TIMEN(Me)(3) imidazolium salt (H(3)5a) with silver oxide yields the silver complex (TIMEN(Me))(2)Ag(3)(3) (9), which, in a ligand transfer reaction, reacts with copper(I) bromide to give the trinuclear copper(I) complex (TIMEN(Me))(2)Cu(3)(3) (10). Deprotonation of the tert-butyl and benzyl derivatives H(3)TIMEN(t-Bu)(3) and H(3)TIMEN(Bz)(3) yields the free tris-carbenes TIMEN(t-Bu) (5b) and TIMEN(Bz) (5c), which react readily with copper(I) salts to give mononuclear complexes (TIMEN(t-Bu))Cu (11b) and [(TIMEN(Bz))Cu]Br (11c). The solid-state structures of 10, 11b, and 11c were determined by single-crystal X-ray diffraction. While the TIMEN(Me) ligand yields trinuclear complex 10, with both T-shaped three-coordinate and linear two-coordinate copper(I) centers, the TIMEN(t-Bu) and TIMEN(Bz) ligands induce mononuclear complexes 11b and 11c, rendering the cuprous ion in a trigonal planar ligand environment of three carbenoid carbon centers and an additional, weak axial nitrogen interaction. Complexes 11b and 11c exhibit reversible one-electron redox events at half-wave potentials of 110 and -100 mV vs Fc/Fc(+), respectively, indicating sufficient electronic and structural flexibility of both TIMEN(R) ligands (R = t-Bu, Bz) to stabilize copper(I) and copper(II) oxidation states. Accordingly, a copper(II) NHC complex, (TIMEN(Bz))Cu(2) (12), was synthesized. Paramagnetic complex 12 was characterized by elemental analysis, EPR spectroscopy, and SQUID magnetization measurements.
将氮官能团引入三脚架型 N - 杂环卡宾配体体系，得到了首个 N 锚定的四齿三卡宾配体 TIMEN(R)（R = 甲基 (5a)、叔丁基 (5b)、苄基 (5c)）。用氧化银处理甲基衍生的 H₃TIMEN(甲基)₃ 咪唑盐（H₃5a），得到银配合物 (TIMEN(甲基))₂Ag₃₃（9），该配合物在配体转移反应中与溴化亚铜反应，生成三核亚铜配合物 (TIMEN(甲基))₂Cu₃₃（10）。叔丁基和苄基衍生物 H₃TIMEN(叔丁基)₃ 和 H₃TIMEN(苄基)₃ 去质子化后得到游离的三卡宾 TIMEN(叔丁基)（5b）和 TIMEN(苄基)（5c），它们能迅速与亚铜盐反应，生成单核配合物 (TIMEN(叔丁基))Cu（11b）和 [(TIMEN(苄基))Cu]Br（11c）。通过单晶 X 射线衍射确定了 10、11b 和 11c 的固态结构。虽然 TIMEN(甲基)配体生成了三核配合物 10，其中包含 T 形三配位和线性二配位的亚铜中心，但 TIMEN(叔丁基)和 TIMEN(苄基)配体诱导生成了单核配合物 11b 和 11c，使亚铜离子处于三个类卡宾碳中心的三角平面配体环境以及一个额外的弱轴向氮相互作用中。配合物 11b 和 11c 分别在相对于 Fc/Fc⁺ 的半波电位为 110 和 -100 mV 处表现出可逆的单电子氧化还原事件，这表明 TIMEN(R)配体（R = 叔丁基、苄基）具有足够的电子和结构灵活性来稳定亚铜和铜(II)氧化态。因此，合成了铜(II) NHC 配合物 (TIMEN(苄基))Cu₂（12）。通过元素分析、电子顺磁共振光谱和超导量子干涉仪磁化测量对顺磁性配合物 12 进行了表征。
