Halide bridged organophosphorus complexes of HgX2 (X: I, Br and Cl): Synthesis, structure and theoretical studies

Three organophosphorus mercury (II) coordination compounds [Hg 2 (µ-X) 2 X 2 (PPh 3 ) 2 ] {X: I (1), Br (2), and Cl (3)} have been synthesized by the reaction of mercury (II) halides with triphenylphosphine. The prepared complexes were characterized by spectroscopic techniques as well as by elemental analysis. The crystal structure of [Hg 2 (µ-I) 2 I 2 (PPh 3 ) 2 ] (1) was obtained by single-crystal X-ray diffraction study. Crystal data for [Hg 2 (µ-I) 2 I 2 (PPh 3 ) 2 ], C 36 H 30 Hg 2 I 4 P 2 : Monoclinic, space group P 2 1 / c (no. 14), a  = 19.2115(13) A, b  = 11.1291(8) A, c  = 19.0599(14) A, β  = 90.461(2)°, V  = 4075.0(5) A 3 , Z  = 4, T  = 293.15 K, μ (MoKα) = 10.657 mm -1 , Dcalc  = 2.336 g/cm 3 , 46095 reflections measured (4.23° ≤ 2Θ ≤ 49.994°), 7182 unique ( R int = 0.0563, R sigma = 0.0365) which were used in all calculations. The final R 1 was 0.0322 (I \u003e 2σ(I)) and wR 2 was 0.0780 (all data). The single crystal analysis of [Hg 2 (µ-I) 2 I 2 (PPh 3 ) 2 ] complex revealed that it has dimeric structure with bridged halides. [Hg 2 (µ-I) 2 I 2 (PPh 3 ) 2 ] complex has also a supramolecular arrangement through I···H-C interactions. The crystal packing and supramolecular features of these coordination compounds have also been studied using geometrical analysis, Hirshfeld surface analysis and DFT studies. Hirshfeld surface analysis indicated that H···H (49.3%), C···H (10.6%), and I···H (12.8%) interactions are the primary contributors to the intermolecular stabilization in the crystal. The equilibrium geometries of the studied complexes are investigated theoretically at the B3LYP/LANL2DZ level of theory. The calculated energy gap between HOMO-LUMO orbitals for complexes 1, 2, and 3 are in the trend of complex 3 \u003e 2 \u003e 1.