From an Isolable Bismolyl Anion to an Yttrium-Bismolyl Complex with μ-Bridging Bismuth(I) Centers and Polar Covalent Y-Bi Bonds

Abstract

The synthesis and first structural characterization of the [K(18-crown-6)] bismolyl Bi^tet (C₄ Me₄ Bi) contact ion pair (1) is presented. Notably, according to Natural Resonance Theory calculations, the Bi^tet anion of 1 features two types of leading mesomeric structures with localized anionic charge and two lone pairs of electrons at the Bi^I center, as well as delocalized anionic charge in the π-conjugated C₄ Bi ring. The lone pairs at Bi enable a unique bridging coordination mode of the bismolyl ligand, as shown for the first rare earth metal bismolyl complex (Cp^tet ₂ Y)₂ (μ-η¹ -Bi^tet )₂ (2). The latter results from the salt metathesis reaction of KBi^tet with Cp^tet ₂ Y(BPh₄ ) (Cp^tet =C₅ Me₄ H). The Y-Bi bonding interaction in 2 of 16.6 % covalency at yttrium is remarkably large.

Keywords: bismole; bismuth; bond theory; covalency; yttrium.