The effects of changing the microstructure of a soluble polymer-bound catalyst in systems where the polymer acts to regulate the reaction through temperature induced phase separation are illustrated. In comparison with a lower molecular weight ligand with inverse temperature dependent solubility and a cationic rhodium(I) ligated by an amidobisdiphenylphosphine ligand, a higher molecular weight ligand with an alkyldiphenylphosphine end group and a neutral rhodium complex was more sensitive to temperature. Both types of soluble polymer-bound catalysts exhibited temperature dependent hydrogenation activity and were active at low temperature (0-degree-C) and inactive at high temperature (room temperature or 50-degrees-C, depending on catalyst and ligand).