A catalyst system comprising palladium acetate and bidentate bis(diphenylphosphino)alkane ligand of general formula Ph2P(CH2)nPPh2 (n = 3-5) was highly active in N,N'-diphenylurea synthesis from nitrobenzene, aniline and carbon monoxide and showed different reactivity from the system with the more common monodentate triphenylphosphine ligand