Phosphorus-31 and Mercury-199 N.M.R. studies on mercury(II) halidetributylphosphine complexes

Abstract

Phosphorus-31 and mercury-199 N.M.R. studies have been carried out on HgX₂P₂,Hg₂X₄P₂, mixtures thereof and the oligomers Hg₂X₄P₃, Hg₃X₆P₂ and Hg₄X₈P₂ where X = Cl, Br, I and P = tributyl-phosphine. The results are consistent with exchange of both phosphine and halogen. The phosphine exchanges slowly on the N.M.R. time scale at room temperature, but rapidly on the preparative time scale. Halogen exchange is fast on both the N.M.R. and preparative time scales at room temperature; cooling to -120°C reduces exchange of terminal halogens to a slow rate on the n.m.r. time scale. Increase in the coupling constant J_P,_Hg at low temperature is attributed to the slowing down of halogen exchange. Exchange of bridging halogens is still fast at -120°C.    

Mercury-199 chemical shifts span a range of over 3000 ppm and shifts have been correlated with ³¹P chemical shifts and with the coupling constants J_P,Hg The ¹⁹⁹Hg n.m.r. data confirm the existence of an asymmetrical isomer of Hg₂I₄(PBu₃)₂.