Synthesis, Crystal Structure and Catalytic Activity of a 1d Chained Ca(ii) Coordination Polymer with 3,5-bis(4-pyridylmethoxy)benzoate Ligand

A new 1D chained Ca(II) coordination polymer—namely, [CaL 2 (H 2 O) 2 ] n (HL = 3,5-bis(4-pyridylmethoxy)benzoic acid)—was synthesized though the reaction of Ca(ClO 4) 2 ·4H 2 O, 3,5-bis(4-pyridylmethoxy)benzoic acid and NaOH in H 2 O/CH 3 CH 2 OH (v:v = 1:2) solution. Its structure was determined by elemental analysis, infrared spectrum, and single-crystal XRD. Structural analyses show that each Ca(II) ion is eight-coordinated by six oxygen atoms of four 3,5-bis(4-pyridylmethoxy)benzoate ligands and two oxygen atoms of two coordinated H 2 O molecules to form a square-antiprismatic CaO 8 polyhedron. The Ca(II) complex displays a 1D chained structure constructed by the bridging effect of the bidentate carboxyl group of 3,5-bis(4-pyridylmethoxy)benzoate ligand. The catalytic activity of the Ca-complex was tested for the preparation of propargylamine in the A 3 coupling reaction.


Structural Description of [CaL 2 (H 2 O) 2 ] n
The X-ray single-crystal structural analysis revealed that [CaL 2 (H 2 O) 2 ] n crystallizes in monoclinic C 2 /c space group, and that the Ca(II) ion is surrounded by six O atoms from four 3,5-bis(4-pyridylmethoxy)benzoate ligands and two O atoms from two coordinated H 2 O molecules (Figure 1).The Figure 1

Catalytic Studies of Three Component Coupling Reaction
The catalytic activity of Ca-complex was tested for the preparation of propargylamine in the A 3 coupling reaction according to the literature method [26].The benzaldehyde conversion of 38.3% was obtained over Ca-complex for the coupling reaction of benzaldehyde, phenylacetylene, and piperidine with 1,4-dioxane as solvent at 120 °C for 12 h.Recovery and reusability of catalysts was an important theme in catalysis.This allows the catalysts to be used in many catalytic cycles, and thereby more commercial for industrial catalysis.The reusability of the Ca-complex was investigated in the A 3 coupling reaction of benzaldehyde, phenylacetylene, and piperidine in 1,4-dioxane at 120 °C.The recovered catalyst worked well up to four catalytic runs.In four successive cycles, the conversion of benzaldehyde was 38.3%, 35.4%, 32.5%, and 29.8% at 120 °C for 12 h, respectively.

Catalytic Studies of Three Component Coupling Reaction
The catalytic activity of Ca-complex was tested for the preparation of propargylamine in the A 3 coupling reaction according to the literature method [26].The benzaldehyde conversion of 38.3% was obtained over Ca-complex for the coupling reaction of benzaldehyde, phenylacetylene, and piperidine with 1,4-dioxane as solvent at 120 °C for 12 h.Recovery and reusability of catalysts was an important theme in catalysis.This allows the catalysts to be used in many catalytic cycles, and thereby more commercial for industrial catalysis.The reusability of the Ca-complex was investigated in the A 3 coupling reaction of benzaldehyde, phenylacetylene, and piperidine in 1,4-dioxane at 120 °C.The recovered catalyst worked well up to four catalytic runs.In four successive cycles, the conversion of benzaldehyde was 38.3%, 35.4%, 32.5%, and 29.8% at 120 °C for 12 h, respectively.

Catalytic Studies of Three Component Coupling Reaction
The catalytic activity of Ca-complex was tested for the preparation of propargylamine in the A 3 coupling reaction according to the literature method [26].The benzaldehyde conversion of 38.3% was obtained over Ca-complex for the coupling reaction of benzaldehyde, phenylacetylene, and piperidine with 1,4-dioxane as solvent at 120 • C for 12 h.Recovery and reusability of catalysts was an important theme in catalysis.This allows the catalysts to be used in many catalytic cycles, and thereby more commercial for industrial catalysis.The reusability of the Ca-complex was investigated in the A 3 coupling reaction of benzaldehyde, phenylacetylene, and piperidine in 1,4-dioxane at 120 • C. The recovered catalyst worked well up to four catalytic runs.In four successive cycles, the conversion of benzaldehyde was 38.3%, 35.4%, 32.5%, and 29.8% at 120 • C for 12 h, respectively.

Crystal Structure Determination
The single crystal data of [CaL 2 (H 2 O) 2 ] n were collected on a Bruker Smart APEX CCD diffractometer with graphite-monochromated MoKα radiation (λ = 0.71073 Å) at 293(2) K.The structure was solved by direct method and refined by full-matrix least squares on F 2 using the SHELX-97 program (University of Göttingen, Göttingen, Germany) [27].The crystallographic data and structural refinement are listed in Table 2.A mixture of catalyst (40 mg), aldehyde (0.13 mmol), amine (0.15 mmol), alkyne (0.17 mmol), and 1,4-dioxane (1.5 g) was stirred for 12 h at 120 • C.After completion of the reaction, the mixture was cooled to room temperature and the product was obtained by centrifugation.The catalyst was dried at 60 • C under vacuum for 3 h and stored in a desiccator for its use in subsequent catalytic runs.The conversion of aldehyde was determined by GC analysis (GC-1100, capillary column, SE-54).

Conclusions
In summary, we obtained a new [CaL 2 (H 2 O) 2 ] n coordination polymer by the reaction of Ca(ClO 4 ) 2 •4H 2 O, 3,5-bis(4-pyridylmethoxy)benzoic acid and NaOH in H 2 O/CH 3 CH 2 OH (v:v = 1:2) solution.Structural analyses show that the Ca(II) complex forms a 1D chained structure constructed by the bridging effect of bidentate carboxyl group of 3,5-bis(4-pyridylmethoxy)benzoate ligand.The catalytic activity of Ca-complex was tested for the preparation of propargylamine in the A 3 coupling reaction.

Figure 1 .
Figure 1.The coordination environment of Ca(II) ion.

Figure 1 .
Figure 1.The coordination environment of Ca(II) ion.

Figure 1 .
Figure 1.The coordination environment of Ca(II) ion.