Mercury(II) halide complexes of tertiary phosphines. Part 9. Study of the tris(2-cyanoethyl)phosphine complexes [HgX2{P(CH2CH2CN)3}m](X = Cl, Br, or I; m= 1 or 2): crystal structures of [HgBr2{P(CH 2CH2CN)3}2]· Me2CO and [{HgCl2[P(CH2CH2CN)3]}n]

Abstract

The complexes [HgX₂{P(CH₂CH₂CN)₃}_m](X = Cl, Br, or I; m= 1 or 2) have been prepared and characterised by analytical and far-i.r. spectroscopic data. In addition, the X-ray crystal structures of [HgBr₂{P(CH₂CH₂CN)₃}₂]·Me₂CO (1) and [{HgCl₂[P(CH₂CH₂CN)₃]}_n](2) have been determined. Crystals of (1) are monoclinic, space group P2₁/n, with a= 9.174(6), b= 15.795(9), c= 20.741 (11)Å, β= 93.01 (5)°:, and Z= 4; those of (2) are orthorhombic, space group P2₁2₁2₁, with a= 20.872(14), b= 7.854(8), c= 8.519(9)Å, and Z= 4. Both structures were solved using the heavy-atom method and refined to final R values of 0.043 for (1) and 0.053 for (2) using 2 511 and 1 252 observed diffractometer data respectively. Complex (1) is found to be monomeric, while (2) adopts a polymeric structure in which almost linear Cl–Hg–P(CH₂CH₂CN)₃ units are linked by chlorine atoms to give single chains. The geometry about mercury in the two complexes indicates tris(2-cyanoethyl)phosphine to be a strong σ-donor and comparable with triethylphosphine in its interactions with mercury(II) halides. This is confirmed by far-i.r. studies of the six complexes prepared.