AlMe3, GaMe3 and InMe3 Adducts of N,N‐Bis(2‐{pyrid‐2‐yl}ethyl)hydroxylaminato Rare‐Earth Metal Complexes and Their Molecular Dynamics

Abstract

AbstractReactions of hydroxylaminato rare‐earth metal complexes of the general type [Cp2Ln{η2‐ON(C2H4‐o‐Py)2}] (Cp = cyclopentadienyl, Py = pyridyl, Ln = Y, Sm, Nd, Pr, La) with the Lewis acids AlMe3, GaMe3 and InMe3 resulted in the formation of the oxygen bonded adducts [Cp2Ln{η2‐ON(C2H4‐η1‐o‐Py)(C2H4‐o‐Py)}·EMe3] where Ln = Y, Sm and E = Al, Ga, In. Combination of the corresponding Nd, Pr and La complexes with the Lewis acids EMe3 gave the doubly pyridyl coordinated complexes [Cp2Ln{η2‐ON(C2H4‐η1‐o‐Py)2}·EMe3] (E = Al, Ga, In). Reactions of the complexes [Cp2Ln{η2‐ON(C2H4‐o‐Py)2}] with two equivalents of the Lewis acids reveal complexes of the type [Cp2Ln{η2‐ON(C2H4‐η1‐o‐Py)(C2H4‐o‐Py)}·2EMe3] (Ln = Y, Sm and E = Al, Ga, In) in which one Lewis acid EMe3 coordinates to the hydroxylaminato oxygen atom and one interacts with a pyridyl nitrogen atom. The possibility of synthesising heterotrimetallic complexes was demonstrated by reacting the compound [Cp2Y{η2‐ON(C2H4‐η1‐o‐Py)(C2H4‐o‐Py)}·AlMe3] with GaMe3 to obtain the complex [Cp2Y{η2‐ON(C2H4‐η1‐o‐Py)(C2H4‐o‐Py)}·AlMe3·GaMe3]. The compounds have been characterised by elemental analysis, NMR spectroscopy (except paramagnetic substances) and single‐crystal X‐ray diffraction experiments. The aggregation trend is found to be directly related to the size of the metal ions. The new complexes exhibit a highly dynamic behaviour in solution. The two pyridyl nitrogen atoms are changing their coordination to the metal atom rapidly at ambient temperature even when the pyridine nitrogen donor atom is blocked by an EMe3 unit. VT‐NMR experiments showed that this dynamic exchange can be frozen on the NMR time scale.