Synthesis, X‐Ray Structures, and Fluxional Properties of Symmetrical, Asymmetrical Binuclear and Cubane Type Copper(I) Complexes Bearing the Pyrrole‐Based P, N‐Hetero Donor Ligand

Abstract

The 1 : 1 reaction between 2-(3,5-dimethylpyrazolylmethyl)-5-(diphenylphosphinomethyl)pyrrole L and CuX (X = Cl, and Br) in THF afforded the symmetrical binuclear copper(I) complexes [Cu(μ-X){μ-C 4 H 2 NH-2-(CH 2 PPh 2 )-5-(CH 2 Me 2 pz)-k 2 P,N}] 2 , having one type of copper environment. When X = I, the asymmetrical complex having two copper environments was isolated, in addition to the symmetrical complex as crystals. Interestingly, the 1 : 2 ratio reaction between L and CuCl gave a distorted cubane type complex [Cu 4 Cl 4 {μ-C 4 H 2 NH-2-(CH 2 PPh 2 )-5-(CH 2 Me 2 pz)-k 2 P,N} 2 ], while the CuBr and CuI reactions did not give similar cubane complexes. Conversely, the 2 : 1 (L : Cu) ratio reactions using CuX (X=Cl, Br and I) in THF suggest the formation of four coordinate bis-chelated copper(I) complex of the type [CuL 2 ] + in solution, in addition to the binuclear complexes. The X-ray solid state structures of [CuL 2 X 2 ] (X = Br and I) are retained in solution, in contrast to its chloride derivative giving two signals in 31 P{ 1 H} NMR spectrum. The formation of the binuclear complexes from [CuL 2 ] + and their equilibria were shown by variable temperature NMR, 31 P{ 1 H} 2D NOESY and HRMS studies. In addition, the reaction of L with [Cu(CH 3 CN) 4 ]BF 4 gave yet another binuclear complex [Cu 2 L 2 ] [BF 4 ] 2 which was characterized by spectroscopic methods. This study lends support for the hemilability of L. Figure 5. (a) Variable-temperature 1 H NMR spectra (400 MHz) of complex 4 in CDCl 3 ; (b) proposed dynamic process in solution. ChemistrySelectFull Papers

Mannich Reaction: An Alternative Synthetic Approach for Various Pyrrole‐Based Anion Receptors and Chelating Ligands

“…The incorporation of the pyrazolyl group in one arm, followed by another Mannich reaction, and finally a nucleophilic substitution reaction by diphenyl phosphine on another arm, afforded the compound 71, which played an important role in the formation of several metal complexes and their catalysis (Scheme 18). [45]…”