The technetium(III) compound (n-Bu4N)2[Tc2Br8] was prepared by metathesis of (n-Bu4N)2[Tc2Cl8] with concentrated aqueous HBr in acetone and recrystallized from acetone–diethyl ether solution (2 : 1 v/v). The acetone solvate obtained, (n-Bu4N)2[Tc2Br8]·4[(CH3)2CO] ( 1), crystallizes in the monoclinic space group P21/n with a = 13.8959(8), b = 15.2597(9), c = 15.5741(9), = 109.107(1)°, R1 = 0.028, and Z = 4. The Tc–Tc distance (2.1625(9) ) and the average Tc–Br distances (2.4734(7) ) are in excellent agreement with those previously determined by EXAFS spectroscopy. These and other experimental data on quadruply metal–metal bonded group 7 [M2X8]2- dimers (M = Tc, Re; X = Cl, Br) are compared to the results of a set of multi-configurational quantum chemical studies. The calculated molecular structures of the ground states are in very good agreement with the structures determined experimentally. The theory overestimates the []* transition energies by some 1000 cm-1, but mimics the trends in * energies across the series.