Multiple Bonds between Transition Metals and Main-Group Elements. 145. Coordination Chemistry of Dirhenium Heptaoxide: Covalent Adducts and Ionic Perrhenyl-Perrhenates

Article abstract of DOI:10.1021/ic00123a001

Dirhenium heptaoxide dissolves in donor solvents such as 1,2-dimethoxyethane, thf, and CH3CN to form adducts of the general formula O3ReOReO3.2L (L = monodentate ligand site). A strong reactivity enhancement of Re2O7 for alkylation, arylation, and similar reactions follows from this unsymmetric Lewis-base coordination. The terminal and bridging oxygens equilibrate in solution ((17)O NMR). These adducts exhibit unsymmetrical bent oxygen bridges in their solid state structures, e.g. O3ReOReO3.dme (X-ray diffraction study; crystal data: space group P21/c, a = 12.162(2) ?, b = 10.830(1) ?, c = 8.195(1) ?, β = 90.80(1)°,Z = 4). With stronger, chelating N-donors L2 such as 2,2'-bipyridine, N,N'-dicyclohexyl-1,4-diazabuta-1,3-diene, and 2,2'-bis(pyrazolyl)propanethe Re2O7.2L complexes have rigid asymmetric bridges even in solution ((17)O NMR). Thermal decomposition liberates Re2O7 (EI-MS) and the respective ligand (EI-MS, TG-MS). With tridentate ligands L3 like tris(pyrazolyl)methane, 1,4,7-triazacyclononane (tacn), N,N',N''-trimethyl-1,4,7-triazacyclononane (tacn*), 1,4,7-trithiacyclononane (ttcn), the Re-O-Re bridge breaks with formation of the ionic perrhenates [ReO3L3](1+)[ReO4](1-). An example is the ionic [ReO3(tacn*)](1+)[ReO4](1-), the structure ofwhich compound has been determined by X-ray diffraction (crystal data: space group P1-, a = 7.389(2) ?, b = 9.143(2) ?, c = 12.294(3) ?, α = 83.68(2)°, β = 77.99(2)°, γ = 89.29(2)°, Z = 2). Intermolecular hydrogen bridging plays a major role in the crystal packing of the ionic perrhenates.