STRUCTURAL STUDIES OF STERIC EFFECTS IN PHOSPHINE COMPLEXES .6. SYNTHESIS, CHARACTERIZATION AND MOLECULAR-STRUCTURE OF THE DINITRATO(TRIMESITYLPHOSPHINE)MERCURY(II) DIMER

The synthesis and crystal and molecular structure of the dinitro(trimesitylphosphine)mercury(II) dimer is reported. The compound [HgP(mesityl)3(NO3)2]2 belongs to the monoclinic space group P21/c (C52h, No. 14) with a = 19.940(3), b = 17.588(2), c = 16.403(2) Å, β = 100.36(1)° and Z = 4; the asymmetric unit contains two independent half dimers. The structure was refined to a final R of 0.056 for 4220 observed reflections measured by diffractometer. The mercury coordination in both dimers I and II is characterized by three strong nearly coplanar bonds (in I HgP 2.395(3), HgO 2.180(12) and 2.257(8), and 2.342(9)) and three weaker HgO bonds in the range 2.58-2.90 Å. Both independent trimesityl phosphine ligands have the same regular propeller conformation (HgPCC torison angles 42 to 49°) and the largest CPC angles (mean value 113.2(5)°) and cone angle (θ = 208°) yet determined. The main difference between the two independent dimers is the orientation of the non-bridging nitrato groups. Nitrato vibrational and phosphine 1H and 31P n.m.r. data are also presented for [HgP(mesityl)3(NO3)2]2. © 1979.