Coordination Chemistry of Methylmercury(II). Complexes of Aromatic Nitrogen DonorTripod Ligands Involving New Coordination Geometries for MeHg(II)

Abstract

Complexes [MeHgL]N03 {L = diphenyl(2-pyridy1)methane (pyCHPh2), bis(2-pyridy1)phenylmethane [(py)2CHPh], and the tripod ligands tris(2-pyridy1)carbinol [(py)3COH] and bis(2-pyridyl)(N-methyl-2-imidazolyl)carbinol [(py)2(NMeIm)COH]} are obtained from addition reactions in acetone. The ligand (py)2CHPh is formed on reaction of (2-benzylpyridy1)lithium with 2-bromopyridine. 1H NMR spectra indicate that (py)2CHPh and (py)2(N-Me1m)COH are present as bidentates in methanol solutions of their complexes, with the latter coordinated via the imidazolyl ring and one pyridyl ring. Spectra are consistent with the presence of weak pi interactions between mercury and phenyl rings in the (py)CHPh2 and (py)2CHPh complexes and the uncoordinated pyridyl ring in the (py)2(N-Me1m)COH complex. In complexes [MeHgL]N03 (L = (py)3OH, (py)3CH) the ligands are present as tridentates in methanol. Crystalline [MeHgL]NO3 [L = (py)3OH, (py)2(N-MeIm)COH] have the tripod ligands coordinating as tridentates, with irregular coordination geometries based on a dominant C-Hg-N’ moiety [Hg-N’ = 2.28 (1) A, C-Hg-N’ = 150(1)O ((py)3COH) and 2.13(1) A, 170(0) ((py)2(N-MeIm)COH)] with weaker Hg-N,N” bonds [2.45(l), 2.53(1) ((py)3OH) and 2.66(l), 2.71(1) A ((py)2(N-MeIm)COH)]. For [MeHg((py)2(N-MeIm)COH)] the coordination geometry resembles a trigonal bipyramid lacking one equatorial donor and with axial direction C-Hg-N’.