Synthesis and electrochemical and structural chemistry of rhenium in high oxidation states with sterically hindered polypyridine ligands

The syntheses and electrochemical properties of several novel rhenium compl exes containing the sterically-hindered ligands 6-methylbipyridine, 6-cyano bipyridine, and 2,9-dimethyl-1,10-phenanthroline are reported. The reaction of the ligands with trans,mer-[Re(NPh)(PPh3)(2)Cl-3] was different in ever y case, as is evident by formation of complexes in which rhenium ion exists in different oxidation states. The structures of the complexes have been d etermined by three-dimensional X-ray diffraction methods, and are found to produce novel coordination environments. Of particular note is the rare exa mple of a five-coordinate Re(IV)-imido complex, [Re(NPh)(dmp)(PPh3)(OEt)](), C40H37F6N3OP2Re, which crystallizes in the space group P21/c (no. 14) of the monoclinic system with four molecules in a cell of dimensions a = 11.1 28(2) Angstrom, b = 30.474(6) Angstrom, c = 11.923(3) Angstrom, and beta = 95.78(3)degrees. The structure has been refined to a final value for the cr ystallographic R factor of 0.059 on the basis of 5248 independent reflectio ns. The complex [Re(NPh)(6-mebpy)(PPh3)(Cl)(OEt)](+), C37H35C11F6N3OP2Re cr ystallizes in the space group P (1) over bar (no. 2) of the triclinic syste m with two molecules in a cell of dimensions a = 10.700(2) Angstrom, b 11.8 66(2) Angstrom, c = 15.280(3) Angstrom, alpha = 93.24(3)degrees, beta = 97. 76(3)degrees, and gamma = 106.89(3)degrees. The structure has been refined to a find value for the crystallographic R factor of 0.040 on the basis of 8424 independent reflections.