Investigations into the reactivity of lithium indenyl with alpha diimines with chlorinated backbones and formation of related functional ligands and metal complexes

Abstract

Reaction between lithium indenyl and a chlorine substituted alpha diimine of the form [{Cl(NPh) 2 }C)] 2 unexpectedly yielded the corresponding NH rearranged derivative [PhN(H)C(C 9 H 6)] 2 (1) rather than the predicted-diimine. This compound 1 was characterised by 1 H NMR, 13 C{ 1 H} and mass spectrometry, and additionally by X-ray diffraction. It was found that 1 was the first indene-substituted and symmetric secondary amine which was also highly fluorescent in DMSO. The reactivity of 1 towards simple inorganic and organometallic transition metals precursors based on the MX 2 fragments, where M = Group 10 metals and X = halides or methyl groups, has been investigated. Surprisingly, the reaction with [PtMe 2 (COD)] led to the coupling reaction between the indenyl groups incorporated at the CC ligand backbone and a new ligand (2) was discovered, in an attempt to synthesise the metal-linked diamine. Single crystal X-ray diffraction studies confirm this compound 2 to feature coupled indenyl residues and delocalised CC bonds in the solid state. Structural authentication by X-ray crystallography showed compound 2 to be a very rare example of flat and extended aromatic organic molecule and mass spectrometry, IR and NMR spectroscopy were carried out to gain further insight into the solid state and solution phase structures. Further experiments to synthesise analogues of [PhN(H)C(Ind)] 2 aiming to shift a likely equilibrium in favour the imine tautomer, by introducing bulky ortho substituents onto the benzene ring (R = Me, iPr) showed the presence of the imine tautomer to be increasingly favoured in 1 H NMR spectra, with an increase in the steric bulk of the ortho substituents. However, the enamine tautomer is still observed to a minor extent even with isopropyl substituents and yields of these desired compounds were low on steric grounds.