The reactivity of the quadruply bonded dirhenium(III) biscarboxylate complexes with monodentate tertiary phosphines and linker ligands

An in-depth study of the reactivity of the quadruply bonded dirhenium(III) carboxylate complexes cis-Re2(μ-O2CCH 3)2Cl4L2 (L = H2O or py) towards monodentate tertiary phosphine ligands in alcohol and chlorocarbon solvents was undertaken. A series of monodentate phosphines (PR3) with known basicities and sterics were chosen to investigate the influence of these factors on the course of the reactions. In our findings, both the basicity and the sterics of the phosphines were found to be important. Depending on these factors, processes such as one or two electron reduction of the dirhenium core, alkoxide ligand incorporation, or cyclodimerization of the dirhenium units can occur. A one-electron reduction process produces complexes of the type cis-Re2Cl4(μ-O2CCH 3)(PR3)2 (R = CH2C6H 5) while a two-electron reduction process produces Re2C1 4(PR3)4(PR3 = PMe3, PMe 2Ph, PMePh2 and PEtPh2) type complexes. Alkoxide ligands, generated from the alcohol reaction solvents, can coordinate to the dirhenium center to form the intramolecular disproportionation complexes of the formula (RO)2X2ReReX2(PAr3) 2(Ar = aryl group; R = Me and Et) or the complex Re2Cl 3(μ-O2CCH3)(OMe)2(PCyPh2) 2. Cyclodimerization of two dirhenium units produces a tetranuclear product with the formula Re4(μ-O)4Cl4(P(p-MeO-phenyl) 3)4. The search for a synthetic route to the ‘non-disproportionation’ alkoxide isomer (Ar3P)(RO)X2ReReX2(OR)(PAr 3) led to a new tris-alkoxide complex, Re2Cl3(OEt) 3(PPh3)2. Finally, the labile axial coordination sites of the dirhenium(III) carboxylate complexes were utilized to form long chain polymeric dirhenium complexes of the type [cis-Re 2(μ-O2CCH3)2Cl4(LL)] n (LL = pyrazine or 4,4′-bipyridine). These complexes exhibit solid state conductivities after oxidative doping. The compound [cis-Re2(μ-O2CCH 3)2Cl4(pyz)]2(μ-pyz), where pyz = pyrazine, was also prepared and structurally characterized