Abstract
Coordination, deprotonation, rearrangement, and cleavage of Ph2PN(iPr)P(Ph)N(iPr)H (1) by trialkylaluminum compounds R3Al (R = Me, Et) are reported that are relevant to the selective ethene trimerization system consisting of the ligand 1, CrCl3(THF)(3) and Et3Al that produces 1-hexene in more than 90% yield and highest purity. With increasing temperature and residence time first the formation of an adduct [Ph2PN(iPr)P(Ph)N(iPr)H][AlR3] (2), second the aluminum amide [Ph2PN(iPr)P(Ph)(AlR3)N(iPr)][AlR2] (3) and third its rearrangement to the cyclic compound [N(iPr)P(Ph)P(Ph-2)N(iPr)][AlR2] (4) were observed. The cleavage of 3 by an excess of R3Al into an amidophosphane and an iminophosphane could be the reason for its rearrangement to complex 4, as well as to the cyclic dimer [R2AlN(iPr)P(Ph)(2)](2) (5). The chemistry of ligand 1 in the presence of alkylaluminum compounds gives hints on possible activation and deactivation mechanisms of 1 in trimerization catalysis.