A systematic investigation of the CuCl2/H2mal/phen reaction system (H2mal = malonic acid): Solution and solid state studies of its products

The systematic investigation of the parameter space of the CuCl2/H2mal/phen reaction system in MeOH resulted in the isolation of seven different complexes either as mixtures or in pure form, six of which have been structurally characterized. The molar ratios of the reactants and the crystallization methods have been systematically varied, leading to the isolation of compounds [Cu(H2O)(phen)(mal)] (1), [Cu(MeOH)(phen)(mal)] (2), [Cu2Li2Cl2(phen)2(mal)2(MeOH)4] (3), [Cu2(phen)4(mal)][CuCl(phen)(mal)](OH) (4), [CuCl(phen)2]Cl (5), and [CuCl(phen)(mal)][CuCl(phen)2][Cu(phen)2(Hmal)]Cl (6). The coordination versatility of the malonato ligand has been confirmed by the presence of three different coordination modes and its two deprotonation states in compounds 1–6. Solution studies on methanolic solutions of 2–4 and 6 by mass spectrometry revealed the absence of parent ion peak and the presence of fragment ions of low relative abundance not previously found in their crystal structure, thus indicating decomposition and rearrangement/reorganization of the complexes in solution and confirming the dynamic character of their solutions. Compounds 3 and 4 have been also studied in the solid state by EPR spectroscopy and magnetic measurements.

Variation of the CuII/H2mal/phen molar ratios and the crystallization methods employed afforded seven complexes either in pure form or as mixtures. All these species, and probably others not yet isolated, coexist in equilibrium in the reaction solution, a fact that has been further corroborated by using mass spectrometry.Figure optionsDownload as PowerPoint slide