Synthesis of Zinc, Copper, Nickel, Cobalt, and Iron Complexes Using Tris(pyrazolyl)methane Sulfonate Ligands:  A Structural Model for N,N,O Binding in Metalloenzymes

Abstract

Ligands of intermediate steric bulk were designed to mimic metalloenzymes with histidine and carboxlyate binding sites. The reaction between tris(3-isopropylpyrazolyl)methane and butyllithium followed by SO3NMe3 in THF yielded the new ligand lithium tris(3-isopropylpyrazolyl)methane sulfonate (LiTpmsiPr). Various metal salts reacted with LiTpmsiPr to give the octahedral complexes M(TpmsiPr)2 (M = Zn, Cu, Ni, Co, Fe) in which each ligand has N,N,O binding to the metal. In the reaction between LiTpmsiPr and ZnCl2, in addition to the major product Zn(TpmsiPr)2, [LiTpmsiPrZnCl2].2THF was also formed as a minor product with a tetrahedral zinc atom coordinated to either N,N,Cl,Cl in the solid phase or N,N,N,Cl in acetonitrile solution. Although TpmsiPr is coordinatively flexible and can act as a bipodal or tripodal ligand, it appears to favor the formation of octahedral L2M complexes.

Synthesis and Structural Features of New Ruthenium(II) Complexes Containing the Scorpionate Ligands Tris(pyrazol‐1‐yl)methanesulfonate (Tpms) and Tris(pyrazol‐1‐yl)methane (Tpm)

“…Thus, for this ligand, apart from the tripodal κ 3 (N,N,N) coordination mode, [4] κ 3 (N,N,O) coordination has been described for several metal complexes, [5] which can be used as models for N,N,O binding in metalloenzymes, [6] regardless that the sulfonate Tpms ligand is favored over κ 3 (N,N,O) coordination. In addition, complexes with water soluble phosphane ligands 1,3,5-triaza-7-phosphatricyclo[3.3.1.1 3,7 ]decane (PTA) and 1-alkyl-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1 3,7 ]decane (1-R-PTA) have been prepared and structurally characterized.…”

Transition‐Metal Complexes Based on a Sulfonate‐Containing N‐Donor Ligand and Their Use as HIV Antiviral Agents

“…[20] The The zinc complex 6 has the same geometry as that shown by complex 4 with the normal variations in bond lengths and angles due to the presence of a different metal. The Zn-N bond length is 2.206(2) Å, also in the expected range for octahedrally coordinated zinc, [16,20,21] and is again longer than the Zn-O bonds. The angles are very similar to those of derivative 4.…”

“…The former value can be ascribed to a chargetransfer band (MLCT or LMCT), whereas the latter is due to a dǞ d transition, which indicates that the geometry around the copper atom in solution is intermediate between a square pyramid (absorption maximum 526-625 nm) and a trigonal bipyramid (absorption maximum 666-1000 nm). [14,15] However, a pseudo-octahedral structure cannot be ruled out in solution because an "N 2 O 4 " ligand should absorb between the strong-field "N 6 " ligand (578 nm) as in [Cu(1-allylimidazole) 6 ] 2+ , [16,17] and…”

“…[16] To confirm that com-plex 5 is sufficiently stable at physiological pH, UV/Vis spectra were recorded at different pHs (see Figure 2). Complex 5 dissolved in pure distilled water afforded a pH of 5.75, which means that both aqua and hydroxido species are present.…”

“…The aminosulfonato ligand occupies four coordination sites with the amine ni- (9) 84.65 (7) O (4) [16,20] and are longer than the Co-O bond lengths. In our case, the Co-O bonds corresponding to the two sulfonate oxygen atoms in trans positions are 2.085(2) Å, shorter than those of the coordinated water ligands, which are 2.147(2) Å.…”