Studies on organometallic hetero-multiple-bridged molecules. Part 7. Synthesis and properties of dichalcogenide-bridged complexes of rhenium(I) and the crystal and molecular structures of the diphenyl ditelluride-bridged complex, [Re2Br2(CO)6(Te2Ph2)]

Abstract

By reaction of halogeno-carbonyl derivatives of rhenium(I) with the appropriate dichalcogenide E₂Ph₂(E = S, Se, or Te), the dimeric rhenium(I) complexes [Re₂X₂(CO)₆(E₂Ph₂)](X = Br, E = Te; X = I, E = S, Se, or Te) have been prepared in good yields. The preparation of the tetrahydrofuran (thf) adduct [Re₂I₂(CO)₆(thf)₂] is also reported. The crystal and molecular structures of one of these compounds, [Re₂Br₂(CO)₆(Te₂Ph₂)], was solved by X-ray diffraction methods. The crystals are monoclinic, space group P2₁/n, with a= 13.238(4), b= 11.035(4), c= 16.615(5)Å, β= 91.29(3)°, U= 2 426.5 ų, D_c= 3.04 g cm^–3 for Z= 4, and µ(Mo-K_α)= 165.2 cm^–1. Data collection yielded 1 782 observed reflections, R= 0.079. The molecular structure is of the hetero-multiple-bridged type, i.e. it consists of two pseudo-octahedral rhenium(I) centres joined by both bromide and Te₂Ph₂ bridges. Average distances are: Re–Br, 2.64(6), Te ⋯ Br, 3.674(6)Å, while Re ⋯ Re is 3.945(2)Å and Te–Te is 2.794(5)Å. Infrared spectra in the carbonyl stretching region have been compared for the two families of dichalcogenide derivatives [Re₂X₂(CO)₆(E₂Ph₂)] and possible explanations for the observed decrease of (CO) in the sequence S > Se > Te are discussed.