Synthesis, structural characterization, and bonding analysis of two-coordinate copper(i) and silver(i) complexes of pyrrole-based bis(phosphinimine): new metal-pyrrole ring π-interactions

The reaction between 2,5-bis(diphenylphosphinomethyl)pyrrole and Me3SiN3 gave the new pyrrole-based bis(phosphinimine) L1H in an excellent yield. L1H reacts with [CuCl(COD)](2), AgBF4, or AgOTf to give the corresponding two-coordinate mononuclear ionic complex formulated as [M{(L1H)-kappa N-2,N}](+)[X](-) where M = Cu and Ag; X = [CuCl2], BF4 or OTf. Their single crystal X-ray diffraction studies confirmed the two-coordinate geometry formed by the chelate bonding mode of L1H. These 10-membered metalacycles exhibit planar chirality and were also characterized by spectroscopic methods. In addition, in all three structures, there exists a hitherto unknown pi-interaction between the pyrrole ring atoms and metal, represented as eta(2)-(C-alpha-N) in the copper(i) complex, and eta(3)-(C-alpha-N-C-alpha ') in the silver(i) complexes. These weak interactions were supported by DFT calculations in terms of their electron densities, non-covalent interaction plots and the decrease in the aromaticity of the pyrrole ring.

Automated summary

In this study, a new pyrrole-based bis(phosphinimine) L1H was successfully synthesized and its two-coordinate mononuclear ionic complexes with copper and silver were characterized. The complexes exhibited planar chirality and a previously unknown pi-interaction between the pyrrole ring atoms and metal was observed in the structures.