Oxo-rhenium(V) complexes with analogs of bis(diphenylphosphino)ethane

Compounds of the types ReOCl₃(L-L) and ReOCl₂(OEt)(L-L) with bis(diphenylphosphino)ethene (dppen) and bis(diphenylphosphino)ferrocene (dppf) were prepared by reacting the diphosphine with ReOCl₃(OPPh₃)(Me₂S). The ReOCl₃(L-L) compound with bis(diphenylarsino)ethane (dpae) was prepared similarly. Crystallographic work on ReOCl₃(dppen) and ReOCl₃(dpae) confirmed the approximate octahedral environment of the metal and the presence of a Cl ligand trans to the ReO bond. The ReOCl₂(OEt)(L-L) compounds contain a transORe-OEt unit. The visible spectra of both types of compounds include a two-component d-d absorption pattern originating from the spin-allowed excitation of a d electron from the interaxial d orbital in the equatorial plane to the empty d_xz and d_yz orbitals. For ReOCl₂(OEt)(dppf), these bands are masked by strong transitions taking place in the ferrocene moiety. The absorptions of the other systems are not greatly displaced compared to the similar dppe compounds, a small decrease in the transition energy being noted for the dpae complex.