Carbon-functionalized 1,4,7-trithiacyclononanes: synthesis, molecular mechanics and co-ordination chemistry

A series of functionalized analogues of 1,4,7-trithiacyclononane has been synthesized and the effects of functionalization on their co-ordination chemistry investigated. The substituents were introduced via substituted 1,2-dibromopropanes, by cyclization with 3-thiapentane-1,5-dithiolate in the form of its molybdenum complex [Mo(CO)3(SCH2CH2SCH2CH2S)]2–. The functionalized macrocycles were then displaced from the metal by additional 3-thiapentane-1,5-dithiolate. A series of complexes [ML2]n+(M = Ag, Hg, Cu, Ni, Co or Fe; L = 2-methyl-1,4,7-trithiacyclononane. the simplest of the new ligands) was prepared. Spectroscopic and electrochemical studies revealed that any effects of substitution on the ring conformational preferences were not manifested in the stability or electrochemistry of the complexes. Molecular-mechanics calculations suggest that no alterations in conformational preferences are caused by a single substitution. Attempts to synthesize analogues with two vicinal methyl groups yielded only polymeric products.