A MIXED-VALENCE TETRANUCLEAR RHENIUM CLUSTER WITH RE(I)-RE(III) DATIVE BONDS

The reaction between Re2I2(CO)8 and S2Ph2 gives Re4I2(SPh)6(CO)8 (2) under forcing conditions. The product has been characterized by X-ray diffractometry: triclinic, space group P1BAR, a = 16.471 (3) angstrom, b = 15.044 (3) angstrom, c = 10.997 (3) angstrom, alpha = 110.91 (2)-degrees, beta = 88.19 (2)-degrees, gamma = 101.83 (2)-degrees, V = 2489 (2) angstrom 3, Z = 2, and R = 0.049 for 2564 observed reflections. The structure consists of a central distorted edge-sharing bioctahedral Re2(SPh)6I2(CO)2 core with all the SPh groups in the equatorial plane and a syn arrangement of the two I and the two CO ligands in the axial positions. Two SPh and one I ligands in a relative cis configuration on each central rhenium atom bridge to lateral Re(CO)3 moieties. The lateral Re(I) centers form dative bonds to the internal Re(III) centers, which are not bonded to each other. Reaction of 2 with PPh3 or CyNC (Cy = cyclohexyl, C6H11) gives Re4I2(SPh)6(CO)6L2 (L = PPh3 (3), CyNC (4), where the carbonyls on the inner rhenium atoms have been selectively substituted. Reaction of 2 with CO gives rise to reductive elimination of S2Ph2 and formation of ReI(CO)5 and Re2(SPh)2(CO)8.