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

Abstract

Reactions 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.

Trinuclear pyridyl functionalised hydroxylaminato complexes of aluminium, gallium and indium

“…As previously reported for the rare-earth metal complexes with additional Lewis-acids, the N,N-bis[2-(pyrid-2yl)ethyl]hydroxylamine ligand is able to act as a hemilabile bonding partner. 10 This ability is also observed for the complexes 1-3, but interestingly the hemilabile behaviour of 2 and 3 is already observed in non-coordinating solvents such as toluene, whereas the hemilability of 1 is only observable in solvents of higher polarityhere we describe the case in thf.…”

“…1a,e Combining cyclopentadienide substituents with hydroxylaminato ligands has led to a variety of rare-earth metal complexes with different binding and aggregation modes including dimeric [YCp 2 (ONBn 2 )] 2 and [SmCp 2 (ONBn 2 )] 2 (with side-on coordinate hydroxylaminato units and four-membered 9 and heterobimetalic and -trimetalic complexes of the type [YCp 2 ON(C 2 H 4 -o-py) 2 •AlMe 3 •GaMe 3 ], if the latter compounds are reacted with the Lewis-acids AlMe 3 , GaMe 3 and InMe 3 . 10 Various hydroxylaminato complexes of aluminium, gallium and indium demonstrating the flexibility of the hydroxylaminato function have been explored Based on the reaction of [LnCp 2 ON(C 2 H 4 -o-py) 2 ] with an excess of AlMe 3 leading to transmetalation and finally to the Ln-free complex [AlMe 2 ON(C 2 H 4 -o-py) 2 •2AlMe 3 ] (1), we report here on the direct introduction of the donor-functionalised N,N-bis[2-(pyrid-2-yl)ethyl]hydroxylamine ligand into group 13 metal alkyl chemistry.…”

Molecular Neodymium and Yttrium Cations with the N,N-Bis[2-(pyrid-2-yl)ethyl]hydroxylaminato Ligand

“…The coordinated EMe 3 units block some of the donor sites of these complexes and thus inhibit further aggregation as observed in some of the underlying EMe 3 -free complexes [9].…”