REACTION OF (PPh3)2ReH7 WITH DIENES: PREPARATION AND SOME PROPERTIES OF TRIHYDRO η4-DIENE COMPLEXES OF RHENIU

Article abstract of DOI:10.1016/S0022-328X(00)93177-2

L2ReH7 (L=PPh3) reacts smoothly with acyclic and cyclic dienes to give crystalline, air-stable, trihydrido-Η⁴-dienerhenium complexes L2(η⁴-diene)ReH3.The majority of these complexes are fluxional at room temperature; their NMR spectra suggest that at low temperature (-50 deg C) they are pentagonal bipyramidal, with the two phosphine ligands apical and the remaining ligands equatorial.Except for L2(η⁴-cyclopentadiene)ReH3, which readily loses dihydrogen to give L2(η⁵-C5H5)ReH, these diene trihydrides are thermally remarkably stable; L2(η⁴-cyclohexa-1,3-diene)ReH3 loses dihydrogen at >100 deg C to afford L2(η⁵-cyclohexadienyl)ReH2 and then L2(η⁶-C6H6)ReH, and L2(η⁴-butadiene)ReH3 and L2(η⁴-cycloocta-1,5-diene)ReH3 are stable in air up to 115 and 130 deg C, respectively.Protonation of the trihydrido-η⁴-diene complexes affords the corresponding saturated hydrocarbons and/or olefins.Hydrogenation of L2(η⁴-2,3-dimethylbutadiene)ReH3 regenerates the heptahydride L2ReH7.