Lewis Base-Free Phenyllithium: Determination of the Solid-State Structure by Synchrotron Powder Diffraction

The solid-state structure of unsolvated, Lewis base-free phenyllithium (LiC 6 H 5 ) is reported. Structure determination of the simplest lithium aryl was performed by high-resolution synchrotron X-ray powder diffraction. The structure was solved by ab initio methods in combination with difference Fourier analysis and consecutive Rietveld refinements. Solid phenyllithium consists of dimeric Li 2 Ph 2 molecules, which strongly interact with adjacent Li 2 Ph 2 moieties, forming a polymeric, infinite-ladder structure along the crystallographic b -axis. In the Li 2 Ph 2 units the two lithium atoms and the C( ipso ) atoms of the two phenyl rings form an absolutely planar, four-membered ring with the two phenyl rings perpendicular to it. The bonding of the C( ipso ) atom to the two Li atoms can be described as a three-center, two-electron bond (Li−C 2.24(1) and 2.32(1) Å; Li−C−Li‘ 63.2(7)°). The π-electrons of the phenyl rings interact strongly with the lithium atoms of neighboring Li 2 Ph 2 moieties.