Synthesis and structural characterisation of ‘solvent-free’ lithium–calcium hexamethyldisilazide, [Li{μ-N(SiMe3)2}2Ca{N(SiMe3)2}], exhibiting a double ration of agostic H3C⋯Li and H3C⋯Ca intramolecular interactions

Addition of lithium hexamethyldisilazide to an equimolar amount of calcium bis(hexamethyldisilazide) in toluene gave ‘solvent-free’, [Li{μ-N(SiMe3)2}2Ca{N(SiMe3)2}] (1). An X-ray study reveals a dinuclear arrangement based on a planar L four-membered ring: both metals engage in additional H3C⋯M (where M=Li, Ca) interactions with the μ-N(SiMe3)2 substituents resulting in a distorted tetrahedral geometry at lithium and a distorted trigonal-bipyramidal geometry at calcium. This contrasts with the previously reported mixed Li–Mg analogue, [Li{μ-N(SiMe3)2}2Mg{N(SiMe3)2}], where only the lithium centre engages in such intramolecular agostic H3C⋯Li interactions.