Bu3SnCH2PPh2, prepared by reaction of Bu3SnCH2I with NaPPh2 in liquid
ammonia and by reaction of Bu3SnCl with LiCH2PPh2/tmeda, reacts with B
uLi in hexane as solvent in the presence of a small amount of THF to g
ive [{Li(CH2PPh2)(thf)}(infinity)] (4). An X-ray structure analysis re
vealed that the (P,P-diphenylphosphino)methyl ligands are arranged in
a mu(3)-1:2 kappa(2)C:3 kappa P fashion. Thus, compound 4 exhibits a p
olymeric ladder-like structure in which six-membered Li2C2P2 rings wit
h a chair conformation and planar four-membered Li2C2 rings are arrang
ed alternately. The interplanar angle between the Li2C2 rings and the
planar Li2C2 units belonging to the neighbored six-membered rings amou
nts to 145.0(4)degrees. The Li-C bonds within the six membered rings a
re shorter than those within the four-membered rings [2.21(1) vs 2.39(
1) Angstrom]. The distorted tetrahedral donor set of Li is made up by
one phosphorus, one oxygen (tetrahydrofuran) and two methylene carbon
atoms. (C) 1997 Elsevier Science Ltd.