Dismutation of Tricyanoboryllead Compounds: The Homoleptic Tetrakis(tricyanoboryl)plumbate Tetraanion

A series of unprecedently air-stable (tricyanoboryl)plumbate anions was obtained by the reaction of the boron-centered nucleophile B(CN)(3)(2)(-) with triorganyllead halides. Salts of the anions [R3PbB(CN)(3)](-) (R=Ph, Et) were isolated and found to be stable in air at room temperature. In the case of Me(3)PbHal (Hal=Cl, Br), a mixture of the anions [Me4-nPb{B(CN)(3)}(n)](n-) (n=1, 2) was obtained. The [Et3PbB(CN)(3)](-) ion undergoes stepwise dismutation in aqueous solution to yield the plumbate anions [Et4-nPb{B(CN)(3)}(n)](n-) (n=1-4) and PbEt4 as by-product. The reaction rate increases with decreasing pH value of the aqueous solution or by bubbling O-2 through the reaction mixture. Adjustment of the conditions allowed the selective formation and isolation of salts of all anions of the series [Et4-nPb{B(CN)(3)}(n)](n-) (n=2-4) including the homoleptic tetraanion [Pb{B(CN)(3)}(4)](4-).