Reaction of three cyclic thioester ligands with triiron dodecacarbonyl and possible reaction mechanisms.

Abstract : Three cyclic thioesters of the formula ' $$-\hbox {SCH}_{2}\hbox {CH}_{2}\hbox {SCO}(\hbox {CH}_{2})_{\mathrm{n}}-$$ ' ( $$\mathbf{L}_{\mathbf{1}}, \hbox {n} = 0; \mathbf{L}_{\mathbf{2}}, = 1, \mathbf{L}_{\mathbf{3}}, \hbox {n} = 2$$ ) and their reactions with $$\hbox {Fe}_{3}(\hbox {CO})_{12}$$ are reported. All the reactions produced a known diiron complex, [ $$\hbox {Fe}_{2}(\upmu \hbox {-}\hbox {S}_{2}\hbox {C}_{2}\hbox {H}_{4})(\hbox {CO})_{6}$$ ] ( 1), which suggested that in the reactions, cleavage of C-S bond to generate ' $$\hbox {SCH}_{2}\hbox {CH}_{2}\hbox {S}$$ ' fragment is a common pathway for all the three ligands. In the case of ligand $$\mathbf{L}_{\mathbf{2}}$$ , a new complex 2, [ $$\hbox {Fe}_{2}\{\upmu \hbox {-}\hbox {SC}_{2}\hbox {H}_{4}(\hbox {SCH}_{2})\hbox {-}\upkappa \}(\hbox {CO})_{6}$$ ] was isolated and structurally characterized. In the reaction of ligand $$\mathbf{L}_{\mathbf{3}}$$ , an unknown iron carbonyl product was isolated in addition to complex 1. Although its precise structure was not established due to its instability and low yield, its infrared spectrum and decomposing into complex 1 implied that the product may be a cluster with higher nuclearity. The experimental observations suggested that with the increase of the ring size of the cyclic thioester ligands, further bond cleavages were involved in the reaction in addition to that leading to complex 1. GRAPHICAL ABSTRACT: SYNOPSIS Reaction of cyclic thioester ligands with triiron dodecacarbonyl leads to scission of C-S (C) bond which is initiated by the coordination of the S atom to the Fe atom. The larger the ring size of the ligand, the more diverse are the bond cleavages. [ABSTRACT FROM AUTHOR]