This invention is directed to a class of compounds that can be both monodentate and bidentate in their association with a transition metal to form a catalyst for reactions such as the hydroformylation of olefins to produce aldehydes. The compounds contain two phosphorus atoms having different steric and/or electronic nature. In hydroformylation catalysts, the compounds advantageously can produce a variable n/iso product mixture of aldehyde products that can be varied by simply changing process variables such as [H2]/[CO] partial pressure gas ratio or temperature/inert gas partial pressure.