Thermally evaporated and laser-ablated Pd atoms interact with H2 in excess argon to form the side-bonded Pd(H2) complex, which is characterized by 2971, 1507, and 950 cm-1 fundamental frequencies. These infrared absorptions are assigned to Pd(H2) on the basis of the HD and D2 shifts and DFT frequency calculations. Higher H2 concentrations favor the Pd(H2)2,3 complexes, which exhibit 3038, 778 cm-1 and 2909, 730, 319 cm-1 fundamentals, respectively. These complexes involve electrostatic bonding owing to a small amount of charge reorganization. Higher Pd concentrations enhance absorptions due to a Pd--Pd(H2) complex and the stable (PdH)2 molecule with no H−H bond. This work shows that one neutral Pd atom cannot insert into a H2 molecule but that two Pd atoms dissociate molecular hydrogen with no activation energy. Laser ablation produces energetic Pd atoms which also form PdH, electrons which are captured to give PdH2-, and radiation which ionizes H and yields ArnH+ in the matrix cage. Diatomic PdH also for...