The self-assembly switching of the group 13 tetrahedral Schiff base complexes by changing the character of coordination centre

Abstract

The reaction of Et₃B with one equivalent of N-substituted salicylideneimine (HsaldR′) yields the monomeric O,N-chelate complexes Et₂B(saldR′), where R′ = Me (1) or Ph (2). The crystal structure of the resulting complexes has been determined by X-ray crystallography. The molecular structure of these complexes consists of monomeric four-coordinate chelates and their primary arrangement in the crystal structure is determined by the C–H⋯O_aryloxide hydrogen bonds. An extended crystal structure analysis reveals that the adjacent monomeric moieties of 1 are interconnected by C–H_imino⋯O hydrogen bridges resulting in a 1-D motif infinite H-bonded chain, whereas the crystalline complex 2 comprises dimeric molecules linked through a pair of intermolecular C–H_arom⋯O interactions. The supramolecular arrangement of both compounds is discussed with relation to the structure of analogous aluminium and gallium complexes, and the role played by the coordination centre on the molecular assembly is analyzed. It is shown that the steric congestion at the hydrogen bond donor and acceptor sites, as a result of changes in the N-alkyl substituents or the coordination centre environment, affect the strength of the intermolecular C–H⋯O hydrogen bonds and may lead to the self-assembly switching of the bidentate Schiff base complexes.