Synthesis and structure of a μ-(E)-vinylene-bis[dimethylglyoximato(1-)-dimethylglyoximato(2-)-(triphenylphosphine) rhodate] complex: A vinylene-bridged dinuclear rhodium complex

Article abstract of DOI:10.1016/S0022-328X(96)06648-X

[Rh(dmgH)₂(PPh₃)]^-(dmgH₂ = dimethylglyoxime), prepared by reduction of [Rh(dmgH)₂(PPh₃)Cl] with NaBH₄ in methanolic KOH, reacts with (E)-1,2-dichloro ethylene to give the (E)-vinylene-bridged dinuclear rhodium complex [{K(MeOH)₂}₂-{(PPh₃)(dmg)(dmgH)Rh-CH=CH-Rh(dmg)(dmgH)(PPh₃)}] (1). Furthermore, 1 is formed in a mixture with [Rh(dmgH)₂(PPh₃)(Z)-CH=CHCl] (2) and [Rh(dmgH)₂(PPh₃)CH=CH₂] (3) in the reaction of [Rh(dmgH)₂(PPh₃)]^- with (Z)-ClCH=CHCl and in a mixture with 3 in the reaction of [Rh(dmgH)₂(PPh₃)]^- with acetylene. 1 crystallizes in the monoclinic space group C2/c with: a = 22.711(5), b = 10.465(2), c = 27.910(6) A, β = 101.71(3)°, Z = 4. The structure was refined up to R1 = 0.0373 for 4903 reflections. The molecule consists of two [Rh(dmg)(dmgH)(PPh₃)] subunits linked by an (E)-CH=CH bridge. The oxygen atoms of the dimethylglyoximato ligands and the solvent molecules (MeOH) are coordinated at the potassium ions. ¹H, ¹³C and ₃₁P NMR spectra of 1 agree definitely with the molecular structure in solid state, as was shown by comparison of the experimental spectra with the computer simulated spectra on the basis of AA′MM′XX′, AMM′XX′ and AA′XX′ spin systems for the vinylene protons, the carbon atoms and the phosphorus atoms respectively. In CDCl₃/CD₃COOD the neutral complex [(PPh₃)(dmgH)₂Rh-CH=CH-Rh(dmgH)₂(PPh₃)] (1′) is formed, as was shown by ¹H, ¹³C and ³¹P NMR spectroscopy.