STUDIES OF METAL CHELATES FORMED FROM DERIVATIIVES OF 2-THIOPHENEALDEHYDE AND FURFURAL

Complexes have been formed from metal halides of the type MX2 and N-methyl-2-thiophenealdimine, bis(2-thiophenealdehyde)ethylenediimine and bis(furfural)ethylenediimine by nonaqueous reactions. Spectroscopic and conductivity studies have been made leading to some interesting observations relative to bonding and the stereochemistry of the molecules. Spectral studies indicate that the formation of a sulfur-to-metal bond does not effectively block the resonance in the thiophene ring. Absorption associated with the stretching vibration of the conjugate CCCCCN group appears at 1635 cm-1 in bis(2-thiophenealdehyde)ethylenediimine and at 1655 cm-1 and 1644 cm-1 in bis(furfural)ethylenediimine. In the complexes studied, the extent of shift on chelation of the bis(2-thiophenealdehyde)ethylenediimine was of comparable magnitude, and of the order of -20 cm-1. No loss of resonance (with its increase of CN character) occurs on formation of the NM bond. Spectral shifts on NM bond formation were somewhat greater for the metal halide complexes of bis(furfural)ethylenediimine. Among the addition compounds studied were: the chlorides and bromides of zinc, cobalt and copper, and the chloride of nickel. All of these formed 1:1 complexes with both bis(2-thiophenealdehyde)ethylenediimine and bis(furfural)ethylenediimine, with the exception of the cobalt bromide in which two moles of cobalt bromide coordinated with one mole of ligand. Studies indicate that palladium formed complexes of the type, [bis(2-thiophenealdehyde)-ethylenediimine Pd] [PdCl4] and di-[bis(furfural)ethylenediimine] Pd. © 1969.