Although H2 activation with heterometallic complexes consisting of both transition and main group metals is gaining increasing attention, to date most examples involve thermal conditions. The discovery of a new photolytic reaction in this area, raises questions as to how the mechanism proceeds under photochemical conditions. The overall reaction of 2a + H2 to form 3a is calculated to be endergonic with ΔG°298K= +14.9 kcal mol -1 , consistent with a lightdriven process. 2a is an 18-electron complex that does not to react in the absence of light.