Novel trivalent organophosphonite ligands having the structure of general formula (I): wherein R is an alkyl or aryl group containing 1 to 30 carbon atoms; Ar1 and Ar2 are aryl groups containing 4 to 30 carbon atoms; R1 to R6 are H or alkyl or aryl hydrocarbon radicals containing 1 to 40 carbon atoms; and X is a connecting group or a simple chemical bond, were developed and found to be very active for hydroformylation processes for ethylenically unsaturated substrates. Catalyst solutions prepared from these ligands with a Rh metal show an unusual “ligand acceleration effect” for simple alkenes, i.e., the hydroformylation activity increases as the concentration of ligand increases, and are capable of producing linear or branched aldehydes under typical hydroformylation conditions.