BIMETALLIC COMPLEXES OF RHENIUM(I) - PREPARATION OF RE(BL)(CO)3CL AND [RE(CO)3CL]2(BL) (BL = 2,3-BIS(2-PYRIDYL)PYRAZINE, 2,3-BIS(2-PYRIDYL)QUINOXALINE AND 2,3-BIS(2-PYRIDYL)BENZO[G]QUINOXALINE)

Mono- and bimetallic complexes of Re(CO)3Cl containing the bidentate, bridging ligands 2,3-bis(2-pyridyl)pyrazine (dpp), 2,3-bis(2-pyridyl)quinoxaline (dpq), and 2,3-bis(2-pyridyl)benzo[g]quinoxaline (dpb) have been prepared and characterized. The synthesis and characterization of the new bidentate bridging ligand dpb are reported. The lowest energy electronic absorption band has been assigned as a metal-to-ligand charge-transfer (MLCT) process, where the acceptor state is localized primarily on the bridging ligand. Unlike the analogous Ru bimetallic complexes of dpp and dpq, the bimetallic complexes of Re that contain these ligands do not luminescence. The first reduction of these complexes occurs between −0.12 and −1.00 V (vs a 3 M NaCl Ag/AgCl reference electrode), and is localized on the bridging ligand. With the exception of Re(dpp)(CO)3Cl, the second reduction of these complexes is also localized on the bridging ligand. Data is presented that shows that the Re(CO)3Cl moiety is more effective at stabilizing the reduced forms of dpp, dpq, and dpb than Ru(bpy)22+. This yields a series of five mono- and bimetallic complexes that have two ligand-centered reductions at relatively positive potentials. © 1990, American Chemical Society. All rights reserved.