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

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). 4H(2)O and 3,3'-pytz in MeOH/CH2Cl2 yields the 1:1 ligand/metal complex {[Cd(mu-3,3'-pytz)(NO3)(2)- (MeOH)(2)]}(infinity), 1 [triclinic space group P (1) over bar; a = 9.011(2) Angstrom, b = 9.338(4) Angstrom, c = 11.941(2) Angstrom, alpha = 74.51(3)degrees, beta = 86.94(4)degrees, gamma = 86.50(5)degrees; Z = 2]. Replacement of MeOH with EtOH or (PrOH)-Pr-i in the above reaction affords respectively the 3:2 ligand/metal complexes {[Cd-2(mu-3,3'-pytz)(3)(NO3)(4)] (EtOH)}(infinity), 2 [triclinic, space group P (1) over bar; a = 9.060(4) Angstrom, b = 9.848(3) Angstrom, c = 13.208(4) Angstrom, alpha = 86.76(3)degrees, beta = 79.04(3)degrees, gamma = 88.14(2)degrees; Z = 2] and {[Cd-2(mu-3,3'-pytz)(3)(NO3)(4)] (CH2Cl2)}(infinity), 3 [triclinic space group P (1) over bar; a = 8.981(16) Angstrom, b = 9.93(2) Angstrom, c = 13.19(2) Angstrom, alpha = 94.18(15)degrees, beta = 102.35(13)degrees, gamma = 88.12(15)degrees; Z = 2]. Complex 1 exhibits a zigzag chain polymer motif, whereas complexes 2 and 3 show noninterpenetrated ladder structures. Reaction of Zn(NO3)(2). 6H(2)O and 3,3'-pytz in MeOH or EtOH/CH2Cl2 solution affords a 3:2 ligand/metal complex {[Zn-2(3,3'-pytz)(2)(NO3)(4)(ROH)(2)(mu-3,3'-pytz)]}(infinity), 4 [R = Me; triclinic, space group P (1) over bar a = 7.5346(12) Angstrom, b = 10.7279(13) Angstrom, c = 15.219(2) Angstrom, alpha = 85.364(11)degrees, beta = 80.627(12)degrees, gamma = 69.343(12)degrees; Z = 2] and 5 [R = Et; triclinic, space group P (1) over bar; a = 7.590(3) Angstrom, b = 10.561(2) Angstrom, c = 15.951(5) Angstrom, alpha = 87.56(2)degrees, beta = 83.49(4)degrees, gamma = 71.12(2)degrees; Z = 2]. The reaction in (PrOH)-Pr-i/CH2Cl2 results in a 3:2 ligand/metal complex {[Zn-2(mu-3,3'-pytz)(3)(NO3)(4)](CH2Cl2)(2)}(infinity), 6 [triclinic, space group P (1) over bar; a = 9.1110(18) Angstrom, b = 12.474(3) Angstrom, c = 13.171.(3) Angstrom, alpha = 117.99(3)degrees, beta = 102.39(3)degrees, gamma = 101.13(3)degrees; 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.