Synthesis and characterisation of new platinum-acetylide complexes containing diimine ligands

A new class of platinum-bipyridyl compounds has been synthesized by the dehydrohalogenative reaction of [4,4′-bis(tert-butyl)-2,2′-bipyridyl]platinum dichloride [PtCl₂(^tBu₂bipy)] 1 with terminal alkynes HC≡CR, in the presence of copper(I) iodide and diisopropylamine. The products [Pt(C≡CR)₂(^tBu₂bipy)] (R = C₆H₄NO₂-p 2, C₆H₅ 3, C₆H₄CH₃-p 4 or SiMe₃ 5), have been characterised by spectroscopic and analytical methods, and a single crystal molecular structure determination has been carried out on 4. Extended Hückel molecular orbital calculations have also been carried out, and the results are used to help rationalise the voltammetric, EPR and spectroelectrochemical properties of the new compounds. These show that compounds 3, 4 and 5 undergo a one-electron bipyridyl based redox process, but that 2 has an unresolved two-electron process located on the nitro groups.