Zinc complexes have been prepared with Schiff bases formed from salicylaldehyde and polymethylenediamines with chains of 2-9 carbon atoms. The anhydrous zinc complexes of ligands with 2-3 carbon chains readily form 1 : 1 adducts with water or bases such as pyridine; the ultraviolet and infrared spectra of these anhydrous compounds indicate that they are polymerio with bridging oxygen atoms, the zinc being 5-coordinate. The zinc complexes of ligands with carbon chains of four or more atoms do not form adducts, even in pyridine solution, and their spectra show that none of the oxygen atoms is bridging, the zinc being 4-coordinate. The stereochemistry of the zinc appears to be determined solely by steric effects: when the ligand is such that 4-coordination can produce a tetrahedral environment, further coordination does not occur; when 4-coordination cannot produce a, tetrahedral environment, 5-coordination always occurs.

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Complexes of CoCl2, CoBr2, CoI2, and Co(NCS)2 with two and four molecules of 4-methylpyridine and two molecules of 2-methylpyridine have been prepared. Their magnetic properties, conductivities, and reflectance and absorption spectra in the visible region show that all the compounds of the type CoX2B2 are tetrahedral except Co(NCS)2(4-mepy)2, which is an octahedral polymer like its pyridine analogue. Infrared spectra in the 3-15 μ region lend no support to the suggestion that there may be differences in the extent of π-bonding between the metal and the base or the metal and NCS- in tetrahedral and octahedral complexes. It is suggested that the position of the ligands in the spectrochemical series and the relative stabilities of the compounds CoX2B2 with respect to dissociation into CoX2B4 and free base can be explained in terms of repulsion effects between the non-bonding electron pairs on the ligands and metal dє-orbitals on the one hand and the non-bonding electron pairs of neighbouring ligands on the other.

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