Highly diastereoselective formation and structural characterization of [2+2] cycloadducts from the phosphenium complexes Cp(OC)2M=P(Ph) (o-Tol) (M = Mo, W) and isocyanates 1

Article abstract of DOI:10.1016/0020-1693(95)04833-2

[2+2] Cycloaddition of the prostereogenic phosphenium complexes Cp(OC)₂M=P(o-Tol)Ph (M = Mo (1a), W (1b)) with the isocyanates RNCO (R=Et (2a), Ph (2b)) leads to the formation of the four-membered phosphametallacycles Cp(OC)₂M-P(o-Tol) (Ph)-C(O)-NR (M = Mo, W; R = Et, Ph) (3a-c) with high diastereoselectivity. The X-ray crystal structure of Cp(OC)₂W-P(o-Tol) (Ph) -C(O)-NEt (3b) reveals that the preferred diastereomer is characterized by a syn arrangement of the tolyl ligand and the cyclopentadienyl unit.