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Solvent Control in the Synthesis of 3,6-Bis(pyridin-3-yl)-1,2,4,5-tetrazine-Bridged Cadmium(II) and Zinc(II) Coordination Polymers

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posted on 30.04.1999, 00:00 by Matthew A. Withersby, Alexander J. Blake, Neil R. Champness, Paul A. Cooke, Peter Hubberstey, Wan-Sheung Li, Martin Schröder
The reaction of cadmium(II) and zinc(II) salts with 3,6-bis(pyridin-3-yl)-1,2,4,5-tetrazine (3,3‘-pytz) affords coordination polymers, the structures of which are controlled by the choice of alcoholic solvent. Reaction of Cd(NO3)2·4H2O and 3,3‘-pytz in MeOH/CH2Cl2 yields the 1:1 ligand/metal complex {[Cd(μ-3,3‘-pytz)(NO3)2(MeOH)2]}, 1 [triclinic space group P1̄; a = 9.011(2) Å, b = 9.338(4) Å, c = 11.941(2) Å, α = 74.51(3)°, β = 86.94(4)°, γ = 86.50(5)°; Z = 2]. Replacement of MeOH with EtOH or iPrOH in the above reaction affords respectively the 3:2 ligand/metal complexes {[Cd2(μ-3,3‘-pytz)3(NO3)4](EtOH)}, 2 [triclinic, space group P1̄; a = 9.060(4) Å, b = 9.848(3) Å, c = 13.208(4) Å, α = 86.76(3)°, β = 79.04(3)°, γ = 88.14(2)°; Z = 2] and {[Cd2(μ-3,3‘-pytz)3(NO3)4](CH2Cl2)}, 3 [triclinic space group P1̄; a = 8.981(16) Å, b = 9.93(2) Å, c = 13.19(2) Å, α = 94.18(15)°, β = 102.35(13)°, γ = 88.12(15)°; Z = 2]. Complex 1 exhibits a zigzag chain polymer motif, whereas complexes 2 and 3 show noninterpenetrated ladder structures. Reaction of Zn(NO3)2·6H2O and 3,3‘-pytz in MeOH or EtOH/CH2Cl2 solution affords a 3:2 ligand/metal complex {[Zn2(3,3‘-pytz)2(NO3)4(ROH)2(μ-3,3‘-pytz)]}, 4 [R = Me; triclinic, space group P1̄; a = 7.5346(12) Å, b = 10.7279(13) Å, c = 15.219(2) Å, α = 85.364(11)°, β = 80.627(12)°, γ = 69.343(12)°; Z = 2] and 5 [R = Et; triclinic, space group P1̄; a = 7.590(3) Å, b = 10.561(2) Å, c = 15.951(5) Å, α = 87.56(2)°, β = 83.49(4)°, γ = 71.12(2)°; Z = 2]. The reaction in iPrOH/CH2Cl2 results in a 3:2 ligand/metal complex {[Zn2(μ-3,3‘-pytz)3(NO3)4](CH2Cl2)2}, 6 [triclinic, space group P1̄; a = 9.1110(18) Å, b = 12.474(3) Å, c = 13.171(3) Å, α = 117.79(3)°, β = 102.39(3)°, γ = 101.13(3)°; Z = 2]. The isostructural complexes 4 and 5 both exhibit a unique hydrogen-bonding motif in coordination polymer chemistry which gives rise to an alternating single- and double-bridged species, whereas 6 exists as a noninterpenetrated ladder complex.

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