Abstract
Different organometallic compounds of the new aminodiphosphinoamine ligand Ph2PN(Pr-i)P(Ph)-N(Pr-i)-H (1) are reported that are relevant model complexes for the selective ethene trimerization system consisting of ligand 1, CrCl3(THF)(3), and Et3Al that produces 1-hexene in more than 90% yield and high purity. The lithiation of 1 by n-BuLi in the presence of tetramethylethylenediamine (tmeda) yields the mononuclear compound Ph2PN(Pr-i)P(Ph)N(Pr-i)-][Li(tmeda)] (2). Without using tmeda the dinuclear species [Ph2N(Pr-i)P(Ph)N(Pr-i)-Li-2] (3) was obtained. By addition of a Grignard reagent to the ligand solution the bis(aminodiphosphinoamide)magnesium complex [Ph2PN(Pr-i)P(Ph)N(Pr-i)-](2)Mg (4) could be isolated. Reaction of Li[CpCrCl3] with 3 leads to the formation of the model compound CpCrCl[-N(Pr-i)P(Ph)N(Pr-i)PPh2] (5), which can be alkylated with Na[Et4Al] to form the corresponding ethyl compound CpCrEt(-N(Pr-i)P(Ph)N(Pr-i)PPh2] (7). In. THF the formation of EtCrCl2(THF)(3) (8) directly from the reaction of CrCl3[Ph2PN(Pr-i)P(Ph)N(Pr-i)-H](THF) (6) with Et3Al could be observed. The organometallic chemistry of 1 gives hints on possible species and activation mechanisms in the catalysis, which have to be considered for a better understanding of the catalytic system.