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

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)‐ κ 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)‐ κ 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 [Cu L 2 ] + in solution, in addition to the binuclear complexes. The X‐ray solid state structures of [Cu L 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 [Cu L 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 .