Insights into the Formation Process of Yttrium-Aluminum Bimetallic Alkyl Complexes Supported by a Bulky Phosphazene Ligand

The reaction of the yttrium dialkyl precursor [N [Ph2PNC6H3 (Pr-i)(2)](2)Y(CH2SiMe3)(2)] (1) with more than 3 equiv of trimethylaluminum or triethylaluminum afforded the dinuclear heterometallic complexes N[Ph2PNC6H3(Pr-i)(2)](2)Y-{(mu-R)(2)AlR2}R (R = Me (2), Et (3)). When trimeth alutni num loading was reduced to 2 equiv, the same reaction gave the product N[Ph2PNC6H3(Pr-i)(2)](2)Y{(mu-Me)(2)(p-CH2SiMe3)-AlMe}Me (4), with quite a different bonding mode. All of these complexes were characterized by NMR spectra, X-ray crystallography, and elemental analysis. We elucidated the step -reaction mechanism between the yttrium dialkyl complex based on bulky phosphazene ligand and trialkylaluminum, which might shed new light on the formation process of active species in organoaluminum-dependent Ziegler-Natta catalytic systems.