Peterson Paul O, Rummelt Stephan M, Wile Bradley M, Stieber S Chantal E, Zhong Hongyu, Chirik Paul J
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States.
Organometallics. 2020 Jan 13;39(1):201-205. doi: 10.1021/acs.organomet.9b00733. Epub 2019 Dec 23.
Transmetallation of the neutral boronate esters, (2-benzofuranyl)BPin and (2-benzofuranyl)BNeo (Pin = pinacolato, Neo = neopentylglycolato) to a representative pyridine(diimine) iron alkoxide complex, (PDI)FeOEt (PDI = 2,6-(2,6-Pr2-CHN=CMe)CHN; R = Me, Et, SiMe), to yield the corresponding iron benzofuranyl derivative was studied. Synthesis of the requisite iron alkoxide complexes was accomplished either by salt metathesis between (PDI)FeCl and NaOR (R = Me, Et, SiMe) or by protonation of the iron alkyl, (PDI)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 (PDI)FeOR compound as an essentially planar, high-spin, = 3/2 compound engaged in antiferromagnetic coupling with a radical anion on the chelate ( = 3/2; = 2, = 1/2). The resulting iron benzofuranyl product, (PDI)Fe(2-benzofuranyl) was characterized by X-ray diffraction and in combination with magnetic measurements, spectroscopic and computational data, was identified as an overall = 1/2 compound, demonstrating that a net spin-state change accompanies transmetallation ( = 1, = 1/2). These findings may be relevant to further development of iron-catalyzed Suzuki-Miyaura cross-coupling with neutral boronate esters and alkoxide bases.
研究了中性硼酸酯（2-苯并呋喃基）BPin和（2-苯并呋喃基）BNeo（Pin = 频哪醇硼酸酯，Neo = 新戊二醇硼酸酯）与代表性的吡啶（二亚胺）铁醇盐配合物（PDI）FeOEt（PDI = 2,6-(2,6-Pr₂-CHN=CMe)CHN；R = Me、Et、SiMe）的金属转移反应，以生成相应的铁苯并呋喃基衍生物。所需的铁醇盐配合物的合成可通过（PDI）FeCl与NaOR（R = Me、Et、SiMe）之间的盐复分解反应，或通过游离醇R'OH（R' = Me、Et）对铁烷基（PDI）FeCH₂SiMe₃进行质子化反应来完成。通过磁性测量、X射线衍射、核磁共振和穆斯堡尔光谱以及密度泛函理论计算相结合，确定每个（PDI）FeOR化合物为基本上平面的高自旋、S = 3/2化合物，与螯合物上的自由基阴离子发生反铁磁耦合（S = 3/2；S₁ = 2，S₂ = 1/2）。所得的铁苯并呋喃基产物（PDI）Fe(2-苯并呋喃基) 通过X射线衍射进行了表征，并结合磁性测量、光谱和计算数据，被确定为总体S = 1/2化合物，表明金属转移伴随着净自旋态变化（S₁ = 1，S₂ = 1/2）。这些发现可能与铁催化的中性硼酸酯和醇盐碱的铃木-宫浦交叉偶联的进一步发展相关。
