Synthesis of bis(diphenylphosphino) ethanenickel(II) organodichalcogenide complexes and cyclotrimerisation reaction of dimethylacetylenedicarboxylate: Structure of Ni(dppe) (SC₆H₄O)

Reaction of Ni(dppe)Cl₂ (dppe = bis(diphenylphosphino)ethane) with organodichalcogenide ligands of the type 1,2-HSC₆H₄EH (E = CO₂, O, NH) in the presence of triethylamine to give the products Ni(dppe)(SC₆H₄CO₂) (1), Ni(dppe)(SC₆H₄O) (2), and Ni(dppe)(SC₆H₄NH) (3). Complex 2 was characterised by single crystal X-ray diffraction, which shows a distorted geometry. Complexes 1-3 and the dithiolato analogues of 1,2-benzenedithiol, Ni(dppe)(SC₆H₄S) (4), and 3,4-toluendithiol, Ni(dppe)(SC₆H₃MeS) (5), upon reflux with dimethylacetylenedicarboxylate (DMAD) formed the cyclotrimeric product hexamethylbenzene hexacarboxylate (HMBC).