Irradiation of Ru(dmpe)(2)H-2 (dmpe = (CH3)(2)PCH2CH2P(CH3)(2)) in cyclohexane solution with a picosecond pulsed laser at 300 nm leads to immediate formation of Ru(dmpe)(2) and H-2. The experiments show that metal-hydrogen bond cleavage, H-H bond formation, and rearrangement of the metal-phosphine skeleton occur within the instrument rise time of ca. 16 ps. A partial decay of the transient with a rate constant of 2.5 x 10(9) s(-1) is also observed. The transient spectral data obtained for the short- and long-lived transients are similar.