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 But2BeNHMe2 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 ButBeNMeC2H4NMe2 on reaction with But2Be.