Coordination compounds of Hg₂²⁺: The crystal structure of Tetrakis-(4-benzylpyridine)dimercury(I) perchlorate

Abstract

Crystals of tetrakis(4-benzylpyridine)dimercury(I) perchlorate, [Hg₂(C₁₂H₁₁N)₄]₂, (ClO₄)₂, are monoclinic,a 11.729(1) Ǻ, b 10.896(1) Ǻ, c 18.392(2) Ǻ, β 96.20(1)°, space group P2₁/c with Z = 2 dimeric formula units. The structure was solved from three-dimensional diffractometer data (2744 independent reflections) by Patterson and Fourier techniques. Block-diagonal least-squares refinement of all non-hydrogen atoms converged at R 0.039, R_w 0.053. The mercury atoms in the centrosymmetric cation are three-coordinate with Hg-Hg 2.5084(7), Hg-N 2.227(7), 2.476(7) Ǻ. The Hg-Hg-N angles are 153.9° and 118.4° respectively. The perchlorate ions span the Hg-Hg bond with long Hg-O contacts of 2.899 and 3.026 Ǻ. This is a new structural type for dimercury(1) coordination compounds. The distortion of the usually linear L-Hg-Hg-L system with the increase in coordination number of the mercury atoms appears to be related to the stability of dimercury(I) complexes with moderately basic N-donor ligands.