catena-Poly[di-μ3-bromido-hexa-μ2-bromido-dibromidobis(O-methyl pyridine-2-carboximidate-κ2 N,N′)pentamercury(II)]

The title compound, [Hg5Br10(C7H8N2O)2]n, contains two μ3-bridging Br atoms, six μ2-bridging Br atoms and two terminal Br atoms. One HgII atom, lying on an inversion center, adopts a distorted octahedral geometry defined by six Br atoms. Two HgII atoms adopt a distorted square-pyramidal geometry by five Br atoms and the other two HgII atoms have a distorted tetrahedral geometry by two N atoms from a chelating O-methyl pyridine-2-carboximidate ligand and two Br atoms. The Br atoms link the HgII atoms into a ribbon structure along [100].

The title compound, [Hg 5 Br 10 (C 7 H 8 N 2 O) 2 ] n , contains two 3bridging Br atoms, six 2 -bridging Br atoms and two terminal Br atoms. One Hg II atom, lying on an inversion center, adopts a distorted octahedral geometry defined by six Br atoms. Two Hg II atoms adopt a distorted square-pyramidal geometry by five Br atoms and the other two Hg II atoms have a distorted tetrahedral geometry by two N atoms from a chelating Omethyl pyridine-2-carboximidate ligand and two Br atoms. The Br atoms link the Hg II atoms into a ribbon structure along [100].
Here, we report the synthesis and structure of the title compound.
The asymmetric unit of the title compound ( Fig. 1) consists of 2.5 crystallographically independent Hg II atoms, five bromide ions and one neutral O-methylpyridine-2-carboximidate ligand. The Br2 atom adopts a µ 3 -mode to bridge three Hg II atoms, while Br1, Br3 and Br5 are coordinated to Hg II atoms in a µ 2 -mode. The Br4 atom is coordinated to one Hg II atom in a terminal fashion. The Hg1 atom adopts a distorted tetrahedral coordination geometry defined by two N atoms from one O-methylpyridine-2-carboximidate ligand and two Br atoms. The Hg2 atom, lying on an inversion center, adopts a distorted octahedral geometry by six Br atoms and Hg3 atom adopts a distorted square-pyramidal geometry by five Br atoms (Table 1). The Hg II atoms are linked by the Br atoms into a ribbon structure along [100].

Experimental
For the preparation of the title compound, a solution of 2-cyanopyridine (0.47 g, 4.42 mmol) in methanol (10 ml) was added to a solution of HgBr 2 (0.82 g, 2.21 mmol) in methanol (10 ml) and the resulting yellow solution was stirred for 20 min at room temperature. This solution was left to evaporate slowly at room temperature. After one week, yellow prismatic crystals of the title compound were isolated (yield: 0.75 g, 83.4%).

Refinement
All H atoms were positioned geometrically and refined as riding atoms, with C-H = 0.93 (aromatic), 0.96 (CH 3 ) and N -H = 0.86 Å and with U iso (H) = 1.2U eq (C, N). The highest residual electron density was found 1.09 Å from Hg3 the deepest hole 1.05 Å from Hg3.

catena-Poly[di-µ 3 -bromido-hexa-µ 2 -bromido-dibromidobis(O-methyl pyridine-2-carboximidateκ 2 N,N′)pentamercury(II)]
Crystal data Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.