Role of basic sites of substituted ferrocenes in interaction with the trinuclear 3,5-bis(trifluoromethyl)pyrazolates: thermodynamics and structure of complexes†
Formation of complexes of the macrocycles (ML)3, where L = 3,5-(CF3)2Pz = 3,5-bis(trifluoromethyl)pyrazolate, M = Cu and Ag, and the acylferrocenes FcC(O)CH2R (Fc = (C5H5)Fe(C5H4); R = H (1), Ph (2)) was studied by means of variable temperature IR, UV-vis, NMR spectroscopy. The sole site of coordination in solution is the oxygen atom of the CO group. The complex composition (1 : 1) and thermodynamic parameters in hexane solution were determined, the formation constants and the enthalpies decreasing from 1 to 2 and from Ag to the Cu macrocycle. The same coordination site featuring triple coordination of oxygen to all metal atoms of a macrocycle was found in the solid state by single crystal X-ray diffraction. There are no shortened contacts of the metal in the macrocycles with π-electron system of the ferrocene's cyclopentadienyl ligands in all complexes. The complexes of (ML)3 with 1 have 1 : 2 composition and bipyramidal structure whereas 2 forms the 1 : 1 complex with (AgL)3. The latter is packed in the infinite stacks involving additional contacts with Ph groups.