Mono‐ and Trinuclear Tripodal Platinum(II) Chelated Complexes Containing a Pyridine/Sulfoxide Based Anchoring Framework

Abstract

AbstractNew tripodal ligands 2,4,6‐triethyl‐1,3,5‐tris{[1‐(2‐pyridinyl)ethenyl]sulfinylmethyl}benzenes 6, characterized by three pendant chains each containing both sulfoxide and pyridine moieties, were synthesized from the corresponding sulfenic acid and 2‐ethynylpyridine. Two diastereomeric mixtures were obtained and separated, one racemic mixture 6a, having a C3 symmetry axis and the other 6b with no symmetry. With the aim of studying the coordination ability of these chelating‐κN,κS type ligands, monobranched racemic [1‐(2‐pyridinyl)ethenyl]sulfinylbenzene 9 was also synthesized. Upon addition of an equivalent amount of the monochelating ligand 9 or the tripodal species 6a to a CD3CN solution of a platinum(II) complex of the type cis‐[PtMe2(Me2SO)2] (Pt1) or trans‐[PtMeCl(Me2SO)2] (Pt2), platinum(II) coordination and chelation occurred, as definitively indicated by a sharp change in the 1H NMR spectrum towards the final corresponding chelated platinum(II) species and free dimethyl sulfoxide. The prepared platinum(II) species contain one or three fragments of the type {PtMe2}(10 or 12) and {PtMeCl}(11 or 13) bound to the pyridinyl/sulfinyl skeleton in the coordinating ligands 9 and 6a. All the prepared species were fully characterized by NMR spectroscopy from the connectivities in 2D‐COSY, 1H‐13C HSQC and phase‐sensitive 2D‐NOESY spectra which confirm the molecular mechanics calculation predictions.