Facile Rearrangement of a Bis(N‐heterocyclic carbene)borate Chelate Ligand and Access to [:GeX] + Complexes (X = H, Cl)

The unexpected isomerization of the potassium bis(N‐heterocyclic carbene)borate [BPh 2 ( t Bu NHC) 2 ]K ( 2′ ) ( t Bu NHC = 3‐ tert ‐butylimidazole‐2‐ylidene) in toluene, affording the unique potassium imidazolyl–NHC–borate [BPh 2 ( t Bu Im)( t Bu NHC)]K ( 2 ) ( t Bu Im = 3‐ tert ‐butyl‐2‐imidazolyl), is reported. The latter crystallizes as the centrosymmetric dimer 2 2 . According to the results of DFT calculations, the rearrangement of 2′ is basically triggered by the solvation of the K + ion: while 2′ is most stable in THF solutions, the formation of 2 is feasible in least coordinating toluene and drastically favored through dimerization to give 2 2 . The latter reacts with GeCl 2 · dioxane to form solely the unprecedented chlorogermyliumylideneborate [BPh 2 ( t Bu Im)( t Bu NHC)]GeCl ( 3 ). Treatment of 3 with KHB( s Bu) 3 furnishes the corresponding hydridogermyliumylideneborate complex [BPh 2 ( t Bu Im)( t Bu NHC)]GeH ( 4 ) in 66 % yield.