Kinetic and DFT computational studies reveal that the reaction of {(IPr)Ni(μ-S)}2 (1, IPr = 1,3-bis(2,6-diisopropyl-phenyl)imidazolin-2-ylidene) with dihydrogen to produce {(IPr)Ni(μ-SH)}2 (2) proceeds by rate-limiting heterolytic addition of H2 across a Ni-S bond of intact dinuclear 1, followed by cis/trans isomerization at Ni and subsequent H migration from Ni to S, to produce the bis-hydrosulfide product 2. Complex 1 reacts in a similar manner with pinacolborane to produce {(IPr)Ni}2(μ-SH)(μ-SBPin) (3), showing that heterolytic activation by this nickel μ-sulfide complex can be generalized to other H-E bonds.