Metal complexes as ligands. X. Investigation of valency and substituent effects in binuclear complexes derived from tetradentate salicylaldimines

Abstract

A series of binuclear complexes has been formed by using planar copper(11) complexes (CUTSB) of tetradentate Schiff bases (TSB) as ligands to coordinate with metal chlorides. The binuclear complexes, (CuTSB)MCl_n (M = Cu¹¹, Fe¹¹¹, Mn¹¹; n. = 2, 3), all exhibit pairwise antiferromagnetic interactions. The nickel complexes (NitsB)Mcl_n (M = Fe^III, Mn^II) can be formed similarly, but the nickel atoms are diamagnetic so that no significant magnetic interactions are expected. The effect of 5-Cl, 5-Br, and 5,6-benzo substituents in the phenyl rings of the TSB groups on the strength of the antiferromagnetic interactions was examined in the complexes (CUTSB)CuCl₂. Although the presence of a substituent usually increases the strength of the interaction, this trend is not systematic and there is no reason to attribute it to electronic effects of ring substituents. In (CUTSB)MCl_n, the main difference between the complexes with M = Fe¹¹¹ and M = Mn¹¹ is the difference in the valencies of the two d⁵ metals. In our limited sampling (one complex of each type), the interaction is stronger between iron(111) and copper(11) than between the manganese(11) and copper(11). These complexes form as hydrates, and since iron(111) and manganese(11) prefer octahedral environments, it is probable that one and two molecules of water respectively are coordinated to these metals. In the case where M = Fe^III, Nössbauer measurements indicate that this is so.