Metal complexes from 1,1′-di(pyrazinyl)ferrocene: coordination polymers and bridged diferrocenes

Abstract

Ferrocene-based ligands 1,1′-di(pyrazinyl)ferrocene (L1) and 1,1′-di(2-pyrimidinyl)ferrocene (L2) were synthesized and copper and silver complexes were obtained from L1. Coordination polymers [{Cu₂(PhCOO)₄}(L1)]_n (1), [{Cu₂(C₅H₁₁COO)₄}(L1)]_n (2), and [{Cu₂(OAc)₄}(L1)]_n·0.5n[Cu₂(OAc)₄(H₂O)₂]·1.5nCH₃CN (3) resulted from the reaction with the corresponding copper carboxylates. In all three complexes, L1 links the dinuclear copper carboxylate units to form one-dimensional step-like chains. In 2, these chains are further linked by [Cu₂(OAc)₄(H₂O)₂] dinuclear units via hydrogen bonding to form sheet structures. The reaction of L1 with copper(I) iodide resulted in a multinuclear complex [(CuI)₄(L1)₂]·(L1) (4), which contains a [(CuI)₄(L1)₂] diferrocene unit with a step-like (CuI)₄ core. Reactions of L1 with silver(I) salts resulted in silver-bridged diferrocenes [Ag₂(L1)₂]X₂ (X = ClO₄ (5a, b), NO₃ (6a–c) and PF₆ (7)), some of which incorporate aromatic solvents into their crystal lattices. The intramolecular Ag⋯Ag separations in these metallamacrocycles (3.211–3.430 Å) depended upon the counter-anions and on the coordination mode of the silver ions. In all of these coordination complexes, L1 adopts a synperiplanar eclipsed conformation and acts as a bidentate ligand, with only the 5-nitrogen of each pyrazine ring involved in coordination.