Synthesis and Coordination Chemistry of Two N₂-Donor Chelating Di(indazolyl)methane Ligands: Structural Characterization and Comparison of Their Metal Chelation Aptitudes

Abstract

The N(2)-donor bidentate ligands di(1H-indazol-1-yl)methane (L(1)) and di(2H-indazol-2-yl)methane (L(2)) (L in general) have been synthesized, and their coordination behavior toward Zn(II), Cd(II), and Hg(II) salts has been studied. Reaction of L(1) and L(2) with ZnX(2) (X = Cl, Br, or I) yields [ZnX(2)L] species (1-6), that, in the solid state, show a tetrahedral structure with dihapto ligand coordination via the pyrazolyl arms. The reaction of L(1) and L(2) with Zn(NO(3))(2)·6H(2)O is strongly dependent on the reaction conditions and on the ligand employed. Reaction of L(1) with equimolar quantities of Zn(NO(3))(2)·6H(2)O yields the neutral six-coordinate species [Zn(NO(3))(2)(L(1))], 7. On the other hand the use of L(1) excess gives the 2:1 adduct [Zn(NO(3))(2)(L(1))(2)], 8 where both nitrates act as a unidentate coordinating ligand. Analogous stoichiometry is found in the compound obtained from the reaction of L(2) with Zn(NO(3))(2)·6H(2)O which gives the ionic [Zn(NO(3))(L(2))(2)](NO(3)), 10. Complete displacement of both nitrates from the zinc coordination sphere is observed when the reaction between L(1) excess and the zinc salt was carried out in hydrothermal conditions. The metal ion type is also determining structure and stoichiometry: the reaction of L(2) with CdCl(2) gave the 2:1 adduct [CdCl(2)(L(2))(2)] 11 where both chlorides complete the coordination sphere of the six-coordinate cadmium center; on the other hand from the reaction of L(1) with CdBr(2) the polynuclear [CdBr(2)(L(1))](n) 12 is obtained, the Br(-) anion acting as bridging ligands in a six-coordinate cadmium coordination environment. The reaction of L(1) and L(2) with HgX(2) (X = Cl, I, SCN) is also dependent on the reaction conditions and the nature of X, two different types of adducts being formed [HgX(L)] (14: L = L(1), 16, 17: L = L(1) or L(2), X = I, 19: L = L(2), X = SCN) and [HgX(L)(2)] (15: L = L(2), X = Cl, 18: L = L(1), X = SCN). The X-ray diffraction analyses of compounds 1, 2, 4, 5, 7, 8, 10-12, 14, 15, and 19 are also reported. The variations of the coordination geometry parameters in the complexes are compared and discussed.

Crystal structure of catena-poly[(μ2-1-((benzotriazol-1-yl)methyl)-1H-1,3-imdazole-κ2 N:N′)-(1-((benzotriazol-1-yl)methyl)-1H-1,3-imdazole-κ1N)-(methanol-κ1 O)mercury(II)] dinitrate, C21H22N12O7Hg

“…Whereas each Hg2 ion is twocoordinated by two N atoms from two bmi ligands. The Hg-O bond length is 2.642(5) Å and Hg-N distances range from 2.076(5) to 2.695(6) Å, respectively; these values are comparable to distances reported in the literature for Hg(II) complexes [10,[12][13][14]. There are two kinds of crystallographically independent bmi ligands.…”

Cobalt(II) and Copper(II) Complexes Constructed from Bis(benzimidazole) and 2,6‐Pyridinedicarboxylate Co‐ligands: Synthesis, Crystal Structures, and Catalytic Properties

“…The ligands L1 and L2 were synthesized according to the reported method21,22 (Scheme ). All the solvents and other reagents for synthesis were purchased from Sinopharm Chemical Reagent Co, Ltd. and used without further purification.…”

High Yielding, One-Pot Synthesis of Bis(1H-indazol-1-yl)methane Catalyzed by 3d-Metal Salts

“…There was a lapse in the literature for the utilization of bis(1 H -indazol-1-yl)methane as a chelating ligand despite the significant indazole moiety that has been highly utilized in the pharmaceutical industry [ 10 - 12 ]. In 2010, Pettinari and coworkers utilized the 1982 synthetic method [ 8 ] (Scheme 1b) with the first reported separation of L 1 and L 2 [ 13 ]. While the spectroscopic evidence for the separation of L 1 and L 2 is compelling [ 13 ], an extensive search of the literature did not yield any experimental details or separation procedures.…”

“…In 2010, Pettinari and coworkers utilized the 1982 synthetic method [ 8 ] (Scheme 1b) with the first reported separation of L 1 and L 2 [ 13 ]. While the spectroscopic evidence for the separation of L 1 and L 2 is compelling [ 13 ], an extensive search of the literature did not yield any experimental details or separation procedures. Reports with the L 1 and L 2 chelating ligands including structural and electronic characteristics of more than 50 new coordination complexes has been published since 2010 with binding to group 9, 10, 11, and 12 metal centers [ 13 - 15 ].…”