Work

Four‐Centre, Multielectron Bonding in Rare‐Earth Germole Sandwich Complexes

Year: 2025

Type: article

Abstract: Reduction of the germole‐ligated sandwich complexes [(η5‐CpGe)M(η5‐Cpttt)]2 (1M, M = Y, Gd, Dy) with one or two equivalents of KC8/2.2.2‐cryptand produces [{(η5‐CpGe)M(η5‐Cpttt)}2]− (2M) and [{(η5‐CpGe)M(η5‐Cpttt)}2]2− (3M), respectively, as salts of [K(2.2.2‐cryptand)]+ (CpGe = [GeC4‐2,5‐(SiMe3)2–3,4‐Me2]2−, Cpttt = 1,2,4‐C5tBu3H2. X‐ray crystallography shows that the bond lengths within the central {M2Ge2} rings contract markedly with each reduction. Computational analysis reveals the presence of unusual four‐center, multielectron {M2Ge2} bonds, with the reduction increasing the germanium–germanium and metal–germanium bond orders while reducing the metal‐Cpttt bond order. Analysis of 2Y by EPR spectroscopy reveals delocalization of the unpaired spin across both yttrium centers. Magnetic measurements on radical‐bridged 2Gd show a large exchange coupling constant of −95 cm−1 (−2 J formalism). Single‐molecule magnet behavior is found for the dysprosium–germole complexes. Complexes 1Y, 2Y, and 3Y can be interconverted by one‐electron oxidation or reduction reactions of 2Y, which itself can also be formed by comproportionation of 1Y and 3Y. The masked divalent reactivity of 3Y is demonstrated through one‐electron reduction of 2,2′‐bipyridyl to give [(η5‐CpGe)Y(η5‐Cpttt)(2,2′‐bipy)]− (4Y) and activation of Ph2Se2 to give [(η5‐CpGe)Y(η5‐Cpttt)(SePh)]− (5Y).

Source: Angewandte Chemie International Edition

DOI: 10.1002/anie.202502455