Oxalate-bridged dirhenium(I) hexacarbonyl complexes: synthesis, reactions, and crystal structures

摘要

The complex [{Re(CO)(5)}(2)(mu,eta(1):eta(1)-C2O4)] 1 undergoes thermal decarbonylation to give [Re-2(CO)(6)(C2O4)(n), which reacts with triphenylphosphine and trans-1,2-bis(diphenylphosphino)ethylene (dppene) to give anti-[Re-2(PPh3)(2)(CO)(6)(mu,eta(2):eta(2)-C2O4)] 2 and [Re-2(mu-dppene)(CO)(6)(mu,eta(2) : mu(2) -C2O4)] 4, respectively. Complex 2 is oxidized on prolonged exposure to air (1 week) to form anti-[Re-2(OPPh3)(2)(CO)(6) (mu, eta(2):eta(2) -C2O4)] 3. In the presence of excess dppene, the complex [Re-2(mu-dppene)(2)(CO)(6)(mu, eta(1): eta(1) -C2O4)] 5 is also formed alongside 4. With the chelating diphosphine 1,3-bis(diphenylphosphino)propane (dppp), the complex [(eta(2) -dppp)Re-(CO)(3)( mu, eta(1): eta(1)-C2O4)Re(CO)(3)(eta(2) -dppp)] 6 is formed. The structures of 3 and 4 have been determined by X-ray crystallography. The dppene ligand in complex 4 adopts an unusual "syn" conformation wherein the two phosphorus lone pairs of electrons are eclipsed, thus forming an "A-frame" type of bridge. (C) 2004 Elsevier B.V. All rights reserved.