Isolation and structural characterisation of two sterically crowded diphosphanes

Under specific conditions the reduction of the chlorophosphanes R(Me2NCH22-C6H4)PCl or RPCl2 [R=(Me3Si)2CH] with LiAlH4 gives the diphosphanes {R(Me2NCH22-C6H4)P}2 (2) and RPHPHR (3), respectively, in moderate to good yields. Compound 2 may be obtained in higher yield from the reaction of {R(Me2NCH22-C6H4)P}Li with PbI2. Compounds 2 and 3 have been characterised by multi-element NMR spectroscopy and the meso-diastereomers of both compounds have been characterised by X-ray crystallography. In the solid state both meso-2 and meso-3 adopt an antiperiplanar conformation.