Iron(II) High‐Spin and Low‐Spin Complexes from Pentaisopropylcyclopentadienyliron(II) Bis(trimethylsilyl)amide

• Published in: European journal of inorganic chemistry Vol. 2017; no. 30; pp. 3635 - 3643
• Main Authors: Groß, Oliver A., Lauk, Sergej, Müller, Carsten, Gidt, Wjatscheslaw, Sun, Yu, Demeshko, Serhiy, Meyer, Franc, Sitzmann, Helmut
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 17.08.2017
• Subjects: Center of gravity; Coordination compounds; Cyclopentadienyl ligands; Dehydrogenation; Diamagnetism; Electron spin; Inorganic chemistry; Iron; Magnetic anisotropy; Magnetic induction; Magnetic properties; Magnetic relaxation; Phosphane ligands; Sandwich complexes
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201700236

Two new complexes, [(C5Me5)FeBr(tmeda)] (tmeda = tetramethylethylenediamine) and [{C5(CHMe2)5}FeN(SiMe3)2], have been synthesized and characterized as high‐spin iron(II) complexes with typical distances between the iron atom and the center of gravity of the C5 ring (Fe–Cpcent) exceeding 190 pm and displaying paramagnetic behavior in solution. Both are analogues of known complexes, namely, the Jonas complex [(C5Me5)FeCl(tmeda)] and the Siemeling “pogo‐stick” complex [(C5Me5)FeN(SiMe3)2]. The silylamide [{C5(CHMe2)5}FeN(SiMe3)2] was treated with water to yield the bridged hydroxo dimer [{C5(CHMe2)5}Fe(µ‐OH)]2 with high‐spin iron(II) configuration. With 2,5‐dimethylpyrrole the azaferrocene derivative [{C5(CHMe2)5}Fe(NC4H2Me2‐2,5)] was obtained, and with diphenylphosphine a few crystals of the diphosphine hydride [{C5(CHMe2)5}FeH(HPPh2)2] as well as a sample of its dehydrogenative P–P coupling product [{C5(CHMe2)5}FeH(Ph2P–PPh2)]n (n = 1 or 2) have been obtained, which are both diamagnetic 18‐valence‐electron complexes. Two‐coordinated [{C5(CHMe2)5}FeN(SiMe3)2] features sizeable negative magnetic anisotropy and slow magnetic relaxation with an effective energy barrier for spin reversal of 113 cm–1 under an applied field of 3000 Oe. Pentaisopropylcyclopentadienyliron(II) bis(trimethylsilyl)amide is a versatile starting compound for the synthesis of diamagnetic or paramagnetic iron(II) half‐sandwich complexes. Reactions with water, 2,5‐dimethylpyrrole, and diphenylphosphine have been studied and the products are discussed, including the magnetic properties of the title complex.