Reactivity with Alkylaluminum of a Chromium Complex of a Pyridine-Containing PNP Ligand: Redox N–P Bond Cleavage

The ligand 2,6-[(Ph2)2PN]2C5H3N based on the popular PNP motif has been used to generate the corresponding chromium adduct {2,6-[(Ph2)2PN]2C5H3N}­CrCl3·2.5THF (1). Its reaction with Et2AlCl and Cl2AlEt afforded the two nearly isostructural complexes {2,6-(Ph2PNH)­[(Et2ClAl)­NPPh2]­C5H3N}­CrCl­(PEtPh2)·0.5­(toluene) (2) and {2,6-(Ph2PNH)­[(EtCl2Al)­NPPh2]­C5H3N}­CrCl­(PEtPh2)·0.5­(toluene) (3). The formation of these two species is the result of a multiple attack of the activator at both the ligand system and the metal center. During the reaction, the two nitrogen atoms lost one phosphine residue each, the metal was reduced, one of the two nitrogens was protonated, and one EtPPh2 molecule was formed and retained by the metal center. The three complexes characterized in this work display activity for catalytic and nonselective ethylene oligomerization.