Mercury halide complexes of tertiary phosphines. Part XVI.: Dimer-monomer trend in the 1:1 complexes of mercury(II) halides with bulky tris(2,6-dimethoxyphenyl)phosphine (DMPP)

Reactions of HgX2 (X = Cl, Br, I) with the very bulky tertiary phosphine, tris(2,6-dimethoxyphenyl)phosphine (DMPP), in either a 1:1 or a 1:2 ratio, result in only the isolation of the 1:1 adducts. The structures adopted in the solid state are markedly influenced by the steric requirement of the phosphine. In contrast to the 1:1 triphenylphosphine adducts reported earlier, which are dimeric, the DMPP mercury(II) chloride and bromide complexes are weakly linked dimers while the iodide is the first example of a mercury iodide-phosphine complex with a monomeric distorted trigonal-planar arrangement around mercury. All three complexes contain secondary interactions with the o-methoxy groups. (C) 2000 Elsevier Science Ltd. All rights reserved.