ELECTRON-SPIN RESONANCE STUDIES OF REDUCTION OF TRANSITION-METAL COMPLEXES WITH GRIGNARD-REAGENTS .1. DIANION RADICALS OF BETA-DIKETONATES
ELECTRON-SPIN RESONANCE STUDIES OF REDUCTION OF TRANSITION-METAL COMPLEXES WITH GRIGNARD-REAGENTS .1. DIANION RADICALS OF BETA-DIKETONATES
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DOI：
10.1021/ja00432a035
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发表时间：
1976-01-01
影响因子：
15
通讯作者：
KOCHI, JK
中科院分区：
文献类型：
--
作者：
KWAN, CL;KOCHI, JK
用Grignard试剂还原一系列金属酮烯醇化物时，在溶液中观察到一系列稳定的β-二酮衍生的二价阴离子自由基（DAR）的高分辨电子自旋共振谱.通过乙酰丙酮和二苯甲酰甲基化物中碳2的特异性氘标记，实现了光谱的非ambibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibibib乙酰丙酮DAR的结构与基于INDO分子轨道计算的螯合物模型相关，通过拟合观察到的质子超精细分裂。在二苯甲酰甲基DAR的ESR谱中观察到的选择性谱线增宽可能与平面构象中苯基碳的受阻旋转有关，这也与苯甲酰丙酮DAR有关。本文比较了格氏试剂还原三（二苯甲酰甲基）铁（Ⅲ）所产生的阴离子自由基与钠镜还原所产生的阴离子自由基的光谱和ESR谱。在冷冻溶液中，由于格氏还原反应导致的三重态光谱（先前显示为DAR二聚体）的缺失归因于DAR作为镁螯合物的结合。讨论了顺磁性铁（I）物种形式的还原铁的存在。
Well-resolved electron spin resonance spectra of a series of stable dianion radicals (DAR) derived from/3-diketones are observed in solution when a variety of metal ketoenolates are reduced with Grignard reagents. Unambiguous assignments of the spectra are achieved by specific deuterium labeling of carbon 2 in acetylacetonateand dibenzoylmethide. The structure of acetylacetonate DAR is related to a chelate model based on INDO molecular orbital calculations by fitting the observed proton hyperfine splittings. Selective line broadening observed in the ESR spectrum of dibenzoylmethide DAR may be related to hindered rotation about the phenyl carbon in the planar conformation, which also pertains to benzoylacetonide DAR. The optical and ESR spectra of anion radicals generated from the reduction of tris (dibenzoylmethido) iron (III) with Grignard re-agent are compared with those obtained by reduction with the sodium mirror technique. The absence of the triplet spectrum (shown previously forDAR dimers) in frozen solutions resulting from the Grignard reduction is attributed to the binding of the DAR as a magnesium chelate. The presence of reduced iron in the form of paramagnetic iron (I) species is discussed.