Poly[tetramethylammonium [tri-μ2-formato-κ6 O:O′-manganate(II)]]

In the title compound, {(C4H12N)[Mn(HCO2)3]}n, the MnII atom lies on an inversion centre and is coordinated by O-atom donors from the three double-bridging formate ligands, one of which lies across a crystallographic mirror plane, giving a slightly distorted octahedral coordination sphere. A three-dimensional NaCl-type framework is generated in which the tetramethylammonium cations, which lie across mirror planes and occupy the cavities in the polymer structure, form weak C—H⋯O hydrogen bonds with the formate ligands.

In the title compound, {(C 4 H 12 N)[Mn(HCO 2 ) 3 ]} n , the Mn II atom lies on an inversion centre and is coordinated by O-atom donors from the three double-bridging formate ligands, one of which lies across a crystallographic mirror plane, giving a slightly distorted octahedral coordination sphere. A threedimensional NaCl-type framework is generated in which the tetramethylammonium cations, which lie across mirror planes and occupy the cavities in the polymer structure, form weak C-HÁ Á ÁO hydrogen bonds with the formate ligands.

Comment
Recently, metal formate frameworks templated by protonated amines attract considerable attention because their special structures and interesting properties (Liu et al., 2012;Zhang et al., 2007). A series of protonated ammonium cations (methylamine, ethylamine, dimethylamine, cyclotrimethyleneamine, N,N-dimethylethylenediammonium) have been employed to synthesize metal formate frameworks Wang et al., 2010;Wang et al., 2004). In the present contribution, we report a new manganese formate complex {(Me 4 N) [Mn(HCO 2 )] 3 } n , templated using tetramethylamine cations. The formate ligand and tetramethylamine cation result from an in situ decomposition reaction of the N,N-dimethylformamide solvent.
In the title complex ( Fig. 1), the Mn II cations lie on crystallographic inversion centres and are coordinated by six Oatom donors from bridging formate ligands, one of which lies across a crystallographic mirror plane and gives an antianti mode. A slightly distorted octahedral geometry is found about Mn II [Mn1-O1, Mn1-O2 and Mn1-O3 are 2.2176 (16), 2.2010 (15) and 2.2089 (16) Å, respectively (Table 1)] while the Mn-Mn separations across the bridging formates are 6.3835 (20)-6.4078 (20) Å. A three-dimensional NaCl-type framework is generated in which the protonated tetramethylamine cations, which also lie on crystallographic mirror planes, occupy the polymer cavities, acting as templates for charge-compensation and space-filling (Fig.2) and are weakly associated with the formate cations through C-H···O hydrogen bonds (Table 2).

Experimental
The title compound compound was synthesized hydrothermally under autogenous pressure. Typically, a mixture of manganese(II) acetate (0.049 g, 0.2 mmol), sodium hydroxide(0.008 g, 0.2 mmol), N,N-dimethylformamide (4 ml) and methanol (2.5 ml) was loaded into a 15 ml Teflon-lined stainless container and stirred in air for 20 minutes, then heated to 180 °C for 5 days. After cooling to room temperature and filtering, colorless block crystals were recovered in 90% yield.

Refinement
Hydrogen atoms of the organic groups were placed at calculated positions with C-H = 0.96 Å (methyl) or C-H = 0.93 Å (formyl) and allowed to ride, with U iso (H) = 1.2 or 1.5U eq (C).

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles 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.