Acenaphtho[5,6-cd]-1,2-dichalcogenoles and their platinum complexes

Abstract

A related series of bis(phosphine) platinum complexes 1–5 and 6–8 bearing dichalcogenate acenaphthylene ligands have been synthesised. The chalcogen–chalcogen bonds in the parent acenaphtho[5,6-cd]-1,2-dichalcogenoles (AcenapylE2; L1 E=S, L2 E=Se; Acenapyl=acenaphthylene-5,6-diyl) were reduced with two equivalents of lithium triethylborohydride to form the dilithio-species. Metathetical addition of the lithium dichalcogenate species to a suspension of the appropriate cis-dichlorobis(phosphine)platinum in THF resulted in the formation of platinum(II) complexes [Pt(5,6-AcenapylE2)(PR3)2] (1 E=S, R3=Ph3; 2 E=S, R3=Ph2Me; 3 E=S, R3=PhMe2; 4 E=S, R3=Me3; 6 E=Se, R3=Ph3; 7 E=Se, R3=Ph2Me; 8 E=Se, R3=PhMe2). The dilithio-species of L1 and L2 were also reacted with (1,5-cyclooctadiene)platinum(II) dichloride. This reaction was successful with L1 resulting in the formation of platinum complex [Pt(5,6-AcenapylS2)(COD)] (5). Complexes 1–3 and 5–8 have been fully characterised, principally by multinuclear magnetic resonance spectroscopy, IR and MS. Secondary isotopomer effects create complex satellite systems observed in both the 31P{1H} NMR and 77Se NMR spectra of selenium complexes 6–8. X-ray structures were determined for L1, 1, 3 and 6 and analysed, where appropriate, by measuring the peri-distance, splay angle magnitude, peri-atom displacement, central naphthalene ring torsions and the geometry around the platinum centre. Platinum was found to adopt a distorted square-planar geometry in all three complexes. Complex 1 was found to have the greatest molecular distortion of all three complexes, showing that changing the phosphine group and also the chalcogen has a noticeable effect. Comparisons were made between 6 and our previously reported [Pt(NapSe2)(PPh3)2] and [Pt(AcenapSe2)(PPh3)2] complexes; the level of distortion was found to decrease as the backbone is altered from naphthalene to acenaphthylene.