Rhenium(V) oxide complexes. Crystal and molecular structures of the compounds trans-ReI 2O(OR)(PPh 3) 2 (R = Et, Me) and of their hydrolysis derivative ReIO 2(PPh 3) 2

The structure of the complex ReI 2O(OEt)(PPh 3) 2·3/2C 6H 6 (I) has been investigated: the dark-yellow crystals are monoclinic, space group P2 1/n, with a = 17.410(8), b = 17.322(6), c = 15.039(5) Å, β = 103.49(3)°, Z = 4. Least-squares refinements based on 3636 significant counter data led to a final R value of 0.059. The compound exhibits a slightly distorted octahedral coordination, with the two PPh 3 groups trans between themselves (mean ReP 2.523 Å), as well as the two iodide ligands (mean ReI 2.789 Å). The ethoxo group (ReO 1.880(9) Å) and the oxide ligand (ReO 1.715(9) Å) occupy the other two coordination sites. Compound I in methanol transforms into ReI 2O(OMe)(PPh 3) 2 (II), which has been characterized by X-ray analysis in crystals containing CHCl 3 molecules of solvation. The crystals are triclinic, space group P1, a = 12.835(3), b = 13.067(4), c = 13.485(4) Å, α = 89.71(2)°, β = 71.61(2)°, γ = 70.19(2)°, Z = 2. The refinements gave a final R value of 0.036, on the basis of 4524 significant counter intensities. The stereochemistry and the bond parameters are similar to those found in compound I. In particular the ReO (methoxo) and ReO (oxide) bond lengths are 1.859(5) and 1.698(5) Å respectively. Hydrolysis reactions of both compounds I and II give the violet derivative ReIO 2(PPh 3) 2 (III). The crystal data are: orthorhombic, space group Aba2, a = 19.834(5), b = 16.144(3), c = 10.560(2) Å, Z = 4. 1435 significant counter reflections were used in the refinements the final R value being 0.039. The compound is an unusual example of a five coordinate Re(V) complex. It possesses a rigorous C 2 crystallographic symmetry and exhibits a distorted trigonal bipyramidal stereochemistry, with the two PPh 3 groups in an axial direction (ReP 2.488(3) Å) and the two oxide and the iodide ligands in equatorial positions. The ReI and ReO interactions have values of 2.664(2) and 1.742(11) Å respectively. © 1983.