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

The synthesis and first structural characterization of the [K(18‐crown‐6)] bismolyl Bitet (C4Me4Bi) contact ion pair 1 is presented. Notably, according to Natural Resonance Theory calculations, the Bitet 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, and delocalized anionic charge in the π‐conjugated C4Bi 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 (Cptet2Y)2(μ‐η1‐Bitet)22. The latter results from salt metathesis reaction of KBitet with Cptet2Y(BPh4) (Cptet = C5Me4H). The Y–Bi bonding interaction in 2 of 16.6% covalency at yttrium is remarkably large.