Complexes of Trinuclear Macrocyclic Copper(I) and Silver(I) 3,5‐Bis(Trifluoromethyl)Pyrazolates with Ketones

The interaction of the copper [{3,5-(CF3)2Pz}Cu]3 and silver [{3,5-(CF3)2Pz}Ag]3 macrocycles {3,5-(CF3)2Pz = 3,5-bis(trifluoromethyl)pyrazole} with 2-butanone and benzophenone was investigated for the first time by IR and NMR spectroscopy and single-crystal X-ray diffraction. New, low-frequency IR bands for ν(CO)bond (in hexane) were observed and the composition (1:1) of all the complexes was determined. These data as well as the 13C NMR chemical shifts (in CD2Cl2) for the complexes of aliphatic and aromatic ketones evidence that the oxygen atom of the CO group is the sole coordination site in both complexes and that the Ph rings of benzophenone do not take part in complexation in solution. The thermodynamic parameters for the formation of the complexes increase on going from the copper to silver macrocycle and grow slightly from butanone to benzophenone. The same coordination site (CO group) was found in the crystal structure. However, the complexes with benzophenone are formulated as 1:2 complexes and feature a wedge-shaped sandwich structure, but [AgL]3 also forms a 1:1 complex with triple coordination of the oxygen atom to each Ag atom. Analysis of the IR spectroscopic data for the complexes in crystal form and in solution revealed that in solution the [Ph2CO][ML]3 complexes also have triple coordination of the CO oxygen atom to the metals of both the Cu and Ag macrocycles. The structure of the 1:1 complex features no interaction between the Ph rings and the macrocycle in contrast to sandwiches (1:2) with shortened distances Ag···C (Ph). It was found that the sandwich complexes pack as infinite stacks, whereas the complex with triple coordination (1:1) forms only cofacial dimers.