The ^3(dσ *pσ) excited state of Ir_2(TMB)_4^(2+) (TMB = 2,5-diisocyano-2,5-dimethylhexane) reacts with hydrogen atom donors to give Ir_2(TMB)_4H_2^(2+) (Ir_2H_2). This d^7-d^7 dihydride has been isolated as a tetraphenylborate salt: v(Ir-H) 1940 cm^(-1), v(Ir-Ir) 136 cm^(-1). [Ir_2(TMB)_4H_2] [B(C_6H_5) _4]_2·CH_3C_6H_5, Ir_2C_(95)H_(114)N_8B_2, crystallizes in the monoclipic system, space group P2_1/c (No. 14), with a = 10.54 (2) Å, b = 31.02 (4) Å, and c = 27.05 (4) Å, β = 91.57 (3)°, V = 8841 (3) Å^3, and Z = 4. The Ir-Ir separation is 2.920 (2) Å, approximately 0.3 Å shorter than Ir-Ir in the d^8 dimer (lr_2) but ~0.1 Å longer than in the diiodide, Ir_2(TMB)_4I_2^(2+). The reaction of Ir_2H_2 with styrene gives Ir_2 and ethylbenzene
