Octa(mu(3)-selenido)hexarhenium(III) complexes containing axial monodentate diphosphine or diphosphine-monoxide ligands

A series of the octahedral hexarhenium(III) complexes containing a variable number of diphosphine (diphos ) or diphosphine-monoxide (diphosO) ligands have been prepared by the substitution of the diphosphine Ph2P(CH2)(n)PPh2 (n=1 to 5) for the iodide ions in the parent octahedral bexarhenium cluster compound [Re6Se8I](3-). The diphosphine Ph2P(CH2)(n)PPh2 ligands adopt an eta (1)-bonding mode with the Re-6(mu (3)-Se)(8) core, and the P donor atom in the pendant arm is noncoordinated and oxygenated in most cases. The ser ies of new hexarhenium(III) complexes have been well-defined by H-1, C-13, and P-31 NMR spectroscopic and FAB-MS data. Four compounds among the series were characterized by X-ray structural determination. Geometrical isomers were identified by NMR spectroscopy as well as by the structural determinat ions. The apical ligand substitution induces significant change in the redo x potentials and the photophysical properties of the Re-6(mu (3)-Se)(8) cor e. The E-1/2 value of the reversible process ReIII6/(Re5ReIV)-Re-III become s more positive with the increasing number of the coordinated P donors. The phosphine-substituted hexarhenium(m) derivatives are highly luminescent, w ith microsecond scale emissive lifetime at ambient temperature, and the ful ly substituted derivatives with the formula [Re6Se8-(eta (1)-diphosO)(6)](2 +) display the strongest luminescence with the longest emission lifetimes.