Synthesis, structure and metal compounds of a novel chromophoric cyanamide ligand
Abstract
The novel compound 2-cyanaminofluoren-9-one (HL) has been synthesized, and is readily deprotonated to form the corresponding cyanamide anion L–. This has been isolated as the Tl+L– and AsPh4+L– salts. The UV/visible spectra of HL and AsPh4+L– show the same amine to carbonyl charge transfer transition seen in other aminofluorenones, although at longer wavelengths. The compound AsPh4+L– undergoes the reversible one electron reduction typical of fluorenones, whilst HL undergoes an irreversible reduction. The crystal structure of AsPh4+L– was determined and related to the solvatochromic behaviour of the L– anion. Some simple EHMO calculations have been carried out on the L– anion of AsPh4+L–, which show the cyanamide based HOMO and carbonyl based LUMO involved in the aforementioned CT transition. The thallium salt Tl+L– has also been used as a transmetallating agent in reaction with trimethyltin chloride to produce the corresponding tin cyanamide complex [SnMe3L], and in reaction with (triphenylphosphine)gold chloride to produce the first reported gold cyanamide compound [AuL(PPh3)], whose crystal structure has been determined.