Synthesis and structure of (P,P-diphenylphosphino)methyl lithium-tetrahydrofuran

Article abstract of DOI:10.1016/S0277-5387(97)00285-4

Bu₃SnCH₂PPh₂, prepared by reaction OfBu3SnCH2I with NaPPh2 in liquid ammonia and by reaction of Bu₃SnCl with LiCH₂PPh₂/tmeda, reacts with BuLi in hexane as solvent in the presence of a small amount of THF to give [{Li(CH₂PPh₂)(thf)}∞] (4). An X-ray structure analysis revealed that the (P,P-diphenylphosphino)methyl ligands are arranged in a μ₃-1 : 2κ²C: 3κP fashion. Thus, compound 4 exhibits a polymeric ladder-like structure in which six-membered Li₂C₂P₂ rings with a chair conformation and planar four-membered Li₂C₂ rings are arranged alternately. The interplanar angle between the Li₂C₂ rings and the planar Li₂C₂ units belonging to the neighbored six-membered rings amounts to 145.0(4)°. The Li - C bonds within the six-membered rings are shorter than those within the four-membered rings [2.21(1) vs 2.39(1) A]. The distorted tetrahedral donor set of Li is made up by one phosphorus, one oxygen (tetrahydrofuran) and two methylene carbon atoms.