Molecular structures of bis(trimethylsilyl)methyl-lithium [(LiR) n , R = CH(SiMe 3 ) 2 ] in the vapour (gas-phase electron diffraction: a monomer, n= 1) and the crystal (X-ray: a polymer, n=∞)

Gaseous bis(trimethylsilyl)methyl-lithium (LiR) at ca. 413K is a monomer with Li–C 2.03(6)Å and the SiMe3 groups only slightly distorted from an eclipsed conformation with respect to each other; crystalline LiR is a polymer, having three ‘molecules’ of monomer in the asymmetric unit, the Li–C distances range from 2.14(3) to 2.27(2)Å and average 2.19(5)Å, <CLiC angles are 147(1), 151(1), and 152(1)°, and