title: Synthesis and characterisation of new bimetallic alkali metal-magnesium mixed diisopropylamide-acetylides: structural variations in bimetallic lithium- and sodium-heteroleptic magnesiates.
abstract: The reactivity of the Brønsted basic mixed-metal tris-amide compounds of empirical formula [MMg(N(i)Pr2)3] [where M = Li (1), Na (2)] towards phenylacetylene (HC[triple bond, length as m-dash]CPh) has been investigated and has led to the synthesis of a series of mixed-metal acetylido-amido-magnesiates. Thus, 1 and 2 molar equivalents of the alkyne with [MMg(N(i)Pr2)3] produce heteroanionic bis(amido)-mono(acetylido) [LiMg(N(i)Pr2)2(C[triple bond, length as m-dash]CPh)]2 (3) and mono(amido)-bis(acetylido) [(TMEDA) x Na(C[triple bond, length as m-dash]CPh)2Mg(N(i)Pr2)](2) (4) (TMEDA = N,N,N',N'-tetramethylethylenediamine) respectively. X-Ray crystallographic studies reveal that the new compounds adopt a different structural motif. Complex can be defined as an inverse crown structure, having a cationic eight-atom [(NaNMgN)2]2+ ring which hosts in its core two acetylido ligands. On the other hand, adopts a tetranuclear NaMgMgNa near-linear chain arrangement, held together by acetylido and amido bridges. The metal coordination geometries in both structures are distorted tetrahedral, and the sodium cations at the end of the mixed-metal chain carry terminal chelating TMEDA ligands. 1H and 13C NMR spectral data recorded in C6D6 solutions are also reported for and , and are consistent with the solid-state structures being retained in solution.
authors.affiliation: WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, UK. r.e.mulvey@strath.ac.uk
authors.forename: Joaquín
authors.initials: J
authors.lastname: García-Alvarez
authors.forename: David V
authors.initials: DV
authors.lastname: Graham
authors.forename: Eva
authors.initials: E
authors.lastname: Hevia
authors.forename: Alan R
authors.initials: AR
authors.lastname: Kennedy
authors.forename: Robert E
authors.initials: RE
authors.lastname: Mulvey