The title complex is highly active and selective for the alternating copolymerisation of carbon monoxide and ethene in CH3COOH-H2O as a solvent. Under typical reaction conditions, 90 degrees C, 4.5 MPa, CO/ethene = 1/1, the productivity passes through a maximum of 15,500 gPK (gPd h)(-1) when the concentration of the acid is 40% (mol mol(-1)), whereas the limiting viscosity number (LVN) increases upon increasing the acid concentration. Under the above conditions, but in the presence of sodium acetate, a polyketone (PK) of higher molecular weight is obtained, though at the expense of the productivity. Under higher pressure of ethene both productivity and LVN increase; under higher pressure of CO the productivity slightly decreases, whereas the LVN increases. These results are discussed taking into account the factors relevant to the chain growing and the termination processes. (c) 2006 Elsevier B.V. All rights reserved.