CRYSTAL STRUCTURES AND DISORDER IN TWO HETEROBIMETALLIC POLYSULFIDO COMPLEXES. Alok Kumar Mukherjee, Department of Physics, Jadavpur University, Calcutta-700032, India, Monika Mukherjee, Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Calcutta-700032, India

Crystal structures and disorder of two heterobimetallic polysulfido complexes (PPh₄)₂[S₂WS₂MR₂], (1) M = Hg and R=CHCH₂ (2) M =Cd and R =I, have been studied by x-ray diffraction. Both the complexes crystallize in triclinic system. With Z =1 (established by density measurements) and the anions containing dissimilar metals [ W,Hg in 1 and W,Cd in 2 ] and terminal ligands [ S,CHCH₂ in 1 and S, I in 2 ] the centrosymmetric space group P1 is accommodated by a two fold anionic disorder. Due to crystallographically imposed inversion centers in the anions, only half of the dimer and one (PPh₄)⁺ cation comprise the asymmetric unit in each case. The molecular geometries of the anions in the complexes containing (WS₂M) cores coordinated by terminal S^2-,CHCH₂- and I-ligands are best described as distorted edge-condensed bitetrahedrons. The bridging sulfur atoms are bonded symmetrically to the metal atoms with W-Hg and W-Cd distances 3.180(1)Å and 3.178(2)Å in complexes 1 and 2 respectively. The discrepancy between the two Hg-C-C angles in 1 [ 177.9(6)deg./ 165.8(4)deg. ] and the two Cd-I distances in 2 [2.714(2)/2.581(2)Å] can be attributed to the unresolved anionic disorder at the terminal sites. The relevant crystallographic data are summarised below:

(1) a=9.841(2), b=10.070(1), c=13.045(3)Å, [[alpha]] =105.11(1), [[beta]] =95.51(2), [[gamma]] =103.75(1)deg.; R (on F)= 0.0318.

(2) a=9.923(6), b=10.089(3), c=13.171(4)Å, [[alpha]] =108.62(4), [[beta]] =94.65(2), [[gamma]] =100.24(3)deg.; R (on F)= 0.0511.