TETRAIODODIBENZOATODIRHENIUM(3)

The new compound Re2I4(O2CC6H6)2 has been isolated. In order to investigate the secondary dependence of Re-Re bond length on steric factors, the crystal and molecular structures of this compound, which was expected to be μ-dibenzoatotetraiododirhenium(III), have been determined from 2559 independent, nonzero reflections collected with a manual counterdiffractometer, using Mo Kα radiation. The compound crystallizes in the triclinic space group C1 with four dinuclear molecules in a unit cell of dimensions: a = 11.224 ± 0.003 Å, b = 17.535 ± 0.005 Å, c = 10.869 ± 0.003 Å, α = 91° 54′ ± 3′, β = 89° 10′ ± 5′ γ = 92° 45′ ± 5′ (ωcalod = 3.49 g cm-1, ωobsd = 3.50 ± 0.04 g cm-1). The structure was solved by conventional Patterson and Fourier methods and refined by the full-matrix leastsquares procedure to final unweighted and weighted residuals of 0.040 and 0.048, respectively. The dinuclear molecular structure is formally derived from the Re2X2-8 ion by replacement of four halide ions by two bridging benzoate ions. The remarkably short Re-Re distance of 2.198 (1) Å indicates the presence of quadruple metal-metal bonding, as has been proposed for other dinuclear compounds of Re(III) and Mo(II). © 1969, American Chemical Society. All rights reserved.