Dirhenium Complexes Re2 Research Articles

The activation and transformations of vinyl acetate at a dirhenium carbonyl center

The reaction of Re2(CO)8(μ-C6H5)(μ-H), 1 with vinyl acetate in methylene chloride by heating at 40 °C yielded three new products: Re3(CO)13(μ-η2-C2H3), 3, (24% yield), Re2(CO)8(μ-η2-O2CCH3)(μ-H), 4, (9% yield) and Re2(CO)8(μ-η2-CHCHO2CCH3)(μ-H), 5, (13% yield). Compound 3 was also obtained in a similar yield from the reaction of Re2(CO)8(μ-H)[μ-η2-C(H) = C(H)Bun], 2 with vinyl acetate, but compounds 4 and 5 were not obtained. All of the products were characterized structurally by single-crystal X-ray diffraction analysis. Compound 3 consists of an open trirhenium cluster containing two rhenium – rhenium bonds. One of the rhenium – rhenium bonds contains a μ-η2-(σ+π)-coordinated C2H3 (vinyl) ligand. Compound 4 contains two rhenium atoms with a bridging η2-acetate ligand and a bridging hydrido ligand. Compound 5 contains two mutually bonded Re–Re atoms with a bridging (σ+π)-coordinated acetate-substituted vinyl group and a bridging hydrido ligand by the cleavage of one of the CH bonds on the β–carbon atom of the vinyl group of the vinyl acetate. The reaction of compound 3 with I2 resulted in cleavage of the Re(CO)5 group to yield the known complex Re(CO)5I and the new dirhenium complex Re2(CO)8I(μ-η2-C2H3), 6 containing a μ-η2-(σ+π)-coordinated vinyl group.

Re2(CO)6(μ-thpymS)2 (thpymSH = pyrimidine-2-thiol) as a versatile precursor to mono- and polynuclear complexes: X-ray crystal structures of fac-Re(CO)3(PPh3)(κ2-thpymS) and two isomers of ReRu3(CO)13(μ3-thpymS)

The dirhenium complexes Re2(CO)6(μ-thpymS)2 (1) and eq-Re2(CO)9{κ1-(S)-SN2C4H8} (2) are obtained from the reaction of tetrahydropyrimidine-2-thiol (thpymSH) with Re2(CO)8(NCMe)2 or Re2(CO)10. Complex 1 proves to be an excellent precursor to a range of monometallic and cluster complexes acting as a source of “Re(CO)3(thpymS)”. Thus, reactions with triphenylphosphine (PPh3) and bis(diphenylphosphino)methane (dppm) afford mononuclear fac-Re(CO)3(PPh3)(κ2-thpymS) (3) and fac-Re(CO)3(κ1-dppm)(κ2-thpymS) (4), respectively. A crystal structure of 3 reveals that the pyrimidine-2-thiolate binds in a chelating fashion. Reactions with M3(CO)12 (M=Ru, Os) at moderate temperatures afford mixed-metal clusters. With Ru3(CO)12 in boiling thf isomeric tetranuclear butterfly clusters ReRu3(CO)13(μ3-thpymS) (5–6) result which differ in the position of the capping pyrimidine-2-thiolate ligand on the cluster surface. Thus in the kinetic isomer 5, the pyrimidine-2-thiolate caps the ReRu2 face while in the thermodynamic isomer 6 it caps the Ru3 face. A similar reaction with Os3(CO)10(NCMe)2 in boiling benzene affords predominantly the ReOs2-capped tetranuclear cluster ReOs3(CO)13(μ3-thpymS) (7), together with small amounts of (μ-H)Os3(CO)9(μ3-thpymS) (8) resulting from loss of rhenium. Cluster 7 is stable in refluxing toluene but slowly converts to isomeric 9 in xylene at 140°C but only in low yields. The crystal structures of isomeric 5–6 have been solved and show only small variations in the cluster core geometry. Density functional calculations show that clusters 6 and 9 are slightly more stable than 5 (ΔG 2.0kcalmol−1) and 7 (ΔG 1.5kcalmol−1), respectively, and a mechanism is proposed for these conversions in which the pyrimidine-2-thiolate becomes bidentate after release of the pyrimidine group.

Assemblies of multiply bonded [Re2]n+ cores possessing bond orders of 3 or 3.5 that are linked by dicarboxylate bridges

An earlier study describing the exchange of the μ-acetato ligands of Re2(μ-O2CCH3)Cl4(μ-dppm)2 (1) and cis-Re2(μ-O2CCH3)2Cl2(μ-dppm)2 (2) by dicarboxylic acids has been expanded to include reactions with the monocarboxylic acid isonicotinic acid, and the dicarboxylic acids adipic acid, 4,4′-biphenyldicarboxylic acid, fumaric acid, trans-1,4-cyclohexanedicarboxylic acid and 1,1′-ferrocenedicarboxylic acid. Further examples of complexes that are “dimers-of-dimers” and triangular supramolecular assemblies involving retention of the basic electronic and molecular structures of the dirhenium units present in 1 and 2 have been obtained. In addition, the dirhenium complexes Re2(μ-O2CC6H4N)Cl4(μ-dppm)2 (7) and cis-Re2(μ-O2C6H10CO2Et)2Cl2(μ-dppm)2 (11) have been isolated, as well as the trimetallic complex cis-Re2Cl2(μ-dppm)2[(μ-O2CC5H4)2Fe] (14) that is formed from the reaction of 2 with (C5H4CO2H)2Fe. The crystal structures of 7, 11 and 14 are reported.