Cyclohexene hydrocarbomethoxylation catalyzed by the Pd(OAc)(2) - p-toluenesulfonic acid - diphosphine systems with broad variation of diphosphine structure and concentration was studied. It was shown that the hydrocarbon part of the structure and the mutual arrangement of the phosphine groups are the factors that control the activity of palladium-containing catalysts. By comparison of the promoting effects of mono and diphosphine ligands, it is demonstrated that bridging trans-diphosphines show higher efficiency with regard to both the kinetic (TOF) and concentration factors (low P/Pd ratios). In particular, their promoting activity is an order of magnitude higher than that for triphenylphosphine at lower P/Pd ratios (8-65 times). The results were interpreted from the standpoint of chelation effect and the geometric matching of the diphosphine structure to the arrangement of vacant s,d-orbitals of the Pd centre. (C) 2011 Elsevier B.V. All rights reserved.