Synthesis, characterization and reactivity of potassium and barium complexes containing phosphane–borane stabilized methanides

Abstract

The polymeric potassium complex [K{CH(PPh₂BH₃)₂}]_∞ (1) was prepared and used as a starting material for the syntheses of related N,N,N′,N′-tetramethylethylenediamine (tmeda) and N,N,N′,N′,N′′-pentamethyldiethylenetriamine (pmdta) ligated potassium derivatives [K{CH(PPh₂BH₃)₂}(tmeda)₂]_∞ (2) and [K{CH(PPh₂BH₃)₂}(pmdta)]₂ (3). Salt metathesis reactions with [BaI₂(thf)₅] allowed the synthesis of the barium derivatives [BaI{CH(PPh₂BH₃)₂}(thf)₅] (5) and [Ba{CH(PPh₂BH₃)₂}₂(solv)₂}] (solv = Et₂O, thf) (6), which are more prone to subsequent reactions than the potassium derivatives. One of the resulting products, [Ba₄O{CH(PPh₂BH₃)₂}₃{Ph₂PCH(BH₃)PPh₂BH₃}₃] (7), which contains two different isomeric forms of the bis(borane) adduct of Ph₂PCHPPh₂, was isolated. The complexes were characterized by NMR techniques and single crystal X-ray diffraction measurements.