Reactivity of a Diphosphorus Complex Towards Phosphenium Ions

Abstract

The reaction of white phosphorus (P4) with phosphenium ions [R2P]+ yields [P5R2]+ cages via insertion of [R2P]+ into a P-P bond of P4. Herein, a systematic study on the reactivity of the to P4 isolobal diphosphorus complex [{CpMo(CO)2}2(µ,η2:2-P2)] (A) towards differently substituted phosphenium ions was conducted. The phosphenium ions [R1R2P]+ (R1 = R2 = Cl, Br and R1 = Ph, R2 = Cl) were found to insert into a Mo-P bond of A followed by an unprecedented halide shift to yield [{CpMo(CO)2}2(µ,η1:1:1:1-P(R1)P(R2)P)][WCA] (1a: R1 = R2 = Cl, [WCA]- = [BArF24]-; 1b: R1 = R2 = Br, [WCA]- = [BArF24]-; 2: R1 = Ph, R2 = Cl, [WCA]- = [TEF]- with [BArF24]- = [B(3,5-C6H3(CF3)2)4]- and [TEF]- = [Al{OC(CF3)3}4] ). In contrast, [Ph2P]+ reacts with A in a complex reaction involving Mo-P and Mo-Mo bond insertion of the phosphenium ion leading to a mixture of [{CpMo(CO)}2(µ4,η2:2:2:1:1-2-(Ph2P)P4)(µ-PPh2){CpMo(CO)2}2][TEF]2 (3) and [{CpMo(CO)}2(µ,η2:1:1-PP(Cl)PPh2)(µ-PPh2)][TEF] (4) depending on the used stoichiometry. Furthermore, the reaction of A with [Cy2P]+ leads to CO elimination and formation of [{CpMo(CO)}2(µ,η2:2-P2)(µ-PCy2)][TEF] (5) in which the phosphenium ion bridges the Mo-Mo bond. Reaction monitoring and additional DFT computations shed light on the ongoing reaction pathways and reveal crucial intermediates of the respective reactions