Novel six-coordinate oxorhenium "3+2" mixed-ligand complexes carrying the SNS/PO donor atom set: Synthesis and characterization

Replacing the monothiolate group of the so-called "3 + 1" mixed-ligand oxor henium(V) complexes with the bidentate phosphinophenolate ligand produces n ovel "3 + 2" mixed-ligand complexes carrying the SNS/PO donor atom set. Thu s, reactions of either [ReOCl3(L)](-) or [ReOCl2(L)(PPh3)] (HL = o-HOC6H4P( C6H5)(2)) with aminedithiol (H2Ln) in dichloromethane methanol solutions le ad to six-coordinate mixed-ligand oxo-Re(V) complexes of the type [ReO(L-n) (L)], where H2L1 = CH3CH2N(CH2CH2SH)(2) (1), H2L2 = (CH3CH2)(2)NCH2 CH2N(CH 2CH2SH)(2) (2), and H2L3 = CH3CH2SCH2CH2N(CH2CH2SH)(2) (3). The co ordinati on geometry around rhenium is distorted octahedral with the SNS donors of t he aminedithiolate and the phosphorus of the phosphinophenolate ligand defi ning the equatorial plane, while the apical positions are occupied by the o xo group and the oxygen atom of the HL ligand, as shown by single-crystal X -ray analyses of 1 and 3. The strong metal-phosphorus bonds together with t he chelating properties of both ligands contribute to the stability of 18-e lectron [ReO(L-n)(L)] complexes. In fact, these six-coordinate species appe ar to be much more substitution inert than the "3 + 1" analogous complexes vs excess thiolate, such as cysteine or glutathione, during appropriate cha llenge reactions.