Dimetal Complexes of a Bibrachial 2+2 Thiolate-based Macrocycle

Protocols for accessing the [2+3] and [2+2] tren + thiophenolate-based cryptands and macrocycles, respectively, have been devised; however, a propensity towards incomplete crypt formation is clear: Cd(II)2, Mn(II)2, Ni(II)2 and Pd(II)2 complexes of the [2+2] bibrachial systems in which one arm of each of the tren head groups is pendant were isolated in attempts to make the crypts. The Mn(II)2 complex can be used in transmetallation reactions and these probably occur in a stepwise fashion for the heavier, softer metal ions since the plausible intermediates Mn(II)M(II), M = Cd, Pd, were identified. There is evidence for the formation of [2+3] cryptand systems using templating Ag(I) and Cd(II); however, reaction conditions need to be strictly controlled to ensure isolation of either the [2+3] cryptand or the [2+2] macrocyclic complex since ensuing reactions leading to intractable oligomers are competing. The template and transmetallation experiments described here emphasise the relatively greater hydrolytic sensitivity of the thiophenol-derived imino macrocycles and crypts than their better-known phenol-based counterparts.