Synthesis and Unexpected Reactivity of Germyliumylidene Hydride [:GeH]⁺ Stabilized by a Bis(N‑heterocyclic carbene)borate Ligand

Employing the potassium salt of the monoanionic bis­(NHC)­borate 1 (NHC = N-Heterocyclic Carbene) enables the synthesis and isolation of the bis­(NHC)­borate-stabilized chlorogermyliumylidene precursor 2 in 61% yield. A Cl/H exchange reaction of 2 using potassium trisec.-butylborhydride as a hydride source leads to the isolation of the first germyliumylidene hydride [HGe:⁺] complex 3 in 91% yield. The Ge­(II)–H bond in the latter compound has an unexpected reactivity as shown by the reaction with the potential hydride scavenger [Ph₃C]⁺[B­(C₆F₅)₄]⁻, furnishing the corresponding HGe: → CPh₃ cation in the ion pair 4 as initial product. Compound 4 liberates HCPh₃ in the presence of 3 to give the unusual dinuclear HGe: → Ge: cation in 5. The latter represents the first three-coordinate dicationic Ge­(II) species stabilized by an anionic bis­(NHC) chelate ligand and a Ge­(II) donor. All novel compounds were fully characterized, including X-ray diffraction analyses.