What is the nature of binding of BF4¯, NO3¯ and ClO4¯ to Cu(II) complexes with Girard's T hydrazine? When can binuclear complexes be formed?

Abstract

Four complexes, [CuLCl]BF4, [CuLCl]NO3, [Cu2L2Cl2](BF4)2 and [CuLCl]ClO4 having the same [CuLCl]+ moiety, (L=(E)-N,N,N-trimethyl-2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene) hydrazi-nyl)ethan-1-amin), were characterized by single crystal X-ray diffraction methods. According to the bond distances, the formulas have been written such that [CuLCl]+ is the inner sphere, while BF4¯, NO3¯ and ClO4¯ belong to the outer sphere. Non-local density-dependent dispersion corrected Density functional theory (DFT) calculations on the X-ray structures have been performed to rationalize interactions of anions to the Cu(II) ion. Results of analysis based on energy decomposition, Non-Covalent Interactions Index, Independent Gradient Model analysis, and Quantum Theory of Atoms in Molecules revealed that in mononuclear complexes, anions are weakly coordinated, while in binuclear complex, BF4¯ is counter-anion, electrostatically bonded to the inner sphere. Furthermore, DFT calculations rationalized the fact that only complex [Cu2L2Cl2](BF4)2 is binuclear with bridging Cl¯ ions. The present study shows that ambiguity about actual coordination number in the real crystal structures of coordination compounds can be solved with thorough analysis of the electron density.

Četiri kompleksa, [CuLCl]BF4, [CuLCl]NO3, [Cu2L2Cl2](BF4)2 i [CuLCl]ClO4, sa istim [CuLCl]+ fragmentom (L=(E)-N,N,N-trimethyl-2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene) hydrazinyl)eth-an-1-amin) su okarakterisani metodom difrakcije X-zraka. Na osnovu dužina veza, formule kompleksa su napisane tako da je [CuLCl]+ unutrašnja sfera kompleksa, a BF4¯, NO3¯ i ClO4¯ pripadaju spoljašnjoj sferi. Proračuni zasnovani na Teoriji funkcionala gustine, u kojoj je disperzija korigovana na ne-lokalan način, na strukturama dobijenim difrakcijom X-zraka, su izvedeni u cilju razjašnjavanja prirode interakcija anjona sa Cu(II) jonom. Rezultati različitih analiza, kao što su dekompozicija interakcione energije, indeks nekovalentnih interakcija, model nezavisnog gradijenta i kvantna teorija atoma u molekulima, pokazuju da su anjoni u mononuklearnim kompleksima slabo koordinovani, dok je BF4¯ u binuklearnom kompleksu kontra jon, elektrostatički vezan za unutrašnju sferu. Takođe, proračuni objašnjavaju činjenicu da je samo kompleks [Cu2L2Cl2](BF4)2 binuklearni sa mostnim Cl¯ jonima. Ova studija pokazuje da se nedoumice oko koordinacionog broja u realnim kristalnim strukturama kompleksa mogu otkloniti detaljnom analizom elektronske gustine.