We selected for study the ligands 2-(diphenylphosphino)biphenyl and its 2,6-dimethoxy and 2,4,6-triisopropyl derivs.  Testing of the ligands in the hydroformylation of 1-octene was performed both at 80 ° and at 60 ° under 2 MPa CO/H2 for 16 h.  Both [Rh4(CO)12] and [Rh(acac)(CO)2] were used as catalyst precursors and were tested with different ligand ratios to check for any changes in selectivity.  Each of the reactions proceeded quickly but with relatively poor chemoselectivity and high isomerization when compared to other successful catalysts.  Overall, these results show that when these ligand complexes and the unligated rhodium carbonyls are in equil. under catalytic conditions the unligated rhodium carbonyls are favored.  We believe that this is due to a mixt. of the poor Lewis basicity of the phosphine and the influence of the biaryl substituent.  In summary, we have shown that, in rhodium-catalyzed hydroformylation reactions, phosphine ligands can be dissocd. depending on their steric and electronic properties.  Thus, whereas the use of ortho-phenyl-substituted monodentate ligands is highly advantageous in cross-coupling chem., in hydroformylation reactions they do not function as bulky monodentate ligands.