Simultaneous Fluoride Binding to Ferrocene-Based Heteronuclear Bidentate Lewis Acids

Abstract

A series of micro2-fluoro-bridged heteronuclear bidentate Lewis acid complexes [K(18-crown-6)THF]+ [Fc(BMeF)(SnMe2Cl)F]- (1-2F), [K(18-crown-6)THF]+ [Fc(BMeF)(SnMe2F)F]- (1-3F), [K(18-crown-6)THF]+ [Fc(BMePh)(SnMe2Cl)F]- (2-F), and [K(18-crown-6)THF]+ [Fc(BMePh)(SnMe2F)F]- (2-2F) (Fc=1,2-ferrocenediyl) was prepared. Compounds 2-F and 2-2F were obtained as a mixture of diastereomers, which arise due to the generation of a stereocenter at boron in addition to their inherent planar chirality. All compounds have been studied in the solid state by single-crystal X-ray diffraction analysis and by multinuclear NMR spectroscopy in solution. As a result of bridging-fluoride interactions, tetrahedral boron and distorted trigonal-bipyramidal tin centers are observed. Comparison with the corresponding monofunctional ferrocenylborates further supports the bridging nature of the fluoride anion. Two-dimensional exchange spectroscopy 19F NMR studies provide evidence for facile intermolecular and intramolecular fluorine exchange processes. All complexes display reversible one-electron oxidation events at lower potentials than those of the tricoordinate ferrocenylborane precursors, which is typical of ferrocenylborate complexes.

Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy

“…Organotin 131 was shown by 19 Sn‐ 19 Sn EXSY to undergo dynamic cyclisation behaviour, involving reversible coordination of the piperidine nitrogen. 19 F‐ 19 F EXSY was utilised in organotin complex 132 , as dynamic exchange was seen between its bridging and terminal fluorine atoms …”

“…Among the NMR-active nuclei, the majority of 2D EXSY experiments employ 1 H. It is worth noting that EXSY is not affected by low isotopea bundancea st he presence of two closely positioned nuclei, for example, 13 C, in the same molecule is not ap re-requisite.K inetic and mechanistic studies based on 1 H, 2 H, 6 Li, 7 Li, 11 B, 13 C, 15 N, 19 F, 23 Na, 29 Si, 31 P, 77 Se, 119 Sn, 129 Xe, 133 Cs, 195 Pt, 205 Tl and 207 Pb, to name af ew,h ave been reporteda nd are becoming ar outineo ccurrence in chemistry.I ns ome cases,2 DE XSY can be combinedw ithq uadrupole resonance (NQR)f or quantitative studies of exchange processes in systems containing quadrupole nuclei. [18] Another recent modification, 2D-IR EXSY,h as been appliedi nt he study of rapidly interconverting conformers, as well as intra-and intermolecular interactions.…”

Synthesis and Applications of Group 14-metalated Arylboranes

“…However, both complexes are less stable when compared with a non-silylated analogue derived from 1-(dimethylboryl)naphtalene. [124]. Their crystal structures were examined showing that fluorine forms the bridge between boron and tin.…”

Ab initio studies of optoelectronic properties of fluorine-substituted ferrocene

“…Although the effect of fluoride substitution on ferrocene was investigated experimentally [27][28][29], to the best of our knowledge the structural and the optoelectronic properties of ferrocene and fluorine substituted derivatives including FeC 10 H 8 F 2 , FeC 10 H 6 F 4 , FeC 10 H 4 F 6 , FeC 10 H 2 F 8 , and FeC 10 F 10 have not been investigated theoretically. The monoclinic crystal lattice with P21/a (No.…”