Formation, Structure, spectra, and reactivity of the adduct between ( η5-Cyclopentadienyl)(1,2-dimethoxycarbonyl-1,2-ethylenedithiolato) rhodium(III) and Dimethyl acetylenedicarboxylate

Abstract

A dithiolatorhodium complex [Rh(Cp)(S 2C 2Z 2)] ( 2, ZCOOMe) reacts with dimethyl acetylenedicarboxylate (DMAD) to give a 1:1 adduct ( 3) in 85% yield. The same adduct is obtained in a prolonged reaction of [Rh(Cp)(cod)] ( 1) with S g and DMAD in 39% yield. In the adduct, DMAD adds between Rh and S. The adduct has been characterized by spectroscopic and by X-ray diffraction techniques. Red-brown crystals of the adduct are triclinic P 1 , with a = 11.789(4), b = 10.789(3), c = 7.960(1) A ̊ , α = 92.33(2), β = 94.07(2), γ = 101.51(2)°, and D c = 1.736( calcd) g cm −1 for Z = 2 . Least-squares refinement gives a final conventional R value of 0.028 for 4091 independent observed reflections. The adduct has a piano-stool structure consisting of a four-memebered ring of ▪ and a five-membered ring of rhodiadithiolene. The adduct is pyrolyzed to afford the decomposition product, tetramethyl 2,3,4,5-thiophenetetracarboxylate (TTME), together with a dissociation product, [Rh(Cp)(S 2C 2Z 2)] ( 2). Adduct 3 is also photochemically dissociated to regenerate [Rh(Cp)(S 2C 2Z 2)] 2.