Organozinc compounds such as Me₂Zn, Et₂Zn, and Ph₂Zn react at room temperature with decaborane in diethyl ether or tetrahydrofuran to yield the corresponding hydrocarbon (MeH, EtH, and PhH) and ZnB₁₀H₁₂,xS (where x= 1·3–2·0 and S is a molecule of ether solvent). The products are considered to be further examples of neutral 6,9-internally bridged derivatives of decaborane and to contain direct Zn–B bonds. The compounds ZnB₁₀H₁₂,xS ionise in aqueous or alcoholic solutions to give the dianion [(B₁₀H₁₂)₂Zn]^2–. The ultraviolet, infrared, and nuclear magnetic resonance spectra of these compounds have been recorded and their structures and probable topology are discussed. A related reaction of decaborane with diethylmagnesium at low temperatures yields the compound MgB₁₀H₁₂, 2Et₂O but this decomposes in hydroxylic solvents with evolution of hydrogen. Dimethylmercury does not react with decaborane even on prolonged refluxing in diethyl ether.