Electronic Modification of a Sterically Demanding Anionic Pyridine Ligand. Issue 19 (20th May 2022)

• Record Type: Journal Article
• Authors: Schmidlin, Nadja M. C.; Radtke, Valentin; Schmidt, Alexei; Lõkov, Märt; Leito, Ivo; Böttcher, Tobias
• Is Part Of: Zeitschrift für anorganische und allgemeine Chemie. Volume 648:Issue 19(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-05-20
• Subjects: pyridine -- ligand design -- redox-active -- sterically demanding -- main group chemistry; Chemistry, Inorganic -- Periodicals; Chemistry -- Periodicals; 540
• DOI: 10.1002/zaac.202200136
• Languages: English
• ISSNs: 0044-2313

Abstract

Abstract: The sterically demanding anionic pyridine ligand [4‐(Ph3 B)‐2, 6‐Mes2 py] − ([1 ] − ) was used in salt metathesis reactions in order to obtain main group and transition metal complexes. Instead, reduction reactions were observed and identified as single electron transfer processes from [1 ] − to the respective Lewis acidic cations. The electron transfer was confirmed by reduction of the trityl cation. In order to reduce the reductive power of [1 ] − the borate function of the ligand was substituted with strongly electron withdrawing 3, 5‐bis(trifluoromethyl)phenyl groups to give [1 F ] − . The redox potential was shifted from +0.56 V to +1.32 V and hence, [1 F ] − cannot reduce the trityl cation in contrast to [1 ] − . Consequently, the measured p K a value of 1 F ‐H (16.44) was lowered by two p K a units compared with 1 ‐H. Unfortunately, [1 F ] − still undergoes single electron transfer processes when used in salt metathesis reactions. We synthesized the anionic borane adduct [Li(THF)4 ][1 F ‐BH3 ] which demonstrates that [1 F ] − can be used as a ligand in main group chemistry. The determination of the crystal structures of [Li(THF)4 ][1 F ] and [Li(THF)4 ][1 F ‐BH3 ] revealed separated ion pairs while their analogs with the more electron rich [1 ] − are contact ion pairs. Abstract :