Neutron Diffraction Characterization of C–H···Li Interactions in a Lithium Aluminate Polymer

The reaction of AlMe3 with tBuLi in the presence of trimethylacetonitrile affords the bimetallic complex [tBu­(Me)­Al­(μ-Me)2Li·NC­(tBu)]∞ (1). Pseudotetrahedral Al centers form by the nucelophilic addition of tBuLi to AlMe3.The alkali-metal center is stabilized through coordination of the unreacted nitrile and polymer formation via the construction of Al­(μ-Me)nLi (n = 1, 2) motifs. Neutron diffraction evidences agostic interactions in the bridging methyl group to give further stabilization. There is only one previous report of a neutron structure of a lithium aluminate compound. This work therefore offers an important structural example of agostic interactions and the precise nature of Al­(μ-Me)2Li bridging.