Dirhenium complexes that contain the ligand 1,1-bis(diphenylphosphino)ethene (dppE). Synthesis, characterization and reactivity of Re2Cl4(μ-dppE)2

The dirhenium(II) compound Re2Cl4(μ-dppE)2 (1), where dppE=(Ph2P)2CCH2, which contains an electron-rich triple bond, has been prepared by the reaction of (n-Bu4N)2Re2Cl8 with CH3CO2Na and dppE in refluxing ethanol. Its reactivity towards CO alone, and CO in combination with XylNC and 2,5-Me2C6H3CN has been explored. The complexes Re2Cl4(μ-dppE)2(CO)2 (2) and [Re2Cl3(μ-dppE)2(CO)2(L)]O3SCF3, where L=CO (3), XylNC (4) or 2,5-Me2C6H3CN (5) have been isolated and characterized by IR and NMR spectroscopy, cyclic voltammetry and X-ray crystallography. The complex trans-Re2(μ-O2CCH3)2Cl2(μ-dppE)2 (6) has been obtained by the reaction of Re2(μ-O2CCH3)4Cl2 with dppE. Crystal structure determinations on 1, 2, 4 and 6 reveal that the ReRe distances are 2.2448(5), 2.5748(5), 2.5767(5) and 2.2861(6) Å, which are in accordance with ReRe bond orders of 3, 2, 2 and 3, respectively.