Metal Complexes of Multitopic, Third Generation Poly(pyrazolyl)­methane Ligands: Multiple Coordination Arrangements

Abstract

The structures of metal complexes of two classes of multitopic, "third generation" poly(pyrazolyl)methane ligands, ligands specifically functionalized at the non-coordinating "back" position, are discussed. For tris(pyrazolyl)methane based [(pz)₃C–CH₂–O–CH₂]_nC₆H_6–n (n = 2, 3, 4 and 6, pz = pyrazolyl ring) ligands, three bonding modes are observed depending on the metal, counterion and solvent: a) the κ³ (tripodal) mode, where all three pyrazolyl rings are coordinated to one metal; b) the κ²-κ⁰ mode, with only two pyrazolyl rings bonded to a metallic center while the third is not involved in a donor bond; and c) in a κ²-κ¹ fashion, in which the tris(pyrazolyl)methane unit acts as a bridge between two metals. For bis(pyrazolyl)methane based [CH₂–O–CH₂–CH(pz)₂]_nC₆H_6–n ligands, the main structural arrangement is a mononuclear cationic unit in which two arms of the ligand bond a single silver(I) cation in a tetradentate fashion, giving rise to 16- or 17-member metallacyclic structures.

Multitopic poly(pyrazolyl)methane ligands form metal complexes that show a variety of bonding modes and intricate overall structures.

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