Facile Access to NaOC≡As and Its Use as an Arsenic Source To Form Germylidenylarsinidene Complexes

A facile, one-pot synthesis of [Na(OC≡As)(dioxane)_x ] (x=2.3-3.3) in 78 % yield is reported through the reaction of arsine gas with dimethylcarbonate in the presence of NaO^t Bu and 1,4-dioxane. It has been employed for the synthesis of the first arsaketenyl-functionalized germylene [LGeAsCO] (2, L=CH[CMeN(Dipp)]₂ ; Dipp=2,6-ⁱ Pr₂ C₆ H₃ ) from the reaction with LGeCl (1). Upon exposure to ambient light, 2 undergoes CO elimination to form the 1,3-digerma-2,4-diarsacyclobutadiene [L₂ Ge₂ As₂ ] (3), which contains a symmetric Ge₂ As₂ ring with ylide-like Ge=As bonds. Remarkably, the CO ligand located at the arsenic center of 2 can be exchanged with PPh₃ or an N-heterocyclic carbene ^iPr NHC donor (^iPr NHC=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) to afford the novel germylidenylarsinidene complexes [LGe-AsPPh₃ ] (4) and [LGe-As(^iPr NHC)] (5), respectively, demonstrating transition-metal-like ligand substitution at the arsinidene-like As atom. The formation of 2-5 and their electronic structures have been studied by DFT calculations.