PROTODEMETALLATION OF PYRIDINEPHENYLMERCURY(II) COMPOUNDS BY DIPHENYLDITHIOPHOSPHINIC ACID - THE MOLECULAR AND CRYSTAL-STRUCTURE OF [HG-2(S2PPH2)(4)]

The reactions of [2-(pyridin-2'-yl)-phenyl]mercury(II) acetate [Hg(PhP y)(OAc)] and 2'-yl)-phenyl]mercury(II)diphenyldithiophosphinate [Hg(Ph Py)(S2PPh2)] with diphenyldithiophosphinic acid in chloroform at room temperature both led to the cleavage of the C-Hg bond, giving phenylpy ridine and [Hg-2(S2PPh2)(4)]. The [Hg(PhPy)(S2PPh2)] reaction was moni tored by H-1 NMR spectroscopy. Although the process went smoothly at t he beginning, the protodemetallation reaction slowed down as more acid was added. A hypothesis is put forward as to the cause of this loss o f effectiveness as protodemetallation progresses. The crystal structur e of [Hg-2(S2PPh2)(4)] was solved by X-ray diffraction. This compound crystallizes in the triclinic space group <P(1)over bar> (No. 2) with a=9.150(3), b=10.560(4), c=13.717(5) Angstrom, alpha=93.46(2), beta=10 2.44(2), gamma=105.34(2)degrees, Z=1. Its structure comprises centrosy mmetric dimers, each forming an eight-membered ring in a twisted chair conformation. Each mercury atom is coordinated to one chelating and t wo bridging ligands, giving rise to a distorted tetrahedral arrangemen t around the metal, with two short Hg-S bonds of 2.428(2) and 2.467(2) Angstrom and two long ones of 2.678(2) and 2.761(2) Angstrom. Each Hg is also involved in a 3.338 Angstrom long secondary bond across the e ight-membered ring. IR, Raman and H-1, P-31 and Hg-199 NMR data for [H g(PhPy)(S2PPh2)] and [Hg-2(S2PPh2)(4)] are also discussed.