Aminoberyllium alkyls, RBeNR′2: their association and reactions with pyridine and with 2,2′-bipyridyl

Abstract

The degree of association, n, of (RBeNR′₂)_n is discussed. Small groups R and R′ result in n= 3, the following being trimeric in benzene solution: MeBeNMe₂, MeBeNEt₂, PhBeNMe₂, EtBeNMe₂, and PrⁱBeNMe₂. Large groups R and particularly R′ result in n= 2: MeBeNPrⁿ₂, MeBeNPh₂, EtBeNEt₂, PhBeNPh₂, EtBeNPh₂, and MeBeNPhCH₂Ph.

With pyridine (py)(3 mol.)(MeBeNMe₂)₃ yields [Me(Me₂N)pyBe]₂, and Me(Me₂N)py₂ Be is formed with pyridine in excess. The complexes Me(Ph₂N)pyBe, Me(Ph₂N)py₂Be, and Et(Ph₂N)py₂Be, are also described. The bipyridyl complexes R(Ph₂N)bipyBe (R = Me or Et) are brick-red. Disproportionation processes sometimes complicate the reactions between RBeNR′₂ and pyridine bases, e.g., MeBrNPrⁿ₂ and pyridine yield Me₂py₂Be. The bisdimethylamino-complex (Me₂N)₂bipyBe is described.

Steric congestion about the NH group in Bu^t₂BeNHMe₂ results in much greater thermal stability than found for secondary amine adducts of other beryllium alkyls; elimination of isobutane, though assisted by the addition of trimethylamine, could not be taken to completion. In contrast NNN′-trimethylethylenediamine yields monomeric Bu^tBeNMeC₂H₄NMe₂ on reaction with Bu^t₂Be.