Cyclic ether fragmentation and identification of a quadruple open cubane motif for hexametallic aggregates

Structural and Magnetic Diversity in Alkali-Metal Manganate Chemistry: Evaluating Donor and Alkali-Metal Effects in Co-complexation Processes

By exploring co-complexation reactions between the manganese alkyl Mn(CH2SiMe3)2 and the heavier alkali-metal alkyls M(CH2SiMe3) (M=Na, K) in a benzene/hexane solvent mixture and in some cases adding Lewis donors (bidentate TMEDA, 1,4-dioxane, and 1,4-diazabicyclo[2,2,2] octane (DABCO)) has produced a new family of alkali-metal tris(alkyl) manganates. The influences that the alkali metal and the donor solvent impose on the structures and magnetic properties of these ates have been assessed by a combination of X-ray, SQUID magnetization measurements, and EPR spectroscopy. These studies uncover a diverse structural chemistry ranging from discrete monomers [(TMEDA)2 MMn(CH2SiMe3)3] (M=Na, 3; M=K, 4) to dimers [{KMn(CH2SiMe3)3 ⋅C6 H6}2] (2) and [{NaMn(CH2SiMe3)3}2 (dioxane)7] (5); and to more complex supramolecular networks [{NaMn(CH2SiMe3)3}∞] (1) and [{Na2Mn2 (CH2SiMe3)6 (DABCO)2}∞] (7)). Interestingly, the identity of the alkali metal exerts a significant effect in the reactions of 1 and 2 with 1,4-dioxane, as 1 produces coordination adduct 5, while 2 forms heteroleptic [{(dioxane)6K2Mn2 (CH2SiMe3)4(O(CH2)2OCH=CH2)2}∞] (6) containing two alkoxide-vinyl anions resulting from α-metalation and ring opening of dioxane. Compounds 6 and 7, containing two spin carriers, exhibit antiferromagnetic coupling of their S=5/2 moments with varying intensity depending on the nature of the exchange pathways.

Synthesis, Structure, and Computational Studies of the Tetrameric Magnesium Imides [2,4,6-Cl3C6H2NMg·S]4 (S = 1,4-Dioxane and Tetrahydrofuran)

The magnesium imide complexes [(ArNMg.diox)4.3(diox)] (4) and [(ArNMg.THF)4.tol] (5) (where Ar=2,4,6-Cl3C6H2, diox=1,4-dioxane, and THF=tetrahydrofuran) were prepared by the equimolar reaction of Bu2Mg with the primary amine in suitable solvent mixtures. The successful synthesis of the halide-substituted imides is notable because similar reactions with the less acidic organo-substituted anilines cease upon monodeprotonation. Both 4 and 5 form unusual Mg4N4 cubane aggregates in the solid state. Computational studies (HF/6-31G*) indicate that a combination of sterics and metal solvation determines the aggregation state adopted.

Lewis base stabilized lithium TMP-aluminates: an unexpected fragmentation and capture reaction involving cyclic ether 1,4-dioxane

Three Lewis base variations of the synthetically useful aluminate [L x Li(TMP)((i)Bu)Al((i)Bu)2], where L is TMPH, Et3N or PhC(=O)N(i)Pr2, are reported, together with the reaction of the benzamide complex with 1,4-dioxane, which surprisingly leads to fragmentation of the cyclic ether and capture of its alkoxy vinyl ether residue within a novel dilithium dialuminium hexaalkyl aggregate.