Cationic Bismuth Amides: Accessibility, Structure, and Reactivity.

Abstract

The synthetic access to cationic bismuth compounds based on simple, monodentate, synthetically useful amido ligands, [Bi(NR2 )2 (L)n ]+ , has been investigated (R=Me, iPr, Ph; L=neutral ligand). With [BPh4 ]- as a counteranion, the formation of contact ion pairs and subsequent phenyl transfer from B to Bi is observed. An intermediate of this reaction, [Bi(NMe2 )2 (HNMe2 )(BPh4 )] (1), could be isolated and fully characterized. The use of a fluorinated tetraarylborate as a counteranion leads to more stable cationic bismuth amides. The solvent-separated ion pairs [Bi2 (μ2 -NMe2 )2 (NMe2 )2 (thf)6 ]2+ (4) and [Bi(NiPr2 )2 (thf)3 ]+ (5) were fully characterized, with [B(3,5-C6 H3 (CF3 )2 )4 ]- anions balancing the positive charge. The coordination chemistry, aggregation in solution, and spectroscopic features of these compounds were investigated. Compounds 4 and 5 show an increased reactivity towards diisopropylcarbodiimide compared to their neutral parent compounds. These reactions result in formation of the first cationic bismuth guanidinates. Characterization techniques include 1 H, 11 B, 13 C, 15 N, 19 F, and 31 P (VT)NMR and IR spectroscopy, single crystal X-ray diffraction analysis, and DFT calculations.