Structural and Magnetic Diversity in Alkali‐Metal Manganate Chemistry: Evaluating Donor and Alkali‐Metal Effects in Co‐complexation Processes. Issue 14 (24th February 2016)

• Record Type: Journal Article
• Authors: Uzelac, Marina; Borilovic, Ivana; Amores, Marco; Cadenbach, Thomas; Kennedy, Alan R.; Aromí, Guillem; Hevia, Eva
• Is Part Of: Chemistry. Volume 22:Issue 14(2016)
• Page Start: 4843
• Page End: 4854
• Publication Date: 2016-02-24
• Subjects: alkali metals -- cooperativity -- Lewis bases -- magnetism -- manganese; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201504956
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: By exploring co‐complexation reactions between the manganese alkyl Mn(CH2 SiMe3 )2 and the heavier alkali‐metal alkyls M(CH2 SiMe3 ) (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(CH2 SiMe3 )3 ] (M=Na, 3 ; M=K, 4 ) to dimers [{KMn(CH2 SiMe3 )3 ⋅C6 H6 }2 ] (2 ) and [{NaMn(CH2 SiMe3 )3 }2 (dioxane)7 ] (5 ); and to more complex supramolecular networks [{NaMn(CH2 SiMe3 )3 }∞ ] (1 ) and [{Na2 Mn2 (CH2 SiMe3 )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)6 K2 Mn2 (CH2 SiMe3 )4 (O(CH2 )2 OCH=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. Abstract : Heavy‐metal influences : By exploring intriguing structural/synthetic/magnetic correlations in manganate chemistry, studies on the reactivity of tris(alkyl)manganates MMnR3 (M=Na, K; R=CH2 SiMe3 ) towards Lewis bases have revealed that the outcome of these processes is controlled by the alkali metal present.