Structural and magnetic insights into the trinuclear ferrocenophane and unexpected hydrido inverse crown products of alkali-metal-mediated manganation(ii) of ferrocene

Blair, V.L. and Carrella, L.M. and Clegg, W. and Klett, J. and Mulvey, R.E. and Rentschler, E. and Russo, L. (2009) Structural and magnetic insights into the trinuclear ferrocenophane and unexpected hydrido inverse crown products of alkali-metal-mediated manganation(ii) of ferrocene. Chemistry - A European Journal, 15 (4). pp. 856-863. ISSN 0947-6539

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Abstract

With the aim of introducing the diisopropylamide [NiPr2]- ligand to alkali-metal-mediated manganation (AMMMn) chemistry, the temperature-dependent reactions of a 1:1:3 mixture of butylsodium, bis(trimethylsilylmethyl)manganese(II), and diisopropylamine with ferrocene in hexane/toluene have been investigated. Performed at reflux temperature, the reaction affords the surprising, ferrocene-free, hydrido product [Na2Mn2 (-H)2{N(iPr)2}4]2 toluene (1), the first Mn hydrido inverse crown complex. Repeating the reaction rationally, excluding ferrocene, produces 1 in an isolated crystalline yield of 62 %. At lower temperatures, the same bimetallic amide mixture leads to the manganation of ferrocene to generate the first trimanganese, trinuclear ferrocenophane, [{Fe(C5H4)2}3{Mn3Na2(NiPr2)2 (HNiPr2)2}] (2) in an isolated crystalline yield of 81 %. Both 1 and 2 have been characterised by X-ray crystallographic studies. The magnetic properties of paramagnetic 1 and 2 have also been examined by variable-temperature magnetisation measurements on powdered samples. For 1, the room-temperature value for T is 3.45 cm3 K mol-1, and on lowering the temperature a strong antiferromagnetic coupling between the two Mn ions is observed. For 2, the room-temperature value for T is 4.06 cm3 K mol-1, which is significantly lower than the expected value for three isolated paramagnetic MnII ions.