Synthesis, characterization and chemistry of bis-(pentafluorophenyl)boryl ferrocene

Abstract

Bis-(pentafluorophenyl)boryl ferrocene, 1, was prepared via borylation of ferrocene with HB(C6F5)2 or via a transmetallation reaction involving FcHgCl and ClB(C6F5)2 in 87–91% yield. The compound is characterized by a deep maroon colour. A significant intramolecular iron–boron interaction is manifested in the solution spectroscopic (Fe [Formula: see text] B charge transfer band at ~230 nm, ε = 1.33 × 104) and solid-state crystallographic data (Fe-B = 2.924 Å) This interaction has an impact on the Lewis acidity of the boron center which, unlike the related compound B(C6F5)3, does not strongly bind Lewis bases such as acetone, THF, or acetonitrile. However, an adduct between the stronger base PMe3 and 1 forms readily and this complex (2) was fully characterized. The electron withdrawing -B(C6F5)2 group causes 1 to be oxidized at +450 mV relative to ferrocene. Oxidation of 1 with [NO][BF4], AgOSO2CF3, or AgC6F5 leads to the zwitterionic ferrocenium borates 3-F, 3-OTf, and 3-C6F5, respectively. Each of these compounds was characterized spectroscopically and via X-ray crystallography. The properties of these compounds relative to 1 suggest that oxidation of the iron center significantly enhances the Lewis acidity of the boron center. Due to the σ-donating ability of the borate substituents, zwitterions 3 are weaker oxidizing agents than unsubstituted ferrocenium salts.Key words: organoboranes, ferrocene derivatives, Lewis acids.

Ring‐Borylated 15‐Electron and 17‐Electron ansa‐Chromocene Complexes, their Physical Properties and Molecular Structures

“…[30] Rather, it is due to the electrostatic stabilizing effect of the borylate group on increased positive charge at the metal. The existence of a significant Cr À F interaction in 3 a is supported by the above observations as well as by large superhyperfine coupling from fluorine found in the low-temperature EPR spectrum of 3 a.…”

“…2,6-Dimethylphenyl isocyanide (Fluka), trimethylphosphane, di-methylphenylphosphane, methyldiphenylphosphane (Aldrich) and CO (Praxair) were used as received. [Cr(CO)A C H T U N G T R E N N U N G {Me 4 C 2 A C H T U N G T R E N N U N G (C 5 H 4 ) 2 }] (1) [6] and BA C H T U N G T R E N N U N G (C 6 F 5 ) 3 [30] were prepared as described in the literature. …”

Perfluoroorganosilver(I) compounds

“…The oxidation of bis(pentafluorophenyl)boryl ferrocene with pentafluorophenylsilver was reported yielding the zwitterionic ferrocenium tris(pentafluorophenyl)borate [38]. Decacarbonyldimetallates of group 6 elements, [M 2 (CO) 10 ] 2À (M ¼ Cr, Mo, W), react with Ag(trans-CF 3 C¼CFCF 3 ) to give [C 4 F 7 M(CO) 5 ] À ions and elemental silver [39].…”

Study of the Reaction of Tridentate Ligands with Ferrocenyl Boronic Acid

“…[6b,7] Borylated ferrocenes are isoelectronic with stable ferrocenyl carbocations. [7,8] Due to possible applications of their unusual properties to electronic materials, boron compounds containing ferrocenyl units have recently been examined as charge-transfer complexes. [9Ϫ12] Moreover, boronic acids are potentially useful for selective recognition of sugars as they can form strong boronic acidϪdiol interactions.…”