A general strategy for the preparation and characterization of high molecular weight coordination polymers based on bifunctional phosphorus ligands and palladium or platinum dichloride is described. Metal-to-ligand stoichiometry is of key importance for the formation of linear coordination polymers with high degrees of polymerization and was studied in detail. Heating of precursor complexes in the melt led to the highest degrees of polymerization. Peak molecular weights of 71 000 g/mol were reached, corresponding to a degree of polymerization of 100 units. The coordination polymers based on palladium dichloride were demonstrated to be linear by performing a stopper experiment. Complexation with platinum resulted in the formation of a network polymer due to platinum's ability to coordinate three phosphorus atoms. The palladium coordination polymers form reversibly and are in equilibrium with rings. The concentration dependence of the ring−chain equilibria was studied for the palladium complexes with 31P NMR and size exclusion chromatography, and critical concentrations of 70−180 mM were determined, below which no polymers are present.