Ligand Design for the Assembly of Polynuclear Complexes: Syntheses and Structures of Trinuclear and Tetranuclear Aluminum Alkyl Complexes Bearing Tripodal Diamidoselenophosphinito Ligands and a Comparison to Related Tripodal Triamidophosphine Complexes

Reactions of the triaminophosphines P(CH2NHArR)3 (1a−c, where ArR = 3,5-(CF3)2C6H3 for a; ArR
= Ph for b, ArR = 3,5-Me2C6H3 for c) with selenium afford the triaminophosphine selenides SeP(CH2NHArR)3 (2a−c). The phosphine selenides 2a−c react with 4 equiv of AlMe3 at room temperature to
generate the triangular trinuclear aluminum complexes [P(CH2NArR)2Se](AlMe2)3 (3a−c). The byproduct
of the formation of 3a was hydrolyzed and provided CH3CH2N(H)-3,5-(CF3)2C6H3. When 2a−c are treated
with excess AlMe3, the corresponding tetranuclear Lewis acid−base adducts Me3Al·[P(CH2NArR)2Se](AlMe2)3 (4b,c) are isolated. The reaction of P(CH2NHArR)3 (1a−c) with 2 equiv of AlMe3 produces the
dinuclear aluminum complexes P(CH2NArR)3Al2Me3 (5a−c). When 1b,c are reacted with excess AlMe3,
the Lewis acid−base adducts Me3Al·P(CH2NArR)3Al2Me3 (6b,c) are isolated. Solid-state molecular
structures were determined for complexes 2a, 2b, 2c, 3a, 3c, 4b, 5a, and 6b by X-ray crystallography.