The reactions of chlorobis(dialkyldithiophosphato)bismuth(III), [{(RO)2P(S)S}2BiCl] with sodium tetraisopropoxoborate(III), NaB(OPri)4 in 1: 1 molar ratio in refluxing benzene solution yield the corresponding heterobinuclear derivatives of the type [{(RO)2P(S)S}2Bi(μ-OPri)2B(OPri)2] [where R = Me(1); Et(2); Pri(3); Prn(4); and Bun(5)]. All these derivatives are moisture sensitive, dark-brown, viscous liquids that are soluble in common organic solvents and have been characterised by elemental analyses and molecular weight measurements. Probable structures for 1–5 have been proposed on the basis of spectroscopic studies.