The introduction of a triphenylborate group at the 4-position of 2,6-dimesitylpyridine afforded a sterically demanding anionic pyridine. The charge introduced through the borate group drastically increases its basicity and measurement of its pK value (18.46) revealed a significantly higher value than that of 4-dimethylaminopyridine (17.95). THF ring-opening was observed upon treating its lithium salt with TMSCl, which demonstrates its high nucleophilicity. The mesityl groups at the 2,6-positions are oriented orthogonal to the pyridine ring and do not block the nitrogen atom of the pyridine. The reaction of the protonated pyridine with Li[BH ] yielded the corresponding Lewis acid/base adduct, which shows that the title compound can be used as a monodentate ligand in coordination chemistry. The crystal structures of all the compounds presented in this work are reported.

The synthesis, isolation and characterization of the pyridyllithium compound 4-Li-2,6-Mes2py is reported. The crystal structure determination revealed a dimer in the solid state. In solution the pyridyllithium was identified as a monomer.

Dedicated to Professor Cameron Jones on the occasion of his 60 th birthdayThe sterically demanding anionic pyridine ligand [4-(Ph 3 B)-2,6-Mes 2 py] À ([1] À ) 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] À 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] À the borate function of the ligand was substituted with strongly electron withdrawing 3,5-bis(trifluoromethyl)phenyl groups to give [1 F ] À . The redox potential was shifted from + 0.56 V to + 1.32 V and hence, [1 F ] À cannot reduce the trityl cation in contrast to [1] À . Consequently, the measured pK a value of 1 F -H (16.44) was lowered by two pK a units compared with 1-H. Unfortunately, [1 F ] À still undergoes single electron transfer processes when used in salt metathesis reactions. We synthesized the anionic borane adduct [Li(THF) 4 ][1 F -BH 3 ] which demonstrates that [1 F ] À 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 -BH 3 ] revealed separated ion pairs while their analogs with the more electron rich [1] À are contact ion pairs.