Transmetalation of the neutral boronate esters, (2-benzofuranyl)BPin and (2-benzofuranyl)BNeo (Pin = pinacolato, Neo = neopentylglycolato), to a representative pyridine(diimine) iron alkoxide complex, (^iPrPDI)FeOEt (^iPrPDI = 2,6-(2,6-ⁱPr₂–C₆H₃N═CMe)₂C₅H₃N; R = Me, Et, SiMe₃), to yield the corresponding iron benzofuranyl derivative was studied. Synthesis of the requisite iron alkoxide complexes was accomplished either by salt metathesis between (^iPrPDI)FeCl and NaOR (R = Me, Et, SiMe₃) or by protonation of the iron alkyl, (^iPrPDI)FeCH₂SiMe₃, by the free alcohol R′OH (R′ = Me, Et). A combination of magnetic measurements, X-ray diffraction, NMR, and Mössbauer spectroscopies and DFT calculations identified each (^iPrPDI)FeOR compound as an essentially planar, high-spin, S = 3/2 compound where the iron is engaged in antiferromagnetic coupling with a radical anion on the chelate (S_Total = 3/2; S_Fe = 2, S_PDI = −1/2). The resulting iron benzofuranyl product, (^iPrPDI)Fe(2-benzofuranyl), was characterized by X-ray diffraction and in combination with magnetic measurements, spectroscopic and computational data, was identified as an overall S = 1/2 compound, demonstrating that a net spin-state change accompanies transmetalation (S_Fe = 1, S_PDI = −1/2). These findings may be relevant to further development of iron-catalyzed Suzuki–Miyaura cross-coupling with neutral boronate esters and alkoxide bases.

中文翻译：

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从中性硼酸酯转变为吡啶（二亚胺）烷氧基铁的金属转移的直接观察。

将中性硼酸酯（2-苯并呋喃基）BPin和（2-苯并呋喃基）BNeo（Pin =松果糖醇，Neo =新戊基糖醇）过渡金属化为代表性的吡啶（二亚胺）醇铁络合物，（^iPr PDI）FeOEt（^iPr PDI =研究了2,6-（_2,6 - ⁱ Pr ₂ –C ₆ H ₃ N = CMe）₂ C ₅ H ₃ N； R = Me，Et，SiMe ₃），得到相应的苯并呋喃铁衍生物。通过（^iPr PDI）FeCl和NaOR之间的盐复分解（R = Me，Et，SiMe ₃）或通过烷基铁的质子化来完成所需的烷氧基铁配合物的合成。^iPr PDI）FeCH ₂ SiMe ₃，通过游离醇R'OH（R'= Me，Et）。磁测量，X射线衍射，NMR和Mössbauer光谱法以及DFT计算的结合将每种（^iPr PDI）FeOR化合物识别为基本上平面的高自旋S = 3/2化合物，其中铁参与反铁磁耦合在螯合物上带有自由基阴离子（S _Total = 3/2；S _Fe = 2，S _PDI = -1/2）。生成的苯并呋喃^基铁产品（^iPrPDI）Fe（2-苯并呋喃基）的特征在于X射线衍射，结合磁测量，光谱和计算数据被确定为总S = 1/2化合物，表明净金属自旋态变化伴随着重金属化（S _Fe＝ 1，S _PDI＝ -1 / 2）。这些发现可能与铁催化的铃木-宫浦与中性硼酸酯和醇盐碱的交叉偶联的进一步发展有关。