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Cyclooctatetraenyl calcium and strontium amido complexes


This paper reports the synthesis and structural characterisation of a series of cyclooctatetraenyl (C8H8) complexes of calcium and strontium, most of them containing the bis(trimethylsilyl)amido ligand. Mixing MI2 (M = Ca, Sr), KN(SiMe3)2 and K2(C8H8) in thf in a 2:2:1 ratio gave the inverse sandwich amido complexes [[{(Me3Si)2N}M(thf)x]2(μ-C8H8)] (M = Ca, x = 1; M = Sr , x = 2) (1-Ca, 1-Sr) in fair to good yields. From a 1:1:1 ratio, the mixed potassium calcium complex [[{(Me3Si)2N}Ca(thf)](μ-C8H8)K] (2) was obtained in good yield. The reaction of 2 with a 1:1 mixture of CaI2 and KN(SiMe3)2 yielded 1-Ca confirming the reaction could be carried out stepwise. Attempts at making heterobimetallic calcium strontium amido complexes from the reaction of 2 with Sr{N(SiMe3)2}2 lead to redistribution reactions which afforded the potassium strontium complex [[K{(Me3Si)2N}2Sr]2(η-C8H8)] (3) among other species. Complex 3 was more conveniently synthesised in fair yield starting from a 2:4:1 molar mixture of SrI2, KN(SiMe3)2 and K2(C8H8), respectively. Treatment of 2 with PhC≡CH in benzene yielded an insoluble complex tentatively formulated as the polymeric complex [CaK(CCPh)(C8H8)(thf)x]n. (4). Upon dissolution in thf, 4 underwent a redistribution reaction yielding the X-ray characterised [{Ca(μ-C8H8)2}K2(thf)2] (5) and a homoleptic calcium alkynyl complex [Ca(CCPh)2(thf)x]. Several compounds were characterised by X-ray diffraction as discrete or polymeric structures where Ca…Cπ interactions were identified in some cases. Despite identified drawbacks, such as the lability of coordinated thf ligands and facile redistribution reactions, this study represent the first synthetic approach to cyclooctatetraenyl heavy alkaline-earth metal amido complexes

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Publication details

The article was received on 01 Jun 2018, accepted on 12 Jun 2018 and first published on 13 Jun 2018

Article type: Paper
DOI: 10.1039/C8DT02257G
Citation: Dalton Trans., 2018, Accepted Manuscript
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    Cyclooctatetraenyl calcium and strontium amido complexes

    F. M. Sroor, L. Vendier and M. Etienne, Dalton Trans., 2018, Accepted Manuscript , DOI: 10.1039/C8DT02257G

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