DIRHENIUM COMPLEXES DERIVED FROM THE LIGAND 2-MERCAPTOQUINOLINE (2-MQH) - STRUCTURE OF [RE2CL3(MU-PH2PCHPPH2)2(2-MQ)]PF6

The triply bonded dirhenium complexes Re2X4(dppm)2(X = CI, Br; dppm = Ph2PCH2PPh2) react with 2-mercaptoquinoline (2-mqH) to afford the 1:1 adducts Re2X4(dppm)2(2-mqH), in which the 2-mqH ligand (in its zwitterionic form) is probably bound in a monodentate fashion through its deprotonated thiol donor. These complexes undergo a reversible one-electron transfer to give [Re2X4(dppm)2(2-mqH)]+(isolable as their PF6−salts). This oxidation is followed by the slow elimination of HX to give paramagnetic [Re2X3(μ-dppm)2(2-mq)]PF6, in which, in addition to two bridging dppm ligands, there is also a bridging 2-mq ligand bound through its N and S atoms. A single-crystal X-ray structure determination of the chloride complex has been carried out at 20 °C. Crystal data are as follows: monoclinic space group P21c, a = 13.594 (3) Å, b = 20.185 (3) Å, c = 21.691 (4) Å,β= 104.459 (9)°, V = 5763 (3) Å3, Z = 4. The structure was refined to R = 0.030 (Rw= 0.037) for 5705 data with I > 3.0σ(I). The Re-Re distance is 2.2540 (5) Å, and the hydrogen atom on the carbon atom adjacent to the nitrogen of the quinoline ring forms a close contact with one of the rhenium atoms (the Re-H distance is 2.3 (1) Å). These compounds are the first multiply bonded dirhenium complexes that contain Re-thiol bonds. © 1990, American Chemical Society. All rights reserved.