The crystal structures of tetrakis(mu-n-butyrat-kappa O-2:O ')bis[bromidorhenium(III)] and tetrakis(mu-n-butyrato-kappa O-2:O ')bis[chloridorhenium(III)] acetonitrile disolvate

The title complexes, [Re2Br2(O2CC3H7)(4)], (1), and [Re-2(O2CC3H7)(4)Cl-2]center dot 2CH(3)CN, (2), both exhibit paddlewheel structures with four carboxylate ligands bridging two Re-III atoms. The Re-Re distances are 2.2325 (2) and 2.2299 (3) angstrom, indicating quadruple bonds between the Re-III atoms in each complex. Both complexes contain an inversion center at the mid-point of the Re-Re bond. The Re-Br bond [2.6712 (3) angstrom] in (1) is 0.1656 (6) angstrom longer than the Re-Cl distance [2.5056 (5) angstrom] of (2). In (2), the N atom of each co-crystallized acetonitrile solvent molecule is nearly equidistant between and in close contact with two carboxylate C atoms.