Simple and easy functionalization of para-hydroxy POCOP-M (M = Ni(ii), Pd(ii)) pincer complexes: synthesis of multimetallic species

Abstract

A facile and efficient method for synthesizing mono- and bi-metallic pincer complexes (3-Ni/Ni and 3-Ni/Pd) has been developed. The procedure involves a 1 : 1 stoichiometric reaction of a para-hydroxy POCOP pincer complex with cyanuric chloride in the presence of [NaB(OMe)₄], which selectively affords the mono-substituted pincer complexes (2-Ni and 2-Pd). These complexes are then further reacted with another equivalent of the para-hydroxy POCOP pincer complex to produce the desired multimetallic species (3-Ni/Ni and 3-Ni/Pd). The complexes can be easily isolated in moderate to good yields using chromatographic column purification. This straightforward synthesis procedure offers an attractive option for the preparation of multimetallic complexes. Furthermore, the molecular structures of complexes 2-Ni, 2-Pd, 3-Ni/Pd and 3-Ni/S were determined. The crystal packing of the structures was stabilized by various interactions including C–H⋯X (X = N, Cl, and F), π⋯π, and C–F⋯F interactions, contributing to their unique topologies. While 2-Ni and 2-Pd complexes exhibit similar molecular structures, they display distinct arrangements in their crystalline packing, such as monomeric chains in 1D arrangement along the c-axis for 2-Ni, and a symmetric dimeric species creating a 2D arrangement in the direction of the bc-axes for 2-Pd. The latter was corroborated by Hirshfeld surface analysis and 2D dimensional fingerprint plots of each crystal structure.