Bidentate Phosphines of Heteroarenes: 9,9-Dimethyl-4,5-bis(diphenylphosphino)xanthene

Article abstract of DOI:10.1016/0040-4039(94)02206-Q

Twofold lithiation of 9,9-dimethylxanthene with n-butyllithium and N,N,N',N'-tetramethylethylenediamine (TMEDA) in boiling n-heptane followed by reaction with chlorodiphenylphosphine (Ph2PCl) yielded the title compound 4.The phosphine ligand was characterised by 1H NMR, 13C NMR, 31P NMR spectroscopy and single crystal X-ray structure analysis.The folded and deformed xanthene unit causes a remarkably short P...P distance of 4.1 Angstroem which in turn results in a large coupling ⁶J_PP' = 27.3 Hz.