Poly[[bis[μ2-8-ethyl-5-oxo-2-(piperazin-1-yl)-5,8-dihydropyrido[2,3-d]pyrimidine-6-carboxylato]manganese(II)] dihydrate]

In the title compound, {[Mn(C14H16N5O3)2]·2H2O}n, the MnII atom (site symmetry ) exhibits a distorted trans-MnN2O4 octahedral geometry defined by two monodentate N-bonded and two bidentate O,O′-bonded 8-ethyl-5-oxo-2-(piperazin-1-yl)-5,8-dihydropyrido[2,3-d]pyrimidine-6-carboxylate anions. An N—H⋯O hydrogen bond is present in the crystal structure. The extended two-dimensional structure is a square grid and the disordered uncoordinated water molecules occupy cavities within the grid.

The Mn II atom in (I) with site symmetry 1 is coordinated by four oxygen atoms and two N atoms from four ppa ligands (two monodentate-N and two O,O-bidentate) ( Table 1) to form a square grid propagating in (Fig. 2). An N-H···O hydrogen bond (Table 2) helps to stabilize this arrangement.
The disordered, uncoordinated, water molecules occupy cavities within the grid. In the present study, their attached H atoms could not be located.

S2. Experimental
A mixture of Mn(CH 3 COO) 2 .4H 2 O (0.061 g, 0.25 mmol), Hppa (0.15 g, 0.5 mmol), sodium hydroxide (0.04 g, 1 mmol) and water (12 ml) was stirred for 30 min in air. The mixture was then transferred to a 23 ml Teflon-lined hydrothermal bomb. The bomb was kept at 433 K for 72 h under autogenous pressure. Upon cooling, colourless prisms of (I) were obtained from the reaction mixture.

S3. Refinement
The carbon-bound H atoms were positioned geometrically (C-H = 0.93-0.97 Å) and refined as riding with U iso (H) = 1.2U eq (C). The N-bound H atom was located in a difference map and its position was freely refined with U iso (H) = 1.2U eq (N).
The water H atoms could not be placed due to disorder.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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.