Activation of white phosphorus by molybdenum- and uranium tris-amides

Abstract

Molybdaziridine-hydride Mo(H)([eta]²-Me₂C=NAr)(N[i-Pr]Ar)₂ (1, Ar = 3,5-C₆H₃Me₂) acts as a source of its three-coordinate isomer Mo(N[i-Pr]Ar)₃ (2). This relationship has been probed via an investigation of the coordination chemistry of 1 and Mo(N[t-Bu]Ar)3 (3), a bulky analog of 2, with isocyanides RNC (R = 1-adamantyl, tert-butyl) and white phosphorus (P₄). A comparison of the rates and activation parameters of these reactions indicates that 2 is not an intermediate on the pathway from 1 to products, but rather than the molybdaziridine-hydride "opens" upon substrate binding in an associative process. Synthesis and characterization of 1:1 and 1:2 isocyanide adducts of 2 and 3, and bridging and terminal Pn compounds of molybdenum derived from the element P4 and their alcoholysis products are presented. The uranium tris-amide compounds (THF)U(N[R]Ar)₃ (R = t-Bu, 1-Ad) reacted with white phosphorus. The unique products contain a square tetraphosphorus moiety characterized formally as the dianion P₄□□₂₋. Structural and theoretical analyses are provided for this system.