Crystal and molecular structure of Octacarbonylbis(diphenylarsino)-methanedimanganese(0)

Abstract

The crystal structure of the complex Mn₂(CO)₈(dam) (dam = Ph₂AsCH₂AsPh₂) has been determined by three-dimensional X-ray diffraction methods. The crystals are triclinic, space group P1, with a 11.191(1), b 16.498(5), c 9.455(1) Å, a 93.64(2), β 109.08(2), γ 89.36(2)º and contain two discrete, binuclear molecules of Mn₂(CO)₈(dam) per unit cell. The structure, solved by direct and Fourier methods, was refined by a least-squares procedure to R and R_w of 0.065 and 0.082 respectively for 1907 independent, statistically significant reflections collected by counter methods. The feature of particular interest in this compound is the accommodation of the bridging bidentate dam ligand [As.. .As separation 3.242(2) Å] across a shorter Mnº-Mnº bond [2.962(3) Å] which constrains the molecule so that a much less staggered configuration of the two manganese coordination octahedra is observed relative to the parent compound Mn₂(CO)₁₀, the rotation of the two equatorial planes in the former being 30º.